WO2023197807A1 - 正极材料及其制备方法、复合正极材料、正极极片及二次电池 - Google Patents

正极材料及其制备方法、复合正极材料、正极极片及二次电池 Download PDF

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WO2023197807A1
WO2023197807A1 PCT/CN2023/081384 CN2023081384W WO2023197807A1 WO 2023197807 A1 WO2023197807 A1 WO 2023197807A1 CN 2023081384 W CN2023081384 W CN 2023081384W WO 2023197807 A1 WO2023197807 A1 WO 2023197807A1
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shell layer
cathode material
positive electrode
cathode
mass
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PCT/CN2023/081384
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English (en)
French (fr)
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尚义博
徐晓富
潘坚福
张新羽
刘倩
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宁德时代新能源科技股份有限公司
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Publication of WO2023197807A1 publication Critical patent/WO2023197807A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • 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
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • H01M4/602—Polymers
    • 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

  • This application relates to the technical field of lithium-ion batteries, specifically to a cathode material and its preparation method, composite cathode material, cathode plate, secondary battery, battery module, battery pack and electrical device.
  • Lithium iron manganese phosphate (LiMn x Fe 1-x PO 4 , referred to as LMFP) has the same ordered and regular olivine structure as lithium iron phosphate. Compared with lithium iron phosphate, it has higher energy density and compaction density and is considered It is one of the upgrade directions of lithium iron phosphate batteries.
  • lithium iron manganese phosphate has poor electrical conductivity, which affects its energy density; and LMFP has problems with manganese dissolution and water absorption, and its poor stability will affect the secondary cycle stability of the battery.
  • this application provides a cathode material and a preparation method thereof, which can improve the problems such as poor electronic conductivity, manganese dissolution and water absorption of lithium manganese iron phosphate material, and has good rate performance and cycle stability. .
  • a composite cathode material including the above cathode material is also provided.
  • cathode plates secondary batteries, battery modules, battery packs and electrical devices using the above cathode materials or composite cathode materials.
  • the first aspect of the present application provides a cathode material, including: a core, a first shell layer and a second shell layer;
  • the first shell layer is wrapped on the surface of the core, and the second shell layer is wrapped on the surface of the first shell layer;
  • the core includes lithium iron manganese phosphate material; the first shell layer includes a polyanionic cathode material, and the polyanionic The sub-type cathode material does not contain manganese; the second shell layer includes hydrophobic conductive material.
  • this application at least includes the following beneficial effects:
  • the above-mentioned positive electrode material has a core-shell structure, the core includes lithium manganese iron phosphate material, the first shell layer includes polyanionic positive electrode material that does not contain manganese element, and the second shell layer includes hydrophobic conductive material.
  • the polyanionic cathode material that does not contain manganese in the first shell layer has good stability and has good contact with the lithium manganese iron phosphate material in the core; the second shell layer includes hydrophobic conductive materials and has good hydrophobicity. properties and higher conductivity.
  • the above-mentioned positive electrode materials can not only ensure the high energy density of the lithium iron manganese phosphate material, but also improve the conductivity and easy water absorption of the lithium iron manganese phosphate material, and reduce the dissolution of manganese during the circulation of the positive electrode material.
  • the above-mentioned cathode materials have good rate performance and cycle stability, and the cathode materials have low water content, which is beneficial to subsequent production and use.
  • the hydrophobic conductive material includes at least one of a hydrophobic conductive polymer and a hydrophobic conductive carbon material.
  • the hydrophobic conductive polymer is selected from at least one selected from the group consisting of polypyrrole, polyaniline, polythiophene and polyacetylene.
  • the hydrophobic conductive carbon material is selected from at least one of carbon nanotubes and carbon nanofibers.
  • the mass percentage of the hydrophobic conductive carbon material in the second shell layer is 2% to 10%
  • the mass percentage of the hydrophobic conductive carbon material in the second shell layer is 4% to 8%.
  • the polyanionic cathode material is selected from at least one of phosphate materials, silicate materials, and borate materials.
  • the phosphate material includes at least one of LiFePO 4 , LiNiPO 4 , LiCoPO 4 , Li 3 V 2 (PO 4 ) 3 , LiVOPO 4 and LiTi 2 (PO 4 ) 3 ;
  • the silicate material includes at least one of Li 2 FeSiO 4 , Li 2 NiSiO 4 and Li 2 CoSiO 4 ;
  • the borate material includes at least one of LiFeBO 3 and LiCoBO 3 .
  • the ratio of the sum of the masses of the first shell layer and the second shell layer to the mass of the cathode material is 0.1% to 50%;
  • the ratio of the mass of the first shell layer and the second shell layer to the mass of the cathode material is 1% to 40%;
  • the ratio of the mass of the first shell layer and the second shell layer to the mass of the cathode material is 1% to 30%;
  • the ratio of the mass of the first shell layer and the second shell layer to the mass of the cathode material is 1% to 20%.
  • the mass percentage of the second shell layer is 10% to 90%
  • the mass percentage of the second shell layer is 20% to 60%;
  • the mass percentage of the second shell layer is 30% to 50%.
  • the ratio of the sum of the thicknesses of the first shell layer and the second shell layer to the Dv50 of the cathode material is 0.01 to 0.45;
  • the ratio of the sum of the thicknesses of the first shell layer and the second shell layer to the Dv50 of the cathode material is 0.03 to 0.39;
  • the ratio of the sum of the thicknesses of the first shell layer and the second shell layer to the Dv50 of the cathode material is 0.03 to 0.31;
  • the ratio of the sum of the thicknesses of the first shell layer and the second shell layer to the Dv50 of the cathode material is 0.03 ⁇ 0.26.
  • the second aspect of the application provides a preparation method of the cathode material of the first aspect, including the following steps:
  • a third aspect of the application provides a composite cathode material, including a ternary cathode material and the cathode material of the first aspect.
  • a fourth aspect of the present application provides a positive electrode sheet, including the positive electrode material selected from the first aspect or the composite positive electrode material of the third aspect.
  • a fifth aspect of the present application provides a secondary battery, including the positive electrode plate of the fourth aspect.
  • a sixth aspect of the present application provides a battery module including the secondary battery of the fifth aspect.
  • a seventh aspect of the present application provides a battery pack, including the battery module of the sixth aspect.
  • An eighth aspect of the present application also provides an electrical device, including at least one selected from the group consisting of the secondary battery of the fifth aspect, the battery module of the sixth aspect, and the battery pack of the seventh aspect.
  • Figure 1 is a schematic structural diagram of a cathode material according to an embodiment of the present application.
  • Figure 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • Figure 3 is an exploded view of the secondary battery according to an embodiment of the present application shown in Figure 2;
  • FIG. 4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 6 is an exploded view of the battery pack according to an embodiment of the present application shown in Figure 5;
  • Figure 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.
  • Figure 8 is a transmission electron microscope (TEM) image of the cathode material in Example 1 of the present application.
  • Figure 9 is a transmission electron microscope (TEM) image of the cathode material of Comparative Example 1 of the present application.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • Ranges disclosed herein are defined in terms of lower and upper limits. 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 of the endpoints, and may be arbitrarily combined, that is, 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, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then 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" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • 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 sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • 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 words “include” and “include” mentioned in this application represent open expressions, which may also be closed expressions.
  • the words “include” and “include” may mean that other components not listed may also be included or included, or may only include or contain the ingredients listed.
  • lithium iron phosphate materials are lithium iron phosphate materials and ternary cathode materials.
  • the voltage platform of ternary cathode materials is generally 3.7V, which is much higher than the 3.4V of lithium iron phosphate. It occupies a dominant position in power batteries.
  • ternary materials contain metals such as cobalt and nickel, and their costs remain high and their safety is low. relatively low.
  • the voltage platform of lithium iron manganese phosphate is 4.1V and 3.4V. It has a higher voltage platform and has higher theoretical energy density and compaction density than lithium iron phosphate materials. It is expected to become a new generation of lithium-ion battery cathode material.
  • lithium iron manganese phosphate has poor electrical conductivity, making it difficult to fully utilize its theoretical energy density.
  • the manganese element on the surface of the lithium manganese iron phosphate material is prone to Jahn-Teller distortion and disproportionation reaction, causing the dissolution of manganese element, resulting in damage to the surface structure of the material and affecting the structural stability of the lithium manganese iron phosphate material.
  • the lithium iron manganese phosphate material has a high water content, which is not conducive to battery preparation and affects battery performance.
  • this application provides a cathode material and its preparation method, as well as composite cathode materials, secondary batteries, battery modules, battery packs and electrical equipment using the cathode material.
  • This kind of secondary battery is suitable for various electrical devices that use batteries, such as mobile phones, portable devices, laptops, battery cars, electric toys, power tools, electric vehicles, ships and spacecraft.
  • spacecraft include aircraft, rockets , space shuttles and spacecrafts, etc.
  • a cathode material 6 including: a core 61 , a first shell 62 and a second shell 63 .
  • the first shell layer 62 wraps the surface of the core 61
  • the second shell layer 63 wraps the surface of the first shell layer 62 .
  • the core 61 includes lithium iron manganese phosphate material; the first shell layer 62 includes a polyanionic cathode material, and the polyanionic cathode material does not contain manganese; the second shell layer 63 includes a hydrophobic conductive material.
  • the above-mentioned positive electrode material 6 has a core-shell structure.
  • the core 61 includes lithium iron manganese phosphate material.
