Strong and tough conductive PVA hydrogels based on the synergistic effect of acetic acid induction and salting-out for flexible solid-state supercapacitors

Practical applications usually require solid conductive hydrogels with outstanding mechanical stability for flexible energy storage devices. Herein, a synergistic strategy of acetic acid induction and salting-out is proposed to achieve strong and tough conductive poly(vinyl alcohol) (PVA) hydrogels for flexible solid-state supercapacitors. Acetic acid introduced into the PVA/dimethyl sulfoxide (DMSO) system robbed the hydrogen bonding sites of DMSO bound to the hydroxyl groups of PVA, further encouraging the restoration of intra/inter-chain hydrogen bonds of PVA to form an organic pre-gel. Immersion of the PVA pre-gel in salt solution triggers the salting-out process coupled with solvent exchange, facilitating the structural microdomain densification and homogenization, forming a densely cross-linking network and endowing the synergistic PVA hydrogel with splendid mechanical capabilities (strength of 9.06 MPa, 1763% fracture elongation, and toughness of 85.8 MJ m-3). Attributed to the incorporation of ions, the synergistic PVA hydrogel attains satisfactory ionic conductivity (18.02 mS cm-1). The assembled supercapacitor based on synergistic PVA hydrogels and carbon cloth/polyaniline composite electrodes delivers a prominent areal-specific capacitance of 73.13 mF cm-2 at 0.5 mA cm-2 and can achieve stable output even under deformation. A practical and efficient avenue for constructing strong tough conductive hydrogels is developed in this work, which has great potential for use in energy storage devices. A synergistic strategy of acetic acid induction and salting-out is proposed for optimizing the microstructure, mechanical properties, and ionic conductivity, thus constructing strong and tough conductive PVA hydrogels for flexible supercapacitors.