Method for separating and recycling positive and negative electrode materials of waste lithium iron phosphate liquid injection battery cell

Abstract

The invention provides a method for separating and recycling positive and negative electrode materials of a waste lithium iron phosphate liquid injection battery cell. The method comprises the following steps: carrying out mechanical and physical treatment on the waste lithium iron phosphate liquid injection battery cell to obtain a pole piece mixed material; mixing the pole piece mixed material with a negative electrode binder denaturant, and then carrying out calcination treatment to obtain a calcined product; screening the calcined product to obtain an undersize product and an oversize product, the undersize product being a positive electrode material, and the oversize product comprising a negative electrode sheet and an aluminum foil; and carrying out post-treatment on the oversize product to respectively obtain the negative electrode material and the current collector recycled material. According to the method, the negative electrode binder is not decomposed during calcination by adding the negative electrode binder denaturing agent by utilizing the pyrolysis behavior difference of the positive and negative electrode binders, so that the combination of the negative electrode material and the current collector is stabilized, and the selective separation of the positive electrode material and the current collector is realized. The positive electrode material separated by the method can meet subsequent repair requirements, use of acid recovered by a black powder wet method is reduced, and the process cost is remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium battery recycling technology, specifically relating to a method for separating and recycling the positive and negative electrode materials of waste lithium iron phosphate electrolyte cells. Background Technology

[0002] With the explosive growth of the new energy vehicle and energy storage industries, the amount of scrapped lithium-ion batteries is increasing exponentially. Industry forecasts predict that by 2030, the global volume of retired lithium batteries will exceed 20 million tons, containing large amounts of high-value metals (such as lithium, cobalt, and nickel) and carbon materials. As core components of batteries (accounting for over 30% of battery mass), the efficient recycling of positive and negative electrodes is crucial for resource recycling. However, current recycling processes face three major challenges: complex electrode composition and difficult separation; long recycling processes; and high risks of secondary pollution.

[0003] Used lithium iron phosphate (LiFePO4, LFP) batteries refer to lithium iron phosphate batteries that have reached the end of their service life (can no longer meet the original performance requirements) or have been discarded. Among them, used electrolyte-filled cells refer to battery cells that have been injected with electrolyte but have been discarded or phased out for various reasons.

[0004] For waste electrolyte-filled battery cells, dismantling them is highly dangerous due to the presence of electrolyte. Therefore, the industry commonly uses a method of on-line crushing combined with high temperature for processing. Specifically, the waste electrolyte-filled battery cells are first crushed while on-line, and the crushed material undergoes high-temperature degumming and electrolyte removal, resulting in a mixture of aluminum shell, positive electrode plate, negative electrode plate, and separator. Next, the separator is separated by air classification, followed by secondary crushing, grinding, and sieving to obtain a mixture of positive and negative electrode powder (black powder) and copper and aluminum granules. This method can automate the processing of waste electrolyte-filled battery cells with high efficiency, but it also has some drawbacks: 1) The black powder has a high copper and aluminum impurity content, which is not conducive to subsequent wet recycling; 2) The positive and negative electrode powders are mixed, making further separation difficult, requiring wet recycling and not suitable for the repair of positive and negative electrode materials; 3) The purity of copper and aluminum granules is around 95%, resulting in low recycling prices and a recovery rate of around 97%, with some copper and aluminum lost.

[0005] In summary, for waste electrolyte-filled battery cells, existing methods can only produce a mixture of positive and negative electrode powders, which cannot be directly used for repair, resulting in low product returns. Subsequent recycling can only be carried out using wet leaching to recover valuable metal elements, which involves the use of large amounts of acid and generates wastewater, resulting in high treatment costs.

