Highly conductive, completely amorphous polymer electrolyte membranes fabricated through photo-polymerization of poly(ethylene glycol diacrylate) in mixtures of solid plasticizer and lithium salt

摘要

Ternary phase diagram of prepolymermixtures containing poly(ethylene glycol diacrylate) (PEGDA), succinonitrile (SCN) and lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) has been established in order to provide guidance for producing completelyamorphous self-standing solid electrolytemembranes. The phase diagram of the precursor mixtures, thus obtained, consisted of a wide isotropic amorphous region, crystal + amorphous coexistence region at high lithium salt concentrations and plastic crystal + amorphous coexistence region at succinonitrile-rich compositions. Of particular interest is that upon photo-polymerization of isotropic compositions, the resulting networks remained completely amorphouswithout undergoing polymerization-induced phase separation or polymerizationinduced crystallization. The ionic conductivitywasmapped out as a function of compositionwithin the isotropic region of the starting ternary phase diagramin conjunctionwith roomtemperature conductivities showing high ionic conductivities on the order of 10~(-3) S cm~(-1) at several compositions. These solid state polymer electrolyte membranes are transparent, light weight, and flexible, which can be shaped in any forms with space saving attributes. More importantly, no solvent is required in the membrane fabrication as well as in the battery operation, thereby improving safety and cost effectiveness.