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WO2022062745A1 - 用于二次电池的正极极片、二次电池、电池模块、电池包和装置 - Google Patents

用于二次电池的正极极片、二次电池、电池模块、电池包和装置 Download PDF

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Publication number
WO2022062745A1
WO2022062745A1 PCT/CN2021/112009 CN2021112009W WO2022062745A1 WO 2022062745 A1 WO2022062745 A1 WO 2022062745A1 CN 2021112009 W CN2021112009 W CN 2021112009W WO 2022062745 A1 WO2022062745 A1 WO 2022062745A1
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Prior art keywords
positive electrode
metal oxide
transition metal
lithium
nickel transition
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PCT/CN2021/112009
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English (en)
French (fr)
Inventor
冷雪
杜锐
柳娜
刘勇超
倪欢
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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 EP21871122.4A priority Critical patent/EP4203106A1/en
Publication of WO2022062745A1 publication Critical patent/WO2022062745A1/zh
Priority to US18/187,718 priority patent/US20230223523A1/en

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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
    • H01M4/13—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
    • H01M4/362—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
    • 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
    • H01M4/139—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
    • 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
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 field of electrochemistry, and in particular, to a positive electrode sheet for a secondary battery, a secondary battery, a battery module, a battery pack and a device.
  • Electric vehicles have higher and higher requirements for cruising range, which puts forward higher requirements for the energy density of power batteries.
  • the improvement of the energy density of power batteries depends largely on the choice of cathode materials.
  • the application of lithium-nickel transition metal oxides eg, nickel-cobalt-manganese ternary materials
  • the increase of nickel content can significantly improve the gram capacity, thereby increasing the energy density, so lithium-nickel transition metal oxides with high nickel content are currently popular choices.
  • the increase of the nickel content in the lithium-nickel transition metal oxide makes the preparation more difficult: if the temperature is high, the lithium volatilization is serious; if the temperature is low, the grains cannot grow sufficiently, and the processability is poor.
  • lithium-nickel transition metal oxide also affects the stability of the material structure, aggravating the transformation of the surface layered structure to the rock-salt phase, and the surface oxygen release also aggravates the side reactions of the electrolyte on the surface of the material.
  • the purpose of the present application is to provide a positive electrode sheet for a secondary battery, a secondary battery, a battery module, a battery pack and a device for solving the problems in the prior art.
  • a first aspect of the present application provides a positive electrode sheet for a secondary battery, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, so
  • the positive electrode active material layer includes a positive electrode active material
  • the positive electrode active material includes a first lithium-nickel transition metal oxide and a second lithium-nickel transition metal oxide
  • the first lithium-nickel transition metal oxide includes a first substrate and The first coating layer on the surface of the first substrate, the first substrate is secondary particles, and the chemical formula of the first substrate is shown in formula I:
  • -0.1 ⁇ a1 ⁇ 0.1, 0.5 ⁇ x1 ⁇ 0.95, 0.05 ⁇ y1 ⁇ 0.2, 0.03 ⁇ z1 ⁇ 0.4, 0 ⁇ b1 ⁇ 0.05, 0 ⁇ e1 ⁇ 0.1, and x1+y1+z1+b1 1; wherein, M is selected from the combination of one or more of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, and Mn, and X is selected from F and/or Cl.
  • the first cladding layer is selected from metal oxides and/or non-metal oxides.
  • the second lithium-nickel transition metal oxide is single crystal or quasi-single crystal morphology particles.
  • the particle size distribution of the positive electrode active material satisfies: D v 90 ranges from 10 ⁇ m to 20 ⁇ m and 40 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 90 ⁇ m.
  • the OI value of the positive electrode sheet is 10 to 40.
  • the OI value of the positive pole piece is the ratio of the diffraction peak area of the (003) crystal plane to the (110) crystal plane of the positive electrode active material in the XRD diffraction spectrum of the positive pole piece.
  • the second lithium nickel transition metal oxide includes a second substrate, and the chemical formula of the second substrate is shown in formula II:
  • M' is selected from the combination of one or more in Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, Mn
  • X' is selected from F and/or Cl
  • the relative contents x1 and x2 of Ni elements in the molecular formulas of the first substrate and the second substrate satisfy: 0.8 ⁇ x1 ⁇ 0.95, 0.8 ⁇ x2 ⁇ 0.95, and ⁇ x1-x2 ⁇ 0.1;
  • the x1 and x2 satisfy: 0 ⁇ x1-x2 ⁇ 0.1.
  • the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide have a relatively close degree of delithiation/intercalation, which is beneficial to improve the battery. charge-discharge cycle life.
  • the Ni element content x1 of the first lithium-nickel transition metal oxide in this application is slightly higher than that of the second lithium-nickel transition metal oxide x2, which effectively balances the desorption/intercalation of the two cathode active materials.
  • the lithium level is conducive to the battery to exert a higher energy density.
  • the OI value of the positive electrode sheet is 10 to 20.
  • the OI value of the positive pole piece is too high, the positive pole piece will have a serious texture after cold pressing, and the pole piece will easily expand during the charging and discharging process of the battery; when the OI value of the positive pole piece is too low, the positive pole piece in the positive pole piece If the particle strength of the active material is too low, particle breakage is likely to occur in the middle and later stages of cold pressing and circulation, causing gas production problems.
  • the positive active material satisfies: 4.4 ⁇ (D v 90-D v 10)/TD ⁇ 8, optionally, 4.6 ⁇ (D v 90-D v 10)/TD ⁇ 6.5, where TD is the tap density of the positive electrode active material, in g/cm 3 .
  • the positive electrode active material further satisfies the value of (D v 90-D v 10)/TD in the above range, the particle size distribution of the positive electrode active material particles with different morphologies is moderate, and the interstitial volume between particles is low, which is beneficial to the positive electrode sheet Increased compaction density.
  • the tap density TD of the positive electrode active material is 2.2 g/cm 3 to 2.8 g/cm 3 .
  • the first lithium-nickel transition metal oxide is spherical particles, and the sphericity ⁇ of the first lithium-nickel transition metal oxide particles is 0.7-1.
  • the sphericity of the first lithium-nickel transition metal oxide is within the above range, it indicates that the size and distribution of the primary particles in the secondary particles are uniform, the secondary particles are compact, and the mechanical strength is high.
  • the size ratio of the longest diameter L max to the shortest diameter L min of the second lithium nickel transition metal oxide particles satisfies: 1 ⁇ L max /L min ⁇ 3.
  • the second lithium-nickel transition metal oxide is a single-crystal or quasi-single-crystal particle.
  • the L max /L min of the single particle is within the above range, it is mixed with the secondary particles with a sphericity between 0.7 and 1. , which can better fill the interstitial volume of the secondary particles, while improving the compaction density of the positive electrode and the volumetric energy density of the battery, it can also effectively suppress the volume expansion rate of the positive electrode during the cycle and improve the cycle performance.
  • the D v 50 of the first lithium-nickel transition metal oxide that is, D v 50 (L) is 5 ⁇ m to 18 ⁇ m
  • the D v 50 of the second lithium-nickel transition metal oxide that is, D v 50(S) is 1 ⁇ m ⁇ 5 ⁇ m
  • the D v 50(L) and the D v 50(S) satisfy: 2 ⁇ D v 50(L)/D v 50(S) ⁇ 7.
  • the weight percent content of the first lithium-nickel transition metal oxide is 50% to 90%, optionally 60% to 85%; and the weight percent content of the second lithium nickel transition metal oxide is 10% to 50%, optionally 15% to 40%.
  • the weight percentages of the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide in the positive electrode plate are controlled within the above range, and the OI value of the positive electrode plate can be adjusted to a certain extent, and the pressure of the electrode plate can be improved at the same time. Solid density and mechanical strength.
  • the second lithium-nickel transition metal oxide further includes a second cladding layer on the surface of the second substrate, the second cladding layer is a metal oxide and/or a non-metal oxide, which may be Optionally, the second coating material is a metal oxide.
  • a second aspect of the present application provides a method for preparing a positive electrode sheet for a secondary battery provided in the first aspect of the present application.
  • a third aspect of the present application provides a secondary battery, which includes the positive electrode sheet described in the first aspect of the present application.
  • a fourth aspect of the present application provides a battery module including the secondary battery described in the third aspect of the present application.
  • a fifth aspect of the present application provides a battery pack including the battery module described in the fourth aspect of the present application.
  • a sixth aspect of the present application provides a device comprising the secondary battery of the third aspect of the present application, the secondary battery being used as a power source for the device.
  • the present application is used in a positive electrode plate of a secondary battery, and the positive electrode active material includes a first lithium-nickel transition metal oxide and a second lithium-nickel transition metal oxide, wherein the first lithium-nickel transition metal oxide is used.
  • the first lithium-nickel transition metal oxide is a coated secondary particle, and the second lithium-nickel transition metal oxide is a single-crystal or single-crystal-like single particle.
  • the OI value of the plate improves the compressive strength of the positive electrode active material particles in the positive electrode plate, effectively suppresses the problem of particle cracking of the positive electrode active material particles, and reduces the relative content of the (003) crystal plane perpendicular to the positive electrode plate.
  • the secondary battery for example, lithium ion battery
  • the battery module, battery pack and device of the present application include the secondary battery and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a perspective view of an embodiment of a battery.
  • FIG. 2 is an exploded view of an embodiment of a battery.
  • FIG. 3 is a perspective view of an embodiment of a battery module.
  • FIG. 4 is a perspective view of an embodiment of a battery pack.
  • FIG. 5 is an exploded view of FIG. 4 .
  • FIG. 6 is a schematic diagram of one embodiment of a device using a battery as a power source.
  • Ranges disclosed herein are defined in the form of lower limits and upper limits, with a given range being defined by the selection of a lower limit and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive, and may be arbitrarily combined, ie, any lower limit may be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is to be understood that the ranges of 60-110 and 80-120 are also contemplated.
  • the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where both a and b are real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" have been listed in the text, and "0-5" is just an abbreviated representation of the combination of these numerical values.
  • a parameter is expressed as an integer greater than or equal to 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.
  • the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • reference to the method may further include step (c), indicating that step (c) may be added to the method in any order, eg, 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), etc.
  • the “comprising” and “comprising” mentioned in this application mean open-ended or closed-ended.
  • the terms “comprising” and “comprising” can mean that other components not listed may also be included or included, or only the listed components may be included or included.
  • the term "or” is inclusive unless otherwise specified.
  • 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 present) and B is false (or absent); A is false (or absent) and B is true (or present) ; or both A and B are true (or present).
  • a first aspect of the present application provides a positive electrode sheet for a secondary battery, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, a positive electrode active material It includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide.
  • the first lithium nickel transition metal oxide includes a first substrate and a first cladding layer on the surface of the first substrate.
  • the first substrate For secondary particles, the chemical formula of the first lithium nickel transition metal oxide is shown in formula I:
  • -0.1 ⁇ a1 ⁇ 0.1, 0.5 ⁇ x1 ⁇ 0.95, 0.05 ⁇ y1 ⁇ 0.2, 0.03 ⁇ z1 ⁇ 0.4, 0 ⁇ b1 ⁇ 0.05, 0 ⁇ e1 ⁇ 0.1, and x1+y1+z1+b1 1; wherein, M is selected from the combination of one or more of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, and Mn, and X is selected from F and/or Cl.
  • the first cladding layer is selected from metal oxides and/or non-metal oxides.
  • the second lithium nickel transition metal oxide is a single crystal or a single crystal-like morphology particle.
  • the particle size distribution characteristics of the positive electrode active material satisfy: the range of D v 90 is 10 ⁇ m-20 ⁇ m and 40 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 90 ⁇ m, wherein D v 10, D v 50, D v 90 is the volume distribution particle size of the positive electrode active material, and the unit is ⁇ m.
  • the OI value of the positive electrode sheet is 10 to 40.
  • D v 10 is the particle size (unit: ⁇ m) corresponding to when the cumulative volume distribution percentage of the positive active material reaches 10%;
  • D v 50 is the corresponding particle size (unit: ⁇ m) when the cumulative volume distribution percentage of the sample reaches 50% : ⁇ m);
  • D v 90 is the corresponding particle size (unit: ⁇ m) when the volume cumulative distribution percentage of the sample reaches 90%.
  • D v 10, D v 50, and D v 90 have meanings known in the art, and can be measured using instruments and methods known in the art. For example, referring to GB/T19077-2016 particle size distribution laser diffraction method, it can be conveniently determined by using a laser particle size analyzer, such as the Mastersizer2000E laser particle size analyzer of Malvern Instruments Ltd., UK.
  • the OI value of the positive pole piece is the ratio of the diffraction peak area corresponding to the (003) crystal plane and the (110) crystal plane of the positive electrode active material in the XRD diffraction spectrum of the positive pole piece.
  • the OI value of the positive pole piece has a well-known meaning in the art, and can be tested by using an XRD diffractometer.
  • the following method can be used: place the prepared positive pole piece horizontally in an XRD diffractometer to test the XRD diffraction spectrum of the positive pole piece, calculate the (003) crystal plane of the positive electrode active material in the XRD diffraction pattern and the (110) The ratio of the diffraction peak area corresponding to the crystal plane is the OI value of the positive pole piece.
  • the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide
  • the first base material in the first lithium-nickel transition metal oxide is secondary particles formed by agglomeration of primary particles, and is coated with metal oxide and/or non-metal oxide
  • the second lithium-nickel transition metal oxide is Single crystal or single crystal-like morphology particles.
  • quasi-single crystal usually refers to the particle shape in which the size of the primary particles is larger than 1 ⁇ m, but the primary particles have a certain agglomeration. The agglomeration is different from the first lithium-nickel transition metal oxide.
