Preparation methods, applications, and uses of aluminum-doped cobalt carbonate

Abstract

This invention discloses a method for preparing aluminum-doped cobalt carbonate, its application, and the preparation method includes: adding aluminum-cobalt binary metal liquid and carbonate solution to a reaction vessel containing a carbonate bottom solution under stirring conditions to obtain aluminum-doped cobalt carbonate. The method involves separating the aluminum-doped cobalt carbonate particles when the D50 is 8.5 μm–10.5 μm and 14 μm–16 μm, respectively. Separating the particles involves: stopping the addition of the aluminum-cobalt binary metal liquid and carbonate solution, increasing the stirring frequency, removing a portion of the material from the reaction vessel, and adding an organic acid solution until the pH deviation from the pre-separation pH is less than 0.05, thus completing the separation operation. In the preparation process of aluminum-doped cobalt carbonate in this invention, the separation process, through adjusting the pH and stirring speed and introducing organic acid, inhibits the adhesion between aluminum-doped cobalt carbonate particles, thereby improving sphericity. Simultaneously, it can suppress cracking during the sintering of aluminum-doped cobalt carbonate to prepare cobalt tetroxide.

Description

Technical Field

[0001] This invention relates to the field of cathode material precursor preparation technology, and more specifically, to a method for preparing aluminum-doped cobalt carbonate, aluminum-doped cobalt carbonate, and its applications. Background Technology

[0002] Doping with aluminum is one of the effective measures to improve the high-voltage electrochemical performance of lithium cobalt oxide because Al-O has a stronger bond energy than Co-O, which can suppress the structural collapse caused by phase transitions during charging and discharging. In practical applications, aluminum is often added to the precursor—cobalt carbonate—in the wet precipitation process to achieve homogeneous bulk doping. However, during precipitation, aluminum can easily cause large aluminum-doped cobalt carbonate particles to agglomerate into peanut-like clusters, thereby reducing the electrochemical performance of lithium cobalt oxide.

[0003] Therefore, a method for preparing aluminum-doped cobalt carbonate that can suppress the adhesion of large aluminum-doped cobalt carbonate particles into peanut-shaped agglomerates is particularly necessary. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing aluminum-doped cobalt carbonate, aluminum-doped cobalt carbonate and its applications, and to reduce the adhesion of large particles of aluminum-doped cobalt carbonate during the preparation process.

[0005] This invention is implemented as follows:

[0006] In a first aspect, the present invention provides a method for preparing aluminum-doped cobalt carbonate, comprising:

[0007] Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to a reaction vessel containing carbonate bottom liquid to obtain aluminum-doped cobalt carbonate particles. When the D50 of the aluminum-doped cobalt carbonate is 8.5μm-10.5μm, the first separation is carried out to obtain the first separation slurry.

[0008] Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to the first batch slurry. When the aluminum-doped cobalt carbonate D50 is 14μm-16μm, the second batch is carried out to obtain the second batch slurry.

[0009] Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to the second batch slurry. When the aluminum-doped cobalt carbonate D50 reaches 18μm-23μm, the reaction ends and the target slurry is obtained.

[0010] The aluminum-doped cobalt carbonate in the target slurry was separated and dried to obtain the aluminum-doped cobalt carbonate.

[0011] Both of the aforementioned separation processes include: stopping the flow of aluminum-cobalt binary metal liquid and carbonate, increasing the stirring frequency, separating some of the material in the reactor and adding organic acid liquid to the reactor until the pH deviation from the pH before separation is less than 0.05, thus completing the separation operation.

[0012] In an optional embodiment, the temperature inside the reactor is 35-50°C, and the stirring frequency in the non-separation reactor step is 12Hz-28Hz.

[0013] And / or, the stirring frequency in the separate vessel step is 2Hz-4Hz higher than the stirring frequency in the non-separate vessel step, and the stirring time in the separate vessel step is 30min-60min;

[0014] And / or, the separation step removes 30wt%-70wt% of the material from the reactor.

