Small-particle-size narrow-distribution cobaltosic oxide and preparation method and application thereof

Abstract

The invention provides a preparation method of cobaltosic oxide with small particle size and narrow distribution. The preparation method comprises the following steps: preparing a raw material solution and a dispersing agent solution; performing synthesis reaction; washing, filtering and drying a product; and calcining. In the initial stage of wet synthesis, lauryl sodium sulfate is adopted as a dispersing agent to prepare a dispersing agent solution, and the dispersing agent solution and a raw material solution are simultaneously introduced into a reaction container according to a certain flow ratio, so that agglomeration of cobaltosic oxide particles in the preparation process is effectively prevented, and a cobaltosic oxide product with small particles and good consistency is obtained. The preparation method provided by the invention is simple in process, easy to operate and suitable for large-scale production; compared with a conventional preparation method, the method has the advantages that the reaction time is shorter, the production efficiency can be improved, the energy consumption can be reduced, and the introduction of impurities in a long-time reaction process can be effectively avoided. The small-particle-size narrow-distribution cobaltosic oxide prepared by the method has a wide application prospect in lithium ion battery positive electrode materials.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery materials, and specifically relates to cobalt tetroxide with small particle size and narrow distribution, and a preparation method and application thereof. Background Art

[0002] As an important cathode material for lithium-ion batteries, lithium cobalt oxide is widely used in 3C products such as laptops, mobile phones, and digital cameras because of its high energy density. With the continuous advancement of science and technology, humans have higher requirements for the battery life and charging rate of electronic products. Therefore, it is urgent to develop lithium cobalt oxide with higher capacity and higher rate. At present, the tap density of lithium cobalt oxide can be increased by mixing large and small cobalt oxide particles, thereby improving the energy density of lithium-ion batteries.

[0003] However, small particles of cobalt tetroxide often have problems such as severe particle agglomeration and uneven particle size distribution during the preparation process. Traditional preparation methods are difficult to effectively control the particle size of cobalt tetroxide, and the preparation process is complicated and costly.

[0004] Based on this, developing a method for preparing cobalt tetroxide with small particle size and narrow distribution with simple and efficient preparation process has important practical significance and is also a technical problem that needs to be solved urgently. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for preparing cobalt tetroxide with small particle size and narrow distribution, which has simple and efficient preparation process.

[0006] The second object of the present invention is to provide a cobalt tetraoxide with small particle size and narrow distribution.

[0007] The third object of the present invention is to provide a method for applying cobalt oxide with small particle size and narrow distribution in lithium ion batteries.

[0008] The technical solution adopted by the present invention to achieve one of the purposes is: to provide a method for preparing cobalt oxide with small particle size and narrow distribution, comprising the following steps: S1, dissolving a cobalt salt and a bicarbonate salt in water respectively to obtain a first solution having a cobalt ion concentration of 110-140 g / L and a second solution having a bicarbonate ion concentration of 220-260 g / L; dissolving sodium dodecyl sulfate in water to obtain a dispersant solution having a concentration of 0.1-0.2 mol / L; S2, using a reaction container with a double-layer stirring device, adding water and a second solution to submerge the bottom stirring device, and heating the reaction container to 40-45° C. under stirring conditions; S3, adding the first solution, the second solution and the dispersant solution into the reaction container at the same time, controlling the flow rate ratio of the first solution to the dispersant solution to be (32-38): (5-6), adjusting the flow rate of the second solution so that the pH value of the reaction system is controlled at 7.0-7.9, reacting at 40-45° C. for 25-30 hours to obtain a synthetic slurry; S4. The synthetic slurry is washed, filtered and dried to obtain cobalt carbonate; the cobalt carbonate is calcined at high temperature to obtain cobalt tetroxide with small particle size and narrow distribution.

[0009] The general idea of ​​the present invention is as follows: In order to prepare a cobalt oxide product with a small particle size and narrow distribution, the present invention adopts a method of simultaneously introducing a reaction solution and a dispersant solution in a certain proportion in the initial stage of wet synthesis to prepare cobalt oxide. In the initial stage of wet synthesis, the substances in the system are in a relatively uniform mixed state, and the dispersant can be fully mixed with the reactants in the entire reaction system, so that the particles always maintain good dispersibility during the synthesis process and avoid local agglomeration. The method of adding a dispersant adopted by the present invention not only has a better dispersion effect and is conducive to obtaining a product with a better uniform distribution of particle size, but also reduces the post-processing process and saves costs.

