Doped cobalt trioxide and methods of making and using the same

Abstract

The application discloses doped tricobalt tetraoxide and a preparation method and application thereof. The doped tricobalt tetraoxide is doped with anions or simultaneously doped with metal cations and anions. The doped tricobalt tetraoxide is prepared by introducing anions and doping, and when metal cations are further introduced, the metal cations and the doped anions play a synergistic doping effect. The anions and the metal cations are uniformly doped in lithium cobaltate prepared by taking the doped tricobalt tetraoxide as a precursor, the structure stability of the lithium cobaltate in a charging and discharging process is improved on the basis of effectively reducing oxygen precipitation of the lithium cobaltate, the cycle stability of the lithium cobaltate at high voltage is effectively improved, and the preparation method of the doped tricobalt tetraoxide can ensure that the structure and electrochemical performance of the prepared doped tricobalt tetraoxide are stable and the efficiency is high.

Description

Technical Field

[0001] This application belongs to the field of cathode material technology, specifically relating to a doped cobalt tetroxide, its preparation method, and its application. Background Technology

[0002] In 3C consumer lithium-ion batteries, lithium cobalt oxide has been widely used due to its high capacity, stable charge and discharge voltage, high charge and discharge voltage platform, and good cycle stability. As users demand increasingly higher battery life and volumetric energy density from 3C electronic products, a mainstream approach adopted by battery manufacturers to meet customer needs is to increase the charging cut-off voltage of lithium cobalt oxide. However, with the increase in charging voltage, lithium cobalt oxide is prone to irreversible structural phase transitions and poor surface and interface stability, thus affecting the battery's range.

[0003] Currently, methods to improve the charging cutoff voltage of lithium cobalt oxide (LCO) include solid-phase doping. While traditional solid-phase doping with metal cations such as Ni, Mg, Mn, and Al can improve the specific capacity and cycle stability of LCO at high voltages, this method easily leads to uneven distribution of metal elements in the LCO, resulting in less than ideal improvement. For example, one currently published report describes the use of Al and Mg metal cations to dope lithium cobalt oxide separately. It was found that within the 3-4.5V range and during 50 cycles at 0.2C, the discharge specific capacity of the doped lithium cobalt oxide was improved, but the cycle stability was not significantly improved. Another currently published report describes the co-doping of Mg and Y into lithium cobalt oxide using a solid-phase mixing and sintering method. Studies show that within the 3-4.6V voltage range and during 50 cycles at 0.5C, the capacity retention of the doped lithium cobalt oxide was improved compared to the undoped version, but the discharge specific capacity decayed significantly with increasing cycle count. Summary of the Invention

[0004] The purpose of this application is to overcome the above-mentioned deficiencies of the prior art and provide a doped cobalt tetroxide, a method for preparing the same, and a doped lithium cobalt oxide cathode material prepared by doping cobalt tetroxide, so as to solve the technical problem of poor stability of existing lithium cobalt oxide.

[0005] Another objective of this application is to provide a secondary battery to solve the technical problem of unsatisfactory cycle performance caused by the poor stability of the lithium cobalt oxide contained in existing secondary batteries.

[0006] To achieve the aforementioned objectives, the first aspect of this application provides a doped cobalt tetroxide (CTO) crystal phase. The CTO crystal phase of this application is doped with anions or simultaneously doped with metal cations and anions.

[0007] Furthermore, the anion occupies the oxygen vacancy in cobalt tetroxide, and the metal cation occupies the cobalt vacancy in cobalt tetroxide.

[0008] Furthermore, the general molecular formula for cobalt tetroxide is Co. 3-x N x O 4-y M y Where 0≤x≤0.11, 0.006≤y≤0.09, N is a metal cation, and M is an anion.

[0009] Furthermore, the metal element in the metal cation includes at least one of Al, Mg, Ni, Mn, Ti, Zr, La, Y, and Ce.

[0010] Furthermore, anions include halide ions, PO4 ions, etc. 3- BO3 3- BO2 - SiO4 4- SiO3 2- At least one of them.

[0011] Furthermore, the content of metal cations in the doped cobalt tetroxide is 0.1-1.2%.

[0012] Furthermore, the content of anions in the doped cobalt tetroxide is 0.05-1.5%.

[0013] Furthermore, the D50 particles doped with cobalt tetroxide have a particle size of 3-20 μm.

[0014] Furthermore, the cobalt tetroxide-doped particles include at least one of spherical, near-spherical, and elliptical shapes.

[0015] The first aspect of this application provides a method for preparing cobalt tetroxide doped with the present application. The method for preparing cobalt tetroxide doped with the present application includes the following steps:

[0016] Provide carbonate solutions containing doped anions;

[0017] A portion of the carbonate solution is mixed with a first cobalt salt solution and subjected to a first hydrothermal reaction to generate doped cobalt carbonate seed crystals containing doped anions, thereby obtaining a doped cobalt carbonate seed crystal dispersion.

[0018] The remaining carbonate solution and the second cobalt salt solution are mixed with the cobalt carbonate seed dispersion in a second mixing process and a second hydrothermal reaction is carried out to grow the cobalt carbonate seed until the cobalt carbonate particles grow to the predetermined particle size.

[0019] Cobalt carbonate particles were calcined to obtain cobalt tetroxide.

[0020] Furthermore, the first cobalt salt solution and / or the second cobalt salt solution also contain soluble metal salts.

[0021] Furthermore, when the first cobalt salt solution and / or the second cobalt salt solution contain a soluble metal salt, the concentration of the soluble metal salt in the first cobalt salt solution and / or the second cobalt salt solution satisfies the following: the mass ratio of the soluble metal element to the cobalt element is 0.0015-0.02:1; and / or

[0022] Furthermore, the soluble metal salt includes at least one of the nitrate, sulfate, and acetate salts of a soluble metal.

[0023] Furthermore, the method of subjecting a portion of the carbonate solution to a first mixing treatment and a first hydrothermal reaction with a first cobalt salt solution includes the following steps:

[0024] A certain amount of carbonate solution is taken as the base liquid. Under the condition of the first stirring treatment, a certain amount of carbonate solution and the first cobalt salt solution are added to the base liquid for the first mixing treatment and the first hydrothermal reaction.

[0025] Furthermore, in the base solution, the carbonate concentration is greater than 0, but less than 200 g / L.

[0026] Furthermore, the carbonate solution and the first cobalt salt solution are added to the base solution at a molar ratio of 0.03-0.28:1 for the first cobalt salt to the carbonate.

[0027] Furthermore, the conditions for the first hydrothermal reaction include at least one of the following:

[0028] The pH of the base solution is 6.7-8.8;

[0029] The temperature is 30-45℃;

[0030] The feeding time for adding carbonate solution and first cobalt salt solution to the base solution is controlled between 2-36 hours, and stirring is continued for 1-5 hours after feeding is completed.

[0031] The stirring speed for the first stirring treatment is 120-400 rpm.

[0032] Furthermore, the method of subjecting the remaining carbonate solution and the second cobalt salt solution to a second mixing treatment and a second hydrothermal reaction with the doped cobalt carbonate seed dispersion includes the following steps:

[0033] The remaining carbonate solution and the second cobalt salt solution were added to the cobalt carbonate seed dispersion in multiple intervals for a second mixing treatment and a second hydrothermal reaction.

[0034] Furthermore, in the steps of the second mixing treatment and the second hydrothermal reaction, the remaining carbonate solution and the second cobalt salt solution are added to the doped cobalt carbonate seed dispersion at a molar ratio of the second cobalt salt to the carbonate of 0.02-1.0:1.

[0035] Furthermore, the conditions for the second hydrothermal reaction include at least one of the following:

[0036] The pH of the mixed solution obtained from the second mixing treatment is 6.5-8.5;

[0037] The temperature is 30-50℃;

[0038] The remaining carbonate solution and the second cobalt salt solution were added to the cobalt carbonate seed dispersion in multiple batches, with the total feeding time controlled at 10-80 hours.

[0039] The second mixing process includes a second stirring process, and the stirring speed of the second stirring process is 60-400 rpm.

[0040] Furthermore, the D50 particle size of the cobalt carbonate seed crystals is 1.5-10 μm.

[0041] Furthermore, the D50 particle size of the cobalt carbonate particles is 3-22 μm.

[0042] Furthermore, the carbonate in the carbonate solution includes at least one of ammonium carbonate or ammonium bicarbonate.

[0043] Furthermore, the doped anions in the carbonate solution include halide ions and PO42-. 3- BO3 3- BO2 - SiO4 4- SiO3 2- At least one of them.

[0044] Furthermore, the calcination treatment includes first performing a first temperature zone sintering treatment, and then performing a second temperature zone sintering treatment; wherein the temperature of the first temperature zone sintering treatment is 200-620℃, and the temperature of the second temperature zone sintering treatment is 630-850℃.

[0045] A third aspect of this application provides a doped lithium cobalt oxide cathode material. The doped lithium cobalt oxide cathode material of this application is formed by calcining a lithium cobalt oxide precursor and a lithium source in a specific ratio. The lithium cobalt oxide precursor includes cobalt tetroxide doped according to this application or cobalt tetroxide doped using the cobalt tetroxide preparation method of this application.

[0046] A fourth aspect of this application provides a secondary battery. The secondary battery of this application includes a positive electrode, a separator, and a negative electrode stacked sequentially, wherein the positive electrode active material contained in the positive electrode includes the lithium cobalt oxide positive electrode material doped according to this application.

[0047] Compared with the prior art, this application has the following technical effects:

[0048] This application describes a method for doping lithium cobalt oxide using cobalt tetroxide as a precursor. By introducing anion and then doping, the resulting lithium cobalt oxide can suppress the participation of lattice oxygen in charge compensation under high voltage, reducing oxygen evolution and improving battery safety. When a metal cation is further introduced, it enhances the doping effect with the doped anion. The lithium cobalt oxide prepared using cobalt tetroxide as a precursor exhibits uniform doping of anions and metal cations. Furthermore, while effectively reducing oxygen evolution in lithium cobalt oxide, it improves the structural stability of lithium cobalt oxide during charge and discharge processes, and effectively enhances the cycle stability of lithium cobalt oxide under high voltage.

