WO2023078047A1 - 正极活性材料、其制备方法、包括其的锂离子电池、电池模块、电池包和用电装置 - Google Patents

正极活性材料、其制备方法、包括其的锂离子电池、电池模块、电池包和用电装置 Download PDF

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WO2023078047A1
WO2023078047A1 PCT/CN2022/124925 CN2022124925W WO2023078047A1 WO 2023078047 A1 WO2023078047 A1 WO 2023078047A1 CN 2022124925 W CN2022124925 W CN 2022124925W WO 2023078047 A1 WO2023078047 A1 WO 2023078047A1
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lithium
positive electrode
lithium salt
active material
electrode active
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PCT/CN2022/124925
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English (en)
French (fr)
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张翠平
韩昌隆
任苗苗
吴则利
黄磊
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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 EP22889072.9A priority Critical patent/EP4333117A1/en
Priority to KR1020247001881A priority patent/KR20240023610A/ko
Publication of WO2023078047A1 publication Critical patent/WO2023078047A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G45/00—Compounds of manganese
    • C01G45/12—Manganates manganites or permanganates
    • C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
    • C01G45/1228—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type [MnO2]n-, e.g. LiMnO2, Li[MxMn1-x]O2
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry, and in particular to a positive electrode active material, a lithium ion battery containing the same, a battery module, a battery pack and an electrical device.
  • lithium-ion batteries are widely used in various large-scale power devices, energy storage systems and various consumer products due to their excellent electrochemical performance, no memory effect, and low environmental pollution. Widely used in pure electric vehicles, hybrid electric vehicles and other new energy vehicles. This has higher requirements for the comprehensive improvement of the service life and fast charging performance of lithium-ion batteries.
  • the present application is made in view of the above-mentioned problems, and the purpose is to provide a positive electrode active material so that lithium-ion batteries have both excellent power performance and cycle life.
  • the first aspect of the present application provides a positive electrode active material, including a matrix and a coating layer on the surface of the substrate.
  • the cladding layer includes a second lithium salt simultaneously containing fluorine, phosphorus and oxygen, and oxygen in the second lithium salt contains lone electron pairs.
  • the mass proportion of the second lithium salt is 0.1%-20%, optionally 1%-10%.
  • the thickness of the positive electrode active material coating layer is 10-100 nm, optionally 20-60 nm.
  • the second lithium salt is selected from at least one of lithium difluorophosphate, lithium difluorobisoxalatephosphate, lithium tetrafluorooxalatephosphate.
  • the positive electrode active material is composed of first particles with a volume average particle diameter Dv50 of 2-8 ⁇ m and second particles with a volume average particle diameter Dv50 of 13-22 ⁇ m.
  • the mass ratio of the first particles to the second particles is 2.3 ⁇ 9:1.
  • the first and/or second particles include both single crystal and polycrystalline crystals, and the mass ratio of single crystal particles to polycrystalline particles is 0.1-1:1, optionally 0.23-0.67 :1.
  • the second aspect of the present application provides a method for preparing a positive electrode active material, comprising the following steps:
  • the matrix includes a first lithium salt selected from LiAO 4 with a spinel structure, LiBO 2 with a layered structure, and lithium-rich manganese-based xLi 2 MnO 3 ⁇ (1-x)LiCO 2 At least one of, wherein, the A is Ni or Co, the B is Ni, Co, Mn or Al, the C is selected from Ni, Co or Mn and 0.1 ⁇ x ⁇ 0.9; the cladding layer includes A second lithium salt containing both fluorine and phosphorus.
  • step S0 is further included before step S1, and step S0 includes the step of preparing the first lithium salt in monocrystalline form and/or the first lithium salt in polymorphic form.
  • step S5 is also included, the step S5 is to adjust the volume average particle diameter Dv50 of the positive electrode active material to obtain the first particle with the volume average particle diameter Dv50 of 2-8 ⁇ m and the volume average particle diameter The second particle with Dv50 in the range of 13-22 ⁇ m.
  • step S6 is further included.
  • the step S6 includes mixing the first particles and the second particles according to a predetermined mass ratio to obtain the positive electrode active material.
  • the drying and dehydration temperature range of the first lithium salt is 100-200°C; and/or,
  • the organic solvent is an ether, carboxylate, or carbonate organic solvent; and/or,
  • the method of uniform mixing is stirring and dispersing at 50-100°C for 4-8 hours; and/or,
  • the heat treatment method is to perform treatment in an air atmosphere at 200-250° C. for 5-10 hours.
  • the third aspect of the present application provides a lithium ion battery, including the high-nickel ternary positive electrode active material described in the first aspect of the present application or the high-nickel ternary positive electrode active material prepared by the preparation method of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery module, including the lithium-ion battery of the third aspect of the present application.
  • the battery module can be prepared using methods known in the prior art for preparing battery modules.
  • the fifth aspect of the present application provides a battery pack, including one or more of the lithium-ion battery of the third aspect of the present application or the battery module of the fourth aspect of the present application.
  • the battery pack can be prepared using methods known in the prior art for preparing battery packs.
  • the sixth aspect of the present application provides an electrical device, including one or more of the lithium-ion battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, or the battery pack of the fifth aspect of the present application.
  • the ion battery or the battery module or the battery pack is used as a power source of the electric device or an energy storage unit of the electric device.
  • the preparation of the electric device can adopt the methods known in the prior art for the preparation of the electric device.
  • the present application by coating the surface of the first lithium salt with a coating layer containing the second lithium salt, on the one hand, it can block the corrosion and decomposition of the first lithium salt by the electrolyte, thereby reducing the occurrence of side reactions; on the other hand, it can make the second lithium salt
  • the dilithium salt forms a CEI (cathode electrolyte interface) film in situ on the surface of the first lithium salt particles, thereby improving the film structure and avoiding the decomposition of the effective components in the electrolyte;
  • the second lithium salt contains both fluorine and Phosphorous element, make the formed film composition keep consistent with the CEI film composition of the lithium hexafluorophosphate (electrolyte) in the electrolytic solution as much as possible, from reducing the active lithium consumption in the electrolytic solution;
  • the cathode active material of the present application can significantly improve the power performance of the battery and cycle life.
  • the battery module, battery pack and electrical device of the present application include the lithium ion battery provided by the present application, and thus have at least the same advantages as the lithium ion battery.
  • Fig. 1 is the structural representation of positive electrode active material of the present application
  • Fig. 2 is the SEM figure (A figure) of the positive electrode active material of one embodiment of the present application and the SEM figure (B figure) of the positive electrode active material of the comparative example 1 of the present application;
  • FIG. 3 is a schematic diagram of a lithium-ion battery according to an embodiment of the present application.
  • Fig. 4 is an exploded view of a lithium-ion battery according to an embodiment of the present application shown in Fig. 2;
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • Fig. 7 is an exploded view of the battery pack according to an embodiment of the present application shown in Fig. 5;
  • FIG. 8 is a schematic diagram of an electrical device according to an embodiment of the present application.
  • a "range” disclosed herein is defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined in any combination, i.e. any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • coating layer refers to the part covering the surface of the substrate.
  • the part may but not necessarily completely cover the “substrate”.
  • coating layer is only for the convenience of description and is not intended to limit this application.
