Lithium iron phosphate waste recovery device and method for preparing battery-grade lithium phosphate

Abstract

A lithium iron phosphate waste recovery device and a method for preparing battery-grade lithium phosphate. The method for preparing battery-grade lithium phosphate comprises: soaking a positive electrode sheet obtained by disassembling a battery in an organic solvent capable of dissolving a bonding material, and carrying out heating and ultrasonic treatment to separate a positive electrode material from an aluminum foil. By heating the organic solvent, the fluidity and solubility of the organic solvent are increased, and the part of the bonding material in contact with the organic solvent swells, a gap between the positive electrode material and an aluminum foil sheet is increased, the amount of the organic solvent contained in the gap is increased accordingly, and then the dissolving speed of the bonding material is increased.

Description

A lithium iron phosphate waste recovery device and a method for preparing battery-grade lithium phosphate Technical Field

[0001] The present invention relates to battery recycling technology, and in particular to a lithium iron phosphate waste recycling device and a method for preparing battery-grade lithium phosphate therefrom. Background Art

[0002] The recycling of spent lithium iron phosphate batteries is of great significance for reducing environmental pollution and alleviating the pressure on lithium resources. In batteries, carbon materials are mostly coated on copper foil to form the negative electrode sheet, and the adhesive material used for coating is generally a water-based adhesive. Lithium-containing metal oxides are coated on aluminum foil to form the positive electrode sheet, and the adhesive material used for coating is generally an oil-based adhesive. At present, the recycling methods for spent lithium iron phosphate batteries are mainly pyrometallurgical recycling, high-temperature solid-phase recycling and hydrometallurgical recycling. However, no matter which method is used, how to peel the lithium-containing positive electrode material from the electrode sheet is a relatively important link. The degree and efficiency of peeling will directly affect the recovery efficiency of subsequent processing and the purity of lithium phosphate prepared using the recycled raw materials.

[0003] For the stripping of positive and negative electrode materials, water-based adhesives can be removed by soaking in deionized water and ultrasonic treatment, while oil-based adhesives generally need to be soaked and ultrasonically treated in organic solvents, such as the commonly used PVDF adhesive, which is insoluble in water but soluble in organic solvents such as NMP.

[0004] However, it generally takes a long time to strip the positive electrode material using an organic solvent. This is because when the organic solvent dissolves the adhesive material, it gradually dissolves from the edge of the adhesive part to the center, and the thickness of the adhesive material between the positive electrode material and the aluminum foil sheet is very thin. During the dissolution process, the gap between the positive electrode material and the aluminum foil sheet is certain, and the amount of organic solvent it can accommodate is limited, and the fluidity is low. As a result, as the organic solvent in the gap dissolves the adhesive material close to saturation, the dissolution rate of the undissolved adhesive material will decrease. Summary of the Invention

[0005] The purpose of the present invention is to provide a lithium iron phosphate waste recovery device and a method for preparing battery-grade lithium phosphate therefrom, so as to solve the above-mentioned deficiencies in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for recycling lithium iron phosphate waste to prepare battery-grade lithium phosphate, comprising disassembling a battery to obtain a positive electrode sheet, the positive electrode sheet comprising aluminum foil, a positive electrode material, and a bonding material, specifically comprising the following steps:

[0007] S1. Immerse the positive electrode sheet in an organic solvent A that can dissolve the adhesive material, and perform heating and ultrasonic treatment to separate the positive electrode material from the aluminum foil. Dry the separated positive electrode material and grind it to obtain positive electrode material powder.

[0008] S2. Mixing the ground positive electrode material powder with water to prepare a slurry, immersing the carbon felt electrode in the slurry, taking it out and drying it to obtain a working electrode B;

[0009] S3, electrolysis is performed in a phosphoric acid solution using the working electrode B as the anode and the stainless steel electrode as the cathode;

[0010] S4, adjusting the pH value of the electrolyte after electrolysis to 1.5-2.0, heating and precipitating, and filtering to obtain filtrate C;

[0011] S5. Adjust the pH value of the filtrate C to 7.5-8.5, heat and precipitate, and then filter to obtain a lithium phosphate residue;

[0012] S6. Dry the lithium phosphate residue at 60-100° C. for 12-24 hours to obtain a lithium phosphate product.

