Comb-like copolymer-based gel polymer electrolytes for lithium ion conductors

A comb-like polymer was prepared by copolymerization of acrylonitrile and poly(ethylene glycol-methyl methacrylate) (PEGMEM). The copolymer was mixed with a propylene carbonate plasticizer and LiClO₄ to form a gel polymer electrolyte (GPE). ⁷Li solid-state NMR analysis was used to elucidate interactions between the lithium ions and unpaired electrons on the gel polymer groups. ⁷Li magic-angle spinning NMR and Fourier-transform infrared spectroscopy revealed that the PEGMEM segment could promote dissociation of the lithium salt. Differential scanning calorimetry was used to study the thermal behavior of GPEs of different compositions. The conductivity increased with PEGMEM content. Furthermore, the conductivity of GPE based on a comb-like copolymer exceeded that based on polyacrylonitrile (PAN) with the same composition (polymer/plasticizer 50:50 wt.%). Notably, the highest conductivity of the copolymer/plasticizer 50:50 wt.% system (2.51 × 10^-3 S cm^-1) was close to that for the PAN/plasticizer 20:80 wt.% system (1.90 × 10^-3 S cm^-1).