CN219497829U - Pole piece, electrode assembly, battery cell, battery module and power utilization device - Google Patents

Abstract

The application provides a pole piece, an electrode assembly, a battery cell, a battery module and an electricity utilization device. The pole piece comprises a current collector, a packaging structure and an active substance layer, wherein the current collector comprises two surfaces which are opposite to each other along the thickness direction of the current collector. The packaging structure is connected to at least one of the two surfaces and forms a containing cavity together with the current collector. The active material layer is arranged in the accommodating cavity and comprises solid-liquid mixed active materials. According to the embodiment of the application, the cycle performance and the energy density of the battery monomer can be effectively improved.

Description

Pole piece, electrode assembly, battery cell, battery module and electrical device

technical field

The present application relates to the field of battery technology, in particular to a pole piece, an electrode assembly, a battery cell, a battery module and an electrical device.

Background technique

In recent years, as the application range of batteries has become more and more extensive, batteries have been widely used in energy storage power systems such as water power, fire power, wind power and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aviation Aerospace and other fields. Among them, the cycle performance and energy density of battery cells have always been one of the focuses of research in the industry.

In order to improve the energy density of battery cells, one of the current mainstream technical means is to mix a certain proportion of silicon-based negative electrode materials in the graphite negative electrode material of the pole sheet in the battery. However, due to the high expansion rate of the silicon-based negative electrode material, it is easy to crack and pulverize after undergoing multiple ion intercalation or extraction processes, thereby causing the electrode piece to lose effective electrical connection, resulting in poor cycle performance of the battery, and also limiting The energy density of the battery cell is improved. In view of this, it is urgent to improve the pole piece.

Utility model content

In view of the above problems, the present application provides a pole piece, an electrode assembly, a battery cell, a battery module and an electrical device, which can effectively improve the cycle performance and energy density of the battery cell.

In a first aspect, an embodiment of the present application provides a pole piece, the pole piece includes a current collector, an encapsulation structure, and an active material layer, and the current collector includes two opposite surfaces along its thickness direction. The encapsulation structure is connected to at least one of the two surfaces, and together with the current collector forms an accommodating cavity. The active material layer is arranged in the accommodating cavity, and the active material layer includes a solid-liquid mixed active material.

In some embodiments of the first aspect, the packaging structure includes a frame and a diaphragm, and the frame is connected between the current collector and the diaphragm.

In some embodiments of the first aspect, the frame surrounds an edge of the membrane.

In some embodiments of the first aspect, a reinforcement structure is provided on the frame, and the reinforcement structure protrudes from the surface of the frame.

In some embodiments of the first aspect, the reinforcement structure is extended along the circumference of the frame.

In some embodiments of the first aspect, the frame and the current collector are integrally formed.

In some embodiments of the first aspect, the thickness d1 of the frame satisfies: 40 μm ≤ d1 ≤ 90 μm, and the thickness d2 of the diaphragm satisfies: 25 μm ≤ d2 ≤ 50 μm.

In some embodiments of the first aspect, the active material layer is a silicon-based active material layer.

In a second aspect, an embodiment of the present application provides an electrode assembly, including the pole piece provided in any implementation manner of the first aspect.

In a third aspect, an embodiment of the present application provides a battery cell, including a casing and the electrode assembly provided in the embodiment of the second aspect, and the electrode assembly is housed in the casing.

In a fourth aspect, the embodiment of the present application provides a battery module, including the battery cell provided in the implementation manner of the third aspect.

In a fifth aspect, an embodiment of the present application provides an electric device, including the battery cell provided in the implementation manner of the fourth aspect, and the battery cell is used to provide electric energy.

