Packaging film, electrochemical device and electronic device

Abstract

A packaging film (100) comprises a protective layer (20), a first adhesive layer (30), a metal layer (40), a second adhesive layer (50) and a sealing layer (60) stacked in sequence, wherein the protective layer (20) comprises a polymer resin layer (21) and a carbon material (22). An electrochemical device (200) and an electronic device (300) are also provided.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a packaging film, an electrochemical device and an electronic device. Background Art

[0002] Since the theoretical lithium-embedded capacity of silicon is as high as 4200mAh / g and its reserves on Earth are very abundant, it has great application prospects in lithium-ion batteries. However, silicon particles will undergo a large volume expansion during the cycle, which will cause the silicon particles to pulverize and reduce the adhesion between the active material layer in the negative electrode sheet and the current collector, causing the active material layer to fall off, thereby reducing the cycle performance of lithium-ion batteries.

[0003] Especially for soft-pack batteries, the packaging film cannot suppress the expansion of silicon particles. When the volume of silicon particles expands, it not only affects the cycle performance of the battery, but also the sealing edge of the packaging film is easily broken, resulting in the risk of leakage. Summary of the invention

[0004] In order to solve the above shortcomings of the prior art, it is necessary to provide a packaging film that can inhibit the expansion of silicon particles.

[0005] In addition, it is also necessary to provide an electrochemical device comprising the above packaging film.

[0006] In addition, it is also necessary to provide an electronic device including the above electrochemical device.

[0007] The present application provides a packaging film, comprising a protective layer, a first adhesive layer, a metal layer, a second adhesive layer and a sealing layer stacked in sequence.

[0008] The present application adds carbon material to the packaging film, and the carbon material can play the role of a skeleton in the packaging film, which can enhance the mechanical properties of the packaging film and help reduce the overall thickness of the packaging film. When the above packaging film is used in an electrochemical device, the energy density of the electrochemical device can be improved, and because the mechanical properties of the packaging film are enhanced, the volume expansion of the electrode assembly in the electrochemical device can be suppressed and the deformation of the electrode assembly can be improved.

[0009] In some embodiments of the present application, the polymer resin layer and the carbon material satisfy at least one of the following relationships: the carbon material is located in the polymer resin layer or on at least one surface of the polymer resin layer.

[0010] In some embodiments of the present application, the mass ratio of the carbon material in the protective layer is 5% to 50%. When the mass ratio of the carbon material in the protective layer is too high, the protective layer cannot effectively prevent air penetration; when the mass ratio of the carbon material in the protective layer is too low, it cannot enhance the mechanical properties of the packaging film and inhibit the volume expansion of the electrode assembly.

[0011] In some embodiments of the present application, the carbon material includes at least one of carbon nanotubes and carbon fibers. Carbon nanotubes and carbon fibers have high tensile strength, elastic modulus, oxidation resistance, wear resistance and low thermal expansion coefficient, which are beneficial to further enhance the mechanical properties of the packaging film.

[0012] In some embodiments of the present application, the carbon material includes carbon fibers, the carbon fibers are interconnected and woven to form a carbon layer, and the carbon layer is located between the polymer resin layer and the first bonding layer. The carbon layer structure obtained by weaving the carbon fibers together is denser, and compared with the structure in which the carbon fibers are filled in the polymer resin layer, the carbon layer can more effectively prevent sharp objects from piercing, thereby further improving the needle puncture strength of the packaging film.

[0013] In some embodiments of the present application, the thickness of the carbon layer is 2 μm to 5 μm.

[0014] In some embodiments of the present application, the carbon nanotubes include at least one of multi-walled carbon nanotubes and single-walled carbon nanotubes.

[0015] In some embodiments of the present application, the thickness of the protective layer is 7 μm to 16 μm.

[0016] In some embodiments of the present application, the polymer resin includes at least one of nylon or polyethylene terephthalate.

[0017] In some embodiments of the present application, the packaging film further includes a matte layer, the protective layer is located between the matte layer and the first bonding layer, and the thickness of the matte layer is 2 μm to 5 μm.

[0018] In some embodiments of the present application, the thickness of the metal layer is 24 μm to 35 μm, and the thickness of the sealing layer is 24 μm to 35 μm.

[0019] In some embodiments of the present application, the sealing layer includes polypropylene.

