Co-reporter:Ming Liang;Yingbin Tan;Zhonghui Cui;Xuebin Yu;Weiwei Sun;Peili Lou
ACS Applied Materials & Interfaces June 15, 2016 Volume 8(Issue 23) pp:14488-14493
Publication Date(Web):2017-2-22
DOI:10.1021/acsami.6b01003
CoS and NiS nanomaterials anchored on reduced graphene oxide (rGO) sheets, synthesized via combination of hydrothermal with sulfidation process, are studied as high-capacity anode materials for the reversible lithium storage. The obtained CoS nanofibers and NiS nanoparticles are uniformly dispersed on rGO sheets without aggregation, forming the sheet-on-sheet composite structure. Such nanoarchitecture can not only facilitate ion/electron transport along the interfaces, but also effectively prevent metal-sulfide nanomaterials aggregation during the lithium reactions. Both the rGO-supported CoS nanofibers (NFs) and NiS nanoparticles (NPs) show superior lithium storage performance. In particular, the CoS NFs-rGO electrodes deliver the discharge capacity as high as 939 mA h g–1 after the 100th cycle at 100 mA g–1 with Coulombic efficiency above 98%. This strategy for construction of such composite structure can also synthesize other metal-sulfide-rGO nanomaterials for high-capacity lithium-ion batteries.Keywords: anode materials; lithium-ion batteries; metal-sulfide nanomaterials; nanofibers; reduced graphene oxide;
Co-reporter:Peili Lou, Zhonghui Cui, Zhiqing Jia, Jiyang Sun, Yingbin Tan, and Xiangxin Guo
ACS Nano April 25, 2017 Volume 11(Issue 4) pp:3705-3705
Publication Date(Web):March 21, 2017
DOI:10.1021/acsnano.6b08223
In search of new electrode materials for lithium-ion batteries, metal phosphides that exhibit desirable properties such as high theoretical capacity, moderate discharge plateau, and relatively low polarization recently have attracted a great deal of attention as anode materials. However, the large volume changes and thus resulting collapse of electrode structure during long-term cycling are still challenges for metal-phosphide-based anodes. Here we report an electrode design strategy to solve these problems. The key to this strategy is to confine the electroactive nanoparticles into flexible conductive hosts (like carbon materials) and meanwhile maintain a monodispersed nature of the electroactive particles within the hosts. Monodispersed carbon-coated cubic NiP2 nanoparticles anchored on carbon nanotubes (NiP2@C-CNTs) as a proof-of-concept were designed and synthesized. Excellent cyclability (more than 1000 cycles) and capacity retention (high capacities of 816 mAh g–1 after 1200 cycles at 1300 mA g–1 and 654.5 mAh g–1 after 1500 cycles at 5000 mA g–1) are characterized, which is among the best performance of the NiP2 anodes and even most of the phosphide-based anodes reported so far. The impressive performance is attributed to the superior structure stability and the enhanced reaction kinetics incurred by our design. Furthermore, a full cell consisting of a NiP2@C-CNTs anode and a LiFePO4 cathode is investigated. It delivers an average discharge capacity of 827 mAh g–1 based on the mass of the NiP2 anode and exhibits a capacity retention of 80.7% over 200 cycles, with an average output of ∼2.32 V. As a proof-of-concept, these results demonstrate the effectiveness of our strategy on improving the electrode performance. We believe that this strategy for construction of high-performance anodes can be extended to other phase-transformation-type materials, which suffer a large volume change upon lithium insertion/extraction.Keywords: lithium storage; monodispersed; nickel phosphide; reaction kinetics; structure stability; volume change;
Co-reporter:Yingbin Tan, Zhiqing Jia, Peili Lou, Zhonghui Cui, Xiangxin Guo
Journal of Power Sources 2017 Volume 341() pp:68-74
Publication Date(Web):15 February 2017
DOI:10.1016/j.jpowsour.2016.11.114
•The P@rGO/ZIF-8(C)-S cathode with 66% sulfur is fabricated.•The sulfur cathodes possess sandwich structure and high nitrogen content.•The sulfur cathodes achieve the high capacity and long cycle life.Confinement of sulfur and alleviation of the polysulfides dissolution are the key issues for development of high-performance lithium-sulfur (Li-S) batteries. Here, we report self-assembly sandwiches composed of zeolitic-imidazolate-frameworks (ZIF-8)-derived mesoporous carbons (ZIF-8(C)) in between reduced graphene oxide (rGO) layers, which are filled with sulfurs inside and coated with poly(3, 4-ethylenedioxythiophene) (PEDOT) outside (noted as P@rGO/ZIF-8(C)). During the synthesis process, the rGO layers stabilize the structure of ZIF-8 nanocrystals to obtain large specific surface area and high electric conductivity of mesoporous materials (rGO/ZIF-8(C)), ensuring accommodation of a large amount of sulfur and the efficient utilization of the confined sulfur. The mesoporous rGO/ZIF-8(C), PEDOT and N-doping provide physical absorption and chemical binding to the polysulfides during cycles. Consequently, the Li-S batteries with the composite cathodes exhibit the high capacity of 1308 mAh g−1 and 865 mAh g−1 at 0.2 C and 1 C, respectively, and a very low capacity fading of 0.03% per cycle after 500 reversible cycles at 1 C rate. The results indicate that the P@rGO/ZIF-8(C)-S composite cathode may offer a feasible strategy for construction of sulfur cathodes for high-performance Li-S batteries.The synthesis of P@rGO/ZIF-8(C)-S cathode with sandwich structure and high nitrogen content exhibits stable long-term cycling performance.
