Method for rapidly and efficiently preparing hydroxyl cobalt oxide uniformly doped with aluminum and magnesium

Abstract

The invention provides a method for rapidly and efficiently preparing hydroxyl cobalt oxide uniformly doped with aluminum and magnesium, which comprises the following steps: adding aluminum salt and magnesium salt into a cobalt ion-containing aqueous solution to obtain a first mixed solution; slowly adding hydrogen peroxide into the first mixed solution under a rapid stirring condition to obtain a second mixed solution; under the stirring condition, adding the second mixed solution and a sodium hydroxide solution into a reaction container according to a certain proportion, and controlling the feeding time, the reaction temperature and the reaction time to obtain a product containing precipitates; and finally, carrying out solid-liquid separation, washing and drying to obtain a target product. The prepared hydroxyl cobalt oxide uniformly doped with aluminum and magnesium has the advantages of small particle size, high specific surface area, uniform doping, controllable doping amount and the like; the preparation process is simple and rapid in reaction, can realize uniform doping of aluminum and magnesium elements and avoid the phenomenon of element aggregation under the conditions of rapidness and low energy consumption, and has certain popularization and application prospects.

Description

Technical Field

[0001] The invention belongs to the field of cobalt material preparation, and in particular relates to a method for quickly and efficiently preparing aluminum-magnesium uniformly doped cobalt oxyhydroxide. Background Art

[0002] With the continuous updating and iteration of 3C products and the rapid development of high-end smart devices, the demand for thinner and lighter batteries with higher capacity is growing. In response to this trend, this research field faces two challenges: one is to improve the compaction density of the material, and the other is to significantly improve the gram-to-gram capacity of lithium cobalt oxide. In this process, the doping of different elements plays a key role in optimizing the structure of lithium cobalt oxide.

[0003] The doping of Al element has attracted wide attention due to its unique advantages: first, Al 3+ With Co 3+ The Al element has a similar ionic radius and the same valence state; secondly, the Al element has a single valence, which is conducive to stabilizing the material structure; thirdly, it can increase the charging voltage of the positive electrode material and enhance the thermal stability of the material; finally, the bond energy of the Al-O bond is higher than that of the CO bond, and aluminum-doped cobalt tetroxide currently dominates the market. Therefore, the present invention aims to further improve the performance of lithium cobalt oxide by optimizing the doping elements.

[0004] Doping lithium cobalt oxide with a proper amount of divalent Mg element can effectively improve the conductivity of the material while keeping the crystal structure unchanged, and maintain the stability of the single-phase structure during the charge and discharge cycle; when the Mg element occupies the Co position, it can significantly improve the voltage performance and cycle stability of the material.

[0005] Patent document with publication number CN118270854A discloses a nano-scale doped cobalt hydroxide oxide and its preparation method and application. The patent prepares nano-scale doped cobalt hydroxide oxide by liquid phase synthesis method. The preparation method includes first preparing a mixed solution of cobalt salt, doped metal aluminum salt and hydrogen peroxide, then preparing a base solution containing sodium hydroxide and ammonia water, mixing the two solutions, and coprecipitating the doped cobalt hydroxide oxide in the solution system. The patent lists several embodiments of changing the order of adding materials. The synthesized cobalt hydroxide oxide has a BET range of 30-120 m 2 / g. However, the patent has the following problems: (1) Only doping with aluminum element cannot guarantee the conductivity and cycle stability of the material; (2) There are many process nodes that need to be controlled during the synthesis process; (3) Ammonia water is used as a complexing agent, which increases the difficulty of wastewater treatment; (4) The synthesis takes 4 hours, the reaction time is long, and the cost is increased.

[0006] Based on this, providing a method for quickly and efficiently preparing aluminum-magnesium uniformly doped cobalt hydroxide oxide is a technical problem that needs to be solved urgently. Summary of the invention

[0007] One of the purposes of the present invention is to provide a method for quickly and efficiently preparing aluminum-magnesium uniformly doped cobalt oxyhydroxide.

