Aluminum-doped cobalt carbonate, and preparation method and application thereof

Abstract

The application belongs to the field of lithium ion batteries, and specifically discloses aluminum-doped cobalt carbonate, a preparation method and application thereof. The aluminum-doped cobalt carbonate with small particle size, wide particle size distribution and high tap density can be prepared by controlling the reaction process for preparing the aluminum-doped cobalt carbonate.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, specifically relating to an aluminum-doped cobalt carbonate, its preparation method, and its application. Background Technology

[0002] Energy density is one of the key performance indicators (KPIs) of lithium-ion batteries. Improving the energy density of the cathode material is a highly effective method for increasing the overall energy density of lithium-ion batteries. According to the energy density calculation formula: Battery weight energy density = Battery capacity × Discharge plateau / Weight, increasing the mass of active material per unit area of ​​the electrode is one of the effective ways to improve energy density.

[0003] Lithium cobalt oxide (LCO) possesses advantages such as high operating voltage, stable discharge, high specific energy, and good cycle performance, making it a commonly used cathode material for lithium-ion batteries. Cobalt carbonate, as a precursor to LCO, inherits certain performance characteristics. Introducing aluminum doping into LCO can improve the stability of the final LCO crystal structure, allowing more lithium ions to participate in charging and discharging, effectively increasing the specific capacity of LCO. Furthermore, current research indicates that high tap density LCO is beneficial for improving the energy density of the resulting LCO cathode material. The tap density of particles is related to their particle size and distribution; generally, mixing particles of different sizes is beneficial for increasing the tap density of the powder. However, the growth process of aluminum-doped LCO is difficult to control, especially since it is generally prepared using a liquid-phase method. This method involves a complex and difficult-to-control environment for crystal growth, making it even more challenging to obtain small, well-dispersed particles. Simultaneously controlling the particle size distribution to achieve a suitable tap density further increases the difficulty. Therefore, current methods for directly preparing aluminum-doped LCO result in products with lower tap density and larger particle size.

[0004] Therefore, it is still necessary to find a method to prepare small-particle-size and high-taper aluminum-doped cobalt carbonate. Summary of the Invention

[0005] In view of the problems of low tap density of aluminum-doped cobalt carbonate products mentioned above, the present invention will provide an aluminum-doped cobalt carbonate, its preparation method and application.

[0006] To achieve the above objectives, the following technical solutions are specifically included:

[0007] A method for preparing aluminum-doped cobalt carbonate includes the following steps:

[0008] Cobalt source and aluminum source solution and carbonate solution are added to carbonate bottom solution in a co-current manner to react and obtain aluminum-doped cobalt carbonate;

[0009] The reaction was carried out under stirring;

[0010] In the reaction, the average particle size of the aluminum-doped cobalt carbonate in the reaction system is d. When d ≤ 2 μm, the temperature of the cobalt-containing and aluminum-containing source solution is 35-50℃. When 2 μm < d < 3 μm, the temperature of the cobalt-containing and aluminum-containing source solution is 20-30℃. When 3 μm ≤ d ≤ 5 μm, the temperature of the cobalt-containing and aluminum-containing source solution is 35-50℃.

[0011] The reaction temperature is 35-50℃.

[0012] This invention divides the reaction temperature control of the growth process of aluminum-doped cobalt carbonate into three stages: In the initial stage (d≤2μm), the cobalt and aluminum source solutions are at the same temperature as the reaction, and the base solution is carbonate; nucleation mainly occurs through supersaturation. In the middle stage (2μm<d<3μm), the temperature of the cobalt and aluminum source solutions is lowered to below the reaction temperature, and nucleation is artificially controlled by the temperature difference. In the later stage (3μm≤d≤5μm), the cobalt and aluminum source solutions are at the same temperature as the reaction, shifting the reaction from the nucleation stage to the growth stage. No more nucleation occurs in this stage; all particles are in a growth state. This is because nucleation at this stage would lead to uncontrollable particle size range in the final sample. Under the temperature control of these three stages, the entire reaction achieves controllable nucleation and growth, ultimately producing aluminum-doped cobalt carbonate particles with small size and suitable particle size distribution, thereby improving the tap density of the aluminum-doped cobalt carbonate particles.

