A cylindrical battery

Abstract

The application discloses a cylindrical battery, and relates to the technical field of batteries, which comprises a first end face part, a battery cell and a current collector, wherein the first end face part comprises a weak part; the battery cell comprises a first tab part; the current collector comprises a target current collector arranged between the first end face part and the first tab part; the first tab part is welded with the target current collector, and a first welding area is formed on the target current collector; the grain size of the material of the current collector is T microns; the ratio of the welding mark area of the first welding area to the end face area of the battery cell body is M; the ratio of the area surrounded by the weak part to the area of the first end face part is K; and the range of T x K / M is 5.0-1013.3. The relationship T x K / M is selected in the range of 5.0-1013.3, so that the connection strength of the target current collector and the first tab part can be improved while ensuring that the weak part can timely direct pressure relief, and the current transmission rate inside and outside the battery is prevented from being affected.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a cylindrical battery. Background Technology

[0002] As people pursue longer driving ranges, battery energy density is increasing, but this also makes the pressure release during thermal runaway more severe. The pursuit of even higher energy density significantly exacerbates the severity of thermal runaway in cylindrical batteries. Even if weak points are designed with specific gas production rates, the actual pressure release rate may still be far lower than the instantaneous gas production rate during thermal runaway. Insufficient pressure release capacity becomes a safety bottleneck; the internal pressure of the battery cannot be released quickly, and the accumulated energy may eventually lead to a battery explosion, posing a serious safety hazard.

[0003] Therefore, how to improve pressure relief capacity and reduce safety hazards is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a cylindrical battery to improve the pressure relief capacity and reduce the safety hazards caused by untimely pressure relief.

[0005] To achieve the above objectives, this application provides the following technical solution: The first aspect of this application provides a cylindrical battery, including a housing and a cell and a current collector disposed within the housing. The housing includes a housing body and a first end face portion disposed at one end of the housing body. The first end face portion includes a first end face body and a weak portion disposed on the first end face body. The thickness of the weak portion is less than the thickness of the first end face body. The battery cell includes a battery cell body and a first electrode tab extending toward the first end face. The current collector includes a target current collector disposed between the first end face and the first electrode tab. The first electrode tab is welded to the target current collector, and a first welding area is formed on the target current collector. The grain size of the target current collector material is Tμm, the ratio of the solder area of ​​the first welding zone to the end face area of ​​the cell body is M, the ratio of the area enclosed by the weak part to the area of ​​the first end face is K, and the range of T×K / M is 5.0~1013.3.

[0006] The cylindrical battery disclosed in the above technical solution optimizes the grain size Tμm of the target current collector material, the ratio M of the solder area of ​​the first welding zone to the end face area of ​​the cell body, and the ratio K of the area enclosed by the weak part to the area of ​​the first end face, so that the relationship T×K / M is within the range of 5.0~1013.3. This avoids the target current collector itself, due to its large grain size, poor yield strength, and easy deformation, resulting in a reduction in the solder area, caused by an excessively large T×K / M (i.e., an excessively large proportion of T, K, and M). A small T×K / M ratio results in poor connection strength between the first electrode tab and the target current collector, making the connection prone to tearing during deformation, and also contributing to the poor connection strength between the target current collector and the first electrode tab. This also avoids the problem of insufficient deformation of the target current collector due to an excessively small T×K / M ratio (i.e., a small T percentage, a small K percentage, and a large M percentage), which would prevent timely pressure relief and blockage of the pressure relief path, potentially leading to severe thermal runaway, casing rupture and explosion, and heat propagation to adjacent batteries. This embodiment selects T×K / M within the range of 5.0 to 1013.3, ensuring timely and directional pressure relief at weak points while improving the connection strength between the target current collector and the first electrode tab, thus avoiding impact on the internal and external current transmission rates of the battery. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is an exploded view of the cylindrical battery disclosed in the embodiments of this application; Figure 2 This is an exploded view of the current collection component disclosed in the embodiments of this application; Figure 3 This is a schematic diagram of the structure of the first data collection device disclosed in the embodiments of this application; Figure 4 This is a top view of the first data stream component disclosed in the embodiments of this application; Figure 5 for Figure 4 Sectional view along AA; Figure 6 This is a schematic diagram of the structure of the second flow collector disclosed in the embodiments of this application; Figure 7 This is a top view of the second flow element disclosed in the embodiments of this application; Figure 8 for Figure 7Sectional view along BB; Figure 9 This is a schematic diagram of the structure of the first end face disclosed in the embodiments of this application; Figure 10 This is a cross-sectional view of the first end face and pole disclosed in an embodiment of this application; Figure 11 for Figure 10 A magnified view of the weakest part; Figure 12 This is a cross-sectional view of the first end face and the current collection assembly disclosed in an embodiment of this application; Figure 13 This is a top view of the battery cell disclosed in the embodiments of this application; Figure 14 This is a top view of the first end face disclosed in the embodiments of this application; Figure 15 This is a top view of the first end face disclosed in another embodiment of this application.

[0009] The meanings of the various reference numerals in the figure are as follows: 100 - Battery cell; 110 - Battery cell body; 120 - First electrode tab; 121 - First positive electrode tab; 122 - First negative electrode tab; 130 - Core winding hole; 210 - First end face; 211 - Welding annular groove; 212 - Weak part; 2121 - First end point; 2122 - Second end point; 213 - End face recess; 230 - Outer shell body; 300 - Current collector; 301 - First welding area; 302 - Second welding area; 310 - First current collector; 311 - First current collector welding area; 312 - First output welding area; 313 - Buffer notch; 314 - First through hole; 315 - Thinning recess; 320 - Second current collector; 321 - Second current collector welding area; 322 - Second output welding area; 323 - Buffer groove; 324 - Second through hole; 330 - Current collector insulating frame; 400-Pole Column. Detailed Implementation

[0010] This application discloses a cylindrical battery to improve pressure relief capacity and reduce safety hazards caused by untimely pressure relief.

[0011] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0012] As energy density increases, the gas production rate of cylindrical batteries increases dramatically during thermal runaway. The pressure relief structure (a weak point originally designed for conventional gas production) can no longer meet actual demands, leading to a sudden surge in internal pressure. This imbalance between the pressure relief rate and the gas production rate can easily trigger a battery explosion, seriously threatening safety.

[0013] Studies have found that cylindrical batteries have a higher internal space utilization rate compared to prismatic batteries, but the smaller spacing between electrode layers results in a very limited effective gas storage volume. Furthermore, the weak points on the current collector and battery end face mean that during thermal runaway, high-temperature gases struggle to break through the current collector, directly obstructing the exhaust path. This not only causes the actual opening pressure at the weak point to far exceed the design threshold, but also leads to structural rupture of the casing due to the excessive internal pressure after the weak point opens. The high-pressure gas, carrying cell fragments and high-temperature electrolyte, is ejected, igniting upon contact with air and significantly exacerbating the severity of thermal runaway.

[0014] Based on this, this application discloses a cylindrical battery to improve pressure relief capability and reduce safety hazards caused by untimely pressure relief.

[0015] like Figure 1 As shown, the cylindrical battery disclosed in this application includes a casing and a cell 100 and a current collector 300 disposed within the casing.

[0016] The outer casing is the external protective structure of the battery cell 100, used to house the battery cell 100 and isolate it from the external environment. The casing is mainly made of metals such as aluminum, iron, steel, and titanium, or their alloys. Typically, the casing includes a casing body 230 and a battery cover plate encapsulated at the open end of the casing body 230. One end of the casing body 230 is an open end to facilitate the installation of the battery cell 100 inside the casing. The battery cover plate is used to close the opening of the casing body 230. In other words, the battery cover plate is a component that covers the opening of the casing body 230 to isolate the housing space of the battery cell 100 from the external environment. The shape of the battery cover plate can be adapted to the shape of the casing body 230 to fit it. The battery cover plate can be made of a material with a certain hardness and strength (such as aluminum alloy).

[0017] The shape of the casing can be determined according to the specific shape and size of the battery cell 100. The casing can be cylindrical. The casing material can be various, including but not limited to copper, iron, aluminum, titanium, stainless steel, aluminum alloy, etc.

[0018] Cell 100 is the component in a battery where electrochemical reactions occur; it is the smallest unit in a battery capable of performing electrochemical reactions such as charging / discharging. Cell 100 is the basic unit in a battery, generally consisting of a positive electrode and a negative electrode, with a separator between them. Lithium-ion cells primarily function by the intercalation and deintercalation of lithium ions between the positive and negative electrodes.

[0019] Cell 100 is formed by winding or stacking a positive electrode sheet, a negative electrode sheet, and a separator. In a cylindrical cell, the thin-film structure of the three layers of materials is wound into a cylindrical electrode assembly. The positive electrode sheet includes a positive current collector and a positive active material. The positive current collector can be made of metals such as aluminum foil, nickel foil, or stainless steel, or a composite foil formed by combining metals and insulating materials. The positive active material includes the main positive active material, a conductive agent, and a binder. The main positive active material includes one or more lithium-containing positive active materials such as lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate.

[0020] Similarly, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material. The negative electrode current collector can be made of metal materials such as copper foil, aluminum foil, and stainless steel, or it can be a composite foil material formed by combining metals and insulating materials. The negative electrode active material includes the negative electrode active material, conductive agent, binder, etc. The negative electrode active material includes one or more of the following: artificial graphite, natural graphite, silicon carbide, silicon oxide, lithium titanate, etc.

