Electrolyte-resistant insulating adhesive film for large cylindrical battery and laminating process of electrolyte-resistant insulating adhesive film

Abstract

The invention relates to an electrolyte-resistant insulating adhesive film for a large cylindrical battery and a laminating process of the electrolyte-resistant insulating adhesive film, the insulating adhesive film comprises a base film layer and an adhesive layer, the base film layer is made of a modified polyolefin material containing a fluorine modifier or a silane modifier, the bonding layer comprises the following raw material components in parts by mass: 60-75 parts of an ethylene-vinyl acetate copolymer, 15-25 parts of hydrogenated petroleum resin, 5-10 parts of hydroxyl-terminated polybutadiene and 1-3 parts of a cross-linking agent. The insulating bonding film can realize insulating bonding with a battery cell assembly through a combined process of hot-melting pre-bonding, hot-pressing curing and cold-pressing shaping. The invention further provides three preparation processes of single-opening blow molding cover die, superposition and lamination and segmented lamination, and the requirements of different production lines are met. The insulating adhesive film has the advantages of high bonding strength with a battery cell shell, stable high and low temperature cycle performance, excellent electrolyte resistance and high dimensional precision, conforms to the industry and national standards, can effectively guarantee the safe and stable operation of a large cylindrical battery, and has wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of power battery insulation materials technology, specifically to an electrolyte-resistant insulating adhesive film for large cylindrical batteries and its bonding process. Background Technology

[0002] With the rapid development of the new energy vehicle industry, large cylindrical batteries have become an important development direction in the power battery field due to their high energy density, excellent heat dissipation performance, and cycle stability. During the assembly of large cylindrical batteries, to ensure reliable insulation between the cell and the metal casing and prevent the risk of thermal runaway caused by short circuits, an insulating adhesive film is typically bonded to the outer surface of the cell or the inside of the casing. This film not only needs to possess durable insulation but also needs to maintain stable physical and chemical properties under long-term charging and discharging and complex operating conditions. As a core component ensuring the stability of the cell's internal structure and avoiding short-circuit risks, its performance directly affects the battery's safety and lifespan.

[0003] The existing insulating adhesive films for large cylindrical batteries generally have the following technical defects: (1) Insufficient resistance to electrolytes. They are prone to swelling, delamination or detachment under long-term immersion in carbonate electrolyte systems, leading to insulation failure and battery safety hazards; (2) Poor bonding reliability. A single bonding process is difficult to adapt to the arc structure of large cylindrical cells. The bonding is prone to loosening under dynamic conditions such as thermal expansion and contraction and vibration; (3) Narrow adaptability to production processes. They cannot meet the automation requirements of different production lines. Moreover, the customization of key parameters such as opening gap and thickness is low, making it difficult to match diverse cell design schemes; (4) Some products cannot simultaneously meet the stringent requirements of power battery industry standards and national standards for insulation performance, dimensional accuracy, etc.

[0004] To address the aforementioned issues, there is an urgent need to develop an insulating adhesive film for cylindrical batteries that exhibits excellent electrolyte resistance, stable and reliable adhesion, wide process adaptability, and customizable parameters, in order to fill the gap in existing technologies and ensure the safe and stable operation of large cylindrical batteries. Summary of the Invention

[0005] To address the shortcomings of existing insulating adhesive films for large cylindrical batteries, such as insufficient electrolyte resistance, poor bonding reliability, narrow adaptability to manufacturing processes, and difficulty in simultaneously meeting industry standards for insulation performance and dimensional accuracy, this invention provides an electrolyte-resistant insulating adhesive film for large cylindrical batteries and its bonding process. This insulating adhesive film can be adapted to the assembly requirements of different large cylindrical battery cells through preparation processes such as single-opening blow molding, superimposed bonding, or segmented bonding. Furthermore, the assembled insulating adhesive film exhibits high bonding strength to the battery cell casing, stable high and low temperature cycling performance, excellent electrolyte resistance, and high dimensional accuracy, meeting industry and national standards. It can effectively ensure the safe and stable operation of large cylindrical batteries and has broad application prospects.

[0006] Specifically, the following technical solutions are provided: The first aspect of this invention provides an electrolyte-resistant insulating adhesive film for large cylindrical batteries, the insulating adhesive film comprising a substrate layer and an adhesive layer; wherein, the substrate layer is made of a modified polyolefin material containing a fluorine modifier or a silane modifier; the adhesive layer is made of a modified hot melt adhesive, the modified hot melt adhesive comprising the following raw material components by mass: 60-75 parts of ethylene-vinyl acetate copolymer, 15-25 parts of hydrogenated petroleum resin, 5-10 parts of hydroxyl-terminated polybutadiene, and 1-3 parts of crosslinking agent.

[0007] The insulating adhesive film provided by this invention has an adhesive layer prepared from raw materials such as ethylene-vinyl acetate copolymer, hydrogenated petroleum resin, hydroxyl-terminated polybutadiene, and crosslinking agent. The ethylene-vinyl acetate copolymer (EVA, the matrix adhesive), as the main resin of the hot melt adhesive, provides the core bonding performance. After melting during the hot pressing process, it can wet the surface of the battery cell assembly. After cooling and solidification, it forms a strong adhesive interface, achieving a tight bond between the film and the battery cell. The vinyl acetate groups endow the material with good flexibility and low-temperature adhesion, adapting to the usage requirements of batteries under low-temperature conditions; it also possesses certain electrolyte resistance, making it less prone to swelling and failure due to electrolyte. The hydrogenated petroleum resin, as a tackifying resin, reduces the melt viscosity of the hot melt adhesive, improves its wetting and spreading properties, and ensures that the adhesive layer uniformly covers the surface of the battery cell during hot pressing, avoiding bonding blind spots. It enhances the initial tack and holding power of the hot melt adhesive, improves the interfacial adhesion between the adhesive layer and the base layer and battery cell assembly, and prevents the film from curling or falling off during the thermal expansion and contraction of the battery cell. After hydrogenation treatment, the resin's weather resistance and oxidation resistance are significantly improved, preventing aging and embrittlement during long-term battery use. Furthermore, introducing an appropriate amount of flexible, hydroxyl-terminated polybutadiene into the hot melt adhesive system enhances the toughness and impact resistance of the adhesive layer, alleviating stress caused by volume changes during cell charging and discharging, and preventing cracking of the adhesive layer. Under the action of a crosslinking agent (preferably an isocyanate-based crosslinking agent), the hydroxyl groups of the copolymer and the terminal hydroxyl groups in the hydroxyl-terminated polybutadiene can react with the crosslinking agent to construct a three-dimensional network crosslinked structure, improving the hot melt adhesive's heat resistance, solvent resistance (electrolyte resistance), and mechanical strength, preventing creep and failure of the adhesive layer under high temperatures or electrolyte immersion. By rationally controlling the mass fraction of each raw material component, the crosslinking density of the adhesive layer can be regulated. If the crosslinking density is too low, the adhesive layer will not be resistant to electrolytes, and if it is too high, the adhesive layer will become brittle and easily crack under stress. Preferably, 60-75 parts of ethylene-vinyl acetate copolymer, 15-25 parts of hydrogenated petroleum resin, 5-10 parts of hydroxyl-terminated polybutadiene and 1-3 parts of crosslinking agent are added to prepare the adhesive layer to balance the adhesive strength and flexibility of the adhesive layer.

