A method for preparing cobalt tetroxide

Abstract

The invention discloses a method for preparing cobalt tetroxide, comprising the following steps: S1: preparing a cobalt liquid and an ammonium bicarbonate solution; S2: taking the ammonium bicarbonate solution as a base liquid, adding the cobalt liquid and the ammonium bicarbonate solution into the base liquid, and collecting a first seed crystal after reaction; S3: adding the cobalt liquid and the ammonium bicarbonate solution into the first seed crystal, collecting a second seed crystal after reaction, repeatedly collecting the seed crystals, and then adding the cobalt liquid and the ammonium bicarbonate solution until the D50 of the obtained seed crystal is 17-18 μm; S4: collecting the seed crystals with a D50 of 17-18 μm, and then adding the cobalt liquid and the ammonium bicarbonate solution to react; in the base liquid of step S2, the volume of the ammonium bicarbonate solution is 1-10 L; the method for preparing cobalt tetroxide of the invention can shorten the reaction cycle and avoid small particles appearing during the reaction process.

Description

Technical Field

[0001] The invention relates to the technical field of battery material preparation, and in particular to a method for preparing cobalt tetroxide. Background Art

[0002] With the replacement of 3C products and the launch of various high-end wearable devices, people's requirements for lithium-ion batteries are getting higher and higher. Positive electrode material manufacturers often use large and small particles to mix to increase the compaction density of the positive electrode, thereby increasing the energy density of lithium-ion batteries. As an important precursor for the preparation of lithium cobalt oxide, a positive electrode material for lithium batteries, cobalt tetroxide has various indicators that affect the performance of lithium cobalt oxide positive electrode materials and downstream lithium-ion batteries. Therefore, the preparation methods of cobalt tetroxide are divided into three categories, namely solid phase method, gas phase method and liquid phase method. The solid phase method is a method of preparing materials by chemical reaction using solid raw materials. The disadvantages of the solid phase method are uneven particle size distribution, difficult to control product morphology and easy product agglomeration; the gas phase method refers to heating the material to directly vaporize and then react chemically, and finally crystallize and precipitate, but the gas phase method has a slow deposition rate and safety hazards; the liquid phase method is currently widely used in laboratories and industrial production to prepare cobalt tetroxide. At present, the liquid phase method for preparing cobalt tetroxide still has the problem of long reaction cycle and easy small particles when the reaction is close to the target particle size.

[0003] Therefore, it is urgent to develop a method for preparing cobalt tetroxide that can solve the problem that the current liquid phase method for preparing cobalt tetroxide still has a long reaction cycle and is prone to produce small particles when the reaction approaches the target particle size. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing cobalt tetroxide, which can shorten the reaction cycle and avoid the small particles appearing during the reaction process.

[0005] According to S1 of the first aspect of the present invention, a cobalt solution and an ammonium bicarbonate solution are prepared;

[0006] S2: using the ammonium bicarbonate solution as a base liquid, adding the cobalt solution and the ammonium bicarbonate solution into the base liquid, and collecting the first seed crystal after the reaction;

[0007] S3: adding the cobalt liquid and the ammonium bicarbonate solution to the first seed crystals, collecting the second seed crystals after the reaction, repeatedly collecting the seed crystals and adding the cobalt liquid and the ammonium bicarbonate solution until the D50 of the obtained seed crystals is 17-18 μm;

[0008] S4: collecting the seed crystals with a D50 of 17 to 18 μm and adding them to the cobalt solution and the ammonium bicarbonate solution for reaction;

[0009] In the base liquid of step S2, the volume of the ammonium bicarbonate solution is 1 to 15 L;

[0010] In step S2, the rate of adding the cobalt solution is 1 to 5 L / h, and the rate of adding the ammonium bicarbonate solution is 1 to 5 L / h;

[0011] In step S4, the rate of adding the cobalt solution is 1 to 8 L / h, and the rate of adding the ammonium bicarbonate solution is 1 to 12 L / h.

