A low-copper, low-aluminum lithium iron phosphate black powder and its preparation method

Abstract

This invention discloses a low-copper-aluminum lithium iron phosphate black powder and its preparation method. First, waste lithium iron phosphate batteries are pre-treated to obtain broken material without electrolyte and separator. The positive and negative electrode sheets are then desorbed, soaked to remove aluminum, and deeply washed with alcohol to remove aluminum. On the one hand, high-value copper and aluminum foil is recovered, and on the other hand, aluminum-free lithium iron phosphate black powder is produced, which can meet the requirements for aluminum impurities in subsequent acid leaching and recycling.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery recycling technology, specifically relating to a low-copper-aluminum lithium iron phosphate black powder and its preparation method. Background Technology

[0002] Lithium iron phosphate (LFP) batteries are highly safe, fast-chargeable, and capable of up to 2000 cycle times, exhibiting excellent safety performance and gradually becoming a new choice for electric vehicle power batteries. With the increasing market share and volume of LFP batteries in power batteries, the recycling of lithium iron phosphate from spent LFP batteries has become a key aspect of power battery recycling. Among various lithium-ion batteries, only LFP batteries do not contain precious metals in their cathode material, instead primarily consisting of aluminum, lithium, iron, phosphorus, and carbon. Because of this, companies are not particularly enthusiastic about recycling LFP, and research on LFP battery recycling is relatively limited.

[0003] Currently, the recycling of spent lithium iron phosphate (LFP) power batteries mainly relies on wet processes. This involves dissolving the pre-treated LFP active material through acid leaching, then purifying it to remove impurities such as aluminum and copper, and finally recovering the metal elements from the leachate. However, aluminum ions, as impurities in the sulfuric acid leachate, can negatively impact the electrochemical performance of subsequent metal element recovery processes using LFP and lithium carbonate precursors.

[0004] Chinese patent CN106910889A discloses a method for regenerating positive electrode active materials from spent lithium iron phosphate batteries. Specifically, it discloses a method for removing copper from the leaching solution of the positive electrode active material and then removing aluminum at a pH of 3-5. This method involves adding an alkali metal hydroxide to the acidic system to remove Al from the system. 3+ The aluminum is precipitated as Al(OH)3. However, this method is not ideal for aluminum removal. The addition of alkali metal hydroxides in the acidic system leads to a localized increase in pH, resulting in the formation of white Fe3(PO4)2 precipitate, which in turn causes PO4 to precipitate. 3- Fe 2+ Significant losses, and the removal of Al is not very effective. 3+ The purpose of impurities.

[0005] Waste lithium iron phosphate can also be directly recycled. The process can be summarized as follows: battery dismantling and electrode sorting → stripping waste LFP from the electrodes → composition adjustment → repair and regeneration. However, none of these processes consider removing copper and aluminum impurities before the repair and regeneration process, resulting in severely excessive aluminum and copper content in the recycled lithium iron phosphate, making it unsuitable for industrial production.

[0006] Chinese patent CN107540004B discloses a method for recovering battery-grade lithium carbonate from waste lithium iron phosphate battery cathode powder. This method employs alkaline pressure leaching, which significantly improves the lithium leaching rate and greatly reduces the impact of impurity metals, facilitating subsequent impurity removal. However, the reaction rate between aluminum and sodium hydroxide is extremely slow, and the presence of a large amount of aluminum foil in the crushed material results in a very high consumption of sodium hydroxide. Subsequent solution preparation requires a large amount of acid for neutralization, and the aluminum foil cannot be recovered.

[0007] Therefore, there is an urgent need for a black powder treatment material that can process aluminum foil and recycle it to obtain aluminum-free material, which can meet the requirements of both subsequent acid leaching and recycling processes for aluminum impurities, and can also recycle high-value aluminum foil. Summary of the Invention

[0008] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a low-copper-aluminum lithium iron phosphate black powder and its preparation method. This method involves recycling spent lithium iron phosphate batteries, performing salt washing and desorption, and deep aluminum removal to obtain aluminum-free lithium iron phosphate black powder, thus meeting the requirements of subsequent processes.