  • the continuous oxidative decomposition of the electrolyte on the surface of the positive electrode is actually a process in which the solvent, electrolyte, additives and other components in the electrolyte are continuously decomposed at the positive electrode to form a CEI (cathode electrolyte interface) film on the surface of the positive electrode. Therefore, if the positive electrode active material can be modified by coating the active ingredient of the pre-formed CEI film in situ, the active ingredient of the pre-formed CEI film can be formed into a film in situ on the surface of the positive electrode active material, which will significantly reduce the oxidation of the electrolyte. The probability, and will not cause the consumption of active lithium and the deposition of electrolyte decomposition by-products, thereby significantly improving the power and cycle performance of the battery.
  • lithium salts containing both fluorine and phosphorus such as lithium difluorophosphate
  • Some lithium salts containing both fluorine and phosphorus are generally added to the electrolyte as an additive to improve battery cycle performance, but in the electrolyte, on the one hand, it is difficult to dissolve and the utilization rate is low; on the other hand
  • lithium difluorophosphate is added to the electrolyte, the conductivity in the electrolyte is low, and the addition of only 1% will seriously deteriorate the conductivity, so it is not conducive to the performance of the battery power performance.
  • the present application solves the above problems at the same time by using the above-mentioned lithium salts such as lithium difluorophosphate as modifiers in the modification of positive electrode active materials, and significantly improves the power and cycle performance of lithium-ion batteries.
  • the present application provides a positive electrode active material, which includes a substrate and a coating layer located on the surface of the substrate,
  • the coating layer includes a second lithium salt containing three elements of fluorine, phosphorus and oxygen, and the oxygen in the second lithium salt contains lone electron pairs.
  • the first lithium salt by coating the surface of the first lithium salt with a coating layer containing the second lithium salt, on the one hand, it can block the corrosion and decomposition of the electrolyte to the first lithium salt in the matrix, thereby reducing the occurrence of side reactions; on the other hand, it can Make the second lithium salt form a CEI film in situ on the surface of the first lithium salt particle, thereby improving the film structure and increasing the transmission rate of lithium ions in the positive electrode active material; on the other hand, the second lithium salt contains both fluorine and phosphorus elements , make the formed film composition keep consistent with the CEI film composition formed by the lithium hexafluorophosphate (electrolyte) in the electrolyte as much as possible, from reducing the consumption of active lithium in the electrolyte; in a word, the positive electrode active material of the present application can significantly improve the power performance of the battery and cycle life.
  • the second lithium salt is selected from at least one of lithium difluorophosphate, lithium difluorobisoxalatephosphate, lithium tetrafluorooxalatephosphate.
  • lithium difluorophosphate lithium difluorobisoxalate phosphate
  • lithium tetrafluorooxalate phosphate The structural formulas of lithium difluorophosphate, lithium difluorobisoxalate phosphate and lithium tetrafluorooxalate phosphate are respectively:
  • the above second lithium salt in addition to being able to in-situ synthesize a CEI film on the surface of the first lithium salt and optimize the film structure, it also has oxygen lone electron pairs.
  • the oxygen lone electron pair in the second lithium salt can make lithium difluorophosphate and the transition metal ion in the first lithium salt adhere closely to the surface of the first lithium salt in the form of a uniform coating layer through complexation (see Figure 1.
  • the surface of the positive electrode active material particles without any treatment in Figure 1 is smooth; with reference to Figure 1.A, the modified surface of the positive electrode active material of the present application has a rough layer and the rough layer surface has a protruding accumulation body Particles) can not only prevent the coating layer from falling off from the substrate, but also effectively prevent the transition metal in the first lithium salt from leaching, thereby preventing the performance of the battery from being reduced.
  • the second lithium salt may be lithium tetrafluorooxalate phosphate
  • the second lithium salt with more fluorine atoms can increase the stability of the formed CEI film, which is more beneficial to the improvement of battery performance.
  • the surface of the coating layer of the cathode active material of the present application has protruding accumulation particles formed by the second lithium salt.
  • the coating layer of the positive electrode active material of the present application is composed of a layer with a relatively flat surface and protruding accumulation particles located on the surface of the layer.
  • the second lithium salt is evenly distributed in the layer with a relatively flat surface, thereby improving the microscopic appearance of the CEI film on the surface of the positive electrode active material. Structure, improve the transmission rate of lithium ions in the positive electrode active material.
  • the protruding accumulation particles are composed of the second lithium salt, which is conducive to supplementing the battery with additional lithium salt after long-term cycling, increasing the amount of active lithium in the electrolyte, and improving the service life of the battery.
  • the mass proportion of the second lithium salt is 0.1%-20%, optionally 1%-10%.
  • the mass ratio of the second lithium salt in the positive electrode is less than 0.1%, an effective coating layer cannot be formed, and the contact between the positive electrode active material and the electrolyte cannot be effectively prevented, that is, the side reaction of the electrolyte at the positive electrode interface cannot be effectively suppressed;
  • the mass ratio of the second lithium salt in the positive electrode is greater than 10%, the effect cannot be further improved, but the cost will be increased, and the transmission of lithium ions will be hindered.
  • the coating layer of the positive electrode active material has a thickness of 10-100 nm, optionally 20-60 nm.
  • the thickness of the cladding layer within a reasonable range can not only maintain the effectiveness of the second lithium salt, but also prevent the power performance from being reduced due to the obstruction of lithium ion transmission.
  • the positive electrode active material is composed of first particles with a volume average particle diameter Dv50 of 2-8 ⁇ m and second particles with a volume average particle diameter Dv50 of 13-22 ⁇ m.
  • the positive electrode active material is composed of first particles and the second particles, and the mass ratio of the two is 2.3 ⁇ 9:1.
  • the adaptability of the first particle and the second particle can make the positive electrode film thickness contain more positive electrode active materials, increase the compaction density of the material, and then increase the energy density of the battery.
  • the mass ratio of the first particle to the second particle is greater than 9:1, since there are more large particles in the material, the path of lithium ions in the solid-phase transport will be prolonged, which will have a certain impact on the power performance of the battery; when the size When the mass ratio of the particles is less than 2.3:1, there are more small particles in the positive electrode active material, and the specific surface area of the material is larger, which may cause uneven coating of the coating layer, thereby affecting the effectiveness of the second lithium salt.
  • the particle size of the positive electrode material can be realized by the pulverization process of the prior art.
  • the first particle of 2-8 ⁇ m can be obtained by using a mechanical pulverizer, and the second particle of 13-22 ⁇ m can be obtained by using a jet pulverizer.
  • the first and/or second particles include both single crystal and polycrystalline crystal forms.
  • the ion transmission path of single crystal is long, but it has a low specific surface area, and there are few side reactions. , the advantages of both can be combined.
  • the application provides a method for preparing a positive electrode active material, which comprises the following steps:
  • the cladding layer includes a second lithium salt containing both fluorine and phosphorus.
  • step S0 is further included before step S1, and step S0 includes the step of preparing the first lithium salt in monocrystalline form and/or the first lithium salt in polymorphic form.
  • step S5 is further included.
  • the step S5 is to adjust the volume average particle diameter Dv50 of the positive electrode active material to obtain the first particle with a volume average particle diameter Dv50 of 2-8 ⁇ m and a volume average particle diameter The second particle with Dv50 in the range of 13-22 ⁇ m.
  • step S6 is further included.
  • the step S6 includes mixing the first particles and the second particles according to a predetermined mass ratio to obtain the positive electrode active material.
