WO2024066892A1

WO2024066892A1 - Manganese-rich oxide precursor, preparation method therefor, and use thereof

Info

Publication number: WO2024066892A1
Application number: PCT/CN2023/115997
Authority: WO
Inventors: 胡进; 胡伟; 彭威
Original assignee: 巴斯夫杉杉电池材料有限公司
Priority date: 2022-09-30
Filing date: 2023-08-31
Publication date: 2024-04-04
Also published as: CN115650315A

Abstract

Provided are a manganese-rich oxide precursor, a preparation method therefor, and use thereof. The precursor contains an oxide phase of nickel and manganese, and the D50, the diameter distance, the FWHW(211) and the BET of the precursor are all controlled within a certain range. Preparation of the manganese-rich oxide precursor comprises: preparing metal salt and precipitant solutions, and firstly preparing a crystal nucleus; then controlling a reaction temperature and a pH value, returning a solid phase after solid-liquid separation to a reaction kettle, repeating the steps, and obtaining a seed crystal after the granularity of a slurry reaches a set value; then adding the metal salt and precipitant solutions in parallel, controlling a reaction temperature and a pH value, meanwhile, continuously adding the seed crystal slurry, and after a target granularity is reached by means of control, obtaining a carbonate precursor by means of solid-liquid separation; and pre-sintering the carbonate precursor in an air atmosphere to obtain an oxide precursor. The manganese-rich oxide precursor can be used for preparing a lithium-rich manganese-based positive electrode material of a lithium ion battery, and the problems of poor specific surface area consistency, internal looseness, cracks and the like of the lithium-rich manganese-based positive electrode material are solved.

Description

Manganese-rich oxide precursor and preparation method and application thereof

Technical Field

The present invention belongs to the field of lithium ion battery materials, and in particular relates to a precursor of a lithium ion battery positive electrode material and a preparation method and application thereof.

Background technique

As a new generation of lithium battery positive electrode material, lithium-rich manganese-based material is not only low in price but also safer than conventional ternary materials. It can well meet the use requirements of electric vehicles, energy storage power stations and small electronic products, and is one of the most promising power battery positive electrode materials in the future.

Precursors for lithium-rich manganese-based materials generally include carbonate precursors and hydroxide precursors. In the coprecipitation reaction system using hydroxide precursors, the reaction system has a high pH and strong corrosiveness. In order to prevent manganese oxidation, a large amount of _N2 is required in the coprecipitation process, and ammonia water is used as a complexing agent. Although a precursor with high density and preferred morphology can be prepared, the production cost is extremely high. The coprecipitation process of carbonate precursors is ammonia-free, does not involve ammonia-containing wastewater treatment and ammonia-related occupational health issues, and does not require a large amount of nitrogen protection. It has low costs and greater industrialization prospects.

The existing carbonate precursors have a high cobalt content and are relatively expensive. In addition, a large amount of CO ₂ is released during the sintering process of preparing the positive electrode, resulting in unstable batch quality of the obtained positive electrode. In particular, the obtained positive electrode material has poor surface area consistency, poor sphericity, and low continuous concentration, which is not conducive to product industrialization. In addition, the internal part is loose, and the sintered positive electrode has many internal cracks, and the electrical performance cannot be fully exerted. Therefore, the production process of the existing lithium-rich manganese-based positive electrode material precursor needs to be further improved to obtain a stable positive electrode with good electrochemical performance.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings and defects mentioned in the above background technology, provide a manganese-rich oxide precursor with dense seed crystals, good sphericity and higher continuous concentration, and a preparation method thereof, and after applying it to the preparation of positive electrode materials, it can also improve the problems of poor consistency of specific surface area of lithium-rich manganese-based positive electrode materials, internal looseness, and cracks inside the sintered positive electrode materials.

In order to solve the above technical problems, the technical solution proposed by the present invention is a manganese-rich oxide precursor, wherein the manganese-rich oxide precursor contains a nickel oxide phase and a manganese oxide phase, the D50 of the manganese-rich oxide precursor is 4 to 13 μm, the diameter span = (D90-D10)/D50 is controlled at 1.1 to 1.4, the FWHW (211) is 0.3 to 0.65, and the BET of the manganese-rich oxide precursor is 30 to 70 m ² /g.

The above manganese-rich oxide precursor is preferably a chemical formula of Ni _x Mn _y Me _(1-xy) O _z (CO ₃ ) _m , wherein 0<x≤0.5, 0.5≤y<1, 0<z<2, 0<m<1, and Me is a doping element of Co, Mg, One of Al, Zr, W, Fe, and Cu.

_NiMn2O4 is a _spinel composite oxide. Our research shows that spinel-structured lithium _nickel manganese oxide is more likely to appear in the positive electrode material prepared from the oxide precursor containing _NiMn2O4 , and the electrochemical performance of the obtained positive electrode material is worse than that of the layered lithium-rich manganese-based positive electrode material, especially in terms of capacity. The above-mentioned manganese-rich oxide precursor, preferably, has substantially no _NiMn2O4 _phase peak in the XRD diagram of the manganese-rich oxide precursor.

