Large-particle lithium-rich manganese-based precursor and preparation method therefor, and positive electrode material and use

Abstract

The present application provides a large-particle lithium-rich manganese-based precursor and a preparation method therefor, and a positive electrode material and the use. The preparation method comprises: (1) introducing a first mixed salt solution, a precipitant solution and a complexing agent solution into a reaction base solution in a co-current mode, and performing a first co-precipitation reaction to obtain a first slurry; and (2) introducing a second mixed salt solution, a precipitant solution and a complexing agent solution into the first slurry obtained in step (1) in a co-current mode, and performing a second co-precipitation reaction to obtain a large-particle lithium-rich manganese-based precursor, wherein the second mixed salt solution contains an anionic surfactant. The anionic surfactant contained in the second mixed salt solution of the preparation method can reduce the surface tension of the reaction slurry, and alleviate the problem of uneven surface stress distribution in the synthesis process; in addition, in the preparation method, the anionic surfactant as such is negatively charged, and primary particles on the surface are more closely bonded through electrostatic attraction; furthermore, the preparation method involves a simple process and has low requirements for equipment.

Description

A large-particle lithium-rich manganese-based precursor, its preparation, cathode material and application Technical Field

[0001] This application belongs to the field of battery technology and relates to a method for preparing a large-particle lithium-rich manganese-based precursor, and more particularly to a large-particle lithium-rich manganese-based precursor, its preparation, cathode material and application. Background Technology

[0002] In recent years, lithium-ion batteries have been successfully applied in various fields, including portable electronics, electric vehicles, and large-scale smart grids. However, with the increasing demand for energy storage, it is becoming increasingly necessary to develop lithium-ion batteries with better electrochemical performance. Lithium-rich manganese-based cathode materials exhibit a high electrochemical performance exceeding 250 mAh / g at voltages ranging from 2.0 to 4.8 V. -1 Its high specific capacity has attracted widespread attention.

[0003] During the synthesis of lithium-rich manganese-based precursors, when the particle size grows to about 10 μm, the solid content of the slurry in the reactor gradually increases with the increase in particle size and the enhancement of particle uniformity. This leads to uneven stress distribution on the surface of secondary particles, and cracks or even broken particles often appear on the particle surface, affecting the performance of cathode materials prepared by subsequent sintering.

[0004] Currently, the preparation of large-particle lithium-rich manganese-based precursors avoids cracking by reducing the rotation speed, but this often leads to problems with poor dispersibility and sphericity. Moreover, the effect of adjusting the rotation speed is limited, only reducing cracking in some particles and failing to completely prevent large particles from colliding and cracking during growth. In addition, increasing the aging alkalinity and time can also repair cracks on the surface of precursor particles, but this method often only repairs surface cracks and cannot change cracks inside the bulk phase. Furthermore, excessive alkalinity can lead to the appearance of small particles and flocculent substances on the surface, affecting the overall physicochemical properties of the precursor.

[0005] CN115321613A proposes a method for preparing a large-particle-size, crack-resistant precursor for nickel-cobalt-manganese alloys. This method employs a special reactor and controls conditions at different growth stages. The prepared large-particle-size precursor exhibits no microcracks, no cracking, no obvious crystal formation, and good sphericity. While this process can control cracking, it requires a reactor with double impellers, specific baffle widths, and a reactor diameter ratio, resulting in high equipment modification costs. Furthermore, the entire process necessitates timely adjustments to pH, ammonia concentration, and gradient feed rate based on the actual growth rate. Overall, this process is complex, difficult to control, and requires sophisticated equipment, making it unsuitable for large-scale industrial applications.

[0006] Existing methods for preparing large-particle lithium-rich manganese-based precursors all have certain drawbacks. These include the tendency of the prepared precursors to crack, complex preparation processes, and high equipment requirements, which hinder large-scale applications. Therefore, developing a novel large-particle lithium-rich manganese-based precursor, its preparation, cathode materials, and applications is crucial. Summary of the Invention

[0007] This application provides a large-particle lithium-rich manganese-based precursor, its preparation, cathode material, and applications. The anionic surfactant in the second mixed salt solution of the preparation method reduces the surface tension of the reaction slurry, alleviating the problem of uneven surface stress distribution during synthesis and reducing the probability of large-particle cracking. Furthermore, the anionic surfactant in the second mixed salt solution of the preparation method is negatively charged, and through electrostatic attraction, it makes the primary particles on the surface more tightly bound, further reducing the risk of large-particle cracking in the later stages. In addition, the preparation method is simple and has low equipment requirements.

