(312c) Electrode-Supported Macroporous Ceramic Membrane Separator for Lithium Ion Batteries

The emergence of lithium-ion batteries as the most popular energy storage system is mainly due to their high energy density and long cycle life. They find application in a wide variety of portable electronic devices as well as electric vehicles and smart grids. However, the relatively frequent occurrences of battery fires and explosions are a major cause of concern. A significant source of this flammability, along with the electrolyte, is the polymeric separator used widely in commercial lithium-ion batteries. Lithium ion batteries with inorganic separators offer advantages of safer operation. An inorganic macroporous membrane separator for lithium-ion battery was prepared by blade coating an α-Al₂O₃ slurry directly on the electrode followed by drying. The improved separator preparation involves a twice-coating process instead of coating the slurry all at once in order to obtain a thin (~40µm) and uniform coat. Unlike state-of-the-art polyolefin separators such as polypropylene (PP) which are selectively wettable with only certain electrolytes, the excellent wettability of α-Al₂O₃ allows the coated separator to function with different electrolytes. The coated α-Al₂O₃ separator has much higher resistance to temperature effects than polyolefin counterparts. The inorganic coated separator retains its dimensional integrity at temperatures as high as 200ºC, thus eliminating the possibility of a short circuit during thermal runaway. Lithium ion batteries half-cells and whole cells with coated α-Al₂O₃ separator exhibit electrochemical performance comparable with that with PP separator at room temperature. However, the coated separator shows better cycling performance than PP separator under extreme temperatures when tested over a wide temperature range of -30°C to +60°C. Therefore, the coated α-Al₂O₃ separator is very promising for uses in safe lithium-ion batteries for energy storage applications.