WO2024113942A1 - 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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WO2024113942A1
WO2024113942A1 PCT/CN2023/111442 CN2023111442W WO2024113942A1 WO 2024113942 A1 WO2024113942 A1 WO 2024113942A1 CN 2023111442 W CN2023111442 W CN 2023111442W WO 2024113942 A1 WO2024113942 A1 WO 2024113942A1
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positive electrode
active material
electrode active
optionally
lithium
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PCT/CN2023/111442
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English (en)
French (fr)
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张其雨
吴奇
陈强
柳娜
范敬鹏
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宁德时代新能源科技股份有限公司
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Publication of WO2024113942A1 publication Critical patent/WO2024113942A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • 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
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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

  • lithium-ion batteries have been 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.
  • lithium-ion batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • Positive electrode materials are an important component of lithium-ion batteries. They not only affect the safety and cost of batteries, but are also the key factors that directly determine the electrochemical performance and life of batteries.
  • common positive electrode materials include layered structure materials (such as lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, etc.), spinel structure materials, polyanion materials, and ternary materials.
  • layered lithium-rich ternary positive electrode materials are a type of positive electrode material that has attracted much attention in recent years. They have the advantages of high discharge capacity (>250mA ⁇ h/g), energy density (above 300Wh/kg), working voltage range (3.7-4.8V), low cost and environmental friendliness.
  • the positive electrode active material is in the shape of particles, including a lithium-rich layer extending from the particle surface to the interior of the particle.
  • the ratio of the average Li element content per unit area in the lithium-rich layer to the average Li element content per unit area in the non-lithium-rich layer is (>1-1.5):1, and can be optionally (1.05-1.2):1.
  • the present application at least includes the following beneficial effects:
  • the positive electrode active material of the present application not only has a high compaction density, which can effectively improve the energy density of the battery, but also has improved structural stability, which effectively prevents the electrolyte from having side reactions on the surface of the positive electrode active material, thereby improving the cycle performance and safety performance of the battery;
  • the positive electrode active material of the present application has a lithium-rich layer.
  • the vacancy clusters formed by Ni migration can fix the activated lattice oxygen and reduce oxygen release, thereby improving the cycle performance and safety performance of the battery.
  • the positive electrode active material satisfies the above formula, the positive electrode active material has good structural stability, and the lithium-rich layer structure of the positive electrode active material can maintain a stable layered structure during the charge and discharge process, inhibit the interlayer migration of Ni, and reduce oxygen release, thereby improving the cycle performance and safety performance of the battery.
  • the Dv50 of the positive electrode active material is 5-15 ⁇ m, optionally 8-10 ⁇ m.
  • the positive electrode active material has good structural stability.
  • the lithium-rich layer structure of the positive electrode active material can maintain a stable layered structure during the charge and discharge process, inhibit the interlayer migration of Ni, and reduce oxygen release, thereby improving the cycle performance and safety performance of the battery.
  • the weight ratio of the M1 element to the M2 element in the positive electrode active material is 1:0.1-1:1, and can be 1:0.1-1:0.5.
  • the structural stability of the material can be improved, thereby improving the cycle performance and safety performance of the battery.
  • the positive electrode active material further has a coating
  • the chemical formula of the coating is LieCoO2 , where 0 ⁇ e ⁇ 1.
  • the coating LieCoO2 can effectively prevent the electrolyte from having side reactions on the surface of the positive electrode active material, reduce oxygen release, and further improve the cycle performance and safety performance of the battery.
  • the coating has a thickness of 0.01-0.2 ⁇ m, and optionally 0.05-0.1 ⁇ m.
  • the coating has a thickness within the above range, it can effectively prevent the electrolyte from having side reactions on the surface of the positive electrode active material, thereby further improving the cycle performance and safety performance of the battery.
  • the weight ratio of the coating to the positive electrode active material is (0.002-0.02): 1, and can be (0.005-0.012): 1.
  • the weight ratio of the coating to the positive electrode active material meets the above range, the cycle performance and safety performance of the battery are effectively improved.
  • (Dv90-Dv10)/Dv50 of the positive electrode active material is ⁇ 1.1, and can be ⁇ 1.2.
  • the filling degree between particles is high, and the dispersibility is good, which can effectively improve the energy density of the battery.
  • the compaction density of the positive electrode active material under a pressure of 5000 kg/1.33 cm 2 is ⁇ 3.4 g/cm 3 .
  • the positive electrode active material has a high compaction density, which can effectively improve the energy density of the battery.
  • a second aspect of the present application provides a method for preparing a positive electrode active material, the method comprising the following steps:
  • step S2) adding the matrix material obtained in step S1) into an aqueous solution containing a soluble Co-containing compound and a soluble Li-containing compound, washing, filtering, and drying to obtain a positive electrode active material;
  • the temperature of the low-temperature co-heating is 150-400° C., optionally 200-300° C., and the time is 1-6 hours, optionally 2-4 hours.
  • the positive electrode active material is in the shape of particles, including a lithium-rich layer extending from the particle surface to the interior of the particle.
  • the ratio of the average Li element content per unit area in the lithium-rich layer to the average Li element content per unit area in the non-lithium-rich layer is (>1-1.5):1, and can be optionally (1.05-1.2):1.
  • the positive electrode active material with a lithium-rich layer structure prepared by the above method not only has a high compaction density, which can effectively improve the energy density of the battery, but also has improved structural stability, effectively preventing the electrolyte from having side reactions on the surface of the positive electrode active material, thereby improving the battery's cycle performance and safety performance.
  • the molar ratio of the Li element in the lithium source to the metal element in the precursor of the positive electrode active material is 1.2-1.5, optionally 1.25-1.4, the metal elements are Ni, Co and Mn, the sintering temperature is 600-850°C, the sintering time is 9-12h, and the sintering atmosphere is air or oxygen, optionally oxygen.
  • the compound containing the M1 element is one or more of an oxide, hydroxide, carbonate, oxalate or nitrate containing the M1 element, and the amount of the M1 element added in the step S1) is 2000-5000 ppm
  • the compound containing the M2 element is one or more of an oxide, hydroxide, carbonate, oxalate or nitrate containing the M2 element, and the amount of the M2 element added in the step S1) is 200-2000ppm, and optionally 400-1000ppm, based on the weight of the precursor of the positive electrode active material.
  • the soluble Co-containing compound is selected from one or more of Co(CH 3 COO) 2 , CoC 2 O 4 , CoSO 4 , Co(NO 3 ) 2 and CoCl 2 , and the amount of Co element added in the step S2) is 1000-20000ppm, optionally 5000-13000ppm, based on the weight of the precursor of the positive active material;
  • the soluble Li-containing compound is selected from one or more of Li 2 SO 4 , LiNO 3 , LiC 2 O 4 , CH 3 COOLi and LiCl, and the amount of Li element added in the step S2) is 500-5000ppm, optionally 1000-1500ppm, based on the weight of the precursor of the positive active material.
  • the water washing temperature is 0-100°C, optionally 5-50°C, and the water washing time is 1-30min, optionally 2-5min.
  • the drying is vacuum drying, and the drying temperature is 40-120° C., optionally 80-100° C., and the drying time is 6-24 hours, optionally 12-18 hours.
  • the lithium source is selected from at least one of LiOH ⁇ H 2 O, Li 2 CO 3 , Li 2 SO 4 , LiNO 3 , LiC 2 O 4 and CH 3 COOLi, and may be selected from at least one of LiOH ⁇ H 2 O, Li 2 SO 4 and LiNO 3 .
  • the method further comprises step S3): mixing the positive electrode active material obtained in step S2) with a Co-containing compound and a Li-containing compound, sintering at a temperature of 500-800°C, optionally 550-750°C, for a sintering time of 5-15h, optionally 5-10h, and sintering in air or O 2 , to obtain a positive electrode active material with a coating, wherein the chemical formula of the coating is Li e CoO 2 , wherein 0 ⁇ e ⁇ 1.
  • a coating layer can be formed on the positive electrode active material, effectively preventing the electrolyte from having side reactions on the surface of the positive electrode active material, and reducing Less oxygen is released, thereby further improving the cycle performance and safety performance of the battery.
  • the Co-containing compound is selected from at least one of Co 3 O 4 , Co(OH) 2 , CoO, CoOOH, Co(CH 3 COO) 2 , CoC 2 O 4 and CoCO 3
  • the Dv50 of the Co-containing compound particles is 0.001-10 ⁇ m, optionally 0.001-1 ⁇ m
  • the amount of Co element added in the step S3) is 500-20000 ppm, optionally 2000-15000 ppm, based on the weight of the precursor of the positive electrode active material
  • the Li-containing compound is selected from LiOH ⁇ H 2 O, Li 2 CO 3 , Li 2 SO 4 , LiNO 3 , LiC 2 O 4 and CH 3
  • At least one of COOLi the Dv50 of the Li-containing compound particles is 0.001-1 ⁇ m, optionally 0.01-0.05 ⁇ m
  • the amount of Li element added in the step S3) is 100-3000 ppm, optionally 500-1500 ppm, based on the weight of the precursor of the positive
  • the third aspect of the present application provides a secondary battery, which includes 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 or the positive electrode plate of the third aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, which includes a secondary battery selected from the fourth 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 schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • 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)
  • steps (a) and (b) it means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) it means that step (c) may be performed randomly.
  • the steps are added sequentially to the method.
  • 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).
  • the electrochemical properties of materials are usually improved by surface coating, ion doping and other means.
  • the positive electrode active material is in the shape of particles, including a lithium-rich layer extending from the particle surface to the inside of the particle.
  • the ratio of the average Li element content per unit area in the lithium-rich layer to the average Li element content per unit area in the non-lithium-rich layer is (>1-1.5):1, which can be optionally (1.05-1.2):1.
  • the applicant unexpectedly found that: it not only has a high compaction density, which can effectively improve the energy density of the battery, but also has improved structural stability, effectively preventing the electrolyte from having side reactions on the surface of the positive electrode active material, thereby improving the battery's cycle performance and safety performance.
  • the positive electrode active material has a lithium-rich layer structure, which can maintain a stable layered structure of the positive electrode active material during the charge and discharge process, promote Ni to migrate within the layer, and effectively reduce the degree of lithium-nickel mixing.
  • the vacancy clusters formed by Ni migration can fix the activated lattice oxygen and reduce oxygen release, thereby improving the battery's cycle performance and safety performance;
  • the M1 and M2 elements doped in the positive electrode active material can stabilize the lattice structure, effectively improve the structural stability of the positive electrode active material, thereby further improving the battery's cycle performance and safety performance.
  • the ratio of the average Li content per unit area in the lithium-rich layer to the average Li content per unit area in the non-lithium-rich layer is, for example, at least 1.01:1, at least 1.05:1, at least 1.1:1, at least 1.18:1, at least 1.2:1, at least 1.3:1, at least 1.4:1 or at least 1.5:1.
  • the Li content and distribution change in the positive electrode active material can be obtained by using the technology commonly used to detect the Li content known in the art, for example, using the PHI NanoTOFII time-of-flight secondary mass spectrometer of Ulvac-Phi Company of Japan to obtain the Li content and distribution change in the material.
