A solvent-exchange strategy to develop stiff and tough hydrogel electrolytes for flexible and stable supercapacitor

Toughness of flexible energy storage devices and a stable energy output during dynamic deformation are two challenges to be solved in their practically application. Herein, we reported a stiff and tough poly(vinyl alcohol) (PVA) hydrogel electrolyte for flexible supercapacitor with toughness and stable energy output. A one-step solvent-exchange strategy was developed to replace the good solvent dimethyl sulfoxide (DMSO) to a poorer one water and simultaneously introduce kosmotropic ions into the PVA pre-hydrogels. This triggered the PVA chains to self-assemble and forming a homogeneous network crosslinked by the PVA crystalline domains and hydrophobic interactions. Benefiting from the excellent energy-dissipating ability of the homogeneous network, the PVA hydrogel electrolytes exhibited remarkable stiffness and toughness with tensile strength 16.54 MPa, elongation at break 1203%, and toughness 111.21 MJ m−3, which surpassed the most reported hydrogels. By utilizing polyaniline as electrodes, a flexible supercapacitor was assembled with superior areal specific capacitance of 156.50 mF cm−2 at 1.0 mA cm−2. The supercapacitor delivered high resistance to mechanical stimuli such as bending and pressure. Moreover, it could well maintain stable energy output even being dynamically deformed. The developed supercapacitor showed great potential in the wearable applications.