A lithium iron phosphate cathode material and its preparation method, and a lithium iron phosphate battery.

Abstract

This invention belongs to the field of lithium iron phosphate battery preparation technology, specifically relating to a lithium iron phosphate cathode material and its preparation method, and a lithium iron phosphate battery. This invention involves simultaneously adding polyethylene glycol (PEG) of a specific molecular weight as a morphology modifier and Ti to the precursor slurry. 4+ Ions (such as titanium dioxide) are used as doping sources to generate a synergistic effect, optimizing crystal growth and electronic structure. This is combined with the process of splitting and grinding the crude lithium iron phosphate after a single sintering into two different particle sizes, mixing them, and then drying and sintering them to prepare lithium iron phosphate cathode materials. Experimental data show that the resistivity of the prepared lithium iron phosphate cathode material powder can be as low as 15 Ω·cm, and the compaction density can be as high as 2.58 g / cm³. 3 The 0.1C discharge capacity reaches 158.89mAh / g.

Description

Technical Field

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

[0002] Lithium-ion batteries, with their moderate energy density, long cycle life, and excellent safety performance, have been widely used in core areas such as power batteries for new energy vehicles, large-scale energy storage power stations, and portable electronic devices. Among them, lithium iron phosphate (LFP) cathode materials, due to their abundant raw material reserves, low cost, strong structural stability, excellent cycle life, absence of heavy metal pollution, and good thermal stability, dominate in low-to-mid-range, high-capacity battery scenarios such as power storage and large-scale grid energy storage, making them one of the most mature and in-demand lithium-ion battery cathode materials currently available. With the rapid development of the new energy industry, the market has placed higher demands on the energy density, charge-discharge performance, conductivity, and compaction density of LFP batteries. High-performance, low-internal-resistance, and high-compact-density LFP cathode materials have become a core research and development direction for the industry.

[0003] Currently, the industry mainly improves the inherent defects of lithium iron phosphate cathode materials through modification methods such as carbon coating, metal ion doping, morphology control, and particle size optimization, thereby enhancing the electrochemical performance of the materials. Among these, metal ion doping can optimize the electronic structure of the material and improve intrinsic conductivity, organic additives can regulate the particle morphology and optimize the crystal growth state, and particle size control can improve the powder packing effect and increase the compaction density, which are the mainstream modification methods. However, existing modification technologies have obvious limitations and singularity. When using organic additives such as PEG to regulate morphology alone, it can only improve particle dispersion and regularity, but cannot effectively optimize the electronic conductivity structure of the material, and it is difficult to reduce the bulk resistivity of the material. When using metal ion doping such as titanium ions alone, although it can improve electronic conductivity, it is prone to problems such as uneven crystal growth, particle agglomeration, and disordered particle size, resulting in low compaction density of the material, and failing to achieve both conductivity and packing performance. Meanwhile, traditional lithium iron phosphate manufacturing processes often employ a single grinding and sintering molding method, resulting in a uniform particle size distribution and large gaps between particles. This easily leads to insufficient compaction density, high powder resistivity, and low utilization of active materials. Ultimately, this makes it difficult to achieve breakthroughs in battery discharge capacity and rate performance. There are technical pain points where conductivity and compaction density are mutually constrained, resulting in significant shortcomings in overall electrochemical performance.

[0004] In existing technologies, various single modification processes and conventional preparation methods are insufficient to achieve a synergistic improvement in the conductivity, compaction density, and discharge capacity of lithium iron phosphate cathode materials, failing to meet the application requirements of high-end power batteries and large-capacity energy storage batteries. Conventional modification systems lack a synergistic coupling design of additive morphology control and metal ion doping, and do not perform fine-grained gradation optimization for powder particle size, resulting in singular modification effects and limited performance improvements. The finished materials generally suffer from defects such as high resistivity, low compaction density, and insufficient discharge capacity, severely restricting the industrialization and high-end application of lithium iron phosphate cathode materials and lithium iron phosphate batteries. Therefore, there is an urgent need to develop a lithium iron phosphate cathode material preparation technology that can synergistically optimize crystal structure, particle morphology, and particle size distribution, while simultaneously achieving high conductivity, high compaction density, and high capacity. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a lithium iron phosphate cathode material, its preparation method, and a lithium iron phosphate battery.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions: The present invention provides a method for preparing lithium iron phosphate cathode material, comprising the following steps: (1) dissolving lithium source, iron source and phosphorus source in solvent, then adding primary carbon source, polyethylene glycol and titanium source, and mixing evenly to obtain precursor slurry; (2) drying the precursor slurry in sequence and sintering to obtain crude lithium iron phosphate; (3) dividing the crude lithium iron phosphate into first crushed material and second crushed material, grinding them to different particle sizes to obtain small particle size slurry and large particle size slurry, and then mixing the two slurries to obtain mixed slurry; (4) drying the mixed slurry in sequence, sintering and pulverizing to obtain lithium iron phosphate cathode material.

