LiNi0.5Mn1.5O4 (LNMO)/poly(3,4-ethylenedioxythiophene) (PEDOT) composite cathode materials were prepared through in-situ polymerization of thiophene monomer (EDOT), with ammonium persulphate (APS) as oxidizing agent, ...LiNi0.5Mn1.5O4 (LNMO)/poly(3,4-ethylenedioxythiophene) (PEDOT) composite cathode materials were prepared through in-situ polymerization of thiophene monomer (EDOT), with ammonium persulphate (APS) as oxidizing agent, p-toluenesulfonic acid (PTSA) as dopant. The morphology, amount of PEDOT coating, electrochemical properties of LNMO/PEDOT were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and galvanostatic charge and discharge tests. The results show that the composite materials show better cycle performance than bare LNMO.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
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
The preparation of Li4SiO4-coated LiNi0.5Mn1.5O4 materials by sintering the SiO2-coated nickel-manganese oxides with lithium salts using abundant and low-cost sodium silicate as the silicon source was reported. The sa...The preparation of Li4SiO4-coated LiNi0.5Mn1.5O4 materials by sintering the SiO2-coated nickel-manganese oxides with lithium salts using abundant and low-cost sodium silicate as the silicon source was reported. The samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It was found that a uniform and complete SiO2 coating layer could be obtained at a suitable pH value of 10, which transformed to a good LiaSiO4 coating layer afterwards. When used as the cathode materials for lithium-ion batteries, the Li4SiO4-coated LiNi0.5Mn1.5O4 samples deliver a better electrochemical performance in terms of the discharge capacity, rate capability, and cycling stability than that of the pristine material. It can still deliver 111.1 mAh/g at 20 C after 300 cycles, with a retention ratio of 93.1% of the stable capacity, which is far beyond that of the pristine material （101.3 mAh/g, 85.6%）.展开更多
文摘LiNi0.5Mn1.5O4 (LNMO)/poly(3,4-ethylenedioxythiophene) (PEDOT) composite cathode materials were prepared through in-situ polymerization of thiophene monomer (EDOT), with ammonium persulphate (APS) as oxidizing agent, p-toluenesulfonic acid (PTSA) as dopant. The morphology, amount of PEDOT coating, electrochemical properties of LNMO/PEDOT were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and galvanostatic charge and discharge tests. The results show that the composite materials show better cycle performance than bare LNMO.
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.
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.
文摘The preparation of Li4SiO4-coated LiNi0.5Mn1.5O4 materials by sintering the SiO2-coated nickel-manganese oxides with lithium salts using abundant and low-cost sodium silicate as the silicon source was reported. The samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It was found that a uniform and complete SiO2 coating layer could be obtained at a suitable pH value of 10, which transformed to a good LiaSiO4 coating layer afterwards. When used as the cathode materials for lithium-ion batteries, the Li4SiO4-coated LiNi0.5Mn1.5O4 samples deliver a better electrochemical performance in terms of the discharge capacity, rate capability, and cycling stability than that of the pristine material. It can still deliver 111.1 mAh/g at 20 C after 300 cycles, with a retention ratio of 93.1% of the stable capacity, which is far beyond that of the pristine material （101.3 mAh/g, 85.6%）.