The pole piece, the electrode assembly, the battery cell, the battery and the electrical device provided by the application are provided with a packaging structure in the pole piece, and the packaging structure is connected to at least one of the two surfaces opposite to each other in the thickness direction of the pole piece, and The current collectors jointly form an accommodating chamber. The active material layer is arranged in the accommodation cavity, and the active material layer includes a solid-liquid mixed active material. Wherein, the active material and the conductive agent in the active material layer are dispersed in the fluid, and the conductive agent forms a dynamic conductive network in the fluid to maintain electrical connection with the active material. After the battery has been cycled many times, even if the active material is broken and pulverized due to expansion, it can still maintain an effective electrical connection with the dynamic conductive network formed by the conductive agent in the fluid, thereby effectively improving the cycle performance of the battery. In addition, since the problem that the pole piece loses effective electrical connection due to the expansion of the active material is solved, the upper limit of the addition ratio of the active material in the pole piece can also be greatly increased, thereby effectively increasing the energy density of the battery cell.

The above description is only an overview of the technical solution of the present application. In order to better understand the technical means of the present application, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and understandable , the following specifically cites the specific implementation manner of the present application.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the application. Also throughout the drawings, the same reference numerals are used to designate the same parts. In the attached picture:

Fig. 1 is a schematic diagram of the explosion structure of a current collector and packaging structure of a pole piece provided by some embodiments of the present application;

Fig. 2 is a schematic structural diagram of the cooperation between the current collector and the packaging structure of a pole piece provided in some embodiments of the present application;

Fig. 3 is a schematic structural diagram of a pole piece provided by some embodiments of the present application;

Fig. 4 is a schematic structural diagram of another pole piece provided by some embodiments of the present application at a first viewing angle;

Fig. 5 is a schematic structural diagram of another pole piece provided by some embodiments of the present application at a second viewing angle.

The reference numerals in the specific embodiment are as follows:

10. Current collector; 20. Encapsulation structure; 21. Frame; 22. Diaphragm; 30. Accommodating chamber; 40. Active material layer; 50. Reinforcing structure.

Detailed ways

Embodiments of the technical solutions of the present application will be described in detail below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the present application more clearly, and therefore are only examples, rather than limiting the protection scope of the present application.

It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the embodiments of the present application shall have ordinary meanings understood by those skilled in the art to which the embodiments of the present application belong.

In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear" , "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom"

The orientation or positional relationship indicated by "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" etc. is based on the orientation or positional relationship shown in the drawings , is only for the convenience of describing the embodiment of the present application and simplifying the description, but does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiment of the present application.

In addition, the technical terms "first", "second" and so on are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. In the description of the embodiments of the present application, "plurality" means two or more, unless otherwise specifically defined.

In the description of the embodiments of this application, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection", and "fixation" should be understood in a broad sense, for example, it can be a fixed connection, or It can be a detachable connection, or integrated; it can also be a mechanical connection, it can also be an electrical connection; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation. Those of ordinary skill in the art can understand the specific meanings of the above terms in the embodiments of the present application according to specific situations.

In the description of the embodiments of the present application, unless otherwise specified and limited, the first feature may be in direct contact with the first feature or the second feature "on" or "under" the second feature. Indirect contact through intermediaries. Moreover, "above", "above" and "above" the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "beneath" and "beneath" the first feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is less horizontally than the second feature.

In recent years, as the application range of batteries has become more and more extensive, batteries have been widely used in energy storage power systems such as water power, fire power, wind power and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aviation Aerospace and other fields. Among them, the cycle performance and energy density of batteries have always been one of the focuses of research in the industry.

In order to improve the energy density of the battery, one of the current mainstream technical means is to mix a certain proportion of silicon-based negative electrode material in the graphite negative electrode material of the pole sheet in the battery. The inventors of the present application have noticed that the silicon-based negative electrode material has a high expansion rate, and is prone to cracking and pulverization after undergoing multiple ion intercalation or extraction processes, thereby causing the pole piece to lose effective electrical connection, resulting in poor cycle performance of the battery. Poor, but also limits the improvement of battery energy density.

