Method for recycling waste lithium iron phosphate positive pole piece material
Through the separation, leaching, impurity removal and lithium precipitation processes of waste lithium iron phosphate positive electrode sheets, the problem of organic matter pollution was solved, the recovery of high-purity lithium carbonate was achieved, and the product quality and economic benefits were improved.
Patent Information
- Application Number
- CN202510721678.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-30
- Publication Date
- 2025-10-17
AI Technical Summary
The existing technology has difficulty in effectively removing organic substances such as PVDF and NMP when recycling waste lithium iron phosphate positive electrode plates, resulting in pollutants in the prepared lithium carbonate product, reducing product quality.
After crushing and separation, the process goes through the first and second stage leaching, impurity removal and lithium precipitation process, using sulfuric acid, hydrogen peroxide and alkali solution to control the pH value, combined with aeration and Fenton treatment, to separate and oxidize organic matter, and finally obtain high-purity lithium carbonate through sodium carbonate precipitation and crystallization.
While achieving efficient recovery of valuable metallic lithium, it effectively removes organic matter from the electrode, improves product purity and quality, reduces processing costs, and achieves a lithium recovery rate of over 90%.
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Figure CN120810045A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of wet recovery of waste lithium ion batteries, and particularly relates to a method for preparing lithium carbonate by preferentially extracting lithium from waste lithium iron phosphate positive electrode sheet materials. BACKGROUND
[0002] In recent years, lithium iron phosphate batteries have been greatly improved in energy density through various technical improvements, and have good cycle performance, low price, good safety, fast charging and other advantages. In recent years, the installed capacity of electric vehicles in China has been increasing year by year, and its proportion has exceeded that of ternary lithium ion batteries. At present, the recovery of waste lithium iron phosphate power batteries mainly adopts a wet process. The mainstream acid leaching method is to dissolve the pretreated waste lithium iron phosphate active material with acid solution, then purify and remove impurity elements such as aluminum and copper, and finally recover lithium in the leaching solution. The acid leaching method includes two routes: one is a full-element leaching process, which has the disadvantages of large reagent consumption, long process, high cost, and environmental unfriendliness; the other is a preferential lithium extraction process, which extracts only lithium in the leaching section, and the lithium phosphate iron is in the form of a precipitate as leaching residue for subsequent preparation of lithium phosphate iron or other uses, which has a cost advantage and can reduce environmental pressure.
[0003] During the preparation process of waste lithium iron phosphate batteries, a part of the waste positive electrode sheet is generated, and the waste positive electrode sheet is also generated during the manual stripping process of the waste lithium iron phosphate battery. The broken material of the waste lithium phosphate iron positive electrode sheet material during recovery and treatment is mostly positive electrode material such as lithium phosphate iron or lithium phosphate iron manganese, and also contains a certain amount of aluminum powder, conductive agent, and a small amount of organic substances such as binder PVDF (polyvinylidene fluoride) and solvent NMP (nitrogen methyl pyrrolidone). The organic substance such as NMP can be completely miscible with water, and PVDF can be partially dissolved. There is no organic removal process in the recovery process, resulting in a small amount of organic matter in the prepared lithium carbonate product, which can cause product pollution and reduce product quality. SUMMARY
[0004] In view of the above problems existing in the recovery of waste lithium iron phosphate positive electrode sheet, the present application provides a method for recovering waste lithium phosphate iron positive electrode sheet, which specifically comprises the following steps:
[0005] Step one: crushing the waste positive electrode sheet generated during the preparation of lithium iron phosphate batteries or the positive electrode sheet after the disassembly of the waste lithium iron phosphate battery to a particle size of less than 1 mm, and sorting out the waste lithium phosphate iron positive electrode powder containing a certain amount of aluminum powder, conductive agent, and a small amount of binder PVDF and solvent NMP;
[0006] Step two: one-stage leaching and organic removal: the crushed positive electrode powder is slurried with the second-stage leaching solution and washing water, one-stage leaching is carried out, sulfuric acid is first added for acid leaching, after the acid leaching is completed, air, oxygen-enriched air or pure oxygen is introduced through the air diffuser at the bottom of the reactor, and hydrogen peroxide is added at the same time, the terminal pH value is 3.0-3.5, the leaching time is 1-3 h, the leaching temperature is 55-65℃, after the leaching is completed, solid-liquid separation is carried out, and one-stage leaching solution and one-stage leaching residue are obtained;
[0007] Step three: two-stage leaching: after the one-stage leaching residue is slurried with washing water, sulfuric acid is added to control the leaching pH value to 1.5-2.0, leaching is carried out for 1-3 h, the leaching temperature is 55-60℃, after the leaching is completed, solid-liquid separation is carried out, two-stage leaching solution and two-stage leaching residue are obtained, the two-stage leaching residue is stored, and the two-stage leaching solution is returned to the one-stage leaching;
[0008] Step four: one-stage impurity removal: the one-stage leaching solution is added with alkali liquor to adjust the pH value to 4.5-7.0, the temperature is 60-70℃, reaction is carried out for 1-3 h, and solid-liquid separation is carried out to obtain one-stage impurity removal filtrate and one-stage impurity removal filter residue;
[0009] Step five: two-stage impurity removal: the one-stage impurity removal filtrate is continuously added with alkali liquor to adjust the pH value to 12.0-13.0, a small amount of sodium carbonate is added, reaction is carried out for 1-3 h, and solid-liquid separation is carried out to obtain two-stage impurity removal solution;
[0010] Step six: lithium precipitation: the two-stage impurity removal solution is added into a lithium precipitation kettle, heated to 90-100℃, and sodium carbonate solution is added, precipitation is carried out for 50-80 min, centrifugal separation and washing are carried out, and drying is carried out to obtain sodium carbonate products;
[0011] Step seven: crystallization: the lithium precipitation filtrate is evaporated and crystallized to obtain sodium sulfate products.
