Endogenous Template-Directed Topological Engineering of Lignite-Derived Hard Carbons for Kinetically Accelerated...

Coal is a promising precursor for the preparation of hard carbon, which shows great commercial potential as an anode material for sodium-ion batteries (SIBs). However, the π-π interactions between planar aromatic molecules and the trend toward graphitization lead to a highly ordered carbon structure with narrow interlayer spacing. In this study, a self-templating strategy is proposed to regulate the closed-pore structures of coal-based hard carbon at the molecular level, and finally improve the plateau capacity. The -OH is beneficial for the formation of closed-pore structure during carbonization by chelation with metal ions, and C═O can help to prevent graphitization, increase the interlayer spacing and form hybrid organic-inorganic SEI through surface functional remodeling with salt in ether-based electrolytes. The coal-based hard carbon displays good cycling stability, exhibiting a high reversible capacity (350 mAh g^-1) at 50 mA g^-1 and capacity retention of up to 88% after 8000 cycles at 5 A g^-1. Moreover, the full battery assembled with NVP demonstrates a stable cycling performance. This work provides new insights into the construction of closed pores and the role of carbonyl groups in hard carbons for enhancing sodium storage performance.