Pouch-type lithium ion battery

Abstract

The utility model relates to the field of lithium ion battery preparation discloses a kind of soft package lithium ion batteries, including aluminium plastic film shell, electrode assembly and electrolyte packaged in the shell, and the metal tab that is led out from the packaging edge of the shell, the metal tab is compounded with tab rubber, and the tab rubber includes: the inside portion sealed in the inside of the shell, the width of the inside portion is greater than the width of the metal tab, the outside portion exposed to the outside of the shell, the width of the outside portion exceeds the metal tab profile on any side is delta, wherein 0mm < delta <=0.3mm.The technical scheme is by optimizing tab rubber structure, under the premise of not affecting sealing and safety, significantly shorten the necessary length of tab extension, to increase the size of battery cell body, effectively improve battery energy density.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery technology, specifically to a soft-pack lithium-ion battery. Background Technology

[0002] Soft-pack lithium-ion batteries use an aluminum-plastic film as the encapsulation shell. For example... Figure 1 , 2 As shown, the dotted line represents the inner part of the tab adhesive sealed within the heat-sealed edge at the top width end. In traditional designs, to ensure sealing reliability and prevent short circuits caused by the tab contacting the aluminum layer of the aluminum-plastic film after bending, the width of the tab adhesive laminated onto the tab needs to be significantly greater than the tab width. This results in the tab adhesive protruding from the tab on both the inner and outer sides of the battery after encapsulation.

[0003] During the research process of this invention, the inventors discovered that the above-mentioned design of the prior art has the following drawbacks: For safety reasons, in order to prevent the overly protruding tab adhesive from touching the aluminum-plastic film during bending, the length of the tab extending beyond the aluminum-plastic film shell (L_extension_old) must be designed to be relatively long to provide a safe bending area. This results in a large proportion of the ineffective "tab extension length" in the total length (L_total) of the battery in the tab lead-out direction, which correspondingly compresses the effective length (L_cell_old) of the cell body (104) and limits the improvement of battery energy density. Summary of the Invention

[0004] One of the objectives of this utility model embodiment is to provide a soft-pack lithium-ion battery. This technical solution optimizes the tab adhesive structure, significantly shortens the necessary extension length of the tab without affecting sealing and safety, thereby increasing the cell body size and effectively improving the battery energy density.

[0005] In a first aspect, this utility model provides a soft-pack lithium-ion battery, including an aluminum-plastic film shell, an electrode assembly and an electrolyte encapsulated within the shell, and metal tabs extending from the encapsulation edge of the shell, wherein the metal tabs are coated with tab adhesive. The tab adhesive includes: An inner portion sealed inside the housing, the width of which is greater than the width of the metal tab. The outer portion exposed outside the housing is narrower than the inner portion, and the width of the outer portion extending beyond the outline of the metal tab on either side is δ, where 0 mm < δ ≤ 0.3 mm; The length of the metal tab extending outside the outer shell is less than or equal to 6.0 mm.

[0006] Optionally, the length of the metal tab extending beyond the outer shell is 2mm to 5mm.

[0007] Optionally, the δ satisfies: 0mm < δ ≤ 0.15mm.

[0008] Optionally, the tab adhesive of the outer portion is trimmed by laser cutting or stamping to such that the width of the outer portion extending beyond the outline of the metal tab on either side is δ.

[0009] As can be seen from the above, compared with the prior art, the application of the present utility model has the following significant advantages: This embodiment, through structural innovation, allows the space saved to be directly converted into the effective length of the cell body without changing the overall size of the battery, thereby increasing the loading of electrode active materials and significantly improving the volumetric energy density and gravimetric energy density of the battery.

[0010] In this embodiment, the inner portion of the tab adhesive extends beyond the metal tab on both sides, with the same protrusion width as in the prior art, ensuring the reliability of the core sealing area. The protrusion width δ of the outer portion of the tab adhesive relative to either side of the metal tab is controlled within a very small range (δ≤0.3mm), fundamentally eliminating the risk of short circuit when the metal tab contacts the aluminum layer of the aluminum-plastic film during bending, thus ensuring the safety and sealing of the battery.

