Method for repairing retired lithium iron phosphate positive electrode material

Abstract

This application discloses a method for repairing retired lithium iron phosphate (LFP) cathode materials. The method includes: mixing the retired LFP cathode material with a lithium salt to obtain a mixture; subjecting the mixture to heat treatment under an inactive atmosphere to obtain repaired LFP cathode material; the heat treatment includes: heating the mixture from T1 to T2 within a time interval t1, holding it at T2 for t2, and then cooling it from T2 to T3 within a time interval t3; t1 = 2–60 seconds, t2 = 0–600 seconds, t3 = 2–60 seconds, T1 = 20–700℃, T2 = 800–1300℃, T3 = 20–700℃. This application achieves ultra-fast regeneration of retired LFP in a short time, effectively reducing production costs. The repaired LFP exhibits excellent performance, with low-rate discharge specific capacity restored to the level of commercial LFP cathodes, high-rate discharge specific capacity exceeding that of commercial LFP, and excellent cycle stability.

Description

Technical Field

[0001] This application belongs to the field of battery materials technology, and in particular relates to a method for repairing retired lithium iron phosphate cathode materials. Background Technology

[0002] With the continuous expansion of lithium-ion batteries in the new energy vehicle market, the efficient, green, and low-cost regeneration of retired lithium-ion battery cathode materials has become a priority. Lithium iron phosphate (LFP) cathode materials, due to their stable olivine structure and excellent safety, have emerged as a leading cathode material in automotive power batteries. In 2022, the installed capacity of LFP batteries alone reached 155 GWh nationwide, accounting for 59% of the total installed capacity. Therefore, the efficient and precise repair and regeneration of LFP cathode materials is of great significance to both the new energy storage market and the ecological environment upon which humanity depends.

[0003] Traditionally, the recycling methods for lithium-ion battery cathode materials have mainly focused on pyrometallurgy and hydrometallurgy. Generally, hydrometallurgy uses large amounts of chemical reagents (acidic and alkaline) to dissolve waste lithium-ion batteries and recover metal elements through precipitation, which is environmentally unfriendly. Pyrometallurgy's calcination process consumes too much energy and has very limited lithium recovery. More importantly, waste lithium iron phosphate cathode materials do not contain metals such as nickel and cobalt, making pyrometallurgy uneconomical. Precisely processing waste lithium iron phosphate to restore it to usable fresh lithium iron phosphate is called the direct regeneration strategy. This restoration method can effectively utilize the intrinsic value of retired lithium iron phosphate cathode materials. However, existing direct regeneration methods are relatively complex, typically involving multiple steps (such as removal of inherent black substances, liquid-phase hydrothermal mixing, and multi-step high-temperature calcination), and the calcination time is very lengthy. Summary of the Invention

[0004] In view of this, this application provides a method for repairing retired lithium iron phosphate cathode materials, the main purpose of which is to solve the technical problems of cumbersome and time-consuming repair methods for retired lithium iron phosphate cathode materials.

[0005] On the one hand, this application provides a method for repairing decommissioned lithium iron phosphate cathode materials, the method comprising the following steps:

[0006] S1: Mix waste lithium iron phosphate cathode material powder with lithium salt to obtain a mixture;

[0007] S2: The mixture is heat-treated under an inactive atmosphere to obtain the repaired lithium iron phosphate cathode material; wherein, the thermal shock treatment process includes:

[0008] The mixture is heated from temperature T1 to temperature T2 within time t1, held at temperature T2 for time t2, and then cooled from temperature T2 to temperature T3 within time t3.

[0009] t1 = 2–60 seconds, t2 = 0–600 seconds, t3 = 2–60 seconds;

[0010] T1=20~700℃, T2=800~1300℃, T3=20~700℃.

[0011] The total duration of the thermal shock treatment described in this application is t. 1+ t 2+ t3, the temperature rises rapidly to T2 within time t1. It can be kept at t2 and then cooled down, or it can be cooled down directly from T2 to T3 within time t3 without keeping it at t1.

[0012] This application enables ultra-fast regeneration of waste lithium iron phosphate in a very short time, effectively reducing production costs.

