A method for preparing positive electrode material

Abstract

The present invention discloses a positive electrode material and its preparation method and application. The preparation method comprises the following steps: (1) mixing a ternary precursor and a lithium source, and performing a calcination once to obtain a ternary positive electrode sinter; (2) using the ternary positive electrode sinter as a raw material, mixing it with a first coating agent and a second coating agent respectively; (3) calcining the mixture obtained in step (2) twice to obtain ternary positive electrode materials NCM (I) and NCM (II); (4) mixing the two ternary materials obtained in step (3) in proportion according to actual needs to obtain the ternary positive electrode material. The process of the present invention is simple, the coating is uniform and stable, and it is easy to mass-produce. The positive electrode material particles of the present invention are not easy to agglomerate, have good fluidity, and can improve the ionic conductivity and chemical stability of the ternary positive electrode material, reduce the internal resistance of the material, and thus improve the electrochemical performance of the ternary positive electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for preparing a positive electrode material. Background Art

[0002] Lithium-ion batteries are widely used due to their high operating voltage, high energy density, and long cycle life. Cathode materials are a crucial component of lithium-ion batteries, determining their primary electrochemical performance. With the pursuit of high energy density and low cost, ternary materials are considered one of the most promising cathode materials. However, these materials are prone to agglomeration and have poor fluidity. This makes screening difficult and leads to blockages in multiple steps during production, complicating subsequent production.

[0003] Therefore, improving the agglomeration of particles in ternary positive electrode materials and enhancing their fluidity are of great significance to industrial production. Summary of the Invention

[0004] To address the above technical issues, the present invention provides a method for preparing a ternary nickel-cobalt-manganese-oxide cathode material. This cathode material comprises ternary materials with different coating schemes. In addition to having a high energy density, this cathode material also exhibits advantages such as low agglomeration, good fluidity, and ease of coating.

[0005] The preparation method of the ternary nickel cobalt lithium manganese oxide positive electrode material provided by the present invention comprises the following steps:

[0006] (1) uniformly mixing a nickel-cobalt-manganese hydroxide precursor and a lithium source, and sintering to obtain a doped and modified ternary nickel-cobalt-manganese positive electrode sintered material;

[0007] (2) using the doped and modified ternary nickel-cobalt-manganese cathode first sinter and the first coating agent as raw materials, mixing them evenly and then calcining them twice to obtain the ternary cathode second sinter [NCM(I)];

[0008] (3) Using the doped and modified ternary nickel-cobalt-manganese cathode first sinter and the second coating agent as raw materials, mixing them evenly and then calcining them twice to obtain the ternary cathode second sinter [NCM(II)];

[0009] (4) The ternary positive electrode sintered material [NCM(I)] obtained in step (2) and the ternary positive electrode sintered material [NCM(II)] obtained in step (3) are mixed in the required proportion to obtain the target ternary nickel cobalt lithium manganese oxide positive electrode material NCM.

[0010] The above steps (2) and (3) are performed in no particular order.

[0011] In step (1) of the above method, preferably, the chemical formula of the nickel-cobalt-manganese hydroxide precursor is (Ni x Coy Mn 1-x-y )OH2, wherein 0.35≤x≤0.9, 0.05≤y≤0.15, 1-xy>0; more preferably, 0.5 <x≤0.9。

[0012] According to one embodiment of the present invention, the chemical formula of the nickel-cobalt-manganese hydroxide precursor is (Ni 0.6 Co 0.2 Mn 0.2 )OH2;

[0013] According to one embodiment of the present invention, the chemical formula of the nickel-cobalt-manganese hydroxide precursor is (Ni 0.8 Co 0.1 Mn 0.1 )OH2.

[0014] In step (1) of the above method, preferably, the lithium source is at least one of lithium hydroxide and lithium carbonate.

[0015] In step (1) of the above method, preferably, the molar ratio of lithium in the lithium source to the sum of nickel, cobalt and manganese in the nickel-cobalt-manganese hydroxide precursor is 1.0 to 1.15:1.

[0016] In step (1) of the above method, a metal element additive is also added to the mixed raw materials; preferably, the metal element additive is a combination of one or more compounds containing the following metal elements: Mg, Zr, Ti, Nb, Mo, Sr, and Y.

[0017] The addition of metal element additives can further improve the material's capacity, rate, cycle, high and low temperature performance, etc.

