Battery cells, batteries and electrical devices

Abstract

A battery cell (100), a battery (1000), and an electrical device, wherein the battery cell (100) includes an electrode assembly (20) and an outer casing (10), the outer casing (10) includes a first wall (11) and two second wall portions (12), the first wall portion (11) is provided with a pressure release portion (40), the pressure release portion (40) is provided with a notch groove (41) recessed in a second direction, the pressure release portion (40) is configured to cleave along at least a portion of the notch groove (41) when the pressure of the battery cell (100) is released, and in the first direction, the notch groove (41) is spaced apart from the outer surface of either of the two second wall portions (12).

Description

Technical Field

[0001] This application relates to the field of batteries, and specifically to battery cells, batteries, and electrical devices.

Background Art

[0002] Energy conservation and emission reduction are the keys to the sustainable development of the automotive industry. Electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of the sustainable development of the automotive industry. In the case of electric vehicles, battery technology is an important factor related to their development.

[0003] To ensure the safety performance of a battery cell, usually, a pressure relief part is installed in the battery cell. The pressure relief part is for releasing the internal pressure of the battery cell when the battery cell reaches a predetermined condition. During the charge and discharge use process of the battery cell, as the electrode assembly expands and deforms, the outer casing that houses the electrode assembly also expands and deforms, and furthermore, the pressure relief part installed on the outer casing is prone to damage, reducing the reliability of the battery cell.

Summary of the Invention

Means for Solving the Problems

[0004] In view of the above problems, this application provides a battery cell, a battery, and an electrical device that can alleviate the problem of damage to the pressure relief part during the battery use process.

[0005] In a first aspect, the present invention includes an electrode assembly comprising at least one positive electrode piece and at least one negative electrode piece, the at least one positive electrode piece and the at least one negative electrode piece stacked together to form a flat region, and at least a portion of the positive electrode piece and at least a portion of the negative electrode piece being stacked in the flat region along a first direction, and a first wall and two second walls used to house the electrode assembly, the two second walls being located on either side of the flat region in the first direction, and the first wall being the The present invention provides a battery cell comprising an outer casing located on one side of the electrode assembly in a second direction, the second direction being parallel to the thickness direction of the first wall and perpendicular to the first direction, wherein the first wall is provided with a pressure release portion, the pressure release portion is provided with a notch groove recessed in the second direction, the pressure release portion is configured to cleave along at least a portion of the notch groove when the pressure of the battery cell is released, and in the first direction, the notch groove is spaced apart from the outer surface of either of the two second walls.

[0006] In the embodiment of the present invention, by separating the notch groove from the outer surface of the second wall, when the electrode assembly expands and the second wall deforms, the probability of the vulnerable area of ​​the pressure release portion being directly pulled and ruptured by the deformation of the second wall is reduced, thereby reducing the probability of liquid leakage occurring in the pressure release portion and improving the reliability of the battery cell.

[0007] In some embodiments, there is a first minimum distance between the notch groove and the outer surface of one of the two second walls, and a second minimum distance between the notch groove and the outer surface of the other of the two second walls, where the smaller of the first and second minimum distances is M1, satisfying 2.5 mm ≤ M1 ≤ 20 mm, preferably 3 mm ≤ M1 ≤ 15 mm. In the above technical proposal, by limiting the distance between the notch groove and the second wall, the impact of expansion of the electrode assembly on the pressure release section can be reduced in order to meet the need for timely pressure release, the risk of the vulnerable area of ​​the pressure release section being pulled and broken can be reduced, the probability of leakage occurring in the pressure release section can be reduced, and the reliability of the battery cell can be improved.

[0008] In some embodiments, the thickness dimension of the second wall in the first direction is D1, where 0.2 mm ≤ D1 ≤ 1.5 mm, and preferably 0.3 mm ≤ D1 ≤ 1.2 mm. In the above technical proposal, by limiting the thickness dimension of the second wall, it is possible to improve the structural strength of the second wall while preventing an excessive decrease in the volumetric energy density of the battery cell, reducing the amount of deformation of the second wall, further reducing the tension on the first wall, reducing the probability of leakage due to damage caused by tension on the pressure release portion, and improving the reliability of the battery cell.

[0009] In some embodiments, the thickness dimension of the second wall in the first direction is D1, there is a first minimum distance between the notch groove and the outer surface of one of the two second walls, there is a second minimum distance between the notch groove and the outer surface of the other of the two second walls, the smaller of the first and second minimum distances is M1, and the condition 0.5 mm² ≤ M1 × D1 ≤ 30 mm² is satisfied. In the above technical proposal, a decrease in the volumetric energy density of the battery cell is avoided to some extent, while at the same time the area of ​​the predetermined pressure release region is improved, the exhaust needs are met, the timeliness of the blasting of the pressure release section is improved, the tension on the surface on which the pressure release section is located is further reduced, the probability of the vulnerable area in the pressure release section being pulled and damaged is reduced, the probability of liquid leakage occurring in the pressure release section is further reduced, and the reliability of the battery cell is improved.

[0010] In some embodiments, the thickness dimension of the first wall in the second direction is E1, satisfying 0.4 mm ≤ E1 ≤ 2 mm, preferably 0.5 mm ≤ E1 ≤ 1.8 mm. In the above technical proposal, by limiting the thickness dimension of the first wall, it is possible to reduce the probability of leakage due to damage at the pressure release section 40 while preventing an excessive decrease in the volumetric energy density of the battery cell, thereby improving the reliability of the battery cell.

[0011] In some embodiments, the thickness dimension of the first wall in the second direction is E1, there is a first minimum distance between the notch groove and the outer surface of one of the two second walls, there is a second minimum distance between the notch groove and the outer surface of the other of the two second walls, the smaller of the first and second minimum distances is M1, and 1 mm² ≤ M1 × E1 ≤ 40 mm². In the above technical proposal, a decrease in the volumetric energy density of the battery cell is avoided to some extent, while increasing the area of ​​the predetermined pressure release region, satisfying the exhaust needs, improving the timeliness of the blasting of the pressure release section, simultaneously reducing tension on the first wall, reducing the probability of the vulnerable region in the pressure release section being pulled and damaged, further reducing the probability of liquid leakage in the pressure release section, and improving the reliability of the battery cell.

[0012] In some embodiments, the orthographic projection area of ​​the first wall along the second direction is smaller than the orthographic projection area of ​​the second wall along the first direction. In the above technical proposal, the first wall may correspond to the end face of the electrode assembly, or the first wall may correspond to the small face of the electrode assembly, and the second wall may correspond to the large face of the electrode assembly, and the orthographic projection area of ​​the second wall in the first direction may be larger than the area of ​​the large face of the electrode assembly. When the electrode assembly expands, the influence of expansion deformation on the second wall is relatively large, and the influence on the first wall from the expansion of the electrode assembly is smaller than the influence on the second wall from the expansion of the electrode assembly. As a result, the amount of deformation of the first wall, which is provided with the pressure release section, is small, further reducing the risk of the pressure release section being destroyed and improving the reliability of the battery cell.

[0013] In some embodiments, the thickness dimension of the first wall in the second direction is E1, and the thickness dimension of the second wall in the first direction is D1, where E1 > D1. In the above technical proposal, on the one hand, it is advantageous in improving the strength of the first wall and reducing the risk of failure at the pressure release section, and on the other hand, the outer casing may be stamped using a mold during manufacturing, the thickness of the first wall is greater than the thickness of the second wall, and the outer casing can be manufactured by stamping a plate material of the same thickness as the first wall, thereby reducing the difficulty of manufacturing the outer casing.

[0014] In some embodiments, the pressure release section is provided with a predetermined pressure release region and a notch groove, the predetermined pressure release region having a predetermined release boundary, the predetermined release boundary being surrounded by the outer edge of the orthographic projection in the second direction of at least a portion of the notch groove, or the predetermined release boundary being surrounded by connecting lines between a plurality of ends of the notch groove, or the predetermined release boundary being jointly surrounded by the connecting lines between a plurality of ends of the notch groove and the outer edge of the orthographic projection in the second direction of at least a portion of the notch groove. In the above technical proposal, adopting a notch groove with the above configuration is advantageous for rapid pressure release in the pressure release section.

[0015] In some embodiments, the area of ​​the orthographic projection of the predetermined pressure release region is S1, the area enclosed by the edges of the orthographic projection of the first wall is S2, and 0.06 ≤ S1 / S2 ≤ 0.30. In the above technical proposal, the area of ​​the predetermined pressure release region can be improved to meet exhaust needs, the timeliness of the blasting of the pressure release section can be improved, and at the same time, the tension on the pressure release section can be reduced, the probability of the vulnerable area in the pressure release section being pulled and damaged can be reduced, and the probability of liquid leakage occurring in the pressure release section can be reduced, thereby improving the reliability of the battery cell.

[0016] In some embodiments, the first wall has a rectangular structure, the width direction of the first wall is parallel to the first direction, the length direction of the first wall is parallel to the third direction, the third direction is perpendicular to the first and second directions, the maximum width dimension of the predetermined pressure release area in the width direction is W1, and the maximum length dimension of the predetermined pressure release area in the length direction is W2, where W2 > W1. In the above technical proposal, by increasing the length of the predetermined pressure release area as much as possible, the pressure release area of ​​the predetermined pressure release area is increased to meet the exhaust needs, while by decreasing the width of the predetermined pressure release area as much as possible, the distance between the edge of the predetermined pressure release area and the edge of the second wall is increased, reducing the tensile force received in the vulnerable area of ​​the pressure release section and reducing the probability of leakage due to damage at the pressure release section. Of course, when meeting the service life of the battery cell, increasing the width and length of the predetermined pressure release area can provide a larger exhaust area and improve the pressure release effect.

[0017] In some embodiments, the condition 0.25 ≤ W1 / W2 ≤ 0.7 is satisfied. In the above technical proposal, exhaust from a predetermined pressure release region is made smoother, increasing exhaust efficiency, while at the same time, the distance between the edge of the predetermined pressure release region and the edge of the first wall is increased, reducing the load on the predetermined pressure release region and lowering the probability of leakage due to damage at the pressure release section. Of course, if the battery cell's service life is met, the width and length of the predetermined pressure release region can be increased to have a larger exhaust area and improve the pressure release effect.

[0018] In some embodiments, the pressure release portion is integrally molded with the first wall portion. In the above-mentioned technical proposal, integrally molding the pressure release portion with the first wall portion improves the reliability of the pressure release portion, eliminates the connection process between the pressure release portion and the first wall portion, and reduces the production cost of the battery cell.

[0019] In some embodiments, the pressure release section is installed separately from the first wall section, a communication hole is provided in the first wall section, and the pressure release section is attached to the communication hole. In the above technical proposal, the pressure release section is a component independent of the outer casing, and the pressure release section and the outer casing can be manufactured separately and reassembled, resulting in low production difficulty and high efficiency.

[0020] In some embodiments, the outer casing includes a casing having an opening on one side and an end cap connected to the casing and used to seal the opening, wherein the first wall portion is formed in the casing. In the above technical proposal, by installing the pressure release portion in the casing, the structure of the end cap can be simplified, the distance between the pressure release portion and the main body of the electrode assembly can be easily shortened, and the path through which the discharge medium flows to the pressure release portion when pressure is released can be shortened, reducing the time it takes for the discharge medium to reach the pressure release portion and improving the timeliness of pressure release of the battery cell, thereby effectively improving the reliability of the battery cell.

[0021] In some embodiments, the casing has openings on both opposing sides, and the two end caps are used to seal the corresponding openings. Providing two openings in the casing facilitates the manufacturing and molding of the casing, while also allowing for easy extraction of tabs from both ends of the electrode assembly, and further enabling easy separation of the two electrical connections, thereby reducing the risk of short circuits in the battery cells.

[0022] In some embodiments, the end cap is provided with an electrical connection portion, which is electrically connected to the positive electrode piece, or to the negative electrode piece. In the above technical proposal, electrical energy from the battery cell is input or output.

[0023] In some embodiments, the first wall portion is used to support the electrode assembly and is located below the electrode assembly. In the above technical solution, the pressure relief portion may be provided at the bottom of the battery cell, or an exhaust passage may be provided at the bottom of the battery cell. The exhaust passage communicates with the pressure relief portion, so that when thermal runaway of the battery cell occurs, high-temperature and high-pressure smoke can be discharged into the exhaust passage through the pressure relief portion at the bottom and further discharged to the outside.

[0024] In some embodiments, the material of the outer casing includes at least one of aluminum, nickel-plated carbon steel, stainless steel, magnesium alloy, nickel alloy, copper alloy, and zirconium alloy. In the above technical solution, by adopting the above materials, the tensile strength of the casing can be improved, the deformation of the casing when the electrode assembly expands can be further reduced, the probability of being pulled and broken by the casing or the pressure relief portion can be reduced, the risk of liquid leakage can be reduced, and the reliability of the battery cell can be improved.

