Thermally conductive, electrically insulating film and battery pack including same

Abstract

The present application discloses a thermally conductive, electrically insulating film, comprising a thermoplastic resin occupying 15%-50% of the weight of the thermally conductive, electrically insulating film, and a thermally conductive filler occupying 40%-70% of the weight of the thermally conductive, electrically insulating film, the thermally conductive filler including a thermally conductive carbon-based filler, a thermally conductive metal oxide or hydroxide filler, and a thermally conductive ceramic filler. The thermally conductive, electrically insulating film is used in electronic products or devices to provide the electronic products and devices with excellent heat dissipation capability as well as to meet the insulation requirements of the electronic products and devices. Meanwhile, such a thermally conductive, electrically insulating film is further characterized by excellent flame retardancy and mechanical properties to meet the requirements of the operating environment.

Description

[Technical field]

[0001] This application relates to the field of thin films, and in particular to a thermally conductive, electrically insulating film and a battery pack including the thermally conductive, electrically insulating film. [Background technology]

[0002] Electronic products or devices generate a large amount of heat during operation. In order to ensure the operation stability of electronic products and devices and to extend their service life, it is desirable for the electronic products or devices to have good heat dissipation ability. In order to provide electronic products and devices with good heat dissipation ability, thermally conductive materials are used in electronic products and devices. Since thermally conductive materials are used in electronic products and devices, it is desirable for the thermally conductive materials to also have good electrical insulation performance. Summary of the Invention

[0003] The objective of the present application is to provide a thermally conductive, electrically insulating film for use in electronic products or devices, not only to provide the electronic products and devices with excellent heat dissipation capability, but also to meet the insulation requirements of the electronic products and devices, while such a thermally conductive, electrically insulating film is further characterized by excellent flame retardancy and mechanical properties to meet the requirements of the operating environment.

[0004] In a first aspect, the present application provides a thermally conductive, electrically insulating film comprising a thermoplastic resin that accounts for 15% to 50% of the weight of the thermally conductive, electrically insulating film, and a thermally conductive filler that accounts for 40% to 70% of the weight of the thermally conductive, electrically insulating film, the thermally conductive filler including a thermally conductive carbon-based filler, a thermally conductive metal oxide or hydroxide filler, and a thermally conductive ceramic filler.

[0005] According to the first aspect described above, the thermally conductive carbon-based filler accounts for 2% to 15% of the weight of the thermally conductive electrically insulating film.

[0006] According to the first aspect described above, the thermally conductive carbon-based filler accounts for 10% to 15% of the weight of the thermally conductive electrically insulating film.

[0007] According to the first aspect described above, the thermally conductive carbon-based filler is one or more fillers selected from graphite, carbon nanotubes, and graphene.

[0008] According to the first aspect mentioned above, the graphite is at least one graphite selected from flake graphite and expanded graphite.

[0009] According to the first embodiment described above, the thermally conductive carbon-based filler is flake graphite.

[0010] According to the first aspect described above, the graphite has a particle size in the range of 10 nm to 200 μm, the carbon nanotubes have a diameter in the range of 2 nm to 200 nm, and the graphene has a diameter-to-thickness ratio in the range of 500 to 8000.

[0011] According to the first aspect described above, the thermally conductive metal oxide or hydroxide filler comprises 5% to 55% by weight of the thermally conductive, electrically insulating film.

[0012] According to the first aspect described above, the thermally conductive metal oxide or hydroxide filler comprises 20% to 50% by weight of the thermally conductive, electrically insulating film.

[0013] According to the first aspect above, the thermally conductive metal oxide or hydroxide filler comprises one or more fillers selected from magnesium oxide, zinc oxide, aluminum oxide, magnesium hydroxide, and aluminum hydroxide.

[0014] According to the first embodiment above, the thermally conductive metal oxide or hydroxide filler is particulate.

[0015] According to the first aspect described above, the thermally conductive ceramic filler comprises 2% to 50% by weight of the thermally conductive, electrically insulating film.

[0016] According to the first aspect described above, the thermally conductive ceramic filler comprises 5% to 40% by weight of the thermally conductive, electrically insulating film.

[0017] According to the first aspect described above, the thermally conductive ceramic filler includes one or more fillers selected from boron nitride, silicon carbide, and aluminum nitride.

[0018] According to the first embodiment described above, the thermally conductive ceramic filler is flake-like or spherical.

[0019] According to the first embodiment described above, the thermoplastic resin is a polypropylene resin.

[0020] According to the first aspect described above, the thermally conductive, electrically insulating film further comprises a flame retardant that accounts for 10% to 45% of the weight of the thermally conductive, electrically insulating film.

