Electrochemical device and electronic device

Abstract

An electrochemical device, comprising a housing, an electrode assembly, an electrolyte, a bonding member, and a first expansion tape. The electrolyte and the electrode assembly are accommodated in the housing. The electrode assembly comprises a first electrode sheet, a second electrode sheet, and a separator, and the electrode assembly is of a winding structure wound around a winding center axis. The outermost side of the electrode assembly is the first electrode sheet; the first electrode sheet comprises a first section as a tail section and a second section located on the secondary outer ring of the first electrode sheet; the inner surface of the first section facing the winding center axis and the outer surface of the first section facing away from the winding center axis are empty foil regions; the second section and the first section are stacked and adjacent; the outer surface of the second section facing away from the winding center axis is an empty foil region; and no second electrode sheet or separator is arranged between the first section and the second section. The first expansion tape is used for bonding the inner surface of the first section and the outer surface of the second section, so that the first section abuts against the housing so as to electrically connect the first electrode sheet to the housing, thereby improving the energy density and the electrical connection stability of the electrochemical device. Also provided is an electronic device.

Description

Electrochemical devices and electronic devices Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to an electrochemical device and an electronic device having the electrochemical device. Background Art

[0002] Electrochemical devices (such as batteries) are widely used in electronic products such as mobile devices, power tools, and electric vehicles. Traditional hard-shell battery assembly typically involves placing a wound battery cell within a rigid casing. The tab of one electrode (e.g., the negative electrode) is then welded (e.g., laser welded) to the casing to achieve an electrical connection between the electrode and the casing.

[0003] However, the method of welding the tab to the shell reduces the energy density of the battery due to the space occupied. At the same time, since a welding needle needs to be inserted into the winding center of the battery cell to hold the tab against the shell during welding, the above-mentioned electrical connection method between the pole piece and the shell is either prone to unstable electrical connection due to the welding needle being too small, or requires a larger space for the large welding needle, resulting in a reduction in the energy density of the battery, thereby affecting the service life of the battery.

[0004] Summary of the Invention

[0005] Therefore, the present application proposes an electrochemical device that is beneficial for improving energy density and electrical connection stability.

[0006] In addition, the present application also provides an electronic device having the electrochemical device.

[0007] In a first aspect, the present application provides an electrochemical device comprising a housing, an electrode assembly, an electrolyte, an adhesive, and a first expansion tape. The electrolyte is contained within the housing. The electrode assembly comprises a first electrode sheet, a second electrode sheet, and a separator disposed between the first electrode sheet and the second electrode sheet. The electrode assembly is a wound structure wound around a winding axis and disposed within the housing, with the outermost portion of the electrode assembly being the first electrode sheet. The first electrode sheet comprises a first section and a second section, the first section being the tail section of the first electrode sheet, and both the inner surface of the first section facing the winding axis and the outer surface of the first section facing away from the winding axis being a hollow foil area. The second section is located at the secondary outer ring of the first electrode sheet, and in the radial direction of the electrode assembly, the second section is stacked and adjacent to the first section, and the outer surface of the second section facing away from the winding axis is a hollow foil area. The first expansion tape is bonded to the inner surface of the first section and the outer surface of the second section, and the outer surface of the first section is abutted against the housing via the first expansion tape to achieve electrical connection between the first electrode sheet and the housing.

[0008] The present application uses a first expansion tape to bond the first and second sections to secure the electrode assembly, facilitating placement of the electrode assembly within the housing. Furthermore, after expansion, the first expansion tape can abut the outer surface of the first section against the housing, thereby improving the stability of the electrical connection between the outer surface of the first section and the housing. Furthermore, the electrical connection between the housing and the first electrode sheet is achieved by directly abutting the first section of the first electrode sheet against the housing, eliminating the need for separate tabs for welding electrical connections to the housing. This not only improves electrical connection stability but also space utilization, thereby increasing the overall energy density of the electrochemical device. After the electrochemical device undergoes subsequent charge and discharge cycles, the electrode assembly will further expand, pressing the outer surface of the first section against the housing, further stabilizing the electrical connection between the first electrode sheet and the housing.

[0009] In some possible implementations, the first expansion tape includes a first adhesive layer, a substrate, and a second adhesive layer stacked in sequence, with the first adhesive layer bonding to the first segment and the second adhesive layer bonding to the second segment. This facilitates designing adhesive layers of different materials to bond different materials, facilitating the attachment of one side to the current collector during manufacturing while the other side minimizes impact during transport and improves bonding stability.

[0010] In some possible implementations, the first pole piece further includes a third section, which connects the first section and the second section. The inner surface of the third section facing the winding center axis and the outer surface away from the winding center axis are both empty foil areas, and the first expansion tape is also bonded to the inner surface of the third section and the isolation film. First, the outer surface of the third section being an empty foil area is beneficial for increasing the area in which the first pole piece can directly contact the shell, thereby facilitating increasing the stability of the electrical connection between the first pole piece and the shell. The first expansion tape is also bonded to the inner surface of the third section and the isolation film, which is beneficial for reducing the risk of short circuit caused by the shrinkage of the tail section of the isolation film while increasing the distribution of the first expansion tape in the circumferential direction of the electrode assembly around the center axis, thereby increasing the area in which the electrode assembly can expand outward in the radial direction in the circumferential direction when the first expansion tape expands, thereby facilitating the stability of the electrical connection between the first pole piece and the shell.

[0011] In some possible implementations, the second pole piece is provided between the third section and the secondary outer circle of the first pole piece, which is beneficial for improving the energy density of the electrochemical device.

[0012] In some possible implementations, the first electrode piece further includes an extension segment, located at the secondary outer circumference of the first electrode piece and connected to the second segment. The outer surface of the extension segment, facing away from the winding center axis, is a hollow foil area. The first expansion tape is also bonded to the outer surface of the extension segment and the separator. This helps reduce the risk of short circuits caused by shrinkage of the trailing segment of the separator. It also increases the distribution of the first expansion tape in the circumferential direction around the winding center axis of the electrode assembly. This increases the area of ​​the electrode assembly that can expand radially outward in the circumferential direction when the first expansion tape expands, thereby stabilizing the electrical connection between the first electrode piece and the housing.

[0013] In some possible implementations, a second pole piece is provided between the extension section and the outermost circle of the first pole piece, which is beneficial for improving the energy density of the electrochemical device.

[0014] In some possible implementations, the first expansion tape is wrapped around the winding center axis at least once, so that when the first expansion tape expands and during subsequent cyclic charge and discharge processes, the entire circumference of the electrode assembly around the winding center axis can expand outward in the radial direction of the electrode assembly, thereby balancing the diameter distribution of the electrode assembly in various directions of the surface perpendicular to the winding center axis, and facilitating the fixation between the electrode assembly and the shell, thereby facilitating further improving the stability of the electrical connection between the first electrode sheet and the shell.

