A low-lithium-nickel mixed NCMA quaternary positive electrode material precursor and preparation method

Abstract

A low-lithium-nickel mixed NCMA quaternary cathode material precursor, with a chemical formula of Ni a Co b Mn c Al d OOH, the preparation method includes: preparing Ni, Co, Mn metal liquid, preparing a mixed solution of aluminate and sodium hydroxide, preparing a precipitant and a complexing agent; adding pure water, precipitant and complexing agent to the kettle to prepare a bottom liquid; keeping stirring, introducing protective gas, adding metal liquid, precipitant, mixed solution and complexing agent to the kettle for co-precipitation; overflow flows to the buffer tank, and the overflow slurry temperature is 45~55℃; ozone is introduced into the buffer tank, and the slurry is pumped back to the reactor after oxidation, and the reflux slurry temperature is 70~85℃; when the particle size grows to 3.0~4.0um, stop feeding the liquid; filter, wash and dry the co-precipitated product to obtain a NCMA quaternary positive electrode material precursor with low lithium nickel mixed arrangement. The present invention can avoid Ni 2+ With Li + The mixed arrangement has low energy consumption in preparation and controllable production cost, which is conducive to industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery positive electrode materials, and in particular to a quaternary positive electrode material precursor having low lithium-nickel mixed arrangement NCMA and a preparation method thereof. Background Art

[0002] NCMA quaternary positive electrode material combines the advantages of NCM and NCA ternary positive electrode materials. It not only has a high energy density, but also has good cycle stability. It has become a new hot spot in the lithium-ion battery positive electrode material market.

[0003] However, as the nickel content of NCMA positive electrode materials increases, the Li / Ni mixing in its crystal structure becomes more serious, and its capacity and cycle performance will decrease. This is mainly because Ni 2+ With Li + The ionic radius of Ni 2+ With Li + The positions of the two electrodes are easily interchanged, resulting in an unstable crystal structure, which in turn reduces the electrical performance. Li / Ni mixing generally occurs during the preparation of NCMA quaternary cathode materials. After the NCMA quaternary cathode material precursor is mixed with the lithium source and calcined in an oxygen environment, some Ni 2+ Not oxidized Ni 3+ , entering the interlayer of lithium, causing Li / Ni mixing. Therefore, people have studied various methods to inhibit the mixing of lithium and nickel in high-nickel materials, among which the more common ones are element doping, coating, and pre-oxidation. Doping and coating can reduce lithium-nickel mixing to a certain extent, but the doped elements are generally not electrochemically active, which will cause a part of the capacity loss; pre-oxidation is to calcine the precursor at high temperature in the presence of oxygen to form Ni 3+ The oxide is then mixed with a lithium source and calcined to obtain the positive electrode material. This method achieves the purpose of reducing the mixing of lithium and nickel. The disadvantage is that the energy consumption of pre-oxidation is high and the production cost is high.

[0004] Therefore, how to prepare a quaternary positive electrode material precursor having a low lithium-nickel mixed arrangement NCMA has become a subject to be studied and solved in the present invention. Summary of the invention

[0005] The purpose of the present invention is to provide a low lithium nickel mixed NCMA quaternary positive electrode material precursor and a preparation method.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention at the product level is:

[0007] A low-lithium-nickel mixed NCMA quaternary cathode material precursor, with a chemical formula of Nia Co b Mn c Al d OOH, wherein 0.91≤a≤0.97, 0<b<0.09, 0<c<0.09, 0<d<0.9.

[0008] In the above scheme, a+b+c+d=1.

[0009] Further technical solution, D50 is 3.0-4.0um, particle size distance is 0.6<(D90-D10) / D50<0.8, and tap density is 1.6-1.8g / cm 3 , with a specific surface area of ​​25 to 45 m 2 / g; the precursor is a porous structure, and its primary particles are flaky structures with a thickness of 10 to 30 nm and a pore size of 200 to 300 nm.

