It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devi...It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devices. By studying the lithiation mechanism of Li_4Ti_5O_12 （LTO） using in-situ electron holography, we find that double charge layers are formed at the interface of the insulating Li_4Ti_5O_12 （Li_4） phase and the semiconducting Li_7Ti_5O_12 （Li_7） phase, and can greatly boost the lithiation kinetics. The electron wave phase of the LTO particle is found to gradually shrink with the interface movement, leaving a positive electric field from Li_7 to Li_4 phase. Once the capacitive interface charges are formed, the lithiation of the core/shell particle could be established within 10 s. The ultrafast kinetics is attributed to the built-in interface potential and the mixed Ti3＋/Ti4＋ sites at the interface that could be maximally lowering the thermodynamic barrier for Li ion migration.展开更多
Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(...Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(12)has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na^(+)intercalation properties.However,a low diffusion coefficient for Na^(+)and the insulating nature of LTO remains challenging for practical sodium-ion battery systems.Herein,we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in LTO.We demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured LTO.Optimized Cr doped LTO shows a superior reversible capacity of 110 m Ah g^(-1) after 400 cycles at 1 C,with a three-fold higher capacity(75 m Ah g^(-1))at 10 C compared with undoped LTO material.This suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.展开更多
Synchrotron-based x-ray absorption near-edge structure(XANES)spectroscopy is applied to investigate the variation of Ti valence in the discharge and charge processes of Li_(4)Ti_(5)O_(12).Through analysis of the XANES...Synchrotron-based x-ray absorption near-edge structure(XANES)spectroscopy is applied to investigate the variation of Ti valence in the discharge and charge processes of Li_(4)Ti_(5)O_(12).Through analysis of the XANES data,the average valence of Ti can be calculated,which allows quantitative determination of the ratios of Ti^(3+)/Ti^(4+) as a function of Li content in the electrodes.It is found that the ratios in the composites of Li_(4)Ti_(5)O_(12)/acetylene black(AB)-carbon are larger than those in Li_(4)Ti_(5)O_(12)/Ag/AB-carbon after the discharge to 1.1 V,indicating a larger amount of Li inserted into the former than that into the latter.This finding provides a good explanation for the fact that the Li_(4)Ti_(5)O_(12)/AB-carbon samples exhibit larger storage capacities than the Li_(4)Ti_(5)O_(12)/Ag/AB-carbon ones prepared in this work,concerning the larger Ti^(3+)/Ti^(4+) ratio and the larger amount of Li^(+) inserted in the electrode for satisfying the charge neutralization requirement.展开更多
A quasi-solid-state lithium battery is assembled by plasma sprayed amorphous Li_(4)Ti_(5)O_(12) to provide the outstanding electrochemical stability and better normal interface contact.Scanning Electron Microscope(SEM...A quasi-solid-state lithium battery is assembled by plasma sprayed amorphous Li_(4)Ti_(5)O_(12) to provide the outstanding electrochemical stability and better normal interface contact.Scanning Electron Microscope(SEM),Scanning Transmission Electron Microscopy(STEM),Transmission Electron Microscopy(TEM),and Energy Dispersive Spectrometer(EDS)were used to analyze the structural evolution and performance of plasma sprayed amorphous LTO electrode and ceramic/polymer composite electrolyte before and after electrochemical experiments.By comparing the electrochemical performance of the amorphous LTO electrode and the traditional LTO electrode,the electrochemical behavior of different electrodes is studied.The results show that plasma spraying can prepare an amorphous LTO electrode coating of about 8μm.After 200 electrochemical cycles,the structure of the electrode evolved,and the inside of the electrode fractured and cracks expanded,because of recrystallization at the interface between the rich fluorine compounds and the amorphous LTO electrode.Similarly,the ceramic/polymer composite electrolyte has undergone structural evolution after 200 test cycles.The electrochemical cycle results show that the cycle stability,capacity retention rate,coulomb efficiency,and internal impedance of amorphous LTO electrode are better than traditional LTO electrode.This innovative and facile quasi-solid-state strategy is aimed to promote the intrinsic safety and stability of working lithium battery,shedding light on the development of next-generation high-performance solid-state lithium batteries.展开更多
