A process for the preparation of spherical cobaltosic oxide in sections

Abstract

The present application relates to a kind of segmented preparation spherical cobaltic tetraoxide process, belong to cobaltic tetraoxide technical field.The present application provides a kind of segmented preparation spherical cobaltic tetraoxide process, its process includes the following steps, step one is that modified PMMA microsphere and cobalt source are mixed according to 1:3.5-4.5 mass ratio, ultrasonic, obtain mixture;Second step is to carry out first stage calcination at lower temperature, obtain initial product;Step three is that initial product is carried out second stage calcination at higher temperature, after calcination, with furnace cooling, it is obtained.The present application is formed with the help of PMMA microsphere first stable core and functionalized shell, enhances the adsorption force to cobalt source, then it is as template to make cobaltic tetraoxide spherical, increase specific surface area, finally through segmented calcination makes PMMA microsphere gradually decompose, form spherical cobaltic tetraoxide with regular pore.

Description

Technical Field

[0001] This invention belongs to the field of cobalt tetroxide technology and relates to a segmented process for preparing spherical cobalt tetroxide. Background Technology

[0002] Cobalt tetroxide (Co3O4) is an important inorganic compound that plays a crucial role in many fields, especially in lithium-ion batteries. In lithium-ion batteries, Co3O4 is the main raw material for preparing lithium cobalt oxide, the cathode material, directly affecting battery performance, cycle life, and safety. Common methods for preparing Co3O4 precursors include chemical precipitation and thermal decomposition. These precursors are then calcined at high temperatures to obtain Co3O4. However, Co3O4 prepared by these methods is prone to irregular shapes or agglomeration, leading to uneven filling or uneven lithium-ion diffusion paths, increasing internal resistance and thus affecting battery performance. Spherical Co3O4, due to its uniform morphology, has a relatively smaller impact on battery performance, and its preparation and application are receiving increasing attention. Summary of the Invention

[0003] The purpose of this invention is to provide a segmented process for preparing spherical cobalt tetroxide. This invention utilizes PMMA microspheres to first form a stable core and a functionalized shell to enhance the adsorption of cobalt source. Then, using these microspheres as templates, cobalt tetroxide is made into a spherical shape to increase the specific surface area. Finally, the PMMA microspheres are gradually decomposed through segmented calcination to form spherical cobalt tetroxide with regular pores.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A segmented process for preparing spherical cobalt tetroxide, comprising the following steps:

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

[0007] Step 2: The mixture is calcined at a lower temperature to obtain the initial product;

[0008] Step 3: The initial product is calcined at a higher temperature in the second stage. After calcination, it is cooled in the furnace to obtain the final product.

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

[0010] Furthermore, the method for preparing PMMA microspheres described in step one includes the following steps:

[0011] Step X1: Add methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile to the reaction vessel, purge with nitrogen for 30 min, and stir at 200-300 rpm at 62-68℃ for 4.5-5.5 h to obtain the core emulsion.

[0012] Step X2: After heating to 72-78℃, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile, and stir at 300-400 rpm for 6-7 hours. After stirring, centrifuge at high speed to separate the solids. Wash the solids three times alternately with water and anhydrous ethanol, and dry them in a vacuum drying oven at 45℃ to constant weight to obtain PMMA microspheres with a core-shell structure.

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

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

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

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

[0017] Further, in step X2, the ratio of solids to water during rinsing is 1:2-4 g / mL, and the volume ratio of water to anhydrous ethanol is 1:1; in step X3, the ratio of precipitate to toluene during washing is 1:3-5 g / mL, and the volume ratio of toluene to anhydrous ethanol is 1:1.

[0018] Further, in step two, the first stage of calcination involves introducing a mixed gas into a tube furnace at a gas flow rate of 50-80 mL / min. The mixed gas includes 78-82 wt% nitrogen and the remainder hydrogen. The temperature is increased from room temperature to 380-420°C at a heating rate of 1.5-2°C / min and held at that temperature for 2-3 hours.

[0019] Furthermore, in step three, the second stage of calcination involves introducing air into the tubular furnace at a gas flow rate of 100-150 mL / min, purging for 20 minutes, and then simultaneously heating the furnace to 680-720℃ at a heating rate of 2.5-3℃ / min, and holding the temperature for 3-4 hours.

