WO2024031792A1

WO2024031792A1 - Manganese-doped cobalt carbonate, preparation method therefor, and use thereof

Info

Publication number: WO2024031792A1
Application number: PCT/CN2022/120629
Authority: WO
Inventors: 卢星华; 李长东; 阮丁山; 刘更好; 周思源; 许建锋
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司
Priority date: 2022-08-12
Filing date: 2022-09-22
Publication date: 2024-02-15
Also published as: CN115417457A; FR3138812A1

Abstract

The present invention belongs to the field of battery materials. Provided are manganese-doped cobalt carbonate, a preparation method therefor, and use thereof. The preparation method for the manganese-doped cobalt carbonate is mainly based on a wet synthesis system. When a manganese-doped cobalt carbonate seed crystal is generated for the first time, it is directly crushed to a specific particle size by means of a wet method, and then the manganese-doped cobalt carbonate seed crystal is mixed with an original mother solution to keep a particle growth environment before wet crushing and continue the growth of particles by means of wet precipitation, so that irregular soft agglomeration caused by excessively high precipitation rate of the manganese element is effectively avoided. Moreover, in the preparation method, ammonium citrate and ammonium bicarbonate are compounded to be jointly selected as a precipitant, so that cobalt and manganese elements in the wet synthesis system can be effectively complexed and released slowly and uniformly. When ammonium citrate is adsorbed on the surface of the generated particle, one negative charge layer can be generated on the surface of the particle, thereby further preventing the agglomeration of the particles generated by the system. The introduction of ammonium citrate can also avoid excessive oxidation of the doped divalent manganese element.

Description

A kind of manganese-doped cobalt carbonate and its preparation method and application

Technical field

The invention relates to the field of battery materials, and specifically relates to a manganese-doped cobalt carbonate and its preparation method and application.

Background technique

Lithium cobalt oxide is widely used in the 3C field, especially in the lithium-ion battery field, due to its high energy density. In the existing technology, in order to increase the discharge capacity of the battery, the charging voltage is often increased. However, when lithium cobalt oxide is used as the cathode material, the crystal structure of lithium cobalt oxide will inevitably undergo a phase change when charged above 4.45V, resulting in its Decreased cycling stability.

In order to improve its cycle performance, existing research mostly uses doping to modify lithium cobalt oxide. Manganese has the advantages of low cost, low toxicity, and large reserves. When doped in lithium cobalt oxide, it can effectively suppress the H2-H3 phase transition of lithium cobalt oxide at high voltage, enhance the order of cations, and inhibit cation mixing. discharge, thereby improving the overall cycle stability of the cathode material. Compared with using solid-phase doping of manganese, doping during the wet synthesis stage of lithium cobalt oxide precursor cobalt carbonate can make manganese more uniformly doped into the material lattice, further improving the structural stability of lithium cobalt oxide materials. However, due to the small precipitation coefficient of manganese, doping manganese during the wet synthesis of the precursor cobalt carbonate will aggravate the irregular soft agglomeration between particles during the synthesis, resulting in poor sphericity of the finished product and uneven sizes between particles.

Contents of the invention

Based on the shortcomings of the existing technology, the purpose of the present invention is to provide a method for preparing manganese-doped cobalt carbonate. The method is a wet synthesis system. By physically pulverizing the generated manganese-doped cobalt carbonate seed crystal, it can effectively The problem of irregular soft agglomeration of particles caused by the small precipitation coefficient of manganese is improved. At the same time, a specific compound precipitant is selected to effectively control the precipitation rate of manganese and cobalt elements and inhibit the oxidation of manganese elements. The morphology of the obtained manganese-doped cobalt carbonate material is spherical. The density is high, the particles are uniform, and the further prepared manganese-doped lithium cobalt oxide material has excellent electrochemical properties.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

A preparation method of manganese-doped cobalt carbonate, including the following steps:

(1) Configure ammonium bicarbonate solution as the bottom liquid in the reaction vessel. The volume ratio of the bottom liquid in the reaction vessel is 20% to 30%; add the mixed metal solution to the reaction vessel simultaneously at 40 to 50°C. Mix A and precipitant B, control the pH of the resulting mixed solution to drop to 7.2~7.7 for reaction, stop feeding the liquid when the reaction vessel is full, and filter to obtain liquid C and solid; wet crush the solid until D50=3 ~5 μm to obtain seed crystal D; the mixed metal solution A includes cobalt salt and divalent manganese salt; the mixed precipitant B is a mixed solution of ammonium bicarbonate and ammonium citrate;

(2) Mix liquid C and seed crystal D in a reaction vessel, add mixed metal solution A and mixed precipitant B into the reaction vessel simultaneously at 40 to 50°C, and control the pH of the resulting mixed solution to drop to 7.2 to 7.7. Reaction, stop adding liquid when the reaction container is full, let it stand and remove the supernatant, continue to add mixed metal solution A and mixed precipitant B to the reaction container at the same time and react, repeat 15 to 20 times until the reaction container is reached The obtained slurry particles D50=17~19μm;

(3) After washing and drying the slurry particles obtained in step (2), keep the particles at 600-700°C for 2-4 hours under an oxygen atmosphere, and then sieve to obtain the manganese-doped cobalt carbonate.

In the preparation method of manganese-doped cobalt carbonate of the present invention, the wet synthesis system is mainly used. When the manganese-doped cobalt carbonate seed crystal is first generated, it is directly pulverized to a specific particle size by wet method, and then combined with The original mother liquor is mixed to maintain the particle growth environment before wet grinding and continues wet precipitation to grow particles. This approach can effectively avoid the irregular soft agglomeration of manganese element caused by the excessive precipitation rate. Without specific wet grinding treatment Or if the degree of treatment is insufficient, the irregular soft agglomeration of the seed crystals will directly affect the morphology of the generated product, and even cause hollowing inside the particles. Controlling the size of the seed crystal particles through wet crushing is also more time-saving than dry crushing. . In addition, the present invention uses ammonium citrate and ammonium bicarbonate as a precipitant together, mainly because the ammonium citrate solution is weakly alkaline, and both ammonium bicarbonate and ammonium citrate can be ionized to produce ammonium ions, effectively converting the wet synthesis system into The cobalt and manganese elements are complexed and released slowly and evenly; at the same time, when ammonium citrate is adsorbed on the surface of the generated particles, a negative charge layer can be generated on the surface. This charge layer can form electrostatic repulsion and prevent the system from forming. The aggregation between particles further reduces the occurrence of agglomeration; finally, ammonium citrate also has a certain antioxidant effect, which can inhibit the oxidation of doped manganese elements.

Preferably, the cobalt salt is at least one of cobalt sulfate, cobalt nitrate, and cobalt chloride; the divalent manganese salt is at least one of manganese sulfate, manganese nitrate, and manganese chloride.

More preferably, the molar concentration of cobalt ions in the mixed metal solution A is 1.5-2 mol/L, and the mass ratio of divalent manganese ions to cobalt ions is (0.005-0.012):1.

Preferably, the mixed precipitant B is a mixed aqueous solution of ammonium bicarbonate and ammonium citrate. The molar concentration of ammonium bicarbonate in the mixed aqueous solution is 2.5~3mol/L, and the molar concentration of ammonium citrate is 0.03~0.08mol/L. L.

The inventor also found that by selecting ammonium citrate and ammonium bicarbonate in this molar concentration range as a precipitant, the anti-agglomeration performance and antioxidant properties of ammonium citrate are better, and the wet synthesis system can be more effectively synthesized. The cobalt and manganese elements in it are complexed and released slowly and evenly.

Preferably, the concentration of the ammonium bicarbonate solution used as the bottom liquid in step (1) is 1.3-1.8 mol/L.

Preferably, the flow rate of mixed metal solution A in steps (1) and (2) is 2-3L/h, and the flow rate of mixed precipitant B is controlled by a PLC control system.

When the flow rate of mixed metal solution A is fixed, the pH of the overall mixed solution can be effectively adjusted to maintain a range of 7.2 to 7.7 by regulating the addition flow rate of mixed precipitant B through the PLC control system.

Preferably, the specific steps for washing and drying the slurry particles in step (3) are: after the slurry particles are centrifugally washed with pure water at 60-80°C until the chloride ion content is ≤200 ppm, the resulting filter cake is filtered under a protective atmosphere. Dry at 100~120℃ for 2~4 hours.

