Positive electrode active materials and their manufacturing methods, secondary batteries, battery modules, battery packs and devices

Abstract

A positive electrode active material and its manufacturing method are disclosed. The positive electrode active material comprises a positive electrode active material matrix and a coating layer, wherein the coating layer covers the surface of the positive electrode active material matrix, and the positive electrode active material matrix is ​​Li. 1+a [Ni x Co y Mn z M b O2, wherein 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1, preferably 0.8 ≤ x < 1, wherein the element M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B, and the coating layer comprises a cobalt-containing compound, an aluminum-containing compound and a boron-containing compound.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and particularly to a positive electrode active material, a manufacturing method thereof, a secondary battery, a battery module, a battery pack and a device. Background Art

[0002] In recent years, with the increasingly wide application range of lithium-ion batteries, lithium-ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Due to the great development of lithium-ion batteries, higher requirements are also put forward for their energy density, cycle performance and safety performance. In addition, due to the increasingly limited choice of positive electrode active materials, high-nickel positive electrode active materials are considered to be the best choice to meet the requirements of high energy density.

[0003] However, with the continuous increase of nickel content, its structural stability becomes worse and worse. Improving the rate performance and cycle performance of materials by means of coating or doping is a relatively effective means at present. However, existing methods will all cause varying degrees of damage to the performance of lithium-ion batteries. For example, the specific capacity of lithium-ion batteries decreases and the cycle performance deteriorates. Therefore, the existing coated or doped positive electrode materials still need to be improved. Summary of the Invention

[0004] The present application is made in view of the above problems, and its purpose is to provide a positive electrode active material and a manufacturing method thereof, which can make a secondary battery containing the material have a high energy density, good cycle performance and safety performance. [[ID=第十八条]]

[0005] To achieve the above object, the present application provides a positive electrode active material, a manufacturing method thereof, a secondary battery, a battery module, a battery pack and a device.

[0006] The first aspect of the present application provides a positive electrode active material, including a positive electrode active material matrix and a coating layer, the coating layer covering the surface of the positive electrode active material matrix, wherein, the positive electrode active material matrix is Li 1+a [Ni x Co y Mn z M b O2, where 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1, optionally 0.8 ≤ x < 1, the M element is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B, and the coating layer contains a cobalt-containing compound, an aluminum-containing compound and a boron-containing compound.

[0007] Therefore, this application achieves this by co-coating the surface of the positive electrode active material with cobalt-containing compounds, aluminum-containing compounds, and boron-containing compounds. The three compounds work synergistically to improve the rate performance and cycle performance of the positive electrode active material, while also significantly reducing interfacial side reactions between the positive electrode active material and the electrolyte, thereby increasing capacity.

[0008] In any embodiment, the cobalt-containing compound is selected from one or more of cobalt oxide, cobalt salts, cobalt hydroxide, and cobalt hydroxyoxide. Thus, the cobalt-containing compound can uniformly and effectively coat the surface of the positive electrode active material.

[0009] In any embodiment, the aluminum-containing compound is selected from one or more of alumina, aluminum hydroxide, aluminum salts, and aluminum halides. Thus, the aluminum-containing compound can uniformly and effectively coat the surface of the positive electrode active material.

[0010] In any embodiment, the boron-containing compound is selected from one or more of boron oxide, boron halide, boric acid, borates, and organoborides. Thus, the boron-containing compound can uniformly and effectively coat the surface of the positive electrode active material.

[0011] In any embodiment, the thickness of the coating layer is 0.01 μm to 2 μm, optionally 0.1 to 1 μm. When the thickness of the coating layer is within the above range, it can effectively prevent side reactions at the interface between the electrolyte and the positive electrode active material, and increase the capacity of the positive electrode active material.

[0012] In any embodiment, the total weight ratio of cobalt, aluminum, and boron elements in the coating layer relative to the total weight of the positive electrode active material matrix is ​​1000–22000 ppm, optionally 1000–15000 ppm. Therefore, due to the appropriate coating amount, the capacity, rate performance, and cycle performance of the positive electrode active material can be improved.

[0013] In any embodiment, the weight ratio of cobalt in the coating layer relative to the total weight of the positive electrode active material matrix is ​​1000–20000 ppm, optionally 1000–19000 ppm, and further optionally 1000–13000 ppm. Therefore, due to the appropriate coating amount, the capacity, rate performance, and cycle performance of the positive electrode active material can be better improved.

[0014] In any embodiment, the weight ratio of aluminum in the coating layer relative to the total weight of the positive electrode active material matrix is ​​100–3000 ppm, optionally 100–2900 ppm, and further optionally 500–2000 ppm. Therefore, due to the appropriate coating amount, the cycling, storage, and safety performance of the positive electrode active material can be better improved.

[0015] In any embodiment, relative to the total weight of the positive electrode active material matrix, the coating amount of boron element in the coating layer is 100-2000 ppm, optionally 100-1900 ppm, and further optionally 500-1500 ppm. Thus, due to the appropriate coating amount, the cycle, storage and safety performance of the positive electrode active material can be further improved better.

[0016] In any embodiment, the weight ratio of aluminum element to boron element in the coating layer is 0.5-2:1, optionally 1-2:1. Thus, the cycle and safety performance of the positive electrode active material can be further improved.

[0017] The second aspect of the present application also provides a manufacturing method of a positive electrode active material,

[0018] including:

[0019] Step S1: Provide a positive electrode active material matrix doped with M element, wherein the M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B;

[0020] Step S2: Mix and sinter the positive electrode active material matrix doped with M element and a cobalt-containing compound to obtain an intermediate; and

[0021] Step S3: Add the intermediate, an aluminum-containing compound and a boron-containing compound into a mixer for mixing and sintering to obtain a positive electrode active material coated with a cobalt-containing compound, an aluminum-containing compound and a boron-containing compound.

[0022] In any embodiment, in Step S1: Add a lithium salt, a positive electrode active material precursor containing nickel, cobalt and manganese, and a compound containing M element into a mixer for mixing to obtain a mixed material a, and add the mixed material a into a kiln for sintering to obtain a positive electrode active material matrix doped with M element, wherein the positive electrode active material precursor containing nickel, cobalt and manganese is [Ni x Co y Mn z (OH)2, where 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, optionally 0.8 ≤ x < 1, and the M element is one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B; Step S2: Add the positive electrode active material matrix doped with M element and a cobalt-containing compound into a mixer for mixing to obtain a mixed material b, and add the mixed material b into a kiln for sintering to obtain an intermediate; and Step S3: Add the intermediate, an aluminum-containing compound and a boron-containing compound into a mixer for mixing to obtain a mixed material c, and add the mixed material c into a kiln for sintering to obtain a positive electrode active material coated with a cobalt-containing compound, an aluminum-containing compound and a boron-containing compound.

[0023] Therefore, the manufacturing method of the positive electrode active material of this application allows the M element to be uniformly doped into the positive electrode active material matrix, effectively improving the structural stability of the positive electrode active material. Simultaneously, a common coating layer containing cobalt, boron, and aluminum compounds is uniformly coated on the surface of the positive electrode active material matrix. Furthermore, by employing the manufacturing method of the positive electrode active material of this application, not only are the complex manufacturing processes of existing methods avoided, but production costs are also reduced.

