CN116374980A - Lithium iron phosphate positive electrode material and preparation method thereof - Google Patents
Lithium iron phosphate positive electrode material and preparation method thereof Download PDFInfo
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- CN116374980A CN116374980A CN202211678858.4A CN202211678858A CN116374980A CN 116374980 A CN116374980 A CN 116374980A CN 202211678858 A CN202211678858 A CN 202211678858A CN 116374980 A CN116374980 A CN 116374980A
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 118
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 96
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- 239000000203 mixture Substances 0.000 claims abstract description 81
- 238000001694 spray drying Methods 0.000 claims abstract description 54
- 238000000034 method Methods 0.000 claims abstract description 37
- 239000007787 solid Substances 0.000 claims abstract description 31
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims abstract description 30
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 26
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 25
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 25
- 239000005955 Ferric phosphate Substances 0.000 claims abstract description 24
- 229940032958 ferric phosphate Drugs 0.000 claims abstract description 24
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims abstract description 24
- 239000002245 particle Substances 0.000 claims abstract description 23
- 239000012798 spherical particle Substances 0.000 claims abstract description 20
- 230000001681 protective effect Effects 0.000 claims abstract description 12
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 238000010438 heat treatment Methods 0.000 claims abstract description 6
- 238000001238 wet grinding Methods 0.000 claims abstract description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 63
- 229910001416 lithium ion Inorganic materials 0.000 claims description 63
- 238000001354 calcination Methods 0.000 claims description 39
- -1 iron ions Chemical class 0.000 claims description 36
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 26
- 229910052742 iron Inorganic materials 0.000 claims description 25
- 239000010405 anode material Substances 0.000 claims description 16
- 230000000630 rising effect Effects 0.000 claims description 15
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 12
- 229910052698 phosphorus Inorganic materials 0.000 claims description 12
- 239000011574 phosphorus Substances 0.000 claims description 12
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 11
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 7
- 229910000398 iron phosphate Inorganic materials 0.000 claims description 6
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 4
- 238000007873 sieving Methods 0.000 claims description 4
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 3
- 229910010707 LiFePO 4 Inorganic materials 0.000 claims description 3
- 239000002202 Polyethylene glycol Substances 0.000 claims description 3
- 229920002125 Sokalan® Polymers 0.000 claims description 3
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 3
- 229920001568 phenolic resin Polymers 0.000 claims description 3
- 239000005011 phenolic resin Substances 0.000 claims description 3
- 239000004584 polyacrylic acid Substances 0.000 claims description 3
- 229920001223 polyethylene glycol Polymers 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 8
- 230000000052 comparative effect Effects 0.000 description 11
- 238000009792 diffusion process Methods 0.000 description 10
- 238000010998 test method Methods 0.000 description 10
- 238000012360 testing method Methods 0.000 description 8
- 238000001878 scanning electron micrograph Methods 0.000 description 7
- 238000007599 discharging Methods 0.000 description 5
- 239000010406 cathode material Substances 0.000 description 3
- 238000007600 charging Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 239000006256 anode slurry Substances 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 238000005056 compaction Methods 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 125000000218 acetic acid group Chemical group C(C)(=O)* 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 238000010280 constant potential charging Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The embodiment of the application discloses a lithium iron phosphate positive electrode material and a preparation method thereof, wherein the preparation method comprises the following steps: mixing a lithium source, ferric phosphate and a carbon source in different proportions respectively to obtain a first mixture; wet grinding the first mixture to obtain a second mixture; adjusting the solid content of the second mixture, feeding the second mixture into spray drying equipment at a feeding speed V, and performing morphology and particle size regulation and control on spray drying pressure P in the spray drying equipment to obtain a third mixture of spherical particles; and carrying out heat treatment on the third mixture in a protective atmosphere to obtain the spherical particle lithium iron phosphate positive electrode material. According to the application, the solid content, the spray drying pressure and the feeding speed of the second mixture in the spray drying process are reasonably adjusted to prepare the spherical particle lithium iron phosphate positive electrode material, and the morphology and the size of the lithium iron phosphate positive electrode material are optimized to improve the tap density of the prepared lithium iron phosphate positive electrode material.
Description
Technical Field
The application relates to the technical field of battery material preparation, in particular to a lithium iron phosphate positive electrode material and a preparation method thereof.
Background
The lithium iron phosphate anode material has the advantages of good safety performance, excellent cycle performance, environmental friendliness, rich raw material sources and the like, and is widely applied to power supplies of electric tools, miner lamps, electric bicycles, electric automobiles, hybrid electric vehicles, satellites, weaponry and other devices.
