Method for regenerating and recycling positive electrode material of waste lithium iron phosphate battery

Abstract

The invention discloses a method for regenerating and recycling a positive electrode material of a waste lithium iron phosphate battery, and relates to the technical field of environmental protection and comprehensive utilization of resources. The invention discloses a method for regenerating and recycling a positive electrode material of a waste lithium iron phosphate battery. The method comprises the following steps: S1, disassembling the battery to obtain a positive electrode plate; s2, pretreating the positive plate to obtain a pretreated positive plate; s3, performing heat treatment for the first time; s4, rolling is carried out; s5, screening to obtain a positive electrode material; s6, mixing an auxiliary agent with the positive electrode material; s7, crushing; s8, adjusting the substance amount ratio of the lithium element, the iron element and the phosphorus element in the mixed material; and S9, performing secondary heat treatment to obtain the lithium iron phosphate positive electrode repair material. The method is simple in step, and the recovered lithium iron phosphate positive electrode repair material has good electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection and comprehensive resource utilization, and in particular to a method for regenerating and recovering positive electrode materials of waste lithium iron phosphate batteries. Background Art

[0002] With the development of new energy technologies, lithium-ion batteries have been widely used in mobile smart terminals, electric vehicles and other fields. Their production and demand have both shown explosive growth. However, there is a certain proportion of defective products in the production process of lithium-ion batteries. If they are not recycled, it will result in huge waste of resources.

[0003] At present, the recycling method of lithium-ion batteries is usually to disassemble the batteries and peel off the positive electrode materials from the aluminum foil after obtaining the positive electrode sheets. The obtained positive electrode materials have high aluminum content, many impurities, and unqualified phosphorus-iron ratio. The electrochemical performance of the lithium iron phosphate battery positive electrode materials finally recovered is poor. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for regenerating and recycling waste lithium iron phosphate battery positive electrode materials to solve the problem that the lithium iron phosphate battery positive electrode materials recycled by the existing method have poor electrochemical properties.

[0005] In order to solve the above technical problems, according to a first aspect of the present invention, a method for regenerating and recycling positive electrode materials of waste lithium iron phosphate batteries is provided, the method comprising the following steps:

[0006] S1, dismantle the waste lithium iron phosphate battery to obtain the positive electrode sheet;

[0007] S2, pre-treating the positive electrode sheet to obtain a pre-treated positive electrode sheet;

[0008] S3, performing a first heat treatment on the pretreated positive electrode sheet to obtain a first mixed material;

[0009] S4, rolling the first mixed material to obtain a second mixed material;

[0010] S5, screening the second mixed material to obtain aluminum foil and positive electrode material;

[0011] S6, mixing the positive electrode material with an auxiliary agent to obtain a third mixed material; the auxiliary agent includes a reducing agent;

[0012] S7, performing a second crushing on the third mixed material to obtain a fourth mixed material;

[0013] S8, adding at least one of a lithium source, an iron source, and a phosphorus source or not adding the lithium source according to the molar ratio of the phosphorus element, the iron element, and the lithium element in the fourth mixed material to obtain a fifth mixed material; controlling the molar ratio of the phosphorus element, the iron element, and the lithium element in the fifth mixed material to be 1:1:(1-1.2);

[0014] S9, performing a second heat treatment on the fifth mixed material to obtain a lithium iron phosphate positive electrode repair material;

[0015] The temperature of the first heat treatment is 350-600°C, and the time of the first heat treatment is 0.5-2h;

[0016] The temperature of the second heat treatment is 600-800°C, and the time of the second heat treatment is 0.5-4h;

[0017] The first heat treatment and the second heat treatment are performed under an inert atmosphere.

[0018] The present invention can remove the adhesive on the positive electrode sheet through the first heat treatment, so that the positive electrode material is easy to separate from the aluminum foil, and the positive electrode material can be further peeled off from the aluminum foil by rolling, and the breakage rate of the aluminum foil is low; in addition, the reducing agent auxiliary is first mixed with the positive electrode material, and then crushed and heat-treated for the second time, and the electrochemical performance of the recovered lithium iron phosphate positive electrode repair material is better.

[0019] Furthermore, in S2, the size of the pre-treated positive electrode sheet is 2 to 15 cm.

[0020] Furthermore, in S2, the pretreatment method includes first crushing or cutting, washing, and drying.

[0021] Furthermore, the drying temperature is 50-120°C.

[0022] Furthermore, the washing liquid used for washing is at least one of water, ethanol, methanol and acetone.

[0023] Furthermore, ultrasonic washing is adopted, the power of ultrasonic washing is 50 to 300 W, and the time of ultrasonic washing is 5 to 20 minutes.

[0024] Furthermore, in S5, the aperture of the screen used for screening is smaller than the size of the pre-treated positive electrode sheet.

[0025] Furthermore, the reducing agent is at least one of glucose, starch, carbon black, citric acid, oxalic acid, and ascorbic acid; and / or the mass ratio of the positive electrode material to the auxiliary agent is 1:(0.05-0.5).

[0026] Furthermore, in S7, the second crushing is performed by a high-speed crusher, the second crushing time is 30 to 120 seconds, and the particle size of the fourth mixed material is ≤ 20 meshes. By performing the second crushing, the additive and the positive electrode material can be mixed more evenly, and the high-temperature repair effect of the lithium iron phosphate positive electrode repair material is better and more fully repaired.

[0027] Furthermore, in S9, after the second heat treatment, the material is crushed and sieved to obtain a lithium iron phosphate positive electrode repair material.

