Co-reporter:Zijia Zhang, Hailei Zhao, Zhihong Du, Xiwang Chang, Lina Zhao, Xuefei Du, Zhaolin Li, Yongqiang Teng, Jiejun Fang, and Konrad Świerczek
ACS Applied Materials & Interfaces October 18, 2017 Volume 9(Issue 41) pp:35880-35880
Publication Date(Web):September 26, 2017
DOI:10.1021/acsami.7b11113
Tin disulfide is considered to be a promising anode material for Li ion batteries because of its high theoretical capacity as well as its natural abundance of sulfur and tin. Practical implementation of tin disulfide is, however, strongly hindered by inferior rate performance and poor cycling stability of unoptimized material. In this work, carbon-encapsulated tin disulfide nanoplates with a (101) plane orientation are prepared via a facile hydrothermal method, using polyethylene glycol as a surfactant to guide the crystal growth orientation, followed by a low-temperature carbon-coating process. Fast lithium ion diffusion channels are abundant and well-exposed on the surface of such obtained tin disulfide nanoplates, while the designed microstructure allows the effective decrease of the Li ion diffusion length in the electrode material. In addition, the outer carbon layer enhances the microscopic electrical conductivity and buffers the volumetric changes of the active particles during cycling. The optimized, carbon coated tin disulfide (101) nanoplates deliver a very high reversible capacity (960 mAh g–1 at a current density of 0.1 A g–1), superior rate capability (796 mAh g–1 at a current density as high as 2 A g–1), and an excellent cycling stability of 0.5 A g–1 for 300 cycles, with only 0.05% capacity decay per cycle.Keywords: anode material; carbon coating; lithium ion battery; oriented growth; tin disulfide;
Co-reporter:Yao Lu;Kui Li;Xuefei Du;Yanhui Ma;Xiwang Chang;Ning Chen;Kun Zheng;Konrad Świerczek
Journal of Materials Chemistry A 2017 vol. 5(Issue 17) pp:7999-8009
Publication Date(Web):2017/05/03
DOI:10.1039/C7TA00907K
A cost-effective doping strategy was developed to enhance the oxygen permeability and structural stability of BaFeO3−δ. We demonstrated that the alkaline earth metal element Ca, which is usually considered an A-site dopant for perovskite oxides, can be successfully introduced into the B-site of BaFeO3−δ. The cubic perovskite structure of BaFe1−xCaxO3−δ was stabilized down to room temperature for the Ca-doping concentration range from 5 to 15 at%. First principles calculations not only proved the preference of Ca at the B-site with lower defect formation energies than the A-site, but also demonstrated that the migration of the oxygens located greater distances from the Ca position is characterized by lower barrier energies than those in the Ca vicinity and even lower than that for the undoped BaFeO3−δ. We found that these favourable, low energy barrier paths away from the Ca sites exert more pronounced effects on the oxygen migration at diluted dopant concentrations, and hence, the material with x = 0.05 level of substitution shows a higher oxygen permeability with a lower activation energy compared to the undoped or highly-doped BaFeO3−δ. The BaFe0.95Ca0.05O3−δ membrane is characterized by a high oxygen permeability of 1.30 mL cm−2 min−1 at 950 °C and good long-term stability at 800/900 °C, as obtained over 200 h. Therefore, the feasibility and applicability of Ca-doping at the B-site of the perovskite can be highlighted, which allows for the enhancement of the oxygen migration ability, originating from the appropriate tuning of the lattice structure.
Co-reporter:Yongqiang Teng, Hailei Zhao, Zijia Zhang, Lina Zhao, Yang Zhang, Zhaolin Li, Qing Xia, Zhihong Du, Konrad Świerczek
Carbon 2017 Volume 119(Volume 119) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.carbon.2017.04.017
Rational material design is a key to develop high performance electrode for sodium ion batteries (SIBs). Sandwich-like graphene@MoS2@C sheets (G@MS@C), with MoS2 nanosheets perpendicularly connecting with reduced graphene oxide (rGO) through the direct chemical coupling (COMo bonds), are synthesized by a facile two-step method, which involves in situ growth of MoS2 on rGO sheets and a followed amorphous carbon coverage process. The interfacial interaction via the COMo bonds can accelerate electron transport rate and enhance structural stability of G@MS@C electrode. Meanwhile, the vertical nanostructure provides more active sites and short diffusion distance for sodium ion reaction, leading to fast electrode reaction kinetics. The rGO sheets and carbon shells not only improve the electrical conductivity of the composite, but also act as buffers to accommodate the volume changes of MoS2 and ensure the integrity of the electrode during cycling. As an anode material for SIBs, the G@MS@C electrode shows superior reversible capacity (520 mAh g−1 after 110 cycles at 100 mA g−1), excellent rate capability (304 mAh g−1 after 200 cycles at 5 A g−1) and stable cycling performance (260 mAh g−1 after 300 cycles at 10 A g−1).Download high-res image (288KB)Download full-size image
Co-reporter:Zhihong Du;Chunlin Yan;Yang Zhang;Chunyang Yang;Sha Yi;Yao Lu;Konrad Świerczek
Journal of Materials Chemistry A 2017 vol. 5(Issue 48) pp:25641-25651
Publication Date(Web):2017/12/12
DOI:10.1039/C7TA08954F
Ca-doping at the Y-site of Y1−xCaxBaCo2O5+δ (YCBC) double perovskites is shown as an effective strategy to develop a highly efficient, stable, lanthanide-free cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The proposed Ca-doping has a beneficial influence on the structural stability, thermal expansion coefficient, electronic and ionic transport, and electrochemical properties of YCBC oxides. The phase stability and durability at evaluated temperature are greatly enhanced by Ca-doping. The thermal expansion coefficients of Y1−xCaxBaCo2O5+δ are calculated to be 18.1–18.7 × 10−6 K−1. At 800 °C, the conductivity is as high as 220 S cm−1 for the Y0.8Ca0.2BaCo2O5+δ sample. Area specific resistances as low as 0.010, 0.018, 0.032, 0.068 and 0.142 Ω cm2 at 850, 800, 750, 700 and 650 °C, respectively, are delivered by the Y0.8Ca0.2BaCo2O5+δ cathode in a La0.8Sr0.2Ga0.8Mg0.2O3−δ electrolyte supported symmetric cell. The maximum power densities of a full cell with the Y0.8Ca0.2BaCo2O5+δ/Ce0.9Gd0.1O2−δ composite cathode are registered to be 1066, 841, 634 and 430 mW cm−2 at 850, 800, 750 and 700 °C, respectively. All the results clearly demonstrate that Ca-doped Y1−xCaxBaCo2O5+δ double perovskites are highly stable and effectively working candidate cathodes for IT-SOFCs.
Co-reporter:Xuefei Du, Hailei Zhao, Yao Lu, Zijia Zhang, Andrzej Kulka, Konrad Świerczek
Electrochimica Acta 2017 Volume 228(Volume 228) pp:
Publication Date(Web):20 February 2017
DOI:10.1016/j.electacta.2017.01.038
•ZnS/C nanoparticle with core/shell structure was prepared by solvothermal method.•ZnS core is composed of ultrasmall ZnS crystals dispersing in carbon matrix.•Hierarchical ZnS/C nanocomposite exhibits excellent electrochemical performance.ZnS/C nanoparticles with core/shell structure are prepared by a simple solvothermal process followed by an annealing process. The core consists of a quite amount of ultrasmall ZnS nanocrystals (∼10 nm) dispersing in in situ formed carbon matrix, which is covered by an outer carbon shell with ∼4 nm thickness. The nano-sized ZnS crystals effectively shorten the lithium ion diffusion paths, while the uniform carbon shell, together with the inner amorphous carbon matrix not only provide fast electron conduction, but also act as a buffer matrix to accommodate volume change occurring on electrochemical cycling. Such hierarchical-type microstructure is beneficial concerning electrochemical performance of the proposed composite. When evaluated as an anode material for rechargeable lithium ion batteries, the ZnS/C nanocomposite shows a high specific capacity of 741 mAh g−1 at a current density of 0.1 A g−1 after 300 cycles. Even at 5 A g−1, a high reversible capacity of 538 mAh g−1 can be still achieved. The lithium diffusion coefficient of ZnS/C electrode is estimated as 6.1 × 10−11 cm2 s−1, contributing to the excellent rate performance of the material.
Co-reporter:Junxiang Jia, Kai Wang, Xiong Zhang, Xianzhong Sun, Hailei Zhao, and Yanwei Ma
Chemistry of Materials 2016 Volume 28(Issue 21) pp:7864
Publication Date(Web):October 14, 2016
DOI:10.1021/acs.chemmater.6b03365
Herein, a hierarchically micro/mesoporous nanocomposite of graphene and carbon nanospheres (HGC) is used as an immobilizer for a lithium–sulfur (Li–S) battery with enhanced performance. HGC derived from graphene oxides and polyvinylidene fluoride polymers, combined with the advantages of graphene and porous carbon nanospheres, exhibits a hierarchically micro/mesoporous structure with an ultralarge specific surface area of up to 3182 m2 g–1 and a large pore volume of 1.91 cm3 g–1. Graphene as a conducting network can enhance electronic conductivity, while porous nanospheres like a reservoir can effectively store and immobilize sulfur particles. HGC/sulfur electrode material obtained via a melting infusion process exhibits high reversible specific capacity of 1250 mA h g–1 with a high sulfur content of 74.5 wt %, and it still has a capacity of 916 mA h g–1 after 100 cycles, which is better than that of pristine porous graphene and carbon nanospheres. Furthermore, the relative capacity decay of the HGC/sulfur electrode is only 0.005 and 0.004% per cycle at 2 C and 4 C, respectively, after 450 charge/discharge cycles, exhibiting remarkable performance in terms of long-term electrochemical stability.
Co-reporter:Yao Lu, Hailei Zhao, Xiwang Chang, Xuefei Du, Kui Li, Yanhui Ma, Sha Yi, Zhihong Du, Kun Zheng and Konrad Świerczek
Journal of Materials Chemistry A 2016 vol. 4(Issue 27) pp:10454-10466
Publication Date(Web):14 Jun 2016
DOI:10.1039/C6TA01749E
A cobalt-free perovskite-type mixed ionic and electronic conductor (MIEC) is of technological and economic importance in many energy-related applications. In this work, a new group of Fe-based perovskite MIECs with BaFe1−xGdxO3−δ (0.025 ≤ x ≤ 0.20) compositions was developed for application in oxygen permeation membranes. Slight Gd doping (x = 0.025) can stabilize the cubic structure of the BaFe1−xGdxO3−δ perovskite. The Gd substitution of BaFe1−xGdxO3−δ materials increases the structural and chemical stability in the atmosphere containing CO2 and H2O, and decreases the thermal expansion coefficient. The BaFe0.975Gd0.025O3−δ membrane exhibits fast oxygen surface exchange kinetics and a high bulk diffusion coefficient, and achieves a high oxygen permeation flux of 1.37 mL cm−2 min−1 for a 1 mm thick membrane at 950 °C under an air/He oxygen gradient, and can maintain stability at 900 °C for 100 h. Compared to the pristine BaFeO3−δ and the well-studied Ba0.95La0.05FeO3−δ membranes, a lower oxygen permeation activation energy and higher oxygen permeability are obtained for the 2.5 at% Gd-doped material, which might be attributed to the expanded lattice by doping large Gd3+ cations and a limited negative effect from the strong Gd–O bond. A combination study of first principles calculation and experimental measurements was further conducted to advance the understanding of Gd effects on the oxygen migration behavior in BaFe1−xGdxO3−δ. These findings are expected to provide guidelines for material design of high performance MIECs.
Co-reporter:Qing Xia, Hailei Zhao, Zhihong Du, Zijia Zhang, Shanming Li, Chunhui Gao and Konrad Świerczek
Journal of Materials Chemistry A 2016 vol. 4(Issue 2) pp:605-611
Publication Date(Web):25 Nov 2015
DOI:10.1039/C5TA07052J
Molybdenum dioxide is an attractive material for anodes of lithium ion batteries due to its high theoretical capacity, more than twice that of graphite. However, slow electrode reaction kinetics and structural degradation caused by large volume changes and phase separation during cycling hinder its practical application. To solve these problems, we design and fabricate a novel, 3-D hierarchical MoO2/Ni/C architecture by a combination of a hydrothermal method with chemical vapor deposition. The nickel nanoparticles are in situ formed and disperse uniformly with flower-like MoO2 particles, which are coated by thin carbon layers. The Ni particles act as a catalyst during the carbon coating process to promote the in situ growth of graphene in the carbon layer. Together, MoO2 and nickel nanoparticles, as well as amorphous carbon and graphene sheets build a 3-D hierarchical robust MoO2/Ni/C structure with a good electronically conductive network and lots of void space. Such a 3-D hierarchical structure combines multiple advantageous features, including an enhanced 3-D electronically conductive network, plenty of tunnels for electrolyte solution penetration, void space for volume change accommodation, and more surface areas for the electrode reaction. The manufactured MoO2/Ni/C composite exhibits a high reversible capacity, and excellent rate capability of 576 and 463 mA h g−1 at current densities of 100 and 1000 mA g−1, respectively. The excellent cycling performance is recorded with a capacity of 445 mA h g−1 maintained at 1000 mA g−1 after 800 cycles. The proposed synthesis process is simple and the design concept can be broadly applied, providing a novel, general approach towards manufacturing of metal oxide/metal/carbon (graphene) composites for high energy density storage or other electrochemical uses.
