Cylindrical battery, battery pack and electric equipment

Abstract

The invention discloses a cylindrical battery, a battery pack and electric equipment. A cylindrical battery includes a housing and an electrode assembly. The electrode assembly comprises a positive plate, a negative plate and a separator, the separator separates the positive plate from the negative plate, and the positive plate, the separator and the negative plate are wound in the winding direction. The positive plate comprises a plurality of positive sections and a plurality of connecting pieces, the plurality of positive sections are arranged at intervals along the winding direction, a gap is formed between any two adjacent positive sections along the winding direction, and the connecting pieces are connected with the two adjacent positive sections along the winding direction. The positive plate is provided with an inner side area, a middle area and an outer side area which are sequentially arranged in the winding direction, the size of the positive plate in the winding direction is L, the size of the inner side area in the winding direction is L / 5-L / 3 from the winding starting end of the positive plate, and the size of the outer side area in the direction opposite to the winding direction is L / 5-L / 3 from the winding ending end of the positive plate. At least one gap is located in the inner side area, and at least one gap is located in the outer side area.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a cylindrical battery, a battery pack, and an electrical device. Background Technology

[0002] With the rapid development of the new energy industry, the application of rechargeable batteries in electric vehicles, electric bicycles, and power tools is becoming a trend. Cylindrical batteries, in particular, are highly favored due to their advantages such as good packability and high stability.

[0003] Cylindrical battery electrode components typically employ a wound structure. When the electrode components expand, the outer electrode plates are easily pulled and may break, while the inner electrode plates are easily squeezed and may sink in. This could lead to the risk of the separator being torn and short-circuited, affecting the reliability of the cylindrical battery. Summary of the Invention

[0004] This application provides a cylindrical battery, battery pack, and electrical device, which helps to reduce the risk of electrode breakage, improve the phenomenon of electrode assembly indentation, and enhance reliability.

[0005] In a first aspect, this application provides a cylindrical battery comprising a casing and an electrode assembly. The electrode assembly is housed within the casing and includes a positive electrode, a negative electrode, and a separator. The separator separates the positive and negative electrode. The positive electrode, separator, and negative electrode are wound along a winding direction. The positive electrode includes multiple positive electrode segments and multiple connectors. The multiple positive electrode segments are spaced apart along the winding direction, and a gap is formed between any two adjacent positive electrode segments along the winding direction. The connectors connect two adjacent positive electrode segments along the winding direction. The positive electrode has an inner region, a middle region, and an outer region arranged sequentially along the winding direction. The dimension of the positive electrode along the winding direction is L. From the starting end of the winding of the positive electrode, the dimension of the inner region along the winding direction is L / 5-L / 3. From the ending end of the winding of the positive electrode, the dimension of the outer region in the direction opposite to the winding direction is L / 5-L / 3. At least one gap is located in the inner region, and at least one gap is located in the outer region. The gap located in the inner region helps to increase the space between the inner region and the negative electrode, thereby relieving the compressive stress on the inner region and the negative electrode in the radial direction of the cylindrical battery, improving the phenomenon of electrode assembly indentation deformation, and reducing the risk of short circuit. The gap located in the outer region helps to relieve the tensile stress on the outer region, reducing the risk of outer region fracture, thus improving the reliability of the cylindrical battery.

[0006] In any one or more of the above optional embodiments, the dimension of the gap in the inner region along the winding direction is d1, and the dimension of the gap in the outer region along the winding direction is d2, where d1 ≤ d2. A smaller dimension of the gap in the inner region along the winding direction is beneficial for reducing the risk of short circuits caused by indentation deformation of the electrode assembly, and also for increasing the effective length of the inner region, thus reducing the impact of the gap on the capacity of the cylindrical battery. In the outer region, the size ratio of the gap to the positive electrode section is more reasonable, which is more conducive to alleviating the tangential tensile stress on the outer region and reducing the risk of breakage in the outer region.

[0007] In any one or more of the above optional embodiments, 2mm ≤ d1 ≤ 4mm, and 2mm ≤ d2 ≤ 8mm. d1 being greater than or equal to 2mm increases the size of the gap in the inner region, thereby providing a larger buffer space and improving the phenomenon of electrode assembly indentation; d1 being less than or equal to 4mm increases the effective length of the inner region, reducing the impact on the capacity of the cylindrical battery 1. d2 being greater than or equal to 2mm increases the size of the gap in the outer region to limit the amount of extension and deformation of the positive electrode segment along the circumference of the cylindrical battery, reducing the risk of breakage in the outer region; d2 being less than or equal to 8mm increases the effective length of the outer region, reducing the impact on the capacity of the cylindrical battery.

[0008] In any one or more of the above optional embodiments, the central region connects the tail end of the inner region along the winding direction and the beginning end of the outer region along the winding direction, with at least one gap located in the central region. On the one hand, this helps to alleviate the tensile stress along the circumference of the cylindrical battery experienced by the outer region as a whole, reducing the risk of breakage in the outer region; on the other hand, a buffer space is formed between the gap between the negative electrode and the central region to buffer the radial compression effect along the cylindrical battery experienced by the inner region and the negative electrode, reducing the risk of short circuit caused by indentation deformation of the electrode assembly.

[0009] In any one or more of the above optional embodiments, the dimension of the gap in the inner region along the winding direction is d1, the dimension of the gap in the outer region along the winding direction is d2, and the dimension of the gap in the middle region along the winding direction is d3, where d1≤d3≤d2. The size ratio of the gap in the middle region to the positive electrode section is more reasonable, which is beneficial to improving the release effect on the tensile stress on the outer region and the radial compressive stress on the inner region.

[0010] In any one or more of the above optional embodiments, the dimension of the connector located in the inner region along the winding direction is a1, the dimension of the connector located in the outer region along the winding direction is a2, and the dimension of the connector located in the middle region along the winding direction is a3, where a1≤a3≤a2. Matching the dimensions of the connectors with the dimensions of the corresponding gaps helps control the dimension of the overlapping portion of the connector and the positive electrode section along the winding direction V, reducing the portion of the positive electrode section that fails due to being covered by the connector, and improving the connection strength between each connector and the positive electrode section.

[0011] In any one or more of the above optional embodiments, 10mm≤a1≤15mm, 10mm≤a3≤20mm, 10mm≤a2≤30mm. Setting a1 to be greater than or equal to 10mm, a3 to be greater than or equal to 10mm, and a2 to be greater than or equal to 10mm can increase the connection area between the connector and the positive electrode section, thereby improving the connection strength. Setting a1 to be less than or equal to 15mm, a3 to be less than or equal to 20mm, and a2 to be less than or equal to 30mm helps to limit the size of the overlapping part between the connector and the positive electrode section, reduce the part of the positive electrode section that is covered by the connector and fails, and reduce the impact of the connector setting on the capacity of the cylindrical battery.