[0025] In some embodiments, the positive electrode plate includes a positive electrode current collector and the positive electrode active material region provided on the surface of the positive electrode current collector. The constituent material of the positive electrode current collector contains aluminum element with a mass percentage of 50% or more. In the above technical solution, by adopting the positive electrode current collector, the manufacturing difficulty of the positive electrode plate can be reduced and the manufacturing cost can be reduced compared with the composite current collector in the prior art.

[0026] [[ID=​​​​​​​​The above description is only an overview of the technical solution of this application. In order to more clearly understand the technical means of this application, be able to implement it according to the content of the specification, and more clearly and easily understand the above and other objects, features and advantages of this application, the specific embodiments of this application are specifically listed below.

Brief Description of the Drawings

[0029] Various other advantages and benefits will become apparent to those skilled in the art by reading the following detailed description of the preferred embodiments. The drawings are only for the purpose of illustrating the preferred embodiments and should not be regarded as limiting this application. Also, in all the drawings, the same members are denoted by the same reference numerals. In the figures, [Figure 1] [[ID=lo]]It is a schematic diagram of an electrical device in the related art. [Figure 2] It is a schematic diagram of a battery in the related art. [Figure 3] [[ID=lo]]It is a schematic diagram of a battery cell provided by some embodiments of this application. [Figure 4] It is an exploded view of a battery cell provided by some embodiments of this application. [Figure 5] It is a schematic diagram of an electrode assembly provided by some embodiments of this application. [Figure 6] It is a schematic diagram of an electrode assembly provided by some other embodiments of this application. [Figure 7] It is a top view of a battery cell provided by some embodiments of this application. [Figure 8] It is a cross-sectional view taken along the line A-A in FIG. 7. [Figure 9] It is an enlarged view of the circled B in FIG. 8 provided by some embodiments of this application. [Figure 10] It is an enlarged view of the circled B in FIG. 8 provided by some other embodiments of this application. [Figure 11] It is a schematic diagram of a first wall portion provided by some embodiments of this application. [Figure 12] It is a schematic diagram of a pressure relief portion provided by some embodiments of this application. [Figure 13] This is a schematic diagram of a pressure relief section provided by some other embodiments of the present invention. [Figure 14] This is a schematic diagram of a pressure relief section provided by some other embodiments of the present application. [Figure 15] This is a schematic diagram of the mounting of a pressure relief section provided by several embodiments of the present application. [Figure 16] This is a cross-sectional view along the CC line in Figure 15, provided by several embodiments. [Figure 17] This is a cross-sectional view along the CC line in Figure 15, provided by several other embodiments. [Figure 18] This is a schematic diagram of a battery cell provided in some other embodiments of the present application. [Figure 19] This is a schematic diagram of a battery cell provided by some other embodiments of the present application. [Explanation of Symbols]

[0030] Battery 1000, vehicle 2000, case 200, first part 210, second part 220, 100 battery cells, Outer casing 10, casing 101, end cap 102, first wall portion 11, first outer surface 111, first inner surface 112, groove 113, second wall portion 12, second outer surface 121, second inner surface 122, third wall portion 13, fourth wall portion 14, fifth wall portion 15, Electrode assembly 20, positive electrode piece 21, negative electrode piece 22, flat region 23, curved region 24, Electrical connection part 30, Pressure release section 40, predetermined pressure release region 401, notch groove 41, first arc segment 411, first straight segment 412, second straight segment 413, third straight segment 414, arc segment 415, fourth straight segment 416, fifth straight segment 417, sixth straight segment 418, seventh straight segment 419 (reverse notch 419), Patch 60, First direction F1, second direction F2, third direction F3, [Modes for carrying out the invention]

[0031] To further clarify the purpose, technical proposal, and advantages of the embodiments of this application, the technical proposal of the embodiments will be clearly described below in conjunction with the drawings of the embodiments of this application. However, it should be clear that the embodiments described are only a selection of embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained without creative work by a person skilled in the art fall within the scope of protection of this application.

[0032] Unless otherwise defined, all technical and scientific terms used in this Application have the same meaning as those generally understood by those skilled in the art relating to the Application. Terms used in the Specification of this Application are for illustrative purposes only and are not intended to limit the Application. The terms “includes” and “have,” and any variations thereof, in the description of the Specification, Claims, and the Drawings are intended to cover non-exclusive inclusion. Terms such as “first,” “second,” etc., in the Specification, Claims, or the Drawings are used to distinguish different subjects and are not intended to indicate a particular order or priority.

[0033] The “Examples” as used in this Application mean that certain features, structures, or characteristics described in conjunction with the Examples may be included in at least one Example of this Application. The occurrence of such phrase at each location in the Specification does not necessarily refer to the same Example, nor do they represent mutually exclusive, independent, or substitutable Examples.

[0034] In this application, the term "and / or" simply describes a related relationship that explains the related objects, indicating that three types of relationships are possible. For example, A and / or B can represent three situations: A existing alone, A and B existing simultaneously, and B existing alone. In addition, the symbol " / " in this application generally indicates that the preceding and following related objects are in an "or" relationship.

[0035] In the embodiments of this application, the same drawing symbols represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the dimensions such as thickness, length, and width of various components in the embodiments of this application shown in the attached drawings, as well as the overall thickness, length, and width of the integrated device, are merely illustrative and should not constitute limitations of this application.

[0036] In this application, "multiple" refers to two or more (including two).

[0037] In the embodiments of the present invention, the battery cell may be a secondary battery, which refers to a battery cell that can be used continuously by activating the active material through charging after the battery cell has been discharged.

[0038] The battery cell may be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to these.

[0039] The battery referred to in the embodiments of this application may include one or more battery cells to provide a single physical module with higher voltage and capacity. If there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in series-parallel by a bus member.

[0040] In some embodiments, the battery may be a battery module, and if there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0041] In some embodiments, the battery may be a battery pack including a case and battery cells, where the battery cells or battery modules are housed within the case.

[0042] In some embodiments, the case may be part of the vehicle's chassis structure. For example, the case portion may be at least part of the vehicle's floor, or it may be at least part of the vehicle's cross members and side members.

[0043] In some embodiments, the battery may be an energy storage device. The energy storage device includes an energy storage container, an energy storage electrical cabinet, and the like.

[0044] The development of battery technology requires simultaneous consideration of various design elements, such as performance parameters including energy density, cycle life, discharge capacity, and charge / discharge rate, as well as battery safety.

[0045] In a battery cell, a pressure release section can be installed in the outer casing of the battery cell to ensure its safety. When the battery cell experiences thermal runaway, the pressure inside the battery cell is released through the pressure release section, thereby improving the safety of the battery cell.

[0046] During the charging and discharging process of a battery cell, the electrode assembly expands, causing the outer casing to expand and deform. The pressure release section is located in the outer casing, and some of these sections are located on the wall relatively close to the electrode assembly. The expansion of the electrode assembly deforms the wall where the pressure release section is located, which pulls on the notch of the pressure release section, causing the section to break at the notch and potentially leading to leakage. This can result in a situation where the pressure release section ruptures when the internal pressure of the battery cell does not reach the detonation pressure of the pressure release section, causing the pressure release section to fail and resulting in relatively low reliability of the pressure release section.

[0047] In view of these, embodiments of the present application provide a battery cell comprising an electrode assembly and an outer casing, wherein at least one positive electrode piece and at least one negative electrode piece are stacked to form a flat region, at least a portion of the positive electrode piece and at least a portion of the negative electrode piece are stacked in the flat region along a first direction, the outer casing comprises a first wall and two second walls connected to the first wall, the two second walls each located on either side of the flat region in the first direction, the first wall located on one side of the electrode assembly in a second direction, the second direction being parallel to the thickness direction of the first wall and perpendicular to the first direction.

[0048] Of these, the first wall portion is provided with a pressure release portion, and the pressure release portion is provided with a notch groove that is recessed in a second direction, and the pressure release portion is configured to rupture along at least a portion of the notch groove when the pressure of the battery cell is released, and in the first direction, the notch groove is installed at a distance from the outer surface of either of the two second wall portions.

[0049] In such a battery cell, by separating the notch groove from the outer surface of the second wall, when the electrode assembly expands, the influence of the deformation of the second wall on the notch groove of the pressure release section can be reduced, thereby reducing the tensile force received by the notch groove of the pressure release section, reducing the probability of electrolyte leakage in the pressure release section, and improving the reliability of the battery cell.

[0050] The technical invention described in the embodiments of this application is applicable to batteries and electrical devices using batteries.

[0051] Electrical devices may include vehicles, mobile phones, portable devices, laptop computers, ships, aerospace vehicles, electric toys, power tools, etc. Vehicles may be fuel-powered vehicles, natural gas vehicles, or new energy vehicles, and new energy vehicles may be pure electric vehicles, hybrid vehicles, or range-extender vehicles, etc. Aerospace vehicles may be airplanes, rockets, space shuttles, spacecraft, etc. Electric toys include stationary or mobile electric toys such as game consoles, electric car toys, electric boat toys, and electric airplane toys, and power tools include metal cutting power tools such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, as well as grinding power tools, assembly power tools, and railway power tools. The embodiments of this application do not impose any special limitations on the above-mentioned electrical devices.

[0052] For the sake of explanation, the following examples will be described using the case where the electrical device is a vehicle.

[0053] Referring to Figure 1, which is a schematic diagram of the structure of a vehicle 2000 provided by several embodiments of the present application. A battery 1000 is installed inside the vehicle 2000, and the battery 1000 can be installed at the bottom, head, or tail of the vehicle 2000. The battery 1000 is used to power the vehicle 2000, and for example, the battery 1000 can function as the operating power source for the vehicle 2000.

[0054] The vehicle 2000 may further include a controller and a motor, the controller being used to control the battery 1000 to supply power to the motor, for example, to meet the operating power needs of the vehicle 2000 during starting, navigation, and driving.

[0055] In some embodiments of the present invention, the battery 1000 can be used not only as an operating power source for the vehicle 2000, but also as a driving power source for the vehicle 2000, providing driving force to the vehicle 2000 by completely or partially replacing fuel or natural gas.

[0056] Referring to Figure 2, which is an exploded view of a battery 1000 provided by some embodiments of the present application, the battery 1000 includes a battery cell 100 and a case 200 for housing the battery cell 100.

[0057] Of these, the case 200 is a component that houses the battery cell 100, and the case 200 provides a space for arranging the battery cell 100, and the case 200 can employ multiple structures. In some embodiments, the case 200 may include a first portion 210 and a second portion 220, and the first portion 210 and the second portion 220 cover each other to define a space for arranging the battery cell 100. The first portion 210 and the second portion 220 may be various shapes, such as a rectangular parallelepiped or a cylindrical shape. The first portion 210 may be a hollow structure with one side open, and the second portion 220 may also be a hollow structure with one side open, and when the open side of the second portion 220 is covered by the open side of the first portion 210, a case 200 having an arrangement space is formed. The first portion 210 is a hollow structure with one side open, and the second portion 220 is a plate-like structure. When the second portion 220 covers the open side of the first portion 210, a case 200 having a space for arrangement may be formed. For example, the battery cell 100 may be a cylindrical battery cell, a prismatic battery cell, a soft pack battery cell, or a battery cell 100 of another shape. The prismatic battery cell includes polygonal prismatic batteries such as prismatic battery cells, blade battery cells, and hexagonal prismatic batteries, and the present invention is not particularly limited.

[0058] In the battery 1000, there may be one battery cell 100 or multiple battery cells 100. If there are multiple battery cells 100, the multiple battery cells 100 can be connected in series, in parallel, or in series-parallel, and series-parallel connection refers to the connection of multiple battery cells 100 in both series and parallel. Multiple battery cells 100 may first be connected in series, in parallel, or in series-parallel to form a battery module, and the multiple battery modules may be further connected in series, in parallel, or in series-parallel to form an entire unit, which may then be housed in the case 200. All battery cells 100 may be directly connected in series, in parallel, or in series-parallel to each other, and the entire unit consisting of all battery cells 100 may be housed in the case 200.

[0059] Referring to Figures 3 and 4, Figure 3 is a schematic diagram of a battery cell 100 provided in some embodiments of the present application, and Figure 4 is an exploded view of a battery cell 100 provided in some embodiments of the present application. The battery cell 100 may include an outer casing 10 and an electrode assembly 20.

[0060] The outer casing 10 is for housing the electrode assembly 20 and components such as the electrolyte. The outer casing 10 may be a steel casing, an aluminum casing, a plastic casing (e.g., polypropylene), a composite metal casing (e.g., a copper-aluminum composite outer casing), or an aluminum-plastic film. For example, the outer casing 10 may include a casing 101 and an end cap 102.

[0061] The casing 101 may be a hollow structure with an opening at one end, or it may be a hollow structure with openings at both opposing ends. The casing 101 may be made of various materials such as copper, iron, aluminum, steel, or aluminum alloy.

