Battery monomer, battery and electric device

Abstract

The utility model discloses a battery monomer, a battery and a power utilization device, and the battery monomer comprises a shell which comprises two first walls and a second wall; the first wall and the end cover are welded to form a first connecting part; an electrode assembly; the pressure relief mechanism is arranged on the second wall and provided with a first nick groove, the first nick groove comprises a first groove section, the size of the groove bottom face of the first groove section in the second direction is A, the width of the second wall in the second direction is B, A / B is larger than or equal to 0.008, the first wall comprises a first area and a second area, and the thickness of the first area is larger than that of the second area. By properly increasing the width ratio of the groove bottom surface of the first groove section on the second wall, the conditions of damage, cracking, liquid leakage and the like of a weak area corresponding to the first groove section due to expansion deformation of the electrode assembly can be reduced, and the risk of fatigue cracking is reduced to a certain extent; and the cracking probability of the welding part of the end cover and the shell during thermal runaway of the battery monomer is reduced.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a battery cell, a battery, and an electrical device. Background Technology

[0002] Energy conservation and emission reduction are key to the sustainable development of the automotive industry, and electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of this sustainable development. For electric vehicles, battery technology is a crucial factor in their development.

[0003] During the charging and discharging process of a battery cell, the electrode assembly will expand and deform, causing the outer casing that houses the electrode assembly to also bulge and deform. This makes the weak areas of the pressure relief mechanism easily pulled and torn, leading to damage to the pressure relief mechanism and leakage, thus reducing the reliability of the battery cell. Utility Model Content

[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 caused by the stretching of the weak area of ​​the pressure relief mechanism during battery use.

[0005] In a first aspect, this application provides a battery cell, comprising: a housing having an opening at at least one end along a first direction, the housing including two first walls and a second wall, the two first walls being arranged opposite each other along a second direction, the second wall being connected between the two first walls, the first direction and the second direction being perpendicular to each other; an end cap closing the opening, the first wall being welded to the end cap to form a first connection portion, the thickness of the end cap being greater than the thickness of the second wall; and an electrode assembly housed within the housing, the electrode assembly including at least one positive electrode, at least one negative electrode, and at least one separator, the separator being used to separate the positive electrode and the negative electrode, the electrode assembly including a flat region, at least a portion of the positive electrode and at least a portion of the negative electrode being... At least a portion of the separator is stacked in the flat area along the second direction; a pressure relief mechanism is disposed on the second wall, the pressure relief mechanism is provided with a first groove, the pressure relief mechanism is configured to crack along at least a portion of the first groove when the battery cell is depressurized, the first groove includes a first groove segment extending along a straight trajectory, the length direction of the first groove segment is perpendicular to the second direction, the width of the bottom surface of the first groove segment in the second direction is A, the width of the second wall in the second direction is B, satisfying: A / B≥0.008, the first wall includes a first area and a second area arranged along the first direction, the first area is located on the side of the second area near the first connection portion, and the thickness of the first area is greater than the thickness of the second area.

[0006] In the technical solution of this application embodiment, by appropriately increasing the width ratio of the bottom surface of the first groove section on the second wall, the damage, cracking and leakage caused by the expansion and deformation of the electrode assembly in the weak area corresponding to the first groove section can be reduced, thereby reducing the risk of fatigue cracking to a certain extent. By thickening the connection between the first wall and the end cap, the probability of cracking at the weld between the end cap and the shell when the burst pressure rises and the battery cell thermally runs away is reduced, thereby improving the reliability of the battery cell.

[0007] In some embodiments, the thickness difference between the first region and the second region is t, which satisfies: 0.1mm≤t≤0.7mm, preferably 0.2mm≤t≤0.5mm. This technical solution can improve the strength of the area near the first connection, increase the burst pressure at the weld between the shell and the end cap, reduce the probability of cracking at the end cap weld during thermal runaway, and facilitate the manufacturing and forming of the shell.

[0008] In some embodiments, the maximum thickness of the first region is D1, satisfying: 0.5mm ≤ D1 ≤ 1.5mm. In the above technical solution, this ensures that the first region has sufficient strength, thereby increasing the strength of the area near the first connection, increasing the burst pressure at the weld between the shell and the end cap, and reducing the probability of cracking at the end cap weld during thermal runaway.

[0009] In some embodiments, the maximum thickness of the second region is D2, satisfying: 0.4mm ≤ D2 ≤ 0.8mm. In the above technical solution, both the strength requirements of the second region and the volumetric energy density requirements of the battery cell 100 are satisfied.

[0010] In some embodiments, the first region includes a first portion and a second portion arranged along the first direction, the second portion connecting the first portion and the second region, the thickness of the first portion being the thickness of the first region, and the thickness of the second portion decreasing along the direction from the end cap towards the electrode assembly. In the above technical solution, this facilitates the manufacturing and forming of the first wall, and also provides a certain degree of reinforcement to the first wall, improving the structural strength of the first region, increasing the burst pressure at the weld between the housing and the end cap, reducing the risk of cracking at the connection between the housing and the end cap during thermal runaway, thereby improving the reliability and service life of the battery cell.

[0011] In some embodiments, the second region has a first inner surface facing the interior space of the housing and a first outer surface facing away from the interior of the housing, the first region including a first protrusion protruding from the first inner surface, and / or, the first region including a second protrusion protruding from the first outer surface.

[0012] In some embodiments, A / B ≤ 0.019 is satisfied. In the above technical solution, the damage, cracking, and leakage that occur in the weak area corresponding to the first groove section due to the expansion of the electrode assembly 20 can be reduced, thus mitigating the risk of fatigue cracking to some extent. Simultaneously, it avoids excessive burst pressure at the first groove, preventing the pressure relief mechanism from failing to release the internal pressure of the battery cell in a timely manner, thereby improving the reliability of the battery cell.

[0013] In some embodiments, the following conditions are met: 0.3mm≤A≤0.8mm, 20mm≤B≤80mm. In the above technical solution, the width of the bottom surface of the first groove is increased to a certain extent, increasing the deformation resistance of the first groove and reducing the deformation of the pressure relief mechanism at the first groove when the electrode assembly expands. This, in turn, can mitigate the risk of fatigue cracking of the pressure relief mechanism during long-cycle charge-discharge use of the battery cell, reduce the probability of leakage due to tearing of the pressure relief mechanism, and improve the reliability of the battery cell. Simultaneously, it avoids excessive burst pressure at the first groove, preventing the pressure relief mechanism from failing to release the internal pressure of the battery cell in a timely manner, further improving the reliability of the battery cell.

[0014] In some embodiments, the minimum residual thickness of the first groove segment is D3, where 0.1mm ≤ D3 ≤ 0.28mm. In the above technical solution, increasing the minimum residual thickness of the first groove segment to a certain extent increases the deformation resistance of the first groove segment and reduces the deformation of the pressure relief mechanism at the first groove segment when the electrode assembly expands. This, in turn, can mitigate the risk of fatigue cracking of the pressure relief mechanism during long-cycle charge-discharge use of the battery cell, reduce the probability of leakage due to tearing of the pressure relief mechanism, and improve the reliability of the battery cell. Simultaneously, it avoids excessive burst pressure at the first groove segment, preventing the pressure relief mechanism from failing to release the internal pressure of the battery cell in a timely manner, further improving the reliability of the battery cell.

[0015] In some embodiments, the first groove defines at least one predetermined pressure relief area, and the pressure relief mechanism is provided with a second groove configured to guide at least a portion of the predetermined pressure relief area to flip, thereby opening at least a portion of the predetermined pressure relief area. In the above technical solution, by providing the second groove, the predetermined pressure relief area can be guided to open, thereby improving the opening effect of the predetermined pressure relief area of ​​the pressure relief mechanism. This, in turn, can increase the pressure relief rate of the battery cell during thermal runaway, reducing the risk of fire, explosion, or connection failure caused by untimely pressure relief, and improving the reliability of the battery cell.

[0016] In some embodiments, the residual thickness of the second groove is greater than the residual thickness of the first groove. In the above technical solution, the strength of the area where the pressure relief mechanism has the first groove can be less than the strength of the area where the pressure relief mechanism has the second groove, so that the pressure relief mechanism can preferentially crack along the first groove to achieve rapid opening of the predetermined pressure relief zone.

[0017] In some embodiments, the width of the second groove perpendicular to the extension direction is greater than the width of the first groove perpendicular to the extension direction. This design allows the pressure relief mechanism to preferentially open along the first groove, thereby enabling rapid opening of the predetermined pressure relief zone.

[0018] In some embodiments, the first groove further includes two second groove segments, which are arranged opposite to each other. The two ends of the first groove segment are respectively connected to one end of each of the two second groove segments, and the other ends of each of the two second groove segments are connected to both ends of the second groove. The first groove segment, the two second groove segments, and the second groove together define a predetermined pressure relief area. In the above technical solution, the first groove segment, the second groove, and the two second groove segments are connected to form a ring structure, making the intersection of the first groove segment and the second groove segment weaker, making it easier to crack and open the predetermined pressure relief area for pressure relief. Simultaneously, this structure helps to increase the opening area of ​​the predetermined pressure relief area, increasing the pressure relief area of ​​the battery cell and improving the pressure relief rate of the battery cell.

[0019] In some embodiments, the second groove is arranged parallel to and opposite to the first groove segment, and the second groove segment extends along a straight line and / or an arc trajectory. In the above technical solution, the second groove segment extends along a straight line trajectory, which can reduce the molding difficulty of the second groove segment; the second groove segment is an arc-shaped groove, which makes it easier for the pressure relief mechanism to crack along the second groove segment when the battery cell is depressurized, so as to realize the predetermined pressure relief area opening more quickly.

[0020] In some embodiments, the pressure relief mechanism includes a main body and a pressure relief section. The main body is connected to the second wall, and the thickness of the pressure relief section is less than the thickness of the main body. The first groove is provided in the pressure relief section, and the thickness of the pressure relief section in the first direction is D4, satisfying: 0.15mm ≤ D4 ≤ 0.4mm, preferably 0.2mm ≤ D4 ≤ 0.3mm. In the above technical solution, reducing the stress concentration at the first groove section to a certain extent avoids the risk of fatigue cracking in the pressure relief mechanism. Simultaneously, it avoids excessive burst pressure of the pressure relief mechanism, reducing the probability that the pressure relief mechanism will not burst in time and is prone to bursting at other locations when thermal runaway occurs in a battery cell, thereby improving the reliability of the battery cell.

[0021] In some embodiments, the pressure relief mechanism is provided with a pressure relief section, and the first groove is provided in the pressure relief section. The minimum residual thickness of the first groove section is D3, and the thickness of the pressure relief section in the first direction is D4, satisfying: 0.55≤D3 / D4≤0.85. In the above technical solution, reducing the stress concentration at the first groove section can, to some extent, avoid the risk of fatigue cracking in the pressure relief mechanism. Simultaneously, it can prevent excessive burst pressure of the pressure relief mechanism. In the event of thermal runaway in a battery cell, it reduces the probability that the pressure relief mechanism will not burst in time and may easily burst at other locations, thereby improving the reliability of the battery cell.

[0022] In some embodiments, the second wall has a pressure relief hole, the pressure relief mechanism is mounted on the pressure relief hole, and the area of ​​the pressure relief hole projected along the first direction is W = 400 mm². 2 ≤W≤1400mm 2 Preferably, 600mm 2 ≤W≤1200mm 2 The above technical solution can, to some extent, avoid the risk of fatigue cracking in the pressure relief mechanism. At the same time, when a battery cell experiences thermal runaway, it reduces the probability that the pressure relief mechanism will not burst in time and will easily burst in other locations, thereby improving the reliability of the battery cell.

[0023] In some embodiments, the second wall has a pressure relief hole, and the pressure relief mechanism is installed in the pressure relief hole. The dimension of the pressure relief hole in the second direction is N, and the dimension of the pressure relief hole in the third direction is L. The third direction is perpendicular to the first direction and the second direction, satisfying: 1.5 ≤ L / N ≤ 5, preferably, 2 ≤ L / N ≤ 4. In the above technical solution, the risk of fatigue cracking in the pressure relief mechanism can be avoided to a certain extent, while reducing manufacturing difficulty and improving manufacturing yield.

[0024] In some embodiments, the electrode assembly comprises N1 units, each electrode assembly having N2 layers of positive electrode sheets stacked in the flat region, the flat region having an outer surface perpendicular to the second direction, the area of ​​the outer surface being S, wherein N1≥1, N2≥1, N1*N2≤500, and S≤80000mm². 2 In the above technical solution, the expansion of the electrode assembly can be reduced during the charging and discharging process of the battery cell, thereby reducing the probability of cracking and damage to the grooves of the pressure relief mechanism and the welded joints of the end cap, and improving the reliability of the battery cell.

[0025] In some embodiments, the electrode assembly is a stacked structure, comprising a plurality of positive electrode sheets and a plurality of negative electrode sheets, which are stacked along the second direction. In the above technical solution, the structure is more compact and has stronger resistance to compression.

[0026] In some embodiments, along a third direction, the size of the first region is larger than the size of the positive electrode and / or the size of the negative electrode, and the first direction, the second direction, and the third direction are perpendicular to each other. In the above technical solution, the strength of the area near the first connection portion can be improved, increasing the burst pressure at the weld between the casing and the end cap, thus avoiding to some extent the risk of cracking at the weld between the casing and the end cap during thermal runaway of the battery cell, and improving the reliability of the battery cell.

[0027] In some embodiments, the number of negative electrode plates is greater than the number of positive electrode plates, and a positive electrode plate is disposed between two adjacent negative electrode plates.

[0028] In some embodiments, each of the negative electrode plates is provided with a negative electrode tab; and / or, each of the positive electrode plates is provided with a positive electrode tab.

[0029] In some embodiments, the electrode assembly is a wound structure, and the electrode assembly further has a corner region. The corner region is provided at least one end of the straight region along a third direction, and at least a portion of the outer surface of the corner region is an arc surface. The first direction, the second direction, and the third direction are not coplanar and intersect each other. In the above technical solution, the strength of the area near the first connection portion can be improved, the burst pressure at the weld between the casing and the end cap can be increased, and the risk of cracking at the weld between the casing and the end cap during thermal runaway of the battery cell can be avoided to a certain extent, thereby improving the reliability of the battery cell.

[0030] In some embodiments, the pressure relief mechanism includes a buffer portion that arches outward along the first direction toward and / or away from the electrode assembly. By providing the buffer portion, during long-term use of the battery cell, the buffer portion can absorb the tensile deformation transmitted to the pressure relief mechanism, thereby reducing the expansion force acting on the groove, reducing the tensile force on the groove, and thus the buffer portion plays a buffering role. This reduces the probability of the groove being torn and damaged, leading to leakage, and improves the service life and reliability of the battery cell.

[0031] In some embodiments, along the thickness direction of the second wall, the second wall has a second outer surface and a second inner surface, the second inner surface being closer to the electrode assembly than the second outer surface. The buffer portion includes a first buffer portion, which arches towards the side closer to the electrode assembly but does not protrude beyond the second inner surface. In the above technical solution, the first buffer portion does not occupy the space outside the battery cell, facilitating the placement of the battery cell, nor does it occupy the space inside the casing, avoiding interference with the electrode assembly or occupying the space of the electrode assembly, thus preventing an excessive reduction in the energy density of the battery cell.