[0012] In any one or more of the above optional embodiments, the thickness of the positive electrode section is T1, and the thickness of the connector is T2, where T2 ≤ T1 / 2. Optionally, T1 / 10 ≤ T2 ≤ T1 / 3. Setting T2 / T1 to be greater than or equal to 1 / 10 is beneficial for improving the strength of the connector and reducing the risk of connector breakage. Setting T2 / T1 to be less than or equal to 1 / 2 is beneficial for improving the ductility and deformation capacity of the connector, releasing the tensile stress on the positive electrode section, and also for forming a buffer space between the connector and the negative electrode plate, alleviating the radial compressive stress on the positive electrode section and the negative electrode plate, and reducing the risk of indentation deformation of the electrode assembly.

[0013] In any one or more of the above optional embodiments, the thickness of the connector located in the inner region is less than or equal to the thickness of the connector located in the outer region. The thinner connector in the inner region occupies less space, and the larger buffer space formed between the inner region and the negative electrode provides more room for deformation after compression, reducing the risk of electrode assembly indentation. The thicker connector in the outer region has stronger resistance to tangential traction forces and is less prone to breakage.

[0014] In any one or more of the above optional embodiments, a portion of the connector overlaps with the positive electrode section along the radial direction of the cylindrical battery; the dimension of the overlapping portion of the connector and the positive electrode section along the winding direction is b, where 2mm ≤ b ≤ 7mm. Setting b to be greater than or equal to 2mm is beneficial for increasing the connection area between the connector and the positive electrode section, improving the connection strength, and reducing the risk of connection breakage; setting b to be less than or equal to 7mm is beneficial for reducing the portion of the positive electrode section that fails due to being covered by the connector, thus reducing the impact of the connector's configuration on the capacity of the cylindrical battery.

[0015] In any one or more of the above optional embodiments, a portion of the connector overlaps with the positive electrode section along the radial direction of the cylindrical battery; the dimension of the portion of the connector in the inner region that overlaps with the positive electrode section along the winding direction is smaller than or equal to the dimension of the portion of the connector in the outer region that overlaps with the positive electrode section along the winding direction. The connector in the outer region experiences a greater traction force, making it easier to break the connection between the connector and the positive electrode section. The greater overlap between the connector in the outer region and the positive electrode section increases the connection area and improves the connection strength.

[0016] In any one or more of the above optional embodiments, the positive electrode section includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; along the axial direction of the cylindrical battery, the two ends of the connector extend beyond the two ends of the positive electrode active material layer. The connector can reduce the possibility of powder shedding from the edge of the positive electrode active material layer, and the portion extending beyond the positive electrode active material layer can support the separator, reduce the deformation of the separator, and reduce the risk of short circuit between the positive and negative electrodes due to separator failure.

[0017] In any one or more of the above optional embodiments, along the axial direction of the cylindrical battery, the two ends of the separator extend beyond the two ends of the connector. This is beneficial to improving the safety of the separator in isolating the positive and negative electrodes, reducing the risk of short circuits caused by the collapse of the two ends of the separator or the connector; and limiting the axial dimension of the connector reduces the space occupied by the connector in the axial direction, which is beneficial to improving the energy density of the cylindrical battery.

[0018] In any one or more of the above optional embodiments, the connector includes two connecting layers. Along the radial direction of the cylindrical battery, the two connecting layers are respectively bonded to both sides of the positive electrode section, and the two connecting layers are interconnected. By providing two connecting layers, it is beneficial to improve the connection strength between the connector and the positive electrode section, reduce the risk of the connector falling off, and the interconnection of the two connecting layers helps to expand the buffer space reserved for electrode expansion, reducing the risk of the electrode being squeezed and wrinkled or broken.

[0019] In any one or more of the above optional embodiments, the connecting layer includes a substrate layer and an adhesive layer, wherein the tensile strength of the substrate layer is 50 MPa-200 MPa. The substrate layer has suitable tensile strength, and the connecting layer can deform when subjected to tensile force along the circumferential direction of the cylindrical battery, thereby alleviating the tensile force on the positive electrode section and reducing the risk of positive electrode section breakage.

[0020] In any one or more of the above optional embodiments, the tensile breaking strength of the connecting layer is less than that of the positive electrode segment. Because the connecting layer has a lower tensile breaking strength, when the connecting layer and the positive electrode segment are subjected to the same tensile force, the connecting layer may break before the positive electrode segment. This helps to release the stress on the positive electrode segment, reduces the risk of positive electrode segment breakage, and improves the reliability of the cylindrical battery.

[0021] In any one or more of the above optional embodiments, the bonding layer includes a substrate layer and an adhesive layer, wherein the substrate layer includes at least one of biaxially oriented polypropylene film, polyester film, polyimide film, biaxially oriented polystyrene film, and film made of meta-aramid or aramid 1313.

[0022] In any one or more of the above optional embodiments, the peel strength between the connector layer and the positive electrode section is greater than or equal to 0.15 N / mm. The high peel strength between the connector layer and the positive electrode section reduces the risk of the connector detaching from the positive electrode section, thereby improving reliability.

[0023] Secondly, this application provides a battery pack that includes a cylindrical battery according to any embodiment of the first aspect.

[0024] Thirdly, this application provides an electrical device that includes a battery pack according to any embodiment of the second aspect. Attached Figure Description

[0025] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0026] Figure 1 This is a schematic diagram of the structure of a cylindrical battery provided in some embodiments of this application; Figure 2 for Figure 1 A cross-sectional view of the cylindrical battery shown. Figure 3 for Figure 1 A cross-sectional view of the electrode assembly of the cylindrical battery shown. Figure 4 for Figure 1 A schematic diagram of the unfolded positive electrode of the cylindrical battery shown. Figure 5 For along Figure 3 The sectional view intercepted by the cutting line AA in the diagram; Figure 6 for Figure 1 A cross-sectional view of the connecting layer of the cylindrical battery shown. Figure 7 Cross-sectional views of a battery pack provided for some embodiments of this application; Figure 8 The diagram shows the structure of electrical equipment provided in some embodiments of this application.

