WO2023169211A1 - 磷酸铁锂正极活性材料及其制备方法、锂离子电池 - Google Patents

磷酸铁锂正极活性材料及其制备方法、锂离子电池 Download PDF

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WO2023169211A1
WO2023169211A1 PCT/CN2023/077668 CN2023077668W WO2023169211A1 WO 2023169211 A1 WO2023169211 A1 WO 2023169211A1 CN 2023077668 W CN2023077668 W CN 2023077668W WO 2023169211 A1 WO2023169211 A1 WO 2023169211A1
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iron phosphate
lithium iron
active material
lithium
positive electrode
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PCT/CN2023/077668
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English (en)
French (fr)
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温鑫
高青青
陈三志
郝嵘
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比亚迪股份有限公司
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Publication of WO2023169211A1 publication Critical patent/WO2023169211A1/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
    • H01M4/58—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
    • 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
    • H01M4/136—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
    • H01M4/36—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
    • 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 field of lithium-ion batteries, specifically to lithium iron phosphate cathode active materials and preparation methods thereof, and lithium-ion batteries.
  • Lithium iron phosphate materials are widely used because of their high safety, low price, and environmental friendliness.
  • lithium iron phosphate materials have an obvious shortcoming.
  • Their maximum compacted density (2.1-2.5g/cm 3 ) is small.
  • batteries made of lithium iron phosphate materials have low energy density and cannot meet the market's demand for battery life.
  • highly compacted lithium iron phosphate materials are currently the mainstream development direction in the industry.
  • increasing the compaction density is often accompanied by a decrease in the electrochemical performance of the battery.
  • this application provides a lithium iron phosphate cathode active material and a preparation method thereof, and a lithium ion battery.
  • the two materials can be mixed in any proportion.
  • the compacted density of the positive active material is higher, and the electrochemical performance of the battery is better.
  • the application provides a lithium iron phosphate cathode active material, which is formed by mixing a first lithium iron phosphate material and a second lithium iron phosphate material; wherein, the third lithium iron phosphate cathode active material is formed by mixing a first lithium iron phosphate material and a second lithium iron phosphate material.
  • the corresponding particle size when the volume distribution percentage of the first lithium iron phosphate material reaches the maximum is D 1 mo ⁇ m, 0.3 ⁇ D 1 mo ⁇ 3.2.
  • the corresponding particle size when the volume distribution percentage of the second lithium iron phosphate material reaches the maximum is D 2 mo ⁇ m, 1 ⁇ D 2 mo ⁇ 5, and D 1 mo ⁇ D 2 mo ;
  • the particle size distribution dispersion of the first lithium iron phosphate material is A 1
  • the particle size distribution of the second lithium iron phosphate material is The degree of dispersion is A 2 , 1 ⁇ A 1 ⁇ 3, 2 ⁇ A 2 ⁇ 4
  • the D 1 mo and the A 1 satisfy the relationship range: 4.07 ⁇ A 1 ⁇ (2.31+D 1 mo ) ⁇ 16
  • the D 2 mo and the A 2 satisfy the following relationship range: -0.4 ⁇ A 2 ⁇ (D 2 mo -1.15) ⁇ 14.
  • the maximum compacted density of the pole piece containing the positive active material can be above 2.6g/ cm3 , and at the same time, the electrochemical performance of the battery is excellent.
  • the lithium iron phosphate cathode active material provided in the embodiments of the present application can be obtained by limiting the range of the particle diameter D mo of the two lithium iron phosphate materials that constitute it, the range of the particle size distribution dispersion A, and the range of the relationship between D mo and A. It ensures that the positive electrode active material formed by mixing the two lithium iron phosphate materials in any proportion has a high compacted density, and the compacted density can reach more than 2.6g/ cm3 , which helps to improve the pass-through rate.
  • the battery made of the cathode active material has excellent electrochemical performance, especially its cycle performance is good.
  • the value range of D 1 mo is: 0.31 ⁇ D 1 mo ⁇ 2.5.
  • the value range of D 1 mo is: 0.35 ⁇ D 1 mo ⁇ 2.46.
  • the value range of D 2 mo is: 1.2 ⁇ D 2 mo ⁇ 4.5.
  • the value range of D 2 mo is: 1.25 ⁇ D 2 mo ⁇ 4.48.
  • the mixing mass ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1: (0.4-4).
  • the mixing mass ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1: (0.6-2.5).
  • the mixing mass ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1: (1-2.5).
  • the surfaces of the first lithium iron phosphate material and the second lithium iron phosphate material have a carbon coating layer.
  • the D 1 mo and the A 1 satisfy the following relationship range: 4.08 ⁇ A 1 ⁇ (2.31+D 1 mo ) ⁇ 15.9.
  • the D 1 mo and the A 1 satisfy the following relationship range: 4.11 ⁇ A 1 ⁇ (2.31+D 1 mo ) ⁇ 15.86.
  • the D 2 mo and the A 2 satisfy the following relationship range: -0.38 ⁇ A 2 ⁇ (D 2 mo -1.15) ⁇ 13.95.
  • the lithium iron phosphate positive active material provided in the first aspect of this application is made by mixing two lithium iron phosphate materials that meet specific particle size parameter requirements in any proportion, and the positive electrode sheet made of the positive active material is compacted
  • the density is high, and the battery can also take into account good cycle performance, rate performance, etc.
  • a second aspect of this application provides a method for preparing a lithium iron phosphate cathode active material, including: providing a first lithium iron phosphate material and a second lithium iron phosphate material, wherein the volume distribution percentage of the first lithium iron phosphate material The corresponding particle diameter when reaching the maximum is D 1 mo ⁇ m, 0.3 ⁇ D 1 mo ⁇ 3.2.
  • the corresponding particle diameter when the volume distribution percentage of the second lithium iron phosphate material reaches the maximum is D 2 mo ⁇ m, 1 ⁇ D 2 mo ⁇ 5, and D 1 mo ⁇ D 2 mo ;
  • the particle size distribution dispersion of the first lithium iron phosphate material is A 1
  • the particle size distribution dispersion of the second lithium iron phosphate material is A 2 , where, 1 ⁇ A 1 ⁇ 3, 2 ⁇ A 2 ⁇ 4, and the D 1 mo and the A 1 satisfy the following relationship range: 4.07 ⁇ A 1 ⁇ (2.31+D 1 mo ) ⁇ 16, the D 2 mo and the A 2 satisfies the following relationship range: -0.4 ⁇ A 2 ⁇ (D 2 mo -1.15) ⁇ 14, and the first lithium iron phosphate material and the second lithium iron phosphate material are mixed to obtain iron phosphate Lithium cathode active material.
  • the above-mentioned preparation method of lithium iron phosphate cathode active material mixes two lithium iron phosphate materials that meet specific particle size parameter requirements in any proportion, which can ensure that the compacted density of the resulting cathode active material is relatively high, and is made of the cathode active material.
  • the battery can also take into account good cycle performance, rate performance, etc.
  • the preparation method has a simple process, is easy to operate, and is suitable for large-scale production.
  • the third aspect of this application provides a lithium-ion battery.
  • the lithium-ion battery includes a positive electrode sheet.
