Optimally Carbonized Mangrove Wood–Derived Hard Carbon with a Soft Carbon Coating for High‐Performance Sodium‐Ion Battery Anodes

Sodium‐ion batteries (SIBs) are emerging as promising alternatives to lithium‐ion batteries owing to the abundance of sodium resources and the limited supply of lithium raw materials. However, the development of high‐performance anode materials remains a critical challenge owing to the relatively low initial coulombic efficiencies (ICEs) and limited reversible capacities of conventional carbon‐based anodes. Herein, hard carbon (HC) from mangrove wood was synthesized via controlled carbonization, and its electrochemical performance was systematically investigated. HC prepared by carbonization at 1200 °C (MWHC‐1200) exhibited the best performance, delivering a high reversible capacity of 266.6 mAh g −1 and an ICE of 75%. Pitch‐derived soft carbon coatings (containing 5, 10, or 15 wt% pitch) were applied to HC synthesized at the optimal carbonization temperature to further enhance Na + ‐storage performance. Notably, the composite containing 10 wt% pitch (PC‐10) exhibited the best electrochemical performance, delivering a high reversible capacity of 291.5 mAh g −1 , an ICE of 82%, a capacity retention of 90.4% after 200 cycles, and an excellent rate capability. These improvements were associated with the suppression of irreversible reactions and improvement in interfacial stability. This study offers a simple yet effective approach for improving the electrochemical properties of biomass‐derived HC and provides insights into the design of practical SIB anodes.