Unraveling the Factors\nof Host Materials Affecting\nthe Kinetics of Electrochemical Anion Intercalation Reaction

Electrochemical intercalation reactions of various ions\ninto host\nmaterials are used as electrode reactions for various secondary batteries,\nand it is important to understand the factors that affect the reaction\nkinetics. In this study, the activation energies of internal anion\ndiffusion and interfacial anion transfer were evaluated using carbon\nmaterials with different properties by electrochemical impedance spectroscopy,\nand the factors of the materials affecting activation energies of\nthese processes were investigated. It was found that the activation\nenergies of internal anion diffusion were dominated by the oxygen\ncontent in the carbon materials, and they linearly increased with\nincreasing oxygen content. On the other hand, the activation energy\nof interfacial anion transfer increased with increasing oxygen content\nnear the edge surface of the material and decreased with increasing\nthe initial interlayer distance. Therefore, it was revealed that the\ndifference in the properties of the host material affects the activation\nenergy of interfacial ion transfer in the case of anion transfer,\nwhich has low desolvation energy, unlike the case of lithium-ion transfer,\nwhich requires large desolvation energy. It suggests that the design\nof active materials become more important than ever for next-generation\nsecondary batteries which employ reactions with small desolvation\nenergies for superior rate capabilities.