Remodeling the Interfacial Electrical Field for Inorganic-Rich SEI Enabling Low-Temperature and Fast-Charging Hard Carbon Anodes

Biomass-based hard carbon anodes are attractive for constructing low-cost sodium-ion batteries, although their practical application remains constrained by poor rate performance and limited cycle life at low temperatures. To address these challenges, we employed NbC nanoparticles to regulate the surface electric field of hard carbon anodes. This approach modulates the surface electric field for homogeneous morphology and robust composition of the SEI interphase, ultimately achieving higher rate performance and long-term capacity retention even at temperatures as low as −30 °C. At low temperature, NbC exhibits cycling stability with 99.8% capacity retention after 120 cycles at 0.05 A g −1 . In situ characterization and density functional theory calculations reveal that the enhanced electrochemical performance stems from NbC nanoparticles creating regions of locally enhanced electric field strength. This study highlights the importance of surface electric field regulation strategies in developing advanced hard carbon anode materials with improved low-temperature tolerance and cycling stability.