Hard carbon derived from Physalis alkekengi L. husks as a stable anode for sodium-ion batteries†

Hard carbon is one of the most promising anode materials for sodium-ion batteries (SIBs). Biomass-derived hard carbon is deemed to be a good choice because of its superior material properties, abundance source, and cost advantages. This work used Physalis alkekengi L.'s husks as precursors to prepare a series of hard carbon materials via a pyrolysis method. It was found that the carbonization temperature is closely linked to the lattice characteristics of PLH-derived hard carbon. Higher temperatures promote the degree of graphitization of the lattice, which produces a smaller carbon interlayer spacing. The optimal sample demonstrated a high electrochemical performance and good reaction kinetics. It maintained a capacity of 291.6 mA h g⁻¹ after 100 cycles at 0.1 A g⁻¹ and delivered an average capacity of 61.9 mA h g⁻¹ at a high rate of 2.0 A g⁻¹. Furthermore, a full cell assembled using the optimal sample as an anode and Na₃V₂(PO₄)₃ as a cathode gave a high reversible capacity of 161.9 mA h g⁻¹ at 0.1 A g⁻¹ after 100 cycles.