[0027] The reference numerals in the accompanying drawings for the specific embodiments are as follows: 1. Cylindrical battery; 100. Battery pack; 1000. Electrical equipment; 10. Outer shell; 11. Shell; 111. Opening; 112. Side wall; 113. Bottom wall; 12. End cap; 20. Electrode assembly; 21. Positive electrode sheet; 21a. Inner region; 21b. Middle region; 21c. Outer region; 21d. Winding start end; 21e. Winding end. 24. Positive electrode section; 241. Positive electrode current collector; 2411. Positive electrode current collector body; 2412. Positive electrode tab; 242. Positive electrode active material layer. 25. Connector; 251. Substrate layer; 252. Adhesive layer; 25a. Connecting layer; 26. Gap; 22. Negative electrode sheet; 221. Negative electrode current collector; 2211. Negative electrode current collector body; 2212. Negative electrode tab; 222. Negative electrode active material layer; 23. Separator. a. Central axis, V. Winding direction, X. Axial direction. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0029] The terms "first," "second," "third," etc., used in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0030] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0031] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0032] In the embodiments of this application, "parallel" includes not only the case of absolute parallelism, but also the case of approximate parallelism as commonly understood in engineering; similarly, "perpendicular" also includes not only the case of absolute perpendicularity, but also the case of approximate perpendicularity as commonly understood in engineering. For example, if the angle between two directions is 80°-90°, the two directions can be considered perpendicular; if the angle between two directions is 0°-10°, the two directions can be considered parallel.

[0033] The cylindrical battery, battery pack, and electrical device of this application are described below with reference to the accompanying drawings.

[0034] Reference Figure 1 and Figure 2 This application provides a cylindrical battery 1, which can be a lithium-ion battery, a sodium-lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, or other types of batteries.

[0035] For example, the cylindrical battery 1 is an 18650 battery, a 21700 battery, a 4680 battery, or other types of cylindrical batteries.

[0036] In some embodiments, the cylindrical battery 1 is a secondary battery. After discharge, the secondary battery can be recharged to activate the active materials and continue to be used.

[0037] In some embodiments, refer to Figure 1 and Figure 2 The cylindrical battery 1 includes a housing 10 and an electrode assembly 20, which is housed within the housing 10. The housing 10 is used to encapsulate the electrode assembly 20 and components such as the electrolyte.

[0038] The housing 10 includes a housing 11 and an end cap 12. The housing 11 has an opening 111 on one side along the axial direction X of the cylindrical battery 1. The end cap 12 is connected to the housing 11 and covers the opening 111. The end cap 12 closes the opening 111, thereby forming a closed cylindrical space between the housing 11 and the end cap 12.

[0039] The housing 11 includes a side wall 112 and a bottom wall 113. The side wall 112 surrounds the electrode assembly 20, and the bottom wall 113 is disposed opposite to the opening 111 along the axial direction X. The side wall 112 is connected to the bottom wall 113.

[0040] The electrode assembly 20 is electrically connected to the end cap 12, and the electrode assembly 20 is electrically connected to the bottom wall 113. The end cap 12 and the bottom wall 113 form two electrode terminals of the cylindrical battery 1, which eliminates the need for traditional electrode terminals and simplifies the structure of the cylindrical battery 1.

[0041] In some embodiments, refer to Figure 3 The electrode assembly 20 includes a positive electrode 21, a negative electrode 22, and a separator 23. The separator 23 separates the positive electrode 21 and the negative electrode 22, and the positive electrode 21, the separator 23, and the negative electrode 22 are wound together in the winding direction V.

[0042] The positive electrode 21, the separator 23 and the negative electrode 22 are stacked in sequence and wound multiple turns along the winding direction V to form the electrode assembly 30.

[0043] During the charging and discharging process of the cylindrical battery 1, active ions (such as lithium ions) are inserted and extracted back and forth between the positive electrode 21 and the negative electrode 22.

[0044] The separator 23 can reduce the risk of short circuit between the positive electrode 21 and the negative electrode 22, while allowing active ions to pass through. Exemplarily, the separator 23 includes a separator membrane.

[0045] In some embodiments, refer to Figure 3 The positive electrode 21 includes multiple positive electrode segments 24 and multiple connectors 25. The multiple positive electrode segments 24 are spaced apart along the winding direction V. A gap 26 is formed between any two adjacent positive electrode segments 24 along the winding direction V. The connectors 25 connect two adjacent positive electrode segments 24 along the winding direction V.

[0046] Optionally, the connector 25 is bonded to two adjacent positive electrode segments 24 along the winding direction V.

[0047] Optionally, the thickness of the connector 25 is less than the thickness of the positive electrode section 24.

[0048] The dimensions of the multiple positive electrode segments 24 along the winding direction V can be the same or different.

[0049] The dimensions of the multiple connectors 25 along the winding direction V can be the same or different.

[0050] There are multiple gaps 26, and the dimensions of the multiple gaps 26 along the winding direction V can be the same or different.

[0051] The positive electrode 21 includes multiple positive electrode segments 24 intermittently arranged along the winding direction V, which can form a non-lithium-intercalated region on the surface of the negative electrode 22, alleviating the expansion and contraction of the negative electrode 22 and thus releasing the stress on the negative electrode 22. The intermittent arrangement of the multiple positive electrode segments 24 helps to release the tensile stress on the positive electrode 21 along the winding direction V, reducing the risk of breakage. The gap 26 helps to increase the space between the positive electrode 21 and the negative electrode 22, thereby releasing the compressive stress on the positive electrode 21 and the negative electrode 22 in the radial direction of the cylindrical battery 1 and reducing the risk of short circuit caused by the collapse of the electrode assembly 20.

[0052] In some embodiments, refer to Figure 3 and Figure 4 The positive electrode 21 has an inner region 21a, a middle region 21b, and an outer region 21c arranged sequentially along the winding direction V. The dimension of the positive electrode 21 along the winding direction V is L; starting from the winding start end 21d of the positive electrode 21, the dimension of the inner region 21a along the winding direction V is L / 5-L / 3; starting from the winding end end 21e of the positive electrode 21, the dimension of the outer region 21c along the direction opposite to the winding direction V is L / 5-L / 3.

[0053] The inner region 21a is the area where the positive electrode 21 is first wound. Along the winding direction V, the end of the inner region 21a away from the middle region 21b is the starting end 21d of the winding of the positive electrode 21. The outer region 21c is the area where the positive electrode 21 is last wound. Along the winding direction V, the end of the outer region 21c away from the middle region 21b is the ending end 21e of the winding of the positive electrode 21.

[0054] Starting from the winding start end 21d of the positive electrode 21, the size of the inner region 21a along the winding direction V is L / 5, L / 4, L / 3, or any value between any two of them.

[0055] Starting from the winding end 21e of the positive electrode 21, the outer region 21c has a dimension of L / 5, L / 4, L / 3 or any value between any two of them in the direction opposite to the winding direction V.

[0056] Along the winding direction V, the dimensions of the inner region 21a and the outer region 21c can be the same or different.

[0057] Optionally, along the winding direction V, the dimensions of the inner region 21a and the outer region 21c are both L / 4.

[0058] The central region 21b is directly or indirectly connected to the inner region 21a through other regions, and the central region 21b is directly or indirectly connected to the outer region 21c through other regions.

[0059] In some embodiments, at least one gap 26 is located in the inner region 21a and at least one gap 26 is located in the outer region 21c.

