Preparation method of lithium iron phosphate material with adhesion and high conductivity and lithium ion secondary battery

Abstract

The application relates to a preparation method of a lithium iron phosphate material with adhesion and high conductivity and a lithium ion secondary battery. The preparation method of the lithium iron phosphate material with adhesion and high conductivity comprises the following steps: mixing a carbon source, an iron source, a phosphorus source and a lithium source to obtain a mixed material; configuring the mixed material into mixed water slurry with a solid content of 30-60%; sand grinding the mixed water slurry to obtain a precursor slurry; performing spray drying on the precursor slurry; obtaining a precursor powder after the spray drying; performing high-temperature heat treatment on the precursor powder under the protection of an inert atmosphere to obtain high-conductivity lithium iron phosphate; performing oxidation treatment on the surface inorganic carbon of the high-conductivity lithium iron phosphate; taking a bonding agent; and grafting the bonding agent onto the surface inorganic carbon through a grafting reaction to obtain the lithium iron phosphate material with adhesion and high conductivity. The preparation method of the lithium iron phosphate material with adhesion and high conductivity has the advantages of high slurry preparation efficiency and good slurry uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a lithium iron phosphate material. BACKGROUND

[0002] Lithium ion batteries are a kind of secondary battery system with two different lithium intercalation compounds that can reversibly deintercalate lithium ions as positive and negative electrodes. With the advantages of high specific capacity, long cycle life, small self-discharge, etc., it is widely used in mobile phones, portable computers, video cameras, cameras, electric vehicles, energy storage and other fields. Lithium iron phosphate is applied to pure electric buses, energy storage and other fields due to its high safety performance, good cycle life, environmental friendliness and other advantages.

[0003] The homogenate process in the existing lithium iron phosphate battery is to disperse the active material powder, the conductive agent and the binder into a slurry in a solvent, then coat it on the aluminum foil current collector to form a positive electrode sheet, and finally assemble it into a lithium ion battery. Since the particle size distribution of the existing lithium iron phosphate positive electrode material is from nanoscale to micrometer scale, and the conductive agent is mostly in the form of micron or even nanometer powder, uneven dispersion of lithium iron phosphate, conductive agent and binder is easily caused during the stirring process of high viscosity slurry, which eventually leads to uneven surface density of the prepared electrode sheet and large difference in internal resistance at different sites.

[0004] In addition, during the entire battery manufacturing process, the addition of conductive agent and binder and the stirring and dispersion result in long slurry preparation time, low battery production efficiency, and are not conducive to energy saving and cost reduction of battery manufacturing end. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a preparation method of lithium iron phosphate material with adhesion and high conductivity, which integrates the conductive agent and the binder into the lithium iron phosphate, so that the prepared lithium iron phosphate material with adhesion and high conductivity not only has high conductivity, but also has adhesion. Another purpose of the present application is to provide a lithium ion secondary battery with uniform and high consistency inside the electrode sheet.

[0006] In a first aspect, the present application provides a preparation method of lithium iron phosphate material with adhesion and high conductivity, characterized in that it comprises the following steps:

[0007] (1) mixing a carbon source, an iron source, a phosphorus source and a lithium source to obtain a mixture, the addition mass of the carbon source being 4-10% of the total mass of the iron source, the phosphorus source and the lithium source; configuring the mixture into a mixed water slurry with a solid content of 30-60%; sand grinding the mixed water slurry to obtain a precursor slurry;

[0008] (2) spray drying the precursor slurry, and obtaining the high-conductivity lithium iron phosphate coated with inorganic carbon on the surface by high-temperature heat treatment of the precursor powder obtained after the spray drying under the protection of an inert atmosphere;

[0009] (3) oxidizing the inorganic carbon on the surface of the high-conductivity lithium iron phosphate, and then taking the binder to graft the binder to the inorganic carbon on the surface through a grafting reaction, thereby obtaining the lithium iron phosphate material with adhesion and high conductivity.

[0010] The preparation method of the lithium iron phosphate material with adhesion and high conductivity combines the carbon source and the lithium iron phosphate and combines the binder and the inorganic carbon on the surface of the lithium iron phosphate through a grafting reaction, thereby obtaining the lithium iron phosphate material with high conductivity and adhesion. Since the material itself has high conductivity and adhesion, it is not necessary to add a conductive agent and a binder in the slurry preparation process of the battery preparation, the slurry preparation efficiency is higher, the slurry uniformity is better, and the electrode sheet has smaller resistance difference at different points, which is beneficial to improving the overall performance of the battery.