[0007] Preferably, in the above preparation method, in step (1), the molecular weight of polyethylene glycol is 200 Da to 20000 Da; and / or the titanium source is selected from one or more combinations of tetrabutyl titanate, titanium dioxide, titanium trichloride or titanium sulfate.

[0008] More preferably, in the above preparation method, the amount of polyethylene glycol added is 0.1 wt% to 5.0 wt% of the mass of lithium iron phosphate; and / or the titanium source is Ti 4+ Ionic doping is performed, with the titanium source doping amount ranging from 0.1 mol% to 3.0 mol% of the lithium iron phosphate molar fraction.

[0009] More preferably, in the above preparation method, the doping amount of the titanium source is 0.5 mol% to 2.0 mol% of the lithium iron phosphate molar fraction.

[0010] Preferably, in the above preparation method, the molar ratio of lithium source, iron source and phosphorus source is (1.04-1.08):(0.92-0.98):(1.01-1.09).

[0011] More preferably, in the above preparation method, in step (4), the D50 of the small particle size slurry is 0.2 μm to 1.0 μm; the D50 of the large particle size slurry is 1.0 μm to 2.0 μm; and the mass ratio of the small particle size slurry to the large particle size slurry is (4-6):(6-4).

[0012] Preferably, in the above preparation method, in step (1), the carbon source is selected from one or more combinations of glucose, sucrose or polyethylene glycol.

[0013] Preferably, in the above preparation method, in step (2), sintering includes a pre-sintering section and a constant temperature section; the temperature of the pre-sintering section is 300℃~550℃, and the holding time is 2h~6h; the temperature of the constant temperature section is 600℃~750℃, and the holding time is 3h~8h; and / or in step (4), the sintering temperature is 700℃~850℃, and the holding time is 4h~12h.

[0014] In another aspect, the present invention provides a lithium iron phosphate cathode material, which is prepared by the above-described preparation method.

[0015] In another aspect, the present invention provides a lithium iron phosphate battery comprising a lithium iron phosphate cathode material prepared by the above-described preparation method, or comprising the above-described lithium iron phosphate cathode material.

[0016] The beneficial effects of this invention include: This invention simultaneously adds polyethylene glycol (PEG) of a specific molecular weight as a morphology modifier and Ti to the precursor slurry. 4+ Ions (such as titanium dioxide) are used as doping sources to generate a synergistic effect, optimizing crystal growth and electronic structure. This is combined with the process of splitting and grinding the crude lithium iron phosphate after a single sintering into two different particle sizes, mixing them, and then drying and sintering them to prepare lithium iron phosphate cathode materials. Experimental data show that the resistivity of the prepared lithium iron phosphate cathode material powder can be as low as 15 Ω·cm, and the compaction density can be as high as 2.58 g / cm³. 3 The 0.1C discharge capacity reaches 158.89mAh / g, which is far superior to lithium iron phosphate cathode materials without PEG / titanium source or with only titanium source. It achieves a comprehensive effect of low resistance, high compaction and high capacity, and the process is controllable and easy to industrialize. Attached Figure Description

[0017] Figure 1 This is a SEM image of the carbon-coated lithium iron phosphate cathode material prepared in Example 5. Detailed Implementation

[0018] The embodiments described are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the embodiments described. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description are still within the scope of protection 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] In a first aspect, embodiments of the present invention provide a method for preparing lithium iron phosphate cathode material, comprising the following steps: (1) dissolving lithium source, iron source and phosphorus source in a solvent, then adding a primary carbon source, polyethylene glycol and titanium source, and mixing evenly to obtain a precursor slurry; (2) drying the precursor slurry in sequence and sintering it to obtain crude lithium iron phosphate; (3) dividing the crude lithium iron phosphate into a first crushed material and a second crushed material, grinding them to different particle sizes to obtain a small particle size slurry and a large particle size slurry, and then mixing the two slurries to obtain a mixed slurry; (4) drying the mixed slurry in sequence, sintering it, and pulverizing it to obtain lithium iron phosphate cathode material.

