Lithium iron phosphate regenerated pole piece of waste lithium ion battery and preparation method of lithium iron phosphate regenerated pole piece

Abstract

The invention provides a lithium iron phosphate regenerated pole piece of a waste lithium ion battery and a preparation method of the lithium iron phosphate regenerated pole piece. The preparation method comprises the following steps: S1, collecting a positive pole piece from the waste lithium iron phosphate battery; s2, washing the waste lithium iron phosphate pole piece with an organic solvent, and drying to obtain a waste lithium iron phosphate positive pole piece; and S3, supplementing lithium to the waste lithium iron phosphate pole piece at 20-30 DEG C by using a chemical regeneration method or an electrochemical regeneration method, washing the pole piece after lithium supplementation by using an organic solvent, and drying to obtain the lithium iron phosphate electrode piece. According to the invention, a chemical / electrochemical regeneration method is utilized to realize conversion from lithium-deficient-phase lithium iron phosphate to pre-lithium-phase lithium iron phosphate, so that the problem of loss of active lithium of the first circle of the graphite soft-package battery caused by lithium iron phosphate is effectively solved, and meanwhile, the regeneration efficiency is greatly improved and the production period of the soft-package battery is shortened by a pole piece regeneration process.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a regenerated lithium iron phosphate electrode sheet for waste lithium-ion batteries and a preparation method thereof. Background Art

[0002] As a commonly used lithium-ion cathode material, lithium iron phosphate is widely used in large-scale energy storage systems, electric vehicles, mobile energy storage and other fields due to its long cycle life, high safety, high thermal stability, low cost and environmental friendliness.

[0003] The failure of the lithium iron phosphate cathode material is caused by the lack of lithium element, and its crystal structure is not damaged. At the same time, only lithium element in the lithium iron phosphate material has a high recycling value, and the economic benefits of using pyrometallurgy or hydrometallurgy are relatively low. Therefore, waste lithium iron phosphate is suitable for the direct lithium replenishment regeneration process. The lithium vacancies in waste lithium iron phosphate can be eliminated by contact pre-lithiation / electrochemical pre-lithiation, and the regeneration of waste lithium iron phosphate can be realized by controlling the reaction conditions.

[0004] Chinese Patent CN117977040A discloses a regeneration method for waste lithium iron phosphate battery electrode sheets, which specifically includes: mixing and soaking waste lithium iron phosphate electrode sheets with a reducing agent, an alkaline lithium source, a metal iodide and a solvent, and obtaining regenerated lithium iron phosphate electrode sheets after washing and drying. Although this method realizes the direct regeneration of waste lithium iron phosphate, the long cycle performance of the regenerated lithium iron phosphate is poor, and at the same time, it cannot supplement the irreversible active lithium loss caused by the first-cycle charging of the graphite soft-pack battery by lithium iron phosphate.

[0005] Chinese Patent CN118782948A discloses a regeneration method for waste lithium iron phosphate battery electrode sheets, which specifically includes: stripping the active substances of waste lithium iron phosphate electrode sheets and then mixing and soaking them with a reducing agent and a low-grade lithium source, and after washing and drying, pasting the sheet-shaped active substances on an aluminum current collector and rolling them for use. This method introduces the processes of active substance stripping and pasting. Although it realizes the lithium replenishment of waste lithium iron phosphate, the additional processes will cause the active substances to be not firmly combined with the current collector, easily resulting in the peeling of the active substances. At the same time, the reducing property of the reducing agent is not sufficient to embed excessive lithium into waste lithium iron phosphate, and it also cannot supplement the irreversible active lithium loss caused by the first-cycle charging of the graphite soft-pack battery by lithium iron phosphate. Based on this, the present invention provides a regenerated lithium iron phosphate electrode sheet for waste lithium-ion batteries and a preparation method thereof. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method for preparing a regenerated lithium iron phosphate electrode sheet from waste lithium-ion batteries, which realizes the upgrading and regeneration of the lithium iron phosphate electrode sheet of waste lithium-ion batteries through a chemical / electrochemical lithium supplementation method. It not only realizes the transformation from lithium-deficient lithium iron phosphate to pre-lithiated lithium iron phosphate, but also effectively solves the problem of the loss of active lithium in the first cycle of graphite soft-pack batteries with lithium iron phosphate. Moreover, the regeneration operation process is simple, and the regenerated lithium iron phosphate electrode sheet can be directly assembled into commercial soft-pack batteries, with a short production cycle, which is conducive to large-scale industrial production.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a method for preparing a regenerated lithium iron phosphate electrode sheet from waste lithium-ion batteries, and the steps include:

[0009] S1. Collect the positive electrode sheet from waste lithium iron phosphate batteries;

[0010] S2. Wash the waste lithium iron phosphate electrode sheet with an organic solvent and then dry it to obtain a waste lithium iron phosphate positive electrode sheet;

[0011] S3. Perform lithium supplementation on the waste lithium iron phosphate electrode sheet by using a chemical regeneration method or an electrochemical regeneration method at 20-30 °C. After lithium supplementation, wash the electrode sheet with an organic solvent and then dry it to obtain the product.

