WO2024017039A1

WO2024017039A1 - Cobaltosic oxide material and preparation method, positive electrode, and lithium battery

Info

Publication number: WO2024017039A1
Application number: PCT/CN2023/105302
Authority: WO
Inventors: 张荣洲; 张克军; 刘人生; 周恩娄
Original assignee: 衢州华友钴新材料有限公司; 浙江华友钴业股份有限公司
Priority date: 2022-07-22
Filing date: 2023-06-30
Publication date: 2024-01-25
Also published as: CN115028208B; CN115028208A

Abstract

A cobaltosic oxide material and a preparation method, a positive electrode, and a lithium battery. The preparation method for the cobaltosic oxide material comprises: synthesizing a metal mixed salt solution and an alkali solution in a reaction kettle, and controlling the pH of a reaction system to be 8-9 and the air flow to be 12-14 m³/h during synthesis, such that the precipitate obtained by synthesis is (Co_aAl_bMg_cNi_dMn_e)₃O₄, wherein 0.9246≤a≤0.9775, 0.0148≤b≤0.037, 0.0042≤c≤0.0208, 0.0017≤d≤0.0085, and 0.0018≤e≤0.0091, and the precipitate grows in a dotted particle accumulation mode. According to the method, particles having an ultrafine particle size, high density and good sphericity are obtained, and the volumetric energy density of a lithium cobalt oxide battery can be improved.

Description

Cobalt tetroxide materials and preparation methods, positive electrodes and lithium batteries

Cross-references to related applications

This application claims priority to the Chinese patent application with application number 202210870482.0 and titled "Cobalt tetroxide materials and preparation methods, cathodes and lithium batteries" submitted to the State Intellectual Property Office of China on July 22, 2022, the entire content of which is incorporated by reference. in this application.

Technical field

This application relates to the field of batteries, specifically to cobalt tetroxide materials and preparation methods, positive electrodes and lithium batteries.

Background technique

As one of the precursors of cathode materials for lithium cobalt oxide batteries, tricobalt tetraoxide has attracted much attention. With the update and iteration of 3C electronic products, lithium-ion batteries are developing in the direction of large capacity and fast charging. Researchers usually use two methods to increase the energy density of lithium cobalt oxide. The first is doping with other elements such as: Mg, Al, Zr, Ti, Ni, Mn, etc. to increase the charging cut-off voltage to increase the energy density of lithium-ion batteries. The second is the size of particles. Blending increases compaction density to increase energy density. Among them, the particle sizes of large and small particles develop towards both ends. The size of large particles develops to 16-18 μm or even more than 20 μm; while the current mainstream size of small particles is 3-5 μm. In the future, the market will demand more and more small particles. Small. Therefore, the technology of cobalt tetroxide with a small particle size of about 2 μm has a long way to go.

The preparation methods of small particle size cobalt tetroxide can be roughly divided into two categories: dry method and wet method. The most common technical method for the dry method is the spray roasting method. This method directly forms the cobalt salt into a mist through physical methods and prepares it through high-temperature roasting. It forms cobalt tetroxide with a minimum particle size of about 2 μm. The wet synthesis technology route can be divided into cobalt carbonate and cobalt hydroxyl. The cobalt carbonate route uses cobalt salt and ammonium carbonate or ammonium bicarbonate solution through a wet precipitation reaction to control the temperature, rotation speed, pH and other parameters of the reaction process to synthesize cobalt carbonate with a target particle size. After washing and impurity removal, and high-temperature thermal decomposition, the cobalt carbonate is finally obtained. Cobalt tetraoxide. The hydroxycobalt route uses a reaction between cobalt salt and sodium hydroxide solution. An oxidant is added during the process. Air is generally used as the oxidant. The temperature, pH, rotation speed, flow rate and other condition parameters are controlled to synthesize hydroxycobalt with the target particle size. It is then filtered, washed, and dried. Calcination yields cobalt tetraoxide.

However, the above technical routes all have the problem of low particle density when the particle size is small.

Contents of the invention

The purpose of the embodiments of the present application is to provide a cobalt tetroxide material and preparation method, a positive electrode and a lithium battery.

In the first aspect, this application provides a method for preparing cobalt tetroxide material, which may include:

The metal mixed salt solution and the alkali solution are synthesized in a reaction kettle. During the synthesis process, the pH of the reaction system is controlled to 8-9, and the air flow rate is 12-14m ³ /h, so that the synthesized precipitate is (Co _a Al _b Mg _c Ni _d Mn _e ) ₃ O ₄ , where 0.9246≤a≤0.9775, 0.0148≤b≤0.037, 0.0042≤c≤0.0208, 0.0017≤d≤0.0085, 0.0018≤e≤0.0091; and the precipitates are accumulated in point-like particles way to grow.