  • step S1 the drying and dehydration temperature of the first lithium salt ranges from 100°C to 200°C.
  • the organic solvent is an ether, carboxylate, or carbonate organic solvent.
  • step S3 the method of uniform mixing is stirring and dispersing at 50-100° C. for 4-8 hours; and/or,
  • step S4 the heat treatment is carried out in an air atmosphere at 200-250° C. for 5-10 hours.
  • the present application provides a positive electrode sheet, and the positive electrode sheet includes the positive electrode active material of the present application.
  • the positive electrode sheet includes a positive electrode collector and a positive electrode material arranged on at least one surface of the positive electrode collector.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode material is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid Ethylene glycol ester (PET), polybutylene terephthalate (PBT), 1,3-propane sultone (PS), polyethylene (PE) and other substrates), but this Applications are not limited to these materials.
  • PP polypropylene
  • PET polyethylene terephthalic acid Ethylene glycol ester
  • PBT polybutylene terephthalate
  • PS 1,3-propane sultone
  • PE polyethylene
  • the positive electrode material also optionally includes a conductive agent.
  • a conductive agent there is no specific limitation on the type of conductive agent, which can be selected by those skilled in the art according to actual needs.
  • the conductive agent used for the positive electrode material may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared according to methods known in the art.
  • the positive electrode active material, conductive agent and binder of the present application can be dispersed in a solvent (such as N-methylpyrrolidone (NMP)) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode assembly On the fluid, after drying, cold pressing and other processes, the positive electrode sheet is obtained.
  • NMP N-methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid Ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates), but the present application is not limited to these Material.
  • PP polypropylene
  • PET polyethylene terephthalic acid Ethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode film layer usually includes negative electrode active materials and optional binders, optional conductive agents and other optional additives, and is usually formed by coating and drying negative electrode slurry .
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring evenly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode film layer may also optionally include other commonly used negative electrode active materials.
  • other commonly used negative electrode active materials artificial graphite, natural graphite, soft Carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate, etc.
  • the silicon-based material can be selected from more than one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material can be selected from more than one of elemental tin, tin oxide compounds and tin alloys.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (ie, electrolyte solution).
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), difluorosulfonyl Lithium amide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium difluorooxalate borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorooxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlorate
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), Dipropyl Carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Butylene Carbonate (BC), Fluoroethylene Carbonate (FEC), Methyl Formate (MF), Methyl Acetate Ester (MA), Ethyl Acetate (EA), Propyl Acetate (PA), Methyl Propionate (MP), Ethyl Propionate (EP), Propyl Propionate (PP), Methyl Butyrate (MB) , ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl s
  • additives may optionally be included in the electrolyte.
  • additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of batteries, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and battery low-temperature performance. additives, etc.
  • the separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from more than one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process, and the positive pole piece includes the lithium iron phosphate positive electrode active material of the present application.
  • a lithium ion battery can include an outer packaging.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the lithium-ion battery can be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the lithium-ion battery can also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of plastic include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • FIG. 2 shows a lithium-ion battery 5 with a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the lithium-ion battery 5 can be one or more, and those skilled in the art can select according to specific needs.
  • lithium-ion batteries can be assembled into a battery module, and the number of lithium-ion batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 4 is a battery module 4 as an example.
  • a plurality of lithium-ion batteries 5 can be arranged sequentially along the length direction of the battery module 4 .
  • the plurality of lithium ion batteries 5 can be fixed by fasteners.
  • the battery module 4 may also include a housing with an accommodating space, and a plurality of lithium-ion batteries 5 are accommodated in the accommodating space.
  • the above battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes more than one of the lithium-ion battery, battery module, or battery pack provided in the present application.
  • the lithium-ion battery, battery module, or battery pack can be used as a power source for the device, or as an energy storage unit for the device.
  • the device can be, but not limited to, a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • a lithium-ion battery, a battery module or a battery pack can be selected according to its use requirements.
  • Figure 7 is an example device.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • battery packs or battery modules can be employed.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is usually required to be light and thin, and a lithium-ion battery can be used as a power source.
  • the positive electrode active material of embodiment 1, conductive agent Super P, binding agent polyvinylidene fluoride (PVDF) are made into positive electrode slurry in N-methylpyrrolidone (NMP), and solid content is 50wt% in positive electrode slurry , the mass ratio of the positive electrode active material, Super P, and PVDF in the solid component is 8:1:1. Coat the positive electrode slurry on the aluminum foil of the current collector and dry it at 85°C, then cold press it, then cut the edge, cut into pieces, and divide into strips, and then dry it under vacuum at 85°C for 4 hours to make the positive electrode sheet .
  • NMP N-methylpyrrolidone
  • Negative electrode slurry was prepared by mixing graphite as the negative electrode active material with conductive agent Super P, thickener CMC, and binder styrene-butadiene rubber (SBR) in deionized water.
  • the solid content in the negative electrode slurry is 30wt%, and the mass ratio of graphite, Super P, CMC and binder styrene-butadiene rubber (SBR) in the solid component is 80:15:3:2.
  • the negative electrode slurry was coated on the copper foil of the current collector and dried at 85°C, then cold pressed, edge trimmed, cut into pieces, and stripped, and then dried under vacuum at 120°C for 12 hours to make negative electrode sheets.
  • the positive pole piece, separator, and negative pole piece in sequence, so that the separator is between the positive and negative pole pieces to play the role of isolation, and then wind it into a square bare cell, put it into an aluminum-plastic film, inject Corresponding non-aqueous electrolyte, sealing, after standing still, hot and cold pressing, chemical formation, fixture, volume separation and other processes, the lithium-ion battery is obtained.
  • LiNi 0.8 Co 0.1 Mn 0.1 O 2 Use commercially available LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the product model is (HAH101 purchased from Hunan Bangpu Cycle Technology Co., Ltd.)
  • the first lithium salt used is LiNiO 2
  • the second lithium salt used is lithium difluorobisoxalate phosphate
  • the amount of the first lithium salt added is 91% of the sum of the mass of the first lithium salt and the second lithium salt
  • the particle size of the first particle is prepared to be 7 ⁇ m
  • the particle size of the second particle is prepared to be 16 ⁇ m; other preparation processes are the same as in Example 1.
  • step S1 the first lithium salt used is LiMnO 2
  • the second lithium salt used is lithium tetrafluorooxalate phosphate
  • step S3 the amount of the first lithium salt added is the second 91% of the mass sum of the first lithium salt and the second lithium salt
  • step S6 the mixing mass ratio of the first particle to the second particle is 4:1; other preparation processes are the same as in Example 1.
  • step S1 the first lithium salt used is 0.5Li 2 MnO 3 ⁇ 0.5LiMn 0.3 Co 0.7 O 2 ; other preparation processes are the same as in Example 1.
  • step S1 and in step S3 the amount of the first lithium salt added is 1.8% of the sum of the mass of the first lithium salt and the second lithium salt, respectively.
  • Example 1 5%, 15%, 20%, 0.9%, 30%, 0.10%, 5%, 20%, 0.01%, 25%; other preparation processes are the same as in Example 1.
  • step S5 the particle sizes of the first particles were prepared to be 2 ⁇ m, 4 ⁇ m, 8 ⁇ m, 1 ⁇ m, and 10 ⁇ m, and the other preparation processes were the same as in Example 1.
