Tab based on micro-riveted structure and preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a tab based on a micro-riveting structure and a preparation method and application thereof.The tab comprises a connecting piece and tab glue, the connecting piece and foil are of an integrated structure, and a micron-sized micropore array is arranged on the connecting piece; the maximum span L of micropores in the micropore array is 0.1-0.8 mm, the transverse center distance A1 is 0.5-1.5 mm, and the longitudinal center distance B1 is 0.5-1.5 mm. The tab glue comprises two tab film bodies, and the two tab film bodies cover the two sides of the thickness direction of the connecting piece respectively and are connected through the micropore array after hot pressing. When the tab is used for a soft package battery, a'colloid rivet 'penetrating through multiple layers of tabs is formed between the tab layers, so that three-dimensional mechanical interlocking is realized, under the requirement of the same stripping force, the width of a tab film is remarkably reduced, and a top sealing area is folded during combined packaging, so that the space of a battery cell is favorably saved for accommodating more active substances, and the service life of the battery cell is prolonged. And the purpose of improving the battery energy density is achieved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a tab based on a micro-riveting structure, its preparation method, and its application. Background Technology

[0002] In traditional lithium-ion pouch battery manufacturing, the wound or stacked cells typically require welding additional metal tabs and bending them to fit the packaging space. This traditional process has the following drawbacks: 1. Welding and bending processes increase manufacturing costs and time, and the bent tabs still occupy internal battery space, limiting the improvement of energy density; 2. Abrupt changes in cross-section are prone to occur at the bending point, leading to local current density and heat concentration, which can easily cause loose connections or even internal short circuits under mechanical vibration; 3. Metal debris generated during the welding process can easily be introduced into the cell, leading to safety hazards such as self-discharge and poor consistency.

[0003] To simplify the process, existing technologies design the tabs as integrated tabs, directly heat-sealing the stacked tabs to the packaging film after winding or stacking. However, this approach relies on the static friction between the tabs and the adhesion of the tab adhesive, resulting in limited bonding strength. Under the stress generated by battery charge-discharge cycles, slippage and misalignment can easily occur between the tab layers, leading to increased interfacial contact resistance, structural instability, and decreased sealing performance. Additionally, existing technologies have proposed connecting the tabs to the metal tab sheet using an additional physical rivet structure, but this introduces a new process, complicating operations and increasing manufacturing costs.

[0004] Therefore, how to fundamentally enhance the stability of integrated tab structures and the reliability of electrical connections without increasing process complexity is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] In view of the background technology, the present invention provides a tab based on a micro-riveting structure, its preparation method and application, which can fundamentally enhance the stability of integrated tab structures and the reliability of electrical connections without increasing the complexity of the process.

[0006] To achieve the above objectives, the main technical solutions adopted by the present invention are as follows.

[0007] On one hand, this invention proposes a tab based on a micro-riveting structure, comprising a connecting piece and tab adhesive. The connecting piece and the foil are integrally formed. The connecting piece has a micron-scale micropore array. The tab adhesive comprises two tab sheets, which respectively cover both sides of the connecting piece in the thickness direction and are connected through the micropore array after hot pressing. The micropore array is specifically composed of several micropore structures arranged in an array. The maximum span L of the micropore structure satisfies: 0.1mm ≤ L ≤ 0.8mm. For example, L can be 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.6mm, 0.65mm, 0.7mm, 0.8mm, etc. The spacing between the centers of two adjacent micropore structures is 0.75mm, 0.8mm, etc., along the length direction of the foil. The center distance A1 between two adjacent micropore structures satisfies the following condition: 0.5mm ≤ A1 ≤ 1.5mm. For example, A1 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, etc. The center distance B1 between two adjacent micropore structures satisfies the following condition: 0.5mm ≤ B1 ≤ 1.5mm. For example, B1 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, etc.

[0008] This invention utilizes a micropore array on the tab. When the tab is hot-pressed with the tab films located on both sides, the films melt and enter the micropores. After cooling and solidification, they form "colloidal rivets" that penetrate the tab, creating a robust integrated tab. Because these "colloidal rivets" have a three-dimensional structure, their larger effective contact area significantly enhances the bonding strength between the tab and the tab film, while also significantly reducing contact resistance. Using interlayer peel force as a benchmark, this invention significantly reduces the width of the tab film required to achieve the same peel force. This helps reduce the amount of tab film used, lightening the battery weight, saving space, facilitating the filling of more active materials, and increasing volumetric energy density.

[0009] Taking the 545562 battery cell as an example, its cell thickness is 5.4mm, width is 55mm, and length is 62mm. The tab width required to achieve the industry standard peel force is 5mm. After adopting the tab proposed in this invention, the tab width is 2-3.5mm; thus, a width of 1.5-3mm can be saved on one side. This saved space can be reused, and calculations show that it can further increase the volumetric energy density of the battery cell by 1.5% to 3.5%.

