Preparation method of cobalt phosphate
By using a double precipitant under suitable pH conditions and performing precipitation conversion at high temperatures, the problem of difficult to prepare cobalt phosphate in the prior art is solved, and a high-performance cobalt phosphate material preparation is achieved.
Patent Information
- Application Number
- CN202411875276.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-19
- Publication Date
- 2025-05-02
AI Technical Summary
It is difficult to prepare cobalt phosphate with small particle size and high specific surface area in the prior art, which affects its performance in new energy lithium battery materials.
By using a biprecipitant (ammonium bicarbonate and ammonium monohydrogen phosphate solution) at suitable pH conditions, coprecipitation of cobalt ions and phosphate roots is achieved, and precipitation conversion is carried out at high temperature to form loose and porous cobalt phosphate particles.
Cobalt phosphate with small primary particle size, large specific surface area, loose and porous cobalt phosphate was successfully prepared, which improved its performance in lithium battery materials.
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Figure CN119911886A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing cobalt phosphate, and belongs to the technical field of new energy lithium battery materials. Background Art
[0002] Cobalt phosphate is also known as cobaltous phosphate. Its molecular formula is Co3(PO4)2, its molecular weight is 336.74, it is light red crystal, its relative density is 2.587 (25℃), it is insoluble in water, but soluble in phosphoric acid and ammonia water. The one with two crystal waters is purple-red powder, insoluble in water, but soluble in phosphoric acid. The one with eight crystal waters is light red powder, its relative density is 2.769, it loses 8 molecules of crystal water when heated to 200℃, it is slightly soluble in water, insoluble in alcohol, but soluble in inorganic acid and phosphoric acid, and it is generally prepared by the reaction of cobalt salt and sodium phosphate. It is used as enamel, glaze, glass colorant and feed additive.
[0003] The theoretical specific capacity of lithium cobalt phosphate (LiCoPO4) (170 mAh / g) is comparable to that of lithium iron phosphate (LiFePO4, 167 mA h / g), and the operating voltage platform is higher [4.8 V (vs. Li / Li + )], with a theoretical energy density of about 800Wh / kg, which is higher than the theoretical energy density of LiFePO4 (578Wh / kg) and the actual energy density of lithium cobalt oxide (LiCoO2) (480Wh / kg), and has attracted the attention of researchers.
[0004] The solid phase method for preparing lithium cobalt phosphate has become the mainstream process for preparing lithium cobalt phosphate. Lithium cobalt phosphate is prepared using cobalt phosphate as a precursor. The prepared product has good consistency and is easy to industrialize, and is gradually attracting everyone's attention. Summary of the invention
[0005] In view of this, the present invention provides a method for preparing cobalt phosphate to obtain cobalt phosphate with a small primary particle size and a large BET.
[0006] The present invention solves the above technical problems by the following technical means:
[0007] A method for preparing cobalt phosphate of the present invention comprises the following steps:
[0008] (1) adding a cobalt salt solution, an ammonium bicarbonate solution and an ammonium monohydrogen phosphate solution into a reaction kettle, wherein a base liquid is added into the reaction kettle, wherein the base liquid is pure water, and the pH of the solution is maintained at 5.5-6.5 during the addition process, the reaction temperature is 30-55° C., the addition time is 15-30 min, and after the addition is completed, the reaction is continued to be stirred at this temperature for 30-60 min to obtain a reaction material;
[0009] (2) filtering the reaction material, adding pure water for washing, and stopping washing after washing until the conductivity of the washing water is ≤300 μS / cm, adding phosphoric acid solution to the obtained slurry for slurrying, heating the temperature to 90-95° C., stirring and reacting at this temperature for 30-60 minutes to obtain a heated material, filtering the heated material, washing, and obtaining a cobalt phosphate slurry;
[0010] (3) After the cobalt phosphate slurry is dried, it is placed in a rotary kiln for calcination at a temperature of 400-650° C. for a calcination time of 2-4 hours to obtain cobalt phosphate.
[0011] In the step (1), the cobalt salt is cobalt sulfate, cobalt chloride, cobalt acetate or cobalt nitrate, the purity of the cobalt salt is industrial purity, the concentrations of the cobalt salt solution, the ammonium bicarbonate solution and the ammonium monohydrogen phosphate solution are 1-3 mol / L, the stirring speed during the reaction is 150-250 r / min, and the molar ratio of cobalt in the cobalt salt solution to phosphate in the ammonium monohydrogen phosphate solution is 1:0.9-0.95.
