Interfacial Chemistry Regulation by Orbital Hybridization for Superior Kinetics of Hard Carbon in Ester-Based Electrolyte

Abstract

Hard carbon is the most commercially viable anode materials for sodium-ion batteries (SIBs), yet its application in ester-based electrolytes is hindered by sluggish interfacial ion diffusion and limited sodium nucleation kinetics. After comprehensive evaluation, an interfacial chemistry regulation strategy was proposed based on the orbital hybridization between bismuth and electrolyte ions, which was realized through the introduction of ammonium bismuth citrate. The surface Bismuth particels regulates the formation of NaF-rich SEI by the improved anion affinity. Collaborated with the in-situ generated highly ion-conductive Na3N, a thin, compact and homogenous SEI was constructed to enable fast and stable interfacial Na+ migration kinetics. Moreover, the Bi atoms can diffused into the hard carbon structures, expanding the carbon interlayers to facilitate the ion diffusion and intercalation as well as enhancing the sodiophilicity in closed pores to lower the nucleation barrier. Benefited by these merits, the resulting T2-BiN exhibits superior sodium-storage kinetics with an outstanding rate capability (185.6 mAh g−1 at 0.5 A g−1) and long-term cycling stability (84.4% after 400 cycles at 0.5 A g−1) in the ester-based electrolyte. Even the practical full cell showed no capacity decay over 400 cycles at 2C. This work provides a simple and effective interfacial modification strategy, offering new insights into advancing hard carbon anodes for high-performance SIBs.