[0012] A method for preparing cobalt tetroxide according to an embodiment of the present invention has at least the following beneficial effects:

[0013] The present invention can achieve rapid preparation of cobalt tetroxide through the above steps. At present, the liquid phase method for preparing cobalt tetroxide has a reaction number of about 30 times, a long cycle, and small particles are produced at the end of the reaction. In the present invention, by controlling the amount of the base liquid and the added cobalt liquid and ammonium bicarbonate solution, the number of first seed crystals is reduced, thereby reducing the collision between the first seed crystals, promoting the growth rate of the seed crystals during the subsequent reaction, thereby shortening the reaction cycle.

[0014] In step S3, the surface of the seed crystal gradually becomes spherical in the later stage of the reaction, and the active sites become fewer, which is not conducive to ion deposition. Therefore, at the addition rate of the cobalt solution and the ammonium bicarbonate solution in step S4, the ions are gradually deposited on the large seed crystals without forming new nuclei alone (i.e., small particles).

[0015] According to some embodiments of the present invention, step S2 further includes adding aluminum sulfate 18hydrate to the cobalt solution.

[0016] The aluminum sulfate 18hydrate in the present invention is used as an additive, which is beneficial to the stability of the structure of cobalt tetroxide.

[0017] According to some embodiments of the present invention, in step S1, the concentration of cobalt ions in the cobalt solution is 1 to 4 mol / L;

[0018] According to some embodiments of the present invention, in step S1, the concentration of the ammonium bicarbonate solution is 180-300 g / L.

[0019] According to some embodiments of the present invention, in step S2, the reaction temperature is 30-60°C.

[0020] According to some embodiments of the present invention, when the pH value of the reaction system in step S2 is 7.0-7.5, the addition of the cobalt solution and the ammonium bicarbonate solution is stopped.

[0021] When the pH is 7.0-7.5, the cobalt carbonate particles (seed crystals) settle the most; when the pH is too high, the ammonium bicarbonate solution is excessive; when the pH is too low, the cobalt salt solution is excessive, and the cobalt ions do not react completely, resulting in waste.

[0022] According to some embodiments of the present invention, in step S2, the reaction is a stirring reaction, and the stirring speed is 150-300 r / min.

[0023] According to some embodiments of the present invention, in step S2, after the reaction, before collecting the first seed crystal, the step further includes standing.

[0024] According to some embodiments of the present invention, the standing time is 0.5 to 1 hour.

[0025] According to some embodiments of the present invention, in step S2, the method for collecting the first seed crystals after the reaction is to extract the upper mother liquid in the reaction system after standing, and the lower first seed crystals remain in the reactor.

[0026] According to some embodiments of the present invention, in step S3, the rate of adding the cobalt solution is 2 L / h, and the rate of adding the ammonium bicarbonate solution is 4 L / h.

[0027] In the above-mentioned addition amounts of cobalt liquid and ammonium bicarbonate, the Ph of the system is about 7.0-7.5, which is suitable for the formation of cobalt carbonate and avoids the waste of cobalt liquid or ammonium bicarbonate.

[0028] According to some embodiments of the present invention, in step S3, the reaction time is 5 to 6 hours.

[0029] According to some embodiments of the present invention, in step S3, after the reaction, before collecting the second seed crystals, the step further includes standing.

[0030] According to some embodiments of the present invention, the standing time is 0.5 to 1 hour.

[0031] According to some embodiments of the present invention, in step S3, the method for collecting the second seed crystals after the reaction is to extract the upper mother liquid in the reaction system after standing, and the lower second seed crystals remain in the reactor.

[0032] According to some embodiments of the present invention, in step S4, the reaction is a stirring reaction, and the stirring speed is 60-300 r / min.

[0033] According to some embodiments of the present invention, in step S4, the reaction time is 5 to 6 hours.

[0034] According to some embodiments of the present invention, in step S4, after the reaction and before the seed crystals are collected, the step further includes standing.

