Aluminum plastic film, secondary battery and electric device

Abstract

The invention discloses an aluminum-plastic film, a secondary battery and a power utilization device, the aluminum-plastic film comprises a nylon layer, a metal layer and a composite layer which are sequentially stacked, the composite layer comprises polypropylene and a boron nitride compound, the boron nitride compound comprises at least one of modified boron nitride and unmodified boron nitride, and the nylon layer, the metal layer and the composite layer are sequentially stacked. Based on the mass of the composite layer, the content ratio of the nitrogen element is W%, and W is larger than or equal to 2 and smaller than or equal to 23. By controlling the content ratio of the nitrogen element in the aluminum-plastic film composite layer, the thermal conductivity and the heat sealing strength of the aluminum-plastic film are improved.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage, and more specifically, to an aluminum-plastic film, a secondary battery, and an electrical device. Background Art

[0002] An aluminum-plastic film is a multi-layer composite material, and its structure generally includes an outer layer of polyamide (PA) or polyethylene terephthalate (PET), an intermediate aluminum foil layer, and an inner layer of polypropylene (CPP). The aluminum-plastic film is favored due to its excellent barrier properties, mechanical properties, and thermal stability, and is widely used in the encapsulation of soft-pack batteries.

[0003] A large amount of heat is generated during the charge and discharge process of a secondary battery. If effective heat dissipation cannot be achieved, it will cause the temperature of the secondary battery to rise, which will in turn affect the performance, lifespan, and even safety of the secondary battery. As the encapsulation material of the secondary battery, the thermal conductivity of the aluminum-plastic film directly affects the thermal management efficiency of the secondary battery. In other words, a low thermal conductivity of the aluminum-plastic film is difficult to meet the heat dissipation requirements of the secondary battery. In addition, the heat seal strength is one of the key performance indicators of the aluminum-plastic film, which directly affects the sealing and safety of the secondary battery encapsulation. In practical applications, the aluminum-plastic film needs to withstand the corrosion of the electrolyte, the internal pressure change of the secondary battery, and external mechanical shocks. If the heat seal strength is insufficient, it may lead to encapsulation failure, causing safety problems such as electrolyte leakage, battery swelling, and even fire.

[0004] Therefore, it is of great significance to develop an aluminum-plastic film with high thermal conductivity and high heat seal strength. Summary of the Invention

[0005] In view of the above problems existing in the prior art, the purpose of the present application is to provide an aluminum-plastic film, a secondary battery, and an electrical device, and the aluminum-plastic film has high thermal conductivity and high heat seal strength.

[0006] The first aspect of the present application provides an aluminum-plastic film, which includes a nylon layer, a metal layer, and a composite layer stacked in sequence. The composite layer contains polypropylene and a boron nitride compound. The boron nitride compound includes at least one of modified boron nitride and unmodified nitrogen. Based on the mass of the composite layer, the content ratio of nitrogen element is W%, and 2 ≤ W ≤ 23.

[0007] By controlling the content ratio of nitrogen element in the composite layer of the aluminum-plastic film, the boron nitride compound is uniformly dispersed in the polypropylene. On the one hand, the composite layer can uniformly transfer a large amount of heat, reducing local overheating, thereby improving the thermal conductivity of the aluminum-plastic film, as well as its encapsulation uniformity and reliability; on the other hand, it can improve the mechanical strength and modulus of the composite layer, so that under the action of external force, the problem of stress concentration inside the aluminum-plastic film can be improved, and thus the thermal seal strength of the aluminum-plastic film can be improved.

[0008] In some embodiments, 2.26 ≤ W ≤ 22.56. When W is within the above range, the thermal conductivity and heat-sealing strength of the aluminum-plastic film can be better improved.

[0009] In some embodiments, the modified boron nitride contains an X group, and the X group is selected from at least one of a hydroxyl group, an amino group, and an epoxy group. When the X group is of the above types, it is beneficial to further improve the thermal conductivity and heat-sealing strength of the aluminum-plastic film.

[0010] In some embodiments, the aspect ratio of the boron nitride compound is from 1 to 1000. When the aspect ratio of the boron nitride compound is within the above range, the boron nitride compound is not easily agglomerated, can be better dispersed and filled in polypropylene, is beneficial to form a continuous thermal conduction network and fully improve the mechanical properties, and thus is beneficial to further improving the thermal conductivity and heat-sealing strength of the aluminum-plastic film.

[0011] In some embodiments, the composite layer contains at least one of flaky boron nitride and tubular boron nitride.

[0012] In some embodiments, based on the mass of the composite layer, the mass percentage content of the boron nitride compound is 4% to 40%.

[0013] In some embodiments, the thickness of the aluminum-plastic film is T μm, and the thickness of the composite layer is T 1 μm, 0.1 ≤ T 1 / T ≤ 0.5. When T 1 / T is within the above range, the aluminum-plastic film has better mechanical properties, heat-sealing properties and barrier properties, which is beneficial to further improving the thermal conductivity and heat-sealing strength of the aluminum-plastic film.

[0014] In some embodiments, W and T 1 satisfy the following relationship: 1 ≤ T 1 / W ≤ 23. In some embodiments, 1.18 ≤ T 1 / W ≤ 22.17. When T 1 / W is within the above range, the boron nitride compound can be more uniformly dispersed in polypropylene, thereby further improving the thermal conductivity and heat-sealing strength of the aluminum-plastic film

[0015] In some embodiments, the peel strength between the composite layer and the metal layer is 7 N / 15 mm to 15 N / 15 mm. When the peel strength between the composite layer and the metal layer is within the above range, the stress generated by the aluminum-plastic film during thermal expansion and contraction is small, reducing the possibility of interface delamination or cracking, which is beneficial to further improving the thermal conductivity of the aluminum-plastic film; at the same time, it can also well maintain the flexibility and ductility of the aluminum-plastic film, which is beneficial to further improving the packaging strength of the aluminum-plastic film.

[0016] The second aspect of the present application provides a secondary battery, including the aluminum-plastic film as in the first aspect.

[0017] The third aspect of the present application provides an electrical device, including a secondary battery as in the second aspect.

[0018] Compared with the prior art, the beneficial effects of the present application are as follows:

[0019] By controlling the content ratio of nitrogen element in the aluminum-plastic film composite layer, the boron nitride compounds are uniformly dispersed in the polypropylene. On the one hand, the composite layer can uniformly transfer a large amount of heat, reduce local overheating, thereby improving the thermal conductivity, packaging uniformity and reliability of the aluminum-plastic film; on the other hand, the mechanical strength and modulus of the composite layer can be improved, so that under the action of external force, the problem of stress concentration inside the aluminum-plastic film can be improved, and further the thermal packaging strength of the aluminum-plastic film can be improved.