[0021] The separator is an insulating membrane placed between the positive and negative electrode plates to prevent electrons from passing through while allowing ions to pass through. The separator is made of at least one of the following materials: glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, etc.

[0022] In this embodiment, the outer shell includes an outer shell body 230 and a first end portion 210 disposed at one end of the outer shell body 230. The first end portion 210 includes a first end face body and a weak portion 212 disposed on the first end face body (e.g., Figure 10 and Figure 11 As shown), the thickness of the weak part 212 is less than the thickness of the first end face body.

[0023] The weak point 212 is a specific structure of an explosion-proof valve. 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 the battery reaches a predetermined threshold. During battery use, the explosion-proof valve is mainly used to allow gas inside the battery to escape and reduce the internal pressure of the battery in order to prevent the battery from deforming or exploding due to excessive increase in internal pressure when the battery experiences thermal runaway or other situations.

[0024] The weak portion 212 can be formed directly on the first end face 210 (e.g., by laser or mechanical etching to create a thinning region on the first end face), or the first end face 210 and the pressure relief plate can be fabricated separately, and the pressure relief plate can be fixed to the first end face 210. If the pressure relief plate with the weak portion 212 is fixed to the first end face 210, a pressure relief port needs to be provided on the first end face 210, and the pressure relief plate is connected to the pressure relief port to seal it. The fixing method can be welding or other connection methods. If the weak portion 212 is formed directly on the first end face 210, then the thinning process can be performed directly on the first end face 210 to form the weak portion 212.

[0025] The area enclosed by the weak portion 212 is called the weak zone. The weak zone is configured such that when the internal pressure of the casing reaches the pressure relief level, the weak portion 212 cracks, causing the weak zone to open for pressure relief. In other words, when the internal pressure of the casing reaches the pressure relief level, the weak portion 212 breaks, causing the weak zone to open for pressure relief. When a large amount of gas is generated inside the cylindrical battery due to abnormal conditions such as overcharging, overheating, or short circuits, causing the internal pressure to rise to a certain level, the pressure generated by the gas will cause the weak portion 212 to break, resulting in the weak zone detaching or bending at the first end face 210, thus forming a pressure relief port on the first end face 210 to release the pressure inside the casing.

[0026] The weak part 212 is formed by reducing the thickness of the pressure relief sheet to achieve pressure relief. The thinned weak part 212 forms a groove. The groove can be formed on the side close to the battery cell 100, on the side away from the battery cell 100, or on both sides. The groove can be formed as a V-shaped groove, a U-shaped groove, or a trapezoidal groove, etc.

[0027] This embodiment does not limit the shape of the weak portion 212, such as circular, oblong, elliptical, racetrack-shaped, etc. This embodiment also does not limit the formation method of the weak portion 212; for example, it can be formed by stamping or laser etching. Furthermore, the groove of the weak portion 212 can be a continuous closed structure or a discontinuous, non-closed structure. Stamped reinforcing ribs can be formed inside the area enclosed by the weak portion 212 (i.e., the weak zone) to improve the strength of the weak zone, or no reinforcing ribs may be provided.

[0028] The battery cell 100 includes a battery cell body 110 and a first electrode tab 120 extending toward the first end face 210. It should be noted that the electrode tab extending toward the first end face 210 of the first electrode tab 120 may include only one of a positive electrode tab and a negative electrode tab, or it may include both a positive electrode tab and a negative electrode tab.

[0029] The positive and negative electrode tabs are key components of the battery, used to transmit the internal current of the cell 100 and draw out the internal current of the cell 100. The material of the positive and negative electrode tabs can be the same as the material of the current collector of the electrode sheet. The positive and negative electrode tabs are located on one side of the positive / negative current collector and are separately / integrated with the current collector.

[0030] For example, the positive and negative electrode tabs can be made of at least one of the following: silver-plated aluminum, silver-plated stainless steel, stainless steel, copper, aluminum, nickel, carbon, or titanium. Furthermore, the positive and negative electrode tabs can be cut from a current collector or are separately formed metal parts. It is understood that the positive electrode tab is electrically connected to the positive electrode plate in the battery cell, and the negative electrode tab is electrically connected to the negative electrode plate in the battery cell. The electrical connection can be achieved through at least one of the following methods: welding, bonding, riveting, etc. Welding can be achieved through at least one of the following methods: resistance welding, ultrasonic welding, laser welding, etc.

[0031] like Figure 2 As shown, the current collector is one of the core components in the internal structure of a cylindrical battery. It is typically made of a metal fan-shaped structure, such as copper, aluminum, or nickel-plated steel strip. Located on the battery casing, where the current output terminal connects to the tabs, it acts as a bridge for current transmission, ensuring uniform current distribution.

[0032] The shape and layout of the current collector assembly depend on the type, size, and application of the battery. Generally, the surface of the current collector assembly is flat, providing ample connection area for the tab assembly. Its surface is also designed with specific connection areas according to the distribution and connection requirements of the tab assembly and the terminals / casing (which serve as the battery's current output terminals). These areas may be equipped with solder points, riveting points, or specialized snap-fit ​​structures to ensure a secure connection with the tabs, terminals / casing.

[0033] The terminal assembly is used to electrically connect the electrode assembly located inside the casing to external devices (adjacent batteries or other electrical equipment) located outside the casing. The battery can discharge to external devices through the cell output terminals (tabs) and the external device output terminals (terminal assembly), and an external power source can charge the battery through the terminal assembly and the tabs. The terminal assembly can be directly electrically connected to the cell tabs or electrically connected to the tabs through metal adapters. The materials of the terminal assembly include, but are not limited to, metals such as copper, aluminum, aluminum alloy, and copper-aluminum alloy.

[0034] As a crucial hub for current conduction within the battery, the current collector assembly collects the current from the tabs and transmits it to the terminals / casing. During battery charging and discharging, the current generated by the electrode reactions is gathered by the tab assembly and then conducted to the current collector assembly, which in turn conducts it to the terminals / casing, thus connecting it to the external circuitry. This process ensures stable and efficient current transfer between the battery's internal and external environments.

[0035] like Figure 2 As shown, the current collector assembly includes a current collector 300, which includes a first current collector 310 and a second current collector 320. One of the first current collector 310 and the second current collector 320 is a positive current collector, and the other is a negative current collector. For ease of understanding, the current collector 300 disposed between the first end face 210 and the first electrode ear 120 is defined as the target current collector. That is, the current collector 300 includes the target current collector, which may include at least one of the first current collector 310 and the second current collector 320. In other words, the target current collector may be only the first current collector 310, or only the second current collector 320, or may include both the first current collector 310 and the second current collector 320.

[0036] The first electrode lug 120 is welded to the target current collector, and a first welding area 301 is formed on the target current collector. It should be noted that if the first electrode lug 120 includes only one polarity electrode lug, then the target current collector includes one of the first current collector 310 and the second current collector 320.

[0037] It should be noted that when the target current collector includes a first current collector 310 and a second current collector 320, in other words, when the first electrode portion 120 includes two polarity electrodes, i.e., the two polarity electrodes are led out from one end of the battery cell, the current collector assembly also includes a current collector insulating frame 330. The first current collector 310 and the second current collector 320 are mounted on the current collector insulating frame 330 to achieve insulation between the first current collector 310 and the second current collector 320, and at the same time, to facilitate the fixation of the first current collector 310 and the second current collector 320, and to maintain the stability of the first current collector 310 and the second current collector 320.

[0038] The electrode tabs extending from the first electrode tab 120 toward the first end face 210 may include one of a first positive electrode tab 121 and a first negative electrode tab 122, or both. Similarly, the target current collector may include one of a first current collector 310 and a second current collector 320, or both.

[0039] When the first electrode tab 120 includes one of the first positive electrode tab 121 and the first negative electrode tab 122, the target current collector includes one of the first current collector 310 and the second current collector 320 for electrical connection with the corresponding electrode tab. When the first electrode tab 120 includes the first positive electrode tab 121 and the first negative electrode tab 122, the target current collector includes the first current collector 310 and the second current collector 320 for electrical connection with the corresponding electrode tab.

[0040] The first tab 120 is welded to the target current collector, and a first welding area 301 is formed on the target current collector. In other words, the tabs of the first tab 120 (first positive tab 121, first negative tab 122, depending on which polarities the first tab 120 includes) are electrically connected to the target current collector (first current collector 310, second current collector 320, depending on which polarities the first tab 120 includes) by welding. The first welding area 301 is formed on the target current collector. For example, when the first tab 120 includes the first positive tab 121 and the first negative tab 122, and the target current collector includes the first current collector 310 and the second current collector 320, the first welding area 301 on the first current collector 310 is the first current collector welding area 311, and the first welding area 301 on the second current collector 320 is the second current collector welding area 321.

[0041] Research has revealed that, in addition to the material, shape, and thickness of the target current collector, a crucial factor affecting its hardness and toughness is the size of the material's micrograins. In this embodiment, the grain size of the target current collector material is Tμm. When the target current collector includes either the first current collector 310 or the second current collector 320, the grain size Tμm of the target current collector is that of the first current collector 310. When the target current collector includes both the first current collector 310 and the second current collector 320, and the grain sizes of the first current collector 310 and the second current collector 320 are the same, the grain size Tμm of the target current collector refers to the grain size of either the first current collector 310 or the second current collector 320. When the target current collector includes both a first current collector 310 and a second current collector 320, and the grain sizes of the first current collector 310 and the second current collector 320 are different, the smaller of the grain sizes of the first current collector 310 and the second current collector 320 can be used as the grain size Tμm of the target current collector. Of course, those skilled in the art can also use the larger of the grain sizes of the first current collector 310 and the second current collector 320 as the grain size Tμm of the target current collector, or use the average of the grain sizes of the first current collector 310 and the second current collector 320 as the grain size Tμm of the target current collector.

