Structural Reconstruction of Lignocellulose toward Hard Carbons for Optimized Sodium-Ion Storage

Lignocellulose-derived hard carbon has emerged as a promising anode material for commercializing sodium-ion batteries owing to the abundance and the relatively low cost of the raw materials. However, hard carbons derived from the direct carbonization of lignocellulose usually exhibit small pore volumes, which leads to low capacity and poor rate capability. Current studies have provided a limited understanding of the structural evolution mechanism of single-component and intercomponent interactions that determine the closed pore and crystalline structure of hard carbon derived from lignocellulose. Additionally, the correlations between the closed pore structure and the sodium-ion storage capabilities in hard carbons need to be better established. Herein, we have developed an effective process to prepare hard carbons derived from lignocellulose for enhanced sodium-ion storage. Specifically, we demonstrate an effective reconstruction strategy where a high closed-pore volume (0.23 cm³ g^-1) and small closed-pore sizes (1.80 nm) were simultaneously achieved, resulting in excellent electrochemical sodium-ion storage performance. The lignocellulose-derived hard carbon thus exhibits high capacities of 350 mA g^-1 at 50 mA g^-1 and 236 mAh g^-1 at 5000 mA g^-1. This study provides both mechanistic understanding and practical strategies for modulating the microstructures of a lignocellulose precursor to design high-performance hard carbon anodes.