Atmosphere-controlled pulse sintering method for lithium iron phosphate positive electrode material rich in oxygen vacancies and application of atmosphere-controlled pulse sintering method

Abstract

The invention discloses a lithium iron phosphate positive electrode material rich in oxygen vacancies and a preparation method and application thereof.The preparation method of the lithium iron phosphate positive electrode material rich in oxygen vacancies has the advantages that the number of heating times can be set in a programmable mode, the heating and cooling speed is high, and the heat treatment time is short; the volatilization amount of the lithium salt is small, and the method is more economical and environment-friendly; according to the method, a programmable constant-current power supply is used for electrifying and heating the carbon-based Joule thermal material, and the carbon-based material is used as a heating stage to realize ultrafast synthesis of the lithium iron phosphate material through a physical contact heat transfer effect; and the oxygen vacancy content can be adjusted by regulating and controlling parameters such as temperature and time. The heat treatment is performed in a specific atmosphere (such as vacuum, inert gas, reducing gas and oxidizing atmosphere), so that the reoxidation of the oxygen vacancies can be reduced, and the formation and the stabilization of the oxygen vacancies are facilitated; the adjustable and controllable range of the oxygen vacancy concentration in the lithium iron phosphate material prepared by the preparation method disclosed by the invention is 2.198 E12 to 7.382 E13Spins / mm < 3 >.

Description

Technical Field

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

[0002] Since the proposal of the "dual carbon" goal in 2020, people have become more aware of and concerned about the concept of low-carbon environmental protection, and are more enthusiastic about passenger electric vehicles, which has increased the production and sales of electric vehicles and promoted the rapid development of electric vehicles. 1-x-y Co x Mn y O2,N 1-x-y C x M y ) and lithium iron phosphate (LiFePO4, LFP) batteries are the mainstream of electric vehicle batteries. Among them, LFP, which has excellent thermodynamic and electrochemical stability, has shown excellent safety and long life, and occupies an important position in the field of power and energy storage. However, due to its poor ionic conductivity and electronic conductivity, the high rate and low temperature performance of LFP cannot meet practical applications (in cold areas, lithium iron phosphate electric vehicles cannot be used). The fundamental reason is that the discontinuity of the FeO6 octahedral network in the LFP crystal structure leads to limited one-dimensional channels and a wide bandgap width of LFP (3.4-3.8eV). In order to improve the ionic conductivity and electronic conductivity of LFP, researchers from schools and enterprises have proposed many strategies, such as reducing particle size, carbon coating, ion (anion or cation) doping, functionalized coating construction, etc. However, these strategies often have problems such as high cost, complex process, poor controllability and even reduced specific capacity.

[0003] Creating oxygen vacancies (a type of point defect) is a simple and effective way to accelerate the transport of ions and electrons in LFP. LFP is a semiconductor material, and the introduction of oxygen vacancies can change its electronic and band structure, reduce the band gap, increase electronic conductivity, and reduce Li + The diffusion barrier and the enhanced kinetic process are expected to improve the fast charging performance of lithium iron phosphate. 5+ Stable (PO4) formed by strong covalent bonds 3- The polyanion groups make it difficult for oxygen in the lattice to be lost. Therefore, there are very few oxygen vacancy defects in LFP synthesized by the traditional tube furnace sintering method, and it is difficult to control the concentration of oxygen vacancy defects.

[0004] For example, Chinese patent document CN201010300023.6 discloses a lithium iron phosphate containing oxygen vacancies and Fe-doped lithium ion positive electrode material and a rapid microwave sintering preparation method thereof. The preparation method using rapid microwave sintering has the characteristics of high production efficiency, low energy consumption, and good product batch stability, but the oxygen vacancy defects are relatively few, which needs further improvement. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a lithium iron phosphate positive electrode material rich in oxygen vacancies and a preparation method and application thereof. The preparation method of the present invention is simple, efficient and has low energy consumption. The oxygen vacancy content in the prepared lithium iron phosphate material is easy to adjust and has excellent electrochemical properties.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] In a first aspect, the present invention provides a method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies, comprising the following steps:

[0008] S1. preparing lithium iron phosphate precursor powder;

[0009] S2. Using carbon-based materials as a heating source, transient pulse heating is performed on lithium iron phosphate precursor powder under a specific atmosphere to obtain lithium iron phosphate positive electrode material.

[0010] In the technical solution of the present invention, in step S1, the specific preparation process of the lithium iron phosphate precursor powder is as follows: adding iron phosphate, lithium source and auxiliary materials to a dispersant, ball milling, and after the ball milling is completed, vacuum drying is performed to obtain the lithium iron phosphate precursor powder.

