Battery cell, battery pack, and electric device

Abstract

The application relates to the new energy technology field and discloses a battery monomer, a battery pack and a power utilization device. The battery monomer comprises a cover plate and a shell which are welded to form a first welding area; the shell comprises a first side wall, the first side wall comprises a base part and a first connecting part, the thickness of the first connecting part is greater than that of the base part, the size of the first connecting part accounts for a proportion h of the total size of the first side wall in the first direction; the battery core comprises a first pole piece, the first pole piece is arranged close to the first side wall; the first pole piece at least partially overlaps the first connecting part; the first pole piece comprises a current collector layer and an active material layer arranged on at least one side surface of the current collector layer, the total thickness of the active material layer accounts for a proportion t of the thickness of the current collector layer, the hardness of the current collector layer is a Mpa; and the following relationship is satisfied: 0.43 <= t <= 28. The battery monomer provided by the application avoids the cracking of the first welding area and simultaneously reduces the risk of pole piece material falling.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a battery cell, a battery pack, and an electrical device. Background Technology

[0002] If the weld strength between the battery casing and the cover is low during battery use, in the event of thermal runaway, the rapid expansion of gas inside the battery may cause the weld to crack before the explosion-proof valve can withstand the pressure. Alternatively, even after the explosion-proof valve opens, the weld may still crack due to insufficient pressure relief. This could easily cause the battery cover to fly off, resulting in an open flame and a potential fire and explosion of the entire battery. Summary of the Invention

[0003] In view of this, the present invention provides a battery cell, a battery pack, and an electrical device to solve the problem that the weld between the casing and the cover plate is prone to cracking under pressure.

[0004] In a first aspect, the present invention provides a battery cell, comprising: A cover plate and a housing are provided. The housing has an opening at at least one end along a first direction, which is perpendicular to the large surface direction of the cover plate. The cover plate seals the opening and is welded to the housing to form a first welding area. The cover plate and the housing enclose a receiving cavity. The housing includes a first sidewall, the plane of which is perpendicular to the plane of the cover plate. The first sidewall includes a base portion and a first connecting portion disposed along the first direction on the side of the base portion near the opening. The base portion and the first connecting portion are connected. In the direction perpendicular to the plane of the first sidewall, the thickness of the first connecting portion is greater than the thickness of the base portion, and the side of the first connecting portion facing the receiving cavity protrudes relative to the base portion. Along the first direction, the size of the first connecting portion accounts for h% of the total size of the first sidewall. A battery cell is disposed within a receiving cavity. The battery cell includes a first electrode plate, at least partially parallel to and close to a first sidewall. In a direction perpendicular to the plane of the first sidewall, the projection of the first electrode plate onto the first sidewall coincides with at least a partial projection of a first connecting portion. The first electrode plate includes a current collector layer and an active material layer disposed on at least one surface of the current collector layer. The ratio of the total thickness of the active material layer to the thickness of the current collector layer is t, and the hardness of the current collector layer is a MPa. And it satisfies the relation: 0.43≤ ≤28.

[0005] Beneficial effects: To ensure the connection strength between the shell and the cover plate, and to avoid the safety risk of cell material falling out due to the first connection, this embodiment comprehensively controls the ratio t of the total thickness of the active material layer to the thickness of the current collector layer, the hardness a of the current collector layer, and the ratio h of the dimension of the first connection along the first direction to the total dimension of the first sidewall, so that the relationship between t, a, and h is as follows: Meeting the above value range will prevent cracking in the first welding area between the casing and the cover plate, while ensuring the overall cycle life of the battery and preventing the casing from protruding and pressing against the electrode, which could cause the active material of the electrode to fall off and lead to the risk of electrode material falling off.

[0006] Secondly, the present invention also provides a battery pack, comprising: Multiple battery cells; the multiple battery cells are arranged sequentially along a second direction, which is perpendicular to the first direction.

[0007] Since the battery pack includes individual battery cells and has the same effect as individual battery cells, it will not be elaborated on here.

[0008] Thirdly, the present invention also provides an electrical device, comprising: The electrical device body and the battery pack as described above, which is electrically connected to the electrical device body.

[0009] Since the electrical device includes individual battery cells and has the same effect as individual battery cells, it will not be elaborated further here. Attached Figure Description

[0010] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0011] Figure 1 This is an exploded view of the battery cell of the present invention; Figure 2 This is a top view of a single battery cell of the present invention; Figure 3 for Figure 2 Schematic diagram of section AA; Figure 4 This is a partially enlarged view of the cross-section of a single battery cell; Figure 5 This is a partially enlarged view of the cross-section of another type of battery cell; Figure 6 This is a partially enlarged view of the cross-section of another type of battery cell; Figure 7 This is a partially enlarged view of the cross-section of the cover plate and the shell of the present invention; Figure 8 for Figure 1 Enlarged view of point B in the middle; Figure 9 for Figure 1 The magnified view at point B is a modified form.

[0012] Explanation of reference numerals in the attached figures: 1. Cover plate; 11. Cover plate body; 12. Boss; 111. Overlapping edge; 2. Shell; 21. First sidewall; 211. Base; 212. First connecting part; 2121. Equal thickness zone; 2122. Transition zone; 22. Second sidewall; 29. ​​Opening; 3. First welding zone; 4. Battery cell; 401. First electrode; 411. Current collector layer; 412. Active material layer; 402. Second electrode; 41. Battery cell body; 42. Tab; 6. Pole post assembly. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0015] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0016] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] During battery use, if the rate of gas generation inside the battery is high at the weld between the casing and the cover, the weld strength is insufficient, or the battery vibrates strongly, in the event of thermal runaway, the rapid expansion of the gas inside the battery may cause the weld to crack before the explosion-proof valve can withstand the excessive pressure; or even after the explosion-proof valve opens, the weld may still crack due to insufficient pressure relief. This can easily cause the battery cover to fly off, resulting in an open flame and posing a safety risk of the entire battery catching fire and exploding.

[0018] Research has found that the cracking at the weld line between the shell and the cover plate is mainly due to the smaller thickness of the shell used for welding to the cover plate. The shell thickness is generally less than the cover plate thickness, resulting in a smaller weld line size and stress concentration at the weld line. By locally thickening the shell near the opening, the size of the shell used for welding to the cover plate is increased, ensuring the overall connection strength.

[0019] However, localized thickening of the casing causes it to bulge outwards towards the cell, forming a protrusion. During charging and discharging, the cell expands and presses against this protrusion. Since the protrusion only exists in a localized area near the opening of the casing, rather than throughout the entire height of the casing, only a portion of the cell presses against the protrusion during expansion. This results in uneven stress on the electrode, localized stress concentration, and consequently, the active material detaches from the electrode, causing electrode shedding. This affects the overall cycle performance of the battery. The detached active material can easily deposit between the cell and the casing, and may even puncture the separator, increasing the risk of internal short circuits.

[0020] The following is combined Figures 1 to 9 The following describes embodiments of the present invention.

[0021] According to an embodiment of the present invention, in one aspect, a battery cell is provided, comprising: The cover plate 1 and the housing 2 are provided. The housing 2 has an opening 29 at at least one end along a first direction, which is perpendicular to the large surface direction of the cover plate 1. The cover plate 1 seals the opening 29 and is welded to the housing 2 to form a first welding area 3. The cover plate 1 and the housing 2 enclose a receiving cavity. The housing 2 includes a first sidewall 21, the plane of which is perpendicular to the plane of the cover plate 1. The first sidewall 21 includes a base portion 211 and a first connecting portion 212 disposed along the first direction on the side of the base portion 211 near the opening 29. The base portion 211 and the first connecting portion 212 are connected. In the direction perpendicular to the plane of the first sidewall 21, the thickness of the first connecting portion 212 is greater than the thickness of the base portion 211, and the side of the first connecting portion 212 facing the receiving cavity protrudes relative to the base portion 211. Along the first direction, the size of the first connecting portion 212 accounts for h of the total size of the first sidewall 21. The battery cell 4 is disposed within the receiving cavity. The battery cell 4 includes a first electrode 401, which is at least partially parallel to and close to the first sidewall 21. In a direction perpendicular to the plane of the first sidewall 21, the projection of the first electrode 401 on the first sidewall 21 coincides with at least a partial projection of the first connecting portion 212. The first electrode 401 includes a current collector layer 411 and an active material layer 412 disposed on at least one side surface of the current collector layer 411. The ratio of the total thickness of the active material layer 412 to the thickness of the current collector layer 411 is t, and the hardness of the current collector layer 411 is a MPa. And it satisfies the relation: 0.43≤ ≤28.

[0022] It should be noted that the first direction can specifically be the height direction of the battery cell. For ease of description, this application further defines the second direction as the width direction of the cover plate 1, and at the same time, the second direction is also the thickness direction of the battery cell, that is, the arrangement direction of multiple battery cells along the thickness direction; the third direction is the length direction of the cover plate 1, and at the same time, the length direction of the battery cell.

[0023] In this embodiment, the shape of the battery cell can be a columnar structure, specifically a cylindrical or prismatic shape; when it is prismatic, its cross-section can be rectangular, elliptical, or polygonal.

[0024] To facilitate understanding of the technical solution of this application, several technical terms that may be involved in this application will first be explained: Shell 2: A housing is a component used to provide a space to house electrode assemblies and other parts and isolate them from the external environment. A housing generally includes a body with an opening at at least one end and a receiving cavity. The opening of the housing can be closed by a cover plate, sealing and isolating the internal environment of the battery cell from the external environment. The materials of the housing 2 include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, and aluminum-plastic film.

[0025] Cover plate 1: A cover is a component that seals the opening of the casing to isolate the internal environment of a battery cell from the external environment. The materials of the cover 1 include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, and aluminum-plastic film.

[0026] Cell 4: A battery cell is the component in a battery where electrochemical reactions occur; it is the smallest unit in a battery capable of performing electrochemical reactions such as charging and discharging. A battery cell is the basic unit of a battery and typically includes a positive electrode, a negative electrode, and a separator. Lithium-ion battery cells primarily function by the movement of lithium ions between the positive and negative electrodes. In cylindrical cells, a three-layer thin-film structure is wound into a cylindrical electrode assembly, while in cuboid cells, the thin-film structure is wound or stacked into an electrode assembly with a roughly cuboid shape.

[0027] Positive electrode tablets: It is one of the core components in a battery that carries the positive electrode active material. During charging, metal ions (such as lithium ions) are extracted from the crystal lattice of the positive electrode active material (oxidation reaction), migrate through the electrolyte, and intercalate into the negative electrode. During discharging, metal ions (such as lithium ions in a lithium battery) are extracted from the negative electrode and intercalated into the crystal lattice of the positive electrode active material (reduction reaction), thus realizing the storage and release of lithium ions.

