Preparation method of basic cobalt aluminum carbonate spherical material

Abstract

The invention discloses a preparation method of a basic cobalt aluminum carbonate spherical material, and belongs to the technical field of lithium ion battery precursor synthesis. The main chemical component of the basic cobalt aluminum carbonate spherical material is basic cobalt aluminum carbonate, primary particles of the basic cobalt aluminum carbonate are of a single crystal strip-shaped structure, the single crystal length of the primary particles is 0.50-1.00 microns, and the width of the primary particles is 0.01-0.05 microns. According to the invention, by controlling key reaction parameters such as temperature and pH value, the reaction temperature is controlled, and the reaction time is shortened. The cobalt and aluminum elements are precipitated in the form of a basic cobalt aluminum carbonate (Co6Al2CO3 (OH) 16. 4H2O) compound, the cobalt and aluminum elements are mixed at the atomic level, the cobalt and aluminum doping uniformity is ensured, the capacity of the high-voltage lithium cobalt oxide material is improved, and the cycle life of the high-voltage lithium cobalt oxide material is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries and relates to a method for preparing a basic aluminum cobalt carbonate spherical material. Background Art

[0002] Lithium cobalt oxide batteries have the advantages of high specific capacity, high tap density, and high operating voltage, and are widely used in the 3C consumer electronics field. With the popularization of smart phones, tablets and other products in the traditional 3C market, and the emergence of a variety of new electronic products, such as wearable devices, AR / VR, drones, e-cigarettes, wireless Bluetooth speakers, etc., people continue to put forward higher requirements for battery energy density and cycle performance. Major domestic companies have begun to reduce the demand for conventional voltage (≤4.40V) lithium cobalt oxide and continue to expand high voltage (≥4.45V) products. Due to its advantages such as high energy density and long cycle life, aluminum-doped cobalt tetroxide for high-voltage lithium cobalt oxide has gradually become the mainstream precursor material.

[0003] Traditional methods for producing aluminum-doped cobalt carbonate mostly use cobalt salt solution, aluminum salt solution and ammonium bicarbonate or sodium bicarbonate solution as raw materials, and use the parallel addition method to synthesize the aluminum-doped cobalt carbonate precursor. Due to different synthesis parameters and other reasons, the precipitation of aluminum elements is mainly in the form of diaspore (a′-AlOOH), aluminum hydroxide (Al(OH) 3 ) or basic ammonium aluminum carbonate (NH 4 Al(OH) 2 CO 3 ), and cobalt mainly appears in the form of cobalt carbonate or basic cobalt carbonate, which causes the cobalt and aluminum to precipitate separately during the co-precipitation process, without reaching the atomic level distribution. The performance of the aluminum-doped cobalt carbonate product produced does not meet expectations, affecting the electrochemical performance of the battery.

[0004] The Chinese patent application with publication number CN114180644A applies for an aluminum-doped cobalt carbonate material and its preparation method, aluminum-doped cobalt tetroxide and lithium cobalt oxide positive electrode material. In order to prevent the segregation of aluminum element, the invention designs the structure of the material into a core-shell structure, in which the core cobalt exists in the form of cobalt carbonate and the aluminum exists in the form of diaspore or aluminum carbonate; in order to prevent the aluminum precipitate from being unstable and segregating, the outer shell is designed to be cobalt in the form of cobalt carbonate and aluminum in the form of a stable compound. Although the aluminum element is doped into the cobalt carbonate precipitate by this method, the cobalt and aluminum still do not reach the atomic level of mixing.

[0005] A Chinese patent application with publication number CN111082007B applies for a nano basic aluminum cobalt carbonate / cobalt carbonate composite spherical precursor. The method adopts a high pH value of 7.4-7.6 and a high temperature of 50-55°C to prepare a basic aluminum cobalt carbonate / cobalt carbonate composite. Although the process achieves the purpose of uniform distribution of cobalt and aluminum elements, the high synthesis temperature will lead to instability of the precipitant carbonate, and the decomposition of the carbonate will occur during the synthesis process. The formed particles mainly appear in a powdery structure with low crystallinity. In addition, a large amount of carbonate will be consumed under high pH conditions, resulting in increased production costs. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a basic aluminum cobalt carbonate spherical material.

