Reference electrode, preparation method thereof and three-electrode lithium ion battery

Abstract

The application discloses a reference electrode and a preparation method thereof and a three-electrode lithium ion battery, and the reference electrode comprises: a first reference electrode tab, a coiled structure and a second reference electrode tab which are sequentially stacked; the coiled structure comprises a first metal foil and a second metal foil which are integrally connected, and a first copper wire and a second copper wire which are integrally connected, the first copper wire is wound on the first metal foil, the first metal foil wound with the first copper wire is coiled on the inner side of the second metal foil, the second copper wire is arranged away from the first reference electrode tab and the second reference electrode tab, and the second copper wire is provided with a lithium layer at the end away from the first copper wire. The application greatly reduces the operation difficulty coefficient of the preparation of the reference electrode, improves the success rate of the preparation of the three-electrode soft package lithium ion battery, and can prevent the copper wire from falling off or sliding off from the surface of the reference electrode tab. In addition, the contact area of the tab and the coiled structure is increased, the polarization caused by the structure of the battery cell is reduced, and the internal resistance of the reference electrode is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of three-electrode lithium ion batteries, and particularly relates to a reference electrode, a preparation method thereof and a three-electrode lithium ion battery. BACKGROUND

[0002] The three-electrode lithium ion battery is a multi-electrode system assembled by implanting a reference electrode into a lithium ion battery, so as to monitor the positive and negative electrode potentials in situ, thereby separately analyzing the electrochemical performance of the positive and negative electrodes of the lithium ion battery. The three-electrode lithium ion battery is a common method for analyzing the safety performance and cycle performance of the lithium ion battery. The preparation of the reference electrode of the three-electrode lithium ion battery is crucial. The current mature process still adopts copper-nickel plating as the reference electrode. The copper wire has a small diameter (20-200 μm) and high toughness, and it is difficult to separately wind and fix the copper wire on the surface of the reference tab. When welding, the distance between the welding points of the ultrasonic welding is greater than the distance of the copper wire, which is easy to form a false weld. Direct contact of the copper wire with the welding equipment is easy to break the copper wire, block the circuit and cause the reference electrode to fail. Therefore, the preparation and packaging of the reference electrode become a key problem. SUMMARY

[0003] The present application aims to at least partially solve one of the problems in the related art. To this end, one object of the present application is to provide a reference electrode, a preparation method thereof and a three-electrode lithium ion battery. The present application avoids direct contact of the reference electrode tab with high hardness with the copper wire, protects the copper wire from being broken, and the metal foil has soft texture and is not easy to damage the copper wire, greatly reduces the operation difficulty coefficient of preparing the reference electrode, and improves the success rate of preparing the three-electrode soft package lithium ion battery. At the same time, the winding structure can also prevent the copper wire from falling off or sliding off the surface of the reference electrode tab, and prevent the copper wire from being broken during welding, so that the copper wire cannot conduct electricity and cannot be plated with lithium. In addition, the contact area between the tab and the winding structure is also increased, the polarization caused by the structure of the battery is reduced, and the internal resistance of the reference electrode is reduced.

[0004] In one aspect of the present application, the present application provides a reference electrode. According to the embodiments of the present application, the reference electrode comprises:

[0005] a first reference electrode tab, a winding structure and a second reference electrode tab which are sequentially stacked;

[0006] The winding structure comprises a first metal foil and a second metal foil which are integrally connected, and a first copper wire and a second copper wire which are integrally connected. The first copper wire is wound on the first metal foil, the first metal foil with the first copper wire wound thereon is wound on the inner side of the second metal foil, the second copper wire is arranged away from the first reference electrode tab and the second reference electrode tab, and the end of the second copper wire away from the first copper wire is provided with a lithium layer.

