A battery upper cover and a preparation method thereof

Abstract

The present application relates to a kind of battery upper cover and its preparation method, the battery upper cover includes cover body and the cover along being arranged in the opening outside of the cover body, the cover body includes first resin matrix and the continuous fiber being arranged in the first resin matrix;The cover along includes first resin matrix and the continuous fiber being arranged in the first resin matrix, also includes second resin matrix and the discontinuous fiber being arranged in the second resin matrix;Wherein, the first resin matrix and second resin matrix all contain polyamide.An embodiment of the present application solves the problems of low strength of thermoplastic resin-based battery upper cover, unstable when battery upper cover is fixedly connected with battery lower shell, poor air tightness, thick battery upper cover parts, etc.

Description

Technical Field

[0001] This invention relates to the field of power battery casing technology, and in particular to a battery top cover and its manufacturing method. Background Technology

[0002] In recent years, electric vehicles have developed rapidly, but issues such as range anxiety still hinder their wider market acceptance to some extent. Improving the space utilization of the battery pack to accommodate more battery modules can increase the total battery capacity and thus improve the driving range, but this also leads to a sharp increase in the weight of the battery pack. As one of the key components of the battery pack, the battery cover is usually made of sheet metal, which is relatively heavy. However, fiber composite materials have high strength and low density, and are gradually becoming an effective alternative for achieving lightweight battery pack structural components.

[0003] Currently, the continuous fiber reinforced composite materials used are mainly thermosetting resin-based composites. Common preparation processes include compression molding of discontinuous fiber thermosetting composites (SMC, sheet molding compound), compression molding of continuous fiber composites (PCM, prepreg), and high-pressure transfer molding (HP-RTM). However, the SMC process uses discontinuous fibers, resulting in low material strength and difficulty in meeting mechanical performance requirements; the PCM process requires manual laying, leading to low production efficiency; HP-RTM molding equipment is complex and has high processing requirements; furthermore, thermosetting resin matrices, such as epoxy resin, polyurethane, and unsaturated resins, also have the problems of being non-recyclable, having high carbon emissions, and long molding cycles.

[0004] Thermoplastic resins, such as polyamide resins, have become a favored potential alternative material for battery covers by OEMs due to their excellent performance and recyclability. However, current thermoplastic materials are mainly produced using long-fiber reinforced compression molding (LFT-D) processes, resulting in battery covers with lower strength than those made from continuously fiber reinforced thermosetting composites. Furthermore, the thickness of the parts is greater, reducing the internal space of the battery casing and lowering battery capacity. Therefore, it is necessary to address these issues by improving the structural materials and manufacturing processes of battery covers. Summary of the Invention

[0005] In order to replace the metal-based or thermosetting resin-based battery cover in the prior art and solve the problems of low strength, unstable connection between the battery cover and the lower battery shell, poor airtightness, and thick battery cover parts, this invention provides a battery cover and its preparation method.

[0006] In a first aspect, one embodiment of the present invention provides a battery cover, which includes a cover body and a cover edge circumferentially disposed outside the opening of the cover body; the cover body includes a first resin matrix and continuous fibers disposed in the first resin matrix; the cover edge includes a first resin matrix and continuous fibers disposed in the first resin matrix, and further includes a second resin matrix and discontinuous fibers disposed in the second resin matrix.

[0007] Both the first resin matrix and the second resin matrix contain polyamide.

[0008] Secondly, one embodiment of the present invention provides a method for preparing a battery cover, comprising sequentially laying a continuous fiber reinforced polyamide composite plate and a discontinuous fiber reinforced polyamide composite plate, preheating and bonding, and molding to obtain a battery cover; wherein the continuous fiber reinforced polyamide composite plate contains a first resin matrix and continuous fibers disposed in the first resin matrix, and the discontinuous fiber reinforced polyamide composite plate contains a second resin matrix and discontinuous fibers disposed in the second resin matrix.

[0009] Thirdly, one embodiment of the present invention provides a battery casing, which includes a battery top cover and a lower casing, wherein the battery top cover is connected to the lower casing, and the battery top cover is a battery top cover as described above or a battery top cover prepared by the method described above.

[0010] Fourthly, one embodiment of the present invention provides a power battery pack, which includes a battery casing and a power battery module located inside the battery casing, wherein the battery casing adopts the battery casing described above.

[0011] The positive and progressive effects of this invention are as follows: using a combination of two different polyamide composite materials as the structural material for the battery cover imparts to the battery cover lightweight, high strength, high modulus, fire resistance, recyclability, and a smooth surface. Furthermore, it improves the stability and airtightness of the connection between the battery cover and the lower battery casing, and reduces processing costs. The corresponding one-step preparation method is simple to operate, has low processing difficulty, and is conducive to industrial-scale production. Attached Figure Description

[0012] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Wherein:

[0013] Figure 1 This is a schematic diagram of the structure of a battery cover according to an embodiment of the present invention;

[0014] Figure 2 for Figure 1 The diagram shows a mold for the battery cover; the arrows indicate the direction of the mold pressing down.

[0015] Icons: 1-Battery top cover; 11-Cover body; 12-Cover edge; 121-Continuous fiber reinforced polyamide composite board layer; 122-Discontinuous fiber reinforced polyamide composite board layer; 2-Female mold; 3-Male mold. Detailed Implementation

[0016] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the description herein is for illustrative purposes only and not intended to limit the present invention.

