Nickel-manganese binary precursor, preparation method thereof, positive electrode material and lithium ion battery

Abstract

The present application discloses a nickel-manganese binary precursor, a preparation method thereof, a cathode material, and a lithium-ion battery. The preparation method of the nickel-manganese binary precursor includes: providing a nickel-manganese salt solution, a precipitating agent, and a complexing agent; mixing the nickel-manganese salt solution, the precipitating agent, and the complexing agent to carry out a coprecipitation reaction to obtain the nickel-manganese binary precursor, and the chemical general formula of the nickel-manganese binary precursor is Ni x Mn y (OH) 2 , where x + y = 1, 0 < x < 0.40, 0 < y < 0.95; wherein, the process of the coprecipitation reaction includes: reacting for 10 - 60 min under the conditions of pH being 11.20 - 12.20 and ammonia concentration being 3.0 - 5.0 g / L to obtain a seed solution, and then reducing the pH to 10.2 - 10.8 to continue the reaction, and ending the reaction when the product particle size D 50 = 10.0 - 11.0 μm. This preparation method not only has a simple process, but also can obtain a nickel-manganese binary precursor with high sphericity and narrow particle size distribution.

Description

Nickel-manganese binary precursors and their preparation methods, cathode materials and lithium-ion batteries Technical Field

[0001] This application belongs to the field of battery materials technology, and particularly relates to a nickel-manganese binary precursor and its preparation method, a cathode material, and a lithium-ion battery. Background Technology

[0002] With the development of the electric vehicle and energy storage industries, the application scope of lithium-ion batteries has further expanded, leading to a demand for lithium-ion batteries with higher energy density. Among the many solutions to improve energy density, cathode materials are a widely recognized and important direction. Currently commercially available lithium-ion battery cathode materials include lithium iron phosphate, lithium manganese oxide, ternary materials such as nickel-cobalt-manganese oxide, and lithium cobalt oxide. However, these cathode materials are limited by factors such as theoretical capacity or safety, making it difficult to achieve the goal of higher energy density in power batteries. Therefore, finding a lithium-ion battery cathode material with high theoretical capacity and good safety performance is particularly important.

[0003] Currently, lithium-rich manganese-based cathode materials are expected to become an important supplement to the cathode material market due to their advantages such as high capacity, high voltage, and low cost, and are considered the most promising cathode materials for lithium-ion batteries. Lithium-manganese-based cathode materials are generally obtained by calcining a mixture of a nickel-manganese binary precursor and a lithium salt. Currently, the preparation process of the nickel-manganese binary precursor is cumbersome, and the resulting precursor has poor sphericity and uniformity, thus affecting the electrochemical performance of the cathode material. Summary of the Invention

[0004] The purpose of this application is to provide a nickel-manganese binary precursor and its preparation method, a cathode material, and a lithium-ion battery, aiming to solve the technical problem of how to prepare a nickel-manganese binary precursor with better dimensions.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a method for preparing a nickel-manganese binary precursor, comprising:

[0007] Provides nickel-manganese salt solutions, precipitants, and complexing agents;

[0008] The nickel-manganese salt solution, the precipitant, and the complexing agent are mixed and subjected to a co-precipitation reaction to obtain a nickel-manganese binary precursor. The general chemical formula of the nickel-manganese binary precursor is Ni. x Mn y (OH)₂, x + y = 1, 0 <x<0.40,0<y<0.95;

[0009] The coprecipitation reaction process includes: reacting for 10-60 minutes at a pH of 11.20-12.20 and an ammonia concentration of 3.0-5.0 g / L to obtain a seed solution, then lowering the pH to 10.2-10.8 and continuing the reaction until the product particle size D... 50 The reaction ends when the atom density reaches 10.0-11.0 μm.

[0010] Secondly, this application provides a nickel-manganese binary precursor, which is prepared by the preparation method provided in the first aspect of this application.

[0011] Thirdly, this application provides a cathode material obtained by calcining a nickel-manganese binary precursor provided in the second aspect of this application with a lithium source.

