Study of the Poly[oxymethylene oligo‐(oxyethylene)]/Lithium Metal Interface: Comparison of Linear, Cross‐Linked, and Alkylated Electrolyte Films

Abstract

The formation and stabilities of interfaces between poly[oxymethylene oligo-(oxyethylenefl (PEM)-salt polymer electrolytes and lithium metal or LiCX are investigated. The Li/PEM25LiC1O4 interface (where x in PEMLiAn indicates the mole ratio of 0/Li in the electrolyte) demonstrates behavior consistent with the formation of a solid electrolyte interface, with a stable interfacial resistance of 900 (1 cm2 at 50°C. UV-cross-linked films do not form a stable interface, R,,, rapidly increases to greater than 10' 11 cm2. When cross-linked samples are treated with methyl iodide, hexamethyldisilazane/ trimethylchlorosilane or upon addition of the plasticizer polyethylene glycol dimethyl ether, R,,, at 50°C stabilizes at approximately 2000 0 cm2. The polymer electrolytes require a plasticizer to form a low impedance interface with LiC,.