Cylindrical battery and electronic device

Abstract

The present application discloses a cylindrical battery and an electronic device. The cylindrical battery comprises a case and an electrode assembly. The electrode assembly is arranged in the case, and the electrode assembly comprises a first electrode sheet. The first electrode sheet comprises a first hollow foil portion; the first hollow foil portion consists of a first part and a second part; the first part extends in a winding direction of the electrode assembly; the second part is formed by bending part of the first hollow foil portion in a direction in which the tail end of the first electrode sheet is close to a first end wall; the second part is connected to the first part and the first end wall of the case; and the area where the second part is connected to the first end wall is a first area. A first edge is provided at the position where the first part is connected to the second part, the first part is provided with a second edge and a third edge, and the first edge intersects the third edge to form a first folding point. The minimum distance between the first end wall and a second end wall of the case is H, the inner radius of a surrounding wall of the case is R, and the minimum distance from the first folding point to the first area is L1, wherein H+R≤L1. The service life of the cylindrical battery is prolonged by providing the second part.

Description

Cylindrical batteries and electronic devices Technical Field

[0001] This application belongs to the field of energy storage technology, and specifically relates to a cylindrical battery and electronic device. Background Technology

[0002] Currently, cylindrical batteries typically consist of an electrode assembly and a casing. The electrode assembly, which includes a positive electrode and a negative electrode, is housed within the casing. The positive electrode is fixed to the casing via an adapter, and the negative electrode is fixed to the casing via another adapter. During the charging and discharging process of a cylindrical battery, the electrode assembly repeatedly expands and contracts, causing the positive and negative electrodes to be repeatedly stretched. This can easily lead to electrode breakage, resulting in the failure of the cylindrical battery. Summary of the Invention

[0003] In view of the above situation, it is necessary to provide a cylindrical battery and electronic device that can reduce the possibility of tearing or breakage of the electrode assembly.

[0004] A first aspect of this application provides a cylindrical battery, including a housing and an electrode assembly. The housing includes a first end wall, a second end wall, and a surrounding wall. The first end wall and the second end wall are disposed opposite each other along a first direction. The surrounding wall connects the first end wall and the second end wall and together with the first end wall and the second end wall, encloses a first space. The electrode assembly is disposed in the first space and includes a first electrode, a second electrode, and a separator. The first electrode, the separator, and the second electrode are stacked and wound to form a wound structure. The winding center axis of the electrode assembly is in the first direction. The first electrode includes a first current collector and a first active material layer stacked together. The first current collector includes a first empty foil portion located on the outermost ring of the winding structure of the first electrode. The first empty foil portion is not covered by the first active material layer. The first empty foil portion consists of a first part and a second part. The first part extends along the winding direction of the electrode assembly. The second part includes the end of the first electrode and is formed by bending the first empty foil portion. The end of the first electrode is located between the first end wall and the electrode assembly. The second part connects the first part and the first end wall. The area where the second part connects to the first end wall is the first region. The connection between the first part and the second part has a first side. The first part has a second side and a third side arranged opposite to each other along a first direction. The second side is closer to the first end wall than the third side. The first side and the third side intersect to form a first fold point. The distance between the first end wall and the second end wall along the first direction is H, and the inner radius of the enclosure is R. Along the extension direction of the second part, the minimum distance from the first fold point to the first region is L1, where H+R≤L1.

[0005] In this cylindrical battery, the minimum distance from the first fold point to the first region is greater than the sum of the height of the electrode assembly along the first direction and the inner radius of the enclosure. When the electrode assembly expands in volume during charging and discharging, under the action of internal stress, the first part moves in the opposite direction along the winding direction of the electrode assembly, and drives the second part to move, so that the second part changes to a tighter state than the original state, thereby releasing at least a part of the stress. This helps to reduce the possibility of the first electrode sheet tearing or breaking due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery.

[0006] In one optional embodiment of this application, the cross-section of the electrode assembly perpendicular to the first direction is annular, with an outer radius of R1 and an inner radius of R2, where L1 ≤ H + R + 30%π(R1 + R2). Setting L1 ≤ H + R + 30%π(R1 + R2) prevents the portion of the second part located between the first end wall and the electrode assembly from becoming excessively long, thus reducing the risk of the second part compressing the surface of the electrode assembly facing the first end wall and causing a poor K value.

[0007] In an optional embodiment of this application, H+R+10%π(R1+R2)≤L1≤H+R+20%π(R1+R2). Setting L1≥H+R+10%π(R1+R2) helps to further reduce the possibility of the first electrode sheet tearing or breaking due to internal stress accumulation; setting L1≤H+R+20%π(R1+R2) helps to further reduce the risk of the second part of the extruded electrode assembly facing the first end wall and causing poor K value.

[0008] In an optional embodiment of this application, the cylindrical battery includes a first adhesive and a second adhesive, both of which adhere to a first portion and a second portion. The first adhesive is adhered to the surfaces of the first and second portions facing the surrounding wall, and the second adhesive is adhered to the surfaces of the first and second portions facing the winding central axis. The first adhesive covers at least a portion of the edges of the first portion and a portion of the edges of the second portion; the second adhesive covers at least a portion of the edges of the first portion and a portion of the edges of the second portion. The first and second adhesives help maintain the stacked state of the first and second portions along the thickness direction of the first electrode, improve the stability of the second portion during connection with the first end wall, and facilitate operation by processing equipment. The second adhesive covers at least a portion of the edges of the first portion and a portion of the edges of the second portion. The first and second adhesives also help reduce the possibility of burrs on the edges of the first and second portions piercing the separator and causing an internal short circuit.

[0009] In an optional embodiment of this application, the projection of the second side onto the second portion along the thickness direction of the first electrode sheet is a first projection line. The first adhesive has a fourth side, which is disposed opposite to the first projection line along a first direction, and the fourth side is closer to the first region than the first projection line. The distance between the first projection line and the fourth side along the extension direction of the second portion is d1, and the width of the first portion along the first direction is W, where 5%W≤d1≤70%W. Setting d1≥5%W ensures that the length of the edge of the second portion covered by the first adhesive is not too short, which helps to reduce the possibility of burrs on the edge of the second portion puncturing the release membrane. Setting d1≤70%W ensures that the distance between the first adhesive and the first region is not too close, which facilitates the connection between the second portion and the first end wall and reduces the probability of poor connection between the second portion and the first end wall due to the presence of the first adhesive.

[0010] In an optional embodiment of this application, the projection of the second side onto the second portion along the thickness direction of the first electrode sheet is a first projection line. The second adhesive has a fifth side, which is disposed opposite to the first projection line along a first direction, and the fifth side is closer to the first region than the first projection line. The distance between the first projection line and the fifth side along the extension direction of the second portion is d2, and the width of the first portion along the first direction is W, where 5%W≤d2≤70%W. Setting d2≥5%W ensures that the length of the edge of the second portion covered by the second adhesive is not too short, which helps to reduce the possibility of burrs on the edge of the second portion puncturing the release membrane. Setting d2≤70%W ensures that the distance between the second adhesive and the first region is not too close, which facilitates the connection between the second portion and the first end wall and reduces the probability of poor connection between the second portion and the first end wall due to the presence of the second adhesive.

[0011] In one optional embodiment of this application, the second part includes a connecting portion and a transition portion. The connecting portion and the first part are integrally formed. The transition portion connects to the connecting portion and is connected to the first end wall. The area where the transition portion connects to the first end wall is a first region, and the area where the connecting portion connects to the transition portion is a second region. The first region and the second region are separate. Providing a transition portion is beneficial for improving the current carrying capacity of the first electrode.

[0012] In one optional embodiment of this application, the adapter is welded to the connecting portion and the adapter is welded to the first end wall. Along the extension direction of the second portion, the minimum distance between the first region and the second region is L2, where 1 / 5R ≤ L2 ≤ 3 / 5R. Setting L2 ≥ 1 / 5R prevents the distance between the first region and the second region from being too small, which helps reduce the possibility of the adapter being damaged due to two welding operations. Setting L2 ≤ 3 / 5R prevents the distance between the first region and the second region from being too large, and prevents the length of the adapter from being too long, which can reduce the possibility of the adapter itself stacking along the first direction. This helps reduce the risk of the adapter pressing the surface of the electrode assembly facing the first end wall, thus causing poor K-value.

