WO2024178675A1 - 正极活性物质、正极极片、二次电池、用电装置和制备方法 - Google Patents

正极活性物质、正极极片、二次电池、用电装置和制备方法 Download PDF

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Publication number
WO2024178675A1
WO2024178675A1 PCT/CN2023/079055 CN2023079055W WO2024178675A1 WO 2024178675 A1 WO2024178675 A1 WO 2024178675A1 CN 2023079055 W CN2023079055 W CN 2023079055W WO 2024178675 A1 WO2024178675 A1 WO 2024178675A1
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Prior art keywords
active
positive electrode
particle
particles
active material
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PCT/CN2023/079055
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English (en)
French (fr)
Inventor
陈宁
金海族
史东洋
邓亚茜
刘智
吕瑞景
李白清
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2023/079055 priority Critical patent/WO2024178675A1/zh
Priority to CN202511903047.3A priority patent/CN121709595A/zh
Priority to EP23924645.7A priority patent/EP4601040A4/en
Priority to CN202511970764.8A priority patent/CN121709596A/zh
Priority to CN202380054323.6A priority patent/CN119604991B/zh
Publication of WO2024178675A1 publication Critical patent/WO2024178675A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/42—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2
    • C01G53/44—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/42—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2
    • C01G53/44—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2
    • C01G53/502—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt
    • C01G53/504—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5
    • C01G53/506—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5 with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.8, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.8
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/80—Compounds containing nickel, with or without oxygen or hydrogen, and containing one or more other elements
    • C01G53/84—Hydroxides
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • 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
    • 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 lithium-ion batteries, and in particular to a positive electrode active material, a positive electrode sheet, a secondary battery, an electrical device and a preparation method.
  • the present application provides a positive electrode active material, a positive electrode plate, a secondary battery, an electrical device and a preparation method.
  • the positive electrode active material By using the positive electrode active material, the storage life can be improved while maintaining basically no loss in energy density.
  • the present application provides a positive electrode active material, comprising a first active particle and a second active particle; wherein the first active particle is a polycrystalline particle in the positive electrode active material, and its particle size parameter (D v 90-D v 10)/D v 50 is recorded as X1; the second active particle is a single crystal or quasi-single crystal particle in the positive electrode active material, and its particle size parameter (D v 90-D v 10)/D v 50 is recorded as X2;
  • X1/X2 satisfies 0.2 ⁇ X1/X2 ⁇ 0.7;
  • D v 90, D v 50 and D v 10 represent the particle sizes corresponding to when the cumulative volume distribution percentage of the multi-particle combination reaches 90%, 50% and 10%, respectively.
  • the positive electrode active material adopts a combination of polycrystalline active particles with special particle size distribution characteristics and single crystal or quasi-single crystal active particles.
  • the ratio of (D v 90-D v 10)/D v 50 of the polycrystalline active particles and (D v 90-D v 10)/D v 50 of the single crystal or quasi-single crystal active particles (denoted as X1/X2) is low, so that the particle size of the active particles is reasonably matched. Under the premise of maintaining basically no loss of energy density, the storage life of the battery can be significantly improved.
  • the inventors of the present application speculate that it is because the content of small-sized polycrystalline particles is reduced, thereby reducing the active surface area, reducing the side reaction of the electrolyte and the positive electrode material during storage, thereby improving the chemical stability of the battery cell and extending the storage life of the battery.
  • the first active particles and the second active particles correspond to two discontinuous independent peaks respectively.
  • the two particles can correspond to two discontinuous independent peaks on the particle size distribution curve of the positive electrode active material.
  • D v 90, D v 50 and D v 10 of the two particles can be fitted and analyzed according to their respective particle size distribution peaks.
  • X1/X2 satisfies 0.25 ⁇ X1/X2 ⁇ 0.55.
  • the first active particles satisfy 0.3 ⁇ X1 ⁇ 1.0.
  • the first active particles satisfy 0.4 ⁇ X1 ⁇ 0.8.
  • the second active particles satisfy 0.7 ⁇ X2 ⁇ 2.5.
  • the second active particles satisfy 0.7 ⁇ X2 ⁇ 2; further optionally, the second active particles satisfy 0.8 ⁇ X2 ⁇ 1.6.
  • the active surface areas of the two sizes of particles can be better coordinated, thereby better balancing the dual needs of high energy density and long storage life, and better improving the battery storage life while maintaining good energy density.
  • a ratio R Dv50 of the D v 50 of the first active particle to the D v 50 of the second active particle satisfies 2 ⁇ R Dv50 ⁇ 4.
  • a ratio R Dv50 of the D v 50 of the first active particle to the D v 50 of the second active particle satisfies 2.3 ⁇ R Dv50 ⁇ 4.0.
  • the D v 50 of the first active particle satisfies 7 ⁇ m ⁇ D v 50 ⁇ 15 ⁇ m.
  • the D v 50 of the first active particle satisfies 7 ⁇ m ⁇ D v 50 ⁇ 14 ⁇ m.
  • the D v 50 of the second active particles satisfies 1 ⁇ m ⁇ D v 50 ⁇ 6 ⁇ m. Further optionally, the D v 50 of the second active particles satisfies 2 ⁇ m ⁇ D v 50 ⁇ 4 ⁇ m.
  • the active surface area of different active particles can be synergistically controlled, thereby better reducing the side reactions between the electrolyte and the positive electrode material during storage, thereby better improving the chemical stability of the battery cell and further extending the storage life of the battery.
  • the ratio R W of the weight of the first active particle to the sum of the weights of the first active particle and the second active particle satisfies 0.5 ⁇ R W ⁇ 0.9.
  • the ratio R W of the weight of the first active particle to the sum of the weights of the first active particle and the second active particle satisfies 0.7 ⁇ R W ⁇ 0.9.
  • the weight proportion of polycrystalline active particles in the positive electrode active particles within a certain range, for example, by adjusting the ratio R W of the weight of the first active particles relative to the sum of the weights of the first active particles (the first active particles, i.e., the polycrystalline active particles in the positive electrode active material) and the second active particles (the second active particles, i.e., the single crystal or quasi-single crystal active particles in the positive electrode active material) within a certain range , such as 0.5 ⁇ R W ⁇ 0.9, etc., it can be more conducive to reducing the active surface area and reducing the side reactions between the electrolyte and the positive electrode material during storage, thereby improving the chemical stability of the battery cell and extending the storage life of the battery.
  • the first active particles and the second active particles are each independently an oxide material containing lithium and nickel elements.
  • the nickel-lithium element quantity ratio R Ni/Li in the first active particles and the nickel-lithium element quantity ratio R Ni/Li in the second active particles each independently satisfy ⁇ 0.65.
  • the nickel-lithium element quantity ratio R Ni/Li in the first active particles and the nickel-lithium element quantity ratio R Ni/Li in the second active particles each independently satisfy 0.8 ⁇ R Ni/Li ⁇ 1.0.
  • the first active particle and the second active particle are each independently a ternary material or a ternary material containing doping and/or coating elements.
  • the first active particles and the second active particles are each independently a NCM ternary material, a NCA ternary material, a NCM ternary material containing doping and/or coating elements, or a NCA ternary material containing doping and/or coating elements.
  • the positive electrode active material provided by the present application can significantly improve the battery storage life without losing energy density in a high nickel system.
  • the nickel-lithium element quantity ratio R Ni/Li in the first active particles is less than the nickel-lithium element quantity ratio R Ni/Li in the second active particles.
  • a difference ⁇ R Ni /Li between a ratio R Ni /Li of nickel elements in the second active particles and that in the first active particles satisfies 0 ⁇ R Ni/Li ⁇ 0.05.
  • the present application provides a positive electrode plate, which includes a positive electrode active material layer, wherein the positive electrode active material layer includes the positive electrode active material described in the first aspect of the present application.
  • the use of the positive electrode plate can give the secondary battery a superior storage performance while maintaining a good energy density.
  • the compaction density of the positive electrode sheet is 3.2-3.8 g/cm 3 ; optionally, the compaction density of the positive electrode sheet is 3.4-3.7 g/cm 3 .
  • the compaction density of the positive electrode sheet is within the above range, it is beneficial to obtain a higher energy density while taking into account both the battery energy density and storage performance.
  • the present application provides a secondary battery, which includes the positive electrode plate described in the second aspect of the present application, and also includes a negative electrode plate and a separator; wherein the separator is arranged between the positive electrode plate and the negative electrode plate.
  • the polycrystalline active particles and the single crystal or quasi-single crystal active particles have unique particle size distribution characteristics, have excellent storage performance, and at the same time maintain good energy density.
  • the present application provides an electrical device, which includes at least one of the positive electrode plate described in the second aspect of the present application and the secondary battery described in the third aspect of the present application.
  • the present application provides a method for preparing a positive electrode active material, which comprises the following steps:
  • the first active particles are prepared by a method comprising the following steps: sintering a precursor material that meets the element stoichiometric ratio at a sintering temperature of 600 to 900° C. for a sintering time of 8 to 15 hours;
  • the second active particles are prepared by a method comprising the following steps: sintering a precursor material that meets the element stoichiometric ratio, the sintering temperature being 700 to 1000° C., and the sintering time being 8 to 15 hours.
  • the unique particle size distribution characteristics of polycrystalline active particles and single crystal or quasi-single crystal active particles can be regulated.
  • FIG1 is a particle size distribution curve of a positive electrode active material in an embodiment of the present application.
  • FIG2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG3 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG2 ;
  • FIG. 4 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.
  • Numerical value " range" disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range.
  • the scope limited in this way can be including end value or excluding end value, and any end value can be included or not included independently, and can be combined arbitrarily, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • 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.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • 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 words “have”, “include”, “contain” and “include” mentioned in this application can each independently represent an open or closed form.
  • the words “include” and “include” can also mean that other members or timing characteristics that are not listed can also be included or included, or can only include or include the listed members or timing characteristics.
  • Members include materials or components, structures, elements, instruments, etc.; non-limiting examples of timing characteristics include actions, conditions for the occurrence of actions, timing, states, etc.
  • A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.
  • the features or solutions corresponding to "and/or” include any one of two or more related listed items, and also include any and all combinations of the related listed items, wherein the arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items.
  • “A and/or B” means a group consisting of A, B, and “a combination of A and B”.
  • “comprising A and/or B” can mean “comprising A, comprising B, and comprising A and B”, and can also mean “comprising A, comprising B, or comprising A and B", which can be properly understood according to the sentence in which it is located.
  • first”, “second”, “third”, “fourth”, etc. in “the first aspect”, “the second aspect”, “the third aspect”, “the fourth aspect”, etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features.
  • first”, “second”, “third”, “fourth”, etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.
  • the weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Furthermore, the weight described in the embodiment description of the present application can be a mass unit known in the chemical industry such as ⁇ g, mg, g, kg, etc.
  • the comprehensive performance requirements for positive active materials are also constantly increasing to meet the comprehensive performance requirements of batteries for high energy density and long storage life.
  • the particle size distribution of active particles is usually relatively wide.
  • the (D v 90-D v 10)/D v 50 of positive active materials is mostly above 1.2 ( ⁇ 1.2).
  • the positive active material has such a wide particle size distribution, it often includes a large number of small-sized polycrystalline particles.
  • the small-sized particles in the polycrystalline particles will lead to the deterioration of the battery storage performance.
  • the present application provides a positive electrode active material, comprising a first active particle and a second active particle; wherein the first active particle is a polycrystalline particle in the positive electrode active material, and its particle size parameter (D v 90-D v 10)/D v 50 is recorded as X1; the second active particle is a single crystal or quasi-single crystal particle in the positive electrode active material, and its particle size parameter (D v 90-D v 10)/D v 50 is recorded as X2;
  • X1/X2 satisfies 0.2 ⁇ X1/X2 ⁇ 0.7;
  • D v 90, D v 50 and D v 10 represent the particle sizes corresponding to when the cumulative volume distribution percentage of the multi-particle combination reaches 90%, 50% and 10%, respectively.
  • the positive electrode active material provided in the present application includes polycrystalline particles recorded as first active particles and single crystal or quasi-single crystal particles recorded as second active particles, and (D v 90-D v 10)/D v 50 of the first active particles and the second active particles are recorded as X1 and X2 respectively, then X1/X2 satisfies 0.2 ⁇ X1/X2 ⁇ 0.7.
  • the electrode plate can be a positive electrode plate or a negative electrode plate
  • the "active material” in the electrode plate refers to a substance that can reversibly embed and release active ions.
  • negative electrode active material refers to a substance used for negative electrode plates that can reversibly embed and release active ions
  • positive electrode active material refers to a substance used for positive electrode plates that can reversibly release and embed active ions.
  • active material and “active substance” have the same meaning and can be used interchangeably; “positive electrode active substance” and “positive electrode active material” have the same meaning and can be used interchangeably; “negative electrode active substance” and “negative electrode active material” have the same meaning and can be used interchangeably.
  • active material layer includes the positive active material layer of the positive electrode sheet and the negative active material layer of the negative electrode sheet, and may refer to the positive active material layer or the negative active material layer according to the detailed circumstances. It is understood that the positive active material layer contains positive active material, and the negative active material layer contains negative active material.
  • polycrystalline is also called secondary particle, which means a particle formed by the aggregation of two or more primary particles. Agglomerated particles.
  • the particle size of the primary particles constituting the polycrystalline particles is generally controlled between 100 nm and 800 nm. If the particle size of the primary particles is smaller, the side reaction with the electrolyte may be aggravated, while if the particle size of the primary particles is larger, it is easy to cause the battery kinetic performance to deteriorate.
  • single crystal particles are also called primary particles, which refer to single crystal grains; the microscopic morphology of single crystals is that the particles are basically not agglomerated, and the particles are dispersed.
  • Single crystals can be irregularly shaped particles. Single particles with a size greater than 1 ⁇ m and no obvious agglomeration are usually judged as single crystal particles.
  • primary particles and “secondary particles” are terms well known in the art.
  • single crystal-like generally refers to particles with some agglomeration of primary particles but similar size and properties to single crystals.
  • the “size” or “particle diameter” of polycrystalline particles and single crystal or quasi-single crystal particles refers to D v 50 unless otherwise specified.