Co-reporter:Beizhou Wang;Ning Zhao;Youwei Wang;Wenqing Zhang;Wencong Lu;Jianjun Liu
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 4) pp:2940-2949
Publication Date(Web):2017/01/25
DOI:10.1039/C6CP07537A
Tuning the composition of discharge products is an important strategy to reduce charge potential, suppress side reactions, and improve the reversibility of metal–oxygen batteries. In the present study, first-principles calculations and experimental confirmation were performed to unravel the influence of O2 pressure, particle size, and electrolyte on the composition of charge products in Na–O2 batteries. The electrolytes with medium and high donor numbers (>12.5) are favorable for the formation of sole NaO2, while those with low donor numbers (<12.5) may permit the formation of Na2O2 by disproportionation reactions. Our comparative experiments under different electrolytes confirmed the calculation prediction. Our calculations indicated that O2 pressure and particle size hardly affect discharge products. On the electrode, only one-electron-transfer electrochemical reaction to form NaO2 takes place, whereas two-electron-transfer electrochemical and chemical reactions to form Na2O2 and Na3O4 are prevented in thermodynamics. The present study explains why metastable NaO2 was identified as a sole discharge product in many experiments, while thermodynamically more stable Na2O2 was not observed. Therefore, to achieve low overpotential, a high-donor-number electrolyte should be applied in the discharge processes of Na–O2 batteries.
Co-reporter:Zhe Peng, Ning Zhao, Zhenggang Zhang, Hao Wan, Huan Lin, Meng Liu, Cai Shen, Haiyong He, Xiangxin Guo, Ji-Guang Zhang, Deyu Wang
Nano Energy 2017 Volume 39(Volume 39) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.nanoen.2017.07.052
•A transplantable LiF-rich layer (TLL) cross-linked by nanoscale LiF domains for Li metal protection.•Li anode protected by the TLL keeps its metal luster after 6 months operation.•Coulombic efficiency on a protected Cu is remained ~ 98% in carbonate electrolyte.Although Li metal has been regarded as one of the most promising anode materials, an unstable Li/electrolyte interface during the cycling process seriously limits its practical application in rechargeable batteries. Herein, we report a transplantable LiF-rich layer (TLL) that can suppress the side reactions between electrolyte and lithium metal. This peelable layer cross-linked by nanoscale LiF domains is obtained by electrochemically reducing NiF2 electrodes and could be used to protect Li metal anodes. Cu-Li cells using the TLL protection can operate for more than 300 cycles with a Coulombic efficiency as high as ~ 98% in carbonate-based electrolytes. In Li-LiFePO4 cells, lithium metal with a TLL still looks shiny after 1000 cycles (~ 6 months) in contrast to the black surface of bare lithium foil after ~ 500 cycles (~ 3 months). These results clearly demonstrate that the TLL could greatly limit the side reactions between lithium metal and the carbonate-based electrolytes, and may enable long-term stable operation of Li metal batteries.Download high-res image (200KB)Download full-size image
Co-reporter:Hanyu Huo, Ning Zhao, Jiyang Sun, Fuming Du, Yiqiu Li, Xiangxin Guo
Journal of Power Sources 2017 Volume 372(Volume 372) pp:
Publication Date(Web):31 December 2017
DOI:10.1016/j.jpowsour.2017.10.059
•The ionic liquid was used to wet the interfaces between PEO and LLZTO.•The ionic liquid of 1.8 μL cm−2 remained the solid state of membrane electrolytes.•The improved conductive paths along the interfaces were studied.•LiFePO4/Li and LiFe0.15Mn0.85PO4/Li batteries were tested at room temperature.Paramount attention has been paid on solid polymer electrolytes due to their potential in enhancement of energy density as well as improvement of safety. Herein, the composite electrolytes consisting of Li-salt-free polyethylene oxides and 200 nm-sized Li6.4La3Zr1.4Ta0.6O12 particles interfacially wetted by [BMIM]TF2N of 1.8 μL cm−2 have been prepared. Such wetted ionic liquid remains the solid state of membrane electrolytes and decreases the interface impedance between the electrodes and the electrolytes. There is no release of the liquid phase from the PEO matrix when the pressure of 5.0 × 104 Pa being applied for 24 h. The interfacially wetted membrane electrolytes show the conductivity of 2.2 × 10−4 S cm−1 at 20 °C, which is one order of magnitude greater than that of the membranes without the wetted ionic liquids. The conduction mechanism is related to a large number of lithium ions releasing from Li6.4La3Zr1.4Ta0.6O12 particles and the improved conductive paths along the ion-liquid-wetted interfaces between the polymer matrix and ceramic grains. When the membranes being used in the solid-state LiFePO4/Li and LiFe0.15Mn0.85PO4/Li cells at 25 °C, the excellent rate capability and superior cycle stability has been shown. The results provide a new prospect for solid polymer electrolytes used for room-temperature solid-state lithium batteries.Download high-res image (169KB)Download full-size image
Co-reporter:Yingbin Tan;Zhihui Zheng;Shiting Huang;Yongzhe Wang;Zhonghui Cui;Jianjun Liu
Journal of Materials Chemistry A 2017 vol. 5(Issue 18) pp:8360-8366
Publication Date(Web):2017/05/10
DOI:10.1039/C7TA01346A
Lithium–sulfur (Li–S) batteries have been considered as next-generation rechargeable energy storage systems due to their high theoretical energy densities and low cost; however, the capacity decay resulting from the shuttle of lithium polysulfides (LiPSs) hinders their practical application. Herein, we describe a strategy to synthesize highly pyridinic-N-doped three-dimensional (3D) carbons for the chemisorption of LiPSs, which consist of zeolitic imidazolate framework-8-derived carbon (ZIF-8(C)) coated on the surface of N-doped carbon nanotubes supported by carbon nanosheets (NCNTs–CS–ZIF-8(C)). Using the obtained carbons as sulfur hosts, the S/NCNTs–CS–ZIF-8(C) cathodes show a high sulfur utilization of 86% at 0.1 C, a low capacity decay rate of 0.052% per cycle over 700 cycles at 1 C and impressive cycling life that is 564 mA h g−1 after 700 cycles at 1 C. First principles calculations based on the Vienna Ab-Initio Simulation Package (VASP) reveal that increasing the amount of the pyridinic-N component can enhance the adsorption of LiPSs, which yields effective suppression of the LiPS shuttle.