  • step S5 the particle sizes of the second particles were prepared to be 13 ⁇ m, 18 ⁇ m, 22 ⁇ m, 10 ⁇ m, and 25 ⁇ m; other preparation processes were the same as in Example 1.
  • step S6 the mixing mass ratios of the first particle and the second particle are respectively 2.3:1, 4:1, 9:1, 1.8:1, 9.5:1, other preparations Process is identical with embodiment 1.
  • step S0 there is no step S02 of preparing the first polymorphic lithium salt, and other processes are similar to those in Example 1.
  • the content of the second lithium salt is tested according to the general rules of ion chromatography analysis method in JY/T 020-1996.
  • D50 test is carried out according to GB/T19077-2016.
  • sample preparation glue a jelly formed by dispersing PVDF into NMP, the mass content of PVDF is 8%
  • sample powder the weight of the powder is about 5 times that of the glue
  • the prepared sample was cut into a size of 6 mm ⁇ 6 mm with scissors, fixed on the sample stage, and put into an ion polisher (model: IB-19500CP) for cutting. According to JBT9352-1999, the cut samples were put into the American FEI Tecnai G2 transmission electron microscope equipment for thickness test.
  • Example 1 compared with the unmodified positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the power performance and cycle life of lithium-ion batteries are significantly improved.
  • Examples 2 to 4 illustrate that for different first lithium salts, coating with different types of second lithium salts described in this application can make lithium ion batteries have excellent power performance and cycle life.
  • Example 9 the power performance and cycle life of the lithium-ion batteries corresponding to Example 1 and Examples 5-9 are better, indicating that the thickness of the coating layer is in the range of 10-100 nm It is the preferred range, when the thickness of the coating layer is in the range of 20-60nm, the performance is better.
  • Example 24 and Example 25 the power performance and cycle life of the lithium-ion batteries corresponding to Example 1 and Examples 16-24 are better, indicating that when the positive electrode active material is changed from the volume average particle size Dv50 The performance is better when the first particle is composed of 2-8 ⁇ m and the second particle has a volume average particle diameter Dv50 of 13-22 ⁇ m.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exhibit the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

Abstract

本申请提供一种正极活性材料，通过在第一锂盐的表面包覆含有第二锂盐的包覆层，不仅能够阻隔电解液对第一锂盐的腐蚀分解，还能够使第二锂盐在第一锂盐颗粒的表面原位形成CEI膜，从而改善膜结构，并避免了电解液中有效成分的分解；此外，第二锂盐同时含有氟和磷元素，使所形成的膜成分尽量与由电解液中的六氟磷酸锂形成的膜成分一致，从而降低电解液中活性锂消耗。本申请的正极活性材料能够显著提高电池的功率性能和循环寿命。

Description

正极活性材料、其制备方法、包括其的锂离子电池、电池模块、电池包和用电装置
相关申请的交叉引用
本申请要求享有于2021年11月2日提交的名称为“正极活性材料、其制备方法、包括其的锂离子电池、电池模块、电池包和用电装置”的中国专利申请202111291132.0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，尤其涉及一种正极活性材料、包含其的锂离子电池、电池模块、电池包和用电装置。
背景技术
随着新能源领域的快速发展，锂离子电池凭借其优良的电化学性能、无记忆效应、环境污染小等优势广泛应用于各类大型动力装置、储能***以及各类消费类产品中，尤其广泛应用于纯电动汽车、混合电动汽车等新能源汽车领域。这就对锂离子电池的使用寿命和快充性能的综合提高有了更高要求。
发明内容
本申请是鉴于上述课题而进行的，目的在于提供一种正极活性材料，使锂离子电池兼具优良功率性能和循环寿命。
本申请第一方面提供一种正极活性材料，包括基体以及位于所述基材表面的包覆层所述基体包括第一锂盐，所述第一锂盐选自层状结构的LiAO 2、Li[Ni aCo bMn c]O 2，以及富锂锰基系xLi 2MnO 3·(1-x)LiMn yB 1-yO 2中的至少一种，其中，所述A为Ni、Co、Mn或Al，所述B选自Ni、Co或Al中一种或两种金属离子，且0.1≤x≤0.9，0.1≤y≤0.9所述0＜a＜1、0＜b＜1、0＜c＜1、a+b+c＝1。所述包覆层包括同时含有氟、磷和氧的第二锂盐，所述第二锂盐中的氧含有孤电子对。
在任意实施方式中，基于所述正极活性材料的总质量计，第二锂盐的质量占比为0.1％～20％，可选为1％～10％。
在任意实施方式中，正极活性材料包覆层的厚度为10～100nm，可选为20～60nm。
在任意实施方式中，第二锂盐选自二氟磷酸锂、二氟双草酸磷酸锂、四氟草酸磷酸锂中的至少一种。
在任意实施方式中，正极活性材料由体积平均粒径Dv50在2～8μm的第一粒子和体积平均粒径Dv50在13～22μm的第二粒子组成。
