Wet recovery method for waste lithium battery

Abstract

The invention discloses a method for wet recovery of waste lithium batteries, and relates to the technical field of lithium battery recovery. The method comprises the following steps: 1, mixing lithium iron phosphate positive electrode powder with an acidic solution, introducing ozone, stirring, and carrying out a reaction; and 2, after the reaction is finished, carrying out vacuum filtration and carrying out solid-liquid separation to obtain a lithium-containing filtrate and an iron-containing filter cake. The method has the beneficial effects that the problems that waste lithium iron phosphate batteries are stacked, high-concentration acid and alkali leaching waste liquid pollutes soil and water quality, and large-scale recycling and sustainable development are not facilitated are solved, and the separation rate is high by adopting the method.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery recycling, and in particular to a method for wet recycling of waste lithium batteries. Background Art

[0002] With the rapid development of the new energy vehicle industry, demand for lithium-ion batteries continues to grow, leading to a massive accumulation of used batteries, and the heavy metals they contain are causing significant soil pollution. Effectively recovering rare metals from used lithium-ion batteries has become a key research focus. Lithium battery recycling requires disassembly, metal leaching, and separation. Currently, the technologies used in the lithium recovery and refining industry primarily include pyrometallurgy, hydrometallurgy, and biometallurgy. These processes are complex, costly, and environmentally harmful. Pyrometallurgy requires high temperatures, resulting in significant waste and primarily oxide-based products, making them difficult to directly utilize. Biometallurgy is significantly more limited. While it can accurately and environmentally extract valuable metals, it requires a long reaction time and a demanding microbial culture environment. Hydrometallurgy, with its advantages of low energy consumption, high metal recovery rates, and high product purity, is the most widely used battery recycling technology. However, the large amounts of acid and alkali in the reaction wastewater can pollute the environment.

[0003] Lithium iron phosphate batteries have the advantages of high operating voltage, high energy density, long cycle life, and high safety. They have broad application prospects in the fields of new energy vehicles and energy storage. Because lithium iron phosphate batteries do not contain precious metals such as cobalt and nickel, there are few companies that recycle LFP. However, waste lithium iron phosphate batteries have piled up into mountains, posing certain hidden dangers to the environment, and the recovery of lithium resources is also imminent. The traditional acid leaching method of recycling is to first leach all the metal ions in LFP into the solution and then separate them by precipitation. Although solubility can be used to separate them, the ions affect each other, the separation rate is low, and the steps are cumbersome. Therefore, it is of great significance to develop an environmentally friendly acid leaching reaction with low acid concentration to recycle waste lithium iron phosphate batteries. Summary of the Invention

[0004] The present invention aims to address the aforementioned technical deficiencies by providing a wet-process recycling method for waste lithium batteries. This method addresses the problem of waste lithium iron phosphate batteries piling up into mountains, polluting soil and water with high-concentration acid and alkali leaching wastewater, and hindering large-scale sustainable recycling. This method achieves a high separation rate.

[0005] The technical solution adopted by the present invention is to provide a method for wet recycling of waste lithium batteries, comprising the following steps:

[0006] Step 1: Mix lithium iron phosphate cathode powder with an acidic solution, introduce ozone and stir to react;

[0007] Step 2: After the reaction is completed, vacuum filtration is performed to separate the solid and liquid to obtain a lithium-containing filtrate and an iron-containing filter cake.

[0008] Further optimizing the technical solution, in step 1 of a method for wet recycling of waste lithium batteries, the acidic solution is 0.1-0.8 mol / L sulfuric acid, 10-21 g of lithium iron phosphate positive electrode powder and 100 mL of sulfuric acid are weighed and mixed evenly in a three-necked flask; then, the outlet valve of the oxygen cylinder, the ozone generator, the fume hood, and the water bath constant temperature magnetic stirrer are opened in sequence, and ozone is continuously introduced into the low-concentration sulfuric acid environment.

[0009] To further optimize this technical solution, a method for wet recovery of waste lithium batteries is provided in which a glass rotor flowmeter is connected before ozone is introduced into the three-necked flask to control the ozone flux to be maintained at 0.1-1.0 L / min.

[0010] To further optimize the technical solution, a method for wet recycling of waste lithium batteries is provided in which lithium iron phosphate positive electrode powder and sulfuric acid are first reacted in a three-necked flask at a water bath temperature of 30-80°C for 0.5-2h, and then magnetic stirring is turned on at a stirring speed of 5-20r / min.