Co-reporter:Peili Lou;Zhonghui Cui
Journal of Materials Chemistry A 2017 vol. 5(Issue 34) pp:18207-18213
Publication Date(Web):2017/08/29
DOI:10.1039/C7TA05009G
Aprotic Li–O2 batteries have attracted a great deal of attention because of their potential to offer much higher energy density than those provided by commercialized lithium-ion batteries. However, their reversible operation is plagued by serious side-reactions from liquid electrolytes and/or carbon-based materials. Recently, carbon-free materials have been proposed and utilized to construct stable cathodes for Li/O2 chemistry. Different from most of the previously reported metal-based carbon-free cathodes, herein we report a non-metal-based carbon-free cathode support consisting of mesoporous boron-doped carbon nitride (m-BCN) and demonstrate its excellent stability and activity for Li/O2 chemistry. Benefiting from the introduction of evenly distributed RuO2 nanoparticles (1–2 nm) in the pores of the boron-doped carbon nitride support, excellent cycle stability with a low overpotential (141 cycles with a pristine Li anode which is extended to 227 cycles after replacing it with a new Li anode at 0.5 mA cm−2) and superior rate capability (1.28 mA h cm−2 at 1 mA cm−2) are obtained. This impressive performance is ascribed to the enhanced stability and activity of such designed cathodes, which is supported by the fact that reversible formation and decomposition of Li2O2 with no accumulation of Li2CO3 is detected during cycling. These results demonstrate that manipulating cathode materials towards stable reaction interfaces is essential for alleviating the formation of by-products and improving the performance of Li–O2 batteries.
Co-reporter:Yingbin Tan;Zhiqing Jia;Jiyang Sun;Yongzhe Wang;Zhonghui Cui
Journal of Materials Chemistry A 2017 vol. 5(Issue 46) pp:24139-24144
Publication Date(Web):2017/11/28
DOI:10.1039/C7TA08236C
Copper oxide is one of the promising anode materials for lithium-ion batteries (LIBs) due to its high energy density. However, it suffers from fast capacity fading and poor cycling stability, arising from the low electrical conductivity and the large volume expansion. Herein, we report a chemical vapor and solid deposition strategy for the synthesis of hollow copper nanoparticles supported by N-doped carbon nanosheets (Cu@NCSs) on Cu foil, adopting a polymer as the carbon source. After successive oxidation treatment, the construction of hollow copper oxide encapsulated into N-doped carbon nanosheets (CuO@NCSs) is achieved. The resulting products are used as anodes in LIBs, displaying a capacity of 688 mA h g−1 over 1000 cycles at 2 A g−1 and a capacity of 400 mA h g−1 at 4 A g−1. Such superior performance is attributed to the well-designed hollow CuO@NCS composites, which not only improve the electrical conductivity of electrode materials, but also allow easy penetration of electrolyte and mitigation of the volume expansion.
Co-reporter:Peili Lou, Chilin Li, Zhonghui Cui and Xiangxin Guo
Journal of Materials Chemistry A 2016 vol. 4(Issue 1) pp:241-249
Publication Date(Web):17 Nov 2015
DOI:10.1039/C5TA07886E
The difficult achievement of high round-trip energy efficiency or low charge overpotential has retarded Li–O2(air) batteries in real applications. Although much effort has been focused on exploring novel catalysts, their potential effects are usually counteracted by a quick passivation of the electrode as a consequence of side reactions, which likely contribute to the widely observed high-voltage reversibility (e.g. >4 V). Here, we report a job-sharing design of a carbon-based cathode, Ru-IL (ionic liquid)–CNT (carbon nanotube), with fine Ru nanodots anchored on the IL-decorated CNT surface. The subnanometer IL cation linker is crucial to seal carbon surface defects without sacrificing Li+/e− charge transfer and therefore efficiently suppresses the occurrence of side reactions. This charged decoration guarantees that Ru functions as the microstructure promoter to stabilize highly disordered Li2O2. It enables achievement of high energy efficiency (80–84%) Li–O2 batteries characterized by a substantial charge plateau with an extremely low overpotential of 0.18 V. Even by using the mode of voltage cut-off, a reversible capacity around 800–1000 mA h g−1 is maintained for more than 100 cycles. When the reversible capacity is limited to 500 mA h g−1, the cycling number can reach up to at least 240 cycles. The disentangled CNT networks, loose precipitation of nanostructured products and high donor number electrolytes allow thick electrode fabrication (8 mg cm−2), leading to a high areal capacity of 3.6–7.6 mA h cm−2. Our results indicate a defect-inspired strategy to bury undesired defect sites in the original electrode framework and to electrochemically synthesize the stable defect-rich Li2O2 product.
Co-reporter:Ruimin Yu, Wugang Fan, Xiangxin Guo, Shaoming Dong
Journal of Power Sources 2016 Volume 306() pp:402-407
Publication Date(Web):29 February 2016
DOI:10.1016/j.jpowsour.2015.12.042
•Highly ordered and ultra-long CNTs on permeable Ta foil were synthesized.•The energy efficiency of Li–O2 cells reached 82% with LiI catalyst.•Their cycling performance superseded other two less ordered CNTs.•Ordered structure benefited the transportation of Li+ ions, gas and electrons.Carbonaceous air cathodes with rational architecture are vital for the nonaqueous Li–O2 batteries to achieve large energy density, high energy efficiency and long cycle life. In this work, we report the cathodes made of highly ordered and vertically aligned carbon nanotubes grown on permeable Ta foil substrates (VACNTs-Ta) via thermal chemical vapour deposition. The VACNTs-Ta, composed of uniform carbon nanotubes with approximately 240 μm in superficial height, has the super large surface area. Meanwhile, the oriented carbon nanotubes provide extremely outstanding passageways for Li ions and oxygen species. Electrochemistry tests of VACNTs-Ta air cathodes show enhancement in discharge capacity and cycle life compared to those made from short-range oriented and disordered carbon nanotubes. By further combining with the LiI redox mediator that is dissolved in the tetraethylene dimethyl glycol based electrolytes, the batteries exhibit more than 200 cycles at the current density of 200 mA g−1 with a cut-off discharge capacity of 1000 mAh g−1, and their energy efficiencies increase from 50% to 82%. The results here demonstrate the importance of cathode construction for high-energy-efficiency and long-life Li–O2 batteries.