[0017] To fully understand this application, a detailed structure will be presented in the following description to illustrate it. Obviously, implementation of this application is not limited to the specific details familiar to those skilled in the art. Preferred embodiments of this application are described in detail below; however, other embodiments may exist besides these detailed descriptions and should not be construed as being limited to the embodiments presented herein.

[0018] It should be understood that the terminology used herein is intended only to describe particular embodiments and is not intended to limit the scope of this application. The singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. When the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof. The terms “upper,” “lower,” “front,” “rear,” “left,” “right,” and similar expressions used in this application are for illustrative purposes only and are not intended to be limiting.

[0019] Ordinal numbers such as “first” and “second” used in this application are merely identifiers and have no other meaning, such as a specific order. Moreover, for example, the term “first component” does not imply the existence of a “second component”, and the term “second component” does not imply the existence of a “first component”.

[0020] One embodiment of the present invention provides a battery cover, which includes a cover body and a cover edge circumferentially disposed outside the opening of the cover body; the cover body includes a first resin matrix and continuous fibers disposed in the first resin matrix; the cover edge includes a first resin matrix and continuous fibers disposed in the first resin matrix, and further includes a second resin matrix and discontinuous fibers disposed in the second resin matrix.

[0021] Both the first resin matrix and the second resin matrix contain polyamide.

[0022] The battery cover of this invention is used to seal the battery casing opening, effectively protecting the battery cells inside the casing from external environmental influences. It features a tight seal and high heat resistance. Both the cover body and the cover edge contain a composite material of continuous fibers and polyamide, giving the battery cover lightweight, high strength, high modulus, fire resistance, and recyclability. It also has a smooth appearance, no warping, and minimal loose fibers. The cover edge also includes a composite material of discontinuous fibers and polyamide, significantly improving the stability and airtightness when holes are drilled in the cover edge and mechanically connected to the lower casing of the battery casing via bolts.

[0023] In some embodiments, the cover body is made of a continuous fiber-reinforced polyamide composite sheet, and the cover rim is made of a continuous fiber-reinforced polyamide composite sheet and a discontinuous fiber-reinforced polyamide composite sheet. For example Figure 1 As shown, 1 is the battery cover, which includes a cover body 11 and a cover edge 12. The cover body 11 is made of a continuous fiber reinforced polyamide composite board, and the cover edge 12 includes a stacked continuous fiber reinforced polyamide composite board layer 121 and a discontinuous fiber reinforced polyamide composite board layer 122.

[0024] In some embodiments, the thickness of the cover is 1 to 3 mm, and further 1 to 2 mm, for example 1 mm, 1.25 mm, or 1.5 mm.

[0025] In some embodiments, the thickness of the cover edge is 2 to 5 mm, further 2 to 4 mm, for example 2.8 mm or 3.05 mm.

[0026] In some embodiments, the continuous fibers account for 50 to 85 wt% of the total mass of the first resin matrix and the continuous fibers, for example, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, and more specifically, 50 to 70 wt%.

[0027] In some embodiments, the discontinuous fibers account for 10 to 55 wt% of the total mass of the second resin matrix and the discontinuous fibers, for example, 15 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, and more preferably 20 to 40 wt%.

[0028] The continuous and discontinuous fibers, within a preferred mass percentage range, will give the battery cover a better overall appearance.

[0029] In some embodiments, the continuous fiber reinforced polyamide composite board is formed by hot pressing a continuous fiber reinforced polyamide prepreg containing polyamide resin and continuous fibers. Specifically, the continuous fiber reinforced polyamide prepreg is selected from one or more combinations of continuous fiber reinforced polyamide unidirectional prepreg tape, polyamide film, and continuous fiber fabric laminate. The continuous fiber reinforced polyamide prepreg of the present invention can be prepared by melt impregnation, solution impregnation, powder impregnation, or film lamination.

[0030] In one embodiment, the continuous fiber includes one or more of glass fiber, carbon fiber, basalt fiber, aramid fiber, natural fiber, metal fiber, and boron fiber.

[0031] In one embodiment, the orientation of the continuous fibers crosses at 0 to 90°, preferably 90° and / or 45°.

[0032] In some embodiments, the continuous fiber reinforced polyamide composite board includes a first surface layer, at least one intermediate layer, and a second surface layer arranged sequentially, wherein the first and second surface layers are both polyamide films, and the at least one intermediate layer includes a fiber fabric or a continuous fiber reinforced polyamide unidirectional prepreg tape. For example, a multilayer structure includes three layers, in the following order: a first surface layer (polyamide film), an intermediate layer (fiber fabric or continuous fiber reinforced polyamide unidirectional prepreg tape), and a second surface layer (polyamide film). Another example is a multilayer structure including five layers, in the following order: a first surface layer (polyamide film), a first intermediate layer (fiber fabric), a second intermediate layer (polyamide film), a third intermediate layer (fiber fabric), and a second surface layer (polyamide film).

[0033] In some embodiments, the continuous fiber reinforced polyamide unidirectional prepreg tape is prepared by melt impregnation, specifically by referring to the preparation process disclosed in Chinese invention patent applications CN115260752A, CN115260753A or CN115536876A.

[0034] In some embodiments, the thickness of the continuous fiber reinforced polyamide composite board is less than 1.5 mm, further 0.8 to 1.5 mm, and even 1 to 1.5 mm.

[0035] In some embodiments, the continuous fiber reinforced polyamide composite board has a multilayer structure, which includes one or more polyamide films, one or more continuous fiber fabrics, and / or one or more continuous fiber reinforced polyamide unidirectional prepreg tapes.

