Electrolyte for electrochemical repair of lithium battery and preparation method therefor, electrochemical repair and regeneration method, and recycling method

Abstract

An electrolyte for electrochemical repair of a lithium battery and a preparation method therefor, an electrochemical repair and regeneration method, and a recycling method, relating to the technical field of resource recycling and regeneration. Raw materials of the electrolyte for electrochemical repair of the lithium battery comprise: a lithium salt, an aromatic agent, a stabilizing additive and a solvent, the final concentration of the lithium salt in the electrolyte is 0.1-15 g / L, the final concentration of the stabilizing additive is 0.1-5 g / L, and a mass ratio of the lithium salt to the aromatic agent is (1-5):(1-5). The electrolyte can improve the effect of repair and regeneration. When the electrolyte is used for electrochemical repair, a decommissioned battery does not need to be destroyed, no additional impurities are introduced, and indexes of an electrode sheet, such as the powder resistance and compaction density would not deteriorate. An electrochemical reaction has high current efficiency.

Description

Electrolyte for electrochemical repair of lithium battery, preparation method thereof, electrochemical repair regeneration method and recycling method Technical Field

[0001] The present disclosure relates to the field of resource recovery and regeneration technology, and in particular to an electrolyte for electrochemical repair of a lithium battery, a preparation method thereof, an electrochemical repair and regeneration method, and a reuse method thereof. Background Art

[0002] Lithium iron phosphate (LiFePO4) is the cathode material for lithium-ion batteries, currently the most widely used in the market. Due to its relatively low price, high energy density, excellent safety, and cycling stability, LiFePO4 batteries are widely used in electric vehicles and energy storage systems. With the implementation of China's "dual carbon" strategy, the new energy vehicle and energy storage markets are expected to grow rapidly. However, the lifespan of lithium-ion batteries is estimated to be 15 to 20 years, while the power batteries in new energy vehicles typically have a lifespan of only 3 to 5 years. TrendForce predicts that by 2030, the global recycling volume for power and energy storage batteries will exceed 1TWh, of which LiFePO4 batteries will account for over 58% (approximately 580GWh). This large number of retired batteries not only creates environmental pressure but also represents a significant waste of resources. Therefore, effective recycling and reuse of LiFePO4 batteries is both essential for environmental protection and a key component of resource recycling.

[0003] Currently, the recycling and reuse of lithium iron phosphate batteries primarily involves two aspects: resource recovery, which involves separating and recovering the more valuable lithium, phosphorus, and iron in lithium iron phosphate through wet dissolution and precipitation, or pyrolysis and sintering to separate the different elemental components for recycling. The second aspect is lithium iron phosphate regeneration, which involves directly recycling retired lithium iron phosphate electrodes through chemical reactions. Direct lithium iron phosphate regeneration offers a shorter process and higher economic value, making it a key option for lithium iron phosphate recycling. Since lithium iron phosphate failure or performance degradation is primarily caused by lithium loss and the occupation of lithium vacancies by iron in the electrode, the key to its repair lies in lithium replenishment and defect repair. Kunming University of Science and Technology has achieved lithium iron phosphate regeneration through pre-oxidation, lithium replenishment, and V5+ doping, using a solid-phase sintering method. However, solid-phase sintering requires precise calculation of the replenishment lithium content, and high-temperature sintering consumes a lot of energy. Therefore, the search for simpler, more efficient, and economical regeneration methods is crucial.

[0004] In order to solve the problems of accurate lithium replenishment and high energy consumption, the solutions currently used are hydrothermal method and three-electrode electrochemical method. Both methods do not require accurate calculation of the lithium loss of retired and failed lithium iron phosphate. At the same time, the reaction conditions are relatively mild and do not require long-term high-temperature heat treatment. However, the hydrothermal method requires a specific reactor and a high-pressure environment, while the three-electrode electrochemical method requires a specific three-electrode device, which hinders its practical application and industrialization. In addition, whether it is solid-phase sintering or hydrothermal method, the three-electrode electrochemical method requires the electrode to be peeled off the current collector and the binder to be pre-treated to remove the binder, so that the obtained powder will introduce new metal impurities (current collector) and cause waste of binder, etc. In addition, the lithium iron phosphate repaired by the above method will also change its physical and chemical indicators, such as compaction density, resistivity and specific surface area, and may not meet customer requirements after repair.

[0005] In view of this, the present disclosure is proposed.

[0006] Summary of the Invention

[0007] The present invention aims to provide an electrolyte for electrochemical repair of lithium batteries, a preparation method thereof, an electrochemical repair and regeneration method, and a recycling method thereof.

[0008] The present disclosure is achieved as follows:

[0009] In a first aspect, the present disclosure provides an electrolyte for electrochemical repair of lithium batteries, the raw materials of which include: lithium salt, aromatic agent, stabilizing additive and solvent, the final concentration of the lithium salt in the electrolyte is 0.1 to 15 g / L, the final concentration of the stabilizing additive is 0.1 to 5 g / L, and the mass ratio of the lithium salt to the aromatic agent is (1-5): (1-5).

[0010] In an optional embodiment, the lithium salt includes at least one of lithium chloride, lithium sulfate, lithium bromide, lithium iodide and lithium nitrate.

[0011] In an optional embodiment, the fragrance includes at least one of benzaldehyde, phenol, pyrrole, pyridine, 1,3-diphenol, benzhydrylamine, dimethylbenzamide and 2-sulfobenzoic acid.

[0012] In an optional embodiment, the stabilizing additive includes at least one of benzoic acid, sorbic acid, ethyl nepal gold ester, propyl nepal gold ester and p-hydroxybenzene.

[0013] In an optional embodiment, the solvent is at least one of water, ethylene glycol, glycerol and isopropyl alcohol.

[0014] In a second aspect, the present disclosure provides a method for preparing an electrolyte for electrochemical repair of a lithium battery, which comprises uniformly mixing raw materials of the electrolyte for electrochemical repair of a lithium battery as described in any one of the aforementioned embodiments.

