Method for recycling negative electrode material of lithium ion battery and extracting lithium from clean water

Abstract

The invention discloses a method for recycling a lithium ion battery negative electrode material and extracting lithium from clear water. The method for recycling the negative electrode material of the lithium ion battery comprises the following steps: carrying out carbon thermal shock treatment on a battery negative electrode plate and an auxiliary medium; carrying out mixing treatment and ultrasonic treatment on the carbon thermal shock treatment product and water to obtain a lithium-containing leachate, a graphite material and a current collector; wherein the auxiliary medium is an alkaline medium with a high melting point. Therefore, by means of the auxiliary medium, the graphite material and the current collector can be rapidly and efficiently separated, meanwhile, hydrogen fluoride gas generated in the high-temperature process is absorbed and fixed, valuable metal lithium can be effectively leached out of the graphite material only under the clean water condition, and the leaching rate of lithium is increased.

Description

Technical Field

[0001] The present application relates to the technical field of lithium battery recycling, and in particular to a method for recycling negative electrode materials of lithium-ion batteries and a method for extracting lithium from clean water. Background Art

[0002] Under the strategic goal of "carbon peak and carbon neutrality" in my country, the rapid development of new energy vehicles has led to a substantial increase in demand for raw materials. Graphite is a typical negative electrode material for waste lithium batteries, with a mass content of 12%-21%, accounting for about 15% of the cost of lithium-ion batteries. The supply and demand of high-quality flake graphite is growing rapidly at a rate of 10%-12% per year, and graphite has been included in the catalog of the most critical materials in the future. Although the supply and demand of battery-grade graphite is growing rapidly, graphite in waste lithium batteries is often overlooked. At present, the recycling of waste lithium batteries mainly focuses on the recovery of high-value cathode materials, while less attention is paid to the resource utilization of negative electrode materials. Improper handling of waste graphite will bring serious environmental risks such as particulate pollution and greenhouse gas emissions. Upgrading and recycling valuable resources in graphite negative electrodes can greatly reduce the energy consumption, carbon dioxide and pollution emissions of traditional primary production processes, while minimizing the release of harmful substances such as metals and electrolytes to the environment.

[0003] In traditional pyrometallurgy, waste graphite acts as a reducing agent when the positive and negative electrode powders undergo carbon thermal reduction reactions, and is burned as fuel and eventually converted into slag, resulting in a low level of resource utilization. Waste graphite, however, contains lithium resources with a higher grade than the original ore, and has a high recycling value. The lithium in waste graphite comes from: lithium that cannot be normally removed from waste graphite during the long-term cycle and deintercalation of the battery, LiPF6 electrolyte, and LiF remaining at the interface of the solid electrolyte. With the rapid consumption of global resources, deep green recycling of valuable metal lithium in retired power batteries, recycling of copper foil current collectors and graphite, will significantly extend its entire life cycle process from "waste disposal" to "waste utilization", in line with the principles of green chemistry and the concept of circular economy.

[0004] Therefore, there is an urgent need to develop a method that is simple to operate, conforms to the principles of green chemistry, and can simultaneously recycle valuable metal lithium, current collectors, and graphite. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present application proposes an environmentally friendly, energy-saving and easy-to-operate method, which effectively overcomes the problems of large environmental pollution, high energy consumption, complex equipment and cumbersome preparation process in the recovery process of traditional lithium-ion battery negative electrode materials. This method not only realizes the instantaneous stripping of negative electrode graphite and current collector, but also avoids the use of acid reagents by extracting lithium with clean water, significantly reducing environmental pollution. At the same time, the method can realize the comprehensive recovery of current collector, graphite and valuable metal lithium, and improve the recovery efficiency of valuable metal lithium.

[0006] Therefore, in the first aspect of the present application, the present application proposes a method for recycling negative electrode materials of lithium-ion batteries. According to an embodiment of the present application, the method comprises: subjecting the negative electrode sheet of the battery and the auxiliary medium to carbon thermal shock treatment; mixing the product of the carbon thermal shock treatment with water and ultrasonic treatment to obtain a lithium-containing leaching solution, a graphite material and a current collector; wherein the auxiliary medium is an alkaline medium with a high melting point.

