Synthesis, microstructure and ionic conductivity of Li1+xAlxTi2−x(PO₄)₃-based composite ceramic electrolyte

Abstract

NASICON-type Li[Formula: see text]Al[Formula: see text]Ti[Formula: see text](PO4)3 (LATP) solid electrolyte features low cost of raw materials, high stability against O2/H2O, high ionic conductivity and high compatibility with cathode. Despite these merits, the direct contact of Li with LATP would trigger the reduction of Ti[Formula: see text] into Ti[Formula: see text], and thereupon decrease ion conductivity and enhance electron conductivity, thus limiting its application. In this work, the garnet Li[Formula: see text]La3Zr[Formula: see text]Ta[Formula: see text]O[Formula: see text] (LLZTO) particles were chosen to disperse in NASICON-type Li[Formula: see text]Al[Formula: see text]Ti[Formula: see text](PO4)3 matrix in order to strengthen stability against Li metal. During sintering, the matrix/particle reaction occurs, where LLZTO reacts with LATP, inducing the formation of LaPO4 particles. By optimization of LLZTO content, an enhanced ionic conductivity of 1.03 × 10[Formula: see text]S cm[Formula: see text] can be harvested. Moreover, introducing LLZTO particles into LATP matrix can slow down the degradation of the electrolyte to a certain extent and provide better interfacial stability of symmetrical battery than pure LATP solid electrolyte.