[0024] In any embodiment, in step S1, the lithium salt, the nickel-cobalt-manganese-containing cathode active material precursor, and the M-containing compound are mixed in a mixer according to the following method: the molar ratio of lithium in the lithium salt to the total amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese-containing cathode active material precursor is Li / (Ni+Co+Mn) = 0.9–1.1, and the M-element doping amount is 1000–5000 ppm. This allows for uniform doping of the M-element, effectively improving the structural stability of the material.

[0025] In any embodiment, the sintering conditions in step S1 are as follows: sintering temperature is 700–950°C, sintering time is 10–20 h, and the sintering atmosphere is air or oxygen. This allows for effective doping of element M.

[0026] In any embodiment, the proportion of the cobalt-containing compound added in step S2 is relative to the total weight of the positive electrode active material matrix, and the amount of cobalt added is 1000ppm to 20000ppm, optionally 1000 to 19000ppm, and further optionally 1000ppm to 13000ppm. This further improves the interfacial side reactions of the material. Moreover, due to the appropriate coating amount, the material's cycleability, storage, and safety performance can be further improved.

[0027] In any embodiment, the sintering conditions in step S2 are as follows: sintering temperature is 500–700°C, sintering time is 5–15 h, and the sintering atmosphere is air or oxygen. This improves the coating effect.

[0028] In any embodiment, in step S3, the addition ratio of the aluminum-containing compound is relative to the total weight of the positive electrode active material matrix, and the amount of aluminum added is 100-3000 ppm, optionally 100-2900 ppm, and further optionally 500-2000 ppm. The addition ratio of the boron-containing compound is relative to the total weight of the positive electrode active material matrix, and the amount of boron added is 100-2000 ppm, optionally 100-1900 ppm, and further optionally 500-1500 ppm. This further improves the interfacial side reactions of the material. Moreover, due to the appropriate coating amount, the cycling, storage, and safety performance of the material can be further improved.

[0029] In any embodiment, the sintering conditions in step S3 are as follows: sintering temperature is 200–500°C, optionally 200–400°C; sintering time is 5–15 h, optionally 5–10 h; and the sintering atmosphere is air or oxygen. This allows aluminum-containing and boron-containing compounds to be firmly coated onto the surface of the positive electrode active material particles without penetrating into the inner layers of the particles, thus improving the coating effect.

[0030] A third aspect of this application provides a secondary battery, including the positive electrode active material of the first aspect of this application or the positive electrode active material prepared according to the method of the second aspect of this application.

[0031] A fourth aspect of this application provides a battery module including the secondary battery of the third aspect of this application.

[0032] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0033] A sixth aspect of this application provides an apparatus comprising one or more of the secondary battery selected from the third aspect of this application, the battery module selected from the fourth aspect of this application, or the battery pack selected from the fifth aspect of this application. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope image of the positive electrode active material obtained in Example 1.

[0035] Figure 2 The first charge-discharge curve of a coin cell made from the positive electrode active material obtained in Example 1.

[0036] Figure 3 Comparison curves show the full-electric 25°C cycle performance test results of secondary batteries made from the positive electrode active materials obtained in Example 1 and Comparative Example 4, respectively.

[0037] Figure 4Comparison curves show the full-electric gas expansion performance test results of secondary batteries made from the positive electrode active materials obtained in Example 1 and Comparative Example 4 at 70°C.

[0038] Figure 5 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0039] Figure 6 yes Figure 5 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0040] Figure 7 This is a schematic diagram of a battery module according to one embodiment of this application.

[0041] Figure 8 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0042] Figure 9 yes Figure 8 An exploded view of a battery pack according to one embodiment of this application is shown.

[0043] Figure 10 This is a schematic diagram of a device that uses a secondary battery as a power source according to one embodiment of this application.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1 battery pack

[0046] 2 upper box

[0047] 3 lower cabinets

[0048] 4 battery modules

[0049] 5 Secondary batteries

[0050] 51 housing

[0051] 52 Electrode Assembly

[0052] 53 Top Cover Assembly Detailed Implementation

[0053] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack, and device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0054] For the sake of simplicity, this application specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recited.

[0055] Positive electrode active material

[0056] In one embodiment of this application, this application provides a positive electrode active material. The positive electrode active material includes a positive electrode active material matrix and a coating layer covering the surface of the positive electrode active material matrix. Among them, the positive electrode active material matrix is Li 1+a [Ni x Co y Mn z M b O2, where 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1. Preferably, 0.8 ≤ x < 1. The M element is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn, and B. The coating layer contains a cobalt compound, an aluminum compound, and a boron compound.

[0057] Although the mechanism is not yet clear, the applicant unexpectedly found that: by co-coating a cobalt compound, an aluminum compound, and a boron compound on the surface of the positive electrode active material in this application, the rate performance and cycling performance of the positive electrode active material can be significantly improved. At the same time, the interfacial side reaction between the positive electrode active material and the electrolyte can also be significantly improved, and the capacity can be increased. In addition, even when this application is applied to a positive electrode active material with a high nickel content (Ni content ≥ 80%) and poor structural stability, by doping the M element in the positive electrode active material and co-coating a cobalt compound, an aluminum compound, and a boron compound on the surface of the positive electrode active material, not only can the structural stability of the positive electrode active material be effectively improved, but also the energy density can be significantly increased, and the cycling performance and rate performance of the positive electrode active material can be improved.

[0058] In some embodiments, for example, from the perspective of being able to uniformly and effectively coat on the surface of the positive electrode active material and further improving the interfacial side reaction between the positive electrode active material and the electrolyte, the cobalt compound is selected from one or more of cobalt oxides, cobalt salts, cobalt hydroxide, and cobalt oxyhydroxide. Examples of cobalt oxides include CoO, Co3O4, etc. Examples of cobalt salts include cobalt acetate, cobalt oxalate, and cobalt carbonate, etc.

[0059] In some embodiments, for example, from the viewpoint of being able to uniformly and effectively coat the surface of the positive electrode active material and further improve the interfacial side reactions between the positive electrode active material and the electrolyte, the aluminum-containing compound is selected from one or more of alumina, aluminum hydroxide, aluminum salts, and aluminum halides. Examples of alumina include Al2O3. Examples of aluminum salts include Al2(SO4)3 and Al(NO)3. Examples of aluminum halides include AlCl3.

[0060] In some embodiments, for example, from the viewpoint of being able to uniformly and effectively coat the surface of the positive electrode active material and further improve the interfacial side reactions between the positive electrode active material and the electrolyte, the boron-containing compound is selected from one or more of boron oxide, boron halide, boric acid, borates, and organoborides. Examples of boron oxide include B2O3. Examples of boron halide include BF3, BCl3, BBr3, and BI3. Examples of boric acid include H3BO3. Examples of borates include B2(SO4)3 and B(NO3)3. Examples of organoborides include BN, H2BO5P, C5H6B(OH)2, C3H9B3O6, (C2H5O)3B, and (C3H7O)3B.

[0061] In some embodiments, for example, the thickness of the coating layer is 0.01 μm to 2 μm, optionally 0.1 to 1 μm. If the thickness of the coating layer is within the above range, it can effectively prevent side reactions at the interface between the electrolyte and the positive electrode active material, and increase the capacity of the positive electrode active material.