  • the positive electrode active material satisfies the above formula, the positive electrode active material has good structural stability, and the lithium-rich layer structure of the positive electrode active material can maintain a stable layered structure during the charge and discharge process, inhibit the interlayer migration of Ni, and reduce oxygen release, thereby improving the cycle performance and safety performance of the battery.
  • the k is, for example, greater than 0.001, greater than 0.01, greater than 0.08, greater than 0.1, greater than 0.2, greater than 0.3, greater than 0.4, greater than 0.5 or greater than 0.6.
  • the thickness t of the lithium-rich layer extending from the particle surface of the positive electrode active material to the interior of the particle is, for example, greater than 0.00475 ⁇ m, greater than 0.0475 ⁇ m, greater than 0.38 ⁇ m, greater than 0.95 ⁇ m, greater than 1.425 ⁇ m, greater than 1.9 ⁇ m or greater than 2.85 ⁇ m.
  • the Dv50 of the positive electrode active material is 5-15 ⁇ m, When the Dv50 of the positive electrode active material is within the above range, the positive electrode active material has good structural stability, and the lithium-rich layer structure of the positive electrode active material can maintain a stable layered structure during the charge and discharge process, inhibit the interlayer migration of Ni, and reduce oxygen release, thereby improving the cycle performance and safety performance of the battery.
  • the lithium-nickel mixing degree of the positive electrode active material is ⁇ 5%, optionally ⁇ 3%. In other embodiments, the lithium-nickel mixing degree of the positive electrode active material is, for example, ⁇ 5%, ⁇ 4%, ⁇ 3.5%, ⁇ 3%, ⁇ 2.5%, ⁇ 2%, ⁇ 1.5% or ⁇ 1%. Since the radius of Ni 2+ is very close to that of Li + , Ni 2+ in the transition metal layer can easily migrate to the lithium layer and occupy the site of lithium, causing cation mixing (i.e., lithium-nickel mixing), resulting in poor structural stability of the positive electrode active material. The performance of the positive electrode active material decreases with the increase of the degree of cation mixing.
  • the lithium-rich layer structure of the positive electrode active material of the present application can promote the intralayer migration of Ni and inhibit its interlayer migration, effectively reduce the degree of lithium-nickel mixing, maintain the stability of the layered structure, and at the same time, the vacancy clusters formed by the migration of Ni can fix the activated lattice oxygen and reduce oxygen release, thereby improving the cycle performance and safety performance of the battery.
  • the XRD pattern of the positive electrode active material can be obtained by using a D8Advance X-ray diffractometer (XRD) of Bruker Corporation of Germany, and the lithium-nickel mixing degree value of the positive electrode active material can be obtained by open source software (ie, GSAS software).
  • XRD D8Advance X-ray diffractometer
  • GSAS software open source software
  • the weight ratio of the M1 element to the M2 element in the positive electrode active material is 1:0.1-1:1, optionally 1:0.1-1:0.5.
  • the structural stability of the material can be improved, thereby improving the cycle performance and safety performance of the battery.
  • the amount of the M1 element and the M2 element is measured by a detection technique commonly used to measure the content of doping elements known in the art, such as inductively coupled plasma emission spectroscopy (ICP).
  • ICP inductively coupled plasma emission spectroscopy
  • the positive electrode active material further has a coating, the chemical formula of which is LieCoO2 , where 0 ⁇ e ⁇ 1.
  • the coating LieCoO2 can effectively prevent the electrolyte from having side reactions on the surface of the positive electrode active material, reduce oxygen release, and further improve the cycle performance and safety performance of the battery.
  • the coating has a thickness of 0.01-0.2 ⁇ m, optionally 0.05-0.1 ⁇ m.
  • the coating has a thickness within the above range, it can effectively prevent the electrolyte from having side reactions on the surface of the positive electrode active material, thereby further improving the cycle performance and safety performance of the battery.
  • the weight ratio of the coating to the positive electrode active material is (0.002-0.02): 1, or optionally (0.005-0.012): 1.
  • the weight ratio of the coating to the positive electrode active material meets the above range, the cycle performance and safety performance of the battery are effectively improved.
  • (Dv90-Dv10)/Dv50 of the positive electrode active material is ⁇ 1.1, and optionally ⁇ 1.2.
  • the filling degree between particles is high, and the dispersibility is good, which can effectively improve the energy density of the battery.
  • the Dv10, Dv50 and Dv90 are the particle sizes of the positive electrode active material measured by volume particle size distribution, wherein the Dv10 is the particle size corresponding to when the cumulative volume percentage of the sample reaches 10%, the Dv50 is the particle size corresponding to when the cumulative volume percentage of the sample reaches 50%, and the Dv90 is the particle size corresponding to when the cumulative volume percentage of the sample reaches 90%.
  • the compaction density of the positive electrode active material under a pressure of 5000 kg/1.33 cm 2 is ⁇ 3.4 g/cm 3.
  • the positive electrode active material has a high compaction density and can effectively improve the energy density of the battery.
  • the compaction density can be measured according to GB/T 24533-2009.
  • a second aspect of the present application provides a method for preparing a positive electrode active material, the method comprising the following steps:
  • step S2) adding the matrix material obtained in step S1) into an aqueous solution containing a soluble Co-containing compound and a soluble Li-containing compound, washing, filtering, and drying to obtain a positive electrode active material;
  • the temperature of the low-temperature co-heating is 150-400° C., optionally 200-300° C., and the time is 1-6 hours, optionally 2-4 hours.
  • the positive electrode active material is in the form of particles, including a particle extending from the particle surface to the inside of the particle.
  • the invention relates to a lithium-rich layer having an extended shape.
  • the ratio of the average Li element content per unit area in the lithium-rich layer to the average Li element content per unit area in the non-lithium-rich layer is (>1-1.5):1, and can be optionally (1.05-1.2):1.
  • the positive electrode active material with a lithium-rich layer structure prepared by the above method not only has a high compaction density, which can effectively improve the energy density of the battery, but also has improved structural stability, effectively preventing the electrolyte from having side reactions on the surface of the positive electrode active material, thereby improving the battery's cycle performance and safety performance.
  • the precursor of the positive electrode active material can be prepared by a method known in the prior art, such as a hydroxide co-precipitation method, for example, by the method described in CN 111384372 A. More specifically, the precursor of the first positive electrode active material A can include but is not limited to Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 , Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 , Ni 0.96 Co 0.03 Mn 0.01 (OH) 2 , and Ni 0.75 Co 0.1 Mn 0.15 (OH) 2 .
  • the precursor of the second positive active material B may include but is not limited to Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 , Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 , Ni 0.96 Co 0.03 Mn 0.01 (OH) 2 , and Ni 0.75 Co 0.1 Mn 0.15 (OH) 2 .
  • the low temperature heating temperature is, for example, 200-250°C.
  • the molar ratio of the Li element in the lithium source to the metal element in the precursor of the positive electrode active material is 1.2-1.5, optionally 1.25-1.4, the metal elements are Ni, Co and Mn, the sintering temperature is 600-850°C, the sintering time is 9-12h, and the sintering atmosphere is air or oxygen, optionally oxygen.
  • the molar ratio of the Li element to the metal element in the precursor, the sintering temperature and the sintering time can make the obtained positive electrode active material have a high compaction density and improved structural stability.
  • the compound containing the M1 element is one or more of an oxide, hydroxide, carbonate, oxalate or nitrate containing the M1 element, and the amount of the M1 element added in the step S1) is 2000-5000ppm, optionally 3000-4000ppm, based on the weight of the precursor of the positive electrode active material;
  • the compound containing the M2 element is one or more of an oxide, hydroxide, carbonate, oxalate or nitrate containing the M2 element, and the amount of the M2 element added in the step S1) is 200-2000ppm, optionally 400-1000ppm, based on the weight of the precursor of the positive electrode active material.
  • a positive electrode active material having a lithium-rich layer structure can be obtained, thereby improving the cycle performance and safety performance of the battery.
  • the water washing temperature is 0-100°C, optionally 5-50°C, and further optionally 10-30°C, and the water washing time is 1-30min, optionally 2-5min.
  • the drying is vacuum drying, and the drying temperature is 40-120° C., optionally 80-100° C., and the drying time is 6-24 hours, optionally 12-18 hours.
  • the lithium source is selected from at least one of LiOH ⁇ H 2 O, Li 2 CO 3 , Li 2 SO 4 , LiNO 3 , LiC 2 O 4 and CH 3 COOLi, and may be selected from at least one of LiOH ⁇ H 2 O, Li 2 SO 4 and LiNO 3 .
  • the method further comprises step S3): mixing the positive electrode active material obtained in step S2) with a Co-containing compound and a Li-containing compound, sintering at a temperature of 500-800°C, optionally 550-750°C, for a sintering time of 5-15h, optionally 5-10h, and in an air or O 2 atmosphere, to obtain a positive electrode active material having a coating, wherein the chemical formula of the coating is Li e CoO 2 , wherein 0 ⁇ e ⁇ 1.
  • a coating layer can be formed on the positive electrode active material, and the coating layer can effectively prevent the electrolyte from having side reactions on the surface of the positive electrode active material, reduce oxygen release, and thus further improve the cycle performance and Safety performance.
  • the Co-containing compound is selected from at least one of Co 3 O 4 , Co(OH) 2 , CoO, CoOOH, Co(CH 3 COO) 2 , CoC 2 O 4 and CoCO 3
  • the Dv50 of the Co-containing compound particles is 0.001-10 ⁇ m, optionally 0.001-1 ⁇ m
  • the amount of Co element added in the step S3) is 500-20000 ppm, optionally 2000-15000 ppm, based on the weight of the precursor of the positive electrode active material
  • the Li-containing compound is selected from LiOH ⁇ H 2 O, Li 2 CO 3 , Li 2 SO 4 , LiNO 3 , LiC 2 O 4 and CH 3
  • At least one of COOLi the Dv50 of the Li-containing compound particles is 0.001-1 ⁇ m, optionally 0.01-0.05 ⁇ m
  • the amount of Li element added in the step S3) is 100-3000 ppm, optionally 500-1500 ppm, based on the weight of the precursor of the
  • the third aspect of the present application provides a positive electrode plate, which includes a positive electrode collector and a positive electrode film layer arranged on at least one surface of the positive electrode collector, the positive electrode film layer includes 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, and the content of the positive electrode active material in the positive electrode film layer is more than 10 weight%, based on the total weight of the positive electrode film layer.
  • the fourth aspect of the present application provides a secondary battery, which includes 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 or the positive electrode plate of the third aspect of the present application.
  • a fifth aspect of the present application provides an electrical device comprising a secondary battery selected from the fourth aspect of the present application.
  • the battery cells may be assembled into a battery module. In some embodiments, the battery cells may be assembled into a battery pack. In some embodiments, the battery modules may be assembled into a battery pack.