[0007] According to the reference electrode of the embodiment of the present application, the first metal foil with the first copper wire wound thereon is wound inside the second metal foil to form a winding structure, and the first reference electrode tab, the winding structure and the second reference electrode tab are stacked to form a sandwich structure, thereby avoiding the direct contact of the first reference electrode tab and the second reference electrode tab with high hardness with the copper wire, protecting the copper wire from being broken, and the metal foil has soft texture and is not easy to damage the copper wire, greatly reducing the operation difficulty coefficient of preparing the reference electrode, improving the success rate of preparing the three-electrode soft package lithium ion battery, and the success rate of the present application can almost reach 100%, while the success rate of directly winding the copper wire on the surface of the reference electrode tab can only reach about 50%-60%; at the same time, the winding structure can also prevent the copper wire from falling off or sliding off from the surface of the reference electrode tab, and prevent the copper wire from being broken during welding, so that the copper wire cannot conduct electricity and cannot be plated with lithium; in addition, the contact area between the tab and the winding structure is increased, the polarization caused by the structure of the battery is reduced, and the internal resistance of the reference electrode is reduced.

[0008] In addition, the reference electrode according to the above-mentioned embodiments of the present application can also have the following additional technical features:

[0009] In some embodiments of the present application, the first reference electrode tab and the second reference electrode tab are each independently a copper-nickel-plated tab, a nickel tab, an aluminum-nickel-plated tab or an aluminum tab.

[0010] In some embodiments of the present application, the first metal foil and the second metal foil are each independently a metal copper foil, a metal aluminum foil or a metal tin foil.

[0011] In some embodiments of the present application, the thickness of the first metal foil and the second metal foil is 1-10 μm.

[0012] In some embodiments of the present application, the diameter of the first copper wire and the second copper wire is 10-200 μm.

[0013] In some embodiments of the present application, the length of the copper wire with the lithium layer is 1-3 mm.

[0014] In some embodiments of the present application, the ratio of the width of the second metal foil to the width of the first metal foil is not less than 2 and not more than 6.

[0015] In some embodiments of the present application, the winding structure is arranged in the overlapping area of the first reference electrode tab and the second reference electrode tab, the width of the winding structure is not greater than the width of the overlapping area of the first reference electrode tab and the second reference electrode tab, and the length of the winding structure is not greater than the length of the overlapping area of the first reference electrode tab and the second reference electrode tab.

[0016] In still another aspect of the present application, a method for preparing the reference electrode is provided. According to an embodiment of the present application, the method comprises:

[0017] (1) providing a first metal foil and a second metal foil integrally connected, a first copper wire and a second copper wire integrally connected, and winding the first copper wire on the first metal foil;

[0018] (2) winding the second metal foil around the first metal foil so that the first metal foil with the first copper wire wound thereon is wound inside the second metal foil, and the second copper wire is placed outside the second metal foil, forming a winding structure;

[0019] (3) placing a first reference electrode tab, the winding structure and a second reference electrode tab in layers, and placing the second copper wire away from the first reference electrode tab and the second reference electrode tab, and welding so that the outer metal foil of the winding structure is fixed with the first reference electrode tab and the second reference electrode tab respectively, and a lithium layer is prepared on the surface of the end of the second copper wire away from the first copper wire, to obtain a reference electrode.

[0020] According to the method for preparing the reference electrode according to the embodiment of the present application, the first metal foil with the first copper wire wound thereon is wound inside the second metal foil to form a winding structure, and the first reference electrode tab, the winding structure and the second reference electrode tab are placed in layers to form a sandwich structure, thereby avoiding direct contact of the first reference electrode tab and the second reference electrode tab with the copper wire, protecting the copper wire from being broken, and the metal foil is soft in texture and is not easy to damage the copper wire, greatly reducing the operation difficulty coefficient of preparing the reference electrode, and improving the success rate of preparing the three-electrode soft-pack lithium ion battery. The success rate of the method of the present application can almost reach 100%, while the success rate of directly winding the copper wire on the surface of the reference electrode tab can only reach about 50%-60%; at the same time, the winding structure can also prevent the copper wire from falling off or sliding off the surface of the reference electrode tab, and prevent it from being broken during welding and unable to conduct electricity, i.e. unable to be plated with lithium; in addition, the contact area between the tab and the winding structure is increased, the polarization caused by the structure of the battery cell is reduced, and the internal resistance of the reference electrode is reduced.

