A regenerated lithium iron phosphate positive electrode sheet and lithium iron phosphate battery

Abstract

The present invention provides a regenerated lithium iron phosphate positive electrode sheet, comprising: 70-90% of recycled waste lithium iron phosphate positive electrode material, 3-15% of lithium supplement additive, 3-10% of fast ion conductor, and 3-5% of binder; wherein the recycled waste lithium iron phosphate positive electrode material is obtained by discharging the retired power battery until the voltage is reduced to below 0.5V, crushing the disassembled and separated positive electrode sheet by physical method, adding it to a NaOH solution with a pH of 10-14, stirring, centrifugal treatment, water washing, and drying. The present invention also provides a lithium iron phosphate battery, which is obtained by pre-fabricating a lithium iron phosphate battery using the regenerated lithium iron phosphate positive electrode sheet, and then undergoing a pre-cycle repair treatment to obtain a repaired and regenerated lithium iron phosphate battery. The present invention solves the problem of recycling lithium iron phosphate positive electrode materials in power batteries, while reducing the manufacturing cost of lithium iron phosphate batteries, reliably guarantees the electrochemical performance of lithium iron phosphate batteries, and can meet the requirements of commercial energy storage lithium batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of waste power battery recycling, and in particular to a repaired and regenerated lithium iron phosphate positive electrode sheet and a lithium iron phosphate battery prepared from the positive electrode sheet. Background Art

[0002] With the gradual popularization of electric vehicles, the number of retired power batteries is also increasing year by year. Power batteries are rich in rare metals and toxic chemicals. If they are not scientifically treated and recycled, they will cause serious harm to the environment and human health. At the same time, scientific recycling and reuse can improve resource utilization and economic benefits.

[0003] At present, lithium iron phosphate batteries account for more than one-third of the lithium battery market. Among them, lithium iron phosphate (LiFePO4) positive electrode materials have the advantages of good safety performance, fast charging speed, and long service life. As the positive electrode material of power batteries with the largest installed capacity, it is now facing a huge amount of waste to be recycled. Traditional wet and fire recycling methods require more process steps and consume a lot of energy. The recovery value of elements such as Fe and P is low, and more "three wastes" are generated, which also pollutes the environment.

[0004] How to provide a short cycle, high economic benefit, and environmentally friendly method for the effective recycling of lithium iron phosphate batteries is a topic that technicians in this field are constantly researching. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and firstly provide a regenerated lithium iron phosphate positive electrode plate.

[0006] The present invention provides a regenerated lithium iron phosphate positive electrode plate, comprising the following raw materials in percentage by weight:

[0007] The recycled waste lithium iron phosphate positive electrode material comprises 70-90%, lithium supplement additive 3-15%, fast ion conductor 3-10%, and binder 3-5%. The recycled waste lithium iron phosphate positive electrode material is obtained by discharging retired power batteries until the voltage drops below 0.5V, crushing the disassembled and separated positive electrode plates by physical methods, adding them to a NaOH solution with a pH of 10-14, stirring, centrifuging, washing with water, and drying.

[0008] The regenerated lithium iron phosphate positive electrode plate provided by the present invention uses the recycled waste lithium iron phosphate positive electrode material as raw material, is mixed with lithium supplement additives and fast ion conductors, and is bonded together by a binder. The high ion conductivity and high speed transmission performance of the selected fast ion conductor are used to enable the lithium ions in the waste lithium iron phosphate and lithium supplement additives to migrate quickly during the charging and discharging process, so that LiFePO4 is changed from a lithium-poor state to a lithium-full state, and the repair and regeneration of the waste lithium iron phosphate positive electrode material is completed, and the positive electrode material for directly preparing lithium iron phosphate lithium batteries is obtained. The whole process does not generate any wastewater, reduces environmental pollution, improves the environmental protection of the recycling process, and meets the current social demand for efficient and environmentally friendly recycling technology.

[0009] The present invention also provides a lithium iron phosphate battery, which is prepared by using the regenerated lithium iron phosphate positive electrode sheet including the above-mentioned regenerated lithium iron phosphate battery, and then undergoing a pre-cycle repair treatment to obtain a repaired and regenerated lithium iron phosphate battery.

[0010] The lithium iron phosphate positive electrode sheet regenerated after repair according to the present invention is used to make a lithium iron phosphate battery. After a pre-cycle repair treatment, the capacity is above 2000 mAh. After 1000 cycles of charge and discharge cycle testing, the capacity retention rate is above 89%.

