A MnOOH/nitrogen-doped graphene hybrid nanowires sandwich film for flexible all-solid-state supercapacitors

Abstract

All-solid-state supercapacitors (SCs) hold great promise as one of the most efficient energy storage devices due to their high power density, ease of use, and excellent reliability. However, their low energy density severely limits their practical application owing to the lack of suitable electrode materials and reasonable electrode design. In this work, an advanced integrated electrode based on MnOOH/nitrogen-doped graphene hybrid nanowires sandwiched by annealing graphene oxide sheets (MNGHNs/AGO) with outstanding electrochemical performance was developed. The as-fabricated electrodes offer numerous pores for easy access of an electrolyte, high conductivity for improved electron transport, high content (70 wt%) of MNGHNs for large electrochemical capacitance and energy density associated with the whole electrode, and effective protection and mechanical robustness for an exceptional cycle life. With this intriguing architecture, MNGHNs/AGO all-solid-state SCs exhibit a volumetric capacitance as high as 26.3 F cm⁻³ at 0.1 A cm⁻³, a maximum energy density of up to 2.34 mW h cm⁻³ at the power density of 0.04 W cm⁻³, and an outstanding cycling stability of retaining 91.5% of the initial capacity even after 200 000 cycles at 5 A cm⁻³. This work described here can provide a method for flexible, lightweight, low-cost, and high-performance graphene-based sandwich films for supercapacitors.