[0013] Furthermore, the organic solvent in step S1 is one or a mixture of N-methylpyrrolidone, dimethylacetamide or N,N-dimethylformamide, and the temperature of the organic solvent is 80-120°C.

[0014] Furthermore, the concentration of the phosphoric acid solution in step S3 is 0.4-0.6 mol / L, and the voltage is 2.0-3.0V.

[0015] Furthermore, the solution for adjusting the pH value of the electrolyte is ammonia water, the solution temperature in step S4 is 80° C., and the time is 4 to 5 hours, and the solution temperature in step S5 is 60° C., and the time is 2 to 3 hours.

[0016] Furthermore, in step S3, the working electrode B is immersed in the electrolyte for 50 to 70 minutes before electrolysis.

[0017] A lithium iron phosphate waste recycling device, which is suitable for the method for recycling lithium iron phosphate waste to prepare battery-grade lithium phosphate as described above, comprises a dissolution tank, a cover plate is provided on the top of the dissolution tank, the cover plate comprises an upper cover and a lower cover, the upper cover and the lower cover are fixedly connected by a support column, and further comprises:

[0018] Driving mechanism 1, which is used to drive the cover to move up and down;

[0019] Several containers, which are hollow inside and have several through holes on the sides, are used to place positive electrode sheets.

[0020] A plurality of clamping mechanisms are installed in an array at the bottom of the lower cover and are used to clamp the containers;

[0021] The telescopic mechanism is installed in the middle of the cover. The telescopic mechanism includes a telescopic frame and a push-pull component. The telescopic frame is connected to each clamping mechanism. A driving mechanism 2 is installed on one side of the push-pull component. The driving mechanism 2 can cooperate with the push-pull component to drive the telescopic frame to extend or retract, so as to drive each clamping mechanism to move closer or farther away from each other.

[0022] Furthermore, the clamping mechanism includes a clamping head and a fixed shaft, one end of the fixed shaft is fixedly connected to one side of the clamping head, and the outer sides of several fixed shafts are movably connected to the inner wall of the lower cover.

[0023] Furthermore, the telescopic mechanism is installed in the middle of the cover plate, and the telescopic mechanism includes a telescopic frame and a push-pull component. One end of the telescopic frame is connected to the top of the lower cover, and the other end of the telescopic frame is connected to the push-pull component. The telescopic frame includes a plurality of X-shaped connecting rods and two V-shaped connecting rods. The X-shaped connecting rod is composed of two long rods crossed, and the middle parts of the two long rods are rotatably connected by the same pin shaft. The V-shaped connecting rod is composed of two short rods, and one end of the two short rods is rotatably connected by another pin shaft. One end of the pin shaft on each of the X-shaped connecting rods is divided into They are rotatably connected to the inner walls of their adjacent fixed shafts, and the two ends of the two adjacent X-shaped connecting rods are rotatably connected respectively. The two ends of the two X-shaped connecting rods at the ends are rotatably connected to the opposite end of the V-shaped connecting rod. One end of the upper pin shaft of one of the V-shaped connecting rods is rotatably connected to the top of the lower cover, and one end of the upper pin shaft of the other V-shaped connecting rod is rotatably connected to a straight rod, and one end of the straight rod is connected to the push-pull component. The top end of each pin shaft is fixedly connected to a rotating wheel, and a straight groove is provided at the bottom of the upper cover, and each rotating wheel is slidably connected to the inner wall of the straight groove.