The main phase of the quaternary homogeneous doped cobalt tetroxide material prepared by the method of the present application is Co ₃ O ₄ and its morphology is spherical. During the preparation process, the precipitates grow in a point-like particle accumulation manner, and the particles have sufficient time and space for growth and self-healing. Using the method of this application, particles with ultra-fine particle size (less than 2 μm), high density, and good sphericity are obtained; therefore, using this material as a precursor for lithium battery cathode materials can increase the volumetric energy density of lithium cobalt oxide batteries.

In some embodiments of the present application, during the synthesis process, the pH of the reaction system is controlled to 8-9, and the air flow rate of 12-14m ³ /h may include:

If the pH of the reaction system is between 8-8.5, adjust the air flow rate to 13-14m ³ /h. If the pH of the reaction system is between 8.5-9, adjust the air flow rate to 12-13m ³ /h.

In some embodiments of the present application, during the synthesis process, the pH of the reaction system can be controlled to be 8.1-8.9, and the air flow rate can be ^12.1-13.9m3 /h. If the pH of the reaction system is between 8.1-8.4, then Adjust the air flow rate to 13.1-13.9m ³ /h. If the pH of the reaction system is between 8.5-9, adjust the air flow rate to 12-12.9m ³ /h.

In some embodiments of the present application, synthesizing the metal mixed salt solution and the alkali solution in the reactor may include:

Add the metal mixed salt solution and the alkali solution into the reaction kettle at the same time. When the particle size D50 of the synthesized precipitate reaches the target particle size, stop adding the metal mixed salt solution and continue adding the alkali solution, where the target particle size Less than or equal to 2μm.

In some embodiments of the present application, when the particle size D50 of the synthetically generated precipitate can be 1.45 μm, 1.5 μm, 1.67 μm or 1.89 μm, the addition of the metal mixed salt solution is stopped and the addition of all the precipitates is continued. The alkaline solution.

In some embodiments of the present application, continuing to add alkali solution may include:

When the pH in the reaction system increases to 10-11, stop adding the alkali solution.

In some embodiments of the present application, adding the metal mixed salt solution and the alkali solution to the reaction kettle simultaneously may include:

The flow rate of the added metal mixed salt solution is controlled to be 210L/h to 290L/h, and the pH of the reaction system is adjusted to 8-9 by adjusting the flow rate of the added alkali solution.

In some embodiments of the present application, before the step of simultaneously adding the metal mixed salt solution and the alkali solution into the reaction kettle, a bottom liquid is also added into the reaction kettle;

The pH of the bottom solution is 8-9.

In some embodiments of the present application, an appropriate amount of pure water is added to the reaction kettle as the bottom liquid.

In some embodiments of the present application, before adding the metal mixed salt solution and the alkali solution to the reaction kettle at the same time, the temperature in the reaction kettle is adjusted to 65-80°C; the rotation speed is 330 rpm to 460 rpm.

In some embodiments of the present application, before the step of simultaneously adding the metal mixed salt solution and the alkali solution into the reaction kettle, the temperature in the reaction kettle is adjusted to 68-78°C; the rotation speed is 350 rpm. ~450rpm.

In some embodiments of the present application, preparing the metal mixed salt solution may include:

Mix the cobalt salt solution, the salt solution of the doping element, and the complexing agent evenly.

In some embodiments of the present application, the complexing agent may be selected from at least one of glutamic acid, glycine or ammonia.

In some embodiments of the present application, in the metal mixed salt solution, the mass ratios of the four metals Al/Co, Mg/Co, Ni/Co, and Mn/Co range from 0.55% to 1.32%, 0.15% to 0.65%, and 0.18 %～0.59%, 0.21%～0.68%.

In some embodiments of the present application, the alkali solution is sodium hydroxide solution.

In some embodiments of the present application, the concentration of the alkali solution is between 221.5g/L and 398.4g/L.

In a second aspect, the present application provides a cobalt tetroxide material, which is prepared by the aforementioned preparation method of cobalt tetroxide material.

In a third aspect, the present application provides a cathode. The precursor material of the cathode includes the aforementioned cobalt tetroxide material.

In a fourth aspect, the present application provides a lithium battery. The cathode material precursor of the lithium battery includes the aforementioned cobalt tetroxide material.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figures 1a and 1b are SEM images of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1 at different magnifications;

Figure 2 is the XRD pattern of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1;

Figures 3a, 3b, 3c, and 3d are respectively cross-sectional distribution diagrams of Al, Mg, Ni, and Mn in the particles of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1;

Figure 4 is an SEM image of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 2;

Figure 5 is an XRD pattern of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 2;

Figure 6 is an SEM image of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 3;

Figure 7 is an XRD pattern of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 3;

Figure 8 is an SEM image of the quaternary homogeneous doped cobalt tetroxide material prepared in Comparative Example 1;

Figure 9 is the XRD pattern of the quaternary homogeneous doped cobalt tetroxide material prepared in Comparative Example 1.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of them. Embodiments.

