A method for recycling ASR fine crushed material

Abstract

This invention relates to a method for recycling ASR (Alternative Residue Scattering) fragments, comprising the following steps: uniformly mixing a first positive electrode sheet from a waste lithium-ion battery with first ASR fragments, heating to react and decomposing the binder in the first positive electrode sheet, and naturally cooling to room temperature after the reaction to obtain a mixture of a second positive electrode sheet and second ASR fragments; removing the second positive electrode sheet, cleaning and drying it, and separating the positive electrode active material and metal foil; and recycling the second ASR fragments. This invention utilizes the co-pyrolysis of waste lithium-ion battery positive electrode sheets and ASR fragments to dispose of and convert the ASR fragments into a flux for separating waste lithium-ion battery positive electrode sheets, effectively separating the positive electrode active material and metal foil; the ASR fragments can also act as an adsorbent for fluorides, preventing the decomposition of binders and other components to produce hydrogen fluoride, while simultaneously forming neutral fluorides, thus reducing the environmental impact of ASR.

Description

Technical Field

[0001] This invention relates to the field of battery and end-of-life vehicle debris recycling, specifically to a method for recycling ASR fine debris. Background Technology

[0002] Lithium-ion batteries (LIBs) are widely favored for their superior performance. With the large-scale entry of LIBs into the market, the recycling and reuse of spent LIBs will inevitably become a major challenge. LIB cathode recycling generally employs physical, chemical, and biological methods. Among these, chemical methods, using inorganic acid leaching, organic acid leaching, alkali leaching, or ammonia leaching to separate and recover valuable components, are the most commonly used. However, the acids, alkalis, and other chemicals used are harmful to the environment. Therefore, research into green recycling and reuse technologies for spent LIB cathode materials that meet stringent environmental protection requirements and are practical is particularly urgent.

[0003] Automobile shredder residue (ASR) has a low moisture content and a complex composition, mainly consisting of metal scrap, fine foam, plastics, rubber, textiles, glass, sand and gravel particles, silicates, and fly ash. It also contains elements such as iron, silicon, and calcium, exhibiting alkalinity in natural environments, thus posing a significant environmental impact. With the rapid development of the automotive market, the number of scrapped vehicles is increasing year by year, making the resource and environmental problems caused by ASR increasingly prominent. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a method for recycling fine ASR materials, thereby solving the technical problems of difficult recycling of lithium-ion battery cathodes and ASR in the prior art.

[0005] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows:

[0006] In a first aspect, the present invention provides a method for recycling ASR (Automatic Residue Shard) fragments, comprising the following steps: mixing a first positive electrode sheet from a waste lithium-ion battery with a first ASR fragment, heating and reacting to decompose the binder in the first positive electrode sheet, and naturally cooling to room temperature after the reaction to obtain a mixture of a second positive electrode sheet and the second ASR fragment; removing the second positive electrode sheet from the second ASR fragment, cleaning and drying it to separate the positive electrode active material and metal foil; and recycling the second ASR fragment.

[0007] Compared with the prior art, the beneficial effects of the present invention include:

[0008] This invention utilizes the co-pyrolysis of waste lithium-ion battery cathode sheets and ASR (Alternating Current) fragments to dispose of industrial solid waste ASR fragments and convert them into a flux for separating waste lithium-ion battery cathode sheets, effectively separating the active material and metal foil of the cathode sheets. Furthermore, the ASR fragments can act as an adsorbent for fluorides, effectively preventing the decomposition of binders such as PVDF, which generate hydrogen fluoride, from corroding equipment and polluting the environment. Simultaneously, the metal elements in the ASR form neutral fluorides, reducing the environmental impact of ASR. The recovered ASR fragments can be used in building materials or for the leaching and purification of valuable metals, achieving ASR reduction, resource recovery, and harmless disposal. Attached Figure Description

