WO2024065647A1 - 正极活性材料及其制备方法、二次电池和用电装置 - Google Patents

正极活性材料及其制备方法、二次电池和用电装置 Download PDF

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WO2024065647A1
WO2024065647A1 PCT/CN2022/123195 CN2022123195W WO2024065647A1 WO 2024065647 A1 WO2024065647 A1 WO 2024065647A1 CN 2022123195 W CN2022123195 W CN 2022123195W WO 2024065647 A1 WO2024065647 A1 WO 2024065647A1
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positive electrode
active material
electrode active
particle size
optionally
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PCT/CN2022/123195
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English (en)
French (fr)
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吴凯
吴奇
陈强
沈重亨
范敬鹏
赵栋
柳娜
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/123195 priority Critical patent/WO2024065647A1/zh
Priority to CN202280007511.9A priority patent/CN118120074A/zh
Publication of WO2024065647A1 publication Critical patent/WO2024065647A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to a positive electrode active material and a preparation method thereof, a secondary battery and an electrical device.
  • secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • high nickel positive electrode active materials are considered to be the best choice to meet the requirements of high energy density.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode active material so that a secondary battery containing the positive electrode active material has a high volume energy density and good cycle performance and safety performance.
  • the present application provides a positive electrode active material and a preparation method thereof, a secondary battery and an electrical device.
  • the first aspect of the present application provides a positive electrode active material, comprising:
  • a first positive electrode active material comprising a matrix of formula (I) doped with an element M1:
  • the element M1 is selected from at least one of Ti, Zr, Al, Sb, W, Sr, Nb, Mo, Ca, K, Na, Mg, Si, Te, Cr, V, and Y; and
  • the second positive electrode active material comprises a matrix of formula (II) doped with an element M2:
  • the average particle size Dv 50 of the first positive electrode active material is greater than the average particle size Dv 50 of the second positive electrode active material, and 0 ⁇ X2-X1 ⁇ 0.4, optionally 0 ⁇ X2-X1 ⁇ 0.1.
  • the present application makes the positive electrode sheet containing the positive electrode active material have a high compaction density by combining a first positive electrode active material with a larger average particle size Dv50 with a second positive electrode active material with a smaller average particle size Dv50 , thereby significantly improving the volume energy density of the secondary battery; in addition, when the Ni content of the second positive electrode active material matrix is higher than the Ni content of the first positive electrode active material matrix and when the difference in Ni content between the two is within the said range, while ensuring the capacity of the secondary battery, the cycle performance and safety performance of the secondary battery can be improved.
  • the energy density of the secondary battery can be further improved.
  • the weight ratio of the first positive electrode active material to the second positive electrode active material is 5:5 or more, and can be 6:4-9:1.
  • the compaction density of the positive electrode sheet can be further improved, thereby further improving the volume energy density of the secondary battery.
  • the first cathode active material is a secondary particle, and the volume particle size distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 ⁇ 0.5, optionally (Dv 90 -Dv 10 )/Dv 50 ⁇ 1.0.
  • the average particle size Dv 50 of the first positive electrode active material is 6-20 ⁇ m.
  • the first positive electrode active material When the average particle size Dv 50 and the volume particle size distribution diameter of the first positive electrode active material are within the given range, the first positive electrode active material has a higher gram capacity; and when combined with the second positive electrode active material, the compaction density of the positive electrode sheet can be further improved.
  • the second positive electrode active material is a secondary particle and/or a primary particle, optionally a primary particle, and the volume particle size distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 ⁇ 0.5, optionally (Dv 90 -Dv 10 )/Dv 50 ⁇ 1.0.
  • the average particle size Dv 50 of the second positive electrode active material is 2-5 ⁇ m.
  • the second positive electrode active material When the average particle size Dv 50 and the volume particle size distribution diameter of the second positive electrode active material are within the given range, the second positive electrode active material has a higher gram capacity and is conducive to sintering into primary particles, and has good cycle performance and safety performance; and when combined with the first positive electrode active material, it can further improve the compaction density of the positive electrode sheet.
  • the doping amount of the element M1 is 500-7000 ppm, optionally 1000-5000 ppm, based on the total weight of the first positive electrode active material.
  • the first positive electrode active material is doped with the element M1 and the doping amount of the element M1 is within the given range, the bulk structural stability of the secondary particles can be further improved.
  • the doping amount of the element M2 is 500-7000 ppm, optionally 1000-5000 ppm, based on the total weight of the second positive electrode active material.
  • the second positive electrode active material is doped with the element M2 and when the doping amount of the element M2 is within the given range, the bulk structure stability of the second positive electrode active material can be further improved.
  • the surface of the first positive electrode active material further has a coating layer, the coating layer contains an N1 element, and the N1 element is selected from at least one of Al, Co, Mn, B, La, Sr, P, F, Zr, Ti, and W.
  • Providing a coating layer containing an N1 element on the surface of the first positive electrode active material can further improve the interface stability of the secondary particles and reduce the side reaction between the secondary particles and the electrolyte.
  • the coating amount of the N1 element is 500-20000 ppm, optionally 1000-15000 ppm, based on the total weight of the first positive electrode active material.
  • the coating amount of the N1 element is within the given range, the interface stability of the first positive electrode active material can be further improved without affecting other properties of the first positive electrode active material.
  • the surface of the second positive electrode active material further has a coating layer, the coating layer contains N2 elements, and the N2 element is selected from at least one of Al, Co, Mn, B, La, Sr, P, F, Zr, Ti, and W.
  • Providing a coating layer containing N2 elements on the surface of the second positive electrode active material can further improve the interface stability of the second positive electrode active material and reduce the side reaction between the second positive electrode active material and the electrolyte.
  • the coating amount of the N2 element is 500-20000 ppm, optionally 1000-15000 ppm, based on the total weight of the second positive electrode active material.
  • the coating amount of the N2 element is within the given range, the interface stability of the second positive electrode active material can be further improved without affecting other properties of the second positive electrode active material.
  • the second aspect of the present application also provides a method for preparing a positive electrode active material, which comprises the following steps:
  • Step A preparing a first positive electrode active material, which comprises:
  • Step A1 mixing a lithium salt, a first positive electrode active material ternary precursor, and a compound containing element M1, and sintering to obtain the first positive electrode active material;
  • Step B preparing a second positive electrode active material, which comprises:
  • Step B1 mixing a lithium salt, a ternary precursor of a second positive electrode active material, and a compound containing the element M2, and sintering them to obtain the second positive electrode active material;
  • Step C mixing the first positive electrode active material and the second positive electrode active material to obtain the positive electrode active material
  • the first positive electrode active material comprises a matrix of formula (I), and the matrix is doped with element M1:
  • the element M1 is selected from at least one of Ti, Zr, Al, Sb, W, Sr, Nb, Mo, Ca, K, Na, Mg, Si, Te, Cr, V, and Y;
  • the second positive electrode active material comprises a matrix of formula (II), wherein the matrix is doped with an element M2:
  • the average particle size Dv 50 of the first positive electrode active material is greater than the average particle size Dv 50 of the second positive electrode active material, and 0 ⁇ X2-X1 ⁇ 0.4, optionally 0 ⁇ X2-X1 ⁇ 0.1.
  • the method of the present application can be used to synthesize a positive electrode active material with a stable bulk structure, excellent material interface stability, and a relatively high capacity.
  • the sintering temperature is 700-950°C
  • the time is 10-20 hours
  • the atmosphere is air or O 2 .
  • the primary sintering process can sinter a first positive electrode active material with excellent crystal structure and can effectively perform uniform doping of element M1.
  • the sintering temperature is 750-1000°C
  • the time is 10-20 hours
  • the atmosphere is air or O 2 .
  • the primary sintering process can sinter a second positive electrode active material with excellent crystal structure and can effectively perform uniform doping of element M2.
  • step A further comprises:
  • Step A2 mixing the first positive electrode active material obtained in step A1 with a compound containing N1, and sintering them to form a coating layer containing the N1 element on the surface of the first positive electrode active material.
  • the sintering temperature is 250-700° C.
  • the sintering time is 5-15 hours
  • the atmosphere is air or O 2 .
  • part of the N1 element can effectively react with the impure lithium on the surface of the first positive electrode active material, thereby reducing the impurity lithium content on the surface of the material; it can also make the coating layer containing the N1 element firmly and evenly coat the surface of the first positive electrode active material, greatly reducing the side reaction between the first positive electrode active material and the electrolyte.
  • step B further comprises:
  • Step B2 mixing the second positive electrode active material obtained in the step B1 with a compound containing N2 and sintering them to form a coating layer containing N2 elements on the surface of the second positive electrode active material.
  • the sintering temperature is 250-700° C.
  • the sintering time is 5-15 hours
  • the atmosphere is air or O 2 .
  • part of the N2 element can effectively react with the impure lithium on the surface of the second positive electrode active material, thereby reducing the impurity lithium content on the surface of the material; it can also make the coating layer containing the N2 element firmly and evenly coat the surface of the second positive electrode active material, greatly reducing the side reaction between the second positive electrode active material and the electrolyte.
  • a third aspect of the present application provides a secondary battery, comprising the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared by the method of the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, comprising the secondary battery of the third aspect of the present application.
  • the electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.
  • FIG. 1 is a scanning electron microscope (SEM) image of the positive electrode active material prepared in Example 1-1 of the present application.
  • FIG. 2 is the first charge and discharge curve of the button battery made of the positive electrode active material prepared in Example 1-1 of the present application.
  • FIG3 is a 25° C. cycle comparison curve of a full battery made of the positive electrode active materials prepared in Example 1-1 of the present application and Comparative Example 2-1.
  • FIG. 4 is a comparison curve of 70° C. storage inflation of full batteries made of the positive electrode active materials prepared in Example 1-1 of the present application and Comparative Example 2-1.
  • FIG. 5 is a schematic diagram of a battery cell according to an embodiment of the present application.
