An all-solid-state fiber-type supercapacitor based on hierarchical Ni/NiO@CoNi-layered double hydroxide core-shell nanoarrays

Abstract Wire-shaped supercapacitors (WSSCs) with high flexibility, tiny volume and high power density are promising candidates for flexible and wearable devices. However, the practical application of WSSCs is still restricted by their low energy density and poor cycling stability. Herein, we report the design and preparation of well-aligned Ni/NiO@CoNi layered double hydroxide (LDH) arrays via a three-step procedure for high performance WSSCs, which consists of NiO nanobelt core and CoNi-LDH nanoplate shell on Ni wire current collector. The obtained hierarchical Ni/NiO@CoNi-LDH electrode exhibits a high specific areal capacitance (1.63 F cm−2 at 2.5 A cm−2), a good rate performance (retention of 90.7% when the current density increases from 2.5 to 20 A cm−2) and an excellent cycling stability (capacitance retention of 97.6% after 1000 cycles). The Ni/NiO@CoNi-LDH electrode was further assembled with Ni/active carbon electrode to construct an all-solid-state WSSC, which can deliver superior energy and power output. When the power density increases from 150 to 900 mW cm−3, the energy density of the device varies from 6.98 to 6.02 mWh cm−3. This new type of supercapacitor deserves a broad application in next-generation wearable and portable electronic products.