Tricobalt tetraoxide material, preparation method thereof, positive electrode material and lithium ion battery

Abstract

The application relates to the material field and discloses a tricobalt tetraoxide material, a preparation method of the tricobalt tetraoxide material, a positive electrode material and a lithium ion battery. The specific surface area of the tricobalt tetraoxide material is greater than or equal to 56 m 2 / g. The material has a high specific surface area, contains a high proportion of particles with a particle size of about 50 nm, is used as a coating material of a lithium ion battery positive electrode material, is favorable for improving the reaction activity of the positive electrode material and the coating material, forms a more uniform and lattice-matched coating layer, and thus the electric performance of the positive electrode material is improved.

Description

Technical Field

[0001] This application relates to the field of materials, specifically to cobalt tetroxide materials and their preparation methods, cathode materials, and lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, as energy storage components, are widely used in electronic devices, electric vehicles, and hybrid vehicles. The cathode material is a crucial electrochemical active material in lithium-ion batteries, significantly determining their performance and cost. Currently, commercially available cathode materials mainly include lithium iron phosphate, ternary materials, and lithium cobalt oxide. To improve the energy density of cathode materials, a common strategy is to increase their operating voltage. However, for layered cathode materials like ternary materials and lithium cobalt oxide, under high voltage conditions, side reactions at the material surface and interface intensify, leading to irreversible capacity decay. Furthermore, lithium-ion batteries also suffer from low initial charge / discharge efficiency and low electron-ion conductivity. One approach to address these issues is to modify the surface and interface of the cathode material through coating. This involves forming an inert material (non-lithium active material) on the cathode material surface, such as alumina, magnesium oxide, zinc oxide, silicon dioxide, or aluminum fluoride, or forming lithium active materials such as lithium cobalt oxide, lithium zirconate, or lithium phosphate.

[0003] However, the coating materials for lithium-ion battery cathodes still need improvement in terms of enhancing the cathode's capacity and cycle stability. Summary of the Invention

[0004] This application aims to at least partially alleviate or resolve at least one of the aforementioned problems.

[0005] In one aspect of this application, a cobalt tetroxide material is provided, wherein the specific surface area of ​​the cobalt tetroxide material is ≥56m². 2 / g. The above material has a high specific surface area and contains a high proportion of particles with a particle size of about 50nm. Using it as a coating material for lithium-ion battery cathode materials is beneficial to improving the reactivity between the cathode material and the coating material, forming a more uniform and lattice-matched coating layer, thereby improving the electrical performance of the cathode material.

[0006] In some embodiments of this application, the cobalt tetroxide material satisfies at least one of the following conditions: the particles of the cobalt tetroxide material are dot-shaped or spherical; the D50 particle size of the cobalt tetroxide material is ≤100nm; the mass content of cobalt element in the cobalt tetroxide material is 70%~73%; and the specific surface area of ​​the cobalt tetroxide material is 56~90m². 2 / g; the D50 particle size of the cobalt tetroxide material is a nanometer, the specific surface area of ​​the cobalt tetroxide material is b square meters / gram, and a / b≤3.5.

[0007] In another aspect of this application, a method for preparing cobalt tetroxide material is proposed. In some embodiments of this application, the method for preparing cobalt tetroxide material includes: (1) Add cobalt salt solution, alkaline solution and carbonate precursor solution to the reaction vessel, control the pH of the reaction system to 7.5~12, and react at 30~80℃ to generate a slurry containing basic cobalt carbonate; (2) Stop feeding materials and allow the material to age; (3) The aged slurry is subjected to solid-liquid separation, and the solid is dried. (4) The dried solid is calcined to obtain calcined material, wherein the calcination temperature is 200~600℃, and the calcination includes at least two calcination steps at different temperatures, wherein the temperature of the first calcination step is lower than the temperature of the second calcination step. (5) The calcined material is pulverized to obtain cobalt tetroxide material. The cobalt tetroxide material prepared by the above method has a large specific surface area, small particle size, good dispersibility and is not easy to agglomerate.

[0008] In some embodiments of this application, the carbonate precursor includes at least one of carbonate and bicarbonate; and / or, the molar ratio of cobalt to carbonate precursor in the reaction system is 1:(0.5~20).

[0009] In some embodiments of this application, the carbonate precursor is a carbonate, and the molar ratio of cobalt to carbonate in the reaction system is 1:(0.5~10); or, the carbonate precursor is a bicarbonate, and the molar ratio of cobalt to bicarbonate in the reaction system is 1:(0.5~20).

[0010] In some embodiments of this application, the method for preparing cobalt tetroxide material satisfies at least one of the following conditions: the solute in the cobalt salt solution includes at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate; the concentration of cobalt ions in the cobalt salt solution is 60~150 g / L; the solvent in the cobalt salt solution includes at least one of water, ethanol, and acetone; the alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water; the concentration of the alkaline solution is 1~440 g / L; the solvent in the alkaline solution includes at least one of water, ethanol, and acetone; the solute in the carbonate precursor solution includes at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate; the concentration of the carbonate precursor solution is 1~220 g / L; the solvent in the carbonate precursor solution includes at least one of water, ethanol, and acetone; in step (1), the pH value of the reaction system is controlled to be 8~12; in step (4), the calcination temperature is 200~400℃.

