Battery monomer, battery and electric device

Abstract

A battery monomer, a battery and a power utilization device, the battery monomer comprises: an electrode assembly, the electrode assembly comprises at least one positive pole piece, at least one negative pole piece and at least one separator, the positive pole piece, the negative pole piece and the separator are stacked to form a straight area, at least one part of the positive pole piece, at least one part of the negative pole piece and at least one part of the separator are stacked in the straight area along the first direction; the shell comprises a first wall part, the first wall part is located on one side of the electrode assembly in the second direction, and the first direction is perpendicular to the second direction; and the pressure relief mechanism is arranged on the first wall part, the pressure relief mechanism is provided with a nick groove, the nick groove defines a pressure relief part, and the pressure relief part is provided with a buffer part which is arched towards one side close to and / or far away from the electrode assembly along the second direction. And the buffer part can play a role in buffering, so that the probability of liquid leakage caused by pulling damage of the nick groove is reduced, and the service life and the reliability of the battery monomer are improved.

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 grooves on the pressure relief mechanism prone to being 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 groove of the pressure relief mechanism being pulled during battery use.

[0005] In a first aspect, this application provides a battery cell, comprising: an electrode assembly including at least one positive electrode, at least one negative electrode, and at least one separator, wherein the positive electrode, the negative electrode, and the separator are stacked to form 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 first direction; a housing for accommodating the electrode assembly, the housing including a shell and an end cap, the shell having an opening at at least one end along a second direction, the end cap being connected to the shell and used to close the opening, the shell including a first wall portion located on one side of the electrode assembly in the second direction, the first direction being perpendicular to the second direction; and a pressure relief mechanism disposed on the first wall portion, the pressure relief mechanism having a groove defining a pressure relief portion, at least a portion of the pressure relief portion being openable when the battery cell is depressurized, the pressure relief portion having a buffer portion arching along the second direction toward and / or away from the electrode assembly.

[0006] In the technical solution of this application embodiment, by setting a buffer part in the pressure relief part, the buffer part can absorb the tensile deformation transmitted to the pressure relief mechanism during the long-term use of the battery cell, thereby reducing the expansion force acting on the groove, reducing the tensile force on the groove, and the buffer part plays a buffering role, thereby reducing the probability of the groove being pulled and broken, leading to leakage, and improving the service life and reliability of the battery cell.

[0007] In some embodiments, along the thickness direction of the first wall portion, the first wall portion has a first outer surface and a first inner surface, the first inner surface being closer to the electrode assembly than the first outer surface, and the buffer portion includes a first buffer portion that arches towards the side closer to the electrode assembly but does not protrude beyond the first 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.

[0008] In some embodiments, along the thickness direction of the first wall portion, the first wall portion has a first outer surface and a first inner surface, the first inner surface being closer to the electrode assembly than the first outer surface, and the buffer portion includes a second buffer portion, the second buffer portion arching away from the electrode assembly and not protruding beyond the first 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 setting of the buffer portion affecting the placement of the battery cell; for example, the first wall portion can be the bottom wall of the battery cell, and the battery cell can be supported in the housing by the first wall portion, the buffer portion being located inside the first outer surface, which can avoid the problem of the first wall portion not fitting properly inside the housing and affecting the placement stability of the battery cell.

[0009] In some embodiments, an insulating member is provided within the housing, located between the first wall portion and the electrode assembly. The insulating member defines a clearance groove opening towards the first wall portion, 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 first wall portion, 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, providing space for the deformation of the buffer portion, which is beneficial for the deformation of the buffer portion.

[0010] In some embodiments, along the thickness direction of the first wall portion, the first wall portion has a first outer surface and a first inner surface, the first inner surface being closer to the electrode assembly than the first outer surface. The buffer portion includes a first buffer portion that arches towards the side closer to the electrode assembly, at least a portion of the first buffer portion protruding from the first 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 first wall portion 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.

[0011] 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 first 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.

[0012] In some embodiments, the second buffer portion extends along a third direction, with the first direction, the second 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.

[0013] In some embodiments, the pressure relief portion includes a body, the groove is disposed on the body, and the buffer portion includes a bottom wall and a side wall surrounding the outer periphery of the bottom wall, the side wall being connected to the body. In the above technical solution, the buffer portion is constructed as a groove structure with a bottom wall and side walls. On the one hand, this facilitates the manufacturing and forming of the buffer portion; on the other hand, it facilitates the control of the width and thickness dimensions of the buffer portion, improving the manufacturing yield; furthermore, it allows for an increase in the size of the arched portion of the buffer portion, improving the buffering effect.

[0014] In some embodiments, the included angle between the sidewall of the buffer portion and the body is α, where 100°≤α≤170°, preferably 120°≤α≤150°. This technical solution reduces stress concentration at the buffer portion, improves its buffering performance, and lowers the probability of fatigue cracking at the groove of the pressure relief mechanism.

[0015] In some embodiments, the thickness of the sidewall of the buffer portion is D1, and the thickness of the body is D2, satisfying: 0 ≤ D1 - D2 ≤ 0.3 mm. This technical solution facilitates the manufacturing and forming of the buffer portion, ensuring manufacturing yield, and also improves the buffering effect. When the electrode assembly expands, the buffer portion undergoes a certain deformation, absorbing at least part of the expansion force of the electrode assembly, reducing the expansion force acting on the groove, lowering the probability of tearing and leakage at the groove, and improving the service life and reliability of the battery cell.

[0016] In some embodiments, 0.2mm≤D1≤0.6mm. The above technical solution facilitates the manufacturing and forming of the buffer portion, ensuring manufacturing yield, and also reduces the stiffness of the buffer portion. When the electrode assembly expands, the buffer portion undergoes a certain deformation, absorbing at least part of the expansion force of the electrode assembly, reducing the expansion force acting on the groove, lowering the probability of the groove being torn and damaged, leading to leakage, and improving the service life and reliability of the battery cell.

[0017] In some embodiments, 0.15mm ≤ D2 ≤ 0.4mm. The above technical solution can improve the manufacturing yield of the pressure relief mechanism, ensure the buffering effect of the buffer section, and reduce the stress concentration at the first groove section. When the electrode assembly expands, the buffer section undergoes a certain deformation, absorbing at least part of the expansion force of the electrode assembly, reducing the expansion force acting on the groove, lowering the probability of the groove being torn and damaged, leading to leakage, and improving the service life and reliability of the battery cell.

[0018] In some embodiments, along the direction approaching and / or away from the electrode assembly, the maximum height dimension of the buffer portion is H, and the thickness dimension of the first wall portion is D3, satisfying: 1.5mm≤H+D3≤5mm. In the above technical solution, the buffer portion's buffering effect can be guaranteed. When the electrode assembly expands, the buffer portion undergoes a certain deformation, absorbing at least part of the expansion force of the electrode assembly, reducing the expansion force acting on the groove, and lowering the probability of the groove being torn and damaged, leading to leakage. It also improves the space utilization rate of the battery cell, and to a certain extent guarantees the energy density of the battery cell.

[0019] In some embodiments, the following condition is satisfied: 0.8mm ≤ D3 ≤ 3mm. The above technical solution can both guarantee the energy density of the battery cell to a certain extent and reduce the probability of fatigue cracking at the groove, thereby improving the reliability of the battery cell.

[0020] In some embodiments, the maximum height dimension H of the buffer portion along the direction approaching and / or away from the electrode assembly satisfies: 0.2mm ≤ H ≤ 3mm, preferably 0.3mm ≤ H ≤ 2mm. This technical solution facilitates the manufacturing and forming of the buffer portion without significantly impacting other structural components. Simultaneously, the buffer portion can deform to a certain extent when the electrode assembly expands, absorbing at least part of the expansion force of the electrode assembly, thereby reducing the expansion force acting on the groove, lowering the probability of tearing and leakage at the groove, and improving the service life and reliability of the battery cell.

[0021] In some embodiments, the pressure relief mechanism further includes a mounting portion disposed on the outer periphery of the pressure relief portion and connected to the first wall portion.

[0022] In some embodiments, the mounting portion includes a first mounting section and a second mounting section. The first mounting section is disposed on the outer periphery of the second mounting section. The thickness of the pressure relief portion is less than the thickness of the first mounting section, and the thickness of the second mounting section is not greater than the thickness of the first mounting section. Therefore, the buffer portion is positioned in the pressure relief portion with a smaller thickness. This facilitates the deformation and stretching of the buffer portion under the expansion force of the electrode assembly. Simultaneously, it avoids the probability of leakage due to the buffer portion being too thin and thus broken. Furthermore, it ensures that the groove is the weakest point of the entire pressure relief mechanism, allowing the internal pressure of the battery cell to be released at a predetermined location when the internal pressure reaches a threshold, achieving the purpose of pressure relief at a specific location.

[0023] 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 first direction, the area of ​​the outer surface being S, N1≥1, N2≥1, N1*N2≤500, 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 at the groove of the pressure relief mechanism and the weld between the casing and the end cap, and improving the reliability of the battery cell.

[0024] In some embodiments, the groove includes a first groove, and the pressure relief mechanism is configured to split 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 being perpendicular to the first direction, and the dimension of the bottom surface of the first groove segment in the first direction being A, satisfying: 0.3mm≤A≤0.8mm. By cooperating with the buffer section, the bottom width of the first tank section is increased to a certain extent, thereby increasing the deformation resistance of the first tank section and reducing the deformation of the pressure relief mechanism at the first tank section when the electrode assembly expands. This relatively reduces the height of the buffer section that needs to protrude, lowering the probability of interference between the buffer section and other components or affecting energy density. During long-cycle charge and discharge use, the risk of fatigue cracking of the pressure relief mechanism can be avoided to a certain extent, reducing the probability of leakage caused by the pressure relief mechanism being pulled and broken, and improving the reliability of the battery cell. At the same time, it can avoid excessive burst pressure of the pressure relief mechanism, reducing the probability that the pressure relief mechanism cannot burst in time and is prone to bursting in other locations when the battery cell experiences thermal runaway, further improving the reliability of the battery cell.

