Nickel‑cobalt oxide nanowires with oxygen vacancies supported on CVD graphene networks for all-solid-state asymmetric supercapacitors

Abstract

NiCo₂O₄ is a promising material for pseudocapacitance because of its exceptional reversible ability and high theoretical specific capacitance. However, its effectiveness in supercapacitors is restrained by a restricted number of active sites and low intrinsic electronic conductivity. To address these challenges, a novel composite electrode, OV-NiCo₂O₄@CGN@NF, has been developed by the introduction of oxygen vacancies (OV)-abundant NiCo₂O₄ nanowires assembly coupled with CVD graphene network (CGN) on nickel foam (NF) to form a heterojunction structure. Incorporating oxygen vacancies and CGN enhances electrical conductivity, active sites and contact area, as well as promotes fast faradic redox reactions. The OV-NiCo₂O₄@CGN@NF electrode exhibits exceptional capacitive properties and impressive cyclic durability due to the strong binding between OV-NiCo₂O₄@CGN and NF. At a current density of 1 A g⁻¹, the electrode delivers a high specific capacitance of 775.4C g⁻¹ and a good capacity retention rate (101 % of its original specific capacity is left at 10 A g⁻¹). Moreover, when used as the cathode in an all-solid-state asymmetric supercapacitor, together with activated carbon (AC) loaded on NF as the anode, the OV-NiCo₂O₄@CGN//AC all-solid-state asymmetric supercapacitor device achieves a high energy density of 53.1 Wh kg⁻¹ at 800.2 W kg⁻¹. This research contributes valuable insights for enhancing electrode materials for energy storage devices in the future.