An analytical study on the diffusion induced contact interactions between ellipsoidal electrode particles in lithium ion batteries

Abstract

Contacts among active particles in Lithium-Ion Batteries play a critical role in their performance. The particle shape influences their structural integrity and consequently affects the battery’s longevity. Analytical expressions for the contact parameters are derived for the ellipsoidal shaped particles of anode/cathode. The state of charge within the particles necessary for the computation of the contact parameters is calculated analytically and numerically for the galvanostatic and the potentiostatic cases, respectively. The derived analytical expressions agree well with the contact parameters for the degenerated spherical particles reported in the literature. A detailed study has been carried out considering the different aspect ratios and sizes of the contacting particles in various contacting orientations for graphite anode. It has been observed that the contacts at the sharper ends suffer from higher contact stresses. For specific contact orientations in these non-spherical particles, the contact stresses are lower than the spherical particles of the same volume. The analysis reveals that a higher contact patch size corresponding to a lower peak pressure facilitates better conduction through the contacts. Furthermore, the packing coefficient and material properties such as maximum stoichiometric concentration and collector stiffness have been found to have a profound impact on the contact parameters.