A Simple and Effective Low-Temperature Pyrolysis Control Strategy to Enhance the Sodium Storage Performance of Lignite-Based Carbon Materials

Coal is considered a promising carbon material precursor for sodium-ion batteries (SIB) anode due to its abundant reserves and low price. Nevertheless, the hard carbon prepared from coal generally exhibits poor sodium storage performance. Therefore, we propose a simple and effective strategy for controlling lowtemperature pyrolysis to significantly improve the sodium storage performance of lignite-derived carbon anode material. By controlling the lignite pyrolysis stage at low temperatures, the ordering tendency of carbon material at high temperatures is reduced, leading to an increase in the content of pseudo-graphitic carbon with larger layer spacing. Simultaneously, the specific surface area of the resulting carbon is decreased and defects are effectively repaired. In comparison to the direct carbonization samples (DC-1400), which demonstrated a lower reversible capacity (269.4 mAh/g) and ICE (82.9 %), the low-temperature pyrolysis optimized sample (HM-4206 h) exhibited a higher reversible capacity (282.9 mAh/g) and an excellent ICE (87.1 %). When coupled with NaFe1/3Ni1/3Mn1/3O2, a full cell can achieve a high energy density of 216.1 Wh kg-1. The proposed strategy for controlling low-temperature pyrolysis offers a distinctive perspective on the mass preparation of highperformance SIB carbon anode materials.