Pouch lithium ion battery and electronic product

Abstract

This utility model relates to the field of lithium-ion battery manufacturing and discloses a soft-pack lithium-ion battery and electronic product. The soft-pack lithium-ion battery includes: a cell body and an aluminum-plastic film shell for sealing the cell body. A plastic film heat-sealing strip is provided on the aluminum-plastic film shell. On the plastic film heat-sealing strip, the polypropylene layers on the surfaces of the bottom aluminum-plastic film and the top aluminum-plastic film are fused and sealed together. The plastic film heat-sealing strip seals the cell body in the cavity between the top and bottom aluminum-plastic films. Except for the ends where the tabs protrude, the inner and outer surfaces of the top and bottom aluminum-plastic films are exposed metal layers. The exposed metal layers are fused together metallurgically and, after cooling, form a sealed metal sealing strip located outside the plastic film heat-sealing strip layer.

Description

Technical Field

[0001] This utility model relates to the field of battery manufacturing, and in particular to a soft-pack lithium-ion battery and electronic products. Background Technology

[0002] See Figure 1 , 2 As shown, existing soft-pack lithium-ion batteries use an aluminum-plastic film polypropylene layer for hot-melt sealing. During the research process for this invention, the inventors discovered that the moisture permeability of polypropylene material is as high as 0.5-2 g·mm / (m²·day) (40℃ / 90%RH). In particular, in high-temperature and high-humidity scenarios such as electric vehicles and outdoor energy storage, moisture easily penetrates into the interior of the aluminum-plastic film casing, leading to: 1. The electrolyte decomposes to produce HF acid, which corrodes the electrode; 2. Gas bulges and increased internal pressure pose a safety hazard; 3. Battery capacity decay >20% (after storage at 85℃ for 500 hours). Summary of the Invention

[0003] One of the objectives of this utility model embodiment is to provide a soft-pack lithium-ion battery and electronic product. This technical solution is beneficial to improving the battery's sealing performance and sealing strength.

[0004] In a first aspect, this embodiment provides a soft-pack lithium-ion battery, comprising: a cell body and an aluminum-plastic film casing for sealing the cell body, wherein a plastic film heat-sealing tape is provided on the aluminum-plastic film casing. On the heat-sealing tape, the polypropylene layer on the surface of the bottom aluminum-plastic film and the top aluminum-plastic film are fused and sealed together. The heat-sealing tape seals the battery cell body in the cavity between the top and bottom aluminum-plastic films. Except for the end of the plastic film heat-sealing strip that protrudes from the electrode tab, the inner and outer surfaces of the top aluminum-plastic film and the bottom aluminum-plastic film are exposed metal layers. The exposed metal layers are fused together and metallurgically bonded. After cooling, they form a sealed metal sealing strip located outside the plastic film heat-sealing strip layer.

[0005] Optionally, the width of the metal sealing strip is greater than or equal to 0.2 mm and less than or equal to 5 mm. Preferably, the width of the metal sealing strip is greater than or equal to 0.1 mm and less than or equal to 0.5 mm.

[0006] Optionally, the metal sealing strip is formed by laser welding.

[0007] Optionally, only the heat-sealing strip of the plastic film is provided at the protruding end of the tab. The tab adhesive pre-applied to the front and back of each tab is fused to the polypropylene layer on the opposite inner surface of the bottom aluminum-plastic film and the top aluminum-plastic film. After cooling, the tab section located in the heat-sealing strip of the plastic film is sealed and bonded between the heat-sealing strips of the plastic film.

[0008] Optionally, the two tabs extend from the first width end of the aluminum-plastic film housing, and the top layer of aluminum-plastic film is formed by folding up from the second width end of the aluminum-plastic film housing.

[0009] Optionally, the plastic film heat-sealing strip and the metal sealing strip are respectively provided on the two length sides of the aluminum-plastic film housing from the inside to the outside.

[0010] Optionally, the heat-sealing strips of the plastic film located on the two length sides of the two aluminum-plastic film shells are folded up along their length edges to the outer surface of the length edge of the aluminum-plastic film shell.

[0011] Optionally, the interfacial bonding strength of the metallurgical bonding structure of the metal sealing strip is greater than or equal to 5 MPa, and the metal interfusion depth is 20~50 μm.

[0012] Optionally, the width of the heat-sealing tape is greater than or equal to 2 mm and less than or equal to 3 mm.

[0013] Secondly, an embodiment of this utility model provides an electronic product in which the power supply battery is an electrode electrical connection of any of the soft-pack lithium-ion batteries described above.

