Cylindrical battery, battery pack, and electric device

Abstract

The present disclosure provides a cylindrical battery, a battery pack and an electrical equipment. The cylindrical battery provided by the present disclosure comprises an electric core, a shell and a first explosion-proof valve. The shell accommodates the electric core and comprises a first end wall, a second end wall and a side wall extending therebetween, and the first end wall and the side wall are integrally connected to form a transition connection portion. The first explosion-proof valve is connected to at least one of the first end wall and the second end wall. The first explosion-proof valve comprises a weak portion, and the thickness of the weak portion is less than the thickness of the end wall body. The ratio of the length a1 and the diameter a2 of the cylindrical battery is a. The thickness difference between the first end wall and the transition connection portion is b. The ratio of the area c1 surrounded by the weak portion and the area c2 of the end wall is c. 0.24≤(a×b) / c≤201.93. Accordingly, while the risk of cracking of the transition connection portion between the first end wall and the side wall is eliminated or significantly reduced, the risk of deformation or cracking of the side wall is also eliminated or significantly reduced.

Description

Technical Field

[0001] This disclosure relates to the field of battery technology, specifically to a cylindrical battery, a battery pack having the cylindrical battery, and an electrical device having the cylindrical battery or the battery pack. Background Technology

[0002] Batteries with cylindrical casings are known, and these are commonly referred to as cylindrical batteries. Compared to prismatic batteries, cylindrical batteries are considered to have advantages such as higher assembly efficiency and better utilization of internal space. Cylindrical batteries are typically equipped with an explosion-proof valve. This valve is intended to open promptly in the event of thermal runaway to reduce internal pressure. If the explosion-proof valve fails to open in time, or fails to release pressure promptly after opening, it can lead to casing cracking, thereby exacerbating thermal runaway and posing a significant safety risk. Summary of the Invention

[0003] In view of this, embodiments of the present disclosure provide a cylindrical battery to reduce the risk of casing cracking.

[0004] The cylindrical battery disclosed herein includes a cell, a casing, and a first explosion-proof valve. The casing houses the cell and includes a first end wall, a second end wall, and a side wall extending between them. The first end wall and the side wall are integrally connected to form a transition connection. An opening is formed at the end of the side wall opposite to the first end wall, and the second end wall seals the opening. The first explosion-proof valve is disposed on at least one of the first and second end walls and connected to the end wall. The first explosion-proof valve includes a weak portion, the thickness of which is less than the thickness of the end wall body. The length of the cylindrical battery is a1 mm, the diameter of the cylindrical battery is a2 mm, and the ratio of a1 to a2, a1 / a2, equals a. The thickness of the first end wall is b1 mm, the minimum thickness of the transition connection is b2 mm, and the difference between b1 and b2, b1-b2, equals b. The area of ​​the region enclosed by the weak portion is c1 mm². 2 The area of ​​the end wall with the weak part is c2mm. 2 The ratio of c1 to c2, c1 / c2, is equal to c. 0.24 ≤ (a × b) / c ≤ 201.93.

[0005] By selecting the value of (a×b) / c in the formula within a reasonable range of 0.24 to 201.93, the timely pressure relief of the battery explosion-proof valve is ensured, reducing the risk of excessive internal pressure or untimely pressure relief, which could lead to high-temperature gas breaking through the transition connection between the first end wall and the side wall, causing the first end wall to fly out and triggering severe thermal runaway, resulting in serious fire and explosion of the battery. At the same time, it enhances the overall structural strength of the casing side wall, improves the production yield and service life of the battery casing, and reduces the risk of side wall deformation or cracking.

[0006] In addition, by selecting the value of (a×b) / c in the formula within the above reasonable range, the gas generated by the cylindrical battery in the event of thermal runaway can be quickly and timely discharged through the first explosion-proof valve, realizing timely pressure relief inside the casing and avoiding dangers such as explosion due to thermal runaway and failure to relieve pressure in time.

[0007] This disclosure also provides a battery pack, including a housing, a fixing member, and a plurality of cylindrical batteries as described above. The housing includes a top plate, a bottom plate, and a side beam extending between the two, the top plate, bottom plate, and side beam enclosing an internal space, in which the plurality of cylindrical batteries are housed. The fixing member is disposed in the internal space, and the plurality of cylindrical batteries are fixed by the fixing member and the bottom plate, and the fixing member at least partially covers the transition connection portion.

[0008] This disclosure also provides an electrical device including a cylindrical battery as described above, or a battery pack as described above. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of a cylindrical battery according to an embodiment of the present disclosure.

[0010] Figure 2 for Figure 1 A schematic diagram of the battery in the image.

[0011] Figure 3 for Figure 1 A schematic diagram of the end face of a cylindrical battery.

[0012] Figure 4 For along Figure 3 A cross-sectional view taken along line AA.

[0013] Figure 5 for Figure 4 A magnified view of part B in the middle section.

[0014] Figure 6 for Figure 4 A magnified view of part C in the middle.

[0015] Figure 7 for Figure 6 The enlarged partial view shown is a schematic diagram of another embodiment.

[0016] Figure 8 for Figure 7 The diagram shows other shapes of the grooves provided, where Figure α is a schematic diagram of a rectangular cross-section of the groove, Figure β is a schematic diagram of an arc-shaped cross-section of the groove, Figure γ is a schematic diagram of a stepped cross-section of the groove, and Figure δ is a schematic diagram of a triangular cross-section of the groove.

[0017] Figure 9 for Figure 7The enlarged partial view shown is a schematic diagram of another embodiment.

[0018] Figure 10 This is a cross-sectional view of a cylindrical battery according to another embodiment of the present disclosure.

[0019] Figure 11 for Figure 10 A magnified view of part D in the middle.

[0020] Figure 12 This is a cross-sectional view of a cylindrical battery according to another embodiment of the present disclosure.

[0021] Figure 13 This is a schematic diagram of the end face of a cylindrical battery according to another embodiment of the present disclosure.

[0022] Figure 14 This is a schematic diagram of the end face of a cylindrical battery according to another embodiment of the present disclosure.

[0023] Figure 15 for Figure 1 A schematic diagram of the cross-section of a cylindrical battery.

[0024] Figure 16 This is an exploded view of a battery pack according to an embodiment of the present disclosure.

[0025] Figure 17 This is a schematic diagram of the structure of an electrical device according to an embodiment of the present disclosure. Detailed Implementation

[0026] Research has found that if the explosion-proof valve of a cylindrical battery does not open in time, high-temperature gas will break through the casing, causing the entire casing wall to fly out, resulting in a high risk of casing cracking. This is mainly due to the following two aspects.

[0027] On the one hand, while higher internal space utilization can improve the energy density of cylindrical batteries, it also increases the risk of casing cracking. This is because higher space utilization means less free space between the casing and the cell, and also means tighter winding of the cell electrodes, resulting in insufficient buffer space between the electrodes. This leads to a situation where, in the event of thermal runaway, the gas transmission path to the explosion-proof valve primarily relies on the winding holes of the cell, resulting in insufficient pressure relief space for the cylindrical battery. Insufficient pressure relief space causes a sudden increase in internal pressure during thermal runaway, exacerbating the risk of casing cracking.

[0028] For example, the distance between the sidewalls of the cell and the casing in the radial direction of the cylindrical battery is L2mm, where L2 can satisfy: 0.1≤L2≤1.5. For example, the above distance can be set to values ​​such as 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, and 1.5mm.

[0029] On the other hand, cylindrical batteries typically have a larger aspect ratio, meaning they are mostly slender cylindrical structures. The explosion-proof valves of cylindrical batteries are also usually located on their end walls. This results in a longer venting path inside the cylindrical battery, making it difficult to avoid situations where pressure cannot be released in time through the explosion-proof valves during thermal runaway. Delayed pressure release also increases the risk of casing cracking.

[0030] Further research revealed that shell cracking frequently occurs at the transition joint between the end walls and side walls. The main reason is that the side walls are cylindrical while the end walls are flat and sheet-like, creating a significant shape difference. The shell is formed by stretching the end walls to create the side walls, which are thinner than the end walls. The transition joint between them is formed by thinning, and its thickness is generally less than that of the side walls and end walls. Therefore, this location has a higher risk of deformation. The transition joint is the area where the shape difference between the two is significant, i.e., where the shell geometry abruptly changes. This means that during thermal runaway, stress will concentrate at the transition joint. If the internal pressure of the battery is not released in time, the transition joint has a high risk of deformation, leading to a greater risk of cracking. In some cases, the entire end wall may fly off, increasing the risk of battery fire and explosion.

[0031] To improve the pressure relief rate of the battery explosion-proof valve, ensure timely pressure relief, and prevent battery end wall cracking, especially reducing the risk of cracking at the transition connection between the end wall and side wall, the present disclosure improves the structure of the cylindrical battery. The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, and not all of them.

[0032] <Example cylindrical battery> First, it should be noted that a battery refers to an energy storage device capable of storing and providing electrical energy. Specifically, in this disclosure, "battery" can refer to an energy storage device capable of repeated charging and discharging, and can be interpreted as a "secondary battery." In this disclosure, the concept of "secondary battery" can include, but is not limited to, lithium-ion secondary batteries, sodium-ion secondary batteries, and nickel-metal hydride batteries, etc. A cylindrical battery is a specific form of battery, with a cylindrical casing and internal cells wound into a cylindrical shape.

[0033] refer to Figure 1 and Figure 2This disclosure provides a cylindrical battery 100, which includes a housing 10 and a battery cell 20 disposed inside the housing 10. The housing 10 includes a first end wall 11, a second end wall 12, and a side wall 13 extending between the two, which are fixedly connected to form a cylindrical structure, enclosing a cavity for accommodating the battery cell 20.

[0034] Here, the first end wall 11 and the second end wall 12 can be arranged at intervals along a first direction. In this text, the first direction can be the length direction of the cylindrical battery 100, or the height direction of the cylindrical battery 100. For ease of understanding, in the accompanying drawings, one side of the first direction is indicated by Y+, and the other side of the first direction is indicated by Y-.

[0035] This disclosure does not impose any particular limitation on the material of the housing 10. For example, the housing 10 may be made of steel to obtain good mechanical strength and corrosion resistance. Alternatively, the housing 10 may be made of aluminum alloy, stainless steel, nickel-plated steel, etc., to obtain high structural strength, good corrosion resistance, and heat dissipation. Conversely, the housing 10 may also be made of titanium alloy, copper alloy, magnesium alloy, or any other suitable material.

[0036] refer to Figure 3 , Figure 4 and Figure 5 The first end wall 11 and the side wall 13 are integrally connected to form a transition connection portion 14. By way of example only, the end of the side wall 13 opposite to the first end wall 11 may form an opening, and the second end wall 12 may be fixedly connected to the side wall 13 to seal the opening.

[0037] The transition connection 14 is an R-angle structure formed during the molding process of the first end wall 11 and the side wall 13. During the preparation of the shell 10, the plate is stretched to form the first end wall 11 and the side wall 13. The thickness of the transition connection 14 (that is, the R-angle) is reduced compared to the first end wall 11.

[0038] The second end wall 12 and the side wall 13 can be fixed by welding, and the seal is achieved through the weld line between the second end wall 12 and the side wall 13; in another embodiment, the second end wall 12 and the side wall 13 can also be fixedly connected by riveting. In other embodiments, other fixing methods commonly used in the art can also be selected to fix the second end wall 12 and the side wall 13.

[0039] The shape of the cylindrical battery 100 is characterized by its aspect ratio, which is the ratio of the length to the diameter of the cylindrical battery 100. Specifically, refer to... Figure 4The cylindrical battery 100 has a length of a1 mm and a diameter of a2 mm. The ratio of a1 to a2, a1 / a2, equals a, which is the length-to-diameter ratio of the cylindrical battery 100. Here, the length of the cylindrical battery 100 refers to its dimension in the first direction, and the diameter of the cylindrical battery 100 refers to the diameter of its cross-section perpendicular to the first direction. As the demand for battery capacity increases, the battery diameter and length increase, resulting in a larger amount of gas generated inside the battery, a greater risk of casing deformation, and a higher likelihood of breakage of the transition connection 14, potentially leading to severe thermal runaway.

[0040] It should be noted that in practice, the cylindrical battery 100 may not be a standard cylinder; its ends may have protrusions (such as terminals) or recesses (such as grooves on the end walls). In the disclosed embodiments, the length of the cylindrical battery 100 can be determined by the distance between the opposing surfaces of the first end wall 11 and the second end wall 12. When the surfaces of the first end wall 11 and the second end wall 12 are not flat, the flat surface portion remaining after removing the protruding and recessed structures is used as the reference.

[0041] Additionally, refer to Figure 5 The thickness of the first end wall 11 is b1 mm, and the minimum thickness of the transition connection portion 14 is b2 mm. The difference between the two, b1 mm - b2 mm, equals b mm. It should be noted that in this disclosure, the thickness of the first end wall 11 and the minimum thickness of the transition connection portion 14 refer to their dimensions in the inward and outward directions of the housing 10, as illustrated in the accompanying drawings. Here, the thickness of the first end wall 11 is the dimension in the first direction, and the thickness of the transition connection portion 14 is the dimension in the inward and outward directions of the housing 10.