[0028] Furthermore, the inert atmosphere is at least one of nitrogen, argon and helium.

[0029] Further, S3, S4, and S5 are performed in a separation device; the separation device comprises:

[0030] The separation cylinder is rotatably arranged, and the separation cylinder has a separation chamber;

[0031] A feeding structure, arranged at the first end of the separation cylinder and connected to the separation chamber;

[0032] A discharge structure, disposed at the second end of the separation cylinder and connected to the separation chamber;

[0033] A heating part is arranged on the outer surface of the split cylinder to heat the material to be separated in the separation chamber;

[0034] A first material lifting structure is connected to the inner surface of the separation cylinder and is arranged corresponding to the heating part;

[0035] In S3, the pre-treated positive electrode sheet enters the separation cylinder from the feeding structure and undergoes a first heat treatment in the separation chamber to obtain a first mixed material;

[0036] In S4, the first mixed material is roller-pressed in the separation chamber to obtain a second mixed material;

[0037] In S5, the second mixed material is screened in the separation chamber to obtain aluminum foil and positive electrode material.

[0038] Furthermore, the separation chamber includes a first chamber and a second chamber which are arranged in sequence in the direction from the feeding structure to the discharging structure. The separation device also includes a first screen plate and a crushing structure. The first screen plate is located between the first chamber and the second chamber. The first lifting structure is located in the first chamber. The crushing structure is movably arranged in the second chamber.

[0039] Furthermore, the separation chamber also includes a third chamber, which is located at one end of the second chamber away from the first chamber, and the separation device also includes a second sieve plate arranged between the second chamber and the third chamber and a second material lifting structure arranged in the third chamber.

[0040] By applying the technical solution of the present invention, the positive electrode sheet is subjected to pretreatment, a first heat treatment, and rolling in sequence, so that the positive electrode material can be fully peeled off from the aluminum foil, and the damage to the aluminum foil is small, and the impurities of the recovered lithium iron phosphate positive electrode repair material are small; in addition, by first mixing the positive electrode material with the reducing agent and then crushing it, the mixing uniformity is good, and then a second heat treatment is performed, the high-temperature repair effect is good, and the obtained lithium iron phosphate positive electrode repair material has high electrochemical performance and is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0042] Figure 1 is a cross-sectional schematic diagram of the separation device in the present invention;

[0043] Figure 2 for Figure 1 A schematic top view of the separation device;

[0044] Figure 3 for Figure 1 A schematic front view of the separation device;

[0045] Figure 4 This is a test diagram of the electrochemical performance of the lithium iron phosphate positive electrode repair material in Example 1.

[0046] The above drawings include the following reference numerals:

[0047] 10. Separation cylinder; 11. Separation chamber; 111. First chamber; 112. Second chamber; 113. Third chamber;

[0048] 20. Feeding structure;

[0049] 30. Discharging structure; 31. First discharging port; 32. Second discharging port;

[0050] 40. First material lifting structure; 41. Material lifting ring; 411. Second material lifting block;

[0051] 51. First sieve plate; 52. Second sieve plate; 53. Observation window;

[0052] 60. Broken structure;

[0053] 70. The second material lifting structure. DETAILED DESCRIPTION

[0054] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0055] As described in the background technology, it is difficult to recover lithium iron phosphate positive electrode materials with good electrochemical performance from waste lithium iron phosphate batteries using existing methods. In order to solve the above technical problems, in a typical embodiment of the present invention, a method for regenerating and recovering waste lithium iron phosphate battery positive electrode materials is provided, and the method comprises the following steps:

[0056] S1, dismantle the waste lithium iron phosphate battery to obtain the positive electrode sheet;

[0057] S2, pre-treating the positive electrode sheet to obtain a pre-treated positive electrode sheet;

[0058] S3, performing a first heat treatment on the pretreated positive electrode sheet to obtain a first mixed material;

[0059] S4, rolling the first mixed material to obtain a second mixed material;

[0060] S5, screening the second mixed material to obtain aluminum foil and positive electrode material;

[0061] S6, mixing the positive electrode material with an auxiliary agent to obtain a third mixed material; the auxiliary agent includes a reducing agent;

[0062] S7, performing a second crushing on the third mixed material to obtain a fourth mixed material;

[0063] S8, adding at least one of a lithium source, an iron source, and a phosphorus source or not adding the lithium source according to the molar ratio of the phosphorus element, the iron element, and the lithium element in the fourth mixed material to obtain a fifth mixed material; controlling the molar ratio of the phosphorus element, the iron element, and the lithium element in the fifth mixed material to be 1:1:(1-1.2);

[0064] S9, performing a second heat treatment on the fifth mixed material to obtain a lithium iron phosphate positive electrode repair material;

[0065] The temperature of the first heat treatment is 350-600°C, and the time of the first heat treatment is 0.5-2h;

[0066] The temperature of the second heat treatment is 600-800°C, and the time of the second heat treatment is 0.5-4h;

[0067] The first heat treatment and the second heat treatment are performed under an inert atmosphere.

[0068] Pretreatment of the positive electrode sheet can remove impurities such as electrolyte on the surface of the positive electrode sheet. The first heat treatment can reduce the adhesion between the positive electrode material and the aluminum foil in the positive electrode sheet. On this basis, rolling can be performed to efficiently peel the positive electrode material from the aluminum foil, and the aluminum content in the positive electrode material is reduced. In addition, by first mixing the positive electrode material with the additive, and then crushing and performing a second heat treatment, the resulting lithium iron phosphate positive electrode repair material has good electrochemical properties and good stability.

