A method for repairing and regenerating lithium iron phosphate

Abstract

The present application discloses a method for repairing and regenerating lithium iron phosphate, belonging to the technical field of lithium-ion batteries. The method for repairing and regenerating lithium iron phosphate in the present application includes first crushing, soaking, screening, ball milling, and separating lithium iron phosphate waste electrode sheets to obtain lithium iron phosphate waste electrode powder, then roasting the lithium iron phosphate waste electrode powder in a carbon dioxide atmosphere at 750-900 °C. After the obtained roasting product is stirred evenly with water, carbon dioxide is introduced, and the resulting mixture is spray granulated to obtain a lithium iron phosphate precursor; finally, the obtained lithium iron phosphate precursor is calcined to obtain regenerated lithium iron phosphate. The method for repairing and regenerating lithium iron phosphate in the present application does not require additional carbon source, phosphorus source, and lithium source. The carbon content in the prepared regenerated lithium iron phosphate is less than 0.15%, the Al content is less than 0.015%, and the charge-discharge capacity is high.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium-ion batteries, and specifically relates to a method for repairing and regenerating lithium iron phosphate. Background Art

[0002] With global energy shortages and environmental damage becoming increasingly severe, reducing resource consumption and protecting the environment are becoming a widely recognized trend. Lithium-ion batteries, due to their high energy density, high voltage, excellent cycle performance, low self-discharge, and environmental friendliness, are widely used in electric vehicles and various electronic devices, providing humanity with a solution to the energy shortage dilemma. Lithium iron phosphate batteries, due to their low cost, safety, excellent thermal stability, and high cycle performance, hold a significant market share among lithium batteries. Lithium iron phosphate batteries have a service life of 5-7 years, and a large number of them have already been retired, with this number expected to increase in the future. Therefore, research on the recycling of spent LiFePO4 batteries is extremely urgent.

[0003] LiFePO4 cathode materials account for approximately 40% of battery costs, making their high-value recycling highly economical. To date, the primary methods for recycling and disposing of spent LiFePO4 cathode materials have been repair, regeneration, and hydrometallurgy. The existing high-temperature sintering and separation of cathode sheets using oxygen or air results in high levels of impurities such as Al and F in the separated lithium iron phosphate waste powder, along with a large amount of residual metal. The sintering process for the LiFePO4 precursor requires the addition of lithium, iron, and phosphorus sources. Furthermore, the pyrolysis of the binder produces fluoride, which reacts with aluminum or lithium iron phosphate, producing lithium fluoride and aluminum fluoride that enter the cathode material. These difficulties hinder the stability of the repaired and regenerated products. Summary of the Invention

[0004] The purpose of this application is to overcome the deficiencies of the prior art and provide a method for repairing and regenerating lithium iron phosphate, which produces regenerated lithium iron phosphate with low carbon content and metal element residue, thereby improving the stability of the regenerated lithium iron phosphate.

[0005] To achieve the above objectives, the technical solution adopted in this application is to provide a method for repairing and regenerating lithium iron phosphate, comprising the following steps:

[0006] S1: ball milling and sorting the waste lithium iron phosphate electrodes to obtain waste lithium iron phosphate electrode powder;

[0007] S2: calcining the lithium iron phosphate waste powder obtained in step S1 at 750-900°C under a carbon dioxide atmosphere, stirring the calcined product with water, introducing carbon dioxide, and spray granulating the reaction mixture to obtain a lithium iron phosphate precursor;

[0008] S3: Add the lithium iron phosphate precursor obtained in step S2 into an atmosphere furnace, and calcine it at 550 - 750 °C under the protection of an inert gas to obtain regenerated lithium iron phosphate.

