Three-electrode lithium battery, preparation method thereof and lithium ion battery performance testing method

Abstract

The application provides a three-electrode lithium battery and a preparation method thereof, and a lithium ion battery performance test method. The three-electrode lithium battery comprises, in sequence, a positive electrode sheet, a first diaphragm, a reference electrode, a second diaphragm and a negative electrode sheet. The reference electrode comprises a copper current collector and a lithium coating layer. The lithium coating layer comprises a first lithium coating layer and a second lithium coating layer arranged on two side surfaces of the copper current collector respectively. The first lithium coating layer faces the first diaphragm, and the second lithium coating layer faces the second diaphragm. The three-electrode lithium battery according to the embodiment of the application is actually connected by two half batteries, i.e., the positive electrode sheet-reference electrode and the reference electrode-negative electrode sheet, because the lithium coating layer is arranged on both sides of the copper current collector. By measuring the potential change of the positive electrode sheet-reference electrode and the reference electrode-negative electrode sheet during the charging and discharging process, the interference of the small reference electrode inserted into the electric field between the positive electrode and the negative electrode is avoided, and the accuracy of the potential test can be improved.

Description

Technical Field

[0001] This invention relates to the field of new energy power lithium battery technology, specifically to three-electrode lithium batteries and their preparation methods, as well as lithium-ion battery performance testing methods. Background Technology

[0002] In recent years, the use of three-electrode lithium-ion batteries to study potential changes, impedance changes, and lithium plating behavior under different conditions has become an important analytical method. To date, many methods for preparing three electrodes have been proposed, involving the selection of the reference electrode type (e.g., copper wire) and the selection of the reference electrode position (e.g., placing the reference electrode at the edge of the positive and negative electrode plates). Factors such as the reference electrode type and position, and the fabrication process, all affect the test results for potential and impedance. Therefore, selecting a suitable three-electrode configuration is extremely important.

[0003] Currently, commonly used lithium-ion battery three electrodes typically employ copper wire or lithium oxide with a potential plateau as the reference electrode. The method involves placing the reference electrode at the edge of the positive and negative electrodes and measuring the potential changes during dynamic charging and discharging. However, when the reference electrode is placed at the edge of the cell, the high impedance between the reference electrode and the positive and negative electrodes causes a shift in the measured potential.

[0004] Therefore, three-electrode lithium batteries, which have minimal impact on the positive and negative electrodes and can accurately measure electrode potentials, are extremely important. Summary of the Invention

[0005] In view of this, the present invention provides a three-electrode lithium battery that has little impact on the positive and negative electrodes and can accurately measure the electrode potential, as well as a method for preparing the same, and a method for testing the performance of lithium-ion batteries using the above-mentioned three-electrode lithium battery.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] According to the first aspect of the present invention

[0008] A three-electrode lithium battery includes a positive electrode, a first separator, a reference electrode, a second separator, and a negative electrode arranged sequentially, wherein the reference electrode includes a copper current collector;

[0009] The lithium coating layer includes a first lithium coating layer facing the first membrane and a second lithium coating layer facing the second membrane, respectively disposed on both sides of the copper current collector.

[0010] Furthermore, the thickness of the copper current collector is 4-10 μm.

[0011] Furthermore, the thickness of the lithium coating layer is 50-100 μm.

[0012] Furthermore, the positive electrode sheet includes a positive current collector and a positive active layer formed on the surface of the positive current collector, and the negative electrode sheet includes a negative current collector and a negative active layer formed on the surface of the negative current collector, wherein the area of ​​the lithium coating layer is greater than the area of ​​the negative active layer and the area of ​​the positive active layer.

[0013] Furthermore, the positive electrode, the first separator, the reference electrode, the second separator, and the negative electrode are sealed together with sealant, which is applied to the blank areas around the positive electrode, the reference electrode, and the negative electrode.

[0014] Furthermore, the sealant is a thermosetting polyolefin resin or an organosilicon compound, and the thermosetting temperature of the sealant is 80-150℃.

[0015] Furthermore, the coating width of the sealant is 2-6 mm, and the coating thickness is 0.1-0.4 mm.