[0012] Fourthly, this application provides a lithium-ion battery, including the positive electrode material provided in the third aspect of this application.

[0013] The method for preparing a nickel-manganese binary precursor provided in the first aspect of this application involves mixing a nickel-manganese salt solution, a precipitant, and a complexing agent to carry out a unique co-precipitation reaction process. Specifically, the reaction is carried out for 10-60 minutes at a pH of 11.20-12.20 and an ammonia concentration of 3.0-5.0 g / L, followed by lowering the pH to 10.2-10.8 and continuing the reaction until the product particle size D... 50 The reaction ends when the particle size reaches 10.0-11.0 μm. This preparation method is not only simple, but also yields nickel-manganese binary precursors with high sphericity, narrow particle size distribution, and high specific surface area and tap density. Using such nickel-manganese binary precursors as cathode materials for lithium-ion batteries can improve electrochemical performance.

[0014] The nickel-manganese binary precursor provided in the second aspect of this application is prepared by a method unique to this application. Therefore, such a nickel-manganese binary precursor has the characteristics of high sphericity, narrow particle size distribution, and high specific surface area and tap density. Thus, when such a nickel-manganese binary precursor is made into a cathode material for lithium-ion batteries, its electrochemical performance can be improved.

[0015] The cathode material provided in the third aspect of this application is obtained by calcining a nickel-manganese binary precursor unique to this application with a lithium source. Based on the characteristics of this nickel-manganese binary precursor, the cathode material of this application exhibits excellent electrochemical performance.

[0016] The lithium-ion battery provided in the fourth aspect of this application uses a cathode material unique to this application, and therefore the lithium-ion battery has excellent electrochemical performance. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is a 3000x scanning electron microscope image of the nickel-manganese binary precursor provided in Example 1 of this application;

[0019] Figure 2 is a 10,000x scanning electron microscope image of the nickel-manganese binary precursor provided in Example 1 of this application;

[0020] Figure 3 is a particle size distribution diagram of the nickel-manganese binary precursor provided in Example 1 of this application;

[0021] Figure 4 is a 3000x scanning electron microscope image of the nickel-manganese binary precursor provided in Example 2 of this application;

[0022] Figure 5 is a 10,000x scanning electron microscope image of the nickel-manganese binary precursor provided in Example 2 of this application;

[0023] Figure 6 is a particle size distribution diagram of the nickel-manganese binary precursor provided in Example 2 of this application;

[0024] Figure 7 is a 3000x scanning electron microscope image of the nickel-manganese binary precursor provided in Example 3 of this application;

[0025] Figure 8 is a 10,000x scanning electron microscope image of the nickel-manganese binary precursor provided in Example 3 of this application;

[0026] Figure 9 is a particle size distribution diagram of the nickel-manganese binary precursor provided in Example 3 of this application. Detailed Implementation

[0027] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items.

[0030] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0031] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0032] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0033] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0034] In the pursuit of high-energy all-solid-state lithium batteries (ASSBs), lithium-rich manganese oxide (LRMO) cathodes offer a promising path forward due to their unexpectedly high capacity, low cost, and excellent processing performance, exhibiting superior energy density and cycle performance. Given the outstanding performance of LRMO materials in all-solid-state batteries, the preparation of related precursor materials is a key influencing factor.

[0035] Some reports suggest that template agents, structure control agents, or hydrogen peroxide can be added during the co-precipitation reaction to assist in the preparation of nickel-manganese binary precursors. However, such processes are complex, have difficulties in wastewater treatment, and result in precursors with loose morphology and low tap density.

[0036] To overcome the shortcomings of current nickel-manganese binary precursor preparation processes, this application employs a wet co-precipitation method. By controlling the process parameters during co-precipitation, a low-nickel, high-manganese precursor for lithium-rich manganese-based cathode materials—namely, a nickel-manganese binary precursor—can be easily prepared, characterized by large particles, high sphericity, narrow particle size distribution, and both high tap density and high specific surface area. The specific scheme is as follows.

