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WO2023046137A1 - 制备磷酸铁锂正极材料的方法、正极极片及锂离子电池 - Google Patents

制备磷酸铁锂正极材料的方法、正极极片及锂离子电池 Download PDF

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WO2023046137A1
WO2023046137A1 PCT/CN2022/121210 CN2022121210W WO2023046137A1 WO 2023046137 A1 WO2023046137 A1 WO 2023046137A1 CN 2022121210 W CN2022121210 W CN 2022121210W WO 2023046137 A1 WO2023046137 A1 WO 2023046137A1
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iron phosphate
lithium iron
positive electrode
lithium
phosphate material
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PCT/CN2022/121210
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English (en)
French (fr)
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杜孟衣
陈三志
郝嵘
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比亚迪股份有限公司
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Priority to KR1020237045093A priority Critical patent/KR20240014510A/ko
Priority to CA3223413A priority patent/CA3223413A1/en
Priority to JP2023579258A priority patent/JP2024532045A/ja
Priority to EP22872181.7A priority patent/EP4345951A1/en
Priority to AU2022350575A priority patent/AU2022350575A1/en
Publication of WO2023046137A1 publication Critical patent/WO2023046137A1/zh
Priority to US18/399,192 priority patent/US20240128452A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/10—Solid density
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of lithium ion batteries, in particular to a method for preparing a lithium iron phosphate positive electrode material, a positive electrode sheet and a lithium ion battery.
  • Lithium iron phosphate material is widely used in power batteries due to its advantages of high structural stability, good safety performance, moderate working voltage, and low cost.
  • lithium iron phosphate has an obvious disadvantage, which is its low compaction density (usually 2.1-2.3g/cm 3 , rarely more than 2.6g/cm 3 ), resulting in low specific capacity and energy density of batteries made of it, hindering the application of this material. Therefore, it is necessary to provide a battery positive electrode material with high compaction density and a preparation method thereof.
  • the present application provides a method for preparing a lithium iron phosphate cathode material.
  • the high-pressure compaction of the lithium iron phosphate cathode material mixed by the two can be realized. Controllable adjustment of density.
  • the present application provides a method for preparing a lithium iron phosphate cathode material, comprising the following steps:
  • the first mixed slurry of iron phosphate, lithium source, carbon source and solvent is sequentially ground, spray-dried and sintered to obtain the first lithium iron phosphate material with a spherical shape;
  • the second mixed slurry of iron phosphate, lithium source, carbon source and solvent is sequentially ground, spray-dried, sintered and crushed to obtain a second lithium iron phosphate material with an irregular shape;
  • the first lithium iron phosphate material and the second lithium iron phosphate material are mixed in an equal mass ratio to obtain a lithium iron phosphate positive electrode material;
  • the fitting value C of the maximum compaction density of the lithium iron phosphate positive electrode material satisfies the following relationship:
  • T 1 and t 1 represent the sintering temperature and sintering time of the first lithium iron phosphate material respectively
  • T 2 and t 2 represent the sintering temperature and sintering time of the second lithium iron phosphate material respectively;
  • the t 1 and said t2 is in the range of 7h-11h, for example, t1 and t2 are independently 7h, 7.2h, 7.4h, 7.6h, 7.8h, 8h, 8.2h, 8.4h, 8.6h, 8.8h , 9h, 9.2h, 9.4h, 9.6h, 9.8h, 10h, 10.2h, 10.4h, 10.6h, 10.8h or 11h
  • the T1 is in the range of 760°C-780°C, for example, T1 is 760 °C, 762 °C, 764 °C, 766 °C, 768 °C, 770 °C, 772 °C, 774 °C, 776 °C, 778
  • the maximum compaction density of the positive electrode material mixed with the two can be made higher, and the obtained positive electrode determined based on the above relational formula
  • the fitting value C of the maximum compacted density of the material is very close to the measured value, which can realize the controllable preparation of the positive electrode material with the required high compacted density, without having to carry out the compaction density of the positive electrode sheet made of the obtained positive electrode material every time. Test, save material and time.
  • the C is above 2.6 g/cm 3 .
  • the compacted density of the lithium iron phosphate positive electrode material is obviously higher than that of the existing lithium iron phosphate positive electrode material (2.1g/cm 3 -2.3g/cm 3 ).
  • the C is in the range of 2.6g/cm 3 -2.85g/cm 3 , such as 2.6g/cm 3 , 2.65g/cm 3 , 2.7g/cm 3 , 2.75g/cm 3 , 2.8g/cm 3 or 2.85g/cm 3 .
  • the compaction density of the lithium iron phosphate positive electrode material is relatively high, and the gram capacity and energy density of the battery made from it are also relatively high.
  • the preparation of the first lithium iron phosphate material and the second lithium iron phosphate material are similar, the main difference being: in the process of preparing the second lithium iron phosphate material, after sintering, crushing treatment is also performed.
  • the appearance of the first lithium iron phosphate material is spherical, and the appearance of the second lithium iron phosphate material obtained after crushing is irregular, and the lithium iron phosphate materials of these two appearances are mixed in a mass ratio of 1:1, which can be
  • the second lithium iron phosphate material is fully filled in the gaps between the first lithium iron phosphate materials with large particle sizes, and the filling rate and compaction density of the mixed material formed by the two are increased.
  • the crushing process can be performed in a jet mill.
  • the maximum compacted density A of the first lithium iron phosphate material is smaller than the maximum compacted density B of the second lithium iron phosphate material.
