Head structure for top sealing of soft package battery and packaging method of soft package battery

Abstract

The present application belongs to the technical field of lithium ion batteries, and particularly relates to a head structure for top sealing of a soft package battery and a packaging method of a soft package battery. The head structure comprises an upper head and a lower head, and the upper head and the lower head are provided with a slotted structure at a position corresponding to the position where the tab is punched out. The slotted structure is provided with a slope transition surface on the side wall near the tab passing area, so that the tab glue in the tab slot without the support of the tab metal matrix is fused and bonded under the action of the slope transition surface during the heat sealing process. By providing the slope transition surface on the side wall of the tab slot, the pure tab glue area obtains uniform pressure conditions and glue flow guidance during the heat sealing process, which significantly improves the fusion state of the tab glue in this area and solves the problem of local insufficient sealing caused by the lack of metal matrix support in the traditional right-angle slotted structure.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a top sealing structure for a pouch battery and a pouch battery packaging method. Background Technology

[0002] Soft-pack lithium-ion batteries use aluminum-plastic composite film as the encapsulation material, which has advantages such as high energy density and flexible design, and is widely used in consumer electronics, power batteries, and energy storage. The aluminum-plastic film is typically composed of a nylon layer, an aluminum foil layer, and a polypropylene (PP) heat-sealing layer. The top-sealing process is one of the key steps in battery encapsulation. The opening edges of the aluminum-plastic film are heat-pressed together by upper and lower sealing heads to encapsulate the battery cell inside the film shell, while allowing the positive and negative electrode tabs to protrude from the top sealing edge. The reliability of the top seal directly affects the battery's leakage risk, insulation performance, and lifespan.

[0003] The top seal head typically has a slotted structure at the position where the electrode lugs protrude, to accommodate the electrode lugs and absorb positional tolerances in the width direction. Due to unavoidable positional fluctuations during electrode lug welding and assembly, the width of the electrode lug slot is generally larger than the actual width of the electrode lug metal substrate. This design results in an area within the electrode lug slot that, in addition to the area containing the electrode lug metal substrate, also contains a region with only electrode lug adhesive and no stainless steel or copper substrate support (i.e., a pure electrode lug adhesive area).

[0004] Existing technologies have implemented end cap structures that improve sealing performance by incorporating curved or beveled surfaces between the tab encapsulation groove and the tab adhesive encapsulation groove. For example, some solutions change the right-angle transition between the tab metal groove and the tab adhesive groove to a 45° bevel transition to reduce excessive pressure on the local PP layer; others incorporate inclined sections on the sidewalls of the tab groove to prevent wrinkles in the seal; still others use a ramp structure to optimize the stepped structure, addressing the difficulty of adhesive filling at the steps. However, existing improvements primarily focus on the transition between the tab metal substrate and the tab adhesive, with insufficient attention paid to the sealing performance of the pure tab adhesive area within the grooved region.

[0005] In the pure tab adhesive area, due to the absence of a metal substrate for support, the pressure and heat conditions of the material during heat sealing differ significantly from those in the area where the tab metal substrate is located. For thin aluminum-plastic film systems with single-layer thicknesses of 88μm, 91μm, 103μm, and 105μm, the overall thickness of the aluminum-plastic film is relatively thin, with the total thickness of two aluminum-plastic film layers being approximately 176μm to 210μm, and the total thickness of the upper and lower tab adhesive layers being approximately 200μm. In such thin systems, if the pure tab adhesive area fails to form a sufficient, continuous, and stable fusion bond, a potential leakage channel extending from the inside of the cell to the outside may form near the tab, posing a risk of leakage during subsequent liquid injection, settling, formation, or handling.

