Flexible, all-solid-state, high-cell potential supercapacitors based on holey reduced graphene oxide/manganese dioxide nanosheets

2D ultrathin nanomaterials have attracted a significant interest for their application in flexible and lightweight energy storage devices. In this work, we report the fabrication, by electrophoretic deposition (EPD), of flexible all-solid-state symmetric high cell potential supercapacitors, comprised of holey reduced graphene oxide – manganese dioxide nanosheets (HGM). HGM films were electrophoretically deposited in a layer-by-layer fashion onto targeted substrates, with net thicknesses ranging from 0.2 to 2.5 μm. The assembled HGM films were highly compact with the density of ∼2.2 g cm−3. The resulting symmetric HGM supercapacitors, using PVA-LiClO4 gel as an electrolyte, exhibited excellent electrochemical capacitive performance over a wide cell potential window of 0.0–1.6 V. Operating at ultra-high charge-discharge rates, up to 5000 mV s−1, the HGM supercapacitors delivered excellent areal specific capacitances of 12–46 mF cm−2, corresponding to volumetric specific capacitances of 557–182 F cm−3 at thickness of 0.2–2.5 μm, respectively. Furthermore, the HGM supercapacitors exhibited long-term cycling stability with a retention over 80% of its initial capacitance after 2000 cycles. Considering the facile scale-up capability of the EPD process, our approach paves a promising route for the manufacture of next-generation flexible all-solid-state supercapacitors with high energy and high power density. [Display omitted] •Flexible solid state supercapacitors of HRGO–MnO2 nanosheets (HGM) were prepared.•Electrophoretic deposition was used to fabricate flexible electrodes.•HGM supercapacitors exhibited excellent volumetric energy density of 48.8 mWh cm-3.•HGM supercapacitors showed long lifespan with over 80% retention after 2000 cycles.