Co-reporter:Shiting Huang, Zhonghui Cui, Ning Zhao, Jiyang Sun, Xiangxin Guo
Electrochimica Acta 2016 Volume 191() pp:473-478
Publication Date(Web):10 February 2016
DOI:10.1016/j.electacta.2016.01.102
•Li-air batteries with TEGDME-based electrolytes could cycle in ambient air.•The discharge products were Li2O2 initially and eventually Li2CO3.•The Li anodes turned LiOH after cycles in ambient air.•Thin polymer-layer protected Li anodes could extend the cycle number.The non-aqueous Li-air battery offers the highest theoretical energy density among currently available rechargeable storage units. However, H2O and CO2 in air are viewed as detrimental factors which hinder its performance. Thus, most previous researches focus on the Li-oxygen battery with pure O2 as working atmosphere. The actual influence of ambient air on the cell chemistry has seldom been investigated. Here, we carry out study of the Li-air batteries with tetraethylene glycol dimethyl ether (TEGDME)-based electrolytes and carbon-nanotube-based cathodes operated in ambient air. The cells show the specific capacity as large as 7000 mAh g−1 upon the first discharge to 2 V and more than 50 cycles when being operated with the capacity cutoff of 500 mAh g−1. It is found that the TEGDME-based electrolytes slightly decompose during cell operation. Li2O2 forms during initial discharge and turns Li2CO3 and LiOH owing to its reaction with CO2 and H2O. The lithium anodes become expanded and pulverized after cycles, the problem of which can be relieved by protection with coated polymer layers. These results give essential information that would be helpful for development of the practical Li-air batteries operated in ambient atmosphere.
Co-reporter:Wugang Fan, Beizhou Wang, Xiangxin Guo, Xiangyang Kong, Jianjun Liu
Nano Energy 2016 Volume 27() pp:577-586
Publication Date(Web):September 2016
DOI:10.1016/j.nanoen.2016.08.007
•Distribution and component of discharge products are manipulated by ZnO/VACNTs.•Li-deficient Li2−xO2 is stabilized by the nanosize effect.•The ZnO/VACNT interfaces play the key role in the Li2−xO2 formation.•Reduced overpotential and prolonged cycles are achieved with the ZnO/VACNTs.Control of discharge products with respect to composition, size and morphology is of importance to reduce charge potential, suppress side reactions and improve reversibility of Li-O2 batteries, but faces significant challenge due to complicated electrochemical reactions. Here, we report a cathode architecture composed of ZnO nanoparticles anchored on vertically aligned carbon nanotubes (ZnO/VACNTs) that significantly suppresses LiO2 disproportionation, forming the composites of LiO2, Li3O4 and Li2O2 in nanometer size as the final discharge products. The exposed surface of VACNTs provides the electrochemical reaction sites for reducing O2 to O2−. Transmission electron microscopy measurements in combination with first-principles calculations reveal that the Li2−xO2 compounds nucleated at the interfaces between the ZnO and the VACNTs are stabilized by the nanosize effect (in the scale of 6 nm), which is related to the semiconductive behavior of ZnO. This discharge chemistry leads to the reduced charge overpotential and extended cycle life. The results here demonstrate that the electrochemical reaction tuned by the cathode architecture is a powerful tool to improve Li-O2 cell performance.
Co-reporter:Z. H. Cui, X. X. Guo and H. Li
Energy & Environmental Science 2015 vol. 8(Issue 1) pp:182-187
Publication Date(Web):04 Sep 2014
DOI:10.1039/C4EE01777C
The Li–air (or Li–O2) battery has attracted wide attention, since it has the highest theoretical specific gravimetric energy density. In spite of the rapid progress made on improving its cyclic performance and reducing its voltage polarization, many key issues on thermodynamics and kinetics in nonaqueous Li–O2 batteries are still unresolved. In this study, by using the galvanostatic intermittent titration technique, several novel phenomena have been observed, such as zero voltage gap for the open circuit voltage (OCV) between charging and discharging, asymmetrical polarization behaviours at different current densities and temperatures, a continuous increase of overpotential during charging, and a negative temperature coefficient of the cell's thermodynamic equilibrium voltage. These results could inspire other researchers to comprehensively investigate the complicated reaction mechanisms, thermodynamics, and kinetic properties of the Li–air battery, as well as other advanced batteries.
Co-reporter:Zhonghui Cui, Chilin Li, Pengfei Yu, Minghui Yang, Xiangxin Guo and Congling Yin
Journal of Materials Chemistry A 2015 vol. 3(Issue 2) pp:509-514
Publication Date(Web):05 Nov 2014
DOI:10.1039/C4TA05241B
Micro-sized or monolithic electrode materials with sufficient mesoporosity and a high intrinsic conductivity are highly desired for high-energy batteries without the trade-off of electrolyte infiltration and accommodation of volume expansion. Here metallic nitrides consisting of mesoporous microparticles were prepared based on a mechanism of solid–solid phase separation and used as conversion anodes for Li and Na storage. Their superior capacity and rate performance during thousands of cycles benefit from the preservation or self-reconstruction of hierarchically conductive wiring networks. The conversion efficiency is also highly dependent on the reaction pathway and product. Exploring more conductive and percolating mass/charge transport networks particularly in a deep sodiation state is a potential solution for activation of Na-driven conversion electrochemistry.