[0024] Furthermore, the push-pull component includes a base plate, a rotating drum and a right-angle plate, the bottom of the base plate is slidably connected to one side of the cover plate, one end of the right-angle plate is fixedly connected to the top of the base plate, one side of the rotating drum is connected to a second driving mechanism, and the second driving mechanism is used to drive the rotating drum to rotate along its axis, one end of the rotating drum is rotatably connected to a vertical plate, one side of the vertical plate is fixedly connected to one side of the base plate, a sliding groove is provided on the right-angle plate, and a slider is slidably connected to the inner wall of the sliding groove, the bottom of the slider is fixedly connected to a limiting pin, a reciprocating groove is provided on the circumference of the rotating drum, the limiting pin is slidably connected to the inner wall of the reciprocating groove, and one side of the slider is fixedly connected to one side of the straight rod.

[0025] Furthermore, the lithium iron phosphate waste recycling device also includes a swinging mechanism, which includes a tooth plate 2 and several gear 2s, and the several gear 2s are respectively fixedly connected to the surfaces of several fixed shafts. The bottom of the tooth plate 2 is slidably connected to the top of the cover plate, and it is located on one side of the several gear 2s. The tooth plate 2 is meshed with each gear 2.

[0026] Compared with the prior art, the lithium iron phosphate waste recovery device and the method for preparing battery-grade lithium phosphate provided by the present invention have the following beneficial effects:

[0027] 1. The lithium iron phosphate waste recycling device and the method for preparing battery-grade lithium phosphate thereof increase the fluidity and solubility of the organic solvent by heating the organic solvent. At the same time, the contact area between the adhesive and the organic solvent will swell, so that the positive electrode material can be peeled off from the aluminum foil surface. In the high-temperature organic solution, the adhesive layer will expand and increase the distance between the lithium iron phosphate positive electrode material and the aluminum foil sheet. During the dissolution process, the gap between the positive electrode material and the aluminum foil sheet increases, and the amount of organic solvent that can be accommodated in the gap increases, thereby improving its fluidity and increasing the dissolution rate of the adhesive material.

[0028] 2. The lithium iron phosphate waste recovery device and the method for preparing battery-grade lithium phosphate thereof improve the lithium ion leaching rate while improving the iron ion leaching rate by soaking the working electrode B in the electrolyte before electrolysis.

[0029] 3. The lithium iron phosphate waste recycling device and the method for preparing battery-grade lithium phosphate thereof drive the container to reciprocately expand and contract by the reciprocating expansion and contraction of the telescopic frame, so that the container stirs the organic solvent by its own movement during dissolution, thereby increasing the fluidity of the surrounding organic solvent. When the adhesive at the edge of the bonding part between the positive electrode material and the aluminum foil begins to swell and dissolve, the relative flow between the positive electrode sheet and the organic solvent can cause the sheet-like positive electrode material to generate a certain peeling force under the thrust of the fluid, so that the swollen part of the adhesive is separated from the surface of the positive electrode material or the aluminum foil, so that the organic solvent continues to penetrate into the unswollen adhesive part, thereby avoiding the swollen part hindering the penetration of the organic solvent, resulting in an increase in the dissolution time and a low stripping efficiency of the positive electrode material. At the same time, the stirring effect of the container on the organic solvent under the action of ultrasound is conducive to the dispersion of the dissolved adhesive into the organic solvent, avoiding the poor fluidity of the organic solvent near the container, resulting in the dissolved adhesive amount approaching saturation and reducing the dissolution efficiency.

