Tab connection method of lithium-containing negative electrode and lithium-containing negative electrode

Abstract

The invention discloses a tab connection method of a lithium-containing negative electrode and the lithium-containing negative electrode, and solves the problem that a conventional welding method is difficult to connect a pole piece and a tab due to the fact that the lithium-containing negative electrode is soft in texture, active in chemical property and low in melting point. According to the method, tab connection with high mechanical strength and low contact resistance can be provided. The battery assembled by the pole piece prepared by the method has lower battery internal resistance, solves the problems of poor tab connection and shedding caused by volume change in the cycle process, can effectively improve the cycle performance, the service life and the safety of the lithium battery, and realizes long-term stable cycle of the lithium battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a method for connecting tabs of a lithium-containing negative electrode and the lithium-containing negative electrode. Background Art

[0002] With the rapid development of new energy production and electric vehicles, the demand for battery technology has become increasingly urgent, especially lithium-ion batteries, which dominate this field.

[0003] However, the lithium-ion batteries currently used in practical applications have many problems, among which low energy density is the most prominent one. Replacing traditional non-lithium negative electrodes such as graphite with lithium-containing negative electrodes can greatly improve battery energy density and provide more reliable and efficient solutions for application areas such as electric vehicles.

[0004] However, compared with traditional graphite negative electrodes, lithium-containing negative electrodes are soft in texture, have a low melting point, and are extremely chemically active. Conventional connection methods such as ultrasonic welding and laser welding cannot be used to tightly connect the pole pieces and tabs, posing new challenges to the battery manufacturing process. Summary of the Invention

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for connecting tabs of a lithium-containing negative electrode.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for connecting the tabs of a lithium-containing negative electrode, comprising:

[0009] Place the tab on the lithium-containing electrode, and the overlapping area of ​​the two forms a connecting belt;

[0010] The connecting strip is pressed by a pressing head to form a connecting area;

[0011] After fixing the connection area with insulating tape, the connection area is pressed again with a pressing head to produce a lithium-containing negative electrode.

[0012] As a preferred solution of the tab connection method of the present invention, the tab is made of one or more materials selected from copper, iron, aluminum, nickel and composites thereof.

[0013] As a preferred embodiment of the tab connection method of the present invention, the lithium-containing electrode comprises an alloy, a composite strip or a three-dimensional skeleton composite composed of lithium metal, lithium metal and potassium, sodium, magnesium, aluminum, zinc, iron, nickel, copper, mercury, tin, silver, indium, boron, carbon and silicon and composites of the above materials.

[0014] As a preferred solution of the tab connection method of the present invention, the material of the pressing head includes one or more of metal, polymer, wood, ceramic, carbon material and silicon material.

[0015] As a preferred solution of the tab connection method of the present invention, the shape of the press head includes one or more of a mesh shape, a grid shape, a single needle shape, and a multi-needle lattice shape.

[0016] As a preferred solution of the tab connection method of the present invention, the mesh line count of the mesh press head and the grid press head is 0.1 to 10,000 lines per inch.

[0017] As a preferred embodiment of the tab connection method of the present invention, the number of needles of the single-needle press head and the multi-needle matrix press head is 1 to 10,000 needles per square centimeter, and the diameter of the needles is 0.01 to 10 mm.

[0018] As a preferred solution of the tab connection method of the present invention, the material of the tape includes one or more of polyethylene, polypropylene, polyester fiber, polyethylene terephthalate, polyvinyl chloride, polyimide, resin and polytetrafluoroethylene.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide a lithium-containing negative electrode produced by a method for connecting tabs of a lithium-containing negative electrode.

[0020] Another object of the present invention is to overcome the deficiencies in the prior art and provide a lithium battery comprising a lithium-containing negative electrode, a positive electrode, an electrolyte and a separator; wherein the lithium-containing negative electrode is a lithium-containing negative electrode obtained by a method for connecting a lithium-containing negative electrode tab.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention provides a method for connecting the tabs of a lithium-containing negative electrode, which is connected by pressing with a pressure head and reinforcing with tape followed by secondary pressing. This effectively solves the problem that the electrode sheet and the tab cannot be connected by welding methods such as ultrasonic welding and laser welding due to the soft, sticky and low melting point properties of the lithium-containing negative electrode material. At the same time, the above method does not require additional wrapping or roughening of the tabs, nor does it require other instruments and equipment, which greatly simplifies the process difficulty and reduces production costs.

