Not sure Separion is key with lithium iron phosphate batteries (promote by BYD), more crucial with higher energy density batteries based on mixed oxide cathode more and more popular choice for EV's such as Tesla, BMW, Daimler, ...

Lithium iron phosphate is much more safe than oxide but bring lower energy density, ceramic coated separator like Separion are game changer for high energy density batteries, unbelievable safety improvement.