  • FIG. 6 is an exploded view of the battery cell according to the embodiment of the present application shown in FIG. 5 .
  • FIG. 7 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 8 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 9 is an exploded view of the battery pack shown in FIG. 8 according to an embodiment of the present application.
  • FIG. 10 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • steps of the present application may be performed sequentially or randomly, preferably sequentially.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • Existing positive electrode active materials are usually a single secondary particle material (larger particle size) or a single primary particle material (smaller particle size), which makes the compaction density of the positive electrode plate low, so the volume energy density of the positive electrode plate needs to be further improved; in addition, the secondary large particle positive electrode active material has general cycle performance and poor storage and safety performance, while the primary particle single crystal positive electrode active material has low capacity and poor rate performance.
  • the present application provides a positive electrode active material with a particle grading, which can significantly increase the compaction density of the positive electrode sheet, thereby increasing its volume energy density, and can effectively improve the cycle and safety performance of the secondary battery.
  • the present application proposes a positive electrode active material, which comprises:
  • a first positive electrode active material comprising a matrix of formula (I) doped with an element M1:
  • element M1 is selected from at least one of Ti, Zr, Al, Sb, W, Sr, Nb, Mo, Ca, K, Na, Mg, Si, Te, Cr, V, and Y; and
  • the second positive electrode active material comprises a matrix of formula (II) doped with an element M2:
  • element M2 is selected from at least one of Ti, Zr, Al, Sb, W, Sr, Nb, Mo, Ca, K, Na, Mg, Si, Te, Cr, V, and Y;
  • the average particle size Dv 50 of the first positive electrode active material is greater than the average particle size Dv 50 of the second positive electrode active material, and 0 ⁇ X2-X1 ⁇ 0.4, optionally 0 ⁇ X2-X1 ⁇ 0.1.
  • the present application makes the positive electrode sheet containing the positive electrode active material have a high compaction density by matching the first positive electrode active material with a larger average particle size Dv 50 with the second positive electrode active material with a smaller average particle size Dv 50 , thereby significantly improving the volume energy density of the secondary battery.
  • the capacity of the positive electrode active material with a smaller average particle size Dv 50 will be significantly higher than the capacity of the positive electrode active material with a larger average particle size Dv 50 , but the cycle life and safety performance of the secondary battery containing the positive electrode active material with a smaller average particle size Dv 50 are worse than those of the secondary battery containing the positive electrode active material with a larger average particle size Dv 50.
  • the cycle performance and safety performance of the secondary battery can be improved.
  • Figure 1 shows a scanning electron microscope image of the positive electrode active material prepared in Example 1-1. As can be seen from Figure 1, the first positive electrode active material with a larger average particle size Dv50 and the second positive electrode active material with a smaller average particle size Dv50 are uniformly dispersed.
  • the first positive electrode active material has the formula:
  • the molecular formula of the second positive electrode active material is:
  • the energy density of the secondary battery can be further improved.
  • the weight ratio of the first positive electrode active material to the second positive electrode active material is 5:5 or more, and may be 6:4-9:1.
  • the compaction density of the positive electrode sheet can be further improved, thereby further improving the volume energy density of the secondary battery.
  • the first positive electrode active material is a secondary particle, and the volume particle size distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 ⁇ 0.5, optionally (Dv 90 -Dv 10 )/Dv 50 ⁇ 1.0.
  • the first positive electrode active material has an average particle size Dv 50 of 6-20 ⁇ m.
  • the first positive electrode active material When the average particle size Dv 50 and the volume particle size distribution diameter of the first positive electrode active material are within the given range, the first positive electrode active material has a higher gram capacity; and when combined with the second positive electrode active material, the compaction density of the positive electrode sheet can be further improved.
  • the second positive electrode active material is a secondary particle and/or a primary particle, optionally a primary particle, and a volume particle size distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 ⁇ 0.5, optionally (Dv 90 -Dv 10 )/Dv 50 ⁇ 1.0.
  • the average particle size Dv 50 of the second positive electrode active material is 2-5 ⁇ m.
  • the second positive electrode active material When the average particle size Dv 50 and the volume particle size distribution diameter of the second positive electrode active material are within the given range, the second positive electrode active material has a higher gram capacity and is conducive to sintering into primary particles, and has good cycle performance and safety performance; and when combined with the first positive electrode active material, it can further improve the compaction density of the positive electrode sheet.
  • Secondary particles have a meaning known in the art. Secondary particles refer to particles in an agglomerated state formed by the aggregation of two or more primary particles. Primary particles have a meaning known in the art. Primary particles refer to particles that have not formed an agglomerated state.
  • particle volume distribution particle size Dv 10 , Dv 50 , and Dv 90 are well-known concepts in the art.
  • Dv 10 is the particle size of the powder particles in the volume-based particle size distribution, starting from the small particle size side, reaching 10% of the cumulative volume, and the unit is usually ⁇ m.
  • Dv 50 is the particle size of the powder particles in the volume-based particle size distribution, starting from the small particle size side, reaching 50% of the cumulative volume.
  • Dv 90 is the particle size of the powder particles in the volume-based particle size distribution, starting from the small particle size side, reaching 90% of the cumulative volume.
  • the test method of particle volume distribution particle size Dv 10 , Dv 50 , and Dv 90 can be tested by methods well-known in the art. As an example, reference can be made to GB/T 19077-2016/ISO 13320:2009 particle size distribution laser diffraction method, and the device Malvern 3000 is used for measurement.
  • the doping amount of the element M1 is 500-7000 ppm, optionally 1000-5000 ppm, based on the total weight of the first positive electrode active material.
  • the bulk structural stability of the secondary particles can be further improved.
  • the amount of the element M2 is 500-7000 ppm, optionally 1000-5000 ppm, based on the total weight of the second positive electrode active material.
  • the bulk structural stability of the second positive electrode active material can be further improved.
  • the surface of the first positive electrode active material further has a coating layer, the coating layer contains an N1 element, and the N1 element is selected from at least one of Al, Co, Mn, B, La, Sr, P, F, Zr, Ti, and W.
  • Providing a coating layer containing the N1 element on the surface of the first positive electrode active material can further improve the interface stability of the secondary particles and reduce the side reaction between the secondary particles and the electrolyte.
  • the coating amount of the N1 element is 500-20000 ppm, optionally 1000-15000 ppm, based on the total weight of the first positive electrode active material.
  • the interface stability of the first positive electrode active material can be further improved without affecting other properties of the first positive electrode active material.
  • the surface of the second positive electrode active material further has a coating layer, the coating layer contains N2 element, and the N2 element is selected from at least one of Al, Co, Mn, B, La, Sr, P, F, Zr, Ti, and W.
  • Providing a coating layer containing N2 elements on the surface of the second positive electrode active material can further improve the interface stability of the second positive electrode active material and reduce the side reaction between the second positive electrode active material and the electrolyte.
  • the coating amount of the N2 element is 500-20000 ppm, optionally 1000-15000 ppm, based on the total weight of the second positive electrode active material.
  • the interface stability of the second positive electrode active material can be further improved without affecting other properties of the second positive electrode active material.
  • the present application proposes a method for preparing a positive electrode active material, which comprises the following steps:
  • Step A preparing a first positive electrode active material, which comprises:
  • Step A1 mixing a lithium salt, a first positive electrode active material ternary precursor, and a compound containing element M1, and sintering to obtain a first positive electrode active material;
  • Step B preparing a second positive electrode active material, which comprises:
  • Step B1 mixing a lithium salt, a ternary precursor of a second positive electrode active material, and a compound containing element M2, and sintering them to obtain a second positive electrode active material;
  • Step C mixing the first positive electrode active material and the second positive electrode active material to obtain a positive electrode active material
  • the first positive electrode active material comprises a matrix of formula (I), wherein the matrix is doped with element M1:
  • element M1 is selected from at least one of Ti, Zr, Al, Sb, W, Sr, Nb, Mo, Ca, K, Na, Mg, Si, Te, Cr, V, and Y;
  • the second positive electrode active material comprises a matrix of formula (II) doped with an element M2:
  • element M2 is selected from at least one of Ti, Zr, Al, Sb, W, Sr, Nb, Mo, Ca, K, Na, Mg, Si, Te, Cr, V, and Y;
  • the average particle size Dv 50 of the first positive electrode active material is greater than the average particle size Dv 50 of the second positive electrode active material, and 0 ⁇ X2-X1 ⁇ 0.4, optionally 0 ⁇ X2-X1 ⁇ 0.1.
  • the method of the present application can be used to synthesize a positive electrode active material with a stable bulk structure, excellent material interface stability, and a relatively high capacity.
  • the lithium salt is one or both of lithium carbonate and lithium hydroxide
  • the compound containing element M1 is one or more of sulfate, nitrate, acetate, carbonate, oxide, hydroxide, etc. of element M1.
  • step A1 the molar ratio of Li to the sum of nickel, cobalt and manganese is (0.9-1.2):1.
  • the sintering temperature is 700-950° C.
  • the sintering time is 10-20 h
  • the atmosphere is air or O 2 .
  • the first positive electrode active material with excellent crystal structure can be sintered, and the element M1 can be uniformly doped effectively.
  • the lithium salt is one or both of lithium carbonate and lithium hydroxide
  • the compound containing element M2 is one or more of sulfate, nitrate, acetate, carbonate, oxide, hydroxide, etc. of element M2.
  • step B1 the molar ratio of Li to the sum of nickel, cobalt and manganese is (0.9-1.2):1.
  • the sintering temperature is 750-1000° C.
  • the sintering time is 10-20 h
  • the atmosphere is air or O 2 .
  • a second positive electrode active material with excellent crystal structure can be sintered, and the element M2 can be uniformly doped effectively.
  • step A further comprises:
  • Step A2 The first positive electrode active material obtained in step A1 is mixed with a compound containing N1, and sintered to form a coating layer containing the N1 element on the surface of the first positive electrode active material.
  • the sintering temperature is 250-700° C.
