Supramolecular Hydrogels for High-Voltage and Neutral-pH Flexible Supercapacitors

Flexible supercapacitors are attracting increasing attention as a potential solution for powering flexible electronics. Flexible and electroactive conducting polymer hydrogels can be used as electrode materials for making flexible supercapacitors. However, most of current flexible supercapacitors based on conductive polymer hydrogels are limited by low operation voltage and the usage of acidic, alkaline or ionic liquid electrolytes, resulting in low energy density and potential safety hazards. Herein, we report the design of poly(3,4-ethylenedioxythiophene) (PEDOT)-based robust hydrogels by supramolecular assembly of PEDOT and poly(vinyl alcohol) (PVA) through dynamic boronate bonds. With PVA-Na2SO4 hydrogels as both neutral-pH solid-state electrolyte and separator, two PEDOT–PVA hydrogel electrodes are assembled to give a flexible solid-state supercapacitor (SSC). Because of the high chemical stability of PEDOT–PVA hydrogel and the neutral-pH solid-state electrolyte, this SSC can operate at a high voltage of 1.4 V, which provides a high energy density of 15.2 Wh kg–1 (with power density of 201.1 W kg1–). The robustness of this SSC is demonstrated by its 89% capacitance retention after 1000 charge–discharge cycles, and the ∼100% capacitance retention after 1000 mechanical folding cycles (at a scan rate of 5 A g–1). And the Coulombic efficiency of this supercapacitor remains ∼100%. The combination of high energy density, chemical and mechanical robustness, and the usage of neutral-pH hydrogel electrolyte enable the PEDOT–PVA hydrogel based SSC as a promising high-voltage and safe power device for flexible electronics.