[0010] It is important to note that the size and distribution density of the microporous structure are crucial to the performance of the tabs. When the maximum span L is 0.2-0.5 mm, the microporous structure presents complete through-holes, ensuring easy flow and filling of the tab film during hot pressing. If the span is too small, the flow resistance of the tab film will increase significantly, making it difficult to fully fill and form effective "colloidal rivets." If the span is too large, stress concentration in the tab is easily caused by the pressure tension during roller pressing, leading to micro-cracks or even breakage of the foil, and also excessively sacrificing the effective conductive area on the electrode. Through repeated experiments, this invention found that when A1 is 0.5-1.5 mm and B1 is 0.5-1.5 mm, there is sufficient foil between adjacent "colloidal rivets" in both the transverse and longitudinal directions to maintain the overall mechanical strength of the tab, while achieving a high-density interlocking point distribution.

[0011] Furthermore, the melt index of the electrode film at 230℃ / 2.16kg is 15-50g / 10min, and the melt index is denoted as M, where L and M satisfy 6≤LM≤15.

[0012] In this technical solution, the tab film that meets the required melt flow index has good flowability and sealing properties. When the tab and the tab film are hot-pressed, the tab films located on opposite sides of the tab can melt and fully fill the micropores, and form a "colloidal rivet" that runs through the tab after cooling and solidification. If the melt flow index is lower than 15 g / 10 min, the flowability of the tab film is poor, which can easily lead to incomplete filling; if the melt flow index is higher than 50 g / 10 min, the tab film flows excessively, which may block the microporous structure and cause glue overflow.

[0013] In this technical solution, the present invention further discovered that when L and M satisfy 6≤LM≤15, the filling effect of the tab film is particularly good, the filling rate of the tab adhesive is relatively high and there is no serious overflow phenomenon, which helps to improve the packaging qualification rate.

[0014] Furthermore, the shape of the microporous structure is selected from one or more of the following: circular, elliptical, fan-shaped, triangular, rectangular, trapezoidal, pentagonal, hexagonal, cross-shaped, I-shaped, rice-shaped, and irregular shapes.

[0015] Furthermore, the bottom of the micropore array is at least 0.5 mm away from the foil material area. This is to prevent the micropore array from being too close to the active material, which could damage the active material in case of misoperation, resulting in a risk of reduced electrode yield and cell capacity. On the other hand, since the connection between the tab and the electrode (the root of the tab) is a weak point under stress, the bottom of the micropore array being too close to the foil material area will greatly increase the risk of the foil being torn due to stress concentration. Preferably, 0.2mm≤L≤0.5mm, 0.8mm≤A1≤1.2mm, and 0.8mm≤A1≤1.2mm; more preferably, L is 0.3mm, A1 is 1mm, and B1 is 1mm, that is, the micropore array is composed of circular holes with a diameter of 0.3mm arranged with a vertical spacing and a horizontal spacing of 1mm. At this time, the number of micropore arrays is large enough and the diameter is large enough to ensure the effectiveness of the riveting structure and ensure that the riveting structure between the electrode and the electrode adhesive is evenly distributed throughout the interface, rather than concentrated on a few points, which greatly improves the uniformity and reliability of the connection. At the same time, such a micropore array, through reasonable micropore spacing design, helps to maintain the integrity and continuity of the foil structure and ensures that the conductivity and mechanical strength of the electrode itself are not damaged.

[0016] On the other hand, the present invention proposes a pouch battery containing the above-mentioned tabs based on the micro-rivet structure.

[0017] Furthermore, this invention also proposes a method for preparing the aforementioned soft-pack battery. S1, Electrode Pre-fabrication Two blank areas are symmetrically arranged on both sides of the electrode material area. When the electrode is rolled, a pressure roller with a micro needle array is used to press the two blank areas simultaneously, and then the micro hole array is arranged on them. Then, the electrode material area is cut in half along the center to obtain two strips with the material area and the blank area respectively. The blank area is die-cut to obtain an electrode with tabs. This process combines rolling, calendering, and perforation in one step: a pressure roller with a micro-needle array creates a regularly distributed array of micro-holes in the blank area, and the blank area and the material area are calendered simultaneously, so that the ductility and mechanical strength of the two areas tend to be consistent. By coordinating the deformation of the material area and the blank area, it effectively reduces the defects such as electrode wrinkles, wavy edges, and even broken strips that are easily generated in subsequent processes due to the mismatch of their ductility, and significantly improves the production efficiency and consistency of the electrode. S2, Cell Molding The electrode sheets obtained in the previous step are processed by stacking or winding to form a multi-tab structure and stacked with the same electrode tabs to form the main body of the battery cell. S3, Electrode Integration First, position the stacked same-pole tabs between the two tab films and align them with their center lines, then hot-press them together to form the cell tabs; S4, Packaging The battery cell body obtained in the previous step is placed into the perforation of the aluminum-plastic film. The width of the top sealing area of ​​the aluminum-plastic film is greater than the width of the tab film. The position of the battery cell body is adjusted so that the upper edge of the tab film extends 0.2-1.0mm beyond the top sealing boundary of the aluminum-plastic film to achieve a reliable seal. Then, the top sealing is performed to form the top sealing area, which is divided into the top sealing tab film area and the top sealing flat sealing area. First, the top sealing area is folded 180° towards the battery cell body along the root of the top sealing tab film area. Then, the tab is folded 180° away from the battery cell body along the top of the top sealing tab film area and extended out. By reducing the width of the tab film and combining the compact design of the top sealing area during packaging, space corresponding to the reduction in the width of the tab film can be saved in the height direction of the battery cell. This space is reused to help improve the volumetric energy density of the battery cell. S5, Post-processing The battery cells undergo processes such as electrolyte injection, formation, and side sealing.