[0011] To further optimize the present technical solution, in step 2 of a method for wet recycling of waste lithium batteries, the separated lithium-containing filtrate is adjusted to 85-95°C in a water bath, and then lithium carbonate is added to the lithium-containing filtrate, wherein the amount of lithium carbonate is greater than the amount that can precipitate lithium. Then, magnetic stirring is turned on, and plastic wrap is covered, and multiple holes are poked in the plastic wrap to carry out the reaction; wherein the above-mentioned reaction time is 0.5-2.0h, and the stirring speed during this period is 5-13rpm; the reaction product is vacuum filtered, and the filter cake product is washed multiple times with prepared boiling deionized water; the washed filter cake product is placed in a vacuum drying oven, and the temperature is set to 115-125°C and the time is 11.5-13h.

[0012] To further optimize this technical solution, in step 2 of a method for wet recycling of waste lithium batteries, the separated iron-containing filter cake is mainly iron phosphate, which is first dried in a constant temperature forced air drying oven for 22-24 hours, then placed in a muffle furnace and calcined at 500-600°C for 4-6 hours.

[0013] To further optimize the technical solution, in step 2 of a method for wet recycling of waste lithium batteries, the lithium-containing filtrate needs to be heated and concentrated to the volume of the solution in the acid leaching reaction.

[0014] To further optimize the technical solution, in a method for wet recovery of waste lithium batteries, the pH value of the lithium-containing filtrate is adjusted to 5-6 before heating and concentration, and the pH value of the lithium-containing filtrate is adjusted to 9-10 after heating and concentration.

[0015] To further optimize this technical solution, in a method for wet recycling of waste lithium batteries, when precipitation is produced, vacuum filtration is required to separate the solid and liquid.

[0016] To further optimize this technical solution, a method for wet recycling of waste lithium batteries has a constant volume of sulfuric acid, and the liquid-solid ratio is increased by adding lithium iron phosphate positive electrode powder, the mass of the lithium iron phosphate positive electrode powder is 8-16g.

[0017] Compared with the traditional recycling method, the present invention has the following advantages:

[0018] 1. Compared with the existing technology, the reaction designed in the present invention is to introduce ozone into low-concentration sulfuric acid. The concentration of the acid is very low, and the subsequent treatment is relatively simple. When excessive ozone is introduced, it will be discharged into the atmosphere and easily decomposed into oxygen. This green economy is very worthy of promotion.

[0019] 2. In an acidic environment, ozone is extremely oxidizing. From the perspective of redox potential, the redox potential of ozone (E=2.07eV) is higher than that of Fe in LFP. 2+ (E=-0.3eV), electrons will flow from low potential to high potential, so ozone can directly oxidize Fe 2+ Fe 3+ ; When the charge is saturated, Li + It falls off from the solid structure of the lithium iron phosphate cathode powder, and the solid structure remains unchanged during the selective leaching of lithium, thus achieving the direct conversion of the lithium iron phosphate cathode powder into iron phosphate;

[0020] 3. A large amount of lithium remains in the solution, and a large amount of iron remains in the solid, so the lithium can be easily separated for subsequent precipitation; from the XRD diagram, the main diffraction peaks of lithium carbonate and iron phosphate are very strong, which also shows that the purity of the solid is very high, and the separated iron phosphate can also be reused in the production of lithium iron phosphate positive electrode powder batteries; the present invention realizes the green recycling technology of waste lithium iron phosphate batteries without introducing organic components. While recycling lithium resources, the spatial molecular structure of iron phosphate is not destroyed. After washing and purification, it can be directly introduced into the downstream lithium battery production link as a product; while directly repairing the positive electrode material of waste power batteries, it greatly saves the cost of battery recycling, and provides a new low-cost, environmentally friendly recycling technology for the rapidly expanding lithium industry chain, promoting the healthy development of the lithium industry chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of the lithium iron phosphate positive electrode powder of the present invention;

[0022] Figure 2 This is an SEM image of the filter cake product after acid leaching of the present invention;

[0023] Figure 3 This is the XRD diagram of the lithium precipitated product of the present invention;

[0024] Figure 4 is the XRD pattern of the filter cake product after acid leaching of the present invention;

[0025] Figure 5 Flow chart of the preparation process of the present invention; DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1-5 As shown, a method for wet recycling of waste lithium batteries comprises the following steps:

[0028] Step 1: Mix lithium iron phosphate cathode powder with an acidic solution, introduce ozone and stir to react;

[0029] Step 2: After the reaction is completed, vacuum filtration is performed to separate the solid and liquid to obtain a lithium-containing filtrate and an iron-containing filter cake;

[0030] In step 1, the acidic solution is 0.1-0.8 mol / L sulfuric acid, 10-21 g of lithium iron phosphate positive electrode powder and 100 mL of sulfuric acid are weighed and mixed evenly in a three-necked flask; then the outlet valve of the oxygen cylinder, the ozone generator, the fume hood and the water bath constant temperature magnetic stirrer are opened in sequence, and ozone is continuously introduced into the low concentration sulfuric acid environment;

[0031] Before ozone is introduced into the three-necked flask, a glass rotor flowmeter is connected to control the ozone flux to maintain at 0.1-1.0 L / min;

[0032] Lithium iron phosphate cathode powder and sulfuric acid are first reacted in a three-necked flask at a water bath temperature of 30-80°C for 0.5-2h, and then magnetic stirring is turned on at a stirring speed of 5-20r / min;

[0033] In step 2, the separated lithium-containing filtrate is adjusted to 85-95° C. in a water bath, and then lithium carbonate is added to the lithium-containing filtrate, the amount of lithium carbonate being greater than the amount capable of precipitating lithium, and then magnetic stirring is turned on, and the plastic wrap is covered, and multiple holes are poked in the plastic wrap to react; wherein the above-mentioned reaction time is 0.5-2.0 hours, and the stirring speed during the reaction is 5-13 rpm; the reaction product is vacuum filtered, and the filter cake product is washed multiple times with prepared boiling deionized water; the washed filter cake product is placed in a vacuum drying oven, and the temperature is set to 115-125° C. and the time is 11.5-13 hours;

[0034] In step 2, the separated iron-containing filter cake is mainly iron phosphate, which is first dried in a constant temperature forced air drying oven for 22-24 hours, and then placed in a muffle furnace and calcined at 500-600°C for 4-6 hours;

[0035] In step 2, the lithium-containing filtrate needs to be heated and concentrated to the volume of the solution in the acid leaching reaction;

[0036] The pH value of the lithium-containing filtrate is adjusted to 5-6 before heating and concentrating, and the pH value of the lithium-containing filtrate is adjusted to 9-10 after heating and concentrating;

[0037] When precipitation occurs, vacuum filtration is required to separate the solid and liquid;

[0038] The volume of sulfuric acid is constant, and the liquid-solid ratio is increased by adding lithium iron phosphate positive electrode powder, and the mass of the lithium iron phosphate positive electrode powder is 8-16g.

[0039] Leaching was performed using low-concentration sulfuric acid and ozone. Using a single-factor approach, the effects of multiple process conditions, including the sulfuric acid to cathode powder mass ratio, sulfuric acid concentration, ozone flux, temperature, and reaction time, on lithium leaching yield were systematically investigated. Leaching conditions were optimized, and samples were taken and diluted during the reaction for analysis by ICP-OES. Low-concentration sulfuric acid addresses the potential for secondary pollution caused by the extensive use of acids and alkalis in hydrometallurgy. Using ozone as an oxidant, lithium is more easily removed from the solid in a sulfuric acid environment. Furthermore, excess ozone decomposes into oxygen upon release into the atmosphere, aligning with environmental principles. After the leaching reaction, vacuum filtration is performed, and the filtrate is used for lithium precipitation. The filter cake is then calcined at high temperature. Finally, XRD analysis is performed to determine the purity, properties, and particle size of the collected solid. This approach addresses the issue of the accumulation of spent lithium iron phosphate batteries and the contamination of soil and water by high-concentration acid and alkali leaching wastewater, which hinders large-scale recycling and sustainable development.

[0040] Example 1

[0041] This embodiment provides a method for wet recycling of waste lithium batteries, comprising the following steps:

[0042] Step 1: Weigh 12.357 g of lithium iron phosphate cathode powder and 100 mL of 0.5 mol / L sulfuric acid in a three-necked flask and mix them evenly;

[0043] Open the outlet valve of the oxygen cylinder, the ozone generator, the fume hood, and the water bath constant temperature magnetic stirrer in sequence to continuously introduce ozone into the low-concentration sulfuric acid environment. Before introducing ozone into the three-necked flask, connect a glass rotor flowmeter to control the ozone flux to maintain at 0.6 L / min.