[0011] Among them, the molar ratio of iron phosphate, lithium source and auxiliary materials is 1:0.4-1.1:0.05-0.15.

[0012] In the technical solution of the present invention, the lithium source is selected from lithium carbonate, lithium hydroxide or lithium acetate.

[0013] In the technical solution of the present invention, the auxiliary material is selected from sucrose, starch or glucose.

[0014] In the technical solution of the present invention, the dispersant is anhydrous ethanol, acetone or deionized water.

[0015] In the technical solution of the present invention, the rotation speed of the ball milling treatment is 300-600rpm, for example, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, and 600rpm can be selected; the ball milling time is 6-12h, for example, 6h, 7h, 8h, 9h, 10h, 11h, and 12h can be selected; but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] In the technical solution of the present invention, in step S2, the specific operation steps of transient pulse heating are as follows:

[0017] The lithium iron phosphate precursor powder is spread evenly on the carbon-based material, and then the two ends of the carbon-based material are connected to a programmable constant current power supply, and transient pulse heating is performed under a specific atmosphere to obtain the lithium iron phosphate positive electrode material.

[0018] Alternatively, the lithium iron phosphate precursor powder is moved to a conveyor belt through vibration screening, and the carbon-based material is used as a heating source. A non-contact roll-to-roll heating method is used to perform transient pulse heating in a specific atmosphere, and the lithium iron phosphate positive electrode material is collected by conveying it through a conveyor belt.

[0019] In the technical solution of the present invention, in step S2, the carbon-based material is selected from carbon cloth, carbon paper, carbon felt, graphene film or graphite paper.

[0020] In the technical solution of the present invention, in step S2, the gas atmosphere for transient pulse heating is vacuum, inert atmosphere, reducing atmosphere or oxidizing atmosphere, for example, nitrogen, helium, argon, hydrogen, argon-hydrogen mixture, carbon monoxide, carbon dioxide, and air can be selected.

[0021] In the technical solution of the present invention, in step S2, the temperature of transient pulse heating is 500-1000°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, and 1000°C can be selected; the time of single transient pulse heating is 100ms-50s, for example, 100ms, 200ms, 300ms, 400ms, 500ms, 800ms, 1s, 2s, 5s, 8s, 10s, 20s, 30s, 40s, and 50s can be selected; the number of transient pulse heating is 1-5 times, for example, 1 time, 2 times, 3 times, 4 times, and 5 times can be selected; but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the heating rate of the ultrafast high temperature heating in step S2 is 10-10 5℃ / s, for example, 10℃ / s, 20℃ / s, 30℃ / s, 40℃ / s, 50℃ / s, 60℃ / s, 70℃ / s, 80℃ / s, 90℃ / s, 100℃ / s, 150℃ / s, 250℃ / s, 300℃ / s, 400℃ / s, 500℃ / s, 1000℃ / s, 2000℃ / s, 3000℃ / s, 4000℃ / s, 5000℃ / s, 10000℃ / s, 20000℃ / s, 30000℃ / s, 40000℃ / s, 50000℃ / s, 10 5 ℃ / s; the cooling rate is 10-10 3 ℃ / s, for example, 10℃ / s, 20℃ / s, 30℃ / s, 40℃ / s, 50℃ / s, 60℃ / s, 70℃ / s, 80℃ / s, 90℃ / s, 100℃ / s, 150℃ / s, 200℃ / s, 300℃ / s, 500℃ / s, 1000℃ / s can be selected; including but not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0023] In a second aspect, the present invention provides a lithium iron phosphate positive electrode material prepared by the above preparation method.

[0024] In a third aspect, the present invention also provides the use of the above-mentioned lithium iron phosphate positive electrode material in battery positive electrode materials.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention provides a method for preparing a lithium iron phosphate material rich in oxygen vacancies, which has the characteristics of programmable heating times, fast heating and cooling speeds, and short heat treatment time. It not only consumes less energy and gas, but also has less volatilization of lithium salts, which is more economical and environmentally friendly.

[0027] (2) The present invention does not introduce other elements and does not change the lithium iron phosphate precursor ingredients. It only achieves dynamic regulation of the oxygen vacancy content by adjusting parameters such as temperature, time, and reaction gas type during the synthesis process. This is simple and effective and can greatly reduce production costs.