[0042] Grain size can be expressed as grain size, commonly represented by the number of grains per unit volume (or unit area) or the average linear length (or diameter) of the grains. There is a clear physical relationship between the grain size and strength of metallic materials, primarily described by the Hall-Petch relation. Within the typical grain size range (approximately 1 μm to 100 μm), finer grains result in higher yield strength. The Hall-Petch relation states that the strength of a metallic material is inversely proportional to the square root of its grain size. Grain refinement increases strength by increasing grain boundary density and hindering dislocation movement. This relationship is widely applicable to most engineering metals and alloys, such as copper, aluminum, iron, titanium, low-carbon steel, aluminum alloys, copper alloys, and titanium alloys.

[0043] In this embodiment, the ratio of the solder area of ​​the first welding area 301 to the end face area of ​​the cell body 110 is M. Specifically, the solder area of ​​the first welding area 301 is the total area enclosed by the solder marks of the first welding area 301. The end face area of ​​the cell body 110 is the area enclosed by the outermost perimeter of the cell body 110, i.e., π × the square of the radius of the cell body 110.

[0044] When the target current collector includes either the first current collector 310 or the second current collector 320, the solder area of ​​the first soldering area 301 is the solder area of ​​the first soldering area 301 on the first current collector 310. When the target current collector includes both the first current collector 310 and the second current collector 320, the solder area of ​​the first soldering area 301 refers to the sum of the solder areas of the first soldering areas 301 on the first current collector 310 and the second current collector 320 (i.e., the sum of the solder areas of the first current collector soldering area 311 and the second current collector soldering area 321). The end face area of ​​the cell body 110 refers to the area of ​​the end face of the cell body 110 facing the first end face 210.

[0045] In this embodiment, the ratio of the area enclosed by the weak portion 212 to the area of ​​the first end portion 210 is K. The range of T×K / M is 5.0~1013.3. For example, T×K / M can be 5.0, 10, 50, 100, 150, 200, 300, 350, 400, 500, 550, 650, 700, 800, 900, 1000, 1013.3, etc. This embodiment does not limit the specific value of T×K / M, and those skilled in the art can select it within the range of 5.0~1013.3 according to their needs.

[0046] The cylindrical battery disclosed in this application optimizes the grain size Tμm of the target current collector material, the ratio M of the solder area of ​​the first welding area 301 to the end face area of ​​the cell body 110, and the ratio K of the area enclosed by the weak part 212 to the area of ​​the first end face 210, so that the relationship T×K / M is in the range of 5.0~1013.3. This approach avoids two problems: Firstly, it avoids the issue of excessively large T×K / M ratios (i.e., excessively large Tμm, K, and M proportions), which leads to a large grain size, poor yield strength, and easy deformation of the target current collector. Secondly, it avoids the problem of insufficient deformation of the target current collector due to a small T×K / M ratio (i.e., excessively small Tμm, K, and M proportions), resulting in blocked pressure relief paths and delayed pressure relief. This could lead to severe thermal runaway, casing rupture and explosion, and thermal propagation to adjacent batteries. By selecting T×K / M within the range of 5.0 to 1013.3, this embodiment can ensure that the weak part 212 can be depressurized in a timely and directional manner, while improving the connection strength between the target current collector and the first electrode tab 120, thus avoiding affecting the current transmission rate inside and outside the battery.

[0047] In a specific embodiment of this application, the range of T×K / M is 21.9 to 609.7. For example, T×K / M can be 21.9, 60, 110, 160, 210, 250, 310, 360, 410, 450, 510, 560, 600, 609.7, etc. This embodiment does not limit the specific value of T×K / M; those skilled in the art can select it within the range of 21.9 to 609.7 according to their needs.

[0048] like Figure 2 , Figure 9 and Figure 12 As shown in a specific embodiment of this application, the target current collector includes a second welding area 302, which is configured to be welded to the current output terminal on the casing. The current output terminal of a cylindrical battery generally includes a positive output terminal and a negative output terminal. Both the positive and negative output terminals can be terminals 400, or one of them can be a terminal 400 disposed on the casing (e.g., disposed on the first end portion 210), and the other can be the casing (e.g., the first end portion 210).

[0049] In other words, when the target current collector located between the cell 100 and the first end face 210 includes one of the first current collector 310 and the second current collector 320, it can be connected to the terminal post 400 or the housing; when the target current collector includes the first current collector 310 and the second current collector 320, one of them is connected to the terminal post 400 and the other is connected to the housing. When the target current collector includes the first current collector 310 and the second current collector 320, the second soldering area 302 on the first current collector 310 is the first output soldering area 312, and the second soldering area 302 on the second current collector 320 is the second output soldering area 322.

[0050] For example, the first output welding area 312 is welded to the electrode post 400, and the second output welding area 322 is welded to the first end face 210. A groove can be formed on the side of the electrode post 400 facing the cell 100. The first output welding area 312 can have a raised structure and be recessed into the groove of the electrode post 400, and welded to the bottom wall of the groove. A welding ring groove 211 can be provided on the first end face 210 to constrain the welding position (the welding ring groove 211 is located at the welding position between the first end face 210 and the second output welding area 322). Simultaneously, the welding ring groove 211 can also reduce the thickness of the first end face 210, ensuring the welding quality between the first end face 210 and the second output welding area 322.

[0051] A buffer structure is provided between the first welding area 301 and the second welding area 302 on the target current collector. If the target current collector only includes the first current collector 310, such as... Figures 3-5 As shown, a buffer structure is provided between the first current collector welding area 311 and the first output welding area 312 on the first current collector 310. The buffer structure on the first current collector 310 may include at least one of a buffer notch 313 and a through hole. One or more buffer notches 313 may be provided; one or more through holes may be provided.

[0052] If the target current collector only includes the second current collector 320, such as Figures 6-8 As shown, a buffer structure is provided between the second current collector welding area 321 and the second output welding area 322 on the second current collector 320. The buffer structure on the second current collector 320 may include at least one of a buffer groove 323 and a through hole. One or more buffer grooves 323 may be provided; one or more through holes may be provided.

[0053] If the target current collector includes both the first current collector 310 and the second current collector 320, a buffer structure is provided between the first current collector welding area 311 and the first output welding area 312 on the first current collector 310; and a buffer structure is provided between the second current collector welding area 321 and the second output welding area 322 on the second current collector 320.

[0054] The buffer structure between the first welding area 301 and the second welding area 302 on the target current collector can be a groove, or the first welding area 301 and the second welding area 302 can be set at different heights, so that the first welding area 301 and the second welding area 302 are connected by a vertical wall or an inclined wall to form a buffer; the buffer structure can also include through holes or cantilever grooves.

[0055] In this embodiment, by adding a buffer structure between the first welding area 301 and the second welding area 302 on the target current collector, when the internal pressure of the cylindrical battery increases to the pressure relief threshold, the target current collector is more likely to deform or even burst along its buffer structure, so that the first welding area 301 and the second welding area 302 can be disconnected, thereby bursting the second welding area 302 of the target current collector and the current output terminal on the casing, forming a larger pressure relief path and quickly releasing pressure.

[0056] It should be noted that the buffer structure shown in the figure (such as buffer notch 313 and buffer groove 323) is only an example. Those skilled in the art can design the shape and position of the buffer structure based on the path of the pressure relief burst.

[0057] In a specific embodiment of this application, the shortest distance between the first welding area 301 and the second welding area 302 is 1mm to 15mm. For example, the shortest distance between the first welding area 301 and the second welding area 302 can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, etc. This embodiment does not limit the specific value of the above-mentioned shortest distance; those skilled in the art can select a value within the range of 1mm to 15mm according to their needs.

[0058] If the target current collector only includes the first current collector 310, such as Figures 3-5 As shown, the shortest distance between the first welding area 301 and the second welding area 302 is 1mm~15mm, which means that the shortest distance L1 between the first current collector welding area 311 and the first output welding area 312 on the first current collector 310 is 1mm~15mm.

[0059] If the target current collector only includes the second current collector 320, such as Figures 6-8 As shown, the shortest distance between the first welding area 301 and the second welding area 302 is 1mm to 15mm, which means that the shortest distance L2 between the second current collector welding area 321 and the second output welding area 322 on the second current collector 320 is 1mm to 15mm.

[0060] If the target current collector includes both the first current collector 310 and the second current collector 320, then the shortest distance L1 between the welding area 311 of the first current collector and the first output welding area 312 is 1mm to 15mm; the shortest distance L2 between the welding area 321 of the second current collector and the second output welding area 322 on the second current collector 320 is 1mm to 15mm.

[0061] In this embodiment, the shortest distance between the first welding area 301 and the second welding area 302 on the same target current collector is selected within the range of 1mm to 15mm. This can avoid the problem of welding failure caused by mutual interference during welding of the first welding area 301 and the second welding area 302 due to the shortest distance being too close, and can also avoid the problem of affecting current transmission due to the shortest distance being too far.