  • the secondary battery in the form of a battery cell
  • a battery module in the form of a battery cell
  • a battery pack in the form of a battery pack
  • an electric device of the present application is described below with appropriate reference to the drawings.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • active ions are embedded and removed 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 arranged 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 battery group margin is 90-95%.
  • 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 active material may be the positive electrode active material of the first aspect of the present application.
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80-100 weight %, based on the total weight of the positive electrode film layer.
  • 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
  • the weight ratio of the binder in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may further include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the weight ratio is 0-20 weight %, based on the total weight of the positive electrode film layer.
  • the positive electrode sheet can be prepared by the following method: 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; wherein the positive electrode slurry has a solid content of 40-80wt%, and the viscosity at room temperature is adjusted to 5000-25000mPa ⁇ s, and 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, the positive electrode powder coating unit area density is 150-350mg/ m2 , and the positive electrode sheet compaction density is 3.0-3.6g/ cm3 , and can be 3.3-3.5g/ cm3 .
  • 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 batteries 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 can 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 can 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 can also be used.
  • the negative active material may have an average particle size (D 10 ) of 1 ⁇ m-15 ⁇ m, preferably 4 ⁇ m-9 ⁇ m, an average particle size (D 50 ) of 12 ⁇ m-22 ⁇ m, preferably 14 ⁇ m-17 ⁇ m, and an average particle size (D 90 ) of 26 ⁇ m to 40 ⁇ m, preferably 30 ⁇ m-37 ⁇ m.
  • D 10 is the particle size corresponding to when the volume cumulative distribution percentage of the sample reaches 10%
  • D 50 is the particle size corresponding to when the volume cumulative distribution percentage of the sample reaches 50%
  • D 90 is the particle size corresponding to when the volume cumulative distribution percentage of the sample reaches 90%.
  • the weight ratio of the negative active material in the negative film layer is 70-100% by weight, based on the total weight of the negative film layer.
  • 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).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include a conductive agent.
  • the conductive agent 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 weight ratio of the conductive agent in the negative electrode film layer is 0-20 weight %, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer may further include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc.
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na)
  • the weight ratio of the other additives in the negative electrode film layer is 0-15% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode sheet can be prepared by the following method: 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, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa ⁇ s; 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.
  • the negative electrode powder coating unit area density is 75-220mg/ m2
  • the negative electrode sheet compaction density is 1.2-2.0g/ m3 .
  • 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 may 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 concentration of the electrolyte salt is typically 0.5-5 mol/L.
  • 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 secondary battery 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 isolation film has a thickness of 6-40 ⁇ m, and optionally 12-20 ⁇ m.
  • 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 secondary battery may include an outer package that can be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery can be a hard shell, such as a hard plastic
  • the outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package.
  • the material of the soft package can be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 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 secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries 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.
  • FIG3 is a battery module 4 as an example.
  • a plurality of secondary batteries 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 secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 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.
  • FIG4 and FIG5 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 electrical device, the electrical device comprising the present application At least one of a secondary battery, a battery module, or a battery pack.
  • the secondary battery, the battery module, or the battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • Fig. 6 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, etc.
  • a battery pack or a battery module may be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • a device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • Nickel sulfate, cobalt sulfate and manganese sulfate were prepared into a 2 mol/L metal salt solution in a molar ratio of 9:0.5:0.5, and then the metal salt solution, 8 mol/L ammonia water and 5 mol/L NaOH solution were continuously added into a reactor for reaction.
  • the precursor of the positive electrode active material Ni 0.9 Co 0.05 Mn 0.05 (OH) 2
  • the precursor of the positive electrode active material (Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 ) with a particle size of Dv50 was prepared by controlling the pH value of the reaction process to 11.30 , the ammonia concentration to 4.0 g/L, the reaction time to 20 h and the stirring rate to 300 r/min. It is 9.5 ⁇ m.
  • lithium hydroxide and the precursor of the prepared positive electrode active material are co-heated at 250°C for 3 hours at a molar ratio of Li/Me (Me is the total molar ratio of Ni, Co and Mn) of 1.3:1 to obtain a mixture, and the mixture is mixed with niobium pentoxide ( Nb2O5 ) and aluminum oxide ( Al2O3 ) in a plow mixer to be uniformly mixed, wherein the molar ratio of lithium hydroxide , the precursor of the positive electrode active material, Nb2O5 and Al2O3 is 1.3:1:0.0020: 0.0036 , and then the materials are placed in a kiln for sintering at a sintering temperature of 780°C, a sintering time of 12 hours, and an oxygen atmosphere. After cooling, a matrix material is obtained;
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 was 1 mol/L.
  • the isolation membrane was purchased from Cellgard, model number is cellgard 2400.
  • buttons cell CR2032 button cell
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • Nitative electrode sheet After mixing the negative electrode active material artificial graphite, hard carbon, conductive agent acetylene black, binder styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) in deionized water at a weight ratio of 90:5:2:2:1, the mixture was coated on copper foil, dried, and cold pressed to obtain a negative electrode sheet. The coating amount was 0.124g/ cm2 , and the compaction density was 1.6g/ cm3 .
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 was 1 mol/L.
  • the positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrodes to isolate them, and then wound to obtain a bare cell.
  • the bare cell is placed in an outer package, injected with electrolyte and packaged to obtain a full battery (hereinafter referred to as "full battery”).
  • the length ⁇ width ⁇ height of the full battery 90 mm ⁇ 30 mm ⁇ 60 mm, and the battery group margin is 91.0%.
  • step S1 the molar ratio of Li/Me is 1.2:1, and in step S2), the amount of Li element added is 1200 ppm.
  • step S1 the molar ratio of Li/Me is 1.25:1, and in step S2), the amount of Li element added is 1500 ppm.
  • step S1 the molar ratio of Li/Me is 1.35:1, and in step S2), the amount of Li element added is 1800 ppm.
  • step S1 the molar ratio of Li/Me is 1.38:1, and in step S2), the amount of Li element added is 2000 ppm.
  • step S1 the molar ratio of Li/Me is 1.4:1, and in step S2), the amount of Li element added is 2500 ppm.
  • step S1 the molar ratio of Li/Me is 1.5:1, and in step S2), the amount of Li element added is 3000 ppm.
  • step S1 zirconium dioxide (ZrO 2 ) and magnesium sulfate (MgSO 4 ) are used, wherein the amount of Zr element is 2000 ppm and the amount of Mg element is 200 ppm, based on the weight of the precursor of the positive electrode active material; the molar ratio of lithium hydroxide, the precursor of the positive electrode active material, ZrO 2 , and MgSO 4 is 1.3:1:0.0021:0.0008.
  • Example 1 The same as Example 1, except that: in the preparation of the positive electrode active material, in step S1), tungstic acid (H 2 WO 4 ) and titanium dioxide (TiO 2 ) are used, wherein the amount of W element is 3000 ppm and the amount of Ti element is 1500 ppm, based on the weight of the precursor of the positive electrode active material; the molar ratio of lithium hydroxide, the precursor of the positive electrode active material, H 2 WO 4 , and TiO 2 is 1.3:1:0.0016:0.0031.
  • tungstic acid H 2 WO 4
  • TiO 2 titanium dioxide
  • step S1 molybdenum trioxide (MoO 3 ) and calcium carbonate (CaCO 3 ) are used, wherein the amount of Mo element is 2000 ppm and the amount of Ca element is 2000 ppm, based on the weight of the precursor of the positive electrode active material; the molar ratio of lithium hydroxide, the precursor of the positive electrode active material, MoO 3 , and CaCO 3 is 1.3:1:0.0020:0.0050.
  • MoO 3 molybdenum trioxide
  • CaCO 3 calcium carbonate
  • step S1 the low-temperature co-heating temperature is 200°C.
  • step S1 the low-temperature co-heating temperature is 400°C.
  • step S2 in the preparation of the positive electrode active material, in step S2), the water washing temperature is 20° C. and the water washing time is 2 min.
  • step S2 in the preparation of the positive electrode active material, in step S2), the water washing temperature is 30° C., and the water washing time is 1 min.
  • the positive electrode active material obtained in Example 1 was mixed with CoOOH and CH 3 COOLi in a slant mixer at a weight ratio of 1:0.0140:0.0094, wherein the Dv50 of the CoOOH particles was 0.05 ⁇ m, the amount of the Co element was 9000 ppm, the Dv50 of the CH 3 COOLi particles was 0.01 ⁇ m, and the amount of the Li element was 1000 ppm.
  • the materials were then placed in a kiln for sintering at a sintering temperature of 600° C. for 8 h in an oxygen atmosphere. After cooling, a coating of Li 0.6 CoO 2 was obtained.
  • Example 15 The same as Example 15, except that the positive electrode active material, CoOOH and CH 3 COOLi were mixed in an oblique mixer at a weight ratio of 1:0.0023:0.0047, wherein the amount of Co element was 1500 ppm and the amount of Li element was 500 ppm.
  • Example 15 The same as Example 15, except that the positive electrode active material, CoOOH and CH 3 COOLi were mixed in an oblique mixer at a weight ratio of 1:0.0062:0.0094, wherein the amount of Co element was 4000 ppm and the amount of Li element was 1000 ppm.
  • Example 15 The same as Example 15, except that the positive electrode active material, CoOOH and CH 3 COOLi were mixed in an oblique mixer at a weight ratio of 1:0.0163:0.0141, wherein the amount of Co element was 10500 ppm and the amount of Li element was 1500 ppm.
  • Example 15 The same as Example 15, except that the positive electrode active material, CoOOH and CH 3 COOLi were mixed in an oblique mixer at a weight ratio of 1:0.0264:0.0282, wherein the amount of Co element was 17000 ppm, and the amount of Li element was 3000 ppm.
  • the preparation of the precursor of the positive electrode active material is the same as that in Example 1.
  • the molar ratio of lithium hydroxide, the precursor of the positive electrode active material, Nb 2 O 5 and Al 2 O 3 is 1.05:1:0.0020:0.0036.
  • the materials are then placed in a kiln for sintering at a sintering temperature of 780°C for 12 hours in an oxygen atmosphere.
  • the positive electrode active material Li 1.03 Ni 0.8950 Co 0.0497 Mn 0.0497 Nb 0.002 Al 0.0036 O 2 is obtained by mechanical crushing with a particle size Dv50 of 9.5 ⁇ m.
  • GB/T 19077.1-2016/ISO 13320:2009 particle size distribution laser diffraction method
  • Determine the particle size of the positive electrode active material Take a clean beaker, add an appropriate amount of the above positive electrode active material, add an appropriate amount of pure water, and use ultrasound at 120W/5min to ensure that the material powder is completely dispersed in the water.
  • the solution is poured into the injection tower of the laser particle size analyzer (Malvern Company, model: Mastersizer3000) and then circulated to the test optical path system with the solution.
  • the particles are irradiated by the laser beam, and the particle size distribution characteristics of the particles (shading degree: 8-12%) can be obtained by receiving and measuring the energy distribution of the scattered light, and the corresponding values of Dv10, Dv50, and Dv90 are read.