[0018] The method for preparing a soft-pack battery proposed in this invention maximizes the utilization of the internal space of the battery cell by combining the cell tabs based on the micro-rivet structure, which can effectively shorten the width of the tab film, with a compact top design, thereby achieving a higher volumetric energy density of the battery cell.

[0019] Furthermore, in step S1, the width of the material area is denoted as H2, and the widths of the upper and lower blank areas are denoted as H1 and H3, respectively. H1, H2, and H3 satisfy: H1=H3, 0.03H2≤H1≤0.3H2.

[0020] In this technical solution, to ensure that the electrode does not break or wrinkle during the rolling process due to the different elongation rates of the blank area and the material area, H1=H3 must be satisfied to ensure the force balance on both sides of the electrode. After the electrode is coated, the thickness of the material area is greater than that of the blank area, and most of the rolling pressure is borne by the material area. Therefore, the elongation rate of the material area is significantly greater than that of the blank area. If the blank area is too narrow, the increased elongation due to perforation is insufficient to compensate for the difference with the material area, which may still lead to wrinkles; if the blank area is too wide, the increased elongation due to perforation will be significantly greater than that of the material area, which may lead to the risk of breakage due to excessive stretching. Through repeated experiments, this invention has found that by simultaneously controlling the widths H1 and H3 of the two blank areas to 3% to 30% of the width H2 of the material area, under the perforation and pressure of the microneedle array, the actual strain of the blank area and the material area during the rolling process can be precisely controlled, making the elongation rates of the two areas tend to be consistent.

[0021] Furthermore, in step S1, the diameter of the microneedles in the microneedle array is 0.1-0.8 mm, and the working pressure of the pressure roller is 0.3-10 MPa; Preferably, the diameter of the microneedles is 0.2-0.5 mm, and the working pressure of the pressure roller is 1-5 MPa; Preferably, the average pore density of the micropore array is 50-200 pores / cm². 2 The area of ​​the micro-pore array occupies 5%-15% of the area of ​​the blank area.

[0022] In this technical solution, a microneedle array with a diameter of 0.1-0.8 mm, combined with a pressure of 0.3-10 MPa, can form a micropore array composed of complete circular micropore structures in the blank area of ​​the electrode sheet. The effect is particularly good when a microneedle array with a diameter of 0.1-0.5 mm is pressed with a pressure of 1-5 MPa, achieving a high filler rate of the tab adhesive, low damage to the electrode sheet, and high strength of the tab. Relatively speaking, the pressure roller with the aforementioned microneedle array is easier to process, has controllable costs, and provides more uniform calendering in the blank area, making it more practical. While using an "I" shape (forming a dumbbell-shaped micropore structure) or a hexagonal shape (such as a regular hexagon, forming a honeycomb-like micropore structure) can further increase the contact area of ​​the "colloidal rivets" and achieve better shear resistance and conductive pathways at the same pore size, the processing difficulty and cost of the pressure roller with the corresponding microneedle array are higher.

[0023] In this technical solution, based on the maximum span of the microporous structure and the center-to-center spacing A1 and intermediate spacing B1, the average pore density of the resulting microporous array is 44-400 pores / cm². 2 The area of ​​the micropore array occupies 4.2%-38.4% of the area of ​​the blank area. The preferred average pore density is 50-200 pores / cm². 2 The area of ​​the micropore array is preferably 5%-15% of the area of ​​the blank area. A micropore array that meets this requirement can achieve effective mechanical interlocking without causing significant adverse effects on the conductive cross section and the strength of the electrode due to the presence of the micropore structure.

[0024] Furthermore, in step S3, a two-stage pressure increase method is adopted during hot pressing: first, pre-pressing is performed at 0.3MPa for 2s to allow the tab film to initially melt and expel interlayer air; then, the pressure is increased to 1.0MPa within 2s and held at 150-180℃ for 10s.

[0025] In this technical solution, when the two-stage pressurization method is used, the molten tab film can overcome the flow resistance under the limited pressure and temperature, completely flow into and fill each microporous structure, and form a "colloidal rivet" that runs through multiple layers of tabs after cooling and solidification, thereby constructing a robust integrated tab.

