Researchers at the UCLA Department of Physics & Astronomy have designed supercapacitors with enhanced energy density and power density properties.
Supercapacitors provide instantaneously high-power density and energy density compared to batteries and conventional dielectric capacitors, making them excellent candidates for applications in hybrid electric vehicles, computers, mobile electric devices and other technologies. An electrochemical capacitor is typically operated based on the electrochemical double-layer capacitance (EDLC) formed along an electrode/electrolyte interface, or a pseudocapacitance resulted from a fast reversible Faradaic process of material that undergoes Faradaic reactions. For a double-layer supercapacitor, the rapid charge/discharge process provides the capacitor with a high-power density, yet the energy density is limited by its effective double layer area. Activated carbon has large surface area, and is the most commonly used material, but it suffers from dramatic capacitance drop at high scanning rate because of its porous structure. On the other hand, psuedocapacitance-based capacitors use metal oxides or conducting polymers and may provide high specific capacitances. However, their application is limited by high cost, low operation voltage, and poor rate capability because of inefficient mass transport or slow Faradaic redox kinetics.
Researchers at UCLA have designed supercapacitors with both high energy and high-power density, by using composite electrodes that incorporate multiple types of electrode materials. With this design, a supercapacitor’s electrode is formed from electrode materials used for double-layer capacitors and pseudocapacitors coated onto the same charge collector. When the desired material properties are combined, the electrode made is highly conductive, capacitive, and cost-effective.
The performance of the composite electrodes has been tested experimentally.
|United States Of America||Issued Patent||8,520,365||08/27/2013||2014-285|