  • the obtained positive electrode material is mixed with a conductive resin, and after solidification, it is thinned on an ion thinning instrument (instrument company: German Leica, model: RES102). The thinned sample is placed in a time-of-flight secondary mass spectrometer (instrument company: Japanese Ulvac-Phi, model: PHI NanoTOFII).
  • a primary ion source (Bi source) is used to bombard the cross section of the positive electrode material and excite ions on the cross section of the material.
  • An ion collector is used to collect the ions.
  • the obtained positive electrode powder material was fully ground and placed on the groove of the XRD diffractometer slide.
  • the slide was placed in the XRD diffractometer (Instrument Company: Germany Bruker, Model: D8 Advance), and the positive electrode material was scanned at a scanning speed of 1 o /min to collect the obtained XRD spectrum.
  • the raw data of the XRD spectrum was imported into the GSAS refinement software (open source software), and the XRD spectrum was refined using the Reitveld refinement method, and finally the lithium-nickel mixing degree value was calculated.
  • the first effect is calculated according to D0/C0*100%.
  • Full batteries with 100% state of charge (SOC) are stored at 70°C.
  • the open circuit voltage (OCV) and AC internal resistance (IMP) of the battery cells are measured before, during and after storage to monitor the SOC, and the volume of the battery cells is measured.
  • the full battery is taken out after every 48 hours of storage, and the OCV and IMP are tested after standing for 1 hour.
  • the volume of the battery cells is measured by the water displacement method after cooling to room temperature.
  • the water displacement method is to first use a balance that automatically converts units using dial data to measure the gravity F1 of the battery cell separately, and then place the battery cell completely in deionized water (density is known to be 1g/ cm3 ), and measure the gravity F2 of the battery cell at this time.
  • the battery cell After each volume test, the battery cell is recharged at a constant current of 1C to 4.25V, and then charged at a constant voltage of 4.25V until the current drops to 0.05C. After the recharging is completed, the battery cell is put into the furnace to continue testing.
  • the cell volume was measured, and the increase in cell volume after storage relative to the cell volume before storage, i.e., the gas production, was calculated.
  • the positive electrode active material of the present application has a high compaction density, so that the battery has a high energy density; on the other hand, the positive electrode active material of the present application has a lithium-rich layer structure, and can maintain excellent structural stability during the charge and discharge process, effectively reduce the degree of lithium-nickel mixing, effectively prevent the electrolyte from having side reactions on the surface of the positive electrode active material, reduce oxygen release, and greatly improve the cycle performance and safety performance of the battery.
  • the formation of a coating Li e CoO 2 on the surface of the positive electrode active material of the present application can further effectively prevent the electrolyte from having side reactions on the surface of the positive electrode active material, thereby further improving the cycle performance and safety performance of the battery.

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Abstract

一种正极活性材料及其制备方法，包括正极活性材料的二次电池和用电装置。正极活性材料的化学式为Li 1+a[Ni xCo yMn zM1 bM2 c]O 2，其中，0.05<a<0.5，1/3≤x<1，0≤y<1/3，0≤z<1/3，0<b<0.1，0<c<0.1，x+y+z+b+c＝1，M1为选自Mo、Zr、W、Sb、Nb、Te和Ga中的一种或多种元素，M2为选自Mg、Al、Ca和Ti中的一种或多种元素，其包括有由颗粒表面向颗粒内部延伸的富锂层，在通过正极活性材料的单个颗粒的几何中心的横截面上，富锂层中每单位面积上的平均Li元素含量与非富锂层中每单位面积上的平均Li元素含量之比为(>1-1.5):1。该正极活性材料具有高的压实密度和改善的结构稳定性，有效提高电池的能量密度，并改善电池的循环性能和安全性能。

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
本申请涉及锂电池技术领域，尤其涉及一种正极活性材料及其制备方法，及包括该正极活性材料的二次电池和用电装置。
背景技术
近年来，随着锂离子电池的应用范围越来越广泛，锂离子电池广泛应用于水力、火力、风力和太阳能电站等储能电源***，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。由于锂离子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。
正极材料是锂离子电池的重要组成部分，不仅影响电池的安全性和成本，而且是直接决定电池的电化学性能和寿命的关键因素。目前常见的正极材料有层状结构材料(例如钴酸锂、锰酸锂、镍酸锂等)、尖晶石结构材料、聚阴离子型材料以及三元材料等。其中层状富锂三元正极材料是近年来备受关注的一类正极材料，它具有高的放电比容量(＞250mA·h/g)、能量密度(300Wh/kg以上)、工作电压区间(3.7-4.8V)以及较低的成本且环境友好等优点，被普遍认为是下一代电池正极材料的最佳选择之一。然而，由于富锂三元正极材料本身存在结构不稳定而导致在充放电过程中会出现比较严重的层状结构破坏、氧析出以及容量衰减等问题，充放电过程等问题，在一定程度上阻碍了富锂三元正极材料的进一步发展。因此，需要采取一定策略来优化富锂三元正极材料，从而提升富锂三元材料结构稳定性，抑制电压衰减，抑制其与电解液的副反应等。
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，该正极活性材料具有改善的结构稳定性，高的压实密度，并提供该 正极活性材料的制备方法以及包含本申请正极活性材料的正极极片、二次电池和用电装置。
为了达到上述目的，本申请的第一方面提供了一种正极活性材料，其特征在于，所述正极活性材料的化学式为Li1+a[NixCoyMnzM1bM2c]O2，其中，0.05<a<0.5，1/3≤x<1，0≤y<1/3，0≤z<1/3，0<b<0.1，0<c<0.1，x+y+z+b+c＝1，M1为选自Mo、Zr、W、Sb、Nb、Te和Ga中的一种或多种元素，M2为选自Mg、Al、Ca和Ti中的一种或多种元素，可选地，0.1<a<0.2，0.6≤x<1，
所述正极活性材料为颗粒形状，包括有由颗粒表面向颗粒内部延伸的富锂层，在所述正极活性材料的单个颗粒中，在通过颗粒的几何中心的横截面上，所述富锂层中每单位面积上的平均Li元素含量与非富锂层中每单位面积上的平均Li元素含量之比为(>1-1.5):1，可选为(1.05-1.2):1。
由此，相对于现有技术，本申请至少包括如下所述的有益效果：
(1)本申请的正极活性材料不仅具有高的压实密度，能够有效提高电池的能量密度，而且具有改善的结构稳定性，有效防止电解液在正极活性材料表面发生副反应，从而改善电池的循环性能和安全性能；
(2)本申请的正极活性材料具有富锂层，在充放电过程中，一方面有利于维持正极活性材料稳定的层状结构，另一方面有利于促使Ni发生层内迁移而抑制Ni的层间迁移，有效降低锂镍混排程度，同时Ni迁移形成的空位簇能够固定活化的晶格氧，减少释氧，从而改善电池的循环性能和安全性能。
在任意实施方式中，所述正极活性材料满足：k＝2t/Dv50，并且k为大于0至0.6、可选为0.01至0.3，其中t为由正极活性材料的颗粒表面向颗粒内部延伸的富锂层的厚度，所述Dv50为所述正极活性材料的体积累计分布百分数达到50％时对应的粒径。当所述正极活性材料满足上式时，所述正极活性材料具有良好的结构稳定性，该正极活性材料具有的富锂层结构能够在充放电过程中维持稳定的层状结构，抑制Ni的层间迁移，减少释氧，从而改善电池的循环性能和安全性能。
在任意实施方式中，所述正极活性材料的Dv50为5-15μm、可选为8-10μm。当所述正极活性材料的Dv50在上述范围时，所述正极活 性材料具有良好的结构稳定性，该正极活性材料具有的富锂层结构能够在充放电过程中维持稳定的层状结构，抑制Ni的层间迁移，减少释氧，从而改善电池的循环性能和安全性能。