[0014] As can be seen from the above, by adopting the technical solution of this embodiment and adding two metal sealing strips to the outside of the plastic film hot air layer on both length sides, the water vapor permeability can be reduced from 3.85×10⁻² g / (m²·h) to 3.0×10⁻ 5 g / (m²·h) demonstrates the effectiveness of the water vapor barrier in this embodiment, and shows that it meets the USABC 2025 target for power batteries (<1×10⁻⁻⁶). 4 g / (m²·h)).

[0015] Furthermore, the solution described in this embodiment significantly slows down the degradation of lithium-ion batteries and extends their lifespan. It is worth noting that in the field of lithium-ion batteries, a 500-hour test at 85°C / 85%RH is equivalent to 10 years of use at room temperature (25°C / 60%RH). Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the present invention and form part of this application, do not constitute an undue limitation of the present invention.

[0017] Figure 1 This is a schematic diagram of the structure of the top aluminum-plastic film and the bottom aluminum-plastic film before they are bonded together in the prior art. Figure 2 This is a schematic diagram of the cross-sectional structure of the heat-sealing tape of the plastic film after the top and bottom aluminum-plastic films are laminated in the aluminum-plastic film shell of the prior art; Figure 3 A schematic diagram of the cross-sectional structure of the top aluminum-plastic film, the bottom aluminum-plastic film after lamination, and the heat-sealing strip and metal sealing strip in the aluminum-plastic film shell provided in this embodiment of the utility model. Figure 4 A schematic diagram of the structure of a soft-pack lithium-ion battery provided in an embodiment of this utility model; Figure 5 for Figure 4 An enlarged structural diagram of part a in the diagram; 1: Aluminum-plastic film casing; 11: Top layer aluminum-plastic film; 12: Bottom layer aluminum-plastic film; 41: Polypropylene layer; 42: Metal layer; 43: Nylon layer; 2: Plastic film heat sealing tape; 3: Metal sealing tape; 5: Electrode; 6: Cavity; 7: Electrode adhesive. Detailed Implementation

[0018] 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.

[0019] Examples of embodiments of the present invention described in detail below are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0020] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, but should not be construed as limiting the invention. In the description of the 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 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 invention.

[0021] Furthermore, the terms "first" 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 as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," 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 invention according to the specific circumstances.

[0023] See Figure 3-5 .

[0024] This embodiment provides a suitable soft-pack lithium-ion battery, which includes a cell body and an aluminum-plastic film casing 1.

[0025] The battery cell consists of a positive electrode, a negative electrode, a separator, and an electrolyte. External tabs 5 are welded onto the positive and negative electrodes to serve as external electrodes. A separator separates each positive and negative electrode. The positive electrode includes an aluminum foil current collector and positive polar active material layers coated on both sides of the aluminum foil current collector. The positive polar active material can be, but is not limited to, lithium iron phosphate, ternary materials, etc. The negative electrode includes a copper foil current collector and negative polar active material layers coated on both sides of the copper foil current collector. The negative polar active material can be, but is not limited to, graphite, silicon carbide, etc.

[0026] On the front and back sides of the tabs 5 located between the heat-sealing strips 2 of the plastic film, tab adhesive 7 is applied to the two tabs 5 of the main body of the battery cell. The tab adhesive 7 fixes the two tabs 5 to prevent displacement and short circuit, and provides electrical insulation (withstand voltage ≥1000V) for the positive and negative tabs. Before entering the aluminum-plastic film shell 1, the welding section is pre-wrapped to prevent welding burrs from piercing the aluminum-plastic film and affecting the sealing reliability of the aluminum-plastic film shell 1. Furthermore, during the heat sealing of the aluminum-plastic film, the two layers of tab adhesive 7 melt and flow under hot pressure to fill the micro gaps between the aluminum-plastic film and the tab section on the top and bottom surfaces. The tab adhesive 7 melts and fully bonds together with the aluminum-plastic film on the bottom and top surfaces. After cooling, the middle section of the tab is sealed and bonded to the heat-sealing strip 2 at this end.

[0027] In this embodiment, the aluminum-plastic film housing 1 is made of aluminum-plastic film, which has a three-layer structure: a polypropylene layer 41, a metal layer 42, and a nylon layer 43. The surface of the polypropylene layer 41 of the aluminum-plastic film is stamped, stretching the film to form a cavity 6 lower than its surface. The shape of the cavity 6 is consistent with that of the battery cell body. The aluminum-plastic film outside the cavity 6 is a flat aluminum-plastic film, and the surface of the opening of the cavity 6 is the surface of the polypropylene layer 41. During packaging, the battery cell body is placed into the cavity 6, and the tabs 5 of the battery cell body are located on the flat aluminum-plastic film outside the wide end of the cavity 6.