[0021] In addition, the method according to the above embodiment of the present application can also have the following additional technical features:

[0022] In some embodiments of the present application, in step (1), the end of the first copper wire away from the second copper wire is first wound at least one turn along the diagonal of the first metal foil, and then the remaining first copper wire is wound on the first metal foil along the length of the first metal foil.

[0023] In some embodiments of the present application, before welding, further comprising: fixing the laminated placement of the first reference electrode tab, the winding structure and the second reference electrode tab with a first high-temperature-resistant insulating tape to facilitate welding.

[0024] In some embodiments of the present application, after welding, further comprising: flattening the welding points of the welding area, covering the welding area with a second high-temperature-resistant insulating tape; and packaging.

[0025] In a third aspect, the present application provides a three-electrode lithium ion battery. According to embodiments of the present application, the three-electrode lithium ion battery has the reference electrode described in the above embodiments or the reference electrode prepared by the method described in the above embodiments. Thus, the three-electrode lithium ion battery has all the advantages of the reference electrode described in the above embodiments, and in particular, the reliability of the three-electrode lithium ion battery in analyzing the electrochemical performance of the positive and negative electrodes of the lithium ion battery is further improved.

[0026] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0027] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings.

[0028] Figure 1 Schematic diagram of the treated copper wire and copper foil of embodiment 1 of the present application;

[0029] Figure 2 Schematic diagram of the structure of the copper wire wound copper foil of embodiment 1 of the present application;

[0030] Figure 3 Schematic diagram of the structure of the winding structure of embodiment 1 of the present application;

[0031] Figure 4 Schematic diagram of the structure of the winding structure and the reference electrode tab of embodiment 1 of the present application;

[0032] Figure 5 Schematic diagram of the process of laminating the winding structure and the reference electrode tab of embodiment 1 of the present application;

[0033] Figure 6 Top view of the laminated placement of the winding structure and the reference electrode tab of embodiment 1 of the present application;

[0034] Figure 7 Schematic diagram of the reference electrode wound with the first high-temperature-resistant insulating tape of embodiment 1 of the present application;

[0035] Figure 8A schematic view of the reference electrode after welding for Example 1 of the present application;

[0036] Figure 9 A schematic view of the reference electrode wound with the third high-temperature-resistant insulating glue for Example 1 of the present application;

[0037] Figure 10 A schematic view of the reference electrode wound with the second high-temperature-resistant insulating glue for Example 1 of the present application;

[0038] Figure 11 A graph of the voltage change with time when charging the three-electrode battery in Example 1 of the present application.

[0039] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated herein and constitute a part of this application. The drawings illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In the drawings: DETAILED DESCRIPTION

[0040] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements throughout. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and should not be understood as limiting the present application.

[0041] In one aspect of the present application, a reference electrode is provided. According to embodiments of the present application, reference is made to the accompanying drawings, in which: Figures 4-6The reference electrode comprises a first reference electrode tab 211, a coiled structure 100 and a second reference electrode tab 212 which are sequentially stacked, the coiled structure 100 comprises a first metal foil and a second metal foil which are integrally connected, a first copper wire and a second copper wire which are integrally connected, the first copper wire is wound on the first metal foil, the first metal foil wound with the first copper wire is coiled on the inner side of the second metal foil, the second copper wire is arranged away from the first reference electrode tab and the second reference electrode tab, and the second copper wire is provided with a lithium layer at the end away from the first copper wire. Thus, by coiling the first metal foil wound with the first copper wire on the inner side of the second metal foil to form a coiled structure, and stacking the first reference electrode tab, the coiled structure and the second reference electrode tab to form a sandwich structure, the first reference electrode tab and the second reference electrode tab with high hardness are prevented from directly contacting the copper wire, the copper wire is protected from being broken, the metal foil is soft and not easy to damage the copper wire, the operation difficulty coefficient of preparing the reference electrode is greatly reduced, the success rate of preparing the three-electrode soft package lithium ion battery is improved, the success rate of the present application can reach almost 100%, while the success rate of directly winding the copper wire on the surface of the reference electrode tab can only reach about 50%-60%; at the same time, the coiled structure can also prevent the copper wire from falling off or sliding off the surface of the reference electrode tab, and prevent the copper wire from being broken during welding, which cannot conduct electricity and cannot be plated with lithium; in addition, the contact area between the tab and the coiled structure is increased, the polarization caused by the structure of the battery cell is reduced, and the internal resistance of the reference electrode is reduced.