[0012] Further, the collection method in step S1 includes: discharging the waste lithium-ion battery at a current of 0.1C to 2V for complete discharge, and then disassembling and collecting the positive electrode sheet.

[0013] Further, the organic solvent includes at least one of dimethyl carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ethylene glycol dimethyl ether, fluoroethylene carbonate, and 1,3-dioxolane.

[0014] Further, the mass ratio of the organic solvent to the lithium iron phosphate electrode sheet is ≥25:1, and the number of washing times is ≥3 times.

[0015] Further, the steps of the chemical regeneration method include: attaching the waste lithium iron phosphate electrode sheet to a lithium metal sheet dropped with an electrolyte solution, and maintaining it at 20-30 °C for 2-30 minutes; the molar ratio of the lithium content in the lithium metal sheet to the lithium missing in the active material of the lithium iron phosphate electrode sheet is ≥2:1; the mass ratio of the electrolyte solution dosage to the active material mass of the lithium iron phosphate electrode sheet is ≥5 μL / mg.

[0016] Further, the steps of the electrochemical regeneration method include: using the waste lithium iron phosphate electrode sheet as the positive electrode, the lithium metal sheet as the negative electrode, adding an electrolyte to assemble a button battery, and performing a constant voltage discharge at 0 V for 1-30 minutes at 20-30 °C; the molar ratio of the lithium content in the lithium metal sheet to the lithium missing in the active material of the sheet-shaped positive electrode ≥ 2:1; the mass ratio of the electrolyte dosage to the mass of the active material of the lithium iron phosphate electrode sheet ≥ 5 μL / mg.

[0017] Further, the drying condition in the steps S2 and S3 is drying at 60-90 °C for 4-24 h.

[0018] Further, the electrolyte in the electrolyte includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalate) borate; the electrolyte concentration is 0.1-2 M.

[0019] Further, the solvent in the electrolyte includes at least one of ethylene carbonate, dimethyl carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ethylene glycol dimethyl ether, fluorinated ethylene carbonate, and 1,3-dioxolane.

[0020] In the second aspect, the present invention also provides a regenerated lithium iron phosphate electrode sheet for waste lithium ion batteries, which is prepared by using the aforementioned method.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) A method for upgrading and regenerating a lithium iron phosphate electrode sheet of a waste lithium ion battery and a regenerated electrode sheet provided by the present invention can directly regenerate the waste lithium iron phosphate electrode sheet by using a chemical / electrochemical lithium supplementation method, and effective lithium supplementation can be achieved without being broken into powder. The initial charge specific capacity of the regenerated sample is increased by 66.1 mAh g -1 compared with the waste lithium iron phosphate and commercial lithium iron phosphate, and 15.8 mAh g -1 .

[0023] (2) Using lithium metal as the lithium source, the lithium insertion reaction energy is reduced by using chemical / electrochemical methods, so as to achieve repair and regeneration at a lower temperature condition, reducing energy consumption. At the same time, the strong reducibility of lithium metal itself can promote the insertion of excessive lithium ions into the lattice of lithium iron phosphate, thereby realizing the transformation of waste lithium iron phosphate into pre-lithiated lithium iron phosphate. The chemical method can efficiently regenerate the waste lithium iron phosphate electrode sheet by simply and conveniently attaching the waste lithium iron phosphate electrode sheet to the lithium metal sheet; the reaction conditions of the electrochemical method are mild and controllable. By assembling the waste lithium iron phosphate electrode sheet and the lithium metal sheet into a battery for an electrochemical reaction, it is convenient to control the lithium supplementation amount, and a pre-lithiated lithium iron phosphate with a uniform lithium content distribution can be obtained.

[0024] (3) The regenerated lithium iron phosphate electrode obtained in the present invention has a higher specific capacity compared with the existing commercial lithium iron phosphate. It can effectively make up for the loss of active lithium in the first cycle of the graphite soft-pack battery with lithium iron phosphate, and greatly improve the battery cycle life.

