Dual Hybrid Effect Endowing Nickel–Cobalt Sulfides with Enhanced Cycling Stability for Asymmetrical Supercapacitors
Man Wang, Juan Yang, Siyu Liu, Chao Hu, Jieshan Qiu
Abstract
The construction and optimization of electrode materials with a stable structure have received great attention to realize high-performance supercapacitors. Herein, we present the fabrication of nickel–cobalt sulfide (NiCo)9S8 nanoparticles protected by NiCo-based oxyhydroxides coupled with nitrogen and sulfur codoped graphene substrates (N, S-doped G) via an ethylenediamine (EDA)-mediated assembly and electrochemical oxidation strategy, named O-(NiCo)9S8/N, S-doped G. It was found that the (NiCo)9S8 nanoparticles coated by the metal oxyhydroxide shell are tightly encapsulated into N, S-doped G frameworks, yielding a unique dual hybrid effect to achieve ample heterojunctions/interfaces and robust architecture, which is conducive to enhance electroactivity and cycling stability. As a proof-of-concept application, the as-fabricated O-(NiCo)9S8/N, S-doped G as the electrode for the supercapacitor achieves a high specific capacity of 1247 F g–1, that is, 166 mA h g–1 at 0.5 A g–1 and a superior rate capability of 89% at 20 A g–1. Further, the asymmetric supercapacitor made of the O-(NiCo)9S8/N, S-doped G//activated carbon along with a high mass loading of about 6 mg cm–2 exhibits an ultralong cycling stability of 70% after 20,000 cycles and a high charge storage capability of 50.8 W h kg–1 at 400 W kg–1, which is much better than those of the other comparative electrode materials.