Battery cell, battery, and electric device

Abstract

A battery cell (100), a battery (1000), and an electric device (2000). The battery cell (100) comprises: a jelly roll (10), which comprises electrode sheets and separators (13) which are wound, wherein the jelly roll (10) has a winding gap (103) and comprises a straight portion (101) and bent portions (102) connected to the end portions of the straight portion (101), the electrode sheets include a first electrode sheet (11), the first electrode sheet (11) is provided with a first straight section (111) and a second straight section (112) which are located at the straight portion (101), and the first straight section (111) and the second straight section (112) are located on two opposite sides of the winding gap (103); and a buffer pad (20), which is arranged in the winding gap (103), wherein at least part of the buffer pad (20) is located between the first straight segment (111) and the second straight segment (112).

Description

Battery cells, batteries and electrical devices Technical Field

[0001] The present application relates to the field of batteries, and in particular to a battery cell, a battery, and an electrical device. Background Art

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

[0003] During the battery's cycle operation, the innermost positive electrode sheet of the wound battery is prone to brittle fracture during hot pressing, resulting in burrs and reducing the reliability of the battery.

[0004] Summary of the Invention

[0005] In view of the above problems, the present application provides a battery cell, a battery and an electrical device, which can improve the reliability of the battery.

[0006] In the first aspect, the present application provides a battery cell, comprising: a winding core, comprising a pole piece and an isolation film arranged in a wound manner, the winding core having a winding gap, the winding core comprising a straight portion and a bend portion connected to the end of the straight portion, the pole piece comprising a first pole piece, the first pole piece having a first straight section and a second straight section located in the straight portion, the first straight section and the second straight section being located on opposite sides of the winding gap, and a buffer pad, the buffer pad being arranged in the winding gap and at least part of the buffer pad being located between the first straight section and the second straight section.

[0007] In the technical solution of the embodiment of the present application, by arranging a buffer pad at the winding gap, on the one hand, the buffer pad can balance the expansion force generated by the expansion of the battery cell during the charging and discharging process, improve the stress uniformity of the innermost circle electrode, and improve the local fracture problem caused by the uneven stress distribution of the innermost circle electrode, thereby improving the reliability of the battery cell; on the other hand, it can increase the curvature of the innermost circle electrode, reduce the probability of brittle fracture after hot pressing of the winding core, and improve the problem of internal short caused by burrs and powder loss due to brittle fracture of the innermost circle electrode, thereby improving the reliability of the battery cell.

[0008] In some embodiments, the first pole piece further comprises a first bend section, which is located at the bend and connects the first straight section and the second straight section. One end of the buffer extends to the first bend section. In the above technical solution, extending one end of the buffer to the first bend section further supports the pole piece at the bend, reduces the gap between adjacent pole pieces at the bend, and further helps to alleviate the lithium deposition problem at the bend.

[0009] In some embodiments, the first pole piece further comprises a second bend section, the second bend section being arranged opposite the first bend section and connected to the second straight section, and one end of the buffer pad extends to the second bend section. In the above technical solution, by extending one end of the buffer pad to the second bend section, it is beneficial to further support the pole piece at the bend, reduce the gap between adjacent pole pieces at the bend, and further help to improve the lithium deposition problem at the bend.

[0010] In some embodiments, a buffer pad is provided in the winding gap, with both ends of the buffer pad extending to the first bend section and the second bend section, respectively. In the above technical solution, the support effect on the bend section is improved, and the gap between adjacent pole pieces at the bend section is reduced, thereby better improving the lithium deposition problem at the bend section.

[0011] In some embodiments, the winding gap is provided with multiple buffer pads, arranged along the second bend section relative to the first bend section, with one end of one buffer pad extending to the first bend section, and one end of another buffer pad extending to the second bend section. In this technical solution, the support effect on the bend section is improved, and the gap between adjacent pole pieces at the bend is reduced, thereby further improving the lithium deposition problem at the bend section.

[0012] In some embodiments, the end surface of the buffer pad near the second bend section is a curved surface. In the above technical solution, the design of the buffer pad end surface allows the end of the buffer pad to better match the second bend section, thereby improving the support effect on the second bend section and reducing the gap between adjacent pole pieces at the bend, thereby better improving the lithium deposition problem at the bend.

[0013] In some embodiments, the end surface of the buffer pad near the first bend section is a curved surface. In the above technical solution, the design of the buffer pad end surface allows the end of the buffer pad to better match the first bend section, thereby improving the support effect on the first bend section and reducing the gap between adjacent pole pieces at the bend, thereby better improving the lithium deposition problem at the bend.

[0014] In some embodiments, the first straight section and the second straight section are arranged relative to each other along a first direction, the first pole piece further comprises a first bend section and a second bend section, the first bend section and the second bend section are arranged relative to each other along a second direction, and the buffer pads comprise a plurality of pads, the plurality of buffer pads being arranged along the first direction and / or the second direction. In the above technical solution, by providing multiple buffer pads, the buffer pads can provide better support for pole pieces at different positions, or when a single buffer pad fails, other buffer pads can be used to provide a buffering effect, thereby balancing the expansion force generated by the battery cell during the charge and discharge process, thereby improving the cycle life.

[0015] In some embodiments, the separator includes a first separator and a second separator, and the cushion is located between the first separator and the second separator. In the above technical solution, the separator separates the cushion from the first electrode, thereby further increasing the distance between the first straight section and the second straight section, reducing the probability of brittle fracture after hot pressing of the winding core, and improving the problem of burrs and powder loss caused by brittle fracture of the innermost electrode, thereby improving the reliability of the battery cell.

[0016] In some embodiments, the buffer pad includes one, and the buffer pad is arranged in a sheet shape or the buffer pad is arranged in a bent shape. In the above technical solution, the buffer pad can be arranged in a sheet shape, and the buffer pad is laid flat as a whole between the first straight section and the second straight section, so that the installation of the buffer pad is simpler; the buffer pad can be arranged in a bent shape, which can increase the thickness of the buffer pad in the first direction as a whole, and on the other hand, can make the bent part of the buffer pad clamped between the first straight section and the second straight section, and the bent part can be fitted with the first bend section or the second bend section, further supporting the electrode at the bend, reducing the gap between adjacent electrode pieces at the bend, and further helping to improve the lithium deposition problem at the bend.

[0017] In some embodiments, the pole piece has a winding starting end along the winding direction of the winding core, and the buffer covers at least a portion of the winding starting end along the stacking direction of the pole piece and the isolation film. In the above technical solution, when the winding core expands, the buffer deforms, which to some extent alleviates the stress concentration caused by the height difference at the winding starting end, ensuring that the two parts with the height difference are evenly stressed.

[0018] In some embodiments, the first pole piece has a first bend section and a second bend section located at the bend portion, the first bend section and the second bend section are located on opposite sides of the winding gap, the second bend section is arranged opposite to the first bend section, and the second bend section is connected to the second straight section, the first bend section and the second bend section are arranged opposite to each other along a second direction, and in the second direction, the maximum distance between the first bend section and the second bend section is b, the maximum width dimension of the buffer pad in the second direction is w, and the following condition is satisfied: 0.5b≤w≤b. In the above technical solution, the flatness of the winding core can be improved, while the curvature of the innermost pole piece can be increased, the probability of brittle fracture of the winding core after hot pressing can be reduced, and the problem of burr and powder loss caused by brittle fracture of the innermost pole piece causing internal short can be improved, thereby improving the reliability of the battery cell.