在任意实施方式中，所述正极活性材料的锂镍混排程度为≤5％、可选为≤3％。本申请的正极活性材料的富锂层结构有效降低该正极活性材料的锂镍混排程度，维持层状结构稳定，从而使电池的循环性能和安全性能得以改善。
在任意实施方式中，所述正极活性材料中的M1元素与M2元素的重量比为1:0.1-1:1、可选为1:0.1-1:0.5。当所述正极活性材料中的M1元素与M2元素的重量比满足上述范围时，能够改善材料的结构稳定性，从而改善电池的循环性能和安全性能。
在任意实施方式中，所述正极活性材料还具有包覆物，所述包覆物的化学式为LieCoO2，其中0<e≤1。所述包覆物LieCoO2可以有效防止电解液在正极活性材料表面发生副反应，减少释氧，从而进一步改善电池的循环性能和安全性能。
在任意实施方式中，所述包覆物的厚度为0.01-0.2μm、可选为0.05-0.1μm。当所述包覆物的厚度在上述范围时，可以有效防止电解液在正极活性材料表面发生副反应，从而进一步改善电池的循环性能和安全性能。
在任意实施方式中，所述包覆物与所述正极活性材料的重量比为(0.002-0.02)：1、可选为(0.005-0.012)：1。当所述包覆物与所述正极活性材料的重量比满足上述范围时，有效改善电池的循环性能和安全性能。
在任意实施方式中，所述正极活性材料的(Dv90-Dv10)/Dv50为≥1.1、可选为≥1.2。当所述正极活性材料满足上述范围时，颗粒间填充度高，具有良好的分散性，能够有效提高电池的能量密度。
在任意实施方式中，所述正极活性材料5000kg/1.33cm2的压力下的压实密度为≥3.4g/cm3。所述正极活性材料具有高的压实密度，能够有效提高电池的能量密度。
本申请的第二方面提供一种正极活性材料的制备方法，所述方法包括以下步骤：
S1)将正极活性材料的前驱体和锂源进行低温共热以得到混合物，将该混合物、含M1元素的化合物、含M2元素的化合物混合，烧结，得到基体材料；
S2)将步骤S1)中得到的基体材料加入包含可溶性含Co的化合物和可溶性含Li的化合物的水溶液中进行水洗，过滤，干燥，得到正极活性材料；
其中，在所述步骤S1)中，所述低温共热的温度为150-400℃、可选为200-300℃，时间为1-6h、可选为2-4h，
所述正极活性材料的化学式为Li1+a[NixCoyMnzM1bM2c]O2，其中，0.05<a<0.5，1/3≤x<1，0≤y<1/3，0≤z<1/3，0<b<0.1，0<c<0.1，x+y+z+b+c＝1，M1为选自Mo、Zr、W、Sb、Nb、Te和Ga中的一种或多种元素，M2为选自Mg、Al、Ca和Ti中的一种或多种元素，可选地，0.1<a<0.2，0.6≤x<1，
所述正极活性材料为颗粒形状，包括有由颗粒表面向颗粒内部延伸的富锂层，在所述正极活性材料的单个颗粒中，在通过颗粒的几何中心的横截面上，所述富锂层中每单位面积上的平均Li元素含量与非富锂层中每单位面积上的平均Li元素含量之比为(>1-1.5):1，可选为(1.05-1.2):1。
由此，通过上述方法制备的具有富锂层结构的正极活性材料，不仅具有高的压实密度，能够有效提高电池的能量密度，而且具有改善的结构稳定性，有效防止电解液在正极活性材料表面发生副反应，从而改善电池的循环性能和安全性能。
在任意实施方式中，在所述步骤S1)中，所述锂源中的Li元素与所述正极活性材料的前驱体中的金属元素的摩尔比为1.2-1.5、可选为1.25-1.4，所述金属元素为Ni、Co和Mn，所述烧结温度为600-850℃，烧结时间为9-12h，烧结气氛为空气或氧气、可选为氧气。通过调控上述参数，能够使获得的正极活性材料具有高的压实密度和改善的结构稳定性。
在任意实施方式中，在所述步骤S1)中，所述含M1元素的化合物为含M1元素的氧化物、氢氧化物、碳酸盐、草酸盐或硝酸盐中的一种或多种，在所述步骤S1)中加入的M1元素的量为2000-5000ppm、 可选为3000-4000ppm，基于所述正极活性材料的前驱体的重量计；所述含M2元素的化合物为含M2元素的氧化物、氢氧化物、碳酸盐、草酸盐或硝酸盐中的一种或多种，在所述步骤S1)中加入的M2元素的量为200-2000ppm、可选为400-1000ppm，基于所述正极活性材料的前驱体的重量计。通过调控上述参数，能够使获得的正极活性材料具有改善的结构稳定性，从而改善电池的循环性能和安全性能。
在任意实施方式中，在所述步骤S2)中，所述可溶性含Co的化合物选自Co(CH3COO)2、CoC2O4、CoSO4、Co(NO3)2和CoCl2中的一种或多种，在所述步骤S2)中加入的Co元素的量为1000-20000ppm、可选为5000-13000ppm，基于所述正极活性材料的前驱体的重量计；所述可溶性含Li的化合物选自Li2SO4、LiNO3、LiC2O4、CH3COOLi和LiCl中的一种或多种，在所述S2)步骤中加入的Li元素的量为500-5000ppm、可选为1000-1500ppm，基于所述正极活性材料的前驱体的重量计。通过调控上述参数，可以获得具有富锂层结构的正极活性材料，从而改善电池的循环性能和安全性能。
在任意实施方式中，在所述步骤S2)中，水洗的温度为0-100℃、可选为5-50℃，水洗的时间为1-30min、可选为2-5min。通过调控上述参数，可以获得具有富锂层结构的正极活性材料，从而改善电池的循环性能和安全性能。
在任意实施方式中，在所述步骤S2)中，所述干燥为真空干燥，并且干燥温度为40-120℃、可选为80-100℃，干燥的时间为6-24h、可选为12-18h。
在任意实施方式中，在所述步骤S1)中，所述锂源选自LiOH·H2O、Li2CO3、Li2SO4、LiNO3、LiC2O4和CH3COOLi中的至少一种，可选为LiOH·H2O、Li2SO4和LiNO3中的至少一种。
在任意实施方式中，所述方法还包括步骤S3)：将步骤S2)得到正极活性材料与含Co化合物、含Li化合物混合，烧结温度为500-800℃、可选为550-750℃，烧结时间为5-15h、可选为5-10h，烧结气氛为空气或者O2，得到具有包覆物的正极活性材料，所述包覆物的化学式为LieCoO2，其中0<e≤1。通过调控上述参数，可以获得在正极活性材料上形成包覆层，有效防止电解液在正极活性材料表面发生副反应，减 少释氧，从而进一步改善电池的循环性能和安全性能。
在任意实施方式中，在所述步骤S3)中，所述含Co化合物选自Co3O4、Co(OH)2、CoO、CoOOH、Co(CH3COO)2、CoC2O4和CoCO3中的至少一种，所述含Co化合物颗粒的Dv50为0.001-10μm、可选为0.001-1μm，在所述步骤S3)中加入的Co元素的量为500-20000ppm、可选为2000-15000ppm，基于所述正极活性材料的前驱体的重量计；所述含Li化合物选自LiOH·H2O、Li2CO3、Li2SO4、LiNO3、LiC2O4和CH3COOLi中的至少一种，所述含Li化合物颗粒的Dv50为0.001-1μm、可选为0.01-0.05μm，在所述步骤S3)中加入的Li元素的量为100-3000ppm、可选为500-1500ppm，基于所述正极活性材料的前驱体的重量计。通过调控上述参数，可以获得在正极活性材料上形成包覆层，有效防止电解液在正极活性材料表面发生副反应，减少释氧，从而进一步改善电池的循环性能和安全性能。
本申请的第三方面提供一种二次电池，其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或本申请第三方面的正极极片。
本申请的第四方面提供一种用电装置，其包括选自本申请的第四方面的二次电池。
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是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6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；5二次电池；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、电池模块、电池包和电学装置的实施方式。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，如果列出的最小范围值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，所述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)。
层状富锂三元正极材料因其高的放电比容量和工作电压区间而备受关注。然而，富锂三元正极材料仍存在诸多问题，例如，由于Ni2+的半径(RNi 2+＝0.069nm)和Li+的半径(RLi+＝0.076nm)很接近，所以过渡金属层中的Ni2+很容易迁移到锂层，占据了锂层中Li+的位置，对Li+的传输造成阻碍，使得脱出的Li+无法嵌入晶格中，造成可逆比容量的减少，库伦效率降低；富锂三元正极材料在循环过程中会有部分过渡金属转移到四面体间隙中，因此材料结构会向尖晶石发生转变，导致电压衰减；层状富锂三元正极材料在高截止电压(>4.6V)下容易引起电解液分解，导致循环性能较差。目前通常是通过表面包覆、离子掺杂等手段来改善材料的电化学性能。但仍然需要不断改进制备工艺和改性手段，以提升富锂三元材料结构稳定性，抑制电压衰减，抑制其与电解液的副反应等，从而获得性能优异的富锂三元正极材料。
针对上述问题，本申请提供了一种正极活性材料，其特征在于，所述正极活性材料的化学式为Li1+a[NixCoyMnzM1bM2c]O2，其中，0.05<a<0.5，1/3≤x<1，0≤y<1/3，0≤z<1/3，0<b<0.1，0<c<0.1，x+y+z+b+c＝1，M1为选自Mo、Zr、W、Sb、Nb、Te和Ga中的一种或多种元素，M2为选自Mg、Al、Ca和Ti中的一种或多种元素，可选地，0.1<a<0.2，0.6≤x<1，
所述正极活性材料为颗粒形状，包括有由颗粒表面向颗粒内部延伸的富锂层，在所述正极活性材料的单个颗粒中，在通过颗粒的几何中心的横截面上，所述富锂层中每单位面积上的平均Li元素含量与非富锂层中每单位面积上的平均Li元素含量之比为(>1-1.5):1，可选为 (1.05-1.2):1。
虽然机理尚不明确，但本申请人意外地发现：不仅具有高的压实密度，能够有效提高电池的能量密度，而且具有改善的结构稳定性，有效防止电解液在正极活性材料表面发生副反应，从而改善电池的循环性能和安全性能。具体地，一方面，所述正极活性材料具有富锂层结构，这种富锂层结构能够在充放电过程中维持正极活性材料稳定的层状结构，促使Ni发生层内迁移，有效降低锂镍混排程度，同时Ni迁移形成的空位簇能够固定活化的晶格氧，减少释氧，从而改善电池的循环性能和安全性能；另一方面，所述正极活性材料中掺杂的M1和M2元素能够稳定晶格结构，有效改善正极活性材料的结构稳定性，从而进一步改善电池的循环性能和安全性能。
在一些实施方案中，述富锂层中每单位面积上的平均Li元素含量与非富锂层中每单位面积上的平均Li元素含量之比为例如至少1.01:1、至少1.05:1、至少1.1:1、至少1.18:1、至少1.2:1、至少1.3:1、至少1.4:1或至少1.5:1。在本申请中，所述正极活性材料中的Li元素含量及分布变化可采用本领域中已知的常用于检测Li元素含量的技术来获得，例如，采用日本Ulvac-Phi公司的PHI NanoTOFII型飞行时间二次质谱仪来获得材料中的Li元素含量及分布变化。
在一些实施方式中，所述正极活性材料满足：k＝2t/Dv50，并且k为大于0至0.6、可选为0.01至0.3，其中t为由正极活性材料的颗粒表面向颗粒内部延伸的富锂层的厚度，所述Dv50为所述正极活性材料的体积累计分布百分数达到50％时对应的粒径。当所述正极活性材料满足上式时，所述正极活性材料具有良好的结构稳定性，该正极活性材料具有的富锂层结构能够在充放电过程中维持稳定的层状结构，抑制Ni的层间迁移，减少释氧，从而改善电池的循环性能和安全性能。在另一些实施方式中，所述k为例如0.001以上、0.01以上、0.08以上、0.1以上、0.2以上、0.3以上、0.4以上、0.5以上或0.6以上。
在本申请中，所述由正极活性材料的颗粒表面向颗粒内部延伸的富锂层的厚度t为例如0.00475μm以上、0.0475μm以上、0.38μm以上、0.95μm以上、1.425μm以上、1.9μm以上或2.85μm以上。
在一些实施方式中，所述正极活性材料的Dv50为5-15μm、可选 为8-10μm。当所述正极活性材料的Dv50在上述范围时，所述正极活性材料具有良好的结构稳定性，该正极活性材料具有的富锂层结构能够在充放电过程中维持稳定的层状结构，抑制Ni的层间迁移，减少释氧，从而改善电池的循环性能和安全性能。
