Ternary positive electrode material, and lithium ion battery

1. A ternary positive electrode material, comprising secondary particles composed of primary particles, wherein the secondary particles have an average particle diameter D50 in a range of 6 μm to 20 μm and a BET in a range of 0.2 m 2 /g to 1 m 2 /g, and a number σ of the primary particles per unit area of the secondary particles is in a range of 5 particles/μm 2 to 100 particles/μm 2 , the primary particles have a length in a range of 100 nm to 1000 nm, and a width in a range of 50 nm to 400 nm; and the primary particles have a ratio of length to width in a range of 2 to 20; and

wherein the ternary positive electrode material has a formula of Li 1+a [Ni x Co y Mn z M1 b M2 c ]O 2−d N d , where element M1 and element M2 are each independently selected from at least one of Al, Zr, Ti, Mg, Zn, B, Ca, Ce, Te and Fe, element N is selected from at least one of F, Cl and S, 0<x<1, 0<y≤0.3, 0<z≤0.3, −0.1<a<0.2, 0<b<0.3, 0<c<0.3, 0≤d<0.2, 0<b+c<0.3, and x+y+z+b=1.

2. The ternary positive electrode material according to claim 1 , wherein the ternary positive electrode material has an compact density greater than or equal to 3.3 g/cc.

3. The ternary positive electrode material according to claim 1 , wherein the number σ of the primary particles per unit area of the secondary particles in the ternary positive electrode material is a range of 5 particles/μm 2 to 50 particles/μm 2 .

4. The ternary positive electrode material according to claim 1 , wherein the BET of the secondary particles is in a range of 0.3 m 2 /g to 0.8 m 2 /g.

5. The ternary positive electrode material according to claim 1 , wherein 0.6<x<1.

6. The ternary positive electrode material according to claim 1 , wherein a total doping amount of the element M1 and element M2 in the ternary positive electrode material is a range of 200 ppm to 9000 ppm.

7. The ternary positive electrode material according to claim 1 , wherein the number σ of the primary particles per unit area of the secondary particles in the ternary positive electrode material is determined by:

(1) performing a SEM measurement on a sample of the ternary positive electrode material comprising the secondary particles having the average particle diameter D50 in a range of 6 μm to 20 μm, so as to obtain a SEM image at a magnification of 10000×;

(2) calculating the number σ of the primary particles per unit area of the secondary particles in the ternary positive electrode material based on the SEM image by using following equations:

σ={( x 1+ x 2)/2*( y 1+ y 2)/2}/( A/C*B/C ), particles/μm 2 , wherein

x1 represents a number of the primary particles along a lower edge of the SEM image of the secondary particles;

x2 represents a number of the primary particles along an upper edge of the SEM image of the secondary particles;

y1 represents a number of the primary particles along a left edge of the SEM image of the secondary particles;

y2 represents a number of the primary particles along a right edge of the SEM image of the secondary particles;

A represents an actual length in millimeter of the upper or lower edge of the SEM image of the secondary particles;

B represents an actual length in millimeter of the left or right edge of the SEM image of the secondary particles; and

C represents an actual length in a unit of mm/μm of a scale of 1 μm in the SEM image of the secondary particles;

wherein when counting the number of the primary particles in the SEM image of the secondary particles, a primary particle, which is partially included in the SEM image, is counted as one primary particle.

8. A lithium ion battery, comprising a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and electrolyte, wherein the positive electrode is made of a positive electrode material, which is the ternary positive electrode material according to claim 1 .