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

Abstract

The invention belongs to the technical field of lithium iron phosphate batteries, and particularly relates to a lithium iron phosphate positive electrode material, a preparation method thereof and a lithium iron phosphate battery. The preparation raw materials are ground into the slurry with different particle sizes in batches according to a certain proportion, then the slurry is mixed, atomized and sintered to obtain the lithium iron phosphate positive electrode material, and a battery based on the prepared lithium iron phosphate positive electrode material is excellent in electrochemical performance and good in chemical stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium iron phosphate battery technology, specifically relating to a lithium iron phosphate cathode material and its preparation method, and a lithium iron phosphate battery. Background Technology

[0002] Currently, lithium iron phosphate (LFP) materials are widely used as cathode materials in lithium-ion batteries for electric buses and energy storage devices. The electrification of automobiles has become one of the future trends in automotive development. However, many problems with electric vehicles have been hindering their development in the automotive market. These problems include insufficient power during startup and hill climbing, excessively long charging times, poor range, and poor safety performance. Therefore, it is particularly important to develop a lithium-ion battery system that can be charged and discharged at high rates, has high specific capacity, long lifespan, and high safety.

[0003] To obtain a lithium-ion battery system capable of high-rate charging and discharging, high specific capacity, long lifespan, and high safety, high-performance lithium iron phosphate materials are essential. While the applicant's current lithium iron phosphate materials meet product qualification requirements, they do not yet meet the requirements for high-performance lithium iron phosphate materials.

[0004] Therefore, it is significant to develop a high-performance lithium iron phosphate material. Summary of the Invention

[0005] This invention develops a lithium iron phosphate cathode material. During the preparation process, the raw materials are ground into slurries of different particle sizes in batches according to a certain proportion, and then mixed, atomized and sintered to obtain the lithium iron phosphate cathode material. The prepared lithium iron phosphate cathode material has excellent performance, and the battery prepared based on the cathode material has excellent electrochemical performance and good chemical stability.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions:

[0007] The present invention provides a method for preparing lithium iron phosphate cathode material, comprising: (1) grinding a first part of raw materials with water to obtain a first part of slurry; grinding a second part of raw materials with water to obtain a second part of slurry; (2) mixing the first part of slurry and the second part of slurry, atomizing, and sintering to obtain lithium iron phosphate cathode material; the first part of raw materials and the second part of raw materials include lithium source, iron source and phosphorus source; the particle size D50 of the first part of raw materials after grinding is 0.8μm-1.3μm, and the particle size D50 of the second part of raw materials after grinding is 0.25μm-0.45μm; the mass ratio of the first part of raw materials and the second part of raw materials is (1.8-4.5):7; and the sintering is segmented sintering.

[0008] Preferably, the above preparation method satisfies one or more of the following conditions: (i) the particle size D50 of the first part of the raw material after grinding is 1μm-1.3μm; and / or the particle size D50 of the second part of the raw material after grinding is 0.4μm-0.45μm; (ii) the mass ratio of the first part of the raw material to the second part of the raw material is (2-4):7.

[0009] More preferably, in the above preparation method, the particle size D50 of the first part of the raw material after grinding is 1.21 μm; and / or the particle size D50 of the second part of the raw material after grinding is 0.42 μm; and / or the mass ratio of the first part of the raw material to the second part of the raw material is 3:7.

[0010] Preferably, the above preparation method satisfies one or more of the following conditions: (a) the mass ratio of lithium source, iron source and phosphorus source in the first part raw material and the second part raw material is (1.04-1.08):(0.92-0.98):(1.01-1.09); (b) the first part raw material further includes a carbon source; (c) the lithium source is selected from one or more of lithium carbonate, lithium phosphate or lithium dihydrogen phosphate; and / or the iron source is selected from one or more of iron phosphate, iron oxide, ferrous oxalate or iron(II,III) oxide; and / or the phosphorus source is selected from one or more of lithium phosphate, iron phosphate, ammonium dihydrogen phosphate or phosphoric acid; (d) the solid content of the first part slurry and the second part slurry is independently 40%-55%; (e) the particle size after mixing is 0.5μm-1μm.