[0026] Furthermore, in step S4, a stepped thermoforming head is used for top sealing. This head is stepped along the thickness direction of the battery cell, including a top sealing flat seal. The top sealing flat seal acts on the top sealing area of ​​the tab film and fuses the upper and lower layers of the encapsulation film together through thermoforming. Two tab adhesive grooves are provided on the top sealing flat seal corresponding to the two tab films. The internal space of the tab adhesive grooves can accommodate the tab films and the molten flow generated by the tab films under heat and pressure. Through continuous pressure and temperature, the tab adhesive and the encapsulation film are firmly bonded, achieving complete encapsulation of the entire top sealing area. Due to the thickness of the top sealing tab adhesive area (i.e., the thickness of the tab film, the tab, and the encapsulation film...), The thickness of the top sealing area (i.e., the thickness of the encapsulation film) is significantly greater than that of the top sealing flat sealing area. After being hot-pressed by the stepped hot-pressing head, the top sealing cross section naturally forms a unique "mushroom head" shaped mechanical anchoring structure wrapped in the encapsulation film. This structure plays a mechanical interlocking role on the one hand, effectively resisting the peeling stress caused by the expansion of the cell, and on the other hand, makes the sealing path much larger than the original thickness of the material, extending the potential leakage channel. Together with the "colloidal rivets", it further improves the reliability of the encapsulation system, so that the soft-pack battery can still maintain good encapsulation performance under the premise of reducing the width of the tab film, creating favorable conditions for improving the volumetric energy density of the cell. Preferably, the width D of the tab adhesive groove is 0.1-0.5mm larger than the width F2 of the tab adhesive sheet. This allows space for the lateral flow of the tab adhesive sheet after it is heated and melted, preventing excessive extrusion of the tab adhesive that could lead to edge contamination or insufficient pressure. The height K of the tab adhesive groove is 0.1-0.5mm smaller than the thickness of the top sealing tab adhesive area. This ensures that sufficient pressure and temperature are applied to the top sealing tab adhesive area, effectively expelling interfacial air, promoting the interdiffusion and bonding of polymer molecular chains, and making the top seal more secure. Preferably, the width of the top sealing area is denoted as F1, the width of the tab film is denoted as F2, and the width of the top sealing flat sealing area is denoted as F3. The width of the top sealing area F1 is equal to the sum of the width of the tab film F2 and the width of the top sealing flat sealing area F3. The depth of the top sealing flat sealing area is denoted as L2, and the size of L2 determines the sealing strength of the top sealing flat sealing area. The depth of the tab groove is denoted as L1, and the size of L1 determines the longitudinal embedding depth of the "mushroom head" shaped mechanical anchoring structure. In order to ensure accurate positioning during top sealing, it is required that L2=F3 and L1+L2=F2+F3. Preferably, the thickness of the battery cell tab in step S3 is 0.05-0.2mm, and the sum of F2 and the thickness of the battery cell tab is equal to F3; when the top sealing area is folded down, the battery cell tab will generate an additional width in the tab film width direction equivalent to its own thickness. In order to facilitate the folding of the top sealing area space and the lead-out of the tab, it is preferable that F2 + battery cell tab thickness = F3.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The anti-delamination and anti-shear properties of the battery cell tabs are significantly enhanced. Compared with the traditional battery cell tabs that achieve layer-to-layer connection through intermolecular forces, the battery cell tabs of the present invention are connected between layers by "colloidal rivets" that penetrate multiple layers of tabs. This can effectively resist peeling forces perpendicular to the plane or shear forces parallel to the plane, making it difficult for the battery cell tabs to separate and delaminate. It also improves the structural rigidity and bending resistance of the battery cell tabs, which is beneficial for subsequent handling and packaging.

[0028] (2) The "colloidal rivet" achieves effective three-dimensional contact, significantly expands the contact area, not only achieves a firm connection between layers, but also helps to significantly reduce contact resistance and improve the rate performance of the soft pack battery.

[0029] (3) A stepped thermo-pressed head is used for top sealing, forming a unique "mushroom head" shaped mechanical anchoring structure wrapped in the encapsulation film in the top sealing area. This structure works together with the "colloidal rivets" to further improve the reliability of the encapsulation system. (4) The top sealing area, through the folded and compact top design, can save space in the height direction of the cell that is equivalent to the reduction in the width of the tab film. This space, after being filled with active material, helps to improve the volumetric energy density of the cell. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is the first structure for electrode strips.

[0032] Figure 2 for Figure 1 A magnified structural diagram of point A in the middle.

[0033] Figure 3 This is the second structure for electrode strips.

[0034] Figure 4 for Figure 3 A magnified structural diagram at point B in the middle.

[0035] Figure 5 This is the third type of structure for electrode strips.

[0036] Figure 6 for Figure 5 A magnified structural diagram at point C.

[0037] Figure 7 This is the fourth structure of electrode strip.

[0038] Figure 8 for Figure 7 A magnified structural diagram at point D.

[0039] Figure 9 This is the fifth structure for electrode strips.

[0040] Figure 10 for Figure 9 A magnified structural diagram at point E in the middle.

[0041] Figure 11 This is the first structure for positive and negative electrodes.

[0042] Figure 12 This is the second structure for positive and negative electrodes.

[0043] Figure 13 It is a structure for the main body of the battery cell.

[0044] Figure 14 This is a schematic diagram showing the placement of the tab film during tab integration.

[0045] Figure 15 This is a schematic diagram of a stepped hot-pressed head.

[0046] Figure 16 for Figure 15 Sectional view of AA.

[0047] Figure 17 A structural comparison between existing pouch batteries and the pouch battery of this invention. Figure 1 .

[0048] Figure 18 A structural comparison between existing pouch batteries and the pouch battery of this invention. Figure 2 .

