Regenerated lithium iron phosphate and repairing method and application thereof

Abstract

The invention belongs to the technical field of lithium iron phosphate material recovery, and particularly relates to regenerated lithium iron phosphate and a repairing method and application thereof. The repair method of the regenerated lithium iron phosphate comprises the following steps: carrying out repair treatment on waste lithium iron phosphate by adopting supercritical low-viscosity fluid; the supercritical low-viscosity fluid contains a repairing lithium source and water. According to the repairing method of the regenerated lithium iron phosphate, the supercritical low-viscosity fluid is adopted to repair the waste lithium iron phosphate, Li < + > in the supercritical low-viscosity fluid permeates into the vacancy of a waste lithium iron phosphate crystal lattice to supplement lithium, and the obtained regenerated lithium iron phosphate meets the requirement.

Description

Technical Field

[0001] This invention belongs to the field of lithium iron phosphate material recycling technology, specifically relating to a regenerated lithium iron phosphate, its repair method, and its application. Background Technology

[0002] The current recycling of waste lithium iron phosphate is based on the recycling of the entire battery. The batteries are separated by mechanical means such as physical crushing, screening and magnetic separation. Then, the metals in the positive / negative electrode materials are dissolved by acid / alkali leaching. After the metal ions are separated and reduced or oxidized, the raw materials for lithium iron phosphate, such as iron source and lithium source, are obtained.

[0003] While these recycling methods are simple and convenient to operate, they have low recovery rates and long recovery periods. Furthermore, these methods require the input of various machines and chemicals, resulting in high recycling costs. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a regenerated lithium iron phosphate, its repair method, and its application, thereby resolving at least one of the aforementioned technical issues.

[0005] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for repairing regenerated lithium iron phosphate, comprising the following steps: Supercritical low-viscosity fluid was used to repair waste lithium iron phosphate. The supercritical low-viscosity fluid contains repaired lithium source and water.

[0006] In some possible implementations, the viscosity of the supercritical low-viscosity fluid is less than 0.1 mPa·s.

[0007] In some possible implementations, the viscosity of the supercritical low-viscosity fluid is 0.03 mPa·s to 0.07 mPa·s.

[0008] In some possible implementations, the repair lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium formate, lithium acetate, and lithium oxalate.

[0009] In some possible implementations, the repair process includes the following steps: Supercritical low-viscosity fluid was introduced into the mixture at 374℃~380℃ and 22.1MPa~25MPa for treatment. The mixture comprises a mixture of waste lithium iron phosphate and lithium iron phosphate raw materials.

[0010] In some possible implementations, the mass ratio of the waste lithium iron phosphate to the lithium iron phosphate raw material is 1:0.01~0.03.

[0011] In some possible implementations, the preparation of the mixture includes the following steps: Waste lithium iron phosphate and lithium iron phosphate raw materials are ball-milled and mixed.

[0012] In some possible implementations, the lithium iron phosphate feedstock includes the addition of a lithium source, an iron source, and a phosphorus source.

[0013] In some possible implementations, the mixture may also include a doped metal salt.

[0014] In some possible implementations, the repair method further includes the following step: pressure relief.

[0015] In some possible implementations, the repair method further includes the following step: sintering.

[0016] In some possible implementations, the added lithium source includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium carbonate, lithium hydroxide, lithium formate, lithium acetate, and lithium oxalate.

[0017] In some possible implementations, the added iron source includes at least one of ferrous phosphate, ferrous nitrate, ferrous oxalate, and ferrous acetate.

[0018] In some possible implementations, the added phosphorus source includes at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

[0019] In some possible implementations, the atomic ratio of Fe, P and Li in the added lithium source, the added iron source and the added phosphorus source is 1:1:(0.95~1).

[0020] In some possible implementations, the content of the doped metal salt is 1 ppm to 3 ppm of waste lithium iron phosphate.

[0021] In some possible implementations, the time for introducing the supercritical low-viscosity fluid is 20 min to 60 min.

[0022] In some possible implementations, the doped metal salt includes at least one of vanadium trioxide, titanium dioxide, magnesium oxide, zirconium dioxide, and manganese oxide.

