Origin of electrochemical voltage range and voltage profile of insertion electrodes

Abstract

AbstractThis study evaluates electrochemical voltage-range and voltage-profile regarding electrodes of insertion (intercalation) batteries. The phrase “voltage-range” expresses the difference between obtained maximum and minimum potential for the cells. It also can be called as operating voltage-range, working voltage-range, electrochemical voltage-range, or voltage window. This paper proposes a new notion regarding electron density of states, i.e. trans-band, which can be implemented to justify the voltage -range and -profile, by means of Fermi levels’ alignment. Voltage -range and -profile of a number of insertion electrode materials are clarified by the proposed theoretical approach, namely LiMn2O4, Li2Mn2O4, ZnMn2O4, LiFePO4, LiCoO2, Li2FeSiO4, LiFeSO4F, and TiS2. Moreover, the probable observed difference between charge and discharge profile is explained by the approach. The theoretical model/approach represents a number of important concepts, which can meet some scientific fields, e.g. electrochemistry, energy storage devices, solid state physics (DFT), and phase diagrams. By means of DFT calculations, this paper deals with quantizing the energy of electrochemical reactions, justifying the configuration of voltage-profile, and explaining the origin of the voltage-range. Accordance with the experimental observations suggests that this paper can extend boundary of quantum mechanics toward territories of classical thermodynamics, and boundary of the modern thermodynamics toward kinetics. Opening a new horizon in the related fields, this paper can help tuning, engineering, and predicting cell-voltage behavior.