Cap and preparation method thereof

Abstract

The invention discloses a cap used for a cylindrical battery, the cylindrical battery comprises a shell and a battery cell, the shell is provided with an opening, the battery cell is accommodated in the shell through the opening, and the cap comprises a cover plate used for sealing the opening and comprising an inner surface facing the battery cell and an outer surface deviating from the battery cell; the first heat conduction coating covers the inner surface and has a first heat conduction coefficient; the second heat conduction coating covers the outer surface and has a second heat conduction coefficient, and the second heat conduction coefficient is larger than the first heat conduction coefficient. According to the invention, serious deformation of the cylindrical battery cap area in the thermal runaway process can be avoided, and the eruption probability of the pole is reduced. The invention further discloses a preparation method of the cap.

Description

Technical Field

[0001] This invention relates to the field of cylindrical battery technology, and in particular to a cap and a method for preparing the cap. Background Technology

[0002] In recent years, large cylindrical batteries have become an important technological route in the field of new energy vehicles, and their industrialization process has been accelerating, which is expected to drive technological innovation and development in related industrial chains. Compared with other existing battery packaging forms, large cylindrical batteries typically adopt a full-tab structure, giving them excellent fast-charging performance. At the same time, their cylindrical structure facilitates compatibility with advanced material systems such as high-nickel cathodes, silicon-based anodes, and silicon-doped lithium supplementation, thereby significantly improving the battery's energy density to meet the ever-increasing demand for driving range.

[0003] The application of the aforementioned high-energy-density material systems poses a severe challenge to the internal thermal stability of batteries. During service, batteries may be subjected to various abuse conditions, such as electrical abuse (overcharging, over-discharging, external short circuits); thermal abuse (high temperature, localized overheating); and mechanical abuse (impact, compression, puncture). These abuse conditions can easily trigger a series of exothermic chemical reactions within the battery, leading to separator shrinkage and melting, exacerbated internal short circuits, electrolyte decomposition and combustion, ultimately resulting in thermal runaway.

[0004] Currently, to improve battery safety under thermal runaway conditions, the mainstream technical approach is to guide the thermal runaway products (high-temperature gases, particles, etc.) to be released in a directional and controllable unidirectional manner, achieving "thermoelectric separation," that is, isolating the release path from the high-voltage electrical circuit, thereby providing valuable escape time for people. Under this design approach, the structural integrity of the battery casing and positive electrode post is crucial during the thermal runaway process.

[0005] However, when thermal runaway occurs, the internal temperature and pressure of the battery rise sharply. The cap area connecting the positive electrode post to the casing is prone to softening, expansion, or even structural failure due to heat. This may cause the positive electrode post to be ejected prematurely, disrupting the preset one-way discharge path and causing the thermal runaway products to erupt disorderly, reducing the effectiveness of the safety design.

[0006] Therefore, it is necessary to develop a cap that can effectively reduce the probability of positive electrode column eruption in the event of thermal runaway, thereby improving the overall safety and reliability of the battery. Summary of the Invention

[0007] To address the aforementioned technical problems, embodiments of the present invention provide a cap and a method for preparing the cap.

[0008] In a first aspect, embodiments of the present invention disclose a cap for a cylindrical battery, the cylindrical battery comprising a casing and a battery cell, the casing having an opening, the battery cell being received within the casing through the opening, the cap comprising:

[0009] A cover plate for sealing the opening, comprising an inner surface facing the battery cell and an outer surface facing away from the battery cell;

[0010] A first thermally conductive coating is applied to the inner surface and has a first thermal conductivity.

[0011] A second thermally conductive coating is applied to the outer surface and has a second thermal conductivity greater than the first thermal conductivity.

[0012] By adopting the above technical solution, severe deformation of the cap area of ​​the cylindrical battery can be avoided during thermal runaway, reducing the probability of the electrode column erupting, thereby enabling thermal propagation protection based on the thermal runaway characteristics of the cylindrical battery.

[0013] Optionally, the first thermal conductivity is 0.02~0.05 W / m·K, and the second thermal conductivity is 3.5~10.0 W / m·K.

[0014] Optionally, the first thermally conductive coating is formed by photocuring a first thermally conductive coating material. The first thermally conductive coating material includes a first photocurable resin, a first thermally conductive filler, a first diluent, and a first photoinitiator. The first thermally conductive filler accounts for 20-40 wt% of the mass of the first photocurable resin, the first diluent accounts for 20-35 wt% of the mass of the first photocurable resin, and the first photoinitiator accounts for 3-8 wt% of the mass of the first photocurable resin.

[0015] And / or, the second thermally conductive coating is formed by photocuring a second thermally conductive coating material, the second thermally conductive coating material comprising a second photocurable resin, a second thermally conductive filler, a second diluent, and a second photoinitiator, wherein the second thermally conductive filler accounts for 15-30 wt% of the mass of the second photocurable resin, the second diluent accounts for 15-30 wt% of the mass of the second photocurable resin, and the second photoinitiator accounts for 3-8 wt% of the mass of the second photocurable resin.

[0016] Optionally, the first photocurable resin is an epoxy resin, and the second photocurable resin is an epoxy acrylate.