  • the positive electrode sheet contains the lithium iron phosphate positive active material as described in the first aspect of this application, or contains the lithium iron phosphate positive electrode active material as described in the first aspect of this application.
  • Lithium iron phosphate cathode active material prepared by the preparation method described in the second aspect.
  • the lithium ion battery further includes a negative electrode plate, an electrolyte and a separator located between the positive electrode plate and the negative electrode plate.
  • the positive electrode sheet includes a positive current collector and a positive active material layer disposed on a surface of the positive current collector.
  • the cathode active material layer includes the lithium iron phosphate cathode active material, a binder, and a conductive agent.
  • the positive electrode current collector includes one of aluminum foil, carbon-coated aluminum foil, and perforated aluminum foil.
  • the conductive agent includes at least one of carbon nanotubes, graphene, carbon black, and carbon fibers.
  • the maximum compacted density of the positive electrode piece is greater than 2.6g/cm 3 .
  • Lithium-ion batteries using the aforementioned positive electrode plates have high energy density and excellent cycle performance.
  • Figure 1 is the cycle performance curve of each soft pack battery in Examples 1-5 and Comparative Examples 1-2 of the present application.
  • Figure 2 is a flow chart of a method for preparing a lithium iron phosphate cathode active material according to an embodiment of the present application.
  • This application provides a lithium iron phosphate cathode active material, a preparation method thereof, and a lithium ion battery.
  • the cathode active material can be mixed in any proportion.
  • the compacted density is higher, and the electrochemical performance of the battery is better.
  • the application provides a lithium iron phosphate cathode active material, which is formed by mixing a first lithium iron phosphate material and a second lithium iron phosphate material; wherein the volume distribution percentage of the first lithium iron phosphate material The corresponding particle diameter when reaching the maximum is D 1 mo ⁇ m, 0.3 ⁇ D 1 mo ⁇ 3.2.
  • the corresponding particle diameter when the volume distribution percentage of the second lithium iron phosphate material reaches the maximum is D 2 mo ⁇ m, 1 ⁇ D 2 mo ⁇ 5, and D 1 mo ⁇ D 2 mo ;
  • the particle size distribution dispersion of the first lithium iron phosphate material is A 1
  • the particle size distribution dispersion of the second lithium iron phosphate material is A 2 , 1 ⁇ A 1 ⁇ 3, 2 ⁇ A 2 ⁇ 4;
  • the D 1 mo and the A 1 satisfy the following relationship range: 4.07 ⁇ A 1 ⁇ (2.31 + D 1 mo ) ⁇ 16, the D 2 mo and the It is said that A 2 satisfies the following relational range: -0.4 ⁇ A 2 ⁇ (D 2 mo -1.15) ⁇ 14.
  • the maximum compacted density of the pole piece containing the positive active material can be above 2.6g/ cm3 , and at the same time, the electrochemical performance of the battery is excellent.
  • the lithium iron phosphate cathode active material provided in this application can ensure that by limiting the D mo range of the two lithium iron phosphate materials that constitute it, the range of the particle size distribution dispersion A, and the related relationship between D mo and A,
  • the compacted density of the positive electrode sheet made of the positive electrode active material mixed with the two lithium iron phosphate materials in any proportion is relatively high, which can be above 2.6g/ cm3 , which helps to improve the battery made of the positive electrode active material. energy density.
  • the electrochemical performance of the battery made of the cathode active material is relatively excellent, especially its cycle performance.
  • 4.08 ⁇ A 1 ⁇ (2.31+D 1 mo ) ⁇ 15.9; in some embodiments, A 1 ⁇ (2.31+D 1 mo ) can be in the range of 4.11-15.86.
  • the D 1 mo value of the first lithium iron phosphate material and the D 2 mo value of the second lithium iron phosphate material can be obtained respectively through their laser particle size distribution diagrams.
  • the specific testing instrument is a laser particle size analyzer (such as Malvern 3000), the test method can be found in GB/T 19077-2016/ISO 13320:2009 Particle size distribution laser diffraction method.
  • D 1 90 represents the particle size value corresponding to the laser particle size distribution diagram of the first lithium iron phosphate material when the volume cumulative distribution percentage reaches 90%
  • D 1 10 represents the volume cumulative distribution percentage of the first lithium iron phosphate material reaches 10 %
  • D 1 50 represents the corresponding particle diameter value when the volume cumulative distribution percentage of the first lithium iron phosphate material reaches 50%.
  • D 2 90 , D 2 10 , and D 2 50 respectively represent the corresponding particle sizes in the laser particle size distribution diagram of the second lithium iron phosphate material when the cumulative volume distribution percentage reaches 90%, 10%, and 50% respectively. value.
  • the D 1 90 , D 1 10 , and D 1 50 values of the above-mentioned first lithium iron phosphate material and the D 2 90 , D 2 10 , and D 2 50 values of the second lithium iron phosphate material can also be determined through their laser particle size distribution diagrams. It is understood that the test method can be found in GB/T 19077-2016/ISO 13320:2009 Particle size distribution laser diffraction method.
  • D 1 mo ⁇ D 2 mo the lithium ion diffusion path of the lithium iron phosphate material with small D 1 mo is relatively small, which has better electrical performance of the battery produced, and the iron phosphate material with large D 2 mo Lithium materials are more conducive to increasing the compaction density of cathode active materials.
  • the D mo particle sizes of the two are within the above range, and combined with the above ranges of A 1 and A 2 and the relationship between them, these two lithium iron phosphates can be guaranteed
  • the materials can form a tight packing when mixed in any proportion, increasing the compaction density of the cathode sheet made from the resulting cathode active material without compromising the cycle performance of the battery.
  • the value range of D 1 mo may be: 0.31 ⁇ D 1 mo ⁇ 2.5. Furthermore, the value range of D 1 mo is: 0.35 ⁇ D 1 mo ⁇ 2.46.
  • the value range of D 2 mo may be: 1.2 ⁇ D 2 mo ⁇ 5. Furthermore, the value range of D 2 mo is The range is: 1.2 ⁇ D 2 mo ⁇ 4.5; further, the value range of D 2 mo is: 1.25 ⁇ D 2 mo ⁇ 4.48.
  • the two lithium iron phosphate materials can better ensure the high compaction density of the positive electrode and the good battery capacity. chemical properties.
  • the mixing mass ratio of the above-mentioned first lithium iron phosphate material and the second lithium iron phosphate material can be any ratio, so as to ensure the maximum compaction density of the cathode plate made from the lithium iron phosphate cathode active material. Higher, the cycle performance of the battery is better.
  • the mixing mass ratio of the first lithium iron phosphate material and the second lithium iron phosphate material can be in the range of 1: (0.4-4), and further can be in the range of 1: (0.6-2.5) Range, for example, in the range of 1: (1-2.5). At this time, the positive active material mixed with these two lithium iron phosphate materials can better ensure the high compaction density of the pole piece and the good cycle performance of the battery.
  • the surfaces of the first lithium iron phosphate material and the second lithium iron phosphate material can be provided with a carbon coating layer, which can be sequentially processed by mixing a slurry of a phosphorus source, an iron source, a lithium source, and a carbon source. Obtained by sanding, spray drying and sintering.
