Process for preparing spherical cobaltosic oxide in sectional manner

Abstract

The invention relates to a process for preparing spherical cobaltosic oxide in a sectional manner, and belongs to the technical field of cobaltosic oxide. The invention provides a process for preparing spherical cobaltosic oxide in a sectional manner, which comprises the following steps of: 1, mixing modified PMMA (polymethyl methacrylate) microspheres and a cobalt source according to a mass ratio of 1: (3.5-4.5), and performing ultrasonic treatment to obtain a mixture; 2, carrying out first-stage calcination at a relatively low temperature to obtain a head product; and step 3, carrying out second-stage calcination on the initial product at a relatively high temperature, and after the calcination is finished, carrying out furnace cooling to obtain the product. The preparation method comprises the following steps: firstly forming a stable inner core and a functional shell layer by virtue of PMMA microspheres to enhance the adsorption capacity to a cobalt source, then enabling cobaltosic oxide to be spherical and increasing the specific surface area by taking the PMMA microspheres as a template, and finally gradually decomposing the PMMA microspheres by virtue of sectional calcination to form spherical cobaltosic oxide with regular pores.

Description

Technical Field

[0001] The present invention belongs to the technical field of cobalt tetroxide and relates to a process for preparing spherical cobalt tetroxide in a segmented manner. Background Art

[0002] Cobalt tetroxide (Co3O4) is an important inorganic compound and plays a key role in multiple fields, especially in lithium-ion batteries. In lithium-ion batteries, cobalt tetroxide is the main raw material for preparing the cathode material lithium cobaltate, which directly affects the use performance, cycle life and safety performance of the battery. Common cobalt tetroxide is prepared by chemical precipitation method, thermal decomposition method, etc. to obtain a precursor, and the precursor is calcined at high temperature to obtain cobalt tetroxide. However, the cobalt tetroxide prepared by this method is prone to irregular shape or agglomeration, resulting in uneven filling or uneven lithium-ion diffusion path, increasing the internal resistance of the battery, and thus affecting the use performance of the battery; while spherical cobalt tetroxide has relatively less influence on battery performance due to its uniform morphology, and its preparation and application have received more and more attention. Summary of the Invention

[0003] The purpose of the present invention is to provide a process for preparing spherical cobalt tetroxide in a segmented manner. The present invention first forms a stable core and a functionalized shell layer with the help of PMMA microspheres to enhance the adsorption force of the cobalt source, then uses it as a template to make cobalt tetroxide spherical, increasing the specific surface area, and finally gradually decomposes the PMMA microspheres through segmented calcination to form spherical cobalt tetroxide with regular pores.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A process for preparing spherical cobalt tetroxide in a segmented manner, the process for preparing spherical cobalt tetroxide in a segmented manner comprises the following steps:

[0006] Step 1: Mix PMMA microspheres and a cobalt source in a mass ratio of 1:3.5 - 4.5, and then perform ultrasonic treatment to obtain a mixture;

[0007] Step 2: Calcinate the mixture at a lower temperature in the first stage to obtain a primary product;

[0008] Step 3: Calcinate the primary product at a higher temperature in the second stage, and after the calcination is completed, cool it with the furnace to obtain the product.

[0009] Further, the cobalt source in Step 1 is obtained by mixing cobalt sulfate and dimethyl sulfoxide in a mass ratio of 1:3 - 5; the parameters of the ultrasonic treatment are: the ultrasonic power is 100 - 300 W, the ultrasonic frequency is 20 - 40 kHz, and the ultrasonic time is 20 - 30 min.

[0010] Further, the preparation method of the PMMA microspheres in Step 1 comprises the following steps:

[0011] Step X1: Add methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile into a reaction kettle. First, purge with nitrogen for 30 min, and then stir at 200 - 300 rpm at 62 - 68 °C for 4.5 - 5.5 h to obtain a core emulsion;

[0012] Step X2: After heating to 72 - 78 °C, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile, and stir at 300 - 400 rpm for 6 - 7 h. After stirring, perform high-speed centrifugation to separate the solid matter, wash the solid matter alternately with water and absolute ethanol 3 times, and dry it to a constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres with a core-shell structure;

[0013] Step X3: Mix the PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane, and toluene, and stir at a rotation speed of 250 - 350 rpm at 52 - 58 °C for 2.5 - 3.5 h. After stirring, filter with a 300-mesh filter cloth to retain the precipitate. Wash the precipitate alternately with toluene and absolute ethanol 3 times, and dry it to a constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres.

