Method for producing high-pressure dense lithium iron phosphate material and its application

Abstract

This invention provides a method for producing high-pressure dense lithium iron phosphate material. [Solution] The manufacturing method includes the steps of: mixing an iron source, a lithium source, and a phosphorus source, adding a carbon source and an additive, sanding, spray drying, sintering, and pulverizing to obtain particle A; mixing an iron source, a lithium source, and a phosphorus source, adding a carbon source and an additive, ball milling, sanding, spray drying, and sintering to obtain particle B; adding a carbon source, a lithium source, and a phosphorus source to particle A, ball milling, spray drying, and sintering to obtain particle C; adding a carbon source, a lithium source, an iron source, and a dopant to particle B, ball milling, sanding, spray drying, and sintering to obtain particle D; and uniformly mixing particle C and particle D in a certain proportion, pulverizing, and mixing the materials to obtain a high-pressure dense lithium iron phosphate material.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing methods for lithium-ion battery cathode materials, and particularly relates to the manufacturing method and application of high-density lithium iron phosphate materials.

Background Art

[0002] The increasingly severe energy crisis has become one of the major challenges faced by humanity in the 21st century. To meet the increasing energy demand of humanity, it is important to develop new energy that is environmentally friendly and sustainable. Lithium-ion batteries have advantages such as high operating voltage and high energy density, and are the most potential secondary batteries. Lithium iron phosphate, as a cathode material for lithium-ion batteries, has advantages such as high capacity, long cycle life, high thermal stability, environmental friendliness, and low cost.

[0003] The compaction density has a great influence on the performance of lithium-ion batteries and is closely related to the specific capacity, efficiency, internal resistance of the electrode sheet, and the cycle performance of the battery.

[0004] Generally, the higher the compaction density, the higher the energy density of the battery can be. Therefore, the compaction density is also regarded as one of the reference indicators of the material energy density.

[0005] <X000020>When the process conditions are constant, the higher the compaction density, the higher the energy density of the battery. Currently, the compaction density of most lithium iron phosphates in the market is 2.2 - 2.4 g / cm , which restricts the energy density of the battery.

Summary of the Invention

Problems to be Solved by the Invention

[0006] In view of the above, the purpose of the present invention is to solve at least one of the technical problems existing in the prior art.

Means for Solving the Problems

[0007] Therefore, the present invention provides a method for producing high-pressure dense lithium iron phosphate material and its applications.

[0008] This method involves ball milling an iron source, a lithium source, and a phosphorus source twice, sanding, spraying, sintering, and grinding to produce two types of particles. Mixing these two types of particles in different proportions and grinding them together yields a high-pressure dense lithium iron phosphate material.

[0009] Therefore, an embodiment of the present invention provides a method for producing a high-pressure dense lithium iron phosphate material, the method comprising: step S1, which involves mixing an iron source with a lithium source and a phosphorus source in a fixed proportion, adding a fixed amount of a carbon source and an additive, ball milling, sanding, spray drying, sintering at a fixed temperature, and grinding to obtain particle A; step S2, which involves mixing an iron source with a lithium source and a phosphorus source in a fixed proportion, adding a fixed amount of a carbon source and an additive, ball milling, sanding, spray drying, and sintering at a fixed temperature to obtain particle B; step S3, which involves adding a carbon source, a lithium source, and a phosphorus source to particle A, ball milling, spray drying, and sintering to obtain particle C; step S4, which involves adding a carbon source, a lithium source, an iron source, and a dopant to particle B, ball milling, sanding, spray drying, and sintering to obtain particle D; and step S5, which involves uniformly mixing particle C and particle D in a fixed proportion, grinding, and mixing the materials to obtain a high-pressure dense lithium iron phosphate material.

[0010] In some embodiments, in step S1, the iron source is one or more of ferric phosphate, ferrous oxalate, ferric oxide, iron hydroxyphosphate, iron powder, and ferric nitrate; the lithium source is one or more of lithium carbonate, lithium phosphate, lithium hydroxide, lithium dihydrogen phosphate, lithium monohydrogen phosphate, lithium acetate, and lithium nitrate; the phosphorus source is one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ferric phosphate; and the amounts of the lithium source, iron source, and phosphorus source added are based on a molar ratio of Li:Fe:P=[1.03~1.04]:1:[1.03~1.04].