[0008] In a first aspect, this application provides a method for preparing a large-particle lithium-rich manganese-based precursor, the method comprising:

[0009] (1) The first mixed salt solution, precipitant solution and complexing agent solution are fed into the reaction base liquid in parallel to carry out the first coprecipitation reaction and obtain the first slurry;

[0010] (2) The second mixed salt solution, precipitant solution and complexing agent solution are fed into the first slurry obtained in step (1) in parallel to carry out the second co-precipitation reaction and obtain large-particle lithium-rich manganese-based precursor;

[0011] The second mixed salt solution contains anionic surfactants.

[0012] In the preparation method of the large-particle lithium-rich manganese-based precursor provided in this application, the anionic surfactant contained in the second mixed salt solution can reduce the surface tension of the reaction slurry, effectively alleviating the problem of uneven surface stress distribution during the synthesis of the large-particle lithium-rich manganese precursor and reducing the probability of large-particle cracking. In addition, the anionic surfactant in the second mixed salt solution of the preparation method is negatively charged and can interact with the precipitate particles in the slurry through long carbon chains or electrostatic adsorption, making the entire surface of the precipitate particles negatively charged, opposite to the charge of the metal ions in the mixed salt. Through electrostatic attraction, the surface co-precipitation reaction is promoted, making the primary particles on the surface more tightly bound, further reducing the risk of large-particle cracking in the later stage. Furthermore, the preparation method only requires the introduction of anionic surfactant in the second co-precipitation reaction, effectively avoiding the generation of internal cracks in the particles during the precursor synthesis process. The process is simple and has low equipment requirements, which is conducive to large-scale promotion and use.

[0013] In one embodiment, the first mixed salt solution in step (1) is a nickel-cobalt-manganese mixed salt solution, and the molar ratio of nickel ions, cobalt ions and manganese ions is a:b:c, a+b+c=1 and c≥0.6. The value of c can be, for example, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 0.95, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] In one embodiment, the total mass concentration of metal ions in the first mixed salt solution in step (1) is 80 to 120 g / L, for example, it can be 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, 115 g / L, or 120 g / L, 125 g / L or 130 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] In one embodiment, the second mixed salt solution in step (2) is obtained by mixing an anionic surfactant and a first mixed salt solution.

[0016] In one embodiment, the anionic surfactant in step (2) includes any one or at least two combinations of anionic polyacrylamide, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, methyl sulfonate of sulfofatty acids, or sodium oleoyloxyethanesulfonate. Typical but non-limiting combinations include anionic polyacrylamide and sodium lauryl sulfate, sodium dodecylbenzene sulfonate and methyl sulfonate of sulfofatty acids, methyl sulfonate of sulfofatty acids and sodium oleoyloxyethanesulfonate, or anionic polyacrylamide, sodium lauryl sulfate, and sodium dodecylbenzene sulfonate.

[0017] In one embodiment, the ratio of the total mass concentration of metal ions to the mass concentration of the anionic surfactant in the second mixed salt solution in step (2) is 1:(0.002~0.03), for example, it can be 1:0.002, 1:0.004, 1:0.006, 1:0.008, 1:0.01, 1:0.012, 1:0.015, 1:0.018, 1:0.02, 1:0.022, 1:0.025, 1:0.028 or 1:0.03, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] In one embodiment, the mass fraction of the precipitant solution in steps (1) and (2) is 25 to 35 wt%, for example, it can be 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, or 35 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] In one embodiment, the precipitant solution in steps (1) and (2) comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0020] In one embodiment, the mass concentration of the complexing agent solution in steps (1) and (2) is 5 to 40 g / L, for example, it can be 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L or 40 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] In one embodiment, the complexing agent solution in steps (1) and (2) includes any one or a combination of at least two of ammonia, citric acid solution, oxalic acid solution, salicylic acid solution or EDTA solution. Typical but non-limiting combinations include a combination of ammonia and citric acid solution, a combination of oxalic acid solution and salicylic acid solution, a combination of salicylic acid solution and EDTA solution, or a combination of ammonia, citric acid solution and oxalic acid solution.