[0013] In one embodiment, during the reaction, when d≤2μm and 3μm≤d≤5μm, the flow rates of the cobalt source and aluminum source solutions are each selected from 7-35L / h, and when 2μm<d<3μm, the flow rates of the cobalt source and aluminum source solutions are 9.5-46.5L / h.

[0014] In one embodiment, during the reaction, the flow rate of the cobalt and aluminum source solutions is lower when d ≤ 2 μm and 3 μm ≤ d ≤ 5 μm than when 2 μm < d < 3 μm. The increased flow rate during the middle of the reaction can intensify the temperature difference change inside the reaction solution system, increase the supersaturation of the system, promote nucleation, and at the same time, the large flow rate will refine the primary particle size, thereby increasing the tap density.

[0015] In one embodiment, during the reaction, when d≤2μm and 3μm≤d≤5μm, the stirring rate is selected from 35-45Hz, and when 2μm<d<3μm, the stirring rate is 40-50Hz.

[0016] In one embodiment, the stirring rate is lower when d≤2μm and 3μm≤d≤5μm than when 2μm<d<3μm. Increasing the stirring rate in the middle of the reaction can accelerate the contact between the metal ions in the cobalt and aluminum source solutions and the carbonates in the reaction solution system. During the contact process, a certain temperature difference exists, which promotes nucleation. High stirring can grind down the edges of the raw materials in the system, which become the basis for heterogeneous nucleation. Heterogeneous nucleation requires less energy and is more likely to occur. Based on the multiple control of temperature, flow rate and stirring, the process of controlling the grain nucleation state of the reaction system to the growth state can be controlled, thereby achieving controllable particle size and its distribution. At the same time, high stirring will refine the primary particle size and improve the tap density.

[0017] In one embodiment, the molar ratio of carbonate ions in the carbonate solution to cobalt in the cobalt-containing and aluminum-containing source solutions is 1.5-3.

[0018] In one embodiment, the mass ratio of aluminum to cobalt in the cobalt-containing and aluminum-containing source solutions is 0.008-0.0165.

[0019] In one embodiment, the cobalt source and aluminum source solution contains at least one of cobalt chloride, cobalt sulfate, and cobalt nitrate, and the aluminum source contains aluminum sulfate octadecahydrate.

[0020] In one embodiment, the molar concentration of the carbonate substrate is 0.5-3 mol / L;

[0021] In one embodiment, the volume of the carbonate substrate is 30-60% of the volume of the reaction vessel;

[0022] In one embodiment, the carbonate in the carbonate solution and the carbonate substrate are each selected from at least one of ammonium bicarbonate, ammonium carbonate, and sodium carbonate.

[0023] In one embodiment, the aluminum-doped cobalt carbonate is further subjected to water washing and drying. The temperature of the water used for washing is 60-70°C, the washing method is centrifugation, the centrifugation frequency is 30-45Hz, the drying temperature is 100-120°C, and the drying time is 10-24 hours.

[0024] In one embodiment, the aluminum-doped cobalt carbonate has an average particle size ≤ 5 μm, a particle size distribution width of 0.95-1.2, and a tap density of 1.69-1.8 g / cm³. 3 .

[0025] In one embodiment, the application of aluminum-doped cobalt carbonate in the preparation of lithium-ion battery cathode materials can significantly improve the current density of lithium-ion batteries, enhance their performance, and expand the application scenarios of lithium cobalt oxide type lithium-ion batteries.

[0026] Compared with related technologies, the present invention has the following beneficial effects: By controlling the reaction process for preparing aluminum-doped cobalt carbonate, the present invention can obtain aluminum-doped cobalt carbonate with small particle size, wide particle size distribution, and high tap density. In particular, the average particle size of the aluminum-doped cobalt carbonate of the present invention is ≤5μm, the particle size distribution width is 0.95-1.2, and the tap density is 1.69-1.8g / cm³. 3 When aluminum-doped cobalt carbonate with the above properties is used to prepare lithium cobalt oxide batteries, it can significantly improve the current density of lithium-ion batteries, enhance the performance of lithium batteries, and expand the application scenarios of lithium cobalt oxide lithium-ion batteries. Attached Figure Description

[0027] Figure 1 This is a SEM image of the aluminum-doped cobalt carbonate finally obtained in Example 1. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] The method for continuously monitoring the average particle size D50 of the aluminum-doped cobalt carbonate particles in the mixed system in the reactor in the following examples and comparative examples is as follows: the slurry of the mixed system in the reactor is taken at intervals, and the average particle size D50 of the aluminum-doped cobalt carbonate particles in the mixed system in the reactor is tested using a laser particle size analyzer.