[0030] 4. The lithium iron phosphate waste recycling device and the method for preparing battery-grade lithium phosphate thereof, in the process of reciprocating expansion and contraction of the container clamped by each clamp, the gear 2 on each fixed shaft reciprocates on the gear plate 2, thereby causing each container to reciprocate and rotate and swing during the process of reciprocating expansion and contraction, thereby further improving the internal fluidity of the organic solvent during use. At the same time, the reciprocating rotation and swing further improves the relative flow between the positive electrode sheet and the organic solvent. When the sheet-like positive electrode material is subjected to the thrust of the fluid to generate a peeling force, the peeling efficiency of the positive electrode material is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0032] FIG1 is a schematic diagram of the overall structure of a lithium iron phosphate waste recovery device provided in Example 2 of the present invention;

[0033] FIG2 is a front view of the overall structure of a lithium iron phosphate waste recovery device provided in Example 2 of the present invention;

[0034] FIG3 is a partial longitudinal cross-sectional schematic diagram of a lithium iron phosphate waste recovery device provided in Example 2 of the present invention;

[0035] FIG4 is a partial longitudinal cross-sectional structural diagram of a lithium iron phosphate waste recovery device (without the telescopic frame) provided in Example 2 of the present invention;

[0036] FIG5 is an enlarged view of point A in FIG4 provided in Example 2 of the present invention;

[0037] FIG6 is a schematic diagram of the container structure provided in the second embodiment of the present invention.

[0038] Description of reference numerals:

[0039] 1. Dissolution tank; 2. Cover plate; 21. Upper cover; 22. Lower cover; 23. Support column; 3. Driving mechanism 1; 4. Container; 5. Driving mechanism 2; 6. Clamping mechanism; 61. Chuck; 62. Fixed shaft; 7. Telescopic mechanism; 71. Telescopic frame; 711. X-type connecting rod; 712. V-type connecting rod; 713. Straight rod; 714. Pin; 715. Rotating wheel; 716. Straight groove; 72. Push-pull component; 721. Bottom plate; 722. Rotating drum; 723. Right-angle plate; 724. Vertical plate; 725. Slide groove; 726. Sliding block; 727. Reciprocating groove; 8. Swinging mechanism; 81. Tooth plate; 82. Gear. Implementation Method

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings. Example

[0041] A method for recycling lithium iron phosphate waste to prepare battery-grade lithium phosphate, comprising disassembling a battery to obtain a positive electrode sheet, wherein the positive electrode sheet comprises aluminum foil, a positive electrode material, and a bonding material, and specifically comprises the following steps:

[0042] S1. Immerse the positive electrode sheet in an organic solvent A that can dissolve the adhesive material, and perform heating and ultrasonic treatment to separate the positive electrode material from the aluminum foil. Dry the separated positive electrode material and grind it to obtain positive electrode material powder.

[0043] S2. Mixing the ground positive electrode material powder with water to prepare a slurry, immersing the carbon felt electrode in the slurry, taking it out and drying it to obtain a working electrode B;

[0044] S3, electrolysis is performed in a phosphoric acid solution using the working electrode B as the anode and the stainless steel electrode as the cathode;

[0045] S4, adjusting the pH value of the electrolyte after electrolysis to 1.5-2.0, heating and precipitating, and filtering to obtain filtrate C;

[0046] S5. Adjust the pH value of the filtrate C to 7.5-8.5, heat and precipitate, and then filter to obtain a lithium phosphate residue;

[0047] S6. Dry the lithium phosphate residue at 60-100° C. for 12-24 hours to obtain a lithium phosphate product.

[0048] In this embodiment, the organic solvent in step S1 is one or a mixture of N-methylpyrrolidone, dimethylacetamide or N,N-dimethylformamide, and the temperature of the organic solvent is 80-120°C. A certain high temperature can increase the fluidity and solubility of the organic solvent. At the same time, the contact area between the adhesive and the organic solvent will swell, so that the positive electrode material can be peeled off from the surface of the aluminum foil. For example, the thermal expansion coefficient of PVDF adhesive is 100-140 μm / (m·K -1 ), in a high-temperature organic solution, the PVDF serving as the bonding layer will also expand, and the distance between the lithium iron phosphate cathode material and the aluminum foil sheet will increase. During the dissolution process, the gap between the cathode material and the aluminum foil sheet will increase, and the amount of organic solvent that can be accommodated in the gap will increase, thereby improving its fluidity and increasing the dissolution rate of the bonding material;