More preferably, the protective atmosphere is a nitrogen atmosphere.

The above washing and drying methods are not only more efficient, but also prevent the manganese element in the product from being over-oxidized, which will lead to product deactivation, making the overall product more pure.

Another object of the present invention is to provide manganese-doped cobalt carbonate prepared by the method for preparing manganese-doped cobalt carbonate.

The manganese-doped cobalt carbonate prepared by the preparation method of the present invention has uniform morphology and size, high sphericity, dispersed particles without agglomeration, and uniform distribution of doped manganese.

The invention also provides the application of the manganese-doped cobalt carbonate in preparing lithium-ion battery cathode materials.

Preferably, the lithium ion battery cathode material is a manganese-doped lithium cobalt oxide binary material.

The lithium-ion battery cathode material further prepared by using the manganese-doped cobalt carbonate as a precursor material of the present invention has excellent crystal structure stability and can maintain good cycle stability in a high-voltage charge and discharge environment.

The beneficial effect of the present invention is that the present invention provides a preparation method for manganese-doped cobalt carbonate. The preparation method is mainly based on a wet synthesis system. When the manganese-doped cobalt carbonate crystal seed is first generated, it is directly passed through a wet process. method to crush to a specific particle size, and then mix it with the original mother liquor to maintain the particle growth environment before wet crushing and continue wet precipitation to grow particles, effectively avoiding irregular soft agglomeration of manganese element caused by excessive precipitation rate; in addition, This preparation method uses a combination of ammonium citrate and ammonium bicarbonate as a precipitant, which can effectively complex the cobalt and manganese elements in the wet synthesis system and release them slowly and evenly. When the ammonium citrate is adsorbed on the generated particles, On the surface, a negative charge layer can be generated on the surface to further prevent aggregation between particles generated by the system; the introduction of ammonium citrate can also avoid excessive oxidation of doped divalent manganese elements.

Description of drawings

Figure 1 is a scanning electron microscope image of manganese-doped cobalt carbonate obtained in Example 1 of the present invention;

Figure 2 is a manganese element Mapping diagram of manganese-doped cobalt carbonate obtained in Example 1 of the present invention;

Figure 3 is a scanning electron microscope image of the particle cross-section of manganese-doped cobalt carbonate obtained in Example 1 of the present invention;

Figure 4 is a scanning electron microscope image of manganese-doped cobalt carbonate obtained in Example 5 of the present invention;

Figure 5 is a scanning electron microscope image of manganese-doped cobalt carbonate obtained in Comparative Example 2 of the present invention;

Figure 6 is a scanning electron microscope image of the particle cross-section of manganese-doped cobalt carbonate obtained in Comparative Example 4 of the present invention;

Figure 7 is a scanning electron microscope image of the particle cross-section of manganese-doped cobalt carbonate obtained in Comparative Example 5 of the present invention.

Detailed ways

In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific examples and comparative examples. The purpose is to understand the content of the present invention in detail, but not to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The experimental reagents, raw materials and instruments designed for the implementation and comparative examples of the present invention are all commonly used common reagents, raw materials and instruments unless otherwise specified.

Example 1

An embodiment of manganese-doped cobalt carbonate and its preparation method and application of the present invention includes the following steps:

(1) Configure an aqueous solution of ammonium bicarbonate with a concentration of 1.8 mol/L in a stainless steel reaction kettle as the bottom liquid. The volume proportion of the bottom liquid in the reaction kettle is 20% to 30%; stir at high speed at 50°C Add mixed metal solution A and mixed precipitant B to the reaction kettle simultaneously under the conditions, where the flow rate of mixed metal solution A is 2L/h, and the flow rate of mixed precipitant B is adjusted through the PLC control system to control the pH drop of the resulting mixed solution. Go to 7.2 to react, stop feeding the liquid when the reaction kettle is full, pump the slurry from the steaming kettle into a centrifuge for filtration, and obtain liquid C and solid; move liquid C to the mother liquor tank for later use, and remove the solid containing a small amount of free water. The ultrafine powder wet grinder is pulverized to D50 = 3.2 μm to obtain seed crystal D; the mixed metal solution A is an aqueous solution of cobalt chloride and manganese chloride, in which the molar concentration of cobalt ions is 1.5 mol/L. , the mass ratio of divalent manganese ions to cobalt ions is 0.012:1; the mixed precipitant B is a mixed solution of ammonium bicarbonate and ammonium citrate, the molar concentration of ammonium bicarbonate is 2mol/L, and the molar concentration of ammonium citrate The concentration is 0.03mol/L;