[0020] Furthermore, the cobalt tetroxide is used as an electrode material in lithium batteries.

[0021] The beneficial effects of this invention are:

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

[0023] (2) The present invention provides a PMMA microsphere, which serves as a template. The cobalt source is uniformly adsorbed on the surface of the microsphere by the interaction of the active groups on the surface. In the subsequent calcination, the PMMA microsphere acts as a sacrificial template and gradually decomposes and volatilizes at high temperature, leaving the oxide skeleton formed by the cobalt source. This allows the cobalt tetroxide particles formed in the end to inherit the spherical structure of the microsphere and obtain a uniform spherical morphology. At the same time, some gas may be generated during the decomposition of the microsphere. The gas escapes and forms a porous structure, which increases the specific surface area of ​​cobalt tetroxide and improves its activity.

[0024] (3) In this invention, after introducing PMMA microspheres and cobalt source to obtain a mixture, a segmented calcination is carried out on this basis. In the first calcination stage, an inert environment is created and hydrogen is used as a reducing agent to reduce some of the cobalt elements in the cobalt source to a low valence state, forming a highly active low valence state cobalt oxide. At this time, the PMMA microspheres begin to undergo thermochemical reactions, but will not completely decompose instantly. The organic matter in the reaction system begins to slowly decompose and slowly release gas, forming a preliminary pore structure, avoiding particle cracking or deformation due to rapid gas escape at high temperature. As the temperature of the second calcination stage gradually increases, the PMMA microspheres gradually decompose completely and volatilize, leaving a regular and stable pore structure. Finally, spherical cobalt tetroxide is prepared, which has less impact on battery performance when used in lithium-ion batteries. Detailed Implementation

[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

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

[0027] Example 1

[0028] A segmented process for preparing spherical cobalt tetroxide, the segmented process for preparing spherical cobalt tetroxide in this embodiment includes the following steps:

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

[0030] Step 2: The mixture is calcined at a lower temperature to obtain the initial product;

[0031] Step 3: The initial product is calcined at a higher temperature in the second stage. After calcination, it is cooled in the furnace to obtain the final product.

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

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

[0034] Step X1: Add methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile to the reaction vessel, purge with nitrogen for 30 min, and stir at 200 rpm for 4.5 h at 62 °C to obtain the core emulsion.

[0035] Step X2: After heating to 72°C, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile. Stir at 300 rpm for 6 hours. After stirring, centrifuge at high speed to separate the solids. Wash the solids three times alternately with water and anhydrous ethanol. Dry in a vacuum drying oven at 45°C to constant weight to obtain PMMA microspheres with a core-shell structure.

[0036] Step X3: PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane, and toluene are mixed and stirred at 250 rpm for 2.5 h at 52 °C. After stirring, the mixture is filtered through a 300-mesh filter cloth to retain the precipitate. The precipitate is washed three times alternately with toluene and anhydrous ethanol and dried in a vacuum drying oven at 45 °C to constant weight to obtain PMMA microspheres.

[0037] In this embodiment, the mass ratio of methyl methacrylate, hydroxyethyl methacrylate, and azobisisobutyronitrile in step X1 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 high-speed centrifugation speed and time are 8000 rpm and 15 min, respectively.

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

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

[0041] In step two of this embodiment, the first stage of calcination involves introducing a mixed gas into a tubular furnace at a gas flow rate of 50 mL / min. The mixed gas includes 78 wt% nitrogen and the remainder hydrogen. The temperature is increased from room temperature to 380°C at a heating rate of 1.5°C / min and held at that temperature for 2 hours.

[0042] In step three of this embodiment, the second stage of calcination involves introducing air into a tubular furnace at a gas flow rate of 100 mL / min, purging for 20 minutes, and then simultaneously heating the furnace to 680°C at a rate of 2.5°C / min and holding the temperature for 3 hours.

[0043] In this embodiment, cobalt tetroxide is used as an electrode material for lithium batteries.

