Novel composite polymer electrolytes containing poly(ethylene glycol)-grafted graphene oxide for all-solid-state lithium-ion battery applications

A series of composite polymer electrolytes were prepared using an organic/inorganic hybrid branched-graft copolymer (BCP) based on poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3-(3,5,7,9,11,13,15-heptaisobutylpentacyclo-[9.5.1.1(3,9).1(5,15).1(7,13)]octasiloxane-1-yl)propyl methacrylate (MA-POSS) as the polymer matrix and poly(ethylene glycol)-grafted graphene oxide (PGO) as the filler material, and they were applied as solid-state polymer electrolytes (SPEs) for lithium-ion battery applications. The ionic conductivity of the composite polymer electrolyte containing 0.2 wt% of PGO (2.1 x 10(-4) S cm(-1) at 30 degrees C) was found to be one order of magnitude higher than that of the BCP (1.1 x 10(-5) S cm(-1) at 30 degrees C); the pristine polymer matrix, because of the larger amount of lithium salt, can be dissociated in the composite polymer electrolyte by Lewis acid-base interactions between the PGO and lithium salt. The thermal and mechanical stabilities of the composite polymer electrolytes were also improved by introducing PGO fillers and reasonable storage modulus values were maintained even at elevated temperatures up to 150 degrees C. All-solid-state battery performance was evaluated with the composite polymer electrolyte containing 0.2 wt% of PGO, resulting in superior cycle performance compared to that of the BCP due to the enhanced ionic conductivity as well as additional ion-conducting paths provided by the PGO fillers.