Pore Structure Modulation and Defect Engineering of Soft Carbon@Coal-Derived Hard Carbon for Enhanced Sodium Storage Application in SIBs

Hard carbon (HC) is regarded as the most promising commercial anode material for sodium-ion batteries (SIBs) due to its low cost, abundant sources, large reversible capacity, and suitability. Nevertheless, HC suffers from low initial coulombic efficiency (ICE), poor rate performance, and long-term cycling performance, significantly restricting its practical application. Herein, we proceed with defined regulation of the microcrystalline structure of coal-derived HC, which obtains the reduced surface defects and the increased interlayer spacing, further enhancing the sodium storage capacity of coal-derived HC as an anode material for SIBs by coating porous HC with soft carbon (SC). Meanwhile, we successfully synthesize high-performance SC@HC composite materials through chemical crosslinking reactions by innovatively adopting the sol-gel method and SC coating for the complex composition of coal. The SC@HC composite material as an anode in SIBs can deliver a reversible capacity of 320 mAh/g at 0.01 A/g, a high ICE of 89%, and good cycling stability (capacity retention of 80% after 400 cycles at 1 A/g). This work can rationally guide the design of low-defect and much more closed pores coal-derived HC materials and provide a feasible route for the development of high-performance HC-based anode materials for SIBs applications.