A method for producing lithium iron phosphate from waste lithium iron phosphate material.

Abstract

A method for producing lithium iron phosphate from waste lithium iron phosphate material is provided. [Solution] The method includes the steps of: crushing the positive electrode sheet of a waste lithium iron phosphate battery, sieving it to obtain lithium iron phosphate raw material, dissolving it in an acidic solution, and collecting the first filtrate after filtration; adding ferrous sulfate solution to the first filtrate to obtain a mixed solution; adding hydrogen peroxide solution and ammonia aqueous solution to the mixed solution, filtering and washing after the reaction to obtain a second filtrate and a filtration cake; washing and drying the filtration cake to obtain iron hydroxyphosphate; adding barium hydroxide aqueous solution to the second filtrate, allowing it to react completely and then filtering to obtain a third filtrate; adding phosphoric acid solution to the third filtrate to obtain a fourth filtrate; mixing iron hydroxyphosphate, the fourth filtrate and a carbon source, sanding the slurry, drying and obtaining a powder; and sintering and pulverizing the powder in an inert atmosphere to obtain a carbon-coated lithium iron phosphate material.

Description

Technical Field

[0001] The present invention relates to the technical field of a method for manufacturing a cathode material for a lithium-ion battery, and particularly to a method for recovering a waste lithium iron phosphate material to produce lithium iron phosphate.

Background Art

[0002] The lithium iron phosphate cathode material is a cathode material for lithium batteries that has been developing most rapidly in China. Its raw material supply sources are wide and inexpensive. In the domestic battery industry in China, it is widely applied in fields such as automobiles, power tools, energy storage devices, emergency power supply devices, and mobile power sources. New energy electric vehicles are the main application fields. Lithium iron phosphate batteries have advantages such as being safe, environmentally friendly, inexpensive, having a long cycle life, and excellent high-temperature performance compared with other batteries. Since the life of lithium iron phosphate batteries is generally 2 to 10 years, a large amount of waste lithium iron phosphate materials will be generated over time. In order to recover and reuse waste lithium iron phosphate materials, they are currently mainly divided into dry recovery and wet recovery. Dry recovery has a simple process and is widely applied, but it consumes a large amount of energy, wastes resources, and generates polluting gases or substances during the manufacturing process. Wet recovery has a stable process, but it is necessary to consume a large amount of sodium hydroxide and oxidants, and it is necessary to further treat the waste liquid in the later stage. The recovery cost is also high, and materials such as iron, phosphorus, and lithium in the waste lithium iron phosphate material cannot be fully recovered.

[0003] Therefore, in the recovery methods in the prior art, there are problems such as high recovery costs for lithium iron phosphate materials, low recovery efficiency, and only recovering precious metal ions, which waste iron and phosphorus materials in the lithium iron phosphate material and do not fully recover and utilize the lithium iron phosphate material.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In view of the above, the present invention aims to solve at least one of the technical problems that exist in the prior art. Therefore, the present invention provides a method for producing lithium iron phosphate by recovering waste lithium iron phosphate material. The method according to the present invention can sufficiently recover phosphorus, iron, and lithium elements from waste lithium iron phosphate material, and the recovered phosphorus, iron, and lithium can be used as raw materials for producing lithium iron phosphate, and the produced nano-order lithium iron phosphate material has a high discharge ratio capacity. Furthermore, this method has high production efficiency, low production cost, is environmentally friendly, is suitable for application to large-scale industrial production, and has high economic and social benefits. [Means for solving the problem]