  • Polycrystalline particles and single crystal or quasi-single crystal particles can be easily distinguished by taking SEM images using a scanning electron microscope.
  • the volume cumulative distribution particle size D v N (wherein N represents any value selected from 0 to 100) can be used to characterize the particle size of the material, which refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching N%, and the volume proportion of the particle size less than or equal to D v N is N%.
  • D v N can be obtained from the volume cumulative distribution curve of the material particle size. If there is no other explanation, the volume cumulative distribution curve starts from zero from the small particle size side.
  • D v 90 refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 90%
  • D v 50 refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%
  • D v 10 refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 10%.
  • D v 50 it means that the particle size of particles accounting for 50% of the volume of the material is less than or equal to D v 50, and the particle size of particles accounting for 50% of the volume of the material is greater than D v 50.
  • D v 90 it means that the particle size of particles accounting for 90% of the volume of the material is less than or equal to D v 90, and the particle size of particles accounting for 10% of the volume of the material is greater than D v 90.
  • D v 10 it means that the particle size of particles accounting for 10% of the volume of the material is less than or equal to D v 10, and the particle size of particles accounting for 90% of the volume of the material is greater than D v 10.
  • a laser particle size analyzer such as Mastersizer 2000E laser particle size analyzer and LS-909 laser particle size analyzer (OMEC) of Malvern Instruments Co., Ltd., UK.
  • OMEC laser particle size analyzer
  • its particle size parameter (D v 90-D v 10)/D v 50 can reflect the distribution characteristics of the particles and is therefore also a particle size distribution parameter.
  • the larger the value of (D v 90-D v 10)/D v 50 the wider the particle size distribution.
  • the smaller the value the narrower the particle size distribution.
  • the positive electrode active material provided in the present application adopts a combination of polycrystalline active particles with special particle size distribution characteristics and single crystal or quasi-single crystal active particles.
  • the ratio of (D v 90-D v 10)/D v 50 of the polycrystalline active particles and (D v 90-D v 10)/D v 50 of the single crystal or quasi-single crystal active particles (denoted as X1/X2) is low, so that the particle size of the active particles is reasonably matched, which can significantly improve the storage life of the battery while maintaining basically no loss of energy density.
  • the inventors of the present application speculate that this is due to the reduction in the content of small-sized polycrystalline particles, thereby reducing the active surface area, reducing the side reactions between the electrolyte and the positive electrode material during storage, thereby improving the chemical stability of the battery cell and extending the storage life of the battery.
  • the particle size and particle size distribution between the polycrystalline active particles and the single crystal or quasi-single crystal active particles are finely matched, so that the balance between the content of small-sized polycrystalline active particles and the compaction density of the positive electrode sheet can be better coordinated, thereby better meeting the battery storage performance. and energy density.
  • the first active particles and the second active particles correspond to two discontinuous independent peaks respectively.
  • the particle size distribution curve can be measured using instruments known in the art, such as a particle size distribution curve obtained by testing with a laser particle size analyzer.
  • a laser particle size analyzer such as the Mastersizer 2000E from Malvern Instruments Ltd. of the United Kingdom or a LS-909 laser particle size analyzer (OMEC) can be used.
  • the two particles can correspond to two discontinuous independent peaks on the particle size distribution curve of the positive electrode active material.
  • D v 90, D v 50 and D v 10 of the two particles can be fitted and analyzed according to their respective particle size distribution peaks.
  • the particle size distribution curve shown in Figure 1 is a particle size distribution curve obtained by testing the positive electrode active material in an embodiment of the present application using a laser particle size analyzer. It is a bimodal distribution, and the curve has two independent peaks, corresponding to the first active particles (large particles) and the second active particles (small particles) in the present application.
  • the particle size distribution curve there is a discontinuity between the two peaks corresponding to the first active particles and the second active particles, which means that the particle size ranges of the two active particles do not overlap, and the two particles can be easily screened out from the mixture of the two particles, and then the two active particles of different sizes can be independently subjected to relevant tests, such as, but not limited to, component testing, specific surface area testing, etc.
  • the particle size distribution curve of the positive electrode active material has only two peaks, and the two peaks are discontinuous independent peaks. In this case, the two peaks correspond to the particle size distribution of the first active particles and the second active particles, respectively.
  • X1/X2 satisfies 0.2 ⁇ X1/X2 ⁇ 0.7.
  • X1/X2 can be selected from any of the following values: 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, etc., and can also be selected from an interval consisting of any two of the above values. Non-limiting examples may include: 0.25 ⁇ X1/X2 ⁇ 0.55.
  • the first active particle satisfies 0.3 ⁇ X1 ⁇ 1.0.
  • X1 of the first active particle can be selected from any of the following values: 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, etc., and can also be selected from an interval consisting of any two of the above values, and non-limiting examples may include: 0.4 ⁇ X1 ⁇ 0.8.
  • the second active particle satisfies 0.7 ⁇ X2 ⁇ 2.5.
  • X2 of the second active particle can be selected from any of the following values: 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2 (such as 2.0), 2.1, 2.2, 2.3, 2.4, 2.45, etc., and can also be selected from an interval consisting of any two of the above values.
  • Non-limiting examples may include: 1.5 ⁇ X2 ⁇ 2.5, 0.7 ⁇ X2 ⁇ 2, 0.7 ⁇ X2 ⁇ 1.6, 0.8 ⁇ X2 ⁇ 1.6, 0.7 ⁇ X2 ⁇ 1.5, 0.8 ⁇ X2 ⁇ 1.5.
  • the active surface areas of the two sizes of particles can be better coordinated, thereby better balancing the dual needs of high energy density and long storage life, and better improving the battery storage life while maintaining good energy density.
  • the ratio R Dv50 of the D v 50 of the first active particle to the D v 50 of the second active particle satisfies 2 ⁇ R Dv50 ⁇ 4.
  • the ratio R Dv50 of the D v 50 of the first active particle to the D v 50 of the second active particle may be selected from any of the following values: 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4 (such as 4.0), etc., and may also be selected from an interval consisting of any two of the above values, and non-limiting examples may include: 2.3 ⁇ R Dv50 ⁇ 4.0.
  • the D v 50 of the first active particle satisfies 7 ⁇ m ⁇ D v 50 ⁇ 15 ⁇ m.
  • the D v 50 of the first active particle may be selected from any of the following sizes: 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, etc., and may also be selected from an interval consisting of any two of the above sizes. Non-limiting examples may include: 7 ⁇ m ⁇ D v 50 ⁇ 14 ⁇ m.
  • the D v 50 of the second active particle satisfies 1 ⁇ m ⁇ D v 50 ⁇ 6 ⁇ m.
  • the D v 50 of the second active particle may be selected from any of the following sizes: 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, etc., and may also be selected from an interval consisting of any two of the above sizes, and non-limiting examples may include: 2 ⁇ m ⁇ D v 50 ⁇ 6 ⁇ m, 1 ⁇ m ⁇ D v 50 ⁇ 4 ⁇ m, 2 ⁇ m ⁇ D v 50 ⁇ 4 ⁇ m, and 3.5 ⁇ m ⁇ D v 50 ⁇ 6 ⁇ m.
  • the specific surface area of the first active particles is 0.35-0.65 m 2 /g; the specific surface area of the first active particles can be selected from any of the following values: 0.35 m 2 /g, 0.4 m 2 /g, 0.45 m 2 /g, 0.5 m 2 /g, 0.55 m 2 /g, 0.6 m 2 /g, 0.65 m 2 /g, etc., and can also be selected from an interval consisting of any two of the above values. Non-limiting examples may include: 0.35-0.55 m 2 /g.
  • the specific surface area of the second active particles is 0.70-0.90 m 2 /g; the specific surface area of the second active particles can be selected from any one of the following values: 0.7 m 2 /g, 0.72 m 2 /g, 0.74 m 2 /g, 0.75 m 2 /g, 0.76 m 2 / g , 0.78 m 2 /g, 0.8 m 2 /g, 0.82 m 2 /g, 0.84 m 2 /g, 0.85 m 2 /g, 0.86 m 2 / g, 0.88 m 2 /g, 0.9 m 2 /g, etc., and can also be selected from the interval consisting of any two of the above values.
  • Non-limiting examples may include: 0.70-0.85 m 2 /g.
  • the specific surface area of a particle refers to the ratio of the surface area of the particle to its weight, which can be measured using instruments and methods known in the art, for example, a nitrogen adsorption specific surface area analysis test method.
  • the active surface area of different active particles can be synergistically controlled, thereby better reducing the side reactions between the electrolyte and the positive electrode material during storage, thereby better improving the chemical stability of the battery cell and further extending the storage life of the battery.
  • the specific surface area (BET) of the positive electrode active material can be obtained by the following method: testing by nitrogen adsorption specific surface area analysis test method, and calculated by BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by the Tri Star II specific surface and pore analyzer of Micromeritics Company of the United States, and the test steps can refer to GB/T 19587-2004.
  • the sample to be tested the prepared positive electrode active material; it can also be the positive electrode active material sampled from the positive electrode active material layer of the positive electrode plate.
  • test analysis method is as follows: the sample to be tested is dried in a vacuum drying oven at 200°C for 2 hours; then argon is used as the adsorption gas, and the adsorption and desorption curve with a relative pressure P/ P0 of 0 to 0.99 is measured by the specific surface and pore analyzer, P is the equilibrium adsorption pressure, P0 is the saturated vapor pressure, and the specific surface area of the positive electrode active material is calculated by the BET method.
  • the ratio R W of the weight of the first active particle to the sum of the weights of the first active particle and the second active particle satisfies 0.5 ⁇ R W ⁇ 0.9.
  • the ratio R W of the weight of the first active particle to the sum of the weights of the first active particle and the second active particle may be selected from any of the following values: 0.5, 0.52, 0.54, 0.55, 0.56, 0.58, 0.6, 0.62, 0.63, 0.64, 0.65, 0.66, 0.68, 0.69, 0.7, 0.72, 0.74, 0.75, 0.76, 0.78, 0.8, 0.82, 0.84, 0.85, 0.86, 0.88, 0.9, etc., and may also be selected from an interval consisting of any two of the above values, and non-limiting examples may include: 0.7 ⁇ R W ⁇ 0.9.
  • the weight proportion of polycrystalline active particles in the positive electrode active particles within a certain range, for example, by adjusting the ratio R W of the weight of the first active particles relative to the sum of the weights of the first active particles (i.e. , the polycrystalline active particles in the positive electrode active material) and the second active particles (i.e., the single crystal or quasi-single crystal active particles in the positive electrode active material) within a certain range, such as 0.5 ⁇ R W ⁇ 0.9, etc., it can be more conducive to reducing the active surface area and reducing the side reactions between the electrolyte and the positive electrode material during storage, thereby improving the chemical stability of the battery cell and extending the storage life of the battery.
  • the higher the nickel content in the positive electrode active material the more significant the deterioration of the battery storage performance caused by the small-sized particles in the polycrystalline active particles (i.e., small-sized polycrystalline active particles), making it more difficult to achieve both high energy density and long storage time. Lifespan.
  • the positive electrode active material provided in this application can significantly improve the battery storage life without substantially losing energy density in high-nickel system batteries.
  • high nickel is a general term used by technicians in this field to refer to a class of substances with a high molar ratio of nickel in lithium transition metal oxides.
  • the molar ratio of nickel is above 0.8 based on 1 mole of lithium transition metal oxide.
  • the molar ratio of nickel, cobalt and manganese is 80:10:10. Increasing the nickel content in the positive electrode active material is conducive to improving energy density and can improve battery capacity.
  • the nickel content can be characterized by the element quantity ratio of nickel element and lithium element, which can be called the nickel-lithium molar ratio, which can be recorded as R Ni/Li , and can be numerically equal to the molar ratio of nickel element to lithium element.
  • R Ni/Li the nickel-lithium molar ratio
  • each occurrence of R Ni/Li can be independently greater than or equal to 0.65, further can be independently greater than or equal to 0.7, and further can be independently greater than or equal to 0.8.
  • the nickel-lithium molar ratio R Ni/Li can also be selected from any of the following values or an interval consisting of any two values: 0.65, 0.7, 0.75, 0.8, 0.82, 0.85, 0.9, 0.95, 1, etc. In some embodiments of the present application, the nickel-lithium molar ratio R Ni/Li can also be selected from any of the following numerical ranges (any numerical endpoints here may be independently included or excluded): 0.65-1.0, 0.7-1.0, 0.8-1.0, 0.8-0.95, etc.
  • the first active particles and the second active particles are each independently an oxide material containing lithium and nickel elements.
  • lithium nickel transition metal oxide may include, but are not limited to, one or more of lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof.
  • non-limiting examples of lithium nickel oxides may include LiNiO 2 , etc.
  • Non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), etc.
  • Non-limiting examples of lithium nickel cobalt aluminum oxides may include LiNi 0.85 Co 0.15 Al 0.05 O 2 , etc.
  • the nickel-lithium element quantity ratio R Ni/Li in the first active particles and the nickel-lithium element quantity ratio R Ni/Li in the second active particles may each independently meet the definition of any of the foregoing embodiments, for example, ⁇ 0.65.
  • R Ni/Li of the first active particle and the second active particle can be independently selected from any of the following values: 0.65, 0.66, 2/3 (i.e., two-thirds), 0.67, 0.68, 0.7, 0.71, 0.75, 0.8, 0.85, 0.88, 0.89, 8/9 (i.e., eight-ninths), 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, etc., and can also be independently selected from the interval consisting of any two of the above values.
  • the first active particles and the second active particles each independently satisfy any one of the following ranges: 0.65 ⁇ R Ni/Li ⁇ 1.1, 0.8 ⁇ R Ni/Li ⁇ 1.0 , 0.8 ⁇ R Ni/Li ⁇ 0.95, 2/3 ⁇ R Ni/ Li ⁇ 8/9, 0.66 ⁇ R Ni/Li ⁇ 0.89, 0.67 ⁇ R Ni/Li ⁇ 0.88, 0.70 ⁇ R Ni/Li ⁇ 1.07, 0.71 ⁇ R Ni/Li ⁇ 1.06, ⁇ 0.7, ⁇ 0.8, ⁇ 0.85, ⁇ 0.9, etc.
