High-performance nickel molybdate/reduce graphene oxide/polypyrrole ternary nanocomposite as flexible all-solid-state asymmetric supercapacitor

Abstract

Ternary nanocomposites of nickel molybdate/reduced graphene oxide/polypyrrole (NiMoO4/rGO/PPy), as the active material of the flexible supercapacitor electrodes, are prepared via a facile two-step route. In these nanocomposites, NiMoO4/rGO binary nanohybrid is grown directly on flexible nickel foam (NF) by hydrothermal method. It is found that this binary nanohybrid under different temperature treatments leads to hydrated and non-hydrated nickel molybdate nanostructures with different morphologies such as the honeycomb-like, nanorod, and their combination. The results reveal the competition of different behaviors of structure, morphology (or specific surface area), and electrical conductivity in the charge storage process of the samples. It is found that the ternary nanocomposite, including the annealed NiMoO4/rGO at a temperature of 450 °C (NiMoO4/rGO−450/PPy), exhibits a maximum specific capacitance of 1805 F g−1 at a current density of 1 A g−1. Moreover, the flexible all-solid-state asymmetric supercapacitor device, fabricated by using NiMoO4/rGO−450/PPy@NF and active carbon (AC)/graphite@NF electrodes, shows a maximum specific capacitance of 218.3 F g−1 in a potential window of 1.2 V and the highest energy density of 43.65 Wh/kg at the power density of 600 W kg−1. In addition, the flexibility of the supercapacitor does not show any adverse effect on its electrochemical performance in the bending state.