Large-particle lithium-rich manganese-based precursor, preparation thereof, positive electrode material and application

Abstract

The invention provides a large-particle lithium-rich manganese-based precursor and preparation thereof, a positive electrode material and application, and the preparation method comprises the following steps: (1) enabling a first mixed salt solution, a precipitator solution and a complexing agent solution to flow into a reaction base solution in parallel, and carrying out a first co-precipitation reaction to obtain first slurry; (2) enabling a second mixed salt solution, a precipitant solution and a complexing agent solution to flow into the first slurry obtained in the step (1) in parallel, and carrying out a second coprecipitation reaction to obtain a large-particle lithium-rich manganese-based precursor; the second mixed salt solution contains an anionic surfactant. The anionic surfactant contained in the second mixed salt solution in the preparation method can reduce the surface tension of the reaction slurry, and alleviate the problem of non-uniform surface stress distribution in the synthesis process; in addition, in the preparation method, the anionic surfactant is negatively charged, and primary particles on the surface are combined more tightly through the electrostatic attraction effect; in addition, the preparation method is simple in process and low in requirements on equipment.

Description

Technical Field

[0001] The present invention belongs to the field of battery technology and relates to a method for preparing a large-particle lithium-rich manganese-based precursor, and in particular to a large-particle lithium-rich manganese-based precursor and its preparation, positive electrode material and application. Background Art

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

[0003] During the synthesis process of the lithium-rich manganese-based precursor, when the particle size grows to about 10μm, with the increase of particle size and the enhancement of particle consistency, the solid content of the slurry in the reactor gradually increases, resulting in uneven stress distribution on the surface of the secondary particles. Cracks often appear on the surface of the particles, and even broken balls occur, affecting the performance of the positive electrode material prepared by the subsequent sintering method.

[0004] At present, the preparation of large-particle lithium-rich manganese-based precursors avoids cracking by reducing the rotation speed, but this often leads to problems of poor dispersion and sphericity, and the effect of adjusting the rotation speed is limited. It only reduces the partial cracking of the particles and cannot completely avoid the collision and cracking of large particles during the growth process. In addition, the cracks on the surface of the precursor particles can be repaired by increasing the aging alkalinity and time, but this method can often only repair the cracks on the surface of the particles and cannot change the cracks inside the bulk phase. Excessive alkalinity will lead to the appearance of small particles and flocculent substances on the surface, affecting the overall physical and chemical properties of the precursor.

[0005] CN115321613A proposes a method for preparing a large-particle crack-resistant precursor of nickel, cobalt and manganese. The method adopts a special kettle body and different growth stage conditions to control the large-particle precursor without microcracks, cracking, obvious crystals and good sphericity. Although the process can control the cracking phenomenon, it is necessary to select a reactor with double blades, a specific baffle width and kettle diameter ratio, and the cost of equipment modification is high. The entire process needs to timely adjust the pH, ammonia concentration and gradient feed rate according to the actual growth rate. Overall, the process is complex, difficult to control, and has high requirements on equipment, which is not conducive to large-scale industrial application.

[0006] The preparation methods of large-particle lithium-rich manganese-based precursors disclosed in the prior art have certain defects. The prepared large-particle lithium-rich manganese-based precursors are easy to crack, and the preparation process is complicated and has high requirements on equipment, which is not conducive to large-scale application. Therefore, it is very important to develop and design a new type of large-particle lithium-rich manganese-based precursor and its preparation, positive electrode material and application. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a large-particle lithium-rich manganese-based precursor and its preparation, positive electrode material and application; the anionic surfactant contained in the second mixed salt solution of the preparation method can reduce the surface tension of the reaction slurry, alleviate the problem of uneven surface stress distribution during the synthesis process, and reduce the probability of large particle cracking; in addition, the anionic surfactant in the second mixed salt solution of the preparation method itself is negatively charged, and through electrostatic attraction, the surface primary particles are more tightly combined, further reducing the risk of large particle cracking in the later stage; in addition, the preparation method is simple in process and has low requirements on equipment.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0010] (1) introducing a first mixed salt solution, a precipitant solution and a complexing agent solution into a reaction base solution in parallel to perform a first coprecipitation reaction to obtain a first slurry;

[0011] (2) introducing the second mixed salt solution, the precipitant solution and the complexing agent solution into the first slurry obtained in step (1) in parallel to carry out a second coprecipitation reaction to obtain a large-particle lithium-rich manganese-based precursor;

[0012] The second mixed salt solution contains an anionic surfactant.

