Severe capacity fading and poor high rate performance of lithium sulfur(Li–S) battery caused by "shuttle effect" and low conductivity of sulfur hampers its further developments and applications. Li_4Ti_5O_(...Severe capacity fading and poor high rate performance of lithium sulfur(Li–S) battery caused by "shuttle effect" and low conductivity of sulfur hampers its further developments and applications. Li_4Ti_5O_(12) (LTO)possesses high lithium ion conductivity, and it is also can be used as an active adsorbent for polysulfide. Herein, fine LTO particle coated carbon nanofibers(CNF) were prepared and a conductive network both for electron and lithium ion was built, which can greatly promote the electrochemical conversion of polysulfide and improve the rate performance of Li–S batteries. Meanwhile, a quantity of adsorption sites is constructed by defects of the surface of LTO-CNF membrane to effectively immobilize polysulfide. The multifunctional LTO-CNF interlayer could impede the shuttle effect and enhance comprehensive electrochemical performance of Li–S batteries, especially high rate performance. With such LTO-CNF interlayer,the Li–S battery presents a specific capacity of 641.9 mAh/g at 5 C rate. After 400 cycles at 1 C, a capacity of 618.0 mAh/g is retained. This work provides a feasible strategy to achieve high performance of Li–S battery for practical utilization.展开更多
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
A sol-gel method using lauric acid as surfactant was used to synthesize Li4Ti5O12 nanocrystals with an ultra-fine particle size distribution between 120 and 250 nm.In order to obtain the electrode materials with the b...A sol-gel method using lauric acid as surfactant was used to synthesize Li4Ti5O12 nanocrystals with an ultra-fine particle size distribution between 120 and 250 nm.In order to obtain the electrode materials with the best electrochemical performance,the content of lauric acid during Li4Ti5O12 synthesis was systematically studied.The physical and electrochemical properties of the synthesized samples were characterized by X-ray diffraction（XRD）,field emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM）,laser particle size analysis,alternating current impedance（AC） and galvanostatic charge-discharge experiments.The highly dispersed Li4Ti5O12 nanocrystals obtained at 800 ℃ for 10 h can deliver a specific capacity of 163.3 mA-h/g at 1C rate without obvious capacity fade up to 50 cycles.The results suggest that well dispersed Li4Ti5O12 nanocrystals shorten the Li-ion diffusion length and enhance the electrochemical kinetics of the samples,which are very crucial to high rate capability.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
It is the core to improve the electron/ion transfer features of Li_(4)Ti_(5)O_(12) for achieving high-rate anode in lithium ion batteries.By directly using graphite oxide powder,nano-Li_(4)Ti_(5)O_(12)/reduced graphit...It is the core to improve the electron/ion transfer features of Li_(4)Ti_(5)O_(12) for achieving high-rate anode in lithium ion batteries.By directly using graphite oxide powder,nano-Li_(4)Ti_(5)O_(12)/reduced graphite oxide composite with mesopore-oriented porosity is prepared through one-pot facile ball-milling method in this work.Synthesis mechanism underlying the self-nucleophilic effect of oxygen-containing functional groups in graphite oxide is substantiated.Reactants can intercalate into graphite oxide bulk and in-situ generate nanoparticles.Subsequently,graphite oxide with nanoparticles generated inside can obtain a mesopore-oriented porous structure under ball-milling.Furthermore,the synergistic effects of Li_(4)Ti_(5)O_(12) nanoparticles and mesopore-oriented porosity strengthen composites with rapid Li^(+)diffusion and electron conductive frameworks.The obtained optimal LTO/GO-1.75 composite displays excellent high-rate capability(136 mA·h/g at 7000 mA/g)and good cycling stability(a capacity retention of 72%after 1000 cycles at 7000 mA/g).Additionally,the reactants concentration in this demonstrated strategy is as high as 30 wt%−40 wt%,which is over 6 times that of traditional methods with GO suspensions.It means that the strategy can significantly increase the yield,showing big potential for large-scale production.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