[0049] Among them, 1. Electrode strip; 11. Blank area; 12. Micropore array; 13. Material area; 2. Electrode I; 21. Electrode tab I; 22. Material area I; 3. Electrode II; 31. Electrode tab II; 32. Material area II; 4. Electrode III; 41. Electrode tab III; 42. Material area III; 5. Electrode IV; 51. Electrode tab IV; 52. Material area IV; 6. Battery cell body; 61. Top sealing tab adhesive area; 62. Encapsulation film; 63. Top sealing flat sealing area; 6'. Original battery cell body; 6'1. Original top sealing area; 6'2. Original encapsulation film; 7. Battery cell tab one; 8. Battery cell tab two; 9. Tab film; 9'. Original tab adhesive; 10. Stepped hot-pressed head; 101. Top sealing flat seal; 102. Tab adhesive groove. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0051] All chemical raw materials used in the following examples and comparative examples were commercially available, and all apparatuses and operations involved were conventional in the art. All testing methods involved were conventional in the art.

[0052] The positive electrode sheets involved in the following examples and comparative examples were prepared by dispersing lithium cobalt oxide, graphite, and PVDF in NMP at a mass ratio of 97.5:1.4:1.1 to form a positive electrode slurry, which was then coated onto both surfaces of an 11 μm thick aluminum foil and dried. The negative electrode sheets involved in the following examples and comparative examples were prepared by dispersing artificial silicon-containing graphite (10 wt% silicon content), conductive carbon, styrene-butadiene rubber, and sodium carboxymethyl cellulose in deionized water at a mass ratio of 97.5:0.4:1.2:0.9 to form a negative electrode slurry, which was then coated onto both surfaces of a 6 μm thick copper foil and dried. The electrolyte of the pouch lithium battery was a 1 M LiPF6 solution, and the solvent was a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) in a molar ratio of 1:1:1. The separator of the pouch lithium battery was a 9 μm thick ceramic separator.

[0053] Example 1

[0054] Prepare a pouch lithium battery according to the following steps. S1, Electrode Pre-fabrication The electrode strip 1 is pressed using a pressure roller with a micro-needle array of 0.3 mm diameter. A micro-hole array 12 is arranged in the blank area 11. The center-to-center distance A1 between two adjacent micro-hole structures is 1 mm along the length of the foil, and the center-to-center distance B1 between two adjacent micro-hole structures is 1 mm along the width of the foil. The rolled strip is as follows: Figure 1 and Figure 2 As shown: the width H2 of the material area is 102mm, the width H1 of the upper blank area is equal to the width H3 of the lower blank area and both are 15mm (0.15H2), and the center-to-center spacing of the micro-hole array 12 in both the length and width directions of the foil is 1mm; then, the electrode strip is cut in half along the center to obtain two strips with the material area and the blank area respectively. The blank area is then die-cut to obtain the following... Figure 11The electrode plates shown are: the left image shows electrode plate I2, which has tab I21 and material area I22; the right image shows electrode plate II3, which has tab II31 and material area II32. It should be noted that the positive electrode plate can be selected from... Figure 11 The negative electrode can also be selected from either the left or right image. Figure 11 (Any one of the left or right images in the middle, as long as the positive and negative electrode structures match), with tabs 8mm wide and 15mm high; S2, Cell Molding The electrode sheets obtained in the previous step are then processed into a multi-tab structure using a stacking process, and the tabs are aligned and stacked together to obtain the following: Figure 13 The battery cell body 6 shown; S3, Electrode Integration like Figure 14 As shown: First, the stacked same-pole tabs are positioned between the two tab films 9 and aligned with their center lines. The tab film 9 is 10mm long and 2.5mm wide (F2), with a 1mm margin on each side. This ensures that the tab film has enough material to fill the micropores and that the sides of the tab are sealed. The melt index of the tab film 9 at 230℃ / 2.16kg is 30g / 10min. Then, a two-stage pressure boosting method is used for hot-pressing composite to form a 1mm thick battery tab 7 and a 1mm thick battery tab 8. The specific operation of the two-stage pressure boosting method is as follows: First, pre-press at 0.3MPa for 2s to allow the tab film 9 to initially melt and expel interlayer air. Then, within 2s, the pressure is increased to 1.0MPa and held at 165℃ for 10s. S4, Overall Packaging The battery cell body 6 obtained in the previous step is placed into the perforation of the aluminum-plastic film. The width of the top sealing area of ​​the aluminum-plastic film is 0.3mm larger than the width of the tab film 9. The position of the battery cell body 6 is adjusted so that the upper edge of the tab film 9 extends 0.6mm beyond the top sealing boundary of the aluminum-plastic film. Then, a stepped hot-pressing head 10 is used to top seal and form a top sealing area with a width of 5mm (F1). Figure 15 and Figure 16As shown: The stepped hot-pressed head includes a top sealing flat seal 101 and two tab adhesive grooves 102 set on it corresponding to the positions of the two tab films. The depth of the top sealing flat seal 101 is 3mm (L2), the width D of the tab adhesive groove 102 is 3.3mm (that is, the width D of the tab adhesive groove 102 is 0.3mm larger than the width F2 of the tab film 9), the depth of the tab adhesive groove 102 is 2mm (L1), and the height K of the tab adhesive groove 102 is 0.3mm smaller than the thickness of the top sealing tab adhesive area 61. The top sealing area is divided into the top sealing tab adhesive area 61 and the top sealing flat seal area 63. The width of the top sealing flat seal area 63 is 3mm (F3). First, the top sealing area is folded 180° along the root of the top sealing tab adhesive area 61 towards the direction close to the battery cell body 6. Then, the tabs are folded 180° along the top of the top sealing tab adhesive area 61 away from the battery cell body 6 and extended out. Then, the side seal and bottom seal are applied. S5, Post-processing Injection, standing, and dissolution are all methods used to prepare the solution.

