Lead sealant film and non-aqueous electrolyte battery

1. A lead sealant film for use in sealing an electrode terminal lead of a non-aqueous electrolyte battery, the lead sealant film comprising:

a laminated structure composed of an inner layer formed directly on a surface of an intermediate layer and an outer layer formed directly on a surface of the intermediate layer opposite to the surface on which the inner layer is formed; and

wherein:

the intermediate layer includes a first acid-modified polypropylene having a first melting-point, and each of the inner layer and the outer layer includes a second acid-modified polypropylene having a second melting-point that is lower than the first melting-point, and

wherein a difference between the first melting point and the second melting point is from 20° C. to 25° C.,

wherein the first and second acid-modified polypropylenes are modified with maleic anhydride and have molecular weights of at least 10,000, and

wherein a difference between the second melting point of the second acid-modified polypropylene and the melting point of a cast polypropylene resin constituting at least an inner layer of an external packaging material of the non-aqueous electrolyte battery is from 0° C. to 10° C.

2. The lead sealant film according to claim 1 , wherein the first melting point is from 150° C. to 168° C. and the second melting point is from 130° C. to 148° C.

3. The lead sealant film according to claim 1 , wherein the first acid-modified polypropylene and the second acid-modified polypropylene each have an adhesion property to the electrode terminal lead and good heat-sealability with an external packaging material.

4. A non-aqueous electrolyte battery comprising:

a battery element including a positive electrode and a negative electrode which are spirally wound or stacked through a separator;

an external packaging material, composed of a laminated film, for packaging the battery element; and

a heat-sealing portion which seals the external packaging material along the periphery of the battery element while introducing electrode terminal leads for the positive electrode and the negative electrode to the outside,

wherein each of the electrode terminal leads is covered with a lead sealant film at a position corresponding to the heat-sealing portion, and

the lead sealant film includes:

a laminated structure composed of an inner layer formed directly on a surface of an intermediate layer and an outer layer formed directly on a surface of the intermediate layer opposite to the surface on which the inner layer is formed, and

wherein the intermediate layer includes a first acid-modified polypropylene having a first melting-point and each of the inner layer and the outer layer includes a second acid-modified polypropylene having a second melting-point that is lower than the first melting-point,

wherein a difference between the first melting point and the second melting point is from 20° C. to 25° C.,

wherein the first and second acid-modified polypropylenes are modified with maleic anhydride and have molecular weights of at least 10,000, and

wherein a difference between the second melting point of the second acid-modified polypropylene and the melting point of a cast polypropylene resin constituting at least an inner layer of the external packaging material is from 0° C. to 10° C.

5. The non-aqueous electrolyte battery according to claim 4 , wherein:

the first melting point is from 150° C. to 168° C., and

the second melting point is from 130° C. to 148° C.

6. The non-aqueous electrolyte battery according to claim 4 , wherein the electrode terminal lead is covered with a primer layer at the position corresponding to the heat-sealing portion, and further covered with the lead sealant film.

7. The non-aqueous electrolyte battery according to claim 4 , wherein the lead sealant film comprises upper and lower resin layers each having a three-layer structure.

8. The non-aqueous electrolyte battery according to claim 7 , wherein one resin layer of the resin layers is in contact with one principal surface of the electrode terminal lead and another resin layer is in contact with another principal surface of the electrode terminal lead, and the resin layer in contact with one principal surface of the electrode terminal lead has an uneven surface reflecting the shape of the electrode terminal lead.

9. The non-aqueous electrolyte battery according to claim 4 , wherein the lead sealant film protrudes from the external packaging material to expose the electrode terminal lead by 0.5 mm or more.

10. The non-aqueous electrolyte battery according to claim 4 , wherein the lead sealant film has a thickness of 10 μm to 500 μm.

11. The non-aqueous electrolyte battery according to claim 4 , wherein the lead sealant film collectively covers a plurality of electrode terminal leads.

12. The non-aqueous electrolyte battery according to claim 4 , wherein the first acid-modified polypropylene and the second acid-modified polypropylene each have an adhesion property to the electrode terminal leads and good heat-sealability with the external packaging material.