[0011] In some embodiments of this application, the method for preparing cobalt tetroxide material satisfies at least one of the following conditions: in step (1), a gas is introduced during the reaction; in step (1), the reaction time is 60 to 180 minutes; in step (1), the reaction is carried out under stirring conditions; in step (2), the aging temperature is 30 to 80°C; in step (2), the aging time is 60 to 180 minutes; in step (2), the aging is carried out under stirring conditions; in step (2), a gas is introduced during aging.

[0012] In some embodiments of this application, the method for preparing cobalt tetroxide material satisfies at least one of the following conditions: the calcination treatment time is 1 to 10 hours; the calcination treatment includes two, three, or four calcination steps at different temperatures; the temperature difference between two adjacent calcination steps is ≥50°C; and the treatment time for each calcination step is 0.5 to 4 hours.

[0013] In some embodiments of this application, the method for preparing cobalt tetroxide material satisfies at least one of the following conditions: in step (1), the gas flow rate is 0.3~3m³. 3 / h; In step (1), the gas is air; In step (2), the gas flow rate is 0.3~3m 3 / h; In step (2), the gas is air.

[0014] In another aspect of this application, a cathode material is proposed, which is prepared by mixing the aforementioned cobalt tetroxide material or the cobalt tetroxide material prepared by the aforementioned method with a lithium-mixed cathode material, followed by sintering to form the cathode material. Therefore, this cathode material exhibits excellent electrical properties.

[0015] In another aspect, this application proposes a lithium-ion battery comprising the aforementioned positive electrode material. Consequently, this lithium-ion battery exhibits high capacity and good cycle stability. Attached Figure Description

[0016] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a scanning electron microscope image of the nano-basic cobalt carbonate obtained in Example 1; Figure 2 This is the XRD diffraction pattern of the nano-basic cobalt carbonate obtained in Example 1; Figure 3 This is a scanning electron microscope image of the nano-cobalt tetroxide obtained in Example 1; Figure 4 This is the XRD diffraction pattern of the nano-cobalt tetroxide obtained in Example 1; Figure 5 This is a scanning electron microscope image of the nano-cobalt carbonate obtained in Comparative Example 1; Figure 6 This is a scanning electron microscope image of the nano-cobalt tetroxide obtained in Comparative Example 1. Detailed Implementation

[0017] The embodiments of this application are described in detail below. These embodiments are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0018] In one aspect of this application, a cobalt tetroxide material is proposed, wherein the specific surface area of ​​the cobalt tetroxide material is ≥56m². 2 / g, for example, the specific surface area of ​​cobalt tetroxide material can be 56m². 2 / g、59m 2 / g、65m 2 / g、68m 2 / g、70m 2 / g、75m 2 / g、85m 2 / g etc. The above materials have a high specific surface area. Using them as coating materials for lithium-ion battery cathode materials can modify the surface and interface of the lithium-ion battery cathode materials, thereby improving the activity of the cathode materials. Using cathode materials in lithium-ion batteries can improve the capacity and cycle stability of lithium-ion batteries.

[0019] In some embodiments of this application, the specific surface area of ​​the cobalt tetroxide material can be 56~90 m². 2 / g, thus, using this cobalt tetroxide material to coat the cathode material of lithium-ion batteries is beneficial to improving the reactivity between the cathode material and the coating material, forming a more uniform and lattice-matched coating layer, which is beneficial to further improving the electrical performance of the cathode material.

[0020] In some embodiments, the cobalt content in the cobalt tetroxide material can be 70% to 73% by mass, for example, 70%, 70.5%, 71%, 71.5%, 72%, 72.5%, 73% by mass, etc. This material has fewer impurities and, when used as a coating material for cathode materials, can improve the electrical performance of the cathode material.

[0021] In some embodiments, reference Figure 3 The particles of cobalt tetroxide are spherical. These particles with the aforementioned microstructure can be used as coating materials for cathode materials. Furthermore, the coating material exhibits high reactivity with the cathode material, which is beneficial for forming a more uniform and lattice-matched coating layer, thereby improving the electrical performance of the cathode material. It should be noted that "spherical" does not strictly require the particles to be perfectly spherical; an approximate spherical shape is sufficient.

[0022] In some embodiments, the D50 particle size of the cobalt tetroxide material is ≤100nm. For example, the D50 particle size of the cobalt tetroxide material can be 50nm~100nm, specifically 55nm, 65nm, 75nm, 85nm, etc. This is beneficial to increasing the specific surface area of ​​the material. Using it as a coating material for cathode materials can improve the activity of cathode materials, thereby improving the electrical performance of cathode materials.

[0023] In some embodiments, the D50 particle size of the cobalt tetroxide material is a nanometer, the specific surface area of ​​the cobalt tetroxide material is b square meters / gram, and a / b ≤ 3.5. For example, a / b can be 0.7~3.5, specifically 0.9, 1.5, 2, 2.5, 3, etc. This is beneficial to further improve the overall performance of the cobalt tetroxide material. Using it as a coating material for cathode materials is beneficial to further improve the cycle stability of cathode materials.