[0022] In one embodiment, the reaction substrate in step (1) is obtained by mixing a solvent, a precipitant solution and a complexing agent solution.

[0023] In one embodiment, the pH of the reaction substrate in step (1) is 11.0 to 13.0, for example, it can be 11.0, 11.2, 11.4, 11.6, 11.8, 12.0, 12.2, 12.4, 12.6, 12.8 or 13.0, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In one embodiment, the concentration of the complexing agent in the reaction substrate in step (1) is 2 to 10 g / L, for example, it can be 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In one embodiment, stirring is also present during the first coprecipitation reaction and the second coprecipitation reaction in steps (1) and (2).

[0026] In one embodiment, the stirring speed during the first coprecipitation reaction and the second coprecipitation reaction in steps (1) and (2) is independently 400 to 800 rpm, for example, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm or 800 rpm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] In one embodiment, the temperatures of the first coprecipitation reaction and the second coprecipitation reaction in steps (1) and (2) are independently controlled to be 45-60°C, for example, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] In one embodiment, the pH of the first coprecipitation reaction and the second coprecipitation reaction in steps (1) and (2) is independently controlled to be 9.0 to 12.0, for example, it can be 9.0, 9.2, 9.5, 9.8, 10.0, 11.2, 10.5, 10.8, 11.0, 11.2, 11.5, 11.8 or 12.0, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] In one embodiment, the D50 particle size of the precipitate in the first slurry obtained in step (1) is 4 to 8 μm, for example, it can be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] In one embodiment, the D50 particle size of the large-particle lithium-rich manganese-based precursor obtained in step (2) is 10 to 18 μm, for example, it can be 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm or 18 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0031] In one embodiment, step (2) further includes sequential filtration, washing, and drying after the second coprecipitation reaction.

[0032] In one embodiment, the filtration and washing method involves sequentially washing with alkaline solution and pure water 3 to 5 times, for example, 3, 4 or 5 times.

[0033] In one embodiment, the drying temperature is 80 to 130°C, for example, it can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] As an optional embodiment of the preparation method described in this application, the preparation method includes:

[0035] (1) A first mixed salt solution with a total metal ion mass concentration of 80-120 g / L, a precipitant solution with a mass fraction of 25-35 wt%, and a complexing agent solution with a mass concentration of 5-40 g / L are simultaneously introduced into a reaction substrate with a pH of 11.0-13.0 and a complexing agent concentration of 2-10 g / L. During the introduction process, stirring is carried out, and the temperature is controlled at 45-60℃, the pH at 9.0-12.0, and the stirring speed at 400-800 rpm to carry out the first coprecipitation reaction, and a first slurry with a D50 particle size of 4-8 μm is obtained.

[0036] (2) A second mixed salt solution with a total metal ion concentration of 80-120 g / L, a precipitant solution with a mass fraction of 25-35 wt%, and a complexing agent solution with a mass concentration of 5-40 g / L are fed into the first slurry obtained in step (1) in parallel. During the feeding process, stirring is carried out, and the temperature is controlled at 45-60℃, the pH is 9.0-12.0, and the stirring speed is 400-800 rpm to carry out the second coprecipitation reaction. After filtration and washing, the mixture is dried at 80-130℃ to obtain a large-particle lithium-rich manganese-based precursor with a D50 particle size of 10-18 μm.

[0037] The second mixed salt solution contains anionic surfactants, and the ratio of the total mass concentration of metal ions to the mass concentration of anionic surfactants in the second mixed salt solution is 1:(0.002~0.03).

[0038] Secondly, this application provides a large-particle lithium-rich manganese-based precursor, which is obtained by the preparation method described in the first aspect.

[0039] The large-particle lithium-rich manganese-based precursor provided in this application has tightly bonded primary particles, no cracks on the surface of secondary particles, and good sphericity. The large-particle lithium-rich manganese-based cathode material prepared by subsequent sintering has excellent cycle stability.