[0013] Optionally, t1 or t3 is independently selected from any value or a range between any two of 2, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 50, 53, 55, 58, 60, in seconds; t2 is selected from any value or a range between any two of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400, 420, 450, 480, 500, 520, 550, 580, 600, in seconds.

[0014] Optionally, T1 or T3 can be independently selected from 20℃, 25℃, 30℃, 35℃, 40℃, 50℃, 55℃, 60℃, 65℃, 70℃, 80℃, 90℃, 100℃, 120℃, 150℃, 180℃, 200℃, 230℃, 250℃, 280℃, 300℃, 320℃, 350℃, 380℃, 400℃, 420℃, 450℃, 480℃, 500℃, 530℃, 550℃, 580℃, 600℃, and 630℃. T1 is any value from 650℃, 680℃, 700℃, or any range between any two, in seconds; T2 is selected from any value from 800℃, 820℃, 850℃, 880℃, 900℃, 920℃, 950℃, 980℃, 1000℃, 1030℃, 1050℃, 1080℃, 1100℃, 1130℃, 1150℃, 1180℃, 1200℃, 1220℃, 1250℃, 1280℃, 1300℃, or any range between any two.

[0015] Optionally, in step S2, t1 = 5 to 20 seconds, t2 = 0 to 60 seconds, and t3 = 2 to 20 seconds;

[0016] T1=20~700℃, T2=800~1200℃, T3=20~700℃.

[0017] Optionally, in step S2, t1 = 5 to 20 seconds, t2 = 0 to 60 seconds, and t3 = 2 to 20 seconds;

[0018] T1=20~300℃, T2=900~1200℃, T3=20~300℃.

[0019] Optionally, in step S2, the mixture is heated from temperature T1 to temperature T2 within time t1 without being kept warm, and then cooled from temperature T2 to temperature T3 within time t3.

[0020] t1 = 3-20 seconds, t2 = 0 seconds, t3 = 3-20 seconds;

[0021] T1=20~30℃, T2=800~1200℃, T3=20~80℃.

[0022] Optionally, in step S2, t1 and t3 may be the same or different.

[0023] Optionally, in step S2, T1 and T3 may be the same or different.

[0024] Optionally, T1 and T3 in this application are room temperature of 20 to 30°C.

[0025] Optionally, in step S1, the amount of lithium salt used is 5 to 80% of the number of moles of iron atoms in the waste lithium iron phosphate cathode material;

[0026] Optionally, in step S1, the amount of lithium salt used is 10 to 60% of the number of moles of iron atoms in the waste lithium iron phosphate cathode material.

[0027] Optionally, in step S1, the amount of lithium salt used is selected from any value or a range between any two of the following: the number of molar iron atoms in the waste lithium iron phosphate cathode material is selected from 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 80%.

[0028] Optionally, in step S1, the lithium salt is selected from at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium sulfate, and lithium acetate.

[0029] Optionally, in step S1, the waste lithium iron phosphate cathode material powder is mixed with the lithium salt by means of a high-speed mixer, a ball mill and / or a sand mill.

[0030] Optionally, the inactive atmosphere is selected from at least one of nitrogen, argon, and a hydrogen-argon mixture.

[0031] Optionally, in step S1, the acquisition of the waste lithium iron phosphate cathode material powder includes: discharging and unpacking the waste lithium iron phosphate battery, collecting the cathode sheet and washing it with ethanol and / or deionized water to remove the residual electrolyte on the surface, sintering the cathode sheet at 350-450°C under argon and / or nitrogen atmosphere for 0.5-6 hours to remove the residual binder polyvinylidene fluoride, and then making it into powder to obtain the waste lithium iron phosphate cathode material powder.

[0032] Optionally, in step S1, the positive electrode sheet is sintered at 400°C under an argon atmosphere for 1 hour to remove the residual adhesive polyvinylidene fluoride.

[0033] Optionally, in step S2, the mixture is subjected to thermal shock treatment in a Joule heating device.

[0034] This application provides a specific method for repairing decommissioned lithium iron phosphate cathode materials, including:

[0035] S1. Mix the waste lithium iron phosphate powder with an appropriate amount of lithium salt evenly.

