Method for plasma-assisted stripping of pole piece active material and current collector of lithium ion battery

Abstract

The invention relates to the technical field of lithium ion battery recovery, and particularly discloses a method for plasma-assisted stripping of a lithium ion battery pole piece active material and a current collector, which comprises the following steps: (1) placing a lithium ion battery positive pole piece in a radio frequency plasma generator; (2) after air is introduced, a vacuum pump is started, and the pressure intensity is adjusted to be a preset value; (3) heating, starting a plasma generator when the temperature reaches a preset value, adjusting the power of the plasma generator to a preset value, and processing for a certain time; and (4) taking out the pole piece, and slightly bending the treated pole piece to separate the active material from the current collector. Compared with the prior art, the stripping effect of the active substance subjected to stripping treatment is good, the stripping rate can reach 99.14%, the aluminum content in the stripped material is only 0.022 wt%, meanwhile, the crystal structure of the treated active material can be kept intact through an X-ray diffraction pattern, and the valence state content of the iron element is not changed through an X-ray photoelectron spectroscopy.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery recycling, and in particular to a method for plasma-assisted stripping of active materials and current collectors of lithium ion battery positive electrode sheets. Background Art

[0002] Lithium-ion batteries are widely used in mobile phones, laptops, new energy vehicles and other fields due to their high energy density, light weight, no memory effect and long life.

[0003] With the rapid development of new energy vehicles, the rapid growth in lithium-ion battery production and utilization has led to an increase in the amount of waste lithium-ion batteries year by year. Direct disposal of waste lithium-ion batteries will lead to environmental and safety problems. Efficient and green recycling of waste lithium battery positive electrode materials can not only save costs and avoid waste of resources, but also reduce environmental pollution.

[0004] Lithium-ion batteries are composed of a shell, positive and negative electrodes, electrolytes and other components. The positive electrode is made of positive active materials adhered to the current collector aluminum foil by the adhesive PVDF. Since the adhesive PVDF has excellent chemical resistance, high temperature stability and weather resistance, the incomplete degradation of PVDF during the recycling process makes it difficult to separate the positive active material from the current collector. Traditional separation methods such as high temperature treatment or dissolving PVDF with organic solvents face problems such as high energy consumption, environmental pollution and high cost. Aluminum becomes brittle under high temperature conditions, and the crystal structure of lithium iron phosphate will also undergo partial changes under high temperature, which is not conducive to the subsequent recycling process. In addition, it is difficult to control its volatilization and degradation products under high temperature conditions, leading to accidental pollution; and organic solvent (NMP) treatment is relatively expensive and toxic.

[0005] Therefore, how to realize a simple, environmentally friendly, widely adaptable and low-temperature method for stripping the active material and current collector of the positive electrode sheet of a lithium-ion battery has become a technical problem that technical personnel in this field urgently need to solve.

[0006] Considering that low-temperature plasma treatment is efficient, uniform, and consistent, compared to high-temperature treatment, the low-temperature environment of plasma treatment not only reduces the degradation of PVDF and thus reduces the uncontrollable harmful gases it produces, but also prevents the brittleness of the aluminum current collector. Compared to organic solvent treatment, plasma treatment has low cost, does not require a toxic gas source during the treatment process, and the treatment product is non-toxic and harmless. Therefore, low-temperature plasma treatment can be used as a simple, environmentally friendly, widely adaptable, and low-temperature method for stripping the active material and current collector of the positive electrode sheet of lithium-ion batteries. Summary of the invention

[0007] The object of the present invention is to provide a method for plasma-assisted stripping of active materials and current collectors of positive electrode sheets of lithium-ion batteries, so as to solve the problems in the current market raised by the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery, comprising the following steps:

[0009] (1) placing a positive electrode of a lithium-ion battery in a radio frequency plasma generator reactor;

[0010] (2) Air is continuously introduced into the reactor and the pressure is adjusted to a preset value;

[0011] (3) heating the plasma, and when the temperature reaches a preset value, turning on the plasma generator and adjusting its power to a preset value, and treating for a certain period of time;

[0012] (4) Take out the electrode and slightly bend the treated electrode to separate the active material from the current collector.

[0013] Preferably, in step (2), the pressure in the reactor is 200 Pa.

