A method for preparing lithium iron phosphate

Abstract

The application discloses a lithium iron phosphate preparation method. Iron-rich Fenton sludge is used as raw material to prepare iron phosphate, then a metal oxide coating and a direct-current power rapid hot-press sintering technology are adopted to prepare a high-density sintered body in a short time and at a low temperature, so that an ultra-high compact lithium iron phosphate material is obtained.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode materials, specifically relating to a method for preparing lithium iron phosphate materials, and more specifically to a method for preparing ultra-high pressure lithium iron phosphate using a rapid hot pressing sintering technology with a DC power supply. Background Technology

[0002] With increasing societal demands for longer driving ranges, improving the energy density of LiFePO4 batteries has become a hot research topic in recent years. To increase energy density without changing the overall volume, it's necessary to increase the compaction density of the LiFePO4 cathode. Currently, the compaction density of LiFePO4 electrodes in most commercially available cells is 2.4-2.5 g / cm³. 3 The target for improvement is around 2.6-2.7 g / cm³. 3 This allows the battery to meet higher energy density requirements. To achieve this, the powder compaction density of LiFePO4 material must be increased accordingly.

[0003] Currently, commonly used improvement methods mainly include: optimizing the types of raw materials, adjusting the sintering regime, and improving particle size distribution. The mainstream process route for LiFePO4 synthesis is the phosphate-iron line. This process route produces far less gas during sintering than the oxalic acid-iron line, making it suitable for preparing high-density products. Particle size distribution is generally achieved through slurry mixing and sintering precursors of different particle sizes. However, small particles tend to agglomerate and grow into large particles during subsequent sintering, often failing to achieve the desired particle size distribution. The sintering process has the greatest impact on the material properties during LiFePO4 synthesis. Improving the sintering process significantly increases the compaction density of LiFePO4 powder. However, increasing the sintering temperature usually leads to problems such as reduced carbon content and the generation of magnetic impurities, resulting in a decrease in electrical properties. Therefore, finding a suitable sintering regime is imperative. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing ultra-high pressure lithium iron phosphate, which uses iron-rich Fenton sludge as raw material to prepare iron phosphate, and then employs a rapid hot pressing sintering technology using a metal oxide coating (additive A) and a DC power supply (Reference: Yang Yue, Ma Tianhui, Zhao Peilei, et al. Rapid hot pressing sintering preparation of cubic phase Li7La3Zr2O). 12 Solid electrolyte [J]. Journal of Jilin University (Engineering Science), 2023, 53(08): 2272-2276.) High-density sintered bodies were prepared in a short time and at a low temperature, thus obtaining ultra-high pressure lithium iron phosphate materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing lithium iron phosphate materials includes the following steps:

[0007] 1) Take iron-rich Fenton sludge and calcine it at a certain temperature to obtain Fe2O3;

[0008] 2) Add H3PO4 to Fe2O3, add the mixed solution to the reaction vessel, react under oxygen-containing conditions, and obtain iron phosphate after washing, drying and calcination.

[0009] 3) After mixing iron phosphate with lithium source, carbon source and additive A in water, the mixture is ground to a certain particle size and then spray-dried to obtain yellow material;

[0010] 4) Place the yellow material in a tube furnace and sinter at the first temperature to obtain sintered material I. Then place sintered material I in a graphite mold and place the graphite mold in a rapid hot pressing sintering furnace cavity to rapidly heat to the second temperature for sintering to obtain sintered material II.

[0011] 5) The obtained sintered material II is crushed to a certain particle size to obtain ultra-high pressure lithium iron phosphate material.

[0012] In step 1) of the above method, the iron-rich Fenton sludge comes from a sewage treatment plant in Hefei and has an iron content of 40-60%.

[0013] The calcination is carried out in a muffle furnace;

[0014] The specified temperature is 400-800℃; the calcination time can be 3-5 hours.

[0015] After calcination, the material is allowed to cool naturally, then filtered, washed, and dried to obtain Fe2O3.

[0016] In step 2) of the above method, the molar ratio of iron oxide to phosphoric acid can be 1:2-5, specifically 1:4;

[0017] The added phosphoric acid has a mass concentration of 20%-50%;

[0018] The temperature of the reactor is 60-90℃, the reaction pressure is 1-5 atm, and the reaction time is 3-8h;

[0019] The calcination temperature is 400-700℃, and the holding time is 2-6 hours.