[0062] The end cap 102 is a component that seals the opening of the casing 101 to isolate the internal environment of the battery cell 100 from the external environment. Together with the casing 101, the end cap 102 defines a housing space for housing the electrode assembly 20, electrolyte, and other components. The end cap 102 can be connected to the casing 101 by welding or crimping to seal the opening of the casing 101. The shape of the end cap 102 can match the shape of the outer casing 10; for example, if the casing 101 has a rectangular parallelepiped structure, the end cap 102 has a rectangular plate-like structure that matches the outer casing 10. The end cap 102 may be made of various materials such as copper, iron, aluminum, steel, or aluminum alloy.

[0063] In the battery cell 10, there may be one or two end caps 102. In an embodiment where the casing 101 is a hollow structure with openings at both ends, two end caps 102 may be installed correspondingly, each sealing two openings in the casing 101, and the two end caps 102 together with the casing 101 define a housing space. In an embodiment where the casing 101 is a hollow structure with an opening at one end, one end cap 102 may be installed correspondingly, the end cap 102 sealing the opening at one end of the casing 101, and the one end cap 102 together with the casing 101 define a housing space.

[0064] The electrode assembly 20 includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell 100, active ions (e.g., lithium ions) repeatedly insert into and remove from between the positive and negative electrodes. The separator is placed between the positive and negative electrodes and can prevent a short circuit between them while simultaneously allowing the active ions to pass through.

[0065] In some embodiments, the positive electrode may be a positive electrode piece 21, and the positive electrode piece 21 may include a positive electrode current collector and a positive electrode active material placed on at least one surface of the positive electrode current collector.

[0066] For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode active material is placed on one or both of the two opposing surfaces of the positive electrode current collector.

[0067] In some embodiments, the negative electrode may be a negative electrode piece 22, and the negative electrode piece 22 may include a negative electrode current collector and a negative electrode active material placed on at least one surface of the negative electrode current collector.

[0068] For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material is placed on one or both of the two opposing surfaces of the negative electrode current collector.

[0069] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0070] In some embodiments, the electrode assembly 20 further includes a separator placed between the positive electrode and the negative electrode.

[0071] In some embodiments, the separator is a separator film. The present application does not impose any particular restrictions on the type of separator film, and any known porous separator film having good chemical and mechanical stability can be selected.

[0072] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is placed between the positive and negative electrodes and serves to transport ions and separate the positive and negative electrodes.

[0073] In some embodiments, the battery cell 100 further includes an electrolyte that plays a role in conducting ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, which can be selected according to the needs. The electrolyte may be in a liquid state, a gel state, or a solid state.

[0074] In some embodiments, the electrode assembly 20 is a wound structure. The positive electrode piece and the negative electrode piece are wound around the wound structure.

[0075] In some embodiments, the electrode assembly 20 has a stacked structure.

[0076] For example, multiple positive electrode pieces 21 and multiple negative electrode pieces 22 can be installed, and the multiple positive electrode pieces 21 and multiple negative electrode pieces 22 are installed in an alternating stack.

[0077] For example, multiple positive electrode pieces 21 can be installed, and the negative electrode pieces 22 can be folded to form multiple folded stages that are stacked and installed, with one positive electrode piece sandwiched between adjacent folded stages.

[0078] As an example, the positive electrode piece 21 and the negative electrode piece 22 are each folded to form a plurality of folded sections that are stacked and installed.

[0079] For example, multiple separators can be installed, each placed between any adjacent positive or negative electrode pieces.

[0080] For example, the separator can be installed in a continuous manner, folded or wound, between any adjacent positive or negative electrode pieces.

[0081] In some embodiments, the shape of the electrode assembly 20 may be flattened or polygonal prism-shaped.

[0082] In some embodiments, the electrode assembly 20 is provided with tabs from which current can be drawn out of the electrode assembly 20. The tabs include a positive electrode tab and a negative electrode tab.

[0083] The battery cell 100 can be installed in the outer casing 10 and may further include an electrical connection that is electrically connected to the tabs of the electrode assembly 20 to output the electrical energy of the battery cell 10. The electrical connection may be directly connected to the tabs, for example, by welding directly to the tabs. The electrical connection and the tabs may be connected indirectly, for example, by a current collector. The current collector may be a metal conductor such as copper, iron, aluminum, steel, or an aluminum alloy.

[0084] As shown in Figures 3 and 4, taking the example that the casing 101 has a hollow structure with an opening at one end, the end cap 102 may be provided with two electrical connection parts, a positive electrical connection part and a negative electrical connection part, respectively. The positive electrical connection part is electrically connected to the positive electrode tab, and the negative electrical connection part is electrically connected to the negative electrode tab.

[0085] Referring to Figures 5 and 6, Figure 5 is a schematic diagram of an electrode assembly 20 provided in some embodiments of the present application, and Figure 6 is a schematic diagram of an electrode assembly 20 provided in some other embodiments of the present application. The electrode assembly 20 includes a positive electrode piece 21 and a negative electrode piece 22, the positive electrode piece 21 includes a positive electrode body and a positive electrode tab, the positive electrode tab is drawn out from one end of the positive electrode body, most of the area of ​​the positive electrode tab is not coated with the positive electrode active material, and most of the area of ​​the positive electrode body is coated with the positive electrode active material, the negative electrode piece 22 includes a negative electrode body and a negative electrode tab, the negative electrode tab is drawn out from one end of the negative electrode body, most of the area of ​​the negative electrode tab is not coated with the negative electrode active material, and most of the area of ​​the negative electrode body is coated with the negative electrode active material, the positive electrode body and the negative electrode body constitute the main body of the electrode assembly.

[0086] As shown in Figure 5, the electrode assembly 20 includes a plurality of pole pieces arranged in a winding manner, and the electrode assembly 20 includes a flat region 23 and a curved region 24 connected to the end of the flat region 23.

[0087] Multiple pole pieces arranged in a winding configuration, namely positive pole piece 21 and negative pole piece 22, are stacked and then wound around a set axis to form an electrode assembly 20. The flat region 23 refers to the portion where the pole piece extends along a plane after winding, and the curved region 24 refers to the portion where the pole piece extends along an arc surface after winding. For example, as shown in Figure 5, the portion between the front and rear surfaces of the electrode assembly 20 is formed in the flat region 23, the direction in which the pole piece extends within the flat region 23 is the length direction of the flat region 23, and as shown in Figure 5, the length dimension of the flat region 23 in the left-right direction is B1, and both the left and right ends of the flat region 23 are curved regions 24.

[0088] As shown in Figure 6, the electrode assembly 20 includes a plurality of electrode pieces arranged in a stack, and the electrode assembly 20 has a flat region 23.

[0089] The multiple pole pieces arranged in a stacked configuration include, for example, at least one positive electrode piece 21 and at least one negative electrode piece 22 stacked to form an electrode assembly 20, and the flat region 23 is formed by stacking at least a portion of the positive electrode piece 21 and the negative electrode piece 22, or it may be formed by stacking the positive electrode piece 21 and at least a portion of the negative electrode piece 22, and within the flat region 23 the direction in which the pole pieces extend is the length direction of the flat region 23, and as shown in Figure 6, the length dimension of the flat region 23 in the left-right direction is B1.

[0090] Referring to Figures 7 to 11, Figure 7 is a top view of a battery cell 100 provided in some embodiments of the present application, Figure 8 is a cross-sectional view of the battery cell 100 shown in Figure 7 along line A-A, Figure 9 is an enlarged view of the circled B in Figure 8 provided in some embodiments of the present application, Figure 10 is an enlarged view of the circled B in Figure 8 provided in some other embodiments of the present application, and Figure 11 is a schematic view of the first wall portion provided in some embodiments of the present application. The battery cell 100 according to the embodiments of the present application includes an electrode assembly 20 and an outer casing 10.

[0091] The electrode assembly 20 includes at least one positive electrode piece 21 and at least one negative electrode piece 22, the at least one positive electrode piece 21 and the at least one negative electrode piece 22 stacked together to form a flat region 23, and at least a portion of the positive electrode piece 21 and at least a portion of the negative electrode piece 22 are stacked and installed in the flat region 23 along a first direction F1.

[0092] An outer casing 10 is used to house an electrode assembly 20, and the outer casing 10 includes a first wall 11 and two second walls 12 connected to the first wall 11, the two second walls 12 each located on either side of a flat region 23 in a first direction F1, the first wall 11 located on one side of the electrode assembly 20 in a second direction F2, the second direction F2 is parallel to the thickness direction of the first wall 11 and perpendicular to the first direction F1.

[0093] Of these, the first wall portion 11 is provided with a pressure release portion 40, and the pressure release portion 40 is provided with a notch groove 41 that is recessed in a second direction F2. The pressure release portion 40 is configured to split along the notch groove 41 when the pressure of the battery cell is released, and in the first direction F1, the notch groove 41 is installed at a distance from the outer surface of either of the two second wall portions 12.

[0094] The outer casing 10 refers to the outermost structural component of the battery cell 100, and the electrode assembly 20 and electrolyte are housed inside the outer casing 10.

[0095] The electrode assembly 20 is installed inside the outer casing 10, and the outer casing 10 may contain one electrode assembly 20 or multiple electrode assemblies 20, each electrode assembly 20 including at least one positive electrode piece 21 and at least one negative electrode piece 22.

[0096] In this configuration, the electrode assembly 20 may be of a stacked type, that is, multiple electrode pieces of the electrode assembly 20 are stacked and arranged, forming a flat region 23 after the electrode pieces are stacked, and in the flat region 23, at least a portion of the positive electrode piece 21 and the negative electrode piece 22 are stacked and installed along the first direction F1, or at least a portion of the positive electrode piece 21 and the negative electrode piece 22 are stacked and installed along the first direction F1, thereby making the expansion deformation of the electrode assembly 20 particularly pronounced in the first direction F1.

[0097] The electrode assembly 20 may be of the wound type, in which the positive electrode piece 21 and negative electrode piece 22 of the electrode assembly 20 and a separator are overlapped and wound together to form a flat region 23, in which a part of the positive electrode piece 21 and a part of the negative electrode piece 22 are stacked and installed along a first direction F1, for example, each layer of the wound-formed positive electrode piece 21 and each layer of the negative electrode piece 22 are perforated by a single axis extending along the first direction F1, thereby the expansion deformation of the electrode assembly 20 is particularly pronounced in the first direction F1.

[0098] As shown in Figures 3 and 4, the first direction F1 is the front-back direction, and the second direction F2 is the up-down direction.

[0099] The outer casing 10 includes a first wall portion 11 and two second wall portions 12, the two second wall portions 12 each located on either side of a flat region 23 in a first direction F1, the majority of the expansion of the electrode assembly 20 acts on the second wall portions 12, the first wall portion 11 is located on one side of the electrode assembly 20 in a second direction F2, the second direction F2 is perpendicular to the first direction F1, the thickness direction of the first wall portion 11 is in the second direction F2, and the first wall portion 11 is provided with a pressure release portion 40.

[0100] When the electrode assembly 20 expands, the first wall portion 11 is less affected by the electrode assembly 20 than the second wall portion 12, and since the pressure release portion 40 is located on the first wall portion 11, the risk of the electrode assembly 20 expanding and blocking or damaging the pressure release portion 40 can be reduced.

[0101] The pressure release section 40 is installed in the outer casing 10 and is a component for releasing the internal pressure of the battery cell 100. When the internal pressure of the battery cell 100 reaches a threshold, the release medium inside the battery cell 100 is discharged through the pressure release section 40 to achieve the purpose of pressure release. The design of the threshold varies depending on the design needs and may depend on one or more materials among the positive electrode piece 21, negative electrode piece 22, electrolyte, and separator in the battery cell 100.

[0102] A notch groove 41 is installed in the pressure release section 40. The notch groove 41 may be installed on a surface of the pressure release section 40 facing the inside of the outer casing 10, or on a surface of the pressure release section 40 that is separated from the inside of the outer casing 10. By installing the notch groove 41 in the pressure release section 40, the area of ​​the pressure release section 40 where the notch groove 41 is installed becomes more vulnerable, and a vulnerable area is formed at the position of the pressure release section 40 corresponding to the notch groove 41. When the internal pressure of the battery cell 100 reaches a threshold, the pressure release section 40 can rupture along at least a portion of the notch groove 41, destroying the vulnerable area and releasing the discharge medium, thereby achieving rapid pressure release, high sensitivity, and high timeliness of pressure release.

[0103] The notch groove 41 can be formed by various methods, such as stamping, milling, or laser etching. The notch groove 41 may extend along a closed trajectory. For example, the notch groove 41 may be an annular groove, which may be a rectangular annular groove extending along a rectangular trajectory, or a circular annular groove extending along a circular trajectory. In the pressure release process, when the pressure release section 40 ruptures along the notch groove 41, a predetermined pressure release region 401 limited by the notch groove 41 is completely opened, increasing the pressure release area and improving the timeliness of pressure release of the battery cell 100. The notch groove 41 may also extend along an unclosed trajectory. For example, the notch groove 41 may be a groove extending along a trajectory such as a "double Y", "I" shape, or "King" shape.

