Battery cell, energy storage apparatus, and electric device

Abstract

The present application provides a battery cell, an energy storage apparatus, and an electric device. The battery cell is formed by winding a first electrode sheet, a separator, and a second electrode sheet. In a winding direction of the first electrode sheet, the first electrode sheet comprises an empty foil segment and a first starting segment connected to the empty foil segment. The empty foil segment is bent relative to the first starting segment, and a flat portion of the empty foil segment and a flat portion of the first starting segment are spaced apart from each other in the thickness direction of the battery cell. In a winding direction of the second electrode sheet, the second electrode sheet comprises a second starting segment. The first starting segment extends beyond the second starting segment in a direction opposite to the winding direction of the first electrode sheet. The empty foil segment comprises a body and embossed portions. The embossed portions are connected to the body and each comprise a raised surface. In the thickness direction of the body, the raised surfaces protrude relative to the body. Each embossed portion is provided with a recess, and an opening of the recess is provided on the surface of the embossed portion opposite to the raised surface.

Description

Battery cells, energy storage devices and electrical equipment

[0001] This application claims priority to Chinese Patent Application No. 202410801074.9, filed on June 19, 2024, entitled "Battery Cell, Energy Storage Device and Electrical Equipment", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and more particularly to a battery cell, an energy storage device, and an electrical device. Background Technology

[0003] Existing battery cells are typically formed by winding a cathode plate, an anode plate, and a separator. These cells are widely used in portable electronic devices and other fields. During application, cycle performance is a crucial indicator of cell performance. Therefore, improving the cycle performance of battery cells is of great significance. Summary of the Invention

[0004] The purpose of this application is to provide a battery cell, an energy storage device, and an electrical device that can improve the cycle performance of the battery cell.

[0005] This application provides a battery cell, which is formed by winding a first electrode, a separator, and a second electrode. The separator is disposed between the first electrode and the second electrode. Along the winding direction of the first electrode, the first electrode includes an empty foil segment and a first starting segment connected to the empty foil segment. Both the empty foil segment and the first starting segment include straight portions. The straight portions of the empty foil segment and the straight portions of the first starting segment are spaced apart along the thickness direction of the battery cell. Along the winding direction of the second electrode, the second electrode includes a second starting segment, which is located on the side of the first starting segment away from the empty foil segment.

[0006] The first starting segment extends beyond the second starting segment in the opposite direction to the winding direction of the first electrode sheet. The empty foil segment includes a body and an imprinting part. The imprinting part is connected to the body and includes a raised surface. The raised surface protrudes relative to the body along the thickness direction of the body. The imprinting part is provided with a groove, and the opening of the groove is located on the surface of the imprinting part away from the raised surface.

[0007] In the battery cell provided in this application embodiment, by setting an empty foil segment in the first electrode and setting an imprinted portion in the empty foil segment, on the one hand, the groove provided in the imprinted portion in the empty foil segment can store electrolyte during battery cell filling. When the battery cell is squeezed by the casing, the electrolyte in the groove is not easily squeezed out. Therefore, in the later stages of battery cell cycling, when the electrolyte inside the first electrode is exhausted, the electrolyte stored in the groove can be replenished to the first electrode in time to ensure the smooth transport path of lithium ions, thereby improving the cycle performance of the battery cell. On the other hand, compared with other methods to improve the cycle performance of the battery cell, this application embodiment can improve the cycle performance of the battery cell by adding a process step of setting an imprinted portion, without increasing material costs, which helps to reduce the production cost of the battery cell. In addition, the empty foil segment does not contain active materials, which is equivalent to saving the cost of active materials, thereby further reducing the production cost of the battery cell.

[0008] Furthermore, the straight portions of the empty foil section and the straight portions of the first starting section are spaced apart in the thickness direction of the battery cell. This effectively increases the thickness of the first electrode within the battery cell's inner space, thereby reducing the curvature of the second electrode at the winding corner when it is wound around the first electrode. This reduces the risk of the active layer material falling off the second electrode or even breaking it. Additionally, because the empty foil section has a large area and thin thickness, its surface stress can easily cause it to curl, affecting winding efficiency and even leading to uneven thickness due to direct folding during inward winding. By providing an imprinted section in the empty foil section, the surface stress distribution can be significantly improved, further reducing the risk of curling.

[0009] Furthermore, by setting the first starting segment of the first electrode to extend beyond the second starting segment of the second electrode in the opposite direction to the winding direction of the first electrode, an excess coefficient of the first electrode over the second electrode is created, thereby ensuring that the first electrode has sufficient lithium insertion sites to prevent lithium deposition.

[0010] This application embodiment also provides an electrical device, including the energy storage device as described above, which is used to supply power to the electrical device. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 is an application scenario diagram of the energy storage device provided in the embodiment of this application;

[0013] Figure 2 is a side view of the energy storage device provided in the first embodiment of this application;

[0014] Figure 3 is a schematic diagram of the cross-sectional structure of the energy storage device shown in Figure 2;

[0015] Figure 4 is a schematic diagram of the disassembled structure of the energy storage device shown in Figure 3 before assembly;

[0016] Figure 5 is a schematic diagram of the cross-sectional structure of the battery cell in the energy storage device shown in Figure 2;

[0017] Figure 6 is a top view of the hollow foil section of the battery cell shown in Figure 4.