Co-reporter:Sha Yi, Yongna Shen, Hailei Zhao, Zhihong Du, Ning Chen, Bingxin Huang
Electrochimica Acta 2016 Volume 219() pp:394-400
Publication Date(Web):20 November 2016
DOI:10.1016/j.electacta.2016.10.025
•Fe-doping reduces polarization resistance of La1.5Sr0.5Ni1-xFexO4+δ (LSNF) cathode.•Single cell performances with LSNF electrode are highly improved by Fe-doping.•Molecular oxygen dissociation and charge transfer process control cathode reaction.La1.5Sr0.5Ni1-xFexO4+δ (LSNF, x = 0, 0.3, 0.5) series materials are synthesized as potential cathode materials for intermediate-temperature solid fuel cells by an EDTA-citrate complexation process. The effects of Fe substitution for Ni on the structure, transport property and electrochemical performances are investigated. X-ray diffraction shows that all samples with Fe-doping are identified as single phase materials with a tetragonal I4/mmm space group. Fe-doping decreases electrical conductivity of La1.5Sr0.5Ni1-xFexO4+δ. The study of symmetrical cells with La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) as an electrolyte shows a decreasing tendency of polarization resistance (Rp) of La1.5Sr0.5Ni1-xFexO4+δ with increasing Fe content. The impedance data at different oxygen partial pressures reveal that the electrode reaction is controlled by the molecular oxygen dissociation and charge transfer processes. The substitution of Fe improves the electrode kinetics and enhances the electrochemical performance of LSNF electrode significantly. The LSGM electrolyte (400 μm) supported single cell with La1.5Sr0.5Ni0.5Fe0.5O4+δ as cathode and Ni-Gd0.1Ce0.9O2-δ as anode delivers relatively high power density of 282 mW cm−2 at 800 °C.
Co-reporter:Xuefei Du, Hailei Zhao, Yao Lu, Chunhui Gao, Qing Xia, Zijia Zhang
Electrochimica Acta 2016 Volume 188() pp:744-751
Publication Date(Web):10 January 2016
DOI:10.1016/j.electacta.2015.12.039
•Nanostructured Li2FeSiO4/C is synthesized by a simple co-precipitation method.•Thermodynamic calculation provides guidance for the synthesis of pure Li2FeSiO4.•Li2FeSiO4/C shows high reversible capacity and excellent cycling performance.Nanostructured Li2FeSiO4/C cathode material is successfully synthesized through a simple co–precipitation method by using Fe3+ salt as iron source and polyethylene glycol as surfactant. Thermodynamic calculation is carried out to get phase predominance diagram as functions of oxygen partial pressure and temperature for Fe–O–C system, which provides effective guidance for synthesis parameter selection of pure phase Li2FeSiO4. The synthesized Li2FeSiO4/C nanoparticles show an average size of 150 nm, which are composed of ultra–small Li2FeSiO4 nanocrystals in 10–25 nm dispersing in amorphous carbon matrix. The in situ formed carbon network and the Li2FeSiO4 nanocrystals provide a fast transport of electron and lithium ion and thus ensure a quick electrode reaction, leading to an excellent electrochemical performance. The synthesized Li2FeSiO4/C exhibits a specific capacity of 190 mAh g−1 at 0.1 C, realizing reversible extraction/insertion of 1.37 Li+, taking into account of 16.1 wt% carbon content in the composite. This work offers a simple, scalable, and low cost approach for the synthesis of high performance Li2FeSiO4/C cathode material for lithium ion batteries.
Co-reporter:Zijia Zhang, Hailei Zhao, Qing Xia, Jason Allen, Zhipeng Zeng, Chunhui Gao, Zhaolin Li, Xuefei Du, Konrad Świerczek
Electrochimica Acta 2016 Volume 211() pp:761-767
Publication Date(Web):1 September 2016
DOI:10.1016/j.electacta.2016.06.103
•Direct growth of Ni3S2 nanoplates on Ni foam is used as binder-free anode.•The Ni3S2/Ni electrode presents nest-like highly porous architecture.•High specific capacity and excellent rate-capability are achieved.A facile one-step method is developed for the direct growth of Ni3S2 nanoplates on a conductive nickel foam, which interwove together to form nest-like highly porous microstructure. When used as a binder- and conductive-agent-free electrode, the Ni3S2/Ni electrode demonstrates remarkable electrochemical performance with a superior cycling stability and a high rate capability, proving its potential applicability as a high performance anode for lithium ion batteries. The excellent electrochemical properties can be attributed to the 3-dimesional (3-D) structure of the Ni foam uniformly covered with a porous layer of Ni3S2 nanoplates. This structure provides excellent electrical contact between the active material and the current collector, a large electroactive surface area as well as well-sustained electrode integrity. The Ni3S2/Ni electrode maintains a reversible capacity of 623 mAh g−1 after 150 cycles at a current density of 0.1 A g−1, and delivers a high reversible capacity of 377 mAh g−1 at a high current density of 1.5 A g−1. The observed surplus capacity is found to originate from an interface storage process via a pseudocapacity-like storage mechanism.
Co-reporter:Jie Wang;Zhaolin Li;Yeting Wen;Qing Xia;Yang Zhang;Gleb Yushin
Advanced Materials Interfaces 2016 Volume 3( Issue 13) pp:
Publication Date(Web):
DOI:10.1002/admi.201600003
Li4Ti5O12 is a promising anode material for lithium ion batteries due to its high safety, excellent cycling stability, environmental friendliness, and low cost. Strategies of incorporation with a conductive component (such as carbon) and constructing nano-structure are frequently adopted to improve the rate-capability of Li4Ti5O12 by means of enhancing the electronic conductivity and promoting the lithium ion transport within electrodes, respectively. However, which charge carrier transport process is the limiting step for Li4Ti5O12 electrode reactions still remains unclear, and this limits the abilities to rationally design high performance Li4Ti5O12 materials. In this work, the nanosized Li4Ti5O12 and Li4Ti5O12/C materials are prepared with nearly identical particle size and morphology. The results demonstrate that the synthesized single phase Li4Ti5O12 delivers a higher specific capacity and superior rate-capability than Li4Ti5O12/C composite. As such, in contrast to a popular belief, it is lithium ion transport that restricts kinetics of the electrochemical reactions on Li4Ti5O12. The synthesized single phase Li4Ti5O12 shows a specific capacity of ≈160 mAh g−1 at 0.5 C and 130 mAhg−1 at 50 C rates, respectively. This rate-capability is the best reported for Li4Ti5O12 anodes. The single phase Li4Ti5O12 also demonstrated remarkable stability at high-temperature (50 °C), showing cycling life of over 4000 cycles at 1 C.
Co-reporter:Zhihong Du, Hailei Zhao, Sha Yi, Qing Xia, Yue Gong, Yang Zhang, Xing Cheng, Yan Li, Lin Gu, and Konrad Świerczek
ACS Nano 2016 Volume 10(Issue 9) pp:8660
Publication Date(Web):August 16, 2016
DOI:10.1021/acsnano.6b03979
A metallic nanoparticle-decorated ceramic anode was prepared by in situ reduction of the perovskite Sr2FeMo0.65Ni0.35O6−δ (SFMNi) in H2 at 850 °C. The reduction converts the pure perovksite phase into mixed phases containing the Ruddlesden–Popper structure Sr3FeMoO7−δ, perovskite Sr(FeMo)O3−δ, and the FeNi3 bimetallic alloy nanoparticle catalyst. The electrochemical performance of the SFMNi ceramic anode is greatly enhanced by the in situ exsolved Fe–Ni alloy nanoparticle catalysts that are homogeneously distributed on the ceramic backbone surface. The maximum power densities of the La0.8Sr0.2Ga0.8Mg0.2O3−δ electrolyte supported a single cell with SFMNi as the anode reached 590, 793, and 960 mW cm–2 in wet H2 at 750, 800, and 850 °C, respectively. The Sr2FeMo0.65Ni0.35O6−δ anode also shows excellent structural stability and good coking resistance in wet CH4. The prepared SFMNi material is a promising high-performance anode for solid oxide fuel cells.Keywords: anode; electrochemical performance; in situ exsolution; nanoparticle catalysts; solid oxide fuel cells
Co-reporter:Yongqiang Teng, Hailei Zhao, Zijia Zhang, Zhaolin Li, Qing Xia, Yang Zhang, Lina Zhao, Xuefei Du, Zhihong Du, Pengpeng Lv, and Konrad Świerczek
ACS Nano 2016 Volume 10(Issue 9) pp:8526
Publication Date(Web):August 24, 2016
DOI:10.1021/acsnano.6b03683
A designed nanostructure with MoS2 nanosheets (NSs) perpendicularly grown on graphene sheets (MoS2/G) is achieved by a facile and scalable hydrothermal method, which involves adsorption of Mo7O246– on a graphene oxide (GO) surface, due to the electrostatic attraction, followed by in situ growth of MoS2. These results give an explicit proof that the presence of oxygen-containing groups and pH of the solution are crucial factors enabling formation of a lamellar structure with MoS2 NSs uniformly decorated on graphene sheets. The direct coupling of edge Mo of MoS2 with the oxygen from functional groups on GO (C–O–Mo bond) is proposed. The interfacial interaction of the C–O–Mo bonds can enhance electron transport rate and structural stability of the MoS2/G electrode, which is beneficial for the improvement of rate performance and long cycle life. The graphene sheets improve the electrical conductivity of the composite and, at the same time, act not only as a substrate to disperse active MoS2 NSs homogeneously but also as a buffer to accommodate the volume changes during cycling. As an anode material for lithium-ion batteries, the manufactured MoS2/G electrode manifests a stable cycling performance (1077 mAh g–1 at 100 mA g–1 after 150 cycles), excellent rate capability, and a long cycle life (907 mAh g–1 at 1000 mA g–1 after 400 cycles).Keywords: C−O−Mo bond; Li-ion batteries; long cycle life; molybdenum disulfide; oxygen-containing groups on GO
Co-reporter:Yao Lu, Hailei Zhao, Xing Cheng, Yibin Jia, Xuefei Du, Mengya Fang, Zhihong Du, Kun Zheng and Konrad Świerczek
Journal of Materials Chemistry A 2015 vol. 3(Issue 11) pp:6202-6214
Publication Date(Web):09 Feb 2015
DOI:10.1039/C4TA06520D
Cobalt-free BaFe1−xInxO3−δ perovskites, with Fe partially substituted by indium at the B-site, were synthesized by a conventional solid state reaction and systematically characterized in terms of their phase composition, crystal structure, thermal reducibility, oxygen permeability, as well as structural stability in order to evaluate their application as oxygen permeation membranes. Introduction of more than 10 at.% of In into BaFe1−xInxO3−δ causes the formation of a single phase material with a cubic perovskite structure, which exhibits no phase transition during the cooling process. The thermal reducibility and thermal expansion coefficient are effectively reduced by indium doping, owing to the less changes of concentration of the oxygen vacancies in these compounds. However, the In occupying B-site breaks the B–O–B double exchange mechanism, and thus results in a gradual decrease of the electrical conductivity upon doping. Rietveld refinement and first principles calculation were performed to get an insight into the In influence on the lattice structure, oxygen migration energy and electron conduction behaviour of BaFe1−xInxO3−δ. When using He/Air as sweep/feed gas, the BaFe0.9In0.1O3−δ dense membrane with 1.0 mm thickness features a high oxygen permeation flux of 1.11 mL cm−2 min−1 at 950 °C. The observed good performance is attributed to the relatively high concentration of oxygen vacancies and low energy barrier for oxygen ion migration. It is also found that for membranes thinner than 0.8 mm, the oxygen flux is no longer limited by the bulk diffusion, while the oxygen surface exchange process becomes the dominant factor.
Co-reporter:Chunhui Gao, Hailei Zhao, Pengpeng Lv, Tianhou Zhang, Qing Xia, and Jie Wang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 3) pp:1693
Publication Date(Web):January 5, 2015
DOI:10.1021/am5072755
Si-based electrodes for lithium ion batteries typically exhibit high specific capacity but poor cycling performance. A possible strategy to improve the cycling performance is to design a novel electrode nanostructure. Here we report the design and fabrication of Ni/Si-nanoparticles/graphite clothing hybrid electrodes with a sandwich structure. An efficient dip-coating of Si-NPs combined with carbon deposition was adopted to synthesize the unique architecture, where the Si-NPs are sandwiched between the Ni matrix and the graphite clothing. This material architecture offers many critical features that are desirable for high-performance Si-based electrodes, including efficient ion diffusion, high conductivity, and structure durability, thus ensuring the electrode with outstanding electrochemical performance (reversible capacity of 1800 mA h g–1 at 2 A g–1 after 500 cycles). In addition, the hybrid anode does not require any polymeric binder and conductive additives and holds great potential for application in Li-ion batteries.Keywords: carbon clothing; lithium-ion battery; sandwich architecture; Si-based anode
Co-reporter:Xin Liu, Hailei Zhao, Andrzej Kulka, Anita Trenczek-Zając, Jingying Xie, Ning Chen, Konrad Świerczek
Acta Materialia 2015 Volume 82() pp:212-223
Publication Date(Web):1 January 2015
DOI:10.1016/j.actamat.2014.08.053
Abstract
In this paper, a novel polymorph of SnS2 having a cubic Fd-3m structure was prepared by a mechanochemical route; its lattice structure and thermal, electronic, transport, electrochemical and photoelectrochemical properties were systematically characterized. Structural studies indicated that no phase transition occurred in the −250 to 300 °C temperature range, with transition to ordinary trigonal P-3m1 phase followed by a significant sulfur loss at higher temperatures. The refined Sn–S interatomic distance of 2.5884(7) Å in the new phase is slightly higher than the one found in other polymorphs, while calculation of the energy gap Eg resulted in similar values (1.9 eV) for Fd-3m and P-3m1 structures. The recorded electrical conductivity has a thermally activated character with lower activation energy Ea = 0.52(1) eV in the 40–160 °C range and 0.87(2) eV at temperatures exceeding 160 °C. Assuming that in the higher temperature range the conductivity is mainly intrinsic, the calculated Eg = 2Ea ≈ 1.7 eV matches well the calculated Eg. The synthesized SnS2 exhibits interesting photoelectrochemical properties, as well as good electrochemical characteristics when used as the anode material in lithium cells. In situ structural studies, performed during first discharge of such cells, clarified the nature of reaction of lithium with SnS2, which was found to be complex, proceeding through intercalation-like, two-phase-like and decomposition-like stages.
