Battery monomer, battery and electric device

Abstract

The invention is suitable for the technical field of batteries, and provides a battery monomer, a battery and an electric device. Each battery monomer comprises a shell and an electrode assembly arranged in the shell; the electrode assembly comprises a positive plate, a negative plate and a diaphragm, the positive plate, the negative plate and the diaphragm are stacked according to a preset sequence and are wound to form the electrode assembly, and the tail end of the negative plate exceeds the positive plate; a first gap is formed between the inner wall of the shell and the end-to-end connection area of the outermost circle of pole piece of the negative pole piece and / or between the part, exceeding the positive pole piece, of the negative pole piece and the end face of the positive pole piece and the secondary outer circle of pole piece of the negative pole piece, and the first gap is filled with a first supporting structure. According to the battery monomer, the battery and the power utilization device provided by the invention, the risk of breakage of the pole piece at the ending part can be reduced to a certain extent.

Description

Technical Field

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

[0002] The electrode assembly is an important part of the battery. It can be divided into wound electrode assemblies and laminated electrode assemblies according to the preparation method of the electrode assembly. Among them, the wound electrode assembly is widely used because it is relatively easy to operate and the quality is easy to control. However, during the continuous aging process of the battery, the electrode sheet at the end of the wound electrode assembly is prone to breakage. Summary of the invention

[0003] In view of the above problems, the present application provides a battery cell, a battery and an electrical device, aiming to alleviate the technical problem that the pole piece is prone to breakage at the end of a wound electrode assembly.

[0004] In the first aspect, an embodiment of the present application provides a battery cell, comprising a shell and an electrode assembly arranged in the shell; the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet, the negative electrode sheet and the separator are stacked in a preset order and wound to form an electrode assembly, and the tail end of the negative electrode sheet extends beyond the positive electrode sheet; there is a first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost electrode sheet of the negative electrode sheet, and / or between the part of the negative electrode sheet extending beyond the positive electrode sheet, the end face of the positive electrode sheet and the second outermost electrode sheet of the negative electrode sheet, and the first gap is filled with a first supporting structure.

[0005] In the electrode assembly provided in the embodiment of the present application, at least one of the first gaps between the inner wall of the housing and the end-to-end junction area of ​​the outermost electrode sheet of the negative electrode sheet, and the first gap between the portion of the negative electrode sheet that exceeds the positive electrode sheet, the end face of the positive electrode sheet, and the sub-outer electrode sheet of the negative electrode sheet is filled with a first support structure, thereby reducing the risk of each electrode sheet being broken at the end of at least one electrode sheet in the electrode assembly. Specifically, when the first support structure is filled in the first gap between the inner wall of the housing and the end-to-end junction area of ​​the outermost electrode sheet of the negative electrode sheet, the risk of each electrode sheet being broken at the end of the negative electrode sheet can be reduced; when the first support structure is filled in the first gap between the portion of the negative electrode sheet that exceeds the positive electrode sheet, the end face of the positive electrode sheet, and the sub-outer electrode sheet of the negative electrode sheet, the risk of each electrode sheet being broken at the end of the positive electrode sheet can be reduced.

[0006] In addition, no matter which of the above-mentioned first gaps is filled with the first support structure, the time difference of the top shell of each pole piece located on both sides of the first gap can be reduced to a certain extent, and the expansion of the pole piece below the first support structure can be suppressed, which can effectively reduce the stress concentration phenomenon of each pole piece at the first gap, so that each pole piece is more evenly stressed, thereby reducing the risk of each pole piece breaking at the first gap. In addition, the first support structure can reduce the risk of the step structure between the positive pole piece and the negative pole piece causing indentations on the pole pieces below, thereby reducing the risk of lithium deposition caused by indentations in the battery cell.

[0007] In some embodiments, there is the first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece of the negative pole piece, and the end-to-end junction area of ​​the outermost pole piece of the negative pole piece includes the area where the negative pole piece exceeds the positive pole piece; at least part of the first support structure abuts against the part of the negative pole piece exceeding the positive pole piece, so that the inner wall of the part of the negative pole piece exceeding the positive pole piece fits with the end face of the positive pole piece and the outer wall of the secondary outer pole piece of the negative pole piece. By adopting the scheme provided in this embodiment, there can be no gap between the part of the negative pole piece exceeding the positive pole piece and the secondary outer pole piece of the negative pole piece and the end face of the positive pole piece, and the pole piece is not easy to crack on both sides of the end face of the positive pole piece, so that the first support structure only needs to be set at one place of the battery cell, and the structure is simple and easy to assemble.

[0008] In some embodiments, the first support structure is protruding from the inner wall of the housing. By adopting the solution provided in this embodiment, the first support structure and the housing can be integrated into one, and the position of the first support structure does not need to be adjusted when installing the electrode assembly, which facilitates the installation of the electrode assembly.

[0009] In some embodiments, there is the first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost circle electrode of the negative electrode, and the first support structure is protruding on the inner wall of the shell. By adopting the solution provided in this embodiment, the first support structure and the shell can be formed into a whole, and the position of the first support structure does not need to be adjusted when installing the electrode assembly, which facilitates the installation of the electrode assembly.

[0010] In some embodiments, there is the first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece of the negative electrode sheet, and there is also the first gap between the portion of the negative electrode sheet that exceeds the positive electrode sheet, the end face of the positive electrode sheet, and the sub-outer pole piece of the negative electrode sheet, and the first support structure located between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece of the negative electrode sheet is protruded on the inner wall of the shell. By adopting the solution provided in this embodiment, the first support structure located between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece of the negative electrode sheet can be formed into a whole with the shell, and the position of the first support structure does not need to be adjusted when installing the electrode assembly, which facilitates the installation of the electrode assembly.

[0011] In some embodiments, the thermal expansion coefficient of the first support structure is smaller than the thermal expansion coefficient of the negative electrode sheet. During the use of the electrode assembly, the internal temperature of the electrode assembly will increase. Selecting a first support structure with a thermal expansion coefficient smaller than that of the negative electrode sheet for filling can reduce the risk of additional pressure on the electrode sheet located at the first gap due to the expansion of the first support structure to a certain extent.

[0012] In some embodiments, the difference between the elastic modulus of the first support structure and the elastic modulus of the active material layer on the negative electrode sheet is within a first preset difference, and the absolute value of the first preset difference is within 50% of the elastic modulus of the active material layer. By adopting the solution provided in this embodiment, the elastic modulus of the first support structure can be equal to the elastic modulus of the active material layer on the negative electrode sheet, so that the two parts of the sub-outer ring electrode sheet in the negative electrode sheet located on both sides of the end face of the positive electrode sheet can be subjected to equal force, so that the sub-outer ring electrode sheet in the negative electrode sheet is deformed evenly after being subjected to force, and the risk of fracture is low.

[0013] In some embodiments, the elastic modulus of the first support structure is 10Mpa to 100Mpa. Since the elastic modulus of the active material layer of the negative electrode sheet is generally between 10Mpa and 100Mpa, the elastic modulus of the first support structure is 10Mpa to 100Mpa, so that the elastic modulus of the first support structure is close to the elastic modulus of the active material layer in the negative electrode sheet, so that the two parts of the sub-outer ring electrode sheet in the negative electrode sheet on both sides of the end face of the positive electrode sheet can be subjected to equal force, so that the sub-outer ring electrode sheet in the negative electrode sheet is deformed evenly after being subjected to force, and the risk of fracture is low.

[0014] In some embodiments, the first support structure is provided with a first liquid guiding structure, and the first liquid guiding structure is used to guide the electrolyte outside the electrode assembly to the positive electrode sheet or the negative electrode sheet. The first liquid guiding structure is provided to facilitate the electrolyte to infiltrate the electrode sheet, so that the performance of the battery cell is stable.

[0015] In some embodiments, the first liquid guiding structure includes a liquid guiding hole penetrating the first supporting structure. The first liquid guiding structure adopts the structure provided by this embodiment, which is simple in structure and makes the supporting strength of the first supporting structure larger, which can meet the use requirements.