  • the A is in the range of 1.8g/cm 3 -2.2g/cm 3 , such as 1.8g/cm 3 , 1.9g/cm 3 , 2.0g/cm 3 , 2.1g/cm 3 or 2.2g/cm 3
  • said B is in the range of 2.3g/cm 3 -2.6g/cm 3 , such as 2.3g/cm 3 , 2.4g/cm 3 , 2.5g/cm 3 or 2.6g/cm 3 .
  • the D50 particle size of the first lithium iron phosphate material is 3 ⁇ m-10 ⁇ m, such as 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m or 10 ⁇ m.
  • the D50 particle size of the second lithium iron phosphate material is 0.5 ⁇ m-3 ⁇ m, such as 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m or 3 ⁇ m.
  • the D50 particle size of the first lithium iron phosphate material is larger than the D50 particle size of the second lithium iron phosphate material. This is more conducive to forming a tighter stack of the spherical first lithium iron phosphate material and the irregular second lithium iron phosphate material.
  • the composition of the first mixed slurry and the second mixed slurry can be the same or different, wherein the lithium source in the first mixed slurry and the second mixed slurry can independently include lithium hydroxide (LiOH), One or more of lithium carbonate (Li 2 CO 3 ), lithium oxalate (Li 2 C 2 O 4 ), lithium acetate (CH 3 COOLi), lithium nitrate (LiNO 3 ), but not limited thereto.
  • the lithium source has a certain loss in the later sintering process
  • the molar amount of lithium element from the lithium source is 1.00- 1.05 times.
  • the lithium source and the iron phosphate are used in an amount such that the molar ratio of lithium element to iron element is (1.00-1.05):1.
  • the carbon source includes glucose, starch, phenolic resin, sucrose, cellulose, polyethylene glycol, citric acid, glycine, ethylenediaminetetraacetic acid, agar, acetylene black, Ketjen black, graphite, carbon nanotubes, graphene One or more of these, but not limited to.
  • organic carbon sources such as glucose and starch can be decomposed during the sintering process to form a carbon coating layer coated on the surface of lithium iron phosphate material to endow it with electrical conductivity; while inorganic carbon sources (such as acetylene black, graphite, etc.) It will decompose during the sintering process, and a carbon coating layer can also be formed on the surface of the lithium iron phosphate material.
  • An appropriate amount of carbon source can make the prepared lithium iron phosphate materials have better conductivity, and can also avoid reducing the specific charge and discharge capacity due to too much carbon coating layer, which is ultimately beneficial to the electrochemical performance of lithium iron phosphate cathode materials promote.
  • the amount of carbon source added in the first mixed slurry can ensure that the carbon content in the prepared first lithium iron phosphate material is 0.5wt%-3wt%, such as 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt% wt%, 0.9wt%, 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, 2.1 wt%, 2.2wt%, 2.3wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.7wt%, 2.8wt%, 2.9wt%, 3wt%; the addition of carbon source in the second mixed slurry can be Ensure that the carbon content in the prepared second lithium iron phosphate material is 0.5wt%-3wt%, such as 0.5wt%, 0.6wt%,
  • the solvent in the first mixed slurry or the second mixed slurry independently includes water, fatty alcohol (such as methanol, ethanol, propanol, etc.), acetone, N-methylpyrrolidone, etc. one or more of.
  • fatty alcohol such as methanol, ethanol, propanol, etc.
  • acetone such as N-methylpyrrolidone, etc. one or more of.
  • the grinding described in this application can be carried out in equipment such as ball mill, bead mill or sand mill. In some embodiments of this application, the grinding is carried out in a grinding equipment with circulating cooling water.
  • the grinding electricity can be 0.5kwh/kg-10kwh/kg, such as 1kwh/kg, 2kwh/kg, 5kwh/kg kg, 8kwh/kg, etc.
  • the D50 particle size of the first mixed slurry after grinding is 0.2 ⁇ m-5 ⁇ m, such as 0.2 ⁇ m, 0.5 ⁇ m, 0.75 ⁇ m, 1 ⁇ m, 1.2 ⁇ m, 1.5 ⁇ m, 1.75 ⁇ m, 2 ⁇ m, 2.2 ⁇ m, 2.5 ⁇ m, 2.75 ⁇ m, 3 ⁇ m, 3.2 ⁇ m, 3.5 ⁇ m, 3.75 ⁇ m, 4 ⁇ m, 4.2 ⁇ m, 4.5 ⁇ m, 4.75 ⁇ m or 5 ⁇ m.
  • the D50 particle size of the second mixed slurry after grinding is 0.2 ⁇ m-5 ⁇ m, such as 0.2 ⁇ m, 0.5 ⁇ m, 0.75 ⁇ m, 1 ⁇ m, 1.2 ⁇ m, 1.5 ⁇ m, 1.75 ⁇ m, 2 ⁇ m, 2.2 ⁇ m, 2.5 ⁇ m, 2.75 ⁇ m ⁇ m, 3 ⁇ m, 3.2 ⁇ m, 3.5 ⁇ m, 3.75 ⁇ m, 4 ⁇ m, 4.2 ⁇ m, 4.5 ⁇ m, 4.75 ⁇ m or 5 ⁇ m.
  • This can ensure that the raw materials are fully recombined, and at the same time avoid excessive bond breakage and lattice defects of the raw materials, which will affect the electrochemical performance of the prepared lithium iron phosphate material.
