Single crystal ncma quaternary precursor and method of making same

Abstract

A single crystal NCMA quaternary precursor and a preparation method thereof.A single crystal NCMA quaternary precursor has a chemical formula of Ni a Al b Zr c (OH)2·Ni d Co e Mn f (OH)2.The preparation method comprises the following steps: one, preparing a first metal liquid of Ni, Zr and a complexing agent A, preparing a second metal liquid of Ni, Co, Mn and H2O2, preparing a precipitant, preparing a complexing agent B, and preparing a mixed solution; two, simultaneously adding the first metal liquid, the precipitant and the mixed solution into a kettle for co-precipitation, the volume of the first metal liquid added per hour is 6-9% of the effective volume of the kettle, and the volume of the mixed solution added per hour is 1.5-2.2%; the solid content is controlled to be 1.2-1.3 g / mL, the pH value is kept at 11.8-12.2, and the concentration of the complexing agent A is 0.1-0.2 mol / L; a core layer Ni a Al b Zr c (OH)2 is obtained after T1 hours; the adding of the first metal liquid and the mixed solution is stopped, the second metal liquid and the complexing agent B are changed, reaction is carried out for T2 hours, the D50 of the slurry reaches 3.1-3.9 um, and the reaction is stopped; three, the co-precipitation product is subjected to pressure filtration, washing and drying to obtain the single crystal NCMA quaternary precursor.The Al in the single crystal NCMA positive electrode material prepared by the method is uniformly distributed, and the electrical performance is good.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material technology, specifically to a single-crystal NCMA quaternary precursor and its preparation method. Background Technology

[0002] Single-crystal NCM cathode materials have attracted much attention due to their advantages such as high mechanical strength, good structural stability, and excellent cycle performance. However, as the number of charge-discharge cycles of single-crystal NCM cathode materials increases, their structural stability gradually decreases, and their cycle performance declines. This is mainly because single-crystal NCM cathode materials are prone to volume expansion and corrosion from acidic substances produced by electrolyte decomposition during charge-discharge processes.

[0003] To address the aforementioned issues, researchers mixed single-crystal NCM cathode material with an appropriate amount of aluminum source and then calcined it to prepare single-crystal NCMA cathode material. The addition of an appropriate amount of aluminum not only stabilizes the cathode material structure but also effectively prevents corrosion from acidic substances generated by electrolyte decomposition, significantly improving cycle performance and rate capability.

[0004] However, the high temperatures (>800℃) during the preparation of single-crystal NCMA cathode materials easily generate a large amount of Li5AlO4 impurity phase, leading to a deterioration in the electrochemical performance of the material. To avoid the generation of Li5AlO4 impurity phase during the preparation process, ternary cathode manufacturers mainly adopt a segmented sintering process to prepare single-crystal NCMA cathode materials: First, the single-crystal NCM cathode material precursor is mixed with an excess lithium source and calcined to obtain the single-crystal NCM cathode material. Then, the obtained single-crystal NCM cathode material is crushed. Next, the crushed single-crystal NCM cathode material is mixed with an appropriate amount of aluminum source and sintered a second time to obtain the single-crystal NCMA cathode material. The above process for preparing single-crystal NCMA cathode materials is relatively complex, with long sintering times and high production costs. Furthermore, the morphology of the crushed material is irregular, with varying particle sizes and severe particle agglomeration. During the mixing process with the aluminum source, uneven mixing is easily generated, resulting in uneven Al distribution in the prepared single-crystal NCMA cathode material, which in turn leads to a decrease in electrical performance.

[0005] Therefore, how to overcome the shortcomings of the existing technology is the subject of this invention. Summary of the Invention

[0006] The purpose of this invention is to provide a single-crystal NCMA quaternary precursor and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention at the product level is as follows:

[0008] A single-crystal NCMA quaternary precursor with the chemical formula Nia Al b Zr c (OH)2·Ni d Co e Mn f (OH)2, where 0.94≤a≤0.98, 0.02≤b≤0.06, 0.001≤c≤0.003, 0.86≤d<1, 0.02<e<0.13, 0.02<f<0.13.

