Dual Regulation on Structure-Interface Enables Coal-Tar-Pitch-Based Hard Carbon Anodes with High Rate and Storage Performance for Sodium Ion Batteries

Coal-tar-pitches-based hard carbons (HCs) are regarded as promising anode materials for sodium-ion batteries (SIBs). However, designing optimal microstructures and surface chemical states of carbon anodes to enhance Na⁺ diffusion kinetics remains a key challenge for superior sodium storage. Herein, a novel strategy of molecular crosslinking-coupled chemical vapor deposition (CVD) with further post-heat treatment is proposed. This approach utilizes molecular cross-linking to restrict the strong π–π interactions among the aromatic rings of polycyclic aromatic hydrocarbons (PAHs) in the coal tar pitches (CTPs) when simultaneously introducing the developed pore structures with large interlayer spacing into the carbon matrix. The surface carbon coatings by the CVD method can facilitate the transition from the open pores to closed pores. The subsequent post-treatment can effectively regulate the surface chemistry of carbon anodes. Benefiting from the dual regulations on structure-interface, the optimized HPCV5-1200 exhibited a high initial cycle efficiency (ICE) of 91.6% and 320.2 mAh g⁻¹ after 300 cycles at 0.2 A g⁻¹. Moreover, the HPCV5-1200 demonstrated the superior rate capacity (112.6 mAh g⁻¹ at 10 A g⁻¹) with 53.1% of reversible capacity below 0.1 V. Furthermore, the Na₃V₂(PO₄)₃ (NVP)//HPCV5-1200 full cell exposes the high energy density of 233.5 Wh kg⁻¹, with desirable cycling stability and rate performance.