[0062] In one specific embodiment of this application, the first welding area 301 and the second welding area 302 have a height difference along a direction perpendicular to the first end face 210. That is, along the axial direction of the cylindrical battery, the second welding area 302 and the first welding area 301 are at a certain distance, so that the second welding area 302 is at a certain distance from the end face of the cell 100. This reduces the welding heat that could damage the cell 100 when the second welding area 302 is welded to the current output terminal on the casing, such as causing the separator to melt.

[0063] Furthermore, the height difference between the first welding area 301 and the second welding area 302 along a direction perpendicular to the first end face 210 is 0.5mm to 4mm. For example, the shortest distance between the first welding area 301 and the second welding area 302 can be 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.7mm, 2mm, 2.3mm, 2.5mm, 2.8mm, 3mm, 3.2mm, 3.5mm, 3.8mm, 4mm, etc. This embodiment does not limit the specific value of the above height difference; those skilled in the art can select a value within the range of 0.5mm to 4mm according to their needs.

[0064] If the target current collector only includes the first current collector 310, such as Figures 3-5 As shown, the height difference of 0.5mm to 4mm between the first welding area 301 and the second welding area 302 along the direction perpendicular to the first end face 210 means that the height difference H1 between the first current collector welding area 311 and the first output welding area 312 on the first current collector 310 along the direction perpendicular to the first end face 210 is 0.5mm to 4mm.

[0065] If the target current collector only includes the second current collector 320, such as Figures 6-8As shown, the height difference of 0.5mm to 4mm between the first welding area 301 and the second welding area 302 along the direction perpendicular to the first end face 210 means that the height difference H2 between the second current collector welding area 321 and the second output welding area 322 on the second current collector 320 along the direction perpendicular to the first end face 210 is 0.5mm to 4mm.

[0066] If the target current collector includes both the first current collector 310 and the second current collector 320, then the height difference H1 between the first current collector welding area 311 and the first output welding area 312 on the first current collector 310 along the direction perpendicular to the first end face 210 is 0.5mm to 4mm; the height difference H2 between the second current collector welding area 321 and the second output welding area 322 on the second current collector 320 along the direction perpendicular to the first end face 210 is 0.5mm to 4mm.

[0067] In this embodiment, the height difference between the first welding area 301 and the second welding area 302 along the direction perpendicular to the first end face 210 is selected within the range of 0.5mm to 4mm. This can avoid the problem of the target current collector occupying too much space in the axial direction due to the excessive height difference, and also avoid the welding heat of the second welding area 302 causing damage to the battery cell 100 due to the excessive height difference.

[0068] In one specific embodiment of this application, the target current collector includes a first region and a second region, wherein the grain size of the first region is larger than that of the second region. That is, in this embodiment, the target current collector includes at least two regions with different grain sizes. The first region has a larger grain size, meaning it is more easily deformed than the second region, and is more prone to tearing and releasing pressure during thermal runaway of the cylindrical battery. The second region has a smaller grain size, meaning it has higher strength than the first region, ensuring the service life of the target current collector even when the cylindrical battery has not thermally runaway, and avoiding welding failures with other components due to insufficient strength. In this embodiment, by setting different grain sizes in different regions, the strength of some areas of the target current collector can be guaranteed. Simultaneously, it also avoids the problem of the target current collector not being able to be broken in time during thermal runaway of the cylindrical battery, leading to untimely pressure release.

[0069] Furthermore, the first welding area 301 is located in the first region, meaning that the first welding area 301, which is to be welded to the first electrode tab 120, is located in the first region with a larger grain size. This arrangement ensures that in the event of thermal runaway of the cylindrical battery, the first region where the first welding area 301 is located has lower strength and is more prone to deformation and tearing, thus ensuring timely pressure relief.

[0070] The target current collector includes a second welding area 302, which is disposed in a second region and configured to be welded to the current output terminal on the casing. Specifically, the second welding area 302, which is to be welded to the current output terminal on the casing, is located in a second region with a smaller grain size. This configuration allows the second welding area 302 to have higher strength, ensuring a stronger connection with the current output terminal on the casing. Furthermore, the second welding area 302 can be only a portion of the second region to ensure sufficient strength of the target current collector and improve the reliability of its overcurrent capacity during normal use of the cylindrical battery.

[0071] In one specific embodiment of this application, the area of ​​the first region is smaller than the area of ​​the second region. Since the grain size of the first region is larger than that of the second region, the first region has lower strength than the second region. In this embodiment, the area of ​​the first region is designed to be smaller than that of the second region, making the first region more easily broken during thermal runaway of the cylindrical battery.

[0072] It should be noted that the first welding area 301 can also be located in the second region, that is, in a region with a smaller grain size, so that the first welding area 301 has greater strength. Based on this, the area of ​​the first welding area 301 is 20 mm². 2 ~400mm 2 In this embodiment, the area of ​​the first welding area 301 is selected within the above range so that when the cylindrical battery experiences thermal runaway, the second region of the target current collector and the first tab 120 are more likely to tear and deform, thereby increasing the pressure relief speed.

[0073] For example, the area of ​​the first welding area 301 can be 20 mm. 2 50mm 2 80mm 2 100mm 2 130mm 2 160mm 2 180mm 2 200mm 2 220mm 2 250mm 2 270mm 2 300mm 2 320mm 2 350mm 2 380mm 2 400mm 2 Etc. This embodiment does not limit the specific value of the area of ​​the first welding zone 301; those skilled in the art can adjust it according to requirements, such as 20mm. 2 ~400mm2 Choose from the range.

[0074] like Figure 3 As shown, in a specific embodiment of this application, the target current collector (i.e., the current collector disposed between the first end face 210 and the first electrode ear 120) includes one of a first current collector 310 and a second current collector 320. One of the first current collector 310 and the second current collector 320 is a positive current collector, and the other is a negative current collector. Taking the target current collector as an example that only includes the first current collector 310, the target current collector (i.e., the first current collector 310) is formed with a thinning recess 315, and the first welding area 301 is disposed in the thinning recess 315. It should be noted that the thinning recess 315 is a thinned area formed on the target current collector, and the thickness of the thinning recess 315 is less than the thickness of other areas of the target current collector. The forming methods of the thinning recess 315 include, but are not limited to, stamping, etching (chemical etching or laser etching), machining, etc.

[0075] In this embodiment, the shape of the thinning recess 315 is not limited; it can be fan-shaped, circular, polygonal, or other shapes. One side of the thinning recess 315 can extend to the side of the target current collector, such as... Figure 3 In the illustrated design, the thinning recess 315 has a fan-shaped structure, comprising an inner edge and an outer edge arranged coaxially, as well as side edges connecting the two ends of the inner edge and the outer edge, respectively. When the outer edge of the target current collector is arc-shaped, the inner edge and the outer edge of the thinning recess 315 can be arranged coaxially with the outer edge of the target current collector. Furthermore, the outer edge of the thinning recess 315 can extend and penetrate the outer edge of the target current collector, while the inner edge and the two side edges of the thinning recess 315 form sidewalls.

[0076] The thinning recess 315 can be obtained on the target current collector through machining processes such as stamping. After the thinning recess 315 is thinned by stamping, the grain size is reduced, making the area where the thinning recess 315 is located stronger than other areas. Setting the first welding area 301 in the thinning recess 315 can make the first electrode tab 120 and the target current collector have higher welding strength, improving the reliability of the cylindrical battery during normal use. When the cylindrical battery experiences thermal runaway, the edge of the thinning recess 315 (the boundary with other areas of the target current collector, i.e., the thickness junction) is more likely to tear, allowing the thermal runaway gas to break through the target current collector for rapid depressurization.

[0077] It should be noted that the area where the thinning recess 315 is located on the surface of the target current collector facing the first electrode ear 120 can be on the same plane as other areas of the target current collector to facilitate welding of the first electrode ear 120. The thickness boundary side of the thinning recess 315 and other areas can be located on the side facing the first end face 210.

[0078] Furthermore, the target current collector may also include a first current collector 310 and a second current collector 320, wherein one of the first current collector 310 and the second current collector 320 is a positive current collector and the other is a negative current collector. In this embodiment, at least one of the first current collector 310 and the second current collector 320 is formed with a thinning recess 315, and a first welding area 301 is disposed in the thinning recess 315. The structure, shape, and forming method of the thinning recess 315 have been disclosed in the above embodiments and will not be repeated here.

[0079] When the target current collector includes a first current collector 310 and a second current collector 320, both the first current collector 310 and the second current collector 320 are arranged between the first end face 210 and the first pole ear 120. The first end face 210 and the first pole ear 120 can be insulated and separated by the current collector insulating frame 330. In addition, both the first current collector 310 and the second current collector 320 can be fan-shaped structures.

[0080] In this embodiment, the thinning recess 315 may be provided on only one of the first current collector 310 and the second current collector 320, or it may be provided on both the first current collector 310 and the second current collector 320. When the thinning recess 315 is provided on both the first current collector 310 and the second current collector 320, the shape and area of ​​the thinning recess 315 on the first current collector 310 and the second current collector 320 may be the same or different; the thickness of the thinning recess 315 may be the same or different as required.