[0009] In the repair and regeneration method of this application, CO2 is used as the reaction atmosphere. At high temperature, PVDF is cracked into carbon, and conductive carbon black becomes CO, achieving the purpose of removing F and carbon. After the lithium iron phosphate waste electrode sheets are crushed, they are soaked in hot water. Soaking can separate the aluminum slag and battery black powder in the waste electrode sheets. After passing through a water sieve, the material on the sieve is aluminum slag, and the material under the sieve is a mixture of battery black powder and aluminum slag; after the obtained material under the sieve is ball-milled and sorted, part of the Al in the lithium iron phosphate waste electrode powder can be separated; roasting can convert the Al in the lithium iron phosphate waste electrode powder into aluminum oxide; after the roasted product and water are stirred evenly, the carbonic acid generated by introducing carbon dioxide can further remove the Al in the roasted product. The specific reaction chemical formula is H2O + CO2 → H2CO3, 3H2CO3 + 2Al → Al2(CO3)3 + 3H2; the combined action of the above several steps can reduce the Al impurities in the regenerated lithium iron phosphate to the greatest extent, and at the same time, no metal impurities brought by other aluminum removal methods using alkaline solutions are introduced, ensuring the safety of the battery. In addition, after the roasted product and water are mixed evenly, carbon dioxide is introduced for reaction, which can make the roasted product slightly soluble, filter out aluminum, and combined with the spray drying method, the consumption of residual carbon, the in-situ coating of Al, and the spheroidization regeneration of lithium iron phosphate can be realized; there is no need to supplement lithium source, iron source, and phosphorus source, and regenerated lithium iron phosphate can be directly obtained through calcination.

[0010] Among them, the roasting temperature is one of the key factors affecting the removal effect of impurities such as Al, carbon, and F in the lithium iron phosphate waste electrode powder. If the roasting temperature is too low, impurities such as Al, carbon, and F in the lithium iron phosphate waste electrode powder cannot be completely converted into other substances that can be removed, such as Al cannot be completely converted into aluminum oxide, and carbon cannot be completely converted into CO; if the roasting temperature is too high, it will cause the decomposition of lithium iron phosphate.

[0011] The lithium iron phosphate waste electrode sheets in this application include the positive electrode sheets scrapped during the production process of lithium iron phosphate positive electrode sheets, the positive electrode sheets decomposed from the batteries that have not been filled with electrolyte and scrapped during the battery production process, and the lithium iron phosphate positive electrode sheets disassembled from various scrapped batteries.

[0012] As a further improvement of this application, in step S2, the heating rate of the roasting temperature is 2 - 5 °C / min.

[0013] If the heating rate of the roasting temperature is too fast, it is easy to damage the service life of the atmosphere furnace, while if the heating rate of the roasting temperature is too slow, it will affect the experimental efficiency. After optimization, the heating rate within the above range can effectively improve the removal effect of impurities such as Al, carbon, and F in the lithium iron phosphate waste electrode powder.

[0014] As a further improvement of the present application, in step S2, the roasting time is 2 - 4 h. Within the above roasting time range, the decomposition effect of the lithium iron phosphate waste electrode powder is better.

[0015] As a further improvement of the present application, in step S2, the method for preparing the mixture is as follows: uniformly stir the roasted product and water, heat to 40 - 80 °C, then introduce carbon dioxide, and stir at a rotation speed of 200 - 300 rpm for 30 - 60 min to obtain the mixture.

[0016] As a further improvement of the present application, in step S2, the flow rate of carbon dioxide is 1 - 100 L / min.

[0017] When the flow rate of carbon dioxide is 1 - 100 L / min, it can better react with Al in the roasted product to remove Al in the roasted product.

[0018] As a further improvement of the present application, in step S2, the conditions for spray granulation include: performing under an inert protective gas, the spray temperature is 170 - 190 °C, the feeding speed is 300 - 650 mL / h, the inlet gas pressure is 0.1 - 0.5 MPa, the outlet temperature is 120 - 150 °C, and the inert protective gas is one of nitrogen, argon, and helium.

[0019] By controlling parameters such as the spray temperature, feeding speed, and inlet gas pressure in spray granulation within the above preferred ranges in the present application, the prepared lithium iron phosphate precursor has a better spherical structure, and can in - situ wrap the Al remaining in the roasted lithium iron phosphate product, avoiding the influence of Al impurities on the stability and electrical properties of the product, reducing the Al content in the recycled lithium iron phosphate, and further improving the electrical properties and stability of the battery.

[0020] As a further improvement of the present application, in step S2, the tail gas generated from the reaction is absorbed by a saturated HCl - CuCl2 solution.