(2) Put liquid C and seed crystal D back into the reactor and mix them. Add mixed metal solution A and mixed precipitant B to the reactor at 50°C and high-speed stirring conditions at the same time. Each condition is the same as step (1). , control the pH of the resulting mixed solution to drop to 7.2 for the reaction. When the reaction kettle is full, stop feeding the liquid, let it stand and extract the supernatant to remove it. Continue to add mixed metal solution A and mixed precipitant B to the reaction kettle at the same time. Carry out the reaction and repeat 17 times until the D50 of the slurry particles obtained in the reaction vessel is 18.4 μm; subject the slurry particles to scanning electron microscopy observation and EDS element content and distribution analysis, and perform cross-section processing and scanning electron microscopy observation on the slurry particles. The results are shown in Figure 1, Figure 2 and Figure 3. The microscopic shape of each particle is regular and the size is uniform. The manganese content is 5644ppm. The particle cross section is smooth and flat, and there is no cavity structure inside the particle;

(3) After the slurry particles obtained in step (2) are centrifugally washed with pure water at 70°C until the chloride ion content is ≤200ppm, the obtained filter cake is dried at 120°C for 2 hours under a nitrogen atmosphere, and finally kept at 700°C for 2 hours under an oxygen atmosphere. , sieve to obtain the manganese-doped cobalt carbonate.

Example 2

(1) Configure an aqueous solution of ammonium bicarbonate with a concentration of 1.3 mol/L in a stainless steel reaction kettle as the bottom liquid. The volume proportion of the bottom liquid in the reaction kettle is 20% to 30%; at 45°C, stir at high speed Add mixed metal solution A and mixed precipitant B to the reaction kettle simultaneously under the conditions, where the flow rate of mixed metal solution A is 2.5L/h, and the flow rate of mixed precipitant B is adjusted through the PLC control system to control the pH of the resulting mixed solution Drop to 7.7 to react. Stop feeding the liquid when the reaction kettle is full. Pump the slurry from the steaming kettle into a centrifuge for filtration to obtain liquid C and solids. Liquid C is moved to the mother liquor tank for later use, and the liquid C containing a small amount of free water is The solid is pulverized by an ultrafine powder wet grinder to D50 = 4 μm to obtain seed crystal D; the mixed metal solution A is an aqueous solution of cobalt chloride and manganese chloride, in which the molar concentration of cobalt ions is 2mol/L. The mass ratio of divalent manganese ions to cobalt ions is 0.005:1; the mixed precipitant B is a mixed solution of ammonium bicarbonate and ammonium citrate, the molar concentration of ammonium bicarbonate is 3mol/L, and the molar concentration of ammonium citrate is 0.05mol/L;

(2) Put liquid C and seed crystal D back into the reactor and mix them. Add mixed metal solution A and mixed precipitant B to the reactor at 45°C and high-speed stirring at the same time. Each condition is the same as step (1). , control the pH of the resulting mixed solution to drop to 7.7 for the reaction. When the reaction kettle is full, stop feeding the liquid, let it stand and extract the supernatant to remove it. Continue to add mixed metal solution A and mixed precipitant B to the reaction kettle at the same time. Carry out the reaction and repeat 20 times until the D50 of the slurry particles obtained in the reaction vessel is 19.5 μm; subject the slurry particles to scanning electron microscopy observation and EDS element content and distribution analysis, and perform cross-section processing and scanning electron microscopy observation on the slurry particles. The results are similar to Example 1. Each particle has a regular microscopic shape and uniform size. The manganese content is 2353 ppm. The cross-section of the particles is smooth and flat, and there is no cavity structure inside the particles;

(3) After centrifugally washing the slurry particles obtained in step (2) with pure water at 70°C until the chloride ion content is ≤200ppm, dry the obtained filter cake at 100°C for 4 hours under a nitrogen atmosphere, and finally keep it at 600°C for 4 hours under an oxygen atmosphere. , sieve to obtain the manganese-doped cobalt carbonate.