  • the positive electrode active material described in the first aspect of the present application also contains doping elements.
  • the doping elements in any positive electrode active material in the present application may independently include one or more of transition metal elements and non-transition metal elements. Suitable doping elements and their contents can be selected according to functional requirements.
  • Doping elements may include but are not limited to one or more of Sb, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P and C.
  • doping elements may include but are not limited to one or more of Na, Sb, K, Ca, Zr, Sr, Al, B, Ba, Nb, W, Mo, Co, P and C.
  • the first active particle and the second active particle are each independently a ternary material or a ternary material containing doping and/or coating elements.
  • ternary material used in this application has a well-known meaning in the field of secondary battery technology, and refers to the positive electrode active material, which includes not only the corresponding elements of active ions (such as lithium), but also nickel (Ni) and cobalt (Co), and may also include an X element, which may be, but is not limited to, manganese (Mn) or aluminum (Al).
  • Mn manganese
  • Al aluminum
  • the ternary material may be recorded as NCM ternary material, and non-limiting examples may include NCM 811 , etc.
  • the ternary material can be recorded as NCA ternary material, and non-limiting examples can include LiNi 0.85 Co 0.15 Al 0.05 O 2 , etc.
  • ternary material containing doping and/or coating elements means a ternary material containing a doped original material, a ternary material containing a coating element, or a ternary material containing both a doping element and a coating element.
  • the first active particle and the second active particle are each independently a NCM ternary material, a NCA ternary material, a NCM ternary material containing doping and/or coating elements, or a NCA ternary material containing doping and/or coating elements.
  • NCM ternary material containing doping and/or coating elements means NCM ternary material containing doped original NCM ternary material, NCM ternary material containing coating elements, or NCM ternary material containing both doping elements and coating elements.
  • NCA ternary material containing doping and/or coating elements means NCA ternary material containing doped original NCA ternary material, NCA ternary material containing coating elements, or NCA ternary material containing both doping elements and coating elements.
  • the positive electrode active material when the positive electrode active material contains a coating element, it means that the positive electrode active material has a coating layer located outside the main body structure, and the coating layer is composed of the coating element.
  • R Ni/Li is numerically equal to a/x.
  • R Ni/Li is selected from (2/3) to (8/9). In other embodiments, R Ni/Li is selected from 0.67 to 0.88.
  • the first active particles and the second active particles each independently contain one or more of the following elements: Na, K, Ca, Ba, Sb, Ti, Zr, W, Sr, Nb, Mo, Si, Mg, B, Cr and Ta.
  • the content of these elements can be flexibly adjusted according to the needs of improving the performance of the positive electrode active material, the positive electrode sheet or the secondary battery.
  • doping Mo, W, Zr, Nb and other elements in the positive electrode active material can regulate the crystal morphology and improve the interface performance of the electrolyte and the cathode material.
  • the molar equivalent of the oxygen element is recorded as 2, but there may be certain non-integer cases.
  • x in the above composition formula can also be the molar equivalent of the feed of the ternary positive electrode material in the manufacturing stage.
  • the positive electrode materials in the batteries appearing on the market have undergone a formation aging process and may have undergone a certain number of charge and discharge cycles. Therefore, as charging and discharging proceed, the amount of Li in the positive electrode is sometimes lost.
  • the lithium content x when discharged to the lower cut-off voltage of the battery, the lithium content x may be between 0.65 and 1.2.
  • the nickel-lithium number ratio R Ni/Li in the first active particle is less than the nickel-lithium number ratio R Ni /Li in the second active particle.
  • the nickel-lithium number ratio R Ni/Li in the first active particle can be denoted as R 1
  • the nickel-lithium number ratio R Ni/Li in the second active particle can be denoted as R 2 .
  • non-limiting examples of ⁇ R Ni/Li may include 0.01, 0.02, 0.03, 0.04, 0.05, and may also be an interval consisting of any two of the foregoing values, for example, 0.01 ⁇ R Ni/Li ⁇ 0.05, 0.02 ⁇ R Ni/Li ⁇ 0.05, 0.02 ⁇ R Ni/Li ⁇ 0.04.
  • any one of the positive electrode active particles (which may be but not limited to the first active particle or the second active particle) includes at least a positive electrode active particle body, and may or may not include a coating layer; when a coating layer is included, the coating layer is disposed on at least a portion of the surface of the positive electrode active particle body.
  • the first active particle includes an active particle body and may or may not include a coating layer.
  • the second active particle includes an active particle body and may or may not include a coating layer.
  • At least one of the first active particle and the second active particle includes a coating layer.
  • the first active particle includes a coating layer, and the composition of the body of the first active particle and the coating layer may be the same or different.
  • the second active particle includes a coating layer, and the composition of the body of the second active particle and the coating layer may be the same or different.
  • the first active particle and the second active particle may each independently include a coating layer or may not include a coating layer.
  • a coating layer is provided on the surface of the positive electrode active particle (which may be but is not limited to the first active particle or the second active particle), one or more of the aforementioned doping elements may be included in the coating layer.
  • the introduction of metal oxides in the coating layer can improve the stability of the electrode/electrolyte interface.
  • the introduction of fluorides in the coating layer can reduce electrolyte side reactions, reduce polarization, and improve the cycle stability of the positive electrode material under high current and high voltage.
  • the introduction of lithium compounds in the coating layer can improve the structural stability of the positive electrode material.
  • the thickness of the coating layer can be flexibly adjusted according to the performance improvement needs of the positive electrode active particles, positive electrode sheets or secondary batteries.
  • the thickness of the coating layer is 1nm to 50nm, and can be optionally 1nm to 10nm.
  • the thickness of the coating layer can be measured by morphological observation methods such as transmission electron microscopy.
  • the quality of the coating layer and the composition and content of each element can be measured by elemental analysis methods such as inductively coupled plasma emission spectrometry.
  • the present application provides a positive electrode plate, which includes a positive electrode active material layer, wherein the positive electrode active material layer includes the positive electrode active material described in the first aspect of the present application.
  • the use of the positive electrode plate can give the secondary battery a superior storage performance while maintaining a good energy density.
  • the compaction density of the positive electrode sheet is 3.2-3.8 g/cm 3.
  • the compaction density of the positive electrode sheet can be selected from any of the following densities: 3.2 g/cm 3 , 3.25 g/cm 3 , 3.3 g/cm 3 , 3.35 g/cm 3 , 3.4 g/cm 3 , 3.45 g/cm 3, 3.5 g/cm 3 , 3.55 g/cm 3 , 3.6 g/cm 3 , 3.65 g/cm 3, 3.7 g/cm 3, 3.75 g/cm 3 , 3.8 g /cm 3 , etc., and can also be selected from the interval consisting of any two of the above values.
  • the compaction density of the positive electrode sheet is 3.4-3.7 g/cm 3 .
  • the compaction density of the positive electrode sheet is within the above range, it is beneficial to obtain a higher energy density while taking into account both the battery energy density and storage performance.
  • the compacted density of the positive electrode sheet refers to the ratio of the mass of the positive electrode active material layer to its volume.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, at least one of the positive electrode film layers includes a positive electrode active material layer, and any of the positive electrode active material layers independently contains a positive electrode active substance. At least one of the positive electrode active material layers contains the positive electrode active substance described in the first aspect of the present application.
  • the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and further, 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.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base layer and a A metal layer on at least one surface.
  • the composite current collector can be obtained by forming a metal material on a polymer material substrate.
  • the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • non-limiting examples of the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and the like.
  • 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 one or more 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 optionally include a conductive agent.
  • the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • 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 to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, compaction (compacting can be performed by cold pressing), etc., the positive electrode sheet can be obtained.
  • the type of solvent can be selected from but not limited to any one of the aforementioned embodiments, such as N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • the surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector.
  • the present application provides a secondary battery, which includes the positive electrode plate described in the second aspect of the present application, and also includes a negative electrode plate and a separator; wherein the separator is arranged between the positive electrode plate and the negative electrode plate.
  • the polycrystalline active particles and the single crystal or quasi-single crystal active particles have unique particle size distribution characteristics, have excellent storage performance, and at the same time maintain good energy density.
  • the secondary battery includes a positive electrode sheet (the positive electrode sheet provided in the second aspect of the present application), a negative electrode sheet, an electrolyte and a separator.
  • a positive electrode sheet the positive electrode sheet provided in the second aspect of the present application
  • a negative electrode sheet the negative electrode sheet
  • an electrolyte the electrolyte
  • 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 active ions to pass through.
  • the positive electrode sheet in the third aspect and the fourth aspect of the present application includes the positive electrode sheet provided in the second aspect of the present application.
  • the secondary battery is a lithium-ion secondary battery.
  • a lithium-ion secondary battery utilizes the insertion and extraction of lithium ions in electrodes and the transmission in electrolytes to realize the charging and discharging process.
  • the active ions in a lithium-ion secondary battery are lithium ions, but are not limited thereto.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged 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.
  • copper foil may be used as the metal foil.
  • 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 obtained by forming a metal material on a polymer material substrate.
  • non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • the negative electrode active material may adopt a negative electrode active material for a battery known in the art.
  • the negative electrode active material may include one or more 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 elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may include one or more 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 include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode film layer may further include other auxiliary agents, such as a thickener, etc.
  • auxiliary agents such as a thickener, etc.
  • thickeners may include sodium carboxymethyl cellulose (CMC-Na) and the like.
  • 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 (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the surface of the negative electrode collector (the surface coated with the negative electrode slurry can be on a single surface or on two surfaces), and after drying, compacting (compacting can be performed by cold pressing), etc., the negative electrode sheet can be obtained.
  • a solvent a non-limiting example of the solvent is deionized water
  • the electrolyte has the function of conducting active ions between the positive electrode and the negative electrode.
  • the present application has no particular 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.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may include an electrolyte lithium salt.
  • the electrolyte lithium salt may include one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • LiClO 4 lithium hexafluoroarsenate
  • LiFSI lithium bis
  • the solvent is an organic solvent.
  • the organic solvent is an ester or an ether. In some embodiments thereof, the organic solvent is an ester.
  • the above-mentioned ester solvent can include one or more of carbonate and halogenated carbonate, as non-limiting examples, such as ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB) and any of the foregoing fluorochemicals.
  • EC ethylene carbonate
  • PC propylene carbon
  • the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), 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, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • EC ethylene carbonate
  • PC propylene carbonate
  • EMC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC dipropyl carbonate
  • the electrolyte may further include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as improving Additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the additive may include one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), methylene methanedisulfonate (MMDS), 1-propylene-1,3-sultone (PST), vinyl sulfite (ES), propylene sulfite (PS), vinyl sulfate (DTD), succinonitrile (SN), adiponitrile (AND), sulfonate cyclic quaternary ammonium salt, tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) borate (TMSB) and anisole.
  • VC vinylene carbonate
  • VEC vinyl ethylene carbonate
  • FEC fluoroethylene carbonate
  • DFEC difluoroethylene carbonate
  • TFPC trifluoromethylethylene carbonate
  • MMDS methylene methane
  • 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 may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer may be the same or different, without particular limitation.
  • Electrode assembly electrochemical energy storage device, secondary battery, power device
  • 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 electrochemical energy storage device may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG2 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 actual needs.
  • the present application provides an electrical device, which includes at least one of the positive electrode plate described in the second aspect of the present application and the secondary battery described in the third aspect of the present application.
  • the secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc.
  • the mobile device may be, for example, a mobile phone, a laptop computer, etc.
  • the electric vehicle may be, for example, 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., but is not limited to these.
  • a secondary battery can be selected according to its usage requirements.
  • Fig. 4 is an example of an electric device 6.
  • 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, tablet computer, laptop computer, etc.
  • the device generally requires Lightweight and thin, secondary batteries can be used as power source.
  • the present application provides a method for preparing a positive electrode active material, which can be used to prepare the positive electrode active material described in the first aspect of the present application.
  • a method for preparing a positive electrode active material comprising the following steps:
  • the first active particles and the second active particles are mixed to obtain the positive electrode active material described in the first aspect of the present application.
  • the first active particles are prepared by a method comprising the following steps: sintering a precursor material that meets the element stoichiometric ratio, and the sintering temperature is 600-900°C.
  • the sintering time can be 8-15h, for example, any one of 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc., and can also be selected from the interval consisting of any two of the above time lengths.
  • the sintering temperature when preparing the first active particles can be 600-900°C, and can also be selected from any of the following temperatures: 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, etc., and can also be selected from the temperature interval consisting of any two of the above temperatures, for example, 750-850°C.
  • the second active particle is prepared by a method comprising the following steps: sintering a precursor material that meets the element stoichiometric ratio, and the sintering temperature is 700-1000°C.
  • the sintering time can be 8-15h, for example, any one of 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc., and can also be selected from the interval consisting of any two of the above time lengths.
  • the sintering temperature when preparing the second active particle can be 700-1000°C, and can also be selected from any of the following temperatures: 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, etc., and can also be selected from the temperature interval consisting of any two of the above temperatures, for example, 650-800°C.
  • the target element composition and content of the positive electrode active particles targeted adjustments can be made on the basis of the conventional method of preparing active particle precursors in the art, so as to achieve the composition control of the precursor and the active particles prepared therefrom.
  • the size of the active particles can be controlled to a certain extent, for example, the particle size distribution parameters such as D v 90, D v 50, and D v 10 can be controlled.
  • the unique particle size distribution characteristics of polycrystalline active particles and single crystal or quasi-single crystal active particles can be regulated.
  • the positive electrode active particles with the coating layer can be prepared by a step-by-step sintering method.
  • the main body precursor material can be first sintered to obtain the main body of the positive electrode active particles, and then the coating layer precursor material can be coated on at least a portion of the surface of the main body, and then sintered for a second time to obtain the positive electrode active particles with the coating layer. This makes it easy for those skilled in the art to obtain or screen out positive electrode active particles with a target structure by adjusting the preparation parameters.
  • the present application provides a method for preparing a positive electrode slurry, comprising the following steps: mixing the positive electrode active material and a solvent as described in the first aspect of the present application to prepare a positive electrode slurry; wherein an auxiliary agent is added or not added to the positive electrode slurry;
  • the first active particle can be prepared by the method described in the fifth aspect of the present application.