[0025] (4) The upgraded regeneration method provided by the present invention has a simple process and a short regeneration process. At the same time, the regeneration strategy at the electrode level can omit the re-coating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a comparison chart of the first-cycle charge and discharge curves of waste lithium iron phosphate, commercial lithium iron phosphate, and regenerated lithium iron phosphate in Embodiment 1 of the present invention;

[0028] Figure 2 It is a comparison chart of the cycling performance of waste lithium iron phosphate, commercial lithium iron phosphate, and regenerated lithium iron phosphate in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0030] The present invention provides a method for preparing a regenerated lithium iron phosphate electrode from waste lithium-ion batteries, and the steps include:

[0031] S1. Collect the positive electrode from waste lithium iron phosphate batteries, specifically, fully discharge, disassemble, wash, and dry the waste lithium-ion batteries to obtain waste lithium iron phosphate positive electrodes;

[0032] S2. Wash the waste lithium iron phosphate electrode with an organic solvent and then dry it;

[0033] S3. Use a chemical regeneration method or an electrochemical regeneration method to replenish lithium to the waste lithium iron phosphate electrode at 20 - 30 °C. After lithium replenishment, wash the electrode with an organic solvent and then dry it to obtain the product.

[0034] In a further embodiment, the organic solvent includes but is not limited to at least one of dimethyl carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ethylene glycol dimethyl ether, fluoroethylene carbonate, and 1,3-dioxolane; the mass ratio of the organic solvent to the lithium iron phosphate electrode is ≥25:1, and the number of washings is ≥3 times; the drying condition in steps S2 and S3 is drying at 60-90°C for 4-24h; the electrolyte in the electrolyte includes but is not limited to at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), and lithium dioxalatoborate; the electrolyte concentration is 0.1-2M; the solvent in the electrolyte includes but is not limited to at least one of ethylene carbonate, dimethyl carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ethylene glycol dimethyl ether, fluoroethylene carbonate, and 1,3-dioxolane.

[0035] Among them, the steps of the chemical regeneration method include: applying the waste lithium iron phosphate pole piece to a lithium metal sheet dripped with electrolyte, and keeping it at 20-30°C for 2-30 minutes; the molar ratio of the lithium content in the lithium metal sheet to the lithium missing from the active material of the lithium iron phosphate pole piece is ≥2:1; the mass ratio of the electrolyte usage to the active material of the lithium iron phosphate pole piece is ≥5μL / mg.

[0036] In a further embodiment, the electrochemical regeneration method comprises the following steps: using the waste lithium iron phosphate pole piece as the positive electrode and the lithium metal sheet as the negative electrode, adding electrolyte to assemble into a button battery, and discharging at a constant voltage of 0V for 1-30 minutes at 20-30°C; the molar ratio of the lithium content in the lithium metal sheet to the lithium missing from the sheet positive electrode active material is ≥2:1; the mass ratio of the electrolyte dosage to the lithium iron phosphate pole piece active material is ≥5μL / mg.

[0037] Unless otherwise specified, the experimental materials and reagents used in the following examples can be obtained from commercial sources. If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0038] Example 1

[0039] This embodiment provides a method for preparing a regenerated lithium iron phosphate electrode sheet of a waste lithium-ion battery, which directly regenerates the waste lithium iron phosphate electrode sheet to obtain a regenerated lithium iron phosphate electrode sheet, and specifically comprises the following steps:

[0040] (1) Positive electrode sheet collection: The complete, non-short-circuited waste lithium-ion batteries were fully discharged at a current of 0.1C to 2V, disassembled, washed with dimethyl carbonate (DMC) three times, and dried at 60°C for 24h to obtain waste lithium iron phosphate positive electrode sheets;

[0041] (2) Electrolyte preparation: Lithium hexafluorophosphate is selected as the electrolyte, and ethylene carbonate and diethyl carbonate are used as solvents; The solvents are prepared by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1:1, and an appropriate amount of lithium hexafluorophosphate is added to make the electrolyte concentration in the solution 1M;

[0042] (3) Chemical regeneration: The used lithium iron phosphate electrode is used as the positive electrode, and a lithium metal sheet is used as the negative electrode. 50 μL of electrolyte is dropped onto the lithium metal sheet, and the used lithium iron phosphate electrode is applied onto the lithium metal sheet with the dropped electrolyte; The mass ratio of the electrolyte to the active material of the lithium iron phosphate electrode is 7 μL / mg -1 , the mass ratio of the lithium metal sheet to the used lithium iron phosphate is 20:1, and the application time is 7 minutes; After the chemical regeneration, the regenerated lithium iron phosphate electrode is washed three times with dimethyl carbonate, and the mass ratio of dimethyl carbonate to the regenerated lithium iron phosphate electrode is 125:1. The washed and clean regenerated lithium iron phosphate electrode is obtained after drying in a forced-air oven at 60 °C for 24 h.

