WO2023108352A1 - 一种正极活性材料及其相关的极片、二次电池、电池模块、电池包和装置 - Google Patents

一种正极活性材料及其相关的极片、二次电池、电池模块、电池包和装置 Download PDF

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WO2023108352A1
WO2023108352A1 PCT/CN2021/137492 CN2021137492W WO2023108352A1 WO 2023108352 A1 WO2023108352 A1 WO 2023108352A1 CN 2021137492 W CN2021137492 W CN 2021137492W WO 2023108352 A1 WO2023108352 A1 WO 2023108352A1
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positive electrode
electrode active
optionally
active material
weight
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PCT/CN2021/137492
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English (en)
French (fr)
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徐晓富
潘坚福
张新羽
叶永煌
孙婧轩
刘倩
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2021/137492 priority Critical patent/WO2023108352A1/zh
Priority to CN202180071747.4A priority patent/CN116601794B/zh
Priority to EP21947358.4A priority patent/EP4224579A4/en
Priority to US18/180,831 priority patent/US20230261175A1/en
Publication of WO2023108352A1 publication Critical patent/WO2023108352A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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 batteries, and in particular to a positive electrode active material, a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical device.
  • lithium-ion secondary batteries generally use ternary materials (such as nickel-cobalt-manganese-aluminate (NCM), nickel-cobalt-aluminate (NCA)) or quaternary materials (such as nickel-cobalt-manganese-aluminate (NCMA)) as Positive active material.
  • ternary materials such as nickel-cobalt-manganese-aluminate (NCM), nickel-cobalt-aluminate (NCA)
  • quaternary materials such as nickel-cobalt-manganese-aluminate (NCMA)
  • Lithium iron phosphate is gradually being widely used due to its advantages of low cost and good safety.
  • the energy density of such materials is not always satisfactory.
  • the improved lithium manganese iron phosphate (LMFP) improves the energy density while maintaining the advantages of LFP's better safety and long life, the improvement is very limited.
  • Such positive electrode active materials should have balanced performance, that is, cost-effective, good safety, and have good cycle life and improved energy density. at least one.
  • the present application was made in view of the above-mentioned problems, and an object thereof is to provide a positive electrode having a performance balance of at least one of cost-effectiveness, safety, improved cycle life, and improved energy density (particularly, gram capacity) active material.
  • the present application provides a positive electrode active material and related pole pieces, a secondary battery, a battery module, a battery pack and a device.
  • the first aspect of the present application provides a positive electrode active material, which includes the A material as described below and the B material as described below, wherein the A material is at least one selected from the following materials:
  • the A material is a single crystal material or a quasi-single crystal material
  • the Dv50 of the material A is from 0.8 ⁇ m to 4.2 ⁇ m, optionally from 0.8 ⁇ m to 3.2 ⁇ m, more preferably from 0.9 ⁇ m to 2.3 ⁇ m, and more preferably from 1 ⁇ m to 1.5 ⁇ m;
  • the B material is selected from at least one of the following materials:
  • LiNi a Co b E 1-ab O 2 is selected from at least one of Mn and Al, 0.50 ⁇ a ⁇ 0.98, 0.001 ⁇ b ⁇ 0.3;
  • the A material is 50% by weight to 97% by weight, optionally 65% by weight to 97% by weight, more preferably 70% by weight to 95% by weight, and more preferably
  • a mixing ratio, ie m, of 80% to 95% by weight is present.
  • the present application obtains a positive electrode active material by blending a relatively large amount of A material with a specific B material. While using a single A material to improve the gram capacity, the cycle life advantage of the A material will not be significantly lost.
  • the B material is mixed with 3% by weight to 50% by weight, optionally 5% by weight to 30% by weight The ratio exists. Mixing material B and material A in such a mixing ratio can improve the gram capacity of the obtained positive electrode active material compared with material A alone without significantly losing the advantage of material A in terms of cycle life.
  • the A material is selected from at least one of the following:
  • Lithium manganese iron phosphate or lithium iron phosphate chemical formula LiMn d Fe 1-d PO 4 , 0 ⁇ d ⁇ 0.9, optionally 0.1 ⁇ d ⁇ 0.9, more optionally 0.1 ⁇ d ⁇ 0.8; and
  • Lithium vanadium phosphate the chemical formula is Li 3 V 2 (PO 4 ) 3 .
  • the positive electrode active material of the present application can be made more cost-effective, have a longer cycle life and have excellent safety performance.
  • the specific surface area (BET) of the A material is 8m 2 /g to 26m 2 /g, optionally 10m 2 /g to 24m 2 /g, more Optionally from 10m 2 /g to 23m 2 /g.
  • the positive electrode active material of the present application in (ii) LiNia Co b E 1-ab O 2 of the B material, 0.5 ⁇ a ⁇ 0.98, optionally 0.50 ⁇ a ⁇ 0.90, more Optionally 0.50 ⁇ a ⁇ 0.88, still more optionally 0.55 ⁇ a ⁇ 0.88; and/or 0.005 ⁇ b ⁇ 0.30, optionally 0.05 ⁇ b ⁇ 0.30, more optionally 0.05 ⁇ b ⁇ 0.20.
  • a and b in the general formula of material B within the above range, it is helpful to further improve the gram capacity and cycle life of the positive electrode active material obtained after mixing material A and material B.
  • the k and m have the following relationship: k*m ⁇ 1, which can be Optionally k*m ⁇ 1.1, more optionally k*m ⁇ 1.6.
  • k*m is within the above range, the positive electrode active material has more excellent gram capacity and cycle life.
  • the B material is LiNia Co b Mn 1-ab O 2 , LiNia Co b Al 1-ab O 2 , LiNi a Co b Mn c Al 1- abc O 2 or a combination thereof, wherein a, b are as defined above, 0.01 ⁇ c ⁇ 0.34.
  • the B material is a single crystal or a single crystal-like material
  • the Dv50 of its particles is 2 ⁇ m to 4.5 ⁇ m, optionally 2.1 ⁇ m to 4.4 ⁇ m, more optionally and/or a BET of 0.40m 2 /g to 1.20m 2 /g, optionally 0.55m 2 /g to 0.95m 2 /g, more preferably 0.55m 2 /g g to 0.89 m 2 /g. Selecting the material B as defined above can further improve the gram capacity of the positive electrode active material.
  • the B material is a secondary particle, and the Dv50 of the secondary particle is 3.5 ⁇ m to 13 ⁇ m, optionally 3.5 ⁇ m to 12 ⁇ m; and/or the specific surface area From 0.31 m 2 /g to 1.51 m 2 /g, optionally from 0.54 m 2 /g to 1.51 m 2 /g.
  • the second aspect of the present application also provides a positive pole piece, which includes a current collector and a pole piece material layer disposed on at least one surface of the current collector, and the material pole piece layer includes the positive pole active material according to the first aspect of the present application. Material.
  • the third aspect of the present application also provides a secondary battery, which includes the positive electrode active material of the first aspect of the present application or the positive electrode sheet of the second aspect.
  • the fourth aspect of the present application further provides a battery module including the secondary battery according to the third aspect of the present application.
  • a fifth aspect of the present application further provides a battery pack, which includes the battery module of the fourth aspect of the present application.
  • the sixth aspect of the present application further provides an electric device, which includes at least one selected from the secondary battery of the third aspect of the present application, the battery module of the fourth aspect, or the battery pack of the fifth aspect.
  • the positive electrode active material of the present application has good comprehensive performance: it is cost-effective, has good safety, and has improved energy density (especially gram capacity) and good cycle life.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • lithium-ion secondary batteries generally use ternary materials (such as NCM, NCA materials) or quaternary materials (such as NCMA materials) as positive electrode active materials-a type of material that is favored due to its high energy density.
  • ternary materials such as NCM, NCA materials
  • NCMA materials quaternary materials
  • this type of material also has many disadvantages that cannot be ignored, such as high price, short cycle life and poor safety.
  • lithium iron phosphate (LFP) materials are gradually being widely used due to their advantages such as low cost, good safety, and long cycle life; however, the fly in the ointment is that the energy density of such materials cannot meet the demand.
  • the lithium manganese iron phosphate (LMFP) material produced as a technical improvement of the LFP material has improved the energy density to a certain extent, but it still cannot fully meet the demand.
  • the inventors of the present application have found that if the energy density of the latter is improved by mixing other positive electrode active materials with high energy density (such as ternary or quaternary materials) with LFP and/or LMFP materials , in most cases, it is not possible to obtain a positive electrode active material with balanced properties - arbitrarily mixed, not only may not be able to improve the gram capacity of LFP and/or LMFP materials, but may even seriously lose its cycle life advantage (even make the cycle life unacceptably worse). The properties of the materials obtained in this way are unbalanced and do not have practical application value.
  • the inventors of the present application proposed a positive electrode active material obtained by blending specific LFP and/or LMFP materials with specific ternary and/or quaternary materials.
  • the cathode active material of the present application has good comprehensive performance. That is, compared to individual LFP and/or LMFP materials, the positive electrode active material of the present application has improved energy density (especially gram capacity) without significantly increasing the cost and not significantly losing the advantage of cycle life . Even in some cases, the positive electrode active material of the present application improves the gram capacity and cycle life at the same time compared with the LFP and/or LMFP materials alone.
  • the present application proposes a positive electrode active material, which includes: A material as described below and material B as described below, wherein
  • the A material is at least one selected from the following materials:
  • M is selected from one of Ni, Co, Mn, Fe, Mg, Al, V, Zn, Zr, F
  • the A material is a single crystal material or a quasi-single crystal material
  • the Dv50 of the material A is 0.8 ⁇ m to 4.2 ⁇ m;
  • the B material is selected from at least one of the following materials:
  • LiNi a Co b E 1-ab O 2 is selected from at least one of Mn and Al, 0.50 ⁇ a ⁇ 0.98, 0.001 ⁇ b ⁇ 0.3;
  • the A material is present in a mixing ratio, ie, m, of 50% by weight to 97% by weight.