[0016] In some embodiments, the battery cell also includes a protective film coated on the outside of the electrode assembly, and there is a second gap between the protective film and the outer wall of the main body of the electrode assembly, and the second gap is filled with a second support structure. The provision of the second support structure can, on the one hand, reduce the time difference between the top shells of the negative electrode sheets located on both sides of the end face of the negative electrode sheet; on the other hand, it can suppress the expansion of the electrode sheet under the second support structure to a certain extent, and can effectively reduce the stress concentration phenomenon at the tail end of the negative electrode sheet, so that the outermost electrode sheet of the negative electrode sheet is more evenly stressed, thereby reducing the risk of the negative electrode sheet breaking at its end face. In addition, the second support structure can reduce the risk of the step structure formed at the tail end of the negative electrode sheet causing indentations on the head end of the outermost electrode sheet of the negative electrode sheet to a certain extent, thereby reducing the risk of lithium deposition caused by indentations.

[0017] In some embodiments, the thermal expansion coefficient of the second support structure is smaller than the thermal expansion coefficient of the negative electrode sheet. During the use of the electrode assembly, the internal temperature of the electrode assembly will increase. Selecting a second support structure with a smaller thermal expansion coefficient than the negative electrode sheet for filling can reduce the risk of additional pressure on the electrode sheet located at the second gap due to the expansion of the second support structure to a certain extent.

[0018] In some embodiments, the difference between the elastic modulus of the second support structure and the elastic modulus of the active material layer on the negative electrode sheet is within a second preset difference, and the absolute value of the second preset difference is within 50% of the elastic modulus of the active material layer. In this way, the elastic modulus of the second support structure is equivalent to the elastic modulus of the active material layer on the positive electrode sheet, so that the force on the electrode sheet below the second gap is equivalent to the force on the electrode sheet on the left side of the second gap, so that the deformation of the electrode sheet after being stressed is more uniform, and the risk of fracture is lower.

[0019] In some embodiments, the elastic modulus of the second support structure is 10Mpa to 100Mpa. The elastic modulus of the second support structure is 10Mpa to 100Mpa, so that the elastic modulus of the second support structure is close to the elastic modulus of the active material layer in the negative electrode sheet, so that the deformation of the negative electrode sheet after being stressed is more uniform, and the risk of fracture is lower.

[0020] In some embodiments, the second support structure is provided with a second liquid guide structure, and the second liquid guide structure is used to guide the electrolyte outside the electrode assembly to the negative electrode sheet. The second liquid guide structure is provided to facilitate the electrolyte to infiltrate the second electrode sheet, so that the performance of the battery cell is stable.

[0021] In some embodiments, the second liquid guiding structure includes a liquid guiding hole penetrating the second supporting structure. The second liquid guiding structure adopts the structure provided by this embodiment, which is simple in structure and makes the supporting strength of the second supporting structure larger, which can meet the use requirements.

[0022] In a second aspect, an embodiment of the present application provides a battery, including a battery cell provided by any of the above embodiments. The battery provided by an embodiment of the present application includes a battery cell provided by any of the above embodiments, which can reduce the risk of fracture of the pole piece at the end.

[0023] In a third aspect, an embodiment of the present application provides an electric device, including the battery provided in the above embodiment. The electric device provided in the embodiment of the present application includes the battery provided in any of the above embodiments, which can reduce the risk of the pole piece breaking at the end.

[0024] 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

[0025] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0026] Figure 1 It is a schematic diagram of the local structure of an electrode assembly in the related art;

[0027] Figure 2 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0028] Figure 3 A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0029] Figure 4 A schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0030] Figure 5 A schematic diagram of a partial structure of an electrode assembly according to some embodiments of the present application;

[0031] Figure 6 Schematic diagram of the partial structure of electrode assemblies of other embodiments of the present application;

[0032] Figure 7Schematic diagram of the partial structure of electrode assemblies of other embodiments of the present application;

[0033] Figure 8 A schematic diagram of a partial cross-sectional structure of a battery cell according to some embodiments of the present application;

[0034] Fig. 9 A schematic diagram of the cross-sectional structure of a battery shell in some embodiments of the present application;

[0035] Fig.10 Schematic diagram of the cross-sectional structure of a battery shell in some other embodiments of the present application;

[0036] Fig.11 Schematic diagram of the partial cross-sectional structure of electrode assemblies according to other embodiments of the present application.

[0037] The reference numerals in the specific implementation manner are as follows:

[0038] 1000. Vehicles;

[0039] 100, battery; 200, controller; 300, motor;

[0040] 10. Box body; 11. First part; 12. Second part;

[0041] 20. Battery cell; 21. End cap; 21a. Electrode terminal; 22. Shell; 23. Electrode assembly; 23a. Tab;

[0042] 231, positive electrode sheet; 231a, end face of positive electrode sheet; 232, negative electrode sheet; 232a, tail end of negative electrode sheet; 232b, outermost electrode sheet; 232c, second outer electrode sheet; 232d, end face of negative electrode sheet; 233, diaphragm; 235, first supporting structure; 236, protective film; 237, second supporting structure; 238, first gap; L1, first reference line; L2, second reference line. DETAILED DESCRIPTION

[0043] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0045] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0046] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0047] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or can represent: A exists alone, A and exist at the same time, and A and A exist alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0048] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0049] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0050] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0051] At present, from the perspective of market development, the application of power batteries is becoming more and more extensive. Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.

[0052] The electrode assembly is an important component of the battery. According to the preparation method of the electrode assembly, it can be divided into a wound electrode assembly and a laminated electrode assembly. Among them, the wound electrode assembly is widely used because it is relatively simple to operate and easy to control the quality.

[0053] The wound electrode assembly can be a square structure or a cylindrical structure. The wound electrode assembly includes a negative electrode sheet, a positive electrode sheet and a separator arranged in a preset order. In order to reduce lithium plating to a certain extent, the size of the negative electrode sheet in the wound electrode assembly is generally larger than the positive electrode sheet, that is, the length of the negative electrode sheet is generally greater than the length of the positive electrode sheet, and the width of the negative electrode sheet is generally greater than the width of the positive electrode sheet. In this way, in the wound state, the tail end of the negative electrode sheet generally exceeds the tail end of the positive electrode sheet and is placed on the secondary outer ring electrode sheet of the negative electrode sheet. The positive electrode sheet and the negative electrode sheet are generally composed of a current collector and an active material layer coated on the current collector, respectively. During use, the temperature inside the battery will increase, and as the temperature increases, the active material layer on the positive electrode sheet and the active material layer on the negative electrode sheet will expand, thereby applying an outward expansion force to the corresponding parts wrapped outside it, such as the electrode sheet located on the outer ring.

[0054] As the electrode assembly expands, the outer wall of the electrode assembly will contact and squeeze the inner wall of the battery shell (for ease of description, this phenomenon is referred to as the top shell below), so that the electrode assembly will receive the pressure applied by the shell to the electrode assembly. After the electrode assembly is wound, two step structures will be formed at the end. The first step structure is formed between the tail end of the positive electrode sheet and the second outer circle electrode sheet of the negative electrode sheet, and the second step structure is formed between the tail end of the negative electrode sheet and the head end of the outermost electrode sheet of the negative electrode sheet, that is, the junction of the head and tail of the outermost electrode sheet of the negative electrode sheet.

[0055] For ease of understanding, Figure 1Taking the structure shown as an example, the force conditions of the pole pieces at the above two step structures when the electrode assembly is used are explained. As the electrode assembly 23 continues to expand, at the first step structure, that is, the position of the end face 231a of the positive electrode sheet 231, the portion of the electrode assembly 23 located on the left side of the end face 231a of the positive electrode sheet 231 will first push against the shell during the expansion process due to the large number of pole piece windings and the large number of active material layers, while the portion of the electrode assembly 23 located on the right side of the end face 231a of the positive electrode sheet 231 will expand less in the same time due to the small number of pole piece windings and the small number of active material layers. The expanded volume of the portion on the left side of the end face 231a of the sheet 231 will continue to expand behind the portion of the top shell of the electrode assembly 23 located on the left side of the end face 231a of the positive electrode sheet 231, causing the shear stress and tensile stress of the electrode sheet located below the end face 231a of the positive electrode sheet 231 to continue to increase. That is, this causes the secondary outer ring electrode sheet of the negative electrode sheet 232 to experience two different expansion phenomena on both sides of the end face 231a of the positive electrode sheet 231, resulting in uneven force, which makes it easy for the negative electrode sheet 232 to break at this point.