[0014] Furthermore, the mass ratio of methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile in Step X1 is 22.5 - 25.5:2.5 - 4.5:0.11 - 0.23.

[0015] Furthermore, the mass ratio of glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile in Step X2 is 16.5 - 19.3:1.44 - 2.64:0.9 - 1.2:0.09 - 0.13; the rotation speed and time of the high-speed centrifugation are 8000 - 10000 rpm and 15 - 20 min, respectively.

[0016] Furthermore, the mass ratio of the PMMA microspheres, 3-aminopropyltriethoxysilane, and toluene in Step X3 is 1:0.03 - 0.05:10 - 20.

[0017] Furthermore, the ratio of the solid matter to water during washing in Step X2 is 1:2 - 4 g / mL, and the volume ratio of water to absolute ethanol is 1:1; the ratio of the precipitate to toluene during washing in Step X3 is 1:3 - 5 g / mL, and the volume ratio of toluene to absolute ethanol is 1:1.

[0018] Further, in the first-stage calcination described in Step 2, a mixed gas is introduced into the tube furnace at a gas flow rate of 50 - 80 mL / min. The mixed gas includes 78 - 82 wt% nitrogen and the balance hydrogen. It is heated from room temperature to 380 - 420 °C at a heating rate of 1.5 - 2 °C / min and kept warm for 2 - 3 h.

[0019] Further, in the second-stage calcination described in Step 3, air is introduced into the tube furnace at a gas flow rate of 100 - 150 mL / min. After displacing for 20 min, while ventilating, it is heated to 680 - 720 °C at a heating rate of 2.5 - 3 °C / min and kept warm for 3 - 4 h.

[0020] Further, the cobalt tetroxide is applied to the electrode material of a lithium battery.

[0021] Advantages of the present invention:

[0022] (1) The present invention provides a PMMA microsphere, which forms a stable microsphere core with methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile. Secondly, by introducing monomers such as glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, and ethylene glycol dimethacrylate, a functionalized shell layer is formed on the outer layer, which not only enhances the mechanical strength of the microsphere but also introduces active groups such as amino groups and epoxy groups on its surface, providing reaction sites for subsequent modification treatment. The introduction of amino groups enhances the adsorption capacity of the microsphere surface for cobalt sources. Finally, the surface of the microsphere is modified with 3-aminopropyltriethoxysilane to increase surface alkalinity and activity, further improving the affinity and adsorption force for cobalt sources.

[0023] (2) The present invention provides a PMMA microsphere. Using it as a template, through the interaction between the active groups on the surface and the cobalt source, the cobalt source is evenly adsorbed on the surface of the microsphere. In the subsequent calcination, the PMMA microsphere serves as a sacrificial template and gradually decomposes and volatilizes at high temperature, leaving an oxide skeleton formed by the cobalt source, so that the finally formed cobalt tetroxide particles can inherit the spherical structure of the microsphere and obtain a uniform spherical morphology. At the same time, some gases may be generated during the decomposition of the microsphere, and the gases escape to form a pore structure, increasing the specific surface area of cobalt tetroxide and improving its activity.

[0024] (3) After introducing PMMA microspheres and cobalt source and mixing them to obtain a mixture, a segmented calcination is carried out on this basis. In the first-stage calcination section, an inert environment is created, and hydrogen is used as a reducing agent to reduce the cobalt element in part of the cobalt source to a low valence state, forming cobalt oxide with high activity in the low valence state. At this time, the PMMA microspheres begin to undergo thermal chemical reactions but do not crack completely instantaneously. The organic matter in the reaction system begins to decompose slowly and release gas slowly, forming a preliminary pore structure, avoiding cracking or deformation of particles caused by rapid gas escape at the high-temperature stage. As the temperature in the second calcination stage gradually increases, the PMMA microspheres are gradually cracked completely and volatilized, leaving a regular and stable pore structure. Finally, when spherical cobalt tetroxide is prepared and applied in lithium-ion batteries, it has less impact on battery performance. Detailed implementation mode

[0025] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines examples to elaborate in detail on the specific implementation mode, structure, characteristics and their effects of the present invention.

