Miniature supercapacitors composed of nickel/cobalt hydroxide on nickel-coated silicon microchannel plates

Silicon microchannel plates with a large surface area coated with a nickel layer are excellent templates for miniature supercapacitors. Three-dimensional Si-MCP/Ni/Ni(OH)₂ and Si-MCP/Ni/Co(OH)₂ sandwiched structures are produced with the Ni(OH)₂ and Co(OH)₂ thin films serving as the active materials in the supercapacitors which consist of microcrystalline and nano-sized flakes or rods. The specific capacitances derived from the CV and typical charge/discharge curves exhibit good consistency. The highest specific capacitance of 3.75 F cm^-2 is obtained at a discharge current density of 10 mA cm^-2 from Si-MCP/Ni/Ni(OH)₂ and 1.46 F cm^-2 from Si-MCP/Ni/Co(OH)₂ at a scanning rate of 10 mV s^-1. At high rates, the specific capacitances measured from both samples are relatively low, but the excellent capacitive properties are restored at low rates after being subjected to several high rate charge/discharge cycles. Owing to the large specific capacitance per unit area, good cycling performance, small volume, and unique three-dimensional structure, these electrodes are excellent supercapacitors suitable for secondary power sources. In addition, the potential of nickel coated Si-MCPs as templates for miniaturization and integration of devices in practical applications is discussed and demonstrated.