[0055] like Figure 17 and Figure 18 As shown in the prior art, when preparing the original cell body 6', the original tab adhesive 9' is 5mm wide, and its upper edge slightly exceeds the original encapsulation film 6'2 to ensure reliable sealing. When preparing the cell body 6 using the preparation method proposed in this invention, the width of the original top sealing area 6'1 is equal to the width of the current top sealing area, and a 2mm wide tab adhesive film can achieve the required peel force. Combined with the improvement of the encapsulation process, this invention saves a 3mm wide (marked as E) margin at the top of the cell body 6. If this margin is reused, theoretically the volumetric energy density of the cell can be increased by 3.5%.

[0056] Example 2

[0057] Compared with Example 1, the material of the tab film was adjusted, and its melt index at 230℃ / 2.16kg was adjusted from 30g / 10min to 5g / 10min, while the rest remained the same as in Example 1.

[0058] Example 3

[0059] Compared with Example 1, the material of the tab film was adjusted, and its melt index at 230℃ / 2.16kg was adjusted from 30g / 10min to 80g / 10min, while the rest remained the same as in Example 1.

[0060] Example 4

[0061] Compared with Example 1, the two-stage hot pressing process in step S3 was adjusted to be hot pressing under a constant static pressure of 0.3 MPa, while the rest remained the same as in Example 1.

[0062] Example 5

[0063] Compared with Example 1, the two-stage hot pressing process in step S3 was adjusted to be hot pressing under a constant static pressure of 1 MPa, while the rest remained the same as in Example 1.

[0064] Example 6

[0065] Compared with Example 1, the diameter of the micropore structure of the micropore array was adjusted from 0.3 mm to 0.2 mm, while the rest remained the same as in Example 1.

[0066] Example 7

[0067] Compared with Example 1, the diameter of the micropore structure of the micropore array was adjusted from 0.3 mm to 0.5 mm, while the rest remained the same as in Example 1.

[0068] Example 8

[0069] Compared with Example 1, the diameter of the micropore structure of the micropore array was adjusted from 0.3 mm to 0.1 mm, while the rest remained the same as in Example 1.

[0070] Example 9

[0071] Compared with Example 1, the diameter of the micropore structure of the micropore array was adjusted from 0.3 mm to 0.8 mm, while the rest remained the same as in Example 1.

[0072] Example 10

[0073] Compared with Example 1, the material of the tab film was adjusted, and its melt index at 230℃ / 2.16kg was adjusted from 30g / 10min to 15g / 10min, while the rest remained the same as in Example 1.

[0074] Example 11

[0075] Compared with Example 1, the material of the tab film was adjusted, and its melt index at 230℃ / 2.16kg was adjusted from 30g / 10min to 50g / 10min, while the rest remained the same as in Example 1.

[0076] Example 12

[0077] Compared with Example 1, the width of the tab film was adjusted from 3mm to 3.5mm, while the rest remained the same as in Example 1.

[0078] Example 13

[0079] Compared with Example 1, the width of the tab film was adjusted from 3mm to 2mm, while the rest remained the same as in Example 1.

[0080] Example 14

[0081] Compared with Example 1, in step S1, when the tab is prefabricated, the center-to-center distance A1 between two adjacent micropore structures in the length direction of the foil is 0.5 mm, and the center-to-center distance B1 between two adjacent micropore structures in the width direction of the foil is 1.5 mm. All other aspects are consistent with Example 1.

[0082] Example 15

[0083] Compared with Example 1, in step S1, when the tab is prefabricated, the center-to-center distance A1 between two adjacent micropore structures in the length direction of the foil is 1.5 mm, and the center-to-center distance B1 between two adjacent micropore structures in the width direction of the foil is 0.5 mm. All other aspects are consistent with Example 1.

[0084] Example 16

[0085] Compared with Example 1, in step S1, when the tab is prefabricated, the center-to-center distance A1 between two adjacent micropore structures in the length direction of the foil is 0.8 mm, and the center-to-center distance B1 between two adjacent micropore structures in the width direction of the foil is 1.2 mm. All other aspects are consistent with Example 1.

[0086] Example 17

[0087] Compared with Example 1, in step S1, when the tab is prefabricated, the center-to-center distance A1 between two adjacent micropore structures in the length direction of the foil is 1.2 mm, and the center-to-center distance B1 between two adjacent micropore structures in the width direction of the foil is 0.8 mm. All other aspects are consistent with Example 1.

[0088] Comparative Example 1 Compared with Example 1, the pressure roller in step S1 does not have a microneedle array, that is, no micropore array is set on the tab, and only rolling is performed; the tab film in step S2 is of conventional width (5mm), and after multiple layers of tabs are stacked, they are directly laminated with the tab film and the encapsulation film under constant static pressure of 0.6MPa and 160℃, and no folding operation is performed after encapsulation; the rest is consistent with Example 1.