[0008] Furthermore, the modified polyolefin material comprises the following raw material components by mass parts: 85-95 parts of polyolefin resin, 3-10 parts of fluorine modifier or silane modifier, and 0.5-2 parts of antioxidant.

[0009] Preferably, the fluorine modifier is selected from one or more of perfluorooctyltrimethoxysilane (PFOTMS), tridecafluorooctyltrimethoxysilane (FAS-13), heptadecafluorodecyltrimethoxysilane (FAS-17), fluoroalkyl polyoxyethylene ether, perfluoroalkyl betaine, and fluorinated acrylate copolymer; the silane modifier is selected from one or more of γ-aminopropyltriethoxysilane (KH-550 / A-1100), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792 / A-1120), γ-ureidopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane (KH-560), and γ-mercaptopropyltrimethoxysilane (KH-590).

[0010] Preferably, the antioxidant is a hindered phenolic antioxidant.

[0011] This invention uses polyolefin resin as the skeleton substrate of the base film layer, providing the basic mechanical properties (tensile strength, elongation at break) and processability of the insulating adhesive film, ensuring that the film material is not easily damaged during hot and cold pressing processes. It inherently possesses excellent electrical insulation properties, blocking current conduction between the battery cell and the casing, and is the core source of the base layer's insulation performance. It also exhibits good chemical corrosion resistance, initially resisting electrolyte erosion and providing a foundation for subsequent modification. Simultaneously, fluorine modifiers and / or silane modifiers are introduced. The addition of fluorine modifiers introduces fluorine-containing groups into the base film, thereby significantly improving the polyolefin material's resistance to electrolyte permeation, preventing electrolyte penetration into the base layer and causing material swelling and cracking; it also reduces the material's surface energy, improving the film material's resistance to high and low temperatures, adapting to the temperature fluctuation environment of battery charging and discharging. The introduction of silane modifiers can combine with the polyolefin molecular chains through grafting reactions, enhancing the interfacial adhesion of the base layer, improving the composite strength with the adhesive layer, and preventing interlayer delamination; at the same time, silane groups can form a dense protective layer, hindering electrolyte erosion of the substrate. In addition, introducing appropriate amounts of antioxidants, such as hindered phenolic antioxidants, can capture free radicals generated by polyolefin resins during processing (hot pressing) and use, inhibiting thermal oxidative degradation of the material and preventing problems such as yellowing, embrittlement, and decreased mechanical properties in the substrate. By introducing appropriate modifiers and antioxidants into polyolefin membranes, the long-term stability of the membrane layer can be effectively improved.

[0012] Furthermore, the size of the reserved gap at the opening of the insulating adhesive film is 2 mm, 3 mm or 5 mm, and the gap deviation is ±0.1 mm; the opening refers to the hole or gap area reserved by the insulating adhesive film for the part that does not need to be covered or needs to be exposed when covering the battery cell assembly; the reserved gap refers to the minimum distance between the boundary of the opening of the insulating adhesive film and the outline of the component that needs to be exposed, that is, the distance from the edge of the film to the edge of the component.

[0013] In this invention, the gap reserved at the opening of the insulating adhesive film ensures the feasibility of battery assembly, electrical safety, and structural stability. The positive and negative tabs of the large cylindrical battery need to be led out from the opening and welded to the top cover. The gap provides clearance for the tabs, effectively preventing poor welding caused by the film covering the tabs. Simultaneously, the gap accommodates minor dimensional deviations when the battery cell is installed in the casing, preventing the film from being damaged by the casing. Furthermore, it releases the thermal expansion and contraction stress of the battery cell. During charging and discharging, the battery cell expands and contracts due to temperature changes. The reserved gap serves as a stress release space, preventing the insulating adhesive film from being stretched and torn due to cell expansion or wrinkled due to contraction, ensuring long-term insulation performance. In addition, the reserved gap provides a rapid wetting channel for the electrolyte, allowing it to penetrate more evenly into the battery cell, improving the battery's charge / discharge performance and cycle life. Without the gap, the film would hinder the contact between the electrolyte and the cell edge, leading to localized polarization.

[0014] Battery production line molds (such as die-cutting molds and hot-pressing fixtures) and positioning jigs are designed with fixed dimensions. If interval values ​​are used, frequent mold changes or jig parameter adjustments are required, which not only reduces production efficiency but also increases mold costs and the risk of process fluctuations. Fixed gaps facilitate the establishment of unified quality inspection standards (such as gap deviation ±0.1mm), while interval values ​​lead to ambiguous inspection standards and make it difficult to ensure batch consistency. This invention, through extensive experimental verification, has found that there is an effective threshold for the gap size of the insulating adhesive film. When it is less than 2 mm, interference and scratches between the tabs and the film material are likely to occur; when it is greater than 5 mm, the insulating protection for the cell edges is lost. Setting the reserved gap size at the opening to 2 mm, 3 mm, or 5 mm can cover the size requirements of mainstream large cylindrical batteries.

[0015] Furthermore, the thickness of the insulating adhesive film is 10-100 μm; when the thickness of the insulating adhesive film is 10-50 μm, the thickness tolerance is ±1 μm; when the thickness of the insulating adhesive film is 50-100 μm, the thickness tolerance is ±2 μm.

[0016] Furthermore, the insulating adhesive film is bonded to the battery cell assembly through a combination of hot-press curing, hot-melt bonding, and cold-press bonding processes.

[0017] Furthermore, the volume resistivity of the insulating adhesive film is ≥1×10¹ 4 Ω·cm; after being immersed in a conventional carbonate electrolyte system for ≥1000 h, the insulating adhesive film shows no delamination, peeling, swelling or deformation, and retains insulation performance at ≥98%; the peel strength between the insulating adhesive film and the aluminum or copper foil substrate is ≥8N / 25mm, and the peel strength decreases by ≤10% after 50 cycles of high and low temperatures from -40 ℃ to 85℃.