[0020] Additional aspects and advantages of the embodiments of the present application will be described, shown, or elucidated in part in the subsequent description, or by the implementation of the embodiments of the present application. Detailed Embodiments

[0021] For the sake of brevity, the present application specifically discloses only some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recited.

[0022] Unless otherwise specified, the terms used in the present application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in the present application can be measured by various commonly used measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of the present application).

[0023] The list of items connected by the terms "at least one of", "at least one in", "at least one kind in" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.

[0024] I. Aluminum-plastic Film

[0025] The first aspect of the present application provides an aluminum-plastic film, which includes a nylon layer, a metal layer, and a composite layer stacked in sequence. The composite layer contains polypropylene and a boron nitride compound, and the boron nitride compound includes at least one of modified boron nitride and unmodified boron nitride. Based on the mass of the composite layer, the content ratio of nitrogen element is W%, and 2 ≤ W ≤ 23.

[0026] By controlling the content ratio of nitrogen element in the composite layer of the aluminum-plastic film, the boron nitride compound is evenly dispersed in the polypropylene. On the one hand, the composite layer can evenly transfer a large amount of heat, reduce local overheating, thereby improving the thermal conductivity, packaging uniformity and reliability of the aluminum-plastic film; on the other hand, it can improve the mechanical strength and modulus of the composite layer, so as to improve the problem of stress concentration inside the aluminum-plastic film under the action of external force, and further improve the thermal packaging strength of the aluminum-plastic film.

[0027] In some embodiments, based on the quality of the composite layer, the content ratio of nitrogen element is W%, where W is 2%, 2.1%, 2.2%, 2.25%, 2.26%, 2.27%, 2.3%, 2.5%, 2.7%, 2.8%, 2.82%, 2.85%, 2.9%, 3%, 3.38%, 3.5%, 3.95%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.51%, 4.52%, 4.55%, 4.6%, 5%, 5.08%, 5.1%, 5.5%, 5.64%, 5.7%, 6%, 6.2%, 6.3%, 6.4%, 6.5%, 6.77%, 7%, 7.33%, 7.5%, 7.90%, 8%, 8.46%, 8.5%, 9%, 9.02%, 9.5%, 9.59%, 10%, 10.15%, 10.5%, 10.72%, 11%, 11.28%, 11.5%, 11.84%, 12%, 12.41%, 12.5%, 12.97%, 13%, 13.5%, 13.54%, 14%, 14.10%, 14.5%, 14.66%, 15%, 15.23%, 15.5%, 15.79%, 16%, 16.36%, 16.5%, 16.92%, 17%, 17.48%, 17.5%, 18%, 18.05%, 18.5%, 18.61%, 19%, 19.18%, 19.5%, 19.74%, 20%, 20.30%, 20.5%, 20.87%, 21%, 21.43%, 21.5%, 21.99%, 22%, 22.5%, 22.56%, 22.6%, 22.7%, 22.9%, 23%, or the range composed of any two of these values. In some embodiments, 2.26 ≤ W ≤ 22.56. In some embodiments, 4.51 ≤ W ≤ 16.92. When W is within the above range, the thermal conductivity and thermal sealing strength of the aluminum-plastic film can be better improved.

[0028] In some embodiments, the modified boron nitride contains an X group, and the X group is selected from at least one of a hydroxyl group, an amino group, and an epoxy group. When the X group is of the above types, it is beneficial to further improve the thermal conductivity and thermal sealing strength of the aluminum-plastic film.

[0029] In some embodiments, the method for preparing modified boron nitride is as follows: a modifier and boron nitride are mixed in a solvent for reaction to obtain modified boron nitride. In some embodiments, the solvent includes, but is not limited to, at least one of ethanol, water, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and acetone. In some embodiments, the modifier is at least one of a hydroxyl modifier, an amino modifier, and an epoxy modifier. In some embodiments, the hydroxyl modifier includes, but is not limited to, a silane coupling agent, and the silane coupling agent includes, but is not limited to, at least one of tetraethyl orthosilicate (TEOS) and ethyltrimethylsilane. In some embodiments, the amino modifier is an organic amine, and the organic amine includes, but is not limited to, at least one of 1,6-hexanediamine and octanediamine. In some embodiments, the epoxy modifier is an epoxy group-containing organic compound, including, but not limited to, at least one of epichlorohydrin, methyl epichlorohydrin, and epoxyfluoropropane. In some embodiments, when the modifier is a silane coupling agent, water needs to be added simultaneously for reaction. In some embodiments, the reaction temperature can be 60°C to 80°C, and the reaction time can be 1 - 24 h. In some embodiments, boron nitride also includes at least one of a cleaning treatment and an activation treatment before use. In some embodiments, the activation treatment refers to pickling and / or plasma treatment to activate boron nitride.

[0030] In some embodiments, the aspect ratio of the boron nitride compound is 1, 2, 5, 7, 10, 20, 50, 70, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, or a range composed of any two of these values. In some embodiments, the aspect ratio of the boron nitride compound is 1 to 1000. When the aspect ratio of the boron nitride compound is within the above range, the boron nitride compound is not easily agglomerated, can be better dispersed and filled in polypropylene, is beneficial to forming a continuous heat conduction network and fully improving mechanical properties, and thus is beneficial to further improving the heat conduction rate and heat seal strength of the aluminum-plastic film.

[0031] In some embodiments, the composite layer contains at least one of flaky boron nitride and tubular boron nitride. In some embodiments, the mass ratio of flaky boron nitride to tubular boron nitride is 1:0.25, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, or a range composed of any two of these values. In some embodiments, the mass ratio of flaky boron nitride to tubular boron nitride is 1:(0.25 - 9). When the mass ratio of flaky boron nitride to tubular boron nitride is within the above range, the boron nitride compounds are not easily agglomerated, can be better dispersed and filled in polypropylene, are beneficial to forming a continuous heat conduction network and fully improving the mechanical properties, and can give full play to the advantages of flaky boron nitride and tubular boron nitride in improving the heat conduction rate and enhancing the interfacial bonding force, thereby being beneficial to further improving the heat conduction rate and heat seal strength of the aluminum-plastic film.

[0032] In some embodiments, based on the mass of the composite layer, the mass percentage content of the boron nitride compounds is 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or a range composed of any two of these values. In some embodiments, based on the mass of the composite layer, the mass percentage content of the boron nitride compounds is 4% to 40%.

[0033] In some embodiments, the thickness of the composite layer is T 1 μm, and T 1 is 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or a range composed of any two of these values. In some embodiments, 20 ≤ T 1 ≤ 100. When T 1 is within the above range, the heat conduction rate and heat packaging strength of the aluminum-plastic film can be better improved.

[0034] In some embodiments, the thickness of the aluminum-plastic film is T μm, where T is 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, or a range formed by any two of these values. In some embodiments, 50 ≤ T ≤ 250.