[0035] According to some embodiments of the present invention, the standing time is 0.5 to 1 hour.

[0036] According to some embodiments of the present invention, in step S4, the method for collecting seed crystals after the reaction is to extract the upper layer of mother liquid in the reaction system after standing, and the lower layer of seed crystals remain in the reactor.

[0037] According to some preferred embodiments of the present invention, the process further comprises repeatedly collecting seed crystals and then adding the cobalt solution and the ammonium bicarbonate solution until seed crystals of a target particle size are obtained.

[0038] According to some embodiments of the present invention, in step S4, the reaction further includes drying and sintering.

[0039] According to some embodiments of the present invention, in step S4, the drying temperature is 60° C. to 90° C., and the drying time is 10 to 20 hours.

[0040] According to some embodiments of the present invention, in step S4, the sintering temperature is 700-800° C., and the sintering time is 1-5 hours.

[0041] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0043] Figure 1 This is a scanning electron microscope (SEM) image of the cobalt carbonate obtained in Example 1 at a high magnification;

[0044] Figure 2 This is a scanning electron microscope (SEM) image of the cobalt carbonate obtained in Example 1 at a low magnification;

[0045] Figure 3 This is a scanning electron microscope (SEM) image of the cobalt tetroxide obtained in Example 1 at a high magnification;

[0046] Figure 4 This is a scanning electron microscope (SEM) image of the cobalt tetroxide obtained in Example 1 at a low magnification;

[0047] Figure 5 This is a cross-sectional polishing (CP) image of the product obtained in Example 1;

[0048] Figure 6 This is an X-ray energy spectrum (EDS) diagram of the product obtained in Example 1; DETAILED DESCRIPTION

[0049] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0050] Example 1

[0051] This embodiment discloses a method for preparing cobalt tetroxide, and the process comprises the following steps:

[0052] S1: Weigh 18.285 kg of cobalt chloride, add pure water to make up to 50 L, filter to remove solid impurities, and obtain a clean cobalt chloride solution for use; prepare an ammonium bicarbonate solution with a concentration of 200 g / L for use;

[0053] S2: Weigh 202 g of aluminum sulfate 18hydrate, add it to the cobalt chloride solution in step S1, mix well and set aside;

[0054] S3: Use a peristaltic pump to pump 2 L of the ammonium bicarbonate solution in step S1 into the reactor as the bottom liquid; set the speed to 200 r / min and the temperature to 40°C;

[0055] S4: Use a peristaltic pump to pump the cobalt solution in step S2 and the ammonium bicarbonate solution in step S1 into the reactor, the flow rate of adding the cobalt salt aqueous solution is 1.5 L / h; the flow rate of the ammonium bicarbonate solution is 1.32 L / h, and the addition is stopped when the pH value in the reactor is 7.0, and the reactor is allowed to stand for 1 hour, and the upper mother liquor is extracted, and the lower precipitate (cobalt carbonate seed crystals) is left in the reactor;

[0056] S5: set the reaction temperature to 40°C, the rotation speed to 300r / min, the cobalt solution flow rate to 2L / h, and the ammonium bicarbonate solution flow rate to 4L / h; add the mixture into the reactor and react for 5h. After the reaction is completed, let it stand for 1h, extract the upper mother liquor, and leave the lower precipitate (cobalt carbonate) in the reactor; repeat the operation in step S5 until the particle size grows to 17μm and stop the reaction;

[0057] S6: When the particle size of cobalt carbonate is 17 μm, the temperature is raised to 48°C, the flow rate of the cobalt salt aqueous solution is 0.5 L / h; the flow rate of the ammonium bicarbonate solution is 0.78 L / h, the speed is 270 r / min, and the reaction is carried out for 5 hours; S6 is repeated to obtain a cobalt carbonate particle size of 18.5 μm; Figure 1 As shown, the cobalt carbonate is uniform in size and has no small particles;

[0058] S7: Wash and dry the seed crystals in step S6, and sinter to obtain a cobalt tetroxide sample, such as Figure 2 As shown; Figure 3 , Figure 4 They are the cross section of cobalt tetroxide and the EDS distribution map of aluminum element in the cross section. Figure 5 This is a cross-sectional polishing (CP) image of the product obtained in Example 1; Figure 6 This is an X-ray energy spectrum (EDS) diagram of the product obtained in Example 1, in which the color of the aluminum element is uniform without obvious bright spots, proving that the aluminum element is uniformly distributed.

