Inhomogeneities in Large Format Lithium Ion Cells: A Study by Battery Modelling Approach

The performance of lithium ion battery cells is influenced besides the cell chemistry, also by microscopic and macroscopic parameters. In short format cells, the macroscopic variables such as cell geometry, aspect ratio, material thickness, tab configuration etc. do not significantly affect current, voltage, state of charge (SOC) and temperature distribution. However, they cannot be neglected as the cell size increases, especially in large format cells, where the distributions becomes non homogeneous. These inhomogeneities adversely affect the cell’s performance and a long exposure leads to localized aging. This paper presents a spatially resolved modelling technique in Matlab/Simulink to evaluate cell inhomogeneity. It compares current, voltage and SOC distribution of 8 Ah and 75 Ah cells and how the distribution changes from a fresh cell to its end of life (EOL).