Process method for recycling waste lithium iron phosphate positive electrode material based on hydrochloric acid

Abstract

The invention discloses a waste lithium iron phosphate positive electrode material recovery process method based on hydrochloric acid, and belongs to the field of waste lithium iron phosphate recovery. Comprising the following steps: S1, calcining the waste lithium iron phosphate positive electrode material; s2, adding hydrochloric acid into the calcined lithium iron phosphate material for soaking, washing iron phosphate residues, and collecting all liquid; s3, the Fe: P molar ratio of the iron phosphate residues is tested, if iron is insufficient, ferric trichloride is added for supplementing iron, and if phosphorus is insufficient, phosphoric acid is added for supplementing phosphorus; s4, adding concentrated hydrochloric acid to obtain a mixture; s5, heating the mixture, carrying out reflux condensation, after the solid is completely dissolved, raising the heating temperature, distilling out hydrogen chloride gas, collecting, and stopping heating when the liquid is concentrated to be viscous; and S6, adding water to obtain the hydrated iron phosphate. According to the method, the lithium element and the iron phosphate are recycled, alkali metal ion pollution is reduced, cyclic utilization of hydrogen chloride is achieved, and pollution emission is reduced.

Description

Technical Field

[0001] The present application relates to a hydrochloric acid-based waste lithium iron phosphate positive electrode material recovery process method, belonging to the field of waste lithium iron phosphate recovery. Background Art

[0002] In recent years, with the popularization of new energy vehicles, the problem of power battery scrapping has gradually become prominent. Among them, lithium iron phosphate power batteries, once one of the mainstream power batteries, have gradually entered the scrapping stage during their use, posing a potential threat to the environment and health. The valuable metal elements in the waste lithium iron phosphate positive electrode materials are separated and extracted by chemical or physical methods to achieve the recycling of materials. The advantage of this solution is that high-purity valuable metals can be obtained while reducing pollution to the environment. However, the key problems that need to be solved by this solution include low recovery rate of valuable metals, high cost, and possible secondary pollution. Therefore, it is necessary to provide a simple and effective way to recycle waste lithium iron phosphate materials. Summary of the Invention

[0003] Based on the above technical problems, this application proposes to recycle waste lithium iron phosphate cathode materials using hydrochloric acid of varying concentrations, ultimately obtaining lithium carbonate and hydrated iron phosphate products. First, the waste lithium iron phosphate cathode materials need to be calcined to remove conductive carbon and related organic matter, while also converting the divalent iron into trivalent iron, which facilitates subsequent processing.

[0004] For lithium ions (Li + ) is not much different from the conventional route. The general process is to soak the calcined lithium iron phosphate material in low concentration hydrochloric acid (5-10%). + Remove it into the solution, wash the iron phosphate residue, collect all the liquid, adjust the pH to 2-3 with sodium hydroxide, collect Fe(OH)3 and Al(OH)3 solids, add appropriate amount of sodium carbonate to the remaining liquid to obtain lithium carbonate, the temperature is 90℃, react, wash and filter to obtain lithium carbonate, and complete the recovery of lithium elements. Figure 1 The recycling process is shown in the left half.

[0005] This application is mainly to recycle the iron phosphate residue, such as Figure 1 The recycling process is shown in the right half. The specific steps are as follows:

[0006] 1) Test the Fe:P molar ratio of the ferric phosphate residue. If the iron is insufficient, add ferric chloride to supplement the iron. If the phosphorus is insufficient, add phosphoric acid to supplement the phosphorus. Strive to achieve a Fe:P ratio between 1:1.0 and 1.5.

[0007] 2) adding concentrated hydrochloric acid (20-35%) to the solid; when the pH is less than 1.5, the ferric phosphate dissolves; when the pH is greater than 1.5, the ferric phosphate precipitates; and controlling the amount of concentrated hydrochloric acid added to form a mixture with a liquid-to-solid mass ratio of 2.0 to 5.0;

[0008] 3) heating the mixture, first by reflux, until the solid is completely dissolved, the heating temperature is 80-100°C;

[0009] 4) Raise the heating temperature to 100-150°C, at which point hydrogen chloride gas is distilled out and collected. When the liquid is concentrated to a bright yellow viscous state and its volume is reduced to 10-20% of its original value, stop heating and begin adding pure water. The volume of the pure water should be 5-10 times that of the original concentrated hydrochloric acid. At this point, a large amount of hydrated iron phosphate (FePO4·2H2O) begins to be produced.

[0010] 5) In order to further promote the formation of FePO4·2H2O, a small amount of NaOH solution is added to the above mixed solution to make the pH between 1.5 and 2.0.

