Memory Effects' Mechanism in the Intercalation Batteries: The Particles' Bipolarization

Origin of electrochemical voltage range and voltage profile of insertion electrodes

This 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.

Inherent Behavior of Electrode Materials of Lithium-Ion Batteries

For independency from the fossil fuels and to save environment, we need to move toward the green energies, which requires better energy storage devices, especially for usage in electric vehicles. Li-ion and beyond-lithium insertion batteries are promising to this aim. However, they suffer from some inherent limitations which must be understood to allow their development and pave the way to find suitable energy storage alternatives. It is found that each positive or negative electrode material (cathode or anode) of the intercalation batteries has its own behavioral (charge-discharge) properties. The modification of preparation parameters (composition, loading density, porosity, particle size, etc.) may improve some aspects of the electrode performance, but cannot change the intrinsic property of the electrode itself. Accordingly, these properties are called as the "inherent behavior characteristics" of the active material. It is concluded that the behavior of a specific electrode substance, even following different preparation routes, depends only on diffusion mechanisms. This work shows that the inherent electrode properties can be visualized by representation of current density vs. capacity.

Normalization of charge/discharge time vs. current rate diagrams for rechargeable batteries

It is vital to comprehend the charge/discharge behaviors of batteries to improve their properties. In this paper, we normalize the electrode materials' behaviors according to the time of the process to allow a rational comparison between different materials and batteries.