[0044] Example 2

[0045] A segmented process for preparing spherical cobalt tetroxide, the segmented process for preparing spherical cobalt tetroxide in this embodiment includes the following steps:

[0046] Step 1: Mix PMMA microspheres and cobalt source at a mass ratio of 1:4.5, then sonicate to obtain a mixture;

[0047] Step 2: The mixture is calcined at a lower temperature to obtain the initial product;

[0048] Step 3: The initial product is calcined at a higher temperature in the second stage. After calcination, it is cooled in the furnace to obtain the final product.

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

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

[0051] Step X1: Add methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile to the reaction vessel, purge with nitrogen for 30 min, and stir at 300 rpm for 5.5 h at 68 °C to obtain the core emulsion.

[0052] Step X2: After heating to 78°C, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile. Stir at 400 rpm for 7 hours. After stirring, centrifuge at high speed to separate the solids. Wash the solids three times alternately with water and anhydrous ethanol. Dry in a vacuum drying oven at 45°C to constant weight to obtain PMMA microspheres with a core-shell structure.

[0053] Step X3: PMMA microspheres with core-shell structure, 3-aminopropyltriethoxysilane, and toluene are mixed and stirred at 250-350 rpm for 3.5 h at 58 °C. After stirring, the mixture is filtered through a 300-mesh filter cloth to retain the precipitate. The precipitate is washed three times alternately with toluene and anhydrous ethanol and dried in a vacuum drying oven at 45 °C to constant weight to obtain PMMA microspheres.

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

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

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

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

[0058] In step two of this embodiment, the first stage of calcination involves introducing a mixed gas into a tubular furnace at a gas flow rate of 80 mL / min. The mixed gas includes 82 wt% nitrogen and the remainder hydrogen. The temperature is increased from room temperature to 420°C at a heating rate of 2°C / min and held for 3 hours.

[0059] In step three of this embodiment, the second stage of calcination involves introducing air into a tubular furnace at a gas flow rate of 150 mL / min, purging for 20 minutes, and then simultaneously heating the furnace to 720°C at a rate of 3°C / min and holding the temperature for 4 hours.

[0060] In this embodiment, cobalt tetroxide is used as an electrode material for lithium batteries.

[0061] Example 3

[0062] A segmented process for preparing spherical cobalt tetroxide, the segmented process for preparing spherical cobalt tetroxide in this embodiment includes the following steps:

[0063] Step 1: Mix PMMA microspheres and cobalt source at a mass ratio of 1:4, then sonicate to obtain a mixture;

[0064] Step 2: The mixture is calcined at a lower temperature to obtain the initial product;

[0065] Step 3: The initial product is calcined at a higher temperature in the second stage. After calcination, it is cooled in the furnace to obtain the final product.

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

[0067] The preparation method of PMMA microspheres in step one of this embodiment includes the following steps:

[0068] Step X1: Add methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile to the reaction vessel, purge with nitrogen for 30 min, and stir at 250 rpm for 5 h at 65 °C to obtain the core emulsion.

[0069] Step X2: After heating to 75°C, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile, stir at 350 rpm for 6.5 h, and after stirring, centrifuge at high speed to separate the solids. Wash the solids three times alternately with water and anhydrous ethanol, and dry them in a vacuum drying oven at 45°C to constant weight to obtain PMMA microspheres with a core-shell structure.

[0070] Step X3: PMMA microspheres with core-shell structure, 3-aminopropyltriethoxysilane, and toluene are mixed and stirred at 300 rpm for 3 hours at 55°C. After stirring, the mixture is filtered through a 300-mesh filter cloth to retain the precipitate. The precipitate is washed three times alternately with toluene and anhydrous ethanol and dried in a vacuum drying oven at 45°C to constant weight to obtain PMMA microspheres.

[0071] In this embodiment, the mass ratio of methyl methacrylate, hydroxyethyl methacrylate, and azobisisobutyronitrile in step X1 is 24:3.5:0.17.

[0072] In step X2 of this embodiment, 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 high-speed centrifugation speed and time are 9000 rpm and 17.5 min, respectively.

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

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

[0075] In step two of this embodiment, the first stage of calcination involves introducing a mixed gas into a tubular furnace at a gas flow rate of 65 mL / min. The mixed gas includes 80 wt% nitrogen and the remainder hydrogen. The temperature is increased from room temperature to 400°C at a heating rate of 1.75°C / min and held at that temperature for 2.5 hours.