[0044] The reaction was carried out in a water bath at 60°C for 30 min, magnetic stirring was turned on, and the stirring speed was 10. Samples were taken every 5 min during this period, and they were diluted and sent for ICP detection in time.

[0045] Step 2: After vacuum filtration, lithium-containing filtrate A and iron-containing filter cake B are obtained.

[0046] Example 2

[0047] This embodiment provides a method for wet recycling of waste lithium batteries, comprising the following steps:

[0048] Step 1: Weigh 10.019 g of lithium iron phosphate positive electrode powder and 100 mL of 0.4 mol / L sulfuric acid in a three-necked flask and mix them evenly;

[0049] Open the outlet valve of the oxygen cylinder, the ozone generator, the fume hood, and the water bath constant temperature magnetic stirrer in sequence to continuously introduce ozone into the low-concentration sulfuric acid environment. Before introducing ozone into the three-necked flask, connect a glass rotor flowmeter to control the ozone flux to maintain at 1.0 L / min.

[0050] The reaction was carried out in a water bath at 60°C for 25 min, and magnetic stirring was turned on at a stirring speed of 10. Samples were taken every 5 min during this period and diluted and sent for ICP detection in a timely manner.

[0051] Step 2: After vacuum filtration, lithium-containing filtrate A and iron-containing filter cake B are obtained.

[0052] Example 3

[0053] This embodiment provides a method for wet recycling of waste lithium batteries, comprising the following steps:

[0054] Step 1: Weigh 15.156 g of lithium iron phosphate positive electrode powder and 100 mL of 0.5 mol / L sulfuric acid in a three-necked flask and mix them evenly;

[0055] Open the outlet valve of the oxygen cylinder, the ozone generator, the fume hood, and the water bath constant temperature magnetic stirrer in sequence to continuously introduce ozone into the low-concentration sulfuric acid environment. Before introducing ozone into the three-necked flask, connect a glass rotor flowmeter to control the ozone flux to maintain at 0.9 L / min.

[0056] The reaction was carried out in a water bath at 60°C for 60 min, magnetic stirring was turned on, and the stirring speed was 10. Samples were taken every 15 min during this period, and they were diluted and sent for ICP detection in time.

[0057] Step 2: After vacuum filtration, lithium-containing filtrate A and iron-containing filter cake B are obtained.

[0058] Comparative Example 1

[0059] This comparative example provides a method for wet recycling of waste lithium batteries, comprising the following steps:

[0060] Step 1: Weigh 12.394 g of lithium iron phosphate cathode powder and 100 mL of 0.1 mol / L sulfuric acid in a three-necked flask and mix them evenly;

[0061] Open the outlet valve of the oxygen cylinder, ozone generator, fume hood and water bath constant temperature magnetic stirrer in sequence, and continuously introduce ozone into the above low concentration sulfuric acid environment. Before introducing into the three-necked flask, connect a glass rotor flowmeter to control the ozone flux to maintain at 0.1L / min.

[0062] The reaction was carried out in a water bath at 40°C for 25 min, and magnetic stirring was turned on at a stirring speed of 10. During this period, samples were taken every 5 min, and diluted and sent for ICP detection in time.

[0063] Step 2: After vacuum filtration, lithium-containing filtrate A and iron-containing filter cake B are obtained.

[0064] Comparative Example 2

[0065] The flow chart of its preparation process is as follows Figure 5 As shown;

[0066] This comparative example provides a method for wet recycling of waste lithium batteries, comprising the following steps:

[0067] Step 1: Weigh 12.342 g of lithium iron phosphate positive electrode powder and 100 mL of 0.2 mol / L sulfuric acid in a three-necked flask and mix them evenly;

[0068] Open the outlet valve of the oxygen cylinder, the ozone generator, the fume hood, and the water bath constant temperature magnetic stirrer in sequence to continuously introduce ozone into the low-concentration sulfuric acid environment. Before introducing ozone into the three-necked flask, connect a glass rotor flowmeter to control the ozone flux to maintain at 0.6 L / min.

[0069] The reaction was carried out in a water bath at 60°C for 30 min, magnetic stirring was turned on, and the stirring speed was 10. Samples were taken every 5 min during this period, and they were diluted and sent for ICP detection in time.

[0070] Step 2: After vacuum filtration, lithium-containing filtrate A and iron-containing filter cake B are obtained.

