Li Conduction in a Polymer/LiAlGe(PO) Solid Electrolyte and Li-Metal/Electrolyte Interface.

The solid oxide electrolyte LiAlGe(PO) (LAGP) with a NASICON structure has a high bulk ionic conductivity of 10 S cm at room temperature and good stability in the air because of the strong P-O covalence bonding. However, the Ge ions in LAGP are quickly reduced to Ge on contact with the metallic lithium anode, and the LAGP ceramic has insufficient physical contact with the electrodes in all-solid-state batteries, which limits the large-scale application of the LAGP electrolyte in all-solid-state Li-metal batteries. Here, we prepared flexible PEO/LiTFSI/LAGP composite electrolytes, and the introduction of LAGP as a ceramic filler in polymer electrolytes increases the total ionic conductivity and the electrochemical stability of the composite electrolyte. Moreover, the flexible polymer shows good contact with the electrodes, resulting in a small interfacial resistance and stable cycling of all-solid-state Li-metal batteries. The influence of the external pressure and temperature on Li transfer across the Li/electrolyte interface is also investigated.