A method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate

Abstract

The present invention discloses a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, belonging to the technical field of battery recycling. The method comprises the following steps: retired lithium batteries are subjected to steps such as disassembly and crushing to obtain battery powder. After removing copper and aluminum from the battery powder, it is subjected to high-pressure conversion in a sodium carbonate solution. The converted material and water are slurried in a reaction kettle, and carbon dioxide is introduced for leaching to obtain sodium iron phosphate and a lithium-containing liquid. The lithium-containing liquid is purified and crystallization is completed in a negative pressure crystallizer. The crystallized lithium carbonate is washed and dried to obtain battery-grade lithium carbonate. The method of the present invention selectively extracts lithium by completing ion exchange between sodium ions and lithium ions in the crystal structure of lithium iron phosphate under high temperature and high pressure. This method can regenerate sodium iron phosphate for preparing battery materials and high-purity lithium carbonate products. The lithium-containing liquid has a simple composition, a high lithium recovery rate, and a simple process, which is easy to implement industrially.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery recycling, and particularly relates to a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate. Background Art

[0002] With the increase in retired power batteries, a large number of waste lithium iron phosphate batteries will flow into the recycling market, which will bring opportunities for the rapid development of the lithium iron phosphate battery recycling industry. The lithium iron phosphate battery recycling market processes with the cathode powder as the raw material. Driven by the demand in the downstream lithium battery industry, the demand for battery-grade lithium carbonate continues to rise rapidly. Given the obvious price advantage of current lithium carbonate and the low lithium content in the battery powder raw material, due to the high impurity content in the lithium iron phosphate battery powder, the traditional full-leaching recycling technical solution has disadvantages such as a large amount of acid and alkali consumption, a large lithium loss in the process of processing battery-grade lithium carbonate with battery powder, etc., and the technical advantages are not obvious.

[0003] Patent CN112142077B discloses a method for recycling lithium iron phosphate cathode waste to prepare battery-grade lithium carbonate and iron phosphate. Specifically, it discloses that air is used as an oxidant to adjust the leaching of lithium iron phosphate, water and organic acid, iron and phosphorus are oxidized to form iron phosphate precipitate, lithium is leached into the solution, and the leaching of other impurity elements is very little. The lithium solution removes impurities by neutralization precipitation, and saturated sodium carbonate is added to obtain lithium carbonate products. This method uses air as an oxidant, with low oxidation efficiency, extended production cycle, increased equipment investment, and the use of organic acid in the leaching process, and the organic matter will remain in the lithium carbonate product, which is not conducive to product sales.

[0004] Patent CN109088120B discloses a method for preparing battery-grade lithium carbonate from waste lithium iron phosphate electrode sheets. Specifically, it discloses that the lithium iron phosphate electrode sheets are first subjected to oxidative roasting to obtain electrode sheet roasting materials containing lithium iron phosphate active substances and current collector aluminum foil, and then the roasting materials are crushed and sieved to obtain separated aluminum powder and lithium iron phosphate electrode sheet powder. The lithium iron phosphate electrode sheet powder is added to hydrochloric acid or sulfuric acid solution for reaction, and finally the lithium-containing solution is obtained by filtration. The lithium-containing solution is purified to prepare lithium carbonate. The raw material used in this method is the electrode sheet material with relatively single composition. After roasting, the electrode sheet is brittle and the aluminum is brittle, and the particles are finer after crushing. It is difficult to effectively screen the aluminum powder and the electrode sheet powder. Aluminum enters the solution during the acid leaching process, and there is a large lithium loss in the process of preparing lithium carbonate.

[0005] Patent CN106450547A discloses a method for recycling iron phosphate and lithium carbonate from lithium iron phosphate waste. Specifically, the following steps are disclosed: oxidative roasting, electrode sheet cleaning, adding phosphoric acid for ball milling activation, pickling to separate iron phosphate, and precipitating lithium from the filtrate. The process flow of this invention is cumbersome, requires adding phosphoric acid for ball milling, and the ball milling process has high requirements for equipment, and it is easy to introduce impurities such as magnetic substances, and has no good removal effect on electrode sheet aluminum and other impurity ions.

