Secondary battery and electronic device

Abstract

The invention relates to the technical field of energy storage, and particularly discloses a secondary battery and an electronic device. The secondary battery comprises an electrode assembly, the electrode assembly comprises a first pole piece and a second pole piece, the first pole piece comprises a first pole lug, a first current collector and a first active substance layer, the first current collector and the first active substance layer are stacked, the first active substance layer is provided with a first groove, and part of the first current collector is exposed through the first groove to form a first empty foil area; the first tab is connected to the first empty foil area; the first area and the second area of the first active material layer surround the periphery of the first groove; the first groove comprises a first wall, a third wall and a third wall, and a second area is defined by extension lines of the second wall and the third wall and the first wall; the minimum distance between the second groove of the second area and the second wall is L1, and L1 is larger than 0. On the premise of improving the infiltration effect of the electrolyte on the pole piece, the structural strength of the pole piece can be improved, and the risk of falling failure of the secondary battery is reduced.

Description

[0001] This application is a divisional application of the patent application filed on July 23, 2025, with application number 202480008860.1 and entitled "Secondary Battery and Electronic Device". Technical Field

[0002] This application relates to the field of energy storage technology, and in particular to a secondary battery and electronic device. Background Technology

[0003] In secondary batteries, the performance is improved by incorporating drainage grooves on the electrodes of the electrode assembly to enhance the wetting effect of the electrolyte on the electrodes. However, the presence of drainage grooves can lead to structural weakness at the tab location. During a drop, the electrode assembly is subjected to impact, and the tab is prone to bending, which in turn can damage the electrode substrate at the tab location. This weakened structure at the tab location can cause the substrate to break, resulting in drop failure of the secondary battery. Summary of the Invention

[0004] In view of this, it is necessary to provide a secondary battery and electronic device that can improve the structural strength of the electrode while improving the wetting effect of the electrolyte on the electrode, thereby reducing the risk of secondary battery failure due to drop.

[0005] A first aspect of this application provides a secondary battery, including an electrode assembly. The electrode assembly includes a first electrode and a second electrode, which are stacked and form a wound structure. The first electrode and the second electrode have opposite polarities. The first electrode includes a first tab and a first current collector and a first active material layer stacked together. Along the thickness direction of the first current collector, at least one side of the first current collector is provided with the first active material layer. The first active material layer is provided with a first groove, and a portion of the first current collector is exposed through the first groove to form a first empty foil area. The first tab is connected to the first empty foil area. The first active material layer includes a first region and a second region. The region is enclosed on the outer periphery of the first groove; the width direction of the first electrode is the first direction, along the first direction, the first groove includes a first wall, along the second direction, the first groove includes a second wall and a third wall arranged opposite to each other, the first wall connects the second wall and the third wall, the second direction is perpendicular to the first direction; the second wall and the third wall are extended along the first direction respectively, the extension lines of the second wall and the third wall and the first wall enclose to form a second region; the first wall connects to the second region; the first active material layer of the first region and the second region is provided with a plurality of second grooves, the depth of the second groove is less than the thickness of the first active material layer; the minimum distance between the second groove of the second region and the first wall is L1, satisfying L1>0.

[0006] In the above embodiments, the second tanks in the first and second regions can accommodate electrolyte, thereby facilitating contact between the electrolyte and the first electrode through the second tank and improving the wetting degree of the electrolyte on the first electrode. Along the first direction, there is a gap between the second tank in the second region and the first wall of the first tank. Compared to the location where the first and second tanks are provided, the first active material layer between the second tank in the second region and the first wall of the first tank is more abundant, resulting in better structural strength. Therefore, when subjected to the impact of electrolyte or shaking of the first electrode tab during a drop, the position between the second tank in the second region and the first wall of the first tank is less likely to break or be damaged, reducing the risk of secondary battery drop failure.

[0007] In one or more of the above embodiments, along the first direction, the length of the first groove is L2, satisfying 0.01L2≤L1≤0.08L2.

[0008] In the above embodiments, maintaining a certain distance between the second tank and the first wall of the first tank can effectively improve the drop test pass rate of the secondary battery. However, when L1 is too large, it is not conducive to the wetting of the electrode assembly by the electrolyte, which will lead to interface problems in the later stages of secondary battery cycling. When the range of 0.01L2≤L1≤0.08L2 is met, not only can the drop test pass rate of the secondary battery be improved, but the interface problem of the first electrode can also be alleviated.

[0009] In one or more of the above embodiments, 0.03L2≤L1≤0.06L2.

[0010] In the above embodiments, when the range of 0.03L2≤L1≤0.06L2 is satisfied, the wetting degree of the electrolyte on the first electrode can be further improved, thereby improving the interface problem, and further improving the structural strength between the first tank and the second tank in the second region, making the first electrode less prone to damage.

[0011] In one or more of the above embodiments, the spacing between two adjacent second grooves is L3, and the first groove has a second wall and a third wall disposed opposite to each other along the winding direction of the electrode assembly; in the winding direction of the electrode assembly, the minimum distance between the second groove and the second wall of the first region is L4, satisfying 0 < L4 ≤ 1.1L3; in the winding direction of the electrode assembly, the minimum distance between the second groove and the third wall of the first region is L5, satisfying 0 < L5 ≤ 1.1L3.

[0012] In the above embodiments, L4 > 0 and L5 > 0, so that the distance between the second tank and the first tank in the second direction is not too small, so as to meet the structural strength requirements between the second wall, the third wall and the second tank; L4 ≤ 1.1L3 and L5 ≤ 1.1L3, so that the distance between the second tank and the first tank is not too large, thereby facilitating the storage of more electrolyte in the first region.

[0013] In one or more of the above embodiments, the first electrode further includes a first adhesive member, which is adhered to the first electrode tab and the first empty foil area; along the first direction, the first adhesive member extends beyond the first wall by a length D1, and the portion of the first adhesive member extending beyond the first wall is adhered to the second region; along the first direction, the second groove of the second region has opposing fourth and fifth walls, the fourth wall being closer to the first wall than the fifth wall, and a portion of the first adhesive member is adhered to the portion of the second region where the second groove is provided; along the first direction, the edge of the first adhesive member located in the second region is a first side, and the maximum distance between the fourth wall and the first side is D2, satisfying 0.1D1≤D2≤0.8D1.

[0014] In the above embodiments, a portion of the first adhesive extends beyond the first wall and is bonded to the second region, thereby further increasing the thickness of the first electrode sheet between the first groove and the second groove of the second region. This helps maintain the structural strength of the portion between the first groove and the second groove of the second region. When 0.1D1≤D2≤0.8D1 is satisfied, not only are the strength requirements of the first electrode sheet met, but the overlap between the first adhesive and the second groove of the second region is also less likely to be too large, reducing the negative impact of the electrolyte on the viscosity of the first adhesive. If the overlap is too large, the electrolyte in the second groove is more likely to come into contact with the first adhesive, causing impact to the first adhesive and easily reducing the viscosity between the first adhesive and the first active material layer.

