Method for recycling all components of waste lithium iron phosphate positive electrode sheet

Abstract

The application discloses a kind of waste old lithium phosphate iron positive plate full component recovery method, it is related to lithium battery recycling technical field.The method includes the following steps: first, after being disassembled, waste old lithium phosphate iron positive plate is soaked in hydrogen peroxide solution, and waste old lithium phosphate iron positive material and aluminum foil are obtained after ultrasonic assisted stripping;Then, using the synergistic effect of plasma and oxidizing agent hydrogen peroxide, lithium element in waste old lithium phosphate iron positive material is selectively and efficiently leached, and lithium-containing leaching solution and iron phosphate leaching residue are obtained;Finally, lithium-containing leaching solution is precipitated with sodium carbonate solution, and high-purity lithium carbonate product is obtained.The present application has simple process flow, is green and pollution-free, and can realize efficient stripping of waste old lithium phosphate iron positive plate, efficient leaching of lithium ions and sustainable recovery of iron phosphate powder.

Description

Technical Field

[0001] This invention relates to the field of lithium battery recycling technology, and in particular to a method for the complete recycling of waste lithium iron phosphate cathode sheets. Background Technology

[0002] As a crucial component of the green industry, the new energy battery industry has ushered in unprecedented development opportunities. Lithium-ion batteries have garnered significant attention for their superior energy storage capabilities and have gained acceptance due to their advantages such as high energy density, long cycle life, low self-discharge rate, absence of memory effect, and relative environmental friendliness. These advantages have led to the widespread application of lithium-ion batteries in electronic devices, energy storage systems, and new energy vehicles, particularly driving the rapid growth of both the consumer and industrial markets for electric vehicles. Currently, the main power batteries for new energy vehicles include lithium cobalt oxide (LCO), lithium iron phosphate (LFP), ternary lithium (nickel cobalt manganese (NCM)), and nickel cobalt aluminum (NCA) batteries. Lithium iron phosphate batteries, as a type of lithium-ion battery, have stood out due to their low cost, good cycle performance, and high stability. However, the lifespan of lithium iron phosphate batteries is generally 5-8 years, and with the large-scale application of lithium iron phosphate batteries, a peak in lithium battery retirement is expected by 2025. If a large number of waste lithium iron phosphate batteries are not properly disposed of, it will not only waste valuable elements (lithium, iron, and aluminum, etc.), but the electrolytes and organic solvents they contain will also cause serious environmental pollution and harm human health.

[0003] Currently, the main recycling processes for spent lithium iron phosphate (LFP) batteries include pyrometallurgical recycling, hydrometallurgical recycling, and direct recycling. Pyrometallurgical technology is simple, but the processing route is long, it easily generates harmful gases, the overall recovery rate of valuable metals is relatively low, and energy consumption is very high; therefore, production using this route has been limited. Traditional hydrometallurgy uses high-concentration inorganic acids, such as HCl, H₂SO₄, and H₃PO₄, to break down the LFP crystal structure and leach lithium and iron. However, this leaching process consumes excessive amounts of acid and generates large amounts of wastewater, causing secondary pollution. Direct recycling is relatively environmentally friendly, but the recycled materials usually contain more impurities, have poor electrochemical performance, and inconsistent quality.

[0004] Therefore, it is of great significance to study a method for the complete recycling of waste lithium iron phosphate cathode sheets to realize the resource utilization and harmless treatment of waste lithium iron phosphate batteries. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the complete recycling of waste lithium iron phosphate cathode sheets, aiming to achieve efficient stripping of lithium iron phosphate cathode sheets without the use of acids, alkalis and organic solvents, while improving the recovery rates of aluminum foil, lithium and iron phosphate.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for the complete recycling of waste lithium iron phosphate cathode sheets includes the following steps:

[0008] (1) Add the disassembled waste lithium iron phosphate cathode sheet to a hydrogen peroxide solution with a volume fraction of 3-20%, and stir until it is completely submerged in the solution. The hydrogen peroxide solution has strong oxidizing properties, which can oxidize the PVDF binder in the cathode material, causing the hydrogen-fluorine polar bonds between PVDF molecules to break, thereby destroying the bonding effect of PVDF.