[0011] In some embodiments, in step S1, the carbon source is one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, the amount of the carbon source added is based on the carbon content in particle A being 0.01% to 0.20%, and the additive is one or more selected from titanium dioxide, ammonium metavanadate, and niobium pentoxide, with the doping amount controlled between 300 and 3000 ppm.

[0012] In some embodiments, in step S1, the sanding particle size is controlled to be between 0.50 and 0.90 μm, the sintering temperature is controlled to be between 700 and 800°C, the sintering time is controlled to be between 5 and 15 hours, and the particle size of particle A is controlled to be between 3.0 and 10.0 μm.

[0013] In some embodiments, in step S2, the iron source is one or more of ferric phosphate, ferrous oxalate, ferric oxide, iron hydroxyphosphate, iron powder, and ferric nitrate; the lithium source is one or more of lithium carbonate, lithium phosphate, lithium hydroxide, lithium dihydrogen phosphate, lithium monohydrogen phosphate, lithium acetate, and lithium nitrate; the phosphorus source is one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ferric phosphate; and the amounts of the lithium source, iron source, and phosphorus source added are based on a molar ratio of Li:Fe:P=[1.03~1.04]:1:[1.03~1.04].

[0014] In some embodiments, in step S2, the carbon source may be one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, the amount of the carbon source added is based on the carbon content in the particles B being 0.05% to 0.30%, and the additive is one or more selected from titanium dioxide, ammonium metavanadate, and niobium pentoxide, with the doping amount controlled between 300 and 3000 ppm.

[0015] In some embodiments, in step S2, the sanding particle size is controlled to be between 0.40 and 0.80 μm, the sintering temperature is controlled to be between 450 and 650°C, the sintering time is controlled to be between 5 and 15 hours, and the particle size of particle B is controlled to be between 2.0 and 5.0 μm.

[0016] In some embodiments, in step S3, the amount of carbon source added is based on the carbon content in the particles C being 1.1% to 1.4%, the carbon source is one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, the lithium source is one or more of lithium carbonate, lithium phosphate, and lithium hydroxide, the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and lithium dihydrogen phosphate, the ball milling particle size is 0.80 to 1.50 μm, the sintering temperature is 750 to 850°C, and the sintering time is 5 to 10 h.

[0017] In some embodiments, in step S4, the amount of carbon source added is based on the carbon content in the particles D being 1.2% to 1.6%, the carbon source is one or more of the following: titanium amino acids, titanium oxalate, and titanium citrate; the lithium source is one or more of the following: lithium carbonate, lithium phosphate, and lithium hydroxide; the iron source is one or more of the following: ferric oxide, ferrous oxalate, ferric phosphate, and iron citrate; the dopant is one or more of the following: titanium amino acids, titanium oxalate, and titanium citrate; the sanding particle size is 0.20 to 0.50 μm; the sintering temperature is 600 to 750°C; and the sintering time is 5 to 10 hours.

[0018] In some embodiments, in step S5, the amounts of particle C and particle D added are based on a mass ratio of particle C:particle D = [8:2] to [2:8], the mixing time is 0.5h to 3h, the pulverized particle diameters satisfy D10 > 0.30 μm, D50 = 0.7 to 1.50 μm, D90 < 8 μm, and D100 < 15 μm, and a secondary mixing is performed for 0.5 to 3h after pulverization to obtain a high-pressure dense lithium iron phosphate material.

[0019] The manufacturing method of the high-density lithium iron phosphate material according to an embodiment of the present invention is as follows: after mixing an iron source, a lithium source, a phosphorus source, a carbon source, and an additive, each is ball-milled, sanded, spray-dried, and sintered to obtain two kinds of particles with different particle diameters. After mixing the two kinds of particles at a certain ratio, they are pulverized and mixed to manufacture a high-density lithium iron phosphate material.

Brief Description of the Drawings

[0020] [Figure 1] It is a flowchart of the manufacturing method of the high-density lithium iron phosphate material according to an embodiment of the present invention. [Figure 2] It is a SEM spectrum diagram of the high-density lithium iron phosphate material manufactured in Example 1 of the present invention. [Figure 3] It is an XRD spectrum diagram of the high-density lithium iron phosphate material manufactured in Example 1 of the present invention. [Figure 4] It is a charge-discharge curve (0.1C and 1C) of a button-type half-cell assembled with the high-density lithium iron phosphate material manufactured in Example 1 of the present invention.