[0062] In some embodiments, for example, the total weight ratio of cobalt, aluminum, and boron in the coating layer relative to the total weight of the positive electrode active material matrix is ​​1000–22000 ppm, optionally 1000–15000 ppm. Therefore, due to the appropriate coating amount, the capacity, rate performance, and cycle performance of the positive electrode active material can be improved.

[0063] In some embodiments, for example, the weight ratio of cobalt in the coating layer relative to the total weight of the cathode active material matrix is ​​1000–20000 ppm, optionally 1000–19000 ppm, and further optionally 1000–13000 ppm. Thus, due to the appropriate coating amount, the coated cobalt compound can improve the interfacial side reactions of the cathode active material and enhance its capacity, rate performance, and cycle performance.

[0064] In some embodiments, for example, the weight ratio of aluminum in the coating layer relative to the total weight of the positive electrode active material matrix is ​​100–3000 ppm, optionally 100–2900 ppm, and further optionally 500–2000 ppm. Therefore, due to the appropriate coating amount, the coating of aluminum-containing compounds can further significantly improve the interfacial side reactions of the positive electrode active material, protect the positive electrode active material, and thus further improve the cycling, storage, and safety performance of the positive electrode active material.

[0065] In some embodiments, for example, the weight ratio of boron in the coating layer relative to the total weight of the positive electrode active material matrix is ​​100–2000 ppm, optionally 100–1900 ppm, and further optionally 500–1500 ppm. Thus, due to the appropriate coating amount, the coating with boron-containing compounds can further improve the interfacial side reactions of the material, increase the capacity of the positive electrode active material, and further improve the rate performance and cycle performance of the positive electrode active material.

[0066] In some embodiments, the weight ratio of aluminum to boron in the coating layer is 0.5 to 2:1, optionally 1 to 2:1. The inventors have discovered that while coating the surface of the positive electrode active material with an aluminum-containing compound can effectively suppress side reactions between the electrolyte and the surface of the positive electrode active material, improving the battery's cycle performance, the specific capacity of the positive electrode material may decrease with increasing aluminum compound content. Simultaneously, coating the surface of the positive electrode active material with a boron-containing compound can effectively reduce the impure lithium content and further increase the specific capacity. Furthermore, the inventors unexpectedly discovered that when the weight ratio of aluminum to boron in the coating layer is within the aforementioned range, it can significantly improve both the capacity and cycle performance of the positive electrode active material. Moreover, when the weight ratio is within the specified range, it can effectively protect the crystal structure of the positive electrode material, thereby further improving the safety performance of the positive electrode active material.

[0067] In some implementations, for example, the positive electrode active material is a secondary particle or a single crystal particle formed by the aggregation of primary particles.

[0068] In some embodiments, when the positive electrode active material is secondary particles formed by the aggregation of primary particles, the average particle size of the primary particles in the secondary particles is 100–1000 nm. It should be noted that the average particle size of the primary particles in the secondary particles refers to the average particle size of all primary particles in a 10Kx scanning electron microscope image.

[0069] In some embodiments, the average volume distribution particle size D50 of the positive electrode active material of the secondary particles is 2 to 15 μm, and can be selected as 2.5 to 12 μm.

[0070] In some embodiments, the specific surface area of ​​the secondary particle positive electrode active material is 0.2 m². 2 / g~1.0m 2 / g, optionally 0.3m 2 / g~0.8m 2 / g.

[0071] In some embodiments, when the positive electrode active material is a single crystal particle, the average volume distribution particle size D50 of the positive electrode active material of the single crystal particle is 1.0 to 8.0 μm, and can be selected as 2.0 to 4.0 μm.

[0072] In some embodiments, the specific surface area of ​​the single-crystal positive electrode active material is 0.4 m². 2 / g~2m 2 / g, optional 0.5m 2 / g~1.5m 2 / g.

[0073] Therefore, the positive electrode active material manufactured by the above manufacturing method has a good crystal structure, which is beneficial to lithium-ion transport and improves rate performance and cycle performance.

[0074] Furthermore, the average volume distribution particle size D50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50% for the positive electrode active material. In this application, the volume average particle size D50 of the positive electrode active material can be determined using laser diffraction particle size analysis. For example, it can be determined using a laser particle size analyzer (e.g., Malvern MasterSize 3000) in accordance with standard GB / T 19077-2016.

[0075] In some embodiments, the cobalt-containing compound is, for example, a cobalt-containing compound as described below, wherein the particle size of the cobalt-containing compound can be 0.001 μm to 10 μm, for example, 0.001 μm to 1 μm. Because of the use of this nanoscale cobalt-containing compound, it can be uniformly and effectively coated on the surface of the cathode material substrate, improving interfacial side reactions between the material and the electrolyte.

[0076] Method for manufacturing positive electrode active materials

[0077] In one embodiment of this application, a method for manufacturing a positive electrode active material is also provided, comprising:

[0078] Step S1: Lithium salt, a precursor of positive electrode active material containing nickel, cobalt, and manganese, and a compound containing element M are added to a mixer for mixing to obtain mixture a. Mixture a is then added to a kiln for sintering to obtain a positive electrode active material matrix doped with element M. The precursor of positive electrode active material containing nickel, cobalt, and manganese is [Nix Co y Mn z (OH)2, where 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, optionally 0.8 ≤ x < 1, and the M element is one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn, and B;

[0079] Step S2: Mix the doped M - element cathode active material matrix and the cobalt - containing compound in a mixer to obtain a mixed material b, and then add the mixed material b into a kiln for sintering to obtain an intermediate (cathode active material coated with a cobalt - containing compound); and

[0080] Step S3: Mix the intermediate, the aluminum - containing compound, and the boron - containing compound in a mixer to obtain a mixed material c, and then add the mixed material c into a kiln for sintering to obtain a cathode active material coated with a cobalt - containing compound, an aluminum - containing compound, and a boron - containing compound.

[0081] Thus, although the mechanism is not yet clear, the applicant unexpectedly found that: through the manufacturing method of the cathode active material of the present application, the M element can be uniformly doped in the core of the cathode active material, effectively improving the structural stability of the cathode active material. At the same time, a co - coating layer of a cobalt - containing compound, a boron - containing compound, and an aluminum - containing compound is uniformly coated on the surface of the cathode active material core, which can effectively inhibit the interfacial side reactions between the cathode active material and the electrolyte, not only improving the capacity of the cathode active material, effectively improving the rate performance of the cathode active material, but also effectively improving the cycle, storage, and safety performance of the cathode active material. In addition, by adopting the manufacturing method of the cathode active material of the present application, not only the complicated manufacturing processes such as wet coating in the existing manufacturing methods are avoided, but also the production cost can be reduced. The step - by - step coating method is adopted in the manufacturing method of the present application, so that the prepared cathode active material can simultaneously have good cycle performance and high capacity. If the three (cobalt - containing compound, boron - containing compound, aluminum - containing compound) are coated simultaneously, when the coating temperature is set too high, aluminum and boron may penetrate into the inner layer of the cathode active material particles, and the boron - containing compound is easily volatilized at high temperature, affecting the coating effect, thus affecting the capacity and cycle performance; when the coating temperature is set too low, the cobalt - containing compound may not be effectively coated on the outer layer of the cathode active material particles, failing to achieve the coating effect of coating the cathode active material particles, thus affecting the cycle and safety performance. Therefore, by coating in steps, the coating effect can be avoided from being affected when the three are coated together.