[0023] In some possible implementations, the pressure relief process includes the following steps: After the waste lithium iron phosphate is repaired, a multi-stage voltage reduction process is performed. The multi-stage voltage reduction process includes a first stage voltage reduction and a second stage voltage reduction.

[0024] In some possible implementations, the first step-down process includes the following steps: The pressure was reduced from 22.1 MPa to 25 MPa to 14 MPa to 16 MPa.

[0025] In some possible implementations, the second stage of voltage reduction processing includes the following steps: The pressure after the first stage of depressurization is reduced to 0.1MPa~0.15MPa.

[0026] In some possible implementations, the sintering temperature is 600°C to 800°C.

[0027] In some possible implementations, the sintering process takes 10 to 15 hours.

[0028] In some possible implementations, the voltage reduction rate in the first stage of voltage reduction is 3 MPa / min to 5 MPa / min.

[0029] In some possible implementations, the voltage reduction rate in the second stage of voltage reduction is 0.1 MPa / min to 0.5 MPa / min.

[0030] Secondly, the present invention provides a regenerated lithium iron phosphate, which is prepared by the above-mentioned regenerated lithium iron phosphate repair method.

[0031] Thirdly, the present invention provides an application of lithium iron phosphate, namely, the application of the above-mentioned recycled lithium iron phosphate in the field of battery materials.

[0032] The remediation method for regenerated lithium iron phosphate provided by this invention has at least the following beneficial technical effects compared with the prior art: (1) The method for repairing regenerated lithium iron phosphate provided by the present invention uses a supercritical low-viscosity fluid to repair waste lithium iron phosphate, wherein the Li in the supercritical low-viscosity fluid is... + Lithium is replenished by infiltrating lattice vacancies in waste lithium iron phosphate, resulting in recycled lithium iron phosphate that meets the requirements.

[0033] (2) The repair method for regenerated lithium iron phosphate provided by the present invention adopts pressure relief treatment, which can significantly improve the discharge specific capacity and capacity retention rate of regenerated lithium iron phosphate.

[0034] (3) The regeneration lithium iron phosphate repair method provided by the present invention further performs sintering treatment after depressurization treatment, thereby allowing the addition of lithium source, iron source and phosphorus source to generate lithium iron phosphate crystals in situ in waste lithium iron phosphate, ultimately resulting in higher purity of regenerated lithium iron phosphate and electrochemical performance meeting requirements. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0036] Figure 1 This is a SEM image of the regenerated lithium iron phosphate from Example 1 of the present invention.

[0037] The purpose, features, and advantages of this accompanying drawing will be further explained in conjunction with the embodiments and with reference to the accompanying drawing. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described and illustrated below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention.

[0039] Obviously, the following description is merely some examples or embodiments of the present invention. Those skilled in the art can apply the present invention to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, modifications to design, manufacturing, or production based on the technical content disclosed in this invention are merely conventional technical means and should not be construed as insufficient disclosure of the present invention.

[0040] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand the invention and is not intended to limit the subject matter of the claims.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0042] The first aspect of this invention provides a method for repairing regenerated lithium iron phosphate, comprising the following steps: S10. Supercritical low-viscosity fluid is used to repair waste lithium iron phosphate; The supercritical low-viscosity fluid contains repaired lithium source and water.

[0043] The remediation method for recycled lithium iron phosphate provided in this invention uses a supercritical low-viscosity fluid to repair waste lithium iron phosphate. The supercritical low-viscosity fluid contains Li... + Lithium is replenished by introducing lithium into the lattice vacancies of waste lithium iron phosphate to obtain recycled lithium iron phosphate.

[0044] In some embodiments, in step S10 above, the viscosity of the supercritical low-viscosity fluid is less than 0.1 mPa·s.

[0045] In some embodiments, in step S10 above, the viscosity of the supercritical low-viscosity fluid is 0.03 mPa·s to 0.07 mPa·s.

[0046] In some embodiments, in step S10 above, the lithium source for repair includes at least one of lithium carbonate, lithium hydroxide, lithium formate, lithium acetate, and lithium oxalate.