[0015] In one or more of the above embodiments, the first side is arranged in a wavy shape.

[0016] In the above embodiments, firstly, the wavy design can disperse the stress at the junction of the first side and the first active material layer and the first current collector, reduce stress concentration, reduce damage to the first adhesive, the first active material layer or the first current collector caused by mechanical stress, and improve the mechanical stability of the electrode assembly; secondly, the wavy design can increase the insulation distance between the first adhesive and the first active material layer, especially during the charging and discharging process of the secondary battery, this design helps to improve the insulation performance of the electrode assembly, reduce the risk of short circuit, and improve the safety of the secondary battery; thirdly, the wavy design is conducive to adapting to thermal expansion and contraction. The secondary battery will experience temperature changes during charging and discharging. The wavy design of the first side can provide a certain elastic space to adapt to thermal expansion and contraction, reduce internal stress caused by temperature changes, and improve the thermal stability of the electrode assembly.

[0017] In one or more of the above embodiments, along the winding direction of the electrode assembly, the first groove has a second wall and a third wall disposed opposite to each other, and at least one of the second wall and the third wall forms a first channel between the second wall and the edge of the first adhesive.

[0018] In the above embodiments, relative to the first adhesive completely covering the first empty foil area, the setting of the first channel makes the first current collector partially exposed in the first channel. The exposed first current collector is conducive to the rapid dissipation of heat, improves the thermal management performance of the electrode assembly, and enhances the safety performance of the battery.

[0019] In one or more of the above embodiments, along the winding direction of the electrode assembly, the width of the first groove is P1 and the width of the first channel is P2, satisfying 0.02P1≤P2≤0.6P1.

[0020] In the above embodiments, if the width of the first channel is too large, the width of the first adhesive component will be too small, which will result in the solder marks of the first tab not being able to be completely covered, making it easy for exposed solder marks to puncture the diaphragm and cause a short circuit; if the width of the first channel is too small, it is difficult to achieve a good heat dissipation effect. When 0.02P1≤P2≤0.6P1 is satisfied, the heat dissipation effect of the first channel can be improved while ensuring that the solder marks are not easily exposed.

[0021] In one or more of the above embodiments, 0.2P1≤P2≤0.45P1.

[0022] In the above embodiments, satisfying 0.2P1≤P2≤0.45P1 can further reduce the possibility of short circuits caused by solder punctures in the diaphragm, and can also improve the heat dissipation capacity of the first channel.

[0023] In one or more of the above embodiments, 0.2D1≤D2≤0.5D1.

[0024] In the above embodiments, it is beneficial to further improve the structural strength of the portion between the first tank and the second tank in the second region, and reduce the negative impact of the electrolyte on the viscosity of the first adhesive.

[0025] In one or more of the above embodiments, the first electrode is a negative electrode and the second electrode is a positive electrode; the second electrode includes a second current collector and a second active material layer stacked together, and at least one side of the second current collector is provided with the second active material layer; along the first direction, the width of the first electrode is greater than the width of the second electrode; along the first direction, the first active material layer has a first edge and a second edge opposite to each other, and the first edge and the second edge extend beyond the edge of the second active material layer on the same side; compared to the fourth wall, the fifth wall is closer to the second edge and is away from the second edge.

[0026] In the above embodiments, if the second tank extends directly to the second edge, the end of the second tank will store more electrolyte, which will make it easier for lithium plating to occur and cause interface problems compared to a design without a second tank. In this embodiment, the fifth wall of the second tank is separated from the second edge, and the second tank does not extend to the second edge. This can guide the electrolyte to wet the middle part of the first electrode, improve the wetting effect on the first electrode, and effectively alleviate the problem of lithium plating.

[0027] In one or more of the above embodiments, the distance between the second edge and the edge of the second active material layer on the same side is W1; the distance between the fifth wall and the second edge is W2, satisfying 0.6W. 11 ≤W3≤1.2W 11 .

[0028] In the above embodiments, when W3 < 0.6W1, the gap width between the fifth wall and the second edge without the second groove is too narrow, and the distance between the fifth wall of the second groove and the second edge is too close, making it difficult to achieve the effect of slowing lithium dissolution. When W1W3 > 1.2W1, the gap between the fifth wall and the second edge without the second groove is too large, and the distance between the fifth wall of the second groove and the second edge is too far, easily hindering the flow of electrolyte into the middle part of the first electrode, resulting in poor wetting of the first electrode and interface problems. Satisfying 0.6W1... 11 ≤W3≤1.2W 11 This not only guides the electrolyte to wet the middle part of the first electrode, improving the wetting effect on the first electrode, but also effectively alleviates the problem of lithium desorption.

[0029] In one or more of the above embodiments, 0.8W 11 ≤W3≤1.1W 11 .

[0030] In the above embodiments, the problem of lithium desorption is further mitigated while ensuring that the electrolyte can effectively wet the middle part of the first electrode.

[0031] In one or more of the above embodiments, the second electrode includes a second current collector and a second active material layer stacked together. Along the thickness direction of the second current collector, the second current collector has two opposing surfaces, and each surface of the second current collector is provided with a second active material layer. A third groove is provided on the second active material layer on the side opposite or back to the first electrode tab. The second electrode includes a second adhesive member disposed in the third groove. Along the stacking direction of the first electrode and the second electrode, the projection of the portion where the first electrode tab connects to the first empty foil area is located within the projection of the second adhesive member.

[0032] In the above embodiments, the second adhesive can further separate the first electrode and the second electrode, protect the position of the first electrode tab, and reduce the possibility of short circuits between the first and second electrodes caused by solder protrusions on the first electrode tab, as well as interface problems. Furthermore, by placing the second adhesive in the third groove, the thickness of the electrode assembly at the first electrode tab position can be effectively reduced, which is beneficial for improving the volumetric energy density of the secondary battery.

[0033] In one or more of the above embodiments, a second channel is formed between at least one edge of the second adhesive and the wall of one side of the third groove along the winding direction of the electrode assembly.

[0034] During hot chamber testing, as the temperature rises, the surface temperature of the electrode assembly continuously increases. Due to side reactions, heat is continuously released, and gas is generated. If the heat generation of the electrode assembly exceeds the heat dissipation, excessive heat accumulation will eventually cause the secondary battery to fail. In this embodiment, due to the design of the second adhesive and the second channel, when a large amount of gas accumulates, the gas can flow out through the second channel, thereby facilitating heat dissipation of the electrode assembly. The gas generated during hot chamber testing is discharged from the electrode assembly through the second channel, reducing the impact of high temperature or gas impact on the viscosity of the second adhesive and improving the pass rate of the hot chamber test.

