Modified lithium iron phosphate, preparation method thereof, positive electrode material, battery and application

Abstract

The invention relates to the technical field of lithium iron phosphate materials, in particular to modified lithium iron phosphate, a preparation method thereof, a positive electrode material, a battery and application. The raw materials of the modified lithium iron phosphate comprise a lithium source, an iron source, a phosphorus source and zinc halide; in the raw materials, the percentage content of zinc atoms is 1%-5% of iron atoms. The modified lithium iron phosphate provided by the invention has very high electronic conductivity and lithium ion diffusion rate.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium iron phosphate materials, and in particular to a modified lithium iron phosphate and a preparation method thereof, a positive electrode material, a battery and applications. Background Art

[0002] At present, the main methods for pore modification of lithium iron phosphate (LiFePO4, LFP) materials include template method, sol-gel method, bio-template method, spray drying method, freeze drying method and etching method. Although these methods can improve the ion / electron transport performance to a certain extent, thereby improving the rate performance and energy density of the battery, the following major technical problems still exist: (1) The template method is complex and costly, the resulting pore structure is prone to collapse, and it is difficult to scale up; (2) The pore size distribution of lithium iron phosphate prepared by sol-gel method and bio-template method is uneven and the pore size is uncontrollable; (3) The spray drying method and freeze drying method have high energy consumption, low particle strength, and difficult to control the pore size gradient (the solvent volatilization rate is uneven during the drying process, which easily forms closed pores or pores with poor connectivity); (4) The etching method uses acid / base etching, which will cause material loss of LFP and lead to loss of active substances. Summary of the Invention

[0003] To solve the above problems, the present invention provides a modified lithium iron phosphate and its preparation method, cathode material, battery and application, so as to solve at least one aspect of the above technical problems.

[0004] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a modified lithium iron phosphate, the raw materials of which include lithium iron phosphate and zinc halide; In the raw material, the atomic percentage of zinc is 1% to 5% of the iron atoms.

[0005] In some possible implementations, the zinc halide is: R1-Zn-R2; Wherein, R1 is Cl, Br, alkyl, alkenyl, phenyl, halogenated alkyl, halogenated alkenyl or halogenated phenyl; R2 is Cl, Br, halogenated alkyl, halogenated alkenyl or halogenated phenyl.

[0006] In some possible implementations, in the R1, the alkyl group is C 1~6 of alkyl.

[0007] In some possible implementations, in the R1, the alkenyl group is C 2~6 of alkenyl.

[0008] In some possible implementations, in said R1, the haloalkyl group is C 1~6 Monohaloalkyl or C 1~6of a dihaloalkyl group.

[0009] In some possible implementations, in the R1, the haloalkenyl group is C 2~6 A monohaloalkenyl group.

[0010] In some possible implementations, in R1, the halophenyl group is a monohalophenyl group or a dihalophenyl group.

[0011] In some possible implementations, in said R2, the haloalkyl group is C 1~6 a monohaloalkyl group or a dihaloalkyl group.

[0012] In some possible implementations, in said R2, the haloalkenyl group is C 2~6 A monohaloalkenyl group.

[0013] In some possible implementations, in R2, the halophenyl group is a monohalophenyl group, an o-dihalophenyl group, an m-dihalophenyl group, or a p-dihalophenyl group.

[0014] In a second aspect, the present invention provides a method for preparing the modified lithium iron phosphate, comprising the following steps: Lithium iron phosphate and zinc halide are mixed and sintered to obtain modified lithium iron phosphate.

[0015] In some possible implementations, the sintering step includes: Heat up to 750℃~800℃ at a heating rate of 8℃ / min~15℃ / min and keep warm.

[0016] In some possible implementations, the insulation time is 2 hours to 6 hours.

[0017] In a third aspect, the present invention provides a positive electrode material, including the modified lithium iron phosphate prepared by the above preparation method.

[0018] In a fourth aspect, the present invention provides a battery comprising the above-mentioned positive electrode material.

[0019] In a fifth aspect, the present invention provides an application of the modified lithium iron phosphate prepared by the above preparation method in the field of battery materials.