[0023] (2) The present invention provides a method for connecting the tabs of a lithium-containing negative electrode. Compared with direct fixation with tape or flat pressing, the connection between the tabs and the lithium-containing negative electrode is firm and has high mechanical strength. The tabs are not easy to fall off from the pole pieces during assembly and actual working cycles, and the contact resistance at the connection is lower. The use of the method provided by the present invention to connect the tabs of a lithium battery is beneficial to the performance of the battery and safe and stable long-term cycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0025] Figure 1 This is a front schematic diagram of the connection of the lithium-containing negative electrode tab provided in Example 1 of the present invention.

[0026] Figure 2 Schematic diagram of the multi-needle matrix indenter used in Example 1 of the present invention.

[0027] Figure 3 Schematic diagram of the mesh pressure head described in the present invention. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0029] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0030] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials with conventional purity in the field of lithium batteries.

[0031] The invention provides a method for connecting tabs of a lithium-containing negative electrode of a lithium battery.

[0032] The present invention also provides a lithium battery comprising a positive electrode, a lithium-containing negative electrode connected to a tab using the above method, and a separator.

[0033] The present invention has no particular limitation on the definition of the lithium battery, and the definition of lithium battery well known to those skilled in the art may be used.

[0034] In principle, the present invention has no special restrictions on the specific material of the positive electrode of the lithium battery. Those skilled in the art can make a choice based on actual production conditions, product morphology and product performance. In order to better ensure the performance of the lithium battery, the present invention preferably includes but is not limited to any one or a combination of lithium cobalt oxide, lithium iron phosphate, nickel cobalt manganese ternary material, nickel cobalt aluminum, lithium vanadium phosphate, lithium manganese oxide, lithium nickel oxide, lithium cobalt nickel manganese oxide, etc.

[0035] Example 1

[0036] This embodiment provides a method for connecting the tabs of a lithium-containing negative electrode. For a schematic diagram of the front view of the tab connection of a lithium-containing negative electrode, see Figure 1 The lithium-containing negative electrode comprises a lithium metal sheet (100), a tab (200), a connecting tape (300) and an insulating tape (400), wherein the tab (200) is placed on the lithium-containing electrode sheet (100), and the overlapping area of ​​the two forms the connecting tape (300);

[0037] The connecting tape (300) is pressed by a pressing head to form a connecting area, the connecting area is fixed by an insulating tape (400), and the connecting area is pressed again by a pressing head to obtain a lithium-containing negative electrode.

[0038] The indenter is a multi-needle matrix indenter, for which see Figure 2 .

[0039] The specific steps for preparing a lithium-containing negative electrode sheet are as follows:

[0040] (1) Cut lithium metal sheets and copper foil tabs of appropriate size;

[0041] (2) Place the copper foil tab on the appropriate position of the lithium-containing negative electrode, and use a multi-needle matrix alloy indenter to press the tab and the electrode connection area; the indenter pressing parameter is 5kg / cm 2 ;The material of the pressure head is tungsten steel alloy.

[0042] (3) Use polyimide tape to fix the connection area of ​​the pole piece and the pole ear.

[0043] (4) After covering with insulating tape, press the connection between the pole piece and the pole ear with the above-mentioned pressing head again, wherein the pressing parameter of the pressing head is 5kg / cm 2 .

[0044] The lithium-containing negative electrode sheet with the connected tabs obtained by the above preparation method is subjected to a tensile test on the connected tabs. The specific method of the tensile test is as follows: clamp the tabs with a tensile gauge, fix the tabs, and slowly apply tension in the horizontal or vertical direction until the tabs break or fall off;

[0045] Use an internal resistance meter to test the resistance of the tab connection. The specific test method for contact resistance is to use an internal resistance tester, clamp the tab with one end of the clamp and the electrode at the other end, and measure the contact resistance between the tab and the electrode.