[0013] In an optional embodiment of this application, the adapter is welded to the connecting portion. The cylindrical battery further includes a third adhesive member, which bonds the connecting portion and the adapter, and is located on the side of the connecting portion and the adapter facing the winding structure. Along the thickness direction of the adapter, the third adhesive member covers a second region, and the third adhesive member is separate from the first region. Along the extension direction of the second portion, the minimum distance between the third adhesive member and the first region is L3, where 1 / 5R ≤ L3 ≤ 2 / 5R. Providing a third adhesive member helps reduce the possibility of the weld point formed by the welding of the adapter and the connecting portion puncturing the separator and causing an internal short circuit in the electrode assembly; setting L3 ≥ 1 / 5R ensures that the distance between the third adhesive member and the first region is not too small, which helps reduce the possibility that the placement of the third adhesive member will affect the effective electrical connection between the adapter and the first end wall; setting L3 ≤ 2 / 5R ensures that the distance between the third adhesive member and the first region is not too far, which helps increase the coverage area of ​​the third adhesive member, thereby improving the bonding stability of the third adhesive member.

[0014] In an optional embodiment of this application, the second part is a folded structure. After a portion of the first empty foil portion is bent in a direction that brings the end of the first electrode sheet closer to the first end wall, the second part includes a sixth side and a seventh side disposed opposite to each other along the winding direction of the electrode assembly. The sixth side and the second side are on the same sideline of the first current collector, and the seventh side and the third side are on the same sideline of the first current collector. The folded structure is formed by bending a portion of the first empty foil portion in a direction that brings the end of the first electrode sheet closer to the first end wall, and then folding the second part so that the sixth side is close to the first part. The height of the electrode assembly along the first direction is h, where h ≥ 4R / 3. h ≥ 4R / 3 means that the width of the first electrode sheet is greater than or equal to 4R / 3. The second part is wider than the inner diameter of the surrounding wall. With the projected area of ​​the second region along the first direction remaining unchanged, the second part is folded and then connected to the first end wall. Compared to the case where the second part is not folded and is directly connected to the first end wall, the proportion of the second part connected to the first end wall is increased, which is beneficial to improving the stability of the connection between the second part and the first end wall.

[0015] In one optional embodiment of this application, along the thickness direction of the first electrode sheet, a portion of the second portion is located on the side of the first portion facing the enclosure wall, and a portion of the second portion is located on the side of the first portion facing the winding center of the electrode assembly. This helps to reduce the resistance encountered by the first portion in moving the second portion due to the folded state of the second portion.

[0016] In an optional embodiment of this application, the second part includes a sixth side and a seventh side disposed opposite to each other along the winding direction of the electrode assembly. The sixth side and the second side are on the same sideline of the first current collector, and the seventh side and the third side are on the same sideline of the first current collector. The angle between the first side and the seventh side is α, where 40°≤α≤70°. Setting α≥40° ensures that α is not too small, facilitating the movement of the second part by the first part. Setting α≤70° ensures that α is not too large, facilitating the connection between the second part and the first end wall, and reducing the possibility of an internal short circuit caused by the angle of the end of the second part connected to the first end wall being inserted into the winding structure of the electrode assembly.

[0017] In an optional embodiment of this application, the second electrode includes a second current collector and a second active material layer stacked together. The second current collector includes a second empty foil portion located at the outermost ring of the winding structure of the second electrode. The second empty foil portion is not covered by the second active material layer. The second empty foil portion is composed of a third part and a fourth part. The third part extends along the winding direction of the electrode assembly, and the fourth part includes the end of the second electrode. The fourth part is formed by bending a portion of the second empty foil portion in a direction that brings the end of the second electrode closer to the second end wall. The fourth part connects the third part and the second end wall. The area where the fourth part connects to the second end wall is the third region. The connection between the third part and the fourth part has an eighth side. The third part has a ninth side and a tenth side disposed opposite each other along a first direction. The tenth side is closer to the first end wall than the ninth side. The ninth side intersects with the eighth side to form a second folding point. Along the extension direction of the fourth part, the minimum distance from the second folding point to the third region is L4, where H+R≤L4. The minimum distance from the second fold point to the third region is greater than the sum of the height of the electrode assembly along the first direction and the inner radius of the enclosure. When the electrode assembly expands in volume during charging and discharging, under the action of internal stress, the third part moves in the opposite direction along the winding direction of the electrode assembly and drives the fourth part to move, so that the fourth part changes to a tighter state than the original state, thereby releasing at least a part of the stress. This helps to reduce the possibility of the second electrode sheet tearing or breaking due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery.

[0018] In an optional embodiment of this application, one of the first electrode and the second electrode is a negative electrode. The negative electrode includes a stacked negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer includes silicon, and the mass content of silicon is more than 3% based on the mass of the negative electrode active material layer. Compared with a silicon-free electrode, the silicon-containing electrode undergoes greater volume change and generates greater internal stress in the electrode assembly during charging and discharging. By providing the second part, it is beneficial to reduce the possibility of tearing or breakage of the first electrode.

[0019] A second aspect of the embodiments of this application provides an electronic device comprising a cylindrical battery as described in any of the foregoing embodiments. Attached Figure Description

[0020] Figure 1 is a schematic diagram of the structure of a cylindrical battery in one embodiment of this application.

[0021] Figure 2 is a cross-sectional view of a cylindrical battery in one embodiment of this application.

[0022] Figure 3 is a schematic diagram of the structure of the electrode assembly in one embodiment of this application.

[0023] Figure 4 is a schematic diagram of the structure of the first electrode in one state in one embodiment of this application.

[0024] Figure 5 is a schematic diagram of the structure in one embodiment of this application, showing the first electrode sheet flattened and connected to the first end wall.

[0025] Figure 6 is a schematic diagram of the structure of a cylindrical battery in one embodiment of this application.

[0026] Figure 7 is a schematic diagram of the structure in the first embodiment of this application, where the first electrode is flattened and connected to the first end wall.

[0027] Figure 8 is a schematic diagram of the structure when the second part is in a folded state in one embodiment of this application.

[0028] Figure 9 is a schematic diagram of the structure of the second part before it is folded in one embodiment of this application.

[0029] Figure 10 is a schematic diagram of the structure when the second part is in a folded state in one embodiment of this application.

[0030] Figure 11 is a schematic diagram of the structure of the second part before it is folded in one embodiment of this application.

[0031] Figure 12 is a schematic diagram of the structure of the second electrode in one state and connected to the second end wall in one embodiment of this application.

[0032] Figure 13 is a schematic diagram of the structure of the second electrode in one state and connected to the second end wall in one embodiment of this application.

[0033] Figure 14 is a schematic diagram of the structure of an electronic device in one embodiment of this application.

[0034] Key Component Symbols: Cylindrical Battery 100; Casing 10; First End Wall 11; First Surface 111; Enclosure 12; Second End Wall 13; Cover 131; Terminal Post 132; First Segment 1321; Second Segment 1322; Third Segment 1323; Second Surface 13231; Insulator 14; First Space 15; Electrode Assembly 20; First Electrode 21; First Current Collector 211; First Empty Foil Section 2111; First Part 2112; Second Side 21121; First Projection Line 21121a; Third Side 21122; Second Part 2113; Sixth Side 21131; Seventh Side 21132; First Side 2114; First Crease 2114a; First Folding Point 2114b; First Region2115 Second crease 2115a Connecting part 2116 Adapter part 2117 Second region 2118 Third crease 2118a First active material layer 212 Second electrode 22 Second current collector 221 Second active material layer 222 Second empty foil part 2221 Third part 2222 Ninth side 22221 Tenth side 22222 Fourth part 2223 Eighth side 2224 Fourth crease 2224a Second folding point 2224b Third region 2225 Separator 23 First adhesive 30 Fourth side 31 Second adhesive 40 Fifth side 41 Third adhesive 50 First adapter 60 First direction X Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0036] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0038] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0039] In the description of the embodiments of this application, the term "perpendicular" is used to describe the ideal state between two components. In actual production or use, two components may exist in a state that is approximately perpendicular. The two components described as "perpendicular" may not be absolutely straight lines or planes, but may be approximately straight lines or planes. From a macroscopic perspective, if the overall extension direction is a straight line or plane, the component can be considered as a "straight line" or "plane".

[0040] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. Where there is no conflict, the various embodiments in this application can be combined with each other.

[0041] This application provides a cylindrical battery, including a housing and an electrode assembly. The housing includes a first end wall, a second end wall, and a surrounding wall. The first end wall and the second end wall are disposed opposite each other along a first direction. The surrounding wall connects the first end wall and the second end wall and together with the first end wall and the second end wall, encloses a first space. The electrode assembly is disposed in the first space and includes a first electrode, a second electrode, and a separator. The first electrode, the separator, and the second electrode are stacked and wound to form a wound structure. The winding center axis of the electrode assembly is in the first direction. The first electrode includes a first current collector and a first active material layer stacked together. The first current collector includes a first empty foil portion located at the outermost ring of the wound structure of the first electrode. The first empty foil portion is not covered by the first active material layer. The first empty foil portion is composed of a first part and a second part. The first part extends along the winding direction of the electrode assembly. The second part includes the end of the first electrode. The second part is formed by bending the first empty foil portion. The end of the first electrode is located between the first end wall and the electrode assembly. The second part connects the first part and the first end wall. The area where the second part connects with the first end wall is the first region. The first part and the second part are connected by a first side. The first part has a second side and a third side that are arranged opposite each other along a first direction. The second side is closer to the first end wall than the third side. The first side and the third side intersect to form a first fold point. The distance between the first end wall and the second end wall along the first direction is H, and the inner radius of the enclosure is R. Along the extension direction of the second part, the minimum distance from the first fold point to the first region is L1, where H+R≤L1.