[0020] In step 3) of the above method, the molar ratio of Li to iron phosphate in the lithium source can be 1-1.2:1, specifically 1:1;

[0021] The lithium source can be selected from one or more of the following: lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, lithium nitrate, lithium oxalate, and lithium acetate;

[0022] The carbon source may be one or more of the following: glucose, sucrose, starch, cyclodextrin, citric acid, polyethylene glycol, polyvinyl alcohol, glycerol, polyethylene oxide, polystyrene, styrene-butadiene-styrene block copolymer, and carbon nanotubes.

[0023] The carbon content is 0.8-2.0% of the final lithium iron phosphate product weight, specifically 1.6%;

[0024] The additive A is a metal oxide, specifically one or more of the following: vanadium pentoxide, magnesium oxide, titanium dioxide, zirconium oxide, yttrium oxide, and niobium oxide;

[0025] Additive A is 800-3000 ppm of the final lithium iron phosphate product;

[0026] In step 3) of the above method, the abrasive particle size is 0.35-0.65 μm;

[0027] In step 4) of the above method, the first temperature is 400-500℃, and the sintering time at the first temperature can be 480-600 min;

[0028] The heating rate inside the rapid hot-pressing sintering furnace is 100-500℃ / min; the vacuum degree is 5-15Pa; the pressure is 20-50MPa; the second temperature is 600-800℃; and the holding time is 20-60min.

[0029] In step 5) of the above method, the material is pulverized to an average particle size of 1.5-3.0 μm; the resulting ultra-high pressure compacted lithium iron phosphate powder has a compaction density of 2.55 g / cm³. 3 above.

[0030] The lithium iron phosphate material prepared by the above method is also within the scope of protection of this invention.

[0031] The present invention also provides a lithium-ion battery, wherein the lithium-ion battery uses the above-mentioned lithium iron phosphate material as the positive electrode active material.

[0032] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0033] This invention utilizes Fenton sludge as an iron source, which reduces production costs and achieves resource utilization of environmental pollutants. First, the mixed materials are subjected to sand milling and low-temperature pre-calcination (referring to sintering at the first temperature in step 4), ensuring uniform mixing and pre-phase formation of the lithium iron phosphate precursor, achieving uniform dispersion and coating of carbon and metal oxides. Second, a high-density sintered body is obtained at a lower temperature and in a shorter time using a rapid hot-pressing sintering technique powered by a DC power supply, thus obtaining a high-compact lithium iron phosphate material.

[0034] This invention uses a DC power supply to drive current through the sample, causing each particle inside the sintered body to generate Joule heat uniformly, activating and growing the particle surface and enhancing the bonding between grains. It can effectively utilize the self-heating effect inside the powder for sintering, enhance the interaction between adjacent grains, promote the graphitization of carbon and the coating and compactness of metal oxides, and significantly reduce production costs compared with traditional pulse current discharge plasma rapid sintering. Attached Figure Description

[0035] Figure 1 This is a SEM image of lithium iron phosphate prepared in Example 3 of the present invention.

[0036] Figure 2 This is a SEM image of lithium iron phosphate prepared in Comparative Example 1 of this invention.

[0037] Figure 3 This is a SEM image of lithium iron phosphate prepared in Comparative Example 2 of this invention. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0040] This invention provides a method for preparing lithium iron phosphate materials, comprising the following steps:

[0041] 1) Take iron-rich Fenton sludge and calcine it at a certain temperature to obtain Fe2O3;

[0042] 2) Add H3PO4 to Fe2O3, add the mixed solution to the reaction vessel, react under oxygen-containing conditions, and obtain iron phosphate after washing, drying and calcination.

[0043] 3) After mixing iron phosphate with lithium source, carbon source and additive A in water, the mixture is ground to a certain particle size and then spray-dried to obtain yellow material;

[0044] 4) Place the yellow material in a tube furnace and sinter at the first temperature to obtain sintered material I. Then place sintered material I in a graphite mold and place the graphite mold in a rapid hot pressing sintering furnace cavity to rapidly heat to the second temperature for sintering to obtain sintered material II.

[0045] 5) The obtained sintered material II is crushed to a certain particle size to obtain ultra-high pressure lithium iron phosphate material.