[0019] In some embodiments, in the third direction, the maximum height of the buffer is h, the maximum height of the pole piece is m, the hard height of the winding core is n, m≤h≤n, the first straight section and the second straight section are arranged relative to each other along the first direction, the first bend section and the second bend section are arranged relative to each other along the second direction, and the third direction is perpendicular to the first and second directions, respectively. In this technical solution, on the one hand, the height of the buffer is sufficient to fully support the pole piece from the entire axial height, and on the other hand, it can avoid the problem of the buffer exceeding the hard height by too much, resulting in excessive space occupation and affecting the energy density of the battery cell.

[0020] In some embodiments, the initial thickness of the buffer pad is d1, the thickness of the buffer pad at 3 MPa is d2, and the compression rate of the buffer pad is ρ, ρ = (d1-d2) / d1, satisfying the following: 10% ≤ ρ ≤ 70%, preferably, 30% ≤ ρ ≤ 50%. In the above technical solution, through the above definition, the buffer pad can not only play an effective supporting role, reducing the probability of electrode fracture, lithium deposition, and other problems, but also avoid the buffer pad occupying too much space, resulting in an increase in expansion force.

[0021] In some embodiments, the initial thickness of the buffer pad is d1, which satisfies: 0.5 mm ≤ d1 ≤ 4 mm. In the above technical solution, the buffer pad can reliably support the winding core, thereby effectively improving the lithium plating problem and improving the reliability of the battery cell.

[0022] In some embodiments, the material of the buffer pad includes at least one of polyethylene, polypropylene, polymethyl methacrylate, and polytetrafluoroethylene. In the above technical solution, by using the buffer pad made of the above materials, the compressibility of the buffer can be improved while reducing the manufacturing cost.

[0023] In some embodiments, the first electrode is a negative electrode. In the above technical solution, the curvature of the innermost circle of any electrode is increased, reducing the probability of brittle fracture after hot pressing of the winding core, and improving the problem of burrs and powder loss caused by brittle fracture of the innermost electrode, thereby improving the reliability of the battery cell.

[0024] In some embodiments, the electrode sheet includes a positive electrode sheet having a third straight segment and a fourth straight segment located in the straight portion, and the minimum distance between the third straight segment and the fourth straight segment is a, a ≥ 0.4 mm, preferably, a ≥ 1.2 mm. In the above technical solution, by providing a buffer pad at the winding gap, the minimum distance between the third straight segment and the fourth straight segment of the positive electrode sheet is not less than 0.4 mm, thereby increasing the curvature of the innermost circle of the positive electrode sheet, reducing the probability of brittle fracture of the positive electrode sheet after hot pressing of the winding core, and improving the problem of burrs and powder loss caused by brittle fracture of the innermost circle of the positive electrode sheet, resulting in internal shorts.

[0025] In some embodiments, the buffer pad is fitted with the isolation film. In the above technical solution, assembly efficiency can be improved and manufacturing and molding can be facilitated.

[0026] In some embodiments, the cushion is bonded to the separator. This technical solution improves the stability of the connection between the cushion and the core, improving the problem of separation between the cushion and the core after hot pressing of the core, which can create a gap between them. This facilitates the subsequent installation of the core into the battery cell housing, making it easier to insert the core into the housing. It also helps to improve the cushion's support reliability for the core, further reducing the risk of lithium deposition caused by loose inner pole pieces.

[0027] In some embodiments, the outer surface of the cushion is provided with a rubber coating layer, the rubber coating layer comprising one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, and polyacrylate. In the above technical solution, by providing the rubber coating layers on the side surfaces of the cushion, the rubber coating layers are utilized to achieve adhesion between the isolation film and the cushion.

[0028] In a second aspect, the present application provides a battery comprising the battery cell in the above embodiment.

[0029] In a third aspect, the present application provides an electrical device, which includes the battery in the above embodiment, and the battery is used to provide electrical energy.

[0030] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0032] FIG1 is a schematic diagram of an electric device in the related art;

[0033] FIG2 is a schematic diagram of a battery in the related art;

[0034] FIG3 is a schematic diagram of a battery cell provided in some embodiments of the present application;

[0035] FIG4 is a partial schematic diagram of a battery cell according to some embodiments of the present application;

[0036] FIG5 is a partial schematic diagram of a battery cell according to some other embodiments of the present application;

[0037] FIG6 is a partial schematic diagram of a battery cell according to some other embodiments of the present application;

[0038] FIG7 is a partial schematic diagram of a battery cell according to some further embodiments of the present application;

[0039] FIG8 is an enlarged view of circle A in FIG7 ;

[0040] FIG9 is a schematic diagram of a cushion according to some embodiments of the present application;

[0041] FIG10 is a schematic diagram of the arrangement of cushions according to some embodiments of the present application;

[0042] FIG11 is a schematic diagram of the arrangement of cushions according to other embodiments of the present application;

[0043] FIG12 is a processing schematic diagram provided by some embodiments of the present application.

[0044] Figure numerals: battery 1000, electrical device 2000, box 200, first part 210, second part 220, winding device 300, battery cell 100, electrode assembly 110, outer shell 120, shell 1201, end cover 1202, winding core 10, straight portion 101, bend portion 102, winding gap 103, winding initial end 104, first pole piece 11, first straight section 111, second straight section 112, first bend section 113, second bend section 114, third straight section 121, fourth straight section 122, isolation membrane 13, first isolation membrane 131, second isolation membrane 132, buffer pad 20, rubber layer 201. DETAILED DESCRIPTION

[0045] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0046] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0047] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0048] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," and "attached" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0049] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0050] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0051] The term "plurality" used in this application refers to two or more (including two).

[0052] In this application, a battery refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the batteries mentioned in this application may include battery modules or battery packs. Some batteries may include a casing for enclosing one or more battery cells or multiple battery modules. The casing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells. Of course, some batteries may not include the above-mentioned casing and are directly installed in the battery installation compartment of the electrical device.

[0053] In this application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and the embodiments of this application do not limit this. Battery cells may be cylindrical, flat, rectangular, or other shapes, etc., and the embodiments of this application do not limit this. Battery cells are generally divided into three types based on the packaging method: cylindrical battery cells, prismatic battery cells, and soft-pack battery cells, and the embodiments of this application do not limit this.

[0054] For example, a battery cell may include a housing, an electrode assembly, and an electrolyte, wherein the housing is used to contain the electrode assembly and the electrolyte. The electrode assembly is composed of a positive electrode sheet, a negative electrode sheet, and a separator. The battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode collector. The positive electrode collector not coated with the positive electrode active material layer protrudes from the positive electrode collector coated with the positive electrode active material layer, and the positive electrode collector not coated with the positive electrode active material layer serves as the positive electrode tab. Taking lithium-ion batteries as an example, the material of the positive electrode collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc.

[0055] The negative electrode sheet consists of a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative current collector. The negative current collector uncoated with the negative active material layer protrudes from the negative current collector coated with the negative active material layer. The negative current collector uncoated with the negative active material layer serves as the negative electrode tab. The negative current collector can be made of copper, and the negative active material can be carbon, silicon, or other materials. To ensure that high currents can pass without melting, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together.