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described in detail. Examples of the above embodiments are shown in the drawings, and throughout, the same or similar reference numerals indicate the same or similar components, or components having the same or similar functions, respectively.

[0022] The embodiments described below with reference to the drawings are exemplary and are intended to interpret the present invention and should not be construed as limiting the present invention.

[0023] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention.

[0024] To simplify the disclosure of the present invention, the members and arrangements of specific examples are described below.

[0025] Naturally, these are merely illustrative examples and are not intended to limit the invention.

[0026] Furthermore, while the present invention provides examples of various specific processes and materials, those skilled in the art will be aware of the reusability of other processes and / or the use of other materials.

[0027] The embodiments of the present invention provide a method for producing a high-pressure dense lithium iron phosphate material, wherein the high-pressure dense lithium iron phosphate material of the present invention has a compaction density of 2.60 g / cm³. 3 It is a larger lithium iron phosphate material.

[0028] Specifically, as shown in Figure 1, this method includes the following steps S1 to S5.

[0029] In step S1, an iron source is mixed with a lithium source and a phosphorus source in a fixed proportion, a fixed amount of carbon source and additives are added, ball milling is performed, sanding is done, spray drying is performed, sintering is done at a fixed temperature, and pulverization is performed to obtain particle A. The iron source is one or more of ferric phosphate, ferrous oxalate, ferric oxide, iron hydroxyphosphate, iron powder, and ferric nitrate; the lithium source is one or more of lithium carbonate, lithium phosphate, lithium hydroxide, lithium dihydrogen phosphate, lithium monohydrogen phosphate, lithium acetate, and lithium nitrate; the phosphorus source is one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ferric phosphate; and the amounts of the lithium source, iron source, and phosphorus source added are based on a molar ratio of Li:Fe:P=[1.03~1.04]:1:[1.03~1.04].

[0030] In embodiments of the present invention, the carbon source is one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, the amount of the carbon source added is based on the carbon content in particle A being 0.01% to 0.20%, and the additive is one or more selected from titanium dioxide, ammonium metavanadate, and niobium pentoxide, with the doping amount controlled between 300 and 3000 ppm.

[0031] The sanding particle size is controlled between 0.50 and 0.90 μm. In spray drying, the intake air temperature is controlled to 200 to 220°C, the exhaust air temperature to 80 to 110°C, the airflow frequency to 80 Hz, the final formed spray particle size D50 is controlled between 20 and 40 μm, the sintering temperature is controlled to 700 to 800°C, the sintering time is controlled to 5 to 15 hours, and the particle size of particle A is controlled to 3.0 to 10.0 μm.

[0032] In step S2, the iron source is mixed with the lithium source and phosphorus source in a fixed proportion, a fixed amount of carbon source and additives are added, ball milling is performed, sanding is carried out, spray drying is performed, and sintering is performed at a fixed temperature to obtain particle B. The iron source is one or more of ferric phosphate, ferrous oxalate, ferric oxide, iron hydroxyphosphate, iron powder, and ferric nitrate; the lithium source is one or more of lithium carbonate, lithium phosphate, lithium hydroxide, lithium dihydrogen phosphate, lithium monohydrogen phosphate, lithium acetate, and lithium nitrate; the phosphorus source is one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ferric phosphate; and the amounts of the lithium source, iron source, and phosphorus source added are based on a molar ratio of Li:Fe:P=[1.03~1.04]:1:[1.03~1.04].

[0033] In embodiments of the present invention, the carbon source may be one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, and the amount of the carbon source added is based on the carbon content in the particles B being 0.05% to 0.30%, and the additive is one or more selected from titanium dioxide, ammonium metavanadate, and niobium pentoxide, and the doping amount is controlled between 300 and 3000 ppm.

[0034] The sanding particle size is controlled between 0.40 and 0.80 μm. In spray drying, the intake air temperature is controlled to 200 to 220°C, the exhaust air temperature to 80 to 110°C, the airflow frequency to 80 Hz, the final formed spray particle size D50 is controlled between 20 and 40 μm, the sintering temperature is controlled to 450 to 650°C, the sintering time is controlled to 5 to 15 hours, and the particle size of particle B is controlled to 2.0 to 5.0 μm.