[0009] (2) The mixture obtained in step (1) is placed in an ultrasonic cleaner for ultrasonic treatment to peel the lithium iron phosphate cathode material from the aluminum foil in the waste lithium iron phosphate cathode sheet. Then the lithium iron phosphate cathode material and the aluminum foil are separated from the mixture. The aluminum foil and the lithium iron phosphate cathode material are rinsed with deionized water and then dried.

[0010] (3) The lithium iron phosphate cathode material obtained in step (2) is added to a hydrogen peroxide solution with a volume fraction of 3%-30%. After stirring evenly, it is transferred to a plasma generator and reacted in a water bath at 0-80℃ for 0.5-5 hours. Preferably, the reaction temperature is 10-30℃. After the reaction, the lithium iron phosphate filter cake and leachate are obtained by vacuum filtration. The plasma generated by the plasma generator can synergistically interact with the hydrogen peroxide solution to promote the generation of a large number of active free radicals. These active free radicals can convert the divalent iron in the iron phosphate lattice into trivalent iron, thereby realizing an efficient lithium resource recovery process.

[0011] (4) Add excess sodium carbonate solution to the leachate obtained in step (3) to obtain lithium carbonate precipitate, and then filter it under vacuum to obtain high-purity lithium carbonate. Sodium carbonate solution is widely used in industrial lithium formation processes due to its high solubility and low cost.

[0012] Preferably, in step (2), the ultrasonic power is less than 700W, preferably in the range of 100-500W, the ultrasonic time is 0.5-5h, the ultrasonic temperature is 20-60℃, and the aluminum foil and positive electrode material sheet are dried in a vacuum drying oven at 65℃ for 24 hours.

[0013] Preferably, the liquid-to-solid ratio of the lithium iron phosphate cathode material to the hydrogen peroxide solution in step (3) is 5-100 g / L.

[0014] Preferably, in step (3), the plasma generating device has the following conditions: air flow rate of 0.5-50 L / min, power supply voltage of 50-350 V, and current of 0.1-10 A.

[0015] Compared with the prior art, the beneficial effects of the present invention are reflected in the following aspects:

[0016] (1) This invention utilizes ultrasonic cavitation to assist in the stripping of waste lithium iron phosphate cathode sheets. By adding a low volume fraction of hydrogen peroxide, the cathode material of the cathode sheet is completely and undamagedly stripped from the aluminum foil, ensuring the purity of the aluminum foil and the cathode material.

[0017] (2) The present invention selectively and efficiently leaches lithium elements from waste lithium iron phosphate cathode materials, while generating high-purity iron phosphate powder, thereby achieving the purpose of recycling and preparing high-purity, high-conversion-rate lithium carbonate and iron phosphate powder, and realizing the full-component recovery of waste lithium iron phosphate cathode materials. Attached Figure Description

[0018] Figure 1 The figures show the separation effect of aluminum foil and positive electrode material in hydrogen peroxide solutions with different volume fractions. Among them, (a) is a 5% volume fraction hydrogen peroxide solution; (b) is a 20% volume fraction hydrogen peroxide solution; and (c) is a 30% volume fraction hydrogen peroxide solution.

[0019] Figure 2 This is a process flow diagram of the present invention for the complete recycling of waste lithium iron phosphate cathode sheets.

[0020] Figure 3 The image shows the XRD pattern of the iron phosphate prepared in Example 2 of this invention.

[0021] Figure 4 The images shown are SEM images of the iron phosphate prepared in Example 2 of this invention. The scale bars for each image are: (a) 10 μm, (b) 5 μm, (c) 2 μm, and (d) 1 μm.

[0022] Figure 5 The images shown are SEM images of lithium carbonate prepared in Example 2 of this invention. The scale bars for each image are: (a) 10 μm, (b) 5 μm.

[0023] Figure 6 The images show the physical samples of lithium carbonate and iron phosphate prepared in Example 2 of this invention. In the images, (a) represents lithium carbonate and (b) represents iron phosphate. Detailed Implementation

[0024] The present invention will be further described below with reference to embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0025] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail.