  • This application does not limit the specific preparation methods of these two lithium iron phosphate materials.
  • the existence of the carbon coating layer allows the first and second lithium iron phosphate materials to have good conductivity and less side reactions with the electrolyte.
  • the positive electrode active material obtained by mixing the two has better conductivity and improves battery cycle performance. better.
  • the lithium iron phosphate positive active material provided in the first aspect of this application is made by mixing two lithium iron phosphate materials that meet specific particle size parameter requirements in any proportion, and the positive electrode sheet made of the positive active material is compacted
  • the density is high, and the battery can also take into account good cycle performance, rate performance, etc.
  • the second aspect of this application provides a method for preparing a lithium iron phosphate cathode active material, as shown in Figure 2, including: S101, providing a first lithium iron phosphate material and a second lithium iron phosphate material, wherein the first The corresponding particle size when the volume distribution percentage of the lithium iron phosphate material reaches the maximum is D 1 mo ⁇ m, 0.3 ⁇ D 1 mo ⁇ 3.2.
  • the corresponding particle size when the volume distribution percentage of the second lithium iron phosphate material reaches the maximum is D 2 mo ⁇ m, 1 ⁇ D 2 mo ⁇ 5, and D 1 mo ⁇ D 2 mo ;
  • the particle size distribution dispersion of the first lithium iron phosphate material is A 1
  • the particle size distribution of the second lithium iron phosphate material is discrete
  • the degree is A 2 , where 1 ⁇ A 1 ⁇ 3, 2 ⁇ A 2 ⁇ 4, and the D 1 mo and the A 1 satisfy the following relationship range: 4.07 ⁇ A 1 ⁇ (2.31+D 1 mo ) ⁇ 16, the D 2 mo and the A 2 satisfy the following relationship range: -0.4 ⁇ A 2 ⁇ (D 2 mo -1.15) ⁇ 14, and, S102, combine the first lithium iron phosphate material and the third Lithium iron phosphate diphosphate materials are mixed to obtain lithium iron phosphate cathode active material.
  • the above-mentioned preparation method of lithium iron phosphate cathode active material mixes two lithium iron phosphate materials that meet specific particle size parameter requirements in any proportion, which can ensure that the compacted density of the resulting cathode active material is relatively high, and is made of the cathode active material.
  • the battery can also take into account good cycle performance, rate performance, etc.
  • the preparation method has a simple process, is easy to operate, and is suitable for large-scale production.
  • a positive electrode sheet, the positive electrode sheet contains the lithium iron phosphate positive electrode active material as described in the first aspect of the application, or contains the lithium iron phosphate positive electrode active material prepared by the preparation method as described in the second aspect of the application. .
  • the positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector.
  • the positive active material layer includes the above-mentioned lithium iron phosphate positive active material, a binder, and a conductive agent.
  • the maximum compacted density of the positive electrode piece is above 2.6 g/cm 3 . In some embodiments, the maximum compacted density is 2.62-2.8g/cm 3 , and further may be 2.65-2.75g/cm 3 . It should be noted that the maximum compaction density of the positive electrode sheet refers to the compaction density of the positive electrode sheet when the active material particles in the positive electrode sheet are crushed until they are crushed under a certain pressure.
  • the cathode material layer may be formed by coating a cathode slurry containing a lithium iron phosphate cathode active material, a conductive agent, a binder and a solvent on the cathode current collector.
  • the solvent may be one or more of N-methylpyrrolidone (NMP), acetone, and dimethylacetamide (DMAC).
  • NMP N-methylpyrrolidone
  • DMAC dimethylacetamide
  • the positive electrode current collector includes any one of aluminum foil, carbon-coated aluminum foil, and perforated aluminum foil.
  • the conductive agent includes but is not limited to one or more of carbon nanotubes, graphene, carbon black and carbon fiber.
  • Binders include but are not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylate, polyacrylonitrile (PAN), sodium carboxymethylcellulose (CMC), sodium alginate, etc.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVA polyvinyl alcohol
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAN polyacrylate
  • PAN polyacrylonitrile
  • CMC sodium carboxymethylcellulose
  • alginate sodium alginate
  • a third aspect of the present application provides a lithium-ion battery, which includes the positive electrode sheet described in the third aspect of the present application.
  • the lithium ion battery further includes a negative electrode plate, an electrolyte and a separator located between the positive electrode plate and the negative electrode plate.
  • Lithium-ion batteries using the aforementioned positive electrode plates have high energy density and excellent cycle performance.
  • a method for preparing a lithium iron phosphate cathode active material including the following steps:
  • the above-mentioned lithium iron phosphate cathode active material LFP-3 is prepared into a cathode plate: the LFP-3 material is mixed with the conductive agent-carbon nanotube, the binder (specifically polyvinylidene fluoride (PVDF)), and the solvent N-methyl Alkanonepyrrole (NMP) is mixed at a mass ratio of 100:3:2:60. After mixing evenly, a positive electrode slurry is obtained; the positive electrode slurry is coated on both sides of the carbon-coated aluminum foil and dried to obtain an area density of 360g. /m 2 double-sided positive electrode piece. Test the maximum compacted density of the positive electrode piece without breaking the particles. The maximum compacted density of the positive electrode piece is 2.70g/cm 3 .
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • a method for preparing a lithium iron phosphate cathode active material The difference from Example 1 is that LFP-1 material and LFP-2 material are mixed in a mass ratio of 4:6. Other steps are the same as in Example 1 to obtain lithium iron phosphate cathode active material LFP-3.
  • the lithium iron phosphate positive active material LFP-3 obtained in Example 2 was made into a positive electrode sheet, and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Example 2 was measured to be 2.68g/cm 3 .
  • a method for preparing lithium iron phosphate cathode active material including:
  • the lithium iron phosphate positive active material LFP-3 obtained in Example 3 was made into a positive electrode sheet, and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Example 3 was measured to be 2.73g/cm 3 .
  • a method for preparing lithium iron phosphate cathode active material including:
  • the lithium iron phosphate cathode active material LFP-3 obtained in Example 4 was made into a cathode sheet, and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Example 4 was measured to be 2.68g/cm 3 .
  • a method for preparing lithium iron phosphate cathode active material including:
  • the lithium iron phosphate cathode active material LFP-3 obtained in Example 5 was made into a cathode sheet, and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Example 5 was measured to be 2.65g/cm 3 .
  • a method for preparing lithium iron phosphate cathode active material including:
  • the lithium iron phosphate cathode active material LFP-3 obtained in Example 6 was made into a cathode sheet, and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Example 6 was measured to be 2.66g/cm 3 .
  • a method for preparing lithium iron phosphate cathode active material including:
  • the lithium iron phosphate cathode active material LFP-3 obtained in Example 7 was made into a cathode sheet, and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Example 7 was measured to be 2.65g/cm 3 .
  • a method for preparing lithium iron phosphate cathode active material including:
  • the lithium iron phosphate cathode active material LFP-3 obtained in Example 1 was made into a cathode sheet and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Comparative Example 1 was measured to be 2.58g/cm 3 .
  • a lithium iron phosphate cathode material uses only one lithium iron phosphate material as the cathode active material. When its volume distribution percentage reaches the maximum, the corresponding particle size is 0.31 ⁇ m, and the particle size distribution dispersion A is 1.92.