Accordingly, the following detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application but is merely representative of selected embodiments of the present application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

In order to ensure the volumetric energy density of lithium cobalt oxide batteries, there are certain requirements for the density of cobalt tetroxide.

However, the density of tricobalt tetroxide obtained by current conventional operations in this field is low and cannot guarantee the volumetric energy density of lithium cobalt oxide batteries.

After research, the inventor found that the cobalt carbonate technical route currently has the following problems: 1. When the particle size is <3 μm, the particle density is low and the TD is small. Especially after doping, the particle density is greatly reduced, and the higher the doping amount, the greater the TD decrease. Large; 2. The doping elements are uneven. Especially after characterization by the high-end detection method - electron microprobe (EPMA), there is obvious local segregation of elements inside the particles. For example, the Al element has serious uneven distribution. 3. The smaller the particle size, the shorter the growth time, the smaller the particle repair morphology space, poor morphology, and poor sphericity; 4. Because the pH of the cobalt carbonate reaction is relatively low <8.5, the doping elements cannot be completely precipitated. , such as Ni, Mg, Co, etc.

The hydroxycobalt technical route currently has the following problems: 1. When the particle size is <3 μm, the particle density is higher than that of the cobalt carbonate technical route, but the density is still not high enough. The reason is that the hydroxycobalt forms flaky or massive particles, and the particle size Larger, the growth time is short, and there are many and large gaps after accumulation; 2. The smaller the particles, the shorter the growth time, the smaller the particle repair morphology space, poor morphology, and poor sphericity; 3. Containing the complexing agent EDTA Wastewater treatment is difficult because EDTA has strong complexing ability for many metal ions, which will increase the residual amount of metal ions in the wastewater.

The inventor found that when the particle size is controlled within 2 μm, it is necessary to prepare spherical or spherical-like particles composed of point-shaped particles to ensure the density of cobalt tetroxide.

According to the potential-pH phase diagram of Co, it can be seen that the higher the pH, the easier it is to be oxidized to +3-valent CoOOH. On the contrary, oxidation under low pH conditions is easy to obtain Co ₃ O ₄ containing 2 +3-valent Co and 1 +2-valent Co. . The inventor creatively discovered that by using low pH 8-9 in the synthesis, controlling the air flow at the same time, and controlling the molar concentration of oxidized Co ³⁺ and Co ²⁺ in the reaction kettle to close to 2 to 1, it can be directly used in the wet synthesis stage. The Co ₃ O ₄ component is obtained directly. Moreover, the morphology of the cobalt tetraoxide particles obtained in the initial stage is point-shaped and the particle size is small. The precipitate grows according to the accumulation of point-like particles to obtain dense spherical particles. If the air flow is too large and the oxidation is excessive, most of the Co ²⁺ will be oxidized into Co ³⁺ , and the precipitates will mainly be flake or block CoOOH particles. Since the primary particle size of CoOOH is larger, it will take longer to reach the target particle size. Short, and the accumulation of flake or block particles is not as dense as that of point particles, so controlling the degree of oxidation has a greater impact on the density of particles.

In order to achieve better electrochemical performance, it is necessary to ensure that the doping elements Al, Mg, Ni, and Mn are evenly distributed from the inside to the outside. The inventor further studied and found that by adjusting the reaction conditions to control the oxidation state of the doping elements, it can be based on eutectic solid solution The principle achieves uniform distribution of doping elements.

Al ³⁺ , Mn ³⁺ , and Co ³⁺ have close ion radii and have the same chemical valence state; similarly, Mg ²⁺ , Ni ²⁺ , and Co ²⁺ have close ion radii and have the same chemical valence state, so it is easier to form co-alerts during the precipitation process. Crystalline solid solution to achieve atomic level homogeneous co-doping.

The Mn element exists in multiple valence states such as +2, +3, +4, etc. The precipitated products after oxidation include Mn ₃ O ₄ , MnOOH, MnO ₂ , etc. which are relatively complex. Among them, Mn in MnO ₂ has a valence of +4, and the MnO ₂ substance precipitates The rate is much higher than that of metal elements, and it is easy to precipitate and segregate alone. Therefore, in order to ensure the uniform distribution of Mn, it is necessary to suppress the generation of MnO ₂ . This application controls the valence state of the Mn element after oxidation by controlling the reaction pH to 8-9 (according to the potential-pH diagram of Mn, it is not easy to obtain MnO ₂ at a pH of 8-9, and the higher the pH, the easier Mn is to oxidize), so that Mn can be converted into MnOOH Or precipitate in the form of Mn ₃ O ₄ , which can form a eutectic solid solution with Co to achieve homogeneous doping.

The embodiment of the present application provides a method for preparing cobalt tetroxide material. This cobalt tetroxide material is a quaternary homogeneous doped cobalt tetroxide material, where homogeneous means forming a solid solution.

Further, the above preparation method includes the following steps:

Step S1: Prepare a metal mixed salt solution.