[0025] In some embodiments, the minimum residual thickness of the first groove segment is D4, satisfying: 0.1mm ≤ D4 ≤ 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 relatively reduces the height of the required buffer protrusion, lowers the probability of interference between the buffer and other components or affecting energy density. During long-cycle charge-discharge use, this can, to some extent, avoid the risk of fatigue cracking of the pressure relief mechanism, reduce the probability of leakage due to tearing of the pressure relief mechanism, and improve the reliability of the battery cell. Simultaneously, it can prevent excessive burst pressure of the pressure relief mechanism, reducing the probability that the pressure relief mechanism cannot burst in time and is prone to bursting at other locations when thermal runaway occurs in the battery cell, further improving the reliability of the battery cell.

[0026] In some embodiments, the first groove defines at least one predetermined pressure relief area, and the groove further includes 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In some embodiments, the housing further includes a second wall portion, which is welded to the end cap to form a first connection portion; wherein the second wall portion includes a first region and a second region arranged along the second direction, the thickness of the first region is greater than the thickness of the second region, and the first region is located between the first connection portion and the second region. In the above technical solution, by increasing the thickness of the first region, the strength in the area near the first connection portion is improved, the burst pressure at the weld between the housing and the end cap is increased, the risk of cracking at the weld between the housing and the end cap when the battery cell experiences thermal runaway after the burst pressure rises is reduced, and the reliability of the battery cell is improved; in addition, compared with the overall thickening of the second wall portion, a significant reduction in the energy density of the battery cell can be avoided.

[0032] 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 weld between the shell and the end cap during thermal runaway, and facilitate the manufacturing and forming of the shell.

[0033] In some embodiments, the maximum thickness of the first region is E1, satisfying: 0.5mm≤E1≤1.5mm. 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 weld between the shell and the end cap during thermal runaway.

[0034] In some embodiments, the maximum thickness of the second region is E2, satisfying: 0.4mm ≤ E2 ≤ 0.8mm. The above technical solution satisfies both the strength requirements of the second region and the volumetric energy density requirements of the individual battery cells.

[0035] In some embodiments, the first wall portion has a pressure relief hole, the pressure relief mechanism is mounted on the pressure relief hole, and the projected area of ​​the pressure relief hole along the second 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.

[0036] In some embodiments, the pressure relief mechanism is integrally formed with the wall of the housing. This technical solution improves the reliability of the pressure relief part, eliminates the need for a connection process between the pressure relief part and the first wall, and reduces the manufacturing cost of the battery cell. The redundant part can be integrally formed on the wall of the housing through a stamping process, simplifying the manufacturing process and reducing costs.

[0037] In some embodiments, the electrode assembly is a stacked structure, comprising a plurality of positive electrode plates and a plurality of negative electrode plates, which are stacked along the first direction. In the above technical solution, the electrode assembly 20 is a stacked electrode assembly, which has a more compact structure and stronger resistance to compression.

[0038] 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.

[0039] 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.

[0040] 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 pairwise. In the above technical solution, the electrode assembly is a wound electrode assembly, which has a relatively simple manufacturing process and low cost.

[0041] In some embodiments, the first wall portion is used to support the electrode assembly and is located below the electrode assembly. In the above technical solution, the pressure relief 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.

[0042] In some embodiments, the material of the first wall portion includes aluminum alloy. In the above technical solution, the first wall portion has advantages such as lightweight, safety, ease of processing, and good corrosion resistance.

[0043] 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. 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 at the groove due to the expansion and deformation of the electrode assembly.

[0044] 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 at the groove.

[0045] In some embodiments, the thickness of the negative electrode film is T1, where 9 μm ≤ T1 ≤ 75 μm.

[0046] Secondly, this application provides a battery that includes the battery cell described in the above embodiments.

[0047] Thirdly, this application provides an electrical device that includes the battery described in the above embodiments, the battery being used to provide electrical energy.

[0048] 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

[0049] 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:

[0050] Figure 1 This is a schematic diagram of an electrical device in related technologies;

[0051] Figure 2 This is a schematic diagram of a battery in related technologies;

[0052] Figure 3 A schematic diagram of a battery cell provided in some embodiments of this application;

[0053] Figure 4 Exploded views of a single battery cell provided in some embodiments of this application;

[0054] Figure 5 A schematic diagram of an electrode assembly provided in some embodiments of this application;

[0055] Figure 6 A schematic diagram of an electrode assembly provided for other embodiments of this application;

[0056] Figure 7 Cross-sectional views of a battery cell provided in some embodiments of this application;

[0057] Figure 8 for Figure 7 The center circle shows a magnified view of point A;

[0058] Figure 9 Cross-sectional views of a battery cell provided in some embodiments of this application;

[0059] Figure 10 for Figure 9 The center circle shows an enlarged view of location B in some embodiments;

[0060] Figure 11 for Figure 9 The center circle shows an enlarged view of location B in some other embodiments;

[0061] Figure 12 for Figure 9 The center circle shows an enlarged view of location B in some other embodiments;

[0062] Figure 13 A schematic diagram of the pressure relief mechanism provided in some embodiments of this application from one perspective;

[0063] Figure 14 A schematic diagram of the pressure relief mechanism provided in some embodiments of this application from another perspective;

[0064] Figure 15 A structural schematic diagram of the pressure relief mechanism provided in some embodiments of this application from yet another perspective;

[0065] Figure 16 For along Figure 15 A cross-sectional view of the CC line;

[0066] Figure 17 For along Figure 15 Sectional view of the DD line;

[0067] Figure 18 for Figure 17 The enlarged view at point E is shown in the center circle;

[0068] Figure 19 A schematic diagram of a pressure relief mechanism provided in some other embodiments of this application;

[0069] Figure 20 A schematic diagram of a pressure relief mechanism provided in some embodiments of this application;

[0070] Figure 21 Schematic diagram of the housing provided for some embodiments of this application;

[0071] Figure 22 For along Figure 21 A cross-sectional view of the middle HH line;

[0072] Figure 23 for Figure 22 The center circle shows an enlarged view of I in some embodiments;

[0073] Figure 24 for Figure 22 The center circle shows an enlarged view of I in some other embodiments;

[0074] Figure 25for Figure 22 The center circle shows an enlarged view of I in some other embodiments;

[0075] Figure 26 This is a schematic diagram showing the connection between the end cap and the electrical connection portion provided in some embodiments of this application.

[0076] Figure label:

[0077] Battery 1000, power device 2000, battery cell 100, casing 200, first shell 201, first shell 202, outer shell 10, casing 101, end cap 102, pressure relief hole 103, first wall portion 11, first inner surface 1101, first outer surface 1102, second wall portion 12, first region 111, first part 111a, second part 111b, first protrusion 1111, second protrusion 1112, second region 112, second inner surface 1121, second outer surface 1122, electrode assembly 20, positive electrode 21, negative electrode 22, straight region 23, bending region 24, separator 2 5. Electrical connection part 30, terminal body 31, first limiting part 32, second limiting part 33, pressure relief mechanism 40, scoring groove 402, first scoring groove 41, first groove segment 411, second groove segment 412, second scoring groove 42, pressure relief part 43, body 431, mounting part 44, first mounting segment 441, second mounting segment 442, 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, first connection part 51, first insulating component 6, second insulating component 7, patch 60, insulating component 70, clearance groove 71. Detailed Implementation

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] In this application, "multiple" means two or more (including two).

[0084] In this embodiment, the battery cell can be a rechargeable battery, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used. 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 this embodiment is not limited to these types.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] In some embodiments, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0090] The development of battery technology must consider multiple design factors simultaneously, such as performance parameters like energy density, cycle life, discharge capacity, and charge / discharge rate. Additionally, battery safety must also be considered. To ensure the safety of individual battery cells, pressure relief mechanisms can be installed on their casings. In the event of thermal runaway, these mechanisms release internal pressure, thereby improving the safety of the battery cell.

[0091] 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, causing it to concave and stretch. Especially in the direction of greater expansion of the electrode assembly, the groove will generate a large strain. The expansion force of a battery cell is large when it is fully charged and small when it is discharged. During long-term use, there is a large amplitude of expansion force during charging and discharging. Coupled with the gas generation inside the battery cell and different external constraints, this will cause the groove to generate a large strain and strain amplitude, which will lead to fatigue cracking of the pressure relief mechanism. The battery cell is prone to problems such as cracking and failure of the pressure relief mechanism and leakage before it reaches the warranty period.

[0092] In view of this, embodiments of this application provide a battery cell, including: an electrode assembly, the electrode assembly including at least one positive electrode, at least one negative electrode, and at least one separator, the positive electrode, negative electrode, and separator being stacked to form a flat region, at least a portion of the positive electrode, at least a portion of the negative electrode, and at least a portion of the separator being stacked in the flat region along a first direction; a housing for accommodating the electrode assembly, the housing including a first wall portion located on one side of the electrode assembly in a second direction, the first direction being perpendicular to the second direction; a pressure relief mechanism disposed on the first wall portion, the pressure relief mechanism having a groove, the groove defining a pressure relief portion, at least a portion of the pressure relief portion being openable when the battery cell is depressurized, the pressure relief portion having a buffer portion arching along the second direction toward and / or away from the electrode assembly.

[0093] In such a battery cell, by setting a buffer section in the pressure relief section, the buffer section can absorb the tensile deformation transmitted to the pressure relief mechanism during the long-term use of the battery cell, thereby reducing the expansion force acting on the groove, reducing the tensile force on the groove, and the buffer section plays a buffering role. This can reduce the probability of the groove being pulled and broken, leading to leakage, and improve the service life and reliability of the battery cell.