[0015] In some possible implementations, the housing is cylindrical, the electrode assembly is cylindrical, the electrode assembly further includes a tab, the second pole piece has a connection region connected to the tab, and the first expansion tape has a first notch, with the first notch corresponding to the connection region in a radial direction of the electrode assembly. Compared to a flat electrode assembly and housing, the cylindrical electrode assembly matches the cylindrical housing, and when the first expansion tape expands, the expansion force is more uniform across the entire circumference of the cylinder, thereby improving the stability of the contact between the first pole piece and the housing. Furthermore, compared to the expansion force required in the bending region of a flat electrode assembly during expansion, the expansion force required in each region of the cylindrical electrode assembly is smaller, thereby reducing the pulling force on the region where the first pole piece and the first expansion tape are bonded, thereby reducing the risk of tearing or even breaking the first pole piece in the bending region. In addition, since the connection between the connection area and the electrode ear will increase the thickness of the electrode assembly in this area, opening a first notch corresponding to the connection area on the first expansion tape can reduce the thickness of the area corresponding to the electrode assembly and the connection area, which is beneficial to balancing the thickness of each area of ​​the electrode assembly and is beneficial to the stability of the contact between the electrode assembly and the shell.

[0016] In some possible implementations, the first expansion tape further comprises a second notch. In the radial direction of the electrode assembly, the second notch corresponds to the connection region, and the second notch and the first notch are located on opposite sides of the connection region. The first and second notches located radially on opposite sides of the connection region can help reduce the thickness of the electrode assembly corresponding to the connection region, thereby further balancing the thickness of various regions of the electrode assembly and further improving the stability of the contact between the electrode assembly and the housing.

[0017] In some possible implementations, the electrode assembly has a center hole, and the projection of the winding center axis is located within the projection of the center hole along the direction of the winding center axis. The electrochemical device also includes an insulating support member, which is at least partially arranged in the center hole. On the one hand, it is conducive to compressing the first electrode piece, the isolation membrane and the second electrode piece. On the other hand, it can also support the first expansion tape and the electrode assembly to expand outward along the radial direction of the electrode assembly when the first expansion tape expands and when the electrode assembly expands during subsequent cyclic charge and discharge processes, thereby helping to improve the stability of the electrical connection between the first electrode piece and the shell.

[0018] In some possible implementations, the insulating support member is cylindrical, and the material of the insulating support member includes at least one of polypropylene or polyethylene, which can provide good supporting effects while also helping to reduce costs.

[0019] In some possible implementations, the first electrode sheet further includes a third segment connecting the first segment and the second segment, with an outer surface of the third segment facing away from the winding center axis being a hollow foil area. The electrochemical device further includes an adhesive member, one end of the adhesive member being bonded to the outer surface of the first segment and the other end being bonded to the outer surface of the third segment. The adhesive member further secures the electrode assembly, reducing the risk of the electrode assembly becoming loose before placement in the housing.

[0020] In some possible implementations, the adhesive is a conductive adhesive film, and the inner surface of the adhesive facing the winding center axis and the outer surface away from the winding center axis are both conductive and electrically connected, so that the adhesive can further fix the electrode assembly to reduce the risk of the electrode assembly loosening before being placed in the shell, and can also contact the shell through the adhesive to further improve the stability of the electrical connection between the shell and the first electrode sheet.

[0021] In some possible implementations, the shell is cylindrical, the electrode assembly is cylindrical, and in the radial direction of the electrode assembly, the adhesive member located on the outer surface of the first section overlaps with the first expansion tape located on the inner surface of the first section. If the adhesive member is bonded too firmly, the outermost ring of the first electrode piece may easily develop a small gap at the edge or even break due to the expansion force of the first expansion tape when it expands. However, the first expansion tape overlaps with the adhesive member in the radial direction of the electrode assembly. In this case, when the first expansion tape expands, it can exert an outward force on the area of ​​the adhesive member that overlaps with the first expansion tape, which helps loosen the bond between the area of ​​the adhesive member that does not overlap with the first expansion tape and the first electrode piece, thereby helping to reduce the binding force of the adhesive member on the electrode assembly. This not only helps reduce the risk of breakage of the outermost ring of the first electrode piece, but also helps to maintain close contact between the outermost ring of the first electrode piece and the shell, thereby improving the stability of the electrical connection between the first electrode piece and the shell.

[0022] In some possible implementations, in the winding direction, the tail end of the first pole piece extends beyond the tail end of the first expansion tape. This is beneficial for reducing the risk of breakage of the outermost circle of the first pole piece and the close contact between the outermost circle of the first pole piece and the shell, and is further beneficial for improving the adverse effects caused by inaccurate positioning of the first pole piece during continuous production.

[0023] In some possible implementations, in the winding direction, the length of the portion where the adhesive is bonded to the outer surface of the first section is L, and the distance between the tail end of the first expansion tape and the tail end of the first pole piece is less than or equal to L / 2. This is conducive to further improving the adverse effects caused by inaccurate positioning of the first pole piece during cutting during continuous production, while also helping to further reduce the risk of breakage of the outermost circle of the first pole piece and to further ensure close contact between the outermost circle of the first pole piece and the shell.

[0024] In some possible implementations, the adhesive is a single-sided adhesive, which is beneficial for reducing the obstruction of loosening caused by the adhesion between the adhesive and the shell when the wound electrode assembly has a certain tendency to loosen under the action of expansion, thereby facilitating the stability of the electrical connection between the first electrode and the shell.

[0025] In some possible implementations, the separator includes a first diaphragm and a second diaphragm stacked between the outermost ring of the first pole piece and the secondary outer ring of the first pole piece, with the first diaphragm positioned between the second diaphragm and the first expansion tape. In the winding direction, the tail end of the first diaphragm is bonded to the first expansion tape, while the tail end of the second diaphragm extends beyond the tail end of the first diaphragm and is bonded to the first expansion tape. The first expansion tape bonds both the first and second diaphragms, thereby further reducing the risk of short circuits caused by shrinkage of the first and second diaphragms, thereby further improving the safety of the electrochemical device.

[0026] In some possible implementations, the tail end of the first expansion tape extends beyond the tail end of the first pole piece along the winding direction, or the tail end of the first expansion tape is flush with the tail end of the first pole piece, which helps to reduce the impact of burrs on the edge of the first pole piece.

[0027] In some possible implementations, the first electrode piece further includes a fourth section, which is the starting section of the first electrode piece. A second expansion tape is further bonded to the surface of the starting section facing the winding center axis. The second expansion tape bonded to the starting section, i.e., the head section, of the first electrode piece, after expansion, exerts a force that further increases the interaction between the first electrode piece, the separator, and the second electrode piece, thereby improving the tightness of the contact interface between the first electrode piece and the separator, and the contact interface between the second electrode piece and the separator, both located in the inner layer of the electrode assembly.

[0028] In some possible implementations, the starting end of the second expansion tape is flush with the starting end of the fourth section. This arrangement of the first and second expansion tapes is beneficial for reducing the adverse effects of inaccurate cutting positioning during continuous production (i.e., first laying the expansion tape on a continuous blank foil area and then cutting the blank foil area). Products with expansion tape on both the leading and trailing sections, where the expansion tape is flush with at least the trailing end of the first electrode, are easier to obtain during continuous production than products with expansion tape only on the trailing section.

[0029] In some possible implementations, the first electrode sheet is a negative electrode sheet, which includes a negative current collector formed of copper foil. Since the electrode assembly itself expands primarily during subsequent charge and discharge cycles of the electrochemical device, with the active material in the negative electrode sheet experiencing the greatest expansion, this expansion generates an extension force along the surface of the negative current collector. Copper foil, as the negative current collector, has high tensile strength and low resistivity, thus reducing the risk of current collector tearing and the contact resistance between the negative current collector and the housing.