[0076] In step three of this embodiment, the second stage of calcination involves introducing air into a tubular furnace at a gas flow rate of 125 mL / min, purging for 20 minutes, and then simultaneously heating the furnace to 700°C at a rate of 2.75°C / min and holding the temperature for 3.5 hours.

[0077] In this embodiment, cobalt tetroxide is used as an electrode material for lithium batteries.

[0078] Example 4

[0079] A segmented process for preparing spherical cobalt tetroxide, the segmented process for preparing spherical cobalt tetroxide in this embodiment includes the following steps:

[0080] Step 1: Mix PMMA microspheres and cobalt source at a mass ratio of 1:3.7, then sonicate to obtain a mixture;

[0081] Step 2: The mixture is calcined at a lower temperature to obtain the initial product;

[0082] Step 3: The initial product is calcined at a higher temperature in the second stage. After calcination, it is cooled in the furnace to obtain the final product.

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

[0084] The preparation method of PMMA microspheres in step one of this embodiment includes the following steps:

[0085] Step X1: Add methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile to the reaction vessel, purge with nitrogen for 30 min, and stir at 280 rpm for 5.3 h at 63 °C to obtain the core emulsion.

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

[0087] Step X3: PMMA microspheres with core-shell structure, 3-aminopropyltriethoxysilane, and toluene are mixed and stirred at 320 rpm for 3.2 h at 56 °C. After stirring, the mixture is filtered through a 300-mesh filter cloth to retain the precipitate. The precipitate is washed three times alternately with toluene and anhydrous ethanol and dried in a vacuum drying oven at 45 °C to constant weight to obtain PMMA microspheres.

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

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

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

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

[0092] In step two of this embodiment, the first stage of calcination involves introducing a mixed gas into a tubular furnace at a gas flow rate of 60 mL / min. The mixed gas includes 79 wt% nitrogen and the remainder hydrogen. The temperature is increased from room temperature to 390°C at a heating rate of 1.6°C / min and held at that temperature for 3 hours.

[0093] In step three of this embodiment, the second stage of calcination involves introducing air into a tubular furnace at a gas flow rate of 130 mL / min, purging for 20 minutes, and then simultaneously heating the furnace to 690°C at a rate of 2.8°C / min and holding the temperature for 3.5 hours.

[0094] In this embodiment, cobalt tetroxide is used as an electrode material for lithium batteries.

[0095] Example 5

[0096] A segmented process for preparing spherical cobalt tetroxide, the segmented process for preparing spherical cobalt tetroxide in this embodiment includes the following steps:

[0097] Step 1: Mix PMMA microspheres and cobalt source at a mass ratio of 1:4.2, then sonicate to obtain a mixture;

[0098] Step 2: The mixture is calcined at a lower temperature to obtain the initial product;

[0099] Step 3: The initial product is calcined at a higher temperature in the second stage. After calcination, it is cooled in the furnace to obtain the final product.

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

[0101] The preparation method of PMMA microspheres in step one of this embodiment includes the following steps:

[0102] Step X1: Add methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile to the reaction vessel, purge with nitrogen for 30 min, and stir at 280 rpm for 5.3 h at 66 °C to obtain the core emulsion;

[0103] Step X2: After heating to 77℃, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile, stir at 380 rpm for 6.8 h, and after stirring, centrifuge at high speed to separate the solids. Wash the solids three times alternately with water and anhydrous ethanol, and dry them in a vacuum drying oven at 45℃ to constant weight to obtain PMMA microspheres with a core-shell structure.

[0104] Step X3: PMMA microspheres with core-shell structure, 3-aminopropyltriethoxysilane, and toluene are mixed and stirred at 320 rpm for 3.1 h at 54 °C. After stirring, the mixture is filtered through a 300-mesh filter cloth to retain the precipitate. The precipitate is washed three times alternately with toluene and anhydrous ethanol and dried in a vacuum drying oven at 45 °C to constant weight to obtain PMMA microspheres.

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

[0106] In step X2 of this embodiment, the mass ratio of glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile is 18.5:2.5:1:0.1; the high-speed centrifugation speed and time 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, during rinsing in step X2, the ratio of solids to water is 1:2.8 g / mL, and the volume ratio of water to anhydrous ethanol is 1:1; during washing in step X3, the ratio of precipitate to toluene is 1:3.5 g / mL, and the volume ratio of toluene to anhydrous ethanol is 1:1.