[0021] According to the first aspect mentioned above, the flame retardant is at least one compound selected from phosphorus / nitrogen-containing flame retardants, phosphorus / nitrogen / silicon-containing flame retardants, and brominated flame retardants.

[0022] In a second aspect, the present application provides a battery pack comprising: a battery pack housing having a bottom wall and a side wall; a battery pack module disposed inside the battery pack housing; and a thermally conductive, electrically insulating film disposed between the battery pack module and at least one of the bottom wall and the side wall of the battery pack housing, the thermally conductive, electrically insulating film being the thermally conductive, electrically insulating film of the first aspect. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic structural diagram of one embodiment of a battery pack having a thermally conductive and electrically insulating film according to the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Various embodiments of the present application are described below with reference to the accompanying drawings, which form a part of this specification. While directional terms such as "front", "rear", "upper", "lower", "left", "right", "top", "bottom", "inner", "outer", and the like are used herein to indicate various exemplary structural parts and elements of the present application, it should be understood that these terms are used herein for convenience of description and are determined based on the exemplary directions shown in the accompanying drawings. Since the embodiments disclosed herein may be disposed in different orientations, these directional terms are intended for illustrative purposes and should not be construed as limiting.

[0025] In this application, unless otherwise specified, all devices and materials are commercially available or commonly used in the art. Unless otherwise specified, the methods referred to in the following embodiments are common methods in the art.

[0026] The thermally conductive, electrically insulating film of the present application comprises a thermoplastic resin and a thermally conductive filler. The thermoplastic resin accounts for 15% to 50% of the total weight of the thermally conductive, electrically insulating film, and the thermally conductive filler accounts for 40% to 70% of the total weight of the thermally conductive, electrically insulating film. In some embodiments, the thermoplastic resin accounts for 17.5% to 32.5% of the total weight of the thermally conductive, electrically insulating film. In some embodiments, the thermally conductive filler accounts for 40% to 65% of the total weight of the thermally conductive, electrically insulating film. Here, the thermally conductive filler includes three types: a thermally conductive carbon-based filler, a thermally conductive metal oxide or hydroxide filler, and a thermally conductive ceramic filler.

[0027] The thermoplastic resin is a polypropylene resin. Here, the polypropylene resin is a homopolymer or copolymer polypropylene having a melt flow index of 0.1 g / 10 min to 100 g / 10 min (230° C., 2.16 kg). In other embodiments, other thermoplastic resins such as polyethylene, polyvinyl chloride, polycarbonate, etc. can be used.

[0028] The thermally conductive carbon-based filler is one or more fillers selected from graphite, carbon nanotubes, and graphene. Here, the graphite is at least one graphite selected from flake graphite and expanded graphite. The graphite has a particle size in the range of 10 nm to 200 μm, the carbon nanotube has a diameter in the range of 2 nm to 200 nm, and the graphene has a diameter-to-thickness ratio in the range of 500 to 8000. In some embodiments, the thermally conductive carbon-based filler is flake graphite. The addition of the thermally conductive carbon-based filler imparts excellent thermal conductivity to the thermally conductive electrical insulating film. However, since the thermally conductive carbon-based filler has electrical conductivity properties, it is generally not considered to add the thermally conductive carbon-based filler to products that require insulation. Surprisingly, the inventors of the present application have found that by controlling the amount of the thermally conductive carbon-based filler to 2% to 15% of the total weight of the thermally conductive, electrically insulating film, the thermally conductive, electrically insulating film can have excellent thermal conductivity and good electrical insulation performance. In some embodiments, the thermally conductive carbon-based filler accounts for 10% to 15% of the total weight of the thermally conductive, electrically insulating film.

[0029] The thermally conductive metal oxide or hydroxide filler comprises 5% to 55% of the total weight of the thermally conductive, electrically insulating film. In some embodiments, the thermally conductive metal oxide or hydroxide filler comprises 20% to 50% of the total weight of the thermally conductive, electrically insulating film. The thermally conductive metal oxide or hydroxide filler comprises one or more fillers selected from magnesium oxide, zinc oxide, aluminum oxide, magnesium hydroxide, and aluminum hydroxide. The thermally conductive metal oxide or hydroxide filler is particulate.

[0030] The thermally conductive ceramic filler comprises 2% to 50% of the total weight of the thermally conductive electrically insulating film. In some embodiments, the thermally conductive ceramic filler comprises 5% to 40% of the total weight of the thermally conductive electrically insulating film. The thermally conductive ceramic filler is one or more fillers selected from boron nitride, silicon carbide, and aluminum nitride. The thermally conductive ceramic filler is flake-shaped or spherical. The thermally conductive ceramic filler has excellent thermal conductivity, and therefore provides excellent thermal conductivity to the thermally conductive electrically insulating film of the present application.