[0040] Thirdly, this application provides a large-particle lithium-rich manganese-based cathode material, which is prepared from the large-particle lithium-rich manganese-based precursor described in the second aspect.

[0041] Fourthly, this application provides a lithium-ion battery, which includes the large-particle lithium-rich manganese-based cathode material described in the third aspect.

[0042] Compared with the prior art, this application has the following advantages:

[0043] (1) In the preparation method of large-particle lithium-rich manganese-based precursor provided in this application, the anionic surfactant contained in the second mixed salt solution can reduce the surface tension of the reaction slurry, effectively alleviate the problem of uneven surface stress distribution during the synthesis of large-particle lithium-rich manganese precursor, and reduce the probability of large-particle cracking.

[0044] (2) In the preparation method of the large-particle lithium-rich manganese-based precursor provided in this application, the anionic surfactant in the second mixed salt solution is negatively charged and can interact with the precipitate particles in the slurry through long carbon chains or electrostatic adsorption, so that the entire surface of the precipitate particles is negatively charged, opposite to the charge of the metal ions in the mixed salt. Through electrostatic attraction, the surface co-precipitation reaction is promoted, making the primary particles on the surface more tightly bound, and further reducing the risk of large particle cracking in the later stage.

[0045] (3) The preparation method of the large-particle lithium-rich manganese-based precursor provided in this application only requires the introduction of anionic surfactant during the second coprecipitation reaction, which can effectively avoid the generation of internal cracks in the particles during the precursor synthesis process. The process is simple and has low requirements for equipment, which is conducive to large-scale promotion and use.

[0046] (4) The primary particles in the large-particle lithium-rich manganese-based precursor provided in this application are tightly bonded, the secondary particles have no cracks on their surface and good sphericity, and the large-particle lithium-rich manganese-based cathode material prepared by subsequent sintering has excellent cycle stability. Attached Figure Description

[0047] Figure 1 is a SEM image of the large-particle lithium-rich manganese-based precursor obtained by the preparation method provided in Example 1.

[0048] Figure 2 is a SEM image of the large-particle lithium-rich manganese-based precursor obtained by the preparation method provided in Example 5.

[0049] Figure 3 is a SEM image of the large-particle lithium-rich manganese-based precursor obtained by the preparation method provided in Example 6.

[0050] Figure 4 is a SEM image of the large-particle lithium-rich manganese-based precursor obtained by the preparation method provided in Comparative Example 3. Detailed Implementation

[0051] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0052] Example 1

[0053] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0054] (1) A first mixed salt solution with a total metal ion mass concentration of 100 g / L (the molar ratio of Ni ions, Co ions and Mn ions is 0.25:0.05:0.70), a sodium hydroxide solution with a mass fraction of 30 wt% and an ammonia solution with a mass concentration of 10 g / L were simultaneously introduced into a reaction substrate with a pH of 12.5 and an ammonia concentration of 5.0 g / L. During the introduction process, stirring was carried out, the temperature was controlled at 56℃, the pH was between 9.5 and 11.5, and the stirring speed was 600 rpm to carry out the first coprecipitation reaction, and a first slurry with a D50 particle size of 7 μm was obtained.

[0055] (2) A second mixed salt solution with a total metal ion mass concentration of 100 g / L (the molar ratio of Ni ions, Co ions and Mn ions is 0.25:0.05:0.70), a sodium hydroxide solution with a mass fraction of 30 wt%, and ammonia water with a mass concentration of 10 g / L are simultaneously introduced into the first slurry obtained in step (1). During the introduction process, stirring is carried out, the temperature is controlled at 56℃, the pH is between 9.5 and 11.5, and the stirring speed is 600 rpm to carry out the second coprecipitation reaction. After filtration and washing, the mixture is dried at 100℃ to obtain a large-particle lithium-rich manganese-based precursor with a D50 particle size of 15 μm.

[0056] The second mixed salt solution contains anionic polyacrylamide, and the ratio of the total mass concentration of metal ions to the mass concentration of anionic polyacrylamide in the second mixed salt solution is 1:0.005.