[0056] The material of the isolation film may be PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly may be a wound structure or a laminated structure, but the embodiments of the present application are not limited thereto.

[0057] Battery cells can be equipped with terminals and other components connected to the tabs, serving as electrical connections. Furthermore, they can have pressure relief features. When the internal pressure in a battery cell becomes excessive (e.g., due to thermal runaway), these features release substances (e.g., gas, liquid, particulate matter, etc.) from the cell to reduce the internal pressure. This prevents excessive internal pressure from causing dangerous accidents such as explosions. For example, these relief features can be explosion-proof valves, explosion-proof discs, and the like.

[0058] For example, as shown in Figures 1 and 2 , some electrical devices 2000 are powered by batteries 1000. Battery 1000 includes a housing 200 and a battery cell 100. Housing 200 includes a first portion 210 and a second portion 220. In conventional technology, as shown in Figure 3 , battery cell 100 includes a housing 120 and an electrode assembly 110. Electrode assembly 110 is disposed within housing 120 and is of a wound type. As shown in Figure 4 , electrode assembly 110 includes a plurality of electrode sheets arranged in a wound manner. Electrode assembly 110 includes a straight portion 101 and a bend 102 connected to the end of straight portion 101. A plurality of electrode sheets arranged in a wound manner, i.e., positive electrode sheets and negative electrode sheets are stacked and wound around a set axis to form an electrode assembly 110. The straight portion 101 refers to the portion of the electrode sheet extending along the plane after winding; the turning portion 102 refers to the portion of the electrode sheet extending along the arc surface after winding. For example, as shown in FIG3 , the portion between the front side surface and the rear side surface of the electrode assembly 110 is formed as the straight portion 101, and the extension direction of the electrode sheet in the straight portion 101 is the length direction of the straight portion 101.

[0059] Among them, the positive electrode sheets have high compression density and high coating quality, and are more prone to brittle fracture than the negative electrode sheets. After multiple sheets are wound into a core and hot-pressed, the innermost positive electrode sheet is almost folded in half, so the curvature radius of the innermost positive electrode sheet is low, which makes the positive electrode sheet prone to brittle fracture. The burrs and powder loss after brittle fracture can easily cause a short circuit in the battery, reducing the reliability of the battery.

[0060] To this end, the present application proposes a battery cell 100, comprising: a winding core 10 and a buffer pad 20, the winding core 10 includes a wound electrode and an isolation film 13, the winding core 10 has a winding gap 103, the winding core 10 includes a straight portion 101 and a bend portion 102 connected to the end of the straight portion 101, the electrode includes a first electrode 11, the first electrode 11 has a first straight section 111 and a second straight section 112 located in the straight portion 101, the first straight section 111 and the second straight section 112 are located on opposite sides of the winding gap 103, the electrode assembly 110 also includes a buffer pad 20, the buffer pad 20 is arranged in the winding gap 103, at least part of the buffer pad 20 is located between the first straight section 111 and the second straight section 112.

[0061] In the battery cell 100 of the above-mentioned structure, by arranging the buffer pad 20 at the winding gap 103, on the one hand, the buffer pad 20 can balance the expansion force generated by the expansion of the battery cell 100 during the charging and discharging process, improve the stress uniformity of the innermost circle electrode, and improve the local fracture problem caused by the uneven stress distribution of the innermost circle electrode, thereby improving the reliability of the battery cell 100; on the other hand, it can increase the curvature of the innermost circle electrode, reduce the probability of brittle fracture of the winding core 10 after hot pressing, and improve the problem of internal short caused by burrs and powder loss due to brittle fracture of the innermost circle electrode, thereby improving the reliability of the battery cell 100.

[0062] The technical solutions described in the embodiments of the present application are applicable to a battery 1000 including a battery cell 100 and an electrical device 2000 using the battery.

[0063] The electrical device 2000 may be, but is not limited to, a vehicle, a mobile phone, a tablet, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. A vehicle may be a fuel vehicle, a gas vehicle, a new energy vehicle, or a rail vehicle. A new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle. Spacecraft include aircraft, rockets, space shuttles, and spacecraft. Electric toys include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric airplane toys. Electric tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0064] For the convenience of description, the following embodiments are described by taking the electric device 2000 as a vehicle as an example.

[0065] Please refer to FIG1 , which is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of the present application. A battery 100 is disposed inside the vehicle 1000. The battery 100 can be disposed at the bottom, head, or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000.

[0066] The vehicle 1000 may further include a controller 200 and a motor 300 . The controller 200 is used to control the battery 100 to supply power to the motor 300 , for example, to meet the power requirements of the vehicle 1000 during startup, navigation, and driving.

[0067] In some embodiments of the present application, the battery 100 can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0068] Please refer to Figure 2, which is an exploded view of a battery 1000 provided in some embodiments of the present application. The battery 1000 includes a battery cell 100 and a box 200 for accommodating the battery cell 100. The box 200 can have various structural forms.

[0069] In some embodiments, the housing 200 may include a first portion 210 and a second portion 220, which overlap each other and together define a storage space for accommodating the battery cells 100. For example, referring to FIG2 , the first portion 210 and the second portion 220 may each be a hollow structure with an opening on one side, with the open side of the first portion 210 overlapping the open side of the second portion 220, thereby forming the housing 200 having a storage space. A seal may also be provided between the first portion 210 and the second portion 220 to achieve a sealed connection between the first portion 210 and the second portion 220. For another example, the second portion 220 may be a hollow structure with an opening on one side, with the first portion 210 overlapping the top of the second portion 220. The first portion 210 and the second portion 220 may have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0070] In the battery 1000, there can be one or more battery cells 100. If there are multiple battery cells 100, the multiple battery cells 100 can be connected in series, in parallel, or in a mixed connection. Mixed connection means that the multiple battery cells 100 are connected both in series and in parallel. The multiple battery cells 100 can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 100 is accommodated in the box 200; of course, it is also possible that the multiple battery cells 100 are first connected in series, in parallel, or in a mixed connection to form a battery 1000 module, and the multiple battery 1000 modules are then connected in series, in parallel, or in a mixed connection to form a whole, and then accommodated in the box 200. In some embodiments, the multiple battery cells 100 can be electrically connected through a busbar to achieve parallel, series, or mixed connection of the multiple battery cells 100.

[0071] Each battery cell 100 can be a secondary battery 1000 or a primary battery 1000; it can also be a lithium-sulfur battery 1000, a sodium-ion battery 1000, or a magnesium-ion battery 1000, but is not limited thereto. The battery cell 100 can be cylindrical, flat, or rectangular. For example, in the embodiment shown in the figure, the battery cell 100 is a rectangular parallelepiped.

[0072] 3 , some embodiments of the present application provide a battery cell 100. The battery cell 100 may include a housing 120 and an electrode assembly 110. The housing 120 defines a receiving cavity. The electrode assembly 110 and the electrolyte are both disposed within the receiving cavity. The electrode assembly 110 includes at least one electrode assembly 110. Specifically, the electrode assembly 110 may include one electrode assembly 110 or multiple electrode assemblies 110. The number of electrode assemblies 110 may be selected based on the capacity requirements of the battery cell 100.