[0016] The method for preparing a three-electrode lithium battery according to a second aspect of the present invention includes the following steps:

[0017] S1 provides a positive electrode, a first separator, a negative electrode, and a second separator;

[0018] S2, Prepare the reference electrode, including:

[0019] Provide copper current collectors;

[0020] A lithium plating layer is respectively applied to both sides of the copper current collector;

[0021] S3, apply sealant to the blank areas around the positive electrode, negative electrode, and reference electrode, and apply the sealant to the corresponding positions around the first diaphragm and the second diaphragm;

[0022] S4. Assemble the positive electrode, first diaphragm, reference electrode, second diaphragm, and negative electrode in that order and cure the sealant on both sides and the bottom to obtain the assembly.

[0023] S5, inject electrolyte into the assembly and cure the sealant at the top of the assembly to obtain a battery cell;

[0024] S6. The battery cell is encapsulated in an aluminum-plastic film to obtain a three-electrode lithium battery.

[0025] A lithium-ion battery performance testing method according to a third aspect of the present invention includes:

[0026] S100, a three-electrode lithium battery is prepared according to the preparation method described in the second aspect embodiment of the present invention;

[0027] S200, the three-electrode lithium battery is immersed at room temperature for more than 48 hours;

[0028] S300, the three-electrode lithium battery is charged and discharged, and the potential is monitored through the positive electrode, the reference electrode, and the negative electrode.

[0029] The above-described technical solution of the present invention has at least one of the following beneficial effects:

[0030] According to an embodiment of the present invention, a three-electrode lithium battery is provided with a reference electrode inserted between the positive and negative electrodes. Since a lithium coating layer is provided on both sides of the copper current collector, the three-electrode lithium battery is actually composed of two half-cells, namely, positive electrode-reference electrode and reference electrode-negative electrode connected together. By measuring the potential changes of positive electrode-reference electrode and reference electrode-negative electrode during charging and discharging, the problem of potential deviation caused by the large impedance between the reference electrode and the positive and negative electrodes when the reference electrode is placed at the edge of the cell in the prior art is overcome.

[0031] Furthermore, by ensuring that the area of ​​the lithium-coated layer is greater than the area of ​​the negative electrode active layer, which is greater than the area of ​​the positive electrode active layer, the reference electrode is ensured to be large enough. This avoids interference with the electric field between the positive and negative electrodes caused by the insertion of a small reference electrode, thereby improving the accuracy of potential testing. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a three-electrode lithium battery according to an embodiment of the present invention;

[0033] Figure 2 This is a front view of the positive electrode in a three-electrode lithium battery according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic flowchart of the preparation method of a three-electrode lithium battery according to an embodiment of the present invention;

[0035] Figure 4 The charge / discharge potential curves are obtained by potential monitoring of the three-electrode lithium battery according to Embodiment 1 of the present invention.

[0036] Figure label:

[0037] 1. Aluminum-plastic film; 2. Positive electrode current collector; 3. Positive electrode active layer; 41. First separator; 42. Second separator; 5. Copper current collector; 61. First lithium coating layer; 62. Second lithium coating layer; 7. Negative electrode active layer; 8. Negative electrode current collector; 9. Sealant; 10. Positive electrode tab; 11. Reference electrode tab; 12. Negative electrode tab. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0039] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0040] The following section will first combine the appendix. Figure 1 A detailed description of a three-electrode lithium battery according to an embodiment of the present invention.

[0041] like Figure 1 As shown, a three-electrode lithium battery according to an embodiment of the present invention includes a positive electrode, a first separator 41, a reference electrode, a second separator 42, and a negative electrode arranged sequentially.

[0042] The reference electrode will be described in detail below.

[0043] The reference electrode according to an embodiment of the present invention includes a copper current collector 5 and a lithium coating layer. The lithium coating layer includes a first lithium coating layer 61 and a second lithium coating layer 62 respectively disposed on both sides of the copper current collector 5, wherein the first lithium coating layer 61 is located on the side facing the first separator 41, and the second lithium coating layer 62 is located on the side facing the second separator 42.

