Nonionic Amphiphilic Copolymers of Poly(poly(ethylene Glycol) Methacrylate) Brushes with Methyl Methacrylate Prepared by Atom Transfer Radical Polymerization as Dry Solid Polymer Electrolytes for Next Generation Li-ion Battery Applications

Amphiphilic copolymers of comb-like poly(poly(ethylene glycol) methacrylate) (PPEGMA) with methyl methacrylate (MMA) synthesized by one-pot atom transfer radical polymerization were mixed with lithium bis (trifluoromethanesulfonyl) imide salt to formulate dry solid polymer electrolytes (DSPE) for semisolid-state Li-ion battery applications. The PEO-type side chain length (EO monomer's number) in the PEGMA macromonomer units was varied, and its influence on the mechanical and electrochemical characteristics was investigated. It was found that the copolymers, due to the presence of PMMA segments, possess viscoelastic behavior and less change in mechanical properties than a PEO homopolymer with 100 kDa molecular weight in the investigated temperature range. In contrast to the PEO homopolymer, it was found that no crystallization of the copolymers occurs in the presence of the Li-salt. Solid-state NMR and cross-polarization NMR studies revealed that no crystallization (i.e., ion-pair formation) of the Li-salt occurs in the case of the copolymer samples at ambient temperatures; thereby, no phase separation takes place, in contrast to the reference PEO homopolymer sample, which resulted in fairly good ionic conductivity of the copolymers at lower temperatures. The temperature-dependent Li-ion conductivity analyses showed that the conductivity of the copolymers falls in the 10