[0026] The disassembled waste lithium iron phosphate cathode sheets were cut into 1cm × 2cm pieces and added to hydrogen peroxide solutions with volume fractions of 5%, 20%, and 30%, respectively. After ultrasonic treatment, lithium iron phosphate cathode material and aluminum foil were obtained. The ultrasonic treatment conditions were: power 500W, ultrasonic time 2h, and ultrasonic temperature 50℃. Intact aluminum foil and cathode material sheets were selected, rinsed with deionized water, and dried in a vacuum drying oven at 65℃ for 24 hours. The resulting photographs of the lithium iron phosphate cathode material and aluminum foil are shown below. Figure 1 As shown in Figures a, b, and c, it can be seen that when the positive electrode is added to a hydrogen peroxide solution with a volume fraction of 5% or 20%, the aluminum foil in the positive electrode is completely separated from the positive electrode material after ultrasonic treatment. However, when the volume fraction of the hydrogen peroxide solution is 30%, the separation between the positive electrode material and the aluminum foil is incomplete.

[0027] Example 1

[0028] A method for the complete recycling of waste lithium iron phosphate cathode materials, with a process flow diagram for reference. Figure 2 Specifically, it includes the following steps:

[0029] (1) The disassembled waste lithium iron phosphate positive electrode sheet was cut into 1cm×2cm pieces, added to a 5% hydrogen peroxide solution, and then ultrasonically treated to obtain lithium iron phosphate positive electrode material and aluminum foil. The ultrasonic treatment conditions were: power of 500W, ultrasonic time of 2h, and ultrasonic temperature of 50℃. The complete aluminum foil and positive electrode material sheet were selected, rinsed with deionized water, and dried in a vacuum drying oven at 65℃ for 24 hours to obtain waste lithium iron phosphate positive electrode material and aluminum foil.

[0030] (2) The waste lithium iron phosphate cathode material obtained in step (1) was added to a plasma generator containing a 10% (v / v) hydrogen peroxide solution, and the solid-liquid ratio was controlled at 50 g / L. The reaction was carried out for 2 h under the conditions of an air flow rate of 8 L / min, a power supply voltage of 250 V, a current of 5 A, and a water bath temperature of 20 °C to obtain a mixed solution. The lithium and iron leaching rates of the mixed solution are shown in Table 1.

[0031] (3) The solution obtained in step (2) was vacuum filtered to obtain leachate and ferric phosphate. After the ferric phosphate was digested, the iron content was detected by inductively coupled plasma mass spectrometry and the ferric phosphate content was calculated to be more than 95%.

[0032] (4) The leachate obtained in step (3) was concentrated to a lithium element concentration of more than 20%, sodium carbonate was added to prepare lithium carbonate, and the purity of the lithium carbonate obtained after digestion was determined by inductively coupled plasma mass spectrometry, as shown in Table 1.

[0033] Example 2

[0034] A method for the complete recycling of waste lithium iron phosphate cathode materials specifically includes the following steps:

[0035] (1) The disassembled waste lithium iron phosphate positive electrode sheet was cut into 1cm×2cm pieces, added to a 5% hydrogen peroxide solution, and then ultrasonically treated to obtain lithium iron phosphate positive electrode material and aluminum foil. The ultrasonic treatment conditions were: power of 500W, ultrasonic time of 2h, and ultrasonic temperature of 50℃. The complete aluminum foil and positive electrode material sheet were selected, rinsed with deionized water, and dried in a vacuum drying oven at 65℃ for 24 hours to obtain waste lithium iron phosphate positive electrode material and aluminum foil.

[0036] (2) The waste lithium iron phosphate cathode material obtained in step (1) was added to a plasma generator containing a 20% (v / v) hydrogen peroxide solution, and the solid-liquid ratio was controlled at 50 g / L. The mixture was reacted for 2 h under the conditions of an air flow rate of 8 L / min, a power supply voltage of 250 V, a current of 5 A, and a water bath temperature of 20 °C to obtain a mixed solution. The lithium and iron leaching rates of the mixed solution are shown in Table 1.

[0037] (3) The solution obtained in step (2) was vacuum filtered to obtain leachate and ferric phosphate. After the ferric phosphate was digested, the iron content was detected by inductively coupled plasma mass spectrometry and the ferric phosphate content was calculated to be more than 99%.