[0035] In step S3, a carbon source, a lithium source, and a phosphorus source are added to the particles A, ball milling is performed, spray drying is performed, and sintering is performed to obtain particles C. The amount of carbon source added is based on the carbon content in particle C being 1.1% to 1.4%, the carbon source is one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, the lithium source is one or more of lithium carbonate, lithium phosphate, and lithium hydroxide, the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and lithium dihydrogen phosphate, the ball milling particle size is controlled between 0.80 and 1.50 μm, in spray drying the intake air temperature is controlled to 200 to 220°C, the exhaust air temperature is controlled to 80 to 110°C, the blowing frequency is controlled to 80 Hz, the final formed spray particle size D50 is controlled between 20 and 40 μm, the sintering temperature is controlled to 750 to 850°C, and the sintering time is controlled to 5 to 10 hours.

[0036] In step S4, a carbon source, a lithium source, an iron source, and a dopant are added to the particles B, and then ball milling, sanding, spray drying, and sintering are performed to obtain particles D. The amount of carbon source added is based on the carbon content in the particles D being 1.2% to 1.6%, the carbon source is one or more of the following: amino acid titanium, titanium oxalate, and titanium citrate; the lithium source is one or more of the following: lithium carbonate, lithium phosphate, and lithium hydroxide; the iron source is one or more of the following: ferric oxide, ferrous oxalate, ferric phosphate, and iron citrate; the dopant is one or more of the following: amino acid titanium, titanium oxalate, and titanium citrate; the sanding particle size is controlled between 0.20 and 0.50 μm; in spray drying, the intake air temperature is controlled to 200 to 220°C, the exhaust air temperature is controlled to 80 to 110°C, the blowing frequency is controlled to 80 Hz; the final formed spray particle size is controlled between D50 = 20 to 40 μm; the sintering temperature is controlled to 600 to 750°C; and the sintering time is controlled to 5 to 10 hours.

[0037] In step S5, particles C and D are uniformly mixed in a fixed ratio, crushed, and the materials are mixed to obtain a high-pressure dense lithium iron phosphate material.

[0038] The amount of particle C and particle D added is based on a mass ratio of particle C:particle D = [8:2] to [2:8], the mixing time is 0.5h to 3h, the atmospheric pressure is controlled between 0.2 and 0.4 MPa during the grinding process, the grading frequency is controlled between 80 and 200 Hz, the ground particle diameters satisfy D10 > 0.30 μm, D50 = 0.7 to 1.50 μm, D90 < 8 μm, and D100 < 15 μm, and after grinding, secondary mixing is performed for 0.5 to 3h to obtain a high-pressure dense lithium iron phosphate material.

[0039] The method for producing high-pressure dense lithium iron phosphate material according to an embodiment of the present invention involves mixing an iron source, a lithium source, a phosphorus source, a carbon source, and an additive, then ball milling, sanding, spray drying, and sintering to produce two types of particles with different particle sizes, mixing the two types of particles in a certain ratio, grinding, and mixing to produce high-pressure dense lithium iron phosphate material.

[0040] The manufacturing method according to the present invention produces large and small particles in a two-step process, thereby avoiding the problems of limited and inconsistent particle size distribution in conventional processes.

[0041] By manufacturing ultrafine particles using a low-temperature solid-phase method, sintering them, and then performing secondary polishing and sintering, the size and ratio of the fine particles can be controlled, resulting in high dispersibility and perfect combination with other particles.

[0042] Primary sintering uses a low-temperature, short-time process to produce and sinter ultrafine particles while reducing manufacturing costs. Secondary sintering uses a high-temperature process to improve coating integrity and provide a restorative effect on the crystal. At this stage, primary particles of different sizes are generated, further improving the compaction density and electrochemical properties of the lithium iron phosphate material.

[0043] The specific process and effects of the method for producing the high-pressure dense lithium iron phosphate material of the present invention will be described in more detail below with reference to several specific examples, but this will not limit the scope of protection of the present invention.