[0010] In order to achieve the above object, the technical solution adopted by the present invention at the method level is:

[0011] A method for preparing a quaternary positive electrode material precursor having a low lithium-nickel mixed arrangement NCMA, comprising:

[0012] Step 1, preparing Ni, Co, and Mn metal liquids, wherein the total molar concentration of Ni, Co, and Mn is 2.0-2.5 mol / L;

[0013] Prepare a mixed solution of metaaluminate and sodium hydroxide, wherein the concentration of sodium metaaluminate is 0.15-0.25 mol / L;

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

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

[0016] Step 2: adding pure water, the precipitant and the complexing agent into a closed reactor to prepare a bottom liquid, controlling the pH value of the bottom liquid to 11.90-12.20 by the precipitant, and maintaining the temperature at 70-85° C.; the ammonia concentration in the bottom liquid is 0.2-0.3 mol / L;

[0017] Step 3, keep the reactor stirring on, introduce protective gas into the reaction system, the amount of protective gas introduced is 0.8 to 1.2 times the effective volume of the reactor per hour, and the molten metal, the precipitant, the mixed solution and the complexing agent in step 1 are continuously added to the reactor at a flow rate of 100 to 800 mL / min for co-precipitation reaction;

[0018] The overflow during the reaction flows to the buffer tank through the overflow pipe. The overflow pipe may be equipped with a cooling system to control the temperature of the slurry overflowing to the buffer tank to be 45-55°C; ozone is introduced into the buffer tank, and the amount introduced is 0.1-0.3 times the effective volume of the reactor per hour. After oxidation, the slurry in the buffer tank flows back to the reactor through a return pump. The return pipe connected to the return pump may be equipped with a heating system to control the temperature of the slurry flowing back to the reactor to be 70-85°C;

[0019] The pH value during the reaction is maintained at 11.90-12.20, the concentration of the complexing agent in the reactor is 0.2-0.3 mol / L, the synthesis temperature is maintained at 70-85°C, the speed of the reactor is 600-800 r / min, and the liquid feeding is stopped when the particle size grows to 3.0-4.0 um;

[0020] Step 4: The co-precipitated products in the reactor and the buffer tank in step 3 are filtered, washed, and dried to obtain a quaternary positive electrode material precursor having a low lithium-nickel mixed arrangement NCMA.

[0021] In a further technical solution, in step 1, the aluminate in the mixed solution includes one or more of sodium aluminate, potassium aluminate, and ammonium aluminate, and the pH of the mixed solution is 12.2 to 12.5. The sodium aluminate solution easily absorbs CO2 in the air and hydrolyzes to produce Al(OH)3 precipitation, so it is necessary to add an appropriate amount of sodium hydroxide to adjust the pH to 12.2 to 12.5 to prevent the sodium aluminate from hydrolyzing.

[0022] A further technical solution is that in step 2, the volume of the bottom liquid is 95-100% of the effective volume of the reactor. Here, adding the bottom liquid to 95-100% of the effective volume of the reactor is beneficial for the slurry in the initial stage of the reaction to flow into the buffer tank for oxidation, ensuring the uniformity of oxidation. If too little bottom liquid is added, the growth time of the initial slurry in the reactor will be prolonged, and the particle size D50 will grow too large, resulting in uneven oxidation in the buffer tank later.

[0023] According to a further technical solution, in step 3, the volume of the slurry in the buffer tank that flows back to the reactor every hour through the return pump is 3 to 5 times the effective volume of the reactor. The return pump quickly returns the slurry in the buffer tank to the reactor, thereby achieving full oxidation of the reactor material in the buffer tank. When the volume of the refluxed slurry is less than 3 times the effective volume of the reactor, some slurry will be unevenly oxidized.

[0024] The working principle and advantages of the present invention are as follows:

[0025] 1. The present invention designs a low lithium nickel mixed NCMA quaternary positive electrode material precursor, whose chemical formula is Ni a Co b Mn c Ald OOH, in which Ni, Co, and Mn elements are all +3 valence, avoiding Ni 2+ In order to avoid the generation of Ni in the preparation process of NCMA quaternary cathode materials 2+ With Li + The preparation method has low energy consumption, controllable production cost, and is conducive to industrial production.