[0049] The method for preparing doped cobalt tetroxide in this application, based on the wet process, directly mixes the dopant anion, or further mixes the dopant anion, metal cation, and cobalt salt solution to achieve atomic-level mixing of the dopant ions. This results in atomic-level doping, ensuring a uniform distribution of dopant ions in the prepared doped cobalt tetroxide. Furthermore, the method for preparing doped cobalt tetroxide guarantees stable morphology and electrochemical performance, and is highly efficient.

[0050] The lithium cobalt oxide cathode material of this application is formed by sintering a lithium cobalt oxide precursor. Therefore, it contains doped anions or further contains doped anions and metal cations, and can achieve atomic-level doping and distribution. It can fully utilize the doping effect and doping synergistic effect of the anions or further the doped anions and metal cations. As a result, the lithium cobalt oxide cathode material of this application can suppress the participation of lithium cobalt oxide lattice oxygen in charge compensation under high voltage, reduce oxygen evolution, and improve structural stability during charge and discharge. Thus, the lithium cobalt oxide cathode material of this application has excellent cycle stability under high voltage and high safety.

[0051] Because the positive electrode active material of the present application contains the present application's doped lithium cobalt oxide positive electrode material, the present application's secondary battery has excellent cycle performance, low gas production, high safety, long life and stable electrochemical performance. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0053] Figure 1 This is a scanning electron microscope (SEM) image of cobalt tetroxide doped with Co. tetroxide provided in Embodiment A1 of this application;

[0054] Figure 2 This is a scanning electron microscope (SEM) image of cobalt tetroxide doped with Co., Ltd. provided in Embodiment A2 of this application;

[0055] Figure 3 This is a schematic diagram of the process flow for preparing cobalt tetroxide doped according to an embodiment of this application;

[0056] Figure 4 The capacity retention curves of lithium-ion batteries using lithium cobalt oxide as positive electrode active material are provided in Example B10 of this application and in Comparative Examples B5 to B6.

[0057] Figure 5 A capacity retention curve of a lithium-ion battery using lithium cobalt oxide as the positive electrode active material, as provided in Embodiment B11 of this application;

[0058] Figure 6 A capacity retention curve of a lithium-ion battery using lithium cobalt oxide as the positive electrode active material, as provided in Embodiment B12 of this application;

[0059] Figure 7 A capacity retention curve of a lithium-ion battery using lithium cobalt oxide as the positive electrode active material, as provided in Embodiment B13 of this application.

[0060] Figure 8 This is a capacity retention curve of a lithium-ion battery using lithium cobalt oxide as the positive electrode active material, as provided in Embodiment B9 of this application. Detailed Implementation

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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,” “the,” and “the” 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.

[0066] 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 described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0067] 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.

[0068] Cobalt tetroxide, a precursor for lithium cobalt oxide, can be prepared by wet synthesis of cobalt carbonate followed by high-temperature calcination. Based on this wet synthesis method, metal-doped cobalt tetroxide has been publicly reported. However, the inventors have found that lithium cobalt oxide prepared using wet-synthesized doped cobalt tetroxide as a precursor still suffers from unstable cycle performance and rapid capacity decay. The applicant's previous research, which involved atomic-level mixing of aluminum cations in a solution system to prepare a doped cobalt carbonate precursor followed by high-temperature calcination, yielded cobalt tetroxide with uniform aluminum doping. After preparing lithium cobalt oxide from aluminum-doped cobalt tetroxide, it was assembled into coin cells. Electrical performance tests showed that while cycle stability improved during 60 cycles at 1C at 3-4.55V, the discharge capacity still decayed rapidly.

[0069] Therefore, although metal cation doping improves the discharge specific capacity and cycle stability of lithium cobalt oxide to some extent, its stability remains poor at high voltages. Consequently, improving the stability of lithium cobalt oxide, such as its discharge specific capacity and cycle stability, has been a technical challenge that the inventors of this application have sought to solve.

[0070] Furthermore, while existing metal cation doping methods have improved the discharge specific capacity and cycle stability of lithium cobalt oxide to some extent, its stability remains poor at high voltages. The inventors discovered that a key reason for this is that under high voltages, lattice oxygen in lithium cobalt oxide readily participates in charge compensation, forming highly oxidizing oxygen and leading to oxygen evolution, resulting in poor battery safety. This also promotes cobalt evolution, exacerbating internal structural collapse. The inventors further discovered that anion doping can replace some oxygen atoms in the lithium cobalt oxide cathode material. Due to its strong covalent bond structure, anion doping can suppress oxygen evolution during the first charge, and its higher bond energy can also stabilize the material's structure. Based on the aforementioned technical problems in this field and the inventors' research findings, the following solution is proposed in this application.

[0071] Firstly, embodiments of this application provide a doped cobalt tetroxide. The cobalt tetroxide crystal phase of this application is doped with anions or simultaneously doped with metal cations and anions. Thus, when anions are introduced and doped with cobalt tetroxide in this application, the lithium cobalt oxide prepared using cobalt tetroxide as a precursor can suppress the participation of lattice oxygen in charge compensation under high voltage, reducing oxygen evolution and improving battery safety. When metal cations are further introduced into the cobalt tetroxide, the metal cations and doped anions can have a synergistic effect. The lithium cobalt oxide prepared using cobalt tetroxide as a precursor contains both anions and metal cations, and the anions and metal cations are uniformly distributed, thereby effectively reducing oxygen evolution and improving the structural stability of lithium cobalt oxide during charge and discharge processes, effectively improving the cycle stability of lithium cobalt oxide under high voltage. Therefore, ideally, the cobalt tetroxide doped in this application contains both doped anions and metal cations.

[0072] In the embodiments, the doping anions in the cobalt tetroxide doped in this application replace part of the oxygen in cobalt tetroxide, that is, the doping anions occupy oxygen vacancies in cobalt tetroxide. When the cobalt tetroxide doped in this application contains metal cation doping, the metal cation occupies part of the cobalt in cobalt tetroxide, that is, the metal cation replaces cobalt vacancies in cobalt tetroxide. By controlling the doping anions or further controlling the doping positions of the doping metal cations in the cobalt tetroxide doped in this application, such as the anions replacing part of the oxygen, the effect of anion doping is further enhanced, improving the suppression of oxygen in the lithium cobalt oxide lattice participating in charge compensation under high voltage, further reducing oxygen evolution, and improving battery safety. Similarly, the metal cations replacing part of the cobalt reduces cobalt evolution in lithium cobalt oxide under high voltage, reducing or preventing the collapse of the internal structure of lithium cobalt oxide. Furthermore, when the cobalt tetroxide doped in this application contains both doping anions and metal cations, the doping anions and metal cations can also exert the doping synergistic effect described above.

[0073] In the embodiments of this application, the general molecular formula of cobalt tetroxide doped with Co can be represented as Co. 3-x N x O 4-y M yIn this general formula, N represents the aforementioned metal cation, and M represents the aforementioned anion; 0 ≤ x ≤ 0.11, and further, 0.003 ≤ x ≤ 0.11; 0.006 ≤ y ≤ 0.09. In a further embodiment, by controlling the doping amount of the anion, such as controlling the value of y, the doping amount in the doped cobalt tetroxide is controlled to be 0.05-1.5%; or by further controlling the doping amount of the metal cation, such as controlling the value of x, the content of the metal cation in the doped cobalt tetroxide can be controlled to be 0.1-1.2%, and further, 0.5-1.2%. By controlling the doping amount of the anion or further metal cation, the respective doping effects and doping synergistic effects of the anion and metal cation as described above are improved, thereby improving the structural stability of lithium cobalt oxide during charge and discharge processes and its cycle stability under high voltage.

[0074] In the embodiments of this application, the anions contained in the cobalt tetroxide doped with cobalt tetroxide include halide ions and PO4 ions. 3- BO3 3- BO2 - SiO4 4- SiO3 2- At least one of the following. In a specific embodiment, the halide ion includes Cl. - F - These doped anions more effectively replace oxygen in cobalt tetroxide, further suppressing the participation of lattice oxygen in charge compensation under high voltage, significantly reducing oxygen evolution, and significantly improving battery safety.

[0075] In the embodiments of this application, the metal element in the metal cations of cobalt tetroxide includes at least one selected from Al, Mg, Ni, Mn, Ti, Zr, La, Y, and Ce. These doped metal cations can more effectively replace cobalt atoms in cobalt tetroxide and reside in situ, improving the doping synergistic effect with anions, thereby enhancing the stability, cycle performance, and safety of the internal structure of lithium cobalt oxide under high voltage.

[0076] Upon testing, the median particle size (D50) of the cobalt tetroxide doped in this application embodiment is 3-20 μm, and its particle morphology includes at least one of spherical, near-spherical, and elliptical shapes. Among them, the spherical morphology is as follows... Figure 1 and Figure 2 As shown, its particle size is uniform and its spherical morphology has a high degree of sphericity.

[0077] Secondly, this application also provides a method for preparing cobalt tetroxide doped with the aforementioned material. The process flow of the preparation method for cobalt tetroxide doped with the material in this application is as follows: Figure 3 As shown, it includes the following steps:

[0078] S01: Provides carbonate solutions containing doped anions;

[0079] S02: A portion of the carbonate solution is mixed with a first cobalt salt solution and subjected to a first hydrothermal reaction to generate doped cobalt carbonate seed crystals containing doped anions, thereby obtaining a doped cobalt carbonate seed crystal dispersion.

[0080] S03: The remaining carbonate solution and the second cobalt salt solution are mixed with the doped cobalt carbonate seed dispersion and subjected to a second hydrothermal reaction to grow the doped cobalt carbonate seed until the doped cobalt carbonate particles grow to the predetermined particle size.

[0081] S04: Calcine the doped cobalt carbonate particles to obtain doped cobalt tetroxide.

