Cylindrical battery and electronic device

Abstract

The application discloses a cylindrical battery and an electronic device. The cylindrical battery comprises a shell and an electrode assembly. The electrode assembly is arranged in the shell, and the electrode assembly comprises a first pole piece. The first pole piece comprises a first hollow foil part, which is composed of a first part and a second part. The first part extends along the winding direction of the electrode assembly, and the second part is formed by bending part of the first hollow foil part in a direction in which the end of the first pole piece is close to a first end wall. The second part is connected to the first part and the first end wall of the shell. The area where the second part is connected to the first end wall is a first area. The connection between the first part and the second part has a first edge. The first part has a second edge and a third edge. 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 shell is H, and the inner radius of the surrounding wall of the shell is R. The minimum distance from the first folding point to the first area is L1, and H+R≤L1. The cylindrical battery improves the service life by arranging the second part.

Description

Technical Field

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

[0002] Currently, cylindrical batteries typically consist of an electrode assembly and a casing. The electrode assembly is housed within the casing and includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet is secured to the casing via an adapter, while the negative electrode sheet is secured to the casing via another adapter. During the charge and discharge process of a cylindrical battery, the volume of the electrode assembly repeatedly expands and contracts, causing repeated tension on the positive and negative electrode sheets, which can easily cause the strips to break and lead to battery failure. Summary of the Invention

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

[0004] The first aspect of an embodiment of the present application provides a cylindrical battery, comprising a housing and an electrode assembly. The housing comprises a first end wall, a second end wall, and a surrounding wall, wherein the first end wall and the second end wall are arranged relative to each other along a first direction, and 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 the electrode assembly comprises a first electrode sheet, a second electrode sheet, and a separator, wherein the first electrode sheet, the separator, and the second electrode sheet are stacked and wound to form a wound structure, and the winding center axis direction of the electrode assembly is the first direction. The first electrode sheet includes a stacked first current collector and a first active material layer. The first current collector includes a first hollow foil portion located at the outermost coil of the first electrode sheet's wound structure. The first hollow foil portion is not covered by the first active material layer. The first hollow foil portion consists of a first portion and a second portion. The first portion extends along the winding direction of the electrode assembly. The second portion includes the end of the first electrode sheet and is formed by bending the first hollow foil portion. The end of the first electrode sheet is located between the first end wall and the electrode assembly. The second portion connects the first portion and the first end wall. The area where the second portion connects to the first end wall is the first region. The junction between the first and second portions has a first edge. The first portion has a second edge and a third edge disposed opposite each other along the first direction. The second edge is closer to the first end wall than the third edge. The first and third edges intersect to form a first inflection point. The distance between the first and second end walls along the first direction is H, and the inner radius of the surrounding wall is R. Along the extension direction of the second portion, the minimum distance from the first inflection point to the first region is L1, where H + R ≤ L1.

[0005] In this cylindrical battery, the minimum distance from the first folding point to the first area is greater than the sum of the height of the electrode assembly along the first direction and the inner radius of the surrounding wall. When the electrode assembly expands in volume during the charging and discharging process, under the action of internal stress, the first part moves in the opposite direction of the winding direction of the electrode assembly and drives the second part to move, so that the second part changes to a state that is tighter than the original state, thereby releasing at least part of the stress, which is beneficial to reducing the possibility of the first electrode sheet being torn or broken due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery.

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

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

[0008] In an optional embodiment of the present application, the cylindrical battery includes a first adhesive and a second adhesive, the first adhesive and the second adhesive are both 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 surrounding 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 part of the edge of the first part and part of the edge of the second part; the second adhesive covers at least part of the edge of the first part and part of the edge of the second part. The provision of the first adhesive and the second adhesive is conducive to maintaining the stacking state of the first part and the second part along the thickness direction of the first electrode, improving the stability of the second part during the connection process with the first end wall, and facilitating the operation of the processing equipment; the second adhesive covers at least part of the edge of at least part of the first part and part of the edge of the second part. The provision of the first adhesive and the second adhesive is conducive to reducing the possibility of burrs on the edges of the first part and the second part piercing the isolation membrane and causing internal short circuits.

[0009] In an optional embodiment of the present application, the projection of the second side along the thickness direction of the first pole piece onto the second portion is a first projection line. The first adhesive has a fourth side, which is arranged relative 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, 5%W≤d1≤70%W. By setting d1≥5%W, the length of the edge of the second portion covered by the first adhesive is not too short, which is beneficial to reducing the possibility of burrs on the edge of the second portion puncturing the isolation membrane; by setting d1≤70%W, 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 the present application, the projection of the second side along the thickness direction of the first pole piece onto the second portion is the first projection line. The second adhesive has a fifth side, which is arranged relative 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 portion is d2, and the width of the first portion along the first direction is W, 5%W≤d2≤70%W. By setting d2≥5%W, the length of the edge of the second portion covered by the second adhesive is not too short, which is beneficial to reducing the possibility of burrs on the edge of the second portion puncturing the isolation membrane; by setting d2≤70%W, 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 an optional embodiment of the present application, the second portion includes a connecting portion and a transition portion, the connecting portion and the first portion are integrally formed, the transition portion is connected to the connecting portion, and the transition portion is connected to the first end wall, the area where the transition portion and the first end wall are connected is the first area, and the area where the connecting portion and the transition portion are connected is the second area, and the first area and the second area are separated. The provision of the transition portion is beneficial for improving the current carrying capacity of the first pole piece.

[0012] In an optional embodiment of the present application, the transition portion is welded to the connecting portion, which is also 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, and 1 / 5R ≤ L2 ≤ 3 / 5R. Setting L2 ≥ 1 / 5R prevents the distance between the first region and the second region from being too small, thereby reducing the possibility of damage to the transition portion due to two welds. Setting L2 ≤ 3 / 5R prevents the distance between the first region and the second region from being too large, and the length of the transition portion from being too long, thereby reducing the possibility of the transition portion itself stacking along the first direction. This, in turn, reduces the risk of the transition portion squeezing the surface of the electrode assembly facing the first end wall, thereby causing a poor K value.

[0013] In an optional embodiment of the present application, the transition portion is welded to the connecting portion, and the cylindrical battery further includes a third adhesive member, which is bonded to the connecting portion and the transition portion and is located on the side of the connecting portion and the transition portion facing the winding structure. Along the thickness direction of the transition portion, the third adhesive member covers the second area and is separated from the first area. Along the extension direction of the second portion, the minimum distance between the third adhesive member and the first area is L3, 1 / 5R≤L3≤2 / 5R. The provision of the third adhesive member helps reduce the possibility of the weld formed by the welding of the transition portion and the connecting portion puncturing the separator and causing an internal short circuit in the electrode assembly; setting L3≥1 / 5R prevents the distance between the third adhesive member and the first area from being too small, which helps reduce the possibility that the provision of the third adhesive member affects the effective electrical connection between the transition portion and the first end wall; setting L3≤2 / 5R prevents the distance between the third adhesive member and the first area from being too far, which helps increase the coverage area of ​​the third adhesive member and thus improves the stability of the third adhesive member's bonding.

[0014] In an optional embodiment of the present application, the second portion has a folded structure. After a portion of the first hollow foil portion is bent in a direction such that the end of the first electrode sheet approaches the first end wall, the second portion includes a sixth side and a seventh side disposed opposite each other along the winding direction of the electrode assembly. The sixth side and the second side coincide with an edge of the first current collector, and the seventh side and the third side coincide with an edge of the first current collector. The folded structure is formed by bending a portion of the first hollow foil portion in a direction such that the end of the first electrode sheet approaches the first end wall, and then folding the second portion so that the sixth side approaches the first portion. 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 portion is wider than the inner diameter of the surrounding wall. When the projected area of ​​the second region along the first direction remains unchanged, the second portion is folded and then connected to the first end wall. Compared to a case where the second portion is unfolded and directly connected to the first end wall, the portion of the second portion connected to the first end wall accounts for a larger proportion of the total second portion, which facilitates improving the stability of the connection between the second portion and the first end wall.