[0011] The present invention solves the problem of recycling lithium iron phosphate positive electrode materials in power batteries, improves resource utilization, and can ensure the total capacity, energy density and cycle life of lithium batteries while reducing the manufacturing cost of lithium iron phosphate batteries, reliably ensuring the electrochemical properties of lithium iron phosphate batteries and meeting the requirements of commercial energy storage lithium batteries. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0013] The present invention first provides a regenerated lithium iron phosphate positive electrode plate, comprising the following raw materials in percentage by weight:

[0014] The recycled waste lithium iron phosphate positive electrode materials include 70-90%, lithium supplement additives 3-15%, fast ion conductors 3-10%, and binders 3-5%.

[0015] Among the above raw materials, the recycled waste lithium iron phosphate positive electrode material is obtained by first discharging the retired lithium iron phosphate power battery until the voltage is reduced to below 0.5V, separating the positive electrode plates by physical methods, crushing them to obtain positive electrode black powder, and then adding them to a NaOH solution with a pH of 10 to 14, stirring, centrifuging, washing with water, and drying.

[0016] The specific steps are:

[0017] (1) The waste lithium iron phosphate battery can be discharged by using the "green, environmentally friendly and safe discharge method for waste lithium-ion batteries" provided by the applicant's patent CN202210429654.0. Through vibration and gradual pressurization linkage, the waste lithium iron phosphate battery is tightly connected with the discharge particles to ensure that the waste lithium battery is discharged evenly and thoroughly. The waste lithium iron phosphate battery can also be soaked in a 5wt% to 20wt% NaCl solution to completely discharge the waste lithium iron phosphate battery until the voltage drops below 0.5V. While ensuring the safety of recycling and processing the waste lithium iron phosphate battery, the recovery of lithium elements in the lithium iron phosphate positive electrode material is ensured;

[0018] (2) Dismantle the discharged waste lithium iron phosphate batteries by mechanical crushing, magnetic separation and screening to separate the mixed material with the separator and the positive and negative electrode sheets;

[0019] (3) Separating the positive electrode sheet from the mixed material can be achieved by using the "Flexible and precise separation method and system for positive and negative electrode materials of waste lithium batteries" provided by the applicant's patent CN202110279054.6;

[0020] (4) The positive electrode sheet is crushed by a ball mill to obtain positive electrode black powder (Dmax≤38μm), and then the positive electrode black powder is added to a NaOH solution with a pH of 10-14 and heated to 80℃-100℃. The solution is stirred for reaction for 30-60min, and then the solid and liquid components are separated by centrifugation. The solid component is then washed with deionized water to fully remove Al impurities, and finally dried in a drying oven at 90℃-120℃ to obtain the recycled waste lithium iron phosphate positive electrode material.

[0021] The chemical expression of waste lithium iron phosphate positive electrode material is: Li 1-x FePO4, where 0.6≤x<1.0.

[0022] Among the above raw materials, the chemical expression of the lithium supplement additive is Li2MO2, where M is at least one of Ni, Mn, Cu, Fe, Cr, Zn, Al, and Mo. These materials are lithium-rich materials with extremely low reversible capacity and can be completely decomposed to provide sufficient active lithium ions.

[0023] Among the above raw materials, the fast ion conductors are LiAlTiPO4 (LATP), Li7La3Zr2O 12 (LLZO), Li3BO3, Li 6.4 Ln3Z 1.4 Ta 0.6 O 12 (LLZTO) or Li 1.5 A 10.5Ge 1.5 At least one of (PO4)3 (LAGP). These fast ion conductor materials are used to mix with recycled waste lithium iron phosphate positive electrode materials and lithium supplement additives, and act between particles of positive electrode materials, lithium supplement additives, etc., with low requirements for particle size, lower ion conductivity activation energy and higher conductivity. Since the lithium battery preparation process and pre-cycling process both involve high temperatures, the conductivity changes of these materials are relatively less affected by temperature, and can maintain electrochemical stability during the preparation process.

[0024] Among the above raw materials, the binder is at least one of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyimide (PI), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyurethane (PUR), and sodium carboxymethyl cellulose (CMC).

