A method and system for regenerating waste lithium iron phosphate positive electrode material

Abstract

The application discloses a waste lithium iron phosphate positive material regeneration method and system, relates to the technical field of battery processing, and comprises the following steps: treating waste lithium iron phosphate batteries to obtain lithium iron phosphate positive sheets, pyrolyzing and weakly soaking the lithium iron phosphate positive sheets to obtain pretreated lithium iron phosphate positive materials; mixing the lithium iron phosphate positive materials with a solvent to prepare lithium iron phosphate suspension, preheating the lithium iron phosphate suspension, mixing the preheated lithium iron phosphate suspension with a lithium source solution, and simultaneously introducing auxiliary gas treated by a micro-bubble generator to form reaction slurry; strengthening the reaction slurry by using a strengthening device, and standing the strengthened reaction slurry to react; and post-treating the reaction slurry to obtain regenerated lithium iron phosphate positive materials. The micro-bubble processor and the strengthening device are combined to reduce the reaction temperature, so that the reaction can be carried out at low temperature, the energy consumption is greatly reduced, the whole treatment process is shortened, and the lithium supplement efficiency is accelerated.

Description

Technical Field

[0001] This application relates to the technical field of waste battery treatment, specifically to a method and system for regenerating waste lithium iron phosphate cathode materials. Background Technology

[0002] Lithium-ion batteries, due to their significant advantages, have been driving the rapid development of the transportation and energy storage sectors in recent years. Considering the average lifespan of batteries, the world is gradually entering a peak period of retired lithium-ion batteries. Since the cathode material accounts for nearly 40% of a lithium-ion battery, it has high recycling value, making the proper disposal of waste batteries an urgent and promising task. Direct recycling of spent cathode materials refers to replenishing the missing lithium element into the failed cathode material in its original form through chemical or physical means, thereby repairing the material's structure.

[0003] Currently, the recycling of waste lithium-ion battery cathode materials mainly uses wet processes. Specifically, the cathode material is acid-leached or alkali-leached to recover valuable elements, which are then converted into precursors. Finally, new cathode materials are synthesized by high-temperature calcination, typically at 600–800°C. While these processes achieve the recycling of battery cathode materials, they are lengthy, require high calcination temperatures, consume a large amount of energy, and generate significant carbon emissions during the process.

[0004] Traditional lithium replenishment and regeneration methods require testing the lithium deficiency of the cathode material, calculating the ratio of the lithium replenishing agent, adding the agent, and then replenishing lithium. This approach necessitates classifying materials with different levels of lithium deficiency for replenishment, which is not conducive to large-scale industrial production. Other methods involve solid-phase high-temperature sintering for lithium replenishment, but the solid-phase reaction efficiency is low, resulting in long reaction times (5–20 hours), significant lithium source waste, and the need to remove excess lithium remaining on the product surface, making the process cumbersome. Compared to solid-phase lithium replenishment, patent publication number WO 2022076904 A1 discloses a liquid-phase lithium replenishment process, which requires more than 5 hours, followed by sintering at 400–800℃ for 50–300 minutes. It can be seen that the liquid-phase lithium replenishment methods disclosed in the above patents require longer processing times, higher temperatures, and greater energy consumption.

[0005] Based on the above problems, there is an urgent need for a method that can regenerate lithium iron phosphate cathode materials under mild conditions. Summary of the Invention

[0006] To address at least one of the problems mentioned in the background art, this application provides a method and system for regenerating waste lithium iron phosphate cathode materials, which can be carried out in a low-temperature liquid phase, greatly reducing energy consumption. By using an enhancement device, heat and mass transfer between the failed lithium iron phosphate cathode material and the lithium source and reducing agent are realized, reducing the reaction temperature. Lithium replenishment can be achieved directly without secondary high-temperature sintering, while shortening the processing flow and improving the lithium replenishment efficiency.

[0007] The specific technical solutions provided in this application are as follows:

[0008] In a first aspect, a method for regenerating waste lithium iron phosphate cathode materials is provided, the method comprising:

[0009] S1: Discharge, crush, and sort waste lithium iron phosphate batteries to obtain lithium iron phosphate positive electrode sheets. Before and after sorting, the crushed lithium iron phosphate material is pyrolyzed to remove organic matter. The lithium iron phosphate positive electrode sheets are soaked in weak acid to obtain pretreated lithium iron phosphate positive electrode material.

