Controllable sulfidation of polymetallic nickel cobalt molybdenum layered double hydroxides on Ni foam for high-performance hybrid supercapacitors

Abstract

In situ construction of polymetallic layered double hydroxide (LDH) @sulfide heterostructures (LDH@sulfides) is a promising strategy to achieve excellent electrochemical performance by providing more redox active sites and facilitating ion/electron pathways. Herein, nickel cobalt molybdenum based LDH@sulfide core–shell composites (NCM-LDH@NCMS) grown on Ni foam have been successfully prepared via a facile hydrothermal method, followed by controllable sulfidation methods. The effect of sulfidation time on the electrochemical performance of NCM-LDH@NCMS was investigated. The NCM-LDH nanosheets minimized the diffusion path of electrolyte ions and accelerated the kinetics of redox reactions, and the outer Ni–Co–Mo sulfides effectively improved the conductivity of LDHs and exposed more active sites. With sulfidation for 2 h, the obtained NCM-LDH@NCMS-2 exhibited excellent electrochemical performance, with a specific capacitance of ∼7.73 F cm⁻² at 10 mA cm⁻², and better capacitance rate performance of 56.7% at 50 mA cm⁻². Furthermore, hybrid NCM-LDH@NCMS-2//activated carbon supercapacitors provided a high energy density of 0.25 mW h cm⁻² at 40 mW cm⁻² and excellent cycling stability of 89.82% after 8000 cycles at 8 mA⁻².