One-Step Carbonization Tailored Functional Groups and Micropores toward Fast and Durable Na-Ion Storage in Hard Carbon.

Sodium-ion batteries offer a cost-effective solution for energy storage and fast charging, but developing anodes with high capacity, fast charging, and long cycle life remains challenging. Micropores combined with specific functional groups constitute the most ideal design for facilitating pseudocapacitive reactions in hard carbon anode. However, there has been scarce research in this field because the methods for customizing micropores and functional groups are different. This study presents a simple one-step carbonization method using chitosan and NaNH to synthesize hard carbon anodes with micropores and functional groups, enhancing pseudocapacitive sodium storage. The micropores with a high specific surface area significantly shorten the diffusion path of sodium ions, while the carbon skeleton, with its abundant surface-active sites, enables the rapid absorption and desorption of sodium ions. By providing abundant and reversible Na⁺ adsorption sites and effectively mitigating volume expansion, the anode demonstrates excellent rate performance (100 mAh g⁻¹ at 20 A g⁻¹) and outstanding cycling stability (138.4% capacity retention after 3500 cycles). These features contribute to its exceptional overall performance, providing a cost-effective solution for durable and high-performance sodium-ion battery anodes.