Graphene oxide-intercalated PVDF nanofibers as a novel piezo separator for self-charging supercapacitors

Incorporation of a piezoelectric separator between supercapacitor electrodes creates a self-charging supercapacitor. When subjected to mechanical stress, the piezoelectric membrane generates an internal potential that spontaneously recharges the supercapacitors without requiring external power. We report a graphene oxide (GO)-intercalated PVDF nanofiber membrane as a high-performance piezoelectric separator for self-charging supercapacitors (SCSCs). A novel approach for the fabrication process generates a layer-by-layer stacking of PVDF NFs and GO nanosheets within an intercalated structure. The morphology, structure, and energy harvesting properties of the fabricated GO-intercalated PVDF NF membrane (GO/PVDF) were investigated. The GO-intercalated PVDF membrane exhibits an enhanced β-phase content (66.2%) and piezoelectric coefficient (d₃₃ = 52.30 ± 0.87 pC N^-1), enabling efficient mechanical energy harvesting. The fabricated piezoelectric nanogenerator (PENG) could generate a voltage of 141.41 ± 2.37 V mm^-1 under a compressive force of 0.5 N. At the device level, the SCSC achieved an areal capacitance of 1.85 mF cm^-2 at a current of 0.05 mA. An energy density of 0.24 µWh cm^-2 and a corresponding power density of 26 µW cm^-2 were achieved. The fabricated SC exhibited an excellent rate capability and the capacitance retention was up to 98% after 5000 cycles. The SCSC could self-charge up to 420 mV in approximately 4 min. These findings demonstrate the effectiveness of the SCSC in converting mechanical energy into usable electrical power. The results provide new insights into the advancement of self-charging energy storage systems.