[0015] In an optional embodiment, after the raw materials are mixed, the mixture is further reacted at 60-150° C. for 2-8 hours.

[0016] In a third aspect, the present disclosure provides an electrochemical repair and regeneration method for a lithium battery, comprising:

[0017] Disassemble the retired lithium battery after discharge and remove the positive electrode and graphite electrode;

[0018] Cleaning, drying and rolling the positive electrode sheet and the graphite electrode sheet;

[0019] Placing the treated positive electrode sheet and the graphite electrode sheet in an electrolytic cell, and connecting the electrolytic cell to a power source; wherein the electrolytic cell contains the electrochemical repair electrolyte as described in any one of the aforementioned embodiments, and taking them out after charging is completed;

[0020] The charged positive electrode sheet and the graphite electrode sheet are cleaned, dried and roller-pressed.

[0021] In an optional embodiment, during the charging process, constant current mode charging is performed first, and then constant voltage mode charging is performed.

[0022] In an optional embodiment, the current density during constant current mode charging is 0.1-2C, and the voltage range is 0-0.5V.

[0023] In an optional embodiment, when the voltage reaches 0.1-4V, charging is performed in the constant voltage mode, and charging is continued until the current density reaches 0.004-0.006C.

[0024] In an optional embodiment, the positive electrode plate is connected to the cathode of the electrolytic cell, and the graphite electrode plate is connected to the anode of the electrolytic cell.

[0025] In an optional embodiment, the drying temperature for drying the cleaned positive electrode sheet and the cleaned graphite electrode sheet before and after charging is 60-150° C., and the drying time is 1-24 hours.

[0026] In an optional embodiment, the pressure of rolling the cleaned positive electrode sheet and the graphite electrode sheet before and after charging is 4-6T.

[0027] In an optional embodiment, cleaning the positive electrode plate and the graphite plate before charging includes first cleaning with AB liquid and then cleaning with deionized water, wherein liquid A is at least one of EC, DEC and DMC, and liquid B is at least one of anhydrous ethanol, acetone, methanol and acetic acid.

[0028] In an optional embodiment, the volume ratio of the A liquid to the B liquid in the AB liquid is (1-5): (1-5).

[0029] In an optional embodiment, the positive electrode plate and the graphite electrode plate are cleaned 1-3 times before charging.

[0030] In an optional embodiment, the discharging includes immersing the retired lithium battery in a salt solution, and the electrolyte of the salt solution includes an inorganic electrolyte and an organic electrolyte.

[0031] In an optional embodiment, the final concentration of the inorganic electrolyte is 0.1 to 100 g / L, and the final concentration of the organic electrolyte is 0.1 to 100 g / L.

[0032] In an optional embodiment, the inorganic electrolyte is at least one of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium nitrate and potassium nitrate.

[0033] In an optional embodiment, the organic electrolyte includes at least one of ethylamine, dimethylamine, trimethylamine, acetic acid, propionic acid, benzoic acid, acetone, acetaldehyde, ethyl acetate, methyl formate, ethyl ether, propyl ether, cresol and phenol.

[0034] In an optional embodiment, the retired lithium battery includes at least one of lithium iron phosphate, lithium iron manganese phosphate and nickel cobalt manganese iron lithium.

[0035] In a second aspect, the present disclosure provides a method for recycling a lithium battery, which includes the electrochemical repair and regeneration method of a lithium battery as described in any of the aforementioned embodiments, and also includes reassembling the repaired positive electrode sheet and graphite electrode sheet into a battery.

[0036] The present disclosure has the following beneficial effects:

[0037] The electrolyte for electrochemical repair of lithium batteries provided by the present disclosure is prepared by compounding lithium salts, aromatics, and stabilizing additives, wherein the lithium salt provides the missing lithium in the lithium iron phosphate; the aromatics contain unsaturated bonds and act as a reducing agent during the repair process; and the stabilizing additives can protect the trivalent iron from being oxidized again during the repair process and stabilize the electrolyte. The lithium salt and the aromatics can react to form a complex, which is conducive to adsorption on the positive electrode during subsequent electrochemical repair, thereby improving the repair and regeneration effect. The electrolyte can be recycled. When the lithium concentration in the electrolyte decreases, it is only necessary to replenish the corresponding lithium salts and aromatics to restore the initial concentration. The electrolyte does not need to be replaced and wasteful. It should be further explained that the electrochemical repair and regeneration method of lithium batteries provided by the present disclosure does not require violent destruction of retired batteries. It is only necessary to disassemble the outer shell and completely remove the positive and negative electrodes of the battery. Even the diaphragm can be recycled and reused if it is not damaged. There is no need to sort the current collector later, that is, the current collector and the black powder of the electrode are recycled and reused simultaneously. The device is simple and easy to expand. It can be implemented with an ordinary electrolytic cell. For wound batteries, it is only necessary to lengthen the electrolytic cell. No additional impurities are introduced. Since there is no need to peel the lithium iron phosphate black powder from the surface of the current collector, there is no risk of aluminum being introduced by mechanical scratching. Indicators such as the powder resistance and compaction density of the electrode will not deteriorate. In addition, the electrochemical repair and regeneration method of the lithium battery provided by the present disclosure does not require high-temperature heat treatment, nor does it require high-voltage resistance for hydrothermal reactions. At the same time, the current efficiency of the electrochemical reaction is high. DETAILED DESCRIPTION

[0038] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0039] The present disclosure provides an electrolyte for electrochemical repair of a lithium battery, the raw materials of which include lithium salt, aromatic agent, stabilizing additive and solvent.

[0040] The solvent is used to dissolve lithium salt, aromatic agent and stabilizing additive. The final concentration of lithium salt in the electrolyte is 0.1-15 g / L, the final concentration of stabilizing additive is 0.1-5 g / L, and the mass ratio of lithium salt to aromatic agent is (1-5): (1-5).