[0009] 1. In a further technical solution, D50 is 3.1–3.9 μm, particle size distribution is 0.55 < (D90 - D10) / D50 < 0.75, and tap density is 1.8–2.1 g / cm³. 3 Specific surface area is 12-20 m² 2 / g; The precursor has a core-shell structure, with the core layer being Ni. a Al b Zr c (OH)2, with a Ni outer shell d Co e Mn f (OH)2, the primary particles on the shell surface are uniformly arranged in a lamellar shape, with a thickness of 100-140 nm and a length of 400-480 nm.

[0010] To achieve the above objectives, the technical solution adopted by the present invention at the method level is as follows:

[0011] A method for preparing a single-crystal NCMA quaternary precursor includes:

[0012] Step 1: Prepare a first metal liquid containing Ni, Zr, and complexing agent A, wherein the total molar concentration of Ni and Zr is 1.8 to 2.4 mol / L, and the molar concentration ratio of Ni to complexing agent A is 6:1 to 4:1.

[0013] Prepare a second metal liquid containing Ni, Co, Mn, and H2O2, wherein the total molar concentration of Ni, Co, and Mn is 1.8–2.4 mol / L, and the ratio of the molar concentration of H2O2 to the total molar concentration of Co and Mn is 1:4–1:6.

[0014] Prepare a sodium hydroxide or potassium hydroxide solution with a concentration of 6–10 mol / L as a precipitant;

[0015] Prepare an ammonia solution with a concentration of 2-3 mol / L as complexing agent B;

[0016] Prepare a mixed solution of aluminate and sodium hydroxide, wherein the concentration of aluminate is 0.1–0.8 mol / L;

[0017] Step 2: Keep the reactor stirred and introduce a protective gas into the reaction system at a rate of 150-200% of the effective volume of the reactor per hour. Simultaneously add the first molten metal, the precipitant, and the mixed solution from Step 1 into the reactor for co-precipitation. The volume of the first molten metal entering the reactor per hour is 6-9% of the effective volume, and the volume of the mixed solution entering the reactor per hour is 1.5-2.2% of the effective volume. The overflow during the reaction flows to the concentrate. Control the solid content in the reactor to 1.2-1.3 g / mL, maintain the pH value at 11.8-12.2, the concentration of complexing agent A in the reactor to 0.1-0.2 mol / L, maintain the synthesis temperature at 50-70℃, and the reactor rotation speed to 600-800 r / min.

[0018] After reaction T1 hours, a Ni core layer was obtained. a Al b Zr c (OH)2, then stop the feeding of the first molten metal and the mixed solution, improve the second molten metal and complexing agent B, the second molten metal has the same flow rate as the first molten metal, the flow rate of the complexing agent B is 1-2% of the effective volume of the reactor per hour; react again for T2 hours, the D50 of the slurry in the reactor reaches 3.1-3.9 μm, then stop the reaction;

[0019] Step 3: The coprecipitated product from Step 2 is subjected to pressure filtration, washing, and drying to obtain a single-crystal NCMA quaternary precursor.

[0020] 1. In a further technical solution, in step one, the complexing agent A is one or both of EDTA and lactic acid. EDTA and lactic acid have strong complexing ability for Ni. Preparing Ni, Zr, and complexing agent A into a first metal liquid facilitates the early formation of a complex between Ni and complexing agent A. This ensures that Ni, Zr, and Al are uniformly precipitated when subsequently added to the reaction vessel along with the mixed solution, forming a Ni core layer. a Al b Zr c (OH)2. In addition, the molar concentration ratio of Ni to complexing agent A needs to be between 6:1 and 4:1. If the ratio is higher than this range, the amount of complexing agent A will be too small, the complexing ability will decrease, and the precipitation of Ni, Zr and Al will be uneven during the co-precipitation process; if the ratio is lower than this range, the amount of complexing agent A will be too large, and the production cost will increase.

