Method for stripping, grading and sorting positive and negative electrode materials of waste lithium battery

Abstract

The invention discloses a method for stripping, grading and sorting positive and negative electrode materials of a waste lithium battery, which comprises the following steps: (1) mixing and dipping the electrode materials of the waste lithium battery and a stripping agent, adding into a mechanical stripping device, and rotating and stripping to obtain a current collector, sheet-shaped positive and negative electrode active materials, a diaphragm and stripping liquid; (2) screening and grading the positive and negative electrode active materials obtained in the step (1) to respectively obtain a waste lithium battery positive and negative electrode mixed material with at least three size fractions; and (3) carrying out gradient magnetic separation on products with different particle sizes screened in the step (2) by adopting different magnetic separation processes. On one hand, the problem that lithium is easy to dissolve and lose in the traditional wet-type mineral separation process is effectively avoided, on the other hand, efficient enrichment and separation of positive and negative electrode materials are effectively achieved, meanwhile, the content of impurities such as copper and aluminum in the recycled materials can be effectively reduced, high-quality raw materials can be provided for metallurgical recycling and repairing regeneration of subsequent materials, and the method is suitable for industrial production. The process is simple and controllable, and industrial application is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of separation and recovery of positive and negative electrode materials of waste batteries, and in particular to a method for stripping, grading and sorting positive and negative electrode materials of waste lithium batteries. Background Art

[0002] Since the Industrial Revolution, human society has entered a stage of rapid development, and the demand for energy has been increasing. The CO generated by the use of traditional primary energy such as coal and oil is 2 Or other harmful gases seriously threaten the ecological environment and life and health.

[0003] As the most common secondary energy source, electricity has been widely developed in recent years due to its environmental protection and renewable characteristics. In the automotive field, new energy batteries mainly based on lithium batteries can replace traditional internal combustion engines to effectively avoid environmental pollution caused by exhaust emissions. At present, new energy vehicles are developing rapidly, and lithium iron phosphate batteries have become the primary battery material for new energy vehicles due to their excellent performance such as many cycles, good stability, and large battery capacity. With multiple charge and discharge cycles, the battery life will gradually decay. Lithium iron phosphate batteries will reach the elimination standard after about 2,000 cycles. It is estimated that by 2030, the amount of waste lithium iron phosphate batteries in my country will exceed 2 million tons. The valuable metal elements in them have great recycling value. If they are not handled properly, they will cause serious pollution to the ecological environment. The recycling of waste lithium batteries is of great significance.

[0004] After completing their service and cascade utilization, used lithium batteries will eventually be scrapped. The recycling of traditional lithium batteries will first go through pre-treatment stages such as discharge, disassembly and crushing, and electrolyte treatment, and then be recycled by physical or chemical separation methods. Physical methods include magnetic separation, gravity separation, eddy current separation, etc., which are separated and recycled according to the differences in certain physical properties between battery materials; chemical methods include wet separation, pyrometallurgy and other processes to directly smelt or leach the valuable metal elements of battery materials. However, methods such as magnetic separation and gravity separation are greatly affected by the particle size of the material, and the separation and recovery efficiency is limited. Pyrometallurgy and hydrometallurgy are more polluting to the environment, and the traditional process flow is relatively complicated. Therefore, it is urgent to propose a low-cost, efficient, selective enrichment, separation and recovery method based on the characteristics of the positive and negative electrode materials of used lithium batteries. Summary of the invention

[0005] The purpose of the present invention is to provide a method for stripping and grading the positive and negative electrode materials of waste lithium batteries. In view of the existing limitations and shortcomings mentioned in the above background technology, the present invention uses a stripping agent and a stripping device to efficiently strip and selectively separate the positive and negative electrode materials from the current collector foil; the stripping liquid after cleaning can be used to recover valuable components such as residual lithium, and the solid-phase flaky positive and negative electrode materials are graded and sorted after screening. Different particle size products are graded by a step-by-step magnetic separation process, and more efficient, environmentally friendly, low-energy, and low-cost selective separation and recovery are achieved according to the properties of materials of different particle sizes.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for stripping and grading positive and negative electrode materials of waste lithium batteries, which mainly comprises the following steps:

[0008] (1) mixing and impregnating waste lithium battery electrode materials with a stripping agent, adding the mixture to a mechanical stripping device, and rotating and stripping the mixture to obtain a current collector, positive and negative electrode active materials, a separator, and a stripping solution;

[0009] The stripping agent is composed of a combination of an organic weak acid and an inorganic salt in a mass ratio of organic weak acid solution: inorganic salt solution = 1.5-25:1, preferably 2-20:1, and more preferably 5-15:1; wherein the organic weak acid comprises at least one of citric acid, oxalic acid, dodecylbenzenesulfonic acid and acetic acid, and the mass concentration of the organic weak acid solution is 0.5-9%, preferably 0.5-8%; the inorganic salt comprises at least one of sodium pyrophosphate, sodium pyrosulfate, potassium phosphate and potassium dihydrogen phosphate, and the mass concentration of the inorganic salt solution is 0.05-11%, preferably 0.05-10%;