[0030] In some possible implementations, the first expandable tape has a thickness of 10 μm to 50 μm, and the negative electrode plate further includes a negative active layer comprising a silicon material, wherein the weight percentage of the silicon material in the negative active layer is 3% to 100%. The above-mentioned specific thickness of the first expandable tape helps ensure the expansion effect of the first expandable tape during formation (i.e., activation of the electrochemical device), thereby facilitating the electrical connection between the first electrode plate and the housing, while also reducing the impact of excessive thickness of the first expandable tape on the energy density of the electrochemical device. Silicon material has a high expansion rate during the cyclic charge and discharge process of the electrochemical device. Therefore, a negative electrode active layer having a silicon material content within a specific range helps ensure the expansion effect of the negative active layer, i.e., the expansion effect of the electrode assembly itself, during the cyclic charge and discharge process, thereby improving the stability of the electrical connection between the first electrode plate and the housing during subsequent use of the electrochemical device.

[0031] In some possible implementations, the first expansion tape is made of at least one of polyisoprene, polybutadiene, or thermoplastic polyurethane elastomer, and further comprises at least one of acrylic glue, rubber, or silicone. Polyisoprene, polybutadiene, or thermoplastic polyurethane elastomers expand rapidly and at a high rate after being infiltrated with electrolyte, and this expansion does not subsequently reduce their volume, thereby ensuring the stability of the electrical connection between the first electrode piece and the housing. The acrylic glue, rubber, or silicone serves as an adhesive material to bond the at least one of polyisoprene, polybutadiene, or thermoplastic polyurethane elastomer to form a film layer, and also serves to bond the first electrode piece.

[0032] In some possible implementations, the conductive adhesive film includes an adhesive layer matrix and a conductor, the conductor is dispersed in the adhesive layer matrix, bonding with the electrode assembly is achieved through the adhesive layer matrix, and electrical connection between the first electrode in contact with the conductive adhesive film and the shell can be achieved through the conductor.

[0033] In some possible implementations, the adhesive layer matrix includes at least one of silicone rubber, polyurethane rubber, chloroprene rubber, hot melt adhesive, or tackifying resin, and the conductor includes at least one of gold, silver, copper, aluminum, nickel, or graphite. The use of such an adhesive layer matrix can maintain high adhesion in an electrolyte environment and is not susceptible to changes in electrolyte composition, thereby facilitating the preservation of the capacity and cycle life of the electrochemical device. Furthermore, the aforementioned conductors all have good electrical conductivity, thereby facilitating the stability of the electrical connection between the first electrode and the housing.

[0034] In some possible implementations, the tail end of the first pole piece is in direct contact with the shell, which helps to ensure the stability of the electrical connection between the first pole piece and the shell.

[0035] In some possible implementations, no second electrode piece and no isolation film are provided between the first section and the second section, which can improve the reliability of the connection between the first section and the second section.

[0036] The present application also provides an electronic device comprising a main body and the electrochemical device. The electronic device is powered by the electrochemical device, and the electrochemical device has high reliability and service life, thereby extending the service life of the electronic device and reducing its use cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic structural diagram of an electrochemical device provided in one embodiment of the present application.

[0038] FIG2 is an exploded view of an electrochemical device provided in one embodiment of the present application.

[0039] FIG3 is a cross-sectional view of the electrochemical device shown in FIG1 along line III-III.

[0040] FIG4 is a cross-sectional view of an electrochemical device along line III-III according to another embodiment of the present application.

[0041] [Corrected 11.06.2024 in accordance with Article 26]

[0042] FIG. 5 is a cross-sectional view of the electrochemical device shown in FIG. 1 taken along line III-III in one embodiment.

[0043] FIG. 6 is a cross-sectional view of the electrochemical device shown in FIG. 1 taken along line III-III in one embodiment.

[0044] FIG. 7 is a cross-sectional view of the electrochemical device shown in FIG. 1 taken along line III-III in one embodiment.

[0045] FIG8 is a cross-sectional view of the electrochemical device shown in FIG1 taken along line III-III in one embodiment.

[0046] FIG. 9 is a cross-sectional view of the electrochemical device shown in FIG. 1 taken along line III-III in one embodiment.

[0047] FIG. 10 is a cross-sectional view of the electrochemical device shown in FIG. 1 taken along line III-III in one embodiment.

[0048] FIG. 11 is a cross-sectional view of the electrochemical device shown in FIG. 1 taken along line III-III in one embodiment.

[0049] FIG. 12 is a cross-sectional view of the electrochemical device shown in FIG. 1 taken along line III-III in one embodiment.

[0050] FIG. 13 is a cross-sectional view of the electrochemical device shown in FIG. 1 taken along line III-III in one embodiment.

[0051] FIG14 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

[0052] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0054] Below, embodiments of the present application will be described in detail. However, the present application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments illustrated herein. Rather, these exemplary embodiments are provided to make the present application thorough and detailed for those skilled in the art.

[0055] In addition, for the sake of brevity and clarity, the size or thickness of various components or layers may be exaggerated in the accompanying drawings. Throughout the text, the same numerical value refers to the same element. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more related enumerated items. In addition, it should be understood that when element A is referred to as "connecting" element B, element A can be directly connected to element B, or there may be an intermediate element C and element A and element B can be indirectly connected to each other.

[0056] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0057] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. As used herein, the singular is intended to include the plural, unless the context clearly indicates otherwise. It should be further understood that the term "comprising", when used in this specification, refers to the presence of the described features, values, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components and / or combinations thereof.

[0058] Spatial related terms, such as "on" etc., can be used herein for convenient description, to describe the relationship between an element or feature and another element (multiple elements) or feature (multiple features) as illustrated in the figure. It should be understood that, in addition to the directions described in the figure, spatial related terms are intended to include different directions of equipment or devices in use or operation. For example, if the equipment in the figure is turned over, the elements described as "above" or "on" other elements or features will be oriented "below" or "below" other elements or features. Therefore, the exemplary term "on" can include the direction above and below. It should be understood that although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are used to distinguish an element, component, region, layer or part from another element, component, region, layer or part. Therefore, the first element, component, region, layer or part discussed below can be referred to as the second element, component, region, layer or part, without departing from the teachings of the exemplary embodiments.

[0059] In this application, the relationship between parameter values ​​that is greater than, less than, or not equal to the design relationship needs to exclude the reasonable error of the measuring equipment.

[0060] 1 to 3 , an embodiment of the present application provides an electrochemical device 100 , comprising a housing 10 , an electrode assembly 20 , an electrolyte (not shown), and a first expansion tape 50 . The electrode assembly 20 , the electrolyte, and the first expansion tape 50 are contained within the housing 10 .

[0061] 1 and 2 , in some embodiments, the housing 10 is a hard housing, and the housing 10 includes a conductive material, such as but not limited to aluminum, steel, etc. In some embodiments, specifically, the housing 10 can be a steel shell or an aluminum shell.