[0028] A positive electrode generally includes a positive current collector and a positive active material layer. The positive active material layer is coated on at least one surface of the positive current collector and includes: a positive active material, a conductive agent, and a binder. The positive active material includes, but is not limited to, at least one of the following: lithium phosphates, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive active materials for batteries. These positive active materials can be used alone or in combination. The lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds.

[0029] The positive electrode conductive agent includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon nanotubes, graphene and carbon nanofibers.

[0030] The positive electrode binder includes, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0031] Negative electrode plate: During battery charging, active ions (such as Li) from the positive electrode are embedded in the negative electrode, while electrons from the positive electrode are transferred to the negative electrode through an external circuit, maintaining charge balance. During discharging, the active ions (such as Li) previously embedded in the negative electrode can be released, while electrons from the negative electrode are transferred to the negative electrode through an external circuit, maintaining charge balance; thus achieving energy storage and release.

[0032] The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). The negative electrode active layer includes a negative electrode active material, a conductive agent, and a binder.

[0033] The negative electrode active material can be carbon-based materials such as graphite, porous carbon, hard carbon, soft carbon, and mesophase carbon microspheres, or silicon-based materials such as elemental silicon, silicon oxides, silicon-carbon composites, and silicon-nitrogen composites. The conductive agent can be conductive carbon black, carbon nanotubes, etc., and the binder can be styrene-butadiene rubber, polyacrylic acid, etc.

[0034] Diaphragm: A diaphragm is placed between the positive and negative electrode plates to separate them and prevent them from short-circuiting due to contact.

[0035] The diaphragm can be at least one of glass fiber, nonwoven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. A coating can also be applied to the diaphragm surface. The coating can be an inorganic coating and, or an organic coating, wherein the inorganic coating material includes at least one of alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, and boehmite; and the organic coating includes at least one of aramid coating and PVDF coating.

[0036] In this embodiment, the housing 2 is provided with an opening 29 at at least one end along the first direction. For example, the housing 2 may be provided with openings 29 at both ends along the first direction, and there may be two cover plates 1, which are used to block the openings 29 at both ends of the housing 2 along the first direction. Alternatively, the housing 2 may be provided with an opening 29 at only one end along the first direction, and there may be one cover plate 1, which is used to block the opening 29.

[0037] In this embodiment, the housing 2 includes a first sidewall 21. Taking a quadrangular prism battery as an example, the housing 2 includes four sidewalls perpendicular to the cover plate 1. The first sidewall 21 can be any one of the sidewalls, and the structure of the other sidewalls can be the same as or different from the first sidewall 21. For example, the first sidewall 21 can be a long sidewall, the short sidewall adjacent to the first sidewall 21 can be a second sidewall 22, the other long sidewall adjacent to the second sidewall 22 and opposite to the first sidewall 21 is a third sidewall, and the short sidewall adjacent to the first sidewall 21 and opposite to the second sidewall 22 is a fourth sidewall. The sidewalls are connected by rounded corners or right angles.

[0038] The first sidewall 21 has a structure with uneven wall thickness. Specifically, the first sidewall 21 includes a first connecting portion 212 and a base portion 211 along a first direction. In a direction perpendicular to the plane of the first sidewall 21, the thickness of the first connecting portion 212 is greater than the thickness of the base portion 211. Furthermore, along the first direction, the first connecting portion 212 is positioned closer to the opening 29 than the base portion 211, thereby enhancing the structural strength around the opening 29. In subsequent welding processes, the increased thickness of the first connecting portion 212 can meet the requirements of higher welding power, improve the welding stability between the shell 2 and the cover plate 1, and enhance the connection strength between the shell 2 and the cover plate 1.

[0039] In this embodiment, the thickness of the cover plate 1 can range from 0.6mm to 4mm, preferably from 1mm to 3mm; the thickness of the shell 2 can range from 0.1mm to 2mm, preferably from 0.2mm to 1.5mm.

[0040] The first sidewall 21 includes a first connecting portion 212 disposed along a first direction on the side of the base portion 211 near the opening 29. It is understood that, in one implementation, the starting position of the thickened area of ​​the first connecting portion 212 along the first direction can be flush with the edge of the opening and extend along the first direction to the inside of the opening. In a second implementation, the starting position of the thickened area of ​​the first connecting portion 212 along the first direction can be spaced apart from the edge of the opening; that is, there is another section of the base portion 211 (not shown in the figure) between the first connecting portion 212 and the edge of the opening. In this case, the increased wall thickness of the first connecting portion 212 can still meet the requirement of improving the structural strength of the shell 2. In the second implementation, the distance between the first connecting portion 212 and the edge of the opening ranges from 0.1mm to 2mm, preferably from 0.2mm to 1mm. This embodiment improves the strength of the sidewall of the shell 2 by providing the first connecting portion 212, ensuring the connection strength between the sidewall of the shell 2 and the cover plate, increasing the overall connection strength and size of the welding area, and preventing cracking of the weld line.

[0041] Additionally, the first connecting portion 212 can be disposed on at least one side of the wall of the housing 2 along the second direction, or symmetrically disposed on both sides along the second direction; that is, the first connecting portion 212 can protrude only towards the battery cell side; or it can protrude both towards the battery cell side and towards the side away from the battery cell side. In this case, the thickness direction of the first connecting portion 212 is the second direction. Furthermore, the first connecting portion 212 can also be disposed on at least one side of the wall of the housing 2 along a third direction, or symmetrically disposed on both sides along the third direction. In this case, the thickness direction of the first connecting portion 212 is the third direction; regardless of which direction it is disposed in, the first connecting portion 212 constitutes a locally thickened area of ​​the housing 2.

[0042] The cover plate 1 and the shell 2 are welded together near the opening 29 to form the first welding area 3. The first welding area 3 refers to the weld structure formed by welding the cover plate 1 and the shell 2. The first welding area 3 can be achieved by laser welding process. By focusing the laser beam on the interface between the shell 2 and the cover plate 1, the local material melts and solidifies rapidly to form a dense weld structure, thereby achieving a reliable connection between the cover plate 1 and the shell 2.

[0043] The first connecting portion 212 protrudes relative to the base portion 211 on the side facing the receiving cavity. That is, in the direction perpendicular to the plane of the first sidewall 21, the first connecting portion 212 is closer to the cell 4 than the base portion 211. This makes it easier for the cell 4 to come into contact with the first connecting portion 212 during the charging and discharging expansion process, resulting in local stress concentration and causing the active material layer on the electrode to peel off. Specifically, during the stretching and forming process of the shell 2, the stretching rate can be controlled, and tooling can be used for shaping, so that the shell 2 forms a locally thickened first connecting portion 212 on the side near the opening 29, thereby achieving structural reinforcement.

[0044] The battery cell 4 includes a positive electrode, a negative electrode, and a separator sandwiched between them. In this embodiment, the battery cell 4 includes a first electrode 401. The first electrode 401 is disposed close to the first sidewall 21. That is, the first electrode 401 is the outermost electrode in the battery cell 4 that is close to the first sidewall 21. Compared with other electrodes, it is disposed closer to the first sidewall 21. The first electrode 401 can be a positive electrode or a negative electrode.

[0045] The first electrode 401 includes a current collector layer 411 and an active material layer 412 disposed on at least one side of the current collector layer 411. The active material layer 412 may be disposed on one or both sides of the current collector layer 411. When the active material layer 412 is disposed on both sides of the current collector layer 411, the total thickness of the active material layer 412 refers to the sum of the thicknesses of the active material layers on both sides. When the active material layer 412 is disposed on one side of the current collector layer 411, the total thickness of the active material layer 412 refers to the thickness of the active material layer on that one side.

[0046] It should be noted that the current collector layer 411 is used to realize the current output of the battery cell 4, and the active material layer 412 is used to provide lithium ions or to provide space for lithium ion insertion, so as to realize the insertion and extraction of ions.

[0047] The first electrode 401 can be either a positive electrode or a negative electrode. It is preferred that the first electrode be a negative electrode, which can increase the intercalation of ions, provide more lithium intercalation vacancies, ensure the cycle life and safety of the battery, and avoid the safety risk of lithium deposition on the electrode, the formation of lithium dendrites, and short circuit between the positive and negative electrodes.

[0048] The projection of the first electrode 401 onto the first sidewall 21 at least partially covers the first connecting portion 212, meaning that the first electrode 401 and the first connecting portion 212 have an overlapping area in space. When the cell 4 expands, it can easily cause the protruding surfaces of the first electrode 401 and the first connecting portion 212 to be squeezed, resulting in uneven stress on the first electrode 401. This can lead to cracking or even peeling of the active material layer 412, affecting the battery's cycle life and safety.

[0049] To ensure the connection strength between the shell 2 and the cover plate 1, and to avoid the safety risk of the battery cell 4 falling off due to the first connection part 212, this embodiment comprehensively controls the ratio t of the total thickness of the active material layer 412 to the thickness of the current collector layer 411, the hardness a of the current collector layer 411, and the ratio h of the dimension of the first connection part 212 along the first direction to the total dimension of the first sidewall 21, so that the relationship between t, a, and h is as follows: By satisfying the above value range, cracks are avoided in the first welding area 3 where the shell 2 and the cover plate 1 are welded, while ensuring the overall cycle life of the battery. This also prevents the shell 2 from protruding and pressing against the electrode, causing the active material of the electrode to fall off and resulting in the risk of electrode material falling off.

[0050] Specifically, when the ratio t of the total thickness of the active material layer 412 to the thickness of the current collector layer 411 is larger, the active material layer 412 is thicker, the bonding force between the active material layer 412 and the current collector layer 411 is weaker, and the active material layer 412 is easier to peel off when the battery cell expands; that is, when the ratio t is too large, the active material layer 412 is too thick, which leads to uneven stress transmission, aggravates the local deformation of the contact area with the first connection part 212, and increases the risk of material loss. Conversely, when the ratio t is too small, the active material layer 412 is too thin. In this case, the more fully the active material layer 412 contacts the electrolyte, the greater the side reaction and the more gas is produced, leading to more drastic changes in internal pressure, greater expansion of the battery cell, and increased risk of cracking in the first welding area 3. In addition, since the current collector layer 411 is usually made of metal and has relatively higher hardness (the active material layer 412 has a porous structure and better compressibility than the current collector layer 411), when t is smaller, the current collector layer 411 accounts for a larger proportion, resulting in increased overall rigidity of the cell 4. During the repeated expansion and contraction of the cell 4, it is more likely to have a hard collision with the first connection part 212, and it is more likely to concentrate stress to the first welding area 3, exacerbating the tendency of weld cracking. Moreover, the smaller t is, the thinner the active material layer 412 is, the insufficient energy density, which can easily lead to a decrease in the energy density of the cell, and the larger the exposed area of ​​the current collector, which can easily cause micro-short circuits. Therefore, it is necessary to control the ratio t within a reasonable range to ensure the mechanical matching and coordination between the active material layer 412 and the current collector layer 411, so as to ensure the stable bonding between the active material layer and the current collector, while taking into account both energy density and structural reliability.

