CN117276498A - Lithium iron phosphate material, preparation method thereof, positive plate and secondary battery - Google Patents

Lithium iron phosphate material, preparation method thereof, positive plate and secondary battery Download PDF

Info

Publication number
CN117276498A
CN117276498A CN202311173774.XA CN202311173774A CN117276498A CN 117276498 A CN117276498 A CN 117276498A CN 202311173774 A CN202311173774 A CN 202311173774A CN 117276498 A CN117276498 A CN 117276498A
Authority
CN
China
Prior art keywords
iron phosphate
lithium iron
lithium
phosphate material
organic carbon
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202311173774.XA
Other languages
Chinese (zh)
Inventor
陈国栋
陈巍
吴永生
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Guangzhou Rongjie Energy Technology Co ltd
Original Assignee
Guangzhou Rongjie Energy Technology Co ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Guangzhou Rongjie Energy Technology Co ltd filed Critical Guangzhou Rongjie Energy Technology Co ltd
Priority to CN202311173774.XA priority Critical patent/CN117276498A/en
Publication of CN117276498A publication Critical patent/CN117276498A/en
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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
    • 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
    • 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
    • H01M4/621—Binders
    • 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
    • C01P2006/40—Electric properties

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Composite Materials (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides a lithium iron phosphate material, a preparation method thereof, a positive plate and a secondary battery. The lithium iron phosphate material with the structure has smaller particle size, fewer inactive areas, better activity, higher gram capacity and better cycle performance. According to the preparation method, soluble organic carbon and insoluble inorganic carbon are added, so that the surface of ferric phosphate is coated with the soluble organic carbon, an organic carbon coating layer can be formed during roasting, an intermediate product with lower water content is obtained through spray drying, roasting is carried out, air current crushing is carried out, a material with smaller particle size is obtained, and impurity removal is carried out, so that the lithium iron phosphate material is obtained.