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

[0110] In step three of this embodiment, the second stage of calcination involves introducing air into a tubular furnace at a gas flow rate of 140 mL / min, purging for 20 minutes, and then simultaneously heating the furnace to 710°C at a rate of 2.6°C / min and holding the temperature for 3.5 hours.

[0111] In this embodiment, cobalt tetroxide is used as an electrode material for lithium batteries.

[0112] Comparative Example 1

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

[0114] Comparative Example 2

[0115] Based on Example 3, PMMA microspheres were replaced with PMMA granules of equal weight, wherein the PMMA granules were purchased from Dongguan Kaiyuan Plastic Raw Materials Co., Ltd., and other conditions remained the same as in Example 3.

[0116] Comparative Example 3

[0117] Based on Example 3, while keeping other conditions the same, an equal weight of modified PMMA particles was used to replace PMMA microspheres. The PMMA particles were purchased from Dongguan Kaiyuan Plastic Raw Materials Co., Ltd., and the preparation method of the modified PMMA particles included the following steps:

[0118] PMMA particles, 3-aminopropyltriethoxysilane, and toluene were mixed and stirred at 300 rpm for 3 hours at 55°C. After stirring, the mixture was filtered through a 300-mesh filter cloth to retain the precipitate. The precipitate was washed three times alternately with toluene and anhydrous ethanol and dried to constant weight in a vacuum drying oven at 45°C to obtain modified PMMA particles.

[0119] Comparative Example 4

[0120] Based on Example 3, the mixed gas used in the first stage of calcination was completely replaced with nitrogen, while other conditions remained the same as in Example 3.

[0121] Comparative Example 5

[0122] Based on Example 3, the amount of hydrogen in the mixed gas used in the first stage of calcination was increased to 25 wt%, while other conditions remained the same as in Example 3.

[0123] Comparative Example 6

[0124] Based on Example 3, the amount of hydrogen in the mixed gas used in the first stage of calcination was reduced to 15 wt%, while other conditions remained the same as in Example 3.

[0125] Comparative Example 7

[0126] Based on Example 3, the temperature of the first stage calcination was changed from 400℃ to 420℃, while other conditions remained the same as in Example 3.

[0127] Comparative Example 8

[0128] Based on Example 3, while keeping other conditions consistent, the segmented process for preparing spherical cobalt tetroxide was modified to the following steps:

[0129] Step 1: Mix PMMA microspheres and cobalt source at a mass ratio of 1:4, then sonicate to obtain a mixture;

[0130] Step 2: Transfer the mixture to a tube furnace and introduce air at a gas flow rate of 125 mL / min. While introducing air, heat the mixture to 700°C at a heating rate of 2.75°C / min, hold at this temperature for 6 hours, and then cool it with the furnace to obtain the final product.

[0131] 1. Performance testing of spherical cobalt tetroxide

[0132] Using the spherical cobalt tetroxide samples prepared in Examples 1-3 and Comparative Examples 1-8 as samples, the morphology and agglomeration of the samples were observed using a high-resolution scanning electron microscope, and the tap density was tested and recorded in Table 1 below.

[0133] Table 1. Performance test results of spherical cobalt tetroxide

[0134]

[0135]

[0136] As shown in Table 1, the spherical cobalt tetroxide prepared by the present invention exhibits a perfect spherical shape, a smooth surface, no agglomeration, and a good tap density.

[0137] 2. Application of spherical cobalt tetroxide in lithium battery cathode materials

[0138] The spherical cobalt tetroxide prepared in Examples 1-3 and Comparative Examples 1-8 were used as positive electrode materials. They were added to N-methylpyrrolidone along with carbon black and polyvinylidene fluoride in a mass ratio of 90:5:5. The solid content of the polyvinylidene fluoride adhesive was 3.5%. After being mixed evenly, the mixture was coated on aluminum foil, dried, and cut into positive electrode sheets with a diameter of 12 mm. The electrodes were then assembled into coin cells using a CR2032 shell. The coin cell cycle performance was tested, and the test results are recorded in Table 2 below.