[0073] For example, with reference to FIG3 , the housing 120 may include a shell 1201 and an end cap 1202 . The shell 1201 has an opening at one end, and the electrode assembly 110 is inserted into the shell 1201 through the opening. The end cap 1202 covers the opening. However, the present application is not limited thereto. The shell 120 may also be in other forms, for example, including two half shells joined together, or the shell 120 may also include a sleeve with open ends and two end caps 1202 provided at both ends of the sleeve. It is worth noting that the material of the shell 120 may be a variety of materials, for example, plastic, copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not impose any particular limitations on this.

[0074] In addition, the outer shell 120 can be in a variety of shapes, such as a cylinder, a cuboid, etc. The shape of the outer shell 120 can be determined according to the specific shape of the electrode assembly 110. For example, if the electrode assembly 110 is a cylindrical structure, the outer shell 120 can be selected as a cylindrical structure; if the electrode assembly 110 is a cuboid structure, the outer shell 120 can be selected as a cuboid structure. For example, in the embodiment shown in Figure 3, the electrode assembly 110 includes two electrode assemblies 110, the electrode assembly 110 is a cuboid structure, and the two electrode assemblies 110 are stacked along the thickness direction of the electrode assembly 110, and the outer shell 120 is a hollow cuboid structure.

[0075] In an embodiment of the present application, the electrode assembly 110 is a wound structure, also known as a winding core 10. After the electrode assembly 110 is wound, the electrode assembly 110 is hot-pressed to obtain a flat, generally rectangular electrode assembly 110. Therefore, the electrode assembly 110 may include a flattened straight portion 101 and a bend portion 102 located at both ends of the straight portion 101 and naturally bent into an arc form. For example, as shown in Figure 3, after hot-pressing, the thickness direction of the electrode assembly 110 is a first direction F1, and the width direction of the electrode assembly 110 is a second direction F2. Before and after hot-pressing, the axial direction of the electrode assembly 110 is a third direction F3. The first direction F1, the second direction F2, and the third direction F3 are perpendicular to each other. The thickness direction of the straight portion 101 is the first direction F1, and the bend portions 102 are located at both ends of the straight portion 101 in the second direction F2. Thus, by hot pressing and shaping the electrode assembly 110, on the one hand, it is easier to install the electrode assembly 110 into the housing 120, and on the other hand, the interlayer gap of the electrode assembly 110 can be reduced by hot pressing, so that the number of windings of the electrode assembly 110 can be increased under the premise of the same housing volume, which is beneficial to improving the energy density of the battery cell 100. Of course, the present application is not limited to this. For example, in other embodiments of the present application, the winding needle can also be designed so that the wound core 10 is directly flat and generally rectangular, including a straight portion 101 and arc-shaped bends 102 at both ends of the straight portion 101. This is not limited here.

[0076] As shown in Figure 4, the battery cell 100 according to an embodiment of the present application includes: a winding core 10, the winding core 10 includes a pole piece and an isolation film 13 that are wound, the winding core 10 has a winding gap 103, the winding core 10 includes a straight portion 101 and a bending portion 102 connected to the end of the straight portion 101, the pole piece includes a first pole piece 11, the first pole piece 11 has a first straight section 111 and a second straight section 112 located in the straight portion 101, the first straight section 111 and the second straight section 112 are located on opposite sides of the winding gap 103, the battery cell 100 also includes a buffer pad 20, the buffer pad 20 is arranged in the winding gap 103, and at least a portion of the buffer pad 20 is located between the first straight section 111 and the second straight section 112.

[0077] The buffer pad 20 is made of elastic material, which is beneficial for the buffer pad 20 to provide better elastic support for the innermost ring pole piece, can effectively balance the expansion force generated by the expansion of the winding core 10, and improve the stress uniformity of the inner ring pole piece.

[0078] At least part of the buffer pad 20 is located between the first straight section 111 and the second straight section 112, that is, there can be one buffer pad 20, at least part of which is located between the first straight section 111 and the second straight section 112, or there can be multiple buffer pads 20, at least one of which is located between the first straight section 111 and the second straight section 112.

[0079] Since at least part of the buffer pad 20 is located between the first straight section 111 and the second straight section 112, the distance between the first straight section 111 and the second straight section 112 is increased, thereby increasing the curvature of the innermost pole piece, reducing the probability of brittle fracture of the winding core 10 after hot pressing, and further reducing the probability of internal shorts caused by burrs and powder loss.

[0080] It can be understood that the buffer pad 20 is located inside the winding core 10 , and the winding core 10 and the buffer pad 20 form the electrode assembly 110 .

[0081] The buffer pad 20 may have pores, which may be pores inherent in the material or pores obtained by machining. Therefore, when the buffer pad 20 is squeezed by the expanded winding core 10, it can be compressed and provide an elastic reaction force to the winding core 10. Since the buffer pad 20 is located between the first straight section 111 and the second straight section 112, it can support the first straight section 111 and the second straight section 112, thereby improving the force uniformity of the first pole piece 11. Moreover, the pores can be used to store electrolyte. Compared with a solid or closed elastic core, the amount of electrolyte injected into the shell 120 can be increased, thereby improving the cycle life of the battery cell 100. Moreover, when the buffer pad 20 is squeezed by the expanded winding core 10, the pores in the buffer pad 20 can be squeezed to discharge the electrolyte or gas, so that the buffer pad 20 is compressed instead of stretching along the axial direction of the winding core 10 (such as the first direction F1). Therefore, the axial end of the buffer pad 20 is stretched, and the axial side isolation film 13 of the winding core 10 is squeezed, causing the problem of shorting the positive and negative electrodes, thereby further improving the reliability of the battery cell 100.

[0082] For example, if a closed structure such as an airbag is used to replace the buffer pad 20, since the airbag is a sealed structure, the residual space in the outer shell 120 is reduced, and the injection amount of electrolyte is relatively low. Moreover, when the electrode assembly 110 expands and squeezes the airbag, since the airbag is a closed structure, the airbag will stretch along the axial direction of the electrode assembly 110 when squeezed, squeezing the axial side isolation membrane 13 of the electrode assembly 110, causing the problem of short inside the positive and negative electrode sheets. The use of a buffer pad 20 with pores can effectively solve the above technical problems.

[0083] According to the battery cell 100 of the embodiment of the present application, by arranging the buffer pad 20 at the winding gap 103, on the one hand, the buffer pad 20 can balance the expansion force generated by the expansion of the battery cell 100 during the charging and discharging process, improve the stress uniformity of the innermost circle electrode, and improve the local fracture problem caused by the uneven stress distribution of the innermost circle electrode, thereby improving the reliability of the battery cell 100; on the other hand, it can increase the curvature of the innermost circle electrode, reduce the probability of brittle fracture of the winding core 10 after hot pressing, and improve the problem of internal short caused by burrs and powder loss due to brittle fracture of the innermost circle electrode, thereby improving the reliability of the battery cell 100.

[0084] As shown in Figures 5 to 8, in some embodiments, the first pole piece 11 further has a first turning section 113, the first turning section 113 is arranged at the turning portion 102, and the first turning section 113 connects the first straight section 111 and the second straight section 112, and one end of the buffer pad 20 extends to the first turning section 113.