[0042] In this cylindrical battery, the minimum distance from the first fold point to the first region is greater than the sum of the height of the electrode assembly along the first direction and the inner radius of the enclosure. When the electrode assembly expands in volume during charging and discharging, under the action of internal stress, the first part moves in the opposite direction along the winding direction of the electrode assembly, and drives the second part to move, so that the second part changes to a tighter state than the original state, thereby releasing at least a part of the stress. This helps to reduce the possibility of the first electrode sheet tearing or breaking due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery.

[0043] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0044] As shown in Figure 1, an embodiment of this application provides a cylindrical battery 100.

[0045] In some embodiments, the cylindrical battery 100 is a button battery.

[0046] In some embodiments, as shown in Figures 1 and 2, the cylindrical battery 100 includes a housing 10 and an electrode assembly 20, the electrode assembly 20 being housed within the housing 10.

[0047] In some embodiments, as shown in FIG2, the housing 10 includes a first end wall 11, a second end wall 13, and a surrounding wall 12. The first end wall 11 and the second end wall 13 are disposed opposite to each other along a first direction X. The surrounding wall 12 connects the first end wall 11 and the second end wall 13 and together with the first end wall 11 and the second end wall 13, it encloses a first space 15. The electrode assembly 20 is disposed in the first space 15.

[0048] It should be noted that the first end wall 11, the second end wall 13, and the surrounding wall 12 are divisions of the overall structure of the housing 10, and do not mean that the housing 10 is composed of three independent components before they are connected. For example, in some embodiments, the surrounding wall 12 and the first end wall 11 are an integral structure.

[0049] In some embodiments, as shown in FIG2, the second end wall 13 includes a cover 131 and an electrode post 132. The electrode post 132 includes a first segment 1321, a second segment 1322, and a third segment 1323 of an integral structure. The second segment 1322 is located between the first segment 1321 and the third segment 1323 and connects the first segment 1321 and the third segment 1323, making the electrode post 132 in the shape of an "I". The cover 131 has a through hole in the middle, through which the second segment 1322 passes. The first segment 1321 is located outside the first space 15, and the third segment 1323 is located inside the first space 15. An insulating member 14 is also provided between the cover 131 and the electrode post 132 to insulate the cover 131 from the electrode post 132.

[0050] In some embodiments, as shown in FIG2, the electrode assembly 20 includes a first electrode 21, a second electrode 22 and an isolation film 23. The first electrode 21, the isolation film 23 and the second electrode 22 are stacked and wound to form a winding structure. The winding center axis direction of the electrode assembly 20 is the first direction X.

[0051] In some embodiments, as shown in FIG2, the first electrode 21 includes a first current collector 211 and a first active material layer 212 stacked together. Specifically, there are two first active material layers 212, which are coated on opposite sides of the first current collector 211 along the thickness direction of the first electrode 21.

[0052] In some embodiments, as shown in FIG2, the second electrode 22 includes a second current collector 221 and a second active material layer 222 stacked together. Specifically, there are two second active material layers 222, which are coated on opposite sides of the second current collector 221 along the thickness direction of the second electrode 22.

[0053] In some embodiments, one of the first current collector 211 and the second current collector 221 is a positive current collector and the other is a negative current collector.

[0054] In some embodiments, both the positive current collector and the negative current collector are metal layers. As an example, the positive current collector may be a metal layer comprising at least one of aluminum, nickel, tantalum, and titanium, such as aluminum foil. The negative current collector may be a metal layer comprising at least one of copper, nickel, tantalum, and titanium, such as copper foil.

[0055] In some embodiments, one of the first active material layer 212 and the second active material layer 222 is a positive electrode active material layer, which includes a positive electrode active material, and the other is a negative electrode active material layer, which includes a negative electrode active material.

[0056] In some embodiments, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.

[0057] In some embodiments, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, and silicon-carbon materials.

[0058] In some embodiments, the separator 23 is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0059] In some embodiments, the cylindrical battery 100 further includes an electrolyte (not shown) contained in a first space 15.

[0060] In some embodiments, the electrolyte is any one of gel, solid, and liquid states.

[0061] In some embodiments, the electrolyte comprises a lithium salt and a non-aqueous solvent.

[0062] In some embodiments, the lithium salt includes at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, or LiPO2F2.

[0063] In some embodiments, the non-aqueous solvent includes at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, nitrile compounds, or other organic solvents. For example, the carbonate compound may include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate.

[0064] In Figures 4 to 11 of this application, to clearly illustrate the structure of the first electrode 21 and the second electrode 22, the first electrode 21 and the second electrode 22 are presented in a fully or partially flattened state. When the first electrode 21 and the second electrode 22 are in a wound state, the first electrode 21 and the second electrode 22 are wound along their respective length directions.

[0065] In some embodiments, as shown in Figures 2 to 4, the first current collector 211 includes a first empty foil portion 2111 located at the outermost ring of the winding structure of the first electrode 21. The first empty foil portion 2111 is not covered by the first active material layer 212. The first empty foil portion 2111 is composed of a first part 2112 and a second part 2113. The first part 2112 extends along the winding direction of the electrode assembly 20, and the second part 2113 includes the end of the first electrode 21. The second part 2113 is formed by bending the first empty foil portion 2111. The end of the first electrode 21 is located between the first end wall 11 and the electrode assembly 20, and the second part 2113 connects the first part 2112 and the first end wall 11. Here, the end of the first electrode 21 refers to the tail end of the first electrode 21 in its winding structure, that is, the end of the first electrode 21 located at the outermost ring of its winding structure.

[0066] In some embodiments, the second portion 2113 is located on the side of the first portion 2112 along the thickness direction of the first electrode 21 toward the winding center of the electrode assembly 20; in other embodiments, the second portion 2113 is located on the side of the first portion 2112 along the thickness direction of the first electrode 21 toward the enclosure 12.

[0067] In some embodiments, as shown in Figures 4 and 5, the connection between the first portion 2112 and the second portion 2113 has a first side 2114. The first portion 2112 has a second side 21121 and a third side 21122 disposed opposite to each other along a first direction X. The second side 21121 is closer to the first end wall 11 than the third side 21122. The first side 2114 intersects the third side 21122 to form a first fold point 2114b.

[0068] Here, the first edge 2114 is a crease (defined as the first crease 2114a) formed by bending the first empty foil portion 2111 to form the second portion 2113, or the first edge 2114 is an extension of the first crease 2114a. Specifically, as shown in Figure 4, the first crease 2114a can be observed when the first empty foil portion 2111 is flattened. Figure 4 shows a complete first crease 2114a, where the first crease 2114a intersects both the second side 21121 and the third side 21122. In this case, the first crease 2114a is the first side 2114. However, in some embodiments of this application, the first crease 2114a is incomplete, meaning it intersects only one of the second side 21121 and the third side 21122, or it does not intersect either of them. In this case, an extension segment can be drawn along the extension direction of the first crease 2114a. This extension segment intersects both the second side 21121 and the third side 21122, and the intersection points of the extension segment with these two sides are the two endpoints of this extension segment. This extension segment is then used as the first side 2114. The first side 2114 is the boundary line between the first part 2112 and the second part 2113.

[0069] In some embodiments, as shown in Figures 2 and 5, the area where the second portion 2113 connects to the first end wall 11 is the first region 2115. The distance between the first end wall 11 and the second end wall 13 along the first direction X is H, the inner radius of the enclosure wall 12 is R, and the minimum distance from the first folding point 2114b to the first region 2115 along the extension direction of the second portion 2113 is L1, where H+R≤L1. The extension direction of the second portion 2113 is the length direction of the first electrode 21 in its flattened state.

[0070] In this embodiment, the minimum distance from the first folding point 2114b to the first region 2115 is greater than the sum of the height of the electrode assembly 20 along the first direction X and the inner radius of the enclosure 12. When the electrode assembly 20 expands in volume during charging and discharging, under the action of internal stress, the first part 2112 moves in the opposite direction of the winding direction of the electrode assembly 20, and drives the second part 2113 to move, so that the second part 2113 changes to a tighter state than the original state, thereby releasing at least a part of the stress, which helps to reduce the possibility of the first electrode 21 tearing or breaking due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery 100.

