A Dual-Phase Pore Engineering Strategy to Enhance Low-Voltage Plateau Capacity of Hard Carbon for Sodium-Ion Batteries

Abstract

Hard carbon is the most commercially viable anode material for sodium-ion batteries (SIBs), and yet, its practical implementation remains constrained by insufficient low-voltage plateau capacity, a critical parameter governing storage capacity. This study introduces a targeted component removal and chemical etching strategy to precisely tailor the porous structure of hard carbon and thus remarkably enhance the plateau capacity. In this strategy, alkaline-dissolved components are removed to form a closed-pore core with tunable size. Subsequently, the in situ occupied alkaline engineers the pore structure through chemical etching. The optimized hard carbon material not only has short-range disordered graphite domains to facilitate Na⁺ ions' intercalation and deintercalation but also has abundant micropores and closed-pore structures with appropriate pore sizes and an ultrathin carbon layer (1−3 layers) to significantly increase the sodium storage sites. The resulting hard carbon delivers a high reversible specific capacity of 389.6 mAh g⁻¹ with a low-voltage plateau capacity as high as up to 261.5 mAh g⁻¹ and an initial Coulombic efficiency of 90.7%. Crucially, this cost-effective methodology shows broad precursor adaptability across lignocellulosic biomass, establishing a universal paradigm for designing high-performance carbonaceous anodes for SIBs.

Keywords

biomass / hard carbon / porous structure / sodium-ion battery

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