  • the first shell layer 62 includes a polyanionic positive electrode material that does not contain manganese element.
  • the second shell layer 63 includes a hydrophobic conductive material.
  • the polyanionic cathode material that does not contain manganese in the first shell layer 62 has good stability and is in good contact with the lithium manganese iron phosphate material in the core 61; the second shell layer 63 includes a hydrophobic conductive material and has better Good hydrophobicity and high conductivity.
  • the above-mentioned positive electrode material 6 can not only ensure a high energy density of the lithium iron manganese phosphate material, but also improve the conductivity and easy water absorption of the lithium iron manganese phosphate material, and reduce the dissolution of manganese during the circulation of the positive electrode material.
  • the above-mentioned cathode material has good rate performance and cycle stability, and the cathode material 6 has low water content, which is beneficial to subsequent production and use.
  • lithium iron manganese phosphate is LiMn x Fe 1-x PO 4 , where 0 ⁇ x ⁇ 1.
  • lithium iron manganese phosphate includes LiMn 0.8 Fe 0.2 PO 4 (LMFP82), LiMn 0.6 Fe 0.4 PO 4 (LMFP64), LiMn 0.4 Fe 0.6 PO 4 (LMFP46) and LiMn 0.2 Fe 0.8 PO 4 (LMFP28) wait.
  • the hydrophobic conductive material includes at least one of a hydrophobic conductive polymer and a hydrophobic conductive carbon material. Furthermore, the contact angle between the hydrophobic conductive material and water is greater than 130°, and the hydrophobic conductive material has good hydrophobicity and conductive properties.
  • the hydrophobic conductive polymer is selected from at least one selected from the group consisting of polypyrrole, polyaniline, polythiophene and polyacetylene.
  • the above-mentioned hydrophobic conductive polymer not only has good conductive properties, but also has good hydrophobicity, and can improve the conductive properties and hydrophobicity of the cathode material 6 .
  • the hydrophobic conductive carbon material is selected from at least one of carbon nanotubes and carbon nanofibers.
  • the above-mentioned hydrophobic conductive carbon material not only has good conductive properties, but also has good hydrophobicity, which can improve the conductive properties and hydrophobicity of the cathode material 6 .
  • the hydrophobic conductive material in the second shell layer 63, includes a hydrophobic conductive polymer and a hydrophobic conductive carbon material; the mass percentage of the hydrophobic conductive carbon material is 2% to 10%.
  • the mass percentage of the hydrophobic conductive carbon material in the second shell layer 63 is 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.
  • the mass percentage of the hydrophobic conductive carbon material in the second shell layer 63 is 4% to 8%.
  • the mass proportion of the hydrophobic conductive carbon material in the second shell layer 63 is 4% to 8%, and the second shell layer 63 has better conductivity and hydrophobicity.
  • the polyanionic cathode material is selected from at least one of phosphate materials, silicate materials, and borate materials.
  • the polyanionic cathode material has a structure closer to that of lithium iron manganese phosphate and is used for the first shell layer 62 can reduce the manganese dissolution of lithium iron manganese phosphate and has no obvious impact on the energy density of cathode material 6.
  • the polyanion cathode material is a phosphate material.
  • the structure of the phosphate material is closer to that of lithium manganese iron phosphate, so the conductive contact between the core 61 and the first shell layer 62 is better.
  • the phosphate material includes at least one of LiFePO 4 , LiNiPO 4 , LiCoPO 4 , Li 3 V 2 (PO 4 ) 3 , LiVOPO 4 and LiTi 2 (PO 4 ) 3 .
  • the silicate material includes at least one of Li 2 FeSiO 4 , Li 2 NiSiO 4 and Li 2 CoSiO 4 .
  • Borate materials include at least one of LiFeBO 3 and LiCoBO 3 .
  • the ratio of the sum of the masses of the first shell layer 62 and the second shell layer 63 to the mass of the cathode material 6 is 0.1% to 50%.
  • the ratio of the sum of the masses of the first shell layer 62 and the second shell layer 63 to the mass of the cathode material 6 is 0.1%, 0.5%, 1%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%.
  • the ratio of the sum of the masses of the first shell layer 62 and the second shell layer 63 to the mass of the cathode material 6 is 1% to 40%.
  • the cycle stability of the cathode material 6 can be further improved. If the mass proportion of the shell layer is too low, it will not affect the lithium iron manganese phosphate. The improvement effect is small; the proportion of the shell layer is too high, the manganese dissolution and water content of cathode material 6 are not improved further, and the cycle performance of cathode material 6 has a smaller improvement, which may be due to the manganese phosphate in cathode material 6 The content of iron lithium is reduced.
  • the ratio of the sum of the masses of the first shell layer 62 and the second shell layer 63 to the mass of the cathode material 6 is 1% to 30%. More preferably, the ratio of the sum of the masses of the first shell layer 62 and the second shell layer 63 to the mass of the cathode material 6 is 1% to 20%.
  • the mass percentage of the second shell layer 63 is 10% to 90% of the total mass of the first shell layer 62 and the second shell layer 63 .
  • the mass percentage of the second shell layer 63 is 10%, 15%, 20%, 25%, 30%, 35%, 40% , 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%.
  • the mass percentage of the second shell layer 63 is 20% to 60%. More preferably, in the total mass of the first shell layer 62 and the second shell layer 63, the mass percentage of the second shell layer 63 is 30% to 50%.
  • the ratio of the sum of the thicknesses of the first shell layer 62 and the second shell layer 63 to the Dv50 of the cathode material 6 is 0.01 ⁇ 0.45.
  • Dv50 represents the average particle size at which the volume distribution is 50%.
  • the ratio of the sum of the thicknesses of the first shell layer 62 and the second shell layer 63 to the Dv50 of the cathode material 6 is 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 or 0.45.
  • the ratio of the sum of the thicknesses of the first shell layer 62 and the second shell layer 63 to the Dv50 of the cathode material 6 is 0.03 ⁇ 0.39.
  • the cycle stability of the cathode material 6 can be further improved.
  • the ratio of the sum of the thicknesses of the first shell layer 62 and the second shell layer 63 to the Dv50 of the cathode material 6 is 0.03 ⁇ 0.31. More preferably, the ratio of the sum of the thicknesses of the first shell layer 62 and the second shell layer 63 to the Dv50 of the cathode material 6 is 0.03 to 0.26.
  • An embodiment of the present application also provides the above-mentioned preparation method of the cathode material, including steps S110 and S120.
  • Step S110 Mix the raw materials for preparing the polyanionic cathode material and the lithium iron manganese phosphate material, and perform heat treatment in an inert atmosphere to coat the surface of the lithium iron manganese phosphate material with a first shell layer to prepare an intermediate.
  • Step S120 Mix the above hydrophobic conductive material and intermediate evenly so that the surface of the first shell layer is coated with the second shell layer to prepare a positive electrode material.
  • the preparation method of the above-mentioned positive electrode material is simple to operate.
  • the prepared positive electrode material has a core-shell structure, in which the lithium iron manganese phosphate is sequentially covered by the first shell layer and the second shell layer, and has improved stability and conductive properties.
  • the positive electrode material It has good rate performance and cycle stability, and the cathode material has low water content, which is beneficial to subsequent production and use.
  • the raw materials for preparing the polyanion cathode material include a lithium source, a doped metal salt and a polyanion corresponding acid source.
  • the polyanionic cathode material is lithium iron phosphate
  • its preparation raw materials include lithium source, iron salt and phosphoric acid source.
  • the lithium source is selected from lithium carbonate, lithium acetate, lithium hydroxide, lithium nitrate, lithium sulfate, lithium chloride, lithium oxalate, lithium phosphate, lithium hydrogen phosphate, lithium citrate, lithium silicate and lithium metaborate. of at least one.
  • the doping metal salt is selected from at least one of oxalate, phosphate, acetate, sulfate, citrate and nitrate.
  • the acid source corresponding to the polyanion includes a phosphoric acid source, a silicic acid source or a boric acid source.
  • the phosphoric acid source is selected from at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.
  • the silicic acid source is selected from at least one of silicic acid, metasilicic acid, silicon tetrachloride, silicon dioxide and ethyl orthosilicate.
  • the boric acid source is selected from at least one of boric acid, ammonium borate and boron oxide.
  • the temperature of the heat treatment is 500°C to 1200°C; the time of the heat treatment is 5h to 20h.
  • step S120 the hydrophobic conductive material and the intermediate are uniformly dispersed and mixed in an organic solvent through ultrasonic dispersion.
  • the organic solvent is N-methylpyrrolidone (NMP). It is understood that the organic solvent is not limited to NMP.
  • step S120 after the hydrophobic conductive material and the intermediate are ultrasonically dispersed and mixed uniformly in an organic solvent, solid-liquid separation, suction filtration, washing, and drying are also included to obtain the cathode material.
  • the hydrophobic conductive material includes a conductive polymer and a hydrophobic conductive carbon material; before step S120, it also includes a step of S121: ultrasonically dispersing and mixing the conductive polymer and the hydrophobic conductive carbon material in an organic solvent.
  • the organic solvent is N-methylpyrrolidone (NMP). It is understood that the organic solvent is not limited to NMP.
  • step S121 ultrasonic dispersion is performed at 50°C to 100°C.
  • An embodiment of the present application also provides a composite cathode material, including a ternary cathode material and the above-mentioned cathode material.
  • the ternary cathode materials include lithium nickel cobalt manganate (NCM), coated modified lithium nickel cobalt manganate (NCM), lithium nickel cobalt aluminate (NCA) and coated modified lithium nickel cobalt aluminate. (NCA) at least one.
  • Lithium nickel cobalt manganate depends on the content of nickel, cobalt and manganese elements, including LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (can also be abbreviated to NCM622) It can be referred to as NCM811), etc. Further, the lithium nickel cobalt manganate is layered lithium nickel cobalt manganate.
  • lithium nickel cobalt aluminate includes LiNi 0.85 Co 0.15 Al 0.05 O 2 and the like.
  • the above-mentioned composite cathode material can obtain a composite cathode material with better rate performance through a reasonable ratio of the ternary cathode material and the above-mentioned cathode material.
  • the mass ratio of the ternary cathode material to the above-mentioned cathode material 6 is (1-9): (9-1). Further, the mass ratio of the ternary cathode material to the above-mentioned cathode material 6 is (2-8): (8-2).
