In-situ repair method and device for positive electrode material of waste power battery

Abstract

The invention belongs to the technical field of electrode in-situ repair, and relates to an in-situ repair method and device of a waste power battery positive electrode material. According to the technical scheme, the performance of the lithium battery positive electrode material is recovered by adopting an electrode in-situ repairing method, so that the battery performance is recovered. A positive pole piece of a waste power battery is disassembled and put into a repairing device, an electrolyte containing a pH and potential double-response type gel repairing agent is injected, and under the repairing voltage, the potential change of an electrode activates the pH change of gel pores to further promote the release of the repairing agent, so that on-demand lithium supplementation is realized, and false triggering or release lag under a single signal is avoided.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of in-situ electrode repair, and in particular to an in-situ repair method and device for a positive electrode material of a waste power battery. BACKGROUND

[0002] In-situ lithium battery repair can be achieved through electrolyte regeneration repair, SEI film repair and reconstruction, and electrode active material repair, wherein electrolyte regeneration repair can be achieved by adding a functional additive to the electrolyte to supplement consumed lithium salt, promoting the migration of Li + in the electrolyte through pulse current, and restoring ionic conductivity.

[0003] A Chinese patent application with the publication number CN116565369A discloses a method for in-situ repair of a positive electrode of a waste lithium ion battery. The technical solution first disassembles the positive electrode lithium cobalt oxide sheet of the waste lithium ion battery, places the positive electrode lithium cobalt oxide sheet in a three-electrode electrolytic cell, and performs in-situ electrochemical lithium supplementation through constant current charging. After the constant current charging is completed, the positive electrode sheet is heat treated to obtain regenerated lithium cobalt oxide. Through in-situ electrochemical lithium supplementation, the in-situ repair of the positive electrode lithium cobalt oxide material of the lithium ion battery can be achieved. However, the method cannot be self-adapted according to the actual lithium deficiency state of the material, and may cause excessive lithium supplementation or insufficient lithium supplementation. SUMMARY

[0004] The application aims to provide an in-situ repair method and device for a positive electrode material of a waste power battery. The method adds a pH and potential dual-responsive gel repair agent to the electrolyte, and in the device, the electrode sheet of the waste power battery is connected to an electrochemical device and maintained at a repair voltage state for repair. The pH and potential dual-responsive gel repair agent is prepared by using 2-dimethylaminoethyl acrylate as a starting material, reacting with N, N'-methylene bisacrylamide and N, N'-bis (acryloyl) cystamine, and loading a lithium source supplement, a conductive enhancer and a flame retardant. The pH and potential dual-responsive gel repair agent has pH response and potential response functions. When the positive electrode interface produces acidic substances due to metal dissolution and electrolyte decomposition, causing a local pH drop, the pH response group of the gel is dissociated in the acidic environment to cause gel swelling, and Li + is released. When the battery voltage is lower than 3.0 V, the gel swells to release Li + ; when the voltage is higher than 3.8 V, the gel shrinks to inhibit the excessive release of Li + , achieving on-demand lithium supplementation; and the potential change first activates the gel pores, and the pH change further promotes the release of the repair agent, avoiding the mis-triggering or release lag under a single signal.

[0005] In order to achieve the above object, the application provides a device for in-situ repairing of positive electrode material of waste power battery, which comprises an electrochemical workstation, a main container, a heating device, a tail gas treatment device and a safety protection circuit; the main container comprises a counter electrode, an electrode fixing device, a diaphragm and an electrolyte containing a repairing agent; the repairing agent is a pH and potential dual-responsive gel repairing agent; the repairing agent comprises a pH and potential dual-responsive gel, a lithium source supplementing agent, a conductive enhancer and a flame retardant; the pH and potential dual-responsive gel is structured as follows:

[0006] ,

[0007] wherein n is an integer between 1 and 10, m is an integer between 1 and 10, alpha is an integer between 1 and 10, and beta is an integer between 1 and 10, and n, m, alpha and beta have the same or different values.

[0008] Preferably, the gas outlet hole on the right side of the main container is connected with the tail gas treatment device; the lower left part of the main container is provided with a liquid inlet, and the electrolyte containing the repairing agent is injected into the main container through a pressurizing pump.