[0021] As a further improvement of the present application, before step S1, the following steps are further included: crushing, soaking, and screening the lithium iron phosphate waste electrode sheets;

[0022] As a further improvement of the present application, the specific steps for crushing, soaking, and screening the lithium iron phosphate waste electrode sheets are as follows: cut the lithium iron phosphate waste electrode sheets into pieces of (1 - 2 cm x 1 - 2 cm) size with scissors; soak the obtained pieces in hot water, the soaking temperature is 50 - 80 °C, the soaking time is 5 - 60 min, and after soaking, pass through a 2 - 15 - mesh water sieve.

[0023] As a further improvement of the present application, in the step S1, the parameters of ball milling are as follows: the ball-to-material ratio is 5-20:1, the ball milling speed is 100-400 rpm, and the ball milling time is 5-60 min.

[0024] As a further improvement of the present application, in the step S1, the classification is air classification, and the parameters of the air classification are as follows: the feeding speed is 3-5 kg / min, the pulsation frequency is 30-50 Hz, and the air flow speed is 10-12 cm / s.

[0025] The present application uses ball milling to further grind and crush the lithium iron phosphate waste electrode sheets. By optimizing and controlling the parameters of ball milling, the battery black powder and aluminum slag can be effectively separated, and through the parameters of air classification, the impurity Al content in the lithium iron phosphate waste powder can be further reduced.

[0026] As a further improvement of the present application, in the step S3, the calcination time is 2-8 h.

[0027] As a further improvement of the present application, in the step S3, the lithium iron phosphate precursor also needs to be pre-sintered. The pre-sintering temperature is 400-500 °C, and the pre-sintering time is 1-4 h.

[0028] By using the method combining pre-sintering and calcination, the bonding, densification, organizational structure change and rearrangement of the lithium iron phosphate precursors can be realized in different temperature ranges, but there is no dissolution between tissues, nor new compositions or new phases appear, and the regenerated lithium iron phosphate can be used as the positive electrode material of a new lithium iron phosphate battery.

[0029] As a further improvement of the present application, in the step S4, both the pre-sintering and the calcination are carried out under the protection of an inert gas, and the inert gas is one of nitrogen, argon and helium.

[0030] In a second aspect, the present application provides a lithium iron phosphate prepared by the above-mentioned repair and regeneration method of lithium iron phosphate.

[0031] In a third aspect, the present application also provides the application of the lithium iron phosphate prepared by the above-mentioned repair and regeneration method of lithium iron phosphate in the preparation of batteries.

[0032] Compared with the prior art, the beneficial effects of the present application are as follows:

[0033] (1) In the repair and regeneration method of the present application, using CO2 as the reaction atmosphere, PVDF is cracked into carbon at high temperature, and conductive carbon black becomes CO, so as to achieve the purpose of removing F and carbon; the carbon content in the regenerated lithium iron phosphate of the present application is less than 0.15%.

[0034] (2) By combining methods such as crushing, soaking, screening, ball milling, sorting, high-temperature CO2 roasting, and removing Al with carbonic acid, the present application can effectively reduce the impurity Al content in the recycled lithium iron phosphate. The Al content in the recycled lithium iron phosphate of the present application is less than 0.015%.

[0035] (3) After weakly dissolving the calcined product, spray drying and granulation are carried out, which can realize the consumption of residual carbon, the in-situ encapsulation of Al, and the spherical regeneration of lithium iron phosphate; without adding lithium source, iron source, and phosphorus source, the recycled lithium iron phosphate can be directly obtained through calcination, and the obtained recycled lithium iron phosphate can be used as the cathode material of a new lithium iron phosphate battery. Description of the Drawings

[0036] Figure 1 It is the process flow chart of the method for repairing and recycling lithium iron phosphate of the present application. Detailed Embodiments

[0037] In order to better illustrate the purpose, technical solution, and advantages of the present application, the present application will be further described below in conjunction with specific examples and comparative examples. The purpose is to understand the content of the present application in detail, rather than a limitation of the present application. All other examples obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present application. The experimental reagents and instruments involved in the implementation of the present application are all common ordinary reagents and instruments unless otherwise specified.