[0044] (Example 1) The method for producing the high-pressure dense lithium iron phosphate material according to this embodiment is: A mixture of iron hydroxyphosphate, lithium phosphate, and phosphoric acid is blended in a molar ratio of Li:Fe:P = 1.03:1:1.03. A carbon source mixture consisting of sucrose and polyethylene glycol is added to form a carbon content of 0.05% in particle A, and titanium dioxide is doped at 1000 ppm to form a mixed material. This mixed material is then sanded, and the sanding particle size is controlled to 0.80 μm to obtain a nano-sized sanding slurry. Step S1 involves spray drying, controlling the intake air temperature to 220°C, the exhaust air temperature to 100°C, and the fan frequency to 80Hz to obtain a spray material with a spray particle size D50 = 20-40 μm, placing the spray material in a box furnace and sintering it under a nitrogen atmosphere with a heating rate of 3°C / min, a sintering temperature of 780°C, a sintering time of 10h, and then allowing it to cool naturally to obtain a sintered material, and then grinding the sintered material with a mechanical pulverizer to obtain particles A with a particle size D50 = 6-10 μm. Step S2 involves blending ferric phosphate and lithium carbonate in a molar ratio of Li:Fe:P = 1.04:1:1.03, adding a carbon source mixture consisting of sucrose and polyethylene glycol to achieve a carbon content of 0.15% in particle B, and titanium dioxide with a dope content of 2500 ppm to form a mixed material, sanding the mixed material to control the sanding particle size to 0.55 μm to obtain a nano-sized sanding slurry, spray-drying the nano-sized sanding slurry, controlling the intake air temperature to 220°C, controlling the exhaust air temperature to 100°C, and controlling the blower frequency to 80 Hz to obtain a spray material with a spray particle size D50 = 20-40 μm, placing the spray material in a box furnace and sintering it under a nitrogen atmosphere at a heating rate of 3°C / min, a sintering temperature of 500°C, a sintering time of 8 hours, and then allowing it to cool naturally to obtain particle B. Step S3 involves mixing particles A and a carbon source consisting of sucrose and polyethylene glycol to form a mixed material, adding 0.01 wt% lithium carbonate and 0.5 wt% phosphoric acid by mass of particle A, ball milling the mixed material, controlling the slurry particle size after ball milling to 1.2 μm, spray drying the slurry, controlling the intake air temperature to 220°C, controlling the exhaust air temperature to 100°C, and controlling the blower frequency to 80 Hz to obtain a spray material with a spray particle size D50 = 20-40 μm, placing the spray material in a box furnace and sintering it under a nitrogen atmosphere, heating at a rate of 3°C / min, sintering at 770°C, sintering for 10 hours, and then allowing it to cool naturally to obtain particle C. Step S4 involves mixing particles B and particles D with a carbon source consisting of titanium amino acid and titanium citrate to form a mixed material with a carbon content of 1.2% in particles B and D, adding 0.01 wt% lithium hydroxide and 0.01 wt% ferric oxide by mass of particle B, ball milling and sanding the mixed material, controlling the slurry particle size after sanding to 0.25 μm, spray drying the slurry, controlling the intake air temperature to 220°C, controlling the exhaust air temperature to 100°C, and controlling the blower frequency to 80 Hz to obtain a spray material with a spray particle size D50 = 20~40 μm, placing the spray material in a box furnace and sintering it under a nitrogen atmosphere, heating at a rate of 3°C / min, sintering at a temperature of 650°C, sintering for 8 hours, and then allowing it to cool naturally to obtain particles D. Step S5 includes the following steps: mixing particles C and D in a mass ratio of 6:4 for 2 hours, then grinding the mixture, controlling the atmospheric pressure between 0.2 and 0.4 MPa during the grinding process, controlling the grading frequency between 80 and 200 Hz, satisfying the following conditions for the ground particle size: D10 > 0.30 μm, D50 = 0.7 to 1.50 μm, D90 < 8 μm, D100 < 15 μm, and then performing a secondary mixing for 2.5 hours after grinding to obtain a high-pressure dense lithium iron phosphate material.

[0045] Figure 2 shows the SEM spectrum of the lithium iron phosphate cathode material produced by Example 1.

[0046] Figure 3 shows the XRD spectrum of the lithium iron phosphate cathode material produced by Example 1.