[0041] The lithium salts in the present disclosure include, but are not limited to, at least one of lithium sulfate, lithium bromide, lithium iodide, and lithium nitrate. Aromatic agents include, but are not limited to, at least one of benzaldehyde, phenol, pyrrole, pyridine, 1,3-diphenol, benzhydrylamine, dimethylbenzamide, and 2-sulfobenzoic acid. Stabilizing additives include, but are not limited to, at least one of benzoic acid, sorbic acid, ethyl nepal gold ester, propyl nepal gold ester, and p-hydroxybenzene. Solvents include, but are not limited to, at least one of water, ethylene glycol, glycerol, and isopropyl alcohol.

[0042] The preparation method is simple, and only requires mixing lithium salt, aromatic agent, stabilizing additive and solvent and reacting them at 60-150° C. for 2-8 hours to obtain the electrolyte.

[0043] The electrolyte disclosed in the present invention is prepared by compounding lithium salts, aromatics, and stabilizing additives, wherein the lithium salts provide the lithium missing in the lithium iron phosphate; the aromatics contain unsaturated bonds and act as a reducing agent during the repair process; the stabilizing additives can protect the trivalent iron from being oxidized again during the repair process, while stabilizing the electrolyte. The lithium salts and aromatics can react to form a complex, which is conducive to adsorption on the positive electrode during subsequent electrochemical repair, thereby improving the repair and regeneration effect. The electrolyte can be recycled. When the concentration of lithium in the electrolyte decreases, it is only necessary to supplement the corresponding lithium salts and aromatics to restore the initial concentration. The electrolyte does not need to be replaced to cause waste.

[0044] Furthermore, the present disclosure provides an electrochemical repair and regeneration method for a lithium battery, which comprises the following steps:

[0045] After discharge, the retired lithium batteries are disassembled and the positive electrode sheets and graphite sheets are taken out; the positive electrode sheets and graphite sheets are cleaned multiple times, dried and subjected to roller pressing; the cleaned positive electrode sheets and graphite sheets are connected to the power supply of the electrolytic cell, which contains electrolyte, and are taken out after charging is completed; the charged positive electrode sheets and graphite sheets are cleaned multiple times, dried and subjected to roller pressing.

[0046] Next, this disclosure explains each step one by one:

[0047] S1. Disassemble the retired lithium battery after discharge and remove the positive electrode and graphite electrode.

[0048] Specifically, a salt solution is prepared. The vents of the retired batteries are opened and the retired lithium batteries are immersed in the salt solution until completely submerged. After three days of complete discharge, the retired batteries are removed and rinsed three times with deionized water. The casing and aluminum-plastic film of the retired batteries are removed, and the positive electrode, graphite electrode, and separator inside are removed. The graphite electrode, lithium iron phosphate electrode, and separator are then separated.

[0049] The electrolytes in the salt solution include inorganic electrolytes and organic electrolytes. The final concentration of the inorganic electrolyte is 0.1 to 100 g / L, and the final concentration of the organic electrolyte is 0.1 to 100 g / L. The inorganic electrolyte is at least one of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium nitrate, and potassium nitrate. The organic electrolyte includes at least one of ethylamine, dimethylamine, trimethylamine, acetic acid, propionic acid, benzoic acid, acetone, acetaldehyde, ethyl acetate, methyl formate, ethyl ether, propyl ether, cresol, and phenol.

[0050] In the present disclosure, by adding an organic electrolyte, the retired battery can be ensured to discharge smoothly and internal short circuit burning damage can be reduced.

[0051] S2. Clean the positive electrode sheet and the graphite electrode sheet multiple times, dry them and perform roller pressing.

[0052] First, use AB solution for cleaning, followed by deionized water. Liquid A is at least one of EC, DEC, and DMC, and liquid B is at least one of anhydrous ethanol, acetone, methanol, and acetic acid. The volume ratio of liquid A to liquid B in the AB solution is (1-5):(1-5). In the present disclosure, using AB solution first for cleaning can achieve better cleaning results. The number of cleaning cycles is 1-3.

[0053] After cleaning, the product is dried at a temperature of 60-150°C and a drying time of 1-24 hours.

[0054] After drying, the dried positive electrode sheets and graphite sheets are subjected to roller pressing treatment with a roller pressing pressure of 4-6T. The roller pressing treatment can strengthen the bonding strength of the positive electrode sheets.

[0055] S3. Pour the electrolyte into the electrolytic cell, connect the cleaned positive electrode and graphite electrode to the power supply of the electrolytic cell, and take them out after charging is completed.

[0056] The lithium iron phosphate is connected to the cathode of the electrolytic cell, and the graphite electrode is connected to the anode of the electrolytic cell. During the charging process, constant current mode charging is first performed, and then constant voltage mode charging is performed.

[0057] The current density during constant current mode charging is 0.1-2C, and the voltage range is 0-0.5V. When the voltage reaches 0.1-4V, constant voltage mode charging is adopted, and charging is continued until the current density reaches 0.004-0.006C.

[0058] S4. Clean the charged positive electrode sheet and graphite electrode sheet multiple times, dry them and perform roller pressing.

[0059] After charging, the positive electrode and graphite electrodes can be directly cleaned with deionized water, and then dried at 60-150°C for 1-24 hours. After drying, the dried positive electrode and graphite electrodes are roller-pressed at a pressure of 4-6T. The roller-pressing process can strengthen the bonding strength of the positive electrode electrodes.

[0060] The present disclosure also provides a method for recycling lithium batteries, which includes the electrochemical repair and regeneration method of the above-mentioned lithium battery, and also includes reassembling the repaired positive electrode plate and graphite electrode plate into a battery.