[0049] In this embodiment, the concentration of the phosphoric acid solution in step S3 is 0.4-0.6 mol / L, the voltage is 2.0-3.0 V, the solution for adjusting the pH value of the electrolyte is ammonia water, and the solution temperature in step S4 is heated to 80° C. for 4-5 hours, at which time ferric phosphate dihydrate precipitates, and the filtrate obtained after filtration is filtrate C;

[0050] During electrolysis, the divalent iron in the lithium iron phosphate waste on the working electrode B will undergo an oxidation reaction and be converted into trivalent iron. The reaction formula is as follows:

[0051] LiFePO4→FePO4+Li + +e - ;

[0052] Part of the oxide produced will remain on the working electrode. At this time, the filtrate C is subjected to cyclic electrolysis to gradually separate the oxidation products from the electrode, thereby increasing the leaching rate of iron ions. This process can also accelerate the dissolution of lithium ions in lithium iron phosphate waste.

[0053] In this embodiment, the temperature of the filtrate C is heated to 60° C. for 2 to 3 hours, and lithium phosphate will precipitate out of the solution. The filter residue obtained after filtration is dried to obtain a high-purity lithium phosphate product.

[0054] In step S3, since iron phosphate will remain on the electrode during the electrolysis process, thereby reducing the leaching rate of iron ions, and at the same time, part of the lithium iron phosphate can be directly dissolved in the phosphoric acid electrolyte, the working electrode B can be immersed in the electrolyte before electrolysis. The method of soaking first and then electrolyzing increases the lithium ion leaching rate while increasing the iron ion leaching rate. The soaking time is 50 to 70 minutes. Example

[0055] Please refer to Figures 1 to 6. A lithium iron phosphate waste recovery device includes a dissolution tank 1. An ultrasonic device and a heating device are provided on one side of the dissolution tank 1. The heating device heats the organic solvent in the dissolution tank 1 to maintain the organic solvent in the dissolution tank 1 at a desired temperature. The ultrasonic device and the heating device are common knowledge in the prior art and are directly applied without modification. Therefore, they are not described in detail in this technical solution, and based on the art, they will not cause trouble to this technical solution. A cover plate 2 is provided on the top of the dissolution tank 1. The cover plate 2 includes an upper cover 21 and a lower cover 22. 2. The upper cover 21 and the lower cover 22 are fixedly connected by a support column 23. A driving mechanism 3 is installed on the top of the upper cover 21 to drive it to move up and down. The driving mechanism 3 includes but is not limited to an electric telescopic rod. The base of the electric telescopic rod is provided with an installation station. The output end of the electric telescopic rod is fixedly connected to the top of the upper cover 21. The electric telescopic rod is electrically connected to an external power supply. The electric telescopic rod drives the cover plate 2 to move upward or downward, so that the cover plate 2 can cover the top of the dissolution tank 1, and a plurality of clamping mechanisms 6 installed on the lower cover 22 clamp each container 4 to immerse or remove the organic solvent;

[0056] A plurality of clamping mechanisms 6 are installed in an array at the bottom of the lower cover 22. The clamping mechanism 6 includes a clamp 61 and a fixed shaft 62. One end of the fixed shaft 62 is fixedly connected to one side of the clamp 61. The outer sides of the plurality of fixed shafts 62 are movably connected to the inner wall of the lower cover 22. The plurality of clamps 61 on the plurality of clamping mechanisms 6 clamp each container 4. Then, the driving mechanism 3 is started to drive the cover plate 2 and the container 4 below it to move downward. Each container 4 will be gradually immersed in the organic solvent from the bottom. A plurality of through holes are opened on the sides of the container 4 so that the organic solvent can flow in or out. The interior of the container 4 can be hollow, or provided with a partition plate that can prevent the positive electrode sheets from being placed in layers. The specific internal structure is not limited. The positive electrode sheets can be inside the container 4. Preferably, a partition plate is provided so that the positive electrode sheets can be regularly placed layer by layer in the container 4.