[0081] Furthermore, for ease of understanding, the area where the target current collector is located in the thinned recess 315 is defined as the recessed region, and the other areas outside the thinned recess 315 are defined as non-recessed regions. In this embodiment, the grain size of the recessed region is smaller than that of the non-recessed region; in other words, the strength of the recessed region is greater than that of the non-recessed region. In this embodiment, the ratio of the total area of ​​the recessed region to the total area of ​​the non-recessed region is 0.25 to 4. It should be noted that the areas of both the recessed region and the non-recessed region refer to their projected areas on a reference plane, which is a plane perpendicular to the axis of the cylindrical battery.

[0082] For example, the ratio of the total area of ​​the concave region to the total area of ​​the non-concave region can be 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, etc. This embodiment does not limit the specific value of the above ratio; those skilled in the art can select a value within the range of 0.25 to 4 according to their needs.

[0083] This setting avoids the problem that if the ratio is too large, the total area of ​​the recessed region will be too large, resulting in a large proportion of the strong area on the target current collector, making it difficult to break through in the event of thermal runaway; it also avoids the problem that if the ratio is too small, the total area of ​​the recessed region will be too small, affecting the welding strength of the first electrode lug 120.

[0084] In a specific embodiment of this application, for ease of understanding, the projection of the target current collector onto the target plane is defined as the current collector projection, and the projection of the weak portion 212 onto the target plane is defined as the weak portion projection. The target plane is a plane parallel to the first end face 210; in other words, the target plane is a plane perpendicular to the axis of the cylindrical battery.

[0085] In this embodiment, the projection of the manifold and the projection of the weak part at least partially overlap. This arrangement ensures that the pressure relief path formed after the target manifold is torn apart and the pressure relief port formed after the weak part 212 bursts open can be partially connected, so that the thermal runaway gas can be discharged from the pressure relief port through the shortest path.

[0086] Furthermore, the projection of the current collector and the projection of the weak part do not necessarily overlap, as long as the pressure relief path formed after the target current collector is torn apart and the pressure relief port formed after the weak part 212 bursts open can remain connected.

[0087] like Figure 3 and Figure 6 As shown, the target current collector is provided with a through hole, which is spaced apart from the first welding area 301. If the target current collector only includes the first current collector 310, the through hole provided in the target current collector can be the first through hole 314 on the first current collector 310; if the target current collector only includes the second current collector 320, the through hole provided in the target current collector can be the second through hole 324 on the second current collector 320; if the target current collector includes both the first current collector 310 and the second current collector 320, the through holes provided in the target current collector can be the first through hole 314 on the first current collector 310 and the second through hole 324 on the second current collector 320, respectively.

[0088] In this embodiment, through holes are provided on the target current collector at intervals from the first welding area 301. The through holes can generate stress concentration, making it easier for the cylindrical battery to tear around the first welding area 301 at the through holes when thermal runaway occurs. That is, the target current collector forms a tearing path along the arrangement path of the through holes, so that the target current collector can be lifted along the torn area, reducing the blocking area of ​​the target current collector on the pressure relief port and ensuring pressure relief as soon as possible.

[0089] Furthermore, the through holes include multiple holes, which are respectively arranged on opposite sides of the first welding area 301. In other words, some through holes are arranged on one side of the first welding area 301, and others are arranged on the other side of the first welding area 301. This allows tearing paths to be formed on both sides of the first welding area 301, ensuring a larger opening area and further reducing the obstruction area of ​​the target manifold to the pressure relief port.

[0090] In some embodiments, at least two through holes are respectively disposed on both sides of the first welding area 301, and are symmetrically disposed on both sides of the first welding area 301 along the radial direction of the first end face 210. Symmetrical arrangement of through holes on both sides of the first welding area 301 can form a regular tear-off area, improving the directional pressure relief effect of thermal runaway gas. It should be noted that through holes can also be asymmetrically arranged on both sides of the first welding area 301, and the corresponding through holes can be arranged according to the desired tear path.

[0091] In one specific embodiment of this application, the sum of the areas of the plurality of through holes is 1.2 mm. 2 ~573.4mm 2 If the target current collector only includes the first current collector 310, the sum of the areas of the multiple through holes refers to the sum of the areas of all the first through holes 314 on the first current collector 310; if the target current collector only includes the second current collector 320, the sum of the areas of the multiple through holes refers to the sum of the areas of all the second through holes 324 on the second current collector 320; if the target current collector includes both the first current collector 310 and the second current collector 320, the sum of the areas of the multiple through holes refers to the sum of the areas of all the first through holes 314 on the first current collector 310 and all the second through holes 324 on the second current collector 320.

[0092] For example, the sum of the areas of multiple through holes can be 1.2 mm. 2 30 mm 2 50 mm 2 80 mm 2 100 mm 2 130 mm 2 160mm 2 180mm 2 200mm 2 220mm 2 250mm 2 270mm 2 300mm 2 320mm 2 350mm 2 380mm 2 400mm 2 450mm2 480mm 2 500mm 2 573.4mm 2 Etc. This embodiment does not limit the specific value of the sum of the above areas; those skilled in the art can adjust it according to requirements, such as within 1.2 mm. 2 ~573.4mm 2 Choose from the range.

[0093] In this embodiment, the sum of the areas of the multiple through holes is 1.2 mm. 2 ~573.4mm 2 Selecting within the range can avoid the problem that the target current collector is not strong enough due to the sum of the above areas being too large, which would affect the welding strength with the first electrode ear 120 and the current output terminal on the housing; it can also avoid the problem that the sum of the above areas is too small, which would prevent the formation of an effective tear path, affecting pressure relief and causing untimely pressure relief.

[0094] In one specific embodiment of this application, the thickness of any region of the target current collector ranges from 0.2mm to 1.2mm. It should be noted that when different regions of the target current collector have different thicknesses, the thickness range of each region must fall within the range of 0.2mm to 1.2mm. When the target current collector includes both a first current collector 310 and a second current collector 320, and the thicknesses of the first current collector 310 and the second current collector 320 are different, the thickness range of both the first current collector 310 and the second current collector 320 must fall within the range of 0.2mm to 1.2mm.

[0095] For example, the thickness of the corresponding area of ​​the target current collector can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, etc. This embodiment does not limit the specific value of the above thickness; those skilled in the art can select a value within the range of 0.2mm to 1.2mm according to their needs.

[0096] In this embodiment, the thickness of the target current collector is selected within the range of 0.2mm to 1.2mm. This avoids the problems of difficulty in breaking through and untimely pressure relief caused by excessive thickness, and also avoids the problem of insufficient strength caused by insufficient thickness, which would affect the welding strength with the first electrode ear 120 and the current output terminal on the outer casing.

[0097] In a specific embodiment of this application, Tμm ranges from 15μm to 100μm. For example, Tμm can be 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, etc. This embodiment does not limit the specific value of Tμm; those skilled in the art can select it within the range of 15μm to 100μm according to their needs.

[0098] In this embodiment, the grain size Tμm of the target current collector material is selected within the range of 15μm to 100μm. This avoids the situation where the yield strength of the target current collector is too low due to an excessively large Tμm, making it prone to deformation under vibration, compression, heat, etc., which could cause the solder joint between the first electrode lug 120 and the target current collector to be partially or completely torn off, thus affecting the welding strength between the target current collector and the first electrode lug 120 and the current output terminal on the casing. It also avoids the situation where the strength of the target current collector is too high due to an excessively small Tμm, making it difficult to deform under the impetus of high-temperature and high-pressure ejected material during thermal runaway, which could block the pressure relief passage during pressure relief and lead to untimely pressure relief.

[0099] Furthermore, the target current collector includes a third region and a fourth region, with the thickness of the third region being less than that of the fourth region. The first welding area 301 is located in the third region. In other words, the first welding area 301 for welding with the first electrode tab 120 is located in the thinner third region. When the thickness of the third region is obtained through processes such as stamping, the grain size Tμm of the third region becomes smaller, making the strength of the third region greater than that of the fourth region. By placing the first welding area 301 in the third region, the connection strength between the target current collector and the first electrode tab 120 can be improved.

[0100] When the thickness of the third region is obtained through processes such as milling, grinding, and casting, and the grain size Tμm of the third region and the fourth region are the same, but the thickness of the third region is thinner, the first welding area 301 is set in the third region, making it easier to tear the area where the target current collector is welded to the first electrode ear 120, so as to open the pressure relief passage and relieve pressure in time.

[0101] In a specific embodiment of this application, the target current collector is made of a first metal, which is either copper or aluminum, and the mass percentage of the first metal is greater than or equal to 90% (when the first metal is copper, the mass percentage is greater than or equal to 99%; when the first metal is aluminum, the mass percentage is greater than or equal to 90%). The first metal is primarily selected from metals with better current transmission performance. Preferably, it also includes a second metal, such as one or more of manganese, magnesium, aluminum, copper, iron, nickel, zinc, titanium, chromium, carbon, silicon, and nitrogen. The addition of the second metal can improve the current carrying performance, weldability, structural strength, melting point, high-temperature softening point, and corrosion resistance of the target current collector. This type of doping element can be selected according to actual needs.

[0102] In a specific embodiment of this application, M is 0.05 to 0.4. For example, M can be 0.05, 0.07, 0.1, 0.13, 0.15, 0.18, 0.2, 0.22, 0.25, 0.27, 0.3, 0.32, 0.35, 0.38, 0.4, etc. This embodiment does not limit the specific value of M; those skilled in the art can select it within the range of 0.05 to 0.4 according to their needs.

