A battery pack which may secure safety when fire or gas occurs therein or when an external impact is applied thereto is provided. The battery pack includes: a cell assembly including a plurality of secondary batteries; and a pack case including a bottom part having a plate shape and located under the cell assembly, and a side wall part protruding from the bottom part to a preset height, the pack case accommodating the cell assembly in an inner space defined by the bottom part and the side wall part, wherein the side wall part of the pack case includes a hollow in a direction at least partially perpendicular to a thickness direction of the side wall part, and the hollow includes an inwardly open inlet and an outwardly open outlet.
1. A battery pack comprising:
a cell assembly comprising a plurality of secondary batteries; and
a pack case comprising:
a bottom part having a plate shape and located under the cell assembly; and
a side wall part provided on the bottom part and protruding vertically from the bottom part to a preset height, the pack case accommodating the cell assembly in an inner space defined by the bottom part and the side wall part,
wherein the side wall part includes a first side wall and a second side wall,
wherein the second side wall includes three planar walls and two protrusions facing towards each other,
wherein the first side wall extends between the two protrusions, and
wherein the first side wall is hollow in a direction at least partially perpendicular to a thickness direction of the first side wall, and comprises an inwardly open inlet open at the inner space and an outwardly open outlet.
2. The battery pack of claim 1 , wherein the first side wall is provided on a periphery of the bottom part.
3. The battery pack of claim 1 , wherein the first side wall includes at least two separate hollow chambers.
4. The battery pack of claim 3 , wherein the at least two separate hollow chambers are vertically arranged in the first side wall,
wherein a vertical through part, in the form of an aperture, is provided between the at least two separate chambers, and
wherein the inlet and the outlet are provided in different chambers among the at least two separate chambers.
5. The battery pack of claim 4 , wherein, in the pack case, the inlet and the outlet are provided at an end part of one side of the at least two chambers, and
wherein the through part is provided at an end part of another side of the at least two chambers.
6. The battery pack of claim 1 , wherein the pack case comprises two or more inlets and two or more outlets.
7. The battery pack of claim 1 , wherein only the first side wall is hollow.
8. The battery pack of claim 7 , wherein the protrusions of the second side wall are formed at respective ends of the second side wall, and
wherein the protrusions are coupled to respective end surfaces of the first side wall.
9. The battery pack of claim 1 , wherein the direction the first side wall is hollow is a vertical direction.
10. The battery pack of claim 1 , wherein the pack case comprises a metallic material.
11. An automobile comprising the battery pack of claim 1 .
12. The battery pack of claim 1 , wherein the three planar walls of the second side wall include:
first and second planar walls extending parallel to one another and in a length direction of the battery pack; and
a third planar wall extending between the first and second planar walls and extending in a width direction of the battery pack, and
wherein the two protrusions extend in the width direction of the battery pack.