The above-mentioned manganese-rich oxide precursor preferably has an average crack rate of 2% to 10%. The average crack rate is determined by the following method: first polish the sample to be tested to obtain a sample with a smooth surface, then use a field emission scanning electron microscope to obtain a CP electron microscope image, and count the number of cracks in the CP electron microscope under multiple different field of view areas. The number of cracks in the single field of view/total number of particles is recorded as a single crack rate, and then the average value is taken as the average crack rate. The manganese-rich oxide precursor is preferably obtained by pre-sintering a carbonate precursor in steps.

As a general technical concept, the present invention also provides a method for preparing a manganese-rich oxide precursor, comprising the following steps:

(1) preparing a metal salt solution including a nickel salt and a manganese salt, and preparing a precipitant solution including carbonate ions, and setting them aside;

(2) preparing a solution containing crystal nuclei using the metal salt solution and the precipitant solution prepared in step (1);

(3) using the solution containing crystal nuclei obtained in step (2) as the base liquid, adding the metal salt solution and the precipitant solution prepared in step (1) into the reactor, controlling the reaction temperature and pH value, stirring and concentrating with a concentrator, returning the solid phase after solid-liquid separation to the reactor, repeating the cycle, and stopping feeding after the particle size of the reaction slurry reaches the set value to obtain a seed slurry;

(4) adding the metal salt solution and the precipitant solution prepared in step (1) into the reactor in parallel, controlling the reaction temperature and pH value, and continuously adding the seed slurry synthesized in step (3) into the reactor, controlling the particle size of the material in the reactor by adjusting the flow rate of the seed slurry, until the target particle size is reached, and collecting the overflow material;

(5) separating the collected overflow material into solid and liquid, and washing and drying the obtained solid phase to obtain a carbonate precursor;

(6) Pre-calcining the carbonate precursor obtained in step (5) in an air atmosphere to obtain an oxide precursor.

In the above-mentioned preparation method, preferably, in step (1), the nickel salt is selected from one or more of nickel sulfate, nickel chloride, nickel nitrate and nickel acetate; the manganese salt is selected from one or more of manganese sulfate, manganese chloride, manganese nitrate and manganese acetate; the precipitant solution is selected from one or more of sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution and potassium bicarbonate solution, the metal salt solution also contains Me salt, the total concentration of the prepared metal salt is 0.5-3 mol/L, and the concentration of the prepared precipitant is 0.5-3 mol/L.

In the above-mentioned preparation method, preferably, in step (2), under stirring conditions and under normal temperature control (preferably 30°C-50°C), the prepared metal salt solution and the precipitant solution are simultaneously added to the reaction kettle in parallel using a precise metering pump, and the pH of the reaction solution is maintained at 11-13 to prepare crystal nuclei; the particle size D50 of the crystal nuclei is 0.5-1.5 μm.

In the above-mentioned preparation method, preferably, in step (4), the target particle size of the seed is controlled such that its D50 is the carbonic acid 1/3 to 1/2 of the salt precursor particle size.

In the above preparation method, preferably, in step (3), the reaction temperature is controlled at 25°C to 55°C, the pH value of the reaction is 7.5 to 9.0, and the stirring rate is controlled at 500 to 1000 rpm/min.

In the above preparation method, preferably, in step (4), the reaction temperature is controlled at 40°C to 70°C, and the reaction pH is 7.5 to 9.0.

In the above preparation method, preferably, in step (6), the pre-sintering is carried out in at least three steps, the pre-sintering temperature is 200°C to 600°C, and the time is 2 to 8 hours. In the process of sintering the carbonate precursor into an oxide, multi-step sintering is adopted, so that the internal cracks of the obtained oxide precursor are less, the cracks of the final lithium-rich manganese-based positive electrode material are greatly reduced, and the material maintains a good specific surface area consistency, so that the electrochemical properties of the lithium-rich manganese-based positive electrode material are better exerted.

More preferably, the step-by-step pre-sintering specifically includes: first sintering at 200°C to 300°C for 1 to 2 hours, then heating to 300°C to 400°C at a heating rate of 1 to 5°C/min for 1 to 3 hours, and then heating to 450°C to 600°C at a heating rate of 1 to 5°C/min for 1 to 3 hours. The preferred pre-sintering process adopts an optimized sintering temperature mechanism and a slow heating rate, which can release CO ₂ to the maximum extent while eliminating the appearance of impure phase NiMn ₂ O ₄ , so that the electrochemical performance of the lithium-rich manganese-based positive electrode material can be further exerted.

In the above-mentioned preparation method of the present invention, a soluble carbonate is used as a precipitant in the co-precipitation reaction, and the crystal nucleus preparation, seed crystal synthesis stage and growth reaction stage are carried out independently. At different stages, the key parameters of the reaction are preferably adjusted and controlled, such as stirring speed, pH and reaction temperature, and the solid content in the slurry is adjusted. Then, the precipitate after the reaction is separated, washed and dried to obtain a carbonate precursor, which is transferred to a rotary kiln for staged pre-burning to obtain an oxide precursor.