  • the lithium iron phosphate cathode material obtained in Comparative Example 2 was made into cathode plates and assembled into a lithium-ion soft-pack battery.
  • the maximum compacted density of the soft-pack battery was 2.55g/cm 3 .
  • a method for preparing lithium iron phosphate cathode active material including:
  • the second lithium iron phosphate material LFP-2 is selected, and the corresponding particle size when its volume distribution percentage reaches the maximum is 5.11 ⁇ m (that is, D 2 mo is 5.11), which is not within the range of (1,5) required by this application.
  • the positive active material LFP-3 obtained in Example 3 was made into a positive electrode sheet and assembled into a soft pack battery.
  • the maximum compacted density of the positive electrode piece of Comparative Example 3 was measured to be 2.63g/cm 3 .
  • the maximum compacted density of the positive electrode plate of Comparative Example 3 can reach more than 2.6g/ cm3 , the battery has poor charge and discharge cycle stability.
  • Table 1 below the first Coulombic efficiency, first discharge specific capacity, and capacity retention rate after 1,000 cycles of the battery of the positive electrode plate of Comparative Example 3 are all lower than those of Example 1.
  • a method for preparing lithium iron phosphate cathode active material including:
  • the lithium iron phosphate cathode active material LFP-3 obtained in Example 4 was made into cathode sheets and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Comparative Example 4 was measured to be only 2.57g/cm 3 .
  • a method for preparing lithium iron phosphate cathode active material including:
  • the corresponding particle size is 3.1 ⁇ m (that is, D 1 mo is 3.1).
  • the distribution dispersion A1 is 2.58 , A1 2 mo is 5.23), which is not within the range of (1,5) required by this application.
  • the lithium iron phosphate cathode active material LFP-3 obtained in Example 5 was made into a cathode sheet and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Comparative Example 5 was measured to be 2.62g/cm 3 . Although the maximum compacted density of the positive electrode plate of Comparative Example 5 can reach more than 2.6g/ cm3 , the battery has poor charge and discharge cycle stability. Referring to Table 1 below, the first Coulombic efficiency, first discharge specific capacity, and capacity retention rate after 1,000 cycles of the battery of the positive electrode plate of Comparative Example 5 are all lower than those of Example 1.
  • a method for preparing lithium iron phosphate cathode active material including:
  • the lithium iron phosphate cathode active material LFP-3 obtained in Example 6 was made into a cathode sheet and assembled into a lithium ion soft pack battery.
  • the maximum compacted density of the positive electrode piece of Comparative Example 6 was measured to be 2.54g/cm 3 .
  • Comparative Example 2 which only uses one kind of lithium iron phosphate material as the positive active material, although the battery has better charge and discharge cycle performance, the maximum compaction density of the electrode piece is low. It is not conducive to the improvement of battery energy density.
  • the compacted density of the positive electrode sheet made of the resulting positive electrode active material is higher, which can be above 2.6g/ cm3 , and some can reach 2.65-2.75g.
  • the battery has excellent electrochemical properties, high first discharge specific capacity, high first Coulombic efficiency, and cycle performance that can match the cycle performance of the battery with low compaction density in Comparative Example 2 (Examples 1-7) .
  • the compacted density of the positive electrode active materials obtained by mixing two raw materials that do not meet the specific requirements of this application is either too low, such as Comparative Examples 1-2, 4, and 6. Or even if the compacted density can sometimes reach more than 2.6g/ cm3 , the charge and discharge cycle stability of the battery is poor, such as Comparative Examples 3 and 5.