[0051] Specifically, the hardness 'a' of the current collector layer 411 reflects its ability to resist plastic deformation. A higher hardness 'a' makes the current collector layer 411 less prone to deformation under pressure, but it also reduces its flexibility, thus affecting the stress buffering capacity of the electrode during cell expansion. In other words, when the hardness 'a' is too high, the active material layer 412 attached to the current collector layer 411 is more susceptible to greater compressive stress due to limited deformation space, thereby increasing the risk of cracking. Therefore, the hardness 'a' needs to be controlled within a reasonable range, balancing structural rigidity and deformation adaptability.

[0052] Specifically, when the proportion h of the dimension of the first connecting part 212 along the first direction to the total dimension h of the first sidewall 21 is too large, the area of ​​the first connecting part 212 increases, the contact area with the active material layer 412 increases, which leads to increased local stress concentration and is prone to causing compression damage to the larger area of ​​the active material layer 412, increasing the risk of peeling off the active material layer; while when h is too small, the weld line size is easily small, resulting in insufficient connection strength between the shell 2 and the cover plate 1. In the event of thermal runaway, due to the rapid expansion of the gas inside the battery, the first weld area 3 is easily blown open, or even the entire battery cover plate flies out, causing a serious safety accident.

[0053] When the relation When the value of is too large, the cell 4 is squeezed by the first connection part 212, increasing the risk of the active material layer 412 shedding and affecting the battery's lifespan; while when the relationship is too large, the cell 4 is squeezed by the first connection part 212, increasing the risk of the active material layer 412 shedding and affecting the battery's lifespan. If the value of is too small, stress concentration is likely to occur in the first welding area 3 where the shell 2 and the cover plate 1 are welded, increasing the risk of cracking and affecting the connection strength between the shell 2 and the cover plate 1. That is, when the relationship... The value of satisfies 0.43 ≤ When the value is ≤28, the risk of the active material layer 412 falling off due to the compression of the cell 4 by the first connection part 212 can be reduced, while ensuring that the first welding area 3 has a certain connection strength, so as to reduce the probability of the weld between the shell 2 and the cover plate 1 cracking.

[0054] In this embodiment, the proportion of the size of the first connecting portion 212 to the total size of the first sidewall 21 is h. The size of the first connecting portion 212 can be denoted as h1mm, where h1mm ranges from 2mm to 16mm, preferably from 7mm to 11mm. The total size of the first sidewall 21 can be denoted as h2mm, where h2mm ranges from 150mm to 280mm, preferably from 200mm to 230mm. By limiting the range of h1mm, it is ensured that the first connecting portion 212 provides sufficient welding strength while avoiding an excessively large contact area with the active material layer 412, which could lead to increased local stress concentration and potentially cause compression damage to the larger area of ​​the active material layer 412, increasing the risk of peeling off the active material layer. By limiting the range of h2mm, the overall size of the first sidewall 21 is guaranteed, avoiding insufficient space utilization due to an excessively small size, while also avoiding structural redundancy and increased weight due to an excessively large size.

[0055] For example, in this embodiment, The value can be 0.43 or 0.44 or 0.45 or 0.47 or 0.5 or 0.53 or 0.56 or 0.6 or 0.65 or 0.72 or 0.81 or 0.93 or 1.05 or 1.12 or 1.18 or 1.25 or 1.31 or 1.38 or 1.42 or 1.49 or 1.56 or 1.67 or 1.78 or 1.92 or 2.08 or 2.27 or 2.49 or 2.75 or 3.05 or 3.4 or 3.8 or 4.25 or 4.5 or 4.83 or 5.22 or 5.6 7 or 6.18 or 6.75 or 7.38 or 8.07 or 8.83 or 9.67 or 10.35 or 10.67 or 11.12 or 11.22 or 12.15 or 13.28 or 14.05 or 14.5 or 14.59 or 15.72 or 16.93 or 18.15 or 18.66 or 19.87 or 21.11 or 22.43 or 23.85 or 25.37 or 26.46 or 26.9 or 27.5 or 28, etc., or it can be any range formed by any two of the above values.

[0056] As a preferred option The range of values ​​is 1.42≤ ≤14.5.

[0057] when The range of values ​​for satisfies 1.42 ≤ When the preferred range is ≤14.5, the risk of the active material layer 412 falling off due to the compression of the cell 4 by the first connection part 212 can be further reduced, while ensuring that the first welding area 3 has sufficient connection strength, thereby better reducing the probability of cracking of the weld between the shell 2 and the cover plate 1.

[0058] For example, in this embodiment, The value can be 1.42 or 1.45 or 1.52 or 1.6 or 1.67 or 1.75 or 1.83 or 1.91 or 2.0 or 2.09 or 2.18 or 2.27 or 2.36 or 2.45 or 2.54 or 2.63 or 2.72 or 2.81 or 2.9 or 3.0 or 3.12 or 3.25 or 3.38 or 3.51 or 3.64 or 3 .77 or 3.9 or 4.03 or 4.16 or 4.29 or 4.42 or 4.55 or 4.68 or 4.83 or 5.0 or 5.17 or 5.34 or 5.51 or 5.68 or 5.85 or 6.02 or 6.19 or 6.36 or 6.53 or 6.7 or 6.87 or 7.04 or 7.21 or 7.38 or 7.55 or 7.72 or 7 The values ​​could be 0.89, 8.06, 8.23, 8.4, 8.57, 8.74, 8.91, 9.08, 9.25, 9.42, 9.59, 9.76, 9.93, 10.1, 10.27, 10.44, 10.61, 10.67, 10.84, 11.01, 11.12, 11.22, 11.39, 11.56, 11.73, 11.9, 12.07, 12.24, 12.41, 12.58, 12.75, 12.92, 13.09, 13.26, 13.43, 13.6, 13.77, 13.94, 14.11, 14.28, 14.45, or 14.5, or any range formed by any two of the above values.

[0059] Regarding the measurement of dimensions, thickness, distance, and area involved in this application, a micrometer, caliper, or scanning electron microscope can be used to measure dimensions, thickness, distance, etc., and the area can be calculated from the dimensions.

[0060] Specifically, in this embodiment, the test method for h is as follows: along the direction perpendicular to the large surface of the cover plate, that is, the first direction, the size of the first connecting part 212 is measured with a micrometer (accuracy 0.001mm), the measurement is taken 3 times, and the average value is recorded as h1 mm. Along the direction perpendicular to the large surface of the cover plate, the size of the first side wall 21 is measured with a ten-thousand-meter, the measurement is taken 3 times, and the average value is recorded as h2 mm. h is h1 / h2.

[0061] Specifically, in this embodiment, the test method for t is as follows: The overall thickness of the electrode sheet is measured using a micrometer (accuracy 0.01 mm), measured three times, and the average value is recorded as t1 mm (e.g., ...). Figure 4 (As shown), then carefully scrape off the active material layer on the surface of the current collector layer to expose the upper and lower surfaces of the current collector layer. Use a micrometer to measure the thickness of the current collector layer, measure it 3 times, and take the average value, which is recorded as t2 mm (e.g. Figure 4 As shown in the figure, the difference between t1 mm and t2 mm is the thickness of the active material layer, denoted as t3 mm, and t = t3 / t2.

[0062] Specifically, in this embodiment, the test method for a is as follows: obtain the electrode sheet, carefully scrape off the active material layer on the surface of the current collector layer to expose the upper and lower surfaces of the current collector layer. Set the maximum load of the nanoindenter to 10mN, measure the hardness of the current collector layer, measure 6 times, and take the average value, which is recorded as a MPa.

[0063] In addition, the adjustment method for a is as follows: the hardness of the current collector layer can be adjusted by adding trace alloying elements during the preparation of the current collector layer, controlling the quality of alloying element addition, rolling process parameters (such as rolling deformation), and adjusting the thickness and density of the current collector layer.

[0064] The battery cells of this application can be prepared using the following methods: (1) Preparation of the positive electrode: The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., PVDF) are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector foil, dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheet is then obtained by rolling and slitting.

[0065] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98): (4~1): (4~1).

[0066] (2) Preparation of negative electrode: The negative electrode active material, conductive agent (e.g., acetylene black), thickener (e.g., carboxymethyl cellulose (CMC)), and binder (e.g., styrene-butadiene rubber (SBR)) are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, the negative electrode sheet is obtained by rolling and slitting.

[0067] Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0068] (3) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0069] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0070] (5) Preparation of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a battery cell. After welding the tabs of the battery cell to the terminal assembly, it is placed in the battery casing, and the cover plate is welded to the casing. The battery is dried, injected with electrolyte, and then packaged, left to stand, formed, and volume-adjusted to obtain a lithium-ion battery.

[0071] In the selection of materials for the aforementioned battery, this application may also select other materials, not limited to those limited by the above preparation method. The positive electrode active material may be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate. The conductive agent in the positive electrode sheet may also be selected from one or more of graphite, superconducting carbon, Ketjen black, Super P, carbon nanotubes, graphene, and carbon nanofibers. The binder in the positive electrode sheet may also be selected from one or more of polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, and carboxymethyl chitosan. The positive electrode current collector may also be selected from one or more of stainless steel with surface silver plating, stainless steel, aluminum, nickel, carbon electrode, carbon, nickel, and titanium. The positive electrode current collector may also include a composite current collector, which may include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming metallic materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on a polymer substrate (such as a substrate of polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.).

[0072] The negative electrode active material can be selected from one or more of the following negative electrode active main materials: artificial graphite, natural graphite, silicon carbide, silicon oxide, lithium titanate, etc.; the conductive agent in the negative electrode sheet can be selected from one or more of the following: conductive carbon black, conductive graphite, carbon nanotubes, graphene, carbon fiber, etc.; the binder in the negative electrode sheet can be selected from one or more of the following: styrene-butadiene rubber, polyacrylic acid and its salts, sodium alginate, etc.; the thickener in the negative electrode sheet can be selected from one or more of the following: sodium carboxymethyl cellulose, polyacrylonitrile multi-component copolymer, etc.; the negative electrode current collector can also be selected from one or more of the following: stainless steel with silver plating, stainless steel, copper, nickel, carbon electrode, carbon, nickel, titanium, etc.; the negative electrode current collector can also include composite current collectors, which can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene, etc.). The negative electrode active layer includes the negative electrode active material, conductive components, adhesives, etc.

[0073] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0074] Referring to Table 1 below, the battery cells provided in this application were subjected to wire bonding cracking tests and electrode shedding tests through several embodiments and comparative tests to verify their qualification.