[0032] In some embodiments, an insulating member is provided within the housing, located between the second wall and the electrode assembly. The insulating member defines a clearance groove opening towards the second wall, the clearance groove corresponding to the position of the buffer portion. In the above technical solution, the insulating member can block direct contact between the electrode assembly and the second wall, reducing the risk of electrochemical corrosion. The clearance groove allows the electrolyte to flow more smoothly, improving the wetting efficiency of the electrolyte on the electrode assembly. During the long-term use of the battery cell, when the buffer portion deforms, a portion can extend into the clearance groove, which provides some space for the deformation of the buffer portion, thus facilitating its deformation.

[0033] In some embodiments, along the thickness direction of the second wall, the second wall has a second outer surface and a second inner surface, the second inner surface being closer to the electrode assembly than the second outer surface. The buffer portion includes a first buffer portion, the first buffer portion arching towards the side closer to the electrode assembly, at least a portion of the first buffer portion protruding from the second inner surface and extending into the clearance groove. In the above technical solution, the space of the insulating member can be fully utilized, the arching degree of the buffer portion can be maximized, the utilization rate in the thickness direction of the second wall can be improved, and the buffering performance of the buffer portion can be enhanced. Under the action of the insulating member, the buffer portion will not interfere with the electrode assembly, thus improving the reliability of the battery cell.

[0034] In some embodiments, along the thickness direction of the second wall, the second wall has a second outer surface and a second inner surface, the second inner surface being closer to the electrode assembly than the second outer surface. The buffer portion includes a second buffer portion that arches away from the electrode assembly and does not protrude beyond the second outer surface. In the above technical solution, the second buffer portion does not protrude beyond the entire outer surface of the housing, thereby avoiding the occupation of space outside the battery cell and affecting the energy density of the battery, and also avoiding the buffer portion affecting the placement of the battery cell. For example, the second wall can be the bottom wall of the battery cell, and the battery cell can be supported in the housing by the second wall. The buffer portion is located inside the second outer surface, which can avoid the problem of the second wall not fitting properly inside the housing and affecting the stability of the battery cell placement.

[0035] In some embodiments, the buffer portion includes a first buffer portion and a second buffer portion. The first buffer portion arches towards the side closer to the electrode assembly, and the second buffer portion arches away from the electrode assembly. At least a portion of the first buffer portion is located on one side of the second buffer portion in the second direction. In the above technical solution, by providing two buffer portions, space can be fully utilized, the deformability of the buffer portion can be increased, the buffering performance of the buffer portion can be improved, the probability of tearing and leakage at the groove can be reduced, and the service life and reliability of the battery cell can be improved.

[0036] In some embodiments, the second buffer portion extends along a third direction, with the second direction, the first direction, and the third direction being perpendicular to each other, and the first buffer portion is connected to the outer periphery of the second buffer portion. This reduces the tensile force on various locations of the entire pressure relief portion to a certain extent. By stretching and deforming the first buffer portion, it can buffer the various locations where the groove is located, reducing the probability of the groove being stretched and damaged, leading to leakage, and improving the service life and reliability of the battery cell.

[0037] In some embodiments, the battery cell further includes an electrical connection portion disposed on the end cap and electrically connected to the electrode assembly. The end cap has a lead-out hole, and the electrical connection portion includes a terminal body, a first limiting portion, and a second limiting portion. The terminal body connects the first limiting portion and the second limiting portion, and the terminal body passes through the lead-out hole. Along the first direction, the first limiting portion is located on the side of the end cap away from the electrode assembly, and the second limiting portion is located on the side of the end cap facing the electrode assembly. In the above technical solution, the electrical connection portion can be installed on the end cap by riveting, which is easy to install and has better economic efficiency.

[0038] In some embodiments, the second wall is located below the electrode assembly and opposite the end cap, and the second wall is used to support the electrode assembly. In the above technical solution, the pressure relief mechanism can be provided at the bottom of the battery cell, and the bottom of the battery cell can be provided with an exhaust channel. The exhaust channel is connected to the pressure relief mechanism so that when the battery cell experiences thermal runaway, the high-temperature and high-pressure flue gas is discharged through the pressure relief mechanism at the bottom into the exhaust channel, and then discharged to the outside.

[0039] In some embodiments, the housing is made of aluminum alloy. The housing, as described above, offers advantages such as lightweight, safety, ease of processing, and good corrosion resistance.

[0040] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector along the thickness direction of the negative electrode sheet and containing a negative electrode active material. The negative electrode active material includes a silicon-based material, and the mass content of silicon element in the silicon-based material is 0.3% to 10.0% based on the total mass of the negative electrode active material. In the above technical solution, by keeping the mass content of silicon element in the silicon-based material within the above range, the capacity of the negative electrode active material can be improved, thereby improving the energy density of the battery cell; increasing the energy density prevents excessive expansion force and reduces damage, cracking, and leakage in weak areas caused by the expansion and deformation of the electrode assembly.

[0041] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector along the thickness direction of the negative electrode sheet and containing a negative electrode active material, wherein the discharge capacity of the negative electrode film layer per unit area is 2.0 mAh / cm². 2 Up to 5.0mAh / cm 2 When the discharge capacity of the negative electrode film per unit area is within the above range, there are sufficient sites in the negative electrode film for lithium insertion, which can reduce the risk of lithium plating; it is also conducive to fast charging, and the expansion force is not too large, reducing the damage, cracking and leakage caused by the expansion and deformation of the electrode components in weak areas.

[0042] In some embodiments, the thickness of the negative electrode film is T1, where 9 μm ≤ T1 ≤ 75 μm.

[0043] Secondly, this application provides a battery that includes the battery cell described in the above embodiments.

[0044] Thirdly, this application provides an electrical device that includes the battery described in the above embodiments, the battery being used to provide electrical energy.

[0045] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0046] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0047] Figure 1 This is a schematic diagram of an electrical device in related technologies;

[0048] Figure 2 This is a schematic diagram of a battery in a related technology;

[0049] Figure 3 A schematic diagram of a battery cell provided in some embodiments of this application;

[0050] Figure 4 Exploded views of individual battery cells provided in some embodiments of this application;

[0051] Figure 5 A schematic diagram of an electrode assembly provided in some embodiments of this application;

[0052] Figure 6A schematic diagram of an electrode assembly provided for other embodiments of this application;

[0053] Figure 7 Cross-sectional views of a battery cell provided in some embodiments of this application;

[0054] Figure 8 A schematic diagram of a pressure relief mechanism provided in some embodiments of this application;

[0055] Figure 9 For along Figure 8 Sectional view of line AA in the middle;

[0056] Figure 10 for Figure 9 The center circle shows a magnified view of point B.

[0057] Figure 11 Schematic diagram of the housing provided for some embodiments of this application;

[0058] Figure 12 Cross-sectional views of the housing provided for some embodiments of this application;

[0059] Figure 13 for Figure 12 The center circle shows an enlarged view of C in some embodiments;

[0060] Figure 14 for Figure 12 The center circle shows an enlarged view of location C in some other embodiments;

[0061] Figure 15 for Figure 12 The center circle shows an enlarged view of location C in some other embodiments;

[0062] Figure 16 Cross-sectional views of a battery cell provided for other embodiments of this application;

[0063] Figure 17 for Figure 16 The center circle shows an enlarged view of D in some embodiments;

[0064] Figure 18 for Figure 16 The center circle shows an enlarged view of D in some other embodiments;

[0065] Figure 19 for Figure 16 The center circle shows an enlarged view of D in some other embodiments;

[0066] Figure 20 A schematic diagram of the pressure relief mechanism provided in some embodiments of this application from one perspective;

[0067] Figure 21A schematic diagram of the pressure relief mechanism provided in some embodiments of this application from another perspective;

[0068] Figure 22 A schematic diagram of a pressure relief mechanism provided in some other embodiments of this application;

[0069] Figure 23 A schematic diagram of a pressure relief mechanism provided in some embodiments of this application;

[0070] Figure 24 This is a schematic diagram showing the connection between the end cap and the electrical connection portion provided in some embodiments of this application.

[0071] Figure label:

[0072] Battery 1000, vehicle 2000, battery cell 100, casing 200, first shell 201, second shell 202.

[0073] Outer shell 10, housing 101, end cap 102, first wall 11, first region 111, first part 111a, second part 111b, first protrusion 1111, second protrusion 1112, second region 112, first inner surface 1121, first outer surface 1122, second wall 12, pressure relief hole 121, second inner surface 1101, second outer surface 1102.

[0074] Electrode assembly 20, positive electrode 21, negative electrode 22, straight region 23, corner region 24, separator 25.

[0075] Electrical connection part 30, terminal body 31, first limiting part 32, second limiting part 33.

[0076] Pressure relief mechanism 40, predetermined pressure relief area 401, first groove 41, first groove segment 411, second groove segment 412, second groove 42, pressure relief part 43, main body part 44, buffer part 45, first buffer part 45a, second buffer part 45b, side wall 451, bottom wall 452, inner buffer surface 4501, outer buffer surface 4502.

[0077] First connecting part 51, first insulating component 6, second insulating component 7.

[0078] Patch 60, insulating part 70, clearance groove 71. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0080] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0081] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0082] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0083] In the embodiments of this application, the same reference numerals denote 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 thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0084] In this application, "multiple" means two or more (including two).

[0085] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0086] The battery cell can 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 this.

[0087] The battery mentioned in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0088] In some embodiments, the battery can be a battery module, and when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0089] In some embodiments, the battery can be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0090] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0091] In some embodiments, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0092] The development of battery technology must take into account multiple design factors, such as energy density, cycle life, discharge capacity, and charge / discharge rate.

[0093] In a single battery cell, a pressure relief mechanism is installed on the outer casing. In the event of thermal runaway, the pressure inside the battery cell is released through the pressure relief mechanism to improve the safety of the battery cell.

[0094] During the charging and discharging process, the electrode assembly of a battery cell expands, causing the outer casing to bulge and deform. This bulging is transmitted to the surface where the pressure relief mechanism is located. The groove of the pressure relief mechanism is a weak area. The expansion of the electrode assembly will cause the pressure relief mechanism to stretch, resulting in the weak area being torn. The battery cell is prone to problems such as pressure relief mechanism failure and leakage before it reaches the warranty period.

[0095] In view of this, this application provides a battery cell, comprising: a housing having an opening at at least one end along a first direction, the housing including two first walls and a second wall, the two first walls being arranged opposite each other along a second direction, the second wall being connected between the two first walls, the first direction and the second direction being perpendicular to each other; an end cap closing the opening, the first wall and the end cap being welded to form a first connection portion, the thickness of the end cap being greater than the thickness of the second wall; and N1 electrode assemblies housed within the housing, the electrode assemblies including at least one positive electrode, at least one negative electrode, and at least one separator, the separator being used to separate the positive electrode and the negative electrode, the electrode assembly including a flat region, at least a portion of the positive electrode, the negative electrode, and the first wall being a flat region, the first wall being a flat region, the second ... At least a portion of the electrode sheet and at least a portion of the separator are stacked in the flat region along the second direction; a pressure relief mechanism is disposed on the second wall, the pressure relief mechanism is provided with a first groove, the pressure relief mechanism is configured to crack along at least a portion of the first groove when the battery cell is depressurized, the first groove includes a first groove segment extending along a straight trajectory, the length direction of the first groove segment is perpendicular to the second direction, the width of the bottom surface of the first groove segment in the second direction is A, the width of the second wall in the second direction is B, satisfying: A / B≥0.008, the first wall includes a first region and a second region arranged along the first direction, the first region is located on the side of the second region near the first connection portion, and the thickness of the first region is greater than the thickness of the second region.

[0096] By appropriately increasing the width ratio of the bottom surface of the first tank section to the second wall, the damage, cracking, and leakage caused by the expansion and deformation of the electrode assembly in the weak area corresponding to the first tank section can be reduced, thereby reducing the risk of fatigue cracking to a certain extent. By thickening the connection between the first wall and the end cap, the probability of cracking at the weld between the end cap and the casing when the burst pressure rises and the battery cell thermally runs away can be reduced, thereby improving the reliability of the battery cell.

[0097] The technical solutions described in the embodiments of this application are applicable to batteries and electrical devices that use batteries.

[0098] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical devices.

[0099] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0100] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 2000 provided in some embodiments of this application. A battery 1000 is disposed inside the vehicle 2000, and the battery 1000 may be located at the bottom, front, or rear of the vehicle 2000. The battery 1000 can be used to power the vehicle 2000; for example, the battery 1000 can serve as the operating power source for the vehicle 2000.

[0101] The vehicle 2000 may also include a controller and a motor. The controller is used to control the battery 1000 to power the motor, for example, for the power needs of the vehicle 2000 during startup, navigation and driving.

[0102] In some embodiments of this application, the battery 1000 can not only serve as the operating power source for the vehicle 2000, but also as the driving power source for the vehicle 2000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 2000.

[0103] Please refer to Figure 2 , Figure 2 This is an exploded view of a battery 1000 provided in some embodiments of this application. The battery 1000 includes a battery cell 100 and a housing 200 for housing the battery cell 100.

[0104] The housing 200 is a component that houses the battery cell 100, providing a placement space for the battery cell 100. The housing 200 can adopt various structures. In some embodiments, the housing 200 may include a first shell 201 and a second shell 202, which overlap each other to define a placement space for accommodating the battery cell 100. The first shell 201 and the second shell 202 can be various shapes, such as cuboids, cylinders, etc. The first shell 201 can be a hollow structure open on one side, and the second shell 202 can also be a hollow structure open on one side. When the open side of the second shell 202 overlaps the open side of the first shell 201, a housing 200 with a placement space is formed. Alternatively, the first shell 201 can be a hollow structure open on one side, and the second shell 202 can be a plate-like structure, overlapping the open side of the first shell 201 to form a housing 200 with a placement space. As an example, the battery cell 100 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell 100 of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0105] In battery 1000, there can be one or more battery cells 100. If there are multiple battery cells 100, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 100 are connected in both series and parallel. Alternatively, multiple battery cells 100 can be first connected in series, parallel, or in a mixed configuration to form a battery module, and then multiple battery modules can be connected in series, parallel, or in a mixed configuration to form a whole, which is then housed within the housing 200. Another option is that all battery cells 100 can be directly connected in series, parallel, or in a mixed configuration, and then the whole consisting of all battery cells 100 is housed within the housing 200.

[0106] Please refer to Figure 3 and Figure 4 , Figure 3 A schematic diagram of a battery cell 100 provided in some embodiments of this application; Figure 4 This is an exploded view of a battery cell 100 provided in some embodiments of this application. The battery cell 10 may include a housing 10 and an electrode assembly 20.

[0107] The housing 10 is used to house the electrode assembly 20 and electrolyte components. The housing 10 can be a steel housing, an aluminum housing, a plastic housing (such as a polypropylene housing), a composite metal housing (such as a copper-aluminum composite housing), or an aluminum-plastic film, etc. As an example, the housing 10 may include a housing 101 and an end cap 102.

[0108] The housing 101 can be a hollow structure with an opening at one end, or it can be a hollow structure with openings at both opposite ends. The housing 101 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc.

[0109] End cap 102 is a component that closes the opening of housing 101 to isolate the internal environment of battery cell 100 from the external environment. End cap 102 and housing 101 together define a space for accommodating electrode assembly 20, electrolyte, and other components. End cap 102 can be welded to housing 101 to close the opening of housing 101. The shape of end cap 102 can be adapted to the shape of housing 10; for example, if housing 101 is a cuboid structure, end cap 102 can be a rectangular plate structure adapted to housing 10. End cap 102 can also be made of various materials, such as copper, iron, aluminum, steel, or aluminum alloy.