[0036] In some embodiments, the continuous fiber reinforced polyamide composite board has a multilayer structure, the multilayer structure including n layers of continuous fiber reinforced polyamide unidirectional prepreg tape, where 2≤n≤10 and n is an integer, the layup is an alternating layup of 0° to 90°, wherein the polyamide resin in the continuous fiber reinforced polyamide unidirectional prepreg tape is used to form a first resin matrix.

[0037] In some embodiments, the continuous fibers in the continuous fiber reinforced polyamide unidirectional prepreg tape include one or more of glass fibers, carbon fibers, basalt fibers, aramid fibers, natural fibers, metal fibers, and boron fibers.

[0038] In some implementations, the alternating layup refers to the layers being laid at a certain angle to satisfy the principle of balanced and symmetrical laying, such as 0° / 90° crossover, 45° / 45° crossover, 0° / 30° crossover, 0° / 60° crossover, etc.

[0039] In some embodiments, the thickness of the continuous fiber reinforced polyamide unidirectional prepreg tape is 0.15–0.5 mm, more specifically 0.15–0.3 mm, and even more specifically 0.2–0.25 mm.

[0040] In some embodiments, the continuous fiber reinforced polyamide composite board has a multilayer structure, the multilayer structure comprising one or more polyamide films and one or more continuous fiber fabrics, the one or more polyamide films forming a first resin matrix, and the one or more continuous fiber fabrics located in the first resin matrix; preferably, the one or more continuous fiber fabrics are disposed between the multilayer polyamide films.

[0041] In one embodiment, the thickness of the polyamide film used to prepare the continuous fiber reinforced polyamide composite board is 0.05 to 1 mm, more specifically 0.05 to 0.3 mm, for example 0.05 mm, 0.08 mm, 0.1 mm, 0.12 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.5 mm, or 0.8 mm.

[0042] In one embodiment, the polyamide film may be the polyamide 56 resin film disclosed in patent application CN111763313A, the raw material of which is bio-based polyamide resin obtained by copolymerization of bio-based pentanediamine and adipic acid.

[0043] In one embodiment, the thickness of the continuous fiber fabric used to prepare the continuous fiber reinforced polyamide composite board can be 0.05 to 0.5 mm, and more preferably 0.1 to 0.4 mm, for example 0.2 mm, 0.3 mm, or 0.35 mm.

[0044] In one embodiment, the continuous fibers in the continuous fiber fabric include one or more of glass fibers, carbon fibers, basalt fibers, aramid fibers, natural fibers, metal fibers, and boron fibers.

[0045] In one embodiment, the continuous fiber fabric comprises continuous fiber cloth and / or continuous fiber yarn.

[0046] In one embodiment, the continuous fiber fabric includes one or more of checkered fabric, non-crimped fabric, and three-dimensional fabric. Further, the checkered fabric may be selected from one or more of plain weave, twill weave, and satin weave; the non-crimped fabric may be selected from one or more of uniaxial, biaxial, triaxial, and quadriaxial structures; and the three-dimensional fabric may be selected from three-dimensional orthogonal structures and / or three-dimensional interlocking structures.

[0047] In one embodiment, the directions of the continuous fibers in the continuous fiber fabric intersect at 0 to 90°, preferably 90° and / or 45°.

[0048] In one embodiment, the continuous fiber fabric is a glass fiber biaxial fabric, wherein the direction of the continuous fibers is 0° / 90° or +45° / -45°.

[0049] In one embodiment, the continuous fiber fabric is a plain weave glass fiber cloth, wherein the direction of the continuous fibers is 0° / 90° or +45° / -45°.

[0050] In one embodiment, the continuous fiber fabric is a twill-weave glass fiber cloth, wherein the direction of the continuous fibers is 0° / 90° or +45° / -45°.

[0051] In one embodiment, the total weight of the polyamide film and the continuous fiber fabric used to prepare the continuous fiber reinforced polyamide composite board is used as a basis, wherein the mass content of the continuous fiber can be 50% to 85%, for example 55%, 60%, 65%, 70%, 75%, 80%, and more preferably 50% to 70%.

[0052] In some embodiments, the first resin matrix contains polyamide and additives, the additives containing at least antioxidants, lubricants and flame retardants, and preferably, may also contain color masterbatch, coupling agents, compatibilizers, flow modifiers or combinations thereof.

[0053] In some embodiments, the antioxidant is selected from one or more of hindered phenols, hindered amines, phosphites, and thiosulfates, such as one or more of antioxidant 168, antioxidant 1098, antioxidant 1010, and antioxidant S9228.

[0054] In some embodiments, the lubricant includes one or more of stearate lubricants, fatty amide lubricants, silicone powder or silicone masterbatch, PE wax or ethylene-acrylic acid copolymer.

[0055] In some embodiments, the flame retardant includes one or more of phosphorus-based flame retardants, halogenated flame retardants, nitrogen-based flame retardants, or inorganic flame retardants.

[0056] In some embodiments, the flame retardant is a combination of phosphorus-based flame retardants and inorganic flame retardants.