  • the sintering time is 5-15 hours
  • the atmosphere is air or O 2 .
  • part of the N1 element can effectively react with the impure lithium on the surface of the first positive electrode active material to form a fast ion conductor material, thereby increasing the transmission speed of lithium ions and reducing the impurity lithium content on the surface of the material; it can also make the coating layer containing the N1 element firmly and evenly coat the surface of the first positive electrode active material, greatly reducing the side reaction between the first positive electrode active material and the electrolyte.
  • the compound containing N1 is one or more of sulfate, nitrate, acetate, carbonate, oxide, hydroxide, etc. of N1.
  • step B further comprises:
  • Step B2 The second positive electrode active material obtained in step B1 is mixed with a compound containing N2, and sintered to form a coating layer containing N2 elements on the surface of the second positive electrode active material.
  • the sintering temperature is 250-700° C.
  • the sintering time is 5-15 hours
  • the atmosphere is air or O 2 .
  • part of the N2 element can effectively react with the impure lithium on the surface of the second positive electrode active material to form a fast ion conductor material, thereby increasing the transmission speed of lithium ions and reducing the impurity lithium content on the surface of the material; it can also make the coating layer containing the N2 element firmly and evenly coat the surface of the second positive electrode active material, greatly reducing the side reaction between the second positive electrode active material and the electrolyte.
  • the N2-containing compound is one or more of N2 sulfate, nitrate, acetate, carbonate, oxide, hydroxide, etc.
  • steps A1, A2, B1 and B2 mixing is performed in a ploughshare mixer, a high speed mixer or a tilting mixer.
  • the secondary battery may be in the form of a battery cell, a battery module, or a battery pack.
  • a battery cell is provided.
  • a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may 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.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the compaction density of the positive electrode sheet is ⁇ 3.3 g/cc, and can be optionally ⁇ 3.4 g/cc.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may 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.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one 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).
  • the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a conductive agent which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the battery cell further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the battery cell may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG5 is a battery cell 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • battery cells may be assembled into a battery module.
  • the number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG7 is a battery module 4 as an example.
  • a plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG8 and FIG9 are battery packs 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, the electric device includes the secondary battery provided in the present application.
  • the secondary battery can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but are not limited thereto.
  • a secondary battery can be selected according to its usage requirements.
  • Fig. 10 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a battery cell may be used as a power source.
  • Step A Preparation of the first positive electrode active material
  • Step A1 lithium hydroxide, a first positive electrode active material ternary precursor [Ni 0.90 Co 0.05 Mn 0.05 ](OH) 2 , and ZrO 2 are mixed in a plowshare mixer, wherein the average particle size Dv 50 of the first positive electrode active material ternary precursor is 10 ⁇ m, the molar ratio of lithium to the sum of nickel, cobalt, and manganese is 1.01, and the Zr doping amount is 5000 ppm.
  • the mixed material is placed in a kiln for sintering at a sintering temperature of 700° C., a sintering time of 20 h, and an O 2 atmosphere to obtain a first positive electrode active material Li 1.01 [Ni 0.895 Co 0.050 Mn 0.050 Zr 0.005 ]O 2 ,
  • Step A2 mixing the first positive electrode active material with H 3 BO 3 in a plowshare mixer, wherein the coating amount of B is 1000 ppm, placing the mixed material in a kiln for sintering, the sintering temperature is 250° C., the sintering time is 15 h, the sintering atmosphere is O 2 , and a coating layer containing B is formed on the surface of the first positive electrode active material.
  • the average particle size Dv 50 of the first positive electrode active material having the coating layer is 10 ⁇ m, and the volume particle size distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 is 1.3;
  • Step B Preparation of the second positive electrode active material
  • Step B1 lithium hydroxide, a second positive electrode active material ternary precursor [Ni 0.92 Co 0.05 Mn 0.03 ](OH) 2 , and TiO 2 are mixed in a plowshare mixer, wherein the average particle size Dv 50 of the second positive electrode active material ternary precursor is 3 ⁇ m, the molar ratio of lithium to the sum of nickel, cobalt, and manganese is 1.01, and the Ti doping amount is 5000 ppm.
  • the mixed material is placed in a kiln for sintering at a sintering temperature of 750° C., a sintering time of 20 h, and an O 2 atmosphere to obtain a second positive electrode active material Li 1.01 [Ni 0.91 Co 0.05 Mn 0.03 Ti 0.01 ]O 2 ,
  • Step B2 Mix the second positive electrode active material with H 3 BO 3 in a plowshare mixer, wherein the coating amount of B is 1000ppm, put the mixed material into a kiln for sintering, the sintering temperature is 250°C, the sintering time is 15h, the sintering atmosphere is O 2 , and a coating layer containing B is formed on the surface of the second positive electrode active material; the average particle size Dv 50 of the second positive electrode active material with the coating layer is 3 ⁇ m, and the volume particle size distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 is 1.0;
  • Step C Mixing the first positive electrode active material having a coating layer and the second positive electrode active material having a coating layer in a ratio of 7:3 to obtain a positive electrode active material.
  • the preparation of the positive electrode active material is generally based on Example 1-1, except that:
  • the ternary precursors of the first positive electrode active material are [Ni 0.50 Co 0.30 Mn 0.20 ](OH) 2 and [Ni 0.80 Co 0.10 Mn 0.10 ](OH) 2 , respectively, so as to obtain the first positive electrode active material Li 1.01 [Ni 0.497 Co 0.298 Mn 0.200 Zr 0.005 ]O 2 and Li 1.01 [Ni 0.796 Co 0.0995 Mn 0.0995 Zr 0.005 ]O 2 , respectively;
  • step B1 the ternary precursors of the second positive electrode active material are [Ni 0.90 Co 0.05 Mn 0.05 ](OH) 2 , thereby obtaining the second positive electrode active material Li 1.01 [Ni 0.891 Co 0.0495 Mn 0.0495 Ti 0.01 ]O 2 .
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in step B1, the second positive electrode active material ternary precursor is [Ni 0.90 Co 0.05 Mn 0.05 ](OH) 2 , thereby obtaining the second positive electrode active material Li 1.01 [Ni 0.891 Co 0.0495 Mn 0.0495 Ti 0.01 ]O 2 .
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in step A1, the first positive electrode active material ternary precursor is [Ni 0.50 Co 0.30 Mn 0.20 ](OH) 2 , thereby obtaining the first positive electrode active material Li 1.01 [Ni 0.497 Co 0.298 Mn 0.200 Zr 0.005 ]O 2 .
  • the preparation of the positive electrode active material generally refers to Example 1-1, except that in step C, the mixing ratios of the first positive electrode active material with a coating layer and the second positive electrode active material with a coating layer are 5:5, 6:4, 9:1, 4:6 and 10:0, respectively.
  • the preparation of the positive electrode active material as a whole refers to Example 1-1, except that, in step A1, the average particle size Dv50 of the first positive electrode active material ternary precursor is 6 ⁇ m, 20 ⁇ m, 5 ⁇ m and 22 ⁇ m, respectively, thereby obtaining a first positive electrode active material with a coating layer having an average particle size Dv50 of 6 ⁇ m, 20 ⁇ m, 5 ⁇ m and 22 ⁇ m, respectively.
  • the preparation of the positive electrode active material as a whole refers to Example 1-1, except that, in step B1, the average particle size Dv50 of the second positive electrode active material ternary precursor is 2 ⁇ m, 5 ⁇ m, 1 ⁇ m and 6 ⁇ m, respectively, thereby obtaining a second positive electrode active material with a coating layer having an average particle size Dv50 of 2 ⁇ m, 5 ⁇ m, 1 ⁇ m and 6 ⁇ m, respectively.
  • the preparation of the positive electrode active material is generally referred to Example 1-1, except that, in step A1, the volume distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 of the first positive electrode active material precursor is adjusted to 0.5 and 0.4 respectively, and the average particle size Dv 50 remains unchanged, and in step A2, a first positive electrode active material having a coating layer is obtained, and its volume particle size distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 is 0.5 and 0.4 respectively.
  • the preparation of the positive electrode active material as a whole refers to Example 1-1, except that, in step B1, by adjusting the volume distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 of the second positive electrode active material precursor to 0.5 and 0.4 respectively, the average particle size Dv 50 remains unchanged, and in step B2, a second positive electrode active material having a coating layer is obtained, and its volume particle size distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 is 0.5 and 0.4 respectively.
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in step A1, the Zr doping amounts are 500 ppm, 1000 ppm, and 7000 ppm, respectively.
  • the preparation of the positive electrode active material generally refers to Example 1-1, except that in step A1, ZrO2 is replaced by WO3 , Nb2O5 , and a mixture of WO3 and ZrO2 (wherein the doping amounts of W and Zr are each 2500 ppm).
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in step B1, the Ti doping amounts are 500 ppm, 1000 ppm, and 7000 ppm, respectively.
  • the preparation of the positive electrode active material is generally based on Example 1-1, except that in step B1, TiO2 is replaced by WO3 , Nb2O5 , and a mixture of WO3 and ZrO2 (wherein the doping amounts of W and Zr are each 2500 ppm).
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in steps A2 and B2, H 3 BO 3 is replaced by Al 2 O 3 and Co(OH) 2 , respectively.
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in steps A2 and B2, the coating amounts of B are 500 ppm, 15000 ppm and 20000 ppm, respectively.
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in step A1, the sintering temperatures are 800° C. and 950° C., and the sintering times are 20 h and 10 h, respectively.
  • Example 6-3 to Example 6-4
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in step B1, the sintering temperatures are 900° C. and 1000° C., and the sintering times are 20 h and 10 h, respectively.
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in step A2, the sintering temperatures are 400° C. and 700° C., and the sintering times are 10 h and 5 h, respectively.
  • the preparation of the positive electrode active material is generally similar to that of Example 1-1, except that in step B2, the sintering temperatures are 400° C. and 700° C., and the sintering times are 10 h and 5 h, respectively.