[0015] In an optional embodiment, the acid in the organic acid solution is selected from at least one of citric acid, tartaric acid, malic acid, ascorbic acid, succinic acid and aspartic acid, and the concentration of the acid in the organic acid solution is 0.05 mol / L-0.15 mol / L;

[0016] And / or, the flow rate of the organic acid is 0.001VL / h to 0.005VL / h, where V is the volume of the reactor measured in L.

[0017] In an optional embodiment, the cobalt ion concentration in the aluminum-cobalt binary metal liquid is 0.5 mol / L-3 mol / L, and the flow rate is 0.014 VL / h-0.07 VL / h, where V is the volume of the reactor measured in L.

[0018] In an optional embodiment, the mass ratio of aluminum ions to cobalt ions in the aluminum-cobalt binary metal liquid is 0.008-0.0165.

[0019] In an optional embodiment, the carbonate solution is selected from at least one of ammonium bicarbonate solution, ammonium carbonate solution, and sodium carbonate solution;

[0020] And / or, the concentration of carbonate in the carbonate solution is 2 mol / L-3 mol / L;

[0021] And / or, the molar ratio of carbonate in the carbonate solution to cobalt salt in the aluminum-cobalt binary metal liquid is 2.2-3.

[0022] In an optional embodiment, the carbonate substrate is selected from at least one of ammonium bicarbonate solution, ammonium carbonate solution, and sodium carbonate solution;

[0023] And / or, the concentration of carbonate in the carbonate solution is 0.5 mol / L to 3 mol / L;

[0024] And / or, the volume of the carbonate bottom liquid is 30%-60% of the total volume of the reactor.

[0025] In an optional embodiment, before the drying step, the separated aluminum-doped cobalt carbonate is centrifuged and washed, wherein the washing solution is pure water, the washing temperature is 50℃-70℃, and the centrifugation frequency is 30Hz-45Hz.

[0026] Secondly, the present invention provides an aluminum-doped cobalt carbonate, which is prepared by any one of the methods described in the foregoing embodiments.

[0027] Thirdly, the present invention provides cobalt tetroxide, which is prepared from aluminum-doped cobalt carbonate as described in the foregoing embodiments.

[0028] The present invention has the following beneficial effects:

[0029] In the preparation process of aluminum-doped cobalt carbonate in this invention, the adhesion between aluminum-doped cobalt carbonate particles is suppressed by adjusting the pH and rotation speed and introducing organic acids during the separation process, thereby improving the sphericity. At the same time, it can suppress the cracking phenomenon that occurs when aluminum-doped cobalt carbonate is sintered to prepare cobalt tetroxide. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 Here is a SEM image of the aluminum-doped cobalt carbonate prepared in Example 1;

[0032] Figure 2 Here is a SEM image of the aluminum-doped cobalt carbonate prepared in Example 2;

[0033] Figure 3 Here is a SEM image of the aluminum-doped cobalt carbonate prepared in Example 3;

[0034] Figure 4 Here is a SEM image of the aluminum-doped cobalt carbonate prepared in Example 6;

[0035] Figure 5 The image shows a SEM image of the aluminum-doped cobalt carbonate prepared in Comparative Example 1.

[0036] Figure 6 The image shows a SEM image of the aluminum-doped cobalt carbonate prepared in Comparative Example 3.

[0037] Figure 7SEM image of aluminum-doped cobalt carbonate prepared in Comparative Example 4;

[0038] Figure 8 The image shows a SEM image of cobalt tetroxide prepared by sintering aluminum-doped cobalt carbonate in Example 1.

[0039] Figure 9 SEM image of cobalt tetroxide prepared by sintering aluminum-doped cobalt carbonate in Comparative Example 1.

[0040] Figure 10 SEM image of cobalt tetroxide prepared by sintering aluminum-doped cobalt carbonate in Comparative Example 2. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0042] This invention provides a method for preparing aluminum-doped cobalt carbonate, comprising:

[0043] Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to a reaction vessel containing carbonate bottom liquid to obtain aluminum-doped cobalt carbonate particles. When the D50 of the aluminum-doped cobalt carbonate is 8.5μm-10.5μm, the first separation is carried out to obtain the first separation slurry.

[0044] Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to the first batch slurry. When the aluminum-doped cobalt carbonate D50 is 14μm-16μm, the second batch is carried out to obtain the second batch slurry.