[0015] In an optional embodiment of the present application, along the thickness direction of the first electrode sheet, part of the second portion is located on the side of the first portion facing the surrounding wall, and part of the second portion is located on the side of the first portion facing the winding center of the electrode assembly. This helps reduce the resistance to movement of the second portion caused by the folded state of the second portion when the first portion drives the second portion.

[0016] In an optional embodiment of the present application, the second portion includes a sixth side and a seventh side disposed opposite each other along the winding direction of the electrode assembly. The sixth side and the second side are the same side of the first current collector, and the seventh side and the third side are the same side of the first current collector. The angle between the first and seventh sides is α, and 40°≤α≤70°. Setting α≥40° prevents α from being too small, thereby facilitating movement of the second portion by the first portion. Setting α≤70° prevents α from being too large, thereby facilitating connection of the second portion to the first end wall and reducing the possibility of an internal short circuit caused by the corner of the end portion of the second portion connected to the first end wall being inserted into the winding structure of the electrode assembly.

[0017] In an optional embodiment of the present application, the second electrode sheet includes a second current collector and a second active material layer arranged in a stacked manner. The second current collector includes a second hollow foil portion located at the outermost circle of the wound structure of the second electrode sheet, the second hollow foil portion not being covered by the second active material layer. The second hollow foil portion is composed of a third portion and a fourth portion. The third portion extends along the winding direction of the electrode assembly. The fourth portion includes the end of the second electrode sheet. The fourth portion is formed by bending a portion of the second hollow foil portion in a direction that brings the end of the second electrode sheet closer to the second end wall. The fourth portion connects the third portion and the second end wall. The area where the fourth portion connects to the second end wall is the third region. The junction between the third and fourth portions has an eighth side. The third portion has a ninth and tenth sides arranged opposite each other along the 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 fold point. Along the extension direction of the fourth portion, the minimum distance from the second fold point to the third region is L4, and H+R≤L4. The minimum distance from the second inflection point to the third area is greater than the sum of the height of the electrode assembly along the first direction and the inner radius of the surrounding wall. When the electrode assembly expands in volume during the charging and discharging process, under the action of internal stress, the third part moves in the opposite direction of the winding direction of the electrode assembly and drives the fourth part to move, so that the fourth part changes to a state that is tighter than the original state, thereby releasing at least part of the stress, which is beneficial to reducing the possibility of tearing or breaking of the second electrode due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery.

[0018] In an optional embodiment of the present application, one of the first and second electrode sheets is a negative electrode sheet, which 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 greater than 3% based on the mass of the negative electrode active material layer. Compared to electrode sheets without silicon, electrode sheets containing silicon experience greater volume changes during charge and discharge, and generate greater internal stress in the electrode assembly. Providing the second portion helps reduce the likelihood of tearing or breaking the first electrode sheet.

[0019] A second aspect of the embodiments of the present application provides an electronic device, which includes the cylindrical battery as described in any of the aforementioned embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of a cylindrical battery in one embodiment of the present application.

[0021] Figure 2 It is a cross-sectional structural diagram of a cylindrical battery in one embodiment of the present application.

[0022] Figure 3 It is a schematic structural diagram of an electrode assembly in one embodiment of the present application.

[0023] Figure 4 This is a schematic structural diagram of the first pole piece in one state in an embodiment of the present application.

[0024] Figure 5 This is a schematic structural diagram of an embodiment of the present application in which the first pole piece is flattened and connected to the first end wall.

[0025] Figure 6 It is a schematic structural diagram of a cylindrical battery in one embodiment of the present application.

[0026] Figure 7 This is a schematic structural diagram of the first embodiment of the present application in a state where the first pole piece is flattened and connected to the first end wall.

[0027] Figure 8 It is a structural schematic diagram of the second part in an embodiment of the present application when it is in a folded state.

[0028] Figure 9 It is a schematic structural diagram of the second part before it forms a folded state in one embodiment of the present application.

[0029] Figure 10 It is a structural schematic diagram of the second part in an embodiment of the present application when it is in a folded state.

[0030] Figure 11 It is a schematic structural diagram of the second part before it forms a folded state in one embodiment of the present application.

[0031] Figure 12 This is a schematic structural diagram of an embodiment of the present application in which the second pole piece is in a state and connected to the second end wall.

[0032] Figure 13 This is a schematic structural diagram of an embodiment of the present application in which the second pole piece is in a state and connected to the second end wall.

[0033] Figure 14 It is a structural diagram of an electronic device in one embodiment of the present application.

[0034] Description of main component symbols

[0035] Cylindrical battery 100

[0036] Housing 10

[0037] First end wall 11

[0038] First side 111

[0039] Wall 12

[0040] Second end wall 13

[0041] Cover 131

[0042] Pole 132

[0043] First paragraph 1321

[0044] Second paragraph 1322

[0045] Section 3 1323

[0046] Second side 13231

[0047] Insulation 14

[0048] First Space 15

[0049] Electrode assembly 20

[0050] First pole piece 21

[0051] First current collector 211

[0052] First empty foil part 2111

[0053] Part 1

[0054] Second side 21121

[0055] First projection line 21121a

[0056] The third side 21122

[0057] Part II

[0058] Sixth Side 21131

[0059] The Seventh Side 21132

[0060] First side

[0061] First crease 2114a

[0062] First turning point 2114b

[0063] First Area 2115

[0064] Second fold 2115a

[0065] Connecting section 2116

[0066] Adapter 2117

[0067] Second Area 2118

[0068] Third fold 2118a

[0069] First active material layer 212

[0070] Second pole piece 22

[0071] Second current collector 221

[0072] Second active material layer 222

[0073] Second empty foil portion 2221

[0074] Part III 2222

[0075] Ninth Side 22221

[0076] The tenth side 22222

[0077] Part 4 2223

[0078] The Eighth Side 2224

[0079] Fourth fold 2224a

[0080] Second turning point 2224b

[0081] Third Area 2225

[0082] Isolation film 23

[0083] First adhesive member 30

[0084] Fourth side 31

[0085] Second adhesive member 40

[0086] Fifth Side 41

[0087] The third adhesive member 50

[0088] First adapter 60

[0089] First direction X DETAILED DESCRIPTION

[0090] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0091] It should be noted that when an element is considered to be “connected” to another element, it may be directly connected to the other element or there may be a centrally disposed element. When an element is considered to be “disposed on” another element, it may be directly disposed on the other element or there may be a centrally disposed element.

[0092] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0093] In the description of the embodiments of this application, the technical terms "first," "second," etc. are used only to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0094] In the description of the embodiments of this application, the term "perpendicular" is used to describe an ideal state between two components. In actual production or use, two components may be approximately perpendicular to each other. Two components described as "perpendicular" do not necessarily need to be absolutely straight lines or planes; they can also be approximately straight lines or planes. From a macroscopic perspective, the components are considered "straight" or "planar" if their overall extension direction is a straight line or plane.

[0095] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearance of such phrases in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. The various embodiments of the present application may be combined with each other unless there is a conflict.

[0096] Embodiments of the present application provide a cylindrical battery comprising a housing and an electrode assembly. The housing comprises a first end wall, a second end wall, and a surrounding wall. The first and second end walls are arranged opposite each other along a first direction. The surrounding wall connects the first and second end walls and, together with the first and second end walls, encloses a first space. The electrode assembly is disposed in the first space and comprises a first electrode sheet, a second electrode sheet, and a separator. The first electrode sheet, the separator, and the second electrode sheet are stacked and wound to form a wound structure, with the winding center axis of the electrode assembly oriented in the first direction. The first electrode sheet comprises a stacked first current collector and a first active material layer. The first current collector comprises a first hollow foil portion located at the outermost circle of the wound structure of the first electrode sheet, the first hollow foil portion not covered by the first active material layer. The first hollow foil portion comprises a first portion and a second portion. The first portion extends along the winding direction of the electrode assembly. The second portion comprises the end of the first electrode sheet and is formed by bending the first hollow foil portion. The end of the first electrode sheet is located between the first end wall and the electrode assembly. The second portion connects the first portion and the first end wall. The area where the second portion connects to the first end wall is the first area. The junction of the first and second portions comprises a first edge. The first portion comprises a second edge and a third edge disposed opposite each other along a first direction. The second edge is closer to the first end wall than the third edge. The first and third edges intersect to form a first inflection point. The distance between the first and second end walls along the first direction is H, and the inner radius of the surrounding wall is R. Along the extension direction of the second portion, the minimum distance from the first inflection point to the first region is L1, where H + R ≤ L1.

