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, which comprises the following steps: a soluble metal source for preparing a positive electrode material is subjected to pre-oxidation treatment with a first oxidizing agent to obtain a pre-oxidized metal ion solution; the pre-oxidized metal ion solution, a complexing agent and a precipitating agent are subjected to first mixing treatment to obtain a seed-containing mixed solution; the seed-containing mixed solution is continuously added with at least the pre-oxidized metal ion solution, the complexing agent and the precipitating agent for second mixing treatment to obtain a crystal-containing mixed solution; the crystal-containing mixed solution is continuously added with at least the precipitating agent for third mixing treatment to obtain the positive electrode material precursor; and the step of adding a second oxidizing agent is further included in at least one mixing treatment process. The steps of pre-oxidation treatment and second oxidizing agent addition can make the prepared precursor particles communicate with the surface, improve the specific surface area, and can be accurately controlled and customized, and the sphericity is good.

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 the liquid-phase synthesis of cathode material precursors, especially ternary precursors, batch processes are often used to maintain consistency and ensure uniform particle residence time in the reactor. To achieve better sphericity, the solid content is often increased to reduce particle growth rate and extend growth time. High-nickel single-crystal cathodes are typically produced using high-nickel small-particle precursors to achieve better solid-phase reactivity. However, increasing the solid content can lead to prolonged growth time and increased pressure during particle movement within the reactor, resulting in a denser precursor surface with a smaller specific surface area. This negatively impacts the diffusion of lithium and sodium ions during subsequent sintering, thus affecting the material's electrochemical performance. Conversely, a large specific surface area can improve the rate performance of cathode materials; therefore, increasing the specific surface area of ​​the precursor to improve lithium and sodium ion diffusion is essential.

[0003] To address this, some technical solutions involve introducing air or oxygen into the reaction process to oxidize metals such as manganese and cobalt, thereby altering their morphology and increasing their specific surface area. However, due to the varying degrees of oxygen supply (the amount of fresh oxidizing gas entering) and contact volume (the amount of oxidizing gas in contact with the material) under conditions of slight positive pressure within the reactor, waste gas collection port, ammonia, and stirring, the oxidation degree and range are uncontrollable. Therefore, this method is difficult to precisely control, resulting in a limited and unpredictable increase in the specific surface area of ​​the cathode material precursor. Another technical solution increases the specific surface area by reducing the solid content. However, reducing the solid content inevitably reduces the single-reactor capacity for a given reactor volume, and products from different reactors will vary due to control factors, leading to poor product consistency. Furthermore, without high solid content, reduced frictional contact between particles also worsens particle sphericity, affecting the structural stability and ion conductivity of the cathode material obtained from the precursor. Summary of the Invention

[0004] The purpose of this application is to provide a cathode material precursor and its preparation method, which aims to solve the problem that existing preparation methods are difficult to accurately control and improve the specific surface area of ​​the cathode material precursor while ensuring sphericity.

[0005] Another objective of this application is to provide the application of cathode material precursors, aiming to solve the problems of poor rate performance, charge-discharge rate and cycle performance of cathode materials and secondary batteries produced by existing technologies.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0007] Firstly, a method for preparing a cathode material precursor. The preparation method includes the following steps:

[0008] A soluble metal source used to prepare the cathode material is pre-oxidized with a first oxidant to obtain a pre-oxidized metal ion solution.

[0009] The solution containing pre-oxidized metal ions is first mixed with a complexing agent and a precipitant to obtain a seed-containing mixed solution.

[0010] Continue to add at least a pre-oxidized metal ion solution, a complexing agent, and a precipitant to the seed crystal mixed solution for a second mixing treatment to obtain a crystal-containing mixed solution;

[0011] Continue to add at least a precipitant to the crystalline mixed solution for a third mixing treatment to obtain the cathode material precursor;

[0012] The process of at least one of the mixing processes in the first mixing process, the second mixing process, and the third mixing process further includes the step of adding a second oxidant.

[0013] The preparation method provided in the first aspect of this application involves a pre-oxidation treatment, which facilitates the early oxidation of at least some metal elements, alters the bond lengths of these metal elements, and adjusts the lattice parameters of the crystal during subsequent seed formation and growth. This helps to expand the lattice and open channels. Then, a second oxidant is added during at least one mixing process, achieving localized controlled oxidation. Therefore, the resulting cathode material precursor particles have interconnected channels and pores from their interior to their surface, increasing the specific surface area of ​​the precursor. More importantly, it allows for precise control of the oxidation amount, thereby precisely controlling the morphology of the primary particles and the specific surface area. This allows for the customization of cathode material precursors with the desired specific surface area, with high control precision and a wide range of customizable specific surface areas. Finally, the cathode material precursor particles prepared by the method of this application are rounded and have good sphericity. The preparation process is controllable, and the resulting cathode material precursor has stable structure and physicochemical properties. The corresponding cathode material obtained after sintering is a single crystal with excellent electrochemical performance.

[0014] Secondly, this application provides a cathode material precursor. The cathode material precursor is prepared by a method including the preparation method of the cathode material precursor of this application.

[0015] The cathode material precursor provided in the second aspect of this application is prepared by the above-described method. Therefore, the precursor particles have interconnected channels and pores from the interior to the surface, resulting in a high specific surface area. The specific surface area of ​​each particle is highly consistent and can be precisely controlled. The primary precursor particles are rounded with good sphericity, and there is little phenomenon of two spheres adhering to each other or multiple spheres being connected in series.

[0016] Thirdly, this application provides a cathode material obtained from a precursor, wherein the cathode material has a single crystal structure, and the precursor includes a cathode material precursor obtained by the preparation method of this application or includes a cathode material precursor of this application.

[0017] The cathode material provided in the third aspect of this application is obtained by using the cathode material precursor of this application and with appropriate sintering process. The resulting cathode material has a single crystal structure, good sphericity, and large specific surface area. It has more reaction interfaces and active sites in the battery, which is beneficial to improving rate performance, charge and discharge rate and cycle performance.

[0018] Fourthly, this application provides a secondary battery, including a positive electrode containing the positive electrode material of this application.

[0019] The secondary battery provided in the fourth aspect of this application has good rate performance, charge / discharge rate and cycle performance because it contains the positive electrode material of this application. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is a flowchart of a preparation method according to an embodiment of this application;

[0022] Figure 2 This is a SEM image of the cathode material precursor of Embodiment 1 of this application;

[0023] Figure 3 This is a SEM image of the cathode material precursor of Comparative Example 1 of this application. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The first aspect of this application provides a method for preparing a cathode material precursor, comprising the following steps:

[0032] S10: The soluble metal source used to prepare the cathode material is pre-oxidized with the first oxidant to obtain a pre-oxidized metal ion solution (the pre-oxidized metal ion solution can be referred to as metal liquid in the following text);

[0033] S20: The molten metal is mixed with a complexing agent and a precipitant to obtain a seed-containing mixed solution;

[0034] S30: Continue to add at least liquid metal, complexing agent and precipitant to the seed crystal mixed solution for a second mixing treatment to obtain a crystal-containing mixed solution;

[0035] S40: Continue to add at least a precipitant to the crystalline mixed solution for a third mixing treatment to obtain the cathode material precursor;

[0036] The process of at least one of the mixing processes in steps S20 (first mixing process), S30 (second mixing process), and S40 (third mixing process) further includes the step of adding a second oxidant.