[0057] The telescopic mechanism 7 is installed in the middle of the cover 2. The telescopic mechanism 7 includes a telescopic frame 71 and a push-pull component 72. One end of the telescopic frame 71 is connected to the top of the lower cover 22, and the other end of the telescopic frame 71 is connected to the push-pull component 72. The telescopic frame 71 includes several X-shaped connecting rods 711 and two V-shaped connecting rods 712. The X-shaped connecting rod 711 is composed of two long rods crossed, and the middle of the two long rods are connected by the same pin 714 for rotation. The V-shaped connecting rod 712 is composed of two short rods, and one end of the two short rods is connected by another pin 714 for rotation. One end of the pin 714 on each X-shaped connecting rod 711 is fixed to its adjacent The inner wall of the shaft 62 is rotatably connected, and the two ends of the two adjacent X-shaped connecting rods 711 are rotatably connected respectively. The two ends of the two X-shaped connecting rods 711 at the ends are rotatably connected to the opposite ends of the V-shaped connecting rod 712. One end of the pin shaft 714 on one of the V-shaped connecting rods 712 is rotatably connected to the top of the lower cover 22, and one end of the pin shaft 714 on the other V-shaped connecting rod 712 is rotatably connected to a straight rod 713, and one end of the straight rod 713 is connected to the push-pull component 72. The top of each pin shaft 714 is fixedly connected to a rotating wheel 715. A straight groove 716 is provided at the bottom of the upper cover 21, and each of the rotating wheels 715 is slidably connected to the inner wall of the straight groove 716.

[0058] The push-pull component 72 includes a base plate 721, a rotating drum 722 and a right-angle plate 723. The bottom of the base plate 721 is slidably connected to one side of the cover plate 2, and one end of the right-angle plate 723 is fixedly connected to the top of the base plate 721. One side of the rotating drum 722 is connected to a driving mechanism 25. The driving mechanism 25 is used to drive the rotating drum 722 to rotate along its axis. The driving mechanism 25 includes but is not limited to a motor. One end of the motor output shaft is fixedly connected to one side of the rotating drum 722. It should be noted that the motor can also be connected to a reducer. The output end of the reducer is fixed to one side of the rotating drum 722. The rotary drum 722 is fixedly connected with a vertical plate 724 at one end, and one side of the vertical plate 724 is fixedly connected to one side of the bottom plate 721. A sliding groove 725 is provided on the right-angle plate 723, and a slider 726 is slidably connected to the inner wall of the sliding groove 725. The bottom of the slider 726 is fixedly connected to a limit pin. A reciprocating groove 727 is provided on the periphery of the rotary drum 722, and the limit pin is slidably connected to the inner wall of the reciprocating groove 727. One side of the slider 726 is fixedly connected to one side of the straight rod 713. The rotary drum 722 is driven to rotate by the driving mechanism 25, so that the slider 726 The straight rod 713 moves back and forth on the slide 725 to drive the straight rod 713 to move back and forth. The reciprocating movement of the straight rod 713 drives the telescopic frame 71 to expand and contract back and forth, thereby causing the container 4 clamped by each clamp 61 to expand and contract back and forth, so that the container 4 stirs the organic solvent by its own movement during dissolution, thereby increasing the fluidity of the surrounding organic solvent. When the adhesive at the edge of the bonding portion between the positive electrode material and the aluminum foil begins to swell and dissolve, the relative flow between the positive electrode sheet and the organic solvent can cause the sheet-shaped positive electrode material to generate a certain peeling force under the thrust of the fluid, so that the swollen part of the adhesive is separated from the surface of the positive electrode material or the aluminum foil, so that the organic solvent continues to penetrate into the unswollen adhesive part, thereby avoiding the swollen part hindering the penetration of the organic solvent, resulting in an increase in the dissolution time and a low stripping efficiency of the positive electrode material. At the same time, the stirring effect of the container 4 on the organic solvent under the action of ultrasound is conducive to the dispersion of the dissolved adhesive into the organic solvent, thereby avoiding the poor fluidity of the organic solvent near the container 4, resulting in the dissolved adhesive amount being close to saturation and reducing the dissolution efficiency.