[0061] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0062] Example 1

[0063] This embodiment provides an electrochemical repair and regeneration method for a lithium battery (lithium iron phosphate), which includes the following steps:

[0064] S1. Prepare a mixed solution of 5g / L sodium chloride and 5g / L ethylamine, open the vent of the retired battery, and completely immerse the retired lithium iron phosphate battery in the solution. After 3 days of complete discharge, remove the retired battery and rinse it with deionized water 3 times; remove the casing, aluminum-plastic film, etc. of the retired battery, remove the lithium iron phosphate electrode, graphite electrode and diaphragm inside, and separate the graphite electrode, lithium iron phosphate electrode and diaphragm;

[0065] S2. Wash the disassembled lithium iron phosphate electrode and graphite electrode with EC, DEC and anhydrous ethanol solution in a volume ratio of 1:1:1 three times, and recycle the cleaning liquid for reuse. Rinse the electrode after AB solution with deionized water three times and recycle the cleaning water. Dry the cleaned lithium iron phosphate electrode and graphite electrode in a vacuum oven at 80℃ for 2h, take out and lay flat and roll under 5T pressure;

[0066] S3. Prepare electrolyte: lithium chloride (1.0 g / L) and phenol in a mass ratio of 1:1, sorbic acid concentration of 0.2 g / L, water as solvent, and mix and stir at 80°C for 2 h.

[0067] S4. Connect the tabs of the rolled lithium iron phosphate electrode and graphite electrode to the negative and positive electrodes of the electrolytic cell power supply respectively, while the electrode pieces are immersed in the electrolyte. When charging, first charge in constant current mode with a current density of 0.1C and a voltage range of 0-0.3V; when the voltage reaches 0.3V, switch to constant voltage mode and continue charging until the current density reaches 0.005C.

[0068] S5. Rinse the charged lithium iron phosphate electrode and graphite electrode in deionized water three times. Recycle the cleaning solution and electrolytic bath solution. Dry the cleaned electrode in a vacuum drying oven at 80°C for 2 hours, take it out and lay it flat on the roller under 5T pressure.

[0069] S6. Reassemble the lithium iron phosphate electrode and the graphite electrode obtained after the repair in S5 into a battery, and test its charge and discharge capacity, initial coulombic efficiency, and rate performance;

[0070] Example 2

[0071] This embodiment provides an electrochemical repair and regeneration method for a lithium battery (lithium iron phosphate), which includes the following steps:

[0072] S1. Prepare a mixed solution of 10g / L sodium carbonate and 1g / L ethylamine, open the vent of the retired battery, and completely immerse the retired lithium iron phosphate battery in the solution. After 3 days of complete discharge, remove the retired battery and rinse it with deionized water 3 times; remove the casing, aluminum-plastic film, etc. of the retired battery, remove the lithium iron phosphate electrode, graphite electrode and diaphragm inside, and separate the graphite electrode, lithium iron phosphate electrode and diaphragm;

[0073] S2. Wash the disassembled lithium iron phosphate electrode and graphite electrode with EC, DMC and anhydrous ethanol solution in a volume ratio of 1:1:1 three times, and recycle the cleaning liquid for reuse. Rinse the electrode after AB solution with deionized water three times and recycle the cleaning water. Dry the cleaned lithium iron phosphate electrode and graphite electrode in a vacuum oven at 80℃ for 2h, take out and lay flat and roll under 5T pressure;

[0074] S3. Prepare electrolyte: lithium chloride (1.0 g / L) and phenol in a mass ratio of 1:2, sorbic acid concentration of 0.2 g / L, water as solvent, and mix and stir at 80°C for 2 h.

[0075] S4. Connect the tabs of the rolled lithium iron phosphate electrode and graphite electrode to the negative and positive electrodes of the electrolytic cell power supply respectively, and immerse the electrode in a 2g / L lithium chloride solution. When charging, first perform constant current mode charging with a current density of 0.1C and a voltage range of 0-0.5V; when the voltage reaches 0.5V, switch to constant voltage mode charging and continue charging until the current density reaches 0.005C.

[0076] S5. Rinse the charged lithium iron phosphate electrode and graphite electrode in deionized water three times. Recycle the cleaning solution and electrolytic bath solution. Dry the cleaned electrode in a vacuum drying oven at 80°C for 2 hours, take it out and lay it flat on the roller under 5T pressure.

[0077] S6. Reassemble the lithium iron phosphate electrode and the graphite electrode obtained after the repair in S5 into a battery, and test its charge and discharge capacity, initial coulombic efficiency, and rate performance;

[0078] Example 3

[0079] This embodiment provides an electrochemical repair and regeneration method for a lithium battery (lithium iron phosphate), which includes the following steps:

[0080] S1. Prepare 10g / L of a mixed solution of sodium carbonate, sodium chloride, and 2g / L of ethylamine in a mass ratio of 1:1:1. Open the vent of the retired battery and completely immerse the retired lithium iron phosphate battery in the solution. After 3 days of complete discharge, remove the retired battery and rinse it 3 times with deionized water. Remove the shell, aluminum-plastic film, etc. of the retired battery, remove the lithium iron phosphate electrode, graphite electrode, and diaphragm inside, and separate the graphite electrode, lithium iron phosphate electrode, and diaphragm.

[0081] S2. Wash the disassembled lithium iron phosphate electrode and graphite electrode twice with EC, DEC and acetone solution with a volume ratio of 1:1:1, and recycle the cleaning solution for reuse. Rinse the electrode after AB solution with deionized water twice and recycle the cleaning water. Dry the cleaned lithium iron phosphate electrode and graphite electrode in a vacuum oven at 100℃ for 2h, take out and lay flat and roll under 5T pressure;

[0082] S3. Prepare electrolyte: lithium bromide (2.0 g / L) and phenol in a mass ratio of 1:1, sorbic acid concentration of 0.2 g / L, water as solvent, and mix and stir at 80°C for 2 h.

[0083] S4. Connect the tabs of the rolled lithium iron phosphate electrode and graphite electrode to the negative and positive electrodes of the electrolytic cell power supply, respectively. At the same time, immerse the electrode in 2g / L of the electrolyte prepared in step S3 at a ratio of 1:1. When charging, first perform constant current mode charging with a current density of 0.1C and a voltage range of 0-0.5V. When the voltage reaches 0.5V, switch to constant voltage mode charging and continue charging until the current density reaches 0.005C.

