Pretreatment process and device for recycling waste positive pole piece

Abstract

The invention provides a pretreatment process and device for recycling waste positive pole pieces. The pretreatment process comprises the following steps: carrying out heat treatment on the waste positive pole piece at 200-600 DEG C; stirring in the medium particles to form positive electrode current collector fragments and positive electrode active layer particles; and then separating the positive current collector fragments, the medium particles and the positive active layer particles. The pre-treatment device comprises a heating chamber, wherein a heater is arranged in the heating chamber; a stirring rotor and medium particles are arranged in the stirring chamber, the stirring chamber is arranged below the heating chamber, and the stirring chamber and the heating chamber are isolated through a first material transfer plate capable of being opened and closed; the vibrating screen is arranged below the stirring chamber, and the vibrating screen is isolated from the stirring chamber through a second material transfer plate which can be opened and closed. The pretreatment process provided by the invention is simple, the positive current collector material and the positive active material can be respectively recovered, and the recovery efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery recycling, and in particular relates to a pretreatment process and device for recycling waste positive electrode sheets. Background Art

[0002] Lithium-ion batteries, with their high capacity and energy density, are key components of electric vehicles. Lithium iron phosphate (LFP) batteries and nickel-cobalt-manganese oxide (NCM) ternary batteries are two common types of lithium-ion batteries. When batteries reach the end of their lifespan, the precious elemental resources and the environmental implications of their disposal have drawn considerable attention.

[0003] Methods for recycling used lithium-ion batteries include pyrolysis and wet methods. Among them, the pyrolysis method is to sinter the used positive electrode sheets at high temperature (usually above 800°C) and then carry out subsequent recycling processes. This method has high energy consumption, and the sintered positive electrode sheets are integrated, making it impossible to recycle the positive current collector material and the positive active material separately. The wet method is to use chemical reagents to directly dissolve the used positive electrode sheets, and then repair the crystal structure of the active material through electrochemical or chemical leaching methods. However, this method requires the use of chemical reagents such as strong acids and strong oxidants, which can easily cause secondary pollution and easily introduce impurity elements. The operation procedure is cumbersome.

[0004] Considering the increasing amount and diversity of waste lithium-ion batteries, the current low recycling efficiency of 70-80% is a major bottleneck, so there is a need to develop a simple and efficient recycling method. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a pretreatment process and apparatus for recycling spent positive electrode sheets. The pretreatment process provided by the present invention is simple, capable of separately recovering positive electrode current collector material and positive electrode active material, with high recovery efficiency, while avoiding the drawbacks of pyrometallurgical and wet recycling processes.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a pretreatment process for recycling waste positive electrode sheets, the pretreatment process comprising the following steps:

[0008] (1) heat treating the waste positive electrode sheet at 200-600°C (for example, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 320°C, 330°C, 350°C, 360°C, 380°C, 400°C, 420°C, 450°C, 480°C, 500°C, 520°C, 550°C, 580°C or 600°C);

[0009] (2) stirring the waste positive electrode sheets after the heat treatment in step (1) in the medium particles to cause the waste positive electrode sheets to be peeled off and broken to form positive electrode current collector fragments and positive electrode active layer particles;

[0010] (3) Separating the positive electrode current collector fragments, dielectric particles and positive electrode active layer particles.

[0011] In the art, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer disposed on the surface of the positive electrode current collector. The positive electrode active layer generally includes a positive electrode active material, a binder, and a conductive agent.

[0012] In the present invention, the pretreatment process for recycling spent positive electrode sheets refers to the pretreatment process within the recycling process for spent positive electrode sheets. The positive electrode active material obtained through this pretreatment process cannot be used directly in batteries and requires subsequent purification, regeneration, and other recycling steps. The present invention does not impose any specific limitations on the subsequent recycling process; conventional processes in the art can be used.

[0013] The pretreatment process provided by the present invention first performs a heat treatment on the waste positive electrode sheets at 200-600°C, which can inactivate the binder in the positive electrode active layer and reduce the binding force between the positive electrode collector and the positive electrode active layer, as well as the binding force between the positive electrode active materials; then, the waste positive electrode sheets after heat treatment are stirred in medium particles, which can quickly cause the positive electrode collector and the positive electrode active layer to be peeled off and broken; because the positive electrode collector is usually a metal foil, and the positive electrode active material as the main component of the positive electrode active layer is a small particle size (micron-level) particle, the positive electrode collector fragments obtained after stirring are larger (particle size>5mm), and the positive electrode active layer particles are smaller (particle size<0.3mm), which can be separated by simple screening.