[0006] Therefore, the present invention provides a technical method for producing battery-grade lithium carbonate and sodium iron phosphate battery materials with simple process, high efficiency and environmental protection. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, so as to solve the problems of large consumption of acids and alkalis and low lithium recovery rate in the existing process of recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] A method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, comprising the following steps:

[0010] S1. Recycling and processing retired lithium iron phosphate batteries to obtain lithium iron phosphate battery powder;

[0011] S2. Mixing lithium iron phosphate battery powder, water and ammonium salt according to a molar ratio of ammonium salt to copper element of 1-10:1 and a liquid-solid ratio of 2-10:1, and stirring and reacting in a reaction kettle to remove copper;

[0012] S3. Mixing the battery powder after copper removal with a sodium hydroxide solution with a mass fraction of 0.5-2% at a liquid-solid ratio of 2-10:1 to remove aluminum;

[0013] S4. Formulating sodium carbonate and the battery powder after aluminum removal according to a molar ratio of sodium to lithium element of 1-10:1 and a liquid-solid ratio = 4-8:1, and performing a high-temperature and high-pressure conversion reaction;

[0014] S5. Mixing the high-temperature and high-pressure conversion material with pure water and / or lithium precipitation mother liquor according to a liquid-solid ratio of 1:3-6, introducing carbon dioxide into a pressure hydrogenation reaction tower for hydrogenation reaction, filtering the obtained material to obtain a lithium-containing hydrogenation solution and sodium iron phosphate, and washing and drying the sodium iron phosphate to obtain a sodium iron phosphate product;

[0015] S6. After impurity removal, the lithium-containing hydrogenation solution is crystallized and lithium is precipitated in a negative pressure crystallizer, and the lithium carbonate slurry is subjected to solid-liquid separation to obtain a battery-grade lithium carbonate product.

[0016] Further, the lithium content in the lithium iron phosphate battery powder in S1 is ≥2.5 wt%, the copper content is ≤1.5 wt%, and the aluminum content is ≤2 wt%.

[0017] Further, the ammonium salt in S2 is one or a mixture of several of ammonium sulfate, ammonium bisulfate, ammonium carbonate, and ammonium bicarbonate.

[0018] Further, the copper removal reaction temperature in S2 is controlled at 20-80 °C.

[0019] Further, the temperature for the aluminum removal reaction in S3 is controlled at 50 - 90 °C.

[0020] Further, the conditions of high temperature and high pressure in S4 are: the reaction temperature is 120 - 250 °C, and the pressure is the saturated vapor pressure.

[0021] Further, the hydrogenation conditions in S5 are: the pressure in the hydrogenation reaction tower is controlled at 0.05 - 1 MPa, and the hydrogenation reaction time is 0.5 - 8 h.

[0022] Further, the negative pressure in the negative pressure crystallizer in S6 is controlled at 0.01 - 0.1 MPa, and the reaction temperature is 50 - 95 °C.

[0023] Advantages of the present invention:

[0024] The present invention discloses a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate. The retired lithium batteries are disassembled and crushed to obtain battery powder. After removing copper and aluminum, the battery powder is subjected to high-pressure conversion in a sodium carbonate solution. The converted material and water are slurried in a reaction kettle, and carbon dioxide is introduced for leaching to obtain sodium iron phosphate and a lithium-containing liquid. The lithium-containing liquid is purified and crystallized in a negative pressure crystallizer. The crystallized lithium carbonate is washed and dried to obtain battery-grade lithium carbonate. The method of the present invention selectively extracts lithium by completing ion exchange between sodium ions and lithium ions in the crystal structure of lithium iron phosphate under high temperature and high pressure. This method can regenerate sodium iron phosphate and high-purity lithium carbonate products for preparing battery materials. The lithium-containing liquid has a simple composition, a high lithium recovery rate, a simple process, and is easy to implement industrially. It realizes the efficient leaching of lithium elements and the efficient utilization of iron and phosphorus elements. The process is simple, without a large amount of acid and alkali consumption, has a high lithium recovery rate, simple production process control, and high purity of lithium carbonate.

[0025] The present invention realizes the transfer of lithium ions and sodium ions through high-temperature and high-pressure reactions to prepare sodium iron phosphate materials. The process route provided by the present invention is short, the quality of lithium carbonate is easy to control, and the lithium leaching efficiency is high. The liquid circulation utilization rate in the process of the present invention is high, and the amount of wastewater treatment is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following further describes the present invention with reference to the drawings.

