Studying charge-carrier intercalation/deintercalation in energy storage materials by optical spectroscopy

Abstract

Understanding how charge-carrier intercalation/deintercalation that affects the charge-discharge process is essential for the development of efficient energy storage materials. So far, a clear understanding about the relationship of charge-discharge process of energy storage materials with the corresponding changes of energy band structure is still lacking. Here, using optical spectroscopy (RGB value, reflectivity, transmittance, UV-vis, XPS, UPS) to study α-Co(OH)2 electrode working in KOH electrolyte as 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 Red-Green-Blue (RGB) value during the charge-discharge process.