[0018] Figure 7 is a schematic diagram of the cross-sectional structure of the empty foil segment shown in Figure 6 at CC;

[0019] Figure 8 is a schematic cross-sectional structure of the energy storage device provided in the second embodiment of this application;

[0020] Figure 9 is a cross-sectional structural diagram of the energy storage device provided in the third embodiment of this application.

[0021] Reference numerals: Energy storage system 5000, power conversion device 4500, wind power conversion device 4000, secondary electrical equipment 3000, energy storage device 1000, outer shell 100, bottom shell 110, side shell 130, top cover 200, battery cell 300, first electrode 310, second electrode 330, diaphragm 350, first current collector 301, first active layer 303, first starting section 10, straight section 11, bent section 13, first starting end face 15, first intermediate section 20, first ending section 30, first ending end face 31, empty foil section 40, this Body 41, First surface 411, Second surface 413, Straight portion 42, Imprinted portion 43, First imprinted portion 431, Second imprinted portion 433, Bending portion 44, Raised surface 45, Groove 46, Second current collector 305, Second active layer 307, Second starting segment 50, Second starting end face 51, Second intermediate segment 60, Second ending segment 70, Second ending end face 71, Starting film segment 80, Intermediate film segment 91, Ending film segment 92, First tab 360, Second tab 370, First surface 380, Second surface 390, Corner position A, Widest position B. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] Taking electrochemical energy storage as an example, this solution provides an energy storage device. The energy storage device is equipped with a set of chemical batteries. It mainly uses the chemical elements in the chemical batteries as the energy storage medium. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage medium. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electricity is released for use, or transferred to places with a shortage of electricity for use.

[0024] Current energy storage applications are quite widespread, including energy storage on the (wind and solar) power generation side, grid-side energy storage, base station-side energy storage, and user-side energy storage. The corresponding types of energy storage devices include:

[0025] (1) Large energy storage containers used in grid-side energy storage scenarios can serve as high-quality active and reactive power regulation power sources in the grid, enabling load matching of electrical energy in time and space, enhancing the absorption capacity of renewable energy, and playing a significant role in grid system backup, alleviating peak load power supply pressure, and peak regulation and frequency regulation.

[0026] (2) Small and medium-sized energy storage cabinets used in industrial and commercial energy storage scenarios (banks, shopping malls, etc.) on the user side mainly operate under the "peak shaving and valley filling" mode. Since there are large price differences in electricity prices at peak and valley times depending on electricity demand, users with energy storage equipment usually charge the energy storage cabinet / box during the low electricity price period in order to reduce costs; and release the electricity in the energy storage equipment for use during the peak electricity price period to achieve the purpose of saving electricity costs.

[0027] It should be noted that the aforementioned energy storage containers, small and medium-sized energy storage cabinets, and small household energy storage boxes, which contain energy storage devices, can be understood as electrical equipment.

[0028] Please refer to Figure 1, which is an application scenario diagram of the energy storage device 1000 provided in the embodiments of this application.

[0029] The energy storage device 1000 provided in this application embodiment is applied to an energy storage system 5000. The energy storage system 5000 includes a power conversion device 4500 (photovoltaic panel), a wind power conversion device 4000 (windmill), a first electrical device (grid), a second electrical device 3000 (base station), and the energy storage device 1000. The energy storage system also includes an energy storage cabinet, in which the energy storage device 1000 is installed. The energy storage cabinet can be installed outdoors. Specifically, the first power conversion device can convert solar energy into electrical energy during periods of low electricity prices. The energy storage device 1000 stores this electrical energy and supplies it to the first or second electrical device during peak electricity demand, or provides power when the first or second electrical device experiences a power outage. The second power conversion device can convert wind energy into electrical energy. The energy storage device 1000 stores this electrical energy and supplies it to the first or second electrical device during peak electricity demand, or provides power when the first or second electrical device experiences a power outage. Among them, electrical energy can be transmitted using high-voltage cables.

[0030] It should be noted that the aforementioned first electrical equipment, second electrical equipment, and other equipment containing the energy storage device 1000 can be understood as electrical equipment.

[0031] Please refer to Figures 2, 3 and 4. Figure 2 is a side view of the energy storage device 1000 provided in the first embodiment of this application. Figure 3 is a cross-sectional structural schematic diagram of the energy storage device 1000 shown in Figure 2. Figure 4 is an exploded structural schematic diagram of the energy storage device 1000 shown in Figure 3 before assembly.

[0032] For ease of description, the length direction of the energy storage device 1000 shown in Figure 2 is defined as the X-axis direction, the width direction as the Y-axis direction, and the thickness direction as the Z-axis direction. The X-axis direction, Y-axis direction, and Z-axis direction are all perpendicular to each other.

[0033] The energy storage device 1000 includes a housing 100, a top cover 200, a battery cell 300, and an electrolyte (not shown in Figures 2 and 3). The top cover 200 is mounted on the housing 100, the battery cell 300 is mounted inside the housing 100, and the electrolyte fills the inside of the housing 100 and wets the battery cell 300. For example, the energy storage device 1000 may include a single battery cell, a battery module, or a battery pack.