[0062] The housing 10 may include a first wall 11, a second wall 13, and a connecting wall 15 connecting the periphery of the first wall 11 and the periphery of the second wall 13. The first wall 11, the second wall 13, and the connecting wall 15 cooperate to form a storage cavity 10a. The connecting wall 15 may be made of a conductive material. The first wall 11 and the second wall 13 may be made of a conductive material or a non-conductive material. In some embodiments, the first wall 11 and the connecting wall are integrally formed. In some embodiments, a pole 17 may be provided on the second wall 13, and when the second wall 13 is conductive, the pole 17 and the second wall 13 may be electrically insulated.

[0063] Referring to FIG3 , the electrode assembly 20 includes a first electrode sheet 21, a second electrode sheet 23, and a separator 25 disposed between the first electrode sheet 21 and the second electrode sheet 23. The first electrode sheet 21, the separator 25, and the second electrode sheet 23 are stacked in sequence and wound around a winding center axis O along a winding direction D so that the electrode assembly 20 has a wound structure wound around the winding center axis O, and the electrode assembly 20 is disposed in the storage cavity 10a. The outermost portion of the electrode assembly 20 is the first electrode sheet 21, and the separator 25 is used to prevent direct contact between the first electrode sheet 21 and the second electrode sheet 23, thereby preventing a short circuit in the electrode assembly 20. As shown in FIG3 , the winding center axis O is perpendicular to the paper surface, and the winding direction D is the direction of counterclockwise rotation around the winding center axis O as shown in FIG3 . In other embodiments, the winding direction D may also be a clockwise rotation direction, as shown in FIG2 . In the present application, the electrode assembly 20 has a radial direction, wherein the radial direction refers to the direction of a straight line passing through the winding center axis O in any cross section of the electrode assembly that is perpendicular to the winding center axis O.

[0064] The electrode assembly 20 can be roughly cylindrical (as shown in Figures 2 and 3), flat (as shown in Figure 4), or other regular or irregular shapes. Correspondingly, the shell 10 roughly matches the shape of the electrode assembly 20. For example, as shown in Figure 3, when the electrode assembly 20 is roughly cylindrical, the shell 10 is also roughly cylindrical. For another example, as shown in Figure 4, when the electrode assembly 20 is roughly flat, the shell 10 is also roughly flat. In the present application, as shown in Figure 4, the flat electrode assembly is an electrode assembly structure that is common in the art and includes a straight portion and a bent portion connected to opposite ends of the straight portion. Below, the subsequent description will be based on the example of the cylindrical electrode assembly 20 and the cylindrical shell 10.

[0065] As shown in Figure 3, the first pole piece 21 includes a first section 211 and a second section 213. The first section 211, as the tail section of the first pole piece 21, is located in the outermost layer of the electrode assembly 20, wherein the inner surface 211a of the first section 211 facing the winding center axis O and the outer surface 211b away from the winding center axis O are both empty foil areas. The second section 213 is located in the secondary outer circle of the first pole piece 21, and in the radial direction of the electrode assembly 20, the first section 211 and the second section 212 are stacked and adjacent. The outer surface 213a of the second section 213 away from the winding center axis O is an empty foil area. In the present application, the empty foil area is the area on the surface of the current collector that is not coated with the active material layer, that is, the first pole piece 21 includes the first current collector 21a and the first active material layer 21b, wherein the tail section of the first current collector 21a is the first section 211. The outermost layer of the electrode assembly 20, i.e., the structure located at the outermost side of the electrode assembly 20 along the winding direction D, can be composed of a single structure, such as a pole piece, or can be composed of a pole piece and a separator. The first segment 211 includes a tail end 211c, which is the tail end of the first pole piece 21 in the winding direction D. In this application, the outermost circle refers to the region of a membrane, such as the first pole piece 21, that is wound around the central axis O from its tail end 211c in a direction opposite to the winding direction D. The outermost circle of the first pole piece 21 includes two ends in the winding direction D, and these two ends (one end is the tail end 211c, and the other end is the starting end of the outermost circle) overlap in the radial direction of the electrode assembly 20. It is understood that the second outermost circle refers to the region where the starting end of the outermost circle is wound around the central axis O in a direction opposite to the winding direction D. In this way, the two ends of each circle of the membrane in the winding direction D overlap in the radial direction of the electrode assembly 20.

[0066] Along the winding direction D, the second pole piece 23 and the isolation film 25 do not extend between the first section 211 and the second section 213 .

[0067] The electrode assembly 20 is located in the receiving cavity 10 a , wherein the outermost layer of the electrode assembly 20 faces the connecting wall 15 , that is, the outer surface 211 b of the first section 211 faces the connecting wall 15 .

[0068] The first expansion tape 50 is bonded to the inner surface 211a of the first section 211 and the outer surface 213a of the second section 213. After expansion, the first expansion tape 50 causes the outer surface 211b of the first section 211 to abut against the connecting wall 15 of the housing 10, thereby achieving electrical connection between the first electrode sheet 21 and the housing 10. Specifically, to facilitate placement of the electrode assembly 20 in the receiving cavity 10a, the electrode assembly 20 must be fixed in a wound form, and the volume of the electrode assembly 20 is typically smaller than the volume of the receiving cavity 10a. That is, there is typically a gap between the electrode assembly 20 and the connecting wall 15 of the housing 10. The first expandable tape 50, by bonding the first section 211 and the second section 213, secures the electrode assembly 20 in a wound form without requiring a separate end-tape for securing. After being soaked in electrolyte, the first expandable tape 50 expands, causing the area of ​​the electrode assembly 20 where the first expandable tape 50 is located to expand radially outward, thereby causing the first section 211 to abut against the connecting wall 15 of the housing 10, thereby achieving electrical connection between the first electrode piece 21 and the housing 10. Furthermore, by directly connecting the housing 10 and the first electrode piece 21 via the first section 211 to the connecting wall 15 of the housing 10, there is no need to separately weld a tab to the housing 10 (e.g., the second wall 13 serving as the bottom wall) for electrical connection. This not only improves electrical connection stability, but also enhances space utilization, thereby increasing the overall energy density of the electrochemical device. After the electrochemical device undergoes subsequent charge and discharge cycles, the electrode assembly 20 will further expand, pressing the outer surface 211b of the first segment 211 against the connecting wall 15 of the housing 10, thereby further stabilizing the electrical connection between the first electrode 21 and the housing 10. Note that in the figures, the outer surface 211b is not positioned in close contact with the connecting wall of the housing 10 to more clearly illustrate the positional relationship of the various components.

[0069] Since the first expandable tape 50 generates an extension force along the surface direction of the component to which it is bonded when it expands, the first expandable tape 50 is directly bonded to the inner surface 211a of the first segment 211 and the outer surface 213a of the second segment 213 instead of directly bonding to the first active material layer 21b. This reduces the risk of the first active material layer 21b being peeled off due to the extension force. In addition, compared to the first active material layer 21b, the first segment 211, as part of the first current collector 21a, has a higher tear resistance when subjected to the extension force, thereby further reducing the adverse effects of the first expandable tape 50 on the performance of the electrochemical device.