  • the binding force is weak; single crystal usually refers to the particle morphology with the size of primary particles greater than 1 ⁇ m and no obvious agglomeration.
  • the present application controls the particle size distribution of the positive electrode active material and the OI value of the positive electrode sheet after mixing, so as to effectively suppress the problem of particle cracking of the positive electrode active material particles, while improving the compressive strength of the positive electrode active material particles in the positive electrode electrode sheet. Reduce the relative amount of the (003) crystal plane of the positive electrode active material in the positive pole piece, effectively solve the problem of the pole piece expansion rate and gas production, thereby obtaining an electrochemical storage device with high energy density, low pole piece expansion rate, and low gas production. able device.
  • the positive electrode active material includes a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide, and the OI value of the positive electrode active material powder does not exceed 10. This is because the positive electrode active material is basically dispersed, the crystals have no specific orientation, and the positive electrode active material powder is basically isotropic. In this application, the OI value test method of the positive electrode active material powder is basically the same as that of the positive electrode piece.
  • the particle size distribution characteristics of the positive electrode active material in the present application should satisfy the D v 90 range of 10-20 ⁇ m and 40 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 90 ⁇ m.
  • (D v 90 ⁇ D v 50)/D v 10 may for example be 40 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 85 ⁇ m, 45 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 90 ⁇ m, 45 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 85 ⁇ m, 40 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 80 ⁇ m, 45 ⁇ m ⁇ (D v 90 ⁇ D v 50)/ D v 10 ⁇ 80 ⁇ m, 40 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 70 ⁇ m, 40 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 65 ⁇ m, 45 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 65 ⁇ m, 40 ⁇ m ⁇ (D v 90 ⁇ D v 50)/D v 10 ⁇ 60 ⁇ m, or 40
  • (D v 90 ⁇ D v 50)/D v 10 can be understood as the product of (D v 90/D v 10) and D v 50, where D v 50 represents the average particle size of the positive active material, and (D v 90 /D v 10) can be approximately understood as the ratio of the average particle size of the large particles to the average particle size of the small particles in the positive electrode active material. Therefore, when (D v 90 ⁇ D v 50)/D v 10 is in an appropriate range, it means that the average particle diameter of the positive electrode active material is moderate and the difference between the particle sizes is also moderate.
  • the lower limit of D v 90 can be, for example, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, etc.
  • the upper limit of D v 90 can be, for example, 19 ⁇ m, 18 ⁇ m, 17 ⁇ m, 16 ⁇ m, etc.
  • the particle size distribution range of the positive electrode active material can be further regulated to ensure that the particle size is moderate, which is beneficial to improve the compaction density and resistance of the positive electrode sheet. The ability to crack, thereby further improving the energy density of the battery and the problem of gas generation.
  • the OI value of the positive electrode piece may be 10-15, 15-20, 20-25 , 25-30, 30-35, or 35-40, optionally 10-20.
  • the OI value of the positive electrode piece reflects the overall orientation of the crystal plane of the positive electrode active material in the electrode piece, and is closely related to the coating speed, drying, cold pressing and other process parameters of the electrode piece manufacturing process.
  • the OI value of the positive pole piece is too high, which means that the relative amount of the (003) crystal plane perpendicular to the length direction of the positive pole piece is too high, reflecting the serious texture of the positive pole piece after cold pressing.
  • the pole piece is prone to expansion; but if the OI value of the positive pole piece is too low, it indicates that the positive active material in the positive pole piece has no obvious orientation at this time, and the particle strength is too low. Gas production problem.
  • the pole piece compaction density can be determined by methods and instruments known in the art (eg, balance, micrometer).
  • the coating areal density CW can be calculated by measuring the weight of the active material layer per unit area, and the thickness of the active material layer on one side of the pole piece is measured with a micrometer.
  • the ratio of the coating areal density to the thickness of the active material on one side is Compaction density PD.
  • the coating surface density of the single-sided active material layer can be obtained by simple data calculation, and then the thickness of the single-sided active material layer can be measured to calculate the active material layer. Compaction Density.
  • the thickness can be measured using a Japanese Mitutoyo micrometer.
  • the second lithium-nickel transition metal oxide includes a second substrate, and the chemical formula of the second substrate is shown in formula II:
  • M' is selected from a combination of one or more of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, and Mn, and X' is selected from F and/or Cl.
  • the molecular formulas of the first substrate and the second substrate may independently include, but are not limited to, LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.5 Co 0.25 Mn 0.25 O 2 , LiNi 0.55 Co .
  • the relative content x1 of Ni element in the molecular formula of the first substrate may satisfy: 0.8 ⁇ x1 ⁇ 0.95, 0.8 ⁇ x1 ⁇ 0.85, 0.85 ⁇ x1 ⁇ 0.9, or 0.9 ⁇ x1 ⁇ 0.95
  • the relative content x2 of Ni element in the molecular formula of the second substrate can satisfy: 0.8 ⁇ x2 ⁇ 0.95, 0.8 ⁇ x1 ⁇ 0.85, 0.85 ⁇ x1 ⁇ 0.9, or 0.9 ⁇ x1 ⁇ 0.95
  • the first substrate and the first The relative contents x1 and x2 of Ni elements in the two substrates can satisfy: ⁇ x1-x2 ⁇ 0.1.
  • the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide in this application are layered lithium transition metal oxides with higher nickel content, which can effectively improve the energy density of the battery.
  • the difference between the relative contents x1 and x2 of the Ni element in the second substrate is not greater than 0.1, which can realize that the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide have closer.
  • the degree of desorption/intercalation of lithium is beneficial to improve the charge-discharge cycle life of the battery.
  • the relative contents x1 and x2 of Ni elements in the first substrate and the second substrate satisfy: 0 ⁇ x1-x2 ⁇ 0.1.
  • the Ni element content x1 of the first lithium-nickel transition metal oxide is slightly higher than that of the second lithium-nickel transition metal oxide x2, which is beneficial to the performance of the battery while effectively balancing the degree of delithiation/intercalation of the two positive electrode active materials. a higher energy density.
  • the volume particle size distribution and tap density TD of the positive electrode active material satisfy: 4.4 ⁇ (D v 90-D v 10)/TD ⁇ 8.
  • the value range of (D v 90-D v 10)/TD may be 7.5-8, 7-7.5, 6.5-7, 6-6.5, 5.5-6, 5-5.5, 4.4-5.
  • the units of D v 10 and D v 90 are ⁇ m;
  • TD is the tap density (unit: g/cm 3 ) of the positive electrode active material.
  • the particle size distribution of the particles with different morphologies of the positive electrode active material is moderate, and the interstitial volume between the particles is low, which is beneficial to The improvement of the compaction density of the positive pole piece.
  • the tap density TD of the positive electrode active material may be 2.2g/cm 3 ⁇ 2.8g/cm 3 , 2.2g/cm 3 ⁇ 2.3g/cm 3 , 2.3g/cm 3 ⁇ 2.4g/ cm3 , 2.4g/ cm3 ⁇ 2.5g/ cm3 , 2.5g/ cm3 ⁇ 2.6g/ cm3 , 2.6g/ cm3 ⁇ 2.7g/ cm3 , or 2.7g/ cm3 ⁇ 2.8 g/cm 3 .
  • the larger the TD the more favorable it is to achieve high compaction density.
  • the TD is affected by factors such as the compactness of a single particle of the material, the particle size distribution of the material, and the shape of the particles, and has a certain upper limit.
  • TD is the powder tap density of the positive electrode active material
  • a specific method for measuring the powder tap density may include: filling the powder in a container (for example, a 25 mL container, and for example, the container used can be a measuring cylinder), after the container is vibrated (for example, the specific conditions of the vibration can be: the vibration frequency is 250 times/min, the amplitude is 3mm, and the vibration is 5000 times), the mass of the powder per unit volume is the powder tap density. .
  • the first lithium-nickel transition metal oxide may be spherical particles, and the sphericity ⁇ of the first lithium-nickel transition metal oxide may be 0.7-1. Specifically, the sphericity ⁇ of the first lithium-nickel transition metal oxide may be 0.7-0.9, 0.7-0.8, 0.8-0.9, or 0.9-1.
  • the first lithium-nickel transition metal oxide is secondary particles. When the sphericity of the secondary particles is within the above range, it indicates that the size of the primary particles in the secondary particles is uniform, the distribution is relatively uniform, and the secondary particles are tight In fact, the mechanical strength is high.
  • the sphericity can be measured in the following way: in the SEM photo of the cross section of the positive electrode, select at least 30 secondary particles with a cross-sectional diameter greater than the value of Dv 10 of the positive active material, and measure the cross-sectional SEM image Calculate the ratio of the maximum inscribed circle radius (R max ) to the minimum circumscribed circle radius (R min ) of the respective secondary particles in , and calculate the average value, that is, ⁇ can be obtained.
  • the size ratio of the longest diameter L max to the shortest diameter L min of the second lithium-nickel transition metal oxide satisfies: 1 ⁇ L max /L min ⁇ 3, 1 ⁇ L max /L min ⁇ 1.5 , 1.5 ⁇ Lmax / Lmin ⁇ 2 , 2 ⁇ Lmax / Lmin ⁇ 2.5 , or 2.5 ⁇ Lmax / Lmin ⁇ 3 .
  • the second lithium-nickel transition metal oxide is a particle with a single crystal or quasi-single crystal morphology. When the L max /L min of the single particle is within the above range, it is different from the second lithium-nickel transition metal oxide whose sphericity is between 0.7 and 1. After the secondary particles are mixed, the interstitial volume of the secondary particles can be better filled. While improving the compaction density of the positive electrode and the volumetric energy density of the battery, it can also effectively suppress the volume expansion rate of the positive electrode during the cycle and improve the cycle performance.
  • the L max /L min can be measured in the following manner: in the SEM photo of the cross section of the positive electrode piece, at least 30 single crystals or single crystals with a cross-sectional diameter greater than the value of D v 10 of the positive electrode active material are selected. For crystal morphology particles, measure the ratio of the longest diameter (L max ) to the shortest diameter (L min ) of each particle in the cross-sectional SEM picture, and calculate the average value to obtain L max /L min .
  • the D v 50 of the first lithium-nickel transition metal oxide that is, the D v 50 (L) can be 5 ⁇ m ⁇ 18 ⁇ m, 5 ⁇ m ⁇ 6 ⁇ m, 6 ⁇ m ⁇ 8 ⁇ m, 8 ⁇ m ⁇ 10 ⁇ m, 10 ⁇ m ⁇ 12 ⁇ m, 12 ⁇ m to 14 ⁇ m, 14 ⁇ m to 16 ⁇ m, or 16 ⁇ m to 18 ⁇ m, optionally 8 ⁇ m to 12 ⁇ m.
  • the D v 50 of the second lithium nickel transition metal oxide, ie, D v 50 (S), may be 1 ⁇ m ⁇ 5 ⁇ m, 1 ⁇ m ⁇ 2 ⁇ m, 2 ⁇ m ⁇ 3 ⁇ m, 3 ⁇ m ⁇ 4 ⁇ m, or 4 ⁇ m ⁇ 5 ⁇ m.
  • the base material in the first lithium-nickel transition metal oxide is secondary particles
  • the second lithium-nickel transition metal oxide is single-crystal or quasi-single-crystal morphology particles
  • the first lithium-nickel transition metal oxide is relative to
  • the second lithium-nickel transition metal oxide has a larger particle size as a whole, and the particle size relationship between the two can optionally satisfy: 2 ⁇ D v 50(L)/D v 50(S) ⁇ 7, 2 ⁇ D v 50(L)/D v 50(S) ⁇ 3, 3 ⁇ D v 50(L)/D v 50(S) ⁇ 4, 4 ⁇ D v 50(L)/D v 50(S) ⁇ 5, 5 ⁇ D v 50(L)/D v 50(S) ⁇ 6, or 6 ⁇ D v 50(L)/D v 50(S) ⁇ 7.
  • the ratio of the first lithium-nickel transition metal oxide D v 50(L) to the second lithium-nickel transition metal oxide D v 50 (S) is within the above range, it is beneficial to suppress the particles with larger particle size.
  • the problem of particle cracking of the secondary particle high nickel material ensures that the positive electrode active material can exert a high gram capacity, and at the same time improves the mechanical strength and compaction density of the overall positive electrode sheet.
  • the content of the positive electrode active material relative to the entire active material layer may be, for example, 95% to 99%.
  • the weight percent content of the first lithium nickel transition metal oxide may be 50%-90%, 85%-90%, 80%-85% , 75% to 80%, 70% to 75%, 65% to 70%, 60% to 65%, 55% to 60%, or 50% to 55%, optionally 60% to 85%.
  • the weight percentage content of the second lithium nickel transition metal oxide can be 10%-50%, 10%-15%, 15%-20%, 20%-25%, 25%-30%, 30%-35%, 35% to 40%, 40% to 45%, or 45% to 50%, optionally 15% to 40%.
  • the weight percentages of the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide in the positive electrode plate are controlled within the above-mentioned range, which can regulate the OI value of the positive electrode plate to a certain extent, while improving the Compaction density and mechanical strength of pole pieces.
  • the second lithium nickel transition metal oxide may further include a second coating layer located on the surface of the second substrate, and the second coating layer is a metal oxide and/or a non-metal oxide .
  • the first coating layer and/or the second coating layer may be metal oxides and/or non-metal oxides, for example, may be oxides containing only metal elements or non-metal elements It can also contain oxides of metal elements and non-metal elements at the same time.
  • the metal elements can usually be, for example, aluminum, zirconium, zinc, titanium, silicon, tin, tungsten, yttrium, cobalt, barium, etc.
  • the non-metal elements can generally be, for example, phosphorus, boron, and the like.