[0021] 2. In a further technical solution, in step one, the molar concentration of H2O2 is in the ratio of the total molar concentration of Co and Mn to 1:4 to 1:6. H2O2 can oxidize some of the divalent Co and Mn, refining the primary particles of the precursor.

[0022] 3. In a further technical solution, in step one, the aluminate in the mixed solution includes one or more of sodium aluminate, potassium aluminate, or ammonium aluminate, and the pH of the mixed solution is 12.2 to 12.8.

[0023] 4. In a further technical solution, in step two, the ratio of the flow rate of the first liquid metal to the flow rate of the mixed solution is 4 to 6. When the ratio of the flow rate of the first liquid metal to the flow rate of the mixed solution is lower than this range, the amount of aluminum added to the mixed solution is too large; when the ratio of the flow rate of the first liquid metal to the flow rate of the mixed solution is higher than this range, the amount of aluminum added to the mixed solution is too small.

[0024] 5. In a further technical solution, in step two, the ratio of the flow rate of the second liquid metal to the flow rate of the complexing agent B is 2.5 to 5. Controlling the ratio of the flow rate of the second liquid metal to the flow rate of the complexing agent B can regulate the complexation of Ni, Co, and Mn elements in the second liquid metal by the complexing agent B, so as to achieve uniform precipitation of the three elements Ni, Co, and Mn. If the ratio is higher than this range, the amount of complexing agent B is too small, the complexing ability decreases, resulting in uneven precipitation of the three elements Ni, Co, and Mn during the co-precipitation process, and the thickness of the primary particles of the product is less than 100-140 nm, the crystallinity decreases, and the electrical properties deteriorate. If the ratio is lower than this range, the amount of complexing agent B is too large, and the thickness of the primary particles of the precursor product is greater than 100-140 nm, which is not conducive to lithium diffusion.

[0025] 6. In the above scheme, in step two, T1 = T2.

[0026] The working principle and advantages of this invention are as follows:

[0027] 1. This invention designs a single-crystal NCMA quaternary precursor with a core-shell structure, wherein the core layer is Ni. a Al b Zr c (OH)2, with a Ni outer shell d Co e Mn f The (OH)2 core structure primarily consists of Ni, Zr, and Al, while the shell structure primarily consists of Ni, Co, and Mn. Since the shell structure does not contain Al, the generation of Li5AlO4 impurities is avoided during the calcination process with the lithium source. As the lithium source diffuses from the outside in, the aluminum in the original precursor core layer diffuses uniformly from the inside out, ultimately producing a single-crystal NCMA cathode material with a uniform aluminum distribution.

[0028] 2. In this invention, Zr element is incorporated into the core layer. Zr element acts as a flux, which lowers the sintering temperature and avoids the formation of Li5AlO4 impurity phase due to high temperature during the preparation of single-crystal NCMA cathode material. In addition, the appropriate amount of Zr element can also improve the structural stability of the cathode material and improve the cycle performance.

[0029] 3. In the process of preparing the second metal liquid, H2O2 is added, and the ratio of the molar concentration of H2O2 to the total molar concentration of Co and Mn is 1:4 to 1:6. H2O2 can oxidize some of the divalent Co and Mn, refine the primary particles of the precursor, and facilitate the diffusion of lithium ions from the outside to the inside during calcination.

[0030] 4. The single-crystal NCMA quaternary precursor prepared in this invention has primary particles on the shell surface arranged in a uniform lath-like pattern, with a thickness of 100–140 nm and a length of 400–480 nm. The lath-like arrangement of primary particles provides a pathway for the diffusion of lithium and aluminum, improving the uniformity of aluminum in the single-crystal NCA cathode material. Furthermore, the thickness of the primary particles (100–140 nm) and the length (400–480 nm) facilitate the formation of single crystals at lower calcination temperatures, avoiding the formation of the Li5AlO4 impurity phase.