[0075] Performance 1, wire bonding cracking test, the method is as follows: Following the battery preparation method described above, 200 batteries were prepared for each of the embodiments and comparative examples. The a, t, and h values ​​of the batteries in each embodiment are shown in Table 1 below. Apart from this, the other structures are the same. The batteries were charged at 1C to the upper limit voltage at 25°C, and then charged at a constant voltage until the cutoff current was 0.05C. A heating wire was placed on the periphery of the battery to continuously heat the battery and trigger thermal runaway. When thermal runaway occurred, heating was stopped. After the thermal runaway ended, it was observed whether cracking occurred at the first weld line position. If cracking occurred, the number of batteries with cracked first weld lines was recorded as N. The weld cracking rate = (N / 200) × 100%. If the weld cracking rate is less than or equal to 2%, it is considered good. If the weld cracking rate is greater than 2% and less than or equal to 5%, it is considered qualified. If the weld cracking rate is greater than 5%, it is considered unqualified.

[0076] Different battery systems require corresponding adjustments to their upper and lower voltage limits: For cathode active materials including LFP (LiFePO4, lithium iron phosphate) – upper limit voltage 3.65V, lower limit voltage 2.5V; for cathode active materials including NCM (lithium nickel cobalt manganese oxide) – upper limit voltage 4.25V, lower limit voltage 2.5V; for cathode active materials including LFMP (lithium manganese iron phosphate) – upper limit voltage 4.25V, lower limit voltage 2.5V; for cathode active materials including lithium nickel manganese oxide – upper limit voltage 4.8V, lower limit voltage 3.5V.

[0077] The positive electrode active material used in this test was selected from LiNi. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, other positive electrode active materials all meet the above test requirements, and the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and other negative electrode active materials all meet the above test requirements, and the mass ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0078] Performance 2, Electrode shedding test, the method is as follows: According to the battery preparation method described above, 100 batteries were prepared for each of the embodiments and comparative examples. The a, t, and h values ​​of the batteries in each embodiment are shown in Table 1 below. Apart from this, the other structures are the same. The lithium-ion batteries prepared in the examples and comparative examples were subjected to cycle tests at 25°C according to the following procedure.

[0079] 1) Charge at a constant current rate of 1C to the upper limit voltage, and then charge at a constant voltage until the current drops to 0.05C; 2) Let it stand for 10 minutes; 3) Discharge the battery at a 1C rate to the lower limit voltage; 4) Let it stand for 10 minutes; Perform 300 charge-discharge cycles following steps 1)-4).

[0080] Disassemble the battery and observe whether the electrode near the first connection point has fallen off. If it has, record the number of batteries with fallen electrode, denoted as N. The electrode shedding rate is calculated as (N / 100) × 100%. If the electrode shedding rate is less than or equal to 3%, it is considered good. If the electrode shedding rate is greater than 3% and less than or equal to 6%, it is considered qualified. If the electrode shedding rate is greater than 6%, it is considered unqualified.

[0081] Different battery systems require corresponding adjustments to their upper and lower voltage limits: For cathode active materials including LFP (LiFePO4, lithium iron phosphate) – upper limit voltage 3.65V, lower limit voltage 2.5V; for cathode active materials including NCM (lithium nickel cobalt manganese oxide) – upper limit voltage 4.25V, lower limit voltage 2.5V; for cathode active materials including LFMP (lithium manganese iron phosphate) – upper limit voltage 4.25V, lower limit voltage 2.5V; for cathode active materials including lithium nickel manganese oxide – upper limit voltage 4.8V, lower limit voltage 3.5V.

[0082] The positive electrode active material used in this test was selected from LiNi. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, other positive electrode active materials all meet the above test requirements, and the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and other negative electrode active materials all meet the above test requirements, and the mass ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0083] Table 1

[0084] Regarding the test results, referring to Table 1 above, the explanation is as follows: As can be seen from Examples 1-19, when When the values ​​of the formula meet the above range, the wire bonding crack test results are all qualified and no unqualified results are found; the electrode material loss test results are all qualified; and the performance requirements are met.

[0085] In Comparative Examples 1 and 3 The formula value was below the lower limit, and the weld cracking test showed a failure result, failing to meet performance requirements. However, in Comparative Examples 2 and 4, The formula value exceeded the upper limit, and the electrode material loss test showed that the result was unqualified and could not meet the performance requirements.

[0086] In some embodiments, along the first direction, the end of the first electrode 401 near the cover plate 1 is spaced apart from the end of the first connecting portion 212 near the opening 29, and the end of the first electrode 401 near the cover plate 1 is further away from the cover plate 1 than the end of the first connecting portion 212 near the opening 29.

[0087] By positioning the end of the first electrode 401 near the cover plate 1 further away from the end of the first connecting portion 212 near the opening 29 than the end of the first electrode 401 near the cover plate 1, that is, by preventing the first electrode 401 from getting too close to the cover plate 1 along the first direction, the first electrode 401 and the first connecting portion 212 are spatially misaligned and avoid each other, thereby reducing the overlapping area of ​​the first electrode 401 and the first connecting portion 212, reducing the mutual compressive stress between the two during the thermal expansion process, and thus reducing the risk of the first electrode 401 falling off.

[0088] In some embodiments, combined with Figure 4 As shown, along the first direction, the distance between the end of the first electrode 401 near the cover plate 1 and the lower surface of the cover plate 1 near the cell 4 is B mm, which satisfies 5mm≤B mm≤20mm.

[0089] By limiting the lower limit of the distance B mm between the end of the first electrode 401 near the cover plate 1 and the end of the first connecting portion 212 near the opening 29, sufficient space can be ensured between the first electrode 401 and the first connecting portion 212, thus avoiding excessive risk of the first electrode 401 falling out. At the same time, by limiting the upper limit of B mm, the space utilization rate can be prevented from decreasing due to the first electrode 401 being too far away from the cover plate 1, which would affect the overall energy density of the battery.

[0090] Preferably, the value of the distance B mm is within the range of 8 mm ≤ B mm ≤ 13 mm.

[0091] For example, in this embodiment, the value of B mm can be 5 mm, 6.3 mm, 7.8 mm, 9.2 mm, 10.7 mm, 12.5 mm, 14.1 mm, 15.8 mm, 17.3 mm, 18.9 mm, or 20 mm, or it can be any range formed by any two of the above values.

[0092] In some embodiments, combined with Figure 4 As shown, the center line S of the first connection part 212 along the first direction is located between the end of the first electrode 401 near the cover plate 1 and the lower surface of the cover plate 1 near the cell 4.

[0093] The center line S of the first connecting part 212 along the first direction refers to the position of half the height of the first connecting part 212 along the first direction, that is, the center line S is located at the half position of the first connecting part 212 in the first direction.

[0094] By positioning the center line S of the first connecting portion 212 along the first direction between the end of the first electrode 401 near the cover plate 1 and the lower surface of the cover plate 1 near the cell 4, that is, by positioning the center line S closer to the cover plate 1 than the end of the first electrode 401 near the cover plate 1, the spatial proportion of the first connecting portion 212 in the height direction can be further compressed, the overlap area between the first connecting portion 212 and the first electrode 401 can be reduced, the mutual compressive stress between the two during the thermal expansion process can be reduced, thereby reducing the risk of the first electrode 401 falling off.

[0095] In some embodiments, the following condition is satisfied: 1.8 ≤ t ≤ 70.

[0096] When the centerline S is positioned closer to the cover plate 1 than the end of the first electrode 401 that is closer to the cover plate 1, the risk of material loss is reduced, and the lower limit of the ratio t of the total thickness of the active material layer 412 to the thickness of the current collector layer 411 can be appropriately increased. This can enhance the electrochemical reaction activity while ensuring structural stability, thereby increasing the energy output per unit volume.

[0097] In some other embodiments, the center line S of the first connecting portion 212 along the first direction is flush with the end of the first electrode 401 near the cover plate 1. Or, combined Figure 5 As shown, the center line S of the first connecting part 212 along the first direction is further away from the cover plate 1 than the end of the first electrode 401 that is closer to the cover plate 1.

[0098] At this time, the overlap area between the first connecting part 212 and the first electrode 401 is larger. During thermal expansion, the area of ​​the first electrode 401 under pressure is likely to increase, which increases the risk of the first electrode 401 falling off. Therefore, it is necessary to appropriately reduce the upper limit of the ratio t of the total thickness of the active material layer 412 to the thickness of the current collector layer 411 in order to further alleviate the interface stress concentration caused by thermal expansion.

[0099] For example, in this embodiment, the value of t can be 1.8 or 3.2 or 6.5 or 10.1 or 15.7 or 22.3 or 29.8 or 37.4 or 45.2 or 53.6 or 62.1 or 70, or it can be any range formed by any two of the above values.

[0100] In some embodiments, combined with Figure 5 As shown, along the first direction, the distance between the center line S of the first connecting part 212 and the end of the first pole piece 401 near the cover plate 1 is C mm, which satisfies 1 mm ≤ C mm ≤ 12 mm.

[0101] By limiting the upper limit of the spacing distance C mm, excessive growth of the first connecting part 212 is avoided, preventing excessive overlap between the first connecting part 212 and the first electrode 401. This would prevent the first electrode 401 from being squeezed too much during thermal expansion, thus increasing the risk of the first electrode 401 falling off. At the same time, by limiting the lower limit of the spacing distance C mm, sufficient height of the first connecting part 212 is ensured, preventing the weld wire size from being too small and affecting the welding strength.

[0102] On the other hand, if the height of the first connecting portion 212 of the housing 2 remains constant, when the center line S of the first connecting portion 212 along the first direction is further away from the cover plate 1 than the end of the first electrode 401 near the cover plate 1, the first electrode 401 is positioned closer to the cover plate 1, which is beneficial for improving energy density. When the value of the interval distance C mm is too small, it is easy to cause the distance between the first electrode 401 and the cover plate 1 to be relatively large, resulting in a decrease in energy density.

[0103] Preferably, the distance C mm is within the range of 1.8 mm ≤ B mm ≤ 10 mm.

[0104] For example, in this embodiment, the value of C mm can be 1 mm, 1.8 mm, 2.5 mm, 3.7 mm, 4.9 mm, 6.2 mm, 7.4 mm, 8.6 mm, 9.8 mm, 10.5 mm, 11.3 mm, or 12 mm, or it can be any range formed by any two of the above values.

[0105] In some embodiments, combined with Figure 6 As shown, the first connecting part 212 includes a uniform thickness region 2121 and a transition region 2122 along the first direction. In the direction perpendicular to the plane where the first sidewall 21 is located, the maximum thickness of the transition region 2122 is less than the thickness of the uniform thickness region 2121. The two ends of the transition region 2122 are connected to the base part 211 and the uniform thickness region 2121, respectively.

