Mechanically Robust and Electrically Conductive Hybrid Hydrogel Electrolyte Enabled by Simultaneous Dual In Situ Sol-Gel Technique and Free Radical Copolymerization

Mechanically robust and ionically conductive hydrogels poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonate-lithium)/TiO₂/SiO₂ (P(AM-co-AMPSLi)/TiO₂/SiO₂) with inorganic hybrid crosslinking are fabricated through dual in situ sol-gel reaction of vinyltriethoxysilane (VTES) and tetrabutyl titanate (TBOT), and in situ radical copolymerization of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonate-lithium (AMPSLi), and vinyl-SiO₂. Due to the introduction of the sulfonic acid groups and Li⁺ by the reaction of AMPS with Li₂CO₃, the conductivity of the ionic hydrogel can reach 0.19 S m^-1. Vinyl-SiO₂ and nano-TiO₂ are used in this hybrid hydrogel as both multifunctional hybrid crosslinkers and fillers. The hybrid hydrogels demonstrate high tensile strength (0.11-0.33 MPa) and elongation at break (98-1867%), ultrahigh compression strength (0.28-1.36 MPa), certain fatigue resistance, self-healing, and self-adhesive properties, which are due to covalent bonds between TiO₂ and SiO₂, as well as P(AM-co-AMPSLi) chains and SiO₂, and noncovalent bonds between TiO₂ and P(AM-co-AMPSLi) chains, as well as the organic frameworks. Furthermore, the specific capacitance, energy density, and power density of the supercapacitors based on ionic hybrid hydrogel electrolytes are 2.88 F g^-1, 0.09 Wh kg^-1, and 3.07 kW kg^-1 at a current density of 0.05 A g^-1, respectively. Consequently, the ionic hybrid hydrogels show great promise as flexible energy storage devices.