[0082] In some embodiments, in step S1, the lithium salt, the nickel-cobalt-manganese-containing cathode active material precursor, and the M-containing compound are mixed in a mixer according to the following method: the molar ratio of lithium in the lithium salt to the total amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese-containing cathode active material precursor is Li / (Ni+Co+Mn) = 0.9–1.1, and the M-element doping amount is 1000–5000 ppm. This allows for uniform doping of the M-element, effectively improving the structural stability of the material.

[0083] In some embodiments, the sintering conditions in step S1 are as follows: sintering temperature of 700–950°C, sintering time of 10–20 h, and sintering atmosphere of air or oxygen. This allows for effective doping of element M, resulting in a cathode material matrix with a good crystal structure, which is beneficial for lithium-ion transport and improves rate performance and cycle performance.

[0084] In some embodiments, in step S2, the proportion of the cobalt-containing compound added is relative to the total weight of the positive electrode active material matrix, and the amount of cobalt added is 1000ppm to 20000ppm, preferably 1000 to 19000ppm, and more preferably 1000ppm to 13000ppm. This allows the cobalt-containing compound to be uniformly and effectively coated on the surface of the positive electrode active material matrix, reducing interfacial side reactions between the positive electrode active material and the electrolyte. Simultaneously, due to the appropriate coating amount, the capacity, rate performance, and cycle performance of the positive electrode active material can be improved.

[0085] In some embodiments, the sintering conditions in step S2 are as follows: sintering temperature of 500–700°C, sintering time of 5–15 h, and sintering atmosphere of air or oxygen. This allows the cobalt-containing compound to be firmly coated onto the surface of the positive electrode active material particles without penetrating into the inner layers of the particles, thus improving the coating effect.

[0086] In some embodiments, in step S3, the addition ratio of the aluminum-containing compound is relative to the total weight of the positive electrode active material matrix, with the amount of aluminum added being 100-3000 ppm, optionally 100-2900 ppm, and further optionally 500-2000 ppm. Similarly, the addition ratio of the boron-containing compound is relative to the total weight of the positive electrode active material matrix, with the amount of boron added being 100-2000 ppm, optionally 100-1900 ppm, and further optionally 500-1500 ppm. This further improves the interfacial side reactions of the material. Moreover, due to the appropriate coating amount, the material's cycleability, storage, and safety performance can be further improved.

[0087] In some embodiments, the sintering conditions in step S3 are as follows: the sintering temperature is 200 - 500, optionally 200 - 400, the sintering time is 5 - 15 h, optionally 5 - 10 h, and the sintering atmosphere is air or oxygen. Thus, the aluminum-containing compound and the boron-containing compound can be firmly coated on the surface of the positive electrode active material particles without penetrating into the inner layer of the particles, effectively improving the coating effect. Moreover, it can further significantly improve the interfacial side reactions of the positive electrode active material and enhance the cycling, storage, and safety performance of the positive electrode active material.

[0088] In some embodiments, for example, the positive electrode active material precursor containing nickel, cobalt, and manganese is [Ni x Co y Mn z (OH)2, where 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, and further, 0.8 ≤ x < 1.

[0089] In some embodiments, for example, the lithium salt can be selected from one or more of lithium carbonate and lithium hydroxide.

[0090] In addition, the secondary battery, battery module, battery pack, and device of the present application will be described below with appropriate reference to the accompanying drawings.

[0091] In one embodiment of the present application, a secondary battery is provided.

[0092] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0093] [Positive electrode plate]

[0094] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0095] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive electrode current collector.

[0096] In the secondary battery of this application, the positive electrode current collector can be a metal foil or a composite current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0097] The positive electrode film may optionally include a conductive agent. However, there is no specific limitation on the type of conductive agent, and those skilled in the art can select it according to actual needs. As an example, the conductive agent used for the positive electrode film may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0098] In this application, the positive electrode sheet can be prepared according to methods known in the art. As an example, the positive active material, conductive agent and binder of this application can be dispersed in a solvent (e.g., N-methylpyrrolidone (NMP)) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet is obtained.

[0099] [Negative electrode plate]

[0100] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0101] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0102] In the secondary battery of this application, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0103] In the secondary battery of this application, the negative electrode film layer typically comprises a negative electrode active material and optional binders, optional conductive agents, and other optional additives, and is usually formed by coating and drying a negative electrode slurry. The negative electrode slurry coating is typically formed by dispersing the negative electrode active material, optional conductive agents, and binders in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

[0104] As an example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0105] As an example, the adhesive may be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0106] Other optional additives include thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).

[0107] In the secondary battery of this application, the negative electrode film layer, in addition to the negative electrode active material, may optionally include other commonly used negative electrode active materials. Examples of other commonly used negative electrode active materials include artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.

[0108] [Electrolytes]

[0109] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0110] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0111] In some embodiments, the electrolyte salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate).

[0112] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0113] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0114] [Isolation membrane]

[0115] Secondary batteries using electrolytes, and some secondary batteries using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, serving a separating function. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. In some embodiments, the separator material can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0116] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0117] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0118] In some implementations, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0119] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 5 This is an example of a square-structured secondary battery 5.

[0120] In some implementations, refer to Figure 6 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0121] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0122] Figure 7 This is battery module 4, used as an example. (See reference...) Figure 7 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0123] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0124] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0125] Figure 8 and Figure 9This is battery pack 1 as an example. (See reference...) Figure 8 and Figure 9 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0126] In addition, this application also provides an apparatus comprising one or more of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the apparatus or as an energy storage unit for the apparatus. The apparatus may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0127] As the device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0128] Figure 10 This is an example device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density in its secondary batteries, a battery pack or battery module can be used.

[0129] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0130] Example

[0131] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0132] Example 1

[0133] The positive electrode active material precursor, lithium hydroxide, and zirconium oxide (ZrO2) were added to a plow mixer and mixed for 1 hour, with the molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt, and manganese in the positive electrode active material precursor being Li / (Ni+Co+Mn) = 1.05, to obtain a mixture. The amount of zirconium added relative to the total weight of the mixture was 2000 ppm. The positive electrode active material precursor was [Ni...]. 0.92 Co 0.05 Mn 0.03 [(OH)2, with an average volumetric particle size D50 of 5 μm.]

[0134] The mixture obtained above was added to a roller kiln and sintered for 20 hours at a sintering temperature of 800°C. The sintering atmosphere was oxygen, and the positive electrode active material matrix was obtained.

[0135] The obtained positive electrode active material matrix and CoO were mixed in a high-speed mixer for 1 hour, with the amount of cobalt added being 8000 ppm relative to the total weight of the positive electrode active material matrix. This mixture was then added to a roller kiln for secondary sintering at a temperature of 600°C for 10 hours in an oxygen atmosphere, resulting in a CoO-coated positive electrode active material. The resulting CoO-coated positive electrode active material consists of secondary particles with an average volumetric particle size (D50) of 5 μm.

