Method for selectively extracting lithium from waste lithium iron phosphate positive electrode material by microdroplets

Abstract

This invention relates to the field of lithium-ion battery recycling technology, specifically to a method for selectively extracting lithium from waste lithium iron phosphate cathode materials using microdroplets. The method includes the following steps: S1, pretreating the waste lithium iron phosphate cathode material to obtain waste lithium iron phosphate powder, then mixing the waste lithium iron phosphate powder with an organic phase and water to form a mixture; S2, subjecting the mixture to ultrasonic treatment to disperse it into micron-sized water-in-oil microdroplets, followed by solid-liquid separation to obtain a lithium-containing aqueous phase and FePO4 solid precipitate. The method of this invention requires no external acid, alkali, or other chemical reagents, using only water and a recyclable organic solvent as the medium, relying on ultrasonic energy to drive the reaction, and produces no secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling technology, specifically to a method for efficiently and selectively extracting lithium ions from waste lithium iron phosphate (LiFePO4) cathode materials using an ultrasonically induced microdroplet water-oil interface. Background Technology

[0002] Lithium iron phosphate (LFP) batteries have been widely used in electric vehicles and energy storage systems due to their high safety, long cycle life, and cost advantages. With the large-scale retirement of these batteries, their recycling has become an urgent issue. Traditional recycling processes are mainly divided into pyrometallurgical and hydrometallurgical methods. Pyrometallurgical processes are energy-intensive, have low lithium recovery rates, and produce harmful gases; hydrometallurgical processes often rely on strong acids (such as sulfuric acid and hydrochloric acid) for leaching. Although they can recover valuable metals, the process is complex, generates large amounts of wastewater, and makes it difficult to achieve efficient and selective separation of lithium and iron, affecting the efficiency and economics of subsequent material regeneration. Therefore, there is an urgent need to develop a new, environmentally friendly recycling method that achieves selective lithium leaching under mild conditions, without the need for strong acids or alkalis. Summary of the Invention

[0003] This invention provides a green, efficient, and highly selective lithium extraction method. By constructing a microdroplet water-oil interface system under ultrasonic action, and utilizing the reactive oxygen species (ROS) generated in situ at the microdroplet interface, near-complete leaching of lithium from waste LiFePO4 is achieved at room temperature and pressure. At the same time, iron precipitates in the form of FePO4, achieving efficient separation of lithium and iron.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for selectively extracting lithium from waste lithium iron phosphate cathode materials using microdroplets includes the following steps: S1. Pre-treat the waste lithium iron phosphate cathode material to obtain waste lithium iron phosphate powder, then mix the waste lithium iron phosphate powder with organic phase and water to form a mixture; S2. The mixture is subjected to ultrasonic treatment to disperse it into micron-sized water-in-oil microdroplets. After solid-liquid separation treatment, lithium-containing aqueous phase and FePO4 solid precipitate are obtained.

[0006] Furthermore, in step S1, the organic phase is preferably a straight-chain alkane with a carbon chain length of C10-C16.

[0007] Furthermore, the organic phase is tridecane.

[0008] Further, in step S1, the water:organic phase ratio is 1:3.3 by volume; and the waste lithium iron phosphate powder:organic phase ratio is 1:4 by solid-liquid ratio.

[0009] Furthermore, in step S2, the ultrasonic treatment power conditions are 360 ​​W, the reaction temperature is 25℃, and the reaction time is 60 min.

[0010] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: (1) The method described in this invention does not require the addition of external acids, bases or other chemical reagents, but only uses water and recyclable organic solvents as media, and relies on ultrasonic energy to drive the reaction, without secondary pollution.

[0011] (2) The method described in this invention can achieve a lithium extraction rate of over 99% and an iron leaching rate of less than 0.1%, thus realizing efficient separation of lithium and iron and exhibiting high selectivity.

[0012] (3) The method described in this invention has mild reaction conditions: it operates at room temperature and pressure, has low energy consumption, and requires simple equipment.

[0013] (4) In the method described in this invention, the solvent organic phase (such as tridecane) is easy to recover and reuse, reducing operating costs.