[0030] Example 1

[0031] This embodiment describes a method for preparing aluminum-doped cobalt carbonate, comprising the following steps:

[0032] (1) Solution preparation: Cobalt chloride, aluminum sulfate octadecahydrate and water are added to a solution preparation tank to prepare a solution containing cobalt source and aluminum source, wherein the cobalt concentration is 2 mol / L and the mass ratio of aluminum to cobalt is 0.01;

[0033] Ammonium bicarbonate and water were added to another mixing tank to obtain a carbonate solution with an ammonium bicarbonate concentration of 2 mol / L.

[0034] Add a 1 mol / L ammonium bicarbonate solution to the reactor as a carbonate bottom solution, the volume of which is 35% of the total volume of the reactor.

[0035] (2) Reaction: The temperature of the carbonate bottom liquid is raised to 40℃ and kept at that temperature. Under stirring, the cobalt source and aluminum source solution and the carbonate solution are added to the carbonate bottom liquid in the reactor in a co-current manner to carry out the reaction. The reaction temperature is kept at 40℃ (controlling the temperature of the mixed system in the reactor is the control of the reaction temperature). The reaction will generate aluminum-doped cobalt carbonate particles. The average particle size D50 of the aluminum-doped cobalt carbonate particles in the mixed system in the reactor is continuously monitored. The average particle size D50 is marked as d.

[0036] The reaction stage is determined by d, and the temperature, flow rate, and stirring rate of the cobalt and aluminum source solutions and the carbonate solution are controlled separately at different reaction stages. The detailed control process is as follows:

[0037] When d≤2μm, the temperature of the cobalt source and aluminum source solution is controlled at 40℃, the flow rate of the cobalt source and aluminum source solution is 25L / h, and the carbonate solution is fed according to the molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source is 2.2, and the stirring rate is 40Hz.

[0038] When 2μm < d < 3μm, the temperature of the cobalt and aluminum source solutions is maintained at 25℃, the flow rate of the cobalt and aluminum source solutions is 33L / h, and the carbonate solution is fed according to a molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source of 2.2, and the stirring rate is 45Hz.

[0039] When 3μm≤d≤4μm, the temperature of the cobalt source and aluminum source solution is controlled at 40℃, the flow rate of the cobalt source and aluminum source solution is 25L / h, and the carbonate solution is fed according to the molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source is 2.2, and the stirring rate is 40Hz.

[0040] The entire reaction ends when d = 4μm. When the reactor is full, the liquid feeding is stopped, the solid material in the reactor settles, the solid material and liquid separate, the separated liquid is pumped out, and then the reaction can be carried out normally. When 2μm < d < 3μm, the reaction time is 18h, and the total reaction time is 55h.

[0041] (3) The product of the reaction was washed by centrifugation with water at 60°C pure water at a centrifugation frequency of 45Hz to obtain a wet material of aluminum-doped cobalt carbonate with a final water content of 10-20%. The wet material of aluminum-doped cobalt carbonate was then dried at 110°C for 12 hours to obtain aluminum-doped cobalt carbonate powder.

[0042] Example 2

[0043] This embodiment describes a method for preparing aluminum-doped cobalt carbonate, comprising the following steps:

[0044] (1) Solution preparation: Cobalt chloride, aluminum sulfate octadecahydrate and water are added to a solution preparation tank to prepare a solution containing cobalt source and aluminum source, wherein the cobalt concentration is 1.5 mol / L and the mass ratio of aluminum to cobalt is 0.008; ammonium bicarbonate and water are added to another solution preparation tank to obtain a carbonate solution, wherein the concentration of ammonium bicarbonate is 3 mol / L; 1 mol / L ammonium bicarbonate solution is added to the reaction vessel as a carbonate bottom solution, the volume of which is 35% of the total volume of the reaction vessel;

[0045] (2) Reaction: The temperature of the carbonate bottom liquid is raised to 35℃ and kept at that temperature. Under stirring, the cobalt source and aluminum source solution and the carbonate solution are added to the carbonate bottom liquid in the reactor in a co-current manner to carry out the reaction. The reaction temperature is kept at 35℃ (the temperature of the mixed system in the reactor is the reaction temperature). The reaction will generate aluminum-doped cobalt carbonate particles. The average particle size D50 of the aluminum-doped cobalt carbonate particles in the mixed system in the reactor is continuously monitored. The average particle size D50 is marked as d.