[0007] The preparation method of the basic aluminum cobalt carbonate spherical material of the present invention comprises the following steps: (1) Add ammonium bicarbonate solution as the base liquid to the reaction kettle, raise the temperature to 44-49°C (preferably 46°C), start stirring and set it to 100-200 rpm, add aluminum-doped cobalt chloride solution and precipitant ammonium bicarbonate solution at the same time, control the reaction pH value to 7.1-7.3 (preferably 7.20-7.25), and continue the reaction until the particle size reaches 9.0-9.5 μm; The concentration of the bottom liquid ammonium bicarbonate solution is 30-60 g / L, and the added volume is 1 / 10-1 / 5 of the volume of the reactor; the concentration of the precipitant ammonium bicarbonate solution is 200-250 g / L; the cobalt concentration in the aluminum-doped cobalt chloride solution is 90-120 g / L, and the aluminum concentration is 0.80-1.10 g / L.

[0008] (2) dispensing 1 / 2 of the slurry prepared in step (1) by volume, heating the remaining slurry to 44-49° C., starting stirring and setting the stirring speed to 50-80 rpm, adding aluminum-doped cobalt chloride solution and precipitant ammonium bicarbonate solution, controlling the pH value of the reaction system to 7.1-7.3, and stopping the reaction until the particle size reaches 19-20 μm; The concentration of the precipitant ammonium bicarbonate solution is 200-250 g / L; the cobalt concentration in the aluminum-doped cobalt chloride solution is 90-120 g / L, and the aluminum concentration is 0.80-1.10 g / L.

[0009] (3) The material obtained in step (2) is heat-aged in a reactor at 44-49° C. for 2 h, filtered, and dried to obtain a basic aluminum cobalt carbonate spherical material.

[0010] The present invention provides a basic aluminum cobalt carbonate spherical material, which is a micron-sized spherical material. The primary particles of the basic aluminum cobalt carbonate spherical material are in a single crystal strip structure. The length of the primary particle single crystal is 0.50 to 1.00 microns and the width is 0.01 to 0.05 microns, realizing the cobalt and aluminum elements in the form of basic cobalt carbonate (Co 6 Al 2 CO 3 (OH) 16 ·4H 2 O) compound to ensure uniform doping of cobalt and aluminum at the atomic level Compared with the existing patents, the present invention achieves the control of the cobalt-aluminum coprecipitation product in the precipitation process by optimizing the pH value and reaction temperature of the synthesis system, and prepares its primary particles into strip-shaped single crystals, realizing the mixing of cobalt and aluminum at the atomic level. In the process of synthesis, the present invention strictly controls the pH of the synthesis process on the one hand. When the pH value is low, the aluminum element is easy to precipitate alone in the form of boehmite; when the pH is high, the aluminum element is easy to precipitate in the form of basic ammonium aluminum carbonate or aluminum hydroxide. In addition, temperature is also the main factor affecting the cobalt-aluminum coprecipitation. When the temperature is low, the reaction activity of the synthesis process is relatively weak, and the cobalt precipitate formed is mainly in the form of powder particles, and the primary particle crystallinity is poor; but when the temperature is high, ammonium bicarbonate is easy to decompose, resulting in the instability of ammonium bicarbonate in the synthesis system, and cobalt is easy to precipitate alone in the form of cobalt carbonate or basic cobalt carbonate, and the aluminum precipitate is easy to agglomerate and segregate. In order to solve the above problems, the present invention optimizes the reaction temperature and the corresponding pH value, so that in the synthesis process, the cobalt-aluminum product is mainly in the form of basic aluminum cobalt carbonate (the main reaction equation is: 6CoCl 2 +Al 2 (SO 4 ) 3 +18NH 4 HCO 3 +H 2 O→Co 6 Al 2 CO 3 (OH) 16 ·4H 2 O↓+3(NH 4 ) 2 SO 4 +12NH 4 Cl+17CO 2 ↑), and in the preparation process, the primary particles are controlled to be in a single crystal strip structure, ensuring the uniformity of aluminum element distribution. This improves the material's processing performance in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the microscopic morphology of material sample 1 prepared in Example 1.

