WO2023155704A1 - 正极极片和锂离子电池 - Google Patents

正极极片和锂离子电池 Download PDF

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Publication number
WO2023155704A1
WO2023155704A1 PCT/CN2023/074704 CN2023074704W WO2023155704A1 WO 2023155704 A1 WO2023155704 A1 WO 2023155704A1 CN 2023074704 W CN2023074704 W CN 2023074704W WO 2023155704 A1 WO2023155704 A1 WO 2023155704A1
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Prior art keywords
positive electrode
iron phosphate
range
active material
lithium iron
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PCT/CN2023/074704
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English (en)
French (fr)
Inventor
刘佳敏
陈三志
杜孟衣
郝嵘
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BYD Co Ltd
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BYD Co Ltd
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Priority to KR1020247029760A priority Critical patent/KR20240140979A/ko
Priority to JP2024547934A priority patent/JP2025505287A/ja
Priority to EP23755707.9A priority patent/EP4478452A4/en
Publication of WO2023155704A1 publication Critical patent/WO2023155704A1/zh
Priority to US18/804,688 priority patent/US20240405209A1/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—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
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—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
    • 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 positive pole piece and a lithium-ion battery.
  • Lithium iron phosphate materials are widely used due to their advantages of high safety, low price, and environmental friendliness.
  • lithium iron phosphate materials have obvious disadvantages, that is, the compaction density of lithium iron phosphate materials is small, which leads to The energy density of batteries made of materials is low, which cannot meet the market demand for batteries with high battery life.
  • a lithium iron phosphate material with a high compacted density is required, but while increasing the compacted density of the lithium iron phosphate material, it is often accompanied by a decrease in the electrochemical performance of the battery.
  • the first aspect of the present application provides a positive electrode sheet, including: a positive electrode current collector and a positive electrode active material layer disposed on at least one side surface of the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, the The positive electrode active material includes a first lithium iron phosphate material and a second lithium iron phosphate material; wherein, when the volume cumulative distribution percentage of the first lithium iron phosphate material reaches 50%, the corresponding particle diameter is D 1 v 50 ⁇ m, and the second When the volume cumulative distribution percentage of the lithium iron diphosphate material reaches 50%, the corresponding particle size is D 2 v 50 ⁇ m, the D 1 v 50 is in the range of 0.3-0.95, and the D 2 v 50 is in the range of 1.0-3.5 Inside; when the bulk density of the positive electrode active material reaches the maximum, the corresponding particle size is D mo ⁇ m; wherein, the compacted density of the positive electrode sheet under the pressure of 1.5Mpa is PD g/cm 3 , and
  • the PD is in the range of 2.25-2.85.
  • the PD is in the range of 2.3-2.7.
  • the PD is in the range of 2.35-2.7.
  • the D 1 v 50 of the first lithium iron phosphate material is in the range of 0.35-0.65, and the D 2 v 50 of the second lithium iron phosphate material is in the range of 1.25-2.85. within range.
  • the PD ⁇ D mo is in the range of 0.6-10.5.
  • the D mo is in the range of 0.2-4.5.
  • the D mo is in the range of 0.3-4.2.
  • the corresponding particle size is D v 50 ⁇ m (median particle size), and the D v 50 is in the range of 0.2-3.1.
  • the mixing mass ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1:(1-9).
  • the surface of the first lithium iron phosphate material has a carbon coating layer and/or the surface of the second lithium iron phosphate material has a carbon coating layer.
  • the positive electrode active material layer further includes a binder and a conductive agent, wherein the compacted density of the positive electrode sheet under a pressure of 1.5 Mpa is in the range of 2.25-2.75 g/cm 3 .
  • the positive electrode active material layer is formed by coating a positive electrode slurry containing a positive electrode active material, a conductive agent, a binder and a solvent on a positive electrode current collector.
  • the second aspect of the present application provides a lithium-ion battery, the lithium-ion battery includes the positive electrode sheet as described in the first aspect of the present application.
  • the lithium-ion battery further includes a negative pole piece, and an electrolyte and a diaphragm located between the positive pole piece and the negative pole piece.
  • FIG. 1 is the cycle performance curves of the pouch batteries of Examples 1 to 5 and Comparative Example 1 of the present application.
  • the present application provides a positive electrode sheet and a preparation method thereof, so as to ensure a high compaction density of the positive electrode sheet and make a battery made of it have good electrochemical performance.
