Ceramic-Coated Separator Containing Reactive Alumina As a Cross-Linker for in-Situ Gel Electrolyte Formation in Lithium-Ion Battery

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Lithium-ion battery (LIB) has been used in many applications such as electric vehicles and electric power storage system over decades owing to its high energy density and good cycle life. As the demand for high energy density lithium-ion batteries is rapidly growing, safety issues have been derived imperatively. A separator plays a key role in cycling performance and battery safety. Separators should prevent short circuits by physical contacts between cathode and anode. However, commonly used polyolefin separators such as polyethylene (PE) and polypropylene (PP) do not have thermal resistance at high temperature over 150 oC. A lot of studies have dealt this critical safety concern by coating thermally stable materials such as ceramic particles and heat- resistant polymers onto the separator. In this work, the reactive alumina nanoparticles as a cross-linker were coated onto the PE separator to promote the radical reaction with cross-linking agent in the electrolyte as well as improve the thermal stability. The reactive alumina-coated separators allowed to maintain good interfacial contacts between separator and electrodes during the repeated cycling. As a result, the lithium-ion cells assembled by in-situ cross-linking using reactive alumina-coated PE separator exhibited good cycling performance and enhanced safety, as compared with the LIB employing PE separator and liquid electrolyte.