Nanosheets self-supported structure in the orderly porous spheres of Co/Mn ions co-substituted α-Ni(OH)2 for high-performance supercapacitors

Abstract

Ni(OH)2 as a battery-type electrode material in Faraday supercapacitors could present low electrochemical performance, which is mainly attributed to its low electrical conductivity and inappropriate pore structure. In this work, we try to address these two issues by co-substituting Co/Mn ions in Ni(OH)2 via a co-precipitation strategy, forming spheres assembled with orderly interlaced nanosheets. The nanosheets self-supporting nanostructure plus the structure stabilization of substituted Co ions result in the high cycling stability of as-prepared Ni(OH)2 spheres (84.2% capacity retention after 10,000 charge–discharge cycles). Meanwhile, the spheres present high electrochemical performance due to the ordered nanostructure and the synergetic contribution of Co/Mn ions. The asymmetrical supercapacitor assembled with the ions-substituted Ni(OH)2 spheres also show high performance. It delivers a high energy density of 55.8 Wh kg−1 at power density of 565.6 W kg−1 and super-high cycling stability (80.2% of capacity retention after 30,000 cycles at 2.0 A g−1). These results demonstrate that the ions-substituted Ni(OH)2 spheres could be a promising electrode material for application in supercapacitors.