Oxygen activation-induced mesoporous structure: enhancing the rate performance of hard carbon anode materials in sodium-ion batteries

Abstract

Hard carbon is a promising anode material for sodium-ion batteries (SIBs) due to its low cost, environmental friendliness, and potential for commercialization. However, its relatively low rate performance limits its application in fast-response energy storage systems, such as smart grids. In this study, bamboo-derived hard carbon was synthesized using a two-step process: low-temperature oxygen activation followed by high-temperature carbonization. Oxygen activation plays a key role in developing a mesoporous structure, enhancing the rate performance and capacity retention of the material. Additionally, oxygen-containing functional groups increase the interlayer spacing, improving intercalation capacity. The optimized anode, OEHC, achieved a reversible capacity of 316.41 mAh g⁻¹ at 0.1C, with high capacities of 210.98 mAh g⁻¹ at 2C and 102.25 mAh g⁻¹ at 5C. The mesoporous structure and oxygen-containing groups promote faster Na⁺ diffusion, reduce polarization effects, and improve kinetics at high rates, resulting in enhanced capacity retention. The preparation method is simple, efficient, and environmentally friendly, contributing to reducing the environmental impact of production.