A method and device for recycling lithium iron phosphate

Abstract

The application relates to the field of lithium iron phosphate positive electrode material recycling, in particular to a lithium iron phosphate recycling method and a lithium iron phosphate recycling device. The lithium iron phosphate recycling method comprises the following steps: (a) performing first stirring treatment and sand milling treatment on a mixed solution of lithium iron phosphate to be recycled and a dispersing agent; (b) performing second stirring treatment on the mixed slurry after the sand milling treatment, and removing surface floating produced in the second stirring treatment; (c) performing standing on the mixed slurry after the second stirring treatment, and collecting the lower layer slurry after the standing; and (d) performing third stirring treatment, spray drying and sintering on the lower layer slurry after supplementing, so that regenerated lithium iron phosphate is obtained. The technical problems existing in the prior art solid-phase direct regeneration process are solved.

Description

Technical Field

[0001] This invention relates to the field of lithium iron phosphate cathode material recycling, and more specifically, to a method and apparatus for recycling lithium iron phosphate. Background Technology

[0002] Currently, there are two main directions for recycling waste lithium iron phosphate cathode materials. One is to extract valuable lithium metal from the powder using hydrometallurgy. However, the metallurgical process is lengthy, consumes a lot of acid and alkali, generates a large amount of wastewater and solid waste, and damages the original lithium iron phosphate crystal structure, resulting in low resource utilization. The recycling value is strongly correlated with the price of lithium salts, making it economically unviable. The other is to repair retired lithium iron phosphate cathode materials by directly regenerating them to supplement lithium and carbon sources. This method has a short process, low pollution, and high economic value, and the academic and industrial communities have invested a lot of resources in its research.

[0003] For direct regeneration technology, existing technologies provide a direct regeneration method that involves ball milling and mixing waste lithium iron phosphate (LFP) cathode powder, a structural repair agent (lithium phosphate or lithium phenyl phosphate), tartaric acid, etc., followed by high-temperature sintering under an inert atmosphere to obtain repaired LFP cathode material. While this method can effectively restore material properties, the solid-state method has shortcomings in terms of lithium mixing uniformity and carbon coating uniformity. The regenerated material prepared by this method suffers from consistency and uniformity issues, and lacks a purification process, resulting in high F and Al content in the regenerated powder. Therefore, to address these problems, a wet regeneration system adapted for waste LFP needs to be developed.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for recycling lithium iron phosphate, aiming to solve the following technical problems existing in the current solid-phase direct regeneration process: uneven mixing leads to poor product consistency and electrochemical performance; the lack of a purification process results in high Al and F impurity content in the recycled powder, which deteriorates the battery cycle life; and the traditional hydrometallurgical process is long, consumes a lot of acid and alkali, and has high emissions of waste.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A method for recycling lithium iron phosphate includes the following steps: (a) The mixture of lithium iron phosphate to be recycled and the dispersant is subjected to a first stirring treatment and a sand milling treatment; (b) The mixed slurry after the sand milling process is subjected to a second stirring process to remove the surface foam generated during the second stirring process; (c) Allow the mixed slurry after the second stirring treatment to stand, and collect the lower layer of slurry after standing; (d) After feeding the lower slurry, a third stirring treatment, spray drying and sintering are performed to obtain recycled lithium iron phosphate.

[0007] The described lithium iron phosphate recycling method employs a six-step synergistic process: "sand milling homogenization—defoaming and impurity removal—static gravity stratification—precise lithium replenishment—spray drying—high-temperature sintering." This process simultaneously achieves particle regularization, physical purification, and uniform liquid-phase coating within the same workflow. Sand milling breaks down agglomerates and removes residual adhesives, providing a particle size basis for subsequent impurity separation. Defoaming and static stratification remove floating impurities using purely physical methods, eliminating the need for acid-base purification. After lithium replenishment, spray drying achieves molecular-level coating, and finally, sintering completes lattice repair. This short process achieves low impurities, high consistency, and high resource utilization.