Description

Lithium iron phosphate material, preparation method thereof, positive plate and secondary battery
Technical Field
The invention relates to the field of secondary batteries, in particular to a lithium iron phosphate material, a preparation method thereof, a positive plate and a secondary battery.
Background
The lithium iron phosphate battery core has excellent cycle performance and safety performance and is widely applied to the fields of energy storage, electric automobiles and the like. At present, the gram capacity of the lithium iron phosphate material is lower, the theoretical gram capacity is 170mAh/g, and the actual reversible capacity is 145mAh/g. In order to improve the conductivity of the material, on one hand, the conductivity of the material is improved by adopting carbon coating, and on the other hand, the migration path of lithium ions is reduced by reducing the particle size. However, increasing the carbon coating reduces the gram capacity of the material, reducing the particle size reduces the compaction density of the material, and reduces the energy density of the battery cell product, so that the development of the high-energy density lithium iron phosphate battery cell is a key point of the development at the present stage. In order to improve the energy density of the battery core, the pole piece with high compaction density can be obtained by adjusting the particle size distribution of materials, such as the mode of size and particle size compounding and the like. However, compared with the lithium ion migration path of the material with small particle size, the lithium iron phosphate material with large particle size has the defects that the DCR of the battery core is bigger, and the capacity exertion and the cycle performance of the battery core in the early stage are affected.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the lithium iron phosphate material has smaller particle size, fewer inactive areas, better activity, higher gram capacity and better cycle performance.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the lithium iron phosphate material comprises modified lithium iron phosphate particles, wherein the modified lithium iron phosphate particles comprise a lithium iron phosphate inner core and an organic carbon coating layer coated on the surface of the lithium iron phosphate inner core, and a binder and inorganic carbon particles are filled between adjacent modified lithium iron phosphate particles.
The lithium iron phosphate material has smaller particle size and fewer inactive areas between materials, so that the whole lithium iron phosphate material has good electrochemical performance. Specifically, the surface of the modified lithium iron phosphate particles is coated with an organic carbon coating layer, so that the growth of lithium iron phosphate can be restrained, meanwhile, inorganic carbon particles and a binder are filled between adjacent modified lithium iron phosphate particles, the agglomeration of the modified lithium iron phosphate particles can be prevented to form compact secondary particles, a loose structure is formed between two adjacent modified lithium iron phosphate particles through heating treatment, a channel is provided for migration of lithium ions, an active area is greatly increased, and the binder can enable the lithium iron phosphate material to have good overall performance.
Wherein the particle diameter D of the lithium iron phosphate material 50 1-10 μm. Particle diameter D of lithium iron phosphate 50 May be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm. The lithium iron phosphate material has the advantages of smaller particle size, short lithium ion migration path, quick activation, high gram capacity and the like, and the small-particle-size material has lower DCR, low impedance in the circulation process and excellent circulation performance. When the lithium iron phosphate material is used for preparing the positive electrode material, slurry dispersion is simpler, the material can be crushed into small particles after rolling, the small particles are filled in the middle of the large particles, and the compaction density of the pole piece is improved, so that the positive electrode material has relatively high impedance and good electrochemical performance.
The second object of the invention is to provide a preparation method of lithium iron phosphate material, which can inhibit the growth of particle size of lithium iron phosphate, reduce the proportion of inactive lithium iron phosphate and improve gram capacity of the material.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the preparation method of the lithium iron phosphate material comprises the following steps:
s1, mixing ferric phosphate, a lithium source, soluble organic carbon, insoluble inorganic carbon, a binder and water, and sanding to obtain a dispersion liquid;
step S2, spray drying the dispersion liquid in the step S1 to obtain an intermediate product;
and S3, heating and roasting the intermediate product in the step S2, carrying out jet milling, and removing impurities to obtain the lithium iron phosphate material.
According to the invention, the soluble organic carbon and the ferric phosphate are dissolved in water, so that the surface of the lithium iron phosphate is coated with a layer of organic carbon, the growth of primary particles of the lithium iron phosphate is effectively prevented, the insoluble inorganic carbon is adhered to the inner surface of the iron phosphate town by the adhesive, the primary particles are prevented from agglomerating into compact secondary particles, a loose structure is formed after the adhesive and the inorganic carbon between adjacent lithium iron phosphate materials are baked, the smooth release and intercalation of lithium ions are ensured, the proportion of the inactive lithium iron phosphate materials is reduced, and the gram capacity of the materials is improved.