[0056] At the second step structure, i.e., where the end face 232d of the negative electrode sheet 232 is located, the portion of the electrode assembly 23 located on the left side of the end face 232d of the negative electrode sheet 232 will first hit the shell during the expansion process due to the large number of electrode sheet windings and the large number of active material layers, while the portion of the electrode assembly 23 located on the right side of the end face 232d of the negative electrode sheet 232 will have a smaller expansion volume than the portion of the electrode assembly 23 located on the left side of the end face 232d of the negative electrode sheet 232 due to the small number of electrode sheet windings and the small number of active material layers. In the same period of time, the electrode assembly 23 will continue to expand after the portion of the electrode assembly 23 located on the left side of the end face 232d of the negative electrode sheet 232 hits the shell, resulting in the shear stress and tensile stress of the electrode sheet located below the end face 232d of the negative electrode sheet 232 continuously increasing, that is, this results in two different expansion phenomena at the connecting portion of the outermost electrode sheet and the second outer electrode sheet of the negative electrode sheet 232 on both sides of the end face 232d of the negative electrode sheet 232, and the force is uneven, which makes it easy for the negative electrode sheet 231 to break here.

[0057] To alleviate this problem, an embodiment of the present application provides an electrode assembly, wherein a first gap is formed between the inner wall of the housing and the end-to-end junction area of ​​the outermost electrode sheet of the negative electrode sheet, and a first gap is formed between the portion of the negative electrode sheet that exceeds the positive electrode sheet, the end face of the positive electrode sheet, and the sub-outer electrode sheet of the negative electrode sheet, and at least one of the first gaps is filled with a first support structure, thereby reducing the risk of each electrode sheet breaking at the end of at least one electrode sheet in the electrode assembly. Specifically, when the first support structure is filled in the first gap between the inner wall of the housing and the end-to-end junction area of ​​the outermost electrode sheet of the negative electrode sheet, the risk of each electrode sheet breaking at the end of the negative electrode sheet can be reduced; when the first support structure is filled in the first gap between the portion of the negative electrode sheet that exceeds the positive electrode sheet, the end face of the positive electrode sheet, and the sub-outer electrode sheet of the negative electrode sheet, the risk of each electrode sheet breaking at the end of the positive electrode sheet can be reduced.

[0058] The battery disclosed in the embodiments of the present application can be used in an electrical device that uses the battery as a power source or in various energy storage systems that use the battery as an energy storage element. The electrical device can be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, and the like. Among them, the electric toy can include a fixed or mobile electric toy, for example, a game console, an electric car toy, an electric ship toy, and an electric airplane toy, and the like, and the spacecraft can include an airplane, a rocket, a space shuttle, and a spacecraft, and the like.

[0059] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device in an embodiment of the present application.

[0060] Please refer to Figure 2 , Figure 2 A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, the front end or the rear end of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0061] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0062] like Figure 3 As shown, the battery 100 generally includes a box body 10 and a battery cell 20, wherein the battery cell 20 is accommodated in the box body 10. The box body 10 is used to provide an accommodation space for the battery cell 20. The box body 10 can be in various shapes, such as a cylinder, a cuboid, and the like.

[0063] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0064] Each battery cell 20 may be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0065] In some cases, the battery cells can also be directly installed in the vehicle without a box or shell, that is, there is no need to form a battery pack, and the structure of the vehicle body itself serves as a fixing structure for the battery cells.

[0066] A battery cell is the smallest unit that makes up a battery. Figure 4 As shown, the battery cell 20 generally includes a shell, an electrode assembly 23 and other functional components. Among them, the shell is a closed structure that can form the internal environment of the battery cell 20, and generally includes an end cap 21 and a shell 22. The shell 22 and the end cap 21 can be two independent components. An opening can be set on the shell 22, and the shell is formed by covering the opening with the end cap 21 at the opening. Without limitation, the shell can also be an integrated structure, that is, the end cap 21 and the shell 22 are integrated. Specifically, the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell. When it is necessary to encapsulate the interior of the shell 22, the end cap 21 is covered with the shell 22.

[0067] Among them, the end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength, such as an aluminum alloy, so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this. In some embodiments, an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0068] The shell 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, electrolyte and other components. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose any special restrictions on this.

[0069] The electrode assembly 23 is a component where electrochemical reactions occur in the battery cell 20. The housing 22 may contain one or more electrode assemblies 23. Figure 4 and Figure 5 As shown, the electrode assembly 23 is mainly formed by winding or stacking a positive electrode sheet 232 and a negative electrode sheet 231, and a separator 233 is usually provided between the positive electrode sheet 232 and the negative electrode sheet 231. The parts of the positive electrode sheet 232 and the negative electrode sheet 231 with active material layers constitute the main body of the electrode assembly 23, and the parts of the positive electrode sheet 232 and the negative electrode sheet 231 without active material layers each constitute a tab 23a. The positive tab and the negative tab can be located at one end of the main body or at both ends of the main body respectively. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tab 23a is connected to the electrode terminal 21a to form a current loop.

[0070] According to some embodiments of the present application, referring to Figure 5As shown, an embodiment of the present application provides a battery cell including a shell and an electrode assembly 23 disposed in the shell.

[0071] The electrode assembly 23 includes a positive electrode sheet 231, a negative electrode sheet 232 and a separator 233. The positive electrode sheet 231, the negative electrode sheet 232 and the separator 233 are stacked and wound in a predetermined order to form the electrode assembly 23, and the tail end of the negative electrode sheet 232 exceeds the positive electrode sheet 231.

[0072] A first gap is provided between the inner wall of the housing and the end-to-end junction of the outermost electrode sheet 232b of the negative electrode sheet 232, and / or between the portion of the negative electrode sheet 232 that exceeds the positive electrode sheet 231, the end surface of the positive electrode sheet 231 and the sub-outer electrode sheet 232c of the negative electrode sheet 232. The first support structure 235 is filled in the first gap.

[0073] As mentioned above, the outer shell is a closed structure used to form the internal environment of the battery cell, generally including an end cap 21 and a shell 22. The shell 22 and the end cap 21 can be two independent components or an integrated structure, which will not be described in detail here.

[0074] The electrode assembly 23 in this embodiment can be a square structure or a cylindrical structure, which can be set according to the needs of use. The positive electrode sheet 231 and the negative electrode sheet 232 can be provided with one or more, which can be set according to the needs of use. When there is one positive electrode sheet 231 and one negative electrode sheet 232 respectively, the positive electrode sheet 231, the negative electrode sheet 232 and the diaphragm 233 are stacked in a preset order, which means that the positive electrode sheet 231, the diaphragm 233, the negative electrode sheet 232, the diaphragm 233, or the negative electrode sheet 232, the diaphragm 233, the positive electrode sheet 231, and the diaphragm 233 are stacked in sequence in the preset order. When the wound battery cell adopts multiple negative electrode sheets 232 and multiple positive electrode sheets 231, the stacking principle is equivalent to the above, which will not be repeated here.

[0075] Winding molding means that when the electrode assembly 23 is a cylindrical structure, the positive electrode sheet 231, the negative electrode sheet 232 and the separator 233 stacked in a preset order are wound around a virtual axis to form a cylindrical winding body; when the electrode assembly 23 is a square structure, the positive electrode sheet 231, the negative electrode sheet 232 and the separator 233 stacked in a preset order are wound around a virtual axis and formed into a flat winding body after hot pressing or cold pressing.