[0013] The anionic surfactant contained in the second mixed salt solution of the preparation method of the large-particle lithium-rich manganese-based precursor provided by the present invention 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-based precursor, and reduce the probability of large particle cracking. In addition, the anionic surfactant in the second mixed salt solution of the preparation method is itself negatively charged and can interact with the precipitate particles in the slurry through a long carbon chain or electrostatic adsorption, so that the surface of the entire precipitate particle is negatively charged, which is opposite to the charge of the metal ions in the mixed salt. Through electrostatic attraction, the occurrence of surface co-precipitation reaction is promoted, the surface primary particles are more tightly combined, and the risk of large particle cracking in the later stage is further reduced. In addition, the preparation method only needs to introduce anionic surfactants during the second co-precipitation reaction to effectively avoid the generation of cracks inside the particles during the precursor synthesis process. The process is simple and the requirements for equipment are low, which is conducive to large-scale promotion and use.

[0014] Preferably, 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, and 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, and other unlisted values ​​within the numerical range are also applicable.

[0015] Preferably, the total mass concentration of metal ions in the first mixed salt solution in step (1) is 80-120 g / L, for example, 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, and other unlisted values ​​within the numerical range are equally applicable.

[0016] Preferably, in step (2), the second mixed salt solution is obtained by mixing an anionic surfactant and the first mixed salt solution.

[0017] Preferably, the anionic surfactant in step (2) comprises any one of anionic polyacrylamide, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sulfo fatty acid methyl ester, and sodium oleoyloxyethane sulfonate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of anionic polyacrylamide and sodium lauryl sulfate, a combination of sodium dodecylbenzene sulfonate and sulfo fatty acid methyl ester, a combination of sulfo fatty acid methyl ester and sodium oleoyloxyethane sulfonate, or a combination of anionic polyacrylamide, sodium lauryl sulfate and sodium dodecylbenzene sulfonate.

[0018] Preferably, 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), 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, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the mass fraction of the precipitant solution in step (1) and step (2) is 25-35wt%, for example, it can be 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt% or 35wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, the precipitant solution in step (1) and step (2) comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0021] Preferably, the mass concentration of the complexing agent solution in step (1) and step (2) is 5 to 40 g / L, for example, 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, and other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the complexing agent solution in step (1) and step (2) comprises any one of ammonia water, citric acid solution, oxalic acid solution, salicylic acid solution and EDTA solution, or a combination of at least two of them. Typical but non-limiting combinations include a combination of ammonia water 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 water, citric acid solution and oxalic acid solution.

[0023] Preferably, the reaction base solution in step (1) is obtained by mixing a solvent, a precipitant solution and a complexing agent solution.

[0024] Preferably, the pH of the reaction base solution in step (1) is 11.0-13.0, for example, 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, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the concentration of the complexing agent in the reaction base solution in step (1) is 2 to 10 g / L, for example, 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, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) are also accompanied by stirring.

[0027] Preferably, the stirring speeds of the first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) are independently controlled to be 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 are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the temperature of the first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) is independently controlled to be 45-60°C, for example, it can be 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the pH of the first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) are controlled to be independently 9.0 to 12.0, for example, 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 are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the D50 particle size of the precipitate in the first slurry obtained in step (1) is 4 to 8 μm, for example, 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 the numerical range are also applicable.

[0031] Preferably, 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, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the second coprecipitation reaction in step (2) further includes sequentially performing filtration, washing and drying.

[0033] Preferably, the suction filtration and washing method is to use alkaline solution and pure water to cycle and wash in sequence for 3 to 5 times, for example, 3 times, 4 times or 5 times.

[0034] Preferably, the drying temperature is 80-130°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, and other unlisted values ​​within the numerical range are also applicable.

