Cylindrical battery and battery pack

Abstract

This application provides a cylindrical battery and a battery pack, relating to the field of battery technology. The cylindrical battery includes: a casing, the casing including a first end plate located at one end along its own axial direction, the first end plate having a pressure relief valve, the pressure relief valve including a thinning region, the thickness of the thinning region being less than the thickness of the first end plate; a battery cell, the battery cell being disposed within the casing; and an adapter piece, disposed between the end face of the first end plate and the battery cell, the adapter piece being electrically connected to the tab portion of the battery cell and the electrode of the cylindrical battery respectively; wherein, the thickness of the thinning region is L mm, and the volume of the cylindrical battery is V mm². 3 The ratio of the area of ​​the adapter plate to the end face area of ​​the cell is P. The capacity of the cylindrical battery is A Ah. L, V, P, and A satisfy: 0.210 ‑5 ≤APL / V≤4.7310 ‑5 Wherein, A Ah ≥ 20Ah. The cylindrical battery provided in this application is used to improve the unobstructed pressure relief path, thermal runaway safety, and current transmission efficiency, thereby improving the safety of the cylindrical battery.

Description

Technical Field

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

[0002] As people's demands for the battery life of electrical devices increase, cylindrical batteries are widely used due to their advantages of high space utilization and higher energy density.

[0003] However, as the range of cylindrical batteries increases, the heat generated inside the cylindrical battery becomes concentrated, which leads to untimely pressure release and high explosion pressure. This can cause severe thermal runaway inside the cylindrical battery, which can result in ejection and fire, affecting the overall safety of the battery pack. Summary of the Invention

[0004] This application provides a cylindrical battery and battery pack to improve the unobstructed pressure relief path, thermal runaway safety, and current transmission efficiency, thereby ensuring the safe use of the cylindrical battery.

[0005] The cylindrical battery provided in this application includes: a housing, the housing including a first end plate located at one end along its own axial direction, the first end plate having a pressure relief valve, the pressure relief valve including a thinning region, the thickness of the thinning region being less than the thickness of the first end plate; a battery cell, the battery cell being disposed within the housing; and an adapter piece disposed between the first end plate and the end face of the battery cell, the adapter piece being electrically connected to the tab portion of the battery cell and the electrode of the cylindrical battery respectively; wherein, the thickness of the thinning region is L mm, and the volume of the inner cavity of the housing is V mm. 3 The ratio of the area of ​​the adapter plate to the end face area of ​​the battery cell is P, and the capacity of the cylindrical battery is A Ah. L, V, P, and A satisfy: 0.2 10 -5 ≤A P L / V≤4.73 10 -5 , where A Ah≥20Ah.

[0006] The cylindrical battery provided in this application, with a capacity of ≥20Ah, improves the ratio P of the adapter area to the end face area of ​​the cell by optimizing the thickness L of the thinning region, and by controlling the volumetric energy density A / V of the cylindrical battery. P By controlling the L / V value within the above range, the problems of untimely pressure relief and accidental opening of the pressure relief valve are solved, the unobstructed pressure relief path, thermal runaway safety and current transmission efficiency are improved, and the safety of cylindrical batteries is guaranteed. Attached Figure Description

[0007] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0008] Figure 1 This is a schematic diagram of the cylindrical battery provided in this application;

[0009] Figure 2 For along Figure 1 Sectional view of mid-section AA;

[0010] Figure 3 A structural schematic diagram of the first end plate at one angle provided in this application;

[0011] Figure 4 A structural schematic diagram of the first end plate provided in this application from another angle;

[0012] Figure 5 This is a schematic diagram of the battery cell structure provided in this application;

[0013] Figure 6 This is a schematic diagram of the structure of the adapter plate provided in this application;

[0014] Figure 7 Assembly drawing of the first end plate and adapter piece provided for this application;

[0015] Figure 8 For along Figure 7 Sectional view of section BB;

[0016] Figure 9 A schematic diagram of the structure provided in this application for providing a first protrusion on the first end plate;

[0017] Figure 10 A schematic diagram of the structure provided in this application, showing a second recess on the first end plate.

[0018] Explanation of reference numerals in the attached figures:

[0019] 100-cylindrical battery;

[0020] 10-Housing; 20-Battery cell; 30-Adapter plate; 40-Electrode; 50-Lower plastic;

[0021] 11-First end plate; 12-Pressure relief valve; 13-Thinning zone;

[0022] 111-the first convex part; 112-the second concave part; 113-the first groove;

[0023] 101 - First bottom wall; 102 - First side wall; 103 - First trench bottom wall; 104 - Second bottom wall; 105 - Second side wall;

[0024] 1030 - Second groove;

[0025] 21-Electrode tab; 22-Cell end face; 23-Core winding hole;

[0026] 211 - Positive electrode; 212 - Negative electrode;

[0027] 31-Through hole; 32-First region; 33-Second region;

[0028] 310 - Positive electrode adapter; 320 - Negative electrode adapter; 330 - Insulating sheet;

[0029] 311 - First convex edge; 321 - Second convex edge;

[0030] 41-Pole post; 42-Insulation component.

[0031] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0032] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0033] As people's demands for the battery life of electrical devices increase, cylindrical batteries are widely used due to their advantages of high space utilization and higher energy density.

[0034] Research has found that compared to prismatic cylindrical batteries, the tighter internal structure of the cylindrical battery cells and the closer connection between the cells and the casing results in insufficient gas storage space. This exacerbates the increase in internal pressure, causing the pressure relief valve to burst at a pressure higher than the preset pressure. Furthermore, when the adapter plate and pressure relief valve are located on the same side in a cylindrical battery, the adapter plate can obstruct the valve, blocking the venting path. In the event of thermal runaway, this further accelerates the rapid increase in internal pressure, and the pressure relief valve cannot open in time to release pressure, compromising the safety of the cylindrical battery.

[0035] In view of this, this application provides a cylindrical battery. When the capacity of the cylindrical battery is greater than or equal to 20 Ah, by optimizing the thickness L of the thinning region, improving the ratio P of the area of ​​the adapter plate to the end face area of ​​the cell, and controlling the volumetric energy density A / V of the cylindrical battery, the A... P The L / V value should be controlled at 0.2. 10 -5 -4.73 10 -5 Within this range, it helps to solve the problem of untimely pressure relief by the pressure relief valve, improves the smoothness of the pressure relief path, the safety of thermal runaway and the efficiency of current transmission, and ensures the safe use of cylindrical batteries.

[0036] Combination Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 The cylindrical battery 100 (hereinafter referred to as cylindrical battery) in this application embodiment may include a casing 10, a cell 20, and an adapter plate 30.

[0037] The housing 10 includes a first end plate 11 located at one end of its own axial direction. The first end plate 11 is provided with a pressure relief valve 12. The pressure relief valve 12 includes a thinning region 13. The thickness of the thinning region 13 is less than the thickness of other regions on the first end plate 11 except for the thinning region 13. The battery cell 20 is disposed inside the housing 10.

[0038] Understandably, the casing 10 is the outer shell of the cylindrical battery 100, providing a space to house the battery cell 20, adapter plate 30, and other components, isolating them from the outside world and preventing external impacts. The materials of the casing 10 include, but are not limited to, aluminum, iron, titanium, copper, aluminum alloy, stainless steel, and titanium alloy.

[0039] The housing 10 may have an opening at one end, and the first end plate 11 may be a cover plate that seals the opening. In this case, the first end plate 11 and the housing 10 may be separate structures connected by mechanical means; or, the first end plate 11 may be the end plate of the closed end of the housing 10, in which case the first end plate 11 is part of the housing 10, that is, integrally formed into the housing 10. The material of the first end plate 11 includes, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, etc.

[0040] Alternatively, both ends of the housing 10 are open, in which case the first end plate 11 is a cover plate that seals one of the openings.

[0041] The pressure relief valve 12 refers to a component or part that can be actuated to release internal pressure or temperature when the internal pressure or temperature of the cylindrical battery 100 reaches a predetermined threshold. During the use of the cylindrical battery 100, the pressure relief valve 12 is mainly used to allow gas inside the cylindrical battery 100 to be discharged in order to reduce the internal pressure of the cylindrical battery 100 in order to prevent the cylindrical battery 100 from deforming or exploding due to excessive increase in internal pressure when thermal runaway or other situations occur.

[0042] Thinning region 13 is a weak part formed by reducing the thickness of the first end plate 11 through methods such as stamping, laser etching, and cutting. The area surrounded by thinning region 13 constitutes pressure relief valve 12. The area on the first end plate 11 corresponding to thinning region 13 forms a groove structure. The groove structure can be located on the surface of the first end plate facing the cell 20 (i.e., the inner surface of the first end plate 11), or on the surface of the first end plate 11 away from the cell 20 (i.e., the outer surface of the first end plate 11), or both surfaces can have groove structures. The cross-section of the groove structure can be V-shaped, U-shaped, trapezoidal, or other shapes.

[0043] The pressure relief valve 12 is a safety protection structure located on the first end plate 11. The pressure relief valve 12 can be broken and opened in time when the gas pressure inside the cylindrical battery 100 rises abnormally and reaches the preset pressure value, so that the gas inside the cylindrical battery 100 can be discharged and prevent the cylindrical battery 100 from exploding.

[0044] In addition to the above-mentioned method of integrally forming the pressure relief valve 12 with the first end plate 11, the pressure relief valve 12 can also be set independently of the first end plate 11, that is, the first end plate 11 and the pressure relief valve 12 are manufactured separately, and then the two are connected by welding or other connection methods.

[0045] The adapter piece 30 can be flat, stepped, boss-shaped, flanged, or perforated, etc., and is not limited to this embodiment. The pressure relief valve 12 can be circular, annular, arc-shaped, fan-shaped, etc., and can also be thinned, scored, flanged, or raised, etc., and is not limited to this embodiment. The adapter piece 30 can be an aluminum adapter piece, a copper adapter piece, or an alloy (e.g., steel) adapter piece, or other conductive materials. The specific material of the adapter piece 30 is selected according to the material of the terminal and the tab of the cylindrical battery 100. For example, the positive electrode adapter piece can be made of the same material as the positive electrode tab, and the negative electrode adapter piece can be made of the same material as the negative electrode tab to ensure welding quality.

