Sealed cell and method for manufacturing same

1. A sealed cell, comprising:

an electrode body in which at least one positive electrode and at least one negative electrode are laminated with a separator interposed therebetween; and

an outer casing can formed in a bottomed cylindrical shape, the outer casing can accommodating the electrode body,

wherein the outer casing can is formed by nickel-plated iron,

a lead connected to one of the positive electrode and the negative electrode is welded to the outer casing can in a welding part formed from an outside surface of the outer casing can toward the lead,

the welding part is formed by molten traces, and includes a first layer, and a second layer having a higher nickel concentration than the first layer,

the first layer is formed from the lead to an inside of the outer casing can,

the second layer is formed so as to adjoin the first layer on the outside surface side of the outer casing can, and

a whole of the first layer is covered with the second layer when the welding part is viewed from outside of the outer casing can.

2. The sealed cell according to claim 1 , wherein

the first layer has a linear planar shape when viewed from the outside of the outer casing can, and

the second layer has a linear planar shape when viewed from the outside of the outer casing can.

3. The sealed cell according to claim 2 , wherein

two first inclined bottom surfaces are formed at both end portions in a long side direction of the first layer so that a depth of the first layer is gradually increased toward a center in the long side direction, and

two second inclined bottom surfaces are formed at both end portions in the long side direction of the second layer so that the depth of the second layer is gradually increased toward the center in the long side direction.

4. The sealed cell according to claim 3 , wherein

gradients of the first inclined bottom surfaces are larger than gradients of the second inclined bottom surfaces with respect to an outside surface of the second layer.

5. A manufacturing method for the sealed cell according to claim 1 , wherein

a welding process of welding the lead and the outer casing can includes:

a first beam irradiation process in which the outside surface of the outer casing can is irradiated with a first energy beam from outside of the outer casing can to weld the outer casing can and the lead; and

a second beam irradiation process in which, after the first beam irradiation process, a wider range than an irradiation range on the outside surface of the outer casing can which is irradiated with the first energy beam is irradiated with a second energy beam from the outside of the outer casing can.

6. The manufacturing method for a sealed cell according to claim 5 , wherein

in the first beam irradiation process, the outside surface of the outer casing can is irradiated with the first energy beam while an irradiation portion of the first energy beam is moved in a first direction, and

in the second beam irradiation process, the outside surface of the outer casing can is irradiated with the second energy beam while the irradiation portion of the second energy beam is moved in a second direction which is a direction opposite to the first direction.

7. The manufacturing method for a sealed cell according to claim 5 , wherein

the first layer has a linear planar shape when viewed from the outside of the outer casing can, and two first inclined bottom surfaces are formed at both end portions in a long side direction so that a depth of the first layer is gradually increased toward a center in the long side direction,

the second layer has a linear shape in which a width when viewed from the outside surface of the outer casing can is larger than the width of the first layer, and two second inclined bottom surfaces are formed at both end portions in the long side direction so that the depth of the second layer is gradually increased toward the center in the long side direction, and

in the second beam irradiation process, the second layer is formed so that gradients of the respective two second inclined bottom surfaces at both end portions in the long side direction of the second layer with respect to an outside surface of the second layer are smaller than gradients of the respective two first inclined bottom surfaces with respect to the outside surface of the second layer.

8. A manufacturing method for the sealed cell according to claim 1 , wherein

in a welding process of welding the lead and the outer casing can,

a diffraction grating is used to divide one energy beam into a first energy beam and a second energy beam, and irradiation portions of the first energy beam and the second energy beam are moved relative to the outer casing can so that the first energy beam is applied, prior to the second energy beam, to a predetermined position on an outside surface of the outer casing can, to weld the outer casing can and the lead, so that the first layer and the second layer are formed.

9. The manufacturing method for a sealed cell according to claim 5 , wherein

each of the first energy beam and the second energy beam is a laser beam.

10. The manufacturing method for a sealed cell according to claim 6 , wherein

each of the first energy beam and the second energy beam is a laser beam.

11. The manufacturing method for a sealed cell according to claim 7 , wherein

each of the first energy beam and the second energy beam is a laser beam.

12. The manufacturing method for a sealed cell according to claim 8 , wherein

each of the first energy beam and the second energy beam is a laser beam.