A lithium battery recycling method

Abstract

The present invention discloses a method for recycling lithium batteries, which relates to the technical field of lithium battery recycling. The method comprises the following steps: subjecting the lithium battery, after mechanical treatment, to magnetic separation of the battery core and the lithium battery shell; then subjecting the battery core to airflow sorting and recovering the diaphragm; then disassembling the lithium battery core in water, filtering the lithium-containing electrolyte solution and the electrolyte to obtain a mixture of positive electrode sheets, negative electrode sheets, and graphite; and calcining, cooling, complete crushing, and screening to obtain black powder, copper sheets, and aluminum sheets. The method provided by the present invention can greatly reduce the content of aluminum and copper impurities in the black powder, so that the content of aluminum and copper impurities in the black powder is less than 2%, thereby improving the recovery rate of valuable metal elements. The method is simple and easy to implement and can be easily promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery recycling, and in particular to a lithium battery recycling method. Background Art

[0002] Currently, after retired lithium-ion batteries reach the end of their useful life, they are typically discharged chemically and mechanically crushed physically. Traditionally, after mechanical crushing, the mixed positive and negative electrodes of bulk lithium-ion batteries are incinerated in an incinerator, and the resulting black powder is transported by wind power. Afterwards, the copper and aluminum sheets are physically separated. This separation process is lengthy, resulting in a saleable battery black powder with high copper and aluminum impurity content, resulting in a low resource recovery rate.

[0003] Patent CN103618120A discloses a method for separating and recovering graphite and copper flakes from waste lithium-ion battery negative electrode materials. While the method includes a method for dispersing graphite and copper flakes, the process requires the use of a large amount of organic solvent, which can easily cause pollution. Furthermore, the raw materials are limited to the separation and recovery of graphite and copper flakes from negative electrode sheets, preventing the separation and recovery of positive electrode sheets. Patent CN107204495A discloses a method for environmentally friendly recycling and reuse of waste lithium battery positive electrode materials. The method involves crushing the material to obtain copper powder, aluminum powder, and a separator. However, the copper and aluminum powders are mixed with the separator and cannot be recovered.

[0004] Currently, battery disassembly workshops discharge batteries by immersion in a sodium chloride solution. This is done to fully discharge the batteries and prevent fires. However, shredding inevitably mixes the various components of used lithium-ion batteries, making them difficult to effectively recycle and reuse. Used lithium-ion batteries contain several valuable metal elements as well as potentially harmful organic matter and fluoride. The shredding method for used lithium-ion batteries using sodium chloride solution discharge cannot recover electrolyte or lithium. After complete discharge, most lithium resides in the positive electrode of the discharged battery, with a small amount remaining in the negative electrode. However, as the battery ages, a significant portion of lithium remains in the solid electrolyte interface film formed on the negative electrode surface. Therefore, if the soluble lithium in used lithium-ion batteries (i.e., lithium in the electrolyte and negative electrode) is not collected, the amount of lithium available for the lithium battery industry is significantly reduced. Mechanical shredding also results in significant amounts of aluminum and copper impurities being mixed into the black powder.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a lithium battery recycling method to solve the above technical problems.

[0007] The present invention is achieved in that:

[0008] The present invention provides a lithium battery recycling method, which comprises the following steps:

[0009] The lithium battery cells and lithium battery shells are separated after mechanical treatment and then magnetically separated to recover the iron in the lithium battery;

[0010] Then the separator is recovered through air flow sorting; the battery electrodes are then dispersed in water;

[0011] The lithium battery cell is then disassembled in water to obtain a lithium-containing electrolyte solution and an electrolyte; after filtering the lithium-containing electrolyte solution and the electrolyte, a mixture of a positive electrode sheet, a negative electrode sheet, and graphite is obtained;

[0012] The mixture of the positive electrode sheet, the negative electrode sheet and the graphite is then calcined, and the cooled mixture of the positive electrode sheet, the negative electrode sheet and the graphite is completely crushed and sieved to obtain black powder, copper sheets and aluminum sheets.

[0013] The inventors first mechanically strip the lithium battery casing to facilitate iron recovery. This avoids the problem of complete crushing (e.g., pulverization) that would mix various components of the used lithium-ion batteries in the water, making it difficult to effectively recover and reuse the electrolyte or lithium. The inventors' underwater disassembly method facilitates better recovery and reuse of the electrolyte or lithium, avoiding the problem of complete pulverization that would cause multiple valuable metal elements to mix with carbon powder, making it impossible to effectively recover.

