An electric device having a power generating element contains a positive electrode with a positive electrode active material formed on a surface of a positive electrode current collector, a negative electrode, and a separator containing an electrolyte. The positive electrode active material contains a lithium nickel-based composite oxide having a layered crystal structure capable of insertion and desorption of lithium ions, the composition represented by: [LiαNiβ]3a[NixMny-rMrCOz]3bO2, wherein M is at least one selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, Sn, V, Cu, Ag, and Zn, and x+y+z≤1, β≤0.032, 0.9≤α+β≤1.2, 0