Coupled cobalt silicate nanobelt-on-nanobelt hierarchy structure with reduced graphene oxide for enhanced supercapacitive performance

Abstract

Cobalt silicate (Co2SiO4, abbreviation as CSO), as one of the sustainable electrode materials, possesses considerable theoretical capacity and excellent structural stability. However, very limited work focuses on hierarchy structure control of CSO although it has an important impact on capacitive capability. In this work, a novel nanobelt-on-nanobelt hierarchy structure of CSO is coupled with reduced graphene oxide (abbreviation as CSO NN/RGO) to realize the remarkable enhancement of their capacitive performance by optimizing electron/ion transportation and decreasing self-aggregation as well as relieving volume expansion during charging and discharging. As it is expected, the capacitance value of CSO NN/RGO can reach 483 F g−1 at 0.5 A g−1 with the 58% capacitance retention after 10000 cycles, which is much higher than those of bulk CSO (217 F g−1), pure CSO nanobelt (244 F g−1) and CSO NN (351 F g−1), clearly demonstrating the significant merit of such a hierarchy NN/RGO structure. Impressively, the hybrid supercapacitor device which is assembled by CSO NN/RGO and activated carbon delivers an excellent performance with a large volume capacitance of 219 mF cm−2 at 1 mA cm−2 and a 98% capacitance retention after 6000 cycles.