[0060] The connector 25 is provided in a one-to-one correspondence with the gap 26. Along the winding direction V, the size of the connector 25 is larger than the size of the corresponding gap 26, so that the connector 25 can connect the two positive electrode sections 24 on both sides of the corresponding gap 26. The inner region 21a is provided with at least one connector 25, and the outer region 21c is provided with at least one connector 25.

[0061] Optionally, the number of gaps 26 located in the inner region 21a is 1-5.

[0062] Optionally, the number of gaps 26 located in the outer region 21c is 1-5.

[0063] The number of gaps 26 located in the inner region 21a and the number of gaps 26 located in the outer region 21c can be the same or different.

[0064] In one example, at least one gap 26 is located in the central region 21b. In another example, the central region 21b does not have a gap 26.

[0065] Compared to the central region 21b and the outer region 21c, the inner region 21a is closer to the central axis a of the cylindrical battery 1. The portion of the negative electrode 22 corresponding to the inner region 21a, as well as the inner region 21a itself, is easily deformed inward toward the side closer to the central axis a by radial compression, leading to a short circuit. The gap 26 located in the inner region 21a helps to increase the space between the inner region 21a and the negative electrode 22, thereby releasing the compressive stress on the inner region 21a and the negative electrode 22 in the radial direction of the cylindrical battery 1, improving the phenomenon of inward deformation of the electrode assembly 20, and reducing the risk of short circuit.

[0066] Compared to the central region 21b and the inner region 21a, the outer region 21c is farther from the central axis a of the cylindrical battery 1. When the electrode assembly 20 expands and deforms, the outer region 21c experiences greater tensile stress along the circumference of the cylindrical battery 1, making it more prone to fracture. The gap 26 located in the outer region 21c helps to release the tensile stress on the outer region 21c, reducing the risk of fracture.

[0067] In some embodiments, refer to Figure 4 The gap 26 located in the inner region 21a has a dimension d1 along the winding direction V, and the gap 26 located in the outer region 21c has a dimension d2 along the winding direction V, where d1 ≤ d2. Optionally, d1 < d2.

[0068] Compared to the outer region 21c, the inner region 21a is closer to the central axis a of the cylindrical battery 1. The radius of each ring of the positive electrode in the inner region 21a is smaller, and the size of the gap 26 in the inner region 21a along the winding direction V is smaller. This is beneficial to reducing the risk of short circuit caused by the indentation deformation of the electrode assembly 20, and also to increasing the effective length of the inner region 21a, thereby reducing the impact of the gap 26 on the capacity of the cylindrical battery 1.

[0069] Compared to the inner region 21a, the radius of each turn of the positive electrode in the outer region 21c is larger. The gap 26 in the outer region 21c has a larger dimension along the winding direction V. In the outer region 21c, the size ratio of the gap 26 and the positive electrode section 24 is more reasonable, which is more conducive to relieving the tangential tensile stress on the outer region 21c and reducing the risk of breakage of the outer region 21c.

[0070] In some embodiments, 2mm≤d1≤4mm, 2mm≤d2≤8mm.

[0071] Optionally, d1 is 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 3.9mm, 4mm, or any value between two of these.

[0072] Optionally, d2 is 2mm, 2.2mm, 2.4mm, 2.6mm, 2.8mm, 3mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm, 4mm, 4.2mm, 4.4mm, 4.6mm, 4.8mm, 5mm, 5.2mm, 5.4mm, 5.6mm, 5.8mm, 6mm, 6.2mm, 6.4mm, 6.6mm, 6.8mm, 7mm, 7.2mm, 7.4mm, 7.6mm, 7.8mm, 8mm, or any value between any two of these.

[0073] In this embodiment, setting d1 to be greater than or equal to 2 mm can increase the size of the gap 26 located in the inner region 21a, thereby providing a larger buffer space and improving the phenomenon of the electrode assembly 20 being sunken; setting d1 to be less than or equal to 4 mm can increase the effective length of the inner region 21a and reduce the impact on the capacity of the cylindrical battery 1.

[0074] In this embodiment, setting d2 to be greater than or equal to 2 mm can increase the size of the gap 26 located in the outer region 21c, thereby limiting the amount of extension and deformation of the positive electrode segment 24 along the circumferential direction of the cylindrical battery and reducing the risk of breakage of the outer region 21c; setting d2 to be less than or equal to 8 mm can increase the effective length of the outer region 21c and reduce the impact on the capacity of the cylindrical battery 1.

[0075] In some embodiments, there are multiple gaps 26 located in the inner region 21a. The multiple gaps 26 located in the inner region 21a may have the same or different dimensions along the winding direction V.

[0076] Optionally, along the winding direction V, the size of the plurality of gaps 26 located in the inner region 21a gradually increases.

[0077] In some embodiments, there are multiple gaps 26 located in the outer region 21c. The multiple gaps 26 located in the outer region 21c may have the same or different dimensions along the winding direction V.

[0078] Optionally, along the winding direction V, the size of the plurality of gaps 26 located in the outer region 21c gradually increases.

[0079] In some embodiments, refer to Figure 3 and Figure 4 The middle region 21b connects the tail end of the inner region 21a along the winding direction V and the beginning end of the outer region 21c along the winding direction V. At least one gap 26 is located in the middle region 21b.

[0080] Optionally, there may be multiple gaps 26 located in the central region 21b. The dimensions of the multiple gaps 26 located in the central region 21b along the winding direction V may be the same or different.

[0081] Optionally, along the winding direction V, the size of the plurality of gaps 26 located in the central region 21b gradually increases.

[0082] Optionally, the number of gaps 26 located in the central region 21b is 1-5.

[0083] At least one gap 26 is located in the middle region 21b. On the one hand, this helps to alleviate the tensile stress along the circumference of the cylindrical battery 1 on the outer region 21c as a whole, reducing the risk of breakage of the outer region 21c. On the other hand, a buffer space is formed between the negative electrode 22 and the gap 26 in the middle region 21b to buffer the radial compression of the inner region 21a and the negative electrode 22 along the cylindrical battery 1, reducing the risk of short circuit caused by inward deformation of the electrode assembly 20.

[0084] In some embodiments, refer to Figure 4The gap 26 located in the inner region 21a has a dimension d1 along the winding direction V, the gap 26 located in the outer region 21c has a dimension d2 along the winding direction V, and the gap 26 located in the middle region 21b has a dimension d3 along the winding direction V, where d1 ≤ d3 ≤ d2. Optionally, d1 < d3 < d2.

[0085] The average radius of each ring of positive electrode in the middle region 21b is larger than that in the inner region 21a, and the average radius of each ring of positive electrode in the middle region 21b is smaller than that in the outer region 21c. Setting d3 to be greater than or equal to d1 and less than or equal to d2 makes the size ratio of the gap 26 and the positive electrode section 24 in the middle region 21b more reasonable, which is beneficial to improving the release effect of tensile stress on the outer region 21c and radial compressive stress on the inner region 21a.