  • the inventors have found that the positive electrode active material of the present application obtained by blending a specific B material in a relatively large amount (based on the total weight of the positive electrode active material, not less than 50% by weight) of the A material has Good comprehensive performance: Compared with the use of A material alone, the positive active material of this application not only has the advantages of safety and cost-effectiveness of A material, but also improves the gram capacity without significantly losing the cycle life of A material Advantage. In particular, in some embodiments, in the positive electrode active material of the present application, there is also a "synergistic effect" between the A material and the B material, so that the obtained positive electrode active material has an improved gram capacity and extended cycle life.
  • the diffusion path of lithium ions can be shortened, thereby effectively improving the gram capacity and cycle life of the positive electrode active material of the present application.
  • the Dv50 of the material A is from 0.8 ⁇ m to 3.2 ⁇ m, more preferably from 0.9 ⁇ m to 2.3 ⁇ m, and even more preferably from 1 ⁇ m to 1.5 ⁇ m.
  • the A material is optionally 65% by weight to 97% by weight, more preferably 70% by weight to 95% by weight %, and more optionally a mixing ratio of 80% by weight to 95% by weight, ie, m exists.
  • single-crystal grains mean individual grains (also That is, primary particles) and/or agglomerated particles consisting of not more than 30 (especially about 5 to 15) particles with an average particle diameter of not less than 0.8 ⁇ m (especially with an average particle diameter in the range of 800 nm to 10000 nm) ) The particles formed by the agglomeration of primary particles.
  • the term "average particle size” is defined as follows: the material is tested with a scanning electron microscope, the test sample and magnification are adjusted so that there are more than 100 primary particles in the field of view, and the size of the particle length direction is measured with a ruler, a total of Measure 100-200 primary particles, and then remove 1/10 of the particles with the largest particle size and 1/10 of the particles with the smallest particle size, and use the particle size data of the remaining 8/10 particles to calculate the average value, which is the average particle size.
  • primary particle means an unagglomerated individual particle, that is, a “primary particle” commonly referred to in the art.
  • second particles and “polycrystalline material particles” generally have similar meanings, which mean more than 30 particles with an average particle size not greater than 0.8 ⁇ m (especially with an average particle size between 50-800 nm) within the range) of particles formed by agglomeration of primary particles.
  • Dv50 means that 50% by volume of the particles in the particle size distribution of a powder have a particle size that does not exceed the current value; that is, the median particle size; in ⁇ m.
  • Dv99 means that 99% by volume of the particles in the particle size distribution of a powder have a particle size that does not exceed the current value, in ⁇ m.
  • BET specific surface area
  • the term "gram capacity” means the amount of electricity that can be released per gram of positive electrode active material, and the unit is milliampere-hour per gram (mAh/g). In this application, the gram capacity value can be used as a reference index for measuring energy density.
  • a material is selected from at least one of the following:
  • Lithium manganese iron phosphate or lithium iron phosphate chemical formula LiMn d Fe 1-d PO 4 , 0 ⁇ d ⁇ 0.9;
  • Lithium vanadium phosphate the chemical formula is Li 3 V 2 (PO 4 ) 3 .
  • the positive electrode active material of the present application can be made more cost-effective, have a longer cycle life, and have excellent safety performance.
  • choosing a lithium manganese iron phosphate material with the chemical formula LiMn d Fe 1-d PO 4 wherein optionally 0.1 ⁇ d ⁇ 0.9, more optionally 0.1 ⁇ d ⁇ 0.8, can be more conducive to simultaneously improving Cycle life and gram capacity.
  • material A has a Dv99 ⁇ 31 ⁇ m, alternatively Dv99 ⁇ 28 ⁇ m, and optionally Dv99>4.2 ⁇ m; more alternatively 10 ⁇ m ⁇ Dv99 ⁇ 28 ⁇ m. Controlling the Dv99 of material A within the above range can not only improve the performance of the positive electrode active material, but also ensure the slurry processing performance of the material, make the coating interface of the slurry on the current collector more uniform, and contribute to further Improve positive electrode sheet and battery performance.
  • the BET of the material A is 8m 2 /g to 26m 2 /g, optionally 10m 2 /g to 24m 2 /g, more preferably 10m 2 /g to 23m 2 / g g.
  • the particle surface of the A material may further have a carbon coating layer of 0.5-5 wt%, optionally 1-2 wt%, based on the total weight of the A material.
  • a carbon coating layer 0.5-5 wt%, optionally 1-2 wt%, based on the total weight of the A material.
  • the material B is present in a mixing ratio of 3% by weight to 50% by weight.
  • the material B is present in a mixing ratio of 5% by weight to 30% by weight. Further selection of the mixing ratio range of the B material can further improve the gram capacity and/or cycle life of the positive electrode active material.
  • B material of formula (ii) LiNiaCobE1 -abO2 0.5 ⁇ a ⁇ 0.98, alternatively 0.50 ⁇ a ⁇ 0.90 , more alternatively 0.50 ⁇ a ⁇ 0.88 , still more optionally 0.55 ⁇ a ⁇ 0.88; and/or 0.005 ⁇ b ⁇ 0.30, optionally 0.05 ⁇ b ⁇ 0.30, more optionally 0.05 ⁇ b ⁇ 0.20.
  • the mixing ratio m (based on the total weight of the positive electrode active material) of the k and the A material has the following relationship: k*m ⁇ 1, optionally, k*m ⁇ 1.1, more optionally k*m ⁇ 1.6.
  • k*m is within the above range, the positive electrode active material has more beneficial gram capacity and cycle life.
  • A, b and k in the chemical formula of the B material are all controlled within the above range, which can significantly improve the gram capacity and/or electron conductance and ion conductance and/or kinetics of the positive electrode active material of the present application, but will not Significant loss of cycle life advantage of the material.
  • the B material is LiNiaCobMn1 -abO2 , LiNiaCobAl1 - abO2 , LiNiaCobMncAl1 - abcO2 , or a combination thereof , a , b are as defined above, 0.01 ⁇ c ⁇ 0.34.
  • the B material may be a single crystal or a quasi-single crystal material, or may be a secondary particle (or a polycrystalline material).
  • the B material is a single crystal or single crystal-like material
  • the Dv50 of its particles is 2 ⁇ m to 4.5 ⁇ m, optionally 2.1 ⁇ m to 4.4 ⁇ m, more preferably 3.5 ⁇ m to 4.4 ⁇ m.
  • the BET of the B material is 0.40 m 2 /g to 1.20 m 2 /g, optionally 0.55 m 2 /g to 0.95 m 2 /g, more preferably from 0.55m 2 /g to 0.89m 2 /g.
  • controlling the particle size and specific surface area of the B material within the above range can improve the performance of the gram capacity of the positive electrode active material obtained after mixing. Specifically, controlling the B material within such a particle size range helps to shorten the lithium ion diffusion path and bulk phase diffusion resistance, reduce the polarization of the material, and improve the capacity of the positive electrode active material of the present application.
  • the Dv99 ⁇ 18 ⁇ m of the B material optionally Dv99 ⁇ 16 ⁇ m, optionally Dv99>4.4 ⁇ m, more optionally 10.5 ⁇ m ⁇ Dv99 ⁇ 15 ⁇ m. Controlling Dv99 within the above range can improve the slurry processing performance of the positive electrode active material of the present application, and further improve the performance of the positive electrode sheet and the battery.
  • the B material is a secondary particle (or polycrystalline material), and the Dv50 of the secondary particle is 3.5 ⁇ m to 13 ⁇ m, optionally 3.5 ⁇ m to 12 ⁇ m.
  • the BET of the B material is 0.31 m 2 /g to 1.51 m 2 /g, optionally 0.54 m 2 /g to 1.51 m 2 /g.
  • the primary particles forming the secondary particles through agglomeration have an average primary particle size range conventional for such materials in the art, for example, 50-800 nm.
  • the diffusion path and bulk phase diffusion resistance of lithium ions can be shortened, the polarization of the material can be reduced, and the performance of the positive electrode active material of the present application can be improved. capacity play.
  • the specific surface area by controlling the specific surface area, side reactions at the interface can be reduced, and battery life deterioration caused by active lithium consumption can be reduced.
  • the B material has a Dv99 of 10 ⁇ m to 25 ⁇ m. Controlling the specific surface area can make the secondary particles of material B have good compactness, and avoid the energy density deterioration caused by the overall low compaction of the mixed system due to the partial core-shell structure and the compaction difference of the hollow material.
  • the performance of the positive electrode active material of the present application can be further improved, such as improving the gram capacity and taking into account a good cycle life.
  • the positive active material of the present application consists of one or more A materials and one or more B materials.
  • the material A and material B are mixed by conventional physical mixing methods (for example, using a stirring tank for stirring and mixing) to obtain the positive electrode active material of the present application.
  • the present application proposes a positive pole piece, which includes a current collector and a pole piece material layer disposed on at least one surface of the current collector, and the material pole piece layer includes the positive pole piece of the present application active material.
  • the positive electrode sheet with the present application has improved gram capacity and good cycle life, and smaller resistance.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode material layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode material layer may optionally further include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode material layer may optionally further include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • a secondary battery which includes the positive electrode active material of the present application or the positive electrode sheet of the present application.
  • the secondary battery is a lithium ion secondary battery.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode material layer includes a negative electrode active material.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode material layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode active material can be a negative electrode active material known in the art for batteries.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like.
  • the silicon-based material can be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of simple tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode material layer may further optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode material layer optionally further includes a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode material layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-shaped secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • a battery module including the secondary battery of the present application is provided.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • a battery pack which includes the battery module of the present application.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 6 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the A material and the B material in the following examples are mixed in a stirring device (such as a stirring tank) Stirring and mixing are carried out, and the resulting mixture is used as the positive electrode active material of the present application.
  • the mass of each component of the positive electrode active material, such as A material, B material, (if any) C material, etc. is obtained by mixing.