[0070] In addition, compared with the flat electrode assembly and shell, the cylindrical electrode assembly 20 matches the cylindrical shell 10, and the expansion force of the entire circumference of the cylinder is more uniform when the first expansion tape 50 expands, which is beneficial to improving the stability of the contact between the first electrode piece 21 and the connecting wall 15 of the shell 10; at the same time, compared with the expansion force required for the bending area of ​​the flat electrode assembly when it expands, the expansion force required for each area of ​​the cylindrical electrode assembly 20 is smaller, which is beneficial to reducing the pulling force on the area where the first electrode piece 21 and the first expansion tape 50 are bonded, and thus helps to reduce the risk of tearing or even breaking the bending area of ​​the first electrode piece 21.

[0071] In some embodiments, the first electrode sheet 21 may further be a negative electrode sheet, in which case the first active material layer 21b is a negative active layer, and the first current collector 21a is a negative current collector, which may be copper foil. Since copper foil has high tensile strength and low resistivity as a current collector, it helps reduce the risk of current collector tearing when subjected to the aforementioned tensile force and reduces the contact resistance between the current collector and the housing. Accordingly, the housing 10 may be a steel shell, which helps reduce the risk of electrochemical corrosion. The above design overall helps extend the service life of the electrochemical device 100.

[0072] The first active material layer 21b may comprise a silicon material. Since silicon material has a high expansion rate during the cyclic charge and discharge process of the electrochemical device, the use of a first active material layer 21b containing a silicon material is beneficial for ensuring the expansion effect of the first active material layer 21b, that is, the expansion effect of the electrode assembly 20 itself, during the cyclic charge and discharge process, thereby facilitating the improvement of the stability of the electrical connection between the first electrode plate 21 and the connecting wall 15 of the housing 10 during subsequent use of the electrochemical device 100. In some embodiments, the weight percentage of silicon in the first active material layer 21b may be 3% to 100%. By ensuring the silicon content, the expansion effect of the electrode assembly 20 itself is ensured, thereby further improving the stability of the electrical connection between the first electrode plate 21 and the connecting wall 15 of the housing 10 during subsequent use of the electrochemical device 100.

[0073] In other embodiments, the first electrode sheet 21 may also be a positive electrode sheet, the first current collector 21 a may include aluminum foil, and the housing 10 may be an aluminum shell.

[0074] The thickness of the first expansion tape 50 can be 10 μm to 50 μm, which is beneficial for ensuring the expansion effect of the first expansion tape 50 during formation (i.e., activation of the electrochemical device) to facilitate the electrical connection between the first electrode 21 and the housing 10, while reducing the impact of the excessive thickness of the first expansion tape 50 on the energy density of the electrochemical device 100.

[0075] The material of the first expansion tape 50 may include, but is not limited to, at least one of polyisoprene, polybutadiene, or thermoplastic polyurethane elastomer, and may also include, but is not limited to, at least one of acrylic glue, rubber, or silicone. Polyisoprene, polybutadiene, or thermoplastic polyurethane elastomers can rapidly expand and have a high expansion rate after being soaked in electrolyte, and this expansion is not easily reduced in volume, thereby facilitating the stability of the electrical connection between the first pole piece 21 and the connecting wall 15 of the housing 10. The acrylic glue, rubber, or silicone acts as a bonding material to bond the at least one of polyisoprene, polybutadiene, or thermoplastic polyurethane elastomer to form a film layer, and also serves to bond the first pole piece 21.

[0076] In some embodiments, the first expandable tape 50 may include a first adhesive layer, a substrate, and a second adhesive layer stacked sequentially, wherein the first adhesive layer is bonded to the first segment 211, and the second adhesive layer is bonded to the second segment 213. The material of the first adhesive layer may be the same as or different from that of the second adhesive layer. In other embodiments, the first expandable tape 50 may also be a single-piece colloidal film layer, i.e., a non-layered film.

[0077] As shown in FIG. 3 , the tail end 211 c of the first pole piece 21 is in direct contact with the connecting wall 15 of the housing 10 , which helps to ensure the stability of the electrical connection between the first pole piece 21 and the housing 10 .

[0078] As shown in FIG5 , the first electrode sheet 21 further includes a third section 215, which connects the first section 211 and the second section 213. In some embodiments, the inner surface 215a of the third section 215 facing the winding center axis O and the outer surface 215b facing away from the winding center axis O may both be hollow foil areas. The outer surface 215b of the third section 215 being a hollow foil area, i.e., the outermost side of the outermost circle of the first electrode sheet 21 is a hollow foil area, is beneficial for increasing the area of ​​the first electrode sheet 21 that can directly abut the connecting wall 15 of the housing 10 after the first expansion tape 50 expands and after subsequent cyclic charge and discharge, and regardless of the shape of the expanded electrode assembly 20, thereby further improving the stability of the electrical connection between the housing 10 and the first electrode sheet 21.

[0079] Furthermore, the first expansion tape 50 can also be bonded between the inner surface 215a of the third section 215 and the isolation film 25, wherein the first expansion tape 50 is bonded to the isolation film 25, which is beneficial to reducing the short circuit risk caused by the shrinkage of the tail section of the isolation film 25; and the first expansion tape 50 is also bonded to the inner surface 215a of the third section 215, which can also distribute the first expansion tape 50 in the circumferential direction around the winding center axis O of the electrode assembly 20, thereby increasing the area of ​​the electrode assembly 20 that can expand outward in the radial direction in the circumferential direction when the first expansion tape 50 expands, which is beneficial to the stability of the electrical connection between the first electrode piece 21 and the connecting wall 15 of the shell 10.

[0080] The separator 25 includes a first separator 25a and a second separator 25b, radially stacked between the outermost ring of the first electrode piece 21 and the second outermost ring of the first electrode piece 21. The first separator 25a is located between the second separator 25b and the first expansion tape 50. In some embodiments, as shown in FIG6 , the tail end 251a of the first separator 25a can be bonded to the first expansion tape 50. In the winding direction D, the tail end 251b of the second separator 25b can extend beyond the tail end 251a of the first separator 25a and bond to the first expansion tape 50. The first expansion tape 50 simultaneously bonds the first separator 25a and the second separator 25b, thereby reducing the risk of short circuits caused by shrinkage of the first separator 25a and the second separator 25b, thereby further improving the safety of the electrochemical device. At the same time, the bonding between the first expansion tape 50 and the second diaphragm 25b is conducive to further compressing the first diaphragm 25a, thereby further reducing the risk of shrinkage of the first diaphragm 25a, and further improving the safety of the electrochemical device.

[0081] As shown in Figures 5 and 6, the first expansion tape 50 can be further wrapped around the winding center axis O at least one circle, so that when the first expansion tape 50 expands and during subsequent cyclic charge and discharge processes, the electrode assembly 20 can expand outward in the radial direction of the electrode assembly 20 around the winding center axis O. This is beneficial to balancing the diameter distribution of the electrode assembly 20 in various directions of the surface perpendicular to the winding center axis O, and is beneficial to the entire outer side of the electrode assembly 20 pressing the connecting wall 15 of the shell 10, thereby facilitating the fixation between the electrode assembly 20 and the shell 10, and further beneficial to further improving the stability of the electrical connection between the first electrode sheet 21 and the shell 10.

[0082] Furthermore, the second pole piece 23 may also extend to between the third section 215 and the secondary outer circle of the first pole piece 21 , thereby facilitating improvement of the energy density of the electrochemical device.