[0037] The first aspect of this application provides a method for preparing a nickel-manganese binary precursor, comprising the following steps:

[0038] S01: Provides nickel-manganese salt solutions, precipitants, and complexing agents;

[0039] SO2: A nickel-manganese salt solution, a precipitant, and a complexing agent are mixed and subjected to a co-precipitation reaction to obtain a nickel-manganese binary precursor. The general chemical formula of the nickel-manganese binary precursor is Ni. x Mn y (OH)₂, x + y = 1, 0 <x<0.40,0<y<0.95;

[0040] The coprecipitation reaction process includes: reacting for 10-60 minutes at a pH of 11.20-12.20 and an ammonia concentration of 3.0-5.0 g / L to obtain a seed solution, then lowering the pH to 10.2-10.8 to continue the reaction, resulting in a product with a particle size D. 50 The reaction ends when the atom density reaches 10.0-11.0 μm.

[0041] In this embodiment, a nickel-manganese salt solution, a precipitant, and a complexing agent are mixed to carry out a unique co-precipitation reaction process. Specifically, the reaction is carried out for 10-60 minutes at a pH of 11.20-12.20 and an ammonia concentration of 3.0-5.0 g / L, followed by lowering the pH to 10.2-10.8 and continuing the reaction until the product particle size D... 50 The reaction ends when the particle size reaches 10.0-11.0 μm. This preparation method is not only simple, but also yields nickel-manganese binary precursors with high sphericity, narrow particle size distribution, and high specific surface area and tap density. Using such nickel-manganese binary precursors as cathode materials for lithium-ion batteries can improve electrochemical performance.

[0042] During the coprecipitation reaction process of the embodiments of the present application: In the conditions for initially reacting to obtain the seed solution, the pH can be 11.2, 11.4, 11.6, 11.8, 12.0, 12.2, etc., the ammonia concentration can be 3.0 g / L, 3.5 g / L, 4.0 g / L, 4.5 g / L, 4.8 g / L, 5.0 g / L, etc. The ammonia concentration can be understood as the concentration of ammonium ions in the reaction system, and the reaction time can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc. Specifically, first react for 10 - 60 min under the conditions of pH being 11.20 - 12.20 and ammonia concentration being 3.0 - 5.0 g / L, so as to obtain a seed solution containing crystals of a certain shape and a certain quantity. Then lower the pH to 10.2 - 10.8 and continue the reaction to obtain the product particle size D 50 When = 10.0 - 11.0 μm, the reaction ends. The specific value after the pH is lowered can be 10.2, 10.4, 10.5, 10.6, 10.8, and the final obtained product particle size D 50 can be 10.2 μm, 10.3 μm, 10.4 μm, 10.6 μm, 10.8 μm, 11.0 μm, etc.

[0043] In some embodiments, when the pH is lowered to 10.2 - 10.8 and the reaction continues, the ammonia concentration can remain unchanged at 3.0 - 5.0 g / L, and the reaction continues for about 60 h - 100 h, such as 60 h, 70 h, 80 h, 85 h, 90 h, 95 h, 100 h, etc. Finally, a nickel - manganese binary precursor with particle size D 50 = 10.0 - 11.0 μm can be obtained.

[0044] The above - mentioned preparation method provided by the embodiments of the present application does not involve the functions of template agents, structure - controlling agents or auxiliary agents such as hydrogen peroxide. Thus, the process is short and the operation is simple. The obtained nickel - manganese binary precursor has a high sphericity, a narrow particle size distribution, and the particles are "twisted" in a "spiral - like" shape, and the primary particles are in a shuttle - like shape.

[0045] In some embodiments, the chemical general formula of the nickel - manganese binary precursor prepared by the above - mentioned preparation method of the embodiments of the present application is Ni x Mn y (OH)2, x + y = 1, 0 < x < 0.40, 0 < y < 0.95. Specifically, 0.1 ≤ x ≤ 0.30, 0.7 ≤ y ≤ 0.90. For example, x = 0.1, y = 0.9, or x = 0.15, y = 0.85, or x = 0.2, y = 0.8, or x = 0.25, y = 0.75, or x = 0.3, y = 0.7. The embodiments of the present application can prepare low - nickel and high - manganese large - particle precursors for lithium - rich manganese - based cathode materials, which are used for lithium - rich manganese - based cathodes of all - solid - state batteries.