[0009] Figure 1 This is a SEM image of NCM before pyrolysis, with a scale bar of 10 μm;

[0010] Figure 2 This is a SEM image of NCM and ASR (NCM:ASR = 1:2) after pyrolysis at 400℃ in Example 2, with a scale bar of 50 μm;

[0011] Figure 3 This is the EDS elemental analysis spectrum of ASR before pyrolysis;

[0012] Figure 4 This is the EDS elemental analysis spectrum after ASR pyrolysis in Example 2. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0014] This invention provides a method for recycling ASR (acetal slag) fragments, specifically a method for recycling waste lithium-ion battery cathode sheets and ASR fragments through co-pyrolysis. The method provided by this invention yields intact metal foils and cathode active materials, not only promoting the decomposition of the binder polyvinylidene fluoride (PVDF) but also absorbing fluorides to reduce equipment corrosion.

[0015] This invention includes the following steps:

[0016] 1) Discharge the waste lithium-ion battery cells in a sodium chloride solution (the specific concentration should meet the discharge standard), disassemble them by cutting, remove the outer shell, and separate the positive electrode, negative electrode and plastic separator.

[0017] 2) Cut the positive electrode sheet from step 1) into small pieces, then mix it evenly with the ASR fine powder and put it into a crucible. Place the crucible into a tube furnace or muffle furnace, and heat it up and keep it at that temperature for a period of time under program control to promote the decomposition of the binder in the positive electrode sheet. After the reaction is complete, let it cool naturally to room temperature.

[0018] 3) Remove the reacted positive electrode from the ASR fine material, wash the surface of the electrode with water, and then dry and separate the active material and aluminum foil of the positive electrode. The ASR fine material can be recycled several times and then used for leaching and purifying building materials or valuable metals.

[0019] The waste lithium-ion batteries mainly include at least one of the following: waste lithium iron phosphate (LFP) batteries, nickel-cobalt-manganese (NCM) ternary lithium batteries, lithium manganese oxide batteries, and lithium cobalt oxide batteries.

[0020] Preferably, in step 1), the waste lithium-ion battery is discharged to 1V or below and then cut using a laser.

[0021] Preferably, in step 2), the positive electrode sheet is cut into a square or strip shape, with a size of, for example, 2cm × 1cm.

[0022] Preferably, in step 2), the temperature is raised to 300-500°C and held for 10-30 minutes.

[0023] Preferably, in step 2), the particle size of the ASR fine powder is 100 mesh or less (less than 0.15 mm) to ensure better contact between the positive electrode sheet and the ASR particles.

[0024] Preferably, in step 2), the mass ratio of the positive electrode to the ASR is 1:2 to 1:4.

[0025] Preferably, in step 2), the atmosphere of the muffle furnace or tubular furnace is air or an inert gas.

[0026] Preferably, in step 3), the ASR fine crushed material is recycled 1 to 4 times.

[0027] Preferably, after the reaction in step 3), the active material of the positive electrode sheet still has a relatively weak adhesion to the aluminum foil, and is separated by manual separation, rod milling separation or air jet sieve instrument.

[0028] Working principle:

[0029] This invention uses finely shredded ASR as the reaction medium. ASR acts as a flux and adsorbent (because the ASR contains elements such as iron, silicon, and calcium, which exhibit alkalinity in natural environments). It not only promotes the elimination reaction of the PVDF binder but also exhibits excellent adsorption properties through a neutralization reaction with fluorides. This effectively solves the problem of separation between the positive electrode active material and the aluminum foil. Simultaneously, the metal elements in the ASR form neutral fluorides, reducing the environmental impact of ASR. This invention achieves the separation of the active material from the current collector while simultaneously reducing the amount of ASR used, thus achieving the goal of "treating waste with waste."

[0030] The present invention will be further described in detail below through specific embodiments.

[0031] The industrial analysis and elemental analysis of the ASR fine crushed material used in this invention are shown in Table 1 below.

