Dielectric gel electrolytes for safe charge storage from −20 to 80°C by double-layer capacitors

Background: Safety and workability under harsh conditions are two of the major challenges for carbon-based electric double layer capacitors (EDLCs). Methods: Gel polymer electrolytes (GPEs), comprising a graphene oxide (GO)-decorated polymer blend of poly(acrylonitrile-co-methyl acrylate) and poly(ethylene glycol) integrated into a liquid electrolyte (LE), are developed. Significant findings: Under firing, the polymer entraps solvent molecules and the GO facilitates the charring of the GO-decorated GPE (GPEG), resulting in low flammability. The GO-polymer framework enhances the dissociation of counter-ion pairs and solvent−ion clusters to increase the ionic conductivity (to a value higher than that of the LE) and reduce the dielectric loss. The GPEG–EDLC outperforms EDLCs assembled using the LE and GO-free GPE with respect to capacitance, rate capability, and cycling stability. The high dissociation of the counter-ion pairs and solvent−ion clusters in the GPEG facilitates ion diffusion into the carbon micropores, thus improving the capacitive performance. The GPEG–EDLC presents excellent performance at −20°C due to the solvent−ion cluster dissociation. Its stable performance at 80°C is ascribable to the low dielectric loss, which minimizes the chemical damage to the system. Our study demonstrates the use of a GO-decorated dielectric polymer to address issues of safety and workability at extreme-temperatures.