[0027] Figure 1 is the process flow diagram of recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate according to the present invention;

[0028] Figure 2 is the XRD pattern of the battery-grade lithium carbonate obtained in Example 6 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] The present invention provides a process flow for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, as shown in Figure 1 shown.

[0031] Example 1

[0032] This example provides a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, including the following steps:

[0033] The retired lithium iron phosphate batteries are disassembled and crushed to obtain battery powder with Li = 2.5 wt%, Cu = 0.5 wt%, and Al = 1.0 wt%. The battery powder reacts with ammonium salt at a liquid-solid ratio of 2:1 according to n(NH4 + ):n(Li) = 1:1 at 20 °C to remove copper. After copper removal, the battery powder is mixed with a 0.5% sodium hydroxide solution by mass at a liquid-solid ratio of 2:1 and de-aluminized at 50 °C. After de-aluminization, the battery powder is mixed with sodium carbonate according to n(Na):n(Li) = 1:1 and subjected to a high-temperature and high-pressure conversion reaction at a liquid-solid ratio of 4:1 and 120 °C. The liquid-solid ratio of the high-temperature and high-pressure conversion material to pure water and / or lithium precipitation mother liquor is 1:3, and it is hydrogenated in a hydrogenation reaction tower at a pressure of 0.05 MPa for 0.5 h. The solid phase obtained from the reaction is washed and dried to obtain a sodium iron phosphate product. The lithium-containing hydrogenated liquid in the liquid phase is subjected to impurity removal and then crystallized to precipitate lithium in a crystallizer at a negative pressure of 0.01 MPa and a temperature of 50 °C, obtaining a battery-grade lithium carbonate product with Li2CO3% = 99.76%, and the lithium leaching rate reaches 99.5%.

[0034] Example 2

[0035] This example provides a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, including the following steps:

[0036] The retired lithium iron phosphate batteries are disassembled and crushed to obtain battery powder with a lithium content of 2.5 wt%, a copper content of 1.5%, and an aluminum content of 2%. The battery powder reacts with ammonium salt at a liquid-solid ratio of 6:1 according to n(NH4 +):n(Li)=3:1. The battery powder after copper removal is mixed with 1.5% sodium hydroxide solution at a liquid-solid ratio of 8:1, and aluminum removal is carried out at 65 °C. The battery powder after aluminum removal is mixed with sodium carbonate at a molar ratio of sodium to lithium elements of 6:1, and a high-temperature and high-pressure conversion reaction is carried out at a liquid-solid ratio of 4:1 and 210 °C. The ratio of the high-temperature and high-pressure conversion material to pure water and / or the lithium precipitation mother liquor is 1:4. Carbon dioxide is introduced into a hydrogenation reaction tower at a pressure of 0.5 MPa for a hydrogenation reaction for 1 h. The solid phase obtained from the reaction is washed and dried to obtain a sodium iron phosphate product. The lithium-containing hydrogenated liquid in the liquid phase is crystallized to precipitate lithium in a crystallizer heated to 65 °C under a negative pressure of 0.1 MPa after impurity removal, and a battery-grade lithium carbonate product with Li₂CO₃% = 99.53% is obtained, and the lithium leaching rate reaches 99.2%.

[0037] Example 3

[0038] This example provides a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, which includes the following steps:

[0039] The retired lithium iron phosphate battery is disassembled and crushed to obtain battery powder with Li = 3.2 wt%, Cu = 1.5 wt%, and Al = 2.0 wt%. The battery powder is mixed with an ammonium salt at a liquid-solid ratio of 10:1 according to n(NH₄ + ):n(Li)=10:1. Copper removal is carried out at 80 °C. The battery powder after copper removal is mixed with 2% sodium hydroxide solution at a liquid-solid ratio of 10:1, and aluminum removal is carried out at 90 °C. The battery powder after aluminum removal is mixed with sodium carbonate at a molar ratio of n(Na):n(Li)=10:1, and a high-temperature and high-pressure conversion reaction is carried out at a liquid-solid ratio of 8:?? and 250 °C. The liquid-solid ratio of the high-temperature and high-pressure conversion material to pure water and / or the lithium precipitation mother liquor is 1:6. Carbon dioxide is introduced into a hydrogenation reaction tower at a pressure of 1 MPa for a hydrogenation reaction for 8 h. The solid phase obtained from the reaction is washed and dried to obtain a sodium iron phosphate product. The lithium-containing hydrogenated liquid in the liquid phase is crystallized to precipitate lithium in a crystallizer heated to 95 °C under a negative pressure of 0.1 MPa after impurity removal, and a battery-grade lithium carbonate product with Li₂CO₃% = 99.56% is obtained, and the lithium leaching rate reaches 99.2%.

