Computer simulation of operation of lithium-ion battery: Galvanostatics, central problem of theory, calculation of characteristics of thin active layers with low diffusion coefficients

Abstract

Computer simulation of lithium-ion battery operating in the galvanostatic discharge mode was performed. Special attention was paid to the complete mathematical description of the processes proceeding in the active layers of electrodes. The central problem of the theory of lithium-ion batteries is a possibility of analyzing two processes proceeding concurrently in space and time: the recovery or filling of active substance (intercalating agent) grains with lithium atoms and redistribution of electrode potentials over the active layer width, which is caused by the ohmic limitations. A new approach to the central problem is proposed. It is based on comparing the characteristic times of two main processes proceeding in the electrodes. Here, the diffusion coefficient of lithium atoms in the intercalating agent grains is of critical importance. Two ranges of diffusion coefficients (high and low diffusion coefficients) can be recognized. The merits and drawbacks of the electrodes exhibiting high and low diffusion coefficients are discussed. The calculations of the working parameters of the electrode (by the example of the anode) are performed for the active layers with low diffusion coefficients. The active layer thickness, complete discharge time, specific electric capacitance, and final potential at the active layer/interelectrode space interface are determined.