[0046] In some embodiments, the particle size distribution of the prepared nickel-manganese binary precursor is 0.30 < k90 < 0.40. For example, k90 = 0.31, or k90 = 0.32, or k90 = 0.33, or k90 = 0.34, or k90 = 0.35, or k90 = 0.36, or k90 = 0.37, etc.

[0047] Particle size D 100 and particle size D 90 and particle size D 50 and particle size D 10 are respectively the equivalent diameters of the largest particles when the cumulative distributions in the particle size distribution curve are 100%, 90%, 50%, and 10%. Specifically, it refers to the volume distribution particle size. k90 = (D 90 - D 10 ) / D 50 is the particle size distribution parameter, also known as the diameter distance, which is a key indicator for measuring the consistency of the particle size of the nickel-manganese binary precursor. The smaller this value, the more uniform the particle distribution and the better the consistency of the particle size. The larger it is, the wider the particle distribution and the worse the consistency of the particle size. The particle size distribution of the nickel-manganese binary precursor in the embodiments of this application is 0.30 < k90 < 0.40, indicating better consistency.

[0048] In some embodiments, the prepared nickel-manganese binary precursor satisfies: the tapped density is 1.80 - 2.2 g / m 3 , the specific surface area is 15 - 30 m 2 / g, and the particle size distribution is 0.30 < k90 < 0.40.

[0049] The tapped density (TD) refers to the mass per unit volume measured after the powder in the container is tapped under certain conditions. The larger the tapped density, the better the capacity can be exerted. The specific surface area (BET) is the total area per unit mass of the material. The larger the specific surface area, the more conducive it is to the diffusion of lithium ions, thereby improving the rate performance and the better the capacity exertion. The tapped density and the specific surface area can be tested by common methods in the battery material industry. Exemplarily, the tapped density of the nickel-manganese binary precursor prepared in the embodiments of this application can be 1.80 g / m 3 , 1.90 g / m 3 , 2.0 g / m 3 , 2.1 g / m 3 , 2.2 g / m 3 , etc.; the specific surface area of the nickel-manganese binary precursor prepared in the embodiments of this application can be 15 m 2 / g, 18 m 2 / g, 20 m 2 / g, 22 m 2 / g, 24 m 2 / g, 26 m2 / g, 28 m 2 / g, 30 m 2 / g, etc.

[0050] The nickel-manganese binary precursor prepared in the embodiments of the present application satisfies: the tapped density is 1.80 - 2.2 g / m 3 , the specific surface area is 15 - 30 m 2 / g, and the particle size distribution is 0.30 < k90 < 0.40. Therefore, it has good particle size. After making the cathode material of the lithium-ion battery based on such a nickel-manganese binary precursor, the electrochemical performance can be improved.

[0051] In some embodiments, the nickel-manganese salt solution is a solution formed by dissolving soluble nickel salt and manganese salt in water. The soluble nickel salt can be at least one of nickel sulfate, nickel nitrate, nickel acetate, and nickel chlorate, and the soluble manganese salt can be at least one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chlorate. The nickel-manganese molar ratio in the nickel-manganese salt solution can be adjusted according to the ratio of x and y in the chemical general formula Ni x Mn y (OH)2. Further, the total concentration of nickel and manganese in the nickel-manganese salt solution is 1 - 2.5 mol / L.

[0052] In some embodiments, the precipitating agent includes at least one of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution. That is, the precipitating agent can be an alkaline solution, and the concentration of the precipitating agent is 8 - 15 mol / L; the above precipitating agent solution can provide hydroxide ions or carbonate ions to ensure the stable precipitation of metal ions.

