An Ionogel Piezo-Electrolyte Derived from Protic Ionic Liquid for High-Performance Wearable Self-Powered Supercapacitors

Piezo-electrolytes have emerged as a kind of multifunctional material for self-charging power cells but well coupling of piezoelectric and conductive components remains a concern. In this work, protic acidic ionic liquid 1-methylimidazolium hydrogen sulfate, which is miscible with piezoelectric barium titanate (BaTiO 3 ), is fabricated into a self-standing ionogel piezo-electrolyte by in situ polymerization of acrylate monomers for self-powered supercapacitors. Attachment of the acidic anions on the surface of the basic BaTiO 3 via acid–base interactions allows the piezoelectric particles to be homogeneously stabilized in the ionogel through electrostatic repulsion. The ionogel piezo-electrolyte exhibits an ionic conductivity of 2.2 mS cm –1 with a proton transference number of 0.234 and an open circuit voltage of 6.75 V at a compressive force of 20 N. A piezo-supercapacitor is constructed by sandwiching the ionogel between polyaniline-coated carbon cloth, delivering a specific capacitance of 1795 mF cm –2 . When a static compressive force is applied, the piezo-supercapacitor is self-charged up to 1259 mV with a maximum rate of 581 mV s –1 . Meanwhile, the piezo-supercapacitor shows a voltage decay of only 5% after 9000 s in the absence of external forces. A single piezo-supercapacitor with 1 cm 2 active area successfully powers an electronic watch by finger pressing. The strategy of coupling proton conduction with piezoelectric response in the protic ionogel efficiently enhances energy conversion in piezo-supercapacitors.