[0037] The preparation method of this application pre-oxidizes the metal elements in the soluble metal source in step S10, oxidizing at least some of the metal elements in advance, changing the bond length of these metal elements, and adjusting the lattice parameters of the crystal during subsequent seed formation and growth, which is beneficial to expanding the lattice and opening channels. In existing preparation methods, metal ions are mixed simultaneously with complexing agents, precipitants, and oxidants during the reaction, resulting in large-scale oxidation of the metal ions. As the reaction proceeds, the seed crystals are gradually encapsulated by dense crystals, blocking the internal and external channels. However, this application achieves localized controlled oxidation rather than large-scale oxidation through pre-oxidation combined with subsequent reactions. As the reaction proceeds, the seed crystals are gradually encapsulated by crystals that retain channels, thus obtaining a cathode material precursor with interconnected channels and pores from the inside to the surface, increasing the specific surface area of ​​the cathode material precursor. Furthermore, during the three mixing processes in steps S20, S30, and S40, due to the mixing of the molten metal, complexing agent, and precipitant, and with the formation of seed crystals and crystal growth, at least one mixing process also includes the addition of a second oxidizing agent (for example, when a second oxidizing agent is added during the first mixing process, refer to...). Figure 1 This method can further oxidize at least one portion of the metal elements in the interior, middle layer, and surface of the prepared cathode material precursor particles, further promoting the connectivity of channels from the particle interior to the surface and increasing the specific surface area. More importantly, by combining the degree of pre-oxidation treatment in step S10 with the step of selecting the addition of a second oxidant, the amount of oxidation can be precisely controlled, thereby precisely controlling the morphology of the primary particles of the cathode material precursor and precisely regulating the specific surface area. It allows for the customization of cathode material precursors with the required specific surface area, and the control precision is high with a large customization range for specific surface area. Finally, the preparation method of this application embodiment does not require reducing the solid content as in the prior art, which is beneficial for obtaining primary particles of the cathode material precursor with roundness and good sphericity. The preparation method of this application embodiment has a controllable process, and the obtained cathode material precursor has stable structure and physicochemical properties. The corresponding cathode material obtained after sintering is a single crystal with excellent electrochemical performance.

[0038] Step S10:

[0039] Step S10 is a step of pre-oxidizing the metal elements in the soluble metal source. The soluble metal source can be determined according to the type of precursor. For example, when the precursor is a cathode material precursor for sodium batteries, the soluble metal source can be, but is not limited to, soluble iron-manganese compounds, copper-manganese compounds, copper-iron-manganese compounds, zinc-iron-manganese compounds, etc. For example, when the precursor is a cathode material precursor for lithium batteries, it can be, but is not limited to, a nickel-cobalt-manganese ternary cathode material precursor. The soluble metal source can include nickel sources, cobalt sources, and manganese sources. The Ni and C in the nickel source, cobalt source, and manganese source... The molar ratio of o to Mn can be (30-98):(1-40):(1-40). In the example, the molar ratio can include, but is not limited to, 30:40:40, 50:30:20, 70:20:10, 90:5:5, 96:2:2, and 98:1:1. These molar ratios can be used to prepare precursors with corresponding molar ratios of Ni, Co, and Mn. When the nickel molar ratio is high, it is difficult to improve the specific surface area of ​​the high-nickel precursor by existing preparation methods, and the specific surface area of ​​the particles is poor. However, the preparation method of this application is still applicable.

[0040] In some embodiments, the first oxidant may include at least one of H₂O₂, peracetic acid, sodium percarbonate, and ammonium persulfate. These first oxidants are beneficial for pre-oxidizing soluble metal sources, thereby increasing the specific surface area of ​​the resulting precursor. For example, when the soluble metal source is a nickel source, a cobalt source, or a manganese source, the pre-oxidation involves reactions that primarily oxidize cobalt and manganese ions to higher valence states. In some embodiments, the molar ratio of the first oxidant to the metal element contained in the soluble metal source is (0.1–10):1000; in exemplary examples, it may include, but is not limited to, 0.1:1000, 1:1000, 3:1000, 5:1000, and 10:1000. At these molar ratios, the amount of the first oxidant is small, which is beneficial for the pre-oxidation treatment to be a localized, minute micro-oxidation rather than large-scale oxidation. This helps ensure the uniformity of the feed reaction and achieves the aforementioned pre-oxidation effect, making the particle interior and surface interconnected, increasing the specific surface area. Furthermore, it facilitates precise control of the specific surface area by combining the step of selecting the addition of the second oxidant. The pre-oxidation treatment involves thoroughly mixing and dispersing the soluble metal source and the first oxidant for a redox reaction until the first oxidant is exhausted. To improve the pre-oxidation effect, the soluble metal source and the first oxidant can be separately prepared into solutions, then mixed for pre-oxidation treatment to obtain a liquid metal.

[0041] Step S20:

[0042] Step S20 is the step of obtaining a seed-containing mixed solution through a first mixing treatment to form seed crystals. This involves mixing a liquid metal with a complexing agent and a precipitating agent, where metal ions form seed crystals through complexation and precipitation reactions. Furthermore, initial reaction conditions can be created to promote seed crystal formation. Therefore, in some embodiments, step S20 may include:

[0043] Step S21: Prepare the base solution;

[0044] Step S22: Add the molten metal, complexing agent, and precipitant to the base liquid for the first mixing treatment described above.

[0045] In step S21, preparing the base solution can create the initial reaction conditions for step S22. The base solution includes at least one of the following: ① A temperature of 30–80°C; in the examples, this may include, but is not limited to, 30°C, 40°C, 45°C, 50°C, 60°C, 70°C, and 80°C. ② A pH of 7.8–13; in the examples, this may include, but is not limited to, 7.8, 10.6, 11, 11.9, and 13. ③ The base solution contains ammonium ions, with an ammonium ion concentration of 0.1–0.8 mol / L; in the examples, this may include, but is not limited to, 0.1 mol / L, 0.25 mol / L, 0.35 mol / L, 0.65 mol / L, and 0.8 mol / L.

[0046] These properties of the base liquid can promote the formation of subsequent seed crystals. It can be prepared by water, complexing agent, and precipitant. The water can be heated, and a protective gas (at least one of nitrogen, helium, and argon, such as 99.99% nitrogen) can be passed under the liquid to reduce the dissolved oxygen content in the water. Then, a complexing agent is added, and finally, a precipitant is added.

[0047] In this embodiment, in step S22, a protective gas can be continuously introduced underwater to prevent large-scale oxidation. The method of adding the molten metal, complexing agent, and precipitant to the base liquid can be as follows: first, the base liquid is placed in the reaction chamber, and then the molten metal, complexing agent, and precipitant are continuously added to the reaction chamber, allowing the molten metal to sequentially contact the complexing agent and precipitant and undergo complexation and precipitation reactions in sequence. Specifically, the mixed solution (i.e., the reaction system) in the reaction chamber can be stirred and circulated, and the continuously added positions can be set sequentially. In an example, for instance, like a clock, the added positions of the molten metal, complexing agent, and precipitant can be set sequentially at 0 o'clock, 3 o'clock, and 6 o'clock (or, in terms of angle, 0°, 90°, and 180°, the specific positions are not limited to these, as long as the order is correct), and the mixed solution in the reaction chamber is stirred clockwise, so that the liquid flow of the mixed solution sequentially contacts the molten metal, complexing agent, and precipitant added to the reaction chamber. This method creates a time difference between the molten metal and the complexing and precipitating agents, which is beneficial for them to come into contact in the order described above. The metal ions first complex and then precipitate, making the millisecond-level reaction process stable and orderly, which is conducive to uniform reaction.