Co-reporter:Zhaolin Li, Hailei Zhao, Jie Wang, Pengpeng Lv, Zijia Zhang, Zhipeng Zeng, Qing Xia
Electrochimica Acta 2015 Volume 182() pp:398-405
Publication Date(Web):10 November 2015
DOI:10.1016/j.electacta.2015.09.086
•Self-supported Fe3O4/Ni/C electrode is prepared by a hydrothermal route.•The electrode presents nanoplate array structure with a 3D conductive network.•A high capacity of 832.5 mAh g−1 and an excellent rate-capability are delivered.An open-up network structure assembled by interconnected 3D heterostructure Fe3O4/Ni/C nanoplate arrays on Ni foam is successfully synthesized via a facile hydrothermal method with subsequent CVD heat treatment. When used as a binder free anode material for lithium-ion battery (LIBs), it shows quite a favorable electrochemical performance with high reversible capacity and good rate capability. A high capacity of 832.5 mAh g−1 is achieved at 0.3C and a specific capacity of 279 mAh g−1 can still be delivered at current density of 4.5C, corresponding to 34% of the capacity at 0.3C. The self-supporting nanoplates are intercrossed and interconnected with robust adhesion on Ni foam, preventing the active material from peeling off during the electrochemical reactions. Ni foam substrate, uniform carbon layer on the nanoplate surface and in-situ formed Ni nanocrystals together play important roles in effectively building a fast 3D electron transport network for electrode reactions. The excellent electrochemical performance makes this composite a promising candidate as anode material for high energy density LIBs.
Co-reporter:Zijia Zhang, Hailei Zhao, Zhipeng Zeng, Chunhui Gao, Jie Wang, Qing Xia
Electrochimica Acta 2015 Volume 155() pp:85-92
Publication Date(Web):10 February 2015
DOI:10.1016/j.electacta.2014.12.074
•NiS@SiO2/graphene is prepared by a simple electrostatic attraction route.•NiS@SiO2/graphene presents nano-porous and hierarchical core-shell structure.•Superior cyclic stability and excellent rate capability are achieved.A well-designed hierarchical architecture NiS@SiO2/graphene is prepared through electrostatic self-assembly between (3-aminopropyl) triethoxysilane (APTES)-modified NiS and graphene in aqueous solutions at room temperature. The obtained composite possesses a unique structure with SiO2 ultrasmall nanoparticles (3–5 nm) derived from the pyrolysis of APTES homogeneously anchored on the surface of NiS nanoparticles (100 nm), forming NiS@SiO2 core-shell hybrid particles, which are well enveloped in graphene sheets. The SiO2 nanoparticles act as pillars to form open space between graphene sheets and NiS particles, which can buffer the volume change and afford easy electrolyte-wetting and fast lithium ion transport channels. The graphene sheets can not only significantly enhance the overall electrical conductivity of the NiS@SiO2/graphene electrode, but also serve as a blanket to wrap NiS particle and so as to avert its exfoliation from electrode due to large volume change during cycling. The prepared NiS@SiO2/graphene nanocomposite exhibits high reversible capacity (∼750 mAh g−1 for 100 cycles), remarkable cycling stability and impressive rate capability.
Co-reporter:Chunyang Yang, Xinxin Zhang, Hailei Zhao, Yongna Shen, Zhihong Du, Cuijuan Zhang
International Journal of Hydrogen Energy 2015 Volume 40(Issue 6) pp:2800-2807
Publication Date(Web):19 February 2015
DOI:10.1016/j.ijhydene.2014.12.084
•BaZr0.1Ce0.7Y0.1Yb0.1O3 − δ-Nd1.95NiO4 + δ was synthesized as cathode for PCFCs.•The two components of the composite cathode exhibit good chemical compatibility.•Charge transfer and diffusion of Oad− are rate limiting steps of cathode reaction.•The cathode with 60 wt% Nd1.95NiO4 + δ shows the best electrochemical performance.A new composite cathode used for protonic ceramic fuel cells was developed, which consisted of BaZr0.1Ce0.7Y0.1Yb0.1O3 − δ (BZCYYb), a protonic conductor, and Nd1.95NiO4 + δ (NNO), a mixed oxygen ionic and electronic conductor. The symmetrical cell investigation under different oxygen and water partial pressures demonstrated that the cathode polarization resistance came from proton transport between electrolyte and cathode, charge transfer and the diffusion of Oad−, and the latter two played the dominant roles. The polarization resistance of BZCYYb-NNO composite cathode decreases with increasing NNO content and the composite cathode with 60 wt% NNO shows the lowest polarization resistance, which is 0.43 Ω cm2 at 750 °C. The power density of 154 mV cm−2 is achieved with anode-supported cell NiO-BZCYYb | BZCYYb (∼60 μm) | BZCYYb-60NNO when humidified hydrogen is used as the fuel and ambient air as the oxidant.
Co-reporter:Pengpeng Lv, Hailei Zhao, Zhipeng Zeng, Chunhui Gao, Xin Liu, Tianhou Zhang
Applied Surface Science 2015 Volume 329() pp:301-305
Publication Date(Web):28 February 2015
DOI:10.1016/j.apsusc.2014.12.170
Highlights
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3D hierarchical NiO porous nano/microspheres were prepared via a hydrothermal route.
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Loose NiO microsphere is composed of a large number of cross-linked nanoparticles.
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A possible self-assembly mechanism is illustrated in detail.
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High specific capacity, good cycleability and superior rate-capability are achieved.
Co-reporter:Qing Xia, Hailei Zhao, Yongqiang Teng, Zhihong Du, Jie Wang, Tianhou Zhang
Materials Letters 2015 Volume 142() pp:67-70
Publication Date(Web):1 March 2015
DOI:10.1016/j.matlet.2014.11.142
•The NiO/Ni nanocomposite is in situ synthesized by a citric–nitrate method.•The as-prepared NiO/Ni powders show uniformly particle size of ca. 30–40 nm.•The NiO/Ni electrode exhibits specific capacity of ca. 800 mAh g−1 after 50 cycles.•The preparation method can be extended for other transition metal oxides.NiO/Ni nanocomposite is in situ prepared by a facile citric–nitrate method. The as-prepared NiO/Ni powders show uniformly distributed particle size of ca. 30–40 nm. The prepared NiO/Ni composite shows high reversible capacity, excellent cycling stability, and superior rate capability, with a specific capacity of ca. 800 mAh g−1 maintained at a current density of 0.1C after 50 cycles. Even at a high current density of 5C (3.59 A g−1), the electrode still exhibits a reversible capacity of 450 mAh g−1. Moreover, the synthesized NiO/Ni composite displays a superior electrochemical performance at high temperature (50 °C), with a reversible capacity of 635 mAh g−1 for 300 cycles at 2C. The preparation method is facile and can be extended for other transition metal oxides for the development of high performance lithium ion batteries.
Co-reporter:Xin Liu, Jingying Xie, Hailei Zhao, Pengpeng Lv, Ke Wang, Zhenhe Feng, Konrad Świerczek
Solid State Ionics 2015 Volume 269() pp:86-92
Publication Date(Web):January 2015
DOI:10.1016/j.ssi.2014.11.008
•CoSn2-C nanocomposite (Sn30Co15C55) was prepared by a simple mechanochemical route.•CoSn2 nanocrystals dispersed in carbon matrix ensure good cycleability.•Capacity of CoSn2-C prepared by mechanical alloying is higher than the milled one.•Apparent lithium diffusion coefficient in CoSn2-C is of the order of 10− 11 cm2·s− 1.CoSn2-C nanocomposites with Sn30Co15C55 average formula, consisting of CoSn2 nanocrystals dispersed in a disordered carbon matrix were obtained by a mechanochemical method from CoSn3, Co and graphite, and for comparison, by a typical mechanical milling. Crystal structure and microstructure of the materials were characterized by XRD, SEM and TEM methods, while electrochemical performance, electrochemical impedance spectra and cyclic voltammetry were tested in lithium cells. Both nanocomposites showed a high initial coulombic efficiency (79%), quite stable cycling performance and excellent rate capability, however, the mechanochemically prepared CoSn2-C exhibited significantly higher reversible capacity (600 mAh·g− 1). The obtained results proved that the mechanochemical method is a simple and effective way of manufacturing anode materials from Sn-Co-C system for application in high-energy-density lithium ion batteries.
Co-reporter:Xin Liu, Yang Dai, Jingying Xie, Hailei Zhao, Pengpeng Lv, Ke Wang, Konrad Świerczek
Solid State Ionics 2015 Volume 281() pp:60-67
Publication Date(Web):15 November 2015
DOI:10.1016/j.ssi.2015.09.003
•Si-TiB2-C nanocomposite was prepared by a simple, two-step ball milling method.•Rigid TiB2 can accelerate the amorphization of silicon during the milling process.•The composite shows a structure of TiB2 core/ Si shell embedded in carbon matrix.•The mole ratio of TiB2/carbon has strong impact on the electrochemical performance.•The optimized sample STC-433 shows a high capacity and good cycling stability.In an attempt to improve silicon-based electrode for lithium ion batteries, a series of core-shell-type nanocomposites, consisting of rigid, nano-sized grains of TiB2, which are covered by electrochemically active silicon layer and enclosed in outer carbon layer, were prepared by a relatively simple, two-step ball milling method. The composites, having different TiB2:C ratios, were characterized in terms of their lattice structural, microstructural and electrochemical properties, by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy, particle size distribution, transmission electron microscopy, as well as by electrochemical impedance spectroscopy and galvanostatic cycling tests. It is shown that with the assist of rigid TiB2 particles, silicon and graphite can be easily refined to nanoscale, and both become amorphous during the milling process, forming desired nanocomposites with TiB2-core/Si-shell-type grains covered and embedded in carbon. The amorphous Si, which is uniformly covering TiB2 cores, is electrochemically active, while both, C and TiB2 contribute to the improved electronic conductivity of the nanocomposites. Si-TiB2-C composite with 30 mol.% of TiB2 content (STC-433) delivers the best electrochemical performance, with a high reversible capacity on the order of 660 mAh g- 1 after 60 cycles. A model depicting microstructural changes of the considered nanocomposites with increasing TiB2 content was elaborated, with the low ionic conductivity of titanium diboride being the limiting factor, which causes a decrease of the reversible capacity of the materials with excessive TiB2 amount.
Co-reporter:Zhihong Du, Hailei Zhao, Yongna Shen, Lu Wang, Mengya Fang, Konrad Świerczek and Kun Zheng
Journal of Materials Chemistry A 2014 vol. 2(Issue 26) pp:10290-10299
Publication Date(Web):16 Apr 2014
DOI:10.1039/C4TA00658E
Perovskites La0.3Sr0.7Ti1−xCoxO3 (LSTCs, x = 0.3–0.6) are systematically evaluated as potential cathode materials for solid oxide fuel cells. The effects of Co substitution for Ti on structural characteristics, thermal expansion coefficients (TECs), electrical conductivity, and electrochemical performance are investigated. All of the synthesized LSTCs exhibit a cubic structure. With Rietveld refinement on the high-temperature X-ray diffraction data, the TECs of LSTCs are calculated to be 20–26 × 10−6 K−1. LSTC shows good thermal cycling stability and is chemically compatible with the LSGM electrolyte below 1250 °C. The substitution of Co for Ti increases significantly the electrical conductivity of LSTC. The role of doping on the conduction behavior is discussed based on defect chemistry theory and first principles calculation. The electrochemical performances of LSTC are remarkably improved with Co substitution. The area specific resistance of sample La0.3Sr0.7Ti0.4Co0.6O3 on the La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte in symmetrical cells is 0.0145, 0.0233, 0.0409, 0.0930 Ω cm2 at 850, 800, 750 and 700 °C, respectively, and the maximum power density of the LSGM electrolyte (400 μm)-supported single cell with the Ni–GDC anode, LDC buffer layer and LSTC cathode reaches 464.5, 648, and 775 mW cm−2 at 850 °C for x = 0.3, 0.45, and 0.6, respectively. All these results suggest that LSTC are promising candidate cathode materials for SOFCs.