[0006] Therefore, for waste electrolyte-filled battery cells, there is an urgent need for a low-cost method that can selectively separate positive and negative electrode materials, reduce acid usage, and ensure that the separated positive electrode material can meet the requirements for use as repair materials. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for separating and recycling the positive and negative electrode materials of waste lithium iron phosphate (LiFePO4) battery cells. This invention utilizes the inherent differences in the pyrolysis behavior of the positive and negative electrode binders. By adding a negative electrode binder modifier, the negative electrode binder does not decompose during calcination, stabilizing the bond between the negative electrode material and the negative electrode current collector. This achieves selective separation, separating the positive electrode material from the positive electrode current collector while maintaining the negative electrode material from it. This overcomes the limitations of traditional "mixed recovery of positive and negative electrode powders," directly obtaining high-purity positive electrode material and structurally intact negative electrode sheets, avoiding the high acid consumption and wastewater problems of wet recovery of mixed powders. Furthermore, the separated positive electrode material can meet subsequent remediation needs, reducing the use of acid in wet recovery of black powder, significantly lowering process costs, and ultimately achieving a synergistic improvement in efficiency and economy of the recycling process.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] This invention provides a method for separating and recycling the positive and negative electrode materials of waste lithium iron phosphate electrolyte cells, the method comprising the following steps:

[0010] Waste lithium iron phosphate electrolyte-filled cells are subjected to mechanical and physical treatment to obtain a mixture of electrode materials.

[0011] The electrode mixture and the negative electrode binder modifier are mixed and then calcined to obtain the calcined product.

[0012] The calcined product is sieved to obtain undersize and oversize, wherein the undersize is positive electrode material and the oversize includes negative electrode sheet and aluminum foil.

[0013] The material remaining on the sieve is then post-processed to obtain negative electrode material and current collector recovery material, respectively.

[0014] This invention utilizes the inherent differences in the pyrolysis behavior of the positive and negative electrode binders. By adding a negative electrode binder modifier, the negative electrode binder does not decompose during calcination, stabilizing the bond between the negative electrode material and the negative electrode current collector. This achieves selective separation, where the positive electrode material separates from the positive electrode current collector while the negative electrode material remains connected to it. This overcomes the limitations of traditional "mixed recovery of positive and negative electrode powders," directly yielding high-purity positive electrode material and structurally intact negative electrode sheets. It avoids the high acid consumption and wastewater problems associated with wet recovery of mixed powders. Furthermore, the separated positive electrode material can meet subsequent remediation needs, reducing the use of acid in wet recovery of black powder and significantly lowering process costs. Ultimately, this achieves a synergistic improvement in both efficiency and economy during the recovery process.

[0015] Preferably, in the waste lithium iron phosphate electrolyte cell, the binder used on the positive electrode is different from the binder used on the negative electrode, and their thermal decomposition temperatures differ.

[0016] Preferably, the binder used in the positive electrode sheet includes polyvinylidene fluoride (PVDF).

[0017] Preferably, the binder used for the negative electrode sheet includes carboxymethyl cellulose (CMC) and / or styrene-butadiene rubber (SBR).

[0018] Preferably, the mechanical and physical processing includes disassembly and crushing performed sequentially.

[0019] Preferably, the negative electrode binder modifier includes any one or a combination of at least two of EC (ethylene carbonate), DMC (dimethyl carbonate), or EMC (ethyl methyl carbonate).

[0020] Preferably, lithium salt is also added during the mixing process.

[0021] The purpose of introducing lithium salt in this invention is to replenish lithium elements into the cathode material during the calcination process, significantly improving its electrochemical performance (such as increasing discharge specific capacity) and making it meet the requirements for remediation raw materials. Specifically, the lithium salt decomposes or diffuses into the cathode material lattice at high temperatures, compensating for lithium losses during charge-discharge cycles and repairing structural defects. Meanwhile, the anode binder modifier can also act as a lithium salt carrier, promoting the uniform distribution and penetration of lithium elements on the cathode material surface. Ultimately, the separated cathode material can be directly used in remediation processes (such as lithium replenishment and regeneration) without the need for wet leaching for lithium extraction, significantly reducing subsequent recycling costs.

[0022] Preferably, the lithium salt comprises lithium fluoride and / or lithium acetate.

[0023] Preferably, the amount of lithium salt added is 1-3% based on the mass of the positive electrode material in the electrode mixture, for example, it can be 1%, 2% or 3%.

[0024] In this invention, the appropriate amount of lithium salt can change the thermal decomposition characteristics of the negative electrode binder under high temperature conditions, preventing the negative electrode material from being de-powdered at high temperatures. In addition, it can supplement the positive electrode material with lithium elements, reducing the difficulty of subsequent positive electrode material repair.