  • the inlet temperature of the spray drying is independently in the range of 150°C-280°C, such as 150°C, 160°C, 170°C °C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C or 280°C; the outlet temperature is independently in the range of 80°C-120°C, e.g. 80°C, 90°C, 100°C, 110°C or 120°C.
  • T1 and T2 are the sintering holding temperatures in the preparation of the first lithium iron phosphate material and the second lithium iron phosphate material.
  • the rate of temperature rise to T1 and T2 may be 2°C/min-10°C/min, such as 2°C/min, 4°C/min, 6°C °C/min, 8°C/min or 10°C/min.
  • Appropriate sintering holding time ie, t 1 , t 2 ) can fully crystallize the lithium iron phosphate material with high crystallization integrity.
  • the holding time during sintering is 8h-10h, such as 8h, 8.2h, 8.4h, 8.6h, 8.8h, 9h, 9.2h, 9.4h, 9.6h, 9.8h or 10h.
  • the method for preparing the lithium iron phosphate positive electrode material provided in the first aspect of the present application by adjusting the sintering temperature and time of the two kinds of lithium iron phosphate materials with different shapes in the preparation process, can make the lithium iron phosphate positive electrode material mixed by the two The compaction density is higher, and the electrochemical performance of the battery made by it is better.
  • the preparation method has simple process, easy operation and is suitable for large-scale production.
  • the second aspect of the present application provides a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, the positive electrode material layer includes the lithium iron phosphate positive electrode material prepared by the aforementioned method , Conductive agent and binder.
  • the conductive agent and the binder in the positive electrode material layer are conventional materials in the field, which can be selected by those skilled in the art according to actual needs, and will not be repeated here.
  • the third aspect of the present application provides a lithium ion battery, the lithium ion battery includes a positive pole piece.
  • the lithium-ion battery also includes a negative pole piece, and an electrolyte and a separator located between the positive pole piece and the negative pole piece.
  • the lithium-ion battery adopting the above-mentioned positive electrode sheet with high compaction density has a higher discharge specific capacity and higher energy density.
  • the discharge specific capacity of the button-type lithium-ion battery using the aforementioned positive pole piece at room temperature 0.1C can be above 158mAh/g, and in some cases can reach above 160mAh/g.
  • FIG. 1 is a scanning electron microscope (SEM) photograph of the LFP-1 material used in Example 1.
  • FIG. 2 is a SEM photo of the LFP-2 material used in Example 1.
  • a preparation method of lithium iron phosphate cathode material comprising the following steps:
  • the D50 particle size of the ground material is about 0.35 ⁇ m, and then spray drying and granulating the ground slurry, wherein the inlet temperature of the spray drying equipment is 200 ° C, and the outlet temperature is 105°C;
  • the difference between it and the preparation of LFP-1 is that the sintering holding temperature T2 during the sintering process is 793°C, and the sintering holding time t2 is 8.3h; after sintering, airflow crushing is also carried out, resulting in irregular morphology.
  • the particle size D50 of the second lithium iron phosphate material LFP-2 (as shown in FIG. 2 in the SEM photo) is 1.02 ⁇ m.
  • the LFP-2 material was prepared into a positive electrode sheet, and its maximum compacted density B was measured to be 2.55 g/cm 3 .
  • the positive electrode material above into a positive electrode sheet mix the positive electrode material with a binder (specifically polyvinylidene fluoride, PVDF) and conductive carbon black at a mass ratio of 90:5:5, and add an appropriate amount of N-formazol NMP was mixed evenly to obtain positive electrode slurry; the positive electrode slurry was coated on one side of carbon-coated aluminum foil, dried, rolled, and punched into discs with a diameter of 15 mm to obtain positive electrode sheets. It is measured that the actual maximum compacted density of the positive electrode sheet is 2.88g/cm 3 , which is basically consistent with the compacted density C of the positive electrode material calculated according to the formula of this application.
  • a binder specifically polyvinylidene fluoride, PVDF
  • conductive carbon black at a mass ratio of 90:5:5
  • N-formazol NMP was mixed evenly to obtain positive electrode slurry
  • the positive electrode slurry was coated on one side of carbon-coated aluminum foil, dried, rolled, and
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • a kind of preparation method of lithium iron phosphate cathode material is:
  • the lithium source used to prepare the first lithium iron phosphate material and the second lithium iron phosphate material is LiOH, and the D50 particle size of the mixed slurry after grinding during the preparation of the first lithium iron phosphate material and the second lithium iron phosphate material is about
  • the sintering temperature T1 is 774°C
  • the sintering holding time t1 is 10h
  • the measured particle size D50 of LFP-1 is 5.3 ⁇ m
  • its maximum compacted density A is 2.05g/cm 3
  • the sintering temperature T2 is 788°C
  • the sintering holding time t2 is 9.8h
  • the measured particle size D50 of LFP-2 is 1.51 ⁇ m
  • Its maximum compacted density B is 2.51g/cm 3 .
  • a kind of preparation method of lithium iron phosphate cathode material is:
  • the D50 particle size of the mixed slurry after grinding is about 0.70 ⁇ m; when preparing the first lithium iron phosphate material LFP-1, the sintering temperature T 1 is 770°C, the sintering holding time t1 is 9h, the measured particle size D50 of LFP-1 is 6.10 ⁇ m, and its maximum compacted density A is 2.01g/cm 3 ; when preparing the second lithium iron phosphate material LFP-2, The sintering temperature T 2 is 795°C, the sintering holding time t 2 is 10.4h, the measured particle size D50 of LFP-2 is 1.32 ⁇ m, and its maximum compacted density B is 2.56g/cm 3 .