  • the first cladding layer and/or the second cladding layer may include but not limited to aluminum oxide, zirconium oxide, zinc oxide, titanium oxide, silicon oxide, tin oxide, tungsten oxide, yttrium oxide, cobalt oxide, Barium, phosphorus oxide, boron oxide, and lithium aluminum oxide, lithium zirconium oxide, lithium zinc oxide, lithium magnesium oxide, lithium tungsten oxide, lithium yttrium oxide, lithium cobalt oxide, lithium barium oxide, lithium A combination of one or more of phosphorus oxides or lithium boron oxides and the like.
  • the above-mentioned metal oxides and/or non-metal oxides are selected as the coating layer of the positive electrode active material.
  • the oxide coating layer has a good bonding force with the base material, and the coating layer is not easy to fall off during the charging and discharging process, reducing the base material.
  • the part of the contact area between the material and the electrolyte can effectively modify the surface of the high-nickel positive electrode material, reduce the side reaction between the positive electrode material and the electrolyte, and effectively suppress the gas generation phenomenon of the battery.
  • the first coating layer optionally contains at least one oxide of a metal element and an oxide of one non-metal element at the same time.
  • Oxides containing the above elements can not only improve the adhesion stability of the coating layer on the surface of the secondary particle substrate, but also make the coating layer have both ionic conductivity and electronic conductivity, reducing the impact of the coating layer on the positive electrode material. impact of the problem.
  • the second aspect of the present application provides the method for preparing the positive electrode sheet for a secondary battery provided in the first aspect of the present application, and suitable methods for preparing the positive electrode sheet should be known to those skilled in the art, for example,
  • the positive pole piece can include:
  • a positive electrode active material comprising a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide
  • the positive electrode active material, the binder, and the conductive agent are mixed to form a slurry, which is then coated on the positive electrode current collector.
  • the first lithium nickel transition metal oxide and/or the second lithium nickel transition metal oxide may be surface-modified, for example, the first lithium nickel transition metal oxide may be and/or the second lithium-nickel transition metal oxide is respectively surface modified, and then mixed, wherein the surface modification methods of the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide can be the same or different; Alternatively, the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide can be mixed first, and then the surface modification process can be performed together.
  • the method may include: providing a first lithium nickel transition metal oxide.
  • the method of providing the first lithium-nickel transition metal oxide should be known to those skilled in the art, for example, it may include: mixing and sintering the raw materials of the base material of the first lithium-nickel transition metal oxide to provide the first lithium-nickel transition metal oxide. a base material; the first base material is coated to provide a first lithium nickel transition metal oxide.
  • Those skilled in the art can select appropriate raw materials and proportions according to the elemental composition of the first lithium-nickel transition metal oxide to further prepare and obtain the first substrate.
  • the raw material of the first lithium-nickel transition metal oxide may include a precursor of the first lithium-nickel transition metal oxide, a lithium source, an M source, an X source, etc., and the ratio between the raw materials is usually referred to the first lithium-nickel transition metal oxide.
  • the ratio of each element in the oxide is matched.
  • the precursor of the first lithium nickel transition metal oxide may include, but is not limited to, Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 , Ni 0.5 Co 0.25 Mn 0.25 (OH) 2 , Ni 0.55 Co 0.15 Mn 0.3 ( OH) 2 , Ni 0.55 Co 0.1 Mn 0.35 (OH) 2 , Ni 0.55 Co 0.05 Mn 0.4 (OH) 2 , Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 , Ni 0.65 Co 0.15 Mn 0.2 (OH) 2 , Ni 0.65 Co 0.12 Mn 0.23 (OH) 2 , Ni 0.65 Co 0.1 Mn 0.25 (OH) 2 , Ni 0.65 Co 0.05 Mn 0.3 (OH) 2 , Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 , Ni 0.75 Co 0.1 Mn 0.15 (OH) 2 ) 2 , Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , Ni 0.88 Co 0.05 Mn 0.07 (OH) 2 , Ni 0.92 Co 0. 0.
  • One or more of the X source can be a compound containing X element, and the above-mentioned compound containing X element can be a combination of one or more including but not limited to LiF, NaCl, and the like.
  • the conditions for sintering the raw material of the base material of the first lithium-nickel transition metal oxide may be sintering conditions of 700° C. to 900° C. and an oxygen concentration of ⁇ 20%.
  • the method for coating the first substrate may specifically include: sintering the first substrate in the presence of a compound containing a coating element, and the compound containing a coating element may be a compound containing Al, Ba, Zn, Ti, Oxides, nitrates, phosphates, carbonates, etc. of one or more elements in Co, W, Y, Si, Sn, B, P, etc., the use amount of coating elements can be usually ⁇ 2wt%,
  • the conditions of sintering in the coating treatment may be 200°C to 700°C.
  • the method may include: providing a second lithium nickel transition metal oxide.
  • the method of providing the second lithium nickel transition metal oxide should be known to those skilled in the art, for example, it may include: mixing and sintering raw materials of the base material of the second lithium nickel transition metal oxide to provide the second lithium nickel transition metal oxide. Two substrates; the second substrate is coated to provide a second lithium-nickel transition metal oxide.
  • the raw material of the second lithium-nickel transition metal oxide may include the precursor, lithium source, M' source, X' source, etc.
  • the precursor of the second lithium nickel transition metal oxide may include, but not limited to, Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 , Ni 0.5 Co 0.25 Mn 0.25 (OH) 2 , Ni 0.55 Co 0.15 Mn 0.3 ( OH) 2 , Ni 0.55 Co 0.1 Mn 0.35 (OH) 2 , Ni 0.55 Co 0.05 Mn 0.4 (OH) 2 , Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 , Ni 0.65 Co 0.15 Mn 0.2 (OH) 2 , Ni 0.65 Co 0.12 Mn 0.23 (OH) 2 , Ni 0.65 Co 0.1 Mn 0.25 (OH) 2 , Ni 0.65 Co 0.05 Mn 0.3 (OH) 2 , Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 , Ni 0.75 Co 0.1 Mn 0.15
  • One or more of the salts, X' source can be a compound containing X' element, and the above-mentioned compound containing X' element can be a combination of one or more including but not limited to LiF, NaCl and the like.
  • the sintering conditions of the raw material of the base material of the second lithium nickel transition metal oxide may be sintering conditions of 750° C. to 950° C. and an oxygen concentration of ⁇ 20%.
  • the method for coating the second substrate may specifically include: sintering the second substrate in the presence of a compound containing a coating element, and the compound containing a coating element may be a compound containing Al, Ba, Zn, Ti, Oxides, nitrates, phosphates, carbonates, etc. of one or more elements in Co, W, Y, Si, Sn, B, P, etc., the use amount of coating elements can be usually ⁇ 2wt%,
  • the conditions of sintering in the coating treatment may be 200°C to
  • the binder usually includes a fluorine-containing polyolefin binder.
  • water is usually a good solvent, that is, the fluoropolyolefin-based binder usually has good solubility in water.
  • the fluorine-containing polyolefin-based binder may be derived from, including but not limited to, polyvinylidene fluoride (PVDF), vinylidene fluoride copolymer, etc., or their modifications (eg, carboxylic acid, acrylic acid, acrylonitrile, etc. modification) things etc.
  • the mass percentage content of the binder may be, for example, 0.1wt%-10wt%, 0.2wt%-8wt%, 0.3wt%-6wt% or 0.5wt%-3wt%. Due to the poor conductivity of the binder itself, the amount of the binder should not be too high.
  • the mass percentage content of the binder in the positive electrode active material layer is 0.5 wt % to 3 wt %, so as to obtain lower pole piece impedance.
  • the conductive agent of the positive electrode sheet can be various conductive agents suitable for lithium ion (secondary) batteries in the art, for example, can include but not limited to acetylene black, conductive agent A combination of one or more of carbon black, carbon fiber (VGCF), carbon nanotube (CNT), ketjen black, and the like.
  • the weight of the conductive agent may account for 0.5 wt % to 10 wt % of the total mass of the positive electrode active material layer.
  • the weight ratio of the conductive agent to the positive active material in the positive electrode sheet is 1.0 wt % to 5.0 wt %.
  • the positive electrode current collector of the positive electrode electrode sheet can usually be a layer body, the positive electrode current collector is usually a structure or part that can collect current, and the positive electrode current collector can be any suitable for As the material of the positive electrode current collector of the lithium ion battery, for example, the positive electrode current collector may include but not limited to metal foil, and more specifically may include but not limited to copper foil, aluminum foil, and the like.
  • a third aspect of the present application provides a secondary battery, including the positive electrode plate provided in the first aspect of the present application.
  • the secondary battery may be a supercapacitor, a lithium ion battery, a lithium metal battery or a sodium ion battery.
  • the secondary battery is a lithium ion battery is shown, but the present application is not limited thereto.
  • FIG. 1 is a perspective view of an embodiment of a lithium-ion battery.
  • FIG. 2 is an exploded view of FIG. 1 .
  • the battery 5 includes a case 51 , an electrode assembly 52 , a cap assembly 53 , and an electrolyte (not shown).
  • the electrode assembly 52 is accommodated in the casing 51 .
  • the number of electrode assemblies 52 is not limited, and may be one or more.
  • the battery 5 shown in FIG. 1 is a can type battery, but not limited thereto, the battery 5 may be a pouch type battery, that is, the casing 51 is replaced by a metal plastic film and the top cover assembly 53 is eliminated.
  • the lithium ion battery may include a positive pole piece, a negative pole piece, a separator spaced between the positive pole piece and the negative pole piece, and an electrolyte, wherein the positive pole piece may be the positive pole provided in the first aspect of the present application. pole piece.
  • Methods for preparing lithium ion batteries should be known to those skilled in the art.
  • each of the positive pole piece, the separator and the negative pole piece can be a layered body, so that they can be cut to a target size and then stacked in sequence, and also It can be wound to a target size for use in forming a cell and can be further combined with an electrolyte to form a lithium-ion battery.
  • the negative electrode sheet may generally include a negative electrode current collector and a negative electrode active material layer located on the surface of the negative electrode current collector, and the negative electrode active material layer usually includes a negative electrode active material.
  • the negative electrode active material can be various materials suitable for the negative electrode active material of lithium ion batteries in the art, for example, it can be including but not limited to graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microspheres, silicon-based materials, tin A combination of one or more of the base material, lithium titanate, or other metals capable of forming alloys with lithium, and the like.
  • graphite can be selected from one or more combinations of artificial graphite, natural graphite and modified graphite; silicon-based material can be selected from one or more of elemental silicon, silicon oxide compound, silicon carbon composite, silicon alloy A variety of combinations; the tin-based material can be selected from a combination of one or more of elemental tin, tin oxide compounds, and tin alloys.
  • the negative electrode current collector is usually a structure or part that collects current.
  • the negative electrode current collector can be any material suitable for use as the negative electrode current collector of lithium ion batteries in the art.
  • the negative electrode current collector can include but not limited to metal foil, etc. More specifically It can be including but not limited to copper foil and the like.
  • the separator can be any material suitable for lithium ion battery separators in the art, for example, it can be polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyterephthalene A combination of one or more of ethylene formate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers.
  • the electrolyte may generally include an electrolyte and a solvent, and suitable electrolytes for lithium-ion batteries should be known to those skilled in the art.
  • the electrolyte may generally include lithium salts, etc.
  • the lithium salt can be an inorganic lithium salt and/or an organic lithium salt, etc., specifically, including but not limited to LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (LiFSI), LiN(CF 3 SO 2 ) 2 ( A combination of one or more of LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), etc.; for another example, the concentration of the electrolyte may be 0.8 mol/L ⁇ 1.5mol/L; for another example, the solvent used in the electrolyte can be various solvents suitable for the electrolyte of lithium ion batteries in the art, usually a non-aqueous solvent, optionally an organic solvent.
  • the solvent can specifically include but not limited to ethylene carbonate, propylene carbonate, butylene carbonate, pentene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, etc. or their A combination of one or more of the halogenated derivatives.
  • a battery module which includes the secondary battery provided in the third aspect of the present application.
  • a battery module may generally include one or more secondary batteries, the battery module may be used as a power source or an energy storage device, and the number of batteries in the battery module may be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a perspective view of an embodiment of a battery module.
  • the battery module 4 includes a plurality of batteries 5 .
  • the plurality of batteries 5 are arranged in the longitudinal direction.
  • a battery pack which includes the secondary battery provided in the third aspect of the present application, or the battery module provided in the fourth aspect.
  • FIG. 4 is a perspective view of a specific embodiment of the battery pack 1 .
  • FIG. 5 is an exploded view of FIG. 4 .
  • the battery pack 1 includes an upper case 2 , a lower case 3 and a battery module 4 .
  • the upper case 2 and the lower case 3 are assembled together to form a space for accommodating the battery module 4 .
  • the battery module 4 is placed in the space of the assembled upper case 2 and the lower case 3 .
  • the output pole of the battery module 4 passes through one or both of the upper case 2 and the lower case 3 to supply power or charge from the outside.
  • the number and arrangement of the battery modules 4 used in the battery pack 1 can be determined according to actual needs.
  • the battery pack 1 can be used as a power source or an energy storage device.
  • a sixth aspect of the present application provides a device comprising the secondary battery provided in the third aspect of the present application, and the secondary battery is used as a power source of the device.
  • FIG. 6 is a perspective view of a specific embodiment of the above device.
  • the device using the battery 5 is an electric vehicle.
  • the device using the battery 5 can be any electric vehicle (such as an electric bus, an electric tram, an electric bicycle, an electric motorcycle, an electric scooter, an electric golf cart, an electric truck), Electric ships, power tools, electronic equipment and energy storage systems.
