Method for recycling and pretreatment of waste lithium-ion batteries

Abstract

The present invention discloses a method for pre-processing the recycling of waste lithium-ion batteries. The waste lithium-ion batteries are discharged, the electrolyte is removed, and the batteries are dried. The dried batteries are crushed, and the crushed materials are sorted on a shaking table to obtain a first mixture containing steel slag, copper flakes, and graphite and a second mixture containing aluminum foil and black powder. The second mixture is roasted and screened under an inert atmosphere to separate the aluminum foil and black powder. The first mixture is subjected to magnetic separation to separate steel slag and a third mixture containing copper flakes and graphite. The third mixture is roasted and screened under an inert atmosphere to separate the copper flakes and graphite. The present invention achieves the overall recycling of waste lithium-ion batteries through processes such as crushing, screening, shaking table, magnetic separation, roasting, and secondary screening. The entire process can be completed mechanically without manual labor. The entire sorting process utilizes the inherent properties of the materials for physical sorting without the addition of chemical reagents, making it a green and efficient separation method.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery recycling, and in particular relates to a method for preprocessing the recycling of waste lithium-ion batteries. Background Art

[0002] With the rapid development of the new energy industry, lithium iron phosphate batteries (LiFePO4) are being widely used in electric and hybrid vehicles due to their low cost and high safety performance. Generally speaking, LiFePO4 batteries have a service life of 5 to 8 years. In recent years, LiFePO4 batteries are expected to enter a retirement phase. If the large number of used LiFePO4 batteries is not properly handled, it will not only cause serious environmental pollution but also lead to the loss of scarce lithium resources. Therefore, the recycling and treatment of used LiFePO4 batteries will be a key research focus in the future.

[0003] The recycling of spent lithium iron phosphate batteries primarily involves pretreatment and metal recovery. While metal recovery has received considerable research, with numerous methods available for recovering the positive electrode active material, the pretreatment phase has been much less studied. Traditional pretreatment methods involve discharging and disassembling the battery pack, manually sorting the positive and negative electrodes, and then separating the positive and negative active materials from the current collector. This process, which inevitably involves manual intervention, is inefficient and unsafe, making it difficult to commercialize. Therefore, finding a convenient and efficient method for processing spent lithium-ion batteries is of great scientific and practical significance.

[0004] Chinese patent CN112961984A discloses a process for selectively recycling collectors of waste lithium-ion batteries. The waste lithium-ion batteries are discharged, dried, and incinerated, and then crushed, screened, and ball-milled to obtain the material after ball milling. The material after ball milling is washed and magnetically separated to obtain a low-magnetic current collector copper-aluminum mixture. The current collector copper-aluminum mixture is pulped and shaken to obtain current collector copper and current collector aluminum respectively. No new impurity ions are introduced in the full separation process of this process, which greatly simplifies the subsequent impurity removal process, improves the purity of the copper-aluminum current collector, and improves the sales value of the current collector. However, the main purpose of this process is to obtain the copper-aluminum current collector, and the recovery of the positive electrode black powder is not taken seriously. It is first subjected to high-temperature incineration and then screened with a large-aperture screen. The incineration process can make the copper current collector brittle. After crushing, a large amount of impurities such as copper, aluminum, and graphite will inevitably enter the positive electrode black powder, resulting in a high impurity content in the positive electrode black powder, increasing the pressure of subsequent recovery of valuable metals, and the copper-aluminum current collector recovery rate is also reduced. In addition, this process of first magnetic separation and then shaking table separation also has certain disadvantages. Since there is very little magnetic material in the material, very little magnetic material is selected by the first magnetic separation, and a large amount of material is left unselected, which will increase unnecessary load and energy consumption in the magnetic separation section. Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, the present invention provides a method for recycling and preprocessing spent lithium-ion batteries. This method utilizes the inherent properties of battery components, such as density, magnetism, volatilization temperature, and toughness, and utilizes a gravity separation and pyrometallurgy process to achieve efficient and harmless recycling and preprocessing of spent lithium-ion batteries.

[0006] According to one aspect of the present invention, a method for recycling and pre-processing waste lithium-ion batteries is proposed, comprising the following steps:

[0007] S1: discharging the waste lithium-ion batteries, removing the electrolyte, and drying them, and crushing the dried batteries to obtain crushed materials;

[0008] S2: sorting the crushed material on a shaking table to obtain a first mixture containing steel slag, copper flakes, and graphite and a second mixture containing aluminum foil and black powder, respectively; calcining and sieving the second mixture under an inert atmosphere to separate the aluminum foil and black powder;

[0009] S3: The first mixture is subjected to magnetic separation to separate steel slag and a third mixture containing copper flakes and graphite. The third mixture is roasted and sieved under an inert atmosphere to separate the copper flakes and graphite.