[0014] Preferably, in step (3), the heating temperature is 50-75°C.

[0015] Preferably, in step (3), the power of the plasma generator is 300W.

[0016] Preferably, in step (3), the treatment time is 20-30 min.

[0017] Compared with the prior art, the invention has the following beneficial effects: the invention provides a method for plasma-assisted stripping of the active material and the current collector of the positive electrode sheet of a lithium-ion battery, wherein the positive electrode sheet of the lithium-ion battery is directly placed in a plasma generator for heating and then subjected to plasma treatment, and after the treatment, the active material can be separated from the current collector by slight bending to obtain the positive electrode active material and the current collector aluminum foil. The measured stripping rate is as high as 99.14%, and the aluminum content in the stripped material is not higher than 0.02wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The X-ray diffraction diagram of the stripped active material of some embodiments is compared with the lithium iron phosphate PDF standard card;

[0019] Figure 2 Fe2p orbital X-ray photoelectron spectrum of the stripped active material of Example 1;

[0020] Figure 3This is a test chart of the positive electrode active material stripping rate obtained in Examples 1-5 and Comparative Examples 1-2;

[0021] Figure 4 It is a schematic diagram of the preparation process of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] A method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery comprises the following steps:

[0025] (1) cutting the positive electrode sheet of the lithium-ion battery into a suitable size and placing it in a radio frequency plasma generator reactor;

[0026] (2) Air is continuously introduced into the reactor and the pressure is adjusted to 200 Pa;

[0027] (3) heating it, and when the temperature reaches 50°C, turning on the plasma generator and adjusting its power to 300W, the treatment time is 60min;

[0028] (4) The electrode was taken out and the active material could be separated from the current collector by slightly bending the treated electrode. The active material stripping rate was measured to be 98.70%. The aluminum content in the stripped material was measured by inductively coupled plasma mass spectrometry to be 0.021 wt%. Figure 1 Its X-ray diffraction pattern shows that its crystal structure has not been changed by plasma treatment. Figure 2 The Fe2p orbital X-ray photoelectron spectrum of the stripped active material of Example 1 shows that the valence content of the iron element has not changed due to the plasma treatment and the complete chemical structure has been maintained.

[0029] Example 2

[0030] A method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery comprises the following steps:

[0031] (1) cutting the positive electrode sheet of the lithium-ion battery into a suitable size and placing it in a radio frequency plasma generator reactor;

[0032] (2) Air is continuously introduced into the reactor and the pressure is adjusted to 200 Pa;

[0033] (3) heating it, and when the temperature reaches 75°C, turning on the plasma generator and adjusting its power to 300 W, the treatment time is 120 min;

[0034] (4) The electrode is taken out and the active material can be separated from the current collector by slightly bending the treated electrode. The measured active material stripping rate is 99.17%, and the aluminum content in the stripped material is 0.037 wt% as measured by inductively coupled plasma mass spectrometry.

[0035] Example 3

[0036] A method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery comprises the following steps:

[0037] (1) cutting the positive electrode sheet of the lithium-ion battery into a suitable size and placing it in a radio frequency plasma generator reactor;

[0038] (2) Air is continuously introduced into the reactor and the pressure is adjusted to 200 Pa;

[0039] (3) heating it, and when the temperature reaches 75°C, turning on the plasma generator and adjusting its power to 300W, the treatment time is 30 minutes;

[0040] (4) The electrode is taken out and the active material can be separated from the current collector by slightly bending the treated electrode. The measured active material stripping rate is 99.14%, and the aluminum content in the stripped material is 0.022 wt% as measured by inductively coupled plasma mass spectrometry. Figure 1 Its X-ray diffraction pattern shows that its crystal structure has not been changed by plasma treatment.

[0041] Example 4

[0042] A method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery comprises the following steps:

[0043] (1) cutting the positive electrode sheet of the lithium-ion battery into a suitable size and placing it in a radio frequency plasma generator reactor;

[0044] (2) Air is continuously introduced into the reactor and the pressure is adjusted to 200 Pa;

[0045] (3) heating it, and when the temperature reaches 150°C, turning on the plasma generator and adjusting its power to 300W, and the treatment time is 120min;

[0046] (4) The electrode is taken out and the active material can be separated from the current collector by slightly bending the treated electrode. The measured active material stripping rate is 99.53%, and the aluminum content in the stripped material is 0.041 wt% as measured by inductively coupled plasma mass spectrometry.

