LITHIUM ION SECONDARY BATTERY

• Main Authors: OSHIMA TSUTOMU, SAKAGUCHI SHINICHIRO
• Format: Patent
• Language: English; Japanese
• Published: 11.07.2016
• Subjects: BASIC ELECTRIC ELEMENTS; ELECTRICITY; PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSIONOF CHEMICAL INTO ELECTRICAL ENERGY

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which enables the prevention of the battery performance due to the precipitation of a lithium compound.SOLUTION: A lithium ion secondary battery comprises an insulator 122 covering a region ranging from a part in a principal plane 121a of a positive electrode current collector 121, where a positive electrode mixture layer 120 is not provided, to a part of a surface 120b of a gradually-decreasing part of the positive electrode mixture layer 120, where the positive electrode mixture layer is gradually decreased in thickness. In a section of the lithium ion secondary battery taken along a plane orthogonal to the principal plane 121a, the area S1 of a first region A1 defined by a perpendicular line V1 extending through a point where an end 122a of the insulator 122 is in contact with the surface 120b of the gradually-decreasing part of the positive electrode mixture layer 120, and orthogonal to the principal plane 121a of the positive electrode current collector 121, the principal plane 121a of the positive electrode current collector 121, and the surface 120b of the gradually-decreasing part is smaller than the area S2 of a second region A2 defined by an orthogonal line H extending through an upper surface 120a of the positive electrode mixture layer 120 and orthogonal to the perpendicular line V1, the perpendicular line V1, and the surface 120b of the gradually-decreasing part.SELECTED DRAWING: Figure 3 【課題】リチウム化合物の析出に起因する電池性能の低下を防止するリチウムイオン二次電池の提供。【解決手段】正極集電体１２１の主面１２１ａのうち正極合剤層１２０が設けられていない部分から、正極合剤層１２０の厚みが漸減する漸減部の表面１２０ｂの一部までの領域を覆う絶縁体１２２を備え、主面１２１ａに直交する平面でリチウムイオン二次電池を切った断面において、正極合剤層１２０の漸減部の表面１２０ｂと絶縁体１２２の端１２２ａとが接する点を通り、かつ、正極集電体１２１の主面１２１ａと直交する垂線Ｖ１と、正極集電体１２１の主面１２１ａと、漸減部の表面１２０ｂと、によって囲まれる第１領域Ａ１の面積Ｓ１が、正極合剤層１２０の上面１２０ａを通り、かつ、垂線Ｖ１に直交する直交線Ｈと、垂線Ｖ１と、漸減部の表面１２０ｂと、によって囲まれる第２領域Ａ２の面積Ｓ２より小さいリチウムイオン二次電池。【選択図】図３