[0106] It should be noted that the equal thickness region 2121 refers to the area where the thickness of the first connecting part 212 is equal, excluding measurement and process errors. It should not be interpreted as the thickness of the equal thickness region 2121 being absolutely consistent; its thickness fluctuation can be within the tolerance range allowed by the process. The transition region 2122 adopts a gradual thinning design.

[0107] By forming a transition zone 2122 between the base portion 211 and the equal thickness zone 2121, that is, the transition zone 2122 is farther away from the opening than the equal thickness zone 2121, the wall thickness transitions smoothly from the equal thickness zone 2121 to the base portion 211, effectively alleviating stress abrupt changes at the junction, avoiding stress concentration between the first connecting portion 212 and the base portion 211, reducing the risk of cracking of the shell 2. At the same time, by setting the transition zone 2122, space can be left for the expansion of the cell 4, avoiding excessive compression of the first electrode 401 by the first connecting portion 212, reducing the risk of the first electrode 401 falling off.

[0108] In some embodiments, the equal thickness region 2121 at least partially forms the first welding region 3.

[0109] By forming at least a portion of the first welding zone 3 in the equal-thickness zone 2121, a stable and uniform thickness base for the welding area can be ensured, thereby improving the consistency and bonding strength of the weld joints and reducing the probability of defects such as incomplete welding and misaligned welding. Furthermore, the absence of the first welding zone 3 in the transition zone 2122 avoids uneven penetration due to gradual changes in wall thickness and ensures physical isolation between the heat-affected zone and the stress-weak zone, further enhancing structural reliability and ensuring welding strength. Simultaneously, it avoids the safety risk of the first connection portion 212 pressing against the battery cell, which could lead to electrode material falling off.

[0110] In some embodiments, along a direction perpendicular to the plane where the first sidewall 21 is located, the orthographic projection of one end of the first electrode 401 near the cover plate 1 onto the first sidewall 21 is located within the transition region 2122.

[0111] That is, the end of the first electrode 401 near the cover plate 1 is positioned opposite to the transition region 2122, so that when the cell 4 expands during charging and discharging, the first electrode 401 and the transition region 2122 come into contact. Compared with the first electrode 401 directly contacting the equal thickness region 2121, the transition region 2122 can reduce the rigid compression of the first electrode 401, thereby significantly alleviating the tendency of the active material on the surface of the first electrode 401 to peel off, and further improving the cycle life and structural reliability of the cell.

[0112] In some embodiments, the thickness of the transition region 2122 gradually decreases in the direction toward the base portion 211.

[0113] By gradually reducing the thickness of the transition region 2122 in the direction toward the base 211, the squeezing force on the first electrode 401 can be gradually reduced, thereby reducing the risk of the first electrode 401 falling off during the cell expansion process.

[0114] The thickness reduction rate of the transition zone 2122 is linear, ensuring a uniform wall thickness transition and avoiding sudden increases in local stress. This facilitates processing and forming. In this case, the thickness of the end of the transition zone 2122 closer to the base 211 is greater than the thickness of the end farther from the base 211. As a variation, the thickness of the transition zone 2122 can also be uniform, with the overall thickness reduced. That is, the first sidewall 21 can be in the form of multiple steps, where the thickness of the uniform thickness zone 2121 is greater than that of the transition zone 2122, and the thickness of the transition zone 2122 is greater than that of the base 211. This ensures structural rigidity while achieving gradual stress release.

[0115] In some embodiments, the cover plate 1 includes a cover plate body 11 and a boss 12. The boss 12 protrudes from the cover plate body 11 along a first direction toward the side of the battery cell 4 and is provided to extend at least partially into the cavity. In the direction perpendicular to the first direction, the edge of the cover body 11 protrudes from the boss 12 to form an overlap portion 111, and the end face of the housing 2 located at the opening 29 is fixedly connected to the overlap portion 111. In a direction perpendicular to the plane of the first sidewall 21, the first connecting portion 212 does not protrude from the overlapping portion 111.

[0116] Combination Figure 7 As shown, the cover plate 1 includes two parts, the upper part being the cover plate body 11 and the lower part being the boss 12; in the assembled state, the cover plate body 11 is fitted with the top end face of the housing 2, while the boss 12 is embedded inside the housing 2.

[0117] Optionally, the boss 12 can be tightly fitted with the inner wall of the housing 2 to enhance structural stability and suppress welding deformation. Additionally, the outer peripheral surface of the boss 12 can form an interference fit or a clearance fit with the inner wall of the first connecting portion 212.

[0118] Perpendicular to the first direction, the edge of the cover body 11 has a protruding boss 12 forming an overlapping part 111. The overlapping part 111 abuts against the end face of the housing 2 located at the opening 29, forming a stable support interface, thereby preventing the cover body 11 from extending too far into the cavity and causing structural interference.

[0119] In the direction perpendicular to the plane of the first sidewall 21, the first connecting part 212 does not protrude from the overlapping part 111, thereby ensuring that the cover plate 1 and the housing 2 can be accurately positioned during assembly, and avoiding the first sidewall 21 from protruding too far outward, which would cause assembly interference; at the same time, the sidewall of the boss 12 is used to limit the first connecting part 212, preventing the first connecting part 212 from shifting too far inward, and ensuring the spacing between the first connecting part 212 and the battery cell 4.

[0120] Conversely, when the first connecting part 212 protrudes from the overlapping part 111, that is, in the direction perpendicular to the plane where the first side wall 21 is located, the thickness of the first connecting part 212 is greater than the size of the overlapping part 111. In this case, although the connection strength between the cover plate 1 and the housing 2 can be improved, it will lead to a greater risk of the battery cell 4 falling off.

[0121] In some embodiments, combined with Figure 7 As shown, along the first direction, the extension dimension of the boss 12 is D mm, which satisfies 0.8 mm ≤ D mm ≤ 4 mm.

[0122] Along the first direction, the extension dimension D mm of the boss 12 refers to the distance from the lower surface of the lap portion 111 (the end face of the lap portion 111 facing the housing 2) to the end face of the boss 12 away from the lower surface of the lap portion 111; when the lap portion 111 and the end face of the housing 2 located at the opening 29 are tightly assembled, D mm is also the depth to which the boss 12 extends into the receiving cavity.

[0123] By limiting the upper limit of D mm, it is possible to effectively prevent the boss 12 from excessively intruding into the cavity and squeezing the space of the cell 4, thus ensuring the energy density of the battery cell.

[0124] Furthermore, since a portion of the boss 12 melts and participates in forming the first welding area 3 during the welding process, by limiting the lower limit of the value of D mm, it can be ensured that the boss 12 has sufficient molten material to participate in the welding, thereby ensuring the weld strength and sealing reliability of the first welding area 3 and avoiding incomplete welding due to insufficient molten material.

[0125] For example, in this embodiment, the value of D mm can be 0.8 mm, 1.1 mm, 1.3 mm, 1.6 mm, 1.9 mm, 2.2 mm, 2.5 mm, 2.7 mm, 3 mm, 3.3 mm, 3.6 mm, 3.9 mm, or 4 mm, or it can be any range formed by any two of the above values.

[0126] In some embodiments, combined with Figure 9 As shown, the housing 2 also includes a second sidewall 22, which is arranged adjacent to the first sidewall 21, and both the second sidewall 22 and the first sidewall 21 are provided with a first connecting portion 212.

[0127] By providing a first connecting part 212 on both the adjacent second sidewall 22 and the first sidewall 21, it can be ensured that the first welding area 3 of the multiple sidewalls welded to the cover plate 1 and the shell 2 have high structural strength, which can further improve the connection strength between the cover plate 1 and the shell 2 and reduce the risk of cracking.

[0128] In some embodiments, the first connecting portion 212 is continuously provided along the circumferential direction of the opening 29.

[0129] By continuously providing the first connecting portion 212 along the circumferential direction of the opening 29, the structural strength of the cover plate 1 and the housing 2 after welding can be significantly improved. Furthermore, the continuously provided first connecting portion 212 can ensure that the first welding area 3 is evenly distributed, avoid stress concentration, and enhance the reliability of the overall structure.

[0130] As a variation, in some other embodiments, the first connecting portion 212 is spaced apart along the circumferential direction of the opening 29. In this case, the forming process of the first connecting portion 212 is more flexible and more conducive to processing and forming. Moreover, the distribution density and single-segment length can be precisely adjusted according to the actual welding strength requirements, so as to ensure the structural strength while taking into account the manufacturing process.

[0131] In some embodiments, the housing 2 further includes a second sidewall 22, which is disposed adjacent to the first sidewall 21, and the area of ​​the first sidewall 21 is larger than the area of ​​the second sidewall 22. In the direction perpendicular to the plane where the first sidewall 21 is located, the difference between the thickness of the first connecting part 212 provided on the first sidewall 21 and the thickness of the base part 211 is ΔE, which satisfies 0.05mm≤ΔE≤1mm.

[0132] The area of ​​the first sidewall 21 is greater than the area of ​​the second sidewall 22. That is, the first sidewall 21 is the long sidewall, and the second sidewall 22 is the short sidewall adjacent to the first sidewall 21.

[0133] Since the first sidewall 21 is a long sidewall, the side of the battery cell 4 opposite to the first sidewall 21 deforms more when the battery cell 4 expands. Furthermore, because the first connecting portion 212 protrudes from the first sidewall 21, the side of the battery cell 4 opposite to the first sidewall 21 is more easily compressed. Therefore, by limiting the upper limit of the difference ΔE between the thickness of the first connecting portion 212 on the first sidewall 21 and the thickness of the base portion 211, the degree of compression on the battery cell 4 can be effectively alleviated, preventing the battery cell 4 from falling off due to excessive compression. Simultaneously, by limiting the lower limit of ΔE, sufficient structural margin can be ensured for the first connecting portion 212 to participate in welding, guaranteeing the welding reliability of the shell 2 and the cover plate 1.

[0134] For example, in this embodiment, the value of ΔE can be 0.05mm or 0.08mm or 0.12mm or 0.17mm or 0.23mm or 0.3mm or 0.38mm or 0.45mm or 0.53mm or 0.62mm or 0.71mm or 0.8mm or 0.92mm or 1mm, or it can be any range formed by any two of the above values.

[0135] In some embodiments, in a direction perpendicular to the plane where the first sidewall 21 is located, the difference between the thickness of the first connecting portion 212 provided on the first sidewall 21 and the thickness of the base portion 211 is ΔE, which satisfies 0.05mm≤ΔE≤1.2mm.

[0136] In this embodiment, the specific areas of the first sidewall 21 and the second sidewall 22 are not specifically limited. That is, the first sidewall 21 may be a long sidewall or a short sidewall, and correspondingly, the second sidewall 22 may be a long sidewall or a short sidewall. When the first sidewall 21 is a short sidewall, its deformation due to the expansion of the battery cell is relatively small. In this case, the upper limit of ΔE can be appropriately increased to enhance the welding strength.