[0097] In this cylindrical battery, the minimum distance from the first folding point to the first area is greater than the sum of the height of the electrode assembly along the first direction and the inner radius of the surrounding wall. When the electrode assembly expands in volume during the charging and discharging process, under the action of internal stress, the first part moves in the opposite direction of the winding direction of the electrode assembly and drives the second part to move, so that the second part changes to a state that is tighter than the original state, thereby releasing at least part of the stress, which is beneficial to reducing the possibility of the first electrode sheet being torn or broken due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery.

[0098] The embodiments of the present application are further described below with reference to the accompanying drawings.

[0099] like Figure 1 As shown, an embodiment of the present application provides a cylindrical battery 100 .

[0100] In some embodiments, the cylindrical battery 100 is a button battery.

[0101] In some embodiments, as Figure 1 and Figure 2 As shown, the cylindrical battery 100 includes a housing 10 and an electrode assembly 20 , wherein the electrode assembly 20 is accommodated in the housing 10 .

[0102] In some embodiments, as Figure 2 As shown, the shell 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 arranged opposite to each other along the 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, forms a first space 15. The electrode assembly 20 is arranged in the first space 15.

[0103] 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 being connected. For example, in some embodiments, the surrounding wall 12 and the first end wall 11 are an integral structure.

[0104] In some embodiments, as Figure 2 As shown, the second end wall 13 includes a cover 131 and a pole 132. The pole 132 comprises a first section 1321, a second section 1322, and a third section 1323, all of which are integrally structured. The second section 1322 is located between the first section 1321 and the third section 1323, connecting the first and third sections 1321 and 1323, forming an "I" shape. A through hole is provided in the middle of the cover 131, through which the second section 1322 extends. The first section 1321 is located outside the first space 15, while the third section 1323 is located within the first space 15. An insulating member 14 is also provided between the cover 131 and the pole 132, insulating the cover 131 from the pole 132.

[0105] In some embodiments, as Figure 2 As shown, the electrode assembly 20 includes a first electrode piece 21, a second electrode piece 22 and an isolation membrane 23. The first electrode piece 21, the isolation membrane 23 and the second electrode piece 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.

[0106] In some embodiments, as Figure 2 As shown, the first electrode 21 includes a stacked first current collector 211 and a first active material layer 212. Specifically, two first active material layers 212 are provided, and the two first active material layers 212 are coated on two opposite sides of the first current collector 211 along the thickness direction of the first electrode 21.

[0107] In some embodiments, as Figure 2 As shown, the second electrode sheet 22 includes a stacked second current collector 221 and a second active material layer 222. Specifically, two second active material layers 222 are provided, and the two second active material layers 222 are coated on two opposite sides of the second current collector 221 along the thickness direction of the second electrode sheet 22.

[0108] In some embodiments, one of the first current collector 211 and the second current collector 221 is a positive electrode current collector, and the other is a negative electrode current collector.

[0109] In some embodiments, both the positive electrode current collector and the negative electrode current collector are metal layers. For example, the positive electrode current collector may be a metal layer comprising at least one of aluminum, nickel, tantalum, and titanium, such as aluminum foil. The negative electrode current collector may be a metal layer comprising at least one of copper, nickel, tantalum, and titanium, such as copper foil.

[0110] In some embodiments, one of the first active material layer 212 and the second active material layer 222 is a positive active material layer including a positive active material, and the other is a negative active material layer including a negative active material.

[0111] 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.

[0112] In some embodiments, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, and silicon-carbon material.

[0113] In some embodiments, the isolation film 23 is made of insulating film materials such as polyethylene film, polypropylene film, polyester film, or polyimide film.

[0114] In some embodiments, the cylindrical battery 100 further includes an electrolyte (not shown), which is contained in the first space 15 .

[0115] In some embodiments, the electrolyte is in any one of a gel state, a solid state, and a liquid state.

[0116] In some embodiments, the electrolyte includes a lithium salt and a non-aqueous solvent.

[0117] 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.

[0118] In some embodiments, the non-aqueous solvent includes at least one of a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, or other organic solvents, etc. For example, the carbonate compound may include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene 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, etc.

[0119] In this application Figures 4 to 11 In order to clearly illustrate the structure of the first pole piece 21 and the second pole piece 22, the first pole piece 21 and the second pole piece 22 are shown in a fully or partially flattened state. When the first pole piece 21 and the second pole piece 33 are in the wound state, the first pole piece 21 and the second pole piece 22 are wound along their respective length directions.

[0120] In some embodiments, as Figures 2 to 4 As shown, the first current collector 211 includes a first hollow foil portion 2111 located at the outermost circle of the winding structure of the first pole piece 21. The first hollow foil portion 2111 is not covered by the first active material layer 212. The first hollow foil portion 2111 is composed of a first portion 2112 and a second portion 2113. The first portion 2112 extends along the winding direction of the electrode assembly 20. The second portion 2113 includes the end of the first pole piece 21. The second portion 2113 is formed by bending the first hollow foil portion 2111. The end of the first pole piece 21 is located between the first end wall 11 and the electrode assembly 20. The second portion 2113 connects the first portion 2112 and the first end wall 11. Here, the end of the first pole piece 21 refers to the tail end of the first pole piece 21 in its winding structure, that is, the end of the first pole piece 21 located at the outermost circle of its winding structure.

[0121] In some embodiments, the second portion 2113 is located on the side of the first portion 2112 toward the winding center of the electrode assembly 20 along the thickness direction of the first pole piece 21; in other embodiments, the second portion 2113 is located on the side of the first portion 2112 toward the surrounding wall 12 along the thickness direction of the first pole piece 21.

[0122] In some embodiments, as Figure 4 and Figure 5As shown, the connection between the first portion 2112 and the second portion 2113 has a first edge 2114. The first portion 2112 has a second edge 21121 and a third edge 21122 arranged opposite each other along the first direction X. The second edge 21121 is closer to the first end wall 11 than the third edge 21122. The first edge 2114 and the third edge 21122 intersect to form a first folding point 2114b.

[0123] The first edge 2114 is a fold (defined as a first fold 2114a) formed when the first hollow foil portion 2111 is bent to form the second portion 2113, or the first edge 2114 is an extended line segment of the first fold 2114a. Figure 4 As shown, when the first hollow foil portion 2111 is flattened, a first fold 2114a can be observed. Figure 4 The figure shows a complete first fold 2114a, i.e., the first fold 2114a intersects both the second side 21121 and the third side 21122. In this case, the first fold 2114a is the first side 2114. However, in some embodiments of the present application, the first fold 2114a is incomplete, i.e., the first fold 2114a intersects only one of the second side 21121 and the third side 21122, or does not intersect either of the second side 21121 and the third side 21122. In this case, an extended line segment can be drawn along the extension direction of the first fold 2114a, intersecting the second side 21121 and the third side 21122. The intersection points of the extended line segment with the second side 21121 and the third side 21122 serve as the two endpoints of the extended line segment, and the extended line segment serves as the first side 2114. The first side 2114 is the boundary between the first portion 2112 and the second portion 2113.

