A preparation method of a lithium iron phosphate positive electrode material, the lithium iron phosphate positive electrode material and a lithium ion battery

Abstract

The application provides a preparation method of a lithium iron phosphate positive electrode material, the lithium iron phosphate positive electrode material and a lithium ion battery. The preparation method comprises the following steps: mixing a lithium source, a phosphorus source, a boron source, an iron source, a reducing agent and a solvent, performing a solvothermal reaction to obtain a precursor material, mixing the precursor material with a carbon source, and sintering to obtain the lithium iron phosphate positive electrode material. In the application, the boron source is mixed with the lithium source, the phosphorus source and the iron source through the solvothermal reaction, the boron element realizes effective doping at the phosphorus position in the lithium iron phosphate, the structural stability of the material is improved, and therefore the capacity of the lithium iron phosphate positive electrode material is obviously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to a preparation method of a lithium iron phosphate positive electrode material, the lithium iron phosphate positive electrode material and a lithium ion battery. BACKGROUND

[0002] Since lithium iron phosphate does not have a continuous FePO4 octahedral network, the electronic conductivity of the material at room temperature is only 10 -7 ~ 10 -9 S / cm, and the commonly used method is a carbon-coated method. In addition, ion doping is also an important method for improving the intrinsic electronic / ion conductivity of lithium iron phosphate. For ion doping, most studies use super-valence cations (Nb 3 + , T 4+ , W 6+ ) to dope part of the Li site or the Fe site.

[0003] CN113611863A discloses a cation-doped lithium iron phosphate positive electrode material and a preparation method and application thereof, and the molecular formula is Li 1-y M x FePO4, wherein: x≤0.03, M is one or more of Na, Mg, Al, Cr, Ti, Zr, Nb and W; the preparation method comprises the following steps: uniformly mixing iron phosphate, a lithium source, a dopant containing element M and a carbon-containing reducing agent in proportion, then sintering at 600-800℃ for 6-15h under a protective atmosphere.

[0004] CN102185138A relates to a lithium ion battery positive electrode material. Main raw materials Fe(NO3)3, LiH2PO4 and doped metal ion oxides and high molecular organic carbon sources are added to a pressure cooker in a stoichiometric ratio, water is added, argon gas is passed, the raw materials are reacted and uniformly mixed, and a slurry is obtained. The slurry is cooled, dried and sieved. The material is calcined under argon protection to obtain a primary sintered material. The primary sintered material is sieved and further sintered under an argon atmosphere. After cooling, a composite lithium iron phosphate material is obtained.

[0005] CN116265387A relates to a process for improving the activity of lithium iron phosphate positive electrode material by doping titanium and manganese. The process for improving the activity of lithium iron phosphate positive electrode material by doping titanium and manganese comprises the following steps: mixing Li2CO3, FePO4.2H2O, NH4H2PO4 and metal powder, weighing the mixed powder; loading the mixed powder into a crucible and heating to perform solid phase reaction and grinding; heating the ground mixed powder to perform secondary solid phase reaction; mixing the powder cooled to room temperature with acetylene black or conductive carbon black and ball milling to obtain a positive electrode material. The present application provides a process for improving the activity of lithium iron phosphate positive electrode material by doping titanium and manganese, and the prepared positive electrode material has good cycle performance and high specific capacity, which is a green and environmentally friendly positive electrode material.

[0006] The above-mentioned documents are all cation doping, and there is less research on polyanion site doping. In fact, polyanion site doping also has important influence on the stability of lithium iron phosphate crystal structure, lithium ion deintercalation rate and path, and electronic conductivity.

[0007] Therefore, how to realize effective doping of polyanion sites in lithium iron phosphate positive electrode material and improve the electrochemical performance is a technical problem to be solved. SUMMARY

[0008] In view of the deficiencies in the prior art, the purpose of the present application is to provide a preparation method of lithium iron phosphate positive electrode material, lithium iron phosphate positive electrode material and lithium ion battery. In the present application, the boron source is mixed with the lithium source, the phosphorus source and the iron source through the solvothermal reaction, and the boron element realizes effective doping at the phosphorus site in the lithium iron phosphate, which improves the structural stability of the material, so that the capacity of the lithium iron phosphate positive electrode material is obviously improved.

