An electrode sheet for a soft-pack button battery, a button battery and a preparation method thereof

Abstract

The present invention provides an electrode sheet for a soft-pack button battery, which comprises a current collector, an active material layer and a tab; the current collector includes a current collector body and at least one foil protruding outside the current collector body; the active material layer is coated on the current collector body; the tab is welded to the foil at one end exposed outside the soft-pack button battery, and at least a part of the foil is reserved between the tab and the current collector body for bending. Compared with the prior art, for the electrode sheet provided by the present invention, by providing a protruding foil in the current collector as the lead-out point of the tab, and reserving a part of the foil between the tab and the current collector body as a bending area, the welding method and bending method of the tab inside the battery cell are improved. The bending of the relatively thick rigid tab is replaced by the bending of the relatively thin foil, which greatly reduces the thickness of the battery at the tab folding position, solves the problems of large thickness of the rigid tab bending and easy puncture of the soft packaging film at the bending corner in the current soft-pack button battery, and improves the volume energy density and safety of the battery.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, and particularly to an electrode sheet for a soft-pack button battery, a button battery, and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have become important power supply devices today due to their high discharge platform voltage, low self-discharge, high energy density, no memory effect, and environmental friendliness, and are widely used in various electronic devices and transportation vehicles. With the gradual increase of portable devices, the size requirements for lithium-ion batteries are getting smaller and smaller, and button-type lithium-ion batteries are specifically designed for such applications. Button batteries refer to a type of small-sized lithium-ion battery with a round or quasi-round shape similar to a button, which can be mainly divided into steel-shell button batteries and soft-pack button batteries. Compared with steel-shell button batteries, soft-pack button batteries have the advantages of explosion prevention, high safety, flexible and variable sizes, and are widely used in fields such as TWS earphones and smart wearable products.

[0003] The structure of traditional soft-pack button batteries requires bending hard tabs inside the battery core, which has the following disadvantages: (1) Since the tabs are made of metals such as aluminum, nickel, and copper with relatively thick materials, generally with a thickness of 0.06 - 0.15 mm, the thickness is relatively large, and after bending, it will greatly increase the diameter of the battery core and reduce the volume energy density of the battery. (2) The corner position after bending the hard tab is very easy to pierce the outer aluminum-plastic film, causing safety problems such as electrolyte leakage and battery swelling. (3) The tabs of button batteries are relatively small, with a large internal resistance and poor rate performance.

[0004] In view of this, it is necessary to provide a technical solution to solve the above problems. Summary of the Invention

[0005] One of the purposes of the present invention is to provide an electrode sheet for a soft-pack button battery. The button battery prepared with this electrode sheet greatly reduces the folding thickness of the tab, avoids piercing the soft packaging film, and improves the volume energy density and safety performance of the battery.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] An electrode sheet for a soft-pack button battery, comprising:

[0008] A current collector, comprising a current collector main body and at least one foil protruding out of the current collector main body;

[0009] An active material layer, coated on the current collector main body;

[0010] A tab, welded to one end of the foil exposed outside the soft-pack button battery, and at least a part of the foil is reserved between the tab and the current collector main body for bending.

[0011] Preferably, the current collector is provided with at least two foils protruding out of the current collector body, and at least two of the foils are bent and overlapped and connected, and the tab is welded to one end of the foil exposed outside the soft-pack button battery after overlapping.

[0012] Preferably, the current collector is provided with a plurality of foils protruding out of the current collector body, and the plurality of foils are bent and overlapped and connected.

[0013] Preferably, the thickness of the foil is 0.005-0.02 mm.

[0014] The second object of the present invention is to provide a button battery, including a battery cell made of a positive electrode sheet, a separator and a negative electrode sheet, and the positive electrode sheet and / or the negative electrode sheet is the electrode sheet for the soft-pack button battery described in any one of the above.

[0015] Preferably, the tab welded on the positive electrode sheet is a positive tab, the tab welded on the negative electrode sheet is a negative tab, and the positive tab and the negative tab are led out from the same end or both ends of the battery cell.