[0110] In the battery cell 10, there can be one or two end caps 102. In an embodiment where the housing 101 is a hollow structure with openings at both ends, two end caps 102 can be provided, each closing one of the two openings of the housing 101, and the two end caps 102 together with the housing 101 define an accommodating space. In an embodiment where the housing 101 is a hollow structure with an opening at one end, one end cap 102 can be provided, closing one opening of the housing 101, and the one end cap 102 together with the housing 101 define an accommodating space.

[0111] 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 (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator is disposed between the positive and negative electrodes to prevent short circuits between them while allowing active ions to pass through.

[0112] In some embodiments, the positive electrode can be a positive electrode sheet 21, and the positive electrode sheet 22 can include a positive current collector and a positive active material region disposed on at least one surface of the positive current collector, the positive active material region having a positive active material.

[0113] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material region is disposed on either or both of the two opposite surfaces of the positive current collector.

[0114] In some embodiments, the negative electrode may be a negative electrode sheet 22, which may include a negative electrode current collector and a negative electrode active material region disposed on at least one surface of the negative electrode current collector.

[0115] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material region is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0116] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0117] In some embodiments, the electrode assembly 20 further includes an isolator disposed between the positive and negative electrodes.

[0118] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0119] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0120] In some embodiments, the battery cell 100 also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel-like, or solid.

[0121] In some embodiments, the electrode assembly 20 is a wound structure. The positive electrode, the negative electrode, and the separator are wound into a wound structure.

[0122] In some embodiments, the electrode assembly 20 has a stacked structure.

[0123] As an example, multiple positive electrode plates 21, multiple negative electrode plates 22 and multiple separators 25 can be provided respectively, and multiple positive electrode plates 21, multiple negative electrode plates 22 and multiple separators 25 can be stacked alternately.

[0124] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0125] As an example, the separator can be set continuously, either by folding or rolling between any adjacent positive or negative electrode plates.

[0126] In some embodiments, the electrode assembly 20 may be flat or polygonal in shape.

[0127] In some embodiments, the electrode assembly 20 is provided with tabs that can conduct current from the electrode assembly 20. The tabs include a positive tab and a negative tab.

[0128] The battery cell 100 may further include an electrical connection portion 30, which may be disposed on the housing 10. The electrical connection portion 30 is used for electrical connection with the tabs of the electrode assembly 20 to output electrical energy from the battery cell 10. The electrical connection portion 30 and the tabs may be directly connected, for example, by direct welding. The electrical connection portion 30 and the tabs may also be indirectly connected, for example, by indirect connection through a current collector. The current collector may be a metallic conductor, such as copper, iron, aluminum, steel, or aluminum alloy.

[0129] like Figure 3 and Figure 4 As shown, taking the shell 101 as a hollow structure with an opening at one end as an example, two electrical connection parts 30 can be provided on the end cover 102. The two electrical connection parts 30 are 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.

[0130] like Figure 3 and Figure 4As shown, the battery cell 100 also has a pressure relief mechanism 40, which is a component used to release the internal pressure of the battery cell 100. When the internal pressure of the battery cell 100 reaches a threshold, the pressure relief mechanism 40 discharges the discharge medium inside the battery cell 100 to achieve the purpose of pressure relief. The threshold design varies depending on the design requirements. The threshold may depend on one or more materials among the positive electrode 21, negative electrode 22, electrolyte and separator 25 in the battery cell 100.

[0131] The pressure relief mechanism 40 has a groove, which allows the battery cell 100 to crack along at least a portion of the groove when pressure is released, such as... Figure 3 As shown, the end cap 102 is equipped with a pressure relief mechanism 40; Figure 4 As shown, the pressure relief mechanism 40 is disposed on the housing 101. The pressure relief mechanism 40 can be integrally formed with the housing 101 or separately disposed from the housing 101. For example, the housing 101 includes a second wall 12, which is located on one side of the electrode assembly 20 in the first direction F1. The thickness direction of the second wall 12 is the first direction F1. The second wall 12 has a pressure relief hole 121, and the pressure relief mechanism 40 is installed at the pressure relief hole 121. A patch 60 is also provided on the outside of the pressure relief mechanism 40. By disposing of the pressure relief mechanism 40 on the housing 101, the structure of the end cap 102 can be simplified, and the distance between the pressure relief mechanism 40 and the main body of the electrode assembly 20 can be shortened. This shortens the path of the discharge medium to the pressure relief mechanism 40 during pressure relief, reduces the time it takes for the discharge medium to reach the pressure relief mechanism 40, improves the timeliness of pressure relief of the battery cell 100, and thus effectively improves the reliability of the battery cell 100.

[0132] Please refer to Figure 5 and Figure 6 , Figure 5 A schematic diagram of the electrode assembly 20 provided in some embodiments of this application; Figure 6 This is a schematic diagram of an electrode assembly 20 provided in other embodiments of this application. The electrode assembly 20 includes a positive electrode plate 21 and a negative electrode plate 22. The positive electrode plate 21 includes a positive electrode body and a positive electrode tab. The positive electrode tab extends from one end of the positive electrode body. Most of the area of ​​the positive electrode tab is not coated with positive active material, while most of the area of ​​the positive electrode body is coated with positive active material. The negative electrode plate 22 includes a negative electrode body and a negative electrode tab. The negative electrode tab extends from one end of the negative electrode body. Most of the area of ​​the negative electrode tab is not coated with negative active material, while most of the area of ​​the negative electrode body is coated with negative active material. The positive electrode body and the negative electrode body constitute the main body of the electrode assembly.

[0133] like Figure 5 As shown, the electrode assembly 20 includes a plurality of wound electrodes, and the electrode assembly 20 includes a flat region 23 and a corner region 24 connected to the end of the flat region 23.

[0134] Multiple electrode sheets arranged in a wound configuration, namely positive electrode sheet 21 and negative electrode sheet 22, are stacked and wound around a predetermined axis to form an electrode assembly 20. The straight region 23 refers to the portion of the electrode sheet extending along a plane after winding; the corner region 24 refers to the portion of the electrode sheet extending along a curved surface after winding, for example... Figure 5 As shown, the portion between the front and rear surfaces of the electrode assembly 20 is formed as a flat region 23, and the left and right ends of the flat region 23 are corner regions 24.

[0135] like Figure 6 As shown, electrode assembly 120 includes multiple electrode sheets arranged in layers, and electrode assembly 20 has a flat region 23.

[0136] Multiple electrodes arranged in a stacked manner, such as at least one positive electrode 21 and at least one negative electrode 22, are stacked to form an electrode assembly 20. The flat region 23 is formed by at least a portion of the positive electrode 21 and the negative electrode 22 stacked together, or it can be formed by at least a portion of the positive electrode 21 and the negative electrode 22 stacked together.

[0137] Please refer to Figures 7-15 , Figure 7 Cross-sectional views of some individual battery cells; Figures 8-10 Schematic diagrams of some pressure relief mechanisms; Figures 12-15 Here are some schematic diagrams of housings.

[0138] Combination Figures 3-15 As shown, the battery cell 100 according to an embodiment of this application includes: a housing 101 and an end cap 102. The housing 101 has an opening at at least one end along a first direction F1. The housing 101 includes two first walls 11 and a second wall 12. The two first walls 11 are arranged opposite to each other along a second direction F2. The second wall 12 is connected between the two first walls 11. The first direction F1 and the second direction F2 are perpendicular to each other.

[0139] The end cap 102 closes the opening, and the first wall 11 is welded to the end cap 102 to form a first connection 51, wherein the thickness of the end cap 102 is greater than the thickness of the second wall 12.

[0140] The housing 101 and the end cap 102 constitute the outer shell of the battery cell 100, that is, the outermost structural component of the battery cell 100. The housing contains the electrode assembly 20 and electrolyte, etc. The electrode assembly 20 contained therein can be one or more.

[0141] The shell 101 can be a hollow structure with an opening at one end, or it can be a hollow structure with openings at both opposite ends. The shell 101 can have various shapes, such as a prism, which can be a triangular prism, square prism, pentagonal prism, hexagonal prism, etc., and a square prism can be a cuboid, cube, etc. A first direction F1 is parallel to the orientation of the opening of the shell 101. In an embodiment where the shell 101 is prism-shaped, the first direction F1 can be parallel to the extension direction of the side edges of the shell 101. A second direction F2 is parallel to the thickness direction of the first wall 11. The shell 101 includes two first walls 11 and one second wall 12. The first walls 11 can be rectangular plate structures. The first direction F1 and the second direction F2 can be set at an acute angle, a right angle or an obtuse angle. The second wall 12 can also be a rectangular plate structure. The first wall 11 and the second wall 12 are connected by a corner wall. In some embodiments, the part of the second wall 12 outside the groove is of uniform thickness. In other embodiments, the second wall 12 can also be of non-uniform thickness. As an example, the first wall 11, the second wall 12 and the corner wall are integrally formed. The cross-section of the outer surface and / or the inner surface of the corner wall can be arc-shaped.

[0142] End cap 102 is a component that closes the opening of housing 101 to isolate the internal environment of battery cell 100 from the external environment. End cap 102 and housing 101 together define a receiving space for accommodating electrode assembly 20, electrolyte, and other components. The shape of end cap 102 can be adapted to the shape of housing; for example, housing 101 may be a cuboid structure, and end cap 102 may be a rectangular plate structure adapted to housing. End cap 102 can also be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, plastic, etc. The materials of end cap 102 and housing 101 can be the same or different.

[0143] In an embodiment where the housing 101 has an opening at one end, one end cap 102 may be provided. In an embodiment where the housing 101 has openings at both opposite ends, two end caps 102 may be provided. The two end caps 102 respectively close the two openings of the housing 101, and the two end caps 102 and the housing 101 together define a receiving space to accommodate the electrode assembly 20 and electrolyte, etc.

[0144] In an embodiment where the housing 101 has openings at opposite ends, two end caps 102 can be provided. The two end caps 102 respectively close the two openings of the housing 101. The two end caps 102 and the housing 101 together define a receiving space to accommodate the electrode assembly 20 and electrolyte, etc.

[0145] The end cap 102 can be welded to the housing 101. Welding the end cap 102 and the housing 101 together forms a connecting portion, which extends circumferentially along the opening of the housing 101. The end cap 102 and the housing 101 are connected and fixed through the connecting portion to achieve a seal between the end cap 102 and the housing 101. The connecting portion is the part with weld marks formed after welding the end cap 102 and the housing 101; it can be the part where the end cap 102 and the housing 101 are welded together.

[0146] The battery cell 100 also includes an electrode assembly 20, which is housed within the housing 101. Each electrode assembly 20 includes at least one positive electrode 21, at least one negative electrode 22, and at least one separator 25. The positive electrode 21, the negative electrode 22, and the separator 25 are stacked to form a flat region 23. At least a portion of the positive electrode 21, at least a portion of the negative electrode 22, and at least a portion of the separator 25 are stacked in the flat region 23 along the second direction F2.

[0147] There can be one or more electrode components 20. If there are multiple electrode components 20, they can be stacked. For example, multiple electrode components 20 can be stacked along the second direction F2.

[0148] The electrode assembly 20 can be a stacked type, that is, multiple electrodes of the electrode assembly 20 are stacked and arranged in layers. After the electrodes are stacked, a flat region 23 is formed. The electrode assembly 20 is in a stacked state. In the flat region 23, at least a portion of the positive electrode 21, the negative electrode 22 and the separator 25 are stacked along the second direction F2. Therefore, the expansion and deformation of the electrode assembly 20 is particularly obvious in the second direction F2.

[0149] The electrode assembly 20 can also be wound. The positive electrode 21 and negative electrode 22 of the electrode assembly 20 are stacked and wound with the separator 25, forming a flat region 23 and a corner region 24. The flat region 23 refers to the part of the electrode extending along the plane after winding. The electrode assembly 20 is stacked in the flat region 23. The corner region 24 refers to the part of the electrode extending along the arc surface after winding. The outer surface of the corner region 24 is at least partially arc surface. The flat region 23 connects the two corner regions 24. In the flat region 23, the positive electrode 21, the negative electrode 22 and the separator 25 are stacked along the second direction F2. For example, after winding, each layer of the positive electrode 21, each layer of the negative electrode 22 and each layer of the separator 25 can be penetrated by a straight line extending along the second direction F2. Thus, the expansion and deformation of the electrode assembly 20 is particularly obvious in the second direction F2.

[0150] The battery cell 100 also includes a pressure relief mechanism 40, which is disposed on the second wall 12. The pressure relief mechanism 40 is provided with a first groove 41. The pressure relief mechanism 40 is configured to crack along at least a portion of the first groove 41 when the battery cell 100 is depressurized. The first groove 41 includes a first groove segment 411 extending along a straight trajectory. The length direction of the first groove segment 411 is perpendicular to the second direction F2. The dimension of the bottom surface of the first groove segment 411 in the second direction F2 is A. The width of the second wall 12 along the second direction F2 is B, satisfying: A / B≥0.008. When the battery cell 100 is depressurized, it can crack along at least a portion of the first groove 41, meaning the first groove 411 of the pressure relief mechanism 40 is a weak point. The first groove 41 includes a first groove segment 411, which extends along a straight trajectory. The length direction of the first groove segment 411 is perpendicular to the second direction F2, i.e., the extension direction of the first groove segment 411 is perpendicular to the second direction F2. Figure 8 As shown, the first groove segment 411 extends along the third direction F3, and the width A of the bottom surface of the first groove segment 411 in the second direction F2 is the width of the bottom surface of the first groove segment 411.

[0151] The pressure relief mechanism 40 is disposed on the second wall 12, which can shorten the distance between the pressure relief mechanism 40 and the main body of the electrode assembly 20, thereby shortening the path of the discharge medium to the pressure relief mechanism 40 during pressure relief, shortening the time for the discharge medium to reach the pressure relief mechanism 40, and improving the timeliness of pressure relief of the battery cell 100. Since the thickness of the second wall 12 is less than the thickness of the end cap 102, the probability of the pressure relief mechanism 40 disposed on the second wall 12 being damaged and cracked when the electrode assembly 20 expands is increased.

[0152] If A / B is too small, the width A of the first groove segment 411 on a battery cell of a certain size will be too small. This weakens the ability of the first groove segment 411 to withstand deformation in the second direction F2. During long-term charging and discharging of the battery cell 100, the strain and strain amplitude generated at the first groove segment 411 will be greater, making the pressure relief mechanism 40 more prone to fatigue cracking and resulting in lower long-term reliability. Therefore, A / B can be limited to a range greater than 0.008, such as 0.008, 0.01, or 0.015.

[0153] The increase in the width of the first groove 411 will correspondingly increase the burst pressure of the pressure relief mechanism 40. Since the shell 101 and the end cap 102 are welded together, as the burst pressure increases, the probability of the weld joint being damaged when the battery cell 100 thermally runs away increases, causing the weld joint between the shell 101 and the end cap 102 to crack. Therefore, the first wall 11 is designed to be thickened.

[0154] Specifically, the first wall 11 includes a first region 111 and a second region 112 arranged along the first direction F1. The first region 111 is located on the side of the second region 112 that is close to the first connecting portion 51, and the thickness of the first region 111 is greater than the thickness of the second region 112.