[0025] The regenerated lithium iron phosphate positive electrode plate provided by the present invention mixes the recycled waste lithium iron phosphate positive electrode material with a certain amount of lithium-rich material and a fast ion conductor. The lithium-rich material and the fast ion conductor work together to solve the defect of active lithium ion deficiency in the waste lithium iron phosphate battery positive electrode material, provide additional lithium ions to be stored in the negative electrode in the subsequent lithium battery preparation, and at the same time, in the pre-cycle discharge process of the subsequent lithium battery preparation, the fast ion conductor has a lower ion conductivity activation energy and a higher conductivity, so that the lithium ions in the waste lithium iron phosphate and the lithium supplement additive can be quickly migrated and embedded into the lithium vacancies of LiFePO4 at the positive terminal during the charging and discharging process, so that the LiFePO4 changes from a lithium-poor state to a lithium-full state, completing the repair and regeneration of the waste lithium iron phosphate. In addition, the waste lithium iron phosphate positive electrode material is mixed with the lithium-rich material and the fast ion conductor through sufficient stirring and slurrying in the process of making the positive electrode plate by using a binder, so that the surface of the lithium iron phosphate particles is in close contact with the fast ion conductor material, which can effectively improve the conductivity and rate performance of the lithium ion battery.

[0026] The present invention also provides a lithium iron phosphate battery, the product preparation of which includes the above-mentioned regenerated lithium iron phosphate positive electrode sheet, and also includes a graphite negative electrode sheet, an electrolyte, a diaphragm, etc., specifically including the following steps:

[0027] (1) Preparation of positive electrode sheet:

[0028] The raw materials of the above-mentioned regenerated lithium iron phosphate positive electrode plates are mixed in the following weight percentages: 70-90% of recycled waste lithium iron phosphate positive electrode materials, 3-15% of lithium supplement additives, 3-10% of fast ion conductors, and 3-5% of binders. Then, a proper amount of solvent, such as N-methylpyrrolidone (NMP), is added to dissolve and swell the waste lithium iron phosphate positive electrode materials, lithium supplement additives, fast ion conductors and binders, so that various components are fully in contact and evenly distributed, and the overall solid content is 70-80%. Stir to a uniform positive electrode slurry under the action of a vacuum mixer.

[0029] The positive electrode slurry is coated on one surface of the positive electrode current collector by a coating machine, dried at 100-120°C, and then the same coating process is repeated on the other surface of the positive electrode current collector to obtain a double-sided coated positive electrode sheet. After cold pressing, cutting, and welding the electrode ears, a positive electrode sheet of set specifications is obtained.

[0030] (2) Preparation of negative electrode sheet:

[0031] Natural graphite, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in proportion, deionized water is added and stirred evenly to obtain negative electrode slurry, and then the negative electrode slurry is coated on both surfaces of the negative electrode current collector, and dried to obtain a negative electrode sheet coated with a negative electrode material layer on both sides, and after cold pressing, cutting and welding of the electrode ears, a negative electrode sheet of set specifications is obtained. The preparation of the negative electrode sheet adopts the existing technology, which will not be repeated here.

[0032] (3) Lithium battery preparation:

[0033] The positive electrode sheet, the isolation film and the negative electrode sheet are wound to obtain a battery cell; the battery cell is placed in a steel shell, an electrolyte is injected, and a prefabricated lithium iron phosphate battery is obtained after packaging.

[0034] (4) Pre-cycle repair treatment:

[0035] Under a temperature environment of 50-80°C, the prefabricated lithium iron phosphate battery was charged to 3.65V using a constant current of 2A, then charged at a constant voltage of A / 2, left to stand for a period of time, and then discharged to 2.0V using a constant current of A, where 0.01C≤A≤0.05C. The above charging and discharging process was repeated three times to obtain a commercial lithium iron phosphate battery.

[0036] The repaired and regenerated lithium iron phosphate positive electrode sheet of the present invention is made into a lithium iron phosphate battery, and a pre-cycle repair treatment is performed. When tested at a rate of 0.1C, the capacity is above 2000mAh, and after 1000 cycles of charge and discharge cycle testing, the capacity retention rate is above 89%. In this way, while reducing the manufacturing cost of the lithium iron phosphate battery, the total capacity, energy density and cycle life of the lithium battery can be guaranteed, and the electrochemical performance of the lithium iron phosphate battery is reliably guaranteed, meeting the requirements of commercial energy storage lithium batteries.

[0037] The following is a specific embodiment of the present invention of using the repaired and regenerated lithium iron phosphate positive electrode sheet to prepare a lithium iron phosphate battery.

