Waste Sawdust-Derived Hard Carbon Anodes with Engineered Interlayer Spacing for Sodium-Ion Batteries Exhibiting High Initial Coulombic Efficiency

In sodium-ion battery systems, hard carbon (HC) is regarded as one of the most promising anode materials. Nevertheless, its limited initial Coulombic efficiency (ICE) or high cost has impeded its widespread application. This study introduces a strategy for synthesizing ultra-high initial efficiency hard carbon using cost-effective biomass precursors, specifically waste sawdust. By integrating theoretical calculations, the heating rate is meticulously controlled to optimize the interlayer spacing of the pseudo-graphite layers, while also appropriately adjusting the layer growth length. This facilitates the folding and bending of layers to form more closed pores. The microstructure of the resulting HC is responsible for the impressive ICE of 89.01% and high specific capacity of 329.31 mAh g−1 (predominantly contributed by the plateau region) without any conductive additives. Furthermore, the full cell assembled with Na3V2(PO4)3 exhibits remarkable cycling stability. This work underscores the potential of biomass-derived hard carbon from wood-based precursors, offering significant reference value for the microstructural regulation and commercial application of hard carbon anodes.