Leveraging co-laminar flow cells for non-aqueous electrochemical systems

Abstract

Non-aqueous flow cells offer expanded electrochemical potential windows, which is desirable for energy storage. The performance of such electrochemical systems is however constrained by high cell resistance due to the low ionic conductivity of electrolytes and membranes in non-aqueous media. In this work, we apply membrane-less cell configurations with flow-through porous electrodes to address the ohmic losses and boost the performance of non-aqueous flow cells. Vanadium acetylacetonate redox chemistry is used as a model system and various performance aspects such as reaction kinetics, electrode wettability, cell resistance and crossover are investigated. The kinetics, measured in flow-through mode, is found competitive due to the enhanced mass transport and surface area utilization in the flow-through porous electrode. The electrode porosity is measured to be 79% and only 6.0% in acetonitrile and water, respectively, indicating superior wettability behaviour for non-aqueous electrolytes. A fully integrated co-laminar flow cell demonstrates negligible crossover and a combined ohmic cell resistance that meets techno-economic targets. Its discharge power density of 550 mW cm−2 is two orders of magnitude higher than for other non-aqueous flow cells, demonstrating that membrane-less cell designs with flow-through porous electrodes are favourable in order to overcome performance limitations in non-aqueous electrochemical systems.