[0008] A lithium iron phosphate recycling device for implementing the lithium iron phosphate recycling method, comprising: a first stirring component, a sand milling component, a second stirring component, a third stirring component, a spray drying component, and a sintering component connected in sequence; The second stirring component is equipped with a foam adsorption component, which is used to adsorb the surface foam generated during the stirring process of the second stirring component.

[0009] The lithium iron phosphate recycling device connects a first stirring component, a sand milling component, a second stirring component, a third stirring component, a spray drying component, and a sintering component in sequence to form a continuous production line. A foam adsorption component is integrated in the second stirring component to remove surface foam containing light impurities such as Al and F online, eliminating the need for offline filtration and achieving closed-loop continuous operation. The device has a compact structure and is suitable for industrial scale-up.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The lithium iron phosphate recycling method provided by this invention achieves particle regularization, physical purification, and uniform liquid-phase coating simultaneously in the same process through a six-step synergistic process: sand milling homogenization, foam adsorption impurity removal, static gravity stratification, precise liquid-phase lithium replenishment, spray drying, and high-temperature sintering. Sand milling effectively breaks down agglomerates and removes residual adhesive, laying the particle size foundation for impurity separation and subsequent coating; static stratification and defoaming operations remove light floating impurities such as aluminum and fluorine through purely physical means, significantly reducing impurity content without the introduction of acids or alkalis; the slurry after lithium replenishment is spray-dried to achieve uniform molecular-level coating, and finally lattice repair is completed by high-temperature sintering. The entire method has no heavy metal hazardous waste or high-salt wastewater discharge, and belongs to low-carbon green recycling technology.

[0011] (2) The lithium iron phosphate recycling device provided by the present invention constructs a continuous recycling production line by sequentially connecting a first stirring component, a sand milling component, a second stirring component, a third stirring component, a spray drying component, and a sintering component. The foam adsorption component installed in the second stirring component can remove the surface foam generated during the stirring process online, so that the floating matter containing light impurities such as aluminum and fluorine is automatically removed before entering the subsequent process, eliminating the need for offline filtration or acid-base purification equipment. The entire production line operates in a closed loop from feeding to the discharge of recycled powder, with each component tightly connected and the control parameters reasonably matched, effectively ensuring process continuity and product consistency. Attached Figure Description

[0012] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of a lithium iron phosphate recycling device.

[0014] Figure label: 1-First stirring component, 2-Grinding component, 3-Second stirring component, 4-Third stirring component, 5-Spray drying component, 6-Sintering component, 7-Foam adsorption component, 8-First pumping component, 9-Second pumping component, 10-Third pumping component, 11-Fourth pumping component, 12-Cyclone collecting component, 13-Dust removal component, 14-Exhaust fan component. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0016] One aspect of the present invention relates to a method for recycling lithium iron phosphate, comprising the following steps: (a) The mixture of lithium iron phosphate to be recycled and the dispersant is subjected to a first stirring treatment and a sand milling treatment; (b) The mixed slurry after the sand milling process is subjected to a second stirring process to remove the surface foam generated during the second stirring process; (c) Allow the mixed slurry after the second stirring treatment to stand, and collect the lower layer of slurry after standing; (d) After feeding the lower slurry, a third stirring treatment, spray drying and sintering are performed to obtain recycled lithium iron phosphate.

[0017] The described lithium iron phosphate recycling method employs a six-step synergistic process: sand milling homogenization, foam adsorption for impurity removal, static gravity stratification, precise liquid-phase lithium replenishment, spray drying, and high-temperature sintering. This process simultaneously achieves particle regularization, physical purification, and uniform liquid-phase coating within the same workflow. Sand milling effectively breaks down agglomerates and removes residual adhesives, laying the particle size foundation for impurity separation and subsequent coating. Static stratification and defoaming remove lightweight floating impurities such as aluminum and fluorine using purely physical methods, significantly reducing impurity content without the introduction of acids or alkalis. The lithium-replenished slurry undergoes spray drying for molecular-level uniform coating, and finally, high-temperature sintering completes lattice repair. The entire method produces no heavy metal hazardous waste or high-salt wastewater discharge, making it a low-carbon, green recycling technology.

