Preparation method of high-nickel ternary positive electrode material

Abstract

The application discloses a preparation method of high-nickel ternary positive electrode material, which comprises the following steps: introducing appropriate water mist into high-speed stirring high-nickel material, so that the water mist forms a water film on the surface of the high-nickel material to dissolve residual alkali on the surface; then adding large-particle-size water-adsorbing molecular sieve material into the high-nickel material; under low-speed stirring, the molecular sieve absorbs water containing residual alkali; then the high-nickel material and the molecular sieve material are separated through a screen, so that the high-nickel ternary positive electrode material with low residual alkali content can be obtained without high-temperature drying on the basis of low water consumption. The method is simple in process, greatly reduces the damage of water washing and high-temperature drying to the material, and the molecular sieve material can be recycled, so that the process cost is reduced and the method is suitable for large-scale production and application.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology, specifically relating to a method for preparing a high-nickel ternary cathode material. Background Technology

[0002] Currently, the two most widely used cathode materials in lithium-ion batteries are lithium iron phosphate and ternary (nickel-cobalt-manganese or nickel-cobalt-aluminum) layered oxide materials. Among these, ternary layered oxide materials are gradually becoming the preferred choice for high-end lithium-ion batteries, especially for automotive power batteries, due to their advantages such as high operating voltage and high energy density. Within ternary cathode materials, high-nickel materials have become an important development direction for layered oxide materials due to their high specific capacity. However, with the increase in nickel content, the surface residual alkali (LiOH and Li₂CO₃) in ternary cathode materials also increases. The presence of residual alkali can seriously affect the processing performance and electrochemical performance of ternary cathode materials. On the one hand, because LiOH is extremely hygroscopic, it can cause the cathode slurry to "jelly-like," affecting the mixing and coating processes. On the other hand, residual alkali is a poor conductor of ions and electrons, which can affect the electrochemical performance of the material, resulting in poor specific capacity and rate performance. In addition, during the long cycle of the battery, lithium hydroxide and lithium carbonate can react with the electrolyte to generate water and carbon dioxide, causing the battery to swell and its capacity to drop sharply, or even explode and catch fire, seriously affecting the safety performance of the battery.

[0003] To eliminate the various adverse effects of residual alkali on the surface of high-nickel materials, the main solution currently used in the industry is to reduce residual alkali through water washing. Water washing involves mixing and stirring the high-alkali material obtained from sintering with water to dissolve the surface alkali, followed by pressure filtration to remove excess alkali with water, and finally high-temperature drying to obtain a low-alkali material. The advantage of this method is its ability to effectively reduce the content of surface residual alkali, but its disadvantages are also very obvious. First, because a slurry needs to be formed, the amount of water used in the process is excessive compared to the amount required to dissolve the residual alkali. This excessive water will intensify the reaction between the alkali and Li in the material's crystal lattice. + / H + The proton exchange reaction not only reduces the lithium content of the main material but also forms hydroxyl oxide impurities on its surface. Furthermore, because the filter-pressed material still contains a high moisture content, the water's reactivity with the main material increases during high-temperature drying, continuing to generate hydroxyl oxides on its surface. Meanwhile, the proton-exchanged lithium reforms as residual alkali, leading to an increase in residual alkali. Finally, hydroxyl oxides are unstable at high temperatures and undergo dehydration and decomposition to form rock salt phase impurities. These factors ultimately result in insufficient lithium source in the washed material and the formation of inert rock salt phase impurities on its surface, significantly reducing the cycling performance of the washed material.

[0004] Therefore, how to improve the preparation method of high-nickel ternary cathode materials so that the water washing and residual alkali reduction process can reduce Li + / H + Taking advantage of proton exchange, while fully leveraging its function of reducing residual alkali, also reduces its damage to the main body and surface of the material, which has become an important direction for improving the residual alkali process on the surface of high-nickel ternary cathode materials. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing high-nickel ternary cathode materials. By improving the water washing process of high-nickel ternary cathode materials, the damage caused by water washing and high-temperature drying is reduced. This method is simple, practical, and low-cost.