基金supported by the National Key Basic Research Program of China (2014CB932400)the National Natural Science Foundation of China (51672156 and 51232005)+3 种基金Guangdong special support program (2015TQ01N401)Guangdong Province Technical Plan Project (2017B010119001 and 2017B090907005)Dongguan City (2015509119213)Shenzhen Technical Plan Project (JCYJ20170817161221958, JCYJ20170412170706047, JCYJ20170307153806471, and GJHS20170314165324888)
文摘Severe capacity fading and poor high rate performance of lithium sulfur(Li–S) battery caused by "shuttle effect" and low conductivity of sulfur hampers its further developments and applications. Li_4Ti_5O_(12) (LTO)possesses high lithium ion conductivity, and it is also can be used as an active adsorbent for polysulfide. Herein, fine LTO particle coated carbon nanofibers(CNF) were prepared and a conductive network both for electron and lithium ion was built, which can greatly promote the electrochemical conversion of polysulfide and improve the rate performance of Li–S batteries. Meanwhile, a quantity of adsorption sites is constructed by defects of the surface of LTO-CNF membrane to effectively immobilize polysulfide. The multifunctional LTO-CNF interlayer could impede the shuttle effect and enhance comprehensive electrochemical performance of Li–S batteries, especially high rate performance. With such LTO-CNF interlayer,the Li–S battery presents a specific capacity of 641.9 mAh/g at 5 C rate. After 400 cycles at 1 C, a capacity of 618.0 mAh/g is retained. This work provides a feasible strategy to achieve high performance of Li–S battery for practical utilization.
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
文摘A sol-gel method using lauric acid as surfactant was used to synthesize Li4Ti5O12 nanocrystals with an ultra-fine particle size distribution between 120 and 250 nm.In order to obtain the electrode materials with the best electrochemical performance,the content of lauric acid during Li4Ti5O12 synthesis was systematically studied.The physical and electrochemical properties of the synthesized samples were characterized by X-ray diffraction（XRD）,field emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM）,laser particle size analysis,alternating current impedance（AC） and galvanostatic charge-discharge experiments.The highly dispersed Li4Ti5O12 nanocrystals obtained at 800 ℃ for 10 h can deliver a specific capacity of 163.3 mA-h/g at 1C rate without obvious capacity fade up to 50 cycles.The results suggest that well dispersed Li4Ti5O12 nanocrystals shorten the Li-ion diffusion length and enhance the electrochemical kinetics of the samples,which are very crucial to high rate capability.
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Project(21875283) supported by the the National Natural Science Foundation of China。
文摘It is the core to improve the electron/ion transfer features of Li_(4)Ti_(5)O_(12) for achieving high-rate anode in lithium ion batteries.By directly using graphite oxide powder,nano-Li_(4)Ti_(5)O_(12)/reduced graphite oxide composite with mesopore-oriented porosity is prepared through one-pot facile ball-milling method in this work.Synthesis mechanism underlying the self-nucleophilic effect of oxygen-containing functional groups in graphite oxide is substantiated.Reactants can intercalate into graphite oxide bulk and in-situ generate nanoparticles.Subsequently,graphite oxide with nanoparticles generated inside can obtain a mesopore-oriented porous structure under ball-milling.Furthermore,the synergistic effects of Li_(4)Ti_(5)O_(12) nanoparticles and mesopore-oriented porosity strengthen composites with rapid Li^(+)diffusion and electron conductive frameworks.The obtained optimal LTO/GO-1.75 composite displays excellent high-rate capability(136 mA·h/g at 7000 mA/g)and good cycling stability(a capacity retention of 72%after 1000 cycles at 7000 mA/g).Additionally,the reactants concentration in this demonstrated strategy is as high as 30 wt%−40 wt%,which is over 6 times that of traditional methods with GO suspensions.It means that the strategy can significantly increase the yield,showing big potential for large-scale production.
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.