[0016] Preferably, after the foil is bent, both the positive tab and the negative tab are arranged on the side surface of the battery cell.

[0017] Preferably, the button battery further includes a soft packaging film, the battery cell is arranged in the soft packaging film, and the tab glue on the positive tab and the tab glue on the negative tab are respectively hermetically connected to the soft packaging film.

[0018] The third object of the present invention is to provide a method for preparing a button battery, including the following steps:

[0019] S1. Cut at least one foil protruding out of the positive current collector body on the positive current collector, and coat a positive active material layer on the positive current collector body to obtain a positive electrode sheet; cut at least one foil protruding out of the negative current collector body on the negative current collector, and coat a negative active material layer on the negative current collector to obtain a negative electrode sheet;

[0020] S2. Wind and prepare the battery cell in sequence according to the positive electrode sheet, the separator and the negative electrode sheet, and the foils of the positive current collector and the foils of the negative current collector are both partially exposed outside the battery cell;

[0021] S3. Weld the positive tab to the foil of the positive current collector exposed outside the battery cell, and at least reserve a part of the foil between the positive tab and the current collector body for bending; weld the negative tab to the foil of the negative current collector exposed outside the battery cell, and at least reserve a part of the foil between the negative tab and the current collector body for bending; thus completing the preparation of the button battery.

[0022] Preferably, when a plurality of foils protruding outside the main body of the positive current collector are cut out on the positive current collector and a plurality of foils protruding outside the main body of the negative current collector are cut out on the negative current collector, after the battery core is wound, the foils on the positive current collector are correspondingly arranged, and the foils on the negative current collector are correspondingly arranged; after being bent, the foils on the positive current collector are overlapped and connected, and one end is welded to the positive electrode tab, and the foils on the negative current collector are overlapped and connected, and one end is welded to the negative electrode tab.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1) For the pole piece provided by the present invention, by providing a protruding foil in the current collector as the lead-out point of the pole tab, and leaving a part of the foil between the pole tab and the main body of the current collector as the bending area, compared with the pole piece used in the conventional soft-pack button battery, the welding method and bending method of the pole tab inside the battery core are improved by the present invention. The bending of the relatively thin foil is used to replace the bending of the relatively thick rigid pole tab, which greatly reduces the thickness of the battery at the folded part of the pole tab and improves the volume energy density of the battery; at the same time, the present invention uses a relatively thin pole piece for bending, and the corner hardness at the bending part is relatively low, which avoids puncturing the aluminum-plastic film, improves the safety of the battery, and significantly reduces the leakage defect rate. The pole piece of the present invention solves the problems of large thickness in the bending of the rigid pole tab and easy puncturing of the soft packaging film at the bending corner in the current soft-pack button battery.

[0025] 2) A plurality of protruding foils are also provided in the present pole piece. By leading out the pole tabs in multiple layers, the migration path of electrons is reduced, and the rate performance of the battery is improved.

[0026] 3) The present invention also provides a button battery and a preparation method thereof, which changes the process of first welding the pole tabs and then winding in the preparation of the traditional soft-pack button battery. The present invention first winds the pole piece with multiple protruding foils cut out, and then welds the pole tabs on the foils. Although the slitting process is increased, due to the relatively small pole tabs of the button battery, welding on the protruding foils can reduce the production difficulty in industry and reduce the defect rate of products; in addition, for the pole piece coated with the active material layer, since there is no need to reserve an empty foil area in the main body of the pole piece for welding the pole tabs, a full coating method can be used to increase the amount of the active material layer, further improving the energy density of the battery. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of a traditional soft-pack button battery.

[0028] Figure 2 It is a schematic structural diagram of the pole piece of the present invention.

[0029] Figure 3 It is one of the schematic structural diagrams in the preparation of the soft-pack button battery of the present invention.

[0030] Figure 4 is Figure 3 Schematic diagram of the structure of a soft-pack button battery after welding the tab.

