LiPF₆ and lithium difluoro(oxalato)borate/ethylene carbonate+dimethyl carbonate +ethyl(methyl)carbonate electrolyte for LiNi_0.5Mn_1.5O₄ cathode

Abstract

LiODFB electrolyte’s compatibility with LiNi_0.5Mn_1.5O₄ high-voltage cathode material was studied by cyclic voltammetry, charge-discharge test and AC impedance. The results show that at 25 and 60 °C, the LiODFB-based electrolyte has better electrochemical stability than LiPF₆. AC impedance plots show that the LiODFB battery has a lower charge-transfer resistance than LiPF₆ battery at 60 °C, which indicates that LiODFB battery has excellent cycling performance at high temperature. At 25 and 60 °C, the LiNi_0.5Mn1_.5O₄/Li half cells with LiODFB or LiPF₆ as electrolyte all have simple redox peak, showing that each of them has an excellent reversibility. LiODFB battery has better cycle performance than LiPF₆ battery at 25 °C and 60 °C. At 25 °C, their 0.5C initial discharge specific capacities are 126.3 and 131.6 mA·h/g, and their capacity retention ratios of the 100th cycle are 97.1% and 94.7%, respectively. At 60 °C, their 0.5C initial discharge specific capacities are 132.6 and 129.1 mA·h/g, and their capacity retention ratios of the 100th cycle are 94.1% and 81.7%, respectively.

Keywords

lithium difluoro(oxalato)borate / LiNi_0.5Mn_1.5O₄ / electrochemical performance / compatibility

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