  • the first aspect of the present application provides a positive electrode sheet, including: a positive electrode current collector and a positive electrode active material layer disposed on at least one side surface of the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, the The positive electrode active material includes a first lithium iron phosphate material and a second lithium iron phosphate material; wherein, when the volume cumulative distribution percentage of the first lithium iron phosphate material reaches 50%, the corresponding particle diameter is D 1 v 50 ⁇ m, and the second When the volume cumulative distribution percentage of the lithium iron diphosphate material reaches 50%, the corresponding particle size is D 2 v 50 ⁇ m, the D 1 v 50 is in the range of 0.3-0.95, and the D 2 v 50 is in the range of 1.0-3.5 Inside; when the bulk density of the positive electrode active material reaches the maximum, the corresponding particle size is D mo ⁇ m; wherein, the compacted density of the positive electrode sheet under the pressure of 1.5Mpa is PD g/cm 3 , and
  • the present application selects two kinds of lithium iron phosphate materials with different particle sizes, and adjusts the blending ratio of these two kinds of lithium iron phosphate materials so that the particle size D mo of the positive electrode active material obtained after blending and the compaction density of the positive electrode sheet PD satisfies a certain relational expression, which can ensure that the positive electrode sheet has an appropriately high compacted density, and the electrochemical performance (especially its cycle performance) of the battery made of the positive electrode sheet is also relatively good.
  • the particle size D 1 v 50 value of the first lithium iron phosphate material, the particle size D 2 v 50 value of the second lithium iron phosphate material, and the particle size D mo of the positive electrode active material can be obtained through their respective laser particle size distribution diagrams.
  • test method can refer to GB/T 19077-2016/ISO 13320:2009 Particle Size Distribution Laser Diffraction Method.
  • the testing instrument is a laser particle size analyzer (such as Malvern 3000).
  • the particle size corresponding to the volume cumulative distribution percentage of a certain material reaching 50% can also be called the "median particle size" of the material.
  • the aforementioned PD can be obtained by testing the positive pole piece using a tablet press.
  • the PD is in the range of 2.25-2.85.
  • the positive electrode sheet satisfies the PD ⁇ D mo of 0.45-12.38, the positive electrode sheet has a relatively high compaction density and a relatively suitable porosity, and the cycle performance and rate performance of the battery can be better. .
  • the PD is in the range of 2.3-2.7.
  • the PD is in the range of 2.35-2.7.
  • the lithium iron phosphate material with a small particle size D 1 v 50 has a relatively small lithium ion diffusion path, which is good for the electrical performance of the battery made, and the particle size D 2 v 50 large lithium iron phosphate materials are more conducive to improving the compaction of positive active materials Density, the particle size D v 50 of the two is in the above range, through the regulation of the blending ratio of the two, it can ensure that the two lithium iron phosphate materials form a close stack, improve the compaction density of the obtained positive electrode sheet, and do not damage the battery. cycle performance.
  • the D 1 v 50 of the first lithium iron phosphate material is in the range of 0.35-0.65, and the D 2 v 50 of the second lithium iron phosphate material is in the range of 1.25-2.85. within range.
  • the compacted density PD of the positive electrode sheet and the particle size D mo of the positive electrode active material are considered in combination, rather than just pursuing the higher the PD, the better.
  • the size of the particles of the positive electrode active material can affect the electron conductance and ion conductance of the electrode sheet, and D mo can indirectly reflect the content of small particles (or fine powder) in the positive electrode active material particles.
  • D mo can indirectly reflect the content of small particles (or fine powder) in the positive electrode active material particles.
  • 0.45 ⁇ PD ⁇ D mo ⁇ 12.38 it can be ensured that when the positive electrode sheet has an appropriately high compacted density, the overall electronic conductivity and ion conductivity of the positive electrode sheet are relatively good, and the battery can take into account Good cycle performance and rate performance, etc.
  • the PD ⁇ D mo is in the range of 0.6-10.5. At this time, the high compaction density of the positive electrode sheet and the good electrochemical performance of the battery can be better guaranteed.
  • the D mo is in the range of 0.2-4.5.
  • there are a suitable number of small and medium-sized particles in the positive electrode active material which can ensure that the resistance of the diffusion/migration of ions inside and between the particles of the positive electrode active material is small, which is conducive to better performance of the battery. cycle performance.
  • the D mo is in the range of 0.3-4.2.
  • the corresponding particle size is D v 50 ⁇ m (median particle size), and the D v 50 is in the range of 0.2-3.1.
  • the median particle size of the positive electrode active material obtained after mixing is in the above range, which can ensure that the accumulation of the positive electrode active material particles is suitable, the polarization strength of the pole piece is low, the lithium ion transmission speed is high in the battery cycle process, and the energy density of the secondary battery is high. high.
  • the mixing mass ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is not particularly limited, as long as the particle size relationship of the positive electrode active material formed by mixing them satisfies the above relational expression.
  • the mixing mass ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1:(1-9), and further can be in the range of 1:(1-4). scope.