[0038] Example 1

[0039] This example provides a method for repairing and recycling lithium iron phosphate, including the following steps:

[0040] (1) Cut the waste lithium iron phosphate electrode sheet into fragments of 2 cm x 2 cm with scissors; soak the obtained fragments in hot water at a soaking temperature of 50 °C and a soaking time of 5 min. After soaking, pass through a 2-mesh water sieve. The material on the sieve is aluminum slag, and the material under the sieve is a mixture of battery black powder and aluminum slag;

[0041] (2) After drying the material under the sieve obtained in step (1), put it into a ball milling tank, add zirconium balls to the ball milling tank with a ball-to-material ratio of 5:1, and then place it on a planetary ball mill and ball mill at a speed of 400 rpm for 60 min; put the obtained ball milling product into a pulsating air current separator, set the feeding speed of the air current separator to 3 kg / min, the pulsating frequency to 30 Hz, and the air current speed to 10 cm / s to separate part of the Al in the ball milling product to obtain the waste lithium iron phosphate electrode powder;

[0042] (3) Load the lithium iron phosphate waste electrode powder obtained in step (2) into a crucible, then place it in a tube furnace and introduce CO2. After 60 minutes, heat it to 750 °C at a heating rate of 5 °C / min and calcine for 240 minutes to remove the impurity carbon in the electrode powder. At the same time, further convert Al into Al2O3 and remove it. The tail gas is absorbed by a saturated HCl-CuCl2 solution to obtain a calcined product;

[0043] (4) Load the calcined product obtained in step (3) and water into a beaker, heat it to 50 °C, then introduce carbon dioxide with a flow rate of 100 L / min, and react for 60 minutes at a stirring speed of 200 r / min. Filter to remove Al to obtain a mixture;

[0044] (5) Spray granulate the mixture obtained in step (4) to obtain a lithium iron phosphate precursor. The parameters of spray granulation are as follows: the spray temperature is 170 °C, the feeding speed is 400 mL / h, the inlet air pressure is 0.2 MPa, the outlet temperature is 130 °C, and the gas is nitrogen;

[0045] (6) Load the lithium iron phosphate precursor obtained in step (5) into a crucible, place it in a tube furnace and pass helium. After 60 minutes, heat it to 400 °C at a heating rate of 5 °C / min and pre-sinter for 180 minutes, then heat it to 550 °C at a heating rate of 5 °C / min and calcine for 300 minutes to obtain regenerated lithium iron phosphate.

[0046] Example 2

[0047] This example provides a method for repairing and regenerating lithium iron phosphate, including the following steps:

[0048] (1) Cut the lithium iron phosphate waste electrode into fragments of 2 cm x 2 cm with scissors; soak the obtained fragments in hot water at a soaking temperature of 65 °C and a soaking time of 30 minutes. After soaking, pass through a 10-mesh water sieve. The material on the sieve is aluminum slag, and the material under the sieve is a mixture of battery black powder and aluminum slag;

[0049] (2) After drying the material under the sieve obtained in step (1), load it into a ball mill tank, add zirconium balls to the ball mill tank, with a ball-to-material ratio of 10:1, and then place it on a planetary ball mill and ball mill at a speed of 400 rpm for 180 minutes; place the obtained ball-milled product in a pulsating air separator, set the feeding speed of the air separator to 4 kg / min, the pulsating frequency to 40 Hz, and the air flow speed to 11 cm / s to separate part of the Al in the ball-milled product to obtain lithium iron phosphate waste electrode powder;

[0050] (3) Load the lithium iron phosphate waste electrode powder obtained in step (2) into a crucible, then place it in a tube furnace and introduce CO2. After 30 minutes, heat it to 800 °C at a heating rate of 5 °C / min and calcine for 180 minutes to remove the impurity carbon in the electrode powder. At the same time, further convert Al into Al2O3 and remove it. The tail gas is absorbed by a saturated HCl-CuCl2 solution to obtain a calcined product;

[0051] (4) Load the calcined product obtained in step (3) and water into a beaker, heat it to 60 °C, then introduce carbon dioxide with a flow rate of 50 L / min, and react for 50 minutes at a stirring speed of 200 r / min to remove Al to obtain a mixture;

