Positive electrode active material, method for manufacturing same, secondary battery, battery module, battery pack, and device

Abstract

The application provides a positive electrode active material and a manufacturing method thereof, a secondary battery, a battery module, a battery pack and a device. The positive electrode active material comprises a positive electrode active material base body and a coating layer, the coating layer coats the surface of the positive electrode active material base body, wherein the particle of the positive electrode active material is a secondary particle formed by agglomeration of primary particles, the average volume distribution particle size D50 of the positive electrode active material is 2-15 mu m; or the particle of the positive electrode active material is a single crystal particle, the average volume distribution particle size D50 of the positive electrode active material is 1.0-8.0 mu m; the coating layer comprises a cobalt-containing compound, an aluminum-containing compound and a boron-containing compound. The secondary battery comprising the material can have higher energy density, better cycle performance and reliability.

Description

[0001] This application is a divisional application based on the invention patent application with application number 202080104536.1, application date October 31, 2020, applicant CATL, and invention title "Positive electrode active material and manufacturing method thereof, secondary battery, battery module, battery pack and device". Technical Field

[0002] This application relates to the field of lithium battery technology, and in particular to a positive electrode active material and its manufacturing method, a secondary battery, a battery module, a battery pack, and an apparatus. Background Technology

[0003] In recent years, with the increasingly widespread application of lithium-ion batteries, they have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant development of lithium-ion batteries, higher requirements have been placed on their energy density, cycle performance, and reliability. Furthermore, due to the increasingly limited selection of positive electrode active materials, high-nickel positive electrode active materials are considered the best choice to meet high energy density requirements.

[0004] However, with the continuous increase of nickel content, its structural stability becomes increasingly poor. Improving the rate performance and cycle performance of materials through coating or doping are currently effective methods; however, existing methods all lead to varying degrees of damage to lithium-ion battery performance, such as reduced specific capacity and worsened cycle performance. Therefore, existing coated or doped cathode materials still need improvement. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode active material and a method for manufacturing the same, which can enable secondary batteries containing the material to have high energy density, good cycle performance and reliability.

[0006] To achieve the above objectives, this application provides a positive electrode active material and its manufacturing method, a secondary battery, a battery module, a battery pack, and an apparatus.

[0007] A first aspect of the present application provides a positive electrode active material, comprising a positive electrode active material substrate and a coating layer, wherein the coating layer coats the surface of the positive electrode active material substrate, the particles of the positive electrode active material are secondary particles formed by agglomeration of primary particles, and the average volume distribution particle diameter D50 of the positive electrode active material is 2 to 15 μm; or, the particles of the positive electrode active material are single crystal particles, and the average volume distribution particle diameter D50 of the positive electrode active material is 1.0 to 8.0 μm; the coating layer comprises a cobalt-containing compound, an aluminum-containing compound and a boron-containing compound.

[0008] Accordingly, in the present application, by jointly coating the cobalt-containing compound, the aluminum-containing compound and the boron-containing compound on the surface of the positive electrode active material, the three components act synergistically, which can improve the rate performance and cycle performance of the positive electrode active material, and at the same time, can significantly mitigate the interfacial side reaction between the positive electrode active material and the electrolyte, so as to increase the capacity.

[0009] In any embodiment, the elements in the positive electrode active material substrate are lithium element, nickel element, cobalt element, manganese element, oxygen element and M element, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0010] In any embodiment, the elements in the positive electrode active material substrate are lithium element, nickel element, cobalt element, oxygen element and M element, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0011] In any embodiment, the elements in the positive electrode active material substrate are lithium element, nickel element, manganese element, oxygen element and M element, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0012] In any embodiment, the elements in the positive electrode active material substrate are lithium element, nickel element, oxygen element and M element, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0013] In any embodiment, the positive electrode active material substrate 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, optionally 0.8≤x<1, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 ​​100~3000ppm, optionally 100~2900ppm, and further optionally 500~2000ppm. Therefore, due to the appropriate coating amount, the cycling, storage, and reliability of the positive electrode active material can be better improved.

[0021] In any embodiment, 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. Therefore, due to the appropriate coating amount, the cycling, storage, and reliability of the positive electrode active material can be further improved.

