Reference electrode and lithium ion battery

Abstract

The reference electrode comprises a copper foil, insulating layers, a lithium plating layer and a diaphragm layer, the insulating layers are arranged on the two sides of the copper foil, through grooves are formed in the insulating layers on the two sides in the height direction of the copper foil, the depth of the grooves is equal to the thickness of the insulating layers, and the diaphragm layer is arranged between the lithium plating layer and the diaphragm layer. The groove is positioned in the middle of the copper foil; the lithium plating layers are arranged in the grooves in the two sides respectively and matched with the grooves in size. The diaphragm layer is coated outside the insulating layer and the lithium plating layer and is used for isolating and protecting the reference electrode; according to the reference electrode disclosed by the invention, the groove part of the region, which is not covered with the insulating layer, on the reference electrode is used as a space for lithium deposition during subsequent lithium plating of the reference electrode, so that the reference electrode after lithium plating cannot form a bulge, and meanwhile, the reference electrode is wrapped by the diaphragm layer, so that lithium dendrites formed on the reference electrode cannot pierce the diaphragm, and the safety is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium ion batteries, in particular to a reference electrode and a lithium ion battery. Background Art

[0002] As an effective means of detecting the performance of lithium-ion batteries, reference electrodes are widely used in the research of lithium-ion batteries. In particular, they can provide real-time and accurate reference data when judging whether the battery has the risk of lithium plating. The currently commonly used method for making reference electrodes is to place a metal wire as a reference electrode between the positive and copper foils, and separate the metal wire and the electrode with a diaphragm. The battery is then made through processes such as packaging, liquid injection, formation, and capacity division. After that, the reference electrode is plated with lithium using a small current to obtain a reference electrode battery for testing.

[0003] Publication number CN111525205B discloses a lithium-ion battery containing a lithium lanthanum zirconium oxide triple electrode and a preparation method thereof, comprising a battery cell and a shell, wherein the battery cell comprises a negative electrode sheet, a negative electrode reference tab, a separator, a positive electrode sheet, a positive electrode reference tab, and a reference electrode, wherein the reference electrode is placed between the outermost negative electrode sheet and the shell, and the reference electrode is composed of a lithium lanthanum zirconium oxide hollow shell, metallic lithium, and a lead-out electrode.

[0004] At present, the reference electrode is mainly placed between the positive and copper foils of the battery core pack in the form of metal wire. After hot pressing, it will hit the electrode, causing the electrode to deform, which in turn affects the battery performance. In addition, during the long-term use of the battery, the free lithium in the battery is easy to gather on the surface of the metal wire to form lithium dendrites. The lithium dendrites will pierce the diaphragm and cause a short circuit between the positive and negative electrodes, posing a safety hazard. Utility Model Content

[0005] In view of this, the present invention proposes a reference electrode and a lithium-ion battery, which can effectively ensure that no protrusions are formed on the reference electrode after lithium plating, and that lithium dendrites formed on the reference electrode will not pierce the diaphragm, thereby improving safety.

[0006] The technical solution of the present invention is implemented as follows: In the first aspect, the present invention provides a reference electrode, comprising a copper foil, an insulating layer, a lithium plating layer and a diaphragm layer, wherein:

[0007] An insulating layer is provided on both sides of the copper foil, and the insulating layers on both sides are provided with a through groove along the height direction of the copper foil, the depth of the groove is equal to the thickness of the insulating layer, and the groove is located in the middle of the copper foil;

[0008] The lithium plating layer is located in the grooves on both sides and has matching sizes;

[0009] The diaphragm layer is coated on the outside of the insulating layer and the lithium plating layer to isolate and protect the reference electrode.

[0010] On the basis of the above technical solution, preferably, the insulating layer is insulating glue and has a thickness of 0.05-0.1 mm.

[0011] On the basis of the above technical solution, preferably, the groove is located at the length center line of the copper foil, and the width of the groove is 1-10 um.

[0012] On the basis of the above technical solution, preferably, the number of the diaphragm layers is two, the two diaphragm layers wrap the insulating layer and the lithium plating layer, and the thickness of each diaphragm layer is at least 20 um.

[0013] On the basis of the above technical solution, preferably, the material of the diaphragm layer is glass fiber.

[0014] On the basis of the above technical solution, preferably, the width and height of the reference electrode are the same as the width and height of the corresponding single-layer negative electrode sheet of the battery.