[0086] In some embodiments, refer to Figure 4 The dimension of the connector 25 located in the inner region 21a along the winding direction V is a1, the dimension of the connector 25 located in the outer region 21c along the winding direction V is a2, and the dimension of the connector 25 located in the middle region 21b along the winding direction V is a3, where a1≤a3≤a2. Optionally, a1<a3<a2.

[0087] Along the winding direction V, the dimensions of the connector 25 located in the inner region 21a match the dimensions of the gap 26 located in the inner region 21a; the dimensions of the connector 25 located in the middle region 21b match the dimensions of the gap 26 located in the middle region 21b; and the dimensions of the connector 25 located in the outer region 21c match the dimensions of the gap 26 located in the outer region 21c. This facilitates control over the dimensions of the overlapping portion of the connector 25 and the positive electrode section 24 along the winding direction V, reduces the portion of the positive electrode section 24 that is covered by the connector 25 and thus fails, and improves the connection strength between each connector 25 and the positive electrode section 24.

[0088] The dimensions of the portion of the connector 25 overlapping with the positive electrode section 24 in the inner region 21a along the winding direction V, the dimensions of the portion of the connector 25 overlapping with the positive electrode section 24 in the middle region 21b along the winding direction V, and the dimensions of the portion of the connector 25 overlapping with the positive electrode section 24 in the outer region 21c along the winding direction V can be the same or different.

[0089] In some embodiments, 10mm≤a1≤15mm, 10mm≤a3≤20mm, and 10mm≤a2≤30mm.

[0090] Optionally, a1 can be 10mm, 10.5mm, 11mm, 11.5mm, 12mm, 12.5mm, 13mm, 13.5mm, 14mm, 14.5mm, 15mm, or any value between any two of these.

[0091] Optionally, a3 can be 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, or any value between any two of these.

[0092] Optionally, a2 can be 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, or any value between two of these.

[0093] In this embodiment, setting a1 to be greater than or equal to 10 mm, a3 to be greater than or equal to 10 mm, and a2 to be greater than or equal to 10 mm increases the connection area between the connector 25 and the positive electrode section 24, thereby improving the connection strength. Setting a1 to be less than or equal to 15 mm, a3 to be less than or equal to 20 mm, and a2 to be less than or equal to 30 mm helps to limit the size of the overlapping part between the connector 25 and the positive electrode section 24, reduces the part of the positive electrode section 24 that is covered by the connector 25 and fails, and reduces the impact of the setting of the connector 25 on the capacity of the cylindrical battery 1.

[0094] In some embodiments, refer to Figure 5 The thickness of the positive electrode section 24 is T1, and the thickness of the connector 25 is T2, where T2 ≤ T1 / 2. Optionally, T1 / 10 ≤ T2 ≤ T1 / 3.

[0095] Optionally, T2 / T1 can be 1 / 10, 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, 1 / 4, 1 / 3, 1 / 2, or any two of these values.

[0096] In this embodiment, T2 / T1 is set to be less than or equal to 1 / 2, which helps to reduce the impact of the connector configuration on the roundness and radius of the electrode assembly and improve the housing fit of the electrode assembly.

[0097] In this embodiment, setting T2 / T1 to be greater than or equal to 1 / 10 is beneficial to improving the strength of the connector 25 and reducing the risk of connector 25 breaking. In this embodiment, setting T2 / T1 to be less than or equal to 1 / 2 is beneficial to improving the ductility and deformation capacity of the connector 25, releasing the tensile stress on the positive electrode section 24, and also beneficial to forming a buffer space between the connector 25 and the negative electrode 22, alleviating the radial compressive stress on the positive electrode section 24 and the negative electrode 22, and reducing the risk of inward deformation of the electrode assembly 20.

[0098] In some embodiments, the thickness of the connector 25 located in the inner region 21a is less than or equal to the thickness of the connector 25 located in the outer region 21c.

[0099] In one example, there are multiple connectors 25 in the inner region 21a, and the thickness of the multiple connectors 25 in the inner region 21a can be the same or different.

[0100] In one example, there are multiple connectors 25 in the outer region 21c, and the thickness of the multiple connectors 25 in the outer region 21c can be the same or different.

[0101] Optionally, at least one connector 25 is located in the central region 21b, the thickness of the connector 25 located in the central region 21b is greater than or equal to the thickness of the connector 25 located in the inner region 21a, and the thickness of the connector 25 located in the central region 21b is less than or equal to the thickness of the connector 25 located in the outer region 21c.

[0102] The connector 25 in the inner region 21a is thinner, occupies less space, and forms a larger buffer space between the inner region 21a and the negative electrode 22. This provides more room for deformation after compression, reducing the risk of the electrode assembly 20 collapsing. The connector 25 in the outer region 21c is thicker, has stronger resistance to tangential traction forces, and is less prone to breakage.

[0103] In some embodiments, refer to Figure 4 Along the radial direction of the cylindrical battery 1, a portion of the connector 25 overlaps with the positive electrode segment 24. The dimension of the overlapping portion of the connector 25 and the positive electrode segment 24 along the winding direction V is b, where 2mm ≤ b ≤ 7mm. The dimension of the overlapping portion of the connector 25 and the positive electrode segment 24 along the winding direction V refers to the dimension of the portion of the connector 25 overlapping with a single positive electrode segment 24 along the winding direction V.

[0104] Optionally, b is 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, or any value between two of these.

[0105] Optionally, the portion of the connector 25 that overlaps with the two adjacent positive electrode sections 24 has the same dimension along the winding direction V.

[0106] In this embodiment, setting b to be greater than or equal to 2mm is beneficial for increasing the connection area between the connector 25 and the positive electrode section 24, improving the connection strength, and reducing the risk of connection breakage. In this embodiment, setting b to be less than or equal to 7mm is beneficial for reducing the portion of the positive electrode section 24 that is covered by the connector 25 and thus fails, reducing the impact of the connector 25's configuration on the cylindrical battery capacity.

[0107] In some embodiments, a portion of the connector 25 overlaps with the positive electrode segment 24 along the radial direction of the cylindrical battery 1. The dimension of the portion of the connector 25 overlapping the positive electrode segment 24 in the inner region 21a along the winding direction V is less than or equal to the dimension of the portion of the connector 25 overlapping the positive electrode segment 24 in the outer region 21c along the winding direction V.

[0108] The connector 25 located in the outer region 21c experiences a greater traction force, making it easier to disconnect from the positive electrode section 24. The connector 25 in the outer region 21c overlaps more with the positive electrode section 24, which helps to increase the connection area between the connector 25 and the positive electrode section 24, thus improving the connection's strength.