[0010] The liquid-to-solid ratio of the stripping agent to the pole piece material is 7 to 21:1, preferably 8 to 20:1;

[0011] (2) Screening and grading the positive and negative electrode active materials obtained in step (1) to obtain at least three particle sizes of waste lithium battery positive and negative electrode mixed materials; the obtained waste lithium battery positive and negative electrode mixed materials of different particle sizes include:

[0012] A coarse-grained mixed material, wherein the particle size of the coarse-grained mixed material is greater than 0.35 mm;

[0013] A medium-sized mixed material, wherein the particle size of the medium-sized mixed material is 0.15 mm to 0.35 mm;

[0014] A fine-grained mixed material, wherein the particle size of the fine-grained mixed material is less than 0.15 mm;

[0015] (3) The products of different particle sizes after screening in step (2) are subjected to cascade magnetic separation by using different magnetic separation processes; wherein the magnetic field strength used for magnetic separation of coarse-grained mixed materials is 0.8 to 1.4 T; the magnetic field strength used for magnetic separation of medium-grained mixed materials is 1 to 1.6 T; and the magnetic field strength used for magnetic separation of fine-grained mixed materials is 1.2 to 1.8 T.

[0016] As a preferred embodiment, the present invention provides a method for stripping and grading positive and negative electrode materials of waste lithium batteries, wherein the waste lithium batteries are lithium iron phosphate batteries and / or ternary lithium batteries.

[0017] As a preferred embodiment, the present invention provides a method for stripping, grading and sorting positive and negative electrode materials of waste lithium batteries. The positive and negative electrode materials of waste lithium batteries can be the positive and negative electrode sheets of disassembled waste lithium iron phosphate or ternary lithium batteries, or the positive and negative electrode sheets of waste lithium iron phosphate or ternary lithium batteries produced after crushing; preferably, the electrode sheet material has been washed with residual electrolyte.

[0018] When used in industry, waste lithium battery electrode materials are mixed and impregnated with a stripping agent, then added to a mechanical stripping device and rotated for stripping to obtain current collectors (aluminum foil, copper foil), sheet-like positive and negative electrode active materials, diaphragms, and stripping liquids; the positive and negative electrode materials on the aluminum foil and copper foil are stripped, and at the same time, the positive and negative electrode materials are selectively fragmented in sheet form, and the stripped materials are subjected to solid-liquid separation, washing, and filter screening to separate the sheet-like positive and negative electrode active materials, aluminum foil, copper foil, diaphragms, and stripping liquids.

[0019] That is, after step (1) is completed, the proportion of lamellar particles in the positive and negative electrode active materials exceeds 50%.

[0020] The stripping solution treated in step (1) can be used to recover residual lithium, or it can be returned to step 1 for continued use, and the composition can be adjusted according to the working conditions.

[0021] The stripping agent designed in the present invention reacts with the current collector, and the reaction mainly takes place on the surface of the current collector, so that the positive and negative active materials are stripped from the surface of the current collector while minimizing the dissolution loss of the current collector.

[0022] The stripping agent designed by the present invention will not quickly destroy the adhesive between the active materials (including the positive electrode active material and the negative electrode active material). Since the organic weak acid is not very acidic, the complex and inorganic salt ions generated by the reaction have a buffering effect to slow down the further corrosion of the current collector. At the same time, it is also beneficial to the acquisition of the sheet-like active material. In combination with the subsequent rotational stripping process with appropriate parameters, the particle size and morphology of the active material can be controlled within a range that is conducive to magnetic separation.

[0023] As a preferred embodiment, during the immersion in step (1), low-speed stirring is adopted; and the immersion time with low-speed stirring is 10 to 20 minutes.

[0024] As a preferred embodiment, in step (1), after the impregnation is completed, a cylindrical stripping device is used to perform rotational stripping of the positive and negative electrode materials, with a rotation time of 5 to 10 minutes and a rotation speed of 200 to 400 rpm.

[0025] The rotational peeling under controlled conditions can achieve the selective fragmentation of the positive and negative active materials. In the present invention, the reason why wet rotation is selected and the rotation time is controlled to be 5 to 10 minutes and the rotation speed is 200 to 400 revolutions per minute is that if the rotation time is too short or the rotation speed is too slow, the positive and negative active materials will not be completely peeled off from the current collector, and the fragmentation effect will not be obvious; if the rotational peeling time is too long or the rotation speed is too fast, the sheet structure of the positive active material will be destroyed, the particle size will be reduced, and the subsequent magnetic separation operation indicators will be deteriorated.

[0026] As a preferred embodiment, after the rotational peeling and selective fragmentation in step (1), washing is performed for 5 to 10 minutes.

[0027] As a preferred solution, after the rotational peeling in step (1) is completed, two layers of filter screens are used for filtering. The first layer of coarse filter screens the copper foil, aluminum foil, diaphragm, etc., and the screened products are then filtered through a fine filter screen to separate the sheet-like positive and negative active materials from the peeling liquid.

[0028] In the present invention, the stripping process allows the negative electrode active material to be stripped from the copper foil and the positive electrode active material to be stripped from the aluminum foil. The negative electrode active material includes graphite; the positive electrode active material includes one of lithium iron phosphate and nickel cobalt manganese.

