Positive electrode active material, positive electrode containing the same, and lithium secondary battery

Abstract

The present invention relates to a cathode active material that includes a lithium-nickel-based transition metal oxide in the form of secondary particles, which are aggregates of primary particles, and that satisfies the following conditions: a) the number ratio of primary particles having an aspect ratio of 1.6 or more within a cross section of the secondary particles at a point 40% to 60% of the diameter of the secondary particles is 0.81 or more; and b) the K value calculated by the following Equation 1 is 12 to 40. The cathode active material having the above characteristics can reduce particle cracking during cycling, suppress battery degradation, and improve stability. [Formula 1] K=R AP ×N P / A S where R AP is the average aspect ratio of the primary particles, and N P is the number of primary particles, and A S is the cross-sectional area of ​​the secondary particle.

Claims

1. It contains lithium nickel-based transition metal oxides in secondary particle form, which are aggregates of primary particles. A positive electrode active material that satisfies the following conditions a) and b) for the cross-section at 40% to 60% of the diameter of the secondary particles. a) The number ratio of primary particles having an aspect ratio of 1.6 or more within the cross-section is 0.81 or more. b) The K value calculated by formula 1 below is between 12 and 40. [Formula 1] K=R ＡＰ ×N Ｐ / A Ｓ Here, R ＡＰ This is the average aspect ratio of the primary particles, N Ｐ This is the number of primary particles, and A Ｓ The cross-sectional area (μm) of the secondary particle is the cross-sectional area (μm) of the secondary particle. ２ It is a unitless number.

2. The D of the secondary particle relative to the short axis of the primary particle ５０ The positive electrode active material according to claim 1, wherein the ratio is 0.025 or less.

3. The ratio of D of the secondary particles to the major axis of the primary particles ５０ is 0.035 or more and 0.075 or less. The positive electrode active material according to claim 1.

4. The positive electrode active material according to claim 1, wherein the average aspect ratio of the primary particles within the secondary particles is 2.0 to 3.

5.

5. The aforementioned secondary particles are D ５０ The positive electrode active material according to claim 1, wherein the diameter is 7 μm or more and 20 μm or less.

6. The degree of crystal deformation of the aforementioned secondary particles is 670 × 10 －６ The positive electrode active material according to claim 1, which is as follows:

7. The degree of crystal deformation of the aforementioned secondary particles is 645 × 10 －６ The positive electrode active material according to claim 6, which is as follows:

8. The lithium nickel-based transition metal oxide is represented by the following chemical formula 1, and is the positive electrode active material according to claim 1. [Chemical formula 1] Li １＋ｘ Ni ａ Co ｂ M １ ｃ M ２ ｄ O ２－ｅ X ｅ In the aforementioned chemical formula 1, M １ M includes one or more selected from Mn and Al, ２ X includes one or more elements selected from the group consisting of W, Zr, Y, Ba, Ca, Ti, V, Mg, Ta, and Nb, and X includes one or more elements selected from the group consisting of N, P, S, F, and Cl, with 0 ≤ x ≤ 0.5, 0.6 ≤ a < 1, 0 < b ≤ 0.4, 0 < c ≤ 0.4, 0 ≤ d ≤ 0.05, and 0 ≤ e ≤ 0.

05.

9. The positive electrode active material according to claim 8, wherein in the chemical formula 1, 0.75 ≤ a ≤ 0.

99.

10. M １ The positive electrode active material according to claim 8, wherein is Mn.

11. A positive electrode comprising the positive electrode active material described in any one of claims 1 to 10.

12. A lithium secondary battery comprising the positive electrode described in claim 11.

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