[0042] The reference electrode according to the embodiments of the present application will be described in detail.

[0043] It can be understood that, in the embodiments of the present application, the first metal foil and the second metal foil which are integrally connected refer to the same metal foil 120, and the first copper wire and the second copper wire which are integrally connected refer to the same copper wire 110.

[0044] In the embodiments of the present application, the materials of the first reference electrode tab and the second reference electrode tab are not particularly limited, the materials of the first reference electrode tab and the second reference electrode tab can be the same or different, as some specific examples, the first reference electrode tab and the second reference electrode tab are each independently a copper-nickel-plated tab, a nickel tab, an aluminum-nickel-plated tab or an aluminum tab. Preferably, the materials of the first reference electrode tab and the second reference electrode tab are the same.

[0045] In the embodiments of the present application, the first metal foil and the second metal foil have the same material, and the specific type is not particularly limited, as long as it can meet the requirements of good electrical conductivity and soft material. Preferably, the first metal foil and the second metal foil are all copper foil, aluminum foil or tin foil. Thus, the metal foil with the above material has soft texture and is not easy to damage the copper wire, greatly reducing the operation difficulty coefficient of preparing the reference electrode and improving the success rate of preparing the three-electrode soft package lithium ion battery.

[0046] According to some specific embodiments of the present application, the thickness of the first metal foil and the second metal foil can be 1-10 μm (for example, it can be 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10 μm). Thus, the first metal foil and the second metal foil are further ensured to have soft texture, avoiding damage to the copper wire.

[0047] In the embodiments of the present application, the diameters of the first copper wire and the second copper wire are not particularly limited, as long as they can meet the requirements of the reference electrode for the copper wire. As some specific examples, the diameters of the first copper wire and the second copper wire can be 20-200 μm (for example, it can be 10 / 20 / 40 / 60 / 80 / 100 / 120 / 140 / 160 / 180 / 200 μm).

[0048] In the embodiments of the present application, the copper wire with the lithium layer is placed between the separators of the lithium ion battery to monitor the positive and negative electrode potentials of the lithium ion battery in situ. Further, the length of the copper wire with the lithium layer can be 1-3 mm (for example, it can be 1 / 2 / 3 mm). Thus, the requirements of the reference electrode for the lithium layer end are further met.

[0049] According to some specific embodiments of the present application, the ratio of the width of the second metal foil to the width of the first metal foil is not less than 2 and not more than 6. Thus, the first metal foil with the first copper wire wound thereon is completely wrapped on the inside of the second metal foil, completely avoiding the direct contact of the first copper wire wound on the first metal foil with the first reference electrode tab and the second reference electrode tab with high hardness, thereby avoiding the risk of the first copper wire being pressed off, and also avoiding the case that the number of layers of the second metal foil wrapped on the outside of the first metal foil is too much, resulting in virtual welding or inability to weld during subsequent welding.

[0050] According to still some specific embodiments of the present application, the winding structure is arranged in the overlapping area of the first reference electrode tab and the second reference electrode tab, the width of the winding structure is not greater than the width of the overlapping area of the first reference electrode tab and the second reference electrode tab, and the length of the winding structure is not greater than the length of the overlapping area of the first reference electrode tab and the second reference electrode tab, thereby further maximizing the contact area of the winding structure with the first reference electrode tab and the second reference electrode tab, and further reducing the polarization caused by the cell structure and the reference electrode internal resistance.

