Reference electrode and long-life three-electrode battery preparation and battery capacity recovery method

Abstract

The invention belongs to the technical field of rechargeable batteries, and particularly relates to a reference electrode and long-life three-electrode battery preparation and battery capacity recovery method. The invention provides a method for preparing, processing and applying a sheet reference electrode, which can realize large-scale mass production, stably monitor the potential information of the positive electrode and the negative electrode in the battery in the long-term service process of the battery, prolong the cycle life of the battery, and supplement additional active lithium / sodium after judging that the battery is aged so as to recover the capacity of the battery. Therefore, the method can directly obtain the internal information of the battery and improve the cycle performance of the battery, and provides a solution for the development and commercial application of a novel battery management system and a battery cell.

Description

Technical Field

[0001] The invention belongs to the technical field of rechargeable batteries, and in particular relates to a reference electrode, a long-life three-electrode battery preparation method and a battery capacity recovery method. Background Art

[0002] The development of clean energy, especially rechargeable secondary batteries, is the main research content of the current new energy industry. Lithium-ion batteries are widely used in energy storage, electric vehicles, consumer electronics and transportation due to their high energy density, high coulombic efficiency and long cycle life. At present, with the increase of battery capacity and the expansion of application scenarios, the traditional battery management system cannot meet the efficient information acquisition and management at the monomer level, and has defects in improving battery safety and reliability.

[0003] In the prior art, the three-electrode design of most batteries is to implant between the positive and negative electrodes of the battery, and is divided into two types: implantation during the initial manufacture of the battery and battery modification during service. The main research content of the above-mentioned battery is the monitoring and impedance analysis of the positive and negative electrode potentials of the battery. First, when the reference electrode is implanted during the initial manufacture of the battery, only materials with stable electrochemical properties can be selected as the active materials of the reference electrode, such as LTO, LFP, etc. The above-mentioned materials are usually coated on copper wire or porous metal mesh, and after the battery is formed, the positive and negative electrodes are respectively activated by forming a current loop with the reference electrode. The above process is cumbersome and not conducive to large-scale mass production. Secondly, for the modification of batteries in the service process, it is often necessary to carry out in a glove box to prevent the battery pole piece and electrolyte from being oxidized by air. At the same time, the modification process faces problems such as damage to the battery pole piece, uneven pole piece caused by the diaphragm and other materials used additionally for implanting the reference electrode, and inability to mass produce. Finally, the above solutions all focus on the reference electrode to improve the monitoring of the positive and negative electrode potential inside the battery and the evaluation of battery SOC, SOH and other parameters obtained by subsequent data processing. In addition, the reference electrode has a small active material load and is difficult to operate stably for a long time. More importantly, in the current technical solutions, there is no solution to achieve the preparation of a reference electrode that is stable in air during battery preparation, has the function of monitoring the positive and negative electrode potential inside the battery during circulation, and realizes the capacity recovery of aged batteries. Summary of the invention

[0004] The purpose of the present invention is to provide a reference electrode, a long-life three-electrode battery preparation and a battery capacity recovery method, so as to overcome the problems in the prior art solutions such as small reference electrode active material loading, unstable potential, difficulty in implantation, capacity-caused battery performance damage, and inability to achieve battery cycle performance improvement and capacity recovery.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a reference electrode, comprising a current collector and an active layer and an anti-oxidation layer sequentially wrapped on the surface of the current collector;

[0007] The material of the active layer includes an active material for lithium ion batteries or an active material for sodium ion batteries; the content of the material of the active layer in the reference electrode is 0.05-0.08 g / cm 2 ;

[0008] The material of the anti-oxidation layer includes a solid electrolyte.

[0009] Preferably, the thickness of the active layer is ≥6 μm; and the thickness of the anti-oxidation layer is 2-3 μm.

[0010] Preferably, one end of the reference electrode further includes a reference electrode lug; the reference electrode lug is a nickel lug with a copper-plated surface.