[0069] In some embodiments, in S2, the size of the pre-treated positive electrode sheet is 2 to 15 cm.

[0070] The size of the pretreated positive electrode sheet is controlled within the above range, on the one hand, to make the pretreated positive electrode sheet easier to process subsequently, and on the other hand, to reduce the aluminum content in the recycled lithium iron phosphate positive electrode repair material and improve the electrochemical performance of the lithium iron phosphate positive electrode repair material.

[0071] In some embodiments, in S2, the pretreatment method includes first crushing or cutting, washing, and drying.

[0072] In some embodiments, the drying temperature is 50-120° C. The drying temperature is controlled within the above range to improve the recovery efficiency on the one hand and to reduce the probability of oxidation of the material on the other hand.

[0073] In some embodiments, the washing liquid used for washing is at least one of water, ethanol, methanol, and acetone.

[0074] In some embodiments, ultrasonic washing is used, the power of ultrasonic washing is 50 to 300 W, and the time of ultrasonic washing is 5 to 20 minutes. Under this condition, washing with water or organic solvent has a good washing effect, preferably washing with water, which can remove the residual electrolyte on the surface of the positive electrode without introducing impurities.

[0075] In some embodiments, in S5, the aperture of the screen used for screening is smaller than the size of the pre-treated positive electrode sheet. After rolling, the size of the positive electrode material will be further reduced and peeled off from the aluminum foil. Controlling the size of the screen can effectively separate the positive electrode material and the aluminum foil.

[0076] In some embodiments, the reducing agent is at least one of glucose, starch, carbon black, citric acid, oxalic acid, and ascorbic acid; and / or the mass ratio of the positive electrode material to the auxiliary agent is 1:(0.05-0.5). The above reducing agent can well reduce the oxidized lithium iron phosphate, so that the recovered lithium iron phosphate positive electrode repair material has good stability.

[0077] In some embodiments, in S7, the second crushing is performed by a high-speed crusher, the second crushing time is 30 to 120 seconds, and the particle size of the fourth mixed material is ≤ 20 mesh. Preferably, the product of the second crushing is sieved through a 20 to 120 mesh sieve to obtain the fourth mixed material; by performing the second crushing, the additive and the positive electrode material can be mixed more evenly, and the high-temperature repair effect of the lithium iron phosphate positive electrode repair material is better and the repair is more sufficient.

[0078] In some embodiments, element detection is performed on the fourth mixed material in S7, and it is determined based on the element detection result whether the fourth mixed material needs to be mixed with at least one of a lithium source, an iron source, and a phosphorus source, so that the molar ratio of phosphorus, iron, and lithium in the fifth mixed material is 1:1:(1 to 1.2).

[0079] In some embodiments, in S9, after the second heat treatment, the material is crushed and sieved to obtain a lithium iron phosphate positive electrode repair material.

[0080] In some embodiments, the pulverization method is one of air flow pulverization, ultrasonic pulverization, high pressure pulverization, and mechanical pulverization, and the screening method is ultrasonic vibration screening, and the sieve aperture is 100 to 300 meshes.

[0081] In some embodiments, the inert atmosphere is at least one of nitrogen, argon, and helium.

[0082] In some embodiments, S3, S4, and S5 are performed in a separation device; the structural schematic diagram of the separation device is as shown in Figures 1 to 3 As shown, including:

[0083] The separation cylinder 10 is rotatably arranged, and the separation cylinder 10 has a separation chamber 11;

[0084] The feeding structure 20 is disposed at the first end of the separation cylinder 10 and communicated with the separation chamber 11;

[0085] The discharge structure 30 is disposed at the second end of the separation cylinder 10 and communicated with the separation chamber 11;

[0086] A heating part is arranged on the outer surface of the split cylinder to heat the material to be separated in the separation chamber 11;

[0087] The first material lifting structure 40 is connected to the inner surface of the separation cylinder 10 and is arranged corresponding to the heating part;

[0088] In S3, the pre-treated positive electrode sheet enters the separation cylinder 10 from the feeding structure 20, and undergoes a first heat treatment in the separation chamber 11 to obtain a first mixed material;

[0089] In S4, the first mixed material is rolled in the separation chamber 11 to obtain a second mixed material;

[0090] In S5, the second mixed material is screened in the separation chamber 11 to obtain aluminum foil and positive electrode material.

[0091] Applying the above embodiment, the separation cylinder 10 has a separation chamber 11, which is used to accommodate the pre-treated positive electrode sheet, the positive electrode material and the aluminum foil. The feeding structure 20 is arranged at the first end of the separation cylinder 10 and is connected to the separation chamber 11. The feeding structure 20 is used to transfer the pre-treated positive electrode sheet to the separation chamber 11 for subsequent separation. The discharging structure 30 is arranged at the second end of the separation cylinder 10 and is connected to the separation chamber 11. The discharging structure 30 is used to transfer the separated aluminum foil and the positive electrode material to the outside of the separation chamber 11. The heating part is arranged on the outer surface of the split cylinder to heat the pre-treated positive electrode sheet in the separation chamber 11, so as to reduce the connection strength between the aluminum foil and the positive electrode material, thereby making the aluminum foil and the positive electrode material easier to separate. The separation cylinder 10 is rotatably arranged, and the first lifting structure 40 is connected to the inner surface of the separation cylinder 10. Connected and arranged corresponding to the heating part, when the separation cylinder 10 rotates, the pre-treated positive electrode sheet in the separation chamber 11 will also rotate with the rotation of the separation cylinder 10 and will contact the first material lifting structure 40. The first material lifting structure 40 can fully mix the pre-treated positive electrode sheet so that different parts of the pre-treated positive electrode sheet can contact the inner surface of the separation cylinder 10, so that different parts of the pre-treated positive electrode sheet can be heated by the heating part, so that the pre-treated positive electrode sheet is heated more evenly, thereby further ensuring that the aluminum foil and the positive electrode material are easy to separate. In addition, the effect of the first material lifting structure 40 lifting the pre-treated positive electrode sheet can also promote the separation of the aluminum foil and the positive electrode material. Through the arrangement of the above-mentioned first material lifting structure 40 and the heating part, the aluminum foil and the positive electrode material can be recycled due to separation instead of always being kept connected. Therefore, the above-mentioned embodiment can effectively solve the problem of low recovery rate of recycled materials.