  • the second active particles can be prepared by the method described in the fifth aspect of the present application.
  • the auxiliary agent includes one or more of a conductive agent and a binder.
  • nickel sulfate, manganese sulfate and cobalt sulfate are prepared into a 1 mol/L solution in a molar ratio, with deionized water as the solvent.
  • Ammonia water, sodium hydroxide and other hydroxides are added for co-precipitation technology to prepare a polycrystalline precursor, and the particle size test is used to confirm whether it meets the preset requirements.
  • the particle size of the precursor particles can be controlled by controlling the reaction time, the pH value during co-precipitation and the ammonia concentration.
  • the precursor material can be subjected to a first-stage sintering to obtain the positive electrode active particle body, which is then evenly blended with the coating layer raw material and subjected to a second-stage sintering under a suitable gas atmosphere, thereby forming a coating layer on at least a portion of the surface of the active particle body.
  • the positive electrode active material can be obtained by mixing the polycrystalline active particles (first active particles) and the single crystal active particles (second active particles) prepared above in a certain weight ratio.
  • Example 1 Take Example 1 below as an example, where the D v 50 of the polycrystalline particles is 9 ⁇ m, (D v 90-D v 10)/D v 50 of the polycrystalline particles is 0.4, and the D v 50 of the single crystal particles is 3.3 ⁇ m, and (D v 90-D v 10)/D v 50 of the single crystal particles is 1.6. That is, it can be calculated that X1/X2 is 0.25. Please also refer to Table 1.
  • Particle size types Testing of D v 10, D v 50 and D v 90.
  • Test process Take an appropriate amount of the sample to be tested (the sample concentration should ensure 8% to 12% shading), add 20mL of anhydrous ethanol, and ultrasonically treat for 5 minutes (53KHz/120W) to ensure that the sample is completely dispersed, and then measure the sample according to GB/T19077-2016/ISO 13320:2009 standard.
  • the polycrystalline active particles in the positive electrode active material are recorded as the first active particles, and the single crystal or quasi-single crystal active particles in the positive electrode active material are recorded as the second active particles.
  • the particle size parameter (D v 90-D v 10)/D v 50 of the first active particle is recorded as X1
  • the particle size parameter (D v 90-D v 10)/D v 50 of the second active particle is recorded as X2.
  • the foil is ductile, so that its film length is 1006mm (extension rate is 0.6%); a small disc of 1540.25mm2 is punched out (area is recorded as A), and the weight W and thickness d of the small disc are measured.
  • the weight W1 and thickness d1 of the positive electrode collector in the small disc are converted, and the weight W2 and thickness d2 of the positive electrode active material layer are obtained by deducting the weight W1 and thickness d1 of the positive electrode collector in the small disc.
  • the compaction density of the electrode sheet is calculated according to the ratio W2/(A ⁇ d2).
  • the lithium-ion battery was placed at a constant temperature of 25°C for 2 hours, then charged to 4.2V at 0.33C at 2.8V-4.2V, then charged at a constant voltage at 4.2V to a current ⁇ 0.05C, placed at rest for 10 minutes, and then discharged to 2.8V at 0.33C, and the initial capacity C0 of the lithium-ion battery was recorded.
  • the battery was placed in a 60°C thermostat for 100 days, then discharged at 0.33C to 2.8V at 25°C, and left to stand for 10 minutes. Then it was charged to 4.2V at 0.33C, and charged at a constant voltage at 4.2V to a current ⁇ 0.05C, left to stand for 10 minutes, and then discharged to 2.8V at 0.33C, and the capacity C1 of the lithium-ion battery was recorded.
  • the capacity retention rate (%) of the battery C1/C0 ⁇ 100%.
  • the first active particles and the second active particles were prepared in sequence using the above-mentioned preparation method of the positive electrode active material.
  • the first active particles and the second active particles are mixed to obtain the positive electrode active material of this example.
  • the positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of 97:2:1 and added into a solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the double-side surfaces of the positive electrode current collector aluminum foil, dried at 85°C and then cold pressed, and then die-cut and slit to prepare a lithium-ion battery positive electrode sheet.
  • NMP N-methylpyrrolidone
  • the negative electrode active material graphite, silicon oxide, conductive agent acetylene black, thickener sodium hydroxymethyl cellulose (CMC-Na), and binder styrene butadiene rubber (SBR) are added into solvent water in a mass ratio of 72:24:2:1:1 and mixed evenly to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the double-side surface of the negative electrode current collector copper foil, dried at 85°C and then cold pressed to prepare a lithium-ion battery negative electrode sheet.
  • a polyethylene microporous film is used as a porous isolation membrane substrate, and inorganic alumina powder, polyvinylpyrrolidone and acetone solvent are uniformly mixed in a weight ratio of 3:1.5:5.5 to form a slurry, which is then coated on one side of the substrate and dried to obtain an isolation membrane.
  • Lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is 1:2:1) to obtain a lithium ion battery electrolyte.
  • the positive electrode sheet, negative electrode sheet and isolation film are wound to obtain a bare battery cell, which is then packaged, injected, formed, exhausted and other processes to obtain the secondary battery of Example 1, which is a lithium-ion battery.
  • Example 2-10 The preparation method of the first active particle, the second active particle, the positive electrode active material, the positive electrode sheet and the secondary battery is basically the same as that of Example 1.
  • the chemical composition, particle size and distribution and active particle content of the active particles can be controlled by referring to Table 1 and Table 2.
  • the preparation parameters of the active particles can be appropriately adjusted according to the parameters in Table 1. number.
  • Comparative Example 1-2 The preparation method of the first active particles, the second active particles, the positive electrode active material, the positive electrode plate and the secondary battery is basically the same as that in Example 1.
  • the chemical composition, particle size and distribution and active particle content of the active particles can be controlled by referring to Tables 1 and 2, and the preparation parameters of the active particles can be appropriately adjusted according to the parameters in Table 1.
  • R W is the percentage of the weight of the first active particles relative to the sum of the weights of the first active particles and the second active particles;
  • R Dv50 is the ratio of D v 50 of the first active particle to the second active particle
  • X1 is (D v 90 - D v 10)/D v 50 of the first active particle
  • X2 is (D v 90 - D v 10)/D v 50 of the second active particle.
  • Examples 1-10 all have excellent high-temperature storage performance.
  • the capacity retention rate after storage at 60°C for 100 days is higher than 93%.