[0011] The present invention also provides a long-life three-electrode battery, comprising a battery cell body, an electrolyte and a battery shell;

[0012] The battery cell body comprises a positive electrode, a negative electrode, a separator and a reference electrode;

[0013] The reference electrode is the reference electrode described in the above technical solution.

[0014] Preferably, the battery cell body comprises a laminated battery cell body or a wound battery cell body;

[0015] The laminated battery cell body comprises a positive electrode, a reference electrode and a negative electrode which are stacked in sequence, and a diaphragm is arranged between the reference electrode and the positive electrode, and between the reference electrode and the negative electrode;

[0016] The wound battery cell body comprises a positive electrode, a reference electrode and a negative electrode which are stacked and wound in sequence, and a separator is arranged between the reference electrode and the positive electrode and between the reference electrode and the negative electrode.

[0017] Preferably, one end of the positive electrode further includes a positive electrode tab, and the positive electrode tab is an aluminum tab;

[0018] One end of the negative electrode further includes a negative electrode tab, and the negative electrode tab is a nickel tab;

[0019] The positive electrode tab and the negative electrode tab are located on the same side of the battery cell body;

[0020] The reference electrode tab is located on the same side or the opposite side of the positive electrode tab.

[0021] Preferably, the long-life three-electrode battery comprises a soft-pack battery or a square-shell battery; the battery shell of the soft-pack battery is an aluminum-plastic film shell.

[0022] The present invention also provides a method for preparing the long-life three-electrode battery described in the above technical solution, comprising the following steps:

[0023] Provide the battery cell body;

[0024] The battery cell body is placed in a battery shell for liquid injection and packaging, and then formed and sorted to obtain the long-life three-electrode battery.

[0025] The present invention also provides a battery capacity recovery method, comprising the following steps:

[0026] The battery is the long-life three-electrode battery described in the above technical solution or the long-life three-electrode battery prepared by the preparation method described in the above technical solution;

[0027] The battery is charged and discharged in cycles. When the cycle capacity of the battery cell is lower than 80% of the initial capacity, the reference electrode is sequentially connected with the negative electrode or the positive electrode to form a current loop, and a pulse current is applied to the battery to replenish lithium or sodium to the negative electrode or the positive electrode, respectively, so as to achieve battery capacity recovery.

[0028] Preferably, the pulse current includes a matrix pulse current, and the procedure of the matrix pulse current is: charging at 3μA for 10 min, charging at 3μA for 10 min after standing for 10 min, charging at 5μA for 10 min after standing for 10 min, charging at 4μA for 10 min after standing for 5 min, and charging at 2μA for 20 min after standing for 10 min.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The present invention has made innovative improvements to the design, processing and use of the reference electrode of the battery, solving the problems of the current reference electrode being difficult to use in the battery, causing damage to the battery performance after implantation, and being unable to be applied on a large scale. Through the design of high-load active material coating, planar reference electrode processing, anti-oxidation coating preparation, integrated electrode implantation and sealing, etc., it is ensured that the reference electrode can be prepared and assembled on a large scale in the existing production line, and the positive and negative electrode potentials of the battery can be efficiently and stably monitored in the battery.

[0031] Second, by designing a sheet reference electrode and implanting the reference electrode in the battery cell, combined with the design of double-sided coating of active materials, it can ensure that the reference electrode and other electrodes in the battery maintain a good ion transmission path, which can improve the monitoring reliability of the reference electrode. The relatively large area and active material loading can ensure that the reference electrode can monitor the positive and negative electrode potentials of the battery for a long time and stably during service and calculate the battery's state of charge and aging status.

[0032] 3. The present invention innovatively uses the active materials in the reference electrode to replenish the active lithium / sodium ions in the battery after battery aging, thereby restoring the battery capacity and repairing the battery. This integrates the secondary capacity recovery and intelligent battery monitoring functions of the battery, realizes the multifunctional application of the reference electrode, and enhances the application value of the reference electrode. In addition, the present invention also innovatively designs a pulse excitation method and application case for repairing battery capacity damage through a reference electrode. This method is universal and can be modified and improved according to actual application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the structure of the reference electrode obtained in Example 1;