[0031] 5. The single-crystal NCMA quaternary precursor prepared by the present invention can directly obtain a single-crystal NCA cathode material by calcination after mixing with a lithium source, which solves the problems of long sintering time and high production cost caused by multi-stage sintering. Attached Figure Description

[0032] Appendix Figure 1 SEM image of the single-crystal NCMA quaternary precursor prepared in an embodiment of the present invention;

[0033] Appendix Figure 2 SEM image of the single-crystal NCA cathode material prepared in an embodiment of the present invention;

[0034] Appendix Figure 3 SEM image of the single-crystal NCMA quaternary precursor prepared in Comparative Example 1 of this invention.

[0035] Appendix Figure 4 SEM image of the single-crystal NCMA quaternary precursor prepared in Comparative Example 2 of this invention.

[0036] Appendix Figure 5 The graphs show the cycle performance test results of the single-crystal NCA cathode materials prepared in the embodiments and comparative examples of the present invention.

[0037] Appendix Figure 6 This is a rate performance test diagram of the single-crystal NCA cathode material prepared in the embodiments of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0039] The present invention will be clearly described below with illustrations and detailed description. Any person skilled in the art who understands the embodiments of the present invention can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0040] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” “having,” etc., as used herein are open-ended, meaning they include, but are not limited to, specific embodiments.

[0041] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing this case.

[0042] Example:

[0043] A method for preparing a single-crystal NCMA quaternary precursor includes:

[0044] Step 1: Prepare a first metal solution of Ni, Zr and lactic acid, wherein the total molar concentration of Ni and Zr is 2 mol / L, the molar concentration ratio of Ni to Zr is 95:4.8, and the molar concentration ratio of Ni to complexing agent A is 5:1.

[0045] A second metal liquid containing Ni, Co, Mn, and H2O2 was prepared, wherein the total molar concentration of Ni, Co, and Mn was 2 mol / L, the molar ratio of Ni, Co, and Mn was 89:3:8, the molar concentration of H2O2 was 0.03 mol / L, and the molar concentration ratio of H2O2 to the total molar concentration of Co and Mn was 1:7.3.

[0046] Prepare a 10 mol / L sodium hydroxide or potassium hydroxide solution as a precipitant;

[0047] Prepare an ammonia solution with a concentration of 2 mol / L as complexing agent B;

[0048] Prepare a mixed solution of sodium aluminate and sodium hydroxide, wherein the concentration of the aluminate is 0.3 mol / L and the pH of the mixed solution is 12.4;

[0049] Step 2: Keep the reactor stirred and introduce a protective gas (such as nitrogen) into the reaction system at a rate of 200% of the effective volume of the reactor per hour. Simultaneously add the first molten metal, the precipitant, and the mixed solution from Step 1 into the reactor for co-precipitation. The volume of the first molten metal entering the reactor per hour is 6% of the effective volume of the reactor, and the volume of the mixed solution entering the reactor per hour is 1.5% of the effective volume of the reactor. The overflow during the reaction flows to the concentrate. Control the solid content in the reactor to 1.2–1.3 g / mL, maintain the pH value at 11.8–12.2, the concentration of complexing agent A in the reactor to 0.17 mol / L, maintain the synthesis temperature at 55℃, and the reactor rotation speed to 750 r / min.

[0050] After a reaction of 45 hours, a Ni core layer was obtained. 0.95 Al 0.048 Zr 0.002 (OH)2, then stop the feeding of the first molten metal and the mixed solution, and at the same time improve the second molten metal and complexing agent B. The flow rate of the second molten metal is the same as that of the first molten metal, and the flow rate of complexing agent B is 2% of the effective volume of the reactor per hour. React again for 45 hours. When the D50 of the slurry in the reactor reaches 3.1 to 3.9 μm, stop the reaction.