[0104] By separating the notch groove 41 from the outer surface of the second wall portion 12, when the electrode assembly 20 expands and the second wall portion 12 deforms, the probability of the vulnerable area of ​​the pressure release portion 40 being directly pulled and ruptured by the deformation of the second wall portion 12 is reduced, thereby reducing the probability of liquid leakage in the pressure release portion 40 and improving the reliability of the battery cell 100.

[0105] As shown in Figures 9 to 11, in some embodiments, there is a first minimum distance between the notch groove 41 and the outer surface of one of the two second wall portions 12, and a second minimum distance between the notch groove 41 and the outer surface of the other second wall portion 12, where the smaller of the first and second minimum distances is M1, and the condition 2.5 mm ≤ M1 ≤ 20 mm is satisfied.

[0106] As shown in Figures 9 to 11, the first direction F1 is the front-rear direction, the outer casing 10 has two second wall portions 12, front and rear, a first minimum distance between the notch groove 41 and the outer surface of the front second wall portion 12, and a second minimum distance between the notch groove 41 and the outer surface of the rear second wall portion 12, the smaller of the first and second minimum distances being M1, where 2.5 mm ≤ M1 ≤ 20 mm.

[0107] Here, the minimum distance M1 between the notch groove 41 and the outer surface of the second wall portion 12 is the distance between the edge of the notch groove 41 and the outer surface of the second wall portion 12. Of these, the first minimum distance and the second minimum distance may be the same or different, and as shown in Figure 11, there is a minimum distance M1 between the notch groove 41 and the outer surface of the rear second wall portion 12.

[0108] When the electrode assembly 20 expands, the expansion force acts directly on the second wall portion 12, and the first wall portion 11 is pulled by the two second wall portions 12. Since the pressure release portion 40 is located on the first wall portion 11, the vulnerable area of ​​the pressure release portion 40 is pulled by the two second wall portions 12. The closer the first wall portion 11 is to the second wall portions 12, the greater the deformation. Therefore, if M1 is too small, the notch groove 41 is close to the second wall portion 12, and when the electrode assembly 20 expands, the deformation in the vulnerable area of ​​the pressure release portion 40 becomes large, making the vulnerable area more susceptible to damage from being pulled and potentially causing leakage. If M1 is too large, the notch groove 41 is close to the center of the first wall portion 11, and the area of ​​the predetermined pressure release region 401 corresponding to the pressure release portion 40 is relatively small, which may make it difficult to meet the need to release gas from inside the battery cell 100 in a timely manner, posing a safety risk.

[0109] This means that 2.5mm ≤ M1 ≤ 20mm, and M1 may be any one point value or a range value between any two of the following: 2.5mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, or 20mm.

[0110] In the technical solution of the embodiment of the present invention, by limiting the distance between the notch groove 41 and the second wall portion 12, the impact of the expansion of the electrode assembly 20 on the pressure release portion 40 can be reduced in order to meet the need for timely pressure release, the risk of the vulnerable area of ​​the pressure release portion 40 being pulled and broken can be reduced, the probability of liquid leakage occurring in the pressure release portion 40 can be reduced, and the reliability of the battery cell 100 can be improved.

[0111] In several examples, 3 mm ≤ M1 ≤ 15 mm.

[0112] M1 may be any one point value from 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.5mm, 11mm, 11.5mm, 12mm, 12.5mm, 13mm, 13.5mm, 14mm, 14.5mm, or 15mm, or a range value between any two of these points.

[0113] This further increases the area of ​​the predetermined pressure release region 401, meeting the need for timely pressure release, while simultaneously reducing the impact of the expansion of the electrode assembly 20 on the pressure release section 40, thereby reducing the risk of the vulnerable area of ​​the pressure release section 40 being pulled and destroyed, reducing the probability of liquid leakage occurring in the pressure release section 40, and improving the reliability of the battery cell 100.

[0114] As shown in Figures 9 and 10, in some embodiments, the thickness dimension of the second wall portion 12 in the first direction F1 is D1, where 0.2 mm ≤ D1 ≤ 1.5 mm.

[0115] The second wall portion 12 can form a flat plate structure, in which case the thickness of the second wall portion 12 is the same at different locations, or the second wall portion 12 may include a main region and a local region, in which the local region may be provided with grooves, protrusions, or other special structures such as holes, for example the local region may have an arch structure that is easily connected to other wall portions, the local region may be located around the main region, in the center of the main region, or further distributed, in which case the thickness dimension of the second wall portion 12 is the thickness dimension of the main region.

[0116] As shown in Figures 9 and 10, if the thickness of the second wall portion 12 is too large, the dimensions of the outer casing 10 will occupy an excessive portion of the total volume of the battery cell 100, reducing the space occupied by the electrode assembly 20 in the first direction F1 and leading to a decrease in the volumetric energy density of the battery cell 100. If the thickness of the second wall portion 12 is too small, the second wall portion 12 will be too thin, and the deformation of the second wall portion 12 will easily become too large when the electrode assembly 20 expands, resulting in increased tension on the first wall portion 11. Furthermore, the pressure release portion 40 will be pulled and easily damaged, potentially causing leakage of liquid in the pressure release portion 40.

[0117] Therefore, D1 may be any one point value from 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, or 1.5mm, or a range value between any two of these points.

[0118] By limiting the thickness of the second wall portion 12, it is possible to prevent an excessive decrease in the volumetric energy density of the battery cell 100, improve the structural strength of the second wall portion 12, reduce the amount of deformation of the second wall portion 12, further reduce tension on the first wall portion 11, reduce the probability of leakage due to damage to the pressure release portion 40 caused by tension, and improve the reliability of the battery cell 100.

[0119] In some cases, 0.3 mm ≤ D1 ≤ 1.2 mm.

[0120] D1 may be any one point value of 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, or 1.2 mm, or a range value between any two of these points. Within the above range, it is possible to further prevent an excessive decrease in the volumetric energy density of the battery cell 100, improve the structural strength of the second wall portion 12, reduce the amount of deformation of the second wall portion 12, further reduce the tension on the first wall portion 11, reduce the probability of leakage due to the pressure release portion 40 being pulled and damaged, and improve the reliability of the battery cell 100.

[0121] As shown in Figures 9 and 10, in some embodiments, the thickness dimension of the second wall portion 12 in the first direction is D1, there is a first minimum distance between the notch groove 41 and the outer surface of one of the two second wall portions 12, there is a second minimum distance between the notch groove 41 and the outer surface of the other of the two second wall portions 12, the relatively smaller of the first and second minimum distances is M1, and the condition 0.5 mm² ≤ M1 × D1 ≤ 30 mm² is satisfied.

[0122] If M1×D1 is too small, M1 is too small, and the distance from the second wall 12 of the notch groove 41 is too small, making the vulnerable area of ​​the pressure release section 40 more susceptible to being pulled and deformed, which can lead to damage to the pressure release section 40 and cause liquid leakage. Alternatively, if D1 is too small, and the second wall 12 is too thin, the deformation of the second wall 12 tends to be excessive when the electrode assembly 20 expands. In this case, the greater the tension on the first wall 11, the more susceptible the vulnerable area of ​​the pressure release section 40 becomes to being pulled and damaged, which can cause liquid leakage in the pressure release section 40.

[0123] If the M1 × D1 product is too large, M1 is relatively large, the notch groove 41 is close to the center of the first wall portion 11, and the area of ​​the corresponding predetermined pressure release region 401 is relatively small, which may make it difficult to meet the need to expel gas from inside the battery cell 100 in a timely manner, thus posing a safety risk. Alternatively, if D1 is too large, the thickness dimension of the second wall portion 12 is too large, and the dimensions of the outer casing 10 occupy too much volume of the entire battery cell 100, the space occupied by the electrode assembly 20 in the first direction F1 is reduced, resulting in a decrease in the volumetric energy density of the battery cell 100.

[0124] For this reason, M1×D1 can be limited to between 0.5mm² and 30mm², and M1×D1 may be any single point value or a range value between any two of the following: 0.5mm², 1mm², 2mm², 3mm², 4mm², 5mm², 6mm², 7mm², 8mm², 9mm², 10mm², 11mm², 12mm², 13mm², 14mm², 15mm², 16mm², 17mm², 18mm², 19mm², 20mm², 21mm², 22mm², 23mm², 24mm², 25mm², 26mm², 27mm², 28mm², 29mm², 30mm².

[0125] Hereinafter, the present application will be described in more detail with reference to the examples and drawings in order to further clarify the technical problems, technical solutions and beneficial effects that the embodiments of this application aim to solve. It is clear that the embodiments described are only a selection of the embodiments of this application, and not all embodiments. The description of at least one exemplary embodiment below is for illustrative purposes only and does not limit the present application or its application. All other embodiments obtained by a person skilled in the art based on the embodiments of this application without any creative work are within the scope of protection of this application.

[0126] Example 1 1) Manufacturing of positive electrode pieces A positive electrode slurry was prepared using the positive electrode active material LiNi0.7Co0.1Mn0.1O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP). The solid content of the positive electrode slurry was 50 wt%, and the mass ratio of LiNi0.7Co0.1Mn0.1O2, Super P, and PVDF in the solid components was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of an aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce positive electrode pieces.

[0127] 2) Manufacturing of negative electrode pieces A negative electrode slurry was prepared by uniformly mixing graphite, the conductive agent Super P, the thickening agent carboxymethylcellulose (CMC), and the adhesive styrene-butadiene rubber (SBR) in deionized water. The solid content of the negative electrode slurry was 30 wt%, and the mass ratio of graphite, silicon monoxide, Super P, CMC, and the adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then, it was cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece.

[0128] 3) Manufacturing of electrolytes In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio) and homogeneously mixed to obtain a liquid electrolyte with a concentration of 1 mol / L.

[0129] 4) Separator A 16 μm polyethylene film was used as the separator.

[0130] 5) Manufacturing of lithium-ion batteries The positive electrode piece, separator, and negative electrode piece were stacked in order, with the separator positioned between the positive and negative electrode pieces to isolate them. The stack was then wound to obtain a bare cell, tabs were welded on, the bare cell was placed in an aluminum outer casing, the manufactured electrolyte was injected into the dried outer casing, and the lithium-ion battery was completed by sealing, standing, chemical conversion, shaping, capacity testing, etc. (Lithium-ion battery thickness 31 mm, width 237.5 mm, length 117.4 mm).

[0131] The manufacturing method for the battery cell 100 in Examples 2-8 and Comparative Examples 1-3 is the same as in Example 1. The differences are that the smaller of the two distances M1 between the notch groove 41 and the outer surfaces of the two second wall portions 12 in the battery cell 100 is different, and the thickness D1 of the second wall portion 12 in the first direction F1 is different, as shown in Table 1.

[0132] The number of cycles (i.e., the number of fatigue cycles of the battery cell 100) at the time of leakage at the pressure release section 40 of the lithium-ion batteries obtained in Examples 1 to 8 and Comparative Examples 1 to 3 was characterized, and the characterization results are shown in Table 1.

[0133] The method for measuring the number of fatigue cycles of battery cell 100 is as follows:

[0134] 1) A dedicated test clamp was prepared, specifically consisting of three 10mm thick steel plates (first, second, and third plates), each plate capable of completely covering the large surface of a battery cell. The first and third plates were positioned at both ends of the clamp and secured by bolts, while the second plate was positioned between the first and third plates and restrained by a guide rail, allowing translational movement only in a direction perpendicular to the plane of the plates. The battery cell could be mounted between the first and second plates, with the large surface of the battery cell (the side with the largest outer surface area) pressed against the first and second plates. A pressure sensor was placed between the second and third plates, and the initial pressing force of the second plate against the battery cell was adjusted by adjusting the position of the second plate.

[0135] 2) A single battery cell was fixed in a dedicated test clamp, ensuring that the large surface of the battery cell was in contact with the first and second steel plates. The position of the second steel plate was adjusted so that the initial pressing force of the second steel plate against the battery cell was 2000N, and the two electrical connections of the battery cell were connected to a dedicated battery charging and discharging facility.

[0136] 3) The battery cells and clamps were left in a constant temperature environment of 35±2℃, and the test was started after the battery cells reached temperature equilibrium.

[0137] 4) The test steps were carried out in reference to Section 6.4 "Standard Cycle Life" of "GBT31484-2015 Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and the test cycle cutoff condition was changed to "Stop the test until damage occurs in the notch groove of the pressure release section."

[0138] Specifically, the test was conducted following these steps: a) The system was discharged using 1I(A) until the discharge termination condition specified by the company was reached.

[0139] b) Left unattended for 30 minutes or longer, or under conditions set by the company.

[0140] c) Charged according to method 6.1.1.3 of "GBT31484-2015 Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles".

[0141] d) Left unattended for 30 minutes or longer, or under conditions set by the company.

[0142] e) The device was discharged to the discharge termination conditions specified by the company in 1I1(A).

[0143] The test was repeated according to f)b)~e) until damage occurred in the notch groove of the pressure release section, at which point the test was stopped.