[0076] Since the electrode assembly 23 is a multi-turn winding structure, the negative electrode sheet 232 is also a multi-turn winding structure. The outermost electrode sheet 232b of the negative electrode sheet 232 refers to the part of the negative electrode sheet 232 located at the outermost periphery. The outermost electrode sheet 232b of the negative electrode sheet 232 uses the end face 232d of the negative electrode sheet 232 as the termination face, and uses the cross section where the projection line of the above-mentioned termination face falls radially onto the inner electrode sheet of the negative electrode sheet 232 as the starting face. The sub-outer electrode sheet 232c of the negative electrode sheet 232 refers to a full circle of electrode sheets that uses the starting face of the above-mentioned outermost electrode sheet 232b as the termination face, extends inward, and uses the cross section where the projection line of the termination face of the sub-outer electrode sheet 232c falls radially onto the inner electrode sheet of the negative electrode sheet 232 as the starting face.

[0077] For ease of understanding, Figure 5 and Figure 6 Two reference lines, L1 and L2, are added, wherein the first reference line L1 can be used as the dividing line between the outermost pole piece and the sub-outer pole piece, that is, the outermost pole piece 232b of the negative pole piece 232 is the first continuous full-circle pole piece in the negative pole piece 232 from the end face 232d of the negative pole piece 232 to the first reference line L1, and the sub-outer pole piece 232c of the negative pole piece 232 is the second continuous full-circle pole piece between the first reference line L1 and the second reference line L2 corresponding to the starting face of the outermost pole piece 232b in the negative pole piece 232.

[0078] The portion of the negative electrode sheet 232 that extends beyond the positive electrode sheet 231 is the portion where the tail end of the negative electrode sheet 232 extends beyond the tail end of the positive electrode sheet 231. The end surface 231a of the positive electrode sheet 231 is the end surface of the tail end of the positive electrode sheet 231.

[0079] The end-to-end junction area of ​​the outermost electrode 232b of the negative electrode 232 refers to an area including the end surface 232d of the negative electrode 232 and having a certain area, including part of the tail end and part of the head end of the outermost electrode 232b of the negative electrode 232, such as Figure 5 The dotted line box is the area. It should be noted that Figure 5 The diagram is only a schematic diagram of the end-to-end junction area of ​​the outermost electrode piece 232b of the negative electrode piece 232 selected in some embodiments. In other embodiments, the end-to-end junction area of ​​the outermost electrode piece 232b of the negative electrode piece 232 may be larger than Figure 5 The area shown, such as Figure 7 As shown, it can also be less than Figure 5 The area shown can be set according to usage requirements.

[0080] The first gap between the inner wall of the housing and the end-to-end junction of the outermost electrode sheet 232b of the negative electrode sheet 232, and / or between the portion of the negative electrode sheet 232 extending beyond the positive electrode sheet 231, the end surface of the positive electrode sheet 231 and the sub-outer electrode sheet 232c of the negative electrode sheet 232 includes the following situations:

[0081] The first type is that there is a first gap between the inner wall of the housing and the end-to-end junction area of ​​the outermost electrode 232b of the negative electrode 232;

[0082] The second type is that the negative electrode sheet 232 extends beyond the positive electrode sheet 231, and a first gap 238 is formed between the end surface of the positive electrode sheet 231 and the secondary outer electrode sheet 232c of the negative electrode sheet 232. Figure 1 As shown;

[0083] The third type is that there is a first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative pole piece 232, and there is also a first gap between the part of the negative pole piece 232 that extends beyond the positive pole piece 231, the end face of the positive pole piece 231 and the sub-outer pole piece 232c of the negative pole piece 232.

[0084] The first support structure 235 is used to fill the first gap to make the first gap disappear, so the shape of the first support structure 235 is generally adapted to the shape of the first gap. The first support structure 235 can be a separate component, or a component or structure connected to other structures.

[0085] For example, when there is a first gap between the inner wall of the housing and the end-to-end junction area of ​​the outermost electrode 232b of the negative electrode 232, the first support structure 235 in the first gap can be a separate component, or a structure integrated with the housing or the protective film 236 in the electrode assembly 23, which can be set according to the use requirements. When the negative electrode 232 exceeds the positive electrode 231, and there is a first gap between the end face of the positive electrode 231 and the sub-outer electrode 232c of the negative electrode 232, the first support structure 235 in the first gap can be a separate component, or a structure integrated with the diaphragm 233 or the negative electrode 232, which can be set according to the use requirements.

[0086] When there is a first gap between the inner wall of the outer shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative pole piece 232, and there is also a first gap between the part of the negative pole piece 232 extending beyond the positive pole piece 231, the end face of the positive pole piece 231 and the sub-outer pole piece 232c of the negative pole piece 232, the materials of the first support structure 235 in the two first gaps can be the same or different, and the specific selection can be made according to the needs of use.

[0087] For ease of understanding, Figure 5 and Figure 6 In the structure shown in FIG. 1 , the negative electrode sheet 232 extends beyond the positive electrode sheet 231, and there is also a first gap between the end surface of the positive electrode sheet 231 and the secondary outer ring electrode sheet 232c of the negative electrode sheet 232. The first gap is filled with the first supporting structure as an example to illustrate the stress condition of the electrode sheet at the end of the battery cell provided by this embodiment:

[0088] As the electrode assembly 23 continues to expand, at the position of the end face 231a of the positive electrode sheet 231, the portion of the electrode assembly 23 located on the left side of the end face 231a of the positive electrode sheet 231 will first hit the shell during the expansion process due to the large number of electrode sheet windings and the large number of active material layers. The portion of the electrode assembly 23 located on the right side of the end face 231a of the positive electrode sheet 231, although the number of electrode sheet windings is small and the number of active material layers is small, has a smaller expansion volume than the portion of the electrode assembly 23 located on the left side of the end face 231a of the positive electrode sheet 231 in the same time. It will continue to expand after the portion of the electrode assembly 23 located on the left side of the end face 231a of the positive electrode sheet 231 hits the shell. However, due to the arrangement of the first support structure 235, the portions of the electrode assembly 23 located on both sides of the end face 231a of the positive electrode sheet 231 are less distant from the inner wall of the shell, thereby shortening the time difference between the two hitting the shell. At the same time, during the expansion process, the portion of the electrode assembly 23 located on the right side of the end surface 231a of the positive electrode sheet 231 will be subjected to the downward pressure exerted by the first supporting structure, thereby affecting the expansion speed of the portion of the electrode assembly 23 located on the right side of the end surface 231a of the positive electrode sheet 231, and inhibiting the expansion of the electrode sheet under the first supporting structure 235. This can effectively reduce the stress concentration phenomenon of each electrode sheet at the first gap, make each electrode sheet more evenly stressed, and reduce the risk of each electrode sheet breaking at the end of the positive electrode sheet 231.

[0089] In addition, the first support structure 235 can also reduce the risk of indentation of the underlying electrode sheets due to the presence of a step structure between the end surface 231a of the positive electrode sheet 231 and the negative electrode sheet 232 during the expansion process, thereby reducing the risk of lithium deposition in the battery cell caused by indentation.

[0090] It can be understood that when there is a first gap between the inner wall of the outer shell and the end-to-end junction area of ​​the outermost electrode 232b of the negative electrode 232, and the first gap is filled with a first supporting structure, it can also have an effect equivalent to the above situation, thereby reducing the risk of each electrode breaking at the end of the negative electrode 232.

[0091] To summarize, the electrode assembly 23 provided in the embodiment of the present application has a first support structure 235 filled in at least one of the first gaps including the first gap between the inner wall of the outer shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative electrode sheet 232, and the first gap between the part of the negative electrode sheet 232 that extends beyond the positive electrode sheet 231, the end face of the positive electrode sheet 231 and the sub-outer pole piece 232c of the negative electrode sheet 232, thereby reducing the risk of each pole sheet breaking at the end of at least one pole sheet in the electrode assembly. Specifically, when the first supporting structure 235 is filled in the first gap between the inner wall of the outer shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative pole piece 232, the risk of each pole piece breaking at the end of the negative pole piece can be reduced; when the first supporting structure 235 is filled in the first gap between the part of the negative pole piece 232 that extends beyond the positive pole piece 231, the end face of the positive pole piece 231 and the sub-outer pole piece 232c of the negative pole piece 232, the risk of each pole piece breaking at the end of the positive pole piece can be reduced.