[0018] Waste lithium iron phosphate batteries are meticulously dismantled to obtain LFP positive electrode sheets. The electrolyte is removed by low-temperature drying to obtain dry positive electrode sheets. Then, the lithium iron phosphate to be recycled is obtained by any one of the following stripping methods: wet stripping, thermal stripping, or mechanical stripping.

[0019] This invention abandons the long process of acid and alkali leaching in metallurgy and uses retired LFP black powder as raw material for direct wet remediation and regeneration. The entire process consumes no strong acids or alkalis, and generates no heavy metal hazardous waste or high-salt wastewater, significantly reducing the cost of treating these three wastes. 100% of the raw material black powder enters the regeneration process, with no waste residue discarded. The resource utilization rate is close to 100%, which is a low-carbon green battery recycling technology with extremely high commercialization value.

[0020] Further, in step (a), the solid content of the mixture of lithium iron phosphate and dispersant to be recovered is 30% to 50%, including but not limited to the point value of any one of 30%, 35%, 40%, 45% or 50% or the range between any two.

[0021] Further, the mass of the dispersant is 0.01wt% to 5wt% of the lithium iron phosphate to be recovered, including but not limited to any one of 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, or 5wt%, or a range between any two. The amount of dispersant ensures the initial dispersibility and flowability of the slurry, meets the requirements for stable feeding during sand milling, avoids excessive dispersant leading to increased foaming and defoaming burden, and prevents residues from affecting the purity and electrochemical performance of the material after high-temperature sintering.

[0022] Furthermore, the dispersant includes, but is not limited to, at least one of: polyvinylpyrrolidone (PVP), PEG, ammonium polymaleate, or sodium polystyrene sulfonate.

[0023] Further, the speed of the first stirring treatment is 150~500 rpm (for example, it can be any value or a range between any two of 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 480 rpm, 490 rpm, or 500 rpm), and the time is 10~60 min (for example, it can be any value or a range between any two of 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min). The purpose of the first stirring treatment is to form a stable slurry system.

[0024] Furthermore, the output particle size D of the sand milling process... 50 The value is 0.2~1.5μm (e.g., it can be a point value or a range between any two of 0.2μm, 0.5μm, 0.8μm, 1.0μm, 1.3μm or 1.5μm, for example, it can be a point value or a range between any two of 0.2μm, 0.5μm, 0.8μm, 1.0μm, 1.3μm or 1.5μm), D max ≤20μm (e.g., a point value or a range between any two of 20μm, 15μm, 10μm, 5μm, 3μm, or 1.5μm). Add appropriately sized zirconia beads for sand milling to break up the lithium iron phosphate agglomerates to be recycled, remove particle defects, and eliminate trace amounts of residual adhesive, ensuring the material particles are within the appropriate range.

[0025] Furthermore, the second stirring process is carried out at a speed of 150-500 rpm (e.g., any value or range between any two of 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, or 500 rpm), and for a time of 10-60 min (e.g., any value or range between any two of 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min). This second stirring promotes the full floating of air bubbles and light impurities within the slurry to the surface, while avoiding over-stirring which could lead to the redispersing of already floated impurities or excessive particle refinement, thus affecting the efficiency of settling and stratification. This provides a stable and sufficient foam layer for subsequent foam adsorption and impurity removal.

[0026] Furthermore, the settling time is 2-8 hours, including but not limited to any one of 2 hours, 4 hours, 6 hours, or 8 hours, or a range between any two. During the settling process, the slurry will separate into layers. F impurities, Al impurities, and carbon impurities, due to their lower density, will enter the upper suspension. The upper suspension will be removed, leaving only the lower slurry, thus reducing the impurity content of the slurry. The second stirring treatment and settling can be repeated 1-3 times.

[0027] Furthermore, the raw materials for the replenishment include at least one of a lithium source, a carbon source, or an additive. Based on the lithium loss rate and carbon loss characteristics of the LFP material to be recycled, trace amounts of lithium source, carbon source, and additives are precisely added.

[0028] Furthermore, the molar ratio of Li to Fe in the slurry after replenishment is 1.03 to 1.10, including but not limited to a point value of any one of 1.03, 1.05, 1.08 or 1.10 or a range between any two.

