Battery module having bus bar and battery pack

1. A battery module comprising:

a plurality of cylindrical battery cells including electrode terminals respectively at upper and lower portions of the plurality of cylindrical cells, the plurality of cylindrical battery cells being arranged in a horizontal direction;

a module housing including an accommodation portion into which the plurality of cylindrical battery cells are accommodated; and

a bus bar configured to contact the electrode terminals of the plurality of cylindrical battery cells to electrically connect the plurality of cylindrical battery cells, the bus bar comprising a main body portion that is over or below the plurality of cylindrical battery cells and has a plate shape that is flat in a horizontal direction, wherein at least one coupling opening perforated vertically is defined in the plate shape,

wherein a first connection extension portion and a second connection extension portion that protrude and extend from an internal boundary of the coupling opening in different horizontal directions from each other and having end portions that are electrically connected and fixed to an electrode terminal of one of the plurality of cylindrical battery cells,

wherein each side of each of the first and second connection extension portions has a concave structure that is inwardly curved such that a width of each of the first connection extension portion and the second connection extension portion at a proximal portion of each of the first and second connection extension portions adjacent to an inner edge of the coupling opening such that a width of each proximal portion is less than a width at a central portion of the each of the first and second connection extension portions.

2. The battery module of claim 1 , wherein at least one of the first connection extension portion and the second connection extension portion comprises a bent structure that is bent at least once in the horizontal direction.

3. The battery module of claim 1 , wherein at least one of the first connection extension portion and the second connection extension portion comprises a curved structure that is curved at least once in the horizontal direction.

4. The battery module of claim 1 , wherein at least one of the first connection extension portion and the second connection extension portion comprises a terminal mounting structure in which a surface of an end of the at least one of the first connection extension portion and the second connection extension portion that is connected to and fixed at the electrode terminal is internally recessed in an outward direction with respect to a center of the battery module, and the internally recessed surface is mounted on the electrode terminal.

5. The battery module of claim 1 , wherein at least one of the first connection extension portion and the second connection extension portion comprises a stepped structure that is configured to be mounted on the electrode terminal as an end portion that is coupled and connected to the electrode terminal and stepped in an outward direction with respect to the battery module.

6. The battery module of claim 1 , wherein an embossed protrusion protruding in a direction toward the electrode terminal is defined on each of the first connection extension portion and the second connection extension portion, and

an insertion groove configured to receive a welding rod therein is defined in the upper portion of the embossed protrusion of each of the first connection extension portion and the second connection extension portion.

7. The battery module of claim 1 , wherein the bus bar comprises copper or a copper alloy.

8. A battery pack comprising at least two battery modules according to claim 1 .

9. A device comprising the battery pack according to claim 8 .