[0028] The aluminum-plastic film containing cavity 6 is the bottom layer aluminum-plastic film 12, and the top layer aluminum-plastic film 11 covers the top surface of the bottom layer aluminum-plastic film 12, covering the opening of cavity 6. The main body of the battery cell is located between the bottom layer aluminum-plastic film and the top layer aluminum-plastic film 11. The two layers of aluminum-plastic film outside cavity 6 are attached to each other, and the polypropylene layer 41 of the two layers of aluminum-plastic film are opposite each other, serving as the inner surface of the aluminum-plastic film shell.

[0029] A side-sealing machine is used to heat-seal the two length sides of the cavity 6 under certain pressure. This causes the polypropylene layers 41 on the opposing inner surfaces of the bottom and top aluminum-plastic films 11 to melt and bond together under pressure and heat. After cooling, they are sealed together to form a plastic film heat-sealing strip 2. Two lateral plastic film heat-sealing strips 2 are formed on each of the two length sides. The battery cell body inside the cavity 6 is located between the two lateral plastic film heat-sealing strips 2. The heat-sealing conditions are 180℃ / 3MPa / 10s.

[0030] A top-sealing machine is used to heat-seal the aluminum-plastic film extending from the wide end of the cavity 6 where the tabs 5 protrude. Under the action of heat and pressure, the tab adhesive 7 on the front and back sides of each tab 5 is fully heat-melted and sealed together with the adhesive layers on the opposing surfaces of the bottom and top layers. After cooling, they form a single unit, creating the end heat-sealing plastic film strip 2. Each tab 5 is sealed and bonded within the end heat-sealing plastic film strip 2, preventing displacement. The end heat-sealing plastic film strip 2 and the two side heat-sealing plastic film strips seal the battery cell body within the cavity 6.

[0031] The heat-sealing strips 2 on both sides and the heat-sealing strips 2 at the ends seal the battery cell body inside the cavity 6 of the aluminum-plastic film.

[0032] In this embodiment, both the top aluminum-plastic film 11 and the bottom aluminum-plastic film located outside the heat-sealing strips 2 on both sides are exposed structures of the intermediate metal layer 42. Both surfaces of the exposed metal layer 42 have the polypropylene layer 41 and the nylon layer 43 completely removed, resulting in smooth metal surfaces. A laser energy beam can be used to irradiate the exposed structures of the adjacent metal layers 42, causing the two adjacent exposed metal layers to melt and fuse together metallurgically, forming a sealed metal sealing strip 3 after cooling. Thus, the inner layer of the lateral heat-sealing strip 2 and the outer layer of the metal sealing strip 3 are formed on both length sides of the aluminum-plastic film shell 1.

[0033] As an illustration of this embodiment, the exposed structure of the outermost metal layer 42 on both sides of the two aluminum-plastic films can be obtained by mechanically or by laser peeling off the polypropylene layer 41 and nylon layer 43 on the front and back sides of the two aluminum-plastic films facing outwards from the heat-sealing strip 2.

[0034] As an illustration of this embodiment, the width of the exposed structure of the metal layer 42 located on both sides outside the heat-sealing strip 2 is 0.2mm~5mm, preferably 0.1~0.5mm, and more preferably 0.3±0.05mm. This technical solution is beneficial to save material costs, reduce space occupation, and improve the volumetric energy density of the battery while ensuring the battery's sealing performance and sealing strength.

[0035] As an illustration of this embodiment, the metal sealing strip 3 can be formed in any of the following ways, but is not limited to: Laser melting; Alternatively, ultrasonic welding (frequency 20~40kHz, amplitude 10~50μm). Alternatively, high-frequency induction heating (frequency 100~500kHz). As an illustration of this embodiment, a laser wavelength of 1064~1080nm and a power density of 1×10 are preferably used. 4 ~5×10 4 An energy beam of W / cm² irradiates the exposed structure of the adjacent metal layer 42. Using this parameter window, the aluminum layer (or aluminum alloy layer, melting point 660℃) can be melted. After cooling, the interfacial bonding strength of the metal sealing strip 3 formed is ≥15MPa, the metal interfusion depth is 20~50μm, preferably >30μm, and the oxygen content is <1 at%. It can be seen that compared with the interfacial bonding strength (5~8 MPa) of the plastic film heat-sealing strip 2 formed by melting the traditional polypropylene layer 41, the soft-pack lithium-ion battery of this embodiment has stronger sealing performance.

[0036] To further illustrate the effects of the embodiments of the present invention, a comparative test of water vapor barrier rate was conducted at 85℃ / 85%RH.

[0037] 1. Testing Standards Basis: IEC 6213:2017 Annex B (High Temperature and High Humidity Storage Test).