[0034] Figure 2 This is a schematic diagram of the structure of a battery cell obtained by assembling the reference electrode in a laminated structure in Example 2;

[0035] Figure 3 This is a working principle diagram of the reference electrode in a lithium-ion battery;

[0036] Figure 4 It is a schematic diagram of the structure of the reference electrode of the present invention in a large-capacity square shell battery;

[0037] Figure 5 Schematic diagram of the sealing process of the reference electrode of the present invention in a large-capacity square shell battery;

[0038] Figure 6 This is a schematic diagram of the sealing process of the soft-pack battery obtained in Example 2;

[0039] Figure 7 Schematic diagram of the reference electrode monitoring the positive and negative electrode potentials in the graphite negative electrode lithium ion battery before sorting in Example 2;

[0040] Figure 8 Schematic diagram of the reference electrode monitoring the positive and negative electrode potentials of lithium-ion batteries during long cycles;

[0041] Fig. 9 Schematic diagram of the reference electrode monitoring the positive and negative electrode potentials during the cycle test of lithium-ion batteries under different rate conditions;

[0042] Fig.10 A schematic diagram of applying a pulse current to a current loop consisting of a reference electrode and positive / negative electrodes in a battery in Example 3 to restore battery capacity;

[0043] Fig.11 Schematic diagram of recovering battery capacity loss by releasing active substances through the reference electrode in Example 3. DETAILED DESCRIPTION

[0044] The present invention provides a reference electrode, comprising a current collector and an active layer and an anti-oxidation layer sequentially wrapped on the surface of the current collector;

[0045] The material of the active layer includes active materials for lithium ion batteries or active materials for sodium ion batteries; the content of the material of the active layer in the reference electrode is 0.05-0.08 g / cm 2 ;

[0046] The material of the anti-oxidation layer includes a solid electrolyte.

[0047] In the present invention, the material of the current collector preferably includes one or more of copper, aluminum, nickel and gold; the shape of the current collector preferably includes a flat metal foil or a porous metal foil.

[0048] In the present invention, the active material for lithium-ion batteries preferably includes one or more of pure lithium, lithium alloy, lithium iron phosphate and lithium titanate; the active material for sodium-ion batteries preferably includes one or more of pure sodium and sodium alloy. In the present invention, the thickness of the active layer is preferably ≥6 μm. In the present invention, the porosity of the activation layer is preferably ≤5%.

[0049] In the present invention, the solid electrolyte preferably includes a hybrid solid electrolyte or an oxide solid electrolyte, and the hybrid solid electrolyte is preferably obtained by mixing a methacrylate-terminated organic / inorganic hybrid polyurethane precursor (m-PPS) and a eutectic system composed of LiTFSI / NMAc and in-situ polymerization initiated by UV. In the present invention, the oxide solid electrolyte preferably includes one or more of lithium lanthanum zirconium tantalum oxide LLZTO, lithium lanthanum zirconium oxide LLZO and lithium aluminum titanium phosphate LATP. In the present invention, the thickness of the anti-oxidation layer is preferably 2 to 3 μm.

[0050] In the present invention, one end of the reference electrode preferably further comprises a reference electrode tab; the reference electrode tab is preferably a nickel tab with a copper-plated surface.

[0051] In the present invention, the preparation method of the reference electrode preferably comprises the following steps:

[0052] Pressing active layer materials on both sides of the current collector and rolling to obtain an active layer;

[0053] An anti-oxidation layer is prepared on the surface of the active layer.

[0054] In the present invention, the pressing temperature is preferably 150°C, the pressure is preferably 0.5 MPa, and the holding time is preferably 3 seconds. In the present invention, the pressing is preferably performed under an inert atmosphere. The present invention has no particular limitation on the rolling process, and the thickness and porosity that can be obtained are sufficient.