  • the positive electrode 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 surface of the first lithium iron phosphate material has a carbon coating layer and/or the surface of the second lithium iron phosphate material has a carbon coating layer.
  • the mixed slurry of carbon source, lithium source and carbon source is sand-milled, spray-dried and sintered in sequence to obtain a carbon coating layer.
  • the present application does not limit the specific preparation methods of these two lithium iron phosphate materials.
  • the existence of the carbon coating layer can make the first and second lithium iron phosphate materials have good electrical conductivity, less side reactions with the electrolyte, and the positive electrode active material obtained by mixing the two has better electrical conductivity and better battery cycle performance better.
  • the positive electrode sheet provided by the first aspect of the present application is mixed with two kinds of lithium iron phosphate materials that meet the requirements of specific particle size parameters, and the particle size D mo of the positive electrode active material obtained by mixing the two lithium iron phosphate materials is controlled.
  • the compaction density PD satisfies 0.45 ⁇ PD ⁇ D mo ⁇ 12.38, which can ensure that the obtained positive electrode sheet can take into account the high compaction density of the electrode sheet and good electrochemical performance, especially the cycle performance and rate performance.
  • the positive electrode active material layer also includes a binder and a conductive agent, wherein the compacted density of the positive electrode sheet under a pressure of 1.5Mpa can be in the range of 2.25-2.75g/cm 3 .
  • the positive electrode active material layer is formed by coating a positive electrode slurry containing a positive electrode active material, a conductive agent, a binder and a solvent on a positive electrode current collector.
  • the solvent may be one or more of N-methylpyrrolidone (NMP), acetone and dimethylacetamide (DMAC).
  • NMP N-methylpyrrolidone
  • DMAC dimethylacetamide
  • the positive 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 fibers.
  • the binder includes but not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylate, poly Acrylonitrile (PAN), Sodium Carboxymethyl Cellulose (CMC) and one or more of sodium alginate, etc.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVA polyvinyl alcohol
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAN polyacrylate
  • PAN poly Acrylonitrile
  • CMC Sodium Carboxymethyl Cellulose
  • the second aspect of the present application provides a lithium-ion battery, the lithium-ion battery includes the positive electrode sheet as described in the first aspect of the present application.
  • the lithium-ion battery further includes a negative pole piece, and an electrolyte and a diaphragm located between the positive pole piece and the negative pole piece.
  • the lithium-ion battery adopting the aforementioned positive electrode sheet has high energy density and excellent cycle performance.
  • a method for preparing a positive pole piece comprising the following steps:
  • the LFP-1 material and the LFP-2 material at a mass ratio of 2:8 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 1.15 ⁇ m, that is, the D mo is 1.15 .
  • a preparation of a lithium-ion soft pack battery the positive electrode sheet made of the positive electrode active material LFP-3 of Example 1 is used as the positive electrode, the graphite electrode sheet is used as the negative electrode, and the polypropylene film is used as the diaphragm, containing 1.0mol/L LiPF 6
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the LFP-1 material and the LFP-2 material at a mass ratio of 1:9 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 1.68 ⁇ m, that is, the D mo is 1.68 .
  • the positive electrode active material LFP-3 obtained in Example 2 was made into a positive electrode sheet, and the compacted density of the positive electrode sheet under a pressure of 1.5Mpa was measured to be 2.59g/cm 3 , that is, the PD was 2.59, and the PD ⁇ D mo of the positive pole piece is 4.35.
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the first lithium iron phosphate material LFP-1 is selected, and when the volume cumulative distribution percentage reaches 50%, the corresponding particle size is 0.43 ⁇ m, that is, D 1 v 50 is 0.43;
  • the LFP-1 material and the LFP-2 material were mixed in a mass ratio of 3:7 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 0.78 ⁇ m, that is, the D mo is 0.78;
  • the positive electrode active material LFP-3 obtained in Example 3 was made into a positive electrode sheet, and the compacted density of the positive electrode sheet under a pressure of 1.5Mpa was measured to be 2.37g/cm 3 , that is, the PD was 2.37, and the PD ⁇ D mo of the positive pole piece is 1.85.
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the LFP-1 material and the LFP-2 material at a mass ratio of 4:6 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 1.22 ⁇ m, that is, the D mo is 1.22 .
  • the positive electrode active material LFP-3 obtained in Example 4 was made into a positive electrode sheet, and the compacted density of the positive electrode sheet under a pressure of 1.5Mpa was measured to be 2.63g/cm 3 , that is, the PD was 2.63, and the PD ⁇ D mo of the positive pole piece is 3.21.