[0028] (3) In the present invention, a programmable constant current power supply is used to electrically heat the carbon-based Joule heat material, and the carbon-based material is used as a hot plate to achieve ultrafast synthesis of lithium iron phosphate materials through physical contact heat transfer; and the oxygen vacancy content can be adjusted by regulating parameters such as temperature and time; heat treatment in a specific atmosphere (such as vacuum, inert gas, reducing gas) can reduce the reoxidation of oxygen vacancies, thereby facilitating the formation and stability of oxygen vacancies. Longer reaction times are generally beneficial to the formation and distribution of oxygen vacancies because there is more time for oxygen atoms to detach from the lattice. As the temperature increases, the speed of LFP synthesis increases, leaving more time for oxygen atoms to return to the equilibrium position, thereby reducing the generation of oxygen vacancies.

[0029] (4) In the present invention, the reaction atmosphere has a greater effect on regulating oxygen vacancies than parameters such as temperature and time. In a reducing atmosphere such as hydrogen and carbon monoxide, the gas can react with the material as a chemical reducing agent, which can cause oxygen atoms to detach from the crystal lattice and form oxygen vacancies. This method can achieve the introduction of oxygen vacancies at a lower temperature, and the concentration of oxygen vacancies can be controlled by adjusting the type and concentration of the reducing agent; in a CO2 atmosphere, CO2 molecules may react with oxygen vacancies to form carbonates or other compounds, thereby reducing the oxygen vacancy content; and in an oxidizing atmosphere (such as O2, air), oxygen vacancies may be filled, resulting in a decrease in the oxygen vacancy content.

[0030] (5) The controllable range of oxygen vacancy concentration in the present invention is 2.198E12 to 7.382E13 Spins / mm 3 , while the LFP sintered in the traditional tube furnace has a very low oxygen vacancy concentration of 1.320E12 Spins / mm 3 The oxygen vacancy concentration of commercial LFP is even lower, only 1.853E9 Spins / mm 3 Medium concentration (1.0E13Spins / mm 3 ) can improve the electronic conductivity and lithium ion diffusion coefficient of lithium iron phosphate materials, thereby achieving better high-rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a temperature-time curve diagram of lithium iron phosphate synthesized by the transient pulse heating method in Example 2 of the present invention;

[0032] Figure 2 The temperature-time curve of sintering lithium iron phosphate in a tubular furnace in Comparative Example 1;

[0033] Figure 3 The XRD spectrum of the lithium iron phosphate material prepared in Example 2-4 of the present invention;

[0034] Figure 4The oxygen vacancy defect concentration distribution diagram of lithium iron phosphate in Examples 1-4, Examples 6-8 and Comparative Examples 1-2 of the present invention;

[0035] Figure 5 The figure is a rate performance diagram of the lithium iron phosphate material synthesized in Example 2 of the present invention and Comparative Example 1;

[0036] Figure 6 The discharge capacity diagram of the lithium iron phosphate material synthesized in Examples 1-3 of the present invention at 0.2C;

[0037] Figure 7 This is a graph of the discharge capacity of the lithium iron phosphate material synthesized in Example 1 and Examples 5-7 of the present invention at 0.2C. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0039] It should be noted that, unless otherwise specified, the chemical reagents involved in the present invention were purchased through commercial channels.

[0040] Example 1

[0041] A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies comprises the following steps:

[0042] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0043] S2. Spread 150 mg of dried lithium iron phosphate precursor powder on a carbon cloth of size 2×5 cm. In an argon atmosphere, heat the mixture to 800°C at a heating rate of 250°C / s and keep the temperature for 10s. Then cool the mixture at a rate of 100°C / s and perform transient pulse heating once to finally obtain lithium iron phosphate material.

[0044] Example 2

[0045] A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies comprises the following steps:

[0046] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0047] S2. Spread 150 mg of dried lithium iron phosphate precursor powder on a carbon cloth of size 2×5 cm. In an argon atmosphere, heat the mixture to 800°C at a heating rate of 300°C / s and keep the temperature for 10 seconds. Then cool the mixture at a rate of 150°C / s and perform transient pulse heating three times to finally obtain lithium iron phosphate material.

[0048] Example 3

[0049] A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies comprises the following steps:

[0050] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0051] S2. Spread 150 mg of dried lithium iron phosphate precursor powder on a carbon cloth of size 2×5 cm. In an argon atmosphere, heat the mixture to 700°C at a heating rate of 250°C / s and keep the temperature for 10s. Then cool the mixture at a rate of 100°C / s and perform transient pulse heating three times to finally obtain lithium iron phosphate material.

