Hierarchical holey Co9S8@S-rGO hybrid electrodes for high-performance asymmetric supercapacitors

• Published in: Electrochimica acta 2019-12, Vol.328, p.135078, Article 135078
• Main Authors: Mao, Xiling, He, Xin, Yang, Wenyao, Liu, Hao, Zhou, Yujiu, Xu, Jianhua, Yang, Yajie
• Format: Article
• Language: English
• Subjects: 3D hierarchical holey composite; Anchoring; Asymmetric supercapacitors; Asymmetry; Capacitance; Co9S8; Cobalt sulfide; Electrodes; Energy storage; Flux density; Graphene; Gravimetry; Hydrogen sulfide; Hydrothermal reactions; Ion transport; Nanoparticles; Stability; Supercapacitors
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2019.135078

Here we report the novel design of Co9S8 nanoparticles anchoring onto three dimensional (3D) porous sulfur-doping reduced graphene oxide network (Co9S8@S-rGO) by the facile hydrothermal reaction and heat annealing process, during which the abundant pores on the S-rGO framework and Co9S8 nanoparticles can be obtained simultaneously. This may be attributed to the Co9S8 nanoparticles as the catalyst, which can contribute to the transformation of the S atoms in rGO into S-relative gases (such as H2S or SO2), resulting in the pores-rich nanostructures. Furthermore, the holey network S-rGO matrix effectively facilitate electron/ion transport, and the Co9S8 nanoparticles intercalating in S-rGO framework can drastically reduce the agglomeration of S-rGO nanosheets and provide abundant pseudocapacitance reaction sites simultaneously. The results demonstrate that the Co9S8@S-rGO-800 electrode delivers a higher gravimetric capacitance of 348.45 F g−1 and an outstanding cycling stability of 92.6% after 5000 charge/discharge cycles at 1 A g−1. As expected, an asymmetric supercapacitor is assembled and exhibits a high energy density of 39.51 Wh kg−1 at a power density of 260 W kg−1 (23.13 Wh kg−1 at 8410 W kg−1), as well as the excellent cycling stability with 90.6% of the initial specific capacitance after 5000 cycles. [Display omitted] •The abundant holes on the S-rGO and Co9S8 particles could be obtained simultaneously.•The 3D hierarchical holey Co9S8@S-rGO composites were designed.•A flexible all-solid-state asymmetric supercapacitor was fabricated.•High energy/power density and outstanding cycle stability of ASC device was obtained.