Further, in some embodiments of the present application, the step of preparing the metal mixed salt solution includes:

Mix the cobalt salt solution (such as cobalt sulfate solution, cobalt chloride solution, cobalt nitrate solution, etc.), doped element salt solution (such as doped element sulfate, hydrochloride, nitrate, etc.) and complexing agent evenly .

Further, in some embodiments of the present application, the complexing agent is selected from at least one of glutamic acid, glycine or ammonia water.

A complexing agent commonly used in this field is EDTA. However, the complexing agent EDTA has a strong ability to complex many metal ions, causing metal ions to exceed the standard during wastewater treatment.

This application plan does not use EDTA as the complexing agent. Instead, choose other complexing agents with weak complexing ability, such as glutamic acid, glycine, and ammonia. This type of complexing agent can effectively reduce the concentration of residual metal ions in wastewater to achieve Emission Standards.

Further, in some embodiments of the present application, in the above-mentioned metal mixed salt solution, the mass ratios of the four metals Al/Co, Mg/Co, Ni/Co, and Mn/Co range from 0.55% to 1.32%, and from 0.15% to 0.15%. 0.65%, 0.18%～0.59%, 0.21%～0.68%.

For example, in the metal mixed salt solution, the mass ratios of the four metals Al/Co, Mg/Co, Ni/Co, and Mn/Co range from 0.55%, 0.15%, 0.18%, and 0.21%; or in the metal mixed salt solution , the mass ratio ranges of the four metals Al/Co, Mg/Co, Ni/Co, and Mn/Co are 0.84%, 0.26%, 0.31%, and 0.46%; or in metal mixed salt solutions, Al/Co, Mg/Co, The mass ratio ranges of the four metals Ni/Co and Mn/Co are 1.32%, 0.65%, 0.59%, and 0.68%.

Step S2: Prepare an alkali solution.

Further, in some embodiments of the present application, the alkali solution is sodium hydroxide solution.

Furthermore, in some embodiments of the present application, the concentration of the alkali solution is between 221.5g/L and 398.4g/L.

Further optionally, in some embodiments of the present application, the concentration of the alkali solution is between 225g/L and 395g/L. Further optionally, in some embodiments of the present application, the concentration of the alkali solution is between 230g/L and 390g/L. For example, the concentration of the alkali solution is 230g/L, 280g/L, 300g/L, 330g/L or 350g/L.

Step S3, synthesis.

During the synthesis process, the pH of the reaction system is controlled to 8-9 and the air flow rate is 12-14m ³ /h, so that the Co ₃ O ₄ component can be obtained directly in the wet synthesis stage. Moreover, the morphology of the cobalt tetraoxide particles obtained in the initial stage is point-shaped and the particle size is small. The precipitate grows according to the accumulation of point-like particles to obtain dense spherical particles.

Further, in some embodiments of the present application, during the synthesis process, the pH of the reaction system is controlled to be 8-9, and the air flow rate is 12-14m ³ /h, including:

By control: if the pH of the reaction system is between 8-8.5, adjust the air flow to 13-14m ³ /h; if the pH of the reaction system is between 8.5-9, adjust the air flow to 12-13m ³ /h , can control the final precipitate form, so that the uniformity of doping of all elements can reach the atomic level, achieving true multi-element homogeneous doping. Moreover, the morphology of Co ₃ O ₄ generated in the initial stage is point-like, and the precipitates grow in a point-like particle accumulation manner, which has the advantages of slow growth, dense particles, and good sphericity.

Furthermore, if the air flow rate is too large and is not within the above control range, excessive oxidation will occur, and most of the Co ²⁺ will be oxidized into Co ³⁺ , and the precipitates will mainly be flake or block-shaped CoOOH particles. Due to the The primary particle size is larger, and the time to reach the target particle size is shorter, and the accumulation of flake or block particles is not as dense as that of point particles, so the control of oxidation degree has a great impact on the particle density.

Further optionally, in some embodiments of the present application, during the synthesis process, the pH of the reaction system is controlled to be 8.1-8.9, and the air flow rate is 12.1-13.9m ³ /h, including:

If the pH of the reaction system is between 8.1-8.4, adjust the air flow rate to 13.1-13.9m ³ /h. If the pH of the reaction system is between 8.5-9, adjust the air flow rate to 12-12.9m ³ /h.

For example, in some embodiments of the present application, during the synthesis process, the pH of the reaction system is controlled to be 8.1-8.9, and the air flow rate is 12.1-13.9m ³ /h, including:

If the pH of the reaction system is between 8.1-8.4, adjust the air flow rate to 13.1m ³ /h, ^{13.2m 3} /h, 13.3m 3 /h, 13.4m ³ /h, 13.5m ³ ^/ h, 13.6m ³ /h, 13.7m ^{3 /} h, 13.8m ³ /h or 13.9m ³ /h; if the pH of the reaction system is between 8.5-9, adjust the air flow to 12.1m ^{3 /} h, 12.2m ³ /h, 12.3m ³ /h, 12.4m ³ /h, 12.5m ³ /h, 12.6m ³ /h, 12.7m ³ /h, 12.8m ³ /h or 12.9m ³ /h.

