Grain Engineering for High-Performance Garnet-Type Li7La3Zr2O12 Solid Electrolytes

Garnet-type solid electrolytes based on cubic Li7La3Zr2O12 (LLZO) are promising candidates for the development of Li metal solid-state batteries due to their high ionic conductivity and excellent chemical stability against metallic lithium. Unfortunately, the leakage of electron through the interface and grain boundaries leads to the nucleation of Li dendrite inside solid electrolyte, making it easier for the failure of solid-state Li metal batteries. Here, we introduce a promising fluorination strategy to suppress Li dendrite formation by blocking electron transport through the interface and along the grain boundaries. Fluorination not only decreases the electronic conductivity of garnet pellet but also improves its wettability toward Li metal. As a result, the optimized LLZOge pellet demonstrates an outstanding critical current density of 2.7 mA cm‒2 and ensures ultra-long cyclability over 5000 h at 0.2 mA cm‒2 and over 300 h at 1 mA cm‒2 at room temperature. This work demonstrates the efficacy of the fluorination strategy in increasing the electronic resistance of garnet-type electrolyte for the suppression of Li dendrite growth. Figure 1