[0089] The gel filling rate, tab peel force, tab contact resistance, glue overflow level, and capacity of the batteries obtained in each embodiment and comparative example were tested. The glue overflow level was divided into four grades: Grade 1 indicates slight glue overflow, Grade 2 indicates moderate glue overflow, Grade 3 indicates severe glue overflow, and Grade 4 indicates failed glue overflow. The important technical parameters and test results of each embodiment and comparative example are shown in Table 1.

[0090]

[0091] As shown in Table 1 and Figures 1-18 As shown in the following: A comparison of the test results of Examples 1-17 and Comparative Example 1 shows that when the battery tabs proposed in this invention are used for lithium-ion pouch battery packaging, their capacity can be increased from 5400mAh to 5560-5595mAh, representing a capacity increase of 3.0%-3.6%. Furthermore, the packaging yield is high, and less tab film is used. As shown in Examples 1, 12, and 13, using tab films with a width of 2-3.5mm can yield pouch batteries with larger capacities without affecting packaging performance, thus contributing to improved energy density of pouch batteries.

[0092] A comparison of the test results from Examples 1, 14, 15, 16, and 17 shows that when the center spacing A1 and center spacing B1 of the micropore structures in the micropore array each meet the requirement of 0.5-1.5 mm, the number and distribution of micropore structures on the battery tabs are reasonable. This ensures the effectiveness of the riveting structure, making the connection between the tab layers uniform, reliable, and stable, without adversely affecting the integrity and stability of the foil structure. At this time, the contact resistance between the tabs is small, and the conductivity and mechanical strength are good, which can significantly improve the battery capacity when used for battery packaging. The effect is even better when the center spacing A1 and center spacing B1 of the micropore structures in the micropore array each meet the requirement of 0.8-1.2 mm, and the effect is best when both A1 and B1 are 1 mm.

[0093] Furthermore, based on the microporous structure meeting the center-to-center spacing A1 and B1 required by this invention, the maximum span L of the microporous structure (i.e., the diameter for a circular microporous structure) significantly affects the encapsulation effect. A comparison of the test results from Examples 1, 6, 7, 8, and 9 shows that when the diameter of the circular microporous structure is 0.2-0.5 mm, the resulting battery tabs not only help improve the capacity of the soft-pack battery, but also exhibit strong interlayer peeling force, low contact resistance between tabs, and good conductivity. When the diameter increases to 0.8 mm, adhesive overflow becomes relatively obvious, which is detrimental to capacity improvement. While reducing the diameter to 0.1 mm helps improve capacity, the filler rate of the tab adhesive decreases significantly, and the contact resistance between tabs increases significantly, resulting in poor conductivity. In summary, a maximum span of 0.1-0.8 mm for the microporous structure meets the usage requirements, with 0.2-0.5 mm showing particularly good results, and 0.3 mm being the best.

[0094] Furthermore, besides the structural parameters of the microporous array, the melt index of the tab film has a significant impact on the performance of the "colloidal rivet". As shown in the comparison of test results from Examples 1, 2, 3, 10, and 11, when the melt index M of the tab film at 230℃ / 2.16kg is 15-50g / 10min, the tab film can melt and fully fill the micropores, forming a "colloidal rivet" that penetrates the tab and has good three-dimensional mechanical interlocking performance after cooling and solidification. However, when M is below 15g / 10min, as in Example 2, incomplete filling occurs; when M is above 50g / 10min, as in Example 3, excessive flow of the tab film causes overflow. Further, this invention unexpectedly discovered that the product of the melt index M of the tab adhesive and the maximum span L of the microporous structure has certain guiding significance for improving the filling effect of the tab film. When L and M satisfy 6≤LM≤15, the filling effect of the tab film is better, the filling rate of the tab adhesive is relatively high, and there is no serious overflow, which helps to improve the packaging qualification rate.

[0095] In addition, this invention found that the two-stage pressure boosting method proposed in this invention is more effective when integrating tabs. As shown in the test results of Examples 1, 4, and 5: In existing transverse hydrostatic hot pressing, if the pressure is too low, the filling rate of the tab adhesive will be too small, the peel force between tab layers will be small, and the contact resistance between tabs will be large, which is not conducive to capacity improvement; if the pressure is too high, although it helps to improve the filling rate of the tab adhesive and improve the peel force between tab layers and the contact resistance between tabs, it will produce adhesive overflow; however, after adjusting to the two-stage pressure boosting method, the molten tab adhesive can overcome the flow resistance under the limited pressure and temperature, completely flow into and fill each microporous structure, and form "colloidal rivets" that penetrate multiple layers of tabs after cooling and solidification. This not only helps to build a robust integrated tab, but also improves capacity, taking into account both good encapsulation performance and improved energy density.