[0038] Embodiment 1:

[0039] 1. Treatment of waste lithium iron phosphate batteries:

[0040] (1) Soak the retired lithium iron phosphate battery in 10% NaCl solution for 5 hours to fully discharge the used lithium iron phosphate battery until the voltage drops below 0.5V;

[0041] (2) Mechanical crushing, magnetic separation and screening are used to disassemble and separate the mixed material with the separator and the positive and negative electrode sheets;

[0042] (3) Use the "Flexible and precise separation method and system for positive and negative electrode materials of waste lithium batteries" provided by CN202110279054.6 to separate the positive electrode sheet from the mixed material;

[0043] (4) The positive electrode sheet was crushed by a ball mill to obtain positive electrode black powder (Dmax < 35 μm), placed in a NaOH solution with a pH of 13 and heated to 80°C, stirred for reaction for 30 min, then centrifuged to separate the solid and liquid components, and then the solid component was washed with deionized water to remove Al impurities, and finally dried in a blast oven at 100°C to obtain the waste lithium iron phosphate positive electrode material Li 0.88 FePO4.

[0044] 2. Preparation of positive electrode:

[0045] Li 0.88 FePO4, Li2NiO2, LATP, and PVDF are added in a mass ratio of 86:5:5:4, and an appropriate amount of N-methylpyrrolidone (NMP) is added to make the overall solid content 70%. The positive electrode slurry is stirred to a uniform state under the action of a vacuum mixer. The positive electrode slurry is coated on one surface of a 10μm thick aluminum foil through a coater and dried at 120°C to obtain a single-sided 90μm thick positive electrode sheet. Then the same coating process is repeated on the other surface of the aluminum foil to obtain a double-sided coated positive electrode sheet. After cold pressing, cutting, and welding the pole ears, a positive electrode sheet with a specification of 62mm×864mm is obtained.

[0046] 3. Preparation of negative electrode sheet:

[0047] Natural graphite, styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 95:2:3, deionized water was added as a solvent, and stirred evenly to obtain a negative electrode slurry with a solid content of 40%. The negative electrode slurry was coated on one surface of a copper foil with a thickness of 6μm, and dried at 105°C to obtain a single-sided negative electrode sheet with a thickness of 75μm. Then the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a negative electrode material layer coated on both sides. After cold pressing, cutting, and welding the pole ears, a negative electrode sheet with a specification of 64mm×872mm was obtained for standby use.

[0048] 4. Lithium battery preparation:

[0049] The positive electrode sheet, the separator, and the negative electrode sheet are rolled up in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound up to obtain a battery cell; the battery cell is placed in a steel shell, and the moisture is removed at 80°C, and the prepared electrolyte is injected, and after vacuum packaging, standing, formation, shaping, capacity division and other processes, a cylindrical lithium-ion battery is obtained.

[0050] The cylindrical lithium-ion battery was charged to 3.65V at a constant current of 0.04C, then fully charged at 3.65V using 0.01C, and discharged to 2.0V using a constant current of 0.02C after standing for 10 minutes. This pre-cycle charge and discharge was repeated three times at 60°C to obtain a regenerated lithium iron phosphate battery. Finally, the battery capacity and cycle performance were tested at a rate of 0.1C.

[0051] The test results are shown in Table 1. From Table 1, it can be seen that the 18650 lithium iron phosphate battery prepared in Example 1 has a capacity of 2330 mAh, and the battery capacity retention rate after 1000T cycles is 97.6%, which has better electrochemical performance.

[0052] Embodiment 2:

[0053] 1. Treatment of waste lithium iron phosphate batteries:

[0054] (1) Soak the retired lithium iron phosphate battery in 15% NaCl solution for 5 hours to fully discharge the used lithium iron phosphate battery until the voltage drops below 0.5V;

[0055] (2) Mechanical crushing, magnetic separation and screening are used to disassemble and separate the mixed material with the separator and the positive and negative electrode sheets;

[0056] (3) Use the "Flexible and precise separation method and system for positive and negative electrode materials of waste lithium batteries" provided by CN202110279054.6 to separate the positive electrode sheet from the mixed material;

[0057] (4) The positive electrode sheet was crushed by a ball mill to obtain positive electrode black powder (Dmax < 38 μm), placed in a NaOH solution with a pH of 10 and heated to 100°C, stirred for 60 minutes, and then centrifuged to separate the solid and liquid components. The solid component was then washed with deionized water and finally dried in a blast oven at 100°C to obtain the waste lithium iron phosphate positive electrode material Li 0.92 FePO4.