  • the electric vehicle may be an electric pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • the device provided by the sixth aspect of the present application may include the battery module 4 provided by the fourth aspect of the present application, and of course, the device provided by the sixth aspect of the present application may also include the fifth aspect of the present application. Supplied battery pack 1.
  • the nickel sulfate, manganese sulfate, and cobalt sulfate were configured into a 1mol/L solution in a molar ratio of 8:1:1, and the first lithium-nickel transition with a particle size D v 50 (L) of 9.7 ⁇ m was prepared by using the hydroxide co-precipitation technology.
  • Precursors of metal oxides; nickel sulfate, manganese sulfate, cobalt sulfate are prepared in a molar ratio of 1 mol/L solution, and the precursor of the second lithium-nickel transition metal oxide with a particle size of 2.9 ⁇ m is prepared by hydroxide co-precipitation technology body.
  • the particle size and morphology of the precursors of the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide are controlled by controlling the reaction time, the pH value during co-precipitation, and the ammonia concentration. regulation.
  • the above-mentioned first lithium nickel transition metal oxide precursor Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 and Li-containing compound LiOH ⁇ H 2 O are placed in a mixing equipment at a molar ratio of 1:1.05 for mixing, Then, it is placed in an atmosphere furnace at 830° C. for sintering, and after cooling, it is the base material of the first lithium-nickel transition metal oxide through mechanical grinding.
  • the above-mentioned base material of the first lithium nickel transition metal oxide, 0.2 wt % of the compound Al 2 O 3 containing the coating element Al, and 0.2 wt % of the compound boric acid containing the coating element B are placed in a mixing device for mixing.
  • the material is then placed in an atmosphere furnace for sintering at 500 °C for 5 hours to form the first coating layer of the first lithium-nickel transition metal oxide, that is, the first lithium-nickel transition metal oxide coated on the surface is obtained . 50. See Table 1 for sphericity and coating materials.
  • the above-mentioned precursor of the second lithium nickel transition metal oxide Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 and Li-containing compound LiOH ⁇ H 2 O are placed in a mixing device for mixing at a molar ratio of 1:1.05, Then, it is placed in an atmosphere furnace with an oxygen concentration of 30% for sintering at 870° C. for 4 hours, and after cooling, it is ground by airflow powder to form the base material of the second lithium nickel transition metal oxide.
  • the base material of the second lithium nickel transition metal oxide and 0.2 wt % of the compound Al 2 O 3 containing the coating element Al were placed in a mixing equipment for mixing, and then placed in an atmosphere furnace for sintering at 500° C. for 5 hours.
  • the coating layer of the lithium -nickel transition metal oxide B is formed , that is, the second surface-modified lithium-nickel transition metal oxide is obtained.
  • Step 1 Mix the above-obtained positive active material, binder polyvinylidene fluoride, and conductive agent acetylene black according to a mass ratio of 98:1:1, add N-methylpyrrolidone (NMP), and stir under the action of a vacuum mixer
  • NMP N-methylpyrrolidone
  • Step 2 drying the coated pole piece in an oven at 100°C to 130°C, cold pressing and slitting to obtain a positive pole piece.
  • the negative electrode active material graphite, thickener sodium carboxymethyl cellulose, binder styrene-butadiene rubber, and conductive agent acetylene black are mixed according to the mass ratio of 97:1:1:1, and deionized water is added.
  • the negative electrode slurry was obtained under the following conditions; the negative electrode slurry was uniformly coated on a copper foil with a thickness of 8 ⁇ m; the copper foil was dried at room temperature and then transferred to a 120 °C oven for 1 h, and then cold-pressed and slitted to obtain a negative electrode pole piece.
  • the organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the fully dried lithium salt is dissolved in an organic solvent and mixed evenly to obtain an electrolyte solution.
  • the concentration of the lithium salt was 1 mol/L.
  • the positive pole piece, the separator film and the negative pole piece in order, so that the separator is placed between the positive and negative pole pieces to play the role of isolation. Then, after baking at 80°C to remove water, the corresponding non-aqueous electrolyte is injected, sealed, and the finished battery is obtained after standing, hot and cold pressing, formation, fixture, and volume separation.
  • the preparation method of the positive electrode and the battery in Example 2 refers to Example 1, the difference is that the mass ratio between the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide is 9:1, and the prepared See Table 1 for the TD, (D v 90-D v 10)/TD, (D v 90 ⁇ D v 50)/D v 10 and OI values of the positive electrode active material of the positive electrode active material.
  • Example 3 The preparation method of the positive electrode and the battery in Example 3 refers to Example 1, the difference is that the mass ratio between the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide is 6:4, and the prepared See Table 1 for the TD, (D v 90-D v 10)/TD, (D v 90 ⁇ D v 50)/D v 10 and OI values of the positive electrode active material of the positive electrode active material.
  • the preparation method of the positive pole piece and the battery in Example 4 refers to Example 1, except that the Ni:Co:Mn element ratio in the second lithium-nickel transition metal oxide is 5:2:3, and the second lithium-nickel transition metal oxide is 5:2:3.
  • the mass ratio between the metal oxide and the second lithium-nickel transition metal oxide is 8:2, and the TD, (D v 90-D v 10)/TD, (D v 90 ⁇ D v of the prepared cathode active material are 50)/D v 10 and the OI value of the positive pole piece are shown in Table 1.
  • the preparation method of the positive pole piece and the battery in Example 5 refers to Example 1, except that the Ni:Co:Mn element ratio in the first lithium-nickel transition metal oxide is 6:2:2, and the first lithium-nickel transition metal oxide is 6:2:2.
  • the preparation method of the positive electrode and the battery in Example 6 refers to Example 1, except that the Ni:Co:Mn element ratio in the second lithium-nickel transition metal oxide is 9:0.5:0.5, and the first lithium-nickel transition metal oxide is 9:0.5:0.5.
  • the mass ratio between the oxide and the second lithium nickel transition metal oxide is 8:2, and the TD, (D v 90-D v 10)/TD, (D v 90 ⁇ D v 50 of the prepared cathode active material are )/D v 10 and the OI value of the positive pole piece are shown in Table 1.
  • Example 7 The preparation method of the positive electrode and the battery in Example 7 refers to Example 1, the difference is that the coating element of the first lithium-nickel transition metal oxide is B, that is, the compound corresponding to Al is not used for sintering, and the preparation is obtained. See Table 1 for the TD, (D v 90-D v 10)/TD, (D v 90 ⁇ D v 50)/D v 10 and OI values of the positive electrode active material of the positive electrode active material.
  • Example 8 The preparation method of the positive electrode and the battery in Example 8 refers to Example 1, the difference is that the coating element of the first lithium nickel transition metal oxide is B, that is, the compound corresponding to Al is not used for sintering, and the second The coating elements of the lithium-nickel transition metal oxide are Al and B, and the compounds used in the sintering process are alumina and boron oxide.
  • the TD, (D v 90-D v 10)/TD See Table 1 for (D v 90 ⁇ D v 50)/D v 10 and the OI value of the positive pole piece.
  • the preparation method of the positive electrode and the battery in Example 9 refers to Example 1, except that the Ni:Co:Mn element ratio in the first lithium-nickel transition metal oxide is 8.3:1.4:0.3, and the first lithium-nickel transition metal oxide is 8.3:1.4:0.3.
  • the preparation method of the positive electrode and the battery in Example 10 refers to Example 1, except that the Ni:Co:Mn element ratio in the first lithium-nickel transition metal oxide is 8.3:1.4:0.3, and the first lithium-nickel transition metal oxide is 8.3:1.4:0.3.
  • the Ni:Co:Mn element ratio in the oxide is 5:2:3
  • L max /L min 1.5
  • the coating element is Al
  • Ti the compounds used in the sintering process are alumina and titania
  • the preparation method of positive pole piece and battery in Comparative Example 2 refers to Example 1, the difference is that in the preparation method of positive active material, the second lithium nickel transition metal oxide is not used, and the TD, ( See Table 1 for D v 90-D v 10)/TD, (D v 90 ⁇ D v 50)/D v 10 and OI values of the positive pole piece.
  • the preparation method of the positive pole piece and the battery in Comparative Example 3 refers to Example 1, the difference is that the mass ratio between the first lithium-nickel transition metal oxide and the second lithium-nickel transition metal oxide is 4:6, and the prepared See Table 1 for the TD, (D v 90-D v 10)/TD, (D v 90 ⁇ D v 50)/D v 10 and OI values of the positive electrode active material of the positive electrode active material.
  • the preparation method of positive pole piece and battery in Comparative Example 5 refers to Example 1, the difference is that the first lithium-nickel transition metal oxide is not used in the process of preparing the positive pole piece, and the TD, (D v 90-D v 10)/TD, (D v 90 ⁇ D v 50)/D v 10 and positive pole piece OI values are shown in Table 1.
  • the preparation method of positive pole piece and battery in Comparative Example 6 refers to Example 1, the difference is that in the process of preparing the first lithium-nickel transition metal oxide, coating treatment is not carried out, and the TD, ( See Table 1 for D v 90-D v 10)/TD, (D v 90 ⁇ D v 50)/D v 10 and OI values of the positive pole piece.
  • the prepared positive pole piece is placed horizontally in an XRD diffractometer to test the XRD diffraction spectrum of the positive pole piece, and the diffraction peaks corresponding to the (003) crystal plane and (110) crystal plane of the positive electrode active material in the XRD diffraction pattern are calculated.
  • the ratio of the area is the OI value of the positive pole piece.
  • the test method for the OI value of the positive active material powder is basically the same as the test method for the positive electrode sheet, the difference is that the tested sample is the positive active material powder.
  • the lithium-ion battery was charged at a constant current of 1C to a voltage of 4.2V, then charged at a constant voltage of 4.2V to a current of 0.05C, and then discharged at a constant current of 1C until the final voltage was 2.8V, and the first cycle was recorded. discharge capacity. Charge and discharge cycles were then performed as described above for 400 cycles, and the discharge capacity after 400 cycles was recorded. According to the discharge capacity of the first cycle and the discharge capacity after 400 cycles, the capacity retention rate of 400 cycles at 45°C was calculated and obtained.
  • the first lithium nickel transition metal oxide in the form of secondary particles and the second lithium nickel transition metal oxide in the form of single crystal or quasi-single crystal particles are mixed and controlled
  • the particle size distribution of the positive active material after mixing and the OI value of the positive electrode sheet can improve the compaction density while improving the particle cracking during cycling, improving cycle life and DCR growth during cycling.
  • Surface-coated metal oxides and non-metal oxides can significantly improve cycle life and cycle DCR growth.