[0092] It should be noted that the positive electrode material is connected to the aluminum foil in the form of a layered structure through a binder. During the heating process, the binder will decompose and fail, making the connection strength between the positive electrode material and the aluminum foil smaller, thereby facilitating the separation of the positive electrode material and the aluminum foil.

[0093] like Figures 1 to 3 As shown, in some embodiments, the separation chamber 11 includes a first chamber 111 and a second chamber 112 which are arranged in sequence in the direction from the feeding structure 20 to the discharging structure 30, and the separation device also includes a first screen plate 51 and a crushing structure 60, the first screen plate 51 is located between the first chamber 111 and the second chamber 112, the first lifting structure 40 is located in the first chamber 111, and the crushing structure 60 is movably arranged in the second chamber 112.

[0094] Specifically, the first chamber 111 is called the "heating section", the first material lifting structure 40 is located in the first chamber 111, the heating part is located on the partial outer surface of the separation cylinder 10 corresponding to the first chamber 111, the second chamber 112 is called the "rolling section", the crushing structure 60 is a hollow stainless steel cylinder, the diameter of the crushing structure 60 is between 30 cm and 40 cm, and the weight of the crushing structure 60 is between 50 kg and 200 kg. When the separation cylinder 10 rotates, the crushing structure 60 moves in the second chamber 112, so that the crushing structure 60 will roll the pretreated positive electrode sheet, and the positive electrode material will be crushed under the rolling of the crushing structure 60, and it will become multiple smaller parts, while the size of the aluminum foil remains basically unchanged, and the rolling of the crushing structure 60 can further reduce the connectivity between the positive electrode material and the aluminum foil, making it easier to separate. In this embodiment, the crushing structure 60 is limited between the first screen plate 51 and the second screen plate 52 (mentioned later). In other embodiments, the crushing structure can also be limited between the first screen plate and the end face of the second end of the separation cylinder.

[0095] like Figures 1 to 3 As shown, in some embodiments, the separation chamber 11 further includes a third chamber 113, and the third chamber 113 is located at one end of the second chamber 112 away from the first chamber 111, and the separation device further includes a second sieve plate 52 arranged between the second chamber 112 and the third chamber 113 and a second material lifting structure 70 arranged in the third chamber 113. Specifically, the third chamber 113 is called a "separation section". In the direction from the first end to the second end of the separation cylinder 10, the first chamber 111, the second chamber 112, and the third chamber 113 are connected in sequence. The setting of the second material lifting structure 70 can separate the crushed positive electrode material and the aluminum foil, further ensuring the recovery rate of the positive electrode material. The second material lifting structure 70 also includes a plurality of material lifting blocks arranged in an array on the inner surface of the separation cylinder. The plurality of material lifting blocks can be arranged only in the axial direction of the separation cylinder 10 to form a single row, or only in the circumferential direction of the separation cylinder 10 to form a single row, or the plurality of material lifting blocks can be arranged in the form of multiple rows and columns.

[0096] In addition, in this embodiment, the ratio between the length of the first chamber 111 and the length of the separation chamber 11 is greater than or equal to 50% and less than or equal to 70%. Specifically, such a configuration can, on the one hand, enable the first chamber 111 to have a sufficiently long length, thereby ensuring that the pre-treated positive electrode sheet can be fully heated before entering the second chamber 112, and on the other hand, enable the length of the first chamber 111 to be not too long, thereby enabling the heating part to be not too long, thereby achieving the effect of energy saving. The ratio between the length of the first chamber 111 and the length of the separation chamber 11 can be 50%, 58%, 60%, 62%, 67% or 70%.

[0097] like Figures 1 to 3 As shown, in some embodiments, the first material lifting structure 40 includes a plurality of material lifting rings 41 spaced apart along the axial direction of the separation cylinder 10, and each material lifting ring 41 includes a plurality of second material lifting blocks 411 spaced apart along the circumferential direction of the separation cylinder 10. In this way, the inner surface of the separation cylinder 10 is provided with second material lifting blocks 411 in both the axial direction and the circumferential direction of the separation cylinder 10, so that when the separation cylinder 10 rotates, the pre-treated positive electrode sheet can be fully contacted with different second material lifting blocks 411, so that the pre-treated positive electrode sheet can be fully heated. Among them, in the material lifting ring 41, the spacing between adjacent second material lifting blocks 411 is between 15 cm and 30 cm; the spacing between two adjacent material lifting rings 41 is between 8 cm and 15 cm. The first material lifting structure 40 that meets the above requirements can, on the one hand, fully mix the pre-treated positive electrode sheets, and on the other hand, can make the pre-treated positive electrode sheets directly contact the inner surface of the separation cylinder 10, so that the heat transfer path between the pre-treated positive electrode sheets and the heating part is shorter. Specifically, the spacing distance between adjacent second material lifting blocks 411 can be 15 cm, 18 cm, 21 cm, 26 cm, 28 cm or 30 cm; the spacing distance between two adjacent material lifting rings 41 can be 8 cm, 9.3 cm, 10.9 cm, 11 cm, 12.5 cm, 13.8 cm or 15 cm. In addition, in other embodiments, in the material lifting ring, the spacing distance between adjacent second material lifting blocks can be adaptively adjusted according to the size of the pre-treated positive electrode sheets; the spacing distance between two adjacent material lifting rings can also be adaptively adjusted according to the size of the pre-treated positive electrode sheets.