[0051] In still another aspect of the present application, the present application provides a method for manufacturing the reference electrode. According to embodiments of the present application, the method comprises:

[0052] S100: providing a first metal foil and a second metal foil integrally connected, a first copper wire and a second copper wire integrally connected, and winding the first copper wire on the first metal foil

[0053] In this step, the first copper wire is wound on the first metal foil with relatively low hardness, thereby avoiding the direct winding of the copper wire on the reference electrode tab with relatively high hardness, protecting the copper wire from being broken, and the metal foil with soft texture is less likely to damage the copper wire, greatly reducing the operation difficulty coefficient of manufacturing the reference electrode.

[0054] Specifically, in order to further ensure that one end of the first copper wire is firmly wound on the first metal foil, according to still some specific embodiments of the present application, the end of the first copper wire away from the second copper wire can be first wound at least one turn along the diagonal of the first metal foil, and then the remaining first copper wire is wound on the first metal foil along the length direction of the first metal foil, so as to tightly press the first turn of copper wire wound diagonally in the subsequently wound copper wire, thereby further ensuring the close contact between the first copper wire and the first metal foil, and further ensuring the electrical connection between the first copper wire and the first metal foil.

[0055] S200: winding the second metal foil around the first metal foil

[0056] In this step, in order to avoid the direct contact between the copper wire and the reference electrode tab, the second metal foil is wound around the first metal foil, so that the first metal foil with the first copper wire wound thereon is wound on the inner side of the second metal foil, and the second copper wire is arranged on the outer side of the second metal foil, forming a winding structure, thereby further avoiding the direct contact between the copper wire and the reference electrode tab, and protecting the copper wire from being damaged by the reference electrode tab with hard texture.

[0057] S300: Laminating the first reference electrode tab, the winding structure and the second reference electrode tab, and placing the second copper wire away from the first reference electrode tab and the second reference electrode tab, welding, and preparing a lithium layer on the end surface of the second copper wire away from the first copper wire

[0058] In this step, the first reference electrode tab, the winding structure and the second reference electrode tab are laminated to form a sandwich structure, and welding is performed to fix the outer metal foil of the winding structure to the first reference electrode tab and the second reference electrode tab, respectively, thereby avoiding direct contact of the first reference electrode tab and the second reference electrode tab with the copper wire, protecting the copper wire from being broken, and the metal foil is soft and not easy to damage the copper wire, greatly reducing the operation difficulty coefficient of preparing the reference electrode, and improving the success rate of preparing the three-electrode soft package lithium ion battery. At the same time, the second copper wire is placed away from the first reference electrode tab and the second reference electrode tab, and then a lithium layer is prepared on the end surface of the second copper wire away from the first copper wire, to obtain the reference electrode.

[0059] In order to facilitate welding, according to some specific embodiments of the present application, before welding, it further includes: using a first high-temperature-resistant insulating tape to fix the laminated first reference electrode tab, winding structure and second reference electrode tab, to facilitate welding, and prevent the prepared reference electrode from being short-circuited. The specific type of the first high-temperature-resistant insulating tape is not particularly limited.

[0060] According to some specific embodiments of the present application, after welding, it further includes:

[0061] The welding points of the welding area are flattened, and the welding area is covered with a second high-temperature-resistant insulating tape, thereby preventing debris from entering the battery during packaging or preventing the protruding welding points from damaging the aluminum plastic film; then using a soft seal head for packaging, leaving about 0.5-2mm of tab adhesive outside to prevent the reference electrode from being short-circuited.

[0062] In the embodiments of the present application, the first reference electrode tab and the second reference electrode tab can each have tab adhesive, the winding structure is aligned with one end of the first reference electrode tab and the second reference electrode tab, respectively, and then the third high-temperature-resistant insulating tape is wound around the area between the tab adhesive and the welding area to prevent the reference electrode from being short-circuited.