[0010] In some embodiments of the present invention, in step S1, the waste lithium-ion battery is at least one of a lithium iron phosphate battery, a ternary lithium battery, a lithium manganese oxide battery, or a lithium cobalt oxide battery.

[0011] In some embodiments of the present invention, in step S1, the drying temperature is 80-200°C.

[0012] In some embodiments of the present invention, in step S1, the crushing process is as follows: coarse crushing is performed first, followed by fine crushing, and after the fine crushing is completed, screening is performed. The oversize material is returned to the fine crushing process, and the undersize material is the crushed material and enters the next step of shaker sorting. Furthermore, the screening is wet screening or dry screening.

[0013] In some embodiments of the present invention, the opening of the coarse crushing is 1-4 cm; the opening of the fine crushing is 1-4 mm. It should be noted that the coarse crushing opening and the fine crushing opening refer to the diameter of the crusher discharge port.

[0014] In some embodiments of the present invention, in step S1, the particle size of the crushed material is ≤2 mm.

[0015] In some embodiments of the present invention, in step S2, the shaker is a hydraulic shaker with a transverse slope of 1.5° to 5°, a shaker stroke of 15-35 mm, and a stroke rate of 100-150 strokes / min. A greater bed slope results in a cleaner separation of heavy matter, but also increases the likelihood that heavy matter will be mixed with light matter. Therefore, the bed slope must be strictly controlled.

[0016] In some embodiments of the present invention, in step S3, the magnetic field strength of the magnetic separation is 600-1500 Gs. Within this preferred range, the higher the magnetic field strength, the better the slag separation effect and the higher the separation rate. Furthermore, the equipment used for the magnetic separation is a wet weak magnetic separator.

[0017] In some embodiments of the present invention, in step S2 and / or step S3, the calcination temperature is 300-800°C. Furthermore, the calcination time is 30-240 minutes. The higher the calcination temperature, the better the binder removal effect and the higher the recovery rate of the positive and negative electrode materials. However, the higher the degree of oxidation of the copper sheet and aluminum foil, the higher the content of copper and aluminum impurities doped in the positive and negative electrode materials. Therefore, the calcination temperature must be controlled within an appropriate range.

[0018] In some embodiments of the present invention, in step S2 and / or step S3, the pore size of the sieve used for screening is 0.025-0.074 mm.

[0019] In some embodiments of the present invention, in step S2 and / or step S3, the inert atmosphere is at least one of nitrogen, argon or helium.

[0020] In some embodiments of the present invention, the steam generated during the drying and roasting process is recovered by entering a condensation system through a pipeline.

[0021] According to a preferred embodiment of the present invention, there are at least the following beneficial effects:

[0022] 1. The present invention first heats and dries the residual electrolyte and moisture, then crushes and screens the entire material to control the particle size of the crushed material. The crushed material contains steel slag, copper sheets, graphite adhered to the copper sheets, aluminum foil, and black powder adhered to the aluminum foil. A shaking table is then used to separate heavy and light materials. Magnetic separation is then used to separate the steel slag, copper sheets, and graphite. Finally, roasting is used to burn off the binder, and screening is used to separate the copper sheets from the graphite, and the aluminum foil from the positive electrode black powder. The black powder is mainly a mixture of positive electrode powder, carbon powder, and a small amount of graphite dropped during the crushing and screening process. In the subsequent wet leaching process of the battery black powder, the positive electrode powder can be dissolved by acid, while the graphite and carbon powder can be filtered out as insoluble matter, which has no effect on the process.

[0023] 2. The present invention utilizes the density difference of different substances, uses water as the medium, and adopts a shaking table sorting process to simultaneously separate different materials. During the separation process, aluminum foil and black powder are relatively light and float to the top layer under the influence of water flow classification, and are subjected to greater lateral water flow impact. The graphite and steel slag bonded to the copper sheet are subjected to greater longitudinal impact force, and can be intercepted at two different positions of the shaking table to obtain light and heavy materials; then, the strong magnetism of steel slag and the non-magnetism of copper sheet are utilized to separate steel slag and copper sheet after magnetic separation.

[0024] 3. The main purpose of the present invention is to obtain a higher purity positive electrode black powder, and at the same time achieve efficient recovery of materials such as copper and aluminum current collectors. Compared with the traditional process, the present invention cleverly places the roasting section at the end, which can avoid the copper current collector from becoming brittle due to roasting and mixing into the black powder in the shaking table section, resulting in excessive copper content in the black powder and reduced copper recovery rate in the copper product. Since the amount of light and heavy materials in the crushed material is similar, the present invention places the shaking table before the magnetic separation, first selects half of the light materials on the shaking table, and then performs magnetic separation on the remaining half of the heavy materials, which greatly reduces the amount of material entering the magnetic separation section, reduces the load on the magnetic separation section, and saves a lot of energy consumption. In addition, the traditional process generally leaves graphite in the positive electrode black powder. Graphite is an insoluble substance in the wet process section and is left in the slag for recovery in the wet process section. The present invention can directly obtain most of the graphite products, and only a small amount of graphite is mixed in the positive electrode black powder to participate in subsequent leaching.

