supercapacitor
Electric double-layer capacitor
Electrical double-layer capacitors (EDLC) are, together with pseudocapacitors, part of a new type of electrochemical capacitors[1] called supercapacitors, also known as ultracapacitors. Supercapacitors do not have a conventional solid dielectric. The capacitance value of an electrochemical capacitor is determined by two storage principles:
Double-layer capacitance – electrostatic storage of the electrical energy achieved by separation of charge in a Helmholtz double layer at the interface between the surface of a conductor electrode and an electrolytic solution electrolyte. The separation of charge distance in a double-layer is on the order of a few Angstroms (0.3–0.8 nm) and is static in origin.[2] Pseudocapacitance – Electrochemical storage of the electrical energy, achieved by redox reactions electrosorption or intercalation on the surface of the electrode by specifically adsorbed ions that results in a reversible faradaic charge-transfer on the electrode.[2]
Double-layer capacitance and pseudocapacitance both contribute to the total capacitance value of a supercapacitor.[3] However, the ratio of the two can vary greatly, depending on the design of the electrodes and the composition of the electrolyte. Pseudocapacitance can increase the capacitance value by as much as an order of magnitude over that of the double-layer by itself.[1]
Supercapacitors are divided into three families, based on the design of the electrodes:
Double-layer capacitors – with carbon electrodes or derivatives with much higher static double-layer capacitance than the faradaic pseudocapacitance Pseudocapacitors – with electrodes made of metal oxides or conducting polymers with much higher faradaic pseudocapacitance than the static double-layer capacitance Hybrid capacitors – capacitors with special electrodes that exhibit both significant double-layer capacitance and pseudocapacitance, such as lithium-ion capacitors
Electrical double-layer capacitors (EDLC) are, together with pseudocapacitors, part of a new type of electrochemical capacitors[1] called supercapacitors, also known as ultracapacitors. Supercapacitors do not have a conventional solid dielectric. The capacitance value of an electrochemical capacitor is determined by two storage principles:
Double-layer capacitance – electrostatic storage of the electrical energy achieved by separation of charge in a Helmholtz double layer at the interface between the surface of a conductor electrode and an electrolytic solution electrolyte. The separation of charge distance in a double-layer is on the order of a few Angstroms (0.3–0.8 nm) and is static in origin.[2] Pseudocapacitance – Electrochemical storage of the electrical energy, achieved by redox reactions electrosorption or intercalation on the surface of the electrode by specifically adsorbed ions that results in a reversible faradaic charge-transfer on the electrode.[2]
Double-layer capacitance and pseudocapacitance both contribute to the total capacitance value of a supercapacitor.[3] However, the ratio of the two can vary greatly, depending on the design of the electrodes and the composition of the electrolyte. Pseudocapacitance can increase the capacitance value by as much as an order of magnitude over that of the double-layer by itself.[1]
Supercapacitors are divided into three families, based on the design of the electrodes:
Double-layer capacitors – with carbon electrodes or derivatives with much higher static double-layer capacitance than the faradaic pseudocapacitance Pseudocapacitors – with electrodes made of metal oxides or conducting polymers with much higher faradaic pseudocapacitance than the static double-layer capacitance Hybrid capacitors – capacitors with special electrodes that exhibit both significant double-layer capacitance and pseudocapacitance, such as lithium-ion capacitors