[0045] Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to the second batch slurry. When the aluminum-doped cobalt carbonate D50 reaches 18μm-23μm, the reaction ends and the target slurry is obtained.

[0046] The aluminum-doped cobalt carbonate in the target slurry was separated and dried to obtain the aluminum-doped cobalt carbonate.

[0047] Both of the aforementioned separation processes include: stopping the flow of aluminum-cobalt binary metal liquid and carbonate, increasing the stirring frequency, separating some of the material in the reactor and adding organic acid liquid to the reactor until the pH deviation from the pH before separation is less than 0.05, thus completing the separation operation.

[0048] In the embodiments of this application, during the preparation of aluminum-doped cobalt carbonate, as aluminum-doped cobalt carbonate particles are generated, the precipitation rate will gradually decrease under the same conditions. Therefore, it is necessary to perform separate batching to improve the precipitation rate.

[0049] In this embodiment, two separation processes were performed. Specifically, during the first separation, the D50 of the cobalt aluminum carbonate could be 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, or any value between 8.5 μm and 10.5 μm. During the second separation, the D50 of the cobalt aluminum carbonate could be 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or any value between 14 μm and 16 μm. After the second separation, the reaction could be terminated when the D50 of the cobalt aluminum carbonate reached 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, or any value between 18 μm and 23 μm. The timing of the separation is related to the degree of adjustment of the precipitation rate, which in turn affects the morphology of the cobalt aluminum carbonate, such as its sphericity.

[0050] In addition, during the separate reactor operation, the reaction liquid feed was suspended, and the Co element in the reactor was basically completely reacted, resulting in a large amount of HCO3. - HCO3 - Both hydrolysis and ionization can occur (hydrolysis equation: Ionization equation: Because its degree of hydrolysis is greater than its degree of ionization, the OH groups in the system... - An increase in concentration manifests as an increase in pH. After the pH increases, when reactants are reintroduced in a co-current flow, Al... 3+ It will prioritize OH - The amorphous colloidal aggregates Al(OH)3 formed on the surface of aluminum-doped cobalt carbonate exhibit strong attraction, leading to adhesion between the cobalt-doped aluminum carbonate particles and the formation of peanut-shaped aggregates. Therefore, in this embodiment of the invention, an organic acid is added to neutralize the OH in the system before the re-co-current flow after the separation process. - The initial pH value was lowered, and the flow was resumed in parallel once the pH value was not significantly different from that before the separation process. This suppressed the formation of amorphous colloidal agglomerates (Al(OH)3), which is beneficial for preparing aluminum-doped cobalt carbonate particles with high sphericity and no agglomeration. Furthermore, the stirring frequency was increased during the separation process, which helped reduce the contact time between particles, thereby inhibiting adhesion between the aluminum-doped cobalt carbonate particles and improving their sphericity.

[0051] Furthermore, organic acids are used to adjust the pH during the separation process. These organic acids refine the primary particles during the synthesis of aluminum-doped cobalt carbonate, resulting in higher BET values ​​for the synthesized aluminum-doped cobalt carbonate in this stage. This creates a "low-high-low-high-low" BET distribution from the inside out. During the sintering of aluminum-doped cobalt carbonate into cobalt tetroxide, the higher BET values ​​allow for the formation of more channels, facilitating the release of carbon dioxide gas. Simultaneously, the shrinkage during the phase transformation to tetravalent cobalt varies among aluminum-doped cobalt carbonates with different BET values. This cross-distribution of BET values ​​helps mitigate drastic particle size changes during high-temperature reactions, acting as a buffer. In summary, the "low-high-low-high-low" BET structure of aluminum-doped cobalt carbonate from the inside out is beneficial for carbon dioxide release during sintering, buffers particle size shrinkage, and prevents sintering cracking. Furthermore, the organic acid undergoes an ionization reaction in the solution, generating charged ions that charge the particle surface. This causes electrostatic repulsion between the particles, further preventing particle agglomeration and improving the sphericity of the aluminum-doped cobalt carbonate product.

