Electrochemical Double Layer Capacitors

Electrochemical capacitors are charge storage devices, which have higher energy density than conventional dielectric capacitors and have higher power density than batteries. Electrochemical capacitors bridge the gap between batteries and conventional capacitors. Electrochemical capacitors are classified into two types depending on the charge storage mechanism as Electrochemical double layer capacitors (EDLC`s)  and Pseudocapacitors.

Electrochemical capacitors are used as back-up memory for electronic devices like VCR circuits, CD players, cameras, computers, clocks, clock radios, telephones and other electronic equipments. Electrochemical capacitors also used in hybrid electric vehicles in combination with batteries as their power density is higher than batteries for load leveling. Electrochemical capacitors in combination with batteries occupy less space and are light, have excellent cold weather starting and increased battery life. Other uses of electrochemical capacitors include regenerative breaking, unmanned monitoring units, uninterruptible power supplies (UPS), and high power lasers.

When ever electronic conducting material ( electrode) is kept in contact with electrolyte there is a formation of opposite charges across the electrode-electrolyte interface. This charge separation acts like a parallel plate capacitor. High surface area carbon is used as a electrode in EDLC`s.

In pseudocapacitors, faradiac charge transfer occurs between electrolyte and electrode in contrast to electrostatic nature of opposite charges in double layer capacitors.  Capacitance in pseudocapcitors arises due to the progressive redox reactions between several oxidation states. These redox transitions occur at the surface and bulk of transition metal oxides with the application of voltage. Transition metal oxides  are preferred as electrode for pseudocapacitors.RuO2. xH2O has been found to be an ideal material.

RuO2. xH2O is an ideal material suitable as an electrode for pseudocapacitors. However, hydrous ruthenium oxide is very expensive. Hence, efforts are made to replace ruthenium oxide by other transition metal oxides as electrodes in electrochemical capacitors. MnO2 appears to be a promising material for electrochemical capacitors. The advantages of MnO2 are its low cost and environmental friendly nature. My research basically preparation and characterization of MnO2. Finally testing the prepared MnO2 for electrode for Electrochemical Capacitors. MnO2 is prepared using sol-gel method. Prepared MnO2 is characterized using various techniques like X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmet-Teller (BET), ICP-ES and Thermogravimetric Analysis (TGA) and finally electrochemical characterzation using Cyclic Voltammetry (CV) technique.