[0048] In the embodiments, the concentration of metal ions contained in the molten metal can be 1 to 2 mol / L; in the exemplary examples, it can include, but is not limited to, 1 mol / L, 1.3 mol / L, 1.7 mol / L, and 2 mol / L; the molten metal can be continuously added to the reaction chamber, and the flow rate can be 1 to 10 L / h; in the exemplary examples, it can include, but is not limited to, 1 L / h, 2 L / h, 4 L / h, 5 L / h, and 10 L / h.

[0049] In the embodiments, the complexing agent may also be continuously added to the reaction chamber in the form of a complexing agent solution, which may contain ammonium ions with a concentration of 1–15 mol / L; in the exemplary examples, it may include, but is not limited to, 1 mol / L, 2 mol / L, 6 mol / L, 8 mol / L, and 15 mol / L; the complexing agent flow rate may be 0.1–0.8 L / h; in the exemplary examples, it may include, but is not limited to, 0.1 L / h, 0.23 L / h, 0.4 L / h, 0.58 L / h, and 0.8 L / h.

[0050] In the embodiments, the precipitant can also be continuously added to the reaction chamber in the form of a precipitant solution. The precipitant solution may contain hydroxide ions, with a hydroxide ion concentration of 2–12 mol / L; in the exemplary examples, this may include, but is not limited to, 2 mol / L, 5 mol / L, 10 mol / L, and 12 mol / L. The precipitant flow rate can be 1–5 L / h; in the exemplary examples, this may include, but is not limited to, 1 L / h, 2 L / h, 2.4 L / h, 4 L / h, and 5 L / h. It is important to note that the flow rate of the molten metal should be determined first based on the reaction time, the flow rate of the precipitant should be calculated using the reaction formula, and finally the flow rate of the complexing agent should be determined.

[0051] The raw materials are in solution form, and the concentrations and flow rates of the molten metal, complexing agent solution, and precipitant solution are conducive to further stabilizing and ordering the above reaction. The flow rate can be adjusted to make the amount of feed at each stage controllable. The flow rate can also be adjusted to regulate the pH and ammonium concentration of the reaction system, thereby controlling the reaction progress.

[0052] In some embodiments, the complexing agent includes at least one selected from ammonium carbonate, ammonium sulfate, and ammonia. The precipitating agent includes at least one selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium phosphate, and potassium sulfite. These complexing and precipitating agents can provide the corresponding ammonium ions and hydroxide ions in the reaction system, and can adjust the concentration of ammonium ions and pH in the reaction system to create the appropriate reaction conditions.

[0053] In some embodiments, by adjusting and controlling the feeding method or feeding ratio of the pre-oxidized metal ion solution, complexing agent, and precipitant, the above-mentioned first mixing treatment can be created to form at least one of the following reaction conditions for seed crystal formation: ① The mixed solution in the reaction chamber contains ammonium ions, with an ammonium ion concentration of 0.1–0.8 mol / L; in exemplary examples, this may include, but is not limited to, 0.1 mol / L, 0.3 mol / L, 0.6 mol / L, and 0.8 mol / L. ② The pH of the mixed solution in the reaction chamber is 7.8–13; in exemplary examples, this may include, but is not limited to, 7.8, 9.4, 9.9, 11, and 13. ③ The temperature can be 30–80°C; in exemplary examples, this may include, but is not limited to, 30°C, 40°C, 50°C, 65°C, and 80°C. ④ The time can be 5–20 h; in exemplary examples, this may include, but is not limited to, 5 h, 8 h, 10 h, 15 h, and 20 h. If the time is too long, the grains will be squeezed and move a lot, resulting in particles that are tight inside and loose outside, which is not conducive to subsequent sintering and use. If the time is too short, the grains will be squeezed and move a little, which will easily result in void particles and poor sphericity.

[0054] In some embodiments, such as Figure 1 As shown, the first mixing process also includes a step of continuously adding a second oxidant to the reaction chamber, which is beneficial for increasing the specific surface area of ​​the precursor and allows for precise control of the oxidation degree, thereby customizing the precursor with the desired specific surface area. During the first mixing process, the pre-oxidized metal ion solution can sequentially contact the complexing agent, precipitant, and second oxidant in the reaction chamber; this facilitates the sequential complexation, precipitation, and oxidation reactions of the metal ions. Specifically, the feeding position can be set as described above, with the second oxidant feeding position set at the 9 o'clock position (or, in terms of angle, 270°), but not limited to this position. As long as the order is correct, it can be after the precipitant feeding position, which is beneficial for a stable and orderly millisecond-level reaction process and for uniform reaction. In the embodiments, the second oxidant may be continuously added to the reaction chamber in the form of a second oxidant solution, and the concentration of the second oxidant solution may be 0.1–10 mol / L; in exemplary examples, it may include, but is not limited to, 0.1 mol / L, 0.5 mol / L, 4 mol / L, 7 mol / L, and 10 mol / L; the flow rate may be 0.1–5 L / h; in exemplary examples, it may include, but is not limited to, 0.1 L / h, 1 L / h, 2 L / h, 4 L / h, and 5 L / h. The second oxidant may include at least one of H₂O₂, peracetic acid, sodium percarbonate, ammonium persulfate, and oxygen.

[0055] When the second oxidant is added during the first mixing process, a protective gas can be omitted to reduce waste of the second oxidant and to allow it to fully exert its oxidizing effect. The addition of the second oxidant can be stopped when the first mixing process is completed.

[0056] Furthermore, the first mixing process includes a mixing process performed at 30–80°C (e.g., 30°C, 40°C, 50°C, 70°C, 80°C), followed by a holding or heating process at 40–80°C (e.g., 40°C, 65°C, 70°C, 80°C). Higher temperatures facilitate the initial crystal growth of some seed crystals, and the 40–80°C temperature can be maintained in subsequent steps S30 and S40, which is particularly beneficial for obtaining primary particle morphology control of the cathode material precursor.

[0057] Step S30:

[0058] Step S30, the second mixing process, is to grow crystals until the target particle size is achieved. In this embodiment, if the liquid level of the mixed solution in the reaction chamber is too high during the third mixing process, it can be concentrated, and the supernatant can be continuously discharged from the reaction chamber to facilitate the reaction and crystal growth. In this embodiment, a protective gas (at least one of nitrogen, helium, and argon) can also be introduced during the second mixing process to prevent large-scale oxidation. Furthermore, molten metal, a complexing agent, and a precipitant can be continuously added to the seed crystal mixed solution, ensuring that the molten metal sequentially contacts the complexing agent and the precipitant in the reaction chamber and undergoes complexation and precipitation reactions sequentially. This ensures a stable and orderly millisecond-level reaction process, promoting uniform reaction. The specific method of continuous addition can refer to the method described in step S20 above.