[0021] It should be noted that this method adopts a synergistic strategy of "liquid-phase homogeneous mixing, titanium ion doping, hierarchical grinding and compounding, and secondary sintering". Polyethylene glycol is used to improve particle dispersibility and suppress agglomeration, while titanium source doping is used to improve the electronic conductivity and ion transport rate of the material. The particle packing density is optimized by compounding particles of different sizes, reducing interfacial impedance and improving compaction density and cycle stability. Secondary sintering further improves the crystal structure and enhances crystallinity, ultimately obtaining a lithium iron phosphate cathode material with synergistic improvement in rate performance, cycle life and energy density.

[0022] It should also be noted that in this invention, polyethylene glycol, through the steric hindrance effect of its molecular chain and the construction effect of pyrolytic carbon network, interacts with Ti. 4+ The lattice doping of ions and the broadening of electron channels produce a synergistic effect, jointly optimizing the crystal morphology and electronic structure of lithium iron phosphate.

[0023] In some specific examples, in the above preparation method, in step (1), the molecular weight of polyethylene glycol is 200 Da to 20000 Da; and / or the titanium source is selected from one or more combinations of tetrabutyl titanate, titanium dioxide, titanium trichloride or titanium sulfate.

[0024] It should be noted that the molecular weight of polyethylene glycol can be specifically selected from 200Da, 1000Da, 2000Da, 4000Da, 6000Da, 8000Da, 10000Da, or 20000Da, etc., and can be used as a dispersant and auxiliary carbon source to improve the uniformity of the slurry and form a uniform carbon coating layer during sintering; tetrabutyl titanate, titanium dioxide, titanium trichloride, and titanium sulfate can all efficiently provide Ti 4+ This allows for bulk doping, enhancing the material's conductivity and structural stability.

[0025] In some specific examples, in the above preparation method, the amount of polyethylene glycol added is 0.1wt% to 5.0wt% of the mass of lithium iron phosphate; and / or the titanium source is Ti. 4+ Ionic doping is performed, with the titanium source doping amount ranging from 0.1 mol% to 3.0 mol% of the lithium iron phosphate molar fraction.

[0026] It should be noted that the specific amount of polyethylene glycol added can be 0.1wt%, 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 3.0wt%, 4.0wt%, or 5.0wt%, etc., which can effectively disperse particles and prevent sintering and agglomeration; Ti 4+ The specific doping amount can be 0.1 mol%, 0.5 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%, or 3.0 mol%, etc. Appropriate doping can introduce lattice defects and increase carrier concentration, while excessive doping can easily cause lattice distortion and reduce structural stability.

[0027] In some specific examples, in the above preparation method, the doping amount of the titanium source is 0.5 mol% to 2.0 mol% of the lithium iron phosphate molar fraction.

[0028] It should be noted that Ti 4+ The doping amount can preferably be 0.5 mol%, 1.0 mol%, 1.5 mol%, or 2.0 mol%, etc. This range can maximize the improvement of electronic conductivity and Li without destroying the olivine structure. + The migration rate enables lithium iron phosphate to combine high rate performance with long cycle life.

[0029] In some specific examples, the molar ratio of lithium source, iron source and phosphorus source in the above preparation method is (1.04-1.08):(0.92-0.98):(1.01-1.09).

[0030] It should be noted that the molar ratio of lithium source, iron source, and phosphorus source can be 1.04:0.92:1.01, 1.05:0.95:1.05, or 1.08:0.98:1.09, etc. Using a ratio of excess lithium, slightly excess phosphorus, and slightly insufficient iron can suppress the formation of impurity phases, ensure the stability of stoichiometry, and improve the purity and electrochemical performance of the material.

[0031] In some specific examples, in the above preparation method, in step (4), the D50 of the small particle size slurry is 0.2μm to 1.0μm; the D50 of the large particle size slurry is 1.0μm to 2.0μm; and the mass ratio of the small particle size slurry to the large particle size slurry is (4-6):(6-4).

