Manipulating interfacial chemistry of hard carbon anodes through single-atom catalysis and formation cycling towards fast-charging sodium-ion batteries.

Hard carbons (HCs) are recognized as the most mature and commercially promising anode materials for sodium-ion batteries. However, they still face the challenge of relatively suboptimal rate performance, which necessitates further improvements. In this study, we employ a dual strategy involving atomic-level cobalt (Co) doping and high-current formation cycling (FC) to effectively enhance the performance of hard carbon materials. The catalytic activity of Co atoms can not only modulate the intrinsic structure of hard carbon but also regulate the electrochemical reactions at the hard carbon-electrolyte interface. After FC process, the hard carbon surface rapidly forms a high-quality solid electrolyte interphase (SEI) film that is rich in inorganic components, exhibits uniformity and possesses an optimal density. These effectively mitigate the adverse effects of surface concentration polarization on Na storage behavior while enhancing the migration kinetics of Na. The optimized Co-GC anode material demonstrates a remarkable Na storage capacity and fast-charging capability, maintaining a capacity of 229.63 mAh g after 3000 cycles at a current density of 1.5 A g. This study highlights the significance and opportunities of regulating the interfacial environment for improving the electrochemical performance of HCs.