Cobalt/nickel ions assisted to synthesize laminated CuO nanospheres based on Cu(OH)2 nanorod arrays for high performance supercapacitors.

The developments for environmental friendly energy conversion and storage equipment have gave rise to tremendous research efforts as a result of the growing requirements for environmental friendly resources and the rapid consumption of traditional fossil fuel. Herein, a novel hierarchical CoO/NiO-Cu@CuO heterostructure is successfully devised and synthesized. The cobalt/nickel ions are assisted to generate the novel CoO/NiO doped laminated CuO nanospheres through the facile in-situ wet oxidation combined with cation-exchange and calcination strategies. As a result, the electrochemical supercapacitance of as-preparative CoO/NiO-Cu@CuO electrode can reach 875 C cm-2 (2035 mF cm-2), which exhibits much better electrochemical performance compared with other precursor electrodes at same current density of 2 mA cm-2. Moreover, an excellent rate capacity of 1395 mF cm-2 (50 mA cm-2) can be achieved when measured at a relative high current density. Compared with the beginning supercapacitance, the capacity can still remain about 90.3 % after 5000 cycles. Furthermore, the as-prepared hierarchical hybrid of laminated CoO/NiO-CuO nanospheres in situ generate on 3D porous Cu foam is applied to prepare a solid-state asymmetric supercapacitor (ASC) equipment unit. The fabricated equipment unit shows an energy density of 69.3 W h kg-1 at power density of 1080 W kg-1. Additionally, the commercial applied 2.5 V light-emitting-diode indicator with blue light can be energized for 4 minutes when two as-fabricated supercapacitor devices are series connection. The unique hierarchical heterostructure of the novel laminated nanospheres combined with the 3D grid structure bring about the outstanding electrochemical capacitor performances. This strategy for the fabrication of hierarchical heterostructure electrodes could have enormous potential for high performance electrochemical equipment.