[0009] According to one aspect of the present invention, a low-copper-aluminum lithium iron phosphate black powder is provided, which is derived from waste lithium iron phosphate batteries, has a black appearance, and contains ≥17.0 wt% iron, ≥9.0 wt% phosphorus, ≥2.2 wt% lithium, ≤0.05 wt% copper, and ≤0.05 wt% aluminum.

[0010] In some embodiments of the present invention, the particle size of the lithium iron phosphate black powder is ≤0.25mm.

[0011] This invention also provides a method for preparing the low-copper-aluminum lithium iron phosphate black powder, comprising the following steps:

[0012] S1: Waste lithium iron phosphate batteries are discharged, dismantled and crushed. The crushed material is pretreated to remove electrolyte and separator to obtain pretreated material.

[0013] S2: The pretreated material is placed in a ferric salt solution for reaction, and the mixture after reaction is sieved to obtain copper aluminum foil and slurry;

[0014] S3: The slurry continues to react for a period of time, and then solid-liquid separation is performed to obtain filtrate and filter cake. The filter cake is dried to obtain dried material.

[0015] S4: The dried material is placed in an anhydrous alcohol solution and heated for soaking, and the solid and liquid are separated. The resulting solid is washed and dried to obtain the lithium iron phosphate black powder.

[0016] In some embodiments of the present invention, in step S1, the particle size of the crushed material is ≤5cm.

[0017] In some embodiments of the present invention, in step S1, the pretreatment process is as follows: the crushed material is heated to 180-220°C for drying, and the dried material is subjected to air classification to obtain the pretreated material. Further, the drying time at 180-220°C is 1-3 hours.

[0018] In some embodiments of the present invention, in step S2, the solid-liquid ratio of the pretreated material to the ferric salt solution is 0.5-2.0 g / mL, and the concentration of iron ions in the ferric salt solution is 0.1-0.5 mol / L.

[0019] In some embodiments of the present invention, in step S2, the ferric salt solution is at least one of ferric sulfate solution or ferric chloride solution.

[0020] In some embodiments of the present invention, in step S2, the reaction temperature is 40-90°C and the reaction time is 0.5-1.0 h.

[0021] In some embodiments of the present invention, in step S2, the mesh size of the sieve used for screening is 0.2-0.3 mm.

[0022] In some embodiments of the present invention, in step S3, the temperature at which the slurry continues to react is 60-90°C, and the reaction time is 2-4 hours.

[0023] In some embodiments of the present invention, in step S3, the filtrate is further treated as follows: iron powder is added to the filtrate to react, the pH is adjusted to 5.0-5.5, solid-liquid separation is performed to obtain copper-aluminum slag and a ferrous salt solution, and hydrogen peroxide is added to the ferrous salt solution to obtain a ferric salt solution. Further, the amount of iron powder added is 1.2-1.5 times the molar amount of copper in the filtrate. Further, the reaction time after adding the iron powder is 1-2 hours.

[0024] In some embodiments of the present invention, in step S3, the drying temperature is 100-120°C and the drying time is 1-2 hours.

[0025] In some embodiments of the present invention, in step S4, the solid-liquid ratio of the dried material to the anhydrous alcohol solution is 0.5-2.0 g / mL.

[0026] In some embodiments of the present invention, in step S4, the heating temperature is 80-110°C. Further, the soaking time is 0.5-1.0 h.

[0027] In some embodiments of the present invention, in step S4, the anhydrous alcohol solution is at least one of anhydrous ethylene glycol, anhydrous propanol, anhydrous n-butanol, or anhydrous isopropanol.

[0028] In some embodiments of the present invention, in step S4, the washing is performed using an anhydrous alcohol solution.

[0029] In some embodiments of the present invention, in step S4, the drying temperature is 100-120°C and the drying time is 1-2 hours.

[0030] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved:

[0031] 1. This invention first pre-treats waste lithium iron phosphate batteries to obtain crushed material without electrolyte and separator. Then, the positive and negative electrode sheets are desorbed by iron salt solution, soaked to remove aluminum, and deeply washed with alcohol to remove aluminum. On the one hand, high-value copper and aluminum foil is recovered, and on the other hand, aluminum-free lithium iron phosphate black powder is produced, which can meet the requirements of subsequent acid leaching and recycling for aluminum impurities.