[0058] 2. Preparation of positive electrode:

[0059] Li 0.92 FePO4, Li2NiO2, LATP, and PVDF are added in a mass ratio of 90:3:3:4, and an appropriate amount of N-methylpyrrolidone (NMP) is added to make the overall solid content 70%. The positive electrode slurry is stirred to a uniform state under the action of a vacuum mixer. The positive electrode slurry is coated on one surface of a 10μm thick aluminum foil through a coater and dried at 120°C to obtain a single-sided 90μm thick positive electrode sheet. Then the same coating process is repeated on the other surface of the aluminum foil to obtain a double-sided coated positive electrode sheet. After cold pressing, cutting, and welding the pole ears, a positive electrode sheet with a specification of 62mm×864mm is obtained.

[0060] 3. Preparation of negative electrode sheet:

[0061] Same as Example 1.

[0062] 4. Lithium battery preparation:

[0063] The positive electrode sheet, the separator, and the negative electrode sheet are rolled up in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound up to obtain a battery cell; the battery cell is placed in a steel shell, and the moisture is removed at 80°C, and the prepared electrolyte is injected, and after vacuum packaging, standing, formation, shaping, capacity division and other processes, a cylindrical lithium-ion battery is obtained.

[0064] The cylindrical lithium-ion battery was charged to 3.65V at a constant current of 0.06C, then fully charged at 0.015C at a constant voltage of 3.65V, and discharged to 2.0V at a constant current of 0.03C after standing for 10 minutes. This pre-cycle charge and discharge was performed three times at 60°C to obtain a regenerated lithium iron phosphate battery. Finally, the battery capacity and cycle performance were tested at a rate of 0.1C.

[0065] The test results are shown in Table 1. From Table 1, it can be seen that the 18650 lithium iron phosphate battery prepared in Example 2 has different mass ratios of waste lithium iron phosphate positive electrode materials, lithium supplement additives, fast ion conductors and additives in the positive electrode plate, and the pre-cycle repair treatment process parameters are different from those in Example 1. The capacity of the prepared lithium iron phosphate battery is 2219 mAh, and the battery capacity retention rate after 1000T cycles is 94.5%, which still has better electrochemical performance.

[0066] Embodiment 3:

[0067] 1. Treatment of waste lithium iron phosphate batteries:

[0068] Same as Example 2.

[0069] 2. Preparation of positive electrode:

[0070] Li 0.92 FePO4, Li2CuO2, LAGP, and PVDF are added in a mass ratio of 90:3:3:4, and an appropriate amount of N-methylpyrrolidone (NMP) is added to make the overall solid content 70%. The positive electrode slurry is stirred to a uniform state under the action of a vacuum mixer. The positive electrode slurry is coated on one surface of a 10μm thick aluminum foil through a coater and dried at 120°C to obtain a single-sided 90μm thick positive electrode sheet. Then the same coating process is repeated on the other surface of the aluminum foil to obtain a double-sided coated positive electrode sheet. After cold pressing, cutting, and welding the pole ears, a positive electrode sheet with a specification of 62mm×864mm is obtained.

[0071] 3. Preparation of negative electrode sheet:

[0072] Same as Example 1 and Example 2.

[0073] 4. Lithium battery preparation:

[0074] Same as Example 2.

[0075] The test results are shown in Table 1. From Table 1, it can be seen that the 18650 lithium iron phosphate battery prepared in Example 3 has different raw materials for lithium supplement additives and fast ion conductors from those in Example 2, and the pre-cycle repair treatment process parameters are the same as those in Example 2. The capacity is 2252 mAh, and the battery capacity retention rate after 1000T cycles is 93.3%, which has better electrochemical performance.

[0076] Embodiment 4:

[0077] 1. Treatment of waste lithium iron phosphate batteries:

[0078] (1) Use the "Green, Environmentally Friendly and Safe Discharge Method for Waste Lithium-ion Batteries" provided in CN202210429654.0 to discharge the waste lithium iron phosphate batteries until the voltage drops below 0.5V;

[0079] (2) Mechanical crushing, magnetic separation and screening are used to disassemble and separate the mixed material with the separator and the positive and negative electrode sheets;

[0080] (3) Use the "Flexible and precise separation method and system for positive and negative electrode materials of waste lithium batteries" provided by CN202110279054.6 to separate the positive electrode sheet from the mixed material;

[0081] (4) The positive electrode sheet is crushed to further obtain positive electrode black powder, which is placed in a NaOH solution with a pH of 14 and heated to 90°C. The mixture is stirred for reaction for 45 minutes, and then the solid and liquid components are separated by centrifugation. The solid component is then washed with deionized water and finally dried in a blast oven at 120°C to obtain the waste lithium iron phosphate positive electrode material Li 0.78 FePO4.

