Postinjection gelation of an electrolyte with high storage permittivity and low loss permittivity for electrochemical capacitors

The use of gel polymer electrolytes (GPEs) in electric double layer capacitors (EDLCs) is limited by the liquid injection assembly line currently used in EDLC manufacturing. This paper proposes a postinjection gelated GPE, which can be synthesized by mixing a polymer blend of poly(acrylonitrile-co-methyl acrylate) and poly(ethylene glycol) (i.e., PANMA:EG) with a conventional liquid electrolyte (LE). The as-synthesized GPE is in liquid state and can be applied in the liquid injection assembly line. The gelation time can be tuned by varying the composition of the polymer blend. The functionalities on the polymer chains facilitate the dissociation of ion pairs and suppress the formation of ion–solvent complexes; thus, the GPE has an ionic conductivity that is three times that of the LE. Under polarization for dielectric analysis, the GPE exhibits high storage permittivity and low loss permittivity because of its swift ion motion and polymeric dipole orientation. Owing to its superior permittivity performance, the resulting GPE-EDLC outperforms the LE-EDLC in terms of the ultimate capacitance, rate capability, and charge–discharge cycling stability. The postinjection gelation feature and outstanding permittivity characteristics indicate the suitability of this GPE in industrial-scale assembly lines and practical applications.