[0015] On the basis of the above technical solution, preferably, a reference tab is further included, wherein the reference tab is fixedly connected to the copper foil, and one end of the reference tab away from the copper foil passes through the diaphragm layer and is led outward.

[0016] On the basis of the above technical solution, preferably, transition chamfers are provided at the connection between the reference tab and the copper foil and at the two corners of the reference tab away from the copper foil.

[0017] On the basis of the above technical solution, preferably, the reference tab is located at the length center line of the copper foil and is on the same straight line as the center line of the lithium plating layer.

[0018] In a second aspect, the present invention further provides a lithium-ion battery comprising the above-mentioned reference electrode.

[0019] The reference electrode and lithium-ion battery of the present invention have the following beneficial effects compared with the prior art:

[0020] (1) The groove portion of the reference electrode that is not covered with the insulating layer is used as a space for lithium deposition when the reference electrode is subsequently plated with lithium, thereby ensuring that no protrusions are formed on the reference electrode after lithium plating. At the same time, the reference electrode is wrapped with a diaphragm layer to ensure that lithium dendrites formed on the reference electrode will not pierce the diaphragm, thereby improving safety;

[0021] (2) By setting the reference electrode size to be the same as the size of the single-layer negative electrode sheet, when the reference electrode is inserted, no protrusion will be formed locally to cause deformation of the electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A side view of the reference electrode of the present invention;

[0024] Figure 2 It is a front view of the reference electrode of the present utility model;

[0025] Figure 3 This is a structural stereogram of the reference electrode and lithium-ion battery of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] like Figure 1-2 As shown, the utility model provides a reference electrode, including a copper foil 1, an insulating layer 2, a lithium-plated layer 3 and a diaphragm layer 4. The insulating layer 2 is provided on both sides of the copper foil 1, and the insulating layers 2 on both sides are provided with penetrating grooves 100 along the height direction of the copper foil 1. The depth of the groove 100 is equal to the thickness of the insulating layer 2, and the groove 100 is located in the middle position of the copper foil 1; the lithium-plated layer 3 is provided in the grooves 100 on both sides, and the sizes are matched; the diaphragm layer 4 is coated on the outside of the insulating layer 2 and the lithium-plated layer 3, and is used to isolate and protect the reference electrode.

[0028] It should be noted that the copper foil 1, as the substrate of the electrode, provides a stable current transmission foundation for the entire electrode due to its good conductivity and ductility. At the same time, the copper foil also has a certain mechanical strength and can withstand a certain external force without being easily damaged. An insulating layer 2 is provided on both sides of the copper foil 1, which effectively prevents the electrode from making unnecessary electrical contact with other components or media during operation, thereby avoiding the risk of short circuit or leakage. The insulating layer has a through groove 100 opened along the height direction of the copper foil, which provides space for the setting of the lithium plating layer 3, ensuring that the reference electrode will not form a protrusion after lithium plating. At the same time, the reference electrode is wrapped with a diaphragm layer 4 to ensure that lithium dendrites formed on the reference electrode will not pierce the diaphragm, thereby improving safety.

[0029] Specifically, the insulating layer 2 is made of insulating adhesive with a thickness of 0.05-0.1 mm. The insulating adhesive, as an insulating layer material, has excellent insulation properties, adhesion, and a certain degree of elasticity. It effectively isolates the copper foil 1 from the external environment, preventing current leakage or short circuits. It also adheres tightly to the copper foil surface and is not easily detached. A thickness of 0.05-0.1 mm ensures effective insulation while maintaining the thinness of the electrode.

[0030] Specifically, the groove 100 is located at the length center line of the copper foil 1, and the width of the groove 100 is 1-10 μm, ensuring that the lithium plating layer 3 can be evenly distributed on both sides of the copper foil, thereby achieving symmetry and stability of the electrode.

[0031] In this embodiment, there are two diaphragm layers 4 , which wrap the insulating layer 2 and the lithium plating layer 3 . The thickness of each diaphragm layer 4 is at least 20 μm, and the material of the diaphragm layer 4 is glass fiber.

[0032] It should be noted that the reference electrode is wrapped with a glass fiber diaphragm with a thickness of more than 20 μm to ensure that the lithium dendrites formed on the reference electrode will not pierce the diaphragm, thereby improving safety.