[0043] Example 2

[0044] This example provides a method for preparing a regenerated lithium iron phosphate electrode of a used lithium-ion battery, directly regenerating the used lithium iron phosphate electrode to obtain a regenerated lithium iron phosphate electrode, which specifically includes the following steps:

[0045] (1) Positive electrode sheet collection: The complete and non-shorted used lithium-ion battery is fully discharged, disassembled, washed 3 times with dimethyl carbonate (DMC) and dried at 60 °C for 24 h to obtain a used lithium iron phosphate positive electrode sheet;

[0046] (2) Electrolyte preparation: Lithium hexafluorophosphate is selected as the electrolyte, and ethylene carbonate and diethyl carbonate are used as solvents; Ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1:1, and 5% of fluoroethylene carbonate based on their total volume is added. After thorough mixing, an appropriate amount of lithium hexafluorophosphate is added to make the electrolyte concentration in the solution 1M.

[0047] (3) Chemical regeneration: The used lithium iron phosphate electrode is used as the positive electrode, and a lithium metal sheet is used as the negative electrode. 50 μL of electrolyte is dropped onto the lithium metal sheet, and the used lithium iron phosphate electrode is applied onto the lithium metal sheet with the dropped electrolyte; The mass ratio of the electrolyte to the active material of the lithium iron phosphate electrode is 7 μL / mg -1 , the mass ratio of the lithium metal sheet to the used lithium iron phosphate is 20:1, and the application time is 7 minutes; After the chemical regeneration, the regenerated lithium iron phosphate electrode is washed three times with dimethyl carbonate, and the mass ratio of dimethyl carbonate to the regenerated lithium iron phosphate electrode is 125:1. The washed and clean regenerated lithium iron phosphate electrode is obtained after drying in a forced-air oven at 60 °C for 24 h.

[0048] Example 3

[0049] This embodiment provides a method for preparing a regenerated lithium iron phosphate electrode for a waste lithium-ion battery, which directly regenerates the waste lithium iron phosphate electrode to obtain a regenerated lithium iron phosphate electrode. The specific steps are as follows:

[0050] (1) Positive electrode sheet collection: Completely discharge, disassemble, wash three times with dimethyl carbonate (DMC), and dry at 60 °C for 24 h the intact and non-shorted waste lithium-ion battery to obtain the waste lithium iron phosphate positive electrode sheet;

[0051] (2) Electrolyte preparation: Select lithium hexafluorophosphate as the electrolyte and ethylene carbonate and diethyl carbonate as the solvents; Prepare the solvent with ethylene carbonate and diethyl carbonate at a volume ratio of 1:1, and add an appropriate amount of lithium hexafluorophosphate to make the electrolyte concentration in the solution 1 M;

[0052] (3) Chemical regeneration: Use the waste lithium iron phosphate electrode as the positive electrode and the lithium metal sheet as the negative electrode. Drop 50 μL of the electrolyte onto the lithium metal sheet, and attach the waste lithium iron phosphate electrode to the lithium metal sheet dropped with the electrolyte; where the mass ratio of the electrolyte to the active material of the lithium iron phosphate electrode is 7 μL / mg -1 , the mass ratio of the lithium metal sheet to the waste lithium iron phosphate is 20:1, and the attachment time is 12 minutes; After the chemical regeneration, wash the regenerated lithium iron phosphate electrode three times with dimethyl carbonate, where the mass ratio of dimethyl carbonate to the regenerated lithium iron phosphate electrode is 125:1. After washing and drying the regenerated lithium iron phosphate electrode in a forced-air oven at 60 °C for 24 h, it is obtained.

[0053] Example 4

[0054] This embodiment provides a method for preparing a regenerated lithium iron phosphate electrode for a waste lithium-ion battery, which directly regenerates the waste lithium iron phosphate electrode to obtain a regenerated lithium iron phosphate electrode. The specific steps are as follows:

[0055] (1) Positive electrode sheet collection: Completely discharge, disassemble, wash three times with dimethyl carbonate (DMC), and dry at 60 °C for 24 h the intact and non-shorted waste lithium-ion battery to obtain the waste lithium iron phosphate positive electrode sheet;

