Cylindrical lithium battery explosion-proof combined cap, preparation method thereof and cylindrical lithium battery

Abstract

The invention discloses an explosion-proof combined cap of a cylindrical lithium battery, a preparation method of the explosion-proof combined cap and the cylindrical lithium battery. The explosion-proof combined cap of the cylindrical lithium battery comprises a sealing piece, a metal piece, a top cover, a bonding piece, a metal pressing piece and a flame-retardant piece, the sealing piece comprises a bearing part, the metal piece is arranged on the bearing part, and a first exhaust hole is formed in the metal piece; the top cover comprises a bottom, a top and a side part, the bottom and the top are arranged in parallel at intervals, and the side part is connected with the bottom and the top and provided with a plurality of second exhaust holes; the metal pressing piece is combined to the upper surface of the metal piece in a sealed mode through the bonding piece, the metal pressing piece seals the first exhaust hole, and the flame-retardant piece is installed on the surface of the side, away from the metal piece, of the metal pressing piece. The cap can realize active pressure relief and flame retardance at the early stage of thermal runaway of the battery, the probability of fire and explosion of the cylindrical lithium battery is greatly reduced, the safety is effectively improved, the cap is relatively simple in structure, the production cost can be effectively reduced, and the product competitiveness can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to an explosion-proof composite cap for a cylindrical lithium battery, its preparation method, and a cylindrical lithium battery. Background Technology

[0002] With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, and consumer electronics, their safety performance has become a core concern in the industry. Cylindrical lithium-ion batteries are widely used due to their compact structure and high energy density. However, under abnormal operating conditions such as overcharging, short circuits, or thermal runaway, violent reactions inside the battery can produce large amounts of flammable gases (such as CO, H2, and alkanes), leading to a rapid increase in internal pressure. If this pressure is not effectively released in time, it may cause the battery to explode or catch fire, posing a serious safety hazard.

[0003] Currently, traditional cylindrical battery caps generally use vents or current interruption devices (CIDs) as safety protection structures. Their working principle is: when the internal pressure exceeds a threshold, the vent ruptures or the CID mechanically disconnects the circuit, achieving pressure relief or power cut-off. However, this type of design has the following drawbacks:

[0004] (a) Lack of flame retardant function: Existing explosion-proof discs only achieve pressure release, but the released flammable gas may still cause secondary deflagration after contact with the outside air, especially in high-temperature environments where the risk is even higher.

[0005] (b) Complex structure: The explosion-proof sheet and CID require multiple layers of components (such as etched aluminum sheet, insulating film, etc.), which leads to complex assembly process and increased cost.

[0006] (c) Insufficient reliability: CID may malfunction or delay response due to metal fatigue under extreme pressure.

[0007] In addition, some improvement solutions enhance safety by adding flame retardants to the electrolyte, but flame retardants are prone to side reactions with the electrolyte, affecting battery cycle life, and cannot effectively suppress combustion during the rapid gas release phase. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide an explosion-proof combination cap for a cylindrical lithium battery, a method for preparing the same, and a cylindrical lithium battery.

[0009] The technical solution adopted by the present invention to solve its technical problem is: to construct a cylindrical lithium battery explosion-proof combination cap, including a sealing component, a metal component, a top cover, an adhesive component, a metal pressure plate, and a flame-retardant component;

[0010] The sealing element has an annular structure and includes a bearing portion. The metal part is disposed on the bearing portion, and the metal part has a plurality of first vent holes penetrating its upper and lower surfaces in the middle portion.

[0011] The top cover has a cylindrical structure and is installed on the side surface of the metal part away from the supporting part. The top cover includes a bottom, a top, and a side. The bottom and the top are arranged parallel to each other and spaced apart. The side connects the bottom and the top and is provided with a plurality of second exhaust holes.

[0012] The metal plate is sealed to the upper surface of the metal part by the adhesive and the metal plate seals the first vent hole. The flame retardant is installed on the side surface of the metal plate away from the metal part.

[0013] In some embodiments, the bearing portion extends around its periphery with an annular limiting portion, and the inner side of the limiting portion is provided with an annular protrusion. The protrusion is disposed opposite to the bearing portion at a distance, and a limiting space is defined between the bearing portion, the limiting portion and the protrusion.