However, the lithium iron phosphate prepared at present has low conductivity, low tap density and poor compactness among particles, so that when the lithium iron phosphate is used as a positive electrode material to be applied to a battery, the lithium ion has a barrier in the transmission process, and the rate capability of the battery is affected. Therefore, how to increase the tap density of the prepared lithium iron phosphate cathode material is a problem to be solved.
Disclosure of Invention
The embodiment of the application provides a lithium iron phosphate positive electrode material and a preparation method thereof, so as to improve the tap density of the prepared lithium iron phosphate positive electrode material.
In order to solve the technical problems, the embodiment of the application discloses the following technical scheme:
in one aspect, a method for preparing a lithium iron phosphate positive electrode material is provided, comprising the following steps:
mixing a lithium source, ferric phosphate and a carbon source in different proportions respectively to obtain a first mixture;
wet grinding the first mixture to obtain a second mixture;
adjusting the solid content of the second mixture, feeding the second mixture into spray drying equipment at a feeding speed V, and performing morphology and particle size regulation and control on spray drying pressure P in the spray drying equipment to obtain a third mixture of spherical particles;
and carrying out heat treatment on the third mixture in a protective atmosphere to obtain the spherical particle lithium iron phosphate positive electrode material.
In addition to or in lieu of one or more of the features disclosed above, the second mixture is defined as having a solids content a, a feed rate V, and a spray drying pressure P that satisfy:
in addition to, or as an alternative to, one or more of the features disclosed above, the solids content a satisfies: a is more than or equal to 20% and less than or equal to 40%; and/or the number of the groups of groups,
the feed rate V satisfies: v is more than or equal to 40kg/h and less than or equal to 80kg/h; and/or;
the spray drying pressure P satisfies: p is more than or equal to 0.2MPa and less than or equal to 0.6MPa.
In addition to, or as an alternative to, one or more of the features disclosed above, the spray drying pressure P satisfies: p is more than or equal to 0.2MPa and less than or equal to 0.4MPa.
In addition to, or in lieu of, one or more of the features disclosed above, the step of mixing the lithium source, iron phosphate, and carbon source in different proportions,
the mole ratio of iron ions to phosphorus ions in the ferric phosphate is (0.99-1.01): 1; and/or the number of the groups of groups,
the molar ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is (0.95-1.05): 1; and/or the number of the groups of groups,
the mass ratio of the carbon source to the lithium iron phosphate positive electrode material is (0.06-0.1): 1.
In addition to or as an alternative to one or more of the features disclosed above, the lithium source includes; one or more of lithium acetate, lithium chloride, lithium carbonate or lithium hydroxide; and/or the number of the groups of groups,
the carbon source includes: one or more of citric acid, polyacrylic acid, phenolic resin, polyethylene glycol or acetic acid.
In addition to, or as an alternative to, one or more of the features disclosed above, the second mixture has a particle size D 50 μm, satisfy: d is more than or equal to 0.3 50 ≤0.5。
In addition to one or more features disclosed above, or alternatively, the heat treating the third mixture in a protective atmosphere to obtain a lithium iron phosphate positive electrode material, comprising:
calcining the third mixture in a protective atmosphere at a calcination temperature elevated at a rate of elevation;
and cooling and sieving the calcined material to obtain the lithium iron phosphate anode material.
In addition to, or as an alternative to, one or more of the features disclosed above, the conditions of calcination are: the temperature rising rate is 1-2 ℃/min, the calcining temperature is 650-700 ℃ and the calcining time is 6-10 h.
On the other hand, further discloses a lithium iron phosphate positive electrode material which is prepared by adopting the preparation method according to any one of the above methods, wherein the lithium iron phosphate positive electrode material has a chemical general formula LiFePO 4 The lithium iron phosphate positive electrode material is spherical particles, and the tap density of the lithium iron phosphate positive electrode material is 0.8-1.8 g/cm 3 。
One of the above technical solutions has the following advantages or beneficial effects: according to the preparation method of the lithium iron phosphate positive electrode material, the solid content, the spray drying pressure and the feeding speed of the second mixture in the spray drying process are reasonably adjusted to prepare the spherical particle lithium iron phosphate positive electrode material, the morphology and the size of the lithium iron phosphate positive electrode material are optimized, so that the tap density of the prepared lithium iron phosphate positive electrode material is improved, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, the rate performance of the battery is finally improved, meanwhile, the preparation method is simple in process, the main flow preparation process is not required to be greatly changed, the cycle is short, and the preparation method is suitable for industrial production.