Co-reporter:Zhipeng Zeng, Hailei Zhao, Jie Wang, Pengpeng Lv, Tianhou Zhang, Qing Xia
Journal of Power Sources 2014 Volume 248() pp:15-21
Publication Date(Web):15 February 2014
DOI:10.1016/j.jpowsour.2013.09.063
•Fe3O4@C was prepared via a facile, economical and one-pot solvothermal route.•Fe3O4@C spheres present nano-porous and mosaic structured morphology.•High specific capacity (∼1000 mAh g−1) and excellent rate-capability were achieved.•Porous carbon matrix ensures a stable cycling performance.The active particle cracking and electrode pulverization of iron oxide anode material as a result of volume expansion during charge/discharge process cause poor reversibility and significant capacity fading in rechargeable lithium-ion batteries. Here, we demonstrate a facile solvothermal route to immobilize the Fe3O4 particles on the porous active carbon. The present method enables us to obtain nano-porous and mosaic structured Fe3O4@C spheres with an average size of ca. 100 nm. The porous active carbon plays an important role in the improvement of electrochemical properties of Fe3O4. It not only acts as a host for the deposition of Fe3O4 particles, but also provides void spaces for active Fe3O4 to buffer the volume expansion. The good contact between Fe3O4 and active carbon ensures the fast electron/Li-ion transport. As a result, the porous Fe3O4@C shows a high reversible specific capacity of ∼1000 mAh g−1, good cycle stability and excellent rate capability. Therefore, we believe that this composite is a potential candidate for anode material of high-energy lithium-ion battery.
Co-reporter:Pengpeng Lv, Hailei Zhao, Zhipeng Zeng, Jie Wang, Tianhou Zhang, Xingwang Li
Journal of Power Sources 2014 Volume 259() pp:92-97
Publication Date(Web):1 August 2014
DOI:10.1016/j.jpowsour.2014.02.081
•Nano-sized Fe3O4/C composite was prepared via a facile and productive route.•Fe3O4/C composite is composed of Fe3O4 nanoparticles and carbon coating layer.•Fe3O4/C electrode exhibits high specific capacity and stable cycling performance.•Fe3O4/C electrode displays good rate-capability.Carbon coated Fe3O4 nanocomposite (Fe3O4/C) is synthesized via a simple sol–gel route and a subsequent carbon CVD process, with Fe2O3 xerogel as intermediate product. The nanoporous Fe2O3 xerogel is reduced to Fe3O4 during the CVD process. The prepared Fe3O4/C composite presents a well-distributed nanostructure composing of Fe3O4 nanoparticles coated with carbon layer. The electrode exhibits a stable reversible capacity of over 850 mAh g−1 at 0.1 A g−1, excellent cycling performance and good rate capability. Both of the nano-scale particle size of Fe3O4 and the carbon layer contribute to the excellent electrochemical performance of Fe3O4/C. An increase in electrode capacity with cycling is observed for the prepared Fe3O4/C composite when cycled at 50 °C, which is similar to other reported transition metal oxides. The preparation process of Fe3O4/C composite is facile, mild and productive.
Co-reporter:Yongna Shen, Hailei Zhao, Jingcan Xu, Xinxin Zhang, Kun Zheng, Konrad Świerczek
International Journal of Hydrogen Energy 2014 Volume 39(Issue 2) pp:1023-1029
Publication Date(Web):13 January 2014
DOI:10.1016/j.ijhydene.2013.10.153
•Both Ba and Sr doping decrease parameters a and b but increase parameter c.•La2−xSrxNiO4+δ exhibits higher electronic conductivities than Ba-doped ones.•Ba-doping causes longer La–O2( × 1) bond, which is favorable for electrode reaction.•Ba-doping leads to a better electrochemical performance than Sr.La2−xMxNiO4+δ (M = Ba, Sr; x = 0.1, 0.3), with a formula of A2BO4, has been prepared and investigated as cathode for solid oxide fuel cells to understand the influence of A-site dopants on the lattice structure, electrical conductivity and electrochemical properties of La2NiO4+δ. All the compositions belong to tetragonal I4/mmm space group. La2−xBaxNiO4+δ shows larger lattice parameters than La2−xSrxNiO4+δ due to the large ionic radius of Ba2+ compared with Sr2+. For both Ba and Sr, the parameters a and b decrease while the c increases with increasing doping level. Rietveld refinement demonstrates that the increase in c parameter is partially originated from the increase in rocksalt layer thickness (La–O2( × 1) bond), which makes the adsorbed oxygen on particle surface much easier to enter the lattice and form interstitials, and thereby promoting the electrode reaction. The electrical conductivity of La2−xMxNiO4+δ increases with doping level but decrease with increasing ionic radius of dopants. Both Ba and Sr doping decrease the electrode polarization and increase the power density of single-cell. La1.7Ba0.3NiO4+δ exhibits superior electrochemical properties than La1.7Sr0.3NiO4+δ. The La1.7Ba0.3NiO4+δ electrode exhibits the best performance with an ASR of 0.13 Ω cm2 and a maximum power density of 310 mW cm−2 at 800 °C under electrolyte (La0.8Sr0.2Ga0.83Mg0.17O3−δ, 300 μm) – supported configuration.
Co-reporter:Tianrang Yang, Hailei Zhao, Jaeho Han, Nansheng Xu, Yongna Shen, Zhihong Du, Jie Wang
Journal of the European Ceramic Society 2014 Volume 34(Issue 6) pp:1563-1569
Publication Date(Web):June 2014
DOI:10.1016/j.jeurceramsoc.2013.12.007
Lanthanum silicate apatite (LSA, La9.33+xSi6O26+1.5x, x = 0–0.67) has been widely investigated as a promising electrolyte material for intermediate temperature solid oxide fuel cell (SOFC). In this work, a facile and low-cost co-precipitation method is used to synthesize LSA precursor powders. The well dispersed nanopowders (ca. 70 nm) with pure hexagonal LSA phase are obtained by calcining the precursor at 900 °C. Impurity of La2SiO5, caused by the different precipitation productivities of La(NO3)3 and TEOS, can be eliminated through lowering the La/Si ratio in the starting mixtures. The dispersant (PEG200) plays a crucial role in co-precipitation processes, which can effectively mitigate the agglomeration and therefore significantly improve the sinterability of the nanoparticles. Dense LSA ceramic with relative density of 98% is obtained after sintering at 1550 °C, which exhibits a conductivity of 0.13 mS cm−1 at 500 °C.
Co-reporter:Jie Wang, Hailei Zhao, Zhipeng Zeng, Pengpeng Lv, Zhaolin Li, Tianhou Zhang, Tianrang Yang
Materials Chemistry and Physics 2014 Volume 148(Issue 3) pp:699-704
Publication Date(Web):15 December 2014
DOI:10.1016/j.matchemphys.2014.08.037
•Nano-sized Fe3O4/C was prepared by a simple citric-nitrate combustion process.•Fe3O4/C particles show core–shell structure.•Fe3O4/C powder displays high specific capacity and good cycling stability.•Fe3O4/C composite exhibits a superior rate-capability.Nano-sized Fe3O4/carbon material is prepared via a simple citric-nitrate combustion method combining with a hydrothermal carbon coating technique. The synthesized Fe3O4/carbon composite shows a high reversible specific capacity (ca. 850 mAh g−1 at 100 mA g−1; ca. 600 mAh g−1 at 500 mA g−1), good rate-capability as well as superior cycling stability as anode for lithium-ion batteries. The ameliorated electrochemical performance of Fe3O4/carbon electrode is associated to the nano-sized particle feature and the continuous carbon coating layer. The former provides short lithium-ion/electron diffusion distance, while the latter enables the fast electron transport pathways. Besides, the carbon layer can act as a protective component to prevent the active particle Fe3O4 from aggregation and pulverization during the charge/discharge processes.
Co-reporter:Zhixiang Xie ; Hailei Zhao ; Zhihong Du ; Ting Chen ;Ning Chen
The Journal of Physical Chemistry C 2014 Volume 118(Issue 33) pp:18853-18860
Publication Date(Web):July 30, 2014
DOI:10.1021/jp502503e
The suitability of double perovskite oxides of composition Sr2Mg1–xNixMoO6−δ (SMNM, x = 0–0.9) as anode materials for solid oxide fuel cells (SOFCs) was evaluated. Single double perovskite structures could be obtained up to x = 0.9 in syntheses at ambient atmosphere. However, after reduction at 800 °C, trace amounts of impurities were detected in the sample with x = 0.9, suggesting that the upper limit for the Ni content (x) in SMNM is less than 0.9 under SOFC operating conditions. The electrical conductivity of SMNM increases with increasing Ni content because of the increase in the concentration of electronic defects, [MoMo6+5+′], and the decreased band gap energy, as revealed by first-principles calculations. The substitution of Ni can facilitate the charge-transfer process of the electrode reaction, decrease the polarization resistance, and thus increase the power density of a single cell. X-ray photoelectron spectroscopy and temperature-programmed reduction measurements were used to explain the reason for the performance improvement. SMNM showed good chemical compatibility with Ce0.8Sm0.2O2−δ (SDC) but a slight reactivity with the electrolyte La0.8Sr0.2Ga0.83Mg0.17O3−δ (LSGM) at 1300 °C. The use of an SDC buffer layer could avoid the interface reaction between the SMNM anode and the LSGM electrolyte, resulting in better cell performance. The Sr2Mg0.3Ni0.7MoO6−δ electrode exhibited a maximal power density of 160 mW cm–2 at 800 °C with an electrolyte (LSGM, 400 μm)-supported cell configuration.
Co-reporter:Qian Yang;Jie Wang;Jing Wang
Materials for Renewable and Sustainable Energy 2014 Volume 3( Issue 2) pp:
Publication Date(Web):2014 June
DOI:10.1007/s40243-014-0024-7
Pure Li4Ti5O12 with high crystallinity was successfully synthesized by a solvothermal process. The effects of initial Li/Ti ratio and post-heating temperature on the phase evolution, particle morphology and electrochemical properties were systematically investigated. Excess lithium, compared to the theoretical value in Li4Ti5O12, was required to get pure Li4Ti5O12 due to the condensation reaction. Low Li/Ti ratio led to the appearance of secondary phase rutile TiO2, while high heat-treatment temperature easily resulted in particle agglomeration of Li4Ti5O12 powder. The existence of rutile TiO2 decreased the specific capacity, and the particle agglomerate had a strong negative effect on the rate capability of electrode. The sample synthesized at the optimized condition exhibited a stable specific capacity of 150 mAh/g and a good rate performance.
Co-reporter:Pengpeng Lv, Hailei Zhao, Jing Wang, Xin Liu, Tianhou Zhang, Qing Xia
Journal of Power Sources 2013 Volume 237() pp:291-294
Publication Date(Web):1 September 2013
DOI:10.1016/j.jpowsour.2013.03.054
An amorphous SiO2/C composite anode material is synthesized via a sol–gel route combining with mechanical milling and post heat-treatment processes. The synthesized amorphous SiO2/C composite presents a nanostructure composing of amorphous SiO2 cluster and coating carbon layer. The amorphous SiO2/C electrode exhibits high reversible capacity (∼600 mA h g−1), stable cycling performance and excellent rate-capability. Mechanical milling causes SiO2/C composite amorphization which makes the active material possess good electrochemical activity. The coating carbon layer can not only increase electronic conductivity, but also accommodate part of the volume expansion occurred during discharge/charge process.Graphical abstractHighlights► Amorphous SiO2/C composite was prepared via a facile route. ► SiO2/C electrode exhibits high specific capacity and stable cycling performance. ► SiO2/C electrode displays excellent rate-capability. ► Amorphous SiO2 shows higher electrochemical activity than crystalline one.
Co-reporter:Jie Wang, Hailei Zhao, Qian Yang, Chunmei Wang, Pengpeng Lv, Qing Xia
Journal of Power Sources 2013 Volume 222() pp:196-201
Publication Date(Web):15 January 2013
DOI:10.1016/j.jpowsour.2012.08.082
In an effort to improve the rate-capability of Li4Ti5O12 anode material, a dual-phase composite Li4Ti5O12–TiO2 is in situ prepared via a solvothermal route. The Li4Ti5O12–TiO2 composite shows higher reversible capacity and better rate-capability compared to single phase Li4Ti5O12. The TiO2 can decrease significantly the particle size of Li4Ti5O12–TiO2 powders due to a steric hindrance effect, which thereby shortens the lithium ion diffusion distance and enhances the electrode reaction. Meanwhile, anatase TiO2 can contribute some capacity to the Li4Ti5O12–TiO2 electrode. Coating the Li4Ti5O12–TiO2 composite with carbon (∼2.5 wt.%) can further improve the rate-capability of Li4Ti5O12–TiO2 electrode, a reversible capacity of ∼140 mA h g−1 is maintained after 100 cycles at 5 C.Highlights► Dual-phase Li4Ti5O12–TiO2 was in situ prepared by a solvothermal route. ► TiO2 can prevent the grain growth and particle aggregation of Li4Ti5O12 phase. ► Li4Ti5O12–TiO2 powder displays high specific capacity and good cycling performance. ► Carbon coated Li4Ti5O12–TiO2 exhibits an excellent rate-capability.
Co-reporter:Qing Xia, Hailei Zhao, Zhihong Du, Jie Wang, Tianhou Zhang, Jing Wang, Pengpeng Lv
Journal of Power Sources 2013 Volume 226() pp:107-111
Publication Date(Web):15 March 2013
DOI:10.1016/j.jpowsour.2012.10.080
MoO3 has been reported as attractive candidate of anode materials for lithium-ion batteries. In this article, a facile one-pot citric-nitrate method is proposed to synthesize MoO3/C nano-composite, which is of general applicability for other oxide/carbon anode materials. The synthesized MoO3/C presents a core–shell structure feature with a thin carbon layer coating on the surface of nano-crystalline MoO3. The MoO3/C anode exhibits superior electrochemical performance, a specific capacity of about 500 mAh g−1 in the voltage range of 0.01–3.0 V vs. Li/Li+ can be maintained after 100 cycles.Highlights► The MoO3/C nano-composite is synthesized by a one-pot citric-nitrate method. ► Carbon is in situ formed in the MoO3 matrix. ► MoO3/C composite powder presents a core–shell structure feature. ► The MoO3/C composite exhibits specific capacity of ca. 500 mAh g−1 after 100 cycles. ► The method is of general applicability for other oxide/carbon anode materials.