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Abstract

本申请涉及电化学领域，特别是涉及一种用于二次电池的正极极片、二次电池、电池模块、电池包和装置。本申请提供一种用于二次电池的正极极片，所述正极极片包括正极集流体和位于正极集流体表面的正极活性物质层，所述正极活性物质层包括正极活性物质，所述正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，所述第一锂镍过渡金属氧化物包括第一基材和位于第一基材表面的第一包覆层，所述第一基材为二次颗粒，所述第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒。本申请所提供的正极极片通过调控混合后正极活性物质的粒径分布和极片OI值，提高了正极极片中正极活性物质颗粒的抗压强度，有效抑制正极活性物质颗粒的颗粒开裂问题。

Description

用于二次电池的正极极片、二次电池、电池模块、电池包和装置
相关申请的交叉引用
本申请要求享有于2020年09月22日提交的名称为“一种用于二次电池的正极极片、二次电池、电池模块、电池包和装置”的中国专利申请202011003864.0的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及电化学领域，特别是涉及一种用于二次电池的正极极片、二次电池、电池模块、电池包和装置。
背景技术
电动汽车对续航里程的要求越来越高，这就对动力电池的能量密度提出了更高要求。动力电池能量密度的提升，很大程度上取决于正极材料的选择。根据高容量、高放电电压平台的选取原则，锂镍过渡金属氧化物(例如，镍钴锰三元材料)的应用越来越多。其中，镍含量增加可以显著提升克容量，从而提高能量密度，因此高镍含量的锂镍过渡金属氧化物是当前的热门选择。
但是，锂镍过渡金属氧化物中镍含量的增加使得制备更加困难：温度高，则锂挥发严重；温度低，则晶粒不能充分长大，加工性能差。
另外，锂镍过渡金属氧化物中镍含量的增加也影响了材料结构的稳定性，加剧了表面层状结构向岩盐相的转变，而且表面释氧也加剧了材料表面电解液的副反应。
发明内容
鉴于以上所述现有技术的缺点，本申请的目的在于提供一种用于二次电池的正极极片、二次电池、电池模块、电池包和装置，用于解决现有技术中的问题。
为实现上述目的及其他相关目的，本申请的第一方面提供一种用于二次电池的正极极片，所述正极极片包括正极集流体和位于正极集流体表面的正极活性物质层，所述正极活性物质层包括正极活性物质，所述正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，所述第一锂镍过渡金属氧化物包括第一基材和位于第一基材表面的第一包覆层，所述第一基材为二次颗粒，所述第一基材的化学式如式I所示：
Li 1+a1Ni x1Co y1Mn z1M b1O 2-e1X e1   (I)
式I中，-0.1<a1<0.1，0.5≤x1≤0.95，0.05≤y1≤0.2，0.03≤z1≤0.4，0≤b1≤0.05，0≤e1≤0.1，且x1+y1+z1+b1＝1；其中，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X选自F和/或Cl。
所述第一包覆层选自金属氧化物和/或非金属氧化物。
所述第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒。
所述正极活性物质的粒径分布满足：D v90的范围为10μm～20μm且40μm<(D v90×D v50)/D v10<90μm。
所述正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，所述正极极片的OI值为10～40。
在上述任意实施方式中，正极极片的OI值为正极极片的XRD衍射谱中对应正极活性物质的(003)晶面与(110)晶面的衍射峰面积的比值。
在上述任意实施方式中，第二锂镍过渡金属氧化物包括第二基材，所述第二基材的化学式如式II所示：
Li 1+a2Ni x2Co y2Mn z2M’ b2O 2-e2X’ e2   (II)
式II中，-0.1<a2<0.1，0.5≤x2≤0.95，0.05≤y2≤0.2，0.03≤z2≤0.4，0≤b2≤0.05，0≤e2≤0.1，且x2+y2+z2+b2＝1，M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X’选自F和/或Cl；可选地，所述第一基材与所述第二基材的分子式中Ni元素的相对含量x1、x2满足：0.8≤x1≤0.95，0.8≤x2≤0.95，且∣x1-x2∣≤0.1；可选地，所述x1、x2满足：0<x1-x2<0.1。∣x1-x2∣≤0.1时，可以实现当在同一充放电电压下，第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物具有较接近的脱/嵌锂程度，有利于提高电池的充放电循环寿命。0<x1-x2<0.1时，本申请中第一锂镍过渡金属氧化物的Ni元素含量x1略高于第二锂镍过渡金属氧化物x2，在有效平衡两种正极活性物质的脱/嵌锂程度的同时，有利于电池发挥出较高的能量密度。
在上述任意实施方式中，正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，所述正极极片的OI值为10～20。正极极片的OI值过高时，正极极片在冷压后出现较严重的织构，在电池充放电过程中极片容易发生膨胀；正极极片OI值过低时，正极极片中正极活性物质颗粒强度过低，在冷压及循环中后期易发生颗粒破碎，引发产气问题。
在上述任意实施方式中，正极活性物质满足：4.4<(D v90-D v10)/TD<8，可选地，4.6<(D v90-D v10)/TD<6.5，其中TD为所述正极活性物质的振实密度，单位为g/cm 3。当正极活性物质进一步满足(D v90-D v10)/TD的取值在上述范围时，正极活性物质不同形貌颗粒的粒度分布适中、颗粒间的间隙体积较低，有利于正极极片压实密度的提高。
在上述任意实施方式中，正极活性物质的振实密度TD为2.2g/cm 3～2.8g/cm 3。
在上述任意实施方式中，第一锂镍过渡金属氧化物为球形颗粒，第一锂镍过渡金属氧化物颗粒的球形度γ为0.7～1。当第一锂镍过渡金属氧化物的球形度在上述范围内时，表明二次颗粒内一次颗粒的尺寸均一、分布较均匀，二次颗粒较紧实，力学强度较高。
在上述任意实施方式中，第二锂镍过渡金属氧化物颗粒的最长径L max与最短径L min的尺寸比例满足：1≤L max/L min≤3。第二锂镍过渡金属氧化物为单晶或类单晶形貌的颗粒，当单颗粒的L max/L min在上述范围内时，与球形度在0.7～1之间的二次颗粒混合后，能够更好的填充二次颗粒的间隙体积，在提升正极极片的压实密度、电池体积能量密度的同时，还可以有效抑制循环过程中正极极片的体积膨胀率，改善循环性能。
在上述任意实施方式中，第一锂镍过渡金属氧化物的D v50，即D v50(L)为5μm～18μm，所述第二锂镍过渡金属氧化物的D v50，即D v50(S)为1μm～5μm；可选地，所述D v50(L)与所述D v50(S)满足：2≤D v50(L)/D v50(S)≤7。这样有利于抑制粒径尺寸较大的 二次颗粒高镍材料的颗粒开裂问题，保证正极活性物质能够发挥出较高的克容量，同时提高整体正极极片的力学强度和压实密度。
在上述任意实施方式中，第一锂镍过渡金属氧化物的重量百分比含量为50％～90％，可选地为60％～85％；且第二锂镍过渡金属氧化物的重量百分比含量为10％～50％，可选地为15％～40％。第一锂镍过渡金属氧化物以及第二锂镍过渡金属氧化物在正极极片中的重量百分比控制在上述范围内，在一定程度上可以调控正极极片的OI值，同时提高极片的压实密度和力学强度。
在上述任意实施方式中，第二锂镍过渡金属氧化物还包括位于第二基材表面的第二包覆层，所述第二包覆层为金属氧化物和/或非金属氧化物，可选地，所述第二包覆层物质为金属氧化物。
本申请第二方面提供本申请第一方面所提供的用于二次电池的正极极片的制备方法。
本申请第三方面提供一种二次电池，其包括本申请的第一方面所述的正极极片。
本申请第四方面提供一种电池模块，其包括本申请的第三方面所述的二次电池。
本申请第五方面提供一种电池包，其包括本申请的第四方面所述的电池模块。
本申请第六方面提供一种装置，其包括本申请的第三方面所述的二次电池，所述二次电池用作所述装置的电源。
相对于现有技术，本申请的有益效果为：本申请用于二次电池的正极极片中，正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，其中第一锂镍过渡金属氧化物为经包覆处理的二次颗粒，第二锂镍过渡金属氧化物为单晶或类单晶结构的单颗粒，通过调控混合后正极活性物质的粒径分布和极片OI值，提高了正极极片中正极活性物质颗粒的抗压强度，有效抑制正极活性物质颗粒的颗粒开裂问题，同时降低垂直于正极极片的(003)晶面的相对含量，使得制备获得的二次电池(例如，锂离子电池)具有能量密度高、产气量低、极片膨胀率低等特点，具有良好的产业化前景。
本申请的电池模块、电池包和装置包括所述的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是电池的一实施方式的立体图。
图2是电池的一实施方式的分解图。
图3是电池模块的一实施方式的立体图。
图4是电池包的一实施方式的立体图。
图5是图4的分解图。
图6是电池作为电源的装置的一实施方式的示意图。
其中，附图标记说明如下：
1电池包
2上箱体
3下箱体
4电池模块
5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用于二次电池的正极极片、二次电池、电池模块、电池包和装置的实施方式。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)。
正极极片
本申请的第一方面提供一种用于二次电池的正极极片，正极极片包括正极集流体和位于正极集流体表面的正极活性物质层，正极活性物质层包括正极活性物质，正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，第一锂镍过渡金属氧化物包括第一基材和位于第一基材表面的第一包覆层，第一基材为二次颗粒，第一锂镍过渡金属氧化物的化学式如式I所示：
Li 1+a1Ni x1Co y1Mn z1M b1O 2-e1X e1    (I)
式I中，-0.1<a1<0.1，0.5≤x1≤0.95，0.05≤y1≤0.2，0.03≤z1≤0.4，0≤b1≤0.05，0≤e1≤0.1，且x1+y1+z1+b1＝1；其中，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X选自F和/或Cl。
第一包覆层选自金属氧化物和/或非金属氧化物。
第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒。
正极活性物质的粒径分布特征满足：D v90的范围为10μm-20μm且40μm<(D v90×D v50)/D v10<90μm，其中，D v10、D v50、D v90分别为所述正极活性物质的体积分布粒径，单位为μm。
正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，正极极片的OI值为10～40。
本申请中，D v10为正极活性物质的体积累计分布百分数达到10％时对应的粒径(单位：μm)；D v50为样品的体积累计分布百分数达到50％时对应的粒径(单位：μm)；D v90为样品的体积累计分布百分数达到90％时对应的粒径(单位：μm)。D v10、D v50、D v90为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T19077-2016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Mastersizer2000E型激光粒度分析仪。
本申请中，正极极片的OI值为正极极片的XRD衍射谱中正极活性物质的(003)晶面与(110)晶面相应的衍射峰面积的比值。正极极片的OI值为本领域公知的含义，可以采用XRD衍射仪进行测试。作为示例的，可以采用如下方法进行：将制备好的正极极片，水平放置于XRD衍射仪中测试正极极片的XRD衍射谱，计算该XRD衍射图谱中正极活性物质的(003)晶面与(110)晶面对应的衍射峰面积的比值，即为正极极片的OI值。
已经发现使用普通高镍含量的锂镍过渡金属氧化物作为正极活性物质的二次电池循环性能较差。申请人对此现象进行了深入研究，发现了目前主流的高镍含量的锂镍过渡金属氧化物是由一次小晶粒聚集成的二次多晶大颗粒，但由于高镍含量的锂镍过渡金属氧化物充放电过程中c轴方向体积变化大，导致一次晶粒间易产生裂纹，从而恶化循环性能。鉴于此，本申请所提供的用于二次电池的正极极片中，正极活性物质层包括正极活性物质，正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，第 一锂镍过渡金属氧化物中的第一基材为由一次颗粒团聚形成的二次颗粒、且经金属氧化物和/或非金属氧化物包覆处理，第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒。本申请中，类单晶通常是指一次颗粒的尺寸大于1μm、但一次颗粒存在一定团聚的颗粒形态，该团聚有别于第一锂镍过渡金属氧化物，为几个颗粒聚集在一起，形状不规则，且结合力较弱；单晶通常是指一次颗粒的尺寸大于1μm、且无明显团聚的颗粒形态。并且，本申请通过调控混合后正极活性物质的粒径分布和正极极片OI值，有效正极活性物质颗粒的抑制颗粒开裂问题，在提高正极极片中正极活性物质颗粒的抗压强度的同时，降低正极极片中的正极活性物质的(003)晶面的相对量，有效解决极片膨胀率和产气的问题，从而获得了高能量密度、低极片膨胀率、低产气量的电化学储能装置。
本申请中，正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，正极活性物质粉体OI值不超过10。这是由于正极活性物质基本为分散状，晶体没有特定取向，正极活性物质粉体基本显示各向同性。本申请中，正极活性物质粉体的OI值测试方法与正极极片测试方法基本一致。
为了获得良好的电池性能，本申请中正极活性物质的粒径分布特征应满足D v90的范围为10～20μm且40μm<(D v90×D v50)/D v10<90μm。(D v90×D v50)/D v10例如可以为40μm<(D v90×D v50)/D v10<85μm，45μm<(D v90×D v50)/D v10<90μm，45μm<(D v90×D v50)/D v10<85μm，40μm<(D v90×D v50)/D v10<80μm，45μm<(D v90×D v50)/D v10<80μm，40μm<(D v90×D v50)/D v10<70μm，40μm<(D v90×D v50)/D v10<65μm，45μm<(D v90×D v50)/D v10<65μm，40μm<(D v90×D v50)/D v10<60μm，或40μm<(D v90×D v50)/D v10<55μm等。(D v90×D v50)/D v10可以理解为(D v90/D v10)与D v50的乘积，其中D v50表示正极活性物质的平均粒径，而(D v90/D v10)可以近似理解为正极活性物质中大颗粒平均粒径与小颗粒平均粒径的比值。因此，(D v90×D v50)/D v10在适当范围内即表示正极活性物质的平均粒径适中、且颗粒尺寸之间的差异也适中。