[0014] The pretreatment process provided by the present invention is simple and can recover the positive electrode current collector material and the positive electrode active material separately, with high recovery efficiency. It also avoids the shortcomings of the pyrometallurgical recovery process, which has high energy consumption and cannot separate the positive electrode current collector and the positive electrode active material; and the problem of the wet recovery process, which requires the use of strong acids and strong oxidants and introduces impurities.

[0015] In some embodiments of the present invention, the heat treatment temperature is 200-250° C. At this temperature, the binder in the positive electrode active layer can be inactivated without decomposition (for example, the decomposition temperature of PVDF, a commonly used binder in the positive electrode active layer, is 380-550° C.), thereby achieving the purpose of heat treatment while reducing energy consumption. Therefore, the heat treatment temperature in the present invention is preferably 200-250° C.

[0016] In some embodiments of the present invention, the heat treatment time is more than 10 minutes, for example, it can be 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 22 minutes, 25 minutes, 28 minutes, 30 minutes, 32 minutes, 35 minutes, 38 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, etc.; preferably, it is 10-20 minutes.

[0017] In the present invention, a fairly high material recovery rate can be achieved by heat treating the waste positive electrode sheets for 10-20 minutes, while further increasing the heat treatment time does not significantly improve the recovery effect. In order to reduce energy consumption, the heat treatment time in the present invention is preferably 10-20 minutes.

[0018] In some embodiments of the present invention, the stirring speed is above 200 rpm, for example, it can be 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 950 rpm or 1000 rpm, etc.; preferably, it can be 200-400 rpm.

[0019] In some embodiments of the present invention, the stirring time is more than 30 s, for example, it can be 30 s, 32 s, 35 s, 38 s, 40 s, 42 s, 45 s, 48 ​​s, 50 s, 52 s, 55 s, 58 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s, 90 s, 95 s, 100 s, 105 s, 110 s, 115 s or 120 s, etc.; preferably, it is 30-60 s.

[0020] In the present invention, a fairly high material recovery rate can be achieved by controlling the stirring speed to 200-400 rpm and the stirring time to 30-60 s. However, further increasing the stirring speed and stirring time does not significantly improve the recovery effect. Therefore, the stirring speed in the present invention is preferably 200-400 rpm and the stirring time is preferably 30-60 s.

[0021] In some embodiments of the present invention, the particle size of the medium particles is 2-5 mm; for example, it can be 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm.

[0022] In some embodiments of the present invention, the material of the media particles is zirconium oxide.

[0023] In the present invention, if the positive electrode active material in the spent positive electrode sheets contains lithium iron phosphate, ferric chloride can be added as a grinding aid during stirring to accelerate the selective recovery of lithium from the spent lithium iron phosphate. The mass ratio of ferric chloride to lithium iron phosphate can be 0.5-2:1; for example, it can be 0.5:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.3:1, 1.5:1, 1.6:1, 1.8:1, or 2:1, and is preferably 1:1.

[0024] In some embodiments of the present invention, the separation method in step (3) is screening using a vibrating screen.

[0025] In some embodiments of the present invention, the pretreatment process further includes the following steps: washing the dielectric particles separated in step (3) to remove and collect the positive electrode active layer particles attached to the surface of the dielectric particles. The washing method may be ultrasonic water washing. After drying, the washed dielectric particles can be used again for stirring in step (2).

[0026] In the present invention, if the recycled waste positive electrode sheets are of the same type and the pretreatment process is continuously performed, the medium particles separated in step (3) can also be directly used for stirring in step (2) without being washed.

[0027] In a second aspect, the present invention provides a pretreatment device for recycling waste positive electrode sheets, the pretreatment device comprising:

[0028] A heating chamber, wherein the heating chamber has a heater;

[0029] A stirring chamber, wherein a stirring rotor and medium particles are provided in the stirring chamber, the stirring chamber being arranged below the heating chamber and isolated from the heating chamber by a switchable first material transfer plate; and,

[0030] A vibrating screen is arranged below the stirring chamber and is isolated from the stirring chamber by a second material transfer plate that can be switched.

[0031] In the pretreatment device provided by the present invention, the heating chamber is used to heat treat the waste positive electrode sheets; after the heat treatment is completed, the first material transfer plate is opened to allow the waste positive electrode sheets to enter the stirring chamber for stirring, so that the waste positive electrode sheets are peeled and broken to form positive electrode collector fragments and positive electrode active layer particles; after the stirring is completed, the second material transfer plate is opened to allow all materials (including positive electrode collector fragments, medium particles and positive electrode active layer particles) to enter the vibrating screen for screening. The vibrating screen can be set with two levels of screens according to the particle size of the material, so as to separate the positive electrode collector fragments, medium particles and positive electrode active layer particles.