[0137] By limiting the upper limit of ΔE, the degree of compression on the battery cell 4 can be effectively alleviated, and the battery cell 4 can be prevented from falling off due to excessive compression. At the same time, by limiting the lower limit of ΔE, it can be ensured that the first connecting part 212 has sufficient structural margin to participate in welding, and the welding reliability of the shell 2 and the cover plate 1 can be guaranteed.

[0138] For example, in this embodiment, the value of ΔE can be 0.05mm or 0.08mm or 0.13mm or 0.19mm or 0.25mm or 0.32mm or 0.4mm or 0.48mm or 0.57mm or 0.68mm or 0.8mm or 0.93mm or 1.05mm or 1.2mm, or it can be any range formed by any two of the above values.

[0139] In some embodiments, the battery cell 4 includes a battery cell body 41 and a tab 42 extending from at least one end of the battery cell body 41, the tab 42 extending toward the side of the cover plate 1; The battery cell also includes a terminal assembly 6, which is disposed on the cover plate 1 and is electrically connected to the tab portion 42.

[0140] The electrode assembly 6 is electrically connected to the tab 42. Specifically, the electrode assembly 6 may include an electrode body, which penetrates the cover plate 1 and is welded and fixed to the tab 42. During the welding process, the contact surfaces of the electrode body and the tab 42 are fully fused to ensure stable and reliable current transmission. As a variation, the electrode assembly 6 may include a combination structure of an electrode body and a conductive sheet. One side of the conductive sheet is firmly connected to the tab 42 by welding, and the other side of the conductive sheet is riveted or welded to the electrode body.

[0141] Since the cell body 41 includes a first electrode 401, by providing an electrode tab 42 between the cell body 41 and the cover plate 1, the distance between the first electrode 401 and the cover plate 1 can be increased, thereby avoiding excessive overlap between the first electrode 401 and the first connection portion 212, and reducing the risk of stress concentration caused by thermal expansion of the first electrode 401 during charging and discharging.

[0142] In some embodiments, the following relationship is satisfied: 0.5 ≤ ≤28.

[0143] Since the electrode assembly 6 is electrically connected to the tab 42, during charging and discharging, current is conducted to the electrode assembly 6 through the tab 42, resulting in a significant local temperature rise in the tab 42. Simultaneously, because the tab 42 is close to the sealing opening 29 of the cover plate 1, heat is easily conducted to the first welding area 3, further exacerbating the accumulation of thermal stress in the first welding area 3. This leads to a high risk of cracking in the first welding area 3, therefore, it is necessary to appropriately lower the temperature. The lower limit of the formula value is used to enhance the thermal stability of the first welding area 3 and prevent cracking of the first welding area 3 when the shell 2 is welded to the cover plate 1.

[0144] For example, in this embodiment, The value can be 0.5 or 1.2 or 2.7 or 4.3 or 6.8 or 9.5 or 12.1 or 15.3 or 18.7 or 22.4 or 25.9 or 28, or it can be any range formed by any two of the above values.

[0145] In some embodiments, at least a portion of the first connection portion 212 forms a first welding area 3.

[0146] In this embodiment, at least a portion of the first connecting portion 212 is further defined to form the first welding area 3. That is, the first welding area 3 is directly located on the thickened area of ​​the housing 2, which better ensures the connection strength between the housing 2 and the cover plate 1.

[0147] In some embodiments, the penetration direction of the first welding zone 3 is perpendicular to the first direction.

[0148] At this time, the battery cell adopts the side welding method. The direction of the penetration of the first weld line 3 is perpendicular to the vibration direction of the cover plate 1, which helps to improve the connection strength between the cover plate 1 and the shell 2, ensure vibration resistance stability, avoid stress concentration of the weld line, and make the welded joint maintain structural integrity under long-term dynamic load.

[0149] As a variation, the penetration direction of the first welding zone 3 can also be parallel to the first direction. That is, the battery cell adopts top welding, which improves the welding rate, ensures the assembly efficiency of the battery, and avoids the side welding laser hitting the inside of the battery casing, causing the internal insulation components of the battery to melt, thus ensuring the internal insulation safety.

[0150] In some embodiments, the battery cell 4 further includes a second electrode 402, which is disposed on the inner side of the battery cell 4 relative to the first electrode 401; The total thickness of the active material layer 412 of the second electrode 402 is greater than the total thickness of the active material layer 412 of the first electrode 401.

[0151] The second electrode 402 is disposed on the inner side of the battery cell 4 relative to the first electrode 401, which reduces the compressive force on the second electrode 402 during expansion. By making the total thickness of the active material layer 412 of the second electrode 402 greater than that of the active material layer 412 of the first electrode 401, the overall energy density of the battery cell 4 can be effectively improved. On the other hand, by making the total thickness of the active material layer 412 of the first electrode 401 smaller, it helps to reduce the risk of material shedding from the outer electrode during charging and discharging.

[0152] In this embodiment, the polarity of the second electrode 402 is the same as that of the first electrode 401.

[0153] In some embodiments, the following is satisfied: 15 MPa ≤ a MPa ≤ 100 MPa; and / or, 1.4 ≤ t ≤ 70; and / or, 0.008 mm ≤ h ≤ 0.12 mm.

[0154] Specifically, when the ratio t of the total thickness of the active material layer 412 to the thickness of the current collector layer 411 is larger, the active material layer 412 is thicker, the bonding force between the active material layer 412 and the current collector layer 411 is weaker, and the active material layer 412 is easier to peel off when the battery cell expands; that is, when the ratio t is too large, the active material layer 412 is too thick, which leads to uneven stress transmission, aggravates the local deformation of the contact area with the first connection part 212, and increases the risk of material loss. Conversely, when the ratio t is too small, the active material layer 412 is too thin. In this case, the more fully the active material layer 412 contacts the electrolyte, the greater the side reaction and the more gas is produced, leading to more drastic changes in internal pressure, greater expansion of the battery cell, and increased risk of cracking in the first welding area 3. In addition, since the current collector layer 411 is usually made of metal and has relatively higher hardness (the active material layer 412 has a porous structure and better compressibility than the current collector layer 411), when t is smaller, the current collector layer 411 accounts for a larger proportion, resulting in increased overall rigidity of the cell 4. During the repeated expansion and contraction of the cell 4, it is more likely to have a hard collision with the first connection part 212, and it is more likely to concentrate stress to the first welding area 3, exacerbating the tendency of weld cracking. Moreover, the smaller t is, the thinner the active material layer 412 is, the insufficient energy density, which can easily lead to a decrease in the energy density of the cell, and the larger the exposed area of ​​the current collector, which can easily cause micro-short circuits. Therefore, it is necessary to control the ratio t within a reasonable range to ensure the mechanical matching and coordination between the active material layer 412 and the current collector layer 411, so as to ensure the stable bonding between the active material layer and the current collector, while taking into account both energy density and structural reliability.

[0155] For example, when the value of t is in the range of 1.4 ≤ t ≤ 70, the value of t can be 1.4 or 1.5 or 1.8 or 2.1 or 2.2 or 2.3 or 2.4 or 2.6 or 2.9 or 3.2 or 3.5 or 3.8 or 4.1 or 4.4 or 4.7 or 5.0 or 5.3 or 5.6 or 5.9 or 6.2 or 6.5 or 6.8 or 7.1 or 7.4 or 7.7 or 8.0 or 8.3 or 8.6 or 8.9 or 9.2 or 9.5 or 9.8 or 10.1 or 10 .4 or 10.7 or 11.0 or 11.3 or 11.6 or 11.9 or 12.2 or 13 or 15 or 17 or 19 or 21 or 23 or 25 or 27 or 29 or 31 or 32.7 or 34 or 36 or 37 or 39 or 41 or 43 or 45.2 or 47 or 49.6 or 50 or 51 or 53 or 54 or 56 or 58.4 or 60 or 61.2 or 63 or 65 or 66.98 or 68 or 70, etc., or any two of the above values ​​forming an interval range.

[0156] Preferably, the ratio t of the total thickness of the active material layer 412 to the thickness of the current collector layer 411 can be in the range of 2.3 ≤ t ≤ 50.

[0157] When the value of t is within the preferred range of 2.3≤t≤50, the risk of cracking in the first welding zone 3 can be better reduced, the active material layer can be better bonded to the current collector, and the energy density can be guaranteed.

[0158] For example, when the value of t is within the preferred range of 2.3 ≤ t ≤ 50, the value of t can be 2.3 or 2.4 or 2.6 or 2.8 or 3.0 or 3.2 or 3.4 or 3.6 or 3.8 or 4.0 or 4.2 or 4.5 or 4.8 or 5.1 or 5.4 or 5.7 or 6.0 or 6.3 or 6.6 or 6.9 or 7.2 or 7.5 or 7.8 or 8.1 or 8.4 or 8.7 or 9.0 or 9.3 or 9.6 or 9.9 or 10.2 or 10.5 or 10.8 or 11.1 or 11.4 or 11.7 or 12.0 or 12.3 or 12.6 or 12.9 or 13 or 14.5 or 16.0 or 17.5 or 19.0 or 20.5 or 22.0 or 23.5 or 25.0 or 26.5 or 27 or 28.5 or 30.0 or 31.5 or 32.7 or 34.0 or 35.5 or 37 or 38.5 or 40.0 or 41.5 or 43.0 or 44.5 or 45.2 or 46.5 or 48.0 or 49.6 or 50, etc., or any two of the above values ​​forming an interval range.

[0159] Specifically, the hardness 'a' of the current collector layer 411 reflects its ability to resist plastic deformation. A higher hardness 'a' makes the current collector layer 411 less prone to deformation under pressure, but it also reduces its flexibility, thus affecting the stress buffering capacity of the electrode during cell expansion. In other words, when the hardness 'a' is too high, the active material layer 412 attached to the current collector layer 411 is more susceptible to greater compressive stress due to limited deformation space, thereby increasing the risk of cracking. Therefore, the hardness 'a' needs to be controlled within a reasonable range, balancing structural rigidity and deformation adaptability.

[0160] For example, when the value of a MPa is within the range of 15 MPa ≤ a MPa ≤ 100 MPa, the value of a MPa can be 15 MPa, 15.5 MPa, 16 MPa, 16.6 MPa, 17.2 MPa, 17.8 MPa, 18.5 MPa, 19.4 MPa, 20 MPa, 20.7 MPa, 21.5 MPa, 22.2 MPa, 23 MPa, 23.5 MPa, 24.2 MPa, 25 MPa, 26.3 MPa, 27.6 MPa, 29 MPa, 30.5 MPa, 32 MPa, 33.5 MPa, 35 MPa, 36.7 MPa, 38.4 MPa, 40 MPa, 42 MPa, 43.8 MPa, 45.6 MPa, 47.5 MPa, or 49 MPa. 4 MPa, 51.3 MPa, 53.2 MPa, 56 MPa, 58.9 MPa, 61.8 MPa, 64.7 MPa, 67.3 MPa, 70 MPa, 72.6 MPa, 74.1 MPa, 76.7 MPa, 79.3 MPa, 80.8 MPa, 82.5 MPa, 84.2 MPa, 85 MPa, 86.2 MPa, 87.5 MPa, 88.7 MPa, 90 MPa, 91.5 MPa, 93 MPa, 94.7 MPa, 96.3 MPa, 97.5 MPa, 98.8 MPa, or 100 MPa, etc., or any range formed by any two of the above values.