[0144] Specifically, during the testing process, the pressure release portion of the battery cell was continuously observed until leakage occurred, and the number of cycles was recorded as the fatigue cycle of the battery cell. The test results are shown in Table 1 below.

[0145] [Table 1]

[0146] By combining the data from Examples 1-8 and Comparative Examples 1-3, it can be seen that when M1×D1 is 0.5 mm2 or more, the number of fatigue cycles increases significantly, and when the number of fatigue cycles is greater than 1000, the battery cell has relatively good cycle performance, and further adjusting the relationship between M1 and D1 within a predetermined range is advantageous for the battery cell 100 to have relatively good cycle performance.

[0147] In other words, by adopting the above embodiment of the present invention, a decrease in the volumetric energy density of the battery cell 100 is avoided to some extent, while at the same time the area of ​​the predetermined pressure release region 401 is increased, the exhaust needs are met, the timeliness of the blasting of the pressure release section 40 is improved, tension on the first wall section 11 is reduced, the probability of the weak area in the pressure release section 40 being pulled and damaged is further reduced, the probability of liquid leakage occurring in the pressure release section 40 is further reduced, and the reliability of the battery cell 100 is improved.

[0148] As shown in Figures 9 and 10, in some embodiments, in the second direction F2, the thickness dimension of the first wall portion 11 is E1, where 0.4 mm ≤ E1 ≤ 2 mm.

[0149] The first wall portion 11 can form a flat plate-like structure, in which case the thickness of the first wall portion 11 is the same at different locations, or the first wall portion 11 may include a main region and a local region, in which the local region may be provided with grooves, protrusions, or other special structures such as holes, and the local region may be located around the main region, in the center of the main region, or further dispersed, in which case the thickness dimension of the first wall portion 11 is the thickness dimension of the main region.

[0150] As shown in Figures 9 and 10, if the thickness of the first wall portion 11 is too large, the dimensions of the outer casing 10 in the second direction F2 will occupy an excessive amount of space in the entire battery cell 100, reducing the space occupied by the corresponding electrode assembly 20 in the second direction F2, leading to a decrease in the volumetric energy density of the battery cell 100. If the thickness of the first wall portion 11 is too small, the first wall portion 11 will be too thin, and when the electrode assembly 20 expands, the second wall portion 12 will deform and pull on the first wall portion 11, making the first wall portion 11 more susceptible to deformation. Furthermore, the vulnerable areas in the pressure release portion 40 will be pulled and more prone to damage, resulting in leakage of liquid from the pressure release portion 40.

[0151] Therefore, E1 may be any one point value from 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, or 2mm, or a range value between any two of these points.

[0152] By limiting the thickness of the first wall portion 11, it is possible to prevent an excessive decrease in the volumetric energy density of the battery cell 100, reduce the probability of leakage due to damage at the pressure release portion 40, and improve the reliability of the battery cell 100.

[0153] In some cases, 0.5 mm ≤ E1 ≤ 1.8 mm.

[0154] E1 may be any one point value of 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, or 1.8mm, or a range value between any two of these points. By having the thickness dimension E1 of the first wall portion 11 within the above range, it is possible to further prevent an excessive decrease in the volumetric energy density of the battery cell 100, reduce the probability of leakage due to damage to the pressure release portion 40, and improve the reliability of the battery cell 100.

[0155] As shown in Figures 9 and 10, in some embodiments, the thickness dimension of the first wall portion 11 in the second direction F2 is E1, satisfying 1 mm² ≤ M1 × E1 ≤ 40 mm².

[0156] If the product of M1 and E1 is too small, M1 is too small, and the distance of the notch groove 41 from the second wall 12 is too small, making the vulnerable area of ​​the pressure release section 40 more susceptible to being pulled and deformed, which in turn makes the pressure release section 40 more prone to damage and causes liquid leakage. Alternatively, if the thickness E1 of the first wall 11 is too small, the strength of the first wall 11 is low, making the first wall 11 more susceptible to being pulled and deformed, which in turn makes the vulnerable area of ​​the pressure release section 40 more prone to being pulled and damaged, creating a risk of liquid leakage in the pressure release section 40.

[0157] If the product of M1 and E1 is too large, M1 may be too large, causing the notch groove 41 to be close to the center of the first wall portion 11, resulting in a relatively small area of ​​the corresponding predetermined pressure release region 401, which may make it difficult to meet the need to expel gas from inside the battery cell 100 in a timely manner, thus posing a safety risk. Alternatively, if the thickness E1 of the first wall portion 11 is too large, the dimensions of the outer casing 10 in the second direction F2 may occupy too much of the entire battery cell 100, resulting in high energy loss in the battery cell 100 and a decrease in the volumetric energy density of the battery cell 100.

[0158] For this purpose, M1×E1 is limited to between 1mm² and 40mm², and M1×E1 may be any one point value or a range value between any two of the following: 1mm², 2mm², 3mm², 4mm², 5mm², 6mm², 7mm², 8mm², 9mm², 10mm², 15mm², 20mm², 25mm², 30mm², 35mm², 40mm².

[0159] Hereinafter, the present application will be described in more detail with reference to the examples and drawings in order to further clarify the technical problems, technical solutions and beneficial effects that the embodiments of this application aim to solve. It is clear that the embodiments described are only a selection of the embodiments of this application, and not all embodiments. The description of at least one exemplary embodiment below is for illustrative purposes only and does not limit the present application or its application. All other embodiments obtained by a person skilled in the art based on the embodiments of this application without any creative work are within the scope of protection of this application.

[0160] The manufacturing method for the battery cell 100 in Examples 9 to 16 and Comparative Examples 4 to 6 is the same as in Example 1. The differences are that the smaller of the two distance values ​​M1 between the notch groove 41 and the outer surfaces of the two second wall portions 12 in the battery cell 100 is different, and the thickness E1 of the first wall portion 11 in the second direction F2 is different, as shown in Table 2.

[0161] The number of cycles (i.e., the fatigue cycles of the battery cell 100) at the time of leakage at the pressure release section 40 of the lithium-ion batteries obtained in Examples 9-16 and Comparative Examples 4-6 was characterized, and the characterization results are shown in Table 2. The method for measuring the fatigue cycles of the battery cell 100 is the same as described above, so its explanation is omitted here.

[0162] [Table 2]

[0163] By combining the data from Examples 9-16 and Comparative Examples 4-6, it was found that when M1×E1 is 1 mm² or more, the number of fatigue cycles clearly increases, and the number of fatigue cycles is greater than 1000, indicating that the battery cell has relatively good cycle performance. Further adjustment of the relationship between M1 and E1 within a predetermined range is advantageous for battery cell 100 to have relatively good cycle performance.

[0164] In other words, by adopting the above embodiment of the present invention, a decrease in the volumetric energy density of the battery cell 100 can be avoided to some extent, while at the same time increasing the area of ​​the predetermined pressure release region 401, satisfying the exhaust needs, improving the timeliness of the blasting of the pressure release section, reducing tension on the first wall portion 11, reducing the probability of the vulnerable region of the pressure release section 40 being pulled and damaged, further reducing the probability of liquid leakage occurring in the pressure release section 40, and improving the reliability of the battery cell 100.

[0165] As shown in Figures 3 and 4, in some examples, the orthographic projection area of ​​the first wall portion 11 along the second direction F2 is smaller than the orthographic projection area of ​​the second wall portion 12 along the first direction F1.

[0166] Some electrode assemblies 20 have two end faces and four side surfaces, of which the area of ​​two opposing side surfaces is relatively large, i.e., they become the large faces of the electrode assembly 20, and the area of ​​the other two opposing side surfaces is relatively small, i.e., they become the small faces of the electrode assembly 20, and the area of ​​the two end faces is relatively small compared to the large faces of the electrode assembly 20, and the two large faces are arranged opposite each other along a first direction F1, and the expansion deformation of the electrode assembly 20 is particularly pronounced in the first direction F1, i.e., the amount of expansion of the large faces of the electrode assembly 20 is greater than the amount of expansion of the small faces of the electrode assembly 20, and the amount of expansion of the large faces of the electrode assembly 20 is greater than the amount of expansion of the end faces.

[0167] By designing the above embodiment, the first wall portion 11 may correspond to the end face of the electrode assembly 20, or the first wall portion 11 may correspond to the small face of the electrode assembly 20, the second wall portion 12 may correspond to the large face of the electrode assembly 20, and the orthographic area of ​​the second wall portion 12 in the first direction F1 may be larger than the area of ​​the large face of the electrode assembly 20. When the electrode assembly 20 expands, the influence of the expansion deformation on the second wall portion 12 is relatively large, and the influence on the first wall portion 11 from the expansion of the electrode assembly 20 is smaller than the influence on the second wall portion 12 from the expansion of the electrode assembly 20. As a result, the amount of deformation of the first wall portion 11, in which the pressure release portion 40 is provided, is reduced, further reducing the risk of the pressure release portion 40 being destroyed and improving the reliability of the battery cell 100.

[0168] In some embodiments, the thickness dimension of the first wall portion 11 in the second direction F2 is E1, and the thickness dimension of the second wall portion 12 in the first direction F1 is D1, where E1 > D1.

[0169] In other words, since the thickness of the first wall portion 11 is greater than the thickness of the second wall portion 12, and the pressure release portion 40 is installed in the first wall portion 11, relatively increasing the thickness of the first wall portion 11 is advantageous in improving the strength of the first wall portion 11 and reducing the risk of damage at the pressure release portion 40, and on the other hand, the outer casing 10 may be stamped using a mold during manufacturing, and since the thickness of the first wall portion 11 is greater than the thickness of the second wall portion 12, the outer casing 10 can be manufactured by stamping a plate material of the same thickness as the first wall portion 11, thereby reducing the difficulty of manufacturing the outer casing 10.

[0170] Referring to Figures 12 to 14, Figure 12 is a schematic diagram of a pressure relief section provided in some embodiments of the present application, Figure 13 is a schematic diagram of a pressure relief section provided in some other embodiments of the present application, and Figure 14 is a schematic diagram of a pressure relief section provided in some other embodiments of the present application.

[0171] In some embodiments, the pressure release section 40 is provided with a predetermined pressure release region 401 and a notch groove 41, the predetermined pressure release region 401 having a predetermined open boundary, the predetermined open boundary being surrounded by the outer edge of the orthographic projection in a second direction F2 of at least a portion of the notch groove 41, or the predetermined open boundary being surrounded by connecting lines between a plurality of ends of the notch groove 41, or the predetermined open boundary being jointly surrounded by the connecting lines between a plurality of ends of the notch groove 41 and the outer edge of the orthographic projection in a second direction F2 of at least a portion of the notch groove 41.

[0172] As shown in Figure 12, in some embodiments, the notch groove 41 includes two opposing first arc segments 411 and two parallel first straight segments 412, the ends of which are connected to the two first arc segments 411, the two first straight segments 412 and the two first arc segments 411 forming a closed annular structure, the outer edge of the orthographic projection of the annular structure in a second direction F2 forming a predetermined open boundary of a predetermined pressure release region 401, i.e., the predetermined open boundary is surrounded by the outer edge of the orthographic projection of the notch groove 41 in the second direction F2.

[0173] At this time, the area of ​​the orthographic projection of the predetermined pressure release region 401 is S1, where S1 = a × b + π × b² / 4, the width of the predetermined pressure release region 401 along the first direction F1 is W1, where W1 = b, and the length of the predetermined pressure release region 401 along the third direction F3 is W2, where W2 = a + b, where a represents the length of the first straight segment 412 and b represents the distance between the outsides of the two first straight segments 412.

[0174] As shown in Figure 13, in some embodiments, the notch groove 41 includes a second straight segment 413 and four third straight segments 414, with two third straight segments 414 connected to each end of the second straight segment 413 at predetermined angles, and in a second direction F2, an arc-shaped segment 415 with a vertex at a predetermined angle as its center is defined between the free ends of the orthographic projection of two third straight segments 414 located at the same end of the second straight segment 413, and a fourth straight segment 416 is defined between the free ends of the orthographic projection of two third straight segments 414 located on the same side of the second straight segment 413, and the two arc-shaped segments 415 and the two fourth straight segments 416 together constitute a predetermined open boundary of a predetermined pressure release region 401, i.e., the predetermined open boundary is enclosed by connecting lines between the multiple ends of the notch groove 41.

[0175] At this time, the area of ​​the orthographic projection of the predetermined pressure release region 401 is S1, where S1 = (c + e) ​​× d × sinα + π × d² × α / 180, the width of the predetermined pressure release region 401 along the first direction F1 is W1, where W1 = c + 2d, the length of the predetermined pressure release region 401 along the third direction F3 is W2, where W2 = 2d × sinα, where c represents the length of the second straight segment 413, d represents the length of the third straight segment 414, e represents the length of the fourth straight segment 416, and the angle between the two third straight segments 414 located at the same end of the second straight segment 413 is 2α.