[0092] In addition, no matter which of the above-mentioned first gaps is filled with the first support structure, the time difference of the top shell of each pole piece located on both sides of the first gap can be reduced to a certain extent, and the expansion of the pole piece below the first support structure 235 can be suppressed, which can effectively reduce the stress concentration phenomenon of each pole piece at the first gap, so that each pole piece is more evenly stressed, thereby reducing the risk of each pole piece breaking at the first gap. In addition, the first support structure 235 can reduce the risk of the step structure between the positive pole piece 231 and the negative pole piece 232 causing indentations to the pole pieces below, thereby reducing the risk of lithium deposition caused by indentations in the battery cell.

[0093] like Figure 7 and Figure 8 As shown, in some embodiments, there is a first gap between the inner wall of the housing and the end-to-end junction area of ​​the outermost pole piece 232b of the negative pole piece 232. The end-to-end junction area of ​​the outermost pole piece 232b of the negative pole piece 232 includes the area where the negative pole piece 232 exceeds the positive pole piece 231. At least part of the first support structure 235 abuts against the part of the negative pole piece 232 that exceeds the positive pole piece 231, so that the inner wall of the part of the negative pole piece 232 that exceeds the positive pole piece 231 is in contact with the end surface of the positive pole piece 231 and the outer wall of the sub-outer pole piece 232c of the negative pole piece 232.

[0094] It can be understood that, in this embodiment, the end-to-end junction area of ​​the outermost electrode piece 232b of the negative electrode piece 232 includes not only the area where the negative electrode piece 232 exceeds the positive electrode piece 231, but also includes the area where the partial head end of the outermost electrode piece 232b of the negative electrode piece 232 is located, and the partial head end here refers to the part of the head end of the outermost electrode piece 232b that is adjacent to the end surface 232d. The area where the negative electrode piece 232 exceeds the positive electrode piece 231 refers to the area where the negative electrode piece 232 exceeds the positive electrode piece 231 and is opposite to the inner wall of the shell.

[0095] At least part of the first support structure 235 is in contact with the part of the negative electrode sheet 232 that protrudes from the positive electrode sheet 231, which means that a part of the first support structure 235 is in contact with the outer wall of the part of the negative electrode sheet 232 that protrudes from the positive electrode sheet 231, and can apply a pressing force toward the end face of the secondary outer ring electrode sheet 232c and / or the positive electrode sheet 231 during the installation of the electrode assembly 23. The inner wall of the part of the negative electrode sheet 232 that protrudes from the positive electrode sheet 231 is in contact with the end face of the positive electrode sheet 231 and the outer wall of the secondary outer ring electrode sheet 232c of the negative electrode sheet 232, which means that a part of the inner wall of the part of the negative electrode sheet 232 that protrudes from the positive electrode sheet 231 is parallel to the end face of the positive electrode sheet 231 and is in contact with each other, and another part of the inner wall of the part of the negative electrode sheet 232 that protrudes from the positive electrode sheet 231 is in the same direction as the outer wall of the secondary outer ring electrode sheet 232c of the negative electrode sheet 232 and is in contact with each other.

[0096] By adopting the solution provided in this embodiment, when the electrode assembly 23 is not installed in the housing, a first gap is formed between the portion of the negative electrode sheet 232 that protrudes beyond the positive electrode sheet 231 , the end surface of the positive electrode sheet 231 and the secondary outer ring electrode sheet 232 c of the negative electrode sheet 232 .

[0097] After the electrode assembly 23 is installed in the outer shell, the part of the negative electrode sheet 232 that extends beyond the positive electrode sheet 231 is deformed under the pressure of the first support member, so that the part of the negative electrode sheet 232 that extends beyond the positive electrode sheet 231 is bent, so that a part of the inner wall of this part is in contact with the end face of the positive electrode sheet 231, and the other part is in contact with the outer wall of the secondary outer ring electrode sheet 232c of the negative electrode sheet 232.

[0098] By adopting the solution provided in this embodiment, there can be no gap between the portion of the negative electrode sheet 232 that protrudes beyond the positive electrode sheet 231 and the secondary outer ring electrode sheet 232c of the negative electrode sheet 232 and the end face of the positive electrode sheet 231, and it is not easy for the electrode sheets to crack on both sides of the end face of the positive electrode sheet 231. In this way, the first supporting structure 235 only needs to be set at one place of the battery cell, and the structure is simple and easy to assemble.

[0099] like Fig. 9 and Fig.10As shown, in some embodiments, the first support structure 235 is convexly arranged on the inner wall of the shell. In this embodiment, the first support structure 235 can be formed integrally with the shell, or can be installed on the inner wall of the shell after the shell is manufactured by gluing, welding, etc. With the solution provided in this embodiment, the first support structure 235 can be made into a whole with the shell, and the position of the first support structure 235 does not need to be adjusted when installing the electrode assembly 23, which facilitates the installation of the electrode assembly 23.

[0100] like Fig. 9 and Fig.10 As shown, in some embodiments, there is a first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost electrode 232b of the negative electrode 232. The first support structure 235 is convexly arranged on the inner wall of the shell. In this embodiment, the first support structure 235 can be integrally formed with the shell, or it can be installed on the inner wall of the shell after the shell is manufactured by gluing, welding, etc. With the solution provided in this embodiment, the first support structure 235 can be made into a whole with the shell, and the position of the first support structure 235 does not need to be adjusted when installing the electrode assembly 23, which facilitates the installation of the electrode assembly 23.

[0101] In some embodiments, there is a first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost electrode piece 232b of the negative electrode piece 232, and there is also a first gap between the portion of the negative electrode piece 232 that exceeds the positive electrode piece 231, the end surface of the positive electrode piece 231, and the sub-outer electrode piece 232c of the negative electrode piece 232. The first support structure 235 located between the inner wall of the shell and the end-to-end junction area of ​​the outermost electrode piece 232b of the negative electrode piece 232 is protruded on the inner wall of the shell.

[0102] In this embodiment, the first support structure 235 located between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative electrode sheet 232 can be formed integrally with the shell, or can be installed on the inner wall of the shell after the shell is manufactured by gluing, welding, etc. With the solution provided in this embodiment, the first support structure 235 located between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative electrode sheet 232 can be formed into a whole with the shell, and the position of the first support structure 235 does not need to be adjusted when installing the electrode assembly 23, which facilitates the installation of the electrode assembly 23.

[0103] In some embodiments, the thermal expansion coefficient of the first support structure 235 is smaller than the thermal expansion coefficient of the negative electrode sheet 232 .

[0104] The coefficient of thermal expansion refers to the change in volume of an object caused by a unit change in temperature under constant pressure (i.e. isobaric) conditions.

[0105] Since the first support structure 235 is generally an irregular structure, the above volume change can be represented by the volume expansion coefficient. The calculation formula of the volume expansion coefficient is: γ = ΔV / (V*ΔT), γ is the volume expansion coefficient, V is the initial volume of the object, ΔV is the volume change value of the object before and after the temperature change, such as the volume of the object at the initial temperature is V1, and the volume of the object after the temperature change is V2, then ΔV = V2-V1, ΔT is the temperature change value, such as the initial temperature is T1, and the temperature after the temperature change is T2, then ΔT = T2-T1.

[0106] The following methods can be used for thermal expansion coefficient testing:

[0107] First, prepare two measuring cups, and put equal amounts of liquid in the two measuring cups, so that the first support structure 235 and the negative electrode sheet 232 can be completely submerged under the surface of the liquid after being placed in the two cups of liquid, and record the initial volume of the liquid, which is recorded as V0. Adjust the ambient air pressure of the liquid to P and the temperature to T1. It can be understood that the volume of the first support structure 235 used in the test can be smaller than the volume of the first support structure 235 in the actual battery cell, and the volume of the negative electrode sheet 232 can be smaller than the volume of the negative electrode sheet 232 in the actual battery cell, that is, a part of the first support structure 235 and a part of the negative electrode sheet 232 can be taken as test materials, and the volumes of the two can be the same or different.

