SEPARATOR FOR POWER STORAGE DEVICE AND POWER STORAGE DEVICE

Provide is a separator for a power storage device, which is able to reliably prevent short circuit between a positive electrode layer and a negative electrode layer while maintaining the function of permeating ions, and able to effectively suppress shrinkage, and a power storage device using the separator. In a separator for a power storage device, which is composed of a composite material including inorganic microparticles and an organic binder, the separator being for use in a power storage device structured such that a positive electrode layer and a negative electrode layer are stacked so as to be opposed to each other with a separator interposed therebetween, and housed along with an electrolyte solution in an outer packaging, (a) the composite material has a pigment volume concentration PVC of 55% or more, and (b) the inorganic microparticles have an average particle size in the range of 0.2 to 3.0 µm, and a general particle shape index in the range of 0.50 to 0.85. In addition, the composite material has a pigment volume concentration PVC in the range of 55 to 80%. Furthermore, the composite material has a pigment volume concentration PVC in the range of 55 to 65%.