[0025] 4. This invention achieves the complete recycling of used lithium-ion batteries through a series of processes, including crushing, screening, shaking, magnetic separation, roasting, and secondary screening. The entire process can be completed mechanically, eliminating the need for manual disassembly. The entire sorting process utilizes the inherent properties of the materials for physical separation, without the addition of chemical reagents. It is a green and efficient separation method with virtually no pollution to the environment and no harm to the human body. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0027] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for recycling and pre-processing waste lithium iron phosphate batteries, referring to Figure 1The specific process is:

[0031] Step 1: Place the fully discharged lithium iron phosphate battery in an oven at 150°C for 3 hours to remove moisture and residual electrolyte. The generated gas is recovered through a pipe into the condensation system. The density of each substance in the lithium iron phosphate battery is as follows: copper 8.9g / cm 3 、Steel 7.85g / cm 3 、Aluminum 2.7g / cm 3 、Lithium iron phosphate 1.523g / cm 3 ;

[0032] Step 2: Take out the dried batteries and put them into a jaw crusher for coarse crushing. The jaw crusher opening is adjusted to 2 cm.

[0033] Step 3: The crushed material is put into a roller crusher for fine crushing, and the opening of the roller crusher is 2mm;

[0034] Step 4: Use a sieve with a mesh size of 2 mm to screen the finely crushed material. The material on the sieve is returned to the roller crusher and continues to be crushed to less than 2 mm. The material under the sieve is processed in the next step.

[0035] Step 5: The shaking table parameters are set to a horizontal slope of 2.5°, a shaking table stroke of 20 cm, and a stroke rate of 140 times / min. The qualified crushed materials are slurried to a concentration of 30%, and then slowly put into the shaking table. After separation on the shaking table, a first mixture containing steel slag, copper sheets, and graphite and a second mixture containing aluminum foil and black powder can be obtained;

[0036] Step 6: The magnetic field strength of the magnetic drum is set to 800 Gs, and the first mixture obtained in step 5 is passed through the magnetic drum to separate the steel slag and the third mixture containing copper flakes and graphite. The steel slag recovery rate is 97%;

[0037] Step 7, placing the third mixture obtained in step 6 into a muffle furnace, setting the temperature to 400° C., and calcining for 60 min under a nitrogen atmosphere, and sieving with a 0.038 mm sieve. The material on the sieve is copper flakes, and the material under the sieve is graphite slag. The recovery rate of copper flakes can reach 98%;

[0038] Step 8: Place the second mixture obtained in step 5 into a muffle furnace, set the temperature to 500° C., and calcine for 40 minutes under a nitrogen atmosphere. Sieve with a sieve with a mesh size of 0.038 mm. The material on the sieve is aluminum foil, and the material under the sieve is black powder. The recovery rate of aluminum foil is 97%, and the recovery rate of positive electrode powder in black powder is 95%.

[0039] Table 1 Element content of each product in Example 1

[0040]

[0041] Example 2

[0042] A method for recycling and pre-processing waste lithium iron phosphate batteries, the specific process is as follows:

[0043] Step 1: Place the fully discharged lithium iron phosphate battery in an oven at 180°C for 2 hours to remove moisture and residual electrolyte. The generated gas is then piped into a condensation system for recovery.

[0044] Step 2: Take out the dried batteries and put them into a jaw crusher for coarse crushing. The jaw crusher opening is adjusted to 2 cm.

[0045] Step 3: The crushed material is put into a roller crusher for fine crushing, and the opening of the roller grinder is 2mm;

[0046] Step 4: Use a sieve with a mesh size of 2 mm to screen the finely crushed material. The material on the sieve is returned to the roller crusher and continues to be crushed to less than 2 mm. The material under the sieve is processed in the next step.

[0047] Step 5: The shaker parameters are set to a horizontal slope of 3.5°, a shaker stroke of 18 cm, and a stroke rate of 140 times / min. The crushed qualified material is slurried to a concentration of 30%, and then slowly put into the shaker. After separation on the shaker, a first mixture containing steel slag, copper sheets, and graphite and a second mixture containing aluminum foil and black powder can be obtained;

[0048] Step 6: The magnetic field strength of the magnetic drum is set to 800 Gs, and the first mixture obtained in step 5 is passed through the magnetic drum to separate the steel slag and the third mixture containing copper flakes and graphite. The steel slag recovery rate is 97%;

[0049] Step 7: placing the third mixture obtained in step 6 into a muffle furnace, setting the temperature to 500° C., and calcining for 40 min under a nitrogen atmosphere. Sieving with a 0.038 mm sieve, the material on the sieve is copper flakes, and the material under the sieve is graphite slag, with a copper flake recovery rate of 97.5%;

[0050] Step 8: Place the second mixture obtained in step 5 into a muffle furnace, set the temperature to 600° C., and calcine for 40 minutes under a nitrogen atmosphere. Sieve with a sieve with a mesh size of 0.038 mm. The material on the sieve is aluminum foil, and the material under the sieve is black powder. The recovery rate of aluminum foil is 98%, and the recovery rate of positive electrode powder in black powder is 94.5%.