[0056] (2) Electrolyte preparation: Select lithium hexafluorophosphate as the electrolyte and ethylene carbonate and diethyl carbonate as the solvents; Prepare the solvent with ethylene carbonate and diethyl carbonate at a volume ratio of 1:1, and add an appropriate amount of lithium hexafluorophosphate to make the electrolyte concentration in the solution 1 M;

[0057] (3) Electrochemical regeneration: Use the waste lithium iron phosphate electrode as the positive electrode and the lithium metal sheet as the negative electrode, and assemble a CR2025 type button battery by adding 50 μL of the electrolyte, where the mass ratio of the electrolyte to the active material of the lithium iron phosphate electrode is 7 μL / mg -1, the mass ratio of the lithium metal sheet to the waste lithium iron phosphate is 20:1; the button battery is discharged at a constant voltage of 0 V for 7 minutes, and after the discharge is completed, the button battery is disassembled to take out the regenerated lithium iron phosphate electrode sheet, and the regenerated lithium iron phosphate electrode sheet is washed three times with dimethyl carbonate, where the mass ratio of dimethyl carbonate to the regenerated lithium iron phosphate electrode sheet is 125:1; the washed regenerated lithium iron phosphate electrode sheet is placed in a blast drying oven and dried at 60 °C for 24 h to obtain the product.

[0058] Example 5

[0059] This example provides a method for preparing a regenerated electrode sheet of lithium iron phosphate from waste lithium-ion batteries, which directly regenerates the waste lithium iron phosphate electrode sheet to obtain a regenerated lithium iron phosphate electrode sheet. The specific steps are as follows:

[0060] (1) Positive electrode sheet collection: The complete and non-shorted waste lithium-ion battery is fully discharged, disassembled, washed 3 times with dimethyl carbonate (DMC) and dried at 60 °C for 24 h to obtain a waste lithium iron phosphate positive electrode sheet;

[0061] (2) Electrolyte preparation: Lithium hexafluorophosphate is selected as the electrolyte, and ethylene carbonate and diethyl carbonate are used as solvents; ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1:1, and then 5% of fluoroethylene carbonate by their volume is added. After being fully mixed evenly, an appropriate amount of lithium hexafluorophosphate is added to make the electrolyte concentration in the solution 1 M;

[0062] (3) Electrochemical regeneration: The waste lithium iron phosphate electrode sheet is used as the positive electrode, and the lithium metal sheet is used as the negative electrode. 50 μL of the electrolyte is added to assemble a CR2025 type button battery, where the mass ratio of the electrolyte to the active material of the lithium iron phosphate electrode sheet is 7 μL / mg -1 , the mass ratio of the lithium metal sheet to the waste lithium iron phosphate is 20:1; the button battery is discharged at a constant voltage of 0 V for 7 minutes, and after the discharge is completed, the button battery is disassembled to take out the regenerated lithium iron phosphate electrode sheet, and the regenerated lithium iron phosphate electrode sheet is washed three times with dimethyl carbonate, where the mass ratio of dimethyl carbonate to the regenerated lithium iron phosphate electrode sheet is 125:1; the washed regenerated lithium iron phosphate electrode sheet is placed in a blast drying oven and dried at 60 °C for 24 h to obtain the product.

[0063] Example 6

[0064] This example provides a method for preparing a regenerated electrode sheet of lithium iron phosphate from waste lithium-ion batteries, which directly regenerates the waste lithium iron phosphate electrode sheet to obtain a regenerated lithium iron phosphate electrode sheet. The specific steps are as follows:

[0065] (1) Positive electrode sheet collection: The complete and non-shorted waste lithium-ion battery is fully discharged, disassembled, washed 3 times with dimethyl carbonate (DMC) and dried at 60 °C for 24 h to obtain a waste lithium iron phosphate positive electrode sheet;

[0066] (2) Electrolyte preparation: Lithium hexafluorophosphate is selected as the electrolyte, and ethylene carbonate and diethyl carbonate are used as solvents; the solvents are prepared with ethylene carbonate and diethyl carbonate at a volume ratio of 1:1, and an appropriate amount of lithium hexafluorophosphate is added to make the electrolyte concentration in the solution 1 M;

[0067] (3) Electrochemical regeneration: The used lithium iron phosphate electrode is used as the positive electrode, and the lithium metal sheet is used as the negative electrode. 50 μL of the electrolyte is added to assemble a CR2025 coin cell, where the mass ratio of the electrolyte to the active material of the lithium iron phosphate electrode is 7 μL / mg -1 , and the mass ratio of the lithium metal sheet to the used lithium iron phosphate is 20:1; the coin cell is discharged at a constant voltage of 0 V for 2 minutes. After the discharge is completed, the coin cell is disassembled to take out the regenerated lithium iron phosphate electrode, and the regenerated lithium iron phosphate electrode is washed three times with dimethyl carbonate, where the mass ratio of dimethyl carbonate to the regenerated lithium iron phosphate electrode is 125:1; the washed and clean regenerated lithium iron phosphate electrode is placed in a blast drying oven and dried at 60 °C for 24 h to obtain the product.

