Lithium ion secondary battery
Provided is a lithium ion secondary battery including, as components accommodated in a container, a positive electrode that intercalates and deintercalates lithium, a negative electrode that intercalates and deintercalates lithium, a nonaqueous electrolytic solution that contains a lithium salt, and a separator that is interposed between the positive electrode and the negative electrode. The separator includes a porous resin layer containing polyolefin as a main component. In a full charge state, when observing a cross-section of the lithium ion secondary battery after performing a nail penetration test in which a metal nail having a diameter of 3 mm penetrates through a central portion of the lithium ion secondary battery at 80 mm/sec for short-circuiting of the lithium ion secondary battery, an average thickness of the porous resin layer in a range of 1 mm to 3 mm in an in-plane direction from a peripheral edge of a nail hole is equal to or greater than 10% of an average thickness of the porous resin layer before the nail penetration test, and the porous resin layer remains at a position within 1 mm in the in-plane direction from the peripheral edge of the nail hole.
1. A lithium ion secondary battery, comprising, as components accommodated in a container:
a positive electrode that intercalates and deintercalates lithium;
a negative electrode that intercalates and deintercalates lithium;
a nonaqueous electrolytic solution that contains a lithium salt; and
a separator that is interposed between the positive electrode and the negative electrode,
wherein the separator includes a porous resin layer containing polyolefin as a main component,
in a full charge state, when observing a cross-section of the lithium ion secondary battery after performing a nail penetration test in which a metal nail having a diameter of 3 mm penetrates through a central portion of the lithium ion secondary battery at 80 mm/sec for short-circuiting of the lithium ion secondary battery,
an average thickness of the porous resin layer in a range of 1 mm to 3 mm in an in-plane direction from a peripheral edge of a nail hole is equal to or greater than 10% of an average thickness of the porous resin layer before the nail penetration test, and
the porous resin layer remains at a position within 1 mm in the in-plane direction from the peripheral edge of the nail hole.
2. The lithium ion secondary battery according to claim 1 ,
wherein the porous resin layer after the nail penetration test has a void in a range of 1 mm to 3 mm in the in-plane direction from the peripheral edge of the nail hole, and
a major axis of the void is in a range of 10 μm to 100 μm.
3. The lithium ion secondary battery according to claim 1 ,
wherein a cross-sectional shape of the porous resin layer after the nail penetration test includes a columnar shape.
4. The lithium ion secondary battery according to claim 1 ,
wherein a cell rated capacity of the lithium ion secondary battery is 7 Ah or greater.
5. The lithium ion secondary battery according to claim 1 ,
wherein the number of laminations or the number of windings in the positive electrode at a central portion of the lithium ion secondary battery is 10 or greater.
6. The lithium ion secondary battery according to claim 1 ,
wherein in a spectrum obtained by X-ray diffraction using a CuKα-ray as a ray source, the separator has a diffraction peak (A) corresponding to a (111) crystal plane of polyolefin.
7. The lithium ion secondary battery according to claim 1 , further comprising:
a ceramic layer on at least one surface of the porous resin layer.
8. The lithium ion secondary battery according to claim 1 ,
wherein the thickness of the porous resin layer is 5 μm to 50 μm.