  • the high-temperature storage life is long, and good compaction density and battery capacity can be maintained at the same time, which means that they have good energy density.
  • X1/X2 of Comparative Example 1 is too high, and X1/X2 of Comparative Example 2 is too low, which results in failure to take into account high-temperature storage performance, compaction density and initial capacity, that is, failure to take into account the dual requirements of battery storage life and energy density.
  • the high-temperature storage performance in Comparative Example 1 deteriorates; the improvement of high-temperature storage performance in Comparative Example 2 is at the expense of severely sacrificing energy density, and the compaction density is severely reduced.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are only examples.
  • the embodiments that have the same structure as the technical idea and play the same effect are all included in the technical scope of the present application.
  • the above-mentioned embodiments only express several embodiments of the present application, and the description is relatively detailed, but it cannot be understood as a limitation on the scope of the patent.
  • various deformations that can be thought of by those skilled in the art and other methods of combining and constructing a part of the constituent elements in the embodiment are also included in the scope of the present application.

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Abstract

本申请提供了一种正极活性物质、正极极片、二次电池、用电装置和制备方法。该正极活性物质包括记为第一活性颗粒的多晶颗粒以及记为第二活性颗粒的单晶或类单晶颗粒，第一活性颗粒和第二活性颗粒的(Dv90-Dv10)/Dv50分别记为X1、X2，且X1/X2满足0.2≤X1/X2≤0.7。

Description

正极活性物质、正极极片、二次电池、用电装置和制备方法 技术领域
本申请涉及锂离子电池技术领域，特别涉及一种正极活性物质、正极极片、二次电池、用电装置和制备方法。
背景技术
这里的陈述仅提供与本申请有关的背景信息，而不必然构成现有技术。
随着锂离子电池技术在的应用推广，生活节奏的加快，以及智能手机、平板电脑、智能穿戴、电动工具和电动汽车等各类电子产品的发展，对正极活性物质的综合性能要求也不断提高，以满足电池对高能量密度以及长存储寿命等方面的综合性能需求。目前，针对电池长存储寿命的改善往往带来能量密度的损失，导致两种性能难以兼顾。
因此，目前亟需开发能够兼顾能量密度及长存储寿命综合需求的锂离子电池。
发明内容
鉴于上述问题，本申请提供了一种正极活性物质、正极极片、二次电池、用电装置和制备方法，采用该正极活性物质，可以在保持能量密度基本不损失的情况下，改善存储寿命。
第一方面，本申请提供了一种正极活性物质，其包括第一活性颗粒和第二活性颗粒；其中，所述第一活性颗粒为所述正极活性物质中的多晶颗粒，其粒径参数(Dv90-Dv10)/Dv50记为X1；所述第二活性颗粒为所述正极活性物质中的单晶或类单晶颗粒，其粒径参数(Dv90-Dv10)/Dv50记为X2；
X1/X2满足0.2≤X1/X2≤0.7；
其中，Dv90、Dv50和Dv10分别表示多颗粒组合的累计体积分布百分数达到90％、50％和10％时对应的粒径。
该正极活性物质采用具有特殊粒径分布特征的多晶活性颗粒与单晶或类单晶活性颗粒的组合，多晶活性颗粒的(Dv90-Dv10)/Dv50与单晶或类单晶活性颗粒的(Dv90-Dv10)/Dv50比值(记为X1/X2)较低，使得活性颗粒粒度合理搭配，在保持能量密度基本不损失的前提下，能够明显改善电池存储寿命，本申请的发明人推测是由于降低了小尺寸多晶颗粒的含量，从而降低活性表面面积，减少存储过程中电解液与正极材料的副反应，进而提高电芯的化学稳定性，延长电池的存储寿命。
在一些实施方式中，在所述正极活性物质的粒度分布曲线中，所述第一活性颗粒和所述第二活性颗粒分别对应两个不连续的独立峰。
通过控制多晶颗粒以及单晶或类单晶颗粒的粒径尺寸及分布，在正极活性物质的粒度分布曲线上，两种颗粒可以分别对应两个不连续的独立峰，此时，两种颗粒的Dv90、Dv50和Dv10可以根据各自的粒度分布峰分别拟合分析得到。
在一些实施方式中，所述X1/X2满足0.25≤X1/X2≤0.55。
在一些实施方式中，所述第一活性颗粒满足0.3≤X1≤1.0。可选地，所述第一活性颗粒满足0.4≤X1≤0.8。
在一些实施方式中，所述第二活性颗粒满足0.7≤X2≤2.5。可选地，所述第二活性颗粒满足0.7≤X2≤2；进一步可选地，所述第二活性颗粒满足0.8≤X2≤1.6。
通过进一步调整X1/X2的取值范围，或者通过进一步调整多晶活性颗粒的X1取值或者选择单晶或类单晶活性颗粒的X2取值从而调控X1/X2的数值，可以更好地协调两种尺寸颗粒的活性表面面积的搭配，从而更好地兼顾高能量密度和长存储寿命的双重需求，在保持良好的能量密度的情况下，更好地改善电池存储寿命。
在一些实施方式中，所述第一活性颗粒的Dv50与所述第二活性颗粒的Dv50的比值RDv50满足2≤RDv50≤4。可选地，所述第一活性颗粒的Dv50与所述第二活性颗粒的Dv50的比值RDv50满足2.3≤RDv50≤4.0。
在一些实施方式中，所述第一活性颗粒的Dv50满足7μm≤Dv50≤15μm。可选地，所述第一活性颗粒的Dv50满足7μm≤Dv50≤14μm。
在一些实施方式中，所述第二活性颗粒的Dv50满足1μm≤Dv50≤6μm。进一步可选地，所述第二活性颗粒的Dv50满足2μm≤Dv50≤4μm。
通过分别调控正极活性物质中多晶活性颗粒及单晶或类单晶活性颗粒的Dv50范围，或者通过二者的Dv50比值，可以协同控制不同活性颗粒的活性表面面积，从而更好地减少存储过程中电解液与正极材料的副反应，进而更好地提高电芯的化学稳定性，进一步延长电池的存储寿命。
在一些实施方式中，所述第一活性颗粒的重量相对于所述第一活性颗粒和所述第二活性颗粒的重量之和的比值RW满足0.5≤RW≤0.9。可选地，所述第一活性颗粒的重量相对于所述第一活性颗粒和所述第二活性颗粒的重量之和的比值RW满足0.7≤RW≤0.9。
通过调节多晶活性颗粒在正极活性颗粒中的重量占比在一定的范围，比如，通过调控第一活性颗粒的重量相对于第一活性颗粒(第一活性颗粒即正极活性物质中的多晶活性颗粒)和第二活性颗粒(第二活性颗粒即正极活性物质中的单晶或类单晶活性颗粒)的重量之和的比值RW在一定范围，如0.5≤RW≤0.9等，可以更有利于降低活性表面面积，减少存储过程中电解液与正极材料的副反应，进而提高电芯的化学稳定性，延长电池的存储寿命。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒各自独立地为含有锂元素和镍元素的氧化物材料。
可选地，所述第一活性颗粒中的镍锂元素数量比RNi/Li和所述第二活性颗粒中的镍锂元素数量比RNi/Li各自独立地满足≥0.65。
进一步可选地，所述第一活性颗粒中的镍锂元素数量比RNi/Li和所述第二活性颗粒中的镍锂元素数量比RNi/Li各自独立地满足0.8≤RNi/Li≤1.0。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒各自独立地为三元材料或含有掺杂和/或包覆元素的三元材料。
可选地，所述第一活性颗粒和所述第二活性颗粒各自独立地为NCM三元材料、NCA三元材料、含有掺杂和/或包覆元素的NCM三元材料、或含有掺杂和/或包覆元素的NCA三元材料。
可选地，所述第一活性颗粒和所述第二活性颗粒各自独立地包含具有如下元素摩尔比的化学组成：Lix(NiaCobMcM’d)O2，其中，0.9≤x≤1.2，0.8≤a＜1，0＜b＜1，0＜c＜1，a+b+c+d＝1，M包括Mn和Al中的至少一种，M’包括Na、K、Ca、Ba、Sb、Ti、Zr、W、Sr、Nb、Mo、Si、Mg、B、Cr和Ta中的一种或多种。
正极活性物质中的镍含量越高，多晶活性颗粒中的小尺寸颗粒(也即小尺寸的多晶活性颗粒)对电池存储性能的恶化越显著，越难以兼顾高能量密度和长存储寿命。采用本申请提供的正极活性物质，可在高镍体系中基本不损失能量密度的前提下，明显改善电池存储寿命。
在一些实施方式中，所述第一活性颗粒中的镍锂元素数量比RNi/Li小于所述第二活性颗粒中的镍锂元素数量比RNi/Li。
可选地，所述第二活性颗粒相对于所述第一活性颗粒中的镍锂元素数量比RNi/Li的差值ΔRNi/Li满足0<ΔRNi/Li≤0.05。
进一步可选地，0.01<ΔRNi/Li≤0.05。
通过调节多晶颗粒以及单晶或类单晶颗粒的镍锂元素数量比RNi/Li的相对大小，使多晶颗粒的RNi/Li低于单晶或类单晶颗粒的RNi/Li，可以在提供较高的正极活性物质的可发挥容量的同时，还有助于提升正极活性物质的热稳定性，改善电池的高温存储性能。
第二方面，本申请提供一种正极极片，其包括正极活性材料层，所述正极活性材料层包括本申请第一方面所述正极活性物质。此时，采用该正极极片可赋予二次电池较优越的存储性能，且同时还能保持良好的能量密度。
在一些实施方式中，所述正极极片的压实密度为3.2～3.8g/cm3；可选地，所述正极极片的压实密度为3.4～3.7g/cm3。当正极极片的压实密度在上述范围时，有利于在兼顾电池能量密度和存储性能的基础上，获得更高的能量密度。
第三方面，本申请提供一种二次电池，其包括本申请第二方面所述正极极片，还包括负极极片和隔离膜；其中，所述隔离膜设置于所述正极极片和所述负极极片之间。
该二次电池的正极极片中，多晶活性颗粒与单晶或类单晶活性颗粒的具有独特的粒径分布特征，具有优越的存储性能，且同时还能保持良好的能量密度。
第四方面，本申请提供一种用电装置，其包括本申请第二方面所述正极极片以及本申请第三方面所述二次电池中的至少一种。
第五方面，本申请提供一种正极活性物质的制备方法，其包括如下步骤：
分别制备第一活性颗粒和第二活性颗粒；
将所述第一活性颗粒和所述第二活性颗粒混合，制得本申请第一方面所述正极活性物质；
其中，所述第一活性颗粒采用包括如下步骤的方法制备得到：将符合元素计量比的前驱体材料进行烧结，烧结温度为600～900℃，烧结时间为8～15h；
所述第二活性颗粒采用包括如下步骤的方法制备得到：将符合元素计量比的前驱体材料进行烧结，烧结温度为700～1000℃，烧结时间为8～15h。
通过控制正极活性物质的烧结参数，可以实现对多晶活性颗粒与单晶或类单晶活性颗粒的独特粒径分布特征的调控。
本申请的一个或多个实施例的细节在下面的附图和描述中提出。本申请的其他特征、目的和优点将从说明书、附图以及权利要求书变得明显。
附图说明
为了更好地描述和说明这里公开的那些申请的实施例或示例，可以参考一幅或多幅附图。用于描述附图的附加细节或示例不应当被认为是对所公开的申请、目前描述的实施例或示例以及目前理解的这些申请的最佳模式中的任何一者的范围的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是本申请一实施例中的正极活性物质的粒度分布曲线图；
图2是本申请一实施例的二次电池的示意图；
图3是图2所示的本申请一实施例的二次电池的分解图；
图4是本申请一实施例的二次电池用作电源的用电装置的示意图。
附图标记说明：
5，二次电池；51，壳体；52，电极组件；53，盖板；6，用电装置。
具体实施方式
以下，适当地参照附图详细说明公开了本申请的正极活性物质、正极极片、二次电池、用电装置和制备方法的一些实施方式。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。
本申请所公开的数值“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，任一个端值可以独立地被包括或不被包括，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，且如果还列出了最大范围值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。比如，当表述某个参数为选自“2-10”的整数，相当于列出了整数2、3、4、5、6、7、8、9和10。
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，本申请的所有步骤可以顺序进行，也可以随机进行，可以优选是顺序进行的。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“具有”、“包括”、“含有”和“包含”各自独立地可以表示开放式，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成员或时序特征，也可以仅包括或包含列出的成员或时序特征。成员例如材料或组分、结构、元件、仪器等；时序特征的非限制性性举例如动作、动作发生的条件、时机、状态等。
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”。进一步地，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)。
在本申请中，如无其他说明，A(如B)，表示B为A中的一种非限制性示例，可以理解A不限于为B。
在本申请中，如无其他说明，“和/或”对应的特征或方案包括两个或两个以上相关所列项目中任一个项目，也包括相关所列项目的任意的和所有的组合，所述任意的和所有的组合包括任意的两个相关所列项目、任意的更多个相关所列项目、或者全部相关所列项目的组合。例如，“A和/或B”表示A、B以及“A与B的组合”构成的组。其中，“包含A和/或B”可以表示“包含A，包含B，以及包含A与B”，还可以表示“包含A，包含B，或者包含A与B”，可根据所在语句恰当理解。
本申请中涉及“多个”、“多种”等，如无特别限定，指在数量上大于2或等于2。例如，“一种或多种”表示一种或大于等于两种。
本文中，“优选”、“更好”仅为描述效果更好的实施方式或实施例，应当理解，并不构成对本申请保护范围的限制。如果一个技术方案中出现多处“优选”，如无特别说明，且无矛盾之处或相互制约关系，则每项“优选”各自独立。
本申请中，“进一步”、“更进一步”、“特别”等用于描述目的，表示内容上的差异，但并不应理解为对本申请保护范围的限制。
本申请中，“第一方面”、“第二方面”、“第三方面”、“第四方面”等中，术语“第一”、“第二”、“第三”、“第四”等仅用于描述目的，不能理解为指示或暗示相对重要性或数量，也不能理解为隐含指明所指示的技术特征的重要性或数量。而且“第一”、“第二”、“第三”、“第四”等仅起到非穷举式的列举描述目的，应当理解并不构成对数量的封闭式限定。
在本申请中，涉及数据范围的单位，如果仅在右端点后带有单位，则表示左端点和右端点的单位是相同的。比如，3～5h或3-5h均表示左端点“3”和右端点“5”的单位都是h(小时)。
本申请实施例说明书中所提到的相关成分的重量不仅仅可以指代各组分的含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请实施例说明书公开的范围之内。进一步地，本申请实施例说明书中所述的重量可以是μg、mg、g、kg等化工领域公知的质量单位。