[0136] The positive electrode active material coated with CoO obtained from secondary sintering, and a mixture of AlCl3 and B2O3, were mixed in a high-speed mixer for 1 hour, with aluminum and boron added at a weight ratio of 1000 ppm and 1000 ppm respectively relative to the total weight of the positive electrode active material matrix, and the weight ratio of aluminum to boron being 1:1. The resulting mixture was then subjected to a third sintering process in a roller kiln at a temperature of 250°C for 5 hours under an oxygen atmosphere, yielding the final coated positive electrode active material. The resulting final coated positive electrode active material consisted of secondary particles with an average volumetric particle size (D50) of 5 μm, and the total thickness of the coating layer, measured using a micrometer, was 0.60 μm. The scanning electron microscope image of the positive electrode active material obtained in Example 1 is shown below. Figure 1 As shown. By Figure 1 It can be seen that the above coating is uniformly coated on the surface of the positive electrode active material particles.

[0137] Example 2

[0138] In addition to replacing the positive electrode active material precursor with [Ni] 0.8 Co 0.1 Mn 0.1The cathode active material obtained by using MgO (OH)₂ with an average volumetric particle size (D50) of 2.5 μm was prepared. The primary sintering temperature was adjusted to 700 °C, and the zirconium oxide (ZrO₂) added during the primary sintering was replaced with MgO. The primary sintering time was 10 h, the amount of magnesium added was 5000 ppm, and the amount of aluminum added was adjusted to 1200 ppm. All other conditions were the same as in Example 1. The resulting coated cathode active material consisted of secondary particles with an average volumetric particle size (D50) of 2.5 μm, and the total thickness of the coating layer, measured using a micrometer, was 0.65 μm.

[0139] Example 3

[0140] In addition to replacing the positive electrode active material precursor with [Ni] 0.6 Co 0.2 Mn 0.2 The cathode active material obtained by using 12μm of titanium oxide (OH)₂ with an average volumetric particle size (D50) of 12μm was prepared. The primary sintering temperature was adjusted to 950°C, the zirconium oxide (ZrO₂) added during the primary sintering was replaced with TiO₂, the primary sintering time was 15h, the amount of titanium added was 1000ppm, and the amount of aluminum added was adjusted to 1500ppm. All other conditions were the same as in Example 1. The resulting coated cathode active material consisted of secondary particles with an average volumetric particle size (D50) of 12μm, and the total thickness of the coating layer, measured using a micrometer, was 0.67μm.

[0141] Example 4

[0142] Except for replacing the average volumetric particle size D50 of the cathode active material precursor with 2 μm, adjusting the primary sintering temperature to 900 °C, the secondary sintering temperature to 500 °C, replacing the CoO added in the secondary sintering with Co(OH)2, setting the cobalt content to 13000 ppm, adjusting the secondary sintering time to 5 h, and adjusting the aluminum content to 1800 ppm, all other conditions were the same as in Example 1. The resulting coated cathode active material consisted of single-crystal particles with an average volumetric particle size D50 of 2 μm, and the total thickness of the coating layer, measured using a micrometer, was 0.88 μm.

[0143] Example 5

[0144] Except for replacing the average volumetric particle size D50 of the cathode active material precursor with 4 μm, adjusting the primary sintering temperature to 950 °C, the secondary sintering temperature to 700 °C, replacing CoO with Co3O4 in the secondary sintering, adjusting the amount of cobalt added to 1000 ppm, adjusting the secondary sintering time to 15 h, adjusting the amount of aluminum added in the tertiary sintering to 1200 ppm, and adjusting the weight ratio of aluminum to boron to 1.2:1, other conditions are the same as in Example 1. The resulting final coated cathode active material consists of single-crystal particles with an average volumetric particle size D50 of 4 μm, and the total thickness of the coating layer, measured using a micrometer, is 0.16 μm.

[0145] Example 6

[0146] In addition to replacing the positive electrode active material precursor with [Ni] 0.95 Co 0.02 Mn 0.03 The process involved adjusting the first sintering temperature to 850°C, replacing the zirconium oxide (ZrO2) added in the first sintering with Al2O3, and adjusting the amount of aluminum added to 2000 ppm. The second sintering temperature was adjusted to 650°C, replacing the CoO added in the second sintering with cobalt acetate, and adjusting the amount of cobalt added to 20000 ppm. The third sintering temperature was adjusted to 200°C, the third sintering time was adjusted to 5 hours, and replacing AlCl3 added in the third sintering with Al2O3, B2O3 with H3BO3, and adjusting the amount of boron added to 2000 ppm. Except for adjusting the weight ratio of aluminum to boron to 0.5:1, all other conditions were the same as in Example 1. The resulting coated positive electrode active material consisted of secondary particles with an average volume particle size D50 of 5 μm, and the total thickness of the coating layer, measured using a micrometer, was 1.42 μm.

[0147] Example 7

[0148] Except for adjusting the sintering temperature to 400°C, the sintering time to 10 hours, replacing Al2O3 with AlCl3, adjusting the amount of aluminum added to 3000 ppm, replacing H3BO3 with (C2H5O)3B, adjusting the amount of boron added to 1500 ppm, and adjusting the weight ratio of aluminum to boron to 2:1, all other conditions were the same as in Example 6. The resulting coated positive electrode active material consisted of secondary particles with an average volumetric particle size (D50) of 5 μm, and the total thickness of the coating layer, measured using a micrometer, was 1.81 μm.

[0149] Example 8

[0150] Except for replacing the D50 of the positive electrode active material precursor with 10 μm, adjusting the sintering temperature to 350°C, the sintering time to 7 h, replacing Al2O3 with Al2(SO4)3, adjusting the amount of aluminum added to 500 ppm, replacing H3BO3 with BCl3, adjusting the amount of boron added to 500 ppm, and adjusting the weight ratio of aluminum to boron to 1:1, all other conditions were the same as in Example 6. The resulting final coated positive electrode active material consisted of secondary particles with an average volume particle size D50 of 10 μm, and the total thickness of the coating layer, measured using a micrometer, was 1.15 μm.

[0151] Example 9

[0152] Except for adjusting the amounts of cobalt (30,000 ppm), aluminum (5,000 ppm), and boron (5,000 ppm), the other conditions were the same as in Example 8. The resulting coated positive electrode active material consisted of secondary particles with an average volume particle size (D50) of 10 μm, and the total thickness of the coating layer, measured using a micrometer, was 2.85 μm.

[0153] Example 10

[0154] Except for adjusting the amount of aluminum added to 5000 ppm, the amount of boron added to 1000 ppm, and the weight ratio of aluminum to boron to 5:1, all other conditions were the same as in Example 8. The resulting final coated positive electrode active material consisted of secondary particles with an average volume particle size D50 of 10 μm, and the total thickness of the coating layer, measured using a micrometer, was 1.35 μm.

[0155] Example 11

[0156] Except for adjusting the average volumetric particle size D50 of the positive electrode active material precursor to 18 μm, the other conditions were the same as in Example 8. The resulting final coated positive electrode active material consisted of secondary particles with an average volumetric particle size D50 of 18 μm, wherein the total thickness of the coating layer, measured using a micrometer, was 1.10 μm.

[0157] Example 12

[0158] Except for adjusting the average volumetric particle size D50 of the cathode active material precursor to 9 μm, the other conditions were the same as in Example 5. The resulting final coated cathode active material consisted of single-crystal particles with an average volumetric particle size D50 of 9 μm, and the total thickness of the coating layer, measured using a micrometer, was 0.10 μm.