[0055] In the present invention, when the material of the anti-oxidation layer is a hybrid solid electrolyte, the preparation method of the anti-oxidation layer is preferably: mixing a methacrylate-terminated organic / inorganic hybrid polyurethane precursor (m-PPS) with a eutectic system composed of LiTFSI / NMAc and then in-situ polymerizing it on the surface of the active layer by UV initiation (for specific steps, see YXJiang, YD Song, X. Chen, HJ Wang, LJ Deng, G. Yang, In situ formed self-healable quasi-solid hybrid electrolyte network coupled with eutectic mixture towards ultra-long cycle life lithium metal batteries, Energy Storage Materials, 2022, 52, 514-523).

[0056] In the present invention, when the material of the anti-oxidation layer is an oxide solid electrolyte, the preparation method of the anti-oxidation layer preferably includes: mixing the oxide solid electrolyte, an organic solvent, a binder and a lithium salt to obtain a slurry; scraping the slurry on the surface of the active layer, and obtaining the anti-oxidation layer after the solvent evaporates.

[0057] In the present invention, the lithium salt preferably includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate and lithium hexafluoroarsenate; the binder preferably includes one or more of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride and polyvinylidene chloride; the organic solvent preferably includes succinonitrile. In the present invention, the mass ratio of the oxide solid electrolyte, organic solvent, binder and lithium salt is preferably 45-60:4-24:30-40:0.4-3. The present invention does not specifically limit the process of scraping and solvent volatilization, and the process well known to those skilled in the art can be adopted.

[0058] In the present invention, after the reference electrode is prepared, it is also preferred to perform a charge-discharge test and voltage monitoring on the reference electrode to ensure that the potential of the reference electrode is accurate. The present invention has no special limitation on the process of the charge-discharge test and voltage monitoring, and those familiar to those skilled in the art can be used.

[0059] The present invention also provides a long-life three-electrode battery, comprising a battery cell body, an electrolyte and a battery shell;

[0060] The battery cell body comprises a positive electrode, a negative electrode, a separator and a reference electrode;

[0061] The reference electrode is the reference electrode described in the above technical solution.

[0062] In the present invention, the diaphragm preferably includes a substrate and a ceramic particle layer coated on the surface of the substrate; the substrate preferably includes a single-layer film or a multi-layer composite film; the single-layer film includes a PP single-layer film or a PE single-layer film, and the multi-layer composite film is preferably a multi-layer composite film composed of a PP single-layer film and / or a PE single-layer film; the material of the ceramic particle layer preferably includes alumina; the thickness of the ceramic particle layer is preferably 0.7 μm.

[0063] In the present invention, the battery cell body preferably includes a laminated battery cell body or a wound battery cell body. In the present invention, the laminated battery cell body preferably includes a positive electrode, a reference electrode and a negative electrode stacked in sequence, and a separator is preferably provided between the reference electrode and the positive electrode, and between the reference electrode and the negative electrode. In the present invention, the size of the reference electrode in the laminated battery cell body is preferably not less than the size of the negative electrode.

[0064] In the present invention, the wound cell body preferably comprises a positive electrode, a reference electrode and a negative electrode stacked and wound in sequence, and a separator is preferably provided between the reference electrode and the positive electrode, and between the reference electrode and the negative electrode. In the present invention, the size of the reference electrode in the wound cell body is preferably consistent with the size of the positive electrode or the negative electrode.

[0065] In the present invention, one end of the positive electrode preferably also includes a positive electrode tab, and the positive electrode tab is preferably an aluminum tab; one end of the negative electrode preferably also includes a negative electrode tab, and the negative electrode tab is preferably a nickel tab; the positive electrode tab and the negative electrode tab are preferably located on the same side of the battery cell body; the reference electrode tab is preferably located on the same side or opposite side of the positive electrode tab.

[0066] In the present invention, the long-life three-electrode battery preferably includes a soft-pack battery or a square-shell battery; the battery shell of the soft-pack battery is preferably an aluminum-plastic film shell. The present invention has no special limitation on the type of battery shell of the square-shell battery, and any type familiar to those skilled in the art can be used.

[0067] The present invention also provides a method for preparing the long-life three-electrode battery described in the above technical solution, comprising the following steps:

[0068] Provide the battery cell body;

[0069] The battery cell body is placed in a battery shell for liquid injection and packaging, and then formed and sorted to obtain the long-life three-electrode battery.