在任意实施方式中，第一粒子与所述第二粒子的质量比为2.3～9：1。
在任意实施方式中，第一和/或第二粒子同时包括单晶和多晶两种晶型，且单晶粒子与多晶粒子的质量比为0.1～1：1，可选为0.23～0.67：1。
本申请第二方面提供一种正极活性材料的制备方法，包括如下步骤：
S1：将第一锂盐干燥脱水，得到干燥后的第一锂盐；
S2：将第二锂盐溶解到有机溶剂中，得到第二锂盐有机溶液；
S3：将所述干燥后的第一锂盐加入到所述第二锂盐有机溶液中，并混合均匀；
S4：将混合均匀的混合物过滤，并对过滤后的固体颗粒进行热处理，得到所述正极活性材料；其中，包括基体以及位于所述基材表面的包覆层，
所述基体包括第一锂盐，所述第一锂盐选自尖晶石结构的LiAO 4、层状结构的LiBO 2以及富锂锰基系xLi 2MnO 3·(1-x)LiCO 2中的至少一种，其中，所述A为Ni或Co，所述B为Ni、Co、Mn或Al，所述C选自Ni、Co或Mn且0.1<x<0.9；所述包覆层包括同时含有氟和磷的第二锂盐。
在任意实施方式中，在步骤S1之前还包括步骤S0，所述步骤S0包括制备单晶型第一锂盐和/或多晶型第一锂盐的步骤。
在任意实施方式中，还包括步骤S5，所述步骤S5为对所述正极活性材料的体积平均粒径Dv50进行调节，得到体积平均粒径Dv50在2～8μm的第一粒子和体积平均粒径Dv50在13～22μm的第二粒子。
在任意实施方式中，还包括步骤S6，所述步骤S6包括按照预定质量比将第一粒子和第二粒子混合，得到所述正极活性材料。
在任意实施方式中，在所述S1中，所述第一锂盐干燥脱水的温度范围为100-200℃；和/或，
在所述S2中，所述有机溶剂为醚类、羧酸酯类、碳酸酯类有机溶剂；和/或，
在所述S3中，混合均匀的方式为在50～100℃中搅拌分散4～8h；和/或，
在所述S4中，所述热处理方式为200～250℃的空气氛围中进行处理5～10h。
本申请第三方面提供一种锂离子电池，包括本申请第一方面所述的高镍三元正极活性材料或本申请第二方面制备方法制备的高镍三元正极活性材料。
本申请第四方面提供一种电池模块，包括本申请第三方面的锂离子电池。电池模块的制备可以采用现有技术已知的用于制备电池模块的方法。
本申请第五方面提供一种电池包，包括本申请第三方面的锂离子电池或本申请第四方面的电池模块中的一种以上。电池包的制备可以采用现有技术已知的用于制备电池包的方法。
本申请第六方面提供一种用电装置，包括本申请第三方面的锂离子电池、本申请第四方面的电池模块、或本申请第五方面的电池包中的一种以上，所述锂离子电池或所述电池模组或所述电池包用作所述用电装置的电源或所述用电装置的能量存储单元。用电装置的制备可以采用现有技术已知的用于制备用电装置的方法。
[有益效果]
本申请通过在第一锂盐的表面包覆含有第二锂盐的包覆层，一方面能够阻隔电解液对第一锂盐的腐蚀分解，进而减少副反应发生；另一方面，能够使第二锂盐在第一锂盐颗粒的表面原位形成CEI(cathode electrolyte interface)膜，从而改善膜结构，并避免了电解液中有效成分的分解；再一方面，第二锂盐同时含有氟和磷元素，使所形成的膜成分尽量与由电解液中的六氟磷酸锂(电解质)的CEI膜组分保持一致，从降低电解液中活性锂消耗；本申请的正极活性材料能够显著提高电池的功率性能和循环寿命。
本申请的电池模块、电池包和用电装置包括本申请提供的锂离子电池，因而至少具有与所述锂离子电池相同的优势。
附图说明
图1是本申请正极活性材料的结构示意图；
图2是本申请一实施方式的正极活性材料的SEM图(A图)和本申请对比例1的正极活性材料的SEM图(B图)；
图3是本申请一实施方式的锂离子电池的示意图；
图4是图2所示的本申请一实施方式的锂离子电池的分解图；
图5是本申请一实施方式的电池模块的示意图；
图6是本申请一实施方式的电池包的示意图；
图7是图5所示的本申请一实施方式的电池包的分解图；
图8是本申请一实施方式的用电装置的示意图。
附图标记说明：
1电池包；
2上箱体；
3下箱体；
4电池模块；
5锂离子电池；
51壳体；
52电极组件；
53顶盖组件。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的正极活性材料及其制造方法、正极极片、二次电池、电池模块、电池包和电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意 地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
需要说明的是，术语“包覆层”是指包覆基体表面的部分，所述部分可以但并不一定完全包覆“基体”，使用“包覆层”只是为了便于描述，并不意图限制本申请。
对锂离子电池的系列正极活性材料而言，特别是镍钴锰三元体系，具有不利于电性能发挥且无法避免的两大缺陷：1)其氧化活性比较高；2)固相锂离子传输速度慢。氧化活性高，导致电池循环过程中，电解液在正极表面被不断的氧化分解，同时消耗正极有限的活性锂，分解产物沉积在正极表面上显著增大锂离子在界面的扩散阻力，从而恶化电池的功率性能和循环寿命。因此，需要对正极活性材料进行改性，以克服上述缺陷。
电解液在正极表面被不断的氧化分解实际上是电解液中的溶剂、电解质、添加剂等组分在正极不断分解而在正极表面形成CEI(cathode electrolyte interface)膜的过程。因此，若能通过对正极活性材料原位包覆预形成CEI膜有效成分的方式进行改性，使预形成CEI膜的有效成分在正极活性材料表面原位成膜，会显著降低电解液被氧化的概率，并且也不会造成活性锂的消耗以及电解液分解副产物的沉积，从而显著改善电池的功率和循环性能。
一些同时含有氟、磷两种元素的锂盐，比如二氟磷酸锂，一般作为添加剂添加到电解液中改善电池循环性能，但是其在电解液中，一方面难溶解度，利用率低；另一方面，二氟磷酸锂加入到电解液中在电解液中电导率低，仅1％的添加量就会严重恶化电导率，故不利于电池功率性能的发挥。
由此，本申请通过将上述比如二氟磷酸锂类的锂盐作为改性剂用于正极活性材料的改性中，同时解决了上述难题，显著改善了锂离子电池的功率和循环性能。
[正极活性材料]
本申请提供一种正极活性材料，其包括基体以及位于所述基材表面的包覆层，
所述基体包括第一锂盐，所述第一锂盐选自层状结构的LiAO 2、Li[Ni aCo bMn c]O 2，以及富锂锰基系xLi 2MnO 3·(1-x)LiMn yB 1-yO 2中的至少一种，其中，所述A为Ni、Co、Mn或Al，所述B选自Ni、Co或Al中一种或两种金属离子，且0.1≤x≤0.9，0.1≤y≤0.9所述0＜a＜1、0＜b＜1、0＜c＜1、a+b+c＝1。所述包覆层包括同时含有氟、磷、氧三种元素的第二锂盐，所述第二锂盐中的氧含有孤电子对。
本申请通过在第一锂盐的表面包覆含有第二锂盐的包覆层，一方面能够阻 隔电解液对基体中第一锂盐的腐蚀分解，进而减少副反应发生；另一方面，能够使第二锂盐在第一锂盐颗粒的表面原位形成CEI膜，从而改善膜结构，提高锂离子在正极活性材料中的传输速率；再一方面，第二锂盐同时含有氟和磷元素，使所形成的膜成分尽量与由电解液中的六氟磷酸锂(电解质)形成的CEI膜成分保持一致，从降低电解液中活性锂消耗；总之，本申请的正极活性材料能够显著提高电池的功率性能和循环寿命。
在一些实施方式中，第二锂盐选自二氟磷酸锂、二氟双草酸磷酸锂、四氟草酸磷酸锂中的至少一种。
二氟磷酸锂、二氟双草酸磷酸锂、四氟草酸磷酸锂的结构式分别为：
Figure PCTCN2022124925-appb-000001
上述第二锂盐的结构式中除了能够在第一锂盐表面原位合成CEI膜并优化膜结构外，还具有氧孤电子对。第二锂盐中的氧孤电子对能够使二氟磷酸锂与第一锂盐中的过渡金属离子通过络合作用以均匀包覆层的形式紧密附着在第一锂盐表面(参考图1.B，图1的未经过任何处理的正极活性材料颗粒表面光滑；参考图1.A，经过改性处理的本申请的正极活性材料表面，具有粗糙的层且粗糙的层表面具有突起的堆积体颗粒)，不仅能够防止包覆层从基体上脱落，还能有效防止第一锂盐中的过渡金属溶出，进而防止降低电池性能。
进一步地，第二锂盐可选为四氟草酸磷酸锂，氟原子含量较多的第二锂盐能够增加形成的CEI膜的稳定性，进而对电池性能的提升更有益。经过实验，在其他各个条件相同的前提下，以四氟草酸磷酸锂为第二锂盐的正极活性材料，循环性能能够提高约5％左右，电池DCR降低约10％。