[0155] The first wall 11 is welded to the end cap 102 to form a first connecting portion 51. The first connecting portion 51 can correspond one-to-one with the first wall 11. The first connecting portion 51 is the part with weld marks formed after the end cap 102 and the first wall 11 are welded together; it can be the part where the end cap 102 and the first wall 11 are fused together. A portion of the first connecting portion 51 is formed on the end cap 102, and another portion is formed on the first wall 11. The first wall 11 and the end cap 102 can form the first connecting portion 51 by seam welding or by through welding. The first connecting portion 51 can be a part of the connecting portion or the entire connecting portion.

[0156] The first wall 11 includes a first region 111 and a second region 112 arranged along the first direction F1. The first region 111 is located on the side of the second region 112 near the first connecting portion 51. The first region 111 is the area where the thickness of the first wall 11 is increased. The first region 111 is thicker than the second region 112.

[0157] The second region 112 has a first inner surface 1121 facing the interior space of the housing 101 and a first outer surface 1122 facing away from the interior space of the housing 101. The first region 111 may partially protrude from the first inner surface 1121 and / or the first outer surface 1122. As an example, in Figure 12 In the illustrated embodiment, a portion of the first region 111 protrudes from the first inner surface 1121, and the outer surface of the first region 111 is coplanar with the first outer surface 1122.

[0158] In other words, the first wall 11 of this application is thickened at the opening of the housing 101. By thickening the first region 111, the strength of the area near the first connection 51 is increased, the burst pressure at the weld between the housing 101 and the end cap 102 is increased, the risk of cracking at the weld between the housing 101 and the end cap 102 when the battery cell 100 thermally runs away after the burst pressure rises is reduced, and the reliability of the battery cell 100 is improved. In addition, compared with the overall thickening of the first wall 11, the significant reduction in the energy density of the battery cell 100 can be avoided.

[0159] According to the battery cell 100 of this application embodiment, by appropriately increasing the width ratio of the bottom surface of the first groove segment 411 on the second wall 12, the damage, cracking and leakage of the weak area corresponding to the first groove segment 411 due to the expansion and deformation of the electrode assembly 20 can be reduced, thereby reducing the risk of fatigue cracking to a certain extent. By thickening the connection between the first wall 11 and the end cap 102, the probability of cracking at the weld between the end cap 102 and the shell 101 when the burst pressure rises and the battery cell 100 undergoes thermal runaway is reduced, thereby improving the reliability of the battery cell.

[0160] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0161] Example 1

[0162] 1) Preparation of positive electrode sheet

[0163] A positive electrode slurry was prepared in N-methylpyrrolidone (NMP) by mixing positive electrode active material LiNi0.7Co0.1Mn0.1O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) with positive electrode active material LiNi0.7Co0.1Mn0.1O2, Super P, and PVDF in a mass ratio of 8:1:1. The positive electrode slurry was coated on the upper and lower surfaces of current collector aluminum foil and dried at 85°C. After cold pressing, the foil was trimmed, cut into sheets, and slit. Finally, it was dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet.

[0164] 2) Preparation of negative electrode sheet

[0165] Graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed evenly in deionized water to prepare a negative electrode slurry. The solid content of the negative electrode slurry is 30 wt%, and the mass ratio of graphite, silicon suboxide, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet.

[0166] 3) Preparation of electrolytes

[0167] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the thoroughly dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50) and mixed evenly to obtain a liquid electrolyte with a concentration of 1 mol / L.

[0168] 4) Isolation components

[0169] A 16μm polyethylene film was used as the separator.

[0170] 5) Lithium-ion battery manufacturing

[0171] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The electrode assembly is then wound up, tabs are welded on, and the electrode assembly is placed inside an aluminum casing. The electrolyte prepared above is injected into the dried casing, followed by encapsulation, settling, formation, shaping, and capacity testing to complete the preparation of the lithium-ion battery.

[0172] In the structure of the lithium-ion battery, the casing contains two electrode assemblies. Each electrode assembly has 64 layers (N2) of positive electrode sheets stacked in the flat region, for a total of 128 layers. The surface area of ​​the positive electrode body of each positive electrode sheet is S, where S = 20000 mm². 2 .

[0173] The outer casing includes a housing and an end cap. The first housing is a cuboid structure with an opening at one end in a first direction. The end cap closes the opening and is welded to the housing. The direction perpendicular to the large surface of the electrode assembly is the second direction. The wall of the housing in the second direction is the first wall, and the wall of the housing opposite to the end cap is the second wall. The second wall has a pressure relief hole.

[0174] The width dimension of the second wall in the second direction F2 is B. The first wall includes a first region and a second region. The first region is closer to the opening side of the shell than the second region, and the thickness of the first region is greater than the thickness of the second region. The thickness difference t between the first region and the second region is 0.1 mm.

[0175] The pressure relief mechanism is located at the pressure relief hole in the second wall. The pressure relief mechanism has a first groove and a second groove. The first groove includes a first groove segment and two second groove segments. The first groove segment and the second groove extend along a third direction. The first groove segment, the two second groove segments, and the second groove together define a predetermined pressure relief area. The width dimension of the first groove segment in the second direction F2 is A, and the minimum residual thickness of the first groove segment is D3, where D3 is 0.18 mm.

[0176] The method for measuring the fatigue cycles of a single battery cell is as follows:

[0177] 1) Prepare a special test fixture. Specifically, the fixture consists of three 10mm steel plates (first steel plate, second steel plate, and third steel plate). Each steel plate can completely cover the large surface of the battery cell. The first and third steel plates are located at both ends of the fixture and are fixed by bolts. The second steel plate is located between the first and third steel plates and is constrained by guide rails. The second steel plate can only move in a direction perpendicular to the plane of the steel plate.

[0178] 2) Support structures are placed between the largest outer surface of one side of the battery cell and the first steel plate, and between the largest outer surface of the other side of the battery cell and the second steel plate (i.e., support structures are placed on both sides of the battery cell in the direction of electrode assembly expansion). The support structures can be heat insulation pads or water cooling plates (consistent with the materials / structures between battery cells in the actual battery). The support structures can be compressed to provide expansion space for the battery cells during charge-discharge cycle aging. The largest outer surface of one side of the battery cell is attached to the support structure, the first steel plate is attached to the corresponding support structure, the second steel plate is attached to the corresponding support structure, and a pressure sensor is provided between the second steel plate and the third steel plate.

[0179] 3) Adjust the position of the second steel plate by adjusting the preload of the bolts, observe the pressure sensor, so that the battery cell is subjected to an initial compressive force of 2000N, and connect the two electrical connection parts of the battery cell to the dedicated battery charging and discharging equipment.

[0180] 4) Place the battery cells and fixtures in a constant temperature environment of 25±2℃ and start the test after the battery cells reach temperature equilibrium.

[0181] 5) The test procedure shall be performed in accordance with the "Standard Cycle Life" section 6.4 of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cutoff condition shall be changed to "the test shall be stopped until the groove of the pressure relief mechanism is damaged".

[0182] Specifically, test according to the following steps:

[0183] a) Discharge to 2.8V with a current of 1I1(A);

[0184] b) Let it rest for no less than 30 minutes;

[0185] c) Charge according to method 6.1.1.3 of GB / T 31484-2015 "Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles";

[0186] d) Let it rest for no less than 30 minutes;

[0187] e) Discharge to 2.8V with a current of 1I1(A);

[0188] f) Repeat steps b) to e) until the groove of the pressure relief mechanism breaks, then stop the test.

[0189] The test process involves continuously observing the pressure relief mechanism of the battery cell until the groove of the pressure relief mechanism breaks and cracks, resulting in leakage. The number of cycles is recorded as the cycle fatigue number of the battery cell. The more cycle fatigue numbers a battery cell has, the lower the probability of its pressure relief mechanism cracking prematurely during long-term use, and the longer its service life. Thus, the cycle fatigue number of the battery cell can be used to reasonably predict whether the pressure relief mechanism of the battery cell will crack prematurely during use.

[0190] The method for testing the thermal runaway of a single battery cell is as follows:

[0191] 1) Select the heating plate according to the size of the battery cell. The size of the heating plate should cover the largest surface of the battery cell as much as possible (coverage area ≥ 60%).

[0192] 2) Before testing, charge each battery cell to 100% SOC and ensure that the temperature of each battery cell is 25±5℃.

[0193] 3) Sensor Arrangement: a) Temperature Sensing Wire Arrangement: Apply a layer of Teflon to the center area of ​​each of the two large surfaces of the battery cell, arrange the temperature sensing wire on top of the Teflon, and then apply another layer of Teflon; b) Voltage Sampling Wire Arrangement: Apply a layer of Teflon to the positive terminal, negative terminal, and outer casing of the battery cell, arrange the voltage sampling wire on top of the Teflon, and then apply another layer of Teflon; c) Connect the temperature sensing wire and voltage sampling wire to the data acquisition instrument to collect and analyze data in real time. The data acquisition instrument's acquisition frequency is ≤0.1s.

[0194] 4) Assemble the fixture so that it completely covers the large surface of the battery cell. The clamping force is 3000N. Note: The arrangement order of the fixture, heating plate and battery cell is: fixture + heating plate + battery cell + fixture.

[0195] 5) Testing: Turn on the data acquisition device to collect temperature and voltage data, and then turn on the heating plate at 500W to heat the battery cells until the battery cells thermally run away.

[0196] 6) Thermal runaway judgment criteria: a) The triggering object generates a voltage drop, and the voltage drops to more than 25% of the initial voltage; b) The temperature of the detection point reaches the maximum operating temperature specified by the manufacturer; c) The temperature rise rate of the detection point dT / dt ≥ 1℃ / s, and lasts for more than 3s. When a) and c) or b) and c) occur, thermal runaway is judged to have occurred, and the moment of thermal runaway is determined.

[0197] 7) After the surface temperature of the battery cell has cooled to room temperature, observe whether cracks or bursts appear at the weld between the battery cell end cap and the casing.

[0198] The battery cell preparation methods of Examples 2-4 are the same as those of Example 1, except that the values ​​of A and / or B and the thickness difference t between the first and second regions are different. The battery cell preparation methods of Comparative Examples 1 and 2 are the same as those of Example 1, except that the values ​​of A and / or B and the first wall is not thickened. As shown in Table 1, the number of cycles (i.e., the number of fatigue cycles) and the thermal runaway of the battery cells 100 when leakage occurs in the pressure relief mechanism 40 of the batteries obtained in Examples 1-4 and Comparative Example 1 are characterized. The characterization results are shown in Table 1.

[0199] Table 1

[0200] serial number A(mm) B(mm) A / B t(mm) Technical effect Comparative Example 1 0.2 40 0.005 0 Fatigue count 902, end cap and shell welds normal. Example 1 0.3 37.5 0.008 0.1 Fatigue count 1104, end cap and shell welds normal. Example 2 0.55 55 0.01 0.2 Fatigue count 1305, end cap and shell welds are normal. Example 3 0.66 44 0.015 0.5 Fatigue count 1954, end cap and shell welds normal. Example 4 0.8 42 0.019 0.7 Fatigue count 2421, end cap and shell welds normal. Comparative Example 2 0.8 32 0.025 0 Fatigue count 2821, cracking at the weld between the end cap and the shell.

[0201] Based on the data from Examples 1-4 and Comparative Examples 1-2, it can be seen that when A / B is less than 0.008 mm, the fatigue cycle is too low and it is difficult to meet the life requirements. Increasing the value of A / B is beneficial for the battery cell 100 to have better cycle performance. However, as A / B increases, there is a risk of cracking if the first wall is not thickened. Therefore, the first region of the first wall can be thickened to improve the strength of the weld between the end cap and the shell and reduce the risk of cracking at the weld between the end cap and the shell during thermal runaway.

[0202] like Figures 12-14 As shown, in some embodiments, the thickness difference between the first region 111 and the second region 112 is t, which satisfies: 0.1mm≤t≤0.7mm.

[0203] like Figures 12-14 As shown, the first region 111 can be a structure with variable thickness, and the thickness of the first region 111 is the maximum thickness D1 of the first region 111. The second region 112 is a structure with uniform thickness, and the thickness of the second region 112 is D2. The difference t between the thickness of the first region 111 and the thickness of the second region 112 is the difference between the maximum thickness D1 of the first region 111 and the thickness D2 of the second region 112, that is, t = D1 - D2.

[0204] If the thickness of the first region 111 is too small relative to the second region 112, it will have little impact on the increase in strength of the area near the first connection. If the thickness of the first region 111 is too large relative to the second region 112, it will make it difficult to manufacture the first wall 11. Therefore, the thickness difference t between the first region 111 and the second region 112 is limited to the range of 0.1mm-0.7mm. t can be any one of 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, and 0.7mm or any range between the two.

[0205] This not only improves the strength of the area near the first connection 51 and increases the burst pressure at the weld between the housing 101 and the end cap 102, reducing the probability of cracking at the weld between the housing 101 and the end cap 102 during thermal runaway, but also facilitates the manufacturing and forming of the housing 101.

[0206] In some embodiments, 0.2mm ≤ t ≤ 0.5mm. t can be any one of 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, or 0.5mm, or a range between any two. This further improves the strength of the area near the first connection portion 51, increases the burst pressure at the weld between the housing 101 and the end cap 102, reduces the probability of cracking at the weld between the housing 101 and the end cap 102 during thermal runaway, and facilitates the manufacturing and forming of the housing 101.

[0207] In some embodiments, the maximum thickness of the first region 111 is D1, satisfying: 0.5mm ≤ D1 ≤ 1.5mm. The maximum thickness of the first region 111 can be any one of 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, and 1.5mm, or a range between any two.

[0208] This gives the first region 111 sufficient strength, thereby increasing the strength of the area near the first connection 51, increasing the burst pressure at the weld between the housing 101 and the end cap 102, and reducing the probability of cracking at the weld between the housing 101 and the end cap 102 during thermal runaway.

[0209] In some embodiments, the maximum thickness of the second region 112 is D2, satisfying: 0.4mm ≤ D2 ≤ 0.8mm. The maximum thickness of the second region 112 can be any one of 0.4mm, 0.5mm, 0.6mm, 0.7mm, and 0.8mm, or a range between any two. This satisfies both the strength requirements of the second region 112 and the volumetric energy density requirements of the battery cell 100.

[0210] like Figures 12-14 As shown, in some embodiments, the first region 111 includes a first portion 111a and a second portion 111b arranged along a first direction F1. The second portion 111b connects the first portion 111a and the second region 112. The thickness of the first portion 111a is the same as the thickness of the first region 111. The thickness of the second portion 111b decreases along the direction from the end cap 102 toward the electrode assembly 20.

[0211] like Figures 12-14As shown, the first part 111a has a uniform thickness, and the second part 111b has a variable thickness. The maximum thickness of the second part 111b is the same as the thickness of the first part 111a, which is equal to the maximum thickness of the first region 111. The minimum thickness of the second part 111b is the same as the thickness of the second region 112. Thus, the first region 111 has a partially uniform and partially variable thickness structure. This reduces the material used in the first region 111, lowers production costs, facilitates the manufacturing and forming of the first wall 11, and also strengthens the first wall 11, improving the structural strength of the first region 111. This increases the burst pressure at the weld between the shell 101 and the end cap 102, reduces the risk of cracking at the connection between the shell 101 and the end cap 102 during thermal runaway, and thus improves the reliability and service life of the battery cell 100.

[0212] The area of ​​the first region 111 near the first connection portion 51 is more prone to heat-affected zone formation, which is more susceptible to fatigue cracking. However, since the second part 111b connects the first part 111a and the second region 112, and the thickness of the first part 111a is greater than the thickness of the second part 111b, the thicker first part 111a in the first region 111 is closer to the first connection portion 51. This effectively weakens the impact of the heat-affected zone on the first region 111 and reduces the risk of cracking in the area of ​​the first wall 11 near the first connection portion 51.