[0034] Specifically, the outer casing 100 can be an aluminum casing. The outer casing 100 includes a bottom casing 110 and side casings 130. The side casings 130 surround the periphery of the bottom casing 110 and together form an accommodating cavity. A top cover 200 is mounted on the side casing 130 and is positioned opposite the bottom casing 110, thus allowing the top cover 200 to be mounted on the outer casing 100. The top cover 200 faces the positive X-axis direction, and the bottom casing 110 faces the negative X-axis direction.

[0035] The battery cell 300 is installed in the receiving cavity of the housing 100, so that the battery cell 300 is installed inside the housing 100. The top of the battery cell 300 faces the top cover 200, and the bottom of the battery cell 300 faces away from the top cover 200. In this embodiment, the length direction of the battery cell 300 is the X-axis direction, the width direction is the Y-axis direction, and the thickness direction is the Z-axis direction. The top of the battery cell 300 faces the positive X-axis direction, and the bottom faces the negative X-axis direction. There can be one or more battery cells 300. When there are multiple battery cells 300, the assembled energy storage device 1000 forms a multi-JR (jelly roll) structure. In this case, the multiple battery cells 300 can be electrically connected in parallel. In this embodiment, there are two battery cells 300, which are installed inside the housing 100 along the thickness direction of the battery cell 300, and the assembled energy storage device 1000 has a 2JR structure.

[0036] The energy storage device 1000 has a width skirt margin and a thickness skirt margin. The width skirt margin is W2 / W1, where W1 represents the inner diameter of the outer casing 100 along the width direction, and W2 represents the length of each battery cell 300 along the width direction. The thickness skirt margin is D2 / D1, where D1 represents the inner diameter of the outer casing 100 along the thickness direction, and D2 represents the total length of the battery cells 300 along the thickness direction. The width direction of the battery cell 300 is the Y-axis direction, and the thickness direction is the Z-axis direction. In this embodiment, the length of a single battery cell 300 along the thickness direction is D3, i.e., the thickness of the battery cell 300 is D3. When there are N battery cells 300 in the energy storage device 1000, N≥2, and N is an integer, D2=N*D3. For example, the thickness D3 of the battery cell 300 is 30mm~38mm, and the width W2 is 166mm~171mm.

[0037] It should be understood that "width skirt margin > 100%" indicates that the outer casing 100 and the battery cell 300 are interference-fitted in the width direction, and "thickness skirt margin > 100%" indicates that the outer casing 100 and the battery cell 300 are interference-fitted in the thickness direction. For example, in this embodiment, the thickness skirt margin of the energy storage device 1000 is 85% to 105%, that is, the energy storage device 1000 satisfies: 85% ≤ D2 / D1 ≤ 105%.

[0038] Referring to Figure 5, which is a schematic cross-sectional view of the cell 300 in the energy storage device 1000 shown in Figure 2, the dashed line in Figure 5 represents the diaphragm 350.

[0039] The length direction of the battery cell 300 is the X-axis direction, the width direction is the Y-axis direction, and the thickness direction is the Z-axis direction. The battery cell 300 is formed by winding a material including a first electrode 310, a second electrode 330, and a separator 350. The separator 350 is disposed between the first electrode 310 and the second electrode 330. Exemplarily, in this embodiment, the winding direction of the battery cell 300 is clockwise, and the winding directions of both the first electrode 310 and the second electrode 330 are clockwise. In this embodiment, after the material including the first electrode 310, the second electrode 330, and the separator 350 is wound clockwise, the battery cell 300 is formed by hot pressing or cold pressing. In this embodiment, the first electrode 310 is an anode sheet, and the second electrode 330 is a cathode sheet. In the wound battery cell 300, the second electrode 330 covers the outside of the first electrode 310, forming a cathode-enclosed anode structure. It is understood that in other embodiments, the first electrode 310 may also be a cathode and the second electrode 330 may be an anode.

[0040] Specifically, the first electrode 310 includes a first current collector 301 and a first active layer 303 coated on the surface of the first current collector 301. In this embodiment, the first active layer 303 is coated on both sides of the first current collector 301 along the thickness direction. For example, the thickness of the first electrode 310 is 100μm to 140μm. Along the winding direction of the first electrode 310, the first electrode 310 includes an empty foil segment 40, a first starting segment 10, a first intermediate segment 20, and a first ending segment 30. The first starting segment 10 is connected to the empty foil segment 40 and is disposed opposite to the first ending segment 30 along the winding direction of the first electrode 310. The first intermediate segment 20 is connected between the first starting segment 10 and the first ending segment 30. In this embodiment, the empty foil segment 40 is the first current collector, which is not coated with the first active layer 303. The first starting segment 10, the first intermediate segment 20, and the first ending segment 30 each include a first current collector 301 and a first active layer 303 covering the surface of the first current collector 301.

[0041] Along the winding direction of the first electrode 310, the first starting segment 10 is provided with a first starting end face 15, which is disposed along the extending direction of the first starting segment 10. In this embodiment, the first starting segment 10 includes a straight portion 11 and a bent portion 13. The straight portion 11 extends along the Y-axis direction, and the bent portion 13 is connected to the straight portion 11 and bent relative to the straight portion 11. The bent portion 13 includes the first starting end face 15, which is disposed along the extending direction of the bent portion 13 and faces away from the straight portion 11.

