Research on the synergistic effect of fluoroethylene carbonate and lithium difluoro(oxalato)borate in electrolyte on LiNi_0.5Mn_1.5O₄-based high-voltage lithium-ion batteries

To meet the increasing demand for energy storage, it is urgent to develop high-voltage lithium-ion batteries. The electrolyte’s electrochemical window is a crucial factor that directly impacts its electrochemical performance at high-voltage. Currently, the most common high-voltage cathode material is LiNi_0.5Mn_1.5O₄ (LNMO). This paper aims to match LNMO cathode material to develop an electrolyte with stable electrochemical performance under high-voltage. Fluoroethylene carbonate (FEC) and lithium difluoro(oxalato)borate (LiDFOB) are studied as co-solvent and additive components in LiNi_0.5Mn_1.5O₄ (LNMO) high-voltage electrolyte, respectively. This paper reports an increase in the electrochemical window from the original 4.3 to 5.5 V through the synergistic effect of two additives. The two additives also promote the formation of CEI layers on the cathode surfaces. This film acts as a protective barrier, safeguarding the electrode material’s structure from potential damage. After undergoing 100 cycles at a temperature of 25 °C, the rate of capacity retention can achieve a value of 75.1%; after 50 cycles at 40 °C, it can reach 78.2%. Our work offers guidance for the commercial production of high-performance, high-voltage lithium-ion batteries.