Power storage device packaging material and power storage device using the packaging material

1. A power storage device packaging material, comprising

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, wherein

the substrate layer is a polyester film, which was exposed to heat treatment at 160° C., wherein the polyester film exhibits ΔA, as expressed by the following Formula (1), of 10% or more and a 50% elongation stress of 75 MPa or more after the heat treatment at 160° C.:

Δ A =(break elongation after the 160° C. heat treatment)−(break elongation before the 160° C. heat treatment)  (1)

wherein the break elongation and the 50% elongation stress are each an average of tensile tests at 23° C. (test piece shape: dumbbell No. 5 according to JIS K7127, length between chucks: 75 mm, gauge length: 25 mm, test speed: 50 mm/min) in four directions (0° (MD), 45°, 90° (TD), 135°) of the substrate layer.

2. The power storage device packaging material of claim 1 , wherein the polyester film has a piercing strength of 0.6 N/μm or more.

3. A power storage device packaging material, comprising:

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, wherein

the substrate layer is a polyester film having a piercing strength of 0.6 N/μm or more, wherein the polyester film was exposed to heat treatment at 160° C., wherein the polyester film exhibits ΔA, as expressed by the following formula (1), of 10% or more:

Δ A =(break elongation after the 160° C. heat treatment)−(break elongation before the 160° C. heat treatment)  (1)

wherein the break elongation is an average of tensile tests at 23° C. (test piece shape: dumbbell No. 5 according to JIS K7127, length between chucks: 75 mm, gauge length: 25 mm, test speed: 50 mm/min) in four directions (0° (MD), 45°, 90° (TD), 135°) of the substrate layer.

4. The power storage device packaging material of claim 3 , wherein the polyester film has a 50% elongation stress of 75 MPa or more after the 160° C. heat treatment.

5. The power storage device packaging material according to claim 1 , wherein the polyester film has a 50% elongation stress of 75 MPa or more after 200° C. heat treatment.

6. The power storage device packaging material of claim 1 , further comprising an adhesion-enhancing treatment layer provided between the substrate layer and the adhesive layer.

7. The power storage device packaging material according to claim 6 , wherein the adhesion-enhancing treatment layer is a layer containing at least one resin selected from a group consisting of a polyester resin, an acrylic resin, a polyurethane resin, an epoxy resin, and an acrylic grafted polyester resin.

8. The power storage device packaging material of claim 1 , further comprising anticorrosion treatment layers respectively provided on both surfaces of the metal foil layer.

9. The power storage device packaging material of claim 8 , wherein the anticorrosion treatment layers contain a rare earth element oxide, and phosphoric acid or a phosphate salt.

10. The power storage device packaging material of claim 9 , wherein the rare earth element oxide is a cerium oxide.

11. The power storage device packaging material of claim 1 , wherein the sealant layer has a surface with a static friction coefficient in a range of 0.10 to 0.30.

12. A power storage device comprising:

battery elements including electrodes, leads respectively extending from the electrodes, and a container sandwiching and holding the leads and storing the battery elements, wherein

the container is formed of the power storage device packaging material of claim 1 , with the sealant layer being located on the inside.