A termination tape for lithium batteries

Abstract

This utility model discloses a termination tape for lithium batteries, belonging to the field of lithium battery technology. It includes a tape body, which, from the outside in, comprises: an outer protective layer, a first adhesive layer, a middle reinforcing layer, a second adhesive layer, and an inner functional layer. Through a five-layer composite structure with a gradient functional design, optimal material performance is achieved. The polyimide film of the outer protective layer provides excellent mechanical protection and high-temperature resistance. The three-dimensional network aramid fiber structure of the middle reinforcing layer increases tear resistance to 3-5 times that of ordinary PET substrates. The fluoropolymer film of the inner functional layer controls electrolyte permeability to ≤0.1 g / m³. 2 Within 24 hours, each layer from the outside to the inside has a clear function and works in concert. The outer protective layer focuses on mechanical protection and weather resistance; the first adhesive layer provides high-strength initial bonding; the middle reinforcing layer ensures overall mechanical performance; the second adhesive layer optimizes long-term stability; and the inner functional layer focuses on electrolyte protection.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery technology, specifically to a termination tape for lithium batteries. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage systems, lithium-ion batteries are constantly evolving towards higher energy density, longer cycle life, and higher safety. As a key auxiliary material for batteries, the performance requirements of termination tape are also increasing.

[0003] Existing technologies disclose several utility model patents in the field of lithium battery processing technology. Among them, utility model patent CN217628219U discloses a termination tape for lithium batteries. This termination tape consists of six layers, arranged from the outside in: a first substrate layer, a first pressure-sensitive adhesive layer, a second substrate layer, a second pressure-sensitive adhesive layer, a third substrate layer, and a third pressure-sensitive adhesive layer, all integrated into a single unit. This utility model's termination tape has a six-layer structure, which, compared to existing two- or four-layer termination tapes, provides higher electrical insulation performance. Furthermore, the third pressure-sensitive adhesive layer in contact with the electrolyte in this termination tape does not contain colorant, flame retardant, or other similar components, avoiding the dissolution and precipitation of colorant and flame retardant caused by long-term immersion, which could lead to electrolyte discoloration and affect electrolyte performance. Meanwhile, the third pressure-sensitive adhesive layer of this invention is more resistant to electrolyte erosion and its adhesion is less likely to decrease compared to pressure-sensitive adhesive layers containing color pastes and other additives.

[0004] However, the above method still has the following drawbacks in actual use: First, the symmetrical structure design fails to fully consider the different environmental stresses that each layer will bear in actual use, resulting in the material properties not being fully utilized. Second, although the stacking of multiple similar materials improves certain performance indicators, it also increases material costs and process complexity. Utility Model Content

[0005] The purpose of this invention is to provide a termination tape for lithium batteries to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a termination tape for lithium batteries, comprising a tape body, wherein the tape body comprises, from the outside to the inside: an outer protective layer, a first adhesive layer, an intermediate reinforcing layer, a second adhesive layer, and an inner functional layer; the outer protective layer is an 8-15μm polyimide film; the intermediate reinforcing layer is a 10-20μm aramid fiber reinforced polyester film, wherein the aramid fiber content is 15-30wt%; the inner functional layer is a 5-12μm fluoropolymer film; the first adhesive layer is a modified epoxy resin adhesive layer with a thickness of 5-10μm; the second adhesive layer is a silicone-modified acrylate adhesive layer with a thickness of 8-15μm.

[0007] As a further preferred embodiment of this technical solution, the surface of the polyimide film of the outer protective layer is subjected to plasma treatment, and the surface energy is ≥50mN / m.

[0008] As a further preferred embodiment of this technical solution, the aramid fibers in the intermediate reinforcing layer have a diameter of 0.5-2 μm and are distributed in a three-dimensional network.

[0009] As a further preferred embodiment of this technical solution, the first adhesive layer contains 10-20 wt% nano-silica and 3-5 wt% organosilicon modifier, and the second adhesive layer contains 1-3 wt% fluorinated silane coupling agent and 2-5 wt% electrolyte-resistant additive.

[0010] As a further preferred embodiment of this technical solution, the inner functional layer is a polyvinylidene fluoride (PVDF) or ethylene-tetrafluoroethylene copolymer (ETFE) film, and the total thickness of the tape body is 40-60 μm.

[0011] As a further preferred embodiment of this technical solution, the peel strength retention rate of the tape body after immersion in an electrolyte at 85°C for 72 hours is ≥90%, and the electrolyte permeability of the tape body is ≤0.1g / m. 2 • After 24 hours, the flame retardancy rating of the tape body reaches the UL94 V-0 standard.