  • the high compacted density of the electrode piece and good cycle performance cannot be taken into account.

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Abstract

一种磷酸铁锂正极活性材料及其制备方法和锂离子电池，该正极活性材料通过第一、第二磷酸铁锂材料混合而成，其中，第一、第二磷酸铁锂材料的体积达到最大时分布百分数对应的粒径分别为D1 moμm、D2 moμm，且0.3≤D1 mo≤3.2，1≤D2 mo≤5，D1 mo＜D2 mo；第一、第二磷酸铁锂材料的粒度分布离散度分别为A1、A2，1≤A1≤3，2≤A2≤4，且4.07＜A1×(2.31+D1 mo)＜16，-0.4＜A2×(D2 mo-1.15)＜14。

Description

磷酸铁锂正极活性材料及其制备方法、锂离子电池
本申请要求于2022年03月07日提交中国专利局、申请号为202210228274.0、申请名称为“一种磷酸铁锂正极活性材料及其制备方法、正极极片及锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及锂离子电池领域，具体涉及磷酸铁锂正极活性材料及其制备方法、锂离子电池。
背景技术
磷酸铁锂材料因具有安全性高、价格低廉、环境友好等优点而得到广泛应用，但磷酸铁锂材料存在一个明显的缺点，其最大压实密度(2.1-2.5g/cm3)较小，导致了由磷酸铁锂材料制成的电池的能量密度偏低，不能满足市场对电池续航能力的需求。为了提升电池的能量密度，高压实的磷酸铁锂材料是目前行业内的主流开发方向。对于高压实的磷酸铁锂材料，在提升其压实密度的同时，却常常伴随着电池的电化学性能的降低。
发明内容
为解决上述技术问题，本申请提供一种磷酸铁锂正极活性材料及其制备方法、锂离子电池，通过调控构成其的两种磷酸铁锂材料的粒径参数可实现二者按任意比例混合成的正极活性材料的压实密度较高，同时电池的电化学性能较优良。
具体地，第一方面，本申请提供了一种磷酸铁锂正极活性材料，该磷酸铁锂正极活性材料通过混合第一磷酸铁锂材料和第二磷酸铁锂材料而形成；其中，所述第一磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D1 moμm，0.3≤D1 mo≤3.2，所述第二磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D2 moμm，1≤D2 mo≤5，且D1 mo＜D2 mo；所述第一磷酸铁锂材料的粒度分布离散度为A1，所述第二磷酸铁锂材料的粒度分布离散度为A2，1≤A1≤3，2≤A2≤4；且所述D1 mo和所述A1满足关系式范围：4.07＜A1×(2.31+D1 mo)＜16，所述D2 mo和所述A2满足以下关系式范围：-0.4＜A2×(D2 mo-1.15)＜14。
含该正极活性材料的极片的最大压实密度可在2.6g/cm3以上，同时电池的电化学性能较优良。
本申请实施例提供的磷酸铁锂正极活性材料，通过限定构成其的两种磷酸铁锂材料的粒径Dmo范围、粒度分布离散度A的范围，及Dmo与A的关系式范围，可保证通过按照任意比例混合这两种磷酸铁锂材料而形成的正极活性材料所制成的正极极片的压实密度较高，压实密度可达到2.6g/cm3以上，有助于提升通过该正极活性材料制成的电池的能量密度。此外，通过该正极活性材料制成的电池的电化学性能优良，特别是其循环性能较好。
在一些实施方式中，所述D1 mo的取值范围为：0.31≤D1 mo≤2.5。
在一些实施方式中，所述D1 mo的取值范围为：0.35≤D1 mo≤2.46。
在一些实施方式中，所述D2 mo的取值范围为：1.2≤D2 mo≤4.5。
在一些实施方式中，所述D2 mo的取值范围为：1.25≤D2 mo≤4.48。
在一些实施方式中，所述第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比在1：(0.4-4)的范围内。
在一些实施方式中，所述第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比在1：(0.6-2.5)的范围内。
在一些实施方式中，所述第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比在1：(1-2.5)的范围内。
在一些实施方式中，第一磷酸铁锂材料和第二磷酸铁锂材料的表面具有碳包覆层。
在一些实施方式中，所述D1 mo和所述A1满足以下关系式范围：4.08≤A1×(2.31+D1 mo)≤15.9。
在一些实施方式中，所述D1 mo和所述A1满足以下关系式范围：4.11≤A1×(2.31+D1 mo)≤15.86。
在一些实施方式中，所述D2 mo和所述A2满足以下关系式范围：-0.38≤A2×(D2 mo-1.15)≤13.95。
本申请第一方面提供的磷酸铁锂正极活性材料，其通过满足特定粒径参数要求的两种磷酸铁锂材料按任意比例混合而成，通过该正极活性材料制成的正极极片的压实密度较高，同时电池还能兼顾良好的循环性能、倍率性能等。
本申请第二方面提供了一种磷酸铁锂正极活性材料的制备方法，包括：提供第一磷酸铁锂材料和第二磷酸铁锂材料，其中，所述第一磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D1 moμm，0.3≤D1 mo≤3.2，所述第二磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D2 moμm，1≤D2 mo≤5，且D1 mo＜D2 mo；所述第一磷酸铁锂材料的粒度分布离散度为A1，所述第二磷酸铁锂材料的粒度分布离散度为A2，其中，1≤A1≤3，2≤A2≤4，且所述D1 mo和所述A1满足以下关系式范围：4.07＜A1×(2.31+D1 mo)＜16，所述D2 mo和所述A2满足以下关系式范围：-0.4＜A2×(D2 mo-1.15)＜14，以及，将所述第一磷酸铁锂材料和第二磷酸铁锂材料混合，得到磷酸铁锂正极活性材料。
上述磷酸铁锂正极活性材料的制备方法，将满足特定粒径参数要求的两种磷酸铁锂材料按任意比例混合，可保证所得正极活性材料的压实密度较高，通过该正极活性材料制成的电池还能兼顾良好的循环性能、倍率性能等。该制备方法该工艺简单，易于操作，适合规模化生产。
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，所述正极极片含有如本申请第一方面所述的磷酸铁锂正极活性材料，或者含有如本申请第二方面所述的制备方法制得的磷酸铁锂正极活性材料。
在一些实施方式中，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。
在一些实施方式中，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活性材料层。
在一些实施方式中，所述正极活性材料层包括所述磷酸铁锂正极活性材料、粘结剂、和导电剂。
在一些实施方式中，所述正极集流体包括铝箔、涂炭铝箔、和打孔铝箔中的一种。
在一些实施方式中，所述导电剂包括碳纳米管、石墨烯、炭黑、和碳纤维中的至少一种。
在一些实施方式中，所述正极极片的最大压实密度大于2.6g/cm3。
采用前述正极极片的锂离子电池的能量密度高，且循环性能还较优异。
附图说明
图1为本申请实施例1-5和对比例1-2的各软包电池的循环性能曲线。
图2为本申请实施例的磷酸铁锂正极活性材料的制备方法的流程图。
具体实施方式
本申请提供一种磷酸铁锂正极活性材料及其制备方法、及锂离子电池，通过调控构成其的两种磷酸铁锂材料的粒径参数可实现二者按任意比例混合成的正极活性材料的压实密度较高，同时电池的电化学性能较优良。
第一方面，本申请提供了一种磷酸铁锂正极活性材料，其通过混合第一磷酸铁锂材料和第二磷酸铁锂材料而形成；其中，所述第一磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D1 moμm，0.3≤D1 mo≤3.2，所述第二磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D2 moμm，1≤D2 mo≤5，且D1 mo＜D2 mo；所述第一磷酸铁锂材料的粒度分布离散度为A1，所述第二磷酸铁锂材料的粒度分布离散度为A2，1≤A1≤3，2≤A2≤4；且所述D1 mo和所述A1满足以下关系式范围：4.07＜A1×(2.31+D1 mo)＜16，所述D2 mo和所述A2满足以下关系式范围：-0.4＜A2×(D2 mo-1.15)＜14。
含该正极活性材料的极片的最大压实密度可在2.6g/cm3以上，同时电池的电化学性能较优良。
本申请提供的磷酸铁锂正极活性材料，通过限定构成其的两种磷酸铁锂材料的Dmo范围、粒度分布离散度A的范围，及相关Dmo与A的关系式范围，可保证通过这两种磷酸铁锂材料按照任意比例混合成的正极活性材料制成的正极极片的压实密度较高，可在2.6g/cm3以上，有助于提升通过该正极活性材料制成的电池的能量密度。此外，通过该正极活性材料制成的电池的电化学性能还较优良，特别是其循环性能。在一些实施方式中，4.08≤A1×(2.31+D1 mo)≤15.9；在一些实施方式中，A1×(2.31+D1 mo)可在4.11-15.86的范围内。