[0018] In step (1) of the above method, preferably, the sintering is carried out in air or oxygen atmosphere at 400-1100° C. More preferably, when x ≥ 0.6 in the chemical formula of the nickel-cobalt-manganese hydroxide precursor, the sintering atmosphere is oxygen.

[0019] In step (1) of the above method, preferably, the sintering is carried out in the following three steps: first, pre-sintering in a range not higher than 700 degrees Celsius for 3 to 8 hours, then sintering in a range of 800 to 1000 degrees Celsius for 10 to 18 hours, and finally lowering the temperature to a range of 600 to 750 degrees Celsius at a constant rate and then cooling naturally.

[0020] In step (1) of the above method, preferably, after the sintering, cooling is performed and then pulverization is performed to obtain a granular doped modified ternary nickel-cobalt-manganese positive electrode sintered material. Its chemical formula is Li a (Ni x Co y Mn 1-x-y)O2, where 1.0≤a≤1.15, 0.35≤x<0.9, 0.05≤y≤0.15, 1-xy>0.

[0021] Furthermore, the crushed ternary one-fired material is also screened, and the mesh number of the screen is not less than 200 meshes.

[0022] In step (2) of the above method, preferably, the first coating agent is a cobalt-containing compound; more preferably, the cobalt-containing compound is cobalt hydroxide or cobalt oxyhydroxide.

[0023] In step (2) of the above method, preferably, the mass ratio of the cobalt-containing compound to the doped and modified ternary nickel-cobalt-manganese positive electrode sinter is controlled to be 500 to 5000 ppm, specifically 3000 ppm or 4000 ppm.

[0024] In step (2) of the above method, preferably, the temperature of the secondary sintering is 400-800° C., and the sintering time is 3-8 hours.

[0025] In step (2) of the above method, preferably, the particle size D50 of the obtained NCM (I) is controlled to be 2.5 to 5 μm.

[0026] In step (3) of the above method, preferably, the second coating agent is selected from compounds containing the following elements or combinations thereof: aluminum, boron, tungsten, zirconium, magnesium, titanium, and calcium. Preferably, the second coating agent must include at least a boron-containing compound. Specifically, the aluminum-containing compound may be aluminum oxide; the tungsten-containing compound may be tungsten oxide, tungstic acid, etc.; and the boron-containing compound may be boric acid.

[0027] In step (3) of the above method, preferably, the mass ratio of the aluminum compound to the doped and modified ternary nickel-cobalt-manganese positive electrode sinter is controlled to be 500 to 2000 ppm, specifically 500 ppm or 1000 ppm.

[0028] In step (3) of the above method, preferably, the mass ratio of the tungsten compound to the doped and modified ternary nickel-cobalt-manganese positive electrode material is controlled to be 300 to 2000 ppm, specifically 300 ppm or 1000 ppm.

[0029] In step (3) of the above method, preferably, the mass ratio of the boron compound to the doped and modified ternary nickel-cobalt-manganese positive electrode material is controlled to be 300 to 2000 ppm, specifically 500 ppm.

[0030] In step (3) of the above method, preferably, the temperature of the secondary sintering is 300-600° C., and the sintering time is 3-8 hours.

[0031] In step (3) of the above method, preferably, the particle size D50 of the obtained NCM (II) is controlled to be 2 to 4 μm.

[0032] In step (4) of the above method, preferably, the mixing ratio of NCM (I) and NCM (II) can be changed as needed, but the addition ratio of NCM (II) is not less than 30% of the total mixed mass; specifically, 50%, 90%, etc.

[0033] The ternary nickel-cobalt-lithium manganese oxide positive electrode material prepared by the above method also falls within the protection scope of the present invention.

[0034] The present invention also protects a lithium ion battery.

[0035] The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and an electrolyte, and the material of the positive electrode comprises the above-mentioned ternary nickel cobalt lithium manganese oxide positive electrode material.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] In the positive electrode material provided by the present invention, the coating layer of cobalt and the coating layer of aluminum tungsten boron have a synergistic relationship with each other, and the synergy between them makes the positive electrode material provided by the present invention have good performance. Specifically, the coating of cobalt can improve the rate performance of the positive electrode material, reduce the internal resistance, reduce the polarization loss, and extend the cycle life of the battery, but the coating of cobalt will make the fluidity of the material worse, making it difficult to transport and screen through pipelines. Al can improve the crystallinity of the material and effectively inhibit the irreversible phase change during the charge and discharge process; B will slowly form a layer of lithium borate compound on the surface of the material during the high-temperature sintering process, thereby improving the capacity and cycle performance of the material; the two work together to make the material have good fluidity, while improving the chemical stability of the ternary positive electrode material, reducing the internal resistance of the material, and thus improving the electrochemical performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a scanning electron microscope image of the positive electrode material prepared in Example 1. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0040] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, were all commercially available.