[0010] In addition, the present invention separately prepares the first solution containing cobalt ions, the second solution containing bicarbonate and the dispersant solution. Compared with directly mixing the above raw materials as the reaction raw material liquid, some unnecessary pre-reactions caused by the mixing of the dispersant solution and the cobalt solution due to mutual contact in the raw material preparation stage are avoided. Under the subsequent appropriate reaction temperature and rotation speed conditions, the two are simultaneously introduced into the reaction system at a certain flow ratio, so that the reaction proceeds along the expected route, ensuring the narrow distribution and consistency of the product particle size.

[0011] Furthermore, in the present invention, after a large number of experiments and comparisons, sodium dodecyl sulfate (SDS) is selected as a dispersant. Compared with other types of dispersants, SDS can maintain a good dispersion effect in a wider pH range and is more suitable for the reaction system of the present invention. In addition, the synthesis process of SDS is relatively simple, the raw material source is wide, and its production cost is relatively low and cheap, which can meet the promotion and application needs of large-scale production and cost control.

[0012] Furthermore, in step S1 of the present invention, a first solution with a cobalt ion concentration of 110-140 g / L and a second solution with a bicarbonate ion concentration of 220-260 g / L are prepared respectively. Compared with the conventional preparation method, the present invention increases the concentration of the raw materials in the reaction solution, and the high concentration of the reaction raw materials can accelerate the seed generation speed and the seed amount, and effectively reduce the starting particle size.

[0013] Furthermore, in the above preparation method, the amount of reaction solution and dispersant is controlled within a reasonable range, which can avoid problems such as uneven distribution of agglomeration caused by too small particles. After a large number of experiments and explorations, based on the premise that the concentration of the first solution of cobalt ions is 110-140g / L, the concentration of the dispersant solution is set to 0.1-0.2mol / L, and the flow ratio of the first solution to the dispersant solution is controlled to (32-38): (5-6) during the reaction feeding stage to ensure that the product particle size is small and evenly distributed, maintaining higher consistency. When the amount of dispersant is higher than the above range, it will excessively inhibit the growth and aggregation of particles, resulting in particles with too small a particle size; and when the amount of dispersant is lower than the above range, the ideal dispersion effect cannot be achieved.

[0014] Furthermore, the present invention uses a reaction container with a double-layer stirring device, which increases mechanical force by using double-layer stirring to prevent particles from being too small and thus being connected.

[0015] Furthermore, in step S1, the cobalt salt is selected from cobalt chloride and / or cobalt sulfate; and the bicarbonate is selected from ammonium bicarbonate and / or sodium bicarbonate.

[0016] Furthermore, in step S2, the volume ratio of water to the second solution is (50-55):(5-8).

[0017] Furthermore, in step S2, the stirring speed is 180-250 rpm, and the speeds of the stirring devices of the upper layer and the bottom layer are kept consistent.

[0018] Preferably, in step S3, the flow rate of the first solution is 320-380 L / h, and the flow rate of the dispersant solution is 50-60 L / h.

[0019] Furthermore, in step S3, the feed mass ratio of the second solution to the first solution per unit time is (3-5): 1. In the present invention, the pH of the reaction system is controlled by adjusting the flow rate of the second solution containing bicarbonate to ensure normal growth of the grains.

[0020] Furthermore, in step S4, the solvent used for washing is ammonium bicarbonate solution, and the temperature of the drying treatment is 80-100°C.

[0021] Furthermore, the temperature of the high temperature calcination treatment is 680-750°C and the time is 3-5 hours. Under such conditions, the product obtained by calcination treatment has high crystallinity and a smooth surface without cracks.

[0022] The technical solution adopted by the present invention to achieve the second purpose is: to provide cobalt tetroxide with small particle size and narrow distribution, which is prepared by the preparation method according to one of the purposes of the present invention.

[0023] Furthermore, the particle size D50 of the cobalt oxide with small particle size and narrow distribution is 3.296-3.538 μm, and the consistency is 0.216-0.418.

