Higher Critical Current Density in Lithium Garnets at Room Temperature by Incorporation of an Li₄SiO₄-Related Glassy Phase and Hot Isostatic Pressing

Inorganic solid electrolytes have achieved an important position in modern battery technology. A garnet-structured inorganic fast lithium-ion conductor is an exceptional solid electrolyte candidate due to its numerous advantages. However, on repeated cycling at high current densities, the growth of lithium dendrites through grain boundaries turns out to be a major impediment to the application of metallic lithium as an anode. This work shows the application of a hot isostatic pressing (HIP) treatment on an Li4SiO4 (LS)-added lithium garnet solid electrolyte, Li6.16Al0.28Zr2La3O12 (LLZA), resulting in a dense microstructure of the electrolyte along with LS-related glassy phase formation at the grain boundaries. This approach is substantiated to enhance the electrochemical performance of an Li|LLZA + LS(H)|Li symmetric cell at room temperature by improving the interfacial contact, effectively suppressing lithium dendrite penetration, and attainment of a higher critical current density (CCD) of 0.40 mA/cm2. The cycling performance achieved here represents a significant advancement toward demonstrating plating/stripping rates in lithium garnets with relevance to practical applications.