Supercapacitor

An electrochemical capacitor that stores energy mainly through charge separation at electrode surfaces. It charges and discharges rapidly and delivers high power, but usually stores less energy per unit mass than a battery.

Electric double layer: A charge-separated region at the boundary between an electrode and an electrolyte. Supercapacitor electrodes store charge by forming this interfacial layer.
Activated carbon: A highly porous carbon material with large internal surface area, produced by activation treatments. Its accessible pores provide extensive surfaces for electric-double-layer charge storage.
Lithium-ion battery: A rechargeable battery that stores energy through lithium-ion transfer between electrode materials. It generally stores more energy per mass, while supercapacitors deliver power and cycle rapidly.
Regenerative braking: A braking method that converts a vehicle's kinetic energy into electrical energy for reuse or storage. Supercapacitors can absorb brief, high-power bursts of braking energy.
Helmholtz layer: A compact layer of ions at a charged surface, described in early models of the electrical double layer. Its interfacial picture is an early foundation for understanding supercapacitor charge storage.
Pseudocapacitance: Capacitive charge storage produced by fast, reversible faradaic reactions at or near an electrode surface. Some supercapacitors gain extra capacitance through rapid surface redox reactions.
Graphene: A single layer of carbon atoms arranged in a two-dimensional honeycomb lattice. Its conductivity and surface area motivate its use in experimental supercapacitor electrodes.
Lead-acid battery: A rechargeable battery that uses lead-based electrodes and sulfuric acid electrolyte. It offers inexpensive bulk energy storage but typically charges and cycles less rapidly.
Hybrid electric vehicle: A vehicle propelled by both an internal-combustion engine and an electric motor. Supercapacitors can support acceleration and capture braking energy alongside a battery.
Gaston Planté: French physicist who invented the lead–acid battery in 1859. His battery established an early electrochemical storage technology against which capacitors are often compared.

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