[0024] The technical solution adopted by the present invention to achieve the third purpose is: to provide a use of cobalt tetroxide with small particle size and narrow distribution according to one of the purposes of the present invention in a lithium ion battery.

[0025] Furthermore, the small-particle cobalt tetroxide with narrow distribution prepared by the present invention is mixed with large-particle cobalt tetroxide to increase the tap density of lithium cobalt oxide, thereby increasing the energy density of lithium ion batteries. The small-particle cobalt tetroxide provided by the present invention has a narrow particle size distribution, and the internal stress distribution of the material is more uniform during the charge and discharge process, which reduces the local stress concentration and structural damage caused by the difference in particle size, helps to improve the cycle stability of lithium cobalt oxide, and thereby prolongs the service life of the battery.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for preparing cobalt tetroxide with small particle size and narrow distribution provided by the present invention adopts a specific dispersant sodium dodecyl sulfate (SDS) to prepare a dispersant solution in the early stage of wet synthesis, and adds the dispersant solution to the reaction container at a certain flow ratio together with the reaction raw material liquid, which can effectively prevent the agglomeration of cobalt tetroxide particles during the preparation process, and obtain a cobalt tetroxide product with small particles and good consistency.

[0027] (2) The method for preparing cobalt tetroxide with small particle size and narrow distribution provided by the present invention is simple in process, easy to operate, and suitable for large-scale production. Compared with conventional preparation methods, the reaction time of the present invention is shorter, which can improve production efficiency, reduce energy consumption, and effectively avoid the introduction of impurities during a long reaction process, thereby ensuring the purity of the product.

[0028] (3) The small-particle cobalt tetroxide provided by the present invention has the advantage of a narrow particle size distribution. When applied to the positive electrode material of a lithium-ion battery, the internal stress distribution of the material is more uniform during the charge and discharge process, which reduces the local stress concentration and structural damage caused by the difference in particle size, helps to improve the cycle stability of lithium cobalt oxide, and thus prolongs the service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The XRD pattern of cobalt tetroxide prepared in Example 1 of the present invention; Figure 2 This is a particle size distribution diagram of cobalt tetroxide prepared in Example 1 of the present invention; Figure 3 This is the particle size distribution diagram of cobalt tetroxide prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] The embodiment of the present invention provides a method for preparing cobalt tetroxide with small particle size and narrow distribution, comprising the following steps: Step 1: dissolving a cobalt salt and a bicarbonate salt in water respectively to obtain a first solution with a cobalt ion concentration of 110-140 g / L and a second solution with a bicarbonate ion concentration of 220-260 g / L; dissolving sodium dodecyl sulfate in water to obtain a dispersant solution with a concentration of 0.1-0.2 mol / L; wherein the cobalt salt is selected from cobalt chloride and / or cobalt sulfate; and the bicarbonate salt is selected from ammonium bicarbonate and / or sodium bicarbonate; Step 2: using a reaction container with a double-layer stirring device, adding water and a second solution to submerge the bottom stirring device, controlling the volume ratio of water to bicarbonate solution to be (50-55):(5-8), and heating the reaction container to 40-45° C. under a stirring condition of a rotation speed of 180-250 rpm; Step 3: Add the first solution, the second solution and the dispersant solution into the reaction container at the same time, the flow rate of the first solution is 320-380 L / h, the flow rate of the dispersant solution is 50-60 L / h, the flow rate of the second solution is adjusted so that the pH value of the reaction system is controlled at 7.0-7.9, react at 40-45° C. for 25-30 hours to obtain a synthetic slurry; Step 4: The synthetic slurry is washed with an ammonium bicarbonate solution, filtered, and dried at 80-100° C. to obtain cobalt carbonate; the cobalt carbonate is placed at 680-750° C. and calcined at high temperature for 3-5 hours to obtain cobalt tetroxide with a small particle size and narrow distribution.