[0009] To achieve this purpose, the technical scheme adopted by the present application is as follows:

[0010] In a first aspect, the present application provides a preparation method of lithium iron phosphate positive electrode material, which comprises the following steps:

[0011] Mixing the lithium source, the phosphorus source, the boron source, the iron source, the reducing agent and the solvent to perform solvothermal reaction to obtain a precursor material, mixing the precursor material with a carbon source, and sintering to obtain the lithium iron phosphate positive electrode material.

[0012] In the present application, boron is doped in the lithium iron phosphate precursor material through solvothermal reaction, which is conducive to controlling the doping amount of boron. After further sintering, the lithium iron phosphate positive electrode material with olivine crystal structure and good crystallinity is obtained, and the boron atom successfully replaces part of the phosphorus atoms at the polyanion site, thereby enhancing the discharge energy ratio and ion conductivity of the material.

[0013] In the present application, if the boron doping is not carried out by the method of solvent-thermal combined with solid phase sintering, but pure solid phase doping, it will lead to inconsistent overall doping, particle agglomeration, thereby seriously affecting the doping effect, and even causing the performance of the doped material to decrease.

[0014] Preferably, the amount of the boron source added is 1-5%, for example 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.3%, 3.5%, 3.8%, 4%, 4.3%, 4.5%, 4.8% or 5%, etc., based on the total mass of the lithium source, the phosphorus source and the iron source being 100%.

[0015] In the present application, the total mass of the lithium source, the phosphorus source and the iron source (i.e. the sum of the masses of the three) is taken as the basis of 100%, and on this basis, the specific proportion of the amount of the boron source added is 100%; if the amount of the boron source added is too small, less than 1%, it is not conducive to improving the capacity performance of the positive electrode material; and if it exceeds 5%, not only can it not achieve the improvement of the performance of the positive electrode material, but it will also affect the structure of the original lithium iron phosphate material, thereby causing the performance to decrease.

[0016] Preferably, the amount of the boron source added is 3-5%, for example 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.4%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9% or 5%, etc., and the mixed raw materials also include a magnesium source.

[0017] In the present application, if the amount of the boron source added is too much, within the range of 3-5%, especially more than 3%, although the boron atoms successfully replace part of the phosphorus atoms, too much boron will cause defects in the oxygen atom stacking during crystal growth, cannot achieve charge balance, and will instead affect the capacity, and cannot continue to improve the capacity of the material, and after synchronous magnesium doping, boron-magnesium co-doping, synergistic cooperation, the above problems are solved, thereby enhancing the capacity of the material and improving the ionic conductivity.

[0018] Preferably, the doping amount of magnesium in the magnesium source in the lithium iron phosphate positive electrode material is consistent with the doping amount of boron in the boron source in the lithium iron phosphate positive electrode material.

[0019] In the present application, the magnesium source and the boron source are added in equimolar amounts, i.e. the doping amount of boron atoms is the same as the doping amount of magnesium atoms, so as to achieve the improvement of the positive electrode capacity while maintaining the original structure unchanged, and if they are not added in equimolar amounts, it will affect the stability of the original material structure, thereby causing the doping effect to decrease.

[0020] Preferably, the molar ratio of the lithium source, the iron source and the phosphorus source is (2-4):(0.8-1.2):(1-2), such as 2:1:1, 2:1:2, 3:1:1, 3:1:2, 2:1.2:2, 4:1:2 or 2:1.2:1, etc.

[0021] Preferably, the amount of the reducing agent added is 1.2-1.6%, such as 1.2%, 1.3%, 1.4%, 1.5% or 1.6%, etc., based on the total mass of the lithium source, the phosphorus source and the iron source being 100%.

[0022] Preferably, the reducing agent comprises any one or a combination of at least two of dehydroascorbic acid, phytic acid or 2,6-di-tert-butyl-p-cresol.

[0023] Preferably, the solvent comprises water and / or an organic solvent, preferably an organic solvent.

[0024] In the present application, an organic solvent is selected as the solvent system for the solvothermal reaction, which can better realize the solid phase reaction, and if water is selected as the solvent, the reaction heat is not enough and doping cannot be achieved.

[0025] Preferably, the organic solvent comprises an alcohol and / or dimethylbenzene.

