Electrochemical Investigation of Spherical Hard Carbon Negative Electrodes for Sodium Secondary Batteries

Abstract

Hard carbon (HC) is receiving widespread attention as a negative electrode material for sodium secondary batteries. In this study, spherical HC with three different diameters (1 µm, 1.5 µm, and 5 µm) are investigated using ionic liquid (IL) and organic electrolytes. The HC with a diameter of 5 µm demonstrated the best performance with IL at 90 °C (capacities of 327 mAh g−1 at 20 mA g−1 and 77 mAh g−1 at 2000 mA g−1 and initial Coulombic efficiency of 78.9 %). The HCs showed stable cycling in ILs as compared to the organic electrolytes in the first few cycles.