[0047] In some embodiments, the repair process in step S10 above includes the following steps: S101. At 374℃~380℃ and 22.1MPa~25MPa, a supercritical low-viscosity fluid is introduced into the mixture for treatment; The mixture includes a mixture of waste lithium iron phosphate and lithium iron phosphate raw materials.

[0048] In some embodiments, in step S101 above, the mass ratio of waste lithium iron phosphate to lithium iron phosphate raw material is 1:(0.01~0.03).

[0049] In some embodiments, the preparation of the mixture in step S101 above includes the following steps: S1011. Waste lithium iron phosphate and lithium iron phosphate raw materials are ball-milled and mixed.

[0050] In some embodiments, in step S101 above, the lithium iron phosphate raw material includes an added lithium source, an added iron source, and an added phosphorus source.

[0051] In some embodiments, the lithium source includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium carbonate, lithium hydroxide, lithium formate, lithium acetate, and lithium oxalate.

[0052] In some embodiments, the added iron source includes at least one of ferrous phosphate, ferrous nitrate, ferrous oxalate, and ferrous acetate.

[0053] In some embodiments, the added phosphorus source includes at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

[0054] In some embodiments, the atomic ratio of Fe, P and Li in the addition of lithium source, iron source and phosphorus source is 1:1:(0.95~1).

[0055] In some embodiments, in step S101 above, the time for introducing supercritical low-viscosity fluid is 20 min to 60 min.

[0056] In some embodiments, in step S101 above, the mixture further includes a doped metal salt.

[0057] In some embodiments, the content of the doped metal salt is 1 ppm to 3 ppm of the waste lithium iron phosphate.

[0058] In some embodiments, the doped metal salt includes at least one of vanadium trioxide (V2O3), titanium dioxide (TiO2), magnesium oxide (MgO), zirconium dioxide (ZrO2), and manganese oxide (MnO).

[0059] In some embodiments, a method for remediating regenerated lithium iron phosphate is provided, which further includes the following steps: S20. Pressure relief procedure.

[0060] In some embodiments, the pressure relief process in step S20 above includes the following steps: S201. After the waste lithium iron phosphate is repaired, a multi-stage voltage reduction process is performed; Multi-stage pressure reduction treatment includes a first stage of pressure reduction and a second stage of pressure reduction.

[0061] In some embodiments, in step S201 above, the first stage of voltage reduction processing includes the following steps: S2011. Reduce the pressure from 22.1MPa~25MPa to 14MPa~16MPa.

[0062] In some embodiments, during step S201 above, the pressure reduction rate in the first stage of pressure reduction is 3 MPa / min to 5 MPa / min. In this case, the sudden pressure drop can trigger micro-explosions in lithium salt crystallization, causing the product to form a porous structure and increasing the specific surface area of ​​the regenerated lithium iron phosphate.

[0063] In some embodiments, in step S201 above, the second stage of voltage reduction processing includes the following steps: S2012. Reduce the pressure after the first stage of pressure reduction to 0.1MPa~0.15MPa.

[0064] In some embodiments, during step S201 above, the voltage reduction rate in the second stage of voltage reduction is 0.1 MPa / min to 0.5 MPa / min. In this case, slow voltage reduction can stabilize the structure of the regenerated lithium iron phosphate formed in the first stage of voltage reduction.

[0065] In some embodiments, a method for remediating regenerated lithium iron phosphate is provided, which further includes the following steps: S30. Sintering treatment.

[0066] In the above steps, the sintering process allows the addition of lithium, iron, and phosphorus sources to generate lithium iron phosphate crystals in situ within the waste lithium iron phosphate, resulting in higher purity and electrochemical performance of the regenerated lithium iron phosphate.

[0067] In some embodiments, the sintering process in step S30 above includes the following steps: S301. The product obtained from the depressurization treatment is mixed with MOF material and then sintered.

[0068] In this context, MOF material coated with recycled lithium iron phosphate can improve the material's ionic conductivity and cycle stability.

[0069] In some embodiments, in step S301 above, the MOF material includes Li-MOF.

[0070] In some embodiments, in step S301 above, the mass of the MOF material is 1% to 5% of the mass of the product obtained from the decompression treatment.