[0103] In this embodiment, the ratio M of the solder area of ​​the first welding area 301 to the end face area of ​​the cell body 110 is selected within the range of 0.05 to 0.4. This avoids the situation where M is too large, resulting in an excessively large solder area of ​​the first welding area 301, leading to excessively strong connection between the target current collector and the first tab 120. In this case, when the battery is depressurized, the first tab 120 pulls on the target current collector, making it difficult for the target current collector to deform and make way for the depressurization path, thus making it difficult for the two to break through and causing the target current collector to block the depressurization path. On the other hand, it also avoids the situation where M is too small, resulting in an insufficient solder area of ​​the first welding area 301, leading to insufficient connection strength between the target current collector and the first tab 120. This would cause the first tab 120 and the target current collector to tear during normal use of the cylindrical battery. Furthermore, an excessively small first welding area 301 would also weaken the battery's current carrying capacity, increase the resistance at the solder joint, and may lead to increased battery heat generation and inducing thermal runaway.

[0104] In a specific embodiment of this application, K is 0.09 to 0.64. Exemplarily, K can be 0.09, 0.1, 0.13, 0.15, 0.18, 0.2, 0.22, 0.25, 0.27, 0.3, 0.32, 0.35, 0.38, 0.4, 0.45, 0.5, 0.55, 0.6, 0.64, etc. This embodiment does not limit the specific value of K; those skilled in the art can select it within the range of 0.09 to 0.64 according to their needs.

[0105] In this embodiment, the ratio K of the area enclosed by the weak part 212 to the area of ​​the first end face 210 is selected within the range of 0.09 to 0.64. This avoids the problem that if K is too large, the area enclosed by the weak part 212 will be too large, making the weak part 212 difficult to process, and the uniformity of the weak part 212 cannot be guaranteed. In addition, the large area may lead to a reduction in the valve opening pressure limit under vibration, impact, corrosion and other conditions, resulting in abnormal valve opening and premature pressure release. On the other hand, it also avoids the problem that if K is too small, the area enclosed by the weak part 212 will be too small, resulting in an insufficient pressure relief port area and untimely pressure release.

[0106] In a specific embodiment of this application, the first electrode tab 120 includes a first positive electrode tab 121 and a first negative electrode tab 122, which are led out from the same end face of the battery cell body 110. Correspondingly, the target current collector includes a first current collector 310 and a second current collector 320, which are respectively welded to the first positive electrode tab 121 and the first negative electrode tab 122.

[0107] Since the first electrode ear portion 120 includes positive and negative electrodes (first positive electrode ear 121 and first negative electrode ear 122), target current collectors need to be provided for the first positive electrode ear 121 and the first negative electrode ear 122 respectively. That is, the target current collectors include the first current collector 310 and the second current collector 320. Therefore, compared to the first electrode ear portion 120 which only includes an electrode ear of one polarity (that is, the target current collector only includes one of the first current collector 310 and the second current collector 320), the areas of the first current collector 310 and the second current collector 320 are smaller, and the area of ​​the first welding area 301 (first current collector welding area 311 and second current collector welding area 321) is smaller.

[0108] Based on this, in this embodiment, the range of T×K / M is 5.0~950, that is, T×K / M is selected within a smaller range to ensure the connection strength between the target current collector and the first electrode 120, and to avoid the problem that the current transmission efficiency between the first electrode 120 of the cylindrical battery and the current output terminal on the casing is too low due to insufficient connection strength.

[0109] For example, T×K / M can be 5.0, 60, 110, 160, 210, 250, 310, 360, 410, 450, 510, 560, 600, 700, 800, 900, 950, etc. This embodiment does not limit the specific value of T×K / M; those skilled in the art can select a value within the range of 5.0 to 950 according to their needs.

[0110] In one specific embodiment of this application, the battery cell 100 further includes a second tab. The first tab 120 and the second tab have opposite polarities and are respectively led out from two opposite end faces of the battery cell body 110. That is, in this embodiment, the two polarity tabs of the battery cell 100 are respectively led out from both ends of the battery cell body 110. This allows the first tab 120 facing the first end face 210 to have only one polarity tab, so the target current collector only includes one of the first current collector 310 and the second current collector 320. The target current collector has a disc-shaped structure with a large area, and when the battery experiences thermal runaway, the target current collector provides a large area of ​​shielding the pressure relief path.

[0111] Based on this, the ratio K of the area enclosed by the weak portion 212 to the area of ​​the first end portion 210 is 0.16 to 0.64. That is, in this embodiment, K is selected within a larger range so that the weak portion 212 has a larger enclosed area, so that when the weak portion 212 bursts open to release pressure, a larger pressure relief port can be formed to ensure timely pressure relief.

[0112] For example, K can be 0.16, 0.19, 0.21, 0.23, 0.26, 0.28, 0.31, 0.33, 0.36, 0.39, 0.42, 0.46, 0.51, 0.56, 0.62, 0.64, etc. This embodiment does not limit the specific value of K; those skilled in the art can select it within the range of 0.16 to 0.64 according to their needs.

[0113] like Figure 1 and Figure 13 As shown, the battery cell body 110 includes a core hole 130, which is located at the center of the battery cell winding structure. The core hole 130 is generally formed when, during the battery cell winding process, the electrode sheets are continuously wound along the outer periphery of the winding needle, forming the negative electrode sheet, separator, and positive electrode sheet. After winding, the core is formed, and the winding needle is pulled out to form the core hole 130.

[0114] In a cylindrical battery, the winding hole 130 is located at the axis of the entire cell body 110. During charging and discharging, the cell 100 generates heat, and good heat dissipation is crucial for maintaining its performance and safety. The winding hole 130 can assist in heat dissipation to some extent; air or other media can flow within the winding hole 130, carrying away some heat and reducing the temperature gradient inside the cell 100. The winding hole 130 also allows for better expansion of the inner electrode plates of the cell body 110, providing electrolyte wetting and internal venting space.

[0115] For ease of understanding, the end of the battery cell body 110 facing the first end face 210 is defined as the target end face of the battery cell. Along the radial direction of the target end face of the battery cell, the distance X mm between the first electrode tab 120 and the winding hole 130 ranges from 0.5 mm to 10 mm. For example, the distance X mm between the first electrode tab 120 and the winding hole 130 can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, etc. This embodiment does not limit the specific value of X mm; those skilled in the art can select a value within the range of 0.5 mm to 10 mm according to their needs.

[0116] This configuration avoids the first electrode ear 120 blocking the core hole 130, ensuring that in the event of thermal runaway, the thermal runaway gas generated below the cell body 110 can be quickly discharged towards the pressure relief port through the core hole 130, thus ensuring timely pressure relief.

[0117] In one specific embodiment of this application, the area enclosed by the core hole 130 and the weak portion 212 is arranged opposite to each other. In other words, the core hole 130 can be directly opposite the area enclosed by the weak portion 212, that is, the core hole 130 and the area enclosed by the weak portion 212 are coaxial; in addition, the core hole 130 can also be eccentrically arranged with respect to the area enclosed by the weak portion 212, as long as the projection of the core hole 130 on the area enclosed by the weak portion 212 falls completely within the area enclosed by the weak portion 212. This arrangement can further improve the timeliness of pressure relief. Of course, the area enclosed by the core hole 130 and the weak portion 212 can also be staggered.

[0118] like Figure 14 and Figure 15 As shown, in a specific embodiment of this application, the weak portion 212 includes a closed annular groove ( Figure 14 In this structure, the weak point 212, after thermal runaway, forms a continuous closed ring structure, and therefore its entire path will break, causing the area enclosed by the weak point 212 to detach from the first end face 210. Because the weak point 212 can detach from the outer shell as a whole, the area of ​​the pressure relief port formed is larger.

[0119] Furthermore, the weak portion 212 includes a discontinuous groove having a first end point 2121 and a second end point 2122. Figure 15The distance between the first end point 2121 and the second end point 2122 of the discontinuous groove is 2mm to 20mm. For example, the distance between the first end point 2121 and the second end point 2122 of the discontinuous groove can be 2mm, 5mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, etc. This embodiment does not limit the specific value of the above-mentioned distance; those skilled in the art can select a value within the range of 2mm to 20mm according to their needs.

[0120] It should be noted that when the weak part 212 is an arc-shaped structure, the distance between its first endpoint 2121 and second endpoint 2122 refers to the arc length between the first endpoint 2121 and the second endpoint 2122 (an arc length with the same radius as the weak part 212). When the weak part 212 is a polygon, the distance between its first endpoint 2121 and second endpoint 2122 refers to the straight-line distance between the first endpoint 2121 and the second endpoint 2122.

[0121] The weak part 212 is a discontinuous groove, meaning that the edge of the weak part 212 is not closed. When the cylindrical battery reaches the pressure relief, the weak part 212 of this structure will not detach from the first end face 210, but will bend open, with the part between the first end face 2121 and the second end face 2122 serving as the bending end. After the weak part 212 breaks, the area it encloses will flip open to relieve pressure, with the bending end as the rotation center. This can prevent the structure of the entire area enclosed by the weak part 212 from flying out when the pressure relief mechanism opens.

[0122] like Figure 10 and Figure 11 As shown, in a specific embodiment of this application, the first end face 210 includes an end face recess 213, and a weak portion 212 is disposed on the bottom wall of the end face recess 213. This arrangement ensures that the opening end of the weak portion 212 is located within the end face recess 213, maintaining a certain distance from the upper surface of the first end face 210 (this distance can be determined by the depth of the end face recess 213). When the first end face 210 is impacted by other components, the impact will not directly affect the weak portion 212, thus preventing the weak portion 212 from rupturing in a non-thermal runaway state. Furthermore, the fact that the weak portion 212 is disposed on the bottom wall of the end face recess 213 also allows the first end face 210 to have a thinner wall thickness at the weak portion 212, which is more conducive to the weak portion 212 being ruptured and depressurized during thermal runaway.