[0025] Preferably, the mixing method includes: mixing the negative electrode binder modifier and lithium salt to obtain a mixed solution, and then immersing the electrode mixture in the mixed solution.

[0026] Preferably, the soaking time is 10-20 minutes, for example, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes or 20 minutes.

[0027] The present invention employs an immersion process. The appropriate immersion time allows the negative electrode binder to fully denature, thus preventing it from decomposing at high temperatures (the negative electrode material remains attached to the copper foil).

[0028] Preferably, the calcination treatment is carried out under a protective atmosphere.

[0029] Preferably, the gas in the protective atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium.

[0030] The present invention selects the above-mentioned inert gas, which can avoid the oxidation of the negative electrode copper foil under an oxygen atmosphere and ensure that the purity of the recovered copper foil is >95%.

[0031] Preferably, the calcination temperature is 400-650℃, for example, it can be 400℃, 450℃, 500℃, 550℃, 600℃ or 650℃, etc., preferably 500℃.

[0032] Within the aforementioned temperature range of the calcination process, this invention allows for complete separation of the positive electrode material from the positive electrode current collector without damage to the aluminum foil, while maintaining stable bonding between the negative electrode material and the negative electrode current collector. If the temperature is too low, the aforementioned separation effect cannot be achieved; if the temperature is too high, the positive electrode current collector risks melting, affecting the purity of the positive electrode material. If the calcination temperature is below 400°C, separation between the positive electrode material and the positive electrode current collector is difficult, making subsequent separation of the positive and negative electrodes impossible. If the calcination temperature is above 650°C, the excessively high temperature will cause the positive electrode current collector (such as the aluminum foil) to melt, making separation between the positive electrode material and the positive electrode current collector difficult.

[0033] Preferably, the holding time for the calcination treatment is 1.5-3 hours, for example, it can be 1.5 hours, 2 hours, 2.5 hours or 3 hours, preferably 2 hours.

[0034] In this invention, a certain calcination time can ensure that the cathode material is completely de-powdered and the aluminum foil is undamaged. If the time is too short, the separation will be insufficient, and if the time is too long, the effect will not be improved and the cost will increase significantly.

[0035] Preferably, the screening method includes vibrating screening.

[0036] Preferably, in the vibrating screening, the mesh size of the screen used is 4-6mm, for example, it can be 4mm, 5mm or 6mm.

[0037] Preferably, the vibrating sieving time is 2.5-20 minutes, for example, 2.5 minutes, 5 minutes, 10 minutes, 15 minutes, or 20 minutes, preferably 4-10 minutes, and more preferably 5 minutes. If the time is too long, aluminum shavings may easily be mixed in, reducing the purity of the positive electrode material; if the time is too short, the separation will be insufficient.

[0038] Preferably, elastic balls are also added during the sieving process.

[0039] This invention also incorporates elastic balls during the sieving process, which can break the cathode material into small-sized materials, allowing them to pass smoothly through the sieve during sieving, facilitating subsequent processing, and helping to obtain high-purity cathode materials to meet subsequent remediation needs and reduce the use of acid in the wet recovery of black powder.

[0040] Preferably, the diameter of the elastic ball is 2-4cm, for example, it can be 2cm, 3cm or 4cm, and preferably 3cm.

[0041] In this invention, elastic balls of suitable diameter can fully break the cathode material into small-sized particles, allowing them to pass smoothly through the screen, thus facilitating subsequent processing and improving the purity of the cathode material. If the diameter is too small, the cathode material cannot be broken down; if the diameter is too large, aluminum shavings are easily mixed in, reducing the purity of the cathode material.

[0042] Preferably, the post-processing includes crushing, grinding, and sieving performed sequentially.

[0043] Preferably, the method includes the following steps:

[0044] (1) Provide waste lithium iron phosphate electrolyte cells, wherein the binder used on the positive electrode is different from the binder used on the negative electrode, and the thermal decomposition temperature is different.

[0045] Disassembling the waste lithium iron phosphate electrolyte cell yields a mixed positive and negative electrode sheet.

[0046] The positive and negative electrode mixture is crushed to obtain an electrode mixture material.

