Zinc-regulated hard carbon as a sodium-ion battery anode material

Due to their excellent stability and low cost, hard carbon (HC) materials have gained significant attention as anode materials in sodium-ion batteries (SIBs). However, the low initial Coulomb efficiency (ICE) and reversible capacity of HC limit its practical application. To address this issue, this study successfully prepared zinc-regulated HC (Zn-HC) with a rich microporous structure, significantly enhancing its sodium-ion storage performance. Electrochemical tests showed that Zn-HC exhibited high reversible capacity (386 mAh g⁻¹ at 1.0 A g⁻¹) and ICE (73.1 %). In-situ Raman spectroscopy, electrochemical impedance spectroscopy, and galvanostatic intermittent titration technique revealed that sodium-ion storage in Zn-HC occurs primarily through surface adsorption and intercalation/pore filling processes. Density functional theory (DFT) calculations further confirmed that the increased interlayer spacing and the introduction of C=O functional groups enhance sodium-ion storage capacity. This study provides important insights for the design of high-performance anode materials for SIBs with superior electrochemical properties.