Tuning Nanopore Structure of Hard Carbon Anodes by in situ incorporation- removal to improve Na-ion storage

Hard carbon, one of the most commercially promising anode materials for sodium-ion batteries (SIBs), faces challenges in balancing rate performance, initial cycle charge efficiency (ICE), and reversible capacity. To enhance specific capacity and achieve high ICE, it is essential to construct hard carbon with abundant sodium-active sites and a controllable graphitization degree. This work presents a comprehensive approach to microstructural regulation of hard carbon through in situ doping and subsequent removal, which introduces active sites and optimizes the microporous structure. It overcomes the limitations of traditional templating methods, such as excessive specific surface area, which leads to low initial coulombic efficiency and poor cycling performance. This method yields high reversible capacity (419.3 mAh g −1 @0.05   A   g −1 ), excellent ICE (95.88%), and outstanding cycling stability. This study presents a viable approach to enhancing the performance of porous hard carbon. It offers a rational design strategy for optimizing HC structures, improving sodium storage performance, and facilitating their practical applications.