An extremely narrow distribution positive electrode material precursor based on regulating Oswald ripening rate and a preparation method thereof

Abstract

The present invention discloses an extremely narrow distribution positive electrode material precursor based on regulating the Oswald ripening rate and a preparation method thereof. The chemical formula of the precursor is (Ni x CoyMn (1‑x‑y) )OH2, wherein x is 0.3-0.9, y is 0.1-0.7, and x+y≤1; the particle size distribution span is between 0.3-0.5; the number of 1.0K SEM balls is between 3-5, and the sizes are consistent; at the same time, the cycle life of the positive electrode material prepared by sintering the precursor is increased by 50%-80%.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to an extremely narrow distribution positive electrode material precursor based on regulating Oswald ripening rate and a preparation method thereof. Background Art

[0002] As an efficient energy storage technology, lithium-ion batteries are widely used in many industries. For example, in the field of electric vehicles, for long-mileage electric vehicles, it is crucial for lithium-ion batteries to maintain high energy density while maintaining stability and safety. Cathode material precursors are the most important component of lithium-ion batteries. The preparation of high-quality cathode material precursors can effectively improve the energy density of lithium-ion batteries and extend the cycle life.

[0003] At present, the industry mostly uses wet co-precipitation process to prepare positive electrode material precursors, but it is often accompanied by uneven size distribution, which indirectly affects the decrease in the cycle stability of the positive electrode material after sintering. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, the present invention proposes a method for preparing an extremely narrow distribution positive electrode material precursor based on regulating the Oswald ripening rate. Oswald ripening is an indispensable method in the grain growth process. Its main feature is that small particles dissolve and adhere to the surface of large particles, prompting large particles to continue to grow. The process is often accompanied by the phenomenon of widening of the particle size distribution. The nickel cobalt manganese hydroxide prepared or post-treated by regulating the Oswald ripening conditions by the method described in the present invention is characterized in that: the particle size distribution span is between 0.2-0.5; the number of 1.0K SEM balls is between 3-5, and the size is basically the same; at the same time, the positive electrode material prepared by sintering the precursor has a cycle life increased by 30%-50%.

[0005] The present invention provides an extremely narrow distribution positive electrode material precursor based on regulating the Oswald ripening rate, the chemical formula of the precursor is (Ni x CoyMn (1-x-y) )OH2, where x is 0.3-0.9, y is 0.1-0.7, and x+y≤1.

[0006] Furthermore, the particle size distribution Span of the precursor is between 0.2-0.5, the particle size is between 2.5-8.0 um, the number of 1.0K SEM spheres is between 3-5, and the size of the secondary spheres is consistent.

[0007] The invention provides a method for preparing the precursor, comprising the following steps: continuously introducing a mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate, a sodium hydroxide solution and an ammonia complexing agent solution into a reaction device for reaction; when the liquid particle size in the reaction solution reaches 1.5-1.7um, stopping the feeding of the reaction device, performing a first stage of temperature increase regulation, and then introducing a quantitative amount of sodium sulfate solution in stages, with the cumulative time maintained at 3-6h; then continuing the reaction after the reaction temperature is restored, and performing a second stage of temperature increase regulation when the liquid particle size reaches 2.2-2.5um; when the liquid particle size reaches 3.2-3.3um, stopping the reaction and concentrating the material to a concentrator, maintaining a pressure of 0.01-0.08Mpa for a duration of 3-6h, and then continuing the reaction, while introducing a quantitative amount of sodium sulfate solution, until the liquid particle size reaches 3.5-4.0um, and the reaction is terminated.

[0008] Furthermore, the total concentration of the mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate is 1.5-2.5 mol / L; the concentration of the sodium hydroxide solution is 5-10 mol / L, and the concentration of the complexing agent is 20-30 mol / L.

[0009] Furthermore, the first stage temperature rise control scheme is: the reaction requires the temperature to rise from 45°C to 80°C, and the required temperature rise range is 4°C-8°C / h.

[0010] Furthermore, the concentration of the first sodium sulfate solution is 5-10 mol / L, the usage amount is 1 / 5 of the flow rate of the mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate, and the usage time is 2-5 hours.

[0011] Furthermore, the second stage of temperature control requires the temperature to be raised to 60-70°C, with a temperature increase range of 2-5°C / h.

[0012] Furthermore, the concentration of the second sodium sulfate solution is 5-10 mol / L, the amount used is 1 / 2 of the flow rate of the nickel-cobalt-manganese mixed solution, and the use time is 2-5 hours.

[0013] Furthermore, the overall reaction time needs to be maintained between 80-150 h.

