Engineering Pseudo-Graphite-Dominated Hard Carbon as Anode for Sodium-Ion Batteries

Abstract

It remains challenging to develop hard carbon that simultaneously meets the requirements of initial Coulombic efficiency (ICE) and capacity for practical sodium-ion batteries (SIBs). Herein, we present a carbon nanotubes (CNT)-templating strategy to engineer pseudo-graphitic domains within hard carbon (PG-HC), resulting in enhanced graphitization extent, optimized closed pores, expanded interlayer spacing, and enriched ultramicropores. These merits enable PG-HC to have decreased defect densities and irreversible side reactions as well as enhanced sodium storage sites and transport kinetics, thus delivering an ICE of 94%, a reversible capacity of 426 mAh g–1, and long-term cycling stability. A “rich ultramicropore adsorption–expanded interlayer insertion–closed pore filling” mechanism is elucidated via in situ XRD and Raman characterizations. This work establishes a direct correlation among structural modulation, performance enhancement, and the sodium storage mechanism of hard carbon, offering valuable insights for the development of SIBs.