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摘要
LiNi0.5 Co0.2 Mn0.3 O2 cathode material is considered as one of the most promising cathode materials for high energy density lithium ion battery due to its high energy density, good cycling stability and high safety. However, LiNi0.5 Co0.2 Mn0.3 O2 cathode material suffers from rapid capacity decay under high?voltage conditions due to the poor oxidation resistance of conventional carbonate?based electrolytes. Based on fluoroethylene carbonate (FEC), the cycle stability of fluorinated linear carbonates such as bis (2, 2, 2?trifluoroethyl) carbonate (TFEC) and methyl (2,2, 2?trifluoroethyl) carbonate (MTFEC) replacing diethyl carbonate (DEC) were studied under high voltage. Electrochemical test results showed that the capacity retention of 4.5 V LiNi0.5 Co0.2 Mn0.3 O2 / artificial graphite pouch cells increased from 45.5% to 72.5% and 81.6% after 700 cycles at 45 ℃ after TFEC and MTFEC replaced DEC. Linear sweep voltammetry (LSV), scanning electron microscope (SEM), transmission electron microscope (TEM), X?ray diffraction (XRD), Raman spectroscopy (Raman) and inductively coupled plasma atomic emission spectroscopy (ICP?OES) studies proved that TFEC and MTFEC had better oxidation resistance at high voltage than DEC. They could obviously inhibit the oxidation decomposition of electrolyte on the surface of the high?voltage cathode, effectively protect the interface stability of cathode and anode materials, and mitigate the damage of solid electrolyte interphase (SEI) film caused by the dissolution of transition metal ions from cathode materials. Fluorinated linear carbonates as electrolyte solvents are of great promise in the application of high?voltage lithium ion batteries. ? 2023 Cailiao Daobaoshe/ Materials Review.
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