  • the D50 particle size of the mixed slurry after grinding is about 1.24 ⁇ m; when preparing the first lithium iron phosphate material LFP-1, the sintering temperature T 1 is 780°C, the sintering holding time t1 is 8.8h, the measured particle size D50 of LFP-1 is 5.50 ⁇ m, and its maximum compacted density A is 2.07g/cm 3 ; when preparing the second lithium iron phosphate material LFP-2 , the sintering temperature T 2 is 782°C, the sintering holding time t 2 is 10.3h, the measured particle size D50 of LFP-2 is 1.02 ⁇ m, and its maximum compacted density B is 2.45g/cm 3 .
  • a kind of preparation method of lithium iron phosphate cathode material is:
  • the D50 particle size of the mixed slurry after grinding is about 1.12 ⁇ m; when preparing the first lithium iron phosphate material LFP-1, the sintering temperature T1 is 778 °C, the sintering holding time t1 is 10.6h, the measured particle size D50 of LFP-1 is 6.8 ⁇ m, and its maximum compacted density A is 2.10g/cm 3 ; when preparing the second lithium iron phosphate material LFP-2, sintering The temperature T 2 is 775°C, the sintering holding time t 2 is 8.6h, the measured particle size D50 of LFP-2 is 1.96 ⁇ m, and its maximum compacted density B is 2.40g/cm 3 .

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Abstract

一种制备磷酸铁锂正极材料的方法、正极极片和锂离子电池，方法包括：对含磷酸铁、锂源、碳源与溶剂的第一混合浆料依次研磨、喷雾干燥和烧结，得到球状第一磷酸铁锂材料；对含磷酸铁、锂源、碳源与溶剂的第二混合浆料依次进行研磨、喷雾干燥、烧结和破碎，得到无规则形貌的第二磷酸铁锂材料；将第一、第二磷酸铁锂材料等质量比混合，得到最大压实密度拟合值为C的磷酸铁锂正极材料，C＝0.0847t 1+0.0196T 1-0.0095t 2+0.0261T 2-33.6716；T 1和t 1分别代表第一磷酸铁锂材料的烧结温度和烧结时间，T 2和t 2分别代表第二磷酸铁锂材料的烧结温度和烧结时间；t 1和t 2在7h-11h的范围内，T 1在760℃-780℃的范围内，T 2在770℃-800℃的范围内；且C在2.6g/cm 3以上。

Description

制备磷酸铁锂正极材料的方法、正极极片及锂离子电池
优先权信息
本公开请求于2021年09月26日向中国国家知识产权局提交的、专利申请号为202111132340.6、公开名称为“磷酸铁锂正极材料的制备方法、正极极片及锂离子电池”的中国专利公开的优先权，并且其全部内容通过引用结合在本公开中。
技术领域
本申请涉及锂离子电池领域，具体涉及一种制备磷酸铁锂正极材料的方法、正极极片及锂离子电池。
背景技术
磷酸铁锂材料因具有结构稳定性高、安全性能好、工作电压适中、成本低等优点而在动力电池中得到广泛应用，但磷酸铁锂存在一个明显的缺点，它的压实密度低(通常为2.1-2.3g/cm 3，很少能做到2.6g/cm 3以上)，导致了由其制成的电池的比容量和能量密度偏低，阻碍了该材料的应用。因此，有必要提供一种压实密度高的电池正极材料及其制备方法。
公开内容
鉴于此，本申请提供一种制备磷酸铁锂正极材料的方法，通过调控两种磷酸铁锂材料在制备过程中的烧结温度和时间可实现二者混合成的磷酸铁锂正极材料的高压实密度的可控调节。
具体地，第一方面，本申请提供了一种制备磷酸铁锂正极材料的方法，包括以下步骤：
对磷酸铁、锂源、碳源与溶剂的第一混合浆料依次进行研磨、喷雾干燥和烧结，得到球状形貌的第一磷酸铁锂材料；