[0098] In addition, in other embodiments, the first material lifting structure includes a plurality of first material lifting blocks arranged in an array on the inner surface of the separation cylinder. Specifically, "a plurality of first material lifting blocks arranged in an array" means that the plurality of first material lifting blocks can be arranged only in the axial direction of the separation cylinder 10 to form a single row, or can be arranged only in the circumferential direction of the separation cylinder 10 to form a single column, or the plurality of first material lifting blocks can be arranged in the form of multiple rows and columns (the first material lifting blocks of two adjacent rows or two adjacent columns can be arranged correspondingly or staggered). Such an arrangement can achieve the effect of uniformly heating the pre-treated positive electrode sheet.

[0099] In this embodiment, the heating part is a heating sleeve sleeved on the outer circumference of the separation cylinder 10. Specifically, the setting of the heating sleeve enables the separation cylinder 10 to be heated in a circumferential manner, so that when the separation cylinder 10 rotates, the pre-treated positive electrode sheet can be heated when it contacts any part of the inner surface of the separation cylinder 10 in the circumferential direction, thereby ensuring the heating effect of the separation device on the pre-treated positive electrode sheet.

[0100] More specifically, the heating sleeve includes a plurality of first electric heating wires, which extend in the axial direction of the separation cylinder 10 and are arranged in the circumferential direction of the separation cylinder 10; the heating sleeve includes a second heating wire, which is wound in the circumferential direction of the separation cylinder 10 and forms a spiral structure in the axial direction of the separation cylinder 10. It should be noted that the heating sleeve may include only the first electric heating wire or only the second electric heating wire or both the first electric heating wire and the second electric heating wire, and the arrangement of the first electric heating wire and the second electric heating wire achieves the effect that the heating sleeve heats the separation cylinder 10 in the circumferential direction.

[0101] like Figures 1 to 3 As shown, the separation cylinder 10 is provided with an observation window 53, which is provided at the first chamber 111. Specifically, the setting of the observation window 53 can facilitate the staff to observe the situation in the first chamber 111 so as to facilitate the staff to adjust the working state of the separation device in time.

[0102] like Figures 1 to 3 As shown, the discharging structure 30 includes a discharging cylinder, which is nested with the separation cylinder 10 and located on the outside of the separation cylinder 10. The second end of the separation cylinder 10 has a sieve hole section. The discharging cylinder includes a first cylinder section and a second cylinder section. The first cylinder section is sleeved on the outer periphery of the sieve hole section, and the second cylinder section is arranged at an end of the first cylinder section away from the first end of the separation cylinder 10. The first cylinder section is provided with a first discharging port 31 for discharging positive electrode materials, and the second cylinder section is provided with a second discharging port 32 for discharging aluminum foil. The size of the positive electrode material is smaller than that of the aluminum foil. Specifically, after separation, the pretreated positive electrode sheet forms a mixture of positive electrode material and aluminum foil present in the third chamber 113, wherein the positive electrode material is smaller-sized positive electrode material fragments, the size of the positive electrode material fragments is approximately between 1 cm and 2 cm, and the size of the aluminum foil is approximately between 7 cm and 8 cm. The diameter of the sieve holes on the sieve hole section can be set between 3 cm and 6 cm, so that the positive electrode material fragments can be screened out, and the screened positive electrode material fragments are discharged from the first discharge port 31, and the remaining aluminum foil is discharged from the second discharge port 32, thereby realizing the separate recovery of the positive electrode material and the aluminum foil. By using the separation device in this embodiment, the separation rate of the positive electrode material can be close to 100%, and the aluminum content of the screened positive electrode material can be lower than 0.05% on average.

[0103] In addition, in this embodiment, the separation cylinder 10 extends in the transverse direction, and the first end of the separation cylinder 10 is higher than the second end of the separation cylinder 10. Specifically, the angle between the axis of the separation cylinder 10 and the horizontal plane is between 1 degree and 3 degrees. In this way, the separation device does not need to set up other pushing structures in the separation chamber 11, and the material can move from the first end of the separation cylinder 10 to the second end of the separation cylinder 10 by its own gravity.

[0104] In addition, in this embodiment, the separation device further includes an air inlet structure and an air outlet structure. The air inlet structure is arranged at the first end of the separation cylinder 10 and introduces protective gas into the separation chamber 11. The air outlet structure is arranged at the second end of the separation cylinder 10 and is used to discharge the gas in the separation chamber 11. Specifically, when the separation device just starts to work, protective gas (specifically, inert gas) is introduced into the separation chamber 11 through the air inlet structure, and the original gas in the separation chamber 11 is discharged through the air outlet structure, thereby playing a role in protecting the pre-treated positive electrode sheet. In addition, during the continuous operation of the separation device, the air outlet structure can also continuously input protective gas into the separation chamber 11, thereby ensuring that there is no other gas in the separation chamber 11.