在一些实施方式中，-0.38≤A2×(D2 mo-1.15)≤13.95。
在一些实施方式中，上述第一磷酸铁锂材料的D1 mo数值及第二磷酸铁锂材料的D2 mo数值可分别通过它们的激光粒度分布图获得，具体的测试仪器是激光粒度仪(如马尔文3000)，测试方法可参见GB/T 19077-2016/ISO 13320:2009粒度分布激光衍射法。
在一些实施方式中，第一磷酸铁锂材料的粒度分布离散度A1＝(D1 90-D1 10)/D1 50，第二磷酸铁锂材料的粒度分布离散度A2＝(D2 90-D2 10)/D2 50。其中，D1 90代表第一磷酸铁锂材料的激光粒度分布图中，体积累积分布百分数达到90％时对应的粒径值；D1 10代表第一磷酸铁锂材料的体积累积分布百分数达到10％时对应的粒径值；D1 50代表第一磷酸铁锂材料的体积累积分布百分数达到50％时对应的粒径值。A1值越小，代表第一磷酸铁锂材料的粒度分布离散度越小(或者说粒径分布宽度越窄)，粒度分布集中度约高。类似地，D2 90、D2 10、D2 50分别代表所述第二磷酸铁锂材料的激光粒度分布图中，体积累积分布百分数分别达到90％、10％、50％时对应的粒径值。上述第一磷酸铁锂材料的D1 90、D1 10、D1 50数值及第二磷酸铁锂材料的D2 90、D2 10、D2 50数值也均可通过它们的激光粒度分布图获知，测试方法可参见GB/T 19077-2016/ISO 13320:2009粒度分布激光衍射法。
在一些实施方式中，D1 mo＜D2 mo，D1 mo小的磷酸铁锂材料的锂离子扩散路径相对较小，对制成的电池的电性能较好，D2 mo大的磷酸铁锂材料更利于提升正极活性材料的压实密度，二者的Dmo粒径在上述范围，并配合上述A1、A2的范围及其之间的关系式，可保证这两种磷酸铁锂材料以任意比例混合时均可形成紧密堆积，提高通过所得正极活性材料制成的正极极片的压实密度，且不损害电池的循环性能。
在一些实施方式中，所述D1 mo的取值范围可以为：0.31≤D1 mo≤2.5。进一步地，D1 mo的取值范围为：0.35≤D1 mo≤2.46。
在一些实施方式中，所述D2 mo的取值范围可以为：1.2≤D2 mo≤5。进一步地，D2 mo的取值范 围为：1.2≤D2 mo≤4.5；更进一步地，D2 mo的取值范围为：1.25≤D2 mo≤4.48。
D1 mo、D2 mo的取值在上述范围内且满足D1 mo＜D2 mo时，两种磷酸铁锂材料能更好地保证兼顾正极极片的高压实密度和电池的良好电化学性能。
在一些实施方式中，上述第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比可以是任意比例，就可保证通过磷酸铁锂正极活性材料制得的正极极片的最大压实密度较高、电池的循环性能较好。在一些实施方式中，所述第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比可以在1：(0.4-4)的范围内，进一步地可在1：(0.6-2.5)的范围，例如在1：(1-2.5)的范围。此时，这两种磷酸铁锂材料混合成的正极活性材料能更好地保证兼顾极片的高压实密度和电池的良好循环性能等。
在一些实施方式中，第一磷酸铁锂材料和第二磷酸铁锂材料的表面可以带有碳包覆层，它们可以通过对磷源、铁源、锂源与碳源的混合浆料依次进行砂磨、喷雾干燥和烧结得到。本申请对这两种磷酸铁锂材料的具体制备方法不作限定。碳包覆层的存在，可使第一、第二磷酸铁锂材料具有良好的导电性、与电解液之间的副反应少，二者混合所得正极活性材料的导电性较好，电池循环性能较好。
本申请第一方面提供的磷酸铁锂正极活性材料，其通过满足特定粒径参数要求的两种磷酸铁锂材料按任意比例混合而成，通过该正极活性材料制成的正极极片的压实密度较高，同时电池还能兼顾良好的循环性能、倍率性能等。
本申请第二方面提供了一种磷酸铁锂正极活性材料的制备方法，如图2所示，包括：S101，提供第一磷酸铁锂材料和第二磷酸铁锂材料，其中，所述第一磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D1 moμm，0.3≤D1 mo≤3.2，所述第二磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D2 moμm，1≤D2 mo≤5，且D1 mo＜D2 mo；所述第一磷酸铁锂材料的粒度分布离散度为A1，所述第二磷酸铁锂材料的粒度分布离散度为A2，其中，1≤A1≤3，2≤A2≤4，且所述D1 mo和所述A1满足以下关系式范围：4.07＜A1×(2.31+D1 mo)＜16，所述D2 mo和所述A2满足以下关系式范围：-0.4＜A2×(D2 mo-1.15)＜14，以及，S102，将所述第一磷酸铁锂材料和第二磷酸铁锂材料混合，得到磷酸铁锂正极活性材料。
上述磷酸铁锂正极活性材料的制备方法，将满足特定粒径参数要求的两种磷酸铁锂材料按任意比例混合，可保证所得正极活性材料的压实密度较高，通过该正极活性材料制成的电池还能兼顾良好的循环性能、倍率性能等。该制备方法该工艺简单，易于操作，适合规模化生产。
一种正极极片，所述正极极片含有如本申请第一方面所述的磷酸铁锂正极活性材料，或者含有如本申请第二方面所述的制备方法制得的磷酸铁锂正极活性材料。
在一些实施方式中，该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活性材料层，该正极活性材料层包括上述磷酸铁锂正极活性材料、粘结剂和导电剂。
在一些实施方式中，所述正极极片的最大压实密度在2.6g/cm3以上。在一些实施方式中，该最大压实密度为2.62-2.8g/cm3，进一步地可以在2.65-2.75g/cm3。需要说明的是，正极极片的最大压实密度是指在某一压力下，将正极极片中的活性材料颗粒压至破碎时所对应的极片压实密度。
所述正极材料层可以通过在正极集流体上涂覆含磷酸铁锂正极活性材料、导电剂、粘结剂和溶剂的正极浆料形成。其中，溶剂可以是N-甲基吡咯烷酮(NMP)、丙酮和二甲基乙酰胺(DMAC)中的一种或多种。正极集流体包括铝箔、涂炭铝箔和打孔铝箔中的任意一种。其中，所述导电剂包括但不限于碳纳米管、石墨烯、炭黑和碳纤维等中的一种或多种。所述 粘结剂包括但不限于聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇(PVA)、丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸酯、聚丙烯腈(PAN)、羧甲基纤维素钠(CMC)和海藻酸钠等中的一种或多种。
本申请第三方面提供了一种锂离子电池，该锂离子电池包括如本申请第三方面所述的正极极片。
在一些实施方式中，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。
采用前述正极极片的锂离子电池的能量密度高，且循环性能还较优异。
以下所述是本申请的示例性实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本申请的保护范围。
下面结合多个具体实施例对本申请的技术方案进行说明。
示例性实施例1
一种磷酸铁锂正极活性材料(以下简称正极活性材料)的制备方法，包括以下步骤：
选取第一磷酸铁锂材料LFP-1，LFP-1的体积分布百分数达到最大时对应的粒径为0.31μm，粒度分布离散度为2.22，即D1 mo为0.31，A1为2.22，且A1×(2.31+D1 mo)＝5.82；选取第二磷酸铁锂材料LFP-2，LFP-2的体积分布百分数达到最大时对应的粒径为1.28μm，粒度分布离散度为2.24，即D2 mo为1.28，A2为2.24，且A2×(D2 mo-1.15)＝0.29；
将LFP-1材料与LFP-2材料按2：8的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
将上述磷酸铁锂正极活性材料LFP-3制备成正极极片：将LFP-3材料与导电剂-碳纳米管、粘结剂(具体为聚偏氟乙烯(PVDF))、溶剂N-甲基烷酮吡咯(NMP)按100:3:2:60的质量比混合，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两面，干燥后，制得面密度为360g/m2的双面正极极片。测试该正极极片在颗粒不破碎下的最大压实密度。该正极极片的最大压实密度为2.70g/cm3。
一种锂离子软包电池的制备：提供负极极片，其通过在铜箔上涂布含石墨：导电剂(炭黑)：粘结剂(具体是SBR)：水＝100:2:5:120(质量比)的混合浆料，再经干燥而成；以实施例1的正极活性材料LFP-3制成的正极极片作正极，采用聚丙烯膜作隔膜，含1.0mol/L LiPF6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，组装得到锂离子软包电池。
示例性实施例2
一种磷酸铁锂正极活性材料的制备方法，其与实施例1的不同之处在于：LFP-1材料与LFP-2材料是按4:6的质量比混合。其他步骤与实施例1相同，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将实施例2所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得实施例2正极极片的最大压实密度为2.68g/cm3。