[0024] In another aspect of this application, a method for preparing cobalt tetroxide material is proposed. In some embodiments of this application, the method for preparing cobalt tetroxide material may include the following steps: (1) Add cobalt salt solution, alkaline solution and carbonate precursor solution to the reaction vessel, control the pH of the reaction system to 7.5~12, and react at 30~80℃ to generate a slurry containing basic cobalt carbonate.

[0025] The pH of the reaction system is controlled between 7.5 and 12, with basic cobalt carbonate as the main product. If the pH is too low, the precipitation rate is affected, and the cobalt carbonate phase increases, which is detrimental to particle size control. Similarly, if the pH is too high, the precipitation rate is also affected, and the cobalt hydroxide phase increases, which is also detrimental to particle size control. Furthermore, it may form flaky products, which is also unfavorable for particle size control. Reacting the raw materials at 30–80°C is beneficial for adjusting the reaction rate and generating basic cobalt carbonate at a suitable rate, thus facilitating control of the product particle size.

[0026] In some embodiments, the pH value of the reaction system can be controlled to be 7.5, 8, 9, 10, 11, 12, etc. In some embodiments, the pH value of the reaction system can be controlled to be 8~12, which is beneficial for obtaining high-purity basic cobalt carbonate and for particle size control.

[0027] In some embodiments, the reaction can be carried out at 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, which is beneficial to improve the precipitation rate and increase the reaction rate while shortening the reaction time.

[0028] In some embodiments, in step (1), gas can be introduced during the reaction process to protect the nano-basic cobalt carbonate from further agglomeration and bonding by utilizing the aeration effect of the gas, thereby facilitating the acquisition of materials with smaller particles and larger specific surface area.

[0029] In some embodiments, in step (1), the gas flow rate can be 0.3~3m³. 3 / h, for example, the gas flow rate can be 0.3m³ / h. 3 / h, 0.5m 3 / h, 0.8m 3 / h、1m 3 / h、2m 3 / h、3m 3 / h, etc., which helps to suppress particle aggregation, thereby more effectively controlling particle size and increasing the specific surface area of ​​the material.

[0030] In some specific embodiments, the gas in step (1) can be air. This helps to reduce the preparation cost of cobalt tetroxide.

[0031] In some embodiments, the solute in the cobalt salt solution may include at least one of cobalt sulfate, cobalt chloride, cobalt nitrate, etc. The cobalt salts mentioned above have high solubility and can provide cobalt element, which reacts with hydroxide and carbonate / bicarbonate ions under certain conditions to generate basic cobalt carbonate.

[0032] In some embodiments, the concentration of cobalt ions in the cobalt salt solution can be 60~150 g / L, for example, the concentration of cobalt ions in the cobalt salt solution can be 60 g / L, 80 g / L, 100 g / L, 130 g / L, or 150 g / L.

[0033] In some embodiments, the solvent in the cobalt salt solution may include at least one of water, ethanol, acetone, etc. For example, the solvent in the cobalt salt solution may be water, ethanol, or acetone, or the solvent in the cobalt salt solution may be composed of two or three of water, ethanol, and acetone.

[0034] In some embodiments, the alkaline solution may include at least one of sodium hydroxide, potassium hydroxide, and ammonia water. Thus, the alkaline solution can adjust the pH of the reaction system and participate in the reaction, promoting the formation of basic cobalt carbonate.

[0035] In some embodiments, the concentration of the alkaline solution can be from 1 to 440 g / L, for example, the concentration of the alkaline solution can be 1 g / L, 10 g / L, 50 g / L, 100 g / L, 200 g / L, 300 g / L, 440 g / L, etc. The alkaline solution of the above concentrations can adjust the pH value of the reaction system to ensure a suitable concentration of hydroxide ions, thereby promoting the formation of basic cobalt carbonate.

[0036] In some embodiments, the solvent in the alkaline solution may include at least one of water, ethanol, and acetone.

[0037] In some embodiments, the carbonate precursor may include at least one of carbonate and bicarbonate. For example, the carbonate precursor may be a carbonate or a bicarbonate, or a mixture of carbonate and bicarbonate.

[0038] In some embodiments, the solute in the carbonate precursor solution may include at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

[0039] In some embodiments, the solvent in the carbonate precursor solution may include at least one of water, ethanol, and acetone.

[0040] In some embodiments, the molar ratio of cobalt to carbonate precursor in the reaction system can be 1:(0.5~20). For example, the molar ratio of cobalt to carbonate precursor in the reaction system can be 1:0.5, 1:1, 1:3, 1:5, 1:7, 1:9, 1:12, 1:15, 1:18, 1:20, etc. When the carbonate precursor concentration is low, the precipitation rate is slow, and nucleation growth exhibits a certain degree of directionality. When the carbonate precursor concentration is high, the precipitation rate is fast, and nucleation growth is scattered. A molar ratio of cobalt to carbonate precursor within the above range is beneficial to improving the precipitation rate, increasing production capacity, and improving the utilization rate of cobalt and carbonate precursor, reducing waste. If the molar ratio of cobalt to carbonate precursor is too low, it is not conducive to improving production capacity and will cause waste of carbonate precursor; if the molar ratio is too high, it will cause waste of cobalt liquid, and direct discharge will cause environmental problems, while waste liquid treatment will increase environmental protection costs.