Co-reporter:Ting Chen, Hailei Zhao, Zhixiang Xie, Jie Wang, Yao Lu, Nansheng Xu
Journal of Power Sources 2013 Volume 223() pp:289-292
Publication Date(Web):1 February 2013
DOI:10.1016/j.jpowsour.2012.09.018
Co-reporter:Jie Wang, Hailei Zhao, Yeting Wen, Jingying Xie, Qing Xia, Tianhou Zhang, Zhipeng Zeng, Xuefei Du
Electrochimica Acta 2013 Volume 113() pp:679-685
Publication Date(Web):15 December 2013
DOI:10.1016/j.electacta.2013.09.086
•Submicro-sized Li4Ti5O12 was prepared by simple citric-nitrate combustion method.•Li4Ti5O12 powder displays good cycling performance and excellent rate-capability.•Li4Ti5O12 exhibits a superior high temperature cycling performance.•The preparation process is mild and scalable.Single phase Li4Ti5O12 powder with porous particle structure is synthesized via a simple, mild and productive citric-acid combustion method. The Li4Ti5O12 particle is composed of submicro-scaled grains with size of 100–200 nm. The synthesized Li4Ti5O12 shows high reversible capacity (ca. 165 mAh g−1 at 0.5 C), excellent rate-capability (ca. 115 and 100 mAh g−1 at 10 and 20 C, respectively) and high temperature cycling stability (50 °C). Under expanded cut-off voltage range of 0.01–2.5 V, it delivers a high specific capacity of ca. 230 and 170 mAh g−1 at 0.5 and 10 C, respectively, while maintaining an excellent cycling stability. The synthesized Li4Ti5O12 shows fast de-lithiation but slow lithiation kinetic processes. When discharged at constant 1 C while charged at 10, 20 and 30 C, respectively, the specific capacity of 162, 160 and 158 mAh g−1 can be achieved. The excellent electrochemical performance of the combustion synthesized Li4Ti5O12 is ascribed to the porous particle structure and small grain size feature, which ensure the good contact with electrolyte and reduce the lithium ion/electron diffusion distance, and therefore enhance the electrode reaction process.
Co-reporter:Cuijuan Zhang, Zhihong Du, Hailei Zhao, Xinxin Zhang
Electrochimica Acta 2013 Volume 108() pp:369-375
Publication Date(Web):1 October 2013
DOI:10.1016/j.electacta.2013.06.124
•Co3O4 reacts with BaCe0.40Sm0.20Fe0.40O3−δ, forming conductive phases.•The Co3O4 addition enhances the electrical conductivity of BaCe0.40Sm0.20Fe0.40O3−δ.•The Co3O4 improves the electrocatalytic activity of BaCe0.40Sm0.20Fe0.40O3−δ.Tailoring the properties of cathode is of great importance to improve the performance of proton-conducting solid oxide fuel cells (SOFC-H). This work demonstrates that the performance of BaCe0.40Sm0.20Fe0.40O3−δ cathode can be optimized by introducing appropriate amount of Co3O4. The 5–10 wt% Co3O4 reacts with BaCe0.40Sm0.20Fe0.40O3−δ, forming conductive mixed oxygen ionic–electronic phases. The materials with 5–10 wt% Co3O4 exhibits protonic and improved oxygen ionic–electronic conductivity in wet air, which contributes greatly to the electrocatalytic activity toward the reaction on the cathode. The (95–90%) BaCe0.40Sm0.20Fe0.40O3−δ (5–10%) Co3O4 demonstrates lower ASR, lower cathode overpotential, higher exchange current density, and higher peak power density. Higher content of Co3O4 (20%) will result in the disappearance of protonic conducting phase and denser electrode microstructure, which are detrimental to the performance. This work demonstrates that designing cathode materials with modified microstructure, which is simultaneously protonic, oxygen ionic and electronic conductive, is crucial to improve the performance of SOFC-H.
Co-reporter:Hailei Zhao, Yu Zheng, Chunyang Yang, Yongna Shen, Zhihong Du, Konrad Świerczek
International Journal of Hydrogen Energy 2013 Volume 38(Issue 36) pp:16365-16372
Publication Date(Web):13 December 2013
DOI:10.1016/j.ijhydene.2013.10.003
•Pr1−xYxBaCo2O5+δ was synthesized as cathode material for SOFC.•Pr1−xYxBaCo2O5+δ exhibits similar TEC with GdBaCo2O5+δ.•Y-doping enhances the structural stability of Pr1−xYxBaCo2O5+δ materials.•Pr1−xYxBaCo2O5+δ (x = 0.3–0.7) shows higher peak power density than GdBaCo2O5+δ.Pr1−xYxBaCo2O5+δ (x = 0.3, 0.5 and 0.7) oxides were prepared and evaluated as cathode materials for intermediate-temperature solid oxide fuel cells. The effect of Y-doping on the crystal structure, oxygen vacancy concentration, thermal expansion coefficient (TEC), electrical conductivity and cathode performance of Pr1−xYxBaCo2O5+δ was investigated. These properties were compared with that of GdBaCo2O5+δ having a middle element of lanthanides. Pr1−xYxBaCo2O5+δ shows TEC (∼17.6 × 10−6 K−1) lower than that of undoped PrBaCo2O5+δ, but similar to the one for GdBaCo2O5+δ. Y-doping causes a decrease in electrical conductivity, but at the same time induces an increase in oxygen vacancy concentration. With increasing Y-doping level, the area specific resistance (ASR) of Pr1−xYxBaCo2O5+δ-based electrode in a symmetrical cell increases, and correspondingly, the peak power density of single-cell decreases slightly. Nevertheless, comparing to GdBaCo2O5+δ-based electrode, Pr1−xYxBaCo2O5+δ (x = 0.3–0.7) exhibits significantly lower ASR, and allows to obtain cells with higher maximum power density.
Co-reporter:Zhihong Du, Hailei Zhao, Xiong Zhou, Zhixiang Xie, Cuijuan Zhang
International Journal of Hydrogen Energy 2013 Volume 38(Issue 2) pp:1068-1073
Publication Date(Web):24 January 2013
DOI:10.1016/j.ijhydene.2012.10.099
The anode materials La0.3Sr0.7Ti1−xCrxO3−δ (LSTC, x = 0, 0.1, 0.2) with cubic structure were prepared via solid state reaction route. The influence of Cr content on the properties of LSTC as anode and interconnect materials for solid oxide fuel cells (SOFCs) was investigated. The Cr-doping decreased the lattice parameter while increased the sinterability of LSTC materials. The total electrical conductivity decreased with Cr doping level, from 230 S cm−1 for x = 0 to 53 S cm−1 for x = 0.2. The total electrical conductivity exhibited good stability and recoverability in alternative atmospheres of air and 5% H2/Ar, showing excellent redox stability. The cell testing showed that the anode performance of LSTC was enhanced somewhat by Cr doping. The present results indicated that the prepared La0.3Sr0.7Ti1−xCrxO3−δ can be potential anode and interconnect materials for SOFCs.Highlights► Enhanced redox stability of La0.3Sr0.7Ti0.8Cr0.2O3−δ with Cr doping. ► Stable electrical conductivity in a wide range of oxygen partial pressure. ► Improved anode performance in a YSZ-supported single cell.
Co-reporter:Jie Wang; Hailei Zhao;Yongna Shen;Zhihong Du;Xiaomin Chen;Qing Xia
ChemPlusChem 2013 Volume 78( Issue 12) pp:1530-1535
Publication Date(Web):
DOI:10.1002/cplu.201300235
Abstract
Li2CoTi3O8 powder has been synthesized by a simple citric nitrate method and was evaluated as an anode material for lithium-ion batteries. The X-ray diffraction (XRD) Rietveld refinement and X-ray photoelectron spectroscopy (XPS) measurements indicate the existence of Ti-site deficiency and a mixed-valence state of Co ions in the Li2CoTi3O8 structure. The refined site-occupation result gave a nonstoichiometric chemical formula of Li2CoTi2.682O8, which corresponds to a theoretical specific capacity of 322 mA h g−1, which is much higher than that of the stoichiometric material (233 mA h g−1). The synthesized Li2CoTi2.682O8 material exhibits high reversible capacity (ca. 320 mA h g−1), and excellent cycling stability and rate capability. A specific capacity of about 240 and 160 mA h g−1 can be achieved at 2 and 6 A g−1, respectively, by the Li2CoTi2.682O8 material. First-principles calculation demonstrates that Ti-site deficiency decreases the bandgap and thus facilitates the electron conduction.
Co-reporter:Yuntong Zhu;Xin Liu;Jie Wang
Ionics 2013 Volume 19( Issue 5) pp:709-715
Publication Date(Web):2013 May
DOI:10.1007/s11581-012-0809-6
The InSn4 intermetallic powders are synthesized via carbothermal reduction route from In2O3 and SnO2. The reaction possibility is estimated by thermodynamic calculation. Pure InSn4 intermetallic powders with spherical morphology can be obtained at 900 °C in flowing nitrogen. The micro-sized InSn4 particle is actually composed of a large number of nano-sized grains with polycrystalline and loose structure. The synthesized InSn4 shows high reversible specific capacity (ca. 500 mAhg−1) and a good cycling performance as an anode material for lithium-ion batteries. Coating InSn4 with carbon can increase the reversible specific capacity and improve significantly the rate capability. The InSn4/C composite displays a stable specific capacity of ca. 600 mAhg−1. In consideration of the simple and moderate synthesis route and the mass productive feature, the InSn4/C composite is a promising anode material for lithium-ion batteries.
Co-reporter:Chunmei Wang;Jing Wang;Jie Wang;Pengpeng Lv
Ionics 2013 Volume 19( Issue 2) pp:221-226
Publication Date(Web):2013 February
DOI:10.1007/s11581-012-0733-9
Artificial graphite anode material was modified by coating an amorphous carbon layer on the particle surface via a sol-gel and pyrolysis route. The electrochemical measurements demonstrate that appropriate carbon coating can increase the specific capacity and the initial coulombic efficiency of the graphite material, while excessive carbon coating leads to the decrease in specific capacity. Thick coating layer is obviously unfavorable for the lithium ion diffusion due to the increased diffusion distance, but the decreased specific surface area caused by carbon coating is beneficial to the decrease of initial irreversible capacity loss. The sample coated with 5 wt.% glucose exhibits a stable specific capacity of 340 mAhg−1. Carbon coating can remarkably enhance the rate capability of the graphite anode material, which is mainly attributed to the increased diffusion coefficient of lithium ion.
Co-reporter:Jie Wang;Qian Yang;Tianhou Zhang;Jing Wang
Ionics 2013 Volume 19( Issue 3) pp:415-419
Publication Date(Web):2013 March
DOI:10.1007/s11581-012-0771-3
Cu-doped Li4Ti5O12 (Li4 − xCuxTi5O12) materials were synthesized by solid-state method. Cu-doping does not change the crystal structure of Li4Ti5O12 material but increases its lattice constant. The particle size of Li4 − xCuxTi5O12 powders decreases with increasing Cu-doping level. Cu-doping does not change the specific capacity at low current density, but can improve the cycling stability and the rate capability of Li4Ti5O12 significantly. This is mainly attributed to the enhanced electronic and ionic conductivity and the decreased charge transfer resistance, caused by the increased specific surface area of active Li4 − xCuxTi5O12 powders. The Li3.8Cu0.2Ti5O12 anode material exhibits the best cycling stability and rate capability.
Co-reporter:Cuijuan Zhang and Hailei Zhao
Journal of Materials Chemistry A 2012 vol. 22(Issue 35) pp:18387-18394
Publication Date(Web):02 Aug 2012
DOI:10.1039/C2JM32627B
Developing a tailored cathode is of great importance for the improvement of proton-conducting solid oxide fuel cell (SOFC-H) performance. In this work, a novel cobalt-free cathode BaCe0.40Sm0.20Fe0.40O3−δ was designed for use in a SOFC-H. It was composed of homogeneously distributed BaCe1−x(Sm/Fe)xO3−δ and BaFe1−y(Sm/Ce)yO3−δ, which were synthesized by a simple in situ method, eliminating the separate synthesis and the mechanical mixing processes for the conventional composite materials. The BaCe0.40Sm0.20Fe0.40O3−δ cathode exhibited protonic, oxygen-ionic, and electronic conduction simultaneously in wet air, expanding the triple phase boundaries to the whole cathode. The symmetrical cell tests with BaCe0.40Sm0.20Fe0.40O3−δ as electrodes showed that the diffusion of O−ad and reduction of O−TPB were the rate limiting steps in wet air. The power density of the anode-supported single cell with Ni–BaCe0.80Sm0.20O3−δ (580 μm) anode, BaCe0.80Sm0.20O3−δ (70 μm) electrolyte and BaCe0.40Sm0.20Fe0.40O3−δ (53 μm) cathode was 194.0, 169.2, and 137.1 mW cm−2 at 750, 710, and 650 °C, respectively. These results are encouraging considering the cobalt-free nature and rather low electrical conductivity of the cathode material. The BaCe0.40Sm0.20Fe0.40O3−δ material demonstrated excellent catalytic activity towards the reactions on the cathode. Accordingly, the BaCe0.40Sm0.20Fe0.40O3−δ material can be a promising cathode for SOFC-H.