[0011] This invention breaks through the traditional mindset that "the tab adhesive must be fully open throughout the entire process" and creates a new structure with "differentiated functions between the inner and outer parts of the tab adhesive". By solving specific short-circuit risk problems, it achieves unexpected technical effects such as saving space and increasing energy density.

[0012] The solution in this embodiment does not require changes to the existing core materials and main processes. It only requires optimization of the tab rubber stamping mold and the addition of a precision cutting process (such as laser cutting). The cost increase is minimal and it is easy to promote and implement. Attached Figure Description

[0013] The accompanying drawings, which are provided to further illustrate the present invention and form part of this application, do not constitute an undue limitation of the present invention.

[0014] Figure 1 This is a schematic diagram of the structure of a current-technology pouch lithium-ion battery. Figure 2 This is a three-dimensional structural diagram of a prior art soft-pack lithium-ion battery; Figure 3 A schematic diagram of the tab structure of a soft-pack lithium-ion battery provided in an embodiment of this utility model; Figure 4 A three-dimensional structural diagram of a soft-pack lithium-ion battery provided in an embodiment of this utility model; Figure 5 for Figure 1 , Figure 3 The diagram shows a top view of the soft-pack lithium-ion battery.

[0015] Figure label: 1. Aluminum-plastic film outer shell; 2. Metal tabs; 31: The inner part of the tab adhesive; 32: The outer part of the tab adhesive; 41: Heat-sealed edge at the top width end; 42: Heat-sealed edge along the length direction. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0017] Examples of embodiments of the present invention are shown in the accompanying drawings in a detailed description below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0018] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that terms such as "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0019] Furthermore, the terms "" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0020] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0021] See Figure 3 , 4 As shown in Figure 5.

[0022] in, Figure 3 The dotted line portion represents the inner portion 31 of the tab adhesive sealed within the heat-sealed edge 41 at the top width end.

[0023] This embodiment provides a soft-pack lithium-ion battery with improved energy density through optimized tab structure, including an aluminum-plastic film shell 1, an electrode assembly (not shown in the figure, but may be, but is not limited to, a wound cell or a stacked cell, as can be, but is not limited to, existing technology implementations) and an electrolyte (not shown in the figure, but may be a liquid electrolyte or a solid electrolyte, as can be, but is not limited to, existing technology implementations), and metal tabs 2 extending from the edge of the shell, with tab adhesive bonded to both the front and back of each metal tab 2.

[0024] In each metal tab 2, the tab adhesive includes: an inner portion 31 sealed inside the aluminum-plastic film housing 1 and an outer portion 32 exposed outside the aluminum-plastic film housing 1.

[0025] The width of the inner portion 31 is greater than the width of the metal tab 2 connected to the electrode sheet, and both sides of the inner portion 31 extend beyond the outline of the metal tab 2. The inner portion 31 and the upper and lower aluminum-plastic films facing each other form a sealing area, forming a heat-sealed edge around the battery cell body.

[0026] On each metal tab 2, the width of the outer portion 32 of the tab adhesive is narrower than the width of the inner portion 31 of the tab adhesive on the same metal tab 2, and the width of the outer portion 32 extending beyond the outline of the metal tab 2 on any side is δ, where 0mm < δ ≤ 0.3mm, so that the outer portion 32 of the tab adhesive on each metal tab 2 that is exposed outside the aluminum-plastic film shell 1 is almost the same as the width of the metal tab 2.

[0027] Furthermore, the length (L_extension_new) of the metal tab 2 extending outside the aluminum-plastic film shell 1 is less than or equal to 6.0 mm.

[0028] Compared to existing technologies, the core improvement of the soft-pack lithium-ion battery in this embodiment of the invention lies in the functional partitioning design of the tab adhesive on each metal tab 2: The width (W1) of the inner portion 31 of the tab adhesive is greater than the width (W) of the metal tab 2 on which it is located, and the distance by which its side extends beyond the tab outline is D (D>0.3mm, typically D is 0.5~1mm). During encapsulation, the inner portion 31 of the tab adhesive is heat-fused with the inner heat-sealing material of the aluminum-plastic film (specifically cast polypropylene, abbreviated as CPP) to form a main sealing area with sufficient width and strength, ensuring the long-term airtightness of the soft-pack lithium-ion battery at the tab protruding end.