[0035] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises:

[0036] (1) introducing a first mixed salt solution having a total mass concentration of metal ions of 80 to 120 g / L, a precipitant solution having a mass fraction of 25 to 35 wt %, and a complexing agent solution having a mass concentration of 5 to 40 g / L into a reaction base solution having a pH of 11.0 to 13.0 and a complexing agent concentration of 2 to 10 g / L in parallel, with stirring during the introduction process, and controlling the temperature to 45 to 60° C., the pH to 9.0 to 12.0, and the stirring speed to 400 to 800 rpm, to perform a first coprecipitation reaction, and obtain a first slurry having a D50 particle size of 4 to 8 μm of the precipitate;

[0037] (2) introducing a second mixed salt solution having a total mass concentration of metal ions of 80 to 120 g / L, a precipitant solution having a mass fraction of 25 to 35 wt %, and a complexing agent solution having a mass concentration of 5 to 40 g / L into the first slurry obtained in step (1) in parallel, with stirring during the introduction process, and controlling the temperature to be 45 to 60° C., the pH to be 9.0 to 12.0, and the stirring speed to be 400 to 800 rpm, to carry out a second coprecipitation reaction, and after suction filtration and washing, drying at 80 to 130° C. to obtain a large-particle lithium-rich manganese-based precursor having a D50 particle size of 10 to 18 μm;

[0038] The second mixed salt solution contains anionic surfactant, and 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).

[0039] In a second aspect, the present invention provides a large-particle lithium-rich manganese-based precursor, wherein the large-particle lithium-rich manganese-based precursor is obtained by the preparation method described in the first aspect.

[0040] The large-particle lithium-rich manganese-based precursor provided by the present invention has primary particles that are tightly combined, secondary particles that have no cracks on the surface, and good sphericity. The large-particle lithium-rich manganese-based positive electrode material prepared by subsequent sintering has excellent cycle stability.

[0041] In a third aspect, the present invention provides a large-particle lithium-rich manganese-based positive electrode material, wherein the large-particle lithium-rich manganese-based positive electrode material is prepared from the large-particle lithium-rich manganese-based precursor described in the second aspect.

[0042] In a fourth aspect, the present invention provides a lithium-ion battery, comprising the large-particle lithium-rich manganese-based positive electrode material described in the third aspect.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The anionic surfactant contained in the second mixed salt solution of the method for preparing the large-particle lithium-rich manganese-based precursor provided by the present invention 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-based precursor, and reduce the probability of large particle cracking;

[0045] (2) The anionic surfactant in the second mixed salt solution of the preparation method of the large-particle lithium-rich manganese-based precursor provided by the present invention is itself negatively charged and can interact with the precipitate particles in the slurry through long carbon chains or electrostatic adsorption, so that the surface of the entire precipitate particles is negatively charged, which is opposite to the charge of the metal ions in the mixed salt. Through electrostatic attraction, the occurrence of surface co-precipitation reaction is promoted, so that the surface primary particles are more tightly combined, and the risk of large particle cracking in the later stage is further reduced;

[0046] (3) The preparation method of the large-particle lithium-rich manganese-based precursor provided by the present invention only needs to introduce anionic surfactant during the second coprecipitation reaction, which can effectively avoid the generation of cracks inside the particles during the precursor synthesis process. The process is simple and has low requirements on equipment, which is conducive to large-scale promotion and use;

[0047] (4) The large-particle lithium-rich manganese-based precursor provided by the present invention has primary particles that are tightly combined, secondary particles that have no cracks on the surface, and good sphericity. The large-particle lithium-rich manganese-based positive electrode material prepared by subsequent sintering has excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a SEM image of the large-particle lithium-rich manganese-based precursor obtained by the preparation method provided in Example 1.

[0049] Figure 2 This is a SEM image of the large-particle lithium-rich manganese-based precursor obtained by the preparation method provided in Example 5.

[0050] Figure 3 This is a SEM image of the large-particle lithium-rich manganese-based precursor obtained by the preparation method provided in Example 6.

