Co-reporter:Cong Tang, Pengcheng Sun, Jian Xie, Zhichu Tang, Zixu Yang, Zexi Dong, Gaoshao Cao, Shichao Zhang, Paul V. Braun, Xinbing Zhao
Energy Storage Materials 2017 Volume 9(Volume 9) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.ensm.2017.07.016
Li–O2 cells have attracted a worldwide attention due to their extremely high energy density compared with current Li-ion batteries. However, great challenges must to be overcome to realize full charge and discharge of Li–O2 cells at high rates over a wide electrochemical window. Herein, we propose a unique design of binder-free catalytic cathode composed of two-dimensional (2D), few-layered δ-MnO2 (5–10 nm) decorated with small-sized IrO2 (around 5 nm). The superior catalytic activity of IrO2/MnO2 enables conformal growth of amorphous Li2O2 on the 2D IrO2/MnO2 nanosheets at high current density, leading to significantly enhanced Li2O2 formation/decomposition kinetics. As a result, Li–O2 cells with the IrO2/MnO2 catalyst exhibit high capacity (16370 mAh g−1 at 200 mA g−1), superior rate capability (2315 mAh g−1 at 1600 mA g−1) and high-rate cycling stability (312 cycles at 1600 mA g−1) between 2.2 and 4.3 V. Even over a wider voltage window of 2–4.4 V, the cell can sustain 247 cycles at 1600 mA g−1 in a full charge/discharge mode. The superior catalytic activity of IrO2/MnO2 makes it a promising catalyst for high-performance Li–O2 cells.Download high-res image (345KB)Download full-size image
Co-reporter:Can Cao;Jian Xie;Shichao Zhang;Bin Pan;Gaoshao Cao;Xinbing Zhao
Journal of Materials Chemistry A 2017 vol. 5(Issue 14) pp:6747-6755
Publication Date(Web):2017/04/04
DOI:10.1039/C7TA00416H
Lithium–oxygen (Li–O2) cells are receiving intense interest because of their extremely high energy density. A highly efficient catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a key factor influencing the performance of lithium–oxygen cells. In this work, we prepared a highly efficient CeO2-decorated δ-MnO2 (CeO2/δ-MnO2) catalyst which is composed of graphene-like δ-MnO2 with ultrafine CeO2 nanocrystals decorated on it. Li–O2 cells with the CeO2/δ-MnO2 catalyst exhibit superior electrochemical performance, including high discharge specific capacity (8260 mA h g−1 at 100 mA g−1), good rate capability (735 mA h g−1 at 1600 mA g−1), and excellent cycling stability (296 cycles at a limited capacity of 500 mA h g−1), which is much better than that with a bare δ-MnO2 catalyst. The achievement of excellent electrochemical performance is attributed to the highly efficient co-catalytic ability of δ-MnO2 and CeO2 and the desirable graphene-like architecture of the CeO2/δ-MnO2 catalyst, as well as the formation of the thin-layered discharge product Li2O2.
Co-reporter:Yehao Wu, Renshuang Zhai, Tiejun Zhu, Xinbing Zhao
Materials Today Physics 2017 Volume 2(Volume 2) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.mtphys.2017.09.001
•A synergetic optimization procedure is performed to boost room temperature zT of n-type Bi2Te2.7Se0.3 alloy.•The carrier concentration is optimized via Ag doping and the carrier mobility is enhanced via hot deformation.•A zT value of 1.0 at 300 K and a peak zT of 1.1 at 350 K are obtained in n-type polycrystalline Bi2Te2.7Se0.3 alloy.Bismuth-telluride-based alloys are the unique thermoelectric materials for state-solid refrigeration around room temperature. For n-type polycrystalline counterparts, maximum figure of merit zTs are often shifted above 400 K due to the increased carrier concentration induced by the donor-like effect during the pulverization of ingots. Herein, we report a synergistic optimization procedure, combining Ag doping with hot deformation, to boost room temperature thermoelectric performance of n-type polycrystalline Bi2Te2.7Se0.3 alloys. The Ag doping optimizes the carrier concentration, contributing to an improved power factor and a reduced electrical thermal conductivity. The hot deformation process improves the carrier mobility due to the enhanced texture. As a consequence, a zT value of 1.0 at 300 K and a peak zT of 1.1 at 350 K are obtained in the twice hot deformed Ag0.011Bi2Te2.7Se0.3 alloy, which makes the n-type polycrystalline Bi2(Te,Se)3 alloys more suitable for solid-state refrigeration near room temperature.Download full-size image
Co-reporter:Can Cao, Yucong Yan, Hui Zhang, Jian Xie, Shichao Zhang, Bin Pan, Gaoshao Cao, and Xinbing Zhao
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 46) pp:31653
Publication Date(Web):November 1, 2016
DOI:10.1021/acsami.6b10716
For Li–O2 batteries, a challenge still remains to achieve high discharge capacity and easy decomposition of the discharge product (Li2O2) simultaneously. In this work, conformal growth of thin-layered Li2O2 on Co3O4 nanowire arrays (Co3O4 NAs) during discharge is realized through the cocatalytic effect of solid/immobile Co3O4 NAs and mobile Pd nanocrystals (Pd NCs), rendering easy decomposition of Li2O2 during recharge. Meanwhile, high discharge capacity is also ensured with unique array-type design of the catalytic cathode despite the surface growth mode of Li2O2. The Li–O2 cells can deliver a high discharge capacity of 5337 mAh g–1 and keep a stable cycling of 258 cycles at a limited capacity of 500 mAh g–1. The achievement of excellent electrochemical performance is attributed to the highly efficient cocatalytic ability of Co3O4 NAs and Pd NCs as well as the desirable array-type architecture of the catalytic electrode free of carbon and binder. The cocatalytic mechanism of Co3O4 NAs and Pd NCs is clarified by systematic electrochemical tests, microstructural analyses, and ζ-potential measurements.Keywords: binder/carbon free; cobalt oxide arrays; cocatalysis; controlled Li2O2 growth; lithium−oxygen batteries; palladium nanocrystals
Co-reporter:Tiezheng Fu, Xianqiang Yue, Haijun Wu, Chenguang Fu, Tiejun Zhu, Xiaohua Liu, Lipeng Hu, Pingjun Ying, Jiaqing He, Xinbing Zhao
Journal of Materiomics 2016 Volume 2(Issue 2) pp:141-149
Publication Date(Web):June 2016
DOI:10.1016/j.jmat.2016.05.005
Forming solid solutions in PbTe based materials can simultaneously reduce lattice thermal conductivity and engineer the band structure to enhance the electrical properties. In this paper, quaternary alloys of Pb1−xMgxTe0.8Se0.2 were designed to improve the figure of merit zT. The significant roles of MgTe in enhancing electrical properties and reducing thermal conductivity of PbTe0.8Se0.2 were investigated. A maximum zT of ∼2.2 at 820 K was achieved in PbTe0.8Se0.2 with 8% MgTe. Subsequently, a large dimension bulk (∼200 g, Φ42 mm × 18 mm) was fabricated and its homogeneity and the repeatability of high zT values were determined. The results show that high zT ∼2.0 can also be achieved even in such a large sample. These results highlight the multi-functional roles of quaternary alloying with Mg and Se, and demonstrate the realistic prospect of large-scale commercial fabrication in high performance PbTe-based thermoelectric materials.Quarternary alloys of Pb1–xMgxTe0.8Se0.2 were designed to improve the figure of merit zT. A maximum zT of ∼2.2 at 820 K was achieved in PbTe0.8Se0.2 with 8% MgTe. High zT of ∼2.0 can also be achieved even in such a large dimension (∼200 g, ϕ42 mm × 18 mm) bulk sample. These results highlight the multi-functional roles of quarternary alloying with Mg and Se, and demonstrate the realistic prospect of large-scale commercial fabrication in high performance PbTe-based thermoelectric materials.Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:Lipeng Hu;Haijun Wu;Tiejun Zhu;Chenguang Fu;Jiaqing He;Pingjun Ying;Xinbing Zhao
Advanced Energy Materials 2015 Volume 5( Issue 17) pp:
Publication Date(Web):
DOI:10.1002/aenm.201500411
Microstructure manipulation plays an important role in enhancing physical and mechanical properties of materials. Here a high figure of merit zT of 1.2 at 357 K for n-type bismuth-telluride-based thermoelectric (TE) materials through directly hot deforming the commercial zone melted (ZM) ingots is reported. The high TE performance is attributed to a synergistic combination of reduced lattice thermal conductivity and maintained high power factor. The lattice thermal conductivity is substantially decreased by broad wavelength phonon scattering via tuning multiscale microstructures, which includes microscale grain size reduction and texture loss, nanoscale distorted regions, and atomic scale lattice distotions and point defects. The high power factor of ZM ingots is maintained by the offset between weak donor-like effect and texture loss during the hot deformation. The resulted high zT highlights the role of multiscale microstructures in improving Bi2Te3-based materials and demonstrates the effective strategy in enhancing TE properties.
Co-reporter:Jingyi Cao, Shuangyu Liu, Jian Xie, Shichao Zhang, Gaoshao Cao, and Xinbing Zhao
ACS Catalysis 2015 Volume 5(Issue 1) pp:241
Publication Date(Web):December 2, 2014
DOI:10.1021/cs501392p
We propose a new design of a binder/carbon-free air electrode with tips-bundled Pt/Co3O4 nanowires grown directly on Ni foam substrate. In this design, the side reactions related to binder/carbon are excluded. The presence of Pt not only promotes the formation of the tips-bundled structure of Co3O4 nanowires but also directs the uniform deposition of a fluffy, thin Li2O2 layer only on the periphery of Pt/Co3O4 nanowires. This crystallization habit of Li2O2 makes it easy to decompose upon recharge with reduced side reactions. As a result, Li–O2 batteries with this cathode show low polarization.Keywords: binder/carbon free; cobalt oxide; directed Li2O2 growth; lithium−oxygen batteries; platinum; tips-bundled nanowires
Co-reporter:Zhenglong Tang, Lipeng Hu, Tiejun Zhu, Xiaohua Liu and Xinbing Zhao
Journal of Materials Chemistry A 2015 vol. 3(Issue 40) pp:10597-10603
Publication Date(Web):18 Aug 2015
DOI:10.1039/C5TC02263K
Currently more than 60% of primary energy used in industry or life is lost as waste heat in the temperature range of 400–900 K, and much attention is paid to mid-temperature thermoelectric (TE) power generation. Here we combine several strategies, i.e. alloying, doping and hot deformation, to improve the TE performance of n-type bismuth telluride based TE alloys for mid-temperature power generation. Se alloying was adopted to widen the band gap and suppress intrinsic conduction at elevated temperatures. When Se atoms completely substitute the Te(2) atoms, the crystal structure of Bi2Te3 based alloys tends to be more ordered, resulting in the maximum value of the band gap. And the induced alloying scattering significantly reduces the lattice thermal conductivity. Then SbI3 donor doping was used to increase the electron concentration to further suppress the detrimental effects of bipolar conduction. Finally we applied repetitive hot deformations to further improve the figure of merit zT and a peak zT of ∼1.1 was obtained at about 600 K in the 0.1 at% SbI3–Bi2Te1.9Se1.1 alloy, which was hot-deformed three times. The results demonstrated the great potential of the alloy for application in mid-temperature TE power generation.