[0124] In some embodiments, as Figure 2 and Figure 5 As shown, the area where the second portion 2113 connects to the first end wall 11 is the first area 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 surrounding wall 12 is R. Along the extension direction of the second portion 2113, the minimum distance from the first inflection point 2114b to the first area 2115 is L1, and H+R≤L1. The extension direction of the second portion 2113 is the length direction of the first pole piece 21 when it is flattened.

[0125] In this embodiment, the minimum distance from the first inflection 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 surrounding wall 12. When the electrode assembly 20 expands in volume during the charge and discharge process, 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 state that is tighter than the original state, thereby releasing at least part of the stress, which is beneficial to reducing the possibility of the first electrode 21 being torn or broken due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery 100.

[0126] The distance H between the first end wall 11 and the second end wall 13 along the first direction X is measured as follows:

[0127] The first end wall 11 has a first surface 111, which is located in the first space 15. The second end wall 13 has a second surface 13231, which is located in the first space 15. The first surface 111 and the second surface 13231 are arranged opposite each other along a 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) device, and H is measured.

[0128] The inner radius R of the surrounding wall 12 is measured by scanning the cylindrical battery 100 with a computed tomography (CT) device and measuring the inner diameter of the surrounding wall 12 , where R is half the length of the inner diameter.

[0129] The minimum distance L1 from the first inflection point 2114b to the first area 2115 is measured as follows:

[0130] Take a slice of the first electrode 21 including the first folding point 2114b and the second portion 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 portion 2113. Flatten the slice of the first electrode 21 and pull the second portion 2113 in a direction that tends to separate the second portion 2113 from the first end wall 11 until the second portion 2113 is limited by the first region 2115 and cannot be pulled further. Press the second portion 2113 downward so that the second portion 2113 and the first end wall 11 are overlapped along the thickness direction of the first electrode 21, thereby forming a crease, which is defined as the second crease 2115a (as shown in FIG. Figure 5(as shown). The second fold 2115a is perpendicular to the edge of the second portion 2113 along the width direction of the first pole piece 21, and the second fold 2115a passes through a point on the edge of the first region 2115 facing the first portion 2112. The slice of the first pole piece 21 is flattened, and the length from the first fold point 2114b to the second fold 2115a along the length direction of the first pole piece 21 is measured and recorded as L1. The measurement can be observed and measured using an optical microscope (OMM).

[0131] In some embodiments, as Figure 2 and Figure 3 As shown, the cross-section of the electrode assembly 20 perpendicular to the first direction X is annular. The outer radius of the electrode assembly 20 is R1, the inner radius of the electrode assembly 20 is R2, and L1 ≤ H + R + 30% π (R1 + R2). Because H + R ≤ L1, the portion of the second portion 2113 that extends beyond the height of the electrode assembly 20 along the first direction is accommodated between the first end wall 11 and the electrode assembly 20. Setting L1 ≤ H + R + 30% π (R1 + R2) prevents the portion of the second portion 2113 located between the first end wall 11 and the electrode assembly 20 from being excessively long, thereby reducing the risk of the second portion 2113 squeezing the surface of the electrode assembly 20 facing the first end wall 11 and causing a poor K value. The K value refers to the voltage drop of the cylindrical battery 100 per unit time.

[0132] The outer radius R1 of the electrode assembly 20 is measured by scanning the cylindrical battery 100 using a computed tomography (CT) scanner and measuring the outer diameter of the electrode assembly 20. Half of the outer diameter is the outer radius R1. The thickness of the second portion must be included in the outer diameter measurement.

[0133] The inner radius R2 of the electrode assembly 20 is measured by scanning the cylindrical battery 100 with a computed tomography (CT) device and measuring the inner diameter of the electrode assembly 20 , where half the length of the inner diameter is the inner radius R2 .

[0134] It should be noted that when measuring R1, the measurement is performed based on the current collector (the first current collector 211 or the second current collector 221) of the outermost circle of the winding structure of the electrode assembly 20. When measuring R2, the measurement is performed based on the current collector (the first current collector 211 or the second current collector 221) of the innermost circle of the winding structure of the electrode assembly 20.

[0135] It should be added that, in the embodiment of the present application, the value of π is 3.14.

[0136] 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 further reduce the possibility of tearing or breaking of the first electrode sheet 21 due to internal stress accumulation. Setting L1≤H+R+20%π(R1+R2) helps further reduce the risk of the second portion 2113 squeezing the surface of the electrode assembly 20 facing the first end wall 11 and causing a poor K value.

[0137] In some embodiments, the second portion 2113 is welded to the first end wall 11 .

[0138] In some embodiments, the second portion 2113 is bonded to the first end wall 11 using conductive adhesive.

[0139] In some embodiments, as Figure 4 As shown, the cylindrical battery 100 includes a first adhesive 30 and a second adhesive 40, and the first adhesive 30 and the second adhesive 40 are both bonded to the first part 2112 and the second part 2113. The first adhesive 30 is bonded to the surface of the first part 2112 and the second part 2113 facing the surrounding wall 12, and the second adhesive 40 is bonded to the surface of the first part 2112 and the second part 2113 facing the winding center axis of the electrode assembly 20. Figure 4 , the projections of the first adhesive 30 and the second adhesive 40 along the thickness direction of the first pole piece 21 overlap. Providing the first adhesive 30 and the second adhesive 40 helps maintain the stacked state of the first portion 2112 and the second portion 2113 along the thickness direction of the first pole piece 21, improves the stability of the second portion 2113 during connection with the first end wall 11, and facilitates operation of the processing equipment. The first adhesive 30 covers at least a portion of the edge of the first portion 2112 and a portion of the edge of the second portion 2113; the second adhesive 40 covers at least a portion of the edge of the first portion 2112 and a portion of the edge of the second portion 2113. Providing the first adhesive 30 and the second adhesive 40 helps reduce the possibility of burrs on the edges of the first portion 2112 and the second portion 2113 piercing the isolation membrane 23 and causing an internal short circuit.

[0140] It should be noted that the viscosity of the first adhesive 30 and the second adhesive 40 is weakened after being infiltrated by the electrolyte, which 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 driving the second part 2113 to move to release stress.

[0141] In some embodiments, as Figure 4 As shown, the first adhesive member 30 is an adhesive tape.

[0142] In some embodiments, the first adhesive member 30 includes a first adhesive portion and a second adhesive portion, both of which are substantially rectangular. The first adhesive portion is bonded to the first portion 2112 and the second portion 2113. The first adhesive portion is bonded to the surfaces of the first portion 2112 and the second portion 2113 facing the surrounding 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 is bonded to the first adhesive portion and the second portion 2113. The second adhesive portion is bonded to the surfaces of the first adhesive portion and the second portion 2113 facing the surrounding wall 12. Along the width direction of the second portion 2113, the two edges of the second adhesive portion extend beyond the edges of the second portion 2113. The first adhesive portion and the second adhesive portion are both adhesive tape.

[0143] In some embodiments, as Figure 4 As shown, the second adhesive member 40 is an adhesive tape.

[0144] In some embodiments, the second adhesive member 40 includes a third adhesive portion and a fourth adhesive portion. The third adhesive portion and the fourth adhesive portion are substantially rectangular. The third adhesive portion is bonded to the first portion 2112 and the second portion 2113. The third adhesive portion 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 edge 21121 and the third edge 21122, respectively. The fourth adhesive portion is bonded to the third adhesive portion and the second portion 2113. The fourth adhesive portion 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, the two edges of the second adhesive portion extend beyond the edges of the second portion 2113. The first adhesive portion and the second adhesive portion are both adhesive tape.

[0145] In some embodiments, the adhesive tape includes a base material layer and an adhesive layer, and the adhesive layer is disposed on a surface of the base material layer facing the first portion 2112 and the second portion 2113 .

[0146] In some embodiments, the substrate layer can be selected from one of polyethylene terephthalate, coextruded polypropylene, oriented polystyrene, thermoplastic polyurethane, polylactic acid, polyolefin, and polyimide.

[0147] In some embodiments, the adhesive layer is made of one or a combination of 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.

