Rubbery Graft Copolymer Electrolytes for Solid-State, Thin-Film Lithium Batteries

• Published in: Journal of the Electrochemical Society 2005, Vol.152 (1), p.A1-A5
• Main Authors: Trapa, Patrick E., Won, You-Yeon, Mui, Simon C., Olivetti, Elsa A., Huang, Biying, Sadoway, Donald R., Mayes, Anne M., Dallek, Steven
• Format: Article
• Language: English
• ISSN: 0013-4651
• DOI: 10.1149/1.1824032

Graft copolymer electrolytes (GCEs) of poly[(oxyethylene)9 methacrylate]-g-poly(dimethyl siloxane) (POEM-g-PDMS) (70:30) have been synthesized by simple free radical polymerization using a macromonomer route. Differential scanning calorimetry, transmission electron microscopy, and small angle neutron scattering confirmed the material to be microphase-separated with a domain periodicity of ~25 nm. Over the temperature range 290 < T < 360 K, the electrical conductivities of the lithium trifate-doped POEM-g-PDMS, which exhibited solid-like mechanical behavior, were nearly identical to those of the liquid POEM homopolymer. Thermal and electrochemical stability studies showed the electrolyte to be stable over a wide temperature range and voltage window. Solid-state, thin-film batteries comprised of a metallic lithium anode, a ~0.2 mm thick vanadium oxide cathode, and an electrolyte of POEM-g-PDMS doped with LiCF3SO3 proved resistant to capacity fade during extended cycling at room temperature ( > 200 cycles) at a discharge rate of 2/3 C and could be cycled (charged and discharged) at subambient temperature (0DGC).