[0010] S2: The pretreated lithium iron phosphate cathode material is mixed with a solvent to form a lithium iron phosphate suspension, and the lithium iron phosphate suspension is preheated;

[0011] S3: Mix the preheated lithium iron phosphate suspension with the lithium source solution, and simultaneously introduce auxiliary gas treated by a microbubble generator to form a reaction slurry;

[0012] S4: The reaction slurry is strengthened by a strengthening device, allowed to stand for reaction, and after the reaction is completed, the slurry is post-processed to obtain regenerated lithium iron phosphate cathode material.

[0013] In one specific embodiment, the weak acid soaking in step S1 specifically includes:

[0014] The weak acid includes at least one or more of citric acid, oxalic acid, sebacic acid, tartaric acid, malic acid, and succinic acid;

[0015] The concentration of the weak acid solution is 5-50 wt%.

[0016] The ratio of the weak acid solution to the lithium iron phosphate cathode is 50–300 g / L;

[0017] The weak acid immersion temperature is 20–85°C;

[0018] The soaking time in the weak acid is 0.3 to 2 hours.

[0019] In a specific embodiment, preheating the lithium iron phosphate suspension in step S2 specifically includes:

[0020] The lithium iron phosphate suspension is preheated using pipeline heating at a temperature of 50-150°C.

[0021] The solvent includes one or more of water, N,N-dimethylformamide, ethylene glycol, or dimethyl sulfoxide.

[0022] In one specific embodiment, the lithium source solution in step S3 includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium bicarbonate, lithium perchlorate, lithium ferrite, and lithium molybdate.

[0023] The lithium ion concentration in the lithium source solution is greater than 0.1 mol / L;

[0024] The flow rate ratio of the lithium source solution to the lithium iron phosphate suspension is 1:3 to 10 L / h.

[0025] In one specific embodiment, the auxiliary gas in step S3 is a mixture of nitrogen and other gases;

[0026] Preferably, the other gases include one or more of hydrogen, carbon monoxide, carbon dioxide, methane, ethane, propane, butane, isobutane, ethylene, propylene, butene, acetylene, propyne, and butyne.

[0027] The volume percentage of the auxiliary gas, excluding nitrogen, is 1-20%.

[0028] Preferably, the volume percentage of gases other than nitrogen in the auxiliary gas is 3-6%.

[0029] In one specific embodiment, the settling reaction time in step S4 is 20 to 60 minutes;

[0030] Post-processing of the reaction slurry yields regenerated lithium iron phosphate cathode material, specifically including:

[0031] After filtration, the slurry is separated into solid and liquid products.

[0032] After adjusting the lithium source concentration, the liquid product can be used as a lithium source solution.

[0033] The solid product is washed, dried, de-ironed, and packaged to obtain recycled lithium iron phosphate cathode material.

[0034] Secondly, a waste lithium iron phosphate cathode material regeneration system is provided, the system comprising:

[0035] Pipeline heating unit is used to preheat lithium iron phosphate suspension;

[0036] An enhanced reaction unit is connected to the outlet end of the pipeline heating unit via a pipe.

[0037] A cavitation unit is connected to the enhanced reaction unit via an auxiliary pipe. The cavitation unit is used to introduce auxiliary gas treated by a microbubble generator into the enhanced reaction unit so that the auxiliary gas treated by the cavitation unit, the preheated lithium iron phosphate suspension and the lithium source are mixed to form a reaction slurry, which then flows into the enhanced reaction unit through the pipe for enhancement.

[0038] The static reaction unit is used to allow the enhanced reaction slurry to undergo static reaction, and the post-reaction process yields recycled lithium iron phosphate cathode material.

[0039] In one specific embodiment, the system further includes:

[0040] A slurry pump, which is connected to the inlet end of the pipeline heating unit via a pipeline, is used to feed pretreated lithium iron phosphate cathode material into the pipeline heating unit;

[0041] A filtration unit is connected to the outlet end of the static reaction unit and is used to separate the slurry after the reaction to obtain solid products and liquid products.

[0042] In one specific embodiment, the system further includes:

[0043] A flow control unit is used to regulate the proportion of the slurry after reaction entering the filtration unit or the circulation channel;

[0044] A circulating reactor, connected to the outlet end of the circulating channel, is used to transport a portion of the reacted slurry back into the reaction system.