[0041] In some specific embodiments, the carbonate precursor can be a carbonate, and the molar ratio of cobalt to carbonate in the reaction system can be 1:(0.5~10).

[0042] In some specific embodiments, the carbonate precursor can be bicarbonate, and the molar ratio of cobalt to bicarbonate in the reaction system can be 1:(0.5~20).

[0043] In some embodiments, the concentration of the carbonate precursor solution can be 1~220 g / L, for example, the concentration of the carbonate precursor solution can be 1 g / L, 15 g / L, 50 g / L, 80 g / L, 100 g / L, 150 g / L, 180 g / L, 200 g / L, 220 g / L, etc.

[0044] In some embodiments, the reaction time in step (1) can be 60 to 180 minutes, for example, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes, etc. This allows for a more complete reaction, which is beneficial for improving the utilization rate of raw materials.

[0045] In some embodiments, in step (1), the reaction is carried out under stirring conditions, which is beneficial to increase the reaction rate of the raw materials and shorten the reaction time.

[0046] In step (1), the cobalt salt solution, alkaline solution and carbonate precursor solution can be added to the reactor in parallel under stirring conditions.

[0047] (2) Stop feeding materials and allow the material to age.

[0048] After stopping feeding, allowing the raw materials to age for a period of time allows for further reaction and improves their utilization rate.

[0049] In some embodiments, gas can be continuously introduced during the aging process to further prevent particle aggregation, thereby making it more advantageous to obtain products with smaller particle sizes.

[0050] In some embodiments, in step (2), the aging temperature can be 30~80℃, for example, the aging temperature can be 35℃, 45℃, 55℃, 65℃, 75℃, etc. Aging at the above temperatures is beneficial to the full reaction of the raw materials.

[0051] In some embodiments, in step (2), the aging time is 60 to 180 minutes. For example, the aging time can be 60 minutes, 80 minutes, 100 minutes, 120 minutes, 150 minutes, 180 minutes, etc., which can promote the full reaction of raw materials, thereby improving the utilization rate of raw materials and the amount of product.

[0052] In some embodiments, in step (2), aging is carried out under stirring conditions, which is more conducive to improving the utilization rate of raw materials.

[0053] In some embodiments, in step (2), the gas flow rate can be 0.3~3m³. 3 / h, thus, the aeration effect of the gas can be used to further prevent particle aggregation, thereby helping to reduce the particle size of the product and improve the dispersibility of the product.

[0054] In some embodiments, in step (2), air can be introduced, and the air flow rate can be 0.3~3m³. 3 / h, for example, the air flow rate can be 0.3m³ / h. 3 / h, 0.8m 3 / h、1m 3 / h, 1.5m 3 / h, 2.5m 3 / h、3m 3 / h etc. This reduces the agglomeration of nano-basic cobalt carbonate, thus facilitating the production of materials with smaller particle sizes and better dispersibility; furthermore, using air for aeration helps reduce the preparation cost of cobalt tetroxide materials.

[0055] In this application, the stirring rates in steps (1) and (2) can be set and adjusted by those skilled in the art according to actual needs, as long as the raw materials react fully and uniformly. In some embodiments, the stirring rate in step (1) can be greater than the stirring rate in step (2), that is, the stirring rate can be appropriately reduced during the aging stage, which is beneficial to reducing costs. In some specific embodiments, the stirring rate in step (1) can be 100~300 rpm, the stirring rate in step (2) can be 50~150 rpm, and the stirring rate in step (1) is greater than the stirring rate in step (2).

[0056] (3) The aged slurry is subjected to solid-liquid separation and the solid is dried.

[0057] In some embodiments of this application, the aged slurry can be filtered and washed, and the solid can be dried to obtain dried nano-basic cobalt carbonate.

[0058] (4) The dried solid is calcined to obtain calcined material.

[0059] In some embodiments, the calcination temperature can be 200~600℃, for example, 200℃, 300℃, 400℃, 500℃, 600℃, etc.; the calcination process includes at least two calcination steps at different temperatures, with the temperature of the first calcination step being lower than the temperature of the second calcination step. Stepwise calcination at a lower temperature can decompose and oxidize nano-basic cobalt carbonate, and can avoid excessive sintering and melting, meeting the requirements of green production with energy conservation and efficiency. After calcination, the surface energy of the nano-sized powder particles decreases, tending towards a more stable state, which is more conducive to suppressing particle aggregation. This results in better dispersibility of the nano-cobalt tetroxide prepared using the method proposed in this application, making it more suitable for application in lithium-ion battery cathode material coating.

[0060] In some embodiments, the calcination temperature can be 200~400°C. Using a lower temperature for calcination is beneficial for obtaining cobalt tetroxide materials with smaller particle size and larger specific surface area.

