| abstract |
The present invention provides a lithium ion secondary battery that is excellent in safety even under high voltage driving. SOLUTION: A general formula: Li a Ni b Co surface-modified with a phosphate ion-containing solution c Mn d D e O f ( 0.2 ≦ a ≦ 1.2, b + c + d + e = 1,0 ≦ e <1, D is Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, A positive electrode active material represented by at least one element selected from K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, 1.7 ≦ f ≦ 2.1), and A positive electrode comprising a high-resistance metal compound having a higher resistance than a positive electrode active material. [Selection figure] None |