[0036] S2. Applying thermal shock to the mixture under an inert atmosphere to repair and obtain a lithium iron phosphate cathode material with upgraded performance;

[0037] In step S1, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium chloride, lithium sulfate, and lithium acetate, and the amount of lithium salt used is 5 to 80% of the molar number of iron in the decommissioned lithium iron phosphate.

[0038] In step S2, the inert atmosphere is one of nitrogen, argon, or a mixture of hydrogen and argon.

[0039] In step S2, the thermal shock parameters are set to rapidly raise the temperature to 800℃ to 1200℃ in 3 to 20 seconds, and then cool it down to room temperature in 3 to 20 seconds.

[0040] Secondly, this application provides a lithium iron phosphate cathode material, which is obtained by the above-mentioned repair method.

[0041] This application finds that the lithium iron phosphate repaired using the above method exhibits excellent performance, with low-rate discharge specific capacity restored to the level of commercial lithium iron phosphate cathodes, high-rate discharge specific capacity exceeding that of commercial lithium iron phosphate, and excellent cycle stability. This indicates that the repair method of this application is not only simple and easy to operate in terms of process and time, but also that the repaired material has a higher discharge specific capacity at high rates than existing technologies.

[0042] Thirdly, this application provides a lithium battery, wherein the positive electrode material of the lithium battery includes the lithium iron phosphate positive electrode material obtained by the above-mentioned repair method.

[0043] Compared with the prior art, this application has the following beneficial effects:

[0044] (1) The repair method of retired lithium iron phosphate in this application achieves ultra-fast regeneration in a short time and effectively reduces production costs.

[0045] (2) The lithium iron phosphate repaired in this application has excellent performance. The specific capacity at low rate discharge is restored to the level of commercial lithium iron phosphate cathode, the specific capacity at high rate discharge is higher than that of commercial lithium iron phosphate, and it has excellent cycle stability.

[0046] (3) The repair method of this application is compatible with existing lithium iron phosphate cathode material production lines, and large-scale production can be achieved by adjusting process parameters. Attached Figure Description

[0047] Figure 1 This is a temperature curve of thermal shock during the repair process in Embodiment 1 of this application;

[0048] Figure 2 These are rate performance test graphs of coin cells made from waste lithium iron phosphate, repaired lithium iron phosphate, and commercial lithium iron phosphate cathode materials in Comparative Examples 1, 1, and 2 of this application.

[0049] Figure 3 Examples 1-5 of this application are in 1C (1C = 170 mA g). -1 Comparison chart of discharge specific capacity at different rates;

[0050] Figure 4 The coin cell prepared from the repaired lithium iron phosphate in Example 1 of this application and the commercial lithium iron phosphate cathode material in Comparative Example 2 is tested at 1C (1C = 170 mA g). -1 Cyclic performance diagram at various scaling ratios;

[0051] Figure 5 This is a graph showing the cycle performance of coin cells made from the repaired lithium iron phosphate cathode material in Example 1 of this application and the commercial lithium iron phosphate cathode material in Comparative Example 2 at an 8C rate. Detailed Implementation

[0052] The present application is further illustrated below with reference to specific embodiments. The following descriptions are merely a few embodiments of the present application and are not intended to limit the present application in any way. Although the present application discloses preferred embodiments as follows, they are not intended to limit the present application. Any modifications or variations made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

[0053] Unless otherwise specified, the raw materials used in the embodiments of this application are all purchased commercially and used directly without any special treatment.

[0054] Example 1 (Repair of Lithium Iron Phosphate Cathode Material)

[0055] Collection of retired lithium iron phosphate cathode materials: After discharging retired lithium iron phosphate batteries, the cathode plates are collected and washed with ethanol and deionized water to remove residual electrolyte from the surface. The active materials are separated from the current collector and ground into powder to obtain retired (waste) lithium iron phosphate cathode materials.