Co-reporter:Longhuan Liao, Hongtao Wang, Hui Guo, Peiyi Zhu, Jian Xie, Chuanhong Jin, Shichao Zhang, Gaoshao Cao, Tiejun Zhu and Xinbing Zhao
Journal of Materials Chemistry A 2015 vol. 3(Issue 38) pp:19368-19375
Publication Date(Web):14 Aug 2015
DOI:10.1039/C5TA05358G
Fe doping is widely used to improve the electrochemical performance of LiMnPO4 by “implanting” the merits of high rate capability and long cycle life of LiFePO4 into LiMnPO4. Nevertheless, great challenges still remain to obtain high-performance LiFexMn1−xPO4 at a low x value. In this work, we synthesized ultrathin LiFexMn1−xPO4 (x ≤ 0.15) nanoplates by a facile, controllable method. The plate-like LiFexMn1−xPO4 with a small lateral size (40–100 nm) and thickness (10–20 nm) exhibits high electrochemical activity, excellent rate capability and superior cycling stability after carbon coating. At a rate as high as 50C (8.5 A g−1), the LiFe0.15Mn0.85PO4/C composite can still yield a high discharge capacity of 96.2 mA h g−1 where the discharge process can be completed in only 40 s. LiFe0.15Mn0.85PO4/C can sustain a long-term cycling up to 1000 cycles at 10C with a capacity retention close to 70%. The fast and stable cycling ability of LiFexMn1−xPO4 makes it promising for applications in electric vehicles and hybrid electric vehicles.
Co-reporter:L.P. Hu, T.J. Zhu, X.Q. Yue, X.H. Liu, Y.G. Wang, Z.J. Xu, X.B. Zhao
Acta Materialia 2015 Volume 85() pp:270-278
Publication Date(Web):15 February 2015
DOI:10.1016/j.actamat.2014.11.023
Abstract
V–VI compounds have been widely investigated as promising thermoelectric materials for room temperature refrigeration. In this paper, we report a systematic study of high performance p-type antimony–telluride-based thermoelectric alloys for mid-temperature power generation. Indium alloying is adopted as an effective approach to widen the band gap and suppress the detrimental bipolar conduction at elevated temperatures. The low Seebeck coefficient of binary antimony telluride, arising from high hole concentration generated by antisite defects, was enhanced by raising the antisite defect energy formation. Meanwhile, the induced alloying scattering significantly reduced the lattice thermal conductivity. Ag acceptor doping was used to further suppress the detrimental bipolar conduction and improve the figure of merit, zT. These combined effects resulted in a peak zT of ∼0.92 at 710 K for the hot-pressed Ag0.01Sb1.85In0.15Te3 alloy, whereas the average zTav of 0.8 was obtained in the temperature range of 500–710 K, indicating a great potential of the alloy for application in mid-temperature thermoelectric power generation.
Co-reporter:H.L. Gao, T.J. Zhu, X.B. Zhao, Y. Deng
Intermetallics 2015 Volume 56() pp:33-36
Publication Date(Web):January 2015
DOI:10.1016/j.intermet.2014.08.010
•Sb-doped Mg2Ge was synthesized by tantalum-tube melting followed by hot pressing.•The effect of Sb doping on thermoelectric properties was studied in 300–740 K.•Sb doping with sufficient Mg excess increased σ, leading to enhanced power factor.The Sb-doped Mg2Ge compounds were successfully synthesized by tantalum-tube weld melting method followed by hot pressing and the thermoelectric properties were examined. The effects of Sb doping on the electrical conductivity, Seebeck coefficient, and thermal conductivity have been investigated in the temperature range of 300–740 K. It was found that the Sb doping with sufficient Mg excess increased the electrical conductivity dramatically, leading to enhancement of the power factors. The thermal conductivity was also reduced upon Sb doping, mainly due to mass fluctuation scattering and strain field effects. Mg2.2Ge0.095Sb0.005 showed a maximum thermoelectric figure of merit of ≈0.2 at 740 K.
Co-reporter:Guangyu Jiang;Jian He;Tiejun Zhu;Chenguang Fu;Xiaohua Liu;Lipeng Hu;Xinbing Zhao
Advanced Functional Materials 2014 Volume 24( Issue 24) pp:3776-3781
Publication Date(Web):
DOI:10.1002/adfm.201400123
A point defect chemistry approach to improving thermoelectric (TE) properties is introduced, and its effectiveness in the emerging mid-temperature TE material Mg2(Si,Sn) is demonstrated. The TE properties of Mg2(Si,Sn) are enhanced via the synergistical implementation of three types of point defects, that is, Sb dopants, Mg vacancies, and Mg interstitials in Mg2Si0.4Sn0.6-xSbx with high Sb content (x > 0.1), and it is found that i) Sb doping at low ratios tunes the carrier concentration while it facilitates the formation of Mg vacancies at high doping ratios (x > 0.1). Mg vacancies act as acceptors and phonon scatters; ii) the concentration of Mg vacancies is effectively controlled by the Sb doping ratio; iii) excess Mg facilitates the formation of Mg interstitials that also tunes the carrier concentration; vi) at the optimal Sb-doping ratio near x ≈ 0.10 the lattice thermal conductivity is significantly reduced, and a state-of-the-art figure of merit ZT > 1.1 is attained at 750 K in 2 at% Zn doped Mg2Si0.4Sn0.5Sb0.1 specimen. These results demonstrate the significance of point defects in thermoelectrics, and the promise of point defect chemistry as a new approach in optimizing TE properties.
Co-reporter:Lipeng Hu;Tiejun Zhu;Xiaohua Liu;Xinbing Zhao
Advanced Functional Materials 2014 Volume 24( Issue 33) pp:5211-5218
Publication Date(Web):
DOI:10.1002/adfm.201400474
Developing high-performance thermoelectric materials is one of the crucial aspects for direct thermal-to-electric energy conversion. Herein, atomic scale point defect engineering is introduced as a new strategy to simultaneously optimize the electrical properties and lattice thermal conductivity of thermoelectric materials, and (Bi,Sb)2(Te,Se)3 thermoelectric solid solutions are selected as a paradigm to demonstrate the applicability of this new approach. Intrinsic point defects play an important role in enhancing the thermoelectric properties. Antisite defects and donor-like effects are engineered in this system by tuning the formation energy of point defects and hot deformation. As a result, a record value of the figure of merit ZT of ≈1.2 at 445 K is obtained for n-type polycrystalline Bi2Te2.3Se0.7 alloys, and a high ZT value of ≈1.3 at 380 K is achieved for p-type polycrystalline Bi0.3Sb1.7Te3 alloys, both values being higher than those of commercial zone-melted ingots. These results demonstrate the promise of point defect engineering as a new strategy to optimize thermoelectric properties.
Co-reporter:Li-Peng Hu, Tie-Jun Zhu, Ya-Guang Wang, Han-Hui Xie, Zhao-Jun Xu and Xin-Bing Zhao
NPG Asia Materials 2014 6(2) pp:e88
Publication Date(Web):2014-02-01
DOI:10.1038/am.2013.86
The abundance of low-temperature waste heat produced by industry and automobile exhaust necessitates the development of power generation with thermoelectric (TE) materials. Commercially available bismuth telluride-based alloys are generally used near room temperature. Materials that are composed of p-type bismuth telluride, which are suitable for low-temperature power generation (near 380 K), were successfully obtained through Sb-alloying, which suppresses detrimental intrinsic conduction at elevated temperatures by increasing hole concentrations and material band gaps. Furthermore, hot deformation (HD)-induced multi-scale microstructures were successfully realized in the high-performance p-type TE materials. Enhanced textures and donor-like effects all contributed to improved electrical transport properties. Multiple phonon scattering centers, including local nanostructures induced by dynamic recrystallization and high-density lattice defects, significantly reduced the lattice thermal conductivity. These combined effects resulted in observable improvement of ZT over the entire temperature range, with all TE parameters measured along the in-plane direction. The maximum ZT of 1.3 for the hot-deformed Bi0.3Sb1.7Te3 alloy was reached at 380 K, whereas the average ZTav of 1.18 was found in the range of 300–480 K, indicating potential for application in low-temperature TE power generation.
Co-reporter:Qin Pan, Jian Xie, Tiejun Zhu, Gaoshao Cao, Xinbing Zhao, and Shichao Zhang
Inorganic Chemistry 2014 Volume 53(Issue 7) pp:3511-3518
Publication Date(Web):March 19, 2014
DOI:10.1021/ic402948s
Preparation of two-dimensional (2D) graphene-like materials is currently an emerging field in materials science since the discovery of single-atom-thick graphene prepared by mechanical cleavage. In this work, we proposed a new method to prepare 2D NiS, where reduced graphene oxide (rGO) was found to induce the recrystallization of NiS from nanorods to nanosheets in a hydrothermal process. The process and mechanism of recrystallization have been clarified by various characterization techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) mapping, and X-ray photoelectron spectroscopy (XPS). The characterization of ex situ NiS/rGO products by SEM and EDS mapping indicates that the recrystallization of NiS from nanorods to nanosheets is realized actually through an exfoliation process, while the characterization of in situ NiS/rGO products by SEM, TEM, and EDS mapping reveals the exfoliation process. The XPS result demonstrates that hydrothermally assisted chemical bonding occurs between NiS and rGO, which induces the exfoliation of NiS nanorods into nanosheets. The obtained NiS/rGO composite shows promising Na-storage properties.