[0061] In some embodiments, the calcination time can be 1 to 10 hours, for example, 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, etc. This facilitates the complete decomposition and oxidation of basic cobalt carbonate, thereby obtaining cobalt tetroxide material with high purity.

[0062] In some embodiments, the calcination process includes two, three, or four calcination steps at different temperatures. Setting two or more calcination steps at different temperatures is more conducive to the complete decomposition and oxidation of basic cobalt carbonate, avoiding excessive sintering and melting.

[0063] In some embodiments, the temperature difference between two adjacent calcination steps is ≥50°C, and the appropriate temperature difference between different calcination steps is beneficial for forming cobalt tetroxide material through calcination.

[0064] In some embodiments, the processing time for each calcination step can be 0.5 to 4 hours. This promotes the gradual decomposition and oxidation of basic cobalt carbonate, converting more basic cobalt carbonate into cobalt tetroxide.

[0065] In some embodiments, a segmented calcination device can be used to calcine the dried solid, for example, a rotary kiln can be used for calcination.

[0066] (5) The calcined material is crushed to obtain cobalt tetroxide material.

[0067] In some embodiments, a general-purpose pulverizing device, such as a butterfly mill, can be used to pulverize the calcined material to obtain nano-cobalt tetroxide.

[0068] In the preparation method of this application, highly dispersed nano-basic cobalt carbonate is first prepared by wet precipitation using a designed reaction solution system, and the nano-basic cobalt carbonate is protected by the aeration effect of gas to prevent further agglomeration. After filtration, washing and drying, the nano-basic cobalt carbonate is decomposed and oxidized by providing a segmented high-temperature environment and air, and excessive sintering and melting are avoided. Finally, the calcined product is deagglomerated using a general-purpose pulverizing device to achieve synergistic control of extremely small particles, large specific surface area and good dispersibility.

[0069] Furthermore, the preparation method proposed in this application does not require the addition of dispersing agents such as surfactants. Highly dispersed nano-basic cobalt carbonate can be easily prepared by controlling the proportions of cobalt salt solution, alkaline solution, and carbonate precursor solution, which helps reduce environmental costs associated with wastewater treatment. To avoid excessive sintering and melting during the calcination of highly active nano-basic cobalt carbonate, this application employs a lower calcination temperature, meeting the requirements of energy conservation and green production. These effects increase the feasibility of industrialization and can promote the large-scale production of cobalt tetroxide with a large specific surface area.

[0070] The cobalt tetroxide material prepared by the above method has a high specific surface area, ≥56m². 2The cobalt tetroxide (Co3O4) has a cobalt content of 70%–73% by mass, exhibiting high purity. The particles possess a spherical microstructure with a D50 particle size ≤100 nm. The cobalt tetroxide material prepared using the above method has a large specific surface area, small particle size, and good dispersibility. Using it as a coating material for lithium-ion battery cathode materials is beneficial for improving the activity of the cathode material, thereby enhancing its electrical performance.

[0071] In another aspect of this application, a cathode material is proposed. In some embodiments, the cathode material is prepared by mixing the aforementioned cobalt tetroxide material or the cobalt tetroxide material prepared by the aforementioned method with a lithium-mixed cathode material, followed by sintering to form the cathode material. Thus, the cathode material exhibits high activity and electrical performance.

[0072] In some embodiments, lithium-mixed cathode materials refer to 8-series ternary cathode materials.

[0073] In another aspect of this application, a lithium-ion battery is proposed. In some embodiments, the lithium-ion battery includes the positive electrode material described above. Thus, the lithium-ion battery possesses all the features and advantages of the aforementioned positive electrode material, which will not be repeated here.

[0074] In some embodiments, a lithium-ion battery may include a positive electrode sheet, which may include a current collector and a positive electrode material layer located on at least one side of the current collector, the positive electrode material layer including the positive electrode material described above.

[0075] In some embodiments, the current collector can be aluminum foil; in addition to the positive electrode material, the positive electrode material layer may also include conductive agents, binders, etc. The specific types and contents of conductive agents and binders are not particularly limited in this application, and those skilled in the art can select and adjust them according to actual needs.

[0076] In some embodiments, the lithium-ion battery may further include a negative electrode, a separator, and an electrolyte. The composition of the negative electrode, the material of the separator, and the composition of the electrolyte are not specifically limited in this application.

[0077] The present application will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the present application in any way. Furthermore, in the following embodiments, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0078] Example 1: Solution preparation: Mix cobalt sulfate with pure water to prepare a cobalt sulfate solution with a cobalt ion concentration of 120 g / L; mix sodium hydroxide with pure water to prepare a sodium hydroxide solution with a concentration of 200 g / L; mix ammonium bicarbonate with pure water to prepare an ammonium bicarbonate solution with a concentration of 200 g / L.

