Electric double-layer capacitor

Hybrid capacitors

A number of newer supercapacitors are "hybrid": only one electrode uses a fast reaction (capacitance or pseudocapacitance), the other using a more "battery-like" (slower but higher-capacity) material. Hybrid capacitors combine the rapid charge/discharge kinetics of electric double-layer capacitors (EDLCs) with the high energy density of pseudocapacitive or battery-type electrodes. These systems bridge the gap between conventional capacitors and batteries, making them critical for applications requiring both power and energy density. For example, an EDLC anode can be combined with an activated carbon–Ni(OH)₂ cathode, the latter being a slow faradaic material. The CV and GCD profiles of a hybrid capacitor have a shape between that of a battery and a supercapacitor, more similar to that of an SC. Hybrid capacitors have much higher energy density, but have inferior cycle life and current capacity owing to the slower electrode.