[0035] In some embodiments, the thickness of the aluminum-plastic film is T μm, and the thickness of the composite layer is T 1 μm, and T 1 / T is 0.1, 0.11, 0.12, 0.13, 0.14, 0.5, 0.16, 0.7, 0.8, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, or a range formed by any two of these values. In some embodiments, 0.1 ≤ T 1 / T ≤ 0.5. When T 1 / T is within the above range, the aluminum-plastic film has better mechanical properties, heat-sealing properties, and barrier properties, which is beneficial to further improving the thermal conductivity and heat-sealing strength of the aluminum-plastic film.

[0036] In some embodiments, W and T 1 satisfy the following relationship: T 1 / W is 1, 1.1, 1.2, 1.5, 1.7, 2, 2.2, 2.5, 2.7, 3, 3.2, 3.5, 3.7, 4, 4.2, 4.4, 4.5, 4.7, 5, 5.2, 5.5, 5.7, 5.9, 6, 6.2, 6.5, 6.7, 6.9, 7, 7.2, 7.5, 7.7, 7.8, 7.9, 8, 8.2, 8.5, 8.7, 8.9, 9, 9.2, 9.5, 9.7, 9.9, 10, 10.2, 10.4, 10.5, 10.7, 10.9, 11, 11.1, 11.2, 11.5, 11.6, 11.7, 11.9, 12, 12.2, 12.5, 12.7, 12.9, 13, 13.2, 13.5, 13.7, 13.9, 14, 14.2, 14.5, 14.9, 15, 15.2, 15.5, 15.7, 15.9, 16, 16.2, 16.5, 16.7, 16.9, 17, 17.2, 17.5, 17.7, 17.9, 18, 18.2, 18.5, 18.7, 18.9, 19, 19.2, 19.5, 19.7, 19.9, 20, 20.2, 20.5, 20.7, 20.9, 22, 22.1, 22.2, 22.5, 22.7, 23 or a range formed by any two of these values. In some embodiments, 1 ≤ T 1 / W ≤ 23. In some embodiments, 1.18 ≤ T 1 / W ≤ 22.17. T 1 / W within the above range, the boron nitride compound can be more evenly dispersed in the polypropylene, thereby further improving the thermal conductivity and heat-sealing strength of the aluminum-plastic film.

[0037] In some embodiments, the peel strength between the composite layer and the metal layer is 7 N / 15 mm, 7.1 N / 15 mm, 7.2 N / 15 mm, 7.3 N / 15 mm, 7.4 N / 15 mm, 7.5 N / 15 mm, 7.6 N / 15 mm, 7.7 N / 15 mm, 7.8 N / 15 mm, 7.9 N / 15 mm, 8 N / 15 mm, 8.1 N / 15 mm, 8.2 N / 15 mm, 8.3 N / 15 mm, 8.4 N / 15 mm, 8.5 N / 15 mm, 8.6 N / 15 mm, 8.7 N / 15 mm, 8.8 N / 15 mm, 8.9 N / 15 mm, 9 N / 15 mm, 9.1 N / 15 mm, 9.2 N / 15 mm, 9.3 N / 15 mm, 9.4 N / 15 mm, 9.5 N / 15 mm, 9.6 N / 15 mm, 9.7 N / 15 mm, 9.8 N / 15 mm, 9.9 N / 15 mm, 10 N / 15 mm, 10.1 N / 15 mm, 10.2 N / 15 mm, 10.3 N / 15 mm, 10.4 N / 15 mm, 10.5 N / 15 mm, 10.6 N / 15 mm, 10.7 N / 15 mm, 10.8 N / 15 mm, 10.9 N / 15 mm, 11 N / 15 mm, 11.1 N / 15 mm, 11.2 N / 15 mm, 11.3 N / 15 mm, 11.4 N / 15 mm, 11.5 N / 15 mm, 11.6 N / 15 mm, 11.7 N / 15 mm, 11.8 N / 15 mm, 11.9 N / 15 mm, 12 N / 15 mm, 12.1 N / 15 mm, 12.2 N / 15 mm, 12.3 N / 15 mm, 12.4 N / 15 mm, 12.5 N / 15 mm, 12.6 N / 15 mm, 12.7 N / 15 mm, 12.8 N / 15 mm, 12.9 N / 15 mm, 13 N / 15 mm, 13.1 N / 15 mm, 13.2 N / 15 mm, 13.3 N / 15 mm, 13.4 N / 15 mm, 13.5 N / 15 mm, 13.6 N / 15 mm, 13.7 N / 15 mm, 13.8 N / 15 mm, 13.9 N / 15 mm, 14 N / 15 mm, 14.1 N / 15 mm, 14.2 N / 15 mm, 14.3 N / 15 mm, 14.4 N / 15 mm, 14.5 N / 15 mm, 14.6 N / 15 mm, 14.7 N / 15 mm, 14.8 N / 15 mm, 14.9 N / 15 mm, 15 N / 15 mm, or a range formed by any two of these values. In some embodiments, the peel strength between the composite layer and the metal layer is from 7 N / 15 mm to 15 N / 15 mm.When the peel strength between the composite layer and the metal layer is within the above range, the stress generated by the thermal expansion and contraction of the aluminum-plastic film is small, reducing the possibility of interface delamination or cracking, which is beneficial to further improve the thermal conductivity of the aluminum-plastic film; at the same time, it can also well maintain the flexibility and ductility of the aluminum-plastic film, which is beneficial to further improve the packaging strength of the aluminum-plastic film.

[0038] In some embodiments, the thickness of the nylon layer is 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, 51μm, 52μm, 53μm, 54μm, 55μm, 56μm, 57μm, 58μm, 59μm, 60μm, 61μm, 62μm, 63μm, 64μm, 65μm, 66μm, 67μm, 68μm, 69μm, 70μm, 71μm, 72μm, 73μm, 74μm, 75μm, 76μm, 77μm, 78μm, 79μm, 80μm, 81μm, 82μm, 83μm, 84μm, 85μm, 86μm, 87μm, 88μm, 89μm, 90μm, 91μm, 92μm, 93μm, 94μm, 95μm, 96μm, 97μm, 98μm, 99μm, 100μm or the range composed of any two of these values. In some embodiments, the thickness of the nylon layer is from 10μm to 100μm.

[0039] In some embodiments, the thickness of the metal layer is 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, 76 μm, 77 μm, 78 μm, 79 μm, 80 μm or a range formed by any two of these values. In some embodiments, the thickness of the metal layer is from 15 μm to 80 μm.

[0040] In some embodiments, the nylon layer comprises at least one of nylon 6 (PA6), nylon 66 (PA66), nylon 610 (PA610), nylon 612 (PA612), nylon 1010 (PA1010), nylon 11 (PA11), nylon 12 (PA12), nylon 46 (PA46), nylon 6T (PA6T), nylon 9T (PA9T), nylon 10T (PA10T), nylon MXD6 (PAMXD6), nylon 655 (PA655).