[0029] The outer portion 32 of the tab adhesive can be narrowed, for example, but not limited to, by laser cutting or precision stamping, or it can be achieved by pre-forming narrowing. This ensures that on each metal tab 2, the outer portion 32 of the tab adhesive extends beyond the outline of the metal tab 2 by a certain width on either side, denoted as δ, where δ satisfies: 0mm < δ ≤ 0.3mm. Preferably, 0mm < δ ≤ 0.15mm.

[0030] Because the protrusion width δ of the outer portion 32 of the tab relative to the metal tab 2 is controlled within a very small range, the risk of short circuit due to contact with the aluminum-plastic film when the tab root is bent is fundamentally eliminated. Therefore, the necessary length L of the metal tab 2 extending outside the aluminum-plastic film shell 1 can be significantly shortened to about 6.0 mm or less. Preferably, it can be shortened to about 2 mm to 5.0 mm.

[0031] See Figure 1 ,and Figure 2 As shown, the two metal tabs 2 of the soft-pack lithium-ion battery extend from the same width end of the battery (referred to as the top width end). The bottom width end of the battery is the end of the lower aluminum-plastic film folded up to become the integrated aluminum-plastic film of the upper aluminum-plastic film. No heat sealing is required at the bottom end. Aluminum-plastic film heat sealing areas are formed on the two length edges of the soft-pack lithium-ion battery, forming heat sealing edges in the length direction of the soft-pack lithium-ion battery. The heat sealing edges in the two length directions and the heat sealing edge 41 at the top width end heat seal the cell body inside the aluminum-plastic film shell 1.

[0032] Among them, see Figure 5 As shown, the heat-sealed edges of the soft-pack lithium-ion battery are folded up on the sides formed by the thickness and length of the battery body.

[0033] For ease of description, the total external length of the battery is denoted as L_total, the heat-sealing width of the heat-sealing edge 41 at the top width end of the battery is denoted as B, and the thickness of the aluminum-plastic film at the bottom width end of the battery is negligible. Assuming the total external length of the battery (L_total) remains strictly constant: See Figure 1 It adopts a traditional design: L_total=L _cell_old+B+L_extension_old, Where L_extension_old ≥ 7.0 mm; See Figure 3 The design adopted in this embodiment is as follows: L_total=L_cell_new+B+L_extension_new, Where L_extension_new≤5.0mm.

[0034] Since the extension length of the metal tab 2 is successfully reduced (ΔL = L_extension_old - L_extension_new), the saved space ΔL is fully used to increase the length of the cell body, i.e., L_cell_new = L_cell_old + ΔL. Here, ΔL ranges from 0.2mm to 2mm. That is, under the premise that the total external length of the battery remains unchanged, using the technical solution of this embodiment, the electrode length (L_cell_new) of the electrode assembly is 0.2 to 2mm longer than the electrode length (L_cell_old) of a battery of the same external size using a traditional tab adhesive structure. The increase in the length of the cell body means that the effective length of the wound or stacked electrode sheets increases accordingly, thereby directly improving the battery's capacity and energy density.

[0035] This embodiment also provides a preparation scheme for the soft-pack lithium-ion battery with the above-described structure.

[0036] Step 1: Provide metal tabs 2 coated with tab adhesive, such as, but not limited to, attaching tab adhesive sheets to both the front and back surfaces of each metal tab 2. The width of the tab adhesive on each metal tab 2 is greater than the width of the metal tab 2 it is attached to.

[0037] Step 2: After connecting the metal tabs 2 to the electrode assembly, perform aluminum-plastic film heat sealing to form a heat-sealed edge. In this embodiment, the inner part 31 of the tab adhesive on each metal tab 2 is sealed within the heat-sealed edge.