[0044] In other words, according to the reference electrode in this embodiment of the invention, lithium plating layers are provided on both sides of the copper current collector 5, that is, a first lithium plating layer 61 and a second lithium plating layer 62 are respectively provided on both sides of the copper current collector 5. A three-electrode lithium battery prepared using this method, such as... Figure 1As shown, a reference electrode is inserted between the positive and negative electrodes. The positive electrode, the first separator 41, the first lithium coating layer 61, and the copper current collector 5 (and the electrolyte filled therein) constitute one half-cell. Similarly, the negative electrode, the second separator 42, the second lithium coating layer 62, and the copper current collector 5 (and the electrolyte filled therein) constitute another half-cell. When monitoring the potential change between the positive and negative electrodes using this three-electrode lithium battery, it is actually monitoring the potential change between the positive electrode-reference electrode pair and the negative electrode-reference electrode pair. That is, the three-electrode lithium battery of the present invention, by setting lithium coating layers on both sides of the reference electrode to form two half-cells, and by monitoring the potential change between the electrode pairs of the two half-cells, not only overcomes the problem of potential shift caused by the high impedance when the reference electrode is placed at the edge of the cell in the prior art, but also overcomes the problem of the electric field distribution between the positive and negative electrodes being affected by directly inserting the "reference electrode" between the positive and negative electrodes in the prior art. Therefore, the three-electrode lithium battery according to the present invention not only has little impact on the positive and negative electrodes, but also enables accurate measurement of electrode potentials.

[0045] According to some embodiments of the present invention, the thickness of the copper current collector is 4-10 μm. The thickness of the copper current collector can be designed according to the power, current intensity, etc. of the battery to be assembled.

[0046] The copper current collector can be, for example, a copper wire or copper strip, or other conventional materials used as current collectors for reference electrodes.

[0047] According to some embodiments of the present invention, the thickness of the lithium coating layer is 50-100 μm. The thickness of the lithium coating layer can be designed according to the specific characteristics of the battery to be assembled, the areal density of the lithium coating layer, etc.

[0048] The thickness of the first lithium coating layer 61 and the second lithium coating layer 62 can be the same or different, but preferably the same.

[0049] In addition, as a method for setting the lithium coating layer, for example, a slurry containing lithium metal particles can be applied to the surface of the copper current collector by coating, sputtering, impregnation, etc., or a lithium metal film can be pressed onto the copper current collector. The present invention does not limit the specific setting method.

[0050] The following describes in more detail the three-electrode lithium battery of the present invention using the above-described reference electrode.

[0051] Furthermore, the positive electrode includes a positive current collector and a positive active layer formed on the surface of the positive current collector, and the negative electrode includes a negative current collector and a negative active layer formed on the surface of the negative current collector.

[0052] The specific materials and formation methods of the positive electrode current collector, positive electrode active layer, negative electrode current collector, and negative electrode active layer in the three-electrode lithium battery of this application are not specifically limited. In other words, the reference electrode of this application can be used in any lithium battery for positive and negative electrode detection.

[0053] According to some embodiments of the present invention, the area of ​​the lithium coating layer is greater than the area of ​​the negative electrode active layer, which is greater than the area of ​​the positive electrode active layer.

[0054] In electrode testing, inserting a small reference electrode between the positive and negative electrodes can affect the electric field distribution between them during charging and discharging, thus impacting the accuracy of potential testing. Therefore, by ensuring that the area of ​​the lithium-coated layer is greater than the area of ​​the negative electrode active layer, which is greater than the area of ​​the positive electrode active layer, interference with the electric field between the positive and negative electrodes can be minimized, overcoming the resulting measurement errors.

[0055] In some embodiments of the present invention, the positive electrode, the first separator, the reference electrode, the second separator, and the negative electrode are sealed together with a sealant, which is applied to the blank areas around the positive electrode, the reference electrode, and the negative electrode.

[0056] In other words, when preparing the positive electrode, reference electrode, and negative electrode, the active layer is placed in the middle area when setting the active layer on the current collector, and a blank area without coating is left around it so that sealant can be applied to the blank area for sealing and filling with electrolyte.

[0057] The sealant, for example, can be a thermosetting polyolefin resin or an organosilicon compound, with a thermosetting temperature of 80-150°C. Thermosetting polyolefin resins or organosilicon compounds possess both insulating properties and excellent resistance to electrolyte corrosion. Using them for sealing can prevent electrolyte leakage and extend battery life. Furthermore, selecting a thermosetting polyolefin resin or organosilicon compound with a thermosetting temperature of 80-150°C, preferably 100-130°C, ensures that the processing temperature does not cause deterioration of the electrolyte, positive and negative electrodes, separator, reference electrode, etc., and simplifies operation.