[0029] As a preferred solution, in step (3), a wet high-gradient magnetic separator is used for magnetic separation, and the magnetic separation medium is a magnetic medium composed of a rod-shaped magnetic alloy material with a special-shaped cross section, and the diameter of the rod-shaped wire is 1.5 mm or 2 mm, preferably 2 mm. The cross section of the special-shaped material can be a diamond, a teardrop, or other different shapes. The magnetic field gradient generated by the magnetic medium is high, the magnetic field force is strong, and it is not easy to be blocked. The separation space is narrow and long, which is conducive to the separation of sheet-like weak magnetic materials.

[0030] As a preferred embodiment, in step (3), the feed concentration of magnetic separation is 5 to 10%. The feed concentration is controlled to ensure the efficiency of magnetic separation and reduce entrainment. If the concentration is too high, the content of positive magnetic separation material in the concentrate will be reduced due to the entrainment of non-magnetic products. When applied in industry, after completing step (2), water is added to each level of material (coarse-grained mixed material, medium-grained mixed material, fine-grained mixed material) to adjust the slurry to a feed concentration of 5 to 10wt%.

[0031] As a preferred embodiment, in step (3), the excitation pulsation frequency of the magnetic separation is 180 to 260 times / min.

[0032] As a preferred solution, in step (3), the magnetic separation process of the coarse-grained product is three sweeps, one coarse and one fine, with a magnetic field strength of 0.8 to 1.4 T; the excitation pulse frequency is set to 180 to 210 times / min, more preferably 195 to 205 times / min;

[0033] The magnetic separation process for medium-sized products is one roughing and one fine sweeping, with a magnetic field strength of 1 to 1.6 T; the frequency of the exciting pulsation is set at 220 to 250 times / min, and more preferably 235 to 245 times / min;

[0034] The magnetic separation process for fine-grained products is one coarse, two fine and one sweep, with a magnetic field strength of 1.2 to 1.8 T; the excitation pulsation frequency is set to 250 to 260 times / min, and further preferably to 255 to 260 times / min.

[0035] As a preferred solution, in step (3), the magnetic separation of coarse-grained and medium-grained products can be supplemented with a scavenging operation, and the magnetic separation of fine-grained products can be supplemented with a concentrating operation.

[0036] When processing waste lithium iron phosphate batteries, the recovery rate of lithium iron phosphate is greater than 94% and the purity is greater than or equal to 94.5%; the copper content is less than 0.11wt% and the aluminum content is less than 0.1wt%; the recovery rate of graphite is greater than 96% and the purity is greater than or equal to 92%; the copper content is less than 0.1wt% and the aluminum content is less than 0.11wt%.

[0037] According to the current recycling status of waste lithium batteries, the present invention proposes for the first time a method of controlling the particle size and morphology of positive and negative electrode active materials by using a special component stripping agent in combination with a stripping process; and cooperates with subsequent cascade magnetic separation to achieve efficient separation and recovery of positive and negative electrode active materials.

[0038] In the present invention, waste lithium iron phosphate batteries are used as raw materials, and the positive electrode sheet is usually made of aluminum foil as a current collector and lithium iron phosphate as an active material; the negative electrode sheet is usually made of copper foil as a current collector and graphite as a negative electrode material, and the positive and negative electrode active materials are bonded to the current collector by organic adhesives such as polyvinylidene fluoride (PVDF), polyimide, polyacrylic acid and sodium carboxymethyl cellulose. Due to the difference in the bonding force between the positive and negative electrode active materials and the current collector, and the difference in the bonding strength of the active materials themselves, the positive and negative electrode materials will show selective fragmentation after being stripped under the process of mechanical stripping after the stripping agent acts, and the structural characteristics of the positive and negative electrode materials are kept stable. That is, after the graphite and lithium iron phosphate are stripped and selectively fragmented, there will be differences in particle size as a whole. Graphite will exist in the positive and negative electrode mixed materials in a flaky form with a smaller particle size, while lithium iron phosphate will exist in a flaky form with a larger particle size. Therefore, the screening of the stripped materials can enrich high-grade products in advance and achieve preliminary separation between active materials at different particle sizes.

[0039] After stripping, the different particle size products obtained by screening meet the particle size requirements of magnetic separation. The adsorption effect of magnetic substances in a magnetic field is related to the magnitude of the magnetic force on the magnetic substance in the magnetic field. In an inhomogeneous magnetic field, the magnitude of the magnetic force on the magnetizable particles in the magnetic field is shown in formula (1):

[0040] F m =μ 0 k 0 VHgradH (1)

[0041] Where: μ 0 is the vacuum permeability; k 0 is the specific magnetic susceptibility; V is the volume of the particle; H is the magnetic field intensity; gradH is the magnetic field force. It can be seen from formula (1) that μ 0 is a constant. When the magnetic field strength is constant, the magnitude of the magnetic force on the particles is mainly related to the basic property k of the material. 0 , V is related.

