Custom-made porous and non-porous micrometer-sized glass platelets made of phase-separating sodium borosilicate glass are used as a new type of separator for lithium-ion batteries with liquid electrolytes as a high-temperature stable alternative for polymer-based separators. The production process of glass platelets as well as the preparation of porous glass platelets by the so-called VYCOR (R)-process is described. The influence of the platelet morphology on the ionic conductivity in a non-aqueous battery electrolyte is shown. Porous glass platelets with a porosity of 52% show an ionic conductivity of 5.5 mS cm(-1) in a standard non-aqueous lithium-ion battery electrolyte. The battery performance of porous and non-porous glass platelets as a separator is tested in a graphite/lithium iron phosphate full-cell configuration and is compared to state-of-the-art polymer-based separators. Charge/discharge tests are performed at different current rates. The results clearly show that glass platelets perform excellently with high charge/discharge currents up to a 10 C rate and capacity retention at a 1 C rate compared to polymer based separators.