[0058] In some embodiments of the present invention, the sealant has a coating width of 2-6 mm and a coating thickness of 0.1-0.4 mm. The specific width and coating thickness of the sealant can be designed according to the size of the assembled battery, the usage environment, etc. Preferably, the amount of sealant used is minimized while ensuring sealing.

[0059] Below, in conjunction with Figure 3 This invention describes a method for preparing a three-electrode lithium battery according to an embodiment of the present invention.

[0060] like Figure 3 As shown, the preparation method of a three-electrode lithium battery according to an embodiment of the present invention includes the following steps:

[0061] S1 provides a positive electrode, a first separator, a negative electrode, and a second separator.

[0062] Specifically, providing the positive electrode sheet may include: providing a positive electrode current collector, providing a positive electrode slurry, coating one side surface of the positive electrode current collector with the positive electrode slurry, and evaporating the solvent to obtain a positive electrode active layer. Referring to the above description of a three-electrode lithium battery, this invention does not impose any limitations on the materials of the positive electrode current collector and the positive electrode active layer, nor on the specific preparation method; therefore, detailed descriptions are omitted here.

[0063] The first and second separators can use the same or different separator materials; this invention does not limit this. Furthermore, the separator materials used in conventional lithium batteries can also be used; this invention does not limit this either.

[0064] Similarly, providing a negative electrode sheet may include: providing a negative electrode current collector, providing a negative electrode slurry, coating one side surface of the negative electrode current collector with the negative electrode slurry, and evaporating the solvent to obtain a negative electrode active layer. Referring to the above description of a three-electrode lithium battery, there are no limitations on the materials of the negative electrode current collector and the negative electrode active layer, or on the specific preparation method, and therefore detailed descriptions are omitted here.

[0065] S2, Prepare the reference electrode, including:

[0066] Provide copper current collectors;

[0067] A lithium coating layer is respectively applied to both sides of the copper current collector.

[0068] Specifically, the copper current collector can be, for example, a copper-lithium-copper composite strip.

[0069] In addition, as a method for setting the lithium coating layer, as described above, for example, a slurry containing lithium metal particles can be set on the surface of the copper current collector by coating, sputtering, impregnation, etc., or a lithium metal film can be pressed onto the copper current collector. The present invention does not limit the specific setting method.

[0070] It should be noted here that when coating the positive electrode slurry on the positive electrode current collector, such as... Figure 2 As shown, a blank area can be left around the perimeter for applying sealant. The same applies to the negative electrode and reference electrode when coating the negative electrode slurry and lithium layer. Alternatively, after coating the positive and negative electrode slurries to form the corresponding active layers, the active layer around the perimeter can be removed by etching.

[0071] S3, tabs are respectively provided on the positive electrode, negative electrode and reference electrode.

[0072] In other words, after the positive electrode, negative electrode, and reference electrode are fabricated, each is fitted with its own tab for connecting wires. For example, the tabs can be welded together.

[0073] In addition, before setting the tabs, the positive electrode, the first diaphragm, the reference electrode, the second diaphragm, and the negative electrode can be cut to ensure that each size corresponds.

[0074] It should be noted that this step can be omitted if the tab and current collector are integrally molded.

[0075] S4, apply sealant to the blank areas around the positive electrode, negative electrode, and reference electrode, and apply the sealant to the corresponding positions around the first diaphragm and the second diaphragm.

[0076] For details regarding the material and dimensions of the sealant, please refer to the description of the three-electrode lithium battery mentioned above; detailed descriptions are omitted here.

[0077] S5. Assemble the positive electrode, first diaphragm, reference electrode, second diaphragm, and negative electrode in that order, and cure the sealant on both sides and the bottom to obtain the assembly.

[0078] In other words, after the positive electrode, the first separator, the reference electrode, the second separator, and the negative electrode are prepared separately, they are first assembled. Then, in order to inject the electrolyte into the assembly, the sealant on the left and right sides and the bottom is first cured and sealed.

[0079] Specifically, the sealant can be heated to its heat-curing temperature and kept at that temperature for an appropriate time to allow it to fully cure and achieve a seal.

[0080] S6, inject electrolyte into the assembly and cure the sealant at the top of the assembly to obtain a battery cell.

[0081] After sealing the left, right, and bottom ends, electrolyte can be injected from the top of the assembly. Specifically, electrolyte is injected from the top of the assembly between the positive electrode and the reference electrode, and between the reference electrode and the negative electrode.