The inventors of the present application have discovered through research that an encapsulation structure can be provided in the pole piece, and the encapsulation structure is connected to at least one of the two surfaces opposite to each other in the thickness direction to form an accommodating cavity together with the current collector. The active material layer is arranged in the accommodation cavity, and the active material layer includes a solid-liquid mixed active material. Wherein, the active material and the conductive agent in the active material layer are dispersed in the fluid, and the conductive agent forms a dynamic conductive network in the fluid to maintain electrical connection with the active material. After the battery has been cycled many times, even if the active material is broken and pulverized due to expansion, it can still maintain an effective electrical connection with the dynamic conductive network formed by the conductive agent in the fluid, thereby effectively improving the cycle performance of the battery. In addition, since the problem that the pole piece loses effective electrical connection due to the expansion of the active material is solved, the upper limit of the addition ratio of the active material in the pole piece can also be greatly increased, thereby effectively increasing the energy density of the battery cell.

In order to solve the problems in the prior art, the embodiments of the present application provide a pole piece, an electrode assembly, a battery cell, a battery and an electrical device, which can effectively improve the cycle performance and energy density of the battery cell. The pole piece provided by the embodiment of the present application will be firstly introduced below.

Fig. 1 is a schematic diagram of a structure in which a current collector and an encapsulation structure of a pole piece cooperate with each other according to some embodiments of the present application. Fig. 2 is a schematic structural diagram of the cooperation between a current collector and an encapsulation structure of a pole piece provided by some embodiments of the present application. Fig. 3 is a schematic structural diagram of a pole piece provided by some embodiments of the present application.

As shown in Figures 1 and 3, the embodiment of the present application provides a pole piece, which includes a current collector 10, an encapsulation structure 20, and an active material layer 40, and the current collector 10 includes two opposing pole pieces along the thickness direction thereof. surface. The encapsulation structure 20 is connected to at least one of the two surfaces, and together with the current collector 10 forms an accommodating cavity 30 . The active material layer 40 is disposed in the housing cavity 30 , and the active material layer 40 includes a solid-liquid mixed active material.

The pole piece includes a positive pole piece and a negative pole piece. Taking a lithium ion battery as an example, the material of the current collector 10 in the positive pole piece can be aluminum, and the active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganate, etc.; The current collector 10 in the negative electrode sheet can be made of copper, and the active material can be carbon or silicon. In order to describe the embodiment of the present application more clearly, the present application will be described by taking the silicon-based active material as an example for the negative electrode sheet and the active material.

Exemplarily, the encapsulation structure 20 may be a cover structure, and the encapsulation structure 20 may be connected to one of the two surfaces of the current collector 10 facing away from the thickness direction thereof, and jointly form an accommodating cavity 30 with the current collector 10; It can also be connected to two opposite surfaces of the current collector 10 along the thickness direction thereof, and form two accommodating cavities 30 together with the current collector 10 . The accommodation cavity 30 is used to accommodate active substances.

In some optional embodiments, the active material layer 40 can be a silicon-based active material layer, and the silicon-based active material layer includes an active material, a solvent and a conductive agent, wherein the solvent can be deionized water, etc.; the active material can be but It is not limited to silicon, silicon alloy, silicon oxide, silicon carbon composite, and silicon oxycarbide; the conductive agent can be but not limited to conductive carbon black, carbon nanotubes, and graphene.

In some optional embodiments, the silicon-based active material layer can also include a binder and a thickener, the binder can be but not limited to styrene butadiene artificial rubber and acrylonitrile multi-polymer water dispersion liquid, etc.; the thickener can be carboxymethyl cellulose, etc.

In some optional embodiments, the silicon-based active material layer includes a dispersion matrix and an active material, wherein the active material is mixed in the dispersion matrix, the dispersion matrix can be graphite, etc., and the active material can be but not limited to silicon, silicon alloys, silicon oxides, etc.

