Highly Graphitized Straw-Derived Carbon via Molten Salt Electrolysis for Potassium-Ion Batteries

The conversion of straw biomass into highly graphitized carbon materials is achieved through an efficient molten salt electrolysis process at moderate temperatures (900–950 °C). Increasing the electrolysis temperature significantly enhances the degree of graphitization, structural ordering, and heteroatom removal efficiency, as evidenced by multiscale characterization and electrochemical simulations. The resulting graphitic material exhibits a highly ordered layered structure with improved crystallinity and a larger specific surface area. When used as a potassium-ion battery anode, this biomass-derived carbon delivers a reversible capacity of 232.9 mA·h·g⁻¹ after 100 cycles and retains 230.8 mA·h·g⁻¹ after 500 cycles, owing to its well-developed graphite framework, which accommodates volume changes and facilitates rapid ion diffusion. This study presents a sustainable and scalable strategy for transforming low-cost agricultural waste into high-performance energy storage materials and provides valuable insights into the electrochemical graphitization process.