[0051] Step 3: The co-precipitated product from Step 2 is subjected to pressure filtration, washing, and drying to obtain a single-crystal NCMA quaternary precursor. The chemical formula of the product is Ni. 0.95 Al 0.048 Zr 0.002 (OH)2·Ni 0.89 Co 0.03 Al 0.08 (OH)2, D50 is 3.65 μm, particle size distribution is 0.68, and tap density is 1.87 g / cm³. 3 The specific surface area is 14.28 m². 2 / g, the primary particles on the shell surface of the precursor are uniformly arranged in a lath shape with a thickness of 100-140nm and a length of 400-480nm. The relevant data are shown in Table 1.

[0052] Comparative Example 1:

[0053] The difference from the embodiment is that the amount of Zr added to the first metal liquid in step one is different. In this comparative example, no Zr was added to the first metal liquid, but otherwise it is exactly the same as in embodiment 1. The precursor obtained after washing and drying is shown in Table 1.

[0054] Comparative Example 2:

[0055] The difference from the embodiment is that the amount of Zr added to the first molten metal in step one is different; the core layer prepared in this comparative example is Ni. 0.947 Al 0.048 Zr 0.005 (OH)2, the rest is exactly the same as in the example. The precursor obtained by washing and drying is shown in Table 1.

[0056] Comparative Example 3:

[0057] The difference from the example is that the ratio of the molar concentration of H2O2 in the second metal liquid to the total molar concentration of Co and Mn in step one is different. In this comparative example, the ratio of the molar concentration of H2O2 in the second metal liquid to the total molar concentration of Co and Mn is 1:3, and the rest is exactly the same as in Example 1. The precursor obtained after washing and drying is shown in Table 1.

[0058] Comparative Example 4:

[0059] The difference from the embodiment is that the ratio of the molar concentration of H2O2 in the second metal liquid to the total molar concentration of Co and Mn in step one is different. In this comparative example, the ratio of the molar concentration of H2O2 in the second metal liquid to the total molar concentration of Co and Mn is 1:10, and the rest is exactly the same as the embodiment. The precursor obtained by washing and drying is shown in Table 1.

[0060] Table 1 compares the finished product data of the products obtained from the examples and the comparative examples.

[0061]

[0062] As shown in Table 1, the amount of Zr added to the core layer has no significant effect on the precursor's D50, particle size distribution, tap density, specific surface area, primary particle thickness, and primary particle length. H2O2 can oxidize some of the divalent Co and Mn, refining the primary particles of the precursor. As the ratio of the molar concentration of H2O2 in the second molten metal to the total molar concentration of Co and Mn increases, the tap density of the precursor gradually decreases, the specific surface area gradually increases, and the thickness of the primary particles also decreases accordingly.

[0063] Figure 1 , Figure 3 and Figure 4 The images show SEM images of the single-crystal NCMA quaternary precursors prepared in Examples 3, 4, and 5, respectively. As can be seen from the images, the primary particles on the surface of the precursors prepared in Examples 3 are uniformly arranged in a lamellar pattern, with a thickness of 100–140 nm and a length of 400–480 nm. Figure 2 The image shown is a SEM image of the single-crystal NCMA cathode material prepared according to an embodiment of the present invention. The single-crystal particles in the image have smooth surfaces, uniform sizes, and no obvious defects.

[0064] Figure 5 The figures show the cycle performance test graphs of the single-crystal NCMA cathode materials prepared according to the embodiments and comparative examples of the present invention. It can be seen from the graphs that the single-crystal NCMA cathode material prepared in the embodiments exhibits the best cycle performance, with a capacity of 197.2 mAh / g after 50 cycles at a current density of 0.2C. Figure 6 In this embodiment of the invention, the single-crystal NCA cathode material exhibits good rate performance, with discharge capacities of 210.2, 189.9, 175.4, and 165.3 mAh / g at discharge current densities of 0.2C, 2C, 5C, and 10C, respectively.