[0070] The present invention has no special limitation on the method for preparing the battery cell body, and any method known to those skilled in the art may be adopted.

[0071] The present invention has no special restrictions on the type and amount of electrolyte used in the injection, and can be adjusted appropriately according to the type of battery required. The present invention has no special restrictions on the packaging process, and can be adopted by those skilled in the art.

[0072] The present invention has no particular limitation to the process of formation and sorting, and adopts what is well known to those skilled in the art. In the present invention, the process of formation also preferably includes the voltage signal of the positive electrode to the reference electrode and the voltage signal of the negative electrode to the reference electrode throughout the process. In the present invention, the process monitoring voltage signal of formation can monitor the battery performance, as the sorting basis.

[0073] In a specific embodiment of the present invention, when the long-life three-electrode battery is a soft-pack battery, the preparation preferably includes:

[0074] The battery cell body is loaded into an aluminum-plastic film shell, and the tab side and the bottom of the tab of the battery cell body are sealed with a heat sealer, wherein the length of the bottom aluminum-plastic film seal in the soft-pack battery is preferably not less than 6 mm; after drying and cooling, liquid injection is performed under a negative pressure environment, and attention is paid to the electrical insulation treatment and protection of the electrodes during the drying and liquid injection process; then a first vacuumization and sealing are performed; after the obtained battery is formed and sorted, a second vacuumization and sealing are performed to obtain the soft-pack battery.

[0075] In the present invention, when the long-life three-electrode battery is a square shell battery, Figure 4 It is a schematic diagram of the structure of the reference electrode of the present invention in a large-capacity square shell battery; Figure 5 It is a schematic diagram of the sealing process of the reference electrode of the present invention in a large-capacity square shell battery.

[0076] The present invention also provides a battery capacity recovery method, comprising the following steps:

[0077] The battery is the long-life three-electrode battery described in the above technical solution or the long-life three-electrode battery prepared by the preparation method described in the above technical solution;

[0078] The battery is charged and discharged in cycles. When the cycle capacity of the battery cell is lower than 80% of the initial capacity, the reference electrode is sequentially connected with the negative electrode or the positive electrode to form a current loop, and a pulse current is applied to the battery to replenish lithium or sodium to the negative electrode or the positive electrode, respectively, so as to achieve battery capacity recovery.

[0079] In the present invention, the process of the charge and discharge cycle also preferably includes full monitoring of the voltage signal of the positive electrode to the reference electrode and the voltage signal of the negative electrode to the reference electrode. In the present invention, the battery state of charge is determined and charge / discharge management is performed by monitoring the voltage signal of the negative electrode to the reference electrode, and the battery aging state is determined by the differential voltage method; at the same time, the potential fluctuation of the positive / negative electrode of the battery to the reference electrode can be used as a reference indicator for safety management. The present invention first monitors and analyzes the potential of the positive and negative electrodes in the battery relative to the reference electrode, and then evaluates and manages the health status of the battery based on the negative electrode potential during the charge and discharge process, the relaxation process of the positive and negative electrode potentials during the battery standing process, and the characteristic peak value of the curve obtained by the incremental capacity or differential selection calculation during the charge and discharge process. In the present invention, the working principle diagram of the reference electrode in the lithium-ion battery is as shown in the figure. Figure 3 shown.

[0080] In the present invention, it is preferred that charging be stopped immediately when the potential of the negative electrode approaches 0V.

[0081] In the present invention, the cycle capacity of the battery cell is preferably detected by the ampere-hour integration method. The present invention has no special limitation on the process of the ampere-hour integration method detection, and the method well known to those skilled in the art can be used.

[0082] In the present invention, the pulse current preferably includes a matrix pulse current, and the procedure of the matrix pulse current is preferably: charging at 3μA for 10 minutes, charging at 3μA for 10 minutes after standing for 10 minutes, charging at 5μA for 10 minutes after standing for 10 minutes, charging at 4μA for 10 minutes after standing for 5 minutes, and charging at 2μA for 20 minutes after standing for 10 minutes.