[0079] Synthesis of nano-basic cobalt carbonate: Pure water was added to the reactor as the base solution. Under conditions of 30℃ and a stirrer speed of 300 rpm, the prepared cobalt sulfate solution, sodium hydroxide solution, and ammonium bicarbonate solution were simultaneously pumped into the reactor. The molar ratio of cobalt to bicarbonate was controlled at 1:7.0, the pH of the reaction was controlled at 10.5~11.0, the reaction time was 120 min, and air was introduced as a dispersion gas at a flow rate of 1 m³ / min. 3 / h.

[0080] Aging treatment: After the reaction for synthesizing nano-basic cobalt carbonate is completed, the temperature is raised to 60℃, and stirring is continued for 120 minutes at a stirrer speed of 150 rpm. During the aging treatment, air is continuously introduced as a dispersion gas at a flow rate of 1 m³ / min. 3 / h.

[0081] Washing and drying: The aged slurry is first filtered, then washed with 60℃ hot pure water, and dried at 80℃.

[0082] Calcination treatment: The dried material is divided into equally spaced temperature zones of 200℃ / 300℃ / 400℃, and the residence time in each temperature zone is controlled to be 2 hours.

[0083] Crushing process: The calcined material is crushed using general crushing equipment to obtain nano cobalt tetroxide finished product.

[0084] Figure 1 The scanning electron microscope image of the nano-basic cobalt carbonate obtained in Example 1 is shown. It can be seen that the nano-basic cobalt carbonate is slightly agglomerated and appears as uniformly dispersed dots. Most of the particles have a particle size of less than 100 nm, and some of the particles have a particle size of less than 60 nm. Figure 2 The XRD pattern of the nano-basic cobalt carbonate obtained in Example 1 is shown. Figure 2 It can be seen that the sample phase composition is mainly composed of basic cobalt carbonate, and its crystallinity is relatively weak. Figure 3 The scanning electron microscope image of the nano-cobalt tetroxide obtained in Example 1 is shown. It can be seen that the nano-cobalt tetroxide has no obvious agglomeration and is uniformly dispersed in spherical shape. Most of the particles are smaller than 100 nm in diameter, and some of the particles are smaller than 60 nm in diameter. Figure 4 The XRD pattern of the nano-cobalt tetroxide obtained in Example 1 is shown. Figure 4 It can be seen that the sample phase composition is mainly composed of cobalt tetroxide, and it has strong crystallinity.

[0085] Example 2: Solution preparation: Mix cobalt nitrate with pure water to prepare a cobalt nitrate solution with a cobalt ion concentration of 60 g / L; mix ammonia water with pure water to prepare an ammonia solution with a concentration of 5 g / L; mix potassium carbonate with pure water to prepare a potassium carbonate solution with a concentration of 80 g / L.

[0086] Synthesis of nano-basic cobalt carbonate: Pure water was added to the reactor as the base solution. Under conditions of 60℃ and a stirrer speed of 200 rpm, the prepared cobalt nitrate solution, ammonia solution, and potassium carbonate solution were simultaneously pumped into the reactor. The molar ratio of cobalt to carbonate was controlled at 1:5.0, the pH of the reaction was controlled at 9.0~9.5, the reaction time was 90 min, and air was introduced as a dispersion gas at a flow rate of 2 m³ / min. 3 / h.

[0087] Aging treatment: After the reaction for synthesizing nano-basic cobalt carbonate is completed, the temperature is raised to 80℃, and stirring is continued for 90 minutes at a stirrer speed of 100 rpm. During the aging treatment, air is continuously introduced as a dispersion gas at a flow rate of 2 m³ / min. 3 / h.

[0088] Washing and drying: The aged slurry is first filtered, then washed with 60℃ hot pure water, and dried at 80℃.

[0089] Calcination treatment: The dried material is divided into equally spaced temperature zones of 200℃ / 300℃ / 400℃, and the residence time in each temperature zone is controlled to be 2 hours.

[0090] Crushing process: The calcined material is crushed using general crushing equipment to obtain nano cobalt tetroxide finished product.

[0091] Example 3: Solution preparation: Mix cobalt chloride with pure water to prepare a cobalt chloride solution with a cobalt ion concentration of 150 g / L; mix potassium hydroxide with pure water to prepare a potassium hydroxide solution with a concentration of 400 g / L; mix ammonium carbonate with pure water to prepare an ammonium carbonate solution with a concentration of 100 g / L.

[0092] Synthesis of nano-basic cobalt carbonate: Pure water was added to the reactor as the base solution. Under conditions of 80℃ and a stirrer speed of 100 rpm, prepared cobalt chloride solution, potassium hydroxide solution, and ammonium carbonate solution were simultaneously pumped into the reactor. The molar ratio of cobalt to carbonate was controlled at 1:1.0, the reaction pH was controlled at 8.5~9.0, the reaction time was 60 min, and air was introduced as a dispersion gas at a flow rate of 0.3 m³ / min. 3 / h.

[0093] Aging treatment: After the reaction for synthesizing nano-basic cobalt carbonate is completed, the temperature is maintained at 80℃, and stirring continues for 60 minutes at a stirrer speed of 50 rpm. During the aging treatment, air is continuously introduced as a dispersion gas at a flow rate of 0.3 m³ / min. 3 / h.