[0035] In one or more of the above embodiments, along the winding direction of the electrode assembly, the width of the third groove is H1, and the width of the second channel is H2, satisfying 0.01H1≤H2≤0.1H1.

[0036] When the width of the second channel is too large, the area covered by the second adhesive in the third groove is too small, resulting in insufficient protection for the first electrode position and potentially causing a short circuit failure between the first and second electrodes. Conversely, when the width of the second channel is too small, the improvement effect on the thermal test is minimal. Meeting the condition 0.01H1≤H2≤0.1H1 provides both adequate protection for the first electrode position and improves the pass rate of the secondary battery's thermal test.

[0037] In one or more of the above embodiments, 0.03H1≤H2≤0.07H1.

[0038] In the above embodiments, when 0.03H1≤H2≤0.07H1 is satisfied, the width of the second channel can be further increased and the exhaust effect of the second channel can be improved, provided that the second adhesive has sufficient protection for the first electrode tab.

[0039] In one or more of the above embodiments, the first electrode is a positive electrode, and the second electrode is a negative electrode. The second electrode includes a second current collector and a second active material layer stacked together. Along the thickness direction of the second current collector, at least one side of the second current collector is provided with the second active material layer. Along a first direction, the width of the first electrode is greater than the width of the second electrode. Along the first direction, the first active material layer has opposing first and second edges, which extend beyond the edge of the second active material layer on the same side. Along the first direction, the second groove in the first region has opposing sixth and seventh walls. Compared to the seventh wall, the sixth wall is closer to the first edge and is separate from the first edge, while the seventh wall is separate from the second edge.

[0040] In the above embodiments, when the second tank extends directly to the first edge and the second edge, the second tank will store more electrolyte at the position of the first edge and the second edge. This is more likely to cause interface problems due to lithium plating compared to the design where the second tank does not extend to the first edge and the second edge. Therefore, the sixth wall is a certain distance from the first edge and the seventh wall is a certain distance from the second edge, which can effectively alleviate the lithium plating problem at the position of the first edge and the second edge.

[0041] In one or more of the above embodiments, the distance by which the first edge extends beyond the edge of the second active material layer on the same side is W1, and the distance by which the second edge extends beyond the edge of the second active material layer on the same side is W. 11 The distance between the sixth wall and the first edge is W2, satisfying 0.6W1≤W2≤1.2W1; the distance between the seventh wall and the second edge is W3, satisfying 0.6W1≤W2≤1.2W1. 11 ≤W3≤1.2W 11 .

[0042] In the above embodiments, the distance between the seventh wall and the second edge is too narrow, and the distance between the second groove and the first and second edges is too close, failing to achieve the effect of slowing lithium dissolution. The distance between the seventh wall and the second edge is too large, easily hindering the flow of electrolyte into the center of the first electrode, resulting in poor wetting of the center of the first electrode and interface problems. The following conditions must be met: 0.6W1≤W2≤1.2W1, 0.6W 11 ≤W3≤1.2W 11 At the same time, it can not only slow down the desorption of lithium, but also meet the requirements of electrolyte wetting effect on the first electrode.

[0043] In one or more of the above embodiments, 0.8W1≤W2≤1.1W1, 0.8W 11 ≤W3≤1.1W 11 .

[0044] In the above embodiments, the lithium plating problem can be further improved while reducing the flow resistance of the electrolyte.

[0045] In one or more of the above embodiments, the first adhesive includes a first substrate layer and a first adhesive layer stacked together. The material of the first substrate layer includes at least one of polyfluoroolefin, polyethylene terephthalate, polyimide, polyamide-imide, polyvinyl chloride, or polyolefin. The first adhesive layer includes an adhesive material, which includes at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyacryl alcohol, sodium polyacrylate, polyetherimide, or acrylate.

[0046] A second aspect of this application also provides an electronic device, which includes the secondary battery in any of the above embodiments. Attached Figure Description

[0047] Figure 1 This is a cross-sectional view of a secondary battery in one embodiment of this application.

[0048] Figure 2 yes Figure 1 Enlarged view of Part II.

[0049] Figure 3 yes Figure 2 Enlarged view of section III.

[0050] Figure 4 This is a partial view of the first electrode in the unfolded state in one embodiment of this application.

[0051] Figure 5 This is a partial view of one embodiment of the present application, showing the positional relationship between the first adhesive member and the first groove.

[0052] Figure 6 This is a partial view of one embodiment of the present application, showing the positional relationship between the first adhesive member and the first groove.

[0053] Figure 7 This is a partial view of one embodiment of the present application, showing the positional relationship between the first adhesive member and the second groove.

[0054] Figure 8 This is a schematic diagram of the structure of the first adhesive element in one embodiment of this application.

[0055] Figure 9 This is a partial schematic diagram of the first and second electrode sheets stacked in one embodiment of this application.

[0056] Figure 10 This is a partial schematic diagram of the first electrode in one embodiment of this application.

[0057] Figure 11 This is a partial schematic diagram of the second electrode in one embodiment of this application.

[0058] Figure 12 This is a schematic diagram of the structure of an electronic device in one embodiment of this application.

[0059] Explanation of main component symbols 1000, Electronic device; 100, Secondary battery; 10, Electrode assembly; 11, First electrode; 111, First current collector; 1111, First empty foil area; 111a, First surface; 111b, Second surface; 112, First active material layer; 1121, First groove; 1121b, First wall; 1121c, Second wall; 1121d, Third wall; 1122, First region; 1123, Second region; 1124, Second groove; 1124a, Fourth wall; 1124b, Fifth wall; 1124c, Sixth wall; 1124d, Seventh wall; 1125 1126. First edge; 113. Second edge; 114. First tab; 115. First adhesive; 116. First side; 117. First channel; 118. First substrate layer; 119. First adhesive layer; 120. Second electrode; 121. Second current collector; 121a. Third surface; 122b. Fourth surface; 122. Second active material layer; 1221. Third groove; 123. Second tab; 124. Second adhesive; 1241. Second channel; 13. Diaphragm; 20. Housing; 200. Device body; X. First direction; Y. Second direction.

[0060] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0061] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0062] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terms "comprising" and "having" in the specification, claims, and drawings of this application are open-ended expressions, not closed-ended expressions.

[0064] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0065] It should be noted that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative examples and should not constitute any limitation on this application.

[0066] In secondary batteries, the performance is improved by incorporating drainage grooves on the electrodes of the electrode assembly to enhance the wetting effect of the electrolyte on the electrodes. However, the presence of drainage grooves can lead to structural weakness at the tab location. During a drop, the electrode assembly is subjected to impact, and the tab is prone to bending, which in turn can damage the electrode substrate at the tab location. This weakened structure at the tab location can cause the substrate to break, resulting in drop failure of the secondary battery.

