Method for preparing positive electrode active material
A method of preparing a positive electrode active material which includes forming a pre-sintered mixture by adding a reaction mixture including a lithium raw material and a nickel-manganese-cobalt precursor to a first crucible and performing a primary heat treatment at a temperature of 500° C. to 800° C., and, after discharging the pre-sintered mixture from the first crucible, adding the pre-sintered mixture to a second crucible and performing a secondary heat treatment at a temperature of 700° C. to 1,000° C. to form a lithium nickel manganese cobalt-based positive electrode active material, wherein a volume of the pre-sintered mixture formed after the primary heat treatment is 20% to 50% of a volume of the reaction mixture added to the first crucible.
1. A method of preparing a positive electrode active material, comprising:
forming a pre-calcinated mixture by adding a reaction mixture including a lithium raw material and a nickel-manganese-cobalt precursor to a first crucible and performing a primary heat treatment at a temperature of 500° C. to 800° C.; and
after discharging the pre-calcinated mixture from the first crucible, adding the pre-calcinated mixture to a second crucible and performing a secondary heat treatment at a temperature of 700° C. to 1,000° C. to form a lithium nickel manganese cobalt-based positive electrode active material,
wherein a volume of the pre-calcinated mixture formed after the primary heat treatment is 20% to 50% of a volume of the reaction mixture added to the first crucible prior to the primary heat treatment, and
wherein an amount of the pre-calcinated mixture added to the second crucible is 2 to 10 times an amount of the pre-calcinated mixture formed in the first crucible.
2. The method of claim 1 , wherein the lithium raw material comprises at least one of a lithium hydroxide or a lithium carbonate.
3. The method of claim 1 , wherein the nickel-manganese-cobalt precursor comprises at least one of a nickel manganese cobalt hydroxide, a nickel manganese cobalt oxyhydroxide, a nickel manganese cobalt carbonate, or a nickel manganese cobalt organic complex.
4. The method of claim 1 , wherein the reaction mixture further comprises a doping raw material.
5. The method of claim 4 , wherein the doping raw material comprises oxides, hydroxides, sulfides, oxyhydroxides, halides or a mixture thereof, which include at least one element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.
6. The method of claim 1 , wherein the first crucible is a stainless steel crucible, a nickel crucible, or an alloy crucible.
7. The method of claim 1 , wherein the primary heat treatment is performed for 1 hour or more.
8. The method of claim 1 , wherein the second crucible is an aluminum crucible.
9. The method of claim 1 , further comprising adding a doping raw material to the second crucible before the secondary heat treatment.
10. The method of claim 1 , wherein the secondary heat treatment is performed for 2 hours or more.
11. The method of claim 1 , wherein at least one of the primary heat treatment and the secondary heat treatment is performed in an air atmosphere.
12. The method of claim 1 , further comprising milling or classifying the pre-calcinated mixture before the pre-calcinated mixture is added to the second crucible.
13. The method of claim 1 , wherein the lithium nickel manganese cobalt-based positive electrode active material is represented by Formula 1:
Li 1+x [Ni a Mn b Co c M 1 1−a−b−c ] 1−x O 2 [Formula 1]
wherein, in Formula 1, −0.2≤x≤0.2, 0<a<1, 0<b<1, and 0<c<1, and
M 1 comprises at least one selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, In, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.