One stone two birds: Regulating carbon microcrystalline structure and stabilize carbon framework via crosslink polymerization of coal/BC composite precursor for sodium-based energy storage devices

The limited interlayer spacing and unsatisfactory pore structure of coal-derived hard carbon present significant challenges for its application in sodium-ion batteries (SIBs) and sodium-ion capacitors (SIHC). Herein, we present a transformative “one stone two birds” strategy using low-rank bituminous coal as a precursor that achieves simultaneous advancements in anode and cathode design. Firstly, introducing bacterial cellulose (BC) into long-flame coal to obtain the hard carbon anode. During the high-temperature carbonization process, the hydroxyl groups (-OH) rich in BC and the carboxyl groups (-COOH) in coal particles undergo the cross-linking polymerization through esterification reaction, successfully inducing the transformation of carbon microcrystalline structure, leading to the dominance of pseudo-graphitic phase with larger carbon interlayer spacing, which facilitates the improvement of sodium storage in plateau region. In addition, the BC had a unique three-dimensional network structure that can effectively promote ion transport and achieve high intercalation pseudo-capacitance, significantly enhancing the rate performance. The synthesized anode (CBC121200) showed a reversible capacity of 341.83 mAh g⁻¹. Furthermore, an activated carbon electrode with ultra-high specific surface area (2999 m² g⁻¹) for SIHC cathode was prepared by introducing NaOH. When paired with CBC121200, the entire SIHC (CBC121200//LFAC700-1) exhibited high energy density of 127 and 108 Wh kg⁻¹ at power densities of 240 and 1199 W kg⁻¹. This work successfully prepared the SIBs anode and SIHC cathode using the same raw material, providing valuable insights for the high-value utilization of coal and developing innovative coal-based carbon materials.