[0067] Embodiments of this application provide a secondary battery, including an electrode assembly. The electrode assembly includes a first electrode and a second electrode, which are stacked and form a wound structure. The first and second electrodes have opposite polarities. The first electrode includes a first tab and a first current collector and a first active material layer stacked together. Along the thickness direction of the first current collector, at least one side of the first current collector is provided with the first active material layer. The first active material layer is provided with a first groove, and a portion of the first current collector is exposed through the first groove to form a first empty foil area. The first tab is connected to the first empty foil area. The first active material layer includes a first region and a second region. The first region is surrounded by a second region on the outer periphery of the first groove; the width direction of the first electrode is the first direction, along the first direction, the first groove includes a first wall, along the second direction, the first groove includes a second wall and a third wall disposed opposite to each other, the first wall connects the second wall and the third wall, the second direction is perpendicular to the first direction; the second wall and the third wall are respectively extended along the first direction, and the extension lines of the second wall and the third wall and the first wall enclose the second region; the first active material layer of the first region and the second region is provided with a plurality of second grooves, the depth of the second groove is less than the thickness of the first active material layer; the minimum distance between the second groove of the second region and the first wall is L1, satisfying L1>0.

[0068] In the aforementioned secondary battery, the second tanks in the first and second regions can accommodate electrolyte, thereby facilitating contact between the electrolyte and the first electrode and improving the wetting degree of the first electrode. Along the second direction, there is a gap between the second tank in the second region and the first wall of the first tank. Compared to the location where the first and second tanks are located, the area between the second tank and the first wall of the first tank in the second region contains more active material, resulting in better structural strength. Therefore, during a drop, when impacted by the electrolyte or when the first electrode tab shakes, the area between the second tank and the first wall of the first tank in the second region is less likely to break or be damaged, reducing the risk of drop failure of the secondary battery.

[0069] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0070] like Figure 1 As shown, an embodiment of this application provides a secondary battery 100, which includes an electrode assembly 10 and a housing 20, with the electrode assembly 10 housed within the housing 20. The electrode assembly 10 includes a first electrode 11 and a second electrode 12, which are stacked and formed into a wound structure, with the first electrode 11 and the second electrode 12 having opposite polarities.

[0071] In some embodiments, the electrode assembly 10 further includes a diaphragm 13, wherein the first electrode 11, the diaphragm 13 and the second electrode 12 are stacked and wound to form a wound structure, and the diaphragm 13 is used to separate the first electrode 11 and the second electrode 12.

[0072] In some embodiments, the diaphragm 13 is an insulating membrane material such as a polyethylene membrane, a polypropylene membrane, a polyester membrane, or a polyimide membrane.

[0073] In some embodiments, the housing 20 is a flexible packaging bag, such as an aluminum-plastic film. In other embodiments, the housing 20 is a rigid outer shell, such as a plastic shell, or a metal shell including at least one of steel alloys, aluminum alloys, and copper alloys.

[0074] In some embodiments, an electrolyte (not shown) is injected into the housing 20, and the electrolyte components include solvents, electrolyte salts, and additives.

[0075] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0076] In some embodiments, the electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium hexafluorocesium oxide (LiCsF6), lithium perchlorate (LiClO4), or lithium trifluoromethanesulfonate (LiCF3SO3).

[0077] Please see Figure 1 and Figure 2 In some embodiments, the first electrode 11 includes a first current collector 111 and a first active material layer 112 stacked together, and a first tab 113 connected to the first current collector 111. The first active material layer 112 is disposed on at least one surface of the first current collector 111 along its thickness direction. A diaphragm 13 is disposed between the first active material layer 112 and the second electrode 12. The thickness direction of the first current collector 111 is... Figure 2 The Z direction is shown in the diagram.

[0078] Please see Figure 2 and Figure 3 In some embodiments, along the thickness direction of the first electrode 11, the first current collector 111 has a first surface 111a and a second surface 111b disposed opposite to each other. The thickness direction of the first electrode 11 is consistent with the thickness direction of the first current collector 111. Figure 2 The Z direction is shown in the figure. At least one of the first surface 111a and the second surface 111b is provided with a first active material layer 112. For example, both the first surface 111a and the second surface 111b are provided with a first active material layer 112.

[0079] Please see Figure 2 and Figure 3 In some embodiments, the second electrode 12 includes a second current collector 121 and a second active material layer 122 stacked together, and a second tab 123 connected to the second current collector 121. Along the thickness direction of the second electrode 12, the second current collector 121 has a third surface 121a and a fourth surface 122b disposed opposite to each other. The thickness direction of the second electrode 12 is consistent with the thickness direction of the second current collector 121. Figure 2 The Z direction is shown in the figure. At least one of the third surface 121a and the fourth surface 122b is provided with a second active material layer 122. For example, both the third surface 121a and the fourth surface 122b are provided with a second active material layer 122.

[0080] In some embodiments, the first active material layer 112 and the second active material layer 122 comprise active materials.

[0081] In some embodiments, the first electrode 11 is a positive electrode and the second electrode 12 is a negative electrode. In other embodiments, the first electrode 11 is a negative electrode and the second electrode 12 is a positive electrode.

[0082] Taking the first electrode 11 as the negative electrode and the second electrode 12 as the positive electrode as an example, the first tab 113 is the negative tab, and the second tab 123 is the positive tab. The first current collector 111 and the second current collector 121 can be metal layers. The first current collector 111 is the negative current collector and can be a metal layer including at least one of copper, nickel, tantalum, and titanium, such as copper foil. The second current collector 121 is the positive current collector and can be a metal layer including at least one of aluminum, nickel, tantalum, and titanium, such as aluminum foil.

[0083] The first active material layer 112 is negatively polar, and the active material of the first active material layer 112 is a negative electrode active material, which may include at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, silicon-carbon materials, etc. The second active material layer 122 is positively polar, and the active material of the second active material layer 122 is a positive electrode active material, which may include 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, etc.

[0084] See Figures 2 to 4 In some embodiments, the first active material layer 112 is provided with a first groove 1121, and a portion of the first current collector 111 is exposed through the first groove 1121 to form a first empty foil area 1111. A first tab 113 is connected to the first empty foil area 1111. The first active material layer 112 includes a first region 1122 and a second region 1123, which surround the outer periphery of the first groove 1121. The width direction of the first electrode 11 is a first direction X. Along the first direction X, the first groove 1121 includes a first wall 1121b. Along the second direction Y, the first groove 1121 includes a second wall 1121c and a third wall 1121d disposed opposite to each other. The first wall 1121b connects the second wall 1121c and the third wall 1121d. The second direction Y is perpendicular to the first direction X. Figure 2 The second wall 1121c and the third wall 1121d are extended along the first direction X by lines Q1 and Q2, respectively. The extension lines Q1 and Q2 of the second wall 1121c and the third wall 1121d, together with the first wall 1121b, form a second region 1123. The first wall 1121b connects to the second region 1123. The first active material layer 112 of the first region 1122 and the second region 1123 is provided with a plurality of second grooves 1124, the depth of the second grooves 1124 being less than the thickness of the first active material layer 112. The minimum distance between the second grooves 1124 of the second region 1123 and the first wall 1121b is L1, which satisfies L1 > 0.