[0029] Furthermore, the amount of carbon source added is 0.5wt% to 30wt% of the lithium iron phosphate to be recovered, including but not limited to any one of 0.5wt%, 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt% or 30wt% or any range between two.

[0030] Furthermore, the amount of the additive added is 0.05wt% to 5wt% of the lithium iron phosphate to be recycled, including but not limited to any one of 0.05wt%, 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt% or 5wt% or any range between two of them.

[0031] Furthermore, the additives include, but are not limited to, at least one of boric acid, sodium borohydride, or vanadium oxysulfate.

[0032] Furthermore, the third stirring treatment speed is 250~800 rpm (for example, it can be any one of 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, or 800 rpm, or a range between any two), and the time is 10~60 min (for example, it can be any one of 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, or a range between any two). The third stirring treatment achieves uniform dispersion of decommissioned materials, lithium sources, carbon sources, and additives, realizing liquid-phase molecular-level coating; it also performs in-situ repair of lattice defects, carbon layer damage, and lithium vacancies in waste LFP, restoring the electrochemical performance of the material. The third stirring provides sufficient and controllable homogenization time for the slurry after lithium replenishment, ensuring that the lithium source, carbon source and additives are uniformly dispersed at the molecular level in the liquid phase, while avoiding the introduction of additional heat or shear stress due to excessive stirring time.

[0033] Further, the inlet air temperature for spray drying is 180~220℃ (e.g., any value or range between any two of 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, or 220℃), the outlet air temperature is 80~110℃ (e.g., any value or range between any two of 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, or 110℃), and the atomization pressure is 1.2~2.0MPa (e.g., any value or range between any two of 1.2MPa, 1.4MPa, 1.6MPa, 1.8MPa, or 2.0MPa). After spray drying, lithium salt, carbon source, etc., are uniformly coated on the surface of the decommissioned LFP material particles.

[0034] Further, the sintering temperature is 500~800℃ (e.g., any value or range between any two of 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃), and the time is 3~15h (e.g., any value or range between any two of 3h, 5h, 8h, 10h, 13h, or 15h), carried out in an inert atmosphere with an oxygen content not exceeding 50ppm and a gas flow rate of 2~50L / min (e.g., any value or range between any two of 2L / min, 5L / min, 10L / min, 20L / min, 30L / min, 40L / min, or 50L / min). The spray-dried powder is then sent to the sintering process for high-temperature repair and regeneration to complete lattice reconstruction and restore the lithium iron phosphate crystal structure. If the sintering temperature is too low or the time is insufficient, the lattice defects will not be repaired adequately. If the temperature is too high or the time is too long, abnormal grain growth or impurity phase formation may occur.

[0035] Another aspect of the present invention relates to a lithium iron phosphate recycling device for implementing the lithium iron phosphate recycling method, comprising: a first stirring component 1, a sand milling component 2, a second stirring component 3, a third stirring component 4, a spray drying component 5, and a sintering component 6 connected in sequence. The second stirring component 3 is provided with a foam adsorption component 7, which is used to adsorb the surface foam generated during the stirring process of the second stirring component 3.

[0036] To address the pain points of existing solid-phase direct regeneration processes for waste lithium iron phosphate (LFP) such as uneven mixing, high impurities, and poor product consistency, an integrated continuous regeneration system combining wet sand milling for classification and impurity removal, precise lithium replenishment and repair, and spray drying has been developed. This system enables low-cost, low-impurity, and high-performance closed-loop regeneration of retired lithium iron phosphate cathode materials, and is suitable for battery recycling production lines with a capacity of tens of thousands of tons.

[0037] The lithium iron phosphate recycling device, consisting of a first stirring component 1, a sand milling component 2, a second stirring component 3, a third stirring component 4, a spray drying component 5, and a sintering component 6 connected in sequence, forms a continuous recycling production line. The foam adsorption component 7 within the second stirring component 3 can remove surface foam generated during the stirring process online, automatically removing floating matter containing light impurities such as aluminum and fluorine before it enters subsequent processes, eliminating the need for offline filtration or acid / alkali purification equipment. The entire production line operates in a closed loop from feeding to recycled powder discharge, with compact connections between components and reasonable matching of control parameters, effectively ensuring process continuity and product consistency.

