Electric Double Layer Capacitors (EDLCs) are electrochemical energy storage devices that are capable of providing quick burst of power (1000’s W/kg) for very short time interval (a few seconds to a few minutes). However, they do not store large amount of energy. In that sense, EDLCs are complementary to batteries, which inherently have high energy density (10-500 Wh/kg), but low power density (<300 W/kg).
EDLCs are also referred to as supercapacitors or ultracapacitors as they typically store 12 to 14 orders of magnitude more charge than a typical dielectric capacitor. EDLCs operate on the same principle as dielectric capacitors, storing electrical charge in form of a potential difference on two electrodes separated by a dielectric; but the surface area of the EDLC electrodes is much larger (1000-3000 m2/g), and the dielectric distance between the charges is much smaller (3 to 8 Å). Moreover, EDLC’s operate in a narrow potential window (up to 2.7 V or 3 V vs. 1000’s V for ceramic capacitors). The resulting energy density of EDLC is significantly higher (2-5 Wh/kg), as compared to ceramic or dielectric capacitors (< 0.1 Wh/kg).
The high power capability of EDLCs enable some niche applications, such as harvesting power from regenerative braking, capturing energy from renewables (wind and solar), providing energy storage for grid stability. Nevertheless, enhancing the energy density without compromising the power density and device life is always the goal of EDLC research, and at E2TAC scientists are focused on developing novel electrode and electrolyte materials that enable expanding the applications space of EDLCs for novel futuristic systems and machines.