[0094] The technical solutions described in the embodiments of this application are applicable to batteries and electrical devices that use batteries.

[0095] 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.

[0096] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0097] Please refer to Figure 1 , Figure 1This 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.

[0098] 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, to meet the power requirements of the vehicle 2000 during startup, navigation and driving.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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 connected to housing 101 by welding or roll sealing 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0114] In some embodiments, the electrode assembly 20 further includes an isolator disposed between the positive and negative electrodes.

[0115] 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.

[0116] In some embodiments, the separator is a solid electrolyte, disposed between the positive and negative electrodes, serving to both transport ions and isolate the positive and negative electrodes.

[0117] 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.

[0118] 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.

[0119] In some embodiments, the electrode assembly 20 has a stacked structure.

[0120] 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.

[0121] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0122] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0123] In some embodiments, the electrode assembly 20 may be flat or polygonal in shape.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] like Figure 5 As shown, the electrode assembly 20 includes a plurality of wound electrodes, and the electrode assembly 20 includes a straight region 23 and a bend region 24 connected to the end of the straight region 23.

[0129] 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 curved region 24 refers to the portion of the electrode sheet extending along an arc 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. Within the flat region 23, the extending direction of the electrode sheet is the length direction of the flat region 23. Figure 5 As shown, within the straight section 23, the left and right ends of the straight section 23 are the turning sections 24.

[0130] like Figure 6 As shown, electrode assembly 120 includes multiple electrode sheets arranged in layers, and electrode assembly 20 has a flat region 23.

[0131] Multiple electrode sheets arranged in a stacked manner, such as at least one positive electrode sheet 21 and at least one negative electrode sheet 22, are stacked to form an electrode assembly 20. The flat region 23 is formed by stacking at least a portion of the positive electrode sheet 21 and the negative electrode sheet 22, or it can be formed by stacking at least a portion of the positive electrode sheet 21 and the negative electrode sheet 22. The extension direction of the electrode sheets in the flat region 23 is the length direction of the flat region 23.

[0132] Please refer to Figures 7-20 , Figures 7-12 The diagram shows some of the individual battery cells in this application; Figures 13-20 This application includes schematic diagrams of some pressure relief mechanisms; combined with Figures 3-20As shown, the battery cell 100 according to an embodiment of this application includes: an electrode assembly 20, the electrode assembly 20 including at least one positive electrode 21, at least one negative electrode 22 and at least one separator 25, the separator 25 being used to isolate the positive electrode 21 and the negative electrode 22, the electrode assembly 20 including 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 being stacked in the flat region 23 along a first direction F1.

[0133] 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 first direction F1. Therefore, the expansion and deformation of the electrode assembly 20 is particularly obvious in the first direction F1.

[0134] 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 straight region 23 and a bend region 24. The straight region 23 refers to the part of the electrode extending along the plane after winding. The electrode assembly 20 is stacked in the straight region 23. The bend region 24 refers to the part of the electrode extending along the arc surface after winding. The outer surface of the bend region 24 is at least partially arc surface. The straight region 23 connects the two bend regions 24. In the straight region 23, the positive electrode 21, the negative electrode 22 and the separator 25 are stacked along the first direction F1. 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 first direction F1. Therefore, the expansion deformation of the electrode assembly 20 is particularly obvious in the first direction F1.

[0135] The positive electrode 21 includes a positive electrode body and a positive electrode tab. The positive electrode tab protrudes from the positive electrode body in the second direction F2. Most or all of the positive electrode body is coated with positive active material. Most or all of the positive electrode tab is not coated with positive active material. A small amount of insulating layer may be coated on the edge of the positive electrode body.

[0136] Correspondingly, the negative electrode sheet 22 includes a negative electrode body and a negative electrode tab. The negative electrode tab protrudes from the negative electrode body in the second direction F2. Most or all of the negative electrode body is coated with negative electrode active material, while most or all of the negative electrode tab is not coated with negative electrode active material.

[0137] The battery cell 100 also includes a housing 10 for accommodating the electrode assembly 20. The housing 10 includes a first wall portion 11 located on one side of the electrode assembly 20 in a second direction F2, where the first direction F1 and the second direction F2 are perpendicular to each other.

[0138] The battery cell 100 also includes a pressure relief mechanism 40, which is disposed on the first wall portion 11. The pressure relief mechanism 40 is provided with a groove 402, which defines a pressure relief portion 43. At least a portion of the pressure relief portion 43 opens when the battery cell 100 is depressurized.

[0139] Combination Figure 7 As shown, the outer casing 10 includes a first wall portion 11 and two second wall portions 12. The two second wall portions 12 are located on both sides of the electrode assembly 20 in the first direction F1. Most of the expansion of the electrode assembly 20 will act on the second wall portions 12. The first wall portion 11 is located on one side of the electrode assembly 20 in the second direction F2. The second direction F2 is perpendicular to the first direction F1. The thickness direction of the first wall portion 11 is the second direction F2. A pressure relief mechanism 40 is provided on the first wall portion 11.

[0140] The pressure relief mechanism 40 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 in the battery cell 100.

[0141] The pressure relief section 43 is also provided with a buffer section 45 that arches along the second direction F2 toward the side closer to and / or away from the electrode assembly 20.

[0142] Combination Figures 8-20 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 first direction F1, 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 first direction F1. The buffer portion 45 can store a certain deformation space to absorb the tensile deformation in the first direction F1, thereby giving the buffer portion 45 buffering performance.

[0143] 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. As a result, 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 402, and thus reducing the probability of the groove 402 being pulled and damaged, resulting in leakage.

[0144] The buffer portion 45 is disposed on the pressure relief portion 43. On the one hand, it makes full use of the space on the pressure relief portion 43, which is conducive to increasing the size of the buffer portion 45 and improving the buffering performance of the buffer portion 45. On the other hand, it facilitates the manufacturing and forming of the buffer portion 45. The buffer portion 45 can be manufactured and formed by stamping process. Compared with the buffer portion 45 being disposed on the outside of the pressure relief portion 43, the pressure relief portion 43 has more space to facilitate the forming of the buffer portion 45. In some examples, the pressure relief mechanism 40 and the first wall portion 11 are separately disposed, and the thickness of the first wall portion 11 is greater than the thickness of the pressure relief mechanism 40. By forming the buffer portion 45 on a component that is thinner than the wall portion 11, it is easier to manufacture and form the buffer portion 45. At the same time, the buffer portion 45 is easier to deform, thereby improving the buffering performance of the buffer portion 45. In addition, the buffer portion 45 is formed on the pressure relief mechanism 40 and then installed on the first wall portion 11, which can also reduce the impact of the buffer portion 45 on the wall portion and ensure the strength and reliability of the wall portion to a certain extent.

[0145] In the technical solution of this application embodiment, by providing a buffer part 45 on the pressure relief part 43, during the long-term use of the battery cell 100, the buffer part 45 can absorb the tensile deformation transmitted to the pressure relief mechanism 40, thereby reducing the expansion force acting on the groove 402, reducing the tensile force on the groove 402, and the buffer part 45 plays a buffering role, thereby reducing the probability of the groove 402 being pulled and damaged, resulting in leakage, and improving the service life and reliability of the battery cell 100.

[0146] like Figures 10-11 As shown, in some embodiments, along the thickness direction of the first wall portion 11, i.e. the second direction F2, the first wall portion 11 has a first outer surface 1102 and a first inner surface 1101. The first inner surface 1101 is closer to the electrode assembly 20 relative to the first outer surface 1102. The buffer portion 45 includes a first buffer portion 45a, which arches towards the side closer to the electrode assembly 20 and does not protrude from the first inner surface 1101.

[0147] like Figure 10As shown, the first buffer portion 45a is located between the first inner surface 1101 and the first outer surface 1102. Thus, the buffer portion 45 does not occupy the space outside the battery cell 100, which facilitates the placement of the battery cell 100. The buffer portion 45 also does not occupy the space inside the housing 10, which avoids interference with the electrode assembly 20 or occupying the space of the electrode assembly 20, thus avoiding an excessive reduction in the energy density of the battery cell 100.

[0148] like Figure 11 As shown, in some embodiments, in the thickness direction of the first wall portion 11, 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 first wall portion 11, the farthest portion of the inner buffer surface 4501 relative to the outer buffer surface 4502 being flush with the first inner surface 1101.

[0149] like Figure 11 , Figure 19 , Figure 20 As shown, the buffer portion 45 has an inner buffer surface 4501, as Figure 20 As shown, the inner buffer surface 4501 is an arc surface. In the second direction F2, the highest point of the arc surface and the first inner surface 1101 can be located at the same height, as shown. Figure 11 As shown, the inner buffer surface 4501 is a bent plane. In the second direction F2, the highest point of the plane is at the same height as the first inner surface 1101. This maximizes the arching of the buffer part 45, improves the utilization rate in the thickness direction of the first wall part 11, 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.

[0150] like Figures 10-12 As shown, the housing 10 is provided with an insulating member 70, which is located between the first wall portion 11 and the electrode assembly 20. The insulating member 70 defines a relief groove 71 that opens toward the first wall portion 11, and the relief groove 71 corresponds to the position of the buffer portion 45.

[0151] The insulating component 70 is located between the first wall portion 11 and the electrode assembly 20. The insulating component 70 can block the direct contact between the electrode assembly 20 and the first wall portion 11, reducing the risk of electrochemical corrosion. At the same time, the insulating component 70 also provides support for 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.

[0152] 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.

[0153] 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.

[0154] like Figure 12 As shown, in some embodiments, along the thickness direction of the first wall portion 11, the first wall portion 11 has a first outer surface 1102 and a first inner surface 1101. The first inner surface 1101 is closer to the electrode assembly 20 relative to the first 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 first inner surface 1101 and extends into the relief groove 71.