[0007] Therefore, the inventors of the present application have developed an innovative method for recycling negative electrode materials of lithium-ion batteries after a large number of experiments. The method realizes the rapid and efficient separation of graphite materials and current collectors, and realizes the selective recovery of valuable metal lithium with the assistance of auxiliary media, and can effectively leach valuable metal lithium from graphite materials only under clear water conditions, thereby improving the leaching rate of lithium. At the same time, the auxiliary medium can absorb harmful gases such as hydrogen fluoride generated during pyrolysis in situ, effectively controlling environmental pollution. This method has the advantages of simple operation, wide application range, fast stripping speed, high lithium leaching efficiency, etc., and can realize the comprehensive recovery of metal copper foil, graphite and valuable metal lithium, providing an efficient and green solution for the environmental protection treatment and resource recycling of waste lithium batteries.

[0008] According to an embodiment of the present application, the method may further include at least one of the following additional technical features:

[0009] According to an embodiment of the present application, the auxiliary medium includes at least one of CaCO3, Al2O3, Fe2O3, and Fe3O4.

[0010] According to an embodiment of the present application, the mass ratio of the auxiliary medium to the battery negative electrode sheet is (1:1)-(7:1).

[0011] According to an embodiment of the present application, the auxiliary medium is located on both sides of the negative electrode sheet of the battery.

[0012] According to an embodiment of the present application, the battery negative electrode sheet is a graphite negative electrode sheet having a current collector.

[0013] According to an embodiment of the present application, the voltage of the carbon thermal shock treatment is 25V-35V.

[0014] According to an embodiment of the present application, the temperature of the carbon thermal shock treatment is 750°C-950°C.

[0015] According to an embodiment of the present application, the carbon thermal shock treatment is performed for 5s-25s.

[0016] According to an embodiment of the present application, the carbon thermal shock treatment is performed 1 to 3 times.

[0017] According to an embodiment of the present application, the auxiliary medium is CaCO3, and the mass ratio of the CaCO3 to the battery negative electrode plate is (1-3):1.

[0018] According to an embodiment of the present application, the temperature of the carbon thermal shock treatment is 780°C-820°C.

[0019] According to an embodiment of the present application, the carbon thermal shock treatment time is 13s-17s.

[0020] According to an embodiment of the present application, the carbon thermal shock treatment is performed once.

[0021] According to an embodiment of the present application, the auxiliary medium is Al2O3, and the mass ratio of the Al2O3 to the battery negative electrode sheet is (3-5):1.

[0022] According to an embodiment of the present application, the temperature of the carbon thermal shock treatment is 880°C-920°C.

[0023] According to an embodiment of the present application, the carbon thermal shock treatment is performed for 18s-22s.

[0024] According to an embodiment of the present application, the carbon thermal shock treatment is performed once.

[0025] According to an embodiment of the present application, the auxiliary medium is Fe2O3, and the mass ratio of the Fe2O3 to the battery negative electrode sheet is (4-6):1.

[0026] According to an embodiment of the present application, the temperature of the carbon thermal shock treatment is 880°C-920°C.

[0027] According to an embodiment of the present application, the carbon thermal shock treatment is performed for 18s-22s.

[0028] According to an embodiment of the present application, the carbon thermal shock treatment is performed twice.

[0029] According to an embodiment of the present application, the lithium-ion battery is selected from at least one of a ternary lithium-ion battery, a lithium iron phosphate battery, a lithium cobalt oxide battery, and a lithium manganese oxide battery.

[0030] In the second aspect of the present application, the present application proposes a method for extracting lithium from clear water. According to an embodiment of the present application, the method comprises: recycling the negative electrode sheet of a lithium-ion battery using the method described in the first aspect to obtain a lithium-containing aqueous solution. As mentioned above, the method for recycling negative electrode materials of lithium-ion batteries in the present application can achieve the selective recovery of valuable metal lithium with the assistance of an auxiliary medium, and can effectively leach valuable metal lithium from graphite materials only under clear water conditions, thereby improving the leaching rate of lithium. Therefore, the method for extracting lithium from clear water in the present application also has a high lithium leaching rate. Those skilled in the art in the present application can understand that the method for extracting lithium from clear water has all the features and advantages of the method for recycling negative electrode materials of lithium-ion batteries described above, and will not be elaborated on here.