[0026] Preferably, the alcohol comprises ethylene glycol.

[0027] Preferably, the temperature of the solvothermal reaction is 150-200℃, such as 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃, etc.

[0028] Preferably, the time of the solvothermal reaction is 2-5h, such as 2h, 3h, 4h or 5h, etc.

[0029] Preferably, the product after the solvothermal reaction is washed and dried.

[0030] Preferably, the sintering temperature is 400-800℃, such as 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, etc.

[0031] Preferably, the sintering time is 5-20h, such as 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h, etc.

[0032] As a preferred technical solution, the preparation method comprises the following steps:

[0033] Mixing a lithium source, a phosphorus source, a boron source, an iron source, a reducing agent and an organic solvent, carrying out a solvothermal reaction at 150-200 DEG C for 2-5 hours to obtain a precursor material, mixing the precursor material with a carbon source, and sintering to obtain the lithium iron phosphate positive electrode material;

[0034] The molar ratio of the lithium source, the iron source and the phosphorus source is (2-4):(0.8-1.2):(1-2), the adding amount of the boron source is 1-5% based on the total mass of the lithium source, the phosphorus source and the iron source being 100%, the adding amount of the magnesium source is consistent with the adding amount of the boron source when the adding amount of the boron source is 3-5%, and the adding amount of the reducing agent is 1.2-1.6% based on the total mass of the lithium source, the phosphorus source and the iron source being 100%.

[0035] It should be noted that the lithium source, the phosphorus source, the iron source, the boron source and the magnesium source in the present application are all selected by conventional technology.

[0036] Exemplarily, the present application provides specific material selection of the above raw materials:

[0037] Optionally, the lithium source includes but is not limited to lithium hydroxide and / or lithium carbonate;

[0038] Optionally, the phosphorus source includes but is not limited to H3PO4, Ca5(PO4)3OH or egg white, etc.

[0039] Optionally, the iron source includes but is not limited to any one or a combination of at least two of FePO4·7H2O, FeCl2 or FeSO4, etc.

[0040] Optionally, the boron source includes but is not limited to boric acid and / or boron trioxide, etc.

[0041] Optionally, the magnesium source includes but is not limited to magnesium sulfate and / or magnesium chloride, etc.

[0042] In the second aspect, the present application provides a lithium iron phosphate positive electrode material prepared by the preparation method in the first aspect.

[0043] In the third aspect, the present application further provides a lithium ion battery comprising the lithium iron phosphate positive electrode material in the second aspect.

[0044] Compared with the prior art, the present application has the following beneficial effects:

[0045] In the present application, boron is doped in the lithium iron phosphate precursor material through a solvothermal reaction, which is beneficial to control the doping amount of boron, and after further sintering, the lithium iron phosphate positive electrode material with an olivine-type crystal structure and good crystallinity is obtained, and the boron atom successfully replaces part of the phosphorus atom in the polyanion site, thereby enhancing the discharge energy ratio and ion conductivity of the material. DETAILED DESCRIPTION

[0046] The technical solutions of the present application are further illustrated below by specific examples. Those skilled in the art should understand that the examples are only for the purpose of understanding the present application and should not be regarded as specific limitations of the present application.

[0047] Example 1

[0048] This example provides a lithium iron phosphate positive electrode material, which is doped with boron.

[0049] The preparation method of the lithium iron phosphate positive electrode material is as follows:

[0050] LiOH H2O is used as the lithium source, FePO4 7H2O is used as the iron source, H3PO4 is used as the phosphorus source, H3BO4 is used as the boron source, and C6H8O6 is used as the reducing agent.

[0051] The starting materials are set to Li:Fe:P = 3:1:1.5;

[0052] (1) LiOH H2O is added to a glycol solution and stirred to dissolve, then H3PO4 and H3BO4 are added and continue to stir to form a uniform solution (the addition amount of boron source is 1% based on the total mass of lithium source, phosphorus source and iron source being 100%);

[0053] Continue to stir and add C6H8O6 until completely dissolved to prevent oxidation (the addition amount of reducing agent is 1.5% based on the total mass of lithium source, phosphorus source and iron source being 100%);

[0054] Then FePO4 7H2O is added and continue to stir for 35 min to obtain a light green mixture;

[0055] (2) The mixture is poured into an autoclave and reacted at a temperature of 180℃ for 4h. After the reaction is completed, the lower precipitate is taken out, washed with deionized water and ethanol for multiple times, and dried to obtain a lithium iron phosphate precursor;

[0056] (3) The lithium iron phosphate precursor is carbon-coated with glucose under an inert atmosphere, and then sintered at 500℃ for 10h to obtain a lithium iron phosphate positive electrode material.