[0042] In some embodiments, the first end wall 11 is provided with pole posts, explosion-proof valves, and other related structures. In this case, when determining the thickness b1 of the first end wall 11, the areas where the first end wall 11 is differentiated due to the provision of pole posts, explosion-proof valves, and other structures should be avoided, such as areas where the first end wall 11 is additionally thickened or thinned. Instead, only the thickness of the areas without the above structures should be considered, that is, flat areas with uniform thickness.

[0043] An explosion-proof valve is a component or part that can be actuated to release internal pressure or temperature when the internal pressure or temperature of a battery cell reaches a predetermined threshold. There are no restrictions on the materials used for explosion-proof valves, including but not limited to aluminum, steel, and alloys. The shape of the explosion-proof valve is also unrestricted, including square, oblong, elliptical, racetrack-shaped, etc. There are no restrictions on the type of explosion-proof valve, such as a notched explosion-proof valve, which can be formed by stamping or laser etching. Explosion-proof valves can be integrally connected to the end wall or separately connected to the end wall via welding, riveting, or other methods.

[0044] The explosion-proof valve includes a weak point, designed to rupture when the internal pressure or temperature of the cylindrical battery reaches a certain value. This allows the internal environment of the cylindrical battery to connect with the external environment, releasing the internal pressure or temperature. The weak point may have a groove formed on at least one end face of the end wall. This groove can be located close to or away from the battery cell, or it can be provided on both the inner and outer surfaces of the end wall. This allows the explosion-proof valve to open more quickly, avoiding the high risk of thermal runaway caused by cracking at the transition connection.

[0045] Furthermore, in some cases, due to processing errors, even the thickness of a uniform thickness region may vary at different locations. Therefore, in this embodiment of the present disclosure, when determining the thickness of the first end wall 11, multiple measurement points are taken at intervals in the aforementioned uniform thickness region, such as ten measurement points. The average value of the measured thicknesses at the ten measurement points is then taken as the thickness of the first end wall 11.

[0046] refer to Figure 4 The battery cell 20 is located inside the housing 10, and includes a battery cell body 21, a first tab 22, and a second tab 23. The first tab 22 and the second tab 23 have opposite polarities. That is, one of the first tab 22 and the second tab 23 is the positive tab, and the other is the negative tab. In the current embodiment, both the first tab 22 and the second tab 23 are led out from the end of the battery cell body 21 facing the second end wall 12.

[0047] In other embodiments, one of the first tab 22 and the second tab 23 may be led out from the end of the cell body 21 facing the first end wall 11, and the other may be led out from the end of the cell body 21 facing the second end wall 12. This arrangement allows the first tab 22 and the second tab 23, with opposite polarities, to be led out from the two end faces of the cell 20, increasing the overall size and current-carrying area of ​​the tabs, improving the heat dissipation rate, preventing gas concentration, and reducing the risk of the casing 10 bursting.

[0048] When the housing 10 serves as a battery output terminal of the cylindrical battery 100, one of the first tab 22 or the second tab 23 can be electrically connected to the housing 10, and the other can be electrically connected to the terminal of the cylindrical battery 100. This design can increase the current-carrying area of ​​the terminal and improve the current-carrying capacity of the terminal while ensuring that the overall height of the cylindrical battery 100 is not too high.

[0049] In another embodiment, the first tab 22 and the second tab 23 can be disposed on the same side of the cell body 21, that is, the first tab 22 and the second tab 23 are both disposed facing the first end wall 11 or the second end wall 12. This arrangement facilitates the positive and negative terminals of the cylindrical battery 100 to be led out from the same end face of the housing 10, which is convenient for the integration of the cylindrical battery 100. At the same time, it ensures that the current paths of the positive and negative terminals are within a suitable range, reduces the heat generation of the cylindrical battery 100 during use, and improves the high-rate charging capability of the battery.

[0050] A battery cell is the component in a battery where electrochemical reactions occur; it is the smallest unit in a battery capable of carrying out electrochemical reactions such as charging and discharging. A battery cell typically consists of a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes.

[0051] The positive electrode is one of the core components in a battery that carries the positive electrode active material. During charging, metal ions (e.g., lithium ions) are released from the positive electrode active material (oxidation reaction), migrate through the electrolyte, and intercalate into the negative electrode. During discharging, metal ions (e.g., lithium ions in a lithium battery) are released from the negative electrode and intercalated into the positive electrode active material (reduction reaction), thus realizing the storage and release of lithium ions.

[0052] A positive electrode generally includes a positive current collector and a positive active material layer. The positive active material layer is coated on at least one surface of the positive current collector and includes: a positive active material, a conductive agent, and a binder. The positive active material includes, but is not limited to, at least one of the following: lithium phosphates, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive active materials for batteries. These positive active materials can be used alone or in combination. The lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, and modified compounds thereof.

[0053] The positive electrode current collector includes a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. The positive electrode current collector can also include a composite current collector, which may include a polymer material substrate and a metal layer. Composite current collectors are formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.).

[0054] The positive electrode conductive agent includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon nanotubes, graphene and carbon nanofibers.

[0055] The positive electrode binder includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0056] During battery charging, active ions (such as lithium ions) from the positive electrode are embedded in the negative electrode, while electrons from the positive electrode are transferred to the negative electrode through an external circuit to maintain charge balance. During discharge, active ions (such as lithium ions) previously embedded in the negative electrode can be released, while electrons from the negative electrode are transferred to the negative electrode through an external circuit to maintain charge balance, thus achieving energy storage and release.

[0057] The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. The negative electrode current collector can also include a composite current collector, which may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.). The negative electrode active layer includes a negative electrode active material, conductive components, adhesives, etc. The negative electrode active material can be carbon-based materials such as graphite, porous carbon, hard carbon, soft carbon, and mesophase carbon microspheres, or silicon-based materials such as elemental silicon, silicon oxides, silicon-carbon composites, and silicon-ammonia composites. The conductive agent can be conductive carbon black, carbon nanotubes, etc., and the binder can be styrene-butadiene rubber, polyacrylic acid, etc.

[0058] A diaphragm is placed between the positive and negative electrode plates to separate them and prevent them from short-circuiting due to contact.

[0059] The diaphragm can be at least one of glass fiber, nonwoven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. A coating can also be applied to the diaphragm surface. The coating can be an inorganic coating and / or an organic coating, wherein the inorganic coating material includes at least one of alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, and boehmite; and the organic coating includes at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0060] The battery cell also includes tabs, which are located on one side of the positive / negative current collector and are either separate from or integrally formed with the current collector. The tabs are electrically connected to the current collector to conduct current through it. When the tabs and current collector are separate, they can be connected by welding. The tabs are made of a highly conductive metal material (such as copper, aluminum, or nickel).

[0061] refer to Figure 1 and Figure 2 The cylindrical battery 100 also includes a first explosion-proof valve 30. In the current embodiment, the first explosion-proof valve 30 is disposed on the second end wall 12, and the first explosion-proof valve 30 includes a weak portion 31, the thickness of which is less than the thickness of the second end wall 12. In other embodiments, the first explosion-proof valve 30 may also be disposed on the first end wall 11, or the first explosion-proof valve 30 may be disposed on both the first end wall 11 and the second end wall 12.

[0062] By way of example only, the weak point 31, the first explosion-proof valve 30, and the corresponding end wall can be integrally formed. The weak point 31 can be a region on the corresponding end wall with reduced thickness, and its thickness is smaller than that of other regions. The weak point 31 and the portion surrounded by the weak point 31 constitute the first explosion-proof valve 30. In other words, the first explosion-proof valve 30 is part of the end wall body, and the first explosion-proof valve 30 and other parts of the end wall body are connected through the weak point 31. Alternatively, the weak point 31 can be used to enclose a relatively independent region, which is the first explosion-proof valve 30. In the event of thermal runaway, the pressure inside the housing 10 exceeds a set threshold, causing the corresponding end wall to fracture in the region of the weak point 31. The first explosion-proof valve 30 separates from the end wall body, achieving the function of pressure relief and explosion prevention.

[0063] Alternatively, the first explosion-proof valve 30 can be a structure independent of the end wall, such as an explosion-proof disc or membrane. An explosion-proof channel for installing the first explosion-proof valve 30 is provided on the end wall, and the first explosion-proof valve 30 is disposed within the explosion-proof channel and fixedly connected to the side wall of the explosion-proof channel. Alternatively, the first explosion-proof valve 30 can abut against the side of the end wall facing inwards or outwards from the housing 10. In this case, the explosion-proof channel only needs to be sealed by the first explosion-proof valve 30. In this scenario, the first explosion-proof valve 30 can be fixedly connected to the end wall using a connecting rib or similar structure. In this case, the weak point 31 is the connection structure between the first explosion-proof valve 30 and the end wall.

[0064] In this embodiment of the disclosure, the first explosion-proof valve 30 is used as an example of a part of the end wall body.

[0065] like Figure 3 As shown, the area of ​​the region enclosed by the weak part 31 is c1mm. 2 The area of ​​the end wall where the first explosion-proof valve 30 is located (in the current embodiment, the second end wall 12) is c2mm. 2 The ratio of c1 to c2, c1 / c2, is equal to c.

[0066] The values ​​of a, b, and c above can satisfy: 0.24 ≤ (a × b) / c ≤ 201.93. For example, the value of (a × b) / c can be 0.24, 0.5, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 201.93, etc.

[0067] By selecting the value of (a×b) / c in the formula within a reasonable range of 0.24 to 201.93, the first explosion-proof valve 30 is guaranteed to release pressure in a timely manner, reducing the possibility of excessive internal pressure in the battery or untimely pressure release, which could cause high-temperature gas to break through the transition connection 14 between the first end wall 11 and the side wall 13, leading to cracking of the transition connection 14, the first end wall 11 flying out, and causing severe thermal runaway, resulting in serious fire and explosion of the battery. At the same time, it enhances the overall structural strength of the side wall 13 of the casing, improves the production yield and service life of the casing 10, and reduces the risk of deformation or cracking of the side wall 13.

[0068] In addition, by selecting the value of (a×b) / c in the formula within the above reasonable range, the gas generated by the cylindrical battery 100 in the event of thermal runaway can be quickly and timely discharged through the first explosion-proof valve 30, thereby achieving timely pressure relief inside the casing 10 and avoiding dangers such as explosions caused by thermal runaway and failure to relieve pressure in time.

[0069] If the value of the formula (a×b) / c is too small, that is, less than 0.24, the sidewall 13 will be more prone to deformation, and the risk of deformation and cracking of the sidewall 13 will be higher. Consequently, the deformation of the sidewall 13 may also cause cracks at the connection between the sidewall 13 and the endwall. This can perhaps be attributed to the following points.

[0070] 1. If the value of 'a' is too small, the cylindrical battery 100 will have a short and thick shape, and the radial dimension of the cylindrical battery 100 will be larger. As the number of charge and discharge cycles increases, the cylindrical battery 100 will expand and deform. The larger the radial dimension of the cylindrical battery 100, the larger the radial expansion will be when it expands and deforms. This will result in a greater squeezing force of the cell 20 on the side wall 13, making the side wall 13 more prone to deformation. The connection between the side wall 13 and the end wall will be more prone to cracking.

[0071] Second, if the value of b is too small, the thickness of the first end wall 11 and the thickness of the transition connection 14 will be closer or even equal; if the thickness of the transition connection 14 is too large, it will be difficult to form a higher side wall 13. The thinning dimension of the transition connection 14 compared to the first end wall 11 is small, resulting in a large thickness deviation between the formed side wall 13 and the end wall, that is, the thickness of the formed side wall 13 is small, which increases the risk of deformation of the side wall 13 and shortens the service life of the shell 10.

[0072] Third, if the value of c is too large, that is, the area of ​​the first explosion-proof valve 30 is too large, the area of ​​the part of the end wall outside the first explosion-proof valve 30, that is, the area of ​​the end wall body, will be reduced, which will lead to a reduction in the external force that the end wall as a whole can withstand. This will also weaken the support of the end wall to the end of the side wall 13, and the risk of deformation of the side wall 13 will be greater.

[0073] If the value of formula (a×b) / c is too large, that is, greater than 201.93, then the risk of cracking in the transition connection 14 between the first end wall 11 and the side wall 13 is too high. This may be attributed to the following reasons.

[0074] First, if the value of 'a' is too large, the cylindrical battery 100 will have a long and thin shape, resulting in an excessively long venting path inside the cylindrical battery 100. In the event of thermal runaway, the gas will be difficult to release pressure from the first explosion-proof valve 30 in a timely manner. This increases the risk of cracking in the transition connection 14, causing the end wall to fly out entirely, and making the risk of explosion and severe thermal runaway of the cylindrical battery 100 even higher.

[0075] Second, if the value of b is too large, it means that the difference in thickness between the first end wall 11 and the transition connection 14 is large; if the thickness of the first end wall 11 meets the requirements, it means that the thickness of the transition connection 14 is too small and the structural strength is insufficient; this leads to an increased risk of cracking at the transition connection 14 in the event of thermal runaway of the cylindrical battery 100.