对磷酸铁、锂源、碳源与溶剂的第二混合浆料依次进行研磨、喷雾干燥、烧结和破碎，得到不规则形貌的第二磷酸铁锂材料；
将所述第一磷酸铁锂材料和第二磷酸铁锂材料等质量比混合，得到磷酸铁锂正极材料；所述磷酸铁锂正极材料的最大压实密度的拟合值C满足以下关系式：
C＝0.0847t 1+0.0196T 1-0.0095t 2+0.0261T 2-33.6716；
其中，T 1和t 1分别代表所述第一磷酸铁锂材料的烧结温度和烧结时间，T 2和t 2分别代表所述第二磷酸铁锂材料的烧结温度和烧结时间；所述t 1和所述t 2在7h-11h的范围内，例如t 1和t 2分别独立地为7h、7.2h、7.4h、7.6h、7.8h、8h、8.2h、8.4h、8.6h、8.8h、9h、9.2h、 9.4h、9.6h、9.8h、10h、10.2h、10.4h、10.6h、10.8h或11h，所述T 1在760℃-780℃的范围内，例如T 1为760℃、762℃、764℃、766℃、768℃、770℃、772℃、774℃、776℃、778℃或780℃，所述T 2在770℃-800℃的范围内，例如T 2为770℃、772℃、774℃、776℃、778℃、780℃、782℃、784℃、786℃、788℃、790℃、792℃、794℃、796℃、798℃或800℃；且所述C在2.6g/cm 3以上。
本申请通过调控两种不同形貌的磷酸铁锂材料在制备过程中的烧结温度和时间，可使二者混合成的正极材料的最大压实密度较高，且基于上述关系式确定的所得正极材料最大压实密度的拟合值C与实测值很接近，可实现所需高压实密度的正极材料的可控制备，而不必每次对所得正极材料制成的正极极片进行压实密度测试，节省物料和时间。
本申请中，所述C在2.6g/cm 3以上。此时该磷酸铁锂正极材料的压实密度明显高于现有的磷酸铁锂正极材料的压实密度(2.1g/cm 3-2.3g/cm 3)。本申请一些实施方式中，所述C在2.6g/cm 3-2.85g/cm 3的范围内，例如2.6g/cm 3、2.65g/cm 3、2.7g/cm 3、2.75g/cm 3、2.8g/cm 3或2.85g/cm 3。此时磷酸铁锂正极材料的压实密度较高，通过其制成的电池的克容量和能量密度也较高。
本申请中，第一磷酸铁锂材料和第二磷酸铁锂材料的制备类似，主要不同之处在于：在制备第二磷酸铁锂材料的过程中，在烧结之后，还进行了破碎处理。第一磷酸铁锂材料的形貌呈球形，破碎后所得第二磷酸铁锂材料的形貌呈不规则状，将这两种形貌的磷酸铁锂材料按1:1的质量比混合，可使第二磷酸铁锂材料充分填充在粒径大的第一磷酸铁锂材料之间的间隙，提高二者形成的混合物料的填充率及压实密度。在一些实施方式中，破碎处理可以在气流粉碎机中进行。
其中，第一磷酸铁锂材料的最大压实密度A小于第二磷酸铁锂材料的最大压实密度B。在一些实施方式中，，所述A在1.8g/cm 3-2.2g/cm 3的范围内，例如1.8g/cm 3、1.9g/cm 3、2.0g/cm 3、2.1g/cm 3或2.2g/cm 3，所述B在2.3g/cm 3-2.6g/cm 3的范围内，例如2.3g/cm 3、2.4g/cm 3、2.5g/cm 3或2.6g/cm 3。这样更利于得到C在2.6g/cm 3以上的磷酸铁锂正极材料。需要说明的是，本申请提及某一材料的最大压实密度时是指通过该材料制成的正极极片的最大压实密度。
本申请实施方式中，所述第一磷酸铁锂材料的D50粒径为3μm-10μm，例如3μm、4μm、5μm、6μm、7μm、8μm、9μm或10μm。所述第二磷酸铁锂材料的D50粒径为0.5μm-3μm，例如0.5μm、1μm、1.5μm、2μm、2.5μm或3μm。一般地，第一磷酸铁锂材料的D50粒径大于第二磷酸铁锂材料的D50粒径。这样更利于球形的第一磷酸铁锂材料与不规则形貌的第二磷酸铁锂材料形成更紧密的堆积。
本申请中，第一混合浆料与第二混合浆料的组成可以相同或者不同，其中，第一混合浆料和第二混合浆料中的锂源可以独立地包括氢氧化锂(LiOH)、碳酸锂(Li 2CO 3)、草酸 锂(Li 2C 2O 4)、醋酸锂(CH 3COOLi)、硝酸锂(LiNO 3)中的一种或多种，但不限于此。考虑到锂源在后期烧结过程中有一定损失，本申请中控制第一混合浆料或第二混合浆料中，来自锂源的锂元素的摩尔量是所述磷酸铁的摩尔量的1.00-1.05倍。换句话说，第一混合浆料或第二混合浆料中，所述锂源和磷酸铁的用量使得锂元素、铁元素摩尔比为(1.00-1.05)：1。