Co-reporter:Chunyang Wu, Jian Xie, Gaoshao Cao, Xinbing Zhao and Shichao Zhang
CrystEngComm 2014 vol. 16(Issue 11) pp:2239-2245
Publication Date(Web):18 Dec 2013
DOI:10.1039/C3CE42377H
Nanoengineering has proven to be an effective strategy to improve the electrochemical properties of LiMPO4 (M = Fe, Mn). In this work, we report an ‘up-to-down’ way to synthesize LiMPO4 nanorods through an ion-exchange route using pre-prepared NH4MPO4·H2O microplates as the precursor and LiAc as the Li source. The similarity in crystal structure between NH4MPO4·H2O and LiMPO4 allows the occurrence of the ion-exchange reaction, while their structural difference induces lattice stress that breaks the NH4MPO4·H2O microplates to form interconnected, orderly arranged LiMPO4 nanorods. This work provides a general method to synthesize nanosized LiMPO4 from microsized NH4MPO4·H2O by taking advantage of their crystallization characteristics. The nanoscaled LiMPO4/C composites exhibit promising electrochemical properties after carbon coating.
Co-reporter:Jian Xie, Wentao Song, Gaoshao Cao, Tiejun Zhu, Xinbing Zhao and Shichao Zhang
RSC Advances 2014 vol. 4(Issue 15) pp:7703-7709
Publication Date(Web):09 Jan 2014
DOI:10.1039/C3RA46904B
A ZnFe2O4-nanocrystals/graphene-nanosheets (ZnFe2O4/G) nanohybrid has been prepared by a facile in situ hydrothermal route using Zn(NO3)2·6H2O, Fe(NO3)3·6H2O and graphite oxide (GO) as the precursors. Ultrafine ZnFe2O4 nanocrystals (below 10 nm) are confined by the few-layer graphene sheets reduced from GO, forming a unique sheet-like hybrid. In this structure, the direct restacking of the hydrophobic graphene sheets is refrained by loading ZnFe2O4 nanocrystals as the spacers and the aggregation of ZnFe2O4 nanocrystals is inhibited by the dispersing and confining effects of the graphene sheets. ZnFe2O4/G shows excellent rate capability and high-rate cycling stability for lithium storage. It also shows a high capacity when used as an anode for a ZnFe2O4/G–LiFePO4/C full cell.
Co-reporter:Shuangyu Liu, Jian Xie, Qingmei Su, Gaohui Du, Shichao Zhang, Gaoshao Cao, Tiejun Zhu, Xinbing Zhao
Nano Energy 2014 Volume 8() pp:84-94
Publication Date(Web):September 2014
DOI:10.1016/j.nanoen.2014.06.001
•We fabricated an all-solid-state nano lithium battery MnFe2O4/GNS–Li2O–Li.•In situ TEM was used to investigate the electrochemical reaction of MnFe2O4 with Li.•Macroscopic electrochemical property was correlated to microscopic characterization.In this work, we fabricated an all-solid-state nano lithium battery MnFe2O4/graphene–Li2O–Li to understand the electrochemical Li-storage mechanism and performance of MnFe2O4 using in situ transmission electron microscopy (TEM) technique. We found that single-crystalline MnFe2O4 is converted into polycrystalline Li2O/Mn/Fe with large volume expansion upon discharge and subsequently into polycrystalline MnO/Fe3O4 with volume shrinkage upon charge. Reversible conversion between MnO/Fe3O4 and Li2O/Mn/Fe occurs during the following cycles with small volume changes. We also found that both MnO/Fe3O4 and Li2O/Mn/Fe can be tightly confined by graphene despite the volume change and particle pulverization, and that free space that buffers the volume changes still exists even at deep lithiation state. In situ TEM characterization also indicates that graphene is a good conductor for both Li ion and electrons. The combined conducting, buffering and confining effects of graphene revealed by in situ TEM characterization can well explain the role it plays in improving the electrochemical properties of MnFe2O4.
Co-reporter:Jian Xie, Fangfang Tu, Qingmei Su, Gaohui Du, Shichao Zhang, Tiejun Zhu, Gaoshao Cao, Xinbing Zhao
Nano Energy 2014 Volume 5() pp:122-131
Publication Date(Web):April 2014
DOI:10.1016/j.nanoen.2014.03.001
•We fabricated an all-solid-state nano lithium battery PbSe/rGO–Li2O–Li.•In situ TEM was used to investigate the electrochemical reaction of PbSe with Li.•Macroscopic electrochemical property is correlated with microscopic characterization.In this work, in situ transmission electron microscopy (TEM) technique has been applied to investigate the structural and phase evolutions of lead selenide (PbSe) nanocrystals loaded on reduced graphene oxide (rGO) nanosheets. An all-solid-state nano lithium battery composed of a single PbSe/rGO sheet cathode, Li2O electrolyte and Li anode has been fabricated to real time monitor the electrochemical lithiation/de-lithiation process of PbSe. It is found that few-layered rGO is a suitable support for PbSe during the in situ TEM observation due to its large surface area and good Li ion and electron conductivity. Based on the in situ characterization, a lithiation/de-lithiation mechanism of PbSe has been proposed. In situ characterization results are correlated with the electrochemical performance of PbSe/rGO. The role that rGO plays in modifying the electrochemical performance of PbSe has also been clarified by the in situ TEM characterization.
Co-reporter:Bin Feng, Jian Xie, Gaoshao Cao, Tiejun Zhu and Xinbing Zhao
Journal of Materials Chemistry A 2013 vol. 1(Issue 42) pp:13111-13119
Publication Date(Web):06 Sep 2013
DOI:10.1039/C3TA13202A
Nanostructuring and second phase incorporation are considered to be promising ways of enhancing the thermoelectric performance of bulk materials. Here, a design principle is proposed which combines these two methods for improving the thermoelectric performance of p-type CoSb3 by fabricating a CoSb3/graphene (CoSb3/G) nanocomposite, where a second phase, graphene, is introduced in the nanostructured CoSb3 matrix via an in situ one-pot solvothermal route. In addition, CoSb3/G bulk materials were prepared by hot pressing the solvothermally synthesized CoSb3/G powder. It was found that addition of a small amount of graphene can drastically enhance the electrical conductivity due to the increase in both carrier concentration and mobility. In addition, the well dispersed graphene in the nanostructured CoSb3 matrix also contributes to the low lattice thermal conductivity. A dimensionless figure of merit ZT = 0.61 at 800 K has been obtained for the CoSb3/G nanocomposite, which is about a 130% improvement over that of graphene-free CoSb3 (∼0.26).
Co-reporter:Shuangyu Liu, Xiang Lu, Jian Xie, Gaoshao Cao, Tiejun Zhu, and Xinbing Zhao
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 5) pp:1588
Publication Date(Web):February 19, 2013
DOI:10.1021/am302124f
A SnS2/graphene (SnS2/G) hybrid was synthesized by a facile one-step solvothermal route using graphite oxide, sodium sulfide, and SnCl4·5H2O as the starting materials. The formation of SnS2 and the reduction of graphite oxide occur simultaneously. Ultrathin SnS2 nanoplates with a lateral size of 5–10 nm are anchored on graphene nanosheets with a preferential (001) orientation, forming a unique plate-on-sheet structure. The electrochemical tests showed that the nanohybrid exhibits a remarkably enhanced cycling stability and rate capability compared with bare SnS2. The excellent electrochemical properties of SnS2/G could be ascribed to the in situ introduced graphene matrix which offers two-dimensional conductive networks, disperses and immobilizes SnS2 nanoplates, buffers the volume changes during cycling, and directs the growth of SnS2 nanoplates with a favorable orientation.Keywords: anode; c-axis orientation; graphene; Li-ion batteries; plate-on-sheet; tin sulfide;
Co-reporter:Jingyi Cao, Jian Xie, Gaoshao Cao, Tiejun Zhu, Xinbing Zhao, Shichao Zhang
Electrochimica Acta 2013 Volume 111() pp:447-454
Publication Date(Web):30 November 2013
DOI:10.1016/j.electacta.2013.08.039
•Tubular 0.5Li2MnO3·0.5Li4Mn5O12 has been synthesized by a self-templating route.•The diameter and wall thickness of the nanotubes are 500 and 200 nm, respectively.•The nanotubes exhibit a well-defined composite character.•The tubular composite shows a stable capacity of around 200 mAh g−1 at 0.1 C.Tubular 0.5Li2MnO3·0.5Li4Mn5O12 has been synthesized by a facile self-templating method starting from tubular β-MnO2. The wall thickness and diameter of 0.5Li2MnO3·0.5Li4Mn5O12 nanotubes are around 200 and 500 nm, respectively. X-ray diffraction and transmission electron microscopy observations confirm the composite character, where the Li4Mn5O12 nano-domains are integrated with the Li2MnO3 nano-domains. The tubular composite synthesized at 600 °C exhibits better electrochemical properties than that synthesized at 700 °C due to the higher ratio of LiMn2O4 decomposed from Li4Mn5O12. The tubular composite also exhibits better electrochemical properties than the microsized aggregated particles due to the unique tubular nanostructure with large specific surface, short Li-ion diffusion pathway, and loose stacking of the tubes.
Co-reporter:Y. Zhang, L. P. Hu, T. J. Zhu, J. Xie, and X. B. Zhao
Crystal Growth & Design 2013 Volume 13(Issue 2) pp:645-651
Publication Date(Web):January 4, 2013
DOI:10.1021/cg3013156
Hexagonal nanosheet of Bi2Te3 single crystals with uniform morphology were facilely synthesized through a high yield solvothermal route at low temperature (180 °C). X-ray diffraction, scanning electron microscope, transmission electron microscope, selected area electron diffraction, and high-resolution transmission electron microscope were employed to characterize the products. In this solvothermal process, ethylene glycol (EG) was used as both reducing agent and solvent to simplify the process. The reaction temperature and alkaline environment play important roles in the formation of Bi2Te3 single crystals, and the morphology of the products can be influenced by the added surfactants. Nanosheets with uniform morphology were obtained when polyvinyl pyrrolidone (PVP) was used as surfactant. Transport properties of hot pressed bulk samples formed by the as-prepared nanosheets were investigated. Thermal conductivity of the hot pressed nanosheets was greatly reduced by up to 60%, compared to the melt sample, with an enhancement of Seebeck coefficient and a decrease of electrical conductivity.