Co-reporter:Ning Zhao
The Journal of Physical Chemistry C 2015 Volume 119(Issue 45) pp:25319-25326
Publication Date(Web):October 20, 2015
DOI:10.1021/acs.jpcc.5b09187
Development of the nonaqueous Na–O2 battery with a high electrical energy efficiency requires the electrolyte stable against attack of highly oxidative species such as nucleophilic anion O2•–. A combined evaluation method was used to investigate the Na–O2 cell chemistry with various solvents, including ethylene carbonate/propylene carbonate (EC/PC)-, N-methyl-N-propylpiperidinium bis(trifluoromethansulfonyl) imide (PP13TFSI)-, and tetraethylene glycol dimethyl ether (TEGDME)-based electrolytes. It is found that the TEGDME-based electrolytes have the best stability with the predominant yield of NaO2 upon discharge and the largest electrical energy efficiency (approaching 90%). Both EC/PC- and PP13TFSI-based electrolytes severely decompose during discharge, forming a large amount of side products. Analysis of the acid dissociation constant (pKa) of these electrolyte solvents reveals that the TEGDME has the relatively large value of pKa, which correlates with good stability of the electrolyte and high round-trip energy efficiency of the battery.
Co-reporter:Shiting Huang, Wugang Fan, Xiangxin Guo, Fanhao Meng, and Xuanyong Liu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 23) pp:21567
Publication Date(Web):November 14, 2014
DOI:10.1021/am506564n
Surface defects on carbon nanotube cathodes have been artificially introduced by bombardment with argon plasma. Their roles in the electrochemical performance of rechargeable Li–O2 batteries have been investigated. In batteries with tetraethylene glycol dimethyl ether (TEGDME)- and N-methyl-N-propylpiperidinium bis(trifluoromethansulfonyl)imide (PP13TFSI)-based electrolytes, the defects increase the number of nucleation sites for the growth of Li2O2 particles and reduce the size of the formed particles. This leads to increased discharge capacity and reduced cycle overpotential. However, in the former batteries, the hydrophilic surfaces induced by the defects promote carbonate formation, which imposes a deteriorating effect on the cycle performance of the Li–O2 batteries. In contrast, in the latter case, the defective cathodes promote Li2O2 formation without enhancing formation of carbonates on the cathode surfaces, resulting in extended cycle life. This is most probably attributable to the passivation effect on the functional groups of the cathode surfaces imposed by the ionic liquid. These results indicate that defects on carbon surfaces may have a positive effect on the cycle performance of Li–O2 batteries if they are combined with a helpful electrolyte solvent such as PP13TFSI.Keywords: argon-plasma bombardment; carbon nanotubes; carbonate species; lithium peroxides; lithium−oxygen batteries; surface defects
Co-reporter:Z.H. Cui, X.X. Guo
Journal of Power Sources 2014 Volume 267() pp:20-25
Publication Date(Web):1 December 2014
DOI:10.1016/j.jpowsour.2014.05.075
•MnO nanoparticles adhered to mesoporous nitrogen-doped carbons were synthesized.•Their function in the nonaquesous Li–O2 batteries was first studied.•They promote both oxygen reduction and oxygen evolution reactions.•They especially reduce the charge overpotentials and extend the cycle operation.•Synergetic effect between the nanosized MnO and the conductive m-N-C plays the role.Manganese monoxide nanoparticles adhered to mesoporous nitrogen-doped carbons (MnO-m-N-C) have been synthesized and their influence on cycle performance of nonaqueous lithium–oxygen (Li–O2) batteries is investigated. It is found that the MnO-m-N-C composites promote both oxygen reduction and oxygen evolution reactions. They lead to reduced charge overpotentials through early decomposition of the Li2O2 particles formed on discharge, especially at the limited depth of discharge during the initial several ten cycles. Such superior activity is attributed to the good coupling between the nanosized MnO particles and the conductive mesoporous nitrogen-doped carbons, which is helpful for improving kinetics of both charge and mass transport during the cathode reactions.
Co-reporter:Yiqiu Li, Zheng Wang, Chilin Li, Yang Cao, Xiangxin Guo
Journal of Power Sources 2014 Volume 248() pp:642-646
Publication Date(Web):15 February 2014
DOI:10.1016/j.jpowsour.2013.09.140
•Flowing oxygen sintering to improve lithium garnet electrolytes is firstly studied.•Densification is enhanced by filling pores with oxygen and its lattice diffusion.•A high density (96%) and overall conductivity (7.4 × 10−4 S cm−1) are achievable.High density (∼96%) garnet-type Al-contained Li6.75La3Zr1.75Ta0.25O12 (LLZTO-Al) solid electrolytes are prepared by conventional solid-state reaction and the following flowing oxygen sintering process. An overall ionic conductivity as high as 7.4 × 10−4 S cm−1 at 25 °C is achievable, remarkably higher than that obtained by sintering in other atmospheres. The dependence of density and conductivity of solid electrolytes on sintering under different oxygen partial pressures is discussed. Atmosphere sintering is proved to be an effective method to improve the relative density of lithium oxide ceramics.
Co-reporter:Ning Zhao, Chilin Li and Xiangxin Guo
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 29) pp:15646-15652
Publication Date(Web):03 Jun 2014
DOI:10.1039/C4CP01961J
Metal–air batteries are thought to be the ultimate solution for energy storage systems owing to their high energy density. Here we report a long-life Na–O2 battery with a high capacity of 750 mA h gcarbon−1 by manipulating the nucleation and growth of nano-sized NaO2 particles in a vertically aligned carbon nanotubes (VACNTs) network with a large surface area. Benefiting from the kinetically favorable formation of NaO2 reaction with a low overpotential of ∼0.2 V, the electrical energy efficiency is as high as 90% for up to 100 cycles. A good rate performance (∼1500 mA h gcarbon−1 at 667 mA gcarbon−1) can be achieved through pre-deposition of a thin NaO2 layer. This study encourages the exploration of the key factors influencing the performance of metal–air batteries, as well as Na-based batteries characterized by phase transformation or conversion reactions.
