Lithium iron phosphate positive electrode material and preparation method and application thereof

Abstract

The invention relates to the field of lithium ion battery positive electrode materials, and discloses a lithium iron phosphate positive electrode material and a preparation method and application thereof. The positive electrode material comprises a matrix and a carbon coating layer coating the surface of the matrix, and based on the total weight of the positive electrode material, the content of the matrix is 94.5-98.9 wt%, and the content of the carbon coating layer is 1.1-5.5 wt%; wherein the matrix is composed of lithium iron titanium phosphate and lithium iron titanium phosphate; the phase composition of the positive electrode material is xLiFe (1-a) TiaPO4. (1-x) LiTi (2-b) Feb (PO4) 3 (at) C, wherein a is more than 0.01 and less than 0.03, b is more than 0.1 and less than 0.3, and x is more than 0.94 and less than 1. The lithium iron phosphate positive electrode material provided by the invention has excellent rate capability, and effectively solves the problem of low energy efficiency of lithium iron phosphate in the prior art.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode materials, specifically to a lithium iron phosphate cathode material, its preparation method, and its application. Background Technology

[0002] Electrochemical energy storage is a crucial support for the construction of new power systems. Lithium-ion batteries play a vital role in electrochemical energy storage, accounting for as much as 97.4% of the installed capacity of new energy storage systems already in operation. Lithium iron phosphate (LFP) materials are widely used in energy storage devices due to their low cost, long lifespan, and high safety. However, LFP is limited by its one-dimensional lithium-ion diffusion channels, resulting in low ionic conductivity, large charge-discharge polarization, and low energy efficiency. Especially under high-power operating conditions, the low energy efficiency causes energy storage devices to lose more energy in each charge-discharge cycle, significantly reducing their economic viability and hindering their further promotion and application.

[0003] Doping with heteroatoms is one of the important methods to improve the ion diffusion capability of lithium iron phosphate (LFP). By introducing heteroatoms into the crystal, defects are induced, thereby enhancing ion transport capability and improving rate performance. From the perspective of crystallography, adding more heteroatoms can form more holes or defects, which can further improve the ion transport capability of LFP. However, doping easily generates impurities and heterogeneous substances. For example, CN118221090A discloses a method for preparing titanium-doped LFP from ilmenite, in which the molar ratio of Li, Fe, and P is 2.5-3:1.02-1:1. The rate performance actually begins to decrease after increasing the Ti doping amount, indicating that the polarization is large at high power and the energy efficiency of LFP is low.

[0004] Therefore, existing technologies often have low doping content for heteroatoms, making it difficult to fully utilize the advantages of doping, and the energy efficiency improvement of lithium iron phosphate is not significant. For example, CN115849326A discloses a method for preparing Ti-doped lithium iron phosphate cathode materials. In this method, 0.01-0.05 mol of titanium source is weighed out relative to 1 mol of phosphorus source for batching. All raw materials are ball-milled and dried to obtain a precursor, and then the precursor is sintered to obtain the cathode material. This cathode material has a high tap density, but its energy efficiency is relatively low at 0.1C rate or even higher.

[0005] Therefore, exploring a modification method with high doping content is of great significance for improving the energy efficiency of lithium iron phosphate and promoting its application in high-power energy storage devices. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing lithium iron phosphate cathode materials, which have low energy efficiency at high power.

[0007] To achieve the above objectives, a first aspect of the present invention provides a lithium iron phosphate cathode material, the cathode material comprising a matrix and a carbon coating layer covering the surface of the matrix, wherein, based on the total weight of the cathode material, the content of the matrix is ​​94.5-98.9 wt% and the content of the carbon coating layer is 1.1-5.5 wt%.

[0008] The matrix is ​​composed of lithium titanium iron phosphate and lithium iron titanium phosphate; the cathode material has the phase composition shown in Formula I: xLiFe (1-a) Ti a PO4·(1-x)LiTi 2-b Fe b (PO4)3@C type I;

[0009] In Equation I, 0.01 < a < 0.03, 0.1 < b < 0.3, and 0.94 < x < 1.

[0010] A second aspect of the present invention provides a method for preparing the lithium iron phosphate cathode material described in the first aspect, the method comprising:

[0011] (1) In the presence of a solvent, iron phosphate, lithium source, carbon source and titanium source are contacted and mixed to obtain a mixture;

[0012] (2) The mixture is spray-dried to obtain the precursor;

[0013] (3) The precursor is calcined to obtain the lithium iron phosphate cathode material;

[0014] In step (1), the molar ratio of the iron phosphate (calculated as P), the lithium source (calculated as Li), the carbon source (calculated as C), and the titanium source (calculated as Ti) is 1:1.03-1.1:0.4-1.0:0.03-0.1.