[0018] A second aspect of the present invention provides a single-opening blow molding process for the electrolyte-resistant insulating adhesive film for large cylindrical batteries as described in the first aspect, comprising the following steps: S1. Modified polyolefin material and modified hot melt adhesive are added to a twin-screw extruder and co-extruded to form a composite film preform. S2. The composite film preform is fed into a blow molding die and a single-opening sleeve film is prepared by blow molding; the blow molding die has an opening allowance reserved at the required opening position; S3. The single-opening sleeve film is cooled and shaped, and then laser-cut and trimmed to obtain an insulating adhesive film.

[0019] Furthermore, the single-opening blow molding process is suitable for 4610 cylindrical batteries (10 mm in length). The 4610 cylindrical battery has the shortest length and the smallest axial dimension of the cell, allowing the blow molding sleeve to be fitted in one go without the risk of axial wrinkles. Short-sized cells experience less stress concentration during assembly, the uniformity of the blow molding film's wall thickness meets insulation requirements, and the single-opening structure precisely matches the single-sided lead-out design of the short cell's tabs.

[0020] Further, in step S1, the extrusion temperature of the modified polyolefin material is 150-220 ℃, for example 180 ℃, and the extrusion temperature of the modified hot melt adhesive is 140-200 ℃, for example 160 ℃.

[0021] Further, in step S2, the inner diameter of the cylindrical battery casing is d1 and the height is h1, and the inner diameter of the blow molding die cavity is d2 and the height is h2, satisfying the following relationship: 0≤d1-d2≤1 mm, for example 0.1 mm, 0≤h1-h2≤0.5 mm, for example 0.2 mm.

[0022] Furthermore, in step S2, the opening allowance is preferably 2 mm, 3 mm, or 5 mm.

[0023] Furthermore, in step S2, the blow molding pressure is 0.3-0.6 MPa, the molding temperature is 140-200 ℃, and the holding time is 20-60 s.

[0024] Furthermore, the single-opening blow molding process also includes the step of assembling the insulating adhesive film with the battery casing.

[0025] A third aspect of the present invention provides a lamination process for the electrolyte-resistant insulating adhesive film for large cylindrical batteries as described in the first aspect, comprising the following steps: S1. Prepare a modified polyolefin-based film and a modified hot melt adhesive film respectively. Stack the modified polyolefin-based film and the modified hot melt adhesive film in a preset order and send them into the bonding equipment together with the battery casing. The modified hot melt adhesive film faces the side of the battery casing. S2. A preliminary fixation process is adopted using hot melt pre-bonding, followed by hot pressing curing and cooling to obtain an insulating adhesive film that adheres to the battery casing.

[0026] Furthermore, the aforementioned overlay bonding process is suitable for 4620 (20 mm long) or 4630 (30 mm long) cylindrical batteries. The 4620 / 4630 cylindrical batteries have a moderate length, and the overlay bonding process can balance the bonding strength and insulation performance by adjusting the adhesive layer thickness. The axial thermal expansion and contraction stress of medium-length cells is controllable, and the interfacial adhesion of the overlay composite can resist stress, avoiding interlayer delamination. The overlay bonding process is highly flexible and compatible with both sizes of tabs with double-sided lead-out designs. If the above-mentioned single-opening blow molding process is used to prepare 4630 cylindrical batteries, it will not only significantly reduce production efficiency and increase manufacturing costs, but also, because the axial volume change rate of 4630 cells during charging and discharging is higher than that of shorter cells, and the blow molding sleeve is an integral structure with no stress release space, the film material is prone to peeling off from the cell after long-term cycling, resulting in edge lifting and loss of insulation and adhesion.

[0027] Further, in step S1, the modified polyolefin-based film is prepared by melt extrusion of modified polyolefin material; the modified hot melt adhesive film is prepared by melt extrusion of modified hot melt adhesive.

[0028] Further, in step S2, the hot melt pre-bonding step has the following conditions: temperature 120-150 ℃, pressure 0.2-0.6 MPa, and time 20-60 s; the hot pressing curing step has the following conditions: temperature 160-180 ℃, pressure 0.5-1.0 MPa, and time 30-60 s; the cooling molding step has the following conditions: temperature ≤50 ℃, pressure 0.3-0.5 MPa, and time 20-60 s.

[0029] Furthermore, step S2 also includes opening the insulating adhesive film and laser cutting to trim its edges; after the opening process, a gap of 2 mm, 3 mm, or 5 mm is reserved at the opening of the insulating adhesive film.

[0030] A fourth aspect of the present invention provides a segmented bonding process for the electrolyte-resistant insulating adhesive film for large cylindrical batteries as described in the first aspect, comprising the following steps: S1. Prepare modified polyolefin-based film and modified hot melt adhesive film respectively, and cut them into corresponding segment sizes according to the requirements of the battery cell structure; S2. The segmented film material of the modified polyolefin base film and the segmented film material of the corresponding modified hot melt adhesive film are stacked in a preset order, and the stacked segmented film material is sequentially bonded to the corresponding area of ​​the battery cell using a hot melt pre-bonding process, with a transition gap reserved at the segment interface. After hot pressing, curing and cooling, an insulating adhesive film bonded to the battery cell is obtained.

[0031] Furthermore, the segmented bonding process is suitable for 4680 (80 mm in length) or 4695 cylindrical batteries (95 mm in length). The long length of the 4680 / 4695 batteries makes whole-film bonding prone to uneven axial stretching and wrinkles, while segmented bonding allows for precise positioning segment by segment. Additionally, long cells exhibit significant differences in axial stress during charging and discharging; segmented bonding strengthens adhesion in stress concentration areas (such as the head and tail), improving stability. It also facilitates adaptation to complex designs of long cells, such as multi-point lead-out tabs and stepped casing structures.

[0032] Further, in step S1, the modified polyolefin-based film is prepared by melt extrusion of modified polyolefin material; the modified hot melt adhesive film is prepared by melt extrusion of modified hot melt adhesive.

[0033] Further, in step S2, the hot melt pre-bonding step has the following conditions: temperature 120-150 ℃, pressure 0.2-0.6 MPa, and time 20-60 s; the hot pressing curing step has the following conditions: temperature 160-180 ℃, pressure 0.5-1.0 MPa, and time 30-60 s; the cooling molding step has the following conditions: temperature ≤50 ℃, pressure 0.3-0.5 MPa, and time 20-60 s.