[0076] Third, if the value of c is too small, the force-bearing area of ​​the first explosion-proof valve 30 will be reduced. This will result in a higher pressure inside the casing 10 required for the first explosion-proof valve 30 to separate and release pressure when the cylindrical battery 100 experiences thermal runaway. Under the action of the higher pressure, the risk of cracking of the transition connection 14 is higher. That is, in the event of thermal runaway, there is a greater risk that the first explosion-proof valve 30 will not open to release pressure, causing the transition connection 14 to crack and the first explosion-proof valve 30 to fail, thereby increasing the risk of the cylindrical battery 100 exploding and exacerbating thermal runaway.

[0077] In addition, by selecting the value of formula (a×b) / c within the above reasonable range, the gas generated by the cylindrical battery 100 in the event of thermal runaway can be quickly and timely discharged through the first explosion-proof valve 30, thereby achieving timely pressure relief inside the casing 10 and avoiding dangers such as explosion due to thermal runaway and failure to relieve pressure in time.

[0078] refer to Figure 3 and Figure 4 The first explosion-proof valve 30 is located on the second end wall 12. Preferably, 0.24 ≤ (a×b) / c ≤ 198.5.

[0079] The transition connection 14 is located at the end where the first end wall 11 is located, and the first explosion-proof valve 30 is located at the end where the second end wall 12 is located. The transition connection 14 and the first explosion-proof valve 30 are located at opposite ends of the cylindrical battery 100. In this case, if the cylindrical battery 100 experiences thermal runaway, the gas inside the casing 10 will be depressurized through the first explosion-proof valve 30. For the gas distributed at the end of the first end wall 11, the transmission path to depressurize through the first explosion-proof valve 30 is longer. Therefore, this part of the gas is more likely to accumulate at the end where the first end wall 11 is located, which means that stress concentration is more likely to occur at the transition connection 14, increasing the risk of cracking of the transition connection 14.

[0080] Based on this situation, by further controlling the range of values ​​for (a×b) / c, the pressure relief and explosion-proof capability of the first explosion-proof valve 30 can be further improved. When the cylindrical battery 100 experiences thermal runaway, the first explosion-proof valve 30 can open in time to relieve pressure, further reducing the risk of cracking in the casing 10, especially at the transition connection 14.

[0081] Preferably, the parameters a, b, and c of the cylindrical battery 100 satisfy 1.01 ≤ (a×b) / c ≤ 85.12. By further controlling the range of values ​​for (a×b) / c, the quality of the cylindrical battery 100 is further improved, and the risk of deformation and damage to the sidewall 13 and cracking of the transition connection 14 is reduced.

[0082] For example, in this embodiment of the disclosure, the value of (a×b) / c can be 50.

[0083] For example, the aspect ratio 'a' of the cylindrical battery 100 can satisfy: 1.5 ≤ a ≤ 7. For instance, the aspect ratio 'a' of the cylindrical battery 100 can be set to values ​​such as 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, etc.

[0084] If the aspect ratio of the cylindrical battery 100 is too small, the battery will be short and thick, and the radial dimension of the cylindrical battery 100 will be larger. As the number of charge and discharge cycles of the cylindrical battery 100 increases, the cylindrical battery 100 will expand and deform. The larger the radial dimension of the cylindrical battery 100, the larger the radial expansion will be when it expands and deforms. This will result in greater pressure on the sidewall 13 of the cylindrical battery 100 cell, making the sidewall 13 more prone to deformation and the connection between the sidewall 13 and the end wall more likely to crack.

[0085] If the aspect ratio of the cylindrical battery 100 is too large, the battery will have a long and thin shape, which will result in an excessively long venting path inside the cylindrical battery 100. In the event of thermal runaway, the gas will be difficult to release pressure from the first explosion-proof valve 30 in a timely manner. This increases the risk of cracking in the transition connection 14, and makes the risk of explosion and severe thermal runaway of the cylindrical battery 100 even higher.

[0086] In this embodiment of the disclosure, by limiting the aspect ratio of the cylindrical battery 100 to a suitable range, the gas generated when the battery experiences thermal runaway can be quickly and timely discharged through the first explosion-proof valve 30, thereby achieving timely pressure relief inside the casing 10, reducing the risk of cracking of the transition connection 14, and reducing the danger of explosion due to thermal runaway and failure to relieve pressure in time.

[0087] Preferably, the aspect ratio α of the cylindrical battery 100 can satisfy: 1.7≤a≤6.5.

[0088] In this embodiment, the aspect ratio a of the cylindrical battery 100 is 5 as an example. Of course, in other embodiments, the aspect ratio a can be set to 1.7, 2, 3, 4, 6, 6.5, etc.

[0089] The length a1mm of the cylindrical battery 100 can satisfy: 60≤a1≤220; for example, the length of the cylindrical battery 100 can be set to values ​​such as 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, 210mm, and 220mm.

[0090] Preferably, the length a1mm of the cylindrical battery 100 can be set to satisfy: 80≤a1≤200. For example, the length of the cylindrical battery 100 can be set to values ​​such as 80mm, 85mm, 95mm, 105mm, 115mm, 125mm, 135mm, 145mm, 155mm, 165mm, 175mm, 185mm, 195mm, and 200mm.

[0091] The diameter a2mm of the cylindrical battery 100 can satisfy: 18≤a2≤62; for example, the diameter of the cylindrical battery 100 can be set to values ​​such as 18mm, 22mm, 26mm, 30mm, 34mm, 38mm, 42mm, 46mm, 50mm, 54mm, 58mm, and 62mm.

[0092] Preferably, the diameter a2mm of the cylindrical battery 100 can be set to satisfy: 32≤a1≤50. For example, the diameter of the cylindrical battery 100 can be set to values ​​such as 32mm, 34mm, 36mm, 38mm, 40mm, 42mm, 44mm, 47mm, 49mm, and 50mm.

[0093] For example, the difference bmm between the thickness of the first end wall 11 and the thickness of the transition connection portion 14 can satisfy: 0.1≤b≤2.7. For example, the difference between the thickness of the first end wall 11 and the thickness of the transition connection portion 14 can be set to values ​​such as 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, and 2.7mm.

[0094] If the value of b is too small, the thickness of the first end wall 11 and the thickness of the transition connection 14 will be closer or even equal. If the thickness of the transition connection 14 is too large, stress concentration will easily occur at the location of the transition connection 14, which will make it difficult to form the shell 10. In the event of thermal runaway, stress concentration at the transition connection 14 will increase the risk of cracking of the transition connection 14. In addition, if the thickness of the transition connection 14 is larger, the thickness of the side wall 13 will be reduced, and the strength of the side wall 13 will be reduced.

[0095] If the value of b is too large, it means that the difference in thickness between the first end wall 11 and the transition connection 14 is large; if the thickness of the first end wall 11 meets the requirements, it means that the thickness of the transition connection 14 is too small and the structural strength is insufficient; this leads to an increased risk of cracking at the transition connection 14 in the event of thermal runaway of the cylindrical battery 100.

[0096] Preferably, the difference bmm between the thickness of the first end wall 11 and the thickness of the transition connection portion 14 can satisfy: 0.3≤b≤2.1.

[0097] In this embodiment, the example given is that the difference in thickness bmm between the first end wall 11 and the transition connection portion 14 is 1mm. Of course, in other embodiments, the difference in thickness bmm can be set to 0.3mm, 0.5mm, 0.8mm, 1.2mm, 1.5mm, 1.7mm, 2.1mm, etc.

[0098] refer to Figure 5 The thickness b1mm of the first end wall 11 can satisfy: 0.4≤b1≤3. For example, the thickness of the first end wall 11 can be set to values ​​such as 0.4mm, 0.7mm, 1mm, 1.3mm, 1.6mm, 1.9mm, 2.2mm, 2.5mm, 2.8mm, and 3mm.

[0099] If the thickness of the first end wall 11 is too small, the structural strength of the first end wall 11 will be insufficient, and it will be unable to provide stable support for the internal battery cell 20. The support of the end wall for the side wall 13 will also be weakened. In the event of thermal runaway, the first end wall 11 is at high risk of cracking under the pressure inside the shell 10.

[0100] If the thickness of the first end wall 11 is too large, it will increase the overall mass of the casing 10 and reduce the energy density of the cylindrical battery 100. In addition, it may also cause the thickness of the transition connection 14 and the side wall 13 to be too small, resulting in insufficient structural strength and making them more prone to cracking.

[0101] In this embodiment of the disclosure, by limiting the thickness of the first end wall 11 within a suitable range, the first end wall 11 is guaranteed to have sufficient structural strength to provide stable support for the battery cell 20 and sufficient support for the side wall 13, thereby improving the overall structural strength of the housing 10.

[0102] Preferably, the thickness b1mm of the first end wall 11 can satisfy: 0.5≤b1≤2.

[0103] In this embodiment, the thickness b1mm of the first end wall 11 is taken as 1mm for illustration. Of course, in other embodiments, the thickness b1mm of the first end wall 11 can also be set to 0.5mm, 0.8mm, 1.2mm, 1.5mm, 1.7mm, 2mm, etc.

[0104] Additionally, refer to Figure 5The minimum thickness b2mm of the transition connection 14 can satisfy: 0.3≤b2≤2. For example, the minimum thickness of the transition connection 14 can be set to values ​​such as 0.3mm, 0.6mm, 1mm, 1.3mm, 1.6mm, 1.9mm, and 2mm.

[0105] If the thickness of the transition connection 14 is too small, the structural strength of the transition connection 14 will be low, the connection stability between the first end wall 11 and the side wall 13 will decrease, and the risk of the transition connection 14 cracking will increase when the cylindrical battery 100 experiences thermal runaway, which will make the thermal runaway of the cylindrical battery 100 more likely to intensify or even cause an explosion.

[0106] If the thickness of the transition connection 14 is too large, it will be difficult to form a higher sidewall 13. The transition connection 14 is thinner than the first end wall 11, resulting in a large thickness deviation between the formed sidewall 13 and the end wall. That is, the thickness of the formed sidewall 13 is small, which increases the risk of deformation of the sidewall 13 and shortens the service life of the housing 10.

[0107] In this embodiment of the disclosure, by limiting the thickness of the transition connection portion 14 to a suitable range, the transition connection portion 14 is made easy to form and is not prone to cracking, while ensuring that the transition connection portion 14 has sufficiently high structural strength. The first end wall 11 and the side wall 13 are stably connected, and the transition connection portion 14 is not prone to cracking when the cylindrical battery 100 experiences thermal runaway.

[0108] Preferably, the minimum thickness b2mm of the transition connection portion 14 can satisfy: 0.5≤b2≤1.8.

[0109] In this embodiment, the minimum thickness b2mm of the transition connection portion 14 is taken as 1mm as an example for explanation. Of course, in other embodiments, the minimum thickness of the transition connection portion 14 can also be set to values ​​such as 0.5mm, 0.8mm, 1.2mm, 1.5mm, 1.8mm, etc.

[0110] For example, the ratio c of c1 and c2 can satisfy: 0.09 ≤ c ≤ 0.64. For instance, the value of c can be set to: 0.09, 0.12, 0.15, 0.2, 0.26, 0.33, 0.38, 0.43, 0.48, 0.53, 0.58, 0.64, etc.

[0111] With the end wall dimensions fixed, the area enclosed by the weak part 31 is kept within a suitable range. When the cylindrical battery 100 experiences thermal runaway, the first explosion-proof valve 30 can quickly and timely release pressure and vent air. At the same time, it avoids the weak part 31 having an excessively large stress area, which could lead to pressure release when the pressure inside the casing 10 is low. This reduces the risk of the first explosion-proof valve 30 being "falsely triggered," ensures the normal use of the cylindrical battery 100, and improves battery quality.

[0112] Preferably, c can satisfy: 0.15≤c≤0.6.

[0113] In this embodiment, the ratio c of c1 and c2 is 0.2 as an example. Of course, in other embodiments, the value of c can also be set to 0.15, 0.18, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, etc.

[0114] The area c1mm of the region enclosed by the weak part 31 is among them. 2 It can satisfy: 22.9 ≤ c1 ≤ 1808.6; for example, the area of ​​the region enclosed by the weak point 31 can be set to 22.9 mm. 2 50mm 2 100mm 2 200mm 2 300mm 2 400mm 2 500mm 2 600mm 2 700mm 2 800mm 2 900mm 2 1000mm 2 1100mm 2 1200mm 2 1300mm 2 1400mm 2 1500mm 2 1600mm 2 1700mm 2 1800mm 2 1808.6mm 2 Equivalent.

[0115] The area of ​​the end wall with the weak part 31 is c2mm. 2 It can satisfy: 254≤c2≤3017.5; for example, the area of ​​the end wall with the weak part 31 can be set to 254mm². 2 300mm 2 400mm 2500mm 2 600mm 2 700mm 2 800mm 2 900mm 2 1000mm 2 1200mm 2 1400mm 2 1600mm 2 1800mm 2 2000mm 2 2200mm 2 2400mm 2 2600mm 2 2800mm 2 3000mm 2 3017.5mm 2 Equivalent.