[0006] This invention provides a method for preparing a high-nickel ternary cathode material, comprising the following steps:

[0007] (1) Mix high-nickel ternary cathode materials with a certain particle size and fill them with a certain amount of water mist so that the water mist is evenly dispersed on the surface of the high-nickel ternary cathode materials.

[0008] (2) Add water-absorbing molecular sieve material of a certain particle size to the high-nickel ternary cathode material that is uniformly mixed with water mist, and stir to mix;

[0009] (3) The mixture obtained in step (2) is sieved to separate the high-nickel ternary cathode material and the molecular sieve material, so as to obtain a high-nickel ternary cathode material with low residual alkali.

[0010] This method, based on the residual alkali content on the surface of high-nickel materials, involves introducing a suitable amount of water mist into the high-nickel material during high-speed stirring. This water mist forms a water film on the surface of the high-nickel material, dissolving the residual alkali. Then, large-particle water-absorbing molecular sieve material is added. Under low-speed stirring, the water containing residual alkali is absorbed by the molecular sieve. Finally, the high-nickel material and the molecular sieve material are separated by a sieve. This allows for the production of high-nickel ternary cathode materials with low residual alkali content using minimal water and without high-temperature drying. This method is simple, significantly reduces the damage to the material caused by washing and high-temperature drying, and allows for the recycling of the molecular sieve material, reducing process costs and making it suitable for large-scale production applications.

[0011] Preferably, the chemical formula of the high-nickel ternary cathode material in step (1) is LiNi. x Co y M 1-x-y O2, where x≥0.8, 0≤y≤0.2, and element M is at least one of Mn or Al.

[0012] Preferably, in step (1), the particle size D of the high-nickel ternary cathode material is... maxPreferably, the wavelength is less than or equal to 45nm, and more preferably less than or equal to 35nm.

[0013] Preferably, in step (1), the high-nickel ternary cathode material is mixed with water mist and stirred at high speed. The stirring rate is preferably 500-1200 r / min, more preferably 800-1000 r / min, and the stirring time is preferably 5-20 min, more preferably 10-15 min.

[0014] Preferably, the mass m1 of the water mist introduced in step (1) should satisfy: 16Mr1+70Mr2≥m1≥8Mr1+50Mr2, where M is the mass of the high-nickel ternary cathode material, r1 is the mass fraction of LiOH on the surface of the high-nickel ternary cathode material, and r2 is the mass fraction of Li2CO3 on the surface of the high-nickel ternary cathode material.

[0015] Preferably, the water-absorbing molecular sieve in step (2) is one or more of 4A or 5A molecular sieves, with 4A molecular sieve preferably being Na2O·Al2O3·2SiO2·4.5H2O and 5A molecular sieve preferably being 0.75CaO·0.25Na2O·Al2O3·2SiO2·4.5H2O.

[0016] Preferably, the water-absorbing molecular sieve in step (2) has a particle size of D. min Spherical molecular sieves ≥2mm in diameter, preferably with a particle size D. min It is 2-3mm.

[0017] Preferably, the mass m2 of the water-absorbing molecular sieve added in step (2) should satisfy: 3m1≤m2≤10m1, preferably 4m1≤m2≤8m1.

[0018] Preferably, the stirring rate of the mixture in step (2) is 100-500 r / min, more preferably 200-300 r / min, and the stirring time is preferably 10-40 min, more preferably 20-30 min.

[0019] Preferably, the mesh size of the sieve in step (3) is 50 to 300 mesh, more preferably 200 to 300 mesh.