Example 3

(1) Configure an aqueous solution of ammonium bicarbonate with a concentration of 1.5 mol/L in a stainless steel reaction kettle as the bottom liquid. The volume proportion of the bottom liquid in the reaction kettle is 20% to 30%; at 40°C, stir at high speed Add mixed metal solution A and mixed precipitant B to the reaction kettle simultaneously under the conditions, where the flow rate of mixed metal solution A is 3L/h, and the flow rate of mixed precipitant B is adjusted through the PLC control system to control the pH drop of the resulting mixed solution The reaction proceeds to 7.5. When the reaction kettle is full, stop feeding the liquid. Pour the slurry from the steaming kettle into a centrifuge for filtration to obtain liquid C and solids. Liquid C is moved to the mother liquor tank for later use, and the solids containing a small amount of free water are removed. The ultrafine powder wet grinder is pulverized to D50 = 4.9 μm to obtain seed crystal D; the mixed metal solution A is an aqueous solution of cobalt chloride and manganese chloride, in which the molar concentration of cobalt ions is 1.8 mol/L. , the mass ratio of divalent manganese ions and cobalt ions is 0.008:1; the mixed precipitant B is a mixed solution of ammonium bicarbonate and ammonium citrate, the molar concentration of ammonium bicarbonate is 2.5mol/L, and the molar concentration of ammonium citrate is The molar concentration is 0.08mol/L;

(2) Put liquid C and seed crystal D back into the reaction kettle and mix them. Add mixed metal solution A and mixed precipitant B into the reaction kettle at 40°C under high-speed stirring conditions. Each condition is the same as step (1). , control the pH of the resulting mixed solution to drop to 7.5 for the reaction. When the reaction kettle is full, stop feeding the liquid, let it stand and extract the supernatant to remove it. Continue to add mixed metal solution A and mixed precipitant B to the reaction kettle at the same time. Carry out the reaction and repeat 15 times until the D50 of the slurry particles obtained in the reaction vessel is 17.8 μm; conduct scanning electron microscopy observation and EDS element content and distribution analysis of the slurry particles, and conduct cross-section processing and scanning electron microscopy observation of the slurry particles. The results are similar to Example 1. Each particle has a regular microscopic shape and uniform size. The manganese content is 3848ppm. The cross-section of the particles is smooth and flat, and there is no cavity structure inside the particles.

(3) After centrifugally washing the slurry particles obtained in step (2) with pure water at 70°C until the chloride ion content is ≤200ppm, dry the obtained filter cake at 110°C for 3 hours under a nitrogen atmosphere, and finally keep it at 650°C for 3 hours under an oxygen atmosphere. , sieve to obtain the manganese-doped cobalt carbonate.

Example 4

The only difference between this example and Example 1 is that the ammonium citrate concentration of the mixed precipitant B is 0.1 mol/L; the slurry particles D50 obtained in the step (2) = 18.2 μm; the manganese content of the slurry particles The element content is 5308ppm.

Example 5

The only difference between this embodiment and Example 1 is that the ammonium citrate concentration of the mixed precipitant B is 0.01 mol/L. The D50 of the slurry particles obtained in step (2) is 18.3 μm; the manganese element content of the slurry particles is 5627 ppm. The slurry particles were observed under a scanning electron microscope. As shown in Figure 4, compared with Example 1, each particle has irregular microscopic shapes and uneven sizes.

Comparative example 1

The only difference between this comparative example and Example 1 is that the mixed precipitant B is a mixed solution of ammonium bicarbonate and sodium hexametaphosphate, the molar concentration of ammonium bicarbonate is 2 mol/L, and the molar concentration of sodium hexametaphosphate is 0.03mol/L. The D50 of the slurry particles obtained in step (2) is 18.6 μm; the manganese element content of the slurry particles is 5658 ppm. The observation and analysis of the slurry particles are similar to those in Example 1.

