Lithium Ion‐Conducting Glass–Ceramics of Li1.5Al0.5Ge1.5(PO4)3–xLi2O (x=0.0–0.20) with Good Electrical and Electrochemical Properties

Abstract

NASICON‐type structured Li1.5Al0.5Ge1.5(PO4)3–xLi2O Li‐ion‐conducting glass–ceramics were successfully prepared from as‐prepared glasses. The differential scanning calorimetry, X‐ray diffraction, nuclear magnetic resonance, and field emission scanning electron microscope results reveal that the excess Li2O is not only incorporated into the crystal lattice of the NASICON‐type structure but also exists as a secondary phase and acts as a nucleating agent to considerably promote the crystallization of the as‐prepared glasses during heat treatment, leading to an improvement in the connection between the glass–ceramic grains and hence a dense microstructure with a uniform grain size. These beneficial effects enhance both the bulk and total ionic conductivities at room temperature, which reach 1.18 × 10−3 and 7.25 × 10−4 S/cm, respectively. In addition, the Li1.5Al0.5Ge1.5(PO4)3–0.05Li2O glass–ceramics display favorable electrochemical stability against lithium metal with an electrochemical window of about 6 V. The high ionic conductivity, good electrochemical stability, and wide electrochemical window of LAGP–0.05LO glass–ceramics suggest that they are promising solid‐state electrolytes for all solid‐state lithium batteries with high power density.