[0108] Then, the air pressure is maintained at P, and the first supporting structure 235 and the negative electrode sheet 232 are placed in two measuring cups respectively. The changes in the liquid levels in the two measuring cups are observed, and the scale values ​​corresponding to the liquid levels after the first supporting structure 235 and the negative electrode sheet 232 are placed in are recorded, that is, the volume values ​​of the objects in the measuring cups. The scale value corresponding to the liquid level in the measuring cup where the first supporting structure 235 is placed is recorded as V1, and the scale value corresponding to the liquid level in the measuring cup where the negative electrode sheet 232 is placed is recorded as V1'.

[0109] Then adjust the liquid temperature to T2, observe the changes in the liquid levels in the two measuring cups, and record the scale values ​​corresponding to the liquid levels in the two measuring cups, that is, the volume values ​​of the objects in the measuring cups. The scale value corresponding to the liquid level in the measuring cup where the first support structure 235 is placed is recorded as V2, and the scale value corresponding to the liquid level in the measuring cup where the negative electrode sheet 232 is placed is recorded as V2'.

[0110] The volume expansion coefficients of the first support structure 235 and the negative electrode sheet 232 are calculated by using the above parameters. The volume expansion coefficient of the first support structure 235 is γ1=(V2-V1) / (V1*(T2-T1)), and the volume expansion coefficient of the negative electrode sheet 232 is γ2=(V2'-V1') / (V1'*(T2-T1)).

[0111] The test results show that if γ1 is less than γ2, it proves that the thermal expansion coefficient of the first support structure 235 is less than the thermal expansion coefficient of the negative electrode sheet 232; if γ1 is greater than γ2, it proves that the thermal expansion coefficient of the first support structure 235 is greater than the thermal expansion coefficient of the negative electrode sheet 232; if γ1 is equal to γ2, it proves that the thermal expansion coefficient of the first support structure 235 is equal to the thermal expansion coefficient of the negative electrode sheet 232.

[0112] Of course, other methods may also be used to calculate the volume expansion system of the first support structure 235 and the negative electrode sheet 232, and this is not the only limitation here.

[0113] During the use of the electrode assembly 23, the internal temperature of the electrode assembly 23 will increase. Selecting a first support structure 235 with a thermal expansion coefficient smaller than that of the negative electrode sheet 232 for filling can reduce the risk of additional pressure on the electrode sheet located in the first gap due to the expansion of the first support structure 235 to a certain extent.

[0114] In some embodiments, the difference between the elastic modulus of the first support structure 235 and the elastic modulus of the active material layer on the negative electrode sheet 232 is within a first preset difference, and the absolute value of the first preset difference is within 50% of the elastic modulus of the active material layer.

[0115] Elastic modulus refers to the slope of the stress-strain curve of an object in the elastic deformation area. It is also the value obtained by dividing the stress in a unidirectional stress state by the strain in that direction. It can be expressed as "Young's modulus", "shear modulus", "bulk modulus", etc.

[0116] The elastic modulus can be measured by any of the following methods:

[0117] Suspension beam method: The first support structure 235 and the active material layer on the negative electrode sheet 232 are respectively made into suspension beams, the deflection of the suspension beams under the action of external force is measured, and the elastic modulus of the first support structure 235 and the active material layer on the negative electrode sheet 232 is calculated by bending theory.

[0118] Compression method: The first support structure 235 and the active material layer on the negative electrode sheet 232 are processed into cylindrical or square specimens respectively, and the strains of the two under different compressive stresses are measured. The elastic modulus of the active material layer on the first support structure 235 and the negative electrode sheet 232 is calculated by Snell's formula.

[0119] Tensile method: The first support structure 235 and the active material layer on the negative electrode sheet 232 are processed into cylindrical or square specimens respectively, the strain under different tensile stresses is measured, and the elastic modulus of the active material layer on the first support structure 235 and the negative electrode sheet 232 is calculated by Hooke's law.

[0120] Acoustic wave method: The propagation speed of the active material layer on the first support structure 235 and the negative electrode sheet 232 under the action of the acoustic wave is measured by ultrasonic technology, thereby calculating the elastic modulus of the active material layer on the first support structure 235 and the negative electrode sheet 232. This method is applicable to any material, but requires relatively professional equipment and technology.

[0121] Other methods may also be used to measure the elastic modulus of the active material layer on the first support structure 235 and the negative electrode sheet 232 , which may be selected based on usage requirements and are not limited here.

[0122] By adopting the solution provided in this embodiment, the elastic modulus of the first supporting structure 235 can be made equivalent to the elastic modulus of the active material layer on the negative electrode sheet 232, so that the two parts of the sub-outer ring electrode sheet 232c in the negative electrode sheet 232 located on both sides of the end face of the positive electrode sheet 231 can be subjected to equivalent forces, so that the sub-outer ring electrode sheet 232c in the negative electrode sheet 232 is deformed evenly after being subjected to force, and the risk of fracture is low.

[0123] In some embodiments, the elastic modulus of the first support structure 235 is 10 MPa to 100 MPa.

[0124] Since the elastic modulus of the active material layer of the negative electrode sheet 232 is generally between 10Mpa and 100Mpa, the elastic modulus of the first support structure 235 is 10 to 100Mpa, so that the elastic modulus of the first support structure 235 is close to the elastic modulus of the active material layer in the negative electrode sheet 232. In this way, the two parts of the sub-outer ring electrode sheet 232c in the negative electrode sheet 232 located on both sides of the end face of the positive electrode sheet 231 can be subjected to equal force, so that the sub-outer ring electrode sheet 232c in the negative electrode sheet 232 is deformed evenly after being subjected to force, and the risk of fracture is low.

[0125] In some embodiments, a first liquid guiding structure is disposed on the first support structure 235. The first liquid guiding structure is used to guide the electrolyte outside the electrode assembly 23 to the positive electrode sheet 231 or the negative electrode sheet 232.

[0126] The first liquid-conducting structure may be a microporous structure, a through structure with multiple straight holes connected, or an irregular hole, as long as the electrolyte outside the electrode assembly 23 can be guided to the positive electrode sheet 231 or the negative electrode sheet 232 through the first liquid-conducting structure.

[0127] The above-mentioned guiding to the positive electrode sheet 231 or the negative electrode sheet 232 means that when the first supporting structure 235 is in contact with the positive electrode sheet 231, the first liquid guiding structure on the first supporting structure 235 is used to guide the electrolyte outside the electrode assembly 23 to the positive electrode sheet 231, and when the first supporting structure 235 is in contact with the negative electrode sheet 232, the first liquid guiding structure on the first supporting structure 235 is used to guide the electrolyte outside the electrode assembly 23 to the negative electrode sheet 232.

[0128] The provision of the first liquid-conducting structure is conducive to the electrolyte infiltration into the pole piece, so that the performance of the battery cell is stable.

[0129] In some embodiments, the first liquid guiding structure includes a liquid guiding hole penetrating through the first supporting structure 235 .

[0130] The liquid guide hole can be a through hole that passes through the first support structure 235, or a hole-shaped structure with multiple straight holes connected, or one or more irregular holes, as long as the electrolyte outside the electrode assembly 23 can be guided to the positive electrode sheet 231 or the negative electrode sheet 232 through the liquid guide hole.

[0131] The first liquid guiding structure adopts the structure provided in this embodiment, which has a simple structure and makes the supporting strength of the first supporting structure 235 larger, thereby meeting the use requirements.

[0132] like Fig.11 As shown, in some embodiments, the battery cell further includes a protective film 236 covering the electrode assembly 23. A second gap exists between the protective film 236 and the outer wall of the main body of the electrode assembly 23. A second support structure 237 is filled in the second gap.

