Surface Porousization of Hard Carbon Anode Materials for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have been considered as a promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage. However, the commercial graphite anode is not suitable for SIBs due to its low Na⁺ ion storage capability. Currently, hard carbon has been considered a promising anode material for SIBs. Herein, the surface porousized hard carbon anode materials have been prepared by using hydrogen peroxide (H₂O₂) with a hydrothermal method (HC-HO) and utilized as the anode material for SIBs. The porous structure of HC-HO provides more storage space for Na⁺ ions and enhances the intercalation/deintercalation reversibility and diffusion rate of Na⁺ ions. Moreover, HC-HO can effectively alleviate the particle volume expansion and generate a thin and stable SEI film during charge/discharge processes. Thus, the HC-HO exhibits a high reversible capacity (314.4 mAh g^-1 with an ICE of 92.3% at 0.05 C), excellent rate performance (241.4 mAh g^-1 at 3 C), and outstanding cycling stability (a capacity retention of 78.6% after 500 cycles at 1 C). The preparation of porous hard carbon provides new ideas for the future development direction of hard carbon.