[0148] In some embodiments, as Figure 4 As shown, the projection of the second edge 21121 along the thickness direction of the first pole piece 21 falling on the second part 2113 is the first projection line 21121a; the first adhesive 30 has a fourth edge 31, and the fourth edge 31 is arranged opposite to the first projection line 21121a along the first direction X, and the fourth edge 31 is closer to the first area 2115 than the first projection line 21121a, the distance between the first projection line 21121a and the fourth edge 31 along the extension direction of the second part 2113 is d1, and the width of the first part 2112 along the first direction X is W, 5%W≤d1≤70%W. Setting d1 ≥ 5% W prevents the first adhesive 30 from covering the edge of the second portion 2113 too short, thereby reducing the possibility of burrs on the edge of the second portion 2113 puncturing the isolation film 23. Setting d1 ≤ 70% W prevents the first adhesive 30 from being too close to the first region 2115, thereby facilitating the connection between the second portion 2113 and the first end wall 11 and reducing the probability of a poor connection between the second portion 2113 and the first end wall 11 due to the presence of the first adhesive 30. Poor connection conditions include, but are not limited to: the fourth edge 31 being too close to the first region 2115, thereby encroaching on the area available for connection between the second portion 2113 and the first end wall 11, thereby reducing the area of ​​the first region 2115; or interference from the first adhesive 30 during welding of the second portion 2113 to the first end wall 11, resulting in a poor weld between the second portion 2113 and the first end wall 11.

[0149] When measuring d1, the width W1 of the first adhesive member 30 and the width W of the first portion 2112 along the first direction X are measured respectively, d1 = W1 - W. The measurement can be observed and measured using an optical measuring instrument (OMM).

[0150] In some embodiments, as Figure 4 As shown, the second adhesive member 40 has a fifth edge 41. The fifth edge 41 is arranged opposite the first projection line 21121a along the first direction X. The fifth edge 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 edge 41 along the extension direction of the second portion 2113 is d2. The width of the first portion 2112 along the first direction X is W, and 5% W ≤ d2 ≤ 70% W. Setting d2 ≥ 5% W prevents the second adhesive member 40 from covering the edge of the second portion 2113 too short, thereby reducing the possibility of burrs on the edge of the second portion 2113 puncturing the isolation film 23. Setting d2 ≤ 70% W prevents the second adhesive member 40 from being too close to the first region 2115, thereby facilitating the connection between the second portion 2113 and the first end wall 11 and reducing the possibility of poor connection between the second portion 2113 and the first end wall 11 due to the presence of the second adhesive member 40.

[0151] When measuring d2, the width W2 of the second adhesive member 40 along the first direction X and the width W of the first portion 2112 along the first direction X are measured respectively, d2 = W2 - W. The measurement can be observed and measured using an optical measuring instrument (OMM).

[0152] In some embodiments, as Figure 6 and Figure 7 As shown, the second portion 2113 includes a connecting portion 2116 and a transition portion 2117. The connecting portion 2116 and the first portion 2112 are integrally formed. The transition portion 2117 is connected to the connecting portion 2116, and the transition portion 2117 is connected to the first end wall 11. The area where the transition portion 2117 connects to the first end wall 11 is the first area 2115, and the area where the connecting portion 2116 and the transition portion 2117 connect is the second area 2118. The provision of the transition portion 2117 is beneficial for improving the current carrying capacity of the first pole piece 21.

[0153] 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 in sequence 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 overlapping the first region 2115 and the second region 2118.

[0154] In some embodiments, the first area 2115 is separated from the second area 2118. At this time, one end of the transition portion 2117 is connected to the connecting portion 2116, and the other end is connected to the first end wall 11.

[0155] In some embodiments, the transition portion 2117 and the connection portion 2116 are bonded with conductive adhesive or welded.

[0156] In some embodiments, the conductive adhesive is one of metal-filled conductive adhesives such as silver, copper, gold, nickel, and aluminum, carbon-filled conductive adhesives, conductive polymer adhesives, and conductive epoxy adhesives.

[0157] In some embodiments, the transition portion 2117 is made of metal foil, for example, aluminum or nickel.

[0158] In some embodiments, as Figure 7As shown, the transition portion 2117 is welded to the connecting portion 2116, which is in turn welded to 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, with 1 / 5R ≤ L2 ≤ 3 / 5R. Setting L2 ≥ 1 / 5R prevents the distance between the first region 2115 and the second region 2118 from being too small, thereby reducing the possibility of damage to the transition portion 2117 due to the two welds. Setting L2 ≤ 3 / 5R prevents the distance between the first region 2115 and the second region 2118 from being too large, thereby reducing the length of the transition portion 2117 and reducing the possibility of the transition portion 2117 itself stacking along the first direction X. This, in turn, reduces the risk of the transition portion 2117 squeezing the surface of the electrode assembly 20 facing the first end wall 11, thereby causing a poor K value.

[0159] The measurement method of L2 is as follows: take a slice of the first pole piece 21 including the connecting portion 2116 and the transition portion 2117, the slice remains connected to the first end cover, the first end cover remains connected to the transition portion 2117, and the second portion 2113 (here, the bent transition portion 2117) is bent by the method mentioned above to form a second fold 2115a; the transition portion 2117 is pulled in a direction that tends to separate the transition portion 2117 from the connecting portion 2116, until the transition portion 2117 is limited by the second area 2118 and cannot be pulled further, and the transition portion 2117 is pressed down so that the transition portion 2117 and the connecting portion 2116 are overlapped along the thickness direction of the first pole piece 21, thereby forming a fold, which is defined as the third fold 2118a. The third fold 2118a passes through a point on the edge of the second region 2118 facing the transition portion 2117, and is perpendicular to the edge of the transition portion 2117 along the width direction of the first pole piece 21. Flatten the slice of the first pole piece 21, and measure the length from the second fold 2115a to the third fold 2118a along the length direction of the first pole piece 21, recording it as L2. This measurement can be observed and measured using an optical measuring instrument (OMM).

[0160] In some embodiments, as Figure 7As shown, the transition portion 2117 is welded to the connection portion 2116. The cylindrical battery 100 also includes a third adhesive member 50. The third adhesive member 50 is bonded to the connection portion 2116 and the transition portion 2117 and is located on the side of the connection portion 2116 and the transition portion 2117 facing the winding structure. Along the thickness direction of the transition portion 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, and 1 / 5R≤L3≤2 / 5R. Setting the third adhesive 50 is beneficial to reducing the possibility that the weld point formed by the welding of the transition part 2117 and the connection part 2116 punctures the isolation membrane 23 and causes an internal short circuit in the electrode assembly 20; setting L3≥1 / 5R, the distance between the third adhesive 50 and the first area 2115 is not too small, which is beneficial to reducing the possibility that the setting of the third adhesive 50 affects the effective electrical connection between the transition part 2117 and the first end wall 11; setting L3≤2 / 5R, the distance between the third adhesive 50 and the first area 2115 is not too far, which is beneficial to increasing the coverage area of ​​the third adhesive 50, so as to improve the bonding stability of the third adhesive 50.

[0161] The measurement method of L3 is as follows: take a slice of the first pole piece 21 including the connecting portion 2116 and the transition portion 2117, the transition portion 2117 remains connected to the first end wall 11, and bend the second portion 2113 (here, the bent transition portion 2117) by the method described above to form a second fold 2115a (such as Figure 7 As shown), flatten the slice of the first pole piece 21, measure the distance from the edge of the third adhesive 50 facing the first area 2115 to the second fold 2115a along the length direction of the first pole piece 21, and record it as L3.

