Method for removing fluorine element in lithium iron phosphate battery black powder based on reducing agent

Abstract

The invention specifically discloses a method for removing fluorine in lithium iron phosphate battery black powder based on a reducing agent, and the method comprises the following steps: S100, placing waste lithium iron phosphate battery black powder into a heating container filled with a reducing gas, and carrying out a reduction reaction at a first preset temperature to generate gaseous fluoride; and S200, cooling after the reaction is finished, and then introducing protective gas to replace the reducing gas and the generated gaseous fluoride in the heating container, so as to obtain the fluoride-free lithium iron phosphate battery black powder. According to the method, the gaseous fluoride is generated through the reaction of the reducing gas and the fluorine atoms with strong oxidizing property, so that the fluorine atoms are separated from the solid battery black powder, and the fluorine element in the battery black powder is rapidly removed. Therefore, the method can quickly and efficiently remove the fluorine element in the battery black powder, and provides guarantee for subsequent recovery treatment of the battery black powder.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium iron phosphate battery recycling, and in particular, relates to a method for removing fluorine from black powder of lithium iron phosphate batteries based on a reducing agent. Background Art

[0002] Lithium iron phosphate batteries have a series of unique advantages such as high operating voltage, high energy density, long cycle life, low self-discharge rate, no memory effect, and green environmental protection. They also support stepless expansion and are suitable for large-scale energy storage. They have good application prospects in new energy vehicles.

[0003] Since the chemical substances such as LiPF6, organic carbonates, and copper contained in lithium iron phosphate batteries are all hazardous wastes, if the lithium iron phosphate batteries are not recycled after being discarded or retired, it will be extremely harmful to the environment and human health. In the prior art, it is generally necessary to dismantle, crush, and sort the waste lithium iron phosphate batteries for recycling. The battery black powder obtained after sorting contains lithium iron phosphate, graphite, PVDF, lithium hexafluorophosphate, trace metals, etc. The fluorine element in the battery black powder has a great impact on the subsequent metal recycling process. Therefore, it is urgent to develop a method that can effectively remove the fluorine element in the waste lithium iron phosphate battery black powder. Summary of the invention

[0004] This application is made in view of the above technical problems and aims to provide a method for removing fluorine from black powder of lithium iron phosphate batteries based on a reducing agent with high yield, short process and low cost.

[0005] In order to solve the above technical problems, the present application provides a method for removing fluorine element in black powder of lithium iron phosphate battery based on a reducing agent, and the method comprises the following steps: S100, placing waste lithium iron phosphate battery black powder into a heating container filled with reducing gas, and performing a reduction reaction at a first preset temperature to generate gaseous fluoride; S200, cooling after the reaction is completed, and then introducing a protective gas to replace the reducing gas and the generated gaseous fluoride in the heating container, thereby obtaining fluorine-free lithium iron phosphate battery black powder.

[0006] In some embodiments, in step S100, the first preset temperature is 500-800°C, and the reduction reaction time is 5-20 minutes.

[0007] In some embodiments, the reducing gas includes at least one of hydrocarbons, hydrogen halides, hydrogen, carbon monoxide and ammonia, wherein the hydrocarbons include methane and the hydrogen halides include hydrogen chloride, hydrogen bromide and hydrogen iodide.

[0008] In some embodiments, the protective gas is one of nitrogen, helium or argon.

[0009] In some embodiments, in step S100, the waste lithium iron phosphate battery black powder is made into a black powder interlayer sheet and then placed in a heating container for reduction reaction.

[0010] In some embodiments, the preparation process of the black powder interlayer sheet is specifically as follows: spreading the waste lithium iron phosphate battery black powder on a foamed nickel mesh, and then covering the waste lithium iron phosphate battery black powder with another foamed nickel mesh to obtain the black powder interlayer sheet.

[0011] In some embodiments, the method further includes step S300 of washing the reduced gas replaced in the heating container and the generated gaseous fluoride with water, thereby converting the gaseous fluoride into a compound soluble in water.

[0012] In some embodiments, step S100 is specifically as follows: black powder of waste lithium iron phosphate battery is made into a black powder interlayer sheet, and then the black powder interlayer sheet is placed in a mesh belt furnace filled with reducing gas, and moved in the reduction zone of the mesh belt furnace at a first preset rate to ensure that the black powder interlayer sheet moves in the reduction zone of the mesh belt furnace for 5-20 minutes.