Co-reporter:Nansheng Xu, Hailei Zhao, Yongna Shen, Ting Chen, Weizhong Ding, Xionggang Lu, Fushen Li
Separation and Purification Technology 2012 Volume 89() pp:16-21
Publication Date(Web):22 March 2012
DOI:10.1016/j.seppur.2011.12.027
Cubic perovskite oxides, Ba0.6Sr0.4Co1−xTixO3−δ (BSCT, x = 0.12–0.30) are prepared by conventional solid state reaction process as oxygen permeation membranes. The effects of Ti-doping on the crystal structure, electrical conductivity and oxygen permeability are investigated. The chemical stability in low oxygen partial pressure atmospheres is enhanced by Ti-doping. The partial substitution of Ti for Co is charge-compensated by the reduction of oxygen vacancy concentration in BSCT. Both the electrical conductivity and the oxygen permeation flux of BSCT decrease with Ti doping level. The large bonding energy of Ti–O and the decreased lattice free volume with Ti substitution lead to increased activation energy of oxygen permeation, which, combined with the decreased oxygen vacancy concentration, is responsible for the decreased oxygen permeation flux. Nevertheless, sufficiently high permeation fluxes, ca. 2.12 and 1.46 mL cm−2 min−1 at 900 °C, are obtained for the samples with x = 0.12 and 0.30, respectively, which were comparable to that of the well known Ba0.6Sr0.4Co0.8Fe0.2O3−δ (BSCF5582) material. Furthermore the BSCT material shows much better phase stability compared to BSCF5582 material under oxygen permeation condition. The prepared BSCT materials are promising candidates for oxygen separation or POM applications.Highlights► Cubic oxides Ba0.6Sr0.4Co1−xTixO3−δ were prepared as oxygen permeation membranes. ► The structure stability of Ba0.6Sr0.4Co1−xTixO3−δ is enhanced with Ti-doping. ► Ba0.6Sr0.4Co1−xTixO3−δ shows high oxygen permeation fluxes. ► The charge compensation mechanism of Ba0.6Sr0.4Co1−xTixO3−δ is concerned. ► The activation energy for oxygen permeation is concerned.
Co-reporter:Ting Chen, Hailei Zhao, Zhixiang Xie, Linchang Feng, Xionggang Lu, Weizhong Ding, Fushen Li
International Journal of Hydrogen Energy 2012 Volume 37(Issue 6) pp:5277-5285
Publication Date(Web):March 2012
DOI:10.1016/j.ijhydene.2011.12.113
A novel dual-phase oxygen permeation membrane based on ion-conducting Ce0.8Sm0.2O2−δ (SDC) and mixed conducting PrBaCo2O5+δ (PBCO) is presented. There is no obvious reaction between the two phases under preparation and oxygen permeation conditions. The percolative network of mixed conducting phase PBCO can be formed in SDC-PBCO composite when the ratio of PBCO is not less than 40 vol.%. Above this threshold, the oxygen permeability of SDC-PBCO membrane increases with increasing SDC content. Compared with pure PBCO membrane, the oxygen permeability of percolative SDC-PBCO composites is improved due to the 3D diffusion ability of SDC, which can shorten the tortuosity of the oxygen diffusion path in layered PBCO. The maximum oxygen flux based on 0.6-mm-thick SDC-PBCO (6/4) is 2.38 × 10−7 mol cm−2 s−1 at 925 °C. The dependence of the oxygen permeation flux on the membrane thickness demonstrates that the bulk diffusion is the limiting step at thickness higher than 0.8 mm and the surface exchange may play an important role when the thickness is below that. Incorporation of SDC into PBCO can not only improve the oxygen permeability but also enhance the structural stability. The SDC-PBCO (6/4) dual-phase membrane is a promising candidate for oxygen separation application.Highlights► Addition of SDC to PBCO improves the oxygen permeation flux of PBCO membrane. ► The 60 vol.% SDC-PBCO composite exhibits the best permeability. ► SDC-PBCO composite has good chemical compatibility and structural stability. ► The limiting step is oxygen bulk diffusion when the membrane is thicker than 0.8 mm.
Co-reporter:Jianying Yang, Hailei Zhao, Xiaotong Liu, Yongna Shen, Lihua Xu
International Journal of Hydrogen Energy 2012 Volume 37(Issue 17) pp:12694-12699
Publication Date(Web):September 2012
DOI:10.1016/j.ijhydene.2012.06.013
A series of Ba0.6Sr0.4Co0.7Fe0.3−xBixO3−δ (BSCFB, x = 0–0.2) ceramic membranes were prepared by solid state reaction method. The doping effects on the phase structure, structural stability, electrical conductivity and oxygen permeability were investigated. Little amount of Bi (x = 0–0.08) can maintain the cubic perovskite structure of BSCFB materials while more Bi (x > 0.08) will result in the generation of other impurities. Even in the Bi solid solution range, Bi doping is unfavorable for the enhancement of structural stability of BSCFB membranes. The electrical conductivity decreases with Bi doping level, while the oxygen permeability of BSCF membrane can be increased remarkably with little amount of Bi doping (x = 0.05). More Bi leads to the structure deterioration of membrane surface under oxygen permeation condition, resulting in a severe decrease in oxygen permeability. Considering the overall performance, a low Bi doping amount such as x = 0.05 is favored for the membrane applications.Highlights► Ba0.6Sr0.4Co0.7Fe0.3−xBixO3−δ were synthesized as oxygen permeation membrane. ► Bi-doping decreases the electrical conductivity. ► Appropriate amount of Bi doping can increase the oxygen permeability.
Co-reporter:Ting Chen, Hailei Zhao, Zhixiang Xie, Yao Lu, Nansheng Xu
International Journal of Hydrogen Energy 2012 Volume 37(Issue 24) pp:19133-19137
Publication Date(Web):December 2012
DOI:10.1016/j.ijhydene.2012.09.144
A porous PrBaCo2O5+δ or Ce0.8Sm0.2O2−δ–50 vol.% PrBaCo2O5+δ (SDC–PBCO (5/5)) layer was deposited on dense Ce0.8Sm0.2O2−δ–40 vol.% PrBaCo2O5+δ (SDC–PBCO (6/4)) membrane (450 μm) to enhance the oxygen permeability by increasing the surface area contacting with air. The oxygen permeation flux was measured in the temperature range of 825–945 °C. The results revealed that the oxygen permeation performance of Ce0.8Sm0.2O2−δ–PrBaCo2O5+δ membranes can be significantly enhanced by coating SDC–PBCO (5/5) porous layer alone on the surface of feed side. The thickness of modification layer has obvious effect on the permeability of surface modified membrane. The modification on the feed side has much better effect than that on the permeate side. At 945 °C, the oxygen permeation flux of dense SDC–PBCO (6/4) membrane modified by porous SDC–PBCO (5/5) layer is 3.56 × 10−7 mol cm−2 s−1, 26% higher than that of the unmodified one.Highlights► SDC–PBCO porous layer can enhance the oxygen permeability of SDC–PBCO membrane. ► The modification on the feed side has better effect than that on both sides. ► SDC–PBCO layer exhibits better modification performance than pure PBCO layer. ► The thickness of modification layer has significant impact on the permeability.
Co-reporter:Zhixiang Xie, Hailei Zhao, Zhihong Du, Ting Chen, Ning Chen, Xiaotong Liu, and Stephen J. Skinner
The Journal of Physical Chemistry C 2012 Volume 116(Issue 17) pp:9734-9743
Publication Date(Web):April 10, 2012
DOI:10.1021/jp212505c
Double-perovskite materials of composition Sr2Mg1–xCoxMoO6−δ (SMCMO, x = 0 to 0.7) were evaluated as potential SOFC anode materials. Their lattice structures, electrical and ionic conductivity, thermal expansion coefficient (TEC), and electrochemical performance were investigated as a function of Co content. Co doping was found to increase the TEC of the Sr2MgMoO6−δ material; however, the TEC was within the range of the commonly used La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte. SMCMO also showed good chemical compatibility with the LSGM electrolyte at temperatures below 1300 °C. Both the electronic and ionic conductivity increased with increasing Co doping. To investigate the effect of Co doping on the conduction properties of SMCMO, we performed first-principle calculations. From these results, the weak Co–O bond is considered to be responsible for the enhanced ionic conductivity of SMCMO materials. The substitution of Co was also found to increase the sinterability of SMCMO, resulting in a decrease in the polarization resistance of the SMMO electrode. Single-cell tests indicated the potential ability of the Co-doped SMMO to be used as SOFC anodes.
Co-reporter:Cuijuan Zhang, Hailei Zhao
Solid State Ionics 2012 Volume 206() pp:17-21
Publication Date(Web):5 January 2012
DOI:10.1016/j.ssi.2011.10.026
The influence of indium content on the electrical conduction behavior of Sm- and In-co-doped BaCe0.80-xSm0.20InxO3-δ proton conductor was investigated by impedance spectroscopy. The structural characteristics were studied by means of X-ray diffraction, Raman spectra, high resolution transmission electron microscopy, and thermogravimetric analysis. Both long and short range structural symmetry increased with In content, from orthorhombic (x = 0–0.50) to cubic structure (x = 0.60–0.80). No oxygen vacancy ordering or micro-domains were detected. The proton concentration of the hydrated samples BaCe0.80-xSm0.20InxO3-δ (x = 0–0.20) decreased with In level. The electrical conductivity of the co-doped samples decreased with In content in wet 5% H2/Ar and wet Ar atmospheres. The reasons for the decreased electrical conductivity were discussed. The variation of electrical conductivity of BaCe0.80-xSm0.20InxO3-δ with In concentration can be applicable to other RE- and In-co-doped BaCeO3 materials.Highlights► Sm- and In-co-doped BaCe0.80-xSm0.20InxO3-δ was prepared. ► The local structural characteristics were studied with Raman spectra and HRTEM. ► Both long and short range structural symmetry increased with In content. ► The lattice volume and proton concentration decreased with In doping level. ► The electrical conductivity of BaCe0.80-xSm0.20InxO3-δ decreased with In content.
Co-reporter:Jing Wang, Hailei Zhao, Jianchao He, Chunmei Wang, Jie Wang
Journal of Power Sources 2011 Volume 196(Issue 10) pp:4811-4815
Publication Date(Web):15 May 2011
DOI:10.1016/j.jpowsour.2011.01.053
Nano-sized SiOx/C composite with core–shell structure is prepared by a modified Stöber method. After heat-treatment, the O/Si ratio in SiOx/C composite is near 1 and the core of SiOx presents a structure composing of amorphous Si clusters and ordered SiO2 domains. SiOx/C composite anode shows high specific capacity (ca. 800 mAh g−1), excellent cycling stability, good rate-capability but low initial coulombic efficiency. Li2O and Li4SiO4 may generate in the initial lithiation process, which, combining with the carbon shell, can buffer the volume change caused by the alloying of Si with Li, and thereby improving the cycling stability of electrode. The nano feature of SiOx/C particle and the electronic conductive nature of carbon coating layer ensure the good rate-capability of SiOx/C electrode.Graphical abstractResearch highlights► SiOx/C composite with nano-scale core–shell structure. ► The core SiOx is consisting of amorphous Si clusters and crystalline SiO2 domains. ► SiOx/C composite anode shows high specific capacity and good cycling stability.
Co-reporter:Cuijuan Zhang, Hailei Zhao
Electrochemistry Communications 2011 Volume 13(Issue 10) pp:1070-1073
Publication Date(Web):October 2011
DOI:10.1016/j.elecom.2011.06.035
A novel cathode material BaCe0.4Sm0.2Co0.4O3−δ composed of two phases BaCe1−x(Sm/Co)xO3−δ and BaCo1-x(Sm/Ce)xO3−δ was prepared in situ via the citric–nitrate route and its performance as cathode material for proton conducting solid oxide fuel cell (SOFC-H) was characterized. BaCe0.4Sm0.2Co0.4O3−δ exhibited simultaneous protonic, electronic, and oxygen ionic conduction in air, leading to a good electrode performance. The polarization resistance of the novel cathode material in symmetrical cell was 0.36 Ω cm2 with Pt as the current collector at 700 °C in wet air. The electrode performance can be further improved through microstructure optimization. It also showed good thermal expansion compatibility with BaCe0.8Sm0.2O3−δ electrolyte over a 100 h duration test. BaCe0.4Sm0.2Co0.4O3−δ is a promising cathode material for SOFC-H.Highlights► A novel cathode BaCe0.4Sm0.2Co0.4O3-δ composed of two phases was prepared in situ. ► The performance of BCSC was comparable with that of some reported composite cathode. ► BCSC exhibited protonic, electronic and oxygen ionic conduction in air. ► BCSC showed good thermal expansion match with the BaCe0.8Sm0.2O3-δ electrolyte. ► BCSC can be potential cathode for proton conducting solid oxide fuel cell.