[0022] In any embodiment, the weight ratio of aluminum to boron in the coating layer is 0.5 to 2:1, optionally 1 to 2:1. This further improves the cycle life and reliability of the positive electrode active material.

[0023] In any embodiment, when the particles of the positive electrode active material are secondary particles formed by the aggregation of primary particles, the positive electrode active material satisfies the following conditions: the average particle size of the primary particles in the secondary particles is 100~1000 nm; or, the average volume distribution particle size D50 of the positive electrode active material is 2.5~12 μm; or, the specific surface area of ​​the positive electrode active material is 0.2 m². 2 / g~1.0m 2 / g, optionally 0.3m 2 / g~0.8m 2 / g.

[0024] In any embodiment, when the positive electrode active material particles are single-crystal particles, the positive electrode active material satisfies the following conditions: the average volume distribution particle size D50 of the positive electrode active material is 2.0~4.0 μm; or, the specific surface area of ​​the positive electrode active material is 0.4 m². 2 / g~2m 2 / g, which can be further selected as 0.5m 2 / g~1.5m 2 / g.

[0025] A second aspect of this application also provides a method for manufacturing a positive electrode active material, comprising: Step S1: Provide a positive electrode active material matrix; Step S2: Mix the positive electrode active material matrix with a cobalt-containing compound and sinter to obtain an intermediate; and Step S3: Mix the intermediate with an aluminum-containing compound and a boron-containing compound and sinter to obtain a positive electrode active material; The positive electrode active material comprises a positive electrode active material matrix and a coating layer. The coating layer covers the surface of the positive electrode active material matrix and contains cobalt-containing compounds, aluminum-containing compounds, and boron-containing compounds. The particles of the positive electrode active material are secondary particles formed by the aggregation of primary particles, and the average volume distribution particle size D50 of the positive electrode active material is 2~15μm. Alternatively, the particles of the positive electrode active material are single crystal particles, and the average volume distribution particle size D50 of the positive electrode active material is 1.0~8.0μm.

[0026] Accordingly, through the above method for producing a positive electrode active material of the present application, a common coating layer containing a cobalt-containing compound, a boron-containing compound, and an aluminum-containing compound is uniformly coated on the surface of the positive electrode active material substrate. In addition, by adopting the method for producing a positive electrode active material of the present application, not only the complicated production procedures in the existing production methods are avoided, but also the production cost can be reduced.

[0027] In any embodiment, the elements in the positive electrode active material substrate are lithium element, nickel element, cobalt element, manganese element, oxygen element and M element, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0028] In any embodiment, the elements in the positive electrode active material substrate are lithium element, nickel element, cobalt element, oxygen element and M element, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0029] In any embodiment, the elements in the positive electrode active material substrate are lithium element, nickel element, manganese element, oxygen element and M element, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0030] In any embodiment, the elements in the positive electrode active material substrate are lithium element, nickel element, oxygen element and M element, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

[0031] In any embodiment, in step S1, the chemical formula of the positive electrode active material substrate 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.

[0032] In any embodiment, in the step S1, the lithium salt, the positive electrode active material precursor containing nickel, cobalt and manganese, and the M element-containing compound are added into a mixer for mixing, in such a manner that the molar ratio of the lithium element in the lithium salt to the sum of the nickel element, cobalt element and manganese element in the positive electrode active material precursor containing nickel, cobalt and manganese is Li / (Ni+Co+Mn)=0.9~1.1, and the doping amount of the M element is 1000~5000ppm. Accordingly, the M element can be uniformly doped, and the structural stability of the material can be effectively improved.

[0033] In any embodiment, the sintering conditions in step S1 are as follows: sintering temperature is 700~950℃, sintering time is 10~20h, and the sintering atmosphere is air or oxygen. This allows for effective doping of element M.

[0034] 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 reliability can be further improved.

[0035] In any embodiment, the sintering conditions in step S2 are as follows: sintering temperature is 500~700℃, sintering time is 5~15h, and the sintering atmosphere is air or oxygen. This improves the coating effect.

[0036] 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 100~3000ppm, optionally 100~2900ppm, and further optionally 500~2000ppm. 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 100~2000ppm, optionally 100~1900ppm, and further optionally 500~1500ppm. This further improves the interfacial side reactions of the material. Moreover, due to the appropriate coating amount, the material's cycleability, storage, and reliability can be further improved.