[0063] In a third aspect, the present application provides a three-electrode lithium ion battery. According to embodiments of the present application, the three-electrode lithium ion battery has the reference electrode described in the above embodiments or the reference electrode prepared by the method described in the above embodiments. Thus, the three-electrode lithium ion battery has all the advantages of the reference electrode described in the above embodiments, and in particular, the reliability of the three-electrode lithium ion battery in analyzing the electrochemical performance of the positive and negative electrodes of the lithium ion battery is further improved.

[0064] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are used to explain the present application, and should not be construed as limiting the present application. In addition, if not specifically stated, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods, and the reaction conditions not listed are also readily available to those skilled in the art.

[0065] Embodiment 1

[0066] The present embodiment provides a method for preparing a reference electrode, comprising the following steps:

[0067] 1) As shown in Figure 1 , prepare a rectangular copper foil 120 and a copper wire 110. The width of the copper foil 120 is 3 times the width of the reference electrode tab, the length of the copper foil 120 is less than the length above the tab adhesive of the reference electrode tab, the thickness of the copper foil 120 is 6 μm, which is convenient for welding. The diameter of the copper wire 110 is 10 μm, the two ends are treated with concentrated sulfuric acid to remove the enameled layer, and the length of the lithium-plated end is 1 mm.

[0068] 2) As shown in Figure 2 , reserve the lithium-plated end of the copper wire 110 (used later to be placed between the separators), and wrap the other end of the copper wire around one end of the rectangular copper foil. The copper foil is soft in texture and will not damage the copper wire; when the first coil of exposed copper wire is wrapped, it should be wrapped diagonally opposite to the copper foil of the same tab width, and after the second coil, it should be wrapped parallel to the length direction of the copper foil, and the first coil should be pressed at the bottom.

[0069] 3) Wrap the copper foil without copper wire around the copper foil with copper wire, ensuring that the copper foil with copper wire is completely wrapped on both sides, forming Figure 3 the winding structure 100 shown in .

[0070] 4) As shown in Figure 4 , prepare two clean and identical copper-nickel-plated reference electrode tabs 211 and 212. The width of the tabs is equal to the width a of the winding structure 100, and the reference electrode tabs 211 and 212 each have a tab adhesive 220. The length of the winding structure is less than the length above the tab adhesive.

[0071] 5) As shown inFigure 5 The winding structure is clamped between Figure 4 The prepared two reference electrodes are placed in alignment from top to bottom, and the end of the copper wire to be plated with lithium is placed outside. The placed structure is shown in Figure 6 .

[0072] 6) As shown in Figure 7 , a first high-temperature-resistant insulating tape 230 is wound below the tab glue to fix the tab of the stacked reference electrode and the winding structure, facilitating welding and preventing the reference electrode from contacting the shell.

[0073] 7) As shown in Figure 8 , the welding area 240 above the tab glue is welded by ultrasonic welding.

[0074] 8) As shown in Figure 9 , a third high-temperature-resistant insulating tape 250 is wound around the exposed area between the tab glue and the welding area 240 to prevent the reference electrode from contacting the shell.

[0075] 9) As shown in Figure 10 , a flat block is used to evenly press the welding point to prevent the surface of the welding area from protruding and piercing the shell, and a second high-temperature-resistant insulating tape 260 is wound around to prevent debris from entering the battery during packaging.

[0076] 10) It is packaged with a soft seal, leaving a 1mm glue block outside to prevent the reference electrode from contacting the shell, thereby preparing the reference electrode.