[0082] In step S01, the doping anion is the doping anion contained in the cobalt tetroxide doped in the above-described embodiments. Therefore, in the embodiments, the doping anion can be a halide ion, PO4, etc., as described above. 3- BO3 3- BO2 - SiO4 4- SiO3 2- At least one of the following. The compound providing the corresponding anion includes the corresponding soluble salt. For example, when the halide ion is chloride, the corresponding soluble chloride salt includes at least one of sodium chloride, potassium chloride, or ammonium chloride; when the halide ion is fluoride, the corresponding soluble fluoride salt includes at least one of sodium fluoride, potassium fluoride, or ammonium fluoride; the corresponding soluble phosphate includes at least one of sodium phosphate, potassium phosphate, or ammonium phosphate; the corresponding soluble borate includes at least one of boric acid, lithium borate, calcium borate, sodium metaborate, or potassium metaborate; and the corresponding soluble silicate includes at least one of potassium silicate, lithium silicate, or sodium metasilicate.

[0083] In the embodiments, the molar concentration of the doped anion in the carbonate solution can be controlled to be 0.0034-0.11 mol / L, and more specifically, 0.0054-0.09 mol / L. In other embodiments, the molar concentration of carbonate in the carbonate solution can be controlled to be 2.2-3.2 mol / L, and more specifically, 2.4-3.0 mol / L. The carbonate solution containing the doped anion can then be prepared according to the ratio of anion to carbonate concentrations. In specific embodiments, the solvent can be, but is not limited to, water. The carbonate can include at least one of ammonium carbonate and ammonium bicarbonate.

[0084] In step S02, the first hydrothermal reaction of a mixture of a portion of the carbonate solution and the first cobalt salt solution is used to generate cobalt tetroxide seed crystals. In this embodiment, in the first mixing step, the carbonate solution containing doped anions and the first cobalt salt solution can be in a molar ratio of 0.02-0.28:1 for the first cobalt salt to the carbonate. The solute concentration in the carbonate solution containing doped anions is as described above, such as a molar concentration of 0.0034-0.11 mol / L, or more specifically, 0.0054-0.09 mol / L; the molar concentration of the carbonate is 2.2-3.2 mol / L, or more specifically, 2.4-3.0 mol / L. In this embodiment, the molar concentration of cobalt ions in the first cobalt salt solution can be 0.4-3.0 mol / L, or more specifically, 0.5-2.8 mol / L. In a specific embodiment, the cobalt salt providing the cobalt ions can include at least one of cobalt nitrate, cobalt sulfate, and cobalt acetate.

[0085] In a further embodiment, the first cobalt salt solution may also contain a soluble metal salt. This soluble metal salt provides soluble metal ions, which are the doped metal cations contained in the cobalt tetroxide doped in the embodiments described above. In the embodiments, the concentration of this soluble metal salt in the first cobalt salt solution can be controlled to a metal element to cobalt element mass ratio of 0.0015-0.02:1, and more specifically, 0.0018-0.018:1. In a specific embodiment, the soluble metal salt may include at least one of a soluble metal nitrate, sulfate, or acetate. For example, when the soluble metal is aluminum, the soluble aluminum salt includes at least one of aluminum nitrate, aluminum sulfate, or aluminum acetate.

[0086] In this embodiment, during the first hydrothermal reaction in step S02, the carbonate, doped anion, and first cobalt salt undergo a reaction to generate doped cobalt carbonate seed crystals. At this time, the doped cobalt carbonate seed crystals contain the doped anion. When the first cobalt salt solution contains the aforementioned soluble metal salt, the carbonate, doped anion, and the first cobalt salt and soluble metal salt together undergo a reaction to generate doped cobalt carbonate seed crystals. At this time, the doped cobalt carbonate seed crystals contain both the doped anion and a soluble metal cation. In this embodiment, the conditions for the first hydrothermal reaction can be set as follows: the temperature can be 30-45℃, more specifically 30-40℃; the pH of the mixed solution after the first mixing treatment can be 6.7-8.8, more specifically 7-8.5. This hydrothermal reaction is beneficial for the generation of doped cobalt carbonate seed crystals. In a further embodiment, the first hydrothermal reaction can also be accompanied by a first stirring treatment, such as a stirring speed of 120-400 rpm, more specifically 150-400 rpm, and a stirring time controlled to be 2-36 h, more specifically 2-30 h. After the first hydrothermal reaction is completed, the first stirring treatment can be controlled to continue stirring and dispersing for 1-5 hours. By further controlling the first stirring treatment, the amount and dispersion of doped cobalt carbonate seed crystals can be improved.

[0087] In this embodiment, the method of performing a first mixing treatment and a first hydrothermal reaction on a portion of the carbonate solution and the first cobalt salt solution in step S02 includes the following steps:

[0088] A certain amount of carbonate solution is taken as the base liquid. Under the condition of the first stirring treatment, a certain amount of carbonate solution and the first cobalt salt solution (or further, the first cobalt salt solution containing the above-mentioned soluble metal salt) are added to the base liquid for the first mixing treatment and the first hydrothermal reaction.

[0089] By using a carbonate solution as the base solution, and then mixing and hydrothermally reacting the carbonate solution and a first cobalt salt solution (or further, a first cobalt salt solution containing a soluble metal salt as described above) in a additive manner, the generation and dispersibility of doped cobalt carbonate seed crystals can be improved. In the embodiments, the concentration of carbonate in the base solution can be controlled to be greater than 0, but within 200 g / L. The carbonate solution and the first cobalt salt solution are added to the base solution according to the molar ratio of the first cobalt salt contained in the first cobalt salt solution (or further, a first cobalt salt solution containing the aforementioned soluble metal salt) to the carbonate solution, specifically the carbonate solution containing anions, which can be 0.03-0.28:1, and further, 0.05-0.25:1. In addition, the volume of the carbonate solution containing doped anions can be 5-20% of the total volume of the hydrothermal reactor. Based on the first mixing treatment conditions, the conditions for the first hydrothermal reaction include at least one of the following: the pH of the base solution is 6.7-8.8, and more preferably 7-8.5; the temperature is 30-45℃, and more preferably 30-40℃; the stirring speed of the first stirring treatment is 120-400 rpm, and more preferably 150-400 rpm; the feeding time of the carbonate solution and the first cobalt salt solution into the base solution is controlled at 2-36 h, and more preferably 2-30 h; after the feeding is completed, stirring treatment continues for 1-5 h.

[0090] Furthermore, in step S02, by controlling the mixing ratio of the carbonate solution and the first cobalt salt solution (or further, the aforementioned first cobalt salt solution containing a soluble metal salt), the carbonate solution is used as a base solution before adding the carbonate solution and the first cobalt salt solution. This allows for concentration control of the carbonate solution in the first hydrothermal reaction, thereby increasing the amount and dispersion of cobalt carbonate seed crystals generated in the first hydrothermal reaction. This is because the inventors discovered in their research that excessively high or low concentrations of carbonates, such as ammonium carbonate, are detrimental to the formation of well-dispersed seed crystals. When the carbonate concentration is too high, the carbonate concentration in the reaction system is too high, leading to excessively rapid precipitation of cobalt carbonate and the formation of agglomerates. Conversely, when the carbonate concentration is too low, the ammonium ion concentration in the reaction system is too low, preventing the cobalt ions from being sufficiently complexed and protected by the ammonium ions. This also results in excessively rapid precipitation of cobalt carbonate, forming large agglomerates and affecting the distribution of the dopant element in the seed crystal. Tests showed that, through the control of the conditions of the first mixing treatment and the first hydrothermal reaction in step S02, the D50 particle size of the generated doped cobalt carbonate seed crystals can be 1.5-10 μm.

[0091] In step S03, the mixture of the remaining carbonate solution containing doped anions, the second cobalt salt solution, and the doped cobalt carbonate seed dispersion from step S01 undergoes a second hydrothermal reaction to achieve the growth of doped cobalt tetroxide seed crystals in step S02, and to control the particle size of the generated doped cobalt tetroxide to reach the expected particle size.

[0092] In this embodiment, the method of performing a second mixing treatment and a second hydrothermal reaction on the remaining carbonate solution and the second cobalt salt solution with the doped cobalt carbonate seed dispersion includes the following steps:

[0093] The remaining carbonate solution and the second cobalt salt solution are added to the cobalt carbonate seed dispersion in multiple intervals for a second mixing treatment and a second hydrothermal reaction.

[0094] The second hydrothermal reaction is carried out by adding carbonate solution and second cobalt salt solution at multiple intervals, resulting in more uniform particle size and morphology of the grown doped cobalt carbonate particles while achieving the expected particle size range. The interval between two consecutive additions can be after the completion of the previous second hydrothermal reaction, or during the process of the previous second hydrothermal reaction. In the embodiment, during the second mixing treatment and second hydrothermal reaction steps, the remaining carbonate solution and second cobalt salt solution are added to the doped cobalt carbonate seed dispersion at a molar ratio of 0.02-1.0:1, or more preferably 0.02-0.8:1, of the second cobalt salt contained in the second cobalt salt solution to the carbonate contained in the remaining carbonate solution (specifically, the anionic carbonate solution). The total feeding time for adding the remaining carbonate solution and second cobalt salt solution to the doped cobalt carbonate seed dispersion in multiple batches can be controlled to be 10-80 hours, or more preferably 10-70 hours. The conditions for the second hydrothermal reaction include at least one of the following: the pH of the mixed solution obtained from the second mixing treatment is 6.5-8.5, more preferably 6.5-8.0; the temperature is 30-50℃, more preferably 30-47℃; the second mixing treatment can be, but is not limited to, the second stirring treatment, in which case the stirring speed is 60-400 rpm, more preferably 80-400 rpm. The conditions for the second hydrothermal reaction within this range can effectively control the growth of doped cobalt carbonate seeds, improve the growth efficiency of doped cobalt carbonate particles, and also improve their particle size and morphology to be more uniform. Testing showed that, through the control of the conditions of the second mixing treatment and the second hydrothermal reaction in step S03, the D50 particle size of the generated doped cobalt carbonate, i.e., the predetermined particle size, can be 3-22 μm.