[0038] Solid-phase regeneration lacks a purification process, leaving residual aluminum and fluorine impurities that continuously damage battery cycle performance. This device employs a triple physical purification process—sand milling to remove residual adhesive, foaming to remove floating impurities, and gravity stratification—to significantly reduce F and Al impurities without the use of acids or alkalis. Simultaneously, wet sand milling unifies particle size, and combined with spray drying for uniform coating, completely resolving the defect of large batch performance variations in traditional solid-phase processes, resulting in a significant improvement in the electrochemical stability of the finished product.

[0039] Furthermore, a first pumping component 8 is provided between the grinding component 2 and the second stirring component 3. This is used to pump the slurry in the grinding component 2 into the second stirring component 3.

[0040] Furthermore, a second pumping component 9 is provided at the waste liquid outlet of the second stirring component 3. This is used to pump out the upper suspension obtained after settling, thereby treating the waste liquid.

[0041] Furthermore, a third pumping component 10 is provided between the second stirring component 3 and the third stirring component 4. This is used to pump the slurry in the second stirring component 3 into the third stirring component 4.

[0042] Furthermore, a fourth pumping component 11 is provided between the third stirring component 4 and the spray drying component 5. This component is used to pump the slurry in the third stirring component 4 into the spray drying component 5.

[0043] Furthermore, the lithium iron phosphate recycling device also includes a cyclone collection component 12.

[0044] Furthermore, the dust-laden gas outlet of the spray drying component 5 is connected to the air inlet of the cyclone collecting component 12; the discharge outlet of the cyclone collecting component 12 is connected to the feed inlet of the sintering component 6.

[0045] Furthermore, the lithium iron phosphate recycling device also includes a dust removal component 13.

[0046] Furthermore, the dust removal component 13 includes, but is not limited to, a bag filter.

[0047] Furthermore, the dust-laden gas outlet of the cyclone collecting component 12 is connected to the inlet of the dust removal component 13.

[0048] Furthermore, an air-guiding component 14 is provided at the air outlet of the dust removal component 13.

[0049] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0050] Example 1 The method for recycling lithium iron phosphate provided in this embodiment includes the following steps: 1. Add the black powder from the retired LFP electrode sheet and pure water to the first stirring unit 1 at a ratio of 1:1.5, and add 0.5wt% PVP dispersant at the same time. Continue mechanical stirring at a speed of 500rpm for 30min to fully premix the mixture.

[0051] 2. The mixed slurry is pumped into the sand mill unit 2 for sand milling. The zircon bead size is 1.5mm. The sand milling time is 5 minutes, and the slurry size D is controlled. 50 =1.5μm, D max =19.3μm.

[0052] 3. The milled slurry is pumped into the second mixing unit 3 and mechanically stirred continuously at a speed of 300 rpm for 15 minutes. The foam generated during stirring is removed by the foam suction unit. After stirring, the slurry is allowed to stand for 6 hours to settle and separate into layers. The upper suspension is then discharged. This process is repeated twice, removing organic F impurities, Al impurities, and some carbon materials by using the foam suction unit and discharging the upper suspension.

[0053] 4. The homogenized slurry was pumped into the third stirring unit 4 and continuously mechanically stirred at 500 rpm for 30 minutes to achieve uniform dispersion of the slurry. ICP testing was then performed on the slurry, confirming that the decommissioned LFP material had a Li / Fe ratio of 0.92, indicating a lack of active lithium. 3 wt% lithium carbonate was added to the third stirring unit 4 to replenish the active lithium, bringing the slurry Li / Fe ratio to 1.05. Simultaneously, to repair the damaged carbon layer and provide a reducing atmosphere for the re-entry of active lithium into the material lattice, 5 wt% glucose was added, and the mixture was mechanically stirred for 30 minutes to achieve uniform mixing of the slurry.

[0054] 5. Pump the slurry in the third stirring component 4 into the spray drying component 5, and control the inlet air temperature to 180℃, the outlet air temperature to 80℃, and the atomization pressure to 1.5MPa, so that lithium salt, carbon source, etc. are uniformly coated on the surface of the decommissioned LFP material particles.