  • Artificial graphite is used as the negative electrode active material, and sodium carboxymethyl cellulose (CMC), conductive carbon Super-P and styrene-butadiene rubber (SBR) are added to deionized water at a mass ratio of 94:1.5:2:2.5, and in a drying room Stir to make a homogeneous slurry with a viscosity of 2000 to 12000mPa ⁇ S. Then, the above slurry is coated on the current collector copper foil with a certain coating quality to form a coated pole piece. The coated pole pieces are dried and cold-pressed to make negative pole pieces.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the coating quality is calculated by the following relational formula:
  • the gram capacity of graphite is 350mAh/g
  • x1 and x2 are the gram capacities of material A and material B respectively measured by the "Deduction Test on Lithium Half-battery Powder" below,
  • w1 and w2 are respectively the blending ratios of material A and material B (weight percentage based on the total weight of the positive electrode active material obtained by blending).
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • FEC Fluoroethylene carbonate
  • the amount of FEC added is the weight percentage based on the total weight of the electrolyte.
  • a porous film made of polyethylene (PE) is used as the separator.
  • the secondary battery is assembled into a secondary battery for testing after pole piece punching, cleaning of tabs, lamination, welding, top sealing, liquid injection, preformation, pumping, formation, forming and other processes.
  • the test instrument uses CT2001A Blue Electric (Blue Electric Blue River), put the lithium half-battery prepared as above in a constant temperature environment of 25°C for 5 minutes, and then follow 1/3C (C represents the charge-discharge capacity ratio, 1C represents 1 hour
  • C represents the charge-discharge capacity ratio
  • 1C represents 1 hour
  • the current intensity of the fully discharged battery, the charge and discharge rate of the battery charge and discharge current/rated capacity; in this article, C can also be directly understood as the nominal capacity) discharge to 2.5V, and then stand for 5 minutes, according to 1/3C constant Charging to 4.35V or 4.3V with a current constant voltage (wherein, when the B material is a single crystal or a quasi-single crystal material with a chemical formula of LiNi a Co b E 1-ab O 2 and a ⁇ 0.7, the charging upper limit voltage is 4.35V; And when the B material is a single crystal or quasi-single crystal material with a chemical formula of LiNi a Co b E 1-ab O 2
  • the initial gram capacity of the material to be tested D0/the mass of the positive electrode active material corresponding to the battery cell under test.
  • Test and calculate the initial gram capacity of 5 parallel samples, remove the highest and lowest values from them, and take the average of the remaining 3 data to obtain the initial gram capacity of the material to be tested.
  • the mass of the positive electrode active material corresponding to the battery under test is determined according to the “quality test of the positive electrode sheet active material” below.
  • the positive pole piece to be tested is punched into a disc with a diameter of 14 mm as the sample to be tested (calculated, its area is approximately 154 mm 2 ), and the current collector for preparing the pole piece to be tested is also punched into a disc with a diameter of 14 mm as the sample to be tested. blank sample.
  • the 20 blank samples were weighed to obtain the total weight, and the total mass was divided by the corresponding number to obtain the average mass m 0 of the blank sample (that is, the current collector of the pole piece), in grams (g). Then weigh 20 samples to be tested respectively, and record them as m 1 , m 2 , m 3 ... m 20 in sequence, and the unit is g.
  • the length of the positive pole piece of the laminated battery cell prepared with such a pole piece is a, the width is b, and the unit is mm; then the mass of the active material of the positive pole piece of the laminated battery cell is calculated as follows:
  • Active substance mass 90%* ⁇ [(m 1 +m 2 +m 3 ...+m 20 )/20]-m 0 ⁇ *(a*b)/154.
  • the test instrument adopts CT 4000-5V6A Xinwei machine (Xinweier Electronics Co., Ltd.).
  • the initial gram capacity of the positive electrode active material D0'/the quality of the positive electrode active material
  • the "mass of the positive electrode active material” is determined according to method 3 above.
  • Test and calculate the initial gram capacity of 5 parallel samples, remove the highest value and the lowest value, and take the average of the remaining 3 data to obtain the initial gram capacity of the secondary battery to be tested.
  • the test instrument adopts CT 4000-5V6A Xinwei machine (Xinweier Electronics Co., Ltd.).
  • Each of the secondary batteries prepared as above was subjected to a test voltage of 2.5 to 4.3V or 2.5 to 4.25V under a constant temperature environment of 25°C (wherein, in the B material LiNi a Co b E 1-ab O 2 , when a>0.7 or when the material is secondary particles (polycrystalline), the test voltage is 2.5 to 4.25V; and when a ⁇ 0.7, and the material is single crystal or similar single crystal, the test voltage is 2.5 to 4.3V ), charge to 4.3V or 4.25V respectively according to 0.5C0'(C0' is measured in the above-mentioned "initial gram capacity test method of secondary battery"), and then charge at constant voltage at 4.3V or 4.25V until the current ⁇ 0.05 mA, let stand for 5min, then discharge to 2.5V according to 0.5C0', this is one cycle, and the discharge capacity is recorded as D1
  • Test 5 parallel samples, remove the highest value and the lowest value of the cycle number, and take the average value of the remaining 3 samples, that is, the cycle number of the tested secondary battery when the final battery capacity decays to 70% SOH.
  • the measured cycle value is treated as an integer of 5 and an integer of 10.
  • the data processing method is as follows: the actual measured number of cycles is divided by 5 to obtain the quotient and (if any) remainder. When the remainder ⁇ 3, the number of recorded cycles is (quotient value*5+5) cycles; when the remainder is ⁇ 3, the recorded cycle number is (quotient value*5) cycles.
  • a Mastersizer 3000 laser diffraction particle size analyzer (Malvern Panalytical Co., Ltd.) was used, in which deionized water was used as the solvent, and the positive electrode active material to be tested was ultrasonically treated for 5 minutes before the test.
  • the particle size distribution of the material can be obtained, generally Dv10, Dv50, Dv90, Dv99 and their distribution curves.
  • this method is mainly used to measure the particle size distribution of single crystal or single crystal-like particles and secondary particles.
  • a material is LiMn 0.6 Fe 0.4 PO 4 (LMFP material), single crystal material, Dv50 is 1.1 ⁇ m, Dv99 is 25 ⁇ m, BET is 21m 2 /g, gram capacity 140mAh/g; B material is LiNi 0.55 Co 0.12 Mn 0.33 O 2 (NCM material), single crystal (or quasi-single crystal) material, Dv50 is 4.2 ⁇ m, Dv99 is 10.5 ⁇ m, BET is 0.55m 2 /g , The gram capacity is 170mAh/g.
  • LMFP material LiMn 0.6 Fe 0.4 PO 4
  • Dv50 is 1.1 ⁇ m
  • Dv99 25 ⁇ m
  • BET is 21m 2 /g
  • B material is LiNi 0.55 Co 0.12 Mn 0.33 O 2 (NCM material), single crystal (or quasi-single crystal) material
  • Dv50 is 4.2 ⁇ m
  • Dv99 is 10.5 ⁇ m
  • BET 0.55m 2
  • Table 1 below shows the gram capacity and cycle life (25° C.) of positive electrode active materials obtained by mixing A and B materials in different mixing ratios. Each mixing ratio in Table 1 below is the weight percentage based on the total weight of A material and B material.
  • the positive electrode active material of the present application has improved gram capacity and/or cycle performance.
  • the A material is optionally added in an amount of 65% by weight to 97% by weight, more preferably 70% by weight to 97% by weight, and more preferably 80% by weight to 97% by weight.
  • the positive electrode active material obtained by mixing the mixing ratio m with the B material has improved gram capacity and/or higher cycle performance.
  • Table 2 shows the positive electrode active materials prepared by mixing lithium iron phosphate as material A or different lithium manganese iron phosphate materials (the general chemical formula is LiMn d Fe 1-d PO 4 ) with NCM as material B performance data.
  • material B (chemical formula LiNi 0.55 Co 0.12 Mn 0.33 O 2 ) has the following parameters: gram capacity of 170mAh/g, Dv50 of 4.2 ⁇ m, Dv99 of 10.5 ⁇ m, and BET of 0.55m 2 /g.
  • the mixing ratio m of material A is 80% by weight
  • the mixing ratio of material B is 20% by weight.
  • the positive electrode active material obtained after mixing with the B material has improved gram capacity and good cycle life.
  • the A material is a lithium manganese iron phosphate material
  • the value of d in the above chemical formula is in the range of 0.1-0.9, optionally in the range of 0.1-0.8
  • the positive electrode active material of the present application has both improved gram capacity and cycle life, and Its gram capacity and cycle life values are relatively high.
  • a material is selected from the following materials or mixtures thereof: LiMn 0.6 Fe 0.4 PO 4 (expressed as LMFP in Table 3), LiFePO 4 (expressed as LFP in Table 3) and Li 3 V 2 (PO 4 ) 3 (expressed as LVP is represented); and, in Table 3 below, when the A material is a mixture of the above materials, it is represented as, for example, LFP+LMFP (ie, a mixture of LiMn 0.6 Fe 0.4 PO 4 and LiFePO 4 ).
  • the A material is the LFP material (the gram capacity is 145mAh/g, the Dv50 is 1 ⁇ m, the Dv99 is 10 ⁇ m, and the BET is 23m 2 /g) and the LMFP material (the gram capacity is 140mAh/g) with the expression as above , Dv50 is 1.1 ⁇ m, Dv99 is 25 ⁇ m, and BET is 21 m 2 /g) at a weight ratio of 1:1 to obtain a mixture.
  • the material A is the LFP material (the gram capacity is 145mAh/g, the Dv50 is 1 ⁇ m, the Dv99 is 10 ⁇ m, and the BET is 23m 2 /g) and the LMFP material (the gram capacity is 140mAh/g) with the expression as above , Dv50 of 1.1 ⁇ m, Dv99 of 25 ⁇ m, and BET of 21 m 2 /g) were mixed at a weight ratio of 2:8 to obtain a mixture.
  • Material B is selected from the following single crystal or single crystal-like materials or their mixtures: LiNi 0.55 Co 0.12 Mn 0.33 O 2 (expressed as NCM in Table 3), LiNi 0.55 Co 0.12 Mn 0.18 Al 0.15 O 2 (expressed as NCMA- 1), LiNi 0.55 Co 0.12 Mn 0.31 Al 0.02 O 2 (expressed as NCMA-2 in Table 3), LiNi 0.55 Co 0.12 Mn 0.03 Al 0.3 O 2 (expressed as NCMA-3 in Table 3), LiNi 0.55 Co 0.15 A mixture of Mn 0.15 Al 0.15 O 2 (indicated as NCMA-4 in Table 3).