[0046] This invention utilizes Fenton sludge as an iron source, reducing production costs while simultaneously achieving the resource utilization of environmental pollutants. First, the mixed materials undergo sand milling and low-temperature pre-calcination to ensure uniform mixing and pre-phase formation of the lithium iron phosphate precursor, achieving uniform dispersion and coating of carbon and metal oxides. Second, a high-density sintered body is obtained at a lower temperature and in a shorter time using a rapid hot-pressing sintering technique powered by a DC power supply, thus obtaining a high-compact lithium iron phosphate material.

[0047] The iron-rich Fenton sludge in the following examples comes from a sewage treatment plant in Hefei and has an iron content of 55%, that is, every 100g of iron-rich Fenton sludge contains 55g of iron.

[0048] Example 1

[0049] S1: Take 100g of iron-rich Fenton sludge and put it into a porcelain boat. Place it in a muffle furnace and calcine at 400℃ for 3 hours. After natural cooling, filter, wash and dry the material to obtain Fe2O3.

[0050] S2: Add 20% (mass concentration, the same below) H3PO4 to Fe2O3 according to the molar ratio of iron oxide to phosphate of 1:4. Add the mixed solution to the reaction vessel. The temperature of the reaction vessel is 60℃. Introduce oxygen into the reaction vessel. The reaction pressure is 2 atm. After reacting for 3 hours, wash, dry and calcine at 400℃ for 2 hours to obtain iron phosphate.

[0051] S3: Iron phosphate, lithium carbonate, glucose, and magnesium oxide are uniformly mixed in water, controlling the Li:FePO4 molar ratio to be 1:1, and the carbon content (calculated based on the carbon in glucose) to be 1.6% (the carbon content is 1.6% of the final lithium iron phosphate product). Mg 2+ The content is 800ppm. After uniform mixing, it is milled to obtain a 0.65μm slurry, which is then spray-dried to obtain a yellow material.

[0052] S4: Place the yellow material in a tube furnace and sinter at 400℃ for 480 min to obtain sintered material I. Then place sintered material I in a graphite mold, and then place the graphite mold in the cavity of a rapid hot pressing sintering furnace (rapid hot pressing sintering with DC power supply, the same below). Under the condition of heating rate of 100℃ / min, hold at 600℃, vacuum degree of 5Pa and pressure of 20MPa for 20 min to obtain sintered material II.

[0053] S5: The sintered material II is pulverized to obtain ultra-high pressure lithium iron phosphate material, and the particle size of the finished product is controlled to be 1.5-3.0μm.

[0054] Example 2

[0055] S1: Take 100g of iron-rich Fenton sludge and put it into a porcelain boat. Place it in a muffle furnace and calcine it at 500℃ for 4 hours. After natural cooling, filter, wash and dry the material to obtain Fe2O3.

[0056] S2: Add 30% H3PO4 to Fe2O3 according to the molar ratio of iron oxide to phosphoric acid of 1:4. Add the mixed solution to the reaction vessel. The temperature of the reaction vessel is 70℃. Oxygen is introduced into the reaction vessel. The reaction pressure is 3 atm. After reacting for 4 hours, wash, dry and calcine at 500℃ for 2 hours to obtain iron phosphate.

[0057] S3: Iron phosphate, lithium carbonate, starch, and vanadium pentoxide are uniformly mixed in water, controlling the Li:FePO4 molar ratio to be 1.05:1 and the carbon content to be 1.4% (the carbon content is 1.4% of the final lithium iron phosphate product). V 5+ The content is 1000ppm. After uniform mixing, it is milled to obtain a 0.55μm slurry, which is then spray-dried to obtain a yellow material.

[0058] S4: Place the yellow material in a tube furnace and sinter at 420℃ for 540 min to obtain sintered material I. Then place sintered material I in a rapid hot pressing sintering furnace powered by DC power and hold it at 650℃, vacuum degree of 10Pa and pressure of 30MPa for 30 min at a heating rate of 200℃ / min to obtain sintered material II.

[0059] S5: The sintered material II is pulverized to obtain ultra-high pressure lithium iron phosphate material, and the particle size of the finished product is controlled to be 1.5-3.0μm.

[0060] Example 3

[0061] S1: Take 100g of iron-rich Fenton sludge and put it into a porcelain boat. Place it in a muffle furnace and calcine it at 600℃ for 5 hours. After natural cooling, filter, wash and dry the material to obtain Fe2O3.