[0085] In some embodiments, at least a portion of the active material in the first active material layer 112 is removed by laser etching to form the first groove 1121 and the second groove 1124.

[0086] The second tank 1124 of the first region 1122 and the second region 1123 can accommodate electrolyte, which facilitates the electrolyte to contact the first electrode 11 through the second tank 1124 and improves the degree of wetting of the first electrode 11 by the electrolyte.

[0087] In related technologies, the first groove 1121 and the second groove 1124 are connected by intersecting. Compared to the first active material layer 112 without the first groove 1121, the structural strength of the first current collector 111 at the location of the first active material layer 112 with the first groove 1121 is reduced due to the removal of some active material. In addition, laser etching of the second groove 1124 will also cause some damage to the structural strength of the first current collector 111. Therefore, when the secondary battery 100 is dropped, the end of the secondary battery 100 with the first tab 113 is impacted. The first tab 113 will drive the first empty foil area 1111. At this time, because the second groove 1124 and the first groove 1121 have less active material and lower structural strength, the first current collector 111 at the junction of the second groove 1124 and the first groove 1121 is more likely to break during the drop, thus causing the secondary battery 100 to fail.

[0088] In this embodiment, along the first direction X, there is a gap between the second groove 1124 of the second region 1123 and the first wall 1121b of the first groove 1121. Compared with the position where the first groove 1121 and the second groove 1124 are provided, there is more first active material layer 112 between the second groove 1124 of the second region 1123 and the first wall 1121b of the first groove 1121, which has better structural strength. Therefore, when the second groove 1124 of the second region 1123 is impacted by the electrolyte or the first tab 113 is shaken during the drop, the position between the second groove 1124 of the second region 1123 and the first wall 1121b of the first groove 1121 is not easily broken or damaged, reducing the risk of the secondary battery 100 failing due to drop.

[0089] See Figure 4 In some embodiments, the first region 1122 comprises two parts. Along the second direction Y, the two parts of the first region 1122 are located on both sides of the first groove 1121. Along the first direction X, the second region 1123 is located on one side of the first groove 1121, and the second region 1123 is located between the two parts of the first region 1122. Along the second direction Y, the first region 1122 and the second region 1123 are divided by extension lines Q1 and Q2.

[0090] See Figure 4 In some embodiments, along the first direction X, the first active material layer 112 has opposing first edges 1125 and second edges 1126.

[0091] See Figure 4In some embodiments, the length of the first groove 1121 along the first direction X is L2, which satisfies 0.01L2≤L1≤0.08L2.

[0092] Maintaining a certain distance between the second tank 1124 and the first wall 1121b of the first tank 1121 can effectively improve the drop test pass rate of the secondary battery 100. However, when L1 is too large, it is not conducive to the wetting of the electrode assembly 10 by the electrolyte, which will lead to interface problems in the later stages of cycling of the secondary battery 100. When the range of 0.01L2≤L1≤0.08L2 is met, not only can the drop test pass rate of the secondary battery 100 be improved, but the interface problem of the first electrode 11 can also be alleviated. The interface problem refers to the problem of "interface purple spot lithium deposition caused by poor wettability in the middle of the electrode assembly 10 during long-term cycling".

[0093] In some embodiments, 0.03L2≤L1≤0.06L2. When the range of 0.03L2≤L1≤0.06L2 is satisfied, the wetting degree of the electrolyte on the first electrode 11 can be further improved, thereby improving the interface problem, and further improving the structural strength between the first groove 1121 and the second groove 1124 of the second region 1123, making the first electrode 11 less prone to damage.

[0094] In some embodiments, the second region 1123 is provided with a plurality of second grooves 1124, and the distance between each second groove 1124 of the second region 1123 and the first wall 1121b of the first groove 1121 is different, and L1 is the distance between the second groove 1124 closest to the first wall 1121b in the second region 1123 and the first wall 1121b.

[0095] In some embodiments, the distance between two adjacent second grooves 1124 is L3. Along the winding direction of the electrode assembly 10, the first groove 1121 has a second wall 1121c and a third wall 1121d disposed opposite to each other. In the winding direction of the electrode assembly 10, the minimum distance between the second groove 1124 and the second wall 1121c of the first region 1122 is L4, satisfying 0 < L4 ≤ 1.1L3; in the winding direction of the electrode assembly 10, the minimum distance between the second groove 1124 and the third wall 1121d of the first region 1122 is L5, satisfying 0 < L5 ≤ 1.1L3.

[0096] When L4 > 0 and L5 > 0, the distance between the second groove 1124 and the first groove 1121 in the second direction Y is not too small, so as to satisfy the structural strength between the second wall 1121c, the third wall 1121d and the second groove 1124; L4 ≤ 1.1L3 and L5 ≤ 1.1L3, the distance between the second groove 1124 and the first groove 1121 is also not too large, which is conducive to storing more electrolyte in the first region 1122.

[0097] In some embodiments, the second groove 1124 extends along a first direction X, with the length direction of the second groove 1124 being the first direction X and the width direction of the second groove 1124 being the second direction Y. The second grooves 1124 of the first region 1122 and the second grooves 1124 of the second region 1123 are arranged at intervals along the second direction Y.

[0098] See Figure 2 and Figure 5 In some embodiments, the first electrode 11 further includes a first adhesive 114, which is attached to the first electrode tab 113 and the first empty foil area 1111.

[0099] See Figure 2 and Figure 5 In some embodiments, along the first direction X, the first adhesive member 114 extends beyond the first wall 1121b by a length D1, and the portion of the first adhesive member 114 extending beyond the first wall 1121b is adhered to the second region 1123. Along the first direction X, the second groove 1124 of the second region 1123 has opposing fourth walls 1124a and fifth walls 1124b. Compared to the fifth wall 1124b, the fourth wall 1124a is closer to the first wall 1121b. A portion of the first adhesive member 114 is adhered to the portion of the second region 1123 where the second groove 1124 is located. Along the first direction X, the edge of the first adhesive member 114 located in the second region 1123 is a first side 1141, and the maximum distance between the fourth wall 1124a and the first side 1141 is D2, satisfying 0.1D1≤D2≤0.8D1.

