CN109148836B - Carbon-coated lithium iron phosphate cathode material and preparation method thereof - Google Patents

Carbon-coated lithium iron phosphate cathode material and preparation method thereof Download PDF

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CN109148836B
CN109148836B CN201710465582.4A CN201710465582A CN109148836B CN 109148836 B CN109148836 B CN 109148836B CN 201710465582 A CN201710465582 A CN 201710465582A CN 109148836 B CN109148836 B CN 109148836B
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iron phosphate
lithium
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CN109148836A (en
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战鹏
方秀利
黄勇
金鹰
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Zhongtian Xinxing Material Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/36—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
    • 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
    • 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
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    • 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

Abstract

The invention provides a carbon-coated lithium iron phosphate positive electrode material and a preparation method thereof, wherein the method comprises the following steps: mixing an iron-containing compound, a lithium-containing compound, a phosphorus-containing compound and a high molecular dispersant with a solvent to form first slurry; mixing the first slurry with an oligosaccharide to form a second slurry; drying the second slurry to prepare a precursor; and calcining the precursor to obtain the graphitized carbon-coated lithium iron phosphate cathode material. The carbon-coated lithium iron phosphate cathode material prepared by the invention has the advantages of uniform and compact carbon coating layer, thin thickness and good conductivity, can effectively improve the electrochemical performance of the material, has low implementation cost, is convenient for production management, and is suitable for large-scale industrial production.

Description

Carbon-coated lithium iron phosphate cathode material and preparation method thereof
Technical Field
The invention relates to the field of lithium ion battery anode materials, in particular to a carbon-coated lithium iron phosphate anode material and a preparation method thereof.
Background
The development of lithium ion battery positive electrode materials is closely related to the performance of lithium ion batteries, so people are always actively developing novel lithium ion battery positive electrode materials. The existing lithium ion battery anode material in the current market mainly comprises: lithium manganate (LiMn)2O4) Lithium iron phosphate (LiFePO)4) Ternary materials (NCA)&NCM) and lithium cobaltate (LiCoO)2). Among them, lithium iron phosphate is a most environmentally friendly cathode material having the highest safety performance, the best cycle performance, the lowest cost so far, and is therefore gaining favor in the field of lithium ion batteries. However, the conventional lithium iron phosphate cathode material has the defects of low conductivity, low lithium ion migration speed and the like, and the lithium ion utilization rate and the conductivity of the lithium iron phosphate cathode material need to be improved through primary particle nanocrystallization, metal ion doping and carbon coating. However, the particle nanocrystallization can reduce the volume energy density of the material while shortening the diffusion distance of lithium ions, and the processability of the material in the preparation of a battery becomes worse, which are all problems to be solved when the lithium iron phosphate cathode material is used. Secondly, the metal ions can be doped to a certain degreeThe conductivity of the material is improved, but the doping effect of metal ions is not thoroughly proved, the accurate substitution of the target ions by the doped ions cannot be realized through the existing doping mode, and the doped ions are in the gap positions and even block the diffusion channels of the lithium ions, so that the electrochemical performance of the material is influenced.
In order to improve the conductivity of the lithium iron phosphate material and ensure the effective exertion of the capacity of the lithium iron phosphate, the important mode is to perform carbon coating on the lithium iron phosphate nano particles. The common carbon coating method is to crack an organic carbon source to form an in-situ carbon coating layer on the surface of the nanoparticles, but the method is difficult to realize uniform coating of each nanoparticle. In addition, the organic carbon source cracking carbon has high disorder degree and poor conductivity, the conductivity of the lithium iron phosphate is difficult to greatly improve by adding a trace amount of the carbon source cracking carbon, the addition amount of the carbon source cracking carbon is too large, and the formed carbon layer is too thick, so that the volume energy density of the material is reduced, and the transmission of lithium ions is also hindered. In order to solve the problem, in patents CN104743537A and CN105810911A, high-conductivity advanced carbon materials such as graphene and carbon nanotubes are used to modify lithium iron phosphate, so as to improve the capacity exertion, rate capability and low-temperature performance of the material. However, these introduced materials are difficult to achieve good dispersion among the nanoparticles on one hand, and on the other hand, they are expensive, so that the original cost performance advantage of the lithium iron phosphate is lost, and the lithium iron phosphate is in a market competition disadvantage.
