Functional current collector for improving thermal runaway safety, preparation method of functional current collector, pole piece and battery

Abstract

The invention discloses a functional current collector for improving thermal runaway safety and a preparation method thereof, a pole piece and a battery, and the functional current collector comprises a shape memory polymer base membrane which is formed by compounding a polymer material and a shape memory polymer; the aluminum oxide base layers are arranged on the front and back surfaces of the shape memory polymer base film; and the aluminum metal coating is arranged on the aluminum oxide base layer. Through structural composition and preparation process improvement of the functional current collector, the defects of an existing aluminum functional current collector are effectively overcome, and the functional current collector has remarkable advantages in the aspects of battery thermal runaway protection, material consistency improvement, structural stability and the like.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a functional current collector for improving thermal runaway safety, its preparation method, electrode, and battery. Background Technology

[0002] Functional current collectors, as an innovative battery material, employ a sandwich structure design of a metal conductive layer, a polymer substrate, and another metal conductive layer. The middle polymer layer (such as PET or PP) possesses both insulating and flame-retardant properties. When the battery is subjected to mechanical abuse such as puncture or impact, the polymer substrate can rapidly melt to form a "point circuit break," effectively blocking the current path and preventing the spread of thermal runaway. This mechanism fundamentally avoids the short-circuit problem caused by metal burrs in traditional current collectors, significantly improving battery safety. Currently, this technology has been applied in CATL's Kirin batteries (used in models such as the Jike 001 and Jike 009) and GAC Aion's cartridge battery 2.0, and its effectiveness in improving the safety of high-energy-density batteries has been proven through practical verification. For example, CATL's NP2.0 thermal runaway-free technology significantly reduces the risk of thermal runaway in batteries through the application of functional current collectors.

[0003] However, existing functional current collector technologies still have significant shortcomings. Their safety performance mainly relies on the melting of the polymer base film at high temperatures, which in turn causes the metal layer to fracture and achieve circuit breaking. However, in practical applications, under the same needle penetration testing conditions, single-layer coated composite aluminum current collectors still exhibit fire phenomena. Subsequent research revealed that the reason why multi-layer coated technology can achieve effective circuit breaking is that its alumina brittle layer generates microcracks during needle penetration, which in turn causes the aluminum layer to fracture; while single-layer coated products lack this brittle layer mechanism, resulting in limited melting and breaking performance. In addition, aluminum sputtering during the vapor deposition process can form pores on the film surface, causing pinhole defects. This not only increases the material defect rate during the manufacturing process and reduces material consistency, but also further weakens the overall safety of the battery. Summary of the Invention

[0004] The purpose of this invention is to provide a functional current collector, its preparation method, electrode, and battery that improve thermal runaway safety, significantly enhancing the battery's thermal runaway protection capability, material consistency, and structural stability, while maintaining compatibility with existing battery production lines, providing a low-cost, mass-producible solution for high-safety batteries.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this application provides a functional current collector to improve thermal runaway safety, comprising: Shape memory polymer base film is composed of polymer materials and shape memory polymer composites; Alumina is used as the base layer and is applied to both the front and back surfaces of the shape memory polymer base film; An aluminum metal coating is applied to an aluminum oxide underlayer.

[0006] To optimize the above technical solution, the specific limitations also include: In the shape memory polymer base film, the mass ratio of shape memory polymer to polymer material is 1.4~2:1, and the thickness of the shape memory polymer base film is 5~12μm.

[0007] Furthermore, the shape memory polymer base film is a three-layer sandwich structure film of shape memory polymer-polymer material-shape memory polymer.

[0008] The thickness of the alumina underlayer is 40~200nm; the thickness of the aluminum metal coating is 0.7~5μm.

