Probing the carbon particle motion in a microfluidic electrochemical flow capacitor*

Electrochemical flow capacitors (EFCs) are promising energy storage devices due to their large storage capacity, low fatigue rates, and fast charge/discharge rates. These devices employ the electric double layer of high-surface-area carbon particles in a flowable slurry, i.e., a ‘flowable electrode’, to store ionic charges from an electrolyte solution. The flow characteristics of the carbon slurry and the particle interactions are therefore directly linked to the charging behaviors of the device. Despite this, there are very few studies that directly observe the particle motion inside the charging channels. To address this issue, we have developed a microfluidic electrochemical flow capacitor (MEFC) that is compatible with optical imaging. This platform allows us to investigate the influence of various slurry flow behaviors on the charging performance of the flowable electrode during the operation of the device. We have examined the effect of slurry flow rate on the particle clustering pattern and consequently the charging performance.  We will report on the fabrication of the MEFC, the experimental setup, and the charging results under different slurry flow rates.