[0042] After selective fragmentation, lithium iron phosphate is mostly in the form of coarse-grained flakes. As can be seen from formula (1), the large-volume flake lithium iron phosphate will be subjected to stronger magnetic force, so the weakly magnetic lithium iron phosphate can be directly enriched and recovered through the strong magnetic separation process. At the same time, the larger particle size difference can enhance the separation effect of lithium iron phosphate and graphite. During the cascade magnetic separation, the background magnetic field intensity of the fine-grained magnetic separation should be higher to ensure that the weakly magnetic particles receive sufficient magnetic field force. After screening, the lithium iron phosphate content of the coarse and medium-grained particles is high, and more scanning operations need to be set up to ensure the recovery rate; the inclusion of non-magnetic particles is more serious during fine-grained magnetic separation, and more concentrating operations need to be set up to increase the lithium iron phosphate content of the concentrate.

[0043] The advantages of the present invention are:

[0044] (1) The mechanical stripping process after the stripping agent used in the present invention avoids the HF, P 2 O 5 It can prevent the production of toxic gases such as aldehydes and aldehydes, and at the same time effectively reduce the content of impurities such as copper and aluminum in the recycled materials.

[0045] (2) After the traditional pyrolysis process, the positive and negative electrode materials become fine powder materials, the differentiation between materials is reduced, and a part of the lithium is easily dissolved, which will cause lithium ion loss during the mineral processing process. The present invention efficiently realizes the selective fragmentation and stripping of the positive and negative electrode active materials, avoids the substantial reduction of the overall particle size of the positive and negative electrodes, enables the positive and negative electrode active materials to be initially separated and enriched by particle size, improves the processing efficiency of subsequent processes, reduces processing costs, and enhances the feasibility of mineral processing separation; and the easily dissolved and lost lithium ions can be recovered in the stripping solution.

[0046] (3) After efficient stripping and selective fragmentation, a method for tiered magnetic separation of materials of different particle sizes was proposed based on the fragmentation of the positive and negative active materials and their own properties. The coarser particle size of lithium iron phosphate and the finer particle size of graphite enhanced the separation effect of magnetic separation.

[0047] (4) The method for stripping and grading the positive and negative electrode materials of waste lithium batteries of the present invention has a simple process, fully utilizes the advantages of low-cost enrichment of mineral processing, is easy to operate, has low production cost, and is clean and efficient. It can provide high-quality raw materials for subsequent metallurgical recovery and repair and regeneration of materials, and has good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Attached Figure 1 This is a schematic diagram of the process flow of the graded recovery method for positive and negative electrode materials of waste lithium batteries.

[0049] Attached Figure 2 This is the SEM image of the positive and negative electrode materials before screening used in Example 1;

[0050] Attached Figure 3 This is a SEM image of the concentrate product after coarse particle magnetic separation in Example 1;

[0051] Attached Figure 4 This is the SEM image of the tailings product after fine-grained magnetic separation in Example 1.

[0052] From the attached Figure 1 The basic process flow of the present invention can be seen in FIG.

[0053] From the attached Figure 2 It can be seen that the particle size distribution of lithium iron phosphate in the positive and negative electrode materials before screening, that is, after stripping and washing, is relatively wide, mainly in the form of large flakes, with a thickness of about 50 to 80 μm and regular fragmented shapes such as rectangles and wedges; the graphite fragments are irregular in shape and have a relatively small particle size.

[0054] From the attached Figure 3 It can be seen that after coarse-grained magnetic separation, the concentrate product is basically only large flakes of lithium iron phosphate.

[0055] From the attached Figure 4 It can be seen that the tailings products after fine-grained magnetic separation are basically graphite, with fine particle size and irregular shape, among which there is a very small amount of lithium iron phosphate scattered, and the particle size is too fine to be further separated. DETAILED DESCRIPTION

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below. Obviously, the embodiments described below are only part of the embodiments of the present invention, rather than all the embodiments. For ordinary technicians in this field, all other drawings and embodiments obtained based on the embodiments of the present invention without creative work are within the protection scope of the present invention.

[0057] Example 1

[0058] For the waste lithium iron phosphate battery pole piece materials of a battery recycling plant, the pole piece materials are mixed with a stripping agent with a liquid-to-solid ratio of 8:1. The stripping agent is a combination of dodecylbenzene sulfonic acid with a mass concentration of 8% and potassium phosphate with a mass concentration of 10%, with a mass ratio of 15:1. The mixture is immersed in water for 20 minutes and then transferred to a mechanical stripping device for rotational stripping for 10 minutes at a speed of 200 rpm. The positive and negative electrode materials are separated from copper foil, aluminum foil, diaphragm, etc. respectively through a coarse filter, and the positive and negative electrode materials are selectively fragmented at the same time. After solid-liquid separation, the fragmented positive and negative electrode materials are washed for 5 minutes, and then sieved using a 0.35mm and 0.15mm double-layer vibrating screen to obtain three different particle sizes of materials: coarse (greater than 0.35mm), medium (0.15-0.35mm), and fine (less than 0.15mm). Then, a wet high-gradient magnetic separator is used to carry out the cascade magnetic separation of raw materials, wherein the background magnetic field strength of the coarse material is 1T, the vibration pulse pulse is set at 200 times / min, the magnetic separation process is one coarse, one fine and three sweeps, and the feed concentration of the magnetic separation is 8%; the background magnetic field strength of the medium material is 1.2T, the vibration pulse pulse is set at 240 times / min, the magnetic separation process is one coarse, one fine and two sweeps, and the feed concentration of the magnetic separation is 8%; the background magnetic field strength of the fine material is 1.6T, the vibration pulse pulse is set at 260 times / min, the magnetic separation process is one coarse, two fine and one sweep, and the feed concentration of the magnetic separation is 8%. The magnetic concentrate obtained by the separation of the three particle sizes is combined as the total concentrate product, and the three magnetic tailings are combined as the total tailings product. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation was 95.64%, the total recovery rate was 95.79%, and the copper and aluminum contents were 0.089% and 0.098% respectively; the graphite content in the total tailings product of magnetic separation was 93.67%, the recovery rate was 96.2%, and the copper and aluminum contents were 0.095% and 0.093% respectively.