[0085] There may be gaps between adjacent pole pieces at the bend 102, especially when the spacing between the inner pole pieces is larger than that between the outer pole pieces, which makes lithium deposition more likely to occur. The large spacing will cause the spacing for metal ions to be transferred from the positive electrode to the negative electrode to become longer. When the spacing becomes longer, some metal ions have not entered the graphite layers before reaching the cutoff potential. The metal ions will be enriched at the graphite position closest to them, causing the potential at that position to drop, and the metal ions will form metal precipitation, thereby reducing the life of the battery cell 100 and reducing safety.

[0086] To this end, extending one end of the buffer pad 20 to the first bend section 113 is beneficial to further support the electrode at the bend portion 102, reduce the gap between adjacent electrode at the bend portion 102, and further help improve the lithium deposition problem at the bend portion 102.

[0087] It should be noted that “one end of the buffer pad 20 extends to the first bend section 113 ” should be understood in a broad sense. As long as one end of the buffer pad 20 is relatively close to the first bend section 113 , it is not required to be completely fitted in a strict sense.

[0088] As shown in Figures 5-8, in some embodiments, the first pole piece 11 further has a second turning section 114, the second turning section 114 is arranged opposite to the first turning section 113, and the second turning section 114 is connected to the second straight section 112, and one end of the buffer pad 20 extends to the second turning section 114.

[0089] By extending one end of the buffer pad 20 to the second bend section 114 , it is beneficial to further support the electrode at the bend portion 102 , reduce the gap between adjacent electrode at the bend portion 102 , and further help improve the lithium plating problem at the bend portion 102 .

[0090] It should be noted that “one end of the buffer pad 20 extends to the second bend section 114 ” should be understood in a broad sense. As long as one end of the buffer pad 20 is relatively close to the second bend section 114 , it is not required to be completely fitted in a strict sense.

[0091] As shown in FIG. 6 and FIG. 7 , in some embodiments, a buffer pad 20 is provided in the winding gap 103 , and two ends of the buffer pad 20 extend to the first turning section 113 and the second turning section 114 , respectively.

[0092] That is to say, the two ends of the same buffer pad 20 extend to the first turning section 113 and the second turning section 114 respectively. By arranging a buffer pad 20 in the winding gap 103, the number of buffer pads 20 is reduced and the cost is reduced, while the assembly of the buffer pad 20 is facilitated and the assembly efficiency is improved. Furthermore, through a buffer pad 20, the support effect of the turning section is improved, and the gap between adjacent pole pieces at the turning portion 102 is reduced, thereby better improving the lithium plating problem at the turning portion 102.

[0093] As shown in Figure 5, in some embodiments, the winding gap 103 is provided with multiple buffer pads 20, and the multiple buffer members are arranged in the relative directions of the second turning section 114 and the first turning section 113, one end of one buffer pad 20 extends to the first turning section 113, and one end of another buffer pad 20 extends to the second turning section 114.

[0094] That is to say, the winding gap 103 may have two or more buffer pads 20, one buffer pad 20 extends to the first turning section 113, and the other buffer pad 20 extends to the second turning section 114. The multiple buffer pads 20 in the winding gap 103 may be the same or different. By providing multiple buffer pads 20, it is beneficial to meet the manufacturing requirements of different electrode assemblies 110 and improve diversity; at the same time, multiple buffer pads 20 are respectively matched with the corresponding turning sections, which can improve the support effect of the turning section and reduce the gap between adjacent pole pieces at the turning portion 102, thereby better improving the lithium plating problem at the turning portion 102.

[0095] As shown in FIG. 7 , in some embodiments, an end surface of the buffer pad 20 close to the second turning section 114 is a curved surface.

[0096] The curvature of the arc surface may be substantially the same as the curvature of the second turning section 114 .

[0097] By designing the end face of the buffer pad 20, the end of the buffer pad 20 can better match the second turning section 114, thereby improving the support effect of the second turning section 114 and reducing the gap between adjacent pole pieces at the turning portion 102, thereby better improving the lithium deposition problem at the turning portion 102.

[0098] As shown in FIG. 7 and FIG. 8 , in some embodiments, an end surface of the buffer pad 20 close to the first turning section 113 is a curved surface.

[0099] The curvature of the arc surface may be substantially the same as the curvature of the first turning section 113 .

[0100] By designing the end face of the buffer pad 20, the end of the buffer pad 20 can better match the first turning section 113, thereby improving the support effect of the first turning section 113 and reducing the gap between adjacent pole pieces at the turning portion 102, thereby better improving the lithium plating problem at the turning portion 102.

[0101] As shown in FIG. 8 , in some embodiments, the isolation film 13 includes a first isolation film 131 and a second isolation film 132 , and the buffer pad 20 is located between the first isolation film 131 and the second isolation film 132 .

[0102] As shown in Figure 8, there is a winding gap 103 between the first isolation membrane 131 and the second isolation membrane 132, the buffer pad 20 is located between the first isolation membrane 131 and the second isolation membrane 132, the first straight section 111 and the second straight section 112 are located on the outside of the first isolation membrane 131 and the second isolation membrane 132, and the isolation membrane 13 separates the buffer pad 20 from the first pole piece 11, thereby further increasing the distance between the first straight section 111 and the second straight section 112, reducing the probability of brittle fracture of the winding core 10 after hot pressing, and improving the problem of internal short caused by burrs and powder loss due to brittle fracture of the innermost pole piece, thereby improving the reliability of the battery cell 100.

[0103] Exemplarily, referring to Figure 12, the winding device 300 may include a winding needle body and a clamping mechanism, the electrode sheets include negative electrode sheets and positive electrode sheets, and the isolation film 13 includes a first isolation film 131 and a second isolation film 132. During winding, the first isolation film 131 and the second isolation film 132 are fed in first and clamped by the clamping mechanism. After winding n turns, the buffer pad 20 is positioned and the buffer pad 20 is fed in so that the buffer pad 20 is located on the side of the second isolation film 132 facing the first isolation film 131 and is close to the second isolation film 132. Then the negative electrode sheet and the positive electrode sheet are fed in. In this way, it can be wound into a stacked and wound structure. After winding and forming, hot pressing is performed so that the buffer pad 20 can effectively support the isolation film 13 and the electrode sheet of the innermost circle within the entire circle, thereby improving the reliability and cycle life of the battery cell 100, and the electrode assembly 110 is easy to process and has high manufacturing efficiency.

[0104] As shown in Figures 5 and 10, in some embodiments, the first straight section 111 and the second straight section 112 are arranged relatively along the first direction F1, the first pole piece 11 further has a first turning section 113 and a second turning section 114, the first turning section 113 and the second turning section 114 are arranged relatively along the second direction F2, and the buffer pad 20 includes a plurality of buffer pads 20, and the plurality of buffer pads 20 are arranged along the first direction F1 and / or the second direction F2.

[0105] The first direction F1 is the front-rear direction as shown in FIG. 5 , and the second direction F2 is the left-right direction as shown in FIG. 5 .

[0106] As shown in Figure 5, the winding gap 103 is provided with two buffer pads 20, and the two buffer pads 20 are arranged at intervals along the first direction F1. The two buffer pads 20 can be the same or different. For example, the thicknesses of the two buffer pads 20 are different, so that the buffer pads 20 can provide better support for the pole pieces at different positions.