示例性实施例3
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，LFP-1的体积分布百分数达到最大时对应的粒径为3.12μm，粒度分布离散度为2.92，即，D1 mo为3.12，A1为2.92，且A1×(2.31+D1 mo)＝15.86；选取第二磷酸 铁锂材料LFP-2，LFP-2的体积分布百分数达到最大时对应的粒径为4.93μm，粒度分布离散度为3.69，即D2 mo为4.93，A2为3.69，且A2×(D2 mo-1.15)＝13.95；
将LFP-1材料与LFP-2材料按5：5的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将实施例3所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得实施例3正极极片的最大压实密度为2.73g/cm3。
示例性实施例4
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，LFP-1的体积分布百分数达到最大时对应的粒径为1.41μm，粒度分布离散度为2.32，即D1 mo为1.41，A1为2.32，且A1×(2.31+D1 mo)＝8.63；选取第二磷酸铁锂材料LFP-2，LFP-2的体积分布百分数达到最大时对应的粒径为3.36μm，粒度分布离散度为2.58，即D2 mo为3.36，A2为2.58，且A2×(D2 mo-1.15)＝5.70；
将LFP-1材料与LFP-2材料按3：7的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将实施例4所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得实施例4正极极片的最大压实密度为2.68g/cm3。
示例性实施例5
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，其体积分布百分数达到最大时对应的粒径为2.46μm，粒度分布离散度为2.16，即，D1 mo为2.46，A1为2.16，且A1×(2.31+D1 mo)＝10.30；选取第二磷酸铁锂材料LFP-2，其体积分布百分数达到最大时对应的粒径为4.48μm，粒度分布离散度为3.92，即D2 mo为4.48μm，A2为3.92，且A2×(D2 mo-1.15)＝13.05；
将LFP-1材料与LFP-2材料按7：3的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将实施例5所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得实施例5正极极片的最大压实密度为2.65g/cm3。
示例性实施例6
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，其体积分布百分数达到最大时对应的粒径为0.8μm，粒度分布离散度为1.32，即，D1 mo为0.8，A1为1.32，且A1×(2.31+D1 mo)＝4.11；选取第二磷酸铁锂材料LFP-2，其体积分布百分数达到最大时对应的粒径为1.65μm，粒度分布离散度为3.6，即，D2 mo为1.65，A2为3.6，且A2×(D2 mo-1.15)＝1.8；
将LFP-1材料与LFP-2材料按3：7的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将实施例6所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得实施例6正极极片的最大压实密度为2.66g/cm3。
示例性实施例7
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，其体积分布百分数达到最大时对应的粒径为0.64μm，粒度分布离散度为2.8，即，D1 mo为0.64，A1为2.8，且A1×(2.31+D1 mo)＝8.26；选取第二磷酸铁锂材料LFP-2，其体积分布百分数达到最大时对应的粒径为1.02μm，粒度分布离散度为2.94，即， D2 mo为1.02，A2为2.94，且A2×(D2 mo-1.15)＝-0.38；
将LFP-1材料与LFP-2材料按6：4的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法将实施例7所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得实施例7正极极片的最大压实密度为2.65g/cm3。
为突出对本申请的有益效果，设置以下对比例1-6。
示例性对比例1
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，其体积分布百分数达到最大时对应的粒径为0.35μm(即，D1 mo为0.35)，粒度分布离散度A1为1.27，但A1×(2.31+D1 mo)＝3.38，不在本申请要求的(4.07,16)范围内；选取第二磷酸铁锂材料LFP-2，其体积分布百分数达到最大时对应的粒径为1.03μm(即，D2 mo为1.03)，粒度分布离散度A2为3.87，但A2×(D2 mo-1.15)＝-0.46，不在本申请要求的(-0.4,14)范围内；
将LFP-1材料与LFP-2材料按1:1的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将对比例1所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得对比例1正极极片的最大压实密度为2.58g/cm3。
示例性对比例2
一种磷酸铁锂正极材料，仅采用一种磷酸铁锂材料作正极活性材料，其体积分布百分数达到最大时对应的粒径为0.31μm，粒度分布离散度A为1.92。
参照实施例1记载的方法，该对比例2所得磷酸铁锂正极材料制成正极极片，并组装成锂离子软包电池，该软包电池的最大压实密度为2.55g/cm3。
示例性对比例3
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，其体积分布百分数达到最大时对应的粒径为0.35μm(即D1 mo为0.35)，粒度分布离散度A1为1.24，但A1×(2.31+D1 mo)＝3.30，不在本申请要求的(4.07,16)范围内；选取第二磷酸铁锂材料LFP-2，其体积分布百分数达到最大时对应的粒径为5.11μm(即D2 mo为5.11)，不在本申请要求的(1,5)范围内，粒度分布离散度A2为3.78，且A2×(D2 mo-1.15)＝14.97，不在本申请要求的(-0.4,14)范围内；
将LFP-1材料与LFP-2材料按2：8的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将对比例3所得正极活性材料LFP-3制成正极极片，并组装成软包电池。测得对比例3正极极片的最大压实密度为2.63g/cm3。虽然对比例3正极极片的最大压实密度可达到2.6g/cm3以上，但电池的充放电循环稳定性较差。参考下表1，对比例3正极极片的电池的首次库伦效率、首次放电比容量、以及循环1000次容量保持率等数据都低于实施例1。
示例性对比例4
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，其体积分布百分数达到最大时对应的粒径为0.46μm(即，D1 mo为0.46)，粒度分布离散度A1为1.22，但A1×(2.31+D1 mo)＝3.38，不在本申请要求的(4.07,16) 范围内；选取第二磷酸铁锂材料LFP-2，其体积分布百分数达到最大时对应的粒径为1.47μm(即，D2 mo为1.47)，粒度分布离散度A2为2.66，A2×(D2 mo-1.15)＝0.85，在本申请要求的(-0.4,14)范围内；
将LFP-1材料与LFP-2材料按3：7的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将对比例4所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得对比例4正极极片的最大压实密度仅为2.57g/cm3。
示例性对比例5
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，其体积分布百分数达到最大时对应的粒径为3.1μm(即，D1 mo为3.1)，在本申请要求的0.3-3.2μm的范围内，其粒度分布离散度A1为2.58，A1×(2.31+D1 mo)＝13.96；选取第二磷酸铁锂材料LFP-2，其体积分布百分数达到最大时对应的粒径为5.23μm(即，D2 mo为5.23)，不在本申请要求的(1,5)范围内，粒度分布离散度A2为3.29，A2×(D2 mo-1.15)＝13.42，在本申请要求的(-0.4,14)范围内；