  • the test method for volume distribution particle size is: refer to GB/T 19077-2016/ISO 13320:2009 particle size distribution laser diffraction method, and the equipment is Malvern 3000. Take a clean beaker, add the sample to be tested to a light shielding degree of 8%-12%, add 20ml of deionized water, and simultaneously perform external ultrasound for 5 minutes, and turn on the particle size tester to start the test.
  • the positive electrode active material, PVDF and conductive carbon are added to a certain amount of NMP in a ratio of 90:5:5, stirred in a drying room to form a slurry, coated on an aluminum foil, dried and cold pressed to form a positive electrode sheet, a lithium sheet is used as the negative electrode, the electrolyte is 1 mol/L LiPF 6 /(EC+DEC+DMC) (volume ratio of 1:1:1), and assembled into a button battery in a button box.
  • the positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone solvent system at a weight ratio of 96:2:2, and then coated on aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.
  • the negative electrode active material artificial graphite, hard carbon, conductive agent acetylene black, binder styrene butadiene rubber (SBR), and thickener sodium carbon methyl cellulose (CMC) are fully stirred and mixed in a deionized water solvent system at a weight ratio of 90:5:2:2:1, and then coated on copper foil, dried, and cold pressed to obtain a negative electrode sheet.
  • a PE porous polymer film is used as a separator.
  • the positive electrode sheet, separator, and negative electrode sheet are stacked in order so that the separator is in the middle of the positive and negative electrodes to play an isolating role, and wound to obtain a bare battery.
  • the bare battery is placed in an outer package, injected with a prepared basic electrolyte, i.e., 1 mol/L LiPF 6 /(EC+EMC+DMC) (volume ratio of 1:1:1), and encapsulated to obtain a full battery.
  • SP conductive agent acetylene black
  • PVDF
  • M is the mass of the small disc with a diameter of 40 mm cut from the positive electrode sheet, which is averaged by 10 weighings
  • d is the thickness of the positive electrode sheet, which is averaged by 10 thickness measurements
  • A is the area of the small disc with a diameter of 40 mm.
  • L1 is the distance between the marks before cold pressing, which is 1000mm
  • L2 is the distance between the marks after cold pressing.
  • the marks are formed in the following way: in the central area of the pole piece, three 1000mm long line segments extending in the length direction of the pole piece are taken at different positions in the width direction of the pole piece, and the two end points of the line segments are marked.
  • L2 is recorded as the average value of the measured value of the distance between the two end points of each line segment after cold pressing.
  • the compaction density value at 0.7% electrode extension is taken as the compaction density of the positive electrode in this application.
  • Example 1-1 and Examples 3-5 to 3-8 when the average particle size Dv 50 of the second positive electrode active material is in the range of 2-5 ⁇ m, the secondary batteries all have good comprehensive performance; when the average particle size Dv 50 of the second positive electrode active material is less than 2 ⁇ m, the compaction density of the positive electrode sheet will be significantly reduced, and the cycle and storage gas production performance of the secondary battery will also be significantly reduced, as shown in Example 3-7; when the average particle size Dv 50 of the second positive electrode active material is greater than 5 ⁇ m, the capacity of the secondary battery will be reduced, and the cycle and storage gas production performance will also be reduced, as shown in Example 3-8.
  • Example 1-1 Comparing Example 1-1 with Examples 3-9 to 3-12, when the particle volume distribution diameter distance (Dv 90 -Dv 10 )/Dv 50 of the first positive electrode active material or the second positive electrode active material is greater than or equal to 0.5, the comprehensive performance of the secondary battery is good. When (Dv 90 -Dv 10 )/Dv 50 is less than 0.5, the compaction density of the positive electrode sheet will be significantly reduced.
  • Example 1-1 and Examples 4-1 to 4-6 when the first positive electrode active material is doped with element M1 and the doping amount of element M1 is 500-7000ppm, the comprehensive performance of the secondary battery is good; when the doping amount of element M1 is 1000-5000ppm, the gram capacity or cycle performance and/or 70°C@40 days flatulence of the secondary battery are further improved.
  • Example 1-1 and Examples 4-7 to 4-12 when the second positive electrode active material is doped with element M2 and the doping amount of element M2 is in the range of 500-7000ppm, the secondary batteries have good comprehensive performance; when the doping amount of element M2 is 1000-5000ppm, the gram capacity or cycle performance and/or 70°C@40 days flatulence of the secondary battery are further improved.

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Abstract