[0065] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a single-crystal NCMA quaternary precursor, characterized in that: include: Step 1: Prepare a first metal liquid containing Ni, Zr, and complexing agent A, wherein the total molar concentration of Ni and Zr is 1.8~2.4 mol / L, and the molar concentration ratio of Ni to complexing agent A is 6:1~4:1; the complexing agent A is one or both of EDTA and lactic acid. Prepare a second metal liquid containing Ni, Co, Mn, and H2O2, wherein the total molar concentration of Ni, Co, and Mn is 1.8~2.4 mol / L, and the ratio of the molar concentration of H2O2 to the total molar concentration of Co and Mn is 1:4~1:

6. Prepare a sodium hydroxide or potassium hydroxide solution with a concentration of 6~10 mol / L as a precipitant; Prepare an ammonia solution with a concentration of 2-3 mol / L as complexing agent B; Prepare a mixed solution of aluminate and sodium hydroxide, wherein the concentration of aluminate is 0.1~0.8 mol / L; Step 2: Keep the reactor stirred and introduce a protective gas into the reaction system at a rate of 150-200% of the effective volume of the reactor per hour. Simultaneously add the first molten metal, the precipitant, and the mixed solution from Step 1 into the reactor for co-precipitation. The volume of the first molten metal entering the reactor per hour is 6-9% of the effective volume, and the volume of the mixed solution entering the reactor per hour is 1.5-2.2% of the effective volume. The flow rate ratio of the first molten metal to the mixed solution is 4-6. Overflow during the reaction flows to the concentrate. Control the solid content in the reactor to be 1.2-1.3 g / mL, maintain the pH value at 11.8-12.2, the concentration of complexing agent A in the reactor to be 0.1-0.2 mol / L, maintain the synthesis temperature at 50-70℃, and the reactor rotation speed at 600-800 r / min. After reaction T1 hours, a Ni core layer was obtained. a Al b Zr c (OH)2, then stop the feeding of the first molten metal and the mixed solution, improve the second molten metal and complexing agent B, the second molten metal has the same flow rate as the first molten metal, the flow rate of the complexing agent B is 1~2% of the effective volume of the reactor per hour; the ratio of the flow rate of the second molten metal to the flow rate of the complexing agent B is 2.5~5; react again for T2 hours, the D50 of the slurry in the reactor reaches 3.1~3.9um, then stop the reaction; Step 3: The co-precipitated product from Step 2 is subjected to pressure filtration, washing, and drying to obtain a single-crystal NCMA quaternary precursor. The chemical formula of this precursor is Ni. a Al b Zr c (OH)2·Ni d Co e Mn f (OH)2, where 0.94≤a≤0.98, 0.02≤b≤0.06, 0.001≤c≤0.003, 0.86≤d<1, 0.02<e<0.13, 0.02<f<0.

13.

2. The method for preparing a single-crystal NCMA quaternary precursor according to claim 1, characterized in that: In step one, the aluminate in the mixed solution includes one or more of sodium aluminate, potassium aluminate, or ammonium aluminate, and the pH of the mixed solution is 12.2 to 12.

8.

3. The method for preparing a single-crystal NCMA quaternary precursor according to claim 1, characterized in that: In step two, T1 = T2.

4. The method for preparing a single-crystal NCMA quaternary precursor according to claim 1, characterized in that: In step three, the precursor has a D50 of 3.1~3.9 μm, a particle size distribution of 0.55 < (D90 - D10) / D50 < 0.75, and a tap density of 1.8~2.1 g / cm³. 3 Specific surface area is 12~20m² 2 / g; The precursor has a core-shell structure, with the core layer being Ni. a Al b Zr c (OH)2, with a Ni outer shell d Co e Mn f (OH)2, the primary particles on the shell surface are uniformly arranged in a lamellar pattern, with a thickness of 100~140nm and a length of 400~480nm.

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