[0045] The embodiments of this application have the following beneficial effects:

[0046] 1. In this embodiment, waste lithium iron phosphate batteries are first discharged and crushed to obtain lithium iron phosphate cathode sheets, which are then soaked in acid to obtain pretreated lithium iron phosphate cathode material. The pretreated lithium iron phosphate cathode material is mixed with a solvent to form a lithium iron phosphate suspension. The lithium iron phosphate suspension is preheated and then mixed with a lithium source solution. At the same time, an auxiliary gas treated by a microbubble generator is introduced to form a reaction slurry. The reaction slurry is strengthened using an intensification device and then allowed to stand for reaction. After the reaction, the slurry is post-treated to obtain regenerated lithium iron phosphate cathode material. Through the above scheme, the heat and mass transfer between the failed lithium iron phosphate cathode material and the lithium source and reducing agent is realized by using a microbubble processor and an intensification device together, reducing the reaction temperature and eliminating the need for secondary high-temperature sintering, thus directly achieving lithium replenishment. This also shortens the processing flow and improves the lithium replenishment efficiency. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 A schematic diagram of the method for regenerating waste lithium iron phosphate cathode material according to this application is shown;

[0049] Figure 2 A schematic diagram of a waste lithium iron phosphate cathode material regeneration system according to this application is shown;

[0050] In the diagram, 1 is the pipeline heating unit; 2 is the slurry pump; 3 is the pipeline; 4 is the enhanced reaction unit; 5 is the cavitation unit; 6 is the static reaction unit; 7 is the filtration unit; 701 is the filter inlet; 702 is the filter outlet; 703 is the discharge port; 8 is the flow control unit; 9 is the circulating reactor; 901 is the circulating discharge port; 10 is the first branch pipe; 11 is the second branch pipe; and 12 is the circulation channel. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] The main reagents and materials used in the following examples

[0054] Sample: Waste lithium iron phosphate batteries;

[0055] Reagents: weak acid solution (self-made, concentration to be specified below), water, lithium source solution (self-made, concentration to be specified below);

[0056] Main instrument: Microbubble generator (ZJC-NM series small experimental micro / nanobubble generator).

[0057] Example 1

[0058] A method for regenerating waste lithium iron phosphate cathode materials, such as Figure 1 As shown, the method includes:

[0059] Step S1: Discharge, crush, and sort the waste lithium iron phosphate batteries to obtain lithium iron phosphate cathode sheets. Before and after sorting, the crushed material is pyrolyzed to remove organic matter. The lithium iron phosphate cathode sheets are then pyrolyzed and soaked in weak acid to obtain pretreated lithium iron phosphate cathode materials.

[0060] Waste lithium iron phosphate (LFP) batteries are collected, discharged, crushed, and sorted to obtain LFP cathode sheets. These cathode sheets are then pyrolyzed at 450°C, followed by soaking in a weak acid solution. The selected weak acid solution is oxalic acid with a concentration of 10 wt%, soaked at 35°C for 0.5 hours. This weak acid soaking process removes impurities and adhesive substances from the waste LFP cathode sheets, yielding T-LFP, or pretreated LFP cathode material.

[0061] Step S2: The pretreated lithium iron phosphate cathode material is mixed with a solvent to form a lithium iron phosphate suspension, and the lithium iron phosphate suspension is preheated.

[0062] Pretreated lithium iron phosphate cathode material is mixed with water and placed in a circulating reactor, where it is stirred to prepare a lithium iron phosphate suspension with a solid content of 10%. Under the action of a slurry pump, the lithium iron phosphate suspension enters a pipeline heating unit for preheating at a temperature of 80°C. In one specific embodiment, the pipeline heating method includes one of electric heating, microwave heating, or electromagnetic coil heating.

[0063] Step S3: Mix the preheated lithium iron phosphate suspension with the lithium source solution, and simultaneously introduce auxiliary gas treated by a microbubble generator to form a reaction slurry.

[0064] First, prepare the lithium source solution by preparing a water-soluble lithium salt solution of lithium hydroxide, with a lithium ion concentration greater than 0.1 mol / L. Next, select the type of auxiliary gas: a mixture of nitrogen and other gases, with hydrogen selected as one of the other gases. The volume percentage of the auxiliary gas other than nitrogen (i.e., hydrogen) is set to 5%, and the flow rate of the auxiliary gas is 250 L / h.

[0065] In one specific embodiment, the flow rate of the lithium source solution in the pipeline is adjusted to 12.5 L / h.

[0066] In one specific embodiment, a microbubble generator is used to process the auxiliary gas. Specifically, the inlet of the microbubble generator is connected to the auxiliary gas pipeline, and the outlet of the microbubble generator is connected to the enhanced reaction unit. The microbubble generated by the microbubble generator has a particle size of less than 10 μm. The cavitation auxiliary gas is passed into a mixture of lithium iron phosphate suspension and lithium source solution to form a reaction slurry, wherein the flow rate of the reaction slurry is 50 L / h.