[0015] The third aspect of the present invention provides the application of the lithium iron phosphate cathode material described in the first aspect in lithium-ion batteries.

[0016] Through the above technical solution, the present invention has at least the following advantages over the prior art:

[0017] The lithium iron phosphate (LFP) cathode material provided by this invention utilizes the three-dimensional lithium-ion diffusion channels of lithium titanium phosphate to improve the lithium-ion transport rate of the material. Furthermore, carbon coating and iron doping enhance the electronic conductivity of lithium titanium phosphate to improve its lithium insertion / extraction capability. Simultaneously, a small amount of titanium is incorporated into the LFP to improve its carrier transport capability, effectively solving the problem of low energy efficiency in existing LFP technologies. The synthesized LFP cathode material exhibits excellent rate performance. Moreover, the preparation method of the LFP cathode material provided by this invention is simple, easy to implement, low in cost, and highly reproducible. Attached Figure Description

[0018] Figure 1 This is the XRD pattern and its refined fitting diagram of the lithium iron phosphate cathode material S1 in Example 1 of the present invention;

[0019] Figure 2 This is a TEM image of lithium iron phosphate material S1 in Example 1 of the present invention;

[0020] Figure 3 These are charge-discharge curves of lithium-ion battery Y1 in Application Example 1 and lithium-ion battery DY1 in Comparative Application Example 1 at a rate of 0.2C.

[0021] Figure 4 This is a voltage differential capacity (dQ / dV) curve of lithium-ion battery Y1 at a 0.2C rate in Application Example 1 of the present invention. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] As mentioned above, a first aspect of the present invention provides a lithium iron phosphate cathode material, the cathode material comprising a matrix and a carbon coating layer covering the surface of the matrix, wherein, based on the total weight of the cathode material, the content of the matrix is ​​94.5-98.9 wt% and the content of the carbon coating layer is 1.1-5.5 wt%.

[0024] The matrix is ​​composed of lithium titanium iron phosphate and lithium iron titanium phosphate; the cathode material has the phase composition shown in Formula I: xLiFe (1-a) Ti a PO4·(1-x)LiTi 2-b Fe b (PO4)3@C type I;

[0025] In Equation I, 0.01 < a < 0.03, 0.1 < b < 0.3, and 0.94 < x < 1.

[0026] Preferably, in formula I, 0.02 < a < 0.03, 0.2 < b < 0.3, and 0.95 ≤ x ≤ 0.96.

[0027] Preferably, the average thickness of the carbon coating layer is 3-10 nm.

[0028] In a preferred embodiment, the particle size D of the cathode material is... 50 The range is 0.8-1.4 μm.

[0029] In this invention, D 50 This refers to the particle size at which the cumulative particle size distribution of lithium iron phosphate cathode material reaches 50%, as measured by a Mastersizer 3000 laser particle size analyzer. In other words, 50% of the particles are smaller than (or larger than) this particle size.

[0030] As previously described, a second aspect of the present invention provides a method for preparing the lithium iron phosphate cathode material described in the first aspect, the method comprising:

[0031] (1) In the presence of a solvent, iron phosphate, lithium source, carbon source and titanium source are contacted and mixed to obtain a mixture;

[0032] (2) The mixture is spray-dried to obtain the precursor;

[0033] (3) The precursor is calcined to obtain the lithium iron phosphate cathode material;

[0034] In step (1), the molar ratio of the iron phosphate (calculated as P), the lithium source (calculated as Li), the carbon source (calculated as C), and the titanium source (calculated as Ti) is 1:1.03-1.1:0.4-1.0:0.03-0.1.

[0035] During the research process, the inventors of this invention discovered that by introducing high-concentration titanium doping and matching an appropriate amount of lithium source supplementation, the driving force for crystal nucleation during the sintering process was significantly enhanced, which promoted the uniform distribution of lithium titanium phosphate crystal nuclei in the lithium iron phosphate matrix, and successfully solved the problem of energy efficiency decay of lithium iron phosphate materials under high power conditions.