[0017] Optionally, the first thermally conductive filler is one or more of methyl urethane, ethyl urethane, tetrabutylphenol, aluminum silicate, aluminum silicate hydrate, expanded perlite, vitrified microspheres, silica aerogel, alumina aerogel, and zirconia aerogel, and the second thermally conductive filler is one or more of silicon nitride, silicon carbide, aluminum nitride, graphene, carbon nanotubes, zinc oxide, and magnesium oxide.

[0018] Optionally, the first diluent is one or more of tripropylene glycol diacrylate and hydroxyethyl acrylate, and the second diluent is trimethylolpropane triacrylate.

[0019] Optionally, the first photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone, and the second photoinitiator is 2,4,6-trimethylbenzoyl diphenylphosphine oxide.

[0020] Optionally, the particle size of the second thermally conductive filler is 20-250 nm.

[0021] Secondly, embodiments of the present invention disclose a method for preparing a cap, used to prepare a cap as described in any embodiment of the first aspect, the method comprising:

[0022] The first thermally conductive coating is applied to the inner surface of the cover plate, and the second thermally conductive coating is applied to the outer surface of the cover plate. Then, a photocuring process is performed to form the first thermally conductive coating and the second thermally conductive coating, thereby obtaining the cap.

[0023] By adopting the above technical solution, high-temperature baking can be eliminated, avoiding deformation of the cap plate due to heat. It also significantly shortens the coating curing time and improves the overall production efficiency of the cap. In addition, the thermally conductive coating structure formed by photocuring is more stable and has stronger adhesion, which can reduce problems such as coating peeling and cracking, and extend the service life of the cap.

[0024] Optionally, the photocuring time is 20-70 seconds, and the light intensity is 220-450 mW / cm². 2 . Attached Figure Description

[0025] Figure 1 A schematic diagram of the cylindrical battery structure in an embodiment of the present invention is shown.

[0026] (Symbol Explanation)

[0027] 1. Cylindrical battery, 10. Cap, 101. Cover plate, 1011. Inner surface, 1012. Outer surface, 102. First thermally conductive coating, 103. Second thermally conductive coating, 11. Casing, 111. Opening, 12. Cell, 13. Terminal. Detailed Implementation

[0028] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0029] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] The terms “first”, “second”, etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0031] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0033] Firstly, reference Figure 1 As shown, an embodiment of the present invention discloses a cap 10 for a cylindrical battery 1. The cylindrical battery 1 includes a casing 11 and a cell 12. The casing 11 has an opening 111, and the cell 12 is housed inside the casing 11 through the opening 111. The cap 10 includes a cover plate 101, a first thermally conductive coating 102, and a second thermally conductive coating 103.

[0034] The cover plate 101 is used to seal the opening 111. The cover plate 101 includes an inner surface 1011 facing the battery cell 12 and an outer surface 1012 facing away from the battery cell 12. A first thermally conductive coating 102 covers the inner surface 1011 and has a first thermal conductivity. A second thermally conductive coating 103 covers the outer surface 1012 and has a second thermal conductivity, which is greater than the first thermal conductivity.

[0035] Specifically, the cover plate 101, as the core load-bearing component of the cap 10, covers the opening 111 of the outer casing 11, achieving a reliable seal. This ensures that the electrolyte inside the cylindrical battery does not leak and that external impurities (such as dust and moisture) do not intrude, maintaining the sealed environment required for the normal operation of the cylindrical battery 1 and meeting the basic structural requirements of the cylindrical battery 1 during assembly and service. The first thermally conductive coating 102 and the second thermally conductive coating 103 cover the inner surface 1011 and the outer surface 1012 of the cover plate 101, respectively. This allows for direct integration into the existing production process of the cylindrical battery 1 without requiring significant modifications to the existing outer casing 11 and cell 12, demonstrating good technical compatibility and industrialization potential, and reducing the cost and difficulty of technology implementation.

[0036] Furthermore, the present invention provides a first thermally conductive coating 102 and a second thermally conductive coating 103 with different thermal conductivityes on the inner surface 1011 and outer surface 1012 of the cover plate 101, respectively, with the second thermal conductivity being greater than the first thermal conductivity, i.e., the thermal conductivity of the second thermally conductive coating 103 being greater than that of the first thermally conductive coating 102. This results in a low thermal conductivity on the inner surface 1011 side of the cover plate 101, which can reduce heat conduction under overheating conditions inside the battery cell 12, reduce the transfer of heat generated by the battery cell 12 to the cover plate 101, and prevent unnecessary temperature rise in the cover plate 101 and surrounding cap 10 area due to continuous heat absorption, thus preventing performance degradation of the cap 10 due to long-term high-temperature aging. On the other hand, the high thermal conductivity on the outer surface 1012 side of the cover plate 101 can improve the heat exchange capacity with the environment. Even if the cover plate 101 absorbs some heat, the heat can be quickly dissipated to the environment through the second thermally conductive coating 103, preventing heat accumulation in the cover plate 101 area.

[0037] By adopting the above technical solution, severe deformation of the cylindrical battery cap 10 area can be avoided during thermal runaway, and the probability of the terminal 13 erupting can be reduced, thereby enabling thermal propagation protection based on the thermal runaway characteristics of the cylindrical battery 1.