[0083] As shown in FIG7 , the first electrode sheet 21 further includes an extension section 217, which is located at the secondary outer circumference of the first electrode sheet 21 and connects to the second section 213. In some embodiments, the outer surface 217a of the extension section 217, facing away from the winding center axis O, may be a hollow foil area, and the first expandable tape 50 is not disposed on the third section 215 but is bonded between the outer surface 217a of the extension section 217 and the separator 25. Similarly, the adhesion of the first expandable tape 50 to the separator 25 helps reduce the risk of short circuits caused by shrinkage of the end section of the separator 25. Furthermore, the fact that the first expandable tape 50 also adheres to the outer surface 217a of the extension section 217 also allows for the first expandable tape 50 to be distributed circumferentially around the winding center axis O of the electrode assembly 20. This increases the area of ​​the electrode assembly 20 that can expand radially outward in the circumferential direction when the first expandable tape 50 expands, thereby stabilizing the electrical connection between the first electrode sheet 21 and the connecting wall 15 of the housing 10.

[0084] Likewise, when the second electrode plate 23 extends to between the extension section 217 and the outermost circle of the first electrode plate 21 , it is beneficial to improve the energy density of the electrochemical device.

[0085] Referring to FIG. 2 , the electrode assembly 20 further includes a tab 26. The second electrode sheet 23 has a connection region 23a. One end of the tab 26 is connected to the electrode post 17, and the other end is connected to the connection region 23a. The connection between the tab 26 and the connection region 23a is typically achieved by welding, or alternatively, by bonding with conductive adhesive. The connection between the tab 26 and the connection region 23a is typically covered with insulating tape (not shown). Therefore, it can be seen that the connection between the connection region 23a and the tab 26 increases the thickness of the electrode assembly 20 in that region. In some embodiments, referring to FIG. 8 , the first expansion tape 50 may have a first notch 51. In the radial direction of the electrode assembly 20, the first notch 51 overlaps and corresponds to the connection region 23a. This reduces the thickness of the electrode assembly 20 in the region corresponding to the connection region 23a, facilitating balancing the thickness of various regions of the electrode assembly 20 and enhancing the stability of the contact between the electrode assembly 20 and the connecting wall 15 of the housing 10.

[0086] In some embodiments, referring to FIG. 9 , the first expansion tape 50 may further include a second notch 53. In the radial direction of the electrode assembly 20, the second notch 53 is stacked and corresponds to the connection region 23a, and the second notch 53 and the first notch 51 are located on opposite sides of the connection region 23a, respectively. This can help reduce the thickness of the region of the electrode assembly 20 corresponding to the connection region 23a, thereby further balancing the thickness of various regions of the electrode assembly 20 and further improving the stability of the contact between the electrode assembly 20 and the connection wall 15 of the housing 10.

[0087] In some embodiments, as shown in Figures 3 to 9, in the winding direction D, the tail end 211c of the first pole piece 21 can extend beyond the tail end 50a of the first expansion tape 50, which facilitates the cutting of the first pole piece 21 during continuous production and helps reduce the adverse effects caused by inaccurate positioning of the first pole piece 21 during continuous production.

[0088] In some embodiments, as shown in FIG10 , the electrochemical device may further include a bonding member 40 , the bonding member 40 including a first end 41 and a second end 43 spaced apart in the winding direction D, the first end 41 of the bonding member 40 being bonded to the outer surface 211 b of the first segment 211 , and the second end 43 extending beyond the tail end 211 c of the first segment 211 along the winding direction D to be bonded to the outer surface 215 b of the third segment 215 , thereby further fixing the electrode assembly 20 to maintain it in a wound state to reduce the risk of the electrode assembly 20 becoming loose before being placed in the shell 10 .

[0089] The adhesive member 40 may be a single-sided tape. In this case, it can reduce the situation where the adhesive member 40 simultaneously adheres to the electrode assembly 20 and the connecting wall 15 of the housing 10. When the electrode assembly 20 expands during subsequent charge and discharge cycles of the electrochemical device, the expansion can cause the adhesive member 40 to loosen. Reducing the adhesion between the adhesive member 40 and the connecting wall 15 of the housing 10 helps reduce the adhesive member 40's resistance to loosening the electrode assembly 20, thereby facilitating contact between the outermost layer of the electrode assembly 20 and the connecting wall 15 of the housing 10, thereby facilitating the stable electrical connection between the outer surface 211b of the first segment 211 and the housing 10. In other embodiments, the adhesive member 40 may also be a double-sided tape.

[0090] Furthermore, in order to improve the stability of the electrical connection between the electrode assembly 20 and the shell 10, the adhesive 40 can also be a conductive adhesive film, wherein the inner surface 40a of the adhesive 40 facing the winding center axis O and the outer surface 40b away from the winding center axis O are both conductive, and there is electrical conduction between the inner surface 40a and the outer surface 40b, so that the adhesive 40 can fix the electrode assembly 20 to facilitate the placement of the electrode assembly 20 in the shell 10, and can also contact the connecting wall 15 of the shell 10 through the conductive adhesive 40 to further improve the stability of the electrical connection between the shell 10 and the first electrode plate 21. When the outermost side of the electrode assembly 20 is the empty foil area of ​​the first electrode piece 21, the entire outer surface of the structure formed by the adhesive 40 and the electrode assembly 20 is made of conductive material, that is, the electrical connection between the first electrode piece 21 and the connecting wall 15 of the shell 10 can be achieved. No matter which area of ​​the structure formed by the adhesive 40 and the electrode assembly 20 contacts the connecting wall 15 of the shell 10, the electrical connection between the first electrode piece 21 and the shell 10 can be guaranteed, thereby ensuring the stability of the electrical connection between the shell 10 and the first electrode piece 21.

[0091] In some embodiments, the conductive adhesive film may specifically include an adhesive layer matrix and a conductor. The adhesive layer matrix may include an adhesive material to achieve adhesion of the conductive adhesive film, while the conductor is dispersed in the adhesive layer matrix and contacts each other to achieve electrical conductivity. The adhesive layer matrix may include, but is not limited to, at least one of silicone rubber, polyurethane rubber, chloroprene rubber, hot melt adhesive, or tackifying resin. The use of such an adhesive layer matrix can maintain high adhesion in an electrolyte environment and is not susceptible to changes in electrolyte composition, thereby ensuring that the capacity and cycle life of the electrochemical device are not affected. The conductor may include, but is not limited to, at least one of gold, silver, copper, aluminum, nickel, or graphite. All of these conductors have good electrical conductivity, which helps ensure the stability of the electrical connection between the first electrode 21 and the housing 10.