Drawings
Technical solutions and other advantageous effects of the present application will be made apparent from the following detailed description of specific embodiments of the present application with reference to the accompanying drawings.
Fig. 1 is a flow chart of a method of preparing a lithium iron phosphate positive electrode material provided according to an embodiment of the present application;
FIG. 2a is an SEM image of a lithium iron phosphate positive electrode material prepared according to example 1 of the present application prior to compaction;
FIG. 2b is a SEM image of a compacted lithium iron phosphate positive electrode material prepared according to example 1 of the present application;
FIG. 3a is an SEM image of a lithium iron phosphate positive electrode material prepared according to comparative example 1 of the present application prior to compaction;
fig. 3b is an SEM image of a compacted lithium iron phosphate positive electrode material prepared according to comparative example 1 of the present application.
Detailed Description
In order to make the objects, technical solutions and advantageous effects of the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and detailed description. It should be understood that the detailed description is presented herein for purposes of illustration only and is not intended to limit the application.
At present, the methods for preparing the lithium iron phosphate anode material are numerous, and tap densities of the lithium iron phosphate anode materials prepared by different preparation methods are different. For example, when the prepared lithium iron phosphate powder particles are irregularly shaped, the tap density of the prepared lithium iron phosphate powder particles is low due to the fact that the irregular powder particles cannot be closely packed, thereby affecting the rate capability of the battery when applied to the battery. The disadvantages are greater for the application of lithium iron phosphate cathode materials.
Based on the method, when the lithium iron phosphate positive electrode material is prepared, the solid content, the spray drying pressure and the feeding speed in the spray drying process of the second mixture are reasonably adjusted to prepare the spherical particle lithium iron phosphate positive electrode material, and the morphology and the size of the lithium iron phosphate positive electrode material are optimized, so that the tap density of the prepared lithium iron phosphate positive electrode material is improved, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
As shown in fig. 1, in an embodiment of the present application, the preparation method of the lithium iron phosphate positive electrode material includes the following steps:
s100, respectively mixing a lithium source, ferric phosphate and a carbon source in different proportions to obtain a first mixture;
in the examples of the present application, the molar ratio of iron ions to phosphorus ions in the iron phosphate was (0.99 to 1.01): 1. That is, the molar ratio of iron ions to phosphorus ions in the iron phosphate can be controlled within the range of (0.99 to 1.01): 1. For example, the molar ratio of iron ions to phosphorus ions in the iron acid may be in the range of one or any two of (0.99:1), (0.994:1), (0.998:1), (1.002:1), (1.006:1), (1.01:1). It is noted that the specific values of the molar ratio are given by way of example only, as long as any value within the range of (0.99 to 1.01): 1 is within the scope of the present application.
It can be understood that the molar ratio of iron ions to phosphorus ions in the ferric phosphate is controlled within the range of (0.99-1.01): 1, so that the prepared lithium iron phosphate positive electrode material has higher discharge capacity and capacity density.
The molar ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is (0.95-1.05): 1. Namely, the molar ratio of lithium ions in the lithium source to iron ions in the iron phosphate can be controlled within the range of (0.95-1.05): 1. For example, the molar ratio of lithium ions in the lithium source to iron ions in the iron phosphate may be in the range of one or any two of 0.95:1, 0.96:1, 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1. It is noted that the specific values of the molar ratio are given by way of example only, as long as any value within the range of (0.95 to 1.05): 1 is within the scope of protection of the present application.
It can be understood that the loss of active lithium in the charge and discharge process of the battery is a main factor of service life attenuation of the secondary battery, in the application, the molar ratio of lithium ions in a lithium source to iron ions in ferric phosphate is controlled within the range of (0.95-1.05): 1, so that the prepared lithium iron phosphate positive electrode material has sufficient lithium ions, the reversible capacity of a positive electrode plate of the battery is increased, the balance of electrochemical reaction of the battery in the working process is maintained, and the rate capability of the battery is finally improved.
The mass ratio of the carbon source to the lithium iron phosphate positive electrode material is (0.06-0.1): 1. Namely, the mass ratio of the carbon source to the lithium iron phosphate positive electrode material can be controlled within the range of (0.06-0.1): 1. For example, the mass ratio of the carbon source to the lithium iron phosphate positive electrode material may be in a range of one or any two of 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1. It is worth noting that specific values of the mass ratio are given by way of example only, as long as any value of the mass ratio in the range of (0.06-0.1): 1 is within the scope of protection of the present application.
