Sulfur Vacancies Enriched Nickel-Cobalt Sulfides Hollow Spheres with High Performance for All-Solid-State Hybrid Supercapacitor

Abstract To pursue excellent performance of supercapacitor, an electrode material with designed morphology and tailored intrinsic properties is indeed desired. Herein, nickel–cobalt sulfides hollow spheres decorated with rich sulfur vacancies r-NiCo2S4 HSs) are prepared via an anion exchange of Ni-Co coordination polymer spheres, combined with wet chemical reduction. The r-NiCo2S4 HSs sample delivers excellent performance as an electrode: it possesses a high specific capacity (763.5C g−1 at 1 A/g), favorable cyclability (91.40% after 5000 cycles at 10 A/g) and rate capacity (522.68C g−1 at 15 A/g). Additionally, an all-solid-state hybrid supercapacitor device, assembled with r-NiCo2S4 HSs as the positive electrode and N/S co-doped activated carbon nanosheets as the negative electrode, presents an excellent energy density of 50.76 Wh kg−1 under 800 W kg−1 and feasible stability. Thus, combining hollow structure with sulfur vacancies could not only increase more active sites and ensure sufficient redox reactions, but also enhance electronic conductivity, facilitate ions / electrons transport and shorten diffusion path, which could be regarded as a promising approach to develop electrode materials with outstanding performance.