As a general technical concept, the present invention also provides a use of the above-mentioned manganese-rich oxide precursor in the preparation of lithium-rich manganese-based positive electrode materials for lithium-ion batteries.

Compared with the prior art, the beneficial effects of the present invention are as follows: the seed crystal reaction of the present invention adopts small-size crystal nuclei, which grow through a concentration process, and the obtained seed crystals are dense and have good sphericity, which can provide a basis for the subsequent preparation of a precursor with good sphericity. At the same time, in the growth stage, the sphericity of the prepared carbonate precursor is further modified by adding seeds, and the final precursor has good sphericity, and the diameter span = (D90-D10)/D50 can be controlled at 1.1 to 1.4, and the distribution is higher than the conventional continuous concentration. Based on the improvement of product performance parameters, the product of the present invention can be further used to improve the problems of poor consistency of specific surface area of lithium-rich manganese-based positive electrode materials, internal looseness, cracks in sintered positive electrode materials, etc., so that the electrical properties of the positive electrode materials can be more fully and completely exerted.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, they can also refer to these drawings without creative work. Get additional drawings.

FIG. 1 is a 5000-fold FEI-SEM image of the seed crystal of Example 1 of the present invention.

FIG. 2 is a 10,000-fold FEI-SEM image of the manganese-rich oxide precursor of Example 1 of the present invention.

FIG. 3 is an XRD diagram of the manganese-rich oxide precursor of Example 1 of the present invention.

FIG. 4 is a 10,000-fold FEI-SEM image of the manganese-rich carbonate precursor of Comparative Example 1 of the present invention.

FIG. 5 is a CP diagram of the manganese-rich oxide precursor of Example 1 of the present invention at a magnification of 5000 times.

FIG6 is a CP diagram of the manganese-rich oxide precursor of Comparative Example 3 of the present invention at a magnification of 5000 times.

FIG. 7 is an XRD diagram of the manganese-rich oxide precursors of Example 1 of the present invention and Comparative Example 3.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

Embodiment 1:

A manganese-rich oxide precursor of the present invention is obtained by pre-sintering a Ni _0.34 Mn _0.66 CO ₃ precursor in steps, and contains a nickel oxide phase and a manganese oxide phase. The D50 of the manganese-rich oxide precursor is 6.50 μm, and the diameter span = (D90-D10)/D50 is controlled at 1.22. The FWHW (211) of the manganese-rich oxide precursor is 0.35, and the BET of the manganese-rich oxide precursor is 65.4 m ² /g.

The method for preparing the high-sphericity manganese-rich oxide precursor described in this embodiment comprises the following steps:

(1) using nickel sulfate and manganese sulfate as raw materials, preparing a metal salt solution with a total concentration of 2 mol/L according to a molar ratio of nickel to manganese of 0.34:0.66, and using sodium carbonate as a precipitant to prepare a precipitant solution of 1.8 mol/L, and using it for later use;

(2) Preparation of crystal nuclei: water was added to a 100 L reactor until the blades were submerged, sodium carbonate was added to adjust the pH to 12, the speed of the stirring blade of the reactor was adjusted to 1000 r/min, the reaction temperature was controlled at 35°C, and the metal salt solution and the precipitant solution prepared in step (1) were added to the reactor simultaneously and in parallel using a precise metering pump, and the pH of the reaction solution was maintained at 11.9-12.1. The reaction was carried out for 2 h to obtain a solution of crystal nuclei with a D50 of 0.8 μm.

(3) Seed synthesis: water was added to a 100 L reactor until the blades were submerged, a solution containing 1 kg of crystal nuclei with a D50 of 0.8 μm was added as the bottom solution, sodium carbonate was added to adjust the pH to 8.5, the stirring blade speed of the reactor was adjusted to 1000 r/min, the reaction temperature was controlled at 35°C, the metal salt solution and the precipitant solution prepared in step (1) were added to the reactor in parallel with a precise metering pump, and the pH of the reaction solution was maintained at 8.0-8.5. The slurry overflowing from the reactor was concentrated by a concentrator and solid-liquid separation was performed. The solid phase is returned to the reactor, and the cycle is repeated. During the reaction, samples are continuously taken to test the particle size. When the D50 of the material in the reactor is detected to reach 2.5 μm, the feeding is stopped, and the material is stirred and aged for 2 hours before being placed in a storage tank with stirring.