[0133] The protective film 236 is an insulating film that is wound around the electrode assembly 23 and covers the electrode assembly 23. The main body of the electrode assembly 23 refers to the portion of the electrode assembly 23 excluding the tab 23a.

[0134] Since the negative electrode sheet 232 in the electrode assembly 23 is long and the separator 233 is thin, there is a second gap between the protective film 236 and the outer wall of the main body of the electrode assembly 23, which can be understood as a second gap between the protective film 236 and the outermost electrode sheet 232b of the negative electrode sheet 232. The second gap is located at the end surface of the tail end of the negative electrode sheet 232.

[0135] The second support structure 237 is used to fill the second gap to make the second gap disappear, so the shape of the second support structure 237 is generally adapted to the shape of the second gap. The second support structure 237 can be a separately provided component, or a component connected to the protective film 236 or the negative electrode sheet 232. The material of the second support structure 237 can be the same as that of the first support structure 235, or it can be different, and can be selected according to the specific use requirements.

[0136] For ease of understanding, Fig.11 The structure shown in the figure is used to illustrate the stress condition at the end of the negative electrode sheet of the battery cell provided by this embodiment:

[0137] As the electrode assembly 23 continues to expand, at the position of the end face 232d of the negative electrode sheet 232, the portion of the electrode assembly 23 located on the left side of the end face 232d of the negative electrode sheet 232 will first hit the shell during the expansion process due to the large number of electrode sheet windings and the large number of active material layers. The portion of the electrode assembly 23 located on the right side of the end face 232d of the negative electrode sheet 232, although the number of electrode sheet windings is small and the number of active material layers is small, has a smaller expansion volume than the portion of the electrode assembly 23 located on the left side of the end face 232d of the negative electrode sheet 232 in the same time. It will continue to expand after the portion of the electrode assembly 23 located on the left side of the end face 232d of the negative electrode sheet 232 hits the shell. However, due to the provision of the first supporting structure, the portions of the electrode assembly 23 located on both sides of the end face 232d of the negative electrode sheet 232 are less distant from the inner wall of the shell, thereby shortening the time difference between the two hitting the shell. At the same time, during the expansion process, the portion of the electrode assembly 23 located on the right side of the end surface 232d of the negative electrode sheet 232 will be subjected to the downward pressure exerted by the first support structure, thereby affecting the expansion speed of the portion of the electrode assembly 23 located on the right side of the end surface 232d of the negative electrode sheet 232, and inhibiting the expansion of the electrode sheet under the second support structure 237. This can effectively reduce the stress concentration phenomenon of each electrode sheet at the first gap, make each electrode sheet more evenly stressed, and reduce the risk of each electrode sheet breaking at the end of the negative electrode sheet 232.

[0138] In addition, the second support structure 237 can also reduce the risk of indentation of the underlying electrode sheets during the expansion process due to the presence of a step structure between the end face 232d of the negative electrode sheet 232 and the head end of the outermost electrode sheet of the negative electrode sheet 232, thereby reducing the risk of lithium plating of the battery cell caused by indentation.

[0139] In summary, the second support structure 237 can, on the one hand, reduce the time difference of the top shell of the negative electrode sheet 232 located on both sides of the end surface 232d of the negative electrode sheet 232; on the other hand, it can suppress the expansion of the electrode sheet below the second support structure 237 to a certain extent, and can effectively reduce the stress concentration phenomenon at the tail end of the negative electrode sheet 232, so that the outermost electrode sheet 232b of the negative electrode sheet 232 is more evenly stressed, thereby reducing the risk of the negative electrode sheet 232 breaking at its end surface. In addition, the second support structure 237 can reduce the risk of the step structure formed at the tail end of the negative electrode sheet 232 causing an indentation on the head end of the outermost electrode sheet 232b of the negative electrode sheet 232 to a certain extent, thereby reducing the risk of lithium deposition caused by the indentation.

[0140] In some embodiments, the thermal expansion coefficient of the second support structure 237 is smaller than the thermal expansion coefficient of the negative electrode sheet 232 .

[0141] During the use of the electrode assembly 23, the internal temperature of the electrode assembly 23 will increase. Selecting a second support structure 237 with a small thermal expansion coefficient and the negative electrode sheet 232 for filling can reduce the risk of additional pressure on the electrode sheet located in the second gap due to the expansion of the second support structure 237 to a certain extent.

[0142] In some embodiments, the difference between the elastic modulus of the second support structure 237 and the elastic modulus of the active material layer on the negative electrode sheet 232 is within a second preset difference, and the absolute value of the second preset difference is within 50% of the elastic modulus of the active material layer.

[0143] In this way, the elastic modulus of the second support structure 237 can be equivalent to the elastic modulus of the active material layer on the positive electrode 231, so that the force on the electrode below the second gap is equivalent to the force on the electrode on the left side of the second gap, so that the deformation of the electrode after being stressed is more uniform and the risk of breakage is lower.

[0144] In some embodiments, the elastic modulus of the second support structure 237 is 10 MPa to 100 MPa.

[0145] The elastic modulus of the second support structure 237 is 10-100 MPa, so that the elastic modulus of the second support structure 237 is close to the elastic modulus of the active material layer in the negative electrode sheet 232, so that the negative electrode sheet 232 deforms more evenly after being stressed, and the risk of fracture is lower.

[0146] In some embodiments, a second liquid guiding structure is disposed on the second supporting structure 237 , and the second liquid guiding structure is used to guide the electrolyte outside the electrode assembly 23 to the negative electrode sheet 232 .

[0147] The second liquid-conducting structure may be a microporous structure, or a through structure with multiple straight holes connected, or an irregular hole, as long as the electrolyte outside the electrode assembly 23 can be guided to the negative electrode sheet 232 through the second liquid-conducting structure. The second liquid-conducting structure may have the same structure as the first liquid-conducting structure, or may have a different structure, which may be set according to the use requirements.

[0148] The provision of the second liquid-conducting structure is conducive to the electrolyte infiltration into the second pole piece, so that the performance of the battery cell is stable.

[0149] In some embodiments, the second liquid-conducting structure includes a liquid-conducting hole that passes through the second supporting structure 237 .

[0150] The liquid guide hole can be a through hole that passes through the first support structure 235, or a hole-shaped structure with multiple straight holes connected, or one or more irregular holes, as long as the electrolyte outside the electrode assembly 23 can be guided to the negative electrode sheet 232 through the liquid guide hole.

[0151] The second liquid guiding structure adopts the structure provided in this embodiment, which has a simple structure and makes the supporting strength of the second supporting structure 237 larger, thereby meeting the use requirements.

[0152] like Figures 4 to 11 As shown, according to some embodiments of the present application, a battery cell is provided, which includes a housing and an electrode assembly 23 disposed in the housing.

[0153] The electrode assembly 23 includes a positive electrode sheet 231 , a negative electrode sheet 232 and a separator 233 . The positive electrode sheet 231 , the negative electrode sheet 232 and the separator 233 are stacked and wound in a preset order to form the electrode assembly 23 . The tail end of the negative electrode sheet 232 extends beyond the positive electrode sheet 231 .

[0154] There is a first gap between the inner wall of the outer shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative pole piece 232, and / or between the part of the negative pole piece 232 extending beyond the positive pole piece 231, the end face of the positive pole piece 231 and the sub-outer pole piece 232c of the negative pole piece 232, and the first gap is filled with a first support structure 235.

[0155] In some embodiments, there is a first gap between the inner wall of the housing and the end-to-end junction area of ​​the outermost electrode sheet 232b of the negative electrode sheet 232, and the first gap is filled with a first support structure 235. At least part of the first support structure 235 abuts against the portion of the negative electrode sheet 232 that exceeds the positive electrode sheet 231, so that the inner wall of the portion of the negative electrode sheet 232 that exceeds the positive electrode sheet 231 fits with the end surface of the positive electrode sheet 231 and the outer wall of the sub-outer electrode sheet 232c of the negative electrode sheet 232. The first support structure 235 is convexly arranged on the inner wall of the housing.