Comparative example 2

The only difference between this comparative example and Example 1 is that the mixed precipitant B is a mixed solution of ammonium bicarbonate and hydrazine hydrate. The molar concentration of ammonium bicarbonate is 2 mol/L and the molar concentration of hydrazine hydrate is 0.03 mol/L. . The D50 of the slurry particles obtained in step (2) is 18.4 μm; the manganese element content of the slurry particles is 5624 ppm. The slurry particles were observed with a scanning electron microscope. The results are shown in Figure 5. The particles have irregular shapes and uneven sizes.

Comparative example 3

The only difference between this comparative example and Example 1 is that the mixed metal solution A does not contain divalent manganese salt.

Comparative example 4

(1) Configure an aqueous solution of ammonium bicarbonate with a concentration of 1.8 mol/L in a stainless steel reaction kettle as the bottom liquid. The volume proportion of the bottom liquid in the reaction kettle is 20% to 30%; stir at high speed at 50°C Add mixed metal solution A and mixed precipitant B to the reaction kettle simultaneously under the conditions, where the flow rate of mixed metal solution A is 2L/h, and the flow rate of mixed precipitant B is adjusted through the PLC control system to control the pH drop of the resulting mixed solution. Go to 7.2 to react, stop feeding the liquid when the reaction kettle is full, pump the slurry from the steaming kettle into a centrifuge for filtration, and obtain liquid C and solid; move liquid C to the mother liquor tank for later use, and remove the solid containing a small amount of free water. The ultrafine powder wet grinder is pulverized to D50 = 6.8 μm to obtain seed crystal D; the mixed metal solution A is an aqueous solution of cobalt chloride and manganese chloride, in which the molar concentration of cobalt ions is 1.5 mol/L. , the mass ratio of divalent manganese ions to cobalt ions is 0.012:1; the mixed precipitant B is a mixed solution of ammonium bicarbonate and ammonium citrate, the molar concentration of ammonium bicarbonate is 2mol/L, and the molar concentration of ammonium citrate The concentration is 0.03mol/L;

(2) Put liquid C and seed crystal D back into the reactor and mix them. Add mixed metal solution A and mixed precipitant B to the reactor at 50°C and high-speed stirring conditions at the same time. Each condition is the same as step (1). , control the pH of the resulting mixed solution to drop to 7.2 for the reaction. When the reaction kettle is full, stop feeding the liquid, let it stand and extract the supernatant to remove it. Continue to add mixed metal solution A and mixed precipitant B to the reaction kettle at the same time. Carry out the reaction and repeat it 17 times until the D50 of the slurry particles obtained in the reaction vessel is 18.35 μm; conduct cross-section processing of the slurry particles and conduct scanning electron microscope observation and element content analysis. The results are shown in Figure 6. The manganese content of the slurry particles is The element content is 5685ppm; the cross-section of the particles is uneven and there are some hollow structures inside;

Comparative example 5

(1) Configure an aqueous solution of ammonium bicarbonate with a concentration of 1.8 mol/L in a stainless steel reaction kettle as the bottom liquid. The volume proportion of the bottom liquid in the reaction kettle is 20% to 30%; stir at high speed at 50°C Add mixed metal solution A and mixed precipitant B to the reaction kettle simultaneously under the conditions, where the flow rate of mixed metal solution A is 2L/h, and the flow rate of mixed precipitant B is adjusted through the PLC control system to control the pH drop of the resulting mixed solution. Go to 7.2 to react. Stop feeding the liquid when the reaction kettle is full. Pump the slurry liquid from the steaming kettle into a centrifuge for filtration to obtain liquid C and seed crystal D. Liquid C is moved to the mother liquor tank for later use. The seed crystal D is D50=8.5μm; the mixed metal solution A is an aqueous solution of cobalt chloride and manganese chloride, in which the molar concentration of cobalt ions is 1.5mol/L, and the mass ratio of divalent manganese ions and cobalt ions is 0.012:1; The mixed precipitant B is a mixed solution of ammonium bicarbonate and ammonium citrate, the molar concentration of ammonium bicarbonate is 2mol/L, and the molar concentration of ammonium citrate is 0.03mol/L;