[0009] The second aspect of this application provides a method for preparing a functional current collector that improves thermal runaway safety, comprising the following steps: S1: Dry the polymer materials and shape memory polymers to remove moisture; S2: Heat and melt the shape memory polymer and the polymer material separately. Add half of the molten shape memory polymer to the mold to form a uniform bottom layer. Then add the molten polymer material to spread it evenly on the bottom layer to form the middle layer. Then add the molten shape memory polymer to spread it evenly on the middle layer to form the top layer. S3: A thin film is formed by extrusion through a mold, and then stretched longitudinally and laterally to obtain a shape memory polymer base film. S4: Prepare an alumina underlayer on both sides of the shape memory polymer base film; S5: Prepare an aluminum metal coating on an alumina underlayer.

[0010] Furthermore, in step S3, the shaping includes heat shaping and air-cooling shaping. The temperature of heat shaping is 190~210℃ and the time is 3~6 seconds. Air-cooling shaping is to cool the functional current collector to 45~50℃ by air cooling.

[0011] The shape memory polymer is selected from polyurethane, polycaprolactone, and cross-linked polyolefins.

[0012] The alumina underlayer and aluminum metal coating are prepared by magnetron sputtering or vapor deposition.

[0013] A third aspect of this application provides an electrode comprising the aforementioned functional current collector for improving thermal runaway safety. A fourth aspect of this application provides a battery comprising the aforementioned electrode. Compared to the prior art, the advantages of this invention are: This invention effectively overcomes the shortcomings of existing aluminum functional current collectors by improving the structural composition and manufacturing process of the functional current collector, and can produce the following technical effects in terms of battery thermal runaway protection, improved material consistency and optimized structural stability: In terms of battery thermal runaway safety protection, this solution addresses the issues of existing single-application aluminum-plated current collectors being prone to fire during needle penetration testing and having limited safety protection effectiveness. By introducing a shape memory polymer into the base film and adopting a three-layer sandwich structure design of "shape memory polymer-polymer material-shape memory polymer," the thermal response characteristics of the shape memory polymer are utilized. When the battery experiences a needle penetration short circuit and temperature rise, the shape memory polymer can accurately restore its original shape upon heating, thereby causing tensile deformation of the base film and aluminum metal coating, achieving rapid circuit breaking and fundamentally preventing the spread of thermal runaway. Compared to multiple plating technologies that rely on the fracture of the brittle alumina layer, this protection mechanism is more stable, more adaptable, and can also provide efficient protection in single-application scenarios.

[0014] In terms of material performance optimization, shape memory polymers possess rigid properties similar to memory metals. Combined with specific mass ratios of composite materials and base film thickness design, they can effectively reduce pinhole defects caused by aluminum sputtering during evaporation or magnetron sputtering, significantly reducing the material defect rate during manufacturing, improving the film surface consistency and overall performance stability of functional current collectors, and providing a fundamental guarantee for battery safety. Simultaneously, the alumina underlayer on the base film surface not only enhances the bonding strength between the base film and the aluminum metal coating but also further optimizes the stability of the film structure, avoiding safety hazards caused by coating peeling or damage.

[0015] In terms of process and structural compatibility, the base film is prepared by melt composite, layer molding and longitudinal and transverse stretching and shaping process. With precise control of heat setting and air cooling setting, the structural integrity and shape memory response sensitivity of the shape memory polymer base film can be ensured. The preparation process of the alumina underlayer and the aluminum metal coating is matched with the film thickness parameters, which can not only ensure the conductivity of the current collector, but also form a synergistic effect with the shape memory base film, taking into account both safety protection and electrochemical performance.

[0016] Furthermore, the functional current collector prepared by this method can be directly applied to the assembly of electrodes and batteries without requiring significant adjustments to the existing battery production process. It has good industrial adaptability and, by improving the battery's thermal runaway protection capability and material consistency, ultimately achieves a significant upgrade in the overall safety of the battery, providing strong support for the research and development and application of high-safety batteries. Detailed Implementation

[0017] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0018] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0019] This invention provides a functional current collector to improve thermal runaway safety, comprising: Shape memory polymer base film is composed of polymer materials and shape memory polymer composites; Alumina is used as the base layer and is applied to both the front and back surfaces of the shape memory polymer base film; An aluminum metal coating is applied to an aluminum oxide underlayer.

[0020] In some embodiments, the mass ratio of shape memory polymer to polymer material in the shape memory polymer base film is 1.4 to 2:1, and the thickness of the shape memory polymer base film is 5 to 12 μm.