Wherein, spray drying is adopted in step S2, which is a device based on air flow and realizing rapid drying of liquid materials by spraying technology. In the production process of lithium iron phosphate, since lithium iron phosphate has a very high specific surface area and a special crystal morphology, it is required to secure its quality and performance by an efficient drying process. In a spray dryer, the lithium iron phosphate slurry is heated and sprayed into a high velocity gas stream to effect removal of water by evaporation in a short period of time to form a solid lithium iron phosphate powder. The efficient drying process not only can rapidly complete the drying process of the lithium iron phosphate, but also can accurately control the drying parameters so as to ensure the quality of the powder. Wherein in the step S3, the air current crushing reduces the particle size of the material, and the particle size D of the material 50 ＜1.5μm，D 99 And < 10 μm. In the step S3, the impurities are removed by passing the materials through a dry type iron removing machine so as to remove the magnetic impurities introduced in the raw materials, and the lithium iron phosphate anode material is obtained after sieving by a screen. Wherein the binder can be polyacrylic acid PAA or polytetrafluoroethylene PTFE. The inorganic carbon may be carbon fiber CNT, acetylene black, graphene, or the like.
Wherein, in the step S1, the molar ratio of the ferric phosphate, the lithium source, the soluble organic carbon, the insoluble inorganic carbon and the binder is 1-3: 1 to 3:0.1 to 0.4:0.1 to 0.3:0.3 to 0.8. Mixing ferric phosphate and a lithium source together, and roasting to obtain lithium ferric phosphate with better binding property, wherein the molar ratio of the ferric phosphate to the lithium source is controlled to be 1:1, the reaction is more complete. Preferably, the molar ratio of the iron phosphate, the lithium source, the soluble organic carbon, the insoluble inorganic carbon, and the binder may be 1:1:0.1:0.1:0.3, 2:1:0.2:0.3:0.5, 2:1:0.3:0.1:0.4, 1:3:0.3:0.2:0.4, 1:1:0.2:0.3:0.6, 1:1:0.2:0.3:0.6, 2:1:0.2:0.3:0.4, 3:1:0.4:0.3:0.5, 2:3:0.3:0.3:0.6, 3:2:0.2:0.3:0.8.
wherein, in the step S1, the grain diameter D is obtained after sand milling 50 300nm to 500nm. Particle diameter D after sanding 50 And can be 300nm, 350nm, 380nm, 400nm, 420nm, 450nm, 500nm.
Wherein the temperature of the heating roasting in the step S2 is 700-800 ℃, and the roasting time is 5-10 h. The temperature of the heating and roasting in the step S2 can be 700 ℃, 720 ℃, 730 ℃, 750 ℃, 770 ℃, 790 ℃ and 800 ℃, and the roasting time can be 5 hours, 6 hours, 7 hours, 8 hours, 9 hours and 10 hours.
Wherein the particle diameter D obtained by jet milling in the step S3 50 1-10 μm. Particle diameter D obtained by jet milling in step S3 50 May be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm.
Wherein, the step S1 also comprises metal doping agent, iron phosphate, lithium source, metal doping agent, soluble organic carbon, insoluble inorganic carbon and binder with the mol ratio of 1-3: 1 to 3:0.5 to 1.2:0.1 to 0.4:0.1 to 0.3:0.3 to 0.8. The metal dopant can be titanium dioxide, magnesium oxide, aluminum hydroxide, titanium dioxide, chromium nitrate, manganese carbonate or zinc oxide, and preferably the metal dopant is titanium dioxide, so that the conductivity and the structural stability of the material can be improved. Specifically, the molar ratio of iron phosphate, lithium source, metal dopant, soluble organic carbon, insoluble inorganic carbon, binder may be 1:1:0.5:0.1:0.1:0.3, 2:1:0.5:0.1:0.1:0.3, 2:1:0.5:0.1:0.1:0.8, 2:3:0.7:0.3:0.3:0.5, 2:2:0.7:0.2:0.2:0.7, 2:3:0.7:0.2:0.2:0.5, 2:1:0.6:0.3:0.2:0.4.
the third object of the present invention is to provide a positive electrode sheet having excellent electrochemical performance and cycle performance.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the positive plate comprises the lithium iron phosphate material. Specifically, the positive plate comprises a positive current collector and a positive active coating layer arranged on the surface of the positive current collector, wherein the positive active coating layer comprises a positive active material, a conductive agent and a binder, and the positive active material can also comprise LiCoO (but not limited to) 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 And the like. The positive electrode active material may be further modified by a modification process, and a method for modifying the positive electrode active material should be known to those skilled in the art, for example, the positive electrode active material may be modified by coating, doping, or the like, and the material used for the modification process may be one or more combinations including, but not limited to, al, B, P, zr, si, ti, ge, sn, mg, ce, W. The positive current collector is usually a structure or a part for collecting current, and the positive current collector may be various materials suitable for being used as a positive current collector of a lithium ion battery in the field, for example, the positive current collector may be a metal foil, and the like, and more particularly may include, but is not limited to, an aluminum foil, and the like.