将LFP-1材料与LFP-2材料按5：5的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将对比例5所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得对比例5正极极片的最大压实密度为2.62g/cm3。虽然对比例5正极极片的最大压实密度可达到2.6g/cm3以上，但电池的充放电循环稳定性较差。参考下表1，对比例5正极极片的电池的首次库伦效率、首次放电比容量、以及循环1000次容量保持率等数据都低于实施例1。
示例性对比例6
一种磷酸铁锂正极活性材料的制备方法，包括：
选取第一磷酸铁锂材料LFP-1，其体积分布百分数达到最大时对应的粒径为0.54μm(即，D1 mo为0.54)，粒度分布离散度A1为1.87，A1×(2.31+D1 mo)＝5.33；选取第二磷酸铁锂材料LFP-2，其体积分布百分数达到最大时对应的粒径为1.12μm(即，D2 mo为1.12)，粒度分布离散度A2为1.61，不在本申请要求的2-4的范围内，A2×(D2mo-1.15)＝-0.05；
将LFP-1材料与LFP-2材料按6：4的质量比混合，得到磷酸铁锂正极活性材料LFP-3。
参照实施例1记载的方法，将对比例6所得磷酸铁锂正极活性材料LFP-3制成正极极片，并组装成锂离子软包电池。测得对比例6正极极片的最大压实密度为2.54g/cm3。
为对本申请的有益效果进行有力支持，对各实施例和对比例的软包电池进行循环性能测试：在25℃下对各软包电池进行0.5C/0.5C充放电循环测试，电压范围为2.0-3.8V。其中，实施例1-5和对比例1-2的软包电池的循环性能曲线如图1所示。各实施例和对比例的电池的首次库伦效率、首次放电比容量、以及循环1000次容量保持率等数据汇总在下表1中。
表1

由图1及表1可以获知，仅采用一种磷酸铁锂材料作正极活性材料的对比例2，虽然其电池的充放电的循环性能较好，但其极片的最大压实密度较低，不利于电池能量密度的提高。当采用本申请提供的方法将两种磷酸铁锂材料混搭时，所得正极活性材料制成的正极极片的压实密度较高，可在2.6g/cm3以上，有些可达2.65-2.75g/cm3，同时，电池的电化学性能较优异，首次放电比容量高，首次库伦效率高，循环性能可与对比例2中低压实密度的电池循环性能相匹配(实施例1-7)。而采用不符合本申请特定要求的两种原料混合得到的正极活性材料(对比例1、3-6)，其极片压实密度要么过低，例如对比例1-2、4、和6，或者即使压实密度有时可达到2.6g/cm3以上，但电池的充放电循环稳定性较差，例如对比例3和5，总的说来不能兼顾极片高压实密度和良好循环性能。
以上所述仅表达了本申请的几种示例性实施方式，其描述较为具体和详细，但并不能因此而理解为对本申请专利范围的限制。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。因此，本申请专利的保护范围应以所附权利要求为准。

Claims (20)

  1. 一种磷酸铁锂正极活性材料，其特征在于，所述磷酸铁锂正极活性材料通过混合第一磷酸铁锂材料和第二磷酸铁锂材料而形成；
    其中，所述第一磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D1 moμm，0.3≤D1 mo≤3.2，所述第二磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D2 moμm，1≤D2 mo≤5，且D1 mo＜D2 mo；
    所述第一磷酸铁锂材料的粒度分布离散度为A1，所述第二磷酸铁锂材料的粒度分布离散度为A2，其中，1≤A1≤3，2≤A2≤4，
    且所述D1 mo和所述A1满足以下关系式范围：4.07＜A1×(2.31+D1 mo)＜16，所述D2 mo和所述A2满足以下关系式范围：-0.4＜A2×(D2 mo-1.15)＜14。
  2. 如权利要求1所述的磷酸铁锂正极活性材料，其特征在于，所述D1 mo的取值范围为：0.31≤D1 mo≤2.5。
  3. 如权利要求1或2所述的磷酸铁锂正极活性材料，其特征在于，所述D1 mo的取值范围为：0.35≤D1 mo≤2.46。
  4. 如权利要求1-3中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述D2 mo的取值范围为：1.2≤D2 mo≤4.5。
  5. 如权利要求1-4中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述D2 mo的取值范围为：1.25≤D2 mo≤4.48。
  6. 如权利要求1-5中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比在1：(0.4-4)的范围内。
  7. 如权利要求1-6中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比在1：(0.6-2.5)的范围内。
  8. 如权利要求1-7中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比在1：(1-2.5)的范围内。
  9. 如权利要求1-8中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述第一磷酸铁锂材料和所述第二磷酸铁锂材料的表面具有碳包覆层。
  10. 如权利要求1-9中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述D1 mo和所述A1满足以下关系式范围：4.08≤A1×(2.31+D1 mo)≤15.9。
  11. 如权利要求1-10中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述D1 mo和所述A1满足以下关系式范围：4.11≤A1×(2.31+D1 mo)≤15.86。
  12. 如权利要求1-11中任一项所述的磷酸铁锂正极活性材料，其特征在于，所述D2 mo和 所述A2满足以下关系式范围：-0.38≤A2×(D2 mo-1.15)≤13.95。
  13. 一种磷酸铁锂正极活性材料的制备方法，其特征在于，包括：
    提供(S101)第一磷酸铁锂材料和第二磷酸铁锂材料，其中，所述第一磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D1 moμm，0.3≤D1 mo≤3.2，所述第二磷酸铁锂材料的体积分布百分数达到最大时对应的粒径为D2 moμm，1≤D2 mo≤5，且D1 mo＜D2 mo；所述第一磷酸铁锂材料的粒度分布离散度为A1，所述第二磷酸铁锂材料的粒度分布离散度为A2，1≤A1≤3，2≤A2≤4，且所述D1 mo和所述A1满足以下关系式范围：4.07＜A1×(2.31+D1 mo)＜16，所述D2 mo和所述A2满足以下关系式范围：-0.4＜A2×(D2 mo-1.15)＜14；以及
    将(S102)所述第一磷酸铁锂材料和第二磷酸铁锂材料混合，得到磷酸铁锂正极活性材料。
  14. 一种锂离子电池，其特征在于，所述锂离子电池包括正极极片，所述正极极片含有如权利要求1-12中任一项所述的磷酸铁锂正极活性材料，或者，所述正极极片包括通过如权利要求13所述的磷酸铁锂正极活性材料的制备方法制得的磷酸铁锂正极活性材料。
  15. 如权利要求14所述的锂离子电池，其特征在于，所述锂离子电池还包括负极极片，以及位于所述正极极片和所述负极极片之间的电解液和隔膜。
  16. 如权利要求14或15所述的锂离子电池，其特征在于，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活性材料层。
  17. 如权利要求16所述的锂离子电池，其特征在于，所述正极活性材料层包括所述磷酸铁锂正极活性材料、粘结剂、和导电剂。
  18. 如权利要求16或17所述的锂离子电池，其特征在于，所述正极集流体包括铝箔、涂炭铝箔、和打孔铝箔中的一种。
  19. 如权利要求17或18所述的锂离子电池，其特征在于，所述导电剂包括碳纳米管、石墨烯、炭黑、和碳纤维中的至少一种。
  20. 如权利要求14-19中任一项所述的锂离子电池，其特征在于，所述正极极片的最大压实密度大于2.6g/cm3。
PCT/CN2023/077668 2022-03-07 2023-02-22 磷酸铁锂正极活性材料及其制备方法、锂离子电池 WO2023169211A1 (zh)

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JP2017068939A (ja) * 2015-09-29 2017-04-06 株式会社日立製作所 リチウム二次電池
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CN114141990A (zh) * 2021-11-19 2022-03-04 上海纳米技术及应用国家工程研究中心有限公司 一种高压实磷酸铁锂极片的制备方法

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JP2017068939A (ja) * 2015-09-29 2017-04-06 株式会社日立製作所 リチウム二次電池
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