Composite diaphragm and three-electrode battery

Abstract

The invention relates to a composite diaphragm and a three-electrode battery, the composite diaphragm is composed of an isolating membrane and a reference electrode, and the reference electrode is longitudinally or transversely embedded in the isolating membrane; the three-electrode battery comprises a positive plate, a negative plate and electrolyte, and further comprises a third tab, a connector and a composite diaphragm, the positive plate and the negative plate are coated with the composite diaphragm, and a reference electrode in the composite diaphragm is connected with the third tab through the connector; the isolating membrane is composed of a first polymer layer, a second polymer layer, a first coating layer and a second coating layer, the first coating layer is located on the outer side of the first polymer layer, and the second coating layer is located on the outer side of the second polymer layer. By introducing the composite diaphragm, the steps of disassembling the electrode group, embedding the reference electrode and then reassembling can be omitted, the operation process and the operation difficulty are reduced, and the diaphragm can effectively protect the reference electrode from failure caused by breakage; the manufacturing efficiency is greatly improved, and the batch production process feasibility is realized.

Description

Technical Field

[0001] The invention relates to a composite diaphragm and a three-electrode battery. Background Art

[0002] With the development of lithium-ion battery technology, lithium-ion batteries have played an important role in new energy vehicles and energy storage fields, as well as electric toys in daily life. The society has paid more attention to and higher requirements for their quality and safety. In order to study the failure causes of lithium-ion batteries, making three-electrode batteries is an important analytical method. The three electrodes of lithium-ion batteries refer to the positive electrode (working electrode), the negative electrode (counter electrode) and the reference electrode. By measuring the potential changes between the positive electrode and the reference electrode and between the negative electrode and the reference electrode, the impedance of the positive and negative electrodes and the redox reaction process can be analyzed separately. The common three-electrode production method is to disassemble the electrode group after the electrode stack or winding, bury the reference electrode, and then reassemble it to make a three-electrode battery. This method can usually only be made by hand, because the reference electrode usually uses a thin wire metal or alloy conductor, and the thin wire is very easy to break. In order to ensure that the reference electrode does not short-circuit with the positive and negative electrodes, the metal wire used is usually enameled wire, and part of the wire needs to be depainted and lithium-plated during the manufacturing process; however, whether using the chemical method or the erasure method, there are inevitable disadvantages. For example, the solvents used in the chemical method are usually corrosive, and the operation process is dangerous and has potential pollution risks; the erasure method is easy to damage the surface of the metal wire, affecting the lithium plating effect. From the existing technology and public patents, there is no effective method to achieve a one-time manufacturing and mass production of a three-electrode design.

[0003] In order to solve the above problems, the present invention is proposed. Summary of the invention

[0004] The object of the present invention is to provide a composite diaphragm.

[0005] The above purpose is achieved by the following technical solutions:

[0006] A composite diaphragm consists of an isolation membrane and a reference electrode, wherein the reference electrode is embedded in the isolation membrane longitudinally or transversely.

[0007] Furthermore: the isolation film includes a first polymer layer and a second polymer layer.

[0008] Preferably, the polymer layer 1 and the polymer layer 2 include but are not limited to polyethylene and polypropylene used alone or in combination.

[0009] Furthermore, the isolation film also includes a coating layer 1 and a coating layer 2, wherein the coating layer 1 is located on the outside of the polymer layer 1, and the coating layer 2 is located on the outside of the polymer layer 2.

[0010] Furthermore: the coating layer 1 and the coating layer 2 include but are not limited to the use of alumina powder and boehmite alone or in combination.

[0011] Furthermore: the thickness of the single-layer polymer layer 1 and polymer layer 2 is usually 3 μm-20 μm, and the thickness of the coating layer 1 and coating layer 2 is usually 1 μm-5 μm.

[0012] Preferably, the reference electrode is a conductive metal wire, including but not limited to a copper wire, a nickel wire or an alloy wire, and the diameter of the conductive metal wire is 5-50 μm.

[0013] Another object of the present invention is to provide a three-electrode battery.

[0014] The above purpose is achieved through the following technical solutions:

[0015] A three-electrode battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, a third pole ear, a connector and the above-mentioned composite diaphragm, wherein the composite diaphragm covers the positive electrode sheet and the negative electrode sheet, and the connector connects the reference electrode in the composite diaphragm with the third pole ear.

[0016] Preferably, the connector comprises a first metal sheet, a second metal sheet, and a first insulating film sheet on the outer side of the first metal sheet and a second insulating film sheet on the outer side of the second metal sheet.

[0017] Furthermore, the insulating film one and the insulating film two are polyimide high temperature adhesives.

[0018] Preferably, the metal sheet 1 and the metal sheet 2 are copper sheets or nickel sheets with a thickness of 2-10 μm.