[0059] Example 2

[0060] The difference from Example 1 is that the pole piece material is mixed with a stripping agent with a liquid-solid ratio of 8:1. The stripping agent is a combination of citric acid with a mass concentration of 8% and sodium pyrophosphate with a mass concentration of 10%, with a mass ratio of 15:1. The mixture is immersed for 10 minutes and then transferred to a mechanical stripping device for rotational stripping for 10 minutes at a speed of 200 rpm. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation is 95.09%, the total recovery rate is 95.56%, and the copper and aluminum contents are 0.087% and 0.099% respectively; the graphite content in the total tailings product of magnetic separation is 92.05%, the recovery rate is 96.28%, and the copper and aluminum contents are 0.099% and 0.091% respectively.

[0061] Example 3

[0062] The difference from Example 1 is that the pole piece material is mixed with a stripping agent with a liquid-solid ratio of 20:1. The stripping agent is a combination of oxalic acid with a mass concentration of 0.5% and potassium dihydrogen phosphate with a mass concentration of 0.05%, with a mass ratio of 5:1, and is impregnated for 20 minutes, and then transferred to a mechanical stripping device for rotational stripping for 5 minutes at a speed of 400 rpm. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation is 94.73%, the total recovery rate is 94.89%, and the copper and aluminum contents are 0.09% and 0.094% respectively; the graphite content in the total tailings product of magnetic separation is 92.51%, the recovery rate is 96.19%, and the copper and aluminum contents are 0.092% and 0.096% respectively.

[0063] Example 4

[0064] The difference from Example 1 is that: the coarse-grained product is subjected to magnetic separation process, the background magnetic field strength is 0.8T, and the feed concentration of magnetic separation is 5%; the medium-grained product is subjected to magnetic separation process, a wet high-gradient magnetic separator is used, the background magnetic field strength is 1T, and the feed concentration of magnetic separation is 8%; the fine-grained product is subjected to magnetic separation process, a wet high-gradient magnetic separator is used, the background magnetic field strength is 1.2T, and the feed concentration of magnetic separation is 5%. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation is 95.76%, the total recovery rate is 94.39%, and the copper and aluminum contents are 0.105% and 0.099% respectively; the graphite content in the total tailings product of magnetic separation is 92.21%, the recovery rate is 96.47%, and the copper and aluminum contents are 0.084% and 0.093% respectively.

[0065] Example 5

[0066] The difference from Example 1 is that: the background magnetic field strength for the roughing of coarse-grained materials is 1T, the vibration pulsation pulse frequency is set to 200 times / min, the magnetic separation process is one coarse, one fine and three sweeps, and the feed concentration of the magnetic separation is 10%; the background magnetic field strength for the roughing of medium-grained materials is 1.2T, the vibration pulsation pulse frequency is set to 240 times / min, the magnetic separation process is one coarse, one fine and two sweeps, and the feed concentration of the magnetic separation is 10%; the background magnetic field strength for the roughing of fine-grained materials is 1.6T, the vibration pulsation pulse frequency is set to 260 times / min, the magnetic separation process is one coarse, two fine and one sweep, and the feed concentration of the magnetic separation is 10%. Finally, the lithium iron phosphate content in the total magnetic separation concentrate product was 95.05%, the total recovery rate was 95.92%, and the copper and aluminum contents were 0.093% and 0.093% respectively; the graphite content in the total magnetic separation tailings product was 93.07%, the recovery rate was 96.41%, and the copper and aluminum contents were 0.095% and 0.101% respectively.

[0067] Comparative Example 1

[0068] The other conditions are the same as those in Example 1, except that different sieves are used to obtain three different particle size products, namely, coarse, medium and fine, which are greater than 0.5 mm, 0.22-0.5 mm and less than 0.22 mm, respectively. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation is 91.12%, the total recovery rate is 95.63%, and the copper and aluminum contents are 0.096% and 0.102%, respectively; the graphite content in the total tailings product of magnetic separation is 94.55%, the recovery rate is 90.48%, and the copper and aluminum contents are 0.104% and 0.093%, respectively.