[0032] It should be noted that the small particle size D50 can be 0.2μm, 0.5μm, 0.8μm or 1.0μm, etc., and the large particle size D50 can be 1.0μm, 1.2μm, 1.5μm, 1.8μm or 2.0μm, etc.; the mass ratio can be 4:6, 5:5 or 6:4, etc. The combination of large and small particles can significantly improve the packing density and compaction density, shorten the ion transport path, and improve the rate capability and cycling performance.

[0033] In some specific examples, in the above preparation method, in step (1), the carbon source is selected from one or more combinations of glucose, sucrose or polyethylene glycol.

[0034] It should be noted that glucose, sucrose, and polyethylene glycol are all high-quality organic carbon sources. After high-temperature pyrolysis, they can form a uniform and continuous amorphous carbon coating layer, which improves the conductivity of the material. The carbon sources can be used alone or in combination, and the coating is uniform and not easy to agglomerate, which can effectively improve the rate performance of lithium iron phosphate.

[0035] In some specific examples, in the above preparation method, in step (2), sintering includes a pre-sintering section and a constant temperature section; the temperature of the pre-sintering section is 300℃~550℃, and the holding time is 2h~6h; the temperature of the constant temperature section is 600℃~750℃, and the holding time is 3h~8h; and / or in step (4), the sintering temperature is 700℃~850℃, and the holding time is 4h~12h.

[0036] It should be noted that in step (2), the pre-firing temperature can be 300, 350, 400, 450, 500 or 550℃, and the holding time can be 2h, 3h, 4h, 5h or 6h, to remove moisture and organic matter; the constant temperature can be 600℃, 650℃, 700℃ or 750℃, and the holding time can be 3h, 4h, 5h, 6h, 7h or 8h, to initially form the lithium iron phosphate crystal phase; in step (4), the sintering temperature can be 700℃, 750℃, 800℃ or 850℃, and the holding time can be 4h, 6h, 8h, 10h or 12h, to further improve crystallinity and repair lattice defects.

[0037] Secondly, embodiments of the present invention provide a lithium iron phosphate cathode material, which is prepared by the above-described preparation method.

[0038] It should be noted that the lithium iron phosphate cathode material in this invention is Ti. 4+ With its doped, carbon-coated, dual-size composite structure, high crystallinity, uniform particle size distribution, high compaction density, and excellent conductivity, this battery features low impedance, high rate capability, long cycle life, and high specific capacity, meeting the requirements of power and energy storage batteries.

[0039] Thirdly, embodiments of the present invention provide a lithium iron phosphate battery comprising a lithium iron phosphate cathode material prepared by the above-described preparation method, or comprising the above-described lithium iron phosphate cathode material.

[0040] It should be noted that the lithium iron phosphate battery prepared using the cathode material of this invention has advantages such as high energy density, excellent rate discharge performance, ultra-long cycle life, and strong high-temperature stability, and is suitable for scenarios such as new energy vehicles, energy storage power stations, and industrial backup power.

[0041] 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.

[0042] Preparation Example Example 1 (1) Preparation of precursor slurry: Lithium source (lithium carbonate), iron source (iron phosphate), and phosphorus source (ammonium dihydrogen phosphate) were dissolved in deionized water at a molar ratio of Li:Fe:P=1.06:0.95:1.05. Glucose (5 wt% of lithium iron phosphate) was added as a primary carbon source. PEG-6000 aqueous solution (1.0 wt% of lithium iron phosphate) was added as a morphology modifier. Titanium dioxide was added at 1.0 mol% of lithium iron phosphate as a titanium source. The mixture was mixed evenly to obtain the precursor slurry.

[0043] (2) Spray drying: The above slurry is sent into the atomizing tower for spray drying. The inlet air temperature is set to 250℃ and the outlet air temperature is set to 120℃.

[0044] (3) Primary sintering: The spray-dried material is fed into a roller kiln for segmented sintering. The pre-sintering section is 400℃ and held for 3 hours to complete crystal nucleation and carbothermic reduction; the constant temperature section is 600℃ and held for 3 hours to achieve preliminary crystal growth and regular morphology. The nitrogen flow rate during sintering is set to 500±50m³. 3 The nitrogen and oxygen content is <50ppm, and the furnace pressure is <50Pa. The sintered material is then crushed to obtain crude lithium iron phosphate.