[0038] Step 3: For each metal tab 2, process the tab adhesive (i.e., the outer part 32 of the tab adhesive) that extends out of the aluminum-plastic film shell 1, so that the width δ of the outer part 32 extending beyond the outline of the metal tab 2 on any side satisfies 0mm < δ ≤ 0.3mm.

[0039] In this step, the tab adhesive extending out of the aluminum-plastic film shell 1 can be processed by laser cutting or precision stamping to obtain the outer part 32 of the tab adhesive that meets the above requirements.

[0040] Other processes for soft-pack lithium-ion batteries can be implemented, but are not limited to, those described in the prior art.

[0041] The embodiment further illustrates a pouch lithium-ion battery for a smartphone.

[0042] Assume the total external length L_total = 100mm.

[0043] In the traditional design, the metal tab 2 extension length L_extension_old needs to be about 7.0mm, and the cell length L_cell_old is 93.0mm.

[0044] According to this utility model, the outer portion 32 of the tab adhesive is trimmed and narrowed, so that the outer portion 32 extends beyond the protruding width δ≈0.1mm of the metal tab 2 on each side. This allows the protruding length L_extension_new of the metal tab 2 in this embodiment to be safely shortened to 5mm, thereby allocating the saved 2.0mm space to the cell body, increasing the length L_cell_new of the cell body to 95.0mm. Compared to the traditional design, the length of the electrode sheet in this embodiment is increased by approximately 2.15%, and the measured battery capacity increases from 3000mAh to over 3060.5mAh, effectively improving the energy density. Furthermore, all safety tests (such as bending tests and drop tests) are passed.

[0045] As can be seen from the above, compared with the prior art, the application of the present utility model has the following significant advantages: This embodiment utilizes structural innovation to actively shorten the necessary extension length of the metal tab 2. Without changing the overall battery size, the saved space is directly converted into the effective length of the cell body, increasing the loading capacity of the electrode active materials and thus significantly improving the battery's volumetric energy density and gravimetric energy density.

[0046] In this embodiment, the inner portion 31 of the tab adhesive extends beyond the metal tab 2 on both sides, with the same protrusion width as in the prior art, ensuring the reliability of the core sealing area. The protrusion width δ of the outer portion 32 of the tab adhesive relative to either side of the metal tab 2 is controlled within a very small range (δ≤0.3mm), fundamentally eliminating the risk of short circuit when the metal tab 2 contacts the aluminum layer of the aluminum-plastic film during bending, thus ensuring the safety and sealing of the battery.

[0047] This invention breaks through the traditional mindset that "the tab adhesive must be wide throughout the entire process" and creates a new structure with "32 functional differences between the inner and outer parts of the tab adhesive". By solving specific short-circuit risk problems, it achieves unexpected technical effects such as saving space and increasing energy density.

[0048] The solution in this embodiment does not require changes to the existing core materials and main processes. It only requires optimization of the tab rubber stamping mold and the addition of a precision cutting process (such as laser cutting). The cost increase is minimal and it is easy to promote and implement.

[0049] To verify the technical effectiveness of this utility model, the applicant conducted a comparative experiment. The experimental design is as follows: Comparative Example (Traditional Structure): A traditional pouch lithium-ion battery was fabricated, in which the width of the tab adhesive on both the inner and outer sides of the battery is 0.8 mm wider than that of the metal tab 2. To ensure safety, the minimum extension length of the metal tab 2 is limited to 7.0 mm.

[0050] This utility model embodiment: A battery of this utility model is prepared under the completely identical cell chemical system, capacity design, aluminum-plastic film material, and external dimensions (length, width, and thickness). The inner portion 31 of the tab adhesive is 0.8 mm wider than the metal tab 2, and the outer portion 32, after laser trimming, has an extension δ = 0.1 mm on each side. The extension length of the metal tab 2 is designed to be 5.0 mm.

