Effect of pore structure regulation in coconut shell-derived hard carbon on sodium storage capacity

Biomass-derived hard carbon (HC) has garnered significant attention due to its wide availability, low cost, and strong tunability. However, its relatively low reversible capacity and initial Coulombic efficiency (ICE) hinder its commercialization. This study proposes a preparation strategy for coconut shell-derived hard carbon (CSHC) as an anode material for sodium-ion batteries. Through chemical activation combined with high-temperature carbonization, a unique porous structure is developed in the CSHC. By optimizing the alkali impregnation concentration and carbonization temperature, the optimized CSHC-15–1400 achieves a high specific capacity of 372 mAh g^-1 and an ICE of 91.6 %. The results indicate that a well-designed porous structure and appropriate graphite interlayer spacing significantly enhance the sodium storage capacity and cycling stability of the HC material. Moreover, cyclic voltammetry (CV) kinetics analysis and galvanostatic intermittent titration technique (GITT) tests revealed the unique sodium storage mechanisms of CSHC-15–1400 in both the slope and plateau regions, providing theoretical insights for further improving the performance of HC materials. This study offers a novel approach for the commercialization of biomass-derived hard carbon in energy storage applications.