Ternary positive electrode material, preparation method thereof and lithium ion battery

Abstract

The application provides a ternary positive electrode material and a preparation method thereof, and a lithium ion battery, so as to provide a ternary positive electrode material with high compaction density and high thermal stability. x Ni a Co b Mn c Al d M y Q z O2; 0.95<=x<1.2, 0.80<=a<=0.95, 0<b<0.2, 0<=c<=0.2, 0<=d<=0.1, 0<y<=0.04, 0<=z<=0.02, a+b+c+d+y+z=1, and c and d are not 0 at the same time; M is a doping element, Q is a coating element, Q and M are each independently selected from at least one of Zr, Mo, Ca, Mg, Ba, B, Y, and Sr; wherein the (104) crystal face spacing of the ternary positive electrode material is 55-75 nm, the compaction density of the ternary positive electrode material under the condition of 3.5T is 3.45-3.70 g / cm 3 ; and the particle size volume distribution of the ternary positive electrode material is a multimodal distribution.

Claims

1. A ternary cathode material, characterized in that, include: The molecular general formula of the ternary cathode material is: Li x Ni a Co b Mn c Al d M y Q z O2; 0.95 ≤ x < 1.2, 0.80 ≤ a ≤ 0.95, 0 < b < 0.2, 0 ≤ c ≤ 0.2, 0 ≤ d ≤ 0.1, 0 < y ≤ 0.04, 0 ≤ z ≤ 0.02, a + b + c + d + y + z = 1, and c and d are not simultaneously 0; M is a doping element, Q is a coating element, and Q and M are each independently selected from at least one of: Zr, Mo, Ca, Mg, Ba, B, Y, and Sr; wherein, The (104) interplanar spacing of the ternary cathode material is 55-75 nm, and the compaction density of the ternary cathode material under 3.5T conditions is 3.45-3.70 g / cm³. 3 The particle size and volume distribution of the ternary cathode material is multi-peaked. The thermal decomposition temperature of the ternary cathode material is not lower than 220°C; wherein, the thermal decomposition temperature is obtained by DSC testing.

2. The ternary cathode material as described in claim 1, characterized in that, The ternary cathode material is a mixture of a first particle and a second particle; wherein the median particle size of the first particle is larger than the median particle size of the second particle. Then the multi-peak distribution is a bimodal distribution, and the distance between the peaks in the bimodal distribution is not less than 7; the molecular formula of the first particle is: Li x1 Ni a1 Co b1 Mn c1 Al d1 M y1 Q z1 O2, and the general molecular formula of the second particle is: Li x2 Ni a2 Co b2 Mn c2 Al d2 M' y2 Q' z2 O2; where, 0.95 ≤ x1 < 1.2, 0.88 < a1 ≤ 0.95, 0 < b1 < 0.2, 0 ≤ c1 ≤ 0.2, 0 ≤ d1 ≤ 0.1, 0 < y1 ≤ 0.02, 0 ≤ z1 ≤ 0.02, a1 + b1 + c1 + d1 + y1 + z1 = 1, and c1 and d1 are not both 0; 0.95 ≤ x2 < 1.2, 0.80 ≤ a2 ≤ 0.88, 0 < b2 < 0.2, 0 ≤ c2 ≤ 0.2, 0 ≤ d2 ≤ 0.1, 0.02 ≤ y2 ≤ 0.04, 0 ≤ z2 ≤ 0.02, a2 + b2 + c2 + d2 + y2 + z2 = 1, and c2 and d2 are not both 0; M and M' are both doping elements, Q and Q' are both coating elements, and M, M', Q, and Q' are each independently selected from at least one of Zr, Mo, Ca, Mg, Ba, B, Y, and Sr.

3. The ternary cathode material as described in claim 2, characterized in that, The median particle size of the first particle is 8-16 μm, and the median particle size of the second particle is 2-8 μm.

4. The ternary cathode material as described in claim 2, characterized in that, When the mass content of the first particle is 60%-90% relative to the mass of the ternary cathode material, and the difference between a1 and a2 is not less than 0.06, the specific capacity of the ternary cathode material is not less than 210 mAh·g. The specific capacity is obtained by testing the ternary cathode material under a voltage window of 0.2C and 2.5-4.25V.

