Cathode material precursor, preparation method and application thereof

Abstract

The application relates to the technical field of positive electrode materials, in particular to a positive electrode material precursor, a preparation method and application thereof. The preparation method comprises the following steps: mixing a soluble metal source for preparing a positive electrode material, a complexing agent and a precipitating agent in a solution containing seeds to obtain a positive electrode material precursor; wherein, during the mixing process, oxygen-containing mixed gas containing an oxidizing gas is also introduced into the mixed solution, the oxygen-containing mixed gas contains the oxidizing gas, and the introduction amount of the oxidizing gas gradually increases per unit time. The oxidizing gas can oxidize metal ions and can be adapted to the process of increasing the primary particle size, so that the oxidation process is uniform and stable, which is beneficial to the uniform distribution of internal pores, and the prepared positive electrode material precursor has large and uniformly distributed primary particle size, large specific surface area and high tap density. The positive electrode material precursor is prepared by the preparation method. The positive electrode material precursor can be used for preparing a positive electrode material and further used for a battery.

Description

Technical Field

[0001] This application relates to the field of cathode material technology, and in particular to cathode material precursors, their preparation methods and applications. Background Technology

[0002] In recent years, the new energy industry has developed rapidly, and cathode materials have received unprecedented development and attention. The upstream cathode material precursors have a significant impact on the performance of cathode materials. Cathode materials, especially ternary materials, have advantages such as high capacity, good cycle performance, and good rate performance. In order to further improve the performance of ternary materials, high-nickel, high-taper, and high-specific-surface precursor materials have been put on the agenda and have become the current and future development trend.

[0003] In actual production, to improve the energy density and charge / discharge performance of batteries, the cathode precursor material needs to possess both high tap density (TD) and high specific surface area (BET). However, tap density and specific surface area are inherently contradictory, especially when large particle size is required, or when uniform primary particle size (nearly uniform particle size with a narrow distribution range) is needed, achieving this goal becomes even more difficult. Taking wet production as an example, some technologies use an oxygen-free substrate and introduce nitrogen gas for nucleation in the early stages of the reaction to reduce agglomeration problems; the entire preparation process is carried out at extremely low ammonia concentrations, which can refine primary particles; however, this technology is designed for small-particle-size products, resulting in severe primary particle hollowing and a low TD (1.21–1.76 g / cm³). 3 Another technique involves adding hydrogen peroxide to a ternary mixed salt solution, and further maintaining oxidation by introducing air or oxygen during the reaction process. This also produces small particles, although the compaction rate is high. However, the main reason is that continuous production results in a wide particle size distribution and low uniformity of primary particle size distribution. Summary of the Invention

[0004] The purpose of this application is to provide a cathode material precursor and its preparation method, aiming to solve the problem that the cathode material precursor prepared by the existing technology cannot simultaneously achieve uniform particle size distribution, large specific surface area and high tap density of primary particles.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a method for preparing a cathode material precursor, comprising the following steps:

[0007] A soluble metal source for preparing cathode materials, along with a complexing agent and a precipitant, are mixed in a seed-containing solution to obtain a cathode material precursor.

[0008] The mixing process also includes introducing an oxygen-containing mixed gas into the mixed solution. This oxygen-containing mixed gas contains oxidizing gases, and the amount of oxidizing gas introduced per unit time gradually increases.

[0009] The preparation method provided in the first aspect of this application involves introducing an oxygen-containing mixed gas, which contains an oxidizing gas, during a mixing process. The amount of oxidizing gas introduced per unit time gradually increases, which oxidizes metal ions and is compatible with the primary particle size increase process, resulting in a uniform and stable oxidation process. This promotes uniform distribution of internal pores, leading to a cathode material precursor with large and uniformly distributed primary particles, a large specific surface area, and high tap density. The preparation method is process-controllable, and the resulting cathode material precursor exhibits stable structure and physicochemical properties.

[0010] Secondly, this application provides a cathode material precursor, which is prepared by the method described in this application.

[0011] The cathode material precursor provided in the second aspect of this application has the characteristics of large specific surface area, high tap density, narrow particle size distribution, and uniform pore distribution inside the primary particles, which is beneficial to improving the various electrochemical performances of the cathode material obtained by the cathode material precursor.

[0012] Thirdly, this application provides a cathode material obtained from a precursor, wherein the precursor includes a cathode material precursor prepared by the preparation method of this application or includes a cathode material precursor of this application.

[0013] The cathode material provided in the third aspect of this application is obtained from the cathode material precursor of this application. Therefore, the cathode material has a large specific surface area and high tap density. It has more reaction interfaces and active sites in the battery and contains more active components per unit volume, which is beneficial to improving rate performance, charge and discharge rate, cycle performance and capacity.

[0014] Fourthly, this application provides a secondary battery, including a positive electrode containing the positive electrode material of this application.

[0015] The secondary battery provided in the fourth aspect of this application has good rate performance, charge / discharge rate, cycle performance and high capacity because it contains the positive electrode material of this application. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a SEM image of the cathode material precursor of Example 1 of this application, magnified 3K times;

[0018] Figure 2 This is a 10K magnification SEM image of the cathode material precursor of Example 1 of this application;

[0019] Figure 3 This is a SEM image of the cathode material precursor of Example 2 of this application, magnified 3K.

[0020] Figure 4 This is a 10K magnification SEM image of the cathode material precursor of Example 2 of this application;

[0021] Figure 5 This is a SEM image of the cathode material precursor of Example 3 of this application, magnified by a factor of 3K.