[0031] In some embodiments, depending on the flame retardancy requirements, the thermally conductive, electrically insulating film further comprises a flame retardant that comprises 10%-45% of the total weight of the thermally conductive, electrically insulating film. In some embodiments, the flame retardant comprises 10%-26% of the total weight of the thermally conductive, electrically insulating film. In some embodiments, the flame retardant is at least one compound selected from phosphorus / nitrogen-containing flame retardants, phosphorus / nitrogen / silicon-containing flame retardants, and brominated flame retardants. In some embodiments, the flame retardant further comprises a supplemental flame retardant, the supplemental flame retardant being one or more compounds selected from antimony trioxide and borates. The thermally conductive, electrically insulating film of the present application is 10 12 It has a surface resistivity of Ω·m or less.

[0032] In some embodiments, the thermally conductive, electrically insulating film optionally further comprises one or more of the following compounds, expressed as weight percent based on the total weight of the thermally conductive, electrically insulating film: 0%-10% toughening agent, 0%-5% compatibilizer, 0.1%-1% lubricant, 0%-1.5% antioxidant, and 0%-2% toner. In some embodiments, the compatibilizer comprises 0%-3% of the total weight of the thermally conductive, electrically insulating film. In some embodiments, the lubricant comprises 0.2%-0.5% of the total weight of the thermally conductive, electrically insulating film. The toughening agent includes one or more compounds selected from propylene-based elastomers, styrene-based elastomers (such as hydrogenated poly(styrene-b-isoprene), hydrogenated poly(styrene-b-butadiene-b-styrene), hydrogenated poly(styrene-b-isoprene-b-styrene), and hydrogenated poly(styrene-b-isoprene / butadiene-b-styrene), copolymerized polyolefin elastomers (such as ethene-octene copolymers, ethene-butene copolymers, and ethene-hexene copolymers), and polyethylene. The compatibilizer includes one or more compounds selected from alkylsilane coupling agents, maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyolefin elastomers (POE). The lubricant includes one or more compounds selected from silicon-based lubricants, amide-based lubricants, stearic acid-based lubricants, and polytetrafluoroethylene. The antioxidant includes one or more compounds selected from hindered phenol-based antioxidants, phosphite-based antioxidants, and sulfur-containing antioxidants. As described above, the thermally conductive carbon-based filler, the thermally conductive granular metal oxide or hydroxide filler, and the thermally conductive flake-shaped ceramic filler used in the thermally conductive electrically insulating film of the present application have excellent thermal conductivity performance, so that the thermally conductive electrically insulating film of the present application also has excellent thermal conductivity performance.

[0033] In addition, the thermal conductivity performance of the thermally conductive electrical insulating film of the present application is further improved by the synergistic effect of the three thermally conductive fillers used in the thermally conductive electrical insulating film of the present application. Specifically, the inventors of the present application have found that the thermally conductive flaky ceramic filler can connect the thermally conductive carbon-based filler with the thermally conductive granular metal oxide or hydroxide filler to form a thermally conductive channel inside the thermally conductive electrical insulating film, thereby further improving the thermal conductivity performance of the thermally conductive electrical insulating film. The thermally conductive spherical ceramic filler is formed by controlling the crystal growth direction of the thermally conductive flaky ceramic filler. Since the thermally conductive spherical ceramic filler is obtained from the thermally conductive flaky ceramic filler, the thermally conductive spherical ceramic filler exhibits the aforementioned advantages of the thermally conductive flaky ceramic filler. In addition, since the thermally conductive spherical ceramic filler is isotropic, the thermally conductive spherical ceramic filler also promotes heat conduction along the flaky surface to further improve the thermal conductivity performance of the thermally conductive electrical insulating film.

[0034] Furthermore, the selection of the thermally conductive filler of the present application ensures that the thermally conductive, electrically insulating film has excellent thermal conductivity performance even when a reduced amount of thermally conductive filler is used. The thermal conductivity of the thermally conductive, electrically insulating film of the present application reaches 1 W / m K to 1.46 W / m K.