[0008] A second object of the present invention is to provide cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

[0009] The technical solution adopted by the present invention to achieve one of the objectives is to provide a method for quickly and efficiently preparing aluminum-magnesium uniformly doped cobalt oxyhydroxide, comprising the following steps: S1, adding aluminum salt and magnesium salt to an aqueous solution having a cobalt ion concentration of 130-140 g / L according to a mass ratio of the metal elements of cobalt, aluminum and magnesium of 1000:(6-14):(2-5) to obtain a first mixed solution; S2. Under the condition of a stirring speed of 1200-1400 r / min, slowly adding hydrogen peroxide to the first mixed solution at a volume percentage of 0.2%-0.6%, to obtain a second mixed solution; S3, under the condition of a stirring speed of 500-700 r / min, the second mixed solution and the sodium hydroxide solution are simultaneously injected into the reaction container containing bottom water according to a volume ratio of 1: (4-6), the feeding time is controlled to be 3-10min, and the temperature is 20-40°C and the stirring is continued for 5-20min to obtain a product; S4. Performing solid-liquid separation, washing and drying on the product to obtain cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

[0010] The overall idea of ​​the present invention is as follows: In order to quickly and efficiently realize the preparation of aluminum-magnesium uniformly doped cobalt hydroxide oxide, the present invention is improved on the basis of the conventional preparation method, mainly by controlling the proportion and method of adding hydrogen peroxide to control the degree of oxidation, and by controlling the feeding method, feeding speed and stirring speed to accelerate the reaction time.

[0011] In the preparation method provided by the present invention, first, during the preparation of the cobalt liquid, after the cobalt, aluminum and magnesium elements are uniformly dissolved, hydrogen peroxide is slowly added under the condition of rapid stirring. The cobalt liquid is rapidly dispersed by increasing the stirring speed when the hydrogen peroxide is fed, and the high stirring speed can quickly oxidize the cobalt ions, so that the cobalt ions are in a highly active state. Secondly, by controlling the ratio of the first cobalt-containing mixed solution to the hydrogen peroxide, rapid oxidation and uniform coprecipitation are achieved. Finally, in the feeding and reaction stages, the feeding method is improved and the feeding time is shortened to 1-10min to achieve the purpose of rapid feeding; in addition, the present invention also controls the feeding time so that the feeding speed and the bottom water speed reach the optimal ratio, promotes uniform coprecipitation of the raw materials and then achieves uniform doping.

[0012] Furthermore, in the present invention, the dosage ratio of hydrogen peroxide to the cobalt-containing solution is a key factor in determining the reaction time, product particle size and morphology. The present invention sets the amount of hydrogen peroxide added to be 0.2%-0.6% of the volume percentage of the first mixed solution containing cobalt. After a lot of research and exploration, when the amount of hydrogen peroxide used is lower than this range, divalent cobalt cannot be completely oxidized to trivalent cobalt, and the reaction time is extended, which cannot meet the needs of rapid preparation; and when the amount of hydrogen peroxide used is higher than this range, the particle size and morphology of the product will change, and the product particles will become solid, reducing the specific surface area, and cannot effectively meet subsequent application requirements. Preferably, the amount of hydrogen peroxide added is 0.5%-0.6% of the volume percentage of the first mixed solution containing cobalt.

[0013] Furthermore, in step S1, the cobalt salt used to prepare the aqueous solution of cobalt ions is selected from cobalt chloride and / or cobalt sulfate; the aluminum salt is selected from a combination of one or more of aluminum chloride hexahydrate, aluminum sulfate 18hydrate, and aluminum nitrate; and the magnesium salt is selected from magnesium chloride hexahydrate and / or magnesium sulfate heptahydrate.

[0014] Furthermore, in step S1, the metal mass ratio of cobalt, aluminum and magnesium is 1000:(6-10):(2-3).

[0015] Furthermore, in step S2, the rate of adding hydrogen peroxide is controlled to be 40-60 mL / min.

[0016] Preferably, in step S2, as the magnesium content in the first mixed solution increases, the rotation speed gradually increases when hydrogen peroxide is added, and the volume percentage of hydrogen peroxide added also increases accordingly. The increase in the volume percentage of hydrogen peroxide added makes it more conducive to the coprecipitation of cobalt with magnesium ions after oxidation; and the external rotation speed also increases accordingly, which can promote rapid and uniform mixing of cobalt, aluminum and magnesium and avoid the occurrence of element segregation.

[0017] Furthermore, in step S2, the concentration of the hydrogen peroxide solution is 25 wt.%-30 wt.%.

[0018] Furthermore, in step S3, the content of bottom water in the reaction container accounts for 40%-50% of the volume of the reaction container.

[0019] Furthermore, in step S3, the concentration of the sodium hydroxide solution is 0.1-0.2 mol / L.

[0020] Furthermore, in step S3, the flow rate of the second mixed solution is 10-30 L / min.