[0084] S5. Rinse the charged lithium iron phosphate electrode and graphite electrode in deionized water three times. Recycle the cleaning solution and electrolytic bath solution. Dry the cleaned electrode in a vacuum drying oven at 100°C for 2 hours, take it out and lay it flat on the roller under 5T pressure.

[0085] S6. Reassemble the lithium iron phosphate electrode and the graphite electrode obtained after the repair in S5 into a battery, and test its charge and discharge capacity, initial coulombic efficiency, and rate performance;

[0086] Example 4

[0087] This embodiment provides an electrochemical repair and regeneration method for a lithium battery (lithium iron phosphate), which includes the following steps:

[0088] S1. Prepare a solution of 5g / L potassium chloride and 1g / L acetic acid, open the vent of the retired battery, and completely immerse the retired lithium iron phosphate battery in the solution. After 3 days of complete discharge, remove the retired battery and rinse it 3 times with deionized water; remove the casing, aluminum-plastic film, etc. of the retired battery, remove the lithium iron phosphate electrode, graphite electrode and diaphragm inside, and separate the graphite electrode, lithium iron phosphate electrode and diaphragm;

[0089] S2. Wash the disassembled lithium iron phosphate electrode and graphite electrode three times with EC solution and acetone in a volume ratio of 1:1, and recycle the cleaning solution for reuse. Rinse the electrode after AB solution with deionized water three times and recycle the cleaning water. Dry the cleaned lithium iron phosphate electrode and graphite electrode in a vacuum oven at 80℃ for 2 hours, take out and lay flat and roll-press at 5T pressure;

[0090] S3. Prepare electrolyte: lithium bromide (2.0 g / L) and dimethylbenzamide in a mass ratio of 1:2, benzoic acid concentration of 0.5 g / L, water as solvent, prepare electrolyte, mix and stir at 100 ° C for 2 h.

[0091] S4. Connect the tabs of the rolled lithium iron phosphate electrode and graphite electrode to the negative and positive electrodes of the electrolytic cell power supply, respectively, while the electrode pieces are immersed in the electrolyte in step S3. When charging, first perform constant current mode charging with a current density of 0.5C and a voltage range of 0-0.3V; when the voltage reaches 0.3V, switch to constant voltage mode charging and continue charging until the current density reaches 0.005C.

[0092] S5. Rinse the charged lithium iron phosphate electrode and graphite electrode in deionized water three times. Recycle the cleaning solution and electrolytic bath solution. Dry the cleaned electrode in a vacuum drying oven at 80°C for 2 hours, take it out and lay it flat on the roller under 5T pressure.

[0093] S6. Reassemble the lithium iron phosphate electrode and the graphite electrode obtained after the repair in S5 into a battery, and test its charge and discharge capacity, initial coulombic efficiency, and rate performance;

[0094] Example 5

[0095] This embodiment provides an electrochemical repair and regeneration method for a lithium battery (lithium iron phosphate), which includes the following steps:

[0096] S1. Prepare a solution of 10g / L sodium chloride and 2g / L acetic acid, open the vent of the retired battery, and completely immerse the retired lithium iron phosphate battery in the solution. After 3 days of complete discharge, remove the retired battery and rinse it 3 times with deionized water; remove the casing, aluminum-plastic film, etc. of the retired battery, remove the lithium iron phosphate electrode, graphite electrode and diaphragm inside, and separate the graphite electrode, lithium iron phosphate electrode and diaphragm;

[0097] S2. Wash the disassembled lithium iron phosphate electrode and graphite electrode with EC, DEC and acetone solution with a volume ratio of 1:1:2 three times, and recycle the cleaning solution for reuse. Rinse the electrode after AB solution with deionized water three times and recycle the cleaning water. Dry the cleaned lithium iron phosphate electrode and graphite electrode in a vacuum oven at 100℃ for 4 hours, take out and lay flat and roll under 5T pressure;

[0098] S3. Prepare electrolyte: lithium nitrate (2.0 g / L) and dimethylbenzamide in a mass ratio of 1:1, benzoic acid concentration of 0.5 g / L, and ethylene glycol as solvent. Mix and stir at 100°C for 2 h.

[0099] S4. Connect the tabs of the rolled lithium iron phosphate electrode and graphite electrode to the negative and positive electrodes of the electrolytic cell power supply respectively, and immerse the electrode in a 2g / L lithium nitrate solution. When charging, first perform constant current mode charging with a current density of 0.2C and a voltage range of 0-0.8V; when the voltage reaches 0.8V, switch to constant voltage mode charging and continue charging until the current density reaches 0.005C.

[0100] S5. Rinse the charged lithium iron phosphate electrode and graphite electrode in deionized water three times. Recycle the cleaning solution and electrolytic bath solution. Dry the cleaned electrode in a vacuum drying oven at 100°C for 4 hours, take it out and lay it flat on the roller under 5T pressure.

[0101] S6. Reassemble the lithium iron phosphate electrode and the graphite electrode obtained after the repair in S5 into a battery, and test its charge and discharge capacity, initial coulombic efficiency, and rate performance;

[0102] Example 6

[0103] This embodiment provides an electrochemical repair and regeneration method for a lithium battery (lithium iron phosphate), which includes the following steps:

[0104] S1. Prepare a 10g / L sodium carbonate and 0.5g / L methyl formate solution, open the vent of the retired battery, and completely immerse the retired lithium iron phosphate battery in the solution. After 3 days of complete discharge, remove the retired battery and rinse it 3 times with deionized water; remove the casing, aluminum-plastic film, etc. of the retired battery, remove the lithium iron phosphate electrode, graphite electrode and diaphragm inside, and separate the graphite electrode, lithium iron phosphate electrode and diaphragm;

[0105] S2. Wash the disassembled lithium iron phosphate electrode and graphite electrode three times with a solution of EC, DMC and anhydrous ethanol in a volume ratio of 1:1:3, and recycle the cleaning solution for reuse. Rinse the electrode after AB solution with deionized water three times and recycle the cleaning water. Dry the cleaned lithium iron phosphate electrode and graphite electrode in a vacuum oven at 80℃ for 8 hours, take out and lay flat and roll under 5T pressure;

[0106] S3. Prepare electrolyte: lithium bromide (2.0 g / L) and dimethylbenzamide in a mass ratio of 2:1, benzoic acid concentration of 1.0 g / L, and ethylene glycol as solvent. Mix and stir at 100°C for 2 h.