[0037] In any embodiment, the sintering conditions in step S3 are as follows: sintering temperature is 200~500℃, optionally 200~400℃; sintering time is 5~15h, optionally 5~10h; and the sintering atmosphere is air or oxygen. Therefore, aluminum-containing compounds and boron-containing compounds can be firmly coated on the surface of the positive electrode active material particles without penetrating into the inner layers of the particles, thus improving the coating effect.

[0038] 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.

[0039] A fourth aspect of this application provides a battery module including the secondary battery of the third aspect of this application.

[0040] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0041] 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

[0042] Figure 1 This is a scanning electron microscope image of the positive electrode active material obtained in Example 1.

[0043] Figure 2 The first charge-discharge curve of a coin cell made from the positive electrode active material obtained in Example 1.

[0044] 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.

[0045] Figure 4 Comparison 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.

[0046] Figure 5 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0047] Figure 6 yes Figure 5 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0048] Figure 7 This is a schematic diagram of a battery module according to one embodiment of this application.

[0049] Figure 8 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0050] Figure 9 yes Figure 8 An exploded view of a battery pack according to one embodiment of this application is shown.

[0051] 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.

[0052] Explanation of reference numerals in the attached figures: 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Top cover assembly. Detailed Implementation

[0053] Hereinafter, embodiments of the positive electrode active material, the manufacturing method thereof, the positive electrode plate, the secondary battery, the battery module, the battery pack and the device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structure may be omitted. This is to avoid the following description from being unnecessarily lengthy, and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0054] For the sake of brevity, the present application specifically discloses some numerical ranges. However, any lower limit may be combined with any upper limit to form a range that is not explicitly stated; any lower limit may be combined with another lower limit to form a range that is not explicitly stated, and similarly, any upper limit may be combined with any other upper limit to form a range that is not explicitly stated. In addition, each individually disclosed point or single numerical value may itself serve as a lower limit or an upper limit to combine with any other point or single numerical value, or combine with other lower limits or upper limits to form a range that is not explicitly stated.

[0055] Positive Electrode Active Material In one embodiment of the present application, the present application provides a positive electrode active material. The positive electrode active material includes a positive electrode active material matrix and a coating layer coating 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, 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, and the coating layer contains a cobalt-containing compound, an aluminum-containing compound and a boron-containing compound.

[0056] Although the mechanism is not yet clear, the applicant unexpectedly discovered that by co-coating the surface of the positive electrode active material with cobalt-containing compounds, aluminum-containing compounds, and boron-containing compounds, the rate performance and cycle performance of the positive electrode active material can be significantly improved. Simultaneously, it can also significantly improve the interfacial side reactions between the positive electrode active material and the electrolyte, thereby increasing capacity. Furthermore, even when applied to high-nickel-content (Ni content ≥ 80%) positive electrode active materials with poor structural stability, by doping the positive electrode active material with element M and simultaneously co-coating the surface of the positive electrode active material with cobalt-containing compounds, aluminum-containing compounds, and boron-containing compounds, 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 cycle performance and rate performance of the positive electrode active material can be enhanced.

[0057] 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 cobalt-containing compound is selected from one or more of cobalt oxides, cobalt salts, cobalt hydroxide, and cobalt hydroxyoxide. Examples of cobalt oxides include CoO, Co3O4, etc. Examples of cobalt salts include cobalt acetate, cobalt oxalate, and cobalt carbonate, etc.

[0058] 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.

[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 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 reliability of the positive electrode active material.

[0064] 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, 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.

[0065] 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 reliability of the positive electrode active material.

[0066] 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.

[0067] 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.

[0068] In some embodiments, the average volume distribution particle size D50 of the secondary particles of the positive electrode active material is 2~15μm, and can be selected as 2.5~12μm.

[0069] 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.

[0070] 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 1.0~8.0μm, and can be selected as 2.0~4.0μm.

[0071] 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.

[0072] Accordingly, the positive electrode active material produced by the above manufacturing method has a good crystal structure, which is beneficial to lithium ion transmission, and can improve the rate performance and cycle performance.