[0009] Preferably, the upper left part of the main container is provided with an air extraction hole connected with an air extraction pump for vacuum treatment of the main container.

[0010] Preferably, the tail gas treatment device contains an alkali solution; the counter electrode is connected with the safety protection circuit through a wire and then connected with the electrochemical workstation.

[0011] Preferably, the positive electrode sheet is fixed on the electrode fixing device and connected with the electrochemical workstation through a wire through a reserved hole on the top of the main container.

[0012] The application further provides a preparation method of the repairing agent, which comprises:

[0013] 2-dimethylaminoethyl acrylate is dissolved in a solvent, N, N'-methylene bisacrylamide and an initiator are added, stirring is performed, N, N'-bis(acryloyl)cystamine, a lithium source supplementing agent, a conductive enhancer and a flame retardant are added, reaction, freeze-drying are performed to obtain the pH and potential dual-responsive gel repairing agent.

[0014] Preferably, the solvent is methanol; the initiator is any one or more of azobisisobutyronitrile and azobisisoheptyl nitrile.

[0015] Preferably, the lithium source supplementing agent is Li2CO3 micro-nanoparticles.

[0016] Preferably, the conductive enhancer is any one or more of carbon nanotubes and graphene; and the flame retardant is triphenyl phosphate.

[0017] Preferably, the stirring temperature is 60-70 DEG C, and the stirring time is 4-6 h.

[0018] Preferably, the reaction temperature is 60-80 DEG C, and the reaction time is 4-8 h.

[0019] Preferably, the freeze-drying temperature is -20--40 DEG C, and the freeze-drying time is 3-5 h.

[0020] Preferably, the mass ratio of the 2-dimethylaminoethyl acrylate, methanol, N, N'-methylenebisacrylamide, initiator, N, N'-bis (acryloyl) cystamine, lithium source supplement, conductive enhancer and flame retardant is 1: (5-10): (0.01-0.05): (0.001-0.005): (0.01-0.05): (0.005-0.015): (0.001-0.003): (0.0015-0.0035).

[0021] The application also provides a method for in-situ repairing of a positive electrode material of a waste power battery, which is realized by an in-situ repairing device for the positive electrode material of the waste power battery and comprises the following steps of:

[0022] The waste power battery is discharged to a safety voltage at a constant current, and a positive electrode is disassembled, cleaned, dried, and obtained as a positive electrode sheet.

[0023] A vacuum pump connected to a gas hole on the upper left side of the main container is opened to vacuumize the main container, and then a heating device is opened to heat.

[0024] 0.005 C is a conventional cutoff current of a lithium battery, indicating that the charging current is 0.5% of the battery capacity, the migration rate of lithium ions in the electrode is extremely low, the polarization effect of the battery is weakened, and it is indicated that the lithium intercalation process has been basically completed.

[0025] Preferably, the positive electrode sheet of the waste power battery is a lithium nickel cobalt manganese oxide material, and the counter electrode is a lithium metal sheet.

[0026] Preferably, the electrolyte containing a repairing agent comprises ethylene carbonate, dimethyl carbonate, diethyl carbonate, lithium hexafluorophosphate and a repairing agent.

[0027] Preferably, the mass ratio of the ethylene carbonate, dimethyl carbonate, diethyl carbonate, lithium hexafluorophosphate and pH and potential dual-responsive gel repair agent is 1: (1-1.5): (0.75-1.25): (0.25-0.8): (0.1-0.15).

[0028] Preferably, the heating temperature is 30-50 DEG C, and the heating time is 10-20 min.

[0029] Preferably, the cleaning solvent is deionized water.

[0030] Preferably, the drying temperature is 40-60 DEG C, and the drying time is 2-3 h.

[0031] Preferably, the repair voltage is 3.8-4.25 V. The working voltage of the lithium battery is 3.6-3.7 V, the full voltage is 4.2-4.35 V, the upper limit of the repair voltage is 4.25 V, the thermal runaway is prevented, and the safety is higher.

[0032] The safety voltage is 3.2 V.

[0033] Preferably, the constant current charging current is 0.1-0.5 C.