本申请涉及一种正极活性材料，其包含第一正极活性材料，其包含式(I)的基体，所述基体掺杂有元素M1：LiA1[NiX1CoY1MnZ1]O2(I)；和第二正极活性材料，其包含式(II)的基体，所述基体掺杂有元素M2：LiA2[NiX2CoY2MnZ2]O2(II)；其中，所述第一正极活性材料的平均粒径Dv50大于所述第二正极活性材料的平均粒径Dv50，并且0<X2-X1≤0.4，可选地0<X2-X1≤0.1。本申请还涉及一种制备正极活性材料的方法、二次电池和用电装置。

Description

正极活性材料及其制备方法、二次电池和用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种正极活性材料及其制备方法、二次电池和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。另外，由于正极活性材料的选择越发局限，高镍正极活性材料被认为是满足高能量密度要求的最佳选择。
但是随着镍含量的不断提高，其结构稳定性越来越差。通过包覆或掺杂等手段来改善材料的倍率性能和循环性能等是目前比较有效的手段，然而现有的方法均会导致对二次电池性能不同程度的破坏，例如，二次电池的克容量降低、循环性能变差等。因此，现有的包覆或掺杂的正极材料仍有待改进。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种正极活性材料，使得包含其的二次电池具有高的体积能量密度以及良好的循环性能和安全性能。
为了达到上述目的，本申请提供了一种正极活性材料及其制备方法、二次电池和用电装置。
本申请的第一方面提供了一种正极活性材料，其包含：
第一正极活性材料，其包含式(I)的基体，所述基体掺杂有元素 M1：
Li A1[Ni X1Co Y1Mn Z1]O 2    (I)，
在式(I)中，0.5≤X1<1、0≤Y1<0.5、0≤Z1<0.5、0.9<A1<1.2，X1+Y1+Z1＝1，所述元素M1选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；和
第二正极活性材料，其包含式(II)的基体，所述基体掺杂有元素M2：
Li A2[Ni X2Co Y2Mn Z2]O 2      (II)，
在式(II)中，0.5≤X2<1、0≤Y2<0.5、0≤Z2<0.5、0.9<A2<1.2，X2+Y2+Z2＝1，所述元素M2选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
其中，所述第一正极活性材料的平均粒径Dv 50大于所述第二正极活性材料的平均粒径Dv 50，并且0<X2-X1≤0.4，可选地0<X2-X1≤0.1。
由此，本申请通过将平均粒径Dv 50较大的第一正极活性材料搭配平均粒径Dv 50较小的第二正极活性材料，使得包含正极活性材料的正极极片具有高的压实密度，从而明显提升二次电池的体积能量密度；此外，当第二正极活性材料基体的Ni含量高于第一正极活性材料基体的Ni含量且当两者Ni含量差值在所述范围内时，在保证二次电池容量的同时，能够改善二次电池的循环性能和安全性能。
在任意实施方式中，0.9≤X2<1。当0.9≤X2<1时，能够进一步改善二次电池的能量密度。
在任意实施方式中，所述第一正极活性材料与所述第二正极活性材料的重量比为5:5以上，可选为6:4-9:1。当第一正极活性材料与第二正极活性材料的重量比在所给范围内时，能够进一步提高正极极片的压实密度，从而进一步提高二次电池的体积能量密度。
在任意实施方式中，所述第一正极活性材料为二次颗粒，体积粒度分布径距(Dv 90-Dv 10)/Dv 50≥0.5，可选地(Dv 90-Dv 10)/Dv 50≥1.0。
在任意实施方式中，所述第一正极活性材料的平均粒径Dv 50为6-20μm。
当第一正极活性材料的平均粒径Dv 50和体积粒度分布径距在所给范围内，第一正极活性材料具有较高的克容量；并且当与第二正极活性材料搭配时，能够进一步提高正极极片的压实密度。
在任意实施方式中，所述第二正极活性材料为二次颗粒和/或一次颗粒，可选地为一次颗粒，体积粒度分布径距(Dv 90-Dv 10)/Dv 50≥0.5，可选地(Dv 90-Dv 10)/Dv 50≥1.0。
在任意实施方式中，所述第二正极活性材料的平均粒径Dv 50为2-5μm。
当第二正极活性材料的平均粒径Dv 50和体积粒度分布径距在所给范围内，第二正极活性材料具有较高的克容量，并有利于烧结成一次颗粒，具有良好的循环性能和安全性能；并且当与第一正极活性材料搭配时，能够进一步提高正极极片的压实密度。
在任意实施方式中，在所述第一正极活性材料中，所述元素M1的掺杂量为500-7000ppm，可选为1000-5000ppm，基于所述第一正极活性材料的总重量计。当对第一正极活性材料掺杂元素M1并当元素M1的掺杂量在所给范围内时，能够进一步改善二次颗粒的体相结构稳定性。
在任意实施方式中，在所述第二正极活性材料中，所述元素M2的掺杂量为500-7000ppm，可选为1000-5000ppm，基于所述第二正极活性材料的总重量计。当对第二正极活性材料掺杂元素M2并当元素M2的掺杂量在所给范围内时，能够进一步改善第二正极活性材料的体相结构稳定性。
在任意实施方式中，所述第一正极活性材料的表面还具有包覆层，所述包覆层含有N1元素，所述N1元素选自Al、Co、Mn、B、La、Sr、P、F、Zr、Ti、W中的至少一种。在第一正极活性材料的表面设置含N1元素的包覆层，能够进一步改善二次颗粒的界面稳定性，降低其与电解液之间的副反应。
在任意实施方式中，所述N1元素的包覆量为500-20000ppm，可选为1000-15000ppm，基于所述第一正极活性材料的总重量计。当 N1元素的包覆量在所给范围内时，在不影响第一正极活性材料其他性能的同时，能够进一步改善其界面稳定性。
在任意实施方式中，所述第二正极活性材料的表面还具有包覆层，所述包覆层包含N2元素，所述N2元素选自Al、Co、Mn、B、La、Sr、P、F、Zr、Ti、W中的至少一种。在第二正极活性材料的表面设置含N2元素的包覆层，能够进一步改善第二正极活性材料的界面稳定性，降低其与电解液之间的副反应。
在任意实施方式中，所述N2元素的包覆量为500-20000ppm，可选为1000-15000ppm，基于所述第二正极活性材料的总重量计。当N2元素的包覆量在所给范围内时，在不影响第二正极活性材料其他性能的同时，能够进一步改善其界面稳定性。
本申请的第二方面还提供一种制备正极活性材料的方法，其包括以下步骤：
步骤A：制备第一正极活性材料，其包括：
步骤A1：将锂盐、第一正极活性材料三元前驱体、含元素M1的化合物混合，烧结，得到所述第一正极活性材料；
步骤B：制备第二正极活性材料，其包括：
步骤B1：将锂盐、第二正极活性材料三元前驱体、含元素M2的化合物混合，烧结，得到所述第二正极活性材料；
步骤C：将所述第一正极活性材料和所述第二正极活性材料混合，得到所述正极活性材料；
其中，所述第一正极活性材料包含式(I)的基体，所述基体掺杂有元素M1：
Li A1[Ni X1Co Y1Mn Z1]O 2      (I)，
在式(I)中，0.5≤X1<1、0≤Y1<0.5、0≤Z1<0.5、0.9<A1<1.2，X1+Y1+Z1＝1，所述元素M1选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
所述第二正极活性材料包含式(II)的基体，所述基体掺杂有元素M2：
Li A2[Ni X2Co Y2Mn Z2]O 2     (II)，
在式(II)中，0.5≤X2<1、0≤Y2<0.5、0≤Z2<0.5、0.9<A2<1.2，X2+Y2+Z2＝1，所述元素M2选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
所述第一正极活性材料的平均粒径Dv 50大于所述第二正极活性材料的平均粒径Dv 50，并且0<X2-X1≤0.4，可选地0<X2-X1≤0.1。
由此，采用本申请的方法可以合成体相结构稳定、材料界面稳定性优良、并具有较高的容量的正极活性材料。
在任意实施方式中，在所述步骤A1中，所述烧结的温度为700-950℃，时间为10-20h，气氛为空气或者O 2。采用该初烧烧结工艺，能够烧结出晶体结构优良的第一正极活性材料，并能够有效地进行元素M1的均匀掺杂。
在任意实施方式中，在所述步骤B1中，所述烧结的温度为750-1000℃，时间为10-20h，气氛为空气或者O 2。采用该初烧烧结工艺，能够烧结出晶体结构优良的第二正极活性材料，并能够有效地进行元素M2的均匀掺杂。
在任意实施方式中，所述步骤A还包括：
步骤A2：将由所述步骤A1得到的所述第一正极活性材料与含N1的化合物混合、烧结，以在所述第一正极活性材料的表面上形成包含N1元素的包覆层。
在任意实施方式中，在所述步骤A2中，所述烧结的温度为250-700℃，时间为5-15h，气氛为空气或者O 2。
采用该包覆烧结工艺，能有效地使部分N1元素与第一正极活性材料表面的杂质锂发生反应，降低材料表面的杂质锂含量；还能使含N1元素的包覆层牢固均匀地包覆在第一正极活性材料表面，大幅度降低第一正极活性材料与电解液之间的副反应。
在任意实施方式中，所述步骤B还包括：
步骤B2：将由所述步骤B1得到的所述第二正极活性材料与含N2的化合物混合、烧结，以在所述第二正极活性材料的表面上形成 包含N2元素的包覆层。
在任意实施方式中，在所述步骤B2中，所述烧结的温度为250-700℃，时间为5-15h，气氛为空气或者O 2。
采用该包覆烧结工艺，能有效地使部分N2元素与第二正极活性材料表面的杂质锂发生反应，降低材料表面的杂质锂含量；还能使含N2元素的包覆层牢固均匀地包覆在第二正极活性材料表面，大幅度降低第二正极活性材料与电解液之间的副反应。
本申请的第三方面提供一种二次电池，包括本申请第一方面的正极活性材料或通过本申请第二方面的方法制备的正极活性材料。
本申请的第四方面提供一种用电装置，包括本申请第三方面的二次电池。
本申请的用电装置包括本申请提供的二次电池，因此至少具有与所述二次电池相同的优势。
附图说明
图1为本申请实施例1-1制备得到的正极活性材料的扫描电子显微镜(SEM)图。
图2为本申请实施例1-1制备得到的正极活性材料制作成的扣电的首次充放电曲线。
图3为本申请实施例1-1与对比例2-1制备得到的正极活性材料制作成的全电池的25℃循环对比曲线。
图4为本申请实施例1-1与对比例2-1制备得到的正极活性材料制作成的全电池的70℃存储胀气对比曲线。
图5是本申请一实施方式的电池单体的示意图。
图6是图5所示的本申请一实施方式的电池单体的分解图。
图7是本申请一实施方式的电池模块的示意图。
图8是本申请一实施方式的电池包的示意图。
图9是图8所示的本申请一实施方式的电池包的分解图。
图10是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5电池单体；51壳体；52电极组件；53顶盖组件
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的正极活性材料及其制备方法、二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出了最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以 随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
现有的正极活性材料通常为单一的二次颗粒材料(粒径较大)或单一的一次颗粒材料(粒径较小)，使得正极极片的压实密度低，因此正极极片的体积能量密度需进一步提升；此外，二次颗粒大颗粒正极活性材料循环性能一般、存储及安全性能较差，而一次颗粒单晶正极活性材料的容量低，倍率性能较差。
本申请提供了一种颗粒级配的正极活性材料，其可以明显提升正极极片的压实密度，从而提升其体积能量密度，并且能够有效改善二次电池的循环及安全性能。
[正极活性材料]
本申请的一个实施方式中，本申请提出了一种正极活性材料，其包含：
第一正极活性材料，其包含式(I)的基体，所述基体掺杂有元素M1：
Li A1[Ni X1Co Y1Mn Z1]O 2，     (I)，