[0011] Preferably, the above preparation method satisfies one or more of the following conditions: 1) the first part of the raw materials also includes a carbon source, and the carbon content of the lithium iron phosphate cathode material is 1.1%-1.5%; 2) the carbon source is selected from one or more of glucose, starch, sucrose, citric acid, ascorbic acid or polyethylene glycol; 3) the solid content of both the first part of the slurry and the second part of the slurry is 42.1%.

[0012] Preferably, in the above preparation method, the segmented sintering includes a first sintering stage and a second sintering stage, the temperature of the first sintering stage is 700℃-750℃, and the temperature of the second sintering stage is 760℃-800℃.

[0013] Preferably, in the above preparation method, the lithium iron phosphate cathode material is obtained by crushing after sintering.

[0014] Preferably, in the above preparation method, the particle size D50 of the crushed lithium iron phosphate cathode material is 0.5μm-2μm.

[0015] Another aspect of the present invention provides a lithium iron phosphate cathode material, which is prepared by the preparation method of the present invention.

[0016] Another aspect of the present invention provides a lithium iron phosphate battery, which includes the lithium iron phosphate cathode material of the present invention.

[0017] The beneficial effects of this invention include: the Fe dissolution amount (ppm / kg) of the lithium iron phosphate battery cathode material provided by this invention can be as low as 68ppm, the 0.1C discharge specific capacity can be as high as 161.03mA·h· / g, the 0.1C discharge plateau can reach 97.53%, the resistivity can be lower than 101Ω·cm, and the magnetic material content can be lower than 0.33ppm, indicating excellent electrochemical performance and good chemical stability. Detailed Implementation

[0018] The illustrated embodiments are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the illustrated embodiments. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description of the invention still fall within the protection scope of the present invention.

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.

[0020] This invention provides a method for preparing a lithium iron phosphate cathode material, comprising: (1) grinding a first part of raw materials with water to obtain a first part of slurry; grinding a second part of raw materials with water to obtain a second part of slurry; (2) mixing the first part of slurry and the second part of slurry, atomizing, and sintering to obtain a lithium iron phosphate cathode material; the first part of raw materials and the second part of raw materials include a lithium source, an iron source, and a phosphorus source; the particle size D50 of the first part of raw materials after grinding is 0.8μm-1.3μm, and the particle size D50 of the second part of raw materials after grinding is 0.25μm-0.45μm; the mass ratio of the first part of raw materials and the second part of raw materials is (1.8-4.5):7; and the sintering is segmented sintering.

[0021] It should be noted that, through research, this invention has found that by dividing the raw materials for preparing lithium iron phosphate cathode materials into two parts according to a certain ratio, grinding them separately to obtain slurries with different particle sizes, then mixing them, and atomizing and sintering them, lithium iron phosphate cathode materials can be prepared. Specifically, the particle size D50 of the first part of the raw materials after grinding is 0.8μm-1.3μm, for example, 1μm-1.3μm, or even 0.9μm, 1μm, 1.1μm, or 1.2μm, etc. The particle size D50 of the second part of the raw materials after grinding is... The diameter D50 is 0.25μm-0.45μm, for example 0.4μm-0.45μm, or 0.27μm, 0.32μm, 0.35μm, 0.37μm, 0.4μm or 0.43μm, etc.; the mass ratio of the first part of raw materials to the second part of raw materials is (1.8-4.5):7, for example 2.2:7, 2.5:7, 2.7:7, 3:7, 3.3:7, 3.5:7, 3.7:7, 4:7, 4.3:7, etc.

[0022] In some specific examples, the above preparation method satisfies one or more of the following conditions:

[0023] (i) The particle size D50 of the first batch of raw materials after grinding is 1 μm-1.3 μm; and / or the particle size D50 of the second batch of raw materials after grinding is 0.4 μm-0.45 μm; specifically, the particle size D50 of the first batch of raw materials in this invention is preferably 1 μm-1.3 μm, and the lithium iron phosphate cathode material prepared within this particle size range has better electrochemical performance; similarly, the particle size D50 of the second batch of raw materials after grinding is preferably 0.4 μm-0.45 μm, and the lithium iron phosphate cathode material prepared within this particle size range has better electrochemical performance; more preferably, the particle size D50 of the first batch of raw materials after grinding is 1.21 μm; and / or the particle size D50 of the second batch of raw materials after grinding is 0.42 μm, and the lithium iron phosphate cathode material prepared with this particle size has better electrochemical performance (0.1C discharge specific capacity, 0.1C discharge plateau and resistivity) and better chemical stability (low Fe dissolution and magnetic material content);

