Lithium ion rechargeable battery, galvanostatics: Computer simulation and calculation of characteristics of the anode active layer of arbitrary thickness with low lithium diffusivity

Abstract

The work of a lithium ion rechargeable battery operating under galvanostatic discharge conditions is simulated. Attention is focused on the complete mathematical description of processes in electrode active layers. The central problem in the theory of lithium ion batteries is the possibility of analyzing the following two processes that proceed simultaneously in space and time: depletion and enrichment of the active substance (intercalator) grains with lithium atoms and the ohmic-limitation-induced redistribution of the electrode potential in time throughout the active layer thickness. A new approach to the central problem is considered. It is based on comparing the characteristic times of two main processes occurring in electrodes. Here, the lithium atom diffusivity in intercalator grains plays the decisive role. Two regions of diffusivity values, i.e., high and low, can be singled out. Algorithms are developed for solving the complete system of equations for the most complicated case, namely, active layers of arbitrary thickness with low diffusivity of lithium atoms. The following electrode working parameters (for anode) are calculated: optimal active layer thickness, discharge time, anode specific capacitance, and final potential at the active layer/interelectrode space interface.