Multilayered paper-like electrodes composed of alternating stacked mesoporous Mo2N nanobelts and reduced graphene oxide for flexible all-solid-state supercapacitors

Flexible all-solid-state supercapacitors (SCs) have great potential in flexible and wearable electronics due to their safety, flexibility, high power density, and portability. The energy storage properties of SCs are determined mainly by their composition and conductivity as well as the configuration of the integrated electrode material. Herein, a freestanding multilayered film electrode consisting of alternating stacked mesoporous Mo2N nanobelts and rGO nanosheets (MMNNBs/rGO) is described. The electrode has a high mass loading of 95.6 wt% of the Mo2N active material and boasts high areal capacitances of 142 and 98 mF cm−2 at current densities of 1 and 150 mA cm−2, respectively. All-solid-state SCs fabricated by sandwiching two thin and flexible freestanding MMNNBs/rGO hybrid electrodes with a poly (vinyl alcohol) (PVA)/H3PO4/silicotungstic acid (SiWA) gel electrolyte show a high volumetric capacitance of 15.4 F cm−3 as well as energy and power densities of 1.05 mW h cm−3 and 0.035 W cm−3 at a current density of 0.1 A cm−3 based on the volume of the entire cell. After 4000 charging–discharging cycles, the flexible SC retains 85.7% initial capacitance, thus exhibiting good cycling stability. This study provides a versatile method for the fabrication of flexible and high-performance ceramic-based nanohybrid films for SCs, and has immense potential in flexible and wearable electronics.