[0006] Therefore, how to improve the pressure and heat conditions of the pure tab adhesive area within the tab groove and enhance the sealing reliability of this area, while taking into account the absorption function of the tab position tolerance, has become a technical issue worthy of attention in the top sealing process of thin aluminum-plastic film soft-pack batteries. Summary of the Invention

[0007] The purpose of this invention is to provide a top sealing structure for soft-pack batteries and a packaging method for soft-pack batteries, thereby solving the technical problems existing in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a top sealing structure for a soft-pack battery, comprising an upper sealing head and a lower sealing head, wherein the upper sealing head and the lower sealing head are provided with a slotted structure at the corresponding tab protrusion position, and the slotted structure is provided with a sloping transition surface on the side wall near the tab passage area, so that during the heat sealing process, the tab adhesive located in the tab slot and in the area without tab metal substrate support is fused and bonded under the action of the sloping transition surface.

[0009] Preferably, the ramp transition surfaces are respectively disposed on opposite sides of the slotted structure.

[0010] Preferably, the upper end cap and the lower end cap are provided with the slope transition surface at the relative positions of the corresponding tab protrusion positions, so that when the upper end cap and the lower end cap are closed, they form a synergistic pressing and heat conduction effect on the area of ​​the tab groove without tab metal substrate support.

[0011] Preferably, the slope transition surface is a straight slope.

[0012] Preferably, the slope transition surface is a circular arc transition surface.

[0013] Preferably, the slope transition surface is a broken slope.

[0014] Preferably, the transverse width of the slope transition surface is 0.2 mm, and the transverse width does not change with the depth of the slotted structure.

[0015] Preferably, the width of the slotted structure is greater than the width of the tab metal substrate to absorb the positional tolerance of the tab in the width direction.

[0016] This invention also discloses a packaging method for a pouch battery, comprising the following steps: The battery cell to be packaged is placed between the upper and lower end caps, so that the tabs pass through the corresponding slotted areas on the upper and lower end caps. Controlling the closure of the upper and lower sealing heads to heat seal the aluminum-plastic film; During the heat sealing process, the sloping transition surface provided on the side wall of the slotted area allows the upper and lower layers of tab adhesive in the tabless metal substrate support area within the tab slot to melt, compress, and bond together to form a seal.

[0017] Preferably, the ramp transition surface is simultaneously provided at the tab slots of the upper end cap and the lower end cap, forming a coordinated pressing and heat conduction effect on the area without tab metal substrate support in the tab slot during the mold closing and heat sealing process, so that the upper and lower tab adhesives in this area are fully fused to form a continuous sealing strip.

[0018] The beneficial effects of this invention are as follows: By setting a sloping transition surface on the sidewall of the tab groove, this invention enables the pure tab adhesive area to obtain uniform pressure conditions and melt flow guidance during the heat sealing process, significantly improving the fusion state of the tab adhesive in this area and solving the problem of insufficient local sealing caused by the lack of metal substrate support in traditional right-angle groove structures. At the same time, fixing the lateral width of the sloping transition surface to 0.2mm matches well with the process allowance after the tab adhesive is compressed, achieving effective coverage and enhanced sealing of the pure tab adhesive area without increasing the overall size of the groove. The above improvements, while still needing to consider the tab position tolerance in the groove width, enable the non-metallic support area in the tab groove to still form a continuous and reliable sealing band, reducing the probability of forming potential leakage channels near the tab. It is especially suitable for thin aluminum-plastic film systems such as 88μm, 91μm, 103μm, and 105μm. Moreover, this structure does not change the overall functional logic of the end cap and can be directly implemented on existing top sealing equipment, possessing good engineering adaptability and promotional application value. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 for Figure 1 Enlarged image. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0021] like Figure 1 and Figure 2 As shown, the present invention provides a top sealing structure for a soft-pack battery, including an upper sealing head and a lower sealing head. Both the upper sealing head and the lower sealing head are provided with a slotted structure 1 at the position where the corresponding tabs protrude. The slotted structure is provided with a sloping transition surface 2 on the side wall near the area where the tabs pass through.

[0022] Example 1 This embodiment provides a double-sided top-sealed sloping grooved end cap for 88μm thin aluminum-plastic film soft-pack batteries and its encapsulation method.