[0020] The present application also provides an electrochemical device, including an electrode assembly. The electrochemical device also includes a packaging film as described above, which is used to package the electrode assembly. Among them, the packaging film can improve the energy density of the electrochemical device on the one hand, and because the mechanical properties of the packaging film are enhanced, it can suppress the volume expansion of the electrode assembly in the electrochemical device and improve the deformation of the electrode assembly; on the other hand, because the carbon material has a high thermal conductivity, it can conduct heat inside the electrochemical device and improve safety.

[0021] In some embodiments of the present application, the electrode assembly includes a positive electrode sheet, a separator and a negative electrode sheet, the separator is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet, the separator and the negative electrode sheet are stacked or wound to form the electrode assembly, and the negative electrode sheet includes a silicon-based material.

[0022] In some embodiments of the present application, the silicon-based material includes at least one of silicon, silicon monoxide, a silicon-carbon composite material, or a composite material of silicon monoxide and carbon.

[0023] The present application also provides an electronic device, comprising the above electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic cross-sectional view of a packaging film provided in accordance with one embodiment of the present application.

[0025] Figure 2 A schematic cross-sectional view of a packaging film provided in another embodiment of the present application.

[0026] Figure 3 for Figure 2 A top view of the carbon layer of the encapsulation film is shown.

[0027] Figure 4 A schematic structural diagram of an electrochemical device provided in one embodiment of the present application.

[0028] Figure 5 A schematic diagram of the structure of an electronic device provided in one embodiment of the present application.

[0029] Main component symbols

[0030] Matte layer 10

[0031] Protective layer 20

[0032] Polymer resin layer 21

[0033] Carbon material 22

[0034] The first adhesive layer 30

[0035] Metal layer 40

[0036] Second adhesive layer 50

[0037] Sealing layer 60

[0038] Packaging film 100

[0039] Electrochemical device 200

[0040] Electrode assembly 201

[0041] Carbon layer 220

[0042] Electronic device 300

[0043] Isolation Film 2011

[0044] Negative plate 2012

[0045] Positive electrode 2013

[0046] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0047] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth to facilitate a full understanding of the present application, and the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes all and any combination of one or more related listed items.

[0049] In the embodiments of the present application, for the convenience of description and not to limit the present application, the term "connection" used in the patent application specification and claims of the present application is not limited to physical or mechanical connection, whether direct or indirect. "Up", "down", "above", "below", "left", "right", etc. are only used to indicate relative position relationship. When the absolute position of the described object changes, the relative position relationship also changes accordingly.

[0050] See also Figure 1 and Figure 2 In one embodiment of the present application, a packaging film 100 is provided, comprising a protective layer 20 , a first bonding layer 30 , a metal layer 40 , a second bonding layer 50 and a sealing layer 60 stacked in sequence, wherein the protective layer 20 comprises a polymer resin layer 21 and a carbon material 22 .

[0051] Among them, the polymer resin layer 21 is used to protect the metal layer 40 in the packaging film 100, prevent the metal layer 40 from being damaged by external forces, and at the same time prevent air from penetrating from the external environment, maintaining the inside of the electrochemical device in a water-free and oxygen-free environment. The metal layer 40 is used to prevent moisture from penetrating from the external environment and prevent external forces from damaging the electrochemical device. In one embodiment, the metal layer 40 can specifically be an aluminum foil layer. The sealing layer 60 is used to encapsulate the packaging film 100 to prevent the packaging film 100 from being dissolved or swollen by the organic solvent inside the electrochemical device. The sealing layer 60 is also used to prevent the electrolyte inside the electrochemical device from contacting the metal layer 40 and causing the metal layer 40 to be corroded. The first bonding layer 30 is used to bond the protective layer 20 and the metal layer 40, and the second bonding layer 50 is used to bond the metal layer 40 and the sealing layer 60, thereby preventing the adjacent two layers from falling off.

[0052] The polymer resin layer 21 and the carbon material 22 satisfy at least one of the following relationships: the carbon material 22 is located in the polymer resin layer 21 (see Figure 1 ) or located on at least one surface of the polymer resin layer 21 (refer to Figure 2 ). The carbon material 22 is located on at least one surface of the polymer resin layer 21. The carbon material 22 may be located between the polymer resin layer 21 and the first bonding layer 30, or located on the surface of the polymer resin layer 21 away from the first bonding layer 30, or a combination of the two. Further, the carbon material 22 may be located on the entire surface of the polymer resin layer 21, or only on a portion of the surface of the polymer resin layer 21.