[0067] Step S4: The reaction slurry is strengthened by a strengthening device, allowed to stand for reaction, and after the reaction is completed, the slurry is post-processed to obtain regenerated lithium iron phosphate cathode material.

[0068] The mixed reaction slurry is further enhanced by an intensification device to improve heat and mass transfer between the degraded lithium iron phosphate cathode material and the lithium source and reducing agent. The specific intensification device is selected from a hypergravity reactor, a homogenizer cavitation device, or a microchannel reactor. Those skilled in the art can choose one of these devices to enhance the reaction based on actual work requirements. Specifically, the hypergravity reactor includes a liquid inlet, a liquid outlet, a gas inlet, and a gas outlet. The liquid at the liquid inlet and the gas at the gas inlet rapidly mix and react in the reactor. The gas outlet discharges the reacted gas, and the liquid outlet discharges the reacted liquid phase. The homogenizer cavitation device includes a liquid inlet, a gas inlet, and a combined gas-liquid outlet. After mixing in the homogenizer, the gas and liquid phases are discharged together into the static reaction unit. The channel diameter of the microchannel reactor is set to 50-200 μm. The microchannel reactor includes two liquid inlets and one gas inlet. The liquid inlets are connected to the lithium iron phosphate reaction slurry and the auxiliary liquid mixture through pipelines, respectively. The gas phase and liquid phase are in countercurrent contact.

[0069] In one specific embodiment, when the reaction slurry enters the enhanced reaction unit, a flow rate regulating device is provided in the enhanced reaction unit. The flow rate regulating device reduces the flow rate of the reaction slurry during the enhanced reaction stage, and the reaction slurry stays in the enhanced reaction stage for 300 seconds to cavitate the auxiliary gas through a microbubble generator. Furthermore, the enhanced device further enhances the heat and mass transfer between the failed lithium iron phosphate cathode material and the lithium source and reducing agent, thereby reducing the reaction temperature. Direct lithium replenishment can be achieved without secondary high-temperature sintering, which greatly saves energy consumption.

[0070] In one specific embodiment, the enhanced reaction slurry was introduced into a static reaction unit and allowed to stand for 40 minutes. After filtration and standing, the slurry yielded solid and liquid products. The lithium source concentration was adjusted and reused as a lithium source solution, while unreacted reagents were recycled, saving lithium source and auxiliary materials. The solid product was washed, dried, de-ironized, and packaged to obtain recycled lithium iron phosphate cathode material. The prepared recycled lithium iron phosphate cathode material was tested, and the results are shown in Table 1. The prepared recycled lithium iron phosphate cathode material was then used in the manufacture of new batteries.

[0071] Table 1 Regenerated lithium iron phosphate cathode materials prepared under different conditions

[0072] Lithium ion content / % 4.3 4.15 4.34 4.38 4.38 Carbon content / % 1.2 1.30 1.24 1.10 1.09 Iron leaching rate / ppm 101 43 110 180 59 First Coulomb Efficiency / % 97 95.3 97.3 96.4 96.3 Capacity per gram (mA.h / g) 159 152 159 159 155 Capacity retention after 100 cycles at 0.5°C / % 99.4 95.3 98.8 99.5 99.3

[0073] The scheme in this embodiment enables the lithium replenishment process to be carried out in a low-temperature liquid phase. During the reaction, the lithium source automatically seeks out lithium-deficient vacancies in the material to be repaired, which shortens the reaction time and improves the lithium replenishment efficiency.

[0074] Example 2

[0075] The difference between this embodiment and Embodiment 1 is that the residence time of the enhanced reaction unit is reduced; that is, the reaction slurry is kept for 30 seconds in the enhanced reaction stage, while other conditions remain the same. The prepared recycled lithium iron phosphate cathode material is then tested, and the results are shown in Table 1. The data in Table 1 show that, under the same conditions, a shorter enhanced treatment time weakens the lithium replenishment effect. Therefore, it is necessary to ensure sufficient enhanced treatment time during the processing of waste lithium iron phosphate cathode materials.

[0076] Example 3

[0077] The difference between this embodiment and Embodiment 2 lies in the preheating temperature. In this embodiment, the preheating temperature is 120℃, while other conditions remain the same. The prepared regenerated lithium iron phosphate cathode material was then tested, and the results are shown in Table 1. The test results in Table 1 show that increasing the preheating temperature can improve the reaction efficiency. Under the same enhanced treatment time, the initial coulombic efficiency and specific capacity are improved, enabling repair. However, the capacity retention is affected, falling below that of materials with longer enhanced treatment times.