[0053] In some embodiments, the complexing agent includes ammonia water solution, and the concentration of the ammonia water solution is 100 - 150 g / L. In the complexing environment of ammonia water, the precipitation of nickel and manganese ions can be made more stable, and a precursor with better particle size can be obtained.

[0054] In some embodiments, the step of mixing the nickel-manganese salt solution, the precipitating agent, and the complexing agent includes: adding the nickel-manganese salt solution, the precipitating agent, and the complexing agent into the bottom liquid in a concurrent flow manner, and the pH of the bottom liquid is 11.20 - 12.20 and the ammonia concentration is 3.0 - 5.0 g / L. The bottom liquid can be a bottom liquid obtained by mixing ammonia water and the precipitating agent alkaline solution. The pH and ammonia concentration of the bottom liquid are consistent with the coprecipitation reaction, so as to provide stable coprecipitation reaction conditions for the initial mixing of the nickel-manganese salt solution, the precipitating agent, and the complexing agent.

[0055] In some embodiments, the conditions for the coprecipitation reaction include a temperature of 50-65°C and a stirring speed of 300-450 rpm. Specifically, throughout the entire coprecipitation reaction, the temperature can be 50°C, 52°C, 54°C, 58°C, 60°C, 62°C, 65°C, etc., and the stirring speed can be 300 rpm, 320 rpm, 340 rpm, 380 rpm, 400 rpm, 420 rpm, 450 rpm, etc. Under these conditions, the coprecipitation reaction proceeds gently, preventing particle breakage.

[0056] In some embodiments, after the co-precipitation reaction is completed, the process further includes aging, washing, and drying in sequence. Aging, washing, and drying can yield a nickel-manganese binary precursor with better purity.

[0057] In one specific embodiment, the specific preparation steps of the nickel-manganese binary precursor include:

[0058] (1) Prepare a nickel-manganese salt solution with a total metal ion concentration of 1-2.5 mol / L, an alkaline solution (such as sodium hydroxide solution) with a concentration of 8-15 mol / L, and an ammonia solution with a concentration of 100-150 g / L.

[0059] (2) Purge the sealed reactor with submerged nitrogen protective gas for 3-8 hours at a flow rate of 2-4 m³ / h. 3 After achieving complete air replacement, add deionized water to the reactor to submerge the middle layer of stirring. Turn on the stirrer at 300-450 rpm and control the temperature at 50-65℃.

[0060] (3) Add complexing agent ammonia water to the main reactor in sequence, control the ammonia value at 3.0-5.0 g / L, and add alkali solution to adjust the pH of the system to 11.20-12.20, which serves as the base liquid and starting condition for the reaction.

[0061] (4) After completing (3) above, adjust the nitrogen flow rate to 1-2m below the liquid level. 3 / h, 0-1.5m above liquid 3 / h.

[0062] (5) Add nickel manganese salt solution, sodium hydroxide solution and ammonia solution to the reaction vessel at the same time and maintain the inert gas flow. During this period, maintain the pH of the system at 11.20-12.20, the ammonia value at 3.0-5.0 g / L, and the temperature at 50-65℃.

[0063] (6) After the reaction is started for 10-60 minutes, a seed solution is obtained. Then, in order to meet the further growth of the particles, the pH is lowered to 10.2-10.8.

[0064] (7) Under the conditions of pH = 10.2 - 10.8 and ammonia value = 3.0 - 5.0 g / L, reacting for about 60 - 100 h can make the particle size D of the reaction product 50 = 10.0 - 11.0 μm. After the reaction ends and the machine stops for 30 - 60 min, when the particle size is复测 without abnormality, the slurry is put into the aging tank for aging and waiting for washing.

[0065] (9) Pump the slurry in the aging tank into the washing equipment and wash it with a sodium hydroxide solution with a concentration of 30 - 80 g / L.