[0031] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0033] Figure 1 A diagram showing the auxiliary medium screening results of one embodiment of the present application is shown;

[0034] Figure 2 The effect of adding different auxiliary media on the separation efficiency between graphite and the current collector according to one embodiment of the present application is shown;

[0035] Figure 3 A diagram showing the lithium leaching effects of different auxiliary media-negative electrode sheets under different experimental conditions in one embodiment of the present application;

[0036] Figure 4 The electron microscope results of an embodiment of the present application are shown to show the effect of adding different auxiliary media on lithium leaching. DETAILED DESCRIPTION

[0037] The embodiments of the present application are described in detail below, which are intended to be used to explain the present application but should not be construed as limiting the present application.

[0038] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0039] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0041] In this document, the terms "include" or "comprising" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0042] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0043] Graphite is widely used as anode material for lithium-ion batteries due to its good structural stability, high reversible capacity and high conductivity. In recent years, the use of portable devices such as mobile phones and computers and new energy vehicles has increased dramatically. The replacement of these electronic products and the scrapping of new energy vehicle batteries will bring a large number of waste lithium-ion batteries. In addition to a large amount of graphite cathode, these waste batteries also contain a large amount of copper and lithium embedded in the cathode material during the charging and discharging process. It is of great practical significance to recycle this valuable element while recycling waste graphite.

[0044] At present, the common recycling methods are mainly wet recycling, pyrolysis and mechanical separation. However, wet recycling requires acid treatment, which has problems such as environmental pollution and equipment corrosion. Conventional pyrolysis has a low recovery rate and takes a long time, with high energy consumption. Mechanical separation can only separate simple components and ultra-fine screening has serious pore blockage. The above methods have limited recovery effects when used alone, and the combination of multiple methods will greatly increase the recovery cost.

[0045] Based on this, this application aims at the problems of metal lithium volatilization loss, addition of toxic and harmful chemical reagents, long recovery time and process in the traditional pyrolysis separation process of the existing scrapped lithium-ion battery negative electrode materials, and proposes a technical route of using alkaline medium-assisted carbon thermal shock technology to achieve instantaneous peeling of negative electrode graphite and current collector, and using clean water to efficiently extract lithium from the product. Carbon thermal shock is an emerging technology that uses electric pulses to instantly (1 to 2 seconds) reach thousands of high temperatures (heating rate> 1000℃ / s), and has been reported in the fields of material synthesis, graphene preparation, and solid waste treatment. The inventor found in the experiment that during the carbon thermal shock process, the added auxiliary medium can effectively promote the deep extraction and leaching of lithium elements on the one hand, and absorb and control the fluorine pollution generated during the high temperature process on the other hand. Therefore, this application realizes the efficient recovery of all components of waste lithium-ion battery negative electrode materials, and has the advantages of low material consumption and energy consumption, clean and environmental protection. The following will introduce the method of recycling lithium-ion battery negative electrode materials and the method of extracting lithium from clean water in detail.

[0046] Method for recycling negative electrode materials of lithium ion batteries

[0047] The present application proposes a method for recycling negative electrode materials of lithium-ion batteries. According to an embodiment of the present application, the method comprises: subjecting the negative electrode sheet of the battery and an auxiliary medium to carbon thermal shock treatment; mixing the product of the carbon thermal shock treatment with water and ultrasonic treatment to obtain a lithium-containing leaching solution, a graphite material and a current collector; wherein the auxiliary medium is an alkaline medium with a high melting point.

[0048] Therefore, the inventor of the present application has developed an innovative method for recycling negative electrode materials of lithium-ion batteries after a large number of experiments. The method uses auxiliary media to mix with negative electrode sheets, and performs carbon thermal shock reaction under inert atmosphere and ultrafast reaction time. The binder in the negative electrode sheet is quickly decomposed under the heat storage effect of the auxiliary medium and high temperature, and the graphite material and the current collector are separated quickly and efficiently; in addition, the auxiliary medium can promote the migration of lithium in the graphite to the surface of the negative electrode material (i.e., the graphite surface), and realize the selective recovery of valuable element lithium, and only under the condition of clear water, the valuable metal lithium can be effectively leached out from the graphite material, and the leaching rate of lithium can be improved; at the same time, the auxiliary medium can absorb harmful gases such as hydrogen fluoride generated during pyrolysis in situ, and effectively control environmental pollution. This method has the advantages of simple operation, wide application range, fast stripping speed, high lithium leaching efficiency, etc., and can realize the comprehensive recovery of metal copper foil, graphite and valuable metal lithium, and provides an efficient and green solution for the environmental protection treatment and resource recycling of waste lithium batteries.