[0052] (5) Spray granulate the mixture obtained in step (4) to obtain a lithium iron phosphate precursor. The parameters of spray granulation are as follows: the spray temperature is 180 °C, the feeding speed is 500 mL / h, the inlet gas pressure is 0.3 MPa, the outlet temperature is 140 °C, and the gas is nitrogen;

[0053] (6) Load the lithium iron phosphate precursor obtained in step (5) into a crucible, place it in a tube furnace and pass helium. After 90 minutes, heat it to 450 °C at a heating rate of 5 °C / min and pre-sinter for 120 minutes, and then heat it to 600 °C at a heating rate of 5 °C / min and calcine for 240 minutes to obtain regenerated lithium iron phosphate.

[0054] Example 3

[0055] This example provides a method for repairing and regenerating lithium iron phosphate, including the following steps:

[0056] (1) Cut the lithium iron phosphate waste electrode into fragments of 2 cm x 2 cm with scissors; soak the obtained fragments in hot water at a soaking temperature of 80 °C and a soaking time of 60 minutes. After soaking, pass through a 15-mesh water sieve. The material on the sieve is aluminum slag, and the material under the sieve is a mixture of battery black powder and aluminum slag;

[0057] (2) After drying the material under the sieve obtained in step (1), load it into a ball mill jar, add zirconium balls to the ball mill jar with a ball-to-material ratio of 15:1, and then place it on a planetary ball mill and ball mill at a speed of 400 rpm for 240 minutes; place the obtained ball-milled product in a pulsating air separator, set the feeding speed of the air separator to 5 kg / min, the pulsating frequency to 50 Hz, and the air flow speed to 12 cm / s to separate part of the Al in the ball-milled product to obtain lithium iron phosphate waste electrode powder;

[0058] (3) Load the lithium iron phosphate waste electrode powder obtained in step (2) into a crucible, then place it in a tube furnace and introduce CO2. After 90 min, heat it to 900 °C at a heating rate of 5 °C / min and calcine for 120 min to remove the impurity carbon in the electrode powder. At the same time, further convert Al into Al2O3 and remove it. Absorb the tail gas with a saturated HCl-CuCl2 solution to obtain a calcined product;

[0059] (4) Load the calcined product obtained in step (3) and water into a beaker, heat it to 70 °C, then introduce carbon dioxide with a flow rate of 1 L / min, and react for 30 min at a stirring speed of 200 r / min to remove Al to obtain a mixture;

[0060] (5) Spray granulate the mixture obtained in step (4) to obtain a lithium iron phosphate precursor. The parameters of spray granulation are as follows: the spray temperature is 190 °C, the feeding speed is 600 mL / h, the inlet gas pressure is 0.4 MPa, the outlet temperature is 150 °C, and the gas is nitrogen;

[0061] (6) Load the lithium iron phosphate precursor obtained in step (5) into a crucible, place it in a tube furnace and pass helium gas. After 120 min, heat it to 500 °C at a heating rate of 5 °C / min and pre-sinter for 90 min, then heat it to 650 °C at a heating rate of 5 °C / min and calcine for 180 min to obtain regenerated lithium iron phosphate.

[0062] Comparative Example 1

[0063] This comparative example provides a method for repairing and regenerating lithium iron phosphate, including the following steps:

[0064] (1) Cut the lithium iron phosphate waste electrode into fragments of 2 cm x 2 cm size with scissors; soak the obtained fragments in hot water at a soaking temperature of 80 °C and a soaking time of 60 min. After soaking, pass through a 15-mesh water sieve. The material on the sieve is aluminum slag, and the material under the sieve is a mixture of battery black powder and aluminum slag;

[0065] (2) After drying the material under the sieve obtained in step (1), load it into a ball mill tank, add zirconium balls to the ball mill tank, with a ball-to-material ratio of 15:1, and then place it on a planetary ball mill and ball mill at a speed of 400 rpm for 240 min; place the obtained ball-milled product in a pulsating air separator, set the feeding speed of the air separator to 5 kg / min, the pulsating frequency to 50 Hz, and the air flow speed to 12 cm / s, and separate part of the Al in the ball-milled product to obtain lithium iron phosphate waste electrode powder;