[0023] like Figure 1 As shown, the end cap structure includes an upper end cap and a lower end cap, which are arranged correspondingly to each other, forming a closed heat-sealed space after mold closing. Both the upper and lower end caps have slotted structures 1 at the corresponding positions where the electrode lugs protrude. The width of the slotted structure 1 is greater than the width of the electrode lug metal substrate to absorb the lateral positional tolerances generated during welding and assembly. The slotted structure 1 has sloping transition surfaces 2 on its opposite side walls near the electrode lug passage area, such as... Figure 2 As shown. In this embodiment, the ramp transition surface 2 is a straight ramp with a fixed lateral width of 0.2 mm, which does not change with the depth of the slotted structure 1. The upper end cap 1 and the lower end cap 2 are both provided with ramp transition surfaces 2 at the relative positions of the corresponding tab protrusion positions, so that when the upper end cap 1 and the lower end cap 2 are closed, they form a synergistic pressing and heat conduction effect on the area without tab metal substrate support in the tab slot (i.e., the pure tab adhesive area).

[0024] In this embodiment, the pouch battery uses a single-layer aluminum-plastic film with a thickness of 88 μm, and the total thickness of the upper and lower aluminum-plastic films is 176 μm; the total thickness of the upper and lower tab adhesives is 200 μm; and the thickness of the tab metal substrate is 100 μm. The tab area needs to balance the remaining amount of tab adhesive compression and the thickness of the metal substrate. According to the encapsulation thickness standard, the encapsulation thickness at the non-tab location of the 88 μm aluminum-plastic film is 155 μm, and the encapsulation thickness at the tab location is 375 μm when using a 100 μm tab substrate.

[0025] During encapsulation, the battery cell to be encapsulated is placed between the upper and lower end caps, with the tabs passing through the corresponding slotted areas on the upper and lower end caps. The heat-sealing drive mechanism is controlled to close the upper and lower end caps at a set temperature, pressure, and time. In this embodiment, the heat-sealing temperature is 180℃~200℃, the heat-sealing pressure is 0.3MPa~0.7MPa, and the holding time is 2s~4s. During the heat-sealing process, the sloping transition surface 2 of the upper and lower end caps applies uniform pressure and heat to the pure tab adhesive area, causing the upper and lower layers of tab adhesive in this area to melt, be squeezed, and bond together to form a continuous sealing strip. Due to the presence of the sloping transition surface, the tab adhesive in the pure tab adhesive area obtains effective melt guidance during the heat-sealing process, avoiding the problem of insufficient local sealing caused by the lack of metal substrate support in the traditional 90° right-angle slotted structure. Tests showed that the 88μm thin aluminum-plastic film soft-pack battery encapsulated using the end cap structure of this embodiment had a significantly lower leakage rate near the tabs compared to the traditional 90° right-angle slotted end cap.

[0026] Example 2 This embodiment provides a double-sided top-sealed sloping grooved end cap for 103μm thin aluminum-plastic film soft-pack batteries and its encapsulation method.

[0027] The end cap structure in this embodiment is basically the same as that in Embodiment 1, the difference being the applicable aluminum-plastic film thickness. In this embodiment, the soft-pack battery uses a single-layer aluminum-plastic film with a thickness of 103μm, the total thickness of the upper and lower aluminum-plastic films is 206μm; the total thickness of the upper and lower tab adhesive layers is 200μm; and the thickness of the tab metal substrate is 100μm. According to the encapsulation thickness standard, the encapsulation thickness at the non-tab area of ​​the 103μm aluminum-plastic film is 185μm, and the encapsulation thickness at the tab area is 405μm when the tab substrate is 100μm.

[0028] The encapsulation process parameters are the same as in Example 1: heat sealing temperature is 180℃~200℃, heat sealing pressure is 0.3MPa~0.7MPa, and holding time is 2s~4s. During the heat sealing process, the sloping transition surfaces of the upper and lower end caps 2 create a synergistic compression and heat conduction effect on the pure tab adhesive area, allowing the upper and lower tab adhesives to fully fuse and form a continuous sealing band. Testing showed that the 103μm thin aluminum-plastic film soft-pack battery encapsulated using the end cap structure of this example exhibits significantly better sealing reliability near the tabs than the traditional 90° right-angle slotted structure.