[0053] like Figure 2 As shown, the carbon material 22 is located between the polymer resin layer 21 and the first bonding layer 30. Moreover, the carbon materials 22 are woven together to form a carbon layer 220 having a network structure.

[0054] The present application adds carbon material 22 to the packaging film 100. The carbon material 22 can play the role of a skeleton in the packaging film 100, can enhance the mechanical properties (such as tensile strength and puncture strength) of the packaging film 100, and is conducive to reducing the overall thickness of the packaging film 100. When the above packaging film 100 is used in an electrochemical device, on the one hand, it can improve the energy density of the electrochemical device, and because the mechanical properties of the packaging film 100 are enhanced, it can inhibit the volume expansion of the electrode assembly in the electrochemical device and improve the deformation of the electrode assembly; on the other hand, because the carbon material has a high thermal conductivity, it can conduct heat inside the electrochemical device and improve safety.

[0055] In some embodiments, the carbon material 22 includes at least one of carbon nanotubes and carbon fibers, which have high tensile strength, elastic modulus, oxidation resistance, wear resistance and low thermal expansion coefficient, which are beneficial to further enhance the mechanical properties of the packaging film 100.

[0056] In some embodiments, the mass ratio of the carbon material 22 in the protective layer 20 is 5% to 50%. When the mass ratio of the carbon material 22 in the protective layer 20 is too high, the resin content of the polymer resin layer 21 is relatively low, so that the protective layer 20 cannot effectively prevent air penetration; when the mass ratio of the carbon material 22 in the protective layer 20 is too low, it cannot enhance the mechanical properties of the packaging film 100 and inhibit the volume expansion of the electrode assembly.

[0057] like Figure 1 As shown, in one embodiment, the carbon material 22 is a carbon nanotube, and the carbon nanotube is filled in the polymer resin layer 21. In this way, the mechanical properties of the protective layer 20 can be improved, so that the packaging film 100 can suppress the volume expansion of the electrode assembly and improve the deformation of the electrode assembly. Of course, in other described methods, the carbon material 22 located in the polymer resin layer 21 can also be carbon fiber.

[0058] Furthermore, the thickness of the protective layer 20 is 7 μm to 16 μm. If the protective layer 20 is too thin, it cannot effectively prevent air penetration, and if the protective layer 20 is too thick, the energy density of the electrochemical device will be reduced.

[0059] like Figure 2 and Figure 3 As shown, in another embodiment, the carbon material 22 is a carbon nanotube. The carbon nanotubes are connected to each other along the tube diameter direction to form carbon fibers, and the carbon fibers are woven together to form a carbon layer 220. The carbon layer 220 obtained by weaving carbon fibers made of carbon nanotubes 22 is denser in structure. Compared with the structure in which the carbon nanotubes 22 are filled in the polymer resin layer 21, the carbon layer 220 can more effectively prevent sharp objects from piercing, thereby further improving the puncture strength of the packaging film 100. In some embodiments, the carbon nanotubes include at least one of multi-walled carbon nanotubes and single-walled carbon nanotubes.

[0060] Further, the thickness of the carbon layer 220 is 2 μm to 5 μm, and the thickness of the polymer resin layer 21 is 7 μm to 13 μm. That is, the total thickness of the protective layer 20 is 9 μm to 18 μm.

[0061] In another embodiment, the carbon material 22 may also be carbon fiber, and the carbon fibers are interconnected and woven to form a carbon layer 220. The carbon layer 220 woven from the carbon fibers is denser in structure, and compared with the structure in which the carbon nanotubes 22 are filled in the polymer resin layer 21, the carbon layer 220 can also more effectively prevent sharp objects from piercing, thereby further improving the puncture strength of the packaging film 100.

[0062] In some embodiments, the material of the polymer resin layer 21 includes at least one of nylon or polyethylene terephthalate. The sealing layer 60 includes polypropylene, and further, the sealing layer 60 can be a polypropylene cast film, that is, a polypropylene film produced by a casting process. The bonding material used in the first bonding layer 30 and the second bonding layer 50 includes at least one of acrylic resin, epoxy resin or polyurethane.