[0012] Figure 2 This is the microscopic morphology of comparative sample 2 prepared in comparative example 1.

[0013] Figure 3 This is the microscopic morphology of material sample 3 prepared in Example 2.

[0014] Figure 4 This is the microscopic morphology of comparative sample 4 prepared in comparative example 2.

[0015] Figure 5 It is the XRD diffraction spectrum of material sample 3 prepared in Example 2 and comparison sample 4 prepared in Comparative Example 2. DETAILED DESCRIPTION

[0016] In order to further disclose the content, features and effects of the present invention, the following examples are given and described in detail with reference to the accompanying drawings.

[0017] Example 1 (1) Prepare 110±1 g / L cobalt chloride solution, add aluminum sulfate crystals to the prepared cobalt chloride solution, and adjust the aluminum content to 0.80±0.01 g / L to obtain aluminum-doped cobalt chloride solution; prepare 240±2 g / L ammonium bicarbonate solution and keep it warm to 25-28°C.

[0018] (2) Add 200L of 30g / L ammonium bicarbonate solution as the base liquid into a 500L reactor, raise the temperature to 44±0.5°C, start stirring and set it to 150 rpm, and simultaneously add aluminum-doped cobalt chloride solution and 240±2g / L of precipitant ammonium bicarbonate solution, wherein the flow rate of the aluminum-doped cobalt chloride solution into the reactor is 20L / h, and the flow rate of the ammonium bicarbonate solution into the reactor is adjusted according to the pH value. The reaction pH value of the synthesis process is controlled to be 7.10-7.15, and the reaction is continued until the particle size reaches 9.0-9.5 μm.

[0019] (3) Dispense 1 / 2 of the slurry prepared in step (2) by volume, heat the remaining slurry to 44±0.5°C, start stirring and set it to 50 rpm, and simultaneously add aluminum-doped cobalt chloride solution and 240±2 g / L of ammonium bicarbonate solution as a precipitant, wherein the flow rate of the aluminum-doped cobalt chloride solution into the kettle is 20 L / h, and the flow rate of the ammonium bicarbonate solution into the kettle is controlled according to the pH value, and the pH value of the reaction system is controlled to be 7.10-7.15, until the particle size reaches 19-20 μm, and the reaction is stopped.

[0020] (4) The material obtained in step (3) was kept in a reactor at 44-49°C for 2 hours, filtered, and dried at 100-150°C to obtain a basic aluminum cobalt carbonate micron-sized spherical material 1 (the microscopic morphology of the material sample 1 is shown in Figure 1 ).

[0021] Comparative Example 1 (1) Prepare 110±1g / L cobalt chloride solution, add aluminum sulfate crystals to the prepared cobalt chloride solution, and adjust the aluminum content to 0.80±0.01g / L; prepare 240±2g / L ammonium bicarbonate solution and keep it warm to 25-28℃.

[0022] (2) Add 200L of 30g / L ammonium bicarbonate solution as the base liquid into a 500L reactor, raise the temperature to 52±0.5°C, start stirring and set it to 150 rpm, and simultaneously add aluminum-doped cobalt chloride solution and 240±2g / L ammonium bicarbonate solution, wherein the flow rate of the aluminum-doped cobalt chloride solution into the reactor is 20L / h, and the flow rate of the ammonium bicarbonate solution into the reactor is controlled according to the pH value. The reaction pH value during the synthesis process is controlled to be 7.10-7.15, and the reaction is continued until the particle size reaches 9.0-9.5 μm.

[0023] (3) 1 / 2 of the slurry prepared in step (2) is dispensed by volume, and the remaining slurry is heated to 52±0.5°C, and stirring is started and set to 50 rpm. At the same time, an aluminum-doped cobalt chloride solution and a 240±2 g / L ammonium bicarbonate solution precipitant are added, wherein the flow rate of the aluminum-doped cobalt chloride solution into the kettle is 20 L / h, and the flow rate of the ammonium bicarbonate solution into the kettle is controlled according to the pH value, and the pH value of the reaction system is controlled to be 7.10-7.15, until the particle size reaches 19-20 μm, and the reaction is stopped.

