Soft template-induced self-assembly strategy for sustainable production of porous carbon spheres as anode towards advanced sodium-ion batteries

Doped porous carbon is a prominent sodium anode material with high specific surface area (SSA) and abundant pore structure. Compared with the traditional “hard template” technique for the synthesis of porous carbon, the “soft template” method offers a more efficient synthesis process and simplified template removal. In response to the urgent need for eco-friendly synthesis methods for functional doping, our research introduces an innovative method using biomass-derived tannic acid as a precursor. We have successfully synthesized N/S double-doped porous spherical carbon materials (DF-N/S) through a self-assembly process driven by hydrogen bonding and solvent evaporation. As an anode material for sodium-ion batteries (SIBs), DF-N/S demonstrates superior electrochemical performance, achieving a specific capacity of 327.04 mAh g⁻¹ at a current density of 0.05 Ag^-1 in ether-based electrolytes. The remarkable sodium storage efficiency of DF-N/S has been thoroughly examined through kinetic analyses and ex-situ characterization methods. This study aims to provide a sustainable and widely adaptable method for the soft template production of doped carbon, while also shedding light on the intricacies of energy storage mechanisms in both ether/ester-based electrolytes.