[0155] like Figure 12 As shown, the insulating member 70 is located between the first inner surface 1101 and the electrode assembly 20, and a portion of the buffer portion 45 is located inside the outer casing 10. This allows full utilization of the space of the insulating member 70, maximizing the arching of the buffer portion 45, improving the utilization rate in the thickness direction of the first wall portion 11, and enhancing 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.

[0156] In some embodiments, along the thickness direction of the first wall portion 11, the first wall portion 11 has a first outer surface 1102 and a first inner surface 1101, the first inner surface 1101 being closer to the electrode assembly 20 relative to the first 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 first outer surface 1102.

[0157] like Figure 19 As shown, the thickness direction of the first wall portion 11 is the second direction F2. In the second direction F2, the first wall portion 11 has a first outer surface 1102 and a first 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 first outer surface 1102 near the first inner surface 1101. The first outer surface 1102 of the first wall portion 11 is part of the outer surface of the entire housing 10. The buffer portion 45b is located inside the first outer surface 1102, so the second buffer portion 45b will not protrude from the entire outer surface 10. The outer surface of the outer casing 10 avoids occupying the space outside the battery cell 100, thus 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 first wall part 11 can be the bottom wall of the battery cell 100, and the battery cell 100 can be supported in the casing 100 by the first wall part 11. The second buffer part 45b is located inside the first outer surface 1102, which can avoid the problem that the first wall part 11 cannot fit in close to the inside of the casing 100, thus affecting the placement stability of the battery cell 100.

[0158] like Figure 19 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 first direction F1.

[0159] like Figure 19As shown, the buffer portion 45 is arranged symmetrically with respect to the pressure relief portion 43. The second buffer portion 45b is located outside the first buffer portion 45a. The sidewall of the second buffer portion 45b is connected to the sidewall of the first buffer portion 45a and has the same inclination angle. The first buffer portion 45a arches towards one side in the second direction F2, and the second buffer portion 45b arches towards the other side in the second direction F2. In the second direction F2, the first wall portion 11 has a first inner surface 1101 and a first outer surface 1102. Normally, the pressure relief mechanism 40 relieves pressure... The pressure part 43 is located between the first inner surface 1101 and the first outer surface 1102. There is a certain space between the pressure relief part 43 and the first inner surface 1101, and there is a certain space between the pressure relief part 43 and the first outer surface 1102. By setting two buffer parts, the inner and outer spaces can be fully utilized, increasing the deformability of the buffer part 45, improving the buffer performance of the buffer part 45, reducing the probability of the groove 402 being pulled and broken, leading to leakage, and improving the service life and reliability of the battery cell 100.

[0160] Furthermore, in the first direction F1, a portion of the first buffer portion 45a is located on one side of the second buffer portion 45b. The expansion deformation of the electrode assembly 20 is particularly noticeable in the first direction F1. The two buffer portions 45 are arranged in the first direction F1, which can absorb the tensile deformation in the first direction F1 as much as possible, thereby reducing the expansion force acting on the groove 402, and thus reducing the probability of the groove 402 being torn and damaged, resulting in leakage.

[0161] 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, with the first direction F1, the second direction F2 and the third direction F3 being perpendicular to each other.

[0162] like Figure 15 and Figure 16 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 an annular shape 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 402 is located, reduce the probability of the groove 402 being stretched and damaged, resulting in leakage, and improve the service life and reliability of the battery cell 100.

[0163] like Figure 17 As shown, in some embodiments, the pressure relief part 43 includes a body 431, and the buffer part 45 includes a bottom wall 452 and a side wall 451 surrounding the outer periphery of the bottom wall 452, the side wall 451 being connected to the body 431.

[0164] like Figure 17 As shown, the groove 402 is located at the edge of the body 431, and the buffer part 45 is located in the middle of the body 431. The buffer part 45 includes a bottom wall 452 and multiple side walls 451, each of which is connected to the body 431. Figure 19 As shown, the buffer section 45 includes multiple buffer sections. The sidewall 451 of the outermost buffer section is connected to the body 431, and the sidewalls 451 of the other buffer sections 45 can be connected to the sidewalls of adjacent buffer sections 45.

[0165] The buffer part 45 is constructed as a groove structure with a bottom wall and side walls. On the one hand, it facilitates the manufacturing and forming of the buffer part 45, and on the other hand, it facilitates the control of the width and thickness dimensions of the buffer part 45, thereby improving the manufacturing qualification rate. Furthermore, it can increase the size of the arched part of the buffer part 45, thereby improving the buffering effect of the buffer part 45.

[0166] like Figure 17 As shown, in some embodiments, the included angle between the sidewall 451 of the buffer portion 45 and the body 431 is α, where 100°≤α≤170°.

[0167] like Figure 17 As shown, the sidewall 451 of the buffer part 45 extends inclinedly to the body 431, forming an obtuse angle α between them. If α is too small, stress concentration is likely to occur at the connection between the sidewall 451 and the body 431. If α is too large, the height of the arch of the buffer part 45 will be too small, the deformation capacity of the buffer part 45 will be weaker, and the buffering effect will be affected. Therefore, α can be limited to between 100° and 170°. α can be any point value of 100°, 110°, 120°, 130°, 140°, 150°, 160°, and 170°, or any value between two of them.

[0168] This can reduce the stress concentration at the buffer section 45, improve the buffer performance of the buffer section 45, and reduce the probability of fatigue cracking at the groove 402 of the pressure relief mechanism 40.

[0169] In some embodiments, 120° ≤ a ≤ 150°. a can be any one of 120°, 125°, 130°, 135°, 140°, 145°, or 150°, or a range between any two. This can further reduce the stress concentration at the buffer section 45, improve the buffering performance of the buffer section 45, and reduce the probability of fatigue cracking at the groove 402 of the pressure relief mechanism 40.

[0170] like Figure 17 As shown, in some embodiments, the thickness of the sidewall 451 of the buffer portion 45 is D1, and the thickness of the body 431 is D2, satisfying: 0≤D1-D2≤0.3mm.

[0171] During the manufacturing process of the buffer part 45, the buffer part 45 can be formed by stamping. During the stamping process, there is stress concentration in the side wall area of ​​the buffer part 45, which is prone to stamping cracking. If the thickness of the side wall 451 formed by stamping is smaller, the stress concentration of the buffer part 451 during the stamping process is greater, the risk of stamping cracking is higher, and the process yield is lower. Therefore, by controlling the process, the thickness of the side wall 451 should be controlled to be greater than the thickness of the pressure relief part 431 as much as possible.

[0172] However, if the thickness difference between the sidewall 451 of the buffer section 45 and the body 431 is greater, the thickness of the sidewall 451 will be greater, the stiffness of the sidewall 451 will be too large, the buffering effect of the buffer section 45 will be poor, and the risk of fatigue cracking of the battery cell 100 during long-term use will be higher.

[0173] Therefore, the difference between the thickness D1 of the sidewall 451 of the buffer section 45 and the thickness D2 of the body 431 is limited to between 0 and 0.3 mm. D1-D2 can be any one of 0, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, or 0.3 mm, or any range between the two.

[0174] This facilitates the manufacturing and molding of the buffer section 45, ensuring manufacturing yield, and also improves the buffering effect of the buffer section 45. When the electrode assembly 20 expands, the buffer section 45 undergoes a certain deformation, absorbing at least part of the expansion force of the electrode assembly 20, reducing the expansion force acting on the groove 402, reducing the probability of the groove 402 being torn and damaged, leading to leakage, and improving the service life and reliability of the battery cell 100.

[0175] like Figure 17 As shown, in some embodiments, 0.2mm≤D1≤0.6mm, 0.15mm≤D2≤0.4mm.

[0176] If the thickness D1 of the sidewall 451 of the buffer part 45 is too small, the stiffness of the buffer part 45 will be too small, and stress concentration at the buffer part 45 will easily lead to damage during the manufacturing process, resulting in a low manufacturing yield. If the thickness D1 of the sidewall 451 of the buffer part 45 is too large, the stiffness of the sidewall 451 will be too large, the buffering effect of the buffer part 45 will be poor, and the risk of fatigue cracking of the battery cell 100 during long-term use will be higher.

[0177] Therefore, the thickness D1 of the sidewall 451 of the buffer section 45 is limited to between 0.2mm and 0.6mm. D1 can be any one of 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, and 0.6mm, or a range between any two.

[0178] This facilitates the manufacturing and forming of the buffer section 45, ensuring manufacturing yield, and also reduces the rigidity of the buffer section 45. When the electrode assembly 20 expands, the buffer section 45 undergoes a certain deformation, absorbing at least part of the expansion force of the electrode assembly 20, reducing the expansion force acting on the groove 402, reducing the probability of the groove 402 being torn and damaged, leading to leakage, and improving the service life and reliability of the battery cell 100.

[0179] Furthermore, if the thickness D2 of the body 431 is too large, the corresponding increase in the thickness of the buffer part 45 will result in excessive stiffness of the buffer part 45, poor buffering effect, and a higher risk of fatigue cracking of the battery cell 100 during long-term use. The smaller D2 is, the more the pressure relief part 43 can absorb some deformation, thereby increasing the number of fatigue crackings of the battery cell 100 during long-term use. If the thickness D2 of the body 431 is too small, it will easily affect the manufacturing yield of the groove 402. At the same time, if the pressure relief part 43 absorbs too much deformation, the stress concentration at the first groove section 411 will be too small, and the burst pressure at the first groove 41 will increase. When the battery cell 100 experiences thermal runaway, it is easy to burst open at the end cap weld, which will reduce reliability.

