METHOD OF MANUFACTURING BATTERY MODULE
Provided is a method of manufacturing a battery module including a) aligning a first base material and a second base material, which are welding objects and housing members that are combined with each other to form an internal accommodating space in which a plurality of battery cells are accommodated and b) forming a welding joint portion including a bonding region and a surface region covering the bonding region by irradiating a contact surface between the first base material and the second base material with a laser, the bonding region and the surface region forming the welding joint portion having different microstructures due to different thermal history.
1 . A method of manufacturing a battery module, the method comprising:
a) aligning a first base material and a second base material, which are welding objects and housing members that are combined with each other to form an internal accommodating space in which a plurality of battery cells are accommodated; and
b) forming a welding joint portion including a bonding region and a surface region covering the bonding region by irradiating a contact surface between the first base material and the second base material with a laser, the bonding region and the surface region forming the welding joint portion having different microstructures due to different thermal history.
2 . The method of claim 1 , wherein
operation b) comprises:
b1) forming a welded bead in which a first alloy of the first base material and a second alloy of the second base material are melted and solidified by irradiating the contact surface between the first base material and the second base material with a laser for welding; and
b2) re-melting and solidifying a surface of the welded bead by irradiating the welded bead with a laser for surface treatment to form a welding joint portion including a bonding region which is not re-melted in the welded bead and a surface region covering the bonding region and having a microstructure different from that of the bonding region due to the re-melting and solidification.
3 . The method of claim 2 , wherein,
in operation b2), a laser for surface treatment is irradiated so that a thickness of the surface region is in the range of 0.05 D to 0.30 D when a penetration depth of the welding joint portion is D.
4 . The method of claim 2 , wherein,
in operation b2), the laser for surface treatment is irradiated n times (n is a natural number greater than or equal to 2),
wherein a j-th (j is a natural number of 2 to n) laser for surface treatment is irradiated so that the surface of the welded bead is re-melted and solidified to be thinner than a depth of a region re-melted and solidified by irradiation of a (j−1)th laser for surface treatment.
5 . The method of claim 2 , wherein
operation b2) is performed after a melt melted by irradiating the laser for welding is solidified into a solid in operation b1).
6 . The method of claim 2 , wherein
the laser for welding and the laser for surface treatment each are a near-infrared laser.
7 . The method of claim 1 , wherein
the surface region has a finer microstructure than the bonding region.
8 . The method of claim 7 , wherein
the surface region has a smaller average grain size or lamellar spacing compared to the bonding region.
9 . The method of claim 1 , wherein
distributions of impurities in the bonding region and the surface region are different due to a difference in the microstructure.
10 . The method of claim 2 , wherein
each of the first alloy and the second alloy is an aluminum-based alloy.