Improved densification, cubic phase stability and ionic conductivity of Ga/Mo co-doped Li7La3Zr2O12 electrolytes suppressed abnormal grain growth

Abstract

With the increasingly urgent safety requirement of lithium-ion batteries, more and more attention has been paid to Li₇La₃Zr₂O₁₂ (LLZO)-based solid electrolytes with high ion conductivity and excellent electrochemical performance. Unfortunately, owing to the serious “Li-loss” and the abnormal grain growth (AGG) during the long-time high-temperature sintering process, it is difficult to achieve the high-quality LLZO electrolyte with uniform and fine grains, high density and excellent electrochemical performance. In this work, Ga/Mo co-doped LLZO solid-state electrolytes have been prepared by traditional sintering (TS) and two-step sintering (TSS). And the sintering mechanism, phase stability, microstructure evolution, and electrochemical performance have been systematically investigated. A small amount of Ga/Mo doping not only promotes the formation of the cubic garnet LLZO phase, but also enhances the stability of cubic phase. High density of 92.3% and uniform microstructure without AGG have been achieved via a small amount of Ga doping and TSS. Li_6.3Ga_0.1La₃Zr_1.8Mo_0.2O₁₂ electrolytes, prepared by TSS of 1200 °C/15 min-1100 °C/8 h, exhibits high ion conductivity of 2.59 × 10^–4 S·cm⁻¹ and critical current density (CCD) value of 0.5 mA·cm⁻², low electric conductivities of 4.77 × 10^–9 S·cm⁻¹, which suggests it is a potential electrolyte to apply in all-solid-state batteries.