[0026] The cobalt sulfate in all examples and comparative examples of the present invention was directly purchased from the market, and all were purchased from Jinan Yushengda Chemical Co., Ltd.; methyl methacrylate was directly purchased from the market, and all were purchased from Shanghai Nanmu Chemical Co., Ltd.; 2-hydroxyethyl methacrylate was directly purchased from the market, and all were purchased from Jining Tangyi Chemical Co., Ltd.; azobisisobutyronitrile was directly purchased from the market, and all were purchased from Jinan Yucai Chemical Co., Ltd.; glycidyl methacrylate was directly purchased from the market, and all were purchased from Jinan Kaichuang Chemical Co., Ltd.; 2-(dimethylamino)ethyl methacrylate hydrochloride was directly purchased from the market, and all were purchased from Henan Weitixi Chemical Technology Co., Ltd.; ethylene glycol dimethacrylate was directly purchased from the market, and all were purchased from Changzhou Aozun Composite New Materials Co., Ltd.; 3-aminopropyltriethoxysilane was directly purchased from the market, and all were purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.

[0027] Example 1

[0028] A process for preparing spherical cobalt tetroxide in a segmented manner. The process for preparing spherical cobalt tetroxide in a segmented manner in this example includes the following steps:

[0029] Step 1: Mix PMMA microspheres and cobalt source according to a mass ratio of 1:3.5, and then ultrasonically treat to obtain a mixture;

[0030] Step 2: Calcinate the mixture at a lower temperature in the first stage to obtain a primary product;

[0031] Step 3: Calcinate the primary product at a higher temperature in the second stage. After the calcination is completed, cool it with the furnace to obtain the product.

[0032] In step 1 of this embodiment, the cobalt source is obtained by mixing cobalt sulfate and dimethyl sulfoxide in a mass ratio of 1:3; the parameters of ultrasonic treatment are: ultrasonic power is 100 W, ultrasonic frequency is 20 kHz, and ultrasonic time is 20 min.

[0033] The preparation method of the PMMA microspheres in step 1 of this embodiment includes the following steps:

[0034] Step X1: Add methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile into a reaction kettle. First, purge with nitrogen for 30 min, and then stir at 200 rpm at 62 °C for 4.5 h to obtain a core emulsion.

[0035] Step X2: After heating to 72 °C, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile, and stir at 300 rpm for 6 h. After stirring, perform high-speed centrifugation to separate the solid matter, wash the solid matter alternately with water and absolute ethanol 3 times, and dry it to constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres with a core-shell structure.

[0036] Step X3: Mix the PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane, and toluene, and stir at 250 rpm at 52 °C for 2.5 h. After stirring, filter through a 300-mesh filter cloth to retain the precipitate. Wash the precipitate alternately with toluene and absolute ethanol 3 times, and dry it to constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres.

[0037] In step X1 of this embodiment, the mass ratio of methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile is 22.5:2.5:0.11.

[0038] In step X2 of this embodiment, the mass ratio of glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile is 16.5:1.44:0.9:0.09; the rotation speed and time of high-speed centrifugation are 8000 rpm and 15 min, respectively.

[0039] In step X3 of this embodiment, the mass ratio of PMMA microspheres, 3-aminopropyltriethoxysilane, and toluene is 1:0.03:10.

[0040] In step X2 of this embodiment, the ratio of the solid matter to water during washing is 1:2 g / mL, and the volume ratio of water to absolute ethanol is 1:1; in step X3, the ratio of the precipitate to toluene during washing is 1:3 g / mL, and the volume ratio of toluene to absolute ethanol is 1:1.

[0041] In the first-stage calcination in Step 2 of this embodiment, a mixed gas is introduced into the tubular furnace at a gas flow rate of 50 mL / min. The mixed gas includes 78 wt% nitrogen and the balance hydrogen. The temperature is raised from room temperature to 380 °C at a heating rate of 1.5 °C / min and held for 2 h.

[0042] In the second-stage calcination in Step 3 of this embodiment, air is introduced into the tubular furnace at a gas flow rate of 100 mL / min. After displacing for 20 min, while ventilating, the temperature is raised to 680 °C at a heating rate of 2.5 °C / min and held for 3 h.

[0043] The cobalt tetroxide of this embodiment is applied to the electrode material of a lithium battery.

[0044] Example 2

[0045] A process for preparing spherical cobalt tetroxide in a segmented manner. The process for preparing spherical cobalt tetroxide in this embodiment includes the following steps:

[0046] Step 1: Mix PMMA microspheres and a cobalt source in a mass ratio of 1:4.5, and then ultrasonicate to obtain a mixture.