Disclosure of Invention
In view of the above, it is necessary to provide a carbon-coated lithium iron phosphate cathode material with uniform and compact carbon coating, thin carbon layer, and good conductivity.
A preparation method of a carbon-coated lithium iron phosphate positive electrode material comprises the following steps:
mixing an iron-containing compound, a lithium-containing compound, a phosphorus-containing compound and a high molecular dispersant with a solvent to form first slurry;
mixing the first slurry with an oligosaccharide to form a second slurry;
drying the second slurry to prepare a precursor;
and calcining the precursor to obtain the graphitized carbon-coated lithium iron phosphate cathode material.
The carbon-coated lithium iron phosphate cathode material prepared by the preparation method of the carbon-coated lithium iron phosphate cathode material comprises the following steps that a carbon layer with the uniform thickness of 1-2nm is coated on the outer surface of lithium iron phosphate, the median particle size of the cathode material is 0.5-5.0 mu m, and the tap density is more than or equal to 0.8g/cm3The carbon content is 1.0 to 2.0 wt%.
The invention adopts oligosaccharide and the macromolecular dispersant as a combined carbon source, wherein the macromolecular dispersant adopts the same macromolecular substance or two or more macromolecular substances with different spatial configurations and different molecular weights and long-short chain matching. Compared with the traditional single dispersant, the combined use of the macromolecular dispersant is beneficial to further enhancing the dispersing effect of the nano particles, and uniform and ultrathin carbon coating can be realized.
In the mixing process, the macromolecular dispersing agent is added firstly, then the oligosaccharide is added, and the principle of intermolecular force and steric hindrance effect of macromolecular dispersing agents with different molecular weights or different spatial configurations is utilized to avoid particle agglomeration caused by one-time addition, so that the macromolecular dispersing agent and the oligosaccharide can be well adsorbed on the particle surface. After the precursor prepared by the method is sintered, the precursor not only has a uniform and ultrathin carbon coating layer, but also can effectively avoid the fusion growth of lithium iron phosphate nano particles, and ensure that lithium ions have a shorter diffusion path, thereby effectively improving the electrochemical performance of the material. The method reduces the usage amount of the dispersing agent, is beneficial to reducing the production cost, is convenient to operate and manage, and is suitable for large-scale industrial production.
Drawings
Fig. 1 is a transmission electron micrograph of the carbon-coated lithium iron phosphate positive electrode material in example 1 of the present invention.
Fig. 2 is a transmission electron micrograph of the carbon-coated lithium iron phosphate positive electrode material in comparative example 3 of the present invention.
Fig. 3 is a raman spectrum graph of the carbon-coated lithium iron phosphate positive electrode material in example 1 of the present invention.
Fig. 4 is a raman spectrum graph of the carbon-coated lithium iron phosphate positive electrode material in comparative example 3 of the present invention.
Fig. 5 is a charge-discharge curve diagram of the carbon-coated lithium iron phosphate positive electrode material in example 1 of the present invention.
Fig. 6 is a charge-discharge curve diagram of the carbon-coated lithium iron phosphate positive electrode material in comparative example 3 of the present invention.
Fig. 7 is a schematic diagram of different adding sequences of a combined carbon source for coating a lithium iron phosphate material according to an embodiment of the present invention.
Description of the main elements
Is free of
The following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
While the present invention is susceptible of embodiment in different forms, there is shown in the drawings and will herein be described in detail specific embodiments of the invention with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated and/or described.
The invention provides a preparation method of a carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps:
mixing an iron-containing compound, a lithium-containing compound, a phosphorus-containing compound and a high molecular dispersant with a solvent to form first slurry;
mixing the first slurry with an oligosaccharide to form a second slurry;
drying the second slurry to prepare a precursor;
and calcining the precursor to obtain the graphitized carbon-coated lithium iron phosphate cathode material.