[0057] In some embodiments, the phosphorus-based flame retardant is selected from one or more of red phosphorus, aluminum methyl ethyl phosphinate, aluminum diethyl phosphinate, zinc methyl ethyl phosphinate, zinc diethyl phosphinate, 3-hydroxyphenylphosphonopropionic acid (CEPPA), [(6-oxo-6H-dibenzo[c,e][1,2]oxophosphorylhexane-6-yl)methyl]succinic acid (DDP), bis(4-carboxyphenyl)phenylphosphine oxide (BCPPO), 4-carboxyphenylphenylphosphine acid (CPPPA), carboxyphenylphosphine acid (CPPA), and 2,3-dicarboxypropyl diphenylphosphine oxide (DPDPO).

[0058] In some embodiments, the inorganic flame retardant is selected from one or more of kaolin, talc, attapulgite, calcium carbonate, silicon dioxide, montmorillonite, antimony trioxide, zinc borate, and barium metaborate.

[0059] In some embodiments, the color masterbatch is a black masterbatch.

[0060] In some embodiments, the coupling agent includes at least one of silane coupling agents, carbonate coupling agents, and aluminate coupling agents.

[0061] In some embodiments, the compatibilizer includes at least one of polyolefin-grafted maleic anhydride compatibilizers, polyolefin-grafted methyl ester-acrylate compatibilizers, and rubber elastomer-grafted maleic anhydride compatibilizers. Specifically, polyolefin-grafted maleic anhydride compatibilizers include PP-g-MAH and POE-g-MAH, polyolefin-grafted methyl ester-acrylate compatibilizers include POE-g-GMA, and rubber elastomer-grafted maleic anhydride compatibilizers include EPDM-g-MAH.

[0062] In some specific embodiments, the first resin matrix contains 75-95 wt% polyamide, 5-12 wt% flame retardant, 0.1-2 wt% antioxidant, and 0.1-2 wt% lubricant; and more preferably, it also contains 0-5 wt% color masterbatch, 0-10 wt% compatibilizer, and 0-2 wt% coupling agent.

[0063] In some specific embodiments, the first resin matrix contains 75-88 wt% polyamide, 6-9 wt% phosphorus-based flame retardant, 0.5-3 wt% inorganic flame retardant, 0.1-1 wt% antioxidant, 0.1-1 wt% lubricant, 0.1-5 wt% colored masterbatch, 0.1-10 wt% compatibilizer, and 0.1-2 wt% coupling agent.

[0064] In some embodiments, the discontinuous fiber reinforced polyamide composite board is formed by hot pressing a second resin matrix and discontinuous fibers after melt mixing, wherein the weight percentage of the discontinuous fibers is 10-55 wt%, and more preferably 20-40 wt%. The weight percentage is based on the total weight of the second resin matrix and discontinuous fibers.

[0065] In some embodiments, the second resin matrix contains polyamide and additives, said additives containing at least antioxidants, lubricants, and flame retardants, and may further contain masterbatches, coupling agents, compatibilizers, flow modifiers, or combinations thereof. The types of additives can be referred to the description of the additives in the first resin matrix described above.

[0066] In some specific embodiments, the second resin matrix contains 75-95 wt% polyamide, 5-12 wt% flame retardant, 0.1-2 wt% antioxidant, and 0.1-2 wt% lubricant; and more preferably, it also contains 0-5 wt% color masterbatch, 0-10 wt% compatibilizer, and 0-2 wt% coupling agent.

[0067] In some specific embodiments, the second resin matrix contains 75-88 wt% polyamide, 6-9 wt% phosphorus-based flame retardant, 0.5-3 wt% inorganic flame retardant, 0.1-1 wt% antioxidant, 0.1-1 wt% lubricant, 0.1-5 wt% colored masterbatch, 0.1-10 wt% compatibilizer, and 0.1-2 wt% coupling agent.

[0068] In some specific embodiments, the first resin matrix and the second resin matrix are the same.

[0069] In some specific embodiments, the discontinuous fiber includes one or more of glass fiber, carbon fiber, basalt fiber, aramid fiber, natural fiber, metal fiber, and boron fiber.

[0070] In some specific embodiments, the discontinuous fiber has a fiber length of 0.1 to 30 mm, for example, short fibers with a length of 0.1 to 6 mm or long fibers with a length of 6 to 25 mm.

[0071] In some embodiments, the thickness of the discontinuous fiber-reinforced polyamide composite board is less than 2.5 mm, and more specifically 1 to 2.5 mm.

[0072] In one embodiment, the monomers for preparing the polyamide include a diamine and a diacid, wherein the diamine contains at least pentamethylenediamine; and the diacid includes one or more of aliphatic diacids having 4 to 18 carbon atoms and aromatic diacids having 8 to 10 carbon atoms (e.g., 9).

[0073] In one embodiment, the molar ratio of the diamine and the diacid used to prepare the polyamide resin can be (1 to 1.05):1, for example, 1.01:1, 1.02:1, 1.03:1, or 1.04:1.

[0074] In one embodiment, the diamine includes pentanediamine and other diamines, wherein the other diamines may be one or more aliphatic diamines (excluding pentanediamine) having 4 to 16 carbon atoms; further, the other diamines may be one or more of butanediamine, hexanediamine, heptadecanediamine, octanediamine, nonanediamine, decanedanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, and hexadecanediamine.

[0075] In one embodiment, the aliphatic dicarboxylic acid having 4 to 18 carbon atoms can be one or more of the following: oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid.

[0076] In one embodiment, the aromatic dicarboxylic acid may be one, two, or three of terephthalic acid, isophthalic acid, and phthalic acid.

[0077] In one specific embodiment, the polyamide is obtained by copolymerization of pentanediamine and a long-chain dicarboxylic acid, with a melting point of 190–220°C; the long-chain dicarboxylic acid is selected from one or more of sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid.

