NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

To increase the reliability of a nonaqueous electrolyte secondary battery in a state of being overcharged.SOLUTION: A nonaqueous electrolyte secondary battery comprises: a wound electrode body 3 including positive and negative electrode plates, provided that the positive electrode plate has a positive electrode active material mixture layer including a positive electrode active material; a nonaqueous electrolyte; a battery case 200 which contains the wound electrode body 3 and the nonaqueous electrolyte; and a current interrupt mechanism 10 which operates when a pressure in the battery case 200 reaches a predetermined value or higher. The nonaqueous electrolyte includes a fluorine-containing electrolytic salt. The positive electrode active material mixture layer includes a lithium carbonate and a lithium phosphate. The lithium carbonate included in the positive electrode active material mixture layer is larger, in average particle diameter, than that of the lithium phosphate included in the positive electrode active material mixture layer. The number of particles of the lithium carbonate included in the positive electrode active material mixture layer is smaller than the number of particles of the lithium phosphate included in the positive electrode active material mixture layer.SELECTED DRAWING: Figure 5 【課題】非水電解質二次電池が過充電状態となったときの信頼性を向上させる。【解決手段】正極活物質を含有する正極活物質合剤層を有する正極板、正極板と負極板を含む巻回電極体３、非水電解質、巻回電極体３と非水電解質を収容する電池ケース２００、及び電池ケース２００内の圧力が所定値以上となったときに作動する電流遮断機構１０を備えた非水電解質二次電池であって、非水電解質はフッ素を含有する電解質塩を含み、正極活物質合剤層は炭酸リチウムとリン酸リチウムを含み、正極活物質合剤層に含まれる炭酸リチウムの平均粒子径は、正極活物質合剤層に含まれるリン酸リチウムの平均粒子径よりも大きく、正極活物質合剤層に含まれる炭酸リチウムの粒子の数は、正極活物質合剤層に含まれるリン酸リチウムの粒子の数よりも少ない。【選択図】図５