[0051] Figure 4 This is a SEM image of the large-particle lithium-rich manganese-based precursor obtained by the preparation method provided in Comparative Example 3. DETAILED DESCRIPTION

[0052] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0053] Example 1

[0054] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0055] (1) a first mixed salt solution having a total mass concentration of 100 g / L of metal ions (a molar ratio of Ni ions, Co ions, and Mn ions being 0.25:0.05:0.70), a sodium hydroxide solution having a mass fraction of 30 wt %, and an ammonia solution having a mass concentration of 10 g / L are introduced in parallel into a reaction base solution having a pH of 12.5 and an ammonia concentration of 5.0 g / L, and the introduction is accompanied by stirring, the temperature is controlled at 56° C., the pH is between 9.5 and 11.5, and the stirring speed is 600 rpm, and a first coprecipitation reaction is performed to obtain a first slurry having a D50 particle size of 7 μm;

[0056] (2) a second mixed salt solution having a total mass concentration of 100 g / L of metal ions (a molar ratio of Ni ions, Co ions and Mn ions being 0.25:0.05:0.70), a sodium hydroxide solution having a mass fraction of 30 wt% and an ammonia solution having a mass concentration of 10 g / L are introduced into the first slurry obtained in step (1) in parallel, and the introduction is accompanied by stirring. The temperature is controlled to be 56° C., the pH is between 9.5 and 11.5, and the stirring speed is 600 rpm. A second coprecipitation reaction is performed, and after suction filtration and washing, the mixture is dried at 100° C. to obtain a large-particle lithium-rich manganese-based precursor having a D50 particle size of 15 μm;

[0057] The second mixed salt solution contains anionic polyacrylamide, and the ratio of the total mass concentration of metal ions in the second mixed salt solution to the mass concentration of anionic polyacrylamide is 1:0.005.

[0058] Example 2

[0059] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0060] (1) a first mixed salt solution having a total mass concentration of 80 g / L of metal ions (a molar ratio of Ni ions, Co ions, and Mn ions being 0.30:0.10:0.60), a sodium hydroxide solution having a mass fraction of 32 wt%, and an ammonia solution having a mass concentration of 15 g / L are introduced in parallel into a reaction base solution having a pH of 12.5 and an ammonia concentration of 7.0 g / L, and the introduction is accompanied by stirring, the temperature is controlled at 56° C., the pH is between 9.0 and 11.5, and the stirring speed is 500 rpm, and a first coprecipitation reaction is performed to obtain a first slurry having a D50 particle size of 6 μm;

[0061] (2) a second mixed salt solution having a total mass concentration of 80 g / L of metal ions (a molar ratio of Ni ions, Co ions and Mn ions being 0.30:0.10:0.60), a sodium hydroxide solution having a mass fraction of 32 wt% and an ammonia solution having a mass concentration of 15 g / L are introduced into the first slurry obtained in step (1) in parallel, and the introduction is accompanied by stirring. The temperature is controlled to be 56° C., the pH is between 9.0 and 11.5, and the stirring speed is 500 rpm. A second coprecipitation reaction is performed, and after suction filtration and washing, the mixture is dried at 120° C. to obtain a large-particle lithium-rich manganese-based precursor having a D50 particle size of 18 μm;

[0062] The second mixed salt solution contains sodium dodecylbenzene sulfonate, and the ratio of the total mass concentration of metal ions in the second mixed salt solution to the mass concentration of sodium dodecylbenzene sulfonate is 1:0.01.

[0063] Example 3

[0064] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0065] (1) a first mixed salt solution having a total mass concentration of 120 g / L of metal ions (a molar ratio of Ni ions, Co ions, and Mn ions being 0.15:0.15:0.70), a sodium hydroxide solution having a mass fraction of 25 wt %, and an ammonia solution having a mass concentration of 5 g / L are introduced in parallel into a reaction base solution having a pH of 11 and an ammonia concentration of 2 g / L, and the introduction is accompanied by stirring, the temperature is controlled at 45° C., the pH is 10.0 to 11.0, and the stirring speed is 800 rpm, and a first coprecipitation reaction is performed to obtain a first slurry having a D50 particle size of 4 μm of the precipitate;

[0066] (2) a second mixed salt solution having a total mass concentration of 120 g / L of metal ions (a molar ratio of Ni ions, Co ions and Mn ions being 0.15:0.15:0.70), a sodium hydroxide solution having a mass fraction of 25 wt% and an ammonia solution having a mass concentration of 5 g / L are introduced into the first slurry obtained in step (1) in parallel, and the introduction is accompanied by stirring. The temperature is controlled to be 45° C., the pH is 10.0-11.0, and the stirring speed is 400 rpm. A second coprecipitation reaction is performed, and after suction filtration and washing, the mixture is dried at 130° C. to obtain a large-particle lithium-rich manganese-based precursor having a D50 particle size of 10 μm;

[0067] The second mixed salt solution contains sulfonated fatty acid methyl ester, and the ratio of the total mass concentration of metal ions in the second mixed salt solution to the mass concentration of sulfonated fatty acid methyl ester is 1:0.002.