[0035] Furthermore, the thermally conductive, electrically insulating film of the present application has excellent thermal conductivity performance, and since it contains a reduced amount of thermally conductive filler, the thermally conductive, electrically insulating film of the present application has improved mechanical properties. The inventors of the present application have found that in order to prepare a film with excellent thermal conductivity performance using a thermoplastic resin, a large amount of thermally conductive filler is required. The more the amount of thermally conductive filler used and the less the amount of thermoplastic resin used, the worse the mechanical properties of the thermally conductive, electrically insulating film. Through the selection of the thermally conductive filler, a reduced amount of thermally conductive filler can be used in the thermally conductive, electrically insulating film of the present application, thereby increasing the proportion of the thermoplastic resin in the thermally conductive, electrically insulating film. Therefore, the thermally conductive, electrically insulating film of the present application has improved mechanical properties, and in particular, exhibits excellent tensile elongation and breaking elongation. The improved mechanical properties of the present thermally conductive, electrically insulating films allow the present thermally conductive, electrically insulating films to withstand failure during packaging, shipping (e.g., when wound into rolls for storage and shipping), and final forming by electronic product and device manufacturers (e.g., when folded, cut, and formed for use in electronic products and devices). For example, the present thermally conductive, electrically insulating films have excellent tenacity, such that the present thermally conductive, electrically insulating films can be folded five times during forming without any damage.

[0036] Due to the excellent heat conduction performance of the thermally conductive and electrically insulating film of the present application, when the thermally conductive and electrically insulating film of the present application is used in an electronic product or device, the thermally conductive and electrically insulating film can be directly laminated to the electronic product or device without the need to apply a thermally conductive adhesive. Therefore, the thermally conductive and electrically insulating film of the present application is convenient to use, saves costs, and helps to reduce the weight and size of electronic products and devices.

[0037] In addition, the thermally conductive, electrically insulating film of the present application can be manufactured by a common casting film process, and therefore the manufacturing process is simple.

[0038] The beneficial effects of the thermally conductive, electrically insulating films of the present application are described below with reference to specific example thermally conductive, electrically insulating film samples and comparative example film samples. Table 1 shows the contents of various components of the example and comparative example film samples of the present application, and Table 2 shows performance data for the example and comparative example film samples.

[0039] The film samples of the examples and comparative examples in Table 1 were prepared in the following manner. The raw materials of the various components were weighed according to the content of the components in Table 1, charged into a high-speed mixer, and mixed for 3 minutes at a rotation speed of 2000 rpm. The mixed raw materials were charged into a twin-screw extruder, extruded, cooled, and granulated. The temperature of the twin-screw extruder was set to 180°C to 230°C, and the rotation speed of the screw was set to 300 rpm. The obtained granular material was dried, extruded into a film, and cut into standard test pieces for performance testing. Samples for thermal conductivity testing were compression molded at 220°C using a flat panel vulcanizer.

[0040] [Table 1]

[0041] In Table 1, the PP resin is a copolymerized polypropylene resin having a melting point of about 160°C, the toughening agent is an ethene-octene copolymer, the compatibilizer is an alkyl silane coupling agent, the flame retardant is a phenyl ether brominated flame retardant, the graphite is surface-alkylated flake graphite having a particle size of 1 μm to 50 μm, the aluminum oxide is surface-alkylated spherical aluminum oxide having a particle size of 5 μm to 20 μm, the magnesium oxide is spherical magnesium oxide having a particle size of 5 μm to 30 μm, the boron nitride is flake boron nitride, the antioxidant is a hindered phenol-based stabilizer, and the lubricant is a stearate.

[0042] [Table 2]

[0043] From the above Tables 1 and 2, it can be seen that the amount of thermally conductive filler added to the comparative film was 60%, the amount of PP resin was 18.3%, and the thermally conductive material only contained magnesium oxide, and the thermal conductivity of the comparative film was up to 0.94 W / m·K, but its tensile yield strength was only 16.3 MPa and its breaking elongation was only 9.2%, which indicates that the comparative film met the requirements of thermal conductivity, but its mechanical properties were insufficient.

[0044] In various examples of the present application, the thermal conductivity of the film was maintained at a level almost equal to or higher than that of the comparative example by using three types of thermally conductive filler. As the content of the thermally conductive filler increased, the thermal conductivity of the film also increased accordingly. In Examples 1, 2, 4, 5, 7, and 8, the amount of thermally conductive filler used was less than that of the comparative example, but the thermal conductivity performance was equal to or higher than that of the comparative example. In Examples 3 and 6, which used a large amount of thermally conductive filler (64.6% in Example 3 and 62% in Example 6), the thermal conductivity of the film was even higher.

[0045] On the other hand, since the amount of thermally conductive filler in the examples was less than that in the comparative examples, a larger amount of PP resin could be used in the films of the examples. As shown in Table 2, as the amount of PP resin increased, the mechanical properties of the films of the examples improved. For example, the tensile yield strength and breaking elongation were obviously better than those of the comparative examples, indicating that the films of the examples showed better toughness. Even in Example 3, in which the amount of PP resin was less than that of the comparative examples, the film showed slightly better mechanical properties than the comparative examples by adding a toughening agent and a compatibilizer.