[0034] Compared with the prior art, the beneficial effects of the present application are reflected in:

[0035] (1) The technical scheme of the present application adopts an electrode in-situ repair method to repair the waste power battery, without the need for crushing treatment of the positive electrode, can maintain the integrity of the electrode sheet structure, reduce the risk of impurity pollution, avoid secondary damage, add a repair agent in the electrolyte, and recover the activity of the electrode under the repair voltage.

[0036] (2) The repair agent used in the present application is a pH and potential dual-responsive gel repair agent. The gel repair agent is crosslinked by 2-dimethylaminoethyl acrylate and N, N'-methylene bisacrylamide under the action of an initiator to obtain a pH-responsive gel. A potential-responsive group (i.e. redox response) is introduced by adding N, N'-bis (acryloyl) cystamine containing a disulfide bond, lithium source supplements, conductivity enhancers and flame retardants are added to obtain the repair agent. The repair agent is dispersed in the electrolyte. After the battery is powered on, when the battery voltage is lower than the working voltage, the gel swells to release the repair components; when the battery is in normal working voltage, the gel shrinks to inhibit the excessive release of the repair components, achieving on-demand lithium supplement; the positive electrode interface produces acidic substances due to the dissolution of transition metals and the decomposition of electrolyte, the local pH of the electrolyte decreases, the pH-responsive group in the gel dissociates in the acidic environment, the gel swells, and lithium source supplements and other repair components are released to repair the battery; the change of potential first activates the gel pores, and the change of pH further promotes the release of the repair agent, avoiding the mis-triggering or release lag under a single signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the in-situ repair device for waste power battery positive electrode materials.

[0038] Figure 2 Schematic diagram of the synthesis route of pH and potential dual-responsive gel.

[0039] Figure 3 This is the constant current charge and discharge curve of the battery after repair in Example 1.

[0040] Figure 4 This is the constant current charge and discharge curve of the battery after repair in Example 2.

[0041] Figure 5 This is the constant current charge and discharge curve of the battery after repair in Example 3.

[0042] Figure 6 This is the constant current charge and discharge curve of the battery after repair in comparative example 1.

[0043] Explanation of the accompanying symbols: 1. Electrochemical workstation; 2. Main container; 3. Heating device; 4. Exhaust gas treatment device; 5. Safety protection circuit; 6. Counter electrode; 7. Electrode fixing device; 8. Diaphragm; 9. Electrolyte; 10. Positive electrode; 11. Alkaline solution; 12. Pressure pump; 13. Vacuum pump. DETAILED DESCRIPTION

[0044] The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0045] The main compounds used in the examples and comparative examples were all commercially available products and were not subjected to any further purification treatment.

[0046] Example 1

[0047] like Figure 1 As shown, the in-situ repair method of waste power battery positive electrode materials includes:

[0048] Step S1, dissolve 10 g of 2-dimethylaminoethyl acrylate in 50 g of methanol, add 0.1 g of N, N'-methylenebisacrylamide and 0.01 g of azobisisobutyronitrile, stir at 60 ° C for 6 h, add 0.1 g of N, N'-bis(acryloyl)cystamine, 0.05 g of Li2CO3 micro-nanoparticles, 0.01 g of carbon nanotubes and 0.015 g of triphenyl phosphate, react at 60 ° C for 8 h, and freeze-dry at -20 ° C for 5 h to obtain a pH and potential dual-responsive gel repair agent, such as Figure 2 shown.

[0049] Step S2, 2.5 g of lithium hexafluorophosphate is dispersed in a mixed solution of 10 g of ethylene carbonate, 10 g of dimethyl carbonate, 7.5 g of diethyl carbonate, 1 g of pH and potential dual-responsive gel repair agent is added to obtain electrolyte 9 containing repair agent.

[0050] Step S3, the waste power battery is discharged at a constant current to 3.2 V, the positive electrode is disassembled, washed with deionized water, and dried at 40℃ for 3 h to obtain the positive electrode sheet 10. The positive electrode sheet 10 is fixed on the electrode fixing device 7, the counter electrode 6 on the other side of the diaphragm 8 is connected to the safety protection circuit 5, and then connected to the electrochemical workstation 1. The positive electrode sheet 10 is connected to the electrochemical workstation 1, and then the pressure pump 12 is opened. The electrolyte 9 containing the repair agent is injected into the main container 2, as shown in Figure 1 .