[0159] Comparative Example 1

[0160] The positive electrode active material precursor, lithium hydroxide, and zirconium oxide (ZrO2) were added to a plow mixer and mixed for 1 hour, with the molar ratio of lithium in the lithium hydroxide to the total amount of nickel, cobalt, and manganese in the positive electrode active material precursor being Li / (Ni+Co+Mn) = 1.05, to obtain a mixture. The amount of zirconium added relative to the total weight of the mixture was 2000 ppm. The positive electrode active material precursor was [Ni...]. 0.92 Co 0.05 Mn 0.03 [(OH)2, with an average volumetric particle size D50 of 5 μm.]

[0161] The mixture obtained above was added to a roller kiln and sintered for 20 hours at a sintering temperature of 800°C. The sintering atmosphere was oxygen, and the positive electrode active material was obtained.

[0162] The resulting positive electrode active material consists of secondary particles with an average volume particle size D50 of 5 μm.

[0163] Comparative Example 2

[0164] Using the positive electrode active material obtained by sintering in Comparative Example 1 as the positive electrode active material matrix, the positive electrode active material matrix and AlCl3 were added to a high-speed mixer and mixed for 1 hour, with the amount of aluminum added being 1000 ppm relative to the total weight of the positive electrode active material matrix. This mixture was then added to a roller kiln for secondary sintering at a temperature of 300°C for 10 hours in an oxygen atmosphere, resulting in an AlCl3-coated positive electrode active material. The final coated positive electrode active material obtained consisted of secondary particles with an average volumetric particle size D50 of 5 μm, and the total thickness of the coating layer was 0.05 μm.

[0165] Comparative Example 3

[0166] Except for replacing AlCl3 with B2O3 and adding 1000 ppm of boron, everything else was the same as in Comparative Example 2. The resulting coated positive electrode active material consisted of secondary particles with an average volume particle size D50 of 5 μm, and the total thickness of the coating layer was 0.06 μm.

[0167] Comparative Example 4

[0168] Except for replacing AlCl3 with a mixture of AlCl3 and B2O3, with aluminum and boron added at 1000 ppm and a weight ratio of aluminum to boron of 1:1, everything else was the same as in Comparative Example 2. The resulting coated positive electrode active material consisted of secondary particles with an average volumetric particle size D50 of 5 μm, and the total thickness of the coating layer, measured using a micrometer, was 0.10 μm.

[0169] Comparative Example 5

[0170] Using the positive electrode active material obtained by sintering in Comparative Example 1 as the positive electrode active material matrix, the positive electrode active material matrix and CoO were added to a high-speed mixer and mixed for 1 hour, with the amount of cobalt added being 8000 ppm relative to the total weight of the positive electrode active material matrix. The mixture was then added to a roller kiln for secondary sintering at a temperature of 600°C for 10 hours in an oxygen atmosphere, resulting in a CoO-coated positive electrode active material. The final coated positive electrode active material obtained consisted of secondary particles with an average volumetric particle size D50 of 5 μm, and the total thickness of the coating layer, measured using a micrometer, was 0.41 μm.

[0171] Comparative Example 6

[0172] The positive electrode active material precursor, lithium hydroxide, and magnesium oxide were added to a plow mixer and mixed for 1 hour, with the molar ratio of lithium metal in lithium hydroxide to the total metals of nickel, cobalt, and manganese in the positive electrode active material precursor being Li / (Ni+Co+Mn) = 1.05, to obtain a mixture. The amount of magnesium added relative to the total weight of the mixture was 5000 ppm. The positive electrode active material precursor was [Ni...]. 0.8 Co 0.1 Mn 0.1 [(OH)2] has an average volumetric particle size D50 of 2.5 μm.

[0173] The mixture obtained above was added to a roller kiln and sintered at a sintering temperature of 700°C for 10 hours in an oxygen atmosphere to obtain the positive electrode active material. The resulting positive electrode active material consists of secondary particles with an average volumetric particle size (D50) of 2.5 μm.

[0174] Comparative Example 7

[0175] The positive electrode active material precursor, lithium hydroxide, and TiO2 were mixed in a plow mixer for 1 hour, with the molar ratio of lithium metal in lithium hydroxide to the total molar ratio of nickel, cobalt, and added manganese in the positive electrode active material precursor being Li / (Ni+Co+Mn) = 1.05, to obtain a mixture. The amount of titanium added relative to the total weight of the mixture was 1000 ppm, and the positive electrode active material precursor was [Ni...]. 0.6 Co 0.2 Mn 0.2 ](OH)2, with an average volumetric particle size D50 of 12 μm.

[0176] The mixture obtained above was added to a roller kiln and sintered at a sintering temperature of 950°C for 15 hours in an oxygen atmosphere to obtain the positive electrode active material. The resulting positive electrode active material consists of secondary particles with an average volume particle size D50 of 12 μm.

[0177] The relevant parameters of the cathode materials of Examples 1 to 12 and Comparative Examples 1 to 7 are shown in Table 1 below.

[0178] Table 1: Parameter results of Examples 1-12 and Comparative Examples 1-7

[0179]

[0180] In addition, the positive electrode active materials obtained in Examples 1-12 and Comparative Examples 1-7 were used to prepare coin cells and secondary cells, respectively, as shown below, and their performance was tested. The test results are shown in Table 2 below.

[0181] (1) Preparation of button cells

[0182] The coated positive electrode active material, polyvinylidene fluoride (PVDF), and conductive carbon from the above embodiments and comparative examples were added to a certain amount of N-methylpyrrolidone (NMP) in a ratio of 90:5:5. The mixture was stirred in a drying room to form a slurry. The slurry was then coated onto aluminum foil, dried, and cold-pressed to form a positive electrode sheet. A lithium sheet was used as the negative electrode, and the electrolyte was 1 mol / L LiPF6 / (ethylene carbonate (EC) + diethyl carbonate (DEC) + dimethyl carbonate (DMC)) (volume ratio 1:1:1). The mixture was then assembled into a coin cell in a coin cell box.

[0183] (2) Initial capacitance test of coin cell

[0184] Each of the coin cells prepared above was charged at 0.1C to 4.3V at a voltage of 2.8–4.3V. Then, it was charged at a constant voltage of 4.3V until the current was ≤0.05mA. After standing for 2 minutes, the charging capacity at this point was recorded as C0. Then, it was discharged at 0.1C to 2.8V. The discharge capacity at this point was the initial discharge capacity, recorded as D0. The first efficiency was D0 / C0*100%.

[0185] Dividing the tested discharge capacity value (i.e., the initial discharge capacity D0) by the mass of the positive electrode active material in the coin cell gives the initial coin cell capacity of the positive electrode active material.

[0186] (3) Preparation of secondary batteries

[0187] The positive electrode active material products in the above embodiments and comparative examples are used as positive electrode active materials. They are mixed with conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone solvent system at a weight ratio of 94:3:3. After being thoroughly stirred and mixed evenly, the mixture is coated on aluminum foil, dried, and cold-pressed to obtain a positive electrode sheet.

[0188] Artificial graphite (as the negative electrode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) are thoroughly mixed in a deionized water solvent system at a weight ratio of 90:5:2:2:1. The mixture is then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0189] A porous polymer film made of polyethylene (PE) is used as a separator.