[0082] 2. Preparation of positive electrode:

[0083] Li 0.78 FePO4, Li2CuO2, LLZO, and PAN are added in a mass ratio of 80:9:7:4, and an appropriate amount of N-methylpyrrolidone (NMP) is added to make the overall solid content 70%. The positive electrode slurry is stirred to a uniform state under the action of a vacuum mixer. The positive electrode slurry is coated on one surface of a 10μm thick aluminum foil through a coater and dried at 120°C to obtain a single-sided 90μm thick positive electrode sheet. Then repeat the same coating process on the other surface of the aluminum foil to obtain a double-sided coated positive electrode sheet. After cold pressing, cutting, and welding the pole ears, a positive electrode sheet with a specification of 62mm×864mm is obtained.

[0084] 3. Preparation of negative electrode sheet:

[0085] Same as Example 1, Example 2 and Example 3.

[0086] 4. Lithium battery preparation:

[0087] The positive electrode sheet, the separator, and the negative electrode sheet are rolled up in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound up to obtain a battery cell; the battery cell is placed in a steel shell, and the moisture is removed at 80°C, and the prepared electrolyte is injected, and after vacuum packaging, standing, formation, shaping, capacity division and other processes, a cylindrical lithium-ion battery is obtained.

[0088] The cylindrical lithium-ion battery was charged to 3.65V at a constant current of 0.02C, then fully charged at 0.005C at a constant voltage of 3.65V, left to stand for 10 minutes, and then discharged to 2.0V at a constant current of 0.01C. This pre-cycle charge and discharge was repeated three times at 80°C to obtain a regenerated lithium iron phosphate battery. Finally, the battery capacity and cycle performance were tested at a rate of 0.1C.

[0089] The test results are shown in Table 1. As can be seen from Table 1, the 18650 lithium iron phosphate battery prepared in Example 4 has different fast ion conductor and adhesive selection and pre-cycle repair treatment process parameters from Example 1, Example 2 and Example 3, and has a capacity of 2286 mAh. The battery capacity retention rate after 1000T cycles is 89.4%, which has better electrochemical performance.

[0090] Embodiment 5:

[0091] 1. Treatment of waste lithium iron phosphate batteries:

[0092] Same as Example 1.

[0093] 2. Preparation of positive electrode:

[0094] Same as Example 1.

[0095] 3. Preparation of negative electrode sheet:

[0096] Same as Example 1.

[0097] 4. Lithium battery preparation:

[0098] The positive electrode sheet, the separator, and the negative electrode sheet are rolled up in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound up to obtain a battery cell; the battery cell is placed in a steel shell, and the moisture is removed at 80°C, and the prepared electrolyte is injected, and after vacuum packaging, standing, formation, shaping, capacity division and other processes, a cylindrical lithium-ion battery is obtained.

[0099] The cylindrical lithium-ion battery was charged to 3.65V at a constant current of 0.1C, then fully charged at 0.025C at a constant voltage of 3.65V, left to stand for 10 minutes, and then discharged to 2.0V at a constant current of 0.05C. This pre-cycle charge and discharge was repeated three times at 50°C to obtain a regenerated lithium iron phosphate battery. Finally, the battery capacity and cycle performance were tested at a rate of 0.1C.

[0100] The test results are shown in Table 1. From Table 1, it can be seen that the pre-cycle repair treatment process parameters of the lithium iron phosphate battery prepared in Example 5 are different from those in Examples 1-4, and the prepared lithium iron phosphate battery has a capacity of 2198 mAh, and a capacity retention rate of 93.2% after 1000T cycles, which still has good electrochemical performance.

[0101] Comparative Example 1:

[0102] 1. Treatment of waste lithium iron phosphate batteries:

[0103] Same as Example 1.

[0104] 2. Preparation of positive electrode:

[0105] Li 0.88 FePO4, Li2NiO2, and PVDF are added in a mass ratio of 88.5:7.5:4, and an appropriate amount of N-methylpyrrolidone (NMP) is added to make the overall solid content 70%. The positive electrode slurry is stirred to a uniform state under the action of a vacuum mixer. The positive electrode slurry is coated on one surface of a 10μm thick aluminum foil through a coater and dried at 120°C to obtain a single-sided 90μm thick positive electrode sheet. Then repeat the same coating process on the other surface of the aluminum foil to obtain a double-sided coated positive electrode sheet. After cold pressing, cutting, and welding the pole ears, a positive electrode sheet with a specification of 62mm×864mm is obtained.

[0106] 3. Preparation of negative electrode sheet:

[0107] Same as Example 1.