[0014] The periphery of the metal part extends toward the side away from the supporting part and toward the side away from the limiting part to form a flange structure. At least a portion of the flange structure is confined within the limiting space, and the flange structure is used to wrap at least a portion of the bottom structure.

[0015] In some embodiments, a plurality of the first exhaust holes are arranged in a ring array, and the first exhaust holes are circular holes with a diameter of 0.4mm-0.6mm.

[0016] In some embodiments, the thickness of the adhesive is 20μm-50μm.

[0017] In some embodiments, the flame retardant component is made of red phosphorus flame retardant, aluminum hydroxide and silicone rubber in a mass ratio of 3:5:2.

[0018] In some embodiments, the volume of the flame-retardant component occupies 40%-60% of the inner cavity volume of the top cover.

[0019] This invention also discloses a method for preparing an explosion-proof composite cap for cylindrical lithium batteries, used to prepare the explosion-proof composite cap for cylindrical lithium batteries as described in any of the above embodiments, comprising the following steps:

[0020] S1: Metal part processing: forming a metal part by stamping on a metal substrate, and stamping the first vent hole on the metal part;

[0021] S2: Thermal bonding treatment: The metal sheet and the metal part are thermally bonded together using adhesives;

[0022] S3: Flame retardant component installation: Bond and fix the flame retardant component to the surface of the metal plate that is away from the metal component after heat bonding;

[0023] S4: Overall assembly: Weld the top cover to the metal parts and then fix them together to the sealing parts to complete the explosion-proof combination cap sealing of the cylindrical lithium battery.

[0024] In some embodiments, in step S2, the metal sheet and the metal part are aligned, an adhesive is sandwiched between the metal sheet and the metal part, and they are placed together in a hot press. The hot pressing temperature is 170℃-190℃, the pressure is 8MPa-12MPa, and the bonding time is 15s-25s, so that the adhesive melts and bonds the metal sheet and the metal part.

[0025] In some embodiments, in step S3, the flame-retardant component is coated with high-temperature resistant epoxy adhesive and bonded to the surface of the metal sheet opposite to the metal component after thermal bonding. The curing conditions are a baking temperature of 70℃-90℃ and a baking time of 1s-3s.

[0026] The present invention also discloses a cylindrical lithium battery, including a battery casing and a cylindrical lithium battery explosion-proof combination cap as described in any of the above embodiments. The battery casing contains a battery cell, and the battery casing has a first end and a second end opposite to each other. The first end of the battery casing is provided with the cylindrical lithium battery explosion-proof combination cap.

[0027] The present invention has the following advantages: the explosion-proof combination cap for cylindrical lithium batteries can achieve active pressure relief and flame retardancy in the early stage of thermal runaway of cylindrical lithium batteries, which greatly reduces the probability of fire and explosion of cylindrical lithium batteries and effectively improves safety. Moreover, the explosion-proof combination cap for cylindrical lithium batteries has a relatively simple structure, which can effectively reduce production costs and improve product competitiveness. Attached Figure Description

[0028] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort. In the drawings:

[0029] Figure 1 This is a three-dimensional structural schematic diagram of the cylindrical lithium battery explosion-proof combination cap in some embodiments of the present invention;

[0030] Figure 2 This is a top view of the cylindrical lithium battery explosion-proof combination cap in some embodiments of the present invention;

[0031] Figure 3 This is a cross-sectional view of the cylindrical lithium battery explosion-proof combination cap in some embodiments of the present invention;

[0032] Figure 4This is a schematic diagram of the pressure relief of the cylindrical lithium battery explosion-proof combination cap in some embodiments of the present invention;

[0033] Figure 5 This is a schematic diagram of the structure of a cylindrical lithium battery in some embodiments of the present invention. Detailed Implementation

[0034] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on this invention.

[0035] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0036] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0037] To address the problems of existing cylindrical lithium battery caps, such as complex explosion-proof structure, lack of flame-retardant function, and susceptibility to secondary deflagration after pressure relief, a cylindrical lithium battery explosion-proof combination cap 10 integrating pressure relief and flame-retardant functions is provided. By simplifying the cap components, optimizing the exhaust channel design, and incorporating built-in solid flame-retardant materials, it can quickly relieve pressure and simultaneously suppress gas deflagration when the internal pressure of the battery rises abnormally, thereby improving the safety performance of the battery under extreme operating conditions.