[0066] (3) Load the lithium iron phosphate waste electrode powder obtained in step (2) into a crucible, then place it in a tube furnace and introduce air. After 90 min, heat it to 600 °C at a heating rate of 5 °C / min and calcine for 120 min. After calcination, the structure of lithium iron phosphate is destroyed, ferrous iron is oxidized to ferric iron, and the lithium iron phosphate waste electrode powder changes from black to red. If carbon source, phosphorus source and lithium source are not replenished and directly calcined under inert gas protection, regenerated lithium iron phosphate cannot be obtained.

[0067] Comparative Example 2

[0068] This comparative example provides a method for repairing and regenerating lithium iron phosphate. The difference between the method for repairing and regenerating lithium iron phosphate in this comparative example and that in Example 1 is only that: the calcination temperature in step (3) is 700 °C. Due to the too low calcination temperature, carbon and Al in the lithium iron phosphate waste electrode powder cannot be completely removed, resulting in high carbon content and Al content in the regenerated lithium iron phosphate.

[0069] Comparative Example 3

[0070] This comparative example provides a method for repairing and regenerating lithium iron phosphate. The difference between the method for repairing and regenerating lithium iron phosphate in this comparative example and that in Example 1 is only that: the calcination temperature in step (3) is 950 °C.

[0071] Comparative Example 4

[0072] This comparative example provides a method for repairing and regenerating lithium iron phosphate. The difference between the method for repairing and regenerating lithium iron phosphate in this comparative example and that in Example 1 is only that: CO2 is not introduced in step (4).

[0073] Example 4

[0074] Test the contents of some elements of the regenerated lithium iron phosphate obtained in each example and comparative example. Among them, the contents of Li, Fe, and Al elements are tested according to the standard of YS / T 1028.5-2015 Chemical analysis method for lithium iron phosphate; the content of P element is tested according to the standard of YS / T 1028.3-2015 Chemical analysis method for lithium iron phosphate; the content of C element is obtained according to the test standard of YS / T 1028.4-2015 Chemical analysis method for lithium iron phosphate; the test results are shown in Table 1.

[0075] Table 1

[0076] Element content (%) Li P Fe Al C Example 1 4.44 19.83 35.84 0.01 1.50 Example 2 4.36 19.61 35.68 0.01 1.41 Example 3 4.52 20.01 36.23 0.01 1.20 Comparative Example 2 4.39 19.78 36.12 0.04 3.00 Comparative Example 3 4.48 19.89 36.10 <0.01 0.81 Comparative Example 4 4.47 19.90 35.94 0.04 2.94

[0077] It can be seen from Table 1 that the main elements, Al and C contents in the regenerated lithium iron phosphate prepared in the examples are all normal and meet the industrial production standards of lithium iron phosphate lithium batteries.

[0078] Example 5

[0079] The regenerated lithium iron phosphate obtained from each example and comparative example was made into a button cell for comparative study of electrochemical performance. The button cell was made by mixing the lithium iron phosphate active material, conductive carbon black, and PCDF in a mass ratio of 8:1:1 to form a slurry. The slurry was coated on aluminum foil, dried at 120 °C for 8 h, and then prepared into small round electrode sheets by rolling and cutting for the production of button cells. The button cells were assembled in a glove box with the conditions of water and oxygen content less than or equal to 0.01 ppm, and the electrolyte was 1.0 M LiPF6 in EC:DMC:DEC = 1:1:1 Vol%. The test conditions for battery performance: the charge-discharge voltage range was 2.5 - 4.2 V (relative to Li + / Li), the ambient temperature was 25 °C, and the charge-discharge was carried out at a current density of 0.1C (1C = 150 mA / g), and the battery performance was obtained, as shown in Table 2.