Co-reporter:Wugang Fan ; Xiangxin Guo ; Dongdong Xiao ;Lin Gu
The Journal of Physical Chemistry C 2014 Volume 118(Issue 14) pp:7344-7350
Publication Date(Web):March 21, 2014
DOI:10.1021/jp500597m
Gold nanoparticles (AuNPs) anchored to vertically aligned carbon nanotubes (VACNTs) act as additional nucleation sites for the Li2O2 growth, leading to the decreased size while increased density of Li2O2 particles in process of discharge. Correspondingly, at the deep discharge to 2.0 V the batteries show increased specific capacity. Upon charge, the AuNPs exhibit promotion effect on the Li2O2 decomposition by improving the conduction property of the discharge-formed particles, rather than by imposing the conventional electrocatalytic effect on the oxygen evolution reaction. Moreover, the AuNPs show promotion effect on decomposition of carbonate species arising from the side reactions. These effects consequently lead to the reduced charge overpotentials and extended cycle operation of the batteries. The results here provide a new as well as clear picture on the role of incorporated AuNPs in the Li2O2 formation and decomposition, which would be helpful for better understanding and constructing of high-performance air cathodes.
Co-reporter:Pengfei Yu ; Chilin Li
The Journal of Physical Chemistry C 2014 Volume 118(Issue 20) pp:10616-10624
Publication Date(Web):May 7, 2014
DOI:10.1021/jp5010693
Phase transformation reactions including alloying or conversion ones have often been utilized recently to improve the capacity performance of Na-ion battery anodes. However, they tend to induce larger volume change and more sluggish Na-ion transport at multiphase solid interfaces than for Li-ion batteries, leading to inefficiency of mixed conductive networks and thus degradation of reversibility, polarization, or rate performance. In this work, we use a structurally stable Li4Ti5O12 spinel thin film as insertion-type model material to investigate its intrinsic Na-ion transport kinetics and coupled pseudocapacitive charging. It is found that the latter effect is remarkably activated by the nanocrystalline microstructure full of defect-rich surface, which can simultaneously promote Na-ion and electron accessibility to the surface/subsurface. It is proposed that the extra pseudocapacitive charge storage is a potential solution to the high-capacity and high-rate insertion anodes without trade-off of serious phase transformation or structural collapse. Therefore, a highly reversible charge capacity of 225 mAh g–1 (exceeding the theoretical value 175 mAh g–1 based on insertion reaction) at 1C is achievable.
Co-reporter:Xiangxin Guo;Ning Zhao
Advanced Energy Materials 2013 Volume 3( Issue 11) pp:1413-1416
Publication Date(Web):
DOI:10.1002/aenm.201300432
Co-reporter:Zhonghui Cui, Xiangxin Guo, Hong Li
Electrochimica Acta 2013 Volume 89() pp:229-238
Publication Date(Web):1 February 2013
DOI:10.1016/j.electacta.2012.10.164
MnO thin films were grown on Cu-foil substrates at various temperatures by the pulsed laser deposition (PLD) technique. The elevated growth temperatures led to the improved storage capacity, initial Coulombic efficiency and rate performance of the thin film anodes. It also had an observable effect on the voltage polarization at the first discharge process, whereas negligible at the subsequent cycles. The origins for these behaviours were clarified. The superior electrochemical performance was attributed to the improved kinetic properties, which relate to the initial better crystallinity and more ordered microstructure of the films caused by the elevated deposition temperatures. The similar behaviour of voltage polarization in the cycles after the first discharge was ascribed to the similar nanocomposited structure induced by the initial conversion reaction. Moreover, the mechanisms for the low initial Coulombic efficiency and the large voltage polarization, which are the appealing and essential topics for the conversion reactions, were elucidated.Highlights► Study of conversion reactions has been carried out in PLD-grown MnO film anodes. ► Better crystallinity and more ordered microstructure induce better initial kinetics. ► The improved kinetics improve the electrochemical performance in the cycles. ► The partial lithiation and delithiation induce the low initial Coulombic efficiency. ► Thermodynamics play a more dominant role in the voltage hysteresis than kinetics.
Co-reporter:Wugang Fan, Zhonghui Cui, and Xiangxin Guo
The Journal of Physical Chemistry C 2013 Volume 117(Issue 6) pp:2623-2627
Publication Date(Web):January 18, 2013
DOI:10.1021/jp310765s
Study of formation and decomposition of Li2O2 during operations of Li–O2 cells is essential for understanding the reaction mechanism and finding solutions to improve the cell performance. Using vertically aligned carbon nanotubes (VACNTs) directly grown on stainless steel meshes as the cathodes in the Li–O2 cells with dimethoxyethane (DME) electrolytes, nucleation, growth, and decomposition processes of the Li2O2 in the first cycle are clearly visualized. Through cycles with the controlled discharge and charge capacities, the abacus-ball-shaped Li2O2 and the rust-like carbonates simultaneously formed around the VACNTs are further identified. It is indicated that the increasing coverage of carbonates on the cathode surface suppresses the formation of Li2O2, which maintains the shape of abacus ball. When the VACNT surfaces are predominantly covered by the carbonates, the cells tend to terminate.