[0005] Therefore, an embodiment of the present invention provides a method for producing lithium iron phosphate by recovering waste lithium iron phosphate material, the method comprising the steps of: crushing the positive electrode sheet of a waste lithium iron phosphate battery, shaking and sieving it to obtain lithium iron phosphate raw material; dissolving the lithium iron phosphate raw material in an acidic solution, filtering it, and collecting a first filtrate; adding a ferrous sulfate solution to the first filtrate to obtain a mixed solution; adding hydrogen peroxide solution and an aqueous ammonia solution to the mixed solution to adjust the pH value, reacting it, filtering and washing to obtain a second filtrate and a filtration cake, respectively; washing and drying the filtration cake to obtain hydroxy iron phosphate; adding an aqueous barium hydroxide solution to the second filtrate, reacting it completely, and then filtering it to obtain a third filtrate; adding a phosphoric acid solution to the third filtrate to obtain a fourth filtrate; mixing the hydroxy iron phosphate, the fourth filtrate, and a carbon source, sanding the slurry, drying it, and obtaining a powder; and sintering the powder in an inert atmosphere, letting it cool naturally, and then grinding it to obtain a carbon-coated lithium iron phosphate material.

[0006] Preferably, the acidic solution is a sulfuric acid solution or a phosphoric acid solution, and the concentration of the acidic solution is greater than 30 wt%.

[0007] Preferably, the mass ratio of the added acidic solution to the lithium iron phosphate raw material is [3-5]:1.

[0008] Preferably, the amount of ferrous sulfate solution added is determined based on the requirement that the molar ratio of iron phosphate in the mixed solution satisfies Fe / P = 1.45 to 1.5.

[0009] Preferably, the concentration of the hydrogen peroxide solution is 20-30 wt%, and the concentration of the ammonia aqueous solution is 20-30 wt%, and the pH value is adjusted to 2.0-4.5 by adding the hydrogen peroxide solution and the ammonia aqueous solution.

[0010] Preferably, an aqueous barium hydroxide solution is added to remove sulfate ions from the second filtrate.

[0011] Preferably, the amount of phosphoric acid solution added is determined based on the lithium phosphorus molar ratio in the fourth filtrate satisfying Li / P = 2.8 to 3.2.

[0012] Preferably, after mixing the iron hydroxyphosphate and the fourth filtrate, the molar ratio of iron to phosphorus satisfies n(Fe):n(Li)=1:[1~1.04], the amount of carbon source added is based on the carbon content in the lithium iron phosphate material being 0.5~3 wt%, the carbon source is a mixture of glucose and polyethylene glycol, and the particle size of the slurry is 0.40~0.95 μm.

[0013] Preferably, the amount of carbon source added is based on the carbon content in the lithium iron phosphate material being 0.8 to 2 wt%, the particle size of the slurry is 0.50 to 0.75 μm, and the particle size of the powder is 20 to 40 μm.

[0014] Preferably, the inert atmosphere is at least one selected from nitrogen gas, argon gas, and helium gas, the sintering temperature may be 750 to 900°C, the sintering time may be 5 to 12 hours, and the particle size of the carbon-coated lithium iron phosphate material is 0.80 to 3 μm. [Effects of the Invention]

[0015] The present invention provides an embodiment of a method for producing lithium iron phosphate by recovering waste lithium iron phosphate material. When processing the waste lithium iron phosphate material, the amount of iron source added and the pH value are adjusted to recover iron and phosphorus elements in the form of iron hydroxyphosphate, and the amount of lithium element precipitated during the precipitation of phosphorus and iron elements is reduced to the greatest extent possible, thereby separating lithium from phosphorus and iron elements. The method according to the present invention improves the recovery rate of lithium, phosphorus, and iron elements by recovering phosphorus and iron elements in the form of iron hydroxyphosphate and lithium element in the form of lithium hydroxide. When subsequently producing lithium iron phosphate material, adding phosphoric acid to the filtrate not only allows the Li / P ratio to be adjusted to an appropriate range, but also prevents the precipitation of lithium element, thereby allowing lithium element to be recovered in the filtrate in the form of lithium hydroxide. Furthermore, this method has high production efficiency, low production costs, is environmentally friendly, is suitable for application to large-scale industrial production, and has high economic and social benefits. [Brief explanation of the drawing]

