The Electrochemical Flow Capacitor: A New Concept for Rapid Energy Storage and Recovery

Abstract Availability of grid‐scale electric energy storage systems with response rates on the order of seconds plays a key role in wide implementation of renewable energy sources. Here, a new concept called the electrochemical flow capacitor (EFC) is presented. This new concept shares the major advantages of both supercapacitors and flow batteries, providing rapid charging/discharging while enabling the decoupling of the power and energy ratings. Like in supercapacitors, energy is stored in the electric double layer of charged carbon particles. A flowable carbon‐electrolyte mixture is employed as the active material for capacitive energy storage, and is handled in a similar fashion to flow or semi‐solid batteries (i.e., for charging/discharging, it is pumped into an electrochemical cell, and for storage, it is pumped into reservoirs). This study presents the proof‐of‐concept of this technology and reports initial EFC performance data obtained under static and intermittent flow operations.