Nonaqueous secondary battery and method of using the same

A nonaqueous secondary battery comprising:

• a positive electrode having a positive electrode mixture layer, a negative electrode, and a nonaqueous electrolyte, wherein
• the positive electrode contains, as an active material, at least two lithium-containing transition metal oxides having different average particle sizes,
• said lithium-containing transition metal oxide having the smallest average particle size is a lithium-containing transition metal oxide represented by the formula (1):
• LixM1yM2zM3yO2 (1)
• wherein M1 represents at least one transition metal element selected from Co, Ni and Mn, M2 represents Mg, or Mg and at least one metal element selected from the group consisting of Ti, Zr, Ge, Nb, Al and Sn, M3 represents an element other than Li, M1 and M2, and x, y, z and v are numbers satisfying the equations respectively:
• 0.97≦x<1.02, 0.8≦y<1.02, 0.002≦z≦0.05, and 0≦v≦0.05;
• a content of Mg in the formula (1) is from 0.15% by mole to less than 2% by mole based on an amount of the metal element M1;
• the positive electrode mixture layer has a density of at least 3.5 g/cm3;
• and the nonaqueous electrode mixture contains a compound having at least two nitrile groups in the molecule.