Process for making a mixed oxide according to the formula Li1+xTM1−xO2 wherein x is in the range of from 0.1 to 0.2 and TM is a combination of elements according to general formula (I) (NiaCobMnc)1-dM1d (I) wherein a is in the range of from 0.30 to 0.38, b being in the range of from zero to 0.05, c being in the range of from 0.60 to 0.70, and d being in the range of from zero to 0.05, M1 is selected from Al, Ti, Zr, W, Mo, Nb, Ta, Mg and combinations of at least two of the forego-ing, a+b+c=1, said process comprising the following steps: (a) providing a particulate hydroxide, oxide or oxyhydroxide of manganese, nickel, and, optionally, at least one of Co and M1, (b) adding a source of lithium, (c) calcining the mixture obtained from step (b) thermally under an atmosphere comprising 0.05 to 5 vol.-% of oxygen at a maximum temperature the range of from 650 to 1000° C.