[0123] In a specific embodiment of this application, under the condition of meeting the target, Tμm is 25μm to 100μm. The range of Tμm is 25μm to 100μm. For example, Tμm can be 25μm, 28μm, 32μm, 38μm, 42μm, 46μm, 51μm, 56μm, 61μm, 66μm, 71μm, 76μm, 81μm, 86μm, 92μm, 97μm, 100μm, etc. This embodiment does not limit the specific value of Tμm, and those skilled in the art can select it within the range of 25μm to 100μm according to their needs.

[0124] In this embodiment, Tμm is selected within a large range so that the target current collector has a large deformation capacity and a small strength. This allows the target current collector to be torn and deformed when the pressure inside the cylindrical battery exceeds the pressure relief threshold, thus opening the pressure relief path and ensuring timely pressure relief.

[0125] The target conditions include at least one of the first and second conditions. The first condition includes: the diameter of the first end face 210 is greater than or equal to 40 mm; the second condition includes: the axial height of the cylindrical battery is greater than or equal to 70 mm. In this embodiment, both the first and second conditions result in a larger cylindrical battery size, meaning a larger capacity, more severe thermal runaway, and more ejected material. Based on this, selecting Tμm within the range of 25 μm to 100 μm ensures that the target current collector is more prone to deformation and tearing, forming a larger pressure relief path and improving pressure relief efficiency.

[0126] The test method for the grain size of the target current collector disclosed in the embodiments of this application can be tested with reference to GB / T 6394-2017.

[0127] The grain size of the target current collector can be controlled by adjusting the material selection (e.g., using copper, aluminum, or their alloys) and regulating the content of doping elements (e.g., Si, Fe, Mn, Cu, Mg, Cr, Zn, Ti, etc.) in the metal material. Alternatively, the initial grain size can be refined or enlarged by intervening in the nucleation rate during the solidification process of the liquid metal (increasing the cooling rate, such as metal mold casting or water-cooled molds, can significantly increase the nucleation rate) and crystal growth rate. Another approach is to heat-treat the metal material of the target current collector, performing recrystallization annealing, and controlling the annealing temperature and time to transform the deformed structure into fine equiaxed grains. Furthermore, high-density dislocations can be introduced into the metal material of the target current collector through cold working, followed by heat treatment to trigger recrystallization and achieve microstructural reconstruction, i.e., by using processes such as rolling, extrusion, and drawing.

[0128] The measurement methods for dimensions and areas disclosed in this application can be implemented using measuring instruments such as micrometers or calipers to measure parameters such as length, width, distance, thickness, and diameter. The area is calculated from the measured parameters such as length, width, distance, thickness, and diameter.

[0129] The ratio M between the solder area of ​​the first welding zone 301 and the end face area of ​​the cell body 110 is M = S1 / S2. The solder area S1 of the first welding zone 301 is the total area of ​​the region surrounding the solder edge of the first welding zone. The end face area of ​​the cell body 110 is the area of ​​the outermost perimeter of the cell. If the radius of the cell body 110 is r1, then the end face area S2 of the cell body 110 is S2 = π × r1. 2 .

[0130] The ratio K of the area enclosed by the weak portion 212 to the area of ​​the first end portion 210 is K = S3 / S4. The area enclosed by the weak portion 212 is S3, and the battery radius of the outer shell 230 is r2 (the radius of the first end portion 210 is equal to the battery radius of the outer shell 230). The area S4 of the first end portion 210 is S4 = π × r2. 2 .

[0131] The cylindrical battery disclosed in this application is prepared as follows.

[0132] (1) Preparation of the positive electrode: The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., PVDF, the Chinese name for PVDF is polyvinylidene fluoride) are mixed, and solvent NMP (N-Methylpyrrolidone) 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, air-dried at room temperature, and then transferred to an oven for further drying. Finally, the positive electrode sheet is obtained by rolling and slitting.

[0133] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98): (4~1): (4~1).

[0134] (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.

[0135] Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0136] (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.

[0137] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0138] (5) Preparation of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a battery cell. After the first electrode tab of the battery cell is welded to the current collector, it is placed in the casing of a cylindrical battery, and the current collector is welded on. The battery is dried, electrolyte is injected, and after encapsulation, settling, formation, and volume adjustment, a lithium-ion battery is obtained.

[0139] In the selection of materials for the battery, this application may also select other materials, not limited to the materials 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 negative electrode active material may be selected from one or more negative electrode active main materials, such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0140] The 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.

[0141] The adhesive includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-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.

[0142] The solvent can be deionized water, NMP (N-methylpyrrolidone), alcohol, ether, ketone or other types of pyrrolidone, etc.

[0143] The positive electrode current collector foil can be a metal foil or a composite current collector. For example, as a metal foil, it can be made of stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium with a silver-plated surface. The composite current collector 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, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0144] The negative electrode current collector foil can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium, and can be surface-plated with silver. Composite current collectors may include a polymer base layer and a metal layer. Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on a polymer base material (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0145] The materials used for current collectors include, but are not limited to, metals or alloys such as copper, iron, aluminum, stainless steel, aluminum alloy, titanium, and magnesium. They can be manufactured through methods such as casting, forging, stamping, cutting, die cutting, 3D printing, and metal injection molding.

[0146] This application discloses two test methods, namely Test Method 1 and Test Method 2. Test Method 1 is for testing the tear ratio between the first electrode tab and the target current collector, and Test Method 2 is for testing the casing damage ratio during battery thermal runaway. The specific test procedures for Test Method 1 and Test Method 2 are as follows.

[0147] Test Method 1: Tear ratio between the first electrode ear and the target current collector.

[0148] Following the battery fabrication method described above, 100 cylindrical batteries were prepared for each embodiment and comparative example. These prepared cylindrical batteries were used as samples, and all other testing conditions remained consistent. The 100 cylindrical batteries from the same embodiment or comparative example were then assembled into a battery pack.

[0149] Next, install the battery pack on the vibration table according to the requirements of GB / T2423.43. The testing process shall be carried out in accordance with the provisions of GB / T2423.56. Apply random and fixed-frequency vibration loads in each direction respectively. The loading sequence should preferably be random z-axis, fixed-frequency z-axis, random y-axis, fixed-frequency y-axis, random x-axis, fixed-frequency x-axis (the direction of the line connecting the front and rear of the battery pack is the x-axis direction, and the other horizontal direction perpendicular to the x-axis direction is the y-axis direction). The vibration frequency, power spectral density (PSD), vibration time, etc. are shown in the table below.

[0150]

[0151] After vibration, disassemble the cylindrical battery and observe the first welding area between the first tab and the target current collector. Record the number of batteries where the first tab is disconnected from the target current collector or where the first tab is torn; these are called "tab-torn batteries". If the number of tab-torn batteries is greater than 5, they are considered unqualified; if the number is greater than 3 but less than or equal to 5, they are considered qualified; if the number is less than or equal to 3, they are considered good.

[0152] Test Method 2: Percentage of casing damage during battery thermal runaway.

[0153] Following the battery fabrication method described above, 150 cylindrical batteries were prepared for each embodiment and comparative example. These prepared cylindrical batteries were used as samples, and all other testing conditions remained consistent. The cylindrical batteries were charged at a current of 1C until the upper voltage limit was reached, and then charged at a constant voltage until the current dropped to 0.05C.

[0154] A heating element is placed on the periphery of the battery casing to heat the triggering object at the maximum power of the heating device. Triggering stops and the heating device is shut off when thermal runaway occurs or the temperature at the monitoring point reaches 300°C. The thermal runaway determination criteria are: a voltage drop occurs at the triggering object, and the drop exceeds 25% of the initial voltage; or the temperature rise rate at the monitoring point, dT / dt, is ≥ 1°C / s and lasts for more than 3 seconds.

[0155] Record the number of cylindrical batteries that experienced thermal runaway, N1. After the pressure relief is completed, observe the casing of the thermally runaway cylindrical batteries to see if the casing cracked outside the pressure relief mechanism (outside the area enclosed by the weak point). Record the number of cylindrical batteries with cracked casings, N2. The casing damage rate during battery thermal runaway is calculated as (N2 / N1) × 100%. If the casing damage rate during battery thermal runaway is greater than 4%, it is considered unqualified; if the casing damage rate during battery thermal runaway is greater than 2% and less than or equal to 4%, it is considered qualified; if the casing damage rate during battery thermal runaway is less than or equal to 2%, it is considered good.

[0156] Different systems require corresponding adjustments to their upper and lower voltage limits: Lithium iron phosphate (LFP) - upper limit 3.65V, lower limit 2.5V; Nickel-cobalt-manganese ternary NCM - upper limit 4.25V, lower limit 2.5V; Lithium manganese iron phosphate (LFMP) - upper limit 4.25V, lower limit 2.5V; Lithium nickel manganese oxide - upper limit 4.8V, lower limit 3.5V.

[0157] In this test, the active material for the positive electrode of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2Taking O2 as an example, 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 the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2. Please refer to the table below for the results of the two tests.