  • material A is mixed with material B at a blending ratio m of 80% by weight, and the blending ratio is based on the total weight of the positive electrode active material.
  • the B material is the NCM material (the gram capacity is 170mAh/g, the Dv50 is 4.2 ⁇ m, the Dv99 is 10.5 ⁇ m, and the BET is 0.55m 2 /g) and the NCMA-4 material (g A capacity of 172 mAh/g, a Dv50 of 3.9 ⁇ m, a Dv99 of 11.0 ⁇ m, and a BET of 0.65 m 2 /g) were mixed at a weight ratio of 1:1 to obtain a mixture.
  • the NCMA-4 material g A capacity of 172 mAh/g, a Dv50 of 3.9 ⁇ m, a Dv99 of 11.0 ⁇ m, and a BET of 0.65 m 2 /g
  • Table 3 shows the gram capacity and cycle life (25° C.) of positive electrode materials obtained by mixing A and B materials having different Dv50 and/or Dv99 and/or BET. Each mixing ratio is a percentage by weight based on the total weight of the cathode active material.
  • the positive electrode active material of the present application can have both good gram capacity and cycle life, that is, in improving gram capacity without significant loss of cycle life.
  • this range is exceeded, the overall performance of the resulting positive electrode active material is not good (that is, the performance is not balanced) (for example, when the Dv50 is 0.7 ⁇ m, the gram capacity is improved, but the cycle life is greatly reduced to an unacceptable level. Acceptance level) makes such materials have no practical application value.
  • the Dv50 of material A is in the range of 0.9 ⁇ m to 2.3 ⁇ m, optionally in the range of 1 ⁇ m to 1.5 ⁇ m, the positive active material of the present application has improved gram capacity and longer cycle life.
  • the material A is LiMn 0.6 Fe 0.4 PO 4 (referred to as LMFP in Table 4), single crystal material, Dv50 is 1.1 ⁇ m, Dv99 is 25 ⁇ m, BET is 21m2 /g, the gram capacity is 140mAh/g, and the cycle life is 3570 cycles.
  • the mixing ratio m of material A is 80% by weight.
  • Material B is LiNiaCobMn1 -abO2 , in which the Dv50 of single crystal material particles is 2.7-5.6 ⁇ m, Dv99 is 5.4-34.5 ⁇ m, and BET is 0.45-1.05m 2 /g; polycrystalline material particles (ie, Secondary particles) Dv50 is 9.2-12.5 ⁇ m, Dv99 is 20-30.5 ⁇ m, BET is 0.32-0.54 m 2 /g. The size of primary particles agglomerated to form secondary particles is 50-800nm. The mixing ratio of the B material was 20% by weight based on the total weight of the cathode active material.
  • Table 4 shows the gram capacity and cycle life (25°C) of the positive electrode material obtained by mixing material A with material B having different a and b values and different k*m values.
  • the positive electrode active material of the present application has improved gram capacity and good cycle life (also That is, without significant loss of the cycle life advantage of the A material).
  • the positive electrode active material of the present application has improved gram capacity and higher cycle life. More optionally, when the Dv50 is 3.5-4.4 ⁇ m and/or the BET is 0.55-0.89 m 2 /g, the positive electrode active material of the present application has simultaneously improved gram capacity and cycle life.
  • the B material is a polycrystalline material (that is, secondary particles, the average particle size of the primary particles that make up the secondary particles is determined by scanning electron microscopy to be within the range of 50-800nm)
  • the Dv50 is 3.5-13 ⁇ m
  • the Dv99 is 10-25 ⁇ m
  • the BET is 0.31-1.51m 2 /g
  • the positive electrode active material of the present application has improved gram capacity and longer cycle compared with the A material alone life.
  • the Dv50 is 3.5-12 ⁇ m and/or the BET is 0.54-1.51 m 2 /g
  • the positive electrode active material of the present application has improved gram capacity and cycle life compared with material A alone.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments 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材料，其包括如下所述的A材料和如下所述的B材料，其中所述A材料为选自以下单晶材料或类单晶材料中的至少一种：Li xM y(PO 4) z，M选自Ni、Co、Mn、Fe、Mg、Al、V、Zn、Zr、F中的一种或多种，v为M的化合价，1≤x≤3，1≤z≤3且x+vy-3z＝0；所述A材料的Dv50为0.8μm至4.2μm；所述B材料选自以下材料中的至少一种：(i)LiAO 2，A为Ni、Co或Mn；或(ii)LiNi aCo bE 1-a-bO 2，E选自Mn和Al中的至少一种，0.50≤a≤0.98，0.001≤b≤0.3；其中，基于所述正极活性材料的总重量计，所述A材料以50重量％至97重量％的混合比例m存在。本申请的正极活性材料具有成本经济、安全性好、循环寿命长、能量密度高等优点。

Description

一种正极活性材料及其相关的极片、二次电池、电池模块、电池包和装置 技术领域
本申请涉及锂电池技术领域，尤其涉及一种正极活性材料、正极极片、二次电池、电池模块、电池包和用电装置。
背景技术
目前锂离子二次电池普遍使用三元材料(如，镍钴锰酸锂(NCM)、镍钴铝酸锂(NCA))或四元材料(如，镍钴锰铝酸锂(NCMA))作为正极活性材料。但是，此类材料在具备能量密度优势的同时，还存在价格高昂、循环寿命较短和安全性差等缺点。
磷酸铁锂(LFP)凭借其成本低、安全性好等优势，逐渐被广泛应用。但是，此类材料的能量密度却不总能令人满意。作为改进的磷酸锰铁锂(LMFP)虽然在保持了LFP较好的安全性和寿命长等优势的同时提高了能量密度，但是提高幅度十分有限。
目前，本领域内存在对于更为理想的正极活性材料的需求，这样的正极活性材料应当性能均衡，也即，成本经济、安全性好，并且要具有良好的循环寿命和改善的能量密度中的至少一者。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种具有成本效益、安全性好、改善的循环寿命长、改善能量密度(特别是克容量)中的至少一者的性能平衡的正极活性材料。