[0014] The separator is recovered through airflow sorting, and the lithium battery cells are then disassembled (or cleaned) in water. This allows the electrolyte and electrolyte solution in the cells to enter the water. The lithium-containing electrolyte solution and electrolyte solution are then filtered. The precipitate is a mixture of positive and negative electrode sheets and graphite.

[0015] High-temperature calcination and cooling can quickly separate the positive electrode material and carbon powder in the positive and negative electrode sheets from the aluminum and copper sheets, thereby facilitating better separation of the subsequent copper sheets, aluminum sheets and graphite.

[0016] After full crushing, the crushed black powder, copper flakes and aluminum flakes are obtained, which are then sieved to obtain the black powder. The copper flakes and aluminum flakes can be separated by the subsequent copper and aluminum separator.

[0017] The method provided by the present invention can greatly reduce the content of aluminum impurities and copper impurities in black powder, so that the content of aluminum and copper impurities in black powder is both below 2%, thereby improving the recovery rate of valuable metal elements.

[0018] In a preferred embodiment of the present invention, the calcination temperature is 400-550°C and the calcination time is 120-125 minutes. Under the above calcination conditions, the positive electrode material and carbon powder in the positive and negative electrode sheets can be quickly separated from the aluminum sheet and the copper sheet.

[0019] For example, the calcination temperature is 420-550° C. and the calcination time is 121-124 minutes.

[0020] In a preferred embodiment of the present invention, during the calcination, the temperature in the calcination furnace is first raised to 400-550° C. within 100-120 minutes, and then kept at this temperature for 120-125 minutes.

[0021] Compared with direct calcination in a high-temperature environment, the above-mentioned gradual temperature increase calcination method can better achieve the rapid separation of the positive electrode material and carbon powder in the positive and negative electrode sheets from the aluminum sheet and copper sheet.

[0022] In a preferred embodiment of the present invention, cooling is performed until the temperature of the calcined product is 20-25°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C or 25°C.

[0023] In a preferred embodiment of the present invention, after the calcination is completed, the temperature in the calcination furnace is first reduced to 200-220°C within 100-120 minutes, and then the calcined positive electrode sheet, negative electrode sheet and graphite products are placed in water with a temperature of 20-25°C to cool.

[0024] Cooling directly in water at 200-220°C can accelerate the separation of the positive electrode material and carbon powder in the positive and negative electrodes from the aluminum and copper sheets.

[0025] In a preferred embodiment of the present invention, a drying step is further included before the cooled mixture of the positive electrode sheet, the negative electrode sheet and the graphite is completely crushed.

[0026] In a preferred embodiment of the present invention, the screening is performed through a 30-80 mesh sieve, wherein the undersize is black powder and the oversize is copper and aluminum sheets.

[0027] In a preferred embodiment of the present invention, the disassembly in water refers to disassembling the lithium battery cell in water at a temperature of 60° C. to 80° C. Disassembly at this temperature helps the metal elements in the electrolyte to be better dispersed in the water.

[0028] When disassembled, the volume mass ratio of water to battery cell is 20-50mL / g.

[0029] Before disassembling in water, the waste lithium-ion batteries are mechanically cut into blocks or other specific shapes.

[0030] In a preferred embodiment of the present invention, the above-mentioned disassembly in water is stirred at a speed of 60-80 r / min to accelerate the dispersion speed, for example, 60-75 r / min.

[0031] In an optional embodiment, the stirring time is 1-2 hours.

[0032] In a preferred embodiment of the present invention, the magnetic separation is a secondary magnetic separation to recover iron from lithium batteries. The crushed steel shells are magnetically separated, and a secondary magnetic separation is performed after the primary magnetic separation.

[0033] The present invention has the following beneficial effects:

[0034] The present invention first mechanically strips the lithium battery casing to facilitate iron recovery. This avoids the problem of complete crushing (e.g., pulverization) that can contaminate the water with various components of the spent lithium-ion batteries, making it difficult to effectively recover and reuse the electrolyte or lithium. The inventor's underwater disassembly method facilitates better recovery and reuse of the electrolyte or lithium, avoiding the problem of complete pulverization that can mix valuable metal elements with carbon powder, preventing effective recovery.

