Prediction of electronic conductivity of a degrading electrode material using finite element method

Abstract

A 2D FEM technique is introduced to determine the effective electronic conductivity of an aging porous composite electrode material experiencing intercalation stress induced fracture. The representative unit cell comprises overlapping circular particles in an electrolyte matrix where electronic conduction takes place through the bulk of the particles or the particle surface conductive coating. Monte-Carlo simulation is employed to model the variation in the micro structural geometries and the loss of conduction is simulated incorporating the fracture. There is a large statistical scatter in the conduction profile but the mean value of the scatter does provide a reasonable measure. Critical stress based selection of fracture location leads to a steeper reduction of the conductivity compared to the random selection approach. When the conduction is restricted to the surface coating, the conductivity reduces more steeply compared to the bulk conduction. The increasing degradation continues to render particles ineffective for conduction and the ineffective volume fraction is treated as apparent porosity. The FEM determined variation of effective conductivity compares favorably with the results of micromechanics based on porosity and the results of an earlier publication.