为了达到上述目的，本申请提供了一种正极活性材料及其相关的极片、二次电池、电池模块、电池包和装置。
本申请的第一方面提供了一种正极活性材料，其包括如下所述的A材料和如下所述的B材料，其中所述A材料为选自以下材料中的至少一种：
Li xM y(PO 4) z
其中，M选自Ni、Co、Mn、Fe、Mg、Al、V、Zn、Zr、F中的一种或 多种，1≤x≤3，1≤z≤3，且v为M的化合价，x+vy-3z＝0；
所述A材料为单晶材料或类单晶材料；
所述A材料的Dv50为0.8μm至4.2μm，可选地为0.8μm至3.2μm，更可选地为0.9μm至2.3μm，再更可选地为1μm至1.5μm；
所述B材料选自以下材料中的至少一种：
(i)LiAO 2，A为Ni、Co或Mn；和
(ii)LiNi aCo bE 1-a-bO 2，E选自Mn和Al中的至少一种，0.50≤a≤0.98，0.001≤b≤0.3；
基于所述正极活性材料的总重量计，所述A材料以50重量％至97重量％，可选地65重量％至97重量％，更可选地70重量％至95重量％，再更可选地80重量％至95重量％的混合比例即m存在。
由此，本申请通过将相对大量的A材料与特定B材料掺混得到正极活性材料，该正极活性材料综合性能良好：其既保留了A材料的安全性和成本效益等优势，并且在相比于采用单独的A材料改善了克容量的同时，又不会明显损失A材料的循环寿命优势。
在任意实施方式中，本申请的正极活性材料中，基于所述正极活性材料的总重量计，所述B材料以3重量％至50重量％，可选地5重量％至30重量％的混合比例存在。以这样的混合比例将B材料与A材料混合，能够使得到的正极活性材料的克容量比单独的A材料有所改善，但又不会显著损失A材料在循环寿命方面的优势。
在任意实施方式中，本申请的正极活性材料中，所述A材料选自以下的至少一种：
磷酸锰铁锂或磷酸铁锂，化学式为LiMn dFe 1-dPO 4，0≤d≤0.9，可选地0.1≤d≤0.9，更可选地0.1≤d≤0.8；和
磷酸钒锂，化学式为Li 3V 2(PO 4) 3。
通过进一步选择上述材料作为A材料，能够使本申请的正极活性材料更具成本效益、循环寿命较长且安全性能优异。
在任意实施方式中，本申请的正极活性材料中，所述A材料的比表面积(BET)为8m 2/g至26m 2/g，可选地为10m 2/g至24m 2/g，更可选地为10m 2/g至23m 2/g。通过将A材料的BET控制在上述范围内，能够有效地限制电化学反应面积，从而减少和抑制循环过程中的界面副反应，降低循环衰减速率 从而延长循环寿命。
在任意实施方式中，本申请的正极活性材料中，所述B材料的(ii)LiNi aCo bE 1-a-bO 2中，0.5≤a≤0.98，可选地0.50≤a≤0.90，更可选地0.50≤a≤0.88，再更可选地0.55≤a≤0.88；和/或0.005≤b≤0.30，可选地0.05≤b≤0.30，更可选地0.05≤b≤0.20。通过将B材料的通式中的a和b控制在上述范围内，有助于进一步改善材料A与材料B混合后所得到的正极活性材料的克容量和循环寿命。
在任意实施方式中，本申请的正极活性材料中，所述B材料的(ii)LiNi aCo bE 1-a-bO 2中，a和b具有如下关系：k＝(a+b)/(1-a-b)，并且1.5≤k≤99，可选地1.5≤k≤19。通过将系数k限定在上述范围内，能够进一步改善克容量和/或循环寿命。
在任意实施方式中，本申请的正极活性材料中，所述B材料的(ii)LiNi aCo bE 1-a-bO 2中，所述k与m具有如下关系：k*m≥1，可选地k*m≥1.1，更可选地k*m≥1.6。当k*m在如上范围内时，正极活性材料具有更优异的克容量和循环寿命。
在任意实施方式中，本申请的正极活性材料中，所述B材料是LiNi aCo bMn 1-a-bO 2、LiNi aCo bAl 1-a-bO 2、LiNi aCo bMn cAl 1-a-b-cO 2或其组合，其中a、b如上文所定义，0.01≤c≤0.34。通过选择上述B材料，能够进一步改善正极活性材料的克容量和/或循环寿命。
在任意实施方式中，本申请的正极活性材料中，所述B材料为单晶或类单晶材料，其颗粒的Dv50为2μm至4.5μm，可选地为2.1μm至4.4μm，更可选地为3.5μm至4.4μm；和/或BET为0.40m 2/g至1.20m 2/g，可选地为0.55m 2/g至0.95m 2/g，更可选地为0.55m 2/g至0.89m 2/g。选用如上限定的B材料，能够进一步改善正极活性材料的克容量。
在任意实施方式中，本申请的正极活性材料中，所述B材料为二次颗粒，所述二次颗粒的Dv50为3.5μm至13μm，可选地为3.5μm至12μm；和/或比表面积为0.31m 2/g至1.51m 2/g，可选地为0.54m 2/g至1.51m 2/g。通过选用上述的二次颗粒形式的B材料，能够缩短锂离子的扩散路径和体相扩散阻抗，降低材料的极化，改善正极活性材料的容量发挥，从而提高正极活性材料的克容量。
本申请的第二方面还提供一种正极极片，其包括集流体和设置于所述集 流体至少一个表面上的极片材料层，所述材料极片层包括本申请第一方面的正极活性材料。
本申请的第三方面还提供一种二次电池，其包括本申请第一方面的正极活性材料或第二方面的正极极片。
本申请的第四方面还提供一种电池模块，其包括本申请第三方面的二次电池。
本申请的第五方面还提供一种电池包，其包括本申请第四方面的电池模块。
本申请的第六方面还提供一种用电装置，其包括选自本申请第三方面的二次电池、第四方面的电池模块或第五方面的电池包中的至少一种。
本申请的正极活性材料综合性能好：具有成本经济、安全性好，并且具有改善的能量密度(特别是克容量)和良好的循环寿命。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的正极活性材料、正极极片、二次电池、电池模块、电池包和电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
目前锂离子二次电池普遍使用三元材料(如，NCM、NCA材料)或四元 材料(如，NCMA材料)作为正极活性材料—一该类材料由于能量密度较高而备受青睐。但是，这类材料在能量密度优势的同时也具有诸多不可忽略的缺点，例如，价格高昂、循环寿命较短和安全性差。
在这种背景下，磷酸铁锂(LFP)材料凭借其成本较低、安全性好、循环寿命长等优势，逐渐被广泛应用；但美中不足的是，此类材料的能量密度却不能满足需求。作为LFP材料的技术改进而产生的磷酸锰铁锂(LMFP)材料，虽然在一定程度上提升了能量密度，但仍不能完全满足需求。
鉴于上述，本领域需要一种成本经济、安全性好，并且具备能量密度较高和循环寿命较长中至少一者的性能均衡的正极活性材料。
不囿于任何理论，本申请的发明人发现，如果通过将能量密度高的其他正极活性材料(如，三元或四元材料)与LFP和/或LMFP材料进行混合来改善后者的能量密度，在大多数情况下，并不能得到性能平衡的正极活性材料——任意地混合，非但可能无法改善LFP和/或LMFP材料克容量，甚至还可能会严重损失其循环寿命优势(甚至使循环寿命变差到不可接受)。如此得到的材料性能不均衡，并不具备实际应用价值。
鉴于上述问题，本申请的发明人提出了一种正极活性材料，其通过将特定的LFP和/或LMFP材料与特定的三元和/或四元材料进行掺混而得到。本申请的正极活性材料综合性能好。也即，相较于单独的LFP和/或LMFP材料，本申请的正极活性材料在不会明显提高成本且不会显著损失循环寿命优势的情况下，具有改善的能量密度(特别是克容量)。甚至在一些情况下，本申请的正极活性材料相较于单独的LFP和/或LMFP材料，同时提高了克容量和循环寿命。
正极活性材料
本申请的一个实施方式中，本申请提出了一种正极活性材料，其包括：如下所述的A材料和如下所述的B材料，其中
所述A材料为选自以下材料中的至少一种：
Li xM y(PO 4) z
其中，M选自Ni、Co、Mn、Fe、Mg、Al、V、Zn、Zr、F中的一
种或多种，1≤x≤3，1≤z≤3，且v为M的化合价，x+vy-3z＝0；
所述A材料为单晶材料或类单晶材料；
所述A材料的Dv50为0.8μm至4.2μm；
所述B材料选自以下材料中的至少一种：
(i)LiAO 2，A为Ni、Co或Mn；或
(ii)LiNi aCo bE 1-a-bO 2，E选自Mn和Al中的至少一种，0.50≤a≤0.98，0.001≤b≤0.3；
基于所述正极活性材料的总重量计，所述A材料以50重量％至97重量％的混合比例即m存在。
不囿于任何理论，发明人发现，在相对大量(基于正极活性材料的总重量计，不少于50重量％)的A材料中掺混特定的B材料所得到的本申请的正极活性材料具有良好的综合性能：相比于采用单独的A材料，本申请的正极活性材料既具有A材料的安全性和成本效益等优势，还在改善克容量的同时，不会显著损失A材料的循环寿命优势。特别地，在一些实施方案中，本申请的正极活性材料中，A材料和B材料之间还具有“协同效应”，使所得到的正极活性材料相较于单独的A材料，同时具有改善的克容量和延长的循环寿命。
通过采用Dv50为0.8μm至4.2μm的单晶材料或类单晶材料作为材料A，能够缩短锂离子的扩散路径，从而有效改善本申请正极活性材料克容量发挥与循环寿命。
在一些实施方式中，可选地，所述A材料的Dv50为0.8μm至3.2μm，更可选地为0.9μm至2.3μm，再更可选地为1μm至1.5μm。通过将所述A材料的Dv50的值控制在上述范围内，能够进一步改善正极活性材料的克容量和/或循环寿命。
在一些实施方式中，在本申请的正极活性材料中，基于正极活性材料的总重量计，所述A材料以可选地65重量％至97重量％，更可选地70重量％至95重量％，再更可选地80重量％至95重量％的混合比例即m存在。通过进一步选择A材料的混合比例即m，能够进一步地改善本申请的正极活性材料的克容量和/或循环寿命。
如本文所使用的，术语“类单晶颗粒”、“准单晶颗粒”、“单晶颗粒”、“单晶材料颗粒”或其类似表述具有基本相似的含义，其意指单个颗粒(也即，一次颗粒)和/或团聚颗粒，所述团聚颗粒是由不多于30个(特别是约5至15个)平均粒径不小于0.8μm(特别是平均粒径在800nm至10000nm范围 内)的一次颗粒团聚形成的颗粒。
如本文所使用的，术语“平均粒径”定义如下：采用扫描电镜对材料进行测试，调整测试样品和放大倍数使视野内具有多于100个一次颗粒，用标尺测量颗粒长度方向的尺寸，共测量100-200个一次颗粒，然后从中去除1/10的具有粒径最大值的颗粒和1/10的具有粒径最小值的颗粒后，用剩余的8/10的颗粒的粒径数据求平均值，即为平均粒径。
如本文所使用的，术语“一次颗粒”意指未团聚的单个颗粒，也即本领域内通常意义上所说的“一次颗粒”。
如本文所使用的，术语“二次颗粒”和“多晶材料颗粒”通常具有类似的含义，其意指由多于30个平均粒径不大于0.8μm(特别是平均粒径在50-800nm范围内)的一次颗粒团聚形成的颗粒。
