Microstructure-controlled Li ion conductive oxide–based ceramic solid electrolytes supporting high current densities

The fabrication of all-solid-state batteries using lithium metal that can be operated at high current densities (free lithium dendrites) is a recognized worldwide goal. We used a glassy lithium borate (LBO)–based microstructure as the grain boundary modifier of a garnet-type solid electrolyte to prevent lithium dendrite formation at high current densities. The relative density (90 %) and ionic conductivity (10 –4 S cm –1 ) were similar for LBO-modified and non-modified solid electrolytes. Notably, a post-annealing step at 175 °C significantly reduces the interfacial resistance between the LBO-modified electrolyte and lithium metal. LBO in the solid electrolyte microstructure distributes the current and prevents dendrite propagation, suppressing lithium dendrites up to 10 mA cm –2 . Low voltage response at a current density of 10 mA cm –2 for 60 galvanostatic plating–stripping cycles establishes the fast-charging capability of this composite electrolyte. Density functional theory calculations reveal that LBO offers a broader electrochemical stability window compared to LLZ, enhancing overall stability within the 0–3.4 V range. This work provides a promising route to simultaneously achieve high current density operation and improved interfacial stability in garnet-based solid-state batteries, accelerating the practical implementation of lithium-metal anodes.