[0012] When the phosphoric acid solution is added to the slurry in step (2), the concentration of the phosphoric acid solution is 0.05-0.15 mol / L, and the mass ratio of the solid in the slurry to the phosphoric acid solution is 1:3-5.
[0013] In the step (2), the heated material is washed until the conductivity of the washing water is ≤150 μS / cm and then the washing is stopped.
[0014] In the step (3), the cobalt phosphate slurry is dried by at least one of spray drying, vacuum drying, flash drying or microwave drying.
[0015] During the calcination process in step (3), the volume of the material in the rotary kiln accounts for 10-20% of the total volume of the rotary kiln.
[0016] During the calcination process in step (3), the rotary kiln is connected to the induced draft fan, and the induced draft fan is turned on to make the air humidity in the rotary kiln ≤ 90%.
[0017] In the step (3), after the cobalt phosphate is calcined and discharged, it is crushed, screened, iron-removed and vacuum-packed. The crushing is performed by air flow crushing to a particle size of 1-10 μm, and the particle size is screened through a sieve of 80-200 mesh.
[0018] The invention uses double precipitants (ammonium bicarbonate solution and ammonium monohydrogen phosphate solution) to make cobalt ions generate precipitation with phosphate radicals and carbonate radicals at a suitable pH value, and then, at a lower pH value and in the presence of phosphoric acid, a small amount of carbonate precipitates and hydroxide precipitates are converted into phosphate precipitates, thereby preparing cobalt phosphate precipitates with higher purity.
[0019] The invention uses a double precipitant to obtain a double precipitate through coprecipitation, and then realizes the precipitation of high-purity cobalt phosphate through precipitation conversion at high temperature. The carbonate precipitate in the coprecipitation can be dissolved and converted into a phosphate precipitate through precipitation conversion, and the phosphate precipitate can re-nucleate and grow on the surface of the original particle, so that the inside of the cobalt phosphate has a loose porous structure. At the same time, in the precipitation conversion process, since carbon dioxide gas is generated, a trace amount of carbon dioxide gas prevents the growth of particles, so that loose and porous cobalt phosphate particles with large BET and small primary particle size can be obtained.
[0020] The present invention effectively controls the BET of the product by calcining in a rotary kiln and then calcining at high temperature and in a short time. By controlling the high temperature, the high-temperature moisture of the product can be effectively reduced. At the same time, at high temperature, because the crystal water inside the cobalt phosphate particles also needs to be released, the higher the temperature, the greater the saturated vapor pressure in the cobalt phosphate containing the crystal water, and the easier it is to form a porous structure. At the same time, the sintering time is shortened, and the generated pores can be prevented from being blocked by melting, thereby reducing the specific surface area. By adopting the sintering process, it is easier to obtain loose, porous and large BET cobalt phosphate.
[0021] The beneficial effects of the present invention are as follows: loose and porous cobalt phosphate with a small primary particle size and a large BET can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is the SEM of the product of Example 1 of the present invention.
[0023] Figure 2 This is the SEM of the product of Example 2 of the present invention.
[0024] Figure 3 This is the SEM of the product of Example 3 of the present invention. DETAILED DESCRIPTION
[0025] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments: A method for preparing cobalt phosphate in this embodiment comprises the following steps:
[0026] (1) adding a cobalt salt solution, an ammonium bicarbonate solution and an ammonium monohydrogen phosphate solution into a reaction kettle, wherein a base liquid is added into the reaction kettle, wherein the base liquid is pure water, and the pH of the solution is maintained at 5.5-6.5 during the addition process, the reaction temperature is 30-55° C., the addition time is 15-30 min, and after the addition is completed, the reaction is continued to be stirred at this temperature for 30-60 min to obtain a reaction material;
[0027] (2) filtering the reaction material, adding pure water for washing, and stopping washing after washing until the conductivity of the washing water is ≤300 μS / cm, adding phosphoric acid solution to the obtained slurry for slurrying, heating the temperature to 90-95° C., stirring and reacting at this temperature for 30-60 minutes to obtain a heated material, filtering the heated material, washing, and obtaining a cobalt phosphate slurry;
[0028] (3) After the cobalt phosphate slurry is dried, it is placed in a rotary kiln for calcination at a temperature of 400-650° C. for a calcination time of 2-4 hours to obtain cobalt phosphate.