[0066] (10) The washed binary nickel - manganese precursor filter cake is placed in an oven for static drying. After the moisture is qualified and the drying ends, a nickel - manganese binary precursor with a narrow particle size distribution (0.30 < k90 < 0.40), primary particles in a shuttle - like shape, and high sphericity can be obtained. At the same time, this nickel - manganese binary precursor exhibits the characteristics of a high specific surface area and a high tap density. Finally, the dried material can also be sieved and demagnetized to obtain the corresponding precursor finished product for use in the sintering of the cathode material.

[0067] The second aspect of the embodiment of the present application provides a nickel - manganese binary precursor, which is prepared by the preparation method provided in the first aspect of the embodiment of the present application.

[0068] Based on the technological characteristics of the above - mentioned preparation method, the nickel - manganese binary precursor of the embodiment of the present application has the characteristics of high sphericity, narrow particle size distribution, and both a relatively high specific surface area and tap density. Therefore, when such a nickel - manganese binary precursor is made into the cathode material of a lithium - ion battery, the electrochemical performance can be improved.

[0069] In some embodiments, the chemical general formula of the nickel - manganese binary precursor is Ni x Mn y (OH)2, x + y = 1, 0 < x < 0.40, 0 < y < 0.95. Specifically, 0.1 ≤ x ≤ 0.30, 0.7 ≤ y ≤ 0.90. Specifically, the nickel - manganese binary precursor particles satisfy: the tap density is 1.80 - 2.2 g / m 3 , the specific surface area is 15 - 30 m 2 / g, and the particle size distribution is 0.30 < k90 < 0.40.

[0070] The third aspect of the embodiment of the present application provides a cathode material, which is obtained by mixing and calcining the nickel - manganese binary precursor provided in the second aspect of the embodiment of the present application with a lithium source. Based on the characteristics of the nickel - manganese binary precursor, the cathode material of the embodiment of the present application has good electrochemical performance.

[0071] Among them, the lithium source can be a lithium salt commonly used in the preparation of the cathode material, and the related sintering process is also a commonly used sintering process.

[0072] A fourth aspect of this application provides a lithium-ion battery, including the positive electrode material provided in the third aspect of this application. Because the lithium-ion battery uses a positive electrode material unique to this application, it exhibits excellent electrochemical performance.

[0073] The following description is based on specific embodiments.

[0074] Example 1

[0075] A method for preparing a nickel-manganese binary precursor includes the following steps:

[0076] (1) Dissolve nickel sulfate and manganese sulfate in deionized water to prepare a nickel-manganese salt solution with a total nickel-manganese metal ion concentration of 2 mol / L, wherein the molar ratio of nickel to manganese is 3:7; dissolve sodium hydroxide in deionized water to prepare a sodium hydroxide solution with a concentration of 10.5 mol / L; dissolve ammonia gas in deionized water to prepare an ammonia solution with a concentration of 125 g / L.

[0077] (2) Purge the sealed reactor with submerged nitrogen protective gas for 4 hours at a flow rate of 2.5 m³ / h. 3 During the process, deionized water is added to the main reactor to submerge the middle layer of the stirrer. The stirrer is started at 340 rpm, and the temperature is controlled at 55℃.

[0078] (3) Add ammonia solution and sodium hydroxide solution to the reaction vessel in sequence to obtain the bottom liquid. Control the ammonia concentration of the bottom liquid at 4.2 g / L and pH = 11.40 as the conditions for starting the reaction.

[0079] (4) After completing (3) above, adjust the nitrogen flow rate to 1.5m below the liquid level. 3 / h, 1m above liquid 3 / h.

[0080] (5) Add nickel manganese salt solution, sodium hydroxide solution and ammonia solution to the reaction vessel at the same time and maintain the inert gas flow. During this period, maintain the pH of the system at 11.40, the ammonia value at 4.2 g / L and the temperature at 55℃.

[0081] (6) Turn on the machine and react for 10 minutes. Then lower the pH to ensure that the pH is 10.40.

[0082] (7) The reaction was continued for about 75 hours under the conditions of pH=10.40 and ammonia value=4.2g / L. The final reaction product particle size D 50 The particle size is approximately 10.445 μm. After the reaction is complete and the machine is stopped for 30-60 minutes, the particle size is retested and found to be normal. The slurry is then placed in an aging tank for aging until it is ready for washing.