[0107] As shown in FIG10 , the winding gap 103 may further be provided with a plurality of buffer pads 20 arranged along the second direction F2. Thus, when a single buffer pad 20 fails, other buffer pads 20 may serve as buffers to balance the expansion force generated by the expansion of the battery cell 100 during the charge and discharge process, thereby improving the cycle life.

[0108] It should be noted that, when the plurality of buffer pads 20 are arranged along the second direction F2, the total thickness of the plurality of buffer pads 20 in the thickness direction of the winding core 10 must be between 0.5 mm and 4 mm.

[0109] As shown in FIG. 9 and FIG. 11 , in some embodiments, the buffer pad 20 includes one, and the buffer pad 20 is arranged in a sheet shape or the buffer pad 20 is arranged in a bent shape.

[0110] As shown in FIG6 and FIG9 , a buffer pad 20 is provided in the winding gap 103 . The buffer pad 20 is arranged in a sheet shape and is laid flat as a whole between the first straight section 111 and the second straight section 112 , making the installation of the buffer pad 20 easier.

[0111] As shown in Figure 11, the buffer pad 20 can be arranged in a bent manner. On the one hand, the overall thickness of the buffer pad 20 in the first direction F1 can be increased. On the other hand, the bent portion of the buffer pad 20 can be clamped between the first straight section 111 and the second straight section 112. The bent portion can be fitted with the first turning section 113 or the second turning section 114 to further support the electrode at the turning portion 102, reduce the gap between adjacent electrode sheets at the turning portion 102, and further help improve the lithium plating problem at the turning portion 102.

[0112] As shown in FIG5-7 , in some embodiments, along the winding direction of the electrode assembly 110 , the electrode sheet has a winding initial end 104 , and along the stacking direction of the electrode sheet and the isolation film 13 , the buffer pad 20 covers at least a portion of the winding initial end 104 .

[0113] When the electrode assembly 110 expands, the buffer member deforms, thereby alleviating to a certain extent the stress concentration problem caused by the height difference at the winding initial end 104 , so that the two parts with the height difference are evenly stressed.

[0114] As shown in Figures 5, 6 and 9, in some embodiments, the first pole piece 11 has a first turning section 113 and a second turning section 114 located at the turning portion 102, the first turning section 113 and the second turning section 114 are located on opposite sides of the winding gap 103, the second turning section 114 is arranged opposite to the first turning section 113, and the second turning section 114 is connected to the second straight section 112, the turning sections are arranged opposite to each other along the second direction F2, in the second direction F2, the maximum distance between the two turning sections is b, the maximum width dimension of the buffer pad 20 in the second direction F2 is w, satisfying: 0.5b≤w≤b.

[0115] As shown in Figure 6, if the width of the buffer pad 20 is too large, stress concentration and stress creases will occur at the contact boundary between the buffer pad 20 and the pole piece, which will cause wrinkling of the pole piece in the later stage. In addition, the buffer pad 20 is also prone to wrinkling inside the winding core 10, affecting the flatness of the winding core 10. If the width of the buffer pad 20 is too small, under the same thermal pressure, the downward pressure of the buffer pad 20 increases, and the supporting effect on the first straight section 111 and the second straight section 112 is relatively small, resulting in a decrease in the curvature of the inner circle of the pole piece and the pole piece is prone to brittle fracture.

[0116] It should be noted that, as shown in FIG. 5 , when there are multiple buffer pads 20 , the buffer pads 20 are arranged along the second direction F2 , and the width of each buffer pad 20 is w1 , w2 , . . . wn , and the sum of w1 , w2 , . . . wn is w.

[0117] To this end, the maximum width dimension w of the buffer pad 20 in the second direction F2 is limited to 0.5bb, and w can be any one of 0.5b, 0.6b, 0.7b, 0.8b, 0.9b, b or a range value between any two of them.

[0118] This can improve the flatness of the electrode assembly 110, while increasing the curvature of the innermost pole piece, reducing the probability of brittle fracture of the winding core 10 after hot pressing, and improving the problem of burrs and powder loss caused by brittle fracture of the innermost pole piece, thereby improving the reliability of the battery cell 100.

[0119] As shown in Figures 3 and 9, in some embodiments, in the third direction F3, the maximum height dimension of the buffer pad 20 is h, the maximum height dimension of the pole piece is m, the hard height dimension of the core 10 is n, m≤h≤n, the first straight section 111 and the second straight section 112 are arranged relatively along the first direction F1, the first turning section 113 and the second turning section 114 are arranged relatively along the second direction F2, and the third direction F3 is perpendicular to the first direction F1 and the second direction F2, respectively.

[0120] The third direction F3 is the up and down direction as shown in Figures 3 and 9. It can be understood that after the core 10 is wound, the part of the isolation film 13 that extends beyond the electrode will be smoothed. After smoothing, the height of the core 10 is the hard height of the core 10, and the maximum height dimension of the electrode is the height dimension of the largest height dimension between the positive electrode sheet and the negative electrode sheet.

[0121] In the third direction F3, if the height of the buffer pad 20 is too large, the buffer pad 20 exceeds the hard height of the core 10, occupies too much space, and affects the energy density of the battery cell 100. If the height of the buffer pad 20 is too small, the buffer pad 20 is shorter than the size of the electrode, and it is difficult to fully support the electrode.

[0122] Therefore, m≤h≤n can ensure that the height of the buffer pad 20 is sufficient to fully support the pole piece from the entire axial height. On the other hand, it can also avoid the problem that the buffer pad 20 exceeds the hard height too much, resulting in excessive space occupation and affecting the energy density of the battery cell 100.

[0123] As shown in Figure 8, in some embodiments, the initial thickness of the buffer pad 20 is d1, the thickness of the buffer pad 20 at 3Mpa is d2, and the downward pressure rate of the buffer pad 20 is ρ, ρ = (d1-d2) / d1, satisfying: 10%≤ρ≤70%, preferably, 30%≤ρ≤50%.

[0124] If the compression rate of the cushion 20 is too large, it cannot provide effective support. If the compression rate of the cushion 20 is too small, the cushion 20 is difficult to buffer deformation, occupies volume space, and cannot provide sufficient expansion space, resulting in increased expansion force.

[0125] For this purpose, ρ is limited to between 10% and 70%. ρ can be any one of 10%, 20%, 30%, 40%, 50%, 60%, 70%, or a range value between any two of them.

[0126] Through the above definition, the buffer pad 20 can play an effective supporting role to reduce the probability of problems such as electrode breakage and lithium deposition, and can also avoid the buffer pad 20 occupying too much space and causing an increase in expansion force.

[0127] In some examples, 30% ≤ ρ ≤ 50%, where ρ can be any one of 30%, 35%, 40%, 45%, or 50%, or a range between any two of them. This allows the cushion 20 to effectively support the electrode, reducing the probability of electrode breakage, lithium deposition, and other issues, while also preventing the cushion 20 from occupying too much space and increasing expansion force.

[0128] As shown in FIG. 8 , in some embodiments, the initial thickness of the buffer pad 20 is d1 , which satisfies the following relationship: 0.5 mm ≤ d1 ≤ 4 mm.