[0033] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0034] The main parameters and experimental conditions of the preparation process of each embodiment of the present invention and the comparative example are shown in Table 1 below: Table 1

[0035] Example 1 This embodiment provides a method for preparing cobalt tetroxide with small particle size and narrow distribution, comprising the following steps: Step 1: dissolving cobalt chloride hexahydrate and ammonium bicarbonate in water respectively to obtain a first solution with a cobalt ion concentration of 130 g / L and a second solution with a bicarbonate ion concentration of 260 g / L; dissolving sodium dodecyl sulfate in water to obtain a dispersant solution with a concentration of 0.1 mol / L; Step 2: Use a reaction vessel with a double-layer stirring device, add 550L of water and 50L of ammonium bicarbonate solution as the bottom liquid in the reaction kettle, and heat it to 41°C; Step 3: Add the first solution, the second solution and the dispersant solution into the reaction container at the same time, strictly control the flow rate of the cobalt solution to 320 L / h, the flow rate of the dispersant solution to 55 L / h, adjust the flow rate of the second solution to control the pH value of the reaction system to about 7.2, react at a temperature of 41° C. and a rotation speed of 220 rpm for 30 hours to obtain a synthetic slurry; Step 4: The synthetic slurry is washed and filtered with a 22 g / L ammonium bicarbonate solution, and dried at 80° C. to obtain cobalt carbonate; the dried cobalt carbonate is calcined in a rotary kiln at a calcination temperature of 680 degrees Celsius for 5 hours to obtain cobalt tetroxide with a small particle size and narrow distribution.

[0036] The sample obtained in Example 1 was subjected to X-ray diffraction analysis (XRD). Figure 1 As shown, multiple sharp and high-intensity diffraction peaks are clearly presented. After comparison with the standard cobalt tetroxide XRD card, the characteristic peaks obtained are all cobalt tetroxide phases, and no other impurity phases exist. This shows that the cobalt tetroxide prepared by the method provided by the present invention is phase-pure and has high crystallinity.

[0037] Figure 2 It can be seen that the particle size D50 of the cobalt tetroxide prepared in this embodiment is 3.38 μm, the consistency is 0.216, the particle size is small and the distribution is narrow.

[0038] Example 2 This embodiment provides a method for preparing cobalt tetroxide with small particle size and narrow distribution, comprising the following steps: Step 1: dissolving cobalt chloride hexahydrate and ammonium bicarbonate in water respectively to obtain a first solution with a cobalt ion concentration of 110 g / L and a second solution with a bicarbonate ion concentration of 220 g / L; dissolving sodium dodecyl sulfate in water to obtain a dispersant solution with a concentration of 0.15 mol / L; Step 2: Use a reaction vessel with a double-layer stirring device, add 520L of water and 80L of ammonium bicarbonate solution as the bottom liquid in the reaction kettle, and heat it to 42°C; Step 3: Add the first solution, the second solution and the dispersant solution into the reaction container at the same time, strictly control the flow rate of the cobalt solution to 350 L / h, the flow rate of the dispersant solution to 50 L / h, adjust the flow rate of the second solution to control the pH value of the reaction system to about 7.9, react at a temperature of 42° C. and a rotation speed of 180 rpm for 25 hours to obtain a synthetic slurry; Step 4: The synthetic slurry is washed and filtered with a 22 g / L ammonium bicarbonate solution, and dried at 80° C. to obtain cobalt carbonate; the dried cobalt carbonate is calcined in a rotary kiln at a calcination temperature of 710 degrees Celsius for 4 hours to obtain cobalt tetroxide with a small particle size and narrow distribution.

[0039] After testing, the particle size D50 of the cobalt tetroxide prepared in this embodiment is 3.296 μm, the consistency is 0.391, the particle size is small and the distribution is narrow.

[0040] Example 3 This embodiment provides a method for preparing cobalt tetroxide with small particle size and narrow distribution, comprising the following steps: Step 1: Dissolve cobalt chloride hexahydrate and ammonium bicarbonate in water respectively to obtain a first solution with a cobalt ion concentration of 120 g / L and a second solution with a bicarbonate ion concentration of 240 g / L; dissolve sodium dodecyl sulfate in water to obtain a dispersant solution with a concentration of 0.2 mol / L; Step 2: Using a reaction vessel with a double-layer stirring device, add 535L of water and 65L of ammonium bicarbonate solution as the bottom liquid in the reaction kettle, and heat it to 42°C; Step 3: Add the first solution, the second solution and the dispersant solution into the reaction container at the same time, strictly control the flow rate of the cobalt solution to 380 L / h, the flow rate of the dispersant solution to 60 L / h, adjust the flow rate of the second solution to control the pH value of the reaction system to about 7.5, react at a temperature of 42° C. and a rotation speed of 150 rpm for 30 hours to obtain a synthetic slurry; Step 4: The synthetic slurry is washed and filtered with a 22 g / L ammonium bicarbonate solution, and dried at 80° C. to obtain cobalt carbonate; the dried cobalt carbonate is calcined in a rotary kiln at a calcination temperature of 750 degrees Celsius for 3 hours to obtain cobalt tetroxide with a small particle size and narrow distribution.