[0022] Figure 6 This is a 10K magnification SEM image of the cathode material precursor of Example 3 of this application;

[0023] Figure 7 This is a SEM image of a particle section of the cathode material precursor of Example 1 of this application;

[0024] Figure 8 This is a particle fragmentation SEM image of the cathode material precursor of Embodiment 1 of this application. Detailed Implementation

[0025] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0026] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0027] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0028] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0029] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0030] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as μg, mg, g, or kg.

[0031] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0032] The first aspect of this application provides a method for preparing a cathode material precursor, comprising the following steps:

[0033] S10. A soluble metal source for preparing cathode materials, a complexing agent, and a precipitant are mixed in a seed-containing solution to obtain a cathode material precursor.

[0034] The mixing process also includes introducing an oxygen-containing mixed gas into the mixed solution. This oxygen-containing mixed gas contains oxidizing gases, and the amount of oxidizing gas introduced per unit time gradually increases.

[0035] The terms are explained as follows: ① Oxidizing gas: refers to a gas with oxidizing properties that can oxidize metal ions in a mixed solution. ② Oxygen-containing mixed gas: refers to a mixed gas containing an oxidizing gas. Other gaseous components in the mixed gas can be non-reactive gases that do not participate in the reaction that generates the precursor of the positive electrode material. Therefore, the oxygen-containing mixed gas is not entirely composed of oxidizing gases. Compared to the method using pure oxidizing gases, the oxygen-containing mixed gas is more conducive to the uniform oxidation of metal ions in the mixed solution. ③ Gradually increasing amount of oxidizing gas introduced: refers to a gradual increase in the amount of oxidizing gas introduced into the mixed solution, or the volume or mass converted from the amount of gas. In addition, under the premise that the temperature and pressure of the oxidizing gas remain stable, a gradual increase in the amount of oxidizing gas introduced means a gradual increase in the volume or mass of the oxidizing gas introduced. ④ Remaining stable: refers to the actual value always being within or near the desired value within a small range. The deviation is negligible in industrial production and can be considered stable. ⑤ Gradually increasing per unit time: refers to a larger amount introduced per unit time in later units compared to earlier units of time. ⑥ Gradually increasing: This can be a continuous, uninterrupted increase; or it can be a step-like change, remaining stable within each time period, with each subsequent time period increasing compared to the previous one. The explanation for gradually decreasing can be understood similarly. The same interpretation applies to the terms used below.

[0036] This application describes a wet process for preparing cathode material precursors. An oxygen-containing mixed gas is introduced into a mixed solution. The oxidizing gas oxidizes metal ions in the mixed solution, altering bond lengths and expanding the crystal lattice. This facilitates the formation of staggered whiskers on the particle surface during the reaction, resulting in uniform pores and improved particle porosity and morphology control. Furthermore, as the primary particle size increases, the contact area between the primary particles and the external environment also increases. The solid content of the mixed solution also increases, reducing the proportion of effective contact area (reaction sites) between the primary particle surface and the external environment. In this application's preparation method, the amount of oxidizing gas introduced per unit time gradually increases. This adapts to the increasing primary particle size, ensuring a uniform and stable oxidation process and a uniform degree of oxidation within the primary particles. This not only promotes uniform internal pore distribution but also further increases the specific surface area, resulting in larger and more uniformly distributed primary particles in the cathode material precursor, achieving high tap density without requiring particle size gradation. Additionally, the preparation method in this application is process-controllable, and the resulting cathode material precursor exhibits stable structure and physicochemical properties.

[0037] Further testing revealed that, for example Figure 7 , Figure 8As shown, the cathode material precursor prepared by the method of this application has a uniform internal pore distribution and has interconnected channels from the inside to the surface, arranged in a radial pattern. This ensures that the cathode material subsequently prepared also has these interconnected channels from the inside to the surface, arranged in a radial pattern. Therefore, it is also beneficial to the diffusion of lithium ions in the cathode material, reduces process impedance, and greatly improves the electrochemical performance of the cathode material.

[0038] There are various ways to gradually increase the amount of oxidizing gas introduced. For example, in some embodiments, the introduction of oxidizing gas may include any one of the following methods (1) to (3):

[0039] (1) It also includes introducing a protective gas into the mixed solution, wherein the protective gas is continuously introduced and the amount of protective gas introduced per unit time gradually decreases.

[0040] (2) The oxygen-containing mixed gas is continuously introduced, the flow rate of the oxygen-containing mixed gas remains stable, and the volume ratio of oxidizing gas in the oxygen-containing mixed gas gradually increases.

[0041] (3) The oxygen-containing mixed gas is continuously introduced, and the volume ratio of oxidizing gas in the oxygen-containing mixed gas remains stable, while the flow rate of the oxygen-containing mixed gas gradually increases.

[0042] All three methods described above can gradually increase the amount of oxidizing gas introduced per unit time, thereby improving the uniformity of internal pore distribution, particle size distribution, specific surface area, and tap density of the prepared cathode material precursor. The three methods will be explained in detail below:

[0043] In method (1):

[0044] The introduced oxygen-containing mixed gas includes oxidizing gases and non-reactive gases (such as at least one of nitrogen, argon, and helium), and also includes a protective gas. The oxygen-containing mixed gas and the protective gas can be introduced separately to control the oxygen-containing mixed gas and the protective gas, creating the required reaction conditions. This is beneficial for precisely controlling the amount of oxygen introduced, thereby improving the specific surface area, tap density, and particle size distribution uniformity of the obtained cathode material precursor.

