A high-efficiency stripping method for positive electrode sheets of lithium-ion batteries

Abstract

The present invention discloses a highly efficient stripping method for lithium ion battery positive plates, comprising: disassembling retired lithium iron phosphate batteries after discharging them, and sorting out lithium iron phosphate positive plates; adding the lithium iron phosphate positive plates into water for ultrasonic stripping treatment, separating lithium iron phosphate from aluminum foil, and obtaining a dispersion containing aluminum foil and lithium iron phosphate. The highly efficient stripping method for lithium ion battery positive plates provided by the present invention is essentially a method for separating lithium iron phosphate positive electrode materials and aluminum foil current collectors in waste lithium ion batteries, and can effectively separate lithium iron phosphate positive electrode materials and aluminum foil current collectors without using organic solvents or high-temperature calcination, and can also recycle electrolytes, so the whole method has a simple process, low requirements on equipment, high recovery efficiency, and achieves the goal of low-cost and harmless disposal.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery recycling, and in particular relates to a high-efficiency stripping method for a lithium ion battery positive electrode sheet. Background Art

[0002] By the end of 2022, 510,000 new energy vehicles had been scrapped in China, generating 241,000 tons of waste power batteries. It is estimated that by 2025, China's electric vehicles will exceed 30 million; by 2030, it will be close to 100 million; by 2035, it will exceed 200 million. Therefore, it is crucial to carry out effective technical recycling of waste lithium batteries. In the process of recycling waste lithium batteries, it is very important to separate the electrode active material from the current collector. At present, the main methods for separating electrode materials include mechanical separation, heat treatment, organic solution dissolution, alkaline dissolution, etc.

[0003] The existing invention patent CN101212074A discloses the use of organic solvents to soak the positive electrode sheet to achieve separation of aluminum foil and positive electrode materials, but the organic solvents used (such as N, N-dimethylformamide, etc.) are slightly toxic and have high costs. The invention patent CN118299704A discloses that the shredded positive electrode sheet is pretreated at 200-400℃ in the low temperature zone for 0.5-2h and nitrogen protection at 300-600℃ in the high temperature zone for 30-100min to achieve the stripping of the current collector, but this method needs to be carried out at high temperature and has high energy consumption. Summary of the invention

[0004] Based on the above technical problems, the present invention provides an efficient stripping method for lithium-ion battery positive plates, which is essentially a method for separating lithium iron phosphate positive electrode materials and aluminum foil current collectors in waste lithium-ion batteries. The lithium iron phosphate positive electrode materials and the aluminum foil current collectors can be effectively separated without the use of organic solvents or high-temperature calcination, and the electrolyte can also be recovered. Therefore, the entire method has a simple process, low requirements on equipment, and high recovery efficiency, achieving the goal of low-cost and harmless disposal.

[0005] The present invention provides a method for efficiently stripping a positive electrode sheet of a lithium-ion battery, comprising the following steps:

[0006] S1. After discharging the retired lithium iron phosphate battery, disassemble it and sort out the lithium iron phosphate positive electrode sheet;

[0007] S2. Add the lithium iron phosphate positive electrode sheet obtained in step S1 into water for ultrasonic stripping treatment to separate the lithium iron phosphate from the aluminum foil, thereby obtaining a dispersion of the aluminum foil and the lithium iron phosphate.

[0008] In the present invention, after the retired lithium iron phosphate battery is directly discharged, the obtained lithium iron phosphate positive electrode sheet is stripped using water. Since the lithium iron phosphate positive electrode sheet contains the infiltration effect of the electrolyte, it provides a basis for directly using water for stripping. Under the action of ultrasound, the power generated by the swelling of the lithium iron phosphate positive electrode sheet promotes the separation of the positive electrode material and the aluminum foil. No chemical reagents are required during the action process, and the lithium iron phosphate positive electrode material and the aluminum foil can be stripped using only water.

[0009] Preferably, step S1 further includes cutting the lithium iron phosphate positive electrode sheet into small-sized sheets;

[0010] Preferably, the length and width of the small-size sheet are both greater than or equal to 1 mm.

[0011] Preferably, in step S2, the power of the ultrasonic stripping treatment is 150-300 W, the stirring rate is 200-400 r / min, and the time is 0.1-1 h.

[0012] Preferably, the method further comprises S3, subjecting the dispersion of the aluminum foil and lithium iron phosphate obtained in step S2 to vacuum drying and condensation treatment to obtain a mixture of lithium iron phosphate and aluminum foil and a condensate.

[0013] Preferably, the temperature of the vacuum drying and condensation treatment is 120-180°C, the vacuum degree is -(0.01-0.1)Mpa, the condensation temperature is 5-15°C, and the time is 0.1-1h.