[0038] In some other possible embodiments provided by the present invention, the first thermal conductivity is 0.02~0.05 W / m·K, and the second thermal conductivity is 3.5~10.0 W / m·K. By limiting the first thermal conductivity of the first thermally conductive coating 102 to the range of 0.02~0.05 W / m·K, it further forms an effective thermal barrier layer on the inner surface 1011 of the cover plate 101. When heat is generated inside the cell 12, this thermal barrier layer can significantly suppress the rapid conduction of heat to the cover plate 101, reduce the temperature rise rate of the cover plate 101 and its surrounding area, and thus reduce the deformation of the cover plate 101 under battery overheating conditions, effectively preventing the cap 10 from experiencing performance degradation, tearing, or aging due to long-term exposure to high temperature environments. At the same time, by setting the second thermal conductivity of the second thermally conductive coating 103 to the range of 3.5~10.0 W / m·K, the second thermally conductive coating 103 constructs an efficient heat dissipation channel on the outer surface 1012 of the cover plate 101. This allows any heat transferred to the cover plate 101 to be quickly conducted to the external environment through the second thermally conductive coating 103, effectively preventing localized heat accumulation in the area of ​​the cover plate 101. Thus, a "internal resistance to external dissipation" management of heat from the cylindrical battery 1 is achieved, ensuring the thermal stability of the cap 10 and further effectively reducing the probability of the terminal post 13 erupting.

[0039] In some other possible embodiments provided by the present invention, the first thermally conductive coating 102 is formed by photocuring a first thermally conductive coating material. The first thermally conductive coating material includes a first photocurable resin, a first thermally conductive filler, a first diluent, and a first photoinitiator. The first thermally conductive filler accounts for 1 to 60 wt% of the mass of the first photocurable resin, the first diluent accounts for 15 to 40 wt% of the mass of the first photocurable resin, and the first photoinitiator accounts for 1 to 15 wt% of the mass of the first photocurable resin.

[0040] In this invention, the first thermally conductive coating 102 is formed by photocuring a first thermally conductive paint. The photocuring process itself has the advantages of fast curing speed, low energy consumption, and no or low solvent evaporation. Combined with the aforementioned limitation on the proportion of components, the preparation process of the first thermally conductive coating 102 can be efficiently compatible with the production line of the cap 10, achieving rapid and batch preparation of the first thermally conductive coating 102 without the need for additional complex equipment. At the same time, it can minimize the impact on the original performance of the cover plate 101.

[0041] The first UV-curable resin, as the film-forming substrate, possesses excellent chemical stability and substrate adhesion. After UV curing, it forms a strong bond with the inner surface 1011 of the cover plate 101. Furthermore, the curing process eliminates the need for high-temperature baking, preventing deformation and strength reduction in the cover plate 101 due to heat exposure, thus ensuring the original structural load-bearing capacity and sealing performance of the cover plate 101 remain intact. Based on the mass of the first UV-curable resin, controlling the mass ratio of the first thermally conductive filler to 1–60 wt% satisfies the low thermal conductivity required for the first thermally conductive coating 102 while avoiding excessive filler content that could increase the brittleness of the first thermally conductive coating 102 and reduce its adhesion to the inner surface 1011 of the cover plate 101. The mass ratio of the first diluent, at 15–40 wt%, effectively adjusts the viscosity of the first thermally conductive coating, ensuring uniform coverage of the inner surface 1011 of the cover plate 101 and preventing uneven thickness and sagging defects in the first thermally conductive coating 102 due to improper viscosity. If the mass ratio of the first photoinitiator is 1 to 15 wt%, it can ensure that the photocuring reaction is efficient and complete, shorten the curing time of the first thermally conductive coating 102, improve production efficiency, and at the same time avoid incomplete curing and coating performance degradation due to insufficient first photoinitiator, or excessive residue of first photoinitiator affecting the insulation and corrosion resistance of the first thermally conductive coating 102.

[0042] Furthermore, the first thermally conductive filler accounts for 20-40 wt% of the first UV-curable resin, the first diluent accounts for 20-35 wt% of the first UV-curable resin, and the first photoinitiator accounts for 3-8 wt% of the first UV-curable resin. Through further optimization of the first thermally conductive coating formulation, the first thermally conductive coating 102 is ensured to have a dense structure, high curing efficiency, and a stable and low thermal conductivity, effectively blocking heat transfer to the cover plate 101, thereby forming a structurally stable thermal barrier on the inner surface 1011 of the cover plate 101.

[0043] In some other possible embodiments provided by the present invention, the second thermally conductive coating 103 is formed by photocuring a second thermally conductive coating material. The second thermally conductive coating material includes a second photocurable resin, a second thermally conductive filler, a second diluent, and a second photoinitiator. The second thermally conductive filler accounts for 1 to 60 wt% of the mass of the second photocurable resin, the second diluent accounts for 15 to 40 wt% of the mass of the second photocurable resin, and the second photoinitiator accounts for 1 to 15 wt% of the mass of the second photocurable resin.

[0044] In this invention, the second thermally conductive coating 103 is formed by photocuring a second thermally conductive coating. The photocuring process itself has the advantages of fast curing speed, low energy consumption, and no or low solvent evaporation. Combined with the aforementioned limitation on the proportion of components, the preparation process of the second thermally conductive coating 103 can be efficiently compatible with the production line of the cap 10, without the need for additional complex equipment, enabling rapid and batch preparation of the first thermally conductive coating 102. At the same time, it can minimize the impact on the original performance of the cover plate 101.