[0095] In this embodiment, the second cobalt salt solution in step S03 can be the same as the first cobalt salt solution in step S02, such as the molar concentration of cobalt ions in the second cobalt salt solution being 0.4-3 mol / L, or more specifically, 0.5-2.8 mol / L. In a specific embodiment, the cobalt salt providing the cobalt ions can include at least one of cobalt nitrate, cobalt sulfate, and cobalt acetate. In a further embodiment, the second cobalt salt solution may also contain a soluble metal salt. This soluble metal salt provides the doped metal cation contained in the cobalt tetroxide doped in the embodiments of the above application. In this embodiment, the concentration of the soluble metal salt in the second cobalt salt solution can be such that the mass ratio of the metal element to the cobalt element is controlled to be 0.0015-0.02:1, or more specifically, 0.0018-0.018:1. In a specific embodiment, the soluble metal salt can include at least one of a soluble metal nitrate, sulfate, and acetate. For example, when the soluble metal is aluminum, the soluble aluminum salt includes at least one of aluminum nitrate, aluminum sulfate, and aluminum acetate. Ideally, when the first cobalt salt solution in step S02 contains a soluble metal salt, the second cobalt salt solution in step S03 should also contain a soluble metal salt. Furthermore, the soluble metal salt contained in the first cobalt salt solution and the soluble metal and its salt contained in the second cobalt salt solution can be the same or different.

[0096] When the second hydrothermal reaction is carried out by adding carbonate solution and second cobalt salt solution in multiple intervals in step S03, if the set particle size is not reached after repeated feeding 8-11 times, some material in the growth container, such as the growth kettle, can be transferred to other empty growth containers, such as the growth kettle, and the feeding process in step S03 can be repeated until the target particle size is reached; the number of kettle divisions can be controlled to 1-5 times until the generated doped cobalt carbonate particles reach the set particle size.

[0097] After the cobalt carbonate particles doped in step S03 grow to the predetermined particle size, the process further includes solid-liquid separation of the reaction solution system after the second hydrothermal reaction, washing of the generated cobalt carbonate, and drying. In this embodiment, solid-liquid separation can be achieved through centrifugation or filtration. Washing can be performed by dispersing the cobalt carbonate obtained from the solid-liquid separation in hot water at 50-80°C, or more preferably 60-80°C, followed by centrifugation for 10-40 minutes, or more preferably 10-25 minutes, and then dehydration for at least 30 minutes, resulting in a moisture content of less than 15% for the dehydrated cobalt carbonate. Drying can be performed using an oven or a flash dryer, or other drying equipment. When using an oven, the drying temperature is controlled at 95-110°C; when using a flash dryer, the drying temperature is controlled at 150-200°C.

[0098] In step S04, during the calcination process, the doped cobalt carbonate particles are sintered to generate doped cobalt trioxide particles. In this embodiment, the calcination process may include first performing a first-temperature-zone sintering process, followed by a second-temperature-zone sintering process; wherein the temperature of the first-temperature-zone sintering process can be 200-620℃, further 220-580℃; and the temperature of the second-temperature-zone sintering process can be 630-830℃. By controlling and optimizing the process steps and conditions of the sintering process, the particle size integrity and uniformity of the generated doped cobalt trioxide particles are improved while ensuring sufficient sintering of the doped cobalt carbonate particles to generate doped cobalt trioxide particles.

[0099] In a further embodiment, the cobalt carbonate particles can be sieved before calcination to control their particle size. Alternatively, after calcination, the resulting cobalt trioxide particles can be further sieved to obtain cobalt trioxide particles of the target particle size. By adding sieving steps before and after sintering, the final cobalt trioxide particles have a uniform particle size. As in the embodiment, the sieving of the cobalt carbonate particles can be performed using a 200-600 mesh sieve, further refined to a 200-400 mesh sieve. The sieving of the cobalt trioxide particles can be performed using a 200-600 mesh sieve.

[0100] Therefore, the above-mentioned method for preparing doped cobalt tetroxide directly mixes the dopant anions, or further mixes the dopant anions, metal cations, and cobalt salt solution to achieve atomic-level mixing of the dopant ions, thereby achieving atomic-level doping and ensuring a uniform distribution of dopant ions in the prepared doped cobalt tetroxide. Furthermore, the generation efficiency, particle size, and morphology of the doped cobalt tetroxide can be improved by controlling and adjusting the feeding method and process conditions. In addition, the preparation method for doped cobalt tetroxide ensures stable morphology and electrochemical performance of the prepared doped cobalt tetroxide, and is highly efficient.

[0101] Thirdly, this application also provides a doped lithium cobalt oxide cathode material. The doped lithium cobalt oxide cathode material of this application is formed by calcining a lithium cobalt oxide precursor and a lithium source in a specific ratio. The lithium cobalt oxide precursor includes cobalt tetroxide (cobalt oxide) as described in the previous application. Thus, the doped lithium cobalt oxide cathode material of this application is formed by sintering the lithium cobalt oxide precursor. Therefore, it contains doped anions or further contains doped anions and metal cations, and can achieve atomic-level doping and distribution. This allows it to fully utilize the doping effects and doping synergistic effects of the anions or further doped anions and metal cations. Consequently, the doped lithium cobalt oxide cathode material of this application can suppress the participation of oxygen in the lithium cobalt oxide lattice for charge compensation under high voltage, reduce oxygen evolution, and improve structural stability during charge and discharge processes. This endows the doped lithium cobalt oxide cathode material of this application with excellent cycle stability under high voltage and high safety.

[0102] In addition, when the cobalt tetroxide precursor and the lithium source are calcined in a certain proportion, the cobalt tetroxide and the lithium source can be mixed in the same proportion as the cobalt tetroxide and lithium source to form lithium cobalt oxide by sintering. The calcination temperature can also be set according to the calcination conditions for the cobalt tetroxide and lithium source to form lithium cobalt oxide by sintering.

[0103] Fourthly, embodiments of this application also provide a secondary battery. The secondary battery of this application embodiment includes a positive electrode, a separator, and a negative electrode stacked sequentially.

[0104] The positive electrode includes a positive current collector and a positive active layer bonded to the current collector. The positive active material contained in this active layer includes the lithium cobalt oxide positive electrode material doped according to the embodiments described above. Thus, the secondary battery of this embodiment exhibits excellent cycle performance, low gas production, high safety, long lifespan, and stable electrochemical performance. Of course, the positive active layer also includes other components such as binders and conductive agents, which can be selected according to the binders and conductive agents commonly found in lithium cobalt oxide positive electrodes.

[0105] The negative electrode and separator in the secondary battery of this application embodiment can also be the negative electrode and separator in a lithium cobalt oxide secondary battery. For example, the negative electrode can be, but is not limited to, a lithium sheet.

[0106] In addition, the secondary battery in the embodiments of the present invention can be a lithium-ion battery or a lithium metal battery.

[0107] The following examples illustrate the doping of cobalt tetroxide, its preparation method, and its application in this application.

[0108] 1. Examples of doped cobalt tetroxide and its preparation method:

[0109] Example A1

[0110] This embodiment provides anion- and cation-doped cobalt tetroxide and its preparation method. The crystal phase of the anion- and cation-doped cobalt tetroxide contains aluminum and BO3 dopants. 3- Specifically, Co 2.93 Al 0.07 O 3.976 (BO3) 0.024 .

[0111] Co-doped cobalt tetroxide with anions and cations and its preparation method include the following steps:

[0112] S1. Prepare the solution: Prepare a solution containing BO3. 3- An aqueous solution of ammonium bicarbonate, and an aqueous solution of cobalt nitrate containing aluminum nitrate; wherein, BO3 3- The concentration of aluminum ions is 0.012 mol / L, the concentration of ammonium bicarbonate is 2.5 mol / L, the concentration of cobalt ions is 0.55 mol / L, and the mass ratio of aluminum to cobalt in the aluminum-cobalt solution is 0.009.

[0113] S2. Seed synthesis: [The following appears to be a separate, unrelated sentence:] Seed crystal synthesis: [The following appears to be a separate, unrelated sentence:] Seed crystals containing BO3... 3- An aqueous solution of ammonium bicarbonate was added to the seed reactor as the base solution, accounting for 10% of the total reactor volume. The ammonium bicarbonate concentration of the base solution was 100 g / L, the pH of the base solution was controlled at 7.6, the rotation speed was controlled at 260 rpm, and the temperature was controlled at 33℃. Cobalt nitrate containing aluminum and BO3 were added. 3- A solution with an ammonium bicarbonate molar ratio of 0.2 was added to a cobalt nitrate solution containing aluminum and a BO3-containing solution. 3- The pH of the ammonium bicarbonate solution was 7.2, and the feeding time was controlled at 5 hours. After the feeding was completed, the mixture was stirred and dispersed for another 4 hours to obtain cobalt carbonate seed crystals with a median particle size D50 of 2 μm.

[0114] S3. Cobalt carbonate doped growth: Rotation speed 300 rpm, temperature 33℃, adding aluminum-cobalt-containing solution and BO3-containing solution. 3- Ammonium bicarbonate solution, specifically containing aluminum, cobalt nitrate, and BO3. 3- Ammonium bicarbonate was added at a molar ratio of cobalt nitrate to ammonium bicarbonate of 0.16. The feed consisted of an aluminum-cobalt solution and a BO3-containing solution. 3- The pH of the ammonium bicarbonate solution was 7.3, and the total feeding time was controlled at 22 hours; the median particle size D50 of the final cobalt carbonate doped solution was 3.88 μm.

[0115] S4. Washing and drying of cobalt carbonate: Pour the cobalt carbonate slurry from step S3 into a centrifuge, wash the cobalt carbonate slurry with hot water at 60-70℃ for 15 minutes, dehydrate for 30 minutes, and after dehydration, the moisture content of the cobalt carbonate is less than 15%. Then put the wet cobalt carbonate slurry into an oven at 108℃ and dry it for more than 8 hours to obtain the dried cobalt carbonate.

[0116] S5. Calcination of doped cobalt carbonate: The dried doped cobalt carbonate is fed into a rotary kiln by a bucket elevator or vacuum feeder for sintering. The temperature of the low temperature zone of the rotary kiln is 300℃ and the temperature of the high temperature zone is 830℃. After calcination, the finished product, co-doped cobalt tetroxide, is obtained by sieving through a 300-mesh vibrating screen.

[0117] S6. Mixing and Packaging: After mixing with cobalt tetroxide for 10 minutes, the mixture is packaged using a packaging machine to obtain the following product: Figure 1 The doped cobalt tetroxide product shown has the molecular formula Co. 2.93 Al 0.07 O 3.976 (BO3) 0.024 The median particle size D50 is 3.91 μm.