[0059] Example 2

[0060] This embodiment discloses a method for preparing cobalt trioxide. The difference between this embodiment and embodiment 1 is that the ammonium bicarbonate solution in the base liquid in step S3 is 5 L, and the rest of the process is the same, and the process comprises the following steps:

[0061] S1: Weigh 18.285 kg of cobalt chloride, add pure water to make up to 50 L, filter to remove solid impurities, and obtain a clean cobalt chloride solution for use; prepare an ammonium bicarbonate solution with a concentration of 200 g / L for use;

[0062] S2: Weigh 202 g of aluminum sulfate 18hydrate, add it to the cobalt chloride solution in step S1, mix well and set aside;

[0063] S3: Use a peristaltic pump to pump 5 L of the ammonium bicarbonate solution in step S1 into the reactor as the bottom liquid; set the speed to 200 r / min and the temperature to 40°C;

[0064] S4: Use a peristaltic pump to pump the cobalt solution in step S2 and the ammonium bicarbonate solution in step S1 into the reactor, the flow rate of adding the cobalt salt aqueous solution is 1.5 L / h; the flow rate of the ammonium bicarbonate solution is 1.32 L / h, and the addition is stopped when the pH value in the reactor is 7.0, and the reactor is allowed to stand for 1 hour, and the upper mother liquor is extracted, and the lower precipitate (cobalt carbonate seed crystals) is left in the reactor;

[0065] S5: set the reaction temperature to 40°C, the rotation speed to 300r / min, the cobalt solution flow rate to 2L / h, and the ammonium bicarbonate solution flow rate to 4L / h; add the mixture into the reactor and react for 5h. After the reaction is completed, let it stand for 1h, extract the upper mother liquor, and leave the lower precipitate (cobalt carbonate) in the reactor; repeat the operation in step S5 until the seed crystal particle size reaches 17.2μm and stop the reaction;

[0066] S6: When the particle size of cobalt carbonate is 17.2μm, the temperature is raised to 48℃, the flow rate of cobalt salt aqueous solution is 0.5L / h; the flow rate of ammonium bicarbonate solution is 0.78L / h, the speed is 270r / min; the final particle size of cobalt carbonate is 18.2μm. The cobalt carbonate is uniform in size without small particles;

[0067] S7: Wash, dry and sinter the seed crystals in step S6 to obtain a cobalt tetroxide sample.

[0068] Example 3

[0069] This embodiment discloses a method for preparing cobalt trioxide. The difference between this embodiment and embodiment 1 is that the amount of ammonium bicarbonate added in the base liquid in step S3 is 10 L, and the flow rate of the cobalt salt aqueous solution in step S6 is 1 L / h. The process comprises the following steps:

[0070] S1: Weigh 18.285 kg of cobalt chloride, add pure water to make up to 50 L, filter to remove solid impurities, and obtain a clean cobalt chloride solution for use; prepare an ammonium bicarbonate solution with a concentration of 200 g / L for use;

[0071] S2: Weigh 202 g of aluminum sulfate 18hydrate, add it to the cobalt chloride solution in step S1, mix well and set aside;

[0072] S3: Use a peristaltic pump to pump 10 L of the ammonium bicarbonate solution in step S1 into the reactor as the bottom liquid; set the speed to 200 r / min and the temperature to 40°C;