本申请所提供的正极极片中，D v90的下限例如可以为11μm、12μm、13μm、14μm等，D v90的上限例如可以为19μm、18μm、17μm、16μm等。本申请中，当正极活性物质的D v90的上下限满足上述范围内时，可进一步调控正极活性物质的粒径分布范围，保证颗粒尺寸适中，有利于提高正极极片的压实密度和抗开裂能力，从而进一步改善电池的能量密度以及产气问题。
本申请所提供的正极极片中，正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，正极极片的OI值可以为10～15、15～20、20～25、25～30、30～35、或35～40，可选地可以为10～20。通常来说，正极极片OI值反映了极片中正极活性物质晶面的整体取向程度，与极片制程工艺的涂布速度、烘干、冷压等多种过程参数密切相关。正极极片的OI值过高，表示垂直于正极极片长度方向的(003)晶面相对量过高，反映出正极极片在冷压后出现较严重的织构，在电池充放电过程中极片容易发生膨胀；但是如果正极极片OI值过低，表明此时正极极片中正极活性物质没有明显的取向性，颗粒强度过低，在冷压及循环中后期易发生颗粒破碎，引发产气问题。
本申请中，极片压实密度可以通过本领域中已知的方法和仪器(例如天平、万分尺)来进行测定。例如，可以通过测量单位面积内活性物质层的重量，来计算涂布面密度CW，以万分尺测量极片单侧活性物质层厚度，涂布面密度与单侧活性物材料厚度的比 值即为压实密度PD。当在集流体的上下表面均设置活性物质层时，可以通过简单的数据计算来得出单面活性物质层的涂布面密度，再测量单侧活性物质层厚度，即可计算得到活性物质层的压实密度。作为示例的，可以使用万分仪测量并记录基材厚度和极片厚度(两侧均设置有活性物质层)，然后按照公式：PD＝CW×2/(极片厚度-基材厚度)，即可以计算得到活性物质层的压实密度，单位：g/cm 3。作为示例的，厚度可以使用日本三丰万分尺仪测量。
本申请所提供的正极极片中，第二锂镍过渡金属氧化物包括第二基材，第二基材的化学式如式II所示：
Li 1+a2Ni x2Co y2Mn z2M’ b2O 2-e2X’ e2   (II)
式II中，-0.1<a2<0.1，0.5≤x2≤0.95，0.05≤y2≤0.2，0.03≤z2≤0.4，0≤b2≤0.05，0≤e2≤0.1，且x2+y2+z2+b2＝1，M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X’选自F和/或Cl。
本申请所提供的正极极片中，第一基材和第二基材的分子式可以各自独立的包括但不限于LiNi 0.5Co 0.2Mn 0.3O 2、LiNi 0.5Co 0.25Mn 0.25O 2、LiNi 0.55Co 0.15Mn 0.3O 2、LiNi 0.55Co 0.1Mn 0.35O 2、LiNi 0.55Co 0.05Mn 0.4O 2、LiNi 0.6Co 0.2Mn 0.2O 2、LiNi 0.65Co 0.15Mn 0.2O 2、LiNi 0.65Co 0.12Mn 0.23O 2、LiNi 0.65Co 0.1Mn 0.25O 2、LiNi 0.65Co 0.05Mn 0.3O 2、LiNi 0.7Co 0.1Mn 0.2O 2、LiNi 0.75Co 0.1Mn 0.15O 2、LiNi 0.8Co 0.1Mn 0.1O 2、LiNi 0.85Co 0.05Mn 0.1O 2、LiNi 0.88Co 0.05Mn 0.07O 2、LiNi 0.9Co 0.05Mn 0.05O 2、LiNi 0.92Co 0.03Mn 0.05O 2、LiNi 0.95Co 0.02Mn 0.03O 2等，也可以为上述物质经过掺杂元素M、M’、X、X’进行部分取代改性后的物质，M、M’各自独立的选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X、X’各自独立的选自F和/或Cl。
在本申请一些可选的实施方式中，第一基材的分子式中Ni元素的相对含量x1可以满足：0.8≤x1≤0.95、0.8≤x1≤0.85、0.85≤x1≤0.9、或0.9≤x1≤0.95，第二基材的分子式中Ni元素的相对含量x2可以满足：0.8≤x2≤0.95，0.8≤x1≤0.85、0.85≤x1≤0.9、或0.9≤x1≤0.95，且第一基材与第二基材中Ni元素的相对含量x1、x2可以满足：∣x1-x2∣≤0.1。本申请中的第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物均选择镍含量较高的层状锂过渡金属氧化物，能够有效提高电池的能量密度，同时第一基材与第二基材中Ni元素的相对含量x1、x2的差值不大于0.1，可以实现当在同一充放电电压下，第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物具有较接近的脱/嵌锂程度，有利于提高电池的充放电循环寿命。
在本申请一些可选的实施方式中，第一基材与第二基材中Ni元素的相对含量x1、x2满足：0<x1-x2<0.1。本申请中第一锂镍过渡金属氧化物的Ni元素含量x1略高于第二锂镍过渡金属氧化物x2，在有效平衡两种正极活性物质的脱/嵌锂程度的同时，有利于电池发挥出较高的能量密度。
本申请所提供的正极极片中，正极活性物质的体积粒径分布以及振实密度TD满足：4.4<(D v90-D v10)/TD<8。具体的，(D v90-D v10)/TD的取值范围可以为7.5～8、7～7.5、6.5～7、6～6.5、5.5～6、5～5.5、4.4～5。可选地，4.6<(D v90-D v10)/TD<6.5。其中，D v10、D v90单位为μm；TD为所述正极活性物质的振实密度(单位：g/cm 3)。本申 请中当正极活性物质进一步满足(D v90-D v10)/TD的取值在上述范围时，正极活性物质不同形貌颗粒的粒度分布适中、颗粒间的间隙体积较低，有利于正极极片压实密度的提高。
本申请所提供的正极极片中，正极活性物质的振实密度TD可以为2.2g/cm 3～2.8g/cm 3、2.2g/cm 3～2.3g/cm 3、2.3g/cm 3～2.4g/cm 3、2.4g/cm 3～2.5g/cm 3、2.5g/cm 3～2.6g/cm 3、2.6g/cm 3～2.7g/cm 3、或2.7g/cm 3～2.8g/cm 3。通常来说，TD越大，越利于实现高压实密度，但TD受材料单个颗粒的紧实度、材料的粒径分布、颗粒的形态等因素影响，有一定的上限。
本申请中，TD为正极活性物质的粉体振实密度，粉体振实密度的具体测量方法可以包括：将粉体填装于容器中(例如，25mL的容器，再例如，所使用的容器可以为量筒)，对容器进行振动后(例如，振动的具体条件可以为：振动频率为250次/分，振幅为3mm，振动5000次)，单位体积粉体的质量即为粉体振实密度。
本申请所提供的正极极片中，第一锂镍过渡金属氧化物可以为球形颗粒，第一锂镍过渡金属氧化物的球形度γ可以为0.7～1。具体的，第一锂镍过渡金属氧化物的球形度γ可以为0.7～0.9、0.7～0.8、0.8～0.9、或0.9～1。本申请中，第一锂镍过渡金属氧化物为二次颗粒，当二次颗粒的球形度在上述范围内时，表明二次颗粒内一次颗粒的尺寸均一、分布较均匀，二次颗粒较紧实，力学强度较高。
本申请中，所述球形度可以通过以下方式测量得到：在正极极片横截面的SEM照片中，选择至少30个截面直径在正极活性物质D v10数值以上的二次颗粒，测量截面SEM图片中各自二次颗粒的最大内接圆半径(R max)与最小外接圆半径(R min)的比值，求平均值，即可以得到γ。
本申请所提供的正极极片中，第二锂镍过渡金属氧化物的最长径L max与最短径L min的尺寸比例满足：1≤L max/L min≤3、1≤L max/L min≤1.5、1.5≤L max/L min≤2、2≤L max/L min≤2.5、或2.5≤L max/L min≤3。本申请中，第二锂镍过渡金属氧化物为单晶或类单晶形貌的颗粒，当单颗粒的L max/L min在上述范围内时，与球形度在0.7～1之间的二次颗粒混合后，能够更好的填充二次颗粒的间隙体积，在提升正极极片的压实密度、电池体积能量密度的同时，还可以有效抑制循环过程中正极极片的体积膨胀率，改善循环性能。
本申请中，所述L max/L min可以通过以下方式测量得到：在正极极片横截面的SEM照片中，选择至少30个截面直径在正极活性物质D v10数值以上的单晶或类单晶形貌颗粒，测量截面SEM图片各自颗粒的最长直径(L max)与最短直径(L min)的比值，求平均值，即可以得到L max/L min。
本申请所提供的正极极片中，第一锂镍过渡金属氧化物的D v50，即D v50(L)可以为5μm～18μm、5μm～6μm、6μm～8μm、8μm～10μm、10μm～12μm、12μm～14μm、14μm～16μm、或16μm～18μm，可选地可以为8μm～12μm。第二锂镍过渡金属氧化物的D v50，即D v50(S)可以为1μm～5μm、1μm～2μm、2μm～3μm、3μm～4μm、或4μm～5μm。本申请中，第一锂镍过渡金属氧化物中的基材为二次颗粒，第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒，第一锂镍过渡金属氧化物相对于第二锂镍过渡金属氧化物整体上具有较大的粒径，两者之间的粒径关系可选地可以满足：2≤D v50(L)/D v50(S)≤7、2≤D v50(L)/D v50(S)≤3、3≤D v50(L)/D v50(S)≤4、4≤D v50(L)/D v50(S)≤5、5≤D v50(L)/D v50(S)≤6、或6≤D v50(L)/D v50(S)≤7。本申请中，第一锂镍过渡金属氧化物 D v50(L)和第二锂镍过渡金属氧化物D v50(S)的比值在上述范围内时，有利于抑制粒径尺寸较大的二次颗粒高镍材料的颗粒开裂问题，保证正极活性物质能够发挥出较高的克容量，同时提高整体正极极片的力学强度和压实密度。
本申请所提供的正极极片中，正极活性物质相对于整个活性物质层的含量范围例如可以为95％～99％。本申请所提供的正极极片中，相对于正极活性物质的总质量，第一锂镍过渡金属氧化物的重量百分比含量可以为50％～90％、85％～90％、80％～85％、75％～80％、70％～75％、65％～70％、60％～65％、55％～60％、或50％～55％，可选地可以为60％～85％。第二锂镍过渡金属氧化物的重量百分比含量可以为10％～50％、10％～15％、15％～20％、20％～25％、25％～30％、30％～35％、35％～40％、40％～45％、或45％～50％，可选地可以为15％～40％。本申请中，第一锂镍过渡金属氧化物以及第二锂镍过渡金属氧化物在正极极片中的重量百分比控制在上述范围内，在一定程度上可以调控正极极片的OI值，同时提高极片的压实密度和力学强度。
本申请所提供的正极极片中，第二锂镍过渡金属氧化物还可以包括位于第二基材表面的第二包覆层，第二包覆层为金属氧化物和/或非金属氧化物。
本申请所提供的正极极片中，第一包覆层和/或第二包覆层可以是金属氧化物和/或非金属氧化物，例如，可以是仅含有金属元素或者非金属元素的氧化物，也可以同时含有金属元素和非金属元素的氧化物。上述氧化物中，金属元素通常可以是例如铝、锆、锌、钛、硅、锡、钨、钇、钴、钡等，非金属元素通常可以是例如磷、硼等。具体的，第一包覆层和/或第二包覆层可以是包括但不限于氧化铝、氧化锆、氧化锌、氧化钛、氧化硅、氧化锡、氧化钨、氧化钇、氧化钴、氧化钡、氧化磷、氧化硼、以及锂铝氧化物、锂锆氧化物、锂锌氧化物、锂镁氧化物、锂钨氧化物、锂钇氧化物、锂钴氧化物、锂钡氧化物、锂磷氧化物或者锂硼氧化物等中的一种或多种的组合。本申请中，正极活性物质的包覆层选用上述金属氧化物和/或非金属氧化物，氧化物包覆层与基材的结合力良好，在充放电过程中包覆层不易脱落，减少基材与电解液接触面积的部分，可以有效地对高镍正极材料的表面进行改性，降低正极材料与电解液的副反应，从而可以有效抑制电池的产气现象。
本申请所提供的正极材料中，第一包覆层中可选地至少同时含有一种金属元素的氧化物和一种非金属元素的氧化物。含有上述元素的氧化物不仅能够提高包覆层在二次颗粒基材表面附着的稳定性，还可以使包覆层兼具一定的导离子性和导电子性，减少包覆层对正极材料极化问题的影响。
正极极片的制备方法
本申请第二方面提供本申请第一方面所提供的用于二次电池的正极极片的制备方法，合适的制备正极极片的方法对于本领域技术人员来说应该是已知的，例如，正极极片可以包括：
提供包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物的正极活性物质；
将正极活性物质、粘结剂、导电剂混合形成浆料后，涂布于正极集流体上。
本申请所提供的正极材料的制备方法中，第一锂镍过渡金属氧化物和/或第二锂镍过渡金属氧化物可以是经过表面修饰的，例如，可以将第一锂镍过渡金属氧化物和/或第 二锂镍过渡金属氧化物分别进行表面修饰后，再进行混合，其中第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物的表面修饰方法可以相同、也可以不同；也可以将第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物先混合，再一起进行表面修饰工艺。
本申请所提供的正极极片的制备方法中，可以包括：提供第一锂镍过渡金属氧化物。提供第一锂镍过渡金属氧化物的方法对于本领域技术人员来说应该是已知的，例如，可以包括：将第一锂镍过渡金属氧化物的基材的原料混合、烧结，以提供第一基材；将第一基材进行包覆处理，以提供第一锂镍过渡金属氧化物。本领域技术人员可根据第一锂镍过渡金属氧化物的元素组成，选择合适的原料和配比，以进一步制备获得第一基材。例如，第一锂镍过渡金属氧化物的原料可以包括第一锂镍过渡金属氧化物的前驱体、锂源、M源、X源等，各原料之间的比例通常参照第一锂镍过渡金属氧化物中各元素的比例进行配比。更具体的，第一锂镍过渡金属氧化物的前驱体可以是包括但不限于Ni 0.5Co 0.2Mn 0.3(OH) 2、Ni 0.5Co 0.25Mn 0.25(OH) 2、Ni 0.55Co 0.15Mn 0.3(OH) 2、Ni 0.55Co 0.1Mn 0.35(OH) 2、Ni 0.55Co 0.05Mn 0.4(OH) 2、Ni 0.6Co 0.2Mn 0.2(OH) 2、Ni 0.65Co 0.15Mn 0.2(OH) 2、Ni 0.65Co 0.12Mn 0.23(OH) 2、Ni 0.65Co 0.1Mn 0.25(OH) 2、Ni 0.65Co 0.05Mn 0.3(OH) 2、Ni 0.7Co 0.1Mn 0.2(OH) 2、Ni 0.75Co 0.1Mn 0.15(OH) 2、Ni 0.8Co 0.1Mn 0.1(OH) 2、Ni 0.88Co 0.05Mn 0.07(OH) 2、Ni 0.92Co 0.03Mn 0.05(OH) 2、Ni 0.95Co 0.02Mn 0.03(OH) 2等，锂源可以是含锂的化合物，含锂化合物可以是包括但不限于LiOH·H 2O、LiOH、Li 2CO 3、Li 2O等中的一种或多种的组合，M源通常可以是含M元素的化合物，上述含M元素的化合物可以是含有Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、Co、Mn中至少一种元素的氧化物、硝酸盐、碳酸盐中的一种或几种，X源可以是含X元素的化合物，上述含X元素的化合物可以是包括但不限于LiF、NaCl等中的一种或多种的组合。第一锂镍过渡金属氧化物的基材的原料的烧结的条件可以是700℃～900℃、氧气浓度≥20％的烧结条件。将第一基材进行包覆处理的方法具体可以包括：将第一基材在含包覆元素的化合物存在的条件下烧结，含包覆元素的化合物可以是含有Al、Ba、Zn、Ti、Co、W、Y、Si、Sn、B、P等中的一种或多种元素的氧化物、硝酸盐、磷酸盐、碳酸盐等，包覆元素的使用量可以是通常≤2wt％，包覆处理中的烧结的条件可以是200℃～700℃。