[0190] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes, and then wound to obtain a bare cell. The bare cell is placed in an outer package, injected with the electrolyte used in the above (1) button cell preparation, and sealed to obtain a secondary battery.

[0191] (4) Initial capacitance test of secondary circuit

[0192] Each of the secondary batteries prepared above was placed at a constant temperature of 25°C for 5 minutes, discharged at 1 / 3C to 2.8V, placed at a constant temperature for 5 minutes, charged at 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V until the current was ≤0.05mA. After being placed at a constant temperature for 5 minutes, the charging capacity at this time was recorded as C0. Then, the batteries were discharged at 1 / 3C to 2.8V. The discharge capacity at this time was the initial discharge capacity, recorded as D0.

[0193] Dividing the tested discharge capacity value (i.e., the initial discharge capacity D0) by the mass of the positive electrode active material in the secondary battery gives the total initial specific capacity of the positive electrode active material.

[0194] (5) Cycle performance test of secondary battery at 25 / 45 cycles

[0195] Each of the secondary batteries prepared above was charged at 1C to 4.25V under a constant temperature environment of 25 or 45°C at a voltage of 2.8–4.25V. Then, it was charged at a constant voltage of 4.25V until the current ≤0.05mA, allowed to stand for 5 minutes, and then discharged at 1C to 2.8V. The capacity is denoted as D. n (n = 0, 1, 2 ...), repeat the above operation for 300 cycles and measure the capacity decay value.

[0196] (6) Secondary battery 70 gas expansion performance test

[0197] For each secondary battery with 100% SOC prepared above (protection voltage range: 2.7-4.3V, nominal capacity 2.25Ah), the initial cell (bare cell) volume before storage was measured using the water displacement method. Then, each of the above secondary batteries was stored in a storage furnace at 70°C. Every 48 hours, the cells were taken out of the storage furnace, cooled to room temperature, and the cell volume was measured again using the water displacement method. The test was completed after 30 days of storage, or storage was stopped when the volume expansion exceeded 50%.

[0198] The amount of gas expansion of a secondary battery after 30 days of storage at 70°C = [the volume of the secondary battery cell after 30 days of storage at 70°C - the initial volume of the secondary battery cell] ÷ the initial discharge capacity D0.

[0199] Table 2: Performance test results of Examples 1-8 and Comparative Examples 1-7

[0200]

[0201] Based on the above results, it can be seen that the positive electrode active materials obtained in Examples 1-12, after being doped, were further coated with cobalt-containing compounds, aluminum-containing compounds, and boron-containing compounds, thus achieving good results in terms of energy density, cycle performance, and safety performance. Furthermore, the initial efficiency of the positive electrode active material was also improved.

[0202] In contrast, the positive electrode active material obtained in Comparative Example 1 was only doped with zirconium, the positive electrode active material obtained in Comparative Example 6 was only doped with magnesium, and the positive electrode active material obtained in Comparative Example 7 was only doped with titanium, but none of them were coated. Therefore, Comparative Example 1 had poor cycle performance and safety performance, while Comparative Examples 6 and 7 had poor capacity of positive electrode active materials, and no effective improvement was achieved in terms of cycle performance and safety performance.

[0203] The positive electrode active material obtained in Comparative Example 2 was doped with zirconium, but only coated with an aluminum-containing compound. The positive electrode active material obtained in Comparative Example 3 was doped with zirconium, but only coated with a boron-containing compound. The positive electrode active material obtained in Comparative Example 4 was doped with zirconium, but only coated with both aluminum-containing and boron-containing compounds. The positive electrode active material obtained in Comparative Example 5 was doped with zirconium, but only coated with a cobalt-containing compound. Although Comparative Examples 2 to 5 all involved coating, and the positive electrode active materials showed better capacity compared to uncoated materials, there was no significant improvement in cycle performance and safety performance because they did not meet the requirement of cobalt-containing, aluminum-containing, and boron-containing compounds being coated simultaneously.

[0204] Furthermore, compared to Example 8, Examples 9 and 10 show that while these examples all achieved good results in improving energy density, cycle performance, and safety performance, Example 9's coating thickness was too thick, reaching 2.85 μm, thus affecting capacity and tending to decrease. It also affected lithium-ion transport during cycling, tending to decrease cycle performance. Example 10's coating ratio was too high, with an aluminum to boron weight ratio (aluminum:boron) reaching 5:1, tending to decrease both capacity and cycle performance.

[0205] Compared with Example 5, Example 12, and Example 11, compared with Example 8, show that although these examples all achieved good results in improving energy density, cycle performance, and safety performance, the average volumetric particle size D50 of the positive electrode active material obtained in Examples 11 and 12 was too large, which had a certain impact on the capacity, cycle performance, and safety performance of the positive electrode active material product.

[0206] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely illustrative, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material includes a positive electrode active material matrix and a coating layer, wherein the coating layer covers the surface of the positive electrode active material matrix. Among them, the positive electrode active material matrix is Li 1+a [Ni x Co y Mn z M b O2, where 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1. The M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn, and B. The coating layer contains a cobalt-containing compound, an aluminum-containing compound, and a boron-containing compound; The method for manufacturing the positive electrode active material includes: Step S1: Provide the positive electrode active material matrix; Step S2: The positive electrode active material matrix is ​​mixed with a cobalt-containing compound and sintered to obtain an intermediate, wherein the sintering temperature is 500~700℃; and Step S3: The intermediate is mixed with an aluminum-containing compound and a boron-containing compound and sintered to obtain a positive electrode active material; wherein the sintering temperature is 200~400℃.

2. The positive electrode active material according to claim 1, characterized in that, 0.8≤x<1。 3. The positive electrode active material according to claim 1, characterized in that, The weight ratio of aluminum to boron in the coating layer is 0.5 to 2:

1.

4. The positive electrode active material according to claim 3, characterized in that, The weight ratio of aluminum to boron in the coating layer is 1~2:

1.

5. The positive electrode active material according to claim 1, characterized in that, The total weight ratio of cobalt, aluminum and boron in the coating layer is 1000~22000ppm relative to the total weight of the positive electrode active material matrix.

6. The positive electrode active material according to claim 5, characterized in that, The total weight ratio of cobalt, aluminum and boron elements in the coating layer is 1000~15000ppm relative to the total weight of the positive electrode active material matrix.

7. The positive electrode active material according to claim 1, characterized in that, The weight ratio of cobalt in the coating layer is 1000~20000ppm relative to the total weight of the positive electrode active material matrix.

8. The positive electrode active material according to claim 7, characterized in that, The weight ratio of cobalt in the coating layer is 1000~19000ppm relative to the total weight of the positive electrode active material matrix.

9. The positive electrode active material according to claim 7, characterized in that, The weight ratio of cobalt in the coating layer is 1000~13000ppm relative to the total weight of the positive electrode active material matrix.

10. The positive electrode active material according to claim 1, characterized in that, The weight ratio of aluminum in the coating layer is 100~3000ppm relative to the total weight of the positive electrode active material matrix.

11. The positive electrode active material according to claim 10, characterized in that, The weight ratio of aluminum in the coating layer is 100~2900ppm relative to the total weight of the positive electrode active material matrix.