[0014] (5) The method described in this invention outputs a lithium-containing solution and high-purity FePO4 solid, which can be directly used for subsequent material regeneration or resource utilization. Attached Figure Description

[0015] Figure 1 This is a graph showing the extraction efficiency of waste lithium iron phosphate using the method described in Example 1 of this invention. Figure 2 The images show the TEM and XRD patterns of the FePO4 solid precipitate prepared by the method described in Example 1 of this invention. Figure 3 This is a schematic diagram illustrating the effect of different organic ions on the extraction efficiency of waste lithium iron phosphate according to the present invention; Figure 4 This is a schematic diagram illustrating the effect of different free radical scavenging agents on the extraction efficiency of waste lithium iron phosphate. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments and accompanying drawings are described in further detail below. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0017] The present invention discloses a method for selectively extracting lithium from waste lithium iron phosphate cathode materials using microdroplets, comprising the following steps: S1. Pre-treat the waste lithium iron phosphate cathode material to obtain waste lithium iron phosphate powder, then mix the waste lithium iron phosphate powder with organic phase and water to form a mixture; In this invention, the organic phase is preferably a straight-chain alkane with a carbon chain length of C10-C16, and more preferably tridecane. The volume ratio of water to organic phase is preferably 1:3.3, and the ratio of waste lithium iron phosphate powder to organic phase is 1:4 based on the solid-liquid ratio.

[0018] S2. The mixture is subjected to ultrasonic treatment to disperse it into micron-sized water-in-oil microdroplets. After solid-liquid separation, a lithium-containing aqueous phase and FePO4 solid precipitate are obtained. In this step, under the synergistic effect of ultrasonic cavitation and the strong electric field at the microdroplet interface, dissolved oxygen and water molecules are activated at the interface, generating O2 in situ. - Reactive oxygen species such as ·OH and H2O2. These species, as mild oxidants, preferentially oxidize Fe in LiFePO4. 2+ This triggers the formation of Li in the crystal lattice + The release of Fe and the promotion of Fe 3+ With PO4 3- The process combines to form solid FePO4. This process does not damage the olivine matrix structure of the material, achieving efficient and selective dissolution of lithium and simultaneous solidification and separation of iron.

[0019] Ideally, in this invention, the ultrasonic treatment power conditions are 360 ​​W, the reaction temperature is 25°C, and the reaction time is 60 minutes.

[0020] <Example 1> A method for selectively extracting lithium from waste lithium iron phosphate cathode materials using microdroplets includes the following steps: Take 5 mg of lithium iron phosphate powder, add 20 mL of organic phase and 6 mL of deionized water to obtain a mixture, wherein the organic phase is tridecane; place the above mixture in an ultrasonic reactor and sonicate for 60 minutes at a power of 360 W (frequency 40 kHz) and a reaction temperature of 25 °C. After the reaction is completed, centrifuge to obtain a lithium-containing aqueous phase and FePO4 solid precipitate.

[0021] <Comparative Example 1> The difference between this comparative example and Example 1 is that the organic phase is tetradecane, while all other preparation conditions are the same as in Example 1.

[0022] <Comparative Example 2> The difference between this comparative example and Example 1 is that the organic phase is pentadecane, while all other preparation conditions are the same as in Example 1.

[0023] <Comparative Example 3> The difference between this comparative example and Example 1 is that the organic phase is hexadecane, while all other preparation conditions are the same as in Example 1.

[0024] <Comparative Example 4> The difference between this comparative example and Example 1 is that 20 mM of the free radical scavenger isopropanol (IPA) was added in step S1 of Example 1, while all other preparation conditions were the same as in Example 1.

[0025] <Comparative Example 5> The difference between this comparative example and Example 1 is that 15 mM of the free radical scavenger p-benzoquinone was added in step S1 of Example 1. p -BQ), and all other preparation conditions were the same as in Example 1.

[0026] <Comparative Example 6> The difference between this comparative example and Example 1 is that 10 mM potassium bromate (KBrO3) was added in step S1 of Example 1. All other preparation conditions were the same as in Example 1.

[0027] <Comparative Example 7> The difference between this comparative example and Example 1 is that 20 mM isopropanol and 15 mM p-benzoquinone were added simultaneously in step S1 of Example 1, while other preparation conditions were the same as in Example 1.