[0057] Example 2

[0058] This example provides a lithium iron phosphate positive electrode material, which is doped with boron.

[0059] The preparation method of the lithium iron phosphate positive electrode material is as follows:

[0060] LiOH H2O as lithium source, FePO4 7H2O as iron source, H3PO4 as phosphorus source, H3BO4 as boron source, C6H8O6 as reducing agent;

[0061] Li:Fe:P=2.5:1:1.3 of starting materials is set;

[0062] (1) LiOH H2O is added into ethylene glycol solution to be dissolved by stirring, then H3PO4 and H3BO4 are added to continue stirring to form a uniform solution (the addition amount of boron source is 2% based on the total mass of lithium source, phosphorus source and iron source);

[0063] C6H8O6 is continuously added to be completely dissolved by stirring to prevent oxidation (the addition amount of reducing agent is 1.3% based on the total mass of lithium source, phosphorus source and iron source);

[0064] Then FePO4 7H2O is added to continue stirring for 35 min to obtain a light green mixture;

[0065] (2) The mixture is poured into an autoclave to react at 150℃ for 5h, and after the reaction is completed, the lower precipitate is taken out, washed with deionized water and ethanol for several times, and dried to obtain a lithium iron phosphate precursor;

[0066] (3) The lithium iron phosphate precursor is coated with carbon by glucose under inert atmosphere, and then sintered at 750℃ for 5h to obtain a lithium iron phosphate positive electrode material.

[0067] Example 3

[0068] The difference between this example and Example 1 is that the addition amount of boron source is 3% based on the total mass of lithium source, phosphorus source and iron source in this example.

[0069] The rest of the preparation method and parameters remain the same as Example 1.

[0070] Example 4

[0071] The difference between this example and Example 1 is that the addition amount of boron source is 3% based on the total mass of lithium source, phosphorus source and iron source in this example; and at the same time, an equal doping amount of magnesium sulfate is added (i.e. the doping amount of boron and magnesium remains the same).

[0072] The rest of the preparation method and parameters remain the same as Example 1.

[0073] Example 5

[0074] The difference between this example and Example 1 is that the addition amount of boron source is 4% based on the total mass of lithium source, phosphorus source and iron source in this example.

[0075] The rest of the preparation method and parameters remain the same as in Example 1.

[0076] Example 6

[0077] The difference between this example and Example 1 is that the amount of boron source added in this example is 4% based on the total mass of lithium source, phosphorus source and iron source being 100%.

[0078] The rest of the preparation method and parameters remain the same as in Example 1.

[0079] Example 7

[0080] The difference between this example and Example 1 is that the amount of boron source added in this example is 5% based on the total mass of lithium source, phosphorus source and iron source being 100%.

[0081] The rest of the preparation method and parameters remain the same as in Example 1.

[0082] Example 8

[0083] The difference between this example and Example 1 is that the amount of boron source added in this example is 5% based on the total mass of lithium source, phosphorus source and iron source being 100%; and at the same time, an equal amount of magnesium sulfate is added (i.e. the doping amount of boron and magnesium remains the same).

[0084] The rest of the preparation method and parameters remain the same as in Example 1.

[0085] Example 9

[0086] The difference between this example and Example 1 is that the amount of boron source added in this example is 6% based on the total mass of lithium source, phosphorus source and iron source being 100%.

[0087] The rest of the preparation method and parameters remain the same as in Example 1.

[0088] Example 10

[0089] The difference between this example and Example 1 is that the solvent in step (1) of this example is deionized water.

[0090] The rest of the preparation method and parameters remain the same as in Example 1.

[0091] Comparative Example 1

[0092] The difference between this example and Example 1 is that the lithium iron phosphate positive electrode material provided in this example does not undergo any doping, i.e. no boron source is added in step (1).