[0096] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

Claims

1. A tab based on a micro-riveting structure, comprising a connecting piece and tab adhesive, wherein the connecting piece and the foil are an integral structure, characterized in that: The connecting piece is provided with a micron-scale micropore array, and the tab adhesive includes two tab sheets, which respectively cover both sides of the connecting piece in the thickness direction and are connected through the micropore array after hot pressing; the micropore array is specifically composed of a number of micropore structures arranged in an array, and the maximum span L of the micropore structure satisfies: 0.1mm≤L≤0.8mm; in the length direction of the foil, the center distance A1 between two adjacent micropore structures satisfies: 0.5mm≤A1≤1.5mm, and in the width direction of the foil, the center distance B1 between two adjacent micropore structures satisfies: 0.5mm≤B1≤1.5mm.

2. The electrode lug based on the micro-riveting structure according to claim 1, characterized in that: The melt index of the electrode film at 230℃ / 2.16kg is 15-50g / 10min. The melt index is denoted as M, and L and M satisfy 6≤LM≤15.

3. The electrode lug based on the micro-riveting structure according to claim 1, characterized in that: The shape of the microporous structure is selected from one or more of the following: circular, elliptical, fan-shaped, triangular, rectangular, trapezoidal, pentagonal, hexagonal, cross-shaped, I-shaped, rice-shaped, and irregular.

4. The electrode lug based on the micro-riveting structure according to claim 1, characterized in that: The bottom of the micropore array is at least 0.5 mm away from the foil material region; Preferably, 0.2mm≤L≤0.5mm, 0.8mm≤A1≤1.2mm, and 0.8mm≤B1≤1.2mm; Preferably, L is 0.3 mm, A1 is 1 mm, and B1 is 1 mm.

5. A pouch cell containing tabs based on a micro-riveting structure as described in any one of claims 1-4.

6. A method for preparing a pouch cell as described in claim 5, characterized in that: S1, Electrode Pre-fabrication Two blank areas are symmetrically arranged on both sides of the electrode material area. When the electrode is rolled, a pressure roller with a micro needle array is used to press the two blank areas simultaneously, and then the micro hole array is arranged on them. Then, the electrode material area is cut in half along the center to obtain two strips with the material area and the blank area respectively. The blank area is die-cut to obtain an electrode with tabs. S2, Cell Molding The electrode sheets obtained in the previous step are processed by stacking or winding to form a multi-tab structure and stacked with the same electrode tabs to form the main body of the battery cell. S3, Electrode Integration First, position the stacked same-pole tabs between the two tab films and align them with their center lines, then hot-press them together to form the cell tabs; S4, Overall Packaging Place the battery cell body obtained in the previous step into the punched pit of the aluminum-plastic film. The width of the top sealing area of ​​the aluminum-plastic film is greater than the width of the tab film. Adjust the position of the battery cell body so that the upper edge of the tab film extends beyond the top sealing boundary of the aluminum-plastic film by 0.2-1.0mm. Then, perform top sealing to form the top sealing area. The top sealing area is divided into the top sealing tab area and the top sealing flat area. First, fold the top sealing area 180° towards the battery cell body along the root of the top sealing tab area. Then, fold the tab 180° away from the battery cell body along the top of the top sealing tab area and extend it out. S5, Post-processing.

7. The method for preparing a soft-pack battery according to claim 6, characterized in that: In step S1, the width of the material area is denoted as H2, and the widths of the upper and lower blank areas are denoted as H1 and H3, respectively. H1, H2, and H3 satisfy: H1=H3, 0.03H2≤H1≤0.3H2.

8. The method for preparing a soft-pack battery according to claim 6, characterized in that: In step S1, the diameter of the microneedles in the microneedle array is 0.1-0.8 mm, and the working pressure of the pressure roller is 0.3-10 MPa; Preferably, the diameter of the microneedles is 0.2-0.5 mm, and the working pressure of the pressure roller is 1-5 MPa; Preferably, the average pore density of the micropore array is 50-200 pores / cm². 2 The area of ​​the micro-pore array occupies 5%-15% of the area of ​​the blank area.

9. The method for preparing a soft-pack battery according to claim 6, characterized in that: In step S3, a two-stage pressure increase method is used during hot pressing: first, pre-press at 0.3MPa for 2s to allow the tab film to initially melt and expel interlayer air; then, increase the pressure to 1.0MPa within 2s and hold at 150-180℃ for 10s.

10. The method for preparing a soft-pack battery according to claim 6, characterized in that: In step S4, a stepped hot-pressed head is used for top sealing. The stepped hot-pressed head includes a top sealing flat seal (101), and two tab grooves (102) are provided on the top sealing flat seal (101) corresponding to the two tab films. Preferably, the width D of the tab adhesive groove (102) is 0.1-0.5 mm larger than the width F2 of the tab adhesive sheet, and the height K of the tab adhesive groove (102) is 0.1-0.5 mm smaller than the thickness of the top sealing tab adhesive area; Preferably, the width of the top sealing area is denoted as F1, the width of the tab film is denoted as F2, the width of the top sealing flat sealing area is denoted as F3, the depth of the top sealing flat sealing (101) is denoted as L2, and the depth of the tab adhesive groove (102) is denoted as L1. Then L2=F3, L1+L2=F2+F3; Preferably, the thickness of the battery cell tab in step S3 is 0.05-0.2 mm, and the sum of the thicknesses of F2 and the battery cell tab is equal to that of F3.

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