在式(I)中，0.5≤X1<1、0≤Y1<0.5、0≤Z1<0.5、0.9<A1<1.2，X1+Y1+Z1＝1，元素M1选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、 Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；和
第二正极活性材料，其包含式(II)的基体，所述基体掺杂有元素M2：
Li A2[Ni X2Co Y2Mn Z2]O 2，      (II)，
在式(II)中，0.5≤X2<1、0≤Y2<0.5、0≤Z2<0.5、0.9<A2<1.2，X2+Y2+Z2＝1，元素M2选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
其中，第一正极活性材料的平均粒径Dv 50大于第二正极活性材料的平均粒径Dv 50，并且0<X2-X1≤0.4，可选地0<X2-X1≤0.1。
虽然机理尚不明确，但本申请人意外地发现：本申请通过将平均粒径Dv 50较大的第一正极活性材料搭配平均粒径Dv 50较小的第二正极活性材料，使得包含正极活性材料的正极极片具有高的压实密度，从而明显提升二次电池的体积能量密度。此外，在同等Ni含量以及同为一次颗粒或者二次颗粒的情况下，平均粒径Dv 50较小的正极活性材料的容量会明显高于平均粒径Dv 50较大的正极活性材料的容量，但包含平均粒径Dv 50较小的正极活性材料的二次电池的循环寿命及安全性能差于包含平均粒径Dv 50较大的正极活性材料的二次电池，因此，当平均粒径Dv 50较小的第二正极活性材料的Ni含量高于平均粒径Dv 50较大的第一正极活性材料的Ni含量且当两者Ni含量差值在所述范围内时，在保证二次电池容量的同时，能够改善二次电池的循环性能和安全性能。
图1示出了实施例1-1制得的正极活性材料的扫描电子显微镜图。从图1可以看出，平均粒径Dv 50较大的第一正极活性材料和平均粒径Dv 50较小的第二正极活性材料均匀分散。
在一些实施方式中，第一正极活性材料的分子式为：
Li a1[Ni x1Co y1Mn z1M1 b1]O 2     (I’)，
在式(I)中，0.5≤x1<1、0≤y1<0.5、0≤z1<0.5、0.9<a1<1.2、0<b1<0.2，x1+y1+z1+b1＝1；
第二正极活性材料的分子式为：
Li a2[Ni x2Co y2Mn z2M2 b2]O 2     (II’)，
在式(II)中，0.5≤x2<1、0≤y2<0.5、0≤z2<0.5、0.9<a2<1.2、0<b2<0.2，x2+y2+z2+b2＝1。
在一些实施方式中，0.9≤X2<1。
当0.9≤X2<1时，能够进一步改善二次电池的能量密度。
在一些实施方式中，第一正极活性材料与第二正极活性材料的重量比为5:5以上，可选为6:4-9:1。
当第一正极活性材料与第二正极活性材料的重量比在所给范围内时，能够进一步提高正极极片的压实密度，从而进一步提高二次电池的体积能量密度。
在一些实施方式中，第一正极活性材料为二次颗粒，体积粒度分布径距(Dv 90-Dv 10)/Dv 50≥0.5，可选地(Dv 90-Dv 10)/Dv 50≥1.0。
在一些实施方式中，第一正极活性材料的平均粒径Dv 50为6-20μm。
当第一正极活性材料的平均粒径Dv 50和体积粒度分布径距在所给范围内，第一正极活性材料具有较高的克容量；并且当与第二正极活性材料搭配时，能够进一步提高正极极片的压实密度。
在一些实施方式中，第二正极活性材料为二次颗粒和/或一次颗粒，可选地为一次颗粒，体积粒度分布径距(Dv 90-Dv 10)/Dv 50≥0.5，可选地(Dv 90-Dv 10)/Dv 50≥1.0。
在一些实施方式中，第二正极活性材料的平均粒径Dv 50为2-5μm。
当第二正极活性材料的平均粒径Dv 50和体积粒度分布径距在所给范围内，第二正极活性材料具有较高的克容量，并有利于烧结成一次颗粒，具有良好的循环性能和安全性能；并且当与第一正极活性材料搭配时，能够进一步提高正极极片的压实密度。
需要说明的是，二次颗粒具有本领域公知的含义。二次颗粒是指由两个或两个以上一次颗粒聚集而成的团聚态的颗粒。一次颗粒具有本领域公知的含义。一次颗粒是指没有形成团聚状态的颗粒。
本申请中，颗粒体积分布粒度Dv 10、Dv 50、Dv 90为本领域的公知 概念。具体地，Dv 10为粉体颗粒以体积为基准的粒度分布中，从小粒径侧起、达到体积累计10％的粒径，单位通常为μm。Dv 50为粉体颗粒以体积为基准的粒度分布中，从小粒径侧起、达到体积累计50％的粒径。Dv 90为粉体颗粒以体积为基准的粒度分布中，从小粒径侧起、达到体积累计90％的粒径。颗粒体积分布粒度Dv 10、Dv 50、Dv 90的测试方法可以采用本领域公知的方法进行测试。作为示例，可以参考GB/T 19077-2016/ISO 13320:2009粒度分布激光衍射法，采用设备马尔文3000进行测定。
在一些实施方式中，在第一正极活性材料中，元素M1的掺杂量为500-7000ppm，可选为1000-5000ppm，基于第一正极活性材料的总重量计。
当对第一正极活性材料掺杂元素M1并当元素M1的掺杂量在所给范围内时，能够进一步改善二次颗粒的体相结构稳定性。
在一些实施方式中，在第二正极活性材料中，元素M2的量为500-7000ppm，可选为1000-5000ppm，基于第二正极活性材料的总重量计。
当对第二正极活性材料掺杂元素M2并当元素M2的掺杂量在所给范围内时，能够进一步改善第二正极活性材料的体相结构稳定性。
在一些实施方式中，第一正极活性材料的表面还具有包覆层，包覆层含有N1元素，N1元素选自Al、Co、Mn、B、La、Sr、P、F、Zr、Ti、W中的至少一种。
在第一正极活性材料的表面设置含N1元素的包覆层，能够进一步改善二次颗粒的界面稳定性，降低其与电解液之间的副反应。
在一些实施方式中，N1元素的包覆量为500-20000ppm，可选为1000-15000ppm，基于第一正极活性材料的总重量计。
当N1元素的包覆量在所给范围内时，在不影响第一正极活性材料其他性能的同时，能够进一步改善其界面稳定性。
在一些实施方式中，第二正极活性材料的表面还具有包覆层，包覆层包含N2元素，N2元素选自Al、Co、Mn、B、La、Sr、P、F、 Zr、Ti、W中的至少一种。
在第二正极活性材料的表面设置含N2元素的包覆层，能够进一步改善第二正极活性材料的界面稳定性，降低其与电解液之间的副反应。
在一些实施方式中，N2元素的包覆量为500-20000ppm，可选为1000-15000ppm，基于第二正极活性材料的总重量计。
当N2元素的包覆量在所给范围内时，在不影响第二正极活性材料其他性能的同时，能够进一步改善其界面稳定性。
本申请的一个实施方式中，本申请提出了一种制备正极活性材料的方法，其包括以下步骤：
步骤A：制备第一正极活性材料，其包括：
步骤A1：将锂盐、第一正极活性材料三元前驱体、含元素M1的化合物混合，烧结，得到第一正极活性材料；
步骤B：制备第二正极活性材料，其包括：
步骤B1：将锂盐、第二正极活性材料三元前驱体、含元素M2的化合物混合，烧结，得到第二正极活性材料；
步骤C：将第一正极活性材料和第二正极活性材料混合，得到正极活性材料；
其中，第一正极活性材料包含式(I)的基体，所述基体掺杂有元素M1：
Li A1[Ni X1Co Y1Mn Z1]O 2     (I)，
在式(I)中，0.5≤X1<1、0≤Y1<0.5、0≤Z1<0.5、0.9<A1<1.2，X1+Y1+Z1＝1，元素M1选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
第二正极活性材料包含式(II)的基体，所述基体掺杂有元素M2：
Li A2[Ni X2Co Y2Mn Z2]O 2      (II)，
在式(II)中，0.5≤X2<1、0≤Y2<0.5、0≤Z2<0.5、0.9<A2<1.2，X2+Y2+Z2＝1，元素M2选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
第一正极活性材料的平均粒径Dv 50大于第二正极活性材料的平均粒径Dv 50，并且0<X2-X1≤0.4，可选地0<X2-X1≤0.1。
由此，采用本申请的方法可以合成体相结构稳定、材料界面稳定性优良、并具有较高的容量的正极活性材料。
在一些实施方式中，在步骤A1中，锂盐为碳酸锂和氢氧化锂中的一种或两种；第一正极活性材料三元前驱体为[Ni X1’Co Y1’Mn Z1’](OH) 2，其中0.5≤X1’<1、0≤Y1’<0.5、0≤Z1’<0.5，X1’+Y1’+Z1’＝1；含元素M1的化合物为元素M1的硫酸盐、硝酸盐、乙酸盐、碳酸盐、氧化物、氢氧化物等中的一种或多种。
在一些实施方式中，在步骤A1中，Li与镍、钴和锰总和的摩尔比为(0.9-1.2):1。
在一些实施方式中，在步骤A1中，烧结的温度为700-950℃，时间为10-20h，气氛为空气或者O 2。
采用该初烧烧结工艺，能够烧结出晶体结构优良的第一正极活性材料，并能够有效地进行元素M1的均匀掺杂。
在一些实施方式中，在步骤B1中，锂盐为碳酸锂和氢氧化锂中的一种或两种；第二正极活性材料三元前驱体为[Ni X2’Co Y2’Mn Z2’](OH) 2，其中0.5≤X2’<1、0≤Y2’<0.5、0≤Z2’<0.5，X2’+Y2’+Z2’＝1；含元素M2的化合物为元素M2的硫酸盐、硝酸盐、乙酸盐、碳酸盐、氧化物、氢氧化物等中的一种或多种。
在一些实施方式中，在步骤B1中，Li与镍、钴和锰总和的摩尔比为(0.9-1.2):1。
在一些实施方式中，在步骤B1中，烧结的温度为750-1000℃，时间为10-20h，气氛为空气或者O 2。
采用该初烧烧结工艺，能烧结出晶体结构优良的第二正极活性材料，并能够有效地进行元素M2的均匀掺杂。
在一些实施方式中，步骤A还包括：
步骤A2：将由步骤A1得到的第一正极活性材料与含N1的化合物混合、烧结，以在第一正极活性材料的表面上形成包含N1元素的 包覆层。
在一些实施方式中，在步骤A2中，烧结的温度为250-700℃，时间为5-15h，气氛为空气或者O 2。
采用该包覆烧结工艺，能有效地使部分N1元素与第一正极活性材料表面的杂质锂发生反应，形成快离子导体材料，提升锂离子的传输速度，降低材料表面的杂质锂含量；还能使含N1元素的包覆层牢固均匀地包覆在第一正极活性材料表面，大幅度降低第一正极活性材料与电解液之间的副反应。
在一些实施方式中，在步骤A2中，含N1的化合物为N1的硫酸盐、硝酸盐、乙酸盐、碳酸盐、氧化物、氢氧化物等中的一种或多种。
在一些实施方式中，步骤B还包括：
步骤B2：将由步骤B1得到的第二正极活性材料与含N2的化合物混合、烧结，以在第二正极活性材料的表面上形成包含N2元素的包覆层。
在一些实施方式中，在步骤B2中，烧结的温度为250-700℃，时间为5-15h，气氛为空气或者O 2。
采用该包覆烧结工艺，能有效地使部分N2元素与第二正极活性材料表面的杂质锂发生反应，形成快离子导体材料，提升锂离子的传输速度，降低材料表面的杂质锂含量；还能使含N2元素的包覆层牢固均匀地包覆在第二正极活性材料表面，大幅度降低第二正极活性材料与电解液之间的副反应。
在一些实施方式中，在步骤B2中，含N2的化合物为N2的硫酸盐、硝酸盐、乙酸盐、碳酸盐、氧化物、氢氧化物等中的一种或多种。
在一些实施方式中，在步骤A1、A2、B1和B2中，混合在犁刀混合机、高混机或斜式混料机中进行。
另外，以下适当参照附图对本申请的二次电池和用电装置进行说明。二次电池可以包括电池单体的形式，可以包括电池模块的形式，可以包括电池包的形式。
本申请的一个实施方式中，提供一种电池单体。
通常情况下，电池单体包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意 其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