[0033] The width and height of the reference electrode in this embodiment are the same as those of the corresponding single-layer negative electrode sheet of the battery. When the reference electrode is inserted, no protrusions will be formed locally to cause deformation of the electrode sheet.

[0034] This embodiment further includes a reference tab 5 , wherein the reference tab 5 is fixedly connected to the copper foil 1 , and one end of the reference tab 5 away from the copper foil 1 passes through the diaphragm layer 4 and is led outward.

[0035] The connection between the reference tab 5 and the copper foil 1 and the two corners of the reference tab 5 away from the copper foil 1 are both provided with transition chamfers.

[0036] It should be noted that by setting a transition chamfer at the connection, stress can be effectively dispersed and the risk of fracture or performance degradation due to stress concentration can be reduced. At the same time, the chamfer design can eliminate sharp edges, making the stress distribution more uniform and improving the mechanical strength and durability of the electrode.

[0037] The reference tab 5 is located at the length center line of the copper foil 1 and is on the same straight line as the center line of the lithium plating layer 3, further enhancing the structural symmetry and performance stability of the electrode.

[0038] like Figure 3 As shown, in a second aspect, the present invention further provides a lithium-ion battery comprising the above-mentioned reference electrode.

[0039] The workflow for installing the reference electrode into the cell is:

[0040] S1, winding the positive electrode sheet, the negative electrode sheet, and the separator to obtain a battery core pack;

[0041] S2. Open the outermost negative electrode sheet of the core package, put the reference electrode in, and then roll back the opened negative electrode sheet and diaphragm;

[0042] S3, hot pressing the core package with a hot press;

[0043] S4, welding the positive and negative tabs of the hot-pressed core package to the positive and negative electrode posts of the top cover by ultrasonic welding;

[0044] S5, welding the reference electrode tab 5 connected to the copper foil 1 of the reference electrode to the reference electrode column;

[0045] S6. Put the core package connected with the top cover into the shell, and weld the shell and the top cover together by laser welding;

[0046] S7. Finally, the three-electrode battery is manufactured through the processes of baking, liquid injection, aging, formation, and capacity division.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A reference electrode, characterized in that It comprises a copper foil (1), an insulating layer (2), a lithium plating layer (3) and a diaphragm layer (4), wherein: Insulating layers (2) are provided on both sides of the copper foil (1), and the insulating layers (2) on both sides are provided with penetrating grooves (100) along the height direction of the copper foil (1), the depth of the grooves (100) is equal to the thickness of the insulating layer (2), and the grooves (100) are located in the middle of the copper foil (1); The lithium plating layers (3) are arranged in the grooves (100) on both sides, and the sizes thereof are matched; The diaphragm layer (4) is coated on the outside of the insulating layer (2) and the lithium plating layer (3) and is used to isolate and protect the reference electrode.

2. The reference electrode according to claim 1, wherein: The insulating layer (2) is insulating glue and has a thickness of 0.05-0.1 mm.

3. The reference electrode according to claim 1, wherein: The groove (100) is located at the length center line of the copper foil (1), and the width of the groove (100) is 1-10 μm.

4. The reference electrode according to claim 1, wherein: The number of the diaphragm layers (4) is two, and the two diaphragm layers (4) wrap the insulating layer (2) and the lithium plating layer (3), and the thickness of each diaphragm layer (4) is at least 20 μm.

5. The reference electrode according to claim 4, wherein: The material of the diaphragm layer (4) is glass fiber.

6. The reference electrode according to claim 1, wherein: The width and height of the reference electrode are the same as the width and height of the corresponding battery single-layer negative electrode sheet.

7. The reference electrode according to claim 1, wherein: It also includes a reference tab (5), wherein the reference tab (5) is fixedly connected to the copper foil (1), and one end of the reference tab (5) away from the copper foil (1) passes through the diaphragm layer (4) and is led outward.

8. The reference electrode according to claim 7, wherein: Transition chamfers are provided at the connection point between the reference tab (5) and the copper foil (1) and at two corners of the reference tab (5) away from the copper foil (1).

9. The reference electrode according to claim 8, wherein: The reference tab (5) is located at the length center line of the copper foil (1) and is on the same straight line as the center line of the lithium plating layer (3).

10. A lithium ion battery, characterized in that: A reference electrode comprising the reference electrode of any one of claims 1 to 9.

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