[0062] S2: Add 40% H3PO4 to Fe2O3 according to the molar ratio of iron oxide to phosphoric acid of 1:4. Add the mixed solution to the reaction vessel. The temperature of the reaction vessel is 80℃. Oxygen is introduced into the reaction vessel. The reaction pressure is 4 atm. After reacting for 4 hours, wash, dry and calcine at 500℃ for 2 hours to obtain iron phosphate.

[0063] S3: Iron phosphate, lithium carbonate, starch, polyethylene glycol, and titanium dioxide are uniformly mixed in water, controlling the Li:FePO4 molar ratio to be 1.05:1 and the carbon content to be 1.2% (the carbon content is 1.2% of the final lithium iron phosphate product). Ti 4+ The content is 1500ppm. After uniform mixing, it is milled to obtain a 0.45μm slurry, which is then spray-dried to obtain a yellow material.

[0064] S4: Place the yellow material in a tube furnace and sinter at 450℃ for 600 min to obtain sintered material I. Then place sintered material I in a rapid hot press sintering furnace powered by DC power and hold it at 680℃, vacuum degree of 15Pa and pressure of 40MPa for 40 min under a heating rate of 300℃ / min to obtain sintered material II.

[0065] S5: The sintered material II is pulverized to obtain ultra-high pressure lithium iron phosphate material, and the particle size of the finished product is controlled to be 1.5-3.0μm.

[0066] Example 4

[0067] S1: Take 100g of iron-rich Fenton sludge and put it into a porcelain boat. Place it in a muffle furnace and calcine it at 600℃ for 5 hours. After natural cooling, filter, wash and dry the material to obtain Fe2O3.

[0068] S2: Add 40% H3PO4 to Fe2O3 according to the molar ratio of iron oxide to phosphoric acid of 1:4. Add the mixed solution to the reaction vessel. The temperature of the reaction vessel is 80℃. Oxygen is introduced into the reaction vessel. The reaction pressure is 5 atm. After reacting for 4 hours, wash, dry and calcine at 500℃ for 2 hours to obtain iron phosphate.

[0069] S3: Iron phosphate, lithium carbonate, starch, polyvinyl alcohol, and titanium dioxide are uniformly mixed in water, controlling the Li:FePO4 molar ratio to be 1.1:1 and the carbon content to be 1.0% (the carbon content is 1.0% of the final lithium iron phosphate product). Ti 4+ The content is 2000ppm. After uniform mixing, it is milled to obtain a 0.40μm slurry, which is then spray-dried to obtain a yellow material.

[0070] S4: Place the yellow material in a tube furnace and sinter at 480℃ for 600 min to obtain sintered material I. Then place sintered material I in a rapid hot pressing sintering furnace powered by DC power and hold it at 700℃, vacuum degree of 15Pa and pressure of 50MPa for 40 min under a heating rate of 400℃ / min to obtain sintered material II.

[0071] S5: The sintered material II is pulverized to obtain ultra-high pressure lithium iron phosphate material, and the particle size of the finished product is controlled to be 1.5-3.0μm.

[0072] Example 5

[0073] S1: Take 100g of iron-rich Fenton sludge and put it into a porcelain boat. Place it in a muffle furnace and calcine it at 600℃ for 5 hours. After natural cooling, filter, wash and dry the material to obtain Fe2O3.

[0074] S2: Add 50% H3PO4 to Fe2O3 according to the molar ratio of iron oxide to phosphoric acid of 1:4. Add the mixed solution to the reaction vessel. The temperature of the reaction vessel is 90℃. Oxygen is introduced into the reaction vessel. The reaction pressure is 5 atm. After reacting for 4 hours, wash, dry and calcine at 500℃ for 2 hours to obtain iron phosphate.

[0075] S3: Iron phosphate, lithium carbonate, polyvinyl alcohol, and niobium oxide are uniformly mixed in water, controlling the Li:FePO4 molar ratio to be 1.1:1, and the carbon content to be 0.8% (0.8% of the final lithium iron phosphate product). Nb 4+ The content is 2500ppm. After uniform mixing, it is milled to obtain a 0.35μm slurry, which is then spray-dried to obtain a yellow material.

[0076] S4: Place the yellow material in a tube furnace and sinter at 500℃ for 600 min to obtain sintered material I. Then place sintered material I in a rapid hot pressing sintering furnace powered by DC power and hold it at 700℃, vacuum degree of 15Pa and pressure of 50MPa for 60 min under a heating rate of 500℃ / min to obtain sintered material II.

