A battery, which can inhibit raise of an internal resistance even when temperature change or mechanical shock is applied, and which has superior productivity is provided. A safety mechanism and a battery cover are installed at an open part of a battery case by caulking through a gasket. Inside of the battery case is sealed. A flange part of the battery cover contacts with a flange part of a safety valve of the safety mechanism. A surface roughness of the contact face is set to be in the range from about 0.5 μm to about 5.5 μm based on an arithmetic average roughness Ra. A contact resistance between the battery cover and the safety valve is thereby reduced. Further, a maximum height Ry of the contact face is preferably in the range from about 8.0 μm to about 50.0 μM.
1. A battery comprising a battery cover and a safety mechanism that are overlapped at an open part of a battery case internally housing a power generation component,
wherein the safety mechanism comprises a safety valve and a support holder that are fit with an insulating holder in between and a disc-shaped contact plate is welded to a bottom part of the support holder;
wherein the safety valve comprises a projecting part that contacts the disk-shaped contact plate and is placed in the center of the bottom part of the safety valve and projects toward the power generation component side; and
wherein an arithmetic average roughness of a contact face of the battery cover that contacts a portion of the safety valve ranges from about 0.5 μm to about 5.5 μm, and the maximum roughness height of the contact face of the battery cover ranges from about 8.0 μm to about 50.0 μm.
2. The battery according to claim 1 , wherein the battery cover includes stainless steel.
3. The battery according to claim 1 , wherein the safety valve includes aluminum.
4. The battery according to claim 1 , wherein the projecting part of the safety valve is inserted into an opening provided in the center of the bottom part of the support holder, and contacts with the contact plate,
wherein the safety valve is provided with a flange part at an outer periphery of the safety valve to secure electrical connection with the battery cover;
wherein the support holder is provided with a plurality of openings on a side wall of the support holder; and
wherein the cathode lead is welded to the contact plate.
5. The battery according to claim 1 , wherein a value of rise contact resistance after mechanical shock ranges from 0 mΩ to 500 mΩ.
6. The battery according to claim 1 wherein the arithmetic average roughness is greater than about 0.6 μm.
7. The battery according to claim 1 wherein the arithmetic average roughness is greater than about 0.8 μm.
8. The battery according to claim 1 , wherein the maximum roughness height is greater than about 8.4 μm.
9. The battery according to claim 1 wherein the arithmetic average roughness ranges from about 0.8 μm to about 5.0 μm.
10. The battery according to claim 1 , wherein the maximum roughness height is greater than 8.4 μm to about 38.3 μm.