In the embodiment of the present application, the active material layer 40 includes a solid-liquid mixed active material, and the solid-liquid mixed active material is filled in the accommodation cavity 30 . Wherein, the active material and the conductive agent in the active material layer 40 are dispersed in the fluid, and the conductive agent forms a dynamic conductive network in the fluid to maintain electrical connection with the active material. After the battery has been cycled many times, even if the active material is broken and pulverized due to expansion, it can still maintain an effective electrical connection with the dynamic conductive network formed by the conductive agent in the fluid, thereby effectively improving the cycle performance of the battery. In addition, since the problem that the pole piece loses effective electrical connection due to the expansion of the active material is solved, the upper limit of the addition ratio of the active material in the pole piece can also be greatly increased, thereby effectively increasing the energy density of the battery cell.

In the above technical solution, by providing the encapsulation structure 20 in the pole piece, the encapsulation structure 20 is connected to at least one of the two opposite surfaces in the thickness direction of itself, and together with the current collector 10 forms the accommodation cavity 30 . The active material layer 40 includes a solid-liquid mixed active material. The solid-liquid mixed active material is arranged in the housing cavity 30, so that the active material can always maintain an effective electrical connection with the dynamic conductive network formed by the conductive agent in the fluid during the cycle of the battery. , which in turn can effectively improve the cycle performance of the battery cell and increase the energy density of the battery cell.

In some embodiments, the packaging structure 20 includes a frame 21 and a diaphragm 22 , and the frame 21 is connected between the current collector 10 and the diaphragm 22 .

Optionally, the frame 21 may be a circular frame with a closed structure, and the frame 21 may be made of a metal material, such as copper, or a non-metal material, such as polyethylene or polypropylene. The diaphragm 22 has a large number of penetrating micropores, which can ensure the free passage of electrolyte ions and have good permeability to lithium ions. The material of the diaphragm 22 can be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene) and the like.

Exemplarily, the frame 21 is connected to at least one of the two opposite surfaces of the current collector 10 along its thickness direction. Optionally, the number of frames 21 can be one, and one frame 21 is connected to one of the two surfaces of the current collector 10 facing away from the thickness direction of itself; the number of frames 21 can also be two, and the two frames 21 are respectively connected to two opposite surfaces of the current collector 10 along its thickness direction. The frame 21 and the current collector 10 together form an accommodating chamber 30 , and the connection method between the frame 21 and the current collector 10 may be but not limited to welding or bonding. The diaphragm 22 is connected to a side of the frame 21 away from the current collector 10 to encapsulate the cavity 30 .

In the above technical solution, by setting the packaging structure 20 in the form of connecting the frame 21 and the diaphragm 22, in the manufacturing process of the pole piece, the frame 21 can be connected with the current collector 10 to form the accommodation cavity 30, and then the active material The slurry is injected into the containing cavity 30 , and finally the diaphragm 22 is connected to the frame 21 to encapsulate the containing cavity 30 and the active material slurry in the containing cavity 30 . The manufacturing method of the pole piece is simplified, which is conducive to improving the yield of finished products.

In some embodiments, the frame 21 surrounds the edge of the diaphragm 22 .

Exemplarily, along the thickness direction of the pole piece, the orthographic projection of the current collector 10 covers the orthographic projection of the diaphragm 22 and the orthographic projection of the frame 21, that is, along the thickness direction of the pole piece, the orthographic projection area of the current collector 10 larger than the orthographic projection area of the encapsulation structure 20 . Wherein, the active material layer 40 is disposed in the housing cavity 30 of the encapsulation structure 20, that is, along the thickness direction of the pole piece, the orthographic area of the current collector 10 is larger than the orthographic area of the active material layer 40, and no active material is provided on the current collector 10. Parts of the substance layer 40 may constitute tabs.

In the above technical solution, the frame 21 is extended and distributed along the edge of the diaphragm 22, which can maximize the orthographic projection area of the accommodation chamber 30 on the current collector 10, thereby making the volume of the accommodation chamber 30 larger and able to accommodate more active substances. , can further increase the energy density of the battery cell.