[0041] After testing, the particle size D50 of the cobalt tetroxide prepared in this embodiment is 3.373 μm, the consistency is 0.294, the particle size is small and the distribution is narrow.

[0042] Example 4 This embodiment provides a method for preparing cobalt tetroxide with small particle size and narrow distribution, comprising the following steps: Step 1: Dissolve cobalt sulfate heptahydrate and sodium bicarbonate in water respectively to obtain a first solution with a cobalt ion concentration of 140 g / L and a second solution with a bicarbonate ion concentration of 260 g / L; dissolve sodium dodecyl sulfate in water to obtain a dispersant solution with a concentration of 0.1 mol / L; Step 2: Use a reaction vessel with a double-layer stirring device, add 550L of water and 50L of ammonium bicarbonate solution as the base liquid in the reaction kettle, and heat it to 45°C; Step 3: Add the first solution, the second solution and the dispersant solution into the reaction container at the same time, strictly control the flow rate of the cobalt solution to 320 L / h, the flow rate of the dispersant solution to 55 L / h, adjust the flow rate of the second solution to control the pH value of the reaction system to about 7.2, react at a temperature of 45° C. and a rotation speed of 180 rpm for 30 hours to obtain a synthetic slurry; Step 4: The synthetic slurry is washed and filtered with a 22 g / L ammonium bicarbonate solution, and dried at 80° C. to obtain cobalt carbonate; the dried cobalt carbonate is calcined in a rotary kiln at a calcination temperature of 680 degrees Celsius for 5 hours to obtain cobalt tetroxide with a small particle size and narrow distribution.

[0043] After testing, the particle size D50 of the cobalt tetroxide prepared in this embodiment is 3.538 μm, the consistency is 0.418, the particle size is small and the distribution is narrow.

[0044] Comparative Example 1 This comparative example provides a method for preparing cobalt oxide with small particle size, comprising the following steps: Step 1: Dissolve a cobalt salt and a bicarbonate salt in water respectively to obtain a first solution with a cobalt ion concentration of 130 g / L and a second solution with a bicarbonate ion concentration of 260 g / L; Step 2: Use a reaction vessel with a double-layer stirring device, add 550L of water and 50L of ammonium bicarbonate solution as the bottom liquid in the reaction kettle, and heat it to 41°C; Step 3: The first solution and the second solution are continuously added to the reactor in parallel, the flow rate of the cobalt solution is strictly controlled to be 320 L / h, the pH value is controlled to be about 7.2, and the reaction is carried out at a temperature of 41° C. and a rotation speed of 220 rpm for 30 hours to obtain a synthetic slurry; Step 4: washing and filtering the synthetic slurry with 22 g / L ammonium bicarbonate solution, and drying at 80° C. to obtain cobalt carbonate; calcining the dried cobalt carbonate in a rotary kiln at a calcination temperature of 680 degrees Celsius for 5 hours to obtain cobalt tetroxide.

[0045] The main difference between this comparative example and the embodiment is that no dispersant solution is added during the reaction process. Figure 3It can be seen from the particle size distribution results that under the same reaction time conditions, although the D50 of the cobalt tetroxide prepared in this comparative example is relatively small, 2.804 μm, the particle size distribution is wide and the consistency is poor, with obvious front and back peaks, and the consistency is 1.263.