[0100] The portion of the first adhesive 114 extends beyond the first wall 1121b and is adhered to the second region 1123, thereby further increasing the thickness of the first electrode 11 between the first groove 1121 and the second groove 1124 of the second region 1123. This helps maintain the structural strength of the portion between the first groove 1121 and the second groove 1124 of the second region 1123. When 0.1D1≤D2≤0.8D1 is satisfied, not only are the strength requirements of the first electrode 11 met, but the overlap between the first adhesive 114 and the second groove 1124 of the second region 1123 is also less likely to be too large, reducing the negative impact of the electrolyte on the viscosity of the first adhesive 114. If the overlap is too large, the electrolyte in the second groove 1124 is more likely to come into contact with the first adhesive, impacting the first adhesive 114 and easily reducing the viscosity between the first adhesive 114 and the first active material layer 112.

[0101] In some embodiments, 0.2D1≤D2≤0.5D1, within this range, is beneficial to further improve the structural strength of the portion between the first groove 1121 and the second groove 1124 of the second region 1123, and to reduce the negative impact of the electrolyte on the viscosity of the first adhesive 114.

[0102] See Figure 1 and Figure 2 In some embodiments, two first adhesive members 114 are provided, one of which is provided on the first surface 111a of the first empty foil area 1111, and the other is provided on the second surface 111b of the first empty foil area 1111. By providing the first adhesive members 114 on opposite sides of the first tab 113, the risk of short circuit caused by the solder joint of the first tab 113 puncturing the diaphragm 13 is further reduced.

[0103] In some embodiments, in the second direction Y, the first adhesive 114 completely covers the first empty foil area 1111, and a portion of the first adhesive 114 is adhered to the first active material layer 112, thereby further reducing the risk of short circuit caused by contact between the first tab 113 and the second electrode 12.

[0104] See Figure 6 In some embodiments, in the second direction Y, the first adhesive 114 partially covers the first empty foil area 1111. At least one of the second wall 1121c and the third wall 1121d forms a first channel 1142 between it and the edge of the first adhesive 114.

[0105] Compared to the first adhesive 114 completely covering the first empty foil area 1111, the arrangement of the first channel 1142 makes the first current collector 111 partially exposed in the first channel 1142. The exposed first current collector 111 is conducive to the rapid dissipation of heat, improves the thermal management performance of the electrode assembly 10, and enhances the safety performance of the battery.

[0106] See Figure 6 In some embodiments, a first channel 1142 is formed between the second wall 1121c and one edge of the first adhesive 114, and another first channel 1142 is formed between the third wall 1121d and the other edge of the first adhesive 114.

[0107] In some embodiments, the first electrode 11 is a negative electrode and the second electrode 12 is a positive electrode. For example, the negative electrode tab is a nickel electrode tab and the positive electrode tab is an aluminum electrode tab. A first adhesive member 114 adheres the nickel electrode tab to the first empty foil area 1111, and a first channel 1142 is formed between the first adhesive member 114 for adhering the nickel electrode tab and the second wall 1121c and the third wall 1121d. Compared to the nickel electrode tab, the aluminum electrode tab has a lower short-circuit resistance and a higher failure risk than the negative electrode active material. Therefore, placing the first channel 1142 at the nickel electrode tab location can improve the safety performance of the secondary battery 100 and reduce the failure risk.

[0108] In some embodiments, along the winding direction of the electrode assembly 10, the width of the first groove 1121 is P1, and the width of the first channel 1142 is P2, satisfying 0.02P1≤P2≤0.6P1. The second direction Y in the unfolded state of the electrode assembly 10 corresponds to the winding direction in the wound state of the electrode assembly 10.

[0109] If the width of the first channel 1142 is too large, the width of the first adhesive component 114 will be too small, resulting in the solder marks on the first tab 113 not being completely covered, which can easily lead to exposed solder marks puncturing the diaphragm 13 and causing a short circuit. If the width of the first channel 1142 is too small, it is difficult to achieve a good heat dissipation effect. When 0.02P1≤P2≤0.6P1 is satisfied, the heat dissipation effect of the first channel 1142 can be improved while ensuring that the solder marks are not easily exposed.

[0110] In one or more of the above embodiments, 0.2P1≤P2≤0.45P1. This can further reduce the possibility of short circuits caused by solder punctures in the diaphragm 13, and also improve the heat dissipation capacity of the first channel 1142.

[0111] See Figure 7 In some embodiments, the first side 1141 is wavy. Firstly, the wavy design can disperse stress at the interface between the first side 1141 and the first active material layer 112 and the first current collector 111, reducing stress concentration and minimizing damage to the first adhesive member 114, the first active material layer 112, or the first current collector 111 caused by mechanical stress, thereby improving the mechanical stability of the electrode assembly 10. Secondly, the wavy design can increase the insulation distance between the first adhesive member 114 and the first active material layer 112. Especially during the charging and discharging process of the secondary battery 100, this design helps improve the insulation performance of the electrode assembly 10, reduces the risk of short circuits, and enhances the safety of the secondary battery 100. Thirdly, the wavy design facilitates adaptation to thermal expansion and contraction. The secondary battery 100 experiences temperature changes during charging and discharging; the wavy design of the first side 1141 provides a certain amount of elastic space to adapt to thermal expansion and contraction, reducing internal stress caused by temperature changes and improving the thermal stability of the electrode assembly 10.

[0112] See Figure 8In some embodiments, the first adhesive 114 includes a first substrate layer 1143 and a first adhesive layer 1144 stacked together. The material of the first substrate layer 1143 includes, but is not limited to, at least one of polyfluoroolefin, polyethylene terephthalate, polyimide, polyamide-imide, polyvinyl chloride, or polyolefin (e.g., biaxially oriented polyolefin heat shrink film). The polyfluoroolefin includes, but is not limited to, polytetrafluoroethylene or polyvinylidene fluoride. The first adhesive layer 1144 includes an adhesive material, which includes, but is not limited to, at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyacryl alcohol, sodium polyacrylate, polyetherimide, or acrylate.

[0113] See Figure 9 In some embodiments, along the first direction X, the width of the first electrode 11 is greater than the width of the second electrode 12. The first edge 1125 and the second edge 1126 of the first active material layer 112 extend beyond the edge of the second active material layer 122 on the same side. Figure 9 The dashed line in the figure is used to indicate the edge of the second active material. When the first electrode 11 is the negative electrode and the second electrode 12 is the positive electrode, this is beneficial to increase the CB (Cell Balance, the ratio of negative electrode capacity per unit area to positive electrode capacity per unit area) of the first electrode 11 and the second electrode 12, and to reduce the possibility of lithium plating in the electrode assembly 10 during cycling.