[0029] In the step (1), the cobalt salt is cobalt sulfate, cobalt chloride, cobalt acetate or cobalt nitrate, the purity of the cobalt salt is industrial purity, the concentrations of the cobalt salt solution, the ammonium bicarbonate solution and the ammonium monohydrogen phosphate solution are 1-3 mol / L, the stirring speed during the reaction is 150-250 r / min, and the molar ratio of cobalt in the cobalt salt solution to phosphate in the ammonium monohydrogen phosphate solution is 1:0.9-0.95.
[0030] When the phosphoric acid solution is added to the slurry in step (2), the concentration of the phosphoric acid solution is 0.05-0.15 mol / L, and the mass ratio of the solid in the slurry to the phosphoric acid solution is 1:3-5.
[0031] In the step (2), the heated material is washed until the conductivity of the washing water is ≤150 μS / cm and then the washing is stopped.
[0032] In the step (3), the cobalt phosphate slurry is dried by at least one of spray drying, vacuum drying, flash drying or microwave drying.
[0033] During the calcination process in step (3), the volume of the material in the rotary kiln accounts for 10-20% of the total volume of the rotary kiln.
[0034] During the calcination process in step (3), the rotary kiln is connected to the induced draft fan, and the induced draft fan is turned on to make the air humidity in the rotary kiln ≤ 90%.
[0035] In the step (3), after the cobalt phosphate is calcined and discharged, it is crushed, screened, iron-removed and vacuum-packed. The crushing is performed by air flow crushing to a particle size of 1-10 μm, and the particle size is screened through a sieve of 80-200 mesh.
[0036] Example 1
[0037] A method for preparing cobalt phosphate comprises the following steps:
[0038] (1) adding a cobalt salt solution, an ammonium bicarbonate solution and an ammonium dihydrogen phosphate solution into a reaction kettle, wherein a base liquid is added into the reaction kettle, wherein the base liquid is pure water, and the pH of the solution is maintained at 6.5 during the addition process, the reaction temperature is 55° C., the addition time is 30 min, and after the addition is completed, the reaction is continued to be stirred at this temperature for 60 min to obtain a reaction material;
[0039] (2) filtering the reaction material, adding pure water for washing, and stopping washing after washing until the conductivity of the washing water is ≤300 μS / cm, adding phosphoric acid solution to the obtained slurry for slurrying, heating the temperature to 95° C., stirring and reacting at this temperature for 60 minutes to obtain a heated material, filtering the heated material, washing, and obtaining a cobalt phosphate slurry;
[0040] (3) After the cobalt phosphate slurry is dried, it is placed in a rotary kiln for calcination at a temperature of 650° C. for a calcination time of 2 h to obtain cobalt phosphate.
[0041] In the step (1), the cobalt salt is cobalt nitrate, the purity of the cobalt salt is industrial purity, the concentrations of the cobalt salt solution, the ammonium bicarbonate solution and the ammonium monohydrogen phosphate solution are 3 mol / L, the stirring speed during the reaction is 250 r / min, and the molar ratio of cobalt in the cobalt salt solution to phosphate in the ammonium monohydrogen phosphate solution is 1:0.9.
[0042] When the phosphoric acid solution is added to the slurry in step (2), the concentration of the phosphoric acid solution is 0.1 mol / L, and the mass ratio of the solid in the slurry to the phosphoric acid solution is 1:4.
[0043] In the step (2), the heated material is washed until the conductivity of the washing water is ≤150 μS / cm and then the washing is stopped.
[0044] In the step (3), the cobalt phosphate slurry is dried by flash drying.
[0045] During the calcination process in step (3), the volume of the material in the rotary kiln accounts for 15% of the total volume of the rotary kiln.
[0046] During the calcination process in step (3), the rotary kiln is connected to the induced draft fan, and the induced draft fan is turned on to make the air humidity in the rotary kiln ≤ 90%.
[0047] In the step (3), after the cobalt phosphate is calcined and discharged, it is crushed, screened, iron-removed and vacuum-packed. The crushing is performed by air flow crushing to a particle size of 3.6 μm, and the particle size is screened through a 100-mesh sieve.