[0032] Table 1. Industrial Analysis and Elemental Analysis of ASR Fine Crushed Materials

[0033]

[0034]

[0035] Ash content indicates that ASR is mostly composed of elements such as iron, silicon, and calcium, and is a substance that exhibits alkalinity in natural environments.

[0036] Example 1

[0037] First, the waste lithium iron phosphate battery cells are placed in a sodium chloride solution and discharged until the voltage is 1V or below. Then, the battery casing is disassembled using a laser cutting machine to remove the casing and separate the positive electrode, negative electrode and plastic separator.

[0038] The positive electrode sheet was cut into small pieces of 2cm × 1cm. These were then mixed with finely ground ASR material (100 mesh or smaller) at a mass ratio of 1:2 and placed in a crucible. The crucible was then placed in a tube furnace or muffle furnace, and the temperature was raised to 300℃ under programmed control for 30 minutes to promote the decomposition of the binder in the positive electrode sheet. After the reaction, the mixture was allowed to cool naturally to room temperature. The reacted positive electrode sheet was then removed from the ASR material, its surface was washed with deionized water, dried, and the active material and aluminum foil were manually separated. The peeling rate of the lithium iron phosphate (LFP) positive electrode sheet was calculated to be 97.81% using the following formula. Using the same treatment steps, the peeling rate of the ternary NCM positive electrode sheet was 60.82% (the active material and aluminum foil of lithium iron phosphate have better stability, while the ternary NCM material has larger particles and an alkaline surface, resulting in relatively poor aluminum foil stability. These factors lead to a significant difference in the ease of peeling the active material and current collector between lithium iron phosphate and ternary NCM).

[0039] Peeling rate = Weight of positive electrode active material / (Weight of electrode sheet - Weight of aluminum foil) (1)

[0040] Weight of aluminum foil = density of aluminum ρ × length l × width d × thickness μ (2)

[0041] The density of aluminum is 2.7 g / cm³. 3 The thickness is 15μm.

[0042] It has been verified that the weight of aluminum foil calculated using formula (2) is basically the same as the result of direct weighing, and it can be directly weighed in actual experiments.

[0043] Example 2

[0044] First, the waste lithium iron phosphate battery cells are placed in a sodium chloride solution and discharged until the voltage is 1V or below. Then, the battery casing is disassembled using a laser cutting machine to remove the casing and separate the positive electrode, negative electrode and plastic separator.

[0045] The positive electrode sheet was cut into small pieces of 2cm × 1cm and mixed evenly with ASR fine powder of 100 mesh or smaller at a mass ratio of 1:2. The mixture was then placed in a crucible and placed in a tube furnace or muffle furnace. The temperature was raised to 400℃ under programmed control for 30 minutes to promote the decomposition of the binder in the positive electrode sheet. After the reaction, the mixture was allowed to cool naturally to room temperature. The reacted positive electrode sheet was then removed from the ASR fine powder, its surface was washed with deionized water, dried, and the active material and aluminum foil of the positive electrode sheet were manually separated. The peeling rate of the lithium iron phosphate (LFP) positive electrode sheet was calculated to be 99.63%, and the peeling rate of the ternary material NCM positive electrode sheet was 91.12%.

[0046] Example 3

[0047] First, the waste lithium iron phosphate battery cells are placed in a sodium chloride solution and discharged until the voltage is 1V or below. Then, the battery casing is disassembled using a laser cutting machine to remove the casing and separate the positive electrode, negative electrode and plastic separator.