[0114] See Figure 4 and Figure 10 In some embodiments, the fifth wall 1124b is closer to the second edge 1126 and separate from the second edge 1126 than the fourth wall 1124a.

[0115] Understandably, there is a gap between the electrode assembly 10 and the inner wall of the housing 20. Compared to the middle of the electrode assembly 10, the position of the electrode assembly 10 closer to the inner wall of the housing 20 is more likely to store more electrolyte. If the second groove 1124 extends directly to the second edge 1126, the end of the second groove 1124 will store more electrolyte, resulting in a larger local impedance. Compared to a design without the second groove 1124, it will be more prone to interface problems caused by lithium plating. In this embodiment, the fifth wall 1124b of the second groove 1124 is separated from the second edge 1126, and the second groove 1124 does not extend to the second edge 1126. This can guide the electrolyte to wet the middle part of the first electrode 11, improving the wetting effect of the first electrode 11, and effectively mitigating the problem of lithium plating.

[0116] See Figure 4 and Figure 9 In some embodiments, the distance between the second edge 1126 and the edge of the second active material layer 122 on the same side is W. 11The distance between the fifth wall 1124b and the second edge 1126 is W3, which satisfies 0.6W. 11 ≤W3≤1.2W 11 .

[0117] When W3 < 0.6W1, the gap width between the fifth wall 1124b and the second edge 1126 without the second groove 1124 is too narrow, and the distance between the fifth wall 1124b of the second groove 1124 and the second edge 1126 is too close, making it difficult to achieve the effect of slowing lithium dissolution. When W1W3 > 1.2W1, the gap width between the fifth wall 1124b and the second edge 1126 without the second groove 1124 is too large, and the distance between the fifth wall 1124b of the second groove 1124 and the second edge 1126 is too far, easily hindering the flow of electrolyte to the middle part of the first electrode 11, resulting in poor wetting of the first electrode 11 and interface problems. Satisfying 0.6W1... 11 ≤W3≤1.2W 11 This not only guides the electrolyte to wet the middle part of the first electrode 11, improving the wetting effect of the first electrode 11, but also effectively alleviates the problem of lithium desorption.

[0118] In some embodiments, 0.8W 11 ≤W3≤1.1W 11 Within this range, the problem of lithium desorption can be further mitigated, provided that the electrolyte can effectively wet the middle part of the first electrode 11.

[0119] See Figure 4 and Figure 9 In some embodiments, along the first direction X, the second groove 1124 of the first region 1122 has a sixth wall 1124c and a seventh wall 1124d opposite each other. Compared with the seventh wall 1124d, the sixth wall 1124c is closer to the first edge 1125 and is separated from the first edge 1125, while the seventh wall 1124d is separated from the second edge 1126.

[0120] In related technologies, the second tank 1124 extends directly to the first edge 1125 and the second edge 1126. This allows the second tank 1124 to store more electrolyte at the positions of the first edge 1125 and the second edge 1126, resulting in a larger local impedance. Compared to a design where the second tank 1124 does not extend to the first edge 1125 and the second edge 1126, this design is more prone to lithium plating and interface problems. Therefore, the sixth wall 1124c is a certain distance from the first edge 1125, and the seventh wall 1124d is a certain distance from the second edge 1126. This reduces the space for storing electrolyte at the positions of the first edge 1125 and the second edge 1126, reduces local impedance, and can effectively alleviate the lithium plating problem at the positions of the first edge 1125 and the second edge 1126.

[0121] See Figure 4 and Figure 9 In some embodiments, the distance by which the first edge 1125 extends beyond the edge of the second active material layer 122 on the same side is W1, and the distance by which the second edge 1126 extends beyond the edge of the second active material layer 122 on the same side is W. 11 The distance between the sixth wall 1124c and the first edge 1125 is W2, satisfying 0.6W1≤W2≤1.2W1; the distance between the seventh wall 1124d and the second edge 1126 is W3, satisfying 0.6W1≤W2≤1.2W1. 11 ≤W3≤1.2W 11 .

[0122] The distance between the seventh wall 1124d and the second edge 1126 is too narrow, and the distance between the second groove 1124 and the first edge 1125 and the second edge 1126 is too close, making it difficult to achieve the effect of slowing lithium desorption. The distance between the seventh wall 1124d and the second edge 1126 is too large, which easily hinders the flow of electrolyte to the center of the first electrode 11, resulting in poor wetting of the center of the first electrode 11 and interface problems. The following conditions must be met: 0.6W1≤W2≤1.2W1, 0.6W 11 ≤W3≤1.2W 11 When W1W3 is used, not only can lithium be slowly desorbed, but the wetting effect of the electrolyte on the first electrode 11 can also be satisfied.

[0123] In some embodiments, 0.8W1≤W2≤1.1W1, 0.8W 11 ≤W3≤1.1W 11 When this range is met, the lithium plating problem can be further improved while reducing the flow resistance of the electrolyte.

[0124] See Figure 3 In some embodiments, the third surface 121a and the fourth surface 122b of the second current collector 121 are both provided with a second active material layer 122, and the second adhesive 124 is disposed on the second active material layer 122 on the side opposite to or away from the first tab 113. Along the stacking direction of the first electrode 11 and the second electrode 12, the projection of the portion where the first tab 113 connects to the first empty foil area 1111 is located within the projection of the second adhesive 124. The second adhesive 124 can further separate the first electrode 11 and the second electrode 12, protect the position of the first tab 113, and reduce the possibility of short circuits between the first electrode 11 and the second electrode 12 caused by solder protrusions on the first tab 113, as well as interface problems.

[0125] Furthermore, a third groove 122 is provided on the second active material layer 122 opposite to or away from the first electrode tab 113, and the second adhesive 124 is disposed in the third groove 1221.

[0126] By placing the second adhesive 124 in the third groove 1221, the thickness of the electrode assembly 10 at the first tab 113 position can be effectively reduced, which is beneficial to reducing the volumetric energy density loss of the secondary battery 100.

[0127] See Figure 3 In some embodiments, along the stacking direction of the first electrode 11 and the second electrode 12, the second adhesive 124 is at least partially stacked with the first adhesive 114. This provides secondary protection for the position of the first electrode tab 113 based on the first adhesive 114, reducing the risk of short circuit caused by the solder burrs of the first electrode tab 113 piercing the diaphragm 13 between the first electrode 11 and the second electrode 12. It also reduces the risk of short circuit caused by misalignment or omission of the first adhesive 114 during the manufacturing process.

[0128] In some embodiments, the active material at the location of the third groove 1221 is milled away by laser etching to form the third groove 1221, such that at least a portion of the second adhesive 124 in the thickness direction is disposed in the third groove 1221, thereby reducing the impact of the second adhesive 124 on the overall thickness of the electrode assembly 10. For example, all the active material at the location of the third groove 1221 is milled away so that a portion of the second current collector 121 is exposed through the third groove 1221, and the second adhesive 124 is adhered to the exposed portion of the second current collector 121. As another example, a portion of the active material at the location of the third groove 1221 is cleaned to form the third groove 1221, and the second adhesive 124 is adhered to the third groove 1221.

