Improving the Sodium Storage Behavior of Anthracite with a Tailored Interface Layer

Coal-derived hard carbon (C-HC) materials have emerged as promising candidates for energy storage applications due to their abundant resource availability and cost-effectiveness. However, large-scale application is limited by a low initial coulombic efficiency (ICE) and reversible capacity. Therefore, this work employed anthracite as a precursor to fabricate HC matrices through the optimized carbonization processes. Leveraging the compositional diversity of solvated asphalt, we successfully constructed an artificial interface layer on anthracite (AN) surfaces via liquid-phase impregnation. Morphological characterization confirmed the formation of AN materials with nanointerface layers (designated as AN@LQ). Electrochemical evaluation in ester-based electrolytes demonstrated that AN@LQ achieved a reversible specific capacity of 283 mAh g–1 at 0.1 C, representing an 11% enhancement over unmodified HC (251 mAh g–1). Notably, the ICE was substantially improved from 74 to 88%, with capacity retention reaching 89% after 100 cycles (versus 78% for the AN1200). Through a constant current intermittent titration technique, cyclic voltammetry, quasi-in situ EIS, and XPS analysis at different etching depths, we have verified the formation of AN@LQ. The diffusion coefficient of sodium ions (DNa+) has been improved compared to AN material. This is attributed to the barrier effect of the coating, which evenly distributes the solid electrolyte. This work not only provides novel insights into the interface construction of HC materials but also provides a cost-effective strategy for facilitating the scaling up of sodium-ion batteries.