[0020] Compared with the prior art, the modified lithium iron phosphate and the preparation method thereof provided by the present invention have at least the following beneficial technical effects: (1) The modified lithium iron phosphate provided by the present invention has high electronic conductivity and lithium ion diffusion rate.

[0021] (2) The preparation method of modified lithium iron phosphate provided by the present invention can produce modified lithium iron phosphate with a porous structure, thereby shortening the Li +The diffusion path of the material is improved, and the rate performance and cycle stability of the material are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0023] Figure 1 This is a SEM image of the modified lithium iron phosphate in Example 1 of the present invention; Figure 2 This is an EDS image of oxygen elements in the modified lithium iron phosphate in Example 1 of the present invention; Figure 3 This is an EDS image of the iron element in the modified lithium iron phosphate in Example 1 of the present invention; Figure 4 This is an EDS image of phosphorus in the modified lithium iron phosphate in Example 1 of the present invention; Figure 5 This is an EDS image of the zinc element in the modified lithium iron phosphate in Example 1 of the present invention; Figure 6 This is an SEM image of the modified lithium iron phosphate in Example 2 of the present invention.

[0024] The purpose, features and advantages of this drawing will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0026] Obviously, the following descriptions are merely examples or embodiments of the present invention, and those skilled in the art will be able to apply the present invention to other similar scenarios without inventive effort. Furthermore, it is understood that while the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the present disclosure, any design, manufacturing, or production changes based on the technical content disclosed in the present disclosure are merely conventional technical means and should not be construed as an inadequacy of the present disclosure.

[0027] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to facilitate a thorough understanding of the present invention by those skilled in the art and is not intended to limit the subject matter recited in the claims.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution, and all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0029] A first aspect of an embodiment of the present invention provides a modified lithium iron phosphate, the raw materials of which include lithium iron phosphate and zinc halide; In the raw materials, the atomic percentage of zinc is 1% to 5% of the iron atoms.

[0030] The modified lithium iron phosphate provided in the embodiments of the present invention contains zinc, which improves the material's electronic conductivity and lithium ion diffusion rate, thereby enhancing its rate performance. It should be noted that the atomic ratio of lithium, iron, and phosphorus in lithium iron phosphate is conventional in the art and is not specifically limited in the embodiments of the present invention. However, as an example, the atomic ratio of lithium, iron, and phosphorus is (1.05-2):1:1.

[0031] In some embodiments, the zinc halide is: R1-Zn-R2; Wherein, R1 is Cl, Br, alkyl, alkenyl, phenyl, halogenated alkyl, halogenated alkenyl or halogenated phenyl; R2 is Cl, Br, halogenated alkyl, halogenated alkenyl or halogenated phenyl.

[0032] In some embodiments, in R1, the alkyl group is C 1~6 of alkyl.

[0033] In some embodiments, C 1~6 The alkyl groups are CH3-, CH3CH2-, CH3CH2CH2-, 、 、CH3CH2CH2CH2-、 、 One of them.

[0034] In some embodiments, in R1, alkenyl is C 2~6 of alkenyl.

[0035] In some embodiments, C 2~6The alkenyl group is one of CH2=CH-, CH3CH=CH-, CH3CH2CH=CH-, CH3CH2CH2CH=CH-, CH3CH2CH2CH=CH-, CH3CH2CH2CH2CH=CH-, and CH3CH=CHCH2CH=CH-.

[0036] In some embodiments, in R1, the haloalkyl group is C 1~6 Monohaloalkyl or C 1~6 of a dihaloalkyl group.

[0037] In some embodiments, C 1~6 The monohalogenated alkyl group is ClCH2-, ClCH2CH2-, ClCH2CH2CH2-, CH3CHClCH2-, 、 、ClCH2CH2CH2CH2-、 、 One of them.

[0038] In some embodiments, C 1~6 The dihaloalkyl group is 、 、 、 、 、 、 、 、 、 One of them.

[0039] In some embodiments, in R1, the haloalkenyl group is C 2~6 A monohaloalkenyl group.

[0040] In some embodiments, C 2~6 The monohaloalkenyl group is 、 、 、 One of them.