[0038] See Figures 1 to 4 This invention discloses a cylindrical lithium battery explosion-proof combination cap 10, suitable for high-energy-density cylindrical lithium batteries (such as electric vehicle power batteries and energy storage system battery modules). This cylindrical lithium battery explosion-proof combination cap 10 eliminates the need for a vent or current interruption device (CID), enabling active pressure relief and flame retardancy in the early stages of thermal runaway in cylindrical lithium batteries, significantly reducing the probability of fire and explosion and effectively improving safety. Furthermore, the structure of this cylindrical lithium battery explosion-proof combination cap is relatively simple, effectively reducing production costs and enhancing product competitiveness.

[0039] See Figures 1 to 4 In some embodiments, the cylindrical lithium battery explosion-proof combination cap 10 may include a sealing element 11, a metal element 12, a top cover 13, an adhesive element 14, a metal pressure plate 15, and a flame-retardant element 16.

[0040] The sealing element 11 has an annular structure and includes a support portion 111. The support portion 111 is annular, and the metal part 12 is disposed on the support portion 111. The metal part 12 has a plurality of first exhaust holes 121 penetrating its upper and lower surfaces in the middle.

[0041] The top cover 13 has a cylindrical structure, which is generally a frustum-shaped cylindrical structure. The top cover 13 is mounted on the side surface of the metal part 12 opposite to the support part 111. The top cover 13 may include a bottom 131, a top 132, and a side 133. The bottom 131 and the top 132 are arranged parallel to each other and spaced apart. The side 133 connects the bottom 131 and the top 132 and is provided with a plurality of second vent holes 1331. The inner cavity of the top cover 13 forms a flame-retardant cavity.

[0042] The metal pressure plate 15 is sealed to the upper surface of the metal part 12 by the adhesive 14, and the metal pressure plate 15 seals the first vent hole 121. The flame retardant 16 is installed on the side surface of the metal pressure plate 15 opposite to the metal part 12. Figure 3 As shown, the flame-retardant component 16 is mounted on the upper surface of the metal pressure plate 15. The adhesive component 14, the metal pressure plate 15, and the flame-retardant component 16 are all located in the inner cavity (flame-retardant cavity) of the top cover 13.

[0043] like Figure 4As shown, when the internal pressure of the cylindrical lithium battery exceeds a threshold (e.g., 2.0 MPa), the gas inside the cylindrical lithium battery pushes open the metal pressure plate 15 and enters the flame-retardant chamber. After reacting with the flame-retardant component 16, it is discharged through the second exhaust port 1331. Throughout the process, the flame-retardant component 16 directly acts on the combustible gas to avoid secondary deflagration.

[0044] In some embodiments, the metal part 12 may be welded to the seal 11, for example, by laser welding. The bottom 131 of the top cover 13 may be welded to the upper surface of the metal part 12, for example, by laser welding.

[0045] In some embodiments, the support portion 111 has an annular limiting portion 112 extending around its periphery. The inner side of the limiting portion 112 has an annular protrusion 113, which is spaced apart from the support portion 111. A limiting space is defined between the support portion 111, the limiting portion 112, and the protrusion 113. The periphery of the metal part 12 extends away from the support portion 111 and away from the limiting portion 112 to form a flange structure 122. At least a portion of the flange structure 122 is confined within the limiting space, and the flange structure 122 is used to wrap at least a portion of the bottom 131. Preferably, the flange structure 122 of the metal part 12 can be formed by a rolling process, with a total folding angle of 180 degrees, a length of 2mm-3mm wrapping the edge of the top cover 13, and a height of 3mm-4mm.

[0046] In some embodiments, the seal 11 may be made of fluororubber material resistant to electrolyte corrosion, and the thickness of the seal 11 is 0.55mm-0.6mm. For example, the thickness of the seal 11 may be 0.55mm, 0.56mm, 0.57mm, 0.58mm, 0.59mm, or 0.6mm. The thickness of the seal 11 can be selected and set according to actual needs, and no specific limitation is made here.

[0047] In some embodiments, the metal part 12 may be an aluminum sheet, such as 3003 aluminum alloy, and the thickness of the metal part 12 is 0.3mm-0.4mm. Further, a plurality of the first exhaust holes 121 are arranged in a circular array, and the first exhaust holes 121 are circular holes with a diameter of 0.4mm-0.6mm. For example, the diameter of the first exhaust holes 121 can be 0.4mm, 0.5mm, or 0.6mm. The diameter of the first exhaust holes 121 can be selected and set according to actual needs, and is not specifically limited here.

