| 摘要 |
There is provided a lithium ion secondary battery that includes a positive electrode having high thermal stability and is capable of greatly reducing the possibility of causing thermal runaway even in a nail penetration test. A lithium ion secondary battery including a positive electrode including a lithium composite oxide and a porous film bonded to at least one of a surface of the positive electrode and a surface of a negative electrode, wherein the porous film includes an inorganic oxide filler and a film binder, and the lithium composite oxide is represented by the formula: Li<SUB>a</SUB>(Co<SUB>1-x-y</SUB>M<SUB>x</SUB><SUP>1</SUP>M<SUB>y</SUB><SUP>2</SUP>)<SUB>b</SUB>O<SUB>2 </SUB>(wherein element M<SUP>1 </SUP>is at least one selected from the group consisting of Mg, Sr, Y, Zr, Ca and Ti, element M<SUP>2 </SUP>is at least one selected from the group consisting of Al, Ga, In and Tl, and 0<a<=1.05, 0.005<=x<=0.15, 0<=y<=0.05 and 0.85<=b<=1.1). |