[0047] Step 2: Calcinate the mixture at a lower temperature in the first stage to obtain a primary product.

[0048] Step 3: Calcinate the primary product at a higher temperature in the second stage. After the calcination is completed, cool it with the furnace to obtain the product.

[0049] In Step 1 of this embodiment, the cobalt source is obtained by mixing cobalt sulfate and dimethyl sulfoxide in a mass ratio of 1:5; the parameters of the ultrasonication are: the ultrasonication power is 300 W, the ultrasonication frequency is 40 kHz, and the ultrasonication time is 30 min.

[0050] The preparation method of the PMMA microspheres in Step 1 of this embodiment includes the following steps:

[0051] Step X1: Add methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile into the reaction kettle. First, displace with nitrogen for 30 min, and stir at 300 rpm at 68 °C for 5.5 h to obtain a core emulsion.

[0052] Step X2: After raising the temperature to 78 °C, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene dimethacrylate, and azobisisobutyronitrile, and stir at 400 rpm for 7 h. After the stirring is completed, perform high-speed centrifugation to separate the solid matter, wash the solid matter alternately with water and absolute ethanol 3 times, and dry it to constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres with a core-shell structure.

[0053] Step X3, mix PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane and toluene, and stir at 58°C at a speed of 250-350 rpm for 3.5 hours. After stirring, use a 300-mesh filter cloth to filter and retain the precipitate. Wash the precipitate alternately with toluene and anhydrous ethanol for 3 times, and dry it in a vacuum drying oven at 45°C to constant weight to obtain PMMA microspheres.

[0054] The mass ratio of methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile in step X1 of this embodiment is 25.5:4.5:0.23.

[0055] The mass ratio of glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile in step X2 of this embodiment is 19.3:2.64:1.2:0.13; the speed and time of high-speed centrifugation are 10000 rpm and 20 min, respectively.

[0056] The mass ratio of PMMA microspheres, 3-aminopropyltriethoxysilane, and toluene in step X3 of this embodiment is 1:0.05:20.

[0057] In the present embodiment, the ratio of solid to water during rinsing in step X2 is 1:4 g / mL, and the volume ratio of water to anhydrous ethanol is 1:1; the ratio of precipitate to toluene during washing in step X3 is 1:5 g / mL, and the volume ratio of toluene to anhydrous ethanol is 1:1.

[0058] The first stage calcination in step 2 of this embodiment is to introduce a mixed gas into the tubular furnace at a gas flow rate of 80 mL / min, wherein the mixed gas includes 82 wt % nitrogen and the balance hydrogen, and heat from room temperature to 420°C at a heating rate of 2°C / min, and keep warm for 3 hours.

[0059] The second stage calcination in step three of this embodiment is to introduce air into the tube furnace at a gas flow rate of 150 mL / min, replace it for 20 minutes, and then increase the temperature to 720°C at a heating rate of 3°C / min while ventilating, and keep it at this temperature for 4 hours.

[0060] The cobalt tetroxide of this embodiment is applied to the electrode material of lithium battery.

[0061] Example 3

[0062] A process for preparing spherical cobalt oxide in a segmented manner. The process for preparing spherical cobalt oxide in a segmented manner in this embodiment comprises the following steps:

[0063] Step 1, mixing PMMA microspheres and a cobalt source in a mass ratio of 1:4, and ultrasonicating to obtain a mixture;

[0064] Step 2: Calcinate the mixture at a lower temperature in the first stage to obtain a primary product;

[0065] Step 3: Calcinate the primary product at a higher temperature in the second stage. After the calcination is completed, cool it with the furnace to obtain the product.

[0066] In Step 1 of this example, the cobalt source is obtained by mixing cobalt sulfate and dimethyl sulfoxide in a mass ratio of 1:4; the parameters of the ultrasonic treatment are: ultrasonic power is 200W, ultrasonic frequency is 30kHz, and ultrasonic time is 25min.