[0048] In some embodiments, the top cover 13 may be made of 304 stainless steel. The overall height of the top cover 13 may be 3.5 mm, the height of the side portion 133 may be 0.5 mm, and the diameter of the top portion 132 may be 15 mm. The number of second vent holes 1331 may be 3-5, and the area of ​​the second vent holes 1331 may be 8 mm². 2 Multiple second exhaust holes 1331 are distributed at equal angles along the circumference.

[0049] In some embodiments, the thickness of the adhesive 14 is 20μm-50μm, for example, the thickness of the adhesive 14 is 20μm, 30μm, 40μm or 50μm. The adhesive 14 can be made of PP adhesive, the thermal bonding temperature of the adhesive 14 can be 170℃-190℃, the pressure can be 8MPa-12MPa, and the bonding time can be 15s-25s. For example, the thermal bonding temperature of the adhesive 14 can be 170℃, 180℃ or 190℃, the pressure can be 8MPa, 9MPa, 10MPa, 11MPa or 12MPa, and the bonding time can be 15s, 16s, 17s, 18s, 19s, 20s, 21s, 22s, 23s, 24 or 25s. The parameter settings can be selected according to actual needs and are not specifically limited here.

[0050] In some embodiments, the metal pressure plate 15 may be a circular sheet, which is made of stainless steel and has a thickness of 0.2mm-0.3mm and a diameter of 16mm-18mm.

[0051] In some embodiments, the flame-retardant component 16 is made of red phosphorus-based flame retardant, aluminum hydroxide, and silicone rubber in a mass ratio of 3:5:2. Specifically, the flame-retardant component 16 can be molded by mixing red phosphorus-based flame retardant (30% by mass), aluminum hydroxide (50%), and silicone rubber (20%). Specifically, the molding pressure after mixing red phosphorus-based flame retardant (30% by mass), aluminum hydroxide (50%), and silicone rubber (20%) is 15 MPa, and the holding time is 3 min to ensure uniform block density (1.8 ± 0.1 g / cm³). 3 When the cylindrical lithium battery is depressurized and combustible gas enters the flame-retardant cavity, the red phosphorus flame retardant in the flame-retardant component 16 decomposes and absorbs heat, aluminum hydroxide releases water of crystallization when heated, and silicone rubber carbonizes to form a heat insulation layer. The gas temperature drops from 250°C to below 150°C, effectively preventing the battery from exploding.

[0052] Preferably, the flame retardant 16 can be cylindrical, and the flame retardant 16 has a diameter of 14 mm and a thickness of 1.2 mm.

[0053] Preferably, the volume of the flame-retardant component 16 accounts for 40%-60% of the volume of the inner cavity (flame-retardant cavity) of the top cover 13.

[0054] The explosion-proof combination cap 10 for cylindrical lithium batteries has the following characteristics:

[0055] 1. Integrated pressure relief and flame retardant structure: A sealing layer is formed by thermal bonding of a metal component 12 (such as an aluminum sheet) and a metal pressure plate 15 through an adhesive component 14. A first vent 121 is provided on the surface of the metal component 12, and a corresponding second vent 1331 is provided on the top cover 13. When the internal pressure of the cylindrical lithium battery exceeds a threshold (such as 2.0 MPa), the gas pushes open the metal pressure plate 15 and enters the flame retardant cavity of the top cover 13. After reacting with the flame retardant component 16, it is discharged through the second vent 1331. Throughout the process, the flame retardant component 16 directly acts on the combustible gas, preventing secondary deflagration.

[0056] 2. Simplified structural design: The traditional explosion-proof plate (Vent) and current cut-off device (CID) are eliminated. The edge of the top cover 13 is mechanically fixed and sealed by the flange structure 122 of the metal part 12, which reduces the number of components and assembly complexity.

[0057] 3. Directional flame retardant control: The flame retardant component 16 is fixed to the upper surface of the metal pressure plate 15. Its volume ratio (40%-60%) and composition (red phosphorus flame retardant / aluminum hydroxide / silicone rubber composite) ensure that the gas is in full contact with the flame retardant, and quickly reduces the concentration and temperature of flammable gas.