如本文所使用的，术语“Dv50”意指粉体粒度分布中50％体积的颗粒的粒径不超过当前值；也即，中位粒径；单位为μm。
如本文所使用的，术语“Dv99”意指粉体粒度分布中99％体积的颗粒的粒径不超过当前值，单位为μm。
如本文所使用的，术语“比表面积(BET)”意指单位质量物料具有总表面积，单位为m 2/g。
如本文所使用的，术语“克容量”意指每克正极活性材料所能够释放的电量，单位为毫安时每克(mAh/g)。在本申请中，克容量值可作为衡量能量密度的一个参考指标。
在一些实施方式中，A材料选自以下的至少一种：
磷酸锰铁锂或磷酸铁锂，化学式为LiMn dFe 1-dPO 4，0≤d≤0.9；和
磷酸钒锂，化学式为Li 3V 2(PO 4) 3。
通过进一步选择上述材料作为A材料，能够使本申请的正极活性材料更具成本效益、循环寿命较长、安全性能优异。在一些实施方式中，选择化学式为LiMn dFe 1-dPO 4的磷酸锰铁锂材料，其中可选地0.1≤d≤0.9，更可选地0.1≤d≤0.8，能够更有利于同时改善循环寿命和克容量。
在一些实施方式中，A材料的Dv99＜31μm，可选地Dv99≤28μm，并且可选地Dv99＞4.2μm；更可选地10μm≤Dv99≤28μm。将A材料的Dv99控制在上述范围内，能够在改善正极活性材料的性能的基础上，还保证材料 的浆料加工性能，使浆料在集流体上的涂布界面更均匀，有助于进一步改善正极极片及电池性能。
在一些实施方式中，所述A材料的BET为8m 2/g至26m 2/g，可选地为10m 2/g至24m 2/g，更可选地为10m 2/g至23m 2/g。通过控制所述A材料的BET在上述范围内，能够有效地限制电化学反应面积，从而减少和抑制循环过程中的界面副反应，降低循环衰减速率，延长循环寿命。
在一些实施方式中，所述A材料的颗粒表面还可具有0.5-5重量％，可选地1-2重量％的碳包覆层，基于所述A材料的总重量计。通过这样的碳包覆层，能够使A材料与B材料的混合更加均匀，并且在混合后，有助于优化材料颗粒导电网络，从而减小极片电阻，并保证克容量能够正常发挥。
在一些实施方式中，在本申请的正极活性材料中，基于所述正极活性材料的总重量计，所述B材料以3重量％至50重量％的混合比例存在。将B材料以这样的混合比例与所述A材料混合，能够得到克容量相较于单独的所述A材料有所改善但又不显著损失所述A材料的循环寿命优势的正极活性材料。
在一些实施方式中，可选地，基于所述正极活性材料的总重量计，所述B材料以5重量％至30重量％的混合比例存在。进一步选择所述B材料的混合比例范围，能够进一步改善正极活性材料的克容量和/或循环寿命。
在一些实施方式中，对于化学式为(ii)LiNi aCo bE 1-a-bO 2的B材料，0.5≤a≤0.98，可选地0.50≤a≤0.90，更可选地0.50≤a≤0.88，再更可选地0.55≤a≤0.88；和/或0.005≤b≤0.30，可选地0.05≤b≤0.30，更可选地0.05≤b≤0.20。通过将B材料的通式中的a和b控制在上述范围内，有助于进一步改善所述材料A与材料B混合后所得到的正极活性材料的克容量和循环寿命。
在一些实施方式中，对于上述化学式为(ii)LiNi aCo bE 1-a-bO 2的B材料，其中的a和b具有如下关系：k＝(a+b)/(1-a-b)，并且1.5≤k≤99，可选地1.5≤k≤19。通过将系数k限定在上述范围内，能够进一步改善克容量和/或循环寿命。
在一些实施方式中，所述k与A材料的混合比例m(基于正极活性材料的总重量计)具有如下关系：k*m≥1，可选地，k*m≥1.1，更可选地k*m≥1.6。当k*m在如上范围内时，正极活性材料具有更有益的克容量和循环寿命。
将B材料化学式中的a、b和k均控制在上述范围内，能够显著改善本申请的正极活性材料的克容量和/或电子电导和离子电导和/或材料的动力学，但 又不会明显损失材料的循环寿命优势。
在一些实施方式中，所述B材料是LiNi aCo bMn 1-a-bO 2、LiNi aCo bAl 1-a-bO 2、LiNi aCo bMn cAl 1-a-b-cO 2或其组合，a、b如上文所定义，0.01≤c≤0.34。通过选择上述B材料，能够进一步改善正极活性材料的克容量和/或循环寿命。
在本申请的各种实施方式中，所述B材料可以为单晶或类单晶材料，或者可以为二次颗粒(或多晶材料)。
在一些实施方式中，所述B材料为单晶或类单晶材料，其颗粒的Dv50为2μm至4.5μm，可选地为2.1μm至4.4μm，更可选地为3.5μm至4.4μm。
在单晶或类单晶材料的情况下，在一些实施方式中，所述B材料的BET为0.40m 2/g至1.20m 2/g，可选地为0.55m 2/g至0.95m 2/g，更可选地为0.55m 2/g至0.89m 2/g。
在单晶或类单晶材料的情况下，将所述B材料的颗粒尺寸及比表面积控制在上述范围，能够改善混合后得到的正极活性材料的克容量的发挥。具体来说，将所述B材料控制在这样的颗粒尺寸范围，有助于缩短锂离子的扩散路径和体相扩散阻抗，降低材料的极化，改善本申请的正极活性材料的容量发挥。
在单晶或类单晶材料的情况下，在一些实施方式中，所述B材料的Dv99≤18μm，可选地Dv99≤16μm，可选地Dv99＞4.4μm，更可选地10.5μm≤Dv99≤15μm。将Dv99控制在上述范围内，能够改善本申请的正极活性材料的浆料加工性能，进一步改善正极极片及电池性能。
或者，在一些实施方式中，所述B材料为二次颗粒(或多晶材料)，所述二次颗粒的Dv50为3.5μm至13μm，可选地为3.5μm至12μm。
在二次颗粒的情况下，在一些实施方式中，所述B材料的BET为0.31m 2/g至1.51m 2/g，可选地为0.54m 2/g至1.51m 2/g。
一般地，通过团聚形成所述二次颗粒的一次颗粒具有本领域此类材料常规的一次颗粒平均粒径范围，例如，50-800nm。
在二次颗粒的情况下，通过将所述B材料的颗粒尺寸限制在上述范围内，能够缩短锂离子的扩散路径和体相扩散阻抗，降低材料的极化，改善本申请的正极活性材料的容量发挥。并且，通过控制比表面积，能够减少界面副反应，减少活性锂消耗而造成的电池寿命恶化。
在二次颗粒的情况下，在一些实施方式中，所述B材料的Dv99为10μm至25μm。控制比表面积能够使B材料二次颗粒具有良好的紧实度，避免由于部分核壳结构及空心材料压密差等原因造成混合体系整体压密偏低而导致的能量密度恶化。
以上，通过进一步选择B材料及相关参数，能够进一步改善本申请的正极活性材料的性能，如，改善克容量并兼顾良好的循环寿命。
在一些实施方式中，本申请的正极活性材料由一种或多种A材料和一种或多种B材料组成。
在一些实施方式中，通过常规的物理混合方式将所述A材料和B材料混合(例如，采用搅拌罐进行搅拌混合)，得到本申请的正极活性材料。
正极极片
本申请的一个实施方式中，本申请提出了一种正极极片，其包括集流体和设置于所述集流体至少一个表面上的极片材料层，所述材料极片层包括本申请的正极活性材料。具有本申请的正极极片具有改善的克容量和良好的循环寿命，以及较小的电阻。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极材料层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极材料层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极材料层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
二次电池、电池模块、电池包和用电装置
下文适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池，其包括本申请的正极活性材料或本申请的正极极片。
在一些实施方式中，二次电池是锂离子二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[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材料层，所述负极材料层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极材料层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至 少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极材料层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极材料层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极材料层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸 甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1，4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据 具体实际需求进行选择。
本申请的一个实施方式中，提供一种电池模块，其包括本申请的二次电池。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
本申请的一个实施方式中，提供一种电池包，其包括本申请的电池模块。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电 动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
方法：
1.二次电池的制备方法
(1)正极极片的制备：
将下述实施例(序号以数字表示，例如，实施例1)和对比例(序号以“C+数字”表示，例如，对比例C1)中的A材料和B材料在搅拌设备(如搅拌罐)中进行搅拌混合，所得到的混合物作为本申请的正极活性材料。A材料的混合比例m为基于正极活性材料总重量计的重量百分比，m＝M A/(M A+M B+Mc……)*100％，其中M A、M B、Mc等分别是用于混合得到正极活性材料的各个组分，如A材料、B材料、(如果有的话)C材料等的质量。
将正极活性材料与粘结剂聚偏二氟乙烯(PVDF)、导电碳Super-P加入溶剂N-甲基吡咯烷酮(NMP)中，使正极活性材料、PVDF、导电碳之间的质量比为90∶5∶5，在干燥房中搅拌制成粘度为3000至10000mPa·S的均匀浆料，然后在铝箔上以20mg/cm 2的负载量涂覆上述浆料，经过干燥、冷压制成正极极片。
(2)负极极片的制备：
将人造石墨作为负极活性材料，与羧甲基纤维素钠(CMC)、导电碳Super-P和丁苯橡胶(SBR)以质量比94∶1.5∶2∶2.5加入去离子水中，在干燥房中搅拌制成粘度为2000至12000mPa·S的均匀浆料。然后，以一定的涂覆质量将上述浆料涂覆在集流体铜箔上，形成经涂覆的极片。经涂覆的极片 经过干燥、冷压制成负极极片。