[0080] Table 2

[0081] Electrochemical performance Charge capacity (mAh / g) Discharge capacity (mAh / g) Initial charge-discharge efficiency (%) Example 1 158.6 149.9 94.5 Example 2 154.9 145.6 94.0 Example 3 156.7 147.5 94.1 Comparative Example 2 148.6 135.7 91.3 Comparative Example 3 89.6 68.4 76.3 Comparative Example 4 142.4 128.5 90.2

[0082] As can be seen from Table 2, the charging capacity of the lithium-ion battery prepared from the regenerated lithium iron phosphate obtained in the examples can reach 158.6 mAh / g, and the first charge-discharge efficiency can reach 94.5%.

[0083] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present application rather than to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for repairing and regenerating lithium iron phosphate, characterized in that, It includes the following steps: Ball-mill and sort the lithium iron phosphate waste electrode sheets to obtain lithium iron phosphate waste electrode powder; Under a carbon dioxide atmosphere, calcine the obtained lithium iron phosphate waste electrode powder at a temperature of 750 - 900 °C. After uniformly stirring the obtained calcined product and water, introduce carbon dioxide. Spray granulate the reacted mixture to obtain a lithium iron phosphate precursor; Add the obtained lithium iron phosphate precursor into an atmosphere furnace, and calcine it at a temperature of 550 - 750 °C under the protection of an inert gas to obtain regenerated lithium iron phosphate.

2. The method for repairing and regenerating lithium iron phosphate according to claim 1, wherein, The heating rate of the temperature during the calcination is 2 - 5 °C / min.

3. The method for repairing and regenerating lithium iron phosphate according to claim 1, characterized in that, The calcination time is 2 - 4 h.

4. The method for repairing and regenerating lithium iron phosphate as described in claim 1, wherein The preparation method of the mixture is as follows: uniformly stir the calcined product and water, heat it to 40 - 80 °C, then introduce carbon dioxide, and stir at a rotation speed of 200 - 300 rpm for 30 - 60 min to obtain it.

5. The method for repairing and regenerating lithium iron phosphate as described in claim 4, wherein The flow rate of the carbon dioxide is 1 - 100 L / min.

6. The method for repairing and regenerating lithium iron phosphate according to claim 1, wherein The conditions for the spray granulation include: carried out under an inert protective gas, the spray temperature is 170 - 190 °C, the feeding speed is 300 - 650 mL / h, the inlet gas pressure is 0.1 - 0.5 MPa, the outlet temperature is 120 - 150 °C, and the inert protective gas is one of nitrogen, argon, and helium.

7. The method for repairing and regenerating lithium iron phosphate according to claim 1, wherein The tail gas obtained from the reaction is absorbed by a saturated HCl - CuCl₂ solution.

8. The method for repairing and regenerating lithium iron phosphate according to claim 1, characterized in that, Before ball-milling the lithium iron phosphate waste electrode sheets, the following steps are also included: crushing, soaking, and screening the lithium iron phosphate waste electrode sheets.

9. The method for repairing and regenerating lithium iron phosphate according to claim 8, wherein, The specific steps for crushing, soaking, and screening the lithium iron phosphate waste electrode sheets are as follows: cut the lithium iron phosphate waste electrode sheets into pieces of (1 - 2) cm × (1 - 2) cm size with scissors; soak the obtained pieces in hot water, the soaking temperature is 50 - 80 °C, the soaking time is 5 - 60 min, and after soaking, screen them through a 2 - 15 mesh water sieve.

10. The method for repairing and regenerating lithium iron phosphate according to claim 1, characterized in that, The parameters of the ball-milling are as follows: the ball-to-material ratio is 5 - 20:1, the ball-milling rotation speed is 100 - 400 rpm, and the ball-milling time is 5 - 60 min.

11. The method for repairing and regenerating lithium iron phosphate according to claim 1, wherein The sorting is air classification, and the parameters of the air classification are as follows: the feeding speed is 3 - 5 kg / min, the pulsation frequency is 30 - 50 Hz, and the air flow speed is 10 - 12 cm / s.

12. The method for repairing and regenerating lithium iron phosphate according to claim 1, characterized in that, The calcination time is 2 - 8 h.

13. The method for repairing and regenerating lithium iron phosphate according to claim 1, characterized in that, Before calcining the lithium iron phosphate precursor, pre-sintering is also required. The pre-sintering temperature is 400 - 500 °C, and the pre-sintering time is 1 - 4 h.

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