[0046] Optionally, the adapter piece 30 and the first end plate 11 can be separated by a lower plastic 50 to insulate the adapter piece 30 from the first end plate 11 and reduce the risk of short circuit. The lower plastic 50 can be plastic, rubber, or other insulating materials. Taking plastic as an example, the lower plastic 50 can be polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), or polyvinyl chloride (PVC); taking rubber as an example, the lower plastic 50 can be fluororubber, nitrile rubber, or isobutyl rubber.

[0047] The battery cell 20 is the component in the cylindrical battery 100 where electrochemical reactions occur. It is the smallest unit in the cylindrical battery 100 capable of electrochemical reactions such as charging or discharging. The battery cell 20 is a cylindrical core formed by winding a positive electrode, a negative electrode, and a separator disposed between them. The battery cell 20 is disposed inside the housing 10 and can be coaxially aligned with the axis of the housing 10 to avoid eccentricity or tilting. Simultaneously, the outer periphery of the battery cell 20 can have a uniform gap with the inner wall of the housing 10 to prevent localized compression or friction. Optionally, a gasket (battery cell 20 support plate) can be provided between the bottom of the battery cell 20 and the inner side of the bottom of the housing 10 to prevent compression or friction between the bottom of the battery cell 20 and the housing 10.

[0048] The adapter piece 30 is disposed between the first end plate 11 and the end face of the cell 20. The adapter piece 30 is electrically connected to the tab 21 of the cell and the electrode 40 of the cylindrical battery 100. Understandably, the adapter piece 30 is located between the first end plate 11 and the end face (upper end face of the cell 20). The lower side of the adapter piece 30 is welded to the tab 21 of the cell to form an electrical connection, thereby collecting the current of the cell 20. The upper side of the adapter piece 30 is electrically connected to the electrode 40 of the cylindrical battery 100 to conduct the current to the outside of the cylindrical battery, realizing the current transmission and transition connection between the cell 20 and the electrode 40. The adapter piece 30 is responsible for conducting electricity without blocking gas, allowing the gas to quickly reach the pressure relief valve 12, ensuring high-temperature gas stress concentration, and allowing the internal pressure to smoothly reach the pressure relief valve 12, ensuring explosion-proof reliability and timely opening of the pressure relief valve 12 to avoid excessive explosion pressure and severe thermal runaway inside the cylindrical battery.

[0049] The electrode tab 21 of the battery cell 20 is an electrical lead-out structure drawn from inside the battery cell 20. It is used to collect the current generated inside the battery cell 20 and conduct it outward. It is a key component for achieving electrical connection between the battery cell 20 and the adapter plate 30. The electrode tab 21 may include a positive electrode tab 211 and a negative electrode tab 212. The positive electrode tab 211 and the negative electrode tab 212 may be located at the same end of the battery cell 20 or at both ends of the battery cell 20. Of course, it is not limited to this embodiment.

[0050] Electrode 40 is a conductive output terminal of cylindrical battery 100 used for external charging and discharging. It is a component for current input and output between the internal electrical energy of cylindrical battery and external circuit. Electrode 40 can be a positive electrode 40 or a negative electrode 40. Electrode 40 can include the terminal post 41 and the first end plate 11 mentioned below, but is not limited to this embodiment.

[0051] More specifically, the adapter 30 includes a positive adapter and a negative adapter. The positive adapter is connected to the positive tab 211 and the terminal 41, respectively, and the negative adapter is connected to the negative tab 212 and the first end plate 11 or the housing 10, respectively; or, the negative adapter is connected to the negative tab 212 and the terminal 41, respectively, and the positive adapter is connected to the positive tab 211 and the first end plate 11 or the housing 10, respectively.

[0052] The aforementioned positive and negative electrode adapters can both face the same end face of the cylindrical battery 100, for example, between the cell 20 and the first end plate 11. One end of the positive electrode adapter is electrically connected to the positive tab 211, and the other end is electrically connected to the housing 10 or the terminal post 41; one end of the negative electrode adapter is electrically connected to the negative tab 212, and the other end is electrically connected to the housing 10 or the terminal post 41. Having the positive and negative electrode adapters on the same side simplifies the structure of the cylindrical battery 100. The housing 10 has an opening on one side, and the opening can be welded to the cover plate to achieve a seal. Furthermore, the positive and negative electrode adapters occupy a small volume in the height direction of the cylindrical battery 100, avoiding the problem of poor energy density in the cylindrical battery 100 caused by the positive and negative tabs being positioned on different end faces, which would affect the height of the cell 20. However, if the positive and negative adapter plates are located on the same side, the pressure relief valve 12 on the first end plate 11 will be blocked more by the adapter plate 30 after it opens, resulting in a slower pressure relief rate. Therefore, A P The L / V value should be controlled at 0.2. 10 -5 -3.8 10 -5 Within the specified range, avoid the problem of untimely pressure relief and bulging of the shell 10 due to an excessively large formula range.

[0053] Compared to prismatic batteries, cylindrical batteries have higher cell assembly efficiency and yield, and fewer internal structural components, improving overall space utilization. However, cylindrical batteries are smaller in size, requiring multiple cells to be assembled into a battery pack. With the increasing demand for higher energy density, the diameter of current cylindrical batteries is gradually increasing, reaching ≥30mm and even exceeding 40mm, compared to traditional 18650 and 2170 batteries. This increased energy density leads to increased gas production within the battery, posing a safety risk during use due to the inability of explosion-proof valves to release pressure in a timely manner, and even the possibility of open flames during pressure release.

[0054] Research has found that compared to prismatic cylindrical batteries, the tighter internal structure of the cylindrical battery cells and the closer connection between the cells and the casing results in insufficient gas storage space. This exacerbates the increase in internal pressure, causing the pressure relief valve to burst at a pressure higher than the preset pressure. Furthermore, when the adapter plate and pressure relief valve are located on the same side in a cylindrical battery, the adapter plate can obstruct the valve, blocking the venting path. In the event of thermal runaway, this further accelerates the rapid increase in internal pressure, and the pressure relief valve cannot open in time to release pressure, compromising the safety of the cylindrical battery.

[0055] The thickness of the thinning region 13 is L mm, and the volume of the cylindrical battery 100 is V mm. 3 The ratio of the area of ​​the adapter plate 30 to the end face area of ​​the cell 20 is P, and the capacity of the cylindrical battery 100 is A Ah. The volume V of the cylindrical battery 100 is the product of the area of ​​the first end plate 11 and the axial height of the casing 10.

[0056] The four variables L, V, P, and A satisfy: 0.2 10 -5 ≤A P L / V≤4.73 10 -5 Where A Ah≥20, for example, A P The value of L / V can be 0.2. 10 -5 0.5 10 -5 1 10 -5 1.5 10 -5 2 10 -5 2.5 10 -5 3 10 -5 3.5 10 -5 4 10 -5 4.5 10 -5 4.7 10 -5 4.73 10 -5 Of course, this application is not limited to this, A P The value of L / V can be flexibly selected within the above range as needed. Optionally, A P The L / V value can be 0.97. 10 -5 -3.80 10 -5 .

[0057] In addition to the above scope, A P The L / V value can also be 0.12 10 -5 -0.599 10 -5 Choose from the range.

[0058] Optionally, the thickness of the first end plate 11 can be 0.4mm-3mm, and the thickness of the thinning region 13 can be 0.03mm-0.3mm.

[0059] It should be noted that the smaller the thickness L of the thinning region 13, the easier it is for the pressure relief valve 12 to be breached under the same internal pressure, and the higher the sensitivity of the pressure relief valve 12, but it is easy to cause the pressure relief valve 12 to open accidentally; the larger the thickness L of the thinning region 13, the more difficult it is for the pressure relief valve 12 to release gas, the more difficult it is to depressurize the cylindrical battery 100, and the more likely it is to cause thermal runaway safety problems.

[0060] The larger the value of P, which is the ratio of the area of ​​the adapter plate 30 to the end face area of ​​the cell 20, the easier it is to block the exhaust channel, affecting the exhaust rate. This makes it more difficult to depressurize the cylindrical battery 100 and increases the risk of thermal runaway. The smaller the value of P, which is the ratio of the area of ​​the adapter plate 30 to the end face area of ​​the cell 20, the smaller the overcurrent area of ​​the adapter plate 30 and the larger the resistance of the adapter plate 30. This makes it easier to generate heat in a concentrated manner and causes the pressure relief valve 12 to open accidentally. The pressure relief valve 12 is a component whose structural strength decreases as the temperature increases.

[0061] The larger the volume V of the inner cavity of the casing 10, the larger the volume of the battery cell 20 that can be accommodated, which is beneficial for increasing the capacity A and energy density of the cylindrical battery 100; it can also accommodate more electrolyte, improving ion transport, reducing internal resistance, and increasing cycle life; the more ample internal space provides greater heat dissipation space, which is beneficial for heat dissipation and improves the safety of the cylindrical battery 100; it can also reserve expansion space to reduce the pressure of the battery cell 20 on the casing 10 during expansion and reduce the problem of bulging. The smaller the volume V of the inner cavity of the casing 10, the more compact the structure of the cylindrical battery 100 and the higher the energy density, but the more difficult it is to depressurize, and the more prone it is to thermal runaway safety issues.

[0062] Wherein, A / V is the unit volume capacity of the cylindrical battery 100. The larger the A / V value, the higher the gas production of the cylindrical battery 100, the slower the exhaust speed, the more difficult it is to depressurize the cylindrical battery 100, and the more likely it is to cause thermal runaway safety issues. The smaller the A / V value, the lower the space utilization of the cylindrical battery 100, and the worse the range. However, the reserved space after removing the battery cell 20 in the casing 10 is larger, and the thermal runaway problem is lower. This provides a buffer space for the expansion and gas production of the cylindrical battery 100, making it less prone to bulging and rupture, thus improving the safety of the cylindrical battery 100 in use.

[0063] Furthermore, when A P A larger value of L results in a larger capacity A of the cylindrical battery, a larger thickness L of the thinning zone 13, and a higher ratio P between the area of ​​the adapter piece 30 and the end face area of ​​the cell 20. Consequently, the gas production and expansion within the cylindrical battery 100 increase, which can compress the exhaust channel and lead to poor exhaust. When A... P The smaller the value of L, the smaller the thickness L of the thinning zone 13 may be, the lower the local strength of the shell 10, and the more sensitive it is to internal pressure and external vibration. Under normal working conditions, it is easy to reach the opening threshold of the pressure relief valve 12, which may cause the pressure relief valve 12 to open erroneously.

[0064] Understandably, when A P The L / V value is too high, exceeding 4.73. 10 -5 At this time, the capacity A of the cylindrical battery 100 is relatively large, the thickness L of the thinning zone 13 is relatively large, and the ratio P of the area of ​​the adapter piece 30 to the area of ​​the cell end face 22 is relatively high, while the volume V of the inner cavity of the casing 10 is relatively insufficient. This results in a large amount of gas generation and expansion inside the cylindrical battery 100, which easily compresses the exhaust channel, causing poor exhaust and excessively rapid rise in internal pressure, affecting the safety performance and pressure relief reliability of the cylindrical battery 100; when A P The L / V value is too small, less than 0.2. 10 -5When the thickness L of the thinning zone 13 is small, the local strength of the shell 10 is low, the internal volume V is large and the energy density is low, the cylindrical battery 100 is prone to prematurely triggering the pressure relief valve 12 under slight expansion, vibration or temperature rise conditions, causing the pressure relief valve 12 to open erroneously, affecting the sealing performance and service life of the cylindrical battery.

[0065] Therefore, in this embodiment, A P The L / V value is controlled within this range, i.e., 0.2. 10 -5 ≤A P L / V≤4.73 10 -5 It can achieve a better balance between smooth venting, reliable opening of pressure relief valve 12, and safety performance and energy density of cylindrical battery 100, thus avoiding both poor venting and accidental opening of pressure relief valve 12, and improving the overall stability and safety of cylindrical battery.

[0066] Considering that when the capacity of the cylindrical battery A Ah < 20Ah, the overall energy of the cylindrical battery 100 is relatively small, and the gas production, expansion force and internal temperature rise during charging and discharging are relatively low, the requirements for smooth exhaust, reliable opening of pressure relief valve 12 and internal buffer space are not high. Therefore, the technical effect of adjusting the parameter relationship to balance smooth exhaust and prevent false opening of pressure relief valve 12 is not significant.

[0067] Therefore, only when A Ah ≥ 20Ah, the cylindrical battery produces more gas, expands more significantly, and undergoes more drastic changes in internal pressure under charging, discharging, and abuse conditions, can the technical advantages of this application in optimizing venting, preventing the pressure relief valve 12 from opening accidentally, and improving the safety performance of the cylindrical battery be better demonstrated, making the technical solution more targeted and practical.

[0068] The cylindrical battery 100 provided in this application improves the ratio P of the area of ​​the adapter 30 to the end face area of ​​the cell 20 by optimizing the thickness L of the thinning region 13, and comprehensively controls the volume V of the inner cavity of the casing 10 and the capacity A of the cylindrical battery. Simultaneously, A... P The L / V value is controlled within the above range, limiting the capacity of the cylindrical battery A Ah≥20Ah, solving the problems of untimely pressure relief valve 12 and accidental opening of pressure relief valve 12, improving the unobstructed pressure relief path, thermal runaway safety and current transmission efficiency, and ensuring the safe use of cylindrical battery 100.

[0069] In some embodiments, the area surrounded by the thinning region 13 at least partially overlaps with the projection of the adapter piece 30 onto the first end plate 11. It can be understood that the area surrounded by the thinning region 13 is the bursting area of ​​the pressure relief valve 12 during pressure relief, from which gas can escape after the area is opened.

[0070] The projection of the adapter plate 30 onto the first end plate 11 is the coverage area of ​​the adapter plate 30 projected in the thickness direction of the first end plate 11. That is, the burst area of ​​the pressure relief valve 12 and the coverage area of ​​the adapter plate 30 on the first end plate 11 overlap by at least a portion.

[0071] Thus, to ensure that the adapter plate 30 has a small obstruction effect on airflow, this embodiment can increase the area of ​​the pressure relief valve 12. Even if the area of ​​the adapter plate 30 is smaller than the area of ​​the pressure relief valve 12, so that part of the pressure relief valve 12 is not blocked by the adapter plate 30, in the event of thermal runaway of the cylindrical battery 100, even if the burst pressure is greater than the preset pressure relief pressure, the pressure relief valve 12 has a large pressure relief area and the airflow can directly act on the pressure relief valve 12, which can improve the pressure relief response speed, achieve faster pressure relief, and improve safety.

[0072] In the above embodiment, 0.03 mm ≤ L mm ≤ 0.25 mm, that is, the thickness of the thinning region 13 is 0.03 mm-0.25 mm. For example, the thickness of the thinning region can be 0.03 mm, 0.05 mm, 0.08 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.22 mm or 0.25 mm. Of course, this embodiment is not limited to this, and the thickness of the thinning region 13 can be flexibly selected within the above range as needed. Since the adapter plate 30 partially blocks the pressure relief valve 12 in this embodiment, in order to reduce the problem of untimely pressure relief caused by this blockage, this embodiment further reduces the thickness of the thinning area 13, that is, by controlling the thickness of the thinning area 13 to be within the range of 0.03mm-0.25mm, to compensate for the problem of increased actual valve opening pressure caused by the adapter plate 30 partially blocking the pressure relief valve 12. In this way, it can prevent the thickness of the thinning area 13 from being too small, for example, less than 0.03mm, so that the strength of the thinning area 13 is too low, causing the pressure relief valve 12 to open before the internal pressure reaches the preset pressure; it can also prevent the thickness of the thinning area 13 from being too large, for example, greater than 0.25mm, so that the strength of the thinning area 13 is too high, resulting in untimely pressure relief and excessive internal pressure of the cylindrical battery 100 causing an explosion.

[0073] In some embodiments, reference Figure 9The first end plate 11 has a first protrusion 111, which protrudes in a direction away from the battery cell 20. For example, the first protrusion 111 can be formed by stamping, injection molding, or other methods. The first protrusion 111 can be formed by only the outer surface of the first end plate 11 protruding outwards, while the inner surface is flat. In this case, the first protrusion 111 is a solid structure, which helps to increase the strength of the first end plate 11. Alternatively, the first protrusion 111 can be formed by both the outer and inner surfaces protruding outwards simultaneously. In this case, the back of the first protrusion 111 forms an inner cavity, which can increase the internal space of the housing 10. The structural shape of the first protrusion 111 can be frustum-shaped, cylindrical, ellipsoidal, hemispherical, polygonal, annular, C-shaped, etc., and is not limited to this embodiment.

[0074] Thus, by providing a first protrusion 111 protruding away from the cell 20 on the first end plate 11, it is beneficial to increase the internal space of the cylindrical battery 100, thereby increasing the gas storage space of the cylindrical battery 100 and improving the pressure threshold during pressure relief. In addition, by providing the first protrusion 111, the structural strength of the first end plate 11 can be improved to a certain extent, thereby enhancing the safety and reliability of the cylindrical battery 100.

[0075] In some embodiments, the first protrusion 111 includes a first bottom wall 101 and a first side wall 102. The first bottom wall 101 is opposite to the battery cell 20, the first side wall 102 surrounds the first bottom wall 101, and the thinning region 13 is disposed on the first bottom wall 101.

[0076] This creates an additional axial gap between the first bottom wall 101 of the first protrusion 111 and the cell 20, increasing the gas storage space inside the cylindrical battery 100. The thinning area 13 is located on the first bottom wall 101, allowing this part of the gas storage space to be directly connected to the thinning area 13, ensuring smooth gas collection and timely pressure transmission, avoiding insufficient internal space of the cylindrical battery 100 that leads to obstructed exhaust, thereby improving the pressure relief reliability of the pressure relief valve 12 and the safety of the cylindrical battery 100.

[0077] In some embodiments, reference Figure 10The first end plate 11 has a second recess 112 that protrudes towards the cell 20. The second recess 112 includes a second bottom wall 104 opposite to the cell and a second side wall 105 surrounding the second bottom wall 104. A thinning region 13 is disposed on the second bottom wall 104. At this time, the pressure relief valve 12 is concave relative to the end face of the housing 10. Thus, during the assembly, transportation, or use of the cylindrical battery, it is beneficial to reduce the risk of the pressure relief valve 12 being accidentally triggered by direct collision or squeezing from external objects. In addition, when the cylindrical battery 100 experiences thermal runaway and the internal pressure reaches the pressure relief threshold, the concave structure helps to guide the pressure to concentrate on the pressure relief valve 12, making the pressure relief valve 12 open more accurately. Moreover, in the depressurized state, after the gas is discharged from the depressurization valve 12, it is guided by the structure of the housing 10 and the first end plate 11 around the second recess 112, which prevents the high-pressure gas from being directly sprayed onto the surrounding cylindrical battery 100 and components, thereby further reducing the risk of thermal runaway chain reaction.

[0078] The second recess 112 can be frustum-shaped, cylindrical, ellipsoidal, hemispherical, polygonal, annular, C-shaped, etc., but is not limited to this embodiment.

[0079] In this embodiment, 20 Ah ≤ Ah ≤ 36 Ah, meaning the cylindrical battery capacity is 20 Ah-36 Ah. Thus, while ensuring the cylindrical battery 100 has a capacity of 20 Ah-36 Ah, the second recess 112 on the first end plate 11 ensures that the cylindrical battery 100 has sufficient capacity to meet power demands, and also facilitates more precise pressure relief and reduces the risk of a chain reaction of thermal runaway.

[0080] In some embodiments, reference Figure 6 The first end plate 11 has a first groove 113, the first groove 113 has a first groove bottom wall 103, the first groove bottom wall 103 is provided with a second groove 1030, and the portion of the first groove bottom wall 103 that is axially opposite to the second groove 1030 is a thinning area 13.

[0081] Understandably, during the manufacturing process, a first groove 113 can be machined on the first end plate 11 first, and then a second groove 1030 can be machined on the bottom wall of the first groove 113 (i.e., the bottom wall 103 of the first groove). The part of the bottom wall 103 of the first groove opposite to the second groove 1030 constitutes the thinning area 13 of the pressure relief valve 12.

[0082] The first groove 113 can be annular, arc-shaped, circular, polygonal, or other similar shapes. The cross-sectional shape of the first groove 113 can be U-shaped, V-shaped, trapezoidal, or other similar shapes, but is not limited to this embodiment. Similarly, the second groove 1030 can be annular, arc-shaped, circular, polygonal, or other similar shapes. The cross-sectional shape of the second groove 1030 can be U-shaped, V-shaped, trapezoidal, or other similar shapes, but is not limited to this embodiment.

[0083] Thus, by sequentially setting a first groove 113 and a second groove 1030 on the first end plate 11, the sidewall of the first groove 113 can provide all-round protection for the bottom wall of the second groove 1030, preventing external vibrations and impacts from directly acting on the weak area of ​​the pressure relief valve, reducing the risk of accidental triggering during transportation and assembly, improving the structural stability of the thinning area 13, and reducing the accidental opening of the pressure relief valve 12; the second groove 1030 can precisely control the thickness of the thinning area 13, reduce the pressure relief trigger threshold, and enable the cylindrical battery 100 to rupture and release pressure more quickly and smoothly when the internal pressure is abnormal, thereby improving the pressure relief effect.

[0084] In addition, the annular space formed by the first groove 113 can serve as a temporary gas guide cavity. When the bottom wall of the second groove 1030 (i.e., the thinning area 13) breaks, the high-pressure gas rushes into the first groove 113 and can be quickly discharged along the side wall of the first groove 113, avoiding gas blockage at the pressure relief port and increasing the exhaust speed.

[0085] In some embodiments, the width of the first groove 113 along the radial direction of the housing 10 is 0.5mm-2.5mm. For example, the width of the first groove 113 can be 0.5mm, 0.8mm, 1mm, 1.3mm, 1.5mm, 1.7mm, 2mm, 2.1mm, 2.4mm, or 2.5mm. Of course, this embodiment is not limited to this, and the width of the first groove 113 can be flexibly selected within the above range as needed.

[0086] Thus, by reasonably setting the width of the first groove 113 along the radial direction of the housing 10, it can not only protect the pressure relief valve 12 and prevent accidental opening, but also ensure that the pressure relief valve 12 can be reliably opened when the cylindrical battery is abnormal, as well as the venting efficiency. It also helps to balance the structural strength and manufacturability of the first end plate 11 with the safety of the cylindrical battery 100, thereby improving the overall performance and reliability of the cylindrical battery 100.

[0087] In some embodiments, the first groove 113 is a continuous annular groove. Understandably, the first end plate 11 has a complete, unbroken, and closed annular groove. Thus, setting the first groove 113 as a continuous annular groove ensures that the area where the pressure relief valve 12 is located experiences uniform force in the circumferential direction and consistent structural strength, which is beneficial for improving the opening pressure stability and opening reliability of the pressure relief valve 12. Simultaneously, it provides continuous and complete structural protection for the pressure relief valve 12, effectively blocking assembly, welding, and external stresses, preventing accidental opening of the pressure relief valve 12 during normal use. Furthermore, the continuous annular structure is easy to process and shape, reducing processing costs.

[0088] In some embodiments, the second groove 1030 is a continuous annular groove. Understandably, the second groove 1030 is a groove formed on the bottom wall 103 of the first groove, and the shape of the second groove 1030 is annular, surrounding the center of the end plate (the center of the first end plate 11) mentioned above, and the annular groove is continuous and uninterrupted without gaps. The area corresponding to the second groove 1030 is the thinning region 13.

[0089] Thus, the second groove 1030 is a continuous annular groove, which can make the circumferential force of the thinning area 13 of the pressure relief valve 12 uniform and the thickness consistent, ensuring that the opening pressure of the pressure relief valve 12 is stable and the pressure relief is reliable, avoiding premature local rupture or accidental opening of the pressure relief valve 12, and facilitating processing, thereby improving the safety and consistency of the cylindrical battery 100.

[0090] In some embodiments, the second groove 1030 is an arc-shaped segment extending circumferentially along the housing 10, 0.2 10 -5 ≤A P L / V≤4.5 10 -5 Accordingly, the thinning zone 13 is an arc-shaped segment. Considering that the pressure relief area of ​​the arc-shaped segment is smaller than that of the annular groove, by making A P L / V is at 0.2 10 -5 -4.5 10 -5 Within a certain range, sufficient pressure relief capacity is ensured to guarantee that the cylindrical battery 100 can reliably open and fully depressurize under abnormal operating conditions, thereby improving the safety of the cylindrical battery 100. The number of arc-shaped segments can be one, two, three, or more.

[0091] In some embodiments, the second groove 1030 is an arc segment. The second groove 1030 has a first end and a second end distributed circumferentially along the housing 10. The first end and the second end are spaced apart in the circumferential direction. The ratio of the distance between the first end and the second end in the circumferential direction to the length of the second groove 1030 in the circumferential direction is 0.05-0.3. For example, the ratio can be 0.05, 0.1, 0.15, 0.2, 0.25 or 0.3.

[0092] Understandably, the distance between the first end and the second end in the circumferential direction is the shortest arc length from the first end to the second end along the circumferential direction; the length of the second groove 1030 along the circumferential direction is the arc length of the arc segment (second groove 1030) itself.

[0093] The larger the ratio of the circumferential distance between the first end and the second end to the circumferential length of the second groove 1030, the smaller the area occupied by the thinning region 13 in the circumferential direction. When the pressure relief valve 12 is breached to release pressure, the area corresponding to the pressure relief valve 12 is less likely to break with other areas of the first end plate 11. Conversely, the smaller the ratio of the circumferential distance between the first end and the second end to the circumferential length of the second groove 1030, the larger the area occupied by the thinning region 13 in the circumferential direction. When the pressure relief valve 12 is breached to release pressure, the area corresponding to the pressure relief valve 12 is more likely to break with other areas.

[0094] Thus, by setting the second groove 1030 as an arc segment and limiting the ratio of the distance between its two ends in the circumferential direction to the arc length of the second groove 1030 itself to a reasonable range, on the one hand, the thinned area 13 of the pressure relief valve 12 is subjected to uniform force and the rupture path is stable and controllable during the pressure relief process; on the other hand, it prevents the pressure relief valve 12 from completely breaking, causing metal to splash and come into contact with other cylindrical batteries or components, thus posing a short circuit risk to adjacent cylindrical batteries. This ensures that the pressure relief valve 12 opens stably and relieves pressure reliably, improving the safety and reliability of the cylindrical battery 100.

[0095] In some embodiments, the adapter piece 30 and the electrode tab 21 of the battery cell 20 are connected by welding. The welding method can be ultrasonic welding, laser penetration welding, resistance welding, etc., and a first weld mark is formed at the connection between the adapter piece 30 and the electrode tab 21. The shape of the first weld mark can be grid-like, striped, dotted, etc., and is not limited to this embodiment.

[0096] At least a portion of the projection of the first solder mark on the first end plate 11 lies within the area enclosed by the thinning region 13. Exemplarily, the projection of the first solder mark on the first end plate 11 may lie entirely within the area enclosed by the thinning region 13, or only a portion of it may lie within the area enclosed by the thinning region 13.

[0097] Since the first solder mark may have microscopic gaps or unevenness, placing at least a portion of the projection of the first solder mark on the first end plate 11 within the area surrounded by the thinning region 13, so that it faces the pressure relief valve, can create a smoother gas channel at the moment of pressure relief, reducing the resistance to gas discharge, thereby reducing the internal pressure more quickly and suppressing the further spread of thermal runaway. In addition, the first solder mark is a key node for current conduction from the cell 20 to the adapter plate 30. Aligning it with the position of the pressure relief valve 12 allows the current path from the tab 21 to the adapter plate 30 and then to the first end plate 11 to be shorter and more direct, reducing the internal resistance loss of the current during transmission and improving the charging and discharging efficiency and energy utilization of the cylindrical battery 100.

[0098] In some embodiments, 0.4 ≤ P ≤ 0.9. It can be understood that, in a specific structure where at least a portion of the projection of the first solder mark on the first end plate 11 lies within the area surrounded by the thinning region 13, the ratio of the area of ​​the adapter piece 30 to the end face area of ​​the cell 20 is in the range of 0.4-0.9. For example, P can be 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, and can of course be flexibly selected within the above range.

[0099] Thus, with the projection portion of the first solder mark located within the area surrounded by the thinning zone 13, the adapter piece 30 can be guaranteed to have sufficient area, improving heat conduction efficiency. This allows the pressure relief valve 12 to respond more quickly and release pressure promptly when the cylindrical battery 100 overheats, while ensuring conductivity and welding structure reliability, thereby improving the safety performance of the cylindrical battery 100.

[0100] In some embodiments, the casing 10 of the cylindrical battery 100 further includes a second end face located at a second end of the casing 10 along its own axial direction. The second end face is disposed opposite to the first end plate 11. When the ratio of the distance between the second end face and the first end plate 11 to the diameter of the first end plate 11 is greater than or equal to 1.5, 1 10 -4 ≤A / V≤1.9 10 -4 That is, in this embodiment, the volumetric energy density of the cylindrical battery 100 is 1. 10 -4 Ah / mm³-1.9 10 -4 Ah / mm³.

[0101] Specifically, in the case of a cylindrical battery 100 with an aspect ratio greater than or equal to 1.5, when the aspect ratio of the cylindrical battery 100 is close to the golden ratio, the stress distribution of its casing 10 under internal pressure is more uniform. Compared with slender (aspect ratio > 2) or short and stout (aspect ratio < 1) cylindrical batteries, it can withstand higher internal pressure and reduce the risk of casing 10 rupture during thermal runaway. Moreover, the heat conduction path can be optimized. At this aspect ratio, the heat conduction distance from the center of the cylindrical battery 100 to the casing 10 is the shortest, and the heat distribution is more uniform, which helps to avoid premature triggering of the pressure relief valve or the spread of thermal runaway caused by local overheating.

[0102] Based on this, by limiting A / V to 1 10 -4 -1.9 10 -4 Within this range, it is beneficial to achieve precise thermal runaway response. When thermal runaway occurs inside the cylindrical battery 100, the 1.5 aspect ratio structure allows the pressure relief valve 12 to receive internal pressure more evenly. With sufficient energy density space, high-temperature gas can be discharged quickly along the optimal path, avoiding the risk of explosion caused by pressure accumulation.

[0103] In addition, the balanced stress distribution and heat conduction path reduce the uneven expansion and contraction of the cell 20 and the accumulation of side reactions during charging and discharging. Combined with the stability design of the high energy density material system, it can significantly improve the cycle life and capacity retention of the cylindrical battery 100.

[0104] In some embodiments, when the diameter of the first end plate 11 of the cylindrical battery 100 is greater than or equal to 40 mm, 1 10 -4 ≤A / V≤1.8 10 -4 That is, in this embodiment, the volumetric energy density of the cylindrical battery 100 is 1. 10 -4 Ah / mm³-1.8 10 -4 Ah / mm³.

[0105] Specifically, when the diameter of the cylindrical battery 100 is greater than or equal to 40mm (large-diameter cylindrical battery 100), if the A / V value is too small and less than 1... 10 -4 Cylindrical batteries have a relatively low energy density (100V), making it difficult to meet power demands; if the A / V value is too high, exceeding 1.8... 10 -4 The cylindrical battery 100 generates a large amount of heat and gas, which can easily lead to thermal runaway. Furthermore, the pressure of the pressure relief valve 12 is difficult to match.

[0106] Thus, when the diameter of the cylindrical battery 100 is greater than or equal to 40mm, by limiting 1 10 -4 ≤A / V≤1.8 10 -4 This allows the capacity density of the cylindrical battery 100 to be within a reasonable range under a large-diameter structure, while also taking into account the energy density, heat dissipation, and safety performance of the cylindrical battery 100, ensuring the reliable operation of the pressure relief valve 12, and improving the safety and stability of the large-diameter cylindrical battery 100.

[0107] In some embodiments, the distance between the cell end face 22 and the thinning region 13 in the axial direction of the housing 10 is h mm, where h mm satisfies: 1 mm ≤ h mm ≤ 5 mm. For example, the value of h can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5. Of course, the value of h can be flexibly selected within the above range as needed.

[0108] Thus, by limiting the axial distance h between the cell end face 22 and the thinning area 13 to a reasonable range, on the one hand, sufficient space can be provided for the installation of the adapter piece 30, and on the other hand, sufficient gas storage space can be provided to ensure that the heat and internal pressure generated by the cell 20 are efficiently and stably transferred to the thinning area 13 of the pressure relief valve 12. This allows the pressure relief valve 12 to open in a timely and accurate manner when the cylindrical battery 100 is abnormal, avoiding structural interference caused by too small a distance and pressure or heat transfer lag caused by too large a distance, thereby improving the safety and structural reliability of the cylindrical battery 100.

[0109] In some embodiments, the tab portion 21 includes a positive tab 211 and a negative tab 212, which are located at the same end of the battery cell 20 (located at the top of the battery cell 20, near the end of the first end plate 11). The distance between the battery cell end face 22 (the upper end face of the battery cell 20) and the thinning area 13 of the pressure relief valve 12 in the axial direction of the housing 10 is 1.5mm-5mm.

[0110] Understandably, since the positive tab 211 and negative tab 212 of the electrode portion are both at the same end of the cell 20, the end face of the cell 20 covered and blocked by the adapter piece 30 (including the positive and negative adapter pieces) on the electrode portion side of the cell 20 is relatively large. If h is too small, under the unfavorable condition of the exhaust path being blocked, the gas storage space on that side will be too small and the heat will be too concentrated, which may increase the risk of thermal runaway of the cylindrical battery 100.

[0111] Thus, when the positive tab 211 and negative tab 212 of the electrode are located at the same end of the cell 20, by limiting 1.5mm≤hmm≤5mm, it can be ensured that there is sufficient gas storage space on one side of the electrode end of the cell 20, so as to make up for the disadvantage of the gas transmission path being blocked, increase the pressure relief threshold to avoid premature triggering of the pressure relief valve 12, and ensure the structural safety of the cylindrical battery 100 and the reliability of the pressure relief performance of the pressure relief valve 12.

[0112] In some embodiments, the positive tab 211 and the negative tab 212 are located at both ends of the cell 20 along the axial direction of the housing 10, and 22Ah≤A Ah≤40 Ah.

[0113] Understandably, the positive tab 211 and negative tab 212 are respectively located at both ends of the cell 20. When thermal runaway occurs inside the cylindrical battery 100 and the pressure relief valve 12 opens to release high-temperature gas, the positive tab 211 and negative tab 212 will not create a short circuit risk near the pressure relief channel, preventing the short circuit from exacerbating the thermal runaway reaction and reducing the probability of the cylindrical battery 100 catching fire or exploding. In addition, it allows the gas inside the cell 20 to diffuse more evenly to both ends during thermal runaway. With the design of the pressure relief valve 12, the gas can be discharged more smoothly, avoiding excessive local pressure that could cause the casing 10 to rupture. By limiting the maximum energy density, it avoids using overly aggressive material systems (such as ultra-high nickel positive electrodes or excessive silicon-carbon negative electrodes) to pursue excessively high energy density, thus avoiding poor stability of such material systems and increasing the risk of thermal runaway. Combined with the separate design of the positive tab 211 and negative tab 212, it can improve the safety redundancy of the cylindrical battery 100 while ensuring a certain energy density.

[0114] Thus, when the positive tab 211 and the negative tab 212 are located at the two ends of the axial direction of the cell 20, by limiting 22 Ah ≤ A Ah ≤ 40 Ah, the capacity A and heat generation of the cylindrical battery 100 can be reasonably controlled, avoiding severe overheating and excessive internal pressure of the cell 20 due to excessive capacity. This ensures that the gas generation and expansion inside the cylindrical battery 100 are matched with the opening pressure of the pressure relief valve 12, thereby improving the safety and reliability of the cylindrical battery 100 under this tab structure.

[0115] In some embodiments, the battery cell 20 includes a positive electrode sheet and a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive active layer coated on both sides of the positive current collector. The negative electrode sheet includes a negative current collector and a negative active layer coated on both sides of the negative current collector.

[0116] Understandably, a separator is positioned between the positive and negative electrode plates to separate them and prevent short circuits. The separator can be at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. A coating can also be applied to the separator surface; this coating can be inorganic or organic. Inorganic coating materials include at least one of alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, and boehmite. Organic coating materials include at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0117] The positive electrode current collector can be in the form of foil, mesh, porous, perforated, or trench, etc., and the material of the positive electrode current collector can be aluminum, aluminum alloy, stainless steel, aluminum-plated composite materials, etc., but is not limited to this embodiment. The positive electrode current collector is used to collect the current generated by the positive electrode active layer, reduce the internal resistance of the positive electrode sheet, improve the conductivity efficiency, and at the same time provide a carrier for the positive electrode active layer to adhere, ensuring the structural stability of the positive electrode sheet. In addition, it enables the positive electrode sheet to uniformly transport electrons. Similarly, the negative electrode current collector can also be in the form of foil, mesh, porous, perforated, or trench, etc., and the material of the negative electrode current collector can be copper, copper alloy, stainless steel, copper-plated composite materials, etc., but is not limited to this embodiment. The negative electrode current collector is used to collect the current generated by the negative electrode active layer, reduce the internal resistance of the negative electrode sheet, improve the conductivity efficiency, and at the same time provide a carrier for the negative electrode active layer to adhere, ensuring the structural stability of the negative electrode sheet. In addition, it enables the negative electrode sheet to uniformly transport electrons.

[0118] Understandably, the positive electrode has a high potential. At high potentials, aluminum will form a dense oxide film, which is not easily corroded and can conduct electricity stably. However, copper will be directly corroded and dissolved at high potentials, rendering a cylindrical battery 100% unusable. Therefore, copper cannot be used as the positive electrode current collector. The negative electrode has a low potential (close to the lithium potential). Copper is very stable at low potentials, does not corrode, and is not easily alloyed. However, aluminum will form an alloy with lithium at low potentials, resulting in pulverization, expansion, and even damage. Therefore, aluminum cannot be used as the negative electrode current collector.

[0119] The positive electrode active layer includes positive electrode active material, positive electrode conductive agent, and positive electrode binder. The positive electrode active material includes, but is not limited to, at least one of the following: lithium phosphate, lithium transition metal oxide and their respective modified compounds, or other conventional materials that can be used as positive electrode active materials for cylindrical batteries; these positive electrode active materials can be used alone or in combination of two or more. The positive electrode conductive agent includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black, carbon nanotubes, graphene, and carbon nanofibers; the positive electrode binder can be at least one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), polyimide (PI), and polytetrafluoroethylene (PTFE).

[0120] For example, lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (LiFePO4, LFP), LFP-carbon composites, lithium manganese phosphate (LiMnPO4, LMP), LMP-carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate-carbon composites. Lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds.

[0121] The negative electrode active layer includes negative electrode active material, negative electrode conductive agent, and negative electrode binder. The negative electrode active material can be carbon-based materials such as graphite, porous carbon, hard carbon, soft carbon, and mesophase carbon microspheres, or silicon-based materials such as elemental silicon, silicon oxide, silicon-carbon composite, and silicon-nitrogen composite. The negative electrode conductive agent can be conductive carbon black, carbon nanotubes, etc., and the negative electrode binder can be styrene-butadiene rubber, polyacrylic acid, etc.

[0122] The compaction density of the positive electrode active layer is 2.45 g / cm³. 3 -3.8g / cm 3 For example, the compaction density of the positive electrode active layer can be 2.45 g / cm³. 3 2.5 g / cm 3 2.7 g / cm 3 2.8 g / cm 3 3 g / cm 3 3.1 g / cm 3 3.3 g / cm 3 3.5 g / cm 3 3.6 g / cm 3 3.8 g / cm 3 In addition, the compaction density of the positive electrode active layer can also be flexibly adjusted within the above range.

[0123] The compaction density of the negative electrode active layer is 0.9 g / cm³. 3 -1.8g / cm 3 For example, the compaction density of the negative electrode active layer can be 0.9 g / cm³. 3 1 g / cm 3 1.1 g / cm 3 1.2 g / cm 3 1.3 g / cm 3 1.4 g / cm 3 1.5 g / cm 3 1.6 g / cm 3 1.7 g / cm 3 Or 1.8 g / cm 3 In addition, the compaction density of the positive electrode active layer can also be flexibly adjusted within the above range.

[0124] Understandably, if the compaction density of the positive and negative active layers is too high, the electrolyte cannot penetrate, causing lithium ions to be unable to move smoothly. This results in poor fast charging performance, easy lithium plating, overheating, and even short circuits. At the same time, it also causes the positive and negative electrode sheets to break and shed material easily during paper winding. If the compaction density of the positive and negative active layers is too low, there is less positive active material per unit volume of the cylindrical battery, leading to problems such as low capacity, low density, high internal resistance, high heat generation, and slow charging and discharging.

[0125] Thus, by controlling the compaction density of the active layers (including the positive and negative active layers) within the aforementioned range, on the one hand, the packing density of the positive and negative active layers can be increased, thereby increasing the content of active materials (positive and negative active materials) per unit volume and thus improving the energy density of the cell 20. On the other hand, a suitable porous structure can be formed inside the active layers, facilitating electrolyte wetting and rapid ion (which can be lithium ions) transport, reducing the internal resistance of the cell 20, and improving its rate performance, cycle performance, and safety performance. Furthermore, it can enhance the bonding strength between the active layers and the current collectors (positive and negative current collectors), preventing the active layers from detaching and improving the structural stability and lifespan of the cell 20.

[0126] In some embodiments, the adapter piece 30 is provided with a through hole 31, and at least a portion of the projection of the through hole 31 onto the first end plate 11 is located within the area surrounded by the thinning region 13. It can be understood that the through hole 31 is a hole that penetrates the thickness direction of the adapter piece 30; when the through hole 31 is projected onto the first end plate 11 in a direction perpendicular to the plate surface, at least a portion of the resulting projection area falls within the area enclosed by the thinning region 13 on the first end plate 11.

[0127] The number of through holes 31 can be one, two, three or more; the shape of the through holes 31 can be a circular hole, an elliptical hole, a square hole, a rectangular hole, a trapezoidal hole, a rhomboid hole, or other polygonal holes, or a conical hole, a stepped hole, or a regular hole, an irregular hole, etc., and is not limited to this embodiment.

[0128] Thus, by at least partially corresponding the through hole 31 of the adapter plate 30 with the thinning area 13 of the first end plate 11 in the thickness direction, the gas generated inside the battery cell 20 can be smoothly discharged through the through hole 31, which is beneficial for timely pressure relief. At the same time, the through hole 31 can reduce the obstruction of the adapter plate 30 to the gas flow, ensure smooth airflow, and further improve the pressure relief efficiency and safety reliability of the battery cell 20.

[0129] Alternatively, in other possible embodiments, the through hole 31 and the thinning region 13 can be staggered to meet different usage requirements.

[0130] In some embodiments, the area of ​​a single through hole 31 is 2 mm². 2 -100mm 2 For example, the area of ​​a single through hole can be 2 mm. 2 5 mm 2 10 mm 2 20 mm 2 30 mm 2 40mm 2 50 mm 2 60mm 2 70 mm 2 80 mm 2 90 mm 2 Or 100mm 2 This serves two purposes. Firstly, it prevents the pressure-relieving gas from failing to pass through when the area of ​​the through hole 31 is too small, thus hindering pressure relief. Secondly, it prevents the effective current-carrying area of ​​the adapter plate from being affected when the area of ​​the through hole 31 is too large, which would weaken the current-carrying capacity of the cylindrical battery and increase heat generation.

[0131] In some embodiments, the battery cell 20 has a winding hole 23 in the middle, and the through hole 31 is at least partially disposed opposite to the winding hole 23, that is, the projection of the through hole 31 on the first end plate 11 and the projection of the winding hole 23 on the first end plate 11 at least partially overlap. The winding hole 23 is a hollow circular hole formed during the winding process of the battery cell 20.

[0132] Thus, the through hole 31 of the adapter plate 30 is at least partially opposite to the winding hole 23 in the middle of the battery cell 20, which allows the gas generated inside the battery cell 20 to be smoothly discharged outward through the winding hole 23 and the through hole 31, achieving rapid pressure relief and preventing pressure buildup inside the battery cell 20; at the same time, it can reduce the obstruction effect of the adapter plate 30 on gas flow, ensure smooth airflow, and improve the pressure relief efficiency and safety reliability of the battery cell 20.

[0133] Alternatively, in other possible embodiments, the through hole 31 and the core hole 23 can be staggered to meet different requirements.

[0134] In some embodiments, the adapter piece 30 includes a first region 32 and a second region 33, with a height difference between the first region 32 and the second region 33 along the axial direction of the housing 10. This height difference can be 0.1mm-0.6mm. Optionally, the first region 32 may be higher than the second region 33, or the second region 33 may be higher than the first region 32. The first region 32 is welded to the tab, and the second region 33 is welded to the electrode 40 of the cylindrical battery 100.

[0135] For example, the adapter 30 may include a positive adapter and a negative adapter. The first region 32 of the positive adapter is welded to the positive tab 211, and the second region 33 of the positive adapter can be connected to one of the terminal post and the housing. The first region 32 of the negative adapter is welded to the negative tab 212, and the second region 33 of the negative adapter can be connected to the other of the terminal post and the housing.

[0136] In this way, by creating a height difference between the first region 32 and the second region 33 of the adapter piece 30 along the axial direction of the housing 10, the position and height differences between the tab and the electrode 40 of the cylindrical battery 100 can be accommodated. This facilitates reliable welding of the first region 32 to the tab and stable welding of the second region 33 to the electrode 40, avoids structural interference during welding, improves welding quality and assembly convenience, optimizes the internal spatial layout of the cylindrical battery, and enhances the structural stability of the cylindrical battery 100.

[0137] In addition, a height difference is provided between the first region 32 and the second region 33, which can be used to form a gap between the cell end face and the adapter piece 30, and make the gap a venting channel, thereby making the gas distribution inside the cylindrical battery more uniform.

[0138] In some embodiments, the thickness of the adapter piece 30 is 0.2 mm to 1.2 mm. For example, the thickness of the adapter piece 30 can be 0.2 mm, 0.4 mm, 0.5 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, or 1.2 mm. Understandably, if the thickness of the adapter piece 30 is too small, the structural strength of the adapter piece 30 is insufficient, making it prone to deformation, tearing, and breakage. Furthermore, problems such as burn-through and incomplete welding may occur during the welding process. At the same time, it will reduce the current-carrying cross-sectional area, increase the internal resistance, and cause severe overheating of the cylindrical battery 100. If the thickness of the adapter piece 30 is too large, it will occupy the internal space of the cylindrical battery 100, affecting the arrangement of the cell 20. Moreover, the adapter piece 30 has high strength and is not easy to bend or break during pressure relief, which may block the pressure relief channel and lead to untimely pressure relief.

[0139] In this way, by controlling the thickness of the adapter piece 30 within the above-mentioned range, it is possible to ensure that the adapter piece 30 has sufficient structural strength and conductivity, reduce the internal resistance of the cylindrical battery 100, improve welding reliability, and avoid deformation, tearing or burn-through due to excessive thickness; at the same time, it is possible to control the space occupied by the adapter piece 30, reduce the occupation of the internal space of the cylindrical battery 100, improve space utilization and energy density, and avoid space waste and excessive weight due to excessive thickness.

[0140] In some embodiments, the value of A / V ranges from 1. 10 -4 ≤A / V≤2.1 10 -4 In this embodiment, the volumetric energy density of the cylindrical battery 100 is 1. 10 -4 Ah / mm³-2.1 10 -4 Ah / mm³.

[0141] Optionally, the value of L is in the range of 0.03 mm ≤ L mm ≤ 0.3 mm, that is, the thickness of the thinning region 13 is 0.03 mm - 0.3 mm.

[0142] Optionally, the value of P can be in the range of 0.4 ≤ P ≤ 0.95.

[0143] In this way, by flexibly selecting and limiting the value range of one, two or more of the above parameters, the volumetric energy density, structural strength, pressure relief performance, conductivity and space utilization of the cylindrical battery 100 can be adjusted and optimized in a targeted manner according to actual product needs. Under the premise of ensuring the safety and reliability of the cylindrical battery 100, the flexibility of parameter matching and design universality can be achieved, the applicability of the solution can be expanded, and the overall performance and production adaptability of the cylindrical battery 100 can be improved.

[0144] In some embodiments, the cylindrical battery 100 may further include a terminal post 41 and an insulating component 42. A terminal post hole may be formed on the first end plate 11, and at least a portion of the terminal post 41 passes through the terminal post hole of the first end plate 11. The insulating component 42 is disposed between the terminal post 41 and the first end plate 11 to ensure insulation between the terminal post 41 and the first end plate 11, preventing short circuits in the cylindrical battery 100.

[0145] The adapter 30 includes a positive adapter 310 and a negative adapter 320. One of the electrode post 41 and the first end plate 11 is connected to the positive adapter 310 and the other is connected to the negative adapter 320. The electrode 40 includes the electrode post 41 and the first end plate 11.

[0146] Understandably, the terminal 41 passes through the first end plate 11. The first end of the terminal 41 is inside the cylindrical battery 100 to connect with the adapter piece 30, and the second end is outside the cylindrical battery 100 to connect with an external circuit. The insulating component 42 separates the terminal 41 from the first end plate 11 to prevent short circuits caused by contact between the terminal 41 and the first end plate 11. Understandably, one of the terminal 41 and the first end plate 11 is connected to the positive adapter piece 310, and the other is connected to the negative adapter piece 320.

[0147] Specifically, the positive electrode adapter 310 has a first protruding edge 311, and the negative electrode adapter 320 has a second protruding edge 321. There is a height difference between the first protruding edge 311 and the second protruding edge 321, meaning that one of the first protruding edge 311 and the second protruding edge 321 connects to the first end plate 11, thereby preventing the positive electrode adapter 310 and the negative electrode adapter 320 from simultaneously overlapping with the first end plate 11 and causing a short circuit. Furthermore, if the first protruding edge 311 is higher than the second protruding edge 321, the negative electrode adapter 320 has a first protrusion (which can be the second region 33 mentioned above); if the second protruding edge 321 is higher than the first protruding edge 311, the positive electrode adapter 310 has a first protrusion. If the positive electrode adapter 310 is connected to the terminal 41, then the positive electrode adapter 310 has a first protrusion, and the positive electrode adapter 310 is connected to the terminal 41 through the first protrusion; if the negative electrode adapter 320 is connected to the terminal 41, then the negative electrode adapter 320 has a first protrusion, and the negative electrode adapter 320 is connected to the terminal 41 through the first protrusion. The first protrusion is higher than the first protrusion 311 and the second protrusion 321.

[0148] The materials of the pole post 41 include, but are not limited to, copper, aluminum, aluminum alloy, copper-aluminum alloy, etc.; the materials of the first end plate 11 include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, aluminum-plastic film, etc.

[0149] Thus, electrical insulation between the terminal post 41 and the first end plate 11 is achieved through the insulating component 42, avoiding direct contact between the two and causing a short circuit. At the same time, connecting the terminal post 41 and the first end plate 11 to the positive electrode adapter 310 and the negative electrode adapter 320 respectively can form independent and non-interfering positive and negative current paths, ensuring stable and reliable current transmission, effectively preventing the formation of a short circuit between the positive and negative electrodes, and improving the conductivity, structural safety and reliability of the cylindrical battery.

[0150] The following section uses cylindrical battery 100 as an example of a lithium-ion cylindrical battery to introduce its preparation method, and provides some embodiments and comparative examples of cylindrical battery 100.

[0151] (1) Preparation of the positive electrode:

[0152] 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.

[0153] The mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98): (4~1): (4~1).

[0154] (2) Preparation of negative electrode:

[0155] 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.

[0156] The ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0157] (3) Preparation of electrolyte:

[0158] 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.

[0159] (4) Preparation of diaphragm: Polyethylene film is used as diaphragm.

[0160] (5) Preparation of lithium-ion cylindrical batteries:

[0161] The aforementioned positive electrode, separator, and negative electrode are stacked in sequence and wound to form a bare cell. The bare cell is placed in the casing 10 of the cylindrical battery 100 to form cell 20. Cell 20 is electrically connected to the electrodes of the cylindrical battery 100 through an adapter 30. The cylindrical battery 100 is dried, injected with electrolyte, and then packaged, allowed to stand, formed, and capacitated to obtain a lithium-ion cylindrical battery.

[0162] In the selection of materials for the cylindrical 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.

[0163] 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.

[0164] 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.

[0165] The solvent can be deionized water, NMP (N-methylpyrrolidone), alcohol, ether, ketone or other types of pyrrolidone, etc.

[0166] 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.).

[0167] 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.).

[0168] The cylindrical battery 100 prepared by the above method was subjected to the following tests:

[0169] (1) Test methods for capacity and volumetric energy density (A / V) of cylindrical battery 100:

[0170] The test methods for the capacity and volumetric energy density of cylindrical batteries 100 shall refer to GB / T 31486-2024 (Electrical performance requirements and test methods for cylindrical power storage batteries for electric vehicles).

[0171] The method for measuring the volume V of the cylindrical battery 100 is as follows:

[0172] The volume V of a cylindrical battery 100 is equal to the area of ​​the first end plate 11. The height of the sidewall of the housing 10 (the dimension along the axial direction of the cylindrical battery 100).

[0173] Methods for controlling the volumetric energy density (A / V) of a cylindrical battery 100:

[0174] Volumetric energy density can be controlled by changing the materials of the positive and negative electrode active materials of the cylindrical battery 100, or by optimizing the cylindrical battery structure to increase the proportion of active materials in the cylindrical battery.

[0175] Changing the material system can improve the capacity of the cell 20. For example, changing the cathode material from lithium iron phosphate to a ternary system, or selecting a high-nickel ternary cathode material (NCM811 / Ni90+), can significantly improve the specific capacity by increasing the nickel content. Replacing the anode material from traditional graphite to silicon-carbon (Si / C) can also improve the volumetric energy density of the cylindrical battery.

[0176] From the perspective of optimizing the cylindrical battery structure, for cell 20, the following measures can be taken: increasing the thickness of the active material layer on the electrode (thickness of lithium iron phosphate system: 70μm-210μm, thickness of ternary system: 30μm-150μm; the above thicknesses cover both single-sided and double-sided coating cases; for double-sided coating, the total thickness of both sides is calculated), reducing the thickness of the current collector in the electrode (current collector thickness of positive electrode: 6μm-18μm, current collector thickness of negative electrode: 4μm-12μm), and increasing the compaction density of the active material (in the positive electrode, the compaction density of lithium iron phosphate system is 2.4 g / cm³). 3 -2.8g / cm 3 The compaction density of the ternary system is 3.2 g / cm³. 3 -3.8 g / cm 3 In the negative electrode, the compaction density of the graphite negative electrode is 1.2 g / cm³. 3 -1.8 g / cm 3 The compaction density of the silicon-carbon anode is 0.9 g / cm³. 3 -1.1g / cm 3 Alternatively, the volume of other components of the cylindrical battery 100 can be reduced to provide more space for the battery cell 20, thereby increasing the volumetric energy density. For example, the thickness of the cylindrical battery casing 10 can be appropriately reduced (the thickness of the casing 10 ranges from 0.2 mm to 1 mm), the gap between the battery cell 20 and the end face of the cylindrical battery 100 cover plate can be reduced (the gap distance is 1 mm to 5 mm), and the diameter of the winding hole of the battery cell 20 can be reduced (2 mm to 10 mm), etc.

[0177] (2) Methods for measuring the dimensions and area of ​​the components of the cylindrical battery 100:

[0178] 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.

[0179] The method for testing the thickness L of the thinning region 13 is to make a cross-section of the area where the thinning region 13 is located along a direction perpendicular to the plane where the first end plate 11 is located, and measure the thickness of the thinning region 13 on the cross-section.

[0180] The area of ​​the adapter piece 30 is the projected area of ​​the adapter piece 30 on the plane where the first end plate 11 is located.

[0181] The end face area of ​​cell 20 is the area of ​​the outermost circumference of cell 20. The radius of cell 20 is R. Therefore, the end face area of ​​cell 20 = π. R 2 .

[0182] (3) Test method for the compaction density of the active layer of both the positive and negative electrode plates:

[0183] The compaction density of the positive electrode is determined in accordance with GB / T 44330-2024 (Determination of compaction density of positive electrode material powder for lithium-ion cylindrical batteries).

[0184] The compaction density of the negative electrode is in accordance with GB / T 24533-2019 (graphite negative electrode materials for lithium-ion cylindrical batteries).

[0185] (4) Test method for early valve opening in thinning zone 13:

[0186] Following the above-described cylindrical battery preparation method, 100 cylindrical batteries 100 were prepared for each embodiment and comparative example. These prepared cylindrical batteries 100 were used as samples, and all other test conditions remained consistent. At room temperature (20°C), the cylindrical batteries 100 were charged at a constant current rate of 4C until the voltage reached the upper limit voltage. Then, constant voltage charging was switched until the current of the cylindrical battery dropped to 0.05C. After standing for 30 minutes, the batteries were discharged at a 1C rate to the lower limit voltage, and then stood for another 30 minutes. This constituted one cycle.

[0187] After cycling the cylindrical battery 100 times, remove the cylindrical battery 100 and observe whether the thinning zone 13 of the pressure relief valve 12 has opened. Specifically, the thinning zone 13 is ruptured, causing the cell 20 to fail to seal against the outside environment. If the number of cylindrical batteries in which the thinning zone 13 has opened prematurely is greater than 3, it is considered unqualified; if the number is less than or equal to 3 but greater than 1, it is considered qualified; if the number is less than or equal to 1, it is considered good.

[0188] The upper and lower voltage limits of cylindrical batteries of different systems need to be adjusted accordingly: Lithium iron phosphate (LFP) - upper limit voltage 3.65V, lower limit voltage 2.5V; Nickel cobalt manganese ternary NCM - upper limit voltage 4.25V, lower limit voltage 2.5V; Lithium manganese iron phosphate (LFMP) - upper limit voltage 4.25V, lower limit voltage 2.5V; Lithium nickel manganese oxide - upper limit voltage 4.8V, lower limit voltage 3.5V.

[0189] In this test, the active material for the positive electrode of the cylindrical battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, all other positive electrode materials meet the above test requirements, and the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0190] (5) Test method for the proportion of casing damage during thermal runaway of cylindrical batteries:

[0191] Following the above-described cylindrical battery preparation method, 150 cylindrical batteries 100 were prepared for each embodiment and comparative example. These prepared cylindrical batteries 100 were used as samples, and all other test conditions remained consistent. The cylindrical batteries 100 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.

[0192] Heating plates are placed on the circumference of the cylindrical battery casing to heat the triggering object at maximum power. 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.

[0193] Record the number N1 of cylindrical batteries 100 that experienced thermal runaway. After the pressure relief is completed, observe the casing 10 of the thermally runaway cylindrical batteries 100 to see if the casing 10 ruptures in an area outside the pressure relief mechanism. Record the number N2 of cylindrical batteries 100 whose casing 10 ruptured. The percentage of casing 10 damaged during thermal runaway of a cylindrical battery = (N2 / N1). 100% When the proportion of casing 10 damage during thermal runaway of a cylindrical battery is greater than 4%, it is recorded as unqualified; when the proportion of casing 10 damage during thermal runaway of a cylindrical battery is greater than 2% and less than or equal to 4%, it is recorded as qualified; when the proportion of casing 10 damage during thermal runaway of a cylindrical battery is less than or equal to 2%, it is recorded as good.

[0194] The upper and lower voltage limits of cylindrical batteries of different systems need to be adjusted accordingly: Lithium iron phosphate (LFP) - upper limit voltage 3.65V, lower limit voltage 2.5V; Nickel cobalt manganese ternary NCM - upper limit voltage 4.25V, lower limit voltage 2.5V; Lithium manganese iron phosphate (LFMP) - upper limit voltage 4.25V, lower limit voltage 2.5V; Lithium nickel manganese oxide - upper limit voltage 4.8V, lower limit voltage 3.5V.

[0195] In this test, the active material for the positive electrode of the cylindrical 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.

[0196] The following table is a statistical table of parameters and performance test results for various embodiments and comparative examples of this application:

[0197]

[0198] As can be seen from Example 1 and Comparative Examples 2 and 3, when the capacity of the cylindrical battery 100 is greater than 20Ah, this application controls A... P The L / V value is greater than or equal to 0.2 10 -5 This helps prevent the thinning zone 13 from opening prematurely before the internal pressure of the cylindrical battery reaches the preset valve opening pressure.

[0199] As can be seen from Examples 9, 11, and Comparative Example 1, when the capacity of the cylindrical battery 100 is greater than 20 Ah, this application controls A... P The L / V value is less than or equal to 4.73 10 -5 This helps prevent the pressure relief valve from failing to open in time when the internal pressure of the cylindrical battery reaches the preset valve opening pressure, which could lead to the internal pressure of the cylindrical battery exceeding the preset valve opening pressure and causing the casing 10 to rupture to a greater extent due to excessive burst pressure.

[0200] As can be seen from embodiments 1-15, in this embodiment, by optimizing the thickness L of the thinning region 13, the ratio P of the area of ​​the adapter piece 30 to the end face area of ​​the cell 20 is improved, and the volumetric energy density A / V of the cylindrical battery 100 is controlled, thus increasing A... P The L / V value should be controlled at 0.2. 10 -5 -4.73 10 -5 Within this range, it helps to solve the problem of untimely pressure relief by the pressure relief valve, improves the smoothness of the pressure relief path and the safety of thermal runaway, and ensures the safe use of the cylindrical battery 100.

[0201] Secondly, this embodiment also provides a battery pack, which may include the cylindrical battery 100 in the above embodiment. There may be multiple cylindrical batteries 100, and the multiple cylindrical batteries 100 are connected in series and / or in parallel to form a battery pack.

[0202] The battery pack of this embodiment, by employing the cylindrical battery 100 of the above embodiment, can reduce the impact on other cylindrical batteries 100 around it in the event of thermal runaway of a certain cylindrical battery 100, thereby improving the overall safety of the battery pack.

[0203] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A cylindrical battery, characterized in that, include: The housing includes a first end plate located at one end along its own axial direction, and a pressure relief valve is provided on the first end plate. The pressure relief valve includes a thinning region, the thickness of which is less than the thickness of the first end plate. A battery cell, wherein the battery cell is disposed within the housing; An adapter piece is disposed between the first end plate and the end face of the battery cell, and the adapter piece is electrically connected to the tab portion of the battery cell and the electrode of the cylindrical battery, respectively. Wherein, the thickness of the thinned region is L mm, and the volume of the cylindrical battery is V mm. 3 The ratio of the area of ​​the adapter plate to the end face area of ​​the battery cell is P, and the capacity of the cylindrical battery is A Ah. L, V, P, and A satisfy: 0.2 10 -5 ≤A P L / V≤4.73 10 -5 , where A Ah≥20Ah.

2. The cylindrical battery according to claim 1, characterized in that, The area enclosed by the thinning zone at least partially overlaps with the projection of the adapter piece on the first end plate.

3. The cylindrical battery according to claim 2, characterized in that, 0.03mm≤L mm≤0.25mm.

4. The cylindrical battery according to claim 1, characterized in that, The first end plate has a first protrusion that protrudes in a direction away from the battery cell.

5. The cylindrical battery according to claim 4, characterized in that, The first protrusion includes a first bottom wall opposite to the battery cell and a first side wall surrounding the first bottom wall, and the thinning region is disposed on the first bottom wall.

6. The cylindrical battery according to claim 1, characterized in that, The first end plate has a second recess, which protrudes toward the battery cell. The second recess includes a second bottom wall opposite to the battery cell and a second side wall surrounding the second bottom wall. The thinning region is located on the second bottom wall, and 20 Ah ≤ A Ah ≤ 36 Ah.

7. The cylindrical battery according to claim 1, characterized in that, The first end plate has a first groove, the first groove has a first bottom wall, the first bottom wall has a second groove, and the portion of the first bottom wall that is axially opposite to the second groove is the thinning area.

8. The cylindrical battery according to claim 7, characterized in that, Along the radial direction of the housing, the width of the first groove is 0.5mm-2.5mm.

9. The cylindrical battery according to claim 7, characterized in that, The first groove is a continuous annular groove.

10. The cylindrical battery according to claim 7, characterized in that, The second groove is a continuous annular groove.

11. The cylindrical battery according to claim 7, characterized in that, The second groove is an arc-shaped segment extending circumferentially along the shell, 0.2 10 -5 ≤A P L / V≤4.5 10 -5 .

12. The cylindrical battery according to claim 11, characterized in that, The second groove is an arc segment. The second groove has a first end and a second end distributed circumferentially along the housing. The first end and the second end are spaced apart in the circumferential direction. The ratio of the distance between the first end and the second end in the circumferential direction to the length of the second groove in the circumferential direction is 0.05-0.

3.

13. The cylindrical battery according to any one of claims 1-12, characterized in that, The adapter piece is welded to the tab of the battery cell to form a first solder mark, and at least a portion of the projection of the first solder mark on the first end plate is located within the area surrounded by the thinning area.

14. The cylindrical battery according to claim 13, characterized in that, P satisfies: 0.4≤P≤0.

9.

15. The cylindrical battery according to any one of claims 1-12, characterized in that, The cylindrical battery casing further includes a second end face, which is disposed opposite to the first end plate. When the ratio of the distance between the second end face and the first end plate to the diameter of the first end plate is greater than or equal to 1.5, 1 10 -4 ≤A / V≤1.9 10 -4 .

16. The cylindrical battery according to claim 15, characterized in that, When the diameter of the first end plate is greater than or equal to 40 mm, 1 10 -4 ≤A / V≤1.8 10 -4 .

17. The cylindrical battery according to any one of claims 1-12, characterized in that, The distance between the end face of the battery cell and the thinning area in the axial direction of the housing is h mm, where h mm satisfies: 1 mm ≤ h mm ≤ 5 mm.

18. The cylindrical battery according to any one of claims 1-12, characterized in that, The electrode portion includes a positive electrode and a negative electrode, which are located at the same end of the battery cell, and h mm satisfies: 1.5 mm ≤ h mm ≤ 5 mm.

19. The cylindrical battery according to any one of claims 1-12, characterized in that, The electrode portion includes a positive electrode and a negative electrode, which are located at both ends of the battery cell along the axial direction of the housing. A Ah satisfies: 22Ah≤A Ah≤40 Ah.

20. The cylindrical battery according to any one of claims 1-12, characterized in that, The battery cell includes a positive electrode plate and a negative electrode plate, as well as a separator disposed between the positive electrode plate and the negative electrode plate. The positive electrode sheet includes a positive current collector and a positive active layer coated on both sides of the positive current collector; The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer coated on both sides of the negative electrode current collector; The compaction density of the positive electrode active layer is 2.45 g / cm³. 3 -3.8g / cm 3 ; and / or, the compaction density of the negative electrode active layer is 0.9 g / cm³. 3 -1.8g / cm 3 .

21. The cylindrical battery according to any one of claims 1-12, characterized in that, The adapter piece is provided with a through hole, and at least a portion of the projection of at least one of the through holes onto the first end plate is located within the area surrounded by the thinning zone.

22. The cylindrical battery according to any one of claims 1-12, characterized in that, The adapter plate has a through hole, and the battery cell has a winding hole in the middle. The through hole is at least partially opposite to the winding hole.

23. The cylindrical battery according to any one of claims 1-12, characterized in that, The adapter plate includes a first region and a second region, which have a height difference in the axial direction of the housing. The first region is welded to the tab, and the second region is welded to the electrode of the cylindrical battery.

24. The cylindrical battery according to any one of claims 1-12, characterized in that, The thickness of the adapter piece is 0.2mm-1.2mm.

25. The cylindrical battery according to any one of claims 1-12, characterized in that, The range of A / V is 1. 10 -4 ≤A / V≤2.1 10 -4 ; and / or, The value of L is in the range of 0.03 ≤ L ≤ 0.3; and / or, The value of P is in the range of 0.4 ≤ P ≤ 0.

95.

26. The cylindrical battery according to any one of claims 1-12, characterized in that, The first end plate is provided with electrode holes, and the cylindrical battery further includes: A pole post, at least a portion of which penetrates a through hole in the first end plate; An insulating component is disposed between the pole and the first end plate; The adapter includes a positive adapter and a negative adapter. One of the electrode post and the first end plate is connected to the positive adapter and the other is connected to the negative adapter. The electrode includes the electrode post and the first end plate.

27. A battery pack, characterized in that, The cylindrical battery includes any one of claims 1-26.

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