Incorporating highly dispersed alumina in PEO-based solid electrolytes by vapor phase infiltration for all-solid-state lithium metal batteries

Solid-state lithium-metal batteries with composite polymer electrolytes are promising for next-generation energy-storage devices. Typical synthesis strategies of preparing inorganic-polymer composite mainly focused on physical mixing of inorganic fillers with polymer or surface coating of inorganic thin films on polymer, which are hard to suppress Li-dendrite penetration. Here, we demonstrate the bulk and interface properties of powdery poly (ethylene oxide) can be modified simultaneously with highly dispersed alumina using a vapor phase infiltration (VPI) approach. The chemically synthesized alumina with under-coordinated aluminum sites shows strong interaction with PEO, and therefore highly dispersed in the polymer matrix as well as on the surface of the polymer. On the lithium metal anode side, it reduces the interfacial resistance and allows Li|Li symmetric battery to cycle more than 1400 h under 0.2 mAh/cm2. On the cathode side, it increases the electrochemical stability window of PEO up to 4.25V without compromising the charge transfer kinetics. The result shows the promise of using VPI as a facile one-step method to tune the properties of the polymer on a large scale for battery applications.