Further, before the step of adding the metal mixed salt solution and the alkali solution into the reaction kettle at the same time, the bottom liquid is also added into the reaction kettle.

Further optionally, the pH of the bottom solution is 8-9.

Further, before adding the metal mixed salt solution and the alkali solution to the reaction kettle at the same time, the temperature in the reaction kettle is adjusted to 65-80°C; the rotation speed is 330rpm to 460rpm. Further optionally, before adding the metal mixed salt solution and the alkali solution to the reaction kettle at the same time, adjust the temperature in the reaction kettle to 68-78°C; and adjust the rotation speed to 350rpm to 450rpm. Exemplarily, before the step of adding the metal mixed salt solution and the alkali solution to the reaction kettle at the same time, adjust the temperature in the reaction kettle to 68°C, 70°C, 72°C, 75°C or 78°C; the rotation speed is 350rpm, 380rpm, 400rpm, 420rpm or 450rpm.

For example, in some embodiments of the present application, an appropriate amount of pure water is added to the reaction kettle as the bottom liquid, the temperature is 77°C-80°C, the rotation speed is 460rpm, and sodium hydroxide is used to adjust the pH of the bottom liquid to between 8 and 9.

Further, the metal mixed salt solution and the alkali solution are added into the reaction kettle at the same time, including:

Further optionally, the metal mixed salt solution and the alkali solution are added to the reaction kettle at the same time, including:

The flow rate of the added metal mixed salt solution is controlled to be 220L/h to 280L/h, and the pH of the reaction system is adjusted to 8-9 by adjusting the flow rate of the added alkali solution.

Exemplarily, the metal mixed salt solution and the alkali solution are added to the reaction kettle at the same time, including:

Control the flow rate of the added metal mixed salt solution to 220L/h, 250L/h, 260L/h or 270L/h, and adjust the flow rate of the added alkali solution to make the pH of the reaction system 8-9.

Further, synthesizing the metal mixed salt solution and the alkali solution in the reactor includes:

Add the metal mixed salt solution and the alkali solution into the reaction kettle at the same time. When the particle size D50 of the synthesized precipitate reaches the target particle size, stop adding the metal mixed salt solution and continue adding the alkali solution. Among them, the target particle size diameter less than or equal to 2 μm.

Exemplarily, the synthesis of a metal mixed salt solution and an alkali solution in a reactor includes:

Add the metal mixed salt solution and the alkali solution into the reaction kettle at the same time. When the particle size D50 of the synthesized precipitate is 1.45 μm, 1.5 μm, 1.67 μm or 1.89 μm, stop adding the metal mixed salt solution and continue adding the metal mixed salt solution. Add alkaline solution.

Further, continuing to add alkaline solution includes:

By increasing the pH in the later stages of synthesis, metal ions can be precipitated more fully, which can effectively reduce the residual amount of metal ions in wastewater. The inventor's research found that when the pH in the reaction system is increased to 10-11, metal ions can be precipitated more fully, and the residual amount of metal ions in waste water can be effectively reduced.

This shows that the method of the present application can be used to directly produce cobalt tetroxide by wet method, and cobalt tetroxide can be obtained without high-temperature calcination.

Some embodiments of the present application provide a tricobalt tetroxide material, which is prepared by using the preparation method of the tricobalt tetroxide material provided in any of the aforementioned embodiments.

Some embodiments of the present application provide a lithium battery. The cathode material precursor of the lithium battery includes the cobalt tetroxide material provided in the previous embodiments.

The features and performance of the present application will be further described in detail below in conjunction with the examples:

Example 1

A quaternary homogeneous doped cobalt tetroxide material is provided, which is prepared according to the following steps:

1. Prepare a cobalt sulfate solution with a cobalt ion concentration of 80.2g/L, add sulfates of Al, Mg, Ni, Mn, and 1.5g/L glycine, stir thoroughly to prepare a metal mixed salt solution, in which Al The mass ratio ranges of the four metals /Co, Mg/Co, Ni/Co, and Mn/Co are 0.55%, 0.15%, 0.18%, and 0.21%;

2. Prepare a sodium hydroxide solution with an alkali concentration of 221.5g/L;

3. Synthesis: Add an appropriate amount of pure water to the reaction kettle to make the bottom liquid, the temperature is 65-68°C, the rotation speed is 330 rpm, use sodium hydroxide to adjust the pH of the bottom liquid to between 8-9, and introduce air at 12-14m ³ /h. Pump the prepared metal mixed salt solution and sodium hydroxide solution into the reaction kettle at the same time. During the process, the metal mixed salt flow rate is maintained at 290L/h, and the pH of the reaction system is controlled between 8-9 by adjusting the sodium hydroxide flow rate. During the synthesis process, monitor and fine-tune the pH and air flow of the slurry in the reaction kettle to control the degree of oxidation in the kettle. If the pH is between 8-8.5, fine-tune the air flow to 13-14m ³ /h. If the pH is between 8.5-9 , then fine-tune the air flow to 12-13m ³ /h. When the particle size reaches 1.45 μm, stop adding the metal mixed salt solution, continue adding sodium hydroxide to increase the pH to 10-11, and stir for 30-60 minutes.