(4) Continuous growth: add water to the overflow port of a clean continuous reactor, adjust the stirring speed of the reactor to 800 r/min, adjust the reaction temperature to 60°C, add sodium carbonate to adjust the pH of the mother liquor to 8.5, continue to use a precision metering pump to add the metal salt solution and the precipitant solution prepared in step (1) to the reactor in parallel, adjust the flow rate of the precipitant solution, and control the pH of the reaction solution to 8.0-8.5. At the same time, use a peristaltic pump to continuously feed the seed slurry synthesized in step (3) into the reactor, and control the particle size of the material in the reactor by adjusting the flow rate of the seed slurry. Take samples every 2 hours to detect that the particle size is stable at 6.5±0.3 μm, and the diameter distance is stable at 1.1-1.4. When the sphericity under the electron microscope is good, collect the overflow material;

(5) washing the collected solid material with pure water for multiple times, and then drying and sieving to obtain a manganese-rich carbonate precursor with good sphericity and a target particle size of 6.50 μm;

(6) The manganese-rich carbonate precursor obtained in the above step (5) is pre-sintered in a rotary kiln, wherein the sintering system is 300°C pre-sintering for 2h, 400°C pre-sintering for 2h, and 450°C pre-sintering for 3h, and the heating rate during the pre-sintering is controlled at 2°C/min, thereby obtaining the target oxide precursor Ni _0.34 Mn _0.66 O _z (CO ₃ ) _m of this embodiment, wherein the nickel-manganese metal molar ratio can be determined by ICP-AES detection, and combined with the main metal content and XRD, it can be known that the synthesized oxide precursor contains carbonate, and the specific content cannot be accurately obtained according to XRD. The FEI-SEM image of the 5000-fold seed crystal obtained in this embodiment is shown in Figure 1, the 10000-fold target oxide precursor is shown in Figure 2, and the XRD image of the target oxide precursor obtained in this embodiment is shown in Figure 3.

Comparative Example 1:

A preparation method of a manganese-rich carbonate precursor comprises the following steps:

(1) using nickel sulfate and manganese sulfate as raw materials, preparing a metal salt solution with a total concentration of 2.0 mol/L according to a molar ratio of nickel to manganese of 0.34:0.66, and using sodium carbonate as a precipitant to prepare a precipitant solution of 1.8 mol/L, and using it for later use;

(2) Continuous growth: Add water to a clean continuous reactor to the overflow port, adjust the stirring speed of the reactor to 800 r/min, adjust the reaction temperature to 60° C., add sodium carbonate to adjust the pH of the mother liquor to 8.5, continue to use a precision metering pump to add the metal salt solution and the precipitant solution prepared in step (1) to the reactor in parallel, adjust the flow rate of the precipitant solution, control the pH of the reaction solution to 7.5-10.5, control the particle size of the reactor by adjusting the pH, and collect the overflow material when the particle size D50 of the reactor is 5.5-7.5 μm;

(3) The collected material is washed with pure water for multiple times, and then dried and sieved to obtain a manganese-rich carbonate precursor.

The 10,000-fold FEI-SEM image of the carbonate precursor prepared in this comparative example is shown in FIG4 .

Comparative Example 2:

The specific implementation method, operation steps and process parameter conditions of Comparative Example 2 are basically the same as those of Example 1, except that the process of step (6) in Example 1 is not implemented, and a manganese-rich carbonate precursor is directly prepared.

Comparative Example 3:

The specific implementation method, operation steps and process parameter conditions of Comparative Example 1 are basically the same as those of Example 1, except that step (6) in Example 1 is replaced by: sintering the manganese-rich carbonate precursor obtained in step (5) at 650° C. in a rotary kiln for 6 hours to obtain the target oxide precursor.

The physical indicators of the above precursors are shown in Table 1 below.

Table 1: Comparison of physical indicators of products in Example 1 and its comparative example

As can be seen from the above, in Comparative Example 1, the precursor prepared by adjusting the pH to control the particle size without adding the seed crystal prepared by the crystal nucleus has a wide distribution, a low tap density, a large specific surface area, and a sphericity worse than that of Example 1. It can be seen from Example 1 and Comparative Example 2 that as the pre-oxidation releases carbon dioxide, the main metal content in the precursor increases, and the oxide precursor after pre-oxidation inherits the particle size and distribution of the carbonate precursor, while the specific surface area tends to decrease, which is more conducive to the preparation of a stable positive electrode material.

Three samples of the precursors of Example 1 and Comparative Example 2 were taken and mixed evenly with lithium carbonate at a molar ratio of metal to lithium of 1:1.3, and then sintered at 900°C for 6 hours in an oxygen atmosphere in a box furnace, and then sintered at 500°C for 5 hours, and then cooled to room temperature and removed from the furnace. After crushing and screening, lithium-rich manganese-based positive electrode materials were obtained. The physical parameters of each positive electrode material sample, such as the specific surface area, are shown in Table 2 below.

Table 2: Physical parameters such as specific surface area of positive electrode material samples of Example and Comparative Example 2

By comparing the positive electrode materials prepared in the above Example 1 and Comparative Example 2, it can be clearly concluded that the positive electrode material prepared by the carbonate precursor has poor BET consistency and large differences between different samples. The positive electrode material obtained by the technical solution provided by the present invention has good consistency and is more conducive to industrialization.