[0118] Example A2

[0119] This embodiment provides anion- and cation-doped cobalt tetroxide and its preparation method. The crystal phase of the anion- and cation-doped cobalt tetroxide contains aluminum and BO3 dopants. 3- Specifically, Co 2.93 Al 0.07 O 3.97 (BO3) 0.03 .

[0120] Co-doped cobalt tetroxide with anions and cations and its preparation method include the following steps:

[0121] S1. Prepare the solution: Prepare a solution containing BO3. 3- An aqueous solution of ammonium bicarbonate, and an aqueous solution of cobalt nitrate containing aluminum nitrate. BO3 3- The concentration of aluminum ions was 0.03 mol / L, the concentration of ammonium bicarbonate was 2.5 mol / L, the concentration of cobalt ions was 1.6 mol / L, and the mass ratio of aluminum to cobalt in the aluminum-cobalt solution was 0.009.

[0122] S2. Seed synthesis: [The following appears to be a separate, unrelated sentence:] Seed crystal synthesis: [The following appears to be a separate, unrelated sentence:] Seed crystals containing BO3... 3- An aqueous solution of ammonium bicarbonate was added to the seed reactor as the base solution, accounting for 11% of the total reactor volume. The ammonium bicarbonate concentration of the base solution was 150 g / L, the pH of the base solution was controlled at 7.8, the rotation speed was controlled at 190 rpm, and the temperature was controlled at 34℃. Cobalt nitrate containing aluminum and BO3 were added. 3- A solution with an ammonium bicarbonate molar ratio of 0.15 was added during the feeding process. The solution contained aluminum cobalt nitrate and BO3. 3- The pH of the ammonium bicarbonate solution was 7.6, the feeding time was controlled at 23h, and after the feeding was completed, the mixture was stirred and dispersed for another 4h to obtain cobalt carbonate seed crystals; the median particle size D50 was 9.75μm.

[0123] S3. Cobalt carbonate doping growth: Rotation speed 145 rpm, temperature 40℃, adding aluminum-doped cobalt solution and BO3-doped solution. 3- Ammonium bicarbonate solution, specifically containing aluminum, cobalt nitrate, and BO3. 3- Ammonium bicarbonate was added at a molar ratio of cobalt nitrate to ammonium bicarbonate of 0.3. During the feeding process, aluminum-cobalt doping solution and BO3 doping solution were added. 3- The pH of the ammonium bicarbonate solution was 6.8, the total feeding time was controlled at 60 h, and the median particle size D50 of the final cobalt carbonate doped was 20.6 μm.

[0124] S4. Washing and drying of cobalt carbonate doped with cobalt carbonate: Pour the cobalt carbonate doped with cobalt carbonate slurry from step S3 into a centrifuge, wash the cobalt carbonate doped with cobalt carbonate slurry with hot water at 70-75℃ for 12 minutes, dehydrate for 30 minutes, and after dehydration, the moisture content of the cobalt carbonate doped with cobalt carbonate is less than 15%. Then place the wet cobalt carbonate doped with cobalt carbonate in an oven for drying for more than 8 hours at a temperature of 105℃ to obtain the dried cobalt carbonate doped with cobalt carbonate.

[0125] S5. Calcination of doped cobalt carbonate: After drying, the doped cobalt carbonate is sieved through a 200-mesh sieve and then calcined in a rotary kiln. The temperature of the low-temperature zone of the rotary kiln is 440℃ and the temperature of the high-temperature zone is 780℃. After calcination, it is sieved through a 300-mesh vibrating sieve to obtain the doped cobalt tetroxide product.

[0126] S6. Mixing and Packaging: After mixing with cobalt tetroxide for 10 minutes, the mixture is packaged using a packaging machine to obtain the following product: Figure 2 The doped cobalt tetroxide product shown has the molecular formula Co. 2.93 Al 0.07 O 3.97 (BO3) 0.03 The median particle size D50 is 16.8 μm.

[0127] Example A3

[0128] This embodiment provides anion- and cation-doped cobalt tetroxide and its preparation method. The crystal phase of the anion- and cation-doped cobalt tetroxide contains aluminum and fluorine dopants. - Specifically, Co 2.92 Al 0.08 O 3.89 F 0.11 .

[0129] Co-doped cobalt tetroxide with anions and cations and its preparation method include the following steps:

[0130] S1. Prepare the solution: Prepare a solution containing F. - An aqueous solution of ammonium carbonate, and an aqueous solution of cobalt sulfate containing aluminum sulfate. Among them, F... -The concentration of aluminum ions is 0.08 mol / L, the concentration of ammonium carbonate is 2.6 mol / L, the concentration of cobalt ions is 0.75 mol / L, and the mass ratio of aluminum to cobalt in the aluminum-cobalt solution is 0.0121.

[0131] S2. Seed Synthesis: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] - An aqueous solution of ammonium carbonate was added to the seed reactor as the base solution, accounting for 12% of the total reactor volume. The ammonium carbonate concentration of the base solution was 120 g / L, the pH of the base solution was controlled at 7.85, the rotation speed was controlled at 280 rpm, and the temperature was controlled at 31℃. Cobalt aluminum sulfate and F-containing compounds were also added. - A solution with an ammonium carbonate molar ratio of 0.22 was added during the feeding process, containing cobalt aluminum sulfate and F. - The pH of the ammonium carbonate solution was 7.4, the feeding time was controlled at 4 hours, and after the feeding was completed, the mixture was stirred and dispersed for another 5 hours to obtain cobalt carbonate seed crystals; the median particle size D50 was 1.9 μm.

[0132] S3. Cobalt carbonate doping growth: Rotation speed 320 rpm, temperature 32℃, adding aluminum-cobalt-containing solution and F-containing solution. - Ammonium carbonate solution, specifically an aluminum-cobalt solution and an F-containing solution. - Ammonium carbonate solution was added at a molar ratio of cobalt sulfate to ammonium carbonate of 0.22. During the feeding process, the aluminum-cobalt solution and the F-containing solution... - The pH of the ammonium carbonate solution was 7.5, and the total feeding time was controlled at 20 hours; the median particle size D50 of the final doped cobalt carbonate was 3.8 μm.

[0133] S4. Washing and drying of cobalt carbonate doped with cobalt carbonate: Pour the cobalt carbonate slurry from step S3 into a centrifuge, wash the cobalt carbonate doped with cobalt carbonate slurry with hot water at 70-80℃ for 12 minutes, dehydrate for 30 minutes, and after dehydration, the moisture content of the cobalt carbonate doped with cobalt carbonate is less than 15%. Then transfer the wet cobalt carbonate doped with cobalt carbonate into a flash dryer for drying at a temperature of 175℃ to obtain cobalt carbonate doped with cobalt carbonate.

[0134] S5. Calcination of doped cobalt carbonate: After drying, the doped cobalt carbonate is sieved through a 300-mesh sieve and then calcined in a rotary kiln. The temperature in the low-temperature zone of the rotary kiln is 260℃, and the temperature in the high-temperature zone is 815℃. After calcination, it is sieved through a 400-mesh vibrating sieve to obtain the doped cobalt tetroxide product.

[0135] S6. Mixing and Packaging: After mixing with cobalt tetroxide for 10 minutes, package the mixture using a packaging machine to obtain the cobalt tetroxide-doped product with the molecular formula Co. 2.92 Al 0.08 O 3.89 F 0.11 The median particle size D50 is 3.78 μm.

[0136] Example A4

[0137] This embodiment provides anion- and cation-doped cobalt tetroxide and its preparation method. The crystal phase of the anion- and cation-doped cobalt tetroxide contains aluminum and fluorine dopants. - Specifically, Co 2.92 Al 0.08 O 3.97 F 0.03 .

[0138] Co-doped cobalt tetroxide with anions and cations and its preparation method include the following steps:

[0139] S1. Prepare the solution: Prepare a solution containing F. - An aqueous solution of ammonium carbonate, and an aqueous solution of cobalt sulfate containing aluminum sulfate. Among them, F... - The concentration of aluminum ions is 0.08 mol / L, the concentration of ammonium carbonate is 2.6 mol / L, the concentration of cobalt ions is 0.75 mol / L, and the mass ratio of aluminum to cobalt in the aluminum-cobalt solution is 0.0121.

[0140] S2. Seed Synthesis: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] - An ammonium carbonate aqueous solution was added to the seed reactor as the base solution, accounting for 12% of the total reactor volume. The ammonium carbonate concentration of the base solution was 120 g / L, the pH of the base solution was controlled at 7.85, the rotation speed was controlled at 185 rpm, and the temperature was controlled at 35℃. Cobalt aluminum sulfate and F-containing compounds were added. - A solution with an ammonium carbonate molar ratio of 0.22 was added during the feeding process. The solution contained cobalt aluminum sulfate and F... - The pH of the ammonium carbonate solution was 7.3, the feeding time was controlled at 25 h, and after the feeding was completed, the mixture was stirred and dispersed for another 5 h to obtain cobalt carbonate seed crystals; the median particle size D50 was 9.65 μm.

[0141] S3. Cobalt carbonate doped growth: Rotation speed 100 rpm, temperature 35℃, adding aluminum-cobalt-containing solution and F-containing solution. - Ammonium carbonate solution, specifically cobalt sulfate containing aluminum and F. - Ammonium carbonate is added at a molar ratio of cobalt sulfate to ammonium carbonate of 0.22. During the feeding process, the aluminum-cobalt-containing solution and the F-containing solution... - The pH of the ammonium carbonate solution was 7.6, and the total feeding time was controlled at 65 hours; the median particle size D50 of the final cobalt carbonate doped solution was 20.5 μm.

[0142] S4. Washing and drying of cobalt carbonate doped with cobalt carbonate: Pour the cobalt carbonate doped with cobalt carbonate slurry from step S3 into a centrifuge, wash the cobalt carbonate doped with cobalt carbonate slurry with hot water at 70-75℃ for 15 minutes, dehydrate for 30 minutes, and after dehydration, the moisture content of the cobalt carbonate doped with cobalt carbonate is less than 15%. Then transfer the wet cobalt carbonate doped with cobalt carbonate to a flash dryer for drying at a temperature of 170℃ to obtain the dried cobalt carbonate doped with cobalt carbonate.