Co-reporter:Jie Wang, Hailei Zhao, Xiaotong Liu, Jing Wang, Chunmei Wang
Electrochimica Acta 2011 Volume 56(Issue 18) pp:6441-6447
Publication Date(Web):15 July 2011
DOI:10.1016/j.electacta.2011.04.134
Co-reporter:Cuijuan Zhang, Hailei Zhao, Shaoyan Zhai
International Journal of Hydrogen Energy 2011 Volume 36(Issue 5) pp:3649-3657
Publication Date(Web):March 2011
DOI:10.1016/j.ijhydene.2010.12.087
Determining the relationship between electrical conductivity and doping level in high temperature proton conductors is of great significance to accelerate their process of practicality and develop new applications. In this work, BaCe1-xSmxO3-δ (x = 0.01–0.50) was synthesized via citric-nitrate method and their electrical conduction behavior in 5% H2/Ar in the intermediate temperature range was investigated. The solubility of Sm in BaCeO3 was between 0.30 and 0.40. Both the bulk and the grain boundary conductivity increased with Sm content up to x = 0.20 and then decreased. The infrared spectra results indicated that the degree of hydrogen bonding decreased with Sm content (x = 0.20–0.30), which should be responsible for the descending bulk conductivity of samples with x = 0.25 and 0.30. BaCe0.80Sm0.20O3-δ, with electrical conductivity of 0.017 S cm−1 at 600 °C, was a promising electrolyte for intermediate temperature solid oxide fuel cells.
Co-reporter:Zhixiang Xie, Hailei Zhao, Ting Chen, Xiong Zhou, Zhihong Du
International Journal of Hydrogen Energy 2011 Volume 36(Issue 12) pp:7257-7264
Publication Date(Web):June 2011
DOI:10.1016/j.ijhydene.2011.03.075
Aluminum doped Sr2MgMoO6-δ (SMMO) was synthesized via citrate-nitrate route. Dense samples of Sr2Mg1-xAlxMoO6−δ (0 ≤ x ≤ 0.05) were prepared by sintering the pellets at 1500 °C in air and then reducing at 1300 °C in 5%H2/Ar. The electrical conductivity strongly depended on the preparing atmosphere, samples reduced in 5%H2/Ar exhibited higher conductivity than those unreduced. Al-doping increased remarkably the electrical conductivity of Sr2Mg1-xAlxMoO6−δ. The reduced samples displayed a relatively stable electrical conductivity under oxygen partial pressure (Po2) from 10−19 to 10−14 atm at 800 °C, and exhibited an excellent recoverability in electrical conductivity when cycled in alternative air and 5%H2/Ar atmospheres. Sr2Mg0.95Al0.05MoO6−δ material showed a good chemical compatibility with LSGM and GDC electrolytes below 1000 °C, while there was an obvious reaction with YSZ. Al-doping improves the anode performance of SMMO in half-cell of Pt/Sr2Mg1-xAlxMoO6−δ∣GDC∣Pt in H2 fuel. The present results demonstrate that Sr2Mg1-xAlxMoO6−δ is a potential anode material for intermediate temperature-Solid Oxide Fuel Cells (IT-SOFCs).Highlights► Double perovskite Sr2Mg1-xAlxMoO6−δ (0 ≤ x ≤ 0.05) was prepared as anode materials for SOFC. ► The electrical conductivity of Sr2Mg1-xAlxMoO6−δ was enhanced by Al introduction. ► Al partial substitution for Mg increased the redox stability and improved the anode performance of Sr2Mg1-xAlxMoO6−δ materials. ► Sr2Mg0.95Al0.05MoO6−δ material showed a good chemical compatibility with LSGM and GDC electrolytes below 1000 °C, but an obvious reaction with YSZ electrolyte.
Co-reporter:Jianying Yang, Mengwei Wang, Yuntong Zhu, Hailei Zhao, Ronglin Wang, Jingbo Chen
Journal of Alloys and Compounds 2011 Volume 509(Issue 28) pp:7657-7661
Publication Date(Web):14 July 2011
DOI:10.1016/j.jallcom.2011.04.143
Thermodynamic calculation and kinetic analysis were performed on the carbothermal reduction process of Co3O4–Sb2O3–C system to clarify the reaction mechanism and synthesize pure CoSb powder for the anode material of secondary lithium-ion batteries. The addition of carbon amount and thus the purity of CoSb powders were critical to the electrochemical property of CoSb anode. It was revealed that in an inert atmosphere, Co3O4 was preferentially reduced to CoO, followed by the reduction of Sb2O3 and CoO. CO2 was the gas product for the reduction of Co3O4 and Sb2O3, while CO was the gas product for that of CoO. Based on the analysis result, pure CoSb powder without any oxides and residual carbon was synthesized, which showed a higher specific capacity and a lower initial irreversible capacity loss, compared to CoSb sample with residual carbon. This work can be a reference for other carbothermal reduction systems.Highlights► Carbothermal reduction mechanism of Co4O3–Sb2O3–C system was clarified based on thermodynamic calculation and kinetic analysis. ► Actually required carbon amount for carbothermal reduction process was suggested. ► Pure CoSb powder was prepared via carbothermal reduction process, which shows high electrochemical performance as anode for lithium ion battery.
Co-reporter:Xue Li, Hailei Zhao, Dawei Luo, Kevin Huang
Materials Letters 2011 Volume 65(17–18) pp:2624-2627
Publication Date(Web):September 2011
DOI:10.1016/j.matlet.2011.05.109
Mixed ionic–electronic conductors with high ionic conductivity play an important role in modern solid-state ionic devices. The ionic conductivity of SrTiO3-based materials can be significantly improved by creating deficiency on the A-site and acceptor-doping on the B-site. We report in this paper a remarkable enhancement of ionic conductivity, sinterability and thermal stability of (La, Sc) co-doped SrTiO3 by creating deficiency on the A-site. The ionic conductivity of (La0.3Sr0.7)0.95Sc0.10Ti0.90O3–δ varies from 0.005 S/cm at 500 °C to 0.01 S/cm at 700 °C and to 0.018 S/cm at 950 °C in 5%H2/Ar. These values are nearly eight times higher than that of La0.3Sr0.7TiO3–δ at T ≥ 700 °C. The A-site deficiency in (La, Sc) co-doped SrTiO3 also improves the thermal and electrical stabilities in various atmospheres. A possible charge compensation mechanism among defects in the (La0.3Sr0.7)0.95Sc0.10Ti0.90O3–δ is also discussed.
Co-reporter:Ting Chen, Hailei Zhao, Nansheng Xu, Yuan Li, Xionggang Lu, Weizhong Ding, Fushen Li
Journal of Membrane Science 2011 370(1–2) pp: 158-165
Publication Date(Web):
DOI:10.1016/j.memsci.2011.01.007
Co-reporter:Xiaotong Liu, Hailei Zhao, Jianying Yang, Yuan Li, Ting Chen, Xionggang Lu, Weizhong Ding, Fushen Li
Journal of Membrane Science 2011 383(1–2) pp: 235-240
Publication Date(Web):
DOI:10.1016/j.memsci.2011.08.059
Co-reporter:Jingbo Chen;Jianchao He;Jing Wang
Rare Metals 2011 Volume 30( Issue 2) pp:166-169
Publication Date(Web):2011 April
DOI:10.1007/s12598-011-0218-4
A Si/MgO composite anode material was prepared by a simple magnesium reduction process using silicon oxide and magnesium as starting reactants. The feasibility of this process is discussed from the thermodynamic viewpoint. The resultant composite material is mainly composed of Si and MgO components. MgO, acting as a buffer layer, can accommodate the large volume change of active Si during the charge/discharge process, thus the cycling stability is improved. Electrochemical tests demonstrate that the first charge and discharge capacities of the synthesized Si/MgO composite anode are ca. 1380 and 1046 mAh·g−1, respectively, with an initial coulomb efficiency of ca. 76%. The magnesium reduction process provides a novel idea for the synthesis of Si-based anode materials.
Co-reporter:Yuan Li, Hailei Zhao, Nansheng Xu, Yongna Shen, Xionggang Lu, Weizhong Ding, Fushen Li
Journal of Membrane Science 2010 Volume 362(1–2) pp:460-470
Publication Date(Web):15 October 2010
DOI:10.1016/j.memsci.2010.06.065
Ba1−xSrxCo0.7Fe0.2Nb0.1O3−δ (BSCFN, 0.0 ≤ x ≤ 0.4) materials were synthesized by the conventional solid-state reaction process for oxygen separation application. The influences of strontium doping in BSCFN oxides on phase structure stability, oxygen nonstoichiometry, electrical conductivity and oxygen permeation behavior were systematically investigated. Improved cubic structure stability under reducing atmosphere and structure reversibility in alternative oxidizing/reducing atmospheres were obtained via strontium doping strategy. Strontium introduction effectively suppressed the phase transformation from cubic to hexagonal under high temperature and harsh atmosphere conditions. Strontium doping increased the electrical conductivity, however, slightly decreased the oxygen permeability. Structural parameters played an important role in charge compensation mechanism and oxygen permeability. Ba0.6Sr0.4Co0.7Fe0.2Nb0.1O3−δ membranes exhibited good structural stability and the sample with a thickness of 1 mm had a high level of oxygen permeation flux of 1.31 mL cm−2 min−1 at 900 °C under an Air/He gradient. It was demonstrated that the oxygen bulk diffusion was the rate-controlling step for oxygen permeation in BSCFN (x = 0.4) membranes when the thickness was higher than 1 mm, while the oxygen surface exchange process should be taken into consideration when the thickness was less than 1 mm.
Co-reporter:Yongna Shen, Hailei Zhao, Xiaotong Liu and Nansheng Xu
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 45) pp:15124-15131
Publication Date(Web):2010/10/22
DOI:10.1039/C0CP00261E
Ca-doped La2NiO4+δ is synthesized via the nitrate–citrate route. The effects of Ca substitution for La on the sinterability, lattice structure and electrical properties of La2NiO4+δ are investigated. Ca-doping is unfavorable for the densification process of La2−xCaxNiO4+δ materials. The introduction of Ca leads to the elongation of the La–O(2) bond length, which provides more space for the migration of oxygen ion in La2O2 rock salt layers. The substitution of Ca increases remarkably the electronic conductivity of La2−xCaxNiO4+δ. With increasing Ca-doping level, both the excess oxygen concentration and the activation energy of oxygen ion migration decrease, resulting in an optimization where a highest ionic conductivity is presented. Ca-doping is charge compensated by the oxidation of Ni2+ to Ni3+ and the desorption of excess oxygen. The substitution of Ca enhances the structural stability of La2NiO4+δ material at high temperatures and renders the material a good thermal cycleability. La1.7Ca0.3NiO4+δ exhibits an excellent chemical compatibility with CGO electrolyte. La2−xCaxNiO4+δ is a promising cathode alternative for solid oxide fuel cells.
Co-reporter:Nansheng Xu, Hailei Zhao, Xiong Zhou, Wenjing Wei, Xionggang Lu, Weizhong Ding, Fushen Li
International Journal of Hydrogen Energy 2010 Volume 35(Issue 14) pp:7295-7301
Publication Date(Web):July 2010
DOI:10.1016/j.ijhydene.2010.04.149
Critical radius (rC) for cubic perovskite structure is an important factor affecting the migration energy of oxygen ions. The monotonic dependence of the critical radius on the ionic radii of A- and B-site cations in cubic perovskite ABO3 structure was systematically investigated by strict mathematical derivation. When the tolerance factor (t) < 1, the critical radius is a decreasing function but an increasing function with respect to the radius of A-site cation (rA) and B-site cation (rB), respectively. For the case of t > 1, there is a reverse dependence of rC on rA and rB. With respect to the case of t = 1, rC displays a decreasing function with respect to both rA and rB.
Co-reporter:Jianchao He, Hailei Zhao, Jing Wang, Jie Wang, Jingbo Chen
Journal of Alloys and Compounds 2010 Volume 508(Issue 2) pp:629-635
Publication Date(Web):22 October 2010
DOI:10.1016/j.jallcom.2010.08.152
Nano-sized Co–Sn alloys with a certain amount of Sn oxides used as potential anode materials for lithium ion batteries were synthesized by hydrothermal route. The effects of hydrothermal conditions and post annealing on the phase compositions and the electrochemical properties of synthesized powders were characterized by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) with energy dispersive spectra (EDS) analysis and galvanostatic cycling tests. Prolonging the dwelling time at the same hydrothermal temperature can increase the content of Sn oxides, which will lead to a high initial irreversible capacity loss but a better cycling stability owing to the buffer effect of irreversible product Li2O. Heat-treatment can increase the crystallinity and cause the presence of a certain amount of inert CoSn component, which both have positive impact on the cycling stability of Co–Sn electrode. By comparison with the lithiation/delithiation processes of metal Sn, a two-step mechanism of CoSn2 alloy during cycling was confirmed.Research highlights▶ Nano-sized Co–Sn alloys were synthesized by hydrothermal route. ▶ Li2O and CoSn can buffer the large volume change associated with lithiation of Sn. ▶ A two-step reaction mechanism of CoSn2 alloy during cycling was confirmed.
Co-reporter:Cuijuan Zhang, Hailei Zhao
Materials Research Bulletin 2010 45(11) pp: 1659-1663
Publication Date(Web):
DOI:10.1016/j.materresbull.2010.07.010
Co-reporter:Hailei Zhao, Yunfei Cheng, Nansheng Xu, Yuan Li, Fushen Li, Weizhong Ding, Xionggang Lu
Solid State Ionics 2010 Volume 181(5–7) pp:354-358
Publication Date(Web):11 March 2010
DOI:10.1016/j.ssi.2009.12.016
Perovskite oxides BaxCo0.7Fe0.2Nb0.1O3 − δ (BxCFN, x = 0.95–1.04) are synthesized by solid-state reaction method. The effect of A-site nonstoichiometry on the phase development, sinterability, electrical conductivity and oxygen permeability of sintered BxCFN are investigated. A-site deficiency reduces the cubic phase formation temperature and promotes the sintering process significantly. The electrical conductivity of BxCFN decreases but oxygen vacancy concentration increases with increasing A-site deficient level, suggesting that the charge compensation is completed via the creation of oxygen vacancies rather than the valence increase of B-site cations. A moderate A-site deficiency increases remarkably the oxygen permeation flux, while excessive A-site deficiency deteriorates the oxygen permeation process due to the occurrence of defect association between oxygen vacancies and other opposite charged defects.