[0077] A three-electrode battery is prepared by stacking in the order of positive electrode-separator-copper wire-separator-negative electrode, where the positive electrode active material is NCM and the negative electrode active material is graphite. The prepared three-electrode battery is tested for charging. By comparing whether the potential difference between the positive electrode potential against lithium and the negative electrode potential against lithium is equal to the full-cell voltage, it can be determined whether the reference electrode is successfully implanted and stable. As shown in Figure 11 It can be seen that the full-cell voltage in the variable current charging curve is always equal to the potential difference between the positive electrode potential against lithium and the negative electrode potential against lithium, and the two lines almost completely coincide, indicating that the stability of the implanted reference electrode is good.

[0078] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0079] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A reference electrode, characterized in that include: A first reference electrode tab, a winding structure, and a second reference electrode tab stacked in sequence; The winding structure includes a first metal foil and a second metal foil connected as an integral whole, and a first copper wire and a second copper wire connected as an integral whole, the first copper wire is wound on the first metal foil, the first metal foil wound with the first copper wire is wound on the inner side of the second metal foil, the second copper wire is arranged away from the first reference electrode tab and the second reference electrode tab, and a lithium layer is provided at one end of the second copper wire away from the first copper wire.

2. The reference electrode according to claim 1, characterized in that The first reference electrode tab and the second reference electrode tab are each independently a copper-nickel-plated tab, a nickel tab, an aluminum-nickel-plated tab or an aluminum tab.

3. The reference electrode according to claim 1, characterized in that The first metal foil and the second metal foil are both metal copper foil, metal aluminum foil or metal tin foil.

4. The reference electrode according to claim 1, characterized in that The thickness of the first metal foil and the second metal foil are both 1-10 μm.

5. The reference electrode according to claim 1, characterized in that The diameters of the first copper wire and the second copper wire are both 10-200 μm.

6. The reference electrode according to claim 1, characterized in that The length of the copper wire provided with the lithium layer is 1-3 mm.

7. The reference electrode according to any one of claims 1 to 6, characterized in that The ratio of the width of the second metal foil to the width of the first metal foil is not less than 2 and not more than 6.

8. The reference electrode according to any one of claims 1 to 6, characterized in that The winding structure is clamped in the overlapping area of ​​the first reference electrode tab and the second reference electrode tab, the width of the winding structure is not greater than the width of the overlapping area of ​​the first reference electrode tab and the second reference electrode tab, and the length of the winding structure is not greater than the length of the overlapping area of ​​the first reference electrode tab and the second reference electrode tab.

9. A method for preparing the reference electrode according to any one of claims 1 to 8, characterized in that: include: (1) providing a first metal foil and a second metal foil connected in an integral manner, and a first copper wire and a second copper wire connected in an integral manner, and winding the first copper wire around the first metal foil; (2) winding the second metal foil around the first metal foil so that the first metal foil wrapped with the first copper wire is wound on the inner side of the second metal foil and the second copper wire is placed on the outer side of the second metal foil, thereby forming a winding structure; (3) The first reference electrode tab, the winding structure, and the second reference electrode tab are stacked, and the second copper wire is placed away from the first reference electrode tab and the second reference electrode tab, and welded so that the outer metal foil of the winding structure is fixed to the first reference electrode tab and the second reference electrode tab, respectively, and a lithium layer is prepared on the surface of one end of the second copper wire away from the first copper wire to obtain a reference electrode.

10. The method according to claim 9, characterized in that In step (1), the end of the first copper wire away from the second copper wire is firstly wound at least once along the diagonal angle of the first metal foil, and then the remaining first copper wire is wound on the first metal foil along the length direction of the first metal foil.

11. The method according to claim 9, characterized in that Before welding, it also includes: The first reference electrode tab, the winding structure and the second reference electrode tab stacked in layers are fixed with a first high-temperature-resistant insulating tape to facilitate welding.

12. The method according to claim 9, characterized in that After welding, it also includes: Flatten the welding points in the welding area and cover the welding area with a second high-temperature resistant insulating tape; Encapsulation.

13. A three-electrode lithium-ion battery, characterized in that: A reference electrode according to any one of claims 1 to 8 or a reference electrode prepared by the method according to any one of claims 9 to 12.

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