4. The synthesized material is filtered, washed with a filter press, and dried at 250°C to obtain an ultra-fine particle size quaternary homogeneous doped cobalt tetroxide product. The metal ion content of Co, Al, Mg, Ni, and Mn in the wastewater is less than 0.001g/L, which meets the emission standards.

Example 2

1. Prepare a cobalt chloride solution with a cobalt ion concentration of 99.5g/L, add chloride salts of Al, Mg, Ni, Mn, and 2.5g/L glutamic acid to it, and stir thoroughly to prepare a metal mixed salt. Solution, in which the mass ratios of the four metals Al/Co, Mg/Co, Ni/Co, and Mn/Co range from 0.84%, 0.26%, 0.31%, and 0.46%;

2. Prepare a sodium hydroxide solution with an alkali concentration of 303.9g/L;

3. Synthesis: Add an appropriate amount of pure water to the reaction kettle to make the bottom liquid, with a temperature of 70-73°C and a rotation speed of 390 rpm. Use sodium hydroxide to adjust the pH of the bottom liquid to between 8-9 and introduce air at 12-14 m ³ /h. Pump the prepared metal mixed salt solution and sodium hydroxide solution into the reaction kettle at the same time. During the process, the metal mixed salt flow rate is maintained at 250L/h, and the pH of the reaction system is controlled between 8-9 by adjusting the sodium hydroxide flow rate. During the synthesis process, monitor and fine-tune the pH and air flow of the slurry in the reaction kettle to control the degree of oxidation in the kettle. If the pH is between 8-8.5, fine-tune the air flow to 13-14m ³ /h. If the pH is between 8.5-9 , then fine-tune the air flow to 12-13m ³ /h. When the particle size reaches 1.67 μm, stop adding the metal mixed salt solution, continue adding sodium hydroxide to increase the pH to 10-11, and stir for 30-60 minutes.

4. The synthesized material is filtered, washed with a centrifuge, and dried at 290°C to obtain an ultra-fine particle size quaternary homogeneous doped cobalt tetroxide product. The metal ion content of Co, Al, Mg, Ni, and Mn in the wastewater is less than 0.001g/L, which meets the emission standards.

Example 3

1. Prepare a cobalt nitrate solution with a cobalt ion concentration of 118.7g/L, add nitrates of Al, Mg, Ni, Mn, and 3.3g/L citric acid, stir thoroughly to prepare a metal mixed salt solution, where The mass ratio ranges of the four metals Al/Co, Mg/Co, Ni/Co, and Mn/Co are 1.32%, 0.65%, 0.59%, and 0.68%;

2. Prepare a sodium hydroxide solution with an alkali concentration of 398.4g/L;

3. Synthesis: Add an appropriate amount of pure water to the reaction kettle to make the bottom liquid, with a temperature of 77-80°C and a rotation speed of 460 rpm. Use sodium hydroxide to adjust the pH of the bottom liquid to between 8-9 and introduce air at 12-14m ³ /h. Pump the prepared metal mixed salt solution and sodium hydroxide solution into the reaction kettle at the same time. Keep the metal mixed salt flow rate constant at 210L/h during the process, and control the pH of the reaction system between 8-9 by adjusting the sodium hydroxide flow rate. During the synthesis process, monitor and fine-tune the pH and air flow of the slurry in the reaction kettle to control the degree of oxidation in the kettle. If the pH is between 8-8.5, fine-tune the air flow to 13-14m ³ /h. If the pH is between 8.5-9 , then fine-tune the air flow to 12-13m ³ /h. When the particle size reaches 1.89 μm, stop adding the metal mixed salt solution, continue adding sodium hydroxide to increase the pH to 10-1, and stir for 30-60 minutes.

4. The synthesized material is filtered, washed with a centrifuge, and dried at 340°C to obtain an ultra-fine particle size quaternary homogeneous doped cobalt tetroxide product. The metal ion content of Co, Al, Mg, Ni, and Mn in the wastewater is less than 0.001g/L, which meets the emission standards.

Comparative example 1

A quaternary homogeneous doped cobalt tetroxide material is provided. The preparation steps are basically the same as those in Example 1, except that:

Step 3. During synthesis: The system pH is always controlled at 10.0-10.5, and the air is 12-14m ³ /h. No fine adjustments are made.

No adjustments are made to other parameters.