[0057] Example 2

[0058] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0059] (1) A first mixed salt solution with a total metal ion mass concentration of 80 g / L (the molar ratio of Ni ions, Co ions and Mn ions is 0.30:0.10:0.60), a sodium hydroxide solution with a mass fraction of 32 wt% and an ammonia solution with a mass concentration of 15 g / L were simultaneously introduced into a reaction substrate with a pH of 12.5 and an ammonia concentration of 7.0 g / L. During the introduction process, stirring was carried out, the temperature was controlled at 56℃, the pH was between 9.0 and 11.5, and the stirring speed was 500 rpm to carry out the first coprecipitation reaction, and a first slurry with a D50 particle size of 6 μm was obtained.

[0060] (2) A second mixed salt solution with a total metal ion mass concentration of 80 g / L (the molar ratio of Ni ions, Co ions and Mn ions is 0.30:0.10:0.60), a sodium hydroxide solution with a mass fraction of 32 wt%, and ammonia water with a mass concentration of 15 g / L were simultaneously introduced into the first slurry obtained in step (1). During the introduction process, stirring was carried out, the temperature was controlled at 56℃, the pH was between 9.0 and 11.5, and the stirring speed was 500 rpm to carry out the second coprecipitation reaction. After filtration and washing, the mixture was dried at 120℃ to obtain a large-particle lithium-rich manganese-based precursor with a D50 particle size of 18 μm.

[0061] The second mixed salt solution contains sodium dodecylbenzenesulfonate, and the ratio of the total mass concentration of metal ions in the second mixed salt solution to the mass concentration of sodium dodecylbenzenesulfonate is 1:0.01.

[0062] Example 3

[0063] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0064] (1) A first mixed salt solution with a total metal ion mass concentration of 120 g / L (the molar ratio of Ni ions, Co ions and Mn ions is 0.15:0.15:0.70), a sodium hydroxide solution with a mass fraction of 25 wt% and ammonia water with a mass concentration of 5 g / L were simultaneously introduced into a reaction substrate with a pH of 11 and an ammonia concentration of 2 g / L. During the introduction process, stirring was carried out, the temperature was controlled at 45℃, the pH was 10.0~11.0, and the stirring speed was 800 rpm to carry out the first coprecipitation reaction, and a first slurry with a D50 particle size of 4 μm was obtained.

[0065] (2) A second mixed salt solution with a total metal ion mass concentration of 120 g / L (the molar ratio of Ni ions, Co ions and Mn ions is 0.15:0.15:0.70), a sodium hydroxide solution with a mass fraction of 25 wt%, and ammonia water with a mass concentration of 5 g / L were simultaneously introduced into the first slurry obtained in step (1). During the introduction process, stirring was carried out, the temperature was controlled at 45℃, the pH was 10.0~11.0, and the stirring speed was 400 rpm to carry out the second coprecipitation reaction. After filtration and washing, the mixture was dried at 130℃ to obtain a large-particle lithium-rich manganese-based precursor with a D50 particle size of 10 μm.

[0066] The second mixed salt solution contains sulfo fatty acid methyl esters, and the ratio of the total mass concentration of metal ions to the mass concentration of sulfo fatty acid methyl esters in the second mixed salt solution is 1:0.002.

[0067] Example 4

[0068] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0069] (1) A first mixed salt solution with a total metal ion mass concentration of 80 g / L (the molar ratio of Ni ions, Co ions and Mn ions is 0.30:0.10:0.60), a sodium hydroxide solution with a mass fraction of 35 wt%, and a citric acid solution with a mass concentration of 40 g / L were simultaneously introduced into a reaction substrate with a pH of 13.0 and a citric acid concentration of 5 g / L. During the introduction process, stirring was carried out, and the temperature was controlled at 60℃, the pH at 11.0~12.0, and the stirring speed at 400 rpm to carry out the first coprecipitation reaction, and a first slurry with a D50 particle size of 8 μm was obtained.