[0055] 6. The spray-dried powder is sintered at 680℃ for 10 hours under an inert N2 atmosphere with an oxygen content not exceeding 50ppm and an N2 flow rate of 10L / min. Active lithium enters the LFP material lattice, repairing the decommissioned material lattice and repairing the surface carbon layer, thus obtaining LFP repair and regeneration material.

[0056] Example 2 This embodiment is the same as embodiment 1 in terms of process, with the following differences: The output particle size D of the sand milling process 50 It is 0.2μm, D max It is 15μm; The settling time is 2 hours; The second stirring process was carried out at a speed of 280 rpm for 30 minutes. The third stirring process was carried out at a speed of 480 rpm for 60 minutes. The mass of the dispersant is 2 wt% of the lithium iron phosphate to be recovered; The sintering temperature was 800℃ and the time was 5 hours.

[0057] Example 3 This embodiment is the same as embodiment 1 in terms of process, with the following differences: The output particle size D of the sand milling process 50 It is 0.8μm, D max It is 10μm; The settling time is 8 hours; The second stirring process was carried out at a speed of 320 rpm for 30 minutes. The third stirring process was carried out at a speed of 520 rpm for 60 minutes. The mass of the dispersant is 1.5 wt% of the lithium iron phosphate to be recovered; The sintering temperature was 500℃ and the time was 12h.

[0058] Example 4 The lithium iron phosphate recycling device provided in this embodiment, such as Figure 1 As shown, a method for recycling lithium iron phosphate includes: a first stirring component 1, a sand milling component 2, a second stirring component 3, a third stirring component 4, a spray drying component 5, and a sintering component 6 connected in sequence. The second stirring component 3 is equipped with a foam adsorption component 7, which is used to adsorb the surface foam generated during the stirring process of the second stirring component 3. A first pumping component 8 is provided between the grinding component 2 and the second stirring component 3 for pumping the slurry in the grinding component 2 to the second stirring component 3; The waste liquid outlet of the second stirring component 3 is provided with a second pumping component 9, which is used to pump out the upper suspension obtained after settling, thereby treating the waste liquid. A third pumping component 10 is provided between the second mixing component 3 and the third mixing component 4, for pumping the slurry in the second mixing component 3 to the third mixing component 4; A fourth pumping component 11 is provided between the third stirring component 4 and the spray drying component 5, for pumping the slurry in the third stirring component 4 to the spray drying component 5; The lithium iron phosphate recycling device also includes: a cyclone collection component 12; The dust-laden gas outlet of the spray drying component 5 is connected to the air inlet of the cyclone collecting component 12; the discharge outlet of the cyclone collecting component 12 is connected to the feed inlet of the sintering component 6. The lithium iron phosphate recycling device also includes: dust removal component 13; The dust-laden gas outlet of the cyclone collecting component 12 is connected to the inlet of the dust removal component 13; An air-guiding component 14 is provided at the air outlet of the dust removal component 13.

[0059] Comparative Example 1 1. Retired LFP electrode black powder (Li / Fe=0.92), 3wt% lithium carbonate, and 5wt% glucose were placed in a ball mill jar and mixed by ball milling at 500 rpm for 30 minutes. The mixed material was then fed into a sintering furnace for high-temperature sintering at 680℃ for 10 hours under an inert N2 atmosphere, with an oxygen content not exceeding 50 ppm and an N2 flow rate of 10 L / min, to obtain the LFP repair material.

[0060] Comparative Example 2 The only difference between this comparative example and Example 1 is that the surface foam generated during the second stirring process was not removed.

[0061] Comparative Example 3 The only difference between this comparative example and Example 1 is that the standing time is 10 hours.

[0062] Performance Evaluation 1) The content of each element in the recycled lithium iron phosphate material was tested using inductively coupled plasma (ICP).

[0063] 2) The F content in the lithium iron phosphate remediation material was tested using an F ion selector.

