Effects of LiBF4 concentration in carbonate-based electrolyte on the stability of high-voltage LiNi0.5Mn1.5O4 cathode

LiBF4 has attracted much attention due to its better thermal stability, lower sensitivity to environmental humidity, and lower charge transfer resistance provided by its solution, especially at high voltage. Herein, the effects of the concentration of LiBF4 salt on the stability and electrochemical properties of LiNi0.5Mn1.5O4 (LNMO) cathode material have been investigated by using the mixed solvents of LiBF4 salt, vinyl carbonate (EC), and diethyl carbonate (DEC) as electrolytes. The surface morphology and structure of cycled LNMO electrode are studied by scanning electron microscopy (SEM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The results show that the optimum concentration of LiBF4 salt is 1.4M LiBF4-EC/DEC (1:5, by volume). Under optimum conditions, the LNMO cathode material has high electrochemical capacity and favorable rate performance. Meanwhile, the prepared electrolyte can easily form a thin and stable SEI film on the surface of LNMO electrode, which can effectively inhibit the continuous decomposition of the electrolyte.