[0092] Silicone rubber is primarily composed of siloxane chains containing methyl groups and a small amount of vinyl groups. Phenyl, trifluoropropyl, and cyano groups may also be introduced. Silicone rubber is divided into heat-vulcanized (high-temperature vulcanized silicone HTV) and room-temperature vulcanized (RTV) types. RTV types are further divided into polycondensation and addition reaction types. Heat-vulcanized silicone rubber is used in greater quantities and is further divided into methyl silicone rubber (MQ), methyl vinyl silicone rubber (VMQ, the most widely used and most widely available product), and methyl vinyl phenyl silicone rubber PVMQ (low-temperature and radiation-resistant). Other types include nitrile silicone rubber and fluorosilicone rubber. Polyurethane rubber (PU) is a series of elastomeric materials with a high concentration of carbamate groups in the polymer backbone. It is actually polyurethane rubber, also known as PU, urethane rubber, or polyurethane elastomer. In addition to carbamate groups, the polymer chain also contains ester, ether, urea, aromatic, and aliphatic chains. It is typically formed by the reaction of oligomeric polyols, polyisocyanates, and chain extenders. Polyurethane rubbers vary in structure and type depending on the raw materials used, their proportions, reaction methods, and conditions. Neoprene, also known as chloroprene rubber, is a synthetic rubber produced by α-polymerization of chloroprene (2-chloro-1,3-butadiene). Specific types include CR122, CR232, CR24412442, and CR321322. Hot melt adhesive is a plastic adhesive whose physical state changes with temperature within a certain temperature range, while its chemical properties remain unchanged. It is non-toxic, odorless, and environmentally friendly. The product itself is a solid, making it easy to package, transport, and store. It is solvent-free, pollution-free, and non-toxic. It also features a simple production process, high added value, and high bonding strength and speed. Tackifying resins are small molecule compounds that increase the adhesiveness of rubber materials, particularly surface adhesiveness. These small molecules typically have molecular weights ranging from several hundred to ten thousand and possess high glass transition temperatures. Based on their source and synthesis routes, they can be broadly categorized into two main groups: natural products and their derivatives, and synthetic resins. Tackifying resins are primarily used for polymer modification and are widely used in adhesives, coatings, inks, rubber compounds, asphalt modifiers, and polyolefin modifiers.

[0093] The conductor may be in the form of, but not limited to, at least one of conductive particles, conductive fibers, or conductive sheets.

[0094] As shown in Figure 10, the first expandable tape 50 and the adhesive member 40 can overlap in the radial direction of the electrode assembly 20. If the adhesive member 40 is too firmly bonded, the outermost ring of the first electrode plate 21 may easily develop small gaps or even break due to the expansion force of the first expandable tape 50. However, if the first expandable tape 50 overlaps with the adhesive member 40 in the radial direction of the electrode assembly 20, the expansion of the first expandable tape 50 can exert an outward force on the overlapping area of ​​the adhesive member 40, which helps loosen the bond between the non-overlapping area of ​​the adhesive member 40 and the first electrode plate 21. This helps reduce the binding force of the adhesive member 40 on the electrode assembly 20. This not only reduces the risk of breakage of the outermost ring of the first electrode plate 21, but also promotes close contact between the outermost ring of the first electrode plate 21 and the connecting wall 15 of the housing 10, thereby improving the stability of the electrical connection between the first electrode plate 21 and the housing 10.

[0095] The distance between the first end 41 of the adhesive member 40 and the tail end 211c of the first electrode piece 21 in the winding direction D is defined as L, that is, the length of the portion of the adhesive member 40 bonded to the outer surface 211b of the first segment 211 is L. In some embodiments, provided that the first expandable tape 50 overlaps with the adhesive member 40 and the tail end 211c of the first electrode piece 21 extends beyond the tail end 50a of the first expandable tape 50, the distance between the tail end 50a of the first expandable tape 50 and the tail end 211c of the first electrode piece 21 may be less than or equal to L / 2. This helps reduce the adverse effects of inaccurate positioning of the first electrode piece 21 during continuous production, further reduces the risk of fracture of the outermost circle of the first electrode piece 21, and further ensures close contact between the outermost circle of the first electrode piece 21 and the connecting wall 15 of the housing 10.

[0096] In some embodiments, as shown in FIG11 , the tail end 50a of the first expansion tape 50 may extend beyond the tail end 211c of the first pole piece 21 along the winding direction, or the tail end 50a of the first expansion tape 50 may be flush with the tail end 211c of the first pole piece 21, which is beneficial to reducing the impact of burrs on the edge of the first pole piece 21.

[0097] As shown in FIG12 , the first electrode sheet 21 further includes a fourth segment 219 , which is the starting segment of the first electrode sheet 21 , i.e., the head segment near the winding center axis O. Furthermore, in some embodiments, the surface of the fourth segment 219 facing the winding center axis O may be a hollow foil area and may be bonded with a second expansion tape 60 . Referring to FIG2 and FIG12 , since a winding needle is used during winding of the electrode assembly 20 to enhance the winding effect, the electrode assembly 20 typically has a central hole 20 a , and along the direction of the winding center axis O, the projection of the winding center axis O lies within the projection of the central hole 20 a . Due to the presence of the center hole 20a, the interfaces of the electrode assembly 20 in the area close to the winding center axis O are relatively loose and not tight enough. However, the presence of the second expansion tape 60, after its expansion, can further increase the interaction between the first electrode piece 21, the isolation membrane 25 and the second electrode piece 23, so as to enhance the tightness of the contact interface between the first electrode piece 21 and the isolation membrane 25 located in the inner layer of the electrode assembly 20 and the contact interface between the second electrode piece 23 and the isolation membrane 25.

[0098] In some embodiments, as shown in Figure 12, when the tail end 50a of the first expandable tape 50 exceeds the tail end 211c of the first electrode 21 or is flush with the tail end 211c of the first electrode 21, the inner surface 219a of the fourth section 219 facing the winding center axis O is bonded with the second expandable tape 60 and the starting end 61 of the second expandable tape 60 is flush with the starting end 219b of the fourth section 219, the above-mentioned arrangement of the first expandable tape 50 and the second expandable tape 60 is conducive to reducing the adverse effects of inaccurate cutting positioning during continuous production (that is, first laying the expandable tape on a continuous empty foil area and then cutting the empty foil area). Products with both the head and tail sections provided with expandable tapes and the expandable tapes at least flush with the tail end 211c of the first electrode 21 are easier to obtain during continuous production than products with only the tail section provided with expandable tape.

[0099] Please refer to Figures 2 and 13 in combination. The electrochemical device may further include an insulating support member 70. The insulating support member 70 is inserted into the central hole 20a of the electrode assembly 20 so that the insulating support member 70 is at least partially disposed in the central hole 20a of the electrode assembly 20. On the one hand, this is conducive to compressing the first electrode piece 21, the isolation membrane 25 and the second electrode piece 23. On the other hand, it can also support the first expansion tape 50 and the electrode assembly 20 to expand outward along the radial direction of the electrode assembly 20 when the first expansion tape 50 expands and when the electrode assembly 20 expands during subsequent cyclic charge and discharge processes, thereby facilitating the improvement of the stability of the electrical connection between the first electrode piece 21 and the connecting wall 15 of the shell 10.

[0100] The material of the insulating support member 70 may include but is not limited to at least one of polypropylene or polyethylene, and the insulating support member 70 may be but is not limited to a cylinder, which can provide good support effects while also helping to reduce costs.

[0101] The electrochemical device 100 of any of the above embodiments may be applied to an electronic device. As shown in FIG14 , the electronic device 200 further includes a body 201 , and the electrochemical device 100 supplies power to the body 201 .