[0067] The preparation method of the PMMA microspheres in Step 1 of this example includes the following steps:

[0068] Step X1: Add methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile into a reaction kettle. First, displace with nitrogen for 30min, and stir at 250rpm at 65°C for 5h to obtain a core emulsion;

[0069] Step X2: After heating to 75°C, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile, stir at 350rpm for 6.5h. After the stirring is completed, perform high-speed centrifugation to separate the solid matter, wash the solid matter alternately with water and absolute ethanol 3 times, and dry it to constant weight in a vacuum drying oven at 45°C to obtain PMMA microspheres with a core-shell structure;

[0070] Step X3: Mix the PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane, and toluene, stir at a rotation speed of 300rpm at 55°C for 3h. After the stirring is completed, filter with a 300-mesh filter cloth to retain the precipitate. Wash the precipitate alternately with toluene and absolute ethanol 3 times, and dry it to constant weight in a vacuum drying oven at 45°C to obtain PMMA microspheres.

[0071] In Step X1 of this example, the mass ratio of methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile is 24:3.5:0.17.

[0072] In Step X2 of this example, the mass ratio of glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile is 17.9:2.04:1.05:0.11; the rotation speed and time of high-speed centrifugation are 9000rpm and 17.5min, respectively.

[0073] In Step X3 of this example, the mass ratio of PMMA microspheres, 3-aminopropyltriethoxysilane, and toluene is 1:0.04:15.

[0074] In the rinsing step X2 of this example, the ratio of solids to water is 1:3 g / mL, and the volume ratio of water to absolute ethanol is 1:1; in the washing step X3, the ratio of precipitate to toluene is 1:4 g / mL, and the volume ratio of toluene to absolute ethanol is 1:1.

[0075] In the first-stage calcination in step two of this example, a mixed gas is introduced into the tubular furnace at a gas flow rate of 65 mL / min. The mixed gas includes 80 wt% nitrogen and the balance hydrogen. It is heated from room temperature to 400 °C at a heating rate of 1.75 °C / min and held for 2.5 h.

[0076] In the second-stage calcination in step three of this example, air is introduced into the tubular furnace at a gas flow rate of 125 mL / min. After purging for 20 min, while ventilating, it is heated to 700 °C at a heating rate of 2.75 °C / min and held for 3.5 h.

[0077] The cobalt tetroxide of this example is applied to the electrode material of a lithium battery.

[0078] Example 4

[0079] A process for segmentally preparing spherical cobalt tetroxide. The process for segmentally preparing spherical cobalt tetroxide in this example comprises the following steps:

[0080] Step 1: Mix PMMA microspheres and a cobalt source in a mass ratio of 1:3.7, and then perform ultrasonic treatment to obtain a mixture;

[0081] Step 2: Perform the first-stage calcination on the mixture at a lower temperature to obtain a primary product;

[0082] Step 3: Perform the second-stage calcination on the primary product at a higher temperature. After the calcination is completed, cool it with the furnace to obtain the product.

[0083] In step 1 of this example, the cobalt source is obtained by mixing cobalt sulfate and dimethyl sulfoxide in a mass ratio of 1:3.5; the parameters of the ultrasonic treatment are: ultrasonic power is 150 W, ultrasonic frequency is 35 kHz, and ultrasonic time is 23 min.

[0084] The preparation method of the PMMA microspheres in step 1 of this example comprises the following steps:

[0085] Step X1: Add methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile into a reaction kettle. First, purge with nitrogen for 30 min, and then stir at 280 rpm at 63 °C for 5.3 h to obtain a core emulsion;

[0086] Step X2, after heating to 74° C., add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile, and stir at 350 rpm for 6.7 h. After stirring, perform high-speed centrifugation to separate the solids, rinse the solids alternately with water and anhydrous ethanol three times, and dry in a vacuum drying oven at 45° C. to constant weight to obtain PMMA microspheres with a core-shell structure;

[0087] Step X3, mix PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane and toluene, and stir at 56°C at 320 rpm for 3.2 hours. After stirring, use a 300-mesh filter cloth to filter and retain the precipitate. Wash the precipitate alternately with toluene and anhydrous ethanol for three times, and dry it in a vacuum drying oven at 45°C to constant weight to obtain PMMA microspheres.

[0088] The mass ratio of methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile in step X1 of this embodiment is 23:3:0.15.

[0089] The mass ratio of glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile in step X2 of this embodiment is 17.5:2:1:0.12; the speed and time of high-speed centrifugation are 9500 rpm and 12 min, respectively.

[0090] The mass ratio of PMMA microspheres, 3-aminopropyltriethoxysilane, and toluene in step X3 of this embodiment is 1:0.04:16.