[0041] Example 1

[0042] The preparation of the positive electrode material of this embodiment includes the following steps:

[0043] 1) (Ni 0.6 Co 0.2 Mn 0.2 )OH2 ternary nickel-cobalt-manganese precursor and lithium carbonate are placed in a ball mill at a ratio of 1:1.06 (the molar ratio of the sum of nickel, cobalt and manganese elements in the ternary nickel-cobalt-manganese precursor to lithium in lithium carbonate), and polyurethane grinding balls are added, with a ball-to-material ratio of 1:1. The ball mill is then placed in a three-dimensional mixer and mixed for 3 hours. The mixed materials are then calcined in air, heated to 650°C at 2°C / min and kept warm for 5 hours, then heated to 900°C at 2°C / min and kept warm for 15 hours, and finally cooled to 650°C at 2°C / min and cooled naturally. After crushing, the ternary LiNi 0.6 Co 0.2 Mn 0.2 O2 positive electrode burning material.

[0044] 2) Ternary LiNi 0.6 Co 0.2 Mn 0.2 O2 and cobalt hydroxide were also mixed in a three-dimensional mixer for 3 hours, wherein the mass of the coated cobalt hydroxide was 4000ppm of the ternary material. The mixture was then heated to 650°C at a rate of 2°C / min and kept warm for 5 hours. The mixture was sieved (250 mesh) to obtain the ternary positive electrode material NCM(Ⅰ).

[0045] 3) Ternary LiNi 0.6 Co 0.2 Mn 0.2 O2 and aluminum oxide, tungsten oxide and boric acid are also mixed in a three-dimensional mixer for 3 hours, wherein the masses of the coating aluminum, tungsten and boron are 500ppm, 300ppm and 500ppm of the ternary material respectively; then the temperature is raised to 350℃ at 2℃ / min and kept warm for 5 hours, and the ternary positive electrode material NCM(Ⅱ) is obtained by sieving (250 mesh).

[0046] 4) The NCM (I) and NCM (II) with the coating layer obtained in step 2) and step 3) were mixed in a mass ratio of 1:9 to obtain the positive electrode material of this embodiment.

[0047] Example 2

[0048] This embodiment provides a method for preparing a ternary nickel cobalt lithium manganese oxide positive electrode material. Except that the mixing mass ratio of NCM (I) and NCM (II) in step 4) is changed to 1:1, the remaining process steps are the same as those in Example 1.

[0049] Example 3

[0050] This embodiment provides a method for preparing a ternary nickel cobalt lithium manganese oxide positive electrode material. Except that the mixing ratio of NCM (I) and NCM (II) in step 4) is changed to 9:1, the remaining process steps are the same as those in Example 1.

[0051] Example 4

[0052] 1) (Ni 0.8 Co 0.1 Mn 0.1 )OH2 ternary nickel cobalt manganese precursor and lithium hydroxide are placed in a ball mill at a ratio of 1:1.06 (the molar ratio of the sum of nickel, cobalt and manganese elements in the ternary nickel cobalt manganese precursor to lithium in lithium carbonate), and polyurethane grinding balls are added, with a ball-to-material ratio of 1:1. The ball mill is then placed in a three-dimensional mixer and mixed for 3 hours. The uniformly mixed materials are then calcined under air conditions, heated to 650°C at 2°C / min and kept warm for 5 hours, then heated to 850°C at 2°C / min and kept warm for 15 hours, and finally cooled to 650°C at 2°C / min and cooled naturally. After crushing, pass through a 300-mesh sieve to obtain ternary LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode burning material.

[0053] 2) Ternary LiNi 0.8 Co 0.1 Mn 0.1 O2 and cobalt hydroxide were also mixed in a three-dimensional mixer for 3 hours, wherein the mass of the coated cobalt hydroxide was 3000ppm of the ternary material. The mixture was then heated to 600°C at a rate of 2°C / min and kept warm for 5 hours. The mixture was sieved (250 mesh) to obtain the ternary positive electrode material NCM(Ⅰ).