[0035] The separator is recovered through airflow sorting, and the lithium battery cells are then disassembled (or cleaned) in water. This allows the electrolyte and electrolyte solution in the cells to enter the water. The lithium-containing electrolyte solution and electrolyte solution are then filtered. The precipitate is a mixture of positive and negative electrode sheets and graphite.

[0036] High-temperature calcination and cooling can quickly separate the positive electrode material and carbon powder in the positive and negative electrode sheets from the aluminum and copper sheets, thereby facilitating better separation of the subsequent copper sheets, aluminum sheets and graphite.

[0037] After full crushing, the crushed black powder, copper flakes and aluminum flakes are obtained, which are then sieved to obtain the black powder. The copper flakes and aluminum flakes can be separated by the subsequent copper and aluminum separator.

[0038] The method provided by the present invention can greatly reduce the content of aluminum and copper impurities in black powder, making the content of aluminum and copper impurities in black powder below 2%, thereby improving the recovery rate of valuable metal elements. The method is simple and easy to implement and can be easily promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 This is a flow chart of the recycling process;

[0041] Figure 2 Membranes for airflow sorting and recovery;

[0042] Figure 3 This is a picture of the negative electrode sheet and the positive electrode sheet after being completely broken after cooling and drying;

[0043] Figure 4 Screening analysis of the positive electrode sheet after 20 seconds of crushing, with the results of the 30-mesh upper aluminum sheet (left) and copper sheet (right);

[0044] Figure 5 This is the result of sieving and analyzing the positive electrode sheet after being crushed for 20 seconds, showing the black powder on the upper layer of 80 mesh;

[0045] Figure 6 This is the result of sieving and analyzing the positive electrode sheet after being crushed for 20 seconds, showing the black powder in the lower layer of 250 mesh;

[0046] Figure 7 This is a picture of the carbon powder on the broken negative electrode sheet;

[0047] Figure 8 This is the process flow chart of the cutting equipment;

[0048] Figure 9 Diagram of the airflow sorting equipment used in the airflow sorting step. DETAILED DESCRIPTION

[0049] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0050] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0051] Example 1

[0052] This embodiment provides a lithium battery recycling method, the process flow is as follows Figure 1 As shown, it includes the following steps:

[0053] (1) After the waste soft-pack batteries are mechanically cut and crushed, they enter the magnetic separator to separate the crushed steel shells. After the first magnetic separation, they are subjected to secondary magnetic separation. After magnetic separation, they enter the air flow separation. The air flow separation recycles the diaphragm. The diaphragm recovered by the air flow separation is as follows: Figure 2 shown.

[0054] The cutting equipment used in this step is as follows Figure 8 As shown, the used soft-pack batteries enter the feed port of the cutting machine through the feeding hopper, are cut in turn by the horizontal cutting machine and the vertical cutting machine, and then undergo magnetic separation.

[0055] Reference for equipment used in airflow sorting Figure 9 As shown, the material after magnetic separation is sent into the air flow separation equipment through the feeding device. Under the action of the air flow, the diaphragm is sorted by the dust collector and discharged from the light product outlet, while the positive and negative electrode sheets are discharged from the heavy product outlet.

[0056] (2) After the diaphragm is recovered, the positive and negative electrodes are placed in water for cleaning. The waste lithium-ion battery cells are manually disassembled and dispersed in water, and the dispersion stirring speed is 60r / min. The stirring time is 1h. The disassembled solution is filtered to obtain a lithium-containing electrolyte solution and an electrolyte. The disassembly and dispersion temperature in water is 50℃, and the liquid-to-solid ratio is a single 18650 battery (38.5g) 600mL water.

[0057] (3) The positive electrode sheet is placed in a pyrolysis furnace for high-temperature calcination. The process conditions are: temperature rise time 120 minutes, holding temperature of 450°C, holding time 120 minutes, temperature drop time after holding is 120 minutes. When the temperature drops to 200°C, the positive electrode sheet and the negative electrode sheet are taken out of the pyrolysis furnace and placed in cold water at a water temperature of 20°C for cooling for 5 minutes. After drying the moisture, the positive electrode sheet and the negative electrode sheet are mechanically crushed with a universal crusher.

[0058] (4) After mechanical crushing for 20 seconds, sieve with a 30-mesh sieve. The undersize is black powder, and the oversize is copper and aluminum flakes. The copper and aluminum are separated by a copper-aluminum separator.