[0083] (8) The slurry in the aging tank is pumped into the washing equipment and washed with a sodium hydroxide solution with a concentration of 40 g / L.

[0084] (9) The washed binary nickel-manganese precursor filter cake was placed in an oven for static drying to obtain the nickel-manganese binary precursor material.

[0085] (10) Finally, the dried material can be sieved and demagnetized to obtain the corresponding Ni. 0.30 Mn 0.70 (OH)2 nickel-manganese binary precursor finished product.

[0086] Example 2

[0087] A method for preparing a nickel-manganese binary precursor includes the following steps:

[0088] The difference from Example 1 is that the pH controlled in steps (3) and (5) is replaced with 12.20, and the pH controlled in steps (6) and (7) is replaced with 10.80; the other step parameters are the same as in Example 1, and the particle size D of the final reaction product is obtained. 50 It is approximately 10.437 μm.

[0089] Example 3

[0090] A method for preparing a nickel-manganese binary precursor includes the following steps:

[0091] The difference from Example 1 is that the ammonia value controlled in steps (3), (5), and (7) is replaced with 3.5 g / L; the other step parameters are the same as in Example 1, and the particle size D of the final reaction product is obtained. 50 It is approximately 10.433 μm.

[0092] Comparative Example 1

[0093] A method for preparing a nickel-manganese binary precursor includes the following steps:

[0094] The difference from Example 1 is that the pH remains constant throughout the reaction process; specifically, steps (3)-(7) are replaced by: simultaneously adding nickel-manganese salt solution, sodium hydroxide solution, and ammonia solution to the bottom liquid of the reactor, while maintaining the introduction of inert gas. The pH of the bottom liquid and the system during the reaction are maintained at 10.4, the ammonia value at 4.2 g / L, the temperature at 55°C, and the total reaction time at 75 h. Other parameters are the same as in Example 1 until the reaction is completed. The final particle size D of the reaction product is obtained. 50 It is approximately 10.50 μm.

[0095] Comparative Example 2

[0096] A method for preparing a nickel-manganese binary precursor includes the following steps:

[0097] The difference from Example 1 is that the decrease in pH during the reaction process is relatively small; specifically, the pH controlled in steps (3) and (5) is replaced with 12.20, and the pH controlled in step (7) is replaced with 11.20. The parameters of other steps are the same as those in Example 1. The particle size D of the finally obtained reaction product 50 is about 10.45 μm.

[0098] Performance test

[0099] The particles of the examples and comparative examples were tested: D 50 The index data of BET, TD, and K90 are shown in Table 1 below.

[0100] Table 1

[0101]

[0102]

[0103] Figures 1 and 2 are SEM images of the nickel-manganese binary precursor in Example 1, and Figure 3 is the particle size distribution diagram of the nickel-manganese binary precursor in Example 1; Figures 4 and 5 are SEM images of the nickel-manganese binary precursor in Example 2, and Figure 6 is the particle size distribution diagram of the nickel-manganese binary precursor in Example 2; Figures 7 and 8 are SEM images of the nickel-manganese binary precursor in Example 3, and Figure 9 is the particle size distribution diagram of the nickel-manganese binary precursor in Example 3.

[0104] It can be seen from the SEM images that the particles of the nickel-manganese binary precursor in Example 1 are "twisted" and wound, and a single whisker is arranged in a "shuttle-like" flat pattern. In Example 2, with the increase of the process pH, the number of process seeds further increases, and finally the sphericity of the particles is improved, and the overall morphology maintains the state of Example 1. In Example 3, during the synthesis process, the ammonia value is reduced to further reduce the thickness of a single whisker of the particles, so as to further increase the specific surface area. It can be seen that the particles of this low-nickel high-manganese binary precursor also show "twisted" winding, and the primary whiskers are slightly thinner. [[ID=�0]]

[0105] From the particle size distribution diagram, the nickel-manganese binary precursors prepared in Examples 1-3 as a whole show a narrow distribution (0.30 < k90 < 0.40), the particle size is concentrated in the range of 10.0-11.0 μm, and the sphericity is high, which is convenient for later centralized processing.