[0029] Example 3 This embodiment provides a double-sided top-sealed sloping grooved end cap for 91μm thin aluminum-plastic film soft-pack batteries and its encapsulation method.

[0030] The end cap structure in this embodiment is basically the same as in Embodiment 1. The soft-pack battery uses a single-layer aluminum-plastic film with a thickness of 91 μm, and the total thickness of the upper and lower aluminum-plastic films is 182 μm; the total thickness of the upper and lower tab adhesives is 200 μm; and the thickness of the tab metal substrate is 100 μm. According to the encapsulation thickness standard, the encapsulation thickness at the non-tab area of ​​the 91 μm aluminum-plastic film is 165 μm, and the encapsulation thickness at the tab area is 385 μm when the tab substrate is 100 μm. The heat sealing temperature is 180℃~200℃, the heat sealing pressure is 0.3MPa~0.7MPa, and the holding time is 2s~4s. In this embodiment, the upper and lower tab adhesives in the pure tab adhesive area are fully fused through the sloped transition surface 2 to form a reliable seal.

[0031] Example 4 This embodiment provides a double-sided top-sealed sloping grooved end cap for 105μm thin aluminum-plastic film soft-pack batteries and its encapsulation method.

[0032] The end cap structure in this embodiment is basically the same as in Embodiment 1. The soft-pack battery uses a single-layer aluminum-plastic film with a thickness of 105μm, and the total thickness of the upper and lower aluminum-plastic films is 210μm; the total thickness of the upper and lower tab adhesive layers is 200μm; and the thickness of the tab metal substrate is 100μm. According to the encapsulation thickness standard, the encapsulation thickness at the non-tab area of ​​the 105μm aluminum-plastic film is 190μm, and the encapsulation thickness at the tab area is 410μm when the tab substrate is 100μm. The heat sealing temperature is 180℃~200℃, the heat sealing pressure is 0.3MPa~0.7MPa, and the holding time is 2s~4s. This embodiment also improves the sealing effect of the pure tab adhesive area through the sloped transition surface 2.

[0033] Example 5 The difference between this embodiment and Embodiment 1 is that the ramp transition surface 2 is a zigzag slope, which is formed by connecting two or more slopes with different angles in sequence. The zigzag slope can provide different melt guiding effects at different stages, further optimizing the melt flow state of the tab adhesive in the pure tab adhesive region. The rest of the structure is the same as in Embodiment 1, and the encapsulation method is the same as in Embodiment 1.

[0034] Example 6 The difference between this embodiment and Embodiment 1 is that the ramp transition surface 2 is a circular arc transition surface. The circular arc transition surface provides a smoother melt guide path, preventing stress concentration in the tab adhesive during the transition area. The remaining structure and encapsulation method are the same as in Embodiment 1.

[0035] Example 7 The difference between this embodiment and Embodiment 1 is that the ramp transition surface 2 is a combination of a straight ramp and a circular arc transition surface, that is, a circular arc transition surface is connected to the end of the straight ramp. The combined transition surface can take into account both the guiding efficiency of the straight ramp and the smoothness of the circular arc transition surface. The rest of the structure is the same as in Embodiment 1, and the packaging method is the same as in Embodiment 1.

[0036] Comparative Example This comparative example provides a traditional 90° right-angle slotted end cap structure and its encapsulation method for comparison with the embodiments of the present invention.

[0037] The comparative head structure includes an upper head and a lower head. Both the upper and lower heads have slotted structures at the corresponding positions where the electrode lugs protrude, but the sidewalls of the slotted structures are 90° right angles and do not have a sloped transition surface. The width of the slotted structure is also greater than the width of the electrode lug metal substrate to absorb the electrode lug position tolerance.