[0068] Example 7

[0069] This example provides a method for preparing a regenerated electrode of lithium iron phosphate from used lithium-ion batteries, directly regenerating the used lithium iron phosphate electrode to obtain a regenerated lithium iron phosphate electrode, which specifically includes the following steps:

[0070] (1) Positive electrode sheet collection: The complete and non-shorted used lithium-ion battery is fully discharged, disassembled, washed 3 times with dimethyl carbonate (DMC) and dried at 60 °C for 24 h to obtain the used lithium iron phosphate positive electrode sheet;

[0071] (2) Electrolyte preparation: Lithium bis(trifluoromethanesulfonyl)imide is selected as the electrolyte, and ethylene glycol dimethyl ether and 1,3-dioxolane are used as solvents; the solvents are prepared with ethylene glycol dimethyl ether and 1,3-dioxolane at a volume ratio of 1:1, and an appropriate amount of lithium bis(trifluoromethanesulfonyl)imide is added to make the electrolyte concentration in the solution 1 M.

[0072] (3) Chemical regeneration: The used lithium iron phosphate electrode is used as the positive electrode, and the lithium metal sheet is used as the negative electrode. 50 μL of the electrolyte is dropped onto the lithium metal sheet, and the used lithium iron phosphate electrode is attached to the lithium metal sheet dropped with the electrolyte; where the mass ratio of the electrolyte to the active material of the lithium iron phosphate electrode is 7 μL / mg -1 , and the mass ratio of the lithium metal sheet to the used lithium iron phosphate is 20:1, and the attachment time is 7 minutes; after the chemical regeneration is completed, the regenerated lithium iron phosphate electrode is washed three times with ethylene glycol dimethyl ether, where the mass ratio of ethylene glycol dimethyl ether to the regenerated lithium iron phosphate electrode is 125:1. The washed and clean regenerated lithium iron phosphate electrode is placed in a blast drying oven and dried at 60 °C for 24 h to obtain the product.

[0073] Example 8

[0074] This embodiment provides a method for preparing a regenerated lithium iron phosphate electrode for waste lithium-ion batteries, which directly regenerates waste lithium iron phosphate electrodes to obtain regenerated lithium iron phosphate electrodes. The specific steps are as follows:

[0075] (1) Positive electrode sheet collection: Completely discharge, disassemble, wash three times with dimethyl carbonate (DMC), and dry at 60 °C for 24 h a complete and non-shorted waste lithium-ion battery to obtain a waste lithium iron phosphate positive electrode sheet;

[0076] (2) Electrolyte configuration: Select lithium bis(trifluoromethanesulfonyl)imide as the electrolyte, and ethylene glycol dimethyl ether and 1,3-dioxolane as the solvents; Configure the solvents with ethylene glycol dimethyl ether and 1,3-dioxolane at a volume ratio of 1:1, and add an appropriate amount of lithium bis(trifluoromethanesulfonyl)imide to make the electrolyte concentration in the solution 1 M;

[0077] (3) Electrochemical regeneration: Use the waste lithium iron phosphate electrode as the positive electrode and a lithium metal sheet as the negative electrode, add 50 μL of electrolyte to assemble a CR2025 type button battery, where the mass ratio of the electrolyte to the active material of the lithium iron phosphate electrode is 7 μL / mg -1 , and the mass ratio of the lithium metal sheet to the waste lithium iron phosphate is 20:1; Discharge the button battery at a constant voltage of 0 V for 7 minutes. After the discharge is completed, disassemble the button battery and take out the regenerated lithium iron phosphate electrode. Wash the regenerated lithium iron phosphate electrode three times with ethylene glycol dimethyl ether, where the mass ratio of ethylene glycol dimethyl ether to the regenerated lithium iron phosphate electrode is 125:1; Put the washed regenerated lithium iron phosphate electrode into a forced-air oven and dry at 60 °C for 24 h to obtain it.

[0078] Table 1 Process parameters of Examples 1-6

[0079]

[0080]

[0081] Application Example

[0082] This application example uses the above Examples 1-8 to prepare lithium-ion batteries. The specific steps are as follows:

[0083] (1) Preparation of the positive electrode sheet: Cut the dried regenerated lithium iron phosphate electrode sheet into a positive electrode sheet with a diameter of 8 mm.