[0048] Example 2
[0049] A method for preparing cobalt phosphate comprises the following steps:
[0050] (1) adding a cobalt salt solution, an ammonium bicarbonate solution and an ammonium monohydrogen phosphate solution into a reaction kettle, wherein a base liquid is added into the reaction kettle, wherein the base liquid is pure water, and the pH of the solution is maintained at 5.5 during the addition process, the reaction temperature is 55° C., the addition time is 30 min, and after the addition is completed, the reaction is continued to be stirred at this temperature for 30 min to obtain a reaction material;
[0051] (2) filtering the reaction material, adding pure water for washing, and stopping washing after washing until the conductivity of the washing water is ≤300 μS / cm, adding phosphoric acid solution to the obtained slurry for slurrying, heating the temperature to 95° C., stirring and reacting at this temperature for 60 minutes to obtain a heated material, filtering the heated material, washing, and obtaining a cobalt phosphate slurry;
[0052] (3) After the cobalt phosphate slurry is dried, it is placed in a rotary kiln for calcination at a temperature of 600° C. for a calcination time of 3 h to obtain cobalt phosphate.
[0053] In the step (1), the cobalt salt is cobalt acetate, the purity of the cobalt salt is industrial purity, the concentrations of the cobalt salt solution, the ammonium bicarbonate solution, and the ammonium monohydrogen phosphate solution are 1 mol / L, the stirring speed during the reaction is 150 r / min, and the molar ratio of cobalt in the cobalt salt solution to phosphate in the ammonium monohydrogen phosphate solution is 1:0.95.
[0054] When the phosphoric acid solution is added to the slurry in step (2), the concentration of the phosphoric acid solution is 0.15 mol / L, and the mass ratio of the solid in the slurry to the phosphoric acid solution is 1:5.
[0055] In the step (2), the heated material is washed until the conductivity of the washing water is ≤150 μS / cm and then the washing is stopped.
[0056] In the step (3), the cobalt phosphate slurry is dried by vacuum drying.
[0057] During the calcination process in step (3), the volume of the material in the rotary kiln accounts for 20% of the total volume of the rotary kiln.
[0058] During the calcination process in step (3), the rotary kiln is connected to the induced draft fan, and the induced draft fan is turned on to make the air humidity in the rotary kiln ≤ 90%.
[0059] In the step (3), after the cobalt phosphate is calcined and discharged, it is crushed, screened, iron-removed and vacuum-packed. The crushing is performed by air flow crushing to a particle size of 5.6 μm, and the particle size is screened through a 100-mesh sieve.
[0060] Example 3
[0061] A method for preparing cobalt phosphate comprises the following steps:
[0062] (1) adding a cobalt salt solution, an ammonium bicarbonate solution and an ammonium monohydrogen phosphate solution into a reaction kettle, wherein a base liquid is added into the reaction kettle, wherein the base liquid is pure water, and the pH value of the solution is maintained at 6 during the addition process, the reaction temperature is 55° C., the addition time is 30 min, and after the addition is completed, the reaction is continued to be stirred at this temperature for 60 min to obtain a reaction material;
[0063] (2) filtering the reaction material, adding pure water for washing, and stopping washing after washing until the conductivity of the washing water is ≤300 μS / cm, adding phosphoric acid solution to the obtained slurry for slurrying, heating the temperature to 90° C., stirring and reacting at this temperature for 60 minutes to obtain a heated material, filtering the heated material, washing, and obtaining a cobalt phosphate slurry;
[0064] (3) After the cobalt phosphate slurry is dried, it is placed in a rotary kiln for calcination at a temperature of 400° C. for a calcination time of 4 h to obtain cobalt phosphate.
[0065] In the step (1), the cobalt salt is cobalt sulfate, the purity of the cobalt salt is industrial purity, the concentrations of the cobalt salt solution, the ammonium bicarbonate solution, and the ammonium monohydrogen phosphate solution are 2 mol / L, the stirring speed during the reaction is 250 r / min, and the molar ratio of cobalt in the cobalt salt solution to phosphate in the ammonium monohydrogen phosphate solution is 1:0.9.
[0066] When the phosphoric acid solution is added to the slurry in step (2), the concentration of the phosphoric acid solution is 0.15 mol / L, and the mass ratio of the solid in the slurry to the phosphoric acid solution is 1:5.
[0067] In the step (2), the heated material is washed until the conductivity of the washing water is ≤150 μS / cm and then the washing is stopped.
[0068] In the step (3), the cobalt phosphate slurry is dried by spray drying.
[0069] During the calcination process in step (3), the volume of the material in the rotary kiln accounts for 10% of the total volume of the rotary kiln.
[0070] During the calcination process in step (3), the rotary kiln is connected to the induced draft fan, and the induced draft fan is turned on to make the air humidity in the rotary kiln ≤ 90%.
[0071] In the step (3), after the cobalt phosphate is calcined and discharged, it is crushed, screened, iron-removed and vacuum-packed. The crushing is performed by air flow crushing to a particle size of 6.9 μm, and the particle size is screened through a 150-mesh sieve.