随着锂离子电池技术在的应用推广，对正极活性物质的综合性能要求也不断提高，以满足电池对高能量密度以及长存储寿命等方面的综合性能需求。对于传统技术中的正极极片，为了获得较高的压实密度，通常活性颗粒的粒径分布会比较宽，比如正极活性物质的(Dv90-Dv10)/Dv50大多在1.2以上(≥1.2)。当正极活性物质具有如此宽的粒径分布时，往往包括大量的小尺寸多晶颗粒。然而，多晶颗粒中的小尺寸颗粒会导致电池存储性能的恶化，如果单方面地降低正极活性物质的(Dv90-Dv10)/Dv50，又会导致压实密度的损失，因此，难以实现对电池长存储寿命的改善和低能量密度损失的兼顾。
针对上述情况，第一方面，本申请提供了一种正极活性物质，其包括第一活性颗粒和第二活性颗粒；其中，所述第一活性颗粒为所述正极活性物质中的多晶颗粒，其粒径参数(Dv90-Dv10)/Dv50记为X1；所述第二活性颗粒为所述正极活性物质中的单晶或类单晶颗粒，其粒径参数(Dv90-Dv10)/Dv50记为X2；
X1/X2满足0.2≤X1/X2≤0.7；
其中，Dv90、Dv50和Dv10分别表示多颗粒组合的累计体积分布百分数达到90％、50％和10％时对应的粒径。
本申请提供的正极活性物质包括记为第一活性颗粒的多晶颗粒以及记为第二活性颗粒的单晶或类单晶颗粒，并将第一活性颗粒和第二活性颗粒的(Dv90-Dv10)/Dv50分别记为X1、X2，则X1/X2满足0.2≤X1/X2≤0.7。
在本申请中，如无其他说明，电极极片可以为正极极片或负极极片，电极极片中的“活性物质”指能够可逆地嵌入与脱出活性离子能力的物质。如无其他说明，“负极活性物质”指用于负极极片的、能够可逆地嵌入与脱出活性离子能力的物质；“正极活性物质”指用于正极极片的、能够可逆地脱出与嵌入活性离子能力的物质。二次电池充电时，活性离子从正极脱出，经过电解质嵌入负极；而二次电池放电时，活性离子则从负极脱出，嵌入正极。活性离子没有特别限定，可以为锂离子，此时对应锂离子二次电池。
在本申请中，“活性材料”和“活性物质”，具有相同含义，可以互换使用；“正极活性物质”与“正极活性材料”具有相同含义，可以互换使用；“负极活性物质”与“负极活性材料”具有相同含义，可以互换使用。
在本申请中，如无特别说明，“活性材料层”包括正极极片的正极活性材料层以及负极极片的负极活性材料层，根据详细的情形，可以指正极活性材料层或负极活性材料层。可以理解，正极活性材料层含有正极活性物质，负极活性材料层含有负极活性物质。
在本申请中，“多晶”也称为二次颗粒，是指由两个或更多个一次颗粒聚集而成 的团聚态颗粒。在本申请中，构成多晶颗粒的一次颗粒的粒径通常控制在100nm～800nm之间。一次颗粒的粒径如果较小，可能加剧与电解液的副反应，而一次颗粒的粒径如果较大，则容易导致电池动力学性能恶化。
在本申请中，“单晶”颗粒也称为一次颗粒，指单晶晶粒；单晶的显微形貌为基本上不聚团的颗粒，颗粒为分散的。单晶可以是不规则形状的颗粒。尺寸大于1μm、无明显团聚的单颗粒通常判定为单晶颗粒。
在本申请中，“一次颗粒”和“二次颗粒”为本领域所熟知的术语。
在本申请中，“类单晶”通常是指一次颗粒存在一定团聚、但尺寸和性质与单晶类似的颗粒。
在本申请中，涉及多晶颗粒以及单晶或类单晶颗粒的“尺寸”或“粒径”，如无其他说明，指Dv50。
多晶颗粒和单晶或类单晶颗粒可以通过使用扫描电子显微镜拍摄SEM图像容易地区分。
在本申请的上下文中，可采用体积累计分布粒径DvN(其中，N表示选自0～100的任意数值)来表征材料的粒径尺寸，指材料的累计体积分布百分数达到N％时所对应的粒径，粒径小于等于DvN的体积占比为N％。DvN可以从材料粒径的体积累积分布曲线上获得，如无其他说明，体积累积分布曲线自小粒径侧从零开始累计。以Dv90、Dv50、Dv10为例，Dv90是指材料的累计体积分布百分数达到90％时所对应的粒径，Dv50是指材料的累计体积分布百分数达到50％时所对应的粒径，Dv10是指材料的累计体积分布百分数达到10％时所对应的粒径。以Dv50为例，表示占材料体积50％的颗粒粒径小于等于Dv50，且占材料体积50％的颗粒粒径大于Dv50。以Dv90为例，表示占材料体积90％的颗粒粒径小于等于Dv90，且占材料体积10％的颗粒粒径大于Dv90。以Dv10为例，表示占材料体积10％的颗粒粒径小于等于Dv10，且占材料体积90％的颗粒粒径大于Dv10。本领域技术人员可以理解Dv90、Dv50、Dv10的含义，而且可以采用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪、LS-909激光粒度仪(欧美克)。
对于多个颗粒组成的混合体系，其粒径参数(Dv90-Dv10)/Dv50可以反映颗粒的分布特征，因此，也是一种粒径分布参数。通常而言，(Dv90-Dv10)/Dv50的数值越大，粒径分布越宽，相反地，该数值越小，则粒径分布越窄。
多晶颗粒中的小尺寸颗粒会导致电池存储性能的恶化。这可能是由于小尺寸多晶颗粒的比表面积大，容易出现颗粒破碎致使正极材料中的过渡金属溶出，进而恶化存储性能。然而，如果单方面地降低正极活性物质的(Dv90-Dv10)/Dv50，又会导致压实密度的损失。
本申请提供的正极活性物质采用具有特殊粒径分布特征的多晶活性颗粒与单晶或类单晶活性颗粒的组合，多晶活性颗粒的(Dv90-Dv10)/Dv50与单晶或类单晶活性颗粒的(Dv90-Dv10)/Dv50比值(记为X1/X2)较低，使得活性颗粒粒度合理搭配，可以在保持能量密度基本不损失的前提下，明显改善电池存储寿命，本申请的发明人推测是由于降低了小尺寸多晶颗粒的含量，从而降低活性表面面积，减少存储过程中电解液与正极材料的副反应，进而提高电芯的化学稳定性，延长电池的存储寿命。
在本申请提供的正极活性物质中，通过调节X1/X2的数值，对多晶活性颗粒与单晶或类单晶活性颗粒之间粒径及粒径分布进行精细匹配，从而可以较好地协调小尺寸多晶活性颗粒含量以及正极极片压实密度之间的平衡，从而较好地满足电池存储性能 及能量密度的双重需求。
在一些实施方式中，在所述正极活性物质的粒度分布曲线中，所述第一活性颗粒和所述第二活性颗粒分别对应两个不连续的独立峰。
在本申请中，如无其他说明，粒度分布曲线可以采用本领域公知的仪器进行测定，比如可以采用激光粒度分析仪测试得到的粒度分布曲线，进一步地，可以利用可以采用如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪、LS-909激光粒度仪(欧美克)。
通过控制多晶颗粒以及单晶或类单晶颗粒的粒径尺寸及分布，在正极活性物质的粒度分布曲线上，两种颗粒可以分别对应两个不连续的独立峰，此时，两种颗粒的Dv90、Dv50和Dv10可以根据各自的粒度分布峰分别拟合分析得到。
图1所示粒度分布曲线是采用激光粒度分析仪对本申请一个实施例中的正极活性物质进行测试得到的粒度分布曲线，其为双峰分布，该曲线具有两个独立的峰，分别对应本申请中的第一活性颗粒(大颗粒)和第二活性颗粒(小颗粒)。
在粒径分布曲线中，第一活性颗粒及第二活性颗粒相对应的两个峰之间不连续，意味着两种活性颗粒的粒径范围不重叠，可以容易地从两种颗粒的混合物中将两种颗粒分别筛选出来，进而分别独立地对两种不同尺寸的活性颗粒进行相关测试，比如，但不限于成分测试、比表面积测试等。
在一些实施方式中，所述正极活性物质的粒度分布曲线中有且仅有两个峰，且所述两个峰为不连续的独立峰，此时，这两个峰分别对应所述第一活性颗粒和所述第二活性颗粒的粒度分布。
在一些实施方式中，所述X1/X2满足0.2≤X1/X2≤0.7。所述X1/X2可以选自下述任一种数值：0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7等，还可以选自上述任两种数值构成的区间，非限制性示例可以包括：0.25≤X1/X2≤0.55。
在一些实施方式中，所述第一活性颗粒满足0.3≤X1≤1.0。所述第一活性颗粒的X1可以选自下述任一种数值：0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95、1等，还可以选自上述任两种数值构成的区间，非限制性示例可以包括：0.4≤X1≤0.8。
在一些实施方式中，所述第二活性颗粒满足0.7≤X2≤2.5。所述第二活性颗粒的X2可以选自下述任一种数值：0.7、0.8、0.9、1.0、1.1、1.2、1.25、1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7、1.75、1.8、1.85、1.9、1.95、2(如2.0)、2.1、2.2、2.3、2.4、2.45等，还可以选自上述任两种数值构成的区间，非限制性示例可以包括：1.5≤X2≤2.5，0.7≤X2≤2，0.7≤X2≤1.6，0.8≤X2≤1.6，0.7≤X2≤1.5，0.8≤X2≤1.5。
通过进一步调整X1/X2的取值范围，或者通过进一步调整多晶活性颗粒的X1取值或者选择单晶或类单晶活性颗粒的X2取值从而调控X1/X2的数值，可以更好地协调两种尺寸颗粒的活性表面面积的搭配，从而更好地兼顾高能量密度和长存储寿命的双重需求，在保持良好的能量密度的情况下，更好地改善电池存储寿命。
在一些实施方式中，所述第一活性颗粒的Dv50与所述第二活性颗粒的Dv50的比值RDv50满足2≤RDv50≤4。所述第一活性颗粒的Dv50与所述第二活性颗粒的Dv50的比值RDv50可以选自下述任一种数值：2、2.1、2.2、2.3、2.4、2.5、2.6、2.7、2.8、2.9、3.0、3.1、3.2、3.3、3.4、3.5、3.6、3.7、3.8、3.9、4(如4.0)等，还可以选自上述任两种数值构成的区间，非限制性示例可以包括：2.3≤RDv50≤4.0。
在一些实施方式中，所述第一活性颗粒的Dv50满足7μm≤Dv50≤15μm。所述第一活性颗粒的Dv50可以选自下述任一种尺寸：7μm、8μm、9μm、10μm、11μm、 12μm、13μm、14μm、15μm等，还可以选自上述任两种尺寸构成的区间，非限制性示例可以包括：7μm≤Dv50≤14μm。
在一些实施方式中，所述第二活性颗粒的Dv50满足1μm≤Dv50≤6μm。所述第二活性颗粒的Dv50可以选自下述任一种尺寸：1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm、5.5μm、6μm等，还可以选自上述任两种尺寸构成的区间，非限制性示例可以包括：2μm≤Dv50≤6μm，1μm≤Dv50≤4μm，2μm≤Dv50≤4μm，3.5μm≤Dv50≤6μm。
在一些实施方式中，所述第一活性颗粒的比表面积为0.35～0.65m2/g；所述第一活性颗粒的比表面积可以选自下述任一种数值：0.35m2/g、0.4m2/g、0.45m2/g、0.5m2/g、0.55m2/g、0.6m2/g、0.65m2/g等，还可以选自上述任两种数值构成的区间，非限制性示例可以包括：0.35～0.55m2/g。
在一些实施方式中，所述第二活性颗粒的比表面积为0.70～0.90m2/g；所述第二活性颗粒的比表面积可以选自下述任一种数值：0.7m2/g、0.72m2/g、0.74m2/g、0.75m2/g、0.76m2/g、0.78m2/g、0.8m2/g、0.82m2/g、0.84m2/g、0.85m2/g、0.86m2/g、0.88m2/g、0.9m2/g等，还可以选自上述任两种数值构成的区间，非限制性示例可以包括：0.70～0.85m2/g。
在本申请中，如无其他说明，颗粒物的比表面积指颗粒物的表面积与重量之比，可以采用本领域公知的仪器及方法进行测定，例如，可以采用氮气吸附比表面积分析测试方法测试。
通过分别调控正极活性物质中多晶活性颗粒及单晶或类单晶活性颗粒的Dv50范围，或者通过二者的Dv50比值，可以协同控制不同活性颗粒的活性表面面积，从而更好地减少存储过程中电解液与正极材料的副反应，进而更好地提高电芯的化学稳定性，进一步延长电池的存储寿命。
在本申请中，正极活性物质的比表面积(BET)可以采用如下的方法测试获得：采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer EmmettTeller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri StarII型比表面与孔隙分析仪进行，测试步骤可以参照GB/T 19587-2004。待测样品：制备得到的正极活性物质；还可以为正极极片的正极活性材料层中取样得到的正极活性物质。测试分析方法如下：将待测样品在真空干燥箱200℃下干燥2小时；然后采用氩气作为吸附气体，通过比表面与孔隙分析仪测绘相对压力P/P0为0～0.99的吸脱附曲线，P为平衡吸附压力，P0为饱和蒸汽压，通过BET方法计算出正极活性物质的比表面积。
在一些实施方式中，所述第一活性颗粒的重量相对于所述第一活性颗粒和所述第二活性颗粒的重量之和的比值RW满足0.5≤RW≤0.9。所述第一活性颗粒的重量相对于所述第一活性颗粒和所述第二活性颗粒的重量之和的比值RW可以选自下述任一种数值：0.5、0.52、0.54、0.55、0.56、0.58、0.6、0.62、0.63、0.64、0.65、0.66、0.68、0.69、0.7、0.72、0.74、0.75、0.76、0.78、0.8、0.82、0.84、0.85、0.86、0.88、0.9等，还可以选自上述任两种数值构成的区间，非限制性示例可以包括：0.7≤RW≤0.9。
通过调节多晶活性颗粒在正极活性颗粒中的重量占比在一定的范围，比如，通过调控第一活性颗粒的重量相对于第一活性颗粒(即正极活性物质中的多晶活性颗粒)和第二活性颗粒(即正极活性物质中的单晶或类单晶活性颗粒)的重量之和的比值RW在一定范围，如0.5≤RW≤0.9等，可以更有利于降低活性表面面积，减少存储过程中电解液与正极材料的副反应，进而提高电芯的化学稳定性，延长电池的存储寿命。
此外，正极活性物质中的镍含量越高，多晶活性颗粒中的小尺寸颗粒(也即小尺寸的多晶活性颗粒)对电池存储性能的恶化越显著，越难以兼顾高能量密度和长存储 寿命。采用本申请提供的正极活性物质，可在高镍体系电池基本不损失能量密度的前提下，明显改善电池存储寿命。
在申请中，“高镍”是本领域技术人员对锂过渡金属氧化物中镍元素的摩尔比例较高的一类物质的统称。通常，以锂过渡金属氧化物为1摩尔计，其中镍元素的摩尔比在0.8以上。以NCM811三元正极材料为例，其中的镍、钴、锰的摩尔比例为80：10：10。在正极活性物质中提高镍含量有利于提升能量密度，可以改善电池容量。
在本申请的锂离子电池体系中，对于正极活性物质、正极极片而言，可以采用镍元素和锂元素的元素数量比来表征镍含量，该元素数量比可称为镍锂摩尔比，可记为RNi/Li，在数值上可等于镍元素与锂元素的摩尔比。在本申请中，RNi/Li每次出现，可以独立地大于等于0.65，进一步地可以独立地大于等于0.7，更进一步地可以独立地大于等于0.8。在本申请的一些实施方式中，镍锂摩尔比RNi/Li还可以选自如下任一种数值或任两种数值构成的区间：0.65、0.7、0.75、0.8、0.82、0.85、0.9、0.95、1等。在本申请的一些实施方式中，镍锂摩尔比RNi/Li还可以选自如下的任一种数值区间(此处的任一个数值端点可以独立地包含或不包含)：0.65～1.0、0.7～1.0、0.8～1.0、0.8～0.95等。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒各自独立地为含有锂元素和镍元素的氧化物材料。
在本申请中，可以将“含有锂元素和镍元素的氧化物”称为锂镍过渡金属氧化物。锂镍过渡金属氧化物的非限制性示例可包括但不限于锂镍氧化物、锂镍钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物等中的一种或多种。其中，锂镍氧化物的非限制性示例可以包括LiNiO2等。锂镍钴锰氧化物的非限制性示例可以包括LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)等。锂镍钴铝氧化物的非限制性示例可以包括LiNi0.85Co0.15Al0.05O2等。
在一些实施方式中，所述第一活性颗粒中的镍锂元素数量比RNi/Li和所述第二活性颗粒中的镍锂元素数量比RNi/Li可以各自独立地符合前述任一实施方式的定义，例如≥0.65。第一活性颗粒和第二活性颗粒的RNi/Li可以各自独立地选自下述任一种数值：0.65、0.66、2/3(即三分之二)、0.67、0.68、0.7、0.71、0.75、0.8、0.85、0.88、0.89、8/9(即九分之八)，0.9、0.91、0.92、0.93、0.94、0.95、0.96、0.97、0.98、0.99、1、1.01、1.02、1.03、1.04、1.05、1.06、1.07、1.08、1.09、1.1等，还可以各自独立地选自上述任两种数值构成的区间。在一些实施方式中，第一活性颗粒和第二活性颗粒各自独立地满足下述范围中的任一种：0.65≤RNi/Li≤1.1，0.8≤RNi/Li≤1.0，0.8≤RNi/Li≤0.95，2/3≤RNi/Li≤8/9，0.66≤RNi/Li≤0.89，0.67≤RNi/Li≤0.88，0.70≤RNi/Li≤1.07，0.71≤RNi/Li≤1.06、≥0.7、≥0.8、≥0.85、≥0.9等。