[0143] S5. Calcination of doped cobalt carbonate: After drying, the doped cobalt carbonate is sieved through a 200-mesh sieve and then calcined in a rotary kiln. The temperature of the low-temperature zone of the rotary kiln is 280℃ and the temperature of the high-temperature zone is 815℃. After calcination, the product is obtained by sieving through a 200-mesh vibrating sieve.

[0144] S6. Mixing and Packaging: After mixing with cobalt tetroxide for 10 minutes, package the mixture using a packaging machine to obtain the cobalt tetroxide-doped product with the molecular formula Co. 2.92 Al 0.08 O 3.97 F 0.03 The median particle size is 17.8 μm.

[0145] Example A5

[0146] This embodiment provides anion- and cation-doped cobalt tetroxide and its preparation method. The crystal phase of the anion- and cation-doped cobalt tetroxide contains aluminum and PO4. 3- Specifically, Co 2.91 Al 0.09 O 3.95 (PO4) 0.05 .

[0147] Co-doped cobalt tetroxide with anions and cations and its preparation method include the following steps:

[0148] S1. Prepare solution: Prepare solution containing PO4. 3- An aqueous solution of ammonium bicarbonate, and an aqueous solution of cobalt nitrate containing aluminum nitrate. PO4 is present. 3- The concentration is 0.006 mol / L, the ammonium bicarbonate concentration is 2.7 mol / L, the cobalt ion concentration is 1 mol / L, and the mass ratio of aluminum to cobalt in the aluminum-cobalt solution is 0.017.

[0149] S2. Seed synthesis: [The process involves] synthesizing PO4-containing crystals... 3- An aqueous solution of ammonium bicarbonate was added to the seed reactor as the base solution, accounting for 14% of the total reactor volume. The ammonium bicarbonate concentration of the base solution was 130 g / L, the pH of the base solution was controlled at 8.1, the rotation speed was controlled at 275 rpm, and the temperature was controlled at 33℃. Cobalt nitrate containing aluminum and PO4 were added. 3- A solution with an ammonium bicarbonate molar ratio of 0.13 was added during the feeding process, along with a solution containing aluminum cobalt nitrate and PO4. 3- The pH of the ammonium bicarbonate solution was 7.7, the feeding time was controlled at 6h, and after the feeding was completed, the mixture was stirred and dispersed for another 3h to obtain cobalt carbonate seed crystals; the median particle size D50 was 2.1μm.

[0150] S3. Cobalt carbonate doped growth: Rotation speed 300 rpm, temperature 33℃, adding aluminum-cobalt-containing solution and PO4-containing solution. 3- Ammonium bicarbonate solution, specifically containing aluminum, cobalt nitrate, and PO4.3- Ammonium bicarbonate was added at a molar ratio of cobalt nitrate to ammonium bicarbonate of 0.45. During the feeding process, the aluminum-cobalt-containing liquid and the PO4-containing liquid were... 3- The pH of the ammonium bicarbonate solution was 7.6, the total feeding time was controlled at 29 h, and the median particle size D50 of the final cobalt carbonate doped was 3.79 μm.

[0151] S4. Washing and drying of cobalt carbonate doped with cobalt carbonate: Pour the cobalt carbonate doped with cobalt carbonate slurry from step S3 into a centrifuge, wash the cobalt carbonate doped with cobalt carbonate slurry with hot water at 75-80℃ for 12 minutes, dehydrate for 30 minutes, and after dehydration, the moisture content of the cobalt carbonate doped with cobalt carbonate is less than 15%. Then place the wet cobalt carbonate doped with cobalt carbonate in an oven to dry for more than 8 hours at a temperature of 105℃ to obtain the dried cobalt carbonate doped with cobalt carbonate.

[0152] S5. Calcination of doped cobalt carbonate: After drying, the doped cobalt carbonate is sieved through a 300-mesh sieve and then calcined in a rotary kiln. The temperature of the low-temperature zone of the rotary kiln is 280℃ and the temperature of the high-temperature zone is 800℃. After calcination, the product is obtained by sieving through a 300-mesh vibrating sieve.

[0153] S6. Mixing and Packaging: After mixing with cobalt tetroxide for 10 minutes, package the mixture using a packaging machine to obtain the cobalt tetroxide-doped product with the molecular formula Co. 2.91 Al 0.09 O 3.95 (PO4) 0.05 The median particle size is 3.76 μm.

[0154] Example A6

[0155] This embodiment provides anion- and cation-doped cobalt tetroxide and its preparation method. The crystal phase of the anion- and cation-doped cobalt tetroxide contains aluminum and PO4. 3- Specifically, Co 2.91 Al 0.09 O 3.93 (PO4) 0.07 .

[0156] Co-doped cobalt tetroxide with anions and cations and its preparation method include the following steps:

[0157] S1. Prepare solution: Prepare solution containing PO4. 3- An aqueous solution of ammonium bicarbonate, and an aqueous solution of cobalt nitrate containing aluminum nitrate. PO4 is present. 3- The concentration is 0.006 mol / L, the ammonium bicarbonate concentration is 2.7 mol / L, the cobalt ion concentration is 1 mol / L, and the mass ratio of aluminum to cobalt in the aluminum-cobalt solution is 0.017.

[0158] S2. Seed synthesis: [The process involves] synthesizing PO4-containing crystals... 3-An aqueous solution of ammonium bicarbonate was added to the seed reactor as the base solution, accounting for 14% of the total reactor volume. The ammonium bicarbonate concentration of the base solution was 130 g / L, the pH of the base solution was controlled at 8, the stirring speed was controlled at 200 rpm, and the temperature was controlled at 35℃. Cobalt nitrate containing aluminum and PO4 were also added. 3- The molar ratio of ammonium bicarbonate to PO4 is 0.13. During the feeding process, the cobalt nitrate solution containing aluminum reacts with the solution containing PO4. 3- The pH of the ammonium bicarbonate solution was 7.3, and the feeding time was controlled at 25 h. After the feeding was completed, the mixture was stirred and dispersed for another 2 h to obtain cobalt carbonate seed crystals; the median particle size D50 was 10 μm.

[0159] S3. Cobalt carbonate doped growth: Rotation speed 130 rpm, temperature 35℃, adding aluminum-cobalt-containing solution and PO4-containing solution. 3- Ammonium bicarbonate solution, specifically an aluminum-cobalt solution containing PO4. 3- Ammonium bicarbonate was added at a molar ratio of cobalt nitrate to ammonium bicarbonate of 0.45. The feed consisted of an aluminum-cobalt solution and a PO4-containing solution. 3- The pH of the ammonium bicarbonate solution was 7.6, the total feeding time was controlled at 65 h, and the median particle size D50 of the final cobalt carbonate doping was 21 μm.

[0160] S4. Washing and drying of cobalt carbonate doped with cobalt carbonate: Pour the cobalt carbonate doped with cobalt carbonate slurry from step S3 into a centrifuge, wash the cobalt carbonate doped with cobalt carbonate slurry with hot water at 65-75℃ for 10 min, dehydrate for 35 min, and after dehydration, the moisture content of the cobalt carbonate doped with cobalt carbonate is less than 15%. Then place the wet cobalt carbonate doped with cobalt carbonate in an oven to dry at a temperature of 105℃ to obtain the dried cobalt carbonate doped with cobalt carbonate.

[0161] S5. Calcination of doped cobalt carbonate: After drying, the doped cobalt carbonate is sieved through a 200-mesh sieve and then calcined in a rotary kiln. The temperature of the low-temperature zone of the rotary kiln is 280℃ and the temperature of the high-temperature zone is 810℃. After calcination, it is sieved through a 300-mesh vibrating sieve to obtain the doped cobalt tetroxide product.

[0162] S6. Mixing and Packaging: After mixing with cobalt tetroxide for 10 minutes, package the mixture using a packaging machine to obtain the cobalt tetroxide-doped product with the molecular formula Co. 2.91 Al 0.09 O 3.93 (PO4) 0.07 The median particle size is 17.6 μm.

[0163] Example A7

[0164] This embodiment provides anion- and cation-doped cobalt tetroxide and its preparation method. The crystal phase of the anion- and cation-doped cobalt tetroxide contains aluminum and SiO3 doping. 3- Specifically, Co 2.92 Al 0.08 O3.96 (SiO3) 0.04 .

[0165] Co-doped cobalt tetroxide with anions and cations and its preparation method include the following steps:

[0166] S1. Solution preparation: Prepare a solution containing SiO3. 3- An aqueous solution of ammonium carbonate, and an aqueous solution of cobalt acetate containing aluminum acetate. SiO3 is present in the solution. 3- The concentration of aluminum ions is 0.053 mol / L, the concentration of ammonium carbonate is 2.85 mol / L, the concentration of cobalt ions is 1.2 mol / L, and the mass ratio of aluminum to cobalt in the aluminum-cobalt solution is 0.007.

[0167] S2. Seed Synthesis: Seed crystals containing SiO3... 3- An aqueous solution of ammonium carbonate was added to the seed reactor as the base solution, accounting for 16% of the total reactor volume. The ammonium carbonate concentration of the base solution was 160 g / L, the pH of the base solution was controlled at 7.75, the rotation speed was controlled at 290 rpm, and the temperature was controlled at 34℃. Cobalt aluminum acetate and SiO3 were added. 3- The molar ratio of ammonium carbonate to sodium carbonate is 0.09. During the feeding process, the cobalt aluminum acetate solution and the SiO3 solution are reacted. 3- The pH of the ammonium carbonate solution was 7.4, the feeding time was controlled at 5h, and after the feeding was completed, the mixture was stirred and dispersed for another 4h to obtain cobalt carbonate seed crystals; the median particle size D50 was 2.06μm.

[0168] S3. Cobalt carbonate doping growth: Rotation speed 300 rpm, temperature 35℃, adding aluminum-cobalt-containing solution and SiO3-containing solution. 3- Ammonium carbonate solution, specifically containing cobalt aluminum acetate and SiO3. 3- Ammonium carbonate is added at a molar ratio of cobalt acetate to ammonium carbonate of 0.5. During the feeding process, the aluminum-cobalt liquid and the SiO3-containing liquid are mixed. 3- The pH of the ammonium carbonate solution was 7.45, the total feeding time was controlled at 28h, and the median particle size D50 of the final cobalt carbonate doped was 3.86μm.