[0064] 3) The lithium iron phosphate repair material was mixed with PVDF binder and conductive carbon black at a mass ratio of 90:5:5 to form a slurry, which was then coated and dried to form a positive electrode sheet. Then, CR2025 coin cells were assembled using a lithium metal sheet as the negative electrode, Celgard 2400 as the separator, and 1 mol / L LiPF6+EC / DMC as the electrolyte. Finally, charge-discharge tests were performed on the coin cell test cabinet. After two charge-discharge cycles at 0.1C, a 1C cycle was performed. The 100-cycle retention rate refers to the capacity retention rate after 100 cycles under 1C cycle performance testing. The test results are shown in Table 1.

[0065] Table 1

[0066] The LFP repair and regeneration material in Example 1 was subjected to ICP / F ion testing, which confirmed that the Li / Fe ratio was restored to 1.05, the impurity Al content was only 156 ppm, the impurity F ion content was only 82 ppm, the material had a first-cycle discharge capacity of up to 158.4 mAh / g, and a 1C 100th cycle retention rate of 98%, demonstrating good electrochemical performance comparable to new materials.

[0067] ICP / F ion testing was performed on the LFP repair and regeneration material of Comparative Example 1, confirming that the Li / Fe ratio was restored to 1.05, the impurity Al content was 408 ppm, the impurity F ion content was 492 ppm, the material's first-cycle discharge capacity was as high as 155.3 mAh / g, and the 1C 100th cycle retention rate was 94%, which is inferior to that of Example 1.

[0068] The regenerated lithium iron phosphate obtained by this invention has a low Al content, not exceeding 300 ppm; a low F content, not exceeding 150 ppm; the regenerated lithium iron phosphate material has an initial discharge capacity ≥156 mAh / g, a capacity retention rate ≥98% after 100 cycles at 1C, and excellent electrochemical performance, which is far superior to traditional direct regeneration products.

[0069] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recycling lithium iron phosphate, characterized in that, Includes the following steps: (a) The mixture of lithium iron phosphate to be recycled and the dispersant is subjected to a first stirring treatment and a sand milling treatment; (b) The mixed slurry after the sand milling process is subjected to a second stirring process to remove the surface foam generated during the second stirring process; (c) Allow the mixed slurry after the second stirring treatment to stand, and collect the lower layer of slurry after standing; (d) After feeding the lower slurry, a third stirring treatment, spray drying and sintering are performed to obtain recycled lithium iron phosphate.

2. The method for recycling lithium iron phosphate according to claim 1, characterized in that, The output particle size D of the sand milling process 50 The range is 0.2~1.5μm, D max ≤20μm.

3. The method for recycling lithium iron phosphate according to claim 1, characterized in that, The settling time is 2 to 8 hours.

4. The method for recycling lithium iron phosphate according to claim 1, characterized in that, The second stirring process is carried out at a speed of 150-500 rpm for a time of 10-60 min.

5. The method for recycling lithium iron phosphate according to claim 1, characterized in that, The third stirring process is carried out at a speed of 250-800 rpm for a time of 10-60 min.

6. The method for recycling lithium iron phosphate according to claim 1, characterized in that, The mass of the dispersant is 0.01wt% to 5wt% of the lithium iron phosphate to be recovered.

7. The method for recycling lithium iron phosphate according to claim 1, characterized in that, The sintering temperature is 500~800℃ and the time is 3~15h.

8. A lithium iron phosphate recycling apparatus, used to implement the lithium iron phosphate recycling method according to any one of claims 1 to 7, characterized in that, include: The components are connected in sequence: a first stirring component, a sand milling component, a second stirring component, a third stirring component, a spray drying component, and a sintering component. The second stirring component is equipped with a foam adsorption component, which is used to adsorb the surface foam generated during the stirring process of the second stirring component.

9. The lithium iron phosphate recycling device according to claim 8, characterized in that, A first pumping component is provided between the grinding component and the second stirring component; And / or, a second pumping component is provided at the waste liquid outlet of the second stirring component.

10. The lithium iron phosphate recycling device according to claim 8, characterized in that, A third pumping component is provided between the second stirring component and the third stirring component; And / or, a fourth pumping component is provided between the third stirring component and the spray drying component.

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