[0071] The method for measuring the distance H along the first direction X between the first end wall 11 and the second end wall 13 is as follows:

[0072] The first end wall 11 has a first surface 111 located in the first space 15. The second end wall 13 has a second surface 13231 located in the first space 15. The first surface 111 and the second surface 13231 are arranged opposite each other along the first direction X. The minimum distance H between the first end wall 11 and the second end wall 13 along the first direction X refers to the distance between the first surface 111 and the second surface 13231 along the first direction X. When measuring H, the cylindrical battery 100 is scanned using a computed tomography (CT) instrument, and H is measured.

[0073] The inner radius R of the enclosure 12 is measured by scanning the cylindrical battery 100 with a computed tomography (CT) instrument and measuring the inner diameter of the enclosure 12. R is half the length of the inner diameter.

[0074] The method for measuring the minimum distance L1 from the first inflection point 2114b to the first region 2115 is as follows:

[0075] Take a slice of the first electrode 21 containing the first fold point 2114b and the second part 2113. To ensure the integrity of the first region 2115, the first end wall 11 is removed along with the slice and remains connected to the second part 2113. Flatten the slice of the first electrode 21 and pull the second part 2113 in a direction that tends to separate the second part 2113 from the first end wall 11 until the second part 2113 is limited by the first region 2115 and cannot be pulled any further. Press down on the second part 2113 so that the second part 2113 and the first end wall 11 are stacked along the thickness direction of the first electrode 21, thereby forming a crease. This crease is defined as the second crease 2115a (as shown in Figure 5). The second crease 2115a is perpendicular to the edge line of the second part 2113 along the width direction of the first electrode 21, and the second crease 2115a passes through a point on the edge of the first region 2115 facing the first part 2112. The slice of the first electrode 21 is flattened, and the length from the first fold point 2114b to the second crease 2115a along the length direction of the first electrode 21 is measured and recorded as L1. Measurement can be performed using an optical microscope (OMM).

[0076] In some embodiments, as shown in Figures 2 and 3, the cross-section of the electrode assembly 20 perpendicular to the first direction X is annular, with an outer radius of R1 and an inner radius of R2, where L1 ≤ H + R + 30%π(R1 + R2). Since H + R ≤ L1, the portion of the second part 2113 extending beyond the height of the electrode assembly 20 along the first direction is housed between the first end wall 11 and the electrode assembly 20. By setting L1 ≤ H + R + 30%π(R1 + R2), the portion of the second part 2113 located between the first end wall 11 and the electrode assembly 20 is not excessively long, which helps reduce the risk of the second part 2113 compressing the surface of the electrode assembly 20 facing the first end wall 11 and causing a poor K-value. Here, K-value refers to the voltage drop of the cylindrical battery 100 per unit time.

[0077] The outer radius R1 of the electrode assembly 20 is measured as follows: the cylindrical battery 100 is scanned using a computed tomography (CT) instrument, and the outer diameter of the electrode assembly 20 is measured. Half of the length of the outer diameter is the outer radius R1. The thickness of the second part must be included when measuring the outer diameter.

[0078] The outer radius R2 of the electrode assembly 20 is measured by scanning the cylindrical battery 100 with a computed tomography (CT) instrument and measuring the inner diameter of the electrode assembly 20. Half of the length of the inner diameter is the inner diameter R2.

[0079] It should be noted that when measuring R1, the measurement is performed based on the outermost current collector (first current collector 211 or second current collector 221) of the winding structure of the electrode assembly 20, and when measuring R2, the measurement is performed based on the innermost current collector (first current collector 211 or second current collector 221) of the winding structure of the electrode assembly 20.

[0080] It should be added that, in the embodiments of this application, the value of π is 3.14.

[0081] In some embodiments, H+R+10%π(R1+R2)≤L1≤H+R+20%π(R1+R2). Setting L1≥H+R+10%π(R1+R2) helps to further reduce the possibility of the first electrode 21 tearing or breaking due to internal stress accumulation; setting L1≤H+R+20%π(R1+R2) helps to further reduce the risk of the second part 2113 extruding the surface of the electrode assembly 20 facing the first end wall 11 and causing poor K value.

[0082] In some embodiments, the second portion 2113 is welded to the first end wall 11.

[0083] In some embodiments, the second portion 2113 is bonded to the first end wall 11 with conductive adhesive.

[0084] In some embodiments, as shown in FIG4, the cylindrical battery 100 includes a first adhesive member 30 and a second adhesive member 40. Both the first adhesive member 30 and the second adhesive member 40 are bonded to a first portion 2112 and a second portion 2113. The first adhesive member 30 is bonded to the surfaces of the first portion 2112 and the second portion 2113 facing the enclosure wall 12, and the second adhesive member 40 is bonded to the surfaces of the first portion 2112 and the second portion 2113 facing the winding central axis of the electrode assembly 20. In FIG4, the projections of the first adhesive member 30 and the second adhesive member 40 along the thickness direction of the first electrode 21 coincide. The first adhesive member 30 and the second adhesive member 40 help maintain the stacked state of the first part 2112 and the second part 2113 along the thickness direction of the first electrode 21, improve the stability of the second part 2113 during the connection process with the first end wall 11, and facilitate the operation of the processing equipment. The first adhesive member 30 covers at least a portion of the edges of the first part 2112 and a portion of the edges of the second part 2113; the second adhesive member 40 covers at least a portion of the edges of the first part 2112 and a portion of the edges of the second part 2113. The first adhesive member 30 and the second adhesive member 40 help reduce the possibility of burrs on the edges of the first part 2112 and the second part 2113 piercing the separator 23 and causing an internal short circuit.

[0085] It should be noted that the adhesion of the first adhesive 30 and the second adhesive 40 weakens after being wetted by the electrolyte. This does not affect the change in the relative position of the first part 2112 and the second part 2113, that is, it does not affect the first part 2112 from driving the second part 2113 to move in order to release stress.

[0086] In some embodiments, as shown in FIG4, the first adhesive 30 is an adhesive tape.

[0087] In some embodiments, the first adhesive member 30 includes a first adhesive portion and a second adhesive portion, both of which are generally rectangular. The first adhesive portion adheres to a first portion 2112 and a second portion 2113, and is adhered to the surfaces of the first portion 2112 and the second portion 2113 facing the enclosure wall 12. Along the width direction of the first portion 2112, the two edges of the first adhesive portion extend beyond the second side 21121 and the third side 21122, respectively. The second adhesive portion adheres to the first adhesive portion and the second portion 2113, and is adhered to the surfaces of the first adhesive portion and the second portion 2113 facing the enclosure wall 12. Along the width direction of the second portion 2113, both edges of the second adhesive portion extend beyond the edges of the second portion 2113. Both the first adhesive portion and the second adhesive portion are adhesive tape.

[0088] In some embodiments, as shown in FIG4, the second adhesive 40 is an adhesive tape.

[0089] In some embodiments, the second adhesive member 40 includes a third adhesive portion and a fourth adhesive portion, both of which are generally rectangular. The third adhesive portion adheres to the first portion 2112 and the second portion 2113, and is bonded to the surfaces of the first portion 2112 and the second portion 2113 facing the winding center of the electrode assembly 20. Along the width direction of the first portion 2112, the two edges of the third adhesive portion extend beyond the second side 21121 and the third side 21122, respectively. The fourth adhesive portion adheres to the third adhesive portion and the second portion 2113, and is bonded to the surfaces of the third adhesive portion and the second portion 2113 facing the winding center of the electrode assembly 20. Along the width direction of the second portion 2113, both edges of the fourth adhesive portion extend beyond the edges of the second portion 2113. Both the first adhesive portion and the second adhesive portion are adhesive tape.

[0090] In some embodiments, the adhesive tape includes a substrate layer and an adhesive layer, the adhesive layer being disposed on the surface of the substrate layer facing the first portion 2112 and the second portion 2113.

[0091] In some embodiments, the substrate layer may be selected from polyethylene terephthalate, co-extruded polypropylene, oriented polystyrene, thermoplastic polyurethane, polylactic acid, polyolefin, and polyimide.

[0092] In some embodiments, the adhesive layer is made of one or more of the following: natural rubber, styrene-butadiene rubber, isoprene rubber, styrene-polybutadiene-styrene block copolymer, hydrogenated styrene-polybutadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-polyisoprene-styrene block copolymer, polyisobutylene, amorphous α-olefin copolymer, petroleum resin, terpene resin, and rosin resin.