[0014] Preferably, the mixture of lithium iron phosphate and aluminum foil is separated into lithium iron phosphate and aluminum foil by sieving; and the condensate is separated into water and an electrolyte of an organic solvent by liquid separation.

[0015] Preferably, the lithium iron phosphate is further ball-milled by adding ionic liquid to remove residual binder PVDF to obtain purified lithium iron phosphate.

[0016] Preferably, the structural formula of the ionic liquid is as follows:

[0017]

[0018] Wherein, R is an alkyl group having 1 to 8 carbon atoms, and X is a halogen ion;

[0019] Preferably, the amount of the ionic liquid is 1-10% of the mass of the lithium iron phosphate.

[0020] Preferably, the ball mill further adds an alcohol solvent, and the alcohol solvent is preferably at least one of methanol, ethanol, isopropanol or cyclohexanol;

[0021] Preferably, the alcohol solvent is used in an amount of 70-90% of the mass of the lithium iron phosphate.

[0022] Preferably, the ball-to-material ratio of the ball mill is 1-8:1, the motor speed is 300-400 rpm, and the time is 1.5-3 h.

[0023] In the present invention, in order to further purify the recovered lithium iron phosphate positive electrode material, ionic liquid is added for ball milling. The ionic liquid can dissolve the trace PVDF remaining in the lithium iron phosphate, and the main chain of the ionic liquid molecule also contains a trifluoromethyl group, which can form a more effective affinity adsorption effect on PVDF, so that the residual binder PVDF in the lithium iron phosphate positive electrode material is effectively removed, thereby achieving the purpose of further purifying the lithium iron phosphate.

[0024] The beneficial effects of the present invention are as follows:

[0025] The invention provides a highly efficient stripping method for a lithium ion battery positive electrode sheet, which can complete the stripping of lithium iron phosphate positive electrode material and aluminum foil using only water, without the need for organic solvents, large amounts of acid and alkali, or high-temperature calcination, and can also recycle the electrolyte. The method is more environmentally friendly and energy-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the process of the efficient stripping method of the positive electrode sheet of a lithium-ion battery according to the present invention. DETAILED DESCRIPTION

[0027] Hereinafter, the present invention will describe the technical solution in detail through specific embodiments, but it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

[0028] Example 1

[0029] Reference Figure 1 This embodiment provides a highly efficient stripping method for a lithium-ion battery positive electrode sheet, comprising the following steps:

[0030] (1) After the retired lithium iron phosphate power battery is completely discharged, it is disassembled, and the lithium iron phosphate positive electrode sheets are sorted out, and the obtained lithium iron phosphate positive electrode sheets are cut into pieces of 10 cm×10 cm;

[0031] (2) adding 500 g of the above-mentioned shredded lithium iron phosphate positive electrode sheet into a beaker containing 2000 g of water, placing the beaker into an ultrasonic device and turning on the stirring device, with an ultrasonic power of 200 W, a stirring speed of 300 r / min, and a time of 0.5 h to obtain a dispersion of aluminum foil and lithium iron phosphate;

[0032] (3) Transfer the beaker containing the aluminum foil and the lithium iron phosphate dispersion to a vacuum drying oven equipped with a condensation device, set the drying oven temperature to 150° C., the vacuum degree to −0.05 MPa, and the temperature of the circulating cooling water to 10° C. After the temperature in the drying oven reaches 150° C., keep the temperature for 0.5 h to obtain a mixture of lithium iron phosphate and aluminum foil and a condensate;

[0033] (4) passing the mixture of lithium iron phosphate and aluminum foil through a 40-mesh vibrating sieve and vibrating and sieving for 30 minutes, wherein the material on the sieve is the aluminum foil and the material under the sieve is the positive electrode material of lithium iron phosphate;

[0034] (5) Pour the collected liquid into a separatory funnel to separate the electrolyte of water and organic solvent.

[0035] Example 2

[0036] This embodiment provides a method for efficiently stripping a positive electrode sheet of a lithium-ion battery, comprising the following steps:

[0037] (1) After the retired lithium iron phosphate power battery is completely discharged, it is disassembled, and the lithium iron phosphate positive electrode sheets are sorted out, and the obtained lithium iron phosphate positive electrode sheets are cut into pieces of 5 cm×5 cm;

[0038] (2) adding 500 g of the above-mentioned shredded lithium iron phosphate positive electrode sheet into a beaker containing 2000 g of water, placing the beaker into an ultrasonic device and turning on the stirring device, with an ultrasonic power of 150 W, a stirring speed of 400 r / min, and a time of 0.1 h to obtain a dispersion of aluminum foil and lithium iron phosphate;

[0039] (3) Transfer the beaker containing the aluminum foil and the lithium iron phosphate dispersion to a vacuum drying oven equipped with a condensation device, set the drying oven temperature to 120° C., the vacuum degree to -0.1 MPa, and the temperature of the circulating cooling water to 5° C. After the temperature in the drying oven reaches 120° C., keep the temperature for 1 hour to obtain a mixture of lithium iron phosphate and aluminum foil and a condensate;

[0040] (4) passing the mixture of lithium iron phosphate and aluminum foil through a 40-mesh vibrating sieve and vibrating and sieving for 30 minutes, wherein the material on the sieve is the aluminum foil and the material under the sieve is the positive electrode material of lithium iron phosphate;

[0041] (5) Pour the collected liquid into a separatory funnel to separate the electrolyte of water and organic solvent.