[0051] Step S4, open the gas suction pump 13 connected to the upper left side of the main container 2, and then open the heating device 3. The main container 2 is vacuumized, and then heated at 30℃ for 20 min. After the system returns to room temperature, it is charged at a constant current of 0.1 C to 3.8 V, and then charged at a constant voltage to a current density of 0.005 C cutoff, and maintained for 3-5 h. The volatile substances generated during the process enter the tail gas treatment device 4 and are neutralized and treated by the alkali solution 11 to obtain the repaired positive electrode material. After washing with deionized water and drying at 40℃ for 2 h, it is assembled back into a battery.

[0052] Example 2

[0053] As shown in Figure 1 , the in-situ repair method of the positive electrode material of the waste power battery comprises:

[0054] Step S1, 10 g of 2-dimethylaminoethyl acrylate is dissolved in 75 g of methanol, 0.3 g of N, N'-methylene bisacrylamide and 0.03 g of azobisisoheptane nitrile are added, stirred at 70℃ for 5 h, 0.3 g of N, N'-bis(acryloyl) cystamine, 0.1 g of Li2CO3 micro-nano particles, 0.02 g of graphene and 0.025 g of triphenyl phosphate are added, and reacted at 70℃ for 6 h. After being frozen and dried at -30℃ for 4 h, a pH and potential dual-responsive gel repair agent is obtained, as shown in Figure 2 .

[0055] Step S2, 5 g of lithium hexafluorophosphate is dispersed in a mixed solution of 10 g of ethylene carbonate, 13 g of dimethyl carbonate, 10 g of diethyl carbonate, and 1 g of pH and potential dual-responsive gel repair agent is added to obtain electrolyte 9 containing repair agent.

[0056] Step S3, the waste power battery is discharged to 3.2 V at a constant current, the positive electrode is disassembled, washed with deionized water, dried at 50°C for 2.5 h, and the positive electrode sheet 10 is obtained. The positive electrode sheet 10 is fixed on the electrode fixing device 7, the counter electrode 6 on the other side of the diaphragm 8 is connected to the safety protection circuit 5, and then connected to the electrochemical workstation 1. The positive electrode sheet 10 is connected to the electrochemical workstation 1, and then the pressure pump 12 is opened. The electrolyte 9 containing the repairing agent is injected into the main container 2, as shown in Figure 1 .

[0057] Step S4, open the vacuum pump 13 connected to the air hole on the left side of the upper part of the main container 2, and then open the heating device 3. The main container 2 is vacuumized, and then heated at 40°C for 15 min. After the system returns to room temperature, it is charged to 4.0 V at a constant current of 0.3 C, and then charged at a constant voltage until the current density is 0.005 C. Cutoff, keep for 3-5 h. The volatile substances generated in the process enter the tail gas treatment device 4 and are neutralized and treated by the alkali solution 11 to obtain the repaired positive electrode material. After washing with deionized water and drying at 50°C for 2.5 h, it is assembled back into a battery.

[0058] Example 3

[0059] As shown in Figure 1 , the in-situ repairing method of the positive electrode material of the waste power battery comprises:

[0060] Step S1, 10 g of 2-dimethylaminoethyl acrylate is dissolved in 100 g of methanol, 0.5 g of N,N'-methylenebisacrylamide and 0.05 g of azobisisobutyronitrile are added, and stirred at 70°C for 4 h. 0.5 g of N, N'-bis(acryloyl)cystamine, 0.15 g of Li2CO3 micro-nano particles, 0.03 g of carbon nanotubes and 0.035 g of triphenyl phosphate are added, and reacted at 80°C for 4 h. Freeze-dried at-40°C for 3 h to obtain a pH and potential dual-responsive gel repairing agent, as shown in Figure 2 .

[0061] Step S2, 8 g of lithium hexafluorophosphate is dispersed in a mixed solution of 10 g of ethylene carbonate, 15 g of dimethyl carbonate and 12.5 g of diethyl carbonate, and 1.5 g of the pH and potential dual-responsive gel repairing agent is added to obtain the electrolyte 9 containing the repairing agent.

