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

Abstract

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 synthesized by an electrodeposition-annealing-electrodeposition step, in which the inner nickel‑cobalt oxide (NiCoOX) 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) exhibits 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.