[0082] After the electrolyte filling is completed, a vacuum is drawn to remove the gas, and the top is heated to the curing temperature of the sealant to complete the sealing and obtain the battery cell.

[0083] S7. The battery cell is packaged to obtain a three-electrode lithium battery.

[0084] Specifically, for example, the aforementioned battery cells such as Figure 1As shown, when sealed inside the aluminum-plastic film 1, a three-electrode lithium battery can be obtained.

[0085] The three-electrode lithium battery obtained above, after being left to stand for, for example, more than 48 hours to allow the electrolyte to fully wet the positive and negative electrodes and the reference electrode, can be used to monitor the potential changes during charging and discharging, thereby testing its electrical performance.

[0086] The following examples further illustrate the three-electrode lithium battery and its preparation method according to embodiments of the present invention.

[0087] Example 1

[0088] Material:

[0089] Positive current collector: aluminum foil

[0090] Negative current collector: copper foil

[0091] The copper current collector for the reference electrode is a copper strip with a thickness of 6 μm.

[0092] First and second diaphragms: 14µm thick polyethylene (PE) diaphragms

[0093] Aluminum-plastic film: 148μm thick aluminum-plastic film. Tabs: Aluminum tabs are used for the positive electrode, while copper-plated nickel tabs are used for the negative electrode and reference electrode. Electrolyte: 1M LiPF6, 1:1 EC / DMC (ethylene carbonate (EC) + dimethyl carbonate (DMC)), 10% FEC (fluoroethylene carbonate).

[0094] Sealant: Epoxy resin, hot melt temperature 130℃.

[0095] The fabrication process of a three-electrode lithium battery is as follows:

[0096] 1) Mixing paste:

[0097] Positive electrode slurry: The positive electrode slurry was prepared according to the ratio of NCM811 (lithium nickel cobalt manganese oxide composite material, wherein nickel:cobalt:manganese = 0.8:0.1:0.1):SP (conductive carbon black):PVDF (polyvinylidene fluoride) = 95:2.5:2.5.

[0098] Negative electrode slurry: The negative electrode slurry was prepared according to the ratio of SiO / C:SP:CMC (sodium carboxymethyl cellulose) = 91.5:1.7:6.8.

[0099] 2) Electrode preparation

[0100] Electrode cutting: The positive electrode current collector is cut to a size of 80*80mm, the negative electrode current collector to a size of 80*80mm, the separator to a size of 85*85mm, and the reference electrode current collector to a size of 80*80mm.

[0101] Positive and negative electrode plates: The positive electrode slurry is coated onto the positive electrode current collector (aluminum foil), and the negative electrode slurry is coated onto the negative electrode current collector (copper foil). The capacity of the positive electrode coating area is 9 mAh / cm2, the capacity of the negative electrode coating area is 10.8 mAh / cm2, and the NP ratio is 1.2.

[0102] The positive electrode coating area is 60*60mm, and the blank area is 20mm; the negative electrode coating area is 65*65mm, and the blank area is 15mm.

[0103] Reference electrode sheet: Lithium metal layers are laminated onto both sides of a copper strip to obtain a lithium-copper-lithium composite strip. The thickness of the lithium layer on each side is 100 μm. The lamination area of ​​the lithium metal layers on both sides of the reference electrode sheet is 70*70 mm, with a blank space of 10 mm.

[0104] Tab welding: The positive electrode, negative electrode, and reference electrode are welded with tabs respectively. The positive electrode is welded to the aluminum tab, the negative electrode is welded to the copper-plated nickel tab, and the reference electrode is welded to the copper-plated nickel tab.

[0105] 3) Battery manufacturing

[0106] 3.1) Assembly: Assemble the battery in the order of positive electrode, separator, reference electrode, separator, and negative electrode.

[0107] 3.2) Applying sealant: Apply sealant to the blank areas of the positive electrode, negative electrode, and reference electrode respectively. The application size is 4mm wide and 0.2mm thick. The sealant application should be the same as the length or width of the electrode to ensure complete sealing.

[0108] 3.3) Primary Encapsulation: The positive electrode and the separator, the negative electrode and the separator, and the reference electrode and the separator are sealed with sealant through heat curing at 130°C, leaving the top as the liquid injection port. This forms two half-cells: one with the positive electrode facing the reference electrode, and the other with the negative electrode facing the reference electrode.