[0047] (2) Provide a mixed solution comprising a negative electrode binder modifier and a lithium salt; the negative electrode binder modifier comprising any one or a combination of at least two of EC, DMC or EMC; the lithium salt comprising lithium fluoride and / or lithium acetate.

[0048] The electrode mixture is immersed in the mixed solution for 10-20 min, and then calcined at 400-650 °C for 1.5-3 h under a protective atmosphere at a heating rate of 4-6 °C / min (e.g., 4 °C / min, 5 °C / min, or 6 °C / min, etc.) to obtain the calcined product.

[0049] The amount of lithium salt added is 1-3%, based on the mass of the positive electrode material in the electrode mixture; the gas in the protective atmosphere includes any one or a combination of at least two of nitrogen, argon or helium.

[0050] (3) The calcined product is subjected to vibration sieving, and elastic balls with a diameter of 2-4 cm are added to the vibration sieving. The sieving time is 2.5-20 min, and the mesh size of the screen is 4-6 mm to obtain the undersize and oversize. The undersize is the positive electrode material, and the oversize includes the negative electrode sheet and aluminum foil.

[0051] (4) The undersize material is mechanically crushed and then air-jet pulverized to obtain the positive electrode repair material.

[0052] The material on the sieve is crushed, ground, and sieved to obtain negative electrode material and current collector recovery material, wherein the current collector recovery material includes aluminum and copper; the current collector recovery material is subjected to gravity separation to obtain copper particles and aluminum particles respectively.

[0053] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] This invention utilizes the inherent differences in the pyrolysis behavior of the positive and negative electrode binders. By adding a negative electrode binder modifier, the negative electrode binder does not decompose during calcination, stabilizing the bond between the negative electrode material and the negative electrode current collector. This achieves selective separation, where the positive electrode material separates from the positive electrode current collector while the negative electrode material remains connected to it. This overcomes the limitations of traditional "mixed recovery of positive and negative electrode powders," directly yielding high-purity positive electrode material and structurally intact negative electrode sheets. It avoids the high acid consumption and wastewater problems associated with wet recovery of mixed powders. Furthermore, the separated positive electrode material can meet subsequent remediation needs, reducing the use of acid in wet recovery of black powder and significantly lowering process costs. Ultimately, this achieves a synergistic improvement in both efficiency and economy during the recovery process. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] Example 1

[0058] This embodiment provides a method for separating and recycling the positive and negative electrode materials of waste lithium iron phosphate electrolyte cells, the method comprising the following steps:

[0059] (1) Provide waste lithium iron phosphate electrolyte cells, wherein the binder used on the positive electrode is different from the binder used on the negative electrode; the binder on the positive electrode is PVDF and the binder on the negative electrode is CMC.

[0060] Disassembling the waste lithium iron phosphate electrolyte cell yields a mixed positive and negative electrode sheet.

[0061] The positive and negative electrode mixture is crushed into flakes with a size of 5x5cm to obtain the electrode mixture material.

[0062] (2) Provide a mixed solution, wherein the mixed solution includes a negative electrode binder modifier and a lithium salt; the negative electrode binder modifier is DMC and the lithium salt is lithium fluoride.

[0063] The electrode mixture was immersed in the mixed solution for 15 minutes, and then calcined for 2 hours under nitrogen atmosphere at a heating rate of 5°C / min to 500°C to obtain the calcined product.

[0064] The amount of lithium salt added is 1%, based on the mass of the positive electrode material in the electrode mixture.

[0065] (3) The calcined product is subjected to vibration sieving, and elastic balls with a diameter of 3 cm are added to the vibration sieving. The sieving time is 5 min, and the mesh size of the screen is 5 mm to obtain the undersize and oversize. The undersize is positive electrode material, and the oversize includes negative electrode sheet and aluminum foil.

[0066] (4) The undersize material is mechanically crushed and then air-jet pulverized to obtain the positive electrode repair material.

[0067] The material on the sieve is crushed, ground, and sieved to obtain negative electrode material and current collector recovery material, wherein the current collector recovery material includes aluminum and copper; the current collector recovery material is subjected to gravity separation to obtain copper particles and aluminum particles respectively.

[0068] Examples 2-4

[0069] The difference between Examples 2-4 and Example 1 is that the protective atmosphere in step (2) (nitrogen in Example 1) is replaced with oxygen atmosphere, helium atmosphere and argon atmosphere, respectively.

