Synergistic Effect of Boron Doping and Oxygen-Containing Functional Groups in Bamboo-Based Hard Carbon for Enhanced Sodium Storage Performance

Since 2012, hard carbon has received significant attention as one of the most promising anode materials for sodium-ion batteries (SIBs). However, their industrial application is limited by low capacity and poor rate performance. This study combines experimental and theoretical investigations to explore the effects of boron doping on bamboo-based hard carbon anode materials after sulfuric acid treatment. The results demonstrate that the synergistic modification of acid treatment and boron doping effectively improves the electrochemical properties of hard carbon. Acid etching removes most of the impurities favoring the increase in active sites but to some extent decreases the interlayer distance, whereas boron doping creates defects in the hard carbon material results, which in turn will add additional ionically active adsorption sites. It exhibits an excellent charging specific capacity of 308.87 mAh g–1, enhanced rate performance, and superior capacity retention. In the long cycle test at 0.5C, B and S dual-doped hard carbon (BHC) maintains 77% capacity retention after 500 cycles, outperforming untreated materials. Doped samples consistently show discharge specific capacities higher than those of undoped ones in rate performance tests. These findings suggest that acid-treated and boron-doped hard carbon is a potential candidate for high-performance anode materials in SIBs.