Co-reporter:Qin Pan, Jian Xie, Shuangyu Liu, Gaoshao Cao, Tiejun Zhu and Xinbing Zhao
RSC Advances 2013 vol. 3(Issue 12) pp:3899-3906
Publication Date(Web):06 Dec 2012
DOI:10.1039/C2RA22410K
A NiS/graphene (NiS/G) nanohybrid has been synthesized by a facile in situ one-pot hydrothermal route using graphite oxide, thiourea, NiCl2·4H2O and sodium citrate as the raw materials. The growth of NiS nanosheets and the reduction of graphite oxide occur simultaneously during the hydrothermal reactions. The hybrid exhibits a unique sheet-on-sheet structure, where ultrathin NiS sheets (below 5 nm) are anchoring on few-layer (below 8 layers) graphene sheets. The electrochemical measurements indicate that the NiS/G hybrid exhibits remarkably improved Li-storage properties compared with bare NiS, due to the ultrathin feature of the NiS sheets, unique sheet-on-sheet structure of the hybrid, and the combined conducting, buffering and confining effects of the in situ introduced graphene nanosheets.
Co-reporter:Jian Xie, Shuangyu Liu, Gaoshao Cao, Tiejun Zhu, Xinbing Zhao
Nano Energy 2013 Volume 2(Issue 1) pp:49-56
Publication Date(Web):January 2013
DOI:10.1016/j.nanoen.2012.07.010
A CoS2/graphene nanoarchitecture was synthesized by a facile one-step hydrothermal route using graphite oxide, thioacetamide, and CoCl2·6H2O as the starting materials. The growth of CoS2 and the reduction of the graphite oxide occur simultaneously. CoS2 nanocrystals with a size of 100−150 nm are uniformly anchored on the both sides of the graphene nanosheets, forming a unique CoS2/graphene hybrid nanostructure. The electrochemical tests showed that the nanocomposite exhibits obviously enhanced Li-storage properties compared with bare CoS2. The improvement in electrochemical properties could be attributed to the formation of two-dimensional conductive networks, homogeneous dispersion and immobilization of CoS2 nanoparticles, and the enhanced wetting of active material with the electrolyte by in situ introduced graphene nanosheets.Graphical abstractHighlights► We synthesized CoS2/graphene nanoarchitecture by a facile one-pot route. ► CoS2/graphene exhibits improved Li-storage properties than bare CoS2. ► The graphene offers combined buffering, conducting, and immobilizing effects.
Co-reporter:Yi Chen;Michele D. Nielsen;Yi-Bin Gao;Tie-Jun Zhu;Xinbing Zhao;Joseph P. Heremans
Advanced Energy Materials 2012 Volume 2( Issue 1) pp:58-62
Publication Date(Web):
DOI:10.1002/aenm.201100460
Co-reporter:Lipeng Hu, Hongli Gao, Xiaohua Liu, Hanhui Xie, Junjie Shen, Tiejun Zhu and Xinbing Zhao
Journal of Materials Chemistry A 2012 vol. 22(Issue 32) pp:16484-16490
Publication Date(Web):25 Jun 2012
DOI:10.1039/C2JM32916F
Decoupling of interdependent thermoelectric parameters was considered as a crucial strategy to enhance the thermoelectric performance of bulk materials. Here multi-scale microstructural effects have been introduced by a simple hot deformation process to obtain high-performance n-type bismuth telluride based alloys. Highly preferred orientation enables a significant improvement in in-plane electrical conductivity. The donor-like effect (an interaction of antisite defects and vacancies), which can be adjusted by varying hot deformation temperature, was also considered responsible for the remarkable enhancement in power factor. Besides, the in-plane lattice thermal conductivity was greatly reduced by in situ nanostructures and high-density lattice defects generated during the hot deformation process. The present study experimentally demonstrates a successful combination of microscale texture enhancement, atomic scale lattice defects and donor-like effect and recrystallization induced nanostructures as a new approach to improve thermoelectric properties. These effects led to a maximum ZT of 0.95 for the Bi2Te2Se1 sample hot deformed at 823 K, about 80% improvement over that without hot deformation.
Co-reporter:L.P. Hu, X.H. Liu, H.H. Xie, J.J. Shen, T.J. Zhu, X.B. Zhao
Acta Materialia 2012 Volume 60(Issue 11) pp:4431-4437
Publication Date(Web):June 2012
DOI:10.1016/j.actamat.2012.05.008
Abstract
Repetitive hot deformation has been demonstrated as a new approach to obtain high-performance n-type bismuth–telluride-based alloys, benefiting from the deformation-induced lattice defects and texture enhancement. X-ray diffraction measurement showed that the oriented textures were greatly enhanced after repetitive hot deformation of the alloys with a quasi-layered crystal structure. The electrical conductivity was remarkably improved by the deformation-induced donor-like defect and texture enhancement, while the Seebeck coefficient remained almost unchanged, and consequently the room temperature power factor was significantly increased from 1.3 W m−1 K2, before hot deformation, to 2.9 W m−1 K2 after four hot deformations. The in-plane lattice thermal conductivity was also largely reduced by the generated high-density lattice defects during the hot-deformation process. The maximum ZT value for the repetitively hot-deformed samples reached 1.0 at 513 K, suggesting that the simple new top-down method is very promising for large-scale production of high-performance bismuth–telluride-based polycrystalline bulk materials.
Co-reporter:Zhao Yang, Hongming Yu, Chunyang Wu, Gaoshao Cao, Jian Xie, Xinbing Zhao
Journal of Materials Science & Technology 2012 Volume 28(Issue 9) pp:823-827
Publication Date(Web):September 2012
DOI:10.1016/S1005-0302(12)60137-6
Co-reporter:Zhengliang Du, Tiejun Zhu, Xinbing Zhao
Materials Letters 2012 Volume 66(Issue 1) pp:76-78
Publication Date(Web):1 January 2012
DOI:10.1016/j.matlet.2011.08.031
N-type Mg2Si0.58Sn0.42 − xBix (0 ≤ x ≤ 0.015) compounds were prepared by melting the element metals in sealed tantalum tubes followed by hot pressing. The XRD results indicate that all samples are composites containing both major magnesium silicide solution phase and minor magnesium stannide solution phase. The Hall measurements show that the carrier concentrations and electrical conductivities increase with the increase of Bi doping amount. It was found that the intrinsic excitation shifts to high temperature due to Bi doping, which leads to the increase of the peak-temperatures of the Seebeck coefficient. The maximum dimensionless figure of merit is 0.65 at 700 K for the sample x = 0.015.Highlights► Mg2Si0.58Sn0.42 alloys have been prepared by melting in sealed tantalum tubes. ► Evaporation and oxidation of Mg are eliminated during the melting. ► Bi is an efficient dopant for Mg2Si with a solubility > 0.015 mol%. ► The ZTmax of 0.65 was obtained at 700 K for the 0.015 mol% Mg doped material.
Co-reporter:Yuan-Li Ding;Jian Xie;Gao-Shao Cao;Tie-Jun Zhu;Hong-Ming Yu
Advanced Functional Materials 2011 Volume 21( Issue 2) pp:348-355
Publication Date(Web):
DOI:10.1002/adfm.201001448
Abstract
Single-crystalline nanotubes of spinel LiMn2O4 with a diameter of about 600 nm, a wall thickness of about 200 nm and a length of 1–4 μm have been synthesized via a template-engaged reaction using β-MnO2 nanotubes as a self-sacrifice template. In this fabrication, a minimal structural reorganization can be responsible for the chemical transformation from [001]-oriented β-MnO2 template to [110]-oriented LiMn2O4. Galvanostatic charge/discharge measurements indicate that the nanotubes exhibit superior high-rate capabilities and good cycling stability. About 70% of its initial capacity can be retained after 1500 cycles at 5 C rate. Importantly, the tubular nanostructures and the single-crystalline nature of the most LiMn2O4 nanotubes are also well preserved after prolonged charge/discharge cycling at a relatively high current density, indicating good structural stability of the single-crystalline nanotubes during lithium intercalation/deintercalation process. As is confirmed from Raman spectra analyses, no evident microstructural changes occur upon long-term cycling. These results reveal that single-crystalline nanotubes of LiMn2O4 will be one of the most promising cathode materials for high-power lithium ion batteries.
Co-reporter:Y.L. Ding, C.Y. Wu, H.M. Yu, J. Xie, G.S. Cao, T.J. Zhu, X.B. Zhao, Y.W. Zeng
Electrochimica Acta 2011 Volume 56(Issue 16) pp:5844-5848
Publication Date(Web):30 June 2011
DOI:10.1016/j.electacta.2011.04.071
Coaxial MnO/C nanotubes with an average diameter of about 450 nm, a wall thickness of about 150 nm, a length of 1–5 μm and a 10 nm thick carbon layer have been prepared using β-MnO2 nanotubes as self-templates in acetylene at 600 °C. The microstructure of the product has been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. The electrochemical performance of the product has been evaluated by galvanostatic charge/discharge cycling. It is found that the product exhibits a reversible capacity of nearly 500 mAh g−1 at a current density of 188.9 mA g−1, and 83.9% of capacity retention, higher than bare MnO nanotubes (58.2%) and MnO nanoparticles (25.8%). The results reveal that coaxial MnO/C nanotubes would be a promising anode material for next-generation lithium-ion batteries.Graphical abstractHighlights► Coaxial MnO/C nanotube with an average diameter of about 450 nm, a wall thickness of about 150 nm, a length of 1-5 μm and a 10 nm thick carbon layer has been prepared based on an in-situ reduction route in acetylene using β-MnO2 nanotubes as self-templates. ► The product exhibits higher rate capability and cycling performance than bare MnO nanotubes and nanoparticles. ► The coaxial carbon layer and one-dimensional structures for MnO/C nanotubes are responsible for the improved rate capabilities and cycling performance. ► The coaxial carbon layer of MnO/C nanotubes is beneficial to improving the electric conductivity and protecting MnO from electrolyte etching.