[0093] In some embodiments, as shown in FIG4, the projection of the second side 21121 along the thickness direction of the first electrode 21 onto the second portion 2113 is the first projection line 21121a; the first adhesive 30 has a fourth side 31, which is disposed opposite to the first projection line 21121a along the first direction X, and the fourth side 31 is closer to the first region 2115 than the first projection line 21121a; the distance between the first projection line 21121a and the fourth side 31 along the extension direction of the second portion 2113 is d1; the width of the first portion 2112 along the first direction X is W, where 5%W≤d1≤70%W. Setting d1 ≥ 5%W ensures that the length of the first adhesive 30 covering the edge of the second part 2113 is not too short, which helps reduce the possibility of burrs on the edge of the second part 2113 puncturing the release membrane 23. Setting d1 ≤ 70%W ensures that the distance between the first adhesive 30 and the first region 2115 is not too close, facilitating the connection between the second part 2113 and the first end wall 11 and reducing the probability of poor connection between the second part 2113 and the first end wall 11 due to the presence of the first adhesive 30. Here, poor connection situations include, but are not limited to: the fourth side 31 being too close to the first region 2115, thus encroaching on the area where the second part 2113 can form a connection with the first end wall 11, resulting in the first region 2115 being too small; or, in the case of welding the second part 2113 and the first end wall 11, interference from the first adhesive 30 leading to a weak weld between the second part 2113 and the first end wall 11.

[0094] When measuring d1, the width W1 of the first adhesive component 30 along the first direction X and the width W of the first portion 2112 along the first direction X are measured respectively, where d1 = W1 - W. The measurement can be performed using an optical measuring instrument (OMM).

[0095] In some embodiments, as shown in FIG4, the second adhesive 40 has a fifth side 41, which is disposed opposite to the first projection line 21121a along the first direction X, and the fifth side 41 is closer to the first region 2115 than the first projection line 21121a. The distance between the first projection line 21121a and the fifth side 41 along the extension direction of the second part 2113 is d2, and the width of the first part 2112 along the first direction X is W, where 5%W≤d2≤70%W. Setting d2≥5%W ensures that the length of the second adhesive 40 covering the edge of the second part 2113 is not too short, which helps to reduce the possibility of burrs on the edge of the second part 2113 puncturing the release membrane 23. Setting d2≤70%W ensures that the distance between the second adhesive 40 and the first region 2115 is not too close, which facilitates the connection between the second part 2113 and the first end wall 11 and reduces the probability of poor connection between the second part 2113 and the first end wall 11 due to the presence of the second adhesive 40.

[0096] When measuring d2, the width W2 of the second adhesive component 40 along the first direction X and the width W of the first portion 2112 along the first direction X are measured respectively, where d2 = W2 - W. An optical measuring instrument (OMM) can be used for observation and measurement during the measurement process.

[0097] In some embodiments, as shown in Figures 6 and 7, the second part 2113 includes a connecting part 2116 and a transition part 2117. The connecting part 2116 is integral with the first part 2112. The transition part 2117 connects to the connecting part 2116 and is connected to the first end wall 11. The area where the transition part 2117 connects to the first end wall 11 is the first region 2115, and the area where the connecting part 2116 connects to the transition part 2117 is the second region 2118. Providing the transition part 2117 is beneficial to improving the current carrying capacity of the first electrode 21.

[0098] In some embodiments, the first region 2115 and the second region 2118 overlap. In this case, the first end wall 11, the transition portion 2117, and the connecting portion 2116 are stacked sequentially along the first direction X. When connecting the first end wall 11, the transition portion 2117, and the connecting portion 2116, the three can be welded together simultaneously, thereby making the first region 2115 and the second region 2118 overlap.

[0099] In some embodiments, the first region 2115 is separate from the second region 2118. In this case, one end of the adapter 2117 is connected to the connecting portion 2116, and the other end is connected to the first end wall 11.

[0100] In some embodiments, the adapter 2117 and the connecting part 2116 are bonded together with conductive adhesive or the adapter 2117 and the connecting part 2116 are welded together.

[0101] In some embodiments, the conductive adhesive is one of the following: metal-filled conductive adhesives such as silver, copper, gold, nickel, and aluminum; carbon-filled conductive adhesives; conductive polymer adhesives; and conductive epoxy adhesives.

[0102] In some embodiments, the adapter 2117 is a metal foil. As an example, the material of the adapter 2117 is aluminum or nickel.

[0103] In some embodiments, as shown in FIG7, the adapter 2117 is welded to the connecting portion 2116 and the first end wall 11. Along the extension direction of the second portion 2113, the minimum distance between the first region 2115 and the second region 2118 is L2, where 1 / 5R ≤ L2 ≤ 3 / 5R. Setting L2 ≥ 1 / 5R ensures that the distance between the first region 2115 and the second region 2118 is not too small, which helps reduce the possibility of the adapter 2117 being damaged due to two welding operations. Setting L2 ≤ 3 / 5R ensures that the distance between the first region 2115 and the second region 2118 is not too large, and the length of the adapter 2117 is not too long, which reduces the possibility of the adapter 2117 itself stacking along the first direction X. This helps reduce the risk of the adapter 2117 pressing the surface of the electrode assembly 20 facing the first end wall 11 and causing poor K value.

[0104] The method for measuring L2 is as follows: Take a slice of the first electrode 21 containing the connecting part 2116 and the transition part 2117. The slice is connected to the first end cap, and the first end cap is connected to the transition part 2117. Bend the second part 2113 (here, the transition part 2117) using the method mentioned above to form a second crease 2115a. Pull the transition part 2117 in a direction that tends to separate the transition part 2117 from the connecting part 2116 until the transition part 2117 is limited by the second region 2118 and cannot be pulled any further. Press down on the transition part 2117 so that the transition part 2117 and the connecting part 2116 are stacked along the thickness direction of the first electrode 21, thereby forming a crease. This crease is defined as the third crease 2118a. The third crease 2118a passes through a point on the edge of the second region 2118 facing the transition portion 2117, and the third crease 2118a is perpendicular to the edge line of the transition portion 2117 along the width direction of the first electrode 21. The slice of the first electrode 21 is flattened, and the length from the second crease 2115a to the third crease 2118a along the length direction of the first electrode 21 is measured and recorded as L2. Measurement can be performed using an optical measuring instrument (OMM).

[0105] In some embodiments, as shown in FIG7, the adapter 2117 is welded to the connecting portion 2116. The cylindrical battery 100 further includes a third adhesive member 50, which adhesively bonds the connecting portion 2116 and the adapter 2117 and is located on the side of the connecting portion 2116 and the adapter 2117 facing the winding structure. Along the thickness direction of the adapter 2117, the third adhesive member 50 covers the second region 2118 and is separated from the first region 2115. Along the extension direction of the second portion 2113, the minimum distance between the third adhesive member 50 and the first region 2115 is L3, where 1 / 5R ≤ L3 ≤ 2 / 5R. The third adhesive 50 is provided to reduce the possibility that the weld point formed by the welding of the adapter 2117 and the connecting part 2116 may puncture the isolation membrane 23 and cause a short circuit inside the electrode assembly 20. Setting L3≥1 / 5R ensures that the distance between the third adhesive 50 and the first region 2115 is not too small, which helps to reduce the possibility that the setting of the third adhesive 50 may affect the effective electrical connection between the adapter 2117 and the first end wall 11. Setting L3≤2 / 5R ensures that the distance between the third adhesive 50 and the first region 2115 is not too far, which helps to increase the coverage area of ​​the third adhesive 50 and improve the bonding stability of the third adhesive 50.

[0106] The method for measuring L3 is as follows: Take a slice of the first electrode 21 including the connecting part 2116 and the transition part 2117, with the transition part 2117 and the first end wall 11 connected. Bend the second part 2113 (here, the transition part 2117) as described above to form a second crease 2115a (as shown in Figure 7). Flatten the slice of the first electrode 21 and measure the distance from the edge of the third adhesive 50 toward the first region 2115 to the second crease 2115a along the length direction of the first electrode 21. Record this distance as L3.

[0107] In some embodiments, the second part 2113 is a folded structure. The folded structure of the second part 2113 is shown in Figures 8 and 10, and the folding process forming the folded structure of the second part 2113 is shown in Figures 9 and 11. In Figures 9 and 11, dashed lines indicate the positions of the creases after folding the second part 2113, and curved arrows indicate the direction of folding the second part 2113. The state of the second part 2113 after folding as shown in Figure 9 is shown in Figure 8. In Figure 8, the sixth side 21131 and the seventh side 31132 are located on the same side of the first part 2112 along its thickness direction. The state of the second part 2113 after folding as shown in Figure 11 is shown in Figure 10. In Figure 10, the sixth side 21131 and the seventh side 31132 are located on opposite sides of the first part 2112 along its thickness direction.