[0012] As a further preferred embodiment of the present application, the acid addition amount of the positive electrode powder one-stage leaching in step two is 150-180 mL of 98% sulfuric acid per kg of positive electrode powder, the air diffuser is installed below the stirring paddle at the bottom of the one-stage leaching reactor, and the organic substances such as binders and conductive agents in the positive electrode powder are removed by Fenton method.
[0013] As a further preferred embodiment of the present application, the solid-liquid separation in steps four and five both adopts precision filtration, wherein the filter membrane pore size is ≤0.45 μm, so that the concentration of suspended solids in the filtrate is ≤10 ppm.
[0014] As a further preferred embodiment of the present application, the concentration of the sodium carbonate solution in step six is 320-350 g / L, the lithium precipitation filtrate is adjusted to a pH value of 7.0, evaporated and concentrated, solid-liquid separated, and crystalline sodium sulfate is obtained.
[0015] The present application provides a method for recovering waste lithium iron phosphate positive electrode sheets, which has the following characteristics and advantages:
[0016] (1) After the waste lithium iron phosphate positive electrode pieces are crushed and separated, the positive electrode powder is obtained. The material is of high purity and contains a small amount of aluminum, conductive agent and organic matter. The positive electrode powder is first leached with sulfuric acid to leach the lithium iron phosphate in the material into divalent iron and lithium sulfate, and manganese, aluminum, etc. are dissolved into aluminum sulfate and manganese sulfate, etc. The leachate is aerated and hydrogen peroxide is added to oxidize the leached ferrous ions into trivalent iron. By controlling the pH value of the leachate, the trivalent iron is precipitated as iron slag in the form of iron phosphate, and the solution is a relatively pure lithium sulfate solution. Sulfuric acid and hydrogen peroxide are added separately to leach out a portion of iron and lithium first. The hydrogen peroxide addition process simultaneously leaches, oxidizes iron and precipitates iron, which can improve the utilization rate of hydrogen peroxide and reduce the amount of hydrogen peroxide used;
[0017] (2) The solution contains a large amount of divalent iron, which can react with hydrogen peroxide to degrade the organic matter in the system. There is no need to add other Fenton reagents separately to achieve the purpose of decomposing the organic matter in the material. The small amount of organic matter contained in the solution can be oxidized and removed, thereby improving the grade and quality of the lithium carbonate product. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Attachment Figure 1 This is a process flow chart for recycling waste lithium iron phosphate positive electrode sheets of the present invention. DETAILED DESCRIPTION
[0019] A certain amount of waste lithium iron phosphate positive electrode sheets were collected and mechanically crushed and separated to obtain waste lithium iron phosphate positive electrode powder, which was used as the raw material for the example. 200g / L sodium hydroxide and 350g / L sodium carbonate solution were prepared for use.
[0020] Example 1
[0021] 100 g of waste lithium iron phosphate positive electrode powder was added to 300 mL of the second-stage leachate for slurry preheating and then 15.4 mL of sulfuric acid was added for leaching. The leaching temperature was 55 ° C and the leaching time was 1 hour. The leachate mainly contained phosphorus, iron and lithium, and also contained a small amount of aluminum and dissolved organic matter. After leaching for 1 hour, aeration was started and 20 ml of hydrogen peroxide was added at the same time. The reaction time was 1 hour and the end pH value was 3.0. After the leaching was completed, the solid-liquid separation was carried out to obtain a first-stage leachate and a first-stage leach residue. The first-stage leach residue was slurried with wash water and 2 ml of sulfuric acid was added to control the pH value to about 2.0 for the second-stage leaching. The leaching time was 1 hour. After the leaching was completed, the solid-liquid separation was carried out to obtain a second-stage leachate and a second-stage leach residue. The second-stage leachate was returned to the first-stage leaching.