[0020] The preparation method of high-nickel ternary cathode material provided by this invention, which reduces residual alkali on the surface of the high-nickel ternary cathode material by improving the water washing method, has the following main advantages:

[0021] 1. This application is the first to employ a water mist method to treat ternary cathode materials, changing the traditional water washing process. This method reduces the amount of water used and the amount of water in contact with the high-nickel cathode material, thereby reducing Li loss and surface structure damage in the main material. Since the method of this invention does not require pressure filtration washing, but instead uses molecular sieve materials to absorb the water after dissolving residual alkali, it does not require the formation of a fluid slurry. The amount of water can be added appropriately in the form of water mist according to the residual alkali content of the material, reducing the amount of Li loss that occurs between excessive water and the cathode material. + / H + The opportunity for proton exchange prevents water washing from affecting the Li deficiency in the host material and damaging the surface structure.

[0022] 2. High-temperature drying is not required, reducing the damage to the surface structure caused by water during the drying process. The method of this invention uses a molecular sieve material with good water absorption to absorb the water after dissolving residual alkali, effectively preventing further reaction between the surface of the wet material after traditional water washing and pressure filtration and water during high-temperature drying. This further reduces the degree of damage to the material surface and is beneficial to the stability of the overall material structure. Attached Figure Description

[0023] Figure 1 These are SEM images of the high-nickel ternary cathode material in Example 1 of this invention before and after water washing.

[0024] a is the SEM image before washing, and b is the SEM image after washing;

[0025] It can be seen that the amorphous residual alkali distributed on the material surface before water washing disappears after water washing.

[0026] Figure 2 The graph shows a comparison of the cycle performance of the high-nickel ternary cathode materials in Example 1 and Comparative Example 1 of this invention. Test conditions: coin cell, voltage window of 3.0-4.3V, two cycles of 0.1C charge and discharge, 49 cycles of 0.3C charge and 1C discharge, 1C = 190mA / g.

[0027] The cycling stability of the material in Example 1 was significantly improved compared to that in Comparative Example 1. This indicates that the improved water washing method for removing residual alkali provided by the present invention can effectively reduce damage to the material body and surface structure and improve its cycling stability compared to the traditional method. Detailed Implementation

[0028] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0029] Raw material source: 4A type molecular sieve, industrial grade spherical 4A type molecular sieve produced by Zibo Henghuan Aluminum Co., Ltd., particle size D min It is 2.00mm;

[0030] 5A type molecular sieve, spherical 5A type molecular sieve material produced by Anhui Tianpuke Environmental Adsorption Materials Co., Ltd., with a particle size D min It is 2.36mm.

[0031] Example 1:

[0032] The method for removing residual alkali from the high-nickel ternary cathode material in this embodiment includes the following steps:

[0033] 1. Particle size D max LiNi, a high-nickel ternary cathode material with a diameter of 32µm. 0.8 Co 0.1 Mn 0.1 O2 was measured by potentiometric titration to have the following residual alkali content on its surface: LiOH 5100ppm, Li2CO3 3200ppm. 100g was added to a stirrer and stirred at 800r / min. 20.08g (8Mr1 + 50Mr2) of water mist was introduced into the mixture and stirred for 10min.

[0034] 2. Add particles with a diameter D to the high-nickel ternary cathode material that was uniformly mixed with water mist in step 1. min 100.4g of 3mm 4A molecular sieve material was stirred continuously at a speed of 200r / min for 20min.

[0035] 3. After stirring in step 2, sieve the mixture using a 200-mesh sieve. The material passing through the sieve is the high-nickel ternary cathode material LiNi after removing residual alkali. 0.8 Co 0.1 Mn 0.1 O2, the material on the screen is a molecular sieve material that has absorbed moisture.

[0036] Table 1 shows the changes in residual alkali content and electrochemical performance of the high-nickel ternary cathode material before and after water washing in Example 1. As can be seen from Table 1, the water washing method provided by the present invention can effectively reduce the surface residual alkali content of the high-nickel ternary cathode material and improve its electrochemical performance.