  • the mass proportion of the above-mentioned positive electrode material 6 is 10% to 90%; further, the mass proportion is 20% to 80%.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte is between the positive electrode piece and the negative electrode piece It plays a role in conducting ions.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application or the composite positive electrode material of the third aspect of the present application.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and is formed on at least one surface of the polymer material base material. metal layer.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl At least one of acrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, formic acid Methyl ester, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, At least one of dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally also includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 2 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 4 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number 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 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 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 electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the power-consuming device, or as an energy storage unit of the power-consuming device.
  • Electric devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric Trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • secondary batteries, battery modules or battery packs can be selected according to its usage requirements.
  • Fig. 7 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • lithium iron manganese phosphate is LiMn 0.6 Fe 0.4 PO 4 , abbreviated as LMFP64.
  • FIG 8 is a transmission electron microscope (TEM) image of the cathode material prepared in Example 1, it can be seen that the prepared cathode material has a double-layer coating structure.
  • the cathode material consists of the core 61 and the first shell from the inside to the outside. layer 62 and the second shell layer 62.
  • the cathode material provided in this comparative example is unmodified lithium iron manganese phosphate, which is the lithium iron manganese phosphate used in the preparation process of Example 1.
  • the preparation methods of the cathode materials in Examples 2 to 9 are basically the same as those in Example 1, except that the mass and ratio of the first shell layer and the second shell layer to the mass of the cathode material (referred to as shell mass and ratio) Different, the ratio of the sum of the thicknesses of the first shell layer and the second shell layer to the Dv50 of the cathode material (referred to as h/d) is different. Specifically, h/d is observed through transmission electron microscopy (TEM) patterns.
  • TEM transmission electron microscopy
  • the shell mass, proportion, and h/d are recorded in Table 1.
  • the amounts of materials used in Examples 2 to 9 are adjusted according to the proportions in Table 1.
  • Table 1 The shell mass and proportion of the cathode materials of Examples 1 to 9, the ratio (h/d) of the sum of the thicknesses of the first shell layer and the second shell layer to the Dv50 of the cathode material, and the position of the second shell layer in the shell layer The proportion of the total mass (first shell and second shell).
  • the cathode material of Example 2 was prepared according to the following steps:
  • lithium iron phosphate-coated lithium manganese iron phosphate can be obtained.
  • the preparation methods of the cathode materials in Examples 10 to 17 are basically the same as those in Example 3, except that the mass proportions of the second shell layer in the shell layers (the first shell layer and the second shell layer) are different.
  • the mass proportion of the second shell layer in the shell layers (first shell layer and second shell layer) in the cathode materials of Examples 3 and 10 to 17 is recorded in Table 2.
  • the amounts of materials used in Examples 10 to 17 were adjusted according to the proportions in Table 2.
  • the cathode material of Example 10 was prepared according to the following steps:
  • the cathode material of this comparative example was prepared according to the following steps:
  • the cathode material of this comparative example was prepared according to the following steps:
  • the mass proportion of the second shell layer in the shell layers (first shell layer and second shell layer) in the cathode materials of Comparative Examples 2 to 3 is recorded in Table 2.
  • the preparation raw materials and dosages of Examples 1 to 17 and Comparative Examples 1 to 3 are recorded in Table 3.
  • Table 2 The mass and proportion of the shell layer in the cathode materials of Examples 3 and 10 to 17 and the proportion of the second shell layer in the sum of the mass of the shell layer (first shell layer and second shell layer).
  • lithium iron manganese phosphate, 3g lithium iron phosphate, 1.88g polyaniline and 1.715g carbon nanotube dispersion were ultrasonically dispersed and mixed in N-methylpyrrolidone (NMP) at 80°C; the mixed solution was subjected to solid-liquid separation operation , and then vacuum filtrate, wash and dry the obtained solid material to obtain the positive electrode material; among the positive electrode materials, the surface of lithium iron manganese phosphate has no coating structure.
  • NMP N-methylpyrrolidone
  • the preparation methods of the cathode materials in Examples 18 to 21 are basically the same as those in Example 14, except that the raw materials for preparing the second shell layer are different.
  • the raw materials for preparing the second shell layer in Examples 14 and 18 to 21 are recorded in Table 4, and the preparation method is adjusted according to Table 4.
  • the cathode material of Example 18 was prepared according to the following steps:
  • the composite cathode material of this embodiment is obtained by mixing the cathode material of Example 1 and the ternary cathode material NCM523 at a mass ratio of 3:7.
  • the composite cathode material of this comparative example was obtained by mixing the cathode material of Example 1 and the ternary cathode material NCM523 at a mass ratio of 3:7.
  • Test examples 1 to 7 are Test examples 1 to 7:
  • Test Examples 1 to 7 respectively tested the electrical conductivity and contact angle of composite films made of polyaniline and carbon nanotubes with different ratios.
  • the conductivity is tested by the SDY-4 four-probe resistance meter.
  • the contact angle is tested by OCA25-HTV1800 contact angle meter.
  • the amounts of polyaniline and carbon nanotubes, the proportion of carbon nanotubes, the electrical conductivity and the contact angle in the composite films of Test Examples 1 to 7 are recorded in Table 5.
  • the composite film of Test Example 2 was prepared according to the following steps:
  • Table 5 Composition, electrical conductivity and contact angle of the composite films of test examples 1 to 7.
  • the core is put into an aluminum plastic film of appropriate size for top side sealing, and the liquid injection (the electrolyte is 1mol/L LiPF 6 / (ethylene carbonate (EC) + diethyl carbonate (DEC) + dimethyl carbonate ( DMC)) (volume ratio 1:1:1)+5wt.% fluoroethylene carbonate (FEC)), let stand, form, age, exhaust, seal twice, and capacity test to get the prepared soft package stack chip battery.
  • the electrolyte is 1mol/L LiPF 6 / (ethylene carbonate (EC) + diethyl carbonate (DEC) + dimethyl carbonate ( DMC)) (volume ratio 1:1:1)+5wt.% fluoroethylene carbonate (FEC)
  • Rate performance test First, perform a capacity test on the soft-packed laminated battery. The process is as follows: Leave it for 5 minutes, discharge it to 2.5V according to 0.33C, let it stand for 5 minutes, charge it to 4.3V according to a constant current of 0.33C, and then convert it to Constant voltage charging, when the charging current reduces to 0.05C, the constant voltage charging ends, let it stand for 5 minutes, and then discharge at 0.33C to 2.5V. The discharge capacity at this time is recorded as C0.
  • the rate performance test process is as follows: Leave it alone for 5 minutes, discharge to 2.5V according to 0.33C. After leaving it alone for 5 minutes, charge it at a constant current of 0.33C to 4.3V and then switch to constant voltage charging. When the charging current is reduced to 0.05C, the constant After the voltage charging is completed, let it sit for 5 minutes, discharge to 2.5V according to 1C, and record the discharge capacity at this time. For different rate tests, replace 1C in the last step "Discharge according to 1C to 2.5V" with the corresponding rate of 2C/3C. Divide the capacity value obtained from the rate performance test by the mass of the (composite) cathode material contained in the soft-packed laminated battery to obtain the gram capacity of the cathode material at different rates.
  • Transition metal manganese dissolution test Disassemble the soft-packed laminated batteries of Examples and Comparative Examples that were cycled to the same number of cycles in the 25°C cycle test, and take out the negative electrode plates using inductively coupled plasma mass spectrometry (ICP-MS). ) Measure the manganese content on the negative electrode piece.
  • ICP-MS inductively coupled plasma mass spectrometry
  • the cathode materials of Examples 1 to 21 can significantly inhibit the dissolution of manganese during the cycle of the cathode material and reduce the The water content of the material and the cycle performance of the cathode materials of Examples 1 to 21 are significantly improved.
  • the mass and proportion of the shell layer and the ratio (h/d) of the shell layer thickness and Dv50 of the positive electrode material are different. It can be seen that in Examples 1 and 3 to 8, The mass and proportion of the shell layer are 1% to 40%; h/d is 0.03 to 0.39, and the manganese dissolution and water content are lower.
  • the proportions of the second shell layer in the total mass of the shell layer are different. It can be seen from the data in Table 6 that when the proportion of the second shell layer in the total mass of the shell layer is 20% to 60%, and further 30% to 50%, the manganese dissolution and water content of the cathode material are lower .
  • the proportion of the second shell layer in the total mass of the shell layer is 0 and 100% respectively.
  • the second shell layer is not included in Comparative Example 2.
  • the cathode material has a certain ability to inhibit manganese dissolution. However, the cathode material has a high water content; Comparative Example 3 does not include the first shell layer and the cathode material has a low water content.
  • the shell combination coating of lithium iron manganese phosphate can inhibit the precipitation of lithium iron manganese phosphate, water absorption and other problems, which is beneficial to improving the cycle performance of the cathode material.
  • Example 14 and 18-21 the material selection of the second shell layer is different. From the data in Table 6, it can be seen that the rate performance and cycle performance of the cathode materials in Examples 14, 18-21 are better, especially when polyaniline, As a conductive polymer, polythiophene has a more prominent effect.
  • the difference between the cathode material of Comparative Example 4 and Example 3 is that lithium iron manganese phosphate, lithium iron phosphate, polyaniline and carbon nanotubes are simply mixed, and no coating structure is formed on the surface of lithium iron manganese phosphate.
  • the water content of the cathode material of Comparative Example 4 is significantly higher than that of Example 3, and the manganese dissolution is significantly increased.
  • the cycle performance of the cathode material of Comparative Example 4 is even worse.
  • the composite cathode material of Example 22 includes the ternary cathode material NCM523 and the cathode material of Example 1. On the basis of Example 1, the rate performance is further improved and has both good rate performance and cycle stability.
  • the composite cathode material of Comparative Example 5 includes the ternary cathode material NCM523 and the cathode material of Comparative Example 1. Although the rate performance is improved, due to the poor conductivity of lithium iron manganese phosphate itself, manganese dissolution and water absorption, etc., the composite cathode material of Comparative Example 5 The cathode material has poor cycle performance.

