Active Material Arrangement and Its Effect on Electronic Conductivity in a Suspension Electrode

Abstract

Flowable or suspension electrodes are multiphase electrode systems, where an active solid material is suspended in electrolytic medium. Suspension electrodes have been demonstrated for large-scale energy storage [1], water deionization [2-4], and energy generation applications [5]. Several material chemistries have been examined in a suspension form, and all systems rely on the use of carbon-based materials to form percolation networks for efficient electron transport. Suspension electrodes based on metal oxides typically demonstrate low electrical conductivities (~10-6 mS/cm) and require the addition of conductive additives to enable efficient charge storage and rate handling. Capacitive suspension electrodes, composed of activated carbon, are significantly more conducting than those based on metal oxides (~10-1-100 mS/cm). Nevertheless, both types of suspension electrodes display electrical conductivities significantly lower than their film counterparts, because of the presence of a highly resistive solution region. One solution to this challenge is the addition of more conducting materials (carbon black or activated carbon) or controlled arrangement of the active material. The former results in high viscosity material systems which are challenging to flow. The arrangement of the active and inactive material in a suspension electrode is expected to affect charge and ion percolation and material utilization in a suspension electrode. In this work we compare DC and AC electronic conductivity measurement techniques, and present work on visualization of the active material arrangement in a suspension electrode.