Boosting the cycling stability of hard carbon with NaODFB-based electrolyte at high temperature

The optimization of electrolyte formulation and the resulting change in the properties of the solid electrolyte interfacial film (SEI) are the key to affecting the cycle stability of sodium ion batteries at high temperatures. Traditional sodium ion electrolytes are prone to decomposition at high temperatures, which leads to a rapid decline in battery performance. Herein, we use an effective strategy to construct a SEI film on hard carbon anodes by introducing self-developed synthetic sodium-difluoro(oxalate)borate (NaODFB)-based ethers electrolyte. This study aims to analyze the compatibility between NaODFB-based electrolyte and hard carbon by theoretical calculations and experimental analysis including Na/Cu cells,In-suit EIS and cyclic voltammetry curves at different scan rates. The results indicate that the Na/HC cells with NaODFB-based electrolyte has excellent cycling stability at 55 °C. The battery delivers a high reversible capacity of 249.9 mAh/g at 100 mA/g due to the stable SEI riched in inorganic substances. This work provides guidance and ideas for the design of sodium-ion battery electrolyte at high temperatures in the future.