[0070] (2) A second mixed salt solution with a total metal ion mass concentration of 80 g / L (the molar ratio of Ni ions, Co ions and Mn ions is 0.30:0.10:0.60), a sodium hydroxide solution with a mass fraction of 35 wt%, and a citric acid solution with a mass concentration of 40 g / L were simultaneously introduced into the first slurry obtained in step (1). During the introduction process, stirring was carried out, the temperature was controlled at 60℃, the pH was 11.0~12.0, and the stirring speed was 800 rpm to carry out the second coprecipitation reaction. After filtration and washing, the mixture was dried at 80℃ to obtain a large-particle lithium-rich manganese-based precursor with a D50 particle size of 18 μm.

[0071] The second mixed salt solution contains sodium oleoyloxyethanesulfonate, and the ratio of the total mass concentration of metal ions in the second mixed salt solution to the mass concentration of sodium oleoyloxyethanesulfonate is 1:0.03.

[0072] Example 5

[0073] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for step (2), in which the ratio of the total mass concentration of metal ions to the mass concentration of anionic surfactant in the second mixed salt solution is 1:0.001, all other steps are the same as in Example 1.

[0074] Example 6

[0075] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for step (2), in which the ratio of the total mass concentration of metal ions to the mass concentration of anionic surfactant in the second mixed salt solution is 1:0.05, all other steps are the same as in Example 1.

[0076] Example 7

[0077] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for controlling the stirring speed to 200 rpm in steps (1) and (2), the rest are the same as in Example 1.

[0078] Example 8

[0079] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for controlling the stirring speed to 1000 rpm in steps (1) and (2), the rest are the same as in Example 1.

[0080] Example 9

[0081] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for controlling the pH to be 7.8 to 8.8 in steps (1) and (2), the rest is the same as in Example 1.

[0082] Example 10

[0083] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for controlling the pH to be 12.5-13.5 in steps (1) and (2), the rest is the same as in Example 1.

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for replacing the anionic polyacrylamide in step (2) with an equal mass of hexadecyltrimethylammonium bromide (a cationic surfactant), the rest is the same as in Example 1.

[0086] Comparative Example 2

[0087] This comparative example provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for replacing the anionic polyacrylamide in step (2) with an equal mass of alkylphenol polyoxyethylene ether (a nonionic surfactant), the rest is the same as in Example 1.

[0088] Comparative Example 3

[0089] This comparative example provides a method for preparing a large-particle lithium-rich manganese-based precursor. Except for omitting the anionic polyacrylamide in step (2), the rest is the same as in Example 1.

[0090] The large-particle lithium-rich manganese-based precursors obtained by the preparation methods provided in Examples 1, 5, 6 and Comparative Example 3 were tested using scanning electron microscopy. The large-particle lithium-rich manganese-based precursor obtained by the preparation method of Example 1 is shown in Figure 1, the large-particle lithium-rich manganese-based precursor obtained by the preparation method of Example 5 is shown in Figure 2, the large-particle lithium-rich manganese-based precursor obtained by the preparation method of Example 6 is shown in Figure 3, and the large-particle lithium-rich manganese-based precursor obtained by the preparation method of Comparative Example 3 is shown in Figure 4.

[0091] The large-particle lithium-rich manganese-based precursors obtained in the above examples and comparative examples were uniformly mixed with lithium carbonate at a molar ratio of 1:1.5 and sintered in air at 900°C for 12 hours to obtain the corresponding lithium-rich manganese-based cathode material. The obtained lithium-rich manganese-based cathode material was used to prepare lithium-ion coin cells, and the capacity retention rate of the obtained lithium-ion coin cells after 50, 100, and 200 cycles was tested. The test results are shown in Table 1.

[0092] Table 1

[0093] From Figures 1 to 4 and Table 1, we can conclude that:

[0094] (1) The lithium-ion battery prepared by the method of preparing the large-particle lithium-rich manganese-based precursor provided in Examples 1-4 exhibits high cycle stability.

[0095] (2) By comparing Example 1 with Examples 5 and 6, it can be seen that the ratio of the total mass concentration of metal ions to the mass concentration of anionic surfactant in the second mixed salt solution in step (2) of this application affects the performance of lithium-ion batteries. When the mass concentration ratio is 1:(0.002~0.03), the lithium-ion battery has good cycle stability. This is because an appropriate amount of anionic surfactant can alleviate the uneven distribution of surface stress during the synthesis of large-particle lithium-rich manganese precursor, thereby solving the problem of large-particle cracking. The resulting large-particle precursor has high sphericity and no cracking. If too little anionic surfactant is added, the resulting large-particle precursor still has a lot of cracking. It can only reduce the probability of large-particle cracking, but cannot completely solve the cracking problem, affecting the electrochemical performance of the subsequent lithium battery. If too much anionic surfactant is added, the resulting large-particle precursor has no cracking, but poor sphericity and serious twinning. Although it can also solve the cracking problem, the precursor morphology is mostly twinning, which is not conducive to the cycle stability of the subsequent cathode material.

