Cylindrical batteries
A cylindrical battery according to an aspect of the present invention includes an electrode assembly including a positive electrode plate and a negative electrode plate wound together via a separator, an electrolytic solution, a bottomed cylindrical housing can, and a sealing unit fixed by crimping of an open end of the housing can via a gasket. The sealing unit includes a valve member having a circular outline, a metal plate connected to a central portion of the valve member so as to be farther inside the battery than the valve member, and an annular insulating member disposed between an outer peripheral portion of the valve member and an outer peripheral portion of the metal plate. The valve member has a sloping region in which the thickness decreases or increases continuously along the radial direction.
1. A cylindrical battery comprising an electrode assembly including a positive electrode plate and a negative electrode plate wound together via a separator, an electrolytic solution, a bottomed cylindrical housing can, and a sealing unit fixed by crimping of an open end of the housing can via a gasket,
the sealing unit including a valve member having a circular outline, a metal plate connected to a central portion of the valve member so as to be farther inside the battery than the valve member, and an annular insulating member disposed between an outer peripheral portion of the valve member and an outer peripheral portion of the metal plate,
the valve member having a sloping region in which the thickness decreases continuously from an inner peripheral portion to an outer peripheral portion along a radial direction,
wherein a length of a portion of the sloping region across which the thickness of the valve member decreases continuously along the radial direction of the valve member and is not less than 10% and not more than 90% of the radius of the valve member.
2. The cylindrical battery according to claim 1 , wherein the sloping region occupies a region enclosed by two circles concentric with the outline of the valve member.
3. The cylindrical battery according to claim 1 , wherein the valve member has a groove-shaped thin portion.
4. The cylindrical battery according to claim 1 , wherein the metal plate is electrically connected to the electrode assembly via a lead.
5. The cylindrical battery according to claim 1 , wherein the valve member is disposed outermost in the sealing unit.
6. The cylindrical battery according to claim 1 , wherein the metal plate has a groove-shaped thin portion around a portion thereof welded to the valve member.