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Abstract

本申请涉及一种正极材料及其制备方法、复合正极材料、正极极片及二次电池。该正极材料，包括：内核、第一壳层及第二壳层；第一壳层包裹于内核的表面，第二壳层包裹于第一壳层的表面；内核包括磷酸锰铁锂材料；第一壳层包括聚阴离子型正极材料，且聚阴离子型正极材料不含有锰元素；第二壳层包括疏水导电材料。该正极材料在保证磷酸锰铁锂材料较高能量密度的同时，能够改善磷酸锰铁锂材料的导电性及易吸水的问题，且循环过程中锰溶出减少。上述正极材料具有较好的倍率性能及循环稳定性，且正极材料的含水量低，有利于后续生产使用。

Description

正极材料及其制备方法、复合正极材料、正极极片及二次电池
相关申请
本申请要求2022年4月14日申请的，申请号为2022103884460，名称为“正极材料及其制备方法、复合正极材料、正极极片及二次电池”的中国专利申请的优先权，在此将其全文引入作为参考。
技术领域
本申请涉及锂离子电池技术领域，具体涉及一种正极材料及其制备方法、复合正极材料、正极极片、二次电池、电池模块、电池包及用电装置。
背景技术
磷酸锰铁锂(LiMnxFe1-xPO4，简称LMFP)与磷酸铁锂相同具有有序规整的橄榄石型结构，相比磷酸铁锂具有更高的能量密度及压实密度，被认为是磷酸铁锂电池的升级方向之一。
然而，磷酸锰铁锂(LMFP)的导电性能较差，影响其能量密度的发挥；并且磷酸锰铁锂存在锰溶出及吸水的问题，稳定性较差，会影响电池的二次循环稳定性。
发明内容
鉴于背景技术中存在的技术问题，本申请提供一种正极材料及其制备方法，能够改善磷酸锰铁锂材料电子电导率差、锰溶出及吸水等问题，具有较好的倍率性能及循环稳定性。
此外，还提供一种包含上述正极材料的复合正极材料。
此外，还提供采用上述正极材料或复合正极材料的正极极片、二次电池、电池模块、电池包及用电装置。
为了实现上述目的，本申请的第一方面提供了一种正极材料，包括：内核、第一壳层及第二壳层；
所述第一壳层包裹于所述内核的表面，所述第二壳层包裹于所述第一壳层的表面；
所述内核包括磷酸锰铁锂材料；所述第一壳层包括聚阴离子型正极材料，且所述聚阴离 子型正极材料不含有锰元素；所述第二壳层包括疏水导电材料。
相对于现有技术，本申请至少包括如下所述的有益效果：
上述正极材料为核壳结构，内核包括磷酸锰铁锂材料，第一壳层包括不含锰元素的聚阴离子型正极材料，第二壳层包括疏水导电材料。第一壳层中不含锰元素的聚阴离子型正极材料具有较好的稳定性，且与内核的磷酸锰铁锂材料接触较好；第二壳层中包括疏水导电材料，具有较好的疏水性及较高的电导率。上述正极材料在保证磷酸锰铁锂材料较高能量密度的同时，能够改善磷酸锰铁锂材料的导电性及易吸水的问题，并且正极材料循环过程中锰溶出减少。上述正极材料具有较好的倍率性能及循环稳定性，且正极材料含水量低，有利于后续生产使用。
在本申请任意实施方式中，所述疏水导电材料包括疏水导电聚合物及疏水导电碳材料中的至少一种。
在本申请任意实施方式中，所述疏水导电聚合物选自聚吡咯、聚苯胺、聚噻吩及聚乙炔中的至少一种。
在本申请任意实施方式中，所述疏水导电碳材料选自碳纳米管及碳纳米纤维中的至少一种。
在本申请任意实施方式中，所述第二壳层中，所述疏水导电碳材料的质量百分比为2％～10％；
可选地，所述第二壳层中，所述疏水导电碳材料的质量百分比为4％～8％。
在本申请任意实施方式中，所述聚阴离子型正极材料选自磷酸盐类材料、硅酸盐类材料及硼酸盐类材料中的至少一种。
在本申请任意实施方式中，所述磷酸盐类材料包括LiFePO4、LiNiPO4、LiCoPO4、Li3V2(PO4)3、LiVOPO4及LiTi2(PO4)3中的至少一种；
所述硅酸盐类材料包括Li2FeSiO4、Li2NiSiO4及Li2CoSiO4中的至少一种；
所述硼酸盐类材料包括LiFeBO3及LiCoBO3中的至少一种。
在本申请任意实施方式中，所述第一壳层及所述第二壳层的质量之和相对于所述正极材料的质量的比值为0.1％～50％；
可选地，所述第一壳层及所述第二壳层的质量和相对于所述正极材料的质量的比值为1％～40％；
可选地，所述第一壳层及所述第二壳层的质量和相对于所述正极材料的质量的比值为1％～30％；
可选地，所述第一壳层及所述第二壳层的质量和相对于所述正极材料的质量的比值为1％～20％。
在本申请任意实施方式中，在所述第一壳层及所述第二壳层的总质量中，所述第二壳层的质量百分比为10％～90％；
可选地，在所述第一壳层及所述第二壳层的总质量中，所述第二壳层的质量百分比为20％～60％；
可选地，在所述第一壳层及所述第二壳层的总质量中，所述第二壳层的质量百分比为30％～50％。
在本申请任意实施方式中，所述第一壳层及所述第二壳层的厚度之和与所述正极材料的Dv50的比值为0.01～0.45；
可选地，所述第一壳层及所述第二壳层的厚度之和与所述正极材料的Dv50的比值为0.03～0.39；
可选地，所述第一壳层及所述第二壳层的厚度之和与所述正极材料的Dv50的比值为0.03～0.31；
可选地，所述第一壳层及所述第二壳层的厚度之和与所述正极材料的Dv50的比值为0.03～0.26。
本申请的第二方面提供了第一方面的正极材料的制备方法，包括以下步骤：
将聚阴离子型正极材料的制备原料与磷酸锰铁锂材料混合，惰性气氛下热处理，以使所述磷酸锰铁锂材料的表面包覆所述第一壳层，制备中间体；
将疏水导电材料及所述中间体混合均匀，以使所述第一壳层的表面包覆所述第二壳层，制备所述正极材料。
本申请的第三方面提供了一种复合正极材料，包括三元正极材料及第一方面的正极材料。
本申请的第四方面提供了一种正极极片，包括选自第一方面的正极材料或者第三方面的复合正极材料。
本申请的第五方面提供了一种二次电池，包括第四方面的正极极片。
本申请的第六方面提供了一种电池模块，包括第五方面的二次电池。
本申请的第七方面提供了一种电池包，包括第六方面的电池模块。
本申请的第八方面还提供了一种用电装置，包括选自第五方面的二次电池、第六方面的电池模块及第七方面的电池包中的至少一种。
附图说明
通过阅读对下文可选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出可选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1为本申请一实施例的正极材料的结构示意图；
图2是本申请一实施方式的二次电池的示意图；
图3是图2所示的本申请一实施方式的二次电池的分解图；
图4是本申请一实施方式的电池模块的示意图；
图5是本申请一实施方式的电池包的示意图；
图6是图5所示的本申请一实施方式的电池包的分解图；
图7是本申请一实施方式的二次电池用作电源的用电装置的示意图；
图8是本申请实施例1的正极材料的透射电镜(TEM)图；
图9是本申请对比例1的正极材料的透射电镜(TEM)图。
附图标记说明：
1、电池包；2、上箱体；3、下箱体；4、电池模块；5、二次电池；51、壳体；52、电极组件；53、顶盖组件；6、正极材料；61、内核；62、第一壳层；63、第二壳层。
具体实施方式
为了便于理解本申请，下面将参照相关附图对本申请进行更全面的描述。附图中给出了本申请的较佳实施例。但是，本申请可以以许多不同的形式来实现，并不限于本文所描述的实施例。相反地，提供这些实施例的目的是使对本申请的公开内容的理解更加透彻全面。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施 例的目的，不是旨在于限制本申请。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任意上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
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。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包括本数，“一种或几种”中“几种”的含义是两种及两种以上。
在本文的描述中，除非另有说明，术语“或(or)”是包括性的。也就是说，短语“A或(or)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)。除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
目前，主流的锂离子电池正极材料为磷酸铁锂材料及三元正极材料。三元正极材料的电压平台一般为3.7V，远高于磷酸铁锂的3.4V，在动力电池中占据主导地位，但三元材料含有钴、镍等金属，其成本居高不下，且安全性相对较低。磷酸锰铁锂的电压平台为4.1V及3.4V，具有较高的电压平台，并且相对于磷酸铁锂材料具有更高的理论能量密度及压实密度，有望成为新一代锂离子电池正极材料。
然而磷酸锰铁锂的导电性能较差，难以充分发挥其理论能量密度。并且由于掺杂了锰元素，磷酸锰铁锂材料表面的锰元素容易发生Jahn-Teller畸变和歧化反应造成锰元素的溶出，导致材料表面结构受损，影响磷酸锰铁锂材料的结构稳定性。此外，磷酸锰铁锂材料的含水量高，不利于电池的制备，且影响电池性能。
为了改善磷酸锰铁锂材料的上述问题，本申请提供了一种正极材料及其制备方法和使用该正极材料的复合正极材料、二次电池、电池模块、电池包及用电设备。这种二次电池适用于各种使用电池的用电装置，例如手机、便携式设备、笔记本电脑、电瓶车、电动玩具、电动工具、电动车辆、船舶和航天器等，例如，航天器包括飞机、火箭、航天飞机和宇宙飞船等。
参阅图1，本申请一实施方式提供了一种正极材料6，包括：内核61、第一壳层62及第二壳层63。
第一壳层62包裹于内核61的表面，第二壳层63包裹于第一壳层62的表面。
内核61包括磷酸锰铁锂材料；第一壳层62包括聚阴离子型正极材料，且聚阴离子型正极材料不含有锰元素；第二壳层63包括疏水导电材料。
上述正极材料6为核壳结构，内核61包括磷酸锰铁锂材料，第一壳层62包括不含锰元素的聚阴离子型正极材料，第二壳层63包括疏水导电材料。第一壳层62中不含锰元素的聚阴离子型正极材料具有较好的稳定性，且与内核61的磷酸锰铁锂材料接触较好；第二壳层63中包括疏水导电材料，具有较好的疏水性及较高的电导率。上述正极材料6在保证磷酸锰铁锂材料较高能量密度的同时，能够改善磷酸锰铁锂材料的导电性及易吸水的问题，并且正极材料循环过程中锰溶出减少。上述正极材料具有较好的倍率性能及循环稳定性，且正极材料6的含水量低，有利于后续生产使用。
具体地，磷酸锰铁锂(LMFP)的化学结构式为LiMnxFe1-xPO4，其中0＜x＜1。根据x值的不同，磷酸锰铁锂包括LiMn0.8Fe0.2PO4(LMFP82)、LiMn0.6Fe0.4PO4(LMFP64)、LiMn0.4Fe0.6PO4(LMFP46)及LiMn0.2Fe0.8PO4(LMFP28)等。
在其中一些实施例中，疏水导电材料包括疏水导电聚合物及疏水导电碳材料中的至少一种。进一步地，疏水导电材料与水的接触角大于130°，疏水导电材料具有良好的疏水性及导电性能。
在其中一些实施例中，疏水导电聚合物选自聚吡咯、聚苯胺、聚噻吩及聚乙炔中的至少一种。上述疏水导电聚合物不仅具有良好导电性能，且疏水性较好，能够改善正极材料6的导电性能及疏水性。
在其中一些实施例中，疏水导电碳材料选自碳纳米管及碳纳米纤维中的至少一种。上述疏水导电碳材料不仅具有良好导电性能，且疏水性较好，能够改善正极材料6的导电性能及疏水性。
在其中一些实施例中，第二壳层63中，疏水导电材料包括疏水导电聚合物及疏水导电碳材料；疏水导电碳材料的质量百分比为2％～10％。通过调整疏水导电碳材料在第二壳层63中的质量占比，能够进一步得到具有较佳导电性能及疏水性能的正极材料6，进一步改善正极材料6的倍率性能及循环稳定性。可选地，第二壳层63中，疏水导电碳材料的质量百分比为2％、3％、4％、5％、6％、7％、8％、9％或者10％。
