Method of preparing positive electrode active material for secondary battery
A method of preparing a positive electrode active material for a secondary battery includes preparing a positive electrode active material precursor including nickel (Ni), cobalt (Co), and at least one selected from the group consisting of manganese (Mn) and aluminum (Al); and forming a lithium composite transition metal oxide by mixing the positive electrode active material precursor and a lithium source and performing calcination, wherein the positive electrode active material precursor includes nickel (Ni) in an amount of 60 mol % or more out of the entire metal element, and a molar ratio (Li/M) of lithium (Li) of the lithium source to the entire metal element (M) of the positive electrode active material precursor is greater than 1.1.
1. A method of preparing a positive electrode active material for a secondary battery, comprising:
preparing a positive electrode active material precursor including nickel (Ni), cobalt (Co), and at least one selected from the group consisting of manganese (Mn) and aluminum (Al); and
forming a lithium composite transition metal oxide by mixing the positive electrode active material precursor and a lithium source and performing calcination,
wherein the positive electrode active material precursor includes nickel (Ni) in an amount of 60 mol % or more based on a total number of moles of metal elements, and
a molar ratio (Li/M) of lithium (Li) of the lithium source to the metal element (M) of the positive electrode active material precursor is greater than 1.1,
wherein the positive electrode active material precursor is represented by Chemical Formula 1 below:
Ni 1−(x1+y1+z1) Co x1 M a y1 M b z1 (OH) 2 [Chemical Formula 1]
wherein M a is at least one element selected from the group consisting of Mn and Al, M b is at least one element selected from the group consisting of Zr, W, Mg, Al, Ce, Hf, Ta, La, Ti, Sr, Ba, Nb, Mo, and Cr, and 0<x1≤0.4, 0<y1≤0.4, 0≤z1≤0.1, and 0<x1+y1+z1≤0.4.
2. The method of claim 1 , wherein the molar ratio (Li/M) is 1.105 to 1.30.
3. The method of claim 1 , wherein the molar ratio (Li/M) 1.13 to 1.20.
4. The method of claim 1 , wherein the positive electrode active material precursor includes nickel (Ni) in an amount of 80 mol % or more based on a total number of moles of metal elements.
5. The method of claim 1 , wherein the positive electrode active material precursor includes nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al).
6. The method of claim 1 , wherein the calcination is carried out at a calcination temperature of 700 to 900° C.
7. The method of claim 1 , wherein the calcination is carried out while raising a temperature to a calcination temperature at a temperature elevation rate of 2 to 10° C./min.
8. The method of claim 1 , wherein the calcination is carried out under an oxygen atmosphere.
9. The method of claim 1 , further comprising, washing the lithium composite transition metal oxide after the formation of a lithium composite transition metal oxide.