[0032] In some embodiments of the present invention, the size of the heater is greater than or equal to the size of the area where the waste positive electrode sheets are placed, so as to ensure that the placed positive electrode sheets can be heated evenly.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The pretreatment process provided by the present invention is simple and can recover the positive electrode current collector material and the positive electrode active material separately, with high recovery efficiency. It also avoids the shortcomings of the pyrometallurgical recovery process, which has high energy consumption and cannot separate the positive electrode current collector and the positive electrode active material; and the problem of the wet recovery process, which requires the use of strong acids and strong oxidants and introduces impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic structural diagram of a pre-processing device for recycling waste positive electrode sheets provided in an embodiment of the present invention;

[0036] The figures are marked as follows: 1-heating chamber, 2-heater, 3-stirring chamber, 4-first material transfer plate, 5-medium particles, 6-stirring rotor, 7-vibrating screen, 8-second material transfer plate. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. It should be understood by those skilled in the art that the specific embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] In the embodiment of the present invention, the waste positive electrode sheets used are obtained by the following method:

[0039] The waste lithium-ion batteries (including NCM batteries and LFP batteries) were soaked in 1 mol / L NaCl solution for 24 h to allow them to completely self-discharge, and then dried in an 80°C oven for 8 h. After cooling to room temperature, the positive and negative electrodes, separators and battery casings were disassembled and separated to obtain waste NCM positive electrode sheets and waste LFP positive electrode sheets (the positive electrode collector was aluminum foil).

[0040] Example 1

[0041] This embodiment provides a pre-processing device for recycling waste positive electrode sheets, the structure of which is as follows: Figure 1 As shown, including:

[0042] A heating chamber 1, wherein a heater 2 is provided in the heating chamber;

[0043] A stirring chamber 3, the stirring chamber 3 is arranged below the heating chamber 1 and is separated from the heating chamber 1 by a switchable first material transfer plate 4; the stirring chamber 3 contains a stirring rotor 6 and medium particles 5; and,

[0044] A vibrating screen 7 is provided below the stirring chamber 3 and is isolated from the stirring chamber 3 by a switchable second material transfer plate 8; two levels of screens are provided in the vibrating screen 7, the aperture of the first level screen is 5 mm, and the aperture of the second level screen is 1 mm.

[0045] Example 2

[0046] This embodiment provides a pretreatment process for recycling waste positive electrode sheets, which is performed using the pretreatment device provided in Example 1, and the steps are as follows:

[0047] (1) placing the waste NCM positive electrode sheet in the heating chamber 1 of the pretreatment device, heating it to 250°C at a rate of 20°C / min and keeping it at that temperature for 20 minutes for heat treatment;

[0048] (2) After the heat treatment is completed, the first material transfer plate 4 is immediately opened to allow the heat-treated waste NCM positive electrode sheets to enter the stirring chamber 3, which is filled with zirconium oxide medium particles (density 6g / cm 3 , particle size 5 mm), start the stirring rotor 6, and stir at a speed of 400 rpm for 60 s to peel and break the waste NCM positive electrode sheet to form positive electrode current collector fragments and positive electrode active layer particles;

[0049] (3) Open the second material transfer plate 8, and allow all materials (including positive electrode current collector fragments, dielectric particles, and positive electrode active layer particles) to enter the vibrating screen 7 for screening. The first layer is positive electrode current collector fragments with a particle size greater than 5 mm, the second layer is dielectric particles, and the third layer is positive electrode active layer particles with a particle size less than 0.3 mm;

[0050] (4) The medium particles separated in step (3) are ultrasonically washed to remove and collect the positive electrode active layer particles attached to the surface thereof, and then dried and combined with the positive electrode active layer particles obtained in step (3); the washed medium particles are dried for subsequent stirring.

[0051] Example 3-13

[0052] Examples 3-13 each provide a pretreatment process for recycling waste positive electrode sheets, which differ from Example 2 only in the raw materials and process conditions, as shown in Table 1. Specifically, Examples 8-9 use waste LFP positive electrode sheets, and Example 9 further adds a ferric chloride grinding aid (FeCl3:LiFePO4 mass ratio = 1:1) before the stirring operation in step (2) to accelerate the selective recovery of lithium from the waste LFP positive electrode sheets.

