Magnesium-induced evolution of micromorphology on layered double hydroxides for enhanced hybrid supercapacitors

Abstract

Layered double hydroxide (LDH) materials have demonstrated great potential in the application of supercapacitors by virtue of high theoretical specific capacity, large specific surface area, ease of fabrication and environmentally benign nature. Nevertheless, the issue of worse electrical conductivity and terrible structural stability severely constrains the practical application of LDH materials in the next-generation high-performance energy supply systems. Morphology regulation and element doping have been proved to be two effective pathways to boost the electrochemical performance of materials. In this work, a novel magnesium-doped nickel cobalt layered double hydroxides (NiCoMg-LDH) has been feasibly synthesized on flexible carbon cloth after introducing small amounts of magnesium ions into NiCo-LDH, which contributes to the evolution of micromorphology from pure nanosheets of NiCo-LDH to 3D nanosphere clusters of NiCoMg-LDH. Although magnesium ions make no direct and great capacity contribution unlike nickel ions and cobalt ions possessing mixed valence states, their successful introduction does play a vital role in regulating and controlling the micro-morphology of the as-fabricated NiCoMg-LDH material, and thus the electrochemical characteristics of the NiCoMg-LDH electrode can be successfully improved in an indirect pattern. Compared with NiCo-LDH electrode, NiCoMg-LDH electrode demonstrates much more remarkable electrochemical properties in the respect of specific capacity, rate performance and cycle life. Additionally, the aqueous hybrid supercapacitor (AHSC) NiCoMg-LDH//AC demonstrates a high gravimetric specific energy of 29.3 Wh kg−1 at 750 W kg−1 as well as a satisfactory cyclic lifespan of enduring 5000 CV scans without capacity decay. The facile fabrication and remarkable electrical performance enable this AHSC device to be an appropriate candidate with enormous potential for practical applications.