Principles of porous reacting electrodes modeling (a review)

Abstract

The production volume of rechargeable batteries and requirements for them, in particular with respect to increasing voltage, specific capacity, charge-discharge currents and reliability, are growing and will grow more rapidly. Today it is clear that the limiting factor of their development is insufficient understanding of processes which taking place there. The review discusses basic equations that describe ion and electron transfers and electrochemical reactions which lead to an uneven distribution of processes in the system. The possibility of obtaining analytical and numerical solutions is analyzed for the stationary case and for the case when characteristics of the local electrode area depend on the state of charge. A large number of works are based on the Doyle-Fuller-Newman model, which considers both the distribution of the process in the electrode and the diffusion into the solid phase of the active component which formed as a result of an electrochemical reaction on the crystals surface. It is noted that such models adequately describe the processes only when empirical or semi-empirical dependences on the state of charge for local current density, equilibrium potential or transfer coefficients are used. Papers based on quantum-chemical calculations of potentials, estimating entropy factors, as well as the decomposition of solid solutions are discussed. A modern classification of approaches applied in battery modeling with the aim of using them in electronic battery management systems is presented. It is concluded that there is insufficient understanding of the processes occurring at the level of active material grains during phase transformations.