[0073] In addition, the average volume distribution particle size D50 refers to the corresponding particle size when the cumulative volume distribution percentage of the positive electrode active material reaches 50%. In the present application, the volume average particle size D50 of the positive electrode active material can be measured by a laser diffraction particle size analysis method. For example, with reference to the standard GB / T 19077-2016, the measurement is performed using a laser particle size analyzer (such as Malvern MasterSize 3000).

[0074] In some embodiments, the cobalt-containing compound is, for example, the cobalt-containing compound described below, and the particle size of the cobalt-containing compound may be 0.001 μm to 10 μm, for example 0.001 μm to 1 μm. Since the nano-scale cobalt-containing compound is used, it can be uniformly and effectively coated on the surface of the positive electrode material matrix, and the interfacial side reaction between the material and the electrolyte is improved.

[0075] Method for Manufacturing Positive Electrode Active Material In one embodiment of the present application, the present application further provides a method for manufacturing a positive electrode active material, comprising: Step S1: adding a lithium salt, a positive electrode active material precursor containing nickel, cobalt and manganese, and an M element-containing compound into a mixer for mixing to obtain a mixed material a, adding 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: adding the M element-doped positive electrode active material matrix and the cobalt-containing compound into a mixer for mixing to obtain a mixed material b, adding the mixed material b into a kiln for sintering to obtain an intermediate (the positive electrode active material coated with the cobalt-containing compound); and Step S3: adding the intermediate, the aluminum-containing compound and the boron-containing compound into a mixer for mixing to obtain a mixed material c, adding the mixed material c into a kiln for sintering to obtain the positive electrode active material coated with the cobalt-containing compound, the aluminum-containing compound and the boron-containing compound.

[0076] Therefore, although the mechanism is not yet clear, the applicant unexpectedly discovered that the manufacturing method of the positive electrode active material described in this application can uniformly dope the M element in the core of the positive electrode active material, effectively improving the structural stability of the positive electrode active material. Simultaneously, a co-coating layer containing cobalt, boron, and aluminum compounds is uniformly coated on the surface of the positive electrode active material core, effectively suppressing interfacial side reactions between the positive electrode active material and the electrolyte. This not only improves the capacity and rate performance of the positive electrode active material but also effectively improves its cycle life, storage performance, and reliability. Furthermore, by adopting the manufacturing method of the positive electrode active material of this application, not only are the complex manufacturing processes such as wet coating in existing methods avoided, but production costs are also reduced. The manufacturing method of this application employs a stepwise coating method, which allows the prepared positive electrode active material to simultaneously achieve good cycle performance and high capacity. If the three compounds (cobalt-containing compound, boron-containing compound, and aluminum-containing compound) are coated simultaneously, if the coating temperature is set too high, aluminum and boron may penetrate into the inner layer of the positive electrode active material particles, and the boron-containing compound is prone to volatilization at high temperatures, affecting the coating effect and thus affecting capacity and cycle performance. If the coating temperature is set too low, the cobalt-containing compound may not be able to effectively coat the outer layer of the positive electrode active material particles, failing to achieve the coating effect, thus affecting cycle performance and reliability. Therefore, by coating in stages, the coating effect can be avoided when all three are coated at the same time.

[0077] 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 1000~5000ppm. This allows for uniform doping of the M-element, effectively improving the structural stability of the material.

[0078] In some embodiments, the sintering conditions in step S1 are as follows: sintering temperature of 700~950℃, sintering time of 10~20h, 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.

[0079] In some embodiments, in step S2, the addition ratio of the cobalt-containing compound is such that relative to the total weight of the positive electrode active material matrix, the added amount of cobalt element is 1000 ppm to 20000 ppm, preferably 1000 ppm to 19000 ppm, and more preferably 1000 ppm to 13000 ppm. Accordingly, the cobalt-containing compound can 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. Meanwhile, due to the appropriate coating amount, the capacity, rate performance and cycle performance of the positive electrode active material can be improved.

[0080] In some embodiments, the sintering conditions in step S2 are as follows: the sintering temperature is 500 to 700°C, the sintering time is 5 to 15 h, and the sintering atmosphere is air or oxygen. Accordingly, the cobalt-containing compound can be firmly coated on the particle surface of the positive electrode active material without penetrating into the inner layer of the particles, so as to improve the coating effect.

