Self-activated micropores tailor carbon layer stacking and graphitic microstructures for high-performance sodium storage

Abstract

Lignin-derived hard carbon shows potential as an anode material for sodium-ion batteries (SIBs) due to its high carbon content and aromatic structure, but its limited reversible adsorption sites and low conductivity hinder performance. This study introduces a self-activation strategy to optimize carbon layer stacking and surface functional groups in microporous carbon, significantly enhancing sodium storage capacity and rate performance. By utilizing oxygen-containing functional groups in organic solvent lignin, we induce micropore formation during pyrolysis, effectively regulating graphite domains and closed pores structures without disrupting carbon layer growth. Unstacked graphene layers serve as efficient electron transport channels and expose additional adsorption sites, simultaneously increasing sodium storage capacity and intrinsic conductivity. The resultant S-OLHC demonstrates a remarkable sodium storage capacity of 358 mA h/g at 0.05 A/g after 200 cycles and maintains 231 mA h/g after 1000 cycles at 2 A/g. This strategy eliminates the need for additional pore-forming agents, offering a simpler, more efficient, and environmentally friendly approach compared to traditional activation methods. This work advances the rational design of high-performance biomass-derived hard carbon for SIBs by leveraging inherent structural characteristics and provides a sustainable low-carbon strategy for lignin valorization in renewable energy storage.