Process strategies for the laser-based surface treatment of garnet-type ceramics used in solid-state batteries

Given the rising demand for energy storage systems characterized by high energy density and safety, next-generation batteries are gaining increasing significance in research. In particular, the application of the garnet-type ceramic solid electrolyte lithium lanthanum zirconium oxide (LLZO) is receiving growing attention due to its high ionic conductivity and exceptional stability towards lithium metal (Li). However, LLZO reacts with water and carbon dioxide in the ambient air, forming an insulating layer of lithium carbonate on the surface of the garnet-type solid electrolyte. This insulating layer leads to a reduction in the wettability of LLZO by Li and in turn, increases the Li/LLZO interfacial resistance. This study explores ultrashort pulsed laser processing under an argon atmosphere as an effective method for removing Li₂CO₃ while minimizing the thermal input and preserving the structural integrity of the LLZO. Energy-dispersive X-ray spectroscopy revealed a distinct decrease in carbon content after the laser-based surface treatment. Furthermore, electrochemical impedance spectroscopy of symmetrical Li/LLZO/Li cells indicated that the laser-based removal of Li₂CO₃ could reduce the total area-specific resistance by up to 94 %. These results demonstrate that the laser-based surface treatment is a promising approach for removing surface contaminations from the garnet-type solid electrolyte. Moreover, the findings of this study contribute to the ongoing efforts to extend the lifespan of next-generation batteries by improving the interfacial stability.