[0024] (ii) The mass ratio of the first part of the raw materials and the second part of the raw materials is (2-4):7; specifically, the mass ratio of the first part of the raw materials and the second part of the raw materials in this invention is preferably (2-4):7. Within this ratio range, the prepared lithium iron phosphate cathode material has a higher 0.1C discharge specific capacity and 0.1C discharge platform, lower resistivity, less Fe dissolution, and less magnetic material content; in addition, it is more preferably 3:7, and the prepared lithium iron phosphate cathode material has a higher 0.1C discharge specific capacity and 0.1C discharge platform, lower resistivity, less Fe dissolution, and less magnetic material content.

[0025] It should be noted that in the above preparation method, one of the above conditions can be satisfied, preferably all of the above conditions are satisfied, and more preferably the particle size D50 of the first part of the raw material after grinding is 1.21 μm, the particle size D50 of the second part of the raw material after grinding is 0.42 μm, and the mass ratio of the first part of the raw material to the second part of the raw material is 3:7.

[0026] In some specific examples, the above preparation method satisfies one or more of the following conditions:

[0027] (a) In the first and second parts of the raw materials, the mass ratio of lithium source, iron source and phosphorus source is (1.04-1.08):(0.92-0.98):(1.01-1.09); specifically, the mass ratio of lithium source, iron source and phosphorus source can be 1.05:0.95:1.03, 1.07:0.96:1.05 or 1.08:0.97:1.07, etc.

[0028] (b) The first part of the raw materials also includes a carbon source; specifically, the first part of the raw materials also includes a carbon source, and the addition of a carbon source can realize lithium iron phosphate carbon coating materials and improve electrochemical performance;

[0029] (c) The lithium source is selected from one or more of lithium carbonate, lithium phosphate, or lithium dihydrogen phosphate; and / or the iron source is selected from one or more of iron phosphate, iron oxide, ferrous oxalate, or iron(II,III) oxide; and / or the phosphorus source is selected from one or more of lithium phosphate, iron phosphate, ammonium dihydrogen phosphate, or phosphoric acid. Specifically, the present invention may also replace lithium carbonate, ammonium dihydrogen phosphate, and iron oxide raw materials with lithium carbonate, lithium phosphate, iron phosphate, and iron oxide. Introducing ion doping in the reaction stage can change the crystal structure of LiFePO4, improve its intrinsic conductivity, lithium ion diffusion coefficient, and charge / discharge voltage plateau, so as to optimize its 0.1C discharge and 0.1C first-efficiency and reduce its powder resistivity.

[0030] (d) The solid content of the first slurry and the second slurry are each independently 40%-55%; specifically, the solid content of the first slurry can be 40%-55%, such as 45%, 50% or 53%, etc., and the solid content of the second slurry can be 40%-55%, such as 45%, 50% or 53%, etc.; more preferably, the solid content is 42.1%, and the prepared lithium iron phosphate cathode material has better electrochemical performance and better chemical stability;

[0031] (e) The particle size after mixing is 0.5μm-1μm.

[0032] In some specific examples, the above preparation method satisfies one or more of the following conditions:

[0033] 1) The first part of the raw materials also includes a carbon source; the carbon content of the lithium iron phosphate cathode material is 1.1%-1.5%.

[0034] 2) The carbon source is selected from one or more of glucose, starch, sucrose, citric acid, ascorbic acid or polyethylene glycol; wherein, the molecular weight of polyethylene glycol can preferably be 800-20000.

[0035] In some specific examples, the above preparation method includes a first sintering stage and a second sintering stage, with the temperature of the first sintering stage being 700℃-750℃ and the temperature of the second sintering stage being 760℃-800℃.

[0036] It should be noted that the Fe dissolution of lithium iron phosphate cathode material prepared by segmented sintering in this invention is significantly lower than that prepared by non-segmented sintering, meaning that the chemical stability is better than that prepared by non-segmented sintering. In addition, the temperature of the first sintering stage can be 700℃-750℃, such as 720℃, 730℃ or 740℃, and the temperature of the second sintering stage can be 760℃-800℃, such as 770℃, 780℃ or 790℃.