[0096] (3) By comparing Example 1 with Examples 7 and 8, it can be seen that the stirring speed in steps (1) and (2) of this application affects the performance of lithium-ion batteries. When the stirring speed is 400-800 rpm, the lithium-ion battery has good cycle stability. This is because the appropriate stirring speed has a greater impact on the morphology of large particle precursors. If the stirring speed is too high, on the one hand, it will increase the probability of large particle cracking during the reaction process, and on the other hand, it will lead to the explosion of small particles in the later stage. Both of these are not conducive to improving the cycle stability of subsequent lithium-ion battery materials. If the stirring speed is too low, on the one hand, the primary particle binding is relatively loose, affecting the physicochemical properties of the precursor. On the other hand, the agglomeration phenomenon is serious during the synthesis of the precursor, resulting in a large number of twins in the final morphology. The precursor with poor sphericity and physicochemical properties leads to poor cycle stability of subsequent lithium-ion battery materials.

[0097] (3) By comparing Example 1 with Examples 9 and 10, it can be seen that the pH in steps (1) and (2) of this application affects the performance of lithium-ion batteries. When the pH of the first coprecipitation reaction and the second coprecipitation reaction in steps (1) and (2) is controlled independently to be 9.0 to 12.0, the lithium-ion battery has good cycle stability. This is because a suitable pH range needs to be controlled in the coprecipitation synthesis process to obtain large-particle lithium-rich manganese-based precursors with excellent physicochemical properties and high sphericity. If the pH is controlled too high, a large number of small particles will explode in the precursor synthesis process, resulting in a wide overall particle size distribution. The small particles in the system reduce the cycle stability of the subsequent lithium-ion battery. If the pH is controlled too low, the nickel-cobalt-manganese transition metal cannot be completely precipitated, resulting in poor overall physicochemical properties and sphericity of the synthesized lithium-rich manganese-based precursor, which leads to poor cycle stability of the subsequent lithium-ion battery material. In addition, it also causes waste of metal raw materials and increases the cost of subsequent wastewater treatment.

[0098] (4) By comparing Example 1 with Comparative Examples 1 to 3, it can be seen that in the preparation method of the large-particle lithium-rich manganese-based precursor provided by this application, the anionic surfactant contained in the second mixed salt solution can reduce the surface tension of the reaction slurry, effectively alleviate the problem of uneven surface stress distribution during the synthesis of the large-particle lithium-rich manganese precursor, and reduce the probability of large particle cracking. In the preparation method of the large-particle lithium-rich manganese-based precursor provided by this application, the anionic surfactant in the second mixed salt solution is negatively charged and can interact with the precipitate particles in the slurry through long carbon chains or electrostatic adsorption, so that the entire precipitate particle surface is negatively charged, opposite to the charge of the metal ions in the mixed salt. Through electrostatic attraction, the surface co-precipitation reaction is promoted, making the primary particles on the surface more tightly bound, further reducing the risk of large particle cracking in the later stage. The preparation method of the large-particle lithium-rich manganese-based precursor provided by this application only needs to introduce anionic surfactant in the second co-precipitation reaction to effectively avoid the generation of internal cracks in the particles during the precursor synthesis process. The process is simple and has low requirements for equipment, which is conducive to large-scale promotion and use.

[0099] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for preparing a large-particle lithium-rich manganese-based precursor, comprising: (1) The first mixed salt solution, precipitant solution and complexing agent solution are fed into the reaction base liquid in parallel to carry out the first coprecipitation reaction to obtain the first slurry; (2) The second mixed salt solution, precipitant solution and complexing agent solution are fed into the first slurry obtained in step (1) in parallel to carry out the second co-precipitation reaction and obtain large-particle lithium-rich manganese-based precursor; The second mixed salt solution contains anionic surfactants.