在一些实施方式中，当正极极片延展为0.7％时，正极极片压实密度≥3.3g/cc，可选为≥3.4g/cc。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，电池单体中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，电池单体可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，电池单体的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。电池单体的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对电池单体的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图5是作为一个示例的方形结构的电池单体5。
在一些实施方式中，参照图6，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。电池单体5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，电池单体可以组装成电池模块，电池模块所含电池单体的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图7是作为一个示例的电池模块4。参照图7，在电池模块4中， 多个电池单体5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电池单体5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个电池单体5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图8和图9是作为一个示例的电池包1。参照图8和图9，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池。所述二次电池可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池。
图10是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用电池单体作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅 用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1-1
步骤A：制备第一正极活性材料
步骤A1：将氢氧化锂、第一正极活性材料三元前驱体[Ni 0.90Co 0.05Mn 0.05](OH) 2、ZrO 2在犁刀混合机中混合，其中第一正极活性材料三元前驱体的平均粒径Dv 50为10μm，锂与镍钴锰之和的摩尔比为1.01，Zr掺杂量为5000ppm，混合物料放入窑炉中进行烧结，烧结温度为700℃，烧结时间为20h，烧结气氛为O 2，得到第一正极活性材料Li 1.01[Ni 0.895Co 0.050Mn 0.050Zr 0.005]O 2，
步骤A2：将第一正极活性材料与H 3BO 3在犁刀混合机中混合，其中B的包覆量为1000ppm，混合物料放入窑炉中进行烧结，烧结温度为250℃，烧结时间为15h，烧结气氛为O 2，在第一正极活性材料的表面上形成含B的包覆层，具有包覆层的第一正极活性材料的平均粒径Dv 50为10μm，体积粒度分布径距(Dv 90-Dv 10)/Dv 50为1.3；
步骤B：制备第二正极活性材料
步骤B1：将氢氧化锂、第二正极活性材料三元前驱体[Ni 0.92Co 0.05Mn 0.03](OH) 2、TiO 2在犁刀混合机中混合，其中第二正极活性材料三元前驱体的平均粒径Dv 50为3μm，锂与镍钴锰之和的摩尔比为1.01，Ti掺杂量为5000ppm，混合物料放入窑炉中进行烧结，烧结温度为750℃，烧结时间为20h，烧结气氛为O 2，得到第二正极活性材料Li 1.01[Ni 0.91Co 0.05Mn 0.03Ti 0.01]O 2，
步骤B2：将第二正极活性材料与H 3BO 3在犁刀混合机中混合，其中B的包覆量为1000ppm，混合物料放入窑炉中进行烧结，烧结温度为250℃，烧结时间为15h，烧结气氛为O 2，在第二正极活性材料的表面上形成含B的包覆层；具有包覆层的第二正极活性材料的平均粒径Dv 50为3μm，体积粒度分布径距(Dv 90-Dv 10)/Dv 50为1.0；
步骤C：将具有包覆层的第一正极活性材料和具有包覆层的第二正极活性材料按照7:3的比例混合，得到正极活性材料。
实施例1-2至实施例1-3
正极活性材料的制备整体上参照实施例1-1，区别在于，
在步骤A1中，第一正极活性材料三元前驱体分别为[Ni 0.50Co 0.30Mn 0.20](OH) 2、[Ni 0.80Co 0.10Mn 0.10](OH) 2，从而分别得到第一正极活性材料Li 1.01[Ni 0.497Co 0.298Mn 0.200Zr 0.005]O 2和Li 1.01[Ni 0.796Co 0.0995Mn 0.0995Zr 0.005]O 2；
在步骤B1中，第二正极活性材料三元前驱体分别为[Ni 0.90Co 0.05Mn 0.05](OH) 2，从而分别得到第二正极活性材料Li 1.01[Ni 0.891Co 0.0495Mn 0.0495Ti 0.01]O 2。
对比例1-1
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤B1中，第二正极活性材料三元前驱体为[Ni 0.90Co 0.05Mn 0.05](OH) 2，从而得到第二正极活性材料Li 1.01[Ni 0.891Co 0.0495Mn 0.0495Ti 0.01]O 2。
对比例1-2
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A1中，第一正极活性材料三元前驱体为[Ni 0.50Co 0.30Mn 0.20](OH) 2，从而得到第一正极活性材料Li 1.01[Ni 0.497Co 0.298Mn 0.200Zr 0.005]O 2。
实施例2-1至实施例2-4和对比例2-1
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤C中，具有包覆层的第一正极活性材料和具有包覆层的第二正极活性材料的混合比例分别为5:5、6:4、9:1、4:6和10:0。
实施例3-1至实施例3-4
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A1中，第一正极活性材料三元前驱体的平均粒径Dv 50分别为6μm、20μm、5μm和22μm，从而得到平均粒径Dv 50分别为6μm、20μm、5μm和22μm的具有包覆层的第一正极活性材料。
实施例3-5至实施例3-8
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤B1中，第二正极活性材料三元前驱体的平均粒径Dv 50分别为2μm、5μm、1μm和6μm，从而得到平均粒径Dv 50分别为2μm、5μm、1μm和6μm的具有包覆层的第二正极活性材料。
实施例3-9至实施例3-10
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A1中，通过调整第一正极活性材料前驱体的体积分布径距(Dv 90-Dv 10)/Dv 50分别0.5和0.4，平均粒径Dv 50保持不变，在步骤A2中得到具有包覆层的第一正极活性材料，其体积粒度分布径距(Dv 90-Dv 10)/Dv 50分别为0.5和0.4。
实施例3-11至实施例3-12
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤B1中，通过调整第二正极活性材料前驱体的体积分布径距(Dv 90-Dv 10)/Dv 50分别0.5和0.4，平均粒径Dv 50保持不变，在步骤B2中得到具有包覆层的第二正极活性材料，其体积粒度分布径距(Dv 90-Dv 10)/Dv 50分别为0.5和0.4。
实施例4-1至实施例4-3
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A1中，Zr掺杂量分别为500ppm、1000ppm、7000ppm。
实施例4-4至实施例4-6
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A1中，将ZrO 2分别替换为WO 3、Nb 2O 5以及WO 3与ZrO 2的混合物(其中W和Zr的掺杂量各为2500ppm)。
实施例4-7至实施例4-9
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤B1中，Ti掺杂量分别为500ppm、1000ppm、7000ppm。
实施例4-10至实施例4-12
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤B1中，将TiO 2分别替换为WO 3、Nb 2O 5以及WO 3与ZrO 2的混合物 (其中W和Zr的掺杂量各为2500ppm)。
实施例5-1至实施例5-2
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A2和B2中，将H 3BO 3均分别替换为Al 2O 3和Co(OH) 2。
实施例5-3至实施例5-5
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A2和B2中，B的包覆量均分别为500ppm、15000ppm和20000ppm。
实施例6-1至实施例6-2
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A1中，烧结的温度分别为800℃和950℃，烧结的时间分别为20h和10h。
实施例6-3至实施例6-4
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤B1中，烧结的温度分别为900℃和1000℃，烧结的时间分别为20h和10h。
实施例6-5至实施例6-6
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤A2中，烧结的温度分别为400℃和700℃，烧结的时间分别为10h和5h。
实施例6-7至实施例6-8
正极活性材料的制备整体上参照实施例1-1，区别在于，在步骤B2中，烧结的温度分别为400℃和700℃，烧结的时间分别为10h和5h。
测试方法
1.体积分布粒度
体积分布粒度的测试方法为：参考GB/T 19077-2016/ISO 13320:2009粒度分布激光衍射法，设备采用马尔文3000。取洁净烧杯，加入待测样品适量至遮光度8％-12％，加入20ml去离子水，同 时外超声5min，开启粒度测试仪开始测试。
2.扣式电池的制备
将正极活性材料、PVDF、导电碳加入至一定量的NMP中，加入比例为90:5:5，在干燥房中搅拌制成浆料，在铝箔上涂敷上述浆料，干燥、冷压制成正极极片，采用锂片作为负极，电解液为1mol/L的LiPF 6/(EC+DEC+DMC)(体积比为1:1:1)，在扣电箱中组装成扣式电池。
扣电初始克容量测试方法
在2.8-4.3V下，按照0.1C充电至4.3V，然后在4.3V下恒压充电至电流≤0.05mA，静置2min，此时的充电容量记为C0，然后按照0.1C放电至2.8V，此时的放电容量为初始克容量，记为D0。
3.全电池的制备
将正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比96:2:2在N-甲基吡咯烷酮溶剂体系中充分搅拌混合均匀后，涂覆于铝箔上烘干、冷压，得到正极极片。将负极活性材料人造石墨、硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂碳甲基纤维素钠(CMC)按照重量比90:5:2:2:1在去离子水溶剂体系中充分搅拌混合均匀后，涂覆于铜箔上烘干、冷压，得到负极极片。以PE多孔聚合薄膜作为隔离膜。将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入配好的基础电解液，即1mol/L的LiPF 6/(EC+EMC+DMC)(体积比为1:1:1)，并封装，得到全电池。