[0081] In some embodiments, in step S3, the addition ratio of the aluminum-containing compound is such that relative to the total weight of the positive electrode active material matrix, the added amount of aluminum element is 100 ppm to 3000 ppm, optionally 100 ppm to 2900 ppm, and further optionally 500 ppm to 2000 ppm; the addition ratio of the boron-containing compound is such that relative to the total weight of the positive electrode active material matrix, the added amount of boron element is 100 ppm to 2000 ppm, optionally 100 ppm to 1900 ppm, and further optionally 500 ppm to 1500 ppm. Accordingly, the interfacial side reactions of the material can be further improved. Moreover, due to the appropriate coating amount, the cycle performance, storage performance and reliability of the material can be further better improved.

[0082] In some embodiments, the sintering conditions in step S3 are as follows: the sintering temperature is 200 to 500°C, optionally 200 to 400°C, the sintering time is 5 to 15 h, optionally 5 to 10 h, and the sintering atmosphere is air or oxygen. Accordingly, the aluminum-containing compound and the boron-containing compound can be firmly coated on the particle surface of the positive electrode active material without penetrating into the inner layer of the particles, effectively improving the coating effect. Moreover, the interfacial side reactions of the positive electrode active material can be further significantly improved, and the cycle performance, storage performance and reliability of the positive electrode active material can be enhanced.

[0083] In some embodiments, for example, the nickel, cobalt and manganese-containing positive electrode active material precursor is [Ni x Co y Mn z (OH)₂, wherein 0<x<1, 0≤y<0.3, 0≤z<0.3, and further, 0.8≤x<1.

[0084] In some embodiments, for example, the lithium salt may be selected from one or more of lithium carbonate and lithium hydroxide.

[0085] In addition, the secondary battery, battery module, battery pack and device of this application will be described below with appropriate reference to the accompanying drawings.

[0086] In one embodiment of this application, a secondary battery is provided.

[0087] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0088] [Positive electrode plate] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0089] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0090] 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.).

[0091] 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.

[0092] 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.

[0093] [Negative electrode plate] 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.

[0094] 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.

[0095] 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.).

[0096] 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.

[0097] 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.

[0098] 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).

[0099] Other optional additives include thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).

[0100] 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.

[0101] [Electrolytes] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on 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).

[0102] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0103] 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).

[0104] 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).

[0105] 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.

[0106] [Isolation membrane] 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.

[0107] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0108] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0109] 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).

[0110] 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.

[0111] In some implementations, refer to Figure 6The 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.

[0112] 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.

[0113] 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.

[0114] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0115] 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.

[0116] Figure 8 and Figure 9 This 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.

[0117] 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.

[0118] As the device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0119] 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.

[0120] 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.

[0121] Example 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.

[0122] Example 1 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.]

[0123] The mixture obtained above was added to a roller kiln and sintered for 20 hours at a sintering temperature of 800℃. The sintering atmosphere was oxygen, and the positive electrode active material matrix was obtained.

[0124] 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 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.

[0125] 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 in 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.

[0126] Example 2 In addition to replacing the positive electrode active material precursor with [Ni] 0.8 Co 0.1 Mn 0.1 The cathode active material, MgO, was prepared using MgO ((OH)₂) with an average volumetric particle size (D50) of 2.5 μm. 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.

[0127] Example 3 In addition to replacing the positive electrode active material precursor with [Ni] 0.6 Co 0.2 Mn 0.2The cathode active material, denoted as OH)₂, has an average volumetric particle size (D50) of 12 μm. The primary sintering temperature was adjusted to 950℃, and the zirconium oxide (ZrO₂) added during the primary sintering was replaced with TiO₂. The primary sintering time was 15 h, the amount of titanium added was 1000 ppm, and the amount of aluminum added was adjusted to 1500 ppm. All other conditions were the same as in Example 1. The resulting coated cathode active material consists of secondary particles with an average volumetric particle size (D50) of 12 μm, and the total thickness of the coating layer, measured using a micrometer, is 0.67 μm.

[0128] Example 4 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℃, the secondary sintering temperature to 500℃, replacing the CoO added in the secondary sintering with Co(OH)2, adding 13000 ppm of cobalt, adjusting the secondary sintering time to 5 h, and adjusting the amount of aluminum added 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.

