Abstract: Provided is a positive electrode active material for a non-aqueous electrolyte secondary battery, the active material including a lithium-transition metal composite oxide containing lithium, nickel, cobalt, and manganese, having a layered structure, having a ratio D50/DSEM of from 1 to 4, and having a ratio of a number of moles of nickel to a total number of moles of metals other than lithium of greater than 0.8 and less than 1, a ratio of a number of moles of cobalt to the total number of moles of metals other than lithium of less than 0.2, a ratio of a number of moles of manganese to the total number of moles of metals other than lithium of less than 0.2, and a ratio of the number of moles of manganese to a sum of the number of moles of cobalt and the number of moles of manganese of less than 0.58.

Abstract: A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. The method includes providing a composition containing a first lithium transition metal composite oxide having a 50% particle size 1D50 in a first volume cumulative particle size distribution of 0.1 ?m or more and less than 3.2 ?m and a first liquid medium; and granulating the composition to obtain a second lithium transition metal composite oxide having a 50% particle size 2D50 in a second volume cumulative particle size distribution greater than 1D50. The second lithium transition metal composite oxide has a ratio of a 90% particle size 3D90 in a third volume cumulative particle size distribution measured after the ultrasonic treatment to a 90% particle size 2D90 in the second volume cumulative particle size distribution measured before the ultrasonic treatment (3D90/2D90) of 0.53 or less.

Abstract: Provided is a positive electrode active material for a non-aqueous electrolyte secondary battery, the active material including a lithium-transition metal composite oxide containing lithium, nickel, cobalt, and manganese, having a layered structure, having a ratio D50/DSEM of from 1 to 4, and having a ratio of a number of moles of nickel to a total number of moles of metals other than lithium of greater than 0.8 and less than 1, a ratio of a number of moles of cobalt to the total number of moles of metals other than lithium of less than 0.2, a ratio of a number of moles of manganese to the total number of moles of metals other than lithium of less than 0.2, and a ratio of the number of moles of manganese to a sum of the number of moles of cobalt and the number of moles of manganese of less than 0.58.