GARNET-LITHIUM TITANATE COMPOSITE ELECTROLYTE

A sintered composite ceramic includes: a lithium-garnet major phase; and a lithium-rich minor phase, such that the lithium-rich minor phase has LiTiO, with 0.66≤x≤4. The sintered composite ceramic may exhibit a relative density of at least 90% of a theoretical maximum density of the ceramic, an ionic conductivity of at least 0.35 mS·cm, or a critical current density (CCD) of at least 1.0 mA·cm.