[0176] As shown in Figure 14, in some embodiments, the notch groove 41 includes a fifth linear segment 417 and two sixth linear segments 418, the fifth linear segment 417 being located between the two sixth linear segments 418, with each end of the fifth linear segment 417 connected to the central portion of the corresponding sixth linear segment 418, a seventh linear segment 419 defined between the ends of the two sixth linear segments 418 located on the same side of the fifth linear segment 417, and the orthographic outer edges of the seventh linear segment 419 and the sixth linear segments 418 in a second direction F2 constitute a predetermined open boundary of a predetermined pressure release region 401, i.e., the predetermined open boundary is jointly enclosed by connecting lines between the multiple ends of the notch groove 41 and the orthographic outer edges of a portion of the notch groove 41 in a second direction.

[0177] Of course, the notch groove 41 may also have a reverse notch 419 installed in the seventh straight segment 419, so that two reverse notches 419 located on both sides of the fifth straight segment 417 are installed in correspondence, and the installation of the reverse notches 419 is advantageous for the pressure release section 40 to release pressure along a predetermined release boundary, and the effectiveness of the pressure release area is guaranteed.

[0178] At this time, the area of ​​the orthographic projection of the predetermined pressure release region 401 is S1, where S1 = j × k; the width of the predetermined pressure release region 401 along the first direction F1 is W1, where W1 = j; and the length of the predetermined pressure release region 401 along the third direction F3 is W2, where W2 = k, where j represents the length of the sixth straight segment 418 and k represents the length of the seventh straight segment 419.

[0179] By adopting the notch groove 41 with the above structure, it is advantageous for the rapid release of pressure in the pressure release section 40.

[0180] As shown in Figures 11 to 15, in some embodiments, in the second direction F2, the orthographic area of ​​a predetermined pressure release region 401 is S1, the area enclosed by the orthographic edge of the first wall portion 11 is S2, and 0.06 ≤ S1 / S2 ≤ 0.3.

[0181] As shown in Figures 11 to 14, the pressure release section 40 has a predetermined pressure release region 401, the predetermined pressure release region 401 has a predetermined opening boundary, the predetermined opening boundary is surrounded by the outer edge of the orthographic projection in a second direction F2 of at least a portion of the notch groove 41, or the predetermined opening boundary is surrounded by connecting lines between a plurality of ends of the notch groove 41, or the predetermined opening boundary is jointly surrounded by the connecting lines between a plurality of ends of the notch groove 41 and the outer edge of the orthographic projection in a second direction F2 of at least a portion of the notch groove 41. When the pressure of the battery cell 100 is released, the pressure release section 40 can rupture along at least a portion of the notch groove 41, further opening the predetermined pressure release region 401 and achieving rapid pressure release. It should be noted that the portion that is actually destroyed when the pressure is released may be smaller than the predetermined pressure release region 401, or slightly larger than the predetermined pressure release region 401.

[0182] When the pressure release portion 40 is integrally molded with the first wall portion 11, the notch groove 41 can be directly installed in the first wall portion 11, the first wall portion 11 forms a weak region in the area where the notch groove 41 is installed, the molding method of the pressure release portion 40 is simple, and the production cost is low. As shown in Figures 16 and 17, in an embodiment in which the pressure release portion 40 is integrally molded with the first wall portion 11, both the predetermined pressure release region 401 and the notch groove 41 are located at the bottom wall of the groove 113.

[0183] The first wall portion 11 forms a rectangle, and the area enclosed by the edges of the orthographic projection of the first wall portion 11 in the second direction F2 is S2, where S2 = f × g, where f represents the length dimension of the first wall portion 11 in the third direction F3, and g represents the width dimension of the first wall portion 11 in the first direction F1.

[0184] In a battery cell of a certain size, if S1 / S2 is less than 0.06, S1 is too small, and the area of ​​the predetermined pressure release region 401 of the pressure release section 40 is too small, which may make it difficult to meet the need to expel gas from inside the battery cell 100 in a timely manner, thus posing a safety risk. If S1 / S2 is greater than 0.3, the area of ​​the predetermined pressure release region 401 of the pressure release section 40 is too large, and the distance from the notch groove 41 of the pressure release section 40 to the second wall portion 12 is too small, which makes the vulnerable area of ​​the pressure release section 40 more susceptible to being pulled and damaged when the electrode assembly 20 expands, and may also lead to leakage of liquid from the pressure release section 40.

[0185] As a result, S1 / S2 may be any one point value from 0.06, 0.1, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or 0.3, or a range value between any two of these.

[0186] By limiting the ratio of S1 to S2, the area of ​​the predetermined pressure release region 401 can be increased, meeting the exhaust needs and improving the timeliness of the pressure release section explosion. At the same time, tensile stress on the pressure release section 40 is reduced, decreasing the probability of the vulnerable area in the pressure release section 40 being pulled and damaged, further reducing the probability of liquid leakage in the pressure release section 40, and improving the reliability of the battery cell 100.

[0187] As shown in Figure 11, in some embodiments, the first wall portion 11 is rectangular, the width direction of the first wall portion 11 is parallel to the first direction F1, the length direction of the first wall portion 11 is parallel to the third direction F3, the third direction F3 is perpendicular to the first direction F1 and the second direction F2, the notch groove 41 defines a predetermined pressure release region 401, the maximum width dimension of the predetermined pressure release region 401 in the width direction is W1, and the maximum length dimension of the predetermined pressure release region 401 in the length direction is W2, of which W2 > W1.

[0188] As shown in Figure 3, the third direction F3 is the left-right direction, the maximum length dimension of the predetermined pressure release area 401 is the dimension of the predetermined pressure release area 401 in the third direction F3, the maximum width dimension of the predetermined pressure release area 401 is the maximum dimension of the predetermined pressure release area 401 in the first direction F1, the length of the predetermined pressure release area 401 is longer than the width of the predetermined pressure release area 401, and by increasing the length of the predetermined pressure release area 401 as much as possible, the pressure release area of ​​the predetermined pressure release area 401 is increased to meet the exhaust needs, while at the same time, by reducing the width of the predetermined pressure release area 401 as much as possible, the distance between the edge of the predetermined pressure release area 401 and the edge of the second wall 12 is increased, reducing the tensile force received in the vulnerable area of ​​the pressure release section 40 and reducing the probability of leakage due to damage in the pressure release section 40. Of course, if the service life of the battery cell 100 is met, increasing the width and length of the predetermined pressure release area 401 can provide a larger exhaust area and improve the pressure release effect.

[0189] As shown in Figure 3, in some embodiments, 0.25 ≤ W1 / W2 ≤ 0.7.

[0190] To meet the pressure release needs, a predetermined pressure release region 401 must have a certain pressure release area. When the pressure release area is constant, the smaller the width of the predetermined pressure release region 401, the larger the length of the predetermined pressure release region 401, forming an elongated pressure release section 40. Such a pressure release section 40 makes it difficult to concentrate the exhaust, the exhaust is dispersed, the airflow is not smooth, and the exhaust efficiency is low. The smaller the length of the predetermined pressure release region 401, the larger the width of the predetermined pressure release region 401, and the pressure release section 40 The distance between the vulnerable region and the edge of the first wall portion 11 is too small, making the pressure release portion 40 susceptible to being pulled and broken when the electrode assembly 20 expands. This can lead to failure at the pressure release portion 40, causing liquid leakage, etc., which limits W1 / W2 to between 0.25 and 0.7. W1 / W2 may be any one of the following values, or a range value between any two of the following: 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7.

[0191] This allows for smoother exhaust from the predetermined pressure release area 401, increasing exhaust efficiency. At the same time, it increases the distance between the edge of the predetermined pressure release area 401 and the edge of the second wall 12, reducing the load on the predetermined pressure release area 401 and lowering the probability of leakage due to damage to the pressure release section 40. Of course, if the battery cell 100 is to meet its service life, the width and length of the predetermined pressure release area 401 can be increased to provide a larger exhaust area and improve the pressure release effect.

[0192] Referring to Figures 15 to 17, Figure 15 is a schematic diagram of the mounting of a pressure relief section provided in some embodiments of the present application, Figure 16 is a cross-sectional view along line CC in Figure 15 provided in some embodiments, and Figure 17 is a cross-sectional view along line CC in Figure 15 provided in some other embodiments.

[0193] In some embodiments, the pressure release portion 40 is integrally molded with the first wall portion 11.

[0194] By integrally molding the pressure release section 40 with the first wall section 11, the reliability of the pressure release section 40 can be improved, and the connection process between the pressure release section 40 and the first wall section 11 can be omitted, thereby reducing the production cost of the battery cell 100.

[0195] As shown in Figures 15 and 16, in some embodiments, grooves 113 are provided on the inner and / or outer surfaces of the first wall portion 11, and the bottom walls of the grooves 113 form a pressure release portion 40.

[0196] As shown in Figures 15 and 16, the inner surface of the first wall portion 11 faces the inside of the exterior casing 10, and the outer surface of the first wall portion 11 faces the outside of the exterior casing 10. Here, a groove 113 may be provided on the inner surface of the first wall portion 11, but not on the outer surface of the first wall portion 11, and the portion of the first wall portion 11 located between the bottom surface of the groove 113 and the outer surface of the first wall portion 11 may be the groove bottom wall of the groove 113; or a groove 113 may not be provided on the inner surface of the first wall portion 11, but a groove 113 may be provided on the outer surface of the first wall portion 11, and the portion of the first wall portion 11 located between the bottom surface of the groove 113 and the inner surface of the first wall portion 11 may be the groove bottom wall of the groove 113; furthermore, a groove 113 may be provided on both the inner and outer surfaces of the first wall portion 11, and the portion of the first wall portion 11 located between the bottom surfaces of the two grooves 113 may be the groove bottom wall of the groove 113. As can be understood, the groove 113 provided on the inner surface of the first wall portion 11 and the groove 113 provided on the outer surface of the first wall portion 11 share one groove bottom wall.

[0197] The first wall portion 11 is thinner than the first wall portion 11 itself in the region where the groove 113 is installed, and this region forms a pressure release portion 40 that is integrally molded with the first wall portion 11. Here, the groove 113 can be formed in the first wall portion 11 by various methods such as stamping, milling, laser etching, and chemical etching.

[0198] The groove 113 may be of various shapes, for example, a rectangular groove, a circular groove, or an elliptical groove. A rectangular groove is a groove with a rectangular cross-section, a circular groove is a groove with a circular cross-section, and an elliptical groove is a groove with an elliptical cross-section. The cross-section is perpendicular to the depth direction of the groove 113. In this case, the pressure release section 40 formed by the bottom wall of the groove 113 is usually further provided with a notch groove 41. The pressure release section 40 can rupture along at least a portion of the notch groove 41 when the battery cell 100 releases pressure, and a predetermined pressure release region 401 defined by the notch groove 41 is opened, enabling rapid pressure release.

[0199] Furthermore, the groove 113 may have other shapes, and the groove 113 is a groove that extends along a trajectory such as a "double Y" shape, an "I" shape, or a "king" shape. In this case, a pressure release portion 40 is formed at the bottom of the groove 113, so that the pressure release portion 40 forms the corresponding shape, and the pressure release portion 40 forms a vulnerable area with respect to the first wall portion 11. The groove 113 here may also be understood as a notch groove 41. In this case, when the pressure of the battery cell 100 is released, the bottom of the groove 113 ruptures, the pressure release portion 40 is destroyed, and the first wall portion 11 forms an opening at the bottom of the groove 113, thereby achieving pressure release.

[0200] By installing a groove 113 in the first wall portion 11, an integrated pressure release portion 40 is formed. This method is simple to implement, has low production costs, and when the groove 113 is installed on the outer surface of the first wall portion 11, the groove 113 provides a relief space for opening the pressure release portion 40, reducing the probability that the pressure release portion 40 cannot be opened due to being blocked by an external barrier.

[0201] As shown in Figures 15 and 17, in some embodiments, grooves 113 extending in the circumferential direction are provided on the inner and / or outer surfaces of the first wall portion 11, and the region surrounded by the grooves 113 forms a pressure release portion 40.

[0202] As shown in Figure 17, the inner surface of the first wall portion 11 faces the inside of the exterior casing 10, and the outer surface of the first wall portion 11 faces the outside of the exterior casing 10. Here, a groove 113 may be provided on the inner surface of the first wall portion 11 but not on the outer surface of the first wall portion 11, or a groove 113 may not be provided on the inner surface of the first wall portion 11 but be provided on the outer surface of the first wall portion 11, or a groove 113 may be provided on both the inner and outer surfaces of the first wall portion 11 and the portion of the first wall portion 11 located between the bottom surfaces of the two grooves 113 may be the groove bottom wall of the groove 113.

[0203] The groove 113 extends along the circumferential direction and can form a closed annular shape. In this case, the region enclosed by the groove 113 forms a pressure release section 40, that is, the pressure release section 40 includes the groove 113 and the region inside the groove 113. Here, the groove 113 may also be understood as a notch groove 41. When the battery cell 100 releases pressure, the first wall portion 11 splits open at the groove 113, the pressure release section 40 can open at the groove 113, and furthermore, the pressure release section 40 detaches from the first wall portion 11, achieving rapid pressure release.