[0037] In some specific examples, in the above preparation method, lithium iron phosphate cathode material is obtained by crushing after sintering.

[0038] It should be noted that the lithium iron phosphate cathode material prepared after sintering can be crushed to obtain lithium iron phosphate cathode material particles, which can significantly improve electrochemical performance and chemical stability. The particle size D50 of the crushed lithium iron phosphate cathode material can be 0.5μm-2μm, such as 0.7μm, 1μm, 1.3μm, 1.5μm, 1.7μm or 1.9μm, etc.

[0039] This invention also provides a lithium iron phosphate cathode material, which is prepared by the preparation method of this invention.

[0040] This invention also provides a lithium iron phosphate battery, which includes the lithium iron phosphate cathode material of this invention.

[0041] It should be noted that the lithium iron phosphate cathode material in this invention has excellent electrochemical performance and chemical stability, and can be used as a cathode material to prepare lithium iron phosphate batteries; in addition, other components of lithium iron phosphate batteries, such as negative electrode materials, electrolytes, battery separators and casings, are known in the art.

[0042] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0043] I. Preparation of carbon-coated lithium iron phosphate battery cathode materials

[0044] In the following examples and comparative examples, the mass ratio of lithium source, iron source, and phosphorus source in the first and second parts of raw materials is 1.05:0.95:1.05. The preparation method of carbon-coated lithium iron phosphate battery cathode material is as follows:

[0045] (1) Reaction grinding: First, dissolve the first part of the raw material in a reaction vessel a containing water and grind it until D50 = 1.21 μm to obtain the first part of the slurry (solid content is 42.1%). At the same time, polyethylene glycol (molecular weight is 10000) is added during the grinding process. The amount of polyethylene glycol added is 2% of the solid content. After the particle size is qualified, it is transferred to the atomizing vessel.

[0046] (2) Dissolve the second part of the raw material in a reaction vessel containing water and grind it to D50 = 0.42 μm to obtain the second part of the slurry (solid content is 42.1%); In addition, the mass ratio of the first part of the raw material and the second part of the raw material is 3:7, and it is transferred into the atomizing vessel;

[0047] (3) Mix the first part of the slurry and the second part of the slurry in the atomizing kettle. After the slurry is mixed evenly, take a sample to measure the particle size. D50 = 0.83 μm;

[0048] (4) The mixed slurry is spray-dried to obtain the dried precursor;

[0049] (5) The dried precursor is transferred to a sintering furnace, nitrogen is introduced, and high-temperature sintering is performed to obtain carbon-coated lithium iron phosphate battery cathode material.

[0050] (6) The carbon-coated lithium iron phosphate battery cathode material is mechanically crushed, and the particle size D50 after crushing is 0.5μm-2μm.

[0051] Examples 1 to 5

[0052] Carbon-coated lithium iron phosphate battery cathode materials were prepared according to the above preparation method. The raw materials, particle size slurry ratio, sintering procedure and crushing particle size are shown in Table 1 below. In addition, in Table 1, 715℃-3h+780℃-2h refers to sintering at 715℃ for 3h and then sintering at 780℃ for 2h, and the same applies below.

[0053] Table 1. Preparation conditions of carbon-coated lithium iron phosphate battery cathode materials in Examples 1 to 5.

[0054]

[0055]

[0056] Examples 6 to 7

[0057] The difference between Examples 6 and 7 and Example 2 is that the mass ratio of the first part of raw materials and the second part of raw materials in Examples 6 and 7 is different from that in Example 2; the rest is the same as in Example 2, as shown in Table 2 below.

[0058] Table 2. Preparation conditions of carbon-coated lithium iron phosphate battery cathode materials in Examples 6 and 7.

[0059]

[0060] Example 8

[0061] The difference between Example 8 and Example 2 is that in Example 6, ammonium dihydrogen phosphate is used instead of lithium phosphate and iron phosphate in Example 2, and the crushed particle size D50 is 1.24 μm; otherwise, it is the same as Example 2, as shown in Table 3 below.

[0062] Table 3. Preparation conditions of carbon-coated lithium iron phosphate battery cathode material in Example 8.

[0063]

[0064] Comparative Examples 1 to 4

[0065] The difference between Comparative Examples 1 to 4 and Example 2 is that the particle size D50 of Comparative Examples 1 to 4 is 1.24 μm; the other aspects are the same as in Example 2, as shown in Table 4 below.