[0045] (4) Secondary grinding and gradation: The crude lithium iron phosphate is transported to the secondary raw material silo and divided into two parts according to the mass ratio of the first crushed material to the second crushed material of 6:4. Secondary grinding is carried out separately: the designed amount of water is added to the reactor, the crude lithium iron phosphate is added to the reactor and stirred, and then a certain proportion of carbon source (glucose, 4% of the mass of crude lithium iron phosphate) is added. Then it is passed into a sand mill containing zirconia balls of different sizes for grinding. During the grinding process, the slurry passes through the sand mill and returns to the reactor to form a circulating ball mill (the weight ratio of 0.3 mm diameter zirconia balls to 3 mm diameter zirconia balls is 1:10). Finally, small particle size slurry (D50=0.4μm) and large particle size slurry (D50=1.6μm) are obtained respectively, and then the two slurries are mixed. During the grinding process, the stirring frequency is set to 45Hz and the ball mill speed is set to 750rpm.

[0046] (5) Secondary spray drying: The mixed slurry is sent into the atomizing tower for secondary spray drying. The inlet air temperature is set to 210℃, the outlet air temperature is set to 70℃, the atomizer frequency is set to 50Hz, the bag temperature is set to 100℃, the air supply frequency is set to 50Hz, and the induced air frequency is set to 50Hz.

[0047] (6) Secondary sintering: The material after the second spray drying is fed into the roller kiln for secondary sintering. The temperature of the kiln constant temperature zone is set to 800℃, and the holding time is 5h. The nitrogen and oxygen content is 10ppm, and the furnace pressure is set to 50Pa.

[0048] (7) Crushing: The material after the second sintering is crushed using a crusher. The feeding screw frequency is set to 50Hz, the crushing frequency is set to 50Hz, the crushing current is set to 60A, the grading frequency is set to 45Hz, and the induced draft frequency is set to 50Hz. After crushing, carbon-coated lithium iron phosphate cathode material is obtained.

[0049] Examples 2 to 9 Examples 2 and 9 are largely the same as Example 1, except that the temperature and holding time of the first sintering constant temperature zone are different. Otherwise, they are the same as Example 1. The temperature and holding time of the first sintering constant temperature zone in Examples 2 and 9 are shown in Table 1 below and are compared with those in Example 1.

[0050] Table 1. Parameters of temperature and holding time in the constant temperature zone during primary sintering. Comparative Example 1 Comparative Example 1 is largely the same as Example 1, except that polyethylene glycol (PEG) and titanium source were not added in Comparative Example 1. That is, only lithium source, iron source, phosphorus source and primary carbon source glucose were used in step (1), and PEG and titanium dioxide were not added. Otherwise, it was the same as Example 1.

[0051] Comparative Example 2 Comparative Example 1 is largely the same as Example 1, except that polyethylene glycol (PEG) was not added in Comparative Example 1. That is, titanium dioxide (1.0 mol%) was added in step (1), but PEG was not added. Otherwise, it is the same as Example 1.

[0052] Related tests The lithium iron phosphate cathode materials prepared in the above embodiments and comparative examples were subjected to the following physical and electrochemical performance tests.

[0053] (1) Powder resistivity test: A four-probe powder resistivity tester was used to apply a set pressure (e.g., 20 MPa) to the sample at room temperature and measure its resistivity value (unit: Ω·cm).

[0054] (2) Compacted density test: Take a certain mass (e.g., 2g) of lithium iron phosphate powder and put it into a special mold. Compact it under a set pressure (e.g., 20MPa). Measure the thickness and diameter of the sample after compaction and calculate the compacted density (unit: g / cm). 3 ).

[0055] (3) Electrochemical performance test: Each sample was assembled into a CR2032 coin cell and constant current charge-discharge test was performed using the Blue Battery Test System. The test voltage range was 2.0V to 4.2V, the test rate was 0.1C (1C=170mA / g), and the first charge specific capacity (first charge) and discharge specific capacity (0.1C discharge capacity) were recorded. The test temperature was 25±2℃.

[0056] The specific assembly method for button cells is as follows: Positive electrode preparation: Lithium iron phosphate positive electrode material, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 90:5:5. An appropriate amount of N-methylpyrrolidone (NMP) was added and ground evenly to form a slurry. The slurry was uniformly coated onto aluminum foil, vacuum dried at 120℃ for 12 hours, and then cut into circular sheets with a diameter of 14 mm.