[0059] In this embodiment, step S30 can also refer to the continuous feeding method in step S20 to add molten metal, complexing agent, precipitant, or further including a second oxidant into the reaction chamber. The complexing agent, precipitant, and second oxidant can also be continuously added to the reaction chamber in solution form as described above. The concentration range can refer to the concentration range of the solution in step S20, and the flow rate can be adjusted according to the reaction conditions required in step S30. The materials of the complexing agent, precipitant, and second oxidant can also be those selected in step S20. Of course, in a specific embodiment, the above content in steps S20 and S30 is not limited to be consistent.

[0060] In this embodiment, the flow rate of the molten metal in the second mixing process can refer to the flow rate range in step S20. In this embodiment, the complexing agent can be continuously added to the seed-containing mixed solution in the form of a complexing agent solution at a flow rate of 0.1–1 L / h. Examples include, but are not limited to, 0.1 L / h, 0.3 L / h, 0.6 L / h, and 1 L / h. The complexing agent solution contains ammonium ions with a concentration of 1–15 mol / L. In this embodiment, the precipitant can be continuously added to the seed-containing mixed solution in the form of a precipitant solution at a flow rate of 1–5 L / h. Examples include, but are not limited to, 1 L / h, 2 L / h, 2.4 L / h, 4 L / h, and 5 L / h. The precipitant solution contains hydroxide ions with a concentration of 2–12 mol / L.

[0061] The above methods are mainly to create at least one of the following reaction conditions for crystal growth: ① The mixed solution in the reaction chamber contains ammonium ions, with an ammonium ion concentration of 0.1–1 mol / L; in the examples, this may include, but is not limited to, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.5 mol / L, and 1 mol / L. ② The pH of the mixed solution in the reaction chamber can be 7.5–11.8; in the examples, this may include, but is not limited to, 7.5, 9.6, 9.8, 10, and 11.8. ③ The temperature is 40–80℃. ④ The time can be 10–40 h to allow the particle size to reach the desired level. Under the above reaction conditions, when the crystal particle size in the crystal-containing mixed solution is 2–6 μm, the addition of molten metal, complexing agent, and precipitant is stopped, i.e., the feeding is stopped. In the examples, the particle size may include, but is not limited to, 2 μm, 2.3 μm, 3.7 μm, 5.6 μm, and 6 μm. Particle size can be detected in real time, for example, by using a laser particle size analyzer to monitor crystal size and thus control the feeding. Furthermore, after feeding is stopped, the crystal-containing solution can be stirred for a period of time to promote the complete reaction of any unreacted residue.

[0062] In some embodiments, the second mixing process further includes a step of continuously adding a second oxidant to the seed-containing mixed solution. This is beneficial for increasing the specific surface area of ​​the precursor and for precisely controlling the degree of oxidation in the middle layer of particles, thereby customizing the precursor with the desired specific surface area. During the second mixing process, the molten metal can sequentially contact the complexing agent, precipitant, and second oxidant in the reaction chamber, as described in step S20 above, where metal ions are first complexed, then precipitated, and finally oxidized. This not only facilitates a stable and orderly millisecond-level reaction process and uniform reaction but also helps to increase the specific surface area and prevent excessive changes in the morphology of the particles. The second oxidant can be continuously added to the seed-containing mixed solution in the form of a second oxidant solution, with a flow rate of 0.02–2 L / h. In exemplary examples, this may include, but is not limited to, 0.02 L / h, 0.11 L / h, 0.8 L / h, and 2 L / h. The concentration of the second oxidant in the second oxidant solution can be 0.1–10 mol / L. Furthermore, if a second oxidant is added during the second mixing process, a protective gas can be omitted to reduce waste of the second oxidant and allow it to fully exert its oxidizing effect. The addition of the second oxidant can be stopped when the desired particle size is achieved.

[0063] Step S40:

[0064] Step S40 involves adding a precipitant to ultimately obtain the cathode material precursor. During the third mixing process, the temperature can be 40–80°C, and a protective gas (at least one of nitrogen, helium, and argon) can be introduced. If a second oxidant is added, the protective gas introduction is not necessary. In some embodiments, the third mixing process may include:

[0065] S41: Continuously add a second oxidizing agent to the mixed solution containing crystals;

[0066] S42: Continue adding precipitant.

[0067] Before adding the precipitant in the third mixing process, a second oxidant is continuously added to the crystal-containing mixed solution. This can modify the morphology of the crystal surface oxidation, which is beneficial to increasing the specific surface area of ​​the precursor. It can also allow for precise control of the degree of oxidation, thereby customizing the precursor with the required specific surface area.

[0068] The second oxidant in step S41 can be continuously added to the crystalline mixed solution in the form of a second oxidant solution at a flow rate of 0.1–2 L / h. In the example, this may include, but is not limited to, 0.1 L / h, 0.5 L / h, 1 L / h, and 2 L / h. The concentration of the second oxidant in the second oxidant solution may be 0.1–10 mol / L. The time for adding the second oxidant may be 1–6 h. In the example, this may include, but is not limited to, 1 h, 2 h, 3 h, 4 h, 5 h, and 6 h.

[0069] In step S42, the precipitant can be continuously added to the mixed solution containing crystals in the form of a precipitant solution at a flow rate of 1–15 L / h. Examples include, but are not limited to, 1 L / h, 2 L / h, 2.4 L / h, 4 L / h, 10 L / h, and 15 L / h. The precipitant solution contains hydroxide ions with a concentration of 2–12 mol / L. The addition of the precipitant is stopped when the pH of the mixed solution containing the cathode material precursor reaches 11–12. Examples include, but are not limited to, 11, 11.5, and 12. After stopping the addition, the mixed solution containing the precursor can be stirred for a period of time to ensure complete reaction. The solid content of the mixed solution containing the cathode material precursor is 100-700 g / L. In the example, it may include, but is not limited to, 100 g / L, 300 g / L, 400 g / L, 500 g / L, 600 g / L, and 700 g / L. These solid contents are beneficial to obtaining cathode material precursors with high sphericity and rounded particles, and to reducing the phenomenon of two spheres sticking together or multiple spheres being connected in series.

[0070] In this embodiment, step S40 can also refer to the continuous feeding method in step S20 to add the precipitant or further including the second oxidant into the reaction chamber. The precipitant and the second oxidant can also be continuously added to the reaction chamber in solution form as described above. The concentration range can refer to the concentration range of the solution in step S20, and the flow rate can be adjusted according to the reaction conditions required in step S40. The materials of the precipitant and the second oxidant can also be those selected in step S20. Of course, in a specific embodiment, the above content in steps S20, S30, and S40 is not limited to be consistent.

[0071] The cathode material precursor obtained in step S40 is still in a mixed solution, so it can also include a dehydration and drying step. For example, the mixed solution containing the cathode material precursor (i.e., the wet reaction material) can be filtered and dehydrated to obtain a primary dehydrated material, which is the material obtained by filtering the supernatant. Then, the primary dehydrated material is rinsed with an alkaline solution, such as sodium hydroxide solution, and filtered to obtain a secondary dehydrated material. Then, it is rinsed with hot pure water and filtered to obtain a final dehydrated material. Finally, it is dried in an oven to obtain a dry sample, i.e., a dried cathode material precursor.

[0072] 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.

[0073] The cathode material precursor of this application is prepared by the above-described method. Therefore, the precursor particles have interconnected channels and pores from the interior to the surface, resulting in a high specific surface area. The specific surface area of ​​each particle is highly consistent and can be precisely controlled. The primary precursor particles are rounded with good sphericity, and there is little phenomenon of two spheres adhering to each other or multiple spheres being connected in series.

