Positive Electrode Material Having a Size Dependent Composition

A lithium metal oxide powder for use as a cathode material in a rechargeable battery, having a general formula LiaNixCoy MnzM′mO2±eAf, with 0.9<a<1.1, 0.2≦x≦0.9, 0<y≦0.4, 0<z≦0.7, 0≦m≦0.35, e<0.02, 0≦f≦0.05 and 0.9<(x+y+z+m+f)<1.1;

• M′ comprising one or more elements selected from the group consisting of Al, Mg, Ti, Cr, V, Fe and Ga;
• A comprising one or more elements selected from the group consisting of F, C, Cl, S, Zr, Ba, Y, Ca, B, Sn, Sb, Na and Zn;
• the powder having a particle size distribution defining a D10 and a D90;
• and wherein either
• x1−x2≧0.005;
• or
• z2−z1≧0.005;
• or
• both x1−x2≧0.005 and z2−z1≧0.005;
• x1 and z1 being the values of x and z of particles having a particle size D90;
• and x2 and z2 being the values of x and z of particles having a particle size D10, and wherein −0.005≦y1−y2≦0.005, y1 being the value of y of particles having a particle size D90;
• and y2 being the value of y of particles having a particle size D10.