[0016] [Figure 1] This is a flowchart illustrating a method for producing lithium iron phosphate from waste lithium iron phosphate material, according to an embodiment of the present invention. [Figure 2] This is a flowchart of a process for producing lithium iron phosphate from waste lithium iron phosphate material, according to an embodiment of the present invention. [Figure 3] This is an SEM spectral diagram of the lithium iron phosphate material produced in Example 1 of the present invention. [Modes for carrying out the invention]

[0017] The embodiments of the present invention will be described in detail below, and the examples of the embodiments are shown in the drawings. Throughout, the same or similar reference numerals indicate the same or similar parts or parts having the same or similar functions. The embodiments described below with reference to the drawings are illustrative and interpretive of the present invention, and should not be understood as limiting the present invention.

[0018] The following disclosure provides many different embodiments or examples to realize different structures of the present invention. For the sake of simplicity in the disclosure of the present invention, the components and arrangements of specific examples are described below. Naturally, these are illustrative only and are not intended to limit the present invention. Furthermore, the present invention may use repeated reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarification and does not in itself indicate relationships between the various embodiments and / or arrangements considered. Furthermore, the present invention provides examples of various specific processes and materials, but those skilled in the art will be aware of the reusability of other processes and / or the use of other materials.

[0019] Examples of the present invention provide a method for producing lithium iron phosphate by recovering waste lithium iron phosphate material, the method comprising separately recovering phosphorus, iron, and lithium elements from waste lithium iron phosphate batteries, recovering all phosphorus and iron elements from waste lithium iron phosphate batteries in the form of iron hydroxyphosphate, recovering all lithium elements in the form of lithium hydroxide in a filtrate, and finally producing nano-order lithium iron phosphate using the recovered iron hydroxyphosphate and lithium-containing filtrate as raw materials. As shown in Figures 1 and 2, the method comprises steps S1 to S7.

[0020] In step S1, the positive electrode sheet of the waste lithium iron phosphate battery is crushed, shaken and sieved to obtain lithium iron phosphate raw material, the lithium iron phosphate raw material is dissolved in an acidic solution, filtered, and the first filtrate is collected. The acidic solution is a sulfuric acid solution or a phosphoric acid solution, and the concentration of the acidic solution is greater than 30 wt%. In the examples of the present invention, the mass ratio of the added acidic solution to the lithium iron phosphate raw material is [3 to 5]:1, for example, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1.

[0021] In step S2, a ferrous sulfate solution is added to the first filtrate to obtain a mixed solution. The addition amount of the ferrous sulfate solution is based on the condition that the iron-phosphorus molar ratio in the mixed solution satisfies Fe / P = 1.45 to 1.5.

[0022] In step S3, hydrogen peroxide solution and aqueous ammonia solution are added to the mixed solution to adjust the pH value, and after reacting, filtration and washing are performed to obtain a second filtrate and a filter cake respectively. The filter cake is washed and dried to obtain iron hydroxyphosphate. The concentration of the hydrogen peroxide solution may be 20 to 30 wt%, for example, 20 wt%, 25 wt% or 30 wt%. The concentration of the aqueous ammonia solution may be 20 to 30 wt%, for example, 20 wt%, 25 wt% or 30 wt%. Hydrogen peroxide solution and aqueous ammonia solution are added to adjust the pH value to 2.0 to 4.5, for example, the pH value may be adjusted to 2, 2.5, 3, 3.5, 4 or 4.5.

[0023] In step S4, an aqueous barium hydroxide solution is added to the second filtrate, and after complete reaction, filtration is performed to obtain a third filtrate. An aqueous barium hydroxide solution is added to remove sulfate ions in the second filtrate.

