Tris(trimethylsilyl) borate as electrolyte additive alleviating cathode electrolyte interphase for enhanced lithium-selenium battery

Abstract Lithium-selenium (Li-Se) batteries have attracted increasing attentions in recent years because of their high energy density and theoretical capacity. One of the keys that influences the cycle stability of Se cathode is the formation of a stable cathode electrolyte interphase (CEI) film between the cathode material and electrolyte. In this work, we report utilizing tris(trimethylsilyl) borate (TMSB) as electrolyte additive to promote the formation of stable CEI film for enhanced Li-Se battery. The TMSB containing electron-deficient boron atoms easily adsorb electron-rich F− and PFx− to form polyanionic groups, which suppress the formation of insulating LiF in the CEI film, promoting the conductivity and stability of the cathode. Furthermore, the TMSB adsorbing PFx− releases more active Li+ for reaction to improve the capacity. These largely improve the compatibility of the electrolyte and the electrode material interface, significantly reducing the interface impedance and increasing the rate capability. As the result, the system with 1 wt% TMSB exhibits a high specific discharge capacity of 462 mA h g –1 at 1 C after 500 cycles, showing 130% improvement for the cathode without TMSB. Our work here confirms that TMSB as electrolyte additive can effectively improve the electrochemical performance of Li-Se batteries.