[0052] In an optional embodiment, the temperature inside the reactor is 35-50°C, and the stirring frequency in the non-separation step is 12Hz-28Hz. Specifically, the stirring frequency can be any value between 12Hz, 16Hz, 20Hz, 24Hz, 28Hz, or 12Hz-28Hz. Controlling the temperature and stirring frequency helps improve the uniformity of the material inside the reactor, while also affecting the sedimentation rate, which in turn affects the sphericity.

[0053] In an optional embodiment, the stirring frequency in the separate vessel step is 2Hz-4Hz higher than the stirring frequency in the non-separate vessel step, and the stirring time in the separate vessel step is 30min-60min.

[0054] Specifically, the stirring frequency can be increased by any value between 2Hz, 3Hz, 4Hz, or 2Hz-4Hz compared to the non-separation process. Excessive stirring during the separation process increases the impact force between aluminum-doped cobalt carbonate particles, preventing precipitation on the original cobalt carbonate particle surface and resulting in smaller particles. Therefore, stirring should not be too fast.

[0055] In an optional implementation, the separation step removes 30wt%-70wt% of the material from the reactor. Typically, for ease of operation, the separation step can remove half of the material from the reactor.

[0056] In an optional embodiment, the acid in the organic acid solution is selected from at least one of citric acid, tartaric acid, malic acid, ascorbic acid, succinic acid and aspartic acid, and the concentration of the acid in the organic acid solution is 0.05 mol / L-0.15 mol / L;

[0057] And / or, the flow rate of the organic acid is 0.001VL / h to 0.005VL / h, where V is the volume of the reactor measured in L.

[0058] In this application, the aluminum-doped cobalt carbonate prepared will dissolve in an organic acid. If the concentration of the organic acid is too high, some of the prepared aluminum-doped cobalt carbonate will dissolve in the organic acid, thereby reducing the sphericity of the aluminum-doped cobalt carbonate in direct contact with the organic acid solution. Therefore, in this application, a dilute acid is used to reduce the dissolution of the aluminum-doped cobalt carbonate, thereby reducing the impact of the addition of the organic acid solution on the sphericity of the aluminum-doped cobalt carbonate. Specifically, the concentration of the acid in the organic acid solution can be any value among 0.05 mol / L, 0.07 mol / L, 0.09 mol / L, 0.11 mol / L, 0.13 mol / L, 0.15 mol / L, or 0.05 mol / L-0.15 mol / L. Specifically, for a 500L reaction vessel, the flow rate of the organic acid can be any value between 0.5 L / h, 1 L / h, 1.5 L / h, 2 L / h, 2.5 L / h, or 0.5-2.5 L / h.

[0059] In an optional embodiment, the cobalt ion concentration in the aluminum-cobalt binary metal liquid is 0.5 mol / L-3 mol / L, and the flow rate is 0.014VL / h-0.07VL / h, where V is the volume of the reactor measured in L; that is, the flow rate of the aluminum-cobalt binary metal liquid is related to the volume of the reactor. For example, when the reactor volume is 500L, the flow rate is 7L / h-35L / h.

[0060] The concentration and flow rate of cobalt ions in binary metal liquids are related to the precipitation rate of aluminum-doped cobalt carbonate, which in turn affects the sphericity of the aluminum-doped cobalt carbonate product.

[0061] In an optional embodiment, the mass ratio of aluminum ions to cobalt ions in the aluminum-cobalt binary metal liquid is 0.008-0.0165. The aluminum ion concentration within this range is more conducive to improving the high-voltage electrochemical performance of lithium cobalt oxide.

[0062] In an optional embodiment, the carbonate solution is selected from at least one of ammonium bicarbonate solution, ammonium carbonate solution, and sodium carbonate solution;

[0063] And / or, the concentration of carbonate in the carbonate solution is 2 mol / L-3 mol / L;

[0064] And / or, the molar ratio of carbonate in the carbonate solution to cobalt salt in the aluminum-cobalt binary metal liquid is 2.2-3.

[0065] As one of the reactants, the concentration and flow rate of carbonates also affect the reaction rate, and thus the sphericity of aluminum-doped cobalt carbonate.

[0066] In an optional embodiment, the carbonate substrate is selected from at least one of ammonium bicarbonate solution, ammonium carbonate solution, and sodium carbonate solution;

[0067] And / or, the concentration of carbonate in the carbonate solution is 0.5 mol / L to 3 mol / L;

[0068] And / or, the volume of the carbonate bottom liquid is 30%-60% of the total volume of the reactor.

