Lithium-ion capacitor-Concept-circuit board pcb

- Feb 15, 2017-

Lithium-ion capacitor-Concept-circuit

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Lithium-ion capacitor

From Wikipedia, the free encyclopedia

Single-ended lithium-ion capacitors up to 200 F for PCB mounting

lithium-ion capacitor (LIC) is a hybrid type of capacitor out of the family of the supercapacitors. Activated carbon is used as cathode. The anode of the LIC consists of carbon material which is pre-doped with lithium ion. This pre-doping process lowers the potential of the anode and allows a relatively high output voltage compared with other supercapacitors.


Hierarchical classification of supercapacitors and related types

A lithium-ion capacitor is a hybrid electrochemical energy storage device which combines the intercalation mechanism of a lithium ion battery with the cathode of an electric double-layer capacitor (EDLC). The packaged energy density of an LIC is approximately 20 Wh/kg generally four times higher than an EDLC and five times lower than a lithium ion battery. The power density however has been shown to match that of EDLCs able to completely discharge in seconds.[4] The negative electrode (cathode) often employs activated carbon material at which charges are stored in an electric double layer that is developed at the interface between the carbon and the electrolyte.

The positive electrode (anode) was originally made with lithium titanate oxide, but is now more commonly made with graphitic carbon material to maximize energy density. The graphitic electrode potential initially at -0.1 V versus SHE (standard hydrogen electrode) is lowered further to -2.8 V by the intercalation of lithium ions. This process step is referred to as doping and often takes place in the device between the anode and a sacrificial lithium electrode. The pre-doping process is critical to the device functioning as it can significantly affect the development of the Solid Electrolyte Interphase layer. Doping the anode lowers the anode potential and leads to a higher output voltage of the capacitor. Typically, output voltages for LICs are in the range of 3.8–4.0 V but are limited to a lower voltage of 1.8–2.2 V. If the voltage is brought any lower lithium ions will deintercalate more rapidly than they can be restored during normal use. Like EDLCs, LIC voltages vary linearly adding to complications integrating them into systems which have power electronics that expect the more stable voltage of batteries. As a consequence, LICs have a high energy density, which varies with the square of the voltage. The capacitance of the anode is several orders of magnitude larger than that of the cathode. As a result, the change of the anode potential during charge and discharge is much smaller than the change in the cathode potential.

The electrolyte used in an LIC is a lithium-ion salt solution that can be combined with other organic components and is generally identical to that used in lithium ion batteries.

A separator prevents direct electrical contact between anode and cathode.

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