In-situ optical observation of Li growth in garnet-type solid state electrolyte

Inorganic solid-state electrolytes (ISSEs) are expected to achieve the application of lithium (Li) metal batteries. However, Li metal can still cause internal short circuit in solid electrolyte. Direct evidence is lacked to show how Li dendrites penetrate the solid electrolytes. Herein, an in-situ mini cell has been set up to study the behavior of Li growth inside garnet-type electrolyte. Transparent Li6.4La3Zr1.4Ta0.6O12 (LLZTO) pellets are prepared and employed in the in-situ optical observation. It is found that Li metal can deposit/dissolve inside LLZTO and a small amount of dead Li is left during dissolution step which may affect the subsequent deposition process. Besides, Li metal morphologies under different currents are characterized, which provides new insights into the mechanism of Li propagation in LLZTO. Finally, raising temperature is introduced to relieve Li dendrite effectively.