[0011] Further, the mass of the binder accounts for 0.5-5% of the mass of the lithium iron phosphate material with adhesion and high conductivity.

[0012] Further, the binder includes a combination of one or more of polyvinylidene fluoride, polystyrene, polytetrafluoroethylene, sodium alginate, polyvinyl alcohol, polyacrylate, and polyacrylic acid block copolymer.

[0013] Further, the mass of the inorganic carbon on the surface accounts for 1-5% of the mass of the lithium iron phosphate material with adhesion and high conductivity.

[0014] Further, the inorganic carbon on the surface includes a combination of one or more of inorganic carbon obtained by high-temperature cracking of an organic carbon source, carbon nanotubes, graphene, conductive carbon black, and VGCF.

[0015] Further, the carbon source includes an organic carbon source and an inorganic carbon source, and the organic carbon source includes at least one of glucose, polyethylene glycol, sucrose, Tween, polyvinyl alcohol, polyvinylpyrrolidone, or starch. The organic carbon source is reacted at high temperature to tightly combine the inorganic carbon source and the lithium iron phosphate, so that the obtained material has high conductivity.

[0016] Further, the molar ratio of Fe, P, and Li in the mixture is 1:(1.0-1.06):(1.0-1.1).

[0017] Further, the particle size of the particles in the precursor slurry is D50=0.2-0.8 μm and D90<3 μm.

[0018] Further, the temperature of the heat treatment is 500-800℃, the heating rate is 1-5℃ / min, and the treatment time is 5-10h.

[0019] In another aspect, the application also provides a lithium ion secondary battery containing the lithium iron phosphate material with adhesion and high conductivity prepared by the preparation method.

[0020] For better understanding and implementation, the application will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The cycle performance test curves of the application examples 1-4 and the comparative examples 1-3 at 1C / 1C rate. DETAILED DESCRIPTION

[0022] It should be noted that the examples in the application and the features in the examples can be combined with each other without conflict. Obviously, the examples described in the application are only a part of the examples of the application, not all the examples. Based on the examples in the application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0023] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0024] The application will be further described below with reference to the examples.

[0025] According to the specific embodiments of the application, a preparation method of a lithium iron phosphate material with adhesion and high conductivity is provided, comprising the following steps:

[0026] (1) mixing a carbon source, an iron source, a phosphorus source and a lithium source to obtain a mixed material, wherein the added mass of the carbon source is 4-10% of the total mass of the iron source, the phosphorus source and the lithium source; in the mixed material, the molar ratio of Fe, P and Li is 1:(1.0-1.06):(1.0-1.1); the mixed material is configured into a mixed water slurry, and the solid content of the mixed water slurry is 30-60%; then the mixed water slurry is sand ground to obtain a precursor slurry, and the particle size of the particles in the precursor slurry is D50=0.2-0.8μm, D90<3μm.

[0027] (2) spray-drying the precursor slurry obtained in step (1) in a spray-drying device, with the inlet temperature of the spray-drying device controlled at 190-280°C and the outlet temperature controlled at 90-110°C; and high-temperature heat-treating the precursor powder obtained after the spray-drying in an inert atmosphere to obtain high-conductivity lithium iron phosphate with inorganic carbon on the surface of the high-conductivity lithium iron phosphate; in some embodiments, the inert atmosphere is one or a mixture of two of nitrogen and argon; in some embodiments, the temperature of the heat-treatment is 500-800°C, the temperature rising rate is 1-5°C / min, and the treatment time is 5-10h.

[0028] (3) oxidizing the inorganic carbon on the surface of the high-conductivity lithium iron phosphate obtained in step (2); in some embodiments, the oxidation method is ozone oxidation or plasma oxidation; then taking a binder and grafting the binder to the surface of the inorganic carbon after the oxidation treatment through a grafting reaction to obtain a lithium iron phosphate material with adhesion and high conductivity.