[0042] An empty foil segment 40 is connected to the first starting end face 15 of the bent portion 13 of the first starting segment 10, which faces away from the straight portion 11. In this embodiment, the empty foil segment 40 is integrally connected to the first current collector 301 of the bent portion 13 of the first starting segment 10 to achieve an integral connection between the empty foil segment 40 and the first current collector 301 of the first starting segment 10. The empty foil segment 40 includes a straight portion 42, which is integrally connected to the first current collector 301 of the bent portion 13 of the first starting segment 10, so that the straight portion 42 of the empty foil segment 40 is connected to the end of the bent portion 13 of the first starting segment 10 facing away from the straight portion 11 of the first starting segment 10. The straight portion 42 of the empty foil segment 40 and the straight portion 11 of the first starting segment 10 are spaced apart along the thickness direction of the cell 300, so that the empty foil segment 40 and the first starting segment 10 are spaced apart along the thickness direction of the cell 300.

[0043] Specifically, the empty foil segment 40 includes a body 41 and an imprinted portion 43. The body 41 is connected to the first current collector 301 in the bent portion 13 to achieve the connection between the empty foil segment 40 and the bent portion 13, thereby achieving the connection between the empty foil segment 40 and the first starting segment 10. The body 41 includes a first surface 411 and a second surface 413 disposed opposite to each other along the thickness direction. The first surface 411 faces the straight portion 11, and the second surface 413 faces away from the straight portion 11. The imprinted portion 43 is connected to the body 41 and protrudes relative to the body 41 along the thickness direction of the body 41. The imprinted portion 43 includes a raised surface 45 that protrudes relative to the body 41 along the thickness direction of the body 41, and the imprinted portion 43 is provided with a groove 46, the opening of which is located on the surface of the imprinted portion 43 facing away from the raised surface 45. The groove 46 can be used to retain electrolyte after the battery cell 300 is injected, facilitating subsequent replenishment of electrolyte inside the battery cell 300. In this embodiment, an embossed portion 43 can be formed by embossing on a flat body 41. For example, the height of the protrusion 45 of the embossed portion 43 relative to the body 41 is H, where 5μm≤H≤50μm. For example, the groove 46 of the embossed portion 43 is a square groove. It is understood that in other embodiments, the shape of the groove 46 of the embossed portion 43 can also be a rectangular groove, a circular groove, etc. This application does not limit the shape of the groove 46.

[0044] As shown in Figure 5, in this embodiment, there are multiple imprinted portions 43 along the width direction of the battery cell 300, including a first imprinted portion 431 and a second imprinted portion 433. The raised surface 45 of the first imprinted portion 431 protrudes relative to the first surface 411 of the body 41 along a first direction, and the raised surface 45 of the second imprinted portion 433 protrudes relative to the second surface 413 of the body 41 along a second direction, which is opposite to the first direction. In this embodiment, the first direction is the positive Z-axis direction, and the second direction is the negative Z-axis direction. It can be understood that the height by which the raised surface 45 of the first imprinted portion 431 protrudes relative to the first surface 411 is the same as the height by which the first imprinted portion 431 protrudes relative to the body 41, and the height by which the raised surface 45 of the second imprinted portion 433 protrudes relative to the second surface 413 is the same as the height by which the second imprinted portion 433 protrudes relative to the body 41. In this embodiment, a plurality of first imprinted portions 431 and a plurality of second imprinted portions 433 are arranged alternately along the width direction of the battery cell 300.

[0045] Referring to Figures 6 and 7, Figure 6 is a top view of the hollow foil segment 40 of the battery cell 300 shown in Figure 4, and Figure 7 is a cross-sectional view of the hollow foil segment 40 at point CC shown in Figure 6. In this embodiment, along the length of the battery cell 300 and along the direction from the bottom to the top of the battery cell 300, i.e., along the positive X-axis direction, there are multiple imprinted portions 43, and the openings of the grooves 46 of the multiple imprinted portions 43 gradually increase in size. In this embodiment, along the length of the battery cell 300, the multiple imprinted portions 43 include first imprinted portions 431 and second imprinted portions 433, and the multiple first imprinted portions 431 and the multiple second imprinted portions 433 are arranged alternately along the length of the battery cell 300. It is understood that in other embodiments, along the length direction of the cell 300, all of the plurality of imprinted portions 43 may be first imprinted portions 431; or, all of the plurality of imprinted portions 43 may be second imprinted portions 433; or, some of the plurality of imprinted portions 43 may be first imprinted portions 431 and some of the imprinted portions 43 may be second imprinted portions 433. This application does not impose any restrictions on this.

[0046] It is understood that in other embodiments, the empty foil segment 40 may also be wound into multiple layers, with the multiple layers of empty foil segments 40 connected sequentially. The multiple layers of empty foil segments 40 are spaced apart along the thickness direction of the battery cell 300. For example, the empty foil segments 40 can be bent multiple times to form a serpentine multilayer of empty foil segments 40.

[0047] Referring again to Figure 5, the first intermediate segment 20 is connected to the end of the straight portion 11 of the first starting segment 10 that is away from the bent portion 13, thereby connecting the first intermediate segment 20 to the end of the first starting segment 10 that is away from the first starting end face 15, thus achieving the connection between the first intermediate segment 20 and the first starting segment 10. In this embodiment, the first intermediate segment 20 is wound into multiple layers along the winding direction of the first electrode 310. The first ending segment 30 is connected to the end of the first intermediate segment 20 that is away from the first starting segment 10, thereby connecting the first intermediate segment 20 between the first starting segment 10 and the first ending segment 30. At this time, the first ending segment 30 and the first starting segment 10 are arranged opposite to each other along the winding direction of the first electrode 310. The first ending segment 30 includes a first ending end face 31, which is arranged along the winding direction of the first ending segment 30 and away from the first intermediate segment 20, thereby achieving the connection between the first ending end face 31 and the first starting segment 10.