[0049] It should be noted that the lithium leaching rate described in this application refers to the ratio of the leached lithium mass to the theoretical lithium content of the electrode. The theoretical lithium content of the electrode is calculated by microwave digestion of multiple parallel samples with aqua regia and ICP metal ion detection of lithium concentration.

[0050] Among them, the lithium leaching efficiency of lithium-ion battery negative electrode graphite is calculated by formula (1-1):

[0051]

[0052] Where η is the leaching rate of a certain element; M is the mass of lithium leached from water after CTS (carbon thermal shock); M0 is the theoretical mass of lithium in the negative electrode sheet, which is obtained through aqua regia digestion experiment.

[0053] The separation efficiency described in this application refers to the efficiency of separating graphite from copper foil.

[0054] Among them, the separation efficiency of lithium-ion battery negative electrode graphite and copper foil is calculated by formula (1-2).

[0055]

[0056] Where W0 is 1×1cm 2 The mass of the negative electrode, W Cu is the actual weight of the copper foil obtained after stripping, and a is the percentage of graphite in the negative electrode, which is calculated by the stripping rate of the negative electrode pyrolysis in a tubular furnace at 600-800°C.

[0057] In some embodiments of the present application, the auxiliary medium includes at least one of CaCO3, Al2O3, Fe2O3, and Fe3O4. Thus, the auxiliary medium of the above type can not only promote the migration of lithium in the graphite to the surface of the negative electrode material (i.e., the graphite surface) and improve the leaching rate of lithium, but also can absorb harmful gases such as hydrogen fluoride generated during the pyrolysis process in situ.

[0058] In some embodiments of the present application, the mass ratio of the auxiliary medium to the negative electrode of the battery is (1:1)-(7:1). For example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, etc., or it can be a range composed of any of the above values. Therefore, by controlling the mass ratio of the auxiliary medium to the negative electrode of the battery within the above range, the lithium leaching rate can be effectively improved.

[0059] In some embodiments of the present application, the auxiliary medium is located on both sides of the negative electrode sheet of the battery. Thus, by evenly spreading the auxiliary medium on the upper and lower sides of the negative electrode sheet to form a sandwich-like structure, it can help the element lithium in the graphite to fully precipitate and improve the lithium leaching rate.

[0060] In some embodiments of the present application, the battery negative electrode sheet is a graphite negative electrode sheet with a current collector. For the graphite negative electrode sheet with a current collector, the method of the present application can not only efficiently separate the graphite material from the current collector, but also effectively improve the lithium leaching rate.

[0061] In some embodiments of the present application, the voltage of the carbon thermal shock treatment is 25V-35V. For example, it can be 25V, 26V, 27V, 28V, 29V, 30V, 31V, 32V, 33V, 34V, 35V, etc., or it can be a range composed of any of the above values. Therefore, by controlling the voltage of the carbon thermal shock treatment within the above range, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0062] In some embodiments of the present application, the temperature of the carbon thermal shock treatment is 750°C-950°C. For example, it can be 750°C, 800°C, 850°C, 900°C, 950°C, etc., or it can be a range composed of any of the above values. Therefore, by controlling the temperature of the carbon thermal shock treatment within the above range, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0063] In some embodiments of the present application, the carbon thermal shock treatment time is 5s-25s. For example, it can be 5s, 10s, 15s, 20s, 25s, etc., or it can be a range composed of any of the above values. Therefore, by controlling the carbon thermal shock treatment time within the above range, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0064] In some embodiments of the present application, the number of carbon thermal shock treatments is 1-3 times. For example, it can be 1 time, 2 times, 3 times, etc., or it can be a range composed of any of the above values. Thus, by controlling the number of carbon thermal shock treatments within the above range, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0065] In some embodiments of the present application, the auxiliary medium is CaCO3, and the mass ratio of the CaCO3 to the negative electrode sheet of the battery is (1-3):1. For example, it can be 1:1, 2:1, 3:1, etc., or it can be a range composed of any of the above values. Therefore, by making the mass ratio of CaCO3 to the negative electrode sheet of the battery within the above range, CaCO3 can play a better role, promote the migration of lithium in graphite, increase the leaching rate of lithium, and absorb harmful gases such as hydrogen fluoride generated during pyrolysis.

