Numerical Investigation on the Impact of Linear Variation of Positive Electrode Porosity upon the Performance of Lithium-Ion Batteries

The diffusion process of lithium-ions in the positive electrode solid phase as within the liquid phase is one of the pivotal factors in determining the battery performance. The effective conductivity and diffusion coefficient of the solid and liquid phases can be regulated by changing the distribution of the volume fraction of active material and porosity on the positive electrode. These crucial parameters can affect the transfer of lithium-ions in the solid and liquid phases and ultimately affect the battery’s performance. In this paper, a pseudo-three-dimensional (P3D) electrochemical-thermal-mechanical (ETM) coupling model is employed to study the non-uniform porosity of the positive electrode, especially the effect of porosity variation on the battery temperature and stress during the discharge process. Through numerical results, we find that reasonable porosity distribution can make the electrode lithiation more uniform and reduce the battery surface temperature by decreasing ionic ohmic heat. In addition, we display the stress distribution on the electrode and inside the active particles after adopting the linear porosity. The results are helpful for an in-depth understanding of the effect of the non-uniform porosity of the positive electrode on the lithium transport mechanism, the stress mechanism, and the thermal mechanism during the operation of lithium-ion batteries (LIBs).