全电初始克容量测试方法：
在25℃恒温环境下，静置5min，按照1/3C放电至2.8V，静置5min，按照1/3C充电至4.25V，然后在4.25V下恒压充电至电流≤0.05mA，静置5min，此时的充电容量记为C 0，然后按照1/3C放电至2.8V，此时的放电容量为初始克容量，记为D 0。
全电25℃循环性能测试方法：
在25℃的恒温环境下，在2.8-4.25V下，按照1C充电至4.25V， 然后在4.25V下恒压充电至电流≤0.05mA，静置5min，然后按照1C放电至2.8V，容量即为D0，重复前面过程，记录容量D n(n＝0,1,2……)，计算500次循环容量保持率：D 500/D 0×100％。
全电70℃胀气测试方法
70℃100％SOC存储，存储前后及过程中测量电芯OCV，IMP，体积(排水法测试)，存储结束测试电芯残余容量和可逆容量，每48h出炉，静置1h后测试OCV、IMP，冷却至室温后用排水法测试电芯体积，存储40天结束测试，或者体积膨胀超过50％停止存储，保护电压范围：2.7-4.3V，标称容量2.25Ah。
4.正极极片压实密度测试方法
将正极活性材料投入5L搅拌罐中，然后加入导电剂乙炔黑(SP)与粘结剂聚偏氟乙烯(PVDF)进行30min的预混合。最后加入溶剂N-甲基吡咯烷酮(NMP)在抽真空的条件下进行快速搅拌，形成浆料。其中，正极活性材料:乙炔黑:聚偏氟乙烯的质量比＝96:2:2，浆料的固含量为70重量％。将浆料均匀涂覆于厚度为12μm的铝箔的双面上，涂覆后的极片在100-130℃烘箱干燥半小时后取出。其中，极片的正极活性材料负载量为21.5mg/cm 2。取出的正极极片过辊冷压后测试得到压实密度、长度方向延展率的数据。
正极极片的压实密度PD是通过公式PD＝M/(d×A)计算得到的。式中，M为在正极极片上切割出的直径40mm小圆片的质量，通过10次称重取平均值；d为正极极片厚度，通过10次测量厚度取平均值；A为该直径40mm小圆片的面积。
极片冷压后的长度方向延展率通过公式ΔEL％＝(L2-L1)/L1×100％计算得到。式中，L1为冷压前标记之间的距离，为1000mm，L2为冷压后标记之间的距离。所述标记通过如下方式形成：在极片的中心区域，在极片宽度方向上的不同位置分别取三段在极片长度方向上延伸的1000mm长的线段，并标记线段的两个端点。L2记为冷压后各线段两端点之间距离的实 测值的平均值。
取0.7％极片延展下的压实密度值为本申请中的正极极片的压实密度。
按照上述过程分别测试上述实施例和对比例，具体数值参见表1-表6。
Figure PCTCN2022123195-appb-000001
Figure PCTCN2022123195-appb-000002
Figure PCTCN2022123195-appb-000003
对比例实施例1-1和实施例3-1至3-4，当第一正极活性材料的平均粒径Dv 50在6-20μm范围内，二次电池均具有较好的综合性能；当第一正极活性材料的平均粒径Dv 50小于6μm时，正极极片的压实密度会明显降低，并且二次电池的循环与存储产气性能也会明显下降，如实施例3-3所示；当第一正极活性材料的平均粒径Dv 50大于20μm时，二次电池的容量会降低，并且循环与存储产气性能也会下降，如实施例3-4所示。
对比实施例1-1和实施例3-5至3-8，当第二正极活性材料的平均粒径Dv 50在2-5μm范围内，二次电池均具有较好的综合性能；当第二正极活性材料的平均粒径Dv 50小于2μm时，正极极片的压实密度会明显降低，并且二次电池的循环与存储产气性能也会明显下降，如实施例3-7所示；当第二正极活性材料的平均粒径Dv 50大于5μm时，二次电池的容量会降低，并且循环与存储产气性能也会下降，如实施例3-8所示。
对比实施例1-1和实施例3-9至3-12，当第一正极活性材料或者第二正极活性材料的颗粒体积分布径距(Dv 90-Dv 10)/Dv 50大于等于0.5时，二次电池的综合性能均良好，当(Dv 90-Dv 10)/Dv 50小于0.5时，会明显降低正极极片的压实密度。
Figure PCTCN2022123195-appb-000004
对比实施例1-1和实施例4-1至4-6，当对第一正极活性材料掺杂元素M1，并且元素M1的掺杂量为500-7000ppm时，二次电池的综合性能均良好；当元素M1的掺杂量为1000-5000ppm时，二次电池的克容量或者循环性能和/或70℃@40天胀气得到进一步改善。
对比实施例1-1和实施例4-7至4-12，当对第二正极活性材料掺杂元素M2，并且元素M2的掺杂量在500-7000ppm的范围内，二次电池均具有较好的综合性能；当元素M2的掺杂量为1000-5000ppm时，二次电池的克容量或者循环性能和/或70℃@40天胀气得到进一步改善。
Figure PCTCN2022123195-appb-000005
Figure PCTCN2022123195-appb-000006
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (22)

  1. 一种正极活性材料，其包含：
    第一正极活性材料，其包含式(I)的基体，所述基体掺杂有元素M1：
    Li A1[Ni X1Co Y1Mn Z1]O 2  (I)，
    在式(I)中，0.5≤X1<1、0≤Y1<0.5、0≤Z1<0.5、0.9<A1<1.2，X1+Y1+Z1＝1，所述元素M1选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；和
    第二正极活性材料，其包含式(II)的基体，所述基体掺杂有元素M2：
    Li A2[Ni X2Co Y2Mn Z2]O 2  (II)，
    在式(II)中，0.5≤X2<1、0≤Y2<0.5、0≤Z2<0.5、0.9<A2<1.2，X2+Y2+Z2＝1，所述元素M2选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
    其中，所述第一正极活性材料的平均粒径Dv 50大于所述第二正极活性材料的平均粒径Dv 50，并且0<X2-X1≤0.4，可选地0<X2-X1≤0.1。
  2. 根据权利要求1所述的正极活性材料，其中，0.9≤X2<1。
  3. 根据权利要求1或2所述的正极活性材料，其中，所述第一正极活性材料与所述第二正极活性材料的重量比为5:5以上，可选为6:4-9:1。
  4. 根据权利要求1至3中任一项所述的正极活性材料，其中，所述第一正极活性材料为二次颗粒，体积粒度分布径距(Dv 90-Dv 10)/Dv 50≥0.5，可选地(Dv 90-Dv 10)/Dv 50≥1.0。
  5. 根据权利要求1至4中任一项所述的正极活性材料，其中，所述第一正极活性材料的平均粒径Dv 50为6-20μm。
  6. 根据权利要求1至5中任一项所述的正极活性材料，其中，所述第二正极活性材料为二次颗粒和/或一次颗粒，可选地为一次颗粒，体积粒度分布径距(Dv 90-Dv 10)/Dv 50≥0.5，可选地(Dv 90-Dv 10)/Dv 50≥1.0。
  7. 根据权利要求1至6中任一项所述的正极活性材料，其中，所述第二正极活性材料的平均粒径Dv 50为2-5μm。
  8. 根据权利要求1至7中任一项所述的正极活性材料，其中，在所述第一正极活性材料中，所述元素M1的掺杂量为500-7000ppm，可选为1000-5000ppm，基于所述第一正极活性材料的总重量计。
  9. 根据权利要求1至8中任一项所述的正极活性材料，其中，在所述第二正极活性材料中，所述元素M2的掺杂量为500-7000ppm，可选为1000-5000ppm，基于所述第二正极活性材料的总重量计。
  10. 根据权利要求1至9中任一项所述的正极活性材料，其中，所述第一正极活性材料的表面还具有包覆层，所述包覆层含有N1元素，所述N1元素选自Al、Co、Mn、B、La、Sr、P、F、Zr、Ti、W中的至少一种。
  11. 根据权利要求10所述的正极活性材料，其中，所述N1元素的包覆量为500-20000ppm，可选为1000-15000ppm，基于所述第一正极活性材料的总重量计。
  12. 根据权利要求1至11中任一项所述的正极活性材料，其中，所述第二正极活性材料的表面还具有包覆层，所述包覆层包含N2元素，所述N2元素选自Al、Co、Mn、B、La、Sr、P、F、Zr、Ti、W中的至少一种。
  13. 根据权利要求12所述的正极活性材料，其中，所述N2元素的包覆量为500-20000ppm，可选为1000-15000ppm，基于所述第二正极活性材料的总重量计。
  14. 一种制备正极活性材料的方法，其包括以下步骤：
    步骤A：制备第一正极活性材料，其包括：
    步骤A1：将锂盐、第一正极活性材料三元前驱体、含元素M1的化合物混合，烧结，得到所述第一正极活性材料；
    步骤B：制备第二正极活性材料，其包括：
    步骤B1：将锂盐、第二正极活性材料三元前驱体、含元素M2的化合物混合，烧结，得到所述第二正极活性材料；
    步骤C：将所述第一正极活性材料和所述第二正极活性材料混合，得到所述正极活性材料；
    其中，所述第一正极活性材料包含式(I)的基体，所述基体掺杂有元素M1：
    Li A1[Ni X1Co Y1Mn Z1]O 2  (I)，
    在式(I)中，0.5≤X1<1、0≤Y1<0.5、0≤Z1<0.5、0.9<A1<1.2，X1+Y1+Z1＝1，所述元素M1选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
    所述第二正极活性材料包含式(II)的基体，所述基体掺杂有元素M2：
    Li A2[Ni X2Co Y2Mn Z2]O 2  (II)，
    在式(II)中，0.5≤X2<1、0≤Y2<0.5、0≤Z2<0.5、0.9<A2<1.2，X2+Y2+Z2＝1，所述元素M2选自Ti、Zr、Al、Sb、W、Sr、Nb、Mo、Ca、K、Na、Mg、Si、Te、Cr、V、Y中的至少一种；
    所述第一正极活性材料的平均粒径Dv 50大于所述第二正极活性材料的平均粒径Dv 50，并且0<X2-X1≤0.4，可选地0<X2-X1≤0.1。
  15. 根据权利要求14所述的方法，其中，在所述步骤A1中，所述烧结的温度为700-950℃，时间为10-20h，气氛为空气或者O 2。
  16. 根据权利要求14或15所述的方法，其中，在所述步骤B1中，所述烧结的温度为750-1000℃，时间为10-20h，气氛为空气或者O 2。
  17. 根据权利要求14至16中任一项所述的方法，其中，所述步骤A还包括：
    步骤A2：将由所述步骤A1得到的所述第一正极活性材料与含N1的化合物混合、烧结，以在所述第一正极活性材料的表面上形成包含N1元素的包覆层。
  18. 根据权利要求17所述的方法，其中，在所述步骤A2中，所述烧结的温度为250-700℃，时间为5-15h，气氛为空气或者O 2。
  19. 根据权利要求14至18中任一项所述的方法，其中，所述步 骤B还包括：
    步骤B2：将由所述步骤B1得到的所述第二正极活性材料与含N2的化合物混合、烧结，以在所述第二正极活性材料的表面上形成包含N2元素的包覆层。
  20. 根据权利要求19所述的方法，其中，在所述步骤B2中，所述烧结的温度为250-700℃，时间为5-15h，气氛为空气或者O 2。
  21. 一种二次电池，其中，包括权利要求1至13中任一项所述的正极活性材料或通过权利要求14至20中任一项所述的方法制备的正极活性材料。
  22. 一种用电装置，其中，包括权利要求21所述的二次电池。
PCT/CN2022/123195 2022-09-30 2022-09-30 正极活性材料及其制备方法、二次电池和用电装置 WO2024065647A1 (zh)

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