[0022] The pH value of the first-stage leaching solution was adjusted to 7.0 by adding alkali solution, and the reaction time was 1 hour. After filtration, a first-stage impurity-removed liquid and a first-stage impurity-removed residue were obtained. The first-stage impurity-removed liquid was further adjusted to a pH value of 12.5 by adding alkali solution, and 1g of sodium carbonate was added at the same time. The reaction time was 1 hour. The impurity removal process temperature was 60-70°C, and the solid-liquid was separated to obtain a second-stage impurity-removed solution.
[0023] The impurity removal liquid is heated to 95 DEG C, 320 g / L sodium carbonate is added, the reaction time is 1 h, solid-liquid separation is carried out, and the lithium carbonate product meeting the composition requirements of the battery grade product is obtained.
[0024] The lithium precipitation liquid is evaporated and concentrated, the pH value is adjusted to about 7.0, and sodium sulfate product is obtained through crystallization.
[0025] The method for recycling waste lithium iron phosphate positive electrode piece material provided by the embodiment of the application effectively removes the organic matter contained in the piece while recycling the valuable metal, has simple process, low processing cost, lithium recovery rate of more than 90%, and recycled product purity of 99.74%.
[0026] Example 2
[0027] The waste lithium iron phosphate positive electrode piece powder 1000 g is slurried and preheated by adding two-stage leaching liquid 2500 mL, and then sulfuric acid 160 mL is added for leaching, the leaching temperature is 60 DEG C, leaching is carried out for 2 h, then aeration is started, and hydrogen peroxide 200 mL is added, the reaction time is 2 h, the terminal pH value is 3.3, after leaching is completed, solid-liquid separation is carried out, and the first-stage leaching liquid and the first-stage leaching residue are obtained; the first-stage leaching residue is slurried by adding washing water, sulfuric acid 23 mL is added to control the pH value to about 1.70 for second-stage leaching, the leaching time is 2 h, after leaching is completed, solid-liquid separation is carried out, and the second-stage leaching liquid and the second-stage leaching residue are obtained, and the second-stage leaching liquid is returned to the first-stage leaching.
[0028] The first-stage leaching liquid is adjusted to the pH value of 5.0 by adding alkali liquid, the reaction time is 2 h, after filtration, the first-stage impurity removal liquid and the first-stage impurity removal residue are obtained, the first-stage impurity removal liquid continues to be adjusted to the pH value of 13 by adding alkali liquid, 10 g of sodium carbonate is added at the same time, the reaction time is 2 h, the impurity removal process temperature is 60-70 DEG C, solid-liquid separation is carried out, and the second-stage impurity removal solution is obtained.
[0029] The impurity removal liquid is heated to 94 DEG C, 330 g / L sodium carbonate is added, the reaction time is 50 min, solid-liquid separation is carried out, and the lithium carbonate product meeting the composition requirements of the battery grade product is obtained.
[0030] The lithium precipitation liquid is evaporated and concentrated, the pH value is adjusted to about 7.0, and sodium sulfate product is obtained through crystallization.
[0031] The method for recycling waste lithium iron phosphate positive electrode piece material provided by the embodiment of the application effectively removes the organic matter contained in the piece while recycling the valuable metal, has simple process, low processing cost, lithium recovery rate of more than 90%, and recycled product purity of 99.69%.
[0032] Example 3
[0033] The waste lithium iron phosphate positive electrode piece powder 3000 kg is slurried and preheated by adding two-stage leaching liquid 9 m 3, after slurry, add sulfuric acid 480L to leach, leaching temperature 65℃, leaching time 3h, then start aeration, while adding hydrogen peroxide 600L, reaction time 3h, end point pH value 3.5, after leaching, solid-liquid separation, to obtain a first leaching solution and a first leaching residue; the first leaching residue is slurried with washing water, and sulfuric acid 80L is added to control the pH value to about 1.5 to carry out second leaching, leaching time 3h, after leaching, solid-liquid separation, to obtain a second leaching solution and a second leaching residue, and the second leaching solution is returned to the first leaching.
[0034] The first leaching solution is added with lye to adjust the pH value to 6.0, reaction time 3h, after filtration, a first impurity removal solution and a first impurity removal residue are obtained, the first impurity removal solution is continuously added with lye to adjust the pH value to 12.5, 200g of sodium carbonate is weighed, dissolved in water and then added into the reaction kettle, reaction time 3h, impurity removal process temperature 60-70℃, solid-liquid separation, to obtain a second impurity removal solution.
