Semicrystalline Conductive Hydrogels for High-Energy and Stable Flexible Supercapacitors

Abstract

Conductive polymer-based hydrogels (CHs) have gained increasing attention as flexible electrode materials for making high-performance flexible supercapacitors (FSCs). However, the amorphous nature of current CHs severely limits their energy density and electrochemical stability due to the structural damage of amorphous CHs at high operation voltages and during repeated redox reactions. We hypothesized that semicrystalline CHs that possess more ordered chemical structure and fewer defects should be more resistant to structural damage. Herein, we report a softlate synthesis strategy to prepare semicrystalline CHs by the supramolecular assembly of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(vinyl alcohol) (PVA, serving as a soft template) for making FSCs with higher energy density and better electrochemical stability. In a water/DMSO mixture solvent, semicrystalline PEDOT nanofibers are formed by oxidative polymerization of EDOT monomer and in situ assemble with PVA to form PEDOT-PVA supramolecular hydrogel (PPSH) with a regular porous microstructure. Owing to the ordered polymer chain alignments in the compact nanosheets of PPSH, both the energy density (24 Wh kg-1) and electrochemical stability (100% capacitance retention after 15000 charge-discharge cycles) of the PPSH-based FSC operating at 1.4 V are far beyond previously reported amorphous CHs-based FSCs. This softlate synthesis method provides an effective strategy to prepare semicrystalline CHs with enhanced electrochemical performance for broad applications.