[0213] like Figures 12-15 As shown, in some embodiments, the second region 112 has a first inner surface 1121 facing the interior space of the housing 101 and a first outer surface 1122 facing away from the interior of the housing 101. The first region 111 includes a first protrusion 1111 protruding from the first inner surface 1121, and / or the first region 111 includes a second protrusion 1112 protruding from the first outer surface 1122.

[0214] like Figure 13 As shown, the first region 111 includes a first protrusion 1111, which protrudes from the first inner surface 1121. The outer surface of the first region 111 is coplanar with the first outer surface 1122, thus making the outer surface of the housing 101 planar, which facilitates the arrangement of multiple battery cells 100 in a direction perpendicular to the first wall 11 (e.g., ...). Figure 12 The second direction F2) is shown in the stacked arrangement.

[0215] like Figure 17As shown, the first region 111 may also include only the second protrusion 1112, which protrudes from the first outer surface 1122. This allows the thickened area of ​​the first wall 11 to not occupy the internal space of the housing 101, making it easier for the electrode assembly 20 to be assembled into the housing 101. This reduces the probability of interference between the electrode assembly 20 and the first region 111 during assembly, and to a certain extent increases the capacity of the electrode assembly 20, thereby improving the energy density of the battery cell 100.

[0216] like Figure 15 As shown, the first region 111 includes a first protrusion 1111 and a second protrusion 1112. The first protrusion 1111 protrudes from the first inner surface 1121, and the second protrusion 1112 protrudes from the first outer surface 1122. Thus, the thickness of the first protrusion 1111 protruding from the first inner surface 1121 is t1, and the thickness of the second protrusion 1112 protruding from the first outer surface 1122 is t2. The sum of t1 and t2 is the thickness difference t between the first region 111 and the second region 112. Thus, by distributing the increased thickness on both the inner and outer sides, the thickness of each protrusion is reduced while increasing the thickness of the first region 111, which further facilitates the manufacturing and forming of the housing 101. At the same time, it helps to reduce the thickness of the inner protrusion, which facilitates the assembly of the electrode assembly 20 into the housing 101.

[0217] In some embodiments, the following condition is met: A / B ≤ 0.019.

[0218] If A / B is too large, the width A of the first groove 411 on a battery cell 100 of a certain size will be too large, and the burst pressure at the first groove 41 will be excessively increased, making it difficult for the pressure relief mechanism 40 to burst in time, which will also reduce the reliability of the battery cell 100.

[0219] Therefore, A / B ≤ 0.019, which means that A / B can be limited to the range of 0.008-0.019. A / B can be any one of the point values ​​of 0.008, 0.009, 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, and 0.019, or a range between any two.

[0220] This can reduce the risk of damage, cracking, and leakage in the weak area corresponding to the first groove 411 due to the expansion of the electrode assembly 20, thereby reducing the risk of fatigue cracking to a certain extent. At the same time, it can prevent the pressure relief mechanism 40 from failing to release the internal pressure of the battery cell 100 in time due to excessive burst pressure at the first groove 41, thus improving the reliability of the battery cell 100.

[0221] In some embodiments, the following conditions are met: 0.3mm≤A≤0.8mm, 20mm≤B≤80mm.

[0222] In the second direction F2, the width A of the first groove segment 411 can be any one of 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, or 0.8mm, or a range between any two. The width B of the second wall 12 is between 20mm and 80mm, for example, the width B of the second wall 12 can be any one of 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, or 80mm, or a range between any two.

[0223] To a certain extent, increasing the width of the bottom surface of the first groove 411 increases the deformation resistance of the first groove 411 and reduces the deformation of the pressure relief mechanism 40 at the first groove 411 when the electrode assembly 20 expands. This can, to a certain extent, avoid the risk of fatigue cracking of the pressure relief mechanism 40 during long-cycle charge and discharge use of the battery cell 100, reduce the probability of leakage caused by the pressure relief mechanism 40 being pulled and broken, and improve the reliability of the battery cell 100. At the same time, it avoids excessive burst pressure at the first groove 41, which would prevent the pressure relief mechanism 40 from being unable to release the internal pressure of the battery cell 100 in time, further improving the reliability of the battery cell 100.

[0224] like Figure 10 As shown, in some embodiments, the minimum residual thickness of the first groove segment 411 is D3, 0.1mm≤D3≤0.28mm.

[0225] The first groove segment 411 is a weak area of ​​the pressure relief mechanism 40. Along the thickness direction of the second wall 12 (second direction F2), the first groove segment 411 has a minimum residual thickness D3. The minimum residual thickness D3 of the first groove segment 411 is the minimum thickness dimension of the pressure relief mechanism 40 in the first groove segment 411 in the second direction F2.

[0226] The smaller the minimum residual thickness D3 of the first groove segment 411, the lower the strength at the first groove segment 411. During the long-term charge and discharge use of the battery cell 100, the strain and strain amplitude generated at the first groove segment 411 are greater, the pressure relief mechanism 40 is more prone to fatigue cracking, affecting the cycle number of the battery cell 100 and the lower the long-term reliability.

[0227] The larger the minimum residual thickness D3 of the first groove 411, the less stress concentration occurs at the first groove 411, and the more fatigue cracks occur during the long-term use of the battery cell 100. However, when D3 is too large, the burst pressure at the first groove 41 increases, making it difficult for the pressure relief mechanism 40 to burst and relieve pressure in time, which will also reduce the reliability of the battery.

[0228] Therefore, D3 is limited to the range of 0.1mm-0.28mm. D3 can be any point value or a range between any two of the following: 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, 0.25mm, 0.26mm, 0.27mm, and 0.28mm.

[0229] This increases the minimum residual thickness of the first groove 411 to a certain extent, increases the deformation resistance of the first groove 411, and reduces the deformation of the pressure relief mechanism 40 at the first groove 411 when the electrode assembly 20 expands. As a result, during long-cycle charge and discharge use of the battery cell 100, the risk of fatigue cracking of the pressure relief mechanism 40 can be avoided to a certain extent, the probability of leakage caused by the pressure relief mechanism 40 being pulled and broken is reduced, and the reliability of the battery cell 100 is improved. At the same time, it avoids the excessive burst pressure at the first groove 41, which would prevent the pressure relief mechanism 40 from releasing the internal pressure of the battery cell 100 in time, further improving the reliability of the battery cell 100.

[0230] like Figure 8 As shown, in some embodiments, a first groove 41 defines at least one predetermined pressure relief area 401, and a pressure relief mechanism 40 is provided with a second groove 42 configured to guide at least a portion of the predetermined pressure relief area 401 to flip over to open at least a portion of the predetermined pressure relief area 401.

[0231] The second groove 42 is a flipping groove provided on the pressure relief mechanism 40. When the pressure relief mechanism 40 splits along at least a portion of the first groove 41, the second groove 42 can guide at least a portion of the predetermined pressure relief area 401 to flip. In other words, the second groove 42 helps the predetermined pressure relief area 401 to flip, making it easier for the predetermined pressure relief area 401 to flip to the outside of the battery cell 100, thereby quickly opening the predetermined pressure relief area 401. The second groove 42 can guide the complete flipping of the predetermined pressure relief area 401, or it can guide only a portion of the predetermined pressure relief area 401 to flip.

[0232] During the depressurization process of the battery cell 100, the depressurization mechanism 40 can crack at least part of the first groove 41, but generally will not crack along the second groove 42. After the predetermined depressurization area 401 cracks in the first groove 41, it can be flipped with the second groove 42 as the flipping axis so that after the predetermined depressurization area 401 is flipped, the inside of the outer casing 10 and the outside of the outer casing 10 can be connected to each other for depressurization.

[0233] The second notch groove 42 can be formed in various ways, such as stamping or milling. The shape of the second notch groove 42 can be varied; for example, it can be a groove extending along an arc or a groove extending along a straight line. The cross-sectional shape of the second notch groove 42 can be varied, such as rectangular or trapezoidal.

[0234] By setting the second groove 42, the predetermined pressure relief area 401 can be guided to open, thereby improving the opening effect of the predetermined pressure relief area 401 of the pressure relief mechanism 40. This can further improve the pressure relief rate of the battery cell 100 when thermal runaway occurs, thereby reducing the risk of fire, explosion, connection failure and other problems caused by untimely pressure relief of the battery cell 100, which is conducive to improving the reliability of the battery cell 100.

[0235] In some embodiments, the residual thickness of the second groove 42 is greater than the residual thickness of the first groove 41.

[0236] The minimum residual thickness of the second groove 42 is the minimum thickness of the residual portion after the pressure relief mechanism 40 has the second groove 42 set. This residual portion can be the bottom wall of the second groove 42. The thickness of the bottom wall of the second groove 42 can be uniform or non-uniform. If the thickness of the bottom wall of the second groove 42 is non-uniform, the thickness of the thinnest part of the bottom wall of the second groove 42 is the minimum residual thickness of the second groove 42.

[0237] In this embodiment, the strength of the area where the pressure relief mechanism 40 is provided with the first groove 41 can be less than the strength of the area where the pressure relief mechanism 40 is provided with the second groove 42, so that the pressure relief mechanism 40 can preferentially crack along the first groove 41 to achieve rapid opening of the predetermined pressure relief area 401.

[0238] In some embodiments, the width of the second groove 42 perpendicular to the extension direction is greater than the width of the first groove 41 perpendicular to the extension direction.

[0239] For example, the second groove 42 extends along the third direction F3, and the first groove segment 411 of the first groove 41 extends along the third direction F3. In the second direction F2, the width of the bottom surface of the second groove 42 is greater than the width of the bottom surface of the first groove segment 411.

[0240] The second groove 42 can be manufactured in the same way as the first groove 41, for example, by integral stamping with a mold, which facilitates the formation of a second groove 42 with a larger residual thickness and a wider size.

[0241] like Figure 8As shown, in some embodiments, the first groove 41 further includes two second groove segments 412, which are arranged opposite to each other. The two ends of the first groove segment 411 are respectively connected to one end of the two second groove segments 412, and the other ends of the two second groove segments 412 are connected to the two ends of the second groove 42. The first groove segment 411, the two second groove segments 412, and the second groove 42 together define a predetermined pressure relief area 401.

[0242] As an example, in Figure 8 In the illustrated embodiment, the first groove segment 411 and the second groove 42 are arranged opposite to each other and are parallel to each other. The two ends of the first groove segment 411 are respectively connected to the two second groove segments 412, and the two ends of the second groove 42 are respectively connected to the two second groove segments 412. The two second groove segments 412, the first groove segment 411, and the second groove 42 form a closed annular structure. In the second direction F2, the outer edge of the orthographic projection of the annular structure forms the predetermined opening boundary of the predetermined pressure relief area 401, that is, the predetermined opening boundary is surrounded by the outer edges of the orthographic projections of the first groove 41 and the second groove 42 in the second direction F2.

[0243] The first groove segment 411 and the second groove 42 extend along a straight trajectory, such as... Figure 8 As shown, the first groove segment 411 and the second groove 42 extend along the third direction F3.

[0244] The second groove segment 412 can extend along a straight trajectory, such as along the second direction F2, thereby forming a square predetermined pressure relief area 401; the second groove segment 412 can also extend along an arc trajectory, thereby forming a racetrack-shaped predetermined pressure relief area 401.

[0245] In this embodiment, the first groove segment 411, the second groove 42, and the two second groove segments 412 are connected to form a ring structure, making the intersection of the first groove segment 411 and the second groove segment 412 weaker, making it easier to crack and open the predetermined pressure relief area 401 for pressure relief; at the same time, this structure is conducive to increasing the opening area of ​​the predetermined pressure relief area 401, increasing the pressure relief area of ​​the battery cell 100, and improving the pressure relief rate of the battery cell 100.

[0246] In some embodiments, the second groove 42 is arranged parallel to and opposite to the first groove segment 411, and the second groove segment 412 extends along a straight line and / or an arc trajectory.

[0247] In some examples, the length of the second groove 42 is the same as that of the first groove segment 411. The second groove segment 412 is a straight groove, perpendicular to the first groove segment 411, and extends along a straight trajectory, which can reduce the molding difficulty of the second groove segment 412.

[0248] In some examples, the length of the second groove 42 is the same as that of the first groove segment 411. The second groove segment 412 extends along an arc trajectory and is an arc-shaped groove. As a result, the pressure relief mechanism 40 can more easily crack along the second groove segment 412 when the battery cell 100 is depressurized, so that the predetermined pressure relief area 401 can be opened more quickly.

[0249] In some examples, the length of the second groove 42 is smaller than the length of the first groove segment 411. Each second groove segment includes two parts, one part extending along an arc and the other part extending along a straight line, thereby forming a ring structure. The shortened length of the second groove 42 and the increased length of the first groove 41 facilitate the faster opening of the predetermined pressure relief zone 401.

[0250] In some embodiments, the pressure relief mechanism 40 includes a main body 44 and a pressure relief part 43. The main body 44 is connected to the second wall. The thickness of the pressure relief part 43 is less than the thickness of the main body 44. A first groove 41 is provided on the pressure relief part 43. The thickness dimension of the pressure relief part 43 in the first direction F1 is D4, which satisfies: 0.15mm≤D4≤0.4mm.

[0251] like Figure 9 and Figure 10 As shown, the pressure relief mechanism 40 includes a main body 44 and a pressure relief part 43. The main body 44 is connected to the second wall 12. The thickness of the pressure relief part 43 is less than the thickness of the main body 44. The pressure relief part 43 can be a structure of equal thickness, where the thickness of the pressure relief part 43 is less than the thickness of the main body 44 and greater than the thickness at the first groove 41. Alternatively, the pressure relief part 43 can be a structure of variable thickness, where the maximum thickness of the pressure relief part 43 is less than the thickness of the main body 44 and the minimum thickness of the pressure relief part 43 is greater than the thickness at the first groove 41.

[0252] The shape of the pressure relief part 43 projected onto the plane of the second wall 12 can be a square with rounded corners, a circle, an oblong shape, or an ellipse. The pressure relief part 43 can also be formed into a ring. The edge of the pressure relief part 43 is arc-shaped, which can reduce the probability of stress concentration at the edge of the pressure relief part 43 and reduce the probability of leakage caused by damage to the edge of the pressure relief part 43.

[0253] The first groove 41 is provided in the pressure relief part 43, that is, a groove is provided on one side surface of the pressure relief part 43 to form the first groove 41. The thickness of the pressure relief part 43 in the first direction F1 is D4. If D4 is too large, stress concentration is likely to occur at the first groove section 411, and the pressure relief mechanism 40 is prone to fatigue cracking. The smaller D4 is, the more the pressure relief part 43 can absorb some deformation, thereby reducing the stress concentration at the first groove section 411 and increasing the number of fatigue cracks in the battery cell 100 during long-term use. However, if D4 is too small, the pressure relief part 43 absorbs too much deformation, the stress concentration at the first groove section 411 is too small, the burst pressure at the first groove 41 increases, and the battery cell 100 is prone to burst at the end cap weld when thermal runaway, which will reduce reliability.

[0254] Therefore, D4 ​​is limited to the range of 0.15mm-0.4mm. D4 can be any point value or a range between any two of the following: 0.15mm, 0.19mm, 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, 0.25mm, 0.26mm, 0.27mm, 0.28mm, 0.29mm, 0.3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, and 0.4mm.