[0021] Furthermore, in step S3, the feeding time is 1-5 min, and the reaction time is 8-12 min.

[0022] Preferably, the feeding method adopted in step S3 is as follows: a reaction liquid pre-storage container is set above the reaction container, and the second mixed solution is pre-pumped into the reaction liquid pre-storage container by a lifting device (such as a lifting pump); and then in the feeding stage, the second mixed solution in the reaction liquid pre-storage container is added to the reaction container at one time by gravity. Compared with the traditional method of introducing the reaction liquid into the reaction container by a pump, this method significantly shortens the feeding time (the feeding time is 1-3 minutes), and better meets the needs of rapid reaction and preparation.

[0023] The technical solution adopted by the present invention to achieve the second purpose is: to provide a cobalt oxyhydroxide uniformly doped with aluminum and magnesium, which is prepared by the preparation method according to one of the purposes of the present invention.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a method for quickly and efficiently preparing aluminum-magnesium uniformly doped cobalt oxyhydroxide, which has a simple and rapid reaction and can achieve uniform doping of aluminum and magnesium elements under fast and low energy consumption conditions, thereby ensuring uniform distribution of the elements in the material, avoiding the occurrence of element aggregation, and ensuring the stability of the doping amount in the product.

[0025] (2) The method provided by the present invention can also prepare cobalt oxyhydroxide uniformly doped with aluminum and magnesium elements without the need to add EDTA or ammonia water as a complexing agent. Compared with the conventional preparation process, the present invention does not add EDTA or ammonia water, which can avoid the introduction of organic matter or impurities, avoid the generation of COD in wastewater and increase treatment costs, and is more in line with the concept of green environmental protection.

[0026] (3) The aluminum-magnesium uniformly doped cobalt hydroxide oxide prepared by the present invention has the advantages of small particle size, high specific surface area, uniform doping and controllable doping amount, and has broad promotion and application prospects in lithium-ion battery positive electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 2 of the present invention; Figure 3 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 3 of the present invention; Figure 4 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 4 of the present invention; Figure 5 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 5 of the present invention; Figure 6 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 6 of the present invention; Figure 7 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 7 of the present invention; Figure 8 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 8 of the present invention; Fig. 9 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 9 of the present invention; Fig.10 This is a scanning electron microscope image of the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 10 of the present invention; Fig.11 This is an element distribution test diagram of the aluminum-magnesium uniformly doped cobalt oxyhydroxide prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] The embodiment of the present invention provides a method for quickly and efficiently preparing aluminum-magnesium uniformly doped cobalt oxyhydroxide, comprising the following steps: Step 1: adding aluminum salt and magnesium salt to an aqueous solution with a cobalt ion concentration of 130-140 g / L according to the mass ratio of the metal elements of cobalt, aluminum and magnesium of 1000:(6-10):(2-3) to obtain a first mixed solution; wherein the cobalt salt is selected from cobalt chloride and / or cobalt sulfate; the aluminum salt is selected from a combination of one or more of aluminum chloride hexahydrate, aluminum sulfate 18hydrate, and aluminum nitrate; and the magnesium salt is selected from magnesium chloride hexahydrate and / or magnesium sulfate heptahydrate; Step 2: under the condition of a stirring speed of 1200-1400 r / min, slowly adding hydrogen peroxide with a mass concentration of 25wt.%-30wt.% to the first mixed solution according to a volume percentage of 0.2%-0.6%, and the addition rate of hydrogen peroxide is controlled to be 40-60mL / min to obtain a second mixed solution; Step 3: injecting bottom water into the reaction container, the bottom water accounting for 40%-50% of the total volume of the reaction container, and injecting the second mixed solution and a sodium hydroxide solution with a concentration of 0.1-0.2 mol / L into the reaction container containing the bottom water at a volume ratio of 1:(4-6) at a stirring speed of 500-700 r / min, controlling the feeding time to be 1-10 min, wherein the flow rate of the second mixed solution is 10-30 L / min, and continuing to react for 5-20 min under stirring at a reaction temperature of 20-40° C. to obtain a product; Step 4: The product is subjected to solid-liquid separation by centrifugation, and then washed and dried to obtain cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

[0031] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0032] In each embodiment of the present invention, the aluminum salt is aluminum chloride hexahydrate, and the magnesium salt is magnesium chloride hexahydrate; the mass concentration of the hydrogen peroxide raw material is 30wt.%; and the concentration of the sodium hydroxide solution is 0.1mol / L.