[0068] Example 4

[0069] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, the preparation method comprising:

[0070] (1) a first mixed salt solution with a total mass concentration of 80 g / L of metal ions (a molar ratio of Ni ions, Co ions and Mn ions of 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 introduced into a reaction base solution with a pH of 13.0 and a citric acid concentration of 5 g / L in parallel, and the introduction process was accompanied by stirring, and the temperature was controlled at 60° C., the pH was 11.0-12.0, and the stirring speed was 400 rpm to perform a first coprecipitation reaction to obtain a first slurry with a D50 particle size of 8 μm;

[0071] (2) a second mixed salt solution having a total mass concentration of 80 g / L of metal ions (a molar ratio of Ni ions, Co ions and Mn ions being 0.30:0.10:0.60), a sodium hydroxide solution having a mass fraction of 35 wt% and a citric acid solution having a mass concentration of 40 g / L are introduced into the first slurry obtained in step (1) in parallel, and the introduction is accompanied by stirring. The temperature is controlled to be 60° C., the pH is 11.0-12.0, and the stirring speed is 800 rpm. A second coprecipitation reaction is performed, and after suction filtration and washing, the mixture is dried at 80° C. to obtain a large-particle lithium-rich manganese-based precursor having a D50 particle size of 18 μm;

[0072] 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.

[0073] Example 5

[0074] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as Example 1 except that in step (2), the ratio of the total mass concentration of metal ions to the mass concentration of the anionic surfactant in the second mixed salt solution is 1:0.001.

[0075] Example 6

[0076] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as Example 1 except that in step (2), the ratio of the total mass concentration of metal ions to the mass concentration of the anionic surfactant in the second mixed salt solution is 1:0.05.

[0077] Example 7

[0078] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as that of Example 1 except that the stirring speed in step (1) and step (2) is controlled to be 200 rpm.

[0079] Example 8

[0080] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as that of Embodiment 1 except that the stirring speed in step (1) and step (2) is controlled to be 1000 rpm.

[0081] Example 9

[0082] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as that of Embodiment 1 except that the pH value in step (1) and step (2) is controlled to be 7.8-8.8.

[0083] Example 10

[0084] This embodiment provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as that of Embodiment 1 except that the pH value in step (1) and step (2) is controlled to be 12.5-13.5.

[0085] Comparative Example 1

[0086] This comparative example provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as Example 1 except that the anionic polyacrylamide in step (2) is replaced by an equal mass of hexadecyltrimethylammonium bromide (cationic surfactant).

[0087] Comparative Example 2

[0088] This comparative example provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as Example 1 except that the anionic polyacrylamide in step (2) is replaced by an alkylphenol polyoxyethylene ether (non-ionic surfactant) of equal mass.

[0089] Comparative Example 3

[0090] This comparative example provides a method for preparing a large-particle lithium-rich manganese-based precursor, which is the same as Example 1 except that the anionic polyacrylamide in step (2) is omitted.

[0091] The large-particle lithium-rich manganese-based precursor obtained by the preparation methods provided in Example 1, Example 5, Example 6 and Comparative Example 3 was tested using a scanning electron microscope, and the large-particle lithium-rich manganese-based precursor obtained by the preparation method of Example 1 was obtained as follows: Figure 1 As shown, the large-particle lithium-rich manganese-based precursor obtained by the preparation method of Example 5 is as follows Figure 2 As shown, the large-particle lithium-rich manganese-based precursor obtained by the preparation method of Example 6 is as follows Figure 3 As shown, the large-particle lithium-rich manganese-based precursor obtained by the preparation method of Comparative Example 3 is as follows Figure 4 shown.