[0070] The remaining methods and parameters are consistent with those in Example 1.

[0071] The recovery rate of the undersize material obtained in Examples 1-4 was tested and calculated using the following formula: Recovery rate = Actual mass of positive (negative) electrode material / Theoretical mass of positive (negative) electrode material. Furthermore, the purity of the recovered copper was tested. The statistical results are shown in Table 1.

[0072] Table 1

[0073]

[0074] As shown in Table 1, if calcination is carried out in an oxygen atmosphere, the recovery rate of the negative electrode material in the sieve material increases significantly. Under oxygen conditions, the negative electrode graphite can be separated from the copper foil. In addition, since the copper foil will be oxidized to copper oxide during calcination, the purity of copper will be significantly reduced.

[0075] Examples 5-8

[0076] The difference between Examples 5-8 and Example 1 is that the diameter of the elastic ball in step (3) (3cm in Example 1) is adjusted to 0.5cm, 1cm, 2cm and 4cm respectively.

[0077] The remaining methods and parameters are consistent with those in Example 1.

[0078] The recovery rate of the cathode materials recovered in Examples 5-8 was tested and calculated, and the calculation formula is shown above. The statistical results are shown in Table 2.

[0079] Table 2

[0080]

[0081] As shown in Table 2, the elastic balls bounce in the vibrating screen and apply force to the positive electrode material, breaking it into small pieces that can pass through the screen. Aluminum foil and negative electrode sheets, however, cannot pass through, thus achieving separation of the positive electrode material. The best results are achieved when the diameter of the elastic balls is 3 cm, resulting in a high yield of positive electrode material, no negative electrode residue on the upper layer of the screen, and no impact on the purity of the positive electrode powder.

[0082] Examples 9-11

[0083] The difference between Examples 9-11 and Example 1 is that the screening time in step (3) (5 min in Example 1) is adjusted to 2.5 min, 10 min and 20 min respectively.

[0084] The remaining methods and parameters are consistent with those in Example 1.

[0085] The recovery rate of the cathode materials recovered in Examples 9-11 was tested and calculated, and the calculation formula is shown above. The statistical results are shown in Table 3.

[0086] Table 3

[0087]

[0088] As shown in Table 3, the sieving time affects the yield of both positive and negative electrodes. If the sieving time is too short, the sieving will be insufficient, resulting in incomplete sieving of the positive electrode material and reducing the yield. If the sieving time is too long, the elastic ball will hit the aluminum foil for a long time, causing fine aluminum shavings to enter the positive electrode material and affecting the purity of the positive electrode material. The sieving effect is best when the sieving time is 5 minutes.

[0089] Examples 12-16

[0090] The difference between Examples 12-16 and Example 1 is that the calcination temperatures in step (2) are 300℃, 400℃, 450℃, 600℃ and 650℃, respectively.

[0091] The remaining methods and parameters are consistent with those in Example 1.

[0092] The recovery rate of the undersize materials obtained in Examples 12-16 was tested and calculated, and the calculation formula is shown above. In addition, the Al and Cu contents in the positive and negative electrode materials were also tested. The statistical results are shown in Table 4.

[0093] Table 4

[0094]

[0095] As shown in Table 4, when the calcination temperature is too low, the positive and negative electrode sheets cannot achieve separation of the electrode material and the current collector. When the calcination temperature is ≥400℃, the positive electrode material can be completely separated, while the negative electrode material is not significantly separated. However, after the calcination temperature reaches 500℃, the separation effect of the positive electrode does not improve significantly with the increase of the calcination temperature.

[0096] Examples 17-21

[0097] The difference between Examples 17-21 and Example 1 is that the calcination time in step (2) is 0.5h, 1h, 1.5h, 2.5h and 3h, respectively.

[0098] The remaining methods and parameters are consistent with those in Example 1.

[0099] The recovery rate of the undersize materials obtained in Examples 17-21 was tested and calculated, and the calculation formula is shown above. In addition, the Al and Cu contents in the positive and negative electrode materials were also tested. The statistical results are shown in Table 5.

[0100] Table 5

[0101]

[0102] As shown in Table 5, the best overall effect is achieved when the calcination time is 2 hours.