[0048] The second electrode 330 includes a second current collector 305 and a second active layer 307 coated on the surface of the second current collector 305. In this embodiment, the second active layer 307 is coated on both sides of the second current collector 305 along its thickness direction. For example, the thickness of the second electrode 330 is 150 μm to 200 μm. For example, in this embodiment, the second electrode 330 is obtained by mixing a material including a cathode active material, a conductive agent, a binder, and a dispersant in a certain proportion, coating it onto the second current collector 305, and then cold-pressing it. For example, the compaction density of the second electrode 330 is 2.30 g / cm³. 3 ~2.60g / cm 3 The cathode active material can be lithium iron phosphate, the conductive agent can be carbon nanotubes (CNTs), the binder can be polyvinylidene fluoride (PVDF), and the dispersant can be polyvinyl pyrrolidone (PVP). For example, in some embodiments, the PVDF content in the second active layer 307 is 1.0% to 4.0%.

[0049] Along the winding direction of the second electrode 330, the second electrode 330 includes a second starting segment 50, a second intermediate segment 60, and a second ending segment 70. The second starting segment 50 and the second ending segment 70 are arranged opposite to each other along the winding direction of the second electrode 330, and the second intermediate segment 60 connects the second starting segment 50 and the second ending segment 70. In this embodiment, the second starting segment 50, the second intermediate segment 60, and the second ending segment 70 each include a second current collector 305 and a second active layer 307 covering the surface of the second current collector 305.

[0050] The second starting segment 50 is located on the side of the first starting segment 10 away from the empty foil segment 40. In the empty foil segment 40, the first surface 411 of the body 41 faces the second starting segment 50, and the second surface 413 faces away from the second starting segment 50. In this embodiment, the second starting segment 50 extends along the Y-axis direction. Along the winding direction of the second electrode 330, the second starting segment 50 includes a second starting end face 51, which is disposed along the extending direction of the second starting segment 50. In this embodiment, the second starting end face 51 faces the negative Y-axis direction and is the starting winding end face of the second electrode 330, i.e., the feed position of the second electrode 330. In this embodiment, the first starting end face 15 protrudes in the opposite direction to the second starting end face 51 relative to the winding direction of the first electrode 310, so that the first starting segment 10 extends beyond the second starting segment 50 in the opposite direction to the winding direction of the first electrode 310, thereby making the feeding position of the second electrode 330 shorter than the feeding position of the first starting segment 10 in the first electrode 310. In this embodiment, along the width direction of the cell 300, the maximum distance between the second starting end face 51 of the second starting segment 50 and the bent portion 13 in the first starting segment 10 is h. For example, 3mm ≤ h ≤ 20mm. The position of the maximum distance between the bent portion 13 in the first starting segment 10 and the second starting end face 51 along the width direction of the cell 300 is the corner position A of the first starting segment 10, and the maximum distance between the corner position A and the second starting end face 51 along the width direction of the cell 300 is the maximum distance h.

[0051] The second intermediate section 60 is connected to the end of the second starting section 50 that is away from the second starting end face 51, thereby connecting the second intermediate section 60 and the second starting section 50. In this embodiment, the second intermediate section 60 is wound into multiple layers along the winding direction of the cell 300. The second ending section 70 is connected to the end of the second intermediate section 60 that is away from the second starting section 50, thereby connecting the second intermediate section 60 between the second starting section 50 and the second ending section 70. At this time, the second ending section 70 and the second starting section 50 are arranged opposite to each other along the winding direction of the second electrode 330. The second ending section 70 includes a second ending end face 71, which is arranged along the extension direction of the second ending section 70 and is away from the second intermediate section 60, thereby making the second ending end face 71 away from the second starting section 50.

[0052] For example, the thickness of the diaphragm 350 is 7 μm to 18 μm. Along the extending direction of the diaphragm 350, the diaphragm 350 includes a starting membrane segment 80, an intermediate membrane segment 91, and a ending membrane segment 92. The intermediate membrane segment 91 connects the starting membrane segment 80 and the ending membrane segment 92. The starting membrane segment 80 is disposed between the first starting segment 10 and the second starting segment 50 to isolate the first starting segment 10 and the second starting segment 50, and is also disposed between the empty foil segment 40 and the first starting segment 10 to isolate the empty foil segment 40 from the first starting segment 10. In this embodiment, the starting membrane segment 80 also covers the portion of the first starting segment 10 that extends beyond the second starting segment 50. The intermediate membrane segment 91 is isolated between the first intermediate segment 20 and the second intermediate segment 60 to isolate the first intermediate segment 20 and the second intermediate segment 60. The first intermediate segment 20 and the second intermediate segment 60 are located on opposite sides of the intermediate membrane segment 91 along its thickness direction. The finishing film segment 92 is isolated between the first finishing segment 30 and the second finishing segment 70 to separate the first finishing segment 30 and the second finishing segment 70. The first finishing segment 30 and the second finishing segment 70 are located on both sides of the finishing film segment 92 along the thickness direction of the finishing film segment 92.