[0078] In one specific embodiment, the polyamide is obtained by copolymerization of pentanediamine, long-chain dicarboxylic acid and terephthalic acid, and has a melting point of 190-320°C; the long-chain dicarboxylic acid is selected from one or more of sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid and octadecanoic acid.

[0079] In one specific embodiment, the polyamide is obtained by copolymerization of pentanediamine, adipic acid and terephthalic acid, and has a melting point of 240–320°C.

[0080] In a preferred embodiment, the pentanediamine is bio-based pentanediamine, which refers to pentanediamine synthesized from compounds derived from biomass, such as glucose and lysine, through enzyme reactions, yeast reactions, or fermentation reactions during the monomer synthesis process.

[0081] In a preferred embodiment, the polyamide is a bio-based polyamide, such as bio-based polyamide PA56, bio-based polyamide PA510, bio-based polyamide PA511, bio-based polyamide PA512, bio-based polyamide PA513, bio-based polyamide PA514, bio-based polyamide PA515, and bio-based polyamide PA516, bio-based polyamide PA56 / 5T, bio-based polyamide PA510 / 5T, bio-based polyamide PA511 / 5T, bio-based polyamide PA512 / 5T, bio-based polyamide PA513 / 5T, bio-based polyamide PA514 / 5T, bio-based polyamide PA515 / 5T, bio-based polyamide PA516 / 5T, bio-based polyamide PA56 / 5I, and commercially available polyamides. Series of resins: one or more of E-6638, E-6308, E-6300, E-6290, E-6635, E-6631, E-6632, E-6520, E-5000, E-3600, E-3601, E-3100, E-3102, E-3300, E-3500, E-2260, E-2262, E-1273, E-1251, and E-1320. The fact that some raw materials for bio-based pentanediamine or bio-based polyamide resins are derived from renewable plant resources further enhances their commercial potential and research value as matrix resins for composite materials.

[0082] One embodiment of the present invention also provides a method for preparing the aforementioned battery cover, comprising: sequentially laying continuous fiber reinforced polyamide composite sheet and discontinuous fiber reinforced polyamide composite sheet, preheating and bonding, and molding to obtain a battery cover; wherein, the continuous fiber reinforced polyamide composite sheet contains a first resin matrix and continuous fibers disposed in the first resin matrix, and the discontinuous fiber reinforced polyamide composite sheet contains a second resin matrix and discontinuous fibers disposed in the second resin matrix.

[0083] In some embodiments, the continuous fiber reinforced polyamide composite sheet and the discontinuous fiber reinforced polyamide composite sheet are cut and laid according to the pre-designed shape of the target product. Preferably, the continuous fiber reinforced polyamide composite sheet is cut into square sheets, and the discontinuous fiber reinforced polyamide composite sheet is cut into strip sheets, and then the strip sheets are laid on the top and / or bottom of the four inner sides of the square sheets, preferably on the top of the inner sides.

[0084] In some embodiments, the temperature during preheating and bonding is 10 to 50°C above the melting point of the higher of the first and second resin matrices, for example, 20°C, 30°C, 40°C, or 50°C.

[0085] In some embodiments, the preheating and bonding time is 60 to 200 seconds, for example, 180 seconds.

[0086] In some embodiments, the mold temperature is controlled to be above 110°C during the compression molding process, and further to be between 110°C and 170°C, for example, 120°C, 130°C, 140°C, 150°C, 160°C, or 170°C.

[0087] In some embodiments, the mold pressure is controlled at 10-15 MPa and the holding time is 30-150 s, for example 120 s, during the compression molding process.

[0088] In some embodiments, the mold used in the compression molding process consists of a female mold and a male mold, which are used to mold the battery cover structure, such as... Figure 2 As shown. Different molds can be set according to the shape requirements of the battery cover. The cover can be a smooth flat structure, or it can have several raised strips added to the flat surface. The raised strips can also be made of the aforementioned continuous fiber reinforced polyamide composite material.

[0089] This invention innovatively proposes a combination of two different composite materials by setting specific battery cover structural materials, and proposes a corresponding integrated molding method, ultimately obtaining a high-performance, recyclable battery cover, and in particular improving the connection stability between the battery cover and the lower shell.

[0090] The present invention also provides a battery casing, comprising a battery upper cover and a lower casing, wherein the battery upper cover is connected to the lower casing, and the battery upper cover is a battery upper cover as described above or a battery upper cover prepared by the above method. The connection method may be a bolt connection.

[0091] The present invention also provides a power battery pack, which includes a battery casing and a power battery module located inside the battery casing, wherein the battery casing adopts the battery casing described above.

[0092] The preparation of a battery cover according to one embodiment of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. All raw materials are dried to a moisture content of less than 500 ppm before use. The raw materials and testing methods involved in each embodiment are as follows.

[0093] raw material:

[0094] (1) Polyamide PA5T / 512: Melting point 302℃, obtained by copolymerization of bio-based pentanediamine, dodecanoic acid and terephthalic acid in a molar ratio of 10.2:2.9:6.9, purchased from Kaisai (Jinxiang) Biomaterials Co., Ltd.

[0095] (2) Polyamide PA56 / 5T: Melting point 282℃, obtained by copolymerization of bio-based pentanediamine, terephthalic acid and adipic acid in a molar ratio of 1:0.6:0.4, purchased from Kaisai (Jinxiang) Biomaterials Co., Ltd.