[0071] In some embodiments, the sintering temperature in step S30 is 600°C to 800°C.

[0072] In some embodiments, the sintering time in step S30 is 10h to 15h.

[0073] A second aspect of the present invention provides a regenerated lithium iron phosphate obtained by the above-described method for repairing regenerated lithium iron phosphate.

[0074] The following description, in conjunction with specific embodiments, provides further details.

[0075] Example 1 Example 1 provides a method for remediating regenerated lithium iron phosphate, the steps of which are as follows: E1. Preparation of the mixture: Waste lithium iron phosphate, lithium bis(trifluoromethanesulfonyl)imide, ferrous phosphate and ammonium dihydrogen phosphate are ball-milled and mixed to obtain a mixture; wherein, the atomic ratio of Fe, P and Li in lithium bis(trifluoromethanesulfonyl)imide, ferrous phosphate and ammonium dihydrogen phosphate is 1:1:1; the mass ratio of waste lithium iron phosphate to the total mass of lithium bis(trifluoromethanesulfonyl)imide, ferrous phosphate and ammonium dihydrogen phosphate is 1:0.02.

[0076] E2. At 374℃ and 22.1MPa, a supercritical low-viscosity fluid was introduced into the mixture for 50 min; wherein the supercritical low-viscosity fluid was composed of lithium carbonate and water and had a viscosity of 0.05 mPa·s.

[0077] E3. Pressure Relief Procedure: E31. First stage of pressure reduction: The pressure is reduced from 22.1 MPa to 15 MPa at a pressure reduction rate of 4 MPa / min.

[0078] E32. Second stage pressure reduction process: Reduce the pressure from 15MPa to 0.1MPa at a pressure reduction rate of 0.3MPa / min.

[0079] E4. Sintering treatment: The product after depressurization treatment is mixed with Li-MOF and sintered at 700℃ for 10h~15h to obtain regenerated lithium iron phosphate; wherein, the mass of Li-MOF is 3% of the mass of the product obtained after depressurization treatment.

[0080] Example 2 Example 2 provides a method for remediating regenerated lithium iron phosphate. The steps are basically the same as in Example 1, except that: In step E2, the viscosity of the supercritical low-viscosity fluid is 0.07 mPa·s.

[0081] Example 3 Example 3 provides a method for remediating regenerated lithium iron phosphate. The steps are basically the same as in Example 1, except that: In step E2, the viscosity of the supercritical low-viscosity fluid is 0.03 mPa·s.

[0082] Example 4 Example 4 provides a method for remediating regenerated lithium iron phosphate. The steps are basically the same as in Example 1, except that: In step E2, the supercritical low-viscosity fluid consists of lithium oxalate and water.

[0083] Example 5 Example 5 provides a method for remediating regenerated lithium iron phosphate. The steps are basically the same as in Example 1, except that: In step E31, the pressure reduction rate of the first stage of pressure reduction treatment is 3 MPa / min.

[0084] In step E32, the pressure reduction rate of the second stage of pressure reduction treatment is 0.5 MPa / min.

[0085] Example 6 Example 6 provides a method for remediating regenerated lithium iron phosphate. The steps are basically the same as in Example 1, except that: In step E31, the pressure reduction rate of the first stage of pressure reduction treatment is 5 MPa / min.

[0086] In step E32, the pressure reduction rate of the second stage of pressure reduction treatment is 0.1 MPa / min.

[0087] Example 7 Example 7 provides a method for remediating regenerated lithium iron phosphate. The steps are basically the same as in Example 1, except that: In step E1, the mixture also includes vanadium trioxide, with a content of 2 ppm of waste lithium iron phosphate.

[0088] Comparative Example 1 Comparative Example 1 provides a method for remediating regenerated lithium iron phosphate, the steps of which are as follows: D1. Preparation of the mixture: Waste lithium iron phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium carbonate, ferrous phosphate and ammonium dihydrogen phosphate are ball-milled and mixed to obtain a mixture; wherein, the atomic ratio of Fe, P and Li in lithium bis(trifluoromethanesulfonyl)imide, ferrous phosphate and ammonium dihydrogen phosphate is 1:1:1; the mass ratio of waste lithium iron phosphate to the total mass of lithium bis(trifluoromethanesulfonyl)imide, ferrous phosphate and ammonium dihydrogen phosphate is 1:0.02.