[0204] In the above proposed technology, a groove 113 is installed in the first wall portion 11 to form an integrated pressure release portion 40, resulting in a simple implementation method and low production costs.

[0205] As shown in Figures 3 and 4, in some embodiments, the pressure release section 40 is installed separately from the first wall section 11, the first wall section 11 is provided with a communication hole, and the pressure release section 40 is attached to the communication hole.

[0206] As shown in Figures 3 and 4, the pressure release section 40 and the outer casing 10 are two independent components, which are molded independently and then attached together. Specifically, the pressure release section 40 may be an explosion-proof sheet, an explosion-proof valve, a safety valve, or the like. The pressure release section 40 may also be attached to the first wall section 11 by methods such as adhesive bonding or welding. A communication hole is provided in the first wall section 11, and the pressure release section 40 is attached to the communication hole. When the pressure inside the battery cell 100 reaches a threshold, the pressure release section 40 opens at least a portion of the communication hole, the discharge medium inside the battery cell 100 is discharged through the communication hole, and the pressure inside the battery cell 100 is released.

[0207] As shown in Figure 4, taking the example that the pressure release section 40 is an explosion-proof sheet, the explosion-proof sheet is a sheet in which the strength of at least a portion of the area is less than the strength of the first wall 11, the explosion-proof sheet covers the communication hole, and the explosion-proof sheet is welded to the first wall 11. When the pressure inside the battery cell 100 reaches a threshold, the explosion-proof sheet is at least partially destroyed, further opening at least a portion of the communication hole and releasing the pressure inside the battery cell 100.

[0208] In this embodiment, the pressure release section 40 is a component independent of the outer casing 10, and the pressure release section 40 and the outer casing 10 can be manufactured separately and reassembled, resulting in low production difficulty and high efficiency.

[0209] As shown in Figures 3 and 4, in some examples, the outer casing 10 includes a casing 101 having an opening on one side and an end cap 102 connected to the casing 101 and used to seal the opening, with a first wall portion 11 formed in the casing 101.

[0210] The casing 101 may be a hollow structure with an opening at one end, or it may be a hollow structure with openings at both opposing ends. The casing 101 may have various shapes, such as a rectangular prism.

[0211] The end cap 102 is a component that seals the opening of the casing 101 so as to isolate the internal environment of the battery cell 100 from the external environment. Together with the casing 101, the end cap 102 defines a housing space for housing the electrode assembly 20, electrolyte, and other components. The shape of the end cap 102 can match the shape of the outer casing 10. For example, if the casing 101 has a rectangular parallelepiped structure, the end cap 102 has a rectangular plate-like structure that matches the outer casing 10. Furthermore, for example, if the casing 101 has a cylindrical structure, the end cap 102 has a circular plate-like structure that matches the casing 101. The material of the end cap 102 may be various materials such as copper, iron, aluminum, steel, aluminum alloy, or plastic. The materials of the end cap 102 and the casing 101 may be the same or different.

[0212] In an embodiment in which the casing 101 forms an opening at one end, one end cap 102 may be installed correspondingly. In an embodiment in which the casing 101 forms openings at both opposing ends, two end caps 102 may be installed correspondingly, with each of the two end caps 102 sealing two openings in the casing 101, and the two end caps 102 together with the casing 101 defining the housing space.

[0213] The casing 101 has a first wall portion 11 and a second wall portion 12, and a pressure release portion 40 is provided in the casing 101. The pressure release portion 40 may be integrally molded with the casing 101 or installed separately from the casing 101. By installing the pressure release portion 40 in the casing 101, the structure of the end cap 102 can be simplified, and the distance between the pressure release portion 40 and the main body of the electrode assembly 20 can be easily shortened. Furthermore, the path through which the discharge medium flows to the pressure release portion 40 during pressure release can be shortened, reducing the time it takes for the discharge medium to reach the pressure release portion 40 and improving the timeliness of pressure release of the battery cell 100, thereby effectively improving the reliability of the battery cell 100.

[0214] As shown in Figure 19, in some embodiments, the casing 101 has openings on both opposing sides, and two end caps 102 are used to seal the openings on the corresponding sides.

[0215] As shown in Figure 19, in an embodiment in which the casing 101 has openings at both opposing ends, two end caps 102 may be installed correspondingly, with each of the two end caps 102 sealing the two openings of the casing 101, and the two end caps 102 together with the casing 101 defining the housing space. The first wall portion 11 is located on the casing 101, the pressure release portion 40 is located between the two openings, and one electrical connection portion 30 is installed on each end cap 102.

[0216] By providing two openings in the casing 101, the manufacturing and molding of the casing 101 is facilitated, tabs can be easily pulled out from both ends of the electrode assembly 20, and the two electrical connection parts 30 can be easily separated and positioned, thereby reducing the risk of short circuits in the battery cell 100.

[0217] As shown in Figures 3 and 4, in some examples, the end cap 102 is provided with an electrical connection portion 30, which is electrically connected to the positive electrode piece 21 or to the negative electrode piece 22.

[0218] The electrical connection portion 30 is installed on the end cap 102, and may be part of the end cap 102, or it may be a pole attached to the end cap 102, and usually two electrical connection portions 30 are provided, one of which is electrically connected to the tab of the positive electrode piece 21, and the other electrical connection portion 30 is electrically connected to the tab of the negative electrode piece 22, to input or output electrical energy from the battery cell 100, and the electrical connection portion 30 may be directly connected to the tab, for example, the electrical connection portion 30 may be directly welded to the tab, and the electrical connection portion 30 may be indirectly connected to the tab, for example, the electrical connection portion 30 may be indirectly connected to the tab via a current collector, and the current collector may be a metal conductor such as copper, iron, aluminum, steel, or aluminum alloy.

[0219] Of these, the electrical connection part 30 and the pressure release part 40 are located on different sides of the outer casing 10; that is, the electrical connection part 30 is located on one wall of the outer casing 10, and the pressure release part 40 is located on the other wall of the outer casing 10. The electrical connection part 30 is connected to a tab of the electrode assembly 20, and there is a certain gap between the wall where the electrical connection part 30 is located and the main body of the electrode assembly 20. However, by installing the electrical connection part 30 and the pressure release part 40 on different walls of the outer casing 10, the distance between the pressure release part 40 and the main body can be shortened. As a result, in the event of thermal runaway of the battery cell 100, most of the discharge medium inside the outer casing 10 can flow directly from the edge of the main body to the pressure release part 40. This shortens the path the discharge medium takes to reach the pressure release part 40, allowing the discharge medium to flow to the pressure release part 40 quickly. This reduces the time it takes for the discharge medium to reach the pressure release part 40, improving the timeliness of pressure release in the battery cell 100 and effectively improving the reliability of the battery cell 100.

[0220] As shown in Figures 3 and 4, the first wall portion 11 is for supporting the electrode assembly 20, and the first wall portion 11 is located below the electrode assembly 20.

[0221] As a result, the pressure release section 40 may be provided at the bottom of the battery cell 100, or an exhaust passage may be provided at the bottom of the battery cell 100, and the exhaust passage will be in communication with the pressure release section 40, so that if thermal runaway occurs in the battery cell 100, high-temperature, high-pressure smoke will be discharged into the exhaust passage via the pressure release section 40 at the bottom, and further discharged to the outside.

[0222] As shown in Figures 3, 4, 18, and 19, in some embodiments, the exterior casing 10 has a third wall portion 13 on which electrical connection portions 30 are provided, and the third wall portion 13 is arranged adjacent to or opposite the first wall portion 11.

[0223] As shown in Figures 3 and 4, the exterior casing 10 may consist of a first wall portion 11, two opposing second wall portions 12, a third wall portion 13, and two opposing fourth wall portions 14, wherein the first wall portion 11 and the third wall portion 13 are arranged opposite each other along a second direction F2 (up and down direction shown in Figure 4), the second wall portion 12 and the fourth wall portion 14 are located between the first wall portion 11 and the third wall portion 13 and are connected to the first wall portion 11 and the third wall portion 13, respectively, the two second wall portions 12 are arranged opposite each other along a first direction F1 (front and back direction shown in Figure 4), and the two fourth wall portions 14 are arranged opposite each other along a third direction F3 (left and right direction shown in Figure 4), and the exterior casing 10 can take the shape of a roughly rectangular prism, have a simple structure and be easy to mold.

[0224] Of these, the electrical connection part 30 is installed on the third wall part 13, and the pressure release part 40 is installed on the first wall part 11. By installing the electrical connection part 30 and the pressure release part 40 on different walls of the outer casing 10, the distance between the pressure release part 40 and the main body of the electrode assembly 20 can be shortened. As a result, when the battery cell 100 experiences thermal runaway, most of the discharge medium inside the outer casing 10 can flow directly from the edge of the main body of the electrode assembly 20 to the pressure release part 40. This shortens the path the discharge medium takes to reach the pressure release part 40, allowing it to flow to the pressure release part 40 quickly. This reduces the time it takes for the discharge medium to reach the pressure release part 40, improving the timely release of pressure in the battery cell 100 and effectively improving the reliability of the battery cell 100.

[0225] Referring to Figures 18 and 19, Figure 18 is a schematic diagram of a battery cell provided in some other embodiments of the present application, and Figure 19 is a schematic diagram of a battery cell provided in some other embodiments of the present application.

[0226] As shown in Figure 18, the exterior casing 10 may consist of a first wall portion 11, two opposing second wall portions 12, two opposing third wall portions 13, and one fourth wall portion 14, wherein the first wall portion 11 and the fourth wall portion 14 are arranged opposite each other along a second direction F2 (up and down direction shown in Figure 18), the second wall portion 12 and the third wall portion 13 are located between the first wall portion 11 and the fourth wall portion 14 and are connected to the first wall portion 11 and the fourth wall portion 14, respectively, the two second wall portions 12 are arranged opposite each other along a first direction F1 (front and back direction shown in Figure 18), and the two third wall portions 13 are arranged opposite each other along a third direction F3 (left and right direction shown in Figure 18), and the exterior casing 10 can take the shape of a roughly rectangular prism, have a simple structure and be easy to mold.

[0227] As a result, the third wall portion 13 is positioned adjacent to the first wall portion 11, the electrical connection portion 30 is installed on the third wall portion 13, and the pressure release portion 40 is installed on the first wall portion 11. By installing the electrical connection portion 30 and the pressure release portion 40 on different walls of the outer casing 10, the distance between the pressure release portion 40 and the main body of the electrode assembly 20 can be shortened. This allows most of the discharge medium inside the outer casing 10 to flow directly from the edge of the main body of the electrode assembly 20 to the pressure release portion 40 in the event of thermal runaway of the battery cell 100. Therefore, the path for the discharge medium to flow to the pressure release portion 40 can be shortened, allowing the discharge medium to flow to the pressure release portion 40 quickly. This reduces the time it takes for the discharge medium to reach the pressure release portion 40, improving the timeliness of pressure release in the battery cell 100 and effectively improving the reliability of the battery cell 100.

[0228] As shown in Figure 19, in some embodiments, the exterior casing 10 may consist of a first wall portion 11, two opposing second wall portions 12, a third wall portion 13, a fourth wall portion 14, and a fifth wall portion 15, wherein the first wall portion 11 and the fifth wall portion 15 are arranged opposite each other along a second direction F2, the two second wall portions 12, the third wall portion 13, and the fourth wall portion 14 are located between the first wall portion 11 and the fifth wall portion 15, and are connected to the first wall portion 11 and the fifth wall portion 15, respectively, the two second wall portions 12 are arranged opposite each other along a first direction F1 (front-to-back direction shown in Figure 19), and the third wall portion 13 and the fourth wall portion 14 are arranged opposite each other along a third direction F3 (left-to-right direction shown in Figure 19), and the exterior casing 10 can take the shape of a substantially rectangular prism, have a simple structure, and be easy to mold.

[0229] As a result, the third wall 13 and the fourth wall 14 are positioned adjacent to the first wall 11, one electrical connection 30 is installed in the third wall 13, the other electrical connection 30 is installed in the fourth wall 14, and the pressure release section 40 is installed in the first wall 11. By installing the electrical connection 30 and the pressure release section 40 in different walls of the outer casing 10, the distance between the pressure release section 40 and the main body of the electrode assembly 20 can be shortened. This allows most of the discharge medium inside the outer casing 10 to flow directly from the edge of the main body of the electrode assembly 20 to the pressure release section 40 in the event of thermal runaway of the battery cell 100. This shortens the path the discharge medium takes to reach the pressure release section 40, allowing it to flow quickly and reducing the time it takes for the discharge medium to reach the pressure release section 40. This improves the timeliness of pressure release in the battery cell 100, effectively enhancing the reliability of the battery cell 100.

[0230] In some embodiments, the material of the outer casing 10 includes at least one of aluminum, nickel-plated carbon steel, stainless steel, magnesium alloy, nickel alloy, copper alloy, and zirconium alloy.