[0051] Table 2 Element content of each product in Example 2

[0052]

[0053] Example 3

[0054] A method for recycling and pre-processing waste lithium iron phosphate batteries, the specific process is as follows:

[0055] Step 1: Place the fully discharged lithium iron phosphate battery in an oven at 180°C for 2 hours to remove moisture and residual electrolyte. The generated gas is then piped into a condensation system for recovery.

[0056] Step 2: Take out the dried batteries and put them into a jaw crusher for coarse crushing. The jaw crusher opening is adjusted to 2 cm.

[0057] Step 3: The crushed material is put into a roller crusher for fine crushing, and the opening of the roller grinder is 2mm;

[0058] Step 4: Use a sieve with a mesh size of 2 mm to screen the finely crushed material. The material on the sieve is returned to the roller crusher and continues to be crushed to less than 2 mm. The material under the sieve is processed in the next step.

[0059] Step 5: The shaker parameters are set to a horizontal slope of 3.5°, a shaker stroke of 23 cm, and a stroke rate of 140 times / min. The crushed qualified materials are slurried to a concentration of 30%, and then slowly put into the shaker. After separation on the shaker, a first mixture containing steel slag, copper sheets, and graphite and a second mixture containing aluminum foil and black powder can be obtained;

[0060] Step 6: The magnetic field strength of the magnetic drum is set to 1500 Gs, and the first mixture obtained in step 5 is passed through the magnetic drum to separate the steel slag and the third mixture containing copper flakes and graphite. The steel slag recovery rate is 98%;

[0061] Step 7, placing the third mixture obtained in step 6 into a muffle furnace, setting the temperature to 500° C., and calcining for 40 minutes under a nitrogen atmosphere, and sieving with a 0.038 mm sieve. The material on the sieve is copper flakes, and the material under the sieve is graphite slag. The recovery rate of copper flakes is 97%;

[0062] Step 8: Place the second mixture obtained in step 5 into a muffle furnace, set the temperature to 600° C., and calcine for 120 min under a nitrogen atmosphere. Sieve with a sieve size of 0.038 mm. The material on the sieve is aluminum foil, and the material under the sieve is black powder. The recovery rate of aluminum foil is 96.5%, and the recovery rate of positive electrode powder in black powder is 96%.

[0063] Table 3 Element content of each product in Example 3

[0064]

[0065] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for recycling and pre-processing waste lithium-ion batteries, characterized in that: The following steps are involved: S1: discharging the waste lithium-ion batteries, removing the electrolyte, and drying them, and crushing the dried batteries to obtain crushed materials; S2: sorting the crushed material on a shaking table to obtain a first mixture containing steel slag, copper flakes, and graphite and a second mixture containing aluminum foil and black powder, respectively; calcining the second mixture under an inert atmosphere to remove a binder, and sieving to separate the aluminum foil and black powder; S3: The first mixture is subjected to magnetic separation to separate steel slag and a third mixture containing copper flakes and graphite. The third mixture is calcined under an inert atmosphere to remove a binder, and sieved to separate the copper flakes and graphite. In step S1, the drying temperature is 80-200° C., and the particle size of the crushed material is ≤2 mm.

2. The method according to claim 1, characterized in that In step S1, the crushing process is: coarse crushing first, then fine crushing, screening after fine crushing, the screened material returns to the fine crushing process, and the screened material is the crushed material and enters the next step of shaking table sorting.

3. The method according to claim 2, characterized in that The opening of the coarse break is 1-4 cm; the opening of the fine break is 1-4 mm.

4. The method according to claim 1, wherein In step S2, the shaking table is a hydraulic shaking table with a transverse slope of 1.5° to 5°, a shaking stroke of 15-35 mm, and a stroke rate of 100-150 times / min.

5. The method according to claim 1, wherein In step S3, the magnetic field strength of the magnetic separation is 600-1500 Gs.

6. The method according to claim 1, characterized in that In step S2 and / or step S3, the calcination temperature is 300-800°C.

7. The method according to claim 1, characterized in that In step S2 and / or step S3, the pore size of the sieve used for screening is 0.025-0.074 mm.

8. The method according to claim 1, characterized in that The steam generated during the drying and roasting process enters the condensation system through a pipeline for recovery.

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