Co-reporter:Cuijuan Zhang, Hailei Zhao
Solid State Ionics 2010 Volume 181(33–34) pp:1478-1485
Publication Date(Web):25 October 2010
DOI:10.1016/j.ssi.2010.08.028
The electrical conduction behavior of Sr substituted proton conductor Ba1 − xSrxCe0.9Nd0.1O3 − δ (x = 0–0.2) synthesized via citrate–nitrate method was investigated by various concentration cell measurements and electrochemical impedance spectroscopy. The structural distortion with Sr substitution obviously decreased the oxygen ion contribution but increased the proton and total ion transference number in both hydrogen-rich and oxygen-rich atmospheres. The increasing structural distortion with Sr content led to a significant decrease in oxygen ion conductivity, whilst slightly reducing proton conductivity. Sr substituted BaCeO3-based compounds seem to be good proton conductors with further modification of the proton conductivity.
Co-reporter:Hailei Zhao ; Nansheng Xu ; Yunfei Cheng ; Wenjing Wei ; Ning Chen ; Weizhong Ding ; Xionggang Lu ;Fushen Li
The Journal of Physical Chemistry C 2010 Volume 114(Issue 41) pp:17975-17981
Publication Date(Web):September 27, 2010
DOI:10.1021/jp106220z
Cubic BaCo0.7Fe0.3−xYxO3−δ (BCFY, x = 0.08−0.2) was prepared by the conventional solid state reaction route as oxygen permeation membranes. The effects of Y-doping on the crystal structure, electrical conductivity, and oxygen permeability are investigated, and the factors influencing the activation energy of oxygen migration are discussed from the viewpoints of metal−oxygen bonding energy and geometric lattice structure. Y-substitution decreases the electrical conductivity but increases the oxygen vacancy concentration of BCFY samples. Nevertheless, the oxygen permeability decreases with increasing Y-doping level. Both the strong Y−O bonding energy and the decreased critical radius (rC) with Y-doping should be responsible for the increased activation energy. First principle calculation reveals that Y-doping results in the nonequivalent positions of the mobile oxygen ions and thus limits the oxygen ion diffusion passages. BaCo0.7Fe0.22Y0.08O3−δ membrane exhibits a high oxygen permeability of 1.73 mL min−1 cm−2 at 900 °C, thus being a promising candidate material for oxygen separation or POM applications.
Co-reporter:Jianchao He, Hailei Zhao, Mengwei Wang, Xidi Jia
Materials Science and Engineering: B 2010 Volume 171(1–3) pp:35-39
Publication Date(Web):25 July 2010
DOI:10.1016/j.mseb.2010.03.051
Co-reporter:Yao Lu, Hailei Zhao, Xiwang Chang, Xuefei Du, Kui Li, Yanhui Ma, Sha Yi, Zhihong Du, Kun Zheng and Konrad Świerczek
Journal of Materials Chemistry A 2016 - vol. 4(Issue 27) pp:NaN10466-10466
Publication Date(Web):2016/06/14
DOI:10.1039/C6TA01749E
A cobalt-free perovskite-type mixed ionic and electronic conductor (MIEC) is of technological and economic importance in many energy-related applications. In this work, a new group of Fe-based perovskite MIECs with BaFe1−xGdxO3−δ (0.025 ≤ x ≤ 0.20) compositions was developed for application in oxygen permeation membranes. Slight Gd doping (x = 0.025) can stabilize the cubic structure of the BaFe1−xGdxO3−δ perovskite. The Gd substitution of BaFe1−xGdxO3−δ materials increases the structural and chemical stability in the atmosphere containing CO2 and H2O, and decreases the thermal expansion coefficient. The BaFe0.975Gd0.025O3−δ membrane exhibits fast oxygen surface exchange kinetics and a high bulk diffusion coefficient, and achieves a high oxygen permeation flux of 1.37 mL cm−2 min−1 for a 1 mm thick membrane at 950 °C under an air/He oxygen gradient, and can maintain stability at 900 °C for 100 h. Compared to the pristine BaFeO3−δ and the well-studied Ba0.95La0.05FeO3−δ membranes, a lower oxygen permeation activation energy and higher oxygen permeability are obtained for the 2.5 at% Gd-doped material, which might be attributed to the expanded lattice by doping large Gd3+ cations and a limited negative effect from the strong Gd–O bond. A combination study of first principles calculation and experimental measurements was further conducted to advance the understanding of Gd effects on the oxygen migration behavior in BaFe1−xGdxO3−δ. These findings are expected to provide guidelines for material design of high performance MIECs.
Co-reporter:Zhihong Du, Hailei Zhao, Yongna Shen, Lu Wang, Mengya Fang, Konrad Świerczek and Kun Zheng
Journal of Materials Chemistry A 2014 - vol. 2(Issue 26) pp:NaN10299-10299
Publication Date(Web):2014/04/16
DOI:10.1039/C4TA00658E
Perovskites La0.3Sr0.7Ti1−xCoxO3 (LSTCs, x = 0.3–0.6) are systematically evaluated as potential cathode materials for solid oxide fuel cells. The effects of Co substitution for Ti on structural characteristics, thermal expansion coefficients (TECs), electrical conductivity, and electrochemical performance are investigated. All of the synthesized LSTCs exhibit a cubic structure. With Rietveld refinement on the high-temperature X-ray diffraction data, the TECs of LSTCs are calculated to be 20–26 × 10−6 K−1. LSTC shows good thermal cycling stability and is chemically compatible with the LSGM electrolyte below 1250 °C. The substitution of Co for Ti increases significantly the electrical conductivity of LSTC. The role of doping on the conduction behavior is discussed based on defect chemistry theory and first principles calculation. The electrochemical performances of LSTC are remarkably improved with Co substitution. The area specific resistance of sample La0.3Sr0.7Ti0.4Co0.6O3 on the La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte in symmetrical cells is 0.0145, 0.0233, 0.0409, 0.0930 Ω cm2 at 850, 800, 750 and 700 °C, respectively, and the maximum power density of the LSGM electrolyte (400 μm)-supported single cell with the Ni–GDC anode, LDC buffer layer and LSTC cathode reaches 464.5, 648, and 775 mW cm−2 at 850 °C for x = 0.3, 0.45, and 0.6, respectively. All these results suggest that LSTC are promising candidate cathode materials for SOFCs.
Co-reporter:Yao Lu, Hailei Zhao, Kui Li, Xuefei Du, Yanhui Ma, Xiwang Chang, Ning Chen, Kun Zheng and Konrad Świerczek
Journal of Materials Chemistry A 2017 - vol. 5(Issue 17) pp:NaN8009-8009
Publication Date(Web):2017/03/28
DOI:10.1039/C7TA00907K
A cost-effective doping strategy was developed to enhance the oxygen permeability and structural stability of BaFeO3−δ. We demonstrated that the alkaline earth metal element Ca, which is usually considered an A-site dopant for perovskite oxides, can be successfully introduced into the B-site of BaFeO3−δ. The cubic perovskite structure of BaFe1−xCaxO3−δ was stabilized down to room temperature for the Ca-doping concentration range from 5 to 15 at%. First principles calculations not only proved the preference of Ca at the B-site with lower defect formation energies than the A-site, but also demonstrated that the migration of the oxygens located greater distances from the Ca position is characterized by lower barrier energies than those in the Ca vicinity and even lower than that for the undoped BaFeO3−δ. We found that these favourable, low energy barrier paths away from the Ca sites exert more pronounced effects on the oxygen migration at diluted dopant concentrations, and hence, the material with x = 0.05 level of substitution shows a higher oxygen permeability with a lower activation energy compared to the undoped or highly-doped BaFeO3−δ. The BaFe0.95Ca0.05O3−δ membrane is characterized by a high oxygen permeability of 1.30 mL cm−2 min−1 at 950 °C and good long-term stability at 800/900 °C, as obtained over 200 h. Therefore, the feasibility and applicability of Ca-doping at the B-site of the perovskite can be highlighted, which allows for the enhancement of the oxygen migration ability, originating from the appropriate tuning of the lattice structure.
Co-reporter:Yongna Shen, Hailei Zhao, Xiaotong Liu and Nansheng Xu
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 45) pp:NaN15131-15131
Publication Date(Web):2010/10/22
DOI:10.1039/C0CP00261E
Ca-doped La2NiO4+δ is synthesized via the nitrate–citrate route. The effects of Ca substitution for La on the sinterability, lattice structure and electrical properties of La2NiO4+δ are investigated. Ca-doping is unfavorable for the densification process of La2−xCaxNiO4+δ materials. The introduction of Ca leads to the elongation of the La–O(2) bond length, which provides more space for the migration of oxygen ion in La2O2 rock salt layers. The substitution of Ca increases remarkably the electronic conductivity of La2−xCaxNiO4+δ. With increasing Ca-doping level, both the excess oxygen concentration and the activation energy of oxygen ion migration decrease, resulting in an optimization where a highest ionic conductivity is presented. Ca-doping is charge compensated by the oxidation of Ni2+ to Ni3+ and the desorption of excess oxygen. The substitution of Ca enhances the structural stability of La2NiO4+δ material at high temperatures and renders the material a good thermal cycleability. La1.7Ca0.3NiO4+δ exhibits an excellent chemical compatibility with CGO electrolyte. La2−xCaxNiO4+δ is a promising cathode alternative for solid oxide fuel cells.
Co-reporter:Qing Xia, Hailei Zhao, Zhihong Du, Zijia Zhang, Shanming Li, Chunhui Gao and Konrad Świerczek
Journal of Materials Chemistry A 2016 - vol. 4(Issue 2) pp:NaN611-611
Publication Date(Web):2015/11/25
DOI:10.1039/C5TA07052J
Molybdenum dioxide is an attractive material for anodes of lithium ion batteries due to its high theoretical capacity, more than twice that of graphite. However, slow electrode reaction kinetics and structural degradation caused by large volume changes and phase separation during cycling hinder its practical application. To solve these problems, we design and fabricate a novel, 3-D hierarchical MoO2/Ni/C architecture by a combination of a hydrothermal method with chemical vapor deposition. The nickel nanoparticles are in situ formed and disperse uniformly with flower-like MoO2 particles, which are coated by thin carbon layers. The Ni particles act as a catalyst during the carbon coating process to promote the in situ growth of graphene in the carbon layer. Together, MoO2 and nickel nanoparticles, as well as amorphous carbon and graphene sheets build a 3-D hierarchical robust MoO2/Ni/C structure with a good electronically conductive network and lots of void space. Such a 3-D hierarchical structure combines multiple advantageous features, including an enhanced 3-D electronically conductive network, plenty of tunnels for electrolyte solution penetration, void space for volume change accommodation, and more surface areas for the electrode reaction. The manufactured MoO2/Ni/C composite exhibits a high reversible capacity, and excellent rate capability of 576 and 463 mA h g−1 at current densities of 100 and 1000 mA g−1, respectively. The excellent cycling performance is recorded with a capacity of 445 mA h g−1 maintained at 1000 mA g−1 after 800 cycles. The proposed synthesis process is simple and the design concept can be broadly applied, providing a novel, general approach towards manufacturing of metal oxide/metal/carbon (graphene) composites for high energy density storage or other electrochemical uses.
Co-reporter:Yao Lu, Hailei Zhao, Xing Cheng, Yibin Jia, Xuefei Du, Mengya Fang, Zhihong Du, Kun Zheng and Konrad Świerczek
Journal of Materials Chemistry A 2015 - vol. 3(Issue 11) pp:NaN6214-6214
Publication Date(Web):2015/02/09
DOI:10.1039/C4TA06520D
Cobalt-free BaFe1−xInxO3−δ perovskites, with Fe partially substituted by indium at the B-site, were synthesized by a conventional solid state reaction and systematically characterized in terms of their phase composition, crystal structure, thermal reducibility, oxygen permeability, as well as structural stability in order to evaluate their application as oxygen permeation membranes. Introduction of more than 10 at.% of In into BaFe1−xInxO3−δ causes the formation of a single phase material with a cubic perovskite structure, which exhibits no phase transition during the cooling process. The thermal reducibility and thermal expansion coefficient are effectively reduced by indium doping, owing to the less changes of concentration of the oxygen vacancies in these compounds. However, the In occupying B-site breaks the B–O–B double exchange mechanism, and thus results in a gradual decrease of the electrical conductivity upon doping. Rietveld refinement and first principles calculation were performed to get an insight into the In influence on the lattice structure, oxygen migration energy and electron conduction behaviour of BaFe1−xInxO3−δ. When using He/Air as sweep/feed gas, the BaFe0.9In0.1O3−δ dense membrane with 1.0 mm thickness features a high oxygen permeation flux of 1.11 mL cm−2 min−1 at 950 °C. The observed good performance is attributed to the relatively high concentration of oxygen vacancies and low energy barrier for oxygen ion migration. It is also found that for membranes thinner than 0.8 mm, the oxygen flux is no longer limited by the bulk diffusion, while the oxygen surface exchange process becomes the dominant factor.
Co-reporter:Cuijuan Zhang and Hailei Zhao
Journal of Materials Chemistry A 2012 - vol. 22(Issue 35) pp:
Publication Date(Web):
DOI:10.1039/C2JM32627B