[0108] 4. Lithium battery preparation:

[0109] Same as Example 1.

[0110] The test results are shown in Table 1. From Table 1, it can be seen that the 18650 lithium iron phosphate battery prepared in Comparative Example 1 lacks the participation of fast ion conductors in the preparation of the positive electrode sheet. The capacity of the prepared lithium iron phosphate battery is 1866mAh, and the battery capacity retention rate after 1000T cycles is 45.4%. Compared with Example 1, its electrochemical performance is greatly reduced and cannot meet the application requirements of lithium iron phosphate batteries at all.

[0111] Comparative Example 2:

[0112] 1. Treatment of waste lithium iron phosphate batteries:

[0113] Same as Example 1.

[0114] 2. Preparation of positive electrode:

[0115] Li 0.88FePO4, LTP, and PVDF are added in a mass ratio of 88.5:7.5:4, and an appropriate amount of N-methylpyrrolidone (NMP) is added to make the overall solid content 70%. The positive electrode slurry is stirred to a uniform state under the action of a vacuum mixer. The positive electrode slurry is coated on one surface of a 10μm thick aluminum foil through a coater and dried at 120°C to obtain a single-sided 90μm thick positive electrode sheet. Then the same coating process is repeated on the other surface of the aluminum foil to obtain a double-sided coated positive electrode sheet. After cold pressing, cutting, and welding the pole ears, a positive electrode sheet with a specification of 62mm×864mm is obtained.

[0116] 3. Preparation of negative electrode sheet:

[0117] Same as Example 1.

[0118] 4. Lithium battery preparation:

[0119] Same as Example 1.

[0120] The test results are shown in Table 1. As can be seen from Table 1, the 18650 lithium iron phosphate battery prepared in Comparative Example 2 has no lithium supplement additive in the preparation of the positive electrode sheet. The capacity of the prepared lithium iron phosphate battery is 1560mAh, and the battery capacity retention rate after 1000T cycles is 21.2%. Similarly, compared with Example 1, its electrochemical performance is greatly reduced and cannot meet the application requirements of lithium iron phosphate batteries at all.

[0121] Comparative Example 3:

[0122] 1. Treatment of waste lithium iron phosphate batteries:

[0123] Same as Example 1.

[0124] 2. Preparation of positive electrode:

[0125] Same as Example 1.

[0126] 3. Preparation of negative electrode sheet:

[0127] Same as Example 1.

[0128] 4. Lithium battery preparation:

[0129] The positive electrode sheet, the separator, and the negative electrode sheet are rolled up in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound up to obtain a battery cell; the battery cell is placed in a steel shell, and the moisture is removed at 80°C, and the prepared electrolyte is injected, and after vacuum packaging, standing, formation, shaping, capacity division and other processes, a cylindrical lithium-ion battery is obtained.

[0130] The cylindrical lithium-ion battery was charged to 3.65V at a constant current of 0.2C, then fully charged at 0.05C at a constant voltage of 3.65V, left to stand for 10 minutes, and then discharged to 2.0V at a constant current of 0.1C. This pre-cycle charge and discharge was repeated three times at 25°C to obtain a regenerated lithium iron phosphate battery. Finally, the battery capacity and cycle performance were tested at a rate of 0.1C.

[0131] The test results are shown in Table 1. From Table 1, it can be seen that in the pre-cycle procedure of the 18650 lithium iron phosphate battery prepared in Comparative Example 3, the charge and discharge current related parameters are higher than the parameters set in the present invention, and the ambient temperature is lower than the parameters set in the present invention. The capacity of the prepared lithium iron phosphate battery is 1933mAh, and the battery capacity retention rate after 1000T cycles is 77.5%. Compared with Example 1, its electrochemical performance is greatly reduced, and it is difficult to meet the application requirements of lithium iron phosphate batteries.

[0132] Table 1 Battery performance test results of various embodiments and comparative examples

[0133]

[0134] The above-mentioned embodiments of the present invention are only part of the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made by those skilled in the art without departing from the essence of the present invention are within the protection scope of the present invention.