[0056] Repair of retired lithium iron phosphate: 3.16g of retired lithium iron phosphate cathode material powder was mixed with 0.147g (20% iron atom ratio) of lithium carbonate by ball milling at 300 rpm for 4 hours. 0.25g of the mixed powder was pressed into a 10mm diameter sheet and placed in a tungsten boat. The Joule heating device was adjusted, and argon gas was introduced to heat the material from room temperature to 1000℃ within 14 seconds, then cooled back to room temperature within 14 seconds, yielding the repaired lithium iron phosphate material. The thermal shock temperature curve during the repair process is shown below. Figure 1 As shown, Figure 1 Note: The detector's lowest detection temperature is 709℃. The heating curve shows the rapid heating process from 709℃ to 1000℃ and the rapid cooling process from 1000℃ to 709℃. It can be seen that the current instantly reaches 240A in the first second, and the heating ends and cooling begins when the current response is 0A. The pentagram curve represents the applied current.

[0057] Example 2 (Repair of Lithium Iron Phosphate Cathode Material)

[0058] The difference between Example 2 and Example 1 is that the thermal shock process includes:

[0059] The Joule heating device was adjusted and argon gas was introduced to heat it from room temperature to 800°C within 9 seconds. It was then held at 800°C for 20 seconds and then cooled to room temperature within 9 seconds to obtain the repaired lithium iron phosphate material.

[0060] Example 3 (Repair of Lithium Iron Phosphate Cathode Material)

[0061] The difference between Example 3 and Example 1 is that the thermal shock process includes:

[0062] The Joule heating device was adjusted and argon gas was introduced to heat it from room temperature to 900°C in 11 seconds. It was then held at 900°C for 17 seconds and then cooled to room temperature in 11 seconds to obtain the repaired lithium iron phosphate material.

[0063] Example 4 (Repair of Lithium Iron Phosphate Cathode Material)

[0064] Example 4 differs from Example 1 in that the thermal shock process includes:

[0065] The Joule heating device was adjusted and argon gas was introduced to heat it from room temperature to 1100℃ in 17 seconds, held at 1100℃ for 15 seconds, and then cooled to room temperature in 17 seconds to obtain the repaired lithium iron phosphate material.

[0066] Example 5 (Repair of Lithium Iron Phosphate Cathode Material)

[0067] Example 5 differs from Example 1 in that the thermal shock process includes:

[0068] The Joule heating device was adjusted and argon gas was introduced to heat it from room temperature to 1200℃ within 20 seconds. It was then held at 1200℃ for 10 seconds and then cooled to room temperature within 20 seconds to obtain the repaired lithium iron phosphate material.

[0069] Comparative Example 1 (Waste Lithium Iron Phosphate Cathode Material)

[0070] The waste lithium iron phosphate cathode material obtained in Example 1 was used for electrode preparation, half-cell assembly, and electrochemical performance testing. The electrode preparation, half-cell assembly, and electrochemical performance testing are as described in Test Example 1.

[0071] Comparative Example 2 (Commercial Lithium Iron Phosphate Cathode Material)

[0072] The lithium iron phosphate cathode material purchased from Defang Nano was used for electrode preparation, half-cell assembly, and electrochemical performance testing. The electrode preparation, half-cell assembly, and electrochemical performance testing are shown in Test Example 1.

[0073] Comparative Example 3 (Existing Technological Repair Method)

[0074] A method for repairing lithium iron phosphate cathode materials includes the following steps:

[0075] S1. The lithium iron phosphate cathode material is mixed with a multifunctional solvent and subjected to solvothermal treatment; the multifunctional solvent is made by mixing ethanol, lithium acetate and polyvinylpyrrolidone.

[0076] S2. The precipitate obtained after solvent heat treatment is vacuum dried;

[0077] The solvent heat treatment temperature is 150-180℃, and the solvent heat treatment time is 5-12 hours. Vacuum drying is carried out at 60-120℃ for 12-24 hours.

[0078] S3. The solid powder obtained by vacuum drying is calcined to obtain the repaired lithium iron phosphate cathode material; calcination is carried out at 600-750℃ for 2-10 hours.

[0079] The following tests were conducted on the electrochemical performance of the lithium iron phosphate cathode material repaired in Example 1, the waste lithium iron phosphate cathode material in Comparative Example 1, and the lithium iron phosphate cathode materials in Comparative Example 2 and Comparative Example 3.