[0129] If the thickness of the buffer pad 20 is relatively thin, the buffer pad 20 will be wrinkled when the winding needle is pulled out, affecting the flatness of the winding core 10. Moreover, if the thickness of the supporting core is relatively thin, it cannot play an effective elastic supporting role, and the inner ring electrode is still prone to breakage and lithium deposition at the corner. If the thickness of a single layer of the buffer pad 20 is relatively large, the deformation variable during winding is relatively large, and it is difficult to control the shape. Moreover, if the thickness of the supporting core is relatively large, it occupies more space, affecting the energy density of the electrode assembly 110.

[0130] Through testing, it was found that when the thickness of the buffer pad 20 is 0.5mm-4mm, the thickness of the buffer pad 20 can be any one of 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm or a range value between any two of them.

[0131] Therefore, through the above theoretical analysis and testing, it can be seen that by setting the thickness of the buffer pad 20 to 0.5 mm-4 mm, the buffer pad 20 can reliably support the core 10, thereby more effectively improving the lithium plating problem and improving the reliability of the battery cell 100.

[0132] In some embodiments, the material of the buffer pad 20 includes at least one of polyethylene, polypropylene, polymethyl methacrylate, and polytetrafluoroethylene.

[0133] The buffer pad 20 can be made of any one of polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), and polytetrafluoroethylene (PTFE), or can be a composite material.

[0134] By using the buffer pad 20 made of the above material, the manufacturing cost can be reduced while improving the compressibility of the buffer component.

[0135] In some embodiments, the first electrode 11 is a negative electrode.

[0136] Usually, the innermost circle of the electrode is the negative electrode. By setting the buffer pad 20 between the two straight sections of the negative electrode, the distance between the two straight sections of the innermost circle of the negative electrode is increased, and the distance between the two straight sections of the innermost circle of the positive electrode is increased, thereby increasing the curvature of the innermost circle of any electrode, reducing the probability of brittle fracture of the core 10 after hot pressing, and improving the problem of internal short caused by burrs and powder loss due to brittle fracture of the innermost circle electrode, thereby improving the reliability of the battery cell 100.

[0137] As shown in Figure 4, in some embodiments, the electrode sheet includes a positive electrode sheet, and the positive electrode sheet has a third straight segment 121 and a fourth straight segment 122 located in the straight portion 101, and the third straight segment 121 and the fourth straight segment 122 are located on opposite sides of the winding gap 103, and the minimum distance between the third straight segment 121 and the fourth straight segment 122 is a, a≥0.4mm, preferably, a≥1.2mm.

[0138] The minimum distance between the third straight segment 121 and the fourth straight segment 122 is the distance between the two innermost straight segments of the positive electrode plate.

[0139] By arranging a buffer pad 20 at the winding gap 103, the minimum distance between the third straight section 121 and the fourth straight section 122 of the positive electrode sheet is not less than 0.4 mm, thereby increasing the curvature of the innermost circle of the positive electrode sheet, reducing the probability of brittle fracture of the positive electrode sheet after hot pressing of the winding core 10, and improving the problem of burrs and powder loss caused by brittle fracture of the innermost circle of the positive electrode sheet, resulting in internal short circuit.

[0140] In some examples, the minimum distance between the third straight section 121 and the fourth straight section 122 of the positive electrode sheet is not less than 1.2 mm, which can further increase the curvature of the innermost circle of the positive electrode sheet, reduce the probability of brittle fracture of the positive electrode sheet after hot pressing of the winding core 10, and improve the problem of burrs and powder loss caused by brittle fracture of the innermost circle of the positive electrode sheet, resulting in internal short circuit.

[0141] In some embodiments, the cushion 20 is in contact with the isolation film 13 .

[0142] The outermost surface of the buffer pad 20 facing the electrode piece and the outermost surface of the isolation membrane 13 facing the buffer pad 20 are directly bonded together, thereby improving assembly efficiency and facilitating the manufacturing and forming of the electrode assembly 110 .

[0143] In some embodiments, the cushion 20 is bonded to the isolation film 13 .

[0144] The outermost surface of the buffer pad 20 facing the electrode piece and the outermost surface of the isolation film 13 facing the buffer pad 20 are bonded together, thereby improving the connection stability between the buffer pad 20 and the core 10, improving the problem of separation of the buffer pad 20 and the core 10 after the electrode assembly 110 is hot-pressed, and forming a gap between the buffer pad 20 and the core 10. This is beneficial for the subsequent installation of the electrode assembly 110 into the outer shell 120 of the battery cell 100, which is convenient for shell insertion, and is beneficial for improving the support reliability of the buffer pad 20 on the core 10, and further reducing the risk of lithium plating caused by loose inner ring electrode pieces.

[0145] As shown in FIG9 , in some embodiments, a rubber coating layer 201 is provided on the outer side of the buffer pad 20 , and the rubber coating layer 201 includes one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, and polyacrylate.

[0146] Since the buffer pad 20 is wound, the adhesive layer 201 can be used to bond the buffer pad 20 to the isolation film 13. Moreover, since the core 10 is wound outside the buffer pad 20 and the isolation film 13 extends along the buffer pad 20, the adhesive layer 201 can also be used to achieve bonding between the isolation film 13 and the buffer pad 20. Furthermore, by respectively arranging the adhesive layer 201 on both side surfaces in the thickness direction of the buffer pad 20, it is convenient to fully meet the above-mentioned multiple bonding requirements, improve production efficiency, and reduce production difficulty.

[0147] It is worth noting that the material of the coating layer is not limited, for example, it can be polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyacrylate, etc. In this way, during hot pressing, the buffer pad 20 and the core 10 can be tightly combined.

[0148] For example, the battery cell 100 may further include a housing 120 and an electrolyte disposed in the housing 120, and the electrode assembly 110 may be received in the housing 120. In addition, the battery cell 100 according to the embodiment of the present application may further include a terminal post, an explosion-proof valve, and the like.

[0149] The present application also provides a battery 1000 comprising a battery cell 100 according to any of the above-described solutions. Since the reliability of the battery cell 100 according to the embodiments of the present application is improved, this helps improve the reliability of the battery 1000. It is worth noting that the battery 1000 according to the embodiments of the present application may or may not include the housing 200.

[0150] Exemplarily, the battery 1000 further includes a busbar component, and there are multiple battery cells 100, with at least two being electrically connected via the busbar component. This allows for the series and / or parallel connection of multiple battery cells 100. For example, when multiple battery cells 100 are connected in series, the anode of one battery cell 100 is connected to the cathode of the next battery cell 100 via one busbar component, while the cathode of the battery cell 100 is connected to the anode of the previous battery cell 100 via another busbar component.

[0151] The present application also provides an electrical device comprising a battery cell 100 according to any of the aforementioned solutions. Battery 1000 is used to provide power to the electrical device. The electrical device may be any of the aforementioned devices or systems utilizing battery cell 100. The improved reliability of battery cell 100 improves the operating performance of the electrical device.

[0152] 3 and 6 , a battery cell 100 according to a specific embodiment of the present application will be described.