[0045] The introduced oxygen-containing mixed gas can be kept at a stable temperature and pressure, with the flow rate gradually increased from 0–20 L / min to 50–100 L / min. In the example, this may include, but is not limited to, starting with flow rates of 0 L / min, 5 L / min, 10 L / min, and 20 L / min, and gradually increasing to 50 L / min, 70 L / min, 90 L / min, and 100 L / min as the final flow rate. This flow rate control achieves a gradual increase in the amount of oxidizing gas introduced per unit time, which is beneficial for improving the specific surface area, tap density, internal pore distribution uniformity, and particle size distribution uniformity of the prepared cathode material precursor. During the process, the flow rate can be increased by 1.00–4.00 L / min every 2–6 hours. In the example, this may include, but is not limited to, increasing by 1.00 L / min, 2.00 L / min, 3.00 L / min, and 4.00 L / min every 2 hours, 4 hours, and 6 hours. This method of increasing the flow rate promotes uniform acceleration and improves the oxidation uniformity during the preparation process. Besides uniform acceleration, non-uniform acceleration is also possible, as long as the oxidizing gas flow rate gradually increases per unit time. The volume percentage of the oxidizing gas in the total gas mixture formed by the oxygen-containing gas mixture and the protective gas can be greater than 0 and less than or equal to 21%. In the example, it can include, but is not limited to, 5%, 10%, 14%, 18%, 21%, and ranges between these values. These proportions of oxidizing gas in the total gas mixture are beneficial for uniform oxidation within the primary particles, preventing over-oxidation, and promoting uniform particle size distribution, uniform internal pore distribution, large specific surface area, and high tap density. The volume percentage of the oxidizing gas can remain stable, gradually increase, or gradually decrease, but it must be ensured that the increased oxidizing gas flow rate, in conjunction with the increased flow rate, can achieve an increase in the oxidizing gas flow rate per unit time. During the process, the temperature and pressure of the oxygen-containing mixed gas can remain stable. For example, in the embodiments, the temperature can be 20–30°C, including but not limited to 20°C, 23°C, 26°C, and 30°C; the pressure can be 0.70–0.80 MPa, including but not limited to 0.70 MPa, 0.72 MPa, 0.75 MPa, 0.77 MPa, and 0.80 MPa. Finally, the oxygen-containing mixed gas can be introduced for 80–120 hours. In the exemplary examples, this can include, but is not limited to, 80 hours, 87 hours, 94 hours, 100 hours, and ranges between these values. The introduction time can be matched with the particle growth time in the mixed solution to improve the uniformity of oxidation inside and on the surface of the particles, i.e., the introduction time is related to the precursor generation reaction time. In this method, the oxygen-containing mixed gas can include at least one of the following: oxygen-nitrogen mixed gas (e.g., compressed air), oxygen-argon mixed gas, oxygen-helium mixed gas, sulfur dioxide-nitrogen mixed gas, and sulfur trioxide-nitrogen mixed gas. Oxidizing gases include at least one of oxygen, sulfur dioxide, and sulfur trioxide, with oxygen being an option.

[0046] In some embodiments, the protective gas in method (1) can also be continuously introduced, and the amount of protective gas introduced per unit time gradually decreases. In this way, the amount of oxidizing gas introduced per unit time gradually increases while the amount of protective gas introduced gradually decreases, which is beneficial to further combine the changes in the protective gas to improve the oxidation uniformity during the preparation process. In particular, in the embodiments, it can be coordinated with the gradual increase of the flow rate of the oxygen-containing mixed gas mentioned above. With one increasing and the other decreasing, a dynamic equilibrium can be reached, which can make the flow rate of the total gas introduced into the mixed solution per unit time relatively stable, which is beneficial to maintaining the stability of the reaction conditions in the reaction system and improving the stability of the reaction. For example, in some embodiments, the flow rate of the protective gas can be gradually reduced from 10 to 30 L / min to 0 L / min. In the exemplary example, it can include, but is not limited to, the starting flow rate of 10 L / min, 20 L / min, 25 L / min, 30 L / min gradually decreasing to 0 L / min as the final flow rate. During the process, the flow rate can be reduced by 0.2 to 5.0 L / min every 2 to 6 hours. In the example, the flow rate can be reduced by 0.2 L / min, 0.6 L / min, 1.0 L / min, 3.0 L / min, and 5.0 L / min every 2 hours, 4 hours, and 6 hours, respectively. This flow rate reduction method is beneficial for uniform rate reduction, facilitating synergy between the protective gas and the oxygen-containing mixed gas, and improving the oxidation uniformity during the preparation process. During the process, the temperature and pressure of the protective gas can also remain stable; specific details can be found in the temperature and pressure range of the oxygen-containing protective gas mentioned above. The protective gas can include at least one of nitrogen, helium, and argon.

[0047] The above method (1) is merely a typical method. Modifying this method still falls under the technical solution of this application. For example, mixing an oxygen-containing mixed gas with a protective gas and then introducing it as a mixed gas into a mixed solution. For example, if the values ​​of the above-mentioned stable temperature, pressure, and flow rate are known, those skilled in the art can use these values ​​to perform corresponding calculations to modify the method to maintain a stable temperature, gradually change the pressure, and make corresponding adjustments to the flow rate. This still falls under the technical solution of this application.