[0078] Example 4

[0079] The difference between this embodiment and Embodiment 1 is that the volume percentage of hydrogen in the auxiliary gas is set to 15%, while other conditions remain the same. The prepared regenerated lithium iron phosphate cathode material was then tested, and the results are shown in Table 1. The test results in Table 1 show that, under the same conditions, increasing the volume percentage of hydrogen in other gases can improve the reaction efficiency, but may lead to over-reduction and a slight increase in the iron ion dissolution rate.

[0080] Example 5

[0081] The difference between this embodiment and Embodiment 4 is that the other gases in the auxiliary gas are a mixture of hydrogen and carbon dioxide, with a hydrogen-to-carbon dioxide ratio of 1:1. The volume percentage of the other gases in the auxiliary gas is 15%, and other conditions remain the same. The prepared regenerated lithium iron phosphate cathode material was then tested, and the results are shown in Table 1. The test results in Table 1 show that when the other gases are a mixture of hydrogen and carbon dioxide, adding a portion of carbon dioxide can adjust the reducing atmosphere of the reducing agent, thus avoiding over-reduction.

[0082] Comparative Example 1

[0083] The difference between this embodiment and Embodiment 1 is that no lithium source is added, while other conditions remain the same. The prepared recycled lithium iron phosphate cathode material was then tested, and the results are shown in Table 2. The test results in Table 2 show that lithium replenishment cannot be achieved without adding a lithium source during the processing.

[0084] Table 2. Test results of regenerated lithium iron phosphate cathode materials prepared under different comparative conditions.

[0085] Lithium ion content / % 3.10 3.31 4.3 4.1 4.1 4.2 Carbon content / % 1.30 3.4 3.4 3.3 3.1 1.14 Iron leaching rate / ppm 33 35 104 45 45 89 First Coulomb Efficiency / % 76.6 77.1 96.8 94.5 95.1 96.3％ Capacity per gram (mA.h / g) 124 119 157 152 155 154 Capacity retention after 100 cycles at 0.5°C / % 88 70 99.3 91 96 98.7％

[0086] Comparative Example 2

[0087] The difference between this embodiment and Embodiment 1 is that no strengthening device is used to strengthen the reaction slurry, while other conditions remain the same. The prepared regenerated lithium iron phosphate cathode material was then tested, and the results are shown in Table 2. The data in Table 2 show that adding a lithium source without a process strengthening device significantly reduces the lithium replenishment effect. Furthermore, the cycle performance of the cathode material is actually worse than in Comparative Embodiment 1, demonstrating that the strengthening device has the function of reshaping the crystal structure.

[0088] Comparative Example 3

[0089] The difference between this embodiment and Embodiment 1 is that the settling time after enhancement is 2 minutes, while other conditions remain the same. The prepared recycled lithium iron phosphate cathode material was then tested, and the results are shown in Table 2. The data in Table 2 show that during the settling reaction, microbubbles gradually diffuse from the bottom to the top of the liquid surface, breaking down and collapsing during this process. This effectively removes the conductive carbon black adhering to the surface of the cathode material. If the settling time is too short, the carbon content in the recycled lithium iron phosphate will include the conductive carbon black from the raw material, resulting in a higher measured carbon content.

[0090] Comparative Example 4

[0091] The difference between this embodiment and Comparative Example 2 is the preheating temperature. In this embodiment, the preheating temperature is 200℃, while other conditions remain the same. The prepared regenerated lithium iron phosphate cathode material was then tested, and the results are shown in Table 2. The data in Table 2 show that increasing the preheating temperature can achieve lithium replenishment without using an enhancement device, but the cycle performance is poor after lithium replenishment.

[0092] Comparative Example 5

[0093] The difference between this embodiment and Comparative Example 4 is that after obtaining the regenerated lithium iron phosphate cathode material, a calcination step is added. The calcination temperature is 690–710℃, and after calcination for 3 hours, the final regenerated lithium iron phosphate cathode material is obtained, with other conditions remaining the same. The prepared regenerated lithium iron phosphate cathode material is then tested, and the results are shown in Table 2. The data in Table 2 show that while the added calcination step achieves lithium replenishment, it requires more energy and increases the regeneration time.