[0255] Therefore, the stress concentration at the first groove section 411 is reduced, which to some extent avoids the risk of fatigue cracking of the pressure relief mechanism 40. At the same time, it can prevent the burst pressure of the pressure relief mechanism 40 from being too large. When the battery cell 100 experiences thermal runaway, it reduces the probability that the pressure relief mechanism 40 will not burst in time and will easily burst in other locations, thereby improving the reliability of the battery cell 100.

[0256] In some preferred examples, 0.2mm ≤ D4 ≤ 0.3mm.

[0257] That is, D4 can be any point value among 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, 0.25mm, 0.26mm, 0.27mm, 0.28mm, 0.29mm, and 0.3mm, or a range between any two.

[0258] This further reduces the stress concentration at the first groove section 411, which to some extent avoids the risk of fatigue cracking of the pressure relief mechanism 40. At the same time, it can prevent the burst pressure of the pressure relief mechanism 40 from being too large. When the battery cell 100 experiences thermal runaway, it reduces the probability that the pressure relief mechanism 40 will not burst in time and will easily burst in other locations, thereby improving the reliability of the battery cell 100.

[0259] like Figure 9 and Figure 10 As shown, in some embodiments, the pressure relief mechanism 40 is provided with a pressure relief part 43, and a first groove 41 is provided on the pressure relief part 43. The thickness dimension of the pressure relief part 43 in the first direction F1 is D4, which satisfies: 0.55≤D3 / D4≤0.85.

[0260] The first groove 41 is provided in the pressure relief part 43, that is, a groove is provided on one side surface of the pressure relief part 43 to form the first groove 41. The thickness dimension of the pressure relief part 43 in the first direction F1 is D4. When the minimum residual thickness D3 of the first groove segment 411 of the first groove 41 is fixed, if D3 / D4 is too small and D4 is too large, the thickness difference between the first groove segment 411 and the pressure relief part 43 of the pressure relief mechanism 40 is large, and stress concentration is easy to occur at the first groove segment 411, and the pressure relief mechanism 40 is prone to fatigue cracking.

[0261] The larger D3 / D4 is and the smaller D4 is, the more the pressure relief part 43 can absorb some of the deformation when the electrode assembly 20 expands, thereby reducing the stress concentration at the first groove section 411 and increasing the number of fatigue cracks in the battery cell 100 during long-term use. However, if D3 / D4 is too large and D4 is too small, the pressure relief part 43 will absorb too much deformation, the stress concentration at the first groove section 411 will be too small, the burst pressure at the first groove 41 will increase, and the battery cell 100 will be prone to bursting at the end cap weld when thermal runaway occurs, which will also reduce reliability.

[0262] Therefore, D3 / D4 is limited to the range of 0.55-0.85. D3 / D4 can be any one of the following values ​​or a range between any two: 0.55, 0.56, 0.57, 0.58, 0.59, 0.6, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.85, 0.81, 0.82, 0.83, 0.84, and 0.85.

[0263] Therefore, reducing the stress concentration at the first groove section 411 can, to some extent, avoid the risk of fatigue cracking of the pressure relief mechanism 40. At the same time, it can prevent the burst pressure of the pressure relief mechanism 40 from being too large. When the battery cell 100 experiences thermal runaway, it reduces the probability that the pressure relief mechanism 40 will not burst in time and will easily burst in other locations, thus improving the reliability of the battery cell 100. In addition, limiting D3 / D4 to the above range is also beneficial to the manufacturing and forming of the groove on the pressure relief section 43, which facilitates the manufacturing of the pressure relief mechanism 40.

[0264] like Figure 11As shown, in some embodiments, the second wall 12 has a pressure relief hole 111, and a pressure relief mechanism 40 is installed in the pressure relief hole 111. The area of ​​the pressure relief hole 111 projected along the first direction F1 is W, which is 400 mm². 2 ≤W≤1400mm 2 .

[0265] like Figures 8-11 As shown, the pressure relief mechanism 40 and the outer casing 10 are two separate components, which are molded separately and then installed together. Specifically, the pressure relief mechanism 40 can be a component such as an explosion-proof plate, an explosion-proof valve, or a safety valve. The pressure relief mechanism 40 can be installed on the second wall 12 by means of bonding, welding, etc. The second wall 12 is provided with a pressure relief hole 111. The pressure relief mechanism 40 is installed in the pressure relief hole 111. When the internal pressure of the battery cell 100 reaches the threshold, the pressure relief mechanism 40 opens at least part of the pressure relief hole 111, and the discharge medium inside the battery cell 100 is discharged through the pressure relief hole 111 to release the pressure inside the battery cell 100.

[0266] like Figure 8 and Figure 11 As shown, taking the pressure relief mechanism 40 as an example, the explosion-proof sheet is a sheet with at least a portion of its strength less than the strength of the second wall 12. The explosion-proof sheet covers the pressure relief hole 111 and is welded to the second wall 12. When the internal pressure of the battery cell 100 reaches a threshold, the explosion-proof sheet is at least partially destroyed, thereby opening at least a portion of the pressure relief hole 111 to release the internal pressure of the battery cell 100. The pressure relief mechanism 40 is a component independent of the outer casing 10. The pressure relief mechanism 40 and the outer casing 10 can be manufactured and reassembled separately, which is easy to produce and highly efficient.

[0267] The larger the area of ​​the pressure relief hole 111, the thinner the second wall 12, and the more easily the first groove 41 will fatigue and crack during the charging and discharging process of the battery cell 100. The smaller the area of ​​the pressure relief hole 111, the smaller the bursting area of ​​the pressure relief mechanism 40, which affects the pressure relief effect and is also prone to bursting in other positions, affecting the reliability of the battery cell 100.

[0268] Therefore, the area W of the pressure relief hole 111 projected along the first direction F1 is limited to 400 mm. 2 -1400mm 2 Between, that is, W can be 400mm 2 500mm 2 600mm 2 700mm 2 800mm 2 900mm 2 1000mm 2 1100mm 2 1200mm 21300mm 2 1400mm 2 The value of any one of the points or the range between any two.

[0269] Therefore, the risk of fatigue cracking of the pressure relief mechanism 40 can be avoided to a certain extent. At the same time, when the battery cell 100 experiences thermal runaway, the probability that the pressure relief mechanism 40 will not be able to burst in time and will easily burst in other locations is reduced, thereby improving the reliability of the battery cell 100.

[0270] Among them, with Figure 11 Taking the runway-shaped pressure relief vent 111 as an example, the dimension of the pressure relief vent 111 in the second direction F2 is N, and the dimension of the pressure relief vent 111 in the third direction is L. W = N*L + (ΠN) 2 ) / 4.

[0271] In some examples, 600mm 2 ≤W≤1200mm 2 That is, the area W of the pressure relief hole 111 can be 600mm². 2 700mm 2 800mm 2 900mm 2 1000mm 2 1100mm 2 1200mm 2 The value of any one of the points or the range between any two.

[0272] This further avoids the risk of fatigue cracking in the pressure relief mechanism 40. At the same time, when thermal runaway occurs in the battery cell 100, the pressure relief mechanism 40 can promptly burst to release the internal air pressure of the battery cell 100, thereby improving the reliability of the battery cell 100.

[0273] like Figure 11 As shown, in some embodiments, the second wall 12 has a pressure relief hole 111, and the pressure relief mechanism 40 is installed in the pressure relief hole 111. The pressure relief hole 111 has a size of N in the second direction F2 and a size of L in the third direction. The third direction is perpendicular to the second direction F2 and the first direction F1, satisfying: 1.5≤L / N≤5.

[0274] The second wall 12 is provided with a pressure relief hole 111. A pressure relief mechanism 40 is installed in the pressure relief hole 111. When the internal pressure of the battery cell 100 reaches the threshold, the pressure relief mechanism 40 opens at least part of the pressure relief hole 111, and the discharge medium inside the battery cell 100 is discharged through the pressure relief hole 111 to release the pressure inside the battery cell 100.

[0275] By controlling the area of ​​the pressure relief hole 111 within a certain range, the pressure relief mechanism 40 has a sufficient burst area to ensure the pressure relief effect. The area of ​​the pressure relief hole 111 is related to the dimension N in the first direction and the dimension L in the third direction. For a pressure relief hole 111 with a certain area, when L / N is too large, the pressure relief hole 111 is relatively slender, the rigidity of the second wall 12 is low, and the pressure relief mechanism 40 is more prone to fatigue cracking, resulting in low reliability. When L / N is too small, the pressure relief hole 111 is too close to the edge of the second wall 12, making manufacturing difficult and the manufacturing yield difficult to meet the requirements.

[0276] Therefore, L / N is limited to between 1.5 and 5. L / N can be any one of the point values ​​of 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5, or any range between two values.

[0277] Therefore, the risk of fatigue cracking of the pressure relief mechanism 40 can be avoided to a certain extent, while reducing manufacturing difficulty and improving manufacturing yield.

[0278] In some preferred examples, 2 ≤ L / N ≤ 4, where L / N can be any one of the following point values ​​or a range between any two: 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.

[0279] This can further avoid the risk of fatigue cracking in the pressure relief mechanism 40, while reducing manufacturing difficulty and improving manufacturing yield.

[0280] like Figure 5 and Figure 6 As shown, in some embodiments, the battery cell 100 includes N1 electrode assemblies 20, and each electrode assembly 20 has N2 layers of positive electrode sheets 21 stacked in the flat region 23. The flat region 23 has an outer surface perpendicular to the second direction F2, and the area of ​​the outer surface is S, where N1≥1, N2≥1, N1*N2≤500, and S≤80000mm². 2 .

[0281] Regardless of whether the electrode assembly 20 is wound or stacked, the more layers of positive electrode sheets 21 stacked within the flat region 23 of the electrode assembly 20, the more corresponding negative electrode sheets 22 are required, resulting in greater expansion and deformation of the electrode assembly 20. Therefore, the expansion of the electrode assembly 20 is positively correlated with the number of layers of positive electrode sheets 21. The larger the area of ​​the flat region 23 on its outer surface perpendicular to the second direction F2, the greater the expansion and deformation of the electrode assembly 20, and the higher the risk of cracking and damage to the groove of the pressure relief mechanism 40 and the weld between the housing 101 and the end cap 102. Therefore, the total number of positive electrode sheet layers N1*N2 stacked in the flat region 23 is limited to 500 or less, and the area S of the flat region 23 on its outer surface perpendicular to the second direction F2 is limited to 80000 mm². 2 Or less than 80000mm 2 Within this range, the expansion of the electrode assembly 20 can be reduced during the charging and discharging process of the battery cell 100, thereby reducing the probability of cracking and damage to the groove of the pressure relief mechanism 40 and the weld between the housing 101 and the end cap 102, and improving the reliability of the battery cell 100.

[0282] The method for measuring N2 here is as follows: After disassembling the battery cell 100, the electrode assembly 20 is removed. Without damaging the integrity of the electrode assembly 20, the number of layers of the positive electrode plate 21 in the straight region 23 in the second direction F2 is measured, such as... Figures 5-7 As shown, S is measured by multiplying the height dimension M2 of the outer plane of the flat region 23 in the first direction F1 and the length dimension M1 in the third direction F3 by the height dimension M2 of the outer plane in the first direction F1 perpendicular to the second direction F2.

[0283] like Figure 6 As shown, in some embodiments, the electrode assembly 20 is a stacked structure, and the electrode assembly 20 includes a plurality of positive electrode plates 21 and a plurality of negative electrode plates 22, which are stacked along the second direction F2.

[0284] As an example, the positive electrode 21 and the negative electrode 22 in the electrode assembly 20 are arranged alternately along the second direction F2, and an isolation member 25 is provided between the positive electrode 21 and the negative electrode 22.

[0285] In this embodiment, the electrode assembly 20 is a stacked electrode assembly 20, which has a more compact structure and stronger resistance to compression.

[0286] In some embodiments, the number of negative electrode plates 22 is greater than the number of positive electrode plates 21, and a positive electrode plate 21 is disposed between two adjacent negative electrode plates 22.

[0287] As an example, the negative electrode 22 has one more electrode than the positive electrode 21.

[0288] In some embodiments, each negative electrode 22 is provided with a negative electrode tab; and / or, each positive electrode 21 is provided with a positive electrode tab.

[0289] In some embodiments, along the third direction F3, the size of the first region 111 is larger than the size of the positive electrode 21 and / or the size of the negative electrode 22, and the first direction F1, the second direction F2 and the third direction F3 are perpendicular to each other.

[0290] If along the third direction F3, the size of the first region 111 is larger than the size of the positive electrode 21, and the first region 111 extends beyond at least one end of the positive electrode 21 along the third direction F3; if along the third direction F3, the size of the first region 111 is larger than the size of the negative electrode 22, and the first region 111 extends beyond at least one end of the negative electrode 22 along the third direction F3.

[0291] In this embodiment, along the third direction F3, the size of the first region 111 is larger than the size of the positive electrode 21 and / or the size of the negative electrode 22, making the size of the first region 111 larger along the third direction F3. This strengthens the first wall 11 along the third direction F3, increases the strength of the area near the first connection 51, and increases the burst pressure at the weld between the housing 101 and the end cap 102. To a certain extent, this avoids the risk of cracking at the weld between the housing 101 and the end cap 102 when the battery cell 100 experiences thermal runaway, thus improving the reliability of the battery cell 100.

[0292] like Figure 5 As shown, in some embodiments, the electrode assembly 20 is a wound structure, and the electrode assembly 20 also has a corner region 24. The straight region 23 is provided with a corner region 24 at least at one end along the third direction F3. At least part of the outer surface of the corner region 24 is an arc surface. The first direction F1, the second direction F2 and the third direction F3 are not coplanar and intersect each other.

[0293] The straight section 23 may have a corner section 24 at only one end along the third direction F3, or it may have corner sections 24 at both opposite ends along the third direction F3. The first direction F1, the second direction F2, and the third direction F3 are not coplanar, and any two of the first direction F1, the second direction F2, and the third direction F3 may be set at acute angles, right angles, or obtuse angles. The outer surface of the corner section 24 may be entirely a curved surface, or only a portion of it may be a curved surface.

[0294] As an example, the positive electrode 21, the separator 25, and the negative electrode 22 are stacked and wound to form a wound structure. The first direction F1, the second direction F2, and the third direction F3 are perpendicular to each other, and the straight region 23 has corner regions 24 at both ends along the third direction F3. The portions of the positive electrode 21, the negative electrode 22, and the separator 25 located in the corner regions 24 are in a bent state. The portion of the positive electrode 21 located in the corner region 24 can be at least partially arc-shaped, the portion of the negative electrode 22 located in the corner region 24 can be at least partially arc-shaped, and the portion of the separator 25 located in the corner region 24 can be at least partially arc-shaped. Along the winding direction of the electrode assembly 20, the outermost ring of the electrode assembly 20 is the separator 25, wherein the outer surface of the straight region 23 and the outer surface of the corner region 24 are part of the outermost surface of the electrode assembly 20.

[0295] The outer surface of the straight area 23 is a plane, and the outer surface of the corner area 24 is an arc surface, with the axis of the arc surface extending along the first direction F1. Along the second direction F2, the surfaces on both sides of the straight area 23 are planes; along the third direction F3, the surface of one corner area 24 facing away from the other corner area 24 is an arc surface, and the surface of the other corner area 24 facing away from the first corner area 24 is another arc surface.