[0046] The reaction stage is determined by d, and the temperature, flow rate, and stirring rate of the cobalt and aluminum source solutions and the carbonate solution are controlled separately at different reaction stages. The detailed control process is as follows:

[0047] When d≤2μm, the temperature of the cobalt source and aluminum source solution is controlled at 35℃, the flow rate of the cobalt source and aluminum source solution is 7L / h, and the carbonate solution is fed according to the molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source is 1.5, and the stirring rate is 35Hz.

[0048] When 2μm < d < 3μm, the temperature of the cobalt source and aluminum source solution is maintained at 20℃, the flow rate of the cobalt source and aluminum source solution is 9.5L / h, and the carbonate solution is fed according to a molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source of 1.5, and the stirring rate is 40Hz.

[0049] When 3μm≤d≤3.5μm, the temperature of the cobalt source and aluminum source solution is controlled at 35℃, the flow rate of the cobalt source and aluminum source solution is 7L / h, and the carbonate solution is fed according to the molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source is 1.5, and the stirring rate is 35Hz.

[0050] The entire reaction ends when d = 3.5 μm. During this process, the liquid feed is stopped whenever the reactor is full, the solid material in the reactor settles, and the solid material and liquid separate. The separated liquid is then removed, and the reaction can proceed normally. When 2 μm < d < 3 μm, the reaction time is 15 h, and the total reaction time is 50 h.

[0051] (3) The product of the reaction was washed by centrifugation with water at 60°C pure water at a centrifugation frequency of 45Hz to obtain a wet material of aluminum-doped cobalt carbonate with a final water content of 10-20%. The wet material of aluminum-doped cobalt carbonate was then dried at 110°C for 12 hours to obtain aluminum-doped cobalt carbonate powder.

[0052] Example 3

[0053] This embodiment describes a method for preparing aluminum-doped cobalt carbonate, comprising the following steps:

[0054] (1) Solution preparation: Cobalt chloride, aluminum sulfate octadecahydrate and water are added to a solution preparation tank to prepare a solution containing cobalt source and aluminum source, wherein the cobalt concentration is 1 mol / L and the mass ratio of aluminum to cobalt is 0.0165; ammonium bicarbonate and water are added to another solution preparation tank to obtain a carbonate solution, wherein the concentration of ammonium bicarbonate is 2.5 mol / L; 1 mol / L sodium carbonate solution is added to the reaction vessel as carbonate bottom solution, the volume of carbonate bottom solution is 35% of the total volume of the reaction vessel;

[0055] (2) Reaction: The temperature of the carbonate bottom liquid is raised to 50℃ and kept at that temperature. Under stirring, the cobalt source and aluminum source solution and the carbonate solution are added to the carbonate bottom liquid in the reactor in a co-current manner to carry out the reaction. The reaction temperature is kept at 50℃ (the temperature of the mixed system in the reactor is the reaction temperature). The reaction will generate aluminum-doped cobalt carbonate particles. The average particle size D50 of the aluminum-doped cobalt carbonate particles in the mixed system in the reactor is continuously monitored. The average particle size D50 is marked as d.

[0056] The reaction stage is determined by d, and the temperature, flow rate, and stirring rate of the cobalt and aluminum source solutions and the carbonate solution are controlled separately at different reaction stages. The detailed control process is as follows:

[0057] When d≤2μm, the temperature of the cobalt source and aluminum source solution is controlled at 50℃, the flow rate of the cobalt source and aluminum source solution is 35L / h, and the carbonate solution is fed according to the molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source is 3, and the stirring rate is 45Hz.