[0107] S4. Connect the tabs of the rolled lithium iron phosphate electrode and graphite electrode to the negative and positive electrodes of the electrolytic cell power supply, respectively, while the electrode pieces are immersed in the electrolyte in step S3. When charging, first perform constant current mode charging with a current density of 0.1C and a voltage range of 0-1.2V; when the voltage reaches 1.2V, switch to constant voltage mode charging and continue charging until the current density reaches 0.005C.

[0108] S5. Rinse the charged lithium iron phosphate electrode and graphite electrode in deionized water three times. Recycle the cleaning solution and electrolytic bath solution. Dry the cleaned electrode in a vacuum drying oven at 80°C for 8 hours, take it out and lay it flat on the roller under 5T pressure.

[0109] S6. Reassemble the lithium iron phosphate electrode and the graphite electrode obtained after the repair in S5 into a battery, and test its charge and discharge capacity, initial coulombic efficiency, and rate performance;

[0110] Example 7

[0111] This embodiment provides an electrochemical repair and regeneration method for a lithium battery (lithium manganese iron phosphate), which includes the following steps:

[0112] S1. Prepare 15g / L of a mixed solution of sodium chloride, sodium carbonate, sodium sulfate, and 2g / L of acetone in a mass ratio of 1:1:1:1. Open the vent of the retired battery and completely immerse the retired lithium iron manganese phosphate in the solution. After 3 days of complete discharge, remove the retired battery and rinse it 3 times with deionized water. Remove the casing, aluminum-plastic film, etc. of the retired battery, remove the lithium iron manganese phosphate electrode, graphite electrode, and diaphragm inside, and separate the graphite electrode, lithium iron phosphate electrode, and diaphragm.

[0113] S2. Wash the disassembled lithium manganese iron phosphate electrode and graphite electrode three times with EC, DEC, DMC and anhydrous ethanol solution with a volume ratio of 1:1:1:3, and recover the cleaning solution for reuse. Rinse the electrode after cleaning with AB solution three times with deionized water and recover the cleaning water. Dry the cleaned lithium manganese iron phosphate electrode and graphite electrode in a vacuum oven at 120℃ for 2h, take out and lay flat and roll under 5T pressure;

[0114] S3. Prepare electrolyte: lithium bromide (2.0 g / L) and dimethylbenzamide in a mass ratio of 2:1, benzoic acid concentration of 1.0 g / L, and ethylene glycol as solvent. Mix and stir at 100°C for 2 h.

[0115] S4. Connect the tabs of the rolled lithium manganese iron phosphate electrode and the graphite electrode to the negative and positive electrodes of the electrolytic cell power supply respectively, and immerse the electrode in a 3g / L lithium hexafluorophosphate solution (the solvent is an EC / DEC solution with a volume ratio of 1:1). When charging, first perform constant current mode charging with a current density of 0.1C and a voltage range of 0-3.6V; when the voltage reaches 3.6V, switch to constant voltage mode charging and continue charging until the current density reaches 0.005C;

[0116] S5. Rinse the charged lithium manganese iron phosphate electrode and graphite electrode in deionized water three times. Recycle the cleaning solution and electrolytic bath solution. Dry the cleaned electrode in a vacuum drying oven at 120°C for 2 hours, remove it, lay it flat, and roll it under 5T pressure.

[0117] S6. Reassemble the lithium manganese iron phosphate electrode and the graphite electrode obtained after the repair in S5 into a battery, and test its charge and discharge capacity, initial coulombic efficiency and rate performance;

[0118] Example 8

[0119] This embodiment provides an electrochemical repair and regeneration method for a lithium battery (lithium iron phosphate), which includes the following steps:

[0120] S1. Prepare 10g / L of a mixed solution of sodium carbonate, potassium carbonate, and 5g / L of phenol in a mass ratio of 1:1. Open the vent of the retired battery and completely immerse the retired lithium iron phosphate battery in the solution. After 3 days of complete discharge, remove the retired battery and rinse it with deionized water 3 times. Remove the casing, aluminum-plastic film, etc. of the retired battery, remove the lithium iron phosphate electrode, graphite electrode, and diaphragm inside, and separate the graphite electrode, lithium iron phosphate electrode, and diaphragm.

[0121] S2. Wash the disassembled lithium iron phosphate electrode and graphite electrode with EC, DMC and acetone solution in a volume ratio of 2:2:1 three times, and recycle the cleaning solution for reuse. Rinse the electrode after AB solution with deionized water three times and recycle the cleaning water. Dry the cleaned lithium iron phosphate electrode and graphite electrode in a vacuum oven at 100℃ for 4 hours, take out and lay flat and roll-press at 5T pressure;

[0122] S3. Prepare electrolyte: lithium bromide (2.0 g / L) and pyrrole in a mass ratio of 2:3, sorbic acid concentration of 1.0 g / L, and ethylene glycol as solvent. Mix and stir at 100°C for 4 h.

[0123] S4. Connect the tabs of the rolled lithium iron phosphate electrode and graphite electrode to the negative and positive electrodes of the electrolytic cell power supply, respectively, while the electrode pieces are immersed in the electrolyte in step S3. When charging, first perform constant current mode charging with a current density of 0.2C and a voltage range of 0-0.3.6V; when the voltage reaches 3.6V, switch to constant voltage mode charging and continue charging until the current density reaches 0.005C.

[0124] S5. Rinse the charged lithium iron phosphate electrode and graphite electrode in deionized water three times. Recycle the cleaning solution and electrolytic bath solution. Dry the cleaned electrode in a vacuum drying oven at 100°C for 4 hours, take it out and lay it flat on the roller under 5T pressure.