[0047] (Example 2) The method for producing the high-pressure dense lithium iron phosphate material according to this embodiment is: A mixture of ferric oxide, lithium carbonate, and ammonium dihydrogen phosphate is blended in a molar ratio of Li:Fe:P = 1.03:1:1.03. A carbon source mixture consisting of sucrose and polyethylene glycol is added to the particle A to achieve a carbon content of 0.05%, and titanium dioxide is doped at a concentration of 1000 ppm to form a mixed material. This mixed material is then sanded, and the sanding particle size is controlled to 0.80 μm to obtain a nano-sized sanding slurry. Step S1 involves spray-drying a material, controlling the intake air temperature to 220°C, the exhaust air temperature to 100°C, and the fan frequency to 80Hz to obtain a spray material with a spray particle size D50 = 20-40 μm, placing the spray material in a box furnace and sintering it under a nitrogen atmosphere with a heating rate of 3°C / min, a sintering temperature of 780°C, a sintering time of 10h, and then allowing it to cool naturally to obtain a sintered material, and then grinding the sintered material with a mechanical pulverizer to obtain particles A with a particle size D50 = 6-10 μm. Step S2 involves mixing ferrous oxalate, lithium hydroxide, and phosphoric acid in a molar ratio of Li:Fe:P = 1.04:1:1.03, adding a carbon source mixture consisting of sucrose and polyethylene glycol to achieve a carbon content of 0.15% in particle B, and titanium dioxide with a dope content of 2500 ppm to form a mixed material, sanding the mixed material to control the sanding particle size to 0.55 μm to obtain a nano-sized sanding slurry, spray-drying the nano-sized sanding slurry, controlling the intake air temperature to 220°C, controlling the exhaust air temperature to 100°C, and controlling the blower frequency to 80 Hz to obtain a spray material with a spray particle size D50 = 20-40 μm, placing the spray material in a box furnace and sintering it under a nitrogen atmosphere at a heating rate of 3°C / min, a sintering temperature of 500°C, a sintering time of 8 hours, and then allowing it to cool naturally to obtain particle B. Step S3 involves mixing particles A and a carbon source consisting of sucrose and polyethylene glycol to form a mixed material, adding 0.01 wt% lithium carbonate and 0.5 wt% phosphoric acid by mass of particle A, ball milling the mixed material, controlling the slurry particle size after ball milling to 1.2 μm, spray drying the slurry, controlling the intake air temperature to 220°C, controlling the exhaust air temperature to 100°C, and controlling the blower frequency to 80 Hz to obtain a spray material with a spray particle size D50 = 20-40 μm, placing the spray material in a box furnace and sintering it under a nitrogen atmosphere, heating at a rate of 3°C / min, sintering at 770°C, sintering for 10 hours, and then allowing it to cool naturally to obtain particle C. Step S4 involves mixing particles B and particles D with a carbon source consisting of titanium amino acid and titanium oxalate to form a mixed material, adding 0.01 wt% lithium hydroxide, 0.45 wt% iron citrate, and 0.02 wt% iron citrate, all based on the mass of particle B, and then ball-milling and sanding the mixed material. The slurry particle size after sanding is controlled to 0.25 μm, and the slurry is spray-dried. The intake air temperature is controlled to 220°C, the exhaust air temperature to 100°C, and the blower frequency to 80 Hz to obtain a spray material with a spray particle size D50 = 20-40 μm. The spray material is then placed in a box furnace and sintered under a nitrogen atmosphere at a heating rate of 3°C / min, a sintering temperature of 650°C, a sintering time of 8 hours, and then allowed to cool naturally to obtain particle D. Step S5 includes the following steps: mixing particles C and D in a mass ratio of 6:4 for 2 hours, then grinding the mixture, controlling the atmospheric pressure between 0.2 and 0.4 MPa during the grinding process, controlling the grading frequency between 80 and 200 Hz, satisfying the following conditions for the ground particle size: D10 > 0.30 μm, D50 = 0.7 to 1.50 μm, D90 < 8 μm, D100 < 15 μm, and then performing a secondary mixing for 2.5 hours after grinding to obtain a high-pressure dense lithium iron phosphate material.