[0048] In method (2), by keeping the flow rate of the oxygen-containing mixed gas stable and gradually increasing the volume percentage of the oxidizing gas, the amount of oxidizing gas introduced per unit time also gradually increases. This is beneficial for obtaining a cathode material precursor with a large specific surface area, high tap density, uniform internal pore distribution, and uniform particle size distribution. Furthermore, keeping the flow rate of the oxygen-containing mixed gas stable is more conducive to creating stable reaction conditions and improving the above-mentioned effects. For example, in some embodiments, the flow rate, temperature, and pressure of the oxygen-containing mixed gas are kept stable, and the volume percentage of the oxidizing gas in the oxygen-containing mixed gas is gradually increased from 0% to 14% to 14% to 21%. In the exemplary examples, the volume percentage can be increased from 0%, 5%, 10%, and 14% as the initial volume percentage to 14%, 16%, 19%, and 21% as the final volume percentage. Such a method of increasing the volume percentage is beneficial for uniform acceleration and for improving the oxidation uniformity during the preparation process. The method of increasing the volume percentage can be uniform (e.g., linearly increasing the percentage) or non-uniform. During the process, the flow rate of the oxygen-containing mixed gas can remain stable, specifically 30–100 L / min. In the example, it may include, but is not limited to, 30 L / min, 40 L / min, 50 L / min, 60 L / min, 80 L / min, and 100 L / min. In this method, the type of oxidizing gas, the type of protective gas, the temperature, and the pressure can refer to the type, temperature, and pressure in the method described in (1) above. The oxygen-containing mixed gas may include at least one of the following: oxygen-nitrogen mixed gas, oxygen-argon mixed gas, oxygen-helium mixed gas, sulfur dioxide-nitrogen mixed gas, and sulfur trioxide-nitrogen mixed gas.

[0049] The above (2) method is only a typical method. Modifying this method still belongs to the technical solution of this application. For example, if the above values ​​of keeping the flow rate, temperature, and pressure stable and the volume ratio of oxidizing gas changing are known, those skilled in the art can use these values ​​to perform corresponding calculations to change the oxygen-containing mixed gas temperature and pressure to keep stable, and the flow rate and the volume ratio of oxidizing gas to gradually increase, or even the flow rate to gradually decrease and the volume ratio of oxidizing gas to rapidly increase, etc., which still belong to the technical solution of this application.

[0050] In method (3), the volume percentage of oxidizing gas in the oxygen-containing mixed gas remains stable, and the flow rate of the oxygen-containing mixed gas gradually increases. Therefore, the amount of oxidizing gas introduced per unit time also gradually increases, which is beneficial to improving the specific surface area, tap density, internal pore distribution, and particle size distribution of the cathode material precursor. For example, in some embodiments, the volume percentage of oxidizing gas in the oxygen-containing mixed gas remains stable, specifically greater than 0 and less than or equal to 21%. In the exemplary examples, it may include, but is not limited to, 5%, 10%, 14%, 18%, and 21%. The temperature and pressure of the oxygen-containing mixed gas can remain stable, and the flow rate of the oxygen-containing mixed gas gradually increases from 0 to 14 L / min to 50 to 100 L / min. In the exemplary examples, it may include, but is not limited to, starting with a flow rate of 0 L / min, 5 L / min, 10 L / min, and 14 L / min and gradually increasing to 50 L / min, 60 L / min, 70 L / min, 90 L / min, and 100 L / min as the final flow rate. This method of increasing the flow rate is beneficial for uniform acceleration and for improving the oxidation uniformity during the preparation process. In addition, the flow rate can be increased uniformly (e.g., linearly) or non-uniformly. In this method, the types of oxygen-containing mixed gas, oxidizing gas, protective gas, temperature, and pressure can refer to the types, temperatures, and pressures in the method described in (1) above.

[0051] The above (3) method is only a typical method. Modifying this method still belongs to the technical solution of this application. For example, if the volume ratio of the oxidizing gas, temperature, pressure and flow rate are known, those skilled in the art can use these values ​​to make corresponding calculations to change the oxygen-containing mixed gas temperature and pressure to remain stable, the flow rate and volume ratio of the oxidizing gas to gradually increase, or even the flow rate to increase rapidly and the volume ratio of the oxidizing gas to gradually decrease, etc., which still belong to the technical solution of this application.

[0052] In addition to the aforementioned gas introduction method, the mixing process in step S10 can maintain certain reaction conditions in the mixed solution, which is beneficial for the metal ions to undergo complexation, precipitation, and oxidation reactions to obtain the cathode material precursor. In some embodiments, the pH of the mixed solution can be 10–11.5, and in exemplary examples, it can include, but is not limited to, 10, 10.5, 11, 11.5, and the range between these values; the mixed solution contains ammonium ions, and the ammonium ion concentration can be 3–4 g / L, and in exemplary examples, it can include, but is not limited to, 3 g / L, 3.3 g / L, 3.6 g / L, and 4 g / L. In some embodiments, the temperature of the mixed solution can be 60–70°C, and in exemplary examples, it can include, but is not limited to, 60°C, 63°C, 66°C, 70°C, and the range between these values. Finally, when the particle size D50 of the cathode material precursor is 15-20 μm (including but not limited to 15 μm, 17 μm, 18 μm, and 20 μm), the feeding is stopped, and the desired cathode material precursor can be obtained. Moreover, the cathode material precursor with such a large particle size still has high internal pore distribution uniformity, particle size distribution uniformity, specific surface area, and tap density.

[0053] Subsequent steps may include aging, washing, and drying to obtain a dry cathode material precursor, which can then be sieved, demagnetized, and used to prepare the cathode material.