[0034] Furthermore, in step S2, the transition gap is 0.2-0.6 mm.

[0035] Furthermore, step S2 also includes opening the insulating adhesive film and laser cutting and trimming it; after the opening process, a gap of 2 mm, 3 mm or 5 mm is reserved at the opening of the insulating adhesive film.

[0036] Furthermore, in the above three manufacturing processes of single-opening blow molding, superposition bonding, and segmented bonding, the dimensional tolerance of the battery casing must be strictly controlled within the range of ±0.2mm (diameter) and ±0.3mm (height), otherwise it will affect the bonding accuracy of the film material; preferably, the roughness Ra of the inner wall of the casing should be ≤0.8 μm. Excessive roughness will lead to loose bonding of the film material and reduce the bonding strength.

[0037] Furthermore, in the overlay and segmented lamination processes, the cutting accuracy and positioning deviation of the film material must be controlled within ±0.2mm and ±0.1mm, respectively, to ensure dimensional compatibility.

[0038] In this invention, the shell size marking rules are as follows: taking "4680" as an example, "46" represents the shell diameter of 46 mm, "80" represents the shell height of 80 mm, and other dimensions follow the same pattern.

[0039] In this invention, the term "adhesion gap" refers to the maximum gap between the insulating adhesive film and the inner wall of the battery casing. A gap of ≤0.1mm is considered acceptable to ensure adhesion stability.

[0040] In this invention, the term "segment coverage ratio" refers to the proportion of a segmented membrane material covering the circumference of the shell, with an error of ≤±2%, to ensure smooth interface transition.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides an insulating adhesive film for large cylindrical batteries. Through the modified design of the base material and the adhesive layer material, the insulating adhesive film remains undelaminated and unshed after being immersed in conventional carbonate electrolyte for ≥1000h, exhibiting a high insulation performance retention rate. This effectively avoids insulation failure caused by electrolyte immersion and ensures the safe operation of the battery.

[0042] 2. The insulating adhesive film provided by the present invention can be bonded to the battery cell assembly through a combination of hot pressing curing, hot melting bonding and cold pressing bonding processes. The peel strength of the insulating adhesive film to the aluminum foil / copper foil substrate is ≥8N / 25mm. The peel strength decreases at a low rate after high and low temperature cycling. It can maintain stable bonding even under dynamic conditions such as battery suspension and vibration, without loosening or displacement.

[0043] 3. The present invention also provides three preparation processes for assembling the above-mentioned insulating adhesive film in large cylindrical batteries: single-opening blow molding, superposition bonding, and segmented bonding. These processes can be flexibly selected according to the automation requirements of different production lines and the characteristics of the cell structure. At the same time, it supports customization of multiple opening gaps of 2 mm, 3 mm, and 5 mm, and the thickness covers the entire range of 10 μm-100 μm, adapting to diverse large cylindrical cell design schemes.

[0044] 4. The insulating adhesive film provided by this invention, combined with the above-mentioned preparation process, can effectively improve the product qualification rate. Moreover, the prepared products fully comply with national standards and power battery industry standards such as "Safety Requirements for Power Batteries for Electric Vehicles" (GB 30081-2023) and "Polyolefin Separator for Lithium-ion Batteries" (GB / T 36363-2018) in terms of dimensional accuracy and insulation. It can be directly applied to power battery production. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms “comprising” or “including” used in this invention may also be replaced with the closed form “is” or “consisting of”.

[0047] The raw material information used in the following examples is as follows: Polyolefin resin: ExxonMobil Exceed™ 1018CA (LLDPE); Fluorine modifier: Luju Chemical PPA2800; Hindered antioxidants: BASF Irganox ® 1010 / Irgafos 168 compound; Ethylene-vinyl acetate copolymer: ExxonMobil HF28 (VA 27.6%, MI 25 g / 10min); Hydrogenated petroleum resin: Arkon™ P140 from Arakawa, Japan; Hydroxyl-terminated polybutadiene: Baling Petrochemical LHB-2000; Isocyanate crosslinking agent; Covestro Desmodur® N3300 (HDI trimer).

[0048] The modified polyolefin film layer and the modified hot melt adhesive film layer involved in the following examples have the same composition, as detailed below: The raw material composition of the modified polyolefin film layer is: 90 parts polyolefin resin, 8 parts fluorine modifier, and 1 part hindered phenolic antioxidant. The raw material composition of the modified hot melt adhesive film layer is as follows: 70 parts of ethylene-vinyl acetate copolymer, 20 parts of hydrogenated petroleum resin, 8 parts of hydroxyl-terminated polybutadiene, and 2 parts of isocyanate crosslinking agent. Example 1

[0049] This embodiment uses a single-opening blow molding process to prepare an insulating adhesive film inside a 4610-sized large cylindrical battery casing, as detailed below: 1. Core parameters of the shell Diameter: 46 mm (tolerance ±0.2 mm); Height: 10 mm (tolerance ±0.1 mm); Housing material: aluminum alloy (grade 6063); Inner wall roughness: Ra≤0.6 μm; Number of top poles: 1 (diameter 6 mm); Diameter of bottom manifold: 40 mm.

[0050] 2. Customized solutions for adapting insulating adhesive films Membrane type: single-opening membrane; membrane thickness: 40 μm (1 layer of 20 μm base membrane + 1 layer of 20 μm adhesive membrane, adjust the thickness of the adhesive layer to improve adhesion); opening size: reserved 2 mm gap (adapt to pole size); membrane inner diameter: 45.9 mm (adhesion gap 0.1 mm); membrane height: 9.8 mm (adapt to shell height 10 mm).

[0051] 3. Preparation process (1) Custom mold: Customize the blow molding mold according to the shell parameters. The cavity size is 45.9 mm (inner diameter) × 9.8 mm (height), and a 2 mm allowance channel is reserved at the opening.

[0052] (2) Co-extrusion composite: The modified polyolefin material and the modified hot melt adhesive are added to a twin-screw extruder, and the extrusion parameters are adjusted. The extrusion temperature of the modified polyolefin material is 180 ℃ and the extrusion temperature of the modified hot melt adhesive material is 160 ℃. The modified polyolefin material is co-extruded to form a 40μm thick double-layer film preform.

[0053] (3) Blow molding: The preform is fed into a custom mold, the blow molding pressure is 0.25 MPa, the molding temperature is 145 ℃, and the holding time is 15 s to prepare a single-opening sleeve film prototype.

[0054] (4) Cooling and shaping: Use 20 ℃ air cooling for 12 s to ensure rapid shaping of the membrane material and avoid shrinkage and deformation.