The non-compact secondary particles obtained from the positive electrode material are crushed in the rolling process to form small-particle-size materials, and the small-particle-size materials can be filled in gaps among large particles to improve the compaction density of the materials. Some of the particles are agglomerated particles after jet milling, and the agglomerated particles can be further crushed into primary particles after rolling. The small particle size formed by rolling the positive electrode material has higher activity and fewer inactive areas, and the first circle gram capacity of the material is more than or equal to 155mAh/g; the small-particle-size material has a shorter lithium ion migration path, smaller impedance and cycle performance, and the capacity retention rate of 8000 circles of normal-temperature cycle is more than or equal to 80%. And the conductive agent is added during preparation of the positive electrode material, so that the conductive agent is uniformly coated on the surface of the lithium iron phosphate, the addition amount of the conductive agent in the preparation process of the positive electrode slurry can be reduced, the time required for dispersing the slurry can be greatly shortened, the uniformity of dispersing the slurry is improved, and the influence on the performance of the battery cell due to uneven dispersing of the conductive agent is avoided. The small-particle-size material in the positive electrode material is relatively low, the material is easier to disperse uniformly, the solid content of the slurry is more than or equal to 64%, the NMP consumption is reduced, the coating speed is improved, and the production cost is reduced. The coating speed is set according to the apparatus, and preferably, the coating speed is 70m/min.
The fourth object of the present invention is to provide a secondary battery having excellent electrochemical performance, capacity and cycle performance.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a secondary battery comprises the positive plate. Specifically, the secondary battery includes a positive electrode sheet, a separator, a negative electrode sheet, an electrolyte, and a case. The isolating film is arranged between the positive plate and the negative plate, and the shell is used for installing and packaging the positive plate, the isolating film, the negative plate and the electrolyte.
The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microsphere, silicon-based material, tin-based material, lithium titanate or other metals capable of forming alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon oxygen compound, silicon carbon compound and silicon alloy; the tin-based material can be selected from one or more of elemental tin, tin oxide and tin alloy. The negative current collector is typically a structure or part that collects current, and may be any of a variety of materials suitable in the art for use as a negative current collector for a lithium ion battery, for example, the negative current collector may be a material including, but not limited to, a metal foil, etc., and more particularly may be a material including, but not limited to, a copper foil, etc.
Wherein the electrolyte comprises an organic solvent, an electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt can be LiPF used in high-temperature electrolyte 6 And/or LiBOB; liBF used in the low-temperature electrolyte may be used 4 、LiBOB、LiPF 6 At least one of (a) and (b); liBF used in the overcharge-preventing electrolyte may also be used 4 、LiBOB、LiPF 6 At least one of LiTFSI; liClO may also be 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of them. And the organic solvent may be a cyclic carbonate, including PC, EC; chain carbonates, including DFC, DMC, or EMC; carboxylic esters, including MF, MA, EA, MP, and the like, are also contemplated. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, and control of H in electrolytes 2 At least one of an additive for O and HF content, an additive for improving low temperature performance, and a multifunctional additive.
The separator may be any of a variety of materials suitable for lithium ion battery separators in the art, and may be, for example, a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fibers, and the like. The shell can be made of one of stainless steel and aluminum plastic films.
Compared with the prior art, the invention has the beneficial effects that: the lithium iron phosphate material has smaller particle size and fewer inactive areas between materials, so that the whole lithium iron phosphate material has good electrochemical performance. Specifically, the organic carbon coating layer is coated on the surfaces of the modified lithium iron phosphate particles, so that the growth of lithium iron phosphate can be restrained, meanwhile, insoluble inorganic carbon is adhered to the inner surface of the iron phosphate town by the adhesive, the primary particles are prevented from being agglomerated into compact secondary particles, a loose structure is formed after the adhesive and the inorganic carbon between adjacent lithium iron phosphate materials are roasted, the smooth release and intercalation of lithium ions are ensured, the proportion of the inactive lithium iron phosphate materials is reduced, and the gram capacity of the material is improved.
Drawings
Fig. 1 is a schematic structural diagram of a lithium iron phosphate material of the present invention.
Fig. 2 is an SEM image of the lithium iron phosphate of example 1 of the present invention after rolling.