Co-reporter:Jiaohui Zhang, Jian Xie, Chunyang Wu, Gaoshao Cao, Xinbing Zhao
Journal of Materials Science & Technology 2011 Volume 27(Issue 11) pp:1001-1005
Publication Date(Web):November 2011
DOI:10.1016/S1005-0302(11)60177-1
Co-reporter:Wujun Qiu, Shenghui Yang, Xinbing Zhao
Thin Solid Films 2011 Volume 519(Issue 19) pp:6399-6402
Publication Date(Web):29 July 2011
DOI:10.1016/j.tsf.2011.04.106
Antimony telluride thin film electrochemically deposited in a triethanol based alkaline electrolyte features amorphous structure, high electrical resistance, as well as fine morphology, minor impurity incorporation and anti-corrosivity. To further improve film thermoelectric performance, this film was subjected to hot-uniaxial-press (HUP) treatment at 170–250 °C. HUP treated films revealed crystallized structures, and exhibited 2–3 orders of magnitude improvement of electrical conductance. The [TeO32−]/[SbO2−] of the deposition electrolyte was utilized to fine tune film composition and thermal electrical performance. Ni diffusion from the substrate into the film was also studied, and it can be reduced by using lower temperature and shorter time of HUP treatment. Film Seebeck coefficient and power factor reached 138 μV/K and 337 μW/K2∙m, respectively, at elaborated deposition and HUP conditions.
Co-reporter:Sheng-nan Zhang;Guang-yu Jiang;Tie-jun Zhu
International Journal of Minerals, Metallurgy, and Materials 2011 Volume 18( Issue 3) pp:
Publication Date(Web):2011 June
DOI:10.1007/s12613-011-0446-5
Nonstoichiometric ternary thermoelectric materials Ag0.84Sb1.15M0.01Te2.16 (M=Ce, Yb, Cu) were prepared by a direct melt-quench and hot press process. The carrier concentration of all the samples increased after doping. Thermoelectric properties, namely electrical conductivity, Seebeck coefficient, and thermal conductivity, were measured from 300 to 673 K. The phase transition occurring at about 418 K representing the phase transition from β-Ag2Te to α-Ag2Te influenced the electrical transport properties. The electrical conductivities of Ce and Yb doped samples increased after doping from 1.9×104 to 2.5×104 and 2.3×104 S·m−1, respectively, at 673 K. Also, at room temperature, the Seebeck coefficient of the Ce doped sample relatively increased corresponding to the high carrier concentration due to the changes in the band structure. However, all the thermal conductivities increased after doping at low temperature. Because of the higher thermal conductivity, the dimensionless figure of merit ZT of these doped samples has not been improved.
Co-reporter:Jina Cao;Gaoshao Cao;Hongming Yu;Jian Xie;Xinbing Zhao
Rare Metals 2011 Volume 30( Issue 1) pp:39-43
Publication Date(Web):2011 February
DOI:10.1007/s12598-011-0193-9
Spinel LiMn2O4 cathodes were coated with 1 mol% YF3. X-ray diffraction (XRD) analyses showed that Y and/or F did not enter the lattice of the LiMn2O4 crystal. Transmission electron microscopy (TEM) showed that a compact YF3 layer of 5–20 nm in thickness was coated onto the surface of LiMn2O4 particles. Scanning electron microscopy (SEM) observation showed that the YF3 coating caused the agglomeration of LiMn2O4 particles. The cycling test demonstrated that the YF3 coating can improve the electrochemical performance of LiMn2O4 at both 20 and 55°C. Moreover, YF3-coated LiMn2O4 exhibited an improved rate capability compared with the uncoated one at high rates over 5C. The immersion test in electrolytes showed that YF3-coated LiMn2O4 is more erosion resistant than the uncoated one.
Co-reporter:Y. L. Ding ; J. Xie ; G. S. Cao ; T. J. Zhu ; H. M. Yu ;X. B. Zhao
The Journal of Physical Chemistry C 2011 Volume 115(Issue 19) pp:9821-9825
Publication Date(Web):April 22, 2011
DOI:10.1021/jp201669x
Al-doped LiMn2O4 nanotubes have been synthesized using β-MnO2 nanotubes as self-templates. Singe-crystalline structure of the Al-doped spinel was verified by high-resolution transmission electron microscopy and selected area electron diffraction techniques. Galvanostatic charge/discharge tests indicate that the Al-doped single-crystalline spinel nanotube delivers a discharge capacity of 110 mAh g–1 at 0.1C rate and retains about 80% of its initial capacity after 200 cycles at 5C rate at 55 °C, indicating superior elevated-temperature cycling performance at a high current rate. Furthermore, high crystallinity, single-crystalline nature, and tubular morphology can be well preserved after aging tests for 30 days at 55 °C, revealing their good structural stability.
Co-reporter:W. J. Qiu;S. H. Yang;T. J. Zhu;J. Xie;X. B. Zhao
Journal of Electronic Materials 2011 Volume 40( Issue 7) pp:1506-1511
Publication Date(Web):2011 July
DOI:10.1007/s11664-011-1647-4
A new alkaline electrolyte containing SbO2−, TeO32−, triethanolamine, and diaminourea polymer (DAUP) was used to deposit Sb2Tex (2 < x < 6) films. Deaeration of the electrolyte with argon was applied to eliminate oxygen interference. Hot uniaxial pressing (HUP) was chosen as the posttreatment process for the deposited films. DAUP can significantly increase the tellurium content in the deposited film, with little influence on deposition thermodynamics. The as-deposited films exhibited amorphous crystal structure. Argon deaeration proved to be favorable for improving the Seebeck coefficient of the films because oxygen contamination was reduced. HUP treatment reduced the electrical resistance of the films by orders of magnitude. The maximum Seebeck coefficient and power factor of 532 μV K−1 and 1.58 mW m−1 K−2, respectively, were obtained with DAUP and argon deaeration, followed by HUP posttreatment.
Co-reporter:Jun-Jie Shen, Tie-Jun Zhu, Xin-Bing Zhao, Sheng-Nan Zhang, Sheng-Hui Yang and Zhen-Zhong Yin
Energy & Environmental Science 2010 vol. 3(Issue 10) pp:1519-1523
Publication Date(Web):12 Aug 2010
DOI:10.1039/C0EE00012D
Recrystallization induced in situ nanostructure formation was used as a new means to obtain high performance polycrystalline thermoelectric materials, which was realized by a simple hot forging process to the coarse-grained Bi0.5Sb1.5Te3 alloys. The pole figure measurement showed that the oriented textures were weakened or eliminated after hot forging of the alloys with a quasi-layered crystal structure, implying the presence of deformation recrystallization. Transmission electron microscopy observation revealed the recrystallization induced in situ nanostructures and high density of defects in the hot forged samples. Transport property measurements indicated that the hot forged samples had both increased electrical power factor and reduced thermal conductivity, compare to the initial alloys without hot forging. The maximum ZT values of >1.3 at room temperature were reproducibly obtained for the hot forged samples, suggesting that the simple new method can be applied for large scale production of high performance polycrystalline thermoelectric materials with in situ nanostructures.
Co-reporter:Y.P. Jiang, J. Xie, G.S. Cao, X.B. Zhao
Electrochimica Acta 2010 Volume 56(Issue 1) pp:412-417
Publication Date(Web):15 December 2010
DOI:10.1016/j.electacta.2010.08.060
Nanosized Li4Mn5O12 has been synthesized by a spray-drying-assisted solid state method. The effect of spray drying and drying temperature on the microstructure and electrochemical performance of the final products has been investigated. The microstructure of the products has been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The electrochemical performance of the products has been studied by galvanostatic cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It has been found that the products prepared with a spray-drying pretreatment of the precursor exhibit a smaller grain size and a narrower size distribution than that prepared without the pretreatment. Among the three samples with a precursor pretreatment, that pretreated at 250 °C shows the best electrochemical performance due to the smallest grain size of below 50 nm and the narrowest size distribution.
Co-reporter:S.N. Zhang, T.J. Zhu, S.H. Yang, C. Yu, X.B. Zhao
Acta Materialia 2010 Volume 58(Issue 12) pp:4160-4169
Publication Date(Web):July 2010
DOI:10.1016/j.actamat.2010.04.007
Abstract
Nonstoichiometric ternary thermoelectric materials Ag2−ySbyTe1+y (y = 1.26, 1.29, 1.32, 1.35, and 1.38) were prepared by a direct melt-quench and hot press process. In situ composites of AgSbTe2 and Sb2Te3 were obtained over the entire composition range with a typical Widmanstätten pattern. Thermoelectric properties were measured from 300 K to 673 K, which changed systematically with Sb2Te3 ratio. The phase transition occurring at about 633 K, forming the single phased AgSbTe2, can significantly influence the electrical transport properties. Various crystallographic defects in different scales, such as atomic ordering, nanodomains, dislocations and stacking faults, have been observed by high-resolution transmission electron microscopy and their influences on lattice thermal conductivity have been discussed. Due to the extremely low thermal conductivity (about 0.6 W m−1 K−1) and large positive Seebeck coefficient of ∼250 μV K−1 detected in Ag0.71Sb1.29Te2.29, the maximum dimensionless figure of merit ZT of 1.37 was obtained at 600 K.
Co-reporter:Jina Cao, Hongquan Liu, Jian Xie, Gaoshao Cao, Xinbing Zhao
Journal of Materials Science & Technology 2010 Volume 26(Issue 7) pp:669-672
Publication Date(Web):July 2010
DOI:10.1016/S1005-0302(10)60104-1
Ca3Co4O9 (CCO) and Ca2.95K0.05Co4O9 (CKCO) powders have been prepared by the polyacrylamide gel method. CKCO shows increased capacity and better cycling stability compared with CCO. After cycled for 50 cycles at 0.5 C, CKCO retains a capacity of 223 mAh·g−1, almost twice than CCO. The electrochemical impedance spectroscopy (EIS) tests shows the CKCO sample has a lower initial charge transfer resistance (Rct) and undergoes smaller Rct change during cycling than the CCO sample, indicating improved electrochemical performance by K-doping.
Co-reporter:A.J. Zhou, X.B. Zhao, T.J. Zhu, S.H. Yang, T. Dasgupta, C. Stiewe, R. Hassdorf, E. Mueller
Materials Chemistry and Physics 2010 Volume 124(2–3) pp:1001-1005
Publication Date(Web):1 December 2010
DOI:10.1016/j.matchemphys.2010.08.017
Polycrystalline higher manganese silicides (HMS) with SiGe-additions were synthesized and their microstructure and thermoelectric properties were investigated. The SiGe-addition was found to have introduced dual effects, namely the substitution of Ge and the precipitation of Si–Ge phases. The volume ratio of MnSi striations in HMS was decreased by increasing amount of SiGe-addition, while the Si–Ge precipitations with various Si/Ge ratios were simultaneously formed. The electrical conductivity and the electronic contribution of the thermal conductivity were increased by SiGe-addition. However, the Seebeck coefficient showed insignificant change and the phonon thermal conductivity was effectively reduced, which was attributed to the enhanced scattering of phonons resulted by the substitution of Ge atoms for Si. The maximum ZT of 0.5 was achieved in polycrystalline MnSi1.733–2%SiGe at 550 °C showing 25% improvement compared to the pure HMS.