进一步地，第二壳层63中，疏水导电碳材料的质量百分比为4％～8％。疏水导电碳材料在第二壳层63中的质量占比为4％～8％，第二壳层63的导电性能及疏水性更佳。
在其中一些实施例中，聚阴离子型正极材料选自磷酸盐类材料、硅酸盐类材料及硼酸盐类材料中的至少一种。聚阴离子型正极材料具有与磷酸锰铁锂较接近的结构，用于第一壳层 62能够降低磷酸锰铁锂的锰溶出，且对正极材料6的能量密度无明显的影响。优选地，聚阴离子正极材料为磷酸盐类材料，磷酸盐类材料与磷酸锰铁锂的结构更相近，因而内核61与第一壳层62之间的导电接触更好。
在其中一些实施例中，磷酸盐类材料包括LiFePO4、LiNiPO4、LiCoPO4、Li3V2(PO4)3、LiVOPO4及LiTi2(PO4)3中的至少一种。硅酸盐类材料包括Li2FeSiO4、Li2NiSiO4及Li2CoSiO4中的至少一种。硼酸盐类材料包括LiFeBO3及LiCoBO3中的至少一种。
在其中一些实施例中，第一壳层62及第二壳层63的质量之和相对于正极材料6的质量的比值为0.1％～50％。可选地，第一壳层62及第二壳层63的质量之和相对于正极材料6的质量的比值为0.1％、0.5％、1％、5％、8％、10％、15％、20％、25％、30％、35％、40％、45％或者50％。
进一步地，第一壳层62及第二壳层63的质量之和相对于正极材料6的质量的比值为1％～40％。通过控制第一壳层62及第二壳层63两者在正极材料6中的质量占比，能够进一步提升正极材料6的循环稳定性，壳层的质量占比过低，对磷酸锰铁锂的改善效果较小；壳层的占比过高，正极材料6的锰溶出及含水量改善无进一步提升，而正极材料6的循环性能的提升较小，这可能是由于正极材料6中磷酸锰铁锂的含量降低。优选地，第一壳层62及第二壳层63的质量之和相对于正极材料6的质量的比值为1％～30％。更优选地，第一壳层62及第二壳层63的质量之和相对于正极材料6的质量的比值为1％～20％。
在其中一些实施例中，在第一壳层62及第二壳层63的总质量中，第二壳层63的质量百分比为10％～90％。通过调整第二壳层63在第一壳层62及第二壳层63的总质量中的占比在上述范围，能够控制锰溶出含量及正极材料6的含水量在较低水平，正极材料6的综合性能较好。可选地，在第一壳层62及第二壳层63的总质量中，第二壳层63的质量百分比为10％、15％、20％、25％、30％、35％、40％、45％、50％、55％、60％、65％、70％、75％、80％、85％或者90％。
优选地，在第一壳层62及第二壳层63的总质量中，第二壳层63的质量百分比为20％～60％。更优选地，在第一壳层62及第二壳层63的总质量中，第二壳层63的质量百分比为30％～50％。通过调整第二壳层63在第一壳层62及第二壳层63的总质量中的占比在上述范围，能够控制锰溶出含量及正极材料6的含水量均处于低水平，尤其是正极材料6的含水量有明显降低，正极材料6的循环性能及倍率性能均较好。
在其中一些实施例中，第一壳层62及第二壳层63的厚度之和与正极材料6的Dv50的比值为0.01～0.45。具体地，Dv50代表体积分布为50％的平均粒径。可选地，第一壳层62及第二壳层63的厚度之和与正极材料6的Dv50的比值为0.01、0.05、0.1、0.15、0.2、0.25、0.3、0.35、0.4或者0.45。
进一步地，第一壳层62及第二壳层63的厚度之和与正极材料6的Dv50的比值为0.03～0.39。通过控制壳层厚度与正极材料6的Dv50之间的比值在上述范围，能够进一步提升正极材料6的循环稳定性。优选地，第一壳层62及第二壳层63的厚度之和与正极材料6的Dv50的比值为0.03～0.31。更优选地，第一壳层62及第二壳层63的厚度之和与正极材料6的Dv50的比值为0.03～0.26。
本申请的一实施方式还提供了上述的正极材料的制备方法，包括步骤S110及S120。
步骤S110：将上述聚阴离子型正极材料的制备原料与上述磷酸锰铁锂材料混合，惰性气氛下进行热处理，以使上述磷酸锰铁锂材料的表面包覆第一壳层，制备中间体。
步骤S120：将上述疏水导电材料及中间体混合均匀，以使第一壳层的表面包覆第二壳层，制得正极材料。
上述正极材料的制备方法操作简单，制得的正极材料为核壳结构，其中的磷酸锰铁锂依次被第一壳层及第二壳层包覆，具有改善的稳定性及导电性能，正极材料具有较好的倍率性能及循环稳定性，且正极材料含水量低，有利于后续生产使用。
具体地，在步骤S110中，聚阴离子型正极材料的制备原料包括锂源、掺杂金属盐及聚阴离子对应酸源。作为示例地，聚阴离子型正极材料为磷酸铁锂，其制备原料包括锂源、铁盐及磷酸源。可选地，锂源选自碳酸锂、乙酸锂、氢氧化锂、硝酸锂、硫酸锂、氯化锂、草酸锂、磷酸锂、磷酸氢锂、柠檬酸锂、硅酸锂及偏硼酸锂中的至少一种。掺杂金属盐选自草酸盐、磷酸盐、醋酸盐、硫酸盐、柠檬酸盐及硝酸盐中的至少一种。聚阴离子对应酸源包括磷酸源、硅酸源或者硼酸源。进一步地，磷酸源选自磷酸、磷酸铵、磷酸二氢铵及磷酸氢二铵中的至少一种。硅酸源选自硅酸、偏硅酸、四氯化硅、二氧化硅及正硅酸乙酯中的至少一种。硼酸源选自硼酸、硼酸铵及氧化硼中的至少一种。
在其中一些实施例中，在步骤S110中，热处理的温度为500℃～1200℃；热处理的时间为5h～20h。
具体地，步骤S120中，疏水导电材料及中间体通过在有机溶剂中超声分散混合均匀。 在本申请实施方式中，有机溶剂为N-甲基吡咯烷酮(NMP)。可以理解地，有机溶剂不限于NMP。
进一步地，步骤S120中，疏水导电材料及中间体在有机溶剂中超声分散混合均匀后，还包括固液分离，抽滤，洗涤，干燥处理，得到正极材料。
在其中一些实施例中，疏水导电材料包括导电聚合物及疏水导电碳材料；在步骤S120之前，还包括S121：将导电聚合物及疏水导电碳材料在有机溶剂中超声分散混合的步骤。在本申请实施方式中，有机溶剂为N-甲基吡咯烷酮(NMP)。可以理解地，有机溶剂不限于NMP。具体地，步骤S121中，超声分散在50℃～100℃下进行。
本申请的一实施方式还提供了一种复合正极材料，包括三元正极材料及上述的正极材料。
具体地，三元正极材料包括镍钴锰酸锂(NCM)、包覆改性的镍钴锰酸锂(NCM)、镍钴铝酸锂(NCA)及包覆改性的镍钴铝酸锂(NCA)中的至少一种。镍钴锰酸锂(NCM)根据镍、钴、锰元素的含量不同，包括LiNi1/3Co1/3Mn1/3O2(也可以简称为NCM333)、LiNi0.5Co0.2Mn0.3O2(也可以简称为NCM523)、LiNi0.5Co0.25Mn0.25O2(也可以简称为NCM211)、LiNi0.6Co0.2Mn0.2O2(也可以简称为NCM622)、LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)等。进一步地，镍钴锰酸锂为层状镍钴锰酸锂。
作为示例地，镍钴铝酸锂(NCA)包括LiNi0.85Co0.15Al0.05O2等。
上述复合正极材料，通过三元正极材料及上述的正极材料的合理配比，能够获得倍率性能更好的复合正极材料。
在其中一些实施例中，三元正极材料与上述正极材料6的质量比为(1～9)：(9～1)。进一步地，三元正极材料与上述正极材料6的质量比为(2～8)：(8～2)。
进一步地，在上述三元正极材料及正极材料6的总质量中，上述正极材料6的质量占比为10％～90％；更进一步为20％～80％。
另外，以下适当参照附图对本申请的正极极片、二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之 间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
正极极片
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括本申请第一方面的正极活性材料或者本申请第三方面的复合正极材料。
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，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
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，负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上 的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
电解质
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸 甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
隔离膜
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图2是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图3，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于开口，以封闭容纳腔。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封装于容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图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，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图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。
另外，本申请还提供一种用电装置，用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图7是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
以下通过具体实施例对本申请作进一步说明。具体地，在以下实施例及对比例中，磷酸锰铁锂为LiMn0.6Fe0.4PO4，简称LMFP64。
实施例1：
本实施例的正极材料根据以下步骤制备：
在水溶液中加入0.253g乙酸锂，0.547g草酸亚铁，0.437g磷酸二氢铵超声搅拌并反应完 全后，加入磷酸锰铁锂超声搅拌，随后对悬浮液进行固液分离，对得到的固体进行洗涤、干燥，随后将干燥后的固体在惰性气氛中700℃热处理10h后，即可得到磷酸铁锂包覆的磷酸锰铁锂。
在80℃的N-甲基吡咯烷酮(N-Methylpyrrolidone，简称NMP)溶剂中加入0.376g聚苯胺和0.343g碳纳米管分散液(7％固含量)超声搅拌混合均匀后，加入磷酸铁锂包覆的磷酸锰铁锂继续超声搅拌，待混合均匀将悬浮液固液分离后，对固态物质真空抽滤、洗涤、干燥，得到正极材料。
参阅图8，为实施例1制备的正极材料的投射电镜(TEM)图，可以看出，制得的正极材料具有双层包覆结构，正极材料从内到外依次为内核61、第一壳层62及第二壳层62。
对比例1：
本对比例提供的正极材料为未经改性处理的磷酸锰铁锂，即实施例1制备过程中所用磷酸锰铁锂。
参阅图9，为对比例1的正极材料的投射电镜(TEM)图，可以看出，正极材料的磷酸铁锂界面清晰，表面无包覆结构。
实施例2～9：
实施例2～9的正极材料的制备方法与实施例1基本相同，区别在于，第一壳层及第二壳层的质量和相对于正极材料的质量的比值(简称壳层质量和占比)不同，第一壳层及第二壳层的厚度之和与正极材料的Dv50的比值(简称为h/d)不同。具体地，h/d通过透射电镜(TEM)图谱观察得到。
实施例1～9的正极材料中，壳层质量和占比、h/d记录在表1中，实施例2～9中物料用量根据表1比例进行调整。
表1实施例1～9的正极材料的壳层质量和占比、第一壳层及第二壳层的厚度之和与正极材料Dv50的比值(h/d)及第二壳层在壳层(第一壳层及第二壳层)总质量的占比。