[0013] In some embodiments, step S200 is specifically as follows: moving the black powder interlayer sheet after the reduction reaction from the reduction zone of the mesh belt furnace to the annealing zone, then introducing a protective gas to replace the reducing gas and the generated gaseous fluoride in the mesh belt furnace, and finally lowering the temperature of the annealing zone to room temperature to obtain a fluorine-free black powder interlayer sheet.

[0014] Compared with the prior art, the present application provides a method for removing fluorine from lithium iron phosphate battery black powder based on a reducing agent. This method generates gaseous fluoride by reacting the reducing gas with the strongly oxidizing fluorine atoms, so that the fluorine atoms are separated from the solid battery black powder, thereby achieving rapid removal of fluorine from the battery black powder. Therefore, this method can quickly and efficiently remove fluorine from the battery black powder, providing a guarantee for the subsequent recycling and treatment of the battery black powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a flow chart of a method for removing fluorine from black powder of lithium iron phosphate batteries based on a reducing agent in some embodiments of the present application. DETAILED DESCRIPTION

[0017] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0018] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0019] refer to Figure 1 As shown, the embodiment of the present application provides a method for removing fluorine element in black powder of lithium iron phosphate battery based on a reducing agent, and the method comprises the following steps: S100, placing waste lithium iron phosphate battery black powder into a heating container filled with reducing gas, and performing a reduction reaction at a first preset temperature to generate gaseous fluoride; In this step, the first preset temperature is 500-800°C, and the reduction reaction time is 5-20 minutes; the reducing gas includes at least one of hydrocarbons, hydrogen halides, hydrogen, carbon monoxide and ammonia, wherein the hydrocarbons include methane, and the hydrogen halides include hydrogen chloride, hydrogen bromide and hydrogen iodide; The first preset temperature may be any value between 500-800°C. For example, the first preset temperature may be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, etc. The reduction reaction time can be any value between 5 and 20 min. For example, the reduction reaction time can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 9 min, 20 min, etc.

[0020] S200, cooling after the reaction is completed, and then introducing a protective gas to replace the reducing gas and the generated gaseous fluoride in the heating container, thereby obtaining fluorine-free lithium iron phosphate battery black powder.

[0021] In this step, the protective gas is one of nitrogen, helium or argon.

[0022] In the embodiment of the present application, the fluorine-containing electrolyte, the binder and the reducing gas in the battery black powder react at a first preset temperature, part of the lithium iron phosphate is decomposed, and phosphorus is reduced to The released oxygen combines with fluorine to form , , ,because The sublimation temperature is -39°C, so at the first preset temperature or room temperature, it is all gaseous fluoride, which is very easy to separate from the solid battery black powder. When the reducing gas is hydrogen and carbon monoxide, the chemical reaction formula of the fluorine-containing electrolyte and adhesive in the battery black powder and the reducing gas is as follows: LiPF6 + H2 + LiFePO4→Li3PO4 + POF3↑+Fe2P + H2O↑ LiPF6 + CO + LiFePO4→Li3PO4 + POF3↑+Fe2P + CO2↑ [(CH2CF2)n] + CO + LiFePO4 → Li3PO4 + POF3↑+ CO2↑ + H2O↑+Fe2P It can be seen that gaseous fluoride can be generated by the reaction of reducing gas with the strong oxidizing fluorine atoms in the battery black powder. , thereby making the fluorine atoms in the battery black powder separate from the solid battery black powder, achieving the effective removal of the fluorine element in the battery black powder. Therefore, the method provided in this application can quickly and efficiently remove the fluorine element in the battery black powder, providing a guarantee for the subsequent recycling and treatment of the battery black powder. In some embodiments of the present application, in step S100, the waste lithium iron phosphate battery black powder is made into a black powder interlayer sheet and then placed in a heating container for a reduction reaction; and the preparation process of the black powder interlayer sheet is specifically as follows: spreading the waste lithium iron phosphate battery black powder on a foamed nickel mesh, and then covering the waste lithium iron phosphate battery black powder with another foamed nickel mesh, thereby obtaining a black powder interlayer sheet.

[0023] In the above embodiment, the waste lithium iron phosphate battery black powder is made into a black powder interlayer sheet sandwiched by two foamed nickel meshes. On the one hand, it is convenient for feeding, and on the other hand, the flat spreading method can also increase the contact area between the battery black powder and the reducing gas, which is beneficial to the reduction reaction.

[0024] In some embodiments of the present application, step S300 is further included, washing the reduced gas replaced in the heating container and the generated gaseous fluoride with water, thereby converting the gaseous fluoride into a compound soluble in water.

