Hard carbon derived from biomass composite as a high initial coulombic efficiency anode for sodium-ion batteries

Promoting the commercialization of sodium-ion batteries (SIBs) requires sustainable and low-cost hard carbon (HC) material. At present, many synthesis routes to prepare HC contain various chemical treatments in order to improve the electrochemical performance, which limits the commercial applications of HC. Here, we report an environmentally friendly and economical HC using the composite of corn starch and cellulose as the precursor. Through the structural and surface chemical analysis, as well as galvanostatic discharge–charge tests, the influence of carbonization temperature on the microcrystalline structures, the oxygen-containing functional groups, and the sodium storage capability of the obtained HCs was explored. When evaluated as an anode for SIBs, the obtained SCHC-1500 has a high reversible capacity of 327.8 mAh g⁻¹ at the current density of 0.1 C, an excellent initial coulombic efficiency (ICE) up to 92.1%, and superior rate performance of 163.7 mAh g⁻¹ at 5 C. Furthermore, sodium storage kinetics was investigated by cyclic voltammetry tests at various scan rates, and the diffusion coefficient of sodium ions was calculated through the galvanostatic intermittent titration technique.