Flavone as a novel multifunctional electrolyte additive to improve the cycle performance of high-voltage LiNi0.5Mn1.5O4 batteries

The high operating voltage of LiNi0.5Mn1.5O4 (LNMO) material poses a challenge to conventional carbonate-based electrolyte, whose continuous decomposition leads to the fast capacity fading of battery. Herein, flavone (FLA) as a novel multifunctional electrolyte additive is introduced into basic electrolyte (1.0 M LiPF6 - ethylene carbonate + dimethyl carbonate) to significantly improve the cycle performance of LNMO/Li battery. Experiments and density functional theory (DFT) calculations manifest that FLA can be preferentially oxidized and reduced to generate stable surface films to ameliorate the decomposition of other electrolyte solvent. Besides, the FLA-derived Li2CO3-rich surface films can improve interfacial stability and ensure high ionic conductivity. In addition, FLA is more inclined to react with HF compared with EC and DMC, thereby alleviating LNMO corrosion and transition metal ions dissolution by HF, and consequently enhance the stability of bulk structure. The preferential reduction of FLA contributes to the formation of a stable passivation layer with high ionic conductivity on Li anode, which is conducive to uniform lithium deposition during the cycling and prolonging battery cycle life. The cycle performances of LNMO/Li and LNMO/Graphite batteries using the electrolyte containing 1 wt% FLA are significantly improved compared with those using basic electrolyte.