The invention provides a method for carrying out combined design on an organic carbon source based on the concept that the carbon layer is generated on the surface of lithium iron phosphate nano-particles in situ by cracking the organic carbon, which comprises the following steps: by the combined use of oligosaccharide and high molecular dispersant, a uniform, ultrathin and high-conductivity carbon layer with high graphitization degree can be formed on the surface of the lithium iron phosphate nano-particles only by adding a small amount of organic carbon source, a three-dimensional high-conductivity network of the lithium iron phosphate powder is constructed, and the defects of nonuniform carbon coating, poor conductivity of the coated carbon layer and the like in the traditional preparation process are overcome. On the basis of ensuring that the lithium iron phosphate powder has excellent conductivity, the ultrathin and high-conductivity carbon layer has the lowest impact on the de-intercalation of lithium ions in the charging and discharging processes, and the 0.2C charging and discharging gram capacity of the prepared high-performance lithium iron phosphate cathode material is 163mAh/g and 160mAh/g respectively, and has excellent rate performance and high volume energy density. The method has simple process and low cost, is suitable for large-scale production, and has good application prospect.
According to a specific embodiment of the present invention, the iron-containing compound includes at least one of iron phosphate, ferrous oxalate, and ferric oxide, the lithium-containing compound includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, and lithium acetate, and the phosphorus-containing compound includes at least one of lithium dihydrogen phosphate, iron phosphate, and ammonium dihydrogen phosphate.
According to a specific embodiment of the present invention, the polymeric dispersant is an alcohol or an ester with a molecular weight greater than 500, and includes at least one of polyethylene glycol, linear polyvinyl alcohol, branched polyvinyl alcohol ester, and polyacrylamide.
According to an embodiment of the present invention, the ratio of the iron-containing compound, the lithium-containing compound, the phosphorus-containing compound and the polymeric dispersant is 1: 1.05-1.15: 1.02-1.10: 0.2 × 10-3～0.5×10-3。
According to an embodiment of the present invention, in the step of mixing the iron-containing compound, the lithium-containing compound, the phosphorus-containing compound, and the polymeric dispersant with the solvent, the mixing includes ball milling and premixing and grinding, and the mixing time is greater than 2 hours.
According to a particular embodiment of the invention, the particles in the first slurry have a size of less than 4 μm.
According to a specific embodiment of the present invention, the step of mixing the first slurry with the oligosaccharide comprises ball milling and premixing, and the mixing time is greater than 2 hours.
According to an embodiment of the present invention, the oligosaccharide is an oligomer with a molecular weight of less than 400, and includes at least one of glucose, sucrose and fructose, and the molar ratio of the oligosaccharide to the polymeric dispersant is 150:1 to 200: 1. Preferably, the molar ratio of the glucose to the polymeric dispersant is 200: 1.
The polymer dispersant of the present invention includes both the combination of different molecular weights of the same polymer substance and the combination of different molecular weights of different polymer substances. The invention can reduce the usage amount of the dispersant and enhance the dispersion effect by combining the substances with different molecular weights.
The macromolecular dispersant composition can be used as a dispersant, can also be used as a secondary carbon source to be matched with a main organic carbon source, is convenient for production management while effectively achieving the purposes of reducing the amount and improving the efficiency, and reduces the cost.
According to an embodiment of the present invention, in the step of mixing the first slurry with the oligosaccharide, the mixing is followed by sanding to form the second slurry.
According to the specific embodiment of the invention, the particle size of the second slurry is 0.20-1.20 μm, the solid content is 25-45%, and the viscosity is 500-15000 mpa.s.
According to a specific embodiment of the present invention, the drying of the second slurry into a precursor is spray drying.
According to a specific embodiment of the present invention, the precursor calcination is preferably performed by a carbothermic method, further comprising: and placing the precursor under the protection of nitrogen, pressurizing by 50-100 Pa, heating to 600-800 ℃ at a heating rate of 2-10 ℃/min, calcining at a constant temperature for 4-20 hours, and cooling to room temperature.