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the LFP-1 material and the LFP-2 material at a mass ratio of 1:1 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 1.14 ⁇ m, that is, the D mo is 1.14 ;
  • the positive electrode active material LFP-3 obtained in Example 5 was made into a positive electrode sheet, and the compacted density of the positive electrode sheet under a pressure of 1.5Mpa was measured to be 2.67g/cm 3 , that is, the PD was 2.67, and the PD ⁇ D mo of the positive pole piece is 3.04.
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the LFP-1 material and the LFP-2 material at a mass ratio of 2:8 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 3.78 ⁇ m, that is, the D mo is 3.78 ;
  • the positive electrode active material LFP-3 obtained in Example 6 was made into a positive electrode sheet, and the The compacted density of the positive electrode sheet under a pressure of 1.5 MPa was 2.56 g/cm 3 , ie PD was 2.56 g/cm 3 , and the PD ⁇ D mo of the positive electrode sheet was 9.68.
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the LFP-1 material and the LFP-2 material at a mass ratio of 3:7 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 3.89 ⁇ m, that is, the D mo is 3.89 ⁇ m;
  • the positive electrode active material LFP-3 obtained in Example 7 was made into a positive electrode sheet, and the compacted density of the positive electrode sheet under a pressure of 1.5Mpa was measured to be 2.53g/cm 3 , that is, the PD was 2.53g/cm 3 , and the PD ⁇ D mo of the positive pole piece is 9.84.
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the LFP-1 material and the LFP-2 material at a mass ratio of 1:9 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 4.41 ⁇ m, that is, the D mo is 4.41 ⁇ m;
  • the positive electrode active material LFP-3 obtained in Example 8 was made into a positive electrode sheet, and the compacted density of the positive electrode sheet under a pressure of 1.5Mpa was measured to be 2.61g/cm 3 , that is, the PD was 2.61g/cm 3 , and the PD ⁇ D mo of the positive pole piece is 11.51.
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the LFP-1 material and the LFP-2 material at a mass ratio of 3:7 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 4.98 ⁇ m, that is, the D mo is 4.98 ;
  • the positive electrode active material LFP-3 obtained in Comparative Example 1 was made into a positive electrode sheet, and the compacted density of the positive electrode sheet under a pressure of 1.5Mpa was measured to be 2.56g/cm 3 , that is, the PD was 2.56, and the PD ⁇ D mo of the positive pole piece is 12.75, which is not within the range of 0.45-12.38 in this application.
  • a kind of preparation method of positive pole piece, its difference with embodiment 1 is:
  • the first lithium iron phosphate material LFP-1 is selected, and its corresponding particle size is 1.04 ⁇ m when the volume cumulative distribution percentage reaches 50%, that is, D 1 v 50 is 1.04, which is not within the range of 0.3-0.95 defined in this application;
  • the second lithium iron phosphate material LFP-2 is selected, and the corresponding particle size when the volume cumulative distribution percentage reaches 50% is 3.74 ⁇ m, that is, D 1 v 50 is 3.74, which is not within the range of 1.0-3.5 defined in this application;
  • the LFP-1 material and the LFP-2 material at a mass ratio of 8:2 to obtain the positive electrode active material LFP-3.
  • the corresponding particle size is 2.96 ⁇ m, that is, the D mo is 2.96 ⁇ m;
  • the positive electrode active material LFP-3 obtained in Comparative Example 2 was made into a positive electrode sheet, and the compacted density of the positive electrode sheet under a pressure of 1.5Mpa was measured to be 2.53g/cm 3 , that is, the PD was 2.53g/cm 3 , and the PD ⁇ D mo of the positive pole piece is 7.49.
  • Cycle performance 0.5C/0.5C charge-discharge cycle test is carried out on each pouch battery at 25°C. The voltage range is 2.0-3.8V. When charging, first charge at a constant current of 0.5C to 3.8V and then charge at a constant voltage. The cut-off current is 0.05C, and the coulombic efficiency of the first cycle and the capacity retention rate after 1000 charge-discharge cycles are tested.
  • the positive electrode sheet prepared by the method provided by the present application not only has a higher electrode
  • the compaction density of the sheet, and the electrochemical performance of the battery assembled by the positive electrode sheet is relatively excellent, such as the first-cycle Coulombic efficiency can be greater than 96%, the positive electrode has a high gram capacity, and the capacity retention rate after 1000 cycles is still 90% %above.
  • the first-cycle Coulombic efficiency and cycle performance of the battery of Comparative Example 1-2 are poor, far inferior to the battery of the present application.