[0045] The second photocurable resin, as the film-forming substrate, possesses excellent chemical stability and substrate adhesion. After photocuring, it forms a strong bond with the outer surface 1012 of the cover plate 101. Furthermore, the curing process eliminates the need for high-temperature baking, preventing deformation and strength reduction of the cover plate 101 due to heat exposure, thus ensuring the original structural load-bearing capacity and sealing performance of the cover plate 101 remain intact. Based on the mass of the second photocurable resin, controlling the mass ratio of the second thermally conductive filler to 1–60 wt% satisfies the low thermal conductivity required for the second thermally conductive coating 103 while avoiding excessive filler content that could increase the brittleness of the second thermally conductive coating 103 and reduce its adhesion to the outer surface 1012 of the cover plate 101. The mass ratio of the second diluent, at 15–40 wt%, effectively adjusts the viscosity of the second thermally conductive coating, ensuring uniform coverage of the outer surface 1012 of the cover plate 101 and preventing uneven thickness and sagging defects in the second thermally conductive coating 103 due to improper viscosity. If the mass ratio of the second photoinitiator is 1 to 15 wt%, the photocuring reaction can be ensured to be efficient and complete, shortening the curing time of the second thermally conductive coating 103 and improving production efficiency. At the same time, it avoids the problems of incomplete curing and coating performance deterioration due to insufficient second photoinitiator, or excessive residue of second photoinitiator affecting the insulation and corrosion resistance of the second thermally conductive coating 103.

[0046] Furthermore, the second thermally conductive filler accounts for 15-30 wt% of the second UV-curable resin, the second diluent accounts for 15-30 wt% of the second UV-curable resin, and the second photoinitiator accounts for 3-8 wt% of the second UV-curable resin. Through further optimization of the second thermally conductive coating formulation, the second thermally conductive coating 103 is ensured to have a dense structure, high curing efficiency, and a stable and high thermal conductivity, effectively promoting the diffusion of heat from the cover plate 101 to the environment, thereby forming a highly efficient heat exchange interface on the outer surface 1012 of the cover plate 101.

[0047] In some other possible embodiments provided by the present invention, the first thermally conductive coating 102 is formed by photocuring a first thermally conductive paint. The first thermally conductive paint includes a first photocurable resin, a first thermally conductive filler, a first diluent, and a first photoinitiator, wherein the first thermally conductive filler accounts for 1-60 wt% of the mass of the first photocurable resin, the first diluent accounts for 15-40 wt% of the mass of the first photocurable resin, and the first photoinitiator accounts for 1-15 wt% of the mass of the first photocurable resin. The second thermally conductive coating 103 is formed by photocuring a second thermally conductive paint. The second thermally conductive paint includes a second photocurable resin, a second thermally conductive filler, a second diluent, and a second photoinitiator, wherein the second thermally conductive filler accounts for 1-60 wt% of the mass of the second photocurable resin, the second diluent accounts for 15-40 wt% of the mass of the second photocurable resin, and the second photoinitiator accounts for 1-15 wt% of the mass of the second photocurable resin. Thus, through the photocuring process and the above-mentioned coating formulation, a first thermally conductive coating 102 that can suppress the transfer of heat to the cover plate 101 and a second thermally conductive coating 103 that can quickly conduct heat out of the cover plate 101 are obtained.

[0048] Further, in this embodiment, the first thermally conductive filler accounts for 20-40 wt% of the first photocurable resin, the first diluent accounts for 20-35 wt% of the first photocurable resin, and the first photoinitiator accounts for 3-8 wt% of the first photocurable resin. The second thermally conductive filler accounts for 15-30 wt% of the second photocurable resin, the second diluent accounts for 15-30 wt% of the second photocurable resin, and the second photoinitiator accounts for 3-8 wt% of the second photocurable resin.

[0049] By further optimizing the ratio of the first and second thermally conductive coatings, a thermal insulation coating and a heat dissipation coating with superior performance and clearly defined functions were obtained. Specifically, in the first thermally conductive coating, the mass ratio of the first thermally conductive filler was controlled at 20–40 wt%. This higher content of the first thermally conductive filler aims to maximize the thermal insulation capacity of the first thermally conductive coating 102 and construct a more effective thermal barrier. At the same time, the mass ratios of the first diluent and the first photoinitiator were optimized to 20–35 wt% and 3–8 wt%, respectively, ensuring that the first thermally conductive coating still possesses excellent application performance and rapid, complete curing characteristics even at a higher solids content, thereby forming a dense, firmly bonded thermal insulation coating with a low thermal conductivity.

[0050] Correspondingly, in the second thermally conductive coating, the mass ratio of the second thermally conductive filler is controlled at 15–30 wt%. This range ensures that the second thermally conductive coating 103 has good thermal conductivity while maintaining excellent mechanical strength and flexibility, preventing cracking of the second thermally conductive coating 103 during long-term use. Simultaneously, the mass ratios of the second diluent and the second photoinitiator are controlled at 15–30 wt% and 3–8 wt%, respectively, ensuring that the heat dissipation layer also has uniform film formation and high curing efficiency, thereby forming a structurally stable, well-conducting, and highly efficient heat dissipation coating.

[0051] In embodiments of the present invention, the first photocurable resin is selected from one or more of epoxy acrylate, polyurethane acrylate, polyether acrylate, epoxy resin, and epoxy-functionalized polysiloxane resin. The second photocurable resin is selected from one or more of epoxy acrylate, polyurethane acrylate, polyether acrylate, epoxy resin, and epoxy-functionalized polysiloxane resin.