[0062] Step S3, the waste power battery is discharged to 3.2 V at a constant current, the positive electrode is disassembled, washed with deionized water, dried at 60 DEG C for 2 h, and the positive electrode sheet 10 is obtained. The positive electrode sheet 10 is fixed on the electrode fixing device 7, the counter electrode 6 on the other side of the diaphragm 8 is connected to the safety protection circuit 5, and then connected to the electrochemical workstation 1. The positive electrode sheet 10 is connected to the electrochemical workstation 1, and then the pressure pump 12 is opened. The electrolyte 9 containing the repairing agent is injected into the main container 2, as shown in Figure 1

[0063] Step S4, the vacuum pump 13 connected to the gas hole on the left upper part of the main container 2 is opened, the main container 2 is vacuumized, and then the heating device 3 is opened. The heating is carried out at 50 DEG C for 10 min. After the system returns to room temperature, the constant current charging is carried out at 0.5 C to 4.25 V, and the constant voltage charging is carried out to the current density of 0.005 C cutoff, and the process is maintained for 3-5 h. The volatile substances generated in the process enter the tail gas treatment device 4 and are neutralized and treated by the alkali solution 11. The positive electrode material after repair is obtained. After washing with deionized water and drying at 60 DEG C for 3 h, the battery is assembled back.

[0064] Comparative example 1

[0065] The in-situ repair method of the positive electrode material of the waste power battery is different from that of example 3. In step S2, no repairing agent is added, and the lithium source supplementing agent is directly dispersed in the electrolyte.

[0066] Performance test: the repaired electrode sheet is assembled to obtain the repaired power battery. The test results of the repair effects of examples 1-3 and comparative example 1 are shown in Figures 3-6

[0067] Figures 3-5 The batteries repaired by the methods of examples 1-3 are respectively. According to the charging and discharging curves in the figure, it can be seen that the voltage and capacitance of the batteries repaired by examples 1-3 are restored, and the capacitance of the battery repaired by example 3 is closest to the capacitance of the battery in the initial state. The degree of recovery of the voltage and capacitance of the battery repaired by comparative example 1 is significantly lower than that of examples 1-3. The experiment proves that the repair effect of the pH and potential dual-responsive gel repairing agent is significantly better than that of directly dispersing the lithium source supplementing agent in the electrolyte. The gel can trigger the release of the repairing component under certain conditions, so as to supplement the lithium source on demand, avoid excessive supplement of the battery during normal cycle, and lag behind when the battery suffers serious lithium loss.

[0068] The above only describes the preferred embodiments of the present application. It should be pointed out that for ordinary skilled persons in the technical field, several improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.​​

Claims

1. An in-situ repair device for waste power battery positive electrode materials, characterized in that: The invention comprises an electrochemical workstation (1), a main container (2), a heating device (3), an exhaust gas treatment device (4) and a safety protection circuit (5); the main container (2) comprises a counter electrode (6), an electrode fixing device (7), a diaphragm (8) and an electrolyte (9) containing a repairing agent; the repairing agent is a pH and potential dual-responsive gel repairing agent; the repairing agent comprises a pH and potential dual-responsive gel, a lithium source supplement, a conductivity enhancer and a flame retardant; the pH and potential dual-responsive gel is structured as follows: ， Wherein, n is an integer between 1 and 10, m is an integer between 1 and 10, α is an integer between 1 and 10, and β is an integer between 1 and 10. The values ​​of n, m, α and β may be the same or different.

2. The in-situ repair device for waste power battery positive electrode materials according to claim 1, characterized in that: The right side air outlet of the main container (2) is connected to the tail gas treatment device (4); the lower left side of the main container (2) is provided with a liquid inlet, and the electrolyte (9) containing the repair agent is injected into the main container (2) through the pressure pump (12); the upper left side of the main container (2) is provided with an air extraction hole, which is connected to the air extraction pump (13) to vacuum the main container (2).