作为示例地，实施例2的正极材料根据以下步骤制备：
在水溶液中加入0.025g乙酸锂，0.055g草酸亚铁，0.044g磷酸二氢铵超声搅拌并反应完全后，加入磷酸锰铁锂超声搅拌，随后对悬浮液进行固液分离，对得到的固体进行洗涤、干燥，随后将干燥后的固体在惰性气氛中700℃热处理10h后，即可得到磷酸铁锂包覆的磷酸锰铁锂。
在80℃的NMP溶剂中加入0.038g聚苯胺和0.034g碳纳米管分散液(7％固含量)超声搅拌混合均匀后，加入磷酸铁锂包覆的磷酸锰铁锂继续超声搅拌，待混合均匀将悬浮液固液分离后，对固态物质真空抽滤、洗涤、干燥，得到正极材料。
实施例10～17：
实施例10～17的正极材料的制备方法与实施例3基本相同，区别在于，壳层(第一壳层及第二壳层)中第二壳层的质量占比不同。实施例3、10～17的正极材料中第二壳层在壳层(第一壳层及第二壳层)中的质量占比记录在表2中。实施例10～17中物料用量根据表2比例进行调整。
作为示例地，实施例10的正极材料根据以下步骤制备：
在水溶液中加入1.899g乙酸锂，4.101g草酸亚铁，3.275g磷酸二氢铵超声搅拌并反应完全后，加入磷酸锰铁锂超声搅拌，随后对悬浮液进行固液分离，对得到的固体进行洗涤、干燥，随后将干燥后的固体在惰性气氛中700℃热处理10h后，即可得到磷酸铁锂包覆的磷酸锰铁锂。
在80℃的NMP溶剂中加入0.47g聚苯胺和0.428g碳纳米管分散液(7％固含量)超声搅拌混合均匀后，加入磷酸铁锂包覆的磷酸锰铁锂继续超声搅拌，待混合均匀将悬浮液固液分离后，对固态物质真空抽滤、洗涤、干燥，得到正极材料。
对比例2：
本对比例的正极材料根据以下步骤制备：
在水溶液中加入10.54g乙酸锂，22.79g草酸亚铁，18.21g磷酸二氢铵超声搅拌并反应完 全后，加入磷酸锰铁锂超声搅拌，随后对悬浮液进行固液分离，对得到的固体进行洗涤、干燥，随后将干燥后的固体在惰性气氛中700℃热处理10h后，即可得到正极材料。
对比例3：
本对比例的正极材料根据以下步骤制备：
在80℃的NMP溶剂中加入23.5g聚苯胺和21.44g碳纳米管分散液(7％固含量)超声搅拌混合均匀后，加入磷酸锰铁锂继续超声搅拌，待混合均匀将悬浮液固液分离后，对固态物质真空抽滤、洗涤、干燥，得到正极材料。
对比例2～3的正极材料中第二壳层在壳层(第一壳层及第二壳层)中的质量占比记录在表2中。实施例1～17及对比例1～3的制备原料及用量记录于表3中。
表2实施例3、10～17的正极材料中壳层质量和占比及第二壳层在壳层(第一壳层及第二壳层)质量和的占比。
对比例4：
将95g磷酸锰铁锂、3g磷酸铁锂、1.88g聚苯胺和1.715g碳纳米管分散液在80℃下N-甲基吡咯烷酮(NMP)中超声分散混合均匀；将混合溶液进行固液分离操作，随后将得到的固态物质进行真空抽滤，洗涤，干燥，即可得到正极材料；其中正极材料中，磷酸锰铁锂表面无包覆结构。
表3实施例1～17及对比例1～3的制备原料及用量。
实施例18～21：
实施例18～21的正极材料的制备方法与实施例14基本相同，区别在于，第二壳层的制备原料不同。实施例14、18～21中第二壳层的制备原料记录于表4中，制备方法根据表4进行调整。
表4实施例14、18～21正极材料中第二壳层的制备原料。
作为示例，实施例18的正极材料根据以下步骤制备：
在水溶液中加入0.844g乙酸锂，1.823g草酸亚铁，1.456g磷酸二氢铵超声搅拌并反应完全后，加入磷酸锰铁锂超声搅拌，随后对悬浮液进行固液分离，对得到的固体进行洗涤、干 燥，随后将干燥后的固体在惰性气氛中700℃热处理10h后，即可得到磷酸铁锂包覆的磷酸锰铁锂。
在80℃的NMP溶剂中加入2.82g聚苯胺和2.571g碳纳米管分散液(7％固含量)超声搅拌混合均匀后，加入磷酸铁锂包覆的磷酸锰铁锂继续超声搅拌，待混合均匀将悬浮液固液分离后，对固态物质真空抽滤、洗涤、干燥，得到正极材料。
实施例22：
本实施例的复合正极材料通过将实施例1的正极材料与三元正极材料NCM523按照质量比为3:7混合得到。
对比例5：
本对比例的复合正极材料通过将对比例1的正极材料与三元正极材料NCM523按照质量比为3:7混合得到。
测试例1～7：
测试例1～7分别测试了不同配比的聚苯胺及碳纳米管制成的复合薄膜的电导率及接触角。其中，电导率通过SDY-4型四探针电阻仪测试，原理如下：首先使用四探针测试仪测试出有机疏水材料膜表面电阻R，根据σ＝1/(R×W)计算出有机疏水材料电导率，其中σ为电导率，W为有机疏水材料膜厚度。接触角通过OCA25-HTV1800型接触角仪测试。测试例1～7的复合薄膜中聚苯胺及碳纳米管的用量、碳纳米管占比、电导率及接触角记录在表5中。
其中，测试例2的复合薄膜根据以下步骤制备：
将9.8g聚苯胺和2.86g碳纳米管分散液(7％固含量)在NMP溶液中超声搅拌混合均匀后，用移液枪将所得溶液滴到预先准备好的玻璃基板上，随后将玻璃基板置于100℃真空干燥箱中烘干12h，待完全干燥后，将其置于去离子水中，剥离出复合薄膜，并置于滤纸上自然干燥即可得到复合薄膜。
表5测试例1～7的复合薄膜的组成、电导率及接触角。