[0162] In some embodiments, the second portion 2113 is a folded structure. Figure 8 and Figure 10 As shown, the folding process of forming the folding structure of the second part 2113 is as follows Figure 9 and Figure 11 As shown, Figure 9 and Figure 11 In the figure, the dotted line indicates the position of the fold after the second part 2113 is folded, and the arc arrow indicates the direction in which the second part 2113 is folded. Figure 9 The folded state is as shown in Figure 8 As shown, Figure 8 , the sixth side 21131 and the seventh side 31132 are located on the same side of the first portion 2112 along the thickness direction thereof; Figure 11 The folded state is as shown in Figure 10 As shown, Figure 10, the sixth side 21131 and the seventh side 31132 are located on different sides of the first portion 2112 along the thickness direction thereof.

[0163] Specifically, after a portion of the first hollow foil portion 2111 is bent in a direction such that the end of the first electrode 21 is close to the first end wall 11 (eg Figure 9 and Figure 11 ), the second portion 2113 includes a sixth side 21131 and a seventh side 21132 arranged opposite to each other along the winding direction of the electrode assembly 20, the sixth side 21131 and the second side 21121 are the same side line of the first current collector 211, and the seventh side 21132 and the third side 21122 are the same side line of the first current collector 211. The folding structure of the second portion 2113 is formed by bending part of the first hollow foil portion 2111 in a direction so that the end of the first electrode sheet 21 is close to the first end wall 11, and then folding the second portion 2113 in a manner so 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 (such as Figure 3 ), h≥4R / 3. h≥4R / 3, that is, the width of the first pole piece 21 is greater than or equal to 4R / 3, the second portion 2113 is wider than the inner diameter of the surrounding wall 12, and when the projected area of ​​the second region 2118 along the first direction X remains unchanged, the second portion 2113 is folded and then connected to the first end wall 11. Compared with the case where the second portion 2113 is not folded and is directly connected to the first end wall 11, the portion of the second portion 2113 connected to the first end wall 11 accounts for a larger proportion of the total second portion 2113, which is beneficial to improving the stability of the connection between the second portion 2113 and the first end wall 11.

[0164] 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 surrounding wall 12 and the electrode assembly 20. In the aforementioned content, "the second part 2113 includes a sixth side 21131 and a seventh side 21132 that are relatively arranged 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 surrounding wall 12 and the electrode assembly 20 is used for determination, and the determined sixth side 21131 and seventh side 21132 are used to 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 a portion of the sixth side 21131 and a portion of the seventh side 211332. Figure 9 and Figure 11 In the illustrated state, the sixth side 21131 and the seventh side 21132 are continuous line segments extending along the first direction X.

[0165] In some embodiments, as Figure 10 and Figure 11As shown, along the thickness direction of the first electrode sheet 21, part of the second portion 2113 is located on the side of the first portion 2112 facing the surrounding wall 12, and part 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 reduce the resistance caused by the folded state of the second portion 2113 when the first portion 2112 drives the second portion 2113 to move.

[0166] In some embodiments, the second portion 2113 in the folded state can be folded at least once more to further reduce the width.

[0167] In some embodiments, as Figure 5 As shown, second portion 2113 includes a sixth side 21131 and a seventh side 21132 disposed opposite each other along the winding direction of electrode assembly 20. Sixth side 21131 and second side 21121 are contiguous with first current collector 211, while seventh side 21132 and third side 21122 are contiguous with first current collector 211. An angle α is defined between first side 2114 and seventh side 21132, with a range of 40°≤α≤70°. Setting α≥40° ensures that α is not too small, facilitating movement of first portion 2112 with second portion 2113. Setting α≤70° ensures that α is not too large, facilitating connection of second portion 2113 with first end wall 11 and reducing the possibility of internal short circuits caused by the corner of the end portion of second portion 2113 connected to first end wall 11 being inserted into the winding structure of electrode assembly 20.

[0168] To measure α, a slice of the first pole piece 21 including the first portion 2112 and the second portion 2113 can be taken, and then the first portion 2112 and the second portion 2113 can be flattened. The angle α between the first side 2114 and the seventh side 21132 can be measured. An optical measuring instrument (OMM) can be used for observation and measurement.

[0169] In some embodiments, as Figure 2 and Figure 6 As shown, the second electrode sheet 22 includes a second current collector 221 and a second active material layer 222 arranged in a stacked manner. The second current collector 221 includes a second empty foil portion 2221 located at the outermost circle of the winding structure of the second electrode sheet 22 , and the second empty foil portion 2221 is not covered by the second active material layer 222 .

[0170] In some embodiments, as Figure 6 As shown, the second empty foil portion 2221 is welded with a first adapter 60, part of the first adapter 60 is located between the second pole piece 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, and the first adapter 60 is welded to the second end wall 13.

[0171] In some embodiments, as Figure 2 、 Figure 12 and Figure 13 As shown, the second empty foil portion 2221 is composed of a third part 2222 and a fourth part 2223. The third part 2222 extends along the winding direction of the electrode assembly 20, and the fourth part 2223 includes the end of the second pole piece 22. The fourth part 2223 is formed by bending part of the second empty foil portion 2221 in a direction so that the end of the second pole piece 22 is close to the second end wall 13. The fourth part 2223 connects the third part 2222 and the second end wall 13. The area where the fourth part 2223 is connected to the second end wall 13 is the third area 2225. The connection between the third portion 2222 and the fourth portion 2223 has an eighth side 2224. The third portion 2222 has a ninth side 22221 and a tenth side 22222 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 portion 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 the fold (defined as the fourth fold 2224a) formed when the second hollow foil portion 2221 is bent to form the fourth portion 2223, or the eighth side 2224 is an extension of the fourth fold 2224a. The minimum distance from the second inflection 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 surrounding wall 12. When the electrode assembly 20 expands in volume during the charge and discharge process, 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 state that is tighter than the original state, thereby releasing at least part of the stress, which is beneficial to reducing the possibility of the second electrode 22 being torn or broken due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery 100.

[0172] In some embodiments, one of the first electrode sheet 21 and the second electrode sheet 22 is a negative electrode sheet. The negative electrode sheet 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 greater than 3% based on the mass of the negative electrode active material layer. Compared to electrode sheets without silicon, electrode sheets containing silicon experience greater volume changes during charge and discharge, and the electrode assembly 20 generates greater internal stress. The provision of the second portion 2113 helps reduce the possibility of tearing or breaking of the first electrode sheet 21.

[0173] The silicon content in the negative electrode can be obtained by the following method:

[0174] The cylindrical battery 100 was discharged at a constant current of 0.1C to 3.0V, and the cylindrical battery 100 was disassembled to obtain the negative electrode sheet. The negative electrode sheet was cleaned with dimethyl carbonate (DMC) for 10 minutes, and then baked at 100°C for 2 hours before use. The negative electrode active material layer on the negative electrode sheet was scraped off, and the powder of the negative electrode active material layer was collected. The silicon and lithium contents in the powder of the negative electrode material layer were tested using an inductively coupled plasma spectrometer (ICP, model Agilent 5800, provided by Agilent). 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).

[0175] like Figure 14 As shown, an embodiment of the present application further provides an electronic device 1000 , comprising the cylindrical battery 100 as described in any of the aforementioned embodiments.

[0176] In some embodiments, the electronic device 1000 includes but is not limited to a mobile phone, a laptop computer, an electric toy, an electric tool, and an electronic cigarette.

[0177] In order to verify the impact of the solution provided in the embodiment of the present application on the service life of the cylindrical battery 100, the inventors of the present application conducted the following experiments.

[0178] The experiment includes two groups of comparative examples and 12 groups of examples, each group of comparative examples and each group of examples includes 30 cylindrical batteries 100. In the cylindrical batteries 100, the first electrode 21 is set as the negative electrode, and the second electrode 22 is set as the positive electrode.

[0179] The preparation process of the cylindrical battery 100 in Example 1 includes the following steps:

[0180] (1) Preparation of positive electrode sheet: The active materials lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), CNT (carbon nanotube), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:0.5:0.5:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode active material with a solid content of 75wt%, and stirred evenly for use. Aluminum foil with a thickness of 10μm is used as the positive electrode current collector. The above active material is evenly coated on 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 coated with a positive electrode active material on one side. The above coating steps are then repeated on the other surface of the positive electrode current collector along its thickness direction to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. At this time, the thickness of each positive electrode active material layer along the thickness direction of the positive electrode sheet is 90μm. The coated positive electrode sheet is then cold-pressed, leaving the positive electrode active material layer with a 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, which marks the starting section of the positive electrode sheet in the wound structure.