[0063] In some embodiments, the packaging film 100 further includes a matte layer 10 , the protective layer 20 is located between the matte layer 10 and the first adhesive layer 30 , and the matte layer 10 has a thickness of 2 μm to 5 μm.

[0064] Moreover, the thickness of the metal layer 40 is 24 μm to 35 μm. If the metal layer 40 is too thin, the strength is insufficient; and if the metal layer 40 is too thick, the overall weight of the electrochemical device will be increased.

[0065] The thickness of the sealing layer 60 is 24 μm to 35 μm. If the sealing layer 60 is too thin, it cannot effectively protect the metal layer 40 ; while if the sealing layer 60 is too thick, it will affect the heat dissipation effect and the punching effect of the packaging film 100 .

[0066] See also Figure 4 , one embodiment of the present application also provides an electrochemical device 200. The electrochemical device 200 includes an electrode assembly 201 and a packaging film 100. The packaging film 100 is used to encapsulate the electrode assembly 201. Among them, the electrochemical device 200 of the present application includes all devices that can undergo electrochemical reactions. Specifically, the electrochemical device 200 includes all kinds of primary batteries, secondary batteries, fuel cells, solar cells and capacitors (such as supercapacitors). Optionally, the electrochemical device 200 can be a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery and a lithium ion polymer secondary battery.

[0067] In one embodiment, the electrode assembly 201 includes a positive electrode sheet 2013, a separator 2011 and a negative electrode sheet 2012, wherein the separator 2011 is located between the positive electrode sheet 2013 and the negative electrode sheet 2012, and the positive electrode sheet 2013, the separator 2011 and the negative electrode sheet 2012 are stacked or wound to form the electrode assembly 201. The negative electrode sheet 2012 includes a silicon-based material.

[0068] Further, the silicon-based material may include at least one of silicon, silicon monoxide, a silicon-carbon composite material, or a composite material of silicon monoxide and carbon.

[0069] See also Figure 5In one embodiment of the present application, an electronic device 300 is provided. The electronic device 300 includes an electrochemical device 200. The electronic device 300 may be a consumer electronic product (such as a mobile communication device, a tablet computer, a laptop computer, etc.), an electric tool, a drone, an energy storage device, a power device, etc. Figure 5 In one embodiment, the electronic device 300 is an electric car.

[0070] The present application is described below through specific examples and comparative examples.

[0071] Example 1

[0072] Preparation of negative electrode sheet: The negative electrode active materials including silicon-based materials and graphite, conductive carbon black and styrene-butadiene rubber (SBR) are dissolved in deionized water at a mass ratio of 95:1.2:1.0:3.8, and stirred under vacuum conditions until the system is uniform to obtain negative electrode slurry. Copper foil is used as the negative electrode current collector, and the negative electrode slurry is coated on both surfaces of the negative electrode current collector. After drying at 80-90°C, it is cold pressed, trimmed, cut, and striped, and then vacuum dried at 110°C for 4 hours to obtain the negative electrode sheet. Among them, the mass proportion of silicon-based materials in the negative electrode sheet is 15%.

[0073] Preparation of positive electrode sheet: The positive electrode active material lithium cobalt oxide (LiCoO2), conductive carbon black and polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone (NMP) solvent at a mass ratio of 96.7:1.7:1.6, and stirred under vacuum conditions until the system is uniform to obtain positive electrode slurry. Aluminum foil is used as the positive electrode current collector, and the positive electrode slurry is coated on the positive electrode current collector. After drying at 85°C, it is cold pressed, trimmed, cut, and striped, and then vacuum dried at 85°C for 4 hours to obtain a positive electrode sheet.

[0074] Preparation of packaging film: Add carbon nanotubes to polymer resin to obtain a protective layer. Then stack a matte layer, a protective layer, a first bonding layer, an aluminum foil layer, a second bonding layer and a sealing layer in sequence to obtain a packaging film. Among them, the carbon nanotubes account for 10% of the mass of the protective layer. The thickness of the protective layer is 12μm, and the total thickness of the packaging film is 67μm.