[0032] 2. During the salt washing process, the aluminum is corroded by the reaction of ferric ions with metallic aluminum, thus removing the positive electrode powder. In this process, ferric salts also react with the negative electrode copper foil, but the ferric salts have a greater desorption effect on the positive electrode. The negative electrode binder can dissolve in water, thus achieving detachment. The reaction equation is as follows:

[0033] Al + 3Fe 3+ →Al 3+ +3Fe 2+

[0034] Cu + 2Fe 3+ →Cu 2+ +2Fe 2+

[0035] 3. After the black powder is desorbed, some aluminum metal particles and alumina still remain in the slurry. The slurry is then further soaked and reacted using a ferric salt solution. The reaction equation is as follows:

[0036] Al + 3Fe 3+ →Al 3+ +3Fe 2+

[0037] Al₂O₃ + 6H₂O + →2Al 3+ +3H2O

[0038] 4. During the soaking process, lithium ions and phosphate ions inevitably dissolve. On the one hand, ferric salts react with phosphate ions to form iron phosphate precipitate; on the other hand, some aluminum ions also form aluminum phosphate. Phosphate ions remain fixed in the black powder throughout the soaking process. Since the generated aluminum phosphate will enter downstream processes, the aluminum phosphate is dissolved in an alcohol solution by heating, taking advantage of the fact that aluminum phosphate is soluble in alcohol while lithium iron phosphate and iron phosphate are insoluble in alcohol, thus obtaining aluminum-free lithium iron phosphate black powder. The reaction equation is:

[0039] Al 3+ +PO4 3- →AlPO4

[0040] Fe 3+ +PO4 3- →FePO4

[0041] 5. The filtrate after soaking in the ferric salt solution does not contain phosphate ions and will not form aluminum phosphate. Therefore, in the preferred embodiment of the present invention, aluminum can be removed by adding iron powder for reduction and adjusting the pH, followed by re-oxidation to prepare the ferric salt solution, which can then be reused in the salt washing and desorption process. The filtrate itself contains a small amount of dissolved lithium ions. As the ferric salt is recycled, the lithium ions gradually accumulate. When the concentration reaches a certain value, lithium is recovered using other processes. Attached Figure Description

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0043] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention. Detailed Implementation

[0044] The following will describe the concept and technical effects of the present invention clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0045] Example 1

[0046] A method for recovering lithium iron phosphate black powder, referring to Figure 1 The specific process is as follows:

[0047] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0048] Step 2: Heat the crushed material to 180℃ and continue for 3 hours to dry it and remove the electrolyte;

[0049] Step 3: Air-separate the dried material to remove the diaphragm;

[0050] Step 4: Add the dried material to a ferric sulfate solution with an iron ion concentration of 0.5 mol / L at a solid-liquid ratio of 0.5 g / mL, and react at 40°C for 1.0 h.

[0051] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0052] Step 6: Continue stirring the resulting slurry at 60°C for 4 hours.

[0053] Step 7: Filter the obtained slurry to obtain filtrate and filter cake. Wash the filter cake with pure water and dry it at 100℃ for 2 hours to obtain dried material. Add iron powder with a theoretical molar amount of copper of 1.2 times to the filtrate, react for 2 hours, adjust the pH to 5.0-5.5, and separate the solid and liquid to obtain copper-aluminum slag and ferrous salt solution. Add hydrogen peroxide to the ferrous salt solution to prepare the iron salt solution again.

[0054] Step 8: Place the dried material in anhydrous propanol at a solid-liquid ratio of 0.5 g / mL, heat to 80°C, and continue for 1.0 h.

[0055] Step 9: Solid-liquid separation, washing with anhydrous alcohol solution, and drying at 100℃ for 2 hours to obtain aluminum-free lithium iron phosphate black powder. The lithium iron phosphate black powder contains 9.63 wt% phosphorus, 17.2 wt% iron, and 2.31 wt% lithium.

[0056] Example 2

[0057] A method for recovering lithium iron phosphate black powder, the specific process of which is as follows:

[0058] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0059] Step 2: Heat the crushed material to 200℃ and continue for 2 hours to dry it and remove the electrolyte;

[0060] Step 3: Air-separate the dried material to remove the diaphragm;

[0061] Step 4: Add the dried material to a ferric chloride salt solution with an iron ion concentration of 0.3 mol / L at a solid-liquid ratio of 1.0 g / mL, and react at 70°C for 1.0 h.