[0102] The electronic device 200 may be, but is not limited to, an electric toy, an electric vehicle, a mobile phone, a wearable device, a tablet, a computer, a drone, an energy storage device, etc.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. An electrochemical device, wherein: include: case; First expansion tape; an electrolyte contained in the housing; an electrode assembly, comprising a first electrode sheet, a second electrode sheet, and a separator disposed between the first electrode sheet and the second electrode sheet, the electrode assembly being a wound structure wound around a winding center axis and disposed within the housing, the outermost portion of the electrode assembly being the first electrode sheet; The first electrode sheet includes a first section and a second section, the first section being the tail section of the first electrode sheet, and the inner surface of the first section facing the winding center axis and the outer surface of the first section facing away from the winding center axis are both hollow foil areas, the second section is located at the secondary outer circle of the first electrode sheet, and is stacked and adjacent to the first section in the radial direction of the electrode assembly, and the outer surface of the second section facing away from the winding center axis is a hollow foil area; The first expansion tape is bonded to the inner surface of the first section and the outer surface of the second section, and the outer surface of the first section is abutted against the housing through the first expansion tape to achieve electrical connection between the first pole piece and the housing.

2. The electrochemical device according to claim 1, wherein The first expansion tape includes a first adhesive layer, a substrate, and a second adhesive layer stacked in sequence. The first adhesive layer is bonded to the first segment, and the second adhesive layer is bonded to the second segment.

3. The electrochemical device according to any one of claims 1 to 2, wherein: The first pole piece also includes a third section, which connects the first section and the second section. The inner surface of the third section facing the winding center axis and the outer surface facing away from the winding center axis are both empty foil areas. The first expansion tape is also bonded to the inner surface of the third section and the isolation film.

4. The electrochemical device according to claim 3, wherein The second pole piece is provided between the third section and the secondary outer circle of the first pole piece.

5. The electrochemical device according to any one of claims 1 to 2, wherein: The first pole piece also includes an extension section, which is located at the secondary outer circle of the first pole piece and connected to the second section. The outer surface of the extension section facing away from the winding center axis is a hollow foil area, and the first expansion tape is also bonded to the outer surface of the extension section and the isolation film.

6. The electrochemical device according to claim 5, wherein The second pole piece is provided between the extension section and the outermost circle of the first pole piece.

7. The electrochemical device according to any one of claims 3 to 6, wherein: The first expansion tape is wound around the winding central axis for at least one turn.

8. The electrochemical device according to claim 7, wherein The shell is cylindrical, the electrode assembly is cylindrical, the electrode assembly also includes a pole ear, the second pole piece has a connection area, the connection area is connected to the pole ear, the first expansion tape has a first notch, and in the radial direction of the electrode assembly, the first notch is stacked corresponding to the connection area.

9. The electrochemical device according to claim 8, wherein The first expansion tape further has a second notch. In the radial direction of the electrode assembly, the second notch is stacked and corresponds to the connection area, and the second notch and the first notch are respectively located on opposite sides of the connection area.

10. The electrochemical device according to any one of claims 1 to 9, wherein The electrode assembly has a central hole. Along the winding central axis, the projection of the winding central axis is located within the projection of the central hole. The electrochemical device further includes an insulating support member, which is at least partially disposed within the central hole.

11. The electrochemical device according to claim 10, wherein The insulating support member is cylindrical, and the material of the insulating support member includes at least one of polypropylene or polyethylene.

12. The electrochemical device according to claim 1, wherein The first pole piece also includes a third section, which connects the first section and the second section, and the outer surface of the third section facing away from the winding center axis is a hollow foil area. The electrochemical device also includes a bonding member, one end of the bonding member is bonded to the outer surface of the first section, and the other end is bonded to the outer surface of the third section.

13. The electrochemical device according to claim 12, wherein The bonding member is a conductive adhesive film, and both the inner surface of the bonding member facing the winding central axis and the outer surface of the bonding member facing away from the winding central axis are conductive and electrically connected.

14. The electrochemical device according to any one of claims 12 to 13, wherein: The shell is cylindrical, the electrode assembly is cylindrical, and in the radial direction of the electrode assembly, the adhesive member located on the outer surface of the first section overlaps with the first expansion tape located on the inner surface of the first section.

15. The electrochemical device according to claim 14, wherein In the winding direction, the tail end of the first pole piece exceeds the tail end of the first expansion tape.

16. The electrochemical device according to claim 15, wherein In the winding direction, the length of the portion where the adhesive member is bonded to the outer surface of the first segment is L, and the distance between the tail end of the first expansion tape and the tail end of the first pole piece is less than or equal to L / 2.

17. The electrochemical device according to any one of claims 12 to 16, wherein: The bonding piece is a single-sided adhesive.

18. The electrochemical device according to any one of claims 3 to 6, wherein: The isolation membrane includes a first diaphragm and a second diaphragm stacked between the outermost circle of the first pole piece and the secondary outer circle of the first pole piece. The first diaphragm is located between the second diaphragm and the first expansion tape. In the winding direction, the tail end of the first diaphragm is bonded to the first expansion tape, and the tail end of the second diaphragm exceeds the tail end of the first diaphragm and is bonded to the first expansion tape.

19. The electrochemical device according to any one of claims 1 to 13, wherein: The tail end of the first expansion tape exceeds the tail end of the first pole piece along the winding direction, or the tail end of the first expansion tape is flush with the tail end of the first pole piece.

20. The electrochemical device according to claim 19, wherein The first pole piece further includes a fourth section, which is a starting section of the first pole piece. A second expansion tape is bonded to a surface of the starting section facing the winding center axis.

21. The electrochemical device according to claim 20, wherein A starting end of the second expansion tape is flush with a starting end of the fourth section.

22. The electrochemical device according to any one of claims 1 to 21, wherein The first electrode sheet is a negative electrode sheet, and the negative electrode sheet includes a negative electrode current collector, and the negative electrode current collector is copper foil.

23. The electrochemical device according to claim 22, wherein: The thickness of the first expansion tape is 10 μm to 50 μm. The negative electrode plate further includes a negative electrode active layer. The negative electrode active layer includes silicon material. The weight percentage of the silicon material in the negative electrode active layer is 3% to 100%.

24. The electrochemical device according to any one of claims 1 to 23, wherein: The material of the first expansion tape includes at least one of polyisoprene, polybutadiene or thermoplastic polyurethane elastomer, and the material of the first expansion tape also includes at least one of acrylic glue, rubber or silicone.

25. The electrochemical device according to claim 13, wherein The conductive adhesive film comprises an adhesive layer matrix and a conductor, and the conductor is dispersed in the adhesive layer matrix.

26. The electrochemical device according to claim 24, wherein The adhesive layer matrix includes at least one of silicone rubber, polyurethane rubber, chloroprene rubber, hot melt adhesive or tackifying resin, and the conductor includes at least one of gold, silver, copper, aluminum, nickel or graphite.

27. The electrochemical device according to any one of claims 1 to 11 and 18 to 24, wherein: The tail end of the first pole piece is in direct contact with the housing.

28. The electrochemical device according to claim 1, wherein The second pole piece and the isolation film are not provided between the first section and the second section.

29. An electronic device comprising a body, wherein: The electronic device further comprises an electrochemical device according to any one of claims 1 to 28, wherein the electrochemical device supplies power to the body.

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