[0071] Comparative Example 3

[0072] The flow chart of its preparation process is as follows Figure 5 As shown;

[0073] This comparative example provides a method for wet recycling of waste lithium batteries, comprising the following steps:

[0074] Step 1: Weigh 21.218 g of lithium iron phosphate cathode powder and 100 mL of 0.7 mol / L sulfuric acid in a three-necked flask and mix them evenly;

[0075] Open the outlet valve of the oxygen cylinder, the ozone generator, the fume hood, and the water bath constant temperature magnetic stirrer in sequence to continuously introduce ozone into the low-concentration sulfuric acid environment. Before introducing ozone into the three-necked flask, connect a glass rotor flowmeter to control the ozone flux to maintain at 0 L / min.

[0076] The reaction was carried out in a water bath at 60°C for 120 min, magnetic stirring was turned on, and the stirring speed was 10. Samples were taken every 15 min during this period, and they were diluted and sent for ICP detection in time.

[0077] Step 2: After vacuum filtration, lithium-containing filtrate A and iron-containing filter cake B are obtained.

[0078] Comparative Example 4

[0079] This comparative example provides a method for wet recycling of waste lithium batteries, comprising the following steps:

[0080] Step 1: Weigh 15.168 g of lithium iron phosphate cathode powder and 100 mL of 0.8 mol / L sulfuric acid in a three-necked flask and mix them evenly;

[0081] Open the outlet valve of the oxygen cylinder, the ozone generator, the fume hood, and the water bath constant temperature magnetic stirrer in sequence to continuously introduce ozone into the low-concentration sulfuric acid environment. Before introducing ozone into the three-necked flask, connect a glass rotor flowmeter to control the ozone flux to maintain at 0.8 L / min.

[0082] The reaction was carried out in a water bath at 30°C for 30 min, magnetic stirring was turned on, and the stirring speed was 10. Samples were taken every 5 min during this period, and they were diluted and sent for ICP detection in time.

[0083] Step 2: After vacuum filtration, lithium-containing filtrate A and iron-containing filter cake B are obtained.

[0084] Comparative Example 5

[0085] This comparative example provides a method for wet recycling of waste lithium batteries, comprising the following steps:

[0086] Step 1: Weigh 10.008 g of lithium iron phosphate cathode powder and 100 mL of 0.4 mol / L sulfuric acid in a three-necked flask and mix them evenly;

[0087] Open the outlet valve of the oxygen cylinder, the ozone generator, the fume hood, and the water bath constant temperature magnetic stirrer in sequence to continuously introduce ozone into the low-concentration sulfuric acid environment. Before introducing ozone into the three-necked flask, connect a glass rotor flowmeter to control the ozone flux to maintain at 0.5 L / min.

[0088] The reaction was carried out in a water bath at 50°C for 60 min, magnetic stirring was turned on, and the stirring speed was 10. Samples were taken every 5 min during this period, and they were diluted and sent for ICP detection in time.

[0089] Step 2: After vacuum filtration, lithium-containing filtrate A and iron-containing filter cake B are obtained.

[0090] Example 4

[0091] This embodiment provides a method for further processing the lithium-containing filtrate A and the iron-containing filter cake B obtained after the leaching reaction to better analyze the products after the leaching reaction, take into account the subsequent recovery of lithium, and verify that the iron is retained in the solid structure. The specific steps are as follows:

[0092] The filtrate A is subjected to simple treatments such as impurity removal, pH adjustment, and heating and concentration in sequence, and the filtrate C is retained after vacuum filtration;

[0093] Add excess sodium carbonate to filtrate C and precipitate lithium at 95°C for 2 h;

[0094] Wash the lithium-containing precipitate D with boiling deionized water, then place the precipitate D in a vacuum drying oven at 120°C and dry it for 12 hours. Collect and weigh it, and send it for XRD testing. Figure 3 As shown;

[0095] After drying, filter cake B was placed in a muffle furnace and calcined at 600℃ for 4h. The cake was collected and weighed, and then sent for XRD testing. Figure 4 shown.

[0096] Test method: The samples in Examples 1-3 and Comparative Examples 1-5 were tested using ICP-OES. The results are shown in Table 1:

[0097] Table 1

[0098] Test items Lithium leaching rate (%) Experimental Example 1 94.81 Experimental Example 2 99.65 Experimental Example 3 96.02 Comparative Example 1 25.49 Comparative Example 2 43.76 Comparative Example 3 59.26 Comparative Example 4 63.73 Comparative Example 5 49.25

[0099] From the test results in Table 1, it can be seen that the lithium leaching rate of recycling waste lithium batteries using the method of the present application reaches more than 96%, which is much higher than that of comparative examples 1-5.