在一些实施方式中，所述正极活性材料的锂镍混排程度为≤5％、可选为≤3％。在另一些实施方式中，所述正极活性材料的锂镍混排程度为例如≤5％、≤4％、≤3.5％、≤3％、≤2.5％、≤2％、≤1.5％或≤1％。由于Ni2+的半径和Li+的半径很接近，所以过渡金属层中的Ni2+很容易迁移到锂层而占据锂的位点，引起阳离子混排(即锂镍混排)，导致正极活性材料结构稳定性变差。正极活性材料的性能随着阳离子混排程度增加而降低。然而，本申请的正极活性材料的富锂层结构能够促使Ni发生层内迁移而抑制其层间迁移，有效降低锂镍混排程度，维持层状结构稳定，同时Ni迁移形成的空位簇能够固定活化的晶格氧，减少释氧，从而使电池的循环性能和安全性能得以改善。
在本申请中，可利用德国布鲁克公司的D8Advance型X射线衍射仪(XRD)得到正极活性材料的XRD图谱，并通过开源软件(即GSAS软件)得到正极活性材料的锂镍混排程度值。
在一些实施方式中，所述正极活性材料中的M1元素与M2元素的重量比为1:0.1-1:1、可选为1:0.1-1:0.5。当所述正极活性材料中的M1元素与M2元素的重量比满足上述范围时，能够改善材料的结构稳定性，从而改善电池的循环性能和安全性能。在本申请中，M1元素与M2元素的量通过本领域中已知的常用于测量掺杂元素含量的检测技术例如电感耦合等离子体发射光谱(ICP)来测得。
在一些实施方式中，所述正极活性材料还具有包覆物，所述包覆物的化学式为LieCoO2，其中0<e≤1。所述包覆物LieCoO2可以有效防止电解液在正极活性材料表面发生副反应，减少释氧，从而进一步改善电池的循环性能和安全性能。
在一些实施方式中，所述包覆物的厚度为0.01-0.2μm、可选为0.05-0.1μm。当所述包覆物的厚度在上述范围时，可以有效防止电解液在正极活性材料表面发生副反应，从而进一步改善电池的循环性能和安全性能。
在一些实施方式中，所述包覆物与所述正极活性材料的重量比为(0.002-0.02)：1、可选为(0.005-0.012)：1。当所述包覆物与所述正极活性材料的重量比满足上述范围时，有效改善电池的循环性能和安全性能。
在一些实施方式中，所述正极活性材料的(Dv90-Dv10)/Dv50为≥1.1、可选为≥1.2。当所述正极活性材料满足上述范围时，颗粒间填充度高，具有良好的分散性，能够有效提高电池的能量密度。
在本申请中，所述Dv10、Dv50和Dv90为所述正极活性材料经体积粒度分布测量的粒径，其中所述Dv10为样品的体积累计百分数达到10％时对应的粒径，所述Dv50为样品的体积累计百分数达到50％时对应的粒径，所述Dv90为样品的体积累计百分数达到90％时对应的粒径。
在一些实施方式中，所述正极活性材料在5000kg/1.33cm2的压力下的压实密度为≥3.4g/cm3。所述正极活性材料具有高的压实密度，能够有效提高电池的能量密度。压实密度可依据GB/T 24533-2009测量。
本申请的第二方面提供一种正极活性材料的制备方法，所述方法包括以下步骤：
S1)将正极活性材料的前驱体和锂源进行低温共热以得到混合物，将该混合物、含M1元素的化合物、含M2元素的化合物混合，烧结，得到基体材料；
S2)将步骤S1)中得到的基体材料加入包含可溶性含Co的化合物和可溶性含Li的化合物的水溶液中进行水洗，过滤，干燥，得到正极活性材料；
其中，在所述步骤S1)中，所述低温共热的温度为150-400℃、可选为200-300℃，时间为1-6h、可选为2-4h，
所述正极活性材料的化学式为Li1+a[NixCoyMnzM1bM2c]O2，其中，0.05<a<0.5，1/3≤x<1，0≤y<1/3，0≤z<1/3，0<b<0.1，0<c<0.1，x+y+z+b+c＝1，M1为选自Mo、Zr、W、Sb、Nb、Te和Ga中的一种或多种元素，M2为选自Mg、Al、Ca和Ti中的一种或多种元素，可选地，0.1<a<0.2，0.6≤x<1，
所述正极活性材料为颗粒形状，包括有由颗粒表面向颗粒内部延 伸的富锂层，在所述正极活性材料的单个颗粒中，在通过颗粒的几何中心的横截面上，所述富锂层中每单位面积上的平均Li元素含量与非富锂层中每单位面积上的平均Li元素含量之比为(>1-1.5):1，可选为(1.05-1.2):1。
由此，通过上述方法制备的具有富锂层结构的正极活性材料，不仅具有高的压实密度，能够有效提高电池的能量密度，而且具有改善的结构稳定性，有效防止电解液在正极活性材料表面发生副反应，从而改善电池的循环性能和安全性能。
在本申请中，所述正极活性材料的前驱体的制备可以通过现有技术中已知的方法例如氢氧化物共沉淀法制得，例如通过CN 111384372 A中记载方法制得。更具体地，所述第一正极活性材料A的前驱体可以是包括但不限于Ni0.8Co0.1Mn0.1(OH)2、Ni0.9Co0.05Mn0.05(OH)2、Ni0.7Co0.1Mn0.2(OH)2、Ni0.96Co0.03Mn0.01(OH)2、Ni0.75Co0.1Mn0.15(OH)2。所述第二正极活性材料B的前驱体可以是包括但不限于Ni0.8Co0.1Mn0.1(OH)2、Ni0.9Co0.05Mn0.05(OH)2、Ni0.7Co0.1Mn0.2(OH)2、Ni0.96Co0.03Mn0.01(OH)2、Ni0.75Co0.1Mn0.15(OH)2。
在一些实施方式中，在所述骤S1)中，所述低温供热温度为例如200-250℃。
在一些实施方式中，在所述步骤S1)中，所述锂源中的Li元素与所述正极活性材料的前驱体中的金属元素的摩尔比为1.2-1.5、可选为1.25-1.4，所述金属元素为Ni、Co和Mn，所述烧结温度为600-850℃，烧结时间为9-12h，烧结气氛为空气或氧气、可选为氧气。通过Li元素与前驱体中的金属元素的摩尔比、烧结温度和烧结时间，能够使获得的正极活性材料具有高的压实密度和改善的结构稳定性。
在一些实施方式中，在所述步骤S1)中，所述含M1元素的化合物为含M1元素的氧化物、氢氧化物、碳酸盐、草酸盐或硝酸盐中的一种或多种，在所述步骤S1)中加入的M1元素的量为2000-5000ppm、可选为3000-4000ppm，基于所述正极活性材料的前驱体的重量计；所述含M2元素的化合物为含M2元素的氧化物、氢氧化物、碳酸盐、草酸盐或硝酸盐中的一种或多种，在所述步骤S1)中加入的M2元素的量为200-2000ppm、可选为400-1000ppm，基于所述正极活性材料的 前驱体的重量计。通过分别选择M1元素与M2元素的来源以及调控其各自的含量，能够使获得的正极活性材料具有改善的结构稳定性，从而改善电池的循环性能和安全性能。
在一些实施方式中，在所述步骤S2)中，所述可溶性含Co的化合物选自Co(CH3COO)2、CoC2O4、CoSO4、Co(NO3)2和CoCl2中的一种或多种，在所述步骤S2)中加入的Co元素的量为1000-20000ppm、可选为5000-13000ppm，基于所述正极活性材料的前驱体的重量计；所述可溶性含Li的化合物选自Li2SO4、LiNO3、LiC2O4、CH3COOLi和LiCl中的一种或多种，在所述S2)步骤中加入的Li元素的量为500-5000ppm、可选为1000-1500ppm，基于所述正极活性材料的前驱体的重量计。通过选择可溶性含Co的化合物并调控加入的Co元素的量以及选择可溶性含Li的化合物并调控加入的Li元素的量，可以获得具有富锂层结构的正极活性材料，从而改善电池的循环性能和安全性能。
在一些实施方式中，在所述步骤S2)中，水洗的温度为0-100℃、可选为5-50℃、进一步可选为10-30℃，水洗的时间为1-30min、可选为2-5min。通过调控步骤S2)中的水洗温度和时间，可以获得具有富锂层结构的正极活性材料，从而改善电池的循环性能和安全性能。
在一些实施方式中，在所述步骤S2)中，所述干燥为真空干燥，并且干燥温度为40-120℃、可选为80-100℃，干燥的时间为6-24h、可选为12-18h。
在一些实施方式中，在所述步骤S1)中，所述锂源选自LiOH·H2O、Li2CO3、Li2SO4、LiNO3、LiC2O4和CH3COOLi中的至少一种，可选为LiOH·H2O、Li2SO4和LiNO3中的至少一种。
在一些实施方式中，所述方法还包括步骤S3)：将步骤S2)得到正极活性材料与含Co化合物、含Li化合物混合，烧结温度为500-800℃、可选为550-750℃，烧结时间为5-15h、可选为5-10h，烧结气氛为空气或者O2，得到具有包覆物的正极活性材料，所述包覆物的化学式为LieCoO2，其中0<e≤1。通过加入含Co化合物和含Li化合物，可以在正极活性材料上形成包覆层，该包覆层能够有效防止电解液在正极活性材料表面发生副反应，减少释氧，从而进一步改善电池的循环性能和 安全性能。
在一些实施方式中，在所述步骤S3)中，所述含Co化合物选自Co3O4、Co(OH)2、CoO、CoOOH、Co(CH3COO)2、CoC2O4和CoCO3中的至少一种，所述含Co化合物颗粒的Dv50为0.001-10μm、可选为0.001-1μm，在所述步骤S3)中加入的Co元素的量为500-20000ppm、可选为2000-15000ppm，基于所述正极活性材料的前驱体的重量计；所述含Li化合物选自LiOH·H2O、Li2CO3、Li2SO4、LiNO3、LiC2O4和CH3COOLi中的至少一种，所述含Li化合物颗粒的Dv50为0.001-1μm、可选为0.01-0.05μm，在所述步骤S3)中加入的Li元素的量为100-3000ppm、可选为500-1500ppm，基于所述正极活性材料的前驱体的重量计。通过调控上述参数，可以获得在正极活性材料上形成包覆层，有效防止电解液在正极活性材料表面发生副反应，减少释氧，从而进一步改善电池的循环性能和安全性能。
本申请的第三方面提供一种正极极片，所述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或通过本申请第二方面的方法制备的正极活性材料，并且所述正极活性材料在所述正极膜层中的含量为10重量％以上，基于所述正极膜层的总重量计。
本申请的第四方面提供一种二次电池，其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或本申请第三方面的正极极片。
本申请的第五方面提供一种用电装置，其包括选自本申请的第四方面的二次电池。
在本申请中，二次电池例如可以为电池单体的形式，可以为电池模块的形式，也可以为电池包的形式。电池模块和电池包中包含电池单体，电池包也可以包含电池模块。
在一些实施方式中，所述电池单体可以组装成电池模块。在一些实施方式中，所述电池单体可以组装成电池包。在一些实施方式中，所述电池模块可以组装成电池包。
另外，以下适当参照附图对本申请的二次电池(以电池单体的形式)、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、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。在本申请中，电池群裕度为90-95％。
[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，正极活性材料可采用本申请第一方面的正极活性材料。所述正极活性材料在正极膜层中的重量比为80-100重量％，基于正极膜层的总重量计。
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。所述粘结剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。
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。所述导电剂在正极膜层中的 重量比为0-20重量％，基于正极膜层的总重量计。
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；其中所述正极浆料固含量为40-80wt％，室温下的粘度调整到5000-25000mPa·s，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,正极粉末涂布单位面密度为150-350mg/m2，正极极片压实密度为3.0-3.6g/cm3，可选为3.3-3.5g/cm3。所述压实密度的计算公式为
压实密度＝涂布面密度/(挤压后极片厚度-集流体厚度)。
[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。所述负极 极活性材料可以具有1μm-15μm、优选4μm-9μm的平均粒径(D10)，具有12μm-22μm、优选14μm-17μm的平均粒径(D50)，并且具有26μm至40μm、优选30μm-37μm的平均粒径(D90)。D10为样品的体积累计分布百分数达到10％时对应的粒径；D50为样品的体积累计分布百分数达到50％时对应的粒径；D90为样品的体积累计分布百分数达到90％时对应的粒径。所述负极活性材料在负极膜层中的重量比为70-100重量％，基于负极膜层的总重量计。
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。所述粘结剂在负极膜层中的重量比为0-30重量％，基于负极膜层的总重量计。