[0040] Example 4

[0041] This example provides a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, which includes the following steps:

[0042] The retired lithium iron phosphate battery is disassembled and crushed to obtain battery powder with Li =?? wt%, Cu = 1.0 wt%, and Al = 1.2 wt%. The battery powder is mixed with an ammonium salt at a liquid-solid ratio of 8:1 according to n(NH₄ + It should be noted that there seems to be an incomplete value in the "liquid-solid ratio = 8:??" part in the translation of Example 3. Please check and correct it if necessary.):n(Li)=3:1. React to remove copper at 40 °C. After copper removal, the battery powder is mixed with 1% sodium hydroxide solution according to a liquid-solid ratio of 6:1, and aluminum is removed at 70 °C. After aluminum removal, the battery powder is mixed with sodium carbonate according to n(Na):n(Li)=5:1, and a high-temperature and high-pressure conversion reaction is carried out at a liquid-solid ratio of 7:1 and 180 °C. The liquid-solid ratio of the high-temperature and high-pressure conversion material to pure water and / or lithium precipitation mother liquor is 1:4. Carbon dioxide is introduced into a hydrogenation reaction tower at a pressure of 0.5 MPa for a hydrogenation reaction for 2 h. The solid phase obtained from the reaction is washed and dried to obtain a sodium iron phosphate product. The lithium-containing hydrogenated liquid phase is purified and then lithium is crystallized out in a crystallizer at a negative pressure of 0.07 MPa and a temperature of 85 °C to obtain a battery-grade lithium carbonate product with Li₂CO₃% = 99.59%, and the lithium leaching rate reaches 99.1%.

[0043] Example 5

[0044] This example provides a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, which includes the following steps:

[0045] The retired lithium iron phosphate battery is disassembled and crushed to obtain battery powder with Li = 3.8 wt%, Cu = 0.5 wt%, and Al = 0.8 wt%. The battery powder is mixed with an ammonium salt according to a liquid-solid ratio of 4:1 according to n(NH₄ + ):n(Li)=2:1. React to remove copper at 50 °C. After copper removal, the battery powder is mixed with 1% sodium hydroxide solution according to a liquid-solid ratio of 5:1, and aluminum is removed at 60 °C. After aluminum removal, the battery powder is mixed with sodium carbonate according to n(Na):n(Li)=3:1, and a high-temperature and high-pressure conversion reaction is carried out at a liquid-solid ratio of 4:1 and 180 °C. The liquid-solid ratio of the high-temperature and high-pressure conversion material to pure water and / or lithium precipitation mother liquor is 1:6. Carbon dioxide is introduced into a hydrogenation reaction tower at a pressure of 0.5 MPa for a hydrogenation reaction for 8 h. The solid phase obtained from the reaction is washed and dried to obtain a sodium iron phosphate product. The lithium-containing hydrogenated liquid phase is purified and then lithium is crystallized out in a crystallizer at a negative pressure of 0.05 MPa and a temperature of 75 °C to obtain a battery-grade lithium carbonate product with Li₂CO₃% = 99.67%, and the lithium leaching rate reaches 99.0%.