[0024] (4) The material obtained in step (3) was kept in a reactor at 44-49°C for 2h, filtered, and dried at 100-150°C to obtain comparative sample 2 (the microscopic morphology of comparative sample 2 is shown in Figure 2 ).

[0025] Example 2 (1) Prepare 120±1g / L cobalt chloride solution, add aluminum sulfate crystals to the prepared cobalt chloride solution, and adjust the aluminum content to 1.10±0.01g / L; prepare 220±2g / L ammonium bicarbonate solution and keep it warm to 25-28℃.

[0026] (2) Add 180L of 60g / L ammonium bicarbonate solution as the base liquid into a 500L reactor, raise the temperature to 48±0.5°C, start stirring and set it to 180 rpm, and add aluminum-doped cobalt chloride solution and ammonium bicarbonate solution precipitant at the same time. The flow rate of aluminum-doped cobalt chloride solution into the reactor is 18L / h, and the flow rate of ammonium bicarbonate solution into the reactor is controlled according to the pH value. The reaction pH value of the synthesis process is controlled to be 7.25-7.30, and the reaction is continued until the particle size reaches 9.0-9.5 μm.

[0027] (3) 1 / 2 of the slurry prepared in step (2) is dispensed by volume, and the remaining slurry is heated to 48±0.5°C, and stirring is started and set to 40 rpm. At the same time, an aluminum-doped cobalt chloride solution and an ammonium bicarbonate solution precipitant are added, wherein the flow rate of the aluminum-doped cobalt chloride solution into the kettle is 18 L / h, and the flow rate of the ammonium bicarbonate solution into the kettle is controlled according to the pH value. The pH value of the reaction system is controlled to be 7.25-7.30, until the particle size reaches 19-20 μm, and the synthesis is stopped.

[0028] (4) The material obtained in step (3) was kept in a reactor at 44-49°C for 2 hours, filtered, and dried at 100-150°C to obtain basic aluminum cobalt carbonate micron-sized spherical material 3 (the microscopic morphology of material sample 3 is shown in Figure 3 ).

[0029] Comparative Example 2 (1) Prepare 120±1g / L cobalt chloride solution, add aluminum sulfate crystals to the prepared cobalt chloride solution and adjust the aluminum content to 1.10g / L; prepare 220±2g / L ammonium bicarbonate solution and keep it warm to 25-28℃.

[0030] (2) Add 180L of 60g / L ammonium bicarbonate solution as the base liquid into a 500L reactor, raise the temperature to 48±0.5°C, start stirring and set it to 180 rpm, and add aluminum-doped cobalt chloride solution and ammonium bicarbonate solution precipitant at the same time. The flow rate of aluminum-doped cobalt chloride solution into the reactor is 18L / h, and the flow rate of ammonium bicarbonate solution into the reactor is controlled according to the pH value. The reaction pH value of the synthesis process is controlled to be 6.95-7.00, and the reaction is continued until the particle size reaches 9.0-9.5 μm.

[0031] (3) Dispense 1 / 2 of the slurry prepared in step (2) by volume, heat the remaining slurry to 48±0.5°C, start stirring and set it to 40 rpm, and add aluminum-doped cobalt chloride solution and ammonium bicarbonate solution as precipitants, wherein the flow rate of the aluminum-doped cobalt chloride solution into the kettle is 18 L / h, and the flow rate of the ammonium bicarbonate solution into the kettle is controlled according to the pH value, and the pH value of the reaction system is controlled to be 6.95-7.00, until the particle size reaches 19-20 μm, and the reaction is stopped.

[0032] (4) The material obtained in step (3) was kept in a reactor at 44-49°C for 2 hours, filtered, and dried at 100-150°C to obtain comparative sample 4 (the microscopic morphology of comparative sample 4 is shown in Figure 4 ).