[0028] <Comparative Example 8> The difference between this comparative example and Example 1 is that 15 mM p-benzoquinone and 10 mM potassium bromate were added simultaneously in step S1 of Example 1, while all other preparation conditions were the same as in Example 1.

[0029] <Comparative Example 9> The difference between this comparative example and Example 1 is that 20 mM isopropanol and 10 mM potassium bromate were added simultaneously in step S1 of Example 1. All other preparation conditions were the same as in Example 1.

[0030] <Comparative Example 10> The difference between this comparative example and Example 1 is that 20 mM isopropanol, 15 mM p-benzoquinone, and 10 mM potassium bromate were added simultaneously in step S1 of Example 1. All other preparation conditions were the same as in Example 1.

[0031] The extraction efficiency graph of waste lithium iron phosphate from Example 1 was obtained, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the lithium extraction rate of the method described in this embodiment reaches 100%, and the iron leaching rate is less than 0.1%, indicating that the method has good applicability to actual waste.

[0032] TEM and XRD patterns of the FePO4 solid precipitate obtained in Example 1 were obtained, and the results are as follows: Figure 2 As shown. By Figure 2 It can be confirmed that the main phase of the FePO4 solid precipitate in this embodiment is FePO4.

[0033] The effects of different organic ions on the extraction efficiency of waste lithium iron phosphate in Example 1 and Comparative Examples 1-3 are shown in the following diagrams. Figure 3 As shown. Where n-13 represents Example 1, n-14 represents Comparative Example 1, n-15 represents Comparative Example 2, and n-16 represents Comparative Example 3. From Figure 3 It can be seen that tridecane has the highest lithium extraction efficiency (100%), followed by pentadecane (56.8%), confirming that alkanes with moderate chain length are more conducive to the formation of highly active microdroplet interfaces.

[0034] Schematic diagrams showing the effects of free radical scavenging agent treatment on the extraction efficiency of waste lithium iron phosphate in Example 1 and Comparative Examples 4-7 are obtained respectively. The results are as follows: Figure 4 As shown. The Control group represents Example 1, and the IPA group represents Comparative Example 4. p -BQ group represents control example 5, KBrO3 group represents control example 6, IPA+ p -BQ group represents the comparison ratio 7. p -BQ+KBrO3 group represents comparative example 8, IPA+KBrO3 group represents comparative example 9, IPA+ p -BQ+KBrO3 group represents control example 10. (From...) Figure 4 It was found that the lithium extraction rate dropped below 50% after adding any one of the free radical scavengers; when three free radical scavengers were added simultaneously, the extraction rate was less than 10%. This demonstrates that reactive oxygen species play a key role in the lithium extraction process.

[0035] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A method for selectively extracting lithium from waste lithium iron phosphate cathode material using microdroplets, characterized in that, Includes the following steps: S1. Pre-treat the waste lithium iron phosphate cathode material to obtain waste lithium iron phosphate powder, then mix the waste lithium iron phosphate powder with organic phase and water to form a mixture; S2. The mixture is subjected to ultrasonic treatment to disperse it into micron-sized water-in-oil microdroplets. After solid-liquid separation treatment, lithium-containing aqueous phase and FePO4 solid precipitate are obtained.

2. The method for selectively extracting lithium from waste lithium iron phosphate cathode material using microdroplets according to claim 1, characterized in that, In step S1, the organic phase is preferably a straight-chain alkane with a carbon chain length of C10-C16.

3. The method for selectively extracting lithium from waste lithium iron phosphate cathode material using microdroplets according to claim 2, characterized in that, The organic phase is tridecane.

4. The method for selectively extracting lithium from waste lithium iron phosphate cathode material using microdroplets according to claim 1, characterized in that, In step S1, the water:organic phase ratio is 1:3.3 by volume.

5. The method for selectively extracting lithium from waste lithium iron phosphate cathode material using microdroplets according to claim 1, characterized in that, In step S1, the ratio of waste lithium iron phosphate powder to organic phase is 1:4, based on the solid-liquid ratio.

6. The method for selectively extracting lithium from waste lithium iron phosphate cathode material using microdroplets according to claim 1, characterized in that, In step S2, the ultrasonic treatment power conditions are 360 ​​W, the reaction temperature is 25℃, and the reaction time is 60 min.

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