[0083] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0084] The present invention is the first to propose a method for preparing, processing and applying a sheet reference electrode, which can achieve large-scale mass production, stably monitor the internal positive and negative electrode potential information of the battery during long-term service, and improve the battery cycle life. After determining that the battery is aged, additional active lithium / sodium is supplemented to restore the battery capacity. Therefore, this method can directly obtain internal battery information and improve battery cycle performance, providing solutions for the development and commercial application of new battery management systems and battery cells.

[0085] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0086] Example 1

[0087] For the current collector required for the reference electrode, a copper sheet current collector of appropriate size is obtained by laser cutting;

[0088] The lithium-rich alloy (wherein the mass percentage of lithium is more than 95%) particles are spread on the current collector, and then the active material is compacted and bonded to the current collector with a press at a pressure of 0.5MPa in an inert gas atmosphere at a high temperature of 150°C, and the pressure is maintained for 3s. The above operation is repeated for the back of the current collector; then it is placed in a roller press for roller pressing to obtain an active layer, wherein the thickness of the active layer is 6μm and the porosity is 5%;

[0089] A eutectic system mixed liquid material composed of an inorganic hybrid polyurethane precursor (m-PPS) and LiTFSI / NMAc is spin-coated on both sides of the active layer by a coating machine, and UV irradiation is performed to cure (for the specific composition and curing conditions of the eutectic system, see YX Jiang, YD Song, X. Chen, HJ Wang, LJ Deng, G. Yang, In situ formed self-healable quasi-solid hybrid electrolyte network coupled with eutectic mixture towards ultra-long cycle life lithium metal batteries, Energy Storage Materials, 2022, 52, 514-523) to obtain an anti-oxidation layer with a thickness of 2 μm, and a reference electrode can be obtained, wherein the content of the lithium-rich alloy on the reference electrode is 0.07 g / cm 2 .

[0090] The structural diagram of the reference electrode is shown in Figure 1 shown.

[0091] Example 2

[0092] A three-electrode battery was prepared using the reference electrode obtained in Example 1;

[0093] The three-electrode battery in this embodiment is a laminated soft-pack battery; a battery with a capacity of 1.2Ah is prepared by a lamination process using an NCM523 positive electrode combined with a graphite negative electrode;

[0094] Determine the capacity of the battery according to the demand to determine the number of positive and negative pole pieces and the surface capacity of the pole pieces. Taking 1.2Ah as an example, there are 11 positive pole pieces and 12 negative pole pieces. According to the cell size in the soft-pack battery and the subsequent battery management requirements, the two-dimensional size of the reference electrode is determined to be 45×58mm. By reasonably designing the functional requirements of the reference electrode inside the battery and combining the battery processing technology, the surface capacity, assembly process and stacking order of the reference electrode are determined.

[0095] The Z-shaped lamination process is adopted (i.e. the reference electrode tab is located on the opposite side of the positive tab), and the reference electrode and other pole pieces are laminated and assembled. It is particularly important to note that the two pole pieces adjacent to the reference electrode are coated on one side and are both positive or negative. The pole pieces at other positions are assembled in a cross-laminated manner with positive and negative pole pieces. After the battery cell is laminated, it is fixed with fixing tape. The assembled battery cell is as follows: Figure 2 shown.

[0096] Lead the reference electrode's tab lead from the bottom of the battery cell and weld it with a copper-plated nickel tab. Weld the aluminum tab and the nickel tab to the positive and negative electrodes respectively to obtain the laminated battery cell body;

[0097] Then put the battery body into the aluminum-plastic film shell, and use a heat sealer to seal the tab side and the bottom of the tab of the battery. The reference electrode tab is also sealed and connected to the external device. To ensure the sealing performance of the battery, the length of the bottom aluminum-plastic film seal in the soft-pack battery is not less than 6 mm;

[0098] Dry in a high-temperature vacuum box, and after cooling, inject electrolyte matching the cell capacity into the soft-pack battery packaging bag under negative pressure (1M LiPF6 in a mixed solvent of EC:DMC:DEC, with a volume ratio of EC:DMC:DEC of 1:1:1). During the drying and injection process, pay attention to the electrical insulation treatment and protection of the reference electrode, positive and negative electrodes;

[0099] After the battery is vacuumed and sealed for the first time, it is formed and sorted, and then vacuumed and sealed for the second time to obtain a three-electrode battery; Figure 6 Schematic diagram of the sealing process of the soft-pack battery obtained in Example 2; the voltage signal during the formation process is monitored throughout, including the voltage signal of the positive electrode to the reference electrode and the voltage signal of the negative electrode to the reference electrode, wherein the potential information obtained before sorting is as follows Figure 7 shown.