[0029] In some embodiments, the carbon source in step (1) includes a combination of one or more of inorganic carbon sources and organic carbon sources, and the organic carbon sources include a combination of one or more of glucose, polyethylene glycol, sucrose, Tween, polyvinyl alcohol, polyvinylpyrrolidone, and starch; the inorganic carbon on the surface of the high-conductivity lithium iron phosphate obtained in step (2) includes a combination of one or more of inorganic carbon obtained by high-temperature cracking of the organic carbon source, carbon nanotubes, graphene, conductive carbon black, and VGCF. By adding the carbon source to the precursor in the material preparation stage, the carbon source is closely combined with the lithium iron phosphate, so that the material itself has high conductivity, and the inorganic carbon on the surface of the high-conductivity lithium iron phosphate provides a reaction target for the grafting reaction in the following step (3).

[0030] In some embodiments, the iron source in step (1) includes a combination of one or more of iron phosphate, iron chloride, iron hydroxide, ferrous oxide, iron acetate, ferrous oxalate, iron hydrogen phosphate, iron nitrate, diiron trioxide, ferrous glycinate, and iron citrate; the phosphorus source includes a combination of one or more of ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, diphosphorus pentoxide, iron phosphate, lithium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and phosphoric acid; the lithium source includes a combination of one or more of lithium carbonate, lithium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and phosphoric acid; in addition, the phosphorus source and the iron source, and the phosphorus source and the lithium source can be the same substance, for example, iron phosphate and lithium phosphate.

[0031] In some embodiments, the binder in step (3) comprises a combination of one or more of polyvinylidene fluoride, polystyrene, polytetrafluoroethylene, sodium alginate, polyvinyl alcohol, polyacrylate, and polyacrylic block copolymer. By grafting the binder to the surface of the inorganic carbon after oxidation treatment, the lithium iron phosphate itself has adhesion, and finally a lithium iron phosphate material with adhesion and high conductivity is obtained.

[0032] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings.

[0033] Example 1

[0034] A method for preparing a lithium iron phosphate material with adhesion and high conductivity, comprising the following steps:

[0035] (1) Take 150.8 g of iron phosphate, 2 g of ammonium phosphate, 38 g of lithium carbonate, 18 g of 4 wt% aqueous carbon nanotube slurry, and 16 g of glucose, and prepare an aqueous slurry with a solid content of 40%; then sand mill to a particle size D50: 0.45 μm, D90 < 2 μm, to obtain a precursor slurry.

[0036] (2) Dry the precursor slurry obtained in step (1) in a spray drying tower, set the spray drying inlet temperature to 250°C, and control the outlet temperature at 105°C, to obtain a dried precursor powder; heat the obtained dried precursor powder to 750°C at a heating rate of 3°C / min under nitrogen protection, and heat treat for 9 h, to obtain a high-conductivity lithium iron phosphate.

[0037] (3) Take 10 g of the high-conductivity lithium iron phosphate obtained in step (2), and perform ozone oxidation treatment on the surface inorganic carbon thereof, for 4 h, to obtain an oxidized high-conductivity lithium iron phosphate; take 10 g of the oxidized high-conductivity lithium iron phosphate, disperse it in 50 ml of dimethyl sulfoxide, and add 2 g of polyvinyl alcohol, stir at 120°C for 1 h, wash with water after the reaction is complete, and dry to obtain polyvinyl alcohol-modified lithium iron phosphate; disperse the polyvinyl alcohol-modified lithium iron phosphate in water, introduce nitrogen to remove oxygen, add 2 g of acrylic acid, 0.1 g of K2S2O8 and NaHS3, set the temperature to 55°C, and heat for 2 h, then wash the product with water and dry, to obtain a lithium iron phosphate material with adhesion and high conductivity.

[0038] Example 2

[0039] A method for preparing a lithium iron phosphate material with adhesion and high conductivity, comprising the following steps:

[0040] (1) Take 150.8 g of iron phosphate, 3 g of ammonium phosphate, 38.5 g of lithium carbonate, 18 g of 4wt% aqueous graphene slurry and 16 g of polyvinylpyrrolidone, configure into an aqueous slurry with a solid content of 40%, and then sand mill to a particle size D50: 0.4 μm, D90 < 2 μm, to obtain a precursor slurry.

[0041] (2) Dry the precursor slurry obtained in step (1) in a spray drying tower, set the spray drying inlet temperature to 250℃, and control the outlet temperature at 105℃, to obtain dried precursor powder; heat the obtained dried precursor powder to 750℃ at a heating rate of 5℃ / min under nitrogen protection, and heat treat for 9h, to obtain high-conductivity lithium iron phosphate.