[0053] The battery cell 300 also includes a first tab 360 and a second tab 370. There may be multiple first tabs 360, and all of the multiple first tabs 360 are electrically connected to the first electrode plate 310. There may be multiple second tabs 370, and all of the multiple second tabs 370 are electrically connected to the second electrode plate 330.

[0054] In the battery cell 300 provided in this application embodiment, by providing an empty foil section 40 in the first electrode 310 and an imprinted portion 43 in the empty foil section 40, on the one hand, the groove 46 provided in the imprinted portion 43 in the empty foil section 40 can store electrolyte when the battery cell 300 is filled with electrolyte. When the outer casing 100 is pressed by the battery cell 300, the electrolyte in the groove 46 is not easily squeezed out. Therefore, in the later stages of the battery cell 300 cycle, when the electrolyte inside the first electrode 310 is exhausted, the electrolyte stored in the groove 46 can be replenished to the first electrode 310 in a timely manner to ensure the smooth transport path of lithium ions, thereby improving the cycle performance of the battery cell 300. On the other hand, compared with other methods to improve the cycle performance of the battery cell 300, this application embodiment can improve the cycle performance of the battery cell 300 by adding the process step of providing the imprinted portion 43, without increasing material costs, which helps to reduce the production cost of the battery cell 300. In addition, the empty foil section 40 does not contain active materials, which is equivalent to saving the cost of active materials, thereby further reducing the production cost of the battery cell 300.

[0055] Furthermore, the applicant's research found that, compared to the first electrode 310, the active layer material in the second electrode 330 typically has a higher coating density and a higher compaction density. Therefore, the second electrode 330 is more prone to the problem of active layer material falling off during winding, and even the risk of breakage. In the battery cell 300 provided in this application embodiment, by adding a hollow foil segment 40 to the first electrode 310, the straight portion 42 of the hollow foil segment 40 and the straight portion 11 of the first starting segment 10 are spaced apart in the thickness direction of the battery cell 300. This is equivalent to increasing the thickness of the first electrode 310 in the inner space of the battery cell 300, thereby reducing the curvature of the second electrode 330 at the winding corner when winding around the first electrode 310, and thus reducing the problem of active layer material falling off the second electrode 330, and even the risk of breakage. In addition, since the empty foil segment 40 has a large area and a thin thickness, the surface stress of the empty foil segment 40 is prone to causing the empty foil segment 40 to curl, thereby affecting the winding efficiency of the empty foil segment 40, or even causing the empty foil segment 40 to be directly folded inward, resulting in uneven thickness of the empty foil segment 40. By setting the imprinting part 43 in the empty foil segment 40, the surface stress distribution of the empty foil segment 40 can be improved, and the risk of curling of the empty foil segment 40 can be reduced.

[0056] Furthermore, by setting the first starting segment 10 of the first electrode 310 to extend beyond the second starting segment 50 of the second electrode 330 in the opposite direction to the winding direction of the first electrode 310, an excess coefficient of the first electrode 310 to the second electrode 330 is created, thereby ensuring that the first electrode 310 has sufficient lithium insertion sites to prevent lithium deposition.

[0057] Furthermore, during the use of the energy storage device 1000, the electrolyte is gradually consumed, with the electrolyte near the top cover 200 of the energy storage device 1000 drying up first. In this embodiment, by setting the openings of the grooves 46 of the multiple imprinted portions 43 in the empty foil section 40 along the length of the cell 300 and towards the top cover 200, the grooves 46 near the imprinted portions 43 of the top cover 200 can store more electrolyte for replenishment, maintain the smooth transport path of lithium ions, and thus improve the cycle performance of the cell 300.

[0058] Furthermore, by setting the starting membrane segment 80 of the diaphragm 350 between the first starting segment 10 of the first electrode 310 and the second starting segment 50 of the second electrode 330, and covering the portion of the first starting segment 10 that extends relative to the second starting segment 50, the starting membrane segment 80 serves to isolate the first electrode 310 and the second electrode 330. On the other hand, after the first electrode 310 is wound, the portion of the first starting segment 10 that extends relative to the second starting segment 50 can be isolated from the first intermediate segment 20 of the first electrode 310 by the starting membrane segment 80, thereby avoiding the problem of short circuit in the cell 300.

[0059] Referring again to Figure 5, the assembled battery cell 300 includes two first surfaces 380 and two second surfaces 390. The two first surfaces 380 are arranged opposite each other along the thickness direction of the battery cell 300, and the two second surfaces 390 are arranged opposite each other along the width direction of the battery cell 300. Each second surface 390 is connected between two first surfaces 380. In this embodiment, the first electrode 310, the second electrode 330, and the separator 350 are wound to form a racetrack-shaped battery cell 300. In this embodiment, the first surfaces 380 are generally planar, and the second surfaces 390 are curved. The second surfaces 390 have a widest position B. Both second surfaces 390 have a widest position B, which refers to the position of one second surface 390 that is furthest from the other second surface 390 along the width direction of the battery cell 300.

[0060] In this embodiment, the first terminal segment 30 of the first electrode 310 terminates at the second surface 390, and the first terminal end face 31 of the first terminal segment 30 is located between the two first surfaces 380. Here, "the first terminal segment 30 terminates at the second surface 390" means that the first terminal end face 31 of the first terminal segment 30 does not extend to the first surface 380. In this embodiment, the first terminal segment 30 extends in a direction parallel to the second surface 390.