[0074] Testing revealed that the specific surface area of ​​the cathode material precursor in this application embodiment can be 13–40 m². 2 / g; In the example, it may include, but is not limited to, 13m 2 / g, 16.3m 2 / g, 23.1m 2 / g, 25.6m 2 / g、40m 2 / g. The particle size of the primary particles can be 2–6 μm; in the examples, it can include, but is not limited to, 2 μm, 2.3 μm, 3.7 μm, 5.6 μm, and 6 μm. These small particle precursors are easily recrystallized to form single crystals or near-single crystals during the preparation of cathode materials, such as during sintering. Subsequent preparation of single crystal or near-single crystal cathode materials using these small particle precursors can reduce grain boundaries, decrease side reactions, and improve compaction density, energy density, and cycle performance.

[0075] The third aspect of this application provides a cathode material, which is obtained by including a precursor. The cathode material has a single crystal structure, and the precursor includes the cathode material precursor obtained by the preparation method of this application or includes the cathode material precursor of this application.

[0076] The cathode material in this application embodiment is obtained from the cathode material precursor of this application embodiment, for example, by sintering the cathode material precursor with a lithium source. The cathode material obtained by appropriate sintering process has a single crystal structure, good sphericity, and large specific surface area. It has more reaction interfaces and active sites in the battery, which is beneficial to improving rate performance, charge and discharge rate and cycle performance.

[0077] A fourth aspect of this application provides a secondary battery, including a positive electrode containing the positive electrode material of this application.

[0078] The secondary battery of this application embodiment has good rate performance, charge / discharge rate and cycle performance because it contains the positive electrode material of this application embodiment.

[0079] The following description is based on specific embodiments.

[0080] Example 1

[0081] This embodiment provides a cathode material precursor and its preparation method.

[0082] The preparation method steps are as follows:

[0083] Step S1: Provide molten metal, complexing agent solution (hereinafter referred to as complexing agent), precipitant solution (hereinafter referred to as precipitant), and second oxidizing agent solution (hereinafter referred to as oxidizing agent).

[0084] Metal liquid: Nickel sulfate, manganese sulfate, and cobalt sulfate are prepared into a solution with a molar ratio of Ni:Co:Mn of 96:2:2, so that the total concentration of metal M (nickel, cobalt, and manganese) in the solution is 2.0 mol / L; then hydrogen peroxide (the primary oxidant) is provided, and hydrogen peroxide is added according to the molar ratio of H2O2:M of 1:1000. Because of the oxidizing properties of hydrogen peroxide, a small portion of cobalt and manganese in the solution will be oxidized, i.e., pre-oxidized, to obtain the metal liquid;

[0085] Complexing agent: Dilute liquid ammonia with pure water to obtain ammonia water, wherein the concentration of ammonium ions is 8 mol / L;

[0086] Precipitant: Dissolve sodium hydroxide in pure water, wherein the hydroxide ion concentration is 10 mol / L;

[0087] Oxidizing agent: Dilute hydrogen peroxide to a concentration of 9 mol / L;

[0088] Step S2: First mixing process

[0089] In a 100L reactor, two layers of stirring paddles are installed. The feed pipe is inserted from the top of the reactor. The feed pipes for the molten metal, complexing agent, precipitant, and oxidant are located at 0°, 90°, 180°, and 270°, respectively. The stirring direction of the stirring paddles ensures that the liquid flow can make the molten metal contact the complexing agent first, then the precipitant, and finally the oxidant as the blades move.

[0090] Before the reaction, prepare the base solution: First, add 50L of pure water to the reactor, so that the pure water in the reactor is exactly half of the reactor's capacity (this makes the liquid flow dispersion state close to that of a full reactor, ensuring a uniform reaction process). Initial reaction conditions can be customized. First, heat the solution to 40℃, and at the same time, introduce nitrogen gas with a concentration of 99.99%. After the temperature is reached, add a complexing agent to make the ammonium ion concentration in the base solution 0.25mol / L. After the ammonium ion concentration reaches the standard, add a precipitant to make the pH of the base solution 11.9.

[0091] Continuously add molten metal, complexing agent, and precipitant to the bottom solution simultaneously, with initial flow rates of 5 L / h, 0.23 L / h, and 2 L / h, respectively. Fine-tune the precipitant flow rate to maintain the pH of the mixed solution in the reactor at 9.9, and fine-tune the complexing agent flow rate to maintain the ammonium ion concentration at 0.3 mol / L. Nitrogen gas is continuously introduced during the feeding process to prevent large-scale oxidation; only micro-oxidation occurs in the molten metal during the reaction. When the total volume of the liquid in the reactor reaches 80% of its capacity, the temperature is increased to 70°C to allow at least some seed crystals to begin growing, continuing until the volume of the mixed solution in the reactor reaches 95% of its capacity (approaching full capacity for the first time), resulting in a mixed solution containing seed crystals.

[0092] Step S3: Second mixing treatment (addition of oxidant)

[0093] Start the concentration unit, simultaneously close the nitrogen inlet valve and open the oxidant feed metering device, setting the flow rate to 0.11 L / h. At this point, the external circulation volume is approximately 20 L. Maintain a stable liquid level in the reactor by controlling the liquid level in the concentration unit. Fine-tune the flow rates of the precipitant and complexing agent to maintain the pH value and ammonium ion concentration at 9.8 and 0.3 mol / L, respectively. Use a laser particle size analyzer to detect the particle size. When the particle size reaches 3.7 μm, simultaneously stop feeding the molten metal, precipitant, complexing agent, and oxidant. Stir for 30 min to obtain a mixed solution containing crystals.

[0094] Step S4: Third mixing process

[0095] The precipitant feed switch was turned on again to add precipitant until the pH reached 11.5. Stirring was continued for 2 hours to obtain a mixed solution (reaction wet material) containing the positive electrode material precursor. The solid content was tested to be 636 g / L.

[0096] Dehydration and drying: First, the wet reaction material is filtered and dehydrated to obtain primary dehydrated material, which is the material obtained from the supernatant of the filter. Then, the primary dehydrated material is washed with a sodium hydroxide solution with a concentration of 0.3 mol / L at 70°C under normal pressure, where the weight ratio of the primary dehydrated material to the sodium hydroxide solution is 1:0.5. After washing, it is filtered to obtain secondary dehydrated material, which is the material obtained by washing and filtering with an alkaline solution. Then, the secondary dehydrated material is washed with hot pure water at 70°C under normal pressure, where the weight ratio of the primary dehydrated material to the hot pure water is 1:10. After filtration, the final dehydrated material is obtained and dried in an oven at 130°C for 18 hours to obtain a dry sample, which is the precursor of the positive electrode material.

[0097] This embodiment provides a cathode material precursor, which is prepared by the method described in this embodiment. The molar ratio of Ni:Co:Mn is 96:2:2, which can be denoted as NCM960202 cathode material precursor.

[0098] Example 2

[0099] This embodiment provides a cathode material precursor and its preparation method.

[0100] The preparation method steps are as follows:

[0101] Step S1: Provide molten metal, complexing agent, precipitant, and oxidizing agent.