[0169] S4. Washing and drying of cobalt carbonate: Pour the cobalt carbonate slurry from step S3 into a centrifuge, wash the cobalt carbonate slurry with hot water at 65-75℃ for 10 minutes, dehydrate for 35 minutes, and after dehydration, the moisture content of the cobalt carbonate is less than 15%. Then place the wet cobalt carbonate in an oven to dry at 110℃ to obtain the dried cobalt carbonate.

[0170] S5. Calcination of doped cobalt carbonate: After drying, the doped cobalt carbonate is sieved through a 400-mesh sieve and then calcined in a rotary kiln. The temperature of the low-temperature zone of the rotary kiln is 310℃ and the temperature of the high-temperature zone is 795℃. After calcination, it is sieved through a 300-mesh vibrating sieve to obtain the doped cobalt tetroxide product.

[0171] S6. Mixing and Packaging: After mixing with cobalt tetroxide for 10 minutes, package the mixture using a packaging machine to obtain the cobalt tetroxide-doped product with the molecular formula Co. 2.92 Al 0.08 O 3.96 (SiO3) 0.04 The median particle size is 3.87 μm.

[0172] Example A8

[0173] This embodiment provides anion- and cation-doped cobalt tetroxide and its preparation method. The crystal phase of the anion- and cation-doped cobalt tetroxide contains aluminum and SiO3 doping. 3- Specifically, Co 2.92 Al 0.08 O 3.91 (SiO3) 0.09 .

[0174] Co-doped cobalt tetroxide with anions and cations and its preparation method include the following steps:

[0175] S1. Solution preparation: Prepare a solution containing SiO3. 3- An aqueous solution of ammonium carbonate, and an aqueous solution of cobalt acetate containing aluminum acetate. SiO3 is present in the solution. 3- The concentration of aluminum ions is 0.053 mol / L, the concentration of ammonium carbonate is 2.85 mol / L, the concentration of cobalt ions is 1.2 mol / L, and the mass ratio of aluminum to cobalt in the aluminum-cobalt solution is 0.007.

[0176] S2. Seed Synthesis: Seed crystals containing SiO3... 3- An aqueous solution of ammonium carbonate was added to the seed reactor as the base solution, accounting for 16% of the total reactor volume. The ammonium carbonate concentration of the base solution was 160 g / L, the pH of the base solution was controlled at 7.6, the rotation speed was controlled at 160 rpm, and the temperature was controlled at 38℃. Cobalt aluminum acetate and SiO3 were added. 3- The molar ratio of ammonium carbonate to sodium carbonate is 0.09. During the feeding process, the cobalt aluminum acetate solution and the SiO3 solution are reacted. 3- The pH of the ammonium carbonate solution was 7.45, the feeding time was controlled at 20h, and after the feeding was completed, the mixture was stirred and dispersed for another 3h to obtain cobalt carbonate seed crystals; the median particle size D50 was 9.6μm.

[0177] S3. Cobalt carbonate doping growth: Rotation speed 110 rpm, temperature 38℃, adding aluminum-cobalt-containing solution and SiO3-containing solution. 3- Ammonium carbonate solution, specifically containing cobalt aluminum acetate and SiO3. 3- Ammonium carbonate is added at a molar ratio of cobalt acetate to ammonium carbonate of 0.5. During the feeding process, the aluminum-cobalt liquid and the SiO3-containing liquid are mixed. 3-The pH of the ammonium carbonate solution was 7.65, the total feeding time was controlled at 70 h, and the median particle size D50 of the final cobalt carbonate doped was 21.5 μm.

[0178] S4. Washing and drying of cobalt carbonate doped with cobalt carbonate: Pour the cobalt carbonate doped with cobalt carbonate slurry from step S3 into a centrifuge, wash the cobalt carbonate doped with cobalt carbonate slurry with hot water at 60-70℃ for 15 minutes, dehydrate for 30 minutes, and after dehydration, the moisture content of the cobalt carbonate doped with cobalt carbonate is less than 15%. Then place the wet cobalt carbonate doped with cobalt carbonate in an oven to dry at a temperature of 110℃ to obtain the dried cobalt carbonate doped with cobalt carbonate.

[0179] S5. Calcination of doped cobalt carbonate: After drying, the doped cobalt carbonate is sieved through a 200-mesh sieve and then calcined in a rotary kiln. The temperature of the low-temperature zone of the rotary kiln is 330℃ and the temperature of the high-temperature zone is 785℃. After calcination, the product is obtained by sieving through a 200-mesh vibrating sieve.

[0180] S6. Mixing and Packaging: After mixing with cobalt tetroxide for 10 minutes, package the mixture using a packaging machine to obtain the cobalt tetroxide-doped product with the molecular formula Co. 2.92 Al 0.08 O 3.91 (SiO3) 0.09 The median particle size is 18 μm.

[0181] Example A9

[0182] Compared to Example A3, all steps and process parameters are identical except that an aluminum-free cobalt sulfate aqueous solution is used instead of an aluminum-containing cobalt sulfate solution. The prepared cobalt tetroxide product has the molecular formula Co3O. 3.89 F 0.11 The median particle size is 3.69 μm.

[0183] Example A10

[0184] Compared to Example A4, all steps and process parameters are identical except that an aluminum-free cobalt sulfate aqueous solution is used instead of an aluminum-containing cobalt sulfate solution. The prepared cobalt tetroxide product has the molecular formula Co3O. 3.89 F 0.11 The median particle size is 17.3 μm.

[0185] Comparative Example A1

[0186] Compared to Example A1, except for the use of BO3-free 3- Ammonium bicarbonate aqueous solution replaces BO3 3- Apart from the ammonium bicarbonate solution, all other steps and process parameters were consistent. The prepared cobalt tetroxide product has the molecular formula Co. 2.93 Al 0.07 O4, median particle size 3.87 μm.

[0187] Comparative Example A2

[0188] Compared to Example 2, except for the use of BO3-free... 3- Ammonium bicarbonate aqueous solution replaces BO3 3- Apart from the ammonium bicarbonate solution, all other steps and process parameters were consistent. The prepared cobalt tetroxide product has the molecular formula Co. 2.93 Al 0.07 O4, median particle size 16.5 μm.

[0189] Comparative Example A3

[0190] Compared to Example 1, except for the use of BO3-free... 3- Ammonium bicarbonate aqueous solution and aluminum-free cobalt nitrate aqueous solution replace BO3-containing solutions. 3- Apart from using ammonium bicarbonate solution and aluminum-containing cobalt nitrate solution, all other steps and process parameters were consistent. The prepared cobalt tetroxide product had the molecular formula Co3O4 and a median particle size of 3.86 μm.

[0191] Comparative Example A4

[0192] Compared to Example 2, except for the use of BO3-free... 3- Ammonium bicarbonate aqueous solution and aluminum-free cobalt nitrate aqueous solution replace BO3-containing solutions. 3- Apart from using ammonium bicarbonate solution and aluminum-containing cobalt nitrate solution, all other steps and process parameters were consistent. The prepared cobalt tetroxide product had the molecular formula Co3O4 and a median particle size of 16.5 μm.

[0193] 2. Examples of doped lithium cobalt oxide and its preparation method:

[0194] Examples B1 to B9

[0195] Examples B1 to B9 each provide a doped lithium cobalt oxide. The doped lithium cobalt oxide provided in Examples B1 to B9 is obtained by thoroughly mixing the doped cobalt tetroxide provided in Examples A1 to A9 with lithium carbonate at a molar ratio of 1:1.03 in a pot mill, and then calcining it in a bell furnace at 920°C for 10 hours.

[0196] Example B10

[0197] Example B10 provides a doped lithium cobalt oxide. It is obtained by mixing the doped cobalt tetroxide obtained in Example A1 and Example A2 in a ball mill at a mass ratio of 1:4, mixing the mixture with lithium carbonate in a pot mill at a molar ratio of 1:1.03, and then calcining the mixture in a bell furnace at 920°C for 10 hours.

[0198] Example B11

[0199] Example B11 provides a doped lithium cobalt oxide. It is obtained by mixing the doped cobalt tetroxide obtained in Example A3 and Example A4 in a ball mill at a mass ratio of 1:4, mixing the mixture with lithium carbonate in a pot mill at a molar ratio of 1:1.03, and then calcining the mixture in a bell furnace at 920°C for 10 hours.

[0200] Example B12

[0201] Example B12 provides a doped lithium cobalt oxide. It is obtained by mixing the doped cobalt tetroxide obtained in Example A5 and Example A6 in a ball mill at a mass ratio of 1:4, mixing the mixture with lithium carbonate in a pot mill at a molar ratio of 1:1.03, and then calcining the mixture in a bell furnace at 920°C for 10 hours.

[0202] Example B13

[0203] Example B13 provides a doped lithium cobalt oxide. It is obtained by mixing the doped cobalt tetroxide obtained in Example A7 and Example A8 in a ball mill at a mass ratio of 1:4, mixing the mixture with lithium carbonate in a pot mill at a molar ratio of 1:1.03, and then calcining the mixture in a bell furnace at 920°C for 10 hours.

[0204] Example B14

[0205] Example B14 provides a lithium cobalt oxide. It is obtained by mixing cobalt tetroxide obtained in Example A9 and Example A10 at a mass ratio of 1:4 in a ball mill, mixing the mixture with lithium carbonate at a molar ratio of 1:1.03 in a pot mill, and then calcining the mixture in a bell furnace at 920°C for 10 hours.

[0206] Comparative Examples B1 to B4

[0207] Comparative Examples B1 to B4 each provide a lithium cobalt oxide. The lithium cobalt oxide provided by Comparative Examples B1 to B4 is obtained by thoroughly mixing cobalt tetroxide and lithium carbonate provided in Comparative Examples A1 to A4 at a molar ratio of 1:1.03 in a pot mill, and then calcining it in a bell furnace at 920°C for 10 hours.