[0181] (2) Preparation of negative electrode sheet: Active materials artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) are mixed in a weight ratio of 97:0.5:1.3:1.2, deionized water is added as a solvent, and the mixture is prepared into a negative electrode active material material with a weight percentage of 50 wt%, and stirred evenly for use. A copper foil with a thickness of 10 μm is used as the negative electrode current collector. The above negative electrode active material is evenly coated on one surface of the negative electrode current collector along its thickness direction using a slit coater, and then dried at 110°C to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. Then, the above steps are repeated on the other side of the negative electrode current collector along its thickness direction to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. At this time, the thickness of each negative electrode active material layer along the thickness direction of the negative electrode sheet is 90 μm. The coated negative electrode sheet is then cold pressed, and the thickness of the negative electrode active material layer after cold pressing is 80 μm.

[0182] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were 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) was 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.

[0183] (4) Preparation of the isolation membrane 23: A 7 μm thick polyethylene porous polymer film was used as the isolation membrane 23.

[0184] (5) Preparation of the electrode assembly 20: 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 first hollow foil portion 2111 at the end of the wound structure of the negative electrode sheet is bent to form the connecting portion 2116 mentioned above, and a transition piece is welded to the connecting portion 2116 to serve as the transition piece 2117 mentioned above; the connecting portion 2116 is bent so that part of the connecting portion 2116 and the transition piece 2117 are close to the winding center of the electrode assembly 20; the transition piece welded to the positive electrode current collector is bent so that its end is close to the winding center of the electrode assembly 20;

[0185] (6) Assembly of the cylindrical battery 100: The electrode assembly 20 is placed in the space formed by the surrounding wall 12 of the shell 10 and the first end wall 11, the adapter 2117 is welded to the first end wall 11, and then the adapter connected to the positive electrode collector is welded to the pole 132 of the second end wall 13, and then the cover 131 of the second end wall 13 and the surrounding wall 12 are sealed and connected; then, after the steps of liquid injection, static standing, and formation, the cylindrical battery 100 is obtained.

[0186] The preparation process of the cylindrical batteries 100 in Comparative Example 2 and Examples 2-12 is basically the same as that in Example 1, with the only difference being that the specific values ​​of the relevant parameters listed in Table 1 below are different during the preparation process.

[0187] The preparation process of the cylindrical battery 100 in comparative example 1 is basically the same as the preparation process of the cylindrical battery 100 in embodiment 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 portion of the negative electrode collector that is not covered by the negative electrode active material layer, wherein the portion 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: the positive electrode sheet, the isolation film 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, and the adapter welded to the negative electrode collector is bent so that its end is close to the winding center of the electrode assembly 20, and the adapter is bent to the positive electrode collector. The welded adapter makes its end close to the winding center of the electrode assembly 20; the assembly process of the cylindrical battery 100 is: the electrode assembly 20 is placed in the space formed by the surrounding wall 12 and the second end wall 13 of the shell 10, the adapter connected to the positive electrode collector is facing the opening of the surrounding wall 12 for connecting to the second end wall 13, and the adapter of the negative electrode collector is facing the first end wall 11, the adapter connecting the negative electrode collector is welded to the first end wall 11, and the adapter connecting the positive electrode collector is welded to the pole 132 of the second end wall 13, and then the cover 131 of the second end wall 13 and the surrounding wall 12 are sealed; and then the cylindrical battery 100 is obtained through the steps of liquid injection, standing, formation and volume separation.

[0188] The dimensions of the manufactured cylindrical battery 100 are: H = 5.72 mm; R = 5.02 mm; R1 = 9.69 / 2 = 4.845 mm; R2 = 2.03 / 2 = 1.015 mm; and 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.

[0189] The cylindrical batteries 100 in the comparative examples 2 and 12 are both provided with a first adhesive 30 and a second adhesive 40 , and 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, so only the value of d1 is recorded in Table 1 below.

[0190] After the cylindrical batteries 100 were prepared, a K value test and a cycle capacity retention test were performed on each group of comparative and example cylindrical batteries 100. For the cylindrical batteries 100 in the same group, the test sequence was to first perform a K value test on each cylindrical battery 100, and then randomly select 10 cylindrical batteries 100 from each group for the cycle capacity retention test.

[0191] The process of K value testing is:

[0192] 1. Charge the cylindrical battery 100 to full power, specifically:

[0193] 1) The test temperature is 25°C;

[0194] 2) Let it stand for 30 minutes;

[0195] 3) 5C constant current charge to 4.25V, then constant voltage charge to 3C;

[0196] 4) 3C constant current charge to 4.35V, then constant voltage charge to 1.5C;

[0197] 5) 1.5C constant current charge to 4.45V, then constant voltage charge to 0.05C;

[0198] 2. Measure the initial voltage: Measure the voltage of the cylindrical battery 100 as the initial voltage OCV1, which serves as a reference value;

[0199] 3. Standing: The standing temperature is 25°C for 24 hours;

[0200] 4. Measure the voltage after rest: After the rest period, immediately measure the voltage OCVB of the cylindrical battery 100;

[0201] 5. Calculate the self-discharge rate K using the formula: K = (OCV1 - OCVB) / 24.

[0202] In this test, the qualified specification of the cylindrical battery 100 is defined as a K value between 0 and 0.06 mV / h.

[0203] The test process of cycle capacity retention is as follows:

[0204] 1) Maintain the test temperature at 25°C;

[0205] 2) Let the cylindrical battery 100 stand for 30 minutes;

[0206] 3) 5C constant current charge to 4.25V, then constant voltage charge to 3C;

[0207] 4) 3C constant current charge to 4.35V, then constant voltage charge to 1.5C;

[0208] 5) 1.5C constant current charge to 4.45V, then constant voltage charge to 0.05C;

[0209] 6) Let stand for 5 minutes;

[0210] 7) Discharge at 0.7C constant current to 3V and record the first discharge cycle capacity;

[0211] 8) Let stand for 5 minutes;

[0212] 9) Cycle steps 3 to 8 1200 times, and record the discharge capacity at the 1200th cycle;

[0213] 10) Calculate the capacity retention rate: Capacity retention rate = (discharge capacity at the 1200th cycle / discharge capacity at the first cycle) × 100%.

[0214] In this test, a capacity retention rate of more than 80% is defined as a pass. After the experiment, the experimental results are recorded in Table 1:

[0215] Table 1

[0216]

[0217] Note: In the table, “ / ” means there is no such data.

[0218] It can be seen from Table 1 that the cylindrical batteries 100 in Examples 1-12 have a higher pass rate in the test of cycle capacity retention than the cylindrical batteries 100 in Comparative Examples 1-2. It can be seen that since part of the first hollow foil portion 2111 of the cylindrical batteries 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 the charge and discharge process, under the action of internal stress, the first portion 2112 moves in the opposite direction of the winding direction of the electrode assembly 20, and drives the second portion 2113 to move, so that the second portion 2113 changes to a state that is tighter than the original state, thereby being able to release at least part of the stress, which is beneficial to reducing the possibility of the first electrode sheet 21 being torn or broken due to the accumulation of internal stress, thereby improving the service life of the cylindrical battery 100.

[0219] It can be seen from Table 1 that the cylindrical batteries 100 in Examples 1-3 satisfy 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 portion 2113 located between the first end wall 11 and the electrode assembly 20 is not too long, which is beneficial to reducing the risk of the second portion 2113 squeezing the surface of the electrode assembly 20 facing the first end wall 11 and causing a poor K value.