It can be understood that the mass ratio of the carbon source to the lithium iron phosphate positive electrode material is controlled within the range of (0.06-0.1): 1, so that the effective capacity of the lithium iron phosphate positive electrode material is ensured, and the carbon source can form a complete conductive network.
In embodiments of the present application, the lithium source includes, but is not limited to, one or more of lithium acetate, lithium chloride, lithium carbonate, or lithium hydroxide. The above lithium source materials may be used alone or in any combination.
In embodiments of the present application, the carbon source includes, but is not limited to, one or more of citric acid, polyacrylic acid, phenolic resin, polyethylene glycol, or acetic acid. The above carbon source materials may be used alone or in any combination.
S200, carrying out wet grinding on the first mixture to obtain a second mixture;
in embodiments of the present application, wet milling of the first mixture may be performed in conventional ball milling equipment, such as at least one of a planetary ball mill, a stirred mill, and a sand mill.
In the examples of the present application, the particle size of the second mixture is D 50 μm, satisfy: d is more than or equal to 0.3 50 Less than or equal to 0.5. I.e. particle size D of the second mixture 50 Can be controlled within the range of 0.3 μm to 0.5 μm. For example, the particle size D of the second mixture 50 Can be one of 0.3 μm, 0.32 μm, 0.34 μm, 0.36 μm, 0.38 μm, 0.4 μm, 0.42 μm, 0.44 μm, 0.46 μm, 0.48 μm, 0.5 μm or a range of any two of themAnd (5) enclosing. It is worth noting that the particle diameter D 50 The specific values of (2) are given by way of example only, as long as the particle diameter D 50 Any value in the range of 0.3 μm to 0.5 μm is within the scope of the present application. The particle diameter D of the second mixture 50 The size of the lithium iron phosphate positive electrode material is optimized by controlling the lithium iron phosphate positive electrode material within the range of 0.3-0.5 mu m, the tap density of the prepared lithium iron phosphate positive electrode material is improved, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
S300, adjusting the solid content of the second mixture, feeding the second mixture into spray drying equipment at a feeding speed V, and regulating and controlling morphology granularity of the spray drying pressure P in the spray drying equipment to obtain a third mixture of spherical particles;
wherein, the solid content refers to the mass percent of the residual part of the emulsion or the coating after being dried under the specified conditions.
In the examples of the present application, the second mixture has a solids content a, a feed rate V and a spray drying pressure P satisfying:
preferably, when
Within the above range, with +.>
The tap density of the prepared lithium iron phosphate anode material is increased, and the rate capability of the lithium iron phosphate anode material is improved.
It can be understood that the solid content A, the feeding speed V and the spray drying pressure P of the second mixture are limited to meet the above relation, so that the solid content, the spray drying pressure and the feeding speed in the spray drying process of the second mixture are reasonably adjusted to prepare the spherical particle lithium iron phosphate positive electrode material, the morphology and the size of the lithium iron phosphate positive electrode material are optimized, the tap density of the prepared lithium iron phosphate positive electrode material is improved, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
In the examples of the present application, the solid content a satisfies: a is more than or equal to 20% and less than or equal to 40%. I.e. the solids content a of the second mixture can be controlled in the range of 20% to 40%. For example, the solids content a of the second mixture may be in the range of one or any two of 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%. It is worth noting that the specific values of the solid content a are given by way of example only, as long as any value of the solid content a in the range of 20% to 40% is within the scope of protection of the present application. In the application, the solid content A of the second mixture is controlled within the range of 20% -40%, so that the solid content of the second mixture is reasonably adjusted, the shape and the size of the spherical particle lithium iron phosphate positive electrode material are guaranteed to be prepared, the tap density of the prepared lithium iron phosphate positive electrode material is improved, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
The feed rate V satisfies: v is more than or equal to 40kg/h and less than or equal to 80kg/h. I.e. the feed rate V of the second mixture can be controlled in the range of 40kg/h to 80kg/h. For example, the feed rate V of the second mixture may be in the range of one or any two of 40kg/h, 45kg/h, 50kg/h, 55kg/h, 60kg/h, 65kg/h, 70kg/h, 75kg/h, 80kg/h. It is worth noting that the specific values of the feed rate V are given by way of example only, as long as any value of the feed rate V in the range of 40kg/h to 80kg/h is within the scope of protection of the present application. According to the method, the feeding speed V of the second mixture is controlled within the range of 40 kg/h-80 kg/h, so that the feeding speed V of the second mixture in spray drying equipment can be reasonably regulated, the morphology and the size of the spherical particle lithium iron phosphate positive electrode material are further guaranteed, the prepared lithium iron phosphate positive electrode material is optimized, the tap density of the prepared lithium iron phosphate positive electrode material is improved, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
The spray drying pressure P satisfies: p is more than or equal to 0.2MPa and less than or equal to 0.6MPa. I.e. the spray-drying pressure P of the second mixture may be controlled in the range of 0.2MPa to 0.6MPa. For example, the spray-drying pressure P of the second mixture may be in the range of one or any two of 0.2MPa, 0.25MPa, 0.3MPa, 0.35MPa, 0.4MPa, 0.45MPa, 0.5MPa, 0.55MPa, 0.6MPa. It is worth noting that the specific values of the spray drying pressure P are given by way of example only, as long as any value of the spray drying pressure P in the range of 0.2MPa to 0.6MPa is within the scope of protection of the present application.