Fig. 3 is a cycle chart of 8000 cycles of charge and discharge of the lithium iron phosphate material of example 1 of the present invention.
Wherein: 1. modified lithium iron phosphate particles; 2. an organic carbon coating layer; 3. inorganic carbon particles; 4. and (3) a binder.
Detailed Description
In order to make the technical solution and advantages of the present invention more apparent, the present invention and its advantageous effects will be described in further detail below with reference to the specific embodiments, but the embodiments of the present invention are not limited thereto.
Example 1
The preparation method of the lithium iron phosphate material comprises the following steps:
step S1, mixing ferric phosphate, a lithium source, soluble organic carbon, insoluble inorganic carbon, a binder 3 and water, and sanding to the particle size D 50 Obtaining a dispersion at 350 nm; wherein the mole ratio of Li to Fe to P is 1:1:1, a lithium source (specifically lithium carbonate and lithium hydroxide) and anhydrous ferric phosphate are weighed, and the molar ratio of the ferric phosphate to the lithium source to the soluble organic carbon to the insoluble inorganic carbon to the binder 3 is 1:1:0.15:0.2:0.55;
step S2, spray drying the dispersion liquid in the step S1 to obtain an intermediate product, wherein the water content of the intermediate product is less than 5%;
step S3, transferring the intermediate product in the step S2 into a sagger, placing the sagger into a roasting furnace, and heating and roasting the sagger for 8 hours under the inert gas environment to react at 780 ℃, wherein ferric phosphate reacts with a lithium source to obtain modified lithium iron phosphate particles, soluble organic carbon forms an organic carbon coating layer 2 coated on the surfaces of the modified lithium iron phosphate particles 1, insoluble inorganic carbon forms inorganic carbon particles 3 andthe adhesive 3 is adhered to the surface of the organic carbon coating layer 2, a loose structure is formed between two adjacent modified lithium iron phosphate particles, and the particles are subjected to jet milling to obtain particle size D 50 <5μm，D 99 And (3) passing the material subjected to jet milling through a dry iron removing machine to remove magnetic impurities introduced into the raw material, and sieving through a screen to obtain the lithium iron phosphate material, wherein the SEM image of the rolled lithium iron phosphate material is shown in figure 1, and the SEM image of the rolled lithium iron phosphate material is shown in figure 2.
Preparation of a positive plate:
the lithium iron phosphate material prepared above, conductive agent superconducting carbon (Super-P) and binder 3 polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 96:2:2, uniformly mixing to prepare lithium ion battery anode slurry with certain viscosity, coating the slurry on a current collector aluminum foil in an extrusion coating or transfer coating mode, drying at 85 ℃ and then cold pressing; then trimming, cutting pieces, splitting, drying at 110 ℃ for 4 hours under vacuum after splitting, and welding the tab to prepare the positive plate.
Preparing a negative plate:
graphite, conductive agent superconducting carbon (Super-P), thickener sodium carboxymethylcellulose (CMC) and binder 3 Styrene Butadiene Rubber (SBR) are mixed according to the mass ratio of 96.5:0.5:1.2:1.8 mixing and adding a certain amount of water to prepare slurry, coating the slurry on a current collector copper foil by adopting an extrusion coating or transfer coating mode, drying at 85 ℃, trimming, cutting pieces, splitting, drying at 110 ℃ for 4 hours under vacuum condition after splitting, and welding electrode lugs to prepare the negative plate.
Preparation of electrolyte:
lithium hexafluorophosphate (LiPF) 6 ) Dissolved in a mixed solvent composed of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) (the mass ratio of the three is 1:2: 1) An electrolyte having a concentration of 1mol/L was obtained.
Preparation of a lithium ion battery:
winding the positive plate, the isolating film and the negative plate into a battery core, wherein the isolating film is positioned between the positive plate and the negative plate, the positive electrode is led out by spot welding of an aluminum tab, and the negative electrode is led out by spot welding of a nickel tab; and then placing the battery core in an aluminum-plastic packaging bag, injecting the electrolyte, and performing procedures such as packaging, formation, capacity and the like to prepare the lithium ion battery.
Example 2
Unlike example 1, the following is: in the step S1, the molar ratio of the ferric phosphate, the lithium source, the soluble organic carbon, the insoluble inorganic carbon and the binder 3 is 2:1:0.2:0.1:0.3.
the rest is the same as in embodiment 1 and will not be described here again.
Example 3
Unlike example 1, the following is: in the step S1, the molar ratio of the ferric phosphate, the lithium source, the soluble organic carbon, the insoluble inorganic carbon and the binder 3 is 2:3:0.3:0.3:0.5.
the rest is the same as in embodiment 1 and will not be described here again.
Example 4
Unlike example 1, the following is: in the step S1, the molar ratio of the ferric phosphate, the lithium source, the soluble organic carbon, the insoluble inorganic carbon and the binder 3 is 3:1:0.2:0.1:0.6.
the rest is the same as in embodiment 1 and will not be described here again.
Example 5
Unlike example 1, the following is: in the step S1, the molar ratio of the ferric phosphate, the lithium source, the soluble organic carbon, the insoluble inorganic carbon and the binder 3 is 3:2:0.2:0.2:0.4.