[0075] Preparation of lithium-ion soft-pack batteries: Use a polyethylene film as a separator, place it between the positive electrode and the negative electrode, and wind it to obtain an electrode assembly. The electrode assembly is loaded into the above-mentioned packaging film and vacuum-baked at 75°C for 10 hours, the electrolyte is injected, and then vacuum-packaged. The packaged electrode assembly is left to stand for 24 hours and then activated, wherein the activation treatment is first charged to 4.2V at a constant current of 0.1C, then charged at a constant voltage of 0.05C at 4.2V, and then discharged to 3.0V at a constant current of 0.1C, repeated 2 charge and discharge cycles, and finally charged at a constant current of 0.1C, the charging voltage is 3.8V, the activation process is completed, and a soft-pack battery is obtained.

[0076] Example 2

[0077] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Example 2 are the same as those of Example 1 and are not described here.

[0078] The preparation of the encapsulation film is different from that of Example 1 in that the carbon nanotubes account for 20% of the mass of the protective layer.

[0079] Example 3

[0080] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Example 3 are the same as those of Example 1 and are not described here.

[0081] The preparation of the encapsulation film is different from that of Example 1 in that the carbon nanotubes account for 30% of the mass of the protective layer.

[0082] Example 4

[0083] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Example 4 are the same as those of Example 1 and are not described here.

[0084] The preparation of the encapsulation film is different from that of Example 1 in that the carbon nanotubes account for 40% of the mass of the protective layer.

[0085] Example 5

[0086] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Example 5 are the same as those of Example 1 and are not described here.

[0087] The preparation of the encapsulation film is different from that of Example 1 in that the carbon nanotubes account for 50% of the mass of the protective layer.

[0088] Example 6

[0089] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Example 6 are the same as those of Example 1 and are not described here.

[0090] Preparation of packaging film: Carbon nanotubes are connected to each other along the tube diameter direction to form carbon fibers, and the carbon fibers are woven together to form a carbon layer. Then, a matte layer, a polymer resin layer, a carbon layer, a first bonding layer, an aluminum foil layer, a second bonding layer and a sealing layer are stacked in sequence to obtain a packaging film. Among them, the carbon nanotubes account for 30% of the total mass of the protective layer (the protective layer includes a polymer resin layer and a carbon mesh layer). The thickness of the carbon layer is 3μm, and the thickness of the polymer resin layer is 9μm.

[0091] Example 7

[0092] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Example 7 are the same as those of Example 6 and are not repeated here.

[0093] The preparation of the encapsulation film is different from that of Example 6 in that the carbon nanotubes account for 50% of the mass of the protective layer, the thickness of the carbon layer is 5 μm, and the thickness of the polymer resin layer is 7 μm.

[0094] Example 8

[0095] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Example 8 are the same as those of Example 1 and are not described here.

[0096] The preparation of the encapsulation film is different from that of Example 1 in that the carbon nanotubes account for 30% of the mass of the protective layer, the thickness of the protective layer is 10 μm, and the total thickness of the encapsulation film is 65 μm.

[0097] Example 9

[0098] The preparation steps of the positive electrode sheet and the lithium-ion soft-pack battery of Example 9 are the same as those of Example 8 and are not described here.

[0099] The preparation of the negative electrode sheet is different from that of Example 8 in that the mass proportion of the silicon-based material in the negative electrode sheet is 20%.

[0100] The preparation of the encapsulation film is different from that of Example 8 in that the carbon nanotubes account for 10% of the mass of the protective layer, the thickness of the protective layer is 10 μm, and the total thickness of the encapsulation film is 67 μm.

[0101] Example 10

[0102] The preparation steps of the positive electrode sheet and the lithium-ion soft-pack battery of Example 10 are the same as those of Example 8 and are not described here.

[0103] The preparation of the negative electrode sheet is different from that of Example 8 in that the mass proportion of the silicon-based material in the negative electrode sheet is 25%.

[0104] The preparation of the encapsulation film is different from that of Example 8 in that the carbon nanotubes account for 16% of the mass of the protective layer, the thickness of the protective layer is 10 μm, and the total thickness of the encapsulation film is 67 μm.

[0105] Embodiment 11

[0106] The preparation steps of the positive electrode sheet and the lithium-ion soft-pack battery of Example 11 are the same as those of Example 8 and are not repeated here.

[0107] The preparation of the negative electrode sheet is different from that of Example 8 in that the mass proportion of the silicon-based material in the negative electrode sheet is 25%.