[0026] 2. The present invention designs a low lithium nickel mixed NCMA quaternary positive electrode material precursor, whose D50 is 3.0-4.0um, particle size distance 0.6<(D90-D10) / D50<0.8, and tap density is 1.6-1.8g / cm 3 , with a specific surface area of ​​25 to 45 m 2 / g; the precursor is a porous structure, and its primary particles are flaky structures with a thickness of 10 to 30 nm and a pore size of 200 to 300 nm. Smaller particle size D50 is conducive to uniform oxidation during the preparation process, ensuring that Ni, Co, and Mn elements are all oxidized to +3 valence, narrower particle size distance can increase the consistency of the product, and higher specific surface area is conducive to increasing the contact area with oxygen during sintering, ensuring that Ni, Co, and Mn elements are fully oxidized, and flaky primary particles and 200 to 300 nm pores are conducive to the diffusion of lithium during sintering.

[0027] 3. When preparing a low-lithium-nickel mixed NCMA quaternary positive electrode material precursor, the present invention first prepares a low-valent NCMA quaternary positive electrode material precursor in a reactor under the condition of passing a protective gas, and then the slurry of the low-valent NCMA quaternary positive electrode material precursor is cooled through an overflow pipe and overflowed to a buffer tank for oxidation. After oxidation, the slurry is heated through a reflux pipe to remove ozone and then returned to the reactor to continue growing, forming a dynamic continuous growth and oxidation process, which is easy to realize large-scale industrial production. In addition, Ni 2+ 、Co 2+ , Mn 2+ 、Al 3+ Homogeneous precipitation can be achieved under the control of complexing agents, and when oxidants are added, Mn 2 + Mn will be oxidized first 3+ / Mn 4+ And precipitation is generated, resulting in uneven distribution of the four elements Ni, Co, Mn, and Al. Therefore, it is necessary to first prepare a NCMA quaternary cathode material precursor with uniform element distribution and low valence, and then oxidize it on this basis. The amount of ozone introduced into the buffer tank is 0.1 to 0.3 times the effective volume of the reactor per hour. If it is too low, it will lead to incomplete oxidation of the slurry. If it is too high, it will enter the reactor with the slurry, causing oxidation of the materials in the reactor.

[0028] 4. When preparing a quaternary positive electrode material precursor with low lithium-nickel mixed arrangement NCMA in the present invention, the slurry in the reactor needs to be cooled because ozone has a greater solubility in water at a lower temperature, which helps ozone to fully contact the material and thus achieve uniform oxidation. The oxidized slurry contains a small amount of ozone, which needs to be heated to remove residual ozone and prevent it from entering the reactor.

[0029] 5. The NCMA quaternary positive electrode material precursor with low lithium-nickel mixing prepared by the present invention is mixed with lithium hydroxide and calcined to obtain the NCMA quaternary positive electrode material with low lithium-nickel mixing, which solves the problems of low capacity and poor cycle caused by Li / Ni mixing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Attached Figure 1 This is a SEM image of the NCMA quaternary cathode material precursor prepared in an embodiment of the present invention;

[0031] Attached Figure 2 This is a SEM image of the NCMA quaternary positive electrode material precursor prepared in Comparative Example 1 of the present invention;

[0032] Attached Figure 3 This is a SEM image of the NCMA quaternary positive electrode material precursor prepared in Comparative Example 2 of the present invention;

[0033] Attached Figure 4 This is a SEM image of the NCMA quaternary positive electrode material precursor prepared in Comparative Example 3 of the present invention;

[0034] Attached Figure 5 This is the SEM image of the NCMA quaternary positive electrode material precursor prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0036] The present invention will be clearly described below with drawings and detailed descriptions. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the techniques taught by the present invention without departing from the spirit and scope of the present invention.

[0037] The terms used herein are only for describing specific embodiments and are not intended to be limiting of the present invention. The terms "include", "including", "have", etc. used herein are all open terms, meaning including but not limited to.

[0038] The terms used herein generally have the ordinary meanings of each term used in the art, in the context of the present invention, and in the specific context, unless otherwise noted. Certain terms used to describe the present invention will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art regarding the description of the present invention.