the rest is the same as in embodiment 1 and will not be described here again.
Example 6
Unlike example 1, the following is: and step S2, heating and roasting at 700 ℃ for 8 hours.
The rest is the same as in embodiment 1 and will not be described here again.
Example 7
Unlike example 1, the following is: and step S2, heating and roasting at 750 ℃ for 6 hours.
The rest is the same as in embodiment 1 and will not be described here again.
Example 8
Unlike example 1, the following is: and step S2, heating and roasting at 780 ℃ for 5 hours.
The remainder is the same as embodiment 1 and will not be described here again.
Example 9
Unlike example 1, the following is: the step S1 also comprises titanium dioxide metal dopant, and the molar ratio of ferric phosphate, lithium source, metal dopant, soluble organic carbon, insoluble inorganic carbon and binder 3 is 1:1:0.8:0.2:0.3:0.55.
the rest is the same as in embodiment 1 and will not be described here again.
Example 10
Unlike example 1, the following is: the step S1 also comprises titanium dioxide metal dopant, iron phosphate, lithium source, metal dopant, soluble organic carbon, insoluble inorganic carbon and binder 3 with the molar ratio of 2:1.5:0.5:0.1:0.2:0.6.
the rest is the same as in embodiment 1 and will not be described here again.
Example 11
Unlike example 1, the following is: the step S1 also comprises titanium dioxide metal dopant, and the molar ratio of ferric phosphate, lithium source, metal dopant, soluble organic carbon, insoluble inorganic carbon and binder 3 is 1:1:0.8:0.3:0.1:0.4.
the rest is the same as in embodiment 1 and will not be described here again.
Example 12
Unlike example 1, the following is: the step S1 also comprises aluminum oxide metal dopant, and the molar ratio of ferric phosphate, lithium source, metal dopant, soluble organic carbon, insoluble inorganic carbon and binder 3 is 1:3:1:0.1:0.2:0.5.
the rest is the same as in embodiment 1 and will not be described here again.
Example 13
Unlike example 9, the following is: s3, carrying out jet milling on the materials with two different particle sizes, wherein the particle sizes are D respectively 50 2 μm and 10 μm.
The rest is the same as in embodiment 1 and will not be described here again.
Comparative example 1
The difference from example 9 is that: in step S1, insoluble inorganic carbon is not added.
The remainder is the same as in example 1 and will not be described again here.
The lithium iron phosphate materials obtained in examples 1 to 13 and comparative example 1 were prepared as positive electrode materials, and were applied to positive electrode sheets and secondary batteries, and tested, with the following table 1.
TABLE 1
As can be seen from the above Table 1, the material prepared by the preparation method of the lithium iron phosphate material of the present invention is used in the positive electrode material, the positive electrode sheet and the secondary battery, and has good electrochemical performance and cycle performance. As can be seen from the combination of FIG. 3, the lithium iron phosphate material prepared in example 1 of the present invention has a capacity retention rate of 84% after 8000 charge and discharge cycles, and has good performance.
From the comparison of examples 1 to 5, when iron phosphate, lithium source, soluble organic carbon, insoluble inorganic carbon and binder are set in a molar ratio of 1:1:0.15:0.2: at 0.55, the prepared lithium iron phosphate material has better performance and good capacity retention rate, and after 6000 charge-discharge cycles, the capacity retention rate of 85% -91% is still maintained, and compared with the capacity retention rate of comparative example 1, the capacity retention rate of 72% is better.
According to comparison of examples 1 and 6-8, when the temperature of the heating roasting in the step S2 is 780 ℃ and the roasting time is 8 hours, the prepared positive electrode material has better performance, the soluble organic carbon is coated on the surface of the ferric phosphate, the growth of the ferric phosphate in the roasting process is inhibited, and the particle size of the prepared lithium iron phosphate is smaller.
From a comparison of examples 1, 9-12, metal dopant was added when the reaction was performed, and the molar ratio of iron phosphate, lithium source, metal dopant, soluble organic carbon, insoluble inorganic carbon, binder was controlled to be 1:1:0.8:0.2:0.3: the positive electrode material prepared at 0.55 has good effect, and when the metal doping agent adopts titanium dioxide, the material has good conductivity and structural stability, so that the material has better performance.
From comparison of examples 1-12 and 13, when two different particle sizes are used for lithium iron phosphate, small particles can be filled in gaps of large particles, so that the compaction density of the material is improved, and meanwhile, the active area is increased, so that the electrochemical performance of the material is improved, and better cycle performance is achieved.
Variations and modifications of the above embodiments will occur to those skilled in the art to which the invention pertains from the foregoing disclosure and teachings. Therefore, the present invention is not limited to the above-described embodiments, but is intended to be capable of modification, substitution or variation in light thereof, which will be apparent to those skilled in the art in light of the present teachings. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.