Fig. 4 is a schematic structural diagram of another pole piece provided by some embodiments of the present application at a first viewing angle. Fig. 5 is a schematic structural diagram of another pole piece provided by some embodiments of the present application at a second viewing angle.

Continuing to refer to FIG. 4 to FIG. 5 , in some embodiments, a reinforcement structure 50 is disposed on the frame 21 , and the reinforcement structure 50 protrudes from the surface of the frame 21 .

Exemplarily, the reinforcing structure 50 may protrude from the surface of the frame 21 near the receiving cavity 30, or protrude from the surface of the frame 21 facing away from the receiving cavity 30, or protrude from the frame 21 close to the receiving cavity 30. The surface on one side of the accommodating cavity 30 also protrudes from the surface of the side of the frame 21 away from the accommodating cavity 30 . Optionally, the reinforcing structure 50 may be a reinforcing rib or a solid bump or the like.

In some optional embodiments, the reinforcement structure 50 is set to protrude from the surface of the side of the frame 21 away from the accommodating chamber 30, which can prevent the reinforcement structure 50 from occupying the space of the accommodating chamber 30, so as to avoid affecting the energy density of the battery cells. .

In the above technical solution, by setting the reinforcement structure 50 on the frame 21, the frame 21 has a concave-convex structure, thereby effectively improving the structural strength of the frame 21 and further improving the reliability of the pole piece.

In some optional embodiments, the reinforcing structure 50 and the frame 21 are integrally formed. The frame 21 integrally forms the reinforcement structure 50 through a stamping process, so that the reinforcement structure 50 and the frame 21 form an integrated structure. The manufacturing process flow of the reinforcement structure 50 is shown. At the same time, compared with connecting the reinforcing structure 50 and the frame 21 through welding or bonding, the connection between the reinforcing structure 50 and the frame 21 in an integrated structure has higher connection firmness.

In some embodiments, the reinforcement structure 50 is extended along the circumference of the frame 21 .

Exemplarily, the reinforcing structure 50 is extended along the circumferential direction of the frame 21, that is, the extending length of the reinforcing structure 50 is consistent with the circumferential length of the frame 21, thereby maximizing the structural strength of the frame 21 and further improving the pole piece reliability.

In some embodiments, the frame 21 and the current collector 10 are integrally formed.

The current collector 10 integrally forms the frame 21 through a stamping process, so that the frame 21 and the current collector 10 form an integrated structure. The manufacturing process of the frame 21 is shown. At the same time, compared with connecting the frame 21 and the current collector 10 through welding or bonding, the integral structure of the frame 21 and the current collector 10 has higher connection firmness.

In some embodiments, the thickness d1 of the frame 21 satisfies: 40 μm≦d1≦90 μm, and the thickness d2 of the diaphragm 22 satisfies: 25 μm≦d2≦50 μm.

In the embodiment of the present application, the thickness d1 of the frame 21 can be understood as the distance between the side surface of the frame 21 close to the accommodating cavity and the side surface of the frame 21 away from the accommodating cavity, and the thickness d2 of the diaphragm 22 is the thickness of the diaphragm 22 itself. thickness.

Exemplarily, the thickness d1 of the frame 21 may be, but not limited to, 45 μm, 50 μm, 55 μm, 60 μm, 80 μm, 85 μm. The thickness d2 of the diaphragm 22 may be, but not limited to, 30 μm, 35 μm, 40 μm, 45 μm, 48 μm.

In the above technical solution, by setting the thickness d1 of the frame 21 and the thickness d2 of the diaphragm 22 within the above range, the overall structural strength of the packaging structure 20 can be further improved.

According to some embodiments of the present application, the present application also provides an electrode assembly, including the pole piece of any one of the above schemes.