[0021] The shape memory polymer base film is a three-layer sandwich structure film consisting of shape memory polymer, polymer material, and shape memory polymer.

[0022] Existing technologies, such as CN112038572A, apply shape memory polymers to the composite adhesive of electrode sheets, while CN120727753A involves attaching a photosensitive adhesive sheet containing shape memory polymer to the current collector. However, both of these methods offer inferior protection and compatibility compared to this solution. This solution introduces shape memory polymers into the current collector substrate film and employs a three-layer sandwich structure design of "shape memory polymer - polymer material - shape memory polymer," resulting in significant core advantages: Firstly, the shape memory polymer forms an integrated structure with the base film, rather than being externally attached or inserted at an off-site location. This results in a more direct and rapid thermal response. When the battery experiences a short circuit due to a needle penetration and heats up, the shape memory polymer inside the base film can quickly recover its original shape upon heating. This directly causes the base film and the surface aluminum metal coating to undergo tensile deformation, achieving efficient circuit breaking and preventing the spread of thermal runaway from the source. Compared to the multiple plating technology that relies on the fracture of the alumina brittle layer and the indirect action mode of existing technologies, this protection mechanism is more stable and has a more precise response. It can also play an efficient protective role in single plating scenarios. Secondly, the integrated design allows the function of shape memory polymer to fully penetrate the entire base film, rather than being limited to a local area. It can optimize the surface performance of the base film by leveraging its rigid properties similar to memory metals, and avoid problems such as detachment and uneven dispersion that may occur with external adhesives or binders, thus ensuring long-term stability. Third, the design of the base film can form a closely coordinated film structure with the subsequent alumina underlayer and aluminum coating, laying the foundation for performance optimization in each stage and realizing the deep integration of shape memory function and the overall structural performance of the current collector.

[0023] Furthermore, the three-layer sandwich structure of the present invention has the following advantages compared with composite base film materials formed by directly mixing shape memory polymers and polymer materials: The three-layer sandwich structure positions the shape memory polymer (SMP) on the upper and lower surfaces of the base film, directly adjacent to the alumina underlayer and the aluminum metal coating. When the battery experiences a short circuit due to needle penetration and temperature rise, the surface SMP can be rapidly heated to trigger shape recovery, directly causing tensile deformation of the surface base film and the attached aluminum layer, achieving efficient circuit breaking and enhancing the shape memory response efficiency and accuracy. In contrast, in a direct mixing system, the SMP is dispersed within the polymer material. Heat conduction to the SMP requires penetration through the entire matrix, resulting in a delayed response and dispersed deformation force, making it difficult to precisely drive the surface aluminum layer to fracture. The protection efficiency is significantly lower than that of the sandwich structure.

[0024] SMP possesses the hardness of shape memory metals. A three-layer structure uses the hard SMP as the surface layer, directly blocking sputtered aluminum particles during evaporation / magnetron sputtering, reducing pinhole formation at the source. In direct mixing systems, SMP is uniformly dispersed, resulting in limited overall hardness improvement. Furthermore, the lack of a concentrated, hard protective layer on the surface weakens its ability to block sputtered aluminum, making it difficult to effectively reduce pinhole defects. The material consistency is also inferior to sandwich structures.

[0025] In a three-layer sandwich structure, the middle layer of polymer material ensures the flexibility and mechanical support of the base film, while the top and bottom surface layers of SMP (Surface Polymer Metal) are responsible for achieving shape memory function and anti-splash aluminum effect, forming a support-functional layered synergistic system that balances structural stability and functional synergy. Direct mixing systems are prone to uneven SMP distribution, resulting in insufficient hardness in some areas and reduced flexibility in others. This affects the compatibility of base film forming and stretching processes and may weaken the bonding stability with the alumina underlayer and aluminum coating. The sandwich structure avoids this problem through layered design, while enhancing the functional synergy between the film layers.

[0026] In some embodiments, the thickness of the alumina underlayer is 40~200nm; the thickness of the aluminum metal coating is 0.7~5μm.