[0047] Example 5

[0048] A method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery comprises the following steps:

[0049] (1) cutting the positive electrode sheet of the lithium-ion battery into a suitable size and placing it in a radio frequency plasma generator reactor;

[0050] (2) Air is continuously introduced into the reactor and the pressure is adjusted to 200 Pa;

[0051] (3) heating it, and when the temperature reaches 150°C, turning on the plasma generator and adjusting its power to 300W, and the treatment time is 60 minutes;

[0052] (4) The electrode is taken out and the active material can be separated from the current collector by slightly bending the treated electrode. The measured active material stripping rate is 99.48%, and the aluminum content in the stripped material is 0.039 wt% as measured by inductively coupled plasma mass spectrometry. Figure 1 Its X-ray diffraction pattern shows that its crystal structure has not been changed by plasma treatment.

[0053] Comparative Example 1

[0054] A method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery comprises the following steps:

[0055] (1) cutting the positive electrode sheet of the lithium-ion battery into a suitable size and placing it in a radio frequency plasma generator reactor;

[0056] (2) Air is continuously introduced into the reactor and the pressure is adjusted to 200 Pa;

[0057] (3) heating it to 150° C. without turning on the plasma generator, and the treatment time is 120 min;

[0058] (4) The electrode was taken out. The treated active material of the electrode could not be separated from the current collector, and the measured active material stripping rate was 0.

[0059] Comparative Example 2

[0060] A method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery comprises the following steps:

[0061] (1) cutting the positive electrode sheet of the lithium-ion battery into a suitable size and placing it in a radio frequency plasma generator reactor;

[0062] (2) Air is continuously introduced into the reactor and the pressure is adjusted to 200 Pa;

[0063] (3) heating it to 300° C. without turning on the plasma generator, and the treatment time is 120 min;

[0064] (4) The electrode is taken out and the active material can be separated from the current collector by slightly bending the treated electrode. The measured active material stripping rate is 95.12%, and the aluminum content in the stripped material is 0.043 wt% as measured by inductively coupled plasma mass spectrometry.

[0065] Among them, the positive electrode active material stripping rate test obtained in Examples 1-5 and Comparative Examples 1-2 is as follows Figure 4 As shown:

[0066] From the test results of Comparative Example 1 and Examples 1-5, the introduction of plasma treatment can significantly enhance the stripping effect of the positive electrode active material and the current collector. The stripping rates of the test results of Examples 1-5 are all higher than 95.12%, which is higher than the stripping rate of Comparative Example 2. In particular, considering the temperature and time, when the temperature is controlled at 75°C and the treatment time is controlled at 30 minutes, the stripping efficiency is optimal, with a stripping rate of 99.14% and a residual aluminum content of only 0.022wt%. Through the method of the present invention, a simple, environmentally friendly, widely adaptable and low-temperature method for stripping the positive electrode sheet active material and the current collector of a lithium-ion battery can be realized, and the current collector structure remains intact after stripping, which is beneficial to the subsequent recycling process.

[0067] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery, comprising the following steps: (1) placing a positive electrode of a lithium-ion battery in a radio frequency plasma generator reactor; (2) After introducing air, turn on the vacuum pump and adjust the pressure to the preset value; (3) heating the plasma, and when the temperature reaches a preset value, turning on the plasma generator and adjusting its power to a preset value, and treating for a certain period of time; (4) Take out the electrode and slightly bend the treated electrode to separate the active material from the current collector.

2. The method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery according to claim 1, characterized in that: The pressure in step (2) is 200 Pa.

3. The method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery according to claim 1, characterized in that: The heating temperature in step (3) is 50-150°C.

4. The method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery according to claim 1, characterized in that: The power of the plasma generator in step (3) is 300W.

5. The method for plasma-assisted stripping of active materials and current collectors of a positive electrode sheet of a lithium-ion battery according to claim 1, characterized in that: The processing time in step (3) is 20-30 minutes.

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