本申请所提供的正极极片的制备方法中，可以包括：提供第二锂镍过渡金属氧化物。提供第二锂镍过渡金属氧化物的方法对于本领域技术人员来说应该是已知的，例如，可以包括：将第二锂镍过渡金属氧化物的基材的原料混合、烧结，以提供第二基材；将第二基材进行包覆处理，以提供第二锂镍过渡金属氧化物。本领域技术人员可根据第二锂镍过渡金属氧化物的元素组成，选择合适的原料和配比，以进一步制备获得第二基材。例如，第二锂镍过渡金属氧化物的原料可以包括第二锂镍过渡金属氧化物的前驱体、锂源、M’源、X’源等，各原料之间的比例通常参照第二锂镍过渡金属氧化物中各元素的比例进行配比。更具体的，第二锂镍过渡金属氧化物的前驱体可以是包括但不限于Ni 0.5Co 0.2Mn 0.3(OH) 2、Ni 0.5Co 0.25Mn 0.25(OH) 2、Ni 0.55Co 0.15Mn 0.3(OH) 2、Ni 0.55Co 0.1Mn 0.35(OH) 2、Ni 0.55Co 0.05Mn 0.4(OH) 2、Ni 0.6Co 0.2Mn 0.2(OH) 2、Ni 0.65Co 0.15Mn 0.2(OH) 2、Ni 0.65Co 0.12Mn 0.23(OH) 2、Ni 0.65Co 0.1Mn 0.25(OH) 2、Ni 0.65Co 0.05Mn 0.3(OH) 2、Ni 0.7Co 0.1Mn 0.2(OH) 2、Ni 0.75Co 0.1Mn 0.15(OH) 2、 Ni 0.8Co 0.1Mn 0.1(OH) 2、Ni 0.88Co 0.05Mn 0.07(OH) 2、Ni 0.92Co 0.03Mn 0.05(OH) 2、Ni 0.95Co 0.02Mn 0.03(OH) 2等，锂源可以是含锂的化合物，含锂化合物可以是包括但不限于LiOH·H 2O、LiOH、Li 2CO 3、Li 2O等中的一种或多种的组合，M’源通常可以是含M元素的化合物，上述含M’元素的化合物可以是含有Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、Co、Mn中至少一种元素的氧化物、硝酸盐、碳酸盐中的一种或几种，X’源可以是含X’元素的化合物，上述含X’元素的化合物可以是包括但不限于LiF、NaCl等中的一种或多种的组合。第二锂镍过渡金属氧化物的基材的原料的烧结的条件可以是750℃～950℃、氧气浓度≥20％的烧结条件。将第二基材进行包覆处理的方法具体可以包括：将第二基材在含包覆元素的化合物存在的条件下烧结，含包覆元素的化合物可以是含有Al、Ba、Zn、Ti、Co、W、Y、Si、Sn、B、P等中的一种或多种元素的氧化物、硝酸盐、磷酸盐、碳酸盐等，包覆元素的使用量可以是通常≤2wt％，包覆处理中的烧结的条件可以是200℃～700℃。
本申请所提供的正极极片的制备方法中，粘结剂通常包括含氟聚烯烃类粘结剂。相对于含氟聚烯烃类粘结剂来说，水通常是良溶剂，即含氟聚烯烃类粘结剂通常在水中具有良好的溶解性。例如，含氟聚烯烃类粘结剂可以是包括但不限于聚偏氟乙烯(PVDF)、偏氟乙烯共聚物等或它们的改性(例如，羧酸、丙烯酸、丙烯腈等改性)衍生物等。在正极活性物质层中，粘结剂的质量百分比含量可以是例如0.1wt％～10wt％，0.2wt％～8wt％0，0.3wt％～6wt％或0.5wt％～3wt％。由于粘结剂本身的导电性较差，因此粘结剂的用量不能过高。可选地，正极活性物质层中粘结剂的质量百分含量为0.5wt％～3wt％，以获得较低的极片阻抗。
本申请所提供的正极极片的制备方法中，正极极片的导电剂可以是本领域各种适用于锂离子(二次)电池的导电剂，例如，可以是包括但不限于乙炔黑、导电炭黑、碳纤维(VGCF)、碳纳米管(CNT)、科琴黑等中的一种或多种的组合。导电剂的重量可以占正极活性物质层总质量的0.5wt％～10wt％。可选地，正极极片中导电剂与正极活性物质的重量比为1.0wt％～5.0wt％。
本申请所提供的正极极片的制备方法中，正极极片的正极集流体通常可以为层体，正极集流体通常是可以汇集电流的结构或零件，正极集流体可以是本领域各种适用于作为锂离子电池正极集流体的材料，例如，正极集流体可以是包括但不限于金属箔等，更具体可以是包括但不限于铜箔、铝箔等。
二次电池
本申请的第三方面提供一种二次电池，包括本申请第一方面所提供的正极极片。
在本申请所提供的二次电池中，需要说明的是，二次电池可为超级电容器、锂离子电池、锂金属电池或钠离子电池。在本申请的实施例中，仅示出二次电池为锂离子电池的实施例，但本申请不限于此。
图1是锂离子电池的一具体实施例的立体图。图2是图1的分解图。参照图1至图2，电池5包括壳体51、电极组件52、顶盖组件53以及电解液(未示出)。电极组件52收容于壳体51内。电极组件52的数量不受限制，可以为一个或多个。
需要注意的是图1所示的电池5为罐型电池，但不限于此，电池5可以是袋型电池，即壳体51由金属塑膜替代且取消顶盖组件53。
在锂离子电池中，可以包括正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜、电解液，其中，正极极片可以是本申请第一方面所提供的正极极片。制备锂离子电池的方法对于本领域技术人员来说应该是已知的，例如，正极极片、隔离膜和负极极片各自都可以是层体，从而可以裁剪成目标尺寸后依次叠放，还可以卷绕至目标尺寸，以用于形成电芯，并可以进一步与电解液结合以形成锂离子电池。
在锂离子电池中，负极极片通常可以包括负极集流体和位于负极集流体表面的负极活性物质层，负极活性物质层通常包括负极活性物质。负极活性物质可以是本领域各种适用于锂离子电池的负极活性物质的材料，例如，可以是包括但不限于石墨、软碳、硬碳、碳纤维、中间相碳微球、硅基材料、锡基材料、钛酸锂或其他能与锂形成合金的金属等中的一种或多种的组合。其中，石墨可选自人造石墨、天然石墨以及改性石墨中的一种或多种的组合；硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅合金中的一种或多种的组合；锡基材料可选自单质锡、锡氧化合物、锡合金中的一种或多种的组合。负极集流体通常是汇集电流的结构或零件，负极集流体可以是本领域各种适用于作为锂离子电池负极集流体的材料，例如，负极集流体可以是包括但不限于金属箔等，更具体可以是包括但不限于铜箔等。
在锂离子电池中，隔离膜可以是本领域各种适用于锂离子电池隔离膜的材料，例如，可以是包括但不限于聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺，聚酰胺、聚酯和天然纤维等中的一种或多种的组合。
在锂离子电池中，电解液通常可以包括电解质和溶剂，合适的适用于锂离子电池的电解液对于本领域技术人员来说应该是已知的，例如，电解质通常可以包括锂盐等，更具体的，锂盐可以是无机锂盐和/或有机锂盐等，具体可以是包括但不限于LiPF 6、LiBF 4、LiN(SO 2F) 2(LiFSI)、LiN(CF 3SO 2) 2(LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)等中的一种或多种的组合；再例如，电解质的浓度可以为0.8mol/L～1.5mol/L之间；再例如，电解液中所使用的溶剂可以是本领域各种适用于锂离子电池的电解液的溶剂，通常为非水溶剂，可选地可以为有机溶剂，具体可以是包括但不限于碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸戊烯酯、碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯等或它们的卤代衍生物中的一种或多种的组合。
电池模块
在本申请的第四方面提供了一种电池模块，其包括本申请的第三方面所提供的二次电池。电池模块中通常可以包括一个或多个二次电池，电池模块可以作为电源或储能装置，电池模块中的电池的数量可以根据电池模块的应用和容量进行调节。
图3是电池模块的一具体实施例的立体图。
参照图3，电池模块4包括多个电池5。多个电池5沿纵向排列。
电池包
在本申请的第五方面提供了一种电池包，其包括本申请的第三方面所提供的二次电池，或第四方面所提供的电池模块。
图4是电池包1的一具体实施例的立体图。图5是图4的分解图。
参照图4和图5，电池包1包括上箱体2、下箱体3以及电池模块4。
上箱体2和下箱体3组装在一起并形成收容电池模块4的空间。电池模块4置于组装在一起的上箱体2和下箱体3的空间内。电池模块4的输出极从上箱体2和下箱体3的其中之一或二者之间穿出，以向外部供电或从外部充电。电池包1采用的电池模块4的数量和排列可以依据实际需要来确定。电池包1可以作为电源或储能装置。
装置
本申请第六方面提供一种装置，其包括本申请的第三方面所提供的二次电池，二次电池用作所述装置的电源。
图6是上述装置的一具体实施例的立体图。在图6中，采用电池5的装置为电动汽车。当然不限于此，采用电池5的装置可以为除电动汽车外的任何电动车辆(例如电动大巴、电动有轨电车、电动自行车、电动摩托车、电动踏板车、电动高尔夫球车、电动卡车)、电动船舶、电动工具、电子设备及储能系统。电动汽车可以为电动纯电动车、混合动力电动车、插电式混合动力电动车。当然，依据实际使用形式，本申请第六方面所提供的装置可包括本申请的第四方面所提供的电池模块4，当然，本申请第六方面提供的装置也可包括本申请的第五方面所提供的电池包1。
以下结合实施例进一步说明本申请的有益效果。
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合实施例进一步详细描述本申请。但是，应当理解的是，本申请的实施例仅仅是为了解释本申请，并非为了限制本申请，且本申请的实施例并不局限于说明书中给出的实施例。实施例中未注明具体实验条件或操作条件的按常规条件制作，或按材料供应商推荐的条件制作。
此外应理解，本申请中提到的一个或多个方法步骤并不排斥在所述组合步骤前后还可以存在其他方法步骤或在这些明确提到的步骤之间还可以插入其他方法步骤，除非另有说明；还应理解，本申请中提到的一个或多个设备/装置之间的组合连接关系并不排斥在所述组合设备/装置前后还可以存在其他设备/装置或在这些明确提到的两个设备/装置之间还可以插入其他设备/装置，除非另有说明。而且，除非另有说明，各方法步骤的编号仅为鉴别各方法步骤的便利工具，而非为限制各方法步骤的排列次序或限定本申请可实施的范围，其相对关系的改变或调整，在无实质变更技术内容的情况下，当亦视为本申请可实施的范畴。
在下述实施例中，所使用到的试剂、材料以及仪器如没有特殊的说明，均可商购获得。
实施例1
1、正极活性物质的制备
1)制备第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物的前驱体：
将硫酸镍、硫酸锰、硫酸钴按摩尔比8:1:1配置成1mol/L溶液，利用氢氧化物共沉淀技术制备得到粒径D v50(L)为9.7μm的第一锂镍过渡金属氧化物的前驱体；硫酸镍、硫酸锰、硫酸钴按摩尔比配置成1mol/L溶液，利用氢氧化物共沉淀技术制备得到粒径为2.9μm的第二锂镍过渡金属氧化物的前驱体。制备前躯体的过程中，通过控制反应时间、共沉淀时的pH值、氨浓度实现对第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物的前驱体的颗粒粒径、形态的调控。
2)第一锂镍过渡金属氧化物(多晶LiNi 0.8Co 0.1Mn 0.1O 2)的制备方法：
将上述第一锂镍过渡金属氧化物的前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、含Li化合物LiOH·H 2O以摩尔比为1:1.05，置于混料设备中进行混料，然后置于气氛炉中830℃进行烧结，冷却后通过机械研磨即为第一锂镍过渡金属氧化物的基材。
将上述第一锂镍过渡金属氧化物的基材与0.2wt％的含包覆元素Al的化合物Al 2O 3、0.2wt％的含包覆元素B的化合物硼酸置于混料设备中进行混料，然后置于气氛炉中进行500℃烧结5h，形成第一锂镍过渡金属氧化物的第一包覆层，即得到表面包覆的第一锂镍过渡金属氧化物，上述材料的D v50、球形度和包覆材料参见表1。
3)第二锂镍过渡金属氧化物(单晶LiNi 0.8Co 0.1Mn 0.1O 2)的制备方法：
将上述第二锂镍过渡金属氧化物的前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2、含Li化合物LiOH·H 2O以摩尔比为1:1.05，置于混料设备中进行混料，然后置于氧气浓度30％的气氛炉中在870℃进行烧结4h，冷却后通过气流粉末进行研磨即为第二锂镍过渡金属氧化物的基材。
将第二锂镍过渡金属氧化物的基材与0.2wt％的含包覆元素Al的化合物Al 2O 3置于混料设备中进行混料，然后置于气氛炉中进行500℃烧结5h，形成锂镍过渡金属氧化物B的包覆层，即得到表面修饰的第二锂镍过渡金属氧化物，材料的D v50、L max/L min的比值和包覆材料参见表1。
4)将上述表面修饰的第一锂镍过渡金属氧化物与表面修饰的第二锂镍过渡金属氧化物以7:3的质量比混合均匀，得到实施例1的正极活性物质，实施例1正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
2、电池的制备
1)正极极片的制备
步骤1：将上述得到的正极活性物质、粘接剂聚偏氟乙烯、导电剂乙炔黑按照质量比98:1:1进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌均匀获得正极浆料；将正极浆料均匀涂覆于厚度为12μm的铝箔上。
步骤2：将涂覆后的极片经过100℃～130℃烘箱干燥，经过冷压、分切得到正极极片。
2)负极极片制备
将负极活性物质石墨、增稠剂羧甲基纤维素钠、粘接剂丁苯橡胶、导电剂乙炔黑，按照质量比97:1:1:1进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在厚度为8μm的铜箔上；将铜箔在室温晾干后转移至120℃烘箱干燥1h，然后经过冷压、分切得到负极极片。
3)电解液制备
有机溶剂为含有碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)的混合液，其中，EC、EMC和DEC的体积比为20:20:60。在含水量<10ppm的氩气气氛手套箱中，将充分干燥的锂盐溶解于有机溶剂中，混合均匀，获得电解液。其中，锂盐的浓度为1mol/L。
4)隔离膜的制备
选用12μm厚的聚丙烯隔离膜。