[0054] 3) Ternary LiNi 0.8 Co 0.1 Mn 0.1 O2 and alumina, tungstic acid and boric acid are also mixed in a three-dimensional mixer for 3 hours, wherein the masses of the coating aluminum, tungsten and boron are 1000ppm, 1000ppm and 500ppm of the ternary material respectively; then the temperature is raised to 350℃ at 2℃ / min and kept warm for 5 hours, and the ternary positive electrode material NCM(Ⅱ) is obtained by sieving (250 mesh).

[0055] 4) The NCM (I) and NCM (II) with the coating layer obtained in step 2) and step 3) were mixed in a mass ratio of 1:1 to obtain the positive electrode material of this embodiment.

[0056] Comparative Example 1

[0057] The NCM (I) in Example 1 was used as the sample of this comparative example, ie, no mixing was performed.

[0058] Comparative Example 2

[0059] The NCM (II) in Example 1 was used as the sample of this comparative example, that is, no mixing was performed.

[0060] The resulting ternary cathode material was then assembled and tested using a button cell. The method involved weighing the prepared cathode material, acetylene black, and polyvinylidene fluoride (PVDF) in a 90:5:5 mass ratio, mixing them evenly, and adding NMP to form a uniform slurry. The slurry was then evenly coated onto aluminum foil. A button cell was assembled in an argon-filled glove box using a lithium metal sheet as the negative electrode, 1 mol / L LiPF6 as the electrolyte, and a polypropylene microporous membrane as the separator. The assembled button cell was then subjected to constant current charge-discharge tests at room temperature and low-temperature DCR tests, with charge and discharge cutoff voltages ranging from 2.8V to 4.4V.

[0061] The obtained ternary cathode material was subjected to a sieve vibrating speed test. The specific method was as follows: a fixed mass of ternary material was placed on a 250-mesh D30 vibrating sieve. The vibrating sieve and ultrasonic switches were turned on and vibrated for 15 seconds before being turned off. The weight of the material under the sieve was weighed and the sieve speed was calculated. The electrochemical performance and sieve speed of the product are shown in Table 1.

[0062] Table 1 shows the electrochemical performance test results of the materials obtained in each embodiment and comparative example.

[0063] 0.2C charging 0.2C First effect / % DCR / Ω <![CDATA[Sieving speed / kgmin -1 > Example 1 222.1 191.1 86.04 489 3.56 Example 2 220.6 190.3 86.26 477 2.79 Example 3 220.3 189.6 86.06 446 1.48 Example 4 234.5 204.6 87.24 483 2.53 Comparative Example 1 220.9 189.5 85.79 442 1.19 Comparative Example 2 221.7 191.5 86.38 503 3.71

[0064] As can be seen from Table 1, the ternary nickel-cobalt-manganese cathode materials prepared in Examples 1-4 exhibit significantly improved sieving speed, i.e., fluidity, compared to the unmixed nickel-cobalt-manganese cathode material of the comparative example, without significant loss in capacity and with minimal change in the internal resistance of the material. These results demonstrate that the present invention provides a ternary cathode material and preparation method thereof, resulting in a ternary cathode material having high capacity, low internal resistance, and excellent fluidity.

[0065] The present invention has been described in detail above. It will be apparent to those skilled in the art that the present invention may be practiced over a wide range of parameters, concentrations, and conditions without departing from the spirit and scope of the present invention and without unnecessary experimentation. Although specific embodiments have been given herein, it should be understood that further modifications may be made to the present invention. In summary, this application is intended to encompass any variations, uses, or improvements to the present invention, including those made by conventional techniques known in the art that depart from the scope of the present invention. Applications of the essential features may be made within the scope of the following claims.