[0059] The swing mechanism 8 includes a second tooth plate 81 and a plurality of second gears 82. The plurality of second gears 82 are fixedly connected to the surfaces of the plurality of fixed shafts 62. The bottom of the second tooth plate 81 is slidably connected to the top of the cover plate 2 and is located on one side of the plurality of second gears 82. The second tooth plate 81 is meshed with each second gear 82. It should be noted that the sliding or rotating connection parts need to be regularly lubricated to reduce friction resistance.

[0060] During the process of reciprocating expansion and contraction of the container 4 clamped by each clamp 61, the gear 2 82 on each fixed shaft 62 rotates back and forth on the tooth plate 2 81, so that each container 4 also performs reciprocating rotation and swing during the process of reciprocating expansion and contraction, so that the internal fluidity of the organic solvent is further improved during use. At the same time, its reciprocating rotation and swing further improves the relative flow between the positive electrode sheet and the organic solvent. When the sheet-like positive electrode material is subjected to the thrust of the fluid, a stripping force is generated, so that the stripping efficiency of the positive electrode material is further improved.

[0061] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A method for recycling lithium iron phosphate waste to prepare battery-grade lithium phosphate, comprising disassembling a battery to obtain a positive electrode sheet, wherein the positive electrode sheet comprises aluminum foil, a positive electrode material and a bonding material, characterized in that: The specific steps include: S1, immersing the positive electrode sheet in an organic solvent A that can dissolve the adhesive material, and performing heating and ultrasonic treatment to separate the positive electrode material from the aluminum foil, and then drying and grinding the separated positive electrode material to obtain positive electrode material powder; S2, mixing the ground positive electrode material powder and water to make a slurry, immersing the carbon felt electrode in the slurry, taking it out and drying it to obtain a working electrode B; S3, electrolysis is performed in a phosphoric acid solution using working electrode B as an anode and a stainless steel electrode as a cathode; S4, adjusting the pH value of the electrolyte after electrolysis to 1.5-2.0, heating and precipitating, and filtering to obtain filtrate C; S5, adjusting the pH value of the filtrate C to 7.5-8.5, heating and precipitating, and filtering to obtain a lithium phosphate residue; S6. Dry the lithium phosphate residue at 60-100° C. for 12-24 hours to obtain a lithium phosphate product.

2. The method for recycling lithium iron phosphate waste to prepare battery-grade lithium phosphate according to claim 1, characterized in that: The organic solvent in step S1 is one or a mixture of N-methylpyrrolidone, dimethylacetamide or N,N-dimethylformamide, and the temperature of the organic solvent is 80-120°C.

3. The method for recycling lithium iron phosphate waste to prepare battery-grade lithium phosphate according to claim 1, characterized in that: The concentration of the phosphoric acid solution in step S3 is 0.4-0.6 mol / L, and the voltage is 2.0-3.0V.

4. The method for recycling lithium iron phosphate waste to prepare battery-grade lithium phosphate according to claim 1, characterized in that: The solution for adjusting the pH value of the electrolyte is ammonia water. The solution temperature in step S4 is 80° C. and the time is 4 to 5 hours. The solution temperature in step S5 is 60° C. and the time is 2 to 3 hours.

5. The method for recycling lithium iron phosphate waste to prepare battery-grade lithium phosphate according to claim 1, characterized in that: In the step S3, the working electrode B is immersed in an electrolyte solution before electrolysis for 50 to 70 minutes.

