Partition member and assembled battery

A partition member that has a thickness direction and a planar direction that is orthogonal to the thickness direction, and that forms a partition between single batteries in the thickness direction, comprising:

• a thermal insulation material that contains a powdered inorganic material and a fibrous inorganic material and that has a density of 0.23 g/cm3 to 1.10 g/cm3;
• and
• an outer package body housing, in a sealed state, the thermal insulation material and a liquid having a boiling point from 80° C. to 250° C.,
• wherein the outer package body includes a sealing region,
• wherein the thermal insulation material is a porous body, and the liquid is held inside cavities in the porous body,
• wherein the partition member, in a planar view of the thickness direction of the partition member, includes a first region S1 in which the outer package body and the thermal insulation material overlap and a second region S2 in which the outer package body and the thermal insulation material do not overlap,
• wherein the second region S2 is a gap provided between the first region S1 and the sealing region, and
• wherein each of the sealing region and the second region S2 extend around an entire perimeter of the first region S1.