[0129] Example 5 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℃, the secondary sintering temperature to 700℃, 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 to 1200 ppm in the tertiary sintering, 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.

[0130] Example 6 In addition to replacing the positive electrode active material precursor with [Ni] 0.95 Co 0.02 Mn 0.03The process involved adjusting the first sintering temperature to 850℃, replacing the zirconium oxide (ZrO2) added in the first sintering with Al2O3, and adjusting the amount of aluminum added to 2000ppm. The second sintering temperature was adjusted to 650℃, replacing the CoO added in the second sintering with cobalt acetate, and adjusting the amount of cobalt added to 20000ppm. The third sintering temperature was adjusted to 200℃, the third sintering time was adjusted to 5h, and replacing AlCl3 added in the third sintering with Al2O3, B2O3 with H3BO3, and adjusting the amount of boron added to 2000ppm. 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 5μm, and the total thickness of the coating layer, measured using a micrometer, was 1.42μm.

[0131] Example 7 Except for adjusting the sintering temperature to 400℃, the sintering time to 10h, replacing Al2O3 with AlCl3, adjusting the amount of aluminum added to 3000ppm, replacing H3BO3 with (C2H5O)3B, adjusting the amount of boron added to 1500ppm, 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 5μm, and the total thickness of the coating layer, measured using a micrometer, was 1.81μm.

[0132] Example 8 Except for replacing the D50 of the positive electrode active material precursor with 10 μm, adjusting the sintering temperature to 350℃, 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.

[0133] Example 9 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.

[0134] Example 10 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.

[0135] Example 11 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.

[0136] Example 12 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.

[0137] Comparative Example 1 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.]

[0138] The mixture obtained above was added to a roller kiln and sintered for 20 hours at a sintering temperature of 800℃. The sintering atmosphere was oxygen, and the positive electrode active material was obtained.

[0139] The resulting positive electrode active material consists of secondary particles with an average volume particle size D50 of 5 μm.

[0140] Comparative Example 2 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 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.

[0141] Comparative Example 3 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.

[0142] Comparative Example 4 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.

[0143] Comparative Example 5 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. 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 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.

[0144] Comparative Example 6 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.

[0145] The mixture obtained above was added to a roller kiln and sintered at 700℃ 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 volume particle size D50 of 2.5 μm.

[0146] Comparative Example 7 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.

[0147] The mixture obtained above was added to a roller kiln and sintered at 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.

[0148] The relevant parameters of the cathode materials of Examples 1-12 and Comparative Examples 1-7 are shown in Table 1 below.

[0149] Table 1

[0150] 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 as shown below, and their performance was tested. The test results are shown in Table 2 below.

[0151] (1) Preparation of button cells 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.

[0152] (2) Initial capacitance test of coin cells Each of the coin cells prepared above was charged at 0.1C to 4.3V at a voltage of 2.8~4.3V, and then charged at a constant voltage of 4.3V until the current was ≤0.05mA. After standing for 2 minutes, the charging capacity at this time was recorded as C0. Then, it was discharged at 0.1C to 2.8V. The discharge capacity at this time was the initial discharge capacity, recorded as D0. The first efficiency was D0 / C0*100%.

[0153] 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.

[0154] (3) Preparation of secondary batteries 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.

[0155] 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.

[0156] A porous polymer film made of polyethylene (PE) is used as a separator.

[0157] 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.

[0158] (4) Initial capacitance test of secondary electrical components Each of the secondary batteries prepared above was placed in a constant temperature environment of 25°C for 5 minutes, discharged at 1 / 3C to 2.8V, placed in a constant temperature environment for 5 minutes, charged at 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V until the current ≤0.05mA. After being placed in a constant temperature environment for 5 minutes, the charging capacity at this time was recorded as C0. Then, it was discharged at 1 / 3C to 2.8V. The discharge capacity at this time was the initial discharge capacity, recorded as D0.

[0159] 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.

[0160] (5) Cyclic performance test of secondary battery at 25 / 45℃ Each of the prepared secondary batteries was charged at 1C to 4.25V under a constant temperature environment of 25℃ or 45℃ at a voltage range 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.