[0062] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0063] Step 6: Continue stirring the resulting slurry at 80°C for 3 hours.

[0064] Step 7: Filter the obtained slurry to obtain filtrate and filter cake. Wash the filter cake with pure water and dry it at 110℃ for 1.5h to obtain dried material. Add iron powder with a theoretical molar amount of copper of 1.3 times to the filtrate, react for 1.5h, adjust the pH to 5.0-5.5, and separate the solid and liquid to obtain copper-aluminum slag and ferrous salt solution. Add hydrogen peroxide to the ferrous salt solution to prepare the iron salt solution again.

[0065] Step 8: Place the dried material in anhydrous n-butanol at a solid-liquid ratio of 1.0 g / mL, heat to 110°C, and continue for 1.0 h.

[0066] Step 9: Solid-liquid separation, washing with anhydrous alcohol solution, and drying at 110℃ for 1.5 hours to obtain aluminum-free lithium iron phosphate black powder. The lithium iron phosphate black powder contains 9.68 wt% phosphorus, 17.6 wt% iron, and 2.28 wt% lithium.

[0067] Example 3

[0068] A method for recovering lithium iron phosphate black powder, the specific process of which is as follows:

[0069] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0070] Step 2: Heat the crushed material to 220℃ and continue for 1 hour to dry it and remove the electrolyte;

[0071] Step 3: Air-separate the dried material to remove the diaphragm;

[0072] Step 4: Add the dried material to a ferric sulfate solution with an iron ion concentration of 0.1 mol / L at a solid-liquid ratio of 2.0 g / mL, and react at 90℃ for 0.5 h.

[0073] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0074] Step 6: Continue stirring the resulting slurry at 90°C for 2 hours.

[0075] Step 7: Filter the obtained slurry to obtain filtrate and filter cake. Wash the filter cake with pure water and dry it at 120℃ for 2 hours to obtain dried material. Add iron powder with a theoretical molar amount of copper to the filtrate, react for 1 hour, adjust the pH to 5.0-5.5, and separate the solid and liquid to obtain copper-aluminum slag and ferrous salt solution. Add hydrogen peroxide to the ferrous salt solution to prepare the iron salt solution again.

[0076] Step 8: Place the dried material in anhydrous isopropanol solution at a solid-liquid ratio of 2.0 g / mL, heat to 80°C, and continue for 1.0 h.

[0077] Step 9: Solid-liquid separation. Wash with anhydrous alcohol solution and dry at 120℃ for 1 hour to obtain aluminum-free lithium iron phosphate black powder. The lithium iron phosphate black powder contains 9.59 wt% phosphorus, 17.3 wt% iron, and 2.29 wt% lithium.

[0078] Comparative Example 1

[0079] A method for recovering lithium iron phosphate black powder, differing from Example 1 in that the lithium iron phosphate black powder is not soaked in anhydrous alcohol solution, and the specific process is as follows:

[0080] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0081] Step 2: Heat the crushed material to 180℃ and continue for 3 hours to dry it and remove the electrolyte;

[0082] Step 3: Air-separate the dried material to remove the diaphragm;

[0083] Step 4: Add the dried material to a ferric sulfate solution with an iron ion concentration of 0.5 mol / L at a solid-liquid ratio of 0.5 g / mL, and react at 40°C for 1.0 h.

[0084] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0085] Step 6: Continue stirring the resulting slurry at 60°C for 4 hours.

[0086] Step 7: The obtained slurry is filtered by pressure to obtain filtrate and filter cake. The filter cake is washed with pure water and dried at 100°C for 2 hours to obtain lithium iron phosphate black powder.

[0087] Comparative Example 2

[0088] A method for recovering lithium iron phosphate black powder, differing from Example 2 in that the lithium iron phosphate black powder is not soaked in anhydrous alcohol solution, and the specific process is as follows:

[0089] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0090] Step 2: Heat the crushed material to 200℃ and continue for 2 hours to dry it and remove the electrolyte;

[0091] Step 3: Air-separate the dried material to remove the diaphragm;

[0092] Step 4: Add the dried material to a ferric chloride salt solution with an iron ion concentration of 0.3 mol / L at a solid-liquid ratio of 1.0 g / mL, and react at 70°C for 1.0 h.