[0158] Table 1 Comparison of Tear Ratio and Fragmentation Ratio

[0159] As can be seen from Table 1, in Examples 1-11, 13 and 17, the value of T×K / M falls within the range of 5 to 609.7, and meets the limited range of 5.0 to 1013.3 for T×K / M, and is on the smaller side of the limited range. After testing, it can be seen that the tear ratio of the first electrode ear and the target current collector is in good condition.

[0160] In Examples 12, 14-16, and 18, the value of T×K / M falls within the range of 631.3 to 1013.3, which meets the limit range of 5.0 to 1013.3 for T×K / M. Moreover, it is a relatively large value within the limit range. After testing, it can be seen that the tear ratio of the first electrode ear and the target current collector are both in a qualified state.

[0161] In Examples 4-16 and Example 18, the value of T×K / M falls within the range of 21.9 to 1013.3, which meets the limit range of 5.0 to 1013.3 for T×K / M. After testing, it can be seen that the proportion of casing damage during battery thermal runaway is in good condition.

[0162] In Examples 1-3 and Example 17, the value of T×K / M falls within the range of 5-10.4, which meets the limit range of 5.0-1013.3 for T×K / M, and is on the smaller side of the limit range. After testing, it can be seen that the proportion of casing damage during battery thermal runaway is in a qualified state.

[0163] In Examples 4-11 and Example 13, the value of T×K / M falls within the range of 21.9 to 609.7, which meets the limit range of 5.0 to 1013.3 for T×K / M and is in the middle range of the limit range. After testing, it can be seen that the tear ratio of the first electrode ear to the target current collector and the shell damage ratio during battery thermal runaway are both in good condition.

[0164] Comparative Examples 1 and 3 show that the values ​​of T×K / M fall within the range of 3.4 to 3.9, which does not meet the limit range of 5.0 to 1013.3 for T×K / M. This is lower than the lower limit of the limit range of T×K / M. After testing, it can be seen that although the tear ratio between the first electrode tab and the target current collector is in good condition, the casing damage ratio during battery thermal runaway is unqualified.

[0165] Comparative Example 2 shows that the value of T×K / M is 1201.3, which does not meet the limit range of 5.0~1013.3 of T×K / M and exceeds the upper limit of the limit range of T×K / M. After testing, it can be seen that although the damage ratio of the casing during battery thermal runaway is in good condition, the tear ratio between the first electrode tab and the target current collector is unqualified.

[0166] As illustrated in this application, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. An element defined by the phrase "comprising an..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0167] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0168] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0169] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A cylindrical battery, characterized in that, The device includes a housing and a battery cell (100) and a current collector (300) disposed within the housing. The housing includes a housing body (230) and a first end face (210) disposed at one end of the housing body (230). The first end face (210) includes a first end face body and a weak portion (212) disposed on the first end face body. The thickness of the weak portion (212) is less than the thickness of the first end face body. The battery cell (100) includes a battery cell body (110) and a first tab (120) extending toward the first end face (210). The current collector (300) includes a target current collector disposed between the first end face (210) and the first tab (120). The first tab (120) is welded to the target current collector, and a first welding area (301) is formed on the target current collector. The grain size of the material of the target current collector is Tμm, the ratio of the solder area of ​​the first welding area (301) to the end face area of ​​the cell body (110) is M, the ratio of the area enclosed by the weak part (212) to the area of ​​the first end face (210) is K, and the range of T×K / M is 5.0~1013.

3.

2. The cylindrical battery according to claim 1, characterized in that, The target current collector includes a second welding area (302) configured to be welded to the current output terminal on the housing; A buffer structure is provided between the first welding area (301) and the second welding area (302).

3. The cylindrical battery according to claim 2, characterized in that, The shortest distance between the first welding area (301) and the second welding area (302) is 1mm to 15mm.

4. The cylindrical battery according to claim 2, characterized in that, The first welding area (301) and the second welding area (302) have a height difference in a direction perpendicular to the first end face (210).

5. The cylindrical battery according to claim 4, characterized in that, The height difference between the first welding area (301) and the second welding area (302) along the direction perpendicular to the first end face (210) is 0.5mm to 4mm.

6. The cylindrical battery according to claim 2, characterized in that, The buffer structure includes at least one of a buffer notch, a buffer groove, and a through hole.

7. The cylindrical battery according to claim 1, characterized in that, The target current collector includes a first region and a second region, wherein the grain size of the first region is larger than the grain size of the second region.

8. The cylindrical battery according to claim 7, characterized in that, The first welding zone (301) is located in the first region.

9. The cylindrical battery according to claim 8, characterized in that, The target current collector includes a second welding area (302) disposed in a second region, and the second welding area (302) is configured to be welded to the current output terminal on the housing.

10. The cylindrical battery according to claim 8, characterized in that, The area of ​​the first region is smaller than the area of ​​the second region.

11. The cylindrical battery according to claim 7, characterized in that, The first welding area (301) is disposed in the second region, and the area of ​​the first welding area (301) is 20 mm. 2 ~400mm 2 .

12. The cylindrical battery according to claim 1, characterized in that, The target current collector includes one of a first current collector (310) and a second current collector (320), one of the first current collector (310) and the second current collector (320) being a positive current collector and the other being a negative current collector. The target current collector has a thinning recess (315), and the first welding area (301) is disposed in the thinning recess (315). or, The target current collector includes a first current collector (310) and a second current collector (320), one of the first current collector (310) and the second current collector (320) is a positive current collector and the other is a negative current collector. At least one of the first current collector (310) and the second current collector (320) is formed with a thinning recess (315), and the first welding area (301) is disposed in the thinning recess (315).

13. The cylindrical battery according to claim 12, characterized in that, The target current collector is located in the area where the thinning recess (315) is located, and other areas outside the thinning recess (315) are non-recessed areas. The grain size of the recessed area is smaller than the grain size of the non-recessed area. The ratio of the total area of ​​the concave region to the total area of ​​the non-concave region is 0.25 to 4.

14. The cylindrical battery according to any one of claims 1-13, characterized in that, The projection of the target current collector on the target plane is the current collector projection, and the projection of the weak part (212) on the target plane is the weak part projection. The target plane is a plane parallel to the first end face (210), and the current collector projection and the weak part projection at least partially overlap.

15. The cylindrical battery according to any one of claims 1-13, characterized in that, The target current collector is provided with a through hole, which is spaced apart from the first welding area (301).

16. The cylindrical battery according to claim 15, characterized in that, The through holes include multiple holes, which are respectively disposed on opposite sides of the first welding area (301).

17. The cylindrical battery according to claim 16, characterized in that, At least two through holes are respectively disposed on both sides of the first welding area (301), and are symmetrically disposed on both sides of the first welding area (301) along the radial direction of the first end face (210).

18. The cylindrical battery according to claim 15, characterized in that, The sum of the areas of the plurality of through holes is 1.2 mm. 2 ~573.4mm 2 .

19. The cylindrical battery according to any one of claims 1-13, characterized in that, The thickness of any region of the target current collector ranges from 0.2 mm to 1.2 mm; And / or, The range of Tμm is 15μm to 100μm.

20. The cylindrical battery according to claim 19, characterized in that, The target current collector includes a third region and a fourth region, the thickness of the third region is less than the thickness of the fourth region, and the first welding area (301) is located in the third region.

21. The cylindrical battery according to any one of claims 1-13, characterized in that, The target current collector is made of a first metal, which is either copper or aluminum, and the mass percentage of the first metal is greater than or equal to 90%.

22. The cylindrical battery according to any one of claims 1-13, characterized in that, M is 0.05~0.4, and / or K is 0.09~0.

64.

23. The cylindrical battery according to any one of claims 1-13, characterized in that, The first electrode portion (120) includes a first positive electrode and a first negative electrode, which are led out from the same end face of the battery cell body (110), and the range of T×K / M is 5.0~950.

24. The cylindrical battery according to any one of claims 1-13, characterized in that, The battery cell (100) also includes a second tab, the first tab (120) and the second tab have opposite polarities and are respectively led out from two opposite end faces of the battery cell body (110), and K is 0.16~0.

64.

25. The cylindrical battery according to any one of claims 1-13, characterized in that, The cell body (110) includes a core hole (130). The end of the cell body (110) facing the first end face (210) is the target end face of the cell. Along the radial direction of the target end face of the cell, the distance X mm between the first electrode tab (120) and the core hole (130) ranges from 0.5 mm to 10 mm.

26. The cylindrical battery according to any one of claims 1-13, characterized in that, The battery cell body (110) includes a core hole (130), which is disposed opposite to the area enclosed by the weak part (212).

27. The cylindrical battery according to any one of claims 1-13, characterized in that, The weak part (212) includes a closed annular groove; or, The weak part (212) includes a discontinuous groove with a first end point (2121) and a second end point (2122), and the distance between the first end point (2121) and the second end point (2122) of the discontinuous groove is 2mm to 20mm.

28. The cylindrical battery according to any one of claims 1-13, characterized in that, The first end face (210) includes an end face recess (213), and the weak part (212) is disposed on the bottom wall of the end face recess (213).

29. The cylindrical battery according to any one of claims 1-13, characterized in that, Under the condition that the target is met, Tμm is 25μm~100μm; The target condition includes at least one of the first condition and the second condition; The first condition includes: the diameter of the first end face (210) is greater than or equal to 40 mm; The second condition includes: the axial height of the cylindrical battery is greater than or equal to 70 mm.

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