Non-aqueous electrolyte secondary battery

1. A non-aqueous electrolyte secondary battery having a power generating element enclosed within an outer casing, wherein

the power generating element has a positive electrode obtained by forming a positive electrode active material layer on a surface of a positive electrode current collector, a negative electrode obtained by forming a negative electrode active material layer comprising an aqueous binder on a surface of a negative electrode current collector, a separator for maintaining an electrolyte liquid, and a gas releasing means for releasing a gas generated within the power generating element to an extra space inside the outer casing, and

the ratio value of a volume of the extra space to a volume of pores included in the power generating element is 0.5 to 1.0.

2. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the separator comprises a ceramic layer comprising inorganic particles and a binder on at least one surface of a resin porous substrate and the gas releasing means is the ceramic layer.

3. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the ratio value of a difference between a volume of the electrolytic solution injected into the outer casing and the volume of pores included in the power generating element, to a volume of the extra space inside the outer casing is 0.4 to 0.7.

4. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the extra space inside the outer casing is disposed at least vertically above the power generating element.

5. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the negative electrode active material layer has a rectangular shape, and a cross sectional area of pores for a cross section in a laminating direction of the power generating element that is parallel to a short side of the rectangle is larger than a cross sectional area of pores for a cross section in a laminating direction of the power generating element that is parallel to a long side of the rectangle.

6. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the negative electrode active material layer has a rectangular shape in which the short side length of the rectangle is 100 mm or more.

7. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the ratio value of a battery area (projected area of a battery including an outer casing of the battery) to rated capacity is 5 cm 2 /Ah or more and the rated capacity is 3 Ah or more.

8. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the aspect ratio of an electrode defined as a horizontal to vertical ratio of the positive electrode active material layer with a rectangular shape is 1 to 3.

9. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the porosity of the separator is 40 to 65%.

10. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the density of the negative electrode active material layer is 1.4 to 1.6 g/cm 3 .

11. The non-aqueous electrolyte secondary battery according to claim 1 , further comprising a pressing member for applying pressure on an outer casing such that the group pressure applied on the power generating element is 0.07 to 0.7 kgf/cm 2 .

12. The non-aqueous electrolyte secondary battery according to claim 1 , wherein the aqueous binder comprises at least one rubber-based binder which is selected from the group consisting of a styrene-butadiene rubber, an acrylonitrile-butadiene rubber, a methyl methacrylate-butadiene rubber, and a methyl methacrylate rubber.

13. The non-aqueous electrolyte secondary battery according to claim 12 , wherein the aqueous binder comprises a styrene-butadiene rubber.