[0041] In some embodiments, in R1, the halophenyl group is a monohalophenyl group, an o-dihalophenyl group, a m-dihalophenyl group, or a p-dihalophenyl group.

[0042] In some embodiments, in R2, the haloalkyl group is C 1~6 a monohaloalkyl group or a dihaloalkyl group.

[0043] In some embodiments, in R2, the haloalkenyl group is C 2~6 A monohaloalkenyl group.

[0044] In some embodiments, in R2, the halophenyl group is a monohalophenyl group, an o-dihalophenyl group, a m-dihalophenyl group, or a p-dihalophenyl group.

[0045] In some specific embodiments, the zinc halide is at least one of zinc chloride, zinc bromide, CH3-Zn-Cl, (CH3)2CHCH2ZnCl, and C7H7ZnCl.

[0046] A second aspect of an embodiment of the present invention provides a method for preparing the modified lithium iron phosphate, comprising the following steps: S10. Mix lithium iron phosphate and zinc halide and sinter them to obtain modified lithium iron phosphate.

[0047] The preparation method of the modified lithium iron phosphate provided by the embodiment of the present invention is to mix lithium iron phosphate and zinc halide and then sinter them to obtain modified lithium iron phosphate with a porous structure, thereby shortening the Li + The diffusion path of the material is shortened, and the rate performance and cycle stability of the material are improved. In addition, when the zinc halide contains carbon, the modified lithium iron phosphate obtained after sintering also contains carbon doping.

[0048] In some embodiments, in the above step S10, the preparation of lithium iron phosphate includes the following steps: S101. subjecting the lithium source, iron source and phosphorus source to a hydrothermal reaction and then removing water.

[0049] In some embodiments, in the above step S101, the lithium source includes at least one of lithium hydroxide, lithium chloride, lithium carbonate, and lithium acetate.

[0050] In some embodiments, in the above step S101, the iron source includes at least one of ferrous sulfate, ferrous chloride, ferrous oxalate, and ferrous phosphate.

[0051] In some embodiments, in the above step S101, the phosphorus source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, and ferrous phosphate.

[0052] In some embodiments, in the above step S101, the temperature of the hydrothermal reaction is 120°C to 160°C.

[0053] In some embodiments, in the above step S101, the hydrothermal reaction time is 12 hours to 24 hours.

[0054] In some embodiments, in the above step S101, the step of removing water includes: filtering the product obtained by the hydrothermal reaction and then drying it at a drying temperature of 80°C to 110°C.

[0055] In some embodiments, in the above step S10, the sintering step includes: Heat up to 750℃~800℃ at a heating rate of 8℃ / min~15℃ / min and keep warm.

[0056] In the above sintering step, the temperature is raised at a heating rate of 8°C / min~15°C / min. At low temperature, zinc is embedded (or further embedded) in the lithium iron phosphate crystal structure to form zinc doping; when the temperature is raised to 750°C~800°C and kept at high temperature, the remaining free zinc halide sublimates and escapes from the system, forming pores in the system to form pores in the system, thereby obtaining porous modified lithium iron phosphate, thereby shortening the Li + The diffusion path of the material is improved, and the rate performance and cycle stability of the material are improved.

[0057] In some embodiments, in the sintering step, the holding time at 750° C. to 800° C. is 2 h to 6 h.

[0058] In other embodiments, a method for preparing the modified lithium iron phosphate is provided, comprising the following steps: S11. After surface treatment of lithium iron phosphate, the lithium iron phosphate is mixed with zinc halide and then sintered to obtain modified lithium iron phosphate.

[0059] In the above-mentioned preparation method of modified lithium iron phosphate, surface treatment of the lithium iron phosphate can improve the compatibility between the lithium iron phosphate precursor and the carbon-containing zinc halide, thereby further improving the conductivity and cycle stability of the modified lithium iron phosphate.

[0060] In some embodiments, in the above step S11, the surface treatment step includes: S111. After the lithium iron phosphate is subjected to carbon coating treatment, a first product is obtained.

[0061] S112. The first product is mixed with a silane coupling agent.