[0220] It can be seen from Table 1 that the cylindrical batteries 100 in Example 2 and Examples 6-7 satisfy 40°≤α≤70°, and the test pass rate of the cycle capacity retention rate of the cylindrical batteries 100 in Example 2 and Examples 6-7 is higher than that in Example 5. It can be seen that setting α≥40° and α is not too small can facilitate the first part 2112 to drive the second part 2113 to move, thereby releasing stress and improving the service life of the cylindrical battery 100; and the pass rate of the K value test of the cylindrical batteries 100 in Example 2 and Examples 6-7 is higher than that in Example 8. It can be seen that setting α≤70° is conducive 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.

[0221] As can be seen from Table 1, the cylindrical batteries 100 in Example 2 and Examples 10-11 meet 5%W≤d1≤70%W, and the pass rate of the K value test of the cylindrical batteries 100 in Example 2 and Examples 10-11 is higher than that in Example 9. It can be seen that setting d1≥5%W prevents the length of the edge of the second portion 2113 covered by the second adhesive 40 from being too short, which is beneficial to reducing the possibility of burrs on the edge of the second portion 2113 piercing the isolation film 23, thereby reducing the possibility of poor K value of the cylindrical battery 100; the pass rate of the cycle capacity retention rate test of the cylindrical batteries 100 in Example 2 and Examples 10-11 is higher than that in Example 12. It can be seen that setting d1≤70%W is beneficial to reducing the probability of poor connection between the second portion 2113 and the first end wall 11 due to the presence of the first adhesive 30.

[0222] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. Any appropriate changes and modifications to the above embodiments fall within the scope of the present application as long as they are within the spirit of the present application.

Claims

1. A cylindrical battery, characterized in that: include: a housing, the housing comprising a first end wall, a second end wall, and a surrounding wall, the first end wall and the second end wall being arranged opposite to each other along a first direction, the surrounding wall connecting the first end wall and the second end wall and enclosing together with the first end wall and the second end wall to form a first space; and an electrode assembly disposed in the first space, the electrode assembly comprising a first electrode sheet, a second electrode sheet, and a separator, wherein the first electrode sheet, the separator, and the second electrode sheet are stacked and wound to form a wound structure, with a winding central axis of the electrode assembly oriented in the first direction; The first electrode sheet includes a first current collector and a first active material layer that are stacked. The first current collector includes a first hollow foil portion located at the outermost circle of the winding structure of the first electrode sheet. The first hollow foil portion is not covered by the first active material layer. The first hollow foil portion consists of a first portion and a second portion. The first portion extends along the winding direction of the electrode assembly. The second portion includes an end of the first electrode sheet. The second portion is formed by bending the first hollow foil portion. The end of the first electrode sheet is located between the first end wall and the electrode assembly. The second portion connects the first portion and the first end wall. The area where the second portion is connected to the first end wall is the first area. The connection between the first portion and the second portion has a first edge, the first portion has a second edge and a third edge arranged opposite to each other along the first direction, the second edge is closer to the first end wall than the third edge, and the first edge and the third edge intersect to form a first folding 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 surrounding wall is R; Along the extension direction of the second portion, the minimum distance from the first folding point to the first area is L1, and H+R≤L1.

2. The cylindrical battery according to claim 1, wherein: The cross-section of the electrode assembly perpendicular to the first direction is annular, the outer radius of the electrode assembly is R1, the inner radius of the electrode assembly is R2, and L1≤H+R+30%π(R1+R2).

3. The cylindrical battery according to claim 2, wherein: H+R+10%π(R1+R2)≤L1≤H+R+20%π(R1+R2).

4. The cylindrical battery according to claim 1, wherein The cylindrical battery includes a first adhesive member and a second adhesive member, wherein the first adhesive member and the second adhesive member are both bonded to the first portion and the second portion, the first adhesive member is bonded to the surfaces of the first portion and the second portion facing the surrounding wall, and the second adhesive member is bonded to the surfaces of the first portion and the second portion facing the winding center axis; The first adhesive member covers at least a portion of an edge of the first portion and a portion of an edge of the second portion; The second adhesive member covers at least a portion of an edge of the first portion and a portion of an edge of the second portion.

5. The cylindrical battery according to claim 4, wherein: A projection of the second side along the thickness direction of the first pole piece falling on the second portion is a first projection line; The first adhesive member has a fourth side, the fourth side is arranged 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, a distance between the first projection line and the fourth side along the extension direction of the second portion is d1, a width of the first portion along the first direction is W, and 5%W≤d1≤70%W; and / or The second adhesive has a fifth edge, which is arranged opposite to the first projection line along the first direction, and the fifth edge is closer to the first area than the first projection line. The distance between the first projection line and the fifth edge along the extension direction of the second part is d2, and the width of the first part along the first direction is W, 5%W≤d2≤70%W.

6. The cylindrical battery according to claim 1, wherein: The second part includes a connecting portion and a transition portion, the connecting portion and the first part are an integral structure, the transition portion is connected to the connecting portion, and the transition portion is connected to the first end wall, the area where the transition portion is connected to the first end wall is the first area, and the area where the connecting portion and the transition portion are connected is the second area, and the first area is separated from the second area.

7. The cylindrical battery according to claim 6, wherein: The transition portion is welded to the connecting portion, and the transition portion is welded to the first end wall. Along the extension direction of the second portion, the minimum distance between the first area and the second area is L2, and 1 / 5R≤L2≤3 / 5R.

8. The cylindrical battery according to claim 6, wherein: The adapter is welded to the connecting portion. The cylindrical battery further includes a third adhesive member, the third adhesive member adhering the connecting portion and the adapter and being located on a side of the connecting portion and the adapter facing the winding structure. Along the thickness direction of the adapter, the third adhesive member covers the second area and is separated from the first area. Along the extending direction of the second portion, a minimum distance between the third adhesive component and the first region is L3, and 1 / 5R≤L3≤2 / 5R.

9. The cylindrical battery according to claim 1, wherein: The second portion is a folded structure. After a portion of the first hollow foil portion is bent in a direction such that the end of the first electrode sheet approaches the first end wall, the second portion includes a sixth side and a seventh side that are oppositely arranged along the winding direction of the electrode assembly. The sixth side and the second side are the same side of the first current collector, and the seventh side and the third side are the same side of the first current collector. The folded structure is formed by bending a portion of the first hollow foil portion in a direction such that the end of the first electrode sheet approaches the first end wall, and then folding the second portion in such a manner that the sixth side approaches the first portion. A height of the electrode assembly along the first direction is h, where h≥4R / 3.

10. The cylindrical battery according to claim 1, wherein: Along the thickness direction of the first pole piece, part of the second portion is located on a side of the first portion facing the surrounding wall, and part of the second portion is located on a side of the first portion facing the winding center of the electrode assembly.

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

12. The cylindrical battery according to any one of claims 1 to 10, wherein: The second electrode sheet includes a second current collector and a second active material layer that are stacked, the second current collector includes a second hollow foil portion located at the outermost circle of the wound structure of the second electrode sheet, the second hollow foil portion is not covered by the second active material layer, the second hollow foil portion is composed of a third portion and a fourth portion, the third portion extends along the winding direction of the electrode assembly, the fourth portion includes the end of the second electrode sheet, the fourth portion is formed by bending a portion of the second hollow foil portion in a direction that brings the end of the second electrode sheet closer to the second end wall, the fourth portion connects the third portion and the second end wall; the area where the fourth portion is connected to the second end wall is the third area; The connection between the third portion and the fourth portion has an eighth side, the third portion 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 folding point; Along the extension direction of the fourth portion, the minimum distance from the second folding point to the third area is L4, and H+R≤L4.

13. The cylindrical battery according to claim 1, wherein: One of the first electrode sheet and the second electrode sheet is a negative electrode sheet, and the negative electrode sheet includes a stacked negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer includes silicon element, and the mass content of the silicon element is greater than 3% based on the mass of the negative electrode active material layer.

14. An electronic device, characterized in that: The invention comprises a cylindrical battery as claimed in any one of claims 1 to 13.

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