[0054] To create the above reaction conditions, the following methods can be used: In some embodiments, the soluble metal source is continuously added to the mixed solution in the form of a metal source solution, with a concentration of 1–2.5 mol / L. In exemplary examples, the concentration may include, but is not limited to, 1 mol / L, 1.5 mol / L, 2 mol / L, and 2.5 mol / L. The soluble metal source can be determined according to the type of cathode material precursor to be prepared. For example, if it is to be used in a sodium battery, the soluble metal source may include an iron source, etc., and if it is to be used in a lithium battery... In the process of preparing ternary cathode material precursors, the soluble metal source can include nickel, cobalt, and manganese sources, such as nickel, cobalt, and manganese sulfates. The molar ratio of Ni, Co, and Mn elements in the nickel, cobalt, and manganese sources can be (80-90):(3-12):(4-12). In exemplary examples, it can include, but is not limited to, (80, 83, 84, or 90):(3, 4, 6, 8, 10, or 12):(4, 5, 7, 9, or 12), and can be selected as 80:10:10, 88:7:5, etc. In some embodiments, the complexing agent includes at least one of ammonia, alkanolamine organic compounds, aminocarboxylate, and ethylenediaminetetraacetic acid (EDTA). In some embodiments, the complexing agent is continuously added to the mixed solution in the form of a complexing agent solution with a concentration of 100–150 g / L. In exemplary embodiments, the concentration may include, but is not limited to, 100 g / L, 1.5 g / L, 2 g / L, and 2.5 g / L. In these embodiments, when the complexing agent is ammonia, the concentration of the complexing agent solution refers to the concentration of NH3·H2O therein. In some embodiments, the precipitant is continuously added to the mixed solution in the form of a precipitant solution containing hydroxide ions with a concentration of 8–15 mol / L. In exemplary embodiments, the concentration may include, but is not limited to, 8 mol / L, 10 mol / L, 12 mol / L, and 15 mol / L. In some embodiments, the precipitant includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium carbonate. By adding the above-mentioned soluble metal source, complexing agent, and precipitant, the reaction can be made uniform, and the desired cathode material precursor can be obtained.

[0055] The aforementioned seed-containing mixed solution can be obtained by reacting a soluble metal source, a complexing agent, and a precipitant. Initial reaction conditions can be created first, and then these raw materials can be added to initiate the seed crystal reaction. Specifically, a protective gas can be introduced into deionized water for 3–8 hours at a flow rate of 100 L / min, while maintaining the deionized water temperature at 60–70°C. The deionized water is continuously stirred at 150–220 rpm. Then, a complexing agent and a precipitant are added to the deionized water, controlling the ammonium ion concentration in the mixed solution to 3–4 g / L and the pH to 11–12. This mixed solution serves as the base solution for the seed crystal reaction, thus successfully creating the initial reaction conditions. The soluble metal source, complexing agent, and precipitant are then continuously added to the base solution while maintaining the protective gas flow, keeping the pH at 11–12 and the ammonium ion concentration at 3–4 g / L. During the feeding process, the initial nitrogen flow rate was maintained at 25–50 L / min for the first 3 hours to ensure no oxidation of the material and allow for gradual reaction to produce seed crystals. Simultaneously, to further promote particle growth, the pH of the mixed solution was lowered to maintain a pH of 10–11.5 during the first 0–2 hours of feeding. After 3 hours from the start of feeding, a mixed solution containing seed crystals was obtained.

[0056] The second aspect of this application provides a cathode material precursor, which is prepared by a method including the cathode material precursor of the present application.

[0057] The cathode material precursor of this application is prepared by the method described in this application. Therefore, the cathode material precursor has a large specific surface area, high tap density, and narrow particle size distribution. The primary particles have uniform pores, which is beneficial to improving the various electrochemical properties of the cathode material obtained from the cathode material precursor.

[0058] Upon testing, the cathode material precursor of this application embodiment possesses at least one of the following characteristics:

[0059] (1) Specific surface area is 15-25 m² 2 / g; may include, but is not limited to, 15m 2 / g、17m 2 / g、20m 2 / g、22m 2 / g, 15m 2 / g and the range between point values.

[0060] (2) Tap density: 1.9–2.3 g / cm³ 3 It can include, but is not limited to, 1.9 g / cm³. 3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 And the range between point values.

[0061] (3) Particle size D50 is 15–20 μm; including but not limited to 15 μm, 17 μm, 19 μm, 20 μm,

[0062] (4) Figure 7 , Figure 8 As shown, the pores inside and on the surface of the primary particles have interconnected channels, which are radially distributed from the interior to the surface. This facilitates the diffusion of lithium ions in the subsequent cathode material, reduces process impedance, and greatly improves the electrochemical performance of the cathode material.

[0063] A third aspect of this application provides a cathode material obtained from a precursor, wherein the precursor includes a cathode material precursor prepared by the preparation method of this application or includes a cathode material precursor of this application.

[0064] The cathode material in this application embodiment is obtained from the cathode material precursor of this application embodiment. Therefore, the cathode material has a large specific surface area and high tap density, resulting in more reaction interfaces and active sites in the battery. Furthermore, it contains more active components per unit volume, which is beneficial for improving rate performance, charge / discharge rate, cycle performance, and capacity. The cathode material precursor can be prepared by methods including, but not limited to, sintering with a lithium source.

[0065] A fourth aspect of this application provides a secondary battery, including a positive electrode containing the positive electrode material of this application.

[0066] The secondary battery of this application embodiment contains the positive electrode material of this application embodiment, and therefore has good rate performance, charge and discharge rate, cycle performance and high capacity.

[0067] The following description is based on specific embodiments.

[0068] Example 1

[0069] This embodiment provides a cathode material precursor and its preparation method.