[0041] In some embodiments, the metal layer comprises aluminum foil.

[0042] In some embodiments, in the composite layer, the polypropylene comprises at least one of crosslinked polypropylene (CPP), modified polypropylene (MPP), homopolypropylene (HPP), random copolymer polypropylene (RPP), block copolymer polypropylene (BPP).

[0043] In some embodiments, the method for preparing the nylon layer is a method well-known in the art and can be used for preparing the nylon layer of the aluminum-plastic film for secondary batteries. For example, the nylon layer can be obtained through the following preparation method: mixing the components in the nylon layer, heating and melting, and extruding into a film, thus obtaining the nylon layer. In some embodiments, in addition to nylon, the nylon layer can also add additives such as fillers (such as carbon nanotubes), reinforcing fibers (such as glass fibers, carbon fibers), antioxidants, and stabilizers as needed. In some embodiments, the heating and melting can be carried out by a single-screw or twin-screw extruder. In some embodiments, after extruding into a film, it also includes rapid cooling through a cooling roll or a water-cooling device, which can ensure that the thickness of the nylon layer is uniform and there is no deformation.

[0044] In some embodiments, the method for preparing the composite layer is a method well-known in the art and can be used for preparing the composite layer of the aluminum-plastic film for secondary batteries. For example, the composite layer can be obtained through the following preparation method: mixing the components in the composite layer (including polypropylene, boron nitride, etc.), extruding and granulating, and then forming a film by the casting method, thus obtaining the composite layer.

[0045] In some embodiments, the method for preparing the aluminum-plastic film is a method well-known in the art and can be used for preparing the aluminum-plastic film for secondary batteries. For example, the aluminum-plastic film can be obtained through the following preparation method: coating and / or spraying an adhesive on one surface of the metal layer, compounding the nylon layer and the metal layer through the adhesive, and then compounding the composite layer on the other surface of the metal layer that is not coated and / or sprayed with the adhesive through hot pressing, thus obtaining the aluminum-plastic film. Another example is that the aluminum-plastic film can be obtained through the following preparation method: coating and / or spraying an adhesive on one surface of the metal layer, aligning the side of the metal layer coated and / or sprayed with the adhesive with the nylon layer, and aligning the other side of the metal layer not coated and / or sprayed with the adhesive with the composite layer, and performing hot pressing and compounding, thus obtaining the aluminum-plastic film. In some embodiments, the adhesive includes at least one of polyurethane, polyolefin, maleic anhydride-modified polyolefin, epoxy resin, acrylic resin, polyvinyl alcohol, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl ester, polyvinyl alcohol, and polyacrylic acid. In some embodiments, the polyolefin is at least one of polyethylene and polypropylene.

[0046] II. Secondary Battery

[0047] The second aspect of the present application provides a secondary battery, including the aluminum-plastic film as in the first aspect.

[0048] In some embodiments, the secondary battery further includes a positive electrode, a negative electrode, an electrolyte, and a separator.

[0049] <Positive Electrode>

[0050] In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector.

[0051] The present application has no particular limitation on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include, but is not limited to, at least one of aluminum foil, aluminum alloy foil, composite current collector, carbon cloth, and carbon paper. In some embodiments, the composite current collector may include, but is not limited to, an aluminum-carbon composite current collector.

[0052] In some embodiments, the positive electrode material layer includes a positive electrode active material. The present application has no particular limitation on the positive electrode active material, as long as the purpose of the present application can be achieved. For example, it may include, but is not limited to, at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO 2 ), lithium manganese oxide, lithium manganese iron phosphate, lithium titanate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate. The chemical formula of the lithium-rich manganese-based material is γLi 2 MnO 3 ·(1 - γ)LiGO 2 , 0 < γ < 1, and G is a transition metal such as nickel, cobalt, or iron. In some embodiments, the lithium nickel cobalt manganese oxide includes at least one of Ni90, NCM811, NCM622, NCM523, and NCM111. In the present application, a substance different from its composition may be attached to the surface of the positive electrode active material. Exemplarily, the substances attached to the surface may include, but are not limited to, at least one of aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, aluminum sulfate, lithium carbonate, calcium carbonate, magnesium carbonate, and carbon. By attaching the above substances to the surface of the positive electrode active material, the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be inhibited, and the service life of the electrochemical device can be improved.

[0053] In some embodiments, the positive electrode material layer further includes at least one of a conductive agent, a binder, and a thickener; the present application places no particular limitation on the conductive agent and the binder, as long as the objectives of the present application can be achieved. For example, the conductive agent may include, but is not limited to, at least one of carbon-based materials, metal-based materials, and conductive polymers. In some embodiments, the carbon-based materials may include, but are not limited to, at least one of graphite, carbon black, acetylene black, Super-P, Ketjen black, carbon fiber, carbon nanotube, graphene, and amorphous carbon. In some embodiments, the metal-based materials may include, but are not limited to, at least one of metal powder and metal fiber, and the metal may include, but is not limited to, at least one of copper, nickel, aluminum, and silver. In some embodiments, the conductive polymers may include, but are not limited to, at least one of polyphenylene derivatives, polythiophene, polypyrrole, polyaniline, polyacetylene, poly(phenylene), and polyfluorene. Again, for example, the binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly(1,1-difluoroethylene), polyethylene, polypropylene, polyacrylate, polyvinyl alcohol, polyacrylic acid, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon. Still, for example, the thickener may include, but is not limited to, at least one of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts.

[0054] In some embodiments, the structure of the positive electrode is a positive electrode structure known to those skilled in the art and can be used for secondary batteries.

[0055] In some embodiments, the preparation method of the positive electrode is a preparation method known to those skilled in the art and can be used for the positive electrode of secondary batteries. For example, the positive electrode can be obtained by the following preparation method: mixing the components in the positive electrode material layer [including the positive electrode active material, and optionally the conductive agent, the binder, and the thickener, etc.] in a solvent, and heating the thickener before use as needed to prepare a positive electrode slurry, and coating and / or spraying the positive electrode slurry on the positive electrode current collector. In some embodiments, the solvent may include, but is not limited to, at least one of water, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, trimethyl phosphate, acetone, and dipropylene glycol dimethyl ether.

[0056] <Negative electrode>

[0057] In some embodiments, the negative electrode includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector.

[0058] The present application has no particular limitation on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include, but is not limited to, at least one of copper foil, aluminum foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and composite current collector. In some embodiments, the composite current collector may include, but is not limited to, at least one of carbon-copper composite current collector, nickel-copper composite current collector, and titanium-copper composite current collector.