[0153] The battery cell 100 includes: a housing 120, an electrode assembly 110 and an electrolyte. The housing 120 defines a receiving cavity. The electrode assembly 110 is disposed in the receiving cavity and includes two electrode assemblies 110. The electrode assembly 110 includes a straight portion 101 and a bend portion 102 located at both ends of the straight portion 101. The electrode assembly 110 includes: a winding core 10 and a buffer pad 20. The winding core 10 includes a wound electrode sheet and a separator 13. The electrode sheet includes a first electrode sheet 11. The first electrode sheet 11 has a first straight section 111 and a second straight section 112 located on the straight portion 101. The first pole piece 11 also has a first turning section 113 and a second turning section 114 provided in the turning area. The first straight section 111 and the second straight section 112 are located on opposite sides of the winding gap 103. The buffer pad 20 is provided in the winding gap 103 of the winding core 10. The buffer pad 20 is located between the first straight section 111 and the second straight section 112. The buffer pad 20 extends along the relative arrangement direction of the first turning section 113 and the second turning section 114. One end of the buffer pad 20 extends to the first turning section 113, and the other end of the buffer pad 20 extends to the second turning section 114.

[0154] When manufacturing the electrode assembly 110, a buffer pad 20 is provided in the winding gap 103. When the winding is completed and the needle is removed, the buffer pad 20 itself has a certain strength and is less likely to wrinkle or misalign, thereby reducing the risk of unevenness of the electrode assembly 110 and improving the flatness of the electrode assembly 110 and the reliability of the battery cell 100. In addition, the two ends of the buffer pad 20 extend to the first bend section 113 and the second bend section 114 respectively, so that the shape of the innermost pole piece and the buffer pad 20 can be more consistent, so that the buffer pad 20 can effectively support the innermost pole piece. On the one hand, it can balance the expansion force generated by the expansion of the battery cell 100 during the charge and discharge process, improve the stress uniformity of the innermost pole piece, and improve the local fracture problem caused by the uneven stress distribution of the innermost pole piece, thereby improving the reliability of the battery cell 100; On the other hand, the curvature of the innermost circle electrode can be increased, and the problem of brittle fracture of the innermost circle electrode causing burrs and powder loss resulting in internal short circuit can be improved, thereby improving the reliability of the battery cell 100; on the other hand, the problem of loose innermost circle electrode can be improved. After hot pressing and shaping, the gap between the inner circle electrode pieces at the bend 102 can be reduced, so that the spacing between the positive electrode piece and the negative electrode piece at the inner circle position at the bend 102 can be reduced, so as to reduce the risk of lithium plating at the inner circle position at the bend 102, and improve the reliability and cycle life of the battery cell 100.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: include: A winding core includes a pole piece and a separator arranged in a wound manner, the winding core having a winding gap, the winding core including a straight portion and a bend portion connected to the end of the straight portion, the pole piece including a first pole piece, the first pole piece having a first straight section and a second straight section located in the straight portion, the first straight section and the second straight section being located on opposite sides of the winding gap, A buffer pad is provided in the winding gap and at least a portion of the buffer pad is located between the first straight section and the second straight section.

2. The battery cell according to claim 1, wherein: The first pole piece further has a first turning section, which is provided at the turning portion and connects the first straight section and the second straight section. One end of the buffer pad extends to the first turning section.

3. The battery cell according to claim 2, characterized in that: The first pole piece further has a second turning section, which is arranged opposite to the first turning section and connected to the second straight section. One end of the buffer pad extends to the second turning section.

4. The battery cell according to claim 3, characterized in that The winding gap is provided with a buffer pad, and both ends of the buffer pad extend to the first turning section and the second turning section respectively.

5. The battery cell according to claim 3, characterized in that: The winding gap is provided with a plurality of buffer pads, and the plurality of buffer members are arranged along the relative direction of the second turning section and the first turning section, one end of one buffer pad extends to the first turning section, and one end of another buffer pad extends to the second turning section.

6. The battery cell according to any one of claims 3 to 5, characterized in that: An end surface of the buffer pad close to the second turning section is a curved surface.

7. The battery cell according to any one of claims 2 to 6, characterized in that: An end surface of the buffer pad close to the first turning section is a curved surface.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The isolation film includes a first isolation film and a second isolation film, and the buffer pad is located between the first isolation film and the second isolation film.

9. The battery cell according to any one of claims 1 to 8, characterized in that: The first straight section and the second straight section are arranged opposite to each other along a first direction. The first pole piece also has a first turning section and a second turning section. The first turning section and the second turning section are arranged opposite to each other along a second direction. The buffer pad includes a plurality of buffer pads, and the plurality of buffer pads are arranged along the first direction and / or the second direction.

10. The battery cell according to any one of claims 1 to 8, characterized in that: The buffer pad includes one, and the buffer pad is arranged in a sheet shape or the buffer pad is arranged in a bent shape.

11. The battery cell according to any one of claims 1 to 10, characterized in that: Along the winding direction of the winding core, the pole piece has a winding initial end, and along the stacking direction of the pole piece and the isolation film, the buffer pad covers at least a portion of the winding initial end.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The first pole piece has a first turning section and a second turning section located at the turning portion, the first turning section and the second turning section are located on opposite sides of the winding gap, the second turning section is arranged opposite to the first turning section, and the second turning section is connected to the second straight section, the first turning section and the second turning section are arranged opposite to each other along the second direction, in the second direction, the maximum distance between the first turning section and the second turning section is b, the maximum width dimension of the buffer pad in the second direction is w, satisfying: 0.5b≤w≤b.

13. The battery cell according to any one of claims 1 to 12, characterized in that: The first pole piece has a first turning section and a second turning section located at the turning portion. In the third direction, the maximum height dimension of the buffer pad is h, the maximum height dimension of the pole piece is m, the hard height dimension of the winding core is n, m≤h≤n, the first straight section and the second straight section are arranged relative to each other along the first direction, the first turning section and the second turning section are arranged relative to each other along the second direction, and the third direction is perpendicular to the first direction and the second direction respectively.

14. The battery cell according to any one of claims 1 to 13, characterized in that: The initial thickness of the buffer pad is d1, the thickness of the buffer pad at 3 MPa is d2, and the compression rate of the buffer pad is ρ, ρ=(d1-d2) / d1, satisfying: 10%≤ρ≤70%, preferably, 30%≤ρ≤50%.

15. The battery cell according to claim 14, characterized in that The initial thickness of the buffer pad is d1, which satisfies: 0.5mm≤d1≤4mm.

16. The battery cell according to claim 1, characterized in that The material of the buffer pad includes at least one of polyethylene, polypropylene, polymethyl methacrylate, and polytetrafluoroethylene.

17. The battery cell according to any one of claims 1 to 16, characterized in that: The first electrode is a negative electrode.

18. The battery cell according to any one of claims 1 to 17, characterized in that: The electrode sheet includes a positive electrode sheet, and the positive electrode sheet has a third straight section and a fourth straight section located in the straight portion, the third straight section and the fourth straight section are located on opposite sides of the winding gap, and the minimum distance between the third straight section and the fourth straight section is a, a≥0.4mm, preferably, a≥1.2mm.

19. The battery cell according to any one of claims 1 to 18, characterized in that: The buffer pad is in contact with the isolation film.

20. The battery cell according to any one of claims 1 to 18, characterized in that: The buffer pad is bonded to the isolation film.

21. The battery cell according to claim 20, characterized in that A rubber coating layer is provided on the outer side of the buffer pad, and the rubber coating layer comprises one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, and polyacrylate.

22. A battery, characterized in that: The invention comprises a battery cell according to any one of claims 1 to 21.

23. An electrical device, characterized in that: The battery according to claim 22 is included for providing electrical energy.

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