[0037] Table 1

[0038]

[0039] Example 2:

[0040] The method for removing residual alkali from the high-nickel ternary cathode material in this embodiment includes the following steps:

[0041] 1. Particle size D max LiNi, a high-nickel ternary cathode material with a diameter of 30 μm. 0.85 Co 0.05 Mn0.1 O2 was measured by potentiometric titration to have the following residual alkali content on its surface: LiOH 5900ppm, Li2CO3 3500ppm. 100g was added to a stirrer and stirred at a speed of 850r / min. 29.22g (8Mr1+70Mr2) of water mist was introduced into the mixture and stirred for 12min.

[0042] 2. Add particles with a diameter D to the high-nickel ternary cathode material that was uniformly mixed with water mist in step 1. min 116.88g of 3mm 5A molecular sieve material was stirred continuously at a stirring speed of 220r / min for 20min.

[0043] 3. After stirring in step 2, sieve the mixture using a 300-mesh sieve. The material passing through the sieve is the high-nickel ternary cathode material LiNi after removing residual alkali. 0.85 Co 0.05 Mn 0.1 O2, the material on the screen is a molecular sieve material that has absorbed moisture.

[0044] Residual alkali content and electrochemical performance of high-nickel ternary cathode material before and after water washing in Example 2

[0045] Table 2

[0046]

[0047] Example 3:

[0048] The method for removing residual alkali from the high-nickel ternary cathode material in this embodiment includes the following steps:

[0049] 1. Particle size D max LiNi, a high-nickel ternary cathode material with a diameter of 28 μm. 0.9 Co 0.05 Mn 0.05 O2 was measured by potentiometric titration to have the following residual alkali content on its surface: LiOH 6500ppm, Li2CO3 4000ppm. 100g was added to a stirrer and stirred at a speed of 900r / min. 38.4g (16Mr1+70Mr2) of water mist was introduced into the mixture and stirred for 14min.

[0050] 2. Add particles with a diameter D to the high-nickel ternary cathode material that was uniformly mixed with water mist in step 1. min 268.8g of 2mm 4A type molecular sieve material was stirred continuously at a stirring speed of 260r / min for 25min.

[0051] 3. After stirring in step 2, sieve the mixture using a 400-mesh sieve. The material passing through the sieve is the high-nickel ternary cathode material LiNi after removing residual alkali. 0.9 Co 0.05 Mn 0.05 O2, the material on the screen is a molecular sieve material that has absorbed moisture.

[0052] Residual alkali content and electrochemical performance of high-nickel ternary cathode material before and after water washing in Example 3

[0053] Table 3

[0054]

[0055] Example 4:

[0056] The method for removing residual alkali from the high-nickel ternary cathode material in this embodiment includes the following steps:

[0057] 1. Particle size D max LiNi, a high-nickel ternary cathode material with a diameter of 25 μm. 0.95 Co 0.03 Mn 0.02 O2 was measured by potentiometric titration to have the following residual alkali content on its surface: LiOH 7000ppm, Li2CO3 4500ppm. 100g of the mixture was added to a stirrer and stirred at a speed of 900r / min. 28.1g of water mist was introduced into the mixture and stirred for 15min.

[0058] 2. Add particles with a diameter D to the high-nickel ternary cathode material that was uniformly mixed with water mist in step 1. min 168.6g of 2mm 5A molecular sieve material was stirred continuously at a stirring speed of 260r / min for 30min.

[0059] 3. After stirring in step 2, sieve the mixture using a 400-mesh sieve. The material passing through the sieve is the high-nickel ternary cathode material LiNi after removing residual alkali. 0.95 Co 0.03 Mn 0.02 O2, the material on the screen is a molecular sieve material that has absorbed moisture.

[0060] Residual alkali content and electrochemical performance of high-nickel ternary cathode material before and after water washing in Example 4

[0061] Table 4

[0062]

[0063] Comparative Example 1:

[0064] The method for removing residual alkali from the high-nickel ternary cathode material in this comparative example includes the following steps:

[0065] 1. Particle size D max LiNi, a high-nickel ternary cathode material with a diameter of 32µm. 0.8 Co 0.1 Mn 0.1 O2, the residual alkali content on its surface was measured by potentiometric titration as follows: LiOH 5100ppm, Li2CO3 3200ppm. 100g was added to a stirrer and stirred at a speed of 800r / min. 100g of water was added and stirred for 10min.