[0066] In some embodiments of the present application, the auxiliary medium is CaCO3, and the temperature of the carbon thermal shock treatment is 780°C-820°C. For example, it can be 780°C, 790°C, 800°C, 810°C, 820°C, etc., or it can be a range composed of any of the above values. Thus, under the heat storage effect of CaCO3 and the above temperature range, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0067] In some embodiments of the present application, the auxiliary medium is CaCO3, and the carbon thermal shock treatment time is 13s-17s. For example, it can be 13s, 14s, 15s, 16s, 17s, etc., or it can be a range of any of the above values. In this way, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0068] In some embodiments of the present application, the auxiliary medium is CaCO3, and the number of carbon thermal shock treatments is 1.

[0069] In some embodiments of the present application, the auxiliary medium is Al2O3, and the mass ratio of Al2O3 to the negative electrode sheet of the battery is (3-5):1. For example, it can be 3:1, 4:1, 5:1, etc., or it can be a range composed of any of the above values. Therefore, by making the mass ratio of Al2O3 to the negative electrode sheet of the battery within the above range, Al2O3 can play a better role, promote the migration of lithium in graphite, increase the leaching rate of lithium, and absorb harmful gases such as hydrogen fluoride generated during pyrolysis.

[0070] In some embodiments of the present application, the auxiliary medium is Al2O3, and the temperature of the carbon thermal shock treatment is 880°C-920°C. For example, it can be 880°C, 890°C, 900°C, 910°C, 920°C, etc., or it can be a range composed of any of the above values. Therefore, under the heat storage effect of Al2O3 and the above temperature range, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0071] In some embodiments of the present application, the auxiliary medium is Al2O3, and the carbon thermal shock treatment time is 18s-22s. For example, it can be 18s, 19s, 20s, 21s, 22s, etc., or it can be a range of any of the above values. In this way, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0072] In some embodiments of the present application, the auxiliary medium is Al2O3, and the number of carbon thermal shock treatments is 1.

[0073] In some embodiments of the present application, the auxiliary medium is Fe2O3, and the mass ratio of the Fe2O3 to the negative electrode sheet of the battery is (4-6):1. For example, it can be 4:1, 5:1, 6:1, etc., or it can be a range composed of any of the above values. Therefore, by making the mass ratio of Fe2O3 to the negative electrode sheet of the battery within the above range, Fe2O3 can play a better role, promote the migration of lithium in graphite, increase the leaching rate of lithium, and absorb harmful gases such as hydrogen fluoride generated during pyrolysis.

[0074] In some embodiments of the present application, the auxiliary medium is Fe2O3, and the temperature of the carbon thermal shock treatment is 880°C-920°C. For example, it can be 880°C, 890°C, 900°C, 910°C, 920°C, etc., or it can be a range composed of any of the above values. Therefore, under the heat storage effect of Fe2O3 and the above temperature range, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0075] In some embodiments of the present application, the auxiliary medium is Fe2O3, and the carbon thermal shock treatment time is 18s-22s. For example, it can be 18s, 19s, 20s, 21s, 22s, etc., or it can be a range of any of the above values. In this way, the graphite material can be efficiently separated from the current collector, and the lithium leaching rate can be effectively improved.

[0076] In some embodiments of the present application, the auxiliary medium is Fe2O3, and the carbon thermal shock treatment is performed twice.

[0077] In some embodiments of the present application, the lithium-ion battery is selected from at least one of a ternary lithium-ion battery, a lithium iron phosphate battery, a lithium cobalt oxide battery, and a lithium manganese oxide battery.

[0078] In some embodiments of the present application, the carbon thermal shock treatment product is first mixed with water, and then the mixed treatment product is ultrasonically treated to obtain a lithium-containing leaching solution, a graphite material and a current collector.

[0079] It should be noted that the present application does not specifically limit the amount of water, as long as it can leach the lithium element. Exemplarily, it can be 10mL-15mL. For example, it can be 10mL, 11mL, 12mL, 13mL, 14mL, 15mL, etc.