[0058] The explosion-proof cap 10 for cylindrical lithium batteries has the following beneficial effects:

[0059] (a) Significantly improved safety performance: During the depressurization process, the combustible gas must be treated by the flame retardant component 16. The flame retardant component 16 suppresses deflagration through the dual effects of physical adsorption and chemical decomposition, effectively solving the risk of secondary combustion of gas in traditional depressurization structures.

[0060] (b) Compact and reliable structure: The design of the metal part 12 (such as aluminum sheet) with the flanged structure 122 wrapping the top cover 13 simplifies the sealing structure and avoids the risk of failure caused by the superposition of multiple components. At the same time, the hot bonding process of the adhesive part 14 ensures the long-term sealing stability of the metal pressure plate 15 and the metal part 12.

[0061] (c) Reduced process costs: By eliminating complex processes such as scoring of explosion-proof sheets and CID assembly, mass production can be achieved through standardized processes such as stamping and hot bonding, reducing manufacturing costs by more than 20%.

[0062] (d) Enhanced environmental adaptability: Compared with traditional explosion-proof sheets that cannot be resealed after breaking and may accelerate battery failure due to the intrusion of external environmental pollutants, the cylindrical lithium battery explosion-proof combination cap 10 of the present invention still maintains partial contact between the metal part 12 and the metal pressure plate 15 after depressurization, reducing the intrusion of external pollutants and extending the service life of the battery in harsh environments.

[0063] This invention also discloses a method for preparing a cylindrical lithium battery explosion-proof composite cap, used to prepare the cylindrical lithium battery explosion-proof composite cap 10 of any of the above embodiments. The preparation method includes the following steps:

[0064] S1: Metal part 12 processing: Metal part 12 is formed by stamping on a metal substrate, and a first vent hole 121 is stamped on the metal part 12.

[0065] S2: Thermal bonding treatment: The metal sheet 15 and the metal part 12 are thermally bonded together by the adhesive 14.

[0066] S3: Installation of flame retardant component 16: Bond and fix the flame retardant component 16 to the surface of the metal plate 15 opposite to the metal component 12 after heat bonding.

[0067] S4: Overall assembly: Weld the top cover 13 to the metal part 12 and fix them together to the sealing part 11 to complete the encapsulation of the cylindrical lithium battery explosion-proof combination cap 10.

[0068] In some embodiments, in step S1, a metal part 12 (such as an aluminum sheet) is formed by stamping on a metal substrate (such as an aluminum sheet substrate) using a precision stamping die, and a plurality of first vent holes 121 are punched out on the metal part 12; the edge of the metal part 12 is flanged by a flanging die, and the flanging height is 3mm-4mm.

[0069] In some embodiments, in step S2, the metal sheet 15 and the metal part 12 are aligned, with an adhesive 14 sandwiched between them, and placed together in a hot press. The hot pressing temperature is 170℃-190℃, the pressure is 8MPa-12MPa, and the bonding time is 15-25s, causing the adhesive 14 to melt and bond the metal sheet 15 and the metal part 12, forming a sealed composite layer. For example, the hot bonding temperature can be 170℃, 180℃, or 190℃, the pressure can be 8MPa, 9MPa, 10MPa, 11MPa, or 12MPa, and the bonding time can be 15s, 16s, 17s, 18s, 19s, 20s, 21s, 22s, 23s, 24s, or 25s. The parameter settings can be selected according to actual needs and are not specifically limited here.

[0070] Furthermore, the adhesive 14 is melted and must completely cover the micro-gap between the metal sheet 15 and the metal part 12. After lamination, it needs to be tested with a helium mass spectrometer leak detector, and the leak rate must be <1×10⁻⁶. -6 Pa·m 3 / s. Preferably, the pressure relief threshold can be adjusted by adjusting the thickness of the adhesive 14 and the strength of the metal pressure plate 15, with a response time of <10ms, thus achieving a fast response.

[0071] In some embodiments, in step S3, the flame-retardant part is coated with high-temperature resistant epoxy adhesive and bonded to the surface of the metal sheet 15 opposite to the metal part 12 after thermal bonding. The curing conditions are a baking temperature of 70℃-90℃ and a baking time of 1s-3s.