[0012] This utility model provides a termination tape for lithium batteries, which has the following beneficial effects:

[0013] (1) This utility model achieves optimal material performance through a five-layer composite structure with gradient functional design. The outer protective layer, made of polyimide film, provides excellent mechanical protection and high-temperature resistance. The three-dimensional network aramid fiber structure of the middle reinforcing layer increases the tear resistance to 3-5 times that of ordinary PET substrates. The inner functional layer, made of fluoropolymer film, controls the electrolyte permeability to ≤0.1g / m³. 2Within 24 hours, each layer from the outside to the inside has a clear function and works in concert. The outer protective layer focuses on mechanical protection and weather resistance; the first adhesive layer provides high-strength initial bonding; the middle reinforcing layer ensures overall mechanical performance; the second adhesive layer optimizes long-term stability; and the inner functional layer focuses on electrolyte protection. This design avoids the waste of material properties and achieves the optimization of overall performance.

[0014] (2) This utility model solves the interlayer compatibility problem through innovative interface treatment technology. The outer protective layer is treated with high surface energy plasma with ≥50mN / m, which increases the interlayer peel strength to 8.5N / 25mm. The second adhesive layer introduces a fluorinated silane coupling agent to form a chemical bonding network, which makes the strength retention rate after immersion in electrolyte at 85℃ ≥90%. Tests show that this design effectively suppresses the interface delamination phenomenon caused by volume change during battery cycling, and reduces the edge warping rate by more than 80%. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0016] Figure 2 This is a cross-sectional structural diagram of the tape body of this utility model.

[0017] In the diagram: 1. Tape body; 101. Outer protective layer; 102. First adhesive layer; 103. Intermediate reinforcing layer; 104. Second adhesive layer; 105. Inner functional layer. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0019] This utility model provides a technical solution: such as Figure 1 and Figure 2As shown, in this embodiment, a termination tape for lithium batteries includes a tape body 1. The tape body 1 comprises, from the outside to the inside, an outer protective layer 101, a first adhesive layer 102, an intermediate reinforcing layer 103, a second adhesive layer 104, and an inner functional layer 105. The outer protective layer 101 is an 8-15μm polyimide film; the intermediate reinforcing layer 103 is a 10-20μm aramid fiber reinforced polyester film, wherein the aramid fiber content is 15-30wt%; the inner functional layer 105 is a 5-12μm fluoropolymer film; the first adhesive layer 102 is a modified epoxy resin adhesive layer with a thickness of 5-10μm; the second adhesive layer 104 is a silicone-modified acrylate adhesive layer with a thickness of 8-15μm; the outer protective layer 101 is a polyimide film with a thickness of 101. The imine film surface is plasma-treated, with a surface energy ≥50mN / m. The aramid fibers in the intermediate reinforcing layer 103 have a diameter of 0.5-2μm and are distributed in a three-dimensional network. The first adhesive layer 102 contains 10-20wt% nano-silica and 3-5wt% organosilicon modifier. The second adhesive layer 104 contains 1-3wt% fluorinated silane coupling agent and 2-5wt% electrolyte-resistant additive. The inner functional layer 105 is a polyvinylidene fluoride (PVDF) or ethylene-tetrafluoroethylene copolymer (ETFE) film. The total thickness of the tape body 1 is 40-60μm. The peel strength retention rate of the tape body 1 after immersion in an electrolyte at 85℃ for 72 hours is ≥90%, and the electrolyte permeability of the tape body 1 is ≤0.1g / m. 2 • After 24 hours, the flame retardancy rating of the tape body 1 reaches the UL94 V-0 standard;

[0020] After plasma treatment, the outer polyimide film maintains more than 95% dimensional stability at a high temperature of 150℃, solving the edge warping problem caused by high temperature shrinkage of traditional PET tape. The three-dimensional network aramid reinforcement structure improves the tape's resistance to deformation during battery charging and discharging by 300%, and it can withstand mechanical stress of ≥500 charge-discharge cycles.

[0021] First embodiment:

[0022] A tape body 1 with a total thickness of 50 μm was prepared, and its specific structure is as follows:

[0023] The outer protective layer is a 101:12μm polyimide film, which is subjected to plasma treatment at 400W atmospheric pressure at a speed of 8m / min.

[0024] The first adhesive layer 102: 8μm modified epoxy resin adhesive layer, the formula is: epoxy resin E-51 (100 parts), nano SiO2 (15 parts), silane coupling agent KH-560 (5 parts), curing agent DDS (30 parts).

[0025] The intermediate reinforcing layer 103: 15μm aramid fiber reinforced polyester film (aramid content 20%, fiber diameter 1μm) is prepared by wet molding process.

[0026] The second adhesive layer 104: 10μm silicone-modified acrylate adhesive layer, the formula is: isooctyl acrylate (60 parts), acrylic acid (5 parts), fluorinated silane (2 parts), electrolyte resistant additive (3 parts), photoinitiator 184 (3 parts).