In addition, the samples of Example 1 and Comparative Example 3 were polished using an argon ion beam to obtain samples with smooth surfaces, and the CP electron microscope was obtained using a field emission scanning electron microscope as shown in Figures 5 and 6 to observe the internal cracks. By counting the number of cracks in the 5000x CP electron microscope in three different areas, the number of cracks/total number of particles in the field of view was recorded as the crack rate, and the average value was taken as the average crack rate. The internal crack conditions of Example 1 and Comparative Example 3 are shown in Table 3 below. From the results in Table 3 below, it can be seen that the average crack rate of Example 1 is 5.4%, and the crack condition is significantly improved compared with Comparative Example 3.

Table 3: Comparison table of average crack rate test of Example 3 and Comparative Example 3

By comparing the XRD patterns of Example 1 and Comparative Example 3 (see FIG7 ), it can be seen that the comparative example 3 adopts 650° C. sintering and the peaks of NiMn ₂ O ₄ (311), (400), (511) and (440) appear, which obviously produces NiMn ₂ O ₄ phase separation, which has a negative impact on the electrochemical performance. The oxide precursor using the technical solution provided by the present invention does not have the NiMn ₂ O ₄ phase separation seen in the comparative example, and is more suitable for preparing lithium-rich manganese-based positive electrode materials.

Embodiment 2:

A manganese-rich oxide precursor of the present invention is obtained by pre-sintering Ni _0.32 Mn _0.66 Co _0.02 CO ₃ precursor in steps, and contains nickel oxide phase and manganese oxide phase. The D50 of the manganese-rich oxide precursor is 6.0 μm, and the diameter span = (D90-D10)/D50 is controlled at 1.30. The FWHW (211) of the manganese-rich oxide precursor is 0.37, and the BET of the manganese-rich oxide precursor is 58.2 m ² /g.

(1) using nickel sulfate, manganese sulfate and cobalt sulfate as raw materials, preparing a metal salt solution with a total concentration of 2 mol/L according to the molar ratio of nickel, manganese and cobalt of 0.32:0.66:0.02, and setting aside; using sodium carbonate as a precipitant, preparing a precipitant solution of 2 mol/L, and setting aside;

(2) Preparation of crystal nuclei: water was added to a 100 L reactor until the blades were submerged, sodium carbonate was added to adjust the pH to 12, the speed of the stirring blade of the reactor was adjusted to 1000 r/min, the reaction temperature was controlled at 35° C., the metal salt solution and the precipitant solution prepared in step (1) were added to the reactor simultaneously by a precise metering pump, and the pH of the reaction solution was maintained at 11.9-12.1, and the reaction was carried out for 2 h to obtain a solution of crystal nuclei with a D50 of 0.8 μm;

(3) Seed synthesis: water was added to a 100L reactor until the blades were submerged, a solution containing 1kg of crystal nuclei with a D50 of 0.8μm was added as the bottom solution, sodium carbonate was added to adjust the pH to 8.5, the speed of the stirring blade of the reactor was adjusted to 1000r/min, the reaction temperature was controlled at 35°C, the metal salt solution and the precipitant solution prepared in step (1) were added to the reactor simultaneously by a precise metering pump, and the pH of the reaction solution was maintained at 8.0-8.5, the slurry overflowing from the reactor was concentrated by a concentrator, and the solid phase after solid-liquid separation was returned to the reactor, and the cycle was repeated. During the reaction process, samples were continuously taken to test the particle size. When the D50 of the material in the reactor was detected to reach 2.5μm, the feeding was stopped, and the stirring and aging was continued for 2 hours before being placed in a storage tank with stirring for storage;

(4) Continuous growth: add water to the overflow port of a clean continuous reactor, adjust the stirring speed of the reactor to 800 r/min, adjust the reaction temperature to 60° C., add sodium carbonate to adjust the pH of the mother liquor to 8.5, continue to use a precision metering pump to add the metal salt solution and the precipitant solution prepared in step (1) to the reactor in parallel, adjust the flow rate of the precipitant solution, and control the pH of the reaction solution to 8.0-8.5. At the same time, use a peristaltic pump to continuously feed the seed slurry synthesized in step (3) into the reactor, and control the particle size of the material in the reactor by adjusting the flow rate of the seed slurry. Take samples every 2 hours to detect that the particle size is stable at 6.0±0.3 μm, and the diameter distance is stable at 1.1-1.4. When the sphericity under an electron microscope is good, collect the overflow material;

(5) washing the collected solid material with pure water for multiple times, and then drying and sieving to obtain a manganese-rich carbonate precursor with good sphericity and a target particle size of 6.0 μm;

(6) The manganese-rich carbonate precursor obtained in the above step (5) is pre-fired in a rotary kiln, wherein the sintering conditions are pre-fired at 300°C for 2h, pre-fired at 400°C for 2h, and pre-fired at 450°C for 3h, and the heating rate during the pre-fired is controlled at 2°C/min, thereby obtaining the target oxide precursor Ni _0.32 Mn _0.66 Co _0.02 O _z (CO ₃ ) _m of this embodiment, wherein the metal molar ratio of nickel, manganese and the doping element cobalt can be determined by ICP-AES detection.