[0125] S6. Reassemble the lithium iron phosphate electrode and the graphite electrode obtained after the repair in S5 into a battery, and test its charge and discharge capacity, initial coulombic efficiency, and rate performance;

[0126] Comparative Example 1

[0127] This comparative example is substantially the same as Example 1, except that, in this comparative example, only 1 g / L lithium sulfate solution is used as the electrolyte.

[0128] Comparative Example 2

[0129] This comparative example is substantially the same as Example 1, except that the fragrance in Example 1 is omitted in this comparative example.

[0130] Comparative Example 3

[0131] This comparative example is substantially the same as Example 1, except that the stabilizing additive in Example 1 is omitted in this comparative example.

[0132] Comparative Example 4

[0133] This comparative example is substantially the same as Example 1, with the only difference being that, in this comparative example, the discharge solution used in step S1 is 5 g / L sodium chloride.

[0134] Comparative Example 5

[0135] This comparative example is basically the same as Example 1, except that in this comparative example, the cleaning solution used in step S2 is EC and DEC in a ratio of 1:1.

[0136] Performance testing

[0137] The positive electrode sheets and graphite electrode sheets obtained in the above Examples 1-8 and Comparative Examples 1-5 were reassembled into batteries, and their charge and discharge capacity, initial coulombic efficiency and rate performance were tested.

[0138] The test results are shown in the table below:

[0139] As can be seen from the above table, the test performance of the batteries provided by Examples 1-8 of the present disclosure is significantly better than that of Comparative Examples 1-5, wherein Comparative Example 1 only uses lithium salt as the electrolyte, and its discharge capacity, first coulomb efficiency and rate performance are significantly lower than those of Example 1. This may be due to the fact that only lithium salt is used as the electrolyte, and its stability is poor, resulting in poor final repair effect. In Comparative Example 2, the aromatic agent is omitted, resulting in the lithium iron phosphate pole piece being easily oxidized during the repair process, and thus the repair effect is poor. In Comparative Example 3, the stabilizing additive is omitted, resulting in the trivalent iron being easily oxidized during the repair process, and the stability of the electrolyte is poor, and thus the repair effect is poor. It can be seen from the data of Comparative Examples 1-3 that the choice of electrolyte in the present disclosure has a synergistic technical effect. In Comparative Example 4, only inorganic electrolyte sodium chloride is used for discharge. At this time, there may be poor stability during the discharge process, and the internal short circuit and burnout may occur easily. In Example 1 of the present disclosure, an organic electrolyte is added, which can achieve stable discharge of waste batteries, and the situation of internal short circuit and burnout is significantly reduced, so it is beneficial to improve the performance of the final product. In comparative example 5, the cleaning liquid only includes liquid A, and its cleaning effect is poor. However, in embodiment 1 of the present disclosure, anhydrous ethanol is added, which can achieve a better cleaning effect.

[0140] In summary, the electrolyte for electrochemical repair of lithium batteries provided by the present disclosure is compounded with lithium salts, aromatics and stabilizing additives, wherein the lithium salt provides the missing lithium in the lithium iron phosphate; the aromatics contain unsaturated bonds and act as a reducing agent during the repair process; the stabilizing additive can protect the trivalent iron in the repair process from being oxidized again, while stabilizing the electrolyte. The lithium salt and the aromatics can react to form a complex, which is conducive to adsorption on the positive electrode during subsequent electrochemical repair, thereby improving the repair and regeneration effect. The electrolyte can be recycled. When the concentration of lithium in the electrolyte decreases, it is only necessary to replenish the corresponding lithium salt and aromatics to restore the initial concentration. The electrolyte does not need to be replaced and waste is caused. It should be further explained that the electrochemical repair and regeneration method of lithium batteries provided by the present disclosure does not require violent destruction of retired batteries. It is only necessary to disassemble the shell and take out the positive and negative electrodes of the battery intact. Even the diaphragm can be recycled and reused if it is not damaged. There is no need to sort the current collector later, that is, the current collector and the black powder of the electrode are recycled and reused simultaneously. The device is simple and easy to expand. It can be implemented with an ordinary electrolytic cell. For wound batteries, it is only necessary to lengthen the electrolytic cell. No additional impurities are introduced. Since there is no need to peel the lithium iron phosphate black powder from the surface of the current collector, there is no risk of aluminum being introduced by mechanical scratching. Indicators such as the powder resistance and compaction density of the electrode will not deteriorate. In addition, the electrochemical repair and regeneration method of the lithium battery provided by the present disclosure does not require high-temperature heat treatment, nor does it require high-voltage resistance for hydrothermal reactions. At the same time, the current efficiency of the electrochemical reaction is high.

[0141] The above describes in detail the optional embodiments of the present disclosure, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure can be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present disclosure and fall within the scope of protection of the present disclosure. Industrial Applicability

[0142] The electrolyte for electrochemical repair of lithium batteries provided by the present disclosure is prepared by compounding lithium salts, aromatics, and stabilizing additives, wherein the lithium salt provides the missing lithium in the lithium iron phosphate; the aromatics contain unsaturated bonds and act as a reducing agent during the repair process; and the stabilizing additives can protect the trivalent iron from being oxidized again during the repair process and stabilize the electrolyte. The lithium salt and the aromatics can react to form a complex, which is conducive to adsorption on the positive electrode during subsequent electrochemical repair, thereby improving the repair and regeneration effect. The electrolyte can be recycled. When the lithium concentration in the electrolyte decreases, it is only necessary to replenish the corresponding lithium salts and aromatics to restore the initial concentration. The electrolyte does not need to be replaced and wasteful. It should be further explained that the electrochemical repair and regeneration method of lithium batteries provided by the present disclosure does not require violent destruction of retired batteries. It is only necessary to disassemble the outer shell and completely remove the positive and negative electrodes of the battery. Even the diaphragm can be recycled and reused if it is not damaged. There is no need to sort the current collector later, that is, the current collector and the black powder of the electrode are recycled and reused simultaneously. The device is simple and easy to expand. It can be implemented with an ordinary electrolytic cell. For wound batteries, it is only necessary to lengthen the electrolytic cell. No additional impurities are introduced. Since there is no need to peel the lithium iron phosphate black powder from the surface of the current collector, there is no risk of aluminum being introduced by mechanical scratching. Indicators such as the powder resistance and compaction density of the electrode will not deteriorate. In addition, the electrochemical repair and regeneration method of the lithium battery provided by the present disclosure does not require high-temperature heat treatment, nor does it require high-voltage resistance for hydrothermal reactions. At the same time, the current efficiency of the electrochemical reaction is high.

