SEPARATOR, BATTERY, BATTERY PACK, ELECTRONIC APPARATUS, ELECTRIC VEHICLE, POWER STORAGE DEVICE, AND POWER SYSTEM

摘要

A separator comprising a base material and a surface layer that is formed on at least one surface of the base material and exhibits a higher porosity than the base material, in which the surface layer is provided with a first layer comprising protrusions and unfilled recesses, and a second layer formed between the first layer and the base material. It is preferable for the second layer to exhibit a higher porosity than the base material, and the first layer to exhibit a higher porosity than the second layer. In such a case, it is preferable for the porosity of the base material to be 25-40% inclusive, the porosity of the first layer to be 60-90% inclusive, and the porosity of the second layer to be 40-65% inclusive.