Regulating lignin aggregation structure to construct high-performance hard carbon anodes for Sodium-Ion batteries

Hard carbon is a highly promising anode material for sodium-ion batteries. Lignin, a major biomass resource featuring low cost and high carbon content, serves as an ideal precursor for the preparation of hard carbon. However, its severe aggregation results in a notably small interlayer spacing (<0.38 nm) and few large closed pores (>2 nm) in hard carbon, which limits the improvement of sodium storage performance. In this study, a PTCDA-mediated chemical modification strategy was employed to effectively mitigate the severe aggregation of lignin, developing a modified lignin-derived hard carbon (APHC-c). Benefiting from the large interlayer spacing of 0.402 nm and abundant small closed pores of 1.50 nm, the APHC-c exhibits a capacity of 312 mAh g −1 at 0.05 A g −1 with an initial coulombic efficiency of 87.2 %. Even at a high current density of 5 A g −1 , it retains a capacity of 212 mAh g −1 , representing a 40 % improvement compared to the unmodified lignin-derived hard carbon. This microstructure regulation strategy not only significantly enhances the rate performance of lignin-derived hard carbon but also provides valuable insights for the development of other carbon-based electrode materials.