[0180] Therefore, the thickness D2 of the body 431 is limited to between 0.15mm and 0.4mm. D2 can be any one of 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, and 0.4mm, or a range between any two. This improves the manufacturing yield of the pressure relief mechanism 40, ensures the buffering effect of the buffer section 45, and reduces the stress concentration at the first groove section 411. When the electrode assembly 20 expands, the buffer section 45 undergoes a certain deformation, absorbing at least part of the expansion force of the electrode assembly 20, reducing the expansion force acting on the groove 402, lowering the probability of the groove 402 being torn and damaged, leading to leakage, and improving the service life and reliability of the battery cell 100.

[0181] In addition, it can prevent the pressure relief mechanism 40 from being too high during bursting. 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.

[0182] like Figure 10 and Figure 17 As shown, in some embodiments, along the direction close to and / or far from the electrode assembly 20, the maximum height dimension of the buffer portion 45 is H, and the thickness dimension of the first wall portion 11 is D3, satisfying: 1.5mm≤H+D3≤5mm.

[0183] In the second direction F2, the maximum height of the buffer section 45 is H, such as Figure 17As shown, the buffer part 45 is a structure with uniform thickness. In the vertical direction, both the upper and lower surfaces of the buffer part 45 arch downwards. In the vertical direction, the maximum height distance between the highest and lowest points of the upper surface is the same as the maximum height distance between the highest and lowest points of the lower surface. This maximum height distance is the maximum height H of the buffer part 45. Of course, if the buffer part 45 is a structure with non-uniform thickness, the larger of the maximum height distance between the highest and lowest points of the upper surface and the maximum height distance between the highest and lowest points of the lower surface is the maximum height H of the buffer part 45.

[0184] like Figure 10 As shown, in the second direction F2, the thickness of the first wall 11 is D3. When D3 is smaller, the stiffness of the first wall 11 is smaller, the deformation of the first wall 11 during long-term use of the battery cell 100 is greater, and the deformation borne by the pressure relief mechanism 40 is greater. At this time, the buffer part 45 needs more height to absorb the larger deformation and prevent fatigue cracking at the groove 402. Therefore, H+D3 has a minimum value. When D3 is larger, the stiffness of the first wall 11 is greater, the deformation of the first wall 11 during long-term use of the battery cell 100 is smaller, the deformation borne by the pressure relief mechanism 40 is smaller, and the requirement for the deformation resistance of the buffer part 45 is smaller. At the same time, when D3 is larger, the space utilization rate of the battery cell 100 is lower. At this time, the height of the buffer part 45 needs to be reduced to prevent the battery space utilization rate from being too small. Therefore, H+D3 has a maximum value.

[0185] Therefore, H+D3 is limited to the range of 1.5mm-5mm. H+D3 can be any point value among 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, and 5mm, or a range between any two.

[0186] This ensures the buffering effect of the buffer section 45. When the electrode assembly 20 expands, the buffer section 45 undergoes a certain deformation, absorbing at least part of the expansion force of the electrode assembly 20, reducing the expansion force acting on the groove 402, and reducing the probability of the groove 402 being torn and damaged, leading to leakage. It also improves the space utilization of the battery cell 100 and ensures the energy density of the battery cell 100 to a certain extent.

[0187] like Figure 10 As shown, in some embodiments, the following condition is satisfied: 0.8mm≤D3≤3mm.

[0188] If D3 is smaller, the stiffness of the first wall 11 is too small, the deformation of the first wall 11 of the battery cell 100 during long-term use is greater, the deformation of the pressure relief mechanism 40 is greater, and the groove 402 is more prone to fatigue cracking. If D3 is larger, the space utilization of the battery cell 100 is lower, and the space utilization of the battery cell 100 is too small.

[0189] Therefore, D3 is limited to the range of 0.8mm-3mm. D3 can be any single value or a range between any two of the following: 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, and 3mm. This ensures the energy density of the battery cell 100 to a certain extent while reducing the probability of fatigue cracking at the groove 402, thus improving the reliability of the battery cell 100.

[0190] like Figure 17 As shown, in some embodiments, the maximum height dimension of the buffer portion 45 along the direction close to and / or far from the electrode assembly 20 is H, satisfying: 0.2mm≤H≤3mm.

[0191] like Figure 17 As shown, in the second direction F2, the maximum height of the buffer part 45 is H. If H is too large, on the one hand, the buffer part 45 protrudes from the wall of the outer casing 10, thus occupying the internal space of the battery cell 100 in the second direction F2, thereby affecting the space of the electrode assembly 20, or protruding from the wall of the outer casing 10 and affecting the placement of the battery cell 100, resulting in a decrease in the energy density of the battery cell 100. On the other hand, in the manufacturing process, the stamping of the buffer part 45 requires stretching the parts around the buffer part 45. The greater the height of the buffer part 45, the more it stretches the parts around the buffer part 45. For the buffer part 45 and the groove 402 located on the same structural component, it is easy to cause the groove to become thinner and harder, thus making it easier for the battery cell 100 to break and leak during use. On the other hand, if H is too small, the less deformable space the buffer part 45 has, the limited ability of the buffer part 45 to absorb the expansion force of the electrode assembly 20, thus making the groove 402 easy to be stretched and broken when the electrode assembly 20 expands.

[0192] Therefore, H can be limited to between 0.2mm and 3mm. H can be any point value or a range between any two of the following: 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, and 3mm.

[0193] Therefore, it is convenient to manufacture the buffer part 45 without causing a significant impact on other structural components. At the same time, the buffer part 45 can undergo a certain deformation when the electrode assembly 20 expands, absorbing at least part of the expansion force of the electrode assembly 20, thereby reducing the expansion force acting on the groove 402, reducing the probability of the groove 402 being pulled and damaged, leading to leakage, and improving the service life and reliability of the battery cell 100.

[0194] In some embodiments, 0.3mm≤H≤2mm, where H can be any one of the following values ​​or a range between any two: 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, and 2mm.

[0195] This further facilitates the manufacturing and molding of the buffer part 45. At the same time, the buffer part 45 can undergo a certain deformation when the electrode assembly 20 expands, absorbing at least part of the expansion force of the electrode assembly 20, thereby reducing the expansion force acting on the groove 402, reducing the probability of the groove 402 being torn and damaged, leading to leakage, and improving the service life and reliability of the battery cell 100.

[0196] Combination Figures 13-18 As shown, in some embodiments, the pressure relief mechanism 40 further includes a mounting portion 44, which is disposed on the outer periphery of the pressure relief portion 43 and is connected to the first wall portion 11.

[0197] like Figure 14 As shown, the pressure relief mechanism 40 includes a mounting part 44 and a pressure relief part 43. The mounting part 44 is connected to the first wall part 11. The mounting part 44 can be integrally formed with the first wall part 11 or it can be separately set. The mounting part 44 is welded to the first wall part 11. The thickness of the pressure relief part 43 is less than the thickness of the mounting part 44. The mounting part 44 can be a structure of equal thickness, and the thickness of the pressure relief part 43 is less than the thickness of the mounting part 44. Alternatively, the mounting part 44 can be a structure of variable thickness, and the thickness of the pressure relief part 43 is less than the maximum thickness of the mounting part 44.

[0198] In some embodiments, the mounting portion 44 includes a first mounting section 441 and a second mounting section 442. The first mounting section 441 is disposed on the outer periphery of the second mounting section 442. The thickness of the pressure relief portion 43 is less than the thickness of the first mounting section 441, and the thickness of the second mounting section 442 is not greater than the thickness of the first mounting section 441.

[0199] The first mounting section 441 is connected to the first wall portion 11. The thickness of the second mounting section 442 can be approximately the same as the thickness of the pressure relief portion 43. That is, the outer periphery of the pressure relief portion 43 is connected to the first connecting section 441 through the second mounting section 442. The second mounting section 442 can also be of variable thickness. The thickness of the second mounting section 442 gradually decreases from the first mounting section 441 toward the pressure relief portion 43.

[0200] A portion of the pressure relief portion 43 arches towards the side closer to the electrode assembly 20 to form a buffer portion 45, and / or a portion of the pressure relief portion 43 arches away from the side further from the electrode assembly 20 to form a buffer portion 45. The buffer portion 45 can be a structure of equal thickness or a structure of variable thickness, wherein the thickness of the buffer portion 45 is greater than the maximum thickness at the groove 402.

[0201] The pressure relief section 43 is a thinned area of ​​the pressure relief mechanism 40, and the pressure relief section 43 is more prone to deformation. The buffer section 45 is set in the pressure relief section 43, so that the buffer section 45 can be deformed and stretched under the expansion force of the electrode assembly 20. At the same time, it can avoid the probability of the buffer section 45 being damaged due to its thinness being too small and the buffer section 45 being stretched, resulting in leakage. In addition, it ensures to a certain extent that the groove 402 is the weakest point of the entire pressure relief mechanism 40, so that when the internal pressure of the battery cell 100 reaches the threshold, the internal pressure of the battery cell 100 is released at a predetermined position, so as to achieve the purpose of pressure relief at a specific position.

[0202] In some embodiments, the electrode assembly 20 includes N1 units, 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 first direction F1, and the area of ​​the outer surface is S, where N1≥1, N2≥1, N1*N2≤500, and S≤80000mm². 2 .

[0203] 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 first direction F1, the greater the expansion and deformation of the electrode assembly 20, and the higher the risk of cracking and breakage of the groove 402 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 first direction F1 is limited to 80000 mm². 2 Or less than 80000mm 2Within 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 402 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.

[0204] 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 sheet 21 in the first direction F1 within the flat region 23 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 second direction F2 perpendicular to the first direction F1 and the length dimension M1 in the third direction F3.

[0205] like Figures 14-18 As shown, in some embodiments, the groove 402 includes a first groove 41, and 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 first direction F1, and the dimension of the bottom surface of the first groove segment 411 in the first direction F1 is A, which satisfies: 0.3mm≤A≤0.8mm.