[0052] Preferably, the first photocurable resin is epoxy resin. The epoxy resin surface has abundant epoxy groups that provide chemical bonding capabilities, enabling it to chemically bond with the active groups on the surface of the cover plate 101, thereby forming a good interfacial bond. This ensures that the first thermally conductive coating 102 will not peel off or crack during long-term use and thermal cycling of the cylindrical battery 1, guaranteeing its long-term effectiveness and reliability as a thermal insulation barrier.

[0053] Preferably, the second photocurable resin is epoxy acrylate. The low viscosity of epoxy acrylate can effectively suppress the agglomeration effect of thermally conductive fillers, thereby ensuring the smooth and efficient thermal conductive network inside the second thermally conductive coating 103, thus maximizing its heat dissipation performance and ensuring that heat can be quickly and uniformly dissipated.

[0054] In embodiments of the present invention, the first thermally conductive filler is one or more of methyl urethane, ethyl urethane, tetrabutylphenol, aluminum silicate, aluminum silicate hydrate, expanded perlite, vitrified microspheres, silica aerogel, alumina aerogel, and zirconia aerogel. Preferably, the first thermally conductive filler is one or more of silica aerogel, alumina aerogel, and zirconia aerogel. Compared to other thermally conductive fillers, aerogel-type thermally conductive fillers have low thermal conductivity and high porosity, which can effectively delay heat transfer and form a thermal barrier effect.

[0055] In embodiments of the present invention, the second thermally conductive filler is one or more of silicon nitride, silicon carbide, aluminum nitride, graphene, carbon nanotubes, zinc oxide, and magnesium oxide. Preferably, the second thermally conductive filler is one or more of silicon nitride and silicon carbide. Compared to other thermally conductive fillers, silicon nitride and silicon carbide have higher thermal conductivity and better corrosion resistance, facilitating effective heat dissipation.

[0056] Furthermore, the particle size of the second thermally conductive filler is 20-250 nm, which is beneficial for the uniform dispersion and dense packing of the second thermally conductive filler in the second photocurable resin, reducing interfacial thermal resistance. Even further, the median particle size of the second thermally conductive filler is 120-180 nm. This size distribution can ensure the packing density of the second thermally conductive filler while reducing the gaps between particles, making the thermal conduction path more continuous and avoiding agglomeration caused by excessively small particle size or uneven dispersion caused by excessively large particle size. This balances the thermal conductivity and mechanical properties of the second thermally conductive coating 103. Thus, it ensures rapid heat transfer, enhances the heat dissipation capacity of the outer surface 1012 of the cover plate 101, and avoids problems such as increased brittleness and easy cracking of the second thermally conductive coating 103 due to uneven filler distribution, ensuring the structural integrity of the second thermally conductive coating 103 during battery operation.

[0057] In embodiments of the present invention, the first diluent is one or more of tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol hexaacrylate, hydroxyethyl acrylate, and hydroxyethyl methacrylate. The second diluent is one or more of tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol hexaacrylate, hydroxyethyl acrylate, and hydroxyethyl methacrylate.

[0058] Preferably, the first diluent is one or more of tripropylene glycol diacrylate and hydroxyethyl acrylate, whose acrylic functional groups can copolymerize rapidly, avoiding the sedimentation of aerogel-type thermally conductive fillers.

[0059] Preferably, the second diluent is trimethylolpropane triacrylate, which can form a highly cross-linked, dense three-dimensional network structure during the curing process. This dense network structure helps to improve the hardness of the second thermally conductive coating 103 and enhance its mechanical strength. The second thermally conductive coating 103 is located on the outside of the cylindrical battery 1 and is easily affected by slight external forces or environmental friction. Higher mechanical strength can prevent scratches and damage to the coating, ensure the integrity of the heat conduction path, and at the same time enhance the bonding strength between the second thermally conductive coating 103 and the outer surface 1012, prevent it from falling off during service, and ensure that the second thermally conductive coating 103 continuously and efficiently conducts heat from the cover plate 101, avoiding heat accumulation that could lead to high-temperature deformation of the cover plate 101.

[0060] In embodiments of the present invention, the first photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 1-hydroxy-cycloethyl-phenyl ketone, benzoin dimethyl ether, and benzophenone. The aforementioned first photoinitiator possesses excellent photoresponsive activity, capable of efficiently decomposing to generate free radicals under light irradiation, initiating the polymerization reaction between the first photocurable resin and the first diluent, ensuring rapid curing of the first thermally conductive coating 102, and avoiding insufficient curing leading to a loose structure of the first thermally conductive coating 102 and a decrease in adhesion to the inner surface of the cover plate 101. The second photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 1-hydroxy-cycloethyl-phenyl ketone, benzoin dimethyl ether, and benzophenone. The aforementioned second photoinitiator possesses excellent photoresponsive activity, and can efficiently decompose to generate free radicals under light irradiation, thereby initiating the polymerization reaction between the second photocurable resin and the second diluent, ensuring that the second thermally conductive coating 103 is densely formed and firmly adhered.

[0061] Preferably, the first photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone, which has the ability to cure quickly with low light intensity, that is, it can achieve rapid curing without the need for a high-intensity light source. This not only reduces the light energy consumption of the production line, but also shortens the curing cycle of a single coating, thus meeting the low-energy consumption and fast turnover requirements of the production line.