The invention also provides a carbon-coated lithium iron phosphate positive electrode material prepared by the preparation method, wherein the outer surface of the lithium iron phosphate is coated with a uniform 1-2nm carbon layer, the median particle size of the positive electrode material is 0.5-5 mu m, and the tap density is more than or equal to 0.8g/cm3The carbon content is 1.0 to 2.0 wt%.
In the preparation method, in the calcining process, the uniformly coated carbon layer can effectively prevent the fusion growth of the lithium iron phosphate nano particles, and ensure that lithium ions have a shorter diffusion path. Therefore, the invention increases the conductivity of the carbon layer and reduces the thickness of the carbon layer, thereby ensuring the realization of the ultrathin and high-conductivity carbon layer.
In addition, the invention adds the high molecular dispersant and the oligosaccharide in sequence, can ensure that the lithium iron phosphate nano-particles can be efficiently and uniformly coated even if a small amount of organic carbon source is added, and a carbon layer generated in situ after pyrolysis is thin, good in conductivity and tight in coating. In order to further illustrate the influence of the sequence of adding the polymeric dispersant and the oligosaccharide on the finally prepared carbon-coated lithium iron phosphate cathode material, the invention respectively provides results references of examples and comparative examples.
Example 1:
accurately weighing 1000g of commercially available ferric orthophosphate, 13.5g of lithium dihydrogen phosphate, 246g of lithium carbonate, 11g of PEG8000 and 5.5g of PEG4000 (the molar ratio of PEG8000 to PEG4000 is 1:1), adding 2000g of deionized water, performing primary grinding and premixing for 2h by using a ball mill, adding 100g of glucose, continuously grinding for 2h, feeding the slurry into a sand mill for grinding until the granularity reaches 0.30 +/-0.05 mu m, performing spray drying on the slurry, placing the dried precursor into a nitrogen atmosphere furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, calcining for 10 h at constant temperature, cooling to room temperature, and crushing the material to obtain the lithium iron phosphate anode material coated with the combined carbon source.
The median particle size of the product obtained in this example was 1.5. mu.m, and the tap density was 1.08g/cm3The carbon content is 1.55 wt%, the charge capacity of the button cell at 0.2C is 163mAh/g, the discharge capacity is 160mAh/g, and the discharge capacity of the button cell at 5C is 140 mAh/g.
Comparative example 1
Accurately weighing 1000g of commercially available ferric orthophosphate, 13.5g of lithium dihydrogen phosphate, 246g of lithium carbonate and 11g of PEG4000, adding 2000g of deionized water, performing primary grinding and premixing for 2h by using a ball mill, adding 100g of glucose, continuously grinding for 2h, feeding the slurry into a sand mill for grinding until the granularity reaches 0.30 +/-0.05 mu m, performing spray drying on the slurry, placing the dried precursor into a nitrogen atmosphere furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, calcining for 10 h at constant temperature, cooling to room temperature, and crushing the material to obtain the lithium iron phosphate cathode material coated by using the combined carbon source.
The product obtained in the comparative example has a median particle size of 1.5 μm and a tap density of 1.01g/cm3The carbon content is 1.52 wt%, the charge capacity of the button cell is 160mAh/g at 0.2C, the discharge capacity is 153mAh/g, and the discharge capacity of the button cell is 137mAh/g at 5C.
Comparative example 2:
accurately weighing 1000g of commercially available ferric phosphate, 13.5g of lithium dihydrogen phosphate, 246g of lithium carbonate and 22g of PEG8000, adding 2000g of deionized water, performing primary grinding and premixing for 2h by using a ball mill, adding 100g of glucose, continuously grinding for 2h, feeding the slurry into a sand mill for grinding until the granularity reaches 0.30 +/-0.05 mu m, performing spray drying on the slurry, placing the dried precursor into a nitrogen atmosphere furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, calcining for 10 h at constant temperature, cooling to room temperature, discharging, and crushing to obtain the lithium iron phosphate cathode material coated by using the combined carbon source.
The product obtained in the comparative example has a median particle size of 1.5 μm and a tap density of 1.05g/cm3The carbon content is 1.56 wt%, the charge capacity of the button cell is 162mAh/g at 0.2C, the discharge capacity is 153mAh/g, and the discharge capacity of the button cell is 138mAh/g at 5C.
