POWER STORAGE DEVICE PACKAGING MATERIAL AND POWER STORAGE DEVICE USING THE PACKAGING MATERIAL

A power storage device packaging material having a structure including at least a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer laminated in this order. The substrate layer is formed of a polyester film exhibiting ΔA, as expressed by the following formula, of 10% or more and a 50% elongation stress of 75 MPa or more after heat treatment at 160° C.: “ΔA=(break elongation after 160° C. heat treatment)−(break elongation before 160° C. heat treatment)”.