5. The ternary cathode material as described in claim 2, characterized in that, The specific surface area of ​​the first particle is 0.25-0.8 m². 2 / g, the specific surface area of ​​the second particle is 0.8-1.5 m² / g. 2 / g.

6. A method for preparing the ternary cathode material as described in any one of claims 1-5, characterized in that, include: Multiple precursors are each mixed with a dopant and a lithium salt, and sintered separately in an oxygen atmosphere at 400-600°C for 5-10 hours to obtain multiple intermediate materials. Among these, the difference in median particle size between any two precursors is not less than 7 μm, the nickel content in any precursor with a larger median particle size is higher than the nickel content in any precursor with a smaller median particle size, and the ratio of the precursor with a larger median particle size to the dopant is greater than the ratio of the precursor with a smaller median particle size to the dopant. The various intermediate materials are mixed and sintered in an oxygen atmosphere at 700-830°C for 5-15 hours to obtain the cathode material to be coated.

7. The method as described in claim 6, characterized in that, After obtaining the cathode material to be coated, the process further includes: The washed cathode material to be coated is mixed with a coating agent and sintered at 250-350°C to obtain a ternary cathode material with a coating layer.

8. The method as described in claim 6, characterized in that, The various precursors are each independently selected from: Ni p Co q Mn h Al f (OH)2 and / or Ni p Co q Mn h Al f CO3; wherein, 0.80 ≤ p ≤ 0.95, 0 < q < 0.2, 0 ≤ h ≤ 0.2, 0 ≤ f ≤ 0.1, and p + q + h + f = 1, and h and f are not both 0.

9. The method according to any one of claims 6-8, characterized in that, The multiple precursors are two precursors with a median particle size difference of not less than 7 μm. The two precursors are a first precursor and a second precursor, and the median particle size of the first precursor is greater than that of the second precursor. The various precursors are each mixed with a dopant and a lithium salt, and sintered in an oxygen atmosphere at 400-600°C for 5-10 hours to obtain various intermediate materials, including: A first mixture consisting of a first precursor, a first dopant, and a first lithium salt, and a second mixture consisting of a second precursor, a second dopant, and a second lithium salt are each disposed in an oxygen atmosphere to obtain a first intermediate material and a second intermediate material; wherein the molar ratio of the first dopant to the first precursor in the first mixture is not greater than 0.02, and the molar ratio of the second dopant to the second precursor in the second mixture is not less than 0.

02.

10. The method as described in claim 9, characterized in that, The first precursor is selected from: Ni p1 Co q1 Mn h1 Al f1 (OH)2 and / or Ni p1 Co q1 Mn h1 Al f1 CO3; the second precursor is selected from: Ni p2 Co q2 Mn h2 Al f2 (OH)2 and / or Ni p2 Co q2 Mn h2 Al f2 CO3; wherein, 0.88 < p1 ≤ 0.95, 0 < q1 < 0.2, 0 ≤ h1 ≤ 0.2, 0 ≤ f1 ≤ 0.1, and p1 + q1 + h1 + f1 = 1, h1 and f1 are not both 0; 0.80 ≤ p2 ≤ 0.88, 0 < q2 < 0.2, 0 ≤ h2 ≤ 0.2, 0 ≤ f2 ≤ 0.1, and p2 + q2 + h2 + f2 = 1, h2 and f2 are not both 0.

11. The method as described in claim 9, characterized in that, The mixing of the various intermediate materials includes: The first intermediate material and the second intermediate material are mixed in a mass ratio of 3:2 to 9:

1.

12. The method as described in claim 9, characterized in that, The dopant, the first dopant, and the second dopant are each independently selected from at least one of the following: ZrO2, Al(OH)2, Al2O3, MoO3, MoO2, CaO, Ca(OH)2, CaCO3, Y2O3, SrO, MgO, Mg(OH)2, MgCO3, BaO, Ba(OH)2, BaCO3, B2O3, and H3BO3.

13. A lithium-ion battery, characterized in that, include: The ternary cathode material as described in any one of claims 1-5, or the ternary cathode material prepared by the method described in any one of claims 6-12.

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