Claims (10)

1. The lithium iron phosphate material is characterized by comprising modified lithium iron phosphate particles, wherein the modified lithium iron phosphate particles comprise a lithium iron phosphate inner core and an organic carbon coating layer coated on the surface of the lithium iron phosphate inner core, and a binder and inorganic carbon particles are filled between adjacent modified lithium iron phosphate particles.
2. The lithium iron phosphate material of claim 1, wherein the lithium iron phosphate material has a particle size D 50 1-10 μm.
3. The method for preparing a lithium iron phosphate material according to claim 1 or 2, comprising the steps of:
s1, mixing ferric phosphate, a lithium source, soluble organic carbon, insoluble inorganic carbon, a binder and water, and sanding to obtain a dispersion liquid;
step S2, spray drying the dispersion liquid in the step S1 to obtain an intermediate product;
and S3, heating and roasting the intermediate product in the step S2, carrying out jet milling, and removing impurities to obtain the lithium iron phosphate material.
4. The method for preparing a lithium iron phosphate material according to claim 3, wherein in the step S1, the molar ratio of the iron phosphate, the lithium source, the soluble organic carbon, the insoluble inorganic carbon, and the binder is 1 to 3:1 to 3:0.1 to 0.4:0.1 to 0.3:0.3 to 0.8.
5. The method for preparing a lithium iron phosphate material according to claim 3, wherein the particle diameter D after sanding in the step S1 50 300nm to 500nm.
6. The method for preparing lithium iron phosphate material according to claim 3, wherein the temperature of the heating and roasting in the step S2 is 700-800 ℃ and the roasting time is 5-10 h.
7. The method for producing a lithium iron phosphate material according to claim 3, wherein the particle diameter D obtained by jet milling in step S3 50 1-10 μm.
8. The method for preparing a lithium iron phosphate material according to claim 3, wherein the step S1 further comprises a metal dopant, wherein the molar ratio of the metal dopant to the iron phosphate to the lithium source to the soluble organic carbon to the insoluble inorganic carbon to the binder is 1-3: 1 to 3:0.5 to 1.2:0.1 to 0.4:0.1 to 0.3:0.3 to 0.8.
9. A positive electrode sheet comprising the lithium iron phosphate material according to claim 1 or 2.
10. A secondary battery comprising the positive electrode sheet according to claim 9.
CN202311173774.XA 2023-09-12 2023-09-12 Lithium iron phosphate material, preparation method thereof, positive plate and secondary battery Pending CN117276498A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202311173774.XA CN117276498A (en) 2023-09-12 2023-09-12 Lithium iron phosphate material, preparation method thereof, positive plate and secondary battery

