Cylindrical battery and battery pack

Abstract

The application relates to the technical field of batteries, and discloses a cylindrical battery and a battery pack. The cylindrical battery comprises a shell, a first wall of the shell is provided with a pressure relief mechanism, a battery cell, a first tab is led out from a first end face, a first current collecting disc, the first current collecting disc is located at least partially between the first wall and the first end face in a first direction, the first current collecting disc is electrically connected with the first tab and the first wall, or the first current collecting disc is electrically connected with the first tab and an electrode terminal, the hardness of the first current collecting disc is KHV, the interval distance between the first end face and the pressure relief mechanism in the first direction is Hmm, the projection area of the first current collecting disc on the first end face in the first direction accounts for E of the area of the first end face, and 2.8<= (K*E) / H<=90.6 is met. The application can guarantee the battery performance and ensure that the pressure relief mechanism can work in time and effectively under extreme conditions.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to cylindrical batteries and battery packs. Background Technology

[0002] Cylindrical batteries have high internal volume utilization, enabling them to achieve higher energy density. However, in the event of thermal runaway, the explosion-proof valve of a cylindrical battery often fails to release high-temperature, high-pressure gases quickly after opening, leading to excessive internal pressure and potential battery fire or explosion, severely compromising battery safety. Summary of the Invention

[0003] This invention provides a cylindrical battery and battery pack to solve the problem of gas not being able to be discharged quickly when runaway occurs.

[0004] In a first aspect, the present invention provides a cylindrical battery, comprising: a housing including a first wall, the first wall having a pressure relief mechanism; a battery cell disposed within the housing, the battery cell including a first tab extending from a first end face of the battery cell, the first end face and the first wall being disposed opposite each other along a first direction, the first direction being parallel to the axial direction of the cylindrical battery; and a first current collector along the first direction, the first current collector being at least partially located between the first wall and the first end face, the first current collector being electrically connected to the current output terminals of the first tab and the first wall; wherein, the hardness of the first current collector is KHV, the distance between the first end face and the pressure relief mechanism along the first direction is Hmm, and the proportion of the projected area of ​​the first current collector on the first end face along the first direction to the area of ​​the first end face is E, satisfying 2.8≤(K*E) / H≤90.6.

[0005] Beneficial effects: With (K*E) / H in the range of 2.8~90.6, the first manifold can deform moderately during thermal runaway, providing a channel for gas discharge. Simultaneously, it ensures a more rational current flow path, avoiding the problem of reduced current carrying capacity due to excessive internal resistance.

[0006] Secondly, the present invention also provides a battery pack, comprising: the cylindrical battery mentioned in the first aspect.

[0007] Beneficial effects: The battery pack includes the cylindrical battery of the first aspect and has the same technical effects as the cylindrical battery, which will not be described in detail here. Attached Figure Description

[0008] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0009] Figure 1 This is a three-dimensional schematic diagram of a cylindrical battery according to an embodiment of the present invention; Figure 2 This is an exploded view of a cylindrical battery according to an embodiment of the present invention; Figure 3 This is a partial cross-sectional schematic diagram of a cylindrical battery according to an embodiment of the present invention; Figure 4 for Figure 3 A magnified view of a portion of position B in the diagram; Figure 5 This is a schematic diagram of the structure of the first wall in an embodiment of the present invention; Figure 6 This is a cross-sectional view of the first wall in an embodiment of the present invention; Figure 7 for Figure 6 Enlarged view of part A in the middle; Figure 8 This is a schematic diagram of the connection structure of two collector disks connected by an insulating connector according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the structure of the first collector disk according to an embodiment of the present invention; Figure 10 This is a cross-sectional view of the first collector disk according to another embodiment of the present invention.

[0010] Explanation of reference numerals in the attached figures: 10-Shell; 11-First wall; 12-Pressure relief mechanism; 13-Groove; 14-Thinning section; 30-Cell; 31-First tab; 32-Second tab; 301-First end face; 302-Core hole; 41-First collector plate; 411-First connecting portion; 411a-Thinning area; 411b-First solder mark; 412-Second connecting portion; 412a-Second solder mark; 401-Through hole; 402-Notch; 42-Second collector plate; 43-Insulating connector; 50 - Electrode terminal; X - First direction; Y - Radial direction. Detailed Implementation

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

[0012] Cylindrical batteries can achieve higher energy density due to their high volume utilization, but they pose safety hazards under thermal runaway conditions. When the explosion-proof valve opens, high-temperature and high-pressure gases often cannot be discharged quickly due to obstructed exhaust paths, causing a sharp increase in internal pressure and ultimately leading to a battery explosion, seriously affecting the battery's safety.

[0013] Research has revealed that the compact internal structure of cylindrical batteries, with a much higher density of components compared to prismatic batteries, results in narrow and easily blocked venting channels. Especially when the current collector and explosion-proof valve are located on the same side of the battery, the metal current collector, due to its high structural strength and melting point, is difficult to deform under gas impact, continuously obstructing the explosion-proof valve area and preventing the effective formation of a pressure relief path. Therefore, ensuring the timely and effective operation of the explosion-proof valve under extreme conditions while maintaining battery electrical performance is a key technical challenge that needs to be addressed.

[0014] In this regard, combined with Figures 1 to 10 This invention provides a cylindrical battery, comprising: a casing 10, a battery cell 30, and a first current collector 41. The casing 10 includes a first wall 11, which is provided with a pressure relief mechanism 12, such as an explosion-proof valve. The battery cell 30 is disposed within the casing 10 and includes a first tab 31 extending from a first end face 301 of the battery cell 30. The first end face 301 and the first wall 11 are disposed opposite each other along a first direction X, which is parallel to the axis of the cylindrical battery. Along the first direction X, the first current collector 41 is at least partially located between the first wall 11 and the first end face 301, and the first current collector 41 is electrically connected to the first tab 31 and the current output terminal of the first wall 11.

[0015] The first manifold 41 has a hardness of KHV, where HV is Vickers hardness; the distance between the first end face 301 and the pressure relief mechanism 12 along the first direction X is H; the proportion of the projected area of ​​the first manifold 41 along the first direction X on the first end face 301 to the area of ​​the first end face 301 is E, satisfying 2.8 ≤ (K*E) / H ≤ 90.6. For example, it can be one of 2.8, 10, 20, 30, 40, 50, 60, 70, 80, 90, 90.6, or any value between two of them. Preferably, the range of (K*E) / H satisfies: 6.2 ≤ (K*E) / H ≤ 51.3.

[0016] A cylindrical battery is a battery with a cylindrical shape. The cell 30 of a cylindrical battery is typically wound into a cylindrical shape and encapsulated inside a metal casing 10. The cell 30 is the component in the battery where electrochemical reactions occur; it is the smallest unit in the battery capable of electrochemical reactions such as charging / discharging. It typically includes a positive electrode, a negative electrode, and a separator. Lithium-ion cells primarily function by the movement of lithium ions between the positive and negative electrodes. In a cylindrical cell, a three-layer thin-film structure is wound into a cylindrical electrode assembly.

[0017] The casing 10 is a protective structure for the cylindrical battery, typically made of metal, used to house and protect the battery cell 30. The casing 10 can be made of metals or alloys including, but not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, titanium, and magnesium.

[0018] The first wall 11 is part of the housing 10 and can be integrally formed with the housing 10. It can also be a separate structure; for example, the first wall 11 can be the top cover or bottom end cover of a cylindrical battery. The first wall 11 is disc-shaped. A pressure relief mechanism 12 is provided on the first wall 11. When the internal pressure of the battery abnormally increases, i.e., after reaching a certain pressure, the pressure relief mechanism 12 is opened or ruptured to release the internal gas and prevent the battery housing 10 from exploding. The pressure relief mechanism 12 can be implemented in various forms. For example, the pressure relief mechanism 12 can be a thinned portion 14 formed on the first wall 11. Figure 7 As shown, when the internal pressure reaches a certain threshold, the thinned part 14 ruptures; the pressure relief mechanism 12 can also be an explosion-proof valve, which opens under pressure through a spring or diaphragm structure when the internal pressure reaches a certain threshold.

[0019] Specifically, the pressure relief mechanism 12 achieves pressure relief by thinning the pressure relief sheet to form a thinned portion 14. The thinned portion 14 forms a groove, which can be formed on the side near the battery cell, the side away from the battery cell, or both sides. The groove can be a V-shaped groove, a U-shaped groove, or a trapezoidal groove, etc. The thinned portion 14 can be continuous, forming a groove similar to a complete circle on the pressure relief mechanism 12. Continuous thinning allows for a larger pressure relief opening area and more timely pressure relief. Alternatively, it can be discontinuous, with the two ends of the discontinuous groove close to each other, with a spacing between 2mm and 20mm, ensuring that the pressure relief mechanism 12 remains connected to the battery during pressure relief and preventing parts from flying out with the high-temperature and high-pressure gas. Stamped reinforcing ribs can be formed around the outer periphery of the area enclosed by the thinned portion 14 to prevent the high-temperature and high-pressure ejected material from tearing the pressure relief mechanism 12 and the battery casing during pressure relief, thus ensuring the structural strength of the battery. The pressure relief mechanism 12 and the first wall 11 can be integrally connected, that is, the thinning part 14 is made by setting grooves on the first wall 11 through stamping, laser or mechanical etching. The pressure relief mechanism 12 can also be a separate structure from the first wall 11. For example, the pressure relief mechanism 12 is an independently manufactured pressure relief plate, and the pressure relief plate is fixedly connected to the first wall 11 by welding, bonding or other methods.

[0020] The first tab 31 is an electrode connection point led out from the battery cell 30, used to lead the current inside the battery cell 30 to an external circuit or other components of the battery. The first tab 31 can be a positive tab or a negative tab. The first tab 31 can be a tab cluster, containing multiple first tabs 31, with at least one first tab 31 disposed between the battery cell body and the first wall 11. The first tab 31 is disposed on one side of the positive or negative current collector, and is separately / integrated with the current collector, electrically connected to the current collector to conduct the current on the corresponding current collector. The first tab 31 is made of a metal material with good conductivity (such as copper, aluminum, nickel, or their alloys).

[0021] The first end face 301 is the end surface of the battery cell 30 facing the first wall 11, which is usually the end face of the body of the battery cell 30.

[0022] The first current collector 41, as a conductive component, collects the current from the first tab 31 of the battery cell 30 and transmits it to the first wall 11 or the electrode terminal 50 disposed on the first wall 11. For example, the first current collector 41 can be welded to both the first tab 31 and the first wall 11, and the welding can be performed by at least one of resistance welding, ultrasonic welding, laser welding, etc. Of course, if necessary, the first current collector 41 can be electrically connected to the first tab 31 and the first wall 11 by riveting, pressing, or bonding.

[0023] The material of the first current collector 41 includes, but is not limited to, metals or alloys such as copper, iron, aluminum, stainless steel, aluminum alloy, titanium, and magnesium. The specific material of the first current collector 41 is selected based on the materials of the first wall 11 and the first tab 31 of the battery. For example, the material of the first current collector 41 can be the same as the materials of the first tab 31 and the first wall 11.

[0024] The current output terminal of the first wall 11 can be understood as the first wall 11 serving as a current output terminal, or the first wall 11 being fixedly equipped with a current output terminal (e.g., electrode terminal 50). One end of the first current collector 41 is electrically connected to the first electrode 31, and the other end is electrically connected to the current output terminal to realize the transmission of current between the inside and the outside.

[0025] Electrode terminal 50 is an external connection component disposed on the first wall 11 for electrical connection between the battery and an external circuit. Electrode terminal 50 and the first wall 11 can be insulated from each other, for example, by a plastic component between them. Electrode terminal 50 can be, for example, a post, for example, a through hole formed in the first wall 11 for the post to pass through, and fixed to the first wall 11 by riveting. Alternatively, the post may not penetrate the first wall, but the current collector portion can penetrate the through hole in the first wall and be electrically connected to the post.

[0026] The first direction X is parallel to the axial direction of the cylindrical battery, which is also the length direction of the cylindrical battery.

[0027] The hardness KHV can be adjusted by selecting different materials or by heat treatment, cold working, etc. Hardness HV is Vickers hardness. When the first manifold 41 is made of copper, its hardness can be 70~100 HV; when the first manifold 41 is made of aluminum or aluminum alloy, its hardness can be 30~100 HV. The method for measuring hardness K is described below.

[0028] Hmm is the distance from the first end face 301 (outermost end) of the battery cell to the weakest point of the pressure relief mechanism 12. Figure 4 (As shown). The range of Hmm can be 1~5mm, for example, it can be any one of 1mm, 2mm, 3mm, 4mm, 5mm or any two of them.

[0029] The area of ​​the first end face 301 is the area of ​​the outermost circumference of the battery cell, which is π * the square of the battery cell radius. The range of E can be 0.4 to 0.95. For example, it can be any one of 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95 or any value between two of them.

[0030] By appropriately reducing the hardness KHV of the first manifold 41, it becomes easier for the first manifold 41 to undergo plastic deformation when impacted by internal high-pressure gas, thus creating a channel for gas discharge. The spacing distance H is appropriately increased to provide greater flow space for gas between the first manifold 41 and the pressure relief mechanism 12. The size of the first manifold 41 is adjusted to reduce its projected area ratio E, thereby reducing obstruction of the space between the first end face 301 and the pressure relief mechanism 12.

[0031] By ensuring that the hardness K of the first manifold 41, the distance H between the first end face 301 and the pressure relief mechanism 12, and the proportion E of the projected area of ​​the first manifold 41 on the first end face 301, (K*E) / H is within the range of 2.8 to 90.6, the first manifold 41 can deform appropriately during thermal runaway, providing a channel for gas discharge. Simultaneously, this ensures a more reasonable current flow path, avoiding the problem of reduced current carrying capacity due to excessive internal resistance. Specifically, this avoids situations where the range is too large, with an excessively high K ratio and an excessively low H ratio, leading to difficulty in deforming the current collector and blocking the pressure relief path. This makes it difficult for the battery to release pressure quickly, causing heat concentration inside the battery, excessive battery explosion pressure, and posing a safety risk of internal fire and explosion, affecting the safety performance of adjacent batteries and the overall battery pack. Conversely, if the range is too small, with an excessively low K ratio and an excessively low E ratio and an excessively high H ratio, it can lead to poor soldering of the current collector, high internal resistance of the battery, and slow current transmission rate, affecting the battery's overcurrent capacity and charge / discharge rate. This ensures that the cylindrical battery can release pressure normally under extreme conditions, guaranteeing the battery's safety in use and its structural stability under normal operating conditions, while maintaining its overcurrent capacity.

[0032] In some embodiments, a through hole 401 extending through both sides of the first collector plate 41 in its thickness direction is provided. The through hole 401 can be of various shapes, such as circular, elliptical, square or irregular shapes.

[0033] By providing a through hole 401 on the first manifold 41, the projection of the through hole 401 along the first direction X is at least partially located on the first end face 301, thereby forming a gas flow channel between the first manifold 41 and the first end face 301.

[0034] When an abnormal situation occurs inside the cylindrical battery (such as thermal runaway), the internal gas can directly pass through the through hole 401 on the first current collector 41 and impact the pressure relief mechanism 12. Due to the presence of the through hole 401, the overall structural rigidity of the first current collector 41 is locally weakened to a certain extent, making it more prone to deformation when subjected to internal gas pressure. This helps to further expand the gas flow space and prevent the first current collector 41 from obstructing the pressure relief path due to excessive rigidity. This ensures that the pressure relief mechanism 12 can be activated in a timely and effective manner, significantly improving the safety of the battery.

[0035] In some embodiments, the pressure relief mechanism 12 includes a thinning portion 14 formed on the first wall 11; along the first direction X, the projection of the through hole 401 on the first wall 11 at least partially overlaps with the projection of the thinning portion 14 on the first wall 11; and / or, along the first direction X, the projection of the through hole 401 on the first wall 11 at least partially overlaps with the projection of the winding hole 302 of the battery cell 30 on the first wall 11.

[0036] The thinned portion 14 is a structure on the first wall 11 with lower strength than the surrounding area. When the internal pressure of the battery reaches a preset threshold, the thinned portion 14 can preferentially rupture or deform, thereby achieving timely release of internal pressure. The thinned portion 14 can be formed in various ways, for example, by performing local thinning treatment on the first wall 11 to make its thickness less than other areas; or by engraving a predetermined shape of grooves or notches 13 on the first wall 11 to guide the rupture path.

[0037] The core hole 302 allows for better expansion of the inner electrode sheet of the core, providing electrolyte wetting and internal venting space for the battery. During the cell winding process, the electrode sheets are continuously wound along the outer periphery of the winding needle, forming the core, negative electrode sheet, separator, and positive electrode sheet. The winding needle is then pulled out to form the core hole.

[0038] Along the first direction X, the projection of the through hole 401 on the first wall 11 at least partially overlaps with the projection of the thinned portion 14 on the first wall 11, ensuring that the gas discharged from the through hole 401 of the first manifold 41 can directly or centrally act on the thinned portion 14 on the first wall 11, accelerating the rupture or deformation of the thinned portion 14, thereby achieving rapid and reliable pressure relief. For example, the through hole 401 can be located directly above the thinned portion 14, allowing the gas to impact the thinned portion 14 vertically; or, multiple through holes 401 can be arranged around the thinned portion 14, acting together on the thinned portion 14.

[0039] Along the first direction X, the projection of the through hole 401 on the first wall 11 at least partially overlaps with the projection of the core hole 302 of the battery cell 30 on the first wall 11, providing an exhaust channel from the inside of the battery cell 30 to the through hole 401 on the first collector plate 41. Gas can be discharged more smoothly from the central region of the battery cell 30, ultimately impacting the thinning section 14, improving exhaust efficiency and providing rapid and reliable pressure relief. For example, the center of the through hole 401 is aligned with the central axis of the core hole 302, or the size and position of the through hole 401 can cover a portion of the core hole 302.

[0040] In some embodiments, the area of ​​the core hole 302 is greater than or equal to the area of ​​the through hole 401, and E ranges from 0.4 to 0.9. For example, it can be any one of 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or a range between any two of them.

[0041] When the area of ​​the winding hole 302 is greater than or equal to the area of ​​the through hole 401, the gas generated inside the cell 30 will be obstructed when passing through the winding hole 302 due to the smaller area of ​​the through hole 401, resulting in insufficient smooth gas flow. If the smoothness of gas venting cannot be fully guaranteed, the projected area E of the first current collector 41 can be appropriately reduced to minimize obstruction of the first end face 301 of the cell 30. This ensures that gas can be vented through the perimeter of the first current collector 41, thereby ensuring timely pressure relief and reducing the risk of battery explosion.

[0042] In other embodiments, the area of ​​the core hole 302 is smaller than the area of ​​the through hole 401 to improve gas exhaust normality, in which case Hmm ranges from 1mm to 4mm. For example, it can be any of 1mm, 2mm, 3mm, and 4mm or a range between any two of them.

[0043] The area of ​​the core hole 302 is the projected area of ​​the central through hole along the first direction X after the battery cell is wound. It is obtained by measuring the inner diameter of the core hole through CT scan and calculating it according to the formula for the area of ​​a circle.

[0044] When the area of ​​the winding hole 302 is smaller than the area of ​​the through hole 401, the gas inside the cell 30, after being discharged from the winding hole 302, will enter a relatively larger space in the through hole 401. In the event of an abnormal situation inside the battery (such as thermal runaway), the generated gas can be discharged more smoothly from the battery, effectively reducing internal pressure and preventing battery explosion. Provided that the gas venting is sufficiently unobstructed, the upper limit of H can be appropriately reduced, thereby reducing the current path, lowering internal resistance, and improving current carrying capacity.

[0045] In some embodiments, refer to Figure 8 and Figure 9 The first collector plate 41 is provided with multiple through holes 401, and the minimum spacing D1mm between two adjacent through holes 401 ranges from 3mm to 40mm. For example, it can be any value or any combination of 3mm, 10mm, 20mm, 30mm, and 40mm.

[0046] Multiple through holes 401 can be arranged in an array or irregularly. The shapes of the multiple through holes 401 can be the same or different.

[0047] The minimum spacing D1 between two adjacent through holes 401 is controlled within an appropriate range to ensure that the material between the through holes 401 of the first collector plate 41 has sufficient strength to maintain the structural integrity and current conduction capability of the first collector plate 41, while not hindering the effective deformation or gas flow of the first collector plate 41 due to excessive material.

[0048] By setting multiple through holes 401 on the first current collector 41 and controlling D1, when thermal runaway occurs inside the battery and a large amount of gas is generated, the multiple through holes 401 together provide a larger gas flow cross section, ensuring that the gas can quickly pass through the first current collector 41. At the same time, the multiple through holes 401 reduce the local strength of the first current collector 41, making it more prone to deformation under gas impact, thereby providing a smooth channel for the gas impact relief mechanism 12, ensuring timely pressure relief and reducing the risk of battery explosion. It also avoids the problem of too many holes due to too small a spacing between the multiple through holes 401, which would reduce the effective connection area between the first current collector 41 and the first tab 31 or the first wall 11, and reduce the current carrying capacity.

[0049] In some embodiments, the area of ​​a single through-hole 401 ranges from 2 mm. 2 ~100mm 2 For example, it can be 2mm. 2 10mm 2 20mm 2 30mm 2 40mm 2 70mm 2 90mm 2 100mm 2 The value of any one of them or any two of them.

[0050] The area of ​​a single through hole 401 refers to the cross-sectional area of ​​a single through hole 401 on the first collector plate 41, that is, the projected area of ​​a single through hole 401 along the first direction X on the collector plate.

[0051] The area of ​​a single through-hole 401 is 2mm. 2 ~100mm 2 This ensures sufficient effective welding area between the first current collector 41 and the first tab 31 to maintain low internal resistance and good current carrying capacity, avoiding battery performance degradation due to insufficient welding area. Simultaneously, the appropriate area of ​​the through hole 401 ensures smooth gas discharge, preventing poor venting caused by an excessively small through hole 401, thus enabling timely activation of the pressure relief mechanism 12 and reducing the risk of battery explosion.

[0052] In some embodiments, refer to Figure 8 and Figure 9 Along the radial direction Y of the first collector plate 41, the distance D2mm between the nearest through hole 401 to the edge of the first collector plate 41 and the edge of the first collector plate 41 ranges from 1mm to 10mm. For example, it can be any one of 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm or any two of these values.

[0053] This design avoids the through-hole 401 being too close to the edge of the first collector plate 41, which could reduce the mechanical strength of that area and affect the stability of the electrical connection between the first collector plate 41 and the first wall 11 or electrode terminal 50. For example, it could lead to problems such as incomplete welding or insufficient connection strength during the welding process. At the same time, a reasonable D2mm value ensures that gas can be discharged more quickly through the through-hole 401, thereby effectively impacting the pressure relief mechanism 12 and achieving timely and reliable pressure relief.

[0054] In some embodiments, the first collector plate 41 is provided with a notch 402, which is located at the edge of the first collector plate 41.

[0055] The notch 402 is a non-closed, inwardly recessed opening formed on the edge of the first collector plate 41. The notch 402 can be U-shaped, V-shaped, or arc-shaped.

[0056] By placing the notch 402 at the edge of the first manifold 41, the impact on the electrical connection area between the first manifold 41 and the first tab 31 can be minimized. At the same time, it ensures that when depressurization occurs, gas can be more easily discharged through the edge notch 402, or the notch 402 can be used to guide the deformation of the first manifold 41, thereby providing a smoother discharge channel for the gas.

[0057] In some embodiments, the first collector plate 41 includes a first connecting portion 411 and a second connecting portion 412. The first connecting portion 411 is electrically connected to the first electrode tab 31 via a first solder mark 411b, and the second connecting portion 412 is electrically connected to the first wall 11 or the electrode terminal 50 via a second solder mark 412a. The first collector plate 41 is provided with a through hole 401, which is located between the first connecting portion 411 and the second connecting portion 412. And / or, the first collector plate 41 is provided with a notch 402, which is located at the edge of the first collector plate 41 and between the first solder mark 411b and the second solder mark 412a.

[0058] The first connecting portion 411 and the second connecting portion 412 are areas on the first current collector 41 used to achieve different electrical connection functions. The first connecting portion 411 is the area on the first current collector 41 that is electrically connected to the first electrode tab 31 and is responsible for drawing the current from the battery cell 30. The second connecting portion 412 is the area on the first current collector 41 that is electrically connected to the first wall 11 or the electrode terminal 50 and is responsible for transmitting the current to the outside of the battery. The first connecting portion 411 and the second connecting portion 412 can be an integral structure.

[0059] The notch 402 is located between the first solder mark 411b and the second solder mark 412a. When the battery experiences thermal runaway, the notch 402 acts as a melting or breaking point, quickly cutting off the electrical connection and effectively preventing the cell 30 from continuing to discharge and further accumulating heat, thereby avoiding the aggravation of thermal runaway and reducing the risk of battery explosion. At the same time, after the first current collector 41 melts at the position of the through hole 401 / notch 402, the gas can pass through the first current collector 41 more smoothly and then impact the pressure relief mechanism 12, so that the pressure relief mechanism 12 can release gas in time, further reducing the risk of battery explosion.

[0060] In some embodiments, refer to Figure 10 The first connecting portion 411 has a thinning region 411a, the thickness of which is less than the thickness of the body portion of the first collector plate 41.

[0061] The body portion of the first collector plate 41 refers to the portion of the first collector plate 41 with its original thickness excluding the thinning zone 411a.

[0062] The first connecting portion 411 has a thinning region 411a, which allows for preferential and easier breakage in the event of abnormal conditions such as thermal runaway, thereby quickly severing the electrical connection between the first current collector 41 and the first tab 31, effectively preventing further current transmission and improving battery safety. Furthermore, during welding of the first tab 31 and the first connecting portion 411, the presence of the thinning region 411a reduces the required welding energy, helping to prevent the first tab 31 from being welded through or damaged by excessive welding energy, protecting the integrity of the tab, ensuring welding quality, and thus ensuring good current carrying capacity. Therefore, by providing a thinning region 411a in the first connecting portion 411 of the first current collector 41, both battery safety and electrical performance can be guaranteed.

[0063] In some embodiments, the thickness ratio T1mm of the thinned region 411a to the thickness Tmm of the body portion of the first collector disk 41, T1mm / Tmm, ranges from 0.4 to 0.8. For example, it can be any one of 0.4, 0.5, 0.6, 0.7, 0.8, or a range between any two. The method of forming the thinned portion needs to be described in the specification, such as stamping, etching (chemical etching or laser etching), machining, etc.

[0064] This configuration ensures that the first current collector 41 maintains sufficient mechanical strength and current carrying capacity under normal operating conditions. Simultaneously, in the event of thermal runaway, it ensures that the thinned region 411a can quickly melt or disconnect, effectively severing the electrical connection, preventing further propagation of thermal runaway, and enhancing battery safety.

[0065] In some embodiments, the pressure relief mechanism 12 includes a thinning portion 14 formed on the first wall 11; the first collector plate 41 is welded to the first wall 11 to form a first weld mark 411b, and the projection of the first weld mark 411b on the first wall 11 along the first direction X does not overlap with the projection of the thinning portion 14 on the first wall 11.

[0066] For example, the groove 13 can be formed by locally thinning, etching, stamping or other methods on the first wall 11.

[0067] The projection of the first solder mark 411b on the first wall 11 and the projection of the thinned portion 14 on the first wall 11 do not overlap, meaning that along the first direction X (e.g., the axial direction of the battery), the projection area of ​​the first solder mark 411b on the first wall 11 and the projection area of ​​the thinned portion 14 on the first wall 11 do not share a common portion.

[0068] Since the first weld mark 411b and the thinned portion 14 are spatially separated, the heat and stress generated during the welding process will not directly act on the thinned portion 14, thereby avoiding the adverse effects of welding heat on the thinned portion 14 and ensuring that the thinned portion 14 can rupture in a timely and reliable manner when the internal pressure of the battery rises abnormally, thus achieving effective pressure release.

[0069] In some embodiments, the thinning portion 14 is located inside the first solder mark 411b in the radial direction Y. That is, the thinning portion 14 is located closer to the central axis of the cylindrical battery relative to the first solder mark 411b.

[0070] Since the central area of ​​the cell 30 (such as the area of ​​the core hole 302) produces a large amount of gas, the thinning part 14 is located inside the first solder mark 411b along the radial direction Y, that is, closer to the central area with a large amount of gas. When the battery experiences thermal runaway, the gas can more directly impact the thinning part 14 on the radially inner side, thereby ensuring that the thinning part 14 can rupture or deform in a timely and reliable manner, thereby quickly releasing the internal pressure and preventing the battery casing 10 from exploding.

[0071] In other embodiments, the thinned portion 14 is located on the outer side of the first solder mark 411b in the radial direction Y, with a thickness H ranging from 1.5 mm to 4 mm. The thinned portion 14 is closer to the outer edge of the cylindrical battery relative to the first solder mark 411b. Hmm can be any one of 1.5 mm, 2 mm, 3 mm, 4 mm, or a range between any two.

[0072] By placing the thinning portion 14 on the radially outer side, it can be ensured that the first solder mark 411b is not affected by the thinning portion 14, thereby ensuring good electrical connection performance and overcurrent capacity. In addition, the optimization of the H range ensures that the distance between the first end face 301 and the pressure relief mechanism 12 is neither too large, which would cause the current path to be too long and increase the internal resistance, nor too small, which would limit the space required for pressure relief, thereby providing sufficient buffer and venting space for pressure relief while ensuring electrical performance.

[0073] In some embodiments, the first solder mark 411b includes a first end and a second end, which are spaced apart along the circumference of the first manifold 41, and the distance between the first end and the second end is in the range of 30mm to 80mm. For example, it can be any one of 30mm, 40mm, 50mm, 60mm, 70mm, 80mm or any range between two of them.

[0074] The first weld mark 411b extends circumferentially along the first current collector 41 and has two spaced-apart first and second ends. This makes the first weld mark 411b a non-circular closed structure, such as a half-circle or a quarter-circle, avoiding the excessive rigidity that might result from continuous welding into a full circle. This allows the first wall 11 to more easily deform locally in the non-welded area when subjected to internal pressure. When the internal pressure of the battery abnormally increases, the thinned portion 14 on the first wall 11 needs to rupture promptly to release the pressure. The non-circular first weld mark, while maintaining sufficient electrical connection and mechanical strength, provides the necessary space and path for the deformation of the first wall 11, reducing the obstruction of the welding area to the deformation of the thinned portion 14. The distance between the first end and the second end ranges from 30mm to 80mm, ensuring effective current conduction while allowing the first wall 11 to deform more easily near the thinned portion 14, thereby ensuring the timely and reliable activation of the pressure relief mechanism 12.

[0075] In some embodiments, the first solder mark 411b is in a continuous ring shape along the circumference of the first manifold 41. That is, the first solder mark 411b is complete and uninterrupted in the circumferential direction, forming a closed ring structure.

[0076] This creates a uniform and low-resistance electrical connection path between the first current collector 41 and the first wall 11, effectively reducing contact resistance and ensuring that current can be efficiently and stably transmitted from the first current collector 41 to the first wall 11 or the electrode terminal 50.

[0077] In some embodiments, refer to Figure 7 The first wall 11 has a groove 13 formed on its surface along its thickness direction, and a thinning portion 14 is disposed on the bottom surface of the groove 13. The groove opening of the groove 13 faces the battery cell 30 and / or faces away from the battery cell 30 along the first direction X. Figure 7The groove 13 is shown with its opening facing away from the cell 30.

[0078] The thinning portion 14 is located at the bottom surface of the groove 13, meaning that the thinning portion 14 is located at the deepest part of the groove 13, i.e., the bottom surface of the groove. That is, the thickness of the thinning portion 14 is less than the thickness of the main body portion of the first wall 11.

[0079] By forming a groove 13 on the surface of the first wall 11 along its thickness direction and placing a thinning portion 14 on the bottom surface of the groove 13, when a large amount of gas is generated inside the battery due to an abnormal situation, the internal pressure will accumulate rapidly, and this pressure will act directly on the inner surface of the first wall 11. Since the thinning portion 14 is located on the bottom surface of the groove 13, its thickness is thinner than other areas of the first wall 11, making it more prone to rupture. This ensures that the pressure relief mechanism 12 can be activated in a timely and reliable manner, quickly expelling the internal gas and effectively reducing the risk of battery explosion.

[0080] In some embodiments, the groove 13 is in a continuous ring shape along the circumferential direction of the battery. The groove 13 is complete and uninterrupted in the circumferential direction of the battery, forming a closed ring structure.

[0081] By designing the groove 13 as a continuous ring along the circumference of the battery, the thinned portion 14 is also continuously ring-shaped. This ensures that the pressure is evenly distributed along the entire circumference when subjected to internal pressure impact. The continuously ring-shaped thinned portion 14 can achieve integral rupture, rapidly forming a large-area annular pressure relief channel. This avoids pressure relief delays or failures caused by localized stress concentration or incomplete rupture, ensuring that internal gas can be quickly and fully discharged, thus effectively preventing battery explosion. Furthermore, the continuous annular groove 13 ensures a sufficiently large valve opening area to meet pressure relief requirements. In some embodiments, the groove 13 is a discontinuous structure, meaning it does not cover the entire circumference, preventing the entire metal sheet from flying out when the pressure relief mechanism is activated.

[0082] In some embodiments, the battery cell 30 further includes a second end face. Along the first direction X, the first end face 301 and the second end face are respectively located at both ends of the battery cell 30. A second tab 32 is led out from the second end face. The polarity of the second tab 32 is opposite to that of the first tab 31. The range of (K*E) / H is 5~90.6.

[0083] Opposite polarity means that the first tab 31 and the second tab 32 are connected to the positive and negative terminals of the battery cell 30, respectively. For example, the first tab 31 is connected to the positive current collector of the battery cell 30, and the second tab 32 is connected to the negative current collector of the battery cell 30; or, the first tab 31 is connected to the negative current collector of the battery cell 30, and the second tab 32 is connected to the positive current collector of the battery cell 30.

[0084] During battery charging and discharging, both the positive and negative tabs generate significant heat. If the heat is concentrated at one end, it will be significantly higher than at the other, leading to localized overheating. This can accelerate the response of the pressure relief mechanism 12 at that end or expose it to a greater risk of failure. By distributing the current from the positive and negative electrodes to both ends of the cell 30, excessive heat concentration on a single end face is avoided. In the event of thermal runaway or other abnormal conditions, the pressure relief mechanism 12 can be activated promptly and reliably. Furthermore, due to the more even heat distribution, parameters such as the hardness K of the first current collector 41, the distance H between the first end face 301 and the pressure relief mechanism 12, and the proportion E of the projected area of ​​the first current collector 41 on the first end face 301 can be more precisely optimized. This allows for a reduction in the maximum value of (K*E) / H, thereby improving overall battery safety while ensuring battery performance.

[0085] In some embodiments, a second tab 32 is also led out from the first end face 301. The second tab 32 has the opposite polarity to the first tab 31 and is spaced apart, i.e., positive and negative tabs are led out from the same end. Correspondingly, the first current collector 41 and the second current collector 42 are on the same side as the positive and negative tabs.

[0086] By leading both the first tab 31 and the second tab 32 of the battery cell 30 to the same first end face 301 of the cylindrical battery, and ensuring that the two tabs with opposite polarities are spaced apart, the wiring and connection structure of the battery pack can be simplified. Simultaneously, by controlling the hardness K of the first current collector 41, the distance H between the first end face 301 and the pressure relief mechanism 12, and the proportion E of the projected area of ​​the first current collector 41 on the first end face 301, it can be ensured that the battery's pressure relief safety and electrical performance are still effectively guaranteed even when the positive and negative tabs are concentrated at the same end.

[0087] In some embodiments, the cylindrical battery further includes a second current collector 42, which is electrically connected to the second tab 32. The spacing between the first current collector 41 and the second current collector 42 along the radial direction of the cylindrical battery ranges from 3mm to 40mm. For example, it can be any one of 3mm, 10mm, 20mm, 30mm, and 40mm, or a range between any two of them.

[0088] This design significantly increases the insulation distance between the positive and negative current collectors, effectively reducing the risk of short circuits caused by component concentration and improving battery safety. Since the two current collectors are no longer concentrated at the same end, the space inside the battery for gas venting is further optimized. When the battery experiences abnormal conditions such as thermal runaway, the gas generated inside can be discharged more smoothly through the pressure relief path, avoiding the problems of insufficient venting space or blocked pressure relief paths caused by excessive concentration of current collectors. This ensures that the pressure relief mechanism 12 can be activated promptly and effectively, reducing the risk of battery explosion. Furthermore, it helps to disperse the current path and heat distribution inside the battery, preventing excessive heat concentration at one end, thereby improving the overall performance and cycle life of the battery.

[0089] Optionally, the first collector plate 41 and the second collector plate 42 can be connected by an insulating connector 43 so that the two collector plates form a single unit, which facilitates assembly.

[0090] In some embodiments, the first collector plate 41 and the second collector plate 42 are respectively provided with through holes 401, ranging from 3mm to 35mm.

[0091] Through holes 401 are respectively provided on the first current collector 41 and the second current collector 42 to provide a flow path for the gas inside the battery. When the cell 30 generates a large amount of gas due to abnormal conditions (such as thermal runaway), the gas needs to be discharged quickly to reduce the internal pressure and prevent the casing 10 from rupturing or exploding. By forming through holes 401 through the thickness direction on the bodies of the first current collector 41 and the second current collector 42, more discharge channels are provided for the gas, so that the gas can not only flow radially or circumferentially along the current collector, but also directly pass through the through holes 401 of the current collector, thereby greatly improving the speed and efficiency of gas discharge. Even under extreme gas generation conditions, the gas can quickly reach the pressure relief mechanism 12 to ensure that the pressure relief mechanism 12 is opened in time, further improving the safety of the battery.

[0092] In some embodiments, the thickness of the first manifold 41 ranges from 0.2 mm to 1.2 mm, for example, it can be any one or any two of 0.2 mm, 0.5 mm, 0.8 mm, 1 mm, and 1.2 mm; and / or, the melting point of the first manifold 41 is less than or equal to 670°C. The thickness of the first manifold 41 is the thickness of the body portion of the first manifold 41. Figure 10 T is shown in the figure.

[0093] The melting point of the first current collector 41 is less than or equal to 670°C and higher than the maximum temperature rise of the battery during normal operation (≤80°C), ensuring structural stability during normal operation and rapid melting and breaking in case of thermal runaway (temperature ≥300°C).

[0094] An appropriate thickness T ensures that the first current collector 41 has a sufficient conductive cross-sectional area, thereby reducing the resistance when current flows through, lowering the battery's internal resistance, and improving battery performance. At the same time, it avoids the problem of excessive thickness T causing difficulty in deformation under gas impact.

[0095] By controlling the melting point of the first current collector 41, the first current collector 41 can be rapidly melted when thermal runaway occurs in the battery, thereby providing a smoother exhaust channel for gas discharge, reducing the spread of thermal runaway, and improving battery safety.

[0096] In some embodiments, the first manifold 41 includes a first metal, the first metal having a mass content of 90% or more. The first metal may be, for example, copper or aluminum.

[0097] The mass content percentage refers to the proportion of the first metal in the total mass of the first collector plate 41. The higher this proportion, the higher the purity of the first collector plate 41. The test method for the elemental content in aluminum and aluminum alloys refers to GB / T 7999-2015 (Direct Reading Photoelectric Emission Spectroscopy Analysis Method for Aluminum and Aluminum Alloys), and the test method for the elemental content in copper and copper alloys refers to GB / T5121.1-2008 (Chemical Analysis Methods for Copper and Copper Alloys Part 1: Determination of Copper Content).

[0098] The high purity of the first current collector 41, with its high content of main metal components and low content of impurities or alloying elements, significantly reduces its internal resistance, thus improving the battery's overcurrent performance. Furthermore, it is more susceptible to deformation or rupture from gas impact when the battery's internal pressure abnormally increases, providing an exhaust channel for the high-pressure gas and preventing blockage of the pressure relief path. This ensures the reliable activation of the pressure relief mechanism 12 and significantly reduces the risk of battery explosion.

[0099] In some embodiments, along the first direction X, the ratio of the projected area of ​​the first wall 11 to the projected area of ​​the first end face 301 is greater than or equal to 0.8.

[0100] If the projected area of ​​the first wall 11 is too small relative to the first end face 301, the gap between the cell 30 and the side wall of the casing 10 will be too small, resulting in obstructed exhaust path and affecting the timeliness of pressure relief, thus increasing the risk of battery explosion. If the projected area of ​​the first wall 11 is too large relative to the first end face 301, although the gas exhaust path will be smoother, the gap between the cell 30 and the side wall of the casing 10 will be too large, resulting in low space utilization and reduced battery energy density.

[0101] In some embodiments, the hardness KHV of the first manifold 41 is preferably in the range of 30.2~102.5HV, which further ensures that the first manifold 41 can deform appropriately under abnormal conditions such as thermal runaway, thereby avoiding blockage of the pressure relief path and ensuring timely pressure relief, while preventing excessive deformation due to excessive softness, which would result in poor welding quality with the first tab 31 or the first wall 11.

[0102] The preferred range of the distance H between the first end face 301 and the pressure relief mechanism 12 along the first direction X is 1mm to 5mm. This provides sufficient pressure relief space while further ensuring a reasonable current flow path, taking into account both the safety and electrical performance of the battery.

[0103] The preferred ratio of the projected area of ​​the first collector plate 41 along the first direction X on the first end face 301 to the area E of the first end face 301 is 0.4 to 0.95, which further ensures that sufficient electrical connection area is provided without significantly obstructing the pressure relief path, so as to guarantee the good electrical performance and safety of the battery.

[0104] In some embodiments, the diameter of the cylindrical battery is greater than or equal to 40 mm, and E is greater than or equal to 0.45.

[0105] In other embodiments, the diameter of the cylindrical battery is greater than or equal to 70 mm, and E is greater than or equal to 0.5.

[0106] The larger the diameter of the cylindrical battery, the larger the total lead-out area of ​​the tabs on the first end face of the cell. The proportion of the current collector projected area E needs to be increased accordingly to ensure the effective welding area between the current collector and the tabs, reduce the contact internal resistance, and improve the current carrying capacity. At the same time, by optimizing the parameters of K and H, the problem of pressure relief path obstruction caused by the increase of E can be compensated.

[0107] The present invention also provides a battery pack comprising at least one cylindrical battery as described in any of the above embodiments.

[0108] A battery pack is an energy storage unit that connects multiple individual cells (such as the cylindrical cells mentioned above) in series, parallel or series-parallel combination, and is usually equipped with a battery management system, a thermal management system and an external packaging structure to form an energy storage unit that can provide the required voltage, capacity and power.

[0109] Its main function is to provide stable and reliable power output for various application scenarios. The battery pack can be implemented in two ways, including but not limited to: multiple cylindrical cells are assembled into one or more battery modules, each module being electrically connected internally via busbars or wires, and structurally fixed and thermally managed. These battery modules are then integrated into a larger battery pack housing 10 to form a complete battery pack. Alternatively, multiple cylindrical cells can be directly connected in series and parallel via electrical connectors (such as nickel strips or copper busbars) and encapsulated within a single battery pack housing 10, while also integrating the necessary battery management system and thermal management components.

[0110] Battery packs can be used in electrical devices. They can serve as the operating power source or the driving power source for these devices, replacing or partially replacing fuel or natural gas to provide propulsion for vehicles. Electrical devices encompass a wide range of technological fields, including energy storage devices, electric ships, aircraft, laptops, power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0111] There are multiple battery packs, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery packs are connected in both series and parallel.

[0112] It is worth noting that the test method for hardness K is as follows: The first current collector of the cylindrical battery is taken out as the test sample. Ten points are randomly selected on the first current collector and their Vickers hardness values ​​are measured. The average value of the Vickers hardness values ​​of the ten points is taken as the hardness value of the test sample.

[0113] The formula for calculating the single-point Vickers hardness value (HV) is as follows: HV=0.102×F / S=0.102×(2Fsin(α / 2) / d²); F = Load (Newton force); S = Indentation surface area (square millimeters); α = Angle between the indenter and the opposite surface = 136°; d = average indentation diagonal length (mm).

[0114] Vickers hardness (HV) test procedure: Step S1: Polish the surface of the sample to be tested until the roughness is ≤Ra0.8μm and it is clean and free of oil. The thickness of the sample to be tested is at least 1.5 to 2 times the length of the indentation diagonal. Step S2: Select a load of 196.1N and press the diamond square pyramid indenter (136° included angle) into the surface of the sample to be tested, hold the pressure for 10~15 seconds to form an indentation; Step S3: After removing the load, measure the lengths of the two perpendicular diagonals of the indentation using a microscope (accuracy must reach 0.1 μm); Step S4, Data Calculation: Calculate the diagonal average value and substitute it into the formula to obtain the Vickers hardness (HV) value.

[0115] The methods for measuring dimensions, area, etc. are as follows: Use 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.

[0116] The method for measuring the distance H between the first end face 301 of the battery cell and the pressure relief mechanism 12 along the first direction X is as follows: a CT (computed tomography) scan is performed on the cylindrical battery. Since the current collectors of the electrode plates in the pressure relief mechanism 12 and the battery cell are both made of metal materials, their density is much higher than that of the separator, electrolyte and active materials. They appear as high-brightness areas in the image and can be distinguished with high precision. Therefore, the shortest distance from the top of the electrode plate closest to the first end face 301 of the battery cell to the bottom of the pressure relief mechanism 12 along the first direction X is taken as the distance H.

[0117] The projection area of ​​the first collector plate 41 along the first direction X onto the first end face 301 accounts for E of the area of ​​the first end face 301. The area of ​​the first end face 301 is the area of ​​the outermost circumference of the battery cell. The battery radius is r0. Then, the area S1 of the first end face 301 is S1 = π * r0. 2 The projected area of ​​the first collector disk 41 along the first direction X on the first end face 301 is S2, then E=S2 / S1.

[0118] Preparation of cylindrical batteries (1) Preparation of the positive electrode: The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., PVDF) are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector foil, dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheet is then obtained by rolling and slitting.

[0119] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98): (4~1): (4~1).

[0120] (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.

[0121] Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0122] (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.

[0123] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0124] (5) Preparation of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a bare cell. The bare cell is then placed in the casing of a cylindrical battery. The battery is dried, injected with electrolyte, and then packaged, allowed to stand, formed, and volume-adjusted to obtain a lithium-ion battery.

[0125] 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.

[0126] 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.

[0127] The adhesive includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0128] The solvent can be deionized water, NMP (N-methylpyrrolidone), alcohol, ether, ketone or other types of pyrrolidone, etc.

[0129] 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.). 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.).

[0130] Test Method 1: Battery Charging Temperature Rise Rate Following the battery fabrication method described above, 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. At room temperature (20°C), the first wall of the cylindrical battery casing was connected to a temperature sensor.

[0131] The cylindrical battery was discharged at a constant current of 0.33C to the lower limit voltage of 2.5V, and then left to stand for 60 minutes. After standing, the temperature measured by the temperature sensor was recorded as t1. The cylindrical battery was then charged at 1C to the upper limit voltage of 4.25V, and the time was recorded as T. The temperature measured by the temperature sensor at this time was t2. The temperature rise rate was calculated using the formula: temperature rise rate = (t2 - t1) / T. If the temperature rise rate is greater than 0.9°C / min, it is unqualified; if the temperature rise rate is less than or equal to 0.9°C / min and greater than 0.7°C / min, it is qualified; if the temperature rise rate is less than or equal to 0.7°C / min, it is good.

[0132] 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.

[0133] 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 0.2 Taking 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.

[0134] Test Method 2: Proportion of casing damage during battery thermal runaway 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.

[0135] 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.

[0136] Record the number of cylindrical batteries that experienced thermal runaway, N1. After the pressure relief is completed, observe the casings of the thermally runaway cylindrical batteries to see if any casing rupture occurred outside the pressure relief mechanism. Record the number of cylindrical batteries with ruptured 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.

[0137] 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.

[0138] 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.

[0139] The example table is as follows:

[0140] As can be seen from the table above, the (K*E) / H ratios of Examples 1-17 are all within the range of 2.8 to 90.6, the charging temperature rise rate is qualified / good, and the shell damage ratio is qualified / good. By limiting 2.8 ≤ (K*E) / H ≤ 90.6, a balance can be achieved between the electrical performance and pressure relief safety performance of the cylindrical battery. This ensures both the low temperature rise during normal charging and discharging of the battery and the timely action of the pressure relief mechanism in case of thermal runaway, thereby reducing the risk of damage to the non-pressure relief area of ​​the shell.

[0141] Comparative Examples 1 and 3 show that (K*E) / H exceeds the upper limit, resulting in an unqualified shell damage ratio; Comparative Example 2 shows that (K*E) / H is below the lower limit, resulting in an unqualified charging temperature rise rate. This indicates that when the (K*E) / H value exceeds the range of 2.8~90.6 defined in this invention, it will lead to battery performance failure. Specifically, when the value is higher than the upper limit, the current collector hardness is too high, the projected area ratio is too large, or the distance between it and the pressure relief mechanism is too close. During thermal runaway, the current collector cannot deform appropriately, blocking the pressure relief path, and the internal high-pressure gas cannot be discharged quickly, thus causing damage to the non-pressure relief area of ​​the shell. When the value is lower than the lower limit, the current collector hardness is insufficient, the projected area ratio is too small, or the distance between it and the pressure relief mechanism is too far. This will increase the internal resistance of current conduction in the battery, causing excessive heat accumulation during charging and discharging, resulting in an excessively high temperature rise rate, which affects the battery's normal electrical performance and cycle life.

[0142] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A cylindrical battery, characterized in that, include: The housing (10) includes a first wall (11), the first wall (11) is provided with a pressure relief mechanism (12), the pressure relief mechanism (12) is used to rupture and relieve pressure when the internal pressure of the battery reaches a preset threshold; A battery cell (30) is disposed inside the housing (10). The battery cell (30) includes a first tab (31). The first tab (31) extends from a first end face (301) of the battery cell (30). The first end face (301) and the first wall (11) are disposed opposite each other along a first direction (X). The first direction is parallel to the axial direction of the cylindrical battery. The first current collector (41) is located at least partially between the first wall (11) and the first end face (301) along the first direction (X). The first current collector (41) is electrically connected to the first tab (31) and the current output terminal of the first wall (11). Wherein, the hardness of the first collector plate (41) is KHV, the distance between the first end face (301) of the battery cell and the pressure relief mechanism (12) along the first direction (X) is Hmm, and the proportion of the projected area of ​​the first collector plate (41) along the first direction (X) on the first end face (301) to the area of ​​the first end face (301) is E, which satisfies 2.8≤(K*E) / H≤90.

6.

2. The cylindrical battery according to claim 1, characterized in that, The first collector plate (41) is provided with a through hole (401) penetrating both sides of its thickness direction, and the projection of the through hole (401) along the first direction (X) is at least partially located on the first end face (301).

3. The cylindrical battery according to claim 2, characterized in that, The pressure relief mechanism (12) includes a thinning portion (14) formed on the first wall (11). Along the first direction (X), the projection of the through hole (401) on the first wall (11) at least partially overlaps with the projection of the thinned portion (14) on the first wall (11); and / or, along the first direction (X), the projection of the through hole (401) on the first wall (11) at least partially overlaps with the projection of the core hole (302) of the battery cell (30) on the first wall (11).

4. The cylindrical battery according to claim 3, characterized in that, The area of ​​the core hole (302) is greater than or equal to the area of ​​a single through hole (401), and the range of E is 0.4 to 0.

9.

5. The cylindrical battery according to claim 3, characterized in that, The area of ​​the core hole (302) is smaller than the area of ​​the through hole (401), and the range of Hmm is 1mm to 4mm.

6. The cylindrical battery according to claim 2, characterized in that, The first collector plate (41) is provided with a plurality of through holes (401), and the minimum distance D1mm between two adjacent through holes (401) ranges from 3mm to 40mm.

7. The cylindrical battery according to claim 2, characterized in that, The area of ​​a single through hole (401) ranges from 2 mm. 2 ~100mm 2 .

8. The cylindrical battery according to claim 2, characterized in that, Along the radial direction (Y) of the first collector plate (41), the distance between the through hole (401) closest to the edge of the first collector plate (41) and the edge of the first collector plate (41) is D2mm, ranging from 1mm to 10mm.

9. The cylindrical battery according to claim 1, characterized in that, The first collector plate (41) is provided with a notch (402), which is located at the edge of the first collector plate (41).

10. The cylindrical battery according to any one of claims 1-9, characterized in that, The first collector plate (41) includes a first connecting part (411) and a second connecting part (412). The first connecting part (411) is electrically connected to the first electrode (31) through a first solder mark (411b), and the second connecting part (412) is electrically connected to the current output terminal of the first wall (11) through a second solder mark (412a). The first collector plate (41) is provided with a through hole (401), the through hole (401) being located between the first connecting portion (411) and the second connecting portion (412); and / or, the first collector plate (41) is provided with a notch (402), the notch (402) being located at the edge of the first collector plate (41), the notch (402) being located between the first solder mark (411b) and the second solder mark (412a).

11. The cylindrical battery according to any one of claims 1-9, characterized in that, The first collector plate (41) includes a first connecting portion (411) and a second connecting portion (412). The first connecting portion (411) is electrically connected to the first tab (31) via a first solder mark (411b), and the second connecting portion (412) is electrically connected to the current output terminal of the first wall (11) via a second solder mark (412a). The first connecting portion (411) has a thinning region (411a), the thickness of which is less than the thickness of the body portion of the first collector plate (41).

12. The cylindrical battery according to claim 11, characterized in that, The thickness T1mm of the thinning zone (411a) is in the range of 0.4 to 0.8 compared with the thickness Tmm of the body portion of the first collector plate (41).

13. The cylindrical battery according to any one of claims 1-9, characterized in that, The pressure relief mechanism (12) includes a thinning portion (14) formed on the first wall (11). The first collector plate (41) is welded to the first wall (11) to form a first weld mark (411b). Along the first direction (X), the projection of the first weld mark (411b) on the first wall (11) does not overlap with the projection of the thinned portion (14) on the first wall (11).

14. The cylindrical battery according to claim 13, characterized in that, The thinned portion (14) is located inside the first solder mark (411b) in the radial direction (Y).

15. The cylindrical battery according to claim 13, characterized in that, The thinned portion (14) is located on the outer side of the first solder mark (411b) in the radial direction (Y), and the Hmm ranges from 1.5mm to 4mm.

16. The cylindrical battery according to claim 13, characterized in that, The first solder mark (411b) extends circumferentially along the first collector plate (41) and has a first end and a second end along the circumferential direction of the first collector plate (41). The first end and the second end are spaced apart. The extension length of the first solder mark (411b) is the arc length between the first end and the second end, and the arc length ranges from 30mm to 80mm.

17. The cylindrical battery according to claim 13, characterized in that, The first solder mark (411b) is in a continuous ring shape along the circumference of the first collector plate (41).

18. The cylindrical battery according to any one of claims 1-9, characterized in that, The pressure relief mechanism (12) includes a thinning portion (14) formed on the first wall (11). The first wall (11) has a groove (13) formed on its surface along its thickness direction. The thinning portion (14) includes a groove provided on the bottom surface of the groove (13). The groove (13) faces the battery cell (30) and / or faces away from the battery cell (30) along the first direction (X).

19. The cylindrical battery according to claim 18, characterized in that, Along the circumferential direction of the battery, the groove (13) is in a continuous ring shape.

20. The cylindrical battery according to any one of claims 1-9, characterized in that, The battery cell (30) also includes a second end face. Along the first direction (X), the first end face (301) and the second end face are located at the two ends of the battery cell (30), respectively. A second tab (32) is led out from the second end face. The polarity of the second tab (32) is opposite to that of the first tab (31), satisfying that (K*E) / H ranges from 5 to 90.

6.

21. The cylindrical battery according to any one of claims 1-9, characterized in that, The first end face (301) also has a second electrode (32) extending out. The second electrode (32) has the opposite polarity to the first electrode (31) and is spaced apart.

22. The cylindrical battery according to claim 21, characterized in that, The cylindrical battery also includes: The second current collector (42) is electrically connected to the second tab (32). Along the radial direction of the cylindrical battery, the distance between the first current collector (41) and the second current collector (42) is 3mm to 40mm.

23. The cylindrical battery according to claim 22, characterized in that, The first collector plate (41) and the second collector plate (42) are respectively provided with through holes (401), and the distance between the first collector plate (41) and the second collector plate (42) is 3mm~35mm.

24. The cylindrical battery according to any one of claims 1-9, characterized in that, The thickness of the first manifold (41) ranges from 0.2 mm to 1.2 mm; and / or the melting point of the first manifold (41) is less than or equal to 670 °C.

25. The cylindrical battery according to any one of claims 1-9, characterized in that, The first collector (41) includes a first metal, which is copper or aluminum, and the mass content of the first metal is greater than or equal to 90%.

26. The cylindrical battery according to any one of claims 1-9, characterized in that, Along the first direction (X), the ratio of the projected area of ​​the first wall (11) to the projected area of ​​the first end face (301) is greater than or equal to 0.

8.

27. The cylindrical battery according to any one of claims 1-9, characterized in that, The range of KHV is 30.2~102.5HV; and / or, the range of Hmm is 1mm~5mm; and / or, the range of E is 0.4~0.

95.

28. The cylindrical battery according to any one of claims 1-9, characterized in that, The diameter of the cylindrical battery is greater than or equal to 40 mm, and E is greater than or equal to 0.45; or, The diameter of the cylindrical battery is greater than or equal to 70 mm, and E is greater than or equal to 0.

5.

29. A battery pack, characterized in that, include: At least one cylindrical battery as described in any one of claims 1-28.

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