[0105] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0106] The separation device used in the following examples and comparative examples is as follows Figures 1 to 3 As shown, including:

[0107] The separation cylinder 10 is rotatably arranged, and the separation cylinder 10 has a separation chamber 11;

[0108] The feeding structure 20 is disposed at the first end of the separation cylinder 10 and communicated with the separation chamber 11;

[0109] The discharge structure 30 is disposed at the second end of the separation cylinder 10 and communicated with the separation chamber 11;

[0110] A heating part is arranged on the outer surface of the split cylinder to heat the material to be separated in the separation chamber 11;

[0111] The first material lifting structure 40 is connected to the inner surface of the separation cylinder 10 and is arranged corresponding to the heating part;

[0112] The separation chamber 11 includes a first chamber 111, a second chamber 112 and a third chamber 113 which are sequentially arranged in the direction from the feeding structure 20 to the discharging structure 30. The separation device also includes a first screen plate 51, a second screen plate 52, a crushing structure 60 and a second material lifting structure 70. The first screen plate 51 is located between the first chamber 111 and the second chamber 112, the second screen plate 52 is located between the second chamber 112 and the third chamber 113, the first material lifting structure 40 is located in the first chamber 111, the crushing structure 60 is movably arranged in the second chamber 112, and the second material lifting structure 70 is located in the third chamber 113.

[0113] In the direction from the first end to the second end of the separation cylinder 10, the first chamber 111, the second chamber 112, and the third chamber 113 are connected in sequence; the second material lifting structure 70 can separate the crushed positive electrode material and the aluminum foil; the second material lifting structure 70 includes a plurality of material lifting blocks arranged in an array on the inner surface of the separation cylinder, and the plurality of material lifting blocks are arranged in the form of multiple rows and columns;

[0114] The ratio between the length of the first chamber 111 and the length of the separation chamber 11 is equal to 50%;

[0115] The first material lifting structure 40 includes a plurality of material lifting rings 41 spaced apart in the axial direction of the separation cylinder 10, and each material lifting ring 41 includes a plurality of second material lifting blocks 411 spaced apart in the circumferential direction of the separation cylinder 10; the distance between two adjacent material lifting rings 41 is 10 cm; the distance between two adjacent second material lifting blocks 411 is 20 cm;

[0116] The first chamber 111 is a heating section, the first material lifting structure 40 is located in the first chamber 111, the heating part is located on the outer surface of the part of the separation cylinder 10 corresponding to the first chamber 111, the second chamber 112 is a rolling section, the crushing structure 60 is a hollow stainless steel cylinder, the diameter of the crushing structure 60 is 35 cm, the weight of the crushing structure 60 is 100 kg, when the separation cylinder 10 rotates, the crushing structure 60 moves in the second chamber 112, so that the crushing structure 60 will roll the pre-treated positive electrode sheet, and the positive electrode material will be crushed under the rolling of the crushing structure 60, while the size of the aluminum foil remains basically unchanged, which is conducive to the separation of the positive electrode material and the aluminum foil;

[0117] The separation cylinder 10 extends in the transverse direction, the first end of the separation cylinder 10 is higher than the second end of the separation cylinder 10, and the angle between the axis of the separation cylinder 10 and the horizontal plane is 1 degree;

[0118] The discharge structure 30 includes a discharge barrel, which is nested with the separation barrel 10 and located outside the separation barrel 10. The second end of the separation barrel 10 has a sieve hole section. The discharge barrel includes a first barrel section and a second barrel section. The first barrel section is sleeved on the outer periphery of the sieve hole section, and the second barrel section is arranged at an end of the first barrel section away from the first end of the separation barrel 10. The first barrel section is provided with a first discharge port 31 for discharging positive electrode materials, and the second barrel section is provided with a second discharge port 32 for discharging aluminum foil.

[0119] The separation device also includes an air inlet structure and an air outlet structure. The air inlet structure is arranged at the first end of the separation cylinder 10 and introduces protective gas into the separation chamber 11. The air outlet structure is arranged at the second end of the separation cylinder 10 and is used to discharge the gas in the separation chamber 11. The above-mentioned protective gas is nitrogen.

[0120] Example 1

[0121] An embodiment of the method for regenerating and recycling the positive electrode material of waste lithium iron phosphate batteries of the present invention comprises the following steps:

[0122] S1, dismantle the waste lithium iron phosphate battery to obtain the positive electrode sheet;

[0123] S2, cutting the positive electrode sheet into square sheets with a side length of 10 cm, washing the sheet for 10 min under ultrasonic conditions with a power of 80 W using ethanol as a detergent, and then drying the sheet at 80° C. for 2 h to obtain a pretreated positive electrode sheet;

[0124] S3, nitrogen is introduced into the separation device, and then the pretreated positive electrode sheet is transported from the feeding structure to the separation chamber 11, and the pretreated positive electrode sheet is heated in the first chamber 111 of the separation chamber 11, the heating temperature is 400° C., and the heating time is 1 hour to obtain a first mixed material;

[0125] S4, in the second chamber 112 of the separation chamber 11, the first mixed material is subjected to roller pressing to obtain a second mixed material;

[0126] S5, the second mixed material is subjected to a material lifting process in the third chamber 113 of the separation chamber 11, and is sieved with a 3 cm sieve to obtain a positive electrode material and an aluminum foil;

[0127] S6, mixing the positive electrode material with glucose accounting for 10% by mass of the positive electrode material to obtain a third mixed material;

[0128] S7, the third mixed material is crushed by a high-speed crusher for 30 seconds, and the crushed material is passed through a 50-mesh sieve to obtain a fourth mixed material;

[0129] S8, performing an element test on the fourth mixed material, and mixing it with at least one of an iron source, a phosphorus source, and a lithium source according to the element test result, so that the molar ratio of the iron element, the phosphorus element, and the lithium element is 1:1:1, to obtain a fifth mixed material;

[0130] S9, calcining the fifth mixed material at high temperature under a nitrogen atmosphere, the calcination temperature is 600°C, the calcination time is 1 hour, and then air flow crushing is performed to crush the material to a particle size of ≤3 μm, and then sieving is performed with an ultrasonic vibration screen with a mesh size of 200 meshes to obtain a lithium iron phosphate positive electrode repair material.