[0069] The concentration of carbonates in the substrate affects the rate and number of aluminum-doped cobalt carbonate crystal nuclei, which in turn affects the subsequent growth rate of aluminum-doped cobalt carbonate.

[0070] In an optional embodiment, before the drying step, the separated aluminum-doped cobalt carbonate is centrifuged and washed, wherein the washing solution is pure water, the washing temperature is 50℃-70℃, and the centrifugation frequency is 30Hz-45Hz.

[0071] Centrifugal washing can complete centrifugation and washing simultaneously, which is beneficial for improving efficiency and is easy to operate.

[0072] The present invention also provides an aluminum-doped cobalt carbonate, which is prepared by any one of the methods described in the foregoing embodiments.

[0073] The present invention also provides a cobalt tetroxide, which is prepared from the aluminum-doped cobalt carbonate described in the foregoing embodiments.

[0074] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0075] Example 1

[0076] This embodiment provides a method for preparing large aluminum-doped cobalt carbonate particles, including:

[0077] (1) 250L of 1mol / L ammonium bicarbonate was added to a 500L reactor as a base solution. Binary metal liquid and carbonate were then added to the reactor at a certain flow rate to prepare large cobalt carbonate particles. The flow rate of the binary metal liquid was 25L / h, and the carbonate was fed at a carbonate to cobalt salt molar ratio of 2.2. The binary metal liquid was prepared from cobalt sulfate and aluminum sulfate octadeca, with a cobalt concentration of 2mol / L and an aluminum to cobalt element mass ratio of 0.01. The carbonate was an ammonium bicarbonate solution with a concentration of 2mol / L. The process for preparing large cobalt carbonate particles was as follows: the temperature was raised to 46℃, stirring was performed at 20Hz, the reactor was allowed to stand and then purged until the D50 reached 9.5μm, at which point half of the reactor was divided. The reaction was then continued in a parallel flow, the reactor was allowed to stand and then purged until the D50 reached 15μm, at which point half of the reactor was divided. The reaction was then continued in a parallel flow, the reactor was allowed to stand and then purged until the D50 reached 19μm, at which point the reaction was terminated. The operation of the separation process is as follows: the binary metal liquid and the carbonate stop liquid are stirred at 2.5 Hz for 40 minutes on the basis of the original stirring. Half of the material is separated and 0.1 mol / L citric acid is added at a rate of 1 L / h until the pH value is consistent with the pH value before separation.

[0078] (2) The cobalt carbonate slurry that has reached the target particle size is centrifuged and washed with 50°C pure water. The centrifuge is used at a frequency of 35Hz. The wet material is dried in an oven at 100°C to obtain the finished cobalt carbonate product.

[0079] Example 2:

[0080] This embodiment provides a method for preparing large aluminum-doped cobalt carbonate particles, including:

[0081] (1) 350L of 1mol / L ammonium bicarbonate was added to a 500L reactor as a base solution. Binary metal liquid and carbonate were then added to the reactor at a certain flow rate to prepare large cobalt carbonate particles. The flow rate of the binary metal liquid was 7L / h, and the carbonate was fed according to a carbonate to cobalt salt molar ratio of 2. The binary metal liquid was prepared from cobalt nitrate and aluminum sulfate octadeca, with a cobalt concentration of 1mol / L and an aluminum to cobalt element mass ratio of 0.0165. The carbonate was an ammonium bicarbonate solution with a concentration of 2.2mol / L. The process for preparing large cobalt carbonate particles was as follows: the temperature was raised to 50℃, stirring was performed at 28Hz, the reactor was allowed to stand and then purged until the D50 reached 10μm, at which point half of the reactor was divided. The reaction was then continued in a parallel flow, the reactor was allowed to stand and then purged until the D50 reached 15.5μm, at which point half of the reactor was divided. The reaction was then continued in a parallel flow, the reactor was allowed to stand and then purged until the D50 reached 18μm, at which point the reaction was terminated. The operation of the separation process is as follows: the binary metal liquid and the carbonate stop liquid are stirred at 2 Hz for 60 min on the basis of the original stirring. Half of the material is separated and 0.05 mol / L malic acid is added at a rate of 1 L / h until the pH value is consistent with the pH value before separation.