[0296] For the wound electrode assembly 20, the flat region 23 expands more in the second direction F2. Since the first region 111 reinforces the first wall 11, it can increase the strength of the area near the first connection 51, increase the burst pressure at the weld between the housing 101 and the end cap 102, and to a certain extent avoid the risk of cracking at the weld between the housing 101 and the end cap 102 in the event of thermal runaway of the battery cell 100, thereby improving the reliability of the battery cell.

[0297] like Figures 16-23 As shown, in some embodiments, the pressure relief portion 43 is further provided with a buffer portion 45 that arches along the first direction F1 toward the side closer to and / or away from the electrode assembly 22.

[0298] Combination Figures 16-23 As shown, the buffer portion 45 may arch towards the side closer to the electrode assembly 20, or it may arch towards the side farther from the electrode assembly 20. Alternatively, a portion of the buffer portion 45 may arch towards the side closer to the electrode assembly 20, while another portion arches towards the side farther from the electrode assembly 20. Along the second direction F2, the length of the buffer surface of the buffer portion 45 is greater than the straight-line distance between the two ends of the buffer portion 45 in the second direction F2. The buffer portion 45 can store a certain deformation space to absorb the tensile deformation in the second direction F2, thereby giving the buffer portion 45 buffering performance.

[0299] During the long-term use of the battery cell 100, when the electrode assembly 20 expands, the expansion force of the electrode assembly 20 can pull the buffer part 45, causing the buffer part 45 to deform to a certain extent, releasing the stored deformation space, and expanding the buffer part 45 to a certain extent. Thus, the buffer part 45 absorbs at least part of the expansion force of the electrode assembly 20, thereby reducing the expansion force acting on the groove, which can reduce the probability of the groove being pulled and broken, leading to leakage. This can also appropriately reduce the size of the widened first groove section 411, or reduce the thickness difference between the first and second regions, making the casing easier to manufacture.

[0300] The buffer section 45 is provided on the pressure relief mechanism 40. On the one hand, it makes full use of the space on the pressure relief mechanism 40, which is conducive to increasing the size of the buffer section 45 and improving its buffering performance. On the other hand, it facilitates the manufacturing and forming of the buffer section 45. The buffer section 45 can be manufactured and formed by stamping. Compared with setting the buffer section 45 on the outside of the pressure relief mechanism 40, the pressure relief mechanism 40 has more space inside to facilitate the forming of the buffer section 45. In some examples, the pressure relief mechanism 40 and the second wall 12 are set separately, and the thickness of the second wall 12 is greater than the thickness of the pressure relief mechanism 40. By forming the buffer section 45 on a component that is thinner than the wall section 11, it is easier to manufacture and form the buffer section 45. At the same time, the buffer section 45 is easier to deform, thereby improving its buffering performance. In addition, the buffer section 45 is formed on the pressure relief mechanism 40 and then installed on the second wall 12, which can also reduce the impact of the buffer section 45 on the wall and ensure the strength and reliability of the wall to a certain extent.

[0301] like Figure 17 and Figure 18 As shown, in some embodiments, along the thickness direction of the second wall 12, the second wall 12 has a second outer surface 1102 and a second inner surface 1101, the second inner surface 1101 being closer to the electrode assembly 20 relative to the second outer surface 1102, and the buffer portion 45 includes a first buffer portion 45a, the first buffer portion 45a arching toward the side closer to the electrode assembly 20 and not protruding from the second inner surface 1101.

[0302] like Figure 17 As shown, the first buffer portion 45a is located between the second inner surface 1101 and the second outer surface 1102. Thus, the buffer portion 45a will not occupy the space outside the battery cell 100, which is convenient for the placement of the battery cell 100. The buffer portion 45a will also not occupy the space inside the outer casing 10, which avoids interference with the electrode assembly 20 or occupying the space of the electrode assembly 20, and avoids the excessive reduction of the energy density of the battery cell 100.

[0303] like Figure 18As shown, in some embodiments, in the thickness direction of the second wall 12, the first buffer portion 45a has an inner buffer surface 4501 and an outer buffer surface 4502, the inner buffer surface 4501 being closer to the electrode assembly 20 relative to the outer buffer surface 4502, and in the thickness direction of the second wall 12, the farthest portion of the inner buffer surface 4501 relative to the outer buffer surface 4502 being flush with the second inner surface 1101.

[0304] like Figure 18 , Figures 22-23 As shown, the buffer portion 45 has an inner buffer surface 4501, as Figure 23 As shown, the inner buffer surface 4501 is an arc surface. In the first direction F1, the highest point of the arc surface is at the same height as the second inner surface 1101, as shown. Figure 21 and Figure 22 As shown, the inner buffer surface 4501 is a bent plane. In the first direction F1, the highest point of the plane is at the same height as the second inner surface 1101. This maximizes the arching of the buffer part 45, improves the utilization rate in the thickness direction of the second wall 12, enhances the buffering performance of the buffer part 45, and avoids the buffer part 45 occupying the space inside and outside the outer casing 10. The buffer part 45 is less likely to interfere with the electrode assembly 20, and it is less likely to occupy the space of the electrode assembly 20. At the same time, it will not affect the placement of the battery cell 100, thus avoiding the excessive reduction of the energy density of the battery cell 100 and the battery 1000.

[0305] like Figures 16-19 As shown, an insulating member 70 is provided inside the housing 10. The insulating member 70 is located between the second wall 12 and the electrode assembly 20. The insulating member 70 defines a clearance groove 71 that opens toward the second wall 12. The clearance groove 71 corresponds to the position of the buffer part 45.

[0306] The insulating component 70 is located between the second wall 12 and the electrode assembly 20. The insulating component 70 can block the direct contact between the electrode assembly 20 and the second wall 12, reducing the risk of electrochemical corrosion. At the same time, the insulating component 70 also supports the electrode assembly 20, preventing the bottom of the electrode assembly 20 from collapsing or deforming. The insulating component 70 may be provided with through holes, which help to vent air during the installation of the insulating component 70 and can also promote the diffusion of electrolyte after installation, achieving a wetting effect. In addition, the insulating component 70 can reduce the impact force when the electrode assembly 20 is inserted into the casing, reduce the risk of the electrode assembly 20 being damaged by impact, and improve the service life and reliability of the battery cell 100.

[0307] The insulating component 70 is provided with a relief groove 71, which allows the electrolyte to flow more smoothly, improves the wetting efficiency of the electrolyte on the electrode assembly 20, and thus improves the performance of the battery cell 100.

[0308] The clearance groove 71 is opposite to the buffer part 45 and is open towards the buffer part 45. Thus, a part of the buffer part 45 can extend into the clearance groove 71, or the buffer part 45 can be located outside the clearance groove 71. During the long-term use of the battery cell 100, when the buffer part 45 deforms, a part of it can extend into the clearance groove 71. The clearance groove 71 can provide a certain space for the deformation of the buffer part 45, which is beneficial to the deformation of the buffer part 45.

[0309] like Figure 19 As shown, in some embodiments, along the thickness direction of the second wall 12, the second wall 12 has a second outer surface 1102 and a second inner surface 1101. The second inner surface 1101 is closer to the electrode assembly 20 relative to the second outer surface 1102. The buffer portion 45 includes a first buffer portion 45a, which arches towards the side closer to the electrode assembly 20. At least a portion of the first buffer portion 45a protrudes from at least a portion of the second inner surface 1101 and extends into the relief groove 71.

[0310] like Figure 19 As shown, the insulating member 70 is located between the second inner surface 1101 and the electrode assembly 20, and a portion of the buffer portion 45 is located inside the housing 10. This allows full utilization of the space of the insulating member 70, maximizes the arching of the buffer portion 45, improves the utilization rate in the thickness direction of the second wall 12, and enhances the buffering performance of the buffer portion 45. Under the action of the insulating member 70, the buffer portion 45 will not interfere with the electrode assembly 20, thereby improving the reliability of the battery cell 100.

[0311] like Figure 22 As shown, in some embodiments, along the thickness direction of the second wall 12, the second wall 12 has a second outer surface 1102 and a second inner surface 1101, the second inner surface 1101 being closer to the electrode assembly 20 relative to the second outer surface 1102, and the buffer portion 45 including a second buffer portion 45b, the second buffer portion 45b arching toward the side away from the electrode assembly 20 and not protruding from the second outer surface 1102.

[0312] The thickness direction of the second wall 12 is the first direction F1. In the first direction F1, the second wall 12 has a second outer surface 1102 and a second inner surface 1101. The second buffer portion 45b arches outward from the side away from the electrode assembly 20. The second buffer portion 45b is located on the side of the second outer surface 1102 closer to the second inner surface 1101. The second outer surface 1102 of the second wall 12 is part of the outer surface of the entire housing 10. The buffer portion 45b is located inside the second outer surface 1102, so that the second buffer portion 45b does not protrude from the entire housing. The outer surface of the second outer surface 1102 avoids both occupying space outside the battery cell 100 and affecting the energy density of the battery 1000, and also avoids the second buffer part 45b affecting the placement of the battery cell 100. For example, the second wall 12 can be the bottom wall of the battery cell 100, and the battery cell 100 can be supported in the housing 100 by the second wall 12. The second buffer part 45b is located inside the second outer surface 1102, which can avoid the problem that the second wall 12 cannot fit in close to the inside of the housing 100, thus affecting the placement stability of the battery cell 100.

[0313] like Figure 22 As shown, in some embodiments, the buffer portion 45 includes a first buffer portion 45a and a second buffer portion 45b. The first buffer portion 45a arches toward the side closer to the electrode assembly 20, and the second buffer portion 45b arches toward the side away from the electrode assembly 20. At least a portion of the first buffer portion 45a is located on one side of the second buffer portion 45b in the second direction F2.

[0314] like Figure 22 As shown, the buffer section 45 is arranged symmetrically with respect to the pressure relief section 43. The second buffer section 45b is located outside the first buffer section 45a. The sidewall of the second buffer section 45b is connected to the sidewall of the first buffer section 45a and has the same inclination angle. The first buffer section 45a arches to one side in the first direction F1, and the second buffer section 45b arches to the other side in the first direction F1. In the first direction F1, the second wall 12 has a second inner surface 1101 and a second outer surface 1102. Normally, the pressure relief section 43 of the pressure relief mechanism 40 is located between the second inner surface 1101 and the second outer surface 1102. There is a certain space between the pressure relief section 43 and the second inner surface 1101, and there is a certain space between the pressure relief section 43 and the second outer surface 1102. By setting two buffer sections, these two spaces can be fully utilized, increasing the deformability of the buffer section 45, improving the buffering performance of the buffer section 45, reducing the probability of the groove being pulled and broken, leading to leakage, and improving the service life and reliability of the battery cell 100.

[0315] Furthermore, in the second direction F2, a portion of the first buffer 45a is located on one side of the second buffer 45b. The expansion deformation of the electrode assembly 20 is particularly noticeable in the second direction F2. The two buffers 45 are arranged in the second direction F2, which can absorb the tensile deformation in the second direction F2 as much as possible, thereby reducing the expansion force acting on the groove, and thus reducing the probability of the groove being torn and damaged, leading to leakage.

[0316] In some embodiments, the second buffer portion 45b extends along a third direction, and the first buffer portion 45a is connected to the outer periphery of the second buffer portion 45b. The second direction F2, the first direction F1, and the third direction F3 are perpendicular to each other.

[0317] like Figures 20-22 As shown, the second buffer portion 45b is inside the pressure relief portion 43, and the two ends of the second buffer portion 45b extend to the area adjacent to the edge of the pressure relief portion 43 in the third direction F3. The first buffer portion 45a forms a ring and is connected to the outer periphery of the second buffer portion 45b. Thus, the tensile force on various positions of the entire pressure relief portion 43 is reduced to a certain extent. By stretching and deforming the buffer portion 45, it can buffer the various positions where the groove is located, reduce the probability of the groove being stretched and broken, resulting in leakage, and improve the service life and reliability of the battery cell 100.

[0318] In some embodiments, please refer to Figure 24 , Figure 24 This is a schematic diagram showing the connection between the end cap 102 and the electrical connection portion 30 provided in some embodiments of this application. The battery cell 100 also includes the electrical connection portion 30, which is disposed on the end cap 102 and electrically connected to the electrode assembly 20. The end cap 102 is provided with a lead-out hole. The electrical connection portion 30 includes a terminal body 31, a first limiting portion 32, and a second limiting portion 33. The terminal body 31 is connected to the first limiting portion 32 and the second limiting portion 33. The terminal body 31 passes through the lead-out hole. Along the first direction F1, the first limiting portion 32 is located on the side of the end cap 102 away from the electrode assembly 20, and the second limiting portion 33 is located on the side of the end cap 102 facing the electrode assembly 20.

[0319] The first limiting part 32 and the second limiting part 33 have a limiting function. The first limiting part 32 and the second limiting part 33 are respectively connected to both ends of the terminal body 31. The first limiting part 32 and the second limiting part 33 cooperate to prevent the terminal body 31 from disengaging from the lead-out hole. Along the first direction F1, the projected area of ​​the first limiting part 32 and the projected area of ​​the second limiting part 33 are both larger than the projected area of ​​the terminal body 31. It is possible that the projected area of ​​the first limiting part 32 is larger than the projected area of ​​the second limiting part 33, or that the projected area of ​​the second limiting part 33 is larger than the projected area of ​​the first limiting part 32. The first limiting part 32, the second limiting part 33 and the terminal body 31 can be integrally formed, or one of the first limiting part 32 and the second limiting part 33 can be integrally formed with the terminal body 31, while the other is separately provided and connected to the terminal body 31.

[0320] As an example, the battery cell 100 may also include a first insulating component 6 and a second insulating component 7. The first insulating component 6 is at least partially disposed between the electrical connection portion 30 and the end cap 102 to insulate and isolate the electrical connection portion 30 and the end cap 102. The second insulating component 7 is disposed on the side of the end cap 102 facing the electrode assembly 20 to insulate and isolate the electrode assembly 20 and the end cap 102.

[0321] In this embodiment, the electrical connection part 30 can be installed on the end cover 102 by riveting, which is easy to install and more economical.

[0322] In some embodiments, the second wall 12 is located below the electrode assembly 20 and opposite the end cap 102, and the second wall 12 is used to support the electrode assembly 20.

[0323] like Figure 3 , Figure 4 and Figure 7 As shown, the second wall 12 is used to support the electrode assembly 20, and the second wall 12 is located below the electrode assembly 20.

[0324] In some embodiments, the housing 101 is made of aluminum alloy, which may be tri-series aluminum, thereby giving the housing 101 advantages such as lightweight, safety, ease of processing and good corrosion resistance.

[0325] In some embodiments, the negative electrode 22 includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector along the thickness direction of the negative electrode and containing a negative electrode active material. The negative electrode active material includes a silicon-based material, wherein the mass content of silicon element in the silicon-based material is 0.3% to 10.0% based on the total mass of the negative electrode active material.

[0326] In the above technical solution, by keeping the mass content of silicon element in the silicon-based material within the above range, the capacity of the negative electrode active material can be improved, thereby improving the energy density of the battery cell; by increasing the energy density, the expansion force is not too large, reducing the damage, cracking and leakage caused by the expansion and deformation of the electrode components in the weak area.

[0327] In some embodiments, the negative electrode 22 includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector along the thickness direction of the negative electrode and containing a negative electrode active material, wherein the discharge capacity of the negative electrode film layer per unit area is 2.0 mAh / cm². 2 Up to 5.0mAh / cm 2 .

