Three-dimensional spherical NiCoOX@NiCo layered double hydroxides nanosheets for high-performance all-solid-state supercapacitors

The low conductivity of cobalt-based oxides greatly limits its application in supercapacitors (SCs). Recently, construction of heterogeneous structural materials has emerged as an effective way to solve this problem. Herein, nickel-cobalt oxide @ nickel-cobalt layered double hydroxides (NiCoOX@NiCo LDH) heterostructure is syn-thesized by an electrodeposition-annealing-electrodeposition step, in which the inner nickel-cobalt oxide (NiC-oOX) layer is firstly deposited on the carbon cloth with a subsequent annealing process, and the outer nickel-cobalt layered double hydroxides (NiCo LDH) layer is electrodeposited on the prepared NiCoOX layer. Benefiting from the multi-channel structure and extensive specific surface area produced by the heterogeneous structure material, as same as its synergistic effect, at 1 A g(-1), NiCoOX@NiCo LDH exhibits an extremely advanced specific capacitance (2451 F g(-1)). It is much better than pure NiCoOX and pure NiCo LDH. Meanwhile, its specific capacitance retention rate still keeps 62.8 % even at 20 A g(-1), indicating its excellent rate property. Furthermore, the assembled all-solid-state asymmetric SCs with NiCoOX@NiCo LDH//Active carbon (AC) ex-hibits a high energy density of 34.9 Wh kg(-1) when the power density is 800 W kg(-1). Meanwhile, it has a high capacitance retention of 81.79 % (10 A g(-1)) after 10,000 cycles, which indicates a remarkable cycle life.

Automated summary

This study successfully solves the low conductivity issue of cobalt-based oxides in supercapacitors by constructing heterogeneous structural materials. The synthesized NiCoOX@NiCo LDH heterostructure exhibits a high specific capacitance and capacitance retention rate, as well as a high energy density and cycle life in the assembled capacitors.