[0031] Figure 5 is Figure 4 Schematic diagram of the structure of the prepared soft-pack button battery.

[0032] Figure 6 This is the second schematic diagram of the structure in the preparation of the soft-pack button battery of the present invention.

[0033] Figure 7 is Figure 6 Schematic diagram of the structure of a soft-pack button battery after welding the tab.

[0034] Figure 8 is Figure 7 Schematic diagram of the structure of the prepared soft-pack button battery.

[0035] In the figure: 1 - electrode plate; 11 - current collector; 111 - foil; 12 - active material layer; 13 - tab; 14 - tab glue; 2 - battery cell; 21 - side surface of the battery cell. Detailed implementation manners

[0036] To make the technical solutions and advantages of the present invention clearer, the present invention and its beneficial effects will be further described in detail below in combination with the specific implementation manners and the accompanying drawings of the specification, but the implementation manners of the present invention are not limited thereto.

[0037] Example 1

[0038] As Figure 2 shown, an electrode plate for a soft-pack button battery includes a current collector 11, an active material layer 12, and a tab 13; the current collector 11 includes a current collector main body and at least one foil 111 protruding out of the current collector main body; the active material layer 12 is coated on the current collector main body; the tab 13 is welded to one end of the foil 111 exposed outside the soft-pack button battery, and at least a part of the foil 111 is reserved between the tab 13 and the current collector main body for bending.

[0039] Among them, at least one protruding foil 111 can be cut out at one end of the electrode plate 1 first, and the methods of cutting the foil 111 include punching, roll cutting, laser cutting, etc. When there are multiple protruding foils 111, the pores between adjacent foils 111 can be different, but it should be ensured that the multiple foils 111 are correspondingly arranged after the battery is wound and can overlap after folding, so as to be more conducive to the subsequent welding of the tab 13. In the specific preparation process, multiple foils 111 can be welded together first, then the tab 13 can be welded to one end of the overlapping foils 111, and then bent; or the foils 111 can be bent first and then welded together, and then the tab 13 can be welded.

[0040] Further, the current collector 11 is provided with at least two foils 111 protruding from the current collector body. At least two foils 111 are bent and overlapped and connected, and the tab 13 is welded to one end of the foil 111 exposed outside the soft-pack button battery after overlapping.

[0041] Further, the current collector 11 is provided with a plurality of foils 111 protruding from the current collector body. The plurality of foils 111 are bent and overlapped and connected.

[0042] Further, the thickness of the foil 111 is 0.005 - 0.02 mm. The thickness of a conventional tab 13 is generally 0.06 - 0.15 mm. For example Figure 1 and Figure 5 , for a conventional soft-pack button battery, the outer diameter D1 of the wound core = the core diameter D + 2 * the thickness T1 of the conventional tab; for the button battery of the present invention, the outer diameter D2 of the wound core = the core diameter D + the number N of foils * the thickness T2 of the foil + the thickness T1 of the conventional tab; assuming that the thickness T1 of the conventional tab = 0.15 mm and the thickness T2 of the foil = 0.006 mm, then when the number N of foils 111 is greater than 25, D2 > D1. Even when the thickness T1 of the conventional tab 13 = 0.06 mm, it is also necessary that the number N of foils 111 is greater than 10 for D2 > D1. However, generally, the number of foils 111 led out from the button battery is less than 10. Then, with the core diameter D unchanged (representing that the energy that the battery can finally release remains unchanged), the diameter of the button battery obtained by the present invention is smaller. The smaller the diameter of the battery, the smaller the space reserved for the battery compartment can be. In this way, the volume energy density of the battery can be effectively improved.

[0043] Example 2

[0044] For example Figures 3 - 8 shown, a button battery includes a battery core 2 made of a positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet and / or the negative electrode sheet is the electrode sheet 1 for the soft-pack button battery described in Example 1.