[0058] When 2μm < d < 3μm, the temperature of the cobalt source and aluminum source solution is maintained at 30℃, the flow rate of the cobalt source and aluminum source solution is 46.5L / h, and the carbonate solution is fed according to the molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source of 3, and the stirring rate is 50Hz.

[0059] When 3μm≤d≤5μm, the temperature of the cobalt source and aluminum source solution is controlled at 50℃, the flow rate of the cobalt source and aluminum source solution is 35L / h, and the carbonate solution is fed according to the molar ratio of carbonate ions in the carbonate solution to cobalt elements in the cobalt source is 3, and the stirring rate is 45Hz.

[0060] The entire reaction ends when d = 5 μm. When the reactor is full, the liquid feeding is stopped, the solid material in the reactor settles, the solid material and liquid separate, the separated liquid is pumped out, and then the reaction can be carried out normally. When 2 μm < d < 3 μm, the reaction time is 28 h, and the total reaction time is 65 h.

[0061] (3) The product of the reaction was washed by centrifugation with water at 70°C pure water at a centrifugation frequency of 40Hz to obtain a wet material of aluminum-doped cobalt carbonate with a final water content of 10-20%. The wet material of aluminum-doped cobalt carbonate was then dried at 110°C for 12 hours to obtain aluminum-doped cobalt carbonate powder.

[0062] Example 4

[0063] The difference between this embodiment and Embodiment 1 is that:

[0064] When d≤2μm, the flow rate of the solution containing cobalt and aluminum sources is 25L / h;

[0065] When 2μm < d < 3μm, the flow rate of the solution containing cobalt and aluminum sources is 25L / h;

[0066] When 3μm≤d≤4μm, the flow rate of the solution containing cobalt and aluminum sources is 25L / h.

[0067] Example 5

[0068] The difference between this embodiment and Embodiment 1 is that:

[0069] When d≤2μm, the flow rate of the solution containing cobalt source and aluminum source is 33L / h;

[0070] When 2μm < d < 3μm, the flow rate of the solution containing cobalt and aluminum sources is 25L / h;

[0071] When 3μm≤d≤4μm, the flow rate of the solution containing cobalt and aluminum sources is 33L / h.

[0072] Example 6

[0073] The difference between this embodiment and Embodiment 1 is that:

[0074] When d≤2μm, the stirring rate is 40Hz;

[0075] When 2μm < d < 3μm, the stirring rate is 40Hz;

[0076] When 3μm≤d≤4μm, the stirring rate is 40Hz.

[0077] Example 7

[0078] The difference between this embodiment and Embodiment 1 is that:

[0079] When d≤2μm, the stirring rate is 45Hz;

[0080] When 2μm < d < 3μm, the stirring rate is 40Hz;

[0081] When 3μm≤d≤4μm, the stirring rate is 45Hz.

[0082] Example 8

[0083] The difference between this embodiment and Embodiment 1 is that:

[0084] When d≤2μm, the stirring rate is 35Hz;

[0085] When 2μm < d < 3μm, the stirring rate is 40Hz;

[0086] When 3μm≤d≤4μm, the stirring rate is 35Hz.

[0087] Comparative Example 1

[0088] The difference between this embodiment and Embodiment 1 is that:

[0089] When d≤2μm, the temperature of the solution containing cobalt source and aluminum source is controlled at 25℃;

[0090] When 2μm < d < 3μm, the temperature of the solution containing cobalt and aluminum sources is maintained at 25℃;

[0091] When 3μm≤d≤4μm, the temperature of the solution containing cobalt source and aluminum source is controlled at 25℃;

[0092] The reaction temperature was maintained at 25℃.

[0093] Comparative Example 2

[0094] The difference between this embodiment and Embodiment 1 is that:

[0095] When d≤2μm, the temperature of the solution containing cobalt source and aluminum source is controlled at 35℃;

[0096] When 2μm < d < 3μm, the temperature of the solution containing cobalt and aluminum sources is maintained at 35℃;

[0097] When 3μm≤d≤4μm, the temperature of the solution containing cobalt source and aluminum source is controlled at 35℃;

[0098] The reaction temperature was maintained at 35℃.