[0048] (Comparative Example 1) The method for producing the high-pressure dense lithium iron phosphate material according to this embodiment is: Step S1 involves blending an iron source and a lithium source in a molar ratio of Li:Fe:P = 1.03:1:1.03, adding a carbon source mixture consisting of sucrose and polyethylene glycol with a carbon content of 1.1% in the product, and titanium dioxide with a dope content of 2000 ppm to form a mixed material. Step S2 involves sanding the above mixed material to control the sanding particle size to 0.80 μm to obtain a nano-sized sanding slurry, spray-drying the nano-sized sanding slurry, controlling the intake air temperature to 220°C, controlling the exhaust air temperature to 100°C, and controlling the blower frequency to 80 Hz to obtain a spray material with a spray particle size D50 = 20-40 μm. Step S3 involves placing the above spray material in a box furnace and sintering it under a nitrogen atmosphere, setting the heating rate to 3°C / min, the sintering temperature to 770°C, the sintering time to 10h, allowing it to cool naturally to obtain the sintered material, grinding the sintered material with a jet mill, controlling the air pressure to 0.35 MPa, and controlling the grading frequency to 140 Hz to obtain a pulverized material with particle sizes D10 > 0.35 μm, D50 = 0.7 ~ 1.5 μm, D90 < 10 μm, and D100 < 30 μm. The process includes step S4, which involves further steps such as sieving, batch synthesis, and packaging of the above-mentioned pulverized material to obtain a lithium iron phosphate product.

[0049] To verify the quality of the lithium iron phosphate material produced by the method for producing high-pressure dense lithium iron phosphate material according to the embodiments of the present invention, the lithium iron phosphate material produced in Example 1 and Comparative Example 1, along with carbon black as a conductive agent and polyvinylidene fluoride as a binder, are dispersed in N-methylpyrrolidone in a mass ratio of 90:5:5. After uniform dispersion by ball milling, the mixture is coated onto aluminum foil and vacuum-dried to produce a positive electrode sheet.

[0050] The electrolyte is 1 mol / L LiPF6 with a solvent volume ratio of EC:DMC:EMC = 1:1:1. The separator is a Celgard polypropylene film, and the metallic lithium sheet is the negative electrode. Both are assembled into a button-type half-cell.

[0051] The test voltage range was 2.0V to 3.75V. The battery was charged to 3.75V using a constant current / constant voltage charging method and discharged to 2.0V using a constant current discharge method. The charge / discharge current was 0.1C for one cycle and 1C for one cycle. The test results are shown in Table 1.

[0052] Figure 4 shows the charge-discharge curves (0.1C and 1C) of a button-type half-cell assembled with the lithium iron phosphate cathode material manufactured in Example 1 of the present invention.

[0053] Table 1 Test items and test results for Example 1 and Comparative Example 1 [Table 1]

[0054] Comparing the test results obtained from the above examples and comparative examples, the button-type half-cell manufactured using the high-pressure dense lithium iron phosphate material produced in Example 1 showed a significant improvement in both the initial charge-discharge ratio capacity at 0.1C and the discharge ratio capacity at 1C compared to Comparative Example 1.

[0055] Furthermore, the high-pressure dense lithium iron phosphate material produced in Example 1 was filled with small particles, resulting in a better particle size distribution and improved compaction density of the lithium iron phosphate material.

[0056] In this specification, any description referring to terms such as “one embodiment,” “several embodiments,” “example,” “specific example,” or “several examples” means that the specific features, structures, materials, or properties described in combination with such embodiment or example are included in at least one embodiment or example of the present invention.

[0057] In this specification, exemplary expressions of the above terms do not necessarily mean the same embodiment or example.

[0058] Furthermore, the specific features, structures, materials, or properties described can be appropriately combined in any one or more embodiments or examples.

[0059] Furthermore, a person skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described herein, as long as they do not contradict each other.

[0060] Although embodiments of the present invention have been described exemplifiedly, as will be understood by those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is limited by the claims and their equivalents.

Claims

1. Step S1 involves mixing an iron source with a lithium source and a phosphorus source in a certain proportion, adding a certain amount of carbon source and additives, ball milling, sanding, spray drying, sintering at a certain temperature, and pulverizing to obtain particle A. Step S2 involves mixing an iron source with a lithium source and a phosphorus source in a certain proportion, adding a certain amount of carbon source and additives, ball milling, sanding, spray drying, and sintering at a certain temperature to obtain particles B. Step S3 involves adding a carbon source and a lithium source and a phosphorus source to the aforementioned particles A, ball milling, spray drying, and sintering to obtain particles C. Step S4 involves adding a carbon source, a lithium source, an iron source, and a dopant to the aforementioned particles B, ball milling, sanding, spray drying, and sintering to obtain particles D. Step S5 includes uniformly mixing the aforementioned particles C and D in a fixed ratio, grinding them, and mixing the materials to obtain a high-pressure dense lithium iron phosphate material. A method for producing a high-pressure dense lithium iron phosphate material, characterized by the features described above.

