Composite transition metal oxide-based precursor, preparing method thereof, and cathode active material using the same
The present disclosure provides a novel composite transition metal oxide-based precursor, a preparing method thereof, and a cathode active material for a secondary battery prepared from the precursor. In the present disclosure, it is possible to enhance productivity and economic efficiency due to a high reaction yield during the synthesis of a cathode active material and to enhance the initial discharge capacity and lifespan characteristics of a secondary battery including a cathode active material by using an oxide-based precursor having a high oxygen fraction instead of a hydroxide-based precursor used as a precursor of a cathode active material in the related art.
1. A composite transition metal oxide-based precursor represented by the following Chemical Formula 1:
Ni a Co b M′ c O x (1< x≤ 1.5) [Chemical Formula 1]
in the formula,
M′ is one or more selected from the group consisting of an alkali metal, an alkaline earth metal, a Group XIII element, a Group XIV element, a Group XV element, a Group XVI element, a Group XVII element, a transition metal, and a rare earth element, and
0.6≤ a< 1.0, 0≤ b≤ 0.4, 0≤ c≤ 0.4, a+b+c= 1.
2. The composite transition metal oxide-based precursor of claim 1 , wherein M′ is one or more selected from the group consisting of Al, Mn, Zr, W, Ti, Mg, Sr, Ba, Ce, Hf, F, P, S, La, and Y.
3. The composite transition metal oxide-based precursor of claim 1 , wherein the precursor is a primary particle or a secondary particle in which a plurality of primary particles is aggregated.
4. The composite transition metal oxide-based precursor of claim 3 , wherein the primary particle has a flake-like or needle-like shape with an average particle diameter in a range of 0.01 to 0.8 μm, and a plurality of pore structures is present on the surface or inside thereof, and the secondary particle has an average particle diameter (D50) in a range of 3 to 30 μm.
5. The composite transition metal oxide-based precursor of claim 1 , wherein the precursor has a tap density of 2.0 g/cc or more.
6. The composite transition metal oxide-based precursor of claim 1 , wherein the precursor has a specific surface area in a range of 5 to 80 m 2 /g measured according to the nitrogen adsorption BET method.
7. The composite transition metal oxide-based precursor of claim 1 , wherein in the precursor, a volume of pores in a range of 5 nm to 50 nm is in a range of 10 −3 to 10 −2 cm 3 /g·nm per weight of particles.
8. A method for preparing the composite transition metal oxide-based precursor of claim 1 , the method comprising a step of oxidizing a composite transition metal hydroxide-based precursor represented by the following Chemical Formula 2:
Ni a Co b M′ c (OH) 2 [Chemical Formula 2]
in the formula,
M′ is one or more selected from the group consisting of an alkali metal, an alkaline earth metal, a Group XIII element, a Group XIV element, a Group XV element, a Group XVI element, a Group XVII element, a transition metal, and a rare earth element, and
0.6≤ a< 1.0, 0≤ b≤ 0.4, 0≤ c≤ 0.4, a+b+c= 1.
9. The method of claim 8 , wherein in the step of oxidizing,
(i) a heat treatment is performed under an oxygen atmosphere,
(ii) an oxidizing agent is used, or
(iii) both (i) and (ii) are applied.
10. The method of claim 8 , wherein in the oxidizing, a heat treatment is performed in a range of 200 to 1,000° C. under an oxygen atmosphere at an oxygen concentration of 80% or more for 1 to 12 hours.
11. The method of claim 9 , wherein the oxidizing agent is one or more selected from the group consisting of KMnO 4 , H 2 O 2 , Na 2 O 2 , FeCl 3 , CuSO 4 , CuO, PbO 2 , MnO 2 , HNO 3 , KNO 3 , K 2 Cr 2 O 7 , CrO 3 , P 2 O 5 , H 2 SO 4 , K 2 S 2 O 8 , a halogen, and C 6 H 5 NO 2 .