A systematic study of glass stability, crystal structure and electrical properties of lithium ion-conducting glass-ceramics of the Li1+xCrx(GeyTi1-y)2-x(PO4)3 system

Abstract

This study examines the effect of substituting Ti by Cr and Ge on the glass stability of the precursor glass and on the electrical properties of the lithium ion-conducting glass-ceramics of the Li1+xCrx(GeyTi1-y)2-x(PO4)3 (LCGTP) system. A set of compositions of this system is synthesized by the melt-quenching method followed by crystallization. The main results indicate that the glass stability of the precursor glasses increases when Ti is replaced by Ge and Cr. After crystallization, all the glass-ceramics present NASICON-type phase, and their lattice parameters decrease with Ge and increase with Cr content, making it possible to adjust the unit cell volume of the NASICON-like structure. Furthermore, the ionic conductivity and activation energy for lithium conduction in the glass-ceramics are notably dependent on the unit cell volume of the NASICON-like structure. The Li1.6Cr0.6(Ge0.2Ti0.8)1.4(PO4)3 glass-ceramic composition shows the highest overall ionic conductivity (2.9 × 10−4 Ω−1 cm−1) at room temperature and reveals remarkably high ionic conductivity (1.2 × 10−3 Ω−1 cm−1) and low activation energy (0.259 eV) regarding grain contribution. The main findings suggest that the proposed system is promising to develop fast Li ion-conducting glass-ceramics, offering a compromise between the glass stability of the precursor glass and the electrical properties of the resulting glass-ceramic.