Highly-branched cross-linked poly(ethylene oxide) with enhanced ionic conductivity

Publication date: 24 February 2017
Source:Polymer, Volume 111
Author(s): Nachiket Paranjape, Praphulla Chandra Mandadapu, Gang Wu, Haiqing Lin
Polymers containing poly(ethylene oxide) (PEO) have been investigated for solid electrolytes for lithium-ion batteries, which are preferred to be amorphous and have flexible polymer chains to achieve high Li ion conductivity. This paper reports ionic conductivity in a series of cross-linked PEOs prepared from poly(ethylene glycol) methyl ether acrylate (PEGMEA, monomer) and poly(ethylene glycol) diacrylate (PEGDA, cross-linker) via photopolymerization. The resulting copolymers contain short PEO side chains and thus high content of amorphous PEO. While the cross-linking enhances mechanical strength for solid electrolytes, the introduction of PEGMEA with methoxyl chain end groups decreases Tg and increases ionic conductivity. The use of acrylate groups for polymerization, instead of methacrylate groups, also yields low Tg and thus high conductivity. The effect of PEGMEA content, salt content, and temperature on the ionic conductivity was thoroughly investigated, and it was satisfactorily described using the Vogel-Fulcher-Tammann (VFT) equation. The effectiveness of PEO-based polymers used for solid electrolytes in advanced lithium batteries was also elucidated based on the VFT equation.

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