[0093] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0094] Step 6: Continue stirring the resulting slurry at 80°C for 3 hours.

[0095] Step 7: Filter the obtained slurry to obtain filtrate and filter cake. Wash the filter cake with pure water and dry it at 110°C for 1.5 hours to obtain lithium iron phosphate black powder.

[0096] Comparative Example 3

[0097] A method for recovering lithium iron phosphate black powder, differing from Example 3 in that the lithium iron phosphate black powder is not soaked in anhydrous alcohol solution, and the specific process is as follows:

[0098] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0099] Step 2: Heat the crushed material to 220℃ and continue for 1 hour to dry it and remove the electrolyte;

[0100] Step 3: Air-separate the dried material to remove the diaphragm;

[0101] Step 4: Add the dried material to a ferric sulfate solution with an iron ion concentration of 0.1 mol / L at a solid-liquid ratio of 2.0 g / mL, and react at 90℃ for 0.5 h.

[0102] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0103] Step 6: Continue stirring the resulting slurry at 90°C for 2 hours.

[0104] Step 7: The obtained slurry is filtered by pressure to obtain filtrate and filter cake. The filter cake is washed with pure water and dried at 120°C for 2 hours to obtain lithium iron phosphate black powder.

[0105] Comparative Example 4

[0106] A method for recovering lithium iron phosphate black powder differs from Example 1 in that the slurry obtained in step 5 is not further reacted, but directly filtered by pressure, and the lithium iron phosphate black powder is not soaked in anhydrous alcohol solution. The specific process is as follows:

[0107] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0108] Step 2: Heat the crushed material to 180℃ and continue for 3 hours to dry it and remove the electrolyte;

[0109] Step 3: Air-separate the dried material to remove the diaphragm;

[0110] Step 4: Add the dried material to a ferric sulfate solution with an iron ion concentration of 0.5 mol / L at a solid-liquid ratio of 0.5 g / mL, and react at 40°C for 1.0 h.

[0111] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0112] Step 6: Filter the obtained slurry to obtain filtrate and filter cake. Wash the filter cake with pure water and dry it at 100°C for 2 hours to obtain lithium iron phosphate black powder.

[0113] Comparative Example 5

[0114] A method for recovering lithium iron phosphate black powder differs from Example 2 in that the slurry obtained in step 5 is not further reacted, but directly filtered by pressure, and the lithium iron phosphate black powder is not soaked in anhydrous alcohol solution. The specific process is as follows:

[0115] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0116] Step 2: Heat the crushed material to 200℃ and continue for 2 hours to dry it and remove the electrolyte;

[0117] Step 3: Air-separate the dried material to remove the diaphragm;

[0118] Step 4: Add the dried material to a ferric chloride salt solution with an iron ion concentration of 0.3 mol / L at a solid-liquid ratio of 1.0 g / mL, and react at 70°C for 1.0 h.

[0119] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0120] Step 6: The obtained slurry is filtered by pressure to obtain filtrate and filter cake. The filter cake is washed with pure water and dried at 110℃ for 1.5h to obtain lithium iron phosphate black powder.

[0121] Comparative Example 6

[0122] A method for recovering lithium iron phosphate black powder differs from Example 3 in that the slurry obtained in step 5 is not further reacted, but directly filtered by pressure, and the lithium iron phosphate black powder is not soaked in anhydrous alcohol solution. The specific process is as follows:

[0123] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0124] Step 2: Heat the crushed material to 220℃ and continue for 1 hour to dry it and remove the electrolyte;

[0125] Step 3: Air-separate the dried material to remove the diaphragm;

[0126] Step 4: Add the dried material to a ferric sulfate solution with an iron ion concentration of 0.1 mol / L at a solid-liquid ratio of 2.0 g / mL, and react at 90℃ for 0.5 h.

[0127] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0128] Step 6: The obtained slurry is filtered by pressure to obtain filtrate and filter cake. The filter cake is washed with pure water and dried at 120°C for 2 hours to obtain lithium iron phosphate black powder.