[0208] Comparative Example B5

[0209] Comparative Example B5 provides a lithium cobalt oxide. It is obtained by mixing cobalt tetroxide obtained from Comparative Example A1 and Comparative Example A2 in a ball mill at a mass ratio of 1:4, mixing the mixture with lithium carbonate in a pot mill at a molar ratio of 1:1.03, and then calcining the mixture in a bell furnace at 920°C for 10 hours.

[0210] Comparative Example B6

[0211] Comparative Example B6 provides a lithium cobalt oxide. It is obtained by mixing cobalt tetroxide obtained from Comparative Example A3 and Comparative Example A4 in a ball mill at a mass ratio of 1:4, mixing the mixture with lithium carbonate in a jar mill at a molar ratio of 1:1.03, and then calcining the mixture in a bell furnace at 920°C for 10 hours.

[0212] 3. Examples of lithium-ion batteries and electrical performance tests of lithium-ion batteries:

[0213] The lithium cobalt oxide doped in Examples B1 to B14 and the lithium cobalt oxide in Comparative Examples B1 to B6 were respectively used as positive electrode active materials to prepare positive electrode sheets, and were respectively assembled into lithium-ion batteries:

[0214] 1) Positive electrode plate:

[0215] Using the doped lithium cobalt oxide provided in Examples B1 to B13 and the lithium cobalt oxide provided in Comparative Examples B1 to B7 as positive electrode active materials, under the same conditions, a slurry was prepared by mixing the positive electrode active material, conductive agent acetylene black, binder PVDF, and solvent NMP in a mass ratio of 18:1:1:36. After homogenization, coating, drying, and cutting, a positive electrode sheet was prepared. The positive electrode sheet was baked in a vacuum oven to remove trace amounts of water.

[0216] 2) Negative electrode: Lithium metal sheet.

[0217] 3) Diaphragm: Polyethylene (PE) diaphragm.

[0218] 4) Electrolyte: 1 mol / L LiPF6 / EC+DEC+EMC (volume ratio 1:1:1).

[0219] 5) Assembly of secondary batteries:

[0220] The above-mentioned positive electrode, negative electrode, electrolyte and separator are assembled into a button lithium-ion battery according to the lithium-ion battery assembly requirements.

[0221] Lithium-ion battery performance tests:

[0222] The capacity retention rate of each lithium-ion battery assembled in Section 3 was tested under the following conditions:

[0223] The battery testing system used was the LAND CT2001A battery testing system (voltage range: 5V, current range: 1mA, 5mA and 10mA). During the test, the discharge voltage was fixed at 3V, the charging voltage was 4.55V, the test rate was 1C, and the test temperature was room temperature.

[0224] Capacity retention test results:

[0225] The capacity retention rate of lithium-ion batteries using doped lithium cobalt oxide provided in Example B10 and lithium cobalt oxide provided in Comparative Examples B5 to B6 as positive electrode active materials was measured as follows: Figure 4 As shown, the capacity retention rate of the lithium-ion battery using the doped lithium cobalt oxide provided in Example B11 as the positive electrode active material is as follows: Figure 5 As shown, the capacity retention rate of the lithium-ion battery using the doped lithium cobalt oxide provided in Example B12 as the positive electrode active material is as follows: Figure 6 As shown, the capacity retention rate of the lithium-ion battery using the doped lithium cobalt oxide provided in Example B13 as the positive electrode active material is as follows: Figure 7 As shown. The capacity retention rate of the lithium-ion battery using the cobalt-doped lithium oxide provided in Example B9 as the positive electrode active material is as follows: Figure 8 As shown.

[0226] Other lithium-ion batteries using lithium cobalt-doped lithium oxide as the positive electrode active material as provided in Examples B1 to B8 have high capacity retention rates and Figure 5 The capacity retention rates shown are similar. The capacity retention rates of the lithium-ion batteries using lithium cobalt oxide as the positive electrode active material provided in Comparative Examples B1 to B4 are relatively worse than those shown in the lithium-ion battery using lithium cobalt oxide as the positive electrode active material provided in Comparative Example B5. Therefore, it can be concluded that the cycle performance of the lithium-ion batteries using doped lithium cobalt oxide as the positive electrode active material provided in Examples B1 to B13 is significantly higher than that of the lithium-ion batteries using lithium cobalt oxide as the positive electrode active material provided in Comparative Examples B1 to B6.

[0227] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A cobalt tetroxide-doped cathode material for preparing cobalt oxide-doped lithium cobalt oxide, characterized in that: The doped cobalt tetroxide crystal phase is simultaneously doped with metal cations and anions; The anions include PO4. 3- BO3 3- BO2 - SiO4 4- SiO3 2- At least one of them.

2. The doped cobalt tetroxide according to claim 1, characterized in that: The anion is located at an oxygen vacancy in cobalt tetroxide, and the metal cation is located at a cobalt vacancy in cobalt tetroxide; and / or The general molecular formula of the doped cobalt tetroxide is Co. 3-x N x O 4-y M y Wherein, 0≤x≤0.11, 0.006≤y≤0.09, N is the metal cation, and M is the anion; and / or The metal element in the metal cation includes at least one of Al, Mg, Ni, Mn, Ti, Zr, La, Y, and Ce.

3. The doped cobalt tetroxide according to claim 1 or 2, characterized in that: The content of the metal cation in the doped cobalt tetroxide is 0.1-1.2%; and / or The anion content in the doped cobalt tetroxide is 0.05-1.5%; and / or The D50 particle size of the cobalt tetroxide doped material is 3-20 μm; and / or The cobalt tetroxide-doped particles include at least one of spherical, near-spherical, and elliptical shapes.

4. A method for preparing cobalt tetroxide as described in any one of claims 1 to 3, characterized in that: Includes the following steps: Provide carbonate solutions containing doped anions; A portion of the carbonate solution is mixed with a first cobalt salt solution and subjected to a first hydrothermal reaction to generate doped cobalt carbonate seed crystals containing the doped anions, thereby obtaining a doped cobalt carbonate seed crystal dispersion. The remaining carbonate solution and the second cobalt salt solution are mixed with the doped cobalt carbonate seed dispersion in a second mixing process and a second hydrothermal reaction is carried out to grow the doped cobalt carbonate seed until the doped cobalt carbonate particles grow to the predetermined particle size. The doped cobalt carbonate particles were calcined to obtain doped cobalt tetroxide. The first cobalt salt solution and / or the second cobalt salt solution further contain a soluble metal salt, wherein the soluble metal salt contains the metal cation.

5. The preparation method according to claim 4, characterized in that: The method of performing a first mixing treatment and a first hydrothermal reaction on a portion of the carbonate solution and the first cobalt salt solution includes the following steps: A certain amount of the carbonate solution is taken as the base liquid. Under the condition of the first stirring treatment, a certain amount of the carbonate solution and the first cobalt salt solution are added to the base liquid to carry out the first mixing treatment and the first hydrothermal reaction. and / or The method for performing a second mixing treatment and a second hydrothermal reaction with the remaining carbonate solution and the second cobalt salt solution and the doped cobalt carbonate seed dispersion includes the following steps: The remaining carbonate solution and the second cobalt salt solution are added to the doped cobalt carbonate seed dispersion in multiple intervals to carry out the second mixing treatment and the second hydrothermal reaction; and / or The D50 particle size of the doped cobalt carbonate seed crystals is 1.5-10 μm; and / or The D50 particle size of the doped cobalt carbonate particles is 3-22 μm.

6. The preparation method according to claim 5, characterized in that: When the first cobalt salt solution and / or the second cobalt salt solution contain the soluble metal salt, the concentration of the soluble metal salt in the first cobalt salt solution and / or the second cobalt salt solution satisfies the following: the mass ratio of the soluble metal element to the cobalt element is 0.0015-0.02:1; and / or The soluble metal salt includes at least one of the following: nitrate, sulfate, and acetate of a soluble metal.

7. The preparation method according to claim 5, characterized in that: In the underlying solution, the carbonate concentration is greater than 0, but less than 200 g / L; and / or The carbonate solution and the first cobalt salt solution are added to the base solution at a molar ratio of the first cobalt salt to the carbonate of 0.03-0.28:1; and / or The conditions for the first hydrothermal reaction include at least one of the following: The pH of the substrate solution is 6.7-8.8; The temperature is 30-45℃; The feeding time for adding the carbonate solution and the first cobalt salt solution to the base liquid is controlled between 2 and 36 hours, and after feeding is completed, stirring is continued for 1 to 5 hours. The stirring speed for the first stirring process is 120-400 rpm.

8. The preparation method according to claim 5, characterized in that: In the steps of the second mixing treatment and the second hydrothermal reaction, the remaining carbonate solution and the second cobalt salt solution are added to the doped cobalt carbonate seed dispersion at a molar ratio of the second cobalt salt to the carbonate of 0.02-1.0:

1. and / or The conditions for the second hydrothermal reaction include at least one of the following: The pH of the mixed solution obtained from the second mixing treatment is 6.5-8.5; The temperature is 30-50℃; The remaining carbonate solution and the second cobalt salt solution are added to the doped cobalt carbonate seed dispersion in multiple batches, with the total feeding time controlled between 10 and 80 hours. The second mixing process includes a second stirring process, and the stirring speed of the second stirring process is 60-400 rpm.

9. The preparation method according to any one of claims 4-8, characterized in that: The carbonate solution contains at least one of ammonium carbonate and ammonium bicarbonate; and / or The doped anions in the carbonate solution include PO4. 3- BO3 3- BO2 - SiO4 4- SiO3 2- At least one of them; and / or The calcination process includes first performing a first temperature zone sintering treatment, and then performing a second temperature zone sintering treatment; wherein the temperature of the first temperature zone sintering treatment is 200-620℃, and the temperature of the second temperature zone sintering treatment is 630-850℃.

10. A lithium cobalt oxide doped cathode material, characterized in that: It is formed by calcining a lithium cobalt oxide precursor and a lithium source in a certain proportion, wherein the lithium cobalt oxide precursor includes doped cobalt tetroxide as described in any one of claims 1 to 3 or doped cobalt tetroxide prepared by the preparation method described in any one of claims 4 to 9.

11. A secondary battery, comprising a positive electrode, a separator, and a negative electrode stacked sequentially, characterized in that: The positive electrode active material contained in the positive electrode sheet includes the doped lithium cobalt oxide positive electrode material as described in claim 10.

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