A dithiol-based new electrolyte additive for improving electrochemical performance of NCM811 lithium ion batteries

Abstract

LiNi0.8Co0.1Mn0.1O2 (NCM811) has received widespread attention due to its high discharge specific capacity. However, poor cycling performance and rate capacity limit its large-scale commercial applications. Here, we develop 4,5-Dicyano-1,3-dithiol-2-one (DDO) as a new type additive to enhance the cycling performance and rate capacity of NCM811/Li+ half cell. Electrochemical tests show that the discharge capacity retention rate of cell is 75.59% after 200 cycles with 0.1 wt% DDO-containing electrolyte, while the cell with blank electrolyte is only 15.11%. The initial coulomb efficiency and rate capacity with 0.1 wt% DDO are higher than the blank one. Through scanning electron microscope (SEM) analysis, the particle of NCM811 is smooth and integral after 50th cycled, while the particle ruptures in blank electrolyte. The outstanding electrochemical performance of NCM811 is attributed to the stable and uniform cathode electrolyte interphase (CEI) film formed by DDO. Moreover, X-ray photoelectron spectroscopy (XPS) reveals that DDO prevents the decomposition of carbonate solvents and nickel element dissolution of NCM811. Other tests also confirm that the robust CEI layer can reduce the polarization and internal resistance of the cell during cycles.