Universal Bulk Pre‐Oxidation Strategy for Programming High‐Performance Pitch‐Derived Hard Carbon Anodes
Shuaipeng Liu, Xiang Wang, Yangyang Chu, Minli Luo, Jinlin Pan, Bin Wu, Ya‐Xia Yin, Sailong Xu
Abstract
Abstract Pre‐oxidation is an essential step to suppress graphitization during the carbonization of pitch‐derived hard carbons (HCs) for sodium‐ion batteries. However, conventional pre‐oxidation typically results in non‐uniform, surface‐gradient crosslinking within pitch precursors, which impedes oxygen diffusion into the bulk and compromises structural homogeneity. Here, we present a chemical bulk‐crosslinking strategy that enables uniform oxygen penetration throughout pitch precursors using ammonium‐based small molecules (NH 4 H 2 PO 4 , (NH 4 ) 2 SO 4 , (NH 4 ) 2 B 4 O 7 , or (NH 4 ) 2 HPO 4 ) as molecular promoters. This approach simultaneously eliminates gradient crosslinking while generating favorable closed porosity and expanded interlayer spacing (0.389 nm). The resulting HC anode achieves a high reversible capacity of 340 mAh g −1 at 30 mA g −1 , with a dominant plateau capacity (263.9 mAh g −1 , 77.3%), and maintains outstanding rate performance (191.2 mAh g −1 at 300 mA g −1 ) in conventional carbonate electrolytes, surpassing most reported pitch‐derived analogues. Through in situ characterization analyses, a sequential “adsorption–intercalation–pore filling” sodium storage mechanism, facilitated by the tailored disorder–pore architecture, is elucidated. This work provides a universal platform for achieving uniform bulk pre‐oxidation of carbon precursors, offering fundamental insights and scalable material design principles for high‐performance sodium‐ion batteries.