Co-reporter:Yiqiu Li, Yang Cao, Xiangxin Guo
Solid State Ionics 2013 Volume 253() pp:76-80
Publication Date(Web):15 December 2013
DOI:10.1016/j.ssi.2013.09.005
•Effects of Li2O additives on densification and conductivity of lithium garnets are studied.•Density of the ceramic electrolyte is improved by introduction of the Li2O additive.•Conductivity of the lithium garnets with the 6 wt.% Li2O can be increased by a factor of 3.The lithium garnet ceramic has been considered as one of promising solid-state electrolytes for secondary lithium batteries. However, improvement of its ionic conductivity is hindered by the high porosity related to the severe volatilization of lithium components during sintering. In order to find the solution for this problem, Li2O additives in concentration of 2–8 wt.% were introduced into the cubic Li6.75La3Zr1.75Ta0.25O12 (LLZTO) at the solid-state reaction processes. It is found that the Li2O additives lead to formation of glassy-like phases at the grain boundaries related to the liquid-phase sintering behavior, which eliminates the residual pores therein and increases the relative density from 91.5% to 97.3%. Measurement of conductivity indicates that 6 wt.% is the optimum concentration of Li2O which leads to an ionic conductivity of 6.4 × 10− 4 S cm− 1 at room temperature. This value is approximately 3 times larger than that of the ceramic without the additive.
Co-reporter:Z.H. Cui, G. Gregori, A.L. Ding, X.X. Guo, J. Maier
Solid State Ionics 2012 Volume 208() pp:4-7
Publication Date(Web):2 February 2012
DOI:10.1016/j.ssi.2011.12.001
Transparent lead lanthanum zirconate titanate (PLZT) ceramics were investigated by ac impedance spectroscopy at temperatures between 300 and 500 °C under different oxygen partial pressures with the purpose of addressing the role of boundary effects on the electrical conduction properties of this compound. It is found that in spite of the high lanthanum content, holes are the dominating electronic charge carriers leading to p-type conductivity in oxidizing conditions. The grain boundaries reveal a blocking behavior (holes depletion), which is explained in the framework of the space charge concept. A positive space charge potential of 0.23 V is obtained.Highlights►The electrical transport properties of transparent PLZT ceramics are studied. ►Holes are found to be the dominating electronic charge carriers in the materials. ►The grain boundaries exhibit the electrically blocking behavior. ►The boundary blocking can be well explained by the space charge effect.
Co-reporter:Zhonghui Cui, Yanwei Huang, Xiangxin Guo
Electrochimica Acta 2012 60() pp: 7-12
Publication Date(Web):
DOI:10.1016/j.electacta.2011.10.104
Co-reporter:Xiangxin Guo;Joachim Maier
Advanced Materials 2009 Volume 21( Issue 25-26) pp:2619-2631
Publication Date(Web):
DOI:10.1002/adma.200900412
Abstract
In the context of revealing interfacial effects on ion conduction, thin films are extremely worthwhile due to defined geometry. Of particular interest are heterostructures as they offer symmetric boundary conditions and a high density of hetero-interfaces. The recent progress in this field is reviewed. Materials classes under concern include halides and oxides, and refer to various degrees of disorder and different mobilities. Even though in its infancy, the field of ionic heterostructures is already characterized by a variety of results of fundamental importance and of technological relevance.
Co-reporter:Xiangxin Guo;Joachim Maier
Advanced Functional Materials 2009 Volume 19( Issue 1) pp:96-101
Publication Date(Web):
DOI:10.1002/adfm.200800805
Abstract
Molecular beam epitaxy-grown CaF2/BaF2 heterolayers are a demonstration of the potential of nanoionics. It has been shown that ion conductivities both parallel and perpendicular to the interfaces increase with decrease in interfacial spacing. This size effect was attributed to the thermodynamically necessary redistribution of the mobile fluoride ions (N. Sata, K. Eberl, K. Eberman, J. Maier, Nature 2000, 408, 946; X. X. Guo, I. Matei, J.-S. Lee, J. Maier, Appl. Phys. Lett. 2007, 91, 103102). On this basis, the striking phenomenon of an upward bending in the effective parallel conductivity as a function of inverse interfacial spacing for low temperatures (T ≤ 593 K) has been satisfactorily explained by application of a modified Mott–Schottky model for BaF2 (X.X. Guo, I. Matei, J. Jamnik, J.-S. Lee, J. Maier, Phys. Rev. B 2007, 76, 125429). This model was further confirmed by measurements perpendicular to the interfaces that offer complementary information on the more resistive parts. Here a successful comprehensive modeling of parallel and perpendicular conductivities for the whole parameter range, namely for interfacial spacings ranging from 6 to 200 nm and investigated temperatures ranging from 455 to 833 K, is presented. The model is based on literature data for carrier mobilities and Frenkel reaction constants and the assumption of a pronounced F− redistribution. Given the fact that an impurity content that was experimentally supported is taken into account and apart from minor assumptions concerning profile homogeneity, the only fit parameter is the space charge potential. In particular, it is worth mentioning that in BaF2 the low temperature Mott–Schottky space charge zone which is determined by impurities changes over, at high temperatures, into a Gouy–Chapman situation owing to increased thermal disorder. (The situation in CaF2 is of Gouy–Chapman type at all temperatures.)
Co-reporter:Zhonghui Cui, Chilin Li, Pengfei Yu, Minghui Yang, Xiangxin Guo and Congling Yin
Journal of Materials Chemistry A 2015 - vol. 3(Issue 2) pp:NaN514-514
Publication Date(Web):2014/11/05
DOI:10.1039/C4TA05241B
Micro-sized or monolithic electrode materials with sufficient mesoporosity and a high intrinsic conductivity are highly desired for high-energy batteries without the trade-off of electrolyte infiltration and accommodation of volume expansion. Here metallic nitrides consisting of mesoporous microparticles were prepared based on a mechanism of solid–solid phase separation and used as conversion anodes for Li and Na storage. Their superior capacity and rate performance during thousands of cycles benefit from the preservation or self-reconstruction of hierarchically conductive wiring networks. The conversion efficiency is also highly dependent on the reaction pathway and product. Exploring more conductive and percolating mass/charge transport networks particularly in a deep sodiation state is a potential solution for activation of Na-driven conversion electrochemistry.