[0062] In the above-mentioned surface treatment step, the lithium iron phosphate is subjected to a carbon coating treatment to obtain a first product, which is then mixed with a silane coupling agent to activate the carbon-coated lithium iron phosphate. The compatibility between the surface-treated lithium iron phosphate and the organic zinc halide is improved, thereby making the modified lithium iron phosphate have higher conductivity and rate performance. It should be noted that carbon coating is a conventional technology in the art and is not particularly limited in the embodiments of the present invention. However, as an example, chemical vapor deposition can be used for carbon coating, and the carbon source is at least one of methane, ethane, and propane.

[0063] In some embodiments, in the above step S112, the mass ratio of the second product to the silane coupling agent is 1:(0.2-0.8).

[0064] In some embodiments, in the above step S112, the silane coupling agent is KH-550.

[0065] A third aspect of the embodiments of the present invention provides a positive electrode material, including modified lithium iron phosphate prepared by the preparation method provided in the embodiments of the present invention.

[0066] A fourth aspect of the embodiments of the present invention provides a battery, comprising the positive electrode material provided by the embodiments of the present invention.

[0067] The following is further described with reference to specific embodiments.

[0068] In Example 2, the CAS number of CH3-Zn-Cl is: 5158-46-3.

[0069] In Example 3, the CAS number of (CH3)2CHCH2ZnCl is: 82510-93-8.

[0070] In Example 4, the CAS number of C7H7ZnCl is: 90252-89-4.

[0071] Example 1 Example 1 provides a modified lithium iron phosphate, the raw materials of which include lithium iron phosphate and zinc chloride; In the raw materials, the atomic percentage of zinc is 1% of the atomic content of iron.

[0072] This embodiment also provides a method for preparing modified lithium iron phosphate, the steps of which are as follows: E11. Lithium chloride, ferrous chloride and phosphoric acid were mixed and subjected to a hydrothermal reaction, filtered and dried to obtain lithium iron phosphate; Among them, the atomic ratio of lithium, iron and phosphorus in lithium chloride, ferrous chloride and phosphoric acid is 1.05:1:1; the temperature of the hydrothermal reaction is 150°C, the reaction time is 18 hours; and the drying temperature is 100°C.

[0073] E21. Lithium iron phosphate and zinc chloride are mixed to obtain a modified lithium iron phosphate precursor.

[0074] E31. Under an argon atmosphere, the modified lithium iron phosphate precursor was heated to 750°C at a heating rate of 10°C / min and then kept at this temperature for 6 h to obtain modified lithium iron phosphate.

[0075] Example 2 Example 2 provides a modified lithium iron phosphate, the raw materials of which include lithium iron phosphate and CH3ZnCl; In the raw materials, the atomic percentage of zinc is 3% of the atomic content of iron.

[0076] This embodiment also provides a method for preparing modified lithium iron phosphate, the steps of which are as follows: E12. Lithium acetate, ferrous oxalate and phosphoric acid were mixed and subjected to a hydrothermal reaction, filtered and dried to obtain lithium iron phosphate; Among them, the atomic ratio of lithium, iron and phosphorus in lithium acetate, ferrous oxalate and phosphoric acid is 2:1:1; the temperature of the hydrothermal reaction is 190°C, the reaction time is 16 hours; and the drying temperature is 80°C.

[0077] E22. Carbon coating of lithium iron phosphate was performed by chemical vapor deposition to obtain a first product; Among them, the carbon source is methane.

[0078] E32. The first product was mixed with a silane coupling agent KH-550 to obtain surface-treated lithium iron phosphate; Among them, the mass ratio of the first product to KH-550 is 1:0.5.

[0079] E42. The surface-treated lithium iron phosphate is mixed with CH3CH2-Zn-Cl to obtain a modified lithium iron phosphate precursor.

[0080] E52. Under an argon atmosphere, the modified lithium iron phosphate precursor was heated to 780°C at a heating rate of 15°C / min and then kept at this temperature for 6 h to obtain modified lithium iron phosphate.

[0081] Example 3 Example 3 provides a modified lithium iron phosphate, the raw materials of which include lithium iron phosphate and (CH3)2CHCH2ZnCl; The atomic percentage of zinc in the raw material is 5% of the atomic content of iron.