[0038] The same 88μm thin aluminum-plastic film pouch cell as in Example 1 was used for encapsulation, and the heat-sealing process parameters were the same as in Example 1. After encapsulation, in the pure tab adhesive area, due to the lack of metal substrate support and the 90° right-angle structure of the slotted sidewalls, there is a lack of geometric guiding structures to promote thermal fusion bonding, making it difficult for the upper and lower tab adhesive layers to form a sufficient, continuous, and stable fusion bond. This area is prone to forming potential leakage channels extending from the inside of the cell to the outside, posing a risk of leakage during subsequent liquid injection, settling, formation, or transportation. In thin aluminum-plastic film systems of 88μm, 91μm, 103μm, and 105μm, the above risks are more prominent due to the thinner overall thickness of the aluminum-plastic film.

[0039] In contrast, the embodiments of the present invention provide a sloping transition surface 2 within the tab groove, which enables the pure tab adhesive area to obtain effective pressure and heat conditions and melt guidance during the heat sealing process, significantly improving the sealing reliability of this area.

[0040] The head structure in the above embodiments can be machined using a CNC machining center. Specifically, the depth and width of the slotted structure 1 are determined based on the width of the tab metal substrate, the thickness of the tab adhesive, the thickness of the aluminum-plastic film, and the target encapsulation thickness. Then, a sloping transition surface 2 is machined on the side wall of the slotted structure 1 using a forming tool. The transverse width of the sloping transition surface 2 is fixed at 0.2 mm, and this dimension is achieved through tool path control and does not change with the slot depth. The upper head 1 and the lower head 2 can be made of mold steel, such as Cr12MoV or SKD11, and are precision machined after quenching to ensure the hardness and wear resistance of the head surface.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sealing head structure for top sealing of a pouch battery, characterized in that, It includes an upper end cap and a lower end cap. Both the upper end cap and the lower end cap have a slotted structure at the position where the corresponding electrode tabs protrude. The slotted structure has a sloping transition surface on the side wall near the area where the electrode tabs pass through, so that during the heat sealing process, the electrode tab adhesive located in the slot of the electrode tab and in the area without the support of the electrode tab metal substrate will be fused and bonded under the action of the sloping transition surface.

2. The head structure according to claim 1, characterized in that, The ramp transition surfaces are respectively located on opposite sides of the slotted structure.

3. The head structure according to claim 1, characterized in that, The upper end cap and the lower end cap are both provided with the sloped transition surface at the relative positions of the corresponding tab protrusion positions, so that when the upper end cap and the lower end cap are closed, they form a synergistic pressing and heat conduction effect on the area of ​​the tab groove without tab metal substrate support.

4. The head structure according to claim 1, characterized in that, The slope transition surface is a straight inclined plane.

5. The head structure according to claim 1, characterized in that, The slope transition surface is a circular arc transition surface.

6. The head structure according to claim 1, characterized in that, The slope transition surface is a broken slope.

7. The head structure according to claim 1, characterized in that, The transverse width of the slope transition surface is 0.2 mm, and the transverse width does not change with the depth of the slotted structure.

8. The head structure according to claim 1, characterized in that, The width of the slotted structure is greater than the width of the tab metal substrate to absorb the positional tolerance of the tab in the width direction.

9. A method for packaging a soft-pack battery, characterized in that, Includes the following steps: The battery cell to be packaged is placed between the upper and lower end caps, so that the tabs pass through the corresponding slotted areas on the upper and lower end caps. Controlling the closure of the upper and lower sealing heads to heat seal the aluminum-plastic film; During the heat sealing process, the sloping transition surface provided on the side wall of the slotted area allows the upper and lower layers of tab adhesive in the tabless metal substrate support area within the tab slot to melt, compress, and bond together to form a seal.

10. The packaging method according to claim 9, characterized in that, The sloping transition surface is simultaneously provided at the tab slots of the upper and lower end caps. During the mold closing and heat sealing process, it forms a coordinated pressing and heat conduction effect on the area without tab metal substrate support in the tab slot, so that the upper and lower tab adhesives in this area are fully fused to form a continuous sealing strip.

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