[0027] This invention also provides a method for preparing a functional current collector to improve thermal runaway safety, comprising the following steps: S1: Dry the polymer materials and shape memory polymers to remove moisture; S2: Heat and melt the shape memory polymer and the polymer material separately. Add half of the molten shape memory polymer to the mold to form a uniform bottom layer. Then add the molten polymer material to spread it evenly on the bottom layer to form the middle layer. Then add the molten shape memory polymer to spread it evenly on the middle layer to form the top layer. S3: A thin film is formed by extrusion through a mold, and then stretched longitudinally and laterally to obtain a shape memory polymer base film. S4: Prepare an alumina underlayer on both sides of the shape memory polymer base film; S5: Prepare an aluminum metal coating on an alumina underlayer.

[0028] In step S3, the setting includes heat setting and air cooling setting. The temperature of heat setting is 190~210℃ and the time is 3~6 seconds. Air cooling setting is to cool the functional current collector to 45~50℃ by air cooling.

[0029] In some embodiments, the shape memory polymer is selected from polyurethane, polycaprolactone, and cross-linked polyolefins.

[0030] Polyurethane is the preferred material in this invention. Its thermal response temperature can be precisely matched to the heating range of the battery needle-puncture short circuit. It has fast shape recovery and strong driving force, which can effectively drive the base film and aluminum layer to break and achieve circuit breaking, solving the problem of needle-puncture fire in single-aluminized functional current collectors. Its hardness can be controlled by cross-linking modification, which can prevent aluminum sputtering by vapor deposition and reduce pinholes. It also has good melt flowability, good compatibility with substrates such as PET / PP, and is suitable for co-extrusion processes. At the same time, it is resistant to electrolyte corrosion and damp heat aging, ensuring the long-term stability of the functional current collector.

[0031] Polycaprolactone is a secondary material suitable for cost-sensitive scenarios. Its melting temperature can match the instantaneous high temperature of battery needle penetration, and it has a high shape recovery rate and moderate tensile strength at break, which can stably achieve circuit breaking. Its low melt viscosity makes it easy to co-extrude with intermediate layer materials, and its crystallinity can be controlled and adjusted to reduce pinholes. Its raw material cost is lower than that of polyurethane, making it suitable for large-scale production to reduce costs.

[0032] Cross-linked polyolefins (such as cross-linked polyethylene and polypropylene) are suitable for applications requiring high rigidity and high temperature resistance of the base film. The cross-linked network structure has high hardness, which can effectively block aluminum sputtering, reduce pinholes, and improve material consistency. It has a high heat distortion temperature, is not easily softened under short-term high temperature, and has stable dimensions after shape recovery, which can avoid secondary short circuits. It has strong interfacial bonding with polyolefin intermediate substrates such as PP, high interlayer peel strength, and resistance to delamination under mechanical action.

[0033] The alumina underlayer and the aluminum metal coating are prepared by magnetron sputtering or vapor deposition.

[0034] The present invention also provides an electrode comprising the above-mentioned functional current collector for improving thermal runaway safety.

[0035] The present invention also provides a battery comprising the above-described electrode.

[0036] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1 This embodiment combines shape memory polymer polyurethane (PU) and PET, encapsulating the PET polymer base film with the shape memory polymer. The mass ratio of shape memory polymer to PET is 1.4:1, and the total thickness of the base film is 6μm. The film is then deposited by vapor deposition. The specific steps are as follows: First, all raw materials are dried to remove moisture. Then, half of the shape memory polymer is hot-melted at high temperature, and the molten shape memory polymer is added to the mold. PET is hot-melted and added to the mold using the same method, followed by the other half of the molten shape memory polymer, forming a shape memory plastic sandwiching a base film. The film is then extruded through the mold to form a preliminary film shape, followed by longitudinal and transverse stretching: For longitudinal stretching, the preheating roller temperature is set to 60-80℃, the slow stretching roller temperature to 80-85℃, the fast stretching roller temperature to 30℃, and the cooling roller temperatures to 30℃ and 50℃, with a longitudinal stretching ratio of 3-3.5. For transverse stretching, the preheating roller temperature is set to 80-100℃, the slow stretching roller temperature to 100-105℃, the longitudinal stretching ratio to 3-3.5, the heat setting temperature is 200℃, the time is 5 seconds, and after setting, it is air-cooled to 50℃.