[0055] (5) Laser trimming: Use a fiber laser cutting machine with a power of 45 W and a cutting speed of 25 mm / s to trim the edges and ends of the opening of the film. After trimming, the opening size accuracy is ±0.05 mm and the end flatness is ≤0.03 mm.

[0056] (6) Pre-assembly treatment: Cleaning: Wipe the outer surface of the housing (corresponding to the area where the film is attached) and the inner wall of the film with anhydrous ethanol to remove oil, dust and other impurities. After wiping, let it air dry for 30 seconds to prevent impurities from affecting the adhesion effect. Inspection: Use precision calipers to measure the outer diameter of the housing (it must be 45.8±0.03 mm, matching the inner diameter after trimming the film). Check that the surface of the housing is free of scratches and dents, and that the film is free of damage and deformation. Only after the base material is qualified can it be put into assembly. Tooling preparation: Wipe and clean the pre-positioning tooling and pressure roller tooling to ensure that there are no impurities on the contact surfaces.

[0057] (7) Pre-positioning assembly (core tooling: pre-positioning tooling for the membrane): First, slowly insert the trimmed opening end of the sleeve into the inner core of the fixture along the C 0.5 mm guide chamfer of the pre-positioning fixture, ensuring that the inner wall of the sleeve is completely in contact with the outer surface of the fixture, the end is aligned with the effective positioning height scale of the fixture, and the sleeve is free of wrinkles and offset. Slowly push the housing to be assembled along the other guide end of the pre-positioning tooling so that the outer surface of the housing fits tightly against the inner wall of the sleeve, and the end of the sleeve is precisely aligned with the pre-positioning step of the housing, thus completing the coaxial pre-positioning of the sleeve and the housing. Gently support the shell and the membrane, and slowly detach them from the pre-positioning fixture, keeping their relative positions unchanged throughout the process to avoid positioning deviation.

[0058] (8) Heat bonding and curing (core tooling: soft pressure roller tooling): Heating: Use a constant temperature hot air gun to heat the area where the sleeve and the shell are bonded. The hot air temperature is controlled at 80-90℃ (below the melting point of the modified polyolefin material to avoid deformation of the sleeve; above the softening temperature of the modified hot melt adhesive to activate the adhesiveness). The distance between the hot air gun outlet and the bonding area is kept at 10-15 mm. Move the hot air gun at a uniform speed along the circumference of the bonding area for heating. The heating time for one circle is 3-5 seconds. Rolling: While heating, use a soft pressure roller to gently roll along the circumference of the bonding area. The rolling pressure is controlled at 5-8N (manually controlled uniform speed rolling, without additional force). The rolling speed is 20 mm / s, so that the modified hot melt adhesive on the inner wall of the film can be fully melted and tightly bonded to the surface of the shell, without bubbles or gaps. Temperature control requirements: During the heating process, a temperature measuring instrument is used to monitor the surface temperature of the bonding area in real time to avoid excessive melting and overflow of hot melt adhesive or insufficient bonding.

[0059] (9) Cooling, shaping and reinforcement (core tooling: soft pressure roller tooling): Cooling: After the heat bonding is completed, immediately cool the bonding area with 25 ℃ cold air for 5-8 seconds. The distance between the cold air outlet and the bonding area should be 15-20 mm. Move the cooling air at a uniform speed to allow the melted hot melt adhesive to solidify quickly. Secondary rolling: After cooling to a temperature that is not hot to the touch, use a soft roller tool to roll the bonding area again with the same force and speed to strengthen the adhesion between the film and the shell, and ensure that there are no air bubbles or curling edges.

[0060] (10) Post-assembly inspection: Dimensional inspection: Use precision calipers to check that the coaxiality of the film and the shell is ≤0.05 mm, the flatness of the ends is ≤0.03 mm, and there is no hot melt adhesive overflow in the bonding area; Firmness test: Manually pull the diaphragm lightly along the axial direction (tension ≤50 N), there is no loosening or falling off, and the surface of the shell and diaphragm is free of scratches and deformation; Acceptance criteria: Once all the above indicators are met, the assembly is deemed qualified and proceeds to the next process; unqualified products must be reworked immediately and are strictly prohibited from entering subsequent stages.

[0061] 4. Adaptation Performance Verification Size compatibility: The inner diameter of the membrane material is compatible with the diameter of the shell, the bonding gap is 0.09 mm, and the height is compatible with the shell without end wrinkles.

[0062] Adhesion performance: The peel strength between the membrane and the shell is 8.8 N / 25 mm. After 50 cycles of high and low temperature (-40 ℃~85 ℃), the peel strength decreases by 9%, indicating a firm bond.

[0063] Electrolyte resistance: After immersing the assembly membrane shell in a conventional carbonate electrolyte solution for 1000 h at 25±2 ℃, no delamination or peeling was observed; the insulation performance retention rate was 98.5%; and the volume resistivity was ≥1×10⁻⁶. 14 Ω·cm.

[0064] Assembly compatibility: The 2 mm pre-drilled opening precisely matches the pole post, ensuring a smooth assembly process without any jamming. Example 2

[0065] In this embodiment, an insulating adhesive film is prepared inside a large cylindrical battery casing of size 4620 using a superposition bonding process, as detailed below: 1. Core parameters of the shell Diameter: 46 mm (tolerance ±0.2 mm); Height: 20 mm (tolerance ±0.2 mm); Housing material: aluminum alloy (grade 6061); Inner wall roughness: Ra≤0.8 μm; Number of top poles: 1 (diameter 8 mm); Diameter of bottom manifold: 42 mm.

[0066] 2. Customized solutions for adapting insulating adhesive films Membrane material type: stacked membrane material; total membrane thickness: 50 μm (2 layers of 20 μm base membrane + 1 layer of 10 μm adhesive membrane); opening size: 3 mm gap reserved (suitable for bipolar column installation layout); unfolded membrane dimensions: length 144.5 mm (suitable for shell circumference π×46 mm≈144.5 mm), width 19.7 mm (suitable for shell height 20 mm, with 0.3 mm assembly allowance reserved).

[0067] 3. Preparation process (1) Single film preparation: 20 μm thick modified polyolefin film (extrusion temperature 180℃) and 10 μm thick modified hot melt adhesive film (extrusion temperature 160℃) were prepared by melt extrusion process.

[0068] (2) Membrane material cutting: According to the unfolded size of the shell, the modified polyolefin membrane and the modified hot melt adhesive membrane are cut into rectangular membrane sheets of 144.5mm×19.7mm with a cutting accuracy of ±0.2mm.