[0116] refer to Figure 2 and Figure 4 The second end wall 12 and the side wall 13 are separate structures. The first end wall 11 and the second end wall 12 are located at opposite ends of the side wall 13 along the first direction. The first end wall 11 and the side wall 13 are integrally formed, and the second end wall 12 and the side wall 13 are welded together.

[0117] refer to Figure 6 A weld bead 121 is formed around the second end wall 12 at the connection between the second end wall 12 and the side wall 13. The weld bead 121 has a penetration depth of h2mm, where 0.3≤h2≤2. For example, the penetration depth of the weld bead 121 can be set to values ​​such as 0.3mm, 0.6mm, 0.9mm, 1.1mm, 1.4mm, 1.7mm, and 2mm.

[0118] If the weld depth of the weld 121 is too small, it will reduce the connection strength between the second end wall 12 and the side wall 13, and damage the overall structural strength of the casing 10. When the cylindrical battery 100 experiences thermal runaway, under the pressure inside the casing 10, the second end wall 12 and the side wall 13 are prone to cracking at the connection or separation.

[0119] If the weld penetration of the weld 121 is too large, it will result in the weld 121 penetrating too far into the interior of the housing 10. To meet this condition, the thickness of the connection between the side wall 13 and the second end wall 12 needs to be further increased, which will reduce the energy density of the cylindrical battery 100. In addition, it will occupy the internal space of the housing 10, causing the gas channel inside the housing 10 to shrink, affecting the gas transmission efficiency when the cylindrical battery 100 experiences thermal runaway, and will also occupy the installation space of other components inside the housing 10.

[0120] In this embodiment of the present disclosure, by limiting the penetration depth of the weld bead 121 within a suitable range, the robustness of the connection between the second end wall 12 and the side wall 13 is improved, and the problem of the weld bead 121 occupying the installation space of other components in the housing 10 is reduced.

[0121] Preferably, h2 can satisfy: 0.5≤h2≤1.8.

[0122] In this embodiment, the penetration depth h2mm of the weld bead 121 is described as 1mm. Of course, in other embodiments, the penetration depth of the weld bead 121 can also be set to values ​​such as 0.5mm, 0.8mm, 1.2mm, 1.5mm, 1.8mm, etc.

[0123] Furthermore, the weld penetration h2mm of the weld portion 121 is greater than the minimum thickness b2mm of the transition connection portion 14. That is, the connection area between the second end wall 12 and the side wall 13 is greater than the connection area between the first end wall 11 and the side wall 13. When the second end wall 12 and the side wall 13 are welded as separate structures, by increasing the connection area between the two, the connection strength between the second end wall 12 and the side wall 13 is ensured to be sufficiently high, reducing the risk of cracks appearing at the connection position between the second end wall 12 and the side wall 13 during subsequent use of the cylindrical battery 100, and improving the structural strength of the casing 10.

[0124] refer to Figure 6 The weld penetration direction of the weld bead 121 is parallel to the plane containing the second end wall 12. For example, the end face of the side wall 13 facing the second end wall 12 is parallel to the plane containing the second end wall 12. The end face of the side wall 13 abuts against the second end wall 12 and is fixed by welding. The weld penetration direction of the weld bead 121 lies within the plane containing the end face of the side wall 13 facing the second end wall 12, i.e., the weld penetration direction of the weld bead 121 is parallel to the plane containing the second end wall 12.

[0125] It is easier to position and fix the second end wall 12 and the side wall 13 during welding, which helps to improve the firmness of the welding fixation of the second end wall 12 and the side wall 13 and reduces the risk of cracking at the welding fixation position of the second end wall 12 and the side wall 13.

[0126] refer to Figure 4 The first explosion-proof valve 30 is mounted on the second end wall 12. The distance between the first end wall 11 and the second end wall 12 is d1 mm, where d1 can satisfy: 55 ≤ d1 ≤ 220. For example, the distance between the first end wall 11 and the second end wall 12 can be set to values ​​such as 55 mm, 65 mm, 75 mm, 85 mm, 95 mm, 105 mm, 115 mm, 125 mm, 135 mm, 145 mm, 155 mm, 165 mm, 175 mm, 185 mm, 195 mm, 205 mm, 215 mm, and 220 mm.

[0127] It should be noted that the distance between the first end wall 11 and the second end wall 12 mentioned above refers to the distance between them in the first direction. In some cases, the first end wall 11 and the second end wall 12 may have protrusions, grooves, bends, or other structures, which makes the first end wall 11 and the second end wall 12 not regular flat structures. When determining the distance between them, the protrusions, grooves, bends, or other structures mentioned above should be avoided, and the measurement should be performed on the flat parts of the first end wall 11 and the second end wall 12.

[0128] For example, multiple measurement points are taken on the first end wall 11 and the second end wall 12 respectively. In this embodiment of the present disclosure, ten measurement points are taken as an example. The ten measurement points on the first end wall 11 and the ten measurement points on the second end wall 12 correspond one-to-one and are arranged along the first direction. The distance between each pair of corresponding measurement points is measured, and the average value of multiple sets of measurement point distances is taken as the distance between the first end wall 11 and the second end wall 12.

[0129] If the distance between the first end wall 11 and the second end wall 12 is too small, the length of the side wall 13 will be reduced. The side wall 13 is formed by stretching, and the reduced length of the side wall 13 will affect the uniformity of the thickness of the side wall 13 and reduce the strength of the side wall 13. In addition, it will cause the length of the electrode in the first direction to be reduced. Correspondingly, the winding length will be too large, which will prolong the electron transmission path and make the heat generation more serious.

[0130] If the distance between the first end wall 11 and the second end wall 12 is too large, the gas transmission path inside the housing 10 will be too long, and the gas at the first end wall 11 will not be able to be discharged through the first explosion-proof valve 30 in time, which will lead to cracking at the transition connection 14.

[0131] In this embodiment of the present disclosure, by limiting the distance between the first end wall 11 and the second end wall 12 to a suitable range, the efficiency of gas in the housing 10 being depressurized through the first explosion-proof valve 30 is improved. In addition, the heating degree of the cylindrical battery 100 is reduced, the structural strength of the housing 10 is improved, and the risk of the housing 10 cracking is reduced when the cylindrical battery 100 experiences thermal runaway.

[0132] Preferably, d1mm can satisfy: 60≤d1≤200.

[0133] In this embodiment, d1mm is set to 100mm as an example. Of course, in other embodiments, the distance between the first end wall 11 and the second end wall 12 can be set to values ​​such as 60mm, 70mm, 80mm, 90mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, and 200mm.

[0134] refer to Figure 10 and Figure 11 The first explosion-proof valve 30 is located on the first end wall 11, the transition connection 14 is located on the outer periphery of the first end wall 11, the first explosion-proof valve 30 and the weak part 31 are located on the inner side of the transition connection 14, and the weak part 31 and the transition connection 14 are spaced apart in the radial direction of the first end wall 11.

[0135] The first explosion-proof valve 30 is set on the first end wall 11. The first end wall 11 and the side wall 13 are integrally formed. Compared with the second end wall 12 and the side wall 13 being a separate structure that is fixedly connected, the connection strength of the first end wall 11 and the side wall 13 is higher, which can reduce the risk of the connection strength of the end wall and the side wall 13 being reduced due to the setting of the weak part 31.

[0136] refer to Figure 11 The distance between the weak portion 31 and the transition connection portion 14 in the radial direction of the first end wall 11 is d2mm, where d2 can satisfy: 2≤d2≤20. For example, the distance between the weak portion 31 and the transition connection portion 14 in the radial direction of the first end wall 11 can be set to values ​​such as 2mm, 3mm, 4mm, 5.5mm, 6.5mm, 7.5mm, 8.5mm, 9.5mm, 10.5mm, 11.5mm, 12.5mm, 13.5mm, 14.5mm, 15.5mm, 16.5mm, 17.5mm, 18.5mm, and 20mm.

[0137] For example, the distance between the weak portion 31 and the transition connection portion 14 in the radial direction of the first end wall 11 refers to the minimum distance between the weak portion 31 and the transition connection portion 14.

[0138] If the value of d2 is too small, that is, the two are too close, stress concentration will easily occur at the transition connection 14, and the transition connection 14 will be more prone to cracking.

[0139] If the value of d2 is too large, it will cause the size of the first explosion-proof valve 30 to be too small. When the cylindrical battery 100 experiences thermal runaway and needs to release pressure through the first explosion-proof valve 30, the small size of the first explosion-proof valve 30 will reduce its pressure release efficiency. In addition, it will also reduce the force-bearing area of ​​the first explosion-proof valve 30, thus increasing the threshold for the first explosion-proof valve 30 to open for pressure release. When the cylindrical battery 100 experiences thermal runaway and the first explosion-proof valve 30 opens for pressure release, the internal pressure of the casing 10 will be higher, and the gas ejection will generate a greater impact force, increasing the risk of the cylindrical battery 100 exploding.

[0140] In this embodiment of the disclosure, by limiting the distance between the weak part 31 and the transition connection part 14 to a suitable range, the first explosion-proof valve 30 is guaranteed to have a sufficiently high pressure relief rate, and the structural strength of the transition connection part 14 is guaranteed, thereby reducing the risk of cracking of the transition connection part 14.

[0141] Preferably, the minimum distance d2mm between the weak part 31 and the transition connection part 14 can satisfy: 5≤d2≤18.

[0142] In this embodiment, the minimum distance d2mm between the weak portion 31 and the transition connection portion 14 is 10mm as an example. Of course, in other embodiments, the value of the above distance d2 can also be set to 5mm, 6mm, 7mm, 8mm, 9mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, etc.

[0143] refer to Figure 11 A buffer protrusion 111 is provided on the first end wall 11. The buffer protrusion 111 protrudes from one side of the first end wall 11 and is located between the weak part 31 and the transition connection part 14. For example, the buffer protrusion 111 can be formed by stamping the first end wall 11. The edge of the formed buffer protrusion 111 will be thinned due to stretching. The strength of the thinned part is weakened. By spaced the buffer protrusions 111 between the weak part 31 and the transition connection part 14, the risk of stress concentration in the weak part 31 and the transition connection part 14 can be reduced.

[0144] Preferably, the buffer protrusion 111 protrudes towards the side where the battery cell 20 is located. This avoids the problem of the buffer protrusion 111 occupying the external space of the cylindrical battery 100. Especially when the first end wall 11 serves as the bottom wall of the cylindrical battery 100, the flatness of the bottom wall of the cylindrical battery 100 is better, which can improve the stability of the cylindrical battery 100 when it is fixed in the installation position.

[0145] Additionally, refer to Figure 6 The thickness of the weak portion 31 is t2 mm, and t2 can satisfy: 0.1 < b2 - t2 ≤ 1.96. Here, the thickness of the weak portion 31 refers to its dimension in the first direction. For example, the value of b2 - t2 can be set to 0.1 mm, 0.13 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 1.96 mm, etc.

[0146] For example, t2 satisfies: 0.04 < t2 ≤ 0.3. For instance, the thickness of the weak part 31 can be set to values ​​such as 0.04 mm, 0.06 mm, 0.08 mm, 0.1 mm, 0.12 mm, 0.14 mm, 0.16 mm, 0.18 mm, 0.2 mm, 0.22 mm, 0.24 mm, 0.26 mm, 0.28 mm, and 0.3 mm.

[0147] If the thickness of the weak part 31 is too large, it will require greater pressure to open the first explosion-proof valve 30 for venting and depressurization. When the cylindrical battery 100 experiences thermal runaway, the first explosion-proof valve 30 will not be able to respond in time to open and depressurize, which will more easily cause the casing 10 to crack or even the cylindrical battery 100 to explode.

[0148] If the thickness of the weak part 31 is too small, it will lead to low structural strength of the end wall and make it prone to cracking.

[0149] By limiting the value of b2-t2 to a suitable range, on the one hand, when the cylindrical battery 100 experiences thermal runaway, the first explosion-proof valve 30 can respond in time to open and release pressure, reducing the risk of aggravated thermal runaway; on the other hand, by appropriately increasing the thickness of the weak part 31, the occurrence of the first explosion-proof valve 30 being "falsely triggered" to open and release pressure when there is a small pressure inside the casing 10 is reduced.

[0150] In another embodiment, reference Figure 12 The cylindrical battery 100 also includes a second explosion-proof valve 40, which is disposed on the end wall away from the location of the first explosion-proof valve 30. For example, the first explosion-proof valve 30 is disposed on the second end wall 12, and the second explosion-proof valve 40 is disposed on the first end wall 11. In this case, the ratio of c1 to c2 can satisfy 0.1 ≤ c ≤ 0.4. For example, the value of c can be set to: 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, etc.

[0151] By setting a second explosion-proof valve 40, when the cylindrical battery 100 experiences thermal runaway, the first explosion-proof valve 30 and the second explosion-proof valve 40 are triggered to open and release pressure, resulting in higher pressure release efficiency and further reducing the risk of the casing 10 cracking.

[0152] Furthermore, with the second explosion-proof valve 40 installed, the range of c is further controlled to ensure that the first explosion-proof valve 30 has sufficient connection strength while being able to respond promptly to the increase in pressure inside the housing 10 and release pressure in a timely manner.

