A supercapacitor is a double-layer capacitor with very high capacity but with low voltage limits. Supercapacitors, compared to capacitors, have a larger area for storing more charge, with capacitance into the farad (F) range, and they store more energy than electrolytic capacitors. They have a low leakage current and are suitable for many applications that can operate in the 1.8V - 2.5V range. The life of a supercapacitor is 10–20 years, though the capacity could be reduced from 100% to 80% after about 8–10 years.

Thanks to their low equivalent series resistance (ESR), supercapacitors provide high load currents and fast charging. Micro-supercapacitors are MEMS-like devices that tolerate repeated bending and thus are suitable for flexible applications. This is ideal for wearables and IoT applications. Flexible solid-state micro-supercapacitor glass, silicon, and paper substrates are being developed.

When a voltage is applied to a supercapacitor, two separate charge layers are produced on the surface with a separation distance that is smaller than those of conventional capacitors. This is why supercapacitors are often referred to as double-layer electrical capacitors or EDLCs.