Co-reporter:Beizhou Wang, Ning Zhao, Youwei Wang, Wenqing Zhang, Wencong Lu, Xiangxin Guo and Jianjun Liu
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 4) pp:NaN2949-2949
Publication Date(Web):2016/12/19
DOI:10.1039/C6CP07537A
Tuning the composition of discharge products is an important strategy to reduce charge potential, suppress side reactions, and improve the reversibility of metal–oxygen batteries. In the present study, first-principles calculations and experimental confirmation were performed to unravel the influence of O2 pressure, particle size, and electrolyte on the composition of charge products in Na–O2 batteries. The electrolytes with medium and high donor numbers (>12.5) are favorable for the formation of sole NaO2, while those with low donor numbers (<12.5) may permit the formation of Na2O2 by disproportionation reactions. Our comparative experiments under different electrolytes confirmed the calculation prediction. Our calculations indicated that O2 pressure and particle size hardly affect discharge products. On the electrode, only one-electron-transfer electrochemical reaction to form NaO2 takes place, whereas two-electron-transfer electrochemical and chemical reactions to form Na2O2 and Na3O4 are prevented in thermodynamics. The present study explains why metastable NaO2 was identified as a sole discharge product in many experiments, while thermodynamically more stable Na2O2 was not observed. Therefore, to achieve low overpotential, a high-donor-number electrolyte should be applied in the discharge processes of Na–O2 batteries.
Co-reporter:Yingbin Tan, Zhihui Zheng, Shiting Huang, Yongzhe Wang, Zhonghui Cui, Jianjun Liu and Xiangxin Guo
Journal of Materials Chemistry A 2017 - vol. 5(Issue 18) pp:NaN8366-8366
Publication Date(Web):2017/03/21
DOI:10.1039/C7TA01346A
Lithium–sulfur (Li–S) batteries have been considered as next-generation rechargeable energy storage systems due to their high theoretical energy densities and low cost; however, the capacity decay resulting from the shuttle of lithium polysulfides (LiPSs) hinders their practical application. Herein, we describe a strategy to synthesize highly pyridinic-N-doped three-dimensional (3D) carbons for the chemisorption of LiPSs, which consist of zeolitic imidazolate framework-8-derived carbon (ZIF-8(C)) coated on the surface of N-doped carbon nanotubes supported by carbon nanosheets (NCNTs–CS–ZIF-8(C)). Using the obtained carbons as sulfur hosts, the S/NCNTs–CS–ZIF-8(C) cathodes show a high sulfur utilization of 86% at 0.1 C, a low capacity decay rate of 0.052% per cycle over 700 cycles at 1 C and impressive cycling life that is 564 mA h g−1 after 700 cycles at 1 C. First principles calculations based on the Vienna Ab-Initio Simulation Package (VASP) reveal that increasing the amount of the pyridinic-N component can enhance the adsorption of LiPSs, which yields effective suppression of the LiPS shuttle.
Co-reporter:Ning Zhao, Chilin Li and Xiangxin Guo
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 29) pp:NaN15652-15652
Publication Date(Web):2014/06/03
DOI:10.1039/C4CP01961J
Metal–air batteries are thought to be the ultimate solution for energy storage systems owing to their high energy density. Here we report a long-life Na–O2 battery with a high capacity of 750 mA h gcarbon−1 by manipulating the nucleation and growth of nano-sized NaO2 particles in a vertically aligned carbon nanotubes (VACNTs) network with a large surface area. Benefiting from the kinetically favorable formation of NaO2 reaction with a low overpotential of ∼0.2 V, the electrical energy efficiency is as high as 90% for up to 100 cycles. A good rate performance (∼1500 mA h gcarbon−1 at 667 mA gcarbon−1) can be achieved through pre-deposition of a thin NaO2 layer. This study encourages the exploration of the key factors influencing the performance of metal–air batteries, as well as Na-based batteries characterized by phase transformation or conversion reactions.
Co-reporter:Peili Lou, Chilin Li, Zhonghui Cui and Xiangxin Guo
Journal of Materials Chemistry A 2016 - vol. 4(Issue 1) pp:NaN249-249
Publication Date(Web):2015/11/17
DOI:10.1039/C5TA07886E
The difficult achievement of high round-trip energy efficiency or low charge overpotential has retarded Li–O2(air) batteries in real applications. Although much effort has been focused on exploring novel catalysts, their potential effects are usually counteracted by a quick passivation of the electrode as a consequence of side reactions, which likely contribute to the widely observed high-voltage reversibility (e.g. >4 V). Here, we report a job-sharing design of a carbon-based cathode, Ru-IL (ionic liquid)–CNT (carbon nanotube), with fine Ru nanodots anchored on the IL-decorated CNT surface. The subnanometer IL cation linker is crucial to seal carbon surface defects without sacrificing Li+/e− charge transfer and therefore efficiently suppresses the occurrence of side reactions. This charged decoration guarantees that Ru functions as the microstructure promoter to stabilize highly disordered Li2O2. It enables achievement of high energy efficiency (80–84%) Li–O2 batteries characterized by a substantial charge plateau with an extremely low overpotential of 0.18 V. Even by using the mode of voltage cut-off, a reversible capacity around 800–1000 mA h g−1 is maintained for more than 100 cycles. When the reversible capacity is limited to 500 mA h g−1, the cycling number can reach up to at least 240 cycles. The disentangled CNT networks, loose precipitation of nanostructured products and high donor number electrolytes allow thick electrode fabrication (8 mg cm−2), leading to a high areal capacity of 3.6–7.6 mA h cm−2. Our results indicate a defect-inspired strategy to bury undesired defect sites in the original electrode framework and to electrochemically synthesize the stable defect-rich Li2O2 product.
