Flexible, sandwich-like CNTs/NiCo2O4 hybrid paper electrodes for all-solid state supercapacitors

Abstract

With the increasing demand for compact storage systems for portable and wearable electronic devices, flexible supercapacitors with high volumetric performance have attracted considerable attention. Here, we report a simple method to fabricate a sandwich-like carbon nanotubes (CNTs)/NiCo₂O₄ hybrid paper electrode, consisting of a layer of conductive CNT buckypaper coated with honeycomb-like NiCo₂O₄ nanosheets at both sides. Owing to the high conductivity of the CNT skeleton and vertically aligned structure of NiCo₂O₄ nanosheets, the free-standing hybrid paper possesses an ultra-high specific capacitance of 1752.3 F g⁻¹ and excellent cycling performance. A flexible all-solid-state symmetrical supercapacitor has been further assembled based on the hybrid paper. The device exhibits excellent volumetric energy and power densities (1.17 mW h cm⁻³ and 2430 mW cm⁻³) and deformability, even under bending at an angle of 180°. The hybrid paper can serve as a freestanding and flexible electrode for various energy devices.