[0052] Example 4

[0053] A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies comprises the following steps:

[0054] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0055] S2. Spread 150 mg of dried lithium iron phosphate precursor powder on a carbon cloth of size 2×5 cm. In an argon atmosphere, heat the mixture to 900°C at a heating rate of 300°C / s and keep the temperature for 10 seconds. Then cool the mixture at a rate of 150°C / s and perform transient pulse heating three times to finally obtain lithium iron phosphate material.

[0056] Example 5

[0057] A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies comprises the following steps:

[0058] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0059] S2. Spread 150 mg of dried lithium iron phosphate precursor powder on a carbon cloth of size 2×5 cm. In an argon atmosphere, heat the mixture to 1000°C at a heating rate of 400°C / s and keep the temperature for 10s. Then cool the mixture at a rate of 200°C / s and perform transient pulse heating for 3 times to finally obtain lithium iron phosphate material.

[0060] Example 6

[0061] A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies comprises the following steps:

[0062] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0063] S2. Spread 150 mg of dried lithium iron phosphate precursor powder on a carbon cloth of size 2×5 cm. In a carbon dioxide atmosphere, heat it to 800°C at a heating rate of 200°C / s and keep it warm for 10s. Then cool it at a rate of 80°C / s and perform transient pulse heating 3 times to finally obtain lithium iron phosphate material.

[0064] Example 7

[0065] A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies comprises the following steps:

[0066] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0067] S2. Spread 150 mg of dried lithium iron phosphate precursor powder on a carbon cloth of size 2×5 cm. In a carbon monoxide atmosphere, heat the mixture to 800°C at a heating rate of 300°C / s and keep the temperature for 10s. Then cool the mixture at a rate of 80°C / s and perform transient pulse heating for 3 times to finally obtain lithium iron phosphate material.

[0068] Example 8

[0069] A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies comprises the following steps:

[0070] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0071] S2. Spread 150 mg of dried lithium iron phosphate precursor powder on a carbon cloth of size 2×5 cm. In an atmosphere of argon-hydrogen mixed gas, heat the mixture to 800°C at a heating rate of 150°C / s and keep it at that temperature for 10s. Then cool it at a rate of 50°C / s and perform transient pulse heating three times to finally obtain lithium iron phosphate material.

[0072] Comparative Example 1

[0073] A method for preparing a lithium iron phosphate positive electrode material comprises the following steps:

[0074] S1. Weighing the three substances according to the molar ratio of iron phosphate: lithium carbonate: sucrose at 1:0.505:0.092, and then using ethanol as a dispersant, using a planetary ball mill to blend the three substances at a ball milling speed of 400 rpm for 8 h, and then vacuum drying at 80 ° C for 12 h to obtain a lithium iron phosphate precursor powder;

[0075] S2. Place 150 mg of dried lithium iron phosphate precursor powder in an alumina crucible and sinter it at 350°C for 3 hours and then at 700°C for 12 hours in a tubular furnace filled with argon at a heating rate of 5°C / min. Finally, cool it to room temperature at a cooling rate of 5°C / min. When the procedure is completed, the lithium iron phosphate material is obtained.

[0076] Comparative Example 2

[0077] Commercial lithium iron phosphate material (Manufacturer: Shenzhen Kejing Technology Co., Ltd.).

[0078] The temperature curve of sintering lithium iron phosphate using the transient pulse heating method in Example 2 is as follows Figure 1 As shown in Comparative Example 1, the temperature curve of sintering lithium iron phosphate using the traditional tube furnace sintering method is as follows: Figure 2 As shown, compared Figure 1 and Figure 2 It takes about 20 hours to sinter lithium iron phosphate in a traditional tubular furnace, but only 30 seconds to synthesize lithium iron phosphate using transient pulse heating, which greatly improves the synthesis efficiency and reduces energy consumption.

[0079] The lithium iron phosphate material prepared in Example 2-5 was subjected to XRD test, and the results were as follows: Figure 3 As shown, from Figure 3 It can be seen that the main diffraction peaks of lithium iron phosphate synthesized at 700-900℃ are similar, and can correspond to the PDF card of LFP (PDF#40-1499), and no other obvious impurity peaks are observed. However, the lithium iron phosphate synthesized at 1000℃ has Fe2P impurity peaks, indicating that this method can prepare relatively pure lithium iron phosphate materials at 700-900℃; however, with the increase of temperature, the intensity of the diffraction peaks is also different. Among them, the diffraction peak of lithium iron phosphate synthesized at 800℃ is the sharpest, the sample has the best crystallinity, and the crystal form is also the most complete.