[0108] Preparation of packaging film: Carbon nanotubes are connected to each other along the tube diameter direction to form carbon fibers, and the carbon fibers are woven together to form a carbon layer. Then, a matte layer, a polymer resin layer, a carbon layer, a first bonding layer, an aluminum foil layer, a second bonding layer and a sealing layer are stacked in sequence to obtain a packaging film. Among them, the carbon nanotubes account for 16% of the mass of the protective layer. The thickness of the carbon layer is 5μm, the thickness of the polymer resin layer is 7μm, and the total thickness of the packaging film is 67μm.

[0109] Example 12

[0110] The preparation steps of the positive electrode sheet and the lithium-ion soft-pack battery of Example 12 are the same as those of Example 8 and are not repeated here.

[0111] The preparation of the negative electrode sheet is different from that of Example 8 in that the mass proportion of the silicon-based material in the negative electrode sheet is 25%.

[0112] The preparation of the encapsulation film is different from that of Example 8 in that the carbon nanotubes account for 27% of the mass of the protective layer, the thickness of the protective layer is 10 μm, and the total thickness of the encapsulation film is 67 μm.

[0113] Comparative Example 1

[0114] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Comparative Example 1 are the same as those of Example 1, which will not be repeated here.

[0115] The preparation of the encapsulation film is different from that of Example 1 in that no carbon nanotubes are added to the encapsulation film, the thickness of the protective layer is 10 μm, and the total thickness of the encapsulation film is 67 μm.

[0116] Comparative Example 2

[0117] The preparation steps of the negative electrode sheet, the positive electrode sheet and the lithium-ion soft-pack battery of Comparative Example 2 are the same as those of Example 1, which will not be repeated here.

[0118] The preparation of the encapsulation film is different from that of Example 1 in that no carbon nanotubes are added to the encapsulation film, the thickness of the protective layer is 10 μm, and the total thickness of the encapsulation film is 65 μm.

[0119] The packaging films prepared in Examples 1-12 and Comparative Examples 1-2 were subjected to a tensile strength test and a needle puncture strength test, and the soft-pack batteries prepared in Examples 1-12 and Comparative Examples 1-2 were subjected to a full charge expansion rate test. The test results are recorded in Table 1.

[0120] The tensile strength test is conducted using a multifunctional tensile testing machine. The test process includes: cutting the packaging film to obtain a sample with a length of 150mm and a width of 15mm, then installing the sample on the two clamps of the tensile testing machine, setting the initial tensile length to 50mm, and conducting the tensile test at a tensile speed of 5mm / min until the sample breaks and stops stretching. The maximum tensile force that the sample withstands when it breaks is recorded, and the ratio of the maximum tensile force to the cross-sectional area of ​​the sample (which can be calculated by multiplying the width and thickness of the sample) is the tensile strength.

[0121] The puncture strength test is carried out using a multifunctional tensile testing machine. The test steps include: using a needle with a spherical radius of 0.5 mm to pierce the packaging film at a speed of 50 mm / min, and reading the value of the tensile testing machine when the needle pierces the packaging film. This data is the puncture strength.

[0122] The test steps for the expansion rate of a fully charged battery include: at 25°C, using a screw micrometer to test the thickness of a fresh battery when it is half charged (50% SOC); when the battery cell is fully charged (100% SOC) after 400 cycles, the thickness of the battery is tested with a screw micrometer at this time, and compared with the thickness of the fresh battery at the initial half charge, the expansion rate of the fully charged (50% SOC) battery can be obtained.

[0123] Table 1

[0124]

[0125]

[0126] From the test results in Table 1, it can be seen that compared with Comparative Examples 1-2, since Examples 1-5 add carbon nanotubes to the polymer resin layer, the expansion of the soft-pack battery is suppressed and the full charge expansion rate is small. Compared with Comparative Examples 1-2, since Examples 6-7 add a carbon layer woven from carbon nanotubes on the surface of the polymer resin layer, the expansion rate of the soft-pack battery is also relatively small. Therefore, whether adding carbon nanotubes to the polymer resin layer (hereinafter referred to as: adding method 1) or adding a carbon layer woven from carbon nanotubes on the surface of the polymer resin layer (hereinafter referred to as: adding method 2), the expansion of the soft-pack battery can be better suppressed.

[0127] Among them, in Examples 1-5, as the carbon nanotube content increases, the tensile strength and puncture strength of the packaging film gradually increase, and the expansion rate of the soft-pack battery shows an overall downward trend. However, when the carbon nanotube content increases to a certain extent (i.e., from 40% to 50%), the improvement in the expansion rate of the soft-pack battery becomes smaller.