[0046] Example 2

[0047] Under the preparation process of Example 1, the pressure head was replaced with a mesh pressure head, and the results were shown in Figure 3 , other conditions are the same as in Example 1, and a lithium-containing negative electrode sheet is prepared.

[0048] Example 3

[0049] Under the preparation process of Example 1, the tabs used were nickel foil tabs, and other conditions were the same as in Example 1, to prepare a lithium-containing negative electrode sheet.

[0050] Example 4

[0051] Under the preparation process of Example 1, the tabs used were aluminum foil tabs, and other conditions were the same as in Example 1, to prepare a lithium-containing negative electrode sheet.

[0052] Example 5

[0053] Under the preparation process of Example 1, the material of the lithium metal sheet used was replaced with a lithium-tin alloy sheet with a tin content of 0.5 wt.%, and other conditions were the same as in Example 1 to prepare a lithium-containing negative electrode sheet.

[0054] Example 6

[0055] Under the preparation process of Example 1, the lithium metal sheet used was replaced with a lithium-magnesium alloy sheet with a magnesium content of 1 wt.%, and other conditions were the same as in Example 1 to prepare a lithium-containing negative electrode sheet.

[0056] Comparative Example 1

[0057] This comparative example is used to illustrate that the conventional planar compaction method for connecting the tabs of a lithium-containing negative electrode is less effective. The steps for preparing a lithium-containing negative electrode sheet are as follows:

[0058] (1) Cut the lithium metal sheets and copper foil tabs to appropriate sizes.

[0059] (2) Sandwich the lithium metal sheet and the copper foil tabs in the appropriate position between two hard plastic plates

[0060] (3) Use a hydraulic press to apply pressure and fix it under a pressure of 1 ton for 30 seconds.

[0061] The lithium-containing negative electrode sheet with the connected tabs obtained by the above preparation method is subjected to a tensile test on the connected tabs. The specific method of the tensile test is as follows: clamp the tabs with a tensile gauge, fix the tabs, and slowly apply tension in the horizontal or vertical direction until the tabs break or fall off;

[0062] Use an internal resistance meter to test the resistance of the tab connection. The specific test method for contact resistance is to use an internal resistance tester, clamp the tab with one end of the clamp and the electrode at the other end, and measure the contact resistance between the tab and the electrode.

[0063] Comparative Example 2

[0064] This comparative example is used to illustrate the poor performance of lithium-containing negative electrodes when the tabs are fixed with tape without compression. The steps for preparing lithium-containing negative electrodes are as follows:

[0065] (1) Cut the lithium metal sheets and copper foil tabs to appropriate sizes.

[0066] (2) Place the copper foil on the appropriate position of the lithium metal sheet and use polyimide tape to fix the connection area of ​​the electrode tab.

[0067] The lithium-containing negative electrode sheet with the connected tabs obtained by the above preparation method is subjected to a tensile test on the connected tabs. The specific method of the tensile test is as follows: clamp the tabs with a tensile gauge, fix the tabs, and slowly apply tension in the horizontal or vertical direction until the tabs break or fall off;

[0068] Use an internal resistance meter to test the resistance of the tab connection. The specific test method for contact resistance is to use an internal resistance tester, clamp the tab with one end of the clamp and the electrode at the other end, and measure the contact resistance between the tab and the electrode.

[0069] Comparative Example 3

[0070] Under the conditions of Example 1, the re-pressing in step (4) was not performed, and the other conditions were the same as in Example 1.

[0071] Comparative Example 4

[0072] Under the conditions of Example 1, step (2) is not performed, and the surface of the indenter used in step (4) is changed to a smooth surface. Other conditions are the same as in Example 1.

[0073] The test results of the embodiments and comparative examples are shown in Table 1.

[0074] Table 1 Resistance and tensile strength limits of various connection methods

[0075]

[0076] It can be seen from the data in Table 1 that the method of using a multi-needle matrix alloy indenter to fix the copper foil tab to the lithium-containing negative electrode plate in Example 1 has the lowest resistance at the tab connection, indicating that the connection of the above method is tighter. Using this method to connect the tabs to assemble the battery can have a lower battery internal resistance and can effectively improve the battery performance using a simple process.