[0096] (3) Plain weave glass fiber cloth: Taian Juli brand EWR600T; thickness is 0.35mm, and the direction of continuous glass fiber is 0° / 90°.

[0097] (4) Short glass fiber: Jushi brand 560A chopped raw glass fiber, fiber diameter ±10%, chopped length ±1.0mm.

[0098] (5) Additives: All were commercially available. Antioxidant was purchased from BASF Group, Germany; lubricant was purchased from Clariant, Germany; coupling agent was purchased from Hangzhou Jessica Chemical Co., Ltd.; black masterbatch was purchased from Cabot Corporation, USA; compatibilizer was purchased from Dow Chemical Company, USA.

[0099] Preparation example:

[0100] (1) Resin matrix A1 raw materials: 81.4wt% PA5T / 512, 7wt% flame retardant red phosphorus, 1.2wt% flame retardant montmorillonite, 0.3wt% antioxidant 1098, 0.5wt% lubricant WAX-C, 6wt% compatibilizer POE-g-MAH, 0.6wt% coupling agent KH570, 3wt% black masterbatch XP6603A.

[0101] (2) Resin matrix A2 raw materials: 81.4wt% PA56 / 5T, 7wt% flame retardant red phosphorus, 1.2wt% flame retardant montmorillonite, 0.3wt% antioxidant 1098, 0.5wt% lubricant WAX-C, 6wt% compatibilizer POE-g-MAH, 0.6wt% coupling agent KH570, 3wt% black masterbatch XP6603A.

[0102] (3) Continuous fiber reinforced polyamide composite board B1: The resin matrix A1 raw material is heated and melted and mixed. The resulting melt is cast through a T-shaped mold to a cooling roller with a surface temperature of 50°C. Then, it is drawn and wound to obtain a polyamide film with a thickness of 0.1 mm. The polyamide film and plain weave glass fiber cloth are alternately laid. The laying sequence is that the polyamide film and plain weave glass fiber cloth are alternately laid with the polyamide film on the surface. After laying, the composite board with continuous glass fiber content of 50 wt%, 65 wt%, and 75 wt% is obtained by molding.

[0103] (4) Non-continuous fiber reinforced polyamide composite board C1: The raw materials of resin matrix A1 and short glass fibers are mixed evenly, with the amount of short glass fibers added being 30wt% or 40wt% (relative to the mass ratio of non-continuous fiber reinforced polyamide composite board). The mixture is heated and melted by a twin-screw extruder and extruded into granules, which are then molded to obtain the final product.

[0104] (5) Non-continuous fiber reinforced polyamide composite board C2: The raw materials of resin matrix A2 and short glass fibers are mixed evenly, and the amount of short glass fibers added is 30wt% (relative to the mass ratio of non-continuous fiber reinforced polyamide composite board). The mixture is heated and melted by a twin-screw extruder and extruded into granules, which are then molded.

[0105] Example 1

[0106] Battery cover: The cover body includes a first resin matrix and continuous fibers disposed on the first resin matrix; the cover edge includes a first resin matrix and continuous fibers disposed on the first resin matrix, and further includes a second resin matrix and discontinuous fibers disposed on the second resin matrix; wherein the first resin matrix and the second resin matrix are both resin matrix A1 (containing polyamide PA5T / 512); the continuous fibers are continuous glass fibers; the discontinuous fibers are short glass fibers. Figure 1 As shown, the cover 11 is composed of a 1.25mm thick continuous fiber reinforced polyamide composite board B1, and the cover edge 12 is composed of a 1.25mm thick continuous fiber reinforced polyamide composite board B1 (121) and a 1.8mm thick discontinuous fiber reinforced polyamide composite board C1 (122) stacked together; the continuous fiber content in composite board B1 is 65wt%, and the short glass fiber content in composite board C1 is 30wt%. The total thickness of the cover is 1.25mm, and the total thickness of the cover edge is 3.05mm (i.e., 1.25 + 1.8).

[0107] Preparation method: Cut the continuous fiber reinforced polyamide composite board B1 into square boards, and cut the discontinuous fiber reinforced polyamide composite board C1 into strips. Then, place the strips on the inner sides of the four sides of the square boards, preheat and bond them at 340℃ for 180 seconds, and then place the preheated and bonded boards in a suitable location. Figure 2 In the mold shown, the mold temperature is controlled at 120℃ and the pressure at 10MPa. The material is then molded and held under pressure for 120 seconds to obtain… Figure 1 The polyamide battery cover shown.

[0108] Example 2

[0109] Battery cover: Same as in Example 1, except that the first resin matrix is ​​resin matrix A1 (containing polyamide PA5T / 512) and the second resin matrix is ​​resin matrix A2 (containing polyamide PA56 / 5T); the cover body is composed of a 1.25mm thick continuous fiber reinforced polyamide composite plate B1, and the cover edge is composed of a 1.25mm thick continuous fiber reinforced polyamide composite plate B1 and a 1.8mm thick discontinuous fiber reinforced polyamide composite plate C2 stacked together. The total thickness of the cover body is 1.25mm and the total thickness of the cover edge is 3.05mm.

[0110] The preparation method is the same as in Example 1.

[0111] Example 3

[0112] Battery cover: Same as in Example 1, except that the cover body is made of a continuous fiber reinforced polyamide composite board B1 with a thickness of 1mm, and the cover edge is made of a continuous fiber reinforced polyamide composite board B1 with a thickness of 1mm and a discontinuous fiber reinforced polyamide composite board C1 with a thickness of 1.8mm stacked together. The total thickness of the cover body is 1mm and the total thickness of the cover edge is 2.8mm.