[0128] The carbon nanotubes of Example 3 and Example 6 are added in the manner of addition one and the manner of addition two, respectively. Under the premise that the content of carbon nanotubes is the same, the tensile strength and full-fill expansion rate of the two are roughly the same. Similarly, the carbon nanotubes of Example 5 and Example 7 are added in the manner of addition one and the manner of addition two, respectively. Under the premise that the content of carbon nanotubes is the same, the tensile strength and full-fill expansion rate of the two are roughly the same. Therefore, it is shown that different addition methods have little effect on the tensile strength and full-fill expansion rate of the packaging film. However, compared with Example 3, the puncture strength of the packaging film of Example 6 is improved. Similarly, compared with Example 5, the puncture strength of the packaging film of Example 7 is also improved. This is because the puncture strength is improved. This is because the carbon layer is obtained by weaving carbon fibers made of carbon nanotubes together, and the carbon layer structure is denser, which can prevent sharp objects from piercing.

[0129] Compared with Comparative Example 1, since carbon nanotubes are added to the polymer resin layer in Example 8, it is not only possible to suppress the expansion of the battery, but also possible to reduce the overall thickness of the packaging film, which is beneficial to improving the energy density of the battery.

[0130] Compared with Example 9, the silicon-based material content in the negative electrode sheets of Examples 10-12 is increased. Therefore, if the full charge expansion rate needs to be maintained at <10%, whether adding method 1 (i.e., Examples 10 and 12) or adding method 2 (i.e., Example 11) is adopted, the carbon nanotube content needs to be increased accordingly. Among them, the comparison between Example 10 and Example 12 shows that when the silicon-based material content in the negative electrode sheet increases by the same gradient, in order to maintain the full charge expansion rate <10%, the carbon nanotube content in the encapsulation film needs to be increased at a higher gradient.

[0131] The above implementation modes are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred implementation modes, a person skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A packaging film for packaging an electrode assembly, the packaging film comprising a protective layer, a first bonding layer, a metal layer, a second bonding layer and a sealing layer stacked in sequence, characterized in that: The protective layer includes a polymer resin layer and a carbon material, the carbon material includes carbon fibers, the carbon fibers are formed by carbon nanotubes connected to each other along the tube diameter direction, the carbon fibers are connected to each other and woven to form a carbon layer, and the carbon layer is located between the polymer resin layer and the first bonding layer, and the thickness of the carbon layer is 2 μm to 5 μm.

2. The packaging film according to claim 1, wherein The mass ratio of the carbon material in the protective layer is 5% to 50%.

3. The packaging film according to claim 1, characterized in that The carbon nanotubes include at least one of multi-walled carbon nanotubes and single-walled carbon nanotubes.

4. The packaging film according to claim 1, wherein The thickness of the protective layer is 7 μm to 16 μm.

5. The packaging film according to claim 1, characterized in that The material of the polymer resin layer includes at least one of nylon and polyethylene terephthalate.

6. The packaging film according to claim 1, wherein The packaging film further includes a matte layer, the protective layer is located between the matte layer and the first bonding layer, and the matte layer has a thickness of 2 μm to 5 μm.

7. The packaging film according to claim 1, wherein The thickness of the metal layer is 24 μm to 35 μm, and the thickness of the sealing layer is 24 μm to 35 μm.

8. The packaging film according to claim 1, characterized in that The sealing layer includes polypropylene.

9. An electrochemical device comprising an electrode assembly, characterized in that: The electrochemical device further comprises a packaging film as claimed in any one of claims 1 to 8, wherein the packaging film is used to package the electrode assembly.

10. The electrochemical device according to claim 9, characterized in that The electrode assembly includes a positive electrode sheet, a separator and a negative electrode sheet, wherein the separator is located between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet, the separator and the negative electrode sheet are stacked or wound to form the electrode assembly, and the negative electrode sheet includes a silicon-based material.

11. The electrochemical device according to claim 10, characterized in that The silicon-based material includes at least one of silicon, silicon monoxide, a silicon-carbon composite material, or a composite material of silicon monoxide and carbon.

12. An electronic device, characterized in that: Comprising the electrochemical device according to any one of claims 9 to 11.

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