[0066] Table 4. Preparation conditions of carbon-coated lithium iron phosphate battery cathode materials for Comparative Examples 1 to 4

[0067]

[0068]

[0069] Comparative Example 5

[0070] The difference between Comparative Example 5 and Example 2 is that the sintering procedure of Comparative Example 5 is different from that of Example 2, and the particle size D50 is 1.24 μm; the rest is the same as that of Example 2, as shown in Table 5 below; in Table 5, 780℃-4h refers to sintering at 780℃ for 4 hours.

[0071] Table 5. Preparation conditions of carbon-coated lithium iron phosphate battery cathode materials (Comparative Example 5)

[0072]

[0073] II. Carbon content and Fe leaching test

[0074] The carbon content (determined by thermogravimetric analysis (TGA)) and Fe dissolution (determined by inductively coupled plasma optical emission spectrometry (ICP-OES)) of the crushed carbon-coated lithium iron phosphate battery cathode materials of the examples and comparative examples were tested respectively, and the results are shown in Table 6 below.

[0075] Table 6 shows the carbon content and Fe dissolution of the carbon-coated lithium iron phosphate battery cathode materials prepared in the examples and comparative examples.

[0076] Examples / Comparative Examples Carbon content Fe leaching amount (ppm / kg) Example 1 1.21％ 110 Example 2 1.21％ 68 Example 3 1.26％ 80 Example 4 1.20％ 73 Example 5 1.21％ 124 Example 6 1.21％ 84 Example 7 1.21％ 93 Example 8 1.21％ 92 Comparative Example 1 1.21％ 120 Comparative Example 2 1.21％ 131 Comparative Example 3 1.21％ 142 Comparative Example 4 1.21％ 124 Comparative Example 5 1.21％ 109

[0077] As can be seen from Table 6 above, the Fe dissolution amount in Examples 1 to 7 and Comparative Example 5 is significantly lower than that in Comparative Examples 1 to 4, indicating that the mass ratio of the first part of raw materials and the second part of raw materials has an impact on the Fe dissolution amount of the prepared carbon-coated lithium iron phosphate battery cathode material. When the mass ratio of the first part of raw materials and the second part of raw materials is <1.8:7 (e.g., 2:8) and >4.5:7 (e.g., 4:6, 5:5 or 2:8), the Fe dissolution amount will increase significantly. In addition, non-stage sintering (Comparative Example 5) will affect the Fe dissolution amount. For example, compared with Example 2 under other identical conditions (stage sintering), the Fe dissolution amount is significantly increased.

[0078] III. Electrochemical Performance Testing

[0079] The carbon-coated lithium iron phosphate battery cathode materials prepared in the examples and comparative examples were respectively fabricated into button batteries. The 0.1C discharge specific capacity and 0.1C discharge plateau were tested (the parameters were adjusted according to the high-temperature performance test method in "GB / T 43092-2023 Electrochemical Performance Test of Lithium-ion Battery Cathode Materials"). In addition, the resistivity (resistivity was determined according to "GB / T 45324-2025 Determination of Powder Resistivity of Lithium-ion Battery Cathode Materials") and magnetic material content (magnetic material content was determined according to "GB / T 41704-2022 Determination of Magnetic Foreign Matter Content of Lithium-ion Battery Cathode Materials") of the carbon-coated lithium iron phosphate battery cathode materials were also tested. The test results are shown in Table 7 below.

[0080] Table 7 Electrochemical performance tests of carbon-coated lithium iron phosphate battery cathode materials prepared in the examples and comparative examples.

[0081]

[0082] From Table 7 above, we can see that:

[0083] Firstly, regarding the 0.1C discharge capacity, the 0.1C discharge capacity of Examples 2 to 8 is higher than that of Comparative Examples 1 to 5; the 0.1C discharge capacity of Example 1 is higher than that of Comparative Examples 1, 3 to 5, and slightly lower than that of Comparative Example 2; in addition, Examples 2 to 4, 6 and 8 are more effective, and Example 2 is the best.

[0084] Secondly, for the 0.1C discharge platform, Examples 1 to 8 are superior to Comparative Examples 1 to 5; among them, Examples 2 to 4, as well as Examples 6 and 8, are more effective, with Example 2 being the best.