所述碳源包括葡萄糖、淀粉、酚醛树脂、蔗糖、纤维素、聚乙二醇、柠檬酸、甘氨酸、乙二胺四乙酸、琼脂、乙炔黑、科琴黑、石墨、碳纳米管、石墨烯等中的一种或多种，但不限于此。其中，葡萄糖、淀粉等有机碳源可在烧结过程中分解，形成包覆在磷酸铁锂材料表面的碳包覆层，以赋予其导电性；而无机碳源(如乙炔黑、石墨等)不会在烧结过程分解，也可在磷酸铁锂材料表面形成碳包覆层。适量的碳源可使制得的各磷酸铁锂材料具有较好的导电性，还可避免因碳包覆层过多而降低其充放电比容量，最终利于磷酸铁锂正极材料的电化学性能提升。其中，第一混合浆料中碳源的加入量可保证所制得的第一磷酸铁锂材料中碳含量为0.5wt％-3wt％，例如0.5wt％、0.6wt％、0.7wt％、0.8wt％、0.9wt％、1wt％、1.1wt％、1.2wt％、1.3wt％、1.4wt％、1.5wt％、1.6wt％、1.7wt％、1.8wt％、1.9wt％、2wt％、2.1wt％、2.2wt％、2.3wt％、2.4wt％、2.5wt％、2.6wt％、2.7wt％、2.8wt％、2.9wt％、3wt％；第二混合浆料中碳源的加入量可保证所制得的第二磷酸铁锂材料中的碳含量为0.5wt％-3wt％，例如0.5wt％、0.6wt％、0.7wt％、0.8wt％、0.9wt％、1wt％、1.1wt％、1.2wt％、1.3wt％、1.4wt％、1.5wt％、1.6wt％、1.7wt％、1.8wt％、1.9wt％、2wt％、2.1wt％、2.2wt％、2.3wt％、2.4wt％、2.5wt％、2.6wt％、2.7wt％、2.8wt％、2.9wt％、3wt％。本申请一些实施方式中，第一磷酸铁锂材料、第二磷酸铁锂材料中的碳含量分别独立地为0.8wt％-2.0wt％。
本申请中，所述第一混合浆料或所述第二混合浆料中的溶剂分别独立地包括水、脂肪醇(如甲醇、乙醇、丙醇等)、丙酮、N-甲基吡咯烷酮等中的一种或多种。
本申请中所述研磨可以在球磨机、珠磨机或砂磨机等设备中进行，本申请一些实施方式中，所述研磨在带循环冷却水的研磨设备中进行。其中，在对所述第一混合浆料或所述第二混合浆料进行研磨的过程中，研磨电量可以为0.5kwh/kg-10kwh/kg，例如是1kwh/kg、2kwh/kg、5kwh/kg、8kwh/kg等。
本申请一些实施方式中，所述第一混合浆料经研磨后的D50粒径为0.2μm-5μm，例如0.2μm、0.5μm、0.75μm、1μm、1.2μm、1.5μm、1.75μm、2μm、2.2μm、2.5μm、2.75μm、3μm、3.2μm、3.5μm、3.75μm、4μm、4.2μm、4.5μm、4.75μm或5μm。所述第二混合浆料经研磨后的D50粒径为0.2μm-5μm，例如0.2μm、0.5μm、0.75μm、1μm、1.2μm、1.5μm、1.75μm、2μm、2.2μm、2.5μm、2.75μm、3μm、3.2μm、3.5μm、3.75μm、4μm、4.2μm、4.5μm、4.75μm或5μm。这样可以保证各原料充分复合，同时可避免各原料的键断裂过多及晶格缺陷过多， 影响制得的磷酸铁锂材料的电化学性能发挥。
本申请实施方式中，在制备第一磷酸铁锂材料和第二磷酸铁锂材料时，所述喷雾干燥的进口温度独立地在150℃-280℃的范围内，例如150℃、160℃、170℃、180℃、190℃、200℃、210℃、220℃、230℃、240℃、250℃、260℃、270℃或280℃；出口温度独立地在80℃-120℃的范围内，例如80℃、90℃、100℃、110℃或120℃。
前述T 1和T 2是制备第一磷酸铁锂材料和第二磷酸铁锂材料中的烧结保温温度。在本申请一些实施方式中，在烧结过程中，温度升至所述T 1和T 2的升温速率可以为2℃/min-10℃/min，例如2℃/min、4℃/min、6℃/min、8℃/min或10℃/min。合适的烧结保温时长(即，t 1、t 2)可使磷酸铁锂材料充分结晶、结晶完整度高。在本申请再一些实施方式中，所述烧结时的保温时长为8h-10h，例如8h、8.2h、8.4h、8.6h、8.8h、9h、9.2h、9.4h、9.6h、9.8h或10h。
本申请第一方面提供的制备磷酸铁锂正极材料的方法，通过调控两种不同形貌的磷酸铁锂材料在制备过程中的烧结温度和时间，可使二者混合成的磷酸铁锂正极材料的压实密度较高，进而通过其制成的电池的电化学性能较优。该制备方法工艺简单，易于操作，适合规模化生产。
本申请第二方面提供了一种正极极片，所述正极极片包括正极集流体和设置在正极集流体表面的正极材料层，该正极材料层包括通过前述方法制得的磷酸铁锂正极材料、导电剂和粘结剂。需要说明的是，该正极材料层中的导电剂和粘结剂均为本领域常规物料，本领域技术人员可以根据实际需要进行选择，此处不再赘述。
其中，上述正极极片的最大压实密度与根据本申请公式计算得到的正极材料的最大压实密度C基本一致。因此可以在不将上述第一、第二磷酸铁锂材料混合成的正极材料制成正极片的情况下，就可根据本申请提供的公式准确预估出该正极材料制成的正极片的最大压实密度，可节省物料和时间。
本申请第三方面提供了一种锂离子电池，该锂离子电池包括正极极片。
其中，该锂离子电池还包括负极极片，以及位于正极极片和负极极片之间的电解液和隔膜。
采用前述压实密度高的正极极片的锂离子电池的放电比容量较高，能量密度也较高。其中，采用前述正极极片的扣式锂离子电池在常温0.1C下的放电比容量可在158mAh/g以上，有些情况下可达160mAh/g以上。
本公开实施例的优点将会在下面的说明书中部分阐明，一部分根据说明书是显而易见的，或者可以通过本公开实施例的实施而获知。
附图说明
图1为实施例1中所用LFP-1材料的扫描电子显微镜(SEM)照片。
图2为实施例1中所用LFP-2材料的SEM照片。
具体实施方式
以下所述是本公开的示例性实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本公开原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本公开的保护范围。
