Interface Properties between Lithium Metal and a Composite Polymer Electrolyte of PEO(18)Li(CF(3)SO(2))(2)N-Tetraethylene Glycol Dimethyl Ether

The electrochemical properties of a composite solid polymer electrolyte, consisting of poly(ethylene oxide) (PEO)-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) was examined as a protective layer between lithium metal and a water-stable lithium ion-conducting glass ceramic of Li(1)(+x+y)(Ti,Ge)(2−x)Al(x)P(3−y)Si(y)O(12) (LTAP). The lithium ion conductivity and salt diffusion coefficient of PEO(18)LiTFSI were dramatically enhanced by the addition of TEGDME. The water-stable lithium electrode with PEO(18)LiTFSI-2TEGDME, as the protective layer, exhibited a low and stable electrode resistance of 85 Ω·cm(2) at 60 °C, after 28 days, and low overpotentials of 0.3 V for lithium plating and 0.4 V for lithium stripping at 4.0 mA·cm(−2) and 60 °C. A Li/PEO(18)LiTFSI-2TEGDME/LTAP/saturated LiCl aqueous solution/Pt, air cell showed excellent cyclability up to 100 cycles at 2.0 mAh·cm(−2).