[0061] This application embodiment also optimizes the design of the termination position of the first electrode 310. By setting the first termination end face 31 between the two first faces 380, the first termination section 30 of the first electrode 310 is not on the first face 380 of the cell 300. This avoids the first termination end face 31 of the first termination section 30 becoming the highest point of the entire first face 380 due to being on the first face 380. On the one hand, it ensures that the capacity of the cell 300 can be fully utilized, and on the other hand, it avoids increasing the thickness of the cell 300. This helps to reduce the thickness margin of the energy storage device 1000 formed by assembling the battery cell 300. On the other hand, it can prevent stress points from being generated at the position of the first end section 30 of the battery cell 300 due to external force during the hot pressing or cold pressing process of forming the battery cell 300, and when the battery cell 300 is circulated to the shell. This stress points can then be transmitted to the inner layers of the battery cell 300, causing the electrolyte at the stress points to be squeezed out of the electrode, resulting in poor electrolyte wetting. This can lead to excessive current density around the stress points, causing problems such as purple spots or lithium plating in the battery cell 300.

[0062] The second terminal segment 70 of the second electrode 330 terminates at the second surface 390. Here, "the second terminal segment 70 terminates at the second surface 390" means that the second terminal end face 71 of the second terminal segment 70 does not extend to the first surface 380. In this embodiment, the second terminal segment 70 extends in a direction parallel to the second surface 390. The second terminal segment 70 and the first terminal segment 30 terminate at the same second surface 390 in the same direction, and along the winding direction of the cell 300, the first terminal end face 31 of the first terminal segment 30 extends beyond the second terminal end face 71 of the second terminal segment 70. For example, the length by which the first terminal end face 31 of the first terminal segment 30 extends beyond the second terminal end face 71 of the second terminal segment 70 is L, where L ≥ 3.5 mm.

[0063] Furthermore, the second terminal face 71 of the second terminal segment 70 in the second electrode 330 does not exceed the widest position B of the second surface 390. Here, "the second terminal face 71 does not exceed the widest position B" means that when the second electrode 330 is wound along the winding direction of the cell 300, the second terminal segment 70 is wound from a first surface 380 to the second surface 390, and the second terminal segment 70 is located between the widest positions B of the first surface 380 and the second surface 390, so that the second terminal face 71 is located between the widest positions B of the first surface 380 and the second surface 390. In this embodiment, the widest position B of the second surface 390 is located at half the thickness of the cell 300, and the second surface 390 is approximately semi-circular; the widest position B is approximately at half the arc of the semi-circular second surface 390.

[0064] This application embodiment also optimizes the design of the termination position of the second electrode 330. By setting the second termination end face 71 to not exceed the widest part B of the second surface 390, the termination of the second electrode 330 does not exceed the widest part of the cell 300. This avoids the second termination section 70 of the second electrode 330 exceeding the widest part B of the second surface 390, which would cause the cell 300 to have an additional layer of winding thickness in the width direction. On the one hand, it avoids increasing the width of the cell 300 while ensuring that the capacity of the cell 300 can be fully utilized. This helps to reduce the width skirt margin of the energy storage device 1000 formed by assembling the cell 300. It avoids the problem that high energy density lithium-ion energy storage devices with a relatively extreme width skirt margin design would make it difficult for the cell 300 to be inserted into the outer casing 100. Moreover, after the cell 300 is inserted into the outer casing 100, the outer casing 100 is more easily squeezed on both sides in the width direction, which would increase the risk of the cell 300 undergoing "S"-shaped deformation.

[0065] Referring to Figure 8, Figure 8 is a cross-sectional structural schematic diagram of the energy storage device 1000 provided in the second embodiment of this application.

[0066] The energy storage device 1000 of the second embodiment differs from the energy storage device 1000 of the first embodiment in that the first starting segment 10 of the first electrode 310 of the energy storage device 1000 of the second embodiment only includes a straight portion 11, and the empty foil segment 40 also includes a bent portion 44.

[0067] Specifically, along the extending direction of the empty foil segment 40, the empty foil segment 40 includes a straight portion 42 and a bent portion 44. The straight portion 42 of the empty foil segment 40 and the straight portion 11 of the first starting segment 10 are spaced apart along the thickness direction of the cell 300. The bent portion 44 of the empty foil segment 40 is connected between the straight portion 42 of the empty foil segment 40 and the first current collector 301 of the straight portion 11 of the first starting segment 10 to realize the connection between the empty foil segment 40 and the first starting segment 10. At this time, the end face of the straight portion 11 of the first starting segment 10 facing the bent portion 44 of the empty foil segment 40 is the first starting end face 15.

[0068] In the second embodiment, the embossing portion 43 is located on the straight portion 42 of the empty foil segment 40. It is understood that in other embodiments, the embossing portion 43 may also be located on both the bent portion 44 and the straight portion 42 of the empty foil segment 40.

[0069] Referring to Figure 9, Figure 9 is a cross-sectional structural schematic diagram of the energy storage device 1000 provided in the third embodiment of this application.

[0070] The energy storage device 1000 of the third embodiment differs from the energy storage device 1000 of the first embodiment in that the first starting segment 10 of the first electrode 310 of the energy storage device 1000 of the third embodiment includes a straight portion 11 and a bent portion 13, and along the extending direction of the empty foil segment 40, the empty foil segment 40 includes a straight portion 42 and a bent portion 44.

