Enhanced performance of HRGO-RuO2 solid state flexible supercapacitors fabricated by electrophoretic deposition

Ruthenium oxide (RuO2) nanomaterials exist as excellent materials for electrochemical capacitors. However, they tend to suffer from low mechanical flexibility when cast into films, which makes them unsuitable for flexible device applications. Herein, we report an environmentally friendly and solution-processable approach to fabricate RuO2-based composite electrodes for flexible solid state supercapacitors. The composites were produced by anchoring RuO2 nanoparticles onto holey reduced graphene oxide (HRGO) via a sol-gel method, followed by the electrophoretic deposition (EPD) of the material into thin films. The uniform anchoring of ultra-small RuO2 nanoparticles on the two-dimensional HRGO sheets resulted in HRGO-RuO2 hybrid sheets with excellent mechanical flexibility of HRGO. EPD induced a layer-by-layer assembly mechanism for the HRGO-RuO2 hybrid sheets, which resulted in a binder-free, flexible electrode. The obtained HRGO-RuO2 flexible supercapacitors exhibited excellent electrochemical capacitive performance in a PVA-H2SO4 gel electrolyte with a specific capacitance of 418 F g−1 and superior cycling stability of 88.5% capacitance retention after 10,000 cycles. In addition, these supercapacitors exhibited high rate performance with capacitance retention of 85% by increasing the current density from 1.0 to 20.0 A g−1, and excellent mechanical flexibility with only 4.9% decay in the performance when bent 180°.