[0100] Example 3

[0101] Performing battery management and capacity recovery on the three-electrode battery obtained in Example 2;

[0102] The three-electrode battery obtained in Example 2 is subjected to charge and discharge cycles, and voltage signals during the charge and discharge cycles are monitored throughout the entire process, including the voltage signal of the positive electrode relative to the reference electrode and the voltage signal of the negative electrode relative to the reference electrode; Figure 8 Schematic diagram of the reference electrode monitoring the positive and negative electrode potentials of lithium-ion batteries during long cycles, where the upper figure is the positive and negative electrode potential information diagram, and the lower figure is the battery cycle capacity; Fig. 9 Schematic diagram of the positive and negative electrode potentials of lithium-ion batteries monitored by the reference electrode during the cycle test at different rates; the upper figure shows the positive and negative electrode potentials at different rates, and the lower figure shows the battery cycle capacity;

[0103] The battery state of charge is determined by monitoring the voltage signal of the negative electrode to the reference electrode and charge / discharge management is performed. The battery aging state is determined by the differential voltage method. At the same time, the potential fluctuation of the positive / negative electrode of the battery to the reference electrode can be used as a reference indicator for safety management. When the potential of the graphite negative electrode is close to 0V, charging should be stopped immediately;

[0104] The cycle capacity of the battery is detected by the ampere-hour integration method. When the cycle capacity of the battery cell is less than 80% of the initial capacity, the reference electrode and the negative electrode form a current loop. By applying external excitation, the active lithium ions in the reference electrode are released and transferred to the negative electrode to compensate for the loss of active lithium during battery cycle aging and the growth of the negative electrode SEI film. The matrix pulse current excitation scheme is used in this implementation case to control the excitation current at the microampere level. The specific steps of applying the excitation are as follows: Fig.10 As shown. After the negative electrode is replenished with lithium, the reference electrode and the positive electrode form a loop, and the above steps are repeated to replenish the positive electrode with lithium. By designing the external circuit and the excitation step, the active lithium ions / sodium ions are released into the electrolyte and the positive and negative electrode active materials to participate in the battery's charge and discharge cycle, thereby realizing the battery's capacity recovery.

[0105] After current excitation, the battery after capacity recovery operation is electrochemically tested, and the capacity and impedance characteristics of the battery are recalibrated. The battery is put into use again after testing and sorting, and the charge state, aging state and safety state of the battery during the cycle application process are monitored. Fig.11 As shown in the figure, the capacity of the soft-pack battery in this embodiment decays to 80% after 800 cycles at a 1C rate. At this point, the cycle test is stopped, and the reference electrode is used to release active lithium to replenish the battery. After the active lithium of the reference electrode is replenished, the battery recovers a capacity of 55mAh and runs stably in the subsequent 400 cycles, with no obvious loss of battery capacity.

[0106] In summary, the solution of the present invention has been successfully applied in rechargeable batteries. It not only realizes the processing of battery cells with internal reference electrodes implanted by conventional solutions, but also can stably detect the positive and negative electrode potentials of the battery during battery formation and long cycle processes. When the battery capacity decays, the reference electrode is stimulated by an external circuit and the active lithium is released, which effectively supplements the active lithium loss of the battery during the cycle and restores the battery capacity. After the capacity was repaired, the battery continued to run stably for 400 cycles without obvious capacity loss.