2. In step S1, the iron source is one or more of ferric phosphate, ferrous oxalate, ferric oxide, iron hydroxyphosphate, iron powder, and ferric nitrate; the lithium source is one or more of lithium carbonate, lithium phosphate, lithium hydroxide, lithium dihydrogen phosphate, lithium monohydrogen phosphate, lithium acetate, and lithium nitrate; the phosphorus source is one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ferric phosphate; and the amounts of the lithium source, iron source, and phosphorus source added are based on a molar ratio of Li:Fe:P = [1.03-1.04]:1:[1.03-1.04]. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

3. In step S1, the carbon source is one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, the amount of the carbon source added is based on the carbon content in the particles A being between 0.01% and 0.20%, and the additive is one or more selected from titanium dioxide, ammonium metavanadate, and niobium pentoxide, with the doping amount controlled between 300 and 3000 ppm. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

4. In step S1, the particle size of the sanding material is controlled to be between 0.50 and 0.90 μm, the sintering temperature is controlled to be between 700 and 800°C, the sintering time is controlled to be between 5 and 15 hours, and the particle size of particle A is controlled to be between 3.0 and 10.0 μm. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

5. In step S2, the iron source is one or more of ferric phosphate, ferrous oxalate, ferric oxide, iron hydroxyphosphate, iron powder, and ferric nitrate; the lithium source is one or more of lithium carbonate, lithium phosphate, lithium hydroxide, lithium dihydrogen phosphate, lithium monohydrogen phosphate, lithium acetate, and lithium nitrate; the phosphorus source is one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ferric phosphate; and the amounts of the lithium source, iron source, and phosphorus source added are based on a molar ratio of Li:Fe:P = [1.03-1.04]:1:[1.03-1.04]. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

6. In step S2, the carbon source may be one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, and the amount of the carbon source added is based on the carbon content in the particles B being 0.05% to 0.30%, and the additive is one or more selected from titanium dioxide, ammonium metavanadate, and niobium pentoxide, and the doping amount is controlled between 300 and 3000 ppm. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

7. In step S2, the sanding particle size is controlled to be between 0.40 and 0.80 μm, the sintering temperature is controlled to be between 450 and 650°C, the sintering time is controlled to be between 5 and 15 hours, and the particle size of particle B is controlled to be between 2.0 and 5.0 μm. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

8. In step S3, the amount of carbon source added is determined based on the carbon content in the particles C being 1.1% to 1.4%, the carbon source being one or more of sucrose, glucose, citric acid, starch, and polyethylene glycol, the lithium source being one or more of lithium carbonate, lithium phosphate, and lithium hydroxide, the phosphorus source being one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and lithium dihydrogen phosphate, the particle size of the ball milled being 0.80 to 1.50 μm, the sintering temperature being 750 to 850°C, and the sintering time being 5 to 10 h. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

9. In step S4, the amount of carbon source added is determined based on the carbon content in the particles D being 1.2% to 1.6%, the carbon source being one or more of titanium amino acids, titanium oxalate, and titanium citrate, the lithium source being one or more of lithium carbonate, lithium phosphate, and lithium hydroxide, the iron source being one or more of ferric oxide, ferrous oxalate, ferric phosphate, and iron citrate, the dopant being one or more of titanium amino acids, titanium oxalate, and titanium citrate, the particle size of the sanding being 0.20 to 0.50 μm, the sintering temperature being 600 to 750°C, and the sintering time being 5 to 10 hours. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

10. In step S5, the amounts of particle C and particle D added are determined based on a mass ratio of particle C:particle D = [8:2] to [2:8], the mixing time is 0.5h to 3h, the pulverized particle size satisfies D10 > 0.30 μm, D50 = 0.7 to 1.50 μm, D90 < 8 μm, and D100 < 15 μm, and after pulverization, secondary mixing is performed for 0.5 to 3h to obtain a high-pressure dense lithium iron phosphate material. A method for producing a high-pressure dense lithium iron phosphate material according to feature 1.

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