[0108] Specifically, after the first empty foil portion 2111 is bent in a direction that brings the end of the first electrode 21 closer to the first end wall 11 (as shown in Figures 9 and 11), the second portion 2113 includes a sixth side 21131 and a seventh side 21132 that are arranged opposite to each other along the winding direction of the electrode assembly 20. The sixth side 21131 and the second side 21121 are on the same sideline of the first current collector 211, and the seventh side 21132 and the third side 21122 are on the same sideline of the first current collector 2111. The folding structure of the second portion 2113 is formed by bending the first empty foil portion 2111 in a direction that brings the end of the first electrode 21 closer to the first end wall 11, and then folding the second portion 2113 in such a way that the sixth side 21131 is close to the first portion 2112. The height of the electrode assembly 20 along the first direction X is h (as shown in Figure 3), and h ≥ 4R / 3. h≥4R / 3, meaning the width of the first electrode 21 is greater than or equal to 4R / 3. The second part 2113 is wider than the inner diameter of the enclosure wall 12. With the projected area of ​​the second region 2118 along the first direction X remaining unchanged, the second part 2113 is folded and then connected to the first end wall 11. Compared with the case where the second part 2113 is not folded and is directly connected to the first end wall 11, the proportion of the part of the second part 2113 that is connected to the first end wall 11 is increased, which is beneficial to improving the stability of the connection between the second part 2113 and the first end wall 11.

[0109] It should be noted that in the cylindrical battery 100, a portion of the second part 2113 is located between the first end wall 11 and the electrode assembly 20, and a portion is located between the enclosure wall 12 and the electrode assembly 20. As mentioned above, "the second part 2113 includes a sixth side 21131 and a seventh side 21132 disposed opposite to each other along the winding direction of the electrode assembly 20." When determining the sixth side 21131 and the seventh side 21132, the portion of the second part 2113 located between the enclosure wall 12 and the electrode assembly 20 is used. The determined sixth side 21131 and seventh side 21132 describe the overall structure of the second part 2113. In other words, the portion of the second part 2113 located between the first end wall 11 and the electrode assembly 20 includes the portion of the sixth side 21131 and the portion of the seventh side 211332. In the states shown in Figures 9 and 11, the sixth side 21131 and the seventh side 21132 are continuous line segments extending along the first direction X.

[0110] In some embodiments, as shown in Figures 10 and 11, along the thickness direction of the first electrode 21, a portion of the second portion 2113 is located on the side of the first portion 2112 facing the enclosure wall 12, and a portion of the second portion 2113 is located on the side of the first portion 2112 facing the winding center of the electrode assembly 20. This helps to reduce the resistance encountered by the folded state of the second portion 2113 when the first portion 2112 moves with the second portion 2113.

[0111] In some embodiments, the second portion 2113 in the folded state may be folded at least once more to further reduce the width.

[0112] In some embodiments, as shown in FIG5, the second part 2113 includes a sixth side 21131 and a seventh side 21132 disposed opposite to each other along the winding direction of the electrode assembly 20. The sixth side 21131 and the second side 21121 are on the same sideline of the first current collector 211, and the seventh side 21132 and the third side 21122 are on the same sideline of the first current collector 211. The angle between the first side 2114 and the seventh side 21132 is α, where 40°≤α≤70°. Setting α≥40° ensures that α is not too small, facilitating the movement of the second part 2113 by the first part 2112; setting α≤70° ensures that α is not too large, facilitating the connection between the second part 2113 and the first end wall 11, and reducing the possibility of an internal short circuit caused by the corner of the end of the second part 2113 connected to the first end wall 11 being inserted into the winding structure of the electrode assembly 20.

[0113] When measuring α, a slice of the first electrode 21 containing the first part 2112 and the second part 2113 can be taken. Then, the first part 2112 and the second part 2113 are flattened, and the angle α between the first side 2114 and the seventh side 21132 is measured. The measurement can be observed and measured using an optical measuring instrument (OMM).

[0114] In some embodiments, as shown in FIG2 and FIG6, the second electrode 22 includes a second current collector 221 and a second active material layer 222 stacked together. The second current collector 221 includes a second empty foil portion 2221 located at the outermost ring of the winding structure of the second electrode 22. The second empty foil portion 2221 is not covered by the second active material layer 222.

[0115] In some embodiments, as shown in FIG6, a first adapter 60 is welded to the second empty foil portion 2221. Part of the first adapter 60 is located between the second electrode 22 and the surrounding wall 12, and part of the first adapter 60 is located between the surface of the electrode assembly 20 facing the second end wall 13 and the second end wall 13. The first adapter 60 is welded to the second end wall 13.

[0116] In some embodiments, as shown in FIG2, FIG12 and FIG13, the second empty foil portion 2221 is composed of a third portion 2222 and a fourth portion 2223. The third portion 2222 extends along the winding direction of the electrode assembly 20, and the fourth portion 2223 includes the end of the second electrode 22. The fourth portion 2223 is formed by bending a portion of the second empty foil portion 2221 in a direction that brings the end of the second electrode 22 closer to the second end wall 13. The fourth portion 2223 connects the third portion 2222 and the second end wall 13. The area where the fourth portion 2223 connects to the second end wall 13 is the third region 2225. The connection between the third part 2222 and the fourth part 2223 has an eighth side 2224. The third part 2222 has a ninth side 22221 and a tenth side 22222 that are arranged opposite each other along the first direction X. The tenth side 22222 is closer to the second end wall 13 than the ninth side 22221. The tenth side 22222 intersects with the eighth side 2224 to form a second folding point 2224b. Along the extension direction of the fourth part 2223, the minimum distance from the second folding point 2224b to the third region 2225 is L4, where H+R≤L4. Here, the eighth side 2224 is a crease (defined as the fourth crease 2224a) formed by bending the second empty foil portion 2221 to form the fourth part 2223, or the eighth side 2224 is an extension segment of the fourth crease 2224a. The minimum distance from the second folding point 2224b to the third region 2225 is greater than the sum of the height of the electrode assembly 20 along the first direction X and the inner radius of the enclosure 12. When the electrode assembly 20 expands in volume during charging and discharging, under the action of internal stress, the third part 2222 moves in the opposite direction of the winding direction of the electrode assembly 20, and drives the fourth part 2223 to move, so that the fourth part 2223 changes to a tighter state than the original state, thereby releasing at least a part of the stress, which helps to reduce the possibility of the second electrode 22 tearing or breaking due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery 100.

[0117] In some embodiments, one of the first electrode 21 and the second electrode 22 is a negative electrode. The negative electrode includes a stacked negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer includes silicon, and the mass content of silicon is more than 3% based on the mass of the negative electrode active material layer. Compared with the electrode without silicon, the electrode containing silicon has a larger volume change during charging and discharging, and the internal stress generated in the electrode assembly 20 is also greater. By providing the second part 2113, it is beneficial to reduce the possibility of tearing or breakage of the first electrode 21.

[0118] The silicon content in the negative electrode can be obtained using the following methods:

[0119] Cylindrical cell 100 was discharged to 3.0V at a constant current of 0.1C, and the negative electrode was obtained by disassembling the cylindrical cell 100. The negative electrode was cleaned with dimethyl carbonate (DMC) for 10 minutes, and then baked at 100℃ for 2 hours before use. The negative electrode active material layer on the negative electrode was scraped off, and the powder of the negative electrode active material layer was collected. The silicon and lithium content in the powder of the negative electrode material layer was tested using an inductively coupled plasma atomic emission spectrometer (ICP, model Agilent 5800, provided by Agilent Technologies). The silicon content in the powder of the negative electrode active material layer was tested using a high-frequency carbon-sulfur analyzer (model DK-606).

[0120] As shown in FIG14, an embodiment of this application also provides an electronic device 1000, including a cylindrical battery 100 as described in any of the foregoing embodiments.

[0121] In some embodiments, the electronic device 1000 includes, but is not limited to, mobile phones, laptops, electric toys, power tools, and electronic cigarettes.

[0122] To verify the impact of the solution provided in the embodiments of this application on the service life of the cylindrical battery 100, the inventors of this application conducted the following experiment.

[0123] The experiment included two sets of comparative examples and 12 sets of exemplary examples, each set of comparative examples and each set of exemplary examples including 30 cylindrical batteries 100. In the cylindrical battery 100, the first electrode 21 is set as the negative electrode and the second electrode 22 is set as the positive electrode.

[0124] The preparation process of the cylindrical battery 100 in Example 1 includes the following steps:

[0125] (1) Preparation of the positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), CNTs (carbon nanotubes), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:0.5:0.5:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode active material with a solid content of 75 wt%, and the mixture was stirred evenly for later use. A 10 μm thick aluminum foil was used as the positive electrode current collector. The above active material was uniformly coated onto one surface of the positive electrode current collector along its thickness direction using a slit coater, and then dried at 90°C to obtain a positive electrode sheet with a single-sided coating of the positive electrode active material. The coating process was then repeated on the other surface of the positive electrode current collector along its thickness direction to obtain a positive electrode sheet with positive electrode active material layers coated on both sides. At this point, the thickness of each positive electrode active material layer along the thickness direction of the positive electrode sheet was 90 μm. The coated positive electrode sheet is then cold-pressed, resulting in a positive electrode active material layer thickness of 80 μm. An adapter is then welded to the portion of the positive electrode current collector not covered by the positive electrode active material layer; this uncovered portion is the initial section of the positive electrode sheet in the winding structure.

