Packaging material for power storage device, method of producing same, and power storage device
A power storage device is constituted by a laminate including, in the stated order, at least a substrate layer, a barrier layer, and an inside layer. The inside layer is provided with an adhesive layer and a heat-sealing resin layer from the barrier layer side; and if dynamic viscoelasticity is measured by tension with respect to the inside layer, the growth rate at 80° C. is 8.0% or lower.
1 . An exterior material for an electrical storage device, comprising a laminate that includes at least a base material layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order,
wherein
the adhesive layer contains a polypropylene-based resin and polyethylene,
a sea-island structure is observed in a cross-sectional image acquired using a scanning electron microscope for a cross section of the adhesive layer in a direction parallel to a transverse direction (TD) and in a thickness direction,
the cross-sectional image is a cross-sectional image acquired within a range from a surface of the adhesive layer on a side of the barrier layer to a portion having a thickness of 25% when a thickness of the adhesive layer is 100%, and
in the cross-sectional image, a ratio of a total number of island portions having an area of less than 0.25 μm 2 to a total number of island portions of the sea-island structure is 40% or more, wherein in the cross-sectional image of the adhesive layer, a ratio of a total number of island portions having an area of less than 0.10 μm 2 to a total number of island portions of the sea-island structure is 10% or more.
2 . The exterior material for an electrical storage device according to claim 1 , wherein in the cross-sectional image of the adhesive layer, a ratio of a total number of island portions having an area of 1.50 μm 2 or more to a total number of island portions of the sea-island structure is 10% or less.
3 . The exterior material for an electrical storage device according to claim 1 , wherein in the cross-sectional image of the adhesive layer, a ratio of a total number of island portions having an area of less than 0.15 μm 2 to a total number of island portions of the sea-island structure is 20% or more.
4 . The exterior material for an electrical storage device according to claim 1 , wherein the polypropylene-based resin of the adhesive layer is acid-modified polypropylene.
5 . The exterior material for an electrical storage device according to claim 1 , wherein the adhesive layer has a thickness of 5 μm or more.
6 . The exterior material for an electrical storage device according to claim 1 , wherein a resin that forms the heat-sealable resin layer contains a polyolefin backbone.
7 . The exterior material for an electrical storage device according to claim 1 , wherein at least one of layers on an inner side of the barrier layer contains at least one selected from the group consisting of an antioxidant and a radical scavenger.
8 . The exterior material for an electrical storage device according to claim 7 , wherein the antioxidant is at least one selected from the group consisting of a phosphorus-based antioxidant and a phenol-based antioxidant.
9 . The exterior material for an electrical storage device according to claim 7 , wherein the radical scavenger is an alkyl radical scavenger.
10 . The exterior material for an electrical storage device according to claim 1 , wherein the base material layer includes a laminate of polyamide film and polyester film, a laminate of polyamide film and polyamide film, or a laminate of polyester film and polyester film.
11 . The exterior material for an electrical storage device according to claim 1 , wherein the thickness of the laminate is 190 μm or less.
12 . The exterior material for an electrical storage device according to claim 1 , wherein the thickness of the base material layer is 50 μm or less.
13 . The exterior material for an electrical storage device according to claim 1 , wherein the barrier layer comprises at least one of stainless foil and aluminum foil.
14 . The exterior material for an electrical storage device according to claim 1 , wherein the thickness of the barrier layer is 45 μm or more.
15 . The exterior material for an electrical storage device according to claim 1 , wherein the heat-sealable resin layer is composed of a resin containing a polyolefin backbone.
16 . The exterior material for an electrical storage device according to claim 1 , wherein the heat-sealable resin layer contains at least one selected from the group consisting of a polyolefin, a cyclic polyolefin, a carboxylic acid-modified polyolefin, and a carboxylic acid-modified cyclic polyolefin.
17 . The exterior material for an electrical storage device according to claim 1 , wherein the heat-sealable resin layer is formed of a blended polymer obtained by combining two or more resin components.
18 . The exterior material for an electrical storage device according to claim 1 , wherein the heat-sealable resin layer contains at least one selected from the group consisting of a polyolefin, a cyclic polyolefin, a carboxylic acid-modified polyolefin, and a carboxylic acid-modified cyclic polyolefin, and
wherein the heat-sealable resin layer is formed of a blended polymer obtained by combining two or more resin components.
19 . The exterior material for an electrical storage device according to claim 1 , wherein the heat-sealable resin layer has two or more layers with an identical resin component or different resin components.
20 . The exterior material for an electrical storage device according to claim 1 , wherein at least one of the surface and the inside of the heat-sealable resin layer contains two or more lubricants.
21 . The exterior material for an electrical storage device according to claim 1 , wherein at least one of the surface and the inside of the heat-sealable resin layer contains at least two species selected from the group consisting of saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides.
22 . The exterior material for an electrical storage device according to claim 1 , further comprising a surface coating layer on a side of the base material layer opposite to the barrier layer.