[0011] A hydrochloric acid-based method for recycling waste lithium iron phosphate cathode materials comprises the following steps:

[0012] S1 calcining the waste lithium iron phosphate positive electrode material to obtain a calcined lithium iron phosphate material;

[0013] S2: soaking the calcined lithium iron phosphate material in hydrochloric acid to wash the iron phosphate residue and collect all the liquid; the concentration of the hydrochloric acid is 5-10%;

[0014] S3 tests the Fe:P molar ratio of the ferric phosphate residue. If the iron is insufficient, ferric chloride is added to supplement the iron. If the phosphorus is insufficient, phosphoric acid is added to supplement the phosphorus so that Fe:P=1:1.0-1.5;

[0015] S4 adds concentrated hydrochloric acid to obtain a mixture; the concentration of the concentrated hydrochloric acid is 20-35%;

[0016] S5: heating the mixture by condensation reflux. After the solid is completely dissolved, the heating temperature is increased to distill out hydrogen chloride gas and collect it. When the liquid is concentrated to a viscous state, the heating is stopped.

[0017] S6 adds water to obtain hydrated iron phosphate.

[0018] Optionally, in step S4, the liquid-to-solid mass ratio of concentrated hydrochloric acid to ferric phosphate residue is 2.0-5.0:1.

[0019] Optionally, in step S4, the liquid-to-solid mass ratio of concentrated hydrochloric acid to ferric phosphate residue is independently selected from any value of 2.0:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, 4.5:1, 5.0:1, or any range between two values.

[0020] Optionally, in step S5, during condensation reflux, the heating temperature is 80-100°C, and the increased heating temperature is 100-150°C.

[0021] The difference between the increased heating temperature and the original heating temperature is 20 to 50°C.

[0022] Optionally, in step S5, heating is stopped when the liquid is concentrated to a viscous state and the volume is reduced to between 10% and 20% of the original volume.

[0023] Optionally, in step S6, the amount of water added is 5 to 10 times the volume of the concentrated hydrochloric acid added in step S4.

[0024] Optionally, step S6 further includes adding alkali to adjust the pH to between 1.5 and 2.0.

[0025] Optionally, in step S2, the concentration of hydrochloric acid is independently selected from any value among 5%, 6%, 7%, 8%, 9%, 10%, or any range between the two.

[0026] Optionally, in step S4, the concentration of hydrochloric acid is independently selected from any value among 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% or any range between two values.

[0027] In step S1, the waste lithium iron phosphate positive electrode material is calcined using conventional operating methods in the art.

[0028] In step S2, all liquids are collected for lithium ion (Li + ) is not much different from the conventional path.

[0029] The beneficial effects of this application include:

[0030] The hydrochloric acid-based waste lithium iron phosphate cathode material recovery process provided in this application has the following advantages: (1) the different reactivity of the product after calcination of waste lithium iron phosphate cathode material under different concentrations of hydrochloric acid is utilized to complete the recovery of lithium element and iron phosphate; (2) the use of large amounts of strong base is avoided, reducing alkali metal ion pollution; (3) the recycling of hydrogen chloride is realized, reducing pollution emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1This is a flow chart for recycling waste lithium iron phosphate cathode materials;

[0032] Figure 2 This is a scanning electron microscope (SEM) image of the hydrated ferric phosphate recovered in Example 1;

[0033] Figure 3 The XRD pattern of the hydrated iron phosphate recovered in Example 1 is shown. DETAILED DESCRIPTION

[0034] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0035] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0036] Unless otherwise specified, conventional methods were used for testing, and instrument settings were those recommended by the manufacturer.

[0037] Figure 1 This is a flow chart for recycling waste lithium iron phosphate positive electrode materials. The left half is the lithium element recovery process, and the right half is the iron phosphate recovery process.

[0038] Example 1

[0039] 1 kg of lithium iron phosphate electrode material (containing PVDF and conductive agent) peeled off from the positive electrode current collector (aluminum foil) was placed in a furnace for calcination in an air atmosphere at a temperature of 800°C for 6 hours to obtain the calcined lithium iron phosphate material.

[0040] Add 2kg of 8% hydrochloric acid to the calcined lithium iron phosphate material and soak it at 50℃ for 3h. + Basically soluble in hydrochloric acid solution, with a small amount of Fe 3+ and Al 3+ Dissolve it; filter, wash the iron phosphate residue twice, collect all the liquid, then adjust the pH to 2-3 with sodium hydroxide, collect Fe(OH)3 and Al(OH)3 solids, add appropriate amount of sodium carbonate to the remaining liquid, the temperature is 90°C, at this time the solubility of lithium carbonate is the lowest, react, wash and filter to obtain lithium carbonate, and complete the recovery of lithium elements.

[0041] Using inductively coupled plasma testing, it was found that the molar ratio of Fe:P was 1:0.9. At this time, an appropriate amount of phosphoric acid was added to adjust the molar ratio of Fe:P to 1:1.2; 31% hydrochloric acid was added in an amount of 3 kg, and the heating temperature was 98°C. The system was condensed and refluxed. After the iron phosphate residue was completely dissolved, the heating temperature was increased to 130°C, and a large amount of hydrogen chloride was discharged. It was condensed and collected for reuse; when the volume was concentrated to 20% of the original volume, a viscous bright yellow liquid appeared. The heating was stopped, 15 L of pure water was added, and FePO4·2H2O was generated. Finally, an appropriate amount of NaOH was added, the pH was adjusted to 1.5, and the solution was filtered, washed, and dried to obtain FePO4·2H2O.