[0072] Finally, the products obtained in Examples 1, 2 and 3 of the present invention were tested, and the results were as follows:
[0073] project Example 1 Example 2 Example 3 D1O 1.4μm 1.8μm 2.3μm D50 3.6μm 5.6μm 6.9μm D90 9.5μm 11.9μm 16.9μm BET <![CDATA[21.4m 2 / g]]> <![CDATA[20.1m 2 / g]]> <![CDATA[20.7m 2 / g]]> Primary particle size 82nm 95nm 86nm
[0074] like Figure 1 and2 , 3 are SEM images of the products obtained in Examples 1 / 2 and 3, respectively. From the scanning electron microscope, loose and porous particles are obtained.
[0075] At the same time, the cobalt phosphate obtained in Example 1-3 was sampled and tested, and the results were as follows:
[0076]
[0077]
[0078] The method for measuring high-temperature moisture is: take 10g of material, weigh it, then put it into a muffle furnace, calcine it at 650℃ for 3 hours, then weigh it after cooling, and divide the difference by the original material weight to get the high-temperature moisture content.
[0079] From the data, it can be seen that the cobalt phosphate obtained by the present invention has a high cobalt-to-phosphorus molar ratio and a low high-temperature moisture content.
[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.
Claims
1. A method for preparing cobalt phosphate, characterized in that: For the following steps: (1) adding a cobalt salt solution, an ammonium bicarbonate solution and an ammonium monohydrogen phosphate solution into a reaction kettle, wherein a base liquid is added into the reaction kettle, wherein the base liquid is pure water, and the pH of the solution is maintained at 5.5-6.5 during the addition process, the reaction temperature is 30-55° C., the addition time is 15-30 min, and after the addition is completed, the reaction is continued to be stirred at this temperature for 30-60 min to obtain a reaction material; (2) filtering the reaction material, adding pure water for washing, and stopping washing after washing until the conductivity of the washing water is ≤300 μS / cm, adding phosphoric acid solution to the obtained slurry for slurrying, heating the temperature to 90-95° C., stirring and reacting at this temperature for 30-60 minutes to obtain a heated material, filtering the heated material, washing, and obtaining a cobalt phosphate slurry; (3) After the cobalt phosphate slurry is dried, it is placed in a rotary kiln for calcination at a temperature of 400-650° C. for a calcination time of 2-4 hours to obtain cobalt phosphate.
2. A method for preparing cobalt phosphate according to claim 1, characterized in that: In the step (1), the cobalt salt is cobalt sulfate, cobalt chloride, cobalt acetate or cobalt nitrate, the purity of the cobalt salt is industrial purity, the concentrations of the cobalt salt solution, the ammonium bicarbonate solution and the ammonium monohydrogen phosphate solution are 1-3 mol / L, the stirring speed during the reaction is 150-250 r / min, and the molar ratio of cobalt in the cobalt salt solution to phosphate in the ammonium monohydrogen phosphate solution is 1:0.9-0.
95.
3. A method for preparing cobalt phosphate according to claim 1, characterized in that: When the phosphoric acid solution is added to the slurry in step (2), the concentration of the phosphoric acid solution is 0.05-0.15 mol / L, and the mass ratio of the solid in the slurry to the phosphoric acid solution is 1:3-5.
4. A method for preparing cobalt phosphate according to claim 1, characterized in that: In the step (2), the heated material is washed until the conductivity of the washing water is ≤150 μS / cm and then the washing is stopped.
5. A method for preparing cobalt phosphate according to claim 1, characterized in that: In the step (3), the cobalt phosphate slurry is dried by at least one of spray drying, vacuum drying, flash drying or microwave drying.
6. The method for preparing cobalt phosphate according to claim 1, characterized in that: During the calcination process in step (3), the volume of the material in the rotary kiln accounts for 10-20% of the total volume of the rotary kiln.
7. The method for preparing cobalt phosphate according to claim 1, characterized in that: During the calcination process in step (3), the rotary kiln is connected to the induced draft fan, and the induced draft fan is turned on to make the air humidity in the rotary kiln ≤ 90%.
8. The method for preparing cobalt phosphate according to claim 1, characterized in that: In the step (3), after the calcination, the cobalt phosphate is crushed, screened, iron-removed and vacuum-packed. The crushing is performed by air flow crushing to a particle size of 1-10 μm, and the particle size is screened through a sieve of 80-200 mesh.