[0042] Example 3

[0043] This embodiment provides a method for efficiently stripping a positive electrode sheet of a lithium-ion battery, comprising the following steps:

[0044] (1) After the retired lithium iron phosphate power battery is completely discharged, it is disassembled, and the lithium iron phosphate positive electrode sheets are sorted out, and the obtained lithium iron phosphate positive electrode sheets are cut into pieces of 10 cm×10 cm;

[0045] (2) Add 500 g of the shredded lithium iron phosphate positive electrode sheet into a beaker containing 2000 g of water, place the beaker in an ultrasonic device and turn on the stirring device, with an ultrasonic power of 300 W, a stirring speed of 200 r / min, and a time of 1 h to obtain a dispersion of aluminum foil and lithium iron phosphate;

[0046] (3) Transfer the beaker containing the aluminum foil and the lithium iron phosphate dispersion to a vacuum drying oven equipped with a condensation device, set the drying oven temperature to 180° C., the vacuum degree to -0.01 MPa, and the temperature of the circulating cooling water to 15° C. After the temperature in the drying oven reaches 180° C., keep the temperature for 0.1 h to obtain a mixture of lithium iron phosphate and aluminum foil and a condensate;

[0047] (4) passing the mixture of lithium iron phosphate and aluminum foil through a 40-mesh vibrating sieve and vibrating and sieving for 30 minutes, wherein the material on the sieve is the aluminum foil and the material under the sieve is the positive electrode material of lithium iron phosphate;

[0048] (5) Pour the collected liquid into a separatory funnel to separate the electrolyte of water and organic solvent.

[0049] Example 4

[0050] This embodiment provides a method for efficiently stripping a positive electrode sheet of a lithium-ion battery, comprising the following steps:

[0051] (1) After the retired lithium iron phosphate power battery is completely discharged, it is disassembled, and the lithium iron phosphate positive electrode sheets are sorted out, and the obtained lithium iron phosphate positive electrode sheets are cut into pieces of 10 cm×10 cm;

[0052] (2) adding 500 g of the above-mentioned shredded lithium iron phosphate positive electrode sheet into a beaker containing 2000 g of water, placing the beaker into an ultrasonic device and turning on the stirring device, with an ultrasonic power of 200 W, a stirring speed of 300 r / min, and a time of 0.5 h to obtain a dispersion of aluminum foil and lithium iron phosphate;

[0053] (3) Transfer the beaker containing the aluminum foil and the lithium iron phosphate dispersion to a vacuum drying oven equipped with a condensation device, set the drying oven temperature to 150° C., the vacuum degree to −0.05 MPa, and the temperature of the circulating cooling water to 10° C. After the temperature in the drying oven reaches 150° C., keep the temperature for 0.5 h to obtain a mixture of lithium iron phosphate and aluminum foil and a condensate;

[0054] (4) passing the mixture of lithium iron phosphate and aluminum foil through a 40-mesh vibrating sieve and vibrating and sieving for 30 minutes, wherein the material on the sieve is the aluminum foil and the material under the sieve is the positive electrode material of lithium iron phosphate;

[0055] (5) adding the lithium iron phosphate, 5 wt% ionic liquid by weight of the lithium iron phosphate and 80 wt% ethanol by weight of the lithium iron phosphate into a zirconium oxide ball mill, adding zirconium balls with a diameter of 5 mm at a ball-to-material ratio of 4:1 into the ball mill, placing the ball mill in a planetary ball mill for ball milling, the electrode speed is 350 rpm, the ball milling time is 2 h, the obtained ball milled product is washed with ethanol, and dried to obtain purified lithium iron phosphate;

[0056] The preparation method and structural formula of the ionic liquid are as follows: a dichloromethane solution containing trifluoromethanesulfonic anhydride is added dropwise to 1-(3-aminopropyl)imidazole with a molar amount twice that of trifluoromethanesulfonic anhydride, and the mixture is stirred at room temperature for 2 hours to obtain trifluoromethanesulfonyl imidazole; 1-bromopropane is added dropwise to an equal molar amount of trifluoromethanesulfonyl imidazole, and the mixture is stirred at room temperature for 1 hour to obtain the ionic liquid.

[0057]

[0058] (6) Pour the collected liquid into a separatory funnel to separate the electrolyte of water and organic solvent.

