Optimizing the Crystallite Structure of Lignin-Based Nanospheres by Resinification for High-Performance Sodium-Ion Battery Anodes

Sodium-ion batteries are expected to be an alternative to lithium-ion batteries because of the inexpensive raw materials. However, the anode materials still face problems of low capacity and initial coulomb efficiency, even for hard carbons that are expected to have commercial applications. Herein, a resin nanosphere derived from lignin through double solvent evaporation and resinification is reported. Benefiting from the phenol-formaldehyde condensation to form linear polymers, the samples possess a large microcrystalline size, moderate interlayer distance, and defect sites in the turbostratic structure, which enhance the sodium-storage capacity. The carbonized lignin-based resin spheres (CLRSs) exhibit promising electrochemical performance with a comparable reversible capacity of 347 mAh g(-1) and high initial columbic efficiency (ICE) of 74%. Furthermore, the sodium-storage mechanism for the obtained samples is also investigated by analyzing the relationship between the structure optimization and electrochemical performance.