[0206] 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 first direction F1, i.e., the extension direction of the first groove segment 411 is perpendicular to the first direction F1. Figure 14 As shown, the first groove segment 411 extends along the third direction F3, and the dimension A of the bottom surface of the first groove segment 411 in the first direction F1 is the width dimension of the bottom surface of the first groove segment 411. If the width A of the first groove segment 411 is too small, the ability of the first groove segment 411 to withstand deformation in the first direction F1 is weaker. 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. In this case, the buffer portion 45 needs to absorb more of the larger deformation to prevent fatigue cracking at the groove 402.

[0207] The increase in the width of the first groove 411 will correspondingly increase the burst pressure of the pressure relief mechanism 40, which will reduce the probability of the pressure relief mechanism 40 bursting and releasing pressure in time. When the battery cell 100 experiences thermal runaway, it is easy to burst open at the end cap weld, which will also reduce reliability.

[0208] Therefore, the bottom surface dimension A of the first groove segment 411 is limited to between 0.3mm and 0.8mm. A 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, and 0.8mm, or a range between any two.

[0209] Therefore, by cooperating with the bottom width of the first groove segment 411, the bottom width of the first groove segment 411 is increased to a certain extent, increasing the deformation resistance of the first groove segment 411. This reduces the deformation of the pressure relief mechanism 40 at the first groove segment 411 when the electrode assembly 20 expands, thereby relatively reducing the height of the protrusion of the buffer part 45 and lowering the probability of interference between the buffer part 45 and other components or affecting energy density. During long-cycle charge and discharge use, the battery cell 100 can avoid the risk of fatigue cracking of the pressure relief mechanism 40 to a certain extent, 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 can avoid excessive burst pressure of the pressure relief mechanism 40, and reduce the probability that the pressure relief mechanism 40 will not burst in time and will easily burst in other locations when the battery cell 100 experiences thermal runaway, further improving the reliability of the battery cell 100.

[0210] like Figure 18 As shown, in some embodiments, the minimum residual thickness of the first groove segment 411 is D4, which satisfies: 0.1mm≤D4≤0.28mm.

[0211] The smaller the minimum residual thickness D4 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. At this time, the buffer part 45 needs to absorb more of the larger deformation to prevent fatigue cracking at the groove 402 and avoid excessive reduction in the cycle number of the battery cell 100.

[0212] The larger the minimum residual thickness D4 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 D4 is too large, the burst pressure at the first groove 41 increases, which reduces the probability of the pressure relief mechanism 40 bursting and releasing pressure in time. When the battery cell 100 experiences thermal runaway, it is easy to burst at the end cap weld, which will also reduce reliability.

[0213] Therefore, the minimum residual thickness D4 of the first groove segment 411 is limited to between 0.1mm and 0.28mm. D4 can be any one of the following values ​​or a range between any two: 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.

[0214] This increases the minimum residual thickness of the first groove segment 411 to a certain extent, increases the deformation resistance of the first groove segment 411, and reduces the deformation of the pressure relief mechanism 40 at the first groove segment 411 when the electrode assembly 20 expands. This relatively reduces the height of the buffer part 45 that needs to protrude, and reduces the probability of the buffer part 45 interfering with other components or affecting energy density. During long-cycle charge and discharge use, the battery cell 100 can avoid the risk of fatigue cracking of the pressure relief mechanism 40 to a certain extent, reduce the probability of the pressure relief mechanism 40 being torn and damaged, leading to leakage, and improve the reliability of the battery cell 100. At the same time, it can avoid excessive burst pressure of the pressure relief mechanism 40. When the battery cell 100 experiences thermal runaway, it reduces the probability that the pressure relief mechanism 40 cannot burst in time and is prone to bursting in other locations, further improving the reliability of the battery cell 100.

[0215] like Figure 15 As shown, in some embodiments, the first groove 41 defines at least one predetermined pressure relief area, and the groove 402 further includes a second groove 42 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.

[0216] The predetermined pressure relief area can be the area formed by the pressure relief section 43. 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 to flip. That is, the second groove 42 helps the predetermined pressure relief area to flip, making it easier for the predetermined pressure relief area to flip to the outside of the battery cell 100, thereby quickly opening the predetermined pressure relief area. The second groove 42 can guide the complete flipping of the predetermined pressure relief area, or it can guide only a portion of the predetermined pressure relief area to flip.

[0217] 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 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 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.

[0218] 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.

[0219] By setting the second groove 42, the predetermined pressure relief zone can be guided to open, thereby improving the opening effect of the predetermined pressure relief zone 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.

[0220] In some embodiments, the residual thickness of the second groove 42 is greater than the residual thickness of the first groove 41.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] 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 first direction F1, 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, which facilitates the pressure relief mechanism 40 to preferentially open along the first groove 41 to achieve rapid opening of the predetermined pressure relief zone.

[0225] 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.

[0226] like Figure 15 As 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.

[0227] As an example, in Figure 15 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 connected to the two second groove segments 412 respectively, and the two ends of the second groove 42 are connected to the two second groove segments 412 respectively. 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 zone, that is, the predetermined opening boundary is surrounded by the outer edge of the orthographic projection of the first groove 41 and the second groove 42 in the second direction F2.

[0228] The first groove segment 411 and the second groove 42 extend along a straight trajectory, such as... Figure 15 As shown, the first groove segment 411 and the second groove 42 extend along the third direction F3. The second groove segment 412 can extend along a straight trajectory, such as along the first direction F1, thereby forming a square predetermined pressure relief area; the second groove segment 412 can also extend along an arc trajectory, thereby forming a racetrack-shaped predetermined pressure relief area.

[0229] 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 for pressure relief; at the same time, this structure is conducive to increasing the opening area of ​​the predetermined pressure relief area, increasing the pressure relief area of ​​the battery cell 100, and improving the pressure relief rate of the battery cell 100.

[0230] 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.

[0231] 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.

[0232] 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 can be opened more quickly.

[0233] 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.

[0234] Please refer to Figures 21-25 , Figures 21-25 This is a schematic diagram of the housing of some embodiments of this application, in conjunction with Figure 4 , Figure 7 and Figures 21-25 As shown, in some embodiments, the housing 10 includes: a housing 101 and an end cap 102. The housing 101 has an opening at at least one end along the second direction F2. The end cap 102 is connected to the housing 101 and is used to close the opening. A first wall portion 11 is formed in the housing 101. The housing 101 also includes a second wall portion 12. The second wall portion 12 is welded to the end cap 102 to form a first connecting portion 51. The second wall portion 12 includes a first region 111 and a second region 112 arranged along the second direction F2. The thickness of the first region 111 is greater than the thickness of the second region 112. The first region 111 is located between the first connecting portion 51 and the second region 112.

[0235] 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 be in various shapes, such as prism.

[0236] 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 10. For example, if housing 101 is a cuboid structure, end cap 102 can be a rectangular plate structure adapted to housing 10; or if housing 101 is a cylindrical structure, end cap 102 can be a circular plate structure adapted to housing 101. End cap 102 can also be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, or plastic. The materials of end cap 102 and housing 101 can be the same or different.

[0237] 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, with the two end caps 102 respectively closing the two openings of the housing 101, and the two end caps 102 and the housing 101 together defining the receiving space.

[0238] 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.

[0239] The housing 101 has a first wall portion 11 and a second wall portion 12. 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 it can be separately disposed from the housing 101. By disposing of the pressure relief mechanism 40 on the housing 101, the structure of the end cover 102 can be simplified. At the same time, it is convenient to shorten the distance between the pressure relief mechanism 40 and the main body of the electrode assembly 20. This shortens the path of the discharge medium to the pressure relief mechanism 40 during pressure relief and shortens the time for the discharge medium to reach the pressure relief mechanism 40, thereby improving the timeliness of pressure relief of the battery cell 100 and effectively improving the reliability of the battery cell 100.

[0240] The second wall portion 12 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 second wall portion 12. The first connecting portion 51 is the portion with weld marks formed after the end cap 102 and the second wall portion 12 are welded together; it can be the portion where the end cap 102 and the second wall portion 12 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 second wall portion 12. The second wall portion 12 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.

[0241] By increasing the width of the first groove 411, the burst pressure of the pressure relief mechanism 40 will be increased accordingly. Since the housing 101 and the end cap 102 are welded together, as the burst pressure increases, the probability of the weld joint breaking when the battery cell 100 thermally runs away increases, causing the weld joint between the housing 101 and the end cap 102 to crack. Therefore, the second wall 12 is designed to be thickened.

[0242] Specifically, the second wall portion 12 includes a first region 111 and a second region 112 arranged along the second direction F2. 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 second wall portion 12 is increased, and the first region 111 is thicker than the second region 112.

[0243] The second region 112 has a second inner surface 1121 facing the interior space of the housing 101 and a second outer surface 1122 facing away from the interior space of the housing 101. The first region 111 may partially protrude from the second inner surface 1121 and / or the second outer surface 1122. As an example, in Figure 23 In the illustrated embodiment, the first region 111 has a first protrusion 1111, which partially protrudes from the second inner surface 1121. The outer surface of the first region 111 is coplanar with the second outer surface 1122, and the height of the first protrusion 1111 is the thickness difference t between the two regions. Figure 24 In the illustrated embodiment, the first region 111 has a second protrusion 1112 that protrudes beyond the second outer surface 1122. The inner surface of the first region 111 is coplanar with the second inner surface 1121, and the height of the second protrusion 1112 is equal to the thickness difference t between the two regions. Figure 25In the illustrated embodiment, the first region 111 has a first protrusion 1111 and a second protrusion 1112. The first protrusion 1111 protrudes partially from the second inner surface 1121, and the height of the first protrusion 1111 is t1. The second protrusion 1112 protrudes from the second outer surface 1122, and the height of the second protrusion 1122 is t2. The thickness difference t between the first region 111 and the second region 112 is t1 + t2.

[0244] In other words, the second wall portion 12 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 connecting portion 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 second wall portion 12, a significant reduction in the energy density of the battery cell 100 can be avoided.