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Abstract

一种正极极片和包括该正极极片的锂离子电池，该正极极片包括正极集流体和设置在该正极集流体上至少一侧表面的正极活性材料层，该正极活性材料层包括正极活性材料，该正极活性材料包括第一磷酸铁锂材料和第二磷酸铁锂材料；第一磷酸铁锂材料的体积累积分布百分数达到50％时的粒径为D1 v50μm，第二磷酸铁锂材料的体积累积分布百分数达到50％时的粒径为D2 v50μm，D1 v50在0.3-0.95的范围内，D2 v50在1.0-3.5的范围内；正极活性材料的体积密度达到最大时的粒径为Dmoμm，正极极片在1.5Mpa压力下的压实密度为PD g/cm3，且0.45≤PD×Dmo≤12.38。

Description

正极极片和锂离子电池
本申请要求于2022年2月15日提交中国专利局、申请号为202210139512.0、发明名称为“正极极片和锂离子电池”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，具体涉及一种正极极片和锂离子电池。
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明显的缺点，即磷酸铁锂材料的压实密度较小，这导致由磷酸铁锂材料制成的电池的能量密度较低，无法满足市场对高续航能力电池的需求。为了提高电池的能量密度，需要具有高压实密度的磷酸铁锂材料，但是在提高磷酸铁锂材料的压实密度的同时，常伴随着电池电化学性能的降低。
发明内容
本申请第一方面提供了一种正极极片，包括：正极集流体和设置在所述正极集流体至少一侧表面上的正极活性材料层，所述正极活性材料层包括正极活性材料，所述正极活性材料包括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累积分布百分数达到50％时对应的粒径为D1 v50μm，所述第二磷酸铁锂材料的体积累积分布百分数达到50％时对应的粒径为D2 v50μm，所述D1 v50在0.3-0.95的范围内，所述D2 v50在1.0-3.5的范围内；所述正极活性材料的体积密度达到最大时对应的粒径为Dmoμm；其中，所述正极极片在1.5Mpa压力下的压实密度为PD g/cm3，且满足：0.45≤PD×Dmo≤12.38。
本申请一些实施方式中，所述PD在2.25-2.85的范围内。
本申请一些实施方式中，所述PD在2.3-2.7的范围内。
本申请一些实施方式中，所述PD在2.35-2.7的范围内。
本申请一些实施方式中，所述第一磷酸铁锂材料的所述D1 v50在0.35-0.65的范围内，所述第二磷酸铁锂材料的所述D2 v50在1.25-2.85的范围内。
本申请一些实施方式中，所述PD×Dmo在0.6-10.5的范围内。
本申请一些实施方式中，所述Dmo在0.2-4.5的范围内。
本申请一些实施方式中，所述Dmo在0.3-4.2的范围内。
本申请一些实施方式中，所述正极活性材料的体积累积分布百分数达到50％时对应的粒径为Dv50μm(中值粒径)，所述Dv50在0.2-3.1的范围内。
本申请一些实施方式中，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：(1-9)的范围内。
本申请一些实施方式中，所述第一磷酸铁锂材料的表面带有碳包覆层和/或所述第二磷酸铁锂材料的表面带有碳包覆层。
本申请一些实施方式中，所述正极活性材料层还包括粘结剂和导电剂，其中，所述正极极片在1.5Mpa压力下的压实密度在2.25-2.75g/cm3的范围内。
本申请一些实施方式中，所述正极活性材料层通过在正极集流体上涂覆含正极活性材料、导电剂、粘结剂和溶剂的正极浆料形成。
本申请第二方面提供了一种锂离子电池，所述锂离子电池包括如本申请第一方面所述的正极极片。
本申请一些实施方式中，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。
附图说明
图1为本申请实施例1至实施例5和对比例1的各软包电池的循环性能曲线。
具体实施方式
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。
本申请提供一种正极极片及其制备方法，以在保证正极极片的压实密度较高的同时，还使由其制成的电池具有良好的电化学性能。
本申请第一方面提供了一种正极极片，包括：正极集流体和设置在所述正极集流体至少一侧表面上的正极活性材料层，所述正极活性材料层包括正极活性材料，所述正极活性材料包括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累积分布百分数达到50％时对应的粒径为D1 v50μm，所述第二磷酸铁锂材料的体积累积分布百分数达到50％时对应的粒径为D2 v50μm，所述D1 v50在0.3-0.95的范围内，所述D2 v50在1.0-3.5的范围内；所述正极活性材料的体积密度达到最大时对应的粒径为Dmoμm；其中，所述正极极片在1.5Mpa压力下的压实密度为PD g/cm3，且满足：0.45≤PD×Dmo≤12.38。
本申请通过选择不同粒径的两种磷酸铁锂材料，并调整这两种磷酸铁锂材料的掺混比例使掺混后所得正极活性材料的颗粒粒径Dmo与正极极片的压实密度PD满足一定关系式，可保证该正极极片在具有适当高的压实密度的同时，通过该正极极片制成的电池的电化学性能(特别是其循环性能)也较优。上述第一磷酸铁锂材料的粒径D1 v50值、第二磷酸铁锂材料的粒径D2 v50值、以及正极活性材料的粒径Dmo均可通过其各自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。测试仪器是激光粒度仪(如马尔文3000)。其中，某一材料的体积累积分布百分数达到50％时对应的粒径又可称为该材料的“中值粒径”。上述PD可通过对正极极片采用压片机测试得到。