[0161] Preferably, the hardness α MPa of the current collector layer 411 can be in the range of 23 MPa ≤ α MPa ≤ 85 MPa.

[0162] When the value of a MPa is within the preferred range of 23 MPa ≤ a MPa ≤ 85 MPa, it can better balance structural rigidity and deformation adaptability.

[0163] For example, when the value of a MPa is within the preferred range of 23 MPa ≤ a MPa ≤ 85 MPa, the value of a MPa can be 23 MPa, 23.5 MPa, 24.2 MPa, 25 MPa, 25.7 MPa, 26.5 MPa, 27.3 MPa, 28.1 MPa, 29 MPa, 29.8 MPa, 30.6 MPa, 31.4 MPa, 32.2 MPa, 33 MPa, 33.8 MPa, 34.6 MPa, 35.5 MPa, 36.3 MPa, 37.1 MPa, 38 MPa, 38.8 MPa, 39.6 MPa, 40.4 MPa, 42 MPa, 42.8 MPa, 43.6 MPa, 44.5 MPa, 45.3 MPa, 46.1 MPa, 47 MPa, or 47.8 MPa. The values ​​can be 48.6 MPa, 49.4 MPa, 50.2 MPa, 52 MPa, 53.8 MPa, 55.6 MPa, 56 MPa, 57.4 MPa, 58.8 MPa, 60.2 MPa, 61.6 MPa, 63 MPa, 64.4 MPa, 65.8 MPa, 67.3 MPa, 68.7 MPa, 70.1 MPa, 71.5 MPa, 73 MPa, 74.1 MPa, 75.5 MPa, 76.9 MPa, 78.3 MPa, 79.7 MPa, 80.8 MPa, 82.2 MPa, 83.6 MPa, or 85 MPa, or any range formed by any two of the above values.

[0164] Specifically, when the proportion h of the dimension of the first connecting part 212 along the first direction to the total dimension h of the first sidewall 21 is too large, the area of ​​the first connecting part 212 increases, the contact area with the active material layer 412 increases, which leads to increased local stress concentration and is prone to causing compression damage to the larger area of ​​the active material layer 412, increasing the risk of peeling off the active material layer; while when h is too small, the weld line size is easily small, resulting in insufficient connection strength between the shell 2 and the cover plate 1. In the event of thermal runaway, due to the rapid expansion of the gas inside the battery, the first weld area 3 is easily blown open, or even the entire battery cover plate flies out, causing a serious safety accident.

[0165] For example, when the value of h is in the range of 0.008 ≤ h ≤ 0.12, the value of h can be 0.008, 0.009, 0.011, 0.013, 0.015, 0.017, 0.02, 0.022, 0.025, 0.028, 0.032, 0.033, 0.035, 0.038, 0.04, 0.041, 0.043, 0.045, 0.047, 0.048, 0.05, 0.051, or 0.05. 2 or 0.055 or 0.058 or 0.061 or 0.064 or 0.067 or 0.07 or 0.071 or 0.074 or 0.077 or 0.08 or 0.083 or 0.086 or 0.089 or 0.092 or 0.095 or 0.098 or 0.1 or 0.102 or 0.105 or 0.108 or 0.11 or 0.112 or 0.115 or 0.118 or 0.12, etc., or it can be any interval range formed by any two of the above values.

[0166] Preferably, along the first direction, the ratio h of the size of the first connecting part 212 to the total size of the first sidewall 21 can be in the range of 0.032≤h≤0.052.

[0167] When the value of h is within the preferred range of 0.032≤h≤0.052, the risk of peeling off the active material layer can be reduced, while the weld line size can be better guaranteed, thereby ensuring the connection strength between the shell 2 and the cover plate 1.

[0168] For example, when the value of h is within the preferred range of 0.032 ≤ h ≤ 0.052, the value of h can be 0.032 or 0.033 or 0.034 or 0.035 or 0.036 or 0.037 or 0.038 or 0.0385 or 0.039 or 0.0395 or 0.04 or 0.0405 or 0.041 or 0.0415 or 0.042 or 0.0425 or 0. 043 or 0.0435 or 0.044 or 0.0445 or 0.045 or 0.0455 or 0.046 or 0.0465 or 0.047 or 0.0475 or 0.048 or 0.0485 or 0.049 or 0.0495 or 0.05 or 0.0505 or 0.051 or 0.0515 or 0.052, etc., or any interval range formed by any two of the above values.

[0169] In some embodiments, the first electrode 401 has an active material layer 412 on both sides of the current collector layer 411 along the thickness direction.

[0170] By providing active material layers 412 on both sides of the first electrode 401 along the thickness direction of the current collector layer 411, the active material layers 412 are coated on both sides of the current collector layer 411 while maintaining the same energy density. This halves the coating thickness on one side, preventing the bonding force between the active material layer 412 and the current collector layer 411 from weakening due to excessive coating thickness on one side. This reduces the risk of interface peeling and material shedding. Simultaneously, the double-sided coating structure balances the stress distribution on both sides of the current collector layer 411, suppressing warping deformation during charging and discharging, and further improving the structural stability of the electrode during cycling.

[0171] In some embodiments, the first electrode 401 has a first protrusion 4011 formed along the thickness direction, and the first protrusion 4011 protrudes toward the first sidewall 21.

[0172] During the preparation of the first electrode 401, after the active material layer 412 is coated onto the current collector layer 411, the active material layer 412 is embossed by an anilox roller to form a first protrusion 4011 on the surface of the active material layer 412, which can better release stress and reduce the risk of material loss.

[0173] In some embodiments, there are multiple first protrusions 4011, which are spaced apart, and the distance between adjacent first protrusions 4011 is F mm, satisfying 1 mm ≤ F mm ≤ 8 mm.

[0174] Since the first protrusion 4011 is formed by pressing with an anilox roller, when the interval F mm between adjacent first protrusions 4011 is too small, the protrusions are too dense, which makes it easy for material to fall off when passing through the roller; while when the interval F mm is too large, the arrangement of the first protrusions 4011 is too sparse, which cannot better release stress and cannot effectively reduce the risk of material falling off.

[0175] As a further preferred option, the value of F mm satisfies 2mm≤F mm≤5mm.

[0176] For example, in this embodiment, the value of F mm can be 1 mm, 1.3 mm, 1.7 mm, 2.2 mm, 2.8 mm, 3.4 mm, 4 mm, 4.5 mm, 5.1 mm, 5.8 mm, 6.3 mm, 7 mm, 7.6 mm, or 8 mm, or it can be any range formed by any two of the above values.

[0177] In some embodiments, the current collector layer 411 includes copper, and the mass percentage of copper in the current collector layer 411 is not less than 98.5%.

[0178] Since copper has good conductivity and ductility, by limiting the mass ratio of copper element in the current collector layer 411 to not less than 98.5%, the hardness a of the current collector layer 411 can be reduced. When the hardness a is lower, the current collector layer 411 has better flexibility. When the active material layer 412 attached to the current collector layer 411 is subjected to extrusion pressure, it can more effectively buffer deformation, thereby reducing the risk of material falling off.

[0179] Preferably, the mass percentage of copper in the current collector layer 411 can be in the range of 99.7% to 99.99%.

[0180] For example, in this embodiment, the value of F mm can be 98.5% or 98.7% or 98.95% or 99.1% or 99.3% or 99.5% or 99.65% or 99.75% or 99.82% or 99.88% or 99.93% or 99.96% or 99.99%, or it can be any range formed by any two of the above values.

[0181] In some embodiments, the current collector layer 411 includes a first non-metallic layer, a metal layer, and a second non-metallic layer, with the metal layer disposed between the first non-metallic layer and the second non-metallic layer.

[0182] The current collector layer 411 includes a metal layer and a non-metal layer. Specifically, the non-metal layer may include a first non-metal layer and a second non-metal layer; in this case, the current collector layer 411 is a composite current collector. Since the current collector layer 411 includes a non-metal layer, the non-metal layer can reduce the overall hardness of the current collector layer 411 and improve its flexibility, making it easier for the active material layer 412 to deform in tandem under extrusion pressure, thereby reducing the risk of material loss.

[0183] In this embodiment, the current collector layer 411 includes a metal layer and a non-metal layer, specifically a polymer material substrate. The current collector layer 411 can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). The negative electrode active layer includes a negative electrode active material, a conductive agent, a binder, etc.

[0184] In some embodiments, the ratio of the thickness of the non-metallic layer to the thickness of the metallic layer ranges from 0.06 to 4.5.

[0185] In this embodiment, the non-metallic layer includes a first non-metallic layer and a second non-metallic layer; the thickness of the non-metallic layer refers to the sum of the thicknesses of the first non-metallic layer and the second non-metallic layer.

[0186] Preferably, the ratio of the thickness of the non-metallic layer to the thickness of the metallic layer is in the range of 0.007-0.28.

[0187] For example, in this embodiment, the ratio of the thickness of the non-metallic layer to the thickness of the metallic layer can be 0.06, 0.15, 0.42, 0.78, 1.23, 1.65, 2.1, 2.55, 3.02, 3.47, 3.9, 4.35, or 4.5, or it can be any range formed by any two of the above values.

[0188] When the ratio of the thickness of the non-metallic layer to the thickness of the metallic layer is too large, although it can further improve flexibility, the conductivity will decrease significantly, affecting current transmission. When the ratio of the thickness of the non-metallic layer to the thickness of the metallic layer is too small, it is easy to cause the overall hardness of the current collector layer 411 to be too large and the flexibility to be insufficient, which cannot effectively relieve the deformation stress of the active material layer 412, and the risk of material falling off is still high.

[0189] The thickness of the non-metallic layer ranges from 0.1 micrometers to 10 micrometers; preferably, the thickness of the non-metallic layer ranges from 0.1 micrometers to 8 micrometers.

[0190] For example, in this embodiment, the thickness of the non-metallic layer can be 0.1 micrometer, 0.3 micrometer, 0.6 micrometer, 1.2 micrometer, 1.8 micrometer, 2.5 micrometer, 3.3 micrometer, 4.2 micrometer, 5.5 micrometer, 6.8 micrometer, 7.9 micrometer, 9.1 micrometer, or 10 micrometer, or it can be a range formed by any two of the above values.

