Regulation on Microstructure of Biomass Hard Carbon Originated From Pinecone

With the development of sodium‐ion batteries (SIBs), biomass‐derived hard carbon has emerged as one of the most promising candidates for commercialized anode materials. However, low first‐cycle charge–discharge efficiency and poor cycling performance still hinder its practical application. In this work, a method for preparing hard carbon by treating pinecone scales is proposed. Firstly, pinecone scales are abundant, low‐cost, easily accessible, and possess a porous structure that can be retained after high‐temperature carbonization. On the other hand, the hard carbon prepared via acid–base treatment achieves effective reduction of impurities and unfavorable oxygen‐containing functional groups. After high‐temperature carbonization, it not only ensures structural stability but also forms an appropriate number of graphite layers, facilitating the intercalation, deintercalation, and transport of sodium ions. Consequently, it exhibits excellent electrochemical performance in SIBs. The initial discharge capacity is 413.43 mAh g −1 . After 100 cycles at a current density of 0.05 A g −1 , the capacity is 360 mAh g −1 , with a capacity retention rate of 86.5%. At a current density of 0.5 A g −1 , after 200 cycles, the capacity remains at 290.4 mAh g −1 , with a retention rate of 87.2%, thus exhibiting great potential as a high‐performance anode material for SIBs.