本申请一些实施方式中，所述PD在2.25-2.85的范围内。此时，该正极极片在满足PD×Dmo在0.45-12.38的情况下，该正极极片在压实密度较大的同时，孔隙率还较合适，电池的循环性能、倍率性能可更好。
本申请一些实施方式中，所述PD在2.3-2.7的范围内。
本申请一些实施方式中，所述PD在2.35-2.7的范围内。
本申请中，D1 v50＜D2 v50，粒径D1 v50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，粒径D2 v50大的磷酸铁锂材料更利于提高正极活性材料的压实 密度，二者的粒径Dv50在上述范围，通过二者的掺混比例调控，可保证这两种磷酸铁锂材料形成紧密堆积，提高所得正极极片的压实密度，且不损害电池的循环性能。
本申请一些实施方式中，所述第一磷酸铁锂材料的所述D1 v50在0.35-0.65的范围内，所述第二磷酸铁锂材料的所述D2 v50在1.25-2.85的范围内。
本申请中将正极极片的压实密度PD与正极活性材料的粒径Dmo结合考虑，而非仅追求PD越高越好。正极活性材料的颗粒的大小能够影响极片的电子电导和离子电导，Dmo可以间接反映正极活性材料颗粒中小颗粒(或细粉)部分的含量。本申请中通过控制0.45≤PD×Dmo≤12.38，可保证正极极片在具有适当高的压实密度时，该正极极片的整体电子电导性和离子电导性均较优，并且电池能兼顾良好的循环性能和倍率性能等。
本申请一些实施方式中，所述PD×Dmo在0.6-10.5的范围内。此时，能较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。
本申请一些实施方式中，所述Dmo在0.2-4.5的范围内。此时，正极活性材料中具有合适数目的中小颗粒，可保证通过离子在该正极活性材料的颗粒内部及颗粒之间进行扩散/迁移的阻力均较小，利于电池更好地发挥良好的倍率、循环性能。
本申请一些实施方式中，所述Dmo在0.3-4.2的范围内。
本申请一些实施方式中，所述正极活性材料的体积累积分布百分数达到50％时对应的粒径为Dv50μm(中值粒径)，所述Dv50在0.2-3.1的范围内。混合后所得正极活性材料的中值粒径在上述范围，可保证正极活性材料颗粒的堆积情况合适，极片极化强度低、电池循环过程中锂离子传输速度较高，二次电池的能量密度高。
本申请中，对第一磷酸铁锂材料和第二磷酸铁锂材料的混合质量比不做特别限定，只要保证二者混合形成的正极活性材料的粒径关系满足上述关系式即可。
本申请一些实施方式中，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：(1-9)的范围内，进一步地可在1：(1-4)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。
本申请一些实施方式中，所述第一磷酸铁锂材料的表面带有碳包覆层和/或所述第二磷酸铁锂材料的表面带有碳包覆层，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碳包覆层。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正极极片，通过满足特定粒径参数要求的两种磷酸铁锂材料混合，并控制两种磷酸铁锂材料混合所得正极活性材料的颗粒粒径Dmo与正极极片的压实密度PD满足0.45≤PD×Dmo≤12.38，可保证所得正极极片能兼顾较高的极片压实密度和良好的电化学性能，尤其是循环性能和倍率性能。
本申请一些实施方式中，所述正极活性材料层还包括粘结剂和导电剂，其中，所述正极极片在1.5Mpa压力下的压实密度可在2.25-2.75g/cm3的范围内。
本申请一些实施方式中，所述正极活性材料层通过在正极集流体上涂覆含正极活性材料、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。
本申请第二方面提供了一种锂离子电池，所述锂离子电池包括如本申请第一方面所述的正极极片。
本申请一些实施方式中，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。
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。
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
一种正极极片的制备方法，包括以下步骤：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.55μm，即D1 v50为0.55；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为1.35μm，即D1 v50为1.35；
将LFP-1材料与LFP-2材料按2：8的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为1.15μm，即Dmo为1.15。
将上述正极活性材料LFP-3制备成正极极片：将LFP-3材料与粘结剂(具体为聚偏氟乙烯，PVDF)、导电炭黑按85:5:10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两面，干燥后，制得双面正极极片。测得该正极极片在1.5Mpa压力下的压实密度为2.45g/cm3，即PD为2.45，正极极片的PD×Dmo为2.82。
一种锂离子软包电池的制备：以实施例1正极活性材料LFP-3制成的正极极片作正极，以石墨极片作负极，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，组装得到软包电池。
实施例2
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.66μm，即D1 v50为0.66；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为1.75μm，即D1 v50为1.75；