[0131] Example 2

[0132] An embodiment of the method for regenerating and recycling the positive electrode material of waste lithium iron phosphate batteries of the present invention comprises the following steps:

[0133] S1, dismantle the waste lithium iron phosphate battery to obtain the positive electrode sheet;

[0134] S2, cutting the positive electrode sheet into square sheets with a side length of 10 cm, washing the sheet with ultrapure water as a detergent under ultrasonic conditions with a power of 80 W for 5 min, and then drying the sheet at 80° C. for 2 h to obtain a pretreated positive electrode sheet;

[0135] S3, nitrogen is introduced into the separation device, and then the pretreated positive electrode sheet is transported from the feeding structure to the separation chamber 11, and the pretreated positive electrode sheet is heated in the first chamber 111 of the separation chamber 11, the heating temperature is 450° C., and the heating time is 1 hour to obtain a first mixed material;

[0136] S4, in the second chamber 112 of the separation chamber 11, the first mixed material is subjected to roller pressing to obtain a second mixed material;

[0137] S5, the second mixed material is subjected to a material lifting process in the third chamber 113 of the separation chamber 11, and is sieved with a 5 cm sieve to obtain a positive electrode material and an aluminum foil;

[0138] S6, mixing the positive electrode material with glucose accounting for 10% by mass of the positive electrode material to obtain a third mixed material;

[0139] S7, the third mixed material is crushed by a high-speed crusher for 30 seconds, and the crushed material is passed through a 50-mesh sieve to obtain a fourth mixed material;

[0140] S8, performing an element test on the fourth mixed material, and mixing it with at least one of an iron source, a phosphorus source, and a lithium source according to the element test result, so that the molar ratio of the iron element, the phosphorus element, and the lithium element is 1:1:1, to obtain a fifth mixed material;

[0141] S9, calcining the fifth mixed material at a high temperature under a nitrogen atmosphere, the calcination temperature is 650°C, the calcination time is 1 hour, and then air flow crushing is performed to crush the particle size to ≤5μm, and then sieving is performed with an ultrasonic vibration screen with a mesh size of 300 meshes to obtain a lithium iron phosphate positive electrode repair material.

[0142] Example 3

[0143] An embodiment of the method for regenerating and recycling positive electrode materials of waste lithium iron phosphate batteries of the present invention, the regeneration and recycling method described in this embodiment is different from that of Example 2 only in that the molar ratio of iron element, phosphorus element and lithium element in S8 is 1:1:1.05.

[0144] Example 4

[0145] An embodiment of the method for regenerating and recycling positive electrode materials of waste lithium iron phosphate batteries of the present invention, the regeneration and recycling method described in this embodiment is different from that of embodiment 2 only in that ultrasound is not used during washing in S2.

[0146] Comparative Example 1

[0147] A method for regenerating and recycling positive electrode materials of waste lithium iron phosphate batteries, which differs from Example 2 only in that step S7 is omitted.

[0148] Comparative Example 2

[0149] A method for regenerating and recycling positive electrode materials of waste lithium iron phosphate batteries, which differs from Example 2 only in that the order of S7 to S8 is different. After obtaining the third mixed material in S6, an element test is performed on it in S7, and according to the element test results, it is mixed with at least one of an iron source, a phosphorus source, and a lithium source to satisfy the molar ratio of the iron element, the phosphorus element, and the lithium element of 1:1:1 to obtain a fourth mixed material; in S8, the fourth mixed material is crushed by a high-speed crusher, and after crushing for 30 seconds, the material is sieved through a 50-mesh sieve to obtain a fifth mixed material.

[0150] Performance Testing

[0151] 1) The aluminum content in the lithium iron phosphate positive electrode repair material is detected by ICP.

[0152] 2) Electrochemical performance: Lithium iron phosphate positive electrode repair material, acetylene black, and PVDF were mixed evenly in a mass ratio of 8:1:1 as the positive electrode material and assembled into button cells for electrochemical performance testing. The charge and discharge voltage range was 2.5-4.2V, the ambient temperature was 25°C, and the charge and discharge current density was 0.1C.

[0153] Table 1 shows the performance test results.

[0154] Table 1

[0155]

[0156] As can be seen from Table 1, the lithium iron phosphate positive electrode repair material prepared by the method for regenerating and recycling waste lithium iron phosphate battery positive electrode materials of the present invention has a low aluminum content, and has a high specific capacity and coulomb efficiency. Its first cycle discharge specific capacity can reach 160mAh / g, and its first coulomb efficiency can reach more than 98%, and it has good electrochemical performance. Although the lithium iron phosphate positive electrode repair material in Comparative Examples 1 to 2 has a low aluminum content, its electrochemical performance is poor, and its application range is not as good as that of the embodiment.

