Starch as an efficient precursor for hard carbon anodes enables high-performance sodium-ion storage

Starch is an ideal choice for hard carbon anode precursors in sodium-ion batteries because of its diverse sources and high carbon content. Nevertheless, starch experiences melting and foaming in the initial stages of pyrolysis, which results in low yields and hinders the large-scale production and application of starch-derived hard carbon. Herein, we employed phenolic resin and maleic anhydride to esterify and cross-link starch to prepare hard carbon. The starch foaming was successfully inhibited through the synergistic effect among composite precursors. Benefiting from abundant micropores/mesopores and larger microcrystalline structure, the prepared hard carbon delivers a high specific capacity of up to 342.28 mA h g^-1 and an impressive initial discharge capacity of 85.89%. The capacity retention is as high as 87.24% after 100 cycles of charge and discharge. Furthermore, the hard carbon demonstrates excellent rate performance with a capacity recovery rate of 95.11%. The stabilized starch-derived hard carbon anode possesses both high sodium storage performance and a lower cost, demonstrating potential for commercialization on a large scale.