(2) Put liquid C and seed crystal D back into the reactor and mix them. Add mixed metal solution A and mixed precipitant B to the reactor at 50°C and high-speed stirring conditions at the same time. Each condition is the same as step (1). , control the pH of the resulting mixed solution to drop to 7.2 for the reaction. When the reaction kettle is full, stop feeding the liquid, let it stand and extract the supernatant to remove it. Continue to add mixed metal solution A and mixed precipitant B to the reaction kettle at the same time. Carry out the reaction and repeat it 17 times until the D50 of the slurry particles obtained in the reaction vessel is 18.8 μm; conduct cross-section processing of the slurry particles and conduct scanning electron microscope observation and element content analysis. The results are shown in Figure 7. The manganese content of the slurry particles is The element content is 5671ppm, and there are many hollow structures inside the particles;

Comparative example 6

The only difference between this comparative example and Example 1 is that there is no nitrogen protection during the drying process in step (3).

Comparative example 7

The difference between this comparative example and Example 1 is that ammonium citrate is not added to the mixed precipitant B and there is no nitrogen protection during the drying process in step (3).

Effect example 1

In order to verify the performance excellence of the products obtained by the preparation method of manganese-doped cobalt carbonate of the present invention, the products of each example and comparative example were mixed with lithium carbonate according to the molar ratio n _Li : n _(Co+Mn) = 1:1. The doped lithium cobalt oxide cathode material is prepared by mixing and sintering, and is further prepared into a cathode sheet. The negative electrode sheet prepared from commercial graphite material and lithium hexafluorophosphate are used as the electrolyte to assemble a lithium ion button half battery. In a constant temperature environment of 45°C, Charge and discharge cycle tests were conducted at a current density of 1C and an operating voltage of 4.55V. The test results are shown in Table 1.

Table 1

It can be seen from Table 1 that the cathode materials prepared from the products of each embodiment as precursors have good cycle stability. After 50 high-temperature and high-voltage cycles, they can still reach a maximum capacity retention rate of 91.5%, and after 70 cycles The capacity retention rate reaches above 80%. It can be seen from the comparison of the product performance of Example 1 and Example 4 that due to the introduction of too much ammonium citrate during the product preparation process, the concentration of ammonium citrate is high, resulting in an increase in its ability to complex manganese, and some metal ions follow. The mother liquor was discharged, causing the doping amount to be lower than the theoretical design value. Although the initial discharge specific capacity of the obtained product was slightly higher than that of Example 1, the cycle performance was slightly worse than that of Example 1; and from the product performance of Example 5 and Example 1 It can be seen from the comparison that if the concentration of ammonium citrate in the composite precipitant is low, its anti-polymerization and antioxidant properties will not reach the optimal effect. In terms of electrochemical performance, the initial discharge ratio of the product obtained in Example 5 The capacity and cycle capacity retention rate are both lower than the product of Example 1. In contrast, Comparative Examples 1 and 2 used other precipitants with ammonium bicarbonate. Among them, sodium hexametaphosphate itself did not have an antioxidant effect. The manganese element was over-oxidized and could not be uniformly doped in the cobalt lattice. Although The prepared precursor particles have good morphology and size uniformity, but the cycle stability of the final product is poor when used. Compared with Comparative Example 3 without manganese element, the improvement is not significant; the preparation process of the product of Comparative Example 2 is Although the hydrazine hydrate used has antioxidant effects, it actually does not have a significant effect on improving particle dispersion. Therefore, the particle size uniformity of the prepared product is poor, which further affects the electrochemical cycle stability of the final prepared cathode material. . During the preparation process of the product of Comparative Example 4, the crushing effect of the seed crystals was not good. The crushed seed crystal particles were too large, which easily caused the formation of cavity structures inside the precursor particles. The stability of the overall structure deteriorated, and the cycle of the further prepared cathode materials was poor. The stability is poor; however, the manganese-doped cobalt carbonate product prepared without seed wet pulverization treatment has many holes in the particle structure. After further application in the preparation of cathode materials, the electrochemical cycle stability is different from that of undoped cobalt carbonate. The product of Comparative Example 3 containing miscellaneous manganese is equivalent. It can be seen from the comparison of the product performance of Comparative Example 6 and Example 1 that without nitrogen protection, the cycle stability of the finally prepared product is poor due to the oxidation of manganese element. It can be seen from Comparative Example 7 and Example 1 that when ammonium citrate is not introduced as a precipitant compound component during the preparation process of the product and nitrogen protection is not introduced during the drying period, it will directly lead to excessive oxidation of the manganese element in the product, and the product's The cycle performance stability is poor.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and do not limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that The technical solution of the present invention may be modified or equivalently substituted without departing from the essence and scope of the technical solution of the present invention.