[0025] In the above embodiment, due to the gaseous fluoride It can react with water to finally generate phosphoric acid and hydrofluoric acid. Therefore, by washing the reducing gas replaced by the protective gas and the generated gaseous fluoride with water, the gaseous fluoride can be It is converted into phosphoric acid and hydrofluoric acid that are soluble in water, thereby preventing gaseous fluorides from volatilizing and polluting the atmospheric environment.

[0026] In some embodiments of the present application, the step S100 is specifically as follows: the waste lithium iron phosphate battery black powder is made into a black powder interlayer sheet, and then the black powder interlayer sheet is placed in a mesh belt furnace filled with reducing gas, and moves in the reduction zone of the mesh belt furnace at a first preset speed, ensuring that the black powder interlayer sheet moves in the reduction zone of the mesh belt furnace for 5-20 minutes; The step S200 specifically includes: moving the black powder interlayer sheet after the reduction reaction from the reduction zone of the mesh belt furnace to the annealing zone, then introducing a protective gas to replace the reducing gas and the generated gaseous fluoride in the mesh belt furnace, and finally reducing the temperature of the annealing zone to room temperature to obtain a fluorine-free black powder interlayer sheet.

[0027] In the above embodiment, the temperature of the reduction zone of the mesh belt furnace is controlled at 500-800°C, and the mesh belt of the mesh belt furnace can be used to move the prepared black powder interlayer sheet from the reduction zone of the mesh belt furnace to the annealing zone at a first preset rate. After the black powder interlayer sheet undergoes a reduction reaction with the reducing gas in the reduction zone, the fluorine element in the battery black powder is converted into gaseous fluoride. Finally, the black powder interlayer sheet after the reduction reaction is cooled to room temperature in the annealing zone to obtain a fluorine-free black powder interlayer sheet, thereby realizing the continuous operation of the process, greatly improving the work efficiency and reducing the labor intensity of the operators.

[0028] Among them, the first preset rate can be any value between 0.4-1.6m / min. For example, it can be 0.4m / min, 0.5m / min, 0.6m / min, 0.7m / min, 0.8m / min, 0.9m / min, 1.0m / min, 1.1m / min, 1.2m / min, 1.3m / min, 1.4m / min, 1.5m / min, 1.6m / min, 1.7m / min, 1.8m / min, etc.

[0029] The following examples describe the disclosure of the present application in more detail, and these examples are merely illustrative, as it will be apparent to those skilled in the art that various modifications and variations within the scope of the disclosure of the present application are possible. Unless otherwise stated, all reagents and raw materials used in the examples are commercially available or synthesized according to conventional methods, and the instruments and equipment used in the examples are commercially available.

[0030] Example 1 200g of waste lithium iron phosphate battery black powder with a fluorine content of 2.931% was made into a black powder interlayer sheet, and the black powder interlayer sheet was placed in a mesh belt furnace filled with reducing gas. The temperature of the reduction zone of the mesh belt furnace was controlled to 500°C, and the length of the mesh belt in the reduction zone was 8m. The mesh belt in the mesh belt furnace moved the black powder interlayer sheet from the reduction zone to the annealing zone at a rate of 0.4m / min. The time for the black powder interlayer sheet to move from the reduction zone to the annealing zone was 20 minutes. After cooling to room temperature, a fluorine-free black powder interlayer sheet was obtained.

[0031] It should be noted that in the actual operation of the embodiment, after the battery black powder defluorination process is completed, it is necessary to use protective gas to replace the reducing gas and the generated gaseous fluoride in the reduction zone of the mesh belt furnace and recover them to avoid the generated gaseous fluoride from polluting the environment.

[0032] Example 2

[0033] 200g of waste lithium iron phosphate battery black powder with a fluorine content of 2.873% was made into a black powder interlayer sheet, and the black powder interlayer sheet was placed in a mesh belt furnace filled with reducing gas. The temperature of the reduction zone of the mesh belt furnace was controlled to 800℃, and the length of the mesh belt in the reduction zone was 8m. The mesh belt in the mesh belt furnace moved the black powder interlayer sheet from the reduction zone to the annealing zone at a rate of 1.6m / min. The time for the black powder interlayer sheet to move from the reduction zone to the annealing zone was 5 minutes. After cooling to room temperature, a fluorine-free black powder interlayer sheet was obtained.

[0034] Example 3

[0035] 200g of waste lithium iron phosphate battery black powder with a fluorine content of 2.884% was made into a black powder interlayer sheet, and the black powder interlayer sheet was placed in a mesh belt furnace filled with reducing gas. The temperature of the reduction zone of the mesh belt furnace was controlled at 650°C, and the length of the mesh belt in the reduction zone was 8m. The mesh belt in the mesh belt furnace moved the black powder interlayer sheet from the reduction zone to the annealing zone at a rate of 0.8m / min. The time for the black powder interlayer sheet to move from the reduction zone to the annealing zone was 10 minutes. After cooling to room temperature, a fluorine-free black powder interlayer sheet was obtained.