[0109] In some embodiments, the central region 21b is provided with at least one connector 25. The dimensions of the portion of the connector 25 overlapping with the positive electrode section 24 in the inner region 21a, the portion of the connector 25 overlapping with the positive electrode section 24 in the central region 21b, and the portion of the connector 25 overlapping with the positive electrode section 24 in the outer region 21c gradually increase in the winding direction V.

[0110] In some embodiments, refer to Figure 5 The positive electrode section 24 includes a positive electrode current collector 241 and a positive electrode active material layer 242 disposed on the surface of the positive electrode current collector 241. Along the axial direction X of the cylindrical battery 1, the two ends of the connector 25 extend beyond the two ends of the positive electrode active material layer 242, respectively.

[0111] The positive electrode active material layer 242 includes a positive electrode active material. Exemplarily, the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, and combinations thereof.

[0112] The positive current collector 241 includes a positive current collector body 2411 and a positive current collector tab 2412, and a positive active material layer 242 is disposed on the surface of the positive current collector body 2411.

[0113] Optionally, the positive current collector 2411 and the positive electrode tab 2412 are integrally formed.

[0114] Optionally, the positive electrode 2412 is electrically connected to the end cap 12.

[0115] The two ends of the connector 25 extend beyond the two ends of the positive electrode active material layer 242. The connector 25 can reduce the possibility of powder falling off the edge of the positive electrode active material layer 242. The part of the connector 25 that extends beyond the positive electrode active material layer 242 can support the separator 23, reduce the deformation of the separator 23, and reduce the risk of short circuit between the positive and negative electrodes due to the failure of the separator.

[0116] During the preparation of the positive electrode 21, the connector 25 can be unwound along the width direction of the positive electrode 21 and cut at a suitable position. The two ends of the connector 25 extend beyond the two ends of the positive electrode active material layer 242, which facilitates the cutting of the connector 25.

[0117] In some embodiments, refer to Figure 5 The negative electrode 22 includes a negative electrode current collector 221 and a negative electrode active material layer 222 disposed on the surface of the negative electrode current collector 221. The negative electrode active material layer 222 includes a negative electrode active material. Exemplarily, the negative electrode active material includes at least one of graphite, silicon carbide, silicon oxide, silicon alloy, and elemental silicon.

[0118] The negative electrode current collector 221 includes a negative electrode current collector body 2211 and a negative electrode tab 2212, and the negative electrode active material layer 222 is disposed on the surface of the negative electrode current collector body 2211.

[0119] Optionally, the negative current collector 2211 and the negative electrode tab 2212 are integrally formed.

[0120] Optionally, the negative electrode 2212 is electrically connected to the bottom wall 113.

[0121] In some embodiments, along the axial direction X of the cylindrical battery 1, the connector 25 extends 2mm-3mm beyond the positive electrode active material layer 242.

[0122] Optionally, along the axial direction X of the cylindrical battery 1, the dimension of the connector 25 extending beyond the positive electrode active material layer 242 is 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, or any value between two of these.

[0123] In some embodiments, along the axial direction X of the cylindrical battery 1, the two ends of the separator 23 extend beyond the two ends of the connector 25.

[0124] The two ends of the separator 23 extend beyond the two ends of the connector 25, which helps to improve the safety of the separator 23 in isolating the positive electrode 21 and the negative electrode 22, and reduces the risk of short circuit between the positive and negative electrodes caused by the collapse of the two ends of the separator 23 or the two ends of the connector 25; and limits the size of the connector 25 along the axial direction X, reducing the space occupied by the connector 25 in the axial direction X, which helps to improve the energy density of the cylindrical battery 1.

[0125] In some embodiments, refer to Figure 5 The connector 25 includes two connecting layers 25a. Along the radial direction of the cylindrical battery 1, the two connecting layers 25a are respectively bonded to both sides of the positive electrode section 24, and the two connecting layers 25a are connected to each other.

[0126] Along the radial direction of the cylindrical battery 1, the two connecting layers 25a at least partially overlap and are connected to each other.

[0127] Optionally, along the radial direction of the cylindrical battery 1, a portion of one connecting layer 25a that does not overlap with the positive electrode section 24 completely overlaps with a portion of another connecting layer 25a that does not overlap with the positive electrode section 24, and they are connected to each other.

[0128] Optionally, the two connecting layers 25a are arranged to completely overlap along the radial direction of the cylindrical battery 1.

[0129] By setting two connecting layers 25a, the connection strength between the connector 25 and the positive electrode section 24 is improved, reducing the risk of the connector 25 detaching. The two connecting layers 25a are interconnected, which helps to expand the buffer space reserved for electrode expansion, reducing the risk of the electrode wrinkling or breaking due to compression.

[0130] In some embodiments, refer to Figure 6 The connecting layer 25a includes a substrate layer 251 and an adhesive layer 252. The tensile strength of the substrate layer 251 is 50MPa-200MPa.

[0131] Optionally, the tensile strength of the substrate layer 251 is 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 190 MPa, 200 MPa, or any value between any two of these.

[0132] The substrate layer 251 has suitable tensile strength, and the connecting layer 25a can deform when subjected to tensile force along the circumferential direction of the cylindrical battery 1, thereby relieving the tensile force on the positive electrode section 24 and reducing the risk of breakage of the positive electrode section 24.

[0133] Optionally, the tensile strength of the connecting layer 25a can be tested with reference to the test method in the national standard GB / T1040.3 "Test of Tensile Properties of Plastics".

[0134] In some embodiments, the tensile strength of the substrate layer 251 of the connector 25 located in the outer region 21c is greater than the tensile strength of the substrate layer 251 of the connector 25 located in the inner region 21a.

[0135] In some embodiments, the tensile breaking strength of the connecting layer 25a is less than that of the positive electrode segment 24.

[0136] Tensile breaking strength refers to the maximum stress a material experiences when it fractures. The tensile breaking strength of the connecting layer 25a and the positive electrode section 24 can be measured using tensile strength testing methods. For example, the connecting layer 25a and the positive electrode section 24 can be subjected to tensile testing according to the test methods in the national standard GB / T1040.3 "Test of Tensile Properties of Plastics", and the maximum stress experienced by the connecting layer 25a and the positive electrode section 24 at fracture can be measured.

[0137] The connecting layer 25a has a lower tensile fracture strength. When the connecting layer 25a and the positive electrode section 24 are subjected to the same tensile force, the connecting layer 25a can break before the positive electrode section 24. This helps to release the stress on the positive electrode section 24, reduce the risk of the positive electrode section 24 breaking, and improve the reliability of the cylindrical battery 1.

[0138] In some embodiments, the connecting layer 25a includes a substrate layer 251 and an adhesive layer 252. The substrate layer 251 includes at least one of a biaxially oriented polypropylene film, a polyester film, a polyimide film, a biaxially oriented polystyrene film, and a film made of meta-aramid or aramid 1313.