[0038] (4) The leachate obtained in step (3) was concentrated to a lithium element concentration of more than 20%, sodium carbonate was added to prepare lithium carbonate, and the purity of the lithium carbonate obtained after digestion was determined by inductively coupled plasma mass spectrometry, as shown in Table 1.

[0039] Figure 3 The image shows the XRD pattern of the iron phosphate prepared in Example 2. Figure 3 As can be seen from the XRD peak positions of the leaching residue, they correspond to those of the ferric phosphate standard card, indicating that the leaching residue is ferric phosphate. Figure 4 The image shows a SEM image of the iron phosphate prepared in Example 2. Figure 4 It can be seen that the iron phosphate lattice is well preserved; Figure 5 Here is a SEM image of the lithium carbonate prepared in Example 2. Figure 5 The morphology of the generated lithium carbonate is good; Figure 6 Images of lithium carbonate and iron phosphate prepared in Example 2 are shown below. Figure 6 As can be seen, this method can efficiently generate lithium carbonate and iron phosphate products.

[0040] Example 3

[0041] A method for the complete recycling of waste lithium iron phosphate cathode materials specifically includes the following steps:

[0042] (1) The disassembled waste lithium iron phosphate positive electrode sheet was cut into 1cm×2cm pieces, added to a 5% hydrogen peroxide solution, and then ultrasonically treated to obtain lithium iron phosphate positive electrode material and aluminum foil. The ultrasonic treatment conditions were: power of 500W, ultrasonic time of 2h, and ultrasonic temperature of 50℃. The complete aluminum foil and positive electrode material sheet were selected, rinsed with deionized water, and dried in a vacuum drying oven at 65℃ for 24 hours to obtain waste lithium iron phosphate positive electrode material and aluminum foil.

[0043] (2) The waste lithium iron phosphate cathode material obtained in step (1) was added to a plasma generator containing a 30% volume fraction of hydrogen peroxide solution, and the solid-liquid ratio was controlled at 50 g / L. The mixture was reacted for 1 h under the conditions of an air flow rate of 8 L / min, a power supply voltage of 250 V, a current of 0.5 A, and a water bath temperature of 10 °C to obtain a mixed solution. The lithium and iron leaching rates of the mixed solution are shown in Table 1.

[0044] (3) The solution obtained in step (2) was vacuum filtered to obtain leachate and ferric phosphate. After the ferric phosphate was digested, the iron content was detected by inductively coupled plasma mass spectrometry and the ferric phosphate content was calculated to be more than 95.7%.

[0045] (4) The leachate obtained in step (3) was concentrated to a lithium element concentration of more than 20%, sodium carbonate was added to prepare lithium carbonate, and the purity of the lithium carbonate obtained after digestion was determined by inductively coupled plasma mass spectrometry, as shown in Table 1.

[0046] Example 4

[0047] A method for the complete recycling of waste lithium iron phosphate cathode materials specifically includes the following steps:

[0048] (1) The disassembled waste lithium iron phosphate positive electrode sheet was cut into 1cm×2cm pieces, added to a 5% hydrogen peroxide solution, and then ultrasonically treated to obtain lithium iron phosphate positive electrode material and aluminum foil. The ultrasonic treatment conditions were: power of 500W, ultrasonic time of 2h, and ultrasonic temperature of 50℃. The complete aluminum foil and positive electrode material sheet were selected, rinsed with deionized water, and dried in a vacuum drying oven at 65℃ for 24 hours to obtain waste lithium iron phosphate positive electrode material and aluminum foil.

[0049] (2) The waste lithium iron phosphate cathode material obtained in step (1) was added to a plasma generator containing a 20% volume fraction of hydrogen peroxide solution, and the solid-liquid ratio was controlled at 50 g / L. The reaction was carried out for 30 min under the conditions of an air flow rate of 4 L / min, a power supply voltage of 250 V, a current of 0.15 A, and a water bath temperature of 30 °C to obtain a mixed solution. The lithium and iron leaching rates of the mixed solution are shown in Table 1.