Claims

A method for preparing manganese-doped cobalt carbonate, which is characterized by comprising the following steps:

(1) Configure ammonium bicarbonate solution as the bottom liquid in the reaction vessel. The volume ratio of the bottom liquid in the reaction vessel is 20% to 30%; add the mixed metal solution to the reaction vessel simultaneously at 40 to 50°C. Mix A and precipitant B, control the pH of the resulting mixed solution to drop to 7.2~7.7 for reaction, stop feeding the liquid when the reaction vessel is full, and filter to obtain liquid C and solid; wet crush the solid until D50=3 ~5 μm to obtain seed crystal D; the mixed metal solution A includes cobalt salt and divalent manganese salt; the mixed precipitant B is a mixed solution of ammonium bicarbonate and ammonium citrate;

(2) Mix liquid C and seed crystal D in a reaction vessel, add mixed metal solution A and mixed precipitant B into the reaction vessel simultaneously at 40 to 50°C, and control the pH of the resulting mixed solution to drop to 7.2 to 7.7. Reaction, stop adding liquid when the reaction container is full, let it stand and remove the supernatant, continue to add mixed metal solution A and mixed precipitant B to the reaction container at the same time and react, repeat 15 to 20 times until the reaction container is reached The obtained slurry particles D50=17~19μm;

(3) After washing and drying the slurry particles obtained in step (2), keep the particles at 600-700°C for 2-4 hours under an oxygen atmosphere, and then sieve to obtain the manganese-doped cobalt carbonate.
The preparation method of manganese-doped cobalt carbonate according to claim 1, wherein the cobalt salt is at least one of cobalt sulfate, cobalt nitrate, and cobalt chloride; the divalent manganese salt is manganese sulfate, nitric acid At least one of manganese and manganese chloride.
The preparation method of manganese-doped cobalt carbonate according to claim 1, characterized in that the molar concentration of cobalt ions in the mixed metal solution A is 1.5-2mol/L, and the mass ratio of divalent manganese ions to cobalt ions is ( 0.005～0.012):1.
The preparation method of manganese-doped cobalt carbonate according to claim 1, characterized in that the mixed precipitant B is a mixed aqueous solution of ammonium bicarbonate and ammonium citrate, and the molar concentration of ammonium bicarbonate in the mixed aqueous solution is 2.5~ 3mol/L, the molar concentration of ammonium citrate is 0.03~0.08mol/L.
The method for preparing manganese-doped cobalt carbonate according to claim 1, characterized in that the concentration of the ammonium bicarbonate solution used as the bottom liquid in step (1) is 1.3-1.8 mol/L.
The preparation method of manganese-doped cobalt carbonate according to claim 1, characterized in that in the steps (1) and (2), the flow rate of the mixed metal solution A is 2-3L/h, and the flow rate of the mixed precipitant B passes through PLC control system regulation.
The preparation method of manganese-doped cobalt carbonate according to claim 1, characterized in that the specific steps of washing and drying the slurry particles in the step (3) are: the slurry particles are centrifugally washed with pure water at 60-80°C After the chloride ion content is ≤200ppm, the obtained filter cake is dried at 100-120°C for 2-4 hours under a protective atmosphere.
The method for preparing manganese-doped cobalt carbonate according to claim 7, wherein the protective atmosphere is a nitrogen atmosphere.
The manganese-doped cobalt carbonate prepared by the method for preparing manganese-doped cobalt carbonate according to any one of claims 1 to 8.
The application of manganese-doped cobalt carbonate in preparing lithium-ion battery cathode materials as claimed in claim 9.