[0157] Figure 4 This is a test diagram of the electrochemical performance of the lithium iron phosphate positive electrode repair material in Example 1. It can be seen from the figure that the battery made with the lithium iron phosphate positive electrode repair material has a high first coulombic efficiency, close to 100%, and its charge and discharge specific capacity is also high, with good electrochemical performance.

[0158] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0159] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for regenerating and recycling the positive electrode material of waste lithium iron phosphate batteries, characterized in that: The steps include: S1, dismantle the waste lithium iron phosphate battery to obtain the positive electrode sheet; S2, pre-treating the positive electrode sheet to obtain a pre-treated positive electrode sheet; S3, performing a first heat treatment on the pretreated positive electrode sheet to obtain a first mixed material; S4, rolling the first mixed material to obtain a second mixed material; S5, screening the second mixed material to obtain aluminum foil and positive electrode material; S6, mixing the positive electrode material with an additive to obtain a third mixed material; S7, performing a second crushing on the third mixed material to obtain a fourth mixed material; S8, adding at least one of a lithium source, an iron source, and a phosphorus source or not adding the lithium source according to the molar ratio of the phosphorus element, the iron element, and the lithium element in the fourth mixed material to obtain a fifth mixed material; controlling the molar ratio of the phosphorus element, the iron element, and the lithium element in the fifth mixed material to be 1:1:(1-1.2); S9, performing a second heat treatment on the fifth mixed material to obtain a lithium iron phosphate positive electrode repair material.

2. The method for regenerating and recovering the positive electrode material of waste lithium iron phosphate batteries according to claim 1, characterized in that: The temperature of the first heat treatment is 350-600°C, and the time of the first heat treatment is 0.5-2h; The temperature of the second heat treatment is 600-800°C, and the time of the second heat treatment is 0.5-4h; The first heat treatment and the second heat treatment are performed under an inert atmosphere; The auxiliary agent includes a reducing agent.

3. The method for regenerating and recycling the positive electrode material of waste lithium iron phosphate batteries according to claim 1, characterized in that: In S2, The size of the pre-treated positive electrode sheet is 2 to 15 cm; and / or, The pretreatment method includes first crushing or cutting, washing, and drying; The drying temperature is 50-120° C.; the washing liquid used for washing is at least one of water, ethanol, methanol and acetone; and / or ultrasonic washing is adopted, the power of the ultrasonic washing is 50-300W, and the time of the ultrasonic washing is 5-20 minutes.

4. The method for regenerating and recovering the positive electrode material of waste lithium iron phosphate batteries according to any one of claims 1 to 3, characterized in that: In S5, the aperture of the sieve used for the screening is smaller than the size of the pre-treated positive electrode sheet.

5. The method for regenerating and recovering the positive electrode material of waste lithium iron phosphate batteries according to any one of claims 1 to 3, characterized in that: The reducing agent is at least one of glucose, starch, carbon black, citric acid, oxalic acid, and ascorbic acid; and / or the mass ratio of the positive electrode material to the auxiliary agent is 1:(0.05-0.5).

6. The method for regenerating and recovering the positive electrode material of waste lithium iron phosphate batteries according to claim 5, characterized in that: In S7, the second crushing is performed by a high-speed crusher, the second crushing time is 30 to 120 seconds, and the particle size of the fourth mixed material is ≤20 mesh.

7. The method for regenerating and recovering the positive electrode material of waste lithium iron phosphate batteries according to claim 5, characterized in that: In S9, after the second heat treatment is completed, the material is crushed and sieved to obtain the lithium iron phosphate positive electrode repair material.

8. The method for regenerating and recovering the positive electrode material of waste lithium iron phosphate batteries according to any one of claims 1 to 3, characterized in that: The S3, S4 and S5 are performed in a separation device; the separation device comprises: A separation cylinder (10) is rotatably arranged, wherein the separation cylinder (10) has a separation chamber (11); A material feeding structure (20) is arranged at the first end of the separation cylinder (10) and is in communication with the separation chamber (11); A discharge structure (30) is arranged at the second end of the separation cylinder (10) and is in communication with the separation chamber (11); A heating part, arranged on the outer surface of the split cylinder, for heating the material to be separated in the separation chamber (11); A first material lifting structure (40) is connected to the inner surface of the separation cylinder (10) and is arranged corresponding to the heating part; In S3, the pretreated positive electrode sheet enters the separation cylinder (10) from the feed structure (20), and undergoes a first heat treatment in the separation chamber (11) to obtain the first mixed material; In S4, the first mixed material is roller-pressed in the separation chamber (11) to obtain the second mixed material; In S5, the second mixed material is screened in the separation chamber (11) to obtain the aluminum foil and the positive electrode material.

9. The method for regenerating and recovering the positive electrode material of waste lithium iron phosphate batteries according to claim 8, characterized in that: The separation chamber (11) comprises a first chamber (111) and a second chamber (112) which are sequentially arranged in the direction from the feeding structure (20) to the discharging structure (30); the separation device further comprises a first screen plate (51) and a crushing structure (60); the first screen plate (51) is located between the first chamber (111) and the second chamber (112); the first lifting structure (40) is located in the first chamber (111); and the crushing structure (60) is movably arranged in the second chamber (112).

10. The method for regenerating and recycling the positive electrode material of waste lithium iron phosphate batteries according to claim 9, characterized in that: The separation chamber (11) further comprises a third chamber (113), wherein the third chamber (113) is located at one end of the second chamber (112) away from the first chamber (111), and the separation device further comprises a second sieve plate (52) arranged between the second chamber (112) and the third chamber (113) and a second material lifting structure (70) arranged in the third chamber (113).

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