[0014] The present invention also provides a lithium ion battery positive electrode material, which is prepared by the above method.

[0015] Beneficial effects: The present invention adjusts the Oswald ripening conditions of key nodes through gradient temperature, pressure gradient and appropriate crystal nucleus inhibitor (sodium sulfate solution). Gradient temperature increase can accelerate the ripening rate, accelerate the dissolution rate of small particles, and promote the Oswald ripening equilibrium point to shift in the direction of accelerating particle size increase, thereby reducing the increase in particle size distribution; by reducing the surface solubility of small particles through pressure gradient, the crystal nucleus inhibitor can adhere to the surface of the grain, hindering the further growth of the grain, while reducing the supersaturation of the solution, preventing the appearance of small grains caused by the increase in slurry concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The graphs are the variation trend of the liquid particle size Span of the embodiment (blue) and the comparative example (red) with the liquid D50 (a) and the reaction time (b);

[0017] Figure 2 The solid particle size distribution diagram after the limit-up of the embodiment (blue) and the comparative example (red) and the comparison diagram of 1.0K times SEM (c) of the embodiment and 1.0K times SEM (d) of the comparative example;

[0018] Figure 3 This is the rate charge and discharge performance diagram. DETAILED DESCRIPTION

[0019] The present invention is explained in detail below with reference to the embodiments. Example

[0020] 80L of water, 1054 ml of sodium hydroxide solution and 2024mL of ammonia water were added to the reactor as the base liquid, and then an aqueous solution containing nickel sulfate, manganese sulfate and cobalt sulfate (the mixed liquid ratio was Ni0.6Co0.1Mn0.3, and the mixed liquid concentration was 1.8mol / L), an ammonia solution (30mol / L) and a sodium hydroxide (8mol / L) aqueous solution were simultaneously introduced into the reactor. The flow rate of the mixed solution was 600mL / min, the flow rate of the sodium hydroxide solution was 328mL / min, and the flow rate of the ammonia solution was 23mL / min. The system reacted at 45°C, a stirring rate of 1400rpm, and a pH of 12.3-12.4.

[0021] During the reaction process, the liquid particle size is detected every 2 hours. When the liquid particle size reaches 1.5-1.7um, the reactor feed is stopped. The temperature is raised from 45℃ to 80℃, the temperature rise is 7℃ / h, and the temperature rise is continued for 7 hours. The stirring speed of the reactor remains unchanged during the process. At the same time, the sodium sulfate solution (8mol / L) is injected into the reactor at a flow rate of 120ml / min. The injection time nodes are 1h, 3h, 5h, and 7h after the start of the temperature rise. Each time node is continuously injected for 1h, and the cumulative injection time is 4h. After the temperature rise is completed, the reactor is lowered to 45℃ and the reaction is continued. When the liquid particle size reaches 2.2-2.5um, the second stage of temperature rise is regulated (this time the reactor keeps feeding, and no sodium sulfate crystal nucleus inhibitor is injected); from 45℃ to 70℃, the temperature rise is 5℃ / h. After that, the temperature was restored to 45°C and the reaction was continued. When the liquid particle size reached 3.2-3.3um, the reaction was stopped and a quantitative sodium sulfate solution (8mol / L, flow rate 300ml / min, time 3.5h) was introduced and concentrated by a concentrator. All the materials were pressed into a concentration tank for pressure-maintaining pulping at a pressure of 0.08Mpa. The pulping time was 5h. After that, the reaction was continued until the liquid particle size reached 3.5-4.0um, and the reaction was terminated. The liquid particle size Span distribution during the reaction process is shown in the figure. Figure 1 (a) As shown in the embodiment; SEM of the material after washing and drying is as follows Figure 2 (c) as shown. Comparative Example

[0022] 80L of water, 1054 ml of sodium hydroxide solution and 2024mL of ammonia water were added to the reactor as the base liquid, and then an aqueous solution containing nickel sulfate, manganese sulfate and cobalt sulfate (the mixed solution ratio was Ni0.6Co0.1Mn0.3, and the mixed solution concentration was 1.8mol / L), an ammonia solution (30mol / L) and an aqueous solution of sodium hydroxide (8mol / L) were simultaneously introduced into the reactor. The flow rate of the mixed solution was 600mL / min, the flow rate of the sodium hydroxide solution was 328mL / min, and the flow rate of the ammonia solution was 23mL / min. The system reacted at 45°C, a stirring rate of 1400rpm, and a pH of 12.3-12.4. The process was stably controlled, and the reaction was stopped when the liquid particle size rose to 3.5-4.0um. The liquid particle size Span distribution of the comparative process is as follows Figure 1 (a) As shown in the comparative example, the SEM of the material after washing and drying is as follows: Figure 2 (d) as shown.