[0042] (3) Take 10 g of high-conductivity lithium iron phosphate obtained in step (2), and perform ozone oxidation treatment on the surface inorganic carbon thereof for 5h, to obtain oxidized high-conductivity lithium iron phosphate; take 10 g of the oxidized high-conductivity lithium iron phosphate, disperse it in 50 ml of diethyl ether, add 2 g of pyridine, 2 g of 2-bromoisobutyl bromide, slowly stir at 0℃ for 2h, and then stir at room temperature for 10h, and then wash and dry with anhydrous ethanol, to obtain hydroxyl brominated lithium iron phosphate; add 50 ml of methanol, 3 g of vinylidene fluoride, 0.02 g of cuprous bromide, and 0.05 g of 2,2'-bipyridine to a reactor, introduce argon into the reactor for 0.5h to remove oxygen in the reactor, add the hydroxyl brominated lithium iron phosphate, and react for 24h, filter after the reaction, wash with anhydrous methanol, and dry, to obtain lithium iron phosphate with adhesion and high conductivity.

[0043] Example 3

[0044] A method for preparing lithium iron phosphate material with adhesion and high conductivity, comprising the following steps:

[0045] (1) Take 150.8 g of iron phosphate, 38.5 g of lithium carbonate, 18 g of 4wt% aqueous graphene slurry and 16 g of polyvinylpyrrolidone, configure into an aqueous slurry with a solid content of 40%, and then sand mill to a particle size D50: 0.4 μm, D90 < 2 μm, to obtain a precursor slurry.

[0046] (2) Dry the precursor slurry obtained in step (1) in a spray drying tower, set the spray drying inlet temperature to 250℃, and control the outlet temperature at 105℃, to obtain dried precursor powder. Heat the obtained dried precursor powder to 750℃ at a heating rate of 5℃ / min under nitrogen protection, and heat treat for 9h, to obtain high-conductivity lithium iron phosphate.

[0047] (3) Take 10 g of the high-conductivity lithium iron phosphate obtained in step (2) and perform oxygen plasma oxidation treatment on the surface inorganic carbon thereof, with an oxidation time of 2 min, to obtain oxidized high-conductivity lithium iron phosphate; take 10 g of the oxidized high-conductivity lithium iron phosphate and 100 ml of deionized water, 10 g of sodium dodecyl sulfonate, and 0.5 g of styrene, and add them into a reactor, and then introduce argon to remove oxygen in the reactor, and then perform ultrasonic treatment for 15 min, and then transfer to an oil bath pot at 80°C, and then add 0.0052 g of potassium persulfate into the reactor, and then reflux for 5 h; after the reaction, filter, wash with anhydrous methanol, and then dry, to obtain lithium iron phosphate with adhesion and high conductivity.

[0048] Example 4

[0049] A method for preparing a lithium iron phosphate material with adhesion and high conductivity, comprising the following steps:

[0050] (1) Take 150.8 g of iron phosphate, 3 g of ammonium phosphate, 38.5 g of lithium carbonate, 10 g of 4 wt% water-based carbon nanotube slurry, 6 g of 4 wt% water-based graphene slurry, 10 g of polyvinylpyrrolidone, and 7 g of glucose, and configure a water-based slurry with a solid content of 40%, and then sand grind to a particle size D50: 0.4 μm, D90 < 2 μm, to obtain a precursor slurry.

[0051] (2) Dry the precursor slurry obtained in step (1) in a spray drying tower, with an inlet temperature of 250°C and an outlet temperature controlled at 105°C, to obtain dried precursor powder. Heat the dried precursor powder to 750°C at a heating rate of 5°C / min under nitrogen protection, and heat treat for 9 h, to obtain high-conductivity lithium iron phosphate.

[0052] (3) Take 10 g of the high-conductivity lithium iron phosphate obtained in step (2) and perform oxygen plasma oxidation treatment on the surface inorganic carbon thereof, with an oxidation time of 2 min, to obtain oxidized high-conductivity lithium iron phosphate; take 10 g of the oxidized high-conductivity lithium iron phosphate and disperse it in 100 ml of dimethyl sulfoxide, and then add 15 g of dichloro sulfoxide, and then react at room temperature for 2 h, and then wash and dry after the reaction is completed, and then disperse in 100 ml of dimethyl sulfoxide, and then add 3 g of sodium alginate, and then react at 120°C for 6 h, and then filter after the reaction, and then wash with deionized water, and then dry, to obtain lithium iron phosphate with adhesion and high conductivity.