[0062] Preferably, the second photoinitiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide, whose high-temperature resistance prevents decomposition under battery overheating conditions. This ensures that the photoinitiator is less prone to decomposition when the battery experiences localized overheating or the initial stage of thermal runaway, preventing the formation of small molecules that could damage the coating structure or degrade its performance. This ensures that the second thermally conductive coating 103 maintains a complete thermal conductivity path under high-temperature conditions, continuously and efficiently dissipating heat from the cover plate 101, and providing stable support for battery thermal runaway protection.

[0063] Further, in another embodiment of the present invention, the first thermally conductive filler accounts for 20-40 wt% of the first photocurable resin, the first diluent accounts for 20-35 wt% of the first photocurable resin, and the first photoinitiator accounts for 3-8 wt% of the first photocurable resin. The second thermally conductive filler accounts for 15-30 wt% of the second photocurable resin, the second diluent accounts for 15-30 wt% of the second photocurable resin, and the second photoinitiator accounts for 3-8 wt% of the second photocurable resin. The first photocurable resin is an epoxy resin, and the second photocurable resin is an epoxy acrylate. The first thermally conductive filler is one or more of silica aerogel, alumina aerogel, and zirconia aerogel, and the second thermally conductive filler is one or more of silicon nitride and silicon carbide. The first diluent is one or more of tripropylene glycol diacrylate and hydroxyethyl acrylate, and the second diluent is trimethylolpropane triacrylate. The first photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone, and the second photoinitiator is 2,4,6-trimethylbenzoyl diphenylphosphine oxide.

[0064] Specifically, in this embodiment, the first thermally conductive coating 102 uses epoxy resin as a matrix, combined with 20-40 wt% aerogel filler to form a dense thermal insulation layer. Tripropylene glycol diacrylate or hydroxyethyl acrylate is selected to ensure uniform dispersion of the aerogel filler, and 1-hydroxy-cyclohexyl-phenyl ketone is used for rapid and mild curing, together constructing a stable and reliable thermal barrier, effectively preventing the transfer of heat from the battery cell to the cover plate 101. The second thermally conductive coating 103 uses low-viscosity epoxy acrylate as a matrix, combined with 15-30 wt% silicon nitride / silicon carbide to construct an efficient thermally conductive path. Trimethylolpropane triacrylate is used to improve crosslinking density and mechanical strength, and 2,4,6-trimethylbenzoyl diphenylphosphine oxide is used to ensure high-temperature stability, forming a durable heat dissipation channel. In addition, both the first thermally conductive coating 102 and the second thermally conductive coating 103 are cured by light, which can be formed without high temperature, avoiding heat deformation or performance damage to the cover plate 101.

[0065] Secondly, embodiments of the present invention disclose a method for preparing a cap, used to prepare a cap as described in any embodiment of the first aspect, the method comprising:

[0066] A first thermally conductive coating is applied to the inner surface 1011 of the cover plate 101, and a second thermally conductive coating is applied to the outer surface 1012 of the cover plate 101. Then, a photocuring process is performed to form a first thermally conductive coating 102 and a second thermally conductive coating 103, thereby obtaining the cap 10. The coating can be performed using a spraying device, and the photocuring process can be performed using a photocuring machine to improve production efficiency.

[0067] Using the above technical solution, a first thermally conductive coating 102 and a second thermally conductive coating 103 are formed on the inner surface 1011 and outer surface 1012 of the cover plate 101, respectively, through a photocuring process. The photocuring process has a fast reaction speed; compared to traditional thermal curing methods, it eliminates the need for high-temperature baking, preventing deformation of the cover plate 101 due to heat, and significantly shortening the coating curing time, thus improving the overall manufacturing efficiency of the cap 10. Furthermore, the thermally conductive coating formed by photocuring has a more stable structure and stronger adhesion, reducing problems such as coating peeling and cracking, and extending the service life of the cap 10.

[0068] Furthermore, the photocuring time is 20-70 seconds, and the light intensity is 220-450 mW / cm². 2 By controlling the time and light intensity of the photocuring process, the preparation efficiency can be considered while ensuring the quality of coating curing, avoiding problems of insufficient or excessive curing. This time range ensures that the first and second thermally conductive coatings are fully cured, forming a thermally conductive coating with a stable structure and strong adhesion. It avoids the situation where the coating is not fully cured due to too short a time, resulting in peeling and poor thermal conductivity, and it also avoids the situation where the production energy consumption and cost are increased due to too long a time. The light intensity of 220-450mW / cm² is matched with this time range, which can provide sufficient energy to promote the coating curing reaction, while avoiding the situation where the coating is overheated and cracked due to excessive light, or the curing cycle is prolonged due to insufficient light. Ultimately, it achieves efficient and low-cost mass production while ensuring the stable performance and high consistency of the first thermally conductive coating 102 and the second thermally conductive coating 103.

[0069] In an embodiment of the present invention, the preparation method further includes:

[0070] Preparation of the first thermally conductive slurry: A first photocurable resin and a first thermally conductive filler are mixed in a solvent (e.g., ethanol), followed by the addition of a first diluent for a first ultrasonic dispersion, and then the addition of a first photoinitiator for a second ultrasonic dispersion, thus obtaining the first thermally conductive slurry. The mixing time is 20-60 min, the first ultrasonic dispersion time is 15-30 min, and the second ultrasonic dispersion time is 15-30 min. Furthermore, the second ultrasonic dispersion is performed under light-protected conditions.