[0024] In step S5, a phosphoric acid solution is added to the third filtrate to obtain a fourth filtrate. The addition amount of the phosphoric acid solution is based on the condition that the lithium-phosphorus molar ratio in the fourth filtrate satisfies Li / P = 2.8 to 3.2, for example, Li / P = 2.8, Li / P = 2.9, Li / P = 3, Li / P = 3.1 or Li / P = 3.2.

[0025] In step S6, the iron hydroxyphosphate, the fourth filtrate, and the carbon source are mixed, the slurry is sanded, and after drying, a powder is obtained. After mixing the iron hydroxyphosphate and the fourth filtrate, the molar ratio of iron to phosphorus satisfies n(Fe):n(Li)=1:[1~1.04], for example, n(Fe):n(Li)=1:1, n(Fe):n(Li)=1:1.01, n(Fe):n(Li)=1:1.02, n(Fe):n(Li)=1:1.03, or n(Fe):n(Li)=1:1.04, and the amount of carbon source added is based on the carbon content in the lithium iron phosphate material being 0.5~3wt%, preferably the amount of carbon source added is based on the carbon content in the lithium iron phosphate material being 0.8~2wt%. It is optimal for the carbon content to be 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, or 2.0 wt%, and in the embodiments of the present invention, the carbon source is a mixture of glucose and polyethylene glycol, the particle size of the slurry is 0.40 to 0.95 μm, preferably 0.50 to 0.75 μm, for example, the particle size of the slurry is 0.50 μm, 0.55 μm, 0.60 μm, 0.65 μm, 0.70 μm, or 0.75 μm, and the particle size of the powder material is 20 to 40 μm.

[0026] In step S7, the powder is sintered in an inert atmosphere, cooled naturally, and then pulverized to obtain a carbon-coated lithium iron phosphate material.

[0027] The inert atmosphere used is at least one selected from nitrogen gas, argon gas, and helium gas, and the sintering temperature may be 750 to 900°C, for example, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, or 900°C, and the sintering time is 5 to 12 hours. The sintering time may be 5h, 6h, 7h, 8h, 9h, 10h, 11h, or 12h, and the particle size of the carbon-coated lithium iron phosphate material is 0.80 to 3 μm, preferably 1 to 2 μm, for example, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, or 2 μm.

[0028] The present invention provides an embodiment of a method for producing lithium iron phosphate by recovering waste lithium iron phosphate material. When processing the waste lithium iron phosphate material, the amount of iron source added and the pH value are adjusted to recover iron and phosphorus elements in the form of iron hydroxyphosphate, resulting in recovery rates of 94.3% and 94.2% or higher for iron and phosphorus elements, and also reducing the amount of lithium element precipitated during the precipitation of phosphorus and iron elements to the greatest extent possible, thereby separating lithium from phosphorus and iron elements. The present invention improves the recovery rates of lithium, phosphorus, and iron elements by recovering phosphorus and iron elements in the form of iron hydroxyphosphate and lithium element in the form of lithium hydroxide.

[0029] When subsequently manufacturing lithium iron phosphate material, adding phosphoric acid to the filtrate not only allows for adjusting the Li / P ratio to an appropriate range, but also prevents the precipitation of lithium element. This allows the lithium element to be recovered in the filtrate in the form of lithium hydroxide, resulting in a lithium element recovery rate of 92.8% or higher.

[0030] Furthermore, the nano-order lithium iron phosphate material produced by the method according to the present invention has a uniform particle size, excellent material performance, an initial discharge capacity of 162 mAh / g or more at 0.1C, and a discharge capacity of 142 mAh / g at 1C. In addition, this method has high manufacturing efficiency, low manufacturing costs, is environmentally friendly, is suitable for application to large-scale industrial manufacturing, and has high economic and social benefits.

[0031] The specific process and effects of the method for recovering waste lithium iron phosphate material and producing lithium iron phosphate according to 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.