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。所述导电剂在负极膜层中的重量比为0-20重量％，基于负极膜层的总重量计。
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。所述其他助剂在负极膜层中的重量比为0-15重量％，基于负极膜层的总重量计。
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，其中所述负极浆料固含量为30-70wt％，室温下的粘度调整到2000-10000mPa·s；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。负极粉末涂布单位面密度为75-220mg/m2，负极极片压实密度1.2-2.0g/m3。
[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。所述电解质盐的浓度通常为0.5-5mol/L。
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，二次电池中还包括隔离膜。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，所述隔离膜的厚度为6-40μm，可选为12-20μm。
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，二次电池可包括外包装。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，二次电池的外包装可以是硬壳，例如硬塑料 壳、铝壳、钢壳等。二次电池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。
本申请对二次电池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1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，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。二次电池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，二次电池可以组装成电池模块，电池模块所含二次电池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3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池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二次电池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，多个二次电池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4和图5是作为一个示例的电池包1。参照图4和图5，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、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包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***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、电池模块或电池包。
图6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，可以采用二次电池作为电源。
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。
一、二次电池的制备
实施例1
1.正极活性材料的制备
1)正极活性材料的前驱体的制备
将硫酸镍、硫酸钴、硫酸锰按摩尔比9:0.5:0.5配置成2mol/L金属盐溶液，随后将该金属盐溶液、8mol/L的氨水、5mol/L的NaOH溶液连续加入反应釜中进行反应，通过控制反应过程中的pH值为11.30、氨浓度为4.0g/L、反应时间20h、搅拌速率300r/min，利用氢氧化物共沉淀法，制备正极活性材料的前驱体(Ni0.9Co0.05Mn0.05(OH)2)，粒径Dv50 为9.5μm。
2)正极活性材料的制备
S1)将氢氧化锂和制得的上述正极活性材料的前驱体按照摩尔比Li/Me(Me为Ni、Co和Mn的总摩尔)为1.3:1在250℃进行低温共热3h，得到混合物，将该混合物与五氧化二铌(Nb2O5)、氧化铝(Al2O3)置于犁刀混合机中混合均匀，其中氢氧化锂、正极活性材料的前驱体、Nb2O5、Al2O3的摩尔比为1.3:1:0.0020:0.0036，随后将物料放入窑炉中烧结，烧结温度为780℃，烧结时间为12h，烧结气氛为氧气，冷却后，得到基体材料；
S2)将上述得到的基体材料加入含醋酸钴((CH3COO)2Co)和醋酸锂(CH3COOLi)的水溶液中，其中Co元素的量为5000ppm，Li元素的量为1000ppm，在10℃下水洗3min，过滤，随后在105℃的真空干燥烘箱中干燥24h，冷却后，通过机械破碎得到正极活性材料Li1.15Ni0.8950Co0.0497Mn0.0497Nb0.002Al0.0036O2，粒径Dv50为9.5μm。
2.扣式电池的制备
【正极极片】将上述获得的正极活性材料、聚偏二氟乙烯(PVDF)、乙炔黑以90：5：5的重量比加入至N-甲基吡咯烷酮(NMP)中，在干燥房中搅拌制成浆料。在铝箔上涂覆上述浆料，干燥、冷压制成正极极片。涂覆量为0.01g/cm2，压实密度为3.5g/cm3。
【负极极片】将0.5mm锂金属片作为负极极片。
【电解液】将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)体积比1:1:1混合，然后将LiPF6均匀溶解在上述溶液中得到电解液，其中LiPF6的浓度为1mol/L。
【隔离膜】
隔离膜采购自Cellgard企业，型号为cellgard 2400。
将上述制备的正极极片、负极极片、隔离膜和电解液在扣电箱中组装成CR2032型扣式电池(下文也称“扣电”)。
3.全电池的制备
【正极极片】将上述获得的正极活性材料与乙炔黑、聚偏二氟乙烯(PVDF)按重量比94:3:3在N-甲基吡咯烷酮(NMP)中混合均匀后，涂覆于铝箔上并烘干、冷压，得到正极极片。涂覆量为0.176g/cm2，压实密度为3.5g/cm3。
【负极极片】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)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比90:5:2:2:1在去离子水中混合均匀后，涂覆于铜箔上烘干、冷压，得到负极极片。涂覆量为0.124g/cm2，压实密度为1.6g/cm3。
【电解液】将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)体积比1:1:1混合，然后将LiPF6均匀溶解在上述溶液中得到电解液，其中LiPF6的浓度为1mol/L。
【隔离膜】以PE多孔聚合薄膜作为隔离膜。
将上述正极极片、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，注入电解液并封装，得到全电池(下文也称“全电”)。全电池的长×宽×高＝90mm×30mm×60mm，电池的群裕度为91.0％。
实施例2
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，摩尔比Li/Me为1.2:1，在步骤S2)中加入的Li元素的量为1200ppm。
实施例3
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，摩尔比Li/Me为1.25:1，在步骤S2)中加入的Li元素的量为1500ppm。
实施例4
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，摩尔比Li/Me为1.35:1，在步骤S2)中加入的Li元素的量为1800ppm。
实施例5
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，摩尔比Li/Me为1.38:1，在步骤S2)中加入的Li元素的量为2000ppm。
实施例6
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，摩尔比Li/Me为1.4:1，在步骤S2)中加入的Li元素的量为2500ppm。
实施例7
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，摩尔比Li/Me为1.5:1，在步骤S2)中加入的Li元素的量为3000ppm。
实施例8
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，使用二氧化锆(ZrO2)和硫酸镁(MgSO4)，其中Zr元素的量为2000ppm且Mg元素的量为200ppm，基于所述正极活性材料的前驱体重量计；氢氧化锂、正极活性材料的前驱体、ZrO2、MgSO4的摩尔比为1.3:1:0.0021:0.0008。
实施例9
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，使用钨酸(H2WO4)和二氧化钛(TiO2)，其中W元素的量为3000ppm且Ti元素的量为1500ppm，基于所述正极活性材料的前驱体重量计；氢氧化锂、正极活性材料的前驱体、H2WO4、TiO2的摩尔比为1.3:1:0.0016:0.0031。
实施例10
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，使用三氧化钼(MoO3)和碳酸钙(CaCO3)，其中Mo元素的量为2000ppm且Ca元素的量为2000ppm，基于所述正极活性材料的前驱体重量计；氢氧化锂、正极活性材料的前驱体、MoO3、CaCO3的摩尔比为1.3:1:0.0020:0.0050。
实施例11
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，低温共热温度为200℃。
实施例12
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S1)中，低温共热温度为400℃。
实施例13
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S2)中，水洗温度为20℃，水洗时间为2min。
实施例14
与实施例1相同，区别在于：在正极活性材料的制备中，在步骤S2)中，水洗温度为30℃，水洗时间为1min。
实施例15
将实施例1中得到的正极活性材料与CoOOH、CH3COOLi在斜混机中按重量比1:0.0140：0.0094进行混合，其中CoOOH颗粒的Dv50为0.05μm、Co元素的量为9000ppm，CH3COOLi颗粒的Dv50为0.01μm、Li元素的量为1000ppm，随后将物料放入窑炉中烧结，烧结温度为600℃，烧结时间为8h，烧结气氛为氧气，冷却后，得到包覆物为Li0.6CoO2。
实施例16
与实施例15相同，区别在于：将正极活性材料与CoOOH、CH3COOLi在斜混机中按重量比1:0.0023:0.0047进行混合，其中Co元素的量为1500ppm，Li元素的量为500ppm。
实施例17
与实施例15相同，区别在于：将正极活性材料与CoOOH、CH3COOLi在斜混机中按重量比1:0.0062:0.0094进行混合，其中Co元素的量为4000ppm，Li元素的量为1000ppm。
实施例18
与实施例15相同，区别在于：将正极活性材料与CoOOH、CH3COOLi在斜混机中按重量比1:0.0163:0.0141进行混合，其中Co元素的量为10500ppm，Li元素的量为1500ppm。
实施例19
与实施例15相同，区别在于：将正极活性材料与CoOOH、CH3COOLi在斜混机中按重量比1:0.0264:0.0282进行混合，其中Co元素的量为17000ppm，Li元素的量为3000ppm。
对比例1
正极活性材料的前驱体的制备与实施例1相同。
将氢氧化锂、正极活性材料的前驱体、Nb2O5、Al2O3的摩尔比为1.05：1：0.0020：0.0036，随后将物料放入窑炉中烧结，烧结温度为780℃，烧结时间为12h，烧结气氛为氧气，冷却后，通过机械破碎得到正极活性材料Li1.03Ni0.8950Co0.0497Mn0.0497Nb0.002Al0.0036O2，粒径Dv50为9.5μm。
二、相关参数的测试
(1)粒径测试
