Electrode based on nanoporous (Co-Ni)@(CoO,NiO) nanocomposites with ultrahigh capacitance after activation

This work introduces a two-step method to fabricate nanoporous (Co-Ni)@(CoO,NiO) nanocomposites with different Ni/Co ratios (2:1, 1:1 and 1:2) by using hydrogen plasma-metal reaction (HPMR) and chemical dealloying techniques. These nanocomposites with average diameters of 43, 44 and 52 nm are nearly-spherical in shape and contain many micropores. The electrode based on the nanocomposite with Co/Ni ratio of 1:1 exhibits the highest initial specific capacitance of 676 F/g at 1A/g and the best rate capability (77% retention at 10 A/g). The subsequent cycling process continuously activates the electrodes based on these nanocomposites, and remarkably enhances their capacitance. The electrode with Co/Ni ratio of 1:1 achieves the highest capacitance of 2051 F/g at 1 A/g after 1000 cycles. The high pseudocapacitive performance of the (Co-Ni)@(CoO,NiO) nanocomposites is mainly attributed to the nanoporous structure which facilitates fast electron/ion transport, the existence of Co-Ni core which serves as an efficient channel for electron conduction to the current collector, and the continuous activation with formation of electrochemically active materials. This specific nanoporous nanocomposite opens a new way to develop the high performance supercapacitor.