[0191] The thickness of the metal layer ranges from 2 micrometers to 20 micrometers; preferably, the thickness of the metal layer ranges from 4 micrometers to 16 micrometers.

[0192] For example, in this embodiment, the thickness of the metal layer can be 2 micrometers, 3.2 micrometers, 4.7 micrometers, 6.1 micrometers, 7.8 micrometers, 9.3 micrometers, 11 micrometers, 13.5 micrometers, 15.2 micrometers, 17 micrometers, 18.8 micrometers, or 20 micrometers, or it can be a range formed by any two of the above values.

[0193] According to an embodiment of the present invention, in another aspect, a battery pack is also provided, comprising: Multiple battery cells as described above; Multiple battery cells are arranged sequentially along a second direction, which is perpendicular to the first direction.

[0194] By stacking multiple battery cells along the second direction to form a compact battery pack structure, the mutual support and limiting effect between the battery cells can be used to reduce the deformation of the side wall of the casing 2 perpendicular to the second direction during charging and discharging, thus avoiding the risk of cracking of the cover plate 1 and the first welding area 3 of the casing 2.

[0195] In some embodiments, the second direction is perpendicular to the plane containing the first sidewall 21.

[0196] The second direction is perpendicular to the plane where the first sidewall 21 is located. That is, the first sidewalls 21 of adjacent battery cells are parallel to each other and closely attached. During charging and discharging, the overall expansion of the cell is suppressed, the deformation of the first sidewall 21 is reduced, and the risk of cracking of the first welding area 3 of the cover plate 1 and the shell 2 is avoided.

[0197] According to an embodiment of the present invention, in another aspect, an electrical device is also provided, comprising: The electrical device body and the battery pack as described above, which is electrically connected to the electrical device body.

[0198] In this embodiment, the electrical device can be a battery pack, electric vehicle, electric ship, aircraft, electric device, energy storage device, laptop, aerospace equipment, etc.

[0199] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope defined by the present invention.

Claims

1. A battery cell, characterized in that, include: A cover plate (1) and a housing (2) are provided. The housing (2) has an opening (29) at least at one end along a first direction, which is perpendicular to the large surface direction of the cover plate (1). The cover plate (1) seals the opening (29) and is welded to the housing (2) to form a first welding area (3). The cover plate (1) and the housing (2) enclose a receiving cavity. The housing (2) includes a first sidewall (21), the plane of which the first sidewall (21) is located is perpendicular to the plane of which the cover plate (1) is located. The first sidewall (21) includes a base part (211) and a portion along the first direction. A first connecting portion (212) is provided on the side of the base part (211) near the opening (29). The base part (211) is connected to the first connecting portion (212). In a direction perpendicular to the plane of the first sidewall (21), the thickness of the first connecting portion (212) is greater than the thickness of the base part (211), and the side of the first connecting portion (212) facing the receiving cavity protrudes relative to the base part (211). Along the first direction, the size of the first connecting portion (212) accounts for h of the total size of the first sidewall (21). A battery cell (4) is disposed within the receiving cavity. The battery cell (4) includes a first electrode (401). The first electrode (401) is at least partially parallel to and close to the first sidewall (21). In a direction perpendicular to the plane of the first sidewall (21), the projection of the first electrode (401) on the first sidewall (21) coincides with at least a portion of the projection of the first connecting portion (212). The first electrode (401) includes a current collector layer (411) and an active material layer (412) disposed on at least one side surface of the current collector layer (411). The ratio of the total thickness of the active material layer (412) to the thickness of the current collector layer (411) is t. The hardness of the current collector layer (411) is a MPa. And it satisfies the relation: 0.43≤ ≤28.

2. The battery cell according to claim 1, characterized in that, Along the first direction, the end of the first electrode (401) near the cover plate (1) is spaced apart from the end of the first connecting portion (212) near the opening (29), and the end of the first electrode (401) near the cover plate (1) is further away from the cover plate (1) than the end of the first connecting portion (212) near the opening (29).

3. The battery cell according to claim 2, characterized in that, Along the first direction, the distance between the end of the first electrode (401) near the cover plate (1) and the lower surface of the cover plate (1) near the cell (4) is B mm, which satisfies 5 mm ≤ B mm ≤ 20 mm.

4. The battery cell according to claim 2, characterized in that, The first connecting part (212) is located along the center line S in the first direction between the end of the first electrode (401) near the cover plate (1) and the lower surface of the cover plate (1) near the cell (4).

5. The battery cell according to claim 4, characterized in that, It satisfies: 1.8≤t≤70.

6. The battery cell according to claim 2, characterized in that, The first connecting part (212) is flush with the end of the first electrode (401) near the cover plate (1) along the center line S in the first direction; Alternatively, the first connecting portion (212) is positioned further away from the cover plate (1) along the center line S in the first direction than the end of the first electrode (401) that is closer to the cover plate (1).

7. The battery cell according to claim 6, characterized in that, Along the first direction, the distance between the center line S of the first connecting part (212) and the end of the first electrode (401) near the cover plate (1) is C mm, which satisfies 1 mm ≤ C mm ≤ 12 mm.

8. The battery cell according to claim 1, characterized in that, The first connecting portion (212) includes a constant thickness region (2121) and a transition region (2122) along the first direction. In the direction perpendicular to the plane where the first sidewall (21) is located, the maximum thickness of the transition region (2122) is less than the thickness of the constant thickness region (2121). The two ends of the transition region (2122) are respectively connected to the base portion (211) and the constant thickness region (2121).

9. The battery cell according to claim 8, characterized in that, The equal thickness zone (2121) at least partially forms the first welding zone (3).

10. The battery cell according to claim 8, characterized in that, Along the direction perpendicular to the plane where the first sidewall (21) is located, the orthographic projection of the end of the first electrode (401) near the cover plate (1) on the first sidewall (21) is located within the transition zone (2122).

11. The battery cell according to claim 8, characterized in that, The thickness of the transition zone (2122) gradually decreases in the direction toward the base (211).

12. The battery cell according to any one of claims 1 to 11, characterized in that, The cover plate (1) includes a cover plate body (11) and a boss (12). The boss (12) protrudes from the cover plate body (11) along the first direction toward the battery cell (4) and extends at least partially into the receiving cavity. In the direction perpendicular to the first direction, the edge of the cover body (11) protrudes from the boss (12) to form an overlap (111), and the end face of the housing (2) located at the opening (29) is fixedly connected to the overlap (111). In a direction perpendicular to the plane of the first sidewall (21), the first connecting portion (212) does not protrude from the overlapping portion (111).

13. The battery cell according to claim 12, characterized in that, Along the first direction, the extension dimension of the boss (12) is D mm, which satisfies 0.8 mm ≤ D mm ≤ 4 mm.

14. The battery cell according to any one of claims 1 to 11, characterized in that, The housing (2) further includes a second sidewall (22), which is arranged adjacent to the first sidewall (21), and both the second sidewall (22) and the first sidewall (21) are provided with the first connecting portion (212).

15. The battery cell according to claim 14, characterized in that, The first connecting portion (212) is continuously arranged along the circumferential direction of the opening (29).

16. The battery cell according to any one of claims 1 to 11, characterized in that, The housing (2) further includes a second sidewall (22), which is arranged adjacent to the first sidewall (21), and the area of ​​the first sidewall (21) is larger than the area of ​​the second sidewall (22); In the direction perpendicular to the plane where the first sidewall (21) is located, the difference between the thickness of the first connecting part (212) provided on the first sidewall (21) and the thickness of the base part (211) is ΔE, which satisfies 0.05mm≤ΔE≤1mm.

17. The battery cell according to any one of claims 1 to 11, characterized in that, In the direction perpendicular to the plane where the first sidewall (21) is located, the difference between the thickness of the first connecting part (212) provided on the first sidewall (21) and the thickness of the base part (211) is ΔE, which satisfies 0.05mm≤ΔE≤1.2mm.

18. The battery cell according to any one of claims 1 to 11, characterized in that, The battery cell (4) includes a battery cell body (41) and a tab (42) extending from at least one end of the battery cell body (41), the tab (42) extending toward the cover plate (1); The battery cell also includes a terminal assembly (6), which is disposed on the cover plate (1) and is electrically connected to the tab (42).

19. The battery cell according to claim 18, characterized in that, Satisfies the relation: 0.5≤ ≤28.

20. The battery cell according to any one of claims 1 to 11, characterized in that, At least a portion of the first connecting portion (212) forms the first welding area (3).

21. The battery cell according to any one of claims 1 to 11, characterized in that, The direction of the penetration depth of the first welding zone (3) is perpendicular to the first direction.

22. The battery cell according to any one of claims 1 to 11, characterized in that, The battery cell (4) further includes a second electrode (402), which is disposed on the inner side of the battery cell (4) relative to the first electrode (401); The total thickness of the active material layer (412) of the second electrode (402) is greater than the total thickness of the active material layer (412) of the first electrode (401).

23. The battery cell according to any one of claims 1 to 11, characterized in that, satisfy: 15 MPa ≤ a MPa ≤ 100 MPa; and / or, 1.4 ≤ t ≤ 70; and / or, 0.008 ≤ h ≤ 0.

12.

24. The battery cell according to any one of claims 1 to 11, characterized in that, The active material layer (412) is provided on both sides of the first electrode (401) along the thickness direction of the current collector layer (411).

25. The battery cell according to any one of claims 1 to 11, characterized in that, The first electrode (401) has a first protrusion (4011) formed along the thickness direction, and the first protrusion (4011) protrudes toward the first sidewall (21).

26. The battery cell according to claim 25, characterized in that, The number of the first protrusions (4011) is multiple, and the multiple first protrusions (4011) are spaced apart. The spacing between adjacent first protrusions (4011) is F mm, which satisfies 1 mm ≤ F mm ≤ 8 mm.

27. The battery cell according to any one of claims 1 to 11, characterized in that, The current collector layer (411) includes copper, and the mass percentage of copper in the current collector layer (411) is not less than 98.5%.

28. The battery cell according to any one of claims 1 to 11, characterized in that, The current collector layer (411) includes a metal layer and a non-metal layer, the non-metal layer including a first non-metal layer and a second non-metal layer; the metal layer is disposed between the first non-metal layer and the second non-metal layer.

29. The battery cell according to claim 28, characterized in that, The ratio of the thickness of the non-metallic layer to the thickness of the metallic layer ranges from 0.06 to 4.

5.

30. A battery pack, characterized in that, include: Multiple battery cells as described in any one of claims 1 to 29; Multiple battery cells are arranged sequentially along a second direction, which is perpendicular to the first direction.

31. The battery pack according to claim 30, characterized in that, The second direction is perpendicular to the plane containing the first sidewall (21).

32. An electrical appliance, characterized in that, include: The electrical device body and the battery pack as described in any one of claims 30 to 31, which is electrically connected to the electrical device body.

Images