进一步地，本申请的正极活性材料的包覆层表面有突起的由所述第二锂盐形成的堆积体颗粒。
本申请正极活性材料的包覆层由表面较为平整的层以及位于层表面的突起的堆积体颗粒组成，表面较为平整的层中第二锂盐均匀分布，进而改善正极活性材料表面CEI膜的微观结构，提高锂离子在正极活性材料中的传输速率。另一方面，突起的堆积体颗粒由第二锂盐组成，有利于为经过长期循环后的电 池补充额外的锂盐，提高电解液中活性锂的量，进而改善提高电池使用寿命。
在一些实施方式中，基于正极活性材料的总质量计，第二锂盐的质量占比为0.1％～20％，可选为1％～10％。
当第二锂盐在正极的质量占比小于0.1％时，无法形成有效的包覆层，无法有效阻碍正极活性材料与电解液的接触，即无法有效的抑制电解液在正极界面的副反应；当第二锂盐在正极的质量比大于10％时，无法进一步改善效果，反而增加成本，还会阻碍锂离子的传输。
在一些实施方式中，正极活性材料的包覆层的厚度为10～100nm，可选为20～60nm。
将包覆层的厚度在合理范围内，既能保持第二锂盐的有效性，又能防止因锂离子传输受阻而降低功率性能。
在一些实施方式中，正极活性材料由体积平均粒径Dv50在2～8μm的第一粒子和体积平均粒径Dv50在13～22μm的第二粒子组成。
在一些实施方式中，正极活性材料由第一粒子与所述第二粒子组成，二者的质量比为2.3～9：1。
第一粒子与第二粒子的适应性搭配，能够使单位正极膜层厚度中含有更多正极活性物质，提高材料压实密度，进而提高电池能量密度。
进一步地，当第一粒子与第二粒子的质量比大于9：1时，由于材料中大颗粒较多，延长锂离子在固相传输中的路径，对电池的功率性能造成一定影响；当大小颗粒的质量比小于2.3：1时，正极活性材料中小颗粒较多，材料的比表面积较大，可能出现包覆层包覆不均匀的现象，从而影响第二锂盐的有效性。
正极材料的颗粒大小可以通过现有技术的粉碎工艺来实现，比如采用机械粉碎机可以得到2～8μm的第一粒子，采用气流粉碎机可以得到13～22μm的第二粒子。
在一些实施方式中，第一和/或第二粒子同时包括单晶和多晶两种晶型。
本申请中，单晶的离子传输路径长，但具有较低的比表面积，副反应较少，多晶比表面大，副反应多，但是锂离子传输路径短，功率性能较好，两者结合，可以综合两者的优点。
本申请提供一种正极活性物质的制备方法，其包括如下步骤：
S1：将第一锂盐干燥脱水，得到干燥后的第一锂盐；
S2：将第二锂盐溶解到有机溶剂中，得到第二锂盐有机溶液；
S3：将所述干燥后的第一锂盐加入到所述第二锂盐有机溶液中，并混合均匀；
S4：将混合均匀的混合物过滤，并对过滤后的固体颗粒进行热处理，得到所述正极活性材料；其中，包括基体以及位于所述基材表面的包覆层，
所述基体包括第一锂盐，所述第一锂盐选自层状结构的LiAO 2、Li[Ni aCo bMn c]O 2，以及富锂锰基系xLi 2MnO 3·(1-x)LiMn yB 1-yO 2中的至少一种，其中，所述A为Ni、Co、Mn或Al，所述B选自Ni、Co或Al中一种或两种金属离子，且0.1≤x≤0.9，0.1≤y≤0.9所述0＜a＜1、0＜b＜1、0＜c＜1、a+b+c＝1。所述包覆层包括同时含有氟和磷的第二锂盐。
在一些实施方式中，在步骤S1之前还包括步骤S0，所述步骤S0包括制备单晶型第一锂盐和/或多晶型第一锂盐的步骤。
在一些实施方式中，进一步包括步骤S5，所述步骤S5为对所述正极活性材料的体积平均粒径Dv50进行调节，得到体积平均粒径Dv50在2～8μm的第一粒子和体积平均粒径Dv50在13～22μm的第二粒子。
在一些实施方式中，进一步包括步骤S6，所述步骤S6包括按照预定质量比将第一粒子和第二粒子混合，得到所述正极活性材料。
在一些实施方式中，在步骤S1中，所述第一锂盐干燥脱水的温度范围为100～200℃。
在一些实施方式中，在步骤S2中，所述有机溶剂为醚类、羧酸酯类、碳酸酯类有机溶剂。
在一些实施方式中，在步骤S3中，混合均匀的方式为在50～100℃中搅拌分散4～8h；和/或，
在一些实施方式中，在步骤S4中，所述热处理方式为200～250℃的空气氛围中进行处理5～10h。
[正极极片]
本申请提供一种正极极片，所述正极极片包括本申请的正极活性材料。
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极材料。 作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极材料设置在正极集流体相对的两个表面的其中任意一者或两者上。
本申请的锂离子电池中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、1,3-丙烷磺酸内酯(PS)、聚乙烯(PE)等的基材)上而形成，但本申请并不限定于这些材料。
所述正极材料还可选地包括导电剂。但对导电剂的种类不做具体限制，本领域技术人员可以根据实际需求进行选择。作为示例，用于正极材料的导电剂可以选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种以上。
本申请中可按照本领域已知的方法制备正极极片。作为示例，可以将本申请的正极活性材料、导电剂和粘结剂分散于溶剂(例如N-甲基吡咯烷酮(NMP))中，形成均匀的正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
本申请的锂离子电池中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成，但本申请并不限定于这些材料。
本申请的负极极片中，所述负极膜层通常包含负极活性材料以及可选的粘结剂、可选的导电剂和其他可选助剂，通常是由负极浆料涂布干燥而成的。负极浆料通常是将负极活性材料以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。
作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种以上。
本申请的负极极片中，所述负极膜层除了包括负极活性材料外，还可选地包括其它常用负极活性材料，例如，作为其它常用负极活性材料，可列举出人造石墨、天然石墨、软炭、硬炭、硅基体料、锡基体料和钛酸锂等。所述硅基体料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的一种以上。所述锡基体料可选自单质锡、锡氧化合物以及锡合金中的一种以上。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可选自固态电解质及液态电解质(即电解液)中的至少一种。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种以上。
在一些实施方式中，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种以上。
在一些实施方式中，所述电解液中还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、以及改善电池低温性能的添加剂等。
[隔离膜]
采用电解液的锂离子电池、以及一些采用固态电解质的锂离子电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种以上。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
[锂离子电池]
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件，所述正极极片包括本申请的磷酸铁锂正极活性材料。
在一些实施方式中，锂离子电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，锂离子电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。锂离子电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)以及聚丁二酸丁二醇酯(PBS)等。
本申请对锂离子电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图2是作为一个示例的方形结构的锂离子电池5。