[0077] On the other hand, Examples 1 and 2 can withstand the maximum tensile force. Compared with the flat-plate pressing process of Comparative Example 1, the problems of the shear stress between the copper foil and the lithium sheet during pressing, such as the lithium sheet being easily broken at the edge of the copper foil, the lithium sheet being easily deformed after being pressed, the lithium sheet being easily adhered to the plywood after pressing, and poor longitudinal tensile resistance, can be avoided.

[0078] The greater tensile strength of Example 1 compared to Comparative Example 2 demonstrates that using a multi-needle matrix alloy indenter to secure the copper foil tab to the lithium-containing negative electrode plate provides a more secure and effective connection than directly securing with tape. This high connection strength ensures a stable connection between the tab and the plate during battery cycling, effectively preventing poor tab connection that can lead to increased internal resistance or even tab detachment. Examples 3 and 4 demonstrate that the method provided by the present invention can achieve relatively secure connections between tabs made of different metal materials; Examples 5 and 6 demonstrate that the method provided by the present invention can effectively connect a variety of lithium alloys.

[0079] The contact resistance and connection strength of Comparative Examples 3 and 4 are both weaker than those of Example 1, which illustrates the improvement of performance by the secondary pressing of the indenter in this method.

[0080] The present invention provides a method for connecting tabs to a lithium-containing negative electrode, a lithium-containing negative electrode using the method to connect tabs, and a lithium battery using the aforementioned tabs or methods. The method of using an alloy indenter to secure a copper foil tab to a lithium-containing negative electrode tab can stably and securely secure the tab to the lithium-containing negative electrode. The process is simple, requiring no additional equipment, and can reduce the tab's resistance, ensuring the tab's securement during cycling. It prevents increased internal resistance and tab detachment due to poor tab connection, effectively improving the performance of the lithium battery.

[0081] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for connecting a tab of a lithium-containing negative electrode, characterized in that: include, The electrode tab is placed on the lithium-containing electrode sheet, and the overlapping area of ​​the two forms a connecting belt; The connecting strip is pressed by a pressing head to form a connecting area; After the connection area is fixed by insulating tape, the connection area is pressed again by a pressing head to obtain a lithium-containing negative electrode.

2. The tab connection method according to claim 1, characterized in that: The material of the tab includes one or more of copper, iron, aluminum, nickel and composites of the above materials.

3. The method for connecting the tabs according to claim 1 or 2, characterized in that: The lithium-containing pole piece includes an alloy, a composite strip or a three-dimensional skeleton composite composed of lithium metal, lithium metal and potassium, sodium, magnesium, aluminum, zinc, iron, nickel, copper, mercury, tin, silver, indium, boron, carbon and silicon and composites of the above materials.

4. The tab connection method according to claim 1, characterized in that: The material of the pressure head includes one or more of metal, polymer, wood, ceramic, carbon material and silicon material.

5. The tab connection method according to claim 4, characterized in that: The shape of the pressure head includes one or more of a mesh shape, a grid shape, a single needle shape, and a multi-needle lattice shape.

6. The tab connection method according to claim 5, characterized in that: The number of dot lines of the mesh press head and the grid press head is 0.1 to 10,000 lines per inch.

7. The tab connection method according to claim 5 or 6, characterized in that: The number of needles of the single-needle indenter and the multi-needle dot matrix indenter is 1 to 10,000 needles per square centimeter, and the diameter of the needle is 0.01 to 10 millimeters.

8. The tab connection method according to claim 1, characterized in that: The material of the adhesive tape includes one or more of polyethylene, polypropylene, polyester fiber, polyethylene terephthalate, polyvinyl chloride, polyimide, resin and polytetrafluoroethylene.

9. A lithium-containing negative electrode made by the tab connection method as claimed in any one of claims 1 to 8.

10. A lithium battery, characterized in that: It comprises a lithium-containing negative electrode, a positive electrode, an electrolyte and a separator; wherein the lithium-containing negative electrode is the lithium-containing negative electrode according to claim 9.

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