[0036] Further research by the inventors revealed that during the preparation of lithium iron phosphate cathode materials, the main culprit is the release of Fe from the iron phosphate precursor. 3+Trace amounts of doping can be incorporated into the lithium titanium phosphate lattice, simultaneously optimizing its ion transport channels and electron migration paths through lattice distortion and charge compensation effects. Lithium titanium phosphate, with its NASICON (sodium superionic conductor) structure, serves as a high-ionic-conductivity solid electrolyte, providing not only a three-stage charge-discharge platform in the 2.5V voltage range, but also significantly enhancing the overall ion transport efficiency of the material through its three-dimensional ion channels. This invention addresses the electrochemical polarization problem caused by the low intrinsic electronic conductivity of lithium titanium phosphate by innovatively utilizing the in-situ pyrolysis of the carbon layer during sintering to achieve uniform coating and construct a highly efficient electron conduction network. This synergistic modification mechanism optimizes charge transport dynamics through high ion conductivity pathways and leverages Fe... 3+ The synergistic effect of doping lattice optimization and carbon coating enhances the overall conductivity of the material, allowing the lithium storage capacity of lithium titanium phosphate to be fully utilized. Under high-power conditions, the multi-voltage plateau characteristics of lithium titanium phosphate effectively alleviate polarization and provide additional capacity support for the system, ultimately achieving a comprehensive improvement in energy efficiency.

[0037] According to a preferred embodiment, in step (1), the molar ratio of the iron phosphate (calculated as P), the lithium source (calculated as Li), the carbon source (calculated as C), and the titanium source (calculated as Ti) is 1:1.05-1.07:0.6-1.0:0.05-0.1. In this preferred embodiment, the technical solution provided by the present invention is more conducive to improving electronic conductivity, avoiding loss of specific capacity, reducing compaction, and further promoting better nucleation and crystal formation of lithium titanium phosphate, thereby further improving the energy efficiency of the lithium iron phosphate cathode material.

[0038] Preferably, in step (1), the solvent is water.

[0039] Preferably, in step (1), the amount of solvent used is such that the solid content of the mixture at 25°C is 20-60 wt%, preferably 30-50 wt%.

[0040] In a preferred embodiment, the particle size D of the iron phosphate is... 50 The thickness ranges from 0.8 to 1.5 μm.

[0041] Preferably, in step (3), the calcination conditions include: a heating rate of 1-10℃ / min, a temperature of 650-750℃, and a time of 6-18h. Under this preferred condition, the technical solution provided by the present invention can obtain lithium iron phosphate cathode materials with more suitable size, higher crystallinity, and better rate performance.

[0042] More preferably, in step (3), the calcination conditions include: a heating rate of 3-5℃ / min, a temperature of 650-750℃, and a time of 6-12h.

[0043] Preferably, in step (3), the calcination is carried out under an inert atmosphere; more preferably, the inert atmosphere is nitrogen or argon.

[0044] Preferably, in step (1), the lithium source is selected from at least one of lithium acetate, lithium carbonate, and lithium hydroxide.

[0045] In a preferred embodiment, the carbon source is selected from at least one of polyethylene glycol, glucose, phenolic resin, sucrose, and fructose, preferably glucose and / or sucrose.

[0046] Preferably, the titanium source is selected from at least one of tetrabutyl titanate, metatitanic acid, titanium oxyacetylacetonate, and titanium dioxide.

[0047] Preferably, in step (1), the contact mixing conditions include: a temperature of 30-80°C, preferably 60-80°C; and a time of 60-180 min, preferably 60-120 min.

[0048] According to a preferred embodiment, in step (2), the spray drying conditions include: a feed rate of 400-2000 mL / h, preferably 600-1200 mL / h; and an inlet air temperature of 200-300℃, preferably 240-260℃. Under this preferred condition, the technical solution of the present invention facilitates the formation of lithium iron phosphate cathode materials with smaller particles and more uniform composition, and can prevent powder particles from adhering to the wall, thereby further improving the yield and energy efficiency of the cathode material.

[0049] As previously stated, the third aspect of the present invention provides the application of the lithium iron phosphate cathode material described in the first aspect in lithium-ion batteries.

[0050] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available products.

[0051] Ferric phosphate-1: Particle size D 50 It is 0.9μm.

[0052] Ferric phosphate-2: Particle size D 50 It is 1.2μm.

[0053] Example 1

[0054] (1) In the presence of deionized water, 3g of iron phosphate, lithium source, carbon source and titanium source were contacted and mixed, and stirred thoroughly to obtain a mixture;

[0055] (2) The above mixture is spray-dried to obtain the precursor;

[0056] (2) Under a nitrogen atmosphere, the above precursor was placed in a tube furnace for calcination and then cooled naturally with the furnace to obtain lithium iron phosphate cathode material S1.