[0037] After the formed film is slit, measured, and corona treated, it is then magnetron sputtering / evaporation deposited onto the film. The unwinding end is at 120N and the winding end at 100N. After the winding carriage enters the evaporation chamber, a vacuum of 5*10 is applied. -3 At Pa, start the winding carriage, controlling the speed at 280~300 m / min, simultaneously heat the evaporation boat and feed the aluminum wire at a speed of 300~350 mm / min, while simultaneously starting the oxygen intake, and apply a 60 nm aluminum oxide primer to the base film surface, controlling the vacuum degree at 5*10 -2 Pa. Then, the vacuum was broken and a 1μm layer of aluminum was deposited in the same manner.

[0038] Example 2 The scheme in this embodiment is basically the same as that in embodiment 1, except that the mass ratio of shape memory polymer to PET is 1.6:1.

[0039] Example 3 The scheme in this embodiment is basically the same as that in embodiment 1, except that the mass ratio of shape memory polymer to PET is 1.8:1.

[0040] Example 4 The scheme in this embodiment is basically the same as that in embodiment 1, except that the mass ratio of shape memory polymer to PET is 2:1.

[0041] Example 5 The scheme in this embodiment is basically the same as that in embodiment 1, except that the shape memory polymer polyurethane (PU) is replaced with polycaprolactone (PCL).

[0042] Comparative Example 1 The scheme in this embodiment is basically the same as that in embodiment 1, except that the mass ratio of shape memory polymer to PET is 1:1.

[0043] Comparative Example 2 The scheme in this embodiment is basically the same as that in embodiment 1, except that the mass ratio of shape memory polymer to PET is 1.2:1.

[0044] Comparative Example 3 The scheme of this comparative example is basically the same as that of Example 1, except that the heat setting temperature is 200°C, the time is 5 seconds, and there is no post-air cooling setting.

[0045] Comparative Example 4 The scheme of this comparative example is basically the same as that of Example 1, except that the mass ratio of shape memory polymer to PET is 0.7:1.

[0046] Comparative Example 5 The scheme of this comparative example is basically the same as that of Example 1, except that the mass ratio of shape memory polymer to PET is 2.5:1.

[0047] Comparative Example 6 This comparative example uses a composite base film material formed by directly mixing shape memory polymer and polymer materials. The specific steps are as follows: Shape memory polymer and PET raw material were directly hot-melted and mixed. The total amount of each raw material was the same as in Example 1. The extrusion film formation step and subsequent process steps were the same as in Example 1.

[0048] Comparative Example 7 This comparative example does not use a combination of shape memory polymer and PET; instead, it directly uses PET as the base film with a thickness of 6μm, and then performs the coating through vapor deposition. The specific steps are as follows: First, all raw materials are dried to remove moisture. Then, the PET film raw material is heat-melted at high temperature. Next, the molten shape memory polymer is added into a mold and extruded to form the initial shape of the film. Then, longitudinal and transverse stretching are performed: For longitudinal stretching, the preheating roller temperature is set at 60~80℃, the slow stretching roller temperature at 80~85℃, the fast stretching roller temperature at 30℃, and the cooling roller temperatures at 30℃ and 50℃, with a longitudinal stretching ratio of 3~3.5. For transverse stretching, the preheating roller temperature is set at 80~100℃, the slow stretching roller temperature at 100~105℃, the longitudinal stretching ratio at 3~3.5, the heat setting temperature is 200℃, the time is 5 seconds, and after setting, it is air-cooled to 50℃.