[0091] In this embodiment, the ratio of solid to water during rinsing in step X2 is 1:3.2 g / mL, and the volume ratio of water to anhydrous ethanol is 1:1; the ratio of precipitate to toluene during washing in step X3 is 1:4.5 g / mL, and the volume ratio of toluene to anhydrous ethanol is 1:1.

[0092] The first stage calcination in step 2 of this embodiment is to introduce a mixed gas into the tubular furnace at a gas flow rate of 60 mL / min, wherein the mixed gas includes 79 wt% nitrogen and the balance hydrogen, and heat from room temperature to 390°C at a heating rate of 1.6°C / min, and keep warm for 3 hours.

[0093] The second stage calcination in step three of this embodiment is to introduce air into the tube furnace at a gas flow rate of 130 mL / min, replace it for 20 minutes, and then increase the temperature to 690°C at a heating rate of 2.8°C / min while ventilating, and keep it at this temperature for 3.5 hours.

[0094] The cobalt tetroxide of this embodiment is applied to the electrode material of lithium battery.

[0095] Example 5

[0096] A process for preparing spherical cobalt tetroxide in stages. The process for preparing spherical cobalt tetroxide in stages in this embodiment comprises the following steps:

[0097] Step 1: Mix PMMA microspheres and a cobalt source in a mass ratio of 1:4.2, and then perform ultrasonic treatment to obtain a mixture.

[0098] Step 2: Calcinate the mixture at a lower temperature in the first stage to obtain a primary product.

[0099] Step 3: Calcinate the primary product at a higher temperature in the second stage. After the calcination is completed, cool it in the furnace to obtain the product.

[0100] In Step 1 of this embodiment, the cobalt source is obtained by mixing cobalt sulfate and dimethyl sulfoxide in a mass ratio of 1:4.5; the parameters of the ultrasonic treatment are: ultrasonic power is 250 W, ultrasonic frequency is 20 kHz, and ultrasonic time is 21 min.

[0101] The preparation method of the PMMA microspheres in Step 1 of this embodiment comprises the following steps:

[0102] Step X1: Add methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile into a reaction kettle. First, displace with nitrogen for 30 min, and then stir at 280 rpm at 66 °C for 5.3 h to obtain a core emulsion.

[0103] Step X2: After heating to 77 °C, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile, and stir at 380 rpm for 6.8 h. After the stirring is completed, perform high-speed centrifugation to separate the solid matter, wash the solid matter alternately with water and absolute ethanol 3 times, and dry it to a constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres with a core-shell structure.

[0104] Step X3: Mix the PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane, and toluene, and stir at 320 rpm at 54 °C for 3.1 h. After the stirring is completed, filter with a 300-mesh filter cloth to retain the precipitate. Wash the precipitate alternately with toluene and absolute ethanol 3 times, and dry it to a constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres.

[0105] In Step X1 of this embodiment, the mass ratio of methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile is 25:3:0.2.

[0106] In this embodiment, the mass ratio of glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile in step X2 is 18.5:2.5:1:0.1; the rotation speed and time of high-speed centrifugation are 8500 rpm and 18 min, respectively.

[0107] In this embodiment, the mass ratio of PMMA microspheres, 3-aminopropyltriethoxysilane, and toluene in step X3 is 1:0.03:14.

[0108] In this embodiment, the ratio of solids to water during rinsing in step X2 is 1:2.8 g / mL, and the volume ratio of water to absolute ethanol is 1:1; the ratio of precipitate to toluene during washing in step X3 is 1:3.5 g / mL, and the volume ratio of toluene to absolute ethanol is 1:1.

[0109] In the first-stage calcination in step two of this embodiment, a mixed gas is introduced into the tubular furnace at a gas flow rate of 70 mL / min. The mixed gas includes 81 wt% nitrogen and the balance hydrogen. The temperature is raised from room temperature to 410 °C at a heating rate of 1.8 °C / min and held for 3 h.

[0110] In the second-stage calcination in step three of this embodiment, air is introduced into the tubular furnace at a gas flow rate of 140 mL / min. After purging for 20 min, while maintaining the gas flow, the temperature is raised to 710 °C at a heating rate of 2.6 °C / min and held for 3.5 h.

[0111] The cobalt ferrite of this embodiment is applied to the electrode material of a lithium battery.

[0112] Comparative Example 1

[0113] Based on Example 3, step X3 is removed, that is, the PMMA microspheres with a core-shell structure are not modified, and other conditions are the same as those in Example 3.

