Secondary battery insulating plate and secondary battery including the same
An insulating plate for a secondary battery includes a wound electrode group, an electrolyte, a cylindrical battery case that houses the electrode group and the electrolyte, and a sealing body that seals an opening of the battery case and includes a discharge valve. The insulating plate is disposed between the electrode group and the sealing body and has a disk shape with a thickness T of 0.1 mm or more. The insulating plate has a first hole formed centrally therein and at least one second hole formed around the first hole so as to extend along the outer periphery of the disk shape. The ratio (=T/D) of the thickness T to a diameter D of the insulating plate is 0.016 or less, and the insulating plate has an opening ratio of 36% or less.
1. A secondary battery comprising:
a wound electrode group;
an electrolyte;
a cylindrical battery case that houses the electrode group and the electrolyte;
a sealing body that seals an opening of the battery case and includes a discharge valve; and
an insulating plate disposed between the electrode group and the sealing body,
wherein the insulating plate has a disk shape with a thickness T of 0.1 mm or more,
the insulating plate has a first hole formed centrally therein and at least one second hole,
a ratio (=T/D) of the thickness T to a diameter D of the insulating plate is 0.016 or less, and
the insulating plate has an opening ratio of 36% or less,
wherein the first hole is smaller than at least one of the at least one second hole.
2. The secondary battery according to claim 1 , wherein the first hole is disposed above a winding axis of the electrode group, and
the second hole is disposed on an outer periphery side of the electrode group.
3. The secondary battery according to claim 1 , wherein the first hole has a vertically elongated shape, and
the first hole has an aspect ratio of 1.2 or more and 4 or less.
4. The secondary battery according to claim 1 , wherein the first hole has an opening ratio of 1% or more and 3% or less.
5. The secondary battery according to claim 1 , wherein the insulating plate has an opening ratio of 20% or more and 32% or less.
6. The secondary battery according to claim 1 , wherein the second hole includes at least one arc-shaped hole and at least one spot hole.
7. The secondary battery according to claim 6 , wherein the arc-shaped hole has two corner portions on an outer periphery side of the disk shape and two corner portions on an inner periphery side of the disk shape,
at least the two corner portions on the outer periphery side are rounded, and
the two corner portions on the outer periphery side each have a radius of curvature of 0.8 mm or more.
8. The secondary battery according to claim 1 , wherein the second hole is formed in a region distant from an outer periphery of the insulating plate by 2.5 mm or more.
9. The secondary battery according to claim 1 , wherein the insulating plate is formed of a material having a flexural strength of 100 MPa or more.
10. The secondary battery according to claim 1 , wherein the discharge valve has an opening size of 10 mm or more.
11. The secondary battery according to claim 10 , wherein the secondary battery has an outer diameter of 20 mm or more.
12. The secondary battery according to claim 1 , wherein the secondary battery has no discharge valves at a bottom of the battery case.