[0089] E2. Supercritical water is introduced into the mixture at 374℃ and 22.1MPa.

[0090] E3. Pressure Relief Procedure: E31. First stage of pressure reduction: The pressure is reduced from 22.1 MPa to 15 MPa at a pressure reduction rate of 4 MPa / min.

[0091] E32. Second stage pressure reduction process: Reduce the pressure from 15MPa to 0.1MPa at a pressure reduction rate of 0.3MPa / min.

[0092] E4. Sintering treatment: Sinter the product after pressure relief treatment at 700℃ for 10h~15h.

[0093] Comparative Example 2 Comparative Example 2 provides a method for remediating regenerated lithium iron phosphate, the steps of which are basically the same as those in Example 1, except that: The pressure relief process in step E3 is as follows: reduce the pressure from 22.1 MPa to 0.1 MPa at a depressurization rate of 4 MPa / min.

[0094] Comparative Example 3 Comparative Example 3 provides a method for repairing regenerated lithium iron phosphate, the steps of which are basically the same as those in Example 1, except that: The pressure relief process in step E3 is as follows: reduce the pressure from 22.1 MPa to 0.1 MPa at a pressure reduction rate of 0.3 MPa / min.

[0095] Comparative Example 4 Comparative Example 4 provides a method for remediating regenerated lithium iron phosphate, the steps of which are basically the same as those in Example 1, except that: In step E31, the pressure reduction rate of the first stage of pressure reduction treatment is 6 MPa / min.

[0096] Comparative Example 5 Comparative Example 5 provides a method for remediating regenerated lithium iron phosphate, the steps of which are basically the same as those in Example 1, except that: In step E2, the viscosity of the supercritical low-viscosity fluid is 1 mPa·s.

[0097] To verify the advancement of the regenerated lithium iron phosphate and its repair method provided in this invention, CR2430 coin cells were fabricated from the regenerated lithium iron phosphate obtained in this invention and the comparative examples. The specific discharge capacity at 1C and the capacity retention rate after 200 cycles at 1C were then tested. The results are shown in Table 1 below.

[0098] Table 1

[0099] From the table above, at least the following conclusions can be drawn: (1) As can be seen from the examples and Comparative Example 1 in Table 1, the regenerated lithium iron phosphate obtained after repair in the examples can meet the battery requirements in terms of discharge specific capacity at 1C and capacity retention rate after 200 cycles at 1C; however, when the supercritical fluid is water, the discharge specific capacity at 1C and capacity retention rate after 200 cycles at 1C are lower. Therefore, it can be seen that in the repair method of regenerated lithium iron phosphate provided by the embodiments of the present invention, the Li in the supercritical low-viscosity fluid... + Injecting lithium into the lattice vacancies of spent lithium iron phosphate to replenish lithium can significantly improve the performance of lithium iron phosphate.

[0100] (2) As can be seen from the examples and comparative examples 2, 3, and 4 in Table 1, in the regeneration lithium iron phosphate repair method of the present invention, the first stage of pressure reduction treatment with a sudden pressure drop, followed by the second stage of slow pressure reduction treatment, can significantly improve the discharge specific capacity and capacity retention rate of the regeneration lithium iron phosphate. This is because a sudden pressure drop at an appropriate rate can trigger micro-explosions in lithium salt crystallization, causing the product to form mesopores and increasing the specific surface area of ​​the regeneration lithium iron phosphate. After the mesopores are formed, slow pressure reduction can stabilize the structure of the regeneration lithium iron phosphate formed in the first stage of pressure reduction. However, an excessively high pressure reduction rate will also reduce the discharge specific capacity and capacity retention rate of the regeneration lithium iron phosphate.

[0101] (3) As can be seen from the examples and comparative example 5 in Table 1, the lithium iron phosphate repair method provided by the present invention can effectively repair waste lithium iron phosphate when the viscosity of the supercritical low viscosity fluid is less than 1 mPa·s. However, when the viscosity is above 1 mPa·s, it cannot effectively replenish lithium, resulting in the discharge specific capacity and capacity retention rate failing to meet the requirements.