[0113] The preparation method is the same as in Example 1.

[0114] Example 4

[0115] Battery cover: Same as in Example 1, except that the continuous fiber content in composite board B1 is 75 wt%.

[0116] The preparation method is the same as in Example 1.

[0117] Example 5

[0118] Battery cover: Same as in Example 1, except that the continuous fiber content in composite board B1 is 50 wt%.

[0119] The preparation method is the same as in Example 1.

[0120] Example 6

[0121] Battery cover: Same as in Example 1, except that the short glass fiber content in composite material C1 is 45 wt%.

[0122] The preparation method is the same as in Example 1.

[0123] Comparative Example 1

[0124] Battery cover: The shape is the same as the battery cover in Example 1, except that it does not contain continuous fibers. That is, the cover body is made of a 1.25mm thick discontinuous fiber reinforced polyamide composite board C1, and the cover edge is made of two discontinuous fiber reinforced polyamide composite boards C1 with a thickness of 1.25mm and 1.8mm respectively. The short glass fiber content in the composite board C1 is 30wt%. The total thickness of the cover body is 1.25mm, and the total thickness of the cover edge is 3.05mm.

[0125] The preparation method is the same as in Example 1.

[0126] Comparative Example 2

[0127] The battery cover has the same shape as the battery cover in Example 1, the difference being the material used:

[0128] Polypropylene resin matrix raw materials: 71.5 wt% polypropylene resin, 25 wt% commercially available 484 intumescent flame retardant, 0.5 wt% antioxidant 1098, 0.5 wt% coupling agent KH570, 0.5 wt% lubricant WAX-C, and 2 wt% black masterbatch XP6603A are mixed in a high-speed mixer and set aside for later use.

[0129] Continuous fiber polypropylene composite board: The polypropylene resin matrix raw material is heated and melted, and the resulting melt is cast through a T-die onto a cooling roller with a surface temperature of 50°C. Then, through traction and winding, a polypropylene film with a thickness of 0.1 mm is obtained. The polypropylene film and plain weave glass fiber cloth are alternately laid in the following order: the polypropylene film and plain weave glass fiber cloth are laid alternately with the polypropylene film on the surface. After laying, it is molded to obtain a polypropylene composite board with a continuous glass fiber content of 65 wt% and a thickness of 1.25 mm.

[0130] Discontinuous fiber polypropylene composite board: Polypropylene resin matrix raw material and short glass fiber are mixed evenly, with the amount of short glass fiber added being 30wt%. The mixture is heated and melted by a twin-screw extruder and extruded into granules, which are then molded to obtain a composite board with a thickness of 1.8mm.

[0131] Battery cover: The cover body is made of 1.25mm thick continuous fiber polypropylene composite sheet, and the cover edge is made of a combination of 1.25mm thick continuous fiber polypropylene composite sheet and 1.8mm thick discontinuous fiber polypropylene composite sheet. The total thickness of the cover body is 1.25mm, and the total thickness of the cover edge is 3.05mm.

[0132] Preparation method of battery cover: Cut continuous fiber polypropylene composite sheet into square sheets, cut discontinuous fiber polypropylene composite sheet into strips, and then lay the strips on the inner sides of the four sides of the square sheet. Preheat and bond at 200℃ for 120 seconds. Place the preheated and bonded sheet on... Figure 2 In the mold shown, the mold temperature is controlled at 80℃ and the pressure at 10MPa. The mold is then pressed and held under pressure for 120s to obtain the polypropylene battery cover.

[0133] The battery covers obtained in the above embodiments and comparative examples were tested as follows, and the results are shown in Table 1:

[0134] 1) The bending test of the cover is performed according to standard ISO-178. The test conditions are 2 mm / min and the span is 64 mm.

[0135] 2) The tensile test of the cover shall be performed in accordance with the standard ISO-572-2, and the test conditions shall be 5 mm / min.

[0136] 3) Fire resistance of the cover: Refer to GB / T 38031-2020, use a propane flame gun for single-point burning test. Test conditions: oxygen 0.5MPa, propane 0.07MPa, nozzle distance 100mm, flame temperature 1100±50℃, record the time from flame burning to the board being burned through.

[0137] 4) Product Appearance: Visually inspect the surface of the battery cover and its edge to see if it is flat and free of warping or loose fibers. Grade 1 indicates a flat surface without warping or loose fibers, while higher grades indicate a rougher surface.

[0138] 5) Air tightness: After the battery top cover and the battery bottom shell are fixedly connected by drilling and bolts, the air tightness test is carried out in accordance with the national standard GB / T31467.3-2015. The amount of gas leakage is recorded. The lower the leakage, the better the air tightness.

[0139] 6) Flame retardancy rating: The UL94 horizontal burning test is adopted. According to the UL94 requirements, the 1.5mm thick sample is placed in the center of the flame of an alcohol lamp with a flame length of 50mm, with the coated side facing down and held horizontally for 20 seconds. After removal, the time until the flame is extinguished is measured to evaluate the flame retardancy rating.

[0140] 7) Double 85 test: Place the sample to be tested into the test chamber, and adjust the temperature and humidity in the test chamber to 85℃ and 85%RH respectively. After 1000 hours, test the tensile strength retention rate of the sample.

