Defect Engineering of Carbon Frameworks Driven All‐Slope Hard Carbon Anodes for Fast‐Charging Sodium‐Ion Batteries

ABSTRACT

Fast‐charging capability is one of the crucial factors determining the application prospects of sodium‐ion batteries (SIBs). Nevertheless, the mismatched sodium storage kinetics and Coulombic efficiency (CE) in hard carbon anodes are bottlenecks in the implementation of fast‐charging SIBs. Herein, we propose a facile pre‐carbonization strategy to precisely tailor the intrinsic structure of hard carbon, enabling the simultaneous achievement of high fast‐charging sodium storage capacity and superior initial CE in hard carbon (EHC‐ X ) anodes. Through comprehensive structural characterizations, the regulation mechanism of pre‐carbonization temperature on the intrinsic structure of EHC‐ X is elucidated. As an anode for SIBs, EHC‐8, which features the lowest graphitization degree and highest mesopore volume, delivers an ultra‐high initial CE (90.3%) and exceptional fast‐charging sodium storage capacity (150 mAh g ⁻¹ at 50 A g ⁻¹ with a recharge time of ∼10.8 s). Combined in situ Raman spectroscopy, theoretical calculations, and ex‐situ characterizations, the fast‐charging sodium storage mechanism of defect sites in EHC‐8 is revealed. Furthermore, a sodium‐ion hybrid capacitor fabricated with the EHC‐8 anode delivers ultra‐high energy/power densities (175 Wh kg ⁻¹ /48.2 kW kg ⁻¹ ), along with acceptable fast‐charging cycling stability. This work provides theoretical and methodological guidance for the construction of fast‐charging hard carbon anodes based on defect engineering.