Shutdown Separators For Protection Of Lithium-Ion Batteries Against Thermal Runaway

79092S Lithium-ion batteries for vehicles must be safe under normal and extreme operating conditions. A major safety goal is to improve abuse tolerance during overcharge and/or abusive discharge conditions that may lead to thermal runaway. Commercial plastic polymer separators that provide shutdown of batteries at 135¿C are available, but the shutdown temperature needs to be lowered to the 100 to 110¿C range to be effective against thermal runaway. This project will address the problems of overcharge and/or abusive discharge by developing coated plastic separators that shut down at 100-110¿C and inhibit thermal runaway by resisting current flow. This improved shutdown property is obtained by applying ultra-thin microporous coatings to plastic separators. In Phase I, a low-cost, less than 2 micron thick, microporous coating for separators will be developed. Shut down will occur in the target range of 100-110¿C, and there will be no interference with any of the performance requirements of the separator. This shutdown separator technology will be demonstrated for use in lithium-ion batteries with polypropylene plastic separators. Commercial Applications and Other Benefits as described by the awardee: Besides providing separators for lithium-ion batteries for vehicles, the coated safety shutdown separators should be applicable to rechargeable lithium batteries of all types, sizes, and shapes. Their safety features should be particularly useful with large high power lithium-ion batteries where there is increased danger from thermal runaway. The coated shutdown separators should be amenable to high volume, low-cost manufacturing.