[0057] Example 2

[0058] Using the same method as in Example 1, with the differences shown in Table 1, lithium iron phosphate cathode material S2 was obtained.

[0059] Table 1

[0060]

[0061] Note: Molar ratio of dosage 1 It refers to the molar ratio of iron phosphate (calculated as P), lithium source (calculated as Li), carbon source (calculated as C), and titanium source (calculated as Ti).

[0062] Example 3

[0063] The procedure was carried out in a similar manner to that of Example 1, except that in step (1), the content of iron phosphate was kept constant, and the molar ratio of iron phosphate (calculated as P), lithium source (calculated as Li), carbon source (calculated as C), and titanium source (calculated as Ti) was adjusted to 1:1.03:0.6:0.03.

[0064] Everything else is the same, resulting in lithium iron phosphate cathode material S3.

[0065] Example 4

[0066] The procedure was carried out in a similar manner to that in Example 1, except that in step (1), the amount of iron phosphate was kept constant, and the molar ratio of iron phosphate (calculated as P), lithium source (calculated as Li), carbon source (calculated as C), and titanium source (calculated as Ti) was adjusted to 1:1.03:0.6:0.05.

[0067] Everything else is the same, resulting in lithium iron phosphate cathode material S4.

[0068] Comparative Example 1

[0069] The procedure was carried out in a similar manner to that in Example 1, except that in step (1), the amount of iron phosphate was kept constant, and the molar ratio of iron phosphate (calculated as P), lithium source (calculated as Li), carbon source (calculated as C), and titanium source (calculated as Ti) was adjusted to 1:1.05:0.6:0.01.

[0070] Everything else is the same, resulting in lithium iron phosphate cathode material S5.

[0071] Comparative Example 2

[0072] The procedure was carried out in a similar manner to that in Example 1, except that in step (1), the amount of iron phosphate was kept constant, and the molar ratio of iron phosphate (calculated as P), lithium source (calculated as Li), carbon source (calculated as C), and titanium source (calculated as Ti) was adjusted to 1:1.01:0.6:0.05.

[0073] Everything else is the same, resulting in lithium iron phosphate cathode material S6.

[0074] Comparative Example 3

[0075] The procedure is similar to that in Example 1, except that no titanium source is added in step (1).

[0076] Everything else is the same, and the lithium iron phosphate cathode material DS1 is obtained.

[0077] Comparative Example 4

[0078] Referring to Example 3 in CN118221090A, the following raw materials were added:

[0079] The amount of raw materials added according to the ratio of Example 3 in Table 1 (Fe%:P%:Ti% = 36.45:20.69:0.21) is used as the amount of raw materials added in this comparative example; that is, in this comparative example, the amount of iron phosphate is kept constant, and the molar ratio of iron phosphate (calculated as P), lithium source (calculated as Li), carbon source (calculated as C), and titanium source (calculated as Ti) is adjusted to 1:1:0.08:0.007.

[0080] Everything else is the same, resulting in the lithium iron phosphate cathode material DS2.

[0081] Test Example 1

[0082] The phase composition and particle size D of the lithium iron phosphate cathode material measured in the test example 50 The average thickness of the carbon coating layer is shown in Table 2.

[0083] The testing methods involved include:

[0084] Phase composition: The phase content and doping element content of lithium titanium iron phosphate and lithium iron titanium phosphate were obtained by using a Smart-lab XRD-X-ray powder diffractometer from Rigaku, Japan. The phase content and doping element content of lithium titanium iron phosphate and lithium iron titanium phosphate were obtained by Rietveld refinement (fitting the original data and calculating the phase content by mathematical methods).

[0085] The content of the matrix and carbon coating layer: The content of the carbon coating layer was obtained by testing with a high-frequency infrared carbon-sulfur analyzer from Sichuan Saines, and the content of the matrix was calculated.

[0086] The thickness of the carbon coating layer was measured using a JEOL JEM-F200 instrument from Japan.

[0087] Table 2

[0088]

[0089]

[0090] Application Example 1

[0091] 0.08g of lithium iron phosphate cathode material S1 as active material, 0.01g of acetylene black as conductive agent, and 0.01g of polyvinylidene fluoride as binder were weighed out separately. The three materials were placed in a mortar and mixed. After mixing evenly, 0.5mL of N-methylpyrrolidone was added as dispersant. After mixing again, the mixture was coated onto aluminum foil to form a cathode sheet. In a glove box under an inert protective atmosphere (argon), a CR2032 coin cell was assembled with lithium metal as the anode. After standing for 12 hours, lithium-ion battery Y1 was obtained.