[0048] The positive electrode sheet was cut into small pieces of 2cm × 1cm and mixed evenly with ASR fine powder of 100 mesh or smaller at a mass ratio of 1:2. The mixture was then placed in a crucible and placed in a tube furnace or muffle furnace. The temperature was raised to 500℃ under programmed control for 30 minutes to promote the decomposition of the binder in the positive electrode sheet. After the reaction, the mixture was allowed to cool naturally to room temperature. The reacted positive electrode sheet was then removed from the ASR fine powder, its surface was washed with deionized water, dried, and the active material and aluminum foil of the positive electrode sheet were manually separated. The peeling rate of the lithium iron phosphate (LFP) positive electrode sheet was calculated to be 99.58%, and the peeling rate of the ternary material NCM positive electrode sheet was 80.75%.

[0049] The conditions (heating for 30 min, different reaction temperatures, positive electrode:ASR mass ratio of 1:2) and test results of Examples 1-3 were statistically analyzed, and the results are shown in Table 1 below.

[0050] Table 1. Conditions and test results for Examples 1-3

[0051] Group Temperature / ℃ LFP cathode stripping rate % NCM peeling rate / % Example 1 300 97.81 60.82 Example 2 400 99.63 91.12 Example 3 500 99.58 80.75

[0052] As shown in Table 1, the peeling rate of LFP positive electrode increases with increasing reaction temperature, reaching over 97% at 300℃. The peeling rate of NCM increases significantly at 400℃, but decreases with further increases in reaction temperature. Increasing the reaction temperature is beneficial for the decomposition of the binder (polyvinylidene fluoride PVDF), but excessively high temperatures can cause the fluorides adsorbed on the ASR surface to decompose and be released again, reacting with the aluminum foil and making it brittle and difficult to effectively peel off from the active material. Therefore, the preferred reaction temperature in this invention is 400℃.

[0053] Example 4

[0054] The only difference from Example 2 is that the mass ratio of the positive electrode to ASR is adjusted to 1:4, while the other steps and conditions are the same as in Example 2.

[0055] Comparative Example 1

[0056] The only difference from Example 2 is that ASR is removed; the other steps and conditions are the same as in Example 2.

[0057] Comparative Example 2

[0058] The only difference from Example 2 is that the mass ratio of positive electrode to ASR is adjusted to 1:1, while the other steps and conditions are the same as in Example 2.

[0059] Examples 2, 4, and Comparative Examples 1-2 (heated to 400°C, reaction time 30 min, different positive electrode:ASR mass ratios) were tested, and the test results are shown in Table 2 below.

[0060] Table 2. Conditions and test results for Examples 2, 4, and Comparative Examples 1-2.

[0061] Group Positive electrode: ASR mass ratio LFP cathode stripping rate % NCM peeling rate / % Example 2 1：2 99.63 91.12 Example 4 1：4 99.91 97.68 Comparative Example 1 No ASR 79.89 52.27 Comparative Example 2 1：1 86.15 71.12

[0062] As shown in Table 2, the stripping rate of the positive electrode sheet increases with the increase of ASR content, and the stripping rate is above 97% when the mass ratio is 1:4. Furthermore, as shown in Example 2 and Comparative Example 1, the addition of ASR in this invention can effectively improve the stripping rate of the positive electrode sheet in waste batteries. Considering factors such as cost and energy consumption, the preferred mass ratio of positive electrode sheet to ASR in this invention is 1:(2-4).

[0063] Example 5

[0064] The only difference from Example 2 is that the reaction time is adjusted to 10 minutes, while the other steps and conditions are the same as in Example 2.

[0065] Example 6

[0066] The only difference from Example 2 is that the reaction time is adjusted to 60 min, while the other steps and conditions are the same as in Example 2.

[0067] Examples 2 and 5-6 (heated to 400°C, different reaction times, positive electrode:ASR mass ratio of 1:2) were tested, and the test results are shown in Table 3 below.