[0069] (3) Stacking and positioning: Stack the modified polyolefin film × 2 + modified hot melt adhesive film in that order, with the modified hot melt adhesive film facing the shell side, and fix it with a positioning clamp to ensure that the stacking deviation is ≤ ±0.1 mm.

[0070] (4) Hot melt pre-lamination: The superimposed membrane material and the shell are sent into the lamination equipment together. The temperature is 130 ℃, the pressure is 0.2MPa, and the time is 20 s to initially fix the position of the membrane material.

[0071] (5) Hot pressing curing: The bonded shell is sent into a hot pressing device, heated to 170 ℃, pressure 0.8 MPa, time 45 s, to achieve cross-linking and bonding of the adhesive layer.

[0072] (6) Cold pressing: Cool to 40 ℃, pressure 0.4 MPa, time 30 s to eliminate thermal stress.

[0073] (7) Opening processing: For the top bipolar column layout, a 3 mm gap is reserved by laser cutting to ensure smooth pole installation channel.

[0074] 4. Adaptation Performance Verification Size adaptability: The unfolded length of the membrane material matches the circumference of the shell by ≥99.8%, the width matches the height of the shell, and there is no end overflow.

[0075] Adhesion performance: The peel strength between the membrane and the shell is 9.1 N / 25 mm. After high and low temperature cycles of -40 ℃ to 85 ℃ (50 times), the peel strength decreases by 8.5%, and the adhesion is firm and there is no loosening.

[0076] Electrolyte resistance: After immersing the shell of the assembled membrane material in a conventional carbonate electrolyte solution for 1000 h at 25±2 ℃, the membrane material showed no delamination, peeling, or swelling, and maintained an insulation performance of 98.8% with a volume resistivity ≥1×10¹. 4 Ω·cm.

[0077] Assembly compatibility: The reserved opening precisely matches the pole post, ensuring no interference during assembly and achieving an assembly efficiency of ≥30 pieces / minute. Example 3

[0078] In this embodiment, an insulating adhesive film is prepared inside a large cylindrical battery casing of size 4630 using a superposition bonding process, as detailed below: 1. Core parameters of the shell Diameter: 46 mm (tolerance ±0.2 mm); Height: 30 mm (tolerance ±0.2 mm); Housing material: aluminum alloy (grade 6063); Inner wall roughness: Ra≤0.8 μm; Number of top poles: 1 (diameter 10 mm); Diameter of bottom manifold: 42 mm.

[0079] 2. Customized solutions for adapting insulating adhesive films Membrane material type: stacked membrane material; total membrane thickness: 50 μm (2 layers of 20 μm base membrane + 1 layer of 10 μm adhesive membrane); opening size: reserved 2 mm gap (suitable for bipolar column installation layout); membrane material unfolded dimensions: length 144.5 mm (suitable for shell circumference π×46 mm≈144.5 mm), width 29.7 mm (suitable for shell height 30 mm, reserved 0.3 mm assembly allowance).

[0080] 3. Preparation process (1) Single film preparation: 20 μm thick modified polyolefin film (extrusion temperature 180℃) and 10 μm thick modified hot melt adhesive film (extrusion temperature 160℃) were prepared by melt extrusion process.

[0081] (2) Membrane material cutting: According to the unfolded size of the shell, the modified polyolefin membrane and the modified hot melt adhesive membrane are cut into rectangular membrane sheets of 144.5mm×29.7mm with a cutting accuracy of ±0.2mm.

[0082] (3) Stacking and positioning: Stack the modified polyolefin film × 2 + modified hot melt adhesive film in that order, with the modified hot melt adhesive film facing the shell side, and fix it with a positioning clamp to ensure that the stacking deviation is ≤ ±0.1 mm.

[0083] (4) Hot melt pre-lamination: The superimposed membrane material and the shell are sent into the lamination equipment together. The temperature is 130 ℃, the pressure is 0.2MPa, and the time is 20 s to initially fix the position of the membrane material.

[0084] (5) Hot pressing curing: The bonded shell is sent into a hot pressing device, heated to 170 ℃, pressure 0.8 MPa, time 45 s, to achieve cross-linking and bonding of the adhesive layer.

[0085] (6) Cold pressing: Cool to 40 ℃, pressure 0.4 MPa, time 30 s to eliminate thermal stress.

[0086] (7) Opening processing: For the top bipolar column layout, a 2 mm gap is reserved by laser cutting to ensure smooth pole installation channel.

[0087] 4. Adaptation Performance Verification Size adaptability: The unfolded length of the membrane material matches the circumference of the shell by ≥99.8%, the width matches the height of the shell, and there is no end overflow.

[0088] Adhesion performance: The peel strength between the membrane and the shell is 8.9 N / 25 mm. After high and low temperature cycles of -40 ℃ to 85 ℃ (50 times), the peel strength decreases by 8.8%, and there is no cracking at the interface.

[0089] Electrolyte resistance: After immersing the shell of the assembled membrane material in a conventional carbonate electrolyte solution for 1000 h at 25±2 ℃, the membrane material showed no delamination, peeling, or swelling, and maintained 98.7% of its insulation performance, with a volume resistivity ≥1×10⁻⁶. 14 Ω·cm.

[0090] Assembly compatibility: The reserved opening precisely matches the pole post, ensuring no interference during assembly and achieving an assembly efficiency of ≥30 pieces / minute. Example 4

[0091] This embodiment employs a segmented bonding process to prepare an insulating adhesive film within a 4680-size cylindrical battery casing, as detailed below: 1. Core parameters of the shell Diameter: 46 mm (tolerance ±0.2 mm); Height: 80 mm (tolerance ±0.3 mm); Housing material: aluminum alloy (grade 6063); Inner wall roughness: Ra≤0.8 μm; Number of top poles: 1 (diameter 10 mm); Diameter of bottom manifold: 42 mm.

[0092] 2. Customized solutions for adapting insulating adhesive films Membrane material type: segmented membrane material; total membrane thickness: 50 μm (2 layers of 20 μm base membrane + 1 layer of 10 μm adhesive membrane); opening size: reserved 2 mm gap (suitable for small poles); number of segments: 3 segments; single segment membrane material dimensions: arc length 48.2 mm (suitable for 1 / 3 of the shell circumference, π×46 mm÷3≈48.2 mm), height 79.8 mm (suitable for shell height 80 mm, reserved 0.2 mm margin); interface transition gap: 0.5 mm.

[0093] 3. Preparation process Single-film preparation: 20 μm thick modified polyolefin film (extrusion temperature 180 ℃) and 10 μm thick modified hot melt adhesive film (extrusion temperature 160 ℃) were prepared by melt extrusion process.