[0069] Comparative Example 2

[0070] Other conditions are consistent with those in Example 1, except that: the coarse-grained product is subjected to magnetic separation process, the background magnetic field strength is 1T, and the feed concentration of the magnetic separation is 12%; the medium-grained product is subjected to magnetic separation process, a wet high-gradient magnetic separator is used, the background magnetic field strength is 1.2T, and the feed concentration of the magnetic separation is 12%; the fine-grained product is subjected to magnetic separation process, a wet high-gradient magnetic separator is used, the background magnetic field strength is 1.6T, and the feed concentration of the magnetic separation is 12%. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation is 92.61%, the total recovery rate is 87.61%, and the copper and aluminum contents are 0.11% and 0.105%, respectively; the graphite content in the total tailings product of magnetic separation is 83.95%, the recovery rate is 95.29%, and the copper and aluminum contents are 0.081% and 0.09%, respectively.

[0071] Comparative Example 3

[0072] Other conditions are consistent with those in Example 1, except that: the coarse-grained product is subjected to magnetic separation process, the background magnetic field strength is 0.6T, and the feed concentration of the magnetic separation is 5%; the medium-grained product is subjected to magnetic separation process, a wet high-gradient magnetic separator is used, the background magnetic field strength is 0.8T, and the feed concentration of the magnetic separation is 5%; the fine-grained product is subjected to magnetic separation process, a wet high-gradient magnetic separator is used, the background magnetic field strength is 1T, and the feed concentration of the magnetic separation is 8%. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation is 93.48%, the total recovery rate is 85.83%, and the copper and aluminum contents are 0.087% and 0.104%, respectively; the graphite content in the total tailings product of magnetic separation is 81.29%, the recovery rate is 95.27%, and the copper and aluminum contents are 0.105% and 0.097%, respectively.

[0073] Comparative Example 4

[0074] Other conditions are consistent with those in Example 1, except that: the background magnetic field strength of the coarse material selection is 1T, the vibration pulse frequency is set to 100 times / min, the magnetic separation process is one coarse, one fine and three sweeps, and the feed concentration of the magnetic separation is 12%; the background magnetic field strength of the medium material selection is 1.2T, the vibration pulse frequency is set to 100 times / min, the magnetic separation process is one coarse, one fine and two sweeps, and the feed concentration of the magnetic separation is 12%; the background magnetic field strength of the fine material selection is 1.6T, the vibration pulse frequency is set to 100 times / min, the magnetic separation process is one coarse, two fine and one sweep, and the feed concentration of the magnetic separation is 12%. The magnetic concentrates obtained by sorting the three kinds of particle sizes are combined as the total concentrate product, and the three kinds of magnetic tailings are combined as the total tailings product. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation was 89.96%, the total recovery rate was 92.47%, and the copper and aluminum contents were 0.091% and 0.108% respectively; the graphite content in the total tailings product of magnetic separation was 88.77%, the recovery rate was 89.49%, and the copper and aluminum contents were 0.114% and 0.083% respectively.

[0075] Comparative Example 5

[0076] Other conditions are consistent with those in Example 1, except that: the pole piece material is mixed with a stripping agent with a liquid-to-solid ratio of 25:1, the stripping agent is a combination of dodecylbenzenesulfonic acid with a mass concentration of 0.2% and potassium phosphate with a mass concentration of 0.01%, with a mass ratio of 20:1, and the immersion is for 30 minutes. Finally, the lithium iron phosphate content in the total magnetic separation concentrate product is 83.71%, the total recovery rate is 79.59%, and the copper and aluminum contents are 0.092% and 0.099%, respectively; the graphite content in the total magnetic separation tailings product is 70.87%, the recovery rate is 80.45%, and the copper and aluminum contents are 0.099% and 0.112%, respectively.

[0077] Comparative Example 6

[0078] The other conditions are the same as those in Example 1, except that the pole piece material is mixed with a stripping agent with a liquid-solid ratio of 8:1, the stripping agent is a combination of sulfuric acid with a mass concentration of 8% and sodium sulfate with a mass concentration of 10%, with a mass ratio of 15:1, and the impregnation is 20 minutes. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation is 73.82%, the total recovery rate is 66.59%, and the copper and aluminum contents are 0.088% and 0.084% respectively; the graphite content in the total tailings product of magnetic separation is 65.24%, the recovery rate is 67.63%, and the copper and aluminum contents are 0.089% and 0.91% respectively.

[0079] Comparative Example 7

[0080] Other conditions are consistent with those in Example 2, except that: the coarse-grained product is subjected to magnetic separation process, the background magnetic field strength is 0.6T, and the feed concentration of the magnetic separation is 5%; the medium-grained product is subjected to magnetic separation process, a wet high-gradient magnetic separator is used, the background magnetic field strength is 0.8T, and the feed concentration of the magnetic separation is 5%; the fine-grained product is subjected to magnetic separation process, a wet high-gradient magnetic separator is used, the background magnetic field strength is 1T, and the feed concentration of the magnetic separation is 5%. Finally, the NCM content in the total concentrate product of magnetic separation is 93.56%, the total recovery rate is 88.19%, and the copper and aluminum contents are 0.088% and 0.091%, respectively; the graphite content in the total tailings product of magnetic separation is 82.86%, the recovery rate is 95.18%, and the copper and aluminum contents are 0.11% and 0.111%, respectively.

