Growth of CoMn-LDH/Co-Ni bimetallic sulfides on nickel foam with enhanced electrochemical properties for asymmetric supercapacitors

Incorporating transition metal sulfide with layered double hydroxide to form the heterostructure is a valid strategy, which helps to reduce volume expansion of active substances during long charging and discharging and enhance diffusion rate of ion. Herein, cobalt-nickel bimetallic sulfides and cobalt-manganese layered double hydroxide composite on nickel foam (CM/CNS/NF) is prepared by hydrothermal method combined with electrodeposition. The structure, morphology and electrochemical characterizations of as-prepared CM/CNS/NF electrodes are studied systematically. The results show that electrochemical properties of CM/CNS/NF electrodes vary with molar ratio of CoCl2·6H2O and MnCl2·4H2O (1:1, 3:1, 5:1 and 7:1). When the molar ratio of CoCl2·6H2O and MnCl2·4H2O is 3:1, CM/CNS/NF is equipped with high specific capacity of 934.0 C g−1 at 1 A g−1. In addition, its retention rate of capacity can still remain 75.27% after 3000 cycles at 20 A g−1. Moreover, when power density is 800 W kg−1, energy density of the asymmetric device composed of positive electrode (CM/CNS/NF) and negative electrode (activated carbon/NF) is as high as 37.53 Wh kg−1. These results show that design and preparation of CM/CNS/NF provide a route to elevate specific capacity for potential application in the field of supercapacitors.