在一些实施方式中，参照图3，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。锂离子电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体需求 进行选择。
[电池模块]
在一些实施方式中，锂离子电池可以组装成电池模块，电池模块所含锂离子电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图4是作为一个示例的电池模块4。参照图4，在电池模块4中，多个锂离子电池5可以沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个锂离子电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个锂离子电池5容纳于该容纳空间。
[电池包]
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量本领域技术人员可以根据电池包的应用和容量进行选择。
图5和图6是作为一个示例的电池包1。参照图5和图6，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
[用电装置]
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的锂离子电池、电池模块、或电池包中的一种以上。所述锂离子电池、电池模块、或电池包可以用作所述装置的电源，也可以用作所述装置的能量存储单元。所述装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能***等。
作为所述用电装置，可以根据其使用需求来选择锂离子电池、电池模块或电池包。
图7是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对锂离子电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用锂离子电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为本领域通常使用的可以通过市购获得的常规产品。本申请实施例中各成分的含量，如果没有特别说明，均以质量计。
实施例
实施例1
【正极活性材料的制备】
S0：单晶型/多晶型第一锂盐LiNi 0.8Co 0.1Mn 0.1O 2的制备
S01)：单晶型LiNi 0.8Co 0.1Mn 0.1O 2的制备
将前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2和碳酸锂加入到研钵中，持续研磨10～15min，混合均匀，其中Li与过渡金属之和的加入摩尔比为1.2～1.25，然后放置在管式炉当中，先用氮气排空空气，然后通入氧气开始升温至820～900℃后煅烧12h，初始加热速率为10℃/min和最终冷却比率为10℃/min，冷却后再用研钵进行研磨过筛网，得到单晶的LiNi 0.8Co 0.1Mn 0.1O 2。
S02)：前驱体Ni 0.8Co 0.1Mn 0.1(OH) 2和碳酸锂加入到研钵中，持续研磨10～15min，混合均匀，其中Li与过渡金属之和的加入摩尔比为1.0～1.15，然后放置在管式炉当中，先用氮气排空空气，然后通入氧气开始升温至600-800℃后煅烧12h，初始加热速率为10℃/min和最终冷却比率为10℃/min，冷却后再用研钵进行研磨过筛网，得到多晶的LiNi 0.8Co 0.1Mn 0.1O 2。
S1：将单晶型的LiNi 0.8Co 0.1Mn 0.1O 2和多晶型的LiNi 0.8Co 0.1Mn 0.1O 2按照0.4：1的质量比均匀混合，并在150℃下干燥脱水2h，得到干燥后的第一锂盐；
S2：将第二锂盐二氟磷酸锂溶解到1,2-二甲氧基乙烷中(使二氟磷酸锂的质量分数为15％；
S3：将干燥后的第一锂盐加入到第二锂盐的1,2-二甲氧基乙烷溶液中， 第一锂盐的加入量为第一锂盐与第二锂盐质量之和的90％，并在30℃下搅拌分散4h；
S4：上述混合均匀的混合物过滤，并对过滤后的固体颗粒在200℃的空气气氛下处理5h，得到单晶型与多晶型混合的正极活性材料；
S5：第一粒子/第二粒子的制备
将步骤S4得到的正极活性材料在特定频率的机械粉碎机粉碎，得到粒径为5μm的第一粒子；将步骤S4得到的正极活性材料在特定频率的气流粉碎机粉碎，得到15μm的第二粒子；
S6：按照质量比3：1的比例将第一粒子和第二粒子混合，得到实施例1的正极活性材料。
【正极极片】
将实施例1的正极活性材料、导电剂Super P、粘结剂聚偏二氟乙烯(PVDF)在N-甲基吡咯烷酮(NMP)中制成正极浆料，正极浆料中固体含量为50wt％，固体成分中正极活性材料、Super P、PVDF的质量比为8：1：1。将正极浆料涂布在集流体铝箔上并在85℃下烘干后进行冷压，然后进行切边、裁片、分条后，在85℃的真空条件下烘干4h，制成正极片。
【负极极片】
将作为负极活性材料的石墨与导电剂Super P、增稠剂CMC、粘接剂丁苯橡胶(SBR)在去离子水中混合均匀，制成负极浆料。负极浆料中固体含量为30wt％，固体成分中石墨、Super P、CMC及粘接剂丁苯橡胶(SBR)的质量比为80：15：3：2。将负极浆料涂布在集流体铜箔上并在85℃下烘干，然后进行冷压、切边、裁片、分条后，在120℃真空条件下烘干12h，制成负极片。
【电解液】
将EC：DEC：DMC按照1：1：1的体积比混合，加入LiPF 6形成电解液，在所述电解液中，LiPF 6的浓度为1mol/L。
【隔离膜】
聚乙烯隔离膜。
【锂离子电池的制备】
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，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，得到锂离子电池。
对比例1
使用常规市售LiNi 0.8Co 0.1Mn 0.1O 2，产品型号为(HAH101购自湖南邦普循环科技有限公司)
其他制备过程与实施例1相同。
实施例2
在【正极活性材料的制备】中，在步骤S1中，所用第一锂盐为LiNiO 2，所用第二锂盐为二氟双草酸磷酸锂；在步骤S3中，第一锂盐的加入量为第一锂盐与第二锂盐质量之和的91％；在步骤S5中，第一粒子的粒径制备为7μm，第二粒子的粒径制备为16μm；其他制备过程与实施例1相同。
实施例3
在【正极活性材料的制备】中，在步骤S1中，所用第一锂盐为LiMnO 2，所用第二锂盐为四氟草酸磷酸锂；在步骤S3中，第一锂盐的加入量为第一锂盐与第二锂盐质量之和的91％；在步骤S6中，第一粒子与第二粒子的混合质量比为4：1；其他制备过程与实施例1相同。
实施例4
在【正极活性材料的制备】中，在步骤S1中，所用第一锂盐为0.5Li 2MnO 3·0.5LiMn 0.3Co 0.7O 2；其他制备过程与实施例1相同。
实施例5～实施例15
在【正极活性材料的制备】中，在步骤S1中，在步骤S3中，第一锂盐的加入量分别为为第一锂盐与第二锂盐质量之和的1.8％、
5％、15％、20％、0.9％、30％、0.10％、5％、20％、0.01％、25％；其他制备过程与实施例1相同。
实施例16～20
在【正极活性材料的制备】中，在步骤S5中，第一粒子的粒径制备分别为2μm、4μm、8μm、1μm、10μm，其他制备过程与实施例1相同。
实施例21～25
在【正极活性材料的制备】中，在步骤S5中，第二粒子的粒径制备分别为13μm、18μm、22μm、10μm、25μm；其他制备过程与实施例1相同。
实施例26～30
在【正极活性材料的制备】中，在步骤S6中，第一粒子与第二粒子的混合质量比分别为2.3:1、4:1、9:1、1.8:1、9.5:1，其他制备过程与实施例1相同。
实施例31
在【正极活性材料的制备】中，在步骤S0中，无制备多晶型第一锂盐的步骤S02，其他过程与实施例1类似。
【正极活性材料相关参数测试】
1、正极活性材料中第二锂盐的成分检测以及质量占比(以二氟磷酸锂为例)
根据JY/T 020-1996中离子色谱分析方法通则对第二锂盐的含量进行测试。
2、体积平均粒径Dv50测试
参照GB/T19077-2016进行D50测试。