Co-reporter:Wu-jun Qiu;Sheng-nan Zhang;Tie-jun Zhu
International Journal of Minerals, Metallurgy, and Materials 2010 Volume 17( Issue 4) pp:489-493
Publication Date(Web):2010 August
DOI:10.1007/s12613-010-0346-0
A new basic electrolyte with two cationic plating additives, polydiaminourea and polyaminosulfone, was investigated for the electrochemical deposition of the bismuth telluride film on a nickel-plated copper foil. Tellurium starts to deposit at a higher potential (−0.35 V) than bismuth (−0.5 V) in this electrolyte. The tellurium-to-bismuth ratio increases while the deposition potential declines from −1 to −1.25 V, indicating a kinetically quicker bismuth deposition at higher potentials. The as-deposited film features good adhesion to the substrate and smooth morphology, and has a nearly amorphous crystal structure disclosed by X-ray diffraction patterns.
Co-reporter:A.J. Zhou, X.B. Zhao, T.J. Zhu, T. Dasgupta, C. Stiewe, R. Hassdorf, E. Mueller
Intermetallics 2010 Volume 18(Issue 11) pp:2051-2056
Publication Date(Web):November 2010
DOI:10.1016/j.intermet.2010.06.008
Higher manganese Silicides (HMS) were found to decompose into MnSi phase in the ball milling process. Effects of the ball milling parameters on the phase decomposition and on the mean grain size of powders were studied. The decomposition was understood as a mechanochemical effect induced by the high-energy mechanical colliding during ball milling, where the structural features of HMS were supposed to play an important role for the decomposition. The ball milling behaviours of HMS were interpreted in terms of their relationships with the grain size ranges. Grain size effects on the structural stability and the corresponding mechanochemical decomposition were also discussed. Meanwhile, HMS powders down to a few tens of nanometers without noticeable MnSi by-product were achieved by optimizing the ball milling parameters, which supported the idea of functional designs using low-dimensional HMS materials.
Co-reporter:Sheng-Nan Zhang, Jian He, Tie-Jun Zhu, Xin-Bing Zhao, Terry M. Tritt
Journal of Non-Crystalline Solids 2009 Volume 355(Issue 2) pp:79-83
Publication Date(Web):15 January 2009
DOI:10.1016/j.jnoncrysol.2008.10.014
Bulk amorphous chalcogenide samples of Ge20Te80−xSex (x = 0, 1, 2, 8) have been prepared using a melting-quench method, and characterized by the differential scanning calorimetry, X-ray powder diffraction, high-resolution transmission electron microscopy, specific heat and thermal conductivity measurements. The low temperature specific heat measurements identified some localized low-frequency oscillation modes (Einstein modes) in conjunction with a Debye-like behavior. It was found that with increasing Se concentration the characteristic Debye temperature did not change whereas the Einstein temperature slightly decreased. The lattice thermal conductivity of all Ge20Te80−xSex samples exhibited typical amorphous heat conduction behavior, which has been discussed in connection with the phonon mean free path and in the context of a phenomenological model of heat conduction for highly disordered system.
Co-reporter:H.Q. Liu, Y. Song, S.N. Zhang, X.B. Zhao, F.P. Wang
Journal of Physics and Chemistry of Solids 2009 Volume 70(3–4) pp:600-603
Publication Date(Web):March–April 2009
DOI:10.1016/j.jpcs.2009.01.003
The Ca3−xYxCo4O9+δ (x=0, 0.15, 0.3) ceramics were prepared by combining the polyacrylamide gel method and the spark plasma sinter (SPS) technology in order to improve the thermoelectric properties of Ca3Co4O9+δ ceramics. The Seebeck coefficients and the resistivities of the Y-doped samples were obviously enhanced due to the decrease of carrier concentration, and their thermal conductivities were decreased due to the impurity scattering effect. The thermoelectric properties were improved at high temperature by Y-doping according to the power factor analysis and the thermoelectric figure of merit (ZT) data. The optimized figure of merit ZT=0.22 at 973 K was obtained for Ca2.7Y0.3Co4O9+δ.
Co-reporter:Jianli Mi;Xinbing Zhao;Tiejun Zhu
Rare Metals 2009 Volume 28( Issue 3) pp:237-240
Publication Date(Web):2009 June
DOI:10.1007/s12598-009-0046-y
Nanostructured skutterudite-related compound Fe0.25Ni0.25Co0.5Sb3 was synthesized by a solvothermal method using FeCl3, NiCl2, CoCl2, and SbCl3 as the precursors and NaBH4 as the reductant. The solvothermally synthesized powders consisted of fine granules with an average particle size of tens of nanometers. The bulk material was prepared by hot pressing the powders. Transport property measurements indicated a heavily doped semiconductor behavior with n-type conduction. The thermal conductivity is about 1.83 W·m−1·K−1 at room temperature and decreases to 1.57 W·m−1·K−1 at 673 K. The low thermal conductivity is attributed to small grain size and high porosity. A maximum dimensionless figure of merit of 0.15 is obtained at 673 K.
Co-reporter:J.L. Mi, X.B. Zhao, T.J. Zhu, J. Ma
Journal of Alloys and Compounds 2008 Volume 452(Issue 2) pp:225-229
Publication Date(Web):20 March 2008
DOI:10.1016/j.jallcom.2006.11.037
Thermoelectric properties of skutterudites FexNiyCo1−x−ySb3 (x = y = 0, 0.125, 0.25, 033, 0.375) have been reported. FexNiyCo1−x−ySb3 compounds were synthesized by direct reactions between the elements. Both p-type and n-type thermoelectric materials can be obtained in FexNiyCo1−x−ySb3 system. The electrical conductivity measurements showed typical semiconductor behavior. The values of thermal conductivity at room temperature were substantially reduced from 9 to 3 W m−1 K−1 by the substitution of Fe and Ni for Co in CoSb3. The highest figure of merit (ZT) of 0.16 is obtained for Fe0.375Ni0.375Co0.25Sb3 at 610 K.
Co-reporter:A.J. Zhou, T.J. Zhu, X.B. Zhao, H.Y. Chen, E. Müller
Journal of Alloys and Compounds 2008 Volume 449(1–2) pp:105-108
Publication Date(Web):31 January 2008
DOI:10.1016/j.jallcom.2005.12.127
P-type perovskite oxides La1−xSrxCoO3 (x = 0, 0.1) have been prepared by solid state reactions and sol–gel processes. The Seebeck coefficient, electrical conductivity and thermal conductivity of the samples have been investigated. It is found that substitution of Sr for La significantly improved the electrical conductivity but reduced the Seebeck coefficients and thermal conductivity. The samples with the same composition prepared from different routes distinguished from each other in morphologies but exhibited similar conductive mechanism and had the same energy gap Eg and motional enthalpy ΔHm. The effects of density on electrical and thermal conductivity were obvious. The room-temperature ZT value of the sol–gel derived La0.9Sr0.1CoO3 was 0.046, which is comparable to that of the single crystal NaCo2O4 (ZT = 0.03).
Co-reporter:H.Y. Chen, X.B. Zhao, T.J. Zhu, J.Z. Jiang, C. Stiewe, C. Lathe, E. Mueller
Journal of Physics and Chemistry of Solids 2008 Volume 69(Issue 8) pp:2013-2018
Publication Date(Web):August 2008
DOI:10.1016/j.jpcs.2008.02.012
The dynamic phase transformation and structure of rapidly solidified Fe1−xCoxSi2 (0.02⩽x⩽0.06) thermoelectric materials were in situ investigated under high temperatures and high pressures by energy dispersive X-ray diffraction using synchrotron radiation. The FeSi2 alloys which solidified as α-Fe2Si5 and ε-FeSi eutectic structures, were transformed to the semiconducting β-FeSi2 phase upon heating by the main reaction α+ε→β and the subsidiary reaction α→β+Si. The low heating rates and Co contents were found to be beneficial for the β phase formation. The decomposition temperature of β→α+ε was weakly dependent on heating rate, but significantly suppressed by the high pressures.
Co-reporter:J.L. Mi, X.B. Zhao, T.J. Zhu, J.P. Tu
Materials Letters 2008 Volume 62(Issue 15) pp:2363-2365
Publication Date(Web):31 May 2008
DOI:10.1016/j.matlet.2007.11.088
Nanostructuring is one of the effective approaches to lower the thermal conductivity of materials. Nanosized La filled CoSb3 was successfully synthesized by a solvothermal-annealing method. It shows that the La atoms were filled into the lattice cages during the annealing process. The average size of the powders after annealing process is about 20 nm, a little larger than the solvothermally prepared powders. The bulk sample was prepared by hot pressing. Electrical properties measurements were performed and the highest power factor is about 0.43 × 10− 3 Wm− 1K− 2 obtained at 520 K.
Co-reporter:A. J. Zhou;T. J. Zhu;X. B. Zhao
Journal of Materials Science 2008 Volume 43( Issue 5) pp:1520-1524
Publication Date(Web):2008 March
DOI:10.1007/s10853-007-2365-4
P-type perovskite oxides La1−xSrxCoO3 (0 ≤ x ≤ 0.2) have been prepared using a polymerlized complex method and sintering. The Seebeck coefficient, electrical conductivity, and thermal conductivity of the oxides were studied from room temperature to 773 K. The ln(σT)−1/T relationships revealed small-polaron hopping mechanism for the higher Sr contents. Large Seebeck coefficients were observed in lightly Sr-doped samples. Sr doping greatly reduced the Seebeck coefficient and enhanced the electrical and thermal conductivity of the samples. The temperature-induced spin-state transition of Co3+ ions strongly influenced the transport properties. The highest ZT value found in this series of oxides was 0.046 at 300 K for x = 0.1.