[0094] Arc-shaped cutting: Based on the shell diameter of 46 mm, an arc-shaped cutting mold was customized. Two layers of modified polyolefin film and one layer of modified hot melt adhesive film were stacked in the order of modified polyolefin film-modified polyolefin film-modified hot melt adhesive film to obtain a 50 μm thick film material. Then, it was cut into 3 arc-shaped film pieces with an arc length of 48.2 mm and a height of 79.8 mm, with an arc length error of ±0.2 mm.

[0095] Housing positioning: Fix the 4680 housing to a special positioning fixture, ensuring that the housing axis coincides with the center of the fixture.

[0096] Segmented pre-bonding: The hot melt pre-bonding process is adopted, with a temperature of 120 ℃, a pressure of 0.15 MPa, and a time of 15 s. The three membrane segments are sequentially bonded to the inner wall of the shell, with a 0.5 mm transition gap reserved at the interface of adjacent membranes. The bonding sequence is "top-middle-bottom", and the positioning deviation is ≤ ±0.1 mm.

[0097] Overall hot-press curing: The bonded shell is sent into a hot-pressing device at a temperature of 165 ℃, a pressure of 0.6 MPa, and a time of 50 s to achieve overall cross-linking and bonding.

[0098] Cold pressing: Cool to 45 ℃, pressure 0.3 MPa, time 25 s, stabilize dimensions.

[0099] Opening processing: For the top pole, a 2 mm gap is laser-cut with no burrs on the edges.

[0100] 4. Adaptation performance verification Size compatibility: The arc length of a single segment of membrane material matches ≥99.6% of the circumference of the shell, the interface transition is smooth and wrinkle-free, and the bonding gap is 0.07 mm.

[0101] Adhesion performance: The peel strength between the membrane and the aluminum alloy shell is 9.2 N / 25 mm. After high and low temperature cycles of -40 ℃ to 85 ℃ (50 times), the peel strength decreases by 8%, with no loosening or displacement.

[0102] Electrolyte resistance: Under conditions of 25±2 ℃, the shell of the assembled membrane material was immersed in a conventional carbonate electrolyte system for 1000 h. The membrane material showed no delamination, peeling, or swelling, and the insulation performance retention rate was 99%, with a volume resistivity ≥1×10⁻⁶. 14 Ω·cm.

[0103] Assembly compatibility: The pre-reserved opening is adapted to the pole post, and the bottom membrane material does not interfere with the integrated current collector, resulting in a 100% assembly qualification rate. Example 5

[0104] This embodiment employs a segmented bonding process to prepare an insulating adhesive film within a large cylindrical battery casing of size 4695, as detailed below: 1. Core parameters of the shell Diameter: 46 mm (tolerance ±0.2 mm); Height: 95 mm (tolerance ±0.3 mm); Housing material: aluminum alloy (grade 6061); Inner wall roughness: Ra≤0.8 μm; Number of top poles: 2 (single pole diameter 8 mm, spacing 15 mm); Bottom manifold diameter: 42 mm.

[0105] 2. Customized solutions for adapting insulating adhesive films Membrane material type: segmented membrane material; total membrane thickness: 60 μm (3 layers of 20 μm base membrane + 1 layer of 10 μm adhesive membrane to improve membrane rigidity); opening size: 5 mm gap reserved (to match pole size); number of segments: 4 segments; single segment membrane material dimensions: arc length 36.1 mm (matches 1 / 4 of the shell circumference, π×46 mm÷4≈36.1 mm), height 94.7 mm (matches 95 mm shell height, with a 0.3 mm allowance); interface transition gap: 0.5 mm.

[0106] 3. Preparation process The process employs a segmented bonding technique, with the following specific steps: (1) Single film preparation: 20 μm thick modified polyolefin film (extrusion temperature 180℃) and 10 μm thick modified hot melt adhesive film (extrusion temperature 160℃) were prepared by melt extrusion process.

[0107] (2) Stacking and cutting: Three layers of modified polyolefin film and one layer of modified hot melt adhesive film are stacked in the order of modified polyolefin film × 3 + modified hot melt adhesive film to obtain a 60 μm thick film material. Then, it is cut into 4 arc-shaped film pieces with an arc length of 36.1 mm and a height of 94.7 mm by an arc mold, with an arc length error of ±0.2 mm.

[0108] (3) Housing positioning: Fix the 4695 housing to a special positioning fixture to ensure that the housing axis coincides with the center of the fixture.

[0109] (4) Segmented pre-bonding: The hot melt pre-bonding process is adopted, with a temperature of 140 ℃, a pressure of 0.2 MPa, and a time of 18 s. The four segments of membrane material are bonded to the inner wall of the shell in sequence according to the principle of "uniform distribution". A 0.5 mm transition gap is reserved between adjacent interfaces, and the positioning deviation is ≤ ±0.1 mm.

[0110] (5) Overall hot pressing curing: The bonded shell is sent into a hot pressing device at a temperature of 175 ℃, a pressure of 0.9 MPa, and a time of 40 s to achieve overall cross-linking and bonding.

[0111] (6) Cold pressing and shaping: Cooling to 48 ℃, pressure 0.45 MPa, time 30 s, to stabilize dimensions; (7) Opening processing: Laser cutting 5 mm reserved gap to fit the top pole installation.

[0112] 4. Adaptation Performance Verification Size compatibility: The arc length of a single segment of membrane material matches ≥99.7% of the circumference of the shell, with smooth interface transition and a bonding gap of 0.06 mm; Adhesion performance: The peel strength between the membrane and the shell is 9.1 N / 25 mm. After high and low temperature cycles of -40 ℃ to 85 ℃ (50 times), the peel strength decreases by 8.5%, and the adhesion is firm and there is no loosening.

[0113] Electrolyte resistance: After immersing the shell of the assembled membrane material in a conventional carbonate electrolyte solution for 1000 h at 25±2 ℃, the membrane material showed no delamination, peeling, or swelling, and maintained an insulation performance of 98.8% with a volume resistivity ≥1×10¹. 4 Ω·cm.

[0114] Assembly compatibility: The pre-drilled opening is designed to fit the electrode post, and there is no interference between the bottom membrane material and the current collector. The assembly qualification rate is 100%.

