Etching strategy synthesis of hierarchical Ni-Mn hydroxide hollow spheres for supercapacitors

Hierarchical hollow structures have been shown excellent performance in supercapacitors. Herein, hierarchical Ni-Mn hydroxide hollow spheres are successfully prepared by an etching strategy. NiMn-glycerate solid spheres are first obtained as templates. After treatment in the mixed solvents of 1-methyl-2-pyrrolidone and water, NiMn-glycerate templates are etched to form hierarchical Ni-Mn hydroxide hollow spheres. Owing to the advantages of hierarchical hollow structures and large surface area, Ni-Mn hydroxide as electrode material manifests a specific capacity of 1680 F g−1 at 2.0 A g−1, and it maintains 1068 F g−1 at 15 A g−1. Meanwhile, a diminished specific capacity of only 3.4 % is achieved over 5500 cycles at 10 A g−1. Furthermore, the fabricated asymmetric supercapacitor comprising of Ni-Mn hydroxide and activated carbon demonstrates a specific energy of 42.8 Wh kg−1 at 1703 W kg−1, indicating as a promising electrode material for high performance supercapacitors.