Preferably, the spray drying pressure P satisfies: p is more than or equal to 0.2MPa and less than or equal to 0.4MPa. I.e. the spray-drying pressure P of the second mixture may be controlled in the range of 0.2MPa to 0.4MPa. For example, the spray-drying pressure P of the second mixture may be in a range of one or any two of 0.2MPa, 0.25MPa, 0.3MPa, 0.35MPa, 0.4MPa. It is worth noting that the specific values of the spray drying pressure P are given by way of example only, as long as any value of the spray drying pressure P in the range of 0.2MPa to 0.4MPa is within the scope of protection of the present application.
It can be understood that the spray drying pressure P of the second mixture is controlled within the range of 0.2 MPa-0.4 MPa, so that the spray drying pressure P of spray drying equipment can be regulated within a reasonable range, the morphology and the size of the prepared spherical particle lithium iron phosphate positive electrode material are further guaranteed, the tap density of the prepared lithium iron phosphate positive electrode material is improved, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
In summary, the solid content, the spray drying pressure and the feeding speed of the spray drying process of the second mixture are reasonably adjusted to prepare the spherical particle lithium iron phosphate positive electrode material, and the morphology and the size of the lithium iron phosphate positive electrode material are optimized, so that the tap density of the prepared lithium iron phosphate positive electrode material is improved, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
And S400, performing heat treatment on the third mixture in a protective atmosphere to obtain the spherical particle lithium iron phosphate anode material.
In an embodiment of the present application, the heat treatment of the third mixture in the protective atmosphere in step S400 to obtain a lithium iron phosphate positive electrode material includes:
s410, calcining the third mixture in a protective atmosphere at a temperature rising and calcining temperature according to a temperature rising rate;
and S420, cooling and sieving the calcined material to obtain the lithium iron phosphate anode material.
In the examples of the present application, the conditions of calcination are: the temperature rising rate is 1-2 ℃/min. Namely, the temperature rising rate can be controlled within the range of 1-2 ℃/min. For example, the heating rate may be in a range of one or any two of 1 ℃/min, 1.1 ℃/min, 1.2 ℃/min, 1.3 ℃/min, 1.4 ℃/min, 1.5 ℃/min, 1.6 ℃/min, 1.7 ℃/min, 1.8 ℃/min, 1.9 ℃/min, 2 ℃/min. It is worth noting that specific values of the temperature rising rate are given by way of example only, as long as any value of the temperature rising rate in the range of 1 to 2 ℃/min is within the scope of protection of the present application.
The calcination temperature is 650-700 ℃. I.e. the calcination temperature can be controlled within the range of 650-700 ℃. For example, the calcination temperature may be in a range of one or both of 650 ℃, 655 ℃, 660 ℃, 665 ℃, 670 ℃, 675 ℃, 680 ℃, 685 ℃, 690 ℃, 695 ℃ and 700 ℃. It is worth noting that specific values of the calcination temperature are given by way of example only, as long as any value of the calcination temperature in the range of 650-700 ℃ is within the scope of protection of the present application.
The calcination time is 6-10 h. I.e. the calcination time can be controlled in the range of 6 to 10 hours. For example, the first calcination time may be in a range consisting of one or any two of 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h. It is worth noting that specific values of the calcination time are given by way of example only, as long as any value of the calcination time in the range of 6 to 10 hours is within the scope of protection of the present application.
According to the method, the temperature rising rate is controlled within the range of 1-2 ℃/min, the calcining temperature is controlled within the range of 650-700 ℃ and the calcining time is controlled within the range of 6-10 h, so that the tap density of the prepared lithium iron phosphate positive electrode material is ensured to be high, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is ensured not to be lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
In the embodiments of the present application, the protective atmosphere may be any one of nitrogen, helium, or argon.