Claims

1. A method for preparing a ternary nickel cobalt lithium manganese oxide positive electrode material, comprising the following steps: (1) uniformly mixing a nickel-cobalt-manganese hydroxide precursor and a lithium source, and sintering to obtain a doped and modified ternary nickel-cobalt-manganese positive electrode sintered material; (2) using a doped and modified ternary nickel-cobalt-manganese cathode first sinter and a first coating agent as raw materials, mixing them evenly and then calcining them twice to obtain a ternary cathode second sinter [NCM(I)]; the first coating agent is a cobalt-containing compound; (3) Using a doped and modified ternary nickel-cobalt-manganese cathode first sinter and a second coating agent as raw materials, mixing them evenly and then calcining them twice to obtain a ternary cathode second sinter [NCM(II)]; the second coating agent must include at least a boron-containing compound; (4) The ternary positive electrode sintered material [NCM(I)] obtained in step (2) and the ternary positive electrode sintered material [NCM(II)] obtained in step (3) are mixed in proportion to obtain the target ternary nickel cobalt lithium manganese oxide positive electrode material NCM.

2. The preparation method according to claim 1, wherein: In the step (1), the chemical formula of the nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.35≤x≤0.9, 0.05≤y≤0.15, 1-xy>0; Or, the chemical formula of the doped modified ternary nickel-cobalt-manganese positive electrode material is Li a (Ni x Co y Mn 1-x-y )O2, where 1.0≤a≤1.15, 0.35≤x<0.9, 0.05≤y≤0.15, 1-xy>0.

3. The preparation method according to claim 1 or 2, characterized in that: In the step (1), the lithium source is at least one of lithium hydroxide and lithium carbonate; Alternatively, in step (1), the molar ratio of lithium in the lithium source to the sum of nickel, cobalt and manganese in the nickel-cobalt-manganese hydroxide precursor is 1.0 to 1.15:

1.

4. The preparation method according to claim 1, wherein: In the step (1), a metal element additive is also added to the mixed raw materials.

5. The preparation method according to claim 4, characterized in that: The metal element additive is one or more combinations of compounds containing the following metal elements: Mg, Zr, Ti, Nb, Mo, Sr, and Y.

6. The preparation method according to claim 1, wherein: In the step (1), the sintering is carried out in air or oxygen atmosphere at 400-1100°C; The sintering is carried out in three steps: first, pre-sintering in a range not higher than 700°C for 3 to 8 hours, then sintering in a range of 800 to 1000°C for 10 to 18 hours, and finally lowering the temperature to a range of 600 to 750°C at a constant speed and then cooling naturally.

7. The preparation method according to claim 1, wherein: In the step (1), after the sintering, the following steps are further included: cooling, and then crushing to obtain a granular doped modified ternary nickel-cobalt-manganese positive electrode sintered material.

8. The preparation method according to claim 1, wherein: In the step (2), the cobalt-containing compound is cobalt hydroxide or cobalt oxyhydroxy.

9. The preparation method according to claim 1 or 8, characterized in that: The mass ratio of the cobalt-containing compound to the doped and modified ternary nickel-cobalt-manganese positive electrode sinter is controlled to be 500-5000 ppm.

10. The preparation method according to claim 1, characterized in that: In the step (2), the secondary sintering temperature is 400-800°C, and the sintering time is 3-8 hours; Alternatively, in step (2), the particle size D50 of the obtained NCM (I) is controlled to be 2.5-5 μm.

11. The preparation method according to claim 1, characterized in that: The second coating agent in step (3) further includes compounds selected from the group consisting of the following elements or their combinations: aluminum, tungsten, zirconium, magnesium, titanium, and calcium.

12. The preparation method according to claim 11, characterized in that: The mass ratio of the aluminum-containing compound to the doped and modified ternary nickel-cobalt-manganese cathode material is controlled to be 500-2000ppm; The mass ratio of the tungsten-containing compound to the doped and modified ternary nickel-cobalt-manganese cathode material is controlled to be 300-2000ppm; The mass ratio of the boron-containing compound to the doped and modified ternary nickel-cobalt-manganese positive electrode material is controlled to be 300~2000ppm.

13. The preparation method according to claim 1, characterized in that: The secondary sintering temperature in step (3) is 300-600° C., and the sintering time is 3-8 hours.

14. The preparation method according to claim 1 or 13, characterized in that: In the step (3), the particle size D50 of the obtained NCM (II) is controlled to be 2-4 μm.

15. The preparation method according to claim 1, wherein: In the step (4), the addition ratio of NCM (II) is not less than 30% of the total mass of the mixture.

16. A ternary nickel-cobalt-lithium manganese oxide positive electrode material prepared by the method according to any one of claims 1 to 15.

17. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that: The material of the positive electrode includes the ternary nickel cobalt lithium manganese oxide positive electrode material according to claim 16.

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