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

[0140]

[0141]

[0142] As shown in Table 2, the spherical cobalt tetroxide prepared by this invention has high battery capacity and cycle performance when used as a positive electrode material for lithium batteries.

[0143] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing spherical cobalt tetroxide in a segmented manner, characterized in that: The segmented process for preparing spherical cobalt tetroxide includes the following steps: Step 1: Mix PMMA microspheres and cobalt source at a mass ratio of 1:3.5-4.5, then sonicate to obtain a mixture; Step 2: The mixture is calcined at 380-420℃ to obtain the initial product; Step 3: The primary product is calcined at 680-720℃ in the second stage. After calcination, it is cooled in the furnace to obtain the final product. The method for preparing PMMA microspheres described in step one includes the following steps: Step X1: Add methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile to the reaction vessel, purge with nitrogen for 30 min, and stir at 200-300 rpm at 62-68℃ for 4.5-5.5 h to obtain the core emulsion. Step X2: After heating to 72-78℃, add glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate and azobisisobutyronitrile, and stir at 300-400 rpm for 6-7 hours. After stirring, centrifuge at high speed to separate the solids. Wash the solids three times alternately with water and anhydrous ethanol, and dry them in a vacuum drying oven at 45℃ to constant weight to obtain PMMA microspheres with a core-shell structure. Step X3: Mix PMMA microspheres with a core-shell structure, 3-aminopropyltriethoxysilane, and toluene, and stir at 250-350 rpm for 2.5-3.5 h at 52-58 °C. After stirring, filter the mixture through a 300-mesh filter cloth to retain the precipitate. Wash the precipitate three times alternately with toluene and anhydrous ethanol, and dry it in a vacuum drying oven at 45 °C to constant weight to obtain PMMA microspheres. Step 2: The first stage of calcination is carried out in a mixture of 78-82 wt% nitrogen and the balance hydrogen.

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

3. The method for segmented preparation of spherical cobalt tetroxide according to claim 1, characterized in that: The mass ratio of methyl methacrylate, hydroxyethyl methacrylate and azobisisobutyronitrile in step X1 is 22.5-25.5:2.5-4.5:0.11-0.

23.

4. The method for segmented preparation of spherical cobalt tetroxide according to claim 1, characterized in that: In step X2, the mass ratio of glycidyl methacrylate, 2-aminoethyl methacrylate hydrochloride, ethylene glycol dimethacrylate, and azobisisobutyronitrile is 16.5-19.3:1.44-2.64:0.9-1.2:0.09-0.13; the high-speed centrifugation speed and time are 8000-10000 rpm and 15-20 min, respectively.

5. The method for segmented preparation of spherical cobalt tetroxide according to claim 1, characterized in that: The mass ratio of PMMA microspheres, 3-aminopropyltriethoxysilane, and toluene in step X3 is 1:0.03-0.05:10-20.

6. The method for segmented preparation of spherical cobalt tetroxide according to claim 1, characterized in that: In step X2, the ratio of solids to water during rinsing is 1:2-4 g / mL, and the volume ratio of water to anhydrous ethanol is 1:1; in step X3, the ratio of precipitate to toluene during washing is 1:3-5 g / mL, and the volume ratio of toluene to anhydrous ethanol is 1:

1.

7. The method for segmented preparation of spherical cobalt tetroxide according to claim 1, characterized in that: Step 2: The first stage of calcination involves introducing a mixed gas into a tubular furnace at a gas flow rate of 50-80 mL / min, raising the temperature from room temperature to 380-420℃ at a heating rate of 1.5-2℃ / min, and holding at that temperature for 2-3 hours.

8. The method for segmented preparation of spherical cobalt tetroxide according to claim 1, characterized in that: Step 3, the second stage of calcination, involves introducing air into the tubular furnace at a gas flow rate of 100-150 mL / min for 20 minutes, followed by heating to 680-720℃ at a rate of 2.5-3℃ / min while simultaneously introducing air, and holding at that temperature for 3-4 hours.

9. The application of cobalt tetroxide prepared by the segmented method for preparing spherical cobalt tetroxide as described in any one of claims 1-8, characterized in that, The cobalt tetroxide is used as an electrode material in lithium batteries.

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