Experimental example 1

The particle size, TD, and Co of the quaternary homogeneous doped cobalt tetroxide materials obtained in Examples 1 to 3 and Comparative Example 1 were detected.

Among them, the particle size detection method: using Malvern 3000 laser particle size analyzer;

TD detection method: using tap density measuring instrument equipment;

Co detection method: using automatic potentiometric titrator equipment;

The results are shown in Table 1.

Table 1

It can be seen from Table 1 that the particle size D50 of the quaternary homogeneous doped cobalt tetroxide materials in Examples 1 to 3 is less than 2 microns. The particle size D50 of the quaternary homogeneously doped cobalt tetroxide material in Comparative Example 1 exceeds 2 microns.

Experimental example 2

Scanning electron microscopy, XRD and EPMA (electron probe) were used to detect the morphology, composition and distribution of doping elements of the quaternary homogeneous doped cobalt tetroxide materials obtained in Examples 1 to 3 and Comparative Example 1 respectively.

Figures 1a and 1b are SEM images of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1 at different magnifications; Figure 4 is an SEM image of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 2; Figure 6 is an SEM image of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 3; it can be seen from Figures 1a and 1b that the morphology of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1 is spherical. It can be seen from Figure 4 that the morphology of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1 is spherical. It can be seen from Figure 6 that the morphology of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1 is spherical.

Figure 8 is an SEM image of the quaternary homogeneous doped cobalt tetroxide material prepared in Comparative Example 1; it can be seen from Figure 8 that the morphology of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1 is mainly thick slices. The particles are loose and have many voids on the surface, and there are newly formed small particles. The reason may be due to the oxidation of Mn to MnO ₂ due to the increase in pH.

Figure 2 is the XRD pattern of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1; Figure 5 is the XRD pattern of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 2; Figure 7 is the XRD pattern prepared in Example 3 The XRD pattern of the quaternary homogeneous doped cobalt tetroxide material; it can be seen from Figure 2, Figure 5, and Figure 7 that the quaternary homogeneous doped cobalt tetroxide material prepared in Examples 1 to 3 is mainly Co ₃ O ₄ physical phase.

Figure 9 is the XRD pattern of the quaternary homogeneous doped cobalt tetroxide material prepared in Comparative Example 1. It can be seen from the XRD results that the phase obtained in Comparative Example 1 is mainly cobalt hydroxyl and a small amount of cobalt tetraoxide.

Figures 3a, 3b, 3c, and 3d are respectively cross-sectional distribution diagrams of Al, Mg, Ni, and Mn in the particles of the quaternary homogeneous doped cobalt tetroxide material prepared in Example 1; from Figures 3a, 3b, It can be seen from Figure 3c and Figure 3d that Al, Mg, Ni, and Mn doping elements are evenly distributed from the inside to the outside of the particle.

In summary, it is shown that the morphology of Co ₃ O ₄ in the quaternary homogeneous doped cobalt tetroxide material prepared in the initial stage using the method of the embodiment of the present application is point-like, the precipitates grow in a point-like particle accumulation manner, and the particles have sufficient growth and Self-repairing time and space, particles with ultra-fine particle size (less than 2 μm), high density, and good sphericity are obtained; therefore, using this material as a precursor for lithium battery cathode materials can increase the volumetric energy density of lithium cobalt oxide batteries.

In Comparative Example 1, the particles on the loose surface have many voids and the particle size exceeds 2 μm. If the particle size is reduced, the density of the particles will be lower, which cannot meet the volumetric energy density requirements of lithium cobalt oxide batteries.

The above descriptions are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included in the protection scope of this application.

Industrial applicability

This application provides that this application relates to the field of batteries, including tricobalt tetroxide materials and preparation methods, positive electrodes and lithium batteries. The preparation method of tricobalt tetroxide material includes: synthesizing a metal mixed salt solution and an alkali solution in a reaction kettle. During the synthesis process, the pH of the reaction system is controlled to 8-9, and the air flow rate is 12-14m3/h, so that the precipitation obtained by the synthesis The material is (CoaAlbMgcNidMne)3O4, where 0.9246≤a≤0.9775, 0.0148≤b≤0.037, 0.0042≤c≤0.0208, 0.0017≤d≤0.0085, 0.0018≤e≤0.0091; and the precipitate grows in the form of point-like particle accumulation. This method obtains particles with ultra-fine particle size, high density, and good sphericity, which can increase the volumetric energy density of lithium cobalt oxide batteries. .

In addition, it can be understood that the cobalt tetroxide material and preparation method, positive electrode and lithium battery of the present application are reproducible and can be used in a variety of industrial applications. For example, the tricobalt tetroxide material and preparation method, positive electrode and lithium battery of the present application can be used in the battery field.

