Fabrication of high performance flexible micro-supercapacitor arrays with hybrid electrodes of MWNT/V₂O₅ nanowires integrated with a SnO₂ nanowire UV sensor

We report on the on-chip fabrication of high performance flexible micro-supercapacitor (MSC) arrays with hybrid electrodes of multi-walled carbon nanotube (MWNT)/V₂O₅ nanowire (NW) composites and a solid electrolyte, which could power the SnO₂ NW UV sensor integrated on the same flexible substrate. The patterned MSC using hybrid electrodes of MWNT/V₂O₅ NW composites with 10 vol% of V₂O₅ NWs exhibited excellent electrochemical performance with a high volume capacitance of 80 F cm^-3 at a scan rate of 10 mV s^-1 in a PVA-LiCl electrolyte and good cycle performance to maintain 82% of the capacitance after 10 000 cycles at a current density of 11.6 A cm^-3. The patterned MSC also showed an excellent energy density of 6.8 mW h cm^-3, comparable to that of a Li-thin film battery (1-10 mW h cm^-3), and a power density of 80.8 W cm^-3 comparable to that of state-of-the-art MSCs. In addition, the flexible MSC array on a PET substrate showed mechanical stability over bending with a bending radius down to 1.5 mm under both compressive and tensile stress. Even after 1000 bending cycles at a bending radius of 7 mm, 94% of the initial capacitance was maintained. Furthermore, we have shown the operation of a SnO₂ NW UV sensor using such a fabricated MSC array integrated into the same circuit on the PET substrate.