[0231] The material of the casing 101 of the outer casing 10 may be nickel-plated carbon steel such as SPCC, stainless steel such as SUS304 or SUS316, magnesium alloy such as AZ31B, nickel alloy such as Inconcel625, copper alloy such as brass, zirconium alloy such as Zr702, and of course, composite material. By using the above materials, the tensile strength of the wall portion of the casing 101 can be increased, deformation of the casing 101 during expansion of the electrode assembly 20 can be further reduced, the probability of rupture due to tension at the casing 101 or pressure release portion 40 can be reduced, the risk of leakage can be reduced, and the reliability of the battery cell 100 can be improved. Of these, the end cap 102 and the casing 101 may be made of the same material or different materials.

[0232] In some embodiments, the tensile strength of the first wall portion 11 and / or the second wall portion 12 is 400 MPa or more.

[0233] The tensile strength of the first wall portion 11 may be 400 MPa, or it may be greater than 400 MPa, for example, 500 MPa, 600 MPa, or 700 MPa, and the tensile strength of the second wall portion 12 may be 400 MPa, or it may be greater than 400 MPa, for example, one point value of 500 MPa, 600 MPa, or 700 MPa, or a range value between any two of them. By limiting the tensile strength of the walls of the casing 101, the tensile strength of the casing 101 is improved, deformation of the casing 101 is reduced when the electrode assembly 20 expands, and tension on the surface where the pressure release portion 40 is located is further reduced, the probability of the casing 101 or the pressure release portion 40 being pulled and ruptured is reduced, the risk of liquid leakage is reduced, and the reliability of the battery cell 100 is improved.

[0234] In some embodiments, the positive electrode piece 21 includes a positive electrode current collector and a positive electrode active material region placed on the surface of the positive electrode current collector, and the constituent material of the positive electrode current collector contains aluminum element at a mass percentage of 50% or more.

[0235] In other words, the constituent material of the positive electrode current collector may include aluminum, and the mass percentage of aluminum in the positive electrode current collector is 50% or more. By adopting the above positive electrode current collector, the difficulty of manufacturing the positive electrode piece 21 can be reduced, and at the same time, manufacturing costs can be reduced, compared to composite current collectors in the conventional technology.

[0236] The battery 1000 according to the second embodiment of the present application includes the battery cell 100 according to the first embodiment of the present application.

[0237] An electrical device according to an embodiment of the third aspect of the present application includes a battery 1000 according to the embodiment of the second aspect of the present application, the battery 1000 being used to provide electrical energy to the electrical device. Thus, by adopting the battery 1000, it is advantageous in improving the safety and reliability of the electrical device.

[0238] Selectively, as shown in Figure 1, when the battery 1000 is used in a vehicle, the battery 1000 can be installed at the bottom, front, or rear of the vehicle. The battery 1000 is used to supply power to the vehicle, and for example, the battery 1000 can function as the vehicle's operating power source. The vehicle may further include a controller and a motor, the controller controlling the battery 1000 to supply power to the motor, and is used, for example, to meet the operating power needs during vehicle startup, navigation, and driving.

[0239] Hereinafter, a specific embodiment of the present invention, including battery 1000 and a vehicle containing it, will be described with reference to the drawings.

[0240] As shown in Figure 1, the battery 1000 is located at the bottom of the vehicle, and as shown in Figure 2, the battery 1000 includes a plurality of battery cells 100, and as shown in Figure 3, each battery cell 100 includes an outer casing 10 and an electrode assembly 20, the outer casing 10 is provided with an electrical connection part 30 and a pressure release part 40, the electrical connection part 30 and the pressure release part 40 are located on different sides of the outer casing 10, and the electrode assembly 20 is located inside the outer casing 10.

[0241] The outer casing 10 may consist of a first wall portion 11, two opposing second wall portions 12, a third wall portion 13, and two opposing fourth wall portions 14, wherein the first wall portion 11 and the third wall portion 13 are arranged opposite each other along a second direction F2 (the vertical direction shown in Figure 3), the first wall portion 11 is located on one side of the electrode assembly 20 in the second direction F2, the first wall portion 11 extends along a third direction F3, both electrical connection portions 30 are installed on the third wall portion 13, and the second wall portion 12 and The fourth wall portion 14 is located between the first wall portion 11 and the third wall portion 13 and is connected to the first wall portion 11 and the third wall portion 13, respectively. The second wall portion 12 faces the large surface of the electrode assembly 20 along the first direction F1, with two second wall portions 12 facing each other along the first direction F1 (front-to-back direction shown in Figure 3), and two fourth wall portions 14 facing each other along the third direction F3 (left-to-right direction shown in Figure 3). The outer casing 10 can have a roughly rectangular prism shape, making it simple in structure and easy to mold.

[0242] Of these, the outer casing 10 includes the casing 101 and the end cap 102, with the third wall portion 13 being the end cap 102. The casing 101 is formed into a hollow structure with an opening on one side by five wall portions: a first wall portion 11, two second wall portions 12, and two fourth wall portions 14. As a result, a pressure release portion 40 is provided in the casing 101, and an electrical connection portion 30 is provided in the end cap 102. The casing 101 can be manufactured using a material with a tensile strength of 400 MPa or more. A communication hole is provided in the first wall portion 11, and the pressure release portion 40 may be attached to the communication hole in the first wall portion 11 by methods such as bonding or welding. The pressure release portion 40 is a component independent of the outer casing 10, and the pressure release portion 40 and the outer casing 10 are manufactured separately and reassembled. A patch 60 may be further provided on the outside of the pressure release portion 40, and the patch 60 fits with the outer casing 10 to serve as a protective element for the pressure release portion 40.

[0243] The thickness dimension of the first wall portion 11 in the second direction F2 is E1, and the thickness dimension of the second wall portion 12 in the first direction F1 is D1, satisfying E1 > D1, and 0.4 mm ≤ E1 ≤ 2 mm and 0.2 mm ≤ D1 ≤ 1.5 mm.

[0244] The pressure release section 40 is provided with a notched groove 41 recessed in a second direction F2, and the pressure release section 40 is configured to cleave along at least a portion of the notched groove 41 when the battery cell releases pressure, and in the first direction F1, there is a first minimum distance between the notched groove 41 and the outer surface of one of the two second wall sections 12, and a second minimum distance between the notched groove 41 and the outer surface of the other second wall section 12, and the relatively smaller of the first and second minimum distances is M1, satisfying 2.5 mm ≤ M1 ≤ 20 mm.

[0245] Finally, it should be noted that the above embodiments are used solely to illustrate the technical concepts of the present application and are not limiting. While the present application has been described in detail with reference to the embodiments described above, those skilled in the art will understand that it is still possible to modify the technical concepts described in the embodiments described above, or to replace some or all of their technical features equally, and that such modifications or substitutions should not cause the essence of the corresponding technical concepts to deviate from the scope of the technical concepts of the embodiments of the present application, and should all be included within the scope of the claims and specification of the present application. In particular, any technical feature mentioned in each embodiment can be combined in any way, as long as it is not structurally contradictory. The present application is not limited to the specific embodiments disclosed herein, but includes all technical concepts included in the claims.

Claims

1. It is a battery cell, An electrode assembly comprising at least one positive electrode piece and at least one negative electrode piece, wherein the at least one positive electrode piece and the at least one negative electrode piece form a flat region when stacked, and at least a portion of the positive electrode piece and at least a portion of the negative electrode piece are stacked in the flat region along a first direction, An outer casing used to house the electrode assembly, comprising a first wall and two second walls connected to the first wall, the two second walls respectively located on both sides of the flat region in the first direction, the first wall located on one side of the electrode assembly in the second direction, the second direction being parallel to the thickness direction of the first wall and perpendicular to the first direction, Of these, the first wall portion is provided with a pressure release portion, the pressure release portion is provided with a notch groove that is recessed in the second direction, the pressure release portion is configured to rupture along at least a portion of the notch groove when the pressure of the battery cell is released, and in the first direction, the notch groove is positioned at a distance from the outer surface of either of the two second wall portions. Battery cell.

2. There is a first minimum distance between the notch groove and the outer surface of one of the two second wall portions, and a second minimum distance between the notch groove and the outer surface of the other of the two second wall portions, where the smaller of the first and second minimum distances is M1, and satisfies 2.5 mm ≤ M1 ≤ 20 mm, preferably 3 mm ≤ M1 ≤ 15 mm. The battery cell according to claim 1.

3. The thickness dimension of the second wall portion in the first direction is D1, and is 0.2 mm ≤ D1 ≤ 1.5 mm, preferably 0.3 mm ≤ D1 ≤ 1.2 mm. The battery cell according to claim 1 or 2.

4. The thickness dimension of the second wall portion in the first direction is D1, there is a first minimum distance between the notch groove and the outer surface of one of the two second wall portions, there is a second minimum distance between the notch groove and the outer surface of the other of the two second wall portions, the smaller of the first and second minimum distances is M1, and the condition 0.5 mm² ≤ M1 × D1 ≤ 30 mm² is satisfied. A battery cell according to any one of claims 1 to 3.

5. The thickness dimension of the first wall portion in the second direction is E1, satisfying 0.4 mm ≤ E1 ≤ 2 mm, preferably 0.5 mm ≤ E1 ≤ 1.8 mm. A battery cell according to any one of claims 1 to 4.

6. The thickness dimension of the first wall portion in the second direction is E1, there is a first minimum distance between the notch groove and the outer surface of one of the two second wall portions, there is a second minimum distance between the notch groove and the outer surface of the other of the two second wall portions, the smaller of the first and second minimum distances is M1, and 1 mm² ≤ M1 × E1 ≤ 40 mm². A battery cell according to any one of claims 1 to 5.

7. The orthographic projection area of ​​the first wall portion along the second direction is smaller than the orthographic projection area of ​​the second wall portion along the first direction. A battery cell according to any one of claims 1 to 6.

8. The thickness dimension of the first wall portion in the second direction is E1, and the thickness dimension of the second wall portion in the first direction is D1, where E1 > D1. A battery cell according to any one of claims 1 to 7.

9. The pressure release portion is provided with a predetermined pressure release region and a notch groove, the predetermined pressure release region has a predetermined opening boundary, the predetermined opening boundary is surrounded by the outer edge of the orthographic projection in the second direction of at least a portion of the notch groove, or the predetermined opening boundary is surrounded by connecting lines between a plurality of ends of the notch groove, or the predetermined opening boundary is jointly surrounded by the connecting lines between a plurality of ends of the notch groove and the outer edge of the orthographic projection in the second direction of at least a portion of the notch groove. A battery cell according to any one of claims 1 to 8.

10. The area of ​​the orthographic projection of the predetermined pressure release region is S1, and the area enclosed by the edge of the orthographic projection of the first wall is S2, such that 0.06 ≤ S1 / S2 ≤ 0.

30. The battery cell according to claim 9.

11. The first wall portion has a rectangular structure, the width direction of the first wall portion is parallel to the first direction, the length direction of the first wall portion is parallel to the third direction, and the third direction is perpendicular to the first direction and the second direction, respectively. The maximum width dimension in the width direction of the predetermined pressure release region is W1, and the maximum length dimension in the length direction of the predetermined pressure release region is W2, where W2 > W1. The battery cell according to claim 9.

12. Satisfying 0.25 ≤ W1 / W2 ≤ 0.7, The battery cell according to claim 11.

13. The pressure release portion is integrally molded with the first wall portion, or, The pressure release section is installed separately from the first wall section, the first wall section is provided with a communication hole, and the pressure release section is attached to the communication hole. A battery cell according to any one of claims 1 to 12.

14. The exterior casing includes a casing having an opening on at least one side, and an end cap connected to the casing and used to seal the opening, the first wall portion being formed in the casing, A battery cell according to any one of claims 1 to 13.

15. Both opposing sides of the casing have openings, and the two end caps are used to seal the corresponding openings. The battery cell according to claim 14.

16. The end cap is provided with an electrical connection portion, the electrical connection portion is electrically connected to the positive electrode piece, or the electrical connection portion is electrically connected to the negative electrode piece. The battery cell according to claim 14 or 15.

17. The first wall portion is used to support the electrode assembly and is located below the electrode assembly. A battery cell according to any one of claims 14 to 16.

18. The material of the exterior casing includes at least one of aluminum, nickel-plated carbon steel, stainless steel, magnesium alloy, nickel alloy, copper alloy, and zirconium alloy. A battery cell according to any one of claims 1 to 17.

19. The positive electrode piece includes a positive electrode current collector and a positive electrode active material region placed on the surface of the positive electrode current collector, and the constituent material of the positive electrode current collector contains aluminum element at a mass percentage of 50% or more. A battery cell according to any one of claims 1 to 18.

20. A battery cell according to any one of claims 1 to 19, battery.

21. An electrical device comprising a battery as described in claim 20, wherein the battery is used to provide electrical energy to the electrical device. Electrical device.

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