[0046] Also, as shown in Table 2, although flake graphite was used as a thermally conductive additive, the thermally conductive, electrically insulating film of the embodiment still exhibited electrical insulation performance equivalent to that of the comparative example. In addition, the thermally conductive, electrically insulating film of the present application exhibited better flame retardant performance and voltage breakdown performance than the comparative example. As shown in Table 2, the thermally conductive, electrically insulating film of the present application provided better overall performance than the comparative example film, and its film weight per unit volume was also lighter, which met the development trend toward miniaturization and weight reduction in electronic products and devices.

[0047] The thermally conductive, electrically insulating films of the present application can be used in various electronic products and devices to help dissipate heat from the electronic products and devices. Such electronic products or devices can be battery packs, notebook computers, and power adapters for computers.

[0048] FIG. 1 is a schematic structural diagram of one embodiment of a battery pack with a thermally conductive and electrically insulating film of the present application, and only a partially exploded structure of the battery pack is shown to better show the location of the thermally conductive and electrically insulating film. As shown in FIG. 1, the battery pack 100 includes a battery pack module 120 including a plurality of battery units 101, and a battery pack housing 110. The battery pack housing 110 includes a top wall (not shown) and a bottom wall 105 arranged opposite to each other, and four side walls 106 surrounding and connecting the top wall and the bottom wall 105. The battery pack module 120 is accommodated in a housing cavity 108 defined by the top wall, the bottom wall 105, and the side walls 106. Each battery unit 101 has an individual connection terminal 103. The individual connection terminals 103 of the battery units 101 are electrically connected according to a predetermined circuit, and the battery units can be powered and / or charged through a main connection terminal (not shown) on the battery pack housing 110.

[0049] The thermally conductive and electrically insulating film 112 is disposed between the battery pack module 120 and the bottom wall 105 of the battery pack housing 110. Through the thermally conductive and electrically insulating film 112, thermal energy generated from the battery pack module 120 during operation can be dissipated in a timely manner to the external environment through the bottom wall 105 of the battery pack housing 110, instead of accumulating in the housing cavity 108 of the battery pack housing 110.

[0050] It should be noted that in the embodiment shown in FIG. 1 , the thermally conductive electrically insulating film 112 is disposed between the battery pack module 120 and the bottom wall 105 of the battery pack housing 110, but it can also be disposed between the battery pack module 120 and the side wall 106 of the battery pack housing 110 based on the actual needs of space design and heat dissipation.

[0051] Finally, the thermally conductive, electrically insulating film of the present application has a variety of beneficial technical effects, at least some of which are listed below.

[0052] 1. Excellent thermal conductivity performance, meet the requirements of heat conduction and heat dissipation of electronic products and devices.

[0053] 2.Excellent mechanical properties ensure it will not break during transportation, packaging, and processing by manufacturers of electronic products and devices.

[0054] 3. Excellent electrical insulation performance, meets the insulation requirements of electronic products and devices.

[0055] 4. The manufacturing process is simple.

[0056] 5. It is convenient to use, and helps to save costs and reduce the weight and size of electronic products and devices.

[0057] 6. Its film weight per unit volume is also lighter, which meets the development trend of miniaturization and light weight in electronic products and devices.

[0058] Although the present application will be described with reference to specific embodiments illustrated in the accompanying drawings, it should be understood that certain modifications can be made to the thermally conductive, electrically insulating film of the present application without departing from the spirit, scope, and context of the teachings of the present application. Those skilled in the art will recognize that different methods for modifying the structure of the embodiments disclosed herein fall within the spirit and scope of the present application and the claims.

Claims

1. A thermally conductive electrical insulating film comprising: a thermoplastic resin accounting for 15% to 50% of the weight of the thermally conductive electrical insulating film; a thermally conductive filler accounting for 40% to 70% of the weight of the thermally conductive electrical insulating film; and the thermally conductive filler includes a thermally conductive carbon-based filler, a thermally conductive metal oxide or hydroxide filler, and a thermally conductive ceramic filler, the thermally conductive electrical insulating film.

2. A battery pack comprising a battery pack housing having a bottom wall and side walls; a battery pack module disposed inside the battery pack housing; and a thermally conductive electrical insulating film disposed between the battery pack module and at least one of the bottom wall and the side walls of the battery pack housing; and the thermally conductive electrical insulating film is the thermally conductive electrical insulating film according to Claim 1, the battery pack.

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