[0073] S4: Use a peristaltic pump to pump the cobalt solution in step S2 and the ammonium bicarbonate solution in step S1 into the reactor, the flow rate of adding the cobalt salt aqueous solution is 1.5 L / h; the flow rate of the ammonium bicarbonate solution is 1.32 L / h, and the addition is stopped when the pH value in the reactor is 7.0, and the reactor is allowed to stand for 1 hour, and the upper mother liquor is extracted, and the lower precipitate (cobalt carbonate seed crystals) is left in the reactor;

[0074] S5: set the reaction temperature to 40°C, the rotation speed to 300r / min, the cobalt solution flow rate to 2L / h, and the ammonium bicarbonate solution flow rate to 4L / h; add the mixture into the reactor and react for 5h. After the reaction is completed, let it stand for 1h, extract the upper mother liquor, and leave the lower precipitate (cobalt carbonate) in the reactor; repeat the operation in step S5 until the seed crystal particle size is 17.6μm and stop the reaction;

[0075] S6: When the seed particle size is 17.6 μm, the temperature is raised to 48°C, the flow rate of the cobalt salt aqueous solution added is 1 L / h; the concentration of the ammonium bicarbonate solution is 1.5 L / h, the rotation speed is 250 r / min; the final particle size of the cobalt carbonate is 18.9 μm.

[0076] S7: Wash, dry and sinter the seed crystals in step S6 to obtain a cobalt tetroxide sample.

[0077] Example 4

[0078] This embodiment discloses a method for preparing cobalt trioxide. The difference between this embodiment and embodiment 1 is that the rotation speed in step S6 is maintained at 300 r / min, and the rest of the process is the same, and the process includes the following steps:

[0079] S1: Weigh 18.285 kg of cobalt chloride, add pure water to make up to 50 L, filter to remove solid impurities, and obtain a clean cobalt chloride solution for use; prepare an ammonium bicarbonate solution with a concentration of 200 g / L for use;

[0080] S2: Weigh 202 g of aluminum sulfate 18hydrate, add it to the cobalt chloride solution in step S1, mix well and set aside;

[0081] S3: Use a peristaltic pump to pump 2 L of the ammonium bicarbonate solution in step S1 into the reactor as the bottom liquid; set the speed to 200 r / min and the temperature to 40°C;

[0082] S4: Use a peristaltic pump to pump the cobalt solution in step S2 and the ammonium bicarbonate solution in step S1 into the reactor, the flow rate of adding the cobalt salt aqueous solution is 1.5 L / h; the flow rate of the ammonium bicarbonate solution is 1.32 L / h, and the addition is stopped when the pH value in the reactor reaches 7.0, and the reactor is allowed to stand for 1 hour, and the upper mother liquor is extracted, and the lower precipitate (seed crystal) is left in the reactor;

[0083] S5: set the reaction temperature to 40°C, the rotation speed to 300r / min, the cobalt solution flow rate to 2L / h, and the ammonium bicarbonate solution flow rate to 4L / h; add the solution to the reactor and react for 5h. After the reaction is completed, let it stand for 1h, extract the upper mother liquor, and leave the lower precipitate (cobalt carbonate) in the reactor; repeat the operation in step S5 until the particle size of the cobalt carbonate is 17μm and stop the reaction;

[0084] S6: When the particle size of cobalt carbonate is 17 μm, the temperature is raised to 48°C, the flow rate of the cobalt salt aqueous solution added is 0.5 L / h; the flow rate of the ammonium bicarbonate solution is 0.78 L / h, and the rotation speed is 300 r / min; the final particle size of cobalt carbonate is 19 μm, as shown in the figure.

[0085] S7: Wash, dry and sinter the seed crystals in step S6 to obtain a cobalt tetroxide sample.