[0092] The large-particle lithium-rich manganese-based precursor obtained in the above embodiments and comparative examples was uniformly mixed with lithium carbonate in a molar ratio of 1:1.5, and sintered in an air atmosphere at 900°C for 12 hours to obtain the corresponding lithium-rich manganese-based positive electrode material; the obtained lithium-rich manganese-based positive electrode material was prepared into a lithium-ion button battery, and the capacity retention rate of the obtained lithium-ion button battery after 50 cycles, 100 cycles and 200 cycles was tested, and the test results are shown in Table 1.

[0093] Table 1

[0094]

[0095] Depend on Figure 1 to Figure 4 And Table 1 shows:

[0096] (1) The large-particle lithium-rich manganese-based precursor prepared by the preparation method of the large-particle lithium-rich manganese-based precursor provided in Examples 1 to 4, the prepared lithium-ion battery exhibits high cycle stability;

[0097] (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 in the second mixed salt solution to the mass concentration of the anionic surfactant in step (2) of the present invention will affect the performance of the lithium ion battery; 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 precursors, thereby solving the problem of large-particle cracking, and the obtained large-particle precursor has a high sphericity and no cracking; if the anionic surfactant is added too little, the obtained large-particle precursor still has a lot of cracking, which can only reduce the probability of large-particle cracking, and cannot completely solve the cracking problem, affecting the subsequent electrochemical performance of the lithium battery; if the anionic surfactant is added too much, the obtained large-particle precursor has no cracking, but the sphericity is poor, and the twin multi-head situation is serious. Although the cracking problem can also be solved, the precursor morphology is mostly twin multi-head, which is not conducive to the subsequent cycle stability of the positive electrode material;

[0098] (3) By comparing Example 1 with Examples 7 and 8, it can be seen that the stirring speed in step (1) and step (2) of the present invention will affect the performance of the lithium-ion battery; when the stirring speed is 400-800 rpm, the lithium-ion battery has good cycle stability, which is because the appropriate stirring speed has a greater impact on the morphology of the large-particle precursor; if the stirring speed is too high, on the one hand, the probability of large particles cracking during the reaction will increase, and on the other hand, it will lead to the explosion of small particles in the later stage, both of which are not conducive to the improvement of the subsequent cycle stability of lithium-ion battery materials; if the stirring speed is too low, on the one hand, the primary particles are loosely bonded, affecting the physical and chemical properties of the precursor, and on the other hand, the agglomeration phenomenon is serious during the synthesis of the precursor, and the final morphology has more twin multi-heads. The precursor with poor sphericity and physical and chemical properties leads to poor cycle stability of the subsequent lithium-ion battery material;

[0099] (3) By comparing Example 1 with Examples 9 and 10, it can be seen that the pH in step (1) and step (2) of the present invention will affect the performance of the lithium-ion battery; when the pH of the first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) is controlled to be 9.0-12.0 respectively, the lithium-ion battery has good cycle stability. This is because it is necessary to control the pH within a suitable range during the coprecipitation synthesis process to obtain a large-particle lithium-rich manganese-based precursor with excellent physical and chemical properties and high sphericity. If the pH is controlled too high, a large number of small particles will explode during the precursor synthesis process, resulting in a wide overall particle size distribution. The small particles present in the system reduce the subsequent cycle stability of the lithium-ion battery; if the pH is controlled too low, the nickel-cobalt-manganese transition metal cannot be completely precipitated, so that the physical and chemical properties and sphericity of the synthesized lithium-rich manganese-based precursor are generally poor, resulting in poor cycle stability of the subsequent lithium-ion battery material, and also causing waste of metal raw materials and an increase in subsequent wastewater treatment costs;

[0100] (4) By comparing Example 1 with Comparative Examples 1 to 3, it can be seen that the anionic surfactant contained in the second mixed salt solution of the method for preparing a large-particle lithium-rich manganese-based precursor provided by the present invention 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-based precursor, and reduce the probability of large particle cracking; the anionic surfactant in the second mixed salt solution of the method for preparing a large-particle lithium-rich manganese-based precursor provided by the present invention is itself negatively charged, and can interact with the precipitate particles in the slurry through a long carbon chain or electrostatic adsorption, so that the surface of the entire precipitate particle is negatively charged, which is opposite to the charge of the metal ions in the mixed salt. Through electrostatic attraction, the occurrence of surface co-precipitation reaction is promoted, and the surface primary particles are more tightly combined, further reducing the risk of large particle cracking in the later stage; the method for preparing a large-particle lithium-rich manganese-based precursor provided by the present invention only needs to introduce anionic surfactants during the second co-precipitation reaction, which can effectively avoid the generation of cracks inside the particles during the precursor synthesis process. The process is simple and the requirements for equipment are low, which is conducive to large-scale promotion and use.