Comparative example 3:
the method comprises the steps of accurately weighing 1000g of commercially available ferric phosphate, 13.5g of phosphoric acid monobasic, 246g of lithium carbonate and 100g of glucose, adding 2000g of deionized water, performing primary grinding and premixing for 2h by using a ball mill, adding 11g of PEG8000 and 5.5g of PEG4000 (the molar ratio of PEG8000 to PEG4000 is 1:1), continuously grinding for 2h, feeding the slurry into a sand mill for grinding, performing spray drying on the slurry after the particle size reaches 0.30 +/-0.05 mu m, placing the dried precursor into a nitrogen atmosphere furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, performing constant-temperature calcination for 10 h, cooling to room temperature, discharging, and crushing to obtain the lithium iron phosphate anode material coated with the combined carbon source.
The product obtained in the comparative example has a median particle size of 1.5 μm and a tap density of 0.95g/cm3The carbon content is 1.62 wt%, the charge capacity of the button cell at 0.2C is 152.9mAh/g, the discharge capacity is 150.2mAh/g, and the discharge capacity of the button cell at 5C is 108 mAh/g.
As can be seen from comparative examples and examples, the button cell prepared by using the lithium iron phosphate positive electrode material prepared in the embodiment has a 0.2C charge capacity of 163mAh/g and a discharge capacity of 160 mAh/g. The button cell prepared by the lithium iron phosphate anode materials prepared in the comparative examples 1-3 has 0.2C discharge capacity less than 155 mAh/g. From the aspect of charge and discharge capacity, the performance of the button cell prepared from the lithium iron phosphate cathode material prepared in the embodiment is superior to that of the button cell prepared from the lithium iron phosphate cathode material prepared in the comparative example.
In addition, from the viewpoint of uniformity of the surface-coated carbon layer, as shown in fig. 1, the surface of the product prepared in example 1 is coated with a uniform 1-2nm ultra-thin carbon layer. And FIG. 2 shows the product of comparative example 3, which has a carbon coating layer with uneven thickness on the surface.
From the Raman spectrum curve, the ID/IG < 1 of the Raman spectrum of the product prepared by the example shown in FIG. 3 shows that the carbon coating layer is a highly graphitized carbon layer and has good electrical conductivity. In contrast, the product prepared in comparative example 3, as can be seen from FIG. 4, has a Raman spectrum ID/IG > 1, indicating a high degree of disorder of the coated carbon layer.
From the charging and discharging conditions, as shown in fig. 5, the button cell made of the product prepared in example 1 has a 0.2C charge gram capacity of 163mAh/g, a discharge capacity of 160mAh/g, and excellent rate capability. While the button cell made of the product prepared in comparative example 3 has a 0.2C charge gram capacity of 152.9mAh/g and a discharge of 150.2mAh/g, as can be seen from fig. 6. From the viewpoint of charge and discharge capacity, the performance of the button cell made of the product of the embodiment is better than that of the button cell made of the product prepared by the comparative example.
As can be seen from fig. 7, the schematic diagram of the formation of the coating on the lithium iron phosphate material by different addition sequences of different carbon sources includes a mode a and a mode B, where the mode a means that the iron phosphate, lithium dihydrogen phosphate, and lithium carbonate are primarily ground and premixed with a polymeric dispersant, and the combination of a polymeric long chain and a polymeric short chain can form a coating on the particle surface, so as to ensure uniform dispersion of the particles, and then a main carbon source (oligosaccharide) is added into the uniformly dispersed system to fill the vacancies on the particle surface, so that the obtained precursor of the carbon source is uniformly distributed, and the agglomeration effect among particles is effectively avoided. Compared with the mode A, the mode B is characterized in that a main carbon source (oligosaccharide) is added firstly and then forms coating on the surfaces of the particles, but the agglomeration phenomenon among the particles cannot be avoided due to weak intermolecular force of the oligosaccharide, and then the dispersing effect of the polymer dispersing agent is poor, so that the prepared lithium iron phosphate particles are large and the electrochemical performance is poor.
Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.

Claims (8)

1. A preparation method of a carbon-coated lithium iron phosphate positive electrode material is characterized by comprising the following steps:
mixing an iron-containing compound, a lithium-containing compound, a phosphorus-containing compound and a high molecular dispersant with a solvent to form first slurry; wherein the molar ratio of the iron element in the iron-containing compound, the lithium element in the lithium-containing compound, the phosphorus element in the phosphorus-containing compound and the polymer dispersant is 1: 1.05-1.15: 1.02-1.10: 0.20 × 10-3～0.5×10-3(ii) a The high molecular dispersing agent comprises at least one of polyethylene glycol, linear polyvinyl alcohol, branched polyvinyl alcohol ester and polyacrylamide, and the high molecular dispersing agent adopts the same high molecular substance or more than two high molecular substances with different spatial configurations, wherein the same high molecular substance or the different high molecular substances have different molecular weights and are matched with long and short chains;
mixing the first slurry with an oligosaccharide to form a second slurry;
drying the second slurry to prepare a precursor;
and calcining the precursor to obtain the graphitized carbon-coated lithium iron phosphate cathode material.
2. The method according to claim 1, wherein the iron-containing compound includes at least one of iron phosphate, ferrous oxalate, and ferric oxide, the lithium-containing compound includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, and lithium acetate, and the phosphorus-containing compound includes at least one of lithium dihydrogen phosphate, iron phosphate, and ammonium dihydrogen phosphate.
3. The method for preparing the carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step of mixing the iron-containing compound, the lithium-containing compound, the phosphorus-containing compound, the polymeric dispersant and the solvent, the mixing comprises ball milling, premixing and grinding.
4. The method for preparing the carbon-coated lithium iron phosphate cathode material according to claim 1, wherein in the step of mixing the first slurry with the oligosaccharide, the mixing comprises ball milling, premixing and grinding, and the mixing time is longer than 2 hours.
5. The method for preparing the carbon-coated lithium iron phosphate cathode material according to claim 1, wherein the oligosaccharide comprises at least one of glucose, sucrose and fructose, and the molar ratio of the oligosaccharide to the polymeric dispersant is 150: 1-200: 1.
6. The method for preparing a carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step of mixing the first slurry with the oligosaccharide, the second slurry is formed by performing sand milling and grinding after the mixing.
7. The method for preparing a carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein the precursor calcination further comprises: and placing the precursor under the protection of nitrogen, pressurizing by 50-100 Pa, heating to 600-800 ℃ at a heating rate of 2-10 ℃/min, calcining at a constant temperature for 4-20 hours, and cooling to room temperature.
8. The carbon-coated lithium iron phosphate positive electrode material prepared by the preparation method of the carbon-coated lithium iron phosphate positive electrode material according to any one of claims 1 to 7, characterized in that the outer surface of the lithium iron phosphate is coated with a uniform carbon layer of 1-2nm, the median particle size of the positive electrode material is 0.5-5 μm, and the tap density is not less than 0.8g/cm3The carbon content is 1.0 to 2.0 wt%.
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CN102275893A (en) * 2011-07-20 2011-12-14 湖南维邦新能源有限公司 Method for preparing lithium iron phosphate and lithium iron phosphate resulting thereby
KR20130029265A (en) * 2011-09-14 2013-03-22 삼성전기주식회사 Method for preparing active agent slurry of electrode, and electrochemical capacitors comprising the electrode
US9966549B2 (en) * 2012-02-23 2018-05-08 Northwestern University Nanostructured carbon electrode, methods of fabricating and applications of the same
CN102760879B (en) * 2012-08-01 2014-10-15 东北师范大学 Method for preparing nanometer lithium iron phosphate/carbon compound with stable low temperature performance
CN106299355A (en) * 2015-10-15 2017-01-04 江西省金锂科技股份有限公司 A kind of preparation method of nano-carbon coated lithium iron phosphate positive material
CN106744780B (en) * 2017-03-22 2019-06-28 广东光华科技股份有限公司 A kind of preparation method of high-pressure solid lithium ion battery anode material lithium iron phosphate

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