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202311173774.XA CN117276498A (en) 2023-09-12 2023-09-12 Lithium iron phosphate material, preparation method thereof, positive plate and secondary battery

Publications (1)

Publication Number Publication Date
CN117276498A true CN117276498A (en) 2023-12-22

Family

ID=89218786

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202311173774.XA Pending CN117276498A (en) 2023-09-12 2023-09-12 Lithium iron phosphate material, preparation method thereof, positive plate and secondary battery

Country Status (1)

Country Link
CN (1) CN117276498A (en)

Similar Documents

Publication Publication Date Title
CN110854382B (en) Positive electrode lithium supplement material, positive electrode containing positive electrode lithium supplement material and preparation method of positive electrode lithium supplement material
CN108539122B (en) Positive plate and lithium ion secondary battery comprising same
CN113036106A (en) Composite lithium supplement additive and preparation method and application thereof
CN112310359B (en) Negative electrode active material and secondary battery
CN111384395B (en) Electrochemical device and electronic device
CN111370695B (en) Negative electrode active material, and electrochemical device and electronic device using same
CN112490518B (en) Positive electrode lithium supplement additive, preparation method thereof, positive electrode and lithium ion battery
CN111082129A (en) Electrochemical device and electronic device
CN111293299B (en) Modified metal lithium negative electrode battery and preparation method thereof
CN111900501A (en) Lithium supplement additive and preparation method and application thereof
CN114784365B (en) Secondary battery
WO2023065909A1 (en) Electrochemical device and electronic device
CN111342137A (en) Electrolyte and electrochemical device
JP2009245917A (en) Positive electrode active material for nonaqueous electrolyte secondary battery, method for manufacturing same, and positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery
CN113675383A (en) Modified positive electrode material and preparation method thereof, positive plate and lithium ion battery
CN112310360A (en) Negative electrode active material and battery
JP2012089464A (en) Nonaqueous electrolyte secondary battery and method for manufacturing nonaqueous electrolyte secondary battery
JP4724912B2 (en) Method for producing positive electrode active material and method for producing non-aqueous electrolyte secondary battery
JP2005302300A (en) Nonaqueous electrolyte battery
CN114144919A (en) Positive pole piece, electrochemical device comprising positive pole piece and electronic device
CN114613963B (en) Negative electrode material, preparation method thereof, negative electrode sheet and secondary battery
CN114614009B (en) Composite material, preparation method thereof, negative electrode plate and secondary battery
KR100696795B1 (en) Negative active material composition for rechargeable lithium ion battery and rechargeable lithium ion battery comprising same
CN115579506A (en) Lithium ion battery
CN113690412A (en) Active slurry, preparation method thereof, positive plate and lithium ion battery

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination