Microporous Structure Engineering of Hard Carbon through Synergistic Catalytic Dehydration and Activation for Enhanced Sodium Ion Storage

Abstract

Hard carbon derived from renewable biomass is a promising anode material for sodium-ion batteries (SIBs), due to its graphite-like microcrystalline structure and porous architecture. However, engineering the porous structure to balance Na⁺ transport and electrolyte stability remains a significant challenge. Excessively large pores may induce electrolyte decomposition, while overly small pores can restrict Na⁺ accessibility. Both of these compromises reversible capacity, rate capability, and initial Coulombic efficiency (ICE). Herein, a synergistic catalytic dehydration and activation strategy is developed to precisely engineer the microporous structure of hard carbon for enhanced Na⁺ storage. By redirecting cellulose dehydration pathways through esterification and chemical activation, the yield of hard carbon is significantly enhanced while generating an abundant desirable micropores (<1.36 nm). These tailored micropores facilitate Na⁺ storage through surface adsorption, intercalation, and pore-filling mechanisms. Furthermore, the optimized structure promotes the pre-desolvation of solvated Na⁺ while suppressing decomposition of large solvated Na⁺ clusters, thereby inhibiting unstable solid-electrolyte interphase (SEI) layer formation. The engineered hard carbon delivers outstanding performance, including a high reversible capacity of 368 mAh g⁻¹ at 0.02 A g⁻¹, an ICE of 90%, and remarkable cycling stability. This scalable strategy is applicable to various biomass precursors, providing a practical pathway for advancing next-generation SIB anode materials.