[0082] This embodiment also provides a method for preparing modified lithium iron phosphate, the steps of which are as follows: E13 lithium acetate, ferrous oxalate and phosphoric acid were mixed and subjected to a hydrothermal reaction, filtered and dried to obtain lithium iron phosphate; Among them, the atomic ratio of lithium, iron and phosphorus in lithium acetate, ferrous oxalate and phosphoric acid is 2:1:1; the temperature of the hydrothermal reaction is 200°C, the reaction time is 12 hours; and the drying temperature is 110°C.

[0083] E23. Carbon coating of lithium iron phosphate using chemical vapor deposition to obtain a first product; Wherein, the carbon source is ethane.

[0084] E33. The first product was mixed with a silane coupling agent KH-550 to obtain surface-treated lithium iron phosphate; Among them, the mass ratio of the first product to KH-550 is 1:0.8.

[0085] E43. The surface-treated lithium iron phosphate is mixed with CH3CH2-Zn-CH2CH2Cl to obtain a modified lithium iron phosphate precursor.

[0086] E53. Under an argon atmosphere, the modified lithium iron phosphate precursor was heated to 800°C at a heating rate of 8°C / min and then kept at this temperature for 2 h to obtain modified lithium iron phosphate.

[0087] Example 4 Example 4 provides a modified lithium iron phosphate and a preparation method thereof, which is basically the same as Example 2, except that: Zinc halide is C7H7ZnCl.

[0088] Comparative Example 1 Comparative Example 1 provides a method for preparing lithium iron phosphate, comprising the following steps: D11. The mixed solution was subjected to a hydrothermal reaction at 190°C for 18 h; The mixed solution contains lithium chloride, ferrous chloride, phosphoric acid and cetyltrimethylammonium bromide (CTAB), the mass fraction of CTAB is 1%, and the atomic ratio of lithium, iron and phosphorus is 1.5:1:1.

[0089] D21. Collect the precipitate obtained by the hydrothermal reaction by centrifugation and wash the precipitate three times with ethanol and water alternately to remove residual CTAB.

[0090] D31. Sinter the washed precipitate at 750°C for 6 hours to obtain lithium iron phosphate.

[0091] Comparative Example 2 Comparative Example 2 provides a preparation method of the modified lithium iron phosphate provided in Example 2, and the steps are basically the same as those in Example 2, except that: In step E52, the modified lithium iron phosphate precursor is directly placed at 780° C. and sintered for 6 hours.

[0092] In order to verify the advancement of a modified lithium iron phosphate and its preparation method provided by the embodiment of the present invention, taking Example 1 and Example 2 as examples, a scanning electron microscope was used to scan the modified lithium iron phosphate prepared in Example 1 and Example 2, and the corresponding Figure 1 and Figure 6 The SEM image shown in FIG. 1 and the EDS elemental analysis of the modified lithium iron phosphate of Example 1 were performed to obtain the following: Figures 2 to 5 The EDS elemental spectrum is shown in Table 1. The content of each element is shown in Table 1.

[0093] Table 1

[0094] Then, the modified lithium iron phosphate or lithium iron phosphate provided in the examples and comparative examples was made into button batteries and tested. 1. The assembly steps of button batteries are as follows: (1) Positive electrode sheet: Lithium iron phosphate / modified lithium iron phosphate, conductive carbon black and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5, and N-methylpyrrolidone (NMP) was used as solvent to prepare a slurry. The slurry was evenly coated on aluminum foil, dried, compacted, and vacuum-dried at 120°C for 12 h to obtain a positive electrode sheet. The mass of the active material in the positive electrode sheet was 12 mg.

[0095] (2) Negative electrode: The negative electrode uses a metal lithium sheet.

[0096] (3) The diaphragm is a polypropylene porous membrane, and the electrolyte is 1 mol / L LiPF6 / EC+DEC+DMC (EC:DEC:DMC=1:1:1 volume ratio).

[0097] EC: Ethylene Carbonate; DEC: Diethyl Carbonate; DMC: Dimethyl Carbonate.

