A new type of separator for lithium-ion batteries (LIBs) has been developed using ultrathin micrometer-sized sodium borosilicate glass platelets coated directly on a battery electrode with a water-based binder. The coating process is described in detail, demonstrating coating thicknesses of the glass separator of less than 50 µm. The high-temperature stability has been investigated and it has been shown that the separator is dimensionally stable to at least 600 °C. With regard to the electrochemical performance, full-cell tests on graphite || lithium iron phosphate cells showed a very good behavior, according to which comparable properties of the electrode/separator compound to a commercial polymer-based separator were achieved. This glass separator/electrode composite shows an interesting property profile and is a temperature-stable alternative to conventional polymer-based separators.