[0046] Comparative Example 2 This comparative example provides a method for preparing cobalt trioxide, comprising the following steps: Step 1: Dissolve a cobalt salt and a bicarbonate salt in water respectively to obtain a first solution with a cobalt ion concentration of 130 g / L and a second solution with a bicarbonate ion concentration of 260 g / L; dissolve sodium dodecyl sulfate in water to obtain a dispersant solution with a concentration of 0.1 mol / L; Step 2: Use a reaction vessel with a double-layer stirring device, add 550L of water and 50L of ammonium bicarbonate solution as the bottom liquid in the reaction kettle, and heat it to 41°C; Step 3: Add the first solution, the second solution and the dispersant solution into the reaction container at the same time, strictly control the flow rate of the cobalt solution to 320 L / h, the flow rate of the dispersant solution to 20 L / h, adjust the flow rate of the second solution to control the pH value of the reaction system to about 7.2, react at a temperature of 41° C. and a rotation speed of 220 rpm for 30 hours to obtain a synthetic slurry; Step 4: washing and filtering the synthetic slurry with 22 g / L ammonium bicarbonate solution, and drying at 80° C. to obtain cobalt carbonate; calcining the dried cobalt carbonate in a rotary kiln at a calcination temperature of 680 degrees Celsius for 5 hours to obtain cobalt tetroxide.

[0047] The main difference between this comparative example and the embodiment is that the flow rate of the dispersant solution in the reaction raw material is adjusted from 55L / h to 20L / h. The cobalt tetraoxide obtained in this comparative example has a D50 of 5.012μm, a D90 of 87.913μm, a consistency of 1.173, and a bimodal state. This shows that in the preparation method of the present invention, controlling the flow rate ratio of the dispersant solution to the cobalt-containing solution within a reasonable range has an important influence on reducing the product particle size and improving the consistency of the particle size distribution.

[0048] 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 preparing cobalt tetroxide with small particle size and narrow distribution, characterized in that: The following steps are involved: S1, dissolving a cobalt salt and a bicarbonate salt in water respectively to obtain a first solution having a cobalt ion concentration of 110-140 g / L and a second solution having a bicarbonate ion concentration of 220-260 g / L; dissolving sodium dodecyl sulfate in water to obtain a dispersant solution having a concentration of 0.1-0.2 mol / L; S2, using a reaction container with a double-layer stirring device, adding water and a second solution to submerge the bottom stirring device, and heating the reaction container to 40-45° C. under stirring conditions; S3, adding the first solution, the second solution and the dispersant solution into the reaction container at the same time, controlling the flow rate ratio of the first solution to the dispersant solution to be (32-38): (5-6), adjusting the flow rate of the second solution so that the pH value of the reaction system is controlled at 7.0-7.9, reacting at 40-45° C. for 25-30 hours to obtain a synthetic slurry; S4, washing, filtering and drying the synthetic slurry to obtain cobalt carbonate; calcining the cobalt carbonate at high temperature to obtain cobalt tetroxide with small particle size and narrow distribution.

2. The preparation method according to claim 1, characterized in that: In step S1, the cobalt salt is selected from cobalt chloride and / or cobalt sulfate; the bicarbonate is selected from ammonium bicarbonate and / or sodium bicarbonate.

3. The preparation method according to claim 1, characterized in that: In step S2, the volume ratio of water to the second solution is (50-55):(5-8).

4. The preparation method according to claim 1, characterized in that: In step S2, the stirring speed is 180-250 rpm.

5. The preparation method according to claim 1, characterized in that: In step S3, the flow rate of the first solution is 320-380 L / h, and the flow rate of the dispersant solution is 50-60 L / h.

6. The preparation method according to claim 1, characterized in that: In step S3, the feed mass ratio of the second solution to the first solution per unit time is (3-5):

1.

7. The preparation method according to claim 1, characterized in that: In step S4, the washing solvent is ammonium bicarbonate solution, and the drying temperature is 80-100°C.

8. The preparation method according to claim 1, characterized in that: The high temperature calcination treatment is performed at a temperature of 680-750° C. and a time of 3-5 hours.

9. A cobalt tetraoxide with a small particle size and narrow distribution, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8; the particle size D50 of the cobalt tetroxide with small particle size and narrow distribution is 3.296-3.538 μm, and the consistency is 0.216-0.

418.

10. Use of the cobalt oxide with small particle size and narrow distribution according to claim 9 in positive electrode materials for lithium-ion batteries.

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