[0033] Example 1 The embodiment of the present invention provides a method for quickly and efficiently preparing aluminum-magnesium uniformly doped cobalt oxyhydroxide, comprising the following steps: Step 1: adding aluminum salt and magnesium salt to an aqueous solution with a cobalt ion concentration of 130 g / L according to a metal mass ratio of cobalt, aluminum and magnesium of 1000:6:2 to obtain a first mixed solution; wherein the cobalt salt is cobalt chloride; Step 2: under the condition of a stirring speed of 1200 r / min, slowly adding hydrogen peroxide to the first mixed solution at a volume percentage of 0.5%, and the addition rate of hydrogen peroxide is controlled to be 50 mL / min, to obtain a second mixed solution; Step 3: Set a reaction liquid pre-storage container above the reaction container, and use a lift pump to pre-pump the second mixed solution and the sodium hydroxide solution required for the reaction into the corresponding reaction liquid pre-storage container; inject bottom water into the reaction container, the bottom water accounts for 50% of the total volume of the reaction container, and under the condition of a stirring speed of 600 r / min, use gravity to add the second mixed solution and the sodium hydroxide solution in the reaction liquid pre-storage container to the reaction container containing bottom water at a volume ratio of 1:5 at one time, and control the feeding time within 3 minutes. Among them, the flow rate of the second mixed solution is 20 L / min, and the reaction is continued under stirring conditions at a reaction temperature of 25°C for 10 minutes to obtain the product; Step 4: The product is subjected to solid-liquid separation by centrifugation, and then washed and dried to obtain cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

[0034] Example 2 The difference between this embodiment and embodiment 1 is that the metal mass ratio of cobalt, aluminum and magnesium in step 1 is adjusted to 1000:7:2, and other conditions and operations remain unchanged to prepare cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

[0035] Example 3 The difference between this embodiment and embodiment 1 is that the metal mass ratio of cobalt, aluminum and magnesium in step 1 is adjusted to 1000:8:2, and other conditions and operations remain unchanged to prepare cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

[0036] Example 4 The difference between this embodiment and embodiment 1 is that the metal mass ratio of cobalt, aluminum and magnesium in step 1 is adjusted to 1000:10:2, and other conditions and operations remain unchanged to prepare cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

[0037] Example 5 The difference between this embodiment and embodiment 1 is that the cobalt chloride in step 1 is replaced by cobalt sulfate, and the other conditions and operations remain unchanged, so as to prepare cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

[0038] Example 6 The difference between this embodiment and embodiment 1 is that in step 2, hydrogen peroxide is slowly added to the first mixed solution at a volume percentage of 0.20%, and other conditions and operations remain unchanged, so as to prepare aluminum-magnesium uniformly doped cobalt oxyhydroxide.

[0039] Example 7 The difference between this embodiment and embodiment 1 is that in step 3, the flow rates of the second mixed solution and the sodium hydroxide solution are adjusted, the feeding time is controlled to be 10 minutes, the reaction time is controlled to be 10 minutes, and the other conditions and operations remain unchanged, so as to prepare aluminum-magnesium uniformly doped cobalt oxyhydroxide.

[0040] Example 8 The difference between this embodiment and embodiment 3 is that the metal mass ratio of cobalt, aluminum and magnesium in step 1 is adjusted to 1000:8:3, and hydrogen peroxide is slowly added to the first mixed solution at a volume percentage of 0.52% under the condition of a stirring speed of 1250 r / min in step 2. The other conditions and operations remain unchanged to prepare aluminum-magnesium uniformly doped cobalt oxyhydroxide.

[0041] Example 9 The difference between this embodiment and embodiment 3 is that the metal mass ratio of cobalt, aluminum and magnesium in step 1 is adjusted to 1000:8:4, and hydrogen peroxide is slowly added to the first mixed solution at a volume percentage of 0.54% under the condition of a stirring speed of 1300 r / min in step 2. The other conditions and operations remain unchanged to prepare aluminum-magnesium uniformly doped cobalt oxyhydroxide.

[0042] Example 10 The difference between this embodiment and embodiment 3 is that the metal mass ratio of cobalt, aluminum and magnesium in step 1 is adjusted to 1000:8:5, and hydrogen peroxide is slowly added to the first mixed solution at a volume percentage of 0.56% under the condition of a stirring speed of 1350 r / min in step 2. The other conditions and operations remain unchanged to prepare aluminum-magnesium uniformly doped cobalt oxyhydroxide.