[0051] Table 1: Comparison of key parameters and test results between the comparative examples and the embodiments of this utility model: The outer edge of the ear glue exceeds the δ amount 0.8mm 0.1mm This utility model significantly reduces the amount of excess material on the outer side through structural innovation. tab extension length L 7.0mm 5.0mm Because the short-circuit risk is eliminated, the extension length of the electrode tab of this utility model is shortened by 2.0 mm (approximately 28.6%). Effective length of battery cell 93.0mm 95.0mm The 2.0mm space saved was used entirely to increase the length of the electrode plates, increasing the effective length of the cell by 2.15%. Nominal capacity (0.2C discharge) 3000mAh 3064.5mAh Due to the increased electrode area, the battery capacity increased by 64.5 mAh (approximately 2.15%), which is highly consistent with theoretical calculations. Energy density 265Wh / L 270.7Wh / L The volumetric energy density is increased by approximately 5.7 Wh / L, demonstrating a significant improvement. Electrode bending short circuit test 3 / 10 expired 0 / 10 failed Traditional designs risk short circuits due to repeated bending of the electrode tabs. However, this invention completely eliminates the short circuit phenomenon caused by bending because the outer electrode tab adhesive is almost flush with the electrode tab, thus significantly improving safety performance. Encapsulation sealing strength Qualified (≥8N / 15mm) Qualified (≥8N / 15mm) Both have comparable and compliant packaging strength. This demonstrates that while significantly improving other performance aspects, this invention fully maintains the original packaging reliability and sealing performance.

[0052] This embodiment demonstrates that the solution remains effective even when the tabs have reached their shortest possible length. By applying this invention, the effective cell length is successfully increased by 2.15% while safely shortening the tab extension length to 5.0mm, thereby significantly improving battery capacity and energy density. This proves the universality and effectiveness of this invention in batteries of different design specifications. The above experimental data fully demonstrates the outstanding substantive features and significant progress of this invention compared to traditional technologies: This invention achieves both performance improvement and safety assurance. Traditionally, safety (preventing short circuits) often comes at the cost of sacrificing space (longer metal tabs). This invention breaks this technological bias through a simple yet ingenious structural innovation: the "inner and outer differences" of the tab adhesive. It successfully and significantly improves battery energy density while simultaneously and substantially enhancing safety performance (reducing the short circuit rate from 30% to 0). This "win-win" result is unexpected and demonstrates a high degree of creativity.

[0053] Experimental data clearly show that the increase in energy density directly stems from the increase in electrode length, which in turn directly results from the reduction in the extension length of the metal tab. This reduction in the extension length of the metal tab is fundamentally due to the optimization of the outer structure of the tab adhesive. This complete and quantified chain of technical effects powerfully demonstrates the directness and inevitability between the technical means and effects of this invention, which cannot be easily obtained by those skilled in the art through conventional reasoning or simple experiments.

[0054] As can be seen from the above, this solution precisely resolves the spatial competition between "high energy density" and "high safety" at the metal tab, and solves a long-standing technical contradiction in the industry. It provides an effective and easy-to-implement solution for the urgent need to improve battery energy density in consumer electronics, new energy vehicles and other fields, and the technological progress is significant.

[0055] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A soft-pack lithium-ion battery, comprising an aluminum-plastic film casing, an electrode assembly and an electrolyte encapsulated within the casing, and metal tabs extending from the encapsulation edge of the casing, wherein the metal tabs are coated with tab adhesive, characterized in that: The tab adhesive includes: An inner portion sealed inside the housing, the width of which is greater than the width of the metal tab. The outer portion exposed outside the housing is narrower than the inner portion, and the width of the outer portion extending beyond the outline of the metal tab on either side is δ, where 0 mm < δ ≤ 0.3 mm.

2. The soft-pack lithium-ion battery according to claim 1, characterized in that: The length of the metal tab extending outside the outer shell is less than or equal to 6.0 mm.

3. The soft-pack lithium-ion battery according to claim 2, characterized in that: The metal tab extends 3mm to 5mm beyond the outer shell.

4. The soft-pack lithium-ion battery according to claim 1, characterized in that: The δ satisfies: 0mm < δ ≤ 0.15mm.

5. The soft-pack lithium-ion battery according to claim 1, characterized in that: The outer portion of the tab adhesive is trimmed by laser cutting or stamping to such that the width of the outer portion extending beyond the outline of the metal tab on any side is δ.

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