[0066] 2. The slurry from step 1 is subjected to pressure filtration. The wet material after pressure filtration is dried in a vacuum oven at 130℃ for 8 hours to obtain the high-nickel ternary cathode material LiNi after removing residual alkali by traditional water washing. 0.8 Co 0.1 Mn 0.1 O2.

[0067] Residual alkali content and electrochemical performance of high-nickel ternary cathode material before and after water washing in Comparative Example 1

[0068] Table 5

[0069]

Claims

1. A method for preparing a high-nickel ternary cathode material, characterized in that, Includes the following steps: (1) Mix high-nickel ternary cathode materials with a certain particle size and fill them with a certain amount of water mist so that the water mist is evenly dispersed on the surface of the high-nickel ternary cathode materials. (2) Add water-absorbing molecular sieve material of a certain particle size to the high-nickel ternary cathode material that is uniformly mixed with water mist, and stir to mix; (3) The mixture obtained in step (2) is sieved to separate the high-nickel ternary cathode material and the molecular sieve material, so as to obtain a high-nickel ternary cathode material with low residual alkali; The mass m1 of water mist introduced in step (1) should satisfy the following: Where M is the mass of the high-nickel ternary cathode material, r1 is the mass fraction of LiOH on the surface of the high-nickel ternary cathode material, and r2 is the mass fraction of Li2CO3 on the surface of the high-nickel ternary cathode material.

2. The preparation method according to claim 1, characterized in that, The chemical formula of the high-nickel ternary cathode material in step (1) is: Where x≥0.8, 0≤y≤0.2, and element M is at least one of Mn or Al.

3. The preparation method according to claim 1, characterized in that, In step (1), the particle size Dmax of the high-nickel ternary cathode material is less than or equal to 45 nm.

4. The preparation method according to claim 3, characterized in that, In step (1), the particle size Dmax of the high-nickel ternary cathode material is less than or equal to 35 nm.

5. The preparation method according to claim 1, characterized in that, In step (1), the high-nickel ternary cathode material is mixed with water mist and stirred at high speed. The stirring rate is 500~1200 r / min and the stirring time is 5~20 min.

6. The preparation method according to claim 5, characterized in that, In step (1), the high-nickel ternary cathode material is mixed with water mist and stirred at high speed. The stirring rate is 800~1000 r / min and the stirring time is 10~15 min.

7. The preparation method according to claim 1, characterized in that, In step (2), the water-absorbing molecular sieve is one or more of 4A or 5A molecular sieves.

8. The preparation method according to claim 1, characterized in that, In step (2), the water-absorbing molecules are spherical molecular sieves with a particle size Dmin≥2mm.

9. The preparation method according to claim 8, characterized in that, In step (2), the particle size Dmin of the water-absorbing molecules is 2-3 mm.

10. The preparation method according to claim 1, characterized in that, The mass m2 of the water-absorbing molecular sieve added in step (2) should meet the following requirements: .

11. The preparation method according to claim 10, characterized in that, The mass m2 of the water-absorbing molecular sieve added in step (2) should meet the following requirements: .

12. The preparation method according to claim 1, characterized in that, In step (2), the mixing rate of the mixture is 100~500 r / min and the mixing time is 10~40 min.

13. The preparation method according to claim 12, characterized in that, In step (2), the mixing rate of the mixture is 200~300 r / min and the mixing time is 20~30 min.

14. The preparation method according to claim 1, characterized in that, In step (3), the mesh size of the sieve is 50~300 mesh.

15. The preparation method according to claim 14, characterized in that, In step (3), the mesh size of the sieve is 200-300 mesh.

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