[0059] Comparative Example 1

[0060] This comparative example proposes an efficient stripping method for a lithium-ion battery positive electrode sheet, which is the same as that of Example 1, except that in step (2), 500 g of the shredded lithium iron phosphate positive electrode sheet is added to a beaker containing 2000 g of N,N-dimethylformamide.

[0061] Comparative Example 2

[0062] This comparative example proposes an efficient stripping method for lithium-ion battery positive electrode sheets, which is the same as Example 1, except that in step (2), 500 g of the above-mentioned shredded lithium iron phosphate positive electrode sheets are first dried at 150° C. for 1 hour and then added to a beaker containing 2000 g of water.

[0063] Comparative Example 3

[0064] This comparative example proposes a highly efficient stripping method for a positive electrode sheet of a lithium-ion battery, which is the same as that of Example 4, except that in step (5), the ionic liquid is selected as 1-propyl-3-methylimidazolium tetrafluoroborate.

[0065] After calculation and testing, the recovery rate and purity of the positive electrode material of lithium iron phosphate described in the above embodiment and comparative example are shown in the following Table 1:

[0066] Table 1 Recovery rate and purity of the positive electrode materials of lithium iron phosphate described in the examples and comparative examples

[0067]

[0068] Recovery rate (%) = weight of recovered lithium iron phosphate / weight of total lithium iron phosphate × 100%.

[0069] It can be seen from Table 1 above that the efficient stripping method of the lithium iron phosphate positive electrode sheet of the present invention can complete the stripping of the lithium iron phosphate positive electrode material and the aluminum foil using only water, and the lithium iron phosphate can be purified more effectively using the ionic liquid.

[0070] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for efficiently stripping a positive electrode sheet of a lithium-ion battery, characterized in that: The steps include: S1. After discharging the retired lithium iron phosphate battery, disassemble it and sort out the lithium iron phosphate positive electrode sheet; S2. Add the lithium iron phosphate positive electrode sheet obtained in step S1 into water for ultrasonic stripping treatment to separate the lithium iron phosphate from the aluminum foil, thereby obtaining a dispersion of the aluminum foil and the lithium iron phosphate.

2. The efficient stripping method for the positive electrode sheet of a lithium-ion battery according to claim 1, characterized in that: Step S1 also includes cutting the lithium iron phosphate positive electrode sheet into small-sized sheets; Preferably, the length and width of the small-size sheet are both greater than or equal to 1 mm.

3. The efficient stripping method for a lithium ion battery positive electrode sheet according to claim 1 or 2, characterized in that: In step S2, the power of the ultrasonic stripping treatment is 150-300 W, the stirring rate is 200-400 r / min, and the time is 0.1-1 h.

4. The efficient stripping method for a lithium-ion battery positive electrode sheet according to any one of claims 1 to 3, characterized in that: The method further comprises S3, subjecting the dispersion of the aluminum foil and lithium iron phosphate obtained in step S2 to vacuum drying and condensation treatment to obtain a mixture of lithium iron phosphate and aluminum foil and a condensate.

5. The efficient stripping method for the positive electrode sheet of a lithium-ion battery according to claim 4, characterized in that: The temperature of the vacuum drying and condensation treatment is 120-180° C., the vacuum degree is -(0.01-0.1)Mpa, the condensation temperature is 5-15° C., and the time is 0.1-1h.

6. The efficient stripping method for a lithium-ion battery positive electrode sheet according to claim 4 or 5, characterized in that: The mixture of lithium iron phosphate and aluminum foil is separated into lithium iron phosphate and aluminum foil by sieving; and the condensate is separated into water and an electrolyte of an organic solvent by liquid separation.

7. The efficient stripping method for a lithium-ion battery positive electrode sheet according to claim 6, characterized in that: The lithium iron phosphate is further ball-milled by adding ionic liquid to remove residual binder PVDF to obtain purified lithium iron phosphate.

8. The efficient stripping method for a lithium-ion battery positive electrode sheet according to claim 7, characterized in that: The structural formula of the ionic liquid is as follows: Wherein, R is an alkyl group having 1 to 8 carbon atoms, and X is a halogen ion; Preferably, the amount of the ionic liquid is 1-10% of the mass of the lithium iron phosphate.

9. The efficient stripping method for a lithium-ion battery positive electrode sheet according to claim 7 or 8, characterized in that: The ball mill also adds an alcohol solvent, which is preferably at least one of methanol, ethanol, isopropanol or cyclohexanol; Preferably, the amount of the alcohol solvent used is 70-90% of the mass of the lithium iron phosphate.

10. The efficient stripping method for a lithium-ion battery positive electrode sheet according to claim 7 or 8, characterized in that: The ball-to-material ratio of the ball mill is 1-8:1, the motor speed is 300-400rpm, and the time is 1.5-3h.

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