[0080] In some embodiments of the present application, the ultrasonic treatment time is 5s-15s. For example, it can be 5s, 8s, 10s, 12s, 15s, etc., or it can be a range of any of the above values. In this way, the leaching of lithium elements can be accelerated, the leaching time can be shortened, and the lithium leaching rate can be increased; at the same time, the "crumbling" graphite powder of the binder due to high temperature decomposition can be separated from the copper foil, thereby improving the separation efficiency.

[0081] Method for extracting lithium from clean water

[0082] The present application proposes a method for extracting lithium from clean water. According to an embodiment of the present application, the method comprises: using the aforementioned method for recovering negative electrode materials of lithium-ion batteries to recover negative electrode sheets of lithium-ion batteries, and obtaining a lithium-containing aqueous solution. As mentioned above, the method for recovering negative electrode materials of lithium-ion batteries in the present application can achieve the selective recovery of valuable metal lithium with the assistance of an auxiliary medium, and can effectively leach valuable metal lithium from graphite materials only under clean water conditions, thereby improving the leaching rate of lithium. Therefore, the method for extracting lithium from clean water in the present application also has a high lithium leaching rate. Those skilled in the art can understand that the method for extracting lithium from clean water has all the features and advantages of the aforementioned method for recovering negative electrode materials of lithium-ion batteries, and will not be elaborated on here.

[0083] The scheme of the present application will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the literature in this area or the product specification are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0084] Example 1: Screening of auxiliary media

[0085] (1) Cut the negative electrode sheet of the discharged waste lithium battery (ternary lithium-ion battery) into 1×1cm 2 Weigh different auxiliary medium particles, such as calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), calcium oxide (CaO), aluminum oxide (Al2O3), iron oxide (Fe2O3), ferroferric oxide (Fe3O4), and iron hydroxide (Fe(OH)3), in a mass ratio of 2:1 between the auxiliary medium and the negative electrode. Place the auxiliary medium and the negative electrode in the groove of the graphite boat. Evenly spread the auxiliary medium on the upper and lower layers of the negative electrode to form a sandwich-like structure.

[0086] (2) Place the graphite boat in the Joule device, set the voltage to 30 V, set the time to fast 5 s, adjust the current parameters, and conduct a carbon thermal shock test in a nitrogen atmosphere at 750 °C;

[0087] (3) After cooling for a few seconds, take out the graphite boat. Separate the auxiliary medium particles, use tweezers to take out the negative electrode sheet in the middle from the auxiliary medium particles, gently scrape off a small amount of auxiliary medium powder attached to the negative electrode sheet, then put the negative electrode sheet in a small beaker and add a small amount of deionized water;

[0088] (4) placing the small beaker in an ultrasonic oscillator, ultrasonicating for 10 seconds, and filtering and separating to obtain the lithium-containing solution, graphite material, and current collector (copper sheet);

[0089] (5) The lithium-containing solution obtained after the carbon thermal shock test using different auxiliary media was subjected to a lithium leaching efficiency test. The specific test process is as follows: the lithium-containing solution in the small beaker and the water washed multiple times in the small beaker were poured into a colorimetric tube and fixed to 25 mL with deionized water. The lithium concentration in the solution was detected by an inductively coupled plasma emission spectrometer (ICP-AES), and the lithium leaching rate was calculated according to formula 1-1:

[0090]

[0091] Where η is the leaching rate of a certain element; M is the mass of lithium leached from water after CTS (carbon thermal shock); M0 is the theoretical mass of lithium in the negative electrode sheet, which is obtained through aqua regia digestion experiment.

[0092] (6) The separation efficiency of the graphite material and the current collector (copper sheet) after the carbon thermal shock test is measured. The specific test process is as follows: By calculating the difference between the mass of the negative electrode sheet before the carbon thermal shock and the mass of the peeled copper foil, the separation rate of graphite and copper foil is calculated according to formula 1-2:

[0093]

[0094] Where W0 is 1×1cm 2 The mass of the negative electrode, W Cu is the actual weight of the copper foil obtained after stripping, and a is the percentage of graphite in the negative electrode, which is calculated by the stripping rate of the negative electrode pyrolysis in a tubular furnace at 600-800°C.

