SEPARATOR WITH HEAT-RESISTANT INSULATING LAYER

A separator with a heat-resistant insulation layer for an electric device according to the present invention includes: a resin porous substrate; and a heat-resistant insulation layer containing heat-resistant particles and a binder, the heat-resistant insulation layer being formed on at least one surface of the resin porous substrate. The heat-resistant particles contain α alumina, and a parameter X represented by a following mathematical expression 1 is 0.018 to 0.336. In the expression, Cis a ratio of the α alumina, which occupies the heat-resistant particles, Ris surface roughness (µm) of a surface of the heat-resistant insulation layer, the surface being opposite with the resin porous substrate, and D is a thickness (µm) of the heat-resistant insulation layer. X = C α × R zjis / D