[0053] Comparative Example 1

[0054] A method for preparing a high-conductivity lithium iron phosphate material, comprising the following steps:

[0055] (1) Take 150.8 g of iron phosphate, 3 g of ammonium phosphate, 38.5 g of lithium carbonate, 18 g of 4wt% water-based graphene slurry and 16 g of polyvinylpyrrolidone, and prepare a water-based slurry with a solid content of 40%, and then sand mill to a particle size D50: 0.4 μm, D90 < 2 μm, to obtain a precursor slurry.

[0056] (2) Dry the precursor slurry obtained in step (1) in a spray drying tower, set the spray drying inlet temperature to 250°C, and control the outlet temperature to 105°C, to obtain a dried precursor powder. Heat the dried precursor powder to 750°C at a heating rate of 5°C / min under nitrogen protection, and heat treat for 9h to obtain high-conductivity lithium iron phosphate.

[0057] Comparative Example 2

[0058] A method for preparing a high-conductivity lithium iron phosphate material, comprising the following steps:

[0059] (1) Take 150.8 g of iron phosphate, 2 g of ammonium phosphate and 38 g of lithium carbonate, 18 g of 4wt% water-based carbon nanotube slurry and 16 g of glucose, and prepare a water-based slurry with a solid content of 40%; then sand mill to a particle size D50: 0.45 μm, D90 < 2 μm, to obtain a precursor slurry.

[0060] (2) Dry the precursor slurry obtained in step (1) in a spray drying tower, set the spray drying inlet temperature to 250°C, and control the outlet temperature to 105°C, to obtain a dried precursor powder. Heat the dried precursor powder to 750°C at a heating rate of 5°C / min under nitrogen protection, and heat treat for 9h to obtain high-conductivity lithium iron phosphate.

[0061] Comparative Example 3

[0062] A method for preparing a high-conductivity lithium iron phosphate material, comprising the following steps:

[0063] (1) Take 150.8 g of iron phosphate, 3 g of ammonium phosphate, 38.5 g of lithium carbonate, 10 g of 4wt% water-based carbon nanotube slurry, 6 g of 4wt% water-based graphene slurry, 10 g of polyvinylpyrrolidone and 7 g of glucose, and prepare a water-based slurry with a solid content of 40%, and then sand mill to a particle size D50: 0.4 μm, D90 < 2 μm, to obtain a precursor slurry.

[0064] (2) The precursor slurry obtained in step (1) is dried in a spray drying tower, the spray drying inlet temperature is set to 250℃, and the outlet temperature is controlled to 105℃, to obtain dried precursor powder. The dried precursor powder is heated to 750℃ at a heating rate of 5℃ / min under nitrogen protection, and heat treated for 9h, to obtain high-conductivity lithium iron phosphate.

[0065] The lithium iron phosphate material with adhesion and high conductivity obtained in Examples 1-4 and the high-conductivity lithium iron phosphate material obtained in Comparative Examples 1-3 are respectively dispersed in N-methyl pyrrolidone solution according to a ratio of 98:2 with PVDF to prepare positive electrode slurry; the obtained positive electrode slurry is coated on an aluminum foil current collector, dried at 105℃, and then rolled to obtain positive electrode sheets; the prepared positive electrode sheets, negative electrode sheets, separators, and cores are wound to obtain battery cores, the battery cores are cased, electrolyte is injected into the battery case, packaged, formed, and tested to obtain lithium ion secondary batteries.

[0066] Please refer to Figure 1 The lithium ion secondary batteries prepared from the lithium iron phosphate material with adhesion and high conductivity in Examples 1-4 are subjected to 1C / 1C cycle performance tests, and the capacity retention rate of the lithium ion secondary batteries after multiple cycles is measured.

[0067] The lithium ion secondary batteries prepared from the lithium iron phosphate material with adhesion and high conductivity in Examples 1-4 are subjected to 1C / 1C cycle performance tests, and the capacity retention rate of the lithium ion secondary batteries after multiple cycles is measured.

[0068] The lithium ion secondary batteries prepared from the high-conductivity lithium iron phosphate material in Comparative Examples 1-3 are subjected to 1C / 1C cycle performance tests, and the capacity retention rate of the lithium ion secondary batteries after multiple cycles is measured.