[0084] (2) Graphite was used as the negative electrode, a single-layer polypropylene (PP) separator with a thickness of 25 μm, 1.0 M LiPF6 was used as the electrolyte, the solvent of the electrolyte was composed of ethylene carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of 1:1, and the electrolyte additive was fluoroethylene carbonate (FEC) with 5 Vol% of the solvent. The positive electrode sheet, separator, negative electrode sheet, electrolyte, gasket, spring piece, and positive and negative electrode cases were assembled into a CR2025 type button battery in a glove box filled with argon.

[0085] (3) During the charge-discharge test, the battery voltage range was 2.5 - 3.8 V. The first-cycle charge-discharge specific capacity of the positive electrode material was tested successively at a current density of 0.1 C, and the cycling performance at a current density of 0.2 C was also tested.

[0086] Experimental Example 1

[0087] The comparison chart of the first-cycle charge-discharge curves of the used lithium iron phosphate, commercial lithium iron phosphate (NE-000207 from Duoduo Chemical Reagent Network), and regenerated lithium iron phosphate in Example 1 is as Figure 1 shown. The first-cycle charge-discharge specific capacity of the regenerated lithium iron phosphate positive electrode sheet to the graphite negative electrode is significantly higher than that of the used lithium iron phosphate electrode sheet. The chemical regeneration method realizes the upgraded regeneration of the used lithium iron phosphate electrode sheet, forms lithium iron phosphate with a pre-lithiated phase while filling lithium vacancies, effectively compensates for the loss of active lithium in the first cycle of lithium iron phosphate to graphite, and has a higher specific capacity than commercial lithium iron phosphate. The comparison chart of the cycling performance of the used lithium iron phosphate, commercial lithium iron phosphate, and regenerated lithium iron phosphate in Example 1 is as Figure 2 shown, Figure 2 The comparison of the cycling performance also shows that the regenerated lithium iron phosphate has a higher specific capacity and capacity retention rate.

[0088] Experimental Example 2

[0089] According to the operation method of the foregoing application example, the regenerated lithium iron phosphate prepared in Examples 1 - 8 was used as the positive electrode material, and the prepared batteries were denoted as B1 - B8. At the same time, the used lithium iron phosphate active material before regeneration in Example 1 (i.e., the positive electrode active substance obtained in Step 2) was used as the positive electrode material, and the prepared battery was denoted as B9. The battery prepared with commercial lithium iron phosphate (NE-000207 from Duoduo Chemical Reagent Network) as the positive electrode material was denoted as B10.

[0090] In this experimental example, the first-cycle charge-discharge performance of lithium-ion batteries B1 - B10 at a current density of 0.1 C and the cycling performance at a current density of 0.2 C were tested. The first-cycle charge-discharge data are shown in Table 2, and the cycling performance data are shown in Table 3.

[0091] Table 2 First-cycle charge-discharge data of the battery at 0.1 C

[0092]

[0093] Table 3 Battery Cycle Performance Data

[0094]

[0095] As can be seen from Table 2 and Table 3 above, the regenerated lithium iron phosphate electrode sheets prepared by the present invention have good initial charge specific capacity and rate performance. This is because the chemical / electrochemical lithium supplementation method not only replenishes the missing lithium in the waste cathode material, but also promotes the embedding of excessive lithium elements into the lattice of lithium iron phosphate, forming a pre-lithiated lithium iron phosphate structure. The present invention can directly supplement lithium to the waste lithium iron phosphate electrode sheets, avoiding the cumbersome steps of stripping and crushing, and shortening the regeneration time; the excessive lithium metal provides a large chemical concentration gradient and sufficient electron donors, effectively reducing the lithium insertion activation energy and providing a driving force for lithium insertion, enabling the reaction to proceed spontaneously at room temperature. At the same time, the strong reducibility of lithium metal can promote the embedding of excessive lithium ions into the lattice of lithium iron phosphate, realizing the transformation of lithium iron phosphate to pre-lithiated lithium iron phosphate.

[0096] In summary, for the upgrading and regeneration method of the lithium iron phosphate electrode sheets of waste lithium ion batteries provided by the present invention, firstly, the waste electrode sheets are regenerated, effectively shortening the regeneration process, avoiding the operation of re-coating, and improving the resource utilization efficiency; secondly, lithium metal gives a spontaneous lithium insertion driving force, without the need to add external reducing agents, saving production costs and enhancing the regeneration efficiency; thirdly, the intrinsic strong reducibility of lithium metal can promote the embedding of excessive lithium ions into the lattice of lithium iron phosphate, thereby realizing the transformation of waste lithium iron phosphate to pre-lithiated lithium iron phosphate. The regenerated lithium iron phosphate electrode sheets can be directly put into use after washing and drying, greatly shortening the production cycle, and having strong practicability and good economic benefits.