[0085] Thirdly, regarding resistivity, the resistivity of Examples 1 to 8 is significantly lower than that of Comparative Examples 1 to 5; among them, Examples 2 to 4, as well as Examples 6 and 8, are more effective, with Example 2 being the best.

[0086] Fourth, regarding the content of magnetic materials, the content of magnetic materials in Examples 1 to 7 is ≤0.5ppm.

[0087] Combining the results in Tables 6 and 7, it can be seen that Examples 1 to 8 are superior to Comparative Examples 1 to 5 in terms of both Fe dissolution and electrochemical performance. Among them, Example 2 has the best overall effect. The Fe dissolution (ppm / kg) of the carbon-coated lithium iron phosphate battery cathode material prepared in Example 2 can be lower than 68ppm, the 0.1C discharge specific capacity can be higher than 161.03mA·h· / g, the 0.1C discharge plateau can reach 97.53%, the resistivity can be lower than 101Ω·cm, and the magnetic material content can be lower than 0.33ppm.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a lithium iron phosphate cathode material, characterized in that, include: (1) Grind the first part of the raw materials with water to obtain the first part of the slurry; The second batch of raw materials was ground with water to obtain the second batch of slurry. (2) The first part of the slurry and the second part of the slurry are mixed, atomized, and sintered to obtain lithium iron phosphate cathode material; the first part of the raw materials and the second part of the raw materials include lithium source, iron source and phosphorus source; the particle size D50 of the first part of the raw materials after grinding is 0.8μm-1.3μm, and the particle size D50 of the second part of the raw materials after grinding is 0.25μm-0.45μm; the mass ratio of the first part of the raw materials and the second part of the raw materials is (1.8-4.5):7; the sintering is segmented sintering.

2. The preparation method according to claim 1, characterized in that, The preparation method satisfies one or more of the following conditions: (i) The particle size D50 of the first batch of raw materials after grinding is 1 μm-1.3 μm; and / or the particle size D50 of the second batch of raw materials after grinding is 0.4 μm-0.45 μm; (ii) The mass ratio of the first part of raw materials to the second part of raw materials is (2-4):

7.

3. The preparation method according to claim 2, characterized in that, The particle size D50 of the first batch of raw materials after grinding is 1.21 μm; and / or the particle size D50 of the second batch of raw materials after grinding is 0.42 μm; and / or the mass ratio of the first batch of raw materials to the second batch of raw materials is 3:

7.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The preparation method satisfies one or more of the following conditions: (a) In the first and second batches of raw materials, the mass ratio of lithium source, iron source and phosphorus source is (1.04-1.08):(0.92-0.98):(1.01-1.09); (b) The first part of the raw materials also includes a carbon source; (c) The lithium source is selected from one or more of lithium carbonate, lithium phosphate or lithium dihydrogen phosphate; and / or the iron source is selected from one or more of iron phosphate, iron oxide, ferrous oxalate or iron(II,III) oxide; and / or the phosphorus source is selected from one or more of lithium phosphate, iron phosphate, ammonium dihydrogen phosphate or phosphoric acid. (d) The solid content of the first and second slurries is 40%-55% respectively; (e) The particle size after mixing is 0.5μm-1μm.

5. The preparation method according to claim 4, wherein the preparation method satisfies one or more of the following conditions: 1) The first part of the raw materials also includes a carbon source; the carbon content of the lithium iron phosphate cathode material is 1.1%-1.5%. 2) The carbon source is selected from one or more of glucose, starch, sucrose, citric acid, ascorbic acid, or polyethylene glycol; 3) The solid content of both the first and second parts of the slurry is 42.1%.

6. The preparation method according to claim 1, 2, 3 or 5, characterized in that, Segmented sintering includes a first sintering stage and a second sintering stage. The temperature of the first sintering stage is 700℃-750℃, and the temperature of the second sintering stage is 760℃-800℃.

7. The preparation method according to claim 1, 2, 3 or 5, characterized in that, After sintering, the material is crushed to obtain lithium iron phosphate cathode material.

8. The preparation method according to claim 7, characterized in that, The particle size D50 of the crushed lithium iron phosphate cathode material is 0.5μm-2μm.

9. A lithium iron phosphate cathode material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. A lithium iron phosphate battery, characterized in that, Including the lithium iron phosphate cathode material as described in claim 9.

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