在一些实施方式中，本申请第一方面所述正极活性物质还含有掺杂元素。如无其他说明，在本申请中的任一种正极活性物质(包括但不限于第一方面所提供的正极活性物质)中的掺杂元素可以独立地包括过渡金属元素和非过渡金属元素中的一种或多种。可以根据功能需求选择合适的掺杂元素及其含量。掺杂元素可以包括但不限于Sb、K、Ca、Zr、Sr、Al、B、Ba、Nb、W、Mo、Co、P和C等中的一种或多种。对于锂离子电池，掺杂元素可以包括但不限于Na、Sb、K、Ca、Zr、Sr、Al、B、Ba、Nb、W、Mo、Co、P和C等中的一种或多种。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒各自独立地为三元材料或含有掺杂和/或包覆元素的三元材料。
本申请所用“三元材料”具有二次电池技术领域中的公知含义，是指正极活性物质中，除包括活性离子的对应元素(如锂元素)外，还可以包括镍(Ni)元素和钴(Co)元素，还可以包括X元素，该X元素可以为但不限于锰(Mn)元素或铝(Al)元素。当X元素为Mn元素时，三元材料可记为NCM三元材料，非限制性示例可以包括 NCM811等；当X元素为Al元素时，三元材料可记为NCA三元材料，非限制性示例可以包括LiNi0.85Co0.15Al0.05O2等。
在本申请中，如无其他说明，“含有掺杂和/或包覆元素的三元材料”表示含有掺杂原始的三元材料、含有包覆元素的三元材料，或者同时含有掺杂元素和包覆元素的三元材料。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒各自独立地为NCM三元材料、NCA三元材料、含有掺杂和/或包覆元素的NCM三元材料或含有掺杂和/或包覆元素的NCA三元材料。
在本申请中，如无其他说明，“含有掺杂和/或包覆元素的NCM三元材料”表示含有掺杂原始的NCM三元材料、含有包覆元素的NCM三元材料，或者同时含有掺杂元素和包覆元素的NCM三元材料。如无其他说明，“含有掺杂和/或包覆元素的NCA三元材料”表示含有掺杂原始的NCA三元材料、含有包覆元素的NCA三元材料，或者同时含有掺杂元素和包覆元素的NCA三元材料。
在本申请中，当正极活性物质含有包覆元素时，表示该正极活性物质具有位于本体结构外侧的包覆层，该包覆层由包覆元素所组成。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒各自独立地包含具有如下元素摩尔比的化学组成：Lix(NiaCobMcM’d)O2，其中，0.9≤x≤1.2，0.8≤a＜1，0＜b＜1，0＜c＜1，a+b+c+d＝1，M包括Mn和Al中的至少一种，M’包括Na、K、Ca、Ba、Sb、Ti、Zr、W、Sr、Nb、Mo、Si、Mg、B、Cr和Ta中的一种或多种。此时，RNi/Li在数值上等于a/x。在其中的一些实施方式中，RNi/Li选自(2/3)～(8/9)。在其中的另一些实施方式中，RNi/Li选自0.67～0.88。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒各自独立地包含如下元素中的一种或多种：Na、K、Ca、Ba、Sb、Ti、Zr、W、Sr、Nb、Mo、Si、Mg、B、Cr和Ta。这些元素的含量可以根据正极活性物质、正极极片或二次电池性能改善的需要灵活调整。比如，在正极活性物质中掺杂Mo、W、Zr、Nb等元素可以调控晶体形貌，改善电解液和阴极材料的界面性能。
需说明的是，上述第一活性颗粒和第二活性颗粒的化学组成式中，为方便起见，将氧元素的摩尔当量记为2，但也可以存在一定的非整数的情况。另外，上述组成式中的x也可以是三元正极材料在制造阶段的投料摩尔当量。通常，市场中出现的电池中的正极材料，已经经过化成老化工艺，并且可能已经过一定次数的充放电循环。因此，伴随着充放电进行，有时正极的Li量会损失。此时，在组成分析上，放电至电池的下限截止电压时，锂含量x可能介于0.65～1.2之间。
在一些实施方式中，所述第一活性颗粒中的镍锂元素数量比RNi/Li小于所述第二活性颗粒中的镍锂元素数量比RNi/Li。可以将第一活性颗粒中的镍锂元素数量比RNi/Li记为R1，将第二活性颗粒中的镍锂元素数量比RNi/Li记为R2。
在一些实施方式中，所述第二活性颗粒相对于所述第一活性颗粒中的镍锂元素数量比RNi/Li的差值ΔRNi/Li满足0<ΔRNi/Li≤0.05。其中，ΔRNi/Li＝R2-R1。
在一些实施方式中，ΔRNi/Li的非限制性示例可以包括0.01、0.02、0.03、0.04、0.05，还可以为前述任两种数值构成的区间，例如0.01≤ΔRNi/Li≤0.05，0.02≤ΔRNi/Li≤0.05，0.02≤ΔRNi/Li≤0.04。
通过调节多晶颗粒以及单晶或类单晶颗粒的镍锂元素数量比RNi/Li的相对大小，使多晶颗粒的RNi/Li低于单晶或类单晶颗粒的RNi/Li，可以在提供较高的正极活性物质的可发挥容量的同时，还有助于提升正极活性物质的热稳定性，改善电池的高温存储性能。
在本申请中，正极活性颗粒中的任一种(可以为但不限于第一活性颗粒或第二活性颗粒)至少包括正极活性颗粒本体，还可以包括或不包括包覆层；当包括包覆层时，所述包覆层设置于所述正极活性颗粒本体至少一部分表面上。通过在正极活性颗粒中引入包覆层，可以起到减少阴极界面副反应的作用。
在一些实施方式中，所述第一活性颗粒包括活性颗粒本体，还包含或者不包括包覆层。
在一些实施方式中，所述第二活性颗粒包括活性颗粒本体，还包含或者不包括包覆层。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒中至少一种包括包覆层。
在一些实施方式中，所述第一活性颗粒包括包覆层，且所述第一活性颗粒的本体和包覆层的成分可以相同或不同。
在一些实施方式中，所述第二活性颗粒包括包覆层，且所述第二活性颗粒的本体和包覆层的成分可以相同或不同。
在一些实施方式中，所述第一活性颗粒和所述第二活性颗粒可以各自独立地包括包覆层或不包括包覆层。
当在正极活性颗粒(可以为但不限于所述第一活性颗粒或所述第二活性颗粒)的表面设置有包覆层时，可以在包覆层中前述掺杂元素中的一种多种。比如，在包覆层中引入金属氧化物可起到提高电极/电解液界面的稳定性的作用。再比如，在包覆层中引入氟化物可起到减少电解液副反应、降低极化、提高正极材料在高电流、高电压下的循环稳定性的作用。再比如，在包覆层中引入锂化物可起到提高正极材料结构稳定性的作用。包覆层的厚度可以根据正极活性颗粒、正极极片或二次电池的性能改善需要进行灵活调节。在一些实施例中，包覆层的厚度为1nm～50nm，可选为1nm～10nm。包覆层的厚度可通过透射电子显微镜方法等形貌观测方法测得。包覆层的质量及各元素组成和含量可通过电感耦合等离子体发射光谱法方法等元素分析方法测得。
第二方面，本申请提供一种正极极片，其包括正极活性材料层，所述正极活性材料层包括本申请第一方面所述正极活性物质。此时，采用该正极极片可赋予二次电池较优越的存储性能，且同时还能保持良好的能量密度。
在一些实施方式中，所述正极极片的压实密度为3.2～3.8g/cm3。所述正极极片的压实密度可以选自下述任一种密度：3.2g/cm3、3.25g/cm3、3.3g/cm3、3.35g/cm3、3.4g/cm3、3.45g/cm3、3.5g/cm3、3.55g/cm3、3.6g/cm3、3.65g/cm3、3.7g/cm3、3.75g/cm3、3.8g/cm3等，还可以选自上述任两种数值构成的区间。在一些实施例中，所述正极极片的压实密度为3.4～3.7g/cm3。当正极极片的压实密度在上述范围时，有利于在兼顾电池能量密度和存储性能的基础上，获得更高的能量密度。
本申请所使用的“压实密度”具有本领域公知的含义，是材料能量密度的参考指标之一。本申请，如无其他说明，正极极片的压实密度指的是正极活性材料层的质量与其体积的比值。
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，至少一个所述正极膜层包括正极活性材料层，任一个所述正极活性材料层独立地含有正极活性物质。至少一个所述正极活性材料层含有本申请第一方面所述正极活性物质。
作为非限制性示例，所述正极集流体具有在其自身厚度方向相对的两个表面，进一步地，所述正极膜层设置在所述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形成在高分子材料基材上而获得。所述正极集流体中，该金属材料的非限制性示例可以包括铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等中的一种或多种。所述正极集流体中，该高分子材料基材的非限制性示例可以包括聚丙烯(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)等基材中的一种或多种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为非限制性示例，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一种或多种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为非限制性示例，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一种或多种。
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，例如正极活性物质、导电剂、粘结剂和任意其他的组分分散于溶剂中，形成正极浆料；将正极浆料涂覆在正极集流体的至少一侧表面上，经烘干、压实(压实可以采用冷压方式)等工序后，即可得到正极极片。溶剂的种类可以选自但不限于前述实施方式中的任一种，例如N-甲基吡咯烷酮(NMP)。正极浆料所涂覆的正极集流体表面可以为正极集流体的单个表面上，也可以为正极集流体的两个表面上。
第三方面，本申请提供一种二次电池，其包括本申请第二方面所述正极极片，还包括负极极片和隔离膜；其中，所述隔离膜设置于所述正极极片和所述负极极片之间。
该二次电池的正极极片中，多晶活性颗粒与单晶或类单晶活性颗粒的具有独特的粒径分布特征，具有优越的存储性能，且同时还能保持良好的能量密度。
在本申请中，二次电池包括正极极片(本申请第二方面提供的正极极片)、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。电解质具有在正极极片和负极极片之间传导活性离子的作用。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，同时可以使活性离子通过。
正极极片
本申请第三方面及第四方面中的正极极片包括本申请第二方面提供的正极极片。
在本申请的一些实施方式中，所述二次电池为锂离子二次电池。锂离子二次电池和利用锂离子的在电极的嵌入与脱嵌以及在电解质中的传输实现充放电过程。通常而言，锂离子二次电池中的活性离子为锂离子，但不限于此。
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物质。
作为非限制性示例，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形成在高分子材料基材上而得到。所述负极集流体中，该金属材料的非限制性示例可以包括铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等中的一种或多种。所述负极集流体中，该高分子材料基材的非限制性示例可以包括聚丙烯(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)等基材中的一种或多种。
在一些实施方式中，负极活性物质可采用本领域公知的用于电池的负极活性物质。作为非限制性示例，负极活性物质可包括以下材料中的一种或多种：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。所述锡基材料可包括单质锡、锡氧化合物以及锡合金中的一种或多种。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物质的传统材料。这些负极活性物质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。所述粘结剂可包括丁苯橡胶(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)中的一种或多种。
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一种或多种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂等。增稠剂的非限制性示例可以包括羧甲基纤维素钠(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，例如负极活性物质、导电剂、粘结剂和任意其他组分分散于溶剂(溶剂的非限制性示例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体的至少一侧表面上(负极浆料所涂覆的表面可以为单个表面上，也可以为两个表面上)，经烘干、压实(压实可以采用冷压方式)等工序后，即可得到负极极片。
电解质
电解质具有在正极极片和负极极片之间传导活性离子的作用。本申请对电解质的种类没有特别的限制，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。在锂离子二次电池中，电解质盐可以包括电解质锂盐。
在一些实施方式中，电解质锂盐可包括六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、高氯酸锂(LiClO4)、六氟砷酸锂、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、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一种或多种。
在一些实施方式中，该溶剂为有机溶剂。
在一些实施方式中，所述有机溶剂为酯类或醚类。在其中的一些实施方式中，所述有机溶剂为酯类。上述酯类溶剂可以包括碳酸酯及卤代碳酸酯中的一种或多种，作为非限制性示例，例如碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)以及前述任一种的氟代物中的一种或多种。
在一些实施方式中，溶剂可包括碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、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一种或多种。
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。
在一些实施方式中，所述添加剂可以包括碳酸亚乙烯酯(VC)、碳酸乙烯亚乙酯(VEC)、氟代碳酸乙烯酯(FEC)、二氟碳酸乙烯酯(DFEC)、三氟甲基碳酸乙烯酯(TFPC)、甲烷二磺酸亚甲酯(MMDS)、1-丙烯-1,3-磺酸内酯(PST)、亚硫酸乙烯酯(ES)、亚硫酸丙烯酯(PS)、硫酸乙烯酯(DTD)、丁二腈(SN)、己二腈(AND)、磺酸酯环状季铵盐、三(三甲基硅烷)磷酸酯(TMSP)、三(三甲基硅烷)硼酸酯(TMSB)及苯甲醚中的一种或多种。
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，隔离膜的材质可包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或多种。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。
电极组件、电化学储能装置、二次电池、用电装置
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，电化学储能装置可包括外包装。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，进一步地，塑料的非限制性示例可以包括聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等中的一种或多种。
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2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3，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实际需求进行选择。
第四方面，本申请提供一种用电装置，其包括本申请第二方面所述正极极片以及本申请第三方面所述二次电池中的至少一种。
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、电动车辆、电气列车、船舶及卫星、储能系统等，但不限于此。其中，移动设备例如可以是手机、笔记本电脑等；电动车辆例如可以是纯电动车、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，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4是作为一个示例的用电装置6。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。