[0059] In some embodiments, the negative electrode material layer includes a negative electrode active material. The present application has no particular limitation on the negative electrode active material, as long as the purpose of the present application can be achieved. For example, it may include, but is not limited to, at least one of graphite, hard carbon, soft carbon, silicon carbon, silicon monoxide, lithium metal, lithium titanate, metal alloy, metal sulfide, and graphene. The metal alloy includes, but is not limited to, at least one of Li-Sn alloy, Li-Sn-O alloy, and Li-Al alloy. The silicon monoxide is SiO x (0.5 < x < 1.6).

[0060] In some embodiments, the negative electrode material layer further includes at least one of a conductive agent, a binder, and a thickening agent; the present application has no particular limitation on the conductive agent and the binder, as long as the purpose of the present application can be achieved. For example, the conductive agent may include, but is not limited to, at least one of metal-based materials and conductive polymers. In some embodiments, the metal-based materials may include, but are not limited to, at least one of metal powder and metal fiber, and the metal may include, but is not limited to, at least one of copper, nickel, aluminum, and silver. In some embodiments, the conductive polymers may include, but is not limited to, at least one of polyphenylene derivatives, polythiophene, polypyrrole, polyaniline, polyacetylene, poly(phenylene), and polyfluorene. Also for example, the binder may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly(1,1-difluoroethylene), polyethylene, polypropylene, polyacrylate, polyvinyl alcohol, polyacrylic acid, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon. Still for example, the thickening agent may include, but is not limited to, at least one of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts.

[0061] In some embodiments, the structure of the negative electrode is a negative electrode structure known to those skilled in the art and can be used in secondary batteries.

[0062] In some embodiments, the method for preparing the negative electrode is a method well-known to those skilled in the art and can be used for preparing the negative electrode of a secondary battery. For example, the negative electrode can be obtained by the following preparation method: mixing the components in the negative electrode material layer (including the negative electrode active material, and optionally a conductive agent, a binder, a thickener, etc.) in a solvent, and heating the thickener before use as needed to prepare a negative electrode slurry, and coating and / or spraying the negative electrode slurry on the negative electrode current collector. In some embodiments, the solvent may include, but is not limited to, at least one of water, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, trimethyl phosphate, acetone, dipropylene glycol dimethyl ether.

[0063] <Electrolyte>

[0064] There is no particular limitation on the electrolyte in this application as long as the object of this application can be achieved. The electrolyte used in this application can be an electrolyte known in the prior art. For example, the electrolyte can be divided into an aqueous electrolyte and a non-aqueous electrolyte. Among them, compared with the aqueous electrolyte, an electrochemical device (battery) using a non-aqueous electrolyte can operate under a wider voltage window, thereby achieving a higher energy density.

[0065] In some of these embodiments, the non-aqueous electrolyte includes an organic solvent and an electrolyte.

[0066] In some of these embodiments, there are no particular restrictions on the organic solvent for this application, as long as the objectives of this application can be achieved. The organic solvents used in this application can be organic solvents known in the prior art. For example, the organic solvents can include, but are not limited to, at least one of carbonate compounds, carboxylate compounds, ether compounds, and other organic solvents. Among them, the carbonate compounds can include, but are not limited to, at least one of linear carbonate compounds, cyclic carbonate compounds, and fluorinated carbonate compounds. The linear carbonate compounds can include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and ethyl methyl carbonate (EMC). The cyclic carbonates can include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene ethylene carbonate (VEC). The fluorinated carbonate compounds can include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethyl ethylene carbonate. The carboxylate compounds can include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, and caprolactone. The ether compounds can include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. The other organic solvents can include, but are not limited to, at least one of dimethyl sulfoxide, 1,3-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, and trioctyl phosphate.

[0067] In some of these embodiments, the electrolyte can include, but is not limited to, at least one of inorganic lithium salts, fluorinated organic lithium salts, and lithium salts containing dicarboxylic acid complexes. Among them, the inorganic lithium salts can include, but are not limited to, LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiSbF 6 , LiSO 3 F, LiPO 2 F 2 , LiN(FSO 2 )2 at least one of. The fluorinated organic lithium salt may include but is not limited to LiCF 3 SO 3 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ), 2 , LiN(C 2 F 5 SO 2 ), 2 , lithium cyclic 1,3 - hexafluoropropane disulfonimide, lithium cyclic 1,2 - tetrafluoroethane disulfonimide, LiPF 4 (CF 3 ), 2 , LiN(CF 3 SO 2 )(C 4 F 9 SO 2 ), LiC(CF 3 SO 2 ), 3 , LiPF 4 (CF 3 SO 2 ), 2 , LiPF 4 (C 2 F 5 ), 2 , LiPF 4 (C 2 F 5 SO 2 ), 2 , LiBF 2 (CF 3 ), 2 , LiBF 2 (C 2 F 5 ), 2 , LiBF 2 (CF 3 SO 2 ), 2 , LiBF 2 (C 2 F 5 SO 2 ), 2 at least one of. The lithium salt of dicarboxylic acid complex may include but is not limited to lithium bis(oxalato)borate, lithium difluoro(oxalato)borate [LiBF 2 (C 2 O 4)], at least one of lithium tris(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0068] In some embodiments, based on the mass of the electrolyte solution, the mass percentage of the electrolyte is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 12.5%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%.

[0069] In some embodiments, the non-aqueous electrolyte solution further includes an additive.

[0070] In some of these embodiments, there are no particular restrictions on the additives in the present application, as long as the objectives of the present application can be achieved. The additives used in the present application can be additives known in the prior art. For example, the additives can include, but are not limited to, at least one of polynitrile compounds, sulfur-containing additives, fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), and 1,4-butane sultone. Among them, the polynitrile compound includes at least one of dinitrile compounds and trinitrile compounds. The dinitrile compound is a compound containing 2 cyano groups (-CN), and can include, but is not limited to, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, sebaconitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile, 2-methylenepentanedinitrile, 1,4-dicyano-3-butene, 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, 2,3,3-trimethylsuccinonitrile, 2,2,3,3-tetramethylsuccinonitrile, 2,3-diethyl-2,3-dimethylsuccinonitrile, 2,2-diethyl-3,3-dimethylsuccinonitrile, bicyclohexyl-1,1-dicarbonitrile, bicyclohexyl-2,2-dicarbonitrile, bicyclohexyl-3,3-dicarbonitrile, 2,5-dimethyl-2,5-hexanedicarbonitrile, 2,3-diisobutyl-2,3-dimethylsuccinonitrile, 2,2-diisobutyl-3,3-dimethylsuccinonitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3'-(ethylenedioxy)dipropionitrile, 3,3'-(ethylenedithio)dipropionitrile, 1,4-dicyano-2-butene, and fumarodinitrile. The trinitrile compound is a compound containing 3 cyano groups (-CN).