[0139] In some embodiments, the peel strength between the connecting layer 25a and the positive electrode segment 24 is greater than or equal to 0.15 N / mm.

[0140] Optionally, the peel strength can be tested in accordance with GB / T 2792-2014 Test Method for Peel Strength of Adhesive Tapes. The connecting layer 25a can be fixed on a tensile testing machine and the connector 25 can be pulled 180° until the connecting layer 25a peels off from the surface of the positive electrode section 24.

[0141] The bonding layer 25a has a high peel strength from the positive electrode section 24, thereby reducing the risk of the bonding layer 25a falling off the positive electrode section 24, reducing the risk of internal short circuit in the cylindrical battery 1, and improving reliability.

[0142] Example The following embodiments describe the contents disclosed in this application in more detail. These embodiments are for illustrative purposes only.

[0143] Example 1 <Cylindrical Cell Fabrication> The positive electrode is prepared by coating both sides of the positive current collector with a positive electrode active material layer, which includes LiNi. 0.9 Co 0.05 Mn 0.05 O2, carbon black, carbon nanotubes, and polyvinylidene fluoride (mass ratio 97:1:0.7:1.3). The total length L of the positive electrode sheet is 1300 mm. The positive electrode sheet includes a first gap and a second gap. Along the length direction of the positive electrode sheet, the distance L1 between the first gap and the starting end of the winding of the positive electrode sheet is 50 mm, and the distance L2 between the second gap and the ending end of the winding of the positive electrode sheet is 50 mm. The length d1 of the first gap is 3 mm, and the length d2 of the second gap is 5 mm. The length a1 of the connector connecting the two positive electrode segments on both sides of the first gap is 10 mm, and the length b1 of the overlapping portion of the connector with the positive electrode segments on both sides of the first gap is 3.5 mm. The length a2 of the connector connecting the two positive electrode segments on both sides of the second gap is 10 mm, and the length b2 of the overlapping portion of the connector with the positive electrode segments on both sides of the second gap is 2.5 mm. The thickness of the positive current collector is 13 μm, the thickness T1 of the positive electrode sheet is 90 μm, and the thickness T2 of the connector is 45 μm. The peel strength F between the connector and the positive electrode segment is 0.2 N / mm.

[0144] The positive electrode, separator, and negative electrode are wound to form an electrode assembly; the electrode assembly, housing, and end cap are assembled to form a cylindrical battery with a diameter of 21 mm and a length of 70 mm.

[0145] Examples 2 to 7: The preparation methods of the cylindrical battery in Example 1 are the same, and the differences are shown in Table 1.

[0146] Example 8: The preparation method of the cylindrical battery is the same as that of Example 1, except that the positive electrode sheet also includes a third gap. Along the length direction of the positive electrode sheet, the distance L3 between the third gap and the starting end of the winding of the positive electrode sheet is 650mm, the length d3 of the third gap is 4mm, the length a3 of the connector connecting the two positive electrode segments on both sides of the third gap is 10mm, and the length b3 of the overlapping part of the connector with the positive electrode segments on both sides of the third gap is 3mm.

[0147] Example 9: The preparation method of the cylindrical battery is the same as that of Example 1, except that: the length a2 of the connector connecting the two positive electrode segments on both sides of the second gap is 20 mm, and the length b2 of the overlapping part of the connector with the positive electrode segments on both sides of the second gap is 7.5 mm; the positive electrode sheet also includes a third gap, and along the length direction of the positive electrode sheet, the distance L3 between the third gap and the winding start end of the positive electrode sheet is 650 mm; the length d3 of the third gap is 4 mm; the length a3 of the connector connecting the two positive electrode segments on both sides of the third gap is 15 mm, and the length b3 of the overlapping part of the connector with the positive electrode segments on both sides of the third gap is 5.5 mm.

[0148] Example 10: The preparation method of the cylindrical battery is the same as that of Example 1, and the differences are shown in Table 2.

[0149] Comparative Example 1: The preparation method of the cylindrical battery is the same as that of Example 1, except that the positive electrode sheet only includes the first gap, and the distance L1 between the first gap and the starting end of the winding of the positive electrode sheet is 50 mm.

[0150] Comparative Example 2: The preparation method of the cylindrical battery is the same as that of Example 1, except that the positive electrode sheet only includes the second gap, the distance L2 between the second gap and the winding end of the positive electrode sheet is 50 mm, and the length d2 of the second gap is 3 mm.

[0151] Comparative Example 3: The preparation method is the same as that of the cylindrical battery in Example 1, except that the distance L2 between the second gap and the winding end of the positive electrode sheet is 600 mm.

[0152] Comparative Example 4: The preparation method is the same as that of the cylindrical battery in Example 1, except that the distance L1 between the first gap and the starting end of the winding of the positive electrode sheet is 600 mm.

[0153] Comparative Example 5: The preparation method is the same as that of the cylindrical battery in Example 1, except that the positive electrode does not include the gap.

[0154] <Peel Strength Test> Referring to GB / T 2792-2014 Test Method for Peel Strength of Adhesive Tapes, the connector was fixed on a tensile testing machine and pulled at 180° until the connecting layer peeled off from the surface of the positive electrode section. The peel strength of each embodiment and comparative example is recorded as shown in Table 1 and Table 2.

[0155] Cyclic Battery Cycle Performance Test Cyclic battery cycle performance test method: At 25℃, the lithium-ion battery is charged at a constant current rate of 1C to 4.25V, then charged at a constant voltage rate to a current of 0.05C, and then discharged at a constant current rate of 10C to 2.8V. This constitutes one charge-discharge cycle. The cylindrical batteries from Examples 1 and 10 are each cycled 200 times according to the above steps. Whether the cylindrical batteries exhibit cycle-induced voltage drops is recorded, and the records are shown in Table 2.

[0156] Table 1 Data from Examples 1 to 9 show that when the positive electrode sheet has a first gap at positions 50mm, 250mm, and 420mm from the starting end of winding, no indentation occurs in the electrode assembly. When the positive electrode sheet has a second gap at positions 50mm, 250mm, and 420mm from the ending end of winding, no breakage occurs in the positive electrode sheet.

[0157] As can be seen from the data in Comparative Example 1, the positive electrode sheet has a first gap only 50mm away from the starting end of the winding. The electrode assembly does not show any indentation, but the positive electrode sheet breaks.

[0158] As can be seen from the data in Comparative Example 2, the positive electrode sheet only has a second gap 50mm away from the winding end. The positive electrode sheet did not break, but the electrode assembly showed signs of indentation.

[0159] As can be seen from the data in Comparative Example 3, when the first gap is set at a position 50 mm from the beginning of the winding and the second gap is set at a position 600 mm from the end of the winding, the electrode assembly does not show any indentation, but the positive electrode sheet does break.