[0072] In some embodiments, in step S3, the top cover 13 is welded and fixed to the metal part 12. The top cover 13 and the metal part 12 are welded and fixed using a laser welding process. Then, the edge of the metal part 12 is bent radially inward by 90 degrees to completely wrap the edge of the steel cap by a rolling process. The assembled structure is then fixed together on the sealing part 11 to complete the encapsulation of the cylindrical lithium battery explosion-proof combination cap 10.

[0073] In some embodiments, after step S4, step S5 is also included: air tightness test: applying 1.5MPa air pressure to the encapsulated cylindrical lithium battery explosion-proof combination cap 10, with a leakage rate ≤0.03mL / min; and burst pressure test: when the pressure tester is gradually increased to 2.0MPa, the metal pressure plate 15 is completely pushed open, and the structure has no permanent deformation after depressurization.

[0074] In some embodiments, the cylindrical lithium battery explosion-proof combination cap 10 undergoes the following pressure relief and flame retardant function verification.

[0075] Test conditions: The explosion-proof cap 10 of the cylindrical lithium battery is assembled onto the cylindrical lithium battery, which includes, but is not limited to, an 18650 type lithium-ion battery (capacity 2000mAh), and thermal runaway is simulated by overcharging to 5V.

[0076] Depressurization process:

[0077] 1. When the pressure in the cylindrical lithium battery section rises to 2.0 MPa, the gas pushes open the metal pressure plate 15 and breaks through the local sealing area of ​​the adhesive 14.

[0078] 2. High-temperature combustible gas enters the flame-retardant cavity of the top cover 12 through the first exhaust hole 121 of the metal part 12 (such as an aluminum sheet) and comes into full contact with the flame-retardant part 16.

[0079] 3. The red phosphorus flame retardant in flame retardant component 16 decomposes and absorbs heat, aluminum hydroxide releases water of crystallization when heated, and silicone rubber carbonizes to form a heat insulation layer, and the gas temperature drops from 250℃ to below 150℃.

[0080] 4. The treated gas was discharged through the second exhaust port 1331 of the top cover 13. No open flame or deflagration was observed, indicating that the flame retardant was effective.

[0081] Comparative experiment: Under the same conditions, when a traditional explosion-proof cap is depressurized, the released gas continues to burn after contact with air (duration > 10s), while the cylindrical lithium battery explosion-proof combination cap 10 of this application shows no combustion throughout the depressurization process. The cylindrical lithium battery explosion-proof combination cap 10 achieves highly efficient flame retardancy: the combustible gas deflagration inhibition rate is ≥95%. In addition, the cylindrical lithium battery explosion-proof combination cap 10 has good structural durability: after 1000 charge-discharge cycle tests, the sealing performance of the cylindrical lithium battery explosion-proof combination cap 10 shows no attenuation, and the flame-retardant component 16 does not powder or fall off.

[0082] like Figure 5 As shown, the present invention also discloses a cylindrical lithium battery, which includes, but is not limited to, high-energy-density cylindrical lithium batteries (such as electric vehicle power batteries and energy storage system battery modules).

[0083] The cylindrical lithium battery may include a battery casing 20 and a cylindrical lithium battery explosion-proof combination cap 10 of any of the above embodiments. The battery casing 20 is provided with a battery cell 30. The battery casing 20 has a first end and a second end opposite to each other. The first end of the battery casing 20 is provided with the cylindrical lithium battery explosion-proof combination cap 10.

[0084] The battery casing 20 may be generally cylindrical and conductive. For example, the battery casing 20 may be, but is not limited to, a steel casing. The cylindrical lithium battery explosion-proof combination cap 10 may be welded and fixed to the inner cavity of the first end of the battery casing 20 (either by laser welding or ultrasonic welding). The battery cell 30 may include a positive electrode assembly and a negative electrode assembly that cooperate with each other. The positive electrode assembly and the negative electrode assembly may be wound into a cylindrical structure by a separator assembly. The positive electrode tab of the positive electrode assembly may be connected to the metal part 12 (e.g., by laser welding), and the negative electrode tab of the negative electrode assembly may be connected to the battery casing 20 (e.g., by laser welding).