[0081] Comparative Example 8

[0082] Other conditions are consistent with those in Example 2, except that: the background magnetic field strength for the roughing of coarse-grained materials is 1T, the excitation pulsation pulse frequency is set to 100 times / min, the magnetic separation process is one coarse and one fine three sweeps, and the feed concentration of the magnetic separation is 12%; the background magnetic field strength for the roughing of medium-grained materials is 1.2T, the excitation pulsation pulse frequency is set to 100 times / min, the magnetic separation process is one coarse and one fine two sweeps, and the feed concentration of the magnetic separation is 12%; the background magnetic field strength for the roughing of fine-grained materials is 1.6T, the excitation pulsation pulse frequency is set to 100 times / min, the magnetic separation process is one coarse and two fine one sweeps, and the feed concentration of the magnetic separation is 12%. Finally, the lithium iron phosphate content in the total concentrate product of magnetic separation was 93.42%, the total recovery rate was 91.29%, and the copper and aluminum contents were 0.095% and 0.098% respectively; the graphite content in the total tailings product of magnetic separation was 86.86%, the recovery rate was 94.84%, and the copper and aluminum contents were 0.097% and 0.094% respectively.

[0083] Example 6

[0084] For the waste ternary lithium battery electrode material of a battery recycling plant, the electrode material is mixed with a stripping agent, which is a combination of dodecylbenzene sulfonic acid with a mass concentration of 8% and potassium phosphate with a mass concentration of 10%, with a mass ratio of 15:1. The mixture is immersed for 20 minutes and the liquid-solid ratio is 8:1. Then the mixture is transferred to a mechanical stripping device and rotated for stripping for 10 minutes at a speed of 200 rpm. The positive and negative electrode materials are separated from copper foil, aluminum foil, diaphragm, etc. respectively through a coarse filter, and the positive and negative electrode materials are selectively fragmented at the same time. After solid-liquid separation, the fragmented positive and negative electrode materials are washed for 5 minutes, and then sieved using a 0.35mm and 0.15mm double-layer vibrating screen to obtain three different particle sizes of materials: coarse (greater than 0.35mm), medium (0.15-0.35mm), and fine (less than 0.15mm). Then, a wet high-gradient magnetic separator is used to carry out the cascade magnetic separation of raw materials, wherein the background magnetic field strength of the coarse material is 1.2T, the vibration pulse pulse is set to 180 times / min, the magnetic separation process is one coarse, one fine and three sweeps, and the feed concentration of the magnetic separation is 8%; the background magnetic field strength of the medium material is 1.4T, the vibration pulse pulse is set to 200 times / min, the magnetic separation process is one coarse, one fine and two sweeps, and the feed concentration of the magnetic separation is 8%; the background magnetic field strength of the fine material is 1.8T, the vibration pulse pulse is set to 220 times / min, the magnetic separation process is one coarse, two fine and one sweep, and the feed concentration of the magnetic separation is 8%. The magnetic concentrate obtained by the separation of the three particle sizes is combined as the total concentrate product, and the three magnetic tailings are combined as the total tailings product. Finally, the NCM content in the total concentrate product of magnetic separation was 95.38%, the total recovery rate was 95.07%, and the copper and aluminum contents were 0.092% and 0.096% respectively; the graphite content in the total tailings product of magnetic separation was 92.33%, the recovery rate was 95.93%, and the copper and aluminum contents were 0.097% and 0.096% respectively.

[0085] Comparative Example 9

[0086] The other conditions are consistent with those of Example 6, except that different sieves are used to obtain three different particle size products, namely, coarse, medium and fine, which are greater than 0.5 mm, 0.22-0.5 mm and less than 0.22 mm. Finally, the NCM content in the total concentrate product of magnetic separation is 92.11%, the total recovery rate is 96.03%, and the copper and aluminum contents are 0.093% and 0.101% respectively; the graphite content in the total tailings product of magnetic separation is 94.31%, the recovery rate is 92.78%, and the copper and aluminum contents are 0.096% and 0.091% respectively.

[0087] Comparative Example 10

[0088] Other conditions are consistent with those in Example 6, except that: the background magnetic field strength for the roughing of coarse-grained materials is 1.4T, the excitation pulsation pulse frequency is set to 200 times / min, the magnetic separation process is one coarse, one fine and three sweeps, and the feed concentration of the magnetic separation is 15%; the background magnetic field strength for the roughing of medium-grained materials is 1.6T, the excitation pulsation pulse frequency is set to 240 times / min, the magnetic separation process is one coarse, one fine and two sweeps, and the feed concentration of the magnetic separation is 15%; the background magnetic field strength for the roughing of fine-grained materials is 1.8T, the excitation pulsation pulse frequency is set to 260 times / min, the magnetic separation process is one coarse, two fine and one sweep, and the feed concentration of the magnetic separation is 15%. Finally, the NCM content in the total concentrate product of magnetic separation was 87.95%, the total recovery rate was 85.79%, and the copper and aluminum contents were 0.096% and 0.099% respectively; the graphite content in the total tailings product of magnetic separation was 79.64%, the recovery rate was 87.16%, and the copper and aluminum contents were 0.089% and 0.091% respectively.