[0328] The discharge capacity per unit area of ​​the negative electrode film refers to the actual lithium intercalation capacity of the negative electrode active material. The testing method is as follows: The battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode sheet is removed, and it is assembled into a CR2430 model semi-button battery with a negative electrode and lithium sheet. The area of ​​the negative electrode sheet used is f mm². 2 The electrolyte used was a 1 mol / L LiPF6 solution in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). The assembled semi-coin cells were then left to stand for 3 hours. The test was conducted at 25°C. Lithium insertion was performed by discharging at 0.1C in the voltage range of 2V-0V, followed by lithium removal by charging at 0.05C to 2V. This cycle was repeated twice. The discharge capacity of the second cycle was recorded as Z mAh. The actual battery design had a negative electrode length of h mm and a width of i mm. The surface area of ​​the negative electrode active material coated on the negative electrode current collector was d. Therefore, the lithium insertion capacity of the negative electrode was Z / f*h*i*d.

[0329] The discharge capacity of the negative electrode film per unit area can be selected as 2 mAh / cm². 2 Up to 5mAh / cm 2 For example, the discharge capacity of the negative electrode film per unit area is 2.0 mAh / cm². 2 2.1mAh / cm 2 2.2mAh / cm 2 2.3mAh / cm 2 2.4mAh / cm 2 2.5mAh / cm 2 2.6mAh / cm 2 2.7mAh / cm 2 2.8mAh / cm 2 2.9mAh / cm 2 3.0mAh / cm 2 3.1mAh / cm 23.2mAh / cm 2 3.3mAh / cm 2 3.4mAh / cm 2 3.5mAh / cm 2 3.6mAh / cm 2 3.7mAh / cm 2 3.8mAh / cm 2 3.9mAh / cm 2 4.0mAh / cm 2 4.1mAh / cm 2 4.2mAh / cm 2 4.4mAh / cm 2 4.8mAh / cm 2 5.0mAh / cm 2 The value of any one of the points or the range between any two.

[0330] When the discharge capacity of the negative electrode film per unit area is within the above range, there are sufficient sites in the negative electrode film for lithium insertion, which can reduce the risk of lithium plating; it is also conducive to fast charging, and the expansion force is not too large, reducing the damage, cracking and leakage caused by the expansion and deformation of the electrode components in weak areas.

[0331] In some embodiments, the thickness of the negative electrode film is T1, where 9μm ≤ T1 ≤ 75μm, and T1 can be selected from 9μm to 75μm. The thickness T1 of the negative electrode film can be any one of 9μm, 15μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, and 75μm, or a range between any two. Therefore, the pressure relief mechanism 40 can be located at the bottom of the battery cell 100. The bottom of the battery cell 100 can be provided with an exhaust channel, which is connected to the pressure relief mechanism 40. This allows high-temperature, high-pressure flue gas to be discharged through the pressure relief mechanism 40 at the bottom into the exhaust channel and then to the outside environment when thermal runaway occurs in the battery cell 100.

[0332] The battery 1000 according to the second aspect embodiment of this application includes the battery cell 100 according to the first aspect embodiment of this application described above. The electrical device 2000 according to the third aspect embodiment of this application includes the battery 1000 according to the second aspect embodiment of this application described above. The battery 1000 is used to provide electrical energy to the electrical device 2000. Therefore, by using the battery 1000 described above, it is beneficial to improve the safety and reliability of the electrical device 2000.

[0333] Optionally, such as Figure 1As shown, when the battery 1000 is used in a vehicle, it can be located at the bottom, front, or rear of the vehicle. The battery 1000 can be used to power the vehicle; for example, it can serve as the vehicle's operating power source. The vehicle may also include a controller and a motor. The controller controls the battery 1000 to power the motor, for example, to meet the vehicle's power needs during starting, navigation, and driving.

[0334] The following describes a specific embodiment of a battery 1000 and a vehicle having the same, in conjunction with the accompanying drawings.

[0335] like Figure 1 As shown, battery 1000 is located at the bottom of the vehicle, and as... Figure 2 As shown, the battery 1000 includes multiple battery cells 100, such as... Figure 4 As shown, each battery cell 100 includes a housing 10 and two electrode assemblies 20. The housing 10 includes a shell 101 and an end cap 102. The end cap 102 is provided with an electrical connection portion 30. The shell 101 includes two first walls 11 and a second wall 12. The second wall 12 has a pressure relief mechanism 40. The electrode assemblies 20 are arranged inside the housing 10.

[0336] The first wall 11 is welded to the end cap 102 to form a first connecting part 51. The first wall 11 includes a first region 111 and a second region 112 arranged along the first direction F1. The first region 111 is located on the side of the second region 112 that is close to the first connecting part 51. The thickness of the first region 111 is greater than the thickness of the second region 112. The maximum thickness of the first region 111 is D1, and the maximum thickness of the second region 112 is D2. 0.5mm≤D1≤1.5mm, 0.4mm≤D2≤0.8mm, and the thickness difference between the first region 111 and the second region 112 is t. 0.1≤t≤0.7mm.

[0337] The pressure relief mechanism 40 is provided with a first groove 41 and a second groove 42. The first groove 41 includes a first groove segment 411 and two second groove segments 412. The first groove segment 411, the two second groove segments 412, and the second groove 42 together define a predetermined pressure relief area. The first groove segment 411 extends along a straight trajectory. The length direction of the first groove segment 411 is perpendicular to the second direction F2. The dimension of the bottom surface of the first groove segment 411 in the second direction F2 is A. The width of the second wall 12 along the second direction F2 is B, satisfying: A / B≥0.008, 0.3mm≤A≤0.8mm, 20mm≤B≤80mm.

[0338] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, wherein, include: The housing has an opening at at least one end along a first direction, the housing includes two first walls and a second wall, the two first walls are arranged opposite each other along a second direction, the second wall connects the two first walls, and the first direction and the second direction are perpendicular to each other; An end cap is provided to close the opening. The first wall is welded to the end cap to form a first connection. The thickness of the end cap is greater than the thickness of the second wall. An electrode assembly is housed within the housing. The electrode assembly includes at least one positive electrode, at least one negative electrode, and at least one separator. The separator is used to isolate the positive electrode and the negative electrode. The electrode assembly includes a flat region, and at least a portion of the positive electrode, at least a portion of the negative electrode, and at least a portion of the separator are stacked in the flat region along a second direction. A pressure relief mechanism is disposed on the second wall. The pressure relief mechanism is provided with a first groove. The pressure relief mechanism is configured to crack along at least a portion of the first groove when the battery cell is depressurized. The first groove includes a first groove segment extending along a straight trajectory. The length direction of the first groove segment is perpendicular to the second direction. The width of the bottom surface of the first groove segment in the second direction is A. The width of the second wall in the second direction is B, satisfying: A / B≥0.

008. The first wall includes a first region and a second region arranged along the first direction, the first region being located on the side of the second region closer to the first connection portion, and the thickness of the first region being greater than the thickness of the second region.

2. The battery cell according to claim 1, wherein, The thickness difference between the first region and the second region is t, which satisfies: 0.1mm≤t≤0.7mm.

3. The battery cell according to claim 2, wherein, 0.2mm≤t≤0.5mm.

4. The battery cell according to claim 1, wherein, The maximum thickness of the first region is D1, which satisfies: 0.5mm≤D1≤1.5mm.

5. The battery cell according to claim 1, wherein, The maximum thickness of the second zone is D2, which satisfies: 0.4mm≤D2≤0.8mm.

6. The battery cell according to claim 1, wherein, The first region includes a first part and a second part arranged along the first direction, the second part connecting the first part and the second region, the thickness of the first part being the thickness of the first region, and the thickness of the second part decreasing along the direction from the end cap toward the electrode assembly.

7. The battery cell according to claim 1, wherein, The second region has a first inner surface facing the interior space of the housing and a first outer surface facing away from the interior of the housing. The first region includes a first protrusion protruding from the first inner surface, and / or the first region includes a second protrusion protruding from the first outer surface.

8. The battery cell according to claim 1, wherein, Satisfies: A / B≤0.

019.

9. The battery cell according to claim 1, wherein, The following conditions must be met: 0.3mm≤A≤0.8mm, 20mm≤B≤80mm.

10. The battery cell according to claim 1, wherein, The minimum residual thickness of the first groove segment is D3, where 0.1mm ≤ D3 ≤ 0.28mm.

11. The battery cell according to claim 1, wherein, The first groove defines at least one predetermined pressure relief area, and the pressure relief mechanism is provided with a second groove configured to guide at least a portion of the predetermined pressure relief area to flip over to open at least a portion of the predetermined pressure relief area.

12. The battery cell according to claim 11, wherein, The residual thickness of the second groove is greater than that of the first groove.

13. The battery cell according to claim 11, wherein, The width of the second groove perpendicular to the extension direction is greater than the width of the first groove perpendicular to the extension direction.

14. The battery cell according to claim 11, characterized in that, The first groove also includes two second groove segments, which are arranged opposite to each other. The two ends of the first groove segment are respectively connected to one end of the two second groove segments, and the other ends of the two second groove segments are connected to the two ends of the second groove. The first groove segment, the two second groove segments, and the second groove together define a predetermined pressure relief area.

15. The battery cell according to claim 14, wherein, The second groove is arranged parallel to and opposite to the first groove segment, and the second groove segment extends along a straight line and / or an arc trajectory.

16. The battery cell according to claim 1, wherein, The pressure relief mechanism includes a main body and a pressure relief part. The main body is connected to the second wall. The thickness of the pressure relief part is less than the thickness of the main body. The first groove is provided on the pressure relief part. The thickness dimension of the pressure relief part in the first direction is D4, which satisfies: 0.15mm≤D4≤0.4mm.

17. The battery cell according to claim 16, wherein, 0.2mm≤D4≤0.3mm.

18. The battery cell according to claim 1, wherein, The pressure relief mechanism is provided with a pressure relief section, the first groove is provided in the pressure relief section, the minimum residual thickness of the first groove section is D3, and the thickness dimension of the pressure relief section in the first direction is D4, satisfying: 0.55≤D3 / D4≤0.

85.

19. The battery cell according to claim 1, wherein, The second wall has a pressure relief hole, and the pressure relief mechanism is installed in the pressure relief hole. The area of ​​the pressure relief hole projected along the first direction is W, where 400mm²≤W≤1400mm².

20. The battery cell according to claim 19, wherein, 600mm²≤W≤1200mm².

21. The battery cell according to claim 1, wherein, The second wall has a pressure relief hole, and the pressure relief mechanism is installed in the pressure relief hole. The size of the pressure relief hole in the second direction is N, and the size of the pressure relief hole in the third direction is L. The third direction is perpendicular to the first direction and the second direction, satisfying: 1.5≤L / N≤5.

22. The battery cell according to claim 21, wherein, 2≤L / N≤4.

23. The battery cell according to claim 1, wherein, The electrode assembly comprises N1 units, and each electrode assembly has N2 layers of positive electrode sheets stacked in the flat region. The flat region has an outer surface perpendicular to the second direction, and the area of ​​the outer surface is S, where N1≥1, N2≥1, N1*N2≤500, and S≤80000mm².

24. The battery cell according to claim 1, wherein, The electrode assembly is a stacked structure, comprising multiple positive electrode plates and multiple negative electrode plates, which are stacked along the second direction.

25. The battery cell according to claim 24, wherein, Along the third direction, the size of the first region is larger than the size of the positive electrode and / or the size of the negative electrode, and the first direction, the second direction and the third direction are perpendicular to each other.

26. The battery cell according to claim 24, wherein, The number of negative electrode plates is greater than the number of positive electrode plates, and a positive electrode plate is disposed between two adjacent negative electrode plates.

27. The battery cell according to claim 24, wherein, Each of the negative electrode plates is provided with a negative electrode tab; and / or, each of the positive electrode plates is provided with a positive electrode tab.

28. The battery cell according to claim 1, wherein, The electrode assembly is a wound structure, and the electrode assembly also has a corner area. The corner area is provided at least one end of the straight area along a third direction. At least a portion of the outer surface of the corner area is an arc surface. The first direction, the second direction and the third direction are not coplanar and intersect each other.

29. The battery cell according to any one of claims 1-28, wherein, The pressure relief mechanism has a buffer portion that arches outward toward and / or away from the electrode assembly along the first direction.

30. The battery cell according to claim 29, wherein, Along the thickness direction of the second wall, the second wall has a second outer surface and a second inner surface, the second inner surface being closer to the electrode assembly than the second outer surface. The buffer portion includes a first buffer portion that arches toward the side closer to the electrode assembly and does not protrude beyond the second inner surface.

31. The battery cell according to claim 29, wherein, An insulating member is provided inside the housing, the insulating member being located between the second wall and the electrode assembly, the insulating member defining a clearance groove that opens toward one side of the second wall, the clearance groove corresponding to the position of the buffer portion.

32. The battery cell according to claim 31, wherein, Along the thickness direction of the second wall, the second wall has a second outer surface and a second inner surface, the second inner surface being closer to the electrode assembly than the second outer surface. The buffer section includes a first buffer section that arches toward the side closer to the electrode assembly, and at least a portion of the first buffer section protrudes from the second inner surface and extends into the clearance groove.

33. The battery cell according to claim 29, wherein, Along the thickness direction of the second wall, the second wall has a second outer surface and a second inner surface, the second inner surface being closer to the electrode assembly than the second outer surface. The buffer portion includes a second buffer portion that arches toward the side away from the electrode assembly and does not protrude beyond the second outer surface.

34. The battery cell according to claim 29, wherein, The buffer portion includes a first buffer portion and a second buffer portion, the first buffer portion arching towards the side closer to the electrode assembly, and the second buffer portion arching towards the side farther from the electrode assembly, with at least a portion of the first buffer portion located on one side of the second buffer portion in the second direction.

35. The battery cell according to claim 34, wherein, The second buffer extends along a third direction, and the first direction, the second direction, and the third direction are perpendicular to each other. The first buffer is connected to the outer periphery of the second buffer.

36. The battery cell according to claim 1, wherein, The battery cell further includes an electrical connection portion, which is disposed on the end cap and electrically connected to the electrode assembly; The end cap is provided with a lead-out hole. The electrical connection part includes a terminal body, a first limiting part and a second limiting part. The terminal body is connected to the first limiting part and the second limiting part. The terminal body passes through the lead-out hole. Along the first direction, the first limiting part is located on the side of the end cap away from the electrode assembly, and the second limiting part is located on the side of the end cap facing the electrode assembly.

37. The battery cell according to claim 1, wherein, The second wall is located below the electrode assembly and opposite the end cap, and the second wall is used to support the electrode assembly.

38. The battery cell according to claim 1, wherein, The shell is made of aluminum alloy.

39. The battery cell according to claim 1, wherein, The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector along the thickness direction of the negative electrode sheet and containing a negative electrode active material. The negative electrode active material includes a silicon-based material, and the silicon content in the silicon-based material is 0.3% to 10.0% by mass, based on the total mass of the negative electrode active material.

40. The battery cell according to claim 1, wherein, The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector along the thickness direction of the negative electrode and containing a negative electrode active material. The discharge capacity of the negative electrode film layer per unit area is 2.0 mAh / cm². 2 Up to 5.0mAh / cm 2 .

41. The battery cell according to claim 40, wherein, The thickness of the negative electrode film is T1, where 9μm≤T1≤75μm.

42. A battery, wherein, Includes the battery cell according to any one of claims 1-41.

43. An electrical appliance, wherein, Includes the battery according to claim 42, the battery being used to provide electrical energy to the electrical device.

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