Room‐Temperature Solid‐State Polymer Electrolyte in Li‐LiFePO4, Li‐S and Li‐O2 Batteries

Abstract

AbstractA solid polymer electrolyte has been developed and employed in lithium‐metal batteries of relevant interest. The material includes crystalline poly(ethylene glycol)dimethyl ether (PEGDME), LiTFSI and LiNO3 salts, and a SiO2 ceramic filler. The electrolyte shows ionic conductivity more than 10−4 S cm−1 at room temperature and approaching 10−3 S cm−1 at 60 °C, a Li+‐transference number exceeding 0.3, electrochemical stability from 0 to 4.4 V vs. Li+/Li, lithium stripping/deposition overvoltage below 0.08 V, and electrode/electrolyte interphase resistance of 400 Ω. Thermogravimetry indicates that the electrolyte stands up to 200 °C without significant weight loss, while FTIR spectroscopy suggests that the LiTFSI conducting salt dissolves in the polymer. The electrolyte is used in solid‐state cells with various cathodes, including LiFePO4 olivine exploiting the Li‐insertion, sulfur–carbon composite operating through Li conversion, and an oxygen electrode in which reduction and evolution reactions (i. e., ORR/OER) evolve on a carbon‐coated gas diffusion layer (GDL). The cells operate reversibly at room temperature with a capacity of 140 mA h g−1 at 3.4 V for LiFePO4, 400 mA h g−1 at 2 V for sulfur electrode, and 500 mA h g−1 at 2.5 V for oxygen. The results suggest that the electrolyte could be applied in room‐temperature solid polymer cells.