Three-dimensional(3D)grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions(Li-ions),thereby reducing the total transport distance of Li-ions and improving the...Three-dimensional(3D)grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions(Li-ions),thereby reducing the total transport distance of Li-ions and improving the reaction kinetics.Although there have been other studies focusing on 3D electrodes fabricated by 3D printing,there still exists a gap between electrode design and their electrochemical performance.In this study,we try to bridge this gap through a comprehensive investigation on the effects of various electrode parameters including the electrode porosity,active material particle diameter,electrode electronic conductivity,electrode thickness,line width,and pore size on the electrochemical performance.Both numerical simulations and experimental investigations are conducted to systematically examine these effects.3D grid porous Li_(4)Ti_(5)O_(12)(LTO)thick electrodes are fabricated by low temperature direct writing technology and the electrodes with the thickness of 1085μm and areal mass loading of 39.44 mg·cm^(−2) are obtained.The electrodes display impressive electrochemical performance with the areal capacity of 5.88 mAh·cm^(−2)@1.0 C,areal energy density of 28.95 J·cm^(−2)@1.0 C,and areal power density of 8.04 mW·cm^(−2)@1.0 C.This study can provide design guidelines for obtaining 3D grid porous electrodes with superior electrochemical performance.展开更多
The Li_(4)Ti_(5)O_(12)(LTO)spinel material,ranking at the second large market share after graphite,is a promising anode material for lithium-ion batteries due to its good cycle stability,rate capability,and safety wit...The Li_(4)Ti_(5)O_(12)(LTO)spinel material,ranking at the second large market share after graphite,is a promising anode material for lithium-ion batteries due to its good cycle stability,rate capability,and safety with both conventional and low-temperature electrolytes.However,several critical challenges,such as the low capacity and gassing issue,hindered the wide applications of LTO anode.Recent progress indicated that the LTO performances are possible to be further improved by novel strategies,such as heterogeneous phase control,surface engineering,or overlithiation.To rethink and develop advanced LTO anodes,this review intensively associates the performances and modification strategies with the electronics/crystal structures.From a thermodynamic/kinetic point of view,we summarized the data obtained from recently developed characterization techniques,and the results of electrochemical performances and fundamental structures of LTO to potentially address several key challenges and issues toward advanced LTO anodes.As a result,light is shed on the future research direction of the LTO anodes.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 51501085, 11704019, 51522212 and 51421002)National Program on Key Basic Research Project (2014CB921002)the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB07030200)
文摘It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devices. By studying the lithiation mechanism of Li_4Ti_5O_12 （LTO） using in-situ electron holography, we find that double charge layers are formed at the interface of the insulating Li_4Ti_5O_12 （Li_4） phase and the semiconducting Li_7Ti_5O_12 （Li_7） phase, and can greatly boost the lithiation kinetics. The electron wave phase of the LTO particle is found to gradually shrink with the interface movement, leaving a positive electric field from Li_7 to Li_4 phase. Once the capacitive interface charges are formed, the lithiation of the core/shell particle could be established within 10 s. The ultrafast kinetics is attributed to the built-in interface potential and the mixed Ti3＋/Ti4＋ sites at the interface that could be maximally lowering the thermodynamic barrier for Li ion migration.
基金Project(2007CB2097050)supported by the National Basic Research Program of ChinaProject(20803035)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China
基金supported by the Korea Institute of Science and Technology(KIST)Institutional Program(Project No.2E30212)the National Research Foundation of Korea(NRF)(NRF-2020M3H4A1A0308297811)。
文摘Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(12)has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na^(+)intercalation properties.However,a low diffusion coefficient for Na^(+)and the insulating nature of LTO remains challenging for practical sodium-ion battery systems.Herein,we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in LTO.We demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured LTO.Optimized Cr doped LTO shows a superior reversible capacity of 110 m Ah g^(-1) after 400 cycles at 1 C,with a three-fold higher capacity(75 m Ah g^(-1))at 10 C compared with undoped LTO material.This suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10979069,U1232111,the One-Hundred Talents Project of Chinese Academy of Sciences.
文摘Synchrotron-based x-ray absorption near-edge structure(XANES)spectroscopy is applied to investigate the variation of Ti valence in the discharge and charge processes of Li_(4)Ti_(5)O_(12).Through analysis of the XANES data,the average valence of Ti can be calculated,which allows quantitative determination of the ratios of Ti^(3+)/Ti^(4+) as a function of Li content in the electrodes.It is found that the ratios in the composites of Li_(4)Ti_(5)O_(12)/acetylene black(AB)-carbon are larger than those in Li_(4)Ti_(5)O_(12)/Ag/AB-carbon after the discharge to 1.1 V,indicating a larger amount of Li inserted into the former than that into the latter.This finding provides a good explanation for the fact that the Li_(4)Ti_(5)O_(12)/AB-carbon samples exhibit larger storage capacities than the Li_(4)Ti_(5)O_(12)/Ag/AB-carbon ones prepared in this work,concerning the larger Ti^(3+)/Ti^(4+) ratio and the larger amount of Li^(+) inserted in the electrode for satisfying the charge neutralization requirement.