[0153] The weak point 31 can have many different specific forms, see reference. Figure 3 and Figure 6In one embodiment, the weak portion 31 is a groove formed on the end wall, and the groove is constructed as a continuous closed pattern on the end wall. Exemplarily, the groove is annular, surrounding and forming a circular first explosion-proof valve 30. In other embodiments, the groove may also be rectangular, pentagonal, or other polygonal structures.

[0154] By setting the weak part 31 as a continuous groove, as the internal pressure of the cylindrical battery 100 increases, the stress is more easily concentrated, the valve opening area is larger, and rapid pressure relief is achieved.

[0155] In another embodiment, reference Figure 13 Alternatively, the weak section 31 can be configured as multiple grooves formed on the end wall, with the grooves arranged circumferentially along the end wall to form a ring structure. In this case, the area c1 of the region enclosed by the weak section 31 refers to the area of ​​the region enclosed when the multiple intermittent grooves are completed to form a ring. Furthermore, the ends of adjacent grooves can be connected by straight line segments, so that the multiple intermittent grooves and the straight line segments form a continuous closed shape, where c1 is the area of ​​the formed continuous closed shape.

[0156] For further reference Figure 14 The weak part 31 is a groove formed on the end wall, which is constructed as a continuously extending, non-closed shape. The circumferential length of the groove along the end wall is L1 mm, and L1 can satisfy 20 ≤ L1 ≤ 200. Here, the length L1 of the groove refers to the circumferential length of the groove along the end wall, which can also be described as the dimension of the groove in its own extension direction. For example, the circumferential length of the groove along the end wall can be set to values ​​such as 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 120 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, and 200 mm.

[0157] For example, the groove is part of a ring, and the length L1 of the groove is the arc length of the arc segment corresponding to the groove.

[0158] If the length of the groove is too small, the connection between the first explosion-proof valve 30 and the end wall will be more secure, reducing the efficiency of opening in response to the pressure inside the housing 10 and increasing the risk of the housing 10 cracking.

[0159] If the groove is too long, it will cause too much ejection of material when the pressure is released through the first explosion-proof valve 30, which will increase the risk of thermal spread of the cylindrical battery 100.

[0160] In this embodiment of the disclosure, by limiting the length of the groove to a suitable range, the first explosion-proof valve 30 can respond in a timely manner to the pressure change inside the housing 10 and open to release pressure. At the same time, it limits the amount of ejected material when releasing pressure through the first explosion-proof valve 30, thereby mitigating the problem of increased risk of battery thermal spread due to excessive ejected material.

[0161] In this embodiment of the disclosure, reference is made to Figure 6 and Figure 7 Taking the weak part 31 as an example, which includes a groove provided on the end wall, the number of grooves can be set to one or more. The groove includes a first groove 311 located on the inner surface of the end wall facing the cell 20, and / or a second groove 312 located on the outer surface of the end wall facing away from the cell 20.

[0162] In some other embodiments, the weak part 31 can also be provided in the form of a through hole in the end wall, and then a first explosion-proof valve 30 structure, such as an explosion-proof sheet or explosion-proof membrane, can be provided at the through hole by welding, bonding or other means.

[0163] In this embodiment, the weak part 31 is set as a groove on the end wall, which makes it easier to control the pressure of the weak part 31 bursting. For example, by designing grooves of different thicknesses, the pressure required for the first explosion-proof valve 30 to burst and release pressure can be set as needed.

[0164] For example, refer to Figure 6 The dimensions of the groove shall satisfy one or more of the following limiting conditions, which include the following three conditions.

[0165] 1. The depth of the groove is h1mm, where h1 can satisfy: 0.03≤h1≤0.3. The depth of the groove refers to the dimension of the groove in the first direction. For example, the groove depth can be set to values ​​such as 0.03mm, 0.06mm, 0.09mm, 0.12mm, 0.15mm, 0.18mm, 0.21mm, 0.24mm, 0.27mm, and 0.3mm.

[0166] 2. The thickness of the end wall where the groove is located is t1mm, and h1 and t1 can satisfy: 0.012≤h1 / t1≤0.6. It should be further explained that t1 corresponds to different end wall thicknesses depending on the end wall where the first explosion-proof valve 30 is located; for example, if the first explosion-proof valve 30 is located on the first end wall 11, then the thickness t1 is the thickness of the first end wall 11; if the first explosion-proof valve 30 is located on the second end wall 12, then the thickness t1 is the thickness of the second end wall 12. This embodiment uses the example of the first explosion-proof valve 30 being located on the second end wall 12 for illustration. Exemplarily, the thickness t1mm of the end wall where the groove is located can be set to satisfy: 0.4≤h1≤3. For example, the thickness of the end wall where the groove is located can be set to values ​​such as 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.5mm, 2mm, 2.5mm, and 3mm.

[0167] 3. The width of the groove is w1mm, where w1 can satisfy: 0.5≤w1≤2.5. The width of the groove is the dimension of the groove in the direction perpendicular to its own extension direction. For example, when the groove has an arc-shaped structure, the width of the groove refers to the radial dimension of the groove on the end wall. For example, the width of the groove can be set to values ​​such as 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.5mm, 2mm, and 2.5mm.

[0168] If the size of the groove is too small, greater pressure is required to open the first explosion-proof valve 30. When the cylindrical battery 100 experiences thermal runaway or other problems that increase the pressure inside the casing 10, the first explosion-proof valve 30 has low opening efficiency and cannot respond to pressure changes in time to release pressure.

[0169] If the groove is too large, the structural strength of the end wall will be too low, making it prone to cracking.

[0170] By limiting the size of the groove to a suitable range, on the one hand, it ensures that when the cylindrical battery 100 experiences thermal runaway, the gas inside the casing 10 can be discharged in time through the first explosion-proof valve 30, reducing the risk of aggravated thermal runaway; on the other hand, it reduces the problem of insufficient end wall structural strength caused by excessively large groove size.

[0171] It should be noted that in this embodiment, the number of grooves provided on the end wall may be one or more. For example, two grooves may be provided: a first groove 311 on the surface of the end wall facing the battery cell 20 and a second groove 312 on the surface facing away from the battery cell 20. When the number of grooves is one, the depth of the groove refers to the depth of a single groove. When the number of grooves is two, the depth of the groove is the sum of the depths of the two grooves. It should also be understood that the aforementioned number of grooves being two refers to two grooves on two opposing surfaces of the end wall. Multiple grooves on the same surface of the end wall, when determining the depth of the groove, refer to the depth of a single groove.

[0172] When measuring the depth of a groove, multiple (e.g., 5 or 10) measurement points can be selected within the groove. The depth of the groove at these multiple measurement points is measured, and the average value is calculated as the depth of the groove.

[0173] Preferably, the depth h1mm of the groove can satisfy: 0.05≤h1≤0.25.

[0174] In this embodiment, the groove depth h1mm is 0.1mm as an example for illustration. Of course, in other embodiments, the value of the above-mentioned depth h1mm can also be set to 0.05mm, 0.08mm, 0.12mm, 0.15mm, 0.17mm, 0.2mm, 0.22mm, 0.25mm, etc.

[0175] Preferably, h1 and t1 can satisfy: 0.02≤h1 / t1≤0.5.

[0176] In this embodiment, the ratio of h1 to t1 is 0.1 as an example. Of course, in other embodiments, the ratio of h1 to t1 can also be set to 0.02, 0.05, 0.08, 0.12, 0.15, 0.18, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0177] Preferably, the width w1mm of the groove can satisfy: 0.7≤w1≤2.2.

[0178] In this embodiment, the width w1mm of the groove is 1mm as an example for illustration. Of course, in other embodiments, the width w1mm of the groove can also be set to 0.7mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2mm, 2.2mm, etc.

[0179] For example, the cross-sectional shape of the groove can be set to various different shapes according to actual needs, see reference. Figure 8The four schematic diagrams α, β, γ, and δ illustrate different shapes that the groove can be set into. Of course, in other embodiments, the cross-sectional shape of the groove can also be set to any other possible shape. Furthermore, when two grooves are set, that is, when a first groove 311 and a second groove 312 are set simultaneously, the first groove 311 and the second groove 312 can be set to have the same shape, or the first groove 311 and the second groove 312 can be set to have different shapes.

[0180] refer to Figure 9 A third groove 313 is also provided on the end wall. The third groove 313 has a bottom wall and a side wall. The first groove 311 and / or the second groove 312 are provided on the bottom wall of the third groove 313. The third groove 313 provides a buffer, ensuring the structural strength of the weak part 31, and reducing the risk that the first explosion-proof valve 30 will be accidentally triggered when the pressure inside the cylindrical battery 100 does not reach the trigger value.

[0181] refer to Figure 12 One of the end walls is provided with a pole post 15, which is electrically connected to one of the tabs of the battery cell 20. Exemplarily, a weak portion 31 and the pole post 15 are disposed on the same end wall, with the weak portion 31 surrounding the outer periphery of the pole post 15. Exemplarily, both the weak portion 31 and the pole post 15 are located on the second end wall 12.

[0182] The pole post 15 and the end wall are separate structures. The end wall has a mounting hole for installing the pole post 15, which passes through the mounting hole. The end of the pole post 15 located outside the housing 10 has a shoulder that abuts against the side of the end wall facing outwards from the housing 10, achieving axial positioning of the pole post 15 and the end wall. Additionally, the end of the pole post 15 inserted into the end wall facing inwards from the housing 10 has a flange that abuts against the side of the end wall facing inwards from the housing 10, cooperating with the shoulder to securely connect the pole post 15 and the end wall. Furthermore, a sealing element and an insulating element are provided between the pole post 15 and the end wall to achieve insulation between the pole post 15 and the end wall, and to seal any gaps between them.

[0183] During the charging and discharging process of the cylindrical battery 100, the heat generation at the terminal 15 position is more concentrated. In this disclosure, the terminal 15 and the first explosion-proof valve 30 are set on the same end wall. When the heat generated by the terminal 15 causes the pressure inside the casing 10 to rise, it can act on the first explosion-proof valve 30 more quickly, so that the first explosion-proof valve 30 responds to the pressure change inside the casing 10 more promptly. When the cylindrical battery 100 experiences thermal runaway, the first explosion-proof valve 30 releases pressure more promptly.

[0184] For example, the minimum distance between the weak part 31 and the pole post 15 is d3mm, where d3 can satisfy: 2≤d3≤15. For instance, the minimum distance between the weak part 31 and the pole post 15 can be set to values ​​such as 2mm, 3.5mm, 4.5mm, 5.5mm, 6.5mm, 7.5mm, 8.5mm, 9.5mm, 10.5mm, 11.5mm, 12.5mm, 13.5mm, 14.5mm, and 15mm.

[0185] If the distance between the weak part 31 and the terminal post 15 is too small, the first explosion-proof valve 30 may open abnormally. When the cylindrical battery 100 is working normally, the first explosion-proof valve 30 opens to release gas and pressure, causing the electrolyte of the cylindrical battery 100 to flow out and making it unusable.

[0186] If the distance between the weak part 31 and the terminal post 15 is too large, the first explosion-proof valve 30 may not open in time when the battery experiences thermal runaway, and the pressure may not be released in time, which may increase the risk of the casing 10 cracking or even cause the battery to explode.

[0187] In this embodiment, the minimum distance between the weak part 31 and the terminal post 15 is set within a suitable range. When the cylindrical battery 100 experiences thermal runaway, the first explosion-proof valve 30 can open in time to relieve pressure. In addition, it reduces the phenomenon that the heat generated by the terminal post 15 during the normal operation of the cylindrical battery 100 causes the first explosion-proof valve 30 to open, thus preventing the cylindrical battery 100 from being used normally.

[0188] Preferably, the minimum distance d3mm between the weak part 31 and the pole post 15 can satisfy: 3≤d3≤12.

[0189] In this embodiment, the minimum distance d3mm between the weak part 31 and the pole post 15 is 5mm as an example. Of course, in other embodiments, the above-mentioned d3mm can also be set to 3mm, 4mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, etc.

[0190] refer to Figure 5 and Figure 6 The cylindrical battery 100 structure can satisfy the following conditions: b1 > t3; and / or b1 > t4; and / or t3 > b2; wherein the thickness of the first end wall 11 is b1 mm, the thickness of the side wall 13 is t3 mm, and the thickness of the second end wall 12 is t4 mm.

[0191] For example, the thickness t3mm of the sidewall 13 can satisfy 0.2≤t3≤1, and the thickness t4mm of the second endwall 12 can satisfy 0.5≤t3≤3. For instance, the thickness of the sidewall 13 can be set to values ​​such as 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, and 1mm; and the thickness of the second endwall 12 can be set to values ​​such as 0.5mm, 0.8mm, 1.1mm, 1.4mm, 1.7mm, 2mm, 2.3mm, 2.6mm, and 3mm.

[0192] By implementing the above limitations, the connection between the first end wall 11 and the side wall 13 is strengthened, and the risk of cracking at the transition connection 14 is reduced.

[0193] refer to Figure 4 and Figure 5 The transition connection 14 has a rounded corner structure with a radius of r1mm, where r1 can satisfy: 0.4≤r1≤2.5. For example, the radius of the rounded corner structure can be set to values ​​such as 0.4mm, 0.6mm, 0.9mm, 1.3mm, 1.5mm, 1.7mm, 1.9mm, 2.1mm, 2.3mm, and 2.5mm.