[0049] After the formed film is slit, measured, and corona treated, it is then magnetron sputtering / evaporation deposited onto the film. The unwinding end is at 120N and the winding end at 100N. After the winding carriage enters the evaporation chamber, a vacuum of 5*10 is applied. -3 At Pa, start the winding carriage, controlling the speed at 280~300 m / min, simultaneously heat the evaporation boat and feed the aluminum wire at a speed of 300~350 mm / min, while simultaneously starting the oxygen intake, and apply a 60 nm aluminum oxide primer to the base film surface, controlling the vacuum degree at 5*10 -2 Pa. Then, the vacuum was broken and a 1μm layer of aluminum was deposited in the same manner.

[0050] The above-mentioned functional current collector materials were subjected to tensile strength (MD), tensile strength (TD), number of pinholes, and needle penetration tests. Tensile strength: The room temperature tensile strength of the functional current collector was determined using an electronic universal testing machine. The test conditions were: gauge length 10 mm, tensile speed 100 mm / min, width 15 mm, and other requirements were determined according to the method specified in GB / T 1040.3-2006.

[0051] Pinhole testing: The number of pinholes on the surface of the functional current collector is tested using a CCD machine. Through backlight imaging, a CCD line scan camera installed on the production line is used to perform real-time synchronous scanning to capture light leakage points and calculate the number of holes.

[0052] Needle penetration test: The functional current collector was used to assemble the battery, and then a needle penetration test was performed after full charging. To verify the feasibility of the solution, the positive electrode of the battery used 8-series ternary lithium material, and the electrolyte used was a conventional ternary electrolyte manufactured by Jiangxi Jinhui Lithium Battery Materials Co., Ltd., with the composition of EC / EMC / DMC / LiPF6 and additives. The equipment used was a benchtop hand press (hydraulic pump with a maximum pressure of 4000 kg, a stroke of 120 mm, and a stroke extension rod of 250 mm), and a needle penetration testing machine with steel nail specifications of (φ3 mm, φ5 mm, φ8 mm, 100 mm long). A φ5 mm steel nail was used for puncture at a needle penetration speed of 1 mm / s. An infrared thermal imager was used to monitor the surface temperature of the battery.

[0053] Table 1 shows the physical data of the composite films in the examples and comparative examples.

[0054] The experimental analysis is as follows: The MD and TD strengths of all embodiments remained at a high level, indicating good structural stability of the base film. As the mass ratio of SMP (polyurethane) to PET increased from 1.4:1 to 2:1, the MD and TD strengths showed a decreasing trend. This may be because the increased SMP ratio leads to increased rigidity of the base film but a slight decrease in toughness. Comparative Example 7 (pure PET base film) had the highest strength, but lacked the synergistic reinforcing effect of SMP, which may affect safety in practical applications due to increased brittleness. Comparative Example 6 (direct mixing of SMP and PET) showed a significant decrease in strength, indicating that the sandwich structure design is crucial for maintaining mechanical properties.

[0055] The number of pinholes in the embodiments is significantly lower than that in the comparative examples, indicating that the sandwich structure effectively reduces aluminum sputtering during the vapor deposition process. For example, the number of pinholes in Examples 1 to 4 ranges from 0.71 pinholes / m. 2 Reduced to 0.52 per m 2 This indicates that increasing the SMP ratio can improve the surface smoothness of the base film. Comparative Example 6 (direct mixing) showed a pinhole count as high as 2.00 pins / m. 2 This verifies the advantage of the sandwich structure in blocking aluminum sputtering through the rigid SMP surface. The pinhole count in Comparative Example 7 (pure PET) was also higher than that in the Example, further demonstrating the contribution of the introduction of SMP to reducing manufacturing defects.

[0056] Examples 1 to 4 did not ignite during the needle penetration test, and the maximum temperature gradually decreased with increasing SMP mass ratio, indicating that increasing the SMP ratio improved thermal response efficiency. SMP rapidly recovers its shape at high temperatures, causing the base film to deform and break the circuit, thus preventing the spread of thermal runaway. Comparative Example 3 (without air cooling) and Comparative Example 4 (too low SMP ratio) both ignited, demonstrating that air cooling is crucial for maintaining SMP response sensitivity. The ignition of Comparative Example 3 indicates that the air cooling step is indispensable for maintaining the shape memory characteristics of SMP, requiring strict control of the cooling rate; insufficient SMP ratio prevents effective triggering of the circuit-breaking mechanism. Comparative Example 5 did not ignite, but the temperature was high (120°C), possibly due to excessive SMP leading to excessive base film rigidity and delayed deformation response. Comparative Example 6 (direct mixing) and Comparative Example 7 (pure PET) ignited, highlighting the irreplaceable role of the sandwich structure in thermal protection.