[0082] (2) The cobalt carbonate slurry that has reached the target particle size is centrifuged and washed with 70°C pure water. The centrifuge is used at a frequency of 40Hz. The wet material is dried in an oven at 90°C to obtain the finished cobalt carbonate product.

[0083] Example 3:

[0084] This embodiment provides a method for preparing large aluminum-doped cobalt carbonate particles, including:

[0085] (1) 100L of 3mol / L ammonium bicarbonate was added to a 500L reactor as a base solution. Binary metal liquid and carbonate were then added to the reactor at a certain flow rate to prepare large cobalt carbonate particles. The flow rate of the binary metal liquid was 35L / h, and the carbonate was fed according to a carbonate to cobalt salt molar ratio of 3. The binary metal liquid was prepared from cobalt chloride and aluminum sulfate octadeca, with a cobalt concentration of 3mol / L and an aluminum to cobalt element mass ratio of 0.008. The carbonate was an ammonium bicarbonate solution with a concentration of 3mol / L. The process for preparing large cobalt carbonate particles was as follows: the temperature was raised to 35℃, stirring was performed at 12Hz, the reactor was allowed to stand and then purged until the D50 reached 10.5μm, at which point half of the particles were removed from the reactor. The reaction was then continued in a parallel flow, the reactor was allowed to stand and then purged until the D50 reached 16μm, at which point the other half of the particles were removed from the reactor. The reaction was then continued in a parallel flow, the reactor was allowed to stand and then purged until the D50 reached 20μm, at which point the reaction was terminated. The operation of the separation process is as follows: the binary metal liquid and the carbonate stop-injection liquid are stirred at 3 Hz for 30 min on the basis of the original stirring. Half of the material is separated and 0.15 mol / L ascorbic acid is added at a rate of 2.5 L / h until the pH value is consistent with the pH value before separation.

[0086] (2) The cobalt carbonate slurry that has reached the target particle size is centrifuged and washed with 50°C pure water. The centrifuge is used at a frequency of 45Hz. The wet material is dried in an oven at 110°C to obtain the finished cobalt carbonate product.

[0087] Example 4

[0088] This embodiment provides a method for preparing large aluminum-doped cobalt carbonate particles. The only difference from Embodiment 1 is that after half of the material is separated in the separate reactor, 0.5 mol / L citric acid is added at a rate of 3 L / h until the pH value is consistent with the pH value before separation.

[0089] Example 5

[0090] This embodiment provides a method for preparing large aluminum-doped cobalt carbonate particles. The only difference from Embodiment 1 is that after half of the material is separated in the separate reactor, 0.05 mol / L citric acid is added at a rate of 0.2 L / h until the pH value is consistent with the pH value before separation.

[0091] Example 6

[0092] This embodiment provides a method for preparing large aluminum-doped cobalt carbonate particles. The only difference from Embodiment 1 is that the stirring frequency is increased by 8 Hz and stirred for 40 min during the separation process.

[0093] Example 7

[0094] This embodiment provides a method for preparing large aluminum-doped cobalt carbonate particles, which differs from Embodiment 1 only in that citric acid is replaced with succinic acid.

[0095] Comparative Example 1:

[0096] This comparative example provides a method for preparing large aluminum-doped cobalt carbonate particles. The only difference from Example 1 is that citric acid was not added during the separation process.

[0097] Comparative Example 2:

[0098] This comparative example provides a method for preparing large aluminum-doped cobalt carbonate particles, which differs from Example 1 only in that citric acid is replaced with nitric acid.

[0099] Comparative Example 3:

[0100] This comparative example provides a method for preparing large aluminum-doped cobalt carbonate particles. The only difference from Example 1 is that the stirring frequency was not increased during the separation process.

[0101] Comparative Example 4:

[0102] This comparative example provides a method for preparing large aluminum-doped cobalt carbonate particles. The only difference from Example 1 is that the aluminum-doped cobalt carbonate D50 is separated into two batches at 7 μm and at 18 μm.