[0038] 2. Sample grouping: control group Traditional plastic film heat sealing tape 2: Single-layer seal n=30 603048 (2000mAh) experimental group Plastic film heat sealing tape 2 + metal sealing tape 3: Double-layer seal n=30 same batch

[0039] 3. Key test parameters: Water vapor permeability Karl Fischer coulomb method Metrohm899 Coulometer Electrolyte water content ASTM E1064 Accuracy 0.1ppm Battery internal pressure differential pressure sensor Keller PA-23Y Capacity retention Discharge at 0.5C to 2.75V Neware BTS-4000

[0040] Comparison of experimental results: Table 1: Water vapor barrier performance (after 500h test): Increase in electrolyte water content 152 ± 18 ppm 0.2 ± 0.05 ppm 99.87%↓ Moisture permeability and weight gain 38.5 ± 4.2 mg 0.03 ± 0.01 mg 99.92%↓ Bulging rate 100% (30 / 30) 0% (0 / 30) 100%↓

[0041] Table 2: Electrochemical performance degradation (after 500h test): Capacity retention 78.2% ± 3.1% 95.6% ± 0.8% Internal resistance growth rate 46.7% ± 5.2% 8.3% ± 1.1% Gas production volume (mL / Ah) 12.5 ± 1.8 0.4 ± 0.1

[0042] As shown in Table 1, adding two metal sealing strips 3 to the outside of the plastic film hot air layer on both length sides can reduce the water vapor permeability from 3.85×10⁻² g / (m²·h) to 3.0×10⁻ 5 g / (m²·h) demonstrates the effectiveness of the water vapor barrier in this embodiment, and shows that it meets the USABC 2025 target for power batteries (<1×10⁻⁻⁶). 4 g / (m²·h)).

[0043] As shown in Table 2, the scheme described in this embodiment significantly slows down the degradation of lithium-ion batteries and improves their lifespan. It is worth noting that in the field of lithium-ion batteries, a 500-hour test at 85℃ / 85%RH is equivalent to 10 years of use at room temperature (25℃ / 60%RH).

[0044] 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 pouch lithium-ion battery, characterized by, include: The battery cell body and an aluminum-plastic film housing for sealing the battery cell body, wherein a plastic film heat-sealing tape is provided on the aluminum-plastic film housing. On the heat-sealing tape, the polypropylene layers on the surfaces of the bottom and top aluminum-plastic films are fused and sealed together. The heat-sealing tape seals the battery cell body within the cavity between the top and bottom aluminum-plastic films. Except for the end of the plastic film heat-sealing strip that protrudes from the electrode tab, the inner and outer surfaces of the top aluminum-plastic film and the bottom aluminum-plastic film are exposed metal layers. The exposed metal layers are fused together and metallurgically bonded. After cooling, they form a sealed metal sealing strip located outside the plastic film heat-sealing strip layer.

2. The soft-pack lithium-ion battery according to claim 1, characterized in that, The width of the metal sealing strip is greater than or equal to 0.2 mm and less than or equal to 5 mm. Preferably, the width of the metal sealing strip is greater than or equal to 0.1 mm and less than or equal to 0.5 mm.

3. The soft-pack lithium-ion battery according to claim 1, characterized in that, The metal sealing strip is formed by laser welding.

4. The soft-pack lithium-ion battery according to claim 1, characterized in that, Only the heat-sealing strip of the plastic film is provided at the protruding end of the electrode tab. The electrode tab adhesive pre-applied to the front and back of each electrode tab is fused and bonded to the polypropylene layer on the opposite inner surface of the bottom aluminum-plastic film and the top aluminum-plastic film. After cooling, the electrode tab section located in the heat-sealing strip of the plastic film is sealed and bonded between the heat-sealing strip of the plastic film.

5. The soft-pack lithium-ion battery according to claim 4, characterized in that, The two tabs extend from the first width end of the aluminum-plastic film housing, and the top layer of aluminum-plastic film is formed by folding up from the second width end of the aluminum-plastic film housing.

6. The soft-pack lithium-ion battery according to claim 5, characterized in that, The plastic film heat-sealing strip and the metal sealing strip are respectively provided on the two length sides of the aluminum-plastic film shell from the inside to the outside.

7. The soft-pack lithium-ion battery according to claim 6, characterized in that, The heat-sealing strips of the plastic film located on the two length sides of the two aluminum-plastic film shells are respectively folded up along the length edge to the outer side of the length edge of the aluminum-plastic film shell.

8. The soft-pack lithium-ion battery according to claim 1, characterized in that, The interfacial bonding strength of the metallurgical bonding structure of the metal sealing strip is greater than or equal to 5 MPa, and the metal interfusion depth is 20~50 μm.

9. The soft-pack lithium-ion battery according to claim 1, characterized in that, The width of the heat-sealing tape is greater than or equal to 2 mm and less than or equal to 3 mm.

10. An electronic product characterized by, The power supply battery of the electronic product is the electrode electrical connection of the soft-pack lithium-ion battery as described in any one of claims 1 to 9.

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