Battery casing and battery module including the same

A battery casing comprising:

• a container configured to house an electrode assembly,
• wherein
• the container comprises a bottom wall and a plurality of side walls,
• the bottom wall and the plurality of side walls are integrated to define an open side opposite to the bottom wall and to define a space for housing the electrode assembly,
• at least one of the bottom wall and the plurality of side walls comprises a composition comprising a base polymer and a plurality of nucleating agent particles dispersed in the base polymer,
• the base polymer comprises a polyethylene polymer,
• the nucleating agent particles have a rod shape, an aspect ratio of the nucleating agent particle is greater than or equal to about 2, and
• an amount of the nucleating agent particles is greater than or equal to about 0.01 parts by weight and less than or equal to about 3 parts by weight based on 100 parts by weight of the base polymer.