[0046] Example 6

[0047] This example provides a method for recycling lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, which includes the following steps:

[0048] The retired lithium iron phosphate battery is disassembled and crushed to obtain battery powder with Li = 2.8 wt%, Cu = 1.1 wt%, and Al = 1.5 wt%. The battery powder is mixed with an ammonium salt according to a liquid-solid ratio of 4:1 according to n(NH₄ +: n(Li)=6:1. Copper is removed by reaction at 60°C. The battery powder after copper removal is mixed with 1% sodium hydroxide solution according to a liquid-solid ratio of 8:1, and aluminum is removed at 50°C. The battery powder after aluminum removal is mixed with sodium carbonate with n(Na):n(Li)=6:1, and a high-temperature and high-pressure conversion reaction is carried out at a liquid-solid ratio of 8:1 and 150°C. The liquid-solid ratio of the high-temperature and high-pressure conversion material to pure water and / or lithium precipitation mother liquor is 1:5. Carbon dioxide is introduced into a hydrogenation reaction tower at a pressure of 0.8 MPa for a hydrogenation reaction for 6 h. The solid phase obtained from the reaction is washed and dried to obtain a sodium iron phosphate product. The lithium-containing hydrogenated liquid in the liquid phase is crystallized to precipitate lithium in a crystallizer heated to 65°C under a negative pressure of 0.04 MPa after impurity removal, and a battery-grade lithium carbonate product with Li₂CO₃% = 99.53% is obtained, and the lithium leaching rate reaches 99.3%. The XRD pattern of the battery-grade lithium carbonate is shown in Figure 2 as shown.

[0049] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0050] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering lithium iron phosphate battery powder to prepare battery-grade lithium carbonate, characterized in that: The steps include: S1. Recycling retired lithium iron batteries to obtain lithium iron phosphate battery powder; S2. Mix lithium iron phosphate battery powder, water and ammonium salt in a molar ratio of ammonium salt to copper element of 1-10:1 and a liquid-to-solid ratio of 2-10:1, and stir in a reactor to remove copper; S3. The battery powder after copper removal is mixed with a sodium hydroxide solution with a mass fraction of 0.5-2% at a liquid-to-solid ratio of 2-10:1 to remove aluminum; S4, sodium carbonate and aluminum-removed battery powder are mixed in a sodium to lithium molar ratio of 1-10:1 and a liquid-to-solid ratio of 4-8:1, and a high-temperature and high-pressure conversion reaction is carried out; the high-temperature and high-pressure conditions are a reaction temperature of 120-250° C. and a pressure of saturated vapor pressure; S5. The material after high temperature and high pressure conversion is mixed with pure water and / or lithium precipitation mother liquor at a liquid-to-solid ratio of 1:3-6, and carbon dioxide is introduced into a pressure hydrogenation reaction tower for hydrogenation reaction. The material obtained by the reaction is filtered to obtain lithium-containing hydrogenation liquid and sodium iron phosphate, and the sodium iron phosphate is washed and dried to obtain a sodium iron phosphate product; the pressure of the hydrogenation reaction tower is controlled at 0.05-1MPa, and the hydrogenation reaction time is 0.5-8h; S6. After the lithium-containing hydride liquid is impurity-removed, lithium is crystallized in a negative pressure crystallizer, and the lithium carbonate slurry is subjected to solid-liquid separation to obtain a battery-grade lithium carbonate product.

2. The method for recovering lithium iron phosphate battery powder to prepare battery-grade lithium carbonate according to claim 1, characterized in that: The lithium content of the lithium iron phosphate battery powder in S1 is ≥2.5wt%, the copper content is ≤1.5wt%, and the aluminum content is ≤2wt%.

3. The method for recovering lithium iron phosphate battery powder to prepare battery-grade lithium carbonate according to claim 1, characterized in that: The ammonium salt in S2 is one or a mixture of ammonium sulfate, ammonium bisulfate, ammonium carbonate, and ammonium bicarbonate.

4. The method for recovering lithium iron phosphate battery powder to prepare battery-grade lithium carbonate according to claim 1, characterized in that: The copper removal reaction temperature in S2 is controlled at 20-80°C.

5. The method for recovering lithium iron phosphate battery powder to prepare battery-grade lithium carbonate according to claim 1, characterized in that: The temperature of the aluminum removal reaction in S3 is controlled at 50-90°C.

6. The method for recovering lithium iron phosphate battery powder to prepare battery-grade lithium carbonate according to claim 1, characterized in that: The negative pressure in the negative pressure crystallizer in S6 is controlled at 0.01-0.1 MPa, and the reaction temperature is 50-95°C.

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