[0100] As the reaction temperature increased, we determined the optimal reaction temperature after multiple experiments. When we adjusted the stirring rate accordingly, we found no increase or decrease in the lithium or iron leaching rate, so we concluded that stirring rate was not an influencing factor. In a large number of experiments, the reaction time was between 0.5 and 2.0 hours, and we found that the optimal experimental conditions could be achieved in 25 minutes, so we did not extend the reaction time.

[0101] After preparing the samples in the comparative example, under the optimal experimental conditions of sulfuric acid concentration of 0.4 mol / L, ozone flux of 0.6 L / min, sulfuric acid / lithium molar ratio of 0.52, 60°C, and 25 min in the experimental example, the leaching rate of lithium was 99.65% and that of iron was 0.015%. This green and efficient method is worthy of market promotion.

[0102] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for wet recycling of waste lithium batteries, characterized by: The following steps are involved: Step 1: Mix lithium iron phosphate cathode powder with an acidic solution, introduce ozone and stir to react; Step 2: After the reaction is completed, vacuum filtration is performed to separate the solid and liquid to obtain a lithium-containing filtrate and an iron-containing filter cake.

2. The method for wet recycling of waste lithium batteries according to claim 1, wherein: In step 1, the acidic solution is 0.1-0.8 mol / L sulfuric acid. 10-21 g of lithium iron phosphate positive electrode powder and 100 mL of sulfuric acid are weighed and mixed evenly in a three-necked flask; then the outlet valve of the oxygen cylinder, the ozone generator, the fume hood and the water bath constant temperature magnetic stirrer are opened in sequence, and ozone is continuously introduced into the low concentration sulfuric acid environment.

3. The method for wet recycling of waste lithium batteries according to claim 2, wherein: Before ozone was introduced into the three-necked flask, a glass rotor flowmeter was connected to control the ozone flux to maintain at 0.1-1.0 L / min.

4. The method for wet recycling of waste lithium batteries according to claim 2, wherein: The lithium iron phosphate positive electrode powder and sulfuric acid are first reacted in a three-necked flask at a water bath temperature of 30-80°C for 0.5-2h, and then magnetic stirring is turned on at a stirring speed of 5-20r / min.

5. The method for wet recycling of waste lithium batteries according to claim 1, wherein: In step 2, the separated lithium-containing filtrate is adjusted to 85-95°C in a water bath, and then lithium carbonate is added to the lithium-containing filtrate, the amount of lithium carbonate is greater than the amount that can precipitate lithium, and then magnetic stirring is turned on, covered with plastic wrap, and multiple holes are poked in the plastic wrap to react; wherein the above-mentioned reaction time is 0.5-2.0h, and the stirring speed during this period is 5-13rpm; the reaction product is vacuum filtered, and then the filter cake product is washed multiple times with prepared boiling deionized water; the washed filter cake product is placed in a vacuum drying oven, and the temperature is set to 115-125°C and the time is 11.5-13h.

6. The method for wet recycling of waste lithium batteries according to claim 1, wherein: In step 2, the separated iron-containing filter cake is mainly iron phosphate, which is first dried in a constant temperature forced air drying oven for 22-24 hours, and then placed in a muffle furnace and calcined at 500-600° C. for 4-6 hours.

7. The method for wet recycling of waste lithium batteries according to claim 1, characterized in that: In step 2, the lithium-containing filtrate needs to be heated and concentrated to the volume of the solution in the acid leaching reaction.

8. The method for wet recycling of waste lithium batteries according to claim 7, wherein: The pH value of the lithium-containing filtrate is adjusted to 5-6 before heating and concentrating, and the pH value of the lithium-containing filtrate is adjusted to 9-10 after heating and concentrating.

9. The method for wet recycling of waste lithium batteries according to claim 8, characterized in that: When precipitation occurs, vacuum filtration is required to separate the solid and liquid.

10. The method for wet recycling of waste lithium batteries according to claim 2, characterized in that: The volume of sulfuric acid is constant, and the liquid-solid ratio is increased by adding lithium iron phosphate positive electrode powder, and the mass of the lithium iron phosphate positive electrode powder is 8-16g.

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