[0086] Comparative Example 1

[0087] Comparative Example 1 of the present invention is: a method for preparing cobalt trioxide, which adopts a traditional liquid phase method with a long reaction cycle, and comprises the following steps:

[0088] S1: Use a peristaltic pump to pump 15L of 220g / L ammonium bicarbonate solution as the base liquid; set the speed to 300r / min and the temperature to 40℃;

[0089] S2: The flow rate of adding the cobalt salt aqueous solution is 3 L / h; the flow rate of the ammonium bicarbonate solution is 2.3 L / h. When the pH value in the reactor reaches 7.0, the addition is stopped, and the reactor is allowed to stand for 1 hour. The upper mother liquor is extracted, and the lower precipitate (cobalt carbonate seed crystals) remains in the reactor;

[0090] S3: Set the reaction temperature to 40°C, the rotation speed to 300r / min, the cobalt liquid flow rate to 3L / h, and the ammonium bicarbonate solution flow rate to 4.5L / h; add to the reactor and react for 5h to pH 7.0-7.1; after the reaction is completed, let it stand for 1h, extract the upper mother liquor, and leave the lower precipitate in the reactor; repeat the operation in step S3 until the particle size of cobalt carbonate is 19μm and stop the reaction; according to the particle size increase of 0.3 micron / time, the reaction takes about 10 days to complete, the synthesized cobalt carbonate has more small particles, and the reaction cycle is long.

[0091] Comparative Example 2

[0092] Comparative Example 2 of the present invention is: a method for preparing cobalt tetroxide, comprising the following steps:

[0093] This comparative example adopts steps similar to those of comparative example 1, and the only difference from comparative example 1 is that in step S1 of this comparative example, the amount of ammonium bicarbonate in the base liquid is reduced, 5L of ammonium bicarbonate is added as the base liquid, and the SEM synthesized cobalt carbonate particles obtained by the rotation speed are smaller. At the same time, due to the reduction in the amount of ammonium bicarbonate in the base liquid, the particle size of the first synthesis increases by 2-3 microns, and the reaction cycle is shortened by 2-3 days;

[0094] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A method for preparing cobalt trioxide, characterized in that: The following steps are involved: S1: prepare cobalt solution and ammonium bicarbonate solution; S2: adding aluminum sulfate 18hydrate to the cobalt solution in step S1 to obtain an aluminum-containing cobalt solution, The ammonium bicarbonate solution is used as a base liquid, the aluminum-cobalt liquid and the ammonium bicarbonate solution are added to the base liquid, and the first seed crystal is collected after the reaction. S3: adding the cobalt liquid and the ammonium bicarbonate solution to the first seed crystals, collecting the second seed crystals after the reaction, repeatedly collecting the seed crystals and adding the cobalt liquid and the ammonium bicarbonate solution until the D50 of the obtained seed crystals is 17-18 μm; S4: collecting seed crystals with a D50 of 17 to 18 μm and adding the cobalt solution and the ammonium bicarbonate solution to react; In the base liquid of step S2, the volume of the ammonium bicarbonate solution is 1 to 10 L; In step S2, the rate of adding the aluminum-cobalt solution is 1 to 5 L / h, and the rate of adding the ammonium bicarbonate solution is 1 to 5 L / h; In step S4, the rate of adding the cobalt solution is 4 to 8 L / h, and the rate of adding the ammonium bicarbonate solution is 4 to 12 L / h; In step S1, the concentration of cobalt ions in the cobalt solution is 1 to 4 mol / L; In step S1, the concentration of the ammonium bicarbonate solution is 180-300 g / L; In step S2, the reaction temperature is 30-60°C; When the pH value of the reaction system in step S2 is 7.0-7.5, stop adding the aluminum-cobalt solution and the ammonium bicarbonate solution; In step S3, the rate of adding the cobalt solution is 2 to 3 L / h, and the rate of adding the ammonium bicarbonate solution is 4 to 6 L / h; In step S4, the reaction temperature is 42-72°C; In step S4, the reaction further includes drying and sintering.

2. The preparation method according to claim 1, characterized in that: In step S3, the reaction time is 5 to 6 hours.

3. The preparation method according to claim 1, characterized in that: In step S4, the reaction is a stirring reaction, and the stirring speed is 60 to 300 r / min.

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