[0103] Example 22

[0104] The difference between this embodiment and embodiment 1 is that lithium salt is not added in step (2).

[0105] The remaining methods and parameters are consistent with those in Example 1.

[0106] Example 23

[0107] The difference between this embodiment and Embodiment 1 is that, based on the mass of the electrode mixture, the amount of lithium salt added is 3.5%.

[0108] The remaining methods and parameters are consistent with those in Example 1.

[0109] Example 24

[0110] The difference between this embodiment and embodiment 1 is that the soaking time in step (2) is 5 minutes.

[0111] The remaining methods and parameters are consistent with those in Example 1.

[0112] Example 25

[0113] The difference between this embodiment and embodiment 1 is that the soaking time in step (2) is 25 minutes.

[0114] The remaining methods and parameters are consistent with those in Example 1.

[0115] Comparative Example 1

[0116] The difference between this comparative example and Example 1 is that no mixing solution is added in step (2), that is, the electrode mixture obtained in step (1) is directly calcined.

[0117] The remaining methods and parameters are consistent with those in Example 1.

[0118] The recovery rate of the undersize material recovered in Examples 1, 22-25 and Comparative Example 1 was tested, and the calculation formula is shown above.

[0119] A button battery was made based on the positive electrode repair materials provided in Examples 1, 22-25 and Comparative Example 1. The specific steps included: drying the positive electrode material, weighing the battery material, slurry preparation, coating, preparing the positive electrode sheet, assembling the battery, and testing the battery.

[0120] The above button batteries were subjected to charge and discharge tests under the following conditions: discharge limit voltage: constant current charging to 3.75V at a rate of 0.1C, followed by constant voltage charging, with a constant voltage charging cutoff current of 0.05C; charging termination voltage: constant current discharge to 2.0V at a rate of 0.1C.

[0121] The above results are summarized in Table 6.

[0122] Table 6

[0123]

[0124] As shown in Table 6, this invention utilizes the inherent differences in the pyrolysis behavior of the positive and negative electrode binders. By adding a negative electrode binder modifier, the negative electrode binder does not decompose during calcination, stabilizing the bond between the negative electrode material and the negative electrode current collector. This achieves selective separation, where the positive electrode material separates from the positive electrode current collector while the negative electrode material remains connected to it. This overcomes the limitations of traditional "mixed recovery of positive and negative electrode powders," directly yielding high-purity positive electrode material and structurally intact negative electrode sheets. It avoids the high acid consumption and wastewater problems associated with wet recovery of mixed powders. Furthermore, the separated positive electrode material can meet subsequent remediation needs, reducing the use of acid in wet recovery of black powder and significantly lowering process costs. Ultimately, this invention achieves a synergistic improvement in both efficiency and economy during the recovery process.

[0125] A comparison between Example 1 and Example 22 shows that without the addition of lithium salt, it is not conducive to improving the electrochemical performance of the cathode material after de-powdering, and it increases the difficulty of subsequent cathode material repair.

[0126] A comparison of Example 1 and Example 23 shows that if too much lithium salt is added, the technical effects of the two are basically the same, which will increase the cost.

[0127] As can be seen from the comparison between Example 1 and Examples 24-25, if the soaking time in step (2) is too short, the performance of the cathode material after powder removal will be poor; if the soaking time in step (2) is too long, the processing time will be increased, resulting in increased processing costs.

[0128] As can be seen from the comparison between Example 1 and Comparative Example 1, if no mixed solution is added in step (2), that is, no negative electrode binder modifier and lithium salt are introduced, the negative electrode material binder is not modified, which causes the negative electrode material to separate from the copper foil during the high temperature process. After sieving, it is mixed into the positive electrode material, resulting in a decrease in the purity of the positive electrode material, thereby increasing the repair cost and difficulty.

[0129] In summary, the preparation process provided by this invention, with its calcination treatment at 500℃, a holding time of 2 hours, and combined with 5 minutes of vibrating sieving and the use of a 3cm diameter elastic ball, achieves a selective separation effect where the positive electrode material separates from the aluminum foil while the negative electrode material remains attached to the copper foil. This helps to obtain a high-purity positive electrode material, which can meet the requirements for subsequent repair. The battery prepared based on this process exhibits excellent electrochemical performance.

