Simple and cost-effective method for engineering tunable defects and functional groups for high-performance coal-derived hard carbon anodes in sodium-ion batteries

Abstract

The development of advanced anode materials for sodium-ion batteries (SIBs) is critical for enhancing energy storage capabilities. Herein, we present a simple and cost-effective one-step carbonization method to engineer tunable defects and functional groups in coal-derived hard carbon (HC) anodes. By exploiting the inherent features of coal, such as its aromatic structure and reactive functionalities, we systematically tailor the HC microstructure through controlled carbonization. The resulting materials exhibit adjustable features, including graphite-like microcrystals, amorphous carbon domains, nanoporous networks, and oxygen-containing functional groups, enabling optimized sodium-ion storage performance. Notably, the lignite-derived HC material (L-1300) synthesized at 1300 °C achieves a reversible capacity of 295 mAh g⁻¹, an initial Coulombic efficiency of 89 %, and exceptional capacity retention (97 %) after 500 cycles at 1 C. The enhanced electrochemical performance is attributed to the synergistic effects of engineered defects and functional groups, which facilitate efficient sodium ion transport and storage. This study demonstrates the potential of coal as a sustainable and low-cost precursor for high-performance HC anodes, offering a promising approach for next-generation SIBs.