[0102] Metal liquid: Prepare a solution by mixing nickel sulfate, manganese sulfate, and cobalt sulfate in a molar ratio of Ni:Co:Mn of 90:5:5, so that the total concentration of metal M (nickel, cobalt, and manganese) in the solution is 1.0 mol / L; then provide hydrogen peroxide and add it according to the molar ratio of H2O2:M of 5:1000 to obtain the metal liquid.

[0103] Complexing agent: Dilute liquid ammonia with pure water to obtain ammonia water, wherein the concentration of ammonium ions is 2 mol / L;

[0104] Precipitant: Dissolve sodium hydroxide in pure water, where the hydroxide ion concentration is 2 mol / L;

[0105] Oxidizing agent: Dilute hydrogen peroxide to a concentration of 0.5 mol / L;

[0106] Step S2: First mixing treatment (addition of oxidant)

[0107] In a 100L reactor, two layers of stirring paddles are installed. The feed pipe is inserted from the top of the reactor. The feed pipes for the molten metal, complexing agent, precipitant, and oxidant are located at 0°, 90°, 180°, and 270°, respectively. The stirring direction of the stirring paddles ensures that the liquid flow can make the molten metal contact the complexing agent first, then the precipitant, and finally the oxidant as the blades move.

[0108] Before the reaction, prepare the base solution: First, add 50L of pure water to the reactor and heat it to 50℃. At the same time, introduce nitrogen gas with a concentration of 99.99%. After the temperature is reached, add a complexing agent to make the ammonium ion concentration in the base solution 0.65mol / L. After the ammonium ion concentration reaches the standard, add a precipitant to make the pH of the base solution 10.6.

[0109] Continuously add molten metal, complexing agent, precipitant, and oxidant to the bottom solution simultaneously, with initial flow rates of 2 L / h, 0.57 L / h, 2 L / h, and 4 L / h, respectively. Adjust the precipitant flow rate to maintain the pH of the mixed solution in the reactor at 9.4, and adjust the complexing agent flow rate to maintain the ammonium ion concentration at 0.6 mol / L. Nitrogen gas is stopped during the feeding process. When the total liquid volume in the reactor reaches 80% of its capacity, the temperature is increased to 65°C until the mixed solution reaches 95% of its capacity, yielding a seed-containing mixed solution.

[0110] Step S3: Second mixing process

[0111] Start the concentration unit, simultaneously open the nitrogen inlet valve and close the oxidant feed metering device. At this point, the external circulation volume is approximately 20L. Maintain a stable liquid level in the reactor by controlling the liquid level in the concentrator. Fine-tune the flow rates of the precipitant and complexing agent to maintain the pH and ammonium ion concentrations at 9.6 and 0.5 mol / L, respectively. Use a laser particle size analyzer to detect the particle size. When the particle size reaches 5.6 μm, simultaneously stop feeding the molten metal, precipitant, and complexing agent to obtain a mixed solution containing crystals.

[0112] Step S4: Third mixing treatment (addition of oxidant)

[0113] The oxidant feed was started at a flow rate of 1 L / h. After feeding for 2 hours, the feed was stopped and stirring continued. After 10 minutes, the precipitant feed switch was turned on again to add precipitant to bring the pH to 11.0. Stirring was continued for 1 hour to obtain a mixed solution (reaction wet material) containing the cathode material precursor. The solid content was tested to be 457 g / L.

[0114] Dehydration and drying: First, the wet reaction material is filtered and dehydrated to obtain primary dehydrated material, which is the material obtained from the supernatant of the filter. Then, the primary dehydrated material is washed with a sodium hydroxide solution with a concentration of 0.3 mol / L at 60℃ under normal pressure, where the weight ratio of primary dehydrated material to sodium hydroxide solution is 1:0.3. After washing, it is filtered to obtain secondary dehydrated material, which is the material obtained by washing and filtering with an alkaline solution. Then, the secondary dehydrated material is washed with hot pure water at 50℃ under normal pressure, where the weight ratio of primary dehydrated material to hot pure water is 1:5. After filtration, the final dehydrated material is obtained and dried in an oven at 120℃ for 28 hours to obtain a dry sample, which is the precursor of the positive electrode material.

[0115] This embodiment provides a cathode material precursor, which is prepared by the method described in this embodiment. The molar ratio of Ni:Co:Mn is 90:5:5, which can be denoted as NCM900505 cathode material precursor.

[0116] Example 3

[0117] This embodiment provides a cathode material precursor and its preparation method.

[0118] The preparation method steps are as follows:

[0119] Step S1: Provide molten metal, complexing agent, precipitant, and oxidizing agent.

[0120] Metal liquid: Prepare a solution by mixing nickel sulfate, manganese sulfate, and cobalt sulfate in a molar ratio of Ni:Co:Mn of 98:1:1, so that the total concentration of metal M (nickel, cobalt, and manganese) in the solution is 1.5 mol / L; then provide hydrogen peroxide and add it according to the molar ratio of H2O2:M of 3:1000 to obtain the metal liquid.

[0121] Complexing agent: Dilute liquid ammonia with pure water to obtain ammonia water, wherein the concentration of ammonium ions is 6 mol / L;

[0122] Precipitant: Dissolve sodium hydroxide in pure water, wherein the hydroxide ion concentration is 5 mol / L;

[0123] Oxidizing agent: Dilute hydrogen peroxide to a concentration of 4 mol / L;

[0124] Step S2: First mixing treatment (addition of oxidant)

[0125] In a 100L reactor, two layers of stirring paddles are installed. The feed pipe is inserted from the top of the reactor. The feed pipes for the molten metal, complexing agent, precipitant, and oxidant are located at 0°, 90°, 180°, and 270°, respectively. The stirring direction of the stirring paddles ensures that the liquid flow can make the molten metal contact the complexing agent first, then the precipitant, and finally the oxidant as the blades move.

[0126] Before the reaction, prepare the base solution: First, add 50L of pure water to the reactor and heat it to 45℃. At the same time, introduce nitrogen gas with a concentration of 99.99%. After the temperature is reached, add a complexing agent to make the ammonium ion concentration in the base solution 0.35mol / L. After the ammonium ion concentration reaches the standard, add a precipitant to make the pH of the base solution 11.0.

[0127] Continuously add molten metal, complexing agent, precipitant, and oxidant to the bottom solution simultaneously, with initial flow rates of 4 L / h, 0.28 L / h, 2.4 L / h, and 0.15 L / h, respectively. Fine-tune the precipitant flow rate to maintain the pH of the mixed solution in the reactor at 11.0, and fine-tune the complexing agent flow rate to maintain the ammonium ion concentration at 0.45 mol / L. Nitrogen gas is stopped during the feeding process. When the total liquid volume in the reactor reaches 80% of its capacity, begin heating to 75°C, continuing until the mixed solution reaches 95% of its capacity, resulting in a seed-containing mixed solution.

[0128] Step S3: Second mixing process

[0129] Start the concentration unit, simultaneously open the nitrogen inlet valve and close the oxidant feed metering device. At this point, the external circulation volume is approximately 20L. Maintain a stable liquid level in the reactor by controlling the liquid level in the concentrator. Fine-tune the flow rates of the precipitant and complexing agent to maintain the pH and ammonium ion concentrations at 10 and 0.2 mol / L, respectively. Use a laser particle size analyzer to detect the particle size. When the particle size reaches 2.3 μm, simultaneously stop feeding the molten metal, precipitant, and complexing agent to obtain a mixed solution containing crystals.

