Simulation of Lithium-Ion Battery with Effect of Volume Expansion of Active Materials

In order to increase cell performance of lithium-ion batteries, not only material development but also optimum design of electrode structure is important. However, it is difficult to examine the effect of volume expansion of anode active material on internal phenomena, so there are few studies to understand the its effect for optimum electrode layer. In this study, we investigate the effects of the expansion ratio of active materials on net charge capacity and net charge rate performance in the case of graphite and silicon for anode active material. Charging properties were calculated using equations based on the porous-electrode theory and expressing the parameter changes caused by expansion. In addition, the validity of this simulation model was confirmed by comparing with the experimental measurement of thickness change and charging curve. As results, in the case of high rate condition, cell capacity of graphite cell is higher than that of Si cell. The dynamic structural property, which is the parameter of effective ionic conductivity depends on the porous structure, decreased near separator, and the resistance of ionic conduction increase. As reaction concentrate remarkably near separator in the case of Si, so the utilization of Si active material was lower than that of graphite.