[0102] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method of rehabilitating regenerated lithium iron phosphate, characterized by, The method comprises the following steps: The waste lithium iron phosphate is repaired by using a supercritical low viscosity fluid; The supercritical low viscosity fluid contains a repairing lithium source and water.

2. The method of claim 1, wherein the method is characterized by: The viscosity of the supercritical low viscosity fluid is less than 0.1 mPa·s.

3. The method of claim 1, wherein the method is characterized by: At least one of the following (1)~(2) characteristics is satisfied: (1) The viscosity of the supercritical low viscosity fluid is 0.03 mPa·s~0.07 mPa·s; (2) The repairing lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium formate, lithium acetate, and lithium oxalate.

4. The method of claim 1 to 3, wherein the method is characterized by, The repairing process comprises the following steps: The supercritical low viscosity fluid is introduced into the mixture at 374℃~380℃ and 22.1 MPa~25 MPa; The mixture includes the waste lithium iron phosphate and lithium iron phosphate raw materials.

5. The method of claim 4, wherein the method is characterized by: At least one of the following (1)~(6) characteristics is satisfied: (1) The mass ratio of the waste lithium iron phosphate to the lithium iron phosphate raw materials is 1:0.01~0.03; (2) The preparation of the mixture comprises the following steps: the waste lithium iron phosphate and the lithium iron phosphate raw materials are ball-mixed; (3) The lithium iron phosphate raw materials include an added lithium source, an added iron source, and an added phosphorus source; (4) The mixture further includes a doped metal salt; (5) The repairing method further comprises the following step: a pressure relief treatment; (6) The repairing method further comprises the following step: a sintering treatment.

6. The method of claim 5, wherein the method is characterized by: At least one of the following (1)~(8) characteristics is satisfied: (1) The added lithium source includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium carbonate, lithium hydroxide, lithium formate, lithium acetate, and lithium oxalate; (2) The added iron source includes at least one of ferrous phosphate, ferrous nitrate, ferrous oxalate, and ferrous acetate; (3) The added phosphorus source includes at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate; (4) Among the added lithium source, the added iron source, and the added phosphorus source, the atomic ratio of Fe, P, and Li is 1:1:0.95~1; (5) The content of the doped metal salt is 1 ppm~3 ppm of the waste lithium iron phosphate; (6) The time for the supercritical low viscosity fluid treatment is 20 min~60 min; (7) The doped metal salt includes at least one of vanadium trioxide, titanium dioxide, magnesium oxide, zirconium dioxide, and manganese oxide; (8) The pressure relief treatment comprises the following steps: After the waste lithium iron phosphate is repaired, a multi-stage pressure reduction treatment is performed; The multi-stage pressure reduction treatment includes a first-stage pressure reduction and a second-stage pressure reduction.

7. The method of claim 6, wherein the method is characterized by: At least one of the following (1)~(4) characteristics is satisfied: (1) The first-stage pressure reduction treatment comprises the following steps: The pressure of 22.1 MPa~25 MPa is reduced to 14 MPa~16 MPa; (2) The second-stage pressure reduction treatment comprises the following steps: The pressure after the first-stage pressure reduction treatment is reduced to 0.1 MPa~0.15 MPa; (3) The sintering treatment is performed at a temperature of 600℃~800℃; (4) The sintering treatment is performed for a time of 10 h~15 h.

8. The method of claim 7, wherein the method is characterized by: At least one of the following (1)~(2) characteristics is satisfied: (1) In the first-stage pressure reduction treatment, the pressure reduction rate is 3 MPa / min~5 MPa / min; (2) In the second step, the pressure reduction rate is 0.1-0.5 MPa / min.

9. A regenerated lithium iron phosphate characterized by, The regenerated lithium iron phosphate is prepared by the repairing method according to any one of claims 1-8.

10. Use of lithium iron phosphate, characterized in that The regenerated lithium iron phosphate according to claim 9 is applied in the field of battery materials.

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