[0161] (6) Gas expansion performance test of secondary battery at 70℃ For each secondary battery prepared with 100% SOC (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 secondary battery was stored in a storage furnace at 70°C. Every 48 hours, the cells were removed from 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%.

[0162] 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.

[0163] Table 2

[0164] 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 reliability. Furthermore, the initial efficiency of the positive electrode active material was also improved.

[0165] In contrast, the positive electrode active material obtained in Comparative Example 1 was doped only with zirconium, the positive electrode active material obtained in Comparative Example 6 was doped only with magnesium, and the positive electrode active material obtained in Comparative Example 7 was doped only with titanium, but none of them were coated. Therefore, Comparative Example 1 had poor cycle performance and reliability, 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 reliability.

[0166] 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 2-5 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 reliability because they did not meet the requirement of co-cobalt-containing, aluminum-containing, and boron-containing compounds being coated simultaneously.

[0167] 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 reliability, Example 9's coating thickness was too thick, reaching 2.85 μm, thus affecting the capacity and tending to decrease it. 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.

[0168] 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 reliability, 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 life, and reliability of the positive electrode active material product.

[0169] 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. Wherein, the particles of the positive electrode active material are secondary particles formed by the aggregation of primary particles, and the average volume distribution particle size D50 of the positive electrode active material is 2~15μm; or, The positive electrode active material particles are single crystal particles, and the average volume distribution particle size D50 of the positive electrode active material is 1.0~8.0μm; The coating layer contains cobalt-containing compounds, aluminum-containing compounds, and boron-containing compounds.

2. The positive electrode active material according to claim 1, characterized in that, The positive electrode active material matrix satisfies any one of the following conditions (1)-(4): (1) The elements in the positive electrode active material matrix are lithium, nickel, cobalt, manganese, oxygen and M, wherein M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B; (2) The elements in the positive electrode active material matrix are lithium, nickel, cobalt, oxygen and M, wherein M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B; (3) The elements in the positive electrode active material matrix are lithium, nickel, manganese, oxygen and M, wherein M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B; (4) The elements in the positive electrode active material matrix are lithium, nickel, oxygen and M, wherein M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

3. The positive electrode active material according to claim 1, characterized in that, 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, and M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

4. The positive electrode active material according to any one of claims 1-3, characterized in that, The weight ratio of aluminum to boron in the coating layer is 0.5 to 2:1, and can be selected as 1 to 2:

1.

5. The positive electrode active material according to any one of claims 1-4, characterized in that, 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 ​​1000~22000ppm, and can be selected as 1000~15000ppm.

6. The positive electrode active material according to any one of claims 1-5, characterized in that, The weight ratio of cobalt in the coating layer relative to the total weight of the positive electrode active material matrix is ​​1000~20000ppm, optionally 1000~19000ppm, and further optionally 1000~13000ppm.

7. The positive electrode active material according to any one of claims 1-6, characterized in that, The weight ratio of aluminum in the coating layer relative to the total weight of the positive electrode active material matrix is ​​100~3000ppm, optionally 100~2900ppm, and further optionally 500~2000ppm.

8. The positive electrode active material according to any one of claims 1-7, characterized in that, Relative to the total weight of the positive electrode active material matrix, the amount of boron in the coating layer is 100~2000ppm, optionally 100~1900ppm, and further optionally 500~1500ppm.

9. The positive electrode active material according to any one of claims 1-8, characterized in that, The thickness of the coating layer is 0.01μm to 2μm, and can be selected as 0.1 to 1μm.

10. The positive electrode active material according to any one of claims 1-9, characterized in that, When the particles of the positive electrode active material are secondary particles formed by the aggregation of primary particles, the positive electrode active material satisfies the following: The average particle size of the primary particles in the secondary particles is 100~1000 nm; or, 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 0.2 m². 2 / g~1.0m 2 / g, optional 0.3m 2 / g~0.8m 2 / g.

11. The positive electrode active material according to any one of claims 1-10, characterized in that, When the particles of the positive electrode active material are single-crystal particles, the positive electrode active material satisfies: The average volume distribution particle size D50 of the positive electrode active material is 2.0~4.0 μm; or, The specific surface area of ​​the positive electrode active material is 0.4 m². 2 / g~2m 2 / g, which can be further selected as 0.5m 2 / g ~1.5m 2 / g.