On the other hand, in the embodiment of the application, the application also provides a lithium iron phosphate positive electrode material which is prepared by adopting the preparation method according to any one of the above methods and has a chemical general formula LiFePO 4 The lithium iron phosphate positive electrode material is spherical particles, and the tap density of the lithium iron phosphate positive electrode material is 0.8-1.8 g/cm 3 。
It will be appreciated that the tap density of the lithium iron phosphate positive electrode material is controlled to be 0.8-1.8 g/cm 3 In the range, the diffusion path of lithium ions is reduced, the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied to the battery, and the rate capability of the battery is finally improved.
The preparation of lithium ion batteries is described below by way of example in connection with specific examples, and those skilled in the art will appreciate that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.
The following description is made of performance evaluation of examples and comparative examples of lithium ion batteries according to the present application.
Example 1
1. Preparation of lithium ion batteries
1. Preparation of cathode Material
Mixing a lithium source, ferric phosphate and a carbon source in different proportions respectively to obtain a first mixture; wet grinding the first mixture to obtain a second mixture; adjusting the solid content of the second mixture, feeding the second mixture into spray drying equipment at a feeding speed V, and performing morphology and particle size regulation and control on spray drying pressure P in the spray drying equipment to obtain a third mixture of spherical particles; calcining the third mixture in a protective atmosphere at a calcination temperature elevated at a rate of elevation; and cooling and sieving the calcined material to obtain the lithium iron phosphate anode material.
Wherein the lithium source is lithium hydroxide, the carbon source is acetic acid, and the molar ratio of iron ions to phosphorus ions in the ferric phosphate is 1:1; the molar ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is 1:1; the mass ratio of the carbon source to the lithium iron phosphate anode material is 0.08:1; particle size D of the second mixture 50 0.5 μm; the solid content A is 20%; the feeding speed V is 80kg/h; the spray drying pressure P is 0.2Mpa,
1.6; the temperature rising rate is 1.5 ℃/min, the calcining temperature is 680 ℃, and the calcining time is 8h.
2. Preparation of positive electrode plate
The prepared lithium iron phosphate anode material, carbon black and polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 96:2:2, mixing, adding N-methyl pyrrolidone (NMP) to prepare anode slurry, uniformly coating the prepared anode slurry on two sides of an anode current collector aluminum foil, drying at 120 ℃, and rolling and cutting to obtain an anode sheet.
3. Preparation of negative electrode plate
The graphite, the carbon black, the sodium carboxymethyl cellulose and the styrene-butadiene rubber are mixed according to the mass ratio of 96.5:1.5:1.5: mixing 0.5, stirring with a solvent under the action of a vacuum stirrer to obtain negative electrode slurry, uniformly coating the prepared negative electrode slurry on two sides of a negative electrode current collector copper foil, baking, drying, and rolling and cutting to obtain a negative electrode plate, wherein the baking temperature is 90-110 ℃.
4. Preparation of electrolyte
Mixing Ethylene Carbonate (EC) and dimethyl carbonate (DMC) according to a volume ratio of 1:1, and then adding 1.15mol/L LiPF6 to uniformly mix to prepare the electrolyte.
5. Preparation of separator
The PP film was used as a separator.
6. Preparation of lithium ion batteries
The negative pole piece and the positive pole piece prepared by the steps are dried, then are wound together with the diaphragm to prepare a winding battery cell, the positive pole aluminum tab and the negative pole copper nickel-plated tab are welded on the battery cell, and the welded battery cell is placed into an aluminum-plastic film with punched pits for packaging; and (3) pouring electrolyte, and forming to a constant volume to prepare the lithium ion battery.
2. Test method
1. Tap density testing method for lithium iron phosphate positive electrode material
The prepared lithium iron phosphate anode material is arranged in a scale measuring cylinder and is fixed on a mechanical vibration device, a vibration motor drives the mechanical vibration device to vibrate vertically, the scale measuring cylinder provided with the lithium iron phosphate anode material vibrates in a beat mode along with the mechanical vibration device, when the vibration times reach set times, the mechanical vibration device stops vibrating, the volume of the scale measuring cylinder is read, and according to the definition of density: and dividing the mass by the volume to obtain the tap density of the tap-compacted lithium iron phosphate positive electrode material.