3、包覆层厚度测试
采用IB-19500CP离子抛光仪。清洗制样用工具，将制样用胶(PVDF分散到NMP中形成的胶状物，PVDF质量含量为8％)与样品粉末混合(粉末重量约为胶的5倍)均匀后涂到铜箔上，60℃烘干30min。用剪刀将制备的样品剪成6mm×6mm大小，固定在样品台上，放入离子抛光仪(型号：IB-19500CP)中进行切割。根据JBT9352-1999将切割好的样品放入美国FEI Tecnai G2透射电子显微镜设备中进行厚度测试。
【电池性能测试】
1、初始放电容量
在25℃下，锂离子电池以1C恒流充电到4.25V，恒压充电至电流为0.05C，电池满充后，静置5min，1C放电30min，(电池带电量为50％SOC)，静置5min，调节温度为25℃，静置1h，记录此时电池的电压V1，0.4C放电15s，记录脉冲放电后的电压V2，则电池50％SOC时的DCR＝(V1-V2)/I，I＝0.4C。
2、循环容量保持率
在25℃下，对所有实施例和对比例的锂离子电池进行充放电测试。一个充放电循环过程如下：1C电流恒流充电到4.25V，然后在4.25V下恒压充电至电流≤0.05mA，静置5min，然后以1C电流恒流放电到2.8V，记录此时电池容量为C1，以上为电池的一个充放电循环。按照上述过程循环200圈，记录此时电池的容量C200。则循环容量保持率＝C200/C1×100％。
实施例和对比例的正极活性材料的产品参数以及锂离子电池性能参数参见表1～表6。
表1：
Figure PCTCN2022124925-appb-000002
由表1可知，由实施例1和对比例1可知，相比于未经改性的正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2，锂离子电池的功率性能和循环寿命显著提高。实施例2～4说明，针对不同的第一锂盐，用不同种类的本申请所述的第二锂盐包覆，都使锂离子电池具有优良的功率性能和循环寿命。
表2：
Figure PCTCN2022124925-appb-000003
由表2可知，相比于实施例9和实施例10，实施例1、实施例5～9对应的锂离子电池的功率性能和循环寿命更优，说明包覆层的厚度在10～100nm范围是优选范围，当包覆层的厚度在20～60nm范围，性能更优。
表3：
Figure PCTCN2022124925-appb-000004
由表3可知，相比于实施例14和实施例15，实施例1、实施例11～14对应的锂离子电池的功率性能和循环寿命更优，说明第二锂盐的质量占比为0.1％～20％是优选范围，当当第二锂盐的质量占比在1％～10％，性能更优。
表4：
Figure PCTCN2022124925-appb-000005
由表4可知，相比于实施例24和实施例25，实施例1、实施例16～24对应的锂离子电池的功率性能和循环寿命更优，说明当正极活性材料由体积平均粒径Dv50在2～8μm的第一粒子和体积平均粒径Dv50在13～22μm的第二粒子组成时，性能更优。
表5：
Figure PCTCN2022124925-appb-000006
由表5可知，相比于实施例29和实施例30，实施例1、实施例26～29对应的锂离子电池的功率性能和循环寿命更优，说明第一粒子与第二粒子的质量比为2.3～9：1范围时，性能更优。
表6：
Figure PCTCN2022124925-appb-000007
由表6可知，当第一粒子和第二粒子同时包括单晶型和多晶型时，锂离子电池的功率性能得以进一步改进。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为例示，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (14)

  1. 一种正极活性材料，其特征在于，包括基体以及位于所述基材表面的包覆层，
    所述基体包括第一锂盐，所述第一锂盐选自层状结构的LiAO 2、Li[Ni aCo bMn c]O 2，以及富锂锰基系xLi 2MnO 3·(1-x)LiMn yB 1-yO 2中的至少一种，其中，所述A为Ni、Co、Mn或Al，所述B选自Ni、Co或Al中一种或两种金属离子，且0.1≤x≤0.9，0.1≤y≤0.9所述0＜a＜1、0＜b＜1、0＜c＜1、a+b+c＝1，
    所述包覆层包括同时含有氟、磷和氧的第二锂盐，所述第二锂盐中的氧含有孤电子对。
  2. 根据权利要求1所述的正极活性材料，其特征在于，
    所述包覆层表面有突起的由所述第二锂盐形成的堆积体颗粒。
  3. 根据权利要求1或2所述的正极活性材料，其特征在于，
    基于所述正极活性材料的总质量计，所述第二锂盐的质量占比为0.1％～20％，可选为1％～10％。
  4. 根据权利要求1-3中任一项所述的正极活性材料，其特征在于，
    所述包覆层的厚度为10～100nm，可选为20～60nm。
  5. 根据权利要求1-4中任一项所述的正极活性材料，其特征在于，
    所述第二锂盐选自二氟磷酸锂、二氟双草酸磷酸锂、四氟草酸磷酸锂中的至少一种。
  6. 根据权利要求1-5中任一项所述的正极活性材料，其特征在于，
    所述正极活性材料由体积平均粒径Dv50在2～8μm的第一粒子和体积平均粒径Dv50在13～22μm的第二粒子组成。
  7. 根据权利要求6所述的正极活性材料，其特征在于，
    所述第一粒子与所述第二粒子的质量比为2.3～9：1。
  8. 根据权利要求7所述的正极活性材料，其特征在于，
    所述第一和/或第二粒子包括单晶和多晶两种晶型，且单晶粒子与多晶粒子的质量比为0.1～1：1，可选为0.23～0.67：1。
  9. 一种正极活性物质的制备方法，其特征在于，包括如下步骤：
    S1：将第一锂盐干燥脱水，得到干燥后的第一锂盐；
    S2：将第二锂盐溶解到有机溶剂中，得到第二锂盐有机溶液；
    S3：将所述干燥后的第一锂盐加入到所述第二锂盐有机溶液中，并混合均匀；
    S4：将混合均匀的混合物过滤，并对过滤后的固体颗粒进行热处理，得到所述正极活性材料；其中，包括基体以及位于所述基材表面的包覆层，
    所述基体包括第一锂盐，所述第一锂盐选自层状结构的LiAO 2、Li[Ni aCo bMn c]O 2，以及富锂锰基系xLi 2MnO 3·(1-x)LiMn yB 1-yO 2中的至少一种，其中，所述A为Ni、Co、Mn或Al，所述B选自Ni、Co或Al中一种或两种金属离子，且0.1≤x≤0.9，0.1≤y≤0.9所述0＜a＜1、0＜b＜1、0＜c＜1、a+b+c＝1；所述包覆层包括同时含有氟和磷的第二锂盐。
  10. 根据权利要求9所述的制备方法，其特征在于，
    在步骤S1之前还包括步骤S0，所述步骤S0包括制备单晶型第一锂盐和/或多晶型第一锂盐的步骤。
  11. 根据权利要求9或10所述的制备方法，其特征在于，
    还包括步骤S5，所述步骤S5为对所述正极活性材料的体积平均粒径Dv50进行调节，得到体积平均粒径Dv50在2～8μm的第一粒子和体积平均粒径Dv50在13～22μm的第二粒子。
  12. 根据权利要求11所述的制备方法，其特征在于，
    还包括步骤S6，所述步骤S6包括按照预定质量比将第一粒子和第二粒子混合，得到所述正极活性材料。
  13. 根据权利要求9-12中任一项所述的制备方法，其特征在于，
    在所述S1中，所述第一锂盐干燥脱水的温度范围为100-200℃；和/或，
    在所述S2中，所述有机溶剂为醚类、羧酸酯类、碳酸酯类有机溶剂；和/或，
    在所述S3中，混合均匀的方式为在50～100℃中搅拌分散4～8h；和/或，
    在所述S4中，所述热处理方式为200～250℃的空气氛围中进行处理5～10h。
  14. 一种锂离子电池，包括正极极片、隔离膜和负极极片，其特征在于，
    所述正极极片包括权利要求1-8中任一项所述的正极活性材料或根据权利要求9-13中任一项所述的制备方法制备的正极活性材料。
PCT/CN2022/124925 2021-11-02 2022-10-12 正极活性材料、其制备方法、包括其的锂离子电池、电池模块、电池包和用电装置 WO2023078047A1 (zh)

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