[0092] Application Examples 2 to 4

[0093] The process is similar to that in Application Example 1, except that lithium iron phosphate cathode material S1 is replaced by lithium iron phosphate cathode material S2, lithium iron phosphate cathode material S3, lithium iron phosphate cathode material S4, lithium iron phosphate cathode material S5, and lithium iron phosphate cathode material S6, respectively.

[0094] The rest are the same, resulting in lithium-ion batteries Y1, Y2, Y3, and Y4 respectively;

[0095] The rest are the same, resulting in lithium-ion batteries DY2, DY3, and DY4 respectively.

[0096] Comparative Application Examples 1 to 4

[0097] The procedure was carried out in a similar manner to Application Example 1, except that lithium iron phosphate cathode material S1 was replaced with lithium iron phosphate cathode material DS1 and lithium iron phosphate cathode material DS2, respectively.

[0098] The rest are the same, resulting in lithium-ion batteries DY1, DY2, DY3, and DY4 respectively.

[0099] Test Example 2

[0100] The electrochemical performance of the assembled lithium-ion batteries in the test examples was evaluated using the following methods: The charge / discharge voltage range was set to 2.0-4.6V. Specific capacity tests were conducted at rates of 0.1C, 0.2C, 0.5C, 1C, 5C, and 10C. Specifically, the batteries were first charged and discharged at 0.1C, then at 0.2C. Finally, with 0.2C fixed as the charging rate, discharge was performed at 0.2C, 0.5C, 1C, 5C, and 10C. The energy efficiency at different rates was then calculated. The test results are shown in Table 3.

[0101] The testing methods involved include:

[0102] Specific capacity and energy efficiency: These were obtained by charging and discharging the battery using a 3001A model charge / discharge tester from Wuhan Landian Electronics Co., Ltd.

[0103] Table 3

[0104] 0.1C(％) 0.2C(％) 0.5C(％) 1C(％) 5C(％) 10C(％) Application Example 1 98.3 97.86 97.62 97.26 94.98 93.32 Application Example 2 97.4 97.72 97.31 96.94 94.42 92.56 Application Example 3 93.77 97.51 97.28 96.45 93.6 91.3 Application Example 4 97.02 97.59 97.24 96.65 93.44 91.78 Comparative Application Example 1 97.72 97.68 96.95 96.45 93.04 90.57 Comparative Application Example 2 97.41 97.36 96.59 95.93 92.65 89.42 Comparative Application Example 3 96.41 96.58 96.08 94.9 89.65 87.26 Comparative Application Example 4 96.33 96.50 95.89 94.66 88.23 86.22

[0105] As can be seen from the results in Table 3, the energy efficiency of Examples 1 to 6 is significantly better than that of Comparative Example 1 as the power increases, indicating that the lithium iron phosphate cathode material provided by the present invention has low electrochemical polarization and can improve energy efficiency at high power.

[0106] The present invention exemplarily in Figure 1 The XRD pattern and its refined fitting plot of lithium iron phosphate material S1 in Example 1 are provided. Figure 1 It can be seen that the fitting results are in high agreement with the experimental results, and the fitting data are highly reliable. After phase content refinement, the phase content of lithium iron phosphate is found to be 96 wt%, and the phase content of lithium titanium phosphate is 4 wt%. Further refinement of atomic occupancy reveals that the phase composition of lithium iron phosphate is LiFe. 0.975 Ti 0.025 PO4, the phase composition of lithium titanium phosphate is LiTi 1.72 Fe 0.28 (PO4)3.

[0107] The present invention exemplarily in Figure 2 The document provides a TEM image of the lithium iron phosphate material S1 from Example 1. Figure 2 As can be seen, in the cathode material, the lithium iron phosphate matrix is ​​black striped, and its particle surface has an amorphous carbon layer with an average thickness of 5 nm. This indicates that the cathode material of the present invention includes a matrix and a carbon coating layer covering the surface of the matrix.