Embodiment 3:

A manganese-rich oxide precursor of the present invention is obtained by step-by-step sintering of a Ni _0.30 Mn _0.70 CO ₃ precursor, and contains a nickel oxide phase and a manganese oxide phase. The D50 of the manganese-rich oxide precursor is 12.1 μm, and the diameter span = (D90-D10)/D50 is controlled at 1.25. The FWHW (211) of the manganese-rich oxide precursor is 0.42, and the BET of the manganese-rich oxide precursor is 58.7 m ² /g.

(1) using nickel sulfate and manganese sulfate as raw materials, preparing a metal salt solution with a total concentration of 2 mol/L according to a molar ratio of nickel to manganese of 0.30:0.70, and setting aside; using sodium bicarbonate as a precipitant, preparing a precipitant solution of 1.8 mol/L, and setting aside;

(2) Preparation of crystal nuclei: water was added to a 100 L reactor until the blades were submerged, sodium bicarbonate was added to adjust the pH to 11.5, the speed of the stirring blade of the reactor was adjusted to 900 r/min, the reaction temperature was controlled at 40° C., the metal salt solution and the precipitant solution prepared in step (1) were simultaneously added to the reactor in parallel using a precise metering pump, and the pH of the reaction solution was maintained at 11.9-12.1. The reaction was continued for 3 h to obtain crystal nuclei with a D50 of 1.2 μm;

(3) Seed synthesis: water was added to a 100L reactor until the blades were submerged, a solution containing 0.8kg of crystal nuclei with a D50 of 1.2μm was added as the bottom solution, sodium bicarbonate was added to adjust the pH to 8.5, the speed of the stirring blade of the reactor was adjusted to 900r/min, the reaction temperature was controlled at 40°C, the metal salt solution and the precipitant solution prepared in step (1) were added to the reactor simultaneously by a precise metering pump, and the pH of the reaction solution was maintained at 8.0-8.5, the slurry overflowing from the reactor was concentrated by a concentrator, and the solid phase after solid-liquid separation was returned to the reactor, and the cycle was repeated. During the reaction, samples were continuously taken to test the particle size. When the D50 of the material in the reactor was detected to reach 4.0μm, the feeding was stopped, and the stirring and aging was continued for 2 hours before being placed in a storage tank with stirring for storage;

(4) Continuous growth: add water to the overflow port of a clean continuous reactor, adjust the stirring speed of the reactor to 900 r/min, adjust the reaction temperature to 60°C, add sodium bicarbonate to adjust the pH of the mother liquor to 8.5, continue to use a precision metering pump to add the metal salt solution and the precipitant solution prepared in step (1) to the reactor in parallel, adjust the flow rate of the precipitant solution, and control the pH of the reaction solution to 8.5-9.0. At the same time, use a peristaltic pump to continuously feed the seed slurry synthesized in step (3) into the reactor, and control the particle size of the material in the reactor by adjusting the flow rate of the seed slurry. Take samples every 2 hours to detect that the particle size is stable at 12.0±0.5 μm, and the diameter distance is stable at 1.1-1.4. When the sphericity under an electron microscope is good, collect the overflow material;

(5) washing the collected solid material with pure water for multiple times, and then drying and sieving to obtain a manganese-rich carbonate precursor with good sphericity of 12.1 μm;

(6) The manganese-rich carbonate precursor obtained in the above step (5) is pre-fired in a rotary kiln, wherein the sintering conditions are pre-fired at 300°C for 2h, pre-fired at 400°C for 3h, and pre-fired at 550°C for 2h, and the heating rate during the pre-fired is controlled at 1°C/min, thereby obtaining the target oxide precursor Ni _0.30 Mn _0.70 O _z (CO ₃ ) _m of this embodiment, wherein the metal molar ratio of nickel to manganese can be determined by ICP-AES detection.

Comparative Example 4:

The specific implementation method, operation steps and process parameter conditions of Comparative Example 4 are basically the same as those of Example 3, except that the process of step (6) in Example 2 is not implemented, and a manganese-rich carbonate precursor is directly prepared.