[0114] Comparative Example 2

[0115] Based on Example 3, PMMA particles of equal weight are used to replace the PMMA microspheres. The PMMA particles are purchased from Dongguan Keyuan Plastic Raw Materials Co., Ltd., and other conditions are the same as those in Example 3.

[0116] Comparative Example 3

[0117] Based on Example 3, while maintaining other conditions the same, PMMA particles of equal weight are used to replace the PMMA microspheres. The PMMA particles are purchased from Dongguan Keyuan Plastic Raw Materials Co., Ltd., and the preparation method of the modified PMMA particles includes the following steps:

[0118] After mixing PMMA particles, 3-aminopropyltriethoxysilane, and toluene, stir at 55 °C at a speed of 300 rpm for 3 h. After stirring, filter using a 300-mesh filter cloth to retain the precipitate. Wash the precipitate alternately with toluene and absolute ethanol 3 times, and dry it in a vacuum drying oven at 45 °C until a constant weight is obtained to get modified PMMA particles.

[0119] Comparative Example 4

[0120] On the basis of Example 3, replace all of the mixed gas used in the first-stage calcination with nitrogen, and keep other conditions the same as those in Example 3.

[0121] Comparative Example 5

[0122] On the basis of Example 3, increase the dosage of hydrogen in the mixed gas used in the first-stage calcination to 25 wt%, and keep other conditions the same as those in Example 3.

[0123] Comparative Example 6

[0124] On the basis of Example 3, reduce the dosage of hydrogen in the mixed gas used in the first-stage calcination to 15 wt%, and keep other conditions the same as those in Example 3.

[0125] Comparative Example 7

[0126] On the basis of Example 3, change the temperature of the first-stage calcination from 400 °C to 420 °C, and keep other conditions the same as those in Example 3.

[0127] Comparative Example 8

[0128] On the basis of Example 3, while keeping other conditions the same, change the process of preparing spherical cobalt ferrite in stages to the following steps:

[0129] Step 1: After mixing PMMA microspheres and a cobalt source in a mass ratio of 1:4, perform ultrasonic treatment to obtain a mixture.

[0130] Step 2: Transfer the mixture to a tubular furnace, introduce air at a gas flow rate of 125 mL / min, while introducing the gas, heat it at a heating rate of 2.75 °C / min to 700 °C, keep it warm for 6 h, and cool it with the furnace to obtain the product.

[0131] 1. Performance test of spherical cobalt ferrite

[0132] Using the spherical cobalt ferrite prepared in Examples 1-3 and Comparative Examples 1-8 as samples, observe the morphology and whether there is agglomeration of the samples using a high-resolution scanning electron microscope, and test their tapped density. The results are recorded in Table 1 below.

[0133] Table 1 Performance test results of spherical cobalt ferrite

[0134]

[0135]

[0136] As can be seen from Table 1, the spherical cobalt tetroxide prepared by the present invention presents a perfect spherical shape in terms of morphology, has a smooth surface, no agglomeration phenomenon, and has a good tapped density.

[0137] 2. Application of Spherical Cobalt Tetroxide in Cathode Materials of Lithium Batteries

[0138] Using the spherical cobalt tetroxide prepared in Examples 1-3 and Comparative Examples 1-8 as cathode materials respectively, carbon black and polyvinylidene fluoride were added to N-methylpyrrolidone according to a mass ratio of 90:5:5. The solid content of the polyvinylidene fluoride colloidal solution was 3.5%. After mixing evenly, it was coated on aluminum foil, dried, and cut into cathode plates with a diameter of 12 mm. A CR2032 housing was used for button cell assembly, and the button cell cycle performance was tested. The test results are recorded in Table 2 below.

[0139] Table 2 Test Results of Button Cell Cycle Performance

[0140]

[0141]

[0142] As can be seen from Table 2, when the spherical cobalt tetroxide prepared by the present invention is used as a cathode material for lithium batteries, it has a high battery capacity and cycle performance.

[0143] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or variations equivalent to the equivalent embodiments within the scope of the technical solution of the present invention without departing from the technical solution of the present invention. However, any indirect modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A process for preparing spherical cobalt tetroxide in a segmented manner, characterized in that: The process for preparing spherical cobalt ferrite in a segmented manner comprises the following steps: Step 1: Mix PMMA microspheres and a cobalt source in a mass ratio of 1:3.5 - 4.5, and then perform ultrasonic treatment to obtain a mixture; Step 2: Calcinate the mixture at a relatively low temperature in the first stage to obtain a primary product; Step 3: Calcinate the primary product at a relatively high temperature in the second stage. After the calcination is completed, cool it in the furnace to obtain the product.

