Modulating Graphitization and Porosity via a Cross-Linking-Oxidation and Metal-Evaporation Bifunctional Approach in Pitch-Derived Hard Carbon for High-Performance Sodium Storage

Hard carbon is regarded as one of the most promising anode materials in sodium-ion batteries (SIBs). Compared with resin or biomass, pitch offers significant advantages in terms of resource availability and cost, making it an attractive precursor for the synthesis of hard carbon. However, the direct carbonization of pitch usually yields soft carbon with a highly ordered structure and limited porosity, which is detrimental to the sodium storage property. In this study, zinc gluconate was employed to modulate pitch graphitization via a cross-linking-oxidation and metal-evaporation approach. Compared with soft carbon derived from pure pitch (P-1300 and P-200-1300), the resulting hard carbon anode (PZ-3:3-200-1300) demonstrated an enhanced sodium storage capacity with an outstanding reversible capacity of 341.2 mAh g–1 at 20 mAg–1 and a high ICE of 87.7%, accompanied by exceptional rate capability and cycling stability. This study represents the first attempt to synthesize high-performance pitch-based hard carbon materials in SIBs via a bifunctional approach involving cross-linking oxidation and metal evaporation.