[0094] Comparative Example 6

[0095] The difference between this embodiment and Embodiment 1 is that the solvent used in the lithium iron phosphate suspension is N-methylpyrrolidone (NMP). The pretreated lithium iron phosphate cathode material is mixed with an NMP solution with a boiling point above 150°C and placed in a circulating reactor, stirred to prepare a lithium iron phosphate suspension. The solid content of the prepared lithium iron phosphate suspension is 10%, and other conditions remain the same. The prepared regenerated lithium iron phosphate cathode material is then tested, and the results are shown in Table 2. The data in Table 2 show that using an organic solvent as the solvent for preparing the slurry can also achieve the lithium replenishment reaction. However, when using an organic solvent as the solvent for preparing the slurry, the pressure within the entire circulating system is significantly reduced at the same preheating temperature, which is beneficial for actual production operations.

[0096] In one specific embodiment, those skilled in the art may choose other organic hydrocarbon solvents, which include at least N,N-dimethylformamide, ethylene glycol, or dimethyl sulfoxide.

[0097] Example 6

[0098] Corresponding to the above embodiments, this application provides a waste lithium iron phosphate cathode material regeneration system, such as... Figure 2 As shown, the system includes:

[0099] Pipe heating unit 1 is used to preheat the lithium iron phosphate suspension; the temperature to which the pipeline is heated is 50-150℃.

[0100] The slurry pump 2 is used to transport the lithium iron phosphate suspension to the pipeline heating unit 1 through the pipeline 3, so that the slurry enters the pipeline 3 through the slurry pump 2 and is preheated by the pipeline heater.

[0101] Enhanced reaction unit 4 is connected to the outlet end of heating unit 1 via pipe 3.

[0102] Cavitation unit 5, connected to enhanced reaction unit 4 via an auxiliary pipeline, is used to introduce auxiliary gas treated by a microbubble generator into enhanced reaction unit 4. This allows the auxiliary gas to undergo cavitation in cavitation unit 5, followed by enhanced reaction unit 4 to enhance the reaction slurry formed by mixing the cavitation-treated auxiliary gas, preheated lithium iron phosphate suspension, and lithium source. Specifically, the inlet of the microbubble generator is connected to the auxiliary gas pipeline, and the outlet is connected to enhanced reaction unit 4; the microbubble generated by the microbubble generator has a particle size <10µm.

[0103] The static reaction unit 6 is connected to the enhanced reaction unit 4 via pipe 3 and is used to perform static reaction on the enhanced reaction slurry; the specific static reaction time is 20 to 60 minutes.

[0104] In one specific embodiment, the heating method for the lithium iron phosphate suspension by the pipeline heating unit 1 is selected from one of the following: indirect heat exchange via heat exchanger, electric heating via pipeline, microwave heating, and electromagnetic coil heating.

[0105] In one specific embodiment, the system further includes a filtration unit 7, which is connected to the outlet of the static reaction unit 6 via a pipe 3. The filtration unit 7 is used to separate the post-reaction slurry to obtain solid and liquid products. Specifically, the filtration unit 7 is a filter, which has a filtration inlet 701, a filtration outlet 702, and a discharge port 703. The filtration inlet 701 is located at the connection between the pipe 3 and the filter, used to feed the post-reaction slurry to be filtered into the filter. The filtration outlet 702 is located near the top of the filter, used to discharge the filtered liquid product. The discharge port 703 is located at the bottom of the filter, used to discharge the filtered solid product. The solid product undergoes further post-processing, namely washing, drying, iron removal, and packaging, to obtain recycled lithium iron phosphate cathode material.

[0106] The system also includes a flow control unit 8 and a circulation reactor 9. The flow control unit 8 is a flow control valve connected to a three-way valve. The inlet of the three-way valve is connected to the outlet of the static reaction unit 6 via a pipe 3. The other two outlets of the three-way valve are connected to a first branch pipe 10 and a second branch pipe 11, respectively. The first branch pipe 10 is connected to the inlet of the filter unit 7, and the outlet of the second branch pipe 11 is connected to the circulation reactor 9. The flow control unit 8 is used to regulate the proportion of slurry entering the filter unit 7 or the circulation pipe after the reaction. The circulation reactor 9 also includes a circulation outlet 901, which is located at the bottom of the circulation reactor 9 and connected to a circulation channel 12. This allows a portion of the slurry after the reaction to enter the circulation reactor 9 through the second branch pipe 11, flow out through the circulation outlet 901 at the bottom of the circulation reactor 9, and then re-enter the slurry pump 2 through the circulation channel 12.