[0129] Comparative Example 7

[0130] A method for recovering lithium iron phosphate black powder, differing from Comparative Example 6 in that step 4 involves soaking in a sodium hydroxide solution. The specific process is as follows:

[0131] Step 1: After being discharged and disassembled, the waste lithium iron phosphate batteries are crushed into crushed material with a particle size of less than 5cm.

[0132] Step 2: Heat the crushed material to 220℃ and continue for 1 hour to dry it and remove the electrolyte;

[0133] Step 3: Air-separate the dried material to remove the diaphragm;

[0134] Step 4: Add the dried material to an 8.0 mol / L sodium hydroxide solution at a solid-liquid ratio of 2.0 g / mL, and react at 150°C for 5 h.

[0135] Step 5: The reacted mixture is sieved through a sieve with a pore size of 0.25 mm to obtain copper-aluminum foil and slurry;

[0136] Step 6: The obtained slurry is filtered by pressure to obtain filtrate and filter cake. The filter cake is washed with pure water and dried at 120°C for 2 hours to obtain lithium iron phosphate black powder.

[0137] The black powder and copper-aluminum foil obtained in Examples 1-3 and Comparative Examples 1-7 were tested, and the results are shown in Table 1.

[0138] Table 1

[0139]

[0140] As shown in Table 1, in Comparative Examples 1-3, the aluminum content in the black powder was still high because it was not thoroughly removed by alcohol washing; in Comparative Examples 4-6, the slurry in step 5 was not further soaked and reacted, and the copper and aluminum contents in the black powder were both high; in Comparative Example 7, the aluminum content in the copper and aluminum foil was extremely low, indicating that no formed aluminum foil was obtained.

[0141] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing a low-copper aluminum lithium iron phosphate black powder, characterized in that, The method comprises the following steps: S1: the waste lithium iron phosphate battery is discharged, disassembled and crushed, the obtained crushed material is pretreated to remove electrolyte and diaphragm, and pretreated material is obtained; S2: the pretreated material is placed in a ferric salt solution for reaction, and the mixture after reaction is screened to obtain copper aluminum foil and slurry; S3: the slurry continues to react for a period of time, and then solid-liquid separation is performed to obtain filtrate and filter cake, and the filter cake is dried to obtain dry material after drying; S4: the dry material is placed in an anhydrous alcohol solution for heating and soaking, and solid-liquid separation is performed, and the obtained solid is washed and dried to obtain the lithium iron phosphate black powder; In step S2, the ferric salt is at least one of ferric sulfate solution or ferric chloride solution; In step S4, the anhydrous alcohol solution is at least one of anhydrous ethylene glycol, anhydrous propanol, anhydrous n-butanol or anhydrous isopropanol; the heating temperature is 80 110°C, and the soaking time is 0.5 1.0h. The lithium iron phosphate black powder has a black appearance, an iron element content of ≥17.0wt%, a phosphorus element content of ≥9.0wt%, a lithium element content of ≥2.2wt%, a copper element content of ≤0.05wt%, and an aluminum element content of ≤0.05wt%.

2. The production method according to claim 1, characterized by, In step S1, the particle size of the crushed material is ≤5cm.

3. The preparation method according to claim 1, characterized in that, In step S1, the pretreatment process is: the crushed material is heated to 180-220℃ for drying, and the obtained dry material is air separated to obtain the pretreated material.

4. The method of claim 1, wherein, In step S2, the solid-liquid ratio of the pretreated material to the ferric salt solution is 0.5-2.0g / mL, and the concentration of iron ions in the ferric salt solution is 0.1-0.5mol / L.

5. The preparation method according to claim 1, characterized in that, In step S2, the reaction temperature is 40-90℃, and the reaction time is 0.5-1.0h.

6. The method of claim 1, wherein, In step S2, the screen mesh aperture for screening is 0.2-0.3mm.

7. The preparation method according to claim 1, characterized in that, In step S3, the filtrate is further treated as follows: iron powder is added to the filtrate for reaction, the pH is adjusted to 5.0-5.5, solid-liquid separation is performed, copper aluminum slag and ferrous salt solution are obtained, hydrogen peroxide is added to the ferrous salt solution to obtain a ferric salt solution.

8. The preparation method according to claim 1, characterized in that, In step S4, the solid-liquid ratio of the dry material to the anhydrous alcohol solution is 0.5-2.0g / mL.

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