[0057] The excessively high SMP ratio in Comparative Example 5 resulted in a loose base film structure, which failed to effectively break the circuit during the needle penetration test, leading to a fire. Specifically, this manifested as decreased tensile strength, an increased number of pinholes, and failure of thermal runaway protection.

[0058] Example 1 performed best in the nail penetration test, while maintaining a low number of pinholes and moderate strength. This ratio balances thermal response efficiency, material consistency, and mechanical properties, providing reliable parameters for industrial applications. Example 5 (polycaprolactone instead of polyurethane) had a higher nail penetration temperature than Example 1, indicating that polyurethane has a faster thermal response and is more suitable for battery short-circuit scenarios, while polycaprolactone can be considered as an alternative in cost-sensitive scenarios.

[0059] This invention utilizes a three-layer base film structure of SMP-polymer material-SMP to achieve rapid heat conduction to the SMP surface, avoiding response delays caused by direct mixing.

[0060] This solution significantly improves battery safety through material ratio optimization and process innovation, while remaining compatible with existing production lines.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A functional current collector for improving thermal runaway safety, characterized in that, include: Shape memory polymer base film is composed of polymer materials and shape memory polymer composites; Alumina is used as the base layer and is applied to both the front and back surfaces of the shape memory polymer base film; An aluminum metal coating is applied to an aluminum oxide underlayer.

2. The functional current collector for improving thermal runaway safety according to claim 1, characterized in that: In the shape memory polymer base film, the mass ratio of shape memory polymer to polymer material is 1.4~2:1, and the thickness of the shape memory polymer base film is 5~12μm.

3. The functional current collector for improving thermal runaway safety according to claim 1, characterized in that: The shape memory polymer base film is a three-layer sandwich structure film consisting of shape memory polymer, polymer material, and shape memory polymer.

4. The functional current collector for improving thermal runaway safety according to claim 1, characterized in that: The thickness of the alumina underlayer is 40~200nm; the thickness of the aluminum metal coating is 0.7~5μm.

5. The method for preparing the functional current collector for improving thermal runaway safety according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Dry the polymer materials and shape memory polymers to remove moisture; S2: Heat and melt the shape memory polymer and the polymer material separately. Add half of the molten shape memory polymer to the mold to form a uniform bottom layer. Then add the molten polymer material to spread it evenly on the bottom layer to form the middle layer. Then add the molten shape memory polymer to spread it evenly on the middle layer to form the top layer. S3: A thin film is formed by extrusion through a mold, and then stretched longitudinally and laterally to obtain a shape memory polymer base film. S4: Prepare an alumina underlayer on both sides of the shape memory polymer base film; S5: Prepare an aluminum metal coating on an alumina underlayer.

6. The method for preparing a functional current collector to improve thermal runaway safety according to claim 5, characterized in that: In step S3, the shaping includes heat shaping and air-cooling shaping. The temperature of heat shaping is 190~210℃ and the time is 3~6 seconds. Air-cooling shaping is to cool the functional current collector to 45~50℃ by air cooling.

7. The method for preparing a functional current collector to improve thermal runaway safety according to claim 5, characterized in that: The shape memory polymer is selected from polyurethane, polycaprolactone, and cross-linked polyolefins.

8. The method for preparing a functional current collector to improve thermal runaway safety according to claim 5, characterized in that: The alumina underlayer and aluminum metal coating are prepared by magnetron sputtering or vapor deposition.

9. An electrode sheet, characterized in that: The present invention comprises a functional current collector for improving thermal runaway safety prepared by the method described in any one of claims 1 to 4 or any one of claims 5 to 8.

10. A battery, characterized in that: It includes the electrode sheet as described in claim 9.

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