[0071] In some of these embodiments, the method for preparing the electrolyte is a method well-known in the art and can be used for preparing electrolytes for electrochemical devices (including batteries). For example, the electrolyte can be obtained by the following method: mixing the components in the electrolyte [including organic solvents, electrolytes, and optional additives, etc.].

[0072] <Separator>

[0073] A separator is disposed between the positive electrode and the negative electrode to prevent internal short circuit of the secondary battery, allow free passage of electrolyte ions, and not affect the progress of the electrochemical charge and discharge process. There is no particular limitation on the separator in this application, as long as the object of this application can be achieved. The separator used in this application can be a separator known in the prior art. For example, the types of separators can include, but are not limited to, at least one of woven membranes, non-woven membranes, microporous membranes, composite membranes, rolled membranes, and spun membranes. The materials of the separator can include, but are not limited to, at least one of polyolefins (PO) mainly composed of polyethylene (PE) and polypropylene (PP), polyesters, celluloses, polyimides (PI), polyamides (PA), spandex, and aramids. The polyester can include, but is not limited to, polyethylene terephthalate (PET) membranes.

[0074] In some embodiments, the separator includes a substrate layer. The substrate layer can include, but is not limited to, at least one of non-woven fabrics, membranes, and composite membranes having a porous structure. The materials of the substrate layer can include, but are not limited to, at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. In some embodiments, the substrate layer can include, but is not limited to, at least one of polypropylene porous membranes, polyethylene porous membranes, polypropylene non-woven fabrics, polyethylene non-woven fabrics, and polypropylene-polyethylene-polypropylene porous composite membranes.

[0075] In some embodiments, the separator further includes a surface treatment layer disposed on at least one surface of the substrate layer. The surface treatment layer can include, but is not limited to, at least one of a polymer layer, an inorganic layer, and a layer formed by mixing a polymer and an inorganic substance. The polymer layer includes a polymer. There is no particular limitation on the polymer in this application, as long as the object of this application can be achieved. For example, the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene). The inorganic layer includes inorganic particles and a binder. There is no particular limitation on the inorganic particles and the binder in this application, as long as the object of this application can be achieved. For example, the inorganic particles can include, but are not limited to, at least one of alumina, silica, magnesia, titania, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. Another example is that the binder can include, but is not limited to, at least one of the binders used in the above positive electrode material layer or negative electrode material layer.

[0076] In some embodiments, there is no particular limitation on the thickness of the separator in this application, as long as the object of this application can be achieved. For example, the thickness of the separator is 3 μm to 20 μm.

[0077] <Method for preparing a secondary battery>

[0078] The preparation methods of secondary batteries are well-known to those skilled in the art. The present application does not particularly limit the preparation methods of secondary batteries, as long as the objectives of the present application can be achieved. For example, the preparation methods of secondary batteries may include but are not limited to the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly, placing the electrode assembly into an aluminum-plastic film, injecting electrolyte into the aluminum-plastic film and sealing it to obtain a secondary battery; or stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire laminated structure with tape to obtain a laminated electrode assembly, placing the electrode assembly into an aluminum-plastic film, injecting electrolyte into the aluminum-plastic film and sealing it to obtain a secondary battery. In addition, an overcurrent protection element, a guide plate, etc. may be placed in the aluminum-plastic film as needed to prevent the pressure inside the secondary battery from rising and overcharging / discharging.

[0079] III. Electrical device

[0080] The third aspect of the present application provides an electrical device, which includes the secondary battery as described in the second aspect.

[0081] The present application does not particularly limit the electrical device, as long as the objectives of the present application can be achieved. The electrical device used in the present application may be an electrical device known in the prior art. For example, the electrical device may include but is not limited to at least one of a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD TV, a hand-held cleaner, a portable CD player, a minidisc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a moped, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, a large household secondary battery, and a lithium-ion capacitor.

[0082] IV. Embodiments

[0083] The following further clearly and completely describes the present application in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application fall within the scope of protection of the present application.

[0084] It should be noted that in the specific embodiments of the present application, a lithium-ion secondary battery is used as an example of the secondary battery to explain the present application, but the secondary battery of the present application is not limited to the lithium-ion secondary battery.

[0085] In the following examples and comparative examples, the reagents, materials and instruments used are all commercially available unless otherwise specified. In addition, "part" and "%" are by mass unless otherwise specified.

[0086] Test methods and equipment:

[0087] (1) Testing method for aspect ratio of boron nitride compounds:

[0088] Take 0.1g of boron nitride compounds, add them to 10mL of ethanol for ultrasonic dispersion, take 10μL and drop it on a conductive substrate (such as a carbon film copper mesh), dry it naturally in the air, and then use SEM under appropriate acceleration voltage (SEM: 5kV to 20kV) and magnification (SEM: 10000 times to 50000 times) conditions to collect high-resolution images of 5 random test areas (25μm×25μm). Use image analysis software (such as Image J) to process the collected images, mark the long axis (L) and short axis (D) of the boron nitride compounds, and calculate the aspect ratio (L / D) of each boron nitride compound particle, and calculate the average value.

[0089] (2) Test method for the content of nitrogen in the composite layer (W%):

[0090] The composite layer was cut into pieces, 0.4 g of the composite layer was taken, 10 mL of aqua regia (a mixture of concentrated nitric acid and concentrated hydrochloric acid in a volume ratio of 1:1) and 2 mL of HF were added to dissolve it, the mixture was transferred into a 100 mL volumetric flask and fixed to volume, and the content of nitrogen in the composite layer (W%) was calculated according to the measured spectral intensity using an inductively coupled plasma optical emission spectrometer (ICP-OES) and a calibration curve.

[0091] (3) Test method for peel strength between composite layer and metal layer:

[0092] The aluminum-plastic film was cut into standard size specimens with a width of 15 mm and a length of 150 mm. Both ends of the specimens were fixed on the fixture of the universal material testing machine. The test was carried out at a peeling angle of 180° and a peeling speed of 300 mm / min. The maximum force value during the peeling process was recorded, which was the peeling strength between the composite layer and the metal layer in N / 15 mm.

[0093] (4) Test of the content of each component in the electrolyte:

[0094] The secondary battery was discharged at a constant current of 0.5C until 3.0V, then disassembled, the electrolyte was collected, and the separated positive electrode sheet, negative electrode sheet, and separator were centrifuged. The liquid obtained after centrifugation was mixed evenly with the above-mentioned electrolyte, and then tested using a gas chromatography-mass spectrometry (instrument model: Agilent 8890) and an ion chromatography (instrument model: AQUION ion chromatography) to obtain each component in the electrolyte and test its content.