所述涂覆质量通过如下关系式算得到：
94％*负极涂覆质量*石墨克容量＝1.15*90％*正极涂覆质量*[(x1*w1+x2*w2)/(w1+w2)]；
其中，
石墨的克容量为350mAh/g，
x1和x2分别为通过下文“对锂半电池粉末扣电测试”测得的A材料和B材料的克容量，
w1和w2分别为A材料和B材料的掺混比例(基于掺混得到的正极活性材料的总重量计的重量百分比)。
(3)电解液：
在体积比为1∶1∶1的碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸二甲酯(DMC)的混合液中加入LiPF6配制1mol/L的溶液，再加入5wt.％氟代碳酸乙烯酯(FEC)，即得到电解液。此处，FEC的加入量为基于电解液总重量计的重量百分比。
(4)隔离膜：
以聚乙烯(PE)制多孔薄膜作为隔离膜。
(5)二次电池的制备：
在干燥房经过极片冲切、清洗极耳、叠片、焊接、顶封、注液、预化成、抽气、化成、成型等工艺组装成二次电池用于测试。
2.对锂半电池的粉末扣电测试方法
将待测材料(例如，A材料或B材料)(粉末状)与粘结剂聚偏二氟乙烯(PVDF)、导电碳Super-P加入溶剂N-甲基吡咯烷酮(NMP)中，使待测材料、PVDF、导电碳之间的质量比为90∶5∶5。在干燥房中使用匀浆机(德国弗鲁克，R30A)搅拌制成粘度为3000至10000mPa·S的均匀浆料，然后在铝箔上以20mg/cm 2的负载量涂覆上述浆料，经过干燥、冷压制成正极极片。
将正极极片与PP隔膜(Celgard，2400)、金属锂片(天津锂能，直径15.6mm，厚度450μm，纯度＞99.9％)和100μL电解液(电解液由体积比为1∶1∶1的碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸二甲酯(DMC)的混合液中加入LiPF6配制1mol/L的溶液，再向其中加入5wt.％氟代碳酸乙烯酯(FEC) 得到)，在手套箱(布劳恩，Ar气氛)中用CR 2032纽扣电池组件(科路得，304不锈钢材质)组装成纽扣对锂半电池，将半电池取出手套箱后环境温度下静置12h，然后按照下文进行容量测试：
测试仪器采用CT2001A蓝电(蓝电蓝河)，将如上述制备的对锂半电池，在25℃恒温环境下静置5min，然后按照1/3C(C表示充放电能力倍率，1C表示1小时完全放完电的电流强度，电池的充放电倍率＝充放电电流/额定容量；本文中，C也可以直接理解为标称容量)放电至2.5V，再静置5min后，按照1/3C恒流恒压充电至4.35V或4.3V(其中，当B材料为化学式为LiNi aCo bE 1-a-bO 2的单晶或类单晶材料且a≤0.7时，充电上限电压为4.35V；而当B材料为化学式为LiNi aCo bE 1-a-bO 2的单晶或类单晶材料且a＞0.7或者为二次颗粒(多晶材料)时，充电上限电压为4.30V)，然后分别在4.35V或4.3V下恒压充电至电流≤0.05mA，静置5min，此时的充电容量记为C0；然后按照1/3C0放电至2.5V，此时的放电容量为初始放电容量，记为D0。
按照下式分别对每个材料样品计算被测材料样品的初始克容量：
被测材料的初始克容量＝D0/被测电芯对应正极活性材料的质量。
测试并计算5个平行样的初始克容量，从其中去除最高和最低值，剩余3个数据取均值，即得到待测材料初始克容量。
上式中，“被测电芯对应正极活性材料的质量”按照以下文中的“正极极片活性物质质量测试”确定。
3.正极极片活性物质质量测试方法
将待测正极极片冲切成直径14mm的圆片作为待测样品(经计算，其面积近似值为154mm 2)，同时将制备该待测极片的集流体也冲切直径为14mm圆片作为空白样品。
对20个空白样品称重得到总重量，用该总质量除以对应个数得到空白样品(也即极片的集流体)平均质量m 0，单位为克(g)。再对20个待测样品分别称重，依次记为m 1、m 2、m 3……m 20，单位为g。
用这样的极片制备的叠片电芯的正极极片长为a，宽为b，单位mm；则叠片电芯的正极极片活性物质质量计算如下：
活性物质质量＝90％*{[(m 1+m 2+m 3……+m 20)/20]-m 0}*(a*b)/154。
4.二次电池中正极活性材料初始克容量测试方法
测试仪器采用CT 4000-5V6A新威机(新威尔电子有限公司)。将如上述制备的二次电池，分别在25℃恒温环境下，静置5min，然后按照1/3C(C表示充放电能力倍率，1C表示1小时完全放完电的电流强度，电池的充放电倍率＝充放电电流/额定容量；本文中，C也可以直接理解为标称容量)放电至2.5V，再静置5min后，按照1/3C恒流恒压充电至4.3V或4.25V(其中，当B材料为化学式为LiNi aCo bE 1-a-bO 2的单晶或类单晶材料且a≤0.7时，充电上限电压为4.3V；而当B材料为化学式为LiNi aCo bE 1-a-bO 2的单晶或类单晶材料且a＞0.7时或者为二次颗粒(多晶材料)时，充电上限电压为4.25V)，然后分别在4.3V或4.25V下恒压充电至电流≤0.05mA，静置5min，此时的充电容量记为C0’；然后按照1/3C0’放电至2.5V，此时的放电容量为初始放电容量，记为D0’。
按照下式分别对每个二次电池样品计算正极活性材料的初始克容量：
正极活性材料的初始克容量＝D0’/正极活性材料的质量；
式中，“正极活性材料的质量”按照上文中的方法3确定。
测试并计算5个平行样的初始克容量，从中去除最高值和最低值，剩余3个数据取均值，即得到待测二次电池初始克容量。
5.二次电池在25℃循环性能测试方法
测试仪器采用CT 4000-5V6A新威机(新威尔电子有限公司)。将如上述制备的各二次电池，在25℃恒温环境下，在2.5至4.3V或2.5至4.25V的测试电压下(其中，在所述B材料LiNi aCo bE 1-a-bO 2中，a＞0.7时或材料为二次颗粒(多晶)时，测试电压为2.5至4.25V；而当a≤0.7时，且材料为单晶或类单晶时，测试电压为2.5至4.3V)，按照0.5C0’(C0’在上述“二次电池初始克容量测试方法”中测得)分别充电至4.3V或4.25V，然后再在4.3V或4.25V下恒压充电至电流≤0.05mA，静置5min，然后按照0.5C0’放电至2.5V，此为一次循环，放电容量记为D1；重复上述操作，进行n次循环的放电容量记为D n(n＝1，2，3......)。计算电芯衰减程度(State of health，SOH)＝D n/D 3*100％。记录电芯容量衰减至70％SOH时被测二次电池的循环圈数，作为循环能力的考查指标。
测试5个平行样，去除循环圈数最高值和最低值，剩余3个样品取均值，即得到最终的电芯容量衰减至70％SOH时被测二次电池的循环圈数。
在本申请中，基于测试精确度±5，对所测得的循环圈数值按照整5整10处理。具体来说，数据处理方法如下：将实际测得的循环圈数除以5，得到商值和(如果有的话)余数。当余数≥3，则记录的循环圈数为(商值*5+5)圈；当余数＜3，则记录的循环圈数为(商值*5)圈。
6.极片电阻测试方法
测试仪器为GDW3-KDY-2两探针膜片电阻测试仪(北京中慧天诚科技)。取如上述方法1(1)中制备的正极极片，制成4cm*25cm的样品。样品应当外观良好(也即，极片样品的界面均匀，无明显色差、漏金属、脱碳、掉粉、划痕等现象)。将样品在85℃真空烘干4小时以上，使用上述电阻测试仪进行测试。测试压力为0.2-0.4MPa，测试20个平行样品，样品数据采集时间t＝15s(因为电阻仪数据显示稳定需要约15s)。将测得的所有电阻数据做箱体图，取箱体图中位数，即得到极片电阻。
7.粉末激光粒度测试方法
参考国标GB/T19077-2016，采用Mastersizer 3000激光衍射粒度分析仪(马尔文帕纳科公司)，其中溶剂使用去离子水，测试前将待测正极活性材料超声处理5min。
通过该测试，能够得到材料的粒度分布，一般为Dv10、Dv50、Dv90、Dv99及其分布曲线。在本申请中，该方法主要用于测量单晶或类单晶颗粒、二次颗粒的粒度分布。
8.比表面积(BET)测试方法
参考GB/T 19587-2004，用比表面积孔隙度分析仪TRISTAR II 3020(美国麦克仪器公司)对本申请中涉及的各种粉末状材料进行比表面积测试。测试前将粉末置于真空烘箱200℃干燥≥2h，粉末需求量称取＞20g。
9.一次颗粒尺寸的测试方法
用sigma 300扫描电子显微镜(蔡司公司)对本申请涉及的各种粉末状材料进行测试，调整测试样品和放大倍数使视野内具有多于100个一次颗粒，用标尺测量颗粒长度方向的尺寸，共测量100-200个一次颗粒，然后从中去除1/10的具有粒径最大值的颗粒和1/10的具有粒径最小值的颗粒后，用剩余的8/10的颗粒的粒径数据求平均值，即为平均粒径。以此方式确认构成二次颗粒的一次颗粒的粒径范围。
10.粉末压实密度测试方法
参考GB/T 24533-2009测试，采用设备粉末压实密度测试仪(型号：YT-101F)，粉末样品量为1.0g，测试平行样3～5次。
压实密度的计算公式如下：
pC＝m/V＝m/(S*H)
式中：
pC---粉末的压实密度，单位是g/cm；
m---试样质量，单位是g；
S---模具底面积，在本文中，根据所采用的设备配套测试模具，其值为1.327cm 2；
H---压实厚度，单位是cm。
实施例1-7和对比例C1-3
实施例1-7和对比例C1-3中，A材料均为LiMn 0.6Fe 0.4PO 4(LMFP材料)，单晶材料，Dv50为1.1μm，Dv99为25μm，BET为21m 2/g，克容量为140mAh/g；B材料均为LiNi 0.55Co 0.12Mn 0.33O 2(NCM材料)，类单晶(或准单晶)材料，Dv50为4.2μm，Dv99为10.5μm，BET为0.55m 2/g，克容量为170mAh/g。
下表1示出了将A和B材料以不同混合比例混合所得到的正极活性材料的克容量和循环寿命(25℃)。下表1中各混合比例是基于A材料和B材料的总重量计的重量百分比。
表1
Figure PCTCN2021137492-appb-000001
由表1可见，相较于单独使用A材料(对比例C1)，将不少于50重量％，特别是50重量％至97重量％的A材料与B材料混合得到的实施例1-7的正极活性材料，本申请的正极活性材料具有改善的克容量和/或循环性能。特别是，相比于单独使用A材料的情况，将A材料可选地以65重量％至97重量％，更可选地70重量％至97重量％，再更可选地80重量％至97重量％的混合比例m与B材料混合得到的正极活性材料具有改善的克容量和/或较高的循环性能。
实施例8-16
下文中，表2示出了作为A材料的磷酸铁锂或不同的磷酸锰铁锂材料(化学通式为LiMn dFe 1-dPO 4)与作为B材料的NCM混合制备得到的正极活性材料的性能数据。其中，在以下各个实施例中，B材料(化学式为LiNi 0.55Co 0.12Mn 0.33O 2)均具有以下参数：克容量为170mAh/g，Dv50为4.2μm，Dv99为10.5μm，并且BET为0.55m 2/g。其中，在以下各个实施例中，基于正极活性材料的总重量计，A材料的混合比例m均为80重量％，B材料的混合比例为20重量％。