第五方面，本申请提供一种正极活性物质的制备方法，可用于制备本申请第一方面所述正极活性物质。
在一些实施方式中，提供一种正极活性物质的制备方法，其包括如下步骤：
分别制备第一活性颗粒和第二活性颗粒；
将所述第一活性颗粒和所述第二活性颗粒混合，制得本申请第一方面所述正极活性物质。
在一些实施方式中，所述第一活性颗粒采用包括如下步骤的方法制备得到：将符合元素计量比的前驱体材料进行烧结，烧结温度为600～900℃，进一步地，烧结时间可以为8～15h，例如8h、9h、10h、11h、12h、13h、14h、15h等任一种时长，还可以选自上述任两种时长构成的区间。制备第一活性颗粒(为多晶颗粒)时的烧结温度可以为600～900℃，还可以选自下述任一种温度：600℃、650℃、700℃、750℃、800℃、850℃、900℃等，还可以选自前述任两种温度构成的温度区间，例如750-850℃。
在一些实施方式中，所述第二活性颗粒采用包括如下步骤的方法制备得到：将符合元素计量比的前驱体材料进行烧结，烧结温度为700～1000℃，进一步地，烧结时间可以为8～15h，例如8h、9h、10h、11h、12h、13h、14h、15h等任一种时长，还可以选自上述任两种时长构成的区间。制备第二活性颗粒(为单晶或类单晶颗粒)时的烧结温度可以为700～1000℃，还可以选自下述任一种温度：700℃、750℃、800℃、850℃、900℃、950℃、1000℃等，还可以选自前述任两种温度构成的温度区间，例如650-800℃。
对本领域技术人员来说，根据正极活性颗粒的目标元素组成及含量的成分设计，可以在本本领域制备活性颗粒前驱体的常规方法基础上进行针对性调整，从而实现对前驱体及其制备的活性颗粒的成分调控。此外，通过调节前驱体溶液中的各元素组成结合对烧结温度的控制，可以一定程度上实现对活性颗粒的大小进行调控，比如可以调控Dv90、Dv50、Dv10等粒径分布参数。
通过控制正极活性物质的烧结参数，可以实现对多晶活性颗粒与单晶或类单晶活性颗粒的独特粒径分布特征的调控。
当正极活性颗粒在活性颗粒本体的至少一部分表面上设置有包覆层时，可以通过分步烧结的方法制备带有包覆层的正极活性颗粒。可以先将本体前驱体材料进行第一次烧结获得正极活性颗粒的本体，然后将包覆层前驱体材料包覆在所述本体的至少一部分表面上，进而第二次烧结，可获得带有包覆层的正极活性颗粒。这对本领域技术人员来说，容易通过调节制备参数而获得或者筛选出具有目标结构的正极活性颗粒。
第六方面，本申请提供一种正极浆料的制备方法，其包括如下步骤：将本申请第一方面所述正极活性物质和溶剂进行混合，制备得到正极浆料；其中，所述正极浆料中添加或者不添加助剂；
其中，所述第一活性颗粒可采用本申请第五方面中所述的方法制备得到；
所述第二活性颗粒可采用本申请第五方面中所述的方法制备得到；
所述助剂包括导电剂和粘合剂中的一种或多种。
以下，说明本申请的一些实施例。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。实施例中未注明技术或条件的，按照上文中的描述进行，或者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，或者可通过市购产品按照常规方式合成。
正极活性物质的制备方法
1、第一活性颗粒(多晶活性颗粒)的制备
于50℃～55℃，将硫酸镍、硫酸锰和硫酸钴按摩尔比配制成1mol/L溶液，溶剂为去离子水，加入氨水、氢氧化钠等氢氧化物进行共沉淀技术，制备得到多晶前驱体，经粒径测试确认是否符合预设要求；制备多晶前驱体的过程中，通过控制反应时间、共沉淀时的pH值以及氨浓度可实现对前驱体颗粒的粒径尺寸的控制。
将多晶前驱体Ni0.9Co0.02Mn0.08(OH)2、LiOH·H2O以合适摩尔比(1:1.08)进行混料，然后置于650℃～800℃(本例中800℃)气氛炉中进行烧结，烧结时间为8～15h，气体氛围为氧气，冷却后经机械研磨即可得到多晶活性颗粒，即前述的第一活性颗粒。
2、第二活性颗粒(本例中为单晶活性颗粒)的制备
于50℃～55℃，硫酸镍、硫酸锰和硫酸钴按摩尔比配制成1mol/L溶液，溶剂为去离子水，加入氨水、氢氧化钠等氢氧化物进行共沉淀技术，制备得到单晶前驱体，经粒径测试确认是否符合预设要求；制备单晶前驱体的过程中，通过控制反应时间、共沉淀时的pH值以及氨浓度等参数可实现对单晶前驱体颗粒的粒径尺寸的控制。
将单晶前驱体Ni0.9Co0.02Mn0.08(OH)2、LiOH·H2O以合适摩尔比混料，然后置于750℃～850℃(本例中850℃)气氛炉中进行烧结，烧结时间为8～15h，气体氛围为氧气，冷却后经机械研磨即可得到单晶活性颗粒，即前述的第二活性颗粒。
经烧结后，前驱体颗粒转化而成的活性颗粒的粒径略有增大，因此，预设的前驱体粒径适当小于烧结后相应活性颗粒的粒径。
当多晶活性颗粒或单晶活性颗粒的至少一部分表面设置有包覆层，可以先对前驱体材料进行第一段烧结获得正极活性颗粒本体，然后与包覆层原料共混均匀，在合适的气体氛围下进行第二段烧结，从而在活性颗粒本体的表面至少一部分形成包覆层。
3、正极活性物质的制备
将前述制备的多晶活性颗粒(第一活性颗粒)和单晶活性颗粒(第二活性颗粒)按照一定的重量比混合，可得到正极活性物质物质。
以下文的实施例1为例，其中，多晶颗粒Dv50为9μm，多晶颗粒的(Dv90-Dv10)/Dv50为0.4，单晶颗粒Dv50为3.3μm、单晶颗粒(Dv90-Dv10)/Dv50为1.6。也即，可计算得到X1/X2为0.25。还可参阅表1。
测试分析方法
1、颗粒尺寸的测试分析
(1)粒径测试
样本制备：制备得到的正极活性物质；还可以为正极极片的正极活性材料层中取样得到的正极活性物质。为了避免干燥过程的团聚影响粒度的测试，取洗涤后湿润样品进行分散测试。
粒径尺寸类型：Dv10、Dv50和Dv90的测试。
设备型号：马尔文2000(MasterSizer 2000)激光粒度仪，参考标准流程：GB/T19077-2016/ISO 13320:2009。
测试流程：取待测样品适量(样品浓度保证8％～12％遮光度即可)，加入20mL无水乙醇，超声处理5min(53KHz/120W)，确保样品完全分散，之后按照GB/T19077-2016/ISO 13320:2009标准对样品进行测定。
(2)X1/X2
根据前文可知，在本申请中，正极活性从物质中的多晶活性颗粒记为第一活性颗粒，正极活性物质中的单晶或类单晶活性颗粒记为第二活性颗粒。其中，第一活性颗粒的粒径参数(Dv90-Dv10)/Dv50记为X1，第二粒活性颗粒的粒径参数(Dv90-Dv10)/Dv50记为X2。
2、极片压实密度的测试方法
将极片裁剪为1000mm长度的膜片；将正极极片在适当压力下进行碾压，由于铝 箔具备延展性，使其膜片长度为1006mm(延展率为0.6％)；冲切1540.25mm2的小圆片(面积记为A)，测量小圆片重量W及厚度d，根据一定体积正极集流体的重量进行换算，扣除小圆片中正极集流体的重量W1和厚度d1，得到正极活性材料层的重量W2及厚度d2，根据比值W2/(A·d2)计算出极片压实密度。
测试结果可参阅表3。
3、电芯或电池性能
(1)电池容量的测试方法
将锂离子电池在25℃的恒温环境下静置2h，然后在2.8V～4.2V下，按照0.33C充电至4.2V，然后在4.2V下恒压充电至电流≤0.05C，静置10min，然后按照0.33C放电至2.8V，记录该锂离子电池的初始容量C0。
测试结果见可参阅表3。
(2)电池高温存储性能测试方法
将电池放在60℃恒温箱中静置100天，然后在重新在25℃下，先按照0.33C放电至2.8V，静置10min。然后按照0.33C充电至4.2V，在4.2V下恒压充电至电流≤0.05C，静置10min，然后按照0.33C放电至2.8V，记录该锂离子电池的容量C1。电池的容量保持率(％)＝C1/C0×100％。
测试结果可参阅表3。
实施例1.
1、制备正极活性物质
根据表1和表2所示的制备参数，采用前述正极活性物质的制备方法，先后制备第一活性颗粒和第二活性颗粒。
将第一活性颗粒和第二活性颗粒混合，制得本例的正极活性物质。
2、正极极片的制备
将上述正极活性物质、导电剂乙炔黑、粘结剂聚偏氟乙烯(PVDF)按质量比97：2：1混合均匀并加入到溶剂N-甲基吡咯烷酮(NMP)中，制成正极浆料；将正极浆料均匀涂布在正极集流体铝箔的双侧表面上，在85℃下烘干后冷压，再进行模切、分条，制成锂离子电池正极片。
3、负极极片的制备
将负极活性物质石墨、硅氧化物、导电剂乙炔黑、增稠剂羟甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比72：24：2：1：1加入到溶剂水中混合均匀，制成负极浆料；将负极浆料均匀涂布在负极集流体铜箔的双侧表面上，在85℃下烘干后进行冷压，制成锂离子电池负极片。
4、隔膜的制备
采用聚乙烯微孔薄膜作为多孔隔离膜基材，将无机三氧化铝粉末、聚乙烯呲咯烷酮各丙酮溶剂按重量比3：1.5：5.5混合均匀制成浆料并涂布于基材的一面并烘干，得到隔离膜。
5、电解液的制备
将六氟磷酸锂溶解于碳酸乙烯酯、碳酸二甲酯和碳酸甲乙酯的混合溶剂中(碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯的体积比为1：2：1)，得到锂离子电池电解液。
6、电池的制备
将上述正极极片、负极极片以及隔离膜进行卷绕，得到裸电芯，之后经过封装、注液、化成、排气等工序，制得实施例1的二次电池，其是一种锂离子电池。
实施例2-10.第一活性颗粒、第二活性颗粒、正极活性物质、正极极片以及二次电池的制备方法与实施例1基本一致，可参照表1和表2控制活性颗粒的化学组成、粒径大小和分布和活性颗粒含量，允许根据表1的参数适当调整活性颗粒的制备参 数。
对比例1-2.第一活性颗粒、第二活性颗粒、正极活性物质、正极极片以及二次电池的制备方法与实施例1中基本一致，可参照表1和表2控制活性颗粒的化学组成、粒径大小和分布和活性颗粒含量，允许根据表1的参数适当调整活性颗粒的制备参数。
表1.
表2.
表2中：
(1)RW为第一活性颗粒的重量相对于第一活性颗粒和第二活性颗粒的重量之和的百分比；
(2)RDv50为第一活性颗粒与第二活性颗粒的Dv50比值；
(3)X1为第一活性颗粒的(Dv90-Dv10)/Dv50，X2为第二活性颗粒的(Dv90-Dv10)/Dv50。
测试结果及分析
以上各实施例和对比例的参数及性能测试结果可参阅表3。
实施例1-10均具有优异的高温存储性能，60℃存储100天容量保持率均高于93％，高温存储寿命较长，而且还能同时保持良好的压实密度及电池容量，意味着兼具良好的能量密度。
对比例1的X1/X2太高，对比例2的X1/X2太低，均导致无法兼顾高温存储性能、压实密度及初始容量，也即无法兼顾电池存储寿命及能量密度的双重需求。对比例1中的高温存储性能变劣；对比例2的高温存储性能的提升以严重牺牲能量密度为代价，压实密度严重下降。
表3.
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
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。以上所述实施例仅表达了本申请的几种实施方式，其描述较为详细，但并不能因此而理解为对专利范围的限制。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。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请的保护范围应以所附权利要求为准，说明书及附图可用于解释权利要求的内容。

Claims (17)

  1. 一种正极活性物质，其包括第一活性颗粒和第二活性颗粒；其中，所述第一活性颗粒为所述正极活性物质中的多晶颗粒，其粒径参数(Dv90-Dv10)/Dv50记为X1；所述第二活性颗粒为所述正极活性物质中的单晶或类单晶颗粒，其粒径参数(Dv90-Dv10)/Dv50记为X2；
    X1/X2满足0.2≤X1/X2≤0.7；
    其中，Dv90、Dv50和Dv10分别表示多颗粒组合的累计体积分布百分数达到90％、50％和10％时对应的粒径。
  2. 根据权利要求1所述的正极活性物质，其中，在所述正极活性物质的粒度分布曲线中，所述第一活性颗粒和所述第二活性颗粒分别对应两个不连续的独立峰。
  3. 根据权利要求1或2所述的正极活性物质，其中，所述X1/X2满足0.25≤X1/X2≤0.55。
  4. 根据权利要1～3中任一项所述的正极活性物质，其中，所述第一活性颗粒满足0.3≤X1≤1.0；
    可选地，所述第一活性颗粒满足0.4≤X1≤0.8。
  5. 根据权利要1～4中任一项所述的正极活性物质，其中，所述第二活性颗粒满足0.7≤X2≤2.5；
    可选地，所述第二活性颗粒满足0.7≤X2≤2；
    进一步可选地，所述第二活性颗粒满足0.8≤X2≤1.6。
  6. 根据权利要1～5中任一项所述的正极活性物质，其中，所述第一活性颗粒的Dv50与所述第二活性颗粒的Dv50的比值RDv50满足2≤RDv50≤4；
    可选地，所述第一活性颗粒的Dv50与所述第二活性颗粒的Dv50的比值RDv50满足2.3≤RDv50≤4.0。
  7. 根据权利要1～6中任一项所述的正极活性物质，其中，所述第一活性颗粒的Dv50满足7μm≤Dv50≤15μm；
    可选地，所述第一活性颗粒的Dv50满足7μm≤Dv50≤14μm。
  8. 根据权利要1～7中任一项所述的正极活性物质，其中，所述第二活性颗粒的Dv50满足1μm≤Dv50≤6μm；
    可选地，所述第二活性颗粒的Dv50满足2μm≤Dv50≤4μm。
  9. 根据权利要1～8中任一项所述的正极活性物质，其中，所述第一活性颗粒的重量相对于所述第一活性颗粒和所述第二活性颗粒的重量之和的比值RW满足0.5≤RW≤0.9；
    可选地，所述第一活性颗粒的重量相对于所述第一活性颗粒和所述第二活性颗粒的重量之和的比值RW满足0.7≤RW≤0.9。
  10. 根据权利要1～9中任一项所述的正极活性物质，其中，所述第一活性颗粒和所述第二活性颗粒各自独立地为含有锂元素和镍元素的氧化物材料；
    可选地，所述第一活性颗粒中的镍锂元素数量比RNi/Li和所述第二活性颗粒中的镍锂元素数量比RNi/Li各自独立地≥0.65；
    进一步可选地，所述第一活性颗粒中的镍锂元素数量比RNi/Li和所述第二活性颗粒中的镍锂元素数量比RNi/Li各自独立地满足0.8≤RNi/Li≤1.0。
  11. 根据权利要1～10中任一项所述的正极活性物质，其中，所述第一活性颗粒和所述第二活性颗粒各自独立地为三元材料或含有掺杂和/或包覆元素的三元材料；
    可选地，所述第一活性颗粒和所述第二活性颗粒各自独立地为NCM三元材料、NCA三元材料、含有掺杂和/或包覆元素的NCM三元材料、或含有掺杂和/或包覆元素的NCA三元材料；
    可选地，所述第一活性颗粒和所述第二活性颗粒各自独立地包含如下的元素组合Lix(NiaCobMcM’d)O2，其中，0.9≤x≤1.2，0.8≤a＜1，0＜b＜1，0＜c＜1，a+b+c+d＝1，M包括Mn和Al中的至少一种，M’包括Na、K、Ca、Ba、Sb、Ti、Zr、W、Sr、Nb、Mo、Si、Mg、B、Cr和Ta中的一种或多种。
  12. 根据权利要10或11所述的正极活性物质，其中，所述第一活性颗粒中的镍锂元素数量比RNi/Li小于所述第二活性颗粒中的镍锂元素数量比RNi/Li；
    可选地，所述第二活性颗粒相对于所述第一活性颗粒中的镍锂元素数量比RNi/Li的差值ΔRNi/Li满足0<ΔRNi/Li≤0.05；
    进一步可选地，0.01<ΔRNi/Li≤0.05。
  13. 一种正极极片，其包括正极活性材料层，所述正极活性材料层包括权利要求1～14中任一项所述正极活性物质。
  14. 根据权利要求13所述正极极片，其中，所述正极极片的压实密度为3.2～3.8g/cm3；
    可选地，所述正极极片的压实密度为3.4～3.7g/cm3。
  15. 一种二次电池，其包括权利要求13或4所述正极极片，还包括负极极片和隔离膜；其中，所述隔离膜设置于所述正极极片和所述负极极片之间。
  16. 一种用电装置，其包括权利要求13或14所述正极极片以及权利要求15所述二次电池中的至少一种。
  17. 一种正极活性物质的制备方法，其包括如下步骤：
    分别制备第一活性颗粒和第二活性颗粒；
    将所述第一活性颗粒和所述第二活性颗粒混合，制得权利要求1～12中任一项所述正极活性物质；
    其中，所述第一活性颗粒采用包括如下步骤的方法制备得到：将符合元素计量比的前驱体材料进行烧结，烧结温度为600～900℃，烧结时间为8～15h；
    所述第二活性颗粒采用包括如下步骤的方法制备得到：将符合元素计量比的前驱体材料进行烧结，烧结温度为700～1000℃，烧结时间为8～15h。
PCT/CN2023/079055 2023-03-01 2023-03-01 正极活性物质、正极极片、二次电池、用电装置和制备方法 Ceased WO2024178675A1 (zh)

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