The present disclosure provides a positive electrode material, and a preparation method thereof, a positive electrode sheet, and a battery. The positive electrode material includes a nickel-cobalt-manganese-aluminum quaternary positive electrode material and a lithium iron phosphate positive electrode material. A chemical formula of the nickel-cobalt-manganese-aluminum quaternary positive electrode material is Li.sub.(1+u)Ni.sub.vMn.sub.wCo.sub.xAl.sub.yA.sub.zO.sub.2, where u0, v+w+x+y+z=1. A chemical formula of the lithium iron phosphate positive electrode material is Li.sub.1+kFe(PO.sub.4).sub.1+mB.sub.n, in which k, m, and n0; and both A and B are doping elements. A mass ratio of the nickel-cobalt-manganese-aluminum quaternary positive electrode material to the lithium iron phosphate positive electrode material is (0.5 to 7.0):(3.0 to 9.5).

A positive electrode material, a preparation method thereof and a lithium-ion battery are provided. A first aspect provides a positive electrode active material, where a chemical composition of the positive electrode active material is Li.sub.1+a[Ni.sub.xCo.sub.yM1.sub.zM2.sub.b]O.sub.2cA.sub.d, M1 is one or two of Mn or Al, M2 is one or more of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, or Y; and A is one of F, Cl, or S. By controlling the Ni content in secondary particles of different particle sizes, the problem of non-uniform degradation of the secondary particles of different particle sizes during battery cycling can be avoided, thereby improving the cycling stability of lithium-ion batteries.

A positive electrode material, a preparation method thereof and a lithium-ion battery are provided. A first aspect provides a positive electrode active material, where a chemical composition of the positive electrode active material is Li.sub.1+a[Ni.sub.xCo.sub.yM1.sub.zM2.sub.b]O.sub.2cA.sub.d, M1 is one or two of Mn or Al, M2 is one or more of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, or Y; and A is one of F, Cl, or S. By controlling the Ni content in secondary particles of different particle sizes, the problem of non-uniform degradation of the secondary particles of different particle sizes during battery cycling can be avoided, thereby improving the cycling stability of lithium-ion batteries.

A cathode active material of the present invention comprises a lithium nickel-based composite oxide comprising secondary particles formed by the aggregation of primary particles, wherein some cations and some anions in the lithium nickel-based composite oxide are replaced by a cation M and a fluoride anion (F.sup.), respectively, which are contained in a fluorine-based compound, and the average Ni occupancy in the Li 3a site, obtained through Rietveld refinement using X-ray diffraction of the secondary particles, is 1.1-1.5%.

A cathode active material of the present invention comprises a lithium nickel-based composite oxide comprising secondary particles formed by the aggregation of primary particles, wherein some cations and some anions in the lithium nickel-based composite oxide are replaced by a cation M and a fluoride anion (F.sup.), respectively, which are contained in a fluorine-based compound, and the average Ni occupancy in the Li 3a site, obtained through Rietveld refinement using X-ray diffraction of the secondary particles, is 1.1-1.5%.