Embodiment 4:

A manganese-rich oxide precursor of the present invention is obtained by step-by-step sintering of a Ni _0.40 Mn _0.60 CO ₃ precursor, and contains a nickel oxide phase and a manganese oxide phase. The D50 of the manganese-rich oxide precursor is 8.2 μm, and the diameter span = (D90-D10)/D50 is controlled at 1.28. The FWHW (211) of the manganese-rich oxide precursor is 0.38, and the BET of the manganese-rich oxide precursor is 62.47 m ² /g. The preparation method of the high-sphericity manganese-rich oxide precursor described in this embodiment comprises the following steps:

(1) using nickel sulfate and manganese sulfate as raw materials, preparing a metal salt solution with a total concentration of 2.2 mol/L according to a molar ratio of nickel to manganese of 0.4:0.6, and setting aside; using sodium carbonate as a precipitant, preparing a precipitant solution of 1.8 mol/L, and setting aside;

(2) Crystal nucleus preparation: Add water to a 100 L reactor until the blades are submerged, add sodium carbonate to adjust the pH to 12, and The stirring blade speed is adjusted to 1000 r/min, the reaction temperature is controlled at 45° C. The metal salt solution and the precipitant solution prepared in step (1) are added to the reactor in parallel by a precise metering pump, and the pH of the reaction solution is maintained at 11.9-12.1. The reaction is continued for 3 h to obtain crystal nuclei with a D50 of 1.0 μm;

(3) Seed synthesis: water was added to a 100L reactor until the blades were submerged, a solution containing 1.0kg of crystal nuclei with a D50 of 1.0μm was added as the bottom solution, sodium carbonate was added to adjust the pH to 8.5, the stirring blade speed of the reactor was adjusted to 800r/min, the reaction temperature was controlled at 45°C, the metal salt solution and the precipitant solution prepared in step (1) were added to the reactor in parallel by a precise metering pump, and the pH of the reaction solution was maintained at 8.0-8.5, the slurry overflowing from the reactor was concentrated by a concentrator, and the solid phase after solid-liquid separation was returned to the reactor, and the cycle was repeated. During the reaction, samples were continuously taken to test the particle size. When the D50 of the material in the reactor was detected to reach 3.0μm, the feeding was stopped, and the stirring and aging was continued for 2 hours before being placed in a storage tank with stirring for storage;

(4) Continuous growth: add water to the overflow port of a clean continuous reactor, adjust the stirring speed of the reactor to 900 r/min, adjust the reaction temperature to 60°C, add sodium carbonate to adjust the pH of the mother liquor to 8.5, continue to use a precision metering pump to add the metal salt solution and the precipitant solution prepared in step (1) to the reactor in parallel, adjust the flow rate of the precipitant solution, and control the pH of the reaction solution to 8.3-8.7. At the same time, use a peristaltic pump to continuously feed the seed slurry synthesized in step (3) into the reactor, and control the particle size of the material in the reactor by adjusting the flow rate of the seed slurry. Take samples every 2 hours to detect that the particle size is stable at 8.0±0.3 μm, and the diameter distance is stable at 1.1-1.4. When the sphericity under the electron microscope is good, collect the overflow material;

(5) washing the collected solid material with pure water for multiple times, and then drying and sieving to obtain a manganese-rich carbonate precursor with a sphericity of 8.2 μm;

(6) The manganese-rich carbonate precursor obtained in the above step (5) is pre-fired in a rotary kiln, wherein the sintering conditions are 200°C for 2h, 400°C for 1h, and 500°C for 3h, and the heating rate during the pre-fire is controlled at 3°C/min, thereby obtaining the target oxide precursor Ni _0.40 Mn _0.60 O _z (CO ₃ ) _m of this embodiment.

Comparative Example 5:

The specific implementation method, operation steps and process parameter conditions of Comparative Example 5 are basically the same as those of Example 4, except that the process of step (6) in Example 4 is not implemented, and a manganese-rich carbonate precursor is directly prepared.

Application examples:

The lithium-rich manganese-based positive electrode materials prepared in Examples 1, 3 and 4 of the present invention and Comparative Examples 2, 3, 4 and 5 were uniformly mixed with carbon black and PVDF, and coated on aluminum foil to make positive electrode sheets, which were assembled into CR2025 button batteries with lithium metal sheets, diaphragms and electrolytes in a vacuum glove box. The batteries were tested by an electrochemical performance tester. The discharge capacity was tested at a rate of 0.1C under a charge and discharge limiting voltage of 2.0-4.7V, and the capacity retention rate was then tested at 0.33C for 50 cycles. The charge and discharge specific capacity and capacity retention rate are shown in Table 4 below.

Table 4: Comparison of electrochemical performance tests of positive electrode materials prepared from precursors of the examples and comparative examples

It can be seen from Table 4 that the discharge capacity and cycle capacity retention rate of the positive electrode after sintering of the oxide precursor obtained by step-by-step pre-calcination are higher than those of the carbonate precursor, while the positive electrode prepared in Comparative Example 3 has the worst electrochemical performance due to phase separation during pre-calcination.

In summary, the oxide precursor product prepared by the present invention has good density and few internal cracks, and the finally obtained lithium-rich manganese positive electrode material product has uniform and stable BET and excellent electrical properties, and is suitable for industrialization.

