Activated Carbon Spheres as a Flowable Electrode in Electrochemical Flow Capacitors

Here, we report modified carbon spheres (CS) as a high energy and power density flowable electrode for use in electrochemical flow capacitors – a new energy storage concept proposed by our group. Activated CS with high specific surface area (SSA) of 1157 m2 g−1 were obtained by CO2 activation. The electrochemical performance of the flowable electrodes as tested in both aqueous (KOH) and organic (TEABF4/PC) electrolytes. It was observed that both the morphology and electrochemical performance of the flowable electrodes are strongly dependent on the activation conditions. Among tested samples, flowable electrode composed of CS activated at 1000°C for one hour yielded the highest capacitance, rate handling ability, and lowest equivalent series resistance (ESR) values. When tested in a static configuration, these suspension electrodes showed a specific capacitance of 139 Fg−1, which is comparable to the performance of traditional film electrodes. The performance of the CS-1000 was further investigated under intermittent flow condition using slurry containing 16 wt% of CS. It was observed that CS-1000 showed significantly enhanced performance due to its high surface area, decreased ohmic resistance, and enhanced conductivity, both in static and under intermittent flow conditions as compared to the flowable electrodes previously reported by our group.