[0071] Specifically, the bent portion 44 of the empty foil segment 40 is connected to the straight portion 42 of the empty foil segment 40, and is connected to the end of the bent portion 13 of the first starting segment 10 away from the straight portion 11 of the first starting segment 10. At this time, the bent portion 44 of the empty foil segment 40 and the bent portion 13 of the first starting segment 10 together constitute the winding corner portion of the first electrode 310. In the third embodiment, the imprinting portion 43 is located on the straight portion 42 of the empty foil segment 40. It is understood that in other embodiments, the imprinting portion 43 may also be located on both the bent portion 44 and the straight portion 42 of the empty foil segment 40.

[0072] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments and equivalent variations made in accordance with the claims of this application are still within the scope of this application.

Claims

1. An electric cell, characterized by, The electric core is wound by a first pole piece, a diaphragm and a second pole piece, the diaphragm is arranged between the first pole piece and the second pole piece, along the winding direction of the first pole piece, the first pole piece comprises an empty foil section and a first starting section connected with the empty foil section, the empty foil section and the first starting section both comprise flat portions, the flat portion of the empty foil section and the flat portion of the first starting section are arranged in a spaced manner along the thickness direction of the electric core, along the winding direction of the second pole piece, the second pole piece comprises a second starting section, the second starting section is located on the side of the first starting section away from the empty foil section; Wherein, the first starting section exceeds the second starting section in the opposite direction of the winding direction of the first pole piece, the empty foil section comprises a body and a stamping part, the stamping part is connected with the body and comprises a convex surface, along the thickness direction of the body, the convex surface is convex relative to the body, the stamping part is provided with a groove, the opening of the groove is arranged on the surface of the stamping part away from the convex surface.

2. The electric cell of claim 1, wherein, The body comprises a first surface and a second surface arranged in a spaced manner along the thickness direction, the first surface faces the second starting section, the second surface is away from the second starting section, the stamping part has a plurality of stamping parts, the plurality of stamping parts comprises a first stamping part and a second stamping part, the convex surface of the first stamping part is convex relative to the first surface of the body, the convex surface of the second stamping part is convex relative to the second surface of the body.

3. The electric cell of claim 2, wherein, The plurality of first stamping parts and the plurality of second stamping parts are arranged alternately.

4. The electric cell of claim 1, wherein, Along the direction from the bottom to the top of the electric core, the stamping part has a plurality of stamping parts, the openings of the grooves of the plurality of stamping parts gradually increase.

5. The electric cell of claim 1, wherein, The height of the convex surface convex relative to the body is H, 5μm≤H≤50μm.

6. The battery cell of any one of claims 1 to 5, wherein, The first starting section further comprises a bending portion, the bending portion of the first starting section is connected between the flat portion of the empty foil section and the flat portion of the first starting section; Or, the empty foil section further comprises a bending portion, the bending portion of the empty foil section is connected between the flat portion of the empty foil section and the flat portion of the first starting section; Or, the first starting section and the empty foil section both comprise a bending portion, the bending portion of the first starting section is connected with the flat portion of the first starting section, the bending portion of the empty foil section is connected with the flat portion of the empty foil section, and is connected to the end of the bending portion of the first starting section away from the flat portion of the first starting section.

7. The cell of any one of claims 1 to 5, wherein, The electric core comprises two first surfaces and two second surfaces, the two first surfaces are arranged in a spaced manner along the thickness direction of the electric core, the two second surfaces are arranged in a spaced manner along the width direction of the electric core; The first pole piece further comprises a first ending section, the first ending section is arranged in the opposite direction of the winding direction of the first pole piece relative to the first starting section, the first ending section comprises a first ending end surface, the first ending end surface is arranged along the winding direction of the first ending section and away from the first starting section, the first ending section ends at one of the second surfaces, and the first ending end surface is located between the two first surfaces.

8. The electric cell of claim 7, wherein, The second surface is a curved surface, and the second surface is provided with a widest position. The second pole piece further comprises a second end section, which is arranged opposite to the second start section along the extension direction of the second pole piece. The second end section comprises a second end surface, which is arranged along the extension direction of the second end section and faces away from the second start section. The second end section ends at one of the second surfaces, and the second end surface does not exceed the widest position.

9. The electric cell of claim 8, wherein, The second end section and the first end section end at the same second surface, and along the winding direction of the battery cell, the first end surface exceeds the second end surface.

10. The electric cell of claim 9, wherein, Along the winding direction of the battery cell, the length by which the first end surface exceeds the second end surface is L, and L≥3.5mm.

11. An energy storage device, characterized by, The energy storage device comprises a housing and at least one battery cell as claimed in any one of claims 1 to 10, which is mounted on the inner side of the housing.

12. The energy storage device of claim 11, wherein, The energy storage device satisfies 85%≤D2 / D1≤105%, wherein D1 represents the inner diameter of the housing along the thickness direction, and D2 represents the total length of the battery cell along the thickness direction.

13. The energy storage device of claim 11, wherein, The energy storage device comprises two battery cells, which are mounted on the inner side of the housing along the thickness direction of the battery cell.

14. An electrical device, characterized by The energy storage device as claimed in any one of claims 11 to 13 is used to supply power to the power consumption device.

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