[0077] S5: The sintered material II is pulverized to obtain ultra-high pressure lithium iron phosphate material, and the particle size of the finished product is controlled to be 1.5-3.0μm.

[0078] Comparative Example 1

[0079] S1: Take 100g of iron-rich Fenton sludge and put it into a porcelain boat. Place it in a muffle furnace and calcine it at 600℃ for 5 hours. After natural cooling, filter, wash and dry the material to obtain Fe2O3.

[0080] S2: Add 40% H3PO4 to Fe2O3 according to the molar ratio of iron oxide to phosphoric acid of 1:4. Add the mixed solution to the reaction vessel. The temperature of the reaction vessel is 80℃. Oxygen is introduced into the reaction vessel. The reaction pressure is 4 atm. After reacting for 4 hours, wash, dry and calcine at 500℃ for 2 hours to obtain iron phosphate.

[0081] S3: Iron phosphate, lithium carbonate, starch, polyethylene glycol, and titanium dioxide are uniformly mixed in water, controlling the Li:FePO4 molar ratio to be 1.05:1 and the carbon content to be 1.2% (the carbon content is 1.2% of the final lithium iron phosphate product). Ti 4+ The content is 1500ppm. After uniform mixing, it is milled to obtain a 0.45μm slurry, which is then spray-dried to obtain a yellow material.

[0082] S4: Place the yellow material in a rapid hot pressing sintering furnace powered by DC power, and hold it at 680℃ for 40 minutes under the conditions of heating rate of 300℃ / min, vacuum degree of 15Pa and pressure of 40MPa to obtain the sintered material.

[0083] S5: The sintered material is crushed to obtain ultra-high pressure lithium iron phosphate material, and the particle size of the finished product is controlled to be 1.5-3.0μm.

[0084] Comparative Example 2

[0085] S1: Take 100g of iron-rich Fenton sludge and put it into a porcelain boat. Place it in a muffle furnace and calcine it at 600℃ for 5 hours. After natural cooling, filter, wash and dry the material to obtain Fe2O3.

[0086] S2: Add 40% H3PO4 to Fe2O3 according to the molar ratio of iron oxide to phosphoric acid of 1:4. Add the mixed solution to the reaction vessel. The temperature of the reaction vessel is 80℃. Oxygen is introduced into the reaction vessel. The reaction pressure is 4 atm. After reacting for 4 hours, wash, dry and calcine at 500℃ for 2 hours to obtain iron phosphate.

[0087] S3: Iron phosphate, lithium carbonate, starch, polyethylene glycol, and titanium dioxide are uniformly mixed in water, controlling the Li:FePO4 molar ratio to be 1.05:1 and the carbon content to be 1.2% (the carbon content is 1.2% of the final lithium iron phosphate product). Ti 4+ The content is 1500ppm. After uniform mixing, it is milled to obtain a 0.45μm slurry, which is then spray-dried to obtain a yellow material.

[0088] S4: Place the yellow material in a tube furnace and sinter at 450℃ for 600 min to obtain sintered material I. Then place it in a pulsed current discharge plasma rapid hot pressing sintering furnace and hold it at 680℃, vacuum degree of 15Pa and pressure of 40MPa for 40 min under a heating rate of 300℃ / min to obtain sintered material.

[0089] S5: The sintered material is crushed to obtain ultra-high pressure lithium iron phosphate material, and the particle size of the finished product is controlled to be 1.5-3.0μm.

[0090] Figure 1 The image shows a SEM image of lithium iron phosphate prepared in Example 3.

[0091] Figure 2 SEM image of lithium iron phosphate prepared in Comparative Example 1.

[0092] Figure 3 SEM image of lithium iron phosphate prepared in Comparative Example 2.

[0093] Figure 2 and Figure 1In contrast, it was found that without low-temperature sintering, the primary particles of lithium iron phosphate failed to grow effectively, resulting in smaller secondary particles and a failure to achieve the desired particle size distribution, leading to lower compaction.

[0094] Figure 3 and Figure 1 In comparison, it was found that the secondary particles of lithium iron phosphate prepared by rapid hot pressing sintering with pulsed current discharge plasma were smaller, and no large columnar particles were found compared with Example 3, resulting in slightly lower compaction.