[0156] In other embodiments, a first gap is formed between the portion of the negative electrode sheet 232 that protrudes beyond the positive electrode sheet 231 , the end surface of the positive electrode sheet 231 and the secondary outer electrode sheet 232 c of the negative electrode sheet 232 , and the first support structure 235 is filled in the first gap.

[0157] In other embodiments, there is a first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative pole piece 232, and there is also a first gap between the portion of the negative pole piece 232 that exceeds the positive pole piece 231, the end surface of the positive pole piece 231, and the sub-outer pole piece 232c of the negative pole piece 232. Each first gap is filled with a first support structure 235. The first support structure 235 located between the inner wall of the shell and the end-to-end junction area of ​​the outermost pole piece 232b of the negative pole piece 232 is protruded on the inner wall of the shell.

[0158] In the above embodiments, the thermal expansion coefficient of the first support structure 235 is less than the thermal expansion coefficient of the negative electrode sheet 232. The elastic modulus of the first support structure 235 is 10Mpa to 100Mpa. A first liquid guide structure is provided on the first support structure 235, and the first liquid guide structure is used to guide the electrolyte outside the electrode assembly 23 to the positive electrode sheet 231 or the negative electrode sheet 232. The first liquid guide structure includes a liquid guide hole that passes through the first support structure 235.

[0159] The battery cell also includes a protective film 236 wrapped around the outside of the electrode assembly 23. There is a second gap between the protective film 236 and the outer wall of the main body of the electrode assembly 23. The second gap is filled with a second support structure 237. The thermal expansion coefficient of the second support structure 237 is smaller than the thermal expansion coefficient of the negative electrode sheet 232. The elastic modulus of the second support structure 237 is 10Mpa to 100Mpa. A second liquid guide structure is provided on the second support structure 237, and the second liquid guide structure is used to guide the electrolyte outside the electrode assembly 23 to the negative electrode sheet 232. The second liquid guide structure includes a liquid guide hole that passes through the second support structure 237.

[0160] like Figure 8 As shown, in some embodiments, the electrode assembly 23 is a square structure, and the end position of the negative electrode sheet 232 is on a large flat area, and a corresponding first support structure 235 is designed on the inner wall of the corresponding shell 22 to fit the shape of the step structure at the end. Fig.10 As shown, in other embodiments, the electrode assembly 23 is a cylindrical structure, and a first support structure 235 is convexly provided on the inner wall of the shell opposite to the end step of the negative electrode sheet 232, and the first support structure 235 is inlaid with the shape of the end step structure. Fig.11 As shown, in other embodiments, the electrode assembly 23 is a cylindrical structure with an external protective film 236, and the end of the positive electrode sheet 231 and the end of the negative electrode sheet 232 in the electrode assembly 23 are both provided with a support structure. Figure 5 As shown, in other embodiments, the electrode assembly 23 is a square structure. If the end position of the negative electrode sheet 232 is on a large flat area, a corresponding first support structure 235 is designed at the step gap of the corresponding positive and negative electrode end positions.

[0161] The battery cells provided by the above embodiments can reduce the risk of the pole piece breaking at the end.

[0162] According to some embodiments of the present application, the present application further provides a battery, which includes the battery cell provided by any of the above embodiments.

[0163] The battery provided in the embodiment of the present application includes the battery cell provided in any of the above embodiments, which can reduce the risk of the pole piece breaking at the end.

[0164] According to some embodiments of the present application, the present application further provides an electric device, which includes a battery provided by any of the above embodiments.

[0165] The power-consuming device may be any of the aforementioned devices or systems using batteries.

[0166] The electrical device provided in the embodiment of the present application includes the battery provided in any of the above embodiments, which can reduce the risk of the pole piece breaking at the end.

[0167] 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 replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate 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: comprising a housing and an electrode assembly disposed in the housing; The electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the positive electrode sheet, the negative electrode sheet and the separator are stacked and wound in a preset order to form the electrode assembly, and the tail end of the negative electrode sheet exceeds the positive electrode sheet; There is a first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost circle of the negative electrode sheet, and / or between the part of the negative electrode sheet that extends beyond the positive electrode sheet, the end face of the positive electrode sheet and the sub-outer circle of the negative electrode sheet, and the first gap is filled with a first supporting structure.

2. The battery cell according to claim 1, characterized in that: There is the first gap between the inner wall of the shell and the end-to-end junction area of ​​the outermost circle electrode sheet of the negative electrode sheet, and the end-to-end junction area of ​​the outermost circle electrode sheet of the negative electrode sheet includes the area where the negative electrode sheet extends beyond the positive electrode sheet; at least part of the first supporting structure abuts against the part of the negative electrode sheet that extends beyond the positive electrode sheet, so that the inner wall of the part of the negative electrode sheet that extends beyond the positive electrode sheet fits with the end face of the positive electrode sheet and the outer wall of the second outer circle electrode sheet of the negative electrode sheet.

3. The battery cell according to claim 2, characterized in that: The first supporting structure is protrudingly disposed on the inner wall of the shell.

4. The battery cell according to claim 1, characterized in that: The first gap is provided between the inner wall of the shell and the end-to-end junction area of ​​the outermost electrode of the negative electrode, and the first supporting structure is protruded on the inner wall of the shell.

5. The battery cell according to claim 1, characterized in that: The first gap is provided between the inner wall of the shell and the end-to-end junction area of ​​the outermost circle electrode sheet of the negative electrode sheet, and the first gap is also provided between the part of the negative electrode sheet extending beyond the positive electrode sheet, the end face of the positive electrode sheet and the sub-outer circle electrode sheet of the negative electrode sheet. The first supporting structure located between the inner wall of the shell and the end-to-end junction area of ​​the outermost circle electrode sheet of the negative electrode sheet is protruded on the inner wall of the shell.

6. The battery cell according to any one of claims 1 to 5, characterized in that: The thermal expansion coefficient of the first support structure is smaller than the thermal expansion coefficient of the negative electrode sheet.

7. The battery cell according to any one of claims 1 to 5, characterized in that: The difference between the elastic modulus of the first support structure and the elastic modulus of the active material layer on the negative electrode sheet is within a first preset difference, and the absolute value of the first preset difference is within 50% of the elastic modulus of the active material layer.

8. The battery cell according to any one of claims 1 to 5, characterized in that: The elastic modulus of the first supporting structure is 10 MPa to 100 MPa.

9. The battery cell according to any one of claims 1 to 5, characterized in that: A first liquid guiding structure is provided on the first supporting structure, and the first liquid guiding structure is used to guide the electrolyte outside the electrode assembly to the positive electrode sheet or the negative electrode sheet.

10. The battery cell according to claim 9, characterized in that: The first liquid-conducting structure includes a liquid-conducting hole penetrating through the first supporting structure.

11. The battery cell according to any one of claims 1 to 5, characterized in that: The battery cell further includes a protective film coated on the outside of the electrode assembly, a second gap exists between the protective film and an outer wall of a main body of the electrode assembly, and a second supporting structure is filled in the second gap.

12. The battery cell according to claim 11, characterized in that: The thermal expansion coefficient of the second support structure is smaller than the thermal expansion coefficient of the negative electrode sheet.

13. The battery cell according to claim 11 or 12, characterized in that: The difference between the elastic modulus of the second support structure and the elastic modulus of the active material layer on the negative electrode sheet is within a second preset difference, and the absolute value of the second preset difference is within 50% of the elastic modulus of the active material layer.

14. The battery cell according to claim 11 or 12, characterized in that: The elastic modulus of the second supporting structure is 10 MPa to 100 MPa.

15. The battery cell according to any one of claims 11 to 14, characterized in that: A second liquid guiding structure is provided on the second supporting structure, and the second liquid guiding structure is used to guide the electrolyte outside the electrode assembly to the negative electrode sheet.

16. The battery cell according to claim 15, characterized in that: The second liquid-conducting structure includes a liquid-conducting hole penetrating through the second supporting structure.

17. A battery, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 16.

18. An electrical device, characterized in that: Comprising the battery of claim 17.

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