6. A lithium iron phosphate waste recycling device, which is applicable to the method for preparing battery-grade lithium phosphate by recycling lithium iron phosphate waste according to any one of claims 1 to 5, characterized in that: It includes a dissolving tank, a cover plate is arranged on the top of the dissolving tank, the cover plate includes an upper cover and a lower cover, the upper cover and the lower cover are fixedly connected by a support column, and also includes: Driving mechanism 1, which is used to drive the cover plate to move up and down; A plurality of containers, which are hollow inside and have a plurality of through holes on the sides, and are used to place positive electrode sheets. A plurality of clamping mechanisms, which are installed in an array at the bottom of the lower cover and are used to clamp the containers; A telescopic mechanism is installed in the middle of the cover plate. The telescopic mechanism includes a telescopic frame and a push-pull component. The telescopic frame is connected to each clamping mechanism. A driving mechanism 2 is installed on one side of the push-pull component. The driving mechanism 2 can cooperate with the push-pull component to drive the telescopic frame to extend or contract, so as to drive the clamping mechanisms to move closer to or away from each other.

7. A lithium iron phosphate waste recovery device according to claim 6, characterized in that: The clamping mechanism comprises a clamp and a fixed shaft, one end of the fixed shaft is fixedly connected to one side of the clamp, and the outer sides of a plurality of the fixed shafts are movably connected to the inner wall of the lower cover.

8. A lithium iron phosphate waste recovery device according to claim 7, characterized in that: The telescopic mechanism is installed in the middle of the cover plate, and the telescopic mechanism includes a telescopic frame and a push-pull component. One end of the telescopic frame is connected to the top of the lower cover, and the other end of the telescopic frame is connected to the push-pull component. The telescopic frame includes a plurality of X-shaped connecting rods and two V-shaped connecting rods. The X-shaped connecting rod is composed of two long rods crossed, and the middle parts of the two long rods are rotatably connected by the same pin shaft. The V-shaped connecting rod is composed of two short rods, and one end of the two short rods is rotatably connected by another pin shaft. One end of the pin shaft on each of the X-shaped connecting rods is respectively rotatably connected to the inner wall of the adjacent fixed shaft, and the two ends of the adjacent two X-shaped connecting rods are respectively rotatably connected. The two ends of the two X-shaped connecting rods located at the ends are respectively rotatably connected to the opposite end of the V-shaped connecting rod, one end of the pin shaft on one of the V-shaped connecting rods is rotatably connected to the top of the lower cover, and one end of the pin shaft on the other V-shaped connecting rod is rotatably connected to a straight rod, and one end of the straight rod is connected to the push-pull component, and the top end of each of the pin shafts is fixedly connected to a rotating wheel, and a straight groove is provided at the bottom of the upper cover, and each of the rotating wheels is slidably connected to the inner wall of the straight groove.

9. A lithium iron phosphate waste recovery device according to claim 8, characterized in that: The push-pull component includes a base plate, a rotating drum and a right-angle plate, the bottom of the base plate is slidably connected to one side of the cover plate, one end of the right-angle plate is fixedly connected to the top of the base plate, one side of the rotating drum is connected to a driving mechanism 2, and the driving mechanism 2 is used to drive the rotating drum to rotate along its axis. One end of the rotating drum is rotatably connected to a vertical plate, one side of the vertical plate is fixedly connected to one side of the base plate, a sliding groove is provided on the right-angle plate, a sliding block is slidably connected to the inner wall of the sliding groove, the bottom of the sliding block is fixedly connected to a limiting pin, a reciprocating groove is provided on the peripheral side of the rotating drum, the limiting pin is slidably connected to the inner wall of the reciprocating groove, and one side of the sliding block is fixedly connected to one side of the straight rod.

10. The lithium iron phosphate waste recovery device according to claim 7, characterized in that: It also includes a swing mechanism, which includes a tooth plate 2 and a plurality of gear 2s. The plurality of gear 2s are fixedly connected to the surfaces of a plurality of fixed shafts respectively. The bottom of the tooth plate 2 is slidably connected to the top of the cover plate and is located on one side of the plurality of gear 2s. The tooth plate 2 is meshedly connected to each gear 2.

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