High-Performance Double-Network Ion Gels with Fast Thermal Healing Capability via Dynamic Covalent Bonds

A tough double-network (DN) ion gel composed of chemically cross-linked poly­(furfuryl methacrylate-co-methyl methacrylate) (P­(FMA-co-MMA)) and physically cross-linked poly­(vinylidene fluoride-co-hexafluoropropylene) (P­(VDF-co-HFP)) networks with 80 wt % of ionic liquid (IL) was fabricated via a one-pot method. This ion gel exhibits excellent mechanical strength and considerable ionic conductivity, which can be used as a solid gel electrolyte. Upon an adjustment of the weight ratio of P­(FMA-co-MMA) to P­(VDF-co-HFP) and the content of the cross-linker, remarkably robust DN ion gel (failure tensile stress 660 kPa, strain 268%; failure compressive stress 17 MPa, strain 85%) was obtained. The high mechanical strength is attributed to the chemical/physical interpenetrating networks. The rigid chemically cross-linked P­(FMA-co-MMA) network dissipates most of the loading energy, and the ductile physically cross-linked P­(VDF-co-HFP) network provides stretchability for the whole gel. More importantly, the P­(FMA-co-MMA) network is formed by dynamic covalent bonds that can undergo a thermally reversible reaction, giving the gel a unique and effective thermal healing capability. Furthermore, with the high content of IL, the DN ion gel possesses a high ionic conductivity of 3.3 mS cm^–1 at room temperature, which is higher than those of most solid polymer electrolytes and comparable to those of commercial organic liquid electrolytes.