A Study on the Effect of Porosity and Particles Size Distribution on Li-Ion Battery Performance

A pseudo two-dimensional model (P2D) is presented that describes the effect of the structural properties of the positive electrode on Li-ion cell performance during discharge. The validation of the mono-modal model was done by using Doyle's experiment and results [C.M. Doyle, University of California, Berkeley (1995)]. A large increase or decrease in the porosity beyond a specific value led to a sharp change in the cell voltage curve and lower cell capacities. The maximum specific energy was obtained in the porosity range of 0.55, while the specific power still had a high value. Furthermore, different particle size distribution models, including mono-modal, bi-modal and 3-particle models, were compared to each other. The mono-modal model was the ideal state with the lowest total polarization. The bi-modal and 3-particle models approached this ideal state when the volume fraction of the smallest particles in their structures increased. This structural arrangement in these models led to more uniform local current density distribution profiles resulting in a greater decrease in cell polarization. Different discharge current densities were applied to different particle size distribution models, and the results showed that the particle size distribution has a greater effect at higher discharge current densities.