Polypyrrole/graphene oxide deposited on two metalized surfaces of porous polypropylene films as all-in-one flexible supercapacitors

Highlights: • Sandwich-structured Au/porous polypropylene films (PPF)/Au have been fabricated. • Polypyrrole-graphene oxide is deposited on Au/PPF/Au to form PPy-GO/ PPF/PPy-GO. • Capacitor of PPy-GO//PPF//PPy-GO has excellent flexibility and bending endurance. • This kind of supercapacitors can be connected in series without further wires. Sandwich-structured composite films with two conductive surface separated by porous insulator have been fabricated after the two sides of porous polypropylene films (PPF) have been covered with gold films via electroless plating method. Subsequently, the composite of polypyrrole-graphene oxide (PPy-GO) has been electrochemically deposited on the two conductive sides via galvanostatic method to form the sandwich structured PPy-GO/PPF/PPy-GO composite films. After gel electrolyte of H₃PO₄/polyvinyl alcohol being coated on the composite films of PPy-GO/PPF/PPy-GO, the integrated flexible supercapacitors (SCs) of PPy-GO//PPF//PPy-GO are fabricated, and the optimal SCs exhibits excellent cycling stability (84.9% capacitance retention after 10000 cycles). Based on the one side electrode, the optimal SCs exhibit relatively high areal specific capacitance (108.0 mF cm^-2 at 2 mV s⁻¹ scanning rate). The integrated SCs exhibit excellent flexibility, the capacitance retention can reach 93.4% after 2000 bending cycles and 80.0% after 5000 bending cycles. Furthermore, this kind of integrated flexible capacitors can be conveniently connected in series without further wires due to their special structure. As a result, they display great potential in flexible and solid integrated energy storage systems.