[0032] (Example 1) The method for producing lithium iron phosphate by recovering waste lithium iron phosphate material according to this embodiment is: Step S1 involves crushing the positive electrode sheet of a waste lithium iron phosphate battery to a particle size of 4-6 μm, shaking and sieving to obtain lithium iron phosphate raw material, adding the lithium iron phosphate raw material to a 30 wt% sulfuric acid solution, making the mass ratio of the sulfuric acid solution to the lithium iron phosphate raw material 4:1, filtering, and then collecting the first filtrate. Step S2 involves adding ferrous sulfate solution to the first filtrate to adjust the Fe / P molar ratio to 1.45 and obtaining a mixed solution. Step S3 involves adding 25 wt% hydrogen peroxide solution and 25 wt% ammonia solution to the mixed solution to adjust the pH to 2.5, allowing the reaction to proceed, then filtering and washing to obtain a second filtrate and a filtration cake, respectively, and washing and drying the filtration cake to obtain iron hydroxyphosphate. Step S4 involves adding an aqueous barium hydroxide solution to the second filtrate, allowing sulfate ions to precipitate, completely reacting, filtering, and washing to obtain a third filtrate. Step S5 involves adding a phosphoric acid solution to the third filtrate and adjusting the Li / P molar ratio to 3 to obtain a fourth filtrate. Step S6 involves uniformly mixing the iron hydroxyphosphate, the fourth filtrate, glucose, and polyethylene glycol, with a molar ratio of iron to phosphorus of 1:1.04 and a carbon content of 1.10 wt%, sanding the slurry to a particle size of 0.65 μm, and thoroughly drying it to obtain a powder. The method includes step S7, in which the powder is kept warm in a nitrogen atmosphere at 780°C for 10 hours, cooled naturally, and then pulverized to a particle size of 1.2 μm to obtain a nano-order carbon-coated lithium iron phosphate material.

[0033] Figure 3 shows the SEM spectrum of the lithium iron phosphate material produced in this embodiment.

[0034] (Example 2) The method for producing lithium iron phosphate by recovering waste lithium iron phosphate material according to this embodiment is: Step S1 involves crushing the positive electrode sheet of a waste lithium iron phosphate battery to a particle size of 7-9 μm, shaking and sieving to obtain lithium iron phosphate raw material, adding the lithium iron phosphate raw material to a 30 wt% sulfuric acid solution, making the mass ratio of the sulfuric acid solution to the lithium iron phosphate raw material 4.5:1, filtering, and then collecting the first filtrate. Step S2 involves adding ferrous sulfate solution to the first filtrate to adjust the Fe / P molar ratio to 1.47 and obtaining a mixed solution. Step S3 involves adding 25 wt% hydrogen peroxide solution and 25 wt% ammonia solution to the mixed solution to adjust the pH to 3.0, allowing the reaction to proceed, then filtering and washing to obtain a second filtrate and a filtration cake, respectively, and washing and drying the filtration cake to obtain iron hydroxyphosphate. Step S4 involves adding an aqueous barium hydroxide solution to the second filtrate, allowing sulfate ions to precipitate, completely reacting, filtering, and washing to obtain a third filtrate. Step S5 involves adding a phosphoric acid solution to the third filtrate to adjust the Li / P molar ratio to 2.9 to obtain a fourth filtrate. Step S6 involves uniformly mixing the iron hydroxyphosphate, the fourth filtrate, glucose, and polyethylene glycol, with a molar ratio of iron to phosphorus of 1:1.03 and a carbon content of 1.30 wt%, sanding the slurry to a particle size of 0.55 μm, and thoroughly drying it to obtain a powder. The method includes step S7, in which the powder is kept warm in a nitrogen atmosphere at 820°C for 12 hours, cooled naturally, and then pulverized to a particle size of 0.95 μm to obtain a nano-order carbon-coated lithium iron phosphate material.

