Battery module
Provided is a battery module including a housing having an internal accommodating space and a plurality of battery cells located in the internal accommodating space, wherein the housing includes a welding joint portion in which a first base material of a first alloy and a second base material of a second alloy are welded, the welding joint portion includes a bonding region in which the first base material and the second base material are melt-bonded and a surface region covering the bonding region, and the bonding region and the surface region have different microstructures.
1 . A battery module comprising:
a housing having an internal accommodating space; and
a plurality of battery cells located in the internal accommodating space,
wherein
the housing includes a welding joint portion in which a first base material of a first alloy and a second base material of a second alloy are welded,
the welding joint portion includes a bonding region in which the first base material and the second base material are melt-bonded and a surface region covering the bonding region,
the bonding region and the surface region have different microstructures and
wherein the bonding region and the surface region have different microstructures due to different thermal histories.
2 . The battery module of claim 1 , wherein,
the surface region has a finer microstructure compared to the bonding region.
3 . The battery module of claim 2 , wherein,
the surface region has a smaller average grain size or lamellar spacing compared to the bonding region.
4 . The battery module of claim 1 , wherein
the bonding region and the surface region have different distributions of impurities due to a difference in the microstructure.
5 . The battery module of claim 1 , wherein,
based on a minimum cross-section traversing the welding joint portion from the first base material side to the second base material side, as a reference plane, a boundary line between the bonding region and the surface region in the reference plane includes a convex region convex to the outside of the housing.
6 . The battery module of claim 1 , wherein
the surface region has a single-layer structure or a multi-layer structure in which two or more layers are stacked.
7 . The battery module of claim 1 , wherein,
when a penetration depth of the welding joint portion is D, a thickness of the surface region is in the range of 0.05 D to 0.30 D.
8 . The battery module of claim 1 , wherein
the microstructure is a lamellar structure.
9 . The battery module of claim 8 , wherein,
when a lamellar spacing of the bonding region is tw, a lamellar spacing ts of the surface region is in the range of 0.05 tw to 0.70 tw.
10 . The battery module of claim 8 , wherein
the first alloy and the second alloy are each an aluminum alloy.
11 . The battery module of claim 10 , wherein
at least one of the first alloy and the second alloy is an aluminum-based alloy including silicon.
12 . The battery module of claim 1 , wherein
the welding joint portion is a butt joint, a corner joint, an edge joint, or a T joint (tee joint).
13 . The battery module of claim 1 , wherein
the first base material and the second base material each have a shape of a quadrangular plate or a bent quadrangular plate in which one or both end portions are vertically bent.
14 . The battery module of claim 1 , wherein
the housing comprises:
a bent quadrangular plate-shaped first housing member including a bottom surface and two left and right side surfaces integrally connected to the bottom surface;
a quadrangular plate-shaped second housing member coupled to the first housing member to form an upper surface facing the bottom surface; and
quadrangular plate-shaped third housing member and fourth housing member coupled to the first housing member and the second housing member to form two front and rear side surfaces,
wherein the first base materials connected to each other by the welding joint portion is one of the first to fourth housing members, and the second base material is different from the first base material and is another member of the first to fourth housing members.