[0042] The yield of FePO4·2H2O in this example is 95%; Figure 2 This is a scanning electron microscope image (SEM) of the recovered hydrated iron phosphate. Figure 3 This is the phase structure spectrum (XRD), the morphology is flake-like, and the phase is a standard hydrated iron phosphate structure.

[0043] Example 2: Effect of different hydrochloric acid concentrations on lithium recovery

[0044] Experimental conditions:

[0045] 1. Waste lithium iron phosphate electrode material: 1kg;

[0046] 2. Calcination conditions: 800°C, 6 hours;

[0047] 3. Hydrochloric acid concentration: 5%, 8%, 10%;

[0048] 4. Soaking temperature: 50℃;

[0049] 5. Soaking time: 3 hours.

[0050] Experimental steps:

[0051] 1. Soak the calcined lithium iron phosphate material in hydrochloric acid of different concentrations;

[0052] 2. Filter and wash the iron phosphate residue and collect the filtrate;

[0053] 3. Adjust the pH of the filtrate to 2-3 with sodium hydroxide to precipitate Fe(OH)3 and Al(OH)3;

[0054] 4. Add sodium carbonate to the remaining liquid and react at 90°C to obtain lithium carbonate. Experimental results:

[0055] 1.5% hydrochloric acid: lithium recovery rate is 90%, lithium carbonate purity is 98%;

[0056] 2. 10% hydrochloric acid: lithium recovery rate of 95%, lithium carbonate purity of 99%;

[0057] 3. 15% hydrochloric acid: lithium recovery rate of 92%, lithium carbonate purity of 98.5%.

[0058] Example 3: Effect of different temperatures on iron phosphate recovery

[0059] Experimental conditions:

[0060] 1. Waste old lithium iron phosphate electrode material: 1 kg;

[0061] 2. Calcination conditions: 800°C, 6 hours;

[0062] 3. Hydrochloric acid concentration: 31%;

[0063] 4. Heating temperature: 80°C, 90°C, 100°C;

[0064] 5. Reaction time: 2 hours.

[0065] Experimental steps:

[0066] 1. Adjust the Fe:P molar ratio of iron phosphate residue to 1:1.2;

[0067] 2. Add 31% hydrochloric acid, control the liquid-solid mass ratio to 3.0;

[0068] 3. Heat the reaction at different temperatures, collect hydrogen chloride gas;

[0069] 4. After the reaction is completed, add pure water to generate hydrated iron phosphate (FePO4·2H2O);

[0070] 5. Adjust the pH to 1.5 with NaOH, filter, wash and dry.

[0071] Experimental results:

[0072] 1. 80°C: FePO4·2H2O yield of 85%, purity of 99%;

[0073] 2. 100°C: FePO4·2H2O yield of 90%, purity of 99.5%;

[0074] 3. 120°C: FePO4·2H2O yield of 95%, purity of 99.8%.

[0075] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A hydrochloric acid-based waste lithium iron phosphate cathode material recovery process, characterized in that: The following steps are involved: S1 calcining the waste lithium iron phosphate positive electrode material to obtain a calcined lithium iron phosphate material; S2: soaking the calcined lithium iron phosphate material in hydrochloric acid to wash the iron phosphate residue and collect all the liquid; the concentration of the hydrochloric acid is 5-10%; S3 tests the Fe:P molar ratio of the ferric phosphate residue. If the iron is insufficient, ferric chloride is added to supplement the iron. If the phosphorus is insufficient, phosphoric acid is added to supplement the phosphorus so that Fe:P=1:1.0-1.5; S4 adds concentrated hydrochloric acid to obtain a mixture; the concentration of the concentrated hydrochloric acid is 20-35%; S5: heating the mixture by condensation reflux. After the solid is completely dissolved, the heating temperature is increased to distill out hydrogen chloride gas and collect it. When the liquid is concentrated to a viscous state, the heating is stopped. S6 adds water to obtain hydrated iron phosphate.

2. The method according to claim 1, characterized in that In step S4, the liquid-to-solid mass ratio of concentrated hydrochloric acid to ferric phosphate residue is 2.0-5.0:

1.

3. The method according to claim 1, characterized in that In step S5, during condensation reflux, the heating temperature is 80-100°C, and the increased heating temperature is 100-150°C.

4. The method according to claim 1, wherein In step S5, when the liquid is concentrated to a viscous state and its volume is reduced to between 10% and 20% of its original volume, heating is stopped.

5. The method according to claim 1, wherein In step S6, the amount of water added is 5 to 10 times the volume of the concentrated hydrochloric acid added in step S4.

6. The method according to claim 1, characterized in that Step S6 further includes adding alkali to adjust the pH to between 1.5 and 2.0.

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