[0053] Comparative Examples 1-4

[0054] Comparative Examples 1-4 each provide a pretreatment process for recycling waste positive electrode sheets, which differs from Example 2 only in the process conditions, as shown in Table 1.

[0055] Recovery test:

[0056] The positive electrode current collector (aluminum foil) fragments and the positive electrode active layer particles obtained in the above examples and comparative examples were dissolved in a digestion reagent consisting of 98 wt % HNO 3 and 32 wt % HCl, and the element concentrations were measured using an inductively coupled plasma optical emission spectrometer (ICP-OES) to obtain the mass of the recovered material.

[0057] The waste positive electrode sheets were directly dissolved with a digestion reagent, and the element concentration was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES) to obtain the original mass of the materials in the waste positive electrode sheets;

[0058] Recovery rate = recovered material mass / original material mass × 100%. The recovery rate test results are shown in Table 1 below.

[0059] Table 1

[0060]

[0061] It can be seen from the test results in Table 1 that the pretreatment process provided by the present invention has a recovery rate of more than 90% for the positive electrode current collector material (aluminum foil), and a recovery rate of more than 98% for the positive electrode active material.

[0062] Among them, compared with Example 3, the heat treatment temperature in Comparative Example 1 is lower, and compared with Example 4, the heat treatment time in Comparative Example 2 is shorter, resulting in insufficient deactivation of the binder in the positive electrode sheet and a decrease in the stripping efficiency of the positive electrode sheet during stirring, thereby reducing the recovery rate of the positive electrode current collector material and the positive electrode active material.

[0063] Compared with Example 6, the stirring rate in Comparative Example 3 is lower, and compared with Example 7, the stirring time in Comparative Example 4 is shorter, resulting in insufficient peeling and crushing of the positive electrode sheet, and thus a decrease in the recovery rate of the positive electrode current collector material and the positive electrode active material.

[0064] The foregoing description is intended only to provide specific embodiments of the present disclosure, intended to enable those skilled in the art to understand and implement the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the embodiments described herein, but rather to be construed in the broadest manner consistent with the principles and novel features disclosed herein.

Claims

1. A pretreatment process for recycling waste positive electrode sheets, characterized in that: The pretreatment process comprises the following steps: (1) heat treating the waste positive electrode sheet at 200-600°C; (2) stirring the waste positive electrode sheets after the heat treatment in step (1) in the medium particles to cause the waste positive electrode sheets to be peeled off and broken to form positive electrode current collector fragments and positive electrode active layer particles; (3) Separating the positive electrode current collector fragments, dielectric particles and positive electrode active layer particles.

2. The pretreatment process according to claim 1, characterized in that The temperature of the heat treatment is 200-250°C.

3. The pretreatment process according to claim 1 or 2, characterized in that: The heat treatment time is more than 10 minutes, preferably 10-20 minutes.

4. The pretreatment process according to any one of claims 1 to 3, characterized in that: The stirring speed is above 200 rpm, preferably 200-400 rpm.

5. The pretreatment process according to any one of claims 1 to 4, characterized in that: The stirring time is more than 30 seconds, preferably 30-60 seconds.

6. The pretreatment process according to any one of claims 1 to 5, characterized in that: The particle size of the medium particles is 2-5 mm; Preferably, the material of the medium particles is zirconium oxide.

7. The pretreatment process according to any one of claims 1 to 6, characterized in that: When the positive electrode active material in the waste positive electrode sheet contains lithium iron phosphate, a grinding aid ferric chloride is also added during stirring in step (2); Preferably, the mass ratio of the ferric chloride to the lithium iron phosphate is 0.5-2:

1.

8. The pretreatment process according to any one of claims 1 to 7, characterized in that: The separation method in step (3) is screening using a vibrating screen.

9. The pretreatment process according to any one of claims 1 to 8, characterized in that: The pretreatment process further comprises the following steps: cleaning the medium particles separated in step (3), removing and collecting the positive electrode active layer particles attached to the surface of the medium particles.

10. A pre-treatment device for recycling waste positive electrode sheets, characterized in that: The pre-processing device comprises: A heating chamber, wherein the heating chamber has a heater; A stirring chamber, wherein a stirring rotor and medium particles are provided in the stirring chamber, the stirring chamber being arranged below the heating chamber and isolated from the heating chamber by a switchable first material transfer plate; and, A vibrating screen is arranged below the stirring chamber and is isolated from the stirring chamber by a second material transfer plate that can be switched.

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