[0245] like Figures 22-25 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, preferably 0.2mm≤t≤0.5mm.

[0246] The first region 111 can be a structure with variable thickness, and the thickness of the first region 111 is the maximum thickness E1 of the first region 111. The second region 112 is a structure with uniform thickness, and the thickness of the second region 112 is E2. 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 E1 of the first region 111 and the thickness E2 of the second region 112, that is, t = E1 - E2.

[0247] 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 connecting part 51. 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 second wall part 12. 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.

[0248] This not only improves the strength of the area near the first connection part 51, increases the burst pressure at the weld between the housing 101 and the end cap 102, and reduces 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.

[0249] 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 molding of the housing 101.

[0250] In some embodiments, the maximum thickness of the first region 111 is E1, satisfying: 0.5mm ≤ E1 ≤ 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.

[0251] 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.

[0252] In some embodiments, the maximum thickness of the second region 112 is E2, satisfying: 0.4mm ≤ E2 ≤ 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.

[0253] like Figures 23-25 As shown, in some embodiments, the first region 111 includes a first portion 111a and a second portion 111b arranged along the second direction F2. 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.

[0254] like Figures 23-25As 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 equivalent 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 second wall 12, and also strengthens the second wall 12. This improves the structural strength of the first region 111, 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.

[0255] 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 second wall portion 12 near the first connection portion 51.

[0256] like Figure 21 As shown, in some embodiments, the first wall portion 11 has a pressure relief hole 103, and a pressure relief mechanism 40 is installed in the pressure relief hole 103. The area of ​​the pressure relief hole 103 projected along the second direction F2 is W, which is 400 mm². 2 ≤W≤1400mm 2 .

[0257] like Figure 13 and Figure 21 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 first wall portion 11 by means of bonding, welding, etc. The first wall portion 11 is provided with a pressure relief hole 103. The pressure relief mechanism 40 is installed in the pressure relief hole 103. 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 103, and the discharge medium inside the battery cell 100 is discharged through the pressure relief hole 103 to release the pressure inside the battery cell 100.

[0258] like Figure 13As 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 that of the first wall portion 11. The explosion-proof sheet covers the pressure relief hole 103 and is welded to the first wall portion 11. 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 103 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.

[0259] The larger the area of ​​the pressure relief hole 103, the thinner the first wall 11, 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 103, 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.

[0260] Therefore, the area W of the pressure relief hole 103 projected along the second direction F2 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 2 1300mm 2 1400mm 2 The value of any one of the points or the range between any two.

[0261] 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.

[0262] Among them, with Figure 21 Taking the runway-shaped pressure relief vent 103 as an example, the size of the pressure relief vent 103 in the first direction F1 is B, and the size of the pressure relief vent 103 in the third direction F3 is L, W=N*L+(ΠN) 2 ) / 4.

[0263] In some examples, 600mm 2 ≤W≤1200mm 2 That is, the area W of the pressure relief hole 103 can be 600 mm². 2700mm 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.

[0264] 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.

[0265] In some embodiments, the pressure relief mechanism 40 is integrally formed with the wall of the housing 10. By integrally forming the pressure relief part 40 with the first wall 11, the reliability of the pressure relief part 40 can be improved, the connection process between the pressure relief part 40 and the first wall 11 can be eliminated, and the manufacturing cost of the battery cell 100 can be reduced; the redundant part 50 can be integrally formed on the wall of the housing 10 by a stamping process, which is simple to manufacture and has low cost.

[0266] 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 a first direction F1.

[0267] As an example, the positive electrode 21 and the negative electrode 22 in the electrode assembly 20 are arranged alternately along the first direction F1, and an insulating element is provided between the positive electrode 21 and the negative electrode 22.

[0268] In this embodiment, the electrode assembly 20 is a stacked electrode assembly, which has a more compact structure and stronger resistance to compression.

[0269] 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.

[0270] As an example, the negative electrode 22 has one more electrode than the positive electrode 21.

[0271] 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.

[0272] like Figure 5As shown, in some embodiments, the electrode assembly 20 is a wound structure, and the electrode assembly 20 also has a corner area. The straight area 23 is provided with a corner area at least at one end along the third direction F3. At least part of the outer surface of the corner area is an arc surface. The first direction F1, the second direction F2 and the third direction F3 are not coplanar and intersect each other.

[0273] 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.

[0274] 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.

[0275] 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 first direction F1, 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.

[0276] In this embodiment, the electrode assembly 20 is a wound electrode assembly, which has a relatively simple manufacturing process and low cost.

[0277] like Figure 7 As shown, in some embodiments, the first wall portion 11 is used to support the electrode assembly 20, and the first wall portion 11 is located below the electrode assembly 20.

[0278] 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 can be connected to the pressure relief mechanism 40. In the event of thermal runaway of the battery cell 100, the high-temperature and high-pressure flue gas can be discharged through the pressure relief mechanism 40 at the bottom into the exhaust channel and then discharged to the outside.

[0279] In some embodiments, please refer to Figure 26 , Figure 26 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 second direction F2. 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.

[0280] 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 second direction F2, 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.

[0281] 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.

[0282] 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.

[0283] In some embodiments, the first wall portion 11 is made of aluminum alloy, and the housing 101 of the outer shell 10 has the same material as the first wall portion. Here, the aluminum alloy can be tri-series aluminum, thereby giving the housing 101 advantages such as lightweight, safety, ease of processing and good corrosion resistance.

[0284] 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, 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.

[0285] 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; the energy density is increased, the expansion force is not too large, and the damage, cracking and leakage caused by the expansion and deformation of the electrode assembly at the groove are reduced.

[0286] In some embodiments, 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, 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 .

[0287] 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 fmm². 2 The electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). The assembled semi-coin cells are then left to stand for 3 hours. The test is carried out at 25°C. Lithium insertion is performed by discharging at 0.1C in the voltage range of 2V-0V, followed by lithium extraction by charging at 0.05C to 2V. This cycle is repeated twice. The discharge capacity of the second cycle is recorded as ZmAh. The actual battery design has a negative electrode length of hmm and a width of imm. The number of surfaces of the negative electrode active material coated on the negative electrode current collector is d. Therefore, the lithium insertion capacity of the negative electrode is Z / f*h*i*d.

[0288] 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. 22.1mAh / 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 2 3.2mAh / 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.

[0289] 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 at the groove.

[0290] In some embodiments, the thickness of the negative electrode film is T1, where 9 μm ≤ T1 ≤ 75 μm. T1 can be selected from 9 μm to 75 μm. The thickness T1 of the negative electrode film can be any one of 9 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, and 75 μm, or a range between any two.

[0291] The battery 1000 according to the second aspect of this application includes the battery cell 100 according to the first aspect of this application. By using the battery cell 100, the risk of fatigue cracking can be reduced to a certain extent. At the same time, when the battery cell 100 experiences thermal runaway, the pressure relief mechanism 40 can promptly burst and release the internal air pressure of the battery cell 100, thereby improving the reliability of the battery.

[0292] The electrical device 2000 according to a third aspect embodiment of this application includes a 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.

[0293] Optionally, such as Figure 1 As 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.

[0294] The following describes a specific embodiment of a battery 1000 and a vehicle having the same, in conjunction with the accompanying drawings.

[0295] 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 3 As shown, each battery cell 100 includes a housing 10 and two electrode assemblies 20. The housing 10 is provided with an electrical connection part 30 and a pressure relief mechanism 40, which are located on different sides of the housing 10. The electrode assemblies 20 are arranged inside the housing 10.

[0296] The housing 10 has a first wall portion 11 and two second walls portion 12. The first wall portion 11 is located on one side of the electrode assembly 20 in the second direction F2, and the two second walls portion 12 are located on both sides of the electrode assembly 20 in the first direction F1. The first wall portion 11 has a first outer surface 1102 and a first inner surface 1101. The first inner surface 1101 is closer to the electrode assembly 20 relative to the first outer surface 1102.

[0297] The first wall portion 11 is provided with a pressure relief hole 103, and the pressure relief mechanism 40 can be installed at the pressure relief hole 103 of the first wall portion 11 by means of welding or other methods. Figure 8As shown, the pressure relief mechanism 40 is a component independent of the housing 10. The pressure relief mechanism 40 and the housing 10 can be manufactured and reassembled separately. The outer side of the pressure relief mechanism 40 can also be provided with a patch 60, which cooperates with the housing 10 to protect the pressure relief mechanism 40.

[0298] The second wall portion 12 includes a first region 111 and a second region 112 arranged along the second direction F2, wherein the thickness of the first region 111 is greater than the thickness of the second region 112.

[0299] like Figure 15 As shown, the pressure relief mechanism 40 is provided with a scoring groove 402. Specifically, the scoring groove 402 includes a first scoring groove 41 and a second scoring groove 42. The first scoring groove 41 includes a first groove segment 411 and two second groove segments 412. The first groove segment 411 and the second scoring groove 42 are arranged opposite to each other and extend along the third direction F3 respectively. The two second groove segments 412 are arranged opposite to each other and form an arc-shaped groove. The two ends of each first groove segment 411 are connected to the two second groove segments 412 respectively. The residual thickness at the first scoring groove 41 is less than the residual thickness at the second scoring groove 42.

[0300] like Figure 15 As shown, the groove 402 defines a pressure relief section 43, at least a portion of which can open when the battery cell is depressurized. A portion of the pressure relief section 43 arches towards the side near the electrode assembly 20 to form a buffer section 45. The pressure relief mechanism 40 also includes a mounting section 44 connected to the first wall section 11. The buffer section 45 includes a side wall 451 and a bottom wall 452. The pressure relief section 43 includes a body 431, the side wall 451 is connected to the body 431, and the included angle α between the side wall 451 and the body 431 is between 100° and 170°. The surface of the bottom wall 452 near the electrode assembly 20 is flush with the first inner surface 1101 of the first wall section 11.