Claims

A manganese-rich oxide precursor, comprising a nickel oxide phase and a manganese oxide phase, characterized in that the D50 of the manganese-rich oxide precursor is 4-13 μm, the diameter span=(D90-D10)/D50 is controlled at 1.1-1.4, the FWHW(211) is 0.3-0.65, and the BET of the manganese-rich oxide precursor is 30-70 m 2 /g.
The manganese-rich oxide precursor according to claim 1 is characterized in that the chemical formula of the manganese-rich oxide precursor is Ni x Mn y Me (1-xy) O z (CO 3 ) m , and 0＜x≤0.5, 0.5≤y＜1, 0<z<2, 0<m<1, and Me is one or more of the doping elements Co, Mg, Al, Zr, W, Fe, and Cu.
The manganese-rich oxide precursor according to claim 1 or 2, characterized in that there is substantially no NiMn 2 O 4 phase peak in the XRD diagram of the manganese-rich oxide precursor.
The manganese-rich oxide precursor according to claim 1 or 2, characterized in that the average crack rate of the manganese-rich oxide precursor is 2% to 10%; the manganese-rich oxide precursor is obtained by pre-sintering a carbonate precursor in steps;

The average crack rate is determined by the following method: first, the sample to be tested is polished to obtain a sample with a smooth surface, and then a CP electron microscope image is obtained using a field emission scanning electron microscope. The number of cracks in the CP electron microscope under multiple different field of view areas is counted, and the number of cracks under the single field of view/total number of particles is recorded as the single crack rate, and the average value is taken as the average crack rate.
A method for preparing a manganese-rich oxide precursor, characterized in that it comprises the following steps:

(1) preparing a metal salt solution including a nickel salt and a manganese salt, and preparing a precipitant solution including carbonate ions, and setting them aside;

(2) preparing a solution containing crystal nuclei using the metal salt solution and the precipitant solution prepared in step (1);

(3) using the solution containing crystal nuclei obtained in step (2) as the base liquid, adding the metal salt solution and the precipitant solution prepared in step (1) into the reactor, controlling the reaction temperature and pH value, stirring and concentrating with a concentrator, returning the solid phase after solid-liquid separation to the reactor, repeating the cycle, and stopping feeding after the particle size of the reaction slurry reaches the set value to obtain a seed slurry;

(4) adding the metal salt solution and the precipitant solution prepared in step (1) into the reactor in parallel, controlling the reaction temperature and pH value, and continuously adding the seed slurry synthesized in step (3) into the reactor, controlling the particle size of the material in the reactor by adjusting the flow rate of the seed slurry, until the target particle size is reached, and collecting the overflow material;

(5) separating the collected overflow material into solid and liquid, and washing and drying the obtained solid phase to obtain a carbonate precursor;

(6) Pre-calcining the carbonate precursor obtained in step (5) in an air atmosphere to obtain an oxide precursor.
The preparation method according to claim 5 is characterized in that in step (1), the nickel salt is selected from one or more of nickel sulfate, nickel chloride, nickel nitrate and nickel acetate; the manganese salt is selected from one or more of manganese sulfate, manganese chloride, manganese nitrate and manganese acetate; the precipitant solution is selected from one or more of sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution and potassium bicarbonate solution, the metal salt solution further contains Me salt, the total concentration of the prepared metal salt is 0.5 to 3 mol/L, and the concentration of the prepared precipitant is 0.5 to 3 mol/L.
The preparation method according to claim 5 is characterized in that in step (2), under stirring conditions and under normal temperature control, the prepared metal salt solution and the precipitant solution are simultaneously added to the reaction kettle by a precise metering pump, and the reaction solution is The pH of the solution is maintained at 11 to 13 to prepare crystal nuclei, wherein the particle size D50 of the crystal nuclei is 0.5 to 1.5 μm.
The preparation method according to claim 5 is characterized in that in step (4), the target particle size of the seed crystal is controlled so that its D50 is 1/3 to 1/2 of the particle size of the carbonate precursor.
The preparation method according to any one of claims 5 to 8, characterized in that in step (3), the reaction temperature is controlled at 25°C to 55°C, the pH value of the reaction is 7.5 to 9.0, and the stirring rate is controlled at 500 to 1000 rpm/min.
The preparation method according to any one of claims 5 to 8, characterized in that in step (4), the reaction temperature is controlled at 40° C. to 70° C., and the pH value of the reaction is 7.5 to 9.0.
The preparation method according to any one of claims 5 to 8, characterized in that in step (6), the pre-calcination is carried out in at least three steps, the pre-calcination temperature is 200° C. to 600° C., and the time is 2 to 8 hours.
The preparation method according to claim 11 is characterized in that the step-by-step pre-sintering specifically includes: first sintering at 200°C to 300°C for 1 to 2 hours, then heating to 300°C to 400°C at a heating rate of 1 to 5°C/min and sintering for 1 to 3 hours, and then heating to 450°C to 600°C at a heating rate of 1-5°C/min and sintering for 1 to 3 hours.
A use of a manganese-rich oxide precursor as claimed in any one of claims 1 to 4 in the preparation of a lithium-rich manganese-based positive electrode material for a lithium-ion battery.