Electrodeposition Of Cobalt Hydroxide/Oxide And Their Energy Storage Properties

Supercapacitor and lithium ion battery play important roles in energy storage devices of modern society. The former is mostly applied as high power density device and the later is mostly applied as high energy density device. However, the developing electric vehicle markets require the power sources with both high energy density and high power density.Cobalt hydroxides/oxides are applicable in both supercapacitors and lithium ion batteries. They are prospective electrode materials for energy storage devices with high power and energy densities. In our works, nanostructured α-Co(OH)2and CO3O4was directly grown on current collectors as electrodes for supercapacitors and lithium ion batteries, respectively. The electrochemical performance of these materials was greatly improved by the special nanostructure, controllable Zn-doping and process optimization of material synthesis.First, we successfully electrodeposited interconnected a-Co(OH)2nanosheets on nickel foam substrates which exhibited a high capacitance of780F g-1at a discharge current density of1A g-1. This performance owns to the efficient contact between the electrode materials and the electrolyte.To further improve the electrochemical property of these materials, metal ion doping was used. It can be seen that Zn-doped a-Co(OH)2nanosheets displayed obvious improvement in cycling performance. Porous and thinner a-Co(OH)2nanosheets doped by9.7at.%Zn exhibited enhanced specific capacitance of870F g-1at a discharge current density of1Ag-1. Moreover, the21.1at.%Zn doped a-Co(OH)2exhibited excellent cycling performance with only0.6%decrease in capacitance after cycled for2000cycles at a current density of10A g-1, and the specific capacitance still remained at652F g-1.Second, the interconnected porous CO3O4nanoflakes were prepared on nickel foam by a simple electrochemical deposition technique combined with subsequent heating treatment. The porous nanoflakes structural feature leads to an excellent electrochemical performance when used as anode for lithium ion battery. The porous CO3O4nanoflake electrode delivers a high discharge capacity of1211mA h g-1after100cycles at1A g-1,and the electrode maintained a capacity around732mA h g-1at a current density as high as5A g-1, which is attributed to the shortened Li+ion diffusion depth resulted by the special nanostructure.