[0080] Test Example 1

[0081] Preparation of lithium iron phosphate cathode sheet: The lithium iron phosphate repaired in Example 1 (or lithium iron phosphate cathode materials of Examples 2, 3, 4, 5, Comparative Examples 1, 2, and 3), conductive agent Super P, and polyvinylidene fluoride (PVDF) were mixed evenly in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added dropwise into a mixing tank and stirred thoroughly to obtain an active slurry. The active slurry was evenly coated onto an aluminum current collector with a thickness of 15 micrometers, and the coating thickness was 200 micrometers. The electrode sheet coated with the slurry was then placed in a vacuum drying oven at 105°C overnight. The electrode sheet was then pressed into a thickness of 60 micrometers using an electric roller press and cut into small round sheets with a diameter of 10 mm.

[0082] Assembly of lithium iron phosphate half-cell: The 2032 button half-cell is prepared by assembling and encapsulating the following components in the order of stainless steel positive electrode shell, lithium iron phosphate positive electrode sheet, separator, lithium negative electrode sheet, gasket, spring sheet, and stainless steel negative electrode shell. The electrolyte addition amount is 30 microliters.

[0083] Electrochemical performance testing of lithium iron phosphate half-cells: The discharge capacity and cycle stability of the batteries were tested using a battery tester from Shenzhen Xinwei Electronics Co., Ltd. Before the cycle stability test, the batteries were activated for three cycles with a small current of 0.2C, with an operating voltage range of 2.4V to 4.2V.

[0084] Analysis of the electrochemical performance test results of the cathode materials in Example 1, Comparative Example 1, and Comparative Example 2:

[0085] from Figure 1 As can be seen from the example, the retired lithium iron phosphate cathode material of Example 1 can be heated to 1000°C within 14 seconds to complete the ultrafast targeted regeneration process of the material.

[0086] from Figure 2As can be seen from the results, the low-rate (0.2C) discharge specific capacity of the lithium iron phosphate in Example 1 after repair was restored to 150.8 mAh / g, reaching the level of the commercial lithium iron phosphate cathode in Comparative Example 2, indicating that the lithium loss in the crystal lattice has been completely restored.

[0087] from Figure 2 As can be seen, with the increase of the rate, the discharge specific capacity advantage of the repaired lithium iron phosphate in Example 1 becomes more and more obvious. At 2.0C, the discharge specific capacity of the repaired lithium iron phosphate in Example 1 is 123.9 mAh / g, which is significantly higher than the discharge specific capacity of the commercial lithium iron phosphate in Comparative Example 2 (92.1 mAh / g). The retired lithium iron phosphate in Comparative Example 1, due to the lack of lithium in the crystal lattice and the degradation of the bulk structure, only released a discharge specific capacity of 72.9 mAh / g.

[0088] from Figure 2 It can be clearly seen that when the rate is increased to a high load state of 8.0C, the discharge specific capacity of the lithium iron phosphate half-cell repaired in Example 1 can still be maintained at 95.5mAh / g, while the discharge specific capacity of the commercial lithium iron phosphate in Comparative Example 2 is only 71.1mAh / g, and the discharge specific capacity of the retired lithium iron phosphate half-cell in Comparative Example 1 is only 61.44mAh / g.

[0089] from Figure 3 As can be seen from the data, the lithium iron phosphate repaired in Example 1 has the highest discharge specific capacity (135 mAh / g) at 1.0C compared to other repair conditions.

[0090] from Figure 4 As can be seen, the lithium iron phosphate repaired in Example 1 has comparable cycle stability to the commercial lithium iron phosphate in Comparative Example 2 at 1.0C, and the discharge specific capacity retention after 300 cycles is greater than 85% (89% vs. 85.5%).

[0091] from Figure 5 As can be seen, the lithium iron phosphate repaired in Example 1 exhibits significantly better cycle stability at 8.0C than the commercial lithium iron phosphate in Comparative Example 2. After 200 cycles, the lithium iron phosphate repaired in Example 1 still retains 85.6% of its initial discharge specific capacity, while the commercial lithium iron phosphate in Comparative Example 2 only retains 20.9% of its initial capacity. This indicates that the lithium iron phosphate cathode material repaired in Example 1 of this application has good rate performance and excellent high-rate stability, demonstrating a significant performance upgrade effect.

