Fostering Li-ion conduction in Zr-Sn-Al-based mid-entropy NASICON electrolyte

Abstract

NASICON (Na Super Ionic CONductor) type materials are an important class of solid-state electrolytes due to their high ionic conductivity along with decent chemical and electrochemical stability. In this study, a medium-entropy Li1.5Zr1.0Sn0.5Al0.5(PO4)3 (LZSAP) ceramic electrolyte was prepared via a solid-state synthesis method. Rietveld refinement confirmed the rhombohedral structure of the conventionally sintered sample (LZSAP-CS) at 1000 °C. The spark plasma sintering (SPS) technique was used for the densification of the pellet and resulted in ∼2.64 times higher room temperature conductivity (∼4.42 × 10−5 S cm−1) than that of the LZSAP-CS. The activation energy, calculated in the 30–100 °C range, decreased from 0.37 ± 0.01 eV for LZSAP-CS to 0.31 ± 0.01 eV for spark plasma sintered LZSAP pellet. The transference number of Li+ was ∼0.98, indicating that Li+ is the predominant charge carrier in this electrolyte. Further investigation of the lithium metal-electrolyte interface was conducted using a symmetric Li|LZSAP-SPS|Li cell configuration, demonstrating stability for over 500 h at 5 μA cm−2. LZSAP extends the list of suitable solid-state electrolytes for all-solid-state lithium batteries. © 2024 Elsevier Ltd and Techna Group S.r.l.