[0130] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for separating and recycling the positive and negative electrode materials of waste lithium iron phosphate electrolyte cells, characterized in that, The method includes the following steps: Mechanical and physical treatment of waste lithium iron phosphate electrolyte-filled cells yields a mixture of electrode materials. The electrode mixture and the negative electrode binder modifier are mixed and then calcined to obtain the calcined product. The calcined product is sieved to obtain undersize and oversize, wherein the undersize is positive electrode material and the oversize includes negative electrode sheet and aluminum foil. The material remaining on the sieve is then post-processed to obtain negative electrode material and current collector recovery material, respectively.

2. The method according to claim 1, characterized in that, In the waste lithium iron phosphate electrolyte cell, the binder used on the positive electrode is different from the binder used on the negative electrode, and their thermal decomposition temperatures are also different. Preferably, the mechanical and physical processing includes disassembly and crushing performed sequentially.

3. The method according to claim 1 or 2, characterized in that, The negative electrode binder modifier includes any one or a combination of at least two of EC, DMC, or EMC.

4. The method according to any one of claims 1-3, characterized in that, Lithium salts are also added during the mixing process; Preferably, the lithium salt comprises lithium fluoride and / or lithium acetate; Preferably, the amount of lithium salt added is 1-3% based on the mass of the positive electrode material in the electrode mixture.

5. The method according to claim 4, characterized in that, The mixing method includes: mixing the negative electrode binder modifier and lithium salt to obtain a mixed solution, and then immersing the electrode mixture in the mixed solution; Preferably, the soaking time is 10-20 minutes.

6. The method according to any one of claims 1-5, characterized in that, The calcination process is carried out under a protective atmosphere; Preferably, the gas in the protective atmosphere includes any one or a combination of at least two of nitrogen, argon, or helium; Preferably, the calcination temperature is 400-650℃; Preferably, the holding time for the calcination treatment is 1.5-3 hours.

7. The method according to any one of claims 1-6, characterized in that, The screening method includes vibrating screening; Preferably, in the vibrating sieving, the mesh size of the screen used is 4-6 mm; Preferably, the vibrating screening time is 2.5-20 min, and more preferably 4-10 min.

8. The method according to any one of claims 1-7, characterized in that, Elastic balls are also added during the sieving process; Preferably, the diameter of the elastic ball is 2-4 cm.

9. The method according to any one of claims 1-8, characterized in that, The post-processing includes crushing, grinding, and sieving performed sequentially.

10. The method according to any one of claims 1-9, characterized in that, The method includes the following steps: (1) Provide waste lithium iron phosphate electrolyte cells, wherein the binder used on the positive electrode is different from the binder used on the negative electrode, and the thermal decomposition temperature is different; Disassembling the waste lithium iron phosphate electrolyte cell yields a mixed positive and negative electrode sheet. The positive and negative electrode mixture is crushed to obtain an electrode mixture material; (2) Provide a mixed solution comprising a negative electrode binder modifier and a lithium salt; the negative electrode binder modifier comprises any one or a combination of at least two of EC, DMC or EMC; the lithium salt comprises lithium fluoride and / or lithium acetate; The electrode mixture is immersed in the mixed solution for 10-20 min, and then calcined at 400-650°C for 1.5-3 h under a protective atmosphere with a heating rate of 4-6°C / min to obtain the calcined product. The amount of lithium salt added is 1-3% based on the mass of the positive electrode material in the electrode mixture; the gas in the protective atmosphere includes any one or a combination of at least two of nitrogen, argon or helium. (3) The calcined product is subjected to vibration sieving, and elastic balls with a diameter of 2-4 cm are added to the vibration sieving. The sieving time is 2.5-20 min, and the mesh size of the screen is 4-6 mm to obtain the undersize and oversize. The undersize is positive electrode material, and the oversize includes negative electrode sheet and aluminum foil. (4) The undersize material is mechanically crushed and then subjected to air jet pulverization to obtain positive electrode repair raw material; The material on the sieve is crushed, ground, and sieved to obtain negative electrode material and current collector recovery material, wherein the current collector recovery material includes aluminum and copper; the current collector recovery material is subjected to gravity separation to obtain copper particles and aluminum particles respectively.

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