Regulating the pore structure of biomass-derived HC by zinc gluconate for high-performance sodium-ion battery

Biomass-derived carbon materials, known for their low cost and high carbon yield, are considered as promising precursors for hard carbon (HC) anodes in sodium-ion batteries (SIBs). Designing the closed pores plays a critical role in improving the sodium storage capacity of HC anode. Herein, the pore structure of durian shell-derived HC is regulated by optimizing the concentration of pore-forming template nano-ZnO which is in-situ generated from zinc gluconate (ZG) during pretreatment. The nano-ZnO particles enable the regulation of pore structure through accurately converting the original open pores into closed pores under high-temperature conditions. The optimal durian shell-derived HC features large size closed pores and expanded interlayer spacing of the surrounding thin graphite layers, delivering a reversible capacity of 318 mAh g^-1 with an impressive initial coulombic efficiency of 85% at 0.03 A g^-1. When paired with a Na₃V₂(PO₄)₃ cathode in a full-cell configuration, the system achieves a high energy density of 226 Wh kg^-1 (based on the mass of anode and cathode materials).