[0101] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a large-particle lithium-rich manganese-based precursor, characterized in that: 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 parallel to perform a first coprecipitation reaction to obtain a first slurry; (2) introducing the second mixed salt solution, the precipitant solution and the complexing agent solution into the first slurry obtained in step (1) in parallel to carry out a second coprecipitation reaction to obtain a large-particle lithium-rich manganese-based precursor; The second mixed salt solution contains an anionic surfactant.

2. The preparation method according to claim 1, characterized in that: 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; Preferably, in step (1), the total mass concentration of metal ions in the first mixed salt solution is 80 to 120 g / L.

3. The preparation method according to claim 1 or 2, characterized in that: In step (2), the second mixed salt solution is obtained by mixing an anionic surfactant and the first mixed salt solution; Preferably, the anionic surfactant in step (2) includes any one or a combination of at least two of anionic polyacrylamide, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sulfonic fatty acid methyl ester, and sodium oleoyloxyethane sulfonate; Preferably, 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).

4. The preparation method according to any one of claims 1 to 3, characterized in that: The mass fraction of the precipitant solution in step (1) and step (2) is 25-35wt%; Preferably, the mass concentration of the complexing agent solution in step (1) and step (2) is 5 to 40 g / L; Preferably, the pH of the reaction base solution in step (1) is 11.0 to 13.

0.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) are also accompanied by stirring; Preferably, the stirring speeds of the first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) are controlled to be 400 to 800 rpm respectively and independently; Preferably, the temperature of the first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) is independently controlled to be 45 to 60° C.; Preferably, the pH of the first coprecipitation reaction and the second coprecipitation reaction in step (1) and step (2) are independently controlled to be 9.0 to 12.

0.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The D50 particle size of the precipitate in the first slurry obtained in step (1) is 4 to 8 μm; Preferably, the D50 particle size of the large-particle lithium-rich manganese-based precursor obtained in step (2) is 10 to 18 μm.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The preparation method comprises: (1) introducing a first mixed salt solution having a total mass concentration of metal ions of 80 to 120 g / L, a precipitant solution having a mass fraction of 25 to 35 wt %, and a complexing agent solution having a mass concentration of 5 to 40 g / L into a reaction base solution having a pH of 11.0 to 13.0 and a complexing agent concentration of 2 to 10 g / L in parallel, stirring the solution during the introduction, controlling the temperature to 45 to 60° C., the pH to 9.0 to 12.0, and the stirring speed to 400 to 800 rpm, and performing a first coprecipitation reaction to obtain a first slurry having a D50 particle size of 4 to 8 μm; (2) introducing a second mixed salt solution having a total mass concentration of metal ions of 80 to 120 g / L, a precipitant solution having a mass fraction of 25 to 35 wt %, and a complexing agent solution having a mass concentration of 5 to 40 g / L into the first slurry obtained in step (1) in parallel, with stirring during the introduction process, and controlling the temperature to be 45 to 60° C., the pH to be 9.0 to 12.0, and the stirring speed to be 400 to 800 rpm, to carry out a second coprecipitation reaction, and after suction filtration and washing, drying at 80 to 130° C. to obtain a large-particle lithium-rich manganese-based precursor having a D50 particle size of 10 to 18 μm; The second mixed salt solution contains anionic surfactant, and 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).

8. A large-particle lithium-rich manganese-based precursor, characterized in that: The large-particle lithium-rich manganese-based precursor is obtained by the preparation method described in any one of claims 1 to 7.

9. A large-particle lithium-rich manganese-based positive electrode material, characterized in that: The large-particle lithium-rich manganese-based positive electrode material is prepared from the large-particle lithium-rich manganese-based precursor described in claim 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the large-particle lithium-rich manganese-based positive electrode material according to claim 9.

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