5)电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，再卷绕成方形的裸电芯后，装入铝塑膜，然后在80℃下烘烤除水后，注入相应的非水电解液、封口，经静置、热冷压、化成、夹具、分容等工序后，得到成品电池。
实施例2
实施例2中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为9:1，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
实施例3
实施例3中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为6:4，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
实施例4
实施例4中正极极片和电池的制备方法参照实施例1，不同之处在于第二锂镍过渡金属氧化物中Ni:Co:Mn元素比为5:2:3，第二锂镍过渡金属氧化物的粒径D v50(S)＝4.3μm，L max/L min＝1.5，包覆元素为Al、Ti，烧结过程中所使用的化合物为氧化铝和氧化钛，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为8:2，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
实施例5
实施例5中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物中Ni:Co:Mn元素比为6:2:2，第一锂镍过渡金属氧化物的粒径D v50(L)＝9.6μm，球形度γ＝0.81，制备获得的正极活性物质的TD、(D v90-D v10)/TD、D v90/D v10*D v50和正极极片OI值参见表1。
实施例6
实施例6中正极极片和电池的制备方法参照实施例1，不同之处在于第二锂镍过渡金属氧化物中Ni:Co:Mn元素比为9:0.5:0.5，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为8:2，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
实施例7
实施例7中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与的包覆元素为B，即未使用Al所对应的化合物进行烧结，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
实施例8
实施例8中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与的包覆元素为B，即未使用Al所对应的化合物进行烧结，第二锂镍过渡金属氧化物的包覆元素为Al、B，烧结过程中所使用的化合物为氧化铝和氧化硼，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
实施例9
实施例9中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物中Ni:Co:Mn元素比为8.3:1.4:0.3，第一锂镍过渡金属氧化物的粒径D v50(L)＝12.3μm，球形度γ＝0.85，包覆元素为Ba，对应包覆时所使用的化合物为氧化钡，第二锂镍过渡金属氧化物的粒径D v50(S)＝2.2μm，L max/L min＝1.7，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为6:4，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
实施例10
实施例10中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物中Ni:Co:Mn元素比为8.3:1.4:0.3，第一锂镍过渡金属氧化物的粒径D v50(L)＝12.3μm，球形度γ＝0.85，对应包覆时所使用的化合物为氧化钡，第二锂镍过渡金属氧化物中Ni:Co:Mn元素比为5:2:3，第二锂镍过渡金属氧化物的粒径D v50(S)＝4.3μm，Lmax/Lmin＝1.5，包覆元素为Al、Ti，烧结过程中所使用的化合物为氧化铝、氧化钛，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为5:5，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
对比例1
对比例1中正极极片和电池的制备方法参照实施例1，第一锂镍过渡金属氧化物的粒径D v50(L)＝7.8μm，球形度γ＝0.77，第二锂镍过渡金属氧化物中Ni:Co:Mn元素比为5:2:3，第二锂镍过渡金属氧化物的粒径D v50(S)＝4.3μm，L max/L min＝1.5，包覆元素为Al、Ti，烧结过程中所使用的化合物为氧化铝、氧化钛，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
对比例2
对比例2中正极极片和电池的制备方法参照实施例1，不同之处在于正极活性物质的制备方法中，未使用第二锂镍过渡金属氧化物，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
对比例3
对比例3中正极极片和电池的制备方法参照实施例1，不同之处在于第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为4:6，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
对比例4
对比例4中正极极片和电池的制备方法参照实施例9，不同之处在于第一锂镍过渡金属氧化物的粒径D v50(L)＝16.8μm，第二锂镍过渡金属氧化物的粒径D v50(S)＝2.9μm，L max/L min＝2，第一锂镍过渡金属氧化物与第二锂镍过渡金属氧化物之间的质量比为9:1，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
对比例5
对比例5中正极极片和电池的制备方法参照实施例1，不同之处在于制备正极极片的过程中未使用第一锂镍过渡金属氧化物，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
对比例6
对比例6中正极极片和电池的制备方法参照实施例1，不同之处在于制备第一锂镍过渡金属氧化物的过程中，未进行包覆处理，制备获得的正极活性物质的TD、(D v90-D v10)/TD、(D v90×D v50)/D v10和正极极片OI值参见表1。
检测方法
(1)二次颗粒球形度的测试方法：
对正极极片的横截面拍摄SEM照片，选择至少30个截面直径在正极活性物质D v10数值以上的二次颗粒，测量SEM图片中每个二次颗粒的最大内接圆半径(R max)与最小外接圆半径(R min)的比值，求平均值，即可以得到二次颗粒的球形度γ。
(2)单晶/类单晶颗粒Lmax/Lmin的测试方法：
对正极极片横截面的SEM照片中，选择至少30个截面直径在正极活性物质D v10数值以上的单晶或类单晶形貌颗粒，测量SEM图片各自颗粒的最长直径(L max)与最短直径(L min)的比值，求平均值，即可以得到L max/L min。各实施例及对比例的测试结果见表2。
(3)振实密度TD的测试方法：
将10g粉体填装于量程为25mL的量筒中，对填料后的量筒以振动频率为250次/分，振幅为3mm，振动5000次，读取此时粉料在量筒中占用的体积，即可计算得出单位体积粉体的质量，即为粉体振实密度TD。各实施例及对比例的测试结果见表2。
(4)正极极片OI值与正极活性物质粉体OI值的测试方法：
将制备好的正极极片，水平放置于XRD衍射仪中测试正极极片的XRD衍射谱，计算该XRD衍射图谱中正极活性物质的(003)晶面与(110)晶面对应的衍射峰面积的比值，即为正极极片的OI值。各实施例及对比例的测试结果见表2。
正极活性物质粉体OI值的测试方法与正极极片的测试方法基本一致，不同之处在于测试的样品为正极活性物质粉体。
(5)压实密度的测试方法：
1)将极片裁剪为1000mm长度的膜片；2)将正极极片通过一定压力进行碾压，由于铝箔具备延展性，使其膜片长度为1006mm；3.)冲切1540.25mm 2的小圆片，测量小圆片重量及厚度，即可计算压实密度。
各实施例及对比例的测试结果见表2。
(6)45℃循环400周容量保持率的测试方法：
在45℃下，将锂离子电池以1C恒流充电至电压4.2V，然后以4.2V恒压充电至电流为0.05C，接着以1C恒流放电，直到最终电压为2.8V，记录首次循环的放电容量。然后按照上述操作进行充电和放电循环400周期，并记录400周期以后的放电容量。根据首次循环的放电容量和400周期以后的放电容量，计算获得45℃循环400周容量保持率。
各实施例及对比例的测试结果见表2。
(7)循环DCR增长的测试：
25℃下，将电池以1C恒流/恒压(以1C恒流充电到4.2V，然后4.2V恒压充电至0.05C)充电到100％SOC，然后以1C恒流放电30min，搁置60min，记录搁置后电压U1；然后以4C恒定电流放电至30s，记录放电后的电压U2。
依照公式计算锂离子电池的直流阻抗：DCR＝(U2-U1)/4C。
各实施例及对比例的测试结果见表2。
通过实施例和对比例的比较，可以看出，将二次颗粒形态的第一锂镍过渡金属氧化物和单晶或类单晶形貌颗粒的第二锂镍过渡金属氧化物混合，并控制混合后正极活性物质的粒径分布以及正极极片的OI值，在改善压实密度的同时，可以改善循环过程中的颗粒开裂、改善循环寿命和循环过程中的DCR增长。表面包覆的金属氧化物和非金属氧化物，可以显著改善循环寿命和循环DCR增长。
以上所述，仅为本申请的较佳实施例，并非对本申请任何形式上和实质上的限制，应当指出，对于本技术领域的普通技术人员，在不脱离本申请方法的前提下，还将可以做出若干改进和补充，这些改进和补充也应视为本申请的保护范围。凡熟悉本专业的技术人员，在不脱离本申请的精神和范围的情况下，当可利用以上所揭示的技术内容而做出的些许更动、修饰与演变的等同变化，均为本申请的等效实施例；同时，凡依据本申请的实质技术对上述实施例所作的任何等同变化的更动、修饰与演变，均仍属于本申请的技术方案的范围内。
Figure PCTCN2021112009-appb-000001
表2
Figure PCTCN2021112009-appb-000002

Claims (15)

  1. 一种用于二次电池的正极极片，所述正极极片包括正极集流体和位于正极集流体表面的正极活性物质层，所述正极活性物质层包括正极活性物质，所述正极活性物质包括第一锂镍过渡金属氧化物和第二锂镍过渡金属氧化物，所述第一锂镍过渡金属氧化物包括第一基材和位于第一基材表面的第一包覆层，所述第一基材为二次颗粒，所述第一基材的化学式如式I所示：
    Li 1+a1Ni x1Co y1Mn z1M b1O 2-e1X e1  (I)
    所述式I中，-0.1<a1<0.1，0.5≤x1≤0.95，0.05≤y1≤0.2，0.03≤z1≤0.4，0≤b1≤0.05，0≤e1≤0.1，且x1+y1+z1+b1＝1，M选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X选自F和/或Cl；
    所述第一包覆层选自金属氧化物和/或非金属氧化物；
    所述第二锂镍过渡金属氧化物为单晶或类单晶形貌颗粒；
    所述正极活性物质的粒径分布满足：D v90的范围为10μm～20μm且40μm<(D v90×D v50)/D v10<90μm；
    所述正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，所述正极极片的OI值为10～40。
  2. 如权利要求1所述的正极极片，其中，所述正极极片的OI值为所述正极极片的XRD衍射谱中对应所述正极活性物质的(003)晶面与(110)晶面的衍射峰面积的比值。
  3. 如权利要求1或2所述的正极极片，其中，所述第二锂镍过渡金属氧化物包括第二基材，所述第二基材的化学式如式II所示：
    Li 1+a2Ni x2Co y2Mn z2M’ b2O 2-e2X’ e2  (II)
    所述式II中，-0.1<a2<0.1，0.5≤x2≤0.95，0.05≤y2≤0.2，0.03≤z2≤0.4，0≤b2≤0.05，0≤e2≤0.1，且x2+y2+z2+b2＝1，M’选自Al、Ti、Zr、Nb、Sr、Sc、Sb、Y、Ba、B、Co、Mn中的一种或多种的组合，X’选自F和/或Cl；
    可选地，所述第一基材与所述第二基材的分子式中Ni元素的相对含量x1、x2满足：
    0.8≤x1≤0.95，0.8≤x2≤0.95，且∣x1-x2∣≤0.1；
    可选地，所述x1、x2满足：0<x1-x2<0.1。
  4. 如权利要求1～3任一项所述的正极极片，其中，所述正极极片的压实密度为3.3g/cm 3～3.5g/cm 3时，所述正极极片的OI值为10～20。
  5. 如权利要求1～4中任一项所述的正极极片，其中，所述正极活性物质满足：4.4<(D v90-D v10)/TD<8，可选地，4.6<(D v90-D v10)/TD<6.5，
    其中，D v10、D v90的单位为μm；TD为所述正极活性物质的振实密度，单位为g/cm 3。
  6. 如权利要求1～5中任一项所述的正极极片，其中，所述正极活性物质的振实密度TD为2.2g/cm 3～2.8g/cm 3。
  7. 如权利要求1～6中任一项所述的正极极片，其中，所述第一锂镍过渡金属氧化物为球形颗粒，所述第一锂镍过渡金属氧化物颗粒的球形度γ为0.7～1。
  8. 如权利要求1～7中任一项所述的正极极片，其中，所述第二锂镍过渡金属氧化物颗粒的最长径L max与最短径L min的尺寸比例满足：1≤L max/L min≤3。
  9. 如权利要求1～8中任一项所述的正极极片，其中，所述第一锂镍过渡金属氧化物的D v50，即D v50(L)为5μm～18μm，所述第二锂镍过渡金属氧化物的D v50，即D v50(S)为1μm～5μm；
    可选地，所述D v50(L)与所述D v50(S)满足：2≤D v50(L)/D v50(S)≤7。
  10. 如权利要求1～9中任一项所述的正极极片，其中，所述正极活性物质中，所述第一锂镍过渡金属氧化物的重量百分比含量为50％～90％，可选地为60％～85％；
    且所述第二锂镍过渡金属氧化物的重量百分比含量为10％～50％，可选地为15％～40％。
  11. 如权利要求1～10中任一项所述的正极极片，其中，所述第二锂镍过渡金属氧化物还包括位于第二基材表面的第二包覆层，所述第二包覆层为金属氧化物和/或非金属氧化物，可选地，所述第二包覆层物质为金属氧化物。
  12. 一种二次电池，包括如权利要求1～11任一项所述的正极极片。
  13. 一种电池模块，其中，包括如权利要求12所述的二次电池。
  14. 一种电池包，其中，包括如权利要求13所述的电池模块。
  15. 一种装置，其中，包括如权利要求12所述的二次电池，所述二次电池用作所述装置的电源，可选地，所述装置包括电动车辆、混合动力电动车辆、插电式混合动力电动车辆、电动自行车、电动踏板车、电动高尔夫球车、电动卡车、电动船舶、储能系统。
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