[0039] Example:

[0040] A method for preparing a quaternary positive electrode material precursor having low lithium-nickel mixed arrangement NCMA, comprising:

[0041] Step 1, preparing Ni, Co, and Mn metal liquids, wherein the total molar concentration of Ni, Co, and Mn is 2.0 mol / L;

[0042] Prepare a mixed solution of sodium aluminate and sodium hydroxide, wherein the concentration of sodium aluminate is 0.15 mol / L and the pH of the mixed solution is 12.2-12.5;

[0043] Prepare a sodium hydroxide or potassium hydroxide solution with a concentration of 10 mol / L as a precipitant;

[0044] Prepare an ammonia solution with a concentration of 2 mol / L as a complexing agent;

[0045] Step 2: adding pure water, the precipitant and the complexing agent into a closed reactor to prepare a bottom liquid, controlling the pH value of the bottom liquid to 11.90-12.20 by the precipitant, maintaining the temperature at 80° C., and the volume of the bottom liquid to 95%-100% of the effective volume of the reactor; the ammonia concentration in the bottom liquid is 0.25 mol / L;

[0046] Step 3, keep the reactor stirring on, introduce protective gas into the reaction system, the amount of protective gas introduced is 1 times the effective volume of the reactor per hour, and the molten metal, the precipitant, the mixed solution and the complexing agent in step 1 are continuously added to the reactor at a flow rate of 100 to 800 mL / min for co-precipitation reaction;

[0047] The overflow during the reaction flows to the buffer tank through the overflow pipe. The overflow pipe is equipped with a cooling system. The temperature of the slurry overflowing to the buffer tank is 50°C. Ozone is introduced into the buffer tank, and the amount introduced is 0.2 times the effective volume of the reactor per hour. After oxidation, the slurry in the buffer tank flows back to the reactor through a return pump. The return pipe connected to the return pump is equipped with a heating system. The temperature of the slurry flowing back to the reactor is 80°C. The volume of the slurry in the buffer tank flowing back to the reactor through the return pump per hour is 2 to 4 times the effective volume of the reactor.

[0048] The pH value during the reaction was maintained at 11.90-12.20, the concentration of the complexing agent in the reactor was 0.25 mol / L, the synthesis temperature was maintained at 80°C, the rotation speed of the reactor was 750 r / min, and the liquid feeding was stopped when the particle size grew to 3.59 um.

[0049] Step 4: The coprecipitated products of the reactor and the buffer tank in step 3 are filtered, washed and dried to obtain a low lithium nickel mixed NCMA quaternary positive electrode material precursor. The chemical formula of the product is Ni 0.92 Co 0.03 Mn 0.03 Al 0.02 OOH, D50 is 3.58um, particle size spacing is 0.75, and tap density is 1.67g / cm 3 , with a specific surface area of ​​31m 2 / g, the precursor is a porous structure, the primary particles are a flaky structure with a thickness of 10 to 30 nm and a pore size of 200 to 300 nm.

[0050] Finally, the above-mentioned low lithium nickel mixed NCMA quaternary positive electrode material precursor is evenly mixed with lithium hydroxide, calcined at 600-800°C for 15-30h under oxygen flow, and then naturally cooled to room temperature to obtain a low lithium nickel mixed NCMA quaternary positive electrode material. Relevant data are shown in Table 1.

[0051] Comparative Example 1:

[0052] The difference from the embodiment is that the amount of the base liquid added in step 2 is different, the volume of the base liquid in this comparative example is 80% of the effective volume of the reactor, and the rest is exactly the same as in embodiment 1. The obtained precursor is washed and dried, and the relevant data are shown in Table 1.

[0053] Comparative Example 2:

[0054] The difference from the embodiment is that the ozone flow rate introduced into the buffer tank in step 3 is different. The ozone introduction amount in this comparative example is 0.08 times of the effective volume of the reactor per hour, and the rest is exactly the same as the embodiment. The obtained precursor is washed and dried, and the relevant data are shown in Table 1.

[0055] Comparative Example 3:

[0056] The difference from the embodiment is that the ozone flow rate introduced into the buffer tank in step 3 is different. The ozone introduction amount in this comparative example is 0.4 times the effective volume of the reactor per hour, and the rest is exactly the same as that of embodiment 1. The obtained precursor is washed and dried, and the relevant data are shown in Table 1.

[0057] Comparative Example 4:

[0058] The difference from the embodiment is that in step 3, the volume of the slurry in the buffer tank that flows back to the reactor through the return pump per hour is different. In this comparative example, the volume of the slurry in the buffer tank that flows back to the reactor through the return pump per hour is 1 times the effective volume of the reactor, and the rest is exactly the same as the embodiment. The precursor is washed and dried, and the relevant data are shown in Table 1.