[0141] Table 1

[0142]

[0143] As can be seen from Table 1, the cover bodies of Examples 1-6 of the present invention exhibit superior mechanical properties compared to Comparative Examples 1-2. They do not burn through after being subjected to fire for more than 80 minutes, and their mechanical properties are retained at over 80% under double 85 conditions, with gas leakage rates all below 80 Pa. Moreover, Example 3 achieves a cover body thickness of only 1 mm and a cover edge thickness of 2.8 mm, which will significantly reduce the weight of the battery cover body.

[0144] Unless otherwise specified, the terminology used in this invention has the meanings commonly understood by those skilled in the art. The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes, and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is defined only by the claims.

Claims

1. A battery cover, comprising a cover body and a cover edge circumferentially disposed outside an opening of the cover body, characterized in that, The cover body includes a first resin matrix and continuous fibers disposed on the first resin matrix; the cover edge includes a first resin matrix and continuous fibers disposed on the first resin matrix, and further includes a second resin matrix and discontinuous fibers disposed on the second resin matrix; Both the first resin matrix and the second resin matrix contain polyamide.

2. The battery cover according to claim 1, characterized in that, The thickness of the cover is 1 to 3 mm, and / or the thickness of the cover edge is 2 to 5 mm.

3. The battery cover according to claim 1, characterized in that, The continuous fibers account for 50-85 wt% of the total mass of the first resin matrix and the continuous fibers, and / or the discontinuous fibers account for 10-55 wt% of the total mass of the second resin matrix and the discontinuous fibers.

4. The battery cover according to claim 1, characterized in that, The continuous fiber includes one or more of glass fiber, carbon fiber, basalt fiber, aramid fiber, natural fiber, metal fiber, and boron fiber, and / or the discontinuous fiber includes one or more of glass fiber, carbon fiber, basalt fiber, aramid fiber, natural fiber, metal fiber, and boron fiber.

5. The battery cover according to claim 1, characterized in that, The cover is made of continuous fiber reinforced polyamide composite board, and the cover edge is made of continuous fiber reinforced polyamide composite board and discontinuous fiber reinforced polyamide composite board.

6. The battery cover according to claim 5, characterized in that, The continuous fiber reinforced polyamide composite board is formed by hot pressing a continuous fiber reinforced polyamide prepreg, which contains polyamide resin and continuous fibers. Preferably, the continuous fiber reinforced polyamide prepreg is selected from one or more combinations of continuous fiber reinforced polyamide unidirectional prepreg tape, polyamide film, and continuous fiber fabric laminate; Preferably, the continuous fiber reinforced polyamide composite board includes a first surface layer, at least one intermediate layer and a second surface layer arranged in sequence, wherein the first surface layer and the second surface layer are both polyamide films, and the at least one intermediate layer includes a fiber fabric or a continuous fiber reinforced polyamide unidirectional prepreg tape.

7. The battery cover according to claim 1, characterized in that, The first resin matrix contains polyamide and additives, wherein the additives contain at least antioxidants, lubricants and flame retardants, and preferably, also contain masterbatch, coupling agents, compatibilizers, flow modifiers or combinations thereof; and / or, the second resin matrix contains polyamide and additives, wherein the additives contain at least antioxidants, lubricants and flame retardants, and preferably, also contain masterbatch, coupling agents, compatibilizers, flow modifiers or combinations thereof; Preferably, the flame retardant includes one or more of phosphorus-based flame retardants, halogenated flame retardants, nitrogen-based flame retardants, or inorganic flame retardants; Preferably, the flame retardant is a combination of phosphorus-based flame retardants and inorganic flame retardants.

8. The battery cover according to claim 1, characterized in that, The monomers for preparing the polyamide include a diamine and a diacid, wherein the diamine contains at least pentamethylenediamine; and the diacid includes one or more of aliphatic diacids having 4 to 18 carbon atoms and aromatic diacids having 8 to 10 carbon atoms.

9. A method for preparing the battery cover according to any one of claims 1 to 8, comprising: A battery cover is obtained by sequentially laying continuous fiber reinforced polyamide composite sheets and discontinuous fiber reinforced polyamide composite sheets, preheating and bonding, and molding. The continuous fiber reinforced polyamide composite sheet contains a first resin matrix and continuous fibers disposed in the first resin matrix, and the discontinuous fiber reinforced polyamide composite sheet contains a second resin matrix and discontinuous fibers disposed in the second resin matrix. Preferably, the continuous fiber reinforced polyamide composite board is cut into square boards, and the discontinuous fiber reinforced polyamide composite board is cut into strip boards, and then the strip boards are laid on the top and / or bottom of the four inner sides of the square boards respectively. Preferably, the temperature during preheating and bonding is 10 to 50°C above the melting point of the resin matrix with the higher melting point of the first resin matrix and the second resin matrix. Preferably, the preheating and bonding time is 60–200 seconds; Preferably, the mold temperature is controlled to be above 110°C, and more specifically 110–170°C, during the compression molding process; Preferably, during the compression molding process, the mold pressure is controlled at 10-15 MPa, and the holding time is 30-150 s.

10. A battery casing comprising a battery upper cover and a lower casing, wherein the battery upper cover is connected to the lower casing, characterized in that, The battery cover is the battery cover as described in any one of claims 1 to 8 or the battery cover prepared by the preparation method described in claim 9.

11. A power battery pack, comprising a battery casing and a power battery module located inside the battery casing, characterized in that, The battery casing is the battery casing according to claim 10.

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