[0070] The cathode material precursor is a nickel-cobalt-manganese ternary cathode material precursor, in which the molar ratio of Ni:Co:Mn is 87:5:8. The pores inside the primary particles are uniformly distributed, and the primary particles are radially distributed from the inside to the surface.

[0071] The preparation method of the cathode material precursor includes the following steps:

[0072] S1: Preparation of seed-containing mixed solution

[0073] A nickel-cobalt-manganese salt solution with a total metal ion concentration of 2 mol / L (120 g / L) was prepared using nickel sulfate, cobalt sulfate, and manganese sulfate, wherein the molar ratio of nickel, cobalt, and manganese was 87:5:8. A 10.5 mol / L sodium hydroxide solution was prepared as a precipitant solution, and a 125 g / L ammonia solution was prepared as a complexing agent solution (concentration refers to the concentration of NH3·H2O).

[0074] Submerged nitrogen protective gas was introduced into the sealed reactor for 4 hours at a flow rate of 100 L / min. During the process, deionized water was added to the reactor to submerge the intermediate layer of the stirrer. The stirrer was started at 200 rpm, and the temperature was controlled at 60℃.

[0075] Complexing agent solution was added to the reactor sequentially to control the ammonia value at 3.5 g / L (i.e., the concentration of NH3·H2O). Precipitating agent solution was added to adjust the pH of the system to 11.50, which served as the base liquid and starting conditions for the reaction.

[0076] Nickel-cobalt-manganese salt solution, sodium hydroxide solution, and ammonia solution were continuously added to the reactor while maintaining the flow of inert gas. During this process, the pH of the system was maintained at 11.50, and the ammonia concentration at 3.50 g / L. To facilitate further particle growth, the pH was lowered to 10.80 after 20 minutes of operation. For the initial 3 hours after startup, a nitrogen flow rate of 30 L / min was maintained to prevent oxidation of the material, resulting in a seed-containing mixed solution.

[0077] S2: An oxygen-containing mixed gas is introduced to carry out the reaction.

[0078] After 3 hours of operation, an oxygen-containing mixed gas (compressed air) is introduced at 25°C and 0.72 MPa. A protective gas (nitrogen) is also introduced. The oxygen-containing mixed gas and the protective gas are introduced into the mixed solution separately. From 3 to 30 hours after operation, the nitrogen flow rate gradually decreases from 30 L / min to 0: 3–5 hours (23 L / min), 5–11 hours (20 L / min), 11–17 hours (15 L / min), 17–22 hours (13 L / min), 22–27 hours (10 L / min), and 27–30 hours (6 L / min). After 30 hours of operation, the nitrogen flow rate is 0. Simultaneously, starting 3 hours after startup, compressed air is introduced into the liquid layer, with the flow rate gradually increased from 10 L / min to 80 L / min, an average increase of 2.0 L / min every 3 hours. Once the flow rate reaches 80 L / min, this rate is maintained until the particle size reaches the target value of 15 μm. At this point, the reactor is shut down, meaning the addition of nickel-cobalt-manganese salt solution, sodium hydroxide solution, and ammonia solution is stopped, and the compressed air supply is also stopped. Alternatively, nitrogen can be introduced after shutdown. After 60 minutes of shutdown, the particle size is re-measured to confirm no abnormalities (within ±0.5 μm of the target value), yielding a slurry containing the cathode material precursor. Since large particles may crack later, the rotation speed can be adjusted in a timely manner throughout the reaction process to prevent particle breakage.

[0079] S3: Follow-up processing

[0080] The slurry is placed in an aging tank for aging, and then the slurry in the aging tank is pumped into a washing device and washed with a sodium hydroxide solution with a concentration of 30-80 g / L. The washed ternary precursor filter cake is placed in an oven for static drying. After the moisture content is qualified, it is dried to obtain the cathode material precursor.

[0081] Example 2

[0082] This embodiment provides a cathode material precursor and its preparation method.

[0083] The cathode material precursor is a nickel-cobalt-manganese ternary cathode material precursor, in which the molar ratio of Ni:Co:Mn is 88:7:5. The pores inside the primary particles are uniformly distributed, and the primary particles are radially distributed from the inside to the surface.

[0084] The preparation method of the cathode material precursor differs from that in Example 1 only in that the nitrogen flow rate reduction method in step S2 is changed to 3–5 h (15 L / min), 5–11 h (12 L / min), 11–17 h (10 L / min); 17–22 h (8 L / min); 22–27 h (5 L / min); 27–30 h (3.0 L / min), and the nitrogen flow rate is 0 after 30 h of operation. Simultaneously, starting from 3 h of operation, compressed air is introduced into the liquid submerged layer, with the flow rate gradually increased from 10 L / min to 80 L / min, increasing by an average of 2.5 L / min every 3 h. Once the flow rate reaches 80 L / min, this flow rate is maintained until the particle size reaches the target value of 16.5 μm, at which point the operation is stopped. Everything else remains the same.

[0085] Example 3

[0086] This embodiment provides a cathode material precursor and its preparation method.

[0087] The cathode material precursor is a nickel-cobalt-manganese ternary cathode material precursor, in which the molar ratio of Ni:Co:Mn is 88:5:7. The pores inside the primary particles are uniformly distributed, and the primary particles are radially distributed from the inside to the surface.

