SECONDARY BATTERY

PROBLEM TO BE SOLVED: To provide a secondary battery of which the productivity is improved.SOLUTION: A wound electrode body 1 including a positive electrode plate and a negative electrode plate is accommodated in a square outer package body 2 including an opening together with a nonaqueous electrolyte, and the opening of the square outer package body 2 is sealed by a metallic sealing plate 3. The wound electrode plate 1 is accommodated in the square outer package body 2 in the state where its outer surface excluding an outer surface closer to the sealing plate 3 is covered by an insulation sheet 14. Arithmetic average roughness (Sa) of at least one surface of the insulation sheet 14 disposed between the wound electrode body 1 and the square outer package body 2 is 0.3 μm or more.SELECTED DRAWING: Figure 4 【課題】生産性が向上した二次電池を提供する。【解決手段】正極板と負極板を有する巻回電極体１が非水電解質と共に開口を有する角形外装体２に収納され、角形外装体２の開口は金属製の封口板３により封口されている。巻回電極体１は、封口板３側の外面を除く外面が絶縁シート１４に覆われた状態で角形外装体２に収納されている。巻回電極体１と角形外装体２の間に配置される絶縁シート１４の少なくとも一方の面の算術平均粗さ（Ｓａ）は、０．３μｍ以上である。【選択図】図４