[0130] Step S4: Third mixing treatment (addition of oxidant)

[0131] The oxidant feed was started at a flow rate of 0.5 L / h. After feeding for 6 hours, the feed was stopped and stirring continued. After 10 minutes, the precipitant feed switch was turned on again to add precipitant to bring the pH to 11.0. Stirring continued for 1 hour to obtain a mixed solution (reaction wet material) containing the cathode material precursor. The solid content was tested to be 517 g / L.

[0132] Dehydration and drying: First, the wet reaction material is filtered and dehydrated to obtain primary dehydrated material, which is the material obtained from the supernatant of the filter. Then, the primary dehydrated material is washed with a sodium hydroxide solution with a concentration of 0.6 mol / L at 60℃ under normal pressure, where the weight ratio of primary dehydrated material to sodium hydroxide solution is 1:0.1. After washing, it is filtered to obtain secondary dehydrated material, which is the material obtained by washing and filtering with an alkaline solution. Then, the secondary dehydrated material is washed with hot pure water at 80℃ under normal pressure, where the weight ratio of primary dehydrated material to hot pure water is 1:15. After filtration, the final dehydrated material is obtained and dried in an oven at 110℃ for 20 hours to obtain a dry sample, which is the precursor of the positive electrode material.

[0133] This embodiment provides a cathode material precursor, which is prepared by the method described in this embodiment. The molar ratio of Ni:Co:Mn is 98:1:1, which can be denoted as NCM980101 cathode material precursor.

[0134] Example 4

[0135] This embodiment provides a cathode material precursor and its preparation method.

[0136] The difference between the preparation method and Example 1 is that when providing the metal liquid in step S1, the molar ratio of H2O2:M is changed from 1:1000 to 0.05:1000, while all other aspects remain unchanged.

[0137] The cathode material precursor in this embodiment was prepared by the method described in this embodiment.

[0138] Example 5

[0139] This embodiment provides a cathode material precursor and its preparation method.

[0140] The difference between the preparation method and Example 1 is that when providing the metal liquid in step S1, the molar ratio of H2O2:M is changed from 1:1000 to 20:1000, while all other aspects remain unchanged.

[0141] The cathode material precursor in this embodiment was prepared by the method described in this embodiment.

[0142] Example 6

[0143] This embodiment provides a cathode material precursor and its preparation method.

[0144] The difference between the preparation method and Example 1 is that an oxidant is also added in the third mixing process of step S4, and it is added before the precipitant is added in step S4. The oxidant feed is turned on at a flow rate of 1L / h. After feeding for 2 hours, the feed is stopped and stirring is continued (refer to the step of adding the oxidant in step S4 of Example 2). After 10 minutes, the original step of adding the precipitant in step S4 of Example 1 is continued. Everything else remains the same.

[0145] The cathode material precursor in this embodiment was prepared by the method described in this embodiment.

[0146] Example 7

[0147] This embodiment provides a cathode material precursor and its preparation method.

[0148] The difference between the preparation method and Example 1 is that in steps S2 to S4, the feed pipes for the molten metal, complexing agent, precipitant, and oxidant are changed from being at 0°, 90°, 180°, and 270° to being at 0°, 180°, 90°, and 270°, respectively. That is, the molten metal first contacts the precipitant, then the complexing agent, and finally the oxidant. Everything else remains the same.

[0149] The cathode material precursor in this embodiment was prepared by the method described in this embodiment.

[0150] Example 8

[0151] This embodiment provides a cathode material precursor and its preparation method.

[0152] The difference between the preparation method and Example 1 is that in steps S2 to S4, the feed pipes for the molten metal, complexing agent, precipitant, and oxidant are changed from being at 0°, 90°, 180°, and 270° to being at 0°, 270°, 180°, and 90°, respectively. That is, the molten metal first contacts the oxidant, then the precipitant, and finally the complexing agent. Everything else remains the same.

[0153] The cathode material precursor in this embodiment was prepared by the method described in this embodiment.

[0154] Comparative Example 1

[0155] This comparative example provides a cathode material precursor and its preparation method.

[0156] The only difference between the preparation method and Example 1 is that hydrogen peroxide (the first oxidant) is not added when preparing the metal liquid in step S1, and the prepared metal ion solution is directly used as the subsequent metal liquid, that is, no pre-oxidation treatment is performed.

[0157] No oxidant is provided in step S1, and no oxidant is added in step S3, while nitrogen gas is kept flowing through; everything else is the same.

[0158] This comparative example provides a cathode material precursor, which is prepared by the method described in this embodiment.

[0159] Comparative Example 2

[0160] This comparative example provides a cathode material precursor and its preparation method.

[0161] The only difference between the preparation method and Example 1 is that hydrogen peroxide (the first oxidant) is not added when preparing the metal liquid in step S1, and the prepared metal ion solution is directly used as the subsequent metal liquid, that is, no pre-oxidation treatment is performed; all other aspects are the same.

[0162] This comparative example provides a cathode material precursor, which is prepared by the method described in this embodiment.

[0163] Relevant performance tests and results analysis

[0164] The cathode material precursors provided in Examples 1 to 8, Comparative Example 1, and Comparative Example 2 were tested:

[0165] SEM: SEM images of each cathode material precursor were obtained using a scanning electron microscope, where the cathode material precursor of Example 1 is shown below. Figure 2 As shown, there are fewer dumbbell-shaped particles, and the particles are round and have good sphericity; the cathode material precursor of Comparative Example 1 is as follows: Figure 3 As shown, we can see that the sphericity is poor, there is a lot of adhesion between the two balls, there are many dumbbell-shaped particles, and the particle surface is more dense.

[0166] Specific surface area: The specific surface area was tested using a specific surface area analyzer, and the results are recorded in Table 1 below.

[0167] Particle size: The particle size was measured using a laser particle size analyzer, and the results are recorded in Table 1 below.

[0168] Table 1

[0169]

[0170]

[0171] As can be seen from Table 1, the preparation methods of Examples 1 to 8 of this application, through pre-oxidation treatment and the addition of an oxidant in at least one of the three mixing treatments, can perform customized oxidation on the interior, middle layer and surface of the obtained particles. Compared with the preparation methods of Comparative Examples 1 and 2, the specific surface area of ​​the obtained cathode material precursor can be increased and the sphericity is better.

[0172] Compared with Examples 4 and 5, Example 1 shows that if the amount of the first oxidant is within a certain range during pre-oxidation, it is more conducive to increasing the specific surface area of ​​the cathode material precursor.

[0173] Compared with Examples 7 and 8, Example 1 shows that by setting the orientation of the feed pipe and combining it with stirring during the reaction process, the molten metal first contacts the complexing agent, then the precipitant, and finally the oxidant, which is more conducive to increasing the specific surface area of ​​the cathode material precursor.