2. Method for testing capacity of lithium ion battery
Standing the lithium ion battery for 30min at 25 ℃, discharging the lithium ion battery to a lower limit voltage by adopting a constant current of 0.1C, and standing for 30min; charging the lithium ion battery to the upper limit voltage by adopting a constant current and constant voltage of 0.1C, obtaining the specific charge capacity, and standing for 30min; and discharging the lithium ion battery to a lower limit voltage by adopting a constant current of 0.1C to obtain the specific discharge capacity.
3. Method for testing specific capacity of lithium ion battery
Standing the lithium ion battery for 30min at 25 ℃, discharging the lithium ion battery to a lower limit voltage by adopting a constant current of 1C, and standing for 30min; charging the lithium ion battery to the upper limit voltage by adopting a constant current and constant voltage of 1C, and standing for 30min; and discharging the lithium ion battery to a lower limit voltage by adopting a 1C constant current to obtain a discharge specific capacity.
4. Method for testing initial charge performance of lithium ion battery
And standing the lithium ion battery at 25 ℃ for 30min, then charging to 4.0V at constant current and constant voltage, obtaining the first charge capacity by constant voltage charging cut-off current of 0.05mA, standing for 10min, then discharging to 2.0V at constant current, obtaining the first discharge capacity, and calculating the first charge and discharge efficiency.
Example 2
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
the molar ratio of iron ions to phosphorus ions in the ferric phosphate is 0.99:1; the molar ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is 0.95:1; the mass ratio of the carbon source to the lithium iron phosphate positive electrode material is 0.06:1.
Example 3
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
the molar ratio of iron ions to phosphorus ions in the ferric phosphate is 1.01:1; the molar ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is 1.05:1; the mass ratio of the carbon source to the lithium iron phosphate positive electrode material is 0.1:1.
Example 4
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
particle size D of the second mixture 50 0.4 μm; the solid content A is 25%; the feeding speed V is 60kg/h; the spray drying pressure P is 0.25Mpa,
0.61.
Example 5
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
particle size D of the second mixture 50 0.35 μm; the solid content A is 30%; the feeding speed V is 50kg/h; the spray drying pressure P is 0.3Mpa,
0.3.
Example 6
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
particle size D of the second mixture 50 0.3 μm; the solid content A is 40%; the feeding speed V is 40kg/h; the spray drying pressure P is 0.4Mpa,
0.1.
Example 7
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
the temperature rising rate is 1 ℃/min, the calcining temperature is 660 ℃, and the calcining time is 6h.
Example 8
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
the temperature rising rate is 2 ℃/min, the calcining temperature is 700 ℃, and the calcining time is 10h.
Comparative example 1
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
the molar ratio of iron ions to phosphorus ions in the ferric phosphate is 0.98:1; the molar ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is 0.9:1; mass ratio of carbon source to lithium iron phosphate positive electrode material0.04:1; particle size D of the second mixture 50 0.2 μm; the solid content A is 10%; the feeding speed V is 90kg/h; the spray drying pressure P is 0.1Mpa,
14.4; the temperature rising rate is 0.5 ℃/min, the calcining temperature is 600 ℃, and the calcining time is 5h.
Comparative example 2
A lithium ion battery was prepared according to the method of example 1, while the lithium ion battery was tested according to the test method in example 1, except for the following differences:
the molar ratio of iron ions to phosphorus ions in the ferric phosphate is 1.02:1; the molar ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is 1.1:1; the mass ratio of the carbon source to the lithium iron phosphate anode material is 0.12:1; particle size D of the second mixture 50 0.6 μm; the solid content A is 50%; the feeding speed V is 30kg/h; the spray drying pressure P is 0.7Mpa,
0.02; the temperature rising rate is 2.5 ℃/min, the calcining temperature is 750 ℃, and the calcining time is 11h.
2. Test results
Table 1 parameters and test results for examples 1 to 3 and comparative examples 1 to 2
The result shows that when the mole ratio of iron ions to phosphorus ions in the ferric phosphate is controlled within the range of (0.99-1.01): 1, the mole ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is controlled within the range of (0.95-1.05): 1, and the mass ratio of the carbon source to the lithium iron phosphate positive electrode material is controlled within the range of (0.06-0.1): 1, the capacity and rate capability of the lithium ion battery can be remarkably improved.