[0115] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. An electrolyte-resistant insulating adhesive film for large cylindrical batteries, characterized in that, The insulating adhesive film comprises a base film layer and an adhesive layer; The base film layer is made of a modified polyolefin material containing fluorine modifiers or silane modifiers; The adhesive layer is made of modified hot melt adhesive, which contains the following raw material components by mass: 60-75 parts of ethylene-vinyl acetate copolymer, 15-25 parts of hydrogenated petroleum resin, 5-10 parts of hydroxyl-terminated polybutadiene, and 1-3 parts of crosslinking agent.

2. The electrolyte-resistant insulating adhesive film for large cylindrical batteries according to claim 1, characterized in that, The modified polyolefin material comprises the following raw material components by mass parts: 85-95 parts of polyolefin resin, 3-10 parts of fluorine modifier or silane modifier, and 0.5-2 parts of antioxidant. The fluorinated modifier is selected from one or more of perfluorooctyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, fluoroalkyl polyoxyethylene ether, perfluoroalkyl betaine, and fluorinated modified acrylate copolymers. The silane modifier is selected from one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane. The antioxidant is a hindered phenolic antioxidant.

3. The electrolyte-resistant insulating adhesive film for large cylindrical batteries according to claim 1, characterized in that, The size of the gap reserved at the opening of the insulating adhesive film is 2 mm, 3 mm or 5 mm, and the gap deviation is ±0.1 mm; The thickness of the insulating adhesive film is 10-100 μm; when the thickness of the insulating adhesive film is 10-50 μm, the thickness tolerance is ±1 μm; when the thickness of the insulating adhesive film is 50-100 μm, the thickness tolerance is ±2 μm. The insulating adhesive film is bonded to the battery cell assembly through a combination of hot-press curing, hot-melt bonding, and cold-press bonding processes.

4. The electrolyte-resistant insulating adhesive film for large cylindrical batteries according to claim 1, characterized in that, The volume resistivity of the insulating adhesive film is ≥1×10⁻⁶. 14 Ω·cm; After being immersed in a carbonate electrolyte solution for ≥1000 h, the insulating adhesive film showed no delamination, peeling, swelling, or deformation, and maintained an insulation performance retention rate of ≥98%. The peel strength between the insulating adhesive film and the aluminum or copper foil substrate is ≥8N / 25mm, and the peel strength decrease rate is ≤10% after 50 cycles of high and low temperature (-40℃~85℃).

5. A single-opening blow molding process for an electrolyte-resistant insulating adhesive film for large cylindrical batteries according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Modified polyolefin material and modified hot melt adhesive are added to a twin-screw extruder and co-extruded to form a composite film preform. S2. The composite film preform is fed into a blow molding die and a single-opening sleeve film is prepared by blow molding; the blow molding die has an opening allowance reserved at the required opening position; S3. The single-opening sleeve film is cooled and shaped, and then laser-cut and trimmed to obtain an insulating adhesive film.

6. The single-opening blow molding process according to claim 1, characterized in that, The large cylindrical battery is a 4610 cylindrical battery; In step S1, the extrusion temperature of the modified polyolefin material is 150-220 ℃, and the extrusion temperature of the modified hot melt adhesive is 140-200 ℃. In step S2, the inner diameter of the cylindrical battery casing is d1 and the height is h1, and the inner diameter of the blow molding die cavity is d2 and the height is h2, satisfying the following relationship: 0≤d1-d2≤1 mm, 0≤h1-h2≤0.5mm; In step S2, the opening allowance is 2 mm, 3 mm, or 5 mm; In step S2, the blow molding pressure is 0.3-0.6 MPa, the molding temperature is 140-200 ℃, and the holding time is 20-60 s; The single-opening blow molding process also includes the step of assembling the insulating adhesive film with the battery casing.

7. A lamination process for an electrolyte-resistant insulating adhesive film for a large cylindrical battery as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Prepare a modified polyolefin-based film and a modified hot melt adhesive film respectively. Stack the modified polyolefin-based film and the modified hot melt adhesive film in a preset order and send them into the bonding equipment together with the battery casing. The modified hot melt adhesive film faces the side of the battery casing. S2. A preliminary fixation process is adopted using hot melt pre-bonding, followed by hot pressing curing and cooling to obtain an insulating adhesive film that adheres to the battery casing.

8. The overlay bonding process according to claim 7, characterized in that, The large cylindrical battery is a 4620 or 4630 cylindrical battery; In step S1, the modified polyolefin-based film is prepared by melt extrusion of modified polyolefin material; the modified hot melt adhesive film is prepared by melt extrusion of modified hot melt adhesive. In step S2, the hot melt pre-bonding step has the following conditions: temperature 120-150 ℃, pressure 0.2-0.6 MPa, and time 20-60 s; the hot pressing curing step has the following conditions: temperature 160-180 ℃, pressure 0.5-1.0 MPa, and time 30-60 s. In the cooling and forming step: the temperature is ≤50℃, the pressure is 0.3-0.5 MPa, and the time is 20-60 s; Step S2 also includes opening the insulating adhesive film and laser cutting and trimming it; after the opening process, a gap of 2 mm, 3 mm or 5 mm is reserved at the opening of the insulating adhesive film.

9. A segmented lamination process for an electrolyte-resistant insulating adhesive film for large cylindrical batteries according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Prepare modified polyolefin-based film and modified hot melt adhesive film respectively, and cut them into corresponding segment sizes according to the requirements of the battery cell structure; S2. The segmented film material of the modified polyolefin base film and the segmented film material of the corresponding modified hot melt adhesive film are stacked in a preset order, and the stacked segmented film material is sequentially bonded to the corresponding area of ​​the battery cell using a hot melt pre-bonding process, with a transition gap reserved at the segment interface. After hot pressing, curing and cooling, an insulating adhesive film bonded to the battery cell is obtained.

10. The segmented bonding process according to claim 9, characterized in that, The large cylindrical battery is a 4680 or 4695 cylindrical battery; In step S1, the modified polyolefin-based film is prepared by melt extrusion of modified polyolefin material; the modified hot melt adhesive film is prepared by melt extrusion of modified hot melt adhesive. In step S2, the hot melt pre-bonding step has the following conditions: temperature 120-150 ℃, pressure 0.2-0.6 MPa, and time 20-60 s; the hot pressing curing step has the following conditions: temperature 160-180 ℃, pressure 0.5-1.0 MPa, and time 30-60 s. In the cooling and forming step: the temperature is ≤50℃, the pressure is 0.3-0.5 MPa, and the time is 20-60 s; In step S2, the transition gap is 0.2-0.6 mm; Step S2 also includes opening the insulating adhesive film and laser cutting and trimming it; after the opening process, a gap of 2 mm, 3 mm or 5 mm is reserved at the opening of the insulating adhesive film.