[0095] (5) Thermal conductivity test method for aluminum-plastic film:

[0096] The aluminum-plastic film was cut into standard-size specimens with a width of 15 mm and a length of 150 mm, placed on the test platform of a thermal conductivity meter, fixed with a clamp to keep the specimen flat and in good contact. Using the laser flash method, the specimen was irradiated with a heating laser beam, and the temperature change curve on the back of the specimen was recorded. The thermal conductivity of the aluminum-plastic film was calculated by combining the test data and the specimen thickness.

[0097] (5) Heat seal strength test method for aluminum-plastic film:

[0098] Part of the sample was taken from the sealed area of the aluminum-plastic film of the secondary battery and then cut into test strips with a width of 8 mm. The middle area of the test strip was the sealed area of the aluminum-plastic film (the double-layer aluminum-plastic film was tightly combined due to sealing), and the two sides were the non-sealed areas of the aluminum-plastic film (the double-layer aluminum-plastic film was separated due to non-sealing). Using a high-speed tensile machine, the test strip was torn at an angle of 180° to completely separate the double-layer aluminum-plastic film, and the stable tensile force F ’ N was recorded, and F ’ N / 8 mm was taken as the heat seal strength of the aluminum-plastic film.

[0099] (6) 5C rate temperature rise test of secondary battery:

[0100] At 25°C, the secondary battery was allowed to stand for 30 min, and the initial temperature of the secondary battery was recorded; then, it was discharged at a constant current of 0.5C until 3V, and allowed to stand for 15 min; then, it was charged at a constant current of 0.7C until 4.5V, and then switched to constant voltage charging until 0.025C, and allowed to stand for 5 min; finally, it was discharged at a constant current of 5C until 3V, and the highest temperature during the discharge process of the secondary battery was recorded and taken as the 5C rate temperature rise of the secondary battery.

[0101] Example 1

[0102] 1. Preparation of aluminum-plastic film

[0103] (1) Nylon 66 (PA66) was heated and melted at 260°C using a twin-screw extruder, then extruded into a film using a die, and rapidly cooled through a cooling roll to obtain a nylon layer;

[0104] (2) Polypropylene (homopolypropylene) and boron nitride compounds (modified boron nitride) in the hybrid composite layer are extruded and pelletized at 180 °C, and then a film is formed by casting at 220 °C, thus obtaining the composite layer;

[0105] (3) Apply the binder polyurethane on one side surface of the metal layer aluminum foil. Align the side of the aluminum foil surface coated with the binder with the nylon layer, and align the other side of the aluminum foil surface not coated with the binder with the composite layer. Use a laminator for hot pressing (hot pressing parameters: temperature 100 °C, time 60 s, pressure 10 MPa). After the lamination is completed, transfer it into a curing furnace and cure at 100 °C for 40 min to ensure that the binder is completely cured and a strong adhesive force is formed, thus obtaining the aluminum-plastic film;

[0106] Among them, based on the mass of the composite layer, the mass percentage content of the boron nitride compound (modified boron nitride) is A%, A = 30; the modified boron nitride contains X groups, specifically hydroxyl groups, and the aspect ratio of the boron nitride compound (modified boron nitride) is 500. The preparation method of the modified boron nitride is:

[0107] Mix flaky boron nitride (aspect ratio 500) and tubular boron nitride (aspect ratio 500) with a mass ratio of 1:5, alternately wash with deionized water and ethanol 3 times, activate with 1.0 mol / L hydrochloric acid pickling, transfer to ethanol for dispersion to form a uniform suspension; add tetraethyl orthosilicate (TEOS) and deionized water, stir at 60 °C for 6 h for reaction, filter, alternately wash with deionized water and ethanol 3 times, and dry at 60 °C for 18 h to obtain modified boron nitride containing hydroxyl groups; among them, the mass ratio of boron nitride (i.e., the total mass of flaky boron nitride and tubular boron nitride) to the mass of tetraethyl orthosilicate (TEOS) is 1:2; the mass ratio of tetraethyl orthosilicate (TEOS) to the volume of deionized water is 1 g:100 mL;

[0108] The thickness of the nylon layer is 50 μm, the thickness of the metal layer aluminum foil is 67 μm. Based on the mass of the composite layer, the content ratio of nitrogen element is W%, W = 4.51, and the thickness of the composite layer is T 1 μm, T 1 = 50, W and T 1 satisfy the following relationship: T 1 / W = 11.1, the thickness of the aluminum-plastic film is T μm, T = 167, T 1 / T = 0.3, the peel strength between the composite layer and the metal layer is B N / 15 mm, B = 13;

[0109] 2. Preparation of the positive electrode

[0110] Mix the cathode material (lithium cobaltate), conductive agent (graphite), and binder (polyvinylpyrrolidone) in a mass ratio of 97.5:1.0:1.5 in the solvent N-methylpyrrolidone to prepare a cathode slurry. Coat the cathode active slurry on one surface of the cathode current collector aluminum foil, and dry it to obtain a cathode with a single-sided coated cathode material layer. Repeat the above steps on the other surface of the cathode current collector aluminum foil to obtain a cathode with a double-sided coated cathode material layer. After cold pressing, slicing, and slitting, dry it to obtain a cathode with a specification of 74 mm × 867 mm.

[0111] Among them, the thickness of the cathode material layer is 85 μm.

[0112] 3. Preparation of the anode

[0113] Mix the anode material (artificial graphite), conductive agent (copper powder), and binder (polyvinyl alcohol) in a mass ratio of 96:1.5:2.5 in the solvent N-methylpyrrolidone to prepare an anode slurry. Coat the anode slurry on one surface of the anode current collector copper foil, and dry it to obtain an anode with a single-sided coated anode material layer. Repeat the above steps on the other surface of the anode current collector copper foil to obtain an anode with a double-sided coated anode material layer. After cold pressing, slicing, and slitting, dry it to obtain an anode with a specification of 78 mm × 875 mm.

[0114] Among them, the thickness of the anode material layer is 110 μm.

[0115] 4. Electrolyte

[0116] In a dry argon atmosphere glove box, mix ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of EC:PC:EMC:DEC = 10:30:30:30 and mix them evenly. Then add fluoroethylene carbonate (FEC) and 1,3-propane sultone (PS), dissolve and stir well, and then add the inorganic lithium salt LiPF 6 , and obtain an electrolyte after mixing evenly.

[0117] Among them, based on the mass of the electrolyte, the mass ratio of fluoroethylene carbonate (FEC) is 2%, and the mass ratio of 1,3-propane sultone (PS) is 2%; the mass ratio of LiPF 6 (electrolyte) is 12.5%;

[0118] 5. Separator

[0119] Use a polyethylene porous membrane with a thickness of 15 μm as the separator.