[0109] 3.4) Secondary encapsulation: Liquid is injected into the two half-cells, the positive electrode-reference electrode and the negative electrode-reference electrode, through the liquid injection port at the top. The liquid injection volume is the same, 5g / Ah. After vacuuming, the top is sealed.

[0110] 3.5) Third encapsulation: The assembled battery cells are encapsulated with an aluminum-plastic film to obtain a three-electrode lithium battery.

[0111] After obtaining the above-mentioned three-electrode lithium battery, the electrical performance was tested as follows:

[0112] (a) Immersion: The three-electrode lithium battery obtained above is immersed at room temperature for 48 hours.

[0113] (b) Battery testing: The positive and negative electrodes are connected to the Xinwei test cabinet for charge and discharge testing; the multi-channel recorder is connected to the positive, negative and reference electrodes for potential monitoring.

[0114] Comparative Example

[0115] The materials of the positive electrode, negative electrode, separator, and electrolyte are the same as those described above, and the preparation methods are also the same.

[0116] Furthermore, the materials of the current collector and the lithium coating layer used as the reference electrode are the same. However, in this comparative example, the lithium metal coating of the reference electrode has a width of 1mm and a length of 10mm.

[0117] Furthermore, during assembly, the battery is assembled in the following order: positive electrode, first separator, negative electrode, second separator, and reference electrode. That is, the reference electrode is located at the edge of the battery.

[0118] Furthermore, the packaging, liquid injection, and testing are the same as in Example 1.

[0119] Figure 4 The test results for Example 1 and the comparative example are shown.

[0120] Depend on Figure 4 It can be seen that in the comparative example, the dynamic potential exhibits potential shift.

[0121] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A three-electrode lithium battery, characterized in that, The device includes a positive electrode, a first separator, a reference electrode, a second separator, and a negative electrode arranged sequentially. The reference electrode includes a copper current collector and a lithium coating layer. The lithium coating layer includes a first lithium coating layer and a second lithium coating layer respectively disposed on both sides of the copper current collector. The first lithium coating layer faces the first separator, and the second lithium coating layer faces the second separator. The positive electrode, the first separator, the reference electrode, the second separator, and the negative electrode are sealed in pairs with sealant. The sealant is applied to the blank areas around the positive electrode, the reference electrode, and the negative electrode.

2. The three-electrode lithium battery according to claim 1, characterized in that, The thickness of the copper current collector is 4-10 μm.

3. The three-electrode lithium battery according to claim 1, characterized in that, The thickness of the lithium coating layer is 50-100 μm.

4. The three-electrode lithium battery according to claim 1, characterized in that, The positive electrode sheet includes a positive current collector and a positive active layer formed on the surface of the positive current collector. The negative electrode sheet includes a negative current collector and a negative active layer formed on the surface of the negative current collector, wherein the area of ​​the lithium coating layer is greater than the area of ​​the negative active layer and the area of ​​the positive active layer.

5. The three-electrode lithium battery according to claim 1, characterized in that, The sealant is a thermosetting polyolefin resin or an organosilicon compound, and the thermosetting temperature of the sealant is 80-150℃.

6. The three-electrode lithium battery according to claim 1, characterized in that, The sealant has a coating width of 2-6 mm and a coating thickness of 0.1-0.4 mm.

7. A method for preparing a three-electrode lithium battery according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1 provides a positive electrode, a first separator, a negative electrode, and a second separator; S2, Prepare the reference electrode, including: Provide copper current collectors; A lithium plating layer is respectively applied to both sides of the copper current collector; S3, apply sealant to the blank areas around the positive electrode, negative electrode, and reference electrode, and apply the sealant to the corresponding positions around the first diaphragm and the second diaphragm; S4. Assemble the positive electrode, first diaphragm, reference electrode, second diaphragm, and negative electrode in that order and cure the sealant on both sides and the bottom to obtain the assembly. S5, inject electrolyte into the assembly and cure the sealant at the top of the assembly to obtain a battery cell; S6. The battery cell is packaged to obtain a three-electrode lithium battery.

8. A method for testing the performance of a lithium-ion battery, characterized in that, include: S100, a three-electrode lithium battery is prepared according to the preparation method described in claim 7; S200, the three-electrode lithium battery is immersed at room temperature for more than 48 hours; S300, the three-electrode lithium battery is charged and discharged, and the potential is monitored through the positive electrode, the reference electrode, and the negative electrode.

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