2. The process for preparing spherical cobalt tetroxide in a segmented manner according to claim 1, characterized in that: The cobalt source described in Step 1 is obtained by mixing cobalt sulfate and dimethyl sulfoxide in a mass ratio of 1:3 - 5; the parameters of the ultrasonic treatment are: ultrasonic power is 100 - 300 W, ultrasonic frequency is 20 - 40 kHz, and ultrasonic time is 20 - 30 min.

3. A process for preparing spherical cobalt tetroxide in a segmented manner according to claim 1, characterized in that: The preparation method of the PMMA microspheres described in Step 1 comprises the following steps: Step X1: Add methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile into a reaction kettle. First, displace with nitrogen for 30 min, and then stir at 200 - 300 rpm at 62 - 68 °C for 4.5 - 5.5 h to obtain a core emulsion; Step X2: After raising the temperature to 72 - 78 °C, add glycidyl methacrylate, 2-(dimethylamino)ethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile, and stir at 300 - 400 rpm for 6 - 7 h. After the stirring is completed, perform high-speed centrifugation to separate the solid matter, wash the solid matter alternately with water and absolute ethanol 3 times, and dry it to a constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres with a core-shell structure; Step X3: Mix the PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane, and toluene, and then stir at a rotation speed of 250 - 350 rpm at 52 - 58 °C for 2.5 - 3.5 h. After the stirring is completed, filter with a 300-mesh filter cloth to retain the precipitate. Wash the precipitate alternately with toluene and absolute ethanol 3 times, and dry it to a constant weight in a vacuum drying oven at 45 °C to obtain PMMA microspheres.

4. A process for preparing spherical cobalt tetroxide in a segmented manner according to claim 3, characterized in that: The mass ratio of methyl methacrylate, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile described in Step X1 is 22.5 - 25.5:2.5 - 4.5:0.11 - 0.

23.

5. A process for preparing spherical cobalt tetroxide in a segmented manner according to claim 3, characterized in that: The mass ratio of glycidyl methacrylate, 2-(dimethylamino)ethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile described in Step X2 is 16.5 - 19.3:1.44 - 2.64:0.9 - 1.2:0.09 - 0.13; the rotation speed and time of the high-speed centrifugation are 8000 - 10000 rpm and 15 - 20 min, respectively.

6. A process for preparing spherical cobalt tetroxide in a segmented manner according to claim 3, characterized in that: The mass ratio of the PMMA microspheres, 3-aminopropyltriethoxysilane, and toluene described in Step X3 is 1:0.03 - 0.05:10 - 20.

7. A process for preparing spherical cobalt tetroxide in a segmented manner according to claim 3, characterized in that: The ratio of the solid matter to water during the washing in Step X2 is 1:2 - 4 g / mL, and the volume ratio of water to absolute ethanol is 1:1; the ratio of the precipitate to toluene during the washing in Step X3 is 1:3 - 5 g / mL, and the volume ratio of toluene to absolute ethanol is 1:

1.

8. A process for preparing spherical cobalt tetroxide in a segmented manner according to claim 1, characterized in that: The first-stage calcination described in Step 2 is to introduce a mixed gas into the tubular furnace at a gas flow rate of 50 - 80 mL / min. The mixed gas includes 78 - 82 wt% nitrogen and the balance hydrogen. It is heated from room temperature to 380 - 420 °C at a heating rate of 1.5 - 2 °C / min and held for 2 - 3 h.

9. A process for preparing spherical cobalt tetroxide in a segmented manner according to claim 1, characterized in that: The second-stage calcination described in Step 3 is to introduce air into the tubular furnace at a gas flow rate of 100 - 150 mL / min. After purging for 20 min, while maintaining the gas flow, it is heated to 680 - 720 °C at a heating rate of 2.5 - 3 °C / min and held for 3 - 4 h.

10. Use of cobalt tetroxide prepared by the process for preparing spherical cobalt tetroxide in segments as described in any one of claims 1-9, characterized in that, The cobalt tetroxide is applied to the electrode material of a lithium battery.

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