[0120] 6. Preparation of the secondary battery

[0121] Connect the positive and negative electrodes made as above to the tab ears respectively, stack the positive electrode, separator, and negative electrode in sequence, and perform operations such as winding and folding as needed to obtain a wound electrode assembly. Place the electrode assembly into an aluminum-plastic film, inject the electrolyte into the aluminum-plastic film and seal it, and then let it stand, age (constant current charging at 0.2C for 120 s, then constant current charging at 1C for 180 s, and finally constant current charging at 1.5C until 4.50 V), measure the capacity, degas, and trim the edges to obtain a secondary battery.

[0122] Examples 2 to 4 and Comparative Examples 1 to 2

[0123] Except for adjusting the condition parameters such as the mass percentage content of the boron nitride compound (modified boron nitride) in the composite layer according to Table 1, the rest are the same as in Example 1. The mass percentage content of the boron nitride compound (modified boron nitride) can be adjusted by adjusting the application amount of the boron nitride compound (modified boron nitride) to be as shown in Table 1. Based on the mass of the composite layer, the mass percentage content of the boron nitride compound (modified boron nitride) is A%; based on the mass of the composite layer, the content ratio of nitrogen element is W%; the thickness of the composite layer is T 1 μm; the peel strength between the composite layer and the metal layer is B N / 15 mm. Changes in the value of A will cause changes in the values of W and B.

[0124] Table 1 Condition parameters and test results of Examples 1 to 4 and Comparative Examples 1 to 2

[0125]

[0126] As can be seen from Table 1, by controlling the content ratio of nitrogen element to satisfy 2 ≤ W ≤ 23 or controlling the mass ratio of the boron nitride compound to satisfy 4% to 40%, the thermal conductivity and heat seal strength of the aluminum-plastic film can be improved. At the same time, it also has a lower temperature rise at 5C rate.

[0127] Examples 5 to 7

[0128] Except for adjusting the type of X group in the modified boron nitride according to Table 2, the rest are the same as in Example 1. The type of X group in the modified boron nitride can be adjusted by adjusting the type of modifier in the preparation method of the modified boron nitride in Example 1 to be as shown in Table 2. Based on the mass of the composite layer, the content ratio of nitrogen element is W%; the thickness of the composite layer is T 1 μm; the peel strength between the composite layer and the metal layer is B N / 15 mm. Changes in the type of X group will cause changes in the values of W and B.

[0129] Table 2 Condition parameters and test results of Examples 1, 5 to 7

[0130]

[0131]

[0132] Note: In the above table, when the type of group X is "none", it means that unmodified boron nitride is used, that is, unmodified boron nitride is used instead of modified boron nitride, and no modifier is required.

[0133] As can be seen from Table 2, when the type of group X in the modified boron nitride is within the scope of this application, and when unmodified boron nitride is used instead of modified boron nitride, the aluminum-plastic film has high thermal conductivity and high heat-sealing strength.

[0134] Examples 8 to 9

[0135] Except for adjusting the aspect ratio of the boron nitride compound according to Table 3, the rest are the same as in Example 1.

[0136] Table 3 Condition parameters and test results of Examples 1, 8 to 9

[0137]

[0138] As can be seen from Table 3, when the aspect ratio of the boron nitride compound is within the scope of this application, the aluminum-plastic film has high thermal conductivity and high heat-sealing strength.

[0139] Examples 10 to 13

[0140] Except for adjusting the mass ratio of flaky boron nitride (aspect ratio of 500) and tubular boron nitride (aspect ratio of 500) according to Table 4, the rest are the same as in Example 1. The mass ratio of flaky boron nitride and tubular boron nitride can be adjusted by adjusting the application amounts of flaky boron nitride and tubular boron nitride as shown in Table 4.

[0141] Table 4 Condition parameters and test results of Examples 1, 10 to 13

[0142]

[0143]

[0144] As can be seen from Table 4, when using flaky boron nitride and tubular boron nitride simultaneously, the thermal conductivity and heat-sealing strength of the aluminum-plastic film can be further improved.

[0145] Examples 14 to 15

[0146] Except for adjusting the thickness T of the composite layer according to Table 5 1 μm and other condition parameters, the rest are the same as in Example 1. Based on the mass of the composite layer, the content ratio of nitrogen element is W%; the thickness of the aluminum-plastic film is T μm; the peel strength between the composite layer and the metal layer is B N / 15mm. The change of the T 1 value will cause changes in the T and B values.

[0147] Table 5 Condition parameters and test results of Examples 1, 14 to 15

[0148]

[0149] As can be seen from Table 5, when T 1 / T is within the scope of this application, the aluminum-plastic film has high thermal conductivity and high heat-sealing strength.

[0150] Examples 16 to 17

[0151] Except for adjusting the peel strength between the composite layer and the metal layer according to Table 6, the rest are the same as in Example 1. The peel strength between the composite layer and the metal layer can be made as shown in Table 6 by adjusting the hot pressing time at 100 °C in step (3) of the preparation method of the aluminum-plastic film in Example 1. The peel strength between the composite layer and the metal layer is B N / 15 mm.

[0152] Table 6 Condition parameters and test results of Examples 1, 16 to 17

[0153]

[0154] As can be seen from Table 6, when the peel strength between the composite layer and the metal layer is within the scope of this application, the aluminum-plastic film has high thermal conductivity and high heat-sealing strength.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application rather than to limit the protection scope of this application. Although the technical solutions of this application have been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of this application can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of this application.

Claims

1. An aluminum-plastic film, characterized in that: The aluminum-plastic film includes a nylon layer, a metal layer and a composite layer stacked in sequence, the composite layer contains polypropylene and a boron nitride compound, the boron nitride compound includes at least one of modified boron nitride and unmodified boron nitride, and based on the mass of the composite layer, the content of nitrogen element accounts for W%, 2≤W≤23.

2. The aluminum-plastic film according to claim 1, characterized in that: The modified boron nitride contains an X group, and the X group is selected from at least one of a hydroxyl group, an amino group, and an epoxy group.

3. The aluminum-plastic film according to claim 1, characterized in that: The aspect ratio of the boron nitride compound is 1 to 1000.

4. The aluminum-plastic film according to claim 1, characterized in that: The composite layer contains at least one of lamellar boron nitride and tubular boron nitride.

5. The aluminum-plastic film according to claim 1, characterized in that: Based on the mass of the composite layer, the mass percentage of the boron nitride compound is 4% to 40%.

6. The aluminum-plastic film according to any one of claims 1 to 5, characterized in that: The thickness of the aluminum-plastic film is T μm, the thickness of the composite layer is T1 μm, and 0.1≤T1 / T≤0.

5.

7. The aluminum-plastic film according to claim 6, characterized in that: 1≤T1 / W≤23.

8. The aluminum-plastic film according to any one of claims 1 to 5, characterized in that: The peel strength between the composite layer and the metal layer is 7N / 15mm to 15N / 15mm.

9. A secondary battery, characterized in that: The invention comprises the aluminum-plastic film according to any one of claims 1 to 8.

10. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to claim 9.

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