[0059] Experimental Example 1

[0060] After disassembling the single 18650 battery, the concentration of metal ions in the water solution was tested. The results are shown in Table 1.

[0061] Table 1 Metal ion concentrations of disassembly solutions in water (g / L).

[0062]

[0063] Take 1 ml from the solution and transfer it to a 50 ml colorimetric tube. Use an atomic absorption spectrophotometer to measure the lithium metal ion concentration. Take 5 ml from the solution and transfer it to a 25 ml colorimetric tube. Use an atomic absorption spectrophotometer to measure the nickel, copper, iron, calcium, magnesium, manganese, zinc, sodium, cadmium, and cobalt metal ion concentrations. Take 5 ml from the solution and transfer it to a 25 ml colorimetric tube. Add 1 ml of sodium sulfate and use an atomic absorption spectrophotometer to measure the chromium metal ion concentration.

[0064] Experimental Example 2

[0065] Take photos of the completely crushed positive and negative electrodes, refer to Figure 3 As shown, the positive electrode sheet was screened and analyzed after being crushed for 20 seconds. The screening results are shown as follows: Figure 4 , Figure 5 and Figure 6shown. Figure 7 This is a carbon powder image of the broken negative electrode sheet.

[0066] The elemental analysis of the raw materials and the screened positive electrode materials is shown in Table 2.

[0067] Table 2 Analysis of element content of positive electrode materials (mass percentage m / %)

[0068]

[0069] As can be seen in Table 2, after crushing the positive electrode sheet for 20 seconds, the aluminum impurity content in the positive electrode material after screening and filtration was also low, at 1.05%. The aluminum impurity content in the black powder was 1.05%, and the copper impurity content was 1.03%, while the black powder sold on the market had a copper impurity content of 4.96% and 8.9%. In other words, the recovery method provided by the present invention greatly reduces the content of copper and aluminum impurities in the black powder, with the aluminum and copper impurity contents in the black powder being below 2%, thereby improving the recovery rate.

[0070] The present invention can wash out the electrolyte and recover the lithium in the electrolyte through dispersion in water. The high-temperature calcination cooling method can quickly separate the positive electrode material and carbon powder in the positive and negative electrode sheets from the aluminum sheet and the copper sheet, thereby facilitating the subsequent better separation of the copper sheet, aluminum sheet and graphite.

[0071] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for recycling lithium batteries, characterized in that: It includes the following steps: The lithium battery cells and lithium battery shells are separated after mechanical treatment and then magnetically separated to recover the iron in the lithium battery; Then the membrane is recovered through air flow sorting; The lithium battery cell is then disassembled in water to obtain an electrolyte; the electrolyte is filtered to obtain a mixture of a positive electrode sheet, a negative electrode sheet, and graphite; Then, the mixture of the positive electrode sheet, the negative electrode sheet and the graphite is calcined, and the cooled mixture of the positive electrode sheet, the negative electrode sheet and the graphite is completely crushed and sieved to obtain black powder, copper sheets and aluminum sheets; The disassembly in water comprises: disassembling the lithium battery cell in water, wherein the water temperature is 60°C-80°C during the disassembly; ball milling the lithium battery cell to be disassembled before disassembly in water; stirring the lithium battery cell in water at a speed of 60 r / min-80 r / min for 1-2 hours; and during disassembly, the volume-to-mass ratio of the water to the cell is 20-50 mL / g. During the calcination, the temperature in the calcination furnace is first raised to 400-550°C within 100-120 minutes; the temperature is kept warm for 120-125 minutes; after the calcination is completed, the temperature in the calcination furnace is first lowered to 200-220°C within 100-120 minutes, and then the calcined positive electrode sheet, negative electrode sheet and graphite products are placed in water with a temperature of 20-25°C for cooling.

2. The lithium battery recycling method according to claim 1, characterized in that: Before the cooled mixture of the positive electrode sheet, the negative electrode sheet and the graphite is completely crushed, a drying step is also included.

3. The lithium battery recycling method according to claim 1, characterized in that: The screening is through a 30-80 mesh sieve, wherein the undersize is black powder and the oversize is copper and aluminum sheets.

4. The lithium battery recycling method according to claim 1, characterized in that: The magnetic separation is secondary magnetic separation to recover iron in lithium batteries.

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