[0089] The above are only some of the preferred specific embodiments of the present invention and some of the cases in the process of technical exploration of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for stripping and grading positive and negative electrode materials of waste lithium batteries, characterized in that: The following steps are involved: (1) mixing and impregnating waste lithium battery electrode materials with a stripping agent, adding the mixture to a mechanical stripping device, and rotating and stripping the mixture to obtain a current collector, sheet-like positive and negative electrode active materials, a separator, and a stripping solution; The stripping agent is composed of a combination of an organic weak acid and an inorganic salt in a mass ratio of organic weak acid solution: inorganic salt solution = 1.5-25:1, preferably 2-20:1, and more preferably 5-15:1; wherein the organic weak acid comprises at least one of citric acid, oxalic acid, dodecylbenzenesulfonic acid and acetic acid, and the mass concentration of the organic weak acid solution is 0.5-9%; the inorganic salt comprises at least one of sodium pyrophosphate, sodium pyrosulfate, potassium phosphate and potassium dihydrogen phosphate, and the mass concentration of the inorganic salt solution is 0.05-11%; The liquid-to-solid ratio of the stripping agent to the pole piece material is 7 to 21:1; (2) Screening and grading the positive and negative electrode active materials obtained in step (1) to obtain at least three particle sizes of waste lithium battery positive and negative electrode mixed materials; the obtained waste lithium battery positive and negative electrode mixed materials of different particle sizes include: A coarse-grained mixed material, wherein the particle size of the coarse-grained mixed material is greater than 0.35 mm; A medium-sized mixed material, wherein the particle size of the medium-sized mixed material is 0.15 mm to 0.35 mm; A fine-grained mixed material, wherein the particle size of the fine-grained mixed material is less than 0.15 mm; (3) The products of different particle sizes after screening in step (2) are subjected to cascade magnetic separation by using different magnetic separation processes; wherein the magnetic field strength used for magnetic separation of coarse-grained mixed materials is 0.8 to 1.4 T; the magnetic field strength used for magnetic separation of medium-grained mixed materials is 1 to 1.6 T; and the magnetic field strength used for magnetic separation of fine-grained mixed materials is 1.2 to 1.8 T.

2. The method for stripping and grading the positive and negative electrode materials of waste lithium batteries according to claim 1, characterized in that: The waste lithium battery is a lithium iron phosphate battery and / or a ternary lithium battery.

3. The method for stripping and grading the positive and negative electrode materials of waste lithium batteries according to claim 1, characterized in that: During the immersion in step (1), low-speed stirring is adopted; and the immersion time with low-speed stirring is 10 to 20 minutes.

4. The method for stripping and grading positive and negative electrode materials of waste lithium batteries according to claim 1, characterized in that: In step (1), after the impregnation is completed, a cylindrical stripping device is used to perform rotational stripping of the positive and negative electrode materials, with a rotation time of 5 to 10 minutes and a rotation speed of 200 to 400 rpm.

5. The method for stripping and grading the positive and negative electrode materials of waste lithium batteries according to claim 1, characterized in that: After the rotational peeling and selective fragmentation in step (1), washing is performed for 5 to 10 minutes.

6. The method for stripping and grading the positive and negative electrode materials of waste lithium batteries according to claim 1, characterized in that: In step (3), a wet gradient magnetic separator is used for magnetic separation. The magnetic separation medium is a magnetic medium composed of a rod-shaped magnetic alloy material with a special-shaped cross-section. The diameter of the rod wire is 1.5 mm or 2 mm, preferably 2 mm. The cross-section of the special-shaped material can be diamond-shaped or tear-shaped.

7. The method for stripping and grading the positive and negative electrode materials of waste lithium batteries according to claim 1, characterized in that: In step (3), the feed concentration of the magnetic separation is 5-10%.

8. The method for stripping and grading the positive and negative electrode materials of waste lithium batteries according to claim 1, characterized in that: In step (3), the exciting pulsation frequency of the magnetic separation is 180 to 260 times / min.

9. The method for stripping and grading the positive and negative electrode materials of waste lithium batteries according to claim 7, characterized in that: In step (3), the magnetic separation process of the coarse-grained product is three sweeps, one coarse and one fine, with a magnetic field strength of 0.8 to 1.4 T; the exciting pulsation pulse frequency is set to 180 to 210 times / min, more preferably 195 to 205 times / min; The magnetic separation process for medium-sized products is one roughing and one fine sweeping, with a magnetic field strength of 1 to 1.6 T; the frequency of the exciting pulsation is set at 220 to 250 times / min, and more preferably 235 to 245 times / min; The magnetic separation process for fine-grained products is one coarse, two fine and one sweep, with a magnetic field strength of 1.2 to 1.8 T; the excitation pulsation frequency is set to 250 to 260 times / min, and further preferably to 255 to 260 times / min.

10. The method for stripping and grading positive and negative electrode materials of waste lithium batteries according to claim 8, characterized in that: In step (3), the magnetic separation of coarse-grained and medium-grained products adds a sweeping operation, and the magnetic separation of fine-grained products adds a concentrating operation.

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