表2
Figure PCTCN2021137492-appb-000002
由表2可见，当在A材料的化学式LiMn dFe 1-dPO 4中，d的值在0至0.9范围内时，与B材料混合后得到的正极活性材料具有改善的克容量和良好的循环寿命。当A材料是磷酸锰铁锂材料时，上述化学式中d的值在0.1-0.9，可选地在0.1-0.8范围内时，本申请的正极活性材料同时具有改善的克容量和循环寿命，并且其克容量和循环寿命值均相对较高。
实施例17-31和对比例C5-C6
A材料选自以下材料或其混合物：LiMn 0.6Fe 0.4PO 4(表3中以LMFP表示)，LiFePO 4(表3中以LFP表示)和Li 3V 2(PO 4) 3(表3中以LVP表示)；并且，在下表3中，当A材料为上述材料的混合物时，表示为，例如，LFP+LMFP(也即，LiMn 0.6Fe 0.4PO 4与LiFePO 4的混合物)。
实施例24中，A材料为表达式如上所述的LFP材料(克容量为145mAh/g，Dv50为1μm，Dv99为10μm，且BET为23m 2/g)与LMFP材料(克容量为140mAh/g，Dv50为1.1μm，Dv99为25μm，且BET为21m 2/g)以重量比1∶1混合得到的混合物。
实施例25中，A材料为表达式如上所述的LFP材料(克容量为145mAh/g，Dv50为1μm，Dv99为10μm，且BET为23m 2/g)与LMFP材料(克容量为140mAh/g，Dv50为1.1μm，Dv99为25μm，且BET为21m 2/g)以重量比2∶8混合得到的混合物。
B材料选自以下单晶或类单晶材料或其混合物：LiNi 0.55Co 0.12Mn 0.33O 2(表3中以NCM表示)、LiNi 0.55Co 0.12Mn 0.18Al 0.15O 2(表3中以NCMA-1表示)、LiNi 0.55Co 0.12Mn 0.31Al 0.02O 2(表3中以NCMA-2表示)、LiNi 0.55Co 0.12Mn 0.03Al 0.3O 2(表3中以NCMA-3表示)、LiNi 0.55Co 0.15Mn 0.15Al 0.15O 2(表3中以NCMA-4表示)的混合物。以下各个实施例中，A材料均是以80重量％的掺混比例m与B材料掺混，该掺混比例是基于正极活性材料的总重量计。
实施例26中，B材料为表达式如上所述的NCM材料(克容量为170mAh/g，Dv50为4.2μm，Dv99为10.5μm，且BET为0.55m 2/g)与NCMA-4材料(克容量为172mAh/g，Dv50为3.9μm，Dv99为11.0μm，且BET为0.65m 2/g)以重量比1∶1混合得到的混合物。
下表3示出了将具有不同Dv50和/或Dv99和/或BET的A和B材料混合所得到的正极材料的克容量和循环寿命(25℃)。各个混合比例均是基于正极活性材料的总重量计的重量百分比。
Figure PCTCN2021137492-appb-000003
由表2可见，当A材料的Dv50在0.8μm至4.2μm范围内时，相较于单独使用A材料，本申请的正极活性材料能够兼具良好的克容量和循环寿命，也即，在提升克容量的同时不会显著损失循环寿命。然而，当超出该范围时，所得到的正极活性材料综合性能不佳(即，性能不均衡)(例如，在Dv50为0.7μm时，克容量虽有所改善，但循环寿命却大幅下降到不可接受的程度)而导致这样的材料无实际应用价值。特别地，当A材料的Dv50在0.9μm至2.3μm，可选地在1μm至1.5μm范围内时，本申请的正极活性材料具有改善的克容量和较长的循环寿命。
实施例32-54和对比例C7-C11
以下实施例32-54和对比例C7-C11中，A材料均为LiMn 0.6Fe 0.4PO 4(表4中记为LMFP)，单晶材料，Dv50为1.1μm，Dv99为25μm，BET为21m 2/g，克容量为140mAh/g，循环寿命为3570圈。表4的各个实施例及对比例中，基于正极活性材料的总重量计，A材料的混合比例m均为80重量％。
B材料为LiNi aCo bMn 1-a-bO 2，其中单晶材料颗粒Dv50为2.7-5.6μm，Dv99为5.4-34.5μm，BET为0.45-1.05m 2/g；多晶材料颗粒(即，二次颗粒)Dv50为9.2-12.5μm，Dv99为20-30.5μm，BET为0.32-0.54m 2/g。团聚组成二次颗粒的一次颗粒尺寸为50-800nm。B材料的混合比例是20重量％，基于正极活性材料的总重量计。
下表4示出了将A材料与具有不同a和b值，以及不同k*m值的B材料混合所得到的正极材料的克容量和循环寿命(25℃)。
Figure PCTCN2021137492-appb-000004
Figure PCTCN2021137492-appb-000005
Figure PCTCN2021137492-appb-000006
Figure PCTCN2021137492-appb-000007
由上表6可见，当所述B材料为单晶材料时，其晶体颗粒的Dv50为2-4.5μm，可选地为2.1-4.5μm，和/或Dv99为10.5-21μm，和/或BET为0.40-1.20m 2/g，可选地为0.41-1.19m 2/g时，本申请的正极活性材料相较于单独使用所述A材料，具有改善的克容量和良好的循环寿命(也即，没有显著损失A材料的循环寿命优势)。可选地，在Dv50为2.1-4.4μm和/或BET为0.55-0.95m 2/g时，本申请的正极活性材料相较于单独使用所述A材料，其具有改善的克容量和较高的循环寿命。更可选地，在Dv50为3.5-4.4μm和/或BET为0.55-0.89m 2/g时，本申请的正极活性材料相较于单独使用所述A材料，其具有同时改善的克容量和循环寿命。
当所述B材料为多晶材料(也即，二次颗粒，通过扫描电镜确定组成该二次颗粒的一次颗粒的平均粒径均在50-800nm范围内)时，当Dv50为3.5-13μm，和/或Dv99为10-25μm，和/或BET为0.31-1.51m 2/g时，本申请的正极活性材料相较于单独使用所述A材料，其具有改善的克容量和较长的循环寿命。可选地，当Dv50为3.5-12μm和/或BET为0.54-1.51m 2/g时，本申请的正极活性材料相较于单独使用A材料，其克容量和循环寿命均提高。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (15)

  1. 一种正极活性材料，其包括如下所述的A材料和如下所述的B材料，其中
    所述A材料为选自以下材料中的至少一种：
    Li xM y(PO 4) z
    其中，M选自Ni、Co、Mn、Fe、Mg、Al、V、Zn、Zr、F中的一种或多种，1≤x≤3，1≤z≤3，且v为M的化合价，x+vy-3z＝0；
    所述A材料为单晶材料或类单晶材料；
    所述A材料的Dv50为0.8μm至4.2μm，可选地为0.8μm至3.2μm，更可选地为0.9μm至2.3μm，再更可选地为1μm至1.5μm；
    所述B材料选自以下材料中的至少一种：
    (i)LiAO 2，A为Ni、Co或Mn；和
    (ii)LiNi aCo bE 1-a-bO 2，E选自Mn和Al中的至少一种，0.50≤a≤0.98，0.001≤b≤0.3；
    基于所述正极活性材料的总重量计，所述A材料以50重量％至97重量％，可选地65重量％至97重量％，更可选地70重量％至95重量％，再更可选地80重量％至95重量％的混合比例m存在。
  2. 根据权利要求1所述的正极活性材料，其中，基于所述正极活性材料的总重量计，所述B材料以3重量％至50重量％，可选地5重量％至30重量％的混合比例存在。
  3. 根据权利要求1或2所述的正极活性材料，其中所述A材料选自以下的至少一种：
    磷酸锰铁锂或磷酸铁锂，化学式为LiMn dFe 1-dPO 4，0≤d≤0.9，可选地0.1≤d≤0.9，更可选地0.1≤d≤0.8；和
    磷酸钒锂，化学式为Li 3V 2(PO 4) 3。
  4. 根据权利要求1至3中任一项所述的正极活性材料，其中所述A材料的比表面积为8m 2/g至26m 2/g，可选地为10m 2/g至24m 2/g，更可选地为10m 2/g至23m 2/g。
  5. 根据权利要求1至4中任一项所述的正极活性材料，其中所 述B材料的(ii)LiNi aCo bE 1-a-bO 2中，0.5≤a≤0.98，可选地0.50≤a≤0.90，更可选地0.50≤a≤0.88，再更可选地0.55≤a≤0.88；和/或0.005≤b≤0.30，可选地0.05≤b≤0.30，更可选地0.05≤b≤0.20。
  6. 根据权利要求1至5中任一项所述的正极活性材料，其中所述B材料的(ii)LiNi aCo bE 1-a-bO 2中，a和b具有如下关系：
    k＝(a+b)/(1-a-b)，并且1.5≤k≤99，可选地1.5≤k≤19。
  7. 根据权利要求6所述的正极活性材料，其中所述k与m具有如下关系：k*m≥1，可选地k*m≥1.1，更可选地k*m≥1.6。
  8. 根据权利要求1至7中任一项所述的正极活性材料，其中所述B材料的(ii)LiNi aCo bE 1-a-bO 2是LiNi aCo bMn 1-a-bO 2、LiNi aCo bAl 1-a-bO 2、LiNi aCo bMn cAl 1-a-b-cO 2或其组合，a、b如权利要求1所定义，0.01≤c≤0.34。
  9. 根据权利要求1至8中任一项所述的正极活性材料，其中所述B材料为单晶或类单晶材料，其颗粒的Dv50为2μm至4.5μm，可选地为2.1μm至4.4μm，更可选地为3.5μm至4.4μm；和/或比表面积为0.40m 2/g至1.20m 2/g，可选地为0.55m 2/g至0.95m 2/g，更可选地为0.55m 2/g至0.89m 2/g。
  10. 根据权利要求1至8中任一项所述的正极活性材料，其中所述B材料为二次颗粒，所述二次颗粒的Dv50为3.5μm至13μm，可选地为3.5μm至12μm；和/或比表面积为0.31m 2/g至1.51m 2/g，可选地为0.54m 2/g至1.51m 2/g。
  11. 一种正极极片，其包括集流体和设置于所述集流体至少一个表面上的极片材料层，所述材料极片层包括权利要求1至10中任一项所述的正极活性材料。
  12. 一种二次电池，其包括权利要求1至10中任一项所述的正极活性材料或权利要求11所述的正极极片。
  13. 一种电池模块，其包括权利要求12所述的二次电池。
  14. 一种电池包，其包括权利要求13所述的电池模块。
  15. 一种用电装置，其包括选自权利要求12所述的二次电池、权利要求13所述的电池模块或权利要求14所述的电池包中的至少一种。
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