[0035] (Comparative Example 1) The method for producing lithium iron phosphate by recovering waste lithium iron phosphate material according to this embodiment is: Step S1 involves crushing the positive electrode sheet of a waste lithium iron phosphate battery to a particle size of 4-6 μm, shaking and sieving to obtain lithium iron phosphate raw material, adding the lithium iron phosphate raw material to a 30 wt% sulfuric acid solution, making the mass ratio of the sulfuric acid solution to the lithium iron phosphate raw material 5:1, filtering, and then collecting the first filtrate. Step S2 involves adding ferrous sulfate solution to the first filtrate to adjust the Fe / P molar ratio to 1.45 and obtaining a mixed solution. Step S3 involves adding 25 wt% hydrogen peroxide solution and 25 wt% ammonia solution to the mixed solution to adjust the pH to 1.0, allowing the reaction to proceed, then filtering and washing to obtain a second filtrate and a filtration cake, respectively, and washing and drying the filtration cake to obtain iron hydroxyphosphate. Step S4 involves adding an aqueous barium hydroxide solution to the second filtrate, allowing sulfate ions to precipitate, completely reacting, filtering, and washing to obtain a third filtrate. Step S5 involves adding a phosphoric acid solution to the third filtrate and adjusting the Li / P molar ratio to 3 to obtain a fourth filtrate. Step S6 involves uniformly mixing the iron hydroxyphosphate, the fourth filtrate, glucose, and polyethylene glycol, adjusting the molar ratio of iron to phosphorus to 1:1.04, the carbon content to 1.50 wt%, sanding the slurry to a particle size of 0.85 μm, and thoroughly drying it to obtain a powder. The method includes step S7, in which the powder is kept warm in a nitrogen atmosphere at 780°C for 5 hours, cooled naturally, and then pulverized to a particle size of 1.0 μm to obtain a nano-order carbon-coated lithium iron phosphate material.

[0036] To verify the product quality of lithium iron phosphate cathode material produced by the method for producing lithium iron phosphate from waste lithium iron phosphate material according to the embodiments of the present invention, the lithium iron phosphate cathode material produced in Examples 1-2 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 80:10:10. After uniform dispersion by ball milling, the mixture is coated onto aluminum foil and vacuum-dried to produce a cathode sheet. 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 anode. Both are assembled into a button-type half-cell. 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. One cycle consisted of a charge / discharge current of 0.1C, and another cycle consisted of a charge / discharge current of 1C. The stopping condition was 0.1C. The test results are shown in Table 1.

[0037] Table 1 Test items and test results for Examples 1-2 and Comparative Example 1 [Table 1]

[0038] Comparing the test results obtained by testing based on the above examples and comparative examples, the button-type half-cells manufactured with lithium iron phosphate cathode materials in Examples 1 and 2 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.

[0039] Based on the above, the method for producing lithium iron phosphate by recovering waste lithium iron phosphate material according to the embodiments of the present invention recovers iron and phosphorus elements in the form of iron hydroxyphosphate by adjusting the amount of iron source added and the pH value when processing waste lithium iron phosphate material, resulting in recovery rates of 94.3% and 94.2% or higher for iron and phosphorus elements, and also reduces the amount of lithium element precipitated during the precipitation of phosphorus and iron elements to the greatest extent possible, thereby separating lithium element from phosphorus and iron elements. The method according to the present invention improves the recovery rates of lithium element, phosphorus element, and iron element by recovering phosphorus and iron elements in the form of iron hydroxyphosphate and lithium element in the form of lithium hydroxide.

[0040] When subsequently manufacturing lithium iron phosphate material, adding phosphoric acid to the filtrate not only allows for adjusting the Li / P ratio to an appropriate range, but also prevents the precipitation of lithium element. This allows the lithium element to be recovered in the filtrate in the form of lithium hydroxide, resulting in a lithium element recovery rate of 92.8% or higher.

