Quantifying Local Heterogeneities in the 3D Morphology of X-PVMPT Battery Electrodes Based on FIB-SEM Measurements

Abstract

Organic electrode-active materials (OAMs) enable a variety of charge and storage mechanisms and are advantageous compared with lithium-ion batteries in terms of costs and safety. Cross-linked poly(3-vinyl-N-methylphenothiazine) (X-PVMPT) is a p-type OAM showing high performance and enabling fast and reversible energy storage in different battery configurations. Beyond its molecular or polymer structure, the performance of an OAM depends strongly on the structure of the composite electrode. The porous nanostructure of an electrode composed of X-PVMPT, a conductive carbon additive, and binder is statistically investigated based on highly resolved 3D image data. Univariate probability distributions of relevant morphological descriptors and bivariate distributions of pairs of such descriptors are parametrically modeled. In this way, local heterogeneities and spatial gradients are quantified. While the observed short transportation paths through the solid phase are beneficial in terms of electrical conductivity, the pathways through the pore phase influencing the effective ionic diffusivity are comparatively long.