Claims

A method for preparing cobalt tetroxide material, which is characterized by including:

The metal mixed salt solution and the alkali solution are synthesized in a reaction kettle. During the synthesis process, the pH of the reaction system is controlled to 8-9, and the air flow rate is 12-14m 3 /h, so that the synthesized precipitate is (Co a Al b Mg c Ni d Mn e ) 3 O 4 , where 0.9246≤a≤0.9775, 0.0148≤b≤0.037, 0.0042≤c≤0.0208, 0.0017≤d≤0.0085, 0.0018≤e≤0.0091; and the precipitate is dot-shaped Particles grow in a packing manner.
The preparation method of cobalt tetroxide material according to claim 1, characterized in that:

During the synthesis process, the pH of the reaction system is controlled to 8-9, and the air flow rate is 12-14m 3 /h, including:

If the pH of the reaction system is between 8-8.5, adjust the air flow rate to 13-14m 3 /h. If the pH of the reaction system is between 8.5-9, adjust the air flow rate to 12-13m 3 /h.
The preparation method of cobalt tetroxide material according to claim 1 or 2, characterized in that:

During the synthesis process, control the pH of the reaction system to 8.1-8.9 and the air flow rate to 12.1-13.9m 3 /h. Among them, if the pH of the reaction system is between 8.1-8.4, adjust the air flow rate to 13.1-13.9m 3 /h. h, if the pH of the reaction system is between 8.5-9, adjust the air flow to 12-12.9m 3 /h.
The preparation method of cobalt tetroxide material according to any one of claims 1 to 3, characterized in that,

The synthesis of the metal mixed salt solution and the alkali solution in the reactor includes:

Add the metal mixed salt solution and the alkali solution into the reaction kettle at the same time. When the particle size D50 of the synthesized precipitate reaches the target particle size, stop adding the metal mixed salt solution. Continue to add the alkali solution, wherein the target particle size is less than or equal to 2 μm.
The preparation method of cobalt tetroxide material according to claim 4, characterized in that:

When the particle size D50 of the synthesized precipitate is 1.45 μm, 1.5 μm, 1.67 μm or 1.89 μm, stop adding the metal mixed salt solution and continue adding the alkali solution.
The preparation method of cobalt tetroxide material according to claim 4 or 5, characterized in that:

The continued addition of the alkali solution includes:

When the pH in the reaction system increases to 10-11, stop adding the alkali solution.
The preparation method of cobalt tetroxide material according to claim 4 or 5, characterized in that:

The step of adding the metal mixed salt solution and the alkali solution into the reaction kettle at the same time includes:

The flow rate of the added metal mixed salt solution is controlled to be 210L/h-290L/h, and the pH of the reaction system is adjusted to 8-9 by adjusting the flow rate of the added alkali solution.
The preparation method of cobalt tetroxide material according to claim 4 or 5, characterized in that:

Before the step of simultaneously adding the metal mixed salt solution and the alkali solution into the reaction kettle, a bottom liquid is also added into the reaction kettle;

The pH of the bottom liquid is 8-9.
The preparation method of cobalt tetroxide material according to claim 8, characterized in that:

Add an appropriate amount of pure water to the reaction kettle to make the bottom liquid.
The preparation method of cobalt tetroxide material according to any one of claims 4 to 9, characterized in that,

Before the step of simultaneously adding the metal mixed salt solution and the alkali solution into the reaction kettle, adjust the temperature in the reaction kettle to 65-80°C; the rotation speed is 330rpm to 460rpm.
The preparation method of cobalt tetroxide material according to claim 10, characterized in that:

Before the step of simultaneously adding the metal mixed salt solution and the alkali solution into the reaction kettle, adjust the temperature in the reaction kettle to 68-78°C; the rotation speed is 350 rpm to 450 rpm.
The preparation method of cobalt tetroxide material according to any one of claims 1 to 11, characterized in that,

Preparing the metal mixed salt solution includes:

Mix the cobalt salt solution, the salt solution of the doping element, and the complexing agent evenly.
The preparation method of cobalt tetroxide material according to claim 12, characterized in that:

The complexing agent is selected from at least one of glutamic acid, glycine or ammonia.
The preparation method of cobalt tetroxide material according to claim 12 or 13, characterized in that:

In the metal mixed salt solution, the mass ratios of the four metals Al/Co, Mg/Co, Ni/Co, and Mn/Co range from 0.55% to 1.32%, 0.15% to 0.65%, 0.18% to 0.59%, and 0.21% ~0.68%.
The preparation method of cobalt tetroxide material according to claim 12, characterized in that:

The alkaline solution is sodium hydroxide solution.
The preparation method of cobalt tetroxide material according to claim 15, characterized in that:

The concentration of the alkali solution is between 221.5g/L and 398.4g/L.
A tricobalt tetroxide material, characterized in that it is prepared by the preparation method of the tricobalt tetroxide material described in any one of claims 1 to 16.
A positive electrode, characterized in that the precursor material of the positive electrode includes the cobalt tetroxide material according to claim 17.
A lithium battery, characterized in that the cathode material precursor of the lithium battery includes the cobalt tetroxide material according to claim 17.