[0068] Table 3. Conditions and test results for Examples 2 and 5-6

[0069] Group Reaction time / min LFP cathode stripping rate % NCM peeling rate / % Example 5 10 99.24 72.02 Example 2 30 99.63 91.12 Example 6 60 99.53 73.74

[0070] As shown in Table 3, the peeling rate of LFP positive electrode increases with increasing reaction time, while the peeling rate of NCM first increases and then decreases. Increasing the reaction time is beneficial to the decomposition of the binder (polyvinylidene fluoride PVDF). However, if the reaction time is too long, the fluorides adsorbed on the surface of ASR will decompose and be released again, reacting with the aluminum foil and making it brittle and difficult to effectively peel off from the active material. Therefore, the preferred reaction time in this invention is 10 to 30 minutes.

[0071] Example 7

[0072] The only difference from Example 2 is that the number of cycles is adjusted to 1, while the other steps and conditions are the same as in Example 2.

[0073] Example 8

[0074] The only difference from Example 2 is that the number of cycles is adjusted to 2, while the other steps and conditions are the same as in Example 2.

[0075] Example 9

[0076] The only difference from Example 2 is that the number of cycles is adjusted to 3, while the other steps and conditions are the same as in Example 2.

[0077] Examples 7-9 (heated at 400°C, reaction time 30 min, positive electrode:ASR mass ratio of 1:2, different number of cycles) were tested, and the test results are shown in Table 4 below.

[0078] Table 4. Conditions and test results for Examples 7-9

[0079]

[0080]

[0081] As shown in Table 4, the peeling rate of the positive electrode sheet decreases with the increase of the number of cycles, and the peeling rate decreases significantly after 3 cycles. Therefore, the preferred number of cycles in this invention is 1 to 2.

[0082] Depend on Figure 1 and Figure 2 Comparison shows that, Figure 1 Before pyrolysis, the particle size of NCM was less than 10 μm, mainly concentrated between 1 and 6 μm; Figure 2 After NCM and ASR are pyrolyzed at 400℃, the particle size is mainly concentrated between 10 and 30 μm, and the spherical particles become larger, indicating that the crystal structure of NCM has changed, which promotes the separation of the active material from the current collector.

[0083] Depend on Figure 3 and Figure 4 The comparison shows that the pyrolyzed ASR sample contains F element, indicating that the method provided by the present invention can obtain complete metal foil and positive electrode active material. It can not only promote the decomposition of the binder polyvinylidene fluoride, but also absorb fluorides to reduce corrosion of equipment, indicating that ASR has an adsorption effect on F.

[0084] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for recycling ASR fine crushed material, characterized in that, Includes the following steps: The first positive electrode sheet of the waste lithium-ion battery and the first ASR fine fragments are mixed evenly at a mass ratio of 1:(2~4), heated to react, so that the binder in the first positive electrode sheet decomposes. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain the second positive electrode sheet and the second ASR fine fragments. The heating reaction temperature is 300~500℃ and the temperature is maintained for 30min. The second positive electrode sheet is removed from the second ASR fine fragments, cleaned and dried, and then separated to obtain the positive electrode active material and metal foil; the second ASR fine fragments are recovered. The waste lithium-ion batteries are waste lithium iron phosphate batteries or nickel-cobalt-manganese ternary lithium batteries.

2. The method for recycling ASR fines according to claim 1, characterized in that, The first positive electrode is obtained by disassembling and separating the cells of a waste lithium-ion battery after they have been discharged to below 1V.

3. The method for recycling ASR fine crushed material according to claim 1, characterized in that, The particle size of the first ASR fine crushed material is less than 0.15 mm.

4. The method for recycling ASR fine crushed material according to claim 1, characterized in that, The heating reaction is carried out in a muffle furnace or a tube furnace.

5. The method for recycling ASR fine crushed material according to claim 4, characterized in that, The atmosphere for the heating reaction is air or an inert gas.

6. The method for recycling ASR fine crushed material according to claim 1, characterized in that, The separation includes manual separation, rod mill separation, or air jet sieve separation.

7. The method for recycling ASR fine crushed material according to claim 1, characterized in that, The second ASR fine crushed material is recycled 1 to 4 times.

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