Ethyl-(2,2,2-trifluoroethyl)carbonate(ETFEC)is investigated as a solvent component in high-voltage electrolytes for LiNi0.5Mn1.5O4(LNMO).Our results show that the self-discharge behavior and the high temperature cycle...Ethyl-(2,2,2-trifluoroethyl)carbonate(ETFEC)is investigated as a solvent component in high-voltage electrolytes for LiNi0.5Mn1.5O4(LNMO).Our results show that the self-discharge behavior and the high temperature cycle performance can be significantly improved by the addition of 10%ETFEC into the normal carbonate electrolytes,e.g.,the capacity retention improved from 65.3%to 77.1%after 200 cycles at 60℃.The main reason can be ascribed to the high stability of ETFEC which prevents large oxidation of the electrolyte on the cathode surface.In addition,we also explore the feasibility of electrolytes using single fluoriated-solvents with and without additives.Our results show that the cycle performance of LNMO material can be greatly improved in 1 MLiPF6+pure ETFEC-solvent system with 2 wt%ethylene carbonate(EC)or ethylene sulfate(DTD).The capacity retention of the LNMO materials is 93%after 300 cycles,even better than that of carbonate-based electrolytes.It is shown that the additives are oxidized on the surface of LNMO particles and contribute to the formation of cathode/electrolyte interphase(CEI)films.This composite CEI film plays a crucial role in suppressing the serious decomposition of the electrolyte at high voltage.展开更多
High-voltage lithium-ion batteries(HVLIBs) are considered as promising devices of energy storage for electric vehicle, hybrid electric vehicle, and other high-power equipment. HVLIBs require their own platform voltage...High-voltage lithium-ion batteries(HVLIBs) are considered as promising devices of energy storage for electric vehicle, hybrid electric vehicle, and other high-power equipment. HVLIBs require their own platform voltages to be higher than 4.5 V on charge. Lithium nickel manganese spinel LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode is the most promising candidate among the 5 V cathode materials for HVLIBs due to its flat plateau at 4.7 V. However, the degradation of cyclic performance is very serious when LNMO cathode operates over 4.2 V. In this review, we summarize some methods for enhancing the cycling stability of LNMO cathodes in lithium-ion batteries, including doping, cathode surface coating,electrolyte modifying, and other methods. We also discuss the advantages and disadvantages of different methods.展开更多
Well-developed crystalline LiNi0.5Mn1.5O4 was prepared by solid-state reaction using Li2CO3, NiO and electrolytic MnO2 at high heating and cooling rate. X-ray diffraction (XRD) patterns and scanning electron microscop...Well-developed crystalline LiNi0.5Mn1.5O4 was prepared by solid-state reaction using Li2CO3, NiO and electrolytic MnO2 at high heating and cooling rate. X-ray diffraction (XRD) patterns and scanning electron microscopic (SEM) images showed that LiNi0.5Mn1.5O4 synthesized at 900 ℃ and 950 ℃ had cubic spinel structure with clearly defined shape. LiNi0.5Mn1.5O4 spinel phase decomposed at 1 000 ℃ accompanying with structural and morphological degradation. TG measurement revealed that the weight loss during heating process could be mostly gained in cooling process, and the upward tendency of weight loss during heating process decreased, while that of irreversible weight loss rapidly increased with the increase of temperature. LiNi0.5Mn1.5O4 powders prepared at 900 ℃ for 12 h delivered the maximum discharge capacity of 134 mAh·g-1 with good cyclic performance at 2/7 C. In addition, by adjusting the calcination time at 900 ℃, the capacity and cycling performance of LiNi0.5Mn1.5O4 were further enhanced.展开更多
基金financially supported by National Key Research and Development Program of China(Grant no.2018YFB010440)the National Natural Science Foundation of China(Grant nos.21761132030,21621091).
文摘Ethyl-(2,2,2-trifluoroethyl)carbonate(ETFEC)is investigated as a solvent component in high-voltage electrolytes for LiNi0.5Mn1.5O4(LNMO).Our results show that the self-discharge behavior and the high temperature cycle performance can be significantly improved by the addition of 10%ETFEC into the normal carbonate electrolytes,e.g.,the capacity retention improved from 65.3%to 77.1%after 200 cycles at 60℃.The main reason can be ascribed to the high stability of ETFEC which prevents large oxidation of the electrolyte on the cathode surface.In addition,we also explore the feasibility of electrolytes using single fluoriated-solvents with and without additives.Our results show that the cycle performance of LNMO material can be greatly improved in 1 MLiPF6+pure ETFEC-solvent system with 2 wt%ethylene carbonate(EC)or ethylene sulfate(DTD).The capacity retention of the LNMO materials is 93%after 300 cycles,even better than that of carbonate-based electrolytes.It is shown that the additives are oxidized on the surface of LNMO particles and contribute to the formation of cathode/electrolyte interphase(CEI)films.This composite CEI film plays a crucial role in suppressing the serious decomposition of the electrolyte at high voltage.
基金supported by the foundation on the Creative Research Team Construction Promotion Project of Beijing Municipal Institutions and Science and Technology Foundation(ykj-2016-00161)partly supported by International Research Promotion Program(IRPR)of Osaka University
文摘High-voltage lithium-ion batteries(HVLIBs) are considered as promising devices of energy storage for electric vehicle, hybrid electric vehicle, and other high-power equipment. HVLIBs require their own platform voltages to be higher than 4.5 V on charge. Lithium nickel manganese spinel LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode is the most promising candidate among the 5 V cathode materials for HVLIBs due to its flat plateau at 4.7 V. However, the degradation of cyclic performance is very serious when LNMO cathode operates over 4.2 V. In this review, we summarize some methods for enhancing the cycling stability of LNMO cathodes in lithium-ion batteries, including doping, cathode surface coating,electrolyte modifying, and other methods. We also discuss the advantages and disadvantages of different methods.
文摘Well-developed crystalline LiNi0.5Mn1.5O4 was prepared by solid-state reaction using Li2CO3, NiO and electrolytic MnO2 at high heating and cooling rate. X-ray diffraction (XRD) patterns and scanning electron microscopic (SEM) images showed that LiNi0.5Mn1.5O4 synthesized at 900 ℃ and 950 ℃ had cubic spinel structure with clearly defined shape. LiNi0.5Mn1.5O4 spinel phase decomposed at 1 000 ℃ accompanying with structural and morphological degradation. TG measurement revealed that the weight loss during heating process could be mostly gained in cooling process, and the upward tendency of weight loss during heating process decreased, while that of irreversible weight loss rapidly increased with the increase of temperature. LiNi0.5Mn1.5O4 powders prepared at 900 ℃ for 12 h delivered the maximum discharge capacity of 134 mAh·g-1 with good cyclic performance at 2/7 C. In addition, by adjusting the calcination time at 900 ℃, the capacity and cycling performance of LiNi0.5Mn1.5O4 were further enhanced.