[0071] Preparation of the second thermally conductive slurry: The second photocurable resin and the second thermally conductive filler are mixed in a solvent (e.g., ethanol), then a second diluent is added for a third ultrasonic dispersion, followed by the addition of a second photoinitiator for a fourth ultrasonic dispersion, thus obtaining the second thermally conductive slurry. The mixing time is 20-60 min, the third ultrasonic dispersion time is 15-30 min, and the fourth ultrasonic dispersion time is 15-30 min. Furthermore, the fourth ultrasonic dispersion is performed under light-protected conditions.

[0072] Therefore, by preparing the first and second thermally conductive slurries in steps and controlling the mixing and ultrasonic dispersion times during the preparation process, it is possible to ensure that the two thermally conductive slurries are uniformly composed, fully dispersed, and have stable performance. Furthermore, the second and fourth ultrasonic dispersions are performed under light-protected conditions, which effectively prevents the photoinitiator from undergoing premature photochemical reactions, ensuring its proper function during subsequent photocuring. Ultimately, this ensures that the prepared first and second thermally conductive slurries have stable composition and performance, thereby guaranteeing the thermal conductivity of the first thermally conductive coating 102 and the second thermally conductive coating 103.

[0073] The following will describe the implementation method in more detail.

[0074] Example 1:

[0075] Preparation of the first thermally conductive paste: 15g of polyurethane acrylate (molecular weight 10000, Wuhan Kemike Biomedical Technology Co., Ltd.) and 36wt% of silica aerogel (density 0.05-0.1g / cm³) were mixed. 3 A mixture of tripropylene glycol diacrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and hydroxyethyl acrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) (with a thermal conductivity of 0.02-0.05 W / mK) was added to a stirring vessel containing 30 mL of ethanol and thoroughly mixed for 45 min. Then, a first diluent consisting of 26.0 wt% of tripropylene glycol diacrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and hydroxyethyl acrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) was added for a first ultrasonic dispersion for 25 min. The mass ratio of the first photoinitiator was 1:3, and then 5.3 wt% of 2-hydroxy-2-methyl-1-phenyl-1-propanone (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and 1-hydroxy-cycloethyl-phenyl methyl ketone (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) were added to the polyurethane acrylate. The mixture was then ultrasonically dispersed for a fourth time for 15 min. The mass ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone and 1-hydroxy-cycloethyl-phenyl methyl ketone was 2:1, and the first thermally conductive slurry was obtained.

[0076] Preparation of the second thermally conductive slurry: 15g of epoxy acrylate (viscosity 1100 mpa.s, 25℃) and 26.7wt% of silicon nitride (median particle size 150nm, Shanghai Aladdin Biochemical Technology Co., Ltd.) were added to a stirring cup containing 30mL of ethanol (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and mixed thoroughly for 45min. Then, a second diluent consisting of 23.0wt% of trimethylolpropane triacrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and hydroxyethyl acrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) was added and ultrasonically dispersed for a third time for 25min. The mass ratio of trimethylolpropane triacrylate to hydroxyethyl acrylate was 1:1. Subsequently, a second photoinitiator, consisting of 2-hydroxy-2-methyl-1-phenyl-1-propanone (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and 1-hydroxy-cycloethyl-phenyl ketone (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), comprising 5.3 wt% of the epoxy acrylate, was added for a fourth ultrasonic dispersion of 15 min. The mass ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone to 1-hydroxy-cycloethyl-phenyl ketone was 2:1, thus obtaining the second thermally conductive slurry.

[0077] Preparation of the cap 10: A first thermally conductive coating is applied to the inner surface 1011 of the cap 101, and a second thermally conductive coating is applied to the outer surface 1012 of the cap 101. Then, a light curing process is performed using a light curing machine. The curing time is 35 seconds, and the light intensity is 380 mW / cm². 2 A first thermally conductive coating 102 and a second thermally conductive coating 103 are formed to obtain a cap 10.

[0078] In Example 1, the first thermal conductivity of the first thermally conductive coating 102 is 0.03 W / m·K, and the second thermal conductivity of the second thermally conductive coating 103 is 8.0 W / m·K.

[0079] Example 2:

[0080] Preparation of the first thermally conductive paste: 15g of epoxy resin (molecular weight 8000, Wuhan Kemike Biomedical Technology Co., Ltd.) and 36wt% of silica aerogel (density 0.05-0.1g / cm³) were mixed. 3A first thermally conductive slurry (with a thermal conductivity of 0.02-0.05 W / mk) was added to a stirring cup containing 30 mL of ethanol (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and mixed thoroughly for 45 min. Then, a first diluent consisting of tripropylene glycol diacrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and hydroxyethyl acrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), accounting for 26.0 wt% of the epoxy resin, was added for the first ultrasonic dispersion for 25 min. The mass ratio of tripropylene glycol diacrylate to hydroxyethyl acrylate was 1:3. Subsequently, a first photoinitiator consisting of 1-hydroxy-cyclohexyl-phenyl ketone (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and benzophenone (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), accounting for 5.3 wt% of the epoxy resin, was added for the fourth ultrasonic dispersion for 15 min. The mass ratio of 2-hydroxy-2-methyl-1-phenyl-1-propenone to 1-hydroxy-cycloethyl-phenyl ketone was 2:1.