[0045] Further, the tab 13 welded on the positive electrode sheet is a positive tab, and the tab 13 welded on the negative electrode sheet is a negative tab. The positive tab and the negative tab are led out from the same end or both ends of the battery core 2. The specific leading-out method of the positive and negative tabs can be determined according to the direction of the foil 111 arranged in the positive and negative electrode sheets. The two leading-out methods can be respectively referred to Figures 3 - 5 and Figures 6 - 8 shown.

[0046] Further, the bent part of the foil 111 is flattened on the end face of the battery core 2. Since the material of the foil 111 is relatively soft, flattening will not form a thick protrusion on the end face of the battery core 2. Compared with the traditional tab folding, the thickness at the folding part is greatly reduced, and the hardness at the corner is also significantly reduced.

[0047] Further, after the foil 111 is bent, both the positive electrode tab and the negative electrode tab are disposed on the side surface 21 of the battery cell.

[0048] Further, this button battery further includes a soft packaging film. The battery cell 2 is disposed in the soft packaging film, and the tab glue 14 on the positive electrode tab and the tab glue 14 on the negative electrode tab are respectively and sealingly connected to the soft packaging film. Specifically, the soft packaging film is an aluminum-plastic film. In the encapsulation of the soft-packaged battery, it is necessary to thermally melt the CPP layer on the tab glue 14 and the PP layer of the aluminum-plastic film to ensure the airtightness of the battery encapsulation.

[0049] Embodiment 3

[0050] A method for manufacturing a button battery, comprising the following steps:

[0051] S1. Cut out at least one foil 111 protruding from the main body of the positive current collector on the positive current collector, and coat a positive active material layer 12 on the main body of the positive current collector to obtain a positive electrode sheet; cut out at least one foil 111 protruding from the main body of the negative current collector on the negative current collector, and coat a negative active material layer 12 on the negative current collector 11 to obtain a negative electrode sheet;

[0052] S2. Wind the positive electrode sheet, the separator and the negative electrode sheet in sequence to prepare the battery cell 2, and the foils 111 of the positive current collector and the foils 111 of the negative current collector are both partially exposed outside the battery cell 2;

[0053] S3. Weld the positive electrode tab to the foil 111 of the positive current collector exposed outside the battery cell 2, and at least a part of the foil 111 is reserved between the positive electrode tab and the main body of the current collector for bending; weld the negative electrode tab to the foil 111 of the negative current collector exposed outside the battery cell 2, and at least a part of the foil 111 is reserved between the negative electrode tab and the main body of the current collector for bending;

[0054] S4. Bend the reserved foil 111. Of course, the foil 111 can also be bent first and then the electrode tab 13 is welded;

[0055] S5. After the welding of the electrode tab 13 is completed, stick the tab glue 14 paper, thermally melt its CPP layer and the PP layer of the aluminum-plastic film, encapsulate, inject electrolyte, perform formation, secondary encapsulation, hemming, and aging to complete the manufacture of the button battery.

[0056] Further, when several foils 111 protruding from the main body of the positive current collector are cut out on the positive current collector 11 and several foils 111 protruding from the main body of the negative current collector are cut out on the negative current collector 11, after the battery cell 2 is wound, the foils 111 on the positive current collector 11 are correspondingly arranged, and the foils 111 on the negative current collector 11 are correspondingly arranged; after bending, the foils 111 on the positive current collector 11 are overlapped and connected and one end is welded to the positive electrode tab, and the foils 111 on the negative current collector 11 are overlapped and connected and one end is welded to the negative electrode tab.

[0057] Comparative Example 1

[0058] As Figure 1 shown, the soft-pack button battery of this comparative example is a conventional soft-pack button battery with a model number of 1056. That is, no foil is reserved at the edge of the electrode sheet, no protruding foil is provided, and the tab is directly welded to the electrode sheet.

[0059] Compare the performance of the soft-pack button batteries in several Example 2 and Comparative Example 1, and the statistical results are shown in Table 1.