[0088] The preparation method of the cathode material precursor differs from that in Example 1 only in that the nitrogen flow rate reduction method in step S2 is changed to 3-4h (15L / min), 4-8h (12L / min), 8-15h (10L / min); 15-20h (8L / min); 20-25h (5L / min); 25-30h (3.0L / min), and the nitrogen flow rate is 0 after 30h of operation. Simultaneously, starting from 3h of operation, compressed air is introduced into the liquid submerged layer, with the flow rate gradually increased from 15L / min to 100L / min, increasing by an average of 3.0L / min every 3h. Once the flow rate reaches 100L / min, this flow rate is maintained until the particle size reaches the target value of 18.5μm, at which point the operation is stopped. Everything else remains the same.

[0089] Example 4

[0090] This embodiment provides a cathode material precursor and its preparation method.

[0091] The preparation method differs from Example 1 only in that: in step S2, the compressed air flow rate is changed to gradually increase from 15 L / min to 90 L / min, with an average increase of 2.0 L / min every 3 hours, and the flow rate is maintained at 90 L / min after reaching that point. Everything else is the same.

[0092] The cathode material precursor was prepared by the method described in this embodiment.

[0093] Example 5

[0094] This embodiment provides a cathode material precursor and its preparation method.

[0095] The preparation method differs from that of Example 1 only in that, in step S2, the flow rate of the oxygen-containing protective gas is increased by an average of 2.0 L / min every 2 hours. Everything else is the same.

[0096] The cathode material precursor was prepared by the method described in this embodiment.

[0097] Example 6

[0098] This embodiment provides a cathode material precursor and its preparation method.

[0099] The preparation method differs from Example 1 only in that, in step S2, the flow rate of nitrogen gas is maintained at 30 L / min without decreasing. Everything else is the same.

[0100] The cathode material precursor was prepared by the method described in this embodiment.

[0101] Example 7

[0102] This embodiment provides a cathode material precursor and its preparation method.

[0103] The preparation method differs from Example 1 only in that, in step S2, instead of compressed air and nitrogen, only another oxygen-containing mixed gas is introduced. This oxygen-containing mixed gas contains only oxygen and nitrogen, is at a temperature of 25°C, a pressure of 0.75 MPa, and its flow rate remains stable at 70 L / min. Furthermore, the volume percentage of oxygen in the oxygen-containing mixed gas is gradually increased from 8% to 21%, increasing by 1% every 6 hours until it reaches 21%. At this point, the percentage is no longer increased, and the oxidizing gas is continued to be introduced while maintaining this percentage until the particle size reaches the same level as in Example 1, at which point the process is stopped. Everything else is the same.

[0104] The cathode material precursor was prepared by the method described in this embodiment.

[0105] Example 8

[0106] This embodiment provides a cathode material precursor and its preparation method.

[0107] The preparation method differs from Example 1 only in that, in step S2, instead of compressed air and nitrogen, only another oxygen-containing mixed gas is introduced. This oxygen-containing mixed gas contains only oxygen and nitrogen, is at a temperature of 25°C, and a pressure of 0.75 MPa. The oxygen volume percentage in the mixed gas remains stable at 15%, and the flow rate is gradually increased from 40 L / min to 80 L / min, increasing by 2 L / min every 4 hours until it reaches 80 L / min. At this point, the flow rate is no longer increased, and the oxidizing gas is continued to be introduced at this flow rate until the particle size reaches the same level as in Example 1, at which point the process is stopped. Everything else remains the same.

[0108] The cathode material precursor was prepared by the method described in this embodiment.

[0109] Comparative Example 1

[0110] This comparative example provides a cathode material precursor and its preparation method.

[0111] The only difference between the preparation method and Example 1 is that the flow rate of compressed air introduced in step S2 is kept constant at 70 L / min, rather than gradually increasing. Therefore, the amount of oxygen introduced per unit time remains unchanged. Everything else is the same.

[0112] The cathode material precursor was prepared by the method described in this embodiment.

[0113] Comparative Example 2

[0114] This comparative example provides a cathode material precursor and its preparation method.

[0115] The preparation method differs from Example 1 only in that the flow rate of compressed air introduced in step S2 is not gradually increased, but gradually decreased, from 80 L / min to 10 L / min, a decrease of 20 L / min every 3 hours on average. Therefore, the amount of oxygen introduced per unit time gradually decreases. Everything else is the same.

[0116] The cathode material precursor was prepared by the method described in this embodiment.

[0117] Relevant performance tests and results analysis

[0118] 1. Morphological testing

[0119] The morphology of the cathode material precursors of Examples 1 to 8 and Comparative Examples 1 and 2 was measured using a scanning electron microscope. The results are as follows: Figures 1-6 As shown. Among them. Figure 1 , Figure 2 These are SEM images of the cathode material precursor from Example 1 at magnifications of 3K and 10K. Figure 3 , Figure 4 These are SEM images of the cathode material precursor from Example 2 at magnifications of 3K and 10K. Figure 5 , Figure 6 The images shown are SEM images of the cathode material precursor from Example 3 at magnifications of 3K and 10K. It can be seen that the cathode material precursor prepared by the method described in this application has a surface with scattered whiskers, numerous pores, and uniform particle size distribution, exhibiting rounded particles and excellent sphericity.

[0120] In addition, the precursors of each cathode material were sliced ​​and fragmented for analysis. The primary particle morphology of the cathode material precursor in Example 1 is as follows: Figure 7 , Figure 8As shown, the pores inside the particles are evenly distributed. Figure 8 The channels circled in the diagram show that the primary particles are arranged radially from the interior to the surface. This is highly beneficial for maintaining this structure in subsequent cathode materials, facilitating lithium-ion diffusion, reducing process impedance, and significantly improving the electrochemical performance of the material.