[0080] The lithium iron phosphates of Examples 1-4, Examples 6-8 and Comparative Examples 1-2 were tested using electron paramagnetic resonance (EPR) to quantitatively characterize the oxygen vacancy concentration. The results are as follows: Figure 4 As shown, from Figure 4 It can be seen that the oxygen vacancy content of lithium iron phosphate in comparative examples 1-2 is extremely low, which is 1.320E12 Spins / mm 3 and 1.853E9 Spins / mm 3 ; The present invention adjusts parameters such as temperature, reaction time, reaction atmosphere, etc., and uses transient pulse heating to synthesize lithium iron phosphate, and the oxygen vacancy content is relatively high and can be adjusted within a certain range.

[0081] The lithium iron phosphate materials synthesized in Example 2 and Comparative Example 1 were prepared into batteries, and their rate performance was tested at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C. The results are as follows: Figure 5 As shown, from Figure 5 It can be seen that compared with lithium iron phosphate sintered in a traditional tubular furnace, although the capacity of lithium iron phosphate sintered by transient pulse sintering is lower at 0.1C and 0.2C, the capacity is higher at a rate not lower than 0.5C; this indicates that under high-rate charge and discharge conditions, the capacity of lithium iron phosphate containing oxygen vacancies is higher, which is beneficial to the fast charging performance of lithium iron phosphate.

[0082] The lithium iron phosphate materials synthesized in Examples 2-4 were prepared into batteries, and their discharge capacities at 0.2C were compared. The results are as follows: Figure 6 As shown; the lithium iron phosphate materials synthesized in Example 2 and Example 6-8 were prepared into batteries, and their discharge capacities at 0.2C were compared. The results are as follows Figure 7 As shown. Figure 6It can be seen that under argon atmosphere, the lithium iron phosphate synthesized at 800°C has the highest discharge capacity at 0.2C, which is attributed to its good crystallinity and more appropriate oxygen vacancy content. In the lithium iron phosphate material containing oxygen vacancies, too high oxygen vacancy content will hinder the transmission of lithium ions, and too low oxygen vacancy content is not enough to improve the discharge capacity; Figure 7 It can be seen that in a carbon monoxide atmosphere, the lithium iron phosphate synthesized at 800°C has the highest discharge capacity at 0.2C, which is attributed to its more suitable oxygen vacancy content.

[0083] Finally, it should be noted that the above embodiments do not limit the present invention in any form. For those skilled in the art, some modifications and improvements can be made to the present invention. Therefore, any modification or improvement made without departing from the spirit of the present invention belongs to the scope of protection claimed in the present invention.

Claims

1. A method for preparing a lithium iron phosphate positive electrode material rich in oxygen vacancies, characterized in that: The following steps are involved: S1. preparing lithium iron phosphate precursor powder; S2. Using carbon-based materials as a heating source, transient pulse heating is performed on lithium iron phosphate precursor powder under a specific atmosphere to obtain lithium iron phosphate positive electrode material.

2. The preparation method according to claim 1, characterized in that: In step S1, the specific preparation process of the lithium iron phosphate precursor powder is as follows: adding iron phosphate, lithium source and auxiliary materials into a dispersant, ball milling, and after the ball milling is completed, vacuum drying is performed to obtain the lithium iron phosphate precursor powder.

3. The preparation method according to claim 2, characterized in that: The molar ratio of iron phosphate, lithium source and auxiliary materials is 1:0.4-1.1:0.05-0.

15.

4. The preparation method according to claim 2, characterized in that: The lithium source is selected from lithium carbonate, lithium hydroxide or lithium acetate, the auxiliary material is selected from sucrose, starch or glucose, and the dispersant is anhydrous ethanol, acetone or deionized water.

5. The preparation method according to claim 2, characterized in that: The rotation speed of the ball milling treatment is 300-600rpm, and the ball milling time is 6-12h.

6. The preparation method according to claim 1, characterized in that: In step S2, the carbon-based material is selected from carbon cloth, carbon paper, carbon felt, graphene film or graphite paper.

7. The preparation method according to claim 1, characterized in that: In step S2, the gas atmosphere for transient pulse heating is vacuum, inert atmosphere, reducing atmosphere or oxidizing atmosphere.

8. The preparation method according to claim 1, characterized in that: In step S2, the temperature of transient pulse heating is 500-1000°C, the time of single transient pulse heating is 100ms-50s, and the number of transient pulse heating is 1-5 times.

9. The lithium iron phosphate positive electrode material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the lithium iron phosphate positive electrode material as claimed in claim 9 in battery positive electrode materials.

Images