Claims

1. A repaired and regenerated lithium iron phosphate battery, characterized in that: A regenerated lithium iron phosphate positive electrode sheet is used to prefabricate a lithium iron phosphate battery, and then a pre-cycle repair process is performed to obtain a repaired and regenerated lithium iron phosphate battery; The regenerated lithium iron phosphate positive electrode plate comprises the following raw materials in weight percentage: 70-90% of recycled waste lithium iron phosphate positive electrode material, 3-15% of lithium supplement additive, 3-10% of fast ion conductor, and 3-5% of binder; wherein, The chemical expression of the waste lithium iron phosphate positive electrode material is: Li 1-x FePO4, where 0.6≤x<1.0; The chemical expression of the lithium supplement additive is Li2MO2, wherein M is at least one of Ni, Mn, Cu, Fe, Cr, Zn, Al, and Mo; The fast ion conductor is LiAlTiPO4, Li7La3Zr2O 12 、Li3BO3、Li 6.4 LqCy 1.4 Ta 0.6 O 12 or Li 1.5 Al 0.5 Ge 1.5 At least one of (PO4)3; The regenerated lithium iron phosphate positive electrode plate is made of recycled waste lithium iron phosphate positive electrode material as raw material, mixed with the lithium supplement additive and the fast ion conductor, and the waste lithium iron phosphate positive electrode material, the lithium supplement additive and the fast ion conductor are mixed together by the binder; the recycled waste lithium iron phosphate positive electrode material is obtained by first discharging the retired lithium iron phosphate power battery until the voltage is reduced to below 0.5V, separating the positive electrode plate by a physical method, crushing to obtain positive electrode black powder, and then adding it to a NaOH solution with a pH of 10 to 14, stirring, centrifugal separation, water washing, and drying; The pre-cycle repair treatment steps are: in a temperature environment of 50-80°C, the prefabricated lithium iron phosphate battery is charged to 3.65V using a constant current of 2A, then charged at a constant voltage of A / 2, and after standing for a period of time, discharged to 2.0V using a constant current of A, and the above charging and discharging process is repeated three times, where 0.01C≤A≤0.05C.

2. The repaired and regenerated lithium iron phosphate battery according to claim 1, characterized in that: The recycled waste lithium iron phosphate positive electrode material is obtained by disassembling retired lithium iron phosphate power batteries by discharging them, then disassembling them by mechanical crushing, magnetic separation and screening methods in sequence, and separating a mixed material having a diaphragm, a positive electrode sheet and a negative electrode sheet, then separating the positive electrode sheet from the mixed material, and then crushing the positive electrode sheet to obtain positive electrode black powder, adding the positive electrode black powder to a NaOH solution with a pH of 10 to 14, heating it to 80° C. to 100° C., stirring for a reaction for 30 to 60 minutes, centrifuging to separate solid and liquid components, and then washing the solid components with deionized water, and drying them in a drying oven at 90° C. to 120° C., so as to obtain the recycled waste lithium iron phosphate positive electrode material.

3. The repaired and regenerated lithium iron phosphate battery according to claim 1 or 2, characterized in that: The binder is at least one of polyvinylidene fluoride, styrene-butadiene rubber, polyimide, polyacrylonitrile, polyvinyl alcohol, polyurethane or sodium carboxymethyl cellulose.

4. The repaired and regenerated lithium iron phosphate battery according to claim 1, characterized in that: The method comprises the following preparation steps: (1) Preparation of regenerated lithium iron phosphate positive electrode: The raw materials constituting the regenerated lithium iron phosphate positive electrode sheet are mixed according to weight percentage, and then a proper amount of solvent is added and stirred evenly to obtain a positive electrode slurry; The positive electrode slurry is coated on the two surfaces of the positive electrode current collector respectively, and dried to obtain a regenerated lithium iron phosphate positive electrode sheet coated with a positive electrode material layer on both sides, and after cold pressing, cutting, and welding the electrode ears, a regenerated lithium iron phosphate positive electrode sheet of set specifications is obtained; (2) Preparation of negative electrode sheet: Natural graphite, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in proportion, deionized water is added and stirred evenly to obtain a negative electrode slurry; The negative electrode slurry is coated on both surfaces of the negative electrode current collector, and dried to obtain a negative electrode sheet coated with a negative electrode material layer on both sides, and after cold pressing, cutting, and welding the electrode ears, a negative electrode sheet of set specifications is obtained; (3) Preparation of prefabricated lithium iron phosphate batteries: The regenerated lithium iron phosphate positive electrode sheet, the separator, and the negative electrode sheet are wound to obtain a battery cell; The battery cell is placed in a steel shell, an electrolyte is injected, and the prefabricated lithium iron phosphate battery is obtained after packaging; (4) Pre-cycle repair treatment: The prefabricated lithium iron phosphate battery is subjected to three charge and discharge cycle treatments to obtain a repaired and regenerated lithium iron phosphate battery with a capacity retention rate higher than 89%.

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