Effects of High-Porosity Conductive Foams on the Electrochemical Performance of Electrochemical Flow Capacitors

Electrochemical flow capacitors (EFCs) are high-power, long-cycle life electrochemical systems that utilize flowable suspensions of activated carbon in certain electrolytes. The unique capability of flowable electrodes, which offers ease of scalability, has found many applications not only in the field of energy storage but also in capacitive deionization [1-2]. Currently, one major challenge that prohibits widespread adaptation of EFCs is the low electrical conductivity of the flowable electrodes when compared to the conductivity of the film electrodes. This is mainly caused by the high percentage of the electrolyte phase in the suspension, which is not electrically conductive. Hence, presence of readily formed electron percolation paths is of critical importance to ensure all particles have a viable electron transfer path towards the current collectors [3]. Here, we hypothesized that large pore size conductive foams such as reticulated vitreous carbons (RVCs) could offer a stationary electron transfer backbone for EFC cell fixtures and help decrease the inter-particle electron conduction distance in large channel thicknesses. Contrary to the common approach used in flowable electrochemical systems, currently proposed cell fixtures for flowable electrodes does not involve any high-surface area electrodes due to concerns over clogging and other flow related issues. Motivated by this, this study aims to investigate the feasibility of high-porosity conductive foams as three-dimensional current collectors in EFC cell fixtures. To accomplish this, flow cells containing RVCs selected from different porosities have been subjected to electrochemical testing under static and intermittent flow conditions. For the same electrode composition, a significant improvement in capacity (up to 2x) and in power density (up to 10x) has been observed with the utilization of conductive foams in the cell fixtures. References [1] B. Kastening, Berichte der Bunsengesellschaft für physikalische Chemie , 1988, 92, 11, 1399-1402. [2] K. B. Hatzell, M. Boota and Y. Gogotsi, Chemical Society Reviews , 2015, 44, 8664-8687. [3] C. R. Dennison, Y. Gogotsi, and E. C. Kumbur, Phys. Chem. Chem. Phsy., 2014, 16, 18241-18252.