[0097] The applicant declares that the present invention uses the above embodiments to illustrate the products and detailed preparation methods of the present invention, but the present invention is not limited to the above products and detailed preparation methods, that is, it does not mean that the present invention must rely on the above products and detailed preparation methods to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the products of the present invention, the addition of auxiliary material components, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0098] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple deformations can be made to the technical solutions of the present invention. These simple deformations all belong to the protection scope of the present invention.

[0099] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, without conflict, they can be combined in any appropriate manner. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0100] In addition, any combinations can also be made among various different embodiments of the present invention, as long as they do not violate the idea of the present invention, and they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing lithium iron phosphate regeneration pole pieces of waste lithium-ion batteries, characterized in that the steps include: S1. Collect positive electrode sheets from waste lithium iron phosphate batteries; S2, washing the waste lithium iron phosphate electrode sheet with an organic solvent and then drying it to obtain a waste lithium iron phosphate positive electrode sheet; S3, replenishing lithium on the waste lithium iron phosphate electrode by chemical regeneration method or electrochemical regeneration method at 20-30°C, and washing the electrode with organic solvent and drying the electrode after replenishing lithium.

2. The method for preparing a recycled lithium iron phosphate electrode from a waste lithium-ion battery according to claim 1, characterized in that: The collection method in step S1 includes: discharging the waste lithium-ion battery to 2V at a current of 0.1C for complete discharge, and disassembling and collecting the positive electrode sheets.

3. The method for preparing a recycled lithium iron phosphate electrode from a waste lithium-ion battery according to claim 1, characterized in that: The organic solvent includes at least one of dimethyl carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ethylene glycol dimethyl ether, fluoroethylene carbonate, and 1,3-dioxolane.

4. The method for preparing a recycled lithium iron phosphate electrode from a waste lithium-ion battery according to claim 1, characterized in that: The mass ratio of the organic solvent to the lithium iron phosphate electrode is ≥25:1, and the number of washing times is ≥3 times.

5. The method for preparing a recycled lithium iron phosphate electrode from a waste lithium-ion battery according to claim 1, characterized in that: The chemical regeneration method comprises the following steps: applying the waste lithium iron phosphate pole piece to a lithium metal sheet dripped with electrolyte, and maintaining it at 20-30°C for 2-30 minutes; the molar ratio of the lithium content in the lithium metal sheet to the lithium missing from the active material of the lithium iron phosphate pole piece is ≥2:1; the mass ratio of the electrolyte dosage to the active material of the lithium iron phosphate pole piece is ≥5μL / mg.

6. The method for preparing a recycled lithium iron phosphate electrode from a waste lithium-ion battery according to claim 1, characterized in that: The electrochemical regeneration method comprises the following steps: using the waste lithium iron phosphate pole piece as the positive electrode and the lithium metal sheet as the negative electrode, adding an electrolyte to assemble a button battery, and discharging at a constant voltage of 0V for 1-30 minutes at 20-30°C; the molar ratio of the lithium content in the lithium metal sheet to the lithium missing from the sheet-shaped positive electrode active material is ≥2:1; the mass ratio of the electrolyte dosage to the lithium iron phosphate pole piece active material is ≥5μL / mg.

7. The method for preparing a recycled lithium iron phosphate electrode from a waste lithium-ion battery according to claim 1, characterized in that: The drying conditions in steps S2 and S3 are drying at 60-90° C. for 4-24 hours.

8. The method for preparing lithium iron phosphate regeneration pole pieces of waste lithium ion batteries according to any one of claims 4 or 5, characterized in that: The electrolyte in the electrolyte solution includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium dioxalatoborate; and the electrolyte concentration is 0.1-2M.

9. The method for preparing lithium iron phosphate regeneration pole pieces of waste lithium ion batteries according to any one of claims 4 or 5, characterized in that: The solvent in the electrolyte includes at least one of ethylene carbonate, dimethyl carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ethylene glycol dimethyl ether, fluoroethylene carbonate, and 1,3-dioxolane.

10. A recycled lithium iron phosphate electrode for waste lithium-ion batteries, characterized in that: The waste lithium iron phosphate regeneration electrode is prepared by the method for preparing the waste lithium ion battery lithium iron phosphate regeneration electrode according to any one of claims 1 to 7.

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