[0057] Negative electrode: Lithium metal sheet is used as the negative electrode.

[0058] Electrolyte: 1M LiPF6 dissolved in a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) (volume ratio 1:1:1).

[0059] Separator: Celgard 2400 polypropylene separator.

[0060] Battery assembly: In a glove box filled with argon (H2O < 0.1ppm, O2 < 0.1ppm), assemble the positive electrode shell, positive electrode plate, separator, negative lithium plate, gasket, spring plate, and negative electrode shell in sequence, then inject electrolyte and seal.

[0061] (II) Test Results The resistivity, compaction density, and electrochemical performance data of the lithium iron phosphate cathode materials prepared in each embodiment and comparative example are shown in the table below.

[0062] Table 2. Resistivity, Compacted Density, and Battery Performance Data Table 2 shows that, compared with Comparative Example 1 (no PEG, no titanium) and Comparative Example 2 (with titanium, no PEG), the lithium iron phosphate cathode materials of Examples 1 to 9 of this invention all exhibited lower resistivity and higher compaction density, while the 0.1C discharge capacity was significantly improved. This indicates that the synergistic use of polyethylene glycol and titanium source can effectively improve the conductivity and compaction performance of the material. Among them, Example 5 (first sintering at a constant temperature of 650℃ for 5 hours) achieved the best overall performance: a resistivity as low as 15 Ω·cm and a compaction density as high as 2.58 g / cm³. 3 The 0.1C discharge capacity reached 158.89 mAh / g. This indicates that under the conditions of a single sintering temperature of 650℃ and a holding time of 5h, the crystal morphology and carbon coating effect achieved the optimal balance (see...). Figure 1 ).

[0063] 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, Includes the following steps: (1) Dissolve lithium source, iron source and phosphorus source in solvent, then add carbon source, polyethylene glycol and titanium source, and mix evenly to obtain precursor slurry; (2) The precursor slurry was dried and sintered to obtain crude lithium iron phosphate; (3) The crude lithium iron phosphate is divided into first crushed material and second crushed material, and ground to different particle sizes to obtain small particle size slurry and large particle size slurry. Then the two slurries are mixed to obtain mixed slurry. (4) The mixed slurry is dried, sintered and crushed in sequence to obtain lithium iron phosphate cathode material.

2. The production method according to claim 1, characterized by, In step (1), The molecular weight of polyethylene glycol is 200 Da to 20000 Da; and / or The titanium source is selected from one or more combinations of tetrabutyl titanate, titanium dioxide, titanium trichloride, or titanium sulfate.

3. The preparation method according to claim 2, characterized in that, The amount of polyethylene glycol added is 0.1 wt% to 5.0 wt% of the mass of lithium iron phosphate; and / or The titanium source is Ti 4+ The titanium source is doped in ionic form in an amount of 0.1 to 3.0 mol% of lithium iron phosphate.

4. The production method according to claim 3, characterized by, The doping amount of the titanium source is 0.5 mol% to 2.0 mol% of the lithium iron phosphate molar fraction.

5. The production method according to any one of claims 1 to 4, characterized by, The molar ratio of lithium source, iron source and phosphorus source is (1.04-1.08):(0.92-0.98):(1.01-1.09).

6. The production method according to any one of claims 1 to 4, characterized by, In step (4), The D50 of small particle size slurry is 0.2μm to 1.0μm; The D50 of large particle size slurry is 1.0μm to 2.0μm; The mass ratio of small-particle-size slurry to large-particle-size slurry is (4-6):(6-4).

7. The production method according to any one of claims 1 to 4, characterized by, In step (1), the carbon source is selected from one or more combinations of glucose, sucrose or polyethylene glycol.

8. The preparation method according to any one of claims 1 to 4, characterized in that, In step (2), sintering includes a pre-sintering section and a constant-temperature section; the temperature of the pre-sintering section is 300℃~550℃, and the holding time is 2h~6h; the temperature of the constant-temperature section is 600℃~750℃, and the holding time is 3h~8h; and / or In step (4), the sintering temperature is 700℃~850℃, and the holding time is 4h~12h.

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, The lithium iron phosphate cathode material prepared by any one of claims 1 to 8, or the lithium iron phosphate cathode material as described in claim 9.

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