将LFP-1材料与LFP-2材料按1:9的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为1.68μm，即Dmo为1.68。
参照实施例1记载的方法，将实施例2所得正极活性材料LFP-3制成正极极片，测得该正极极片在1.5Mpa压力下的压实密度为2.59g/cm3，即PD为2.59，正极极片的PD×Dmo为4.35。
实施例3
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.43μm，即D1 v50为0.43；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为1.05μm，即D1 v50为1.05；
将LFP-1材料与LFP-2材料按3:7的质量比混合，得到正极活性材料LFP-3。该LFP-3的体积密度达到最大时对应的粒径为0.78μm，即Dmo为0.78；
参照实施例1记载的方法，将实施例3所得正极活性材料LFP-3制成正极极片，测得该正极极片在1.5Mpa压力下的压实密度为2.37g/cm3，即PD为2.37，正极极片的PD×Dmo为1.85。
实施例4
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.35μm，即D1 v50为0.35；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为1.79μm，即D1 v50为1.79；
将LFP-1材料与LFP-2材料按4:6的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为1.22μm，即Dmo为1.22。
参照实施例1记载的方法，将实施例4所得正极活性材料LFP-3制成正极极片，测得该正极极片在1.5Mpa压力下的压实密度为2.63g/cm3，即PD为2.63，正极极片的PD×Dmo为3.21。
实施例5
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.47μm，即D1 v50为0.47；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为1.48μm，即D1 v50为1.48；
将LFP-1材料与LFP-2材料按1:1的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为1.14μm，即Dmo为1.14；
参照实施例1记载的方法，将实施例5所得正极活性材料LFP-3制成正极极片，测得该正极极片在1.5Mpa压力下的压实密度为2.67g/cm3，即PD为2.67，正极极片的PD×Dmo为3.04。
实施例6
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.91μm，即D1 v50为0.91μm；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为2.32μm，即D1 v50为2.32μm；
将LFP-1材料与LFP-2材料按2:8的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为3.78μm，即Dmo为3.78；
参照实施例1记载的方法，将实施例6所得正极活性材料LFP-3制成正极极片，测 得该正极极片在1.5Mpa压力下的压实密度为2.56g/cm3，即PD为2.56g/cm3，正极极片的PD×Dmo为9.68。
实施例7
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.91μm，即D1 v50为0.91μm；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为3.24μm，即D1 v50为3.24μm；
将LFP-1材料与LFP-2材料按3:7的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为3.89μm，即Dmo为3.89μm；
参照实施例1记载的方法，将实施例7所得正极活性材料LFP-3制成正极极片，测得该正极极片在1.5Mpa压力下的压实密度为2.53g/cm3，即PD为2.53g/cm3，正极极片的PD×Dmo为9.84。
实施例8
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.89μm，即D1 v50为0.89μm；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为3.21μm，即D1 v50为3.21μm；
将LFP-1材料与LFP-2材料按1:9的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为4.41μm，即Dmo为4.41μm；
参照实施例1记载的方法，将实施例8所得正极活性材料LFP-3制成正极极片，测得该正极极片在1.5Mpa压力下的压实密度为2.61g/cm3，即PD为2.61g/cm3，正极极片的PD×Dmo为11.51。
为突出对本申请的有益效果，设置以下对比例。
对比例1
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为0.45μm，即D1 v50为0.45；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为3.45μm，即D1 v50为3.45；
将LFP-1材料与LFP-2材料按3:7的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为4.98μm，即Dmo为4.98；