Claims

1. An electrolyte for electrochemically repairing a lithium battery, characterized in that, Its raw materials include: lithium salt, fragrance, stabilizing additive and solvent. The final concentration of the lithium salt in the electrolyte is 0.1 - 15 g / L, the final concentration of the stabilizing additive is 0.1 - 5 g / L, and the mass ratio of the lithium salt to the fragrance is (1 - 5):(1 - 5).

2. The electrolyte for electrochemically repairing a lithium battery according to claim 1, wherein The lithium salt includes at least one of lithium chloride, lithium sulfate, lithium bromide, lithium iodide and lithium nitrate.

3. The electrolyte for electrochemical repair of the lithium battery according to any one of claims 1-2, characterized in that, The fragrance includes at least one of benzaldehyde, phenol, pyrrole, pyridine, 1,3 - resorcinol, dibenzylamine, dimethylbenzamide and 2 - sulfobenzoic acid.

4. The electrolyte for electrochemically repairing a lithium battery according to any one of claims 1-3, characterized in that, The stabilizing additive includes at least one of benzoic acid, sorbic acid, ethyl p - hydroxybenzoate, propyl p - hydroxybenzoate and p - hydroxybenzene.

5. The electrolyte for electrochemical repair of the lithium battery according to any one of claims 1-4, characterized in that, The solvent is at least one of water, ethylene glycol, glycerol and isopropyl alcohol.

6. A preparation method of an electrolyte for electrochemical repair of a lithium battery, characterized in that, It includes mixing evenly the raw materials of the electrolyte for electrochemically repairing the lithium battery as described in any one of claims 1 - 5.

7. The preparation method of the electrolyte for electrochemical repair of the lithium battery according to claim 6, wherein, After the raw materials are mixed, it further includes reacting at 60 - 150 °C for 2 - 8 h.

8. An electrochemical repair and regeneration method for a lithium battery, characterized in that, It includes: Discharging the retired lithium battery and then disassembling it to take out the positive electrode plate and the graphite electrode plate. Cleaning, drying and roll - pressing the positive electrode plate and the graphite electrode plate. Placing the processed positive electrode plate and the graphite electrode plate in an electrolytic cell, connecting a power supply. The electrolytic cell contains the electrolyte for electrochemically repairing as described in any one of claims 1 - 5, and taking them out after the charging ends. Cleaning, drying and roll - pressing the charged positive electrode plate and the graphite electrode plate.

9. The electrochemical repair and regeneration method of the lithium battery according to claim 8, characterized in that, During the charging process, constant - current mode charging is carried out first, and then constant - voltage mode charging is carried out.

10. The electrochemical repair and regeneration method of the lithium battery according to claim 9, wherein When charging in the constant - current mode, the current density is 0.1 - 2 C and the voltage range is 0 - 0.5 V.

11. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 9-10, characterized in that, After the voltage reaches 0.1 - 4 V, constant - voltage mode charging is adopted and charging continues until the current density reaches 0.004 - 0.006 C and then stops.

12. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 8-11, characterized in that, The positive electrode plate is connected to the cathode of the electrolytic cell, and the graphite electrode plate is connected to the anode of the electrolytic cell.

13. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 8-12, characterized in that, The drying temperature for drying the cleaned positive electrode plate and the graphite electrode plate before and after charging is 60 - 150 °C, and the drying time is 1 - 24 h.

14. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 8-13, characterized in that, The pressure for roll - pressing the cleaned positive electrode plate and the graphite electrode plate before and after charging is 4 - 6 T.

15. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 8-14, characterized in that, Cleaning the positive electrode plate and the graphite electrode plate before charging includes first cleaning with AB solution and then cleaning with deionized water. Among them, solution A is at least one of EC, DEC and DMC, and solution B is at least one of absolute ethanol, acetone, methanol and acetic acid.

16. The electrochemical repair and regeneration method of the lithium battery according to claim 15, wherein, The volume ratio of solution A to solution B in the AB solution is (1 - 5):(1 - 5).

17. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 15-16, characterized in that, The number of times of cleaning the positive electrode plate and the graphite electrode plate before charging is 1 - 3 times.

18. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 8-17, characterized in that, The discharging includes soaking the retired lithium battery in a salt solution, and the electrolyte of the salt solution includes inorganic electrolyte and organic electrolyte.

19. The electrochemical repair and regeneration method of the lithium battery according to claim 18, wherein, The final concentration of the inorganic electrolyte is 0.1 - 100 g / L, and the final concentration of the organic electrolyte is 0.1 - 100 g / L.

20. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 18-19, characterized in that, The inorganic electrolyte is at least one of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium nitrate and potassium nitrate.

21. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 18-19, characterized in that, The organic electrolyte includes at least one of ethylamine, dimethylamine, trimethylamine, acetic acid, propionic acid, benzoic acid, acetone, acetaldehyde, ethyl acetate, methyl formate, diethyl ether, dipropyl ether, cresol and phenol.

22. The electrochemical repair and regeneration method of the lithium battery according to any one of claims 8-21, characterized in that, The retired lithium battery includes at least one of lithium iron phosphate, lithium manganese iron phosphate and lithium nickel cobalt manganese iron phosphate.

23. A method for the reuse of a lithium battery, characterized in that, It includes the electrochemical repair and regeneration method of the lithium battery according to any one of claims 1-22, and further includes reassembling the repaired positive electrode plate and graphite electrode plate into a battery.

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