[0126] (2) Preparation of the negative electrode sheet: Artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) were mixed in a weight ratio of 97:0.5:1.3:1.2, with deionized water added as a solvent to prepare a negative electrode active material with a weight percentage of 50 wt%, and stirred evenly for later use. A 10 μm thick copper foil was used as the negative electrode current collector. The above negative electrode active material was uniformly coated onto one surface of the negative electrode current collector along its thickness direction using a slot coater, and then dried at 110°C to obtain a negative electrode sheet with a single-sided coating of the negative electrode active material layer. The above steps were then repeated on the other side of the negative electrode current collector along its thickness direction to obtain a negative electrode sheet with a double-sided coating of the negative electrode active material layer. At this time, the thickness of each negative electrode active material layer along the thickness direction of the negative electrode sheet was 90 μm. The coated negative electrode sheet was then cold-pressed, and the thickness of the negative electrode active material layer after cold pressing was 80 μm.

[0127] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0128] (4) Preparation of the isolation membrane 23: A 7 μm thick polyethylene porous polymer film was used as the isolation membrane 23.

[0129] (5) Preparation of electrode assembly 20: The positive electrode sheet, the separator 23 and the negative electrode sheet are stacked and wound together along the thickness direction of the negative electrode sheet to obtain the electrode assembly 20. The first empty foil portion 2111 at the end of the winding structure of the negative electrode sheet is bent to form the connecting portion 2116 mentioned above. An adapter is welded to the connecting portion 2116 to serve as the adapter portion 2117 mentioned above. The connecting portion 2116 is bent so that part of the connecting portion 2116 and the adapter portion 2117 are close to the winding center of the electrode assembly 20. The adapter welded to the positive current collector is bent so that its end is close to the winding center of the electrode assembly 20.

[0130] (6) Assembly of cylindrical battery 100: The electrode assembly 20 is placed in the space formed by the enclosure wall 12 and the first end wall 11 of the housing 10. The adapter 2117 is welded to the first end wall 11. The adapter connecting the positive current collector is then welded to the electrode post 132 of the second end wall 13. The cover 131 of the second end wall 13 and the enclosure wall 12 are then sealed and connected. After liquid injection, standing, formation and other steps, cylindrical battery 100 is obtained.

[0131] The preparation process of the cylindrical battery 100 in Comparative Example 2 and Examples 2-12 is basically the same as that in Example 1. The only difference is that the specific values ​​of the relevant parameters listed in Table 1 below are different during the preparation process.

[0132] The preparation process of the cylindrical battery 100 in Comparative Example 1 is basically the same as that of the cylindrical battery 100 in Example 1. The difference is that, in the preparation process of the negative electrode sheet, after the negative electrode sheet is cold-pressed, an adapter is welded to the part of the negative electrode current collector that is not covered by the negative electrode active material layer. The part not covered by the negative electrode active material layer is the starting section of the negative electrode sheet in the winding structure. The preparation process of the electrode assembly 20 is as follows: the positive electrode sheet, the separator 23 and the negative electrode sheet are stacked and wound along the thickness direction of the negative electrode sheet to obtain the electrode assembly 20. The adapter welded to the negative electrode current collector is bent so that its end is close to the winding center of the electrode assembly 20. The adapter is then bent to the positive electrode current collector. The welding of the adapter is such that its end is close to the winding center of the electrode assembly 20; the assembly process of the cylindrical battery 100 is as follows: the electrode assembly 20 is placed in the space formed by the enclosure wall 12 and the second end wall 13 of the housing 10, the adapter connecting the positive electrode current collector faces the opening of the enclosure wall 12 for connecting the second end wall 13, the adapter connecting the negative electrode current collector faces the first end wall 11, the adapter connecting the negative electrode current collector is welded to the first end wall 11, the adapter connecting the positive electrode current collector is welded to the electrode post 132 of the second end wall 13, and then the cover 131 connecting the second end wall 13 and the enclosure wall 12 are sealed; after liquid injection, standing, formation and capacity testing, the cylindrical battery 100 is obtained.

[0133] The dimensions of the cylindrical battery 100 are as follows: H = 5.72 mm; R = 5.02 mm; R1 = 9.69 / 2 = 4.845 mm; R2 = 2.03 / 2 = 1.015 mm; W = 4.2 mm. Based on this data, H + R = 10.74 mm; H + R + 30%π(R1 + R2) = 16.26 mm, 5%W = 0.21 mm, and 70%W = 2.94 mm.

[0134] In Comparative Examples 2 and 12, the cylindrical battery 100 is provided with a first adhesive 30 and a second adhesive 40. For each cylindrical battery 100, the projections of the first adhesive 30 and the second adhesive 40 along the thickness direction of the first electrode 21 coincide, and the values ​​of d1 and d2 are equal. Therefore, only the value of d1 is recorded in Table 1 below.

[0135] After the cylindrical battery 100 is prepared, K-value tests and cycle capacity retention rate tests are performed on the cylindrical batteries 100 in each comparative example and embodiment. For the cylindrical batteries 100 in the same group, the testing order is as follows: first, K-value tests are performed on each cylindrical battery 100, and then 10 cylindrical batteries 100 are randomly selected from each group for cycle capacity retention rate tests.

[0136] The process of K-value testing is as follows:

[0137] 1. Charge the cylindrical battery to full charge, specifically as follows:

[0138] 1) The test temperature is 25℃;

[0139] 2) Let stand for 30 minutes;

[0140] 3) Charge at a constant current of 5C to 4.25V, then charge at a constant voltage of 3C;

[0141] 4) Charge at 3C constant current to 4.35V, then charge at constant voltage to 1.5C;

[0142] 5) Charge at a constant current of 1.5C to 4.45V, then charge at a constant voltage to 0.05C;

[0143] 2. Measure the initial voltage: Measure the voltage of the cylindrical battery 100 as the initial voltage OCV1, which serves as a reference value;

[0144] 3. Let stand: The temperature for standing is 25℃, and the standing time is 24 hours;

[0145] 4. Measure the voltage after resting: Immediately after the resting period, measure the voltage OCVB of the cylindrical battery 100;

[0146] 5. Calculate the self-discharge rate K using the formula: K = (OCV1 - OCVB) / 24.

[0147] In this test, the acceptable specification for cylindrical battery 100 is defined as a K value between 0 and 0.06 mV / h.

[0148] The test procedure for cycle capacity retention is as follows:

[0149] 1) Maintain the test temperature at 25℃;

[0150] 2) Let the cylindrical battery 100 stand for 30 minutes;

[0151] 3) Charge at a constant current of 5C to 4.25V, then charge at a constant voltage of 3C;

[0152] 4) Charge at 3C constant current to 4.35V, then charge at constant voltage to 1.5C;

[0153] 5) Charge at a constant current of 1.5C to 4.45V, then charge at a constant voltage to 0.05C;

[0154] 6) Let stand for 5 minutes;

[0155] 7) Discharge at a constant current of 0.7C to 3V and record the first discharge cycle capacity;

[0156] 8) Let stand for 5 minutes;

[0157] 9) Repeat steps 3 to 8 1200 times, and record the discharge capacity on the 1200th cycle;

[0158] 10) Calculate the capacity retention rate. Capacity retention rate = (discharge capacity of the 1200th cycle / discharge capacity of the first cycle) × 100%.

[0159] In this test, a capacity retention rate of 80% or higher was defined as passing the test. The experimental results are recorded in Table 1.

[0160] Table 1 Note: In the table, " / " indicates that the data is not present.

[0161] As shown in Table 1, the cylindrical battery 100 in Examples 1-12 has a higher pass rate in the cycle capacity retention test than the cylindrical battery 100 in Comparative Examples 1-2. This is because, since part of the first empty foil portion 2111 of the cylindrical battery 100 in Examples 1-12 is bent to form the second portion 2113, and H+R≤L1, when the electrode assembly 20 expands in volume during charging and discharging, under the action of internal stress, the first portion 2112 moves in the opposite direction along the winding direction of the electrode assembly 20, and drives the second portion 2113 to move. This causes the second portion 2113 to change to a tighter state than the original state, thereby releasing at least a portion of the stress. This helps to reduce the possibility of the first electrode 21 tearing or breaking due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery 100.