[0027] Inner functional layer 105: 5μm PVDF film ( 5130, Solvay).

[0028] Test results:

[0029] Initial peel strength: 8.5 N / 25 mm

[0030] Peel strength after immersion in electrolyte at 85℃ for 72 hours: 7.8 N / 25 mm (retention rate 91.8%)

[0031] Insulation resistance: 2.5 × 10⁻⁶ 12 Ω

[0032] Flame retardant rating: UL94 V-0

[0033] Electrolyte permeability: 0.08 g / m³ 2 24h

[0034] Heat shrinkage rate (150℃, 1h): 0.3%

[0035] Second embodiment:

[0036] A tape body 1 with a total thickness of 45 μm was prepared, and its specific structure is as follows:

[0037] The outer protective layer is a 101:10μm polyimide film, which is plasma treated.

[0038] First adhesive layer 102: 6μm modified epoxy resin adhesive layer (nano SiO2 content 20%).

[0039] Intermediate reinforcing layer 103: 12μm aramid fiber reinforced polyester film (aramid content 25%).

[0040] Second adhesive layer 104: 12μm silicone-modified acrylate adhesive layer (containing 3% fluorosilane).

[0041] Inner functional layer 105: 5μm ETFE film.

[0042] Test results:

[0043] Initial peel strength: 8.2 N / 25 mm

[0044] Peel strength retention rate after high-temperature aging: 90.5%

[0045] Insulation resistance: 3.1 × 10⁻⁶ 12 Ω

[0046] Electrolyte contact angle: 115°

[0047] Comparative Example

[0048] Comparative tests were conducted using traditional PET-based acrylic tape (total thickness 50μm):

[0049] Test results:

[0050] Initial peel strength: 5.0 N / 25 mm

[0051] Peel strength after immersion in electrolyte at 85℃ for 72 hours: 2.8 N / 25 mm (retention rate 56%)

[0052] Insulation resistance: 5.0 × 10⁻⁶ 11 Ω

[0053] Flame retardant rating: UL94 HB

[0054] Electrolyte permeability: 0.35 g / m³ 2 24h

[0055] Working principle:

[0056] First, the outer layer of the polyimide film is subjected to plasma treatment at 300-500W atmospheric pressure (5-10m / min) to activate its surface. Then, a modified epoxy resin solution with a solid content of 30-40% is applied to the treated surface at a thickness of 8-12μm using microgravure coating, and pre-cured at 80-100℃ for 3-5 minutes to form the first adhesive layer 102. Next, it is hot-pressed at 120-140℃ and 0.3-0.5MPa pressure for 10-20 seconds to fully bond the aramid fiber-reinforced polyester interlayer with the first adhesive layer 102. Subsequently, a silicone-modified acrylate solution with a viscosity of 500-1000cps is applied to the other side of the interlayer at a thickness of 10-15μm using slit extrusion coating, and cured at 300-500mJ / cm². 2 The PVDF functional layer is cured by UV light; finally, the PVDF functional layer is pressed at room temperature with a pressure of 0.1-0.2 MPa, and the finished product is obtained after final curing at 60-80℃ for 24-48 hours.

[0057] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A termination tape for lithium batteries comprising a tape body (1), characterized in that: The tape body (1) comprises, from the outside to the inside, an outer protective layer (101), a first adhesive layer (102), an intermediate reinforcing layer (103), a second adhesive layer (104), and an inner functional layer (105); the outer protective layer (101) is an 8-15μm polyimide film; the intermediate reinforcing layer (103) is a 10-20μm aramid fiber reinforced polyester film; and the inner functional layer (105) is a 5-12μm fluoropolymer film; the first adhesive layer (102) is a modified epoxy resin adhesive layer with a thickness of 5-10μm; and the second adhesive layer (104) is a silicone modified acrylate adhesive layer with a thickness of 8-15μm.

2. The termination tape for lithium batteries according to claim 1, characterized in that: The surface of the polyimide film of the outer protective layer (101) is plasma treated, and the surface energy is ≥50mN / m.

3. The termination tape for lithium batteries according to claim 1, characterized in that: The aramid fibers in the intermediate reinforcing layer (103) have a diameter of 0.5-2 μm and are distributed in a three-dimensional network.

4. The termination tape for lithium batteries according to claim 1, characterized in that: The inner functional layer (105) is a polyvinylidene fluoride or ethylene-tetrafluoroethylene copolymer film, and the total thickness of the tape body (1) is 40-60 μm.

5. The termination tape for lithium batteries according to claim 1, characterized in that: The peel strength retention rate of the tape body (1) after being immersed in electrolyte at 85°C for 72 hours is ≥90%, the electrolyte permeability of the tape body (1) is ≤0.1g / m²·24h, and the flame retardancy rating of the tape body (1) reaches UL94 V-0 standard.

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