[0194] If the radius is too small, stress concentration may easily occur at the transition connection 14, making cracking more likely at the transition connection 14.

[0195] If the radius is too large, the transition connection 14 may squeeze the end of the cell 20. This squeezing of the cell 20 end can cause the cell 20 to lose material, resulting in a decrease in the energy density of the cell 20.

[0196] In this embodiment of the disclosure, by limiting the radius of the above-mentioned rounded corner structure to a suitable range, the problem of stress concentration at the transition connection 14 is reduced, the risk of cracking of the transition connection 14 is reduced, and the problem of the transition connection 14 occupying too much internal space of the housing 10 and causing compression to the battery cell 20 is reduced.

[0197] Preferably, the radius r1mm of the above-mentioned rounded corner structure can satisfy: 0.5≤r1≤2.2.

[0198] In this embodiment, the radius of the rounded corner structure of the transition connection portion 14 is 1 mm as an example. Of course, in other embodiments, the radius of the rounded corner structure of the transition connection portion 14 can also be set to 0.5 mm, 0.7 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2 mm, 2.2 mm, etc.

[0199] It should be noted that the radius of the aforementioned rounded corner structure refers to the radius of the outer surface of the transition connection portion 14. The radius corresponding to the surface of the transition connection portion 14 facing the interior of the housing 10 is r2mm, where 0.2≤r2≤1. For example, the radius corresponding to the surface of the transition connection portion 14 facing the interior of the housing 10 can be set to values ​​such as 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, and 1mm.

[0200] refer to Figure 12 The battery cell 20 is located inside the housing 10. The minimum distance between the battery cell 20 and the first end wall 11 is d4mm, where d4 can satisfy: 0.5≤d4≤5. For example, the minimum distance between the battery cell 20 and the first end wall 11 can be set to values ​​such as 0.5mm, 0.7mm, 1.2mm, 1.5mm, 1.8mm, 2.2mm, 2.6mm, 2.9mm, 3.2mm, 3.5mm, 3.8mm, 4.2mm, 4.7mm, and 5mm.

[0201] It should be noted that the minimum distance between the battery cell 20 and the first end wall 11 referred to in this embodiment refers to the minimum distance between the battery cell body 21 and the first end wall 11. When measuring the minimum distance, multiple (e.g., 5 or 10) measurement points can be selected at the end of the battery cell body 21 facing the first end wall 11, and the minimum distance between the multiple measurement points and the first end wall 11 can be measured respectively. The average value is taken as the minimum distance between the battery cell body 21 (battery cell 20) and the first end wall 11.

[0202] If the distance between the cell 20 and the first end wall 11 is too small, accidental contact may occur, leading to insulation failure between the cell 20 and the casing 10 (first end wall 11), causing the cylindrical battery 100 to short-circuit and become unusable.

[0203] If the distance between the battery cell 20 and the first end wall 11 is too large, gas will be more likely to accumulate in the space between the battery cell 20 and the first end wall 11, which will cause the transition connection 14 to be subjected to more concentrated stress, increasing the risk of cracking of the transition connection 14.

[0204] In this embodiment of the present disclosure, the distance between the battery cell 20 and the first end wall 11 is limited to a suitable range, thereby improving the stability of the insulation between the battery cell 20 and the first end wall 11, reducing the phenomenon of gas accumulation at one end of the first end wall 11, and reducing the risk of cracking of the transition connection 14.

[0205] Preferably, the minimum distance d4mm between the battery cell 20 and the first end wall 11 can satisfy: 0.7≤d4≤4.5.

[0206] In this set of embodiments, the minimum distance d4mm between the battery cell 20 and the first end wall 11 is described as 1mm as an example. In other embodiments, the value of d4 can also be set to 0.7mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, etc.

[0207] For example, the minimum distance between the battery cell 20 and the second end wall 12 is d5mm, and d4 and d5 can satisfy: d4 < d5. It should be noted that the minimum distance between the battery cell 20 and the second end wall 12 referred to in this embodiment refers to the minimum distance between the battery cell body 21 and the second end wall 12. When measuring the above minimum distance, multiple (such as 5 or 10) measurement points can be selected at the end of the battery cell body 21 facing the second end wall 12, and the minimum distance between the above multiple measurement points and the second end wall 12 can be measured respectively. The average value is taken as the minimum distance between the battery cell body 21 (battery cell 20) and the second end wall 12.

[0208] The transition connection 14 is located at the end where the first end wall 11 is located. By reducing the distance between the battery cell 20 and the first end wall 11, the stress concentration phenomenon at the transition connection 14 is reduced, and the risk of cracking of the transition connection 14 is reduced.

[0209] Additionally, refer to Figure 10 and Figure 15 The battery cell 20 has a wound structure, and a core hole 201 is formed at the axis of the battery cell 20. The orthographic projection of the core hole 201 on the end wall overlaps at least partially with the first explosion-proof valve 30.

[0210] With this configuration, when the cylindrical battery 100 experiences thermal runaway, the core hole 201 serves as a rapid gas channel, ensuring that the gas generated inside the casing 10 can be quickly transmitted to the location of the first explosion-proof valve 30 through the core hole 201, so that the first explosion-proof valve 30 can promptly release gas and pressure, resulting in higher pressure relief efficiency when the cylindrical battery 100 experiences thermal runaway.

[0211] For example, refer to Figure 15 The cross-sectional area of ​​the core hole 201 is s1mm. 2 The area c2 of the end wall and s1 can satisfy: 0.01≤s1 / c2≤0.31. For example, the value of s1 / c2 can be set to 0.01, 0.02, 0.05, 0.08, 0.12, 0.15, 0.19, 0.22, 0.25, 0.28, 0.31, etc.

[0212] It should be noted that the above-mentioned end wall refers to either of the two end walls. For ease of explanation, this embodiment of the disclosure uses the example of two end walls having the same size.

[0213] If the size of the core hole 201 is too small, the size of the gas transmission path in the cylindrical battery 100 will be reduced, which will reduce the gas transmission rate. That is, in the event of thermal runaway of the cylindrical battery 100, the time required for the gas generated in the casing 10 to be transmitted to the first explosion-proof valve 30 will be longer, making it difficult to achieve rapid and timely depressurization.

[0214] If the size of the core hole 201 is too large, it will result in a lot of space inside the cylindrical battery 100 not being effectively utilized, leading to a decrease in the energy density of the cylindrical battery 100.

[0215] In this embodiment of the disclosure, by limiting the value of s1 / c2 to a suitable range, the size of the core hole 201 is kept within a suitable range. This improves the transmission rate of gas inside the housing 10 to the first explosion-proof valve 30, avoids the problem of reduced energy density of the cylindrical battery 100, and improves battery quality.

[0216] Preferably, s1 and c2 can satisfy: 0.02≤s1 / c2≤0.25.

[0217] In this embodiment, the value of s1 / c2 is 0.05 as an example. Of course, in other embodiments, the value of s1 / c2 can also be set to 0.02, 0.04, 0.07, 0.1, 0.14, 0.17, 0.2, 0.22, 0.25, etc.

[0218] Additionally, refer to Figure 15 The diameter D1 of the battery cell 20 satisfies: D1≥40mm. For example, the diameter of the battery cell 20 can be set to 40mm, 50mm, 60mm, 70mm, 80mm, etc.

[0219] If the diameter of the battery cell 20 is too small, the size of the winding hole 201 will be relatively large compared to the overall size of the battery cell 20. This means that the proportion of the electrode in the battery cell 20 will be reduced, and most of the battery cell 20 will consist of the winding hole 201, resulting in a lower energy density. By limiting the diameter of the battery cell 20 to no less than 40mm, the proportion of the winding hole 201 in the battery cell 20 will be reduced, thereby increasing the energy density of the battery cell 20.

[0220] At this point, a, b, and c satisfy: 1 ​​≤ (a × b) / c ≤ 120. For example, the value of (a × b) / c can be set to 1, 5, 15, 25, 35, 45, 55, 65, 75, 85, 95, 105, 115, 120, etc.

[0221] As the diameter of the battery cell 20 increases, the amount of deformation in the radial dimension also increases when the battery cell 20 expands and deforms. When the diameter of the battery cell 20 is not less than 40mm, by further controlling the range of values ​​of (a×b) / c, the problem of end wall flying out can be avoided, ensuring that the side wall 13 has sufficient structural strength and reducing the risk of deformation and cracking of the shell 10.

[0222] refer to Figure 12 A current collector 16 is provided between the end wall and the core hole 201. The battery cell 20 includes a tab extending towards the end wall. One end of the current collector 16 is electrically connected to the tab, and the other end is electrically connected to the output terminal of the cylindrical battery 100, wherein the output terminal of the cylindrical battery 100 is located on the end wall. An exposed area 161 is provided on the current collector 16, and the exposed area 161 at least partially exposes the core hole 201.

[0223] The current collector 16 has one end for electrical connection to the output terminal (tab) of the battery cell 20, and the other end for electrical connection to the output terminal (post) of the cylindrical battery 100, so that the output terminal of the battery cell 20 and the output terminal of the cylindrical battery 100 are connected by current. The current collector 16 is made of at least one of the following conductive metals: copper, aluminum, aluminum alloy, or steel. Preferably, the material of the current collector 16 is the same as the material of the output terminal of the battery cell 20.

[0224] The output terminal of the cylindrical battery 100 can refer to the end wall of the housing 10, such as the first end wall 11 or the second end wall 12; in addition, the output terminal of the cylindrical battery 100 can also refer to the terminal post 15. The terminal post 15 and the end wall of the housing 10 are separate structures and are fixedly connected.

[0225] When the cylindrical battery 100 experiences thermal runaway, the pressure inside the casing 10 increases until it triggers the opening of the first explosion-proof valve 30 to release pressure. The first explosion-proof valve 30 is located on the end wall of the cylindrical battery 100. During the gradual increase in pressure, the winding hole 201 serves as a crucial channel for gas to travel from the casing 10 to the first explosion-proof valve 30. By providing an exposed area 161 on the collector plate 16, and at least partially exposing the winding hole 201, the problem of gas inside the cell 20 not being able to escape in time, leading to excessive pressure inside the casing 10 when the first explosion-proof valve 30 is triggered, thus preventing severe thermal runaway of the cylindrical battery 100, can be avoided. This allows the first explosion-proof valve 30 to respond more promptly to pressure changes within the casing 10, preventing excessively severe thermal runaway of the cylindrical battery 100.

[0226] Furthermore, in the orthographic projection on the end wall, the radial distance between the center of the core hole 201 and the center of the area enclosed by the weak portion 31 on the end wall is d6mm, where 0≤d6≤5. For example, the value of d6mm can be set to 0mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, etc.

[0227] For example, in the embodiment of this disclosure, in the orthographic projection on the end wall, the center of the core hole 201 and the center of the area enclosed by the weak portion 31 coincide, that is, the value of d6 is 0.

[0228] With the above settings, the first explosion-proof valve 30 is located at the center of the end wall or near the center. When the cylindrical battery 100 experiences thermal runaway, causing the internal pressure of the housing 10 to increase, the pressure acts on the end wall, causing the weak part 31 to crack and release pressure. This allows the center of the end wall to reliably deform, and the high-pressure gas to be evenly distributed within the range of the first explosion-proof valve 30. When the pressure inside the housing 10 meets the preset value and triggers the first explosion-proof valve 30, the weak part 31 can be rapidly opened, resulting in a better pressure relief effect.

[0229] For example, refer to Figure 12 The first explosion-proof valve 30 is located on the second end wall 12. The first tab 22 is led out from the end of the cell body 21 facing the first end wall 11, and the second tab 23 is led out from the end of the cell body 21 facing the second end wall 12. The thermal conductivity of the first tab 22 is greater than that of the second tab 23.

[0230] During the operation of the cell 20, the heat generated at the positions of the first tab 22 and the second tab 23 is greater than the heat generated in the electrode area of ​​the cell 20. By setting the first tab 22 and the second tab 23 to be distributed at opposite ends of the cell 20, the area with the greatest heat generation is distributed at both ends of the cylindrical battery 100, which alleviates the problem of concentrated heat generation in the cylindrical battery 100 and improves the safety of the cylindrical battery 100.

[0231] Taking the first tab 22 as the negative tab as an example, its material is generally copper, and the second tab 23 as the positive tab, its material is generally aluminum. Copper has a higher thermal conductivity than aluminum.

[0232] In other embodiments, the shape of the tabs can be differentiated. When the materials are the same, the first tab 22 and the second tab 23 can be configured to satisfy one or more of the following limiting conditions: the thickness of the first tab 22 is greater than the thickness of the second tab 23, the cross-sectional area of ​​the first tab 22 is greater than the cross-sectional area of ​​the second tab 23, the length of the first tab 22 is less than the length of the second tab 23, etc.