从表5相关数据可以看出，测试例1～7的复合薄膜中，碳纳米管的质量占比为0～12％，测试例1～7的接触角均在130°以上，具有较好的疏水性能。测试例1的复合薄膜中不含碳纳米管，测试例7的复合薄膜中碳纳米管的质量占比为12％，测试例1、7的电导率不及测试例2～6的复合薄膜。可见，第二壳层中疏水导电碳材料的质量百分比为2％～10％时，第二壳层兼具较好的导电性能和疏水性能。当第二壳层中疏水导电碳材料的质量百分比为4％～8％时，第二壳层的导电性能和疏水性能更佳。
软包叠片电池制备：
(1)正极极片制备：将实施例/对比例提供的(复合)正极材料与聚偏二氟乙烯(PVDF)、导电碳加入一定量的N-甲基吡咯烷酮(NMP)中，(复合)正极材料、粘接剂及导电剂的质量比为90：5：5，在干燥房中搅拌制成均匀的浆料，控制粘度为3000mPa·S～10000mPa·S，在铝箔上涂敷上述浆料，经过烘干处理制成正极极片。
(2)负极极片制备：将石墨、羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)、导电碳加入一定量的去离子水中，石墨、羧甲基纤维素钠、丁苯橡胶及导电剂的质量比为90：2：3：5，搅拌制成均匀的浆料，控制粘度为3000mPa·S～10000mPa·S，在铜箔上涂敷上述浆料，经过烘干处理制成负极极片。
(3)软包叠片电池制备：将制备好的正极极片、负极极片和隔膜(聚乙烯(PE)多孔聚合薄膜)按照Z字型叠片结构制成相应电芯，将电芯在90℃的环境下真空烘干12h，随后进行正负极极耳超声焊接，正极采用铝极耳，负极采用镍极耳，正负极极耳位于电芯同侧，将极耳焊接后的电芯装入合适尺寸的铝塑膜中进行顶侧封封装，注液(电解液采用为1mol/L LiPF6/(碳酸乙烯酯(EC)+碳酸二乙酯(DEC)+碳酸二甲酯(DMC))(体积比1：1：1)+5wt.％氟代碳酸乙烯酯(FEC))，静置，化成，老化，排气，二封，容量测试即可得到制备好的软包叠片电池。
测试部分：
(1)倍率性能测试：首先对软包叠片电池进行容量测试，流程如下：静置5min，按照0.33C放电至2.5V，静置5min后，按照0.33C恒流充电至4.3V后转为恒压充电，当充电电流减小至0.05C时，恒压充电结束，静置5min，随后0.33C放电至2.5V，此时的放电容量记为C0。
倍率性能测试流程如下：静置5min，按照0.33C放电至2.5V，静置5min后，按照0.33C恒流充电至4.3V后转为恒压充电，当充电电流减小至0.05C时，恒压充电结束，静置5min，按照1C放电至2.5V，记录此时的放电容量，不同倍率测试则将最后一步“按照1C放电至2.5V”中的1C替换为相应倍率2C/3C即可。将倍率性能测试所得的容量值除以软包叠片电池中所含的(复合)正极材料质量，即可得到不同倍率下正极材料的克容量。
(2)25℃循环测试：将上述制备的软包叠片电池，在25℃恒温环境，2.5～4.3V下，按照0.5C0充电至4.3V，然后在4.3V下恒压充电至电流≤0.05mA，静置5min，然后按照0.5C放电至2.5V，容量记为Cn(n＝1,2,3……)，重复上述操作，测定容量衰减(fading)值，容量衰减按照Cn/C3的比值作为电芯衰减程度(State of health SOH)，对比衰减至80％SOH时，每个电芯的循环圈数，作为循环能力的考查指标。
(3)过渡金属锰溶出测试：将25℃循环测试中循环到相同圈数的实施例和对比例软包叠片电池进行拆解，取出负极极片借助电感耦合等离子体质谱法(ICP-MS)测量负极极片上锰元素含量。
(4)材料含水量测试：取1g的实施例/对比例中制备的正极材料先在120℃环境下烘烤24h，然后放置在5％RH环境湿度下4h，再次测量材料含水量，根据含水量情况作为考查指标。
实施例1～22及对比例1～5的正极材料制备得到的软包叠片电池的倍率性能、循环性能、过渡金属锰溶出及含水量记录于表6中。
表6实施例1～22及对比例1～5的正极材料制备得到的软包叠片电池的倍率性能、循环性能、过渡金属锰溶出及含水量

