Enhanced Ionic Conductivity of Ga/Nb Co-doped LLZO Ceramic Electrolyte via Sintering Regime Optimization

To enhance the room-temperature lithium-ion conductivity and interfacial stability of Li 7 La 3 Zr 2 O 12 (LLZO) solid-state electrolytes, a co-doping strategy with Ga 3+ and Nb 5+ was employed. By systematically optimizing the sintering protocol–including heating rate, temperature, and dwell time–highly dense and phase-pure cubic-phase LLZO ceramics were successfully synthesized. The co-doping approach effectively stabilized the cubic garnet structure and regulated the lattice framework to facilitate Li + transport pathways. Under optimized conditions, compared to undoped LLZO (0.31 mS cm -1 , 0.362 eV), the co-doped ceramic exhibited significantly enhanced total ionic conductivity (0.81 mS cm -1 ) and reduced activation energy (0.207 eV), confirming the superior transport performance enabled by the co-doping strategy. Furthermore, the electrolyte showed good wettability and interfacial compatibility with metallic lithium, enabling stable cycling performance in symmetric Li∥Ga/Nb-LLZO∥Li cells over short durations. These results confirm the practical potential of the co-doped LLZO electrolyte in all-solid-state lithium batteries. This study provides a viable pathway for the material design and processing of high-performance LLZO-based solid electrolytes.