[0103] The morphology of the aluminum-doped cobalt carbonate prepared in the above embodiments and comparative examples was characterized, wherein, Figure 1-3 The images shown are SEM images of the aluminum-doped cobalt carbonate prepared in Examples 1-3, respectively. Figure 5 The image shows a SEM image of the aluminum-doped cobalt carbonate prepared in Comparative Example 1. Figure 1-3 and Figure 5 It can be seen that the aluminum-doped cobalt carbonate particles prepared in the example have a uniform particle size distribution, good dispersibility, and almost no agglomeration behavior. In contrast, the aluminum-doped cobalt carbonate particles prepared in the comparative example have multiple peanut-shaped agglomerates, which is in stark contrast to the example. Figure 4 The image shows a SEM image of the aluminum-doped cobalt carbonate prepared in Example 6. Although the particles in the image have good sphericity and no agglomeration, there are many small particles. These small particles are due to the increased stirring intensity after separation of the batch. Figure 6 and Figure 7 The images show SEM images of aluminum-doped cobalt carbonate prepared in Comparative Examples 3 and 4, respectively. The aluminum-doped cobalt carbonate exhibits severe agglomeration of large particles.

[0104] The degree of agglomeration of aluminum-doped cobalt carbonate prepared in the above examples and comparative examples and the specific surface area of ​​samples with different particle sizes during the preparation process were tested. The degree of agglomeration of aluminum-doped cobalt carbonate in each example is shown in Table 1, and the specific surface area of ​​aluminum-doped cobalt carbonate at different particle sizes in Example 1 and Comparative Example 1 is shown in Table 2.

[0105] Table 1

[0106]

[0107]

[0108] Note: The agglomeration degree of aluminum-doped cobalt carbonate particles in Table 1 refers to the number of agglomerated cobalt carbonate particles / the total number of cobalt carbonate particles × 100% in a 500x SEM image. The total number of cobalt carbonate particles refers to particles with a volume greater than 8 / 9πR. 3 The number of particles (R = Dv50 / 2), where the particle volume is (4 / 3)π(d / 2)3, and d is the particle size measured in the SEM image; agglomerated cobalt carbonate particles refer to particles with an aspect ratio greater than 1.3 in the SEM image.

[0109] Table 2

[0110] 9.5μm 11.5μm 15μm 16μm 19μm Example 1 90 106 75 86 65 Comparative Example 1 93 80 74 69 63

[0111] The aluminum-doped cobalt carbonate products prepared in the above embodiments and comparative examples were sintered in a rotary kiln, first held at 350°C for 3 hours, and then held at 750°C for 3 hours to obtain cobalt tetroxide. The SEM images of the cobalt tetroxide in Example 1 and Comparative Example 1 are shown below. Figure 8 and Figure 9 As shown, the cobalt tetroxide in Example 1 showed almost no cracking and almost no residue, while the cobalt tetroxide in the comparative example showed obvious cracking and residue on the surface of some particles.

[0112] In Comparative Example 2, the use of strong acid nitric acid, which is corrosive to cobalt carbonate, resulted in roughened surfaces of the cobalt carbonate particles, hindering subsequent cobalt carbonate precipitation. The abrupt morphological changes within the particles of Comparative Example 2 also made them prone to cracking. (See...) Figure 10 .

[0113] Cobalt tetroxide prepared according to the above method in Examples 1, 1, and 2 was uniformly mixed with lithium carbonate at a Li:Co molar ratio of 1.05 and then sintered at 950°C for 12 hours in a pusher furnace to obtain lithium cobalt oxide cathode material. Its electrochemical performance was then tested. The specific steps for electrochemical performance testing were as follows: A certain amount of lithium cobalt oxide cathode material, polyvinylidene fluoride (PVDF), and acetylene black were weighed according to a mass ratio of 8:1:1. These three materials were then uniformly mixed in an agate mortar, and N-methyl-2-pyrrolidone (NMP) was added dropwise to form a uniform slurry. The slurry was uniformly coated onto the surface of aluminum foil, vacuum dried, and punched into a circular cathode sheet. Subsequently, using lithium metal as the anode, a CR2025 button cell was assembled in a glove box. The electrochemical performance was tested using a CT2001A blue battery testing system, with a test voltage range of 3.0–4.55V and a current density of 1C = 200 mAg. -1 The electrochemical test results are shown in the table below:

[0114]

[0115]

[0116] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing aluminum-doped cobalt carbonate, characterized in that, include: Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to a reaction vessel containing carbonate bottom liquid to obtain aluminum-doped cobalt carbonate particles. When the D50 of the aluminum-doped cobalt carbonate is 8.5μm-10.5μm, the first separation is carried out to obtain the first separation slurry. Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to the first separation slurry. When the aluminum-doped cobalt carbonate D50 is 14μm-16μm, the second separation is carried out to obtain the second separation slurry. Under stirring conditions, aluminum-cobalt binary metal liquid and carbonate solution are added to the second batch slurry. When the aluminum-doped cobalt carbonate D50 reaches 18μm-23μm, the reaction ends and the target slurry is obtained. The aluminum-doped cobalt carbonate in the target slurry was separated and dried to obtain the aluminum-doped cobalt carbonate. Both of the aforementioned separation processes include: stopping the flow of aluminum-cobalt binary metal liquid and carbonate, increasing the stirring frequency, separating some of the material in the reactor and adding organic acid liquid to the reactor until the pH deviation from the pH before separation is less than 0.05, thus completing the separation operation.

2. The method for preparing aluminum-doped cobalt carbonate according to claim 1, characterized in that, The temperature inside the reactor is 35-50℃, and the stirring frequency in the non-separate reactor steps is 12Hz-28Hz; And / or, the stirring frequency in the separate vessel step is 2Hz-4Hz higher than the stirring frequency in the non-separate vessel step, and the stirring time in the separate vessel step is 30min-60min; And / or, the separation step removes 30wt%-70wt% of the material from the reactor.

3. The method for preparing aluminum-doped cobalt carbonate according to claim 1, characterized in that, The acid in the organic acid solution is selected from at least one of citric acid, tartaric acid, malic acid, ascorbic acid, succinic acid and aspartic acid, and the concentration of the acid in the organic acid solution is 0.05 mol / L-0.15 mol / L; And / or, the flow rate of the organic acid is 0.001VL / h to 0.005VL / h, where V is the volume of the reactor measured in L.

4. The method for preparing aluminum-doped cobalt carbonate according to claim 1, characterized in that, The cobalt ion concentration in the aluminum-cobalt binary molten metal is 0.5 mol / L-3 mol / L, and the flow rate is 0.014 V L / h-0.07 V L / h, where V is the volume of the reactor measured in L.

5. The method for preparing aluminum-doped cobalt carbonate according to claim 1, characterized in that, The mass ratio of aluminum ions to cobalt ions in the aluminum-cobalt binary metal liquid is 0.008-0.0165.

6. The method for preparing aluminum-doped cobalt carbonate according to claim 1, characterized in that, The carbonate solution is selected from at least one of ammonium bicarbonate solution, ammonium carbonate solution and sodium carbonate solution; And / or, the concentration of carbonate in the carbonate solution is 2 mol / L-3 mol / L; And / or, the molar ratio of carbonate in the carbonate solution to cobalt salt in the aluminum-cobalt binary metal liquid is 2.2-3.

7. The method for preparing aluminum-doped cobalt carbonate according to claim 1, characterized in that, The carbonate substrate is selected from at least one of ammonium bicarbonate solution, ammonium carbonate solution and sodium carbonate solution; And / or, the concentration of carbonate in the carbonate solution is 0.5 mol / L to 3 mol / L; And / or, the volume of the carbonate bottom liquid is 30%-60% of the total volume of the reactor.

8. The method for preparing aluminum-doped cobalt carbonate according to claim 1, characterized in that, Before the drying step, the separated aluminum-doped cobalt carbonate is centrifuged and washed with pure water as the washing solution, at a temperature of 50℃-70℃ and a centrifugation frequency of 30Hz-45Hz.

9. A cobalt carbonate doped with aluminum, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. A cobalt tetroxide, characterized in that, It is prepared from aluminum-doped cobalt carbonate as described in claim 9.

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