Studying the variable energy band structure for energy storage materials in charge/discharge process

So far, a clear understanding about the relationship of variable energy band structure with the corresponding charge-discharge process of energy storage materials is still lacking. Here, using optical spectroscopy (red-green-blue (RGB) value, reflectivity, transmittance, UV-vis, XPS, UPS) to study alpha-Co(OH)2 electrode working in KOH electrolyte as the research object, we provide direct experimental evidence that: (1) The intercalation of OH- ions will reduce the valence/conduction band (VB and CB) and band gap energy ( Eg ) values; (2) The deintercalation of OH- ions corresponds with the reversion of VB, CB and Eg to the initial values; (3) The color of Co(OH)2 electrode also exhibit regular variations in RGB value during the charge-discharge process. (c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.