A composition of active material for a positive electrode of a lithium-ion electrochemical cell is provided comprising: (a) a lithiated oxide of formula Li1+xMO2 in which: 0≤x≤0.15, M designates NiaMnbCocM′d where a>0; b>0; c>0; d≥0 and a+b+c+d=1; M′ being chosen from B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, Mo or a mixture of these; (b) a lithiated phosphate of formula LiMn1−yM″yPO4 where M″ represents at least one element chosen from the group consisting of Fe, Ni, Co, Mg and Zn; and 0