Electrochemical Conversion of CO ₂ via Molten Salt Electrolysis to Produce Hard Carbon Materials for Sodium-Ion Battery

The conversion of CO₂ into valuable carbon materials is essential for establishing a circular economy. This study syntheses hard carbon materials from CO₂ using high-temperature molten salt electrolysis and explores their use as anodes in sodium-ion batteries. CO₂ gases are absorbed as carbonate ions in molten salts and then electrochemically decomposed into solid carbon. When electrolysis was conducted at 600 °C in molten LiCl-KCl containing Li₂CO₃, the generated carbon was amorphous and nongraphitizable, as determined by XRD analysis and Raman spectroscopy. The obtained carbons before and after heat treatments at 900-1800 °C were employed as the anode materials in two-electrode cells with metallic sodium counter electrodes and 1 M NaPF₆/EC-DMC electrolyte. for sodium ion battery. The carbon treated at 900 °C showed the highest capacity, exceeding that of commercial hard carbon materials. These results demonstrate the potential of CO₂ reduction and technologies for converting CO₂ into valuable carbon materials for energy storage devices.