[0121] 2. Other physicochemical property tests:

[0122] The particle size, specific surface area, and tap density of the above-mentioned cathode material precursor were measured using a laser particle size analyzer, a specific surface area analyzer, and a tap density analyzer, respectively. The test results are shown in Table 1 below.

[0123] Table 1

[0124]

[0125] As can be seen from Table 1, the preparation method of this application, by gradually increasing the amount of oxygen introduced per unit time, results in a cathode material precursor with larger particle size, larger specific surface area, and higher tap density compared to the preparation method of the comparative example. Furthermore, the combination of these precursors... Figure 7 , Figure 8 It can be seen that the primary pore distribution of the cathode material precursor prepared by the method of this application is uniform, indicating uniform internal oxidation. In Comparative Example 1, the amount of oxygen introduced per unit time remains the same, but its degree of oxidation and the total amount introduced are much greater than those of Example 1. This results in a porous overall morphology of the cathode material precursor, with finer grain whiskers. Although the specific surface area is large, the tap density is quite low, which is not conducive to improving the capacity and other properties of the cathode material subsequently prepared.

[0126] Compared with Example 5, Example 1 shows that if the rate of increase in the amount of oxygen introduced per unit time is within a certain range, it will be beneficial to match the growth rate of particles and improve the performance of the cathode material precursor.

[0127] Compared with Example 6, Example 1 shows that in method (1), gradually reducing the flow rate of the protective gas is beneficial to the synergistic effect of gradually increasing the flow rate of the oxygen-containing mixed gas, which is beneficial to improving the performance of the cathode material precursor.

[0128] As can be seen from Examples 1 to 4, 7 and 8, the preparation method of this application can adopt a variety of ways of introducing oxidizing gas. As the amount of oxygen introduced per unit time gradually increases, it is beneficial to improve the performance of the cathode material precursor.

[0129] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a cathode material precursor, characterized in that, Includes the following steps: S1: Preparation of seed-containing mixed solution A nickel-cobalt-manganese salt solution with a total metal ion concentration of 2 mol / L was prepared using nickel sulfate, cobalt sulfate, and manganese sulfate, wherein the molar ratio of nickel, cobalt, and manganese was 87:5:

8. A sodium hydroxide solution with a concentration of 10.5 mol / L was prepared as a precipitant solution, and an ammonia solution with a concentration of 125 g / L was prepared as a complexing agent solution. Submerged nitrogen protective gas was introduced into the sealed reactor for 4 hours at a flow rate of 100 L / min. During the process, deionized water was added to the reactor to submerge the middle layer of the stirrer. The stirrer was turned on at 200 rpm and the temperature was controlled at 60℃. Complexing agent solution was added to the reaction vessel in sequence to control the ammonia value at 3.5 g / L. Precipitating agent solution was added to adjust the pH of the system to 11.50, which served as the base liquid and starting conditions for the reaction. Nickel-cobalt-manganese salt solution, sodium hydroxide solution, and ammonia solution were continuously added to the reactor while maintaining the inert gas supply. During this period, the pH of the system was maintained at 11.50 and the ammonia value at 3.50 g / L. To allow for further particle growth, the pH was lowered to 10.80 after 20 minutes of operation. For the first 3 hours after startup, the nitrogen flow rate was maintained at 30 L / min to ensure that no oxidation of the material occurred, resulting in a mixed solution containing seed crystals. S2: An oxygen-containing mixed gas is introduced to carry out the reaction. Three hours after startup, an oxygen-containing gas mixture (compressed air) at 25°C and 0.72 MPa is introduced. Nitrogen gas is also introduced. The oxygen-containing gas mixture and protective gas are introduced into the mixed solution separately. From 3 to 30 hours after startup, the nitrogen flow rate is gradually reduced from 30 L / min to 0. Specifically, the flow rate is 23 L / min from 3 to 5 hours, 20 L / min from 5 to 11 hours, 15 L / min from 11 to 17 hours, 13 L / min from 17 to 22 hours, and [missing information - likely a flow rate range]. The flow rate is 10 L / min; the flow rate is 6 L / min from 27 to 30 hours after startup, and the nitrogen flow rate is 0 after 30 hours of startup; at the same time, starting from 3 hours after startup, compressed air is introduced into the liquid, and the flow rate is gradually increased from 15 L / min to 90 L / min, with an average increase of 2.0 L / min every 3 hours. After the flow rate reaches 90 L / min, the flow rate is maintained until the particle size reaches the target value of 15 μm, then the machine is stopped, that is, the addition of nickel cobalt manganese salt solution, sodium hydroxide solution, and ammonia solution is stopped, and the introduction of compressed air is also stopped. In addition, nitrogen gas was introduced again after the machine was shut down. After 60 minutes of shutdown, the particle size was retested and confirmed to be normal. According to the target value of ±0.5μm, a slurry containing the cathode material precursor was obtained. S3: Follow-up processing The slurry is placed in an aging tank for aging, and then the slurry in the aging tank is pumped into a washing device and washed with a sodium hydroxide solution with a concentration of 30-80 g / L. The washed ternary precursor filter cake is placed in an oven for static drying. After the moisture content is qualified, it is dried to obtain the cathode material precursor.

2. A cathode material precursor, characterized in that: It is prepared by the preparation method described in claim 1.

3. A cathode material, characterized in that: The precursor is obtained by including the precursor, which includes the cathode material precursor prepared by the preparation method of claim 1 or the cathode material precursor of claim 2.

4. A secondary battery, comprising a positive electrode, characterized in that: The positive electrode contains the positive electrode material as described in claim 3.

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