The electrode assembly is mainly formed by winding or stacking the positive electrode sheet and the negative electrode sheet, and usually a separator is provided between the positive electrode sheet and the negative electrode sheet. The part of the positive electrode sheet and the negative electrode sheet with the active material constitutes the main body of the electrode assembly, and the parts of the positive electrode sheet and the negative electrode sheet without the active material respectively constitute tabs. The positive pole tab and the negative pole tab can be located at one end of the main body together or at two 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 tabs are connected to the electrode terminals to form a current loop.

According to some embodiments of the present application, the present application also provides a battery cell, including a casing and the electrode assembly of the above solution, and the electrode assembly is accommodated in the casing.

The battery cell provided in the embodiment of the present application includes an electrode assembly and a casing, and the electrode assembly is accommodated in the casing. The housing can also be used to contain an electrolyte, such as electrolytic solution.

The shell can be in various shapes, such as cylinder, cuboid and so on. The shape of the casing can be determined according to the specific shape of the electrode assembly. For example, if the electrode assembly has a cylindrical structure, a cylindrical shell can be selected; if the electrode assembly has a rectangular parallelepiped structure, a rectangular parallelepiped shell can be selected.

In a battery cell, there may be one, two or more electrode assemblies accommodated in the casing.

According to some embodiments of the present application, the present application also provides a battery module, including the battery cell of the above solution.

The battery module mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity. A battery module generally includes a box for enclosing one or more battery cells. The box can prevent liquid or other foreign objects from affecting the charging or discharging of the battery cells.

A plurality of battery cells in the battery module can be electrically connected through a bus component, so as to realize parallel connection, series connection or mixed connection of the plurality of battery cells in the battery module.

According to some embodiments of the present application, the present application also provides an electric device, including the battery cell of the above solution, and the battery cell is used to provide electric energy.

Electric devices can be vehicles, mobile phones, portable devices, notebook computers, ships, spacecraft, electric toys and electric tools, and so on. Vehicles can be fuel vehicles, gas vehicles or new energy vehicles, and new energy vehicles can be pure electric vehicles, hybrid vehicles or extended-range vehicles; spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.; electric toys include fixed Type or mobile electric toys, such as game consoles, electric car toys, electric boat toys and electric airplane toys, etc.; electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, for example, Electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, electric planers, and more. The embodiments of the present application do not impose special limitations on the above-mentioned electrical devices.

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present application. All of them should be covered by the scope of the claims and description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims (12)

1. A pole piece, characterized in that, comprising: A current collector, including two opposite surfaces along its thickness direction; An encapsulation structure, connected to at least one of the two surfaces, forms an accommodation chamber together with the current collector; The active material layer is arranged in the accommodating cavity, and the active material layer includes a solid-liquid mixed active material. 2 . The pole piece according to claim 1 , wherein the packaging structure comprises a frame and a diaphragm, and the frame is connected between the current collector and the diaphragm. 3 . The pole piece according to claim 2 , wherein the frame surrounds the edge of the diaphragm. 4 . 4. The pole piece according to claim 2, wherein a reinforcement structure is provided on the frame, and the reinforcement structure protrudes from the surface of the frame. 5 . The pole piece according to claim 4 , wherein the reinforcing structure extends along the circumferential direction of the frame. 5 . 6 . The pole piece according to claim 2 , wherein the frame and the current collector are integrally formed. 7 . The pole piece according to claim 2 , wherein the thickness d1 of the frame satisfies: 40 μm ≤ d1 ≤ 90 μm, and the thickness d2 of the diaphragm satisfies: 25 μm ≤ d2 ≤ 50 μm. 8. The pole piece according to claim 1, wherein the active material layer is a silicon-based active material layer. 9. An electrode assembly, characterized by comprising the pole piece according to any one of claims 1-8. 10 . A battery cell, characterized by comprising a casing and the electrode assembly according to claim 9 , the electrode assembly is accommodated in the casing. 11 . 11. A battery module, comprising a plurality of battery cells according to claim 10. 12. An electrical device, characterized by comprising the battery cell according to claim 10, the battery cell being used to provide electric energy.