参照实施例1记载的方法，将对比例1所得正极活性材料LFP-3制成正极极片，测得该正极极片在1.5Mpa压力下的压实密度为2.56g/cm3，即PD为2.56，正极极片的PD×Dmo为12.75，不在本申请0.45-12.38的范围内。
对比例2
一种正极极片的制备方法，其与实施例1的不同之处在于：
选取第一磷酸铁锂材料LFP-1，其体积累积分布百分数达到50％时对应的粒径为1.04μm，即D1 v50为1.04，不在本申请定义的0.3-0.95的范围内；
选取第二磷酸铁锂材料LFP-2，其体积累积分布百分数达到50％时对应的粒径为3.74μm，即D1 v50为3.74，不在本申请定义的1.0-3.5的范围内；
将LFP-1材料与LFP-2材料按8:2的质量比混合，得到正极活性材料LFP-3，该LFP-3的体积密度达到最大时对应的粒径为2.96μm，即Dmo为2.96μm；
参照实施例1记载的方法，将对比例2所得正极活性材料LFP-3制成正极极片，测得该正极极片在1.5Mpa压力下的压实密度为2.53g/cm3，即PD为2.53g/cm3，正极极片的PD×Dmo为7.49。
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以下电化学性能测试：
1)循环性能：在25℃下对各软包电池进行0.5C/0.5C充放电循环测试，电压范围是2.0-3.8V，其中充电时先0.5C恒流充电至3.8V再恒压充电，截止电流为0.05C，测试首圈库伦效率和进行1000次充放电循环后的容量保持率。
2)正极活性材料的放克容量：在2.0-3.8V的电压范围内，对各实施例及对比例的正极活性材料以0.1C恒流恒压充电至3.8V，恒压充电时截止电流为0.05C，然后再以0.1C恒流放电到2.0V，重复上述充放电过程3次，将第3次放出的容量记作C0，C0与各例子中LFP-3的质量之比作为各LFP-3发挥的克容量。
其中，实施例1至实施例5和对比例1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圈库伦效率和循环1000次后的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，采用本申请提供的方法制得的正极极片不仅具有较高的极 片压实密度，且通过该正极极片装配成的电池的电化学性能还较优异，如首圈库伦效率可大于96％，正极克容量较高，循环1000圈后的容量保持率仍在90％以上。而对比例1-2的电池的首圈库伦效率和循环性能均较差，远远逊色于本申请电池。
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 (15)

  1. 一种正极极片，其特征在于，包括：
    正极集流体；以及
    设置在所述正极集流体至少一侧表面上的正极活性材料层，所述正极活性材料层包括正极活性材料，所述正极活性材料包括：
    第一磷酸铁锂材料；以及
    第二磷酸铁锂材料；
    其中，所述第一磷酸铁锂材料的体积累积分布百分数达到50％时对应的粒径为D1 v50μm，所述第二磷酸铁锂材料的体积累积分布百分数达到50％时对应的粒径为D2 v50μm，所述D1 v50在0.3-0.95的范围内，所述D2 v50在1.0-3.5的范围内；所述正极活性材料的体积密度达到最大时对应的粒径为Dmoμm；其中，所述正极极片在1.5Mpa压力下的压实密度为PD g/cm3，且满足：0.45≤PD×Dmo≤12.38。
  2. 如权利要求1所述的正极极片，其特征在于，所述PD在2.25-2.85的范围内。
  3. 如权利要求1或2所述的正极极片，其特征在于，所述PD在2.3-2.7的范围内。
  4. 如权利要求1-3中任一项所述的正极极片，其特征在于，所述PD在2.35-2.7的范围内。
  5. 如权利要求1-4中任一项所述的正极极片，其特征在于，所述第一磷酸铁锂材料的所述D1 v50在0.35-0.65的范围内，所述第二磷酸铁锂材料的所述D2 v50在1.25-2.85的范围内。
  6. 如权利要求1-5中任一项所述的正极极片，其特征在于，所述PD×Dmo在0.6-10.5的范围内。
  7. 如权利要求1-6中任一项所述的正极极片，其特征在于，所述Dmo在0.2-4.5的范围内。
  8. 如权利要求1-7中任一项所述的正极极片，其特征在于，所述Dmo在0.3-4.2的范围内。
  9. 如权利要求1-8中任一项所述的正极极片，其特征在于，所述正极活性材料的体积累积分布百分数达到50％时对应的粒径为Dv50μm，所述Dv50在0.2-3.1的范围内。
  10. 如权利要求1-9中任一项所述的正极极片，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质量比在1：(1-9)的范围内。
  11. 如权利要求1-10中任一项所述的正极极片，其特征在于，所述第一磷酸铁锂材料的表面带有碳包覆层和/或所述第二磷酸铁锂材料的表面带有碳包覆层。
  12. 如权利要求1-11中任一项所述的正极极片，其特征在于，所述正极活性材料层还包括粘结剂和导电剂，其中，所述正极极片在1.5Mpa压力下的压实密度在2.25-2.75g/cm3的范围内。
  13. 如权利要求12所述的正极极片，其特征在于，所述正极活性材料层通过在正极集流体上涂覆含正极活性材料、导电剂、粘结剂和溶剂的正极浆料形成。
  14. 一种锂离子电池，其特征在于，所述锂离子电池包括如权利要求1-13任一项所述的正极极片。
  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。
PCT/CN2023/074704 2022-02-15 2023-02-07 正极极片和锂离子电池 Ceased WO2023155704A1 (zh)

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