[0085] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A cylindrical lithium battery explosion-proof combination cap, characterized in that, It includes a seal (11), a metal part (12), a top cover (13), an adhesive part (14), a metal pressure plate (15), and a flame retardant part (16); The sealing element (11) has an annular structure. The sealing element (11) includes a supporting part (111). The metal part (12) is disposed on the supporting part (111). The metal part (12) has a plurality of first exhaust holes (121) penetrating its upper and lower surfaces in the middle part. The top cover (13) has a cylindrical structure and is mounted on the side surface of the metal part (12) away from the supporting part (111). The top cover (13) includes a bottom (131), a top (132) and a side (133). The bottom (131) and the top (132) are arranged parallel and spaced apart. The side (133) connects the bottom (131) and the top (132). The side (133) is provided with a plurality of second exhaust holes (1331). The metal plate (15) is sealed to the upper surface of the metal part (12) by the adhesive (14), and the metal plate (15) seals the first vent hole (121). The flame retardant (16) is installed on the side surface of the metal plate (15) away from the metal part (12).

2. The explosion-proof combination cap for cylindrical lithium batteries according to claim 1, characterized in that, The bearing portion (111) has an annular limiting portion (112) extending around its periphery. The inner side of the limiting portion (112) is provided with an annular protrusion (113). The protrusion (113) is spaced apart from the bearing portion (111) and a limiting space is defined between the bearing portion (111), the limiting portion (112) and the protrusion (113). The periphery of the metal part (12) extends toward the side away from the support portion (111) and toward the side away from the limiting portion (112) to form a flange structure (122). At least a portion of the flange structure (122) is confined within the limiting space, and the flange structure (122) is used to wrap at least a portion of the bottom (131).

3. The explosion-proof combination cap for cylindrical lithium batteries according to claim 1, characterized in that, A plurality of the first exhaust holes (121) are arranged in a ring array, and the first exhaust holes (121) are circular holes with a diameter of 0.4mm-0.6mm.

4. The explosion-proof combination cap for cylindrical lithium batteries according to claim 1, characterized in that, The thickness of the adhesive (14) is 20μm-50μm.

5. The explosion-proof combination cap for cylindrical lithium batteries according to claim 1, characterized in that, The flame retardant component (16) is made of red phosphorus flame retardant, aluminum hydroxide and silicone rubber in a mass ratio of 3:5:

2.

6. The explosion-proof combination cap for cylindrical lithium batteries according to claim 5, characterized in that, The volume of the flame-retardant component (16) accounts for 40%-60% of the inner cavity volume of the top cover (13).

7. A method for preparing an explosion-proof composite cap for a cylindrical lithium battery, used to prepare the explosion-proof composite cap for a cylindrical lithium battery as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Metal part (12) processing: A metal part (12) is formed by stamping on a metal substrate, and a first vent hole (121) is stamped on the metal part (12); S2: Thermal bonding treatment: The metal sheet (15) and the metal part (12) are thermally bonded together by the adhesive (14); S3: Installation of flame retardant component (16): Bond and fix the flame retardant component (16) to the surface of the metal plate (15) after heat bonding away from the metal component (12); S4: Overall assembly: Weld the top cover (13) to the metal part (12) and fix them together on the sealing part (11) to complete the sealing of the cylindrical lithium battery explosion-proof combination cap.

8. The method for preparing the explosion-proof combined cap for a cylindrical lithium battery according to claim 7, characterized in that, In step S2, the metal sheet (15) and the metal part (12) are aligned, and an adhesive (14) is sandwiched between the metal sheet (15) and the metal part (12). They are then placed together in a hot press. The hot pressing temperature is 170℃-190℃, the pressure is 8MPa-12MPa, and the bonding time is 15s-25s, so that the adhesive (14) melts and bonds the metal sheet (15) and the metal part (12).

9. The method for preparing the explosion-proof combined cap for a cylindrical lithium battery according to claim 7, characterized in that, In step S3, the flame-retardant part (16) is coated with high-temperature resistant epoxy adhesive and bonded to the side surface of the metal sheet (15) after thermal bonding that is away from the metal part (12). The curing conditions are a baking temperature of 70℃-90℃ and a baking time of 1s-3s.

10. A cylindrical lithium battery, characterized in that, Includes a battery casing (20) and a cylindrical lithium battery explosion-proof combination cap as described in any one of claims 1 to 6, wherein a battery cell (30) is provided inside the battery casing (20), the battery casing (20) has a first end and a second end opposite to each other, and the first end of the battery casing (20) is provided with the cylindrical lithium battery explosion-proof combination cap.

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