[0033] In order to verify the electrochemical properties of samples prepared by different processes, Sample 1, Comparative Sample 2, Sample 3 and Comparative Sample 4 were further prepared into aluminum-doped lithium cobalt oxide products, assembled into button cells and tested for electrochemical properties.

[0034] Sample 1 and comparative sample 2 are prepared under the same pH conditions. The temperature of comparative sample 2 is raised to 52±0.5℃. As the temperature rises, the primary particles of the material appear in a flaky structure, but the arrangement is loose and not dense. From the electrochemical performance test of the samples in Table 1, it can be seen that the discharge capacity of comparative sample 2 is basically equivalent to that of sample 1, but the room temperature cycle decay decreases faster, and it decreases by about 10% in the 50th cycle; Sample 3 and comparative sample 4 are prepared under the same temperature conditions. The pH value of the comparative sample is lowered to 6.95-7.00. As the pH decreases, the morphology of the comparative sample is a powdery structure, and no single crystal structure like sample 3 is formed. Figure 5 From the XRD diffraction spectrum, we can see that the spectrum of sample 3 has obvious characteristic peaks of 006 and 102 of basic cobalt aluminum carbonate, from which we can infer that its main component is basic aluminum cobalt carbonate. By comparison, the peaks of 012, 104, 110, 113, 202, 024, 018, and 116 in the spectrum of sample 4 are consistent with the characteristic peaks of the standard cobalt carbonate spectrum, and its main component is CoCO 3 From the electrochemical performance test data in Table 1, it can be seen that the capacity of the comparison sample is basically equivalent to that of sample 3, but the room temperature cycle decay is faster. After the 50th cycle, the capacity decreases by 10%. It can be seen that the electrochemical performance of the prepared sample is excellent when the synthesis conditions are controlled at a pH value of 7.1-7.3 and a synthesis temperature of 44-49°C.

[0035] The above are preferred embodiments of the present invention. Any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a basic aluminum cobalt carbonate spherical material, comprising the following steps: (1) Add ammonium bicarbonate solution as the base liquid to the reaction kettle, raise the temperature to 44-49°C, start stirring and set it to 100-200 rpm, add aluminum-doped cobalt chloride solution and precipitant ammonium bicarbonate solution at the same time, control the reaction pH value to 7.1-7.3, and continue the reaction until the particle size reaches 9.0-9.5 μm; (2) dispensing 1 / 2 of the slurry prepared in step (1) by volume, heating the remaining slurry to 44-49° C., starting stirring and setting the stirring speed to 50-80 rpm, adding aluminum-doped cobalt chloride solution and precipitant ammonium bicarbonate solution, controlling the pH value of the reaction system to 7.1-7.3, and stopping the reaction until the particle size reaches 19-20 μm; (3) The material obtained in step (2) is heat-aged, filtered, and dried in a reactor to obtain a basic aluminum cobalt carbonate spherical material.

2. The method for preparing the basic aluminum cobalt carbonate spherical material according to claim 1, characterized in that: In step (1), the concentration of the base liquid ammonium bicarbonate solution is 30-60 g / L, and the volume added is 1 / 10-1 / 5 of the volume of the reactor.

3. The method for preparing the basic aluminum cobalt carbonate spherical material according to claim 1, characterized in that: In steps (1) and (2), the concentration of the precipitant ammonium bicarbonate solution is 200-250 g / L; the cobalt concentration in the aluminum-doped cobalt chloride solution is 90-120 g / L, and the aluminum concentration is 0.80-1.10 g / L.

4. The basic aluminum cobalt carbonate spherical material prepared by the method according to claim 1, characterized in that: The basic aluminum cobalt carbonate spherical material is a micron-sized spherical material. The primary particles of the basic aluminum cobalt carbonate spherical material are in a single crystal strip structure. The length of the primary particle single crystal is 0.50 to 1.00 microns and the width is 0.01 to 0.05 microns. The cobalt and aluminum elements are converted into basic cobalt aluminum carbonate (Co6Al2CO3(OH) 16 ·4H2O) compounds to ensure uniform doping of cobalt and aluminum at the atomic level.

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