Effects of current collector shape and configuration on charge percolation and electric conductivity of slurry electrodes for electrochemical systems

Abstract

In flowable slurry electrodes, charge transfer coincides with particle/particle and particle/current collector interactions, and it is challenging to investigate these effects experimentally. We present a novel CFD-DEM approach by introducing the charge transfer efficiency coefficient to model the charge transfer process in slurry electrodes. For the first time, we investigate the effects of contact and electrolyte resistances, and current collector shapes and configurations on percolation threshold and electric conductivity of slurry electrodes. Our results show that contact and electrolyte resistances play a vital role on efficiency of slurry electrodes. We show that, with a perpendicular current collector configuration the conductivity of slurry electrodes doubles as the velocity increases almost 3 orders of magnitude, while with a traditional parallel configuration it decreases by approximately 50% over the same velocity range. Additionally, we demonstrate that the charge percolation network associated with rapid increases in conductivity forms after 12 vol% with a perpendicular current collector and after 20 vol% with a parallel configuration. HTAB surfactant (5 mM) is used in the slurries to avoid agglomeration and sedimentation of the carbon particles in the channel. It decreased the conductivity of slurry electrodes by roughly 10% while reducing the viscosity by 30%.