[0301] 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.

[0302] Example 1

[0303] 1) Preparation of positive electrode sheet

[0304] 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.

[0305] 2) Preparation of negative electrode sheet

[0306] 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.

[0307] 3) Preparation of electrolytes

[0308] 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.

[0309] 4) Isolation components

[0310] A 16μm polyethylene film was used as the separator.

[0311] 5) Lithium-ion battery manufacturing

[0312] 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.

[0313] 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 .

[0314] The thickness of the first wall portion is D3, where D3 = 1.5 mm. The first wall portion has a pressure relief hole, and the area of ​​the pressure relief hole projected along the second direction F2 is W, where W = 860 mm². 2 The pressure relief mechanism has a buffer section that arches towards the electrode assembly. The height of the buffer section is 1 mm. The angle between the sidewall of the buffer section and the body of the pressure relief section is 130°. The sidewall of the buffer section and the body of the pressure relief section have the same thickness. The width of the first groove section in the first direction F1 is A, where A is 0.3 mm. The minimum residual thickness of the first groove section is D4, where D4 is 0.18 mm. The thickness of the first region of the second wall section is greater than the thickness of the second region, and the thickness difference t between the first and second regions is 0.1 mm.

[0315] The method for measuring the fatigue cycles of a single battery cell is as follows:

[0316] 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.

[0317] 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.

[0318] 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.

[0319] 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.

[0320] 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".

[0321] Specifically, test according to the following steps:

[0322] a) Discharge to 2.8V with a current of 1I1(A);

[0323] b) Let it rest for no less than 30 minutes;

[0324] 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";

[0325] d) Let it rest for no less than 30 minutes;

[0326] e) Discharge to 2.8V with a current of 1I1(A);

[0327] f) Repeat steps b) to e) until the groove of the pressure relief mechanism breaks, then stop the test.

[0328] 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.

[0329] The method for testing the thermal runaway of a single battery cell is as follows:

[0330] 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%).

[0331] 2) Before testing, charge each battery cell to 100% SOC and ensure that the temperature of each battery cell is 25±5℃.

[0332] 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.

[0333] 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.

[0334] 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.

[0335] 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.

[0336] 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.

[0337] The battery cell preparation methods in Examples 2-4 are the same as those in Example 1, except that the value of A and the thickness difference t between the first and second regions are shown in Table 1. The number of cycles (i.e., the number of fatigue cycles of the battery cell) and the thermal runaway of the battery cell 100 when leakage occurs in the pressure relief mechanism 40 are characterized by the batteries obtained in Examples 1-4. The characterization results are shown in Table 1.

[0338] Table 1

[0339] serial number A(mm) t(mm) Technical effect Example 1 0.3 0.1 Fatigue count 1321, end cap and shell welds normal. Example 2 0.55 0.2 Fatigue count 1555, end cap and shell welds normal. Example 3 0.66 0.5 Fatigue count 2354, end cap and shell welds normal. Example 4 0.8 0.7 Fatigue count 2627, end cap and shell welds normal.

[0340] Based on the data from Examples 1-4, it can be seen that when A is between 0.3mm and 0.8mm, and the thickness difference t between the first and second regions is between 0.1mm and 0.7mm, the fatigue cycle of the battery cell will not be too low, which can meet the life requirements. It can also improve the strength of the end cap and the casing weld, and reduce the risk of cracking at the end cap and casing weld during thermal runaway.

[0341] 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: An electrode assembly includes at least one positive electrode, at least one negative electrode, and at least one separator, the separator being 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 first direction. A housing for accommodating the electrode assembly, the housing including a shell and an end cap, the shell having an opening at at least one end along a second direction, the end cap being connected to the shell and used to close the opening, the shell including a first wall portion located on one side of the electrode assembly in the second direction, the first direction being perpendicular to the second direction; A pressure relief mechanism is disposed on the first wall portion. The pressure relief mechanism has a groove that defines a pressure relief portion. At least a portion of the pressure relief portion can be opened when the battery cell is depressurized. The pressure relief portion has a buffer portion that arches towards and / or away from the electrode assembly along the second direction.

2. The battery cell according to claim 1, wherein, Along the thickness direction of the first wall portion, the first wall portion has a first outer surface and a first inner surface, the first inner surface being closer to the electrode assembly than the first outer surface. The buffer portion includes a first buffer portion that arches toward the side closer to the electrode assembly but does not protrude beyond the first inner surface.

3. The battery cell according to claim 1, wherein, An insulating member is provided inside the housing. The insulating member is located between the first wall portion and the electrode assembly. The insulating member defines a clearance groove that opens toward one side of the first wall portion. The clearance groove corresponds to the position of the buffer portion.

4. The battery cell according to claim 3, wherein, Along the thickness direction of the first wall portion, the first wall portion has a first outer surface and a first inner surface, the first inner surface being closer to the electrode assembly than the first 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 first inner surface and extends into the clearance groove.

5. The battery cell according to claim 1, wherein, Along the thickness direction of the first wall portion, the first wall portion has a first outer surface and a first inner surface, the first inner surface being closer to the electrode assembly than the first 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 first outer surface.

6. The battery cell according to claim 1, 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 away 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 first direction.

7. The battery cell according to claim 6, 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.

8. The battery cell according to claim 1, wherein, The pressure relief section includes a body, and the buffer section includes a bottom wall and a side wall surrounding the outer periphery of the bottom wall, the side wall being connected to the body.

9. The battery cell according to claim 8, wherein, The included angle between the sidewall of the buffer section and the main body is α, where 100°≤α≤170°.

10. The battery cell according to claim 9, wherein, 120°≤a≤150°。 11. The battery cell according to claim 8, wherein, The thickness of the sidewall of the buffer section is D1, and the thickness of the body is D2, satisfying: 0≤D1-D2≤0.3mm.

12. The battery cell according to claim 11, wherein, 0.2mm≤D1≤0.6mm, 0.15mm≤D2≤0.4mm.

13. The battery cell according to claim 1, wherein, Along the direction approaching and / or away from the electrode assembly, the maximum height dimension of the buffer portion is H, and the thickness dimension of the first wall portion is D3, satisfying: 1.5mm≤H+D3≤5mm.

14. The battery cell according to claim 13, wherein, The following conditions must be met: 0.8mm≤D3≤3mm.

15. The battery cell according to claim 1, wherein, Along the direction approaching and / or away from the electrode assembly, the maximum height dimension of the buffer portion is H, satisfying: 0.2mm≤H≤3mm.

16. The battery cell according to claim 15, wherein, 0.3mm≤H≤2mm.

17. The battery cell according to claim 1, wherein, The pressure relief mechanism further includes a mounting part, which is located on the outer periphery of the pressure relief part and is connected to the first wall portion.

18. The battery cell according to claim 17, wherein, The mounting portion includes a first mounting section and a second mounting section. The first mounting section is disposed on the outer periphery of the second mounting section. The thickness of the pressure relief portion is less than the thickness of the first mounting section, and the thickness of the second mounting section is not greater than the thickness of the first mounting section.

19. 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 first direction, and the area of ​​the outer surface is S, where N1≥1, N2≥1, N1*N2≤500, and S≤80000mm².

20. The battery cell according to any one of claims 1-19, wherein, The groove includes a first groove, and the pressure relief mechanism is configured to split 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 first direction. The dimension of the bottom surface of the first groove segment in the first direction is A, which satisfies: 0.3mm≤A≤0.8mm.

21. The battery cell according to claim 20, wherein, The minimum residual thickness of the first groove segment is D4, which satisfies: 0.1mm≤D4≤0.28mm.

22. The battery cell according to claim 20, wherein, The first groove defines at least one predetermined pressure relief area, and the groove further includes 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.

23. The battery cell according to claim 22, wherein, The residual thickness of the second groove is greater than that of the first groove.

24. The battery cell according to claim 22, 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.

25. The battery cell according to claim 22, wherein, 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.

26. The battery cell according to claim 25, 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.

27. The battery cell according to claim 20, wherein, The housing also includes a second wall portion, which is welded to the end cap to form a first connection portion; The second wall portion includes a first region and a second region arranged along the second direction, wherein the thickness of the first region is greater than the thickness of the second region, and the first region is located between the first connecting portion and the second region.

28. The battery cell according to claim 27, wherein, The thickness difference between the first region and the second region is t, which satisfies: 0.1mm≤t≤0.7mm.

29. The battery cell according to claim 28, wherein, 0.2mm≤t≤0.5mm.

30. The battery cell according to claim 27, wherein, The maximum thickness of the first region is E1, which satisfies: 0.5mm≤E1≤1.5mm.

31. The battery cell according to claim 27, wherein, The maximum thickness of the second zone is E2, which satisfies: 0.4mm≤E2≤0.8mm.

32. The battery cell according to claim 1, wherein, The first wall portion 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 second direction is W, where 400mm²≤W≤1400mm².

33. The battery cell according to claim 32, wherein, 600mm²≤W≤1200mm².

34. The battery cell according to claim 1, wherein, The pressure relief mechanism is integrally formed with the first wall portion.

35. 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 first direction.

36. The battery cell according to claim 35, 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.

37. The battery cell according to claim 35, 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.

38. 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.

39. The battery cell according to claim 1, wherein, The first wall portion is used to support the electrode assembly and is located below the electrode assembly.

40. The battery cell according to claim 1, wherein, The material of the first wall portion includes aluminum alloy.

41. 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.

42. 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 .

43. The battery cell according to claim 42, characterized in that, The thickness of the negative electrode film is T1, where 9μm≤T1≤75μm.

44. A battery, wherein, Includes the battery cell according to any one of claims 1-43.

45. An electrical appliance, wherein, Includes the battery according to claim 44, the battery being used to provide electrical energy to the electrical device.

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