Table 2 parameters and test results of example 1 and examples 4 to 6 and comparative examples 1 to 2
The result shows that when the particle diameter D of the second mixture 50 Controlling the solid content A of the second mixture to be 20-40% and the feeding speed V of the second mixture to be 40kg/h within the range of 0.3-0.5 mu m
The spray-drying pressure P of the second mixture is controlled within the range of 0.2MPa to 0.4MPa within the range of 80kg/h
Table 3 parameters and test results of example 1 and examples 7 to 9 and comparative examples 1 to 2
The result shows that when the temperature rising rate is controlled within the range of 1-2 ℃/min, the calcination temperature is controlled within the range of 650-700 ℃ and the calcination time is controlled within the range of 6-10 h, the capacity and the rate capability of the lithium ion battery can be obviously improved.
Meanwhile, as can be seen from fig. 2a to fig. 3b, fig. 2a and fig. 2b show comparative SEM images of the lithium iron phosphate positive electrode material prepared in example 1 under a certain pressure condition, and fig. 3a and fig. 3b show comparative SEM images of the lithium iron phosphate positive electrode material prepared in comparative example 1 under a certain pressure condition, and as can be seen from the SEM images in fig. 2a to fig. 3b, the tap density of the lithium iron phosphate positive electrode material prepared by adopting the above conditions in the present application is higher, so that the discharge capacity of the battery is not lost when the lithium iron phosphate positive electrode material is applied in the battery, and the rate capability of the battery is improved.
The above steps are presented merely to aid in understanding the method, structure, and core ideas of the present application. It will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the principles of the application, which are also intended to be within the scope of the appended claims.
Claims (10)
1. The preparation method of the lithium iron phosphate anode material is characterized by comprising the following steps of:
mixing a lithium source, ferric phosphate and a carbon source in different proportions respectively to obtain a first mixture;
wet grinding the first mixture to obtain a second mixture;
adjusting the solid content of the second mixture, feeding the second mixture into spray drying equipment at a feeding speed V, and performing morphology and particle size regulation and control on spray drying pressure P in the spray drying equipment to obtain a third mixture of spherical particles;
and carrying out heat treatment on the third mixture in a protective atmosphere to obtain the spherical particle lithium iron phosphate positive electrode material.
2. The method of preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the second mixture is defined as having a solids content a, a feed rate V, and a spray drying pressure P that satisfy:
3. the method for preparing a lithium iron phosphate positive electrode material according to claim 2, wherein the solid content a satisfies: a is more than or equal to 20% and less than or equal to 40%; and/or the number of the groups of groups,
the feed rate V satisfies: v is more than or equal to 40kg/h and less than or equal to 80kg/h; and/or;
the spray drying pressure P satisfies: p is more than or equal to 0.2MPa and less than or equal to 0.6MPa.
4. The method for preparing a lithium iron phosphate positive electrode material according to claim 3, wherein the spray-drying pressure P satisfies: p is more than or equal to 0.2MPa and less than or equal to 0.4MPa.
5. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the lithium source, the iron phosphate and the carbon source are mixed in different proportions,
the mole ratio of iron ions to phosphorus ions in the ferric phosphate is (0.99-1.01): 1; and/or the number of the groups of groups,
the molar ratio of lithium ions in the lithium source to iron ions in the ferric phosphate is (0.95-1.05): 1; and/or the number of the groups of groups,
the mass ratio of the carbon source to the lithium iron phosphate positive electrode material is (0.06-0.1): 1.
6. The method of preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the lithium source comprises; one or more of lithium acetate, lithium chloride, lithium carbonate or lithium hydroxide; and/or the number of the groups of groups,
the carbon source includes: one or more of citric acid, polyacrylic acid, phenolic resin, polyethylene glycol or acetic acid.
7. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the second mixture has a particle size D 50 μm, satisfy: d is more than or equal to 0.3 50 ≤0.5。
8. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the heat-treating the third mixture in a protective atmosphere to obtain the lithium iron phosphate positive electrode material comprises:
calcining the third mixture in a protective atmosphere at a calcination temperature elevated at a rate of elevation;
and cooling and sieving the calcined material to obtain the lithium iron phosphate anode material.
9. The method for preparing a lithium iron phosphate positive electrode material according to claim 8, wherein the conditions for calcination are: the temperature rising rate is 1-2 ℃/min, the calcining temperature is 650-700 ℃ and the calcining time is 6-10 h.
10. A lithium iron phosphate positive electrode material prepared by the preparation method according to any one of claims 1 to 9, characterized in that the lithium iron phosphate positive electrode material has a chemical formula of LiFePO 4 The lithium iron phosphate positive electrode material is spherical particles, and the tap density of the lithium iron phosphate positive electrode material is 0.8-1.8 g/cm 3 。
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