[0093] The rest of the preparation method and parameters remain the same as in Example 1.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that the comparative example provides a preparation method of a lithium iron phosphate positive electrode material:

[0096] The lithium source, phosphorus source, iron source, boron source and carbon source are mixed, and then directly sintered at 500°C for 10h to obtain the lithium iron phosphate positive electrode material; that is, a pure solid phase sintering reaction.

[0097] The specific substances of the rest of the raw materials remain the same as in Example 1.

[0098] The lithium iron phosphate positive electrode materials provided by Example 1-10 and Comparative Example 1-2, conductive carbon black (Super P) and binder (PVDF) are mixed uniformly according to a mass ratio of 8:1:1. An appropriate amount of N-methyl-2-pyrrolidone (NMP) organic solvent is added as a dispersant, and the mixture is ground thoroughly to obtain a paste-like slurry; the slurry is coated on an aluminum foil current collector and dried in a vacuum drying oven at 80°C for 12h. The dried electrode sheet is punched into a circular sheet with a diameter of Φ14mm using a sheet cutting machine as the positive electrode sheet of the button cell. The mass of the positive electrode sheet and the aluminum foil is weighed to calculate the actual mass of the active material. At the same time, the nickel foam and the separator are punched into small round sheets with diameters of Φ16mm and Φ12mm, respectively.

[0099] The above prepared electrode sheet is used as the positive electrode, a lithium metal sheet is used as the negative electrode, Celgard2400 is used as the separator, and 1mol / L LiPF6 is dissolved in a solution of EC+DMC+EMC (volume ratio of 1:1:1) as the electrolyte. In a glove box under a high-purity argon atmosphere, the positive electrode shell, the electrode sheet, the separator, the lithium sheet, the nickel mesh and the negative electrode shell are sequentially assembled and sealed in the order from bottom to top. The assembled battery is left to stand for 12h and is ready for use. At the same time, the glove box requires that the water and oxygen contents are both less than 0.5ppm.

[0100] The performance of the obtained battery is tested under the following conditions: constant current charge and discharge test at 1C, and the test results are shown in Table 1.

[0101] Table 1

[0102]

[0103] From the data results of examples 1-8, it can be seen that when the addition amount of boron source is in the range of 1-5%, the capacity and ionic conductivity of the material can be improved, but when the addition amount of boron source is in the range of 3-5%, due to excessive doping of boron, new problems occur, the capacity improvement is not obvious, after doping magnesium synchronously, magnesium and boron cooperate to balance the charge in the material, avoid the defects caused by the stacking of oxygen atoms, and realize the great improvement of the capacity and ionic conductivity of the positive electrode material.

[0104] From the data results of examples 1 and 9, it can be seen that when the addition amount of boron source exceeds 5%, excessive doping cannot improve the capacity of the material, but affects the stability of the material structure, causing capacity loss.

[0105] From the data results of examples 1 and 10, it can be seen that when water is selected as the solvent, the doping effect is poor, and the introduction of water also causes capacity loss.

[0106] From the data results of examples 1-8 and comparative example 1, it can be seen that without any treatment of lithium iron phosphate, the capacity cannot be improved, and the damage to the stability of the material gradually increases with the improvement of boron, so the corresponding magnesium needs to be added to maintain the stability of the material.

[0107] From the data results of examples 1 and comparative example 2, it can be seen that the boron doping by the pure solid phase method has poor doping effect, and instead destroys the material structure.

[0108] In summary, the boron is doped in the lithium iron phosphate precursor material through the solvothermal reaction, which is beneficial to control the doping amount of boron, and after further sintering, the lithium iron phosphate positive electrode material with an olivine crystal structure and good crystallinity is obtained, and the boron atoms successfully replace part of the phosphorus atoms in the polyanion site, thereby enhancing the discharge energy ratio and ionic conductivity of the material.

[0109] The above examples are used to illustrate the detailed structural features of the present application, but the present application is not limited to the above detailed structural features, that is, it does not mean that the present application must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present application, equivalent replacement of the components selected by the present application, addition of auxiliary components, selection of specific modes, etc., all fall within the protection scope and disclosure scope of the present application.

[0110] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above embodiments, and within the technical concept range of the present application, the technical solutions of the present application can be subjected to various simple modifications, and these simple modifications all belong to the protection scope of the present application.