[0095] Experimental results: The control group was a carbon thermal shock test on the negative electrode sheet without adding auxiliary media. The experimental results are as follows: Figure 1 and Figure 2 As shown in the figure, compared with not adding auxiliary media, adding different auxiliary media can promote lithium leaching and improve the separation efficiency of graphite and copper foil. Among them, calcium carbonate, aluminum oxide and iron oxide have the best effect on promoting lithium leaching, and can significantly improve the separation efficiency of graphite and current collector. Calcium carbonate, aluminum oxide and iron oxide will be used as auxiliary media for subsequent research.

[0096] Example 2: Selection of carbon thermal shock test conditions

[0097] 1. Temperature selection

[0098] Cut the negative electrode sheet of the discharged waste lithium battery (ternary lithium-ion battery) into 1×1cm 2About, different auxiliary media and negative electrode sheets were respectively placed in a mass ratio of 2:1, calcium carbonate, aluminum oxide and iron oxide were weighed, and the auxiliary media and negative electrode sheets were placed in the grooves of the graphite boat in a sandwich structure. According to the method described in Example 1, carbon thermal shock tests were performed at temperatures of 800°C, 850°C, 900°C and 950°C.

[0099] The experimental results are as follows Figure 3 As shown in a. The optimal temperature of carbon thermal shock assisted by calcium carbonate medium is 800℃, and the optimal temperature of carbon thermal shock assisted by aluminum oxide and iron oxide medium is 900℃.

[0100] 2. Time selection

[0101] Cut the negative electrode sheet of the discharged waste lithium battery (ternary lithium-ion battery) into 1×1cm 2 About, different auxiliary media and negative electrode sheets were respectively placed in a mass ratio of 2:1, calcium carbonate, aluminum oxide and iron oxide were weighed, and the auxiliary media and negative electrode sheets were placed in the grooves of the graphite boat in a sandwich structure. According to the method described in Example 1, carbon thermal shock tests were carried out at the optimal temperature, wherein the carbon thermal shock time was kept warm for 5s, 10s, 15s, and 20s, respectively.

[0102] The experimental results are as follows Figure 3 As shown in b. The optimal retention time of carbon thermal shock assisted by calcium carbonate medium is 15s, and the optimal retention time of carbon thermal shock assisted by aluminum oxide and iron oxide medium is 20s.

[0103] 3. Selection of the mass ratio of auxiliary medium to negative electrode

[0104] Cut the negative electrode sheet of the discharged waste lithium battery (ternary lithium-ion battery) into 1×1cm 2 Calcium carbonate, aluminum oxide and iron oxide were weighed and placed in the grooves of the graphite boat in a sandwich structure. Carbon thermal shock tests were performed at the optimal temperature and optimal retention time according to the method described in Example 1.

[0105] The experimental results are as follows Figure 3 As shown in Figure c, when the mass ratio of calcium carbonate to the negative electrode sheet is 2:1, the lithium leaching rate can reach more than 95%; when the mass ratio of aluminum oxide to the negative electrode sheet is 4:1, the lithium leaching rate can also reach more than 95%; when the mass ratio of iron oxide to the negative electrode sheet is 5:1, the lithium leaching rate can reach more than 60%. This shows that the auxiliary medium can significantly improve the lithium leaching rate in the negative electrode sheet.

[0106] 4. Choice of impact times

[0107] Cut the negative electrode sheet of the discharged waste lithium battery (ternary lithium-ion battery) into 1×1cm 2 About, different auxiliary media and negative electrode sheets were respectively placed in a mass ratio of 2:1, calcium carbonate, aluminum oxide and iron oxide were weighed, and the auxiliary media and negative electrode sheets were placed in the grooves of the graphite boat in a sandwich structure. According to the method described in Example 1, carbon thermal shock tests were carried out at the optimal temperature and optimal retention time, wherein the number of carbon thermal shocks was 1, 2, and 3, respectively.

[0108] The experimental results are as follows Figure 3 d. The optimal number of carbon thermal shocks assisted by calcium carbonate medium and alumina medium is 1, and the optimal number of carbon thermal shocks assisted by iron oxide medium is 2.