[0233] For example, the thermal conductivity rate of the first tab 22 and the second tab 23 can be tested using the following method: High-precision thermocouples (T-type or K-type) are placed at the root of the tab (the end closest to the cell body) and the end of the tab (the section furthest from the cell body). The temperature change values ​​at these two locations are measured during the charging and discharging process of the battery. The magnitudes of the temperature change values ​​at the two tabs are compared. A larger temperature change value indicates a slower thermal conductivity rate (heat accumulates at the root); a smaller temperature change value indicates a faster thermal conductivity rate (heat is quickly conducted away). Of course, in other embodiments, other testing methods well known to those skilled in the art can also be used.

[0234] The first tab 22 is located at the end of the housing 10 away from the first explosion-proof valve 30. The first tab 22 has a higher thermal conductivity, which can reduce the phenomenon of heat concentration at the end of the housing 10 away from the first explosion-proof valve 30. The heat dissipation rate of the first tab 22 corresponding to the first end wall 11 is faster, which reduces the risk of heat concentration at the first end wall 11. The transition connection 14 is less likely to crack.

[0235] In another embodiment, reference Figure 4 Alternatively, the first tab 22 and the second tab 23 can be located on the same side of the cell body 21, such as the first tab 22 being the negative tab and the second tab 23 being the positive tab. The cell body 21 includes a positive electrode plate, and the active material of the positive electrode plate includes lithium iron phosphate. The first tab 22 and the second tab 23 are led out from the same end of the cell body 21 and face the second end wall 12. The first explosion-proof valve 30 is located on the second end wall 12.

[0236] The active material of the positive electrode includes lithium iron phosphate. This type of battery produces less gas during use. By placing both the first tab 22 and the second tab 23 on the same side as the first explosion-proof valve 30, the generated gas can be discharged to the outside of the casing 10 more quickly through the first explosion-proof valve 30, achieving rapid pressure relief. The pressure relief effect of the first explosion-proof valve 30 is better.

[0237] In other embodiments, reference is made to... Figure 10 Alternatively, the first tab 22 and the second tab 23 can be located on the same side of the cell body 21; the cell body 21 includes a positive electrode plate, and the active material of the positive electrode plate includes a lithium ternary material. The first tab 22 and the second tab 23 are led out from the same end of the cell body 21 and face the second end wall 12. The first explosion-proof valve 30 is located on the first end wall 11.

[0238] Lithium ternary materials include nickel-cobalt-manganese ternary materials and / or nickel-cobalt-aluminum ternary materials, wherein the nickel-cobalt-manganese ternary materials satisfy the general chemical formula LiNi. x Co y Mn z M fO2, wherein 0.1 < x < 1, 0.1 < y < 1, 0.1 < z < 1, 0.1 < f < 1, and x + y + z + f = 1, and M is a dopant element, which includes at least one of Al, Mg, Ti, Zr, B, P, Nb, Ta, W, Zr, and V.

[0239] The active material of the positive electrode includes lithium ternary material. This type of battery produces gas violently. The first tab 22 and the second tab 23 are located at the end away from the first end wall 11 and the transition connection 14. The first explosion-proof valve 30 and the transition connection 14 are both located at the end where the first end wall 11 is located.

[0240] In this way, when a large amount of gas is generated during the use of the cylindrical battery 100, the gas is transmitted to one end of the first end wall 11 and can be discharged in time through the first explosion-proof valve 30. This reduces the problem of untimely pressure relief due to poor venting at the transition connection 14, cracking at the transition connection 14, or even separation of the first end wall 11 and the side wall 13, thus reducing the risk of danger.

[0241] <Example Battery Pack> refer to Figure 16 This disclosure also provides a battery pack 200, which includes a housing 50, a fixing member 60, and a cylindrical battery 100 as described above. The housing 50 includes a top plate 51, a bottom plate 52, and a side beam 53 extending between the two. The top plate 51, the bottom plate 52, and the side beam 53 enclose an internal space for accommodating the cylindrical battery 100.

[0242] The fastener 60 is disposed within the internal space of the enclosure to secure the cylindrical battery 100 to the base plate 52. The first explosion-proof valve 30 on the cylindrical battery 100 faces the base plate 52. Thus, in the event of thermal runaway of the cylindrical battery 100, the material ejected from the cylindrical battery 100 can be prevented from spraying into the internal space of the enclosure or into structures such as circuit boards within the battery pack 200, thereby reducing damage to the battery pack 200.

[0243] Of course, in other embodiments, the first explosion-proof valve 30 may also be located on the cylindrical battery 100 at the end opposite to the base plate 52.

[0244] For example, the fastener 60 at least partially covers the transition connection portion 14 on the cylindrical battery 100. By fixing the cylindrical battery 100 and the housing 50 with the fastener 60, the risk of the cylindrical battery 100 shaking or shifting within the housing 50 is reduced. In addition, by providing the fastener to at least partially cover the transition connection portion 14, the fastener 60 can support the transition connection portion 14. When the pressure inside the housing 10 increases, the fastener 60 supports the transition connection portion 14, which can offset part of the pressure force and reduce the risk of the transition connection portion 14 cracking.

[0245] For example, in this embodiment of the disclosure, the fastener 60 is made of an adhesive, which includes at least one of polyurethane adhesive, epoxy resin adhesive, silicone adhesive, acrylic adhesive, etc. The adhesive fills the box 50 and its height is higher than the height of the transition connection 14, that is, the fastener 60 covers the transition connection 14, which has a better effect of reducing the risk of cracking of the transition connection 14.

[0246] In other embodiments, the fastener 60 may also be a bracket, plate or other structure fixed in the housing 50.

[0247] The battery pack 200 also includes a battery management system 70 housed inside the housing 50. In addition, the battery pack 200 may also include a thermal management system, an electrical connection system (high-voltage / low-voltage connectors, wiring harnesses, etc.), and protective components, which are also housed in the housing 50, working together with other parts to form a complete functional unit that can directly output electrical energy.

[0248] The battery pack may comprise multiple cylindrical batteries 100 with comparable capacity and internal resistance connected together. For example, the multiple cylindrical batteries 100 may be connected in series to form the battery pack, or they may be connected in parallel to form the battery pack, or some of the cylindrical batteries 100 may be connected in series and others in parallel to form the battery pack. For example, the battery pack 200 may also include conductive elements (not shown). These conductive elements may electrically connect the terminals of at least two cylindrical batteries 100, i.e., the current output terminals of the cylindrical batteries 100, to enable the series or parallel connection of the multiple cylindrical batteries 100. The battery pack 200 may also include a busbar, through which the battery management system 70 can be electrically connected to the battery pack to monitor and regulate the charging and discharging process of the battery pack.

[0249] <Example Electrical Equipment> This disclosure also provides an electrical device that may include the battery or battery pack described above.

[0250] By way of example only, the electrical equipment in the embodiments of this disclosure can be, but is not limited to, vehicles, ships, aircraft, household appliances, or industrial equipment. Vehicles referred to herein can be, but are not limited to, passenger cars, trucks, and construction vehicles. Furthermore, the electrical equipment in the embodiments of this disclosure can also be an energy storage system for storing, converting, and releasing recyclable electrical energy.

[0251] According to a non-limiting embodiment of the present disclosure, an electrical appliance 1000 is... Figure 17 As shown in the image. (Reference) Figure 17The electrical equipment 1000 can be an electric vehicle, which may include the aforementioned battery pack 200. In the electric vehicle, the battery pack 200 can be used as a power source to provide power to the electric vehicle.

[0252] <Examples and Comparative Examples> The following specific embodiments and comparative examples are provided to illustrate how the cylindrical battery 100 provided in this disclosure helps reduce the risk of cracking of the casing 10.

[0253] The measurement method of 'a'.

[0254] The diameter of the cylindrical battery 100 was measured with a vernier caliper. The average value of the three measurements was recorded as a2mm. The distance from the first end face to the second end face was also measured with three measurements and the average value was recorded as a1mm. The value of a was calculated using the formula a=a1 / a2.

[0255] The measurement method for b.

[0256] Cut the transition connection 14 between the first end wall 11 and the side wall 13 along the radial direction of the first end wall 11 of the cylindrical battery 100, and polish the cut transition connection 14 to remove burrs. Measure the minimum thickness of the transition connection 14 using an image measuring instrument, take 5 measurements and take the average value, which is recorded as b2mm. Measure the thickness of the first end wall 11 using a micrometer and record it as b1mm (if the first end wall 11 has a uniform thickness, measure at any position, take 5 measurements and take the average value; if the thickness of the first end wall 11 is inconsistent, measure the thickness of the first end wall 11 in the radial direction within 5mm of the transition connection 14, take 5 measurements and take the average value). Calculate the value of b using the formula b=b1-b2.

[0257] Adjustment method for b.

[0258] The value of b can be adjusted by adjusting the radius of the rounded corner structure at the transition connection 14 (the radius of the rounded corner structure ranges from 0.4 to 2.5 mm). The larger the radius of the rounded corner structure, the smaller the thickness of the transition connection 14 and the larger the value of b. The smaller the radius of the rounded corner structure, the larger the thickness of the transition connection 14 and the smaller the value of b. Alternatively, the value of b can be adjusted by adjusting the stretching rate during stretching (stretching rate 40 to 60 mm / min). The smaller the stretching rate, the smaller the thickness of the transition connection 14 and the larger the value of b. The larger the stretching rate, the larger the thickness of the transition connection 14 and the smaller the value of b.

[0259] The measurement method for c.

[0260] The diameter of the end wall where the first explosion-proof valve 30 is located in the cylindrical battery is measured using vernier calipers and denoted as D3mm. The area of ​​the end wall where the first explosion-proof valve 30 is located is c2=π×(D3 / 2). 2The size of the area enclosed by the weak part 31 of the first explosion-proof valve 30 in the cylindrical battery is measured using a vernier caliper. If the enclosed area is circular, the diameter of the area enclosed by the weak part 31 is measured using a vernier caliper and recorded as D4mm. The area of ​​the area enclosed by the weak part 31 is c1=π×(D4 / 2). 2 If the enclosed area is square, measure its length L3mm and width L4mm using vernier calipers. The area c1 of the enclosed area is then calculated as c1 = L3 × L4. If the enclosed area is an irregular shape, measure the area c1mm of the weakest part 31 using an electronic planimeter. 2 The value of c is calculated using the formula c = c1 / c2.

[0261] Method for preparing cylindrical battery 100.

[0262] (1) Preparation of the positive electrode: The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., PVDF) are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector foil, dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheet is then obtained by rolling and slitting.

[0263] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98): (4~1): (4~1).

[0264] (2) Preparation of negative electrode: The negative electrode active material, conductive agent (e.g., acetylene black), thickener (e.g., carboxymethyl cellulose (CMC)), and binder (e.g., styrene-butadiene rubber (SBR)) are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, the negative electrode sheet is obtained by rolling and slitting.

[0265] Specifically, the mass ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0266] (3) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0267] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0268] (5) Preparation of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a battery cell; the battery cell is then placed in the casing of a cylindrical battery. The battery is dried, injected with electrolyte, and then packaged, allowed to stand, formed, and volume-adjusted to obtain a lithium-ion battery.

[0269] In the selection of materials for the aforementioned battery, this application may also select other materials, not limited to those limited by the above preparation method. The positive electrode active material may be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate. The conductive agent in the positive electrode sheet may also be selected from one or more of graphite, superconducting carbon, Ketjen black, Super P, carbon nanotubes, graphene, and carbon nanofibers. The binder in the positive electrode sheet may also be selected from one or more of polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, and carboxymethyl chitosan. The positive electrode current collector may also be selected from one or more of stainless steel with surface silver plating, stainless steel, aluminum, nickel, carbon electrode, carbon, nickel, and titanium. The positive electrode current collector may also include a composite current collector, which may include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming metallic materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer substrates (such as polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.).

[0270] The negative electrode active material can be selected from one or more of the following main negative electrode materials: artificial graphite, natural graphite, silicon carbide, silicon oxide, lithium titanate, etc.; the conductive agent in the negative electrode sheet can be selected from one or more of the following: conductive carbon black, conductive graphite, carbon nanotubes, graphene, carbon fiber, etc.; the binder in the negative electrode sheet can be selected from one or more of the following: styrene-butadiene rubber, polyacrylic acid and its salts, sodium alginate, etc.; the thickener in the negative electrode sheet can be selected from one or more of the following: sodium carboxymethyl cellulose, polyacrylonitrile multi-component copolymer, etc.; the negative electrode current collector can also be selected from one or more of the following: stainless steel with silver plating, stainless steel, copper, nickel, carbon electrode, carbon, nickel, titanium, etc.; the negative electrode current collector can also include composite current collectors, which can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.). The negative electrode active layer includes the negative electrode active material, conductive components, adhesives, etc.

[0271] The diaphragm may also include at least one of glass fiber, nonwoven fabric, polypropylene (PP) and polyvinylidene fluoride.

[0272] Performance Test 1: Cracking Test at Transition Connection.