[0059] Table 1 is a comparison of the finished product data of the products obtained in the embodiments and the comparative examples.

[0060]

[0061] From the data in Table 1, it can be seen that the D50 of the embodiment and the comparative examples are close, while the particle size of the NCMA quaternary positive electrode material precursor prepared in comparative example 3 is wider than the others. This is mainly because excessive ozone is introduced into the reactor from the buffer tank, resulting in uneven precipitation of the four elements Ni, Co, Mn, and Al, producing fine powder, which in turn causes the particle size distribution to become wider. After the embodiment and the comparative examples are prepared into positive electrode materials, the electrical performance of the embodiment is the best, corresponding to the lowest Li / Ni mixed arrangement.

[0062] Figure 1 to Figure 5 The SEM images of the NCMA quaternary positive electrode material precursors prepared in Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are shown in FIG. Figure 4 It can be seen that the primary particles of Comparative Example 3 are loose and contain fine powder, which is caused by oxidation after excessive ozone enters the reactor.

[0063] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A low lithium nickel mixed NCMA quaternary positive electrode material precursor, characterized in that: The chemical formula is Ni a Co b Mn c Al d OOH, where 0.91≤a≤0.97, 0<b<0.09, 0<c<0.09, 0<d<0.9; D50 is 3.0~4.0um, particle size distance is 0.6<(D90-D10) / D50<0.8, and tap density is 1.6~1.8g / cm 3 , with a specific surface area of ​​25~45m 2 / g; the precursor has a porous structure, and its primary particles are flaky structures with a thickness of 10-30nm and a pore size of 200-300nm.

2. A method for preparing a quaternary positive electrode material precursor having low lithium-nickel mixed NCMA, characterized in that: Used to prepare the low lithium nickel mixed NCMA quaternary positive electrode material precursor in claim 1; The preparation method comprises: Step 1, preparing Ni, Co, and Mn metal liquids, wherein the total molar concentration of Ni, Co, and Mn is 2.0-2.5 mol / L; Prepare a mixed solution of metaaluminate and sodium hydroxide, wherein the concentration of sodium metaaluminate is 0.15-0.25 mol / L; 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 a complexing agent; Step 2: adding pure water, the precipitant and the complexing agent into a closed reactor to prepare a bottom liquid, controlling the pH value of the bottom liquid to 11.90-12.20 by the precipitant, and maintaining the temperature at 70-85° C.; the ammonia concentration in the bottom liquid is 0.2-0.3 mol / L; Step 3, keep the reactor stirring on, introduce protective gas into the reaction system, the amount of protective gas introduced is 0.8 to 1.2 times the effective volume of the reactor per hour, and the molten metal, the precipitant, the mixed solution and the complexing agent in step 1 are continuously added to the reactor at a flow rate of 100 to 800 mL / min for co-precipitation reaction; The overflow during the reaction flows to the buffer tank, and the temperature of the slurry overflowing to the buffer tank is controlled to be 45~55°C; ozone is introduced into the buffer tank, and the amount introduced is 0.1~0.3 times the effective volume of the reactor per hour. After the slurry in the buffer tank is oxidized, it is pumped back to the reactor, and the temperature of the slurry returning to the reactor is controlled to be 70~85°C; The pH value during the reaction was maintained at 11.90-12.20, the concentration of the complexing agent in the reactor was 0.2-0.3 mol / L, the synthesis temperature was maintained at 70-85°C, the speed of the reactor was 600-800 r / min, and the liquid was stopped when the particle size grew to 3.0-4.0 um; Step 4: The co-precipitated products in the reactor and the buffer tank in step 3 are filtered, washed, and dried to obtain a quaternary positive electrode material precursor having a low lithium-nickel mixed arrangement NCMA.

3. The preparation method according to claim 2, characterized in that: In step 1, the aluminate in the mixed solution includes one or more of sodium aluminate, potassium aluminate, and ammonium aluminate, and the pH of the mixed solution is 12.2-12.

5.

4. The preparation method according to claim 2, characterized in that: In step 2, the volume of the base liquid is 95-100% of the effective volume of the reactor.

5. The preparation method according to claim 2 or 4, characterized in that: In step three, the volume of the slurry in the buffer tank that flows back to the reactor through the return pump per hour is 3 to 5 times the effective volume of the reactor.

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