[0162] As shown in Table 1, the cylindrical battery 100 in Examples 1-3 satisfies L1≤H+R+30%π(R1+R2), and the pass rate of the K value test is higher than that in Example 4. It can be seen that by setting L1≤H+R+30%π(R1+R2), the portion of the second part 2113 located between the first end wall 11 and the electrode assembly 20 will not be too long, which helps to reduce the risk of the second part 2113 squeezing the surface of the electrode assembly 20 facing the first end wall 11 and causing poor K value.

[0163] As shown in Table 1, the cylindrical batteries 100 in Examples 2 and 6-7 satisfy 40°≤α≤70°. The cycle capacity retention rate of the cylindrical batteries 100 in Examples 2 and 6-7 is higher than that in Example 5. It can be seen that setting α≥40°, α is not too small, which facilitates the movement of the first part 2112 and the second part 2113, thereby releasing stress and improving the service life of the cylindrical battery 100. Furthermore, the K value test pass rate of the cylindrical batteries 100 in Examples 2 and 6-7 is higher than that in Example 8. It can be seen that setting α≤70° is beneficial to reducing the possibility of internal short circuit caused by the corner of the end of the second part 2113 connected to the first end wall 11 being inserted into the winding structure of the electrode assembly 20.

[0164] As shown in Table 1, the cylindrical batteries 100 in Examples 2 and 10-11 satisfy 5%W≤d1≤70%W. The pass rate of the K-value test for the cylindrical batteries 100 in Examples 2 and 10-11 is higher than that in Example 9. It can be seen that setting d1≥5%W ensures that the length of the second adhesive 40 covering the edge of the second part 2113 is not too short, which helps to reduce the possibility of burrs on the edge of the second part 2113 puncturing the separator 23, thereby reducing the possibility of poor K-value of the cylindrical battery 100. The pass rate of the cycle capacity retention test for the cylindrical batteries 100 in Examples 2 and 10-11 is higher than that in Example 12. It can be seen that setting d1≤70%W helps to reduce the probability of poor connection between the second part 2113 and the first end wall 11 due to the presence of the first adhesive 30.

[0165] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of this application.

Claims

1. A cylindrical battery, characterized in that, include: A housing, the housing including a first end wall, a second end wall and a surrounding wall, the first end wall and the second end wall being disposed opposite each other along a first direction, the surrounding wall connecting the first end wall and the second end wall, and together with the first end wall and the second end wall enclosing a first space; and An electrode assembly is disposed in the first space. The electrode assembly includes a first electrode, a second electrode, and a separator. The first electrode, the separator, and the second electrode are stacked and wound to form a wound structure. The winding center axis of the electrode assembly is in the first direction. The first electrode includes a first current collector and a first active material layer stacked together. The first current collector includes a first empty foil portion located at the outermost ring of the winding structure of the first electrode. The first empty foil portion is not covered by the first active material layer. The first empty foil portion is composed of a first part and a second part. The first part extends along the winding direction of the electrode assembly. The second part includes the end of the first electrode. The second part is formed by bending the first empty foil portion. The end of the first electrode is located between the first end wall and the electrode assembly. The second part connects the first part and the first end wall. The area where the second part connects with the first end wall is the first area. The connection between the first part and the second part has a first side, the first part has a second side and a third side arranged opposite to each other along the first direction, the second side is closer to the first end wall than the third side, and the first side and the third side intersect to form a first fold point; The distance between the first end wall and the second end wall along the first direction is H, and the inner radius of the enclosure is R; Along the extension direction of the second part, the minimum distance from the first fold point to the first region is L1, where H+R≤L1.

2. The cylindrical battery as described in claim 1, characterized in that, The electrode assembly has a ring-shaped cross-section perpendicular to the first direction, with an outer radius of R1 and an inner radius of R2, where L1 ≤ H + R + 30%π(R1 + R2).

3. The cylindrical battery as described in claim 2, characterized in that, H+R+10%π(R1+R2)≤L1≤H+R+20%π(R1+R2).

4. The cylindrical battery according to any one of claims 1-3, characterized in that, The cylindrical battery includes a first adhesive and a second adhesive, both of which are bonded to the first part and the second part. The first adhesive is bonded to the surface of the first part and the second part facing the enclosure wall, and the second adhesive is bonded to the surface of the first part and the second part facing the winding center axis. The first adhesive covers at least a portion of the edge of the first portion and a portion of the edge of the second portion; The second adhesive covers at least a portion of the edge of the first portion and a portion of the edge of the second portion.

5. The cylindrical battery as described in claim 4, characterized in that, The projection of the second side onto the second part along the thickness direction of the first electrode sheet is the first projection line; The first adhesive has a fourth side, which is disposed opposite to the first projection line along the first direction, and the fourth side is closer to the first region than the first projection line. The distance between the first projection line and the fourth side along the extension direction of the second portion is d1, and the width of the first portion along the first direction is W, where 5%W ≤ d1 ≤ 70%W; and / or The second adhesive has a fifth side, which is disposed opposite to the first projection line along the first direction, and the fifth side is closer to the first region than the first projection line. The distance between the first projection line and the fifth side along the extension direction of the second part is d2, and the width of the first part along the first direction is W, where 5%W≤d2≤70%W.

6. The cylindrical battery according to any one of claims 1-5, characterized in that, The second part includes a connecting part and a transition part. The connecting part and the first part are integrally formed. The transition part is connected to the connecting part and is connected to the first end wall. The area where the transition part is connected to the first end wall is the first area, and the area where the connecting part is connected to the transition part is the second area. The first area and the second area are separate.

7. The cylindrical battery as described in claim 6, characterized in that, The adapter is welded to the connecting part and the adapter is welded to the first end wall. Along the extension direction of the second part, the minimum distance between the first region and the second region is L2, where 1 / 5R≤L2≤3 / 5R.

8. The cylindrical battery as described in claim 6, characterized in that, The adapter is welded to the connecting part. The cylindrical battery also includes a third adhesive member, which adheres to the connecting part and the adapter and is located on the side of the connecting part and the adapter facing the winding structure. Along the thickness direction of the adapter, the third adhesive member covers the second region and is separate from the first region. Along the extension direction of the second portion, the minimum distance between the third adhesive and the first region is L3, where 1 / 5R ≤ L3 ≤ 2 / 5R.

9. The cylindrical battery according to any one of claims 1-8, characterized in that, The second part is a folded structure. After a portion of the first empty foil portion is bent toward the direction that brings the end of the first electrode sheet closer to the first end wall, the second part includes a sixth side and a seventh side that are arranged opposite to each other along the winding direction of the electrode assembly. The sixth side and the second side are the same sideline of the first current collector, and the seventh side and the third side are the same sideline of the first current collector. The folded structure is formed by bending a portion of the first empty foil portion toward the direction that brings the end of the first electrode sheet closer to the first end wall, and then folding the second part in such a way that the sixth side is close to the first part. The height of the electrode assembly along the first direction is h, where h ≥ 4R / 3.

10. The cylindrical battery as described in claim 1, characterized in that, Along the thickness direction of the first electrode sheet, a portion of the second portion is located on the side of the first portion facing the enclosure wall, and a portion of the second portion is located on the side of the first portion facing the winding center of the electrode assembly.

11. The cylindrical battery according to any one of claims 1-10, characterized in that, The second part includes a sixth side and a seventh side that are arranged opposite to each other along the winding direction of the electrode assembly. The sixth side and the second side are the same sideline of the first current collector, and the seventh side and the third side are the same sideline of the first current collector. The angle between the first side and the seventh side is α, where 40°≤α≤70°.

12. The cylindrical battery according to any one of claims 1-11, characterized in that, The second electrode includes a second current collector and a second active material layer stacked together. The second current collector includes a second empty foil portion located at the outermost ring of the winding structure of the second electrode. The second empty foil portion is not covered by the second active material layer. The second empty foil portion is composed of a third part and a fourth part. The third part extends along the winding direction of the electrode assembly. The fourth part includes the end of the second electrode. The fourth part is formed by bending a portion of the second empty foil portion in a direction that brings the end of the second electrode closer to the second end wall. The fourth part connects the third part and the second end wall. The area where the fourth part connects to the second end wall is the third region. The connection between the third part and the fourth part has an eighth side, the third part has a ninth side and a tenth side arranged opposite to each other along the first direction, the tenth side is closer to the first end wall than the ninth side, and the ninth side intersects with the eighth side to form a second fold point; Along the extension direction of the fourth part, the minimum distance from the second fold point to the third region is L4, where H+R≤L4.

13. The cylindrical battery as described in claim 1, characterized in that, One of the first electrode and the second electrode is a negative electrode. The negative electrode includes a negative electrode active material layer and a negative electrode current collector stacked together. The negative electrode active material layer includes silicon element, and the mass content of the silicon element is more than 3% based on the mass of the negative electrode active material layer.

14. An electronic device, characterized in that, Includes the cylindrical battery as described in any one of claims 1 to 13.

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