Impact of Mg/Ca Substitution on Electrochemical Properties of Li1.3Al0.3Ti1.7(PO4)3 Solid Electrolyte

NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) is a promising solid electrolyte for all-solid-state batteries, yet interfacial instability and limited mechanical robustness hinder practical deployment. We use first-principles calculations to examine the effect of substituting Al3+ with Mg2+ or Ca2+, with charge compensation from additional Li+, on the properties of LATP. Mg- and Ca-substituted compositions remain thermodynamically stable, and Ca substitution is energetically preferred. Both dopants leave the electronic structure nearly unchanged. Nudged elastic band (NEB) calculations show that Mg and Ca both reduce the Li+ migration barrier relative to pristine LATP and thus improve ionic transport. Ca substitution produces a larger lattice expansion ( 3