[0160] As can be seen from the data in Comparative Example 4, when the positive electrode sheet has a first gap 600mm from the beginning of winding and a second gap 50mm from the end of winding, the positive electrode sheet does not break, but the electrode assembly shows signs of indentation.

[0161] As can be seen from the data in Comparative Example 5, when no gap is set in the positive electrode, the electrode assembly shows indentation and the positive electrode breaks.

[0162] In conjunction with Examples 1 to 9 and Comparative Examples 1 to 5, the embodiments of this application configure the positive electrode sheet as multiple positive electrode segments spaced apart, with at least one gap located in the inner region and at least one gap located in the outer region. This is beneficial for improving the phenomenon of indentation deformation of the electrode assembly 20 and reducing the risk of positive electrode sheet breakage.

[0163] As can be seen from the data of Examples 1 and 6, increasing the size of the first gap and the second gap helps to improve the phenomenon of wrinkles in the electrode assembly.

[0164] Table 2 As shown in Table 2, by increasing the peel strength between the connector and the positive electrode section, the risk of cycle failure caused by the separation of the connector and the positive electrode section can be reduced, thereby improving the reliability of cylindrical batteries.

[0165] According to the second aspect of this application, referring to Figure 7 This application also provides a battery pack 100, which includes a plurality of cylindrical batteries 1 provided according to any embodiment of this application.

[0166] In some embodiments, the battery pack 100 further includes a plurality of busbars. The busbars connect to the cylindrical batteries 1. At least two cylindrical batteries 1 can be connected in series or in parallel via the busbars.

[0167] According to the third aspect of this application, referring to Figure 8 This application also provides an electrical device 1000, which includes a battery pack 100 provided in any embodiment of this application. The battery pack 100 can provide electrical energy to the electrical device 1000.

[0168] The electrical device 1000 in this application embodiment can be a portable device, an electric toy, a drone, a power tool, an energy storage system, etc. Power tools include metal cutting power tools, cleaning tools, etc., such as electric drills, electric wrenches, vacuum cleaners, robot vacuum cleaners, etc. This application embodiment does not impose any special limitations on the above-mentioned electrical device.

[0169] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A cylindrical battery, characterized in that, include: shell; as well as An electrode assembly is housed within the housing. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator separates the positive electrode and the negative electrode. The positive electrode, the separator, and the negative electrode are wound together along a winding direction. The positive electrode sheet includes multiple positive electrode segments and multiple connectors. The multiple positive electrode segments are spaced apart along the winding direction. A gap is formed between any two adjacent positive electrode segments along the winding direction. The connectors connect two adjacent positive electrode segments along the winding direction. The positive electrode sheet has an inner region, a middle region, and an outer region arranged sequentially along the winding direction. The dimension of the positive electrode sheet along the winding direction is L. Starting from the starting end of the winding of the positive electrode sheet, the dimension of the inner region along the winding direction is L / 5-L / 3. Starting from the ending end of the winding of the positive electrode sheet, the dimension of the outer region along the direction opposite to the winding direction is L / 5-L / 3. At least one gap is located in the inner region, and at least one gap is located in the outer region.

2. The cylindrical battery according to claim 1, characterized in that, The gap located in the inner region has a dimension d1 along the winding direction, and the gap located in the outer region has a dimension d2 along the winding direction, where d1 ≤ d2.

3. The cylindrical battery according to claim 2, characterized in that, 2mm≤d1≤4mm, 2mm≤d2≤8mm.

4. The cylindrical battery according to any one of claims 1-3, characterized in that, The central region connects the tail end of the inner region along the winding direction and the beginning end of the outer region along the winding direction, and at least one of the gaps is located in the central region.

5. The cylindrical battery according to claim 4, characterized in that, The gap located in the inner region has a dimension d1 along the winding direction, the gap located in the outer region has a dimension d2 along the winding direction, and the gap located in the middle region has a dimension d3 along the winding direction, where d1≤d3≤d2.

6. The cylindrical battery according to claim 4 or 5, characterized in that, The dimension of the connector located in the inner region along the winding direction is a1, the dimension of the connector located in the outer region along the winding direction is a2, and the dimension of the connector located in the middle region along the winding direction is a3, where a1≤a3≤a2.

7. The cylindrical battery according to claim 6, characterized in that, 10mm≤a1≤15mm, 10mm≤a3≤20mm, 10mm≤a2≤30mm.

8. The cylindrical battery according to any one of claims 1-7, characterized in that, The thickness of the positive electrode section is T1, and the thickness of the connector is T2, where T2 ≤ T1 / 2, and optionally, T1 / 10 ≤ T2 ≤ T1 / 3.

9. The cylindrical battery according to any one of claims 1-8, characterized in that, The thickness of the connector located in the inner region is less than or equal to the thickness of the connector located in the outer region.

10. The cylindrical battery according to any one of claims 1-9, characterized in that, Along the radial direction of the cylindrical battery, a portion of the connector overlaps with the positive electrode segment; The dimension of the portion of the connector that overlaps with the positive electrode section along the winding direction is b, where 2mm ≤ b ≤ 7mm.

11. The cylindrical battery according to any one of claims 1-10, characterized in that, Along the radial direction of the cylindrical battery, a portion of the connector overlaps with the positive electrode segment; The dimension of the portion of the connector located in the inner region that overlaps with the positive electrode segment along the winding direction is less than or equal to the dimension of the portion of the connector located in the outer region that overlaps with the positive electrode segment along the winding direction.

12. The cylindrical battery according to any one of claims 1-11, characterized in that, The positive electrode section includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; along the axial direction of the cylindrical battery, the two ends of the connector extend beyond the two ends of the positive electrode active material layer.

13. The cylindrical battery according to any one of claims 1-12, characterized in that, Along the axial direction of the cylindrical battery, the two ends of the separator extend beyond the two ends of the connector.

14. The cylindrical battery according to any one of claims 1-13, characterized in that, The connector includes two connecting layers. Along the radial direction of the cylindrical battery, the two connecting layers are respectively bonded to both sides of the positive electrode segment, and the two connecting layers are connected to each other.

15. The cylindrical battery according to claim 14, characterized in that, The tensile breaking strength of the connecting layer is less than that of the positive electrode segment.

16. The cylindrical battery according to claim 14 or 15, characterized in that, The connecting layer includes a substrate layer and an adhesive layer. The substrate layer includes at least one of biaxially oriented polypropylene film, polyester film, polyimide film, biaxially oriented polystyrene film, and film made of meta-aramid or aramid 1313.

17. The cylindrical battery according to any one of claims 14-16, characterized in that, The peel strength between the connecting layer and the positive electrode segment is greater than or equal to 0.15 N / mm.

18. A battery pack, characterized in that, Includes multiple cylindrical batteries according to any one of claims 1-17.

19. An electrical appliance, characterized in that, Includes the battery pack according to claim 18.

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