High performance electrochemical capacitor materials focusing on nickel based materials
Of the two major capacitances contributing to electrochemical storage devices, pseudo-capacitance, which results from the reversible faradaic reactions, can be much higher than the electric double layer capacitance. Transition metal compounds are emerging electrode materials for pseudo-capacitors due to their multiple oxidation states and different ions. As one of the most well-known electroactive inorganic materials, nickel based materials are being developed for this purpose. Nickel based materials have been intensively investigated and evaluated as potential electrode materials for pseudo-capacitors due to their thermal stability and chemical stability, high theoretical specific capacity, low price and environment friendliness. A variety of synthetic methods such as hydrothermal/solvothermal methods, sol–gel, electrodeposition, and the spray deposition method have been successfully applied to prepare nickel based compounds and composite materials. In this review, comprehensive summaries and evaluations have been given to show the recent progress. And we introduce the nickel based compounds and composites electrode materials for supercapacitors via synthesis methods, the electrochemical performances of the electrode materials and the devices.