[0095] The lithium iron phosphate materials prepared in Examples 1-5 and Comparative Examples 1-2 were used as positive electrode materials. A lithium iron phosphate positive electrode sheet was prepared with a mass ratio of positive electrode material: conductive agent SP: polyvinylidene fluoride = 8:1:1. These were then assembled into CR2016 coin cells (mixing and slurrying the active material: SP: PVDF = 8:1:1, followed by coating and rolling (the lithium sheet was used as the negative electrode of the coin cell). The battery was then assembled in the following order: negative electrode shell, nickel foam sheet (ф14mm), electrolyte, lithium sheet (15.6*0.45mm), electrolyte, separator (ф18mm), electrolyte, positive electrode sheet, electrolyte, positive electrode shell, and finally sealed. After standing for 4 hours, a charge-discharge test was conducted. The test was performed at 25°C with test rates of 0.2C and 1C. The test results are shown in Table 1 below.

[0096] Table 1

[0097]

[0098]

[0099] As shown in Table 1, the lithium iron phosphate prepared from iron-rich Fenton sludge using metal oxide coating and rapid hot-pressing sintering with DC power supply exhibits electrical performance comparable to existing market-ready products (Peking University Pioneer), with a 1C specific capacity greater than 141 mAh / g and a powder compaction density reaching 2.55 g / cm³. 3 The above have excellent application prospects.

[0100] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A method for preparing lithium iron phosphate materials, characterized in that, The method includes the following steps: 1) Iron-rich Fenton sludge was calcined at a certain temperature to obtain Fe2O3; 2) Add H3PO4 to Fe2O3, add the mixed solution to the reaction vessel, react under oxygen-containing conditions, and obtain iron phosphate after washing, drying and calcination. 3) After mixing iron phosphate with lithium source, carbon source and additive A in water, the mixture is ground to a certain particle size and then spray-dried to obtain yellow material; 4) Place the yellow material in a tube furnace and sinter at the first temperature to obtain sintered material I. Then place sintered material I in a graphite mold and place the graphite mold in a rapid hot pressing sintering furnace cavity to rapidly heat to the second temperature for sintering to obtain sintered material II. 5) The obtained sintered material II is crushed to a certain particle size to obtain lithium iron phosphate material; In step 4), the first temperature is 400-500℃, and the sintering time at the first temperature is 480-600 min; The rapid hot pressing sintering furnace has a heating rate of 100-500℃ / min; a vacuum degree of 5-15Pa; a pressure of 20-50MPa; a second temperature of 600-800℃; and a holding time of 20-60min. Additive A is one or more of the following: vanadium pentoxide, magnesium oxide, titanium dioxide, zirconium oxide, yttrium oxide, and niobium oxide.

2. The method according to claim 1, characterized in that, In step 1), the calcination is carried out in a muffle furnace; The specified temperature is 400-800℃; the calcination time is 3-5 hours. After calcination, the material is allowed to cool naturally, then filtered, washed, and dried to obtain Fe2O3.

3. The method according to claim 1, characterized in that, In step 2), the molar ratio of iron oxide to phosphoric acid is 1:2-5; The added phosphoric acid has a mass concentration of 20%-50%; The temperature of the reactor is 60-90℃, the reaction pressure is 1-5 atm, and the reaction time is 3-8h; The calcination temperature is 400-700℃, and the holding time is 2-6 hours.

4. The method according to claim 1, characterized in that, In step 3), the molar ratio of Li to iron phosphate in the lithium source is 1-1.2:1; The lithium source is selected from one or more of the following: lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, lithium nitrate, lithium oxalate, and lithium acetate. In step 3), the carbon source is one or more of the following: glucose, sucrose, starch, cyclodextrin, citric acid, polyethylene glycol, polyvinyl alcohol, glycerol, polyethylene oxide, polystyrene, styrene-butadiene-styrene block copolymer, and carbon nanotubes. The carbon content is 0.8-2.0% of the final lithium iron phosphate product weight.

5. The method according to claim 1, characterized in that, Additive A is 800-3000 ppm of the final lithium iron phosphate product.

6. The method according to claim 1, characterized in that, In step 3), the abrasive particle size is 0.35-0.65μm.

7. The method according to claim 1, characterized in that, In step 5), the material is pulverized to an average particle size of 1.5-3.0 μm; the resulting ultra-high pressure compacted lithium iron phosphate powder has a compaction density of 2.6 g / cm³. 3 .

8. Lithium iron phosphate material prepared by any one of claims 1-7.

9. A lithium-ion battery, characterized in that, The lithium-ion battery uses the lithium iron phosphate material as the positive electrode active material as described in claim 8.

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