下面结合多个具体实施例对本申请的技术方案进行说明。
实施例1
一种磷酸铁锂正极材料的制备方法，包括以下步骤：
1)制备第一磷酸铁锂材料
a、按Li：Fe的摩尔比为1.03：1称取磷酸铁和锂源(具体为Li 2CO 3)以及碳源(具体为一水合葡萄糖)，其中，碳源的加入量可保证第一磷酸铁锂材料中的碳含量为1.5wt％，将这些原料分散到去离子水中，混合均匀，制成固含量为50wt％的混合浆料；
b、对上述混合浆料进行研磨，研磨后物料的D50粒径约为0.35μm，之后对研磨完成的浆料进行喷雾干燥造粒，其中，喷雾干燥设备的进口温度为200℃，出口温度为105℃；
c、将喷雾干燥得到的造粒粉在氮气气氛下进行烧结，其中，烧结过程中的烧结保温温度T 1为775℃，烧结保温时间t 1为9h，得到形貌呈球形的第一磷酸铁锂材料LFP-1(SEM照片如图1所示)，其粒度D50为4.80μm。将该LFP-1材料制备成正极极片(参照本实施例下述的方法)，测得其最大压实密度A为2.04g/cm 3。
2)制备第二磷酸铁锂材料
其与制备LFP-1的不同之处在于：烧结过程中的烧结保温温度T 2为793℃，烧结保温时间t 2为8.3h；在烧结后还进行气流破碎，得到形貌呈无规则结果的第二磷酸铁锂材料LFP-2(SEM照片如图2所示)，其粒度D50为1.02μm。将该LFP-2材料制备成正极极片，测得其最大压实密度B为2.55g/cm 3。
3)将上述LFP-1与LFP-2以等质量比混合，得到正极材料，根据前述公式C＝0.0847t 1+0.0196T 1-0.0095t 2+0.0261T 2-33.6716计算得到该正极材料的最大压实密度的拟合值C＝2.8991g/cm 3。
将上述正极材料制备成正极片：将该正极材料与粘结剂(具体为聚偏氟乙烯，PVDF)、导电炭黑按90:5:5的质量比混合，向其中加入适量的N-甲基烷酮吡咯(NMP)，混合均匀后，得到正极浆料；将该正极浆料涂覆在涂炭铝箔的一面，干燥后辊压，冲切成直径15mm 的圆片，得到正极极片。测得该正极极片的实际最大压实密度为2.88g/cm 3，与根据本申请公式计算得到的正极材料的压实密度C基本一致。
一种锂离子电池的制备：以上述正极材料制成的正极极片作正极，以金属锂片作负极，采用聚丙烯膜作隔膜，含1.0mol/L LiPF 6的碳酸乙烯酯(EC)：碳酸二甲酯(DMC)＝1:1(体积比)的溶液作电解液，在手套箱中组装成扣式电池。
实施例2
一种磷酸铁锂正极材料的制备方法，其与实施例1的区别在于：
制备第一磷酸铁锂材料和第二磷酸铁锂材料所用锂源为LiOH，并且制备第一磷酸铁锂材料和第二磷酸铁锂材料过程中所述混合浆料经研磨后的D50粒径约为0.4μm；在制备第一磷酸铁锂材料LFP-1时，烧结温度T 1为774℃，烧结保温时间t 1为10h，测得LFP-1的粒度D50为5.3μm，其最大压实密度A为2.05g/cm 3；在制备第二磷酸铁锂材料LFP-2时，烧结温度T 2为788℃，烧结保温时间t 2为9.8h，测得LFP-2的粒度D50为1.51μm，其最大压实密度B为2.51g/cm 3。
根据前述公式C＝0.0847t 1+0.0196T 1-0.0095t 2+0.0261T 2-33.6716计算得到实施例2制得的正极材料的最大压实密度的拟合值C＝2.8195g/cm 3。若将该正极材料按照实施例1相同方法制备成正极片，测得其实际最大压实密度为2.81g/cm 3，与公式计算结果基本一致。同时按实施例1相同的方法，将实施例2的正极片组装成扣式电池。
实施例3
一种磷酸铁锂正极材料的制备方法，其与实施例1的区别在于：
制备第一磷酸铁锂材料和第二磷酸铁锂材料过程中所述混合浆料经研磨后的D50粒径约为0.70μm；在制备第一磷酸铁锂材料LFP-1时，烧结温度T 1为770℃，烧结保温时间t 1为9h，测得LFP-1的粒度D50为6.10μm，其最大压实密度A为2.01g/cm 3；在制备第二磷酸铁锂材料LFP-2时，烧结温度T 2为795℃，烧结保温时间t 2为10.4h，测得LFP-2的粒度D50为1.32μm，其最大压实密度B为2.56g/cm 3。
根据前述公式C＝0.0847t 1+0.0196T 1-0.0095t 2+0.0261T 2-33.6716计算得到实施例2制得的正极材料的最大压实密度的拟合值C＝2.8334g/cm 3。若将该正极材料按照实施例1相同方法制备成正极片，测得其实际最大压实密度为2.82g/cm 3，与公式计算结果基本一致。同时按实施例1相同的方法，将实施例3的正极片组装成扣式电池。
实施例4
一种磷酸铁锂正极材料的制备方法，其与实施例1的区别在于：
制备第一磷酸铁锂材料和第二磷酸铁锂材料过程中所述混合浆料经研磨后的D50粒径约为1.24μm；在制备第一磷酸铁锂材料LFP-1时，烧结温度T 1为780℃，烧结保温时间t 1为8.8h，测得LFP-1的粒度D50为5.50μm，其最大压实密度A为2.07g/cm 3；在制备第二磷酸铁锂材料LFP-2时，烧结温度T 2为782℃，烧结保温时间t 2为10.3h，测得LFP-2的粒度D50为1.02μm，其最大压实密度B为2.45g/cm 3。