[0107] In one specific embodiment, pretreated lithium iron phosphate particles are added to a circulating reactor 9 and mixed with water to form a lithium iron phosphate suspension. The solid content of the lithium iron phosphate suspension is 5-30%. The pretreatment steps of lithium iron phosphate include discharging and crushing waste lithium iron phosphate batteries to obtain lithium iron phosphate positive electrode sheets, which are then pyrolyzed and soaked in a weak acid to obtain pretreated lithium iron phosphate particles.

[0108] In one specific embodiment, when the reaction slurry enters the enhanced reaction unit 4, a flow rate regulating device is provided in the enhanced reaction unit 4. The flow rate regulating device reduces the flow rate of the reaction slurry in the enhanced reaction stage and makes the residence time of the reaction slurry in the enhanced reaction stage greater than or equal to 2 seconds.

[0109] In one specific embodiment, the enhanced reaction unit 4 is one of a hypergravity reaction device, a homogenizer cavitation device, or a microchannel reactor. Those skilled in the art can select one of these devices for enhanced reaction based on actual work requirements. Specifically, the hypergravity reaction device includes a liquid inlet, a liquid outlet, a gas inlet, and a gas outlet. The liquid at the liquid inlet and the liquid at the gas inlet rapidly mix and react in the reactor. The gas outlet discharges the reacted gas, and the liquid outlet discharges the reacted liquid phase. The homogenizer cavitation device includes a liquid inlet, a gas inlet, and a combined gas-liquid outlet. The gas and liquid phases mix in the homogenizer and are then discharged together into the settling reaction unit 6. The microchannel reactor has a channel diameter of 50–200 μm and includes two liquid inlets and one gas inlet. The liquid inlets are connected to the lithium iron phosphate reaction slurry and the auxiliary liquid mixture via pipelines, respectively, with the gas and liquid phases in countercurrent contact.

[0110] In a specific embodiment, when a microchannel reactor is selected by those skilled in the art as the device in the enhanced reaction unit 4, an auxiliary liquid needs to be added. Specifically, the auxiliary liquid is a solution or suspension prepared from one or more of citric acid, adipic acid, diacid, tartaric acid, malic acid, and succinic acid.

[0111] Example 7

[0112] Corresponding to the above embodiments, this embodiment provides a lithium iron phosphate cathode material prepared based on a method for regenerating waste lithium iron phosphate cathode materials. The prepared recycled lithium iron phosphate cathode material is reused in the preparation of new batteries. The preparation of the recycled lithium iron phosphate cathode material includes the following steps:

[0113] Step 101: Discharge and crush the waste lithium iron phosphate batteries to obtain lithium iron phosphate positive electrode sheets. The lithium iron phosphate positive electrode sheets are then subjected to pyrolysis and weak acid soaking to obtain pretreated lithium iron phosphate positive electrode materials.

[0114] Step 102: The pretreated lithium iron phosphate cathode material is mixed with a solvent to form a lithium iron phosphate suspension, and the lithium iron phosphate suspension is preheated;

[0115] Step 103: Mix the preheated lithium iron phosphate suspension with the lithium source solution, and simultaneously introduce auxiliary gas treated by a microbubble generator to form a reaction slurry;

[0116] Step 104: The reaction slurry is strengthened by an intensification device, allowed to stand for reaction, and after the reaction is completed, the slurry is post-processed to obtain regenerated lithium iron phosphate cathode material.

[0117] Although preferred embodiments have been described in this application, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of this application.

[0118] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for regenerating waste lithium iron phosphate cathode material, characterized in that, The method includes: S1: Discharge, crush, and sort waste lithium iron phosphate batteries to obtain lithium iron phosphate positive electrode sheets. Before and after sorting, the crushed lithium iron phosphate material is pyrolyzed to remove organic matter. The lithium iron phosphate positive electrode sheets are soaked in a weak acid solution to obtain pretreated lithium iron phosphate positive electrode material. S2: The pretreated lithium iron phosphate cathode material is mixed with a solvent to form a lithium iron phosphate suspension, and the lithium iron phosphate suspension is preheated; S3: Mix the preheated lithium iron phosphate suspension with the lithium source solution, and simultaneously introduce auxiliary gas treated by a microbubble generator to form a reaction slurry; The auxiliary gas is a mixture of nitrogen and other gases, including hydrogen and / or carbon monoxide. S4: The reaction slurry is strengthened by an intensification device and allowed to stand for reaction; after the reaction is completed, the slurry is post-processed to obtain recycled lithium iron phosphate cathode material. The strengthening device is selected from one of the following: a supergravity reaction device, a homogenizer cavitation device, or a microchannel reactor; The process of post-processing the reaction slurry to obtain regenerated lithium iron phosphate cathode material specifically includes: filtering the reaction slurry to separate it into solid and liquid products; adjusting the lithium source concentration of the liquid product and using it as a lithium source solution for continued use; and washing, drying, removing iron, and packaging the solid product to obtain regenerated lithium iron phosphate cathode material.