[0108] The present invention exemplarily in Figure 3The document provides charge-discharge curves of lithium-ion battery Y1 in Application Example 1 and lithium-ion battery DY1 in Comparative Application Example 1 at a 0.2C rate. Figure 3 It can be seen that, compared with lithium-ion battery DY1, lithium-ion battery Y1 has a smaller voltage difference between the charge and discharge voltage plateaus, and higher charging and discharging specific capacities, indicating that lithium-ion battery DY1 has faster ion transport performance and better rate performance. In addition, slight inflection points were observed at voltages of approximately 2.4V, 2.8V, and 2.3V, which correspond to the lithium insertion / extraction voltage plateau of lithium titanium phosphate, while lithium-ion battery DY1 did not exhibit this phenomenon.

[0109] The present invention exemplarily in Figure 4 The document provides a voltage-differential capacity (dQ / dV) curve for lithium-ion battery Y1 at a 0.2C rate, as shown in Application Example 1. (From...) Figure 4 As can be seen, converting the charge / discharge curve of lithium-ion battery Y1 into a dQ / dV graph reveals two sharp, high-intensity peaks around 3.4V, corresponding to Fe in lithium iron phosphate. 3+ / Fe 2+ The redox reaction was observed, and in the voltage range of 2.0–2.9 V, three pairs of characteristic peaks were observed. These three characteristic peaks correspond to 2.85 / 2.76 V, 2.47 / 2.37 V, and 2.36 / 2.25 V, respectively, which are characteristic peaks of lithium titanium phosphate, confirming the presence of lithium titanium phosphate. This indicates that the lithium titanium phosphate component in the cathode material provided by this invention has the ability to insert and extract lithium, thus playing its role as a fast ion conductor and improving energy efficiency.

[0110] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A lithium iron phosphate cathode material, characterized in that, The cathode material includes a matrix and a carbon coating layer covering the surface of the matrix. Based on the total weight of the cathode material, the content of the matrix is ​​94.5-98.9 wt%, and the content of the carbon coating layer is 1.1-5.5 wt%. The matrix is ​​composed of lithium titanium iron phosphate and lithium iron titanium phosphate; the cathode material has the phase composition shown in Formula I: xLiFe (1-a) Ti a PO4·(1-x)LiTi 2-b Fe b (PO4)3@C type I; In Equation I, 0.01 < a < 0.03, 0.1 < b < 0.3, and 0.94 < x < 1.

2. The cathode material according to claim 1, wherein, In Equation I, 0.02 < a < 0.03, 0.2 < b < 0.3, and 0.95 ≤ x ≤ 0.

96.

3. The cathode material according to claim 1, wherein, The average thickness of the carbon coating layer is 3-10 nm; And / or, the particle size D of the cathode material 50 The range is 0.8-1.4 μm.

4. A method for preparing the lithium iron phosphate cathode material according to any one of claims 1-3, characterized in that, The method includes: (1) In the presence of a solvent, iron phosphate, lithium source, carbon source and titanium source are contacted and mixed to obtain a mixture; (2) The mixture is spray-dried to obtain the precursor; (3) The precursor is calcined to obtain the lithium iron phosphate cathode material; In step (1), the molar ratio of the iron phosphate (calculated as P), the lithium source (calculated as Li), the carbon source (calculated as C), and the titanium source (calculated as Ti) is 1:1.03-1.1:0.4-1.0:0.03-0.

1.

5. The method according to claim 4, wherein, In step (1), the amount of solvent used is such that the solid content of the mixture at 25°C is 20-60 wt%. And / or, the particle size D of the iron phosphate 50 The thickness ranges from 0.8 to 1.5 μm.

6. The method according to claim 4 or 5, wherein, In step (3), the calcination conditions include: a heating rate of 1-10℃ / min, a temperature of 650-750℃, and a time of 6-18h.

7. The method according to any one of claims 4-6, wherein, In step (1), the lithium source is selected from at least one of lithium acetate, lithium carbonate, and lithium hydroxide; And / or, the carbon source is selected from at least one of polyethylene glycol, glucose, phenolic resin, sucrose and fructose; And / or, the titanium source is selected from at least one of tetrabutyl titanate, metatitanic acid, titanium oxyacetylacetonate, and titanium dioxide.

8. The method according to any one of claims 4-7, wherein, In step (1), the conditions for contact mixing include: a temperature of 30-80°C and a time of 60-180 min.

9. The method according to any one of claims 4-8, wherein, In step (2), the conditions for spray drying include: a feed rate of 400-2000 mL / h and an air inlet temperature of 200-300℃.

10. The application of the lithium iron phosphate cathode material according to any one of claims 1-3 in lithium-ion batteries.

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