[0098] Table 2

[0099] From the above table and the accompanying drawings, we can at least draw the following conclusions: (1) In Table 2, it can be seen from the comparison between Examples 1 to 4 and Comparative Example 1 that the modified lithium iron phosphate provided by the embodiments of the present invention, in which zinc halide is doped as both a zinc source and a pore-forming agent, has excellent conductivity, cycle stability and rate performance.

[0100] (2) In Table 2, it can be seen from the comparison between Example 1 and Comparative Example 2 that the preparation method of the modified lithium iron phosphate provided by the embodiment of the present invention, which gradually increases the temperature during sintering and then keeps the temperature, can make zinc chloride embed into the crystal structure of lithium iron phosphate at low temperature to form zinc doping; when the temperature is kept at a high temperature of 750℃~800℃, the remaining free zinc halide is removed from the system to obtain porous modified lithium iron phosphate, thereby shortening the Li + The diffusion path of the material is improved, and the rate performance and cycle stability of the material are improved.

[0101] (3) In Table 2, it can be seen from the comparison between Example 1 and Examples 2 to 4 that the selection of carbon-containing organic matter as zinc halide can further improve the conductivity, cycle stability and rate performance of the modified lithium iron phosphate.

[0102] (4) It can be seen from the accompanying drawings and Table 1 that the modified lithium iron phosphate provided in the embodiment of the present invention has a rich porous structure and is doped with zinc.

[0103] It should be noted that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the technical solution of the present invention are all included in the technical scope of the present invention. In addition, without departing from the scope of the present invention, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present invention.

Claims

1. A modified lithium iron phosphate, characterized in that: Raw materials include lithium iron phosphate and zinc halide; In the raw material, the atomic percentage of zinc is 1% to 5% of the iron atoms.

2. The modified lithium iron phosphate according to claim 1, characterized in that The zinc halide is: R1-Zn-R2; Wherein, R1 is Cl, Br, alkyl, alkenyl, phenyl, halogenated alkyl, halogenated alkenyl or halogenated phenyl; R2 is Cl, Br, halogenated alkyl, halogenated alkenyl or halogenated phenyl.

3. The modified lithium iron phosphate according to claim 2, characterized in that The R1 satisfies any one of the following characteristics (1) to (5): (1) Alkyl is C 1~6 Alkyl; (2) Alkenyl is C 2~6 alkenyl; (3) The alkyl halide is C 1~6 Monohaloalkyl or C 1~6 dihaloalkyl; (4) The haloalkenyl group is C 2~6 a monohaloalkenyl group; (5) The halophenyl group is a monohalophenyl group, an o-dihalophenyl group, an m-dihalophenyl group or a p-dihalophenyl group.

4. The modified lithium iron phosphate according to claim 2 or 3, characterized in that: The R2 satisfies any one of the following characteristics (1) to (3): (1) Haloalkyl is C 1~6 a monohaloalkyl or dihaloalkyl group; (2) The haloalkenyl group is C 2~6 a monohaloalkenyl group; (3) The halogenated phenyl group is a monohalogenated phenyl group, an o-dihalogenated phenyl group, an m-dihalogenated phenyl group or a p-dihalogenated phenyl group.

5. A method for preparing modified lithium iron phosphate, characterized in that: The method for preparing the modified lithium iron phosphate according to any one of claims 1 to 4 comprises the following steps: Lithium iron phosphate and zinc halide are mixed and sintered to obtain modified lithium iron phosphate.

6. The method for preparing modified lithium iron phosphate according to claim 5, characterized in that: The sintering step comprises: Heat up to 750℃~800℃ at a heating rate of 8℃ / min~15℃ / min and keep warm.

7. The method for preparing modified lithium iron phosphate according to claim 6, characterized in that: The insulation time is 2h~6h.

8. A positive electrode material, characterized in that The modified lithium iron phosphate is prepared by the preparation method according to any one of claims 5 to 7.

9. A battery, characterized in that: Comprising the positive electrode material according to claim 8.

10. Use of the modified lithium iron phosphate prepared by the preparation method according to any one of claims 5 to 7 in the field of battery materials.

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