[0035] The impurity removal solution is heated to a temperature of 98℃, 350g / L of sodium carbonate is added, reaction time 80min, to obtain a lithium carbonate product meeting the composition requirements of a battery grade product.
[0036] The lithium precipitation filtrate is evaporated and concentrated to adjust the pH value to about 7.0, and sodium sulfate product is obtained by crystallization.
[0037] The method for recycling waste lithium iron phosphate positive electrode sheet material provided by the embodiments of the present application can effectively remove the organic matter contained in the electrode sheet while recycling valuable metals, and has the advantages of simple process, low processing cost, lithium recovery rate of 90% or more, and product purity of 99.76%.
[0038] The lithium carbonate product compositions obtained by the embodiments are shown in Table 1, and all meet the requirements of a battery grade lithium carbonate.
[0039] Table 1
[0040]
[0041]
[0042] The above embodiments are only used to illustrate the technical solutions of the present application and are not limiting, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the present application, and all should be covered in the scope of the claims of the present application.
Claims
1. A method for recycling waste lithium iron phosphate positive electrode sheet materials, comprising the following steps: Step 1: crush the waste positive electrode sheets generated in the process of preparing lithium iron phosphate batteries or the positive electrode sheets after disassembling waste lithium iron phosphate batteries to a particle size of less than 1 mm, and select the waste lithium iron phosphate positive electrode powder containing a certain amount of aluminum powder, a conductive agent, and a small amount of binder PVDF and solvent NMP; Step 2: Primary leaching and organic removal: The crushed cathode powder is slurried with the second-stage leachate and washing water for primary leaching. Sulfuric acid is first added for acid leaching. After the acid leaching is completed, air, enriched oxygen or pure oxygen is introduced through the aeration plate at the bottom of the reactor, and hydrogen peroxide is added at the same time. The end point pH value is 3.0-3.5, the leaching time is 1-3 hours, and the leaching temperature is 55-65°C. After the leaching is completed, the solid-liquid separation is performed to obtain a primary leachate and a primary leach residue; Step 3: Secondary leaching: After the primary leaching residue is slurried with washing water, sulfuric acid is added to control the leaching pH value to 1.5-2.0, and the leaching is carried out for 1-3 hours at a leaching temperature of 55-60°C. After the leaching is completed, the solid-liquid separation is carried out to obtain the secondary leaching liquid and the secondary leaching residue. The secondary leaching residue is stored and the secondary leaching liquid returns to the primary leaching; Step 4: First stage impurity removal: add alkali solution to the first stage leachate to adjust the pH value to 4.5-7.0, the temperature is 60-70°C, react for 1-3 hours, and separate the solid and liquid to obtain the first stage impurity removal filtrate and the first stage impurity removal residue; Step 5: Second stage impurity removal: Alkaline solution is added to the first stage impurity removal filtrate to adjust the pH value to 12.0-13.0, and a small amount of sodium carbonate is added. The reaction is carried out for 1-3 hours, and the solid-liquid separation is carried out to obtain the second stage impurity removal liquid; Step 6: Lithium precipitation: Add the second stage impurity removal solution into the lithium precipitation kettle, heat to 90-100°C and add sodium carbonate solution, precipitate for 50-80 minutes, centrifuge and wash and dry to obtain sodium carbonate product; Step 7: Crystallization: Evaporate and crystallize the lithium precipitation filtrate to obtain sodium sulfate product.
2. The method for recycling waste lithium iron phosphate positive electrode sheets according to claim 1, characterized in that: The amount of acid added for the first-stage leaching of the positive electrode powder in step 2 is 150-180 mL / kg of 98% sulfuric acid. The aeration plate is installed below the stirring paddle at the bottom of the first-stage leaching reactor to remove organic substances such as binders and conductive agents in the positive electrode powder through the Fenton method.
3. The method for recycling waste lithium iron phosphate positive electrode sheets according to claim 1, characterized in that: The solid-liquid separation in steps 4 and 5 is carried out by precision filtration, wherein the pore size of the filter membrane is ≤0.45 μm, so that the concentration of suspended matter in the filtrate is ≤10 ppm.
4. The method for recycling waste lithium iron phosphate positive electrode sheets according to claim 1, characterized in that: The concentration of the sodium carbonate solution in step six is 320-350 g / L. The pH value of the filtrate after lithium precipitation is adjusted to 7.0, and evaporation concentration and solid-liquid separation are performed to obtain crystalline sodium sulfate.