Crosslinking modification of starch improves the structural stability of hard carbon anodes for high-capacity sodium storage

Compared with the complex components of raw biomass, biomass derivatives with defined structures are more conducive to the controllable synthesis of hard carbon (HC) materials. Starch-based HC has garnered significant attention because of its cost-effectiveness; however, its practical applicability is limited by poor thermal stability. Herein, we propose a strategy for improving the stability of starch through self-assembly crosslinking modification, yielding high-performance HC. Starch and citric acid form a dense crosslinked structure through esterification between hydroxyl and carboxyl groups, effectively overcoming the poor thermal stability. The resulting HC exhibits a low specific surface area (SSA) and abundant closed pore structures, thereby enabling substantial sodium-ion storage. The optimized HC exhibits an improved reversible capacity of 378 mAh g