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

Abstract

The application belongs to the technical field of electrode in-situ repair, and relates to an in-situ repair method and device for a positive electrode material of a waste power battery. The technical scheme adopts an electrode in-situ repair method to recover the performance of a lithium battery positive electrode material, and further recover the battery performance. The positive electrode sheet of the waste power battery is disassembled and placed in a repair device, and an electrolyte containing a pH and potential dual-response type gel repair agent is injected. Under a repair voltage, electrode potential change activates pH change in gel pores to further promote release of the repair agent, on-demand lithium supplement 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 the gel to swell and release Li + 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 false 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, a is an integer between 1 and 10, β is an integer between 1 and 10, and n, m, a and β 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 outlet 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 tab 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; 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:

[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. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of an in-situ repair device for the positive electrode material of waste power batteries.

[0038] Figure 2 This is a schematic diagram of the synthesis route for a pH and potential dual-response gel.

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

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

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

[0042] Figure 6 The constant current charge-discharge curves of the battery after repair in Comparative Example 1 are shown.

[0043] Explanation of reference numerals in the attached drawings: 1. Electrochemical workstation; 2. Main container; 3. Heating device; 4. Tail gas treatment device; 5. Safety protection circuit; 6. Counter electrode; 7. Electrode fixing device; 8. Diaphragm; 9. Electrolyte; 10. Positive electrode plate; 11. Alkaline solution; 12. Pressurization pump; 13. Vacuum pump. Detailed Implementation

[0044] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used 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 remediation method for the positive electrode material of spent power batteries 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, then add 0.1 g of N,N'-bis(acryloyl)cysteine, 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 As 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 repairing device for positive electrode material of waste power battery, characterized in that, The application relates to a device for in-situ repairing of waste power battery positive electrode materials, which comprises an electrochemical workstation (1), a main container (2), a heating device (3), a tail 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 electrolyte containing a repairing agent (9); the repairing agent is a pH and potential dual-response type gel repairing agent; the repairing agent comprises a pH and potential dual-response type gel, a lithium source supplementing agent, a conductive enhancing agent and a flame retardant; the pH and potential dual-response type gel is structured as follows: ， Wherein, n is an integer between 1 and 10, m is an integer between 1 and 10, a is an integer between 1 and 10, beta is an integer between 1 and 10, n, m, a and beta have the same or different values. 2.The device for in-situ repairing of positive material of waste and old power battery according to claim 1, characterized in that, The right gas outlet of the main container (2) is connected with the tail gas treatment device (4); the left lower part of the main container (2) is provided with a liquid inlet, the electrolyte containing the repairing agent (9) is injected into the main container (2) through a pressurizing pump (12); the left upper part of the main container (2) is provided with a gas extraction hole and is connected with a gas extraction pump (13) to extract the vacuum of the main container (2). 3.The device for in-situ repairing of positive material of waste and old power battery according to claim 1, characterized in that, The tail gas treatment device (4) contains an alkali solution (11); the counter electrode (6) is connected with the safety protection circuit (5) through a wire and is connected with the electrochemical workstation (1); the positive electrode sheet (10) is fixed on the electrode fixing device (7) and is connected with the electrochemical workstation (1) through a reserved hole in the top of the main container (2) and a wire. 4.The device for in-situ repairing of positive material of waste and old power battery according to claim 1, characterized in that, The preparation method of the repairing agent comprises the following steps: The 2-dimethylaminoethyl acrylate is dissolved in a solvent, N, N'-methylene bisacrylamide and an initiator are added, stirring is conducted, N, N'-bis (acryloyl) cystamine, a lithium source supplementing agent, a conductive enhancing agent and a flame retardant are added, reaction, freeze drying are conducted to obtain the pH and potential dual-response type gel repairing agent. 5.The device for in-situ repairing of positive material of waste and old power battery according to claim 4, characterized in that, The solvent is methanol; the initiator is any one or more of azobisisobutyronitrile and azobisisoheptyl nitrile; the lithium source supplementing agent is Li2CO3 micro-nanoparticles; the conductive enhancing agent is any one or more of carbon nanotubes and graphene; and the flame retardant is triphenyl phosphate. 6.The device for in-situ repairing of positive material of waste and old power battery according to claim 4, characterized in that, The stirring temperature is 60-70 DEG C, the stirring time is 4-6 h; the reaction temperature is 60-80 DEG C, the reaction time is 4-8 h; the freeze drying temperature is-20 to-40 DEG C, and the freeze drying time is 3-5 h. 7.The device for in-situ repairing of positive material of waste and old power battery according to claim 4, characterized in that, The mass ratio of the 2-dimethylaminoethyl acrylate, methanol, N, N'-methylene bisacrylamide, initiator, N, N'-bis (acryloyl) cystamine, lithium source supplementing agent, conductive enhancing agent 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 repairing method for waste power battery positive electrode materials, which is realized by the in-situ repairing device for waste power battery positive electrode materials in any one of claims 1-7 and comprises the following steps: The waste power battery is discharged to a safety voltage by a constant current, the positive electrode is disassembled, washed and dried to obtain a positive electrode sheet (10), the positive electrode sheet (10) is fixed on an electrode fixing device (7), a safety protection circuit (5) is connected to the electrode (6), and then connected to an electrochemical workstation (1), the positive electrode sheet (10) is connected to the electrochemical workstation (1), then a pressurizing pump (12) is opened, and an electrolyte (9) containing a pH and potential dual-responsive gel repair agent is injected into a main container (2); A 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, then a heating device (3) is opened for heating, after the system returns to room temperature, constant current charging to the repair voltage is carried out, constant voltage charging to the current density of 0.005 C is stopped, and the process is maintained for 3-5 h to obtain the repaired positive electrode material, which is washed, dried and assembled back into a battery. 9.The method according to claim 8, characterized in that, The positive electrode sheet (10) of the waste power battery is a lithium nickel cobalt manganese oxide material; the counter electrode (6) is a lithium metal sheet; the electrolyte (9) containing the repair agent includes ethylene carbonate, dimethyl carbonate, diethyl carbonate, lithium hexafluorophosphate and a 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 method according to claim 8, characterized in that, The heating temperature is 30-50 DEG C, and the heating time is 10-20 min; the washing solvent is deionized water; the drying temperature is 40-60 DEG C, 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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