[0092] The electrochemical performance of the repaired lithium iron phosphate in Examples 2-4 of this application is similar to that in Example 1. The repaired lithium iron phosphate exhibits excellent performance, with its low-rate discharge specific capacity restored to the level of commercial lithium iron phosphate cathodes, and its high-rate discharge specific capacity exceeding that of commercial lithium iron phosphate, and it also has excellent cycle stability.

[0093] Comparative Example 3 shows that the repaired lithium iron phosphate cathode material, within a voltage window of 2.9–4.2V and a current density of 0.3C, produces a soft-pack battery with a discharge capacity of approximately 270mAh, and retains nearly 99% of its capacity after 300 cycles.

[0094] The electrochemical performance of the repaired lithium iron phosphate cathode material obtained by the ultrafast thermal shock treatment method of Example 1 of this application is similar to that of the repaired lithium iron phosphate cathode material obtained by the prior art in Comparative Example 3. However, in terms of process, the process of Example 1 of this application is simpler and easier to operate, with a heat treatment time of a few seconds, while the heat treatment time of Comparative Example 3 is 2-10 hours. The heat treatment temperature of this application is much lower than the heat treatment time of Comparative Example 3, which greatly reduces heating cost and material cost.

[0095] This application achieves ultrafast regeneration within tens of seconds by mixing retired lithium iron phosphate cathode material with an appropriate amount of lithium source and then subjecting it to thermal shock. Compared to traditional pyrometallurgical and hydrometallurgical methods, this technique offers greater economic efficiency and environmental sustainability, and is also simpler than other targeted regeneration methods. Furthermore, the repaired lithium iron phosphate cathode material exhibits superior rate performance and high-rate cycling stability compared to commercially available lithium iron phosphate cathode materials, representing a performance upgrade.

[0096] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for repairing decommissioned lithium iron phosphate cathode materials, characterized in that, The method includes the following steps: S1: Mix waste lithium iron phosphate cathode material powder with lithium salt to obtain a mixture; S2: The mixture is subjected to thermal shock treatment under an inactive atmosphere to obtain repaired lithium iron phosphate cathode material; wherein, the thermal shock treatment process includes: In step S2, the mixture is heated from temperature T1 to temperature T2 within time t1 without being kept warm, and then cooled from temperature T2 to temperature T3 within time t3. t1 = 3~20 seconds, t3 = 3~20 seconds; T1=20~30℃, T2=800~1200℃, T3=20~80℃.

2. The method for repairing decommissioned lithium iron phosphate cathode materials according to claim 1, characterized in that, In step S1, the amount of lithium salt used is 5% to 80% of the number of iron atoms in the waste lithium iron phosphate cathode material.

3. The method for repairing decommissioned lithium iron phosphate cathode materials according to claim 2, characterized in that, In step S1, the amount of lithium salt used is 10 to 60% of the number of iron atoms in the waste lithium iron phosphate cathode material.

4. The method for repairing decommissioned lithium iron phosphate cathode materials according to claim 1, characterized in that, In step S1, the lithium salt is selected from at least one of lithium carbonate, lithium chloride, lithium sulfate, and lithium acetate.

5. The method for repairing decommissioned lithium iron phosphate cathode materials according to claim 1, characterized in that, In step S1, the waste lithium iron phosphate cathode material powder and the lithium salt are mixed by means of a high-speed mixer, a ball mill and / or a sand mill.

6. The method for repairing decommissioned lithium iron phosphate cathode materials according to claim 1, characterized in that, In step S1, the acquisition of the waste lithium iron phosphate cathode material powder includes: discharging and unpacking the waste lithium iron phosphate battery, collecting the cathode sheet and washing it with ethanol and / or deionized water to remove the residual electrolyte on the surface, sintering the cathode sheet at 350~450℃ under argon and / or nitrogen atmosphere for 0.5~6 hours to remove the residual binder polyvinylidene fluoride, and then making it into powder to obtain the waste lithium iron phosphate cathode material powder.

7. The method for repairing decommissioned lithium iron phosphate cathode materials according to claim 1, characterized in that, The inactive atmosphere is selected from at least one of nitrogen, argon, and a hydrogen-argon mixture.

8. The method for repairing decommissioned lithium iron phosphate cathode materials according to claim 1, characterized in that, In step S2, T2 = 900~1200℃.

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