[0050] (3) The solution obtained in step (2) was vacuum filtered to obtain leachate and ferric phosphate. After the ferric phosphate was digested, the iron content was detected by inductively coupled plasma mass spectrometry and the ferric phosphate content was calculated to be more than 97%.

[0051] (4) The leachate obtained in step (3) was concentrated to a lithium element concentration of more than 20%, sodium carbonate was added to prepare lithium carbonate, and the purity of the lithium carbonate obtained after digestion was determined by inductively coupled plasma mass spectrometry, as shown in Table 1.

[0052] Comparative Example 1

[0053] The difference between this comparative example and Example 2 is that in this comparative example, in step (2), deionized water is directly added to the plasma device to control the solid-liquid ratio at 50 g / L; all other processes are the same as in Example 2. (This comparative example does not use a 20% volume fraction hydrogen peroxide solution). The results are shown in Table 1, indicating that the poor lithium leaching effect of waste lithium iron phosphate cathode material may be due to insufficient active nitrogen oxides generated by the single plasma generator, resulting in a low lithium leaching rate.

[0054] Comparative Example 2

[0055] The difference between this comparative example and Example 2 is that in step (2) of this comparative example, the waste lithium iron phosphate cathode material obtained by separating it according to step (1) of Example 2 is directly added to a beaker containing a 20% volume fraction hydrogen peroxide solution, and the solid-liquid ratio is controlled at 50 g / L. All other processes are the same as in Example 2. (This comparative example does not utilize a plasma generator). The results are shown in Table 1, indicating that the leaching effect of 20% volume fraction hydrogen peroxide alone is poor, and the leaching rate of lithium is low.

[0056] Table 1

[0057]

[0058] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for the complete recovery of components from waste lithium iron phosphate cathode sheets, characterized in that: Includes the following steps: (1) The disassembled waste lithium iron phosphate cathode sheet was immersed in hydrogen peroxide solution to obtain a mixed solution; (2) The mixture is ultrasonically treated to peel the lithium iron phosphate cathode material from the aluminum foil in the waste lithium iron phosphate cathode sheet. Then the lithium iron phosphate cathode material and aluminum foil are separated from the mixture and washed and dried. (3) The lithium iron phosphate cathode material obtained in step (2) is added to hydrogen peroxide solution and then transferred to a plasma generator for reaction. The reaction temperature is 10-30℃. After the reaction is completed, the obtained material is separated to obtain iron phosphate filter cake and leachate. (4) After concentrating the leachate obtained in step (3), add excess sodium carbonate solution to obtain lithium carbonate precipitate, and then separate it to obtain high-purity lithium carbonate. In step (1), the volume fraction of the hydrogen peroxide solution is 3-20%; The plasma generated by the plasma generator works synergistically with the hydrogen peroxide solution to promote the generation of active free radicals. These active free radicals convert the divalent iron in the iron phosphate lattice into trivalent iron, thereby achieving lithium resource recovery. The plasma generating conditions are: air flow rate 0.5-50 L / min, power supply voltage 50-350 V, and current 0.1-10 A.

2. The method for the complete component recovery of waste lithium iron phosphate cathode sheets according to claim 1, characterized in that: In step (2), the power of the ultrasonic treatment is 100-700 W.

3. The method for the complete component recovery of waste lithium iron phosphate cathode sheets according to claim 1, characterized in that: In step (2), the temperature of the ultrasonic treatment is 20-60 ℃ and the ultrasonic time is 0.5-5 h.

4. The method for the complete component recovery of waste lithium iron phosphate cathode sheets according to claim 1, characterized in that: In step (2), the drying temperature is 65°C.

5. The method for the complete component recovery of waste lithium iron phosphate cathode sheets according to claim 1, characterized in that: In step (3), the volume fraction of the hydrogen peroxide solution is 3-30%.

6. The method for the complete component recovery of waste lithium iron phosphate cathode sheets according to claim 1, characterized in that: In step (3), the liquid-to-solid ratio of the lithium iron phosphate cathode material to the hydrogen peroxide solution is 5-100 g / L.

7. The method for the complete component recovery of waste lithium iron phosphate cathode sheets according to claim 1, characterized in that: In step (3), the reaction time is 0.5-5 h.

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