根据前述公式C＝0.0847t 1+0.0196T 1-0.0095t 2+0.0261T 2-33.6716计算得到实施例2制得的正极材料的最大压实密度的拟合值C＝2.67411g/cm 3。若将该正极材料按照实施例1相同方法制备成正极片，测得其实际最大压实密度为2.65g/cm 3，与公式计算结果基本一致。同时按实施例1相同的方法，将实施例4的正极片组装成扣式电池。
实施例5
一种磷酸铁锂正极材料的制备方法，其与实施例1的区别在于：
制备第一磷酸铁锂材料和第二磷酸铁锂材料过程中混合浆料经研磨后的D50粒径约为1.12μm；在制备第一磷酸铁锂材料LFP-1时，烧结温度T 1为778℃，烧结保温时间t 1为10.6h，测得LFP-1的粒度D50为6.8μm，其最大压实密度A为2.10g/cm 3；在制备第二磷酸铁锂材料LFP-2时，烧结温度T 2为775℃，烧结保温时间t 2为8.6h，测得LFP-2的粒度D50为1.96μm，其最大压实密度B为2.40g/cm 3。
根据前述公式C＝0.0847t 1+0.0196T 1-0.0095t 2+0.0261T 2-33.6716计算得到实施例3制得的正极材料的最大压实密度的拟合值C＝2.62082g/cm 3。若将该正极材料按照实施例1相同方法制备成正极片，测得其实际最大压实密度为2.61g/cm 3，与公式计算结果基本一致。同时按实施例1相同的方法，将实施例3的正极片组装成扣式电池。
对各实施例的扣式电池进行正极材料的放电比容量和首次库伦效率测试，其中，在2.5-3.8V的电压范围之间，以0.1C恒流对扣式电池进行充放电测试。结果汇总在下表1中。
表1
Figure PCTCN2022121210-appb-000001
Figure PCTCN2022121210-appb-000002
由表1可以获知，由于采用本申请实施例的正极材料制成的正极极片的最大压实密度较高，含该正极极片的扣式电池的电化学性能较优异，放电比容量高，利于电池能量密度提高。
以上所述实施例仅表达了本公开的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本公开专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本公开构思的前提下，还可以做出若干变形和改进，这些都属于本公开的保护范围。因此，本公开专利的保护范围应以所附权利要求为准。

Claims (10)

  1. 一种制备磷酸铁锂正极材料的方法，其中，包括以下步骤：
    对磷酸铁、锂源、碳源与溶剂的第一混合浆料依次进行研磨、喷雾干燥和烧结，得到球状形貌的第一磷酸铁锂材料；
    对磷酸铁、锂源、碳源与溶剂的第二混合浆料依次进行研磨、喷雾干燥、烧结和破碎，得到无规则形貌的第二磷酸铁锂材料；
    将所述第一磷酸铁锂材料和第二磷酸铁锂材料等质量比混合，得到磷酸铁锂正极材料；所述磷酸铁锂正极材料的最大压实密度的拟合值记作C，所述C满足以下关系式：
    C＝0.0847t 1+0.0196T 1-0.0095t 2+0.0261T 2-33.6716；
    其中，T 1和t 1分别代表所述第一磷酸铁锂材料的烧结温度和烧结时间，T 2和t 2分别代表所述第二磷酸铁锂材料的烧结温度和烧结时间；所述t 1和所述t 2在7h-11h的范围内，所述T 1在760℃-780℃的范围内，所述T 2在770℃-800℃的范围内；且所述C在2.6g/cm 3以上。
  2. 如权利要求1所述的方法，其中，所述C在2.6g/cm 3-2.85g/cm 3的范围内。
  3. 如权利要求1或2所述的方法，其中，所述第一磷酸铁锂材料的最大压实密度小于所述第二磷酸铁锂材料的最大压实密度。
  4. 如权利要求1-3中任意一项所述的方法，其中，所述第一磷酸铁锂材料的最大压实密度在1.8g/cm 3-2.2g/cm 3的范围内；所述第二磷酸铁锂材料的最大压实密度在2.3g/cm 3-2.6g/cm 3的范围内。
  5. 如权利要求1-4中任意一项所述的方法，其中，所述第一磷酸铁锂材料D50粒径为3μm-10μm。
  6. 如权利要求1-5中任意一项所述的方法，其中，所述第二磷酸铁锂材料的D50粒径为0.5μm-3μm。
  7. 如权利要求1-6中任意一项所述的方法，其中，所述第一混合浆料或所述第二混合浆料经研磨后的D50粒径在0.2μm-5μm的范围内。
  8. 如权利要求1-7任意一项所述的方法，其中，所述第一混合浆料或第二混合浆料中，所述锂源中锂元素的摩尔量是所述磷酸铁的摩尔量的1.00-1.05倍。
  9. 一种正极极片，其中，所述正极极片含有权利要求1-9任意一项所述的方法制得的磷酸铁锂正极材料。
  10. 一种锂离子电池，其中，所述锂离子电池包括权利要求9所述的正极极片。
PCT/CN2022/121210 2021-09-26 2022-09-26 制备磷酸铁锂正极材料的方法、正极极片及锂离子电池 WO2023046137A1 (zh)

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