PARTITION MEMBER AND ASSEMBLED BATTERY

A partition member which has a thickness direction and a planar direction orthogonal to the thickness direction and which constitutes a partition between single batteries in the thickness direction or between a single battery and a member other than the single battery, wherein the partition member includes a thermal insulation material, and an auxiliary member which is disposed so as to be adjacent to the thermal insulation material in the planar direction and regulates a degree of contraction of the thermal insulation material in the thickness direction. A ratio of a density of the auxiliary member relative to a density of the thermal insulation material is 0.50 to 6.0.