[0060] Table 1

[0061] Comparative Example 1 Example 2 Cell diameter 10 mm 10 mm Cell capacity (average) 44.2 mAh 47.3 mAh Leakage failure rate 89.7％ 0％

[0062] Then conduct a discharge rate performance test on the soft-pack button batteries in Example 2 and Comparative Example 1, and the test results are shown in Table 2.

[0063] Table 2

[0064] Discharge rate Comparative Example 1 Example 2 0.2C 100％ 100％ 0.5C 97.2％ 98.3％ 1C 95.3％ 96.8％ 2C 75.2％ 86.5％ 3C 24.1％ 70.3％

[0065] It can be seen from the above test results that compared with the conventional soft-pack button battery, the soft-pack button battery of the present invention can still achieve a cycle performance of more than 70% under high-rate discharge, the cell capacity is increased, and the sealing performance is good, and the leakage failure rate is 0.

[0066] According to the disclosure and teachings of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments, and any obvious improvements, substitutions, or variations made by those skilled in the art on the basis of the present invention fall within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A button battery, comprising a wound battery core (2) made of a positive electrode sheet, a separator and a negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet is an electrode sheet (1) for a soft-pack button battery, and is characterized in that, The electrode includes: A current collector (11), including a current collector body and a plurality of foils (111) protruding out of the current collector body; the foils (111) of the positive current collector are led out from the upper end face or the lower end face of the battery cell (2), and the foils (111) of the negative current collector are led out from the upper end face or the lower end face of the battery cell (2); An active material layer (12), coated on the current collector body; Tabs, a plurality of the foils (111) are bent and overlapped and connected, the tab (13) is welded to one end of the foil (111) exposed outside the soft-pack button battery after overlapping, and at least a part of the foil (111) is reserved between the tab and the current collector body for bending; The tab welded on the positive electrode sheet is a positive tab, and the tab welded on the negative electrode sheet is a negative tab; After the foil (111) is bent, the bent part of the foil (111) is flattened on the end face of the battery cell (2), and both the positive tab and the negative tab are arranged on the side surface of the battery cell (2).

2. The button cell according to claim 1, wherein The thickness of the foil (111) is 0.005 - 0.02 mm.

3. The button cell according to claim 1, wherein It further includes a soft packaging film, the battery cell (2) is arranged in the soft packaging film, and the tab glue (14) on the positive tab and the tab glue (14) on the negative tab are respectively hermetically connected to the soft packaging film.

4. A method for preparing a button battery according to claim 1, wherein, It includes the following steps: S1. Cut out a plurality of foils (111) protruding out of the positive current collector body on the positive current collector, and coat a positive active material layer on the positive current collector body to obtain a positive electrode sheet; cut out a plurality of foils (111) protruding out of the negative current collector body on the negative current collector, and coat a negative active material layer on the negative current collector to obtain a negative electrode sheet; S2. Wind and prepare the battery cell (2) in sequence according to the positive electrode sheet, the separator and the negative electrode sheet, and the foils (111) of the positive current collector and the foils (111) of the negative current collector are both partially exposed outside the battery cell (2); S3. Weld the positive tab to the foil (111) of the positive current collector exposed outside the battery cell (2), and at least a part of the foil (111) is reserved between the positive tab and the current collector body for bending; weld the negative tab to the foil (111) of the negative current collector exposed outside the battery cell (2), and at least a part of the foil (111) is reserved between the negative tab and the current collector body for bending; complete the preparation of the button battery.

5. The preparation method according to claim 4, characterized in that, When a plurality of foils (111) protruding out of the positive current collector body are cut out on the positive current collector, and a plurality of foils (111) protruding out of the negative current collector body are cut out on the negative current collector, after the battery cell (2) is wound, the foils (111) on the positive current collector are correspondingly arranged, and the foils (111) on the negative current collector are correspondingly arranged; after bending, the foils (111) on the positive current collector are overlapped and connected and one end is welded with the positive tab, and the foils (111) on the negative current collector are overlapped and connected and one end is welded with the negative tab.

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