The synergetic modification on ionic conductivity and air stability of Ga ³⁺ and Ta ⁵⁺ co‐doped Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO)

Abstract The garnet‐type oxide Li 7 La 3 Zr 2 O 12 solid‐state electrolytes (SSEs) are considered as a reliable option in all‐solid‐state lithium batteries (ASSLBs) due to its excellent properties. However, it still faces challenges such as limited ionic conductivity and low air stability. In this work, Ga 3+ and Ta 5+ co‐doped samples Li 7−3 x − y Ga x La 3 Zr 2− y Ta y O 12 (Ga x Ta y ‐LLZO) synthesized via the solid‐state method are demonstrated to stabilize the cubic phase, regulate the concentration of Li vacancies in LLZO, and improving the Li + transport channels. As a result, the Ga0.1Ta0.3‐LLZO sample achieves a high conductivity of ∼1 mS cm −1 . Furthermore, we discovered that in addition to the previously reported effects of decreasing grain boundary density and the inert LiGaO 2 secondary phase at grain boundaries, the synergistic effect of introducing multiple dopant ions, which enhances lattice stability, is also a key factor contributing to improved air stability. Our findings demonstrate that co‐doping strategy with Ga 3+ /Ta 5+ is an effective method for simultaneously enhancing conductivity and air stability of LLZO, laying solid foundation for the application of SSEs in ASSLBs.