[0019] Beneficial technical effects:

[0020] The present invention introduces a composite diaphragm, which can save the steps of disassembling the electrode group, burying the reference electrode and then reassembling it, reducing the operation process and operation difficulty. The diaphragm can effectively protect the reference electrode from failure due to breakage; the production efficiency is greatly improved, and the feasibility of mass production process is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] Figure 1 It is a schematic diagram of the composite diaphragm structure of the present invention.

[0023] Figure 2 It is a schematic diagram of the structure of the composite diaphragm of the present invention from another angle.

[0024] Figure 3 It is a schematic diagram of the connector structure of the present invention.

[0025] Figure 4It is a schematic diagram of the connector connection structure of the present invention.

[0026] Figure 5 Schematic diagram of a three-electrode battery of the present invention. DETAILED DESCRIPTION

[0027] Reference Figure 1-2 As shown, a composite diaphragm is composed of an isolation membrane and a reference electrode 1, and the reference electrode 1 is embedded in the isolation membrane longitudinally or transversely.

[0028] The isolation membrane includes a polymer layer 2 and a polymer layer 3, wherein the polymer layer 2 and the polymer layer 3 include but are not limited to polyethylene and polypropylene used alone or in combination, and the isolation membrane also includes a coating layer 4 and a coating layer 5, wherein the coating layer 4 is located on the outside of the polymer layer 2, and the coating layer 5 is located on the outside of the polymer layer 3, and the coating layer 4 and the coating layer 5 include but are not limited to alumina powder and boehmite used alone or in combination.

[0029] The thickness of the single-layer polymer layer 1 2 and polymer layer 2 3 is usually 3 μm-20 μm, and the thickness of the coating layer 1 4 and coating layer 2 5 is usually 1 μm-5 μm.

[0030] The reference electrode 1 is a conductive metal wire, including but not limited to a copper wire, a nickel wire or an alloy wire, and the diameter of the conductive metal wire is 5-50 μm.

[0031] The reference electrode 1 is wrapped by polymer layer 1 2 and polymer layer 2 3 in the composite membrane, and its arrangement scheme can be perpendicular to the length direction of the composite membrane or parallel to the length direction of the composite membrane, or arranged in a grid shape. The number can be one or more, and the spacing can be equal or unequal.

[0032] The reference electrode 1 is built into a double-layer or multi-layer isolation membrane. The reference electrode 1 is integrated with the isolation membrane, and the reference electrode 1 is introduced while laminating or winding, thereby realizing the one-time assembly of the positive electrode sheet, the negative electrode sheet and the reference electrode 1, without the need to disassemble the electrode group, bury the electrode and then reassemble it, which can greatly simplify the production process and improve the production efficiency.

[0033] The problem that an additional diaphragm has to be introduced when burying the reference electrode in the prior art is solved, resulting in the diaphragm being thicker at the reference electrode than at other places, increasing the resistance to lithium ion transmission and destroying the regional uniformity.

[0034] Reference Figure 3 A connector includes a metal sheet 1 6, a metal sheet 2 7, an insulating film 1 8 on the outside of the metal sheet 1 6, and an insulating film 2 9 on the outside of the metal sheet 2 7. The insulating film 1 8 and the insulating film 2 9 are polyimide high-temperature adhesives. The metal sheet 1 6 and the metal sheet 2 7 are copper sheets or nickel sheets with a thickness of 2-10 μm.

[0035] Reference Figure 4 and Figure 5 A three-electrode battery includes a three-electrode electrode group 16, and the diaphragm of the three-electrode electrode group is a composite diaphragm. Specifically, a three-electrode battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, a first pole ear 10, a second pole ear 11, a third pole ear 12, a composite diaphragm 13, and a connector 14. The composite diaphragm 13 covers the positive electrode sheet and the negative electrode sheet, and the connector 14 connects the reference electrode in the composite diaphragm 13 with the third pole ear 12. The first pole ear 10 is welded on the positive electrode sheet, and the second pole ear 11 is welded on the negative electrode sheet. The third pole ear 12 includes a pole ear hot melt adhesive 15.

[0036] Figure 5 In the figure, the direction of the arrow indicates the coating direction of the composite diaphragm 13.

[0037] When in use, after the composite separator is stacked or wound with the positive electrode sheet and the negative electrode sheet, the current of the reference electrode 1 in the separator is led out to the third electrode tab 12 using the connector 14 .

[0038] The connector 14 of the composite diaphragm and the external third pole tab 12, since the reference electrode 1 is embedded in the isolation membrane, how to connect the reference electrode in the isolation membrane with the third pole tab 12 without affecting the normal operation of the battery is a difficulty of the present invention.

[0039] The connection may be in the form of contact or non-contact connection, a method of connecting the composite separator to the third pole ear 12 through a certain form of connector to realize the function of a three-electrode battery, and is not limited to a specific connector form proposed.

