Battery pack

A battery pack comprising:

• a plurality of rectangular secondary batteries that are disposed along a predetermined arrangement direction;
• and
• a spacer that is disposed between the rectangular secondary batteries that are adjacent in the arrangement direction, wherein
• the spacer includes a first part and a second part that are stacked in the arrangement direction,
• the first part has an elastic modulus of 1 MPa or more and 10 MPa or less,
• the second part includes a porous part,
• 50 mass % or more of the entire porous part is occupied by a material that satisfies both the following conditions:
• (1) a classification of heat resistance based on JIS K 6380 (2014) is E or more;
• and
• (2) the elastic modulus is 0.02 MPa or more and 0.9 MPa or less, and
• the elastic modulus is a value obtained as an inclination of an approximation line in a range of a compression ratio from 1 to 20% from a compression load-compression ratio curve (horizontal axis:compression ratio, vertical axis:compression load) formed by performing compression until a compression load becomes 3.9 MPa in the arrangement direction at a compression speed of 12 kPa/min.