[0041] Furthermore, the nano-order lithium iron phosphate material produced by the method according to the present invention has a uniform particle size, excellent material performance, an initial discharge capacity of 162 mAh / g or more at 0.1C, and a discharge capacity of 142 mAh / g at 1C. In addition, this method has high manufacturing efficiency, low manufacturing costs, is environmentally friendly, is suitable for application to large-scale industrial manufacturing, and has high economic and social benefits.

[0042] In this specification, any reference 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. In this specification, exemplary expressions of the above terms do not necessarily mean the same embodiment or example. Furthermore, the specific features, structures, materials, or properties described can be appropriately combined in any one or more embodiments or examples. Also, 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 conflict with each other.

[0043] 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 crushing the positive electrode sheet of a waste lithium iron phosphate battery, shaking and sieving it to obtain lithium iron phosphate raw material, dissolving the lithium iron phosphate raw material in an acidic solution, filtering it, and then collecting the first filtrate. Step S2 involves adding ferrous sulfate solution to the first filtrate to obtain a mixed solution, Step S3 involves adding hydrogen peroxide solution and ammonia solution to the mixed solution to adjust the pH value, allowing the reaction to proceed, then filtering and washing to obtain a second filtrate and a filtration cake, respectively, and washing and drying the filtration cake to obtain iron hydroxyphosphate. Step S4 involves adding an aqueous barium hydroxide solution to the second filtrate, allowing it to react completely, and then filtering it to obtain a third filtrate. Step S5 involves adding a phosphoric acid solution to the third filtrate to obtain a fourth filtrate, Step S6 involves mixing the iron hydroxyphosphate, the fourth filtrate, and the carbon source, sanding the slurry, drying it, and then obtaining a powder. Step S7 includes sintering the aforementioned powder in an inert atmosphere, allowing it to cool naturally, and then grinding it to obtain a carbon-coated lithium iron phosphate material. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material, characterized by the following:

2. In step S1, the acidic solution is a sulfuric acid solution or a phosphoric acid solution, and the concentration of the acidic solution is greater than 30 wt%. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 1.

3. In step S1, the mass ratio of the added acidic solution to the lithium iron phosphate raw material is [3-5]:

1. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 1.

4. In step S2, the amount of ferrous sulfate solution added is determined based on the criterion that the molar ratio of iron phosphate in the mixed solution satisfies Fe / P = 1.45 to 1.

5. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 1.

5. In step S3, the concentration of the hydrogen peroxide solution is 20-30 wt%, the concentration of the ammonia aqueous solution is 20-30 wt%, and the hydrogen peroxide solution and ammonia aqueous solution are added to adjust the pH value to 2.0-4.

5. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 1.

6. In step S4, an aqueous barium hydroxide solution is added to remove sulfate ions from the second filtrate. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 1.

7. In step S5, the amount of phosphoric acid solution added is determined based on the requirement that the lithium phosphorus molar ratio in the fourth filtrate satisfies Li / P = 2.8 to 3.

2. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 1.

8. In step S6, after mixing the iron hydroxyphosphate and the fourth filtrate, the molar ratio of iron to phosphorus satisfies n(Fe):n(Li) = 1:[1-1.04], the amount of carbon source added is based on the carbon content in the lithium iron phosphate material being 0.5-3 wt%, the carbon source is a mixture of glucose and polyethylene glycol, and the particle size of the slurry is 0.40-0.95 μm. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 1.

9. In step S6, the amount of carbon source added is based on the carbon content in the lithium iron phosphate material being 0.8 to 2 wt%, the particle size of the slurry is 0.50 to 0.75 μm, and the particle size of the powder is 20 to 40 μm. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 8.

10. In step S7, the inert atmosphere is at least one selected from nitrogen gas, argon gas, and helium gas, the sintering temperature is 750 to 900°C, the sintering time is 5 to 12 hours, and the particle size of the carbon-coated lithium iron phosphate material is 0.80 to 3.0 μm. A method for producing lithium iron phosphate by recovering waste lithium iron phosphate material as described in feature 1.

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