[0273] Following the battery fabrication method described above, 200 cylindrical batteries 100 were prepared for each of the embodiments and comparative examples. The values ​​of a, b, and c of the cylindrical batteries 100 in each embodiment are shown in Table 1. Apart from these, the remaining structures are identical. The cylindrical batteries 100 were charged at 1C to the upper limit voltage at 25°C, and then charged at a constant voltage until the cutoff current was 0.05C. A heating wire was placed on the peripheral surface of the cylindrical battery 100 to continuously heat it, triggering thermal runaway of the cylindrical battery 100. When thermal runaway occurs, heating should be stopped immediately. After the thermal runaway ends, observe whether cracks occur at the transition connection 14. If cracks occur, record the number of cylindrical batteries 100 with cracks at the transition connection 14 as N. The cracking rate of the transition connection 14 is calculated as (N / 200) × 100%. If the cracking rate of the transition connection 14 is less than or equal to 2%, it is considered good. If the cracking rate of the transition connection 14 is greater than 2% and less than or equal to 5%, it is considered qualified. If the cracking rate of the transition connection 14 is greater than 5%, it is considered unqualified.

[0274] For different battery systems, the upper and lower voltage limits of cylindrical batteries 100 need to be adjusted accordingly: For cathode active materials including LFP (LiFePO4, lithium iron phosphate) - upper voltage limit 3.65V, lower voltage limit 2.5V; for cathode active materials including NCM (lithium nickel cobalt manganese oxide) - upper voltage limit 4.25V, lower voltage limit 2.5V; for cathode active materials including LFMP (lithium manganese iron phosphate) - upper voltage limit 4.25V, lower voltage limit 2.5V; for cathode active materials including lithium nickel manganese oxide - upper voltage limit 4.8V, lower voltage limit 3.5V.

[0275] The positive electrode active material used in this test was selected from LiNi. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, other positive electrode active materials all meet the above test requirements, and the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and other negative electrode active materials all meet the above test requirements, and the mass ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0276] Performance Test 2: Uniformity Test of Housing Sidewalls.

[0277] Following the battery preparation method described above, 200 cylindrical batteries 100 were prepared for each of the embodiments and comparative examples. The values ​​of a, b, and c of the cylindrical batteries 100 in each embodiment are shown in Table 1. Apart from these, the remaining structures are the same. After the cylindrical batteries 100 were left to stand at 25°C for 4 hours, they were first charged at a charging rate of 0.33C to the upper limit voltage, and then discharged at a rate of 0.33C to the lower limit voltage. This cycle was repeated 3 times. The actual capacity C1 of the cylindrical battery 100 was recorded as the discharge voltage of the third cycle. At an ambient temperature of 25°C, the batteries were charged at a charging rate of 2C1 (twice the actual capacity) to the upper limit voltage. After standing for 30 minutes, they were then discharged at a discharge rate of 2C1 (twice the actual capacity) to the lower limit voltage. Limit the voltage and let it stand for 30 minutes. After 800 charge-discharge cycles, observe whether the connection between the side wall 13 and the second end wall 12 of the cylindrical battery 100 is cracked or whether the side wall 13 is bulging (the side wall deformation is greater than 1 mm). If the connection between the side wall 13 and the second end wall 12 is cracked or the side wall is bulging, it is considered that the side wall is cracked. Record the number of batteries with cracked side walls as N. Calculate the side wall non-crack rate according to the formula: side wall non-crack rate = ((100-N) / 100)×100%. If the side wall non-crack rate is greater than or equal to 99%, the test is good. If the side wall non-crack rate is less than 99% but greater than or equal to 96%, the test is qualified. If the side wall non-crack rate is less than 96%, the test is considered unqualified.

[0278] For different battery systems, the upper and lower voltage limits of cylindrical batteries 100 need to be adjusted accordingly: For cathode active materials including LFP (LiFePO4, lithium iron phosphate) - upper voltage limit 3.65V, lower voltage limit 2.5V; for cathode active materials including NCM (lithium nickel cobalt manganese oxide) - upper voltage limit 4.25V, lower voltage limit 2.5V; for cathode active materials including LFMP (lithium manganese iron phosphate) - upper voltage limit 4.25V, lower voltage limit 2.5V; for cathode active materials including lithium nickel manganese oxide - upper voltage limit 4.8V, lower voltage limit 3.5V.

[0279] The positive electrode active material used in this test was selected from LiNi. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, other positive electrode active materials all meet the above test requirements, and the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and other negative electrode active materials all meet the above test requirements, and the mass ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0280] Table 1: Performance Comparison of Cylindrical Batteries in Various Examples and Comparative Examples The data above shows that when the value of (a×b) / c is below the lower limit of 0.24, the uniformity of the sidewall 13 after fabrication is poor. Under stress, the sidewall 13 is prone to stress concentration, leading to deformation and cracking risks. Furthermore, poor uniformity of the sidewall 13 also results in lower structural strength in certain areas, making it more susceptible to cracking and damage under stress. Deformation of the sidewall 13 can also cause cracking at the connection point between the sidewall 13 and the endwall.

[0281] Furthermore, when the value of (a×b) / c exceeds the upper limit of 201.93, there is a risk of cracking in the transition connection 14. Specifically, when the value of (a×b) / c is too large, the pressure inside the cylindrical battery 100 will be too high before the first explosion-proof valve 30 is triggered to open and release pressure. In addition, there may also be a problem that the thickness of the transition connection 14 is too small. Therefore, when the cylindrical battery 100 experiences thermal runaway, causing the pressure inside the cylindrical battery 100 to increase, the transition connection 14 is prone to cracking due to excessive pressure inside the casing 10, and even the end wall may fly out entirely, increasing the risk of battery fire and explosion.

[0282] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Any modifications or equivalent substitutions made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A cylindrical battery, characterized in that, include: Battery cell; A housing for accommodating the battery cell, comprising a first end wall, a second end wall, and a side wall extending therebetween, wherein the first end wall and the side wall are integrally connected to form a transition connection, and an opening is formed at the end of the side wall opposite to the first end wall, the second end wall sealing the opening; and, A first explosion-proof valve is disposed on at least one of the first end wall and the second end wall and connected to the end wall. The first explosion-proof valve includes a weak part, the thickness of which is less than the thickness of the body of the end wall. Wherein, the length of the cylindrical battery is a1mm, the diameter of the cylindrical battery is a2mm, the ratio of a1 to a2 is a / a2, the thickness of the first end wall is b1mm, the minimum thickness of the transition connection is b2mm, the difference between b1 and b2 is b1-b2, and the area of ​​the region enclosed by the weak part is c1mm. 2 The area of ​​the end wall with the weak portion is c2mm. 2 The ratio of c1 to c2, c1 / c2, is equal to c, and 0.24 ≤ (a×b) / c ≤ 201.

93.

2. The cylindrical battery according to claim 1, characterized in that, The first explosion-proof valve is located on the second end wall, and 0.24≤(a×b) / c≤198.

5.

3. The cylindrical battery according to claim 2, characterized in that, The battery cell includes a battery cell body, a first tab and a second tab, the first tab and the second tab having opposite polarities, the first tab being led out from the end of the battery cell body facing the first end wall, and the second tab being led out from the end of the battery cell body facing the second end wall.

4. The cylindrical battery according to claim 3, characterized in that, The thermal conductivity of the first electrode is greater than that of the second electrode.

5. The cylindrical battery according to claim 2, characterized in that, The distance between the first end wall and the second end wall is d1mm, where 55≤d1≤220.

6. The cylindrical battery according to claim 1, characterized in that, The first explosion-proof valve is located on the first end wall, and the weak part and the transition connection part are spaced apart in the radial direction of the first end wall.

7. The cylindrical battery according to claim 6, characterized in that, The distance between the weak part and the transition connection part in the radial direction of the first end wall is d2mm, where 3≤d2≤20.

8. The cylindrical battery according to claim 6, characterized in that, A buffer protrusion is provided between the weak part and the transition connection part, and the buffer protrusion protrudes from one side of the first end wall.

9. The cylindrical battery according to claim 8, characterized in that, The buffer protrusion is designed to protrude toward the side where the battery cell is located.

10. The cylindrical battery according to claim 1, characterized in that, The weak part is a groove formed on the end wall, and the groove is constructed as a continuous closed pattern on the end wall.

11. The cylindrical battery according to claim 1, characterized in that, The end wall has a groove to form the weak part. The groove is constructed as a continuously extending non-closed pattern on the end wall. The length of the groove along the circumference of the end wall is L1mm, and 20≤L1≤200.

12. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The end wall of the first explosion-proof valve is provided with a pole post, and the weak part at least partially surrounds the pole post.

13. The cylindrical battery according to claim 12, characterized in that, The minimum distance between the weak part and the pole post is d3mm, where 2≤d3≤15.

14. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The end wall has at least one groove to form the weak portion, the at least one groove including a first groove located on the inner surface of the end wall facing the cell, and / or including a second groove located on the outer surface of the end wall facing away from the cell.

15. The cylindrical battery according to claim 14, characterized in that, A third groove is also provided on the end wall. The third groove has a bottom wall and a side wall, and the first groove and / or the second groove are provided on the bottom wall of the third groove.

16. The cylindrical battery according to claim 14, characterized in that, The depth of the at least one groove is h1mm, the thickness of the end wall is t1mm, and the width of the at least one groove is w1mm; 0.03≤h1≤0.3; and / or, 0.012≤h1 / t1≤0.6; and / or, 0.5≤w1≤2.5。 17. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The thickness of the weak part is t2mm, and 0.1 < b2 - t2 ≤ 1.

96.

18. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The second end wall is welded to the side wall to form a weld bead around the second end wall at the junction of the two, the weld bead having a penetration depth of h2mm, where 0.3≤h2≤2.

19. The cylindrical battery according to claim 18, characterized in that, h2 > b2.

20. The cylindrical battery according to claim 18, characterized in that, The direction of the weld penetration is parallel to the plane containing the second end wall.

21. The cylindrical battery according to any one of claims 1-11, characterized in that, 0.1 ≤ b ≤ 2.7; and / or, 0.4≤b1≤3; and / or, 0.3≤b2≤2; and / or, 1.5≤a≤7; and / or, 0.09≤c≤0.64。 22. The cylindrical battery according to any one of claims 1-11, characterized in that, The thickness of the sidewall is t3mm, and the thickness of the second endwall is t4mm; b1 > t3; and / or, b1 > t4; and / or, t3 > b2.

23. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The transition connection has a rounded corner structure with a radius of r1mm, where 0.4≤r1≤2.

5.

24. The cylindrical battery according to claim 1, characterized in that, The minimum distance between the battery cell and the first end wall is d4mm, where 0.5≤d4≤5.

25. The cylindrical battery according to any one of claims 1 to 8, characterized in that, It also includes a second explosion-proof valve, which is located on the other end wall of the first end wall and the second end wall, where 0.09≤c≤0.

6.

26. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The battery cell includes a battery cell body, the distance from the battery cell body to the first end wall is d4mm, the distance from the battery cell body to the second end wall is d5mm, and d4 < d5.

27. The cylindrical battery according to any one of claims 1, 2, or 5 to 11, characterized in that, The battery cell includes a battery cell body, a positive electrode tab, and a negative electrode tab. The battery cell body includes a positive electrode plate, and the active material of the positive electrode plate includes lithium iron phosphate. The positive electrode tab and the negative electrode tab are led out from the same end of the battery cell body and face the second end wall. The first explosion-proof valve is disposed on the second end wall.

28. The cylindrical battery according to claim 1, characterized in that, The battery cell includes a battery cell body, a positive electrode tab, and a negative electrode tab. The battery cell body includes a positive electrode sheet, and the active material of the positive electrode sheet includes a lithium ternary material. The positive electrode tab and the negative electrode tab are led out from the same end of the battery cell body and face the second end wall. The first explosion-proof valve is disposed on the first end wall.

29. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The battery cell has a core hole, and the orthographic projection of the core hole on the end wall at least partially overlaps with the first explosion-proof valve.

30. The cylindrical battery according to claim 29, characterized in that, A current collector is provided between the first explosion-proof valve and the core hole. The battery cell includes a tab extending toward the first explosion-proof valve. One end of the current collector is electrically connected to the tab, and the other end is electrically connected to the output end of the cylindrical battery. The output end of the cylindrical battery is located on the end wall where the first explosion-proof valve is located. An exposed area is provided on the current collector, and the exposed area at least partially exposes the core hole.

31. The cylindrical battery according to claim 29, characterized in that, In the orthographic projection on the end wall, the distance between the center of the core hole and the center of the area enclosed by the weak part in the radial direction of the end wall is d6mm, 0≤d6≤5.

32. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The diameter of the battery cell is D1mm, where D1≥40mm; The conditions a, b, and c satisfy: 1 ​​≤ (a × b) / c ≤ 120.

33. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The material of the end wall of the housing where the first explosion-proof valve is located is steel, aluminum, or aluminum alloy.

34. A battery pack, characterized in that, include: Multiple cylindrical batteries as described in any one of claims 1 to 33; The enclosure includes a top plate, a bottom plate, and side beams extending between them, the top plate, the bottom plate, and the side beams enclosing an internal space for accommodating the plurality of cylindrical batteries; as well as A fastener, disposed within the space inside the box, is used to fix the plurality of cylindrical batteries to the base plate, and the fastener at least partially covers the transition connection portion.

35. The battery pack according to claim 34, characterized in that, The first explosion-proof valve is positioned facing the base plate.

36. An electrical appliance, characterized in that, It includes a cylindrical battery as described in any one of claims 1 to 33, or a battery pack as described in claims 34 or 35.

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