Co-reporter:H.Y. Chen, X.B. Zhao, C. Stiewe, D. Platzek, E. Mueller
Journal of Alloys and Compounds 2007 Volume 433(1–2) pp:338-344
Publication Date(Web):16 May 2007
DOI:10.1016/j.jallcom.2006.06.080
Iron disilicide based alloys Fe0.94Co0.06Si2.00 were prepared by rapid solidification and hot uniaxial pressing. The effects of pre-annealing of the powders and hot pressing temperature on the microstructures and thermoelectric properties were investigated. X-ray diffraction and scanning electron microscopy show that after pre-annealing at 800 °C for only 2 h, the high temperature phases (α-Fe2Si5 and ɛ-FeSi) in the rapidly solidified powders have been completely transformed to β-FeSi2 phase, while the fine grain structures were maintained. It is found that the grain growth during hot pressing was successfully suppressed for the pre-annealed samples, especially at a lower pressing temperature of 880 °C. The Seebeck coefficient was markedly enhanced by the pre-annealing treatment, also by a lower pressing temperature, while both the electrical conductivity and the thermal conductivity were decreased by them. The maximum dimensionless figure of merit ZT = 0.25 at 908 K was obtained for Fe0.94Co0.06Si2.00, which is pre-annealed, followed by hot pressing at 880 °C with 70 MPa for 30 min.
Co-reporter:Y.H. Zhang, T.J. Zhu, J.P. Tu, X.B. Zhao
Materials Chemistry and Physics 2007 Volume 103(2–3) pp:484-488
Publication Date(Web):15 June 2007
DOI:10.1016/j.matchemphys.2007.02.059
Co-reporter:Dagao Zhuang, Xinbing Zhao, Jian Xie, Jian Tu, Tiejun Zhu, Gaoshao Cao
Acta Physico-Chimica Sinica 2006 Volume 22(Issue 7) pp:840-844
Publication Date(Web):July 2006
DOI:10.1016/S1872-1508(06)60037-5
Nb-doped LiFePO4/C was synthesized using one-step solid-state method. The effect of Nb contents on the electrochemical performance was investigated. The results showed that the electrochemical performances were remarkably promoted. The discharge capacities of Li0.96Nb0.008FePO4/C cathode materials were 161, 148, and 132 mAh·g−1 at the charge and discharge current rates of 0.5C, 1C, and 2C, respectively. The results of cyclic voltammetry and EIS analyses showed that the resistance and polarization of the LiFePO4/C composite electrode could be effectively decreased by Nb doping, which would improve the electronic conductivity of LiFePO4.
Co-reporter:A.J. Zhou, T.J. Zhu, X.B. Zhao
Materials Science and Engineering: B 2006 Volume 128(1–3) pp:174-178
Publication Date(Web):15 March 2006
DOI:10.1016/j.mseb.2005.11.032
P-type perovskite oxides La1−xSrxCoO3 (x = 0, 0.1) have been prepared by solid state reactions. The phase structures and microstructures of the oxides were investigated and the Seebeck coefficient, electrical conductivity and thermal conductivity were measured from room temperature to 773 K. It was found that Sr substitution can improve the electrical conductivity but significantly reduce the Seebeck coefficient of La1−xSrxCoO3. The thermal conductivity was also reduced after Sr substitution. In the measured temperature range, the maximum ZT values of the oxides were 0.015 at 673 K for x = 0 and 0.013 at 423 K for x = 0.1. Optimizations of the materials are necessary for the practical applications of La1−xSrxCoO3 oxides.
Co-reporter:X. B. Zhao, T. Sun, T. J. Zhu and J. P. Tu
Journal of Materials Chemistry A 2005 vol. 15(Issue 16) pp:1621-1625
Publication Date(Web):14 Feb 2005
DOI:10.1039/B500759C
Bi2Te3 nanocapsules with hollow structure have been successfully synthesized by a low temperature aqueous chemical route in an open system at 65 °C. The nanocapsules are 50–200 nm in diameter and 100–800 nm in length. The tube walls have a thickness of about 6 nm with the normal parallel to the c-axis of the Bi2Te3 crystal lattice. Chemical reactions during synthesis and the formation of the nanocapsules were investigated in-situ.
Co-reporter:X.H. Ji, X.B. Zhao, Y.H. Zhang, B.H. Lu, H.L. Ni
Journal of Alloys and Compounds 2005 Volume 387(1–2) pp:282-286
Publication Date(Web):25 January 2005
DOI:10.1016/j.jallcom.2004.06.047
Rare earth (RE) (Ce, Sm and Er) containing bismuth telluride nano-powders were synthesized in ethanol at 150 °C for 24 h by solvothermal processes using rare earth oxides, bismuth chloride, tellurium powders as the precursors. Bulk thermoelectric (TE) materials were prepared by hot-pressing the powders in a vacuum of about 0.1 Pa with a pressure of 65 MPa at 300 °C for 30 min. The rare earth contents in the Bi2Te3 based compounds were about 3–4 at.%. They occupy the Bi-position in the Bi2Te3 lattice and act as n-type dopant in Bi2Te3 based semiconductors. Texture with the Bi2Te3 (0 0 1) planes parallel to the disk base-face formed during hot-pressing of the solvothermally synthesized nano-powder. A maximal figure of merit ZT ≈ 0.22 has been obtained for a sample of Ce–Bi2Te3 at about 450 K.
Co-reporter:C.H. Mi, G.S. Cao, X.B. Zhao
Materials Letters 2005 Volume 59(Issue 1) pp:127-130
Publication Date(Web):January 2005
DOI:10.1016/j.matlet.2004.07.051
Carbon-coated LiFePO4 cathode materials were synthesized by a one-step solid-state reaction route using inexpensive FePO4 as the iron precursor and polypropylene as both reductive agent and carbon source. The pyrolysis of polypropylene at high temperature reduces Fe3+ to Fe2+ and coats carbon on the synthesized LiFePO4 particles in situ. Electrochemical measurements show that the carbon-coated LiFePO4 reaches an initial discharge capacity of 160 mA h g−1 at 30 °C and 0.1 C rate and a good cycling property at 0.3 and 0.5 C. The results indicate that the one-step solid-state reaction is a promising method suitable for mass production of LiFePO4/C composite with improved electrochemical performances and low cost.
Co-reporter:X.H. Ji, X.B. Zhao, Y.H. Zhang, B.H. Lu, H.L. Ni
Materials Letters 2005 Volume 59(Issue 6) pp:682-685
Publication Date(Web):March 2005
DOI:10.1016/j.matlet.2004.11.008
Novel nano-sized lanthanum contained Bi2Te3 and Bi2Se0.3Te2.7 powders have been synthesized in ethanol at 150 °C for 24 h via solvothermal processes. It was found that alloying of lanthanum in both Bi2Te3 and Bi2Se0.3Te2.7 does not change their crystal structures. The maximal dimensionless figure of merit measured is about 0.11 for La–Bi2Se0.3Te2.7 at 450 K. However, the very low thermal conductivity of 0.4–0.5 W (m K)−1 and the moderate Seebeck coefficient of about 170 μV K−1 indicate the potential to improve the thermoelectric properties of the material by doping optimization.
Co-reporter:H.L. Ni, T.J. Zhu, X.B. Zhao
Materials Science and Engineering: B 2005 Volume 117(Issue 2) pp:119-122
Publication Date(Web):15 March 2005
DOI:10.1016/j.mseb.2004.11.001
Nanosized Bi2Te3 based powders with the designed compositions of Bi2Tex (x = 2.85, 3.00, 3.15, 3.30, 3.45) have been synthesized by hydrothermal method. Bulk thermoelectric materials with crystal sizes smaller than 200 nm have been obtained by hot pressing of the hydrothermally synthesized Bi2Te3 based powders. It was found that all samples are n-type. A maximum power factor of 2.35 × 10−3 W m−1 K−2 was obtained at 312 K in the sample with a nominal composition of Bi2Te3.30.
Co-reporter:H.Y. Chen, X.B. Zhao, T.J. Zhu, Y.F. Lu, H.L. Ni, E. Müller, A. Mrotzek
Intermetallics 2005 Volume 13(Issue 7) pp:704-709
Publication Date(Web):July 2005
DOI:10.1016/j.intermet.2004.12.019
Aluminium doped iron disilicide based thermoelectric materials FeAlxSi2 (x=0.05, 0.10) were prepared by rapid solidification, nitrogenizing treatment and hot uniaxial pressing. β-FeSi2 phase with dispersed silicon have been obtained for all the hot-pressed samples after annealing at 1073 K for 20 h. The Seebeck coefficient α, electrical conductivity σ and thermal conductivity κ were measured from room temperature to 973 K. It was found that the Seebeck coefficients were markedly enhanced by the nitrogenizing treatment, but they decreased with increasing aluminium concentration x. The nitrogenizing treatment also significantly decreased the thermal conductivities of the Al-doped samples, especially for the sample with higher aluminium concentration. The maximum figure of merit of Z=1.55×10−4 K−1 at 743 K was obtained for FeAl0.05Si2 without nitrogenizing. It is concluded that nitrogenizing treatment is promising to improve the thermoelectric properties for more heavily Al-doped FeSi2.
Co-reporter:X.B. Zhao, H.Y. Chen, E. Müller, C. Drasar
Journal of Alloys and Compounds 2004 Volume 365(1–2) pp:206-210
Publication Date(Web):25 February 2004
DOI:10.1016/S0925-8388(03)00673-X
Fine crystallinity may improve the figure of merit of iron disilicide-based thermoelectric materials. Manganese doped iron disilicide based alloys with the chemical composition of Fe1.92Mn0.08Si5 have been prepared by rapid solidification and hot uniaxial pressing (HUP), and the microstructure development during the preparation has been studied. Textures have been found in the annealed samples hot-pressed from the melt spun ribbon powders. Large polyhedral silicon grains with a size of about 2 μm and small silicon rods about 200 nm in diameter have been observed in the annealed samples, which are considered to be formed during HUP at about 900 °C and annealing at 800 °C, respectively.
Co-reporter:X.B Zhao, X.H Ji, Y.H Zhang, B.H Lu
Journal of Alloys and Compounds 2004 Volume 368(1–2) pp:349-352
Publication Date(Web):14 April 2004
DOI:10.1016/j.jallcom.2003.08.070
Nanostructured materials are of much interest for improving the thermoelectric figure of merit. Bi2Te3 nanoparticles with average sizes of 15–20 nm and nanowires with a diameter less than 100 nm and a length of about 10 μm were prepared by solvothermal synthesis at 150 °C for 24 h using various solvents as the reaction medium and NaBH4 as the reductant. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses showed that the phase distributions, microstructures and grain sizes of the nanostructured Bi2Te3 are mainly related with the dielectric constant and surface tension of the solvent used in the solvothermal synthesis.
