Completely Amorphous Poly(ethylene oxide)-Based Electrolyte Enables High Ionic Conductivity for Room-Temperature All-Solid-State Lithium Metal Batteries

The practical application of poly(ethylene oxide) (PEO)-based electrolytes in all-solid-state lithium metal batteries is hindered by its low ionic conductivity at room temperature, resulting from the high crystallinity of PEO. Decreasing the crystallinity of PEO can increase the ionic conductivity of PEO-based electrolytes but sacrifice its mechanical property that also affects its practical application. Herein, we design and experimentally realize a completely amorphous PEO-based electrolyte with promising high mechanical strength. It is a glass fiber-reinforced PEO-based electrolyte functionalized with nano-LiF and succinonitrile additives. The electrolyte has 0 crystallinity and a high tensile strength of 6.06 MPa, resulting in a high ionic conductivity (2.6 × 10–4 S/cm, 25 °C) and a widened electrochemically stable window (4.9 V). It also has good interfacial stability with lithium and can stably work for 500 h in symmetrical lithium batteries (Li/Li) at 25 °C and 0.2 mA/cm2. It is also evaluated in all-solid-state batteries with LiFePO4 as the cathode and Li as the anode and shows promising electrochemical performance. This work provides a solution for the development of high-performance PEO-based solid-state batteries operating normally at room temperature.