[0094] Washing and drying: The aged slurry is first filtered, then washed with 60℃ hot pure water, and dried at 80℃.

[0095] Calcination treatment: The dried material is divided into equally spaced temperature zones of 200℃ / 400℃, and the residence time in each temperature zone is controlled to be 4 hours.

[0096] Crushing process: The calcined material is crushed using general crushing equipment to obtain nano cobalt tetroxide finished product.

[0097] Example 4: Example 4 prepared cobalt tetroxide using the same method as Example 1, except that no air was introduced during the synthesis of nano-basic cobalt carbonate and the aging process in Example 4.

[0098] Example 5: Cobalt tetroxide was prepared using the same method as in Example 1, except that the amount of sodium hydroxide solution with a concentration of 200 g / L was controlled and the pH was controlled to be 8.0-8.5.

[0099] Example 6: Cobalt tetroxide was prepared using the same method as in Example 1, except that the calcination treatment was performed: the dried material was placed in non-equally spaced temperature zones of 300℃ / 400℃ / 500℃ / 600℃, with residence times of 1h / 1h / 2h / 2h respectively.

[0100] Comparative Example 1: Solution preparation: Mix cobalt sulfate with pure water to prepare a cobalt sulfate solution with a cobalt ion concentration of 120 g / L; mix ammonium bicarbonate with pure water to prepare an ammonium bicarbonate solution with a concentration of 200 g / L.

[0101] Synthesis of nano-cobalt carbonate: Pure water is added to the reactor as the base liquid. Under the conditions of 30℃ and 300rpm of stirrer, the prepared cobalt sulfate solution and ammonium bicarbonate solution are simultaneously pumped into the reactor. The molar ratio of cobalt to bicarbonate is controlled at 1:7.0, the reaction pH is 7.0-7.3, and the reaction time is 120min. No air is introduced during this process.

[0102] Aging treatment: After the reaction to synthesize nano-cobalt carbonate is completed, the temperature is raised to 60℃ and stirring is continued for 120 minutes at a stirring speed of 150 rpm. No air is introduced during this process.

[0103] Washing and drying: The aged slurry is first filtered, then washed with 60℃ hot pure water, and dried at 80℃.

[0104] Calcination treatment: The dried material is divided into equally spaced temperature zones of 200℃ / 300℃ / 400℃, and the residence time in each temperature zone is controlled to be 2 hours.

[0105] Crushing process: The calcined material is crushed using general crushing equipment to obtain nano cobalt tetroxide finished product.

[0106] Figure 5 The scanning electron microscope image of the nano-cobalt carbonate obtained in Comparative Example 1 is shown. It can be seen that the nano-cobalt carbonate has no obvious agglomeration and is unevenly dispersed in spindle or spherical shapes. A large number of particles have a diameter greater than 100 nm, or even greater than 200 nm. Figure 6 The scanning electron microscope image of the nano-cobalt tetroxide obtained in Comparative Example 1 is shown. It can be seen that the nano-cobalt tetroxide does not have obvious agglomeration and is in the form of unevenly dispersed columnar or spherical shapes, with a large number of particles having a diameter greater than 100 nm.

[0107] Using the cobalt tetroxide products prepared in Examples 1-6 and Comparative Example 1 as coating materials, lithium-ion battery cathode materials with coating layers were prepared, and batteries were assembled. The specific steps are as follows: Preparation of lithium-ion battery cathode material with coating layer: Take the nano cobalt tetroxide prepared in Examples 1-6 and Comparative Example 1, and mix them at a mass ratio of 2% (the mass of cobalt tetroxide is 2% of the mass of the mixed lithium cathode material) with the mixed lithium 8-series ternary cathode material that has been calcined once at high speed for 40 min. Then, the resulting mixture is calcined again at 650°C for 8 h. The calcined material obtained from the second calcination is cooled, crushed and sieved in sequence to obtain the cathode material.

[0108] The positive electrode materials prepared by nano-cobalt tetroxide in Examples 1-6 and the control group were respectively mixed with conductive agent and binder PVDF in a preset mass ratio to form a slurry, which was then coated on aluminum foil to form a positive electrode sheet. The negative electrode sheet was a lithium metal sheet, and the electrolyte was 1 mol / L LiPF6 / EC:DMC (the volume ratio of EC to DMC was 1:1). The battery case, positive and negative electrode sheets, separator, spring sheet and gasket were assembled into a button battery in a vacuum glove box.

[0109] The D50 particle size of the cobalt tetroxide materials in Examples 1-6 and Comparative Example 1 was measured using a laser particle size analyzer, and the test results are recorded in Table 2. The BET specific surface area of ​​the cobalt tetroxide materials in Examples 1-6 and Comparative Example 1 was also measured, and the test results are recorded in Table 2.

[0110] Flowability (AD / TD) test method: TD test adopts GBT 5162-2021 "Determination of tap density of metal powder"; AD adopts GBT 1479.2-2011 "Determination of loose density of metal powder - Part 2: Scott volumetric method".