2. The preparation method according to claim 1, wherein, In step (1), the first mixed salt solution is a nickel-cobalt-manganese mixed salt solution, and the molar ratio of nickel ions, cobalt ions and manganese ions is a:b:c, a+b+c=1 and c≥0.

6.

3. The preparation method according to claim 1 or 2, wherein, In step (1), the total mass concentration of metal ions in the first mixed salt solution is 80-120 g / L.

4. The preparation method according to any one of claims 1 to 3, wherein, In step (2), the second mixed salt solution is obtained by mixing anionic surfactant and the first mixed salt solution; Optionally, the anionic surfactant in step (2) includes any one or at least two combinations of anionic polyacrylamide, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, methyl sulfonate of sulfofatty acids, and sodium oleoyloxyethanesulfonate. Optionally, in step (2), the ratio of the total mass concentration of metal ions in the second mixed salt solution to the mass concentration of the anionic surfactant is 1:(0.002-0.03).

5. The preparation method according to any one of claims 1 to 4, wherein, The mass fraction of the precipitant solution in steps (1) and (2) is 25-35 wt%. Optionally, the mass concentration of the complexing agent solution in steps (1) and (2) is 5–40 g / L; Optionally, the pH of the reaction substrate in step (1) is 11.0 to 13.

0.

6. The preparation method according to any one of claims 1 to 5, wherein, In steps (1) and (2), the first coprecipitation reaction and the second coprecipitation reaction are also accompanied by stirring; Optionally, the stirring speeds during the first coprecipitation reaction and the second coprecipitation reaction in steps (1) and (2) are each independently controlled to be 400-800 rpm; Optionally, the temperatures of the first coprecipitation reaction and the second coprecipitation reaction in steps (1) and (2) are controlled independently to be 45–60°C. Optionally, the pH of the first coprecipitation reaction and the second coprecipitation reaction in steps (1) and (2) are controlled independently to be 9.0 to 12.

0.

7. The preparation method according to any one of claims 1 to 6, wherein, The D50 particle size of the precipitate in the first slurry obtained in step (1) is 4-8 μm; Optionally, the D50 particle size of the large-particle lithium-rich manganese-based precursor obtained in step (2) is 10–18 μm.

8. The preparation method according to any one of claims 1 to 7, wherein, The preparation method includes: (1) A first mixed salt solution with a total metal ion mass concentration of 80-120 g / L, a precipitant solution with a mass fraction of 25-35 wt%, and a complexing agent solution with a mass concentration of 5-40 g / L are simultaneously introduced into a reaction substrate with a pH of 11.0-13.0 and a complexing agent concentration of 2-10 g / L. During the introduction process, stirring is carried out, and the temperature is controlled at 45-60℃, the pH at 9.0-12.0, and the stirring speed at 400-800 rpm to carry out the first coprecipitation reaction, and a first slurry with a D50 particle size of 4-8 μm is obtained. (2) A second mixed salt solution with a total metal ion concentration of 80-120 g / L, a precipitant solution with a mass fraction of 25-35 wt%, and a complexing agent solution with a mass concentration of 5-40 g / L are fed into the first slurry obtained in step (1) in parallel. During the feeding process, stirring is carried out, and the temperature is controlled at 45-60℃, the pH is 9.0-12.0, and the stirring speed is 400-800 rpm to carry out the second coprecipitation reaction. After filtration and washing, the mixture is dried at 80-130℃ to obtain a large-particle lithium-rich manganese-based precursor with a D50 particle size of 10-18 μm. The second mixed salt solution contains anionic surfactants, and the ratio of the total mass concentration of metal ions to the mass concentration of anionic surfactants in the second mixed salt solution is 1:(0.002~0.03).

9. A large-particle lithium-rich manganese-based precursor, obtained by the preparation method according to any one of claims 1 to 8.

10. A large-particle lithium-rich manganese-based cathode material, which is prepared from the large-particle lithium-rich manganese-based precursor as described in claim 9.

11. A lithium-ion battery comprising the large-particle lithium-rich manganese-based cathode material as described in claim 10.

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