12. The positive electrode active material according to claim 10, characterized in that, The weight ratio of aluminum in the coating layer is 500~2000ppm relative to the total weight of the positive electrode active material matrix.

13. The positive electrode active material according to claim 1, characterized in that, The amount of boron in the coating layer is 100~2000ppm relative to the total weight of the positive electrode active material matrix.

14. The positive electrode active material according to claim 13, characterized in that, The amount of boron in the coating layer is 100~1900 ppm relative to the total weight of the positive electrode active material matrix.

15. The positive electrode active material according to claim 13, characterized in that, The amount of boron in the coating layer is 500-1500 ppm relative to the total weight of the positive electrode active material matrix.

16. The positive electrode active material according to claim 1, characterized in that, The thickness of the coating layer is 0.01µm to 2µm.

17. The positive electrode active material according to claim 16, characterized in that, The thickness of the coating layer is 0.1~1µm.

18. The positive electrode active material according to claim 1, characterized in that, The particles of the positive electrode active material are secondary particles formed by the aggregation of primary particles.

19. The positive electrode active material according to claim 18, characterized in that, The average particle size of the primary particles in the secondary particles is 100~1000nm.

20. The positive electrode active material according to claim 18, characterized in that, The average volume distribution particle size D50 of the positive electrode active material is 2~15µm.

21. The positive electrode active material according to claim 18, characterized in that, The specific surface area of ​​the positive electrode active material is 0.2 m². 2 / g~1.0m 2 / g.

22. The positive electrode active material according to claim 18, characterized in that, The average volume distribution particle size D50 of the positive electrode active material is 2.5~12µm; or, The specific surface area of ​​the positive electrode active material is 0.3 m². 2 / g~0.8m 2 / g.

23. The positive electrode active material according to claim 1, characterized in that, The positive electrode active material consists of single-crystal particles.

24. The positive electrode active material according to claim 23, characterized in that, The average volume distribution particle size D50 of the positive electrode active material is 1.0~8.0µm.

25. The positive electrode active material according to claim 23, characterized in that, The specific surface area of ​​the positive electrode active material is 0.4 m². 2 / g~2m 2 / g.

26. The positive electrode active material according to claim 23, characterized in that, The average volume distribution particle size D50 of the positive electrode active material is 2.0~4.0µm; or, The specific surface area of ​​the positive electrode active material is 0.5 m². 2 / g~1.5m 2 / g.

27. The positive electrode active material according to claim 1, characterized in that, The cobalt-containing compound is selected from one or more of cobalt oxide, cobalt salts, cobalt hydroxide, and cobalt hydroxyoxide; or the aluminum-containing compound is selected from one or more of alumina, aluminum hydroxide, aluminum salts, and aluminum halides; or, The boron-containing compound is selected from one or more of boron oxide, boron halide, boric acid, borates, and organoborides.

28. A method for manufacturing a positive electrode active material, characterized in that, include: Step S1: Provide a cathode active material matrix, and the chemical formula of the cathode active material matrix is Li 1+a [Ni x Co y Mn z M b O2, where 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn, and B; Step S2: The positive electrode active material matrix is ​​mixed with a cobalt-containing compound and sintered to obtain an intermediate, wherein the sintering temperature is 500~700℃; and Step S3: Mix the intermediate with an aluminum-containing compound and a boron-containing compound and sinter them to obtain a positive electrode active material; wherein, the sintering temperature is 200~400°C, the positive electrode active material includes a positive electrode active material matrix and a coating layer, the coating layer coats the surface of the positive electrode active material matrix, and the positive electrode active material matrix is Li 1+a [Ni x Co y Mn z M b O2, where 0 < x < 1, 0 ≤ y < 0.3, 0 ≤ z < 0.3, 0 < a < 0.2, 0 < b < 0.2, M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn, and B, and the coating layer contains a cobalt-containing compound, an aluminum-containing compound, and a boron-containing compound.

29. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, 0.8≤x<1。 30. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S1, lithium salt, a positive electrode active material precursor containing nickel, cobalt and manganese, and a compound containing element M are mixed to obtain mixture a, and mixture a is sintered to obtain the positive electrode active material matrix. In step S2, the positive electrode active material matrix is ​​mixed with the cobalt-containing compound to obtain mixture b, and the mixture b is sintered to obtain an intermediate. as well as In step S3, the intermediate is mixed with the aluminum-containing compound and the boron-containing compound to obtain mixture c, and the mixture c is sintered to obtain the positive electrode active material.

31. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S1, the lithium salt, the nickel-cobalt-manganese-containing cathode active material precursor, and the M-containing compound are mixed in such a way that the molar ratio of lithium in the lithium salt to the total amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese-containing cathode active material precursor is Li / (Ni+Co+Mn)=0.9~1.1, and the doping amount of M element is 1000~5000ppm.

32. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S1, the sintering temperature is 700~950℃; the sintering time is 10~20h; and the sintering atmosphere is air or oxygen.

33. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S2, the amount of cobalt added to the cobalt-containing compound is 1000ppm to 20000ppm relative to the total weight of the positive electrode active material matrix.

34. The method for manufacturing the positive electrode active material according to claim 33, characterized in that, In step S2, the amount of cobalt added to the cobalt-containing compound is 1000~19000 ppm relative to the total weight of the positive electrode active material matrix.

35. The method for manufacturing the positive electrode active material according to claim 33, characterized in that, In step S2, the amount of cobalt added to the cobalt-containing compound is 1000ppm to 13000ppm relative to the total weight of the positive electrode active material matrix.

36. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S2, the sintering time is 5 to 15 hours; the sintering atmosphere is air or oxygen.

37. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S3, the amount of aluminum added to the aluminum-containing compound is 100~3000 ppm relative to the total weight of the positive electrode active material matrix; or, In step S3, the amount of boron added to the boron-containing compound is 100~2000 ppm relative to the total weight of the positive electrode active material matrix.

38. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S3, the amount of aluminum added to the aluminum-containing compound is 100~2900 ppm relative to the total weight of the positive electrode active material matrix; or, In step S3, the amount of boron added to the boron-containing compound is 100~1900 ppm relative to the total weight of the positive electrode active material matrix.

39. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S3, the amount of aluminum added to the aluminum-containing compound is 500-2000 ppm relative to the total weight of the positive electrode active material matrix; or, In step S3, the amount of boron added to the boron-containing compound is 500-1500 ppm relative to the total weight of the positive electrode active material matrix.

40. The method for manufacturing the positive electrode active material according to claim 28, characterized in that, In step S3, the sintering time is 5 to 15 hours; the sintering atmosphere is air or oxygen.

41. The method for manufacturing the positive electrode active material according to claim 40, characterized in that, In step S3, the sintering time is 5-10 hours.

42. A secondary battery, characterized in that, It includes the positive electrode material according to any one of claims 1 to 27 or the positive electrode active material obtained by the manufacturing method of the positive electrode active material according to any one of claims 28 to 41.

43. A battery module, characterized in that, Includes the secondary battery as described in claim 42.

44. A battery pack, characterized in that, Includes the battery module as described in claim 43.

45. An apparatus, characterized in that, It includes one or more selected from the secondary battery of claim 42, the battery module of claim 43, or the battery pack of claim 44.

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