[0111] Electrochemical performance tests were conducted on the coin cells prepared above. The test temperature was 25℃, the test voltage range was 3.0~4.35V, 1C=180mAh / g, the capacity test was the capacity after the first charge and discharge at 0.1C / 0.1C, and the capacity retention rate was the capacity retention rate after 100 cycles at 0.5C. The test data are recorded in Table 3.

[0112] Table 1. Parameters for the preparation method of cobalt tetroxide material

[0113] In Table 1, "-" indicates that there is none.

[0114] Table 2 Parameters of Cobalt Tetraoxide

[0115] Table 3. Parameters of Cobalt Tetraoxide and Test Results of Corresponding Ternary Cathode Materials

[0116] As shown in Tables 1, 2, and 3, compared with Comparative Example 1, the cobalt tetroxide in Examples 1-6 has a smaller D50 particle size and a larger specific surface area, which can improve the capacity and cycle stability of the cathode material when used for coating. Compared with Comparative Example 1, the cobalt tetroxide material in Examples 1-6 has a smaller a / b value, resulting in better coating effect when used to coat the cathode material.

[0117] In the description of this specification, references to terms such as "some embodiments" and "some specific embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0118] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A cobalt tetroxide material, characterized in that, The specific surface area of ​​the cobalt tetroxide material is ≥56m². 2 / g.

2. The cobalt tetroxide material according to claim 1, characterized in that, The cobalt tetroxide material satisfies at least one of the following conditions: The cobalt tetroxide material particles are spherical; The D50 particle size of the cobalt tetroxide material is ≤100nm; The cobalt tetroxide material contains 70% to 73% cobalt by mass. The specific surface area of ​​the cobalt tetroxide material is 56~90m². 2 / g; The D50 particle size of the cobalt tetroxide material is a nanometer, the specific surface area of ​​the cobalt tetroxide material is b square meters per gram, and a / b ≤ 3.

5.

3. A method for preparing cobalt tetroxide material, characterized in that, include: (1) Add cobalt salt solution, alkaline solution and carbonate precursor solution to the reaction vessel, control the pH of the reaction system to 7.5~12, and react at 30~80℃ to generate a slurry containing basic cobalt carbonate; (2) Stop feeding materials and allow the material to age; (3) The aged slurry is subjected to solid-liquid separation, and the solid is dried. (4) The dried solid is calcined to obtain calcined material, wherein the calcination temperature is 200~600℃, and the calcination includes at least two calcination steps at different temperatures, wherein the temperature of the first calcination step is lower than the temperature of the second calcination step. (5) The calcined material is crushed to obtain cobalt tetroxide material.

4. The method according to claim 3, characterized in that, The carbonate precursor includes at least one of carbonate and bicarbonate; And / or, the molar ratio of cobalt to carbonate precursor in the reaction system is 1:(0.5~20).

5. The method according to claim 4, characterized in that, The carbonate precursor is a carbonate, and the molar ratio of cobalt to carbonate in the reaction system is 1:(0.5~10). Alternatively, the carbonate precursor is a bicarbonate, and the molar ratio of cobalt to bicarbonate in the reaction system is 1:(0.5~20).

6. The method according to claim 3, characterized in that, At least one of the following conditions must be met: The solute in the cobalt salt solution includes at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate; The concentration of cobalt ions in the cobalt salt solution is 60~150 g / L; The solvent in the cobalt salt solution includes at least one of water, ethanol, and acetone; The alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water; The concentration of the alkaline solution is 1~440 g / L; The solvent in the alkaline solution includes at least one of water, ethanol, and acetone; The solute in the carbonate precursor solution includes at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate. The concentration of the carbonate precursor solution is 1~220 g / L; The solvent in the carbonate precursor solution includes at least one of water, ethanol, and acetone; In step (1), the pH value of the reaction system is controlled to be 8~12; In step (4), the calcination temperature is 200~400℃.

7. The method according to any one of claims 3 to 6, characterized in that, At least one of the following conditions must be met: In step (1), a gas is introduced during the reaction; In step (1), the reaction time is 60~180 minutes; In step (1), the reaction is carried out under stirring conditions; In step (2), the aging temperature is 30~80℃; In step (2), the aging time is 60-180 minutes; In step (2), aging is carried out under stirring conditions; In step (2), gas is introduced during aging; The calcination treatment time is 1~10h; The calcination process includes two, three, or four calcination steps at different temperatures; The temperature difference between two adjacent calcination steps is ≥50℃; The processing time for each calcination step is 0.5 to 4 hours.

8. The method according to claim 7, characterized in that, At least one of the following conditions must be met: In step (1), the gas flow rate is 0.3~3m³. 3 / h; In step (1), the gas is air; In step (2), the gas flow rate is 0.3~3m³. 3 / h; In step (2), the gas is air.

9. A positive electrode material, characterized in that, The cathode material is prepared by the following method: the cobalt tetroxide material according to claim 1 or 2 or the cobalt tetroxide material prepared by any one of claims 3 to 8 is mixed with the lithium mixed cathode material and then fired to form the cathode material.

10. A lithium-ion battery, characterized in that, Includes the cathode material as described in claim 9.

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