[0036] The fluorine content of the fluorine-free black powder interlayer sheets obtained in Examples 1-3 was tested respectively. The test results are shown in Table 1.

[0037] Table 1 Detection results of fluorine content of battery black powder in fluorine-free black powder interlayer sheets in Examples 1-3

[0038] As can be seen from Table 1, the method provided in the present application for removing fluorine from lithium iron phosphate battery black powder based on a reducing agent has a defluorination rate of more than 93%. Therefore, the method provided in the present application can effectively remove fluorine from lithium iron phosphate battery black powder, providing favorable conditions for the subsequent recycling and treatment of waste lithium iron phosphate battery black powder.

[0039] The above is a detailed introduction to a method for removing fluorine from black powder of lithium iron phosphate batteries based on a reducing agent provided by the present application. This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the core idea of ​​the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for removing fluorine from black powder of lithium iron phosphate batteries based on a reducing agent, characterized in that: The method comprises: S100, placing waste lithium iron phosphate battery black powder into a heating container filled with reducing gas, and performing a reduction reaction at a first preset temperature to generate gaseous fluoride; S200, cooling after the reaction is completed, and then introducing a protective gas to replace the reducing gas and the generated gaseous fluoride in the heating container, thereby obtaining fluorine-free lithium iron phosphate battery black powder.

2. The method for removing fluorine from black powder of lithium iron phosphate battery based on a reducing agent as claimed in claim 1, characterized in that: In the step S100, the first preset temperature is 500-800°C, and the reduction reaction time is 5-20 minutes.

3. The method for removing fluorine from black powder of lithium iron phosphate battery based on a reducing agent as claimed in claim 2, characterized in that: The reducing gas includes at least one of hydrocarbons, hydrogen halides, hydrogen, carbon monoxide and ammonia, wherein the hydrocarbons include methane and the hydrogen halides include hydrogen chloride, hydrogen bromide and hydrogen iodide.

4. The method for removing fluorine from black powder of lithium iron phosphate battery based on a reducing agent as claimed in claim 3, characterized in that: The protective gas is one of nitrogen, helium or argon.

5. The method for removing fluorine from black powder of lithium iron phosphate battery based on a reducing agent as claimed in claim 4, characterized in that: In the step S100, the waste lithium iron phosphate battery black powder is made into a black powder interlayer sheet and then placed in a heating container for reduction reaction.

6. The method for removing fluorine from black powder of lithium iron phosphate battery based on a reducing agent as claimed in claim 5, characterized in that: The preparation process of the black powder interlayer sheet is specifically as follows: spreading the black powder of the waste lithium iron phosphate battery on a foamed nickel mesh, and then covering the black powder of the waste lithium iron phosphate battery with another foamed nickel mesh, thereby obtaining the black powder interlayer sheet.

7. The method for removing fluorine from black powder of lithium iron phosphate batteries based on a reducing agent according to any one of claims 1 to 6, characterized in that: The method further includes step S300 of washing the reduced gas replaced in the heating container and the generated gaseous fluoride with water, thereby converting the gaseous fluoride into a compound soluble in water.

8. The method for removing fluorine from black powder of lithium iron phosphate battery based on a reducing agent as claimed in claim 6, characterized in that: The heating container in step S100 is a mesh belt furnace including a reduction zone and an annealing zone.

9. The method for removing fluorine from black powder of lithium iron phosphate battery based on a reducing agent as claimed in claim 8, characterized in that: The step S100 is specifically as follows: the black powder of waste lithium iron phosphate battery is made into a black powder interlayer sheet, and then the black powder interlayer sheet is placed in a mesh belt furnace filled with reducing gas, and moved in the reduction zone of the mesh belt furnace at a first preset speed to ensure that the black powder interlayer sheet moves in the reduction zone of the mesh belt furnace for 5-20 minutes.

10. The method for removing fluorine from black powder of lithium iron phosphate battery based on a reducing agent as claimed in claim 9, characterized in that: The step S200 specifically includes: moving the black powder interlayer sheet after the reduction reaction from the reduction zone of the mesh belt furnace to the annealing zone, then introducing a protective gas to replace the reducing gas and the generated gaseous fluoride in the mesh belt furnace, and finally reducing the temperature of the annealing zone to room temperature to obtain a fluorine-free black powder interlayer sheet.

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