[0174] 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: A soluble metal source used to prepare the cathode material is pre-oxidized with a first oxidant to obtain a pre-oxidized metal ion solution. The pre-oxidized metal ion solution is mixed with a complexing agent and a precipitant to obtain a seed-containing mixed solution. Continue to add at least the pre-oxidized metal ion solution, the complexing agent, and the precipitant to the seed crystal mixed solution for a second mixing treatment to obtain a crystal-containing mixed solution; Continue to add at least the precipitant to the crystal-containing mixed solution for a third mixing treatment to obtain the cathode material precursor; The process of at least one of the mixing processes, namely the first mixing process, the second mixing process, and the third mixing process, further includes the step of adding a second oxidant. The third mixing process includes at least one of the following (1) to (5): (1) Introduce protective gas; (2) The precipitant is continuously added to the crystal-containing mixed solution in the form of a precipitant solution at a flow rate of 1 to 15 L / h. The precipitant solution contains hydroxide ions with a hydroxide ion concentration of 2 to 12 mol / L. (3) The temperature is 40-80℃; (4) Stop adding the precipitant when the pH of the mixed solution containing the cathode material precursor is 11-12; (5) The solid content of the mixed solution containing the cathode material precursor is 100-700 g / L.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the first oxidant to the metal element contained in the soluble metal source is (0.1-10):1000.

3. The preparation method according to claim 1 or 2, characterized in that: The first mixing process includes at least one of the following (1) to (9): (1) Introduce protective gas; (2) The pre-oxidized metal ion solution, the complexing agent, and the precipitant are continuously added to the reaction chamber, and the pre-oxidized metal ion solution is sequentially contacted with the complexing agent and the precipitant in the reaction chamber and undergoes complexation and precipitation reactions in sequence. (3) The flow rate of the pre-oxidized metal ion solution is 1-10 L / h, and the concentration of metal ions in the pre-oxidized metal ion solution is 1-2 mol / L; (4) The complexing agent is continuously added to the reaction chamber in the form of a complexing agent solution at a flow rate of 0.1 to 0.8 L / h. The complexing agent solution contains ammonium ions with a concentration of 1 to 15 mol / L. (5) The precipitant is continuously added to the reaction chamber in the form of a precipitant solution at a flow rate of 1 to 5 L / h. The precipitant solution contains hydroxide ions with a hydroxide ion concentration of 2 to 12 mol / L. (6) The mixed solution in the reaction chamber contains ammonium ions, and the concentration of ammonium ions is 0.1 to 0.8 mol / L; (7) The temperature is 30–80℃; (8) The pH of the mixed solution in the reaction chamber is 7.8–13; (9) The time is 5 to 20 hours.

4. The preparation method according to claim 3, characterized in that: The first mixing process further includes the step of continuously adding the second oxidant into the reaction chamber, wherein the first mixing process includes at least one of the following (1) to (2): (1) The pre-oxidized metal ion solution is sequentially contacted with the complexing agent, the precipitant, and the second oxidizing agent in the reaction chamber; (2) The second oxidant is continuously added to the reaction chamber in the form of a second oxidant solution at a flow rate of 0.1 to 5 L / h and the concentration of the second oxidant in the second oxidant solution is 0.1 to 10 mol / L.

5. The preparation method according to any one of claims 1, 2, or 4, characterized in that: The first mixing process includes mixing at 30–80°C first, and then holding or heating to 40–80°C for mixing.

6. The preparation method according to any one of claims 1, 2 or 4, characterized in that: The second mixing process includes at least one of the following (1) to (10): (1) Introduce protective gas; (2) The pre-oxidized metal ion solution, the complexing agent, and the precipitant are continuously added to the seed-containing mixed solution, and the pre-oxidized metal ion solution is sequentially contacted with the complexing agent and the precipitant in the reaction chamber and undergoes complexation and precipitation reactions in sequence. (3) The flow rate of the pre-oxidized metal ion solution is 1-10 L / h, and the concentration of the metal ions is 1-2 mol / L; (4) The complexing agent is continuously added to the seed-containing mixed solution in the form of a complexing agent solution at a flow rate of 0.1 to 1 L / h. The complexing agent solution contains ammonium ions with a concentration of 1 to 15 mol / L. (5) The precipitant is continuously added to the seed-containing mixed solution in the form of a precipitant solution at a flow rate of 1 to 5 L / h. The precipitant solution contains hydroxide ions with a hydroxide ion concentration of 2 to 12 mol / L. (6) The time is 10 to 40 hours; (7) The mixed solution in the reaction chamber contains ammonium ions, and the concentration of ammonium ions is 0.1 to 1 mol / L; (8) The temperature is 40–80℃; (9) The pH of the mixed solution in the reaction chamber is 7.5 to 11.8; (10) When the crystal particle size in the crystal-containing mixed solution is 2 to 6 μm, stop adding the pre-oxidized metal ion solution, the complexing agent, and the precipitant.

7. The preparation method according to claim 6, characterized in that: The second mixing process further includes the step of continuously adding the second oxidant to the seed-containing mixed solution, wherein the second mixing process includes at least one of the following (1) to (2): (1) The pre-oxidized metal ion solution is sequentially contacted with the complexing agent, the precipitant, and the second oxidizing agent in the reaction chamber; (2) The second oxidant is continuously added to the seed-containing mixed solution in the form of a second oxidant solution at a flow rate of 0.02 to 2 L / h and the concentration of the second oxidant in the second oxidant solution is 0.1 to 10 mol / L.

8. The preparation method according to claim 7, characterized in that: Before adding the precipitant in the third mixing process, the method further includes a step of continuously adding the second oxidant to the crystal-containing mixed solution. The third mixing process includes at least one of the following (1) to (2): (1) The second oxidant is continuously added to the crystal-containing mixed solution in the form of a second oxidant solution at a flow rate of 0.1 to 2 L / h, and the concentration of the second oxidant in the second oxidant solution is 0.1 to 10 mol / L; (2) The second oxidant is added at a time of 1 to 6 hours.

9. The preparation method according to any one of claims 1, 2, 4, 7, and 8, characterized in that: The soluble metal source includes a nickel source, a cobalt source, and a manganese source, wherein the molar ratio of Ni, Co, and Mn in the nickel source, cobalt source, and manganese source is (30–98):(1–40):(1–40); and / or The first oxidant includes at least one of H2O2, peracetic acid, sodium percarbonate, and ammonium persulfate; and / or The complexing agent includes at least one of ammonium carbonate, ammonium sulfate, and ammonia; and / or The precipitant includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium phosphate, and potassium sulfite; and / or The second oxidant includes at least one of H2O2, peracetic acid, sodium percarbonate, ammonium persulfate, and oxygen.

10. The preparation method according to any one of claims 1, 2, 4, 7, and 8, characterized in that: In the first mixing process, the pre-oxidized metal ion solution, the complexing agent, and the precipitant are added to the base solution, which includes at least one of the following (1) to (3): (1) The temperature is 30-80℃; (2) pH is 7.8–13; (3) The bottom solution contains ammonium ions, and the concentration of ammonium ions is 0.1 to 0.8 mol / L.

11. A cathode material precursor, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 10.

12. The cathode material precursor according to claim 11, characterized in that: Includes at least one of the following features (1) to (2): (1) Specific surface area is 13-40 m² 2 / g; (2) The particle size of the primary particles is 2 to 6 μm.

13. A positive electrode material, characterized in that: The cathode material is obtained by including a precursor, and the crystal structure of the cathode material is a single crystal. The precursor includes the cathode material precursor prepared by the preparation method according to any one of claims 1 to 10 or includes the cathode material precursor according to claim 11 or 12.

14. A secondary battery, comprising a positive electrode, characterized in that: The positive electrode contains the positive electrode material as described in claim 13.

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