从表6相关数据可以看出，与未经过包覆改性处理的对比例1的正极材料相比，实施例1～21的正极材料能够显著抑制正极材料循环过程中的锰溶出、并降低正极材料的含水量，实施例1～21的正极材料的循环性能显著提升。
具体地，实施例1～9正极材料中，壳层的质量和占比及壳层厚度和与正极材料Dv50的比值(h/d)不同，可以看出，实施例1、3～8中，壳层的质量和占比为1％～40％；h/d为0.03～0.39，锰溶出量及含水量更低。
实施例3、10～17中，第二壳层在壳层总质量中的占比不同。从表6数据可以看出，当第二壳层在壳层总质量中的占比为20％～60％，更进一步为30％～50％时，正极材料的锰溶出量及含水量更低。对比例2、3的正极材料中，第二壳层在壳层总质量中的占比分别为0、100％，对比例2中不包含第二壳层，正极材料有一定的抑制锰溶出的效果，然而正极材料含水量高；对比例3中不包含第一壳层，正极材料的含水量较低，然而锰溶出增加，循环性能变差，说明本申请中采用第一壳层、第二壳层组合包覆磷酸锰铁锂能够抑制磷酸锰铁锂锰析出、吸水等问题，有利于提高正极材料的循环性能。
实施例14、18～21中，第二壳层的材料选择不同，从表6数据可以看出，实施例14、18～21正极材料的倍率性能及循环性能较好，尤其是采用聚苯胺、聚噻吩作为导电聚合物，效果更为突出。
对比例4的正极材料与实施例3的区别在于，磷酸锰铁锂、磷酸铁锂、聚苯胺及碳纳米管仅简单混合，磷酸锰铁锂表面未形成包覆结构。而对比例4的正极材料的含水量明显高于实施例3，且锰溶出明显增加，对比例4的正极材料的循环性能更差。
实施例22的复合正极材料包括三元正极材料NCM523及实施例1的正极材料，在实施例1的基础上进一步提升了倍率性能，兼具较好的倍率性能和循环稳定性。而对比例5的复合正极材料包括三元正极材料NCM523及对比例1的正极材料，倍率性能虽然提升，但由于磷酸锰铁锂本身导电性能差、锰溶出及吸水等问题，对比例5的复合正极材料循环性能较差。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，便于具体和详细地理解本申请的技术方案，但并不能因此而理解为对发明专利保护范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。应当理解，本领域技术人员在本申请提供的技术方案的基础上，通过合乎逻辑的分析、推理或者有限的试验得到的技术方案，均在本申请所述附权利要求的保护范围内。因此，本申请专利的保护范围应以所附权利要求的内容为准，说明书及附图可以用于解释权利要求的内容。

Claims (16)

  1. 一种正极材料，包括：内核、第一壳层及第二壳层；
    所述第一壳层包裹于所述内核的表面，所述第二壳层包裹于所述第一壳层的表面；
    所述内核包括磷酸锰铁锂材料；所述第一壳层包括聚阴离子型正极材料，且所述聚阴离子型正极材料不含有锰元素；所述第二壳层包括疏水导电材料。
  2. 根据权利要求1所述的正极材料，其中所述疏水导电材料包括疏水导电聚合物及疏水导电碳材料中的至少一种。
  3. 根据权利要求2所述的正极材料，其中所述疏水导电聚合物选自聚吡咯、聚苯胺、聚噻吩及聚乙炔中的至少一种；
    和/或，所述疏水导电碳材料选自碳纳米管及碳纳米纤维中的至少一种。
  4. 根据权利要求1至3任一项所述的正极材料，其中所述第二壳层中，所述疏水导电碳材料的质量百分比为2％～10％；
    可选地，所述第二壳层中，所述疏水导电碳材料的质量百分比为4％～8％。
  5. 根据权利要求1至4任一项所述的正极材料，其中所述聚阴离子型正极材料选自磷酸盐类材料、硅酸盐类材料及硼酸盐类材料中的至少一种。
  6. 根据权利要求5所述的正极材料，其中所述磷酸盐类材料包括LiFePO4、LiNiPO4、LiCoPO4、Li3V2(PO4)3、LiVOPO4及LiTi2(PO4)3中的至少一种；
    所述硅酸盐类材料包括Li2FeSiO4、Li2NiSiO4及Li2CoSiO4中的至少一种；
    所述硼酸盐类材料包括LiFeBO3及LiCoBO3中的至少一种。
  7. 根据权利要求1至6任一项所述的正极材料，其中所述第一壳层及所述第二壳层的质量之和相对于所述正极材料的质量的比值为0.1％～50％；
    可选地，所述第一壳层及所述第二壳层的质量之和相对于所述正极材料的质量的比值为1％～40％；
    可选地，所述第一壳层及所述第二壳层的质量之和相对于所述正极材料的质量的比值为1％～30％；
    可选地，所述第一壳层及所述第二壳层的质量之和相对于所述正极材料的质量的比值为1％～20％。
  8. 根据权利要求1至7任一项所述的正极材料，其中在所述第一壳层及所述第二壳层的 总质量中，所述第二壳层的质量百分比为10％～90％；
    可选地，在所述第一壳层及所述第二壳层的总质量中，所述第二壳层的质量百分比为20％～60％；
    可选地，在所述第一壳层及所述第二壳层的总质量中，所述第二壳层的质量百分比为30％～50％。
  9. 根据权利要求1至8任一项所述的正极材料，其中所述第一壳层及所述第二壳层的厚度之和与所述正极材料的Dv50的比值为0.01～0.45；
    可选地，所述第一壳层及所述第二壳层的厚度之和与所述正极材料的Dv50的比值为0.03～0.39；
    可选地，所述第一壳层及所述第二壳层的厚度之和与所述正极材料的Dv50的比值为0.03～0.31；
    可选地，所述第一壳层及所述第二壳层的厚度之和与所述正极材料的Dv50的比值为0.03～0.26。
  10. 根据权利要求1至9任一项所述的正极材料的制备方法，包括以下步骤：
    将聚阴离子型正极材料的制备原料与磷酸锰铁锂材料混合，惰性气氛下进行热处理，以使所述磷酸锰铁锂材料的表面包覆所述第一壳层，制备中间体；
    将疏水导电材料及所述中间体混合均匀，以使所述第一壳层的表面包覆所述第二壳层，制得所述正极材料。
  11. 一种复合正极材料，包括三元正极材料及权利要求1至9任一项所述的正极材料。
  12. 一种正极极片，包括选自权利要求1至9任一项所述的正极材料或者权利要求11所述的复合正极材料。
  13. 一种二次电池，包括权利要求12所述的正极极片。
  14. 一种电池模块，包括权利要求13所述的二次电池。
  15. 一种电池包，包括权利要求14所述的电池模块。
  16. 一种用电装置，包括选自权利要求13所述的二次电池、权利要求14所述的电池模块及权利要求15所述的电池包中的至少一种。
PCT/CN2023/081384 2022-04-14 2023-03-14 正极材料及其制备方法、复合正极材料、正极极片及二次电池 WO2023197807A1 (zh)

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Cited By (1)

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CN117542961A (zh) * 2024-01-10 2024-02-09 宁德时代新能源科技股份有限公司 电池单体、电池及用电装置

Citations (2)

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Publication number Priority date Publication date Assignee Title
US20140199475A1 (en) * 2011-09-29 2014-07-17 Showa Denko K.K. Positive electrode active material for lithium secondary battery and production method of same
CN114203991A (zh) * 2021-12-01 2022-03-18 远景动力技术(江苏)有限公司 正极材料添加剂、正极及锂离子电池

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140199475A1 (en) * 2011-09-29 2014-07-17 Showa Denko K.K. Positive electrode active material for lithium secondary battery and production method of same
CN114203991A (zh) * 2021-12-01 2022-03-18 远景动力技术(江苏)有限公司 正极材料添加剂、正极及锂离子电池

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117542961A (zh) * 2024-01-10 2024-02-09 宁德时代新能源科技股份有限公司 电池单体、电池及用电装置

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