[0111] It should be further noted that any technically feasible combination of the various technical features described in the above embodiments is possible, provided that there is no contradiction, and the present application does not make any further statement on the various possible combinations.

[0112] Furthermore, any combination of the various embodiments of the present application is possible, provided that there is no contradiction, and should be considered as disclosed by the present application.

Claims

1. A method for preparing a lithium iron phosphate cathode material, characterized in that, The preparation method comprises the following steps: mixing a lithium source, a phosphorus source, a boron source, an iron source, a reducing agent and a solvent, performing a solvothermal reaction to obtain a precursor material, mixing the precursor material with a carbon source, and sintering to obtain the lithium iron phosphate positive electrode material; the boron source is added in an amount of 3-5% based on 100% of the total mass of the lithium source, the phosphorus source and the iron source, and the mixed raw materials further comprise a magnesium source; the doping amount of magnesium in the lithium iron phosphate positive electrode material in the magnesium source is consistent with the doping amount of boron in the lithium iron phosphate positive electrode material in the boron source; the molar ratio of the lithium source, the iron source and the phosphorus source is (2-4):(0.8-1.2):(1-2); the reducing agent is added in an amount of 1.2-1.6% based on 100% of the total mass of the lithium source, the phosphorus source and the iron source.

2. The method of claim 1, wherein the lithium iron phosphate cathode material is prepared by the steps of: The reducing agent comprises any one or a combination of at least two of dehydroascorbic acid, phytic acid or 2,6-di-tert-butyl-p-cresol. ​ 3. The method of claim 1, wherein the lithium iron phosphate cathode material is prepared by the steps of: The solvent comprises water and / or an organic solvent. ​ 4. The method of claim 1, wherein the lithium iron phosphate cathode material is prepared by the steps of: The solvent is an organic solvent. ​ 5. The method of claim 3, wherein the lithium iron phosphate cathode material is prepared by the steps of: mixing lithium carbonate, iron oxide, and phosphoric acid; and heating the mixture at a temperature of 600 to 800°C for 6 to 10 hours. The organic solvent comprises an alcohol and / or dimethylbenzene.

6. The method of claim 5, wherein the lithium iron phosphate cathode material is prepared by the steps of: The alcohol comprises ethylene glycol. ​ 7. The method for preparing the lithium iron phosphate cathode material according to claim 1, characterized in that, The temperature of the solvothermal reaction is 150-200°C.

8. The method for preparing lithium iron phosphate cathode material according to claim 1, characterized in that, The time of the solvothermal reaction is 2-5h.

9. The method for preparing the lithium iron phosphate cathode material according to claim 1, characterized in that, The product after the solvothermal reaction is washed and dried.

10. The method of claim 1, wherein the lithium iron phosphate cathode material is prepared by the steps of: The temperature of the sintering is 400-800°C. ​ 11. The method of claim 1-10, wherein the lithium iron phosphate cathode material is prepared by the steps of: The time of the sintering is 5-20h. ​ 12. The method of claim 1, wherein the lithium iron phosphate cathode material is prepared by the steps of: The preparation method comprises the following steps: ​ mixing a lithium source, a phosphorus source, a boron source, an iron source, a reducing agent and an organic solvent, performing a solvothermal reaction at 150-200°C for 2-5h to obtain a precursor material, mixing the precursor material with a carbon source, and sintering to obtain the lithium iron phosphate positive electrode material; wherein the molar ratio of the lithium source, the iron source and the phosphorus source is (2-4):(0.8-1.2):(1-2), the boron source is added in an amount of 3-5% based on 100% of the total mass of the lithium source, the phosphorus source and the iron source, the mixed raw materials further comprise a magnesium source, the addition amount of the magnesium source is consistent with the addition amount of the boron source, and the reducing agent is added in an amount of 1.2-1.6% based on 100% of the total mass of the lithium source, the phosphorus source and the iron source.

13. A lithium iron phosphate cathode material, characterized in that, The lithium iron phosphate positive electrode material is prepared by the preparation method in any one of claims 1-12.

14. A lithium-ion battery, characterized by, The lithium ion battery comprises the lithium iron phosphate positive electrode material in claim 13.

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