Co-reporter:J. Xie, G.S. Cao, X.B. Zhao
Materials Chemistry and Physics 2004 Volume 88(2–3) pp:295-299
Publication Date(Web):15 December 2004
DOI:10.1016/j.matchemphys.2004.06.045
Crystalline silicon has been deposited onto the surface of mesocarbon microbeads (MCMB) particles by chemical vapor deposition (CVD) using silane as the precursor gas. The microstructure of the Si-coated MCMB was characterized by Raman spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) analysis. It was found that the Si coated on the surface of MCMB particles exists in the crystalline state, and Si-coated MCMB exhibits increased reversible capacity compared to pristine MCMB without sacrificing its cycling behavior. As a result, Si-coated MCMB emerges as a promising anode material for secondary lithium-ion batteries.
Co-reporter:J. Xie, X.B. Zhao, G.S. Cao, M.J. Zhao, Y.D. Zhong, L.Z. Deng
Materials Letters 2003 Volume 57(Issue 30) pp:4673-4677
Publication Date(Web):December 2003
DOI:10.1016/S0167-577X(03)00383-5
Iron antimonide, FeSb2, has been prepared by levitation melting. The electrochemical cycling behaviors of FeSb2 were evaluated using lithium-ion model cell Li/LiPF6(EC+DMC)/FeSb2. It was found that the reversible capacity of FeSb2 in the first cycle reached 507 mA h g−1, and a reversible capacity of about 282 mA h g−1 was still maintained after 15 cycles. In our present work, we also found that the FeSb2/mesocarbon microbeads (MCMB) composite material possessed higher initial reversible capacity and better cycle life than pure FeSb2, which made it suitable for use as anode material in rechargeable lithium-ion batteries.
Co-reporter:Jiazhan Xin, Haijun Wu, Xiaohua Liu, Tiejun Zhu, Guanting Yu, Xinbing Zhao
Nano Energy (April 2017) Volume 34() pp:
Publication Date(Web):April 2017
DOI:10.1016/j.nanoen.2017.03.012
•Sb alloying in Mg2Si can suppress the lattice thermal conductivity, lower than conventional Mg2(Si,Sn) solid solutions.•Detailed microstructure observation for Sb alloyed Mg2Si reveal the existence of dense dislocations.•By introducing phonon scattering from dislocations, the model calculation can well match the experimental data.•This work offers a comprehensive understanding of the role of vacancies and dislocations in reducing thermal conductivity.Mg2Si based solid solutions have unique advantages in the direct thermal to electrical energy conversion due to environmentally friendly and abundant constituent elements, and high thermoelectric performance. Further enhancing figure of merit zT of this materials system lies in the reduction of the relatively high lattice thermal conductivity. Alloying by high content of aliovalent Sb (>10%) in Mg2Si can greatly suppress the lattice thermal conductivity, lower than conventional Mg2(Si,Sn) solid solutions, due to the enhanced phonon scattering from Mg vacancy and concomitant strains. In this work, detailed microstructure observation for Sb alloyed Mg2Si reveal the existence of dense dislocations, around which the strip-like defects are viewed with isotropic strain. By introducing dislocations and vacancies as the additional phonon scattering sources, the model calculation can well match the experimental lattice thermal conductivity. The present work offers a comprehensive understanding of the role of vacancies and concomitant strains in reducing thermal conductivity, and may open a new venue for zT enhancement.The high contents of aliovalent Sb alloying in Mg2Si not only result in Mg vacancy, but also induce dense dislocations with intensive strain accumulation, which act as extra phonon scatterers and contribute to the significantly reduced lattice thermal conductivity in the Sb alloyed Mg2Si, compared to the Sn alloyed Mg2Si with the same amount of Si sites substituted.
Co-reporter:Zhenglong Tang, Lipeng Hu, Tiejun Zhu, Xiaohua Liu and Xinbing Zhao
Journal of Materials Chemistry A 2015 - vol. 3(Issue 40) pp:NaN10603-10603
Publication Date(Web):2015/08/18
DOI:10.1039/C5TC02263K
Currently more than 60% of primary energy used in industry or life is lost as waste heat in the temperature range of 400–900 K, and much attention is paid to mid-temperature thermoelectric (TE) power generation. Here we combine several strategies, i.e. alloying, doping and hot deformation, to improve the TE performance of n-type bismuth telluride based TE alloys for mid-temperature power generation. Se alloying was adopted to widen the band gap and suppress intrinsic conduction at elevated temperatures. When Se atoms completely substitute the Te(2) atoms, the crystal structure of Bi2Te3 based alloys tends to be more ordered, resulting in the maximum value of the band gap. And the induced alloying scattering significantly reduces the lattice thermal conductivity. Then SbI3 donor doping was used to increase the electron concentration to further suppress the detrimental effects of bipolar conduction. Finally we applied repetitive hot deformations to further improve the figure of merit zT and a peak zT of ∼1.1 was obtained at about 600 K in the 0.1 at% SbI3–Bi2Te1.9Se1.1 alloy, which was hot-deformed three times. The results demonstrated the great potential of the alloy for application in mid-temperature TE power generation.
Co-reporter:Lipeng Hu, Hongli Gao, Xiaohua Liu, Hanhui Xie, Junjie Shen, Tiejun Zhu and Xinbing Zhao
Journal of Materials Chemistry A 2012 - vol. 22(Issue 32) pp:NaN16490-16490
Publication Date(Web):2012/06/25
DOI:10.1039/C2JM32916F
Decoupling of interdependent thermoelectric parameters was considered as a crucial strategy to enhance the thermoelectric performance of bulk materials. Here multi-scale microstructural effects have been introduced by a simple hot deformation process to obtain high-performance n-type bismuth telluride based alloys. Highly preferred orientation enables a significant improvement in in-plane electrical conductivity. The donor-like effect (an interaction of antisite defects and vacancies), which can be adjusted by varying hot deformation temperature, was also considered responsible for the remarkable enhancement in power factor. Besides, the in-plane lattice thermal conductivity was greatly reduced by in situ nanostructures and high-density lattice defects generated during the hot deformation process. The present study experimentally demonstrates a successful combination of microscale texture enhancement, atomic scale lattice defects and donor-like effect and recrystallization induced nanostructures as a new approach to improve thermoelectric properties. These effects led to a maximum ZT of 0.95 for the Bi2Te2Se1 sample hot deformed at 823 K, about 80% improvement over that without hot deformation.
Co-reporter:Bin Feng, Jian Xie, Gaoshao Cao, Tiejun Zhu and Xinbing Zhao
Journal of Materials Chemistry A 2013 - vol. 1(Issue 42) pp:NaN13119-13119
Publication Date(Web):2013/09/06
DOI:10.1039/C3TA13202A
Nanostructuring and second phase incorporation are considered to be promising ways of enhancing the thermoelectric performance of bulk materials. Here, a design principle is proposed which combines these two methods for improving the thermoelectric performance of p-type CoSb3 by fabricating a CoSb3/graphene (CoSb3/G) nanocomposite, where a second phase, graphene, is introduced in the nanostructured CoSb3 matrix via an in situ one-pot solvothermal route. In addition, CoSb3/G bulk materials were prepared by hot pressing the solvothermally synthesized CoSb3/G powder. It was found that addition of a small amount of graphene can drastically enhance the electrical conductivity due to the increase in both carrier concentration and mobility. In addition, the well dispersed graphene in the nanostructured CoSb3 matrix also contributes to the low lattice thermal conductivity. A dimensionless figure of merit ZT = 0.61 at 800 K has been obtained for the CoSb3/G nanocomposite, which is about a 130% improvement over that of graphene-free CoSb3 (∼0.26).
Co-reporter:Longhuan Liao, Hongtao Wang, Hui Guo, Peiyi Zhu, Jian Xie, Chuanhong Jin, Shichao Zhang, Gaoshao Cao, Tiejun Zhu and Xinbing Zhao
Journal of Materials Chemistry A 2015 - vol. 3(Issue 38) pp:NaN19375-19375
Publication Date(Web):2015/08/14
DOI:10.1039/C5TA05358G
Fe doping is widely used to improve the electrochemical performance of LiMnPO4 by “implanting” the merits of high rate capability and long cycle life of LiFePO4 into LiMnPO4. Nevertheless, great challenges still remain to obtain high-performance LiFexMn1−xPO4 at a low x value. In this work, we synthesized ultrathin LiFexMn1−xPO4 (x ≤ 0.15) nanoplates by a facile, controllable method. The plate-like LiFexMn1−xPO4 with a small lateral size (40–100 nm) and thickness (10–20 nm) exhibits high electrochemical activity, excellent rate capability and superior cycling stability after carbon coating. At a rate as high as 50C (8.5 A g−1), the LiFe0.15Mn0.85PO4/C composite can still yield a high discharge capacity of 96.2 mA h g−1 where the discharge process can be completed in only 40 s. LiFe0.15Mn0.85PO4/C can sustain a long-term cycling up to 1000 cycles at 10C with a capacity retention close to 70%. The fast and stable cycling ability of LiFexMn1−xPO4 makes it promising for applications in electric vehicles and hybrid electric vehicles.
Co-reporter:Can Cao, Jian Xie, Shichao Zhang, Bin Pan, Gaoshao Cao and Xinbing Zhao
Journal of Materials Chemistry A 2017 - vol. 5(Issue 14) pp:NaN6755-6755
Publication Date(Web):2017/03/09
DOI:10.1039/C7TA00416H
Lithium–oxygen (Li–O2) cells are receiving intense interest because of their extremely high energy density. A highly efficient catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a key factor influencing the performance of lithium–oxygen cells. In this work, we prepared a highly efficient CeO2-decorated δ-MnO2 (CeO2/δ-MnO2) catalyst which is composed of graphene-like δ-MnO2 with ultrafine CeO2 nanocrystals decorated on it. Li–O2 cells with the CeO2/δ-MnO2 catalyst exhibit superior electrochemical performance, including high discharge specific capacity (8260 mA h g−1 at 100 mA g−1), good rate capability (735 mA h g−1 at 1600 mA g−1), and excellent cycling stability (296 cycles at a limited capacity of 500 mA h g−1), which is much better than that with a bare δ-MnO2 catalyst. The achievement of excellent electrochemical performance is attributed to the highly efficient co-catalytic ability of δ-MnO2 and CeO2 and the desirable graphene-like architecture of the CeO2/δ-MnO2 catalyst, as well as the formation of the thin-layered discharge product Li2O2.