根据GB/T 19077.1-2016/ISO 13320:2009(粒度分布激光衍射法)测 定正极活性材料的粒径。取一洁净烧杯，加入适量的上述正极活性材料，加入适量纯水，超声120W/5min确保材料粉末在水中完全分散。溶液倒入激光粒度分析仪(马尔文公司，型号：Mastersizer3000)的进样塔后随溶液循环到测试光路***，颗粒在激光束的照射下，通过接受和测量散向光的能量分布可得到颗粒的粒度分布特征(遮光度：8-12％)，读取Dv10、Dv50、Dv90的相应数值。
结果参见表1和表2。
(2)Li元素含量及分布变化的测试
将所得正极材料与导电树脂进行混合，待其凝固后在离子减薄仪上进行减薄(仪器公司：德国徕卡，型号：RES102)，将减薄后的样品置于飞行时间二次质谱仪中(仪器公司：日本Ulvac-Phi，型号：PHI NanoTOFII)，采用初级离子源(Bi源)轰击正极材料切面并激发出材料切面上的离子，采用离子收集器进行收集，通过计算离子质量M＝6.99(Li+)处的含量变化来收集Li元素含量情况，并观察正极材料切面上的Li元素分布情况。
结果参见表1和表2。
(3)锂镍混排程度测试
将所得正极粉末材料充分研磨，放置于在XRD衍射仪载玻片凹槽上，将载玻片置于XRD衍射仪中(仪器公司：德国布鲁克，型号：D8 Advance)，以1o/min的扫描速度对正极材料进行扫描，收集得到的XRD图谱。将XRD图谱原始数据导入GSAS精修软件(开源软件)中，采用Reitveld精修法对XRD图谱进行精修，并最终计算出锂镍混排程度值。
结果参见表1和表2。
(4)压实密度测试
取一定量的粉末放于压实专用模具中,然后将模具放在压实密度仪器上。施加5000kg(加压面积为1.33cm2)的压力，在设备上读出压力下粉末的厚度(卸压后的厚度)，通过ρ＝m/v，计算出压实密度。
结果参见表1和表2。
三、电池性能的测试
(1)扣式电池初始克容量及首效测试
在2.8～4.3V下，将扣式电池按照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。
首效按照D0/C0*100％计算得到。
结果参见表3。
(2)全电初始克容量测试
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≤0.05C，静置5min，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D0。
结果参见表3。
(3)25℃下全电池容量保持率
在25℃下，以1C的恒定电流充电至4.25V，后以4.25V恒压充电至电流降到0.05C，再以1C的恒定电流放电至2.8V，得首周放电比容量(Cd1)；如此反复充放电至第300周，得锂离子电池循环n周后的放电比容量记为Cdn。容量保持率＝循环n周后的放电比容量(Cdn)/首周放电比容量(Cd1)。
结果参见表3。
(4)45℃下全电池容量保持率
在45℃下，以1C的恒定电流充电至4.25V，后以4.25V恒压充电至电流降到0.05C，再以1C的恒定电流放电至2.8V，得首周放电比容量(Cd1)；如此反复充放电至第300周，得锂离子电池循环n周后的放电比容量记为Cdn。容量保持率＝循环n周后的放电比容量(Cdn)/首周放电比容量(Cd1)。
结果参见表3。
(5)全电池70℃胀气测试
在70℃下，存储100％充电状态(SOC)的全电池。在存储前后及过程中测量电芯的开路电压(OCV)和交流内阻(IMP)以监控SOC，并测量电芯的体积。其中在每存储48h后取出全电池，静置1h后测试OCV、IMP，并在冷却至室温后用排水法测量电芯体积。排水法即先用表盘数据自动进行单位转换的天平单独测量电芯的重力F1，然后将电芯完全置于去离子水(密度已知为1g/cm3)中，测量此时的电芯的重力F2，电芯受到的浮力F浮即为F1-F2，然后根据阿基米德原理F浮＝ρgV_排，计算得到电芯体积V＝(F1-F2)/ρg。
每次测试完体积后，对电芯进行补电，以1C的恒定电流充电至4.25V，后以4.25V恒压充电至电流降到0.05C，补电完成后入炉继续测试。
存储30天后，测量电芯体积，并计算相对于存储前的电芯体积，存储后的电芯体积增加量，即产气量。
结果参见表3。
从表1至表3中的结果可以看出，与对比例1相比，一方面本申请的正极活性材料具有高的压实密度，从而使电池具有高的能量密度；另一方面，本申请的正极活性材料因具有富锂层结构，在充放电过程中，能够保持优异的结构稳定性，有效降低锂镍混排程度，有效防止电解液在正极活性材料表面发生副反应，减少释氧，大大提高的电池的循环性能和安全性能。此外，在本申请的正极活性材料表面上形成包覆物LieCoO2能够进进一步有效防止电解液在正极活性材料表面发生副反应，从而进一步改善电池的循环性能和安全性能。
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 (21)

  1. 一种正极活性材料，其特征在于，所述正极活性材料的化学式为Li1+a[NixCoyMnzM1bM2c]O2，其中，0.05<a<0.5，1/3≤x<1，0≤y<1/3，0≤z<1/3，0<b<0.1，0<c<0.1，x+y+z+b+c＝1，M1为选自Mo、Zr、W、Sb、Nb、Te和Ga中的一种或多种元素，M2为选自Mg、Al、Ca和Ti中的一种或多种元素，可选地，0.1<a<0.2，0.6≤x<1，
    所述正极活性材料为颗粒形状，包括有由颗粒表面向颗粒内部延伸的富锂层，在所述正极活性材料的单个颗粒中，在通过颗粒的几何中心的横截面上，所述富锂层中每单位面积上的平均Li元素含量与非富锂层中每单位面积上的平均Li元素含量之比为(>1-1.5):1，可选为(1.05-1.2):1。
  2. 根据权利要求1所述的正极活性材料，其特征在于，所述正极活性材料满足：k＝2t/Dv50，并且k为大于0至0.6、可选为0.01至0.3，其中t为由正极活性材料的颗粒表面向颗粒内部延伸的富锂层的厚度，所述Dv50为所述正极活性材料的体积累计分布百分数达到50％时对应的粒径。
  3. 根据权利要求1或2所述的正极活性材料，其特征在于，所述正极活性材料的Dv50为5-15μm、可选为8-10μm。
  4. 根据权利要求1或2所述的正极活性材料，其特征在于，所述正极活性材料的锂镍混排程度为≤5％、可选为≤3％。
  5. 根据权利要求1或2所述的正极活性材料，其特征在于，所述正极活性材料中的M1元素与M2元素的重量比为1:0.1-1:1、可选为1:0.1-1:0.5。
  6. 根据权利要求1或2所述的正极活性材料，其特征在于，所述正极活性材料还具有包覆物，所述包覆物的化学式为LieCoO2，其中0<e≤1。
  7. 根据权利要求6所述的正极活性材料，其特征在于，所述包覆物的厚度为0.01-0.2μm、可选为0.05-0.1μm。
  8. 根据权利要求6所述的正极活性材料，其特征在于，所述包覆物与所述正极活性材料的重量比为(0.002-0.02)：1、可选为 (0.005-0.012)：1。
  9. 根据权利要求1或2所述的正极活性材料，其特征在于，所述正极活性材料的(Dv90-Dv10)/Dv50为≥1.1、可选为≥1.2。
  10. 根据权利要求1或2所述的正极活性材料，其特征在于，所述正极活性材料在5000kg/1.33cm2的压力下的压实密度为≥3.4g/cm3。
  11. 一种正极活性材料的制备方法，其特征在于，所述方法包括以下步骤：
    S1)将正极活性材料的前驱体和锂源进行低温共热以得到混合物，将该混合物、含M1元素的化合物、含M2元素的化合物混合，烧结，得到基体材料；
    S2)将步骤S1)中得到的基体材料加入包含可溶性含Co的化合物和可溶性含Li的化合物的水溶液中进行水洗，过滤，干燥，得到正极活性材料；
    其中，在所述步骤S1)中，所述低温共热的温度为150-400℃、可选为200-300℃，时间为1-6h、可选为2-4h，
    所述正极活性材料的化学式为Li1+a[NixCoyMnzM1bM2c]O2，其中，0.05<a<0.5，1/3≤x<1，0≤y<1/3，0≤z<1/3，0<b<0.1，0<c<0.1，x+y+z+b+c＝1，M1为选自Mo、Zr、W、Sb、Nb、Te和Ga中的一种或多种元素，M2为选自Mg、Al、Ca和Ti中的一种或多种元素，可选地，0.1<a<0.2，0.6≤x<1，
    所述正极活性材料为颗粒形状，包括有由颗粒表面向颗粒内部延伸的富锂层，在所述正极活性材料的单个颗粒中，在通过颗粒的几何中心的横截面上，所述富锂层中每单位面积上的平均Li元素含量与非富锂层中每单位面积上的平均Li元素含量之比为(>1-1.5):1，可选为(1.05-1.2):1。
  12. 根据权利要求11所述的正极活性材料的制备方法，其特征在于，在所述步骤S1)中，所述锂源中的Li元素与所述正极活性材料的前驱体中的金属元素的摩尔比为1.2-1.5、可选为1.25-1.4，所述金属元素为Ni、Co和Mn，所述烧结温度为600-850℃，烧结时间为9-12h，烧结气氛为空气或氧气、可选为氧气。
  13. 根据权利要求11所述的正极活性材料的制备方法，其特征在 于，在所述步骤S1)中，所述含M1元素的化合物为含M1元素的氧化物、氢氧化物、碳酸盐、草酸盐或硝酸盐中的一种或多种，在所述步骤S1)中加入的M1元素的量为2000-5000ppm、可选为3000-4000ppm，基于所述正极活性材料的前驱体的重量计；所述含M2元素的化合物为含M2元素的氧化物、氢氧化物、碳酸盐、草酸盐或硝酸盐中的一种或多种，在所述步骤S1)中加入的M2元素的量为200-2000ppm、可选为400-1000ppm，基于所述正极活性材料的前驱体的重量计。
  14. 根据权利要求11所述的正极活性材料的制备方法，其特征在于，在所述步骤S2)中，所述可溶性含Co的化合物选自Co(CH3COO)2、CoC2O4、CoSO4、Co(NO3)2和CoCl2中的一种或多种，在所述步骤S2)中加入的Co元素的量为1000-20000ppm、可选为5000-13000ppm，基于所述正极活性材料的前驱体的重量计；所述可溶性含Li的化合物选自Li2SO4、LiNO3、LiC2O4、CH3COOLi和LiCl中的一种或多种，在所述S2)步骤中加入的Li元素的量为500-5000ppm、可选为1000-1500ppm，基于所述正极活性材料的前驱体的重量计。
  15. 根据权利要求11所述的正极活性材料的制备方法，其特征在于，在所述步骤S2)中，水洗的温度为0-100℃、可选为5-50℃，水洗的时间为1-30min、可选为2-5min。
  16. 根据权利要求11所述的正极活性材料的制备方法，其特征在于，在所述步骤S2)中，所述干燥为真空干燥，并且干燥温度为40-120℃、可选为80-100℃，干燥的时间为6-24h、可选为12-18h。
  17. 根据权利要求11所述的正极活性材料的制备方法，其特征在于，在所述步骤S1)中，所述锂源选自LiOH·H2O、Li2CO3、Li2SO4、LiNO3、LiC2O4和CH3COOLi中的至少一种，可选为LiOH·H2O、Li2SO4和LiNO3中的至少一种。
  18. 根据权利要求11所述的正极活性材料的制备方法，其特征在于，所述方法还包括步骤S3)：将步骤S2)得到正极活性材料与含Co化合物、含Li化合物混合，烧结温度为500-800℃、可选为550-750℃，烧结时间为5-15h、可选为5-10h，烧结气氛为空气或者O2，得到具有包覆物的正极活性材料，所述包覆物的化学式为LieCoO2，其中0<e≤1。
  19. 根据权利要求18所述的正极活性材料的制备方法，其特征在 于，在所述步骤S3)中，所述含Co化合物选自Co3O4、Co(OH)2、CoO、CoOOH、Co(CH3COO)2、CoC2O4和CoCO3中的至少一种，所述含Co化合物颗粒的Dv50为0.001-10μm、可选为0.001-1μm，在所述步骤S3)中加入的Co元素的量为500-20000ppm、可选为2000-15000ppm，基于所述正极活性材料的前驱体的重量计；所述含Li化合物选自LiOH·H2O、Li2CO3、Li2SO4、LiNO3、LiC2O4和CH3COOLi中的至少一种，所述含Li化合物颗粒的Dv50为0.001-1μm、可选为0.01-0.05μm，在所述步骤S3)中加入的Li元素的量为100-3000ppm、可选为500-1500ppm，基于所述正极活性材料的前驱体的重量计。
  20. 一种二次电池，其特征在于，所述二次电池包括权利要求1-10中任一项所述的正极活性材料或通过权利要求11-19中任一项所述的方法制得的正极活性材料。
  21. 一种用电装置，其特征在于，包括权利要求20所述的二次电池。
PCT/CN2023/111442 2022-12-01 2023-08-07 正极活性材料及其制备方法、二次电池和用电装置 WO2024113942A1 (zh)

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