基金supported by the Fund Project of the GDAS Special Project of Science and Technology Development,Guangdong Academy of Sciences Program(No.2020GDASYL-20200104030)the Innovation Project of Guangxi University of Science and Technology Graduate Education(No.YCSW2020217)+2 种基金Guangxi Innovation Driven Development Project(No.AA18242036-2)Innovation Team Project of Guangxi University of Science and Technology(No.3)the Fund Project of the Key Lab of Guangdong for Modern Surface Engineering Technology(No.2018KFKT01)。
文摘A quasi-solid-state lithium battery is assembled by plasma sprayed amorphous Li_(4)Ti_(5)O_(12) to provide the outstanding electrochemical stability and better normal interface contact.Scanning Electron Microscope(SEM),Scanning Transmission Electron Microscopy(STEM),Transmission Electron Microscopy(TEM),and Energy Dispersive Spectrometer(EDS)were used to analyze the structural evolution and performance of plasma sprayed amorphous LTO electrode and ceramic/polymer composite electrolyte before and after electrochemical experiments.By comparing the electrochemical performance of the amorphous LTO electrode and the traditional LTO electrode,the electrochemical behavior of different electrodes is studied.The results show that plasma spraying can prepare an amorphous LTO electrode coating of about 8μm.After 200 electrochemical cycles,the structure of the electrode evolved,and the inside of the electrode fractured and cracks expanded,because of recrystallization at the interface between the rich fluorine compounds and the amorphous LTO electrode.Similarly,the ceramic/polymer composite electrolyte has undergone structural evolution after 200 test cycles.The electrochemical cycle results show that the cycle stability,capacity retention rate,coulomb efficiency,and internal impedance of amorphous LTO electrode are better than traditional LTO electrode.This innovative and facile quasi-solid-state strategy is aimed to promote the intrinsic safety and stability of working lithium battery,shedding light on the development of next-generation high-performance solid-state lithium batteries.
基金This work is supported by the National Natural Science Foundation of China(Nos.51705334 and 51975384)the Shenzhen Science&Technology Projects(Nos.JCYJ20180305125025855 and JCYJ20200109105618137).
文摘Three-dimensional(3D)grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions(Li-ions),thereby reducing the total transport distance of Li-ions and improving the reaction kinetics.Although there have been other studies focusing on 3D electrodes fabricated by 3D printing,there still exists a gap between electrode design and their electrochemical performance.In this study,we try to bridge this gap through a comprehensive investigation on the effects of various electrode parameters including the electrode porosity,active material particle diameter,electrode electronic conductivity,electrode thickness,line width,and pore size on the electrochemical performance.Both numerical simulations and experimental investigations are conducted to systematically examine these effects.3D grid porous Li_(4)Ti_(5)O_(12)(LTO)thick electrodes are fabricated by low temperature direct writing technology and the electrodes with the thickness of 1085μm and areal mass loading of 39.44 mg·cm^(−2) are obtained.The electrodes display impressive electrochemical performance with the areal capacity of 5.88 mAh·cm^(−2)@1.0 C,areal energy density of 28.95 J·cm^(−2)@1.0 C,and areal power density of 8.04 mW·cm^(−2)@1.0 C.This study can provide design guidelines for obtaining 3D grid porous electrodes with superior electrochemical performance.
基金National Natural Science Foundation of China,Grant/Award Numbers:21875284,22075320,52073161National Science and Technology Major Project,Grant/Award Numbers:2019YFA0705703,2019YFE0100200Tsinghua University Initiative Scientific Research Program,Grant/Award Number:2019Z02UTY06。
文摘The Li_(4)Ti_(5)O_(12)(LTO)spinel material,ranking at the second large market share after graphite,is a promising anode material for lithium-ion batteries due to its good cycle stability,rate capability,and safety with both conventional and low-temperature electrolytes.However,several critical challenges,such as the low capacity and gassing issue,hindered the wide applications of LTO anode.Recent progress indicated that the LTO performances are possible to be further improved by novel strategies,such as heterogeneous phase control,surface engineering,or overlithiation.To rethink and develop advanced LTO anodes,this review intensively associates the performances and modification strategies with the electronics/crystal structures.From a thermodynamic/kinetic point of view,we summarized the data obtained from recently developed characterization techniques,and the results of electrochemical performances and fundamental structures of LTO to potentially address several key challenges and issues toward advanced LTO anodes.As a result,light is shed on the future research direction of the LTO anodes.