[0107] The present invention effectively simplifies the implantation process and cost of the reference electrode in the battery, and integrates multiple functions of potential monitoring and capacity repair in the reference electrode. In practical applications, the reference electrode proposed in the present invention accurately monitors the positive and negative electrode potentials of the battery during operation, and greatly reduces the use cost of the reference electrode. Therefore, the technical solution proposed in the present invention can be applied to lithium-ion batteries and sodium-ion batteries, and is applicable to both soft-pack batteries and square-shell batteries. The designed capacity recovery method can effectively improve the cycle life and economic efficiency of the battery. The above scheme ensures the large-scale preparation of the reference electrode, realizes the stable monitoring of the positive and negative electrode potentials during the operation of the battery, and can restore the battery capacity after battery aging.

[0108] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A reference electrode, characterized in that It comprises a current collector and an active layer and an anti-oxidation layer sequentially wrapped on the surface of the current collector; The material of the active layer includes an active material for lithium ion batteries or an active material for sodium ion batteries; the content of the material of the active layer in the reference electrode is 0.05-0.08 g / cm 2 ; The material of the anti-oxidation layer includes a solid electrolyte.

2. The reference electrode according to claim 1, characterized in that The thickness of the active layer is ≥6 μm; the thickness of the anti-oxidation layer is 2-3 μm.

3. The reference electrode according to claim 1, characterized in that One end of the reference electrode also includes a reference electrode tab; the reference electrode tab is a nickel tab with a copper-plated surface.

4. A long-life three-electrode battery, characterized in that: Including battery cell body, electrolyte and battery shell; The battery cell body comprises a positive electrode, a negative electrode, a separator and a reference electrode; The reference electrode is the reference electrode according to any one of claims 1 to 3.

5. The long-life three-electrode battery according to claim 4, characterized in that: The battery cell body comprises a laminated battery cell body or a wound battery cell body; The laminated battery cell body comprises a positive electrode, a reference electrode and a negative electrode which are stacked in sequence, and a diaphragm is arranged between the reference electrode and the positive electrode, and between the reference electrode and the negative electrode; The wound battery cell body comprises a positive electrode, a reference electrode and a negative electrode which are stacked and wound in sequence, and a separator is arranged between the reference electrode and the positive electrode and between the reference electrode and the negative electrode.

6. The long-life three-electrode battery according to claim 4, characterized in that: One end of the positive electrode further includes a positive electrode tab, and the positive electrode tab is an aluminum tab; One end of the negative electrode further includes a negative electrode tab, and the negative electrode tab is a nickel tab; The positive electrode tab and the negative electrode tab are located on the same side of the battery cell body; The reference electrode tab is located on the same side or the opposite side of the positive electrode tab.

7. The long-life three-electrode battery according to claim 4, characterized in that: The long-life three-electrode battery comprises a soft-pack battery or a square-shell battery; the battery shell of the soft-pack battery is an aluminum-plastic film shell.

8. The method for preparing a long-life three-electrode battery according to any one of claims 4 to 7, characterized in that: The following steps are involved: Provide the battery cell body; The battery cell body is placed in a battery shell for liquid injection and packaging, and then formed and sorted to obtain the long-life three-electrode battery.

9. A method for restoring battery capacity, characterized in that: The following steps are involved: The battery is a long-life three-electrode battery according to any one of claims 4 to 7 or a long-life three-electrode battery prepared by the preparation method according to claim 8; The battery is charged and discharged in cycles. When the cycle capacity of the battery cell is lower than 80% of the initial capacity, the reference electrode is sequentially connected with the negative electrode or the positive electrode to form a current loop, and a pulse current is applied to the battery to replenish lithium or sodium to the negative electrode or the positive electrode, respectively, so as to achieve battery capacity recovery.

10. The capacity recovery method according to claim 9, characterized in that: The pulse current includes a matrix pulse current, and the procedure of the matrix pulse current is: charging at 3μA for 10 minutes, charging at 3μA for 10 minutes after standing for 10 minutes, charging at 5μA for 10 minutes after standing for 10 minutes, charging at 4μA for 10 minutes after standing for 5 minutes, and charging at 2μA for 20 minutes after standing for 10 minutes.

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