[0023] Comparing the liquid particle size Span distribution of the embodiment and the comparative example, it can be clearly found that by adjusting the Oswald ripening conditions, the Span distribution of the embodiment is smaller. After the post-treatment, the solid particle size Span of the embodiment is 0.352, and the solid particle size Span of the comparative example is 0.687. Comparing the 1.0K times SEM of the two, the embodiment obviously has a narrower particle size distribution and better sphericity.

[0024] Comparative Examples and Examples Preparation Method of Nickel-Cobalt-Manganese Positive Electrode Material

[0025] The nickel-cobalt-manganese hydroxide precursor and lithium salt are mixed and sintered. The first sintering temperature is 300-400°C, the heating rate is 4-5°C / min, and the sintering time is 10-20h; the second sintering temperature is 700-800°C, the heating rate is 2-3°C, and the sintering time is 10-20h.

[0026] After sintering, the positive electrode material was tested for electrical properties, and the capacity retention rate ( Figure 3 a) and the discharge capacity at different current densities from 0.1 to 5.0C ( Figure 3 b), it can be found that after 1000 cycles, the capacity retention rates of the embodiment and the comparative example are 81.5% and 61%, respectively ( Figure 3 a), the embodiment is improved by 33% compared with the comparative example.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an extremely narrow distribution positive electrode material precursor based on regulating the Oswald ripening rate, characterized in that: The chemical formula of the precursor is (Ni x CoyMn (1-x-y) )OH2, wherein x is 0.3-0.9, y is 0.1-0.7, x+y≤1, the particle size distribution Span of the precursor is between 0.2-0.5, the particle size is between 2.5-8.0um, and the secondary ball size is consistent; the preparation method of the precursor comprises the following steps: continuously introducing a mixed solution containing nickel sulfate, cobalt sulfate, manganese sulfate, sodium hydroxide solution and ammonia complexing agent solution into a reaction device for reaction; when the liquid particle size in the reaction liquid reaches 1.5-1.7um, stopping the reaction device from feeding, The first stage of temperature increase and regulation is carried out, and then a quantitative amount of sodium sulfate solution is introduced in stages, and the cumulative time is maintained at 3-6 hours; then the reaction is continued after the reaction temperature is restored, and when the liquid particle size reaches 2.2-2.5um, the second stage of temperature increase and regulation is carried out; when the liquid particle size reaches 3.2-3.3um, the reaction is stopped and the material is concentrated to a concentrator, maintaining a pressure of 0.01-0.08Mpa for 3-6 hours, and then the reaction is continued, and a quantitative amount of sodium sulfate solution is introduced at the same time, until the liquid particle size reaches 3.5-4.0um, and the reaction is completed.

2. The method for preparing a positive electrode material precursor with extremely narrow distribution based on regulating Oswald ripening rate according to claim 1, characterized in that: The total concentration of the mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate is 1.5-2.5 mol / L; the concentration of the sodium hydroxide solution is 5-10 mol / L, and the concentration of the complexing agent is 20-30 mol / L.

3. The method for preparing an extremely narrow distribution positive electrode material precursor based on regulating the Oswald ripening rate according to claim 1, characterized in that: The first stage of temperature rise control plan is: the reaction requires the temperature to rise from 45°C to 80°C, and the required temperature rise range is 4°C-8°C / h.

4. The method for preparing a positive electrode material precursor with extremely narrow distribution based on regulating Oswald ripening rate according to claim 1, characterized in that: The concentration of the first sodium sulfate solution is 5-10 mol / L, the usage amount is 1 / 5 of the flow rate of the mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate, and the usage time is 2-5h.

5. The method for preparing an extremely narrow distribution positive electrode material precursor based on regulating the Oswald ripening rate according to claim 1, characterized in that: The second stage of temperature control requires the temperature to rise to 60-70℃, and the required temperature increase range is 2-5℃ / h.

6. The method for preparing a positive electrode material precursor with extremely narrow distribution based on regulating Oswald ripening rate according to claim 1, characterized in that: The concentration of the second sodium sulfate solution is 5-10 mol / L, the amount used is 1 / 2 of the flow rate of the mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate, and the use time is 2-5h.

7. The method for preparing an extremely narrow distribution positive electrode material precursor based on regulating the Oswald ripening rate according to claim 1, characterized in that: The overall reaction time needs to be maintained between 80-150h.

8. A precursor of a positive electrode material for a lithium-ion battery, prepared by the method according to any one of claims 1 to 7.

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