[0109] In summary, when the auxiliary medium is calcium carbonate, the lithium leaching efficiency is highest when the carbon thermal shock temperature is 800°C, the carbon thermal shock time is 15s, the mass ratio of calcium carbonate particles to negative electrode sheets is 2:1, and the carbon thermal shock is performed once; when the auxiliary medium is aluminum oxide, the lithium leaching efficiency is highest when the carbon thermal shock temperature is 900°C, the carbon thermal shock time is 20s, the mass ratio of aluminum oxide particles to negative electrode sheets is 4:1, and the carbon thermal shock is performed once; when the auxiliary medium is iron oxide, the lithium leaching efficiency is highest when the carbon thermal shock temperature is 900°C, the carbon thermal shock time is 20s, the mass ratio of iron oxide particles to negative electrode sheets is 5:1, and the carbon thermal shock is performed twice.

[0110] The effect of adding auxiliary medium on the lithium leaching rate can be seen from the electron microscopy image. Figure 4 Further supplement. Among them, (a) is the raw material waste graphite, (b) is the graphite after carbon thermal shock without auxiliary medium, (c) is the graphite after carbon thermal shock with auxiliary medium CaCO3, (d) is the residue of carbon thermal shock-water immersion with auxiliary medium CaCO3, (e) is the graphite after carbon thermal shock with auxiliary medium Al2O3, (f) is the residue of carbon thermal shock-water immersion with auxiliary medium Al2O3, (g) is the graphite after carbon thermal shock with auxiliary medium Fe2O3, and (h) is the residue of carbon thermal shock-water immersion with auxiliary medium Fe2O3. The comparison of each morphology shows that a large number of small particles grow on the surface of the graphite after carbon thermal shock with auxiliary medium, and the small particles disappear after water immersion. It shows that the auxiliary medium induces the lithium in the graphite to migrate to the surface, thereby improving the lithium leaching rate.

[0111] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for recycling negative electrode materials of lithium ion batteries, characterized in that: include: Carbide thermal shock treatment is performed on the negative electrode sheet of the battery and the auxiliary medium; The carbon thermal shock treatment product is mixed with water and subjected to ultrasonic treatment to obtain a lithium-containing leaching solution, a graphite material and a current collector; Wherein, the auxiliary medium is an alkaline medium with a high melting point.

2. The method according to claim 1, characterized in that The auxiliary medium includes at least one of CaCO3, Al2O3, Fe2O3, and Fe3O4.

3. The method according to claim 2, characterized in that The mass ratio of the auxiliary medium to the battery negative electrode sheet is (1:1)-(7:1); And / or, the auxiliary medium is located on both sides of the negative electrode sheet of the battery; And / or, the battery negative electrode sheet is a graphite negative electrode sheet with a current collector.

4. The method according to claim 3, characterized in that Satisfy at least one of the following conditions: The voltage of the carbon thermal shock treatment is 25V-35V; The temperature of the carbon thermal shock treatment is 750°C-950°C; The carbon thermal shock treatment time is 5s-25s; The carbon thermal shock treatment is performed 1 to 3 times.

5. The method according to claim 4, characterized in that The auxiliary medium is CaCO3, and the mass ratio of CaCO3 to the battery negative electrode sheet is (1-3):1; And / or, the temperature of the carbon thermal shock treatment is 780°C-820°C; And / or, the carbon thermal shock treatment time is 13s-17s; And / or, the carbon thermal shock treatment is performed once.

6. The method according to claim 4, characterized in that The auxiliary medium is Al2O3, and the mass ratio of Al2O3 to the battery negative electrode sheet is (3-5):1; And / or, the temperature of the carbon thermal shock treatment is 880°C-920°C; And / or, the carbon thermal shock treatment time is 18s-22s; And / or, the carbon thermal shock treatment is performed once.

7. The method according to claim 4, characterized in that The auxiliary medium is Fe2O3, and the mass ratio of Fe2O3 to the battery negative electrode sheet is (4-6):1; And / or, the temperature of the carbon thermal shock treatment is 880°C-920°C; And / or, the carbon thermal shock treatment time is 18s-22s; And / or, the carbon thermal shock treatment is performed twice.

8. The method according to claim 1, characterized in that The lithium-ion battery is selected from at least one of a ternary lithium-ion battery, a lithium iron phosphate battery, a lithium cobalt oxide battery, and a lithium manganese oxide battery.

9. A method for extracting lithium from clean water, characterized in that: include: The negative electrode sheet of a lithium-ion battery is recovered by the method described in any one of claims 1 to 8 to obtain a lithium-containing aqueous solution.

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