A rectification-free piezo-supercapacitor with a polyvinylidene fluoride separator and functionalized carbon cloth electrodes

The integration of energy harvesting and energy storage in this device not only enables the conversion of ambient energy into electricity, but also provides a sustainable power source for various electronic devices and systems. It is highly desirable to improve the integration level and minimize unnecessary energy loss in the power-management circuits between energy harvesting and storage devices. In our work, we integrate a PVDF film into a supercapacitor as both the separator and the energy harvester. The double-sides of the polarized PVDF films are coated with H2SO4/poly(vinyl alcohol) (PVA) gel electrolyte. Functionalized carbon cloths are assembled with H2SO4/PVA electrolyte as both anode and cathode, forming a flexible all-solid-state supercapacitor. Externally mechanical impacts establish a piezoelectric potential across the PVDF films, and drive ions in the electrolyte to migrate towards the interface of the supercapacitor electrode, storing the electricity in the form of electrochemical energy. The asymmetric output characteristic of the piezoelectric PVDF film under mechanical impact results in the effective charging of the supercapacitor without any rectification device. The integrated piezo-supercapacitor exhibits a specific capacitance of 357.6 F m(-2), a power density of 49.67 mW h m(-2), and an energy density of 400 mW m(-2). Our hybridized energy harvesting and storage device can be further extended for providing sustainable power source of various types of sensors.