[0106] (2) Electrochemical performance test

[0107] The nickel-manganese binary precursors prepared in the examples and comparative examples were used to prepare cathode materials. The preparation steps included: mixing the nickel-manganese binary precursor with lithium oxide in an oxygen atmosphere at a mass ratio of 1:1.05, and then calcining it in a tube furnace using a two-stage calcination process: heating to 400℃ and holding for 6 hours, followed by heating to 750℃ and holding for 18 hours. After sieving, demagnetizing, and packaging, the nickel-manganese binary cathode material was obtained. Then, the same mass of the nickel-manganese binary cathode material was used to prepare button half-cells according to the ratio of nickel-manganese binary cathode material: acetylene black: PVDF = 91:3.5:5.5, with lithium metal sheets used as the anode. The prepared button half-cells were subjected to electrochemical performance tests under conditions of 2.75-4.30V and 200-cycle performance tests at room temperature (25℃). The results are shown in Table 2 below.

[0108] Table 2

[0109]

[0110] Based on the test performance, the cathode material prepared in the embodiments of this application exhibits excellent electrochemical performance.

[0111] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a nickel-manganese binary precursor, characterized in that, include: Provide nickel-manganese salt solutions, precipitants, and complexing agents; Mix the nickel-manganese salt solution, the precipitant and the complexing agent to carry out a coprecipitation reaction to obtain a nickel-manganese binary precursor with a particle size distribution of 0.30 < k90 < 0.

40. The chemical general formula of the nickel-manganese binary precursor is Ni x Mn y (OH)2, where x + y = 1, 0 < x < 0.40, and 0 < y < 0.

95. Among them, the process of the coprecipitation reaction includes: reacting for 10 - 60 min under the conditions of pH being 11.20 - 12.20 and ammonia concentration being 3.0 - 5.0 g / L to obtain a seed solution, and then reducing the pH to 10.2 - 10.8 and keeping the ammonia concentration unchanged to continue the reaction until the product particle size D 50 = 10.0 - 11.0 μm, and then ending the reaction.

2. The preparation method according to claim 1, characterized in that, In the general chemical formula of the nickel-manganese binary precursor, 0.1≤x≤0.30, 0.7≤y≤0.

90.

3. The preparation method according to claim 1, characterized in that, The step of mixing the nickel-manganese salt solution, the precipitant, and the complexing agent includes: adding the nickel-manganese salt solution, the precipitant, and the complexing agent in a co-current manner to a base solution, wherein the pH of the base solution is 11.20-12.20 and the ammonia concentration is 3.0-5.0 g / L; and / or after the co-precipitation reaction is completed, the step further includes aging, washing, and drying in sequence.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The total concentration of nickel and manganese in the nickel-manganese salt solution is 1-2.5 mol / L; and / or the precipitant includes at least one of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution, and the concentration of the precipitant is 8-15 mol / L; and / or the complexing agent includes an ammonia solution, and the concentration of the ammonia solution is 100-150 g / L.

5. The preparation method according to any one of claims 1 to 3, characterized in that, The conditions for the coprecipitation reaction include: a temperature of 50-65℃ and a stirring speed of 300-450 rpm.

6. A nickel-manganese binary precursor, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

7. The nickel-manganese binary precursor as described in claim 6, characterized in that, The nickel-manganese binary precursor satisfies the following condition: tap density of 1.80-2.2 g / m³. 3 Specific surface area is 15-30m² 2 / g, particle size distribution is 0.30 <k90<0.40。 8. A positive electrode material, characterized in that, It is obtained by calcining the nickel-manganese binary precursor as described in claim 6 or 7 with a lithium source.

9. A lithium-ion battery, characterized in that, Includes the cathode material as described in claim 8.

Images