[0081] Preparation of the second thermally conductive slurry: 15g of epoxy acrylate (viscosity 1100 mpa.s, 25℃) and 26.7wt% of silicon nitride (median particle size 150nm, Shanghai Aladdin Biochemical Technology Co., Ltd.) were added to a stirring cup containing 30mL of ethanol (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and mixed thoroughly for 45min. Then, 23.0wt% of trimethylolpropane triacrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and a second diluent compounded with trimethylolpropane triacrylate (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) were added and ultrasonically dispersed for a third time for 25min. The mass ratio of trimethylolpropane triacrylate to hydroxyethyl acrylate was 1:1. Subsequently, a second photoinitiator, consisting of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.) and 1-hydroxy-cycloethyl-phenyl ketone (analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.), comprising 5.3 wt% of the epoxy acrylate, was added for a fourth ultrasonic dispersion of 15 min. The mass ratio of 2-hydroxy-2-methyl-1-phenyl-1-propenolone to 1-hydroxy-cycloethyl-phenyl ketone was 2:1, thus obtaining the second thermally conductive slurry.

[0082] Preparation of the cap 10: A first thermally conductive coating is applied to the inner surface 1011 of the cap 101, and a second thermally conductive coating is applied to the outer surface 1012 of the cap 101. Then, a light curing process is performed using a light curing machine. The curing time is 35 seconds, and the light intensity is 380 mW / cm². 2 A first thermally conductive coating 102 and a second thermally conductive coating 103 are formed to obtain a cap 10.

[0083] In Example 2, the first thermal conductivity of the first thermally conductive coating 102 is 0.04 W / m·K, and the second thermal conductivity of the second thermally conductive coating 103 is 6.5 W / m·K.

[0084] The batteries using cap 10 in Examples 1 and 2 exhibit lower deformation under overheating conditions, suppressing the risk of casing tearing and increasing the heat exchange capacity between cap 10 and the outside, effectively reducing the probability of positive electrode eruption. Compared to Example 1, the battery using Example 2 has superior performance.

[0085] While the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the invention to these descriptions. Various changes in form and detail can be made by those skilled in the art, including several simple deductions or substitutions, without departing from the spirit and scope of the invention.

Claims

1. A cap for a cylindrical battery, the cylindrical battery comprising a casing and a battery cell, the casing having an opening, the battery cell being received within the casing through the opening, characterized in that, The cap includes: A cover plate for sealing the opening, comprising an inner surface facing the battery cell and an outer surface facing away from the battery cell; A first thermally conductive coating is applied to the inner surface and has a first thermal conductivity. A second thermally conductive coating is applied to the outer surface and has a second thermal conductivity greater than the first thermal conductivity.

2. The cap as described in claim 1, characterized in that, The first thermal conductivity is 0.02~0.05 W / m·K, and the second thermal conductivity is 3.5~10.0 W / m·K.

3. The cap as described in claim 1, characterized in that, The first thermally conductive coating is formed by photocuring a first thermally conductive coating material. The first thermally conductive coating material includes a first photocurable resin, a first thermally conductive filler, a first diluent, and a first photoinitiator. The first thermally conductive filler accounts for 20-40 wt% of the mass of the first photocurable resin, the first diluent accounts for 20-35 wt% of the mass of the first photocurable resin, and the first photoinitiator accounts for 3-8 wt% of the mass of the first photocurable resin. And / or, the second thermally conductive coating is formed by photocuring a second thermally conductive coating material, the second thermally conductive coating material comprising a second photocurable resin, a second thermally conductive filler, a second diluent, and a second photoinitiator, wherein the second thermally conductive filler accounts for 15-30 wt% of the mass of the second photocurable resin, the second diluent accounts for 15-30 wt% of the mass of the second photocurable resin, and the second photoinitiator accounts for 3-8 wt% of the mass of the second photocurable resin.

4. The cap as described in claim 3, characterized in that, The first photocurable resin is epoxy resin, and the second photocurable resin is epoxy acrylate.

5. The cap as described in claim 3, characterized in that, The first thermally conductive filler is one or more of methyl urethane, ethyl urethane, tetrabutylphenol, aluminum silicate, aluminum silicate hydrate, expanded perlite, vitrified microspheres, silica aerogel, alumina aerogel, and zirconium oxide aerogel, and the second thermally conductive filler is one or more of silicon nitride, silicon carbide, aluminum nitride, graphene, carbon nanotubes, zinc oxide, and magnesium oxide.

6. The cap as described in claim 3, characterized in that, The first diluent is one or more of tripropylene glycol diacrylate and hydroxyethyl acrylate, and the second diluent is trimethylolpropane triacrylate.

7. The cap as described in claim 3, characterized in that, The first photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone, and the second photoinitiator is 2,4,6-trimethylbenzoyl diphenylphosphine oxide.

8. The cap as described in claim 3, characterized in that, The particle size of the second thermally conductive filler is 20-250 nm.

9. A method for preparing a cap, characterized in that, The method for preparing the cap as described in any one of claims 1-8 comprises: The first thermally conductive coating is applied to the inner surface of the cover plate, and the second thermally conductive coating is applied to the outer surface of the cover plate. Then, a photocuring process is performed to form the first thermally conductive coating and the second thermally conductive coating, thereby obtaining the cap.

10. The preparation method according to claim 9, characterized in that, The photocuring time is 20-70 seconds, and the light intensity is 220-450 mW / cm². 2 .

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