Tailoring morphology of cobalt-nickel layered double hydroxide via different surfactants for high-performance supercapacitor.

Tailoring the morphology of cobalt-nickel layered double hydroxide (LDH) electrode material was successfully achieved via the process of cathodic electrodeposition by adding different surfactants (hexamethylenetetramine, dodecyltrimethylammonium bromide (DTAB) or cetyltrimethylammonium bromide). The as-prepared Co0.75Ni0.25(OH)2 samples with surfactants exhibited wrinkle-like, cauliflower-like or net-like structures that corresponded to better electrochemical performances than the untreated one. In particular, a specific capacitance of 1209.1 F g-1 was found for the cauliflower-like Co0.75Ni0.25(OH)2 electrode material using DTAB as the surfactant at a current density of 1 A g-1, whose structure boosted ion diffusion to present a good rate ability of 64% with a 50-fold increase in current density from 1 A g-1 to 50 A g-1. Accordingly, the asymmetric supercapacitor assembled by current LDH electrode and activated carbon electrode showed an energy density as high as 21.3 Wh kg-1 at a power density of 3625 W kg-1. The relationship between surfactant and electrochemical performance of the LDH electrode materials has been discussed.