2. The method for regenerating waste lithium iron phosphate cathode material according to claim 1, characterized in that, The weak acid solution soaking in step S1 specifically includes: The weak acid solution includes at least one or more of citric acid, oxalic acid, sebacic acid, tartaric acid, malic acid, and succinic acid; The concentration of the weak acid solution is 5-50 wt%; The ratio of the weak acid solution to the lithium iron phosphate cathode is 50~300g / L; The immersion temperature of the weak acid solution is 20~85℃; The soaking time in the weak acid solution is 0.3~2 hours.

3. The method for regenerating waste lithium iron phosphate cathode material according to claim 1 or 2, characterized in that, The preheating of the lithium iron phosphate suspension in step S2 specifically includes: The lithium iron phosphate suspension is preheated using pipeline heating at a temperature of 50-150°C. The solvent includes one or more of water, N,N-dimethylformamide, ethylene glycol, or dimethyl sulfoxide.

4. The method for regenerating waste lithium iron phosphate cathode material according to claim 1 or 2, characterized in that, The lithium source solution in step S3 includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium bicarbonate, lithium perchlorate, lithium ferrite, and lithium molybdate. The lithium ion concentration in the lithium source solution is greater than 0.1 mol / L; The flow rate ratio of the lithium source solution to the lithium iron phosphate suspension is 1:3~10L / h.

5. The method for regenerating waste lithium iron phosphate cathode material according to claim 4, characterized in that, The volume percentage of the auxiliary gas, excluding nitrogen, is 1-20%.

6. The method for regenerating waste lithium iron phosphate cathode material according to claim 5, characterized in that, The volume percentage of the auxiliary gas, excluding nitrogen, is 3-6%.

7. The method for regenerating waste lithium iron phosphate cathode material according to claim 1 or 2, characterized in that, The static reaction time in step S4 is 20~60 min.

8. The method for regenerating waste lithium iron phosphate cathode material according to claim 1 or 2, characterized in that, The other gases also include one or more of carbon dioxide, methane, ethane, propane, butane, isobutane, ethylene, propylene, butene, acetylene, propyne, and butyne.

9. A waste lithium iron phosphate cathode material regeneration system for use in the method according to any one of claims 1 to 8, characterized in that, The system includes: Pipeline heating unit (1) is used to preheat lithium iron phosphate suspension; Enhanced reaction unit (4) is connected to the outlet end of the pipeline heating unit (1) via pipe (3); Cavitation unit (5) is connected to the enhanced reaction unit (4) through an auxiliary pipe. It is used to introduce the auxiliary gas treated by the microbubble generator into the enhanced reaction unit (4) so ​​that the auxiliary gas treated by the cavitation unit (5), the preheated lithium iron phosphate suspension and the lithium source are mixed to form a reaction slurry, which flows into the enhanced reaction unit (4) through the pipe (3) for enhancement. The static reaction unit (6) is used to allow the enhanced reaction slurry to undergo static reaction, and the post-reaction process is carried out to obtain the regenerated lithium iron phosphate cathode material.

10. The waste lithium iron phosphate cathode material regeneration system according to claim 9, characterized in that, The system also includes: A slurry pump (2) is connected to the inlet end of the pipeline heating unit (1) via a pipe (3) for feeding pretreated lithium iron phosphate cathode material into the pipeline heating unit (1); A filtration unit (7) is connected to the outlet end of the static reaction unit (6) and is used to separate the slurry after the reaction to obtain solid products and liquid products.

11. The waste lithium iron phosphate cathode material regeneration system according to claim 10, characterized in that, The system also includes: A flow control unit (8) is used to regulate the proportion of slurry entering the filter unit (7) or the circulation channel (12) after the reaction. A circulating reactor (9) is connected to the outlet end of the circulating channel (12) for conveying part of the slurry after the reaction back into the reaction system.

12. A lithium iron phosphate cathode material prepared by the method for regenerating waste lithium iron phosphate cathode material according to any one of claims 1 to 8.

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