[0069] The lithium iron phosphate material with adhesion and high conductivity prepared by the method of the present application combines a carbon source, a binder, and lithium iron phosphate, so that the lithium iron phosphate is in closer contact with the carbon source, thereby reducing the contact resistance between the conductive agent and the lithium iron phosphate when the conductive agent is used. The lithium ion secondary battery prepared from the lithium iron phosphate material with adhesion and high conductivity has excellent capacity retention performance. Since the material itself has high conductivity and adhesion, the simultaneous use of a binder and a conductive agent in the slurry preparation process is avoided, which leads to uneven dispersion of the components in the slurry and unevenness in the internal structure of the electrode sheet, and the consistency of the prepared lithium ion secondary battery is insufficient. At the same time, the dispersion process time is reduced, which is beneficial to production.

[0070] The applicant states that the present application is illustrated by the above-mentioned embodiments, but the present application is not limited to the above-mentioned detailed process equipment and process flow, that is, the present application does not mean that the present application must rely on the above-mentioned detailed process equipment and process flow to be implemented. The above-mentioned embodiments only express several embodiments of the present application, which are described in detail and in detail, but it cannot be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, and the present application also intends to include these changes and modifications.

Claims

1. A method for preparing a lithium iron phosphate material with adhesive properties and high conductivity, characterized in that, Includes the following steps: (1) A mixture of carbon source, iron source, phosphorus source and lithium source is prepared to obtain a mixture, wherein the added mass of carbon source is 4 to 10% of the total mass of iron source, phosphorus source and lithium source; the mixture is prepared into a mixed water slurry with a solid content of 30 to 60%; the mixed water slurry is milled to obtain a precursor slurry; (2) The precursor slurry is spray-dried, and the precursor powder obtained after spray drying is subjected to high-temperature heat treatment under inert atmosphere protection to obtain lithium iron phosphate with inorganic carbon coating on the surface. (3) After oxidizing the inorganic carbon on the surface of the highly conductive lithium iron phosphate, a lithium iron phosphate material with adhesiveness and high conductivity is obtained by grafting an adhesive; the mass of the adhesive accounts for 0.5 to 5% of the mass of the lithium iron phosphate material with adhesiveness and high conductivity; the mass of the inorganic carbon on the surface accounts for 1 to 5% of the mass of the lithium iron phosphate material with adhesiveness and high conductivity.

2. The method for preparing the lithium iron phosphate material with adhesiveness and high conductivity according to claim 1, characterized in that: The adhesive mentioned in step (3) includes one or more of the following: polyvinylidene fluoride, polystyrene, polytetrafluoroethylene, sodium alginate, polyvinyl alcohol, polyacrylate, and block copolymer of polyacrylic acid.

3. The method for preparing the lithium iron phosphate material with adhesiveness and high conductivity according to claim 2, characterized in that: The surface inorganic carbon includes one or more of the following: carbon nanotubes, graphene, conductive carbon black, and VGCF, obtained by high-temperature pyrolysis of organic carbon sources.

4. The method for preparing the lithium iron phosphate material with adhesiveness and high conductivity according to claim 3, characterized in that: The carbon source mentioned in step (1) includes organic carbon sources and inorganic carbon sources. The organic carbon source includes at least one of glucose, polyethylene glycol, sucrose, Tween, polyvinyl alcohol, polyvinylpyrrolidone, or starch.

5. The method for preparing the lithium iron phosphate material with adhesiveness and high conductivity according to claim 4, characterized in that: In the mixture, the molar ratio of Fe, P and Li is 1:(1.0~1.06):(1.0~1.1).

6. The method for preparing the lithium iron phosphate material with adhesiveness and high conductivity according to claim 5, characterized in that: The particle size of the precursor slurry in step (1) is D50 = 0.2~0.8μm and D90 < 3μm.

7. The method for preparing the lithium iron phosphate material with adhesiveness and high conductivity according to claim 6, characterized in that: The heat treatment temperature in step (2) is 500~800℃, the heating rate is 1~5℃ / min, and the treatment time is 5~10h.

8. A lithium-ion secondary battery, characterized in that, The lithium-ion secondary battery contains lithium iron phosphate material with adhesive properties and high conductivity prepared by the preparation method according to any one of claims 1-7.

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