[0099] The aluminum-doped cobalt carbonate prepared in Example 1 was subjected to scanning electron microscopy (SEM); the aluminum-doped cobalt carbonate prepared in Examples 1-8 and Comparative Examples 1-2 was subjected to particle size and distribution and tap density tests; the specific test methods are as follows:

[0100] (1) SEM test: SEM is mainly used to observe the microstructure of cobalt carbonate materials prepared under different conditions. During the test, the surface morphology of the sample is observed by field emission scanning electron microscope at a voltage of 1KV.

[0101] (2) Particle size and distribution: Using deionized water as a dispersant, the aluminum cobalt carbonate powder was ultrasonically dispersed for 1 minute and then analyzed using a laser particle size analyzer. In the test results, D10 indicates that 10% of the particles are smaller than this size, D50, also called the median particle size, indicates that 50% of the particles are smaller than this size, and D90 indicates that 90% of the particles are smaller than this size. The particle size distribution width is calculated by the formula: Particle size distribution width (span) = (D90-D10) / D50.

[0102] (3) Tap density test: Weigh a certain mass (m) of cobalt aluminum carbonate powder sample and place it in a graduated vibrating cylinder. Then vibrate it 2000 times on a vibration density tester at a vibration frequency of 300 times / minute to obtain the volume (v) of the material. Finally, according to the formula: ρ=m / v, the tap density of the sample is obtained. The experiment is repeated three times in parallel and the average value is taken.

[0103] The test results are shown in Table 1. The SEM images of aluminum-doped cobalt carbonate from Example 1 are attached. Figure 1 As shown.

[0104] sample D10(μm) D50(μm) D90(μm) span <![CDATA[Tap density (g / cm 3 )]]> Example 1 2.35 4.01 6.64 1.07 1.76 Example 2 2.02 3.48 5.89 1.11 1.72 Example 3 2.68 4.91 8.01 1.08 1.80 Example 4 2.47 4.08 6.48 0.98 1.70 Example 5 2.58 3.98 6.35 0.95 1.69 Example 6 2.37 3.96 6.42 1.02 1.70 Example 7 2.31 4.04 6.53 1.04 1.69 Example 8 2.3 4.1 6.64 1.06 1.72 Comparative Example 1 2.7 4.06 5.94 0.8 1.65 Comparative Example 2 2.6 3.99 6.06 0.87 1.67

[0105] From the appendix Figure 1 It can be seen that the aluminum-doped cobalt carbonate prepared by this invention has good dispersibility, no aluminum segregation, and fine primary particles.

[0106] As can be seen from the above embodiments, by controlling the reaction process for preparing aluminum-doped cobalt carbonate, the present invention can obtain aluminum-doped cobalt carbonate with small particle size, wide particle size distribution, and high tap density. Specifically, the average particle size of the aluminum-doped cobalt carbonate is 3-5 μm, the span is 0.95-1.2, and the tap density is 1.69-1.8 g / cm³. 3 .

[0107] As can be seen from Example 1 and Comparative Examples 1-2, the temperature of the cobalt source and aluminum source solution in the preparation of aluminum-doped cobalt carbonate in Comparative Examples 1-2 remained constant throughout the process, without staged temperature control. As a result, the prepared aluminum-doped cobalt carbonate had a smaller span and a lower tap density.

[0108] The aluminum-doped cobalt carbonates obtained in Examples 1-3 and Comparative Examples 1-2 were sintered at 350°C for 3 hours and 750°C for 3 hours respectively to obtain aluminum-doped cobalt tetroxide. Then, aluminum-doped cobalt tetroxide and lithium carbonate were uniformly mixed at a Li:Co molar ratio of 1.05 and placed in a pusher kiln for high-temperature solid-state sintering at 950°C for 12 hours to obtain lithium cobalt oxide cathode material.

[0109] Electrode preparation by coating method: Lithium cobalt oxide positive electrode material, conductive carbon and binder (polyvinylidene fluoride, PVDF) are weighed in a mass ratio of 90:6:4, and thoroughly mixed in an agate mortar. An appropriate amount of organic solvent (N-methyl-2-pyrrolidone, NMP) is added and mixed evenly. The mixture is then evenly coated onto a pretreated aluminum foil and dried in a vacuum drying oven at 120°C for 12 hours to obtain the positive electrode sheet.