[0040] The composite diaphragm is stacked or wound with the positive electrode sheet and the negative electrode sheet, and the reference electrode is conductively connected to the connector 14 at the edge of the diaphragm, and the connector 14 is connected to the third electrode ear 12 to form a three-electrode electrode group, which is then baked, injected and sealed to form a three-electrode battery.

[0041] The three-electrode battery of the present invention can be mass-produced without the need for additional operation of embedding a reference electrode. The reference electrode can be assembled simultaneously with the positive and negative electrodes and the negative electrode sheet. The three-electrode battery completed at one time improves the manufacturability of the three electrodes while improving the quality reliability.

[0042] At the same time, this patent has made structural improvements to the reference electrode of the three-electrode system. By integrating the reference electrode with the isolation membrane to form a composite diaphragm containing the reference electrode, the previous steps of disassembling the electrode group, burying the reference electrode and then reassembling it can be eliminated; and the reference electrode usually uses an extremely fine metal wire, which is built into the diaphragm to effectively protect the reference electrode from breaking and failing; one-time assembly greatly improves production efficiency and has the feasibility of mass production process.

[0043] Example 1

[0044] The preparation of a laminated three-electrode battery comprises the following steps:

[0045] 1. The composite diaphragm is composed of a reference electrode 1, a polymer layer 2, a polymer layer 3, a coating layer 4 and a coating layer 5. The polymer layer 2 and the polymer layer 3 are both porous polyethylene diaphragms with a thickness of 8 μm. The coating layer 4 and the coating layer 5 are both alumina ceramic coatings with a thickness of 2 μm.

[0046] 2. Assemble the positive electrode sheet, the negative electrode sheet and the composite diaphragm laminate into an electrode group, and weld the first electrode tab 10 and the second electrode tab 11 to the positive electrode sheet and the negative electrode sheet respectively;

[0047] 3. Use a 300°C heating wire to melt and remove the polymer and ceramic layer at the end of the composite diaphragm, and use a connector to connect the reference electrode and the pole ear 12;

[0048] 4. The connector shown is composed of an outer layer of insulating glue and an inner layer of metal sheet;

[0049] 5. After packaging, bake and inject liquid. After the battery is aged and soaked, lithium is plated on the reference electrode. Then the battery can be charged for relevant testing and use.

[0050] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A composite diaphragm, characterized in that: It consists of an isolation membrane and a reference electrode (1), wherein the reference electrode (1) is embedded in the isolation membrane longitudinally or transversely.

2. The composite diaphragm according to claim 1, characterized in that: The isolation film comprises a polymer layer 1 (2) and a polymer layer 2 (3).

3. The composite diaphragm according to claim 2, characterized in that: The polymer layer one (2) and the polymer layer two (3) include but are not limited to polyethylene and polypropylene used alone or in combination.

4. The composite diaphragm according to claim 3, characterized in that: The isolation film also includes a coating layer 1 (4) and a coating layer 2 (5), wherein the coating layer 1 (4) is located on the outside of the polymer layer 1 (2), and the coating layer 2 (5) is located on the outside of the polymer layer 2 (3), and the coating layer 1 (4) and the coating layer 2 (5) include but are not limited to the use of alumina powder and boehmite alone or in combination.

5. The composite diaphragm according to claim 4, characterized in that: The thickness of the single-layer polymer layer 1 (2) and polymer layer 2 (3) is usually 3 μm-20 μm, and the thickness of the coating layer 1 (4) and coating layer 2 (5) is usually 1 μm-5 μm.

6. The composite diaphragm according to claim 1, characterized in that: The reference electrode (1) is a conductive metal wire, including but not limited to a copper wire, a nickel wire or an alloy wire, and the diameter of the conductive metal wire is 5-50 μm.

7. A three-electrode battery, comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, characterized in that: It also includes a third electrode tab (12), a connector (14) and a composite diaphragm (13) as described in any one of claims 1 to 6, wherein the composite diaphragm (13) covers the positive electrode sheet and the negative electrode sheet, and the connector (14) connects the reference electrode in the composite diaphragm (13) to the third electrode tab (12).

8. The three-electrode battery according to claim 7, characterized in that: The connector comprises a metal sheet 1 (6), a metal sheet 2 (7), an insulating film 1 (8) outside the metal sheet 1 (6), and an insulating film 2 (9) outside the metal sheet 2 (7).

9. The three-electrode battery according to claim 8, characterized in that: The insulating film one (8) and the insulating film two (9) are polyimide high temperature adhesives.

10. The three-electrode battery according to claim 8, characterized in that: The metal sheet 1 (6) and the metal sheet 2 (7) are copper sheets or nickel sheets with a thickness of 2-10 μm.

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