3. The in-situ repair device for waste power battery positive electrode materials according to claim 1, characterized in that: The tail gas treatment device (4) contains an alkaline solution (11); the counter electrode (6) is connected to the safety protection circuit (5) via a wire, and then connected to the electrochemical workstation (1); the positive electrode plate (10) is fixed on the electrode fixing device (7), and is connected to the electrochemical workstation (1) via a wire through a reserved hole on the top of the main container (2).

4. The in-situ repair device for waste power battery positive electrode materials according to claim 1, characterized in that: The preparation method of the repair agent comprises: 2-Dimethylaminoethyl acrylate was dissolved in a solvent, N, N'-methylenebisacrylamide and an initiator were added, and the mixture was stirred. N, N'-bis(acryloyl)cystamine, a lithium source supplement, a conductive enhancer, and a flame retardant were added, and the mixture was reacted and freeze-dried to obtain a pH and potential dual-responsive gel repair agent.

5. The in-situ repair device for waste power battery positive electrode materials according to claim 4, characterized in that: The solvent is methanol; the initiator is any one or more of azobisisobutyronitrile and azobisisoheptylonitrile; the lithium source supplement is Li2CO3 micro-nanoparticles; the conductivity enhancer is any one or more of carbon nanotubes and graphene; and the flame retardant is triphenyl phosphate.

6. The in-situ repair device for waste power battery positive electrode materials according to claim 4, characterized in that: The stirring temperature is 60-70°C, and the stirring time is 4-6 hours; the reaction temperature is 60-80°C, and the reaction time is 4-8 hours; the freeze-drying temperature is -20--40°C, and the freeze-drying time is 3-5 hours.

7. The in-situ repair device for waste power battery positive electrode materials according to claim 4, characterized in that: The mass ratio of the 2-dimethylaminoethyl acrylate, methanol, N, N'-methylenebisacrylamide, initiator, N, N'-bis(acryloyl)cystamine, lithium source supplement, conductive enhancer and flame retardant is 1:(5-10):(0.01-0.05):(0.001-0.005):(0.01-0.05):(0.005-0.015):(0.001-0.003):(0.0015-0.0035).

8. An in-situ repair method for waste power battery positive electrode materials, implemented by the in-situ repair device for waste power battery positive electrode materials according to any one of claims 1 to 7, comprising: The waste power battery is discharged at a constant current to a safe voltage, the positive electrode is disassembled, cleaned, and dried to obtain a positive electrode sheet (10), the positive electrode sheet (10) is fixed on an electrode fixing device (7), the electrode (6) is connected to a safety protection circuit (5), and then connected to an electrochemical workstation (1), the positive electrode sheet (10) is connected to the electrochemical workstation (1), and then a pressure pump (12) is turned on to inject an electrolyte (9) containing a pH and potential dual-responsive gel repair agent into the main container (2); Open the vacuum pump (13) connected to the air hole on the upper left side of the main container (2), evacuate the main container (2), and then turn on the heating device (3) to heat. After the system returns to room temperature, charge it with constant current to the repair voltage, and charge it with constant voltage until the current density reaches 0.005 C and then hold it for 3 to 5 hours to obtain the repaired positive electrode material. After cleaning and drying, assemble it back into the battery.

9. The in-situ repair method for waste power battery positive electrode materials according to claim 8, characterized in that: The positive electrode plate (10) of the waste power battery is made of lithium nickel cobalt manganese oxide material; the counter electrode (6) is a metal lithium plate; the electrolyte (9) containing the repair agent includes ethylene carbonate, dimethyl carbonate, diethyl carbonate, lithium hexafluorophosphate and the repair agent; the mass ratio of the ethylene carbonate, dimethyl carbonate, diethyl carbonate, lithium hexafluorophosphate and the pH and potential dual-responsive gel repair agent is 1: (1-1.5): (0.75-1.25): (0.25-0.8): (0.1-0.15).

10. The in-situ repair method for waste power battery positive electrode materials according to claim 8, characterized in that: The heating temperature is 30~50℃, and the heating time is 10~20 min; the cleaning solvent is deionized water; the drying temperature is 40~60℃, and the drying time is 2~3 h; the repair voltage is 3.8~4.25 V; the safety voltage is 3.2 V; and the constant current charging current is 0.1~0.5 C.

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