12. The positive electrode active material according to any one of claims 1-11, 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.

13. A method for manufacturing a positive electrode active material, characterized in that, include: Step S1: Provide a positive electrode active material matrix; Step S2: Mix the positive electrode active material matrix with a cobalt-containing compound and sinter to obtain an intermediate; as well as Step S3: Mix the intermediate with an aluminum-containing compound and a boron-containing compound and sinter to obtain a positive electrode active material; The positive electrode active material comprises a positive electrode active material matrix and a coating layer. The coating layer covers the surface of the positive electrode active material matrix and contains cobalt-containing compounds, aluminum-containing compounds, and boron-containing compounds. The particles of the positive electrode active material are secondary particles formed by the aggregation of primary particles, and the average volume distribution particle size D50 of the positive electrode active material is 2~15μm. Alternatively, the particles of the positive electrode active material are single crystal particles, and the average volume distribution particle size D50 of the positive electrode active material is 1.0~8.0μm.

14. The method for manufacturing the positive electrode active material according to claim 13, characterized in that, The positive electrode active material matrix satisfies any one of the following conditions (1)-(4): (1) The elements in the positive electrode active material matrix are lithium, nickel, cobalt, manganese, oxygen and M, wherein M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B; (2) The elements in the positive electrode active material matrix are lithium, nickel, cobalt, oxygen and M, wherein M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B; (3) The elements in the positive electrode active material matrix are lithium, nickel, manganese, oxygen and M, wherein M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B; (4) The elements in the positive electrode active material matrix are lithium, nickel, oxygen and M, wherein M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

15. The method for manufacturing the positive electrode active material according to claim 13, characterized in that, In step S1, the chemical formula of 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 M is selected from one or more of Mg, Ca, Sb, Ce, Ti, Zr, Al, Zn and B.

16. The method for manufacturing the positive electrode active material according to claim 14 or 15, 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. The particle size of the cobalt-containing compound is 0.001 μm to 10 μm. 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.

17. The method for manufacturing the positive electrode active material according to claim 16, characterized in that, In step S1, the lithium salt, the nickel-cobalt-manganese-containing positive electrode 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 positive electrode active material precursor is Li / (Ni+Co+Mn)=0.9~1.1, and the doping amount of M element is 1000~5000ppm.

18. The method for manufacturing the positive electrode active material according to any one of claims 13-17, 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.

19. The method for manufacturing the positive electrode active material according to any one of claims 13-18, characterized in that, In step S2, the amount of cobalt added in the cobalt-containing compound is 1000ppm to 20000ppm relative to the total weight of the positive electrode active material matrix, optionally 1000 to 19000ppm, and further optionally 1000ppm to 13000ppm.

20. The method for manufacturing the positive electrode active material according to any one of claims 13-19, characterized in that, In step S2, the sintering temperature is 500~700℃; the sintering time is 5~15h; and the sintering atmosphere is air or oxygen.

21. The method for manufacturing the positive electrode active material according to any one of claims 13-20, characterized in that, In step S3, the amount of aluminum added to the aluminum-containing compound relative to the total weight of the positive electrode active material matrix is ​​100~3000ppm, optionally 100~2900ppm, and further optionally 500~2000ppm; or, In step S3, the amount of boron added in the boron-containing compound is 100~2000ppm relative to the total weight of the positive electrode active material matrix, optionally 100~1900ppm, and further optionally 500~1500ppm.

22. The method for manufacturing the positive electrode active material according to any one of claims 13-21, characterized in that, In step S3, the sintering temperature is 200~500℃, or optionally 200~400℃; the sintering time is 5~15h, or optionally 5~10h; and the sintering atmosphere is air or oxygen.

23. A secondary battery, characterized in that, It includes the positive electrode material according to any one of claims 1-12 or the positive electrode active material obtained by the manufacturing method of the positive electrode active material according to any one of claims 13-22.

24. A battery module, characterized in that, Includes the secondary battery as described in claim 23.

25. A battery pack, characterized in that, Includes the battery module as described in claim 24.

26. An apparatus, characterized in that, It includes one or more selected from the secondary battery of claim 23, the battery module of claim 24, or the battery pack of claim 25.

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