[0043] Performance Testing and Characterization The particle size and specific surface area of ​​the aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Examples 1-10 of the present invention were tested, and the results are shown in Table 1 below: Table 1

[0044] It can be seen from the above table that the cobalt oxyhydroxide prepared in each embodiment of the present invention has the advantages of small particle size and high specific surface area.

[0045] Figure 1-10 The scanning electron microscope images of the aluminum-magnesium uniformly doped cobalt oxyhydroxide prepared in Examples 1-10 of the present invention are shown respectively. Figure 1-10 It can be seen that in the present invention, controlling the cobalt concentration at 130 g / L, the feeding time at 3 min, the reaction time at 10 min, the volume percentage of hydrogen peroxide added to the raw material solution at 0.5%, and the stirring speed at 600 r / min can further optimize the product performance.

[0046] Furthermore, while increasing the magnesium content in the first mixed solution, Examples 8-10 also simultaneously increased the stirring speed and the volume percentage of hydrogen peroxide added during the preparation of the second mixed solution. The prepared products not only maintained the advantages of small particle size and high specific surface area, but also promoted rapid and uniform mixing of cobalt, aluminum and magnesium, avoiding the occurrence of element segregation.

[0047] Fig.11 This is a test diagram of element distribution of aluminum-magnesium uniformly doped cobalt oxyhydroxide obtained in Example 3 of the present invention. Fig.11 It can be seen that the distribution of aluminum and magnesium elements is relatively uniform, without segregation.

[0048] Furthermore, the content of doping elements in the products under different cobalt-aluminum-magnesium ratios in Examples 1-4 was tested, and the results are shown in Table 2 below.

[0049] Table 2

[0050] It can be seen from Table 2 that the content of doping elements in the aluminum-magnesium uniformly doped cobalt oxyhydroxide prepared by the present invention is basically consistent with that of the raw materials (within ±200).

[0051] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for rapidly and efficiently preparing aluminum-magnesium uniformly doped cobalt oxyhydroxide, characterized in that: The following steps are involved: S1, adding aluminum salt and magnesium salt to an aqueous solution having a cobalt ion concentration of 130-140 g / L according to a mass ratio of the metal elements of cobalt, aluminum and magnesium of 1000:(6-14):(2-5) to obtain a first mixed solution; S2. Under the condition of a stirring speed of 1200-1400 r / min, slowly adding hydrogen peroxide to the first mixed solution at a volume percentage of 0.2%-0.6%, to obtain a second mixed solution; S3, under the condition of a stirring speed of 500-700 r / min, the second mixed solution and the sodium hydroxide solution are simultaneously injected into the reaction container containing bottom water according to a volume ratio of 1: (4-6), the feeding time is controlled to be 1-10min, and the temperature is 20-40°C and the stirring is continued for 5-20min to obtain a product; S4. Performing solid-liquid separation, washing and drying on the product to obtain cobalt oxyhydroxide uniformly doped with aluminum and magnesium.

2. The method according to claim 1, characterized in that: In step S1, the cobalt salt used to prepare the aqueous solution of cobalt ions is selected from cobalt chloride and / or cobalt sulfate; the aluminum salt is selected from a combination of one or more of aluminum chloride hexahydrate, aluminum sulfate 18hydrate, and aluminum nitrate; and the magnesium salt is selected from magnesium chloride hexahydrate and / or magnesium sulfate heptahydrate.

3. The method according to claim 1, characterized in that In step S1, the mass ratio of the metal elements of cobalt, aluminum and magnesium is 1000:(6-10):(2-3).

4. The method according to claim 1, characterized in that In step S2, the rate of adding hydrogen peroxide is 40-60 mL / min.

5. The method according to claim 1, characterized in that In step S2, the concentration of hydrogen peroxide is 25wt.%-30wt.%.

6. The method according to claim 1, characterized in that In step S3, the content of bottom water in the reaction container accounts for 40%-50% of the volume of the reaction container.

7. The method according to claim 1, characterized in that In step S3, the concentration of the sodium hydroxide solution is 0.1-0.2 mol / L.

8. The method according to claim 1, characterized in that In step S3, the flow rate of the second mixed solution is 10-30 L / min.

9. The method according to claim 1, characterized in that: In step S3, the feeding time is 1-5 min, and the reaction time is 8-12 min.

10. A cobalt oxyhydroxide uniformly doped with aluminum and magnesium, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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