[0110] Electrochemical performance tests were conducted using CR2025 coin cells. The positive electrode was punched into circular plates with a diameter of φ10mm using a hollow cannon, and the mass of the active material in each plate was recorded. Assembly of the coin cells was completed in a glove box filled with high-purity argon gas. A lithium metal sheet was used as the negative electrode, and a porous polyethylene membrane (Celgard 2400) was used as the separator. 1 mol L... -1 A mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (volume ratio 1:1:1) of LiPF6 was used as the electrolyte. Cyclic performance tests were conducted on a Land electrochemical analyzer, with the battery charge / discharge voltage range of 3.0–4.2 V and the test environment temperature at 25°C. The first-cycle discharge capacity results for Examples 1–3 and Comparative Examples 1–2 are shown in Table 2.

[0111] Table 2

[0112]

[0113] As can be seen from the first-cycle discharge capacity of Examples 1-3 and Comparative Examples 1-2 above, the application of aluminum-doped cobalt carbonate of the present invention in the preparation of lithium-ion battery cathode materials can significantly improve the capacity and energy density of lithium-ion batteries.

Claims

1. A method for preparing aluminum-doped cobalt carbonate, characterized in that, Includes the following steps: Cobalt source and aluminum source solution and carbonate solution are added to carbonate bottom solution in a co-current manner to react and obtain aluminum-doped cobalt carbonate; The reaction was carried out under stirring; In the reaction, the average particle size of the aluminum-doped cobalt carbonate in the reaction system is d; when d ≤ 2 μm, the temperature of the cobalt-containing and aluminum-containing source solutions is 35-50℃ and is consistent with the reaction temperature; when 2 μm < d < 3 μm, the temperature of the cobalt-containing and aluminum-containing source solutions is 20-30℃; when 3 μm ≤ d ≤ 5 μm, the temperature of the cobalt-containing and aluminum-containing source solutions is 35-50℃ and is consistent with the reaction temperature. The reaction temperature is 35-50℃.

2. The method for preparing aluminum-doped cobalt carbonate as described in claim 1, characterized in that, In the reaction, when d≤2μm and 3μm≤d≤5μm, the flow rates of the cobalt source and aluminum source solutions are each selected from 7-35L / h, and when 2μm<d<3μm, the flow rates of the cobalt source and aluminum source solutions are 9.5-46.5L / h.

3. The method for preparing aluminum-doped cobalt carbonate as described in claim 1, characterized in that, In the reaction, when d≤2μm and 3μm≤d≤5μm, the stirring rate is selected from 35-45Hz, and when 2μm<d<3μm, the stirring rate is 40-50Hz.

4. The method for preparing aluminum-doped cobalt carbonate as described in claim 1, characterized in that, The molar ratio of carbonate ions in the carbonate solution to cobalt ions in the solutions containing cobalt and aluminum sources is 1.5-3.

5. The method for preparing aluminum-doped cobalt carbonate as described in claim 1, characterized in that, In the cobalt-containing and aluminum-containing source solutions, the mass ratio of aluminum to cobalt is 0.008-0.0165.

6. The method for preparing aluminum-doped cobalt carbonate as described in claim 1, characterized in that, The cobalt source and aluminum source solution contains at least one of cobalt chloride, cobalt sulfate and cobalt nitrate, and the aluminum source contains aluminum sulfate octadecahydrate.

7. The method for preparing aluminum-doped cobalt carbonate as described in claim 1, characterized in that, Includes at least one of the following: The molar concentration of the carbonate substrate is 0.5-3 mol / L; The volume of the carbonate substrate is 30-60% of the volume of the reaction vessel; The carbonates in the carbonate solution and the carbonate substrate are each selected from at least one of ammonium carbonate and sodium carbonate.

8. Aluminum-doped cobalt carbonate prepared by the method of any one of claims 1-7.

9. The aluminum-doped cobalt carbonate as described in claim 8, characterized in that, The aluminum-doped cobalt carbonate has an average particle size ≤ 5 μm, a particle size distribution width of 0.95-1.2, and a tap density of 1.69-1.8 g / cm³. 3 .

10. The application of aluminum-doped cobalt carbonate as described in claim 8 or 9 in the preparation of cathode materials for lithium-ion batteries.

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