[0129] See Figure 3 and Figure 11 In some embodiments, a second channel 1241 is formed between at least one edge of the second adhesive 124 and the groove wall of one side of the third groove 1221 along the winding direction of the electrode assembly 10.

[0130] During the hot chamber test, as the temperature rises, the surface temperature of the electrode assembly 10 continuously increases. Due to the occurrence of side reactions, heat is continuously released, and gas is generated. If the heat generation of the electrode assembly 10 exceeds the heat dissipation, excessive heat accumulation will eventually cause the secondary battery 100 to fail. In this embodiment, due to the design of the second adhesive 124 and the second channel 1241, when a large amount of gas accumulates, the gas can flow out through the second channel 1241, thereby facilitating the heat dissipation of the electrode assembly 10. The gas generated during the hot chamber test is discharged from the electrode assembly 10 through the second channel 1241, reducing the impact on the viscosity of the second adhesive 124 under high temperature or gas impact conditions, and improving the pass rate of the hot chamber test.

[0131] In some embodiments, along the winding direction of the electrode assembly 10, the edges of the second adhesive member 124 on opposite sides form a second channel 1241 between the groove wall of the third groove 1221.

[0132] In some embodiments, the first electrode 11 is a negative electrode, and the second electrode 12 is a positive electrode. For example, the negative electrode tab is a nickel electrode tab, and the positive electrode tab is an aluminum electrode tab. The second adhesive 124 is adhered to the second active material layer 122 on the side opposite or to the side of the nickel electrode tab, and the second channel 1241 is located on the second active material layer 122 on the side opposite or to the side of the nickel electrode tab. Compared to the nickel electrode tab, the short-circuit resistance between the aluminum electrode tab and the negative electrode active material is smaller, and the failure risk is higher. Therefore, placing the second channel 1241 at the nickel electrode tab location can improve the safety performance of the secondary battery 100 and reduce the failure risk.

[0133] In some embodiments, along the winding direction of the electrode assembly 10, the width of the third groove 1221 is H1 and the width of the second channel 1241 is H2, satisfying 0.01H1≤H2≤0.1H1.

[0134] When the width of the second channel 1241 is too large, the area covered by the second adhesive 124 within the third groove 1221 is too small, resulting in insufficient protection for the first tab 113 and potentially causing a short circuit failure between the first electrode 11 and the second electrode 12. Conversely, when the width of the second channel 1241 is too small, the improvement effect on the hot box test is minimal. Meeting the condition 0.01H1≤H2≤0.1H1 provides adequate protection for the first tab 113 and also improves the pass rate of the hot box test for the secondary battery 100.

[0135] In some embodiments, 0.03H1≤H2≤0.07H1. When 0.03H1≤H2≤0.07H1 is satisfied, the width of the second channel 1241 can be further increased, thereby improving the exhaust effect of the second channel 1241, while ensuring that the second adhesive 124 provides sufficient protection for the first electrode tab 113.

[0136] In some embodiments, the second adhesive 124 includes a second substrate layer and a second adhesive layer stacked together. The material of the second substrate layer includes, but is not limited to, at least one of polyfluoroolefin, polyethylene terephthalate, polyimide, polyamide-imide, polyvinyl chloride, or polyolefin (e.g., biaxially oriented polyolefin heat shrink film). The polyfluoroolefin includes, but is not limited to, polytetrafluoroethylene or polyvinylidene fluoride. The second adhesive layer includes an adhesive material, including, but not limited to, at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyacrylamide, sodium polyacrylate, polyetherimide, or acrylate. For example, the second adhesive 124 has the same structure as the first adhesive.

[0137] See Figure 3 In some embodiments, a second adhesive member 124 is provided on the second active material layer 122 opposite to the first tab 113, and another second adhesive member 124 is provided on the second active material layer 122 opposite to the first tab 113. The second adhesive member 124 opposite to the first tab 113 is disposed in a third groove 1221 and is directly adhered to the second active material layer 122. By disposing of one of the second adhesive members 124 in the third groove 1221, the thickness of the electrode assembly 10 at the position of the first tab 113 is less likely to be too small, reducing the risk of a thickness difference between the thickness at the position of the first tab 113 and the thickness at the position where the first tab 113 is not provided.

[0138] See Figure 1 In some embodiments, the first electrode 11 includes a plurality of first tabs 113. For example, the first electrode 11 is a positive electrode, and the first electrode 11 includes two first tabs 113. Each first tab 113 is provided with a corresponding first empty foil area 1111, and the first tab 113 is connected to the corresponding first empty foil area 1111.

[0139] See Figure 12 The embodiments of this application also provide an electronic device 1000, which includes the secondary battery 100 in any of the above embodiments.

[0140] In some embodiments, the electronic device 1000 may be a mobile phone, a laptop computer, a tablet computer, a drone, a power tool, an electric toy, a game console, a video recorder, a portable recorder, a radio, or a smartwatch, etc., which will not be listed here.

[0141] In some embodiments, the electronic device 1000 further includes a device body 200, and a secondary battery 100 is mounted on the device body 200. Since the electronic device 1000 adopts the technical solution of the secondary battery 100 in any of the above embodiments, it has at least the beneficial effects brought about by the technical solution of any of the above embodiments of the secondary battery 100, which will not be described in detail here.

[0142] To verify the influence of parameters such as the positional relationship between the second groove 1124 and the first groove 1121, the first adhesive component 114, and the second adhesive component 124 on the performance of the secondary battery 100, the inventors conducted the following experiments: (1) Cycle life test: 50 secondary batteries 100 were tested in each comparative example and each embodiment. The cycle life of the 50 secondary batteries 100 in each comparative example and each embodiment was recorded and the average value was calculated.

[0143] Experimental conditions for cycle life (CR=80% as the limit): In an environment of 25°C, the electrode assembly 10 is charged to full charge voltage at a charging current of 1C (the secondary battery 100 is designed with a maximum voltage of 4.5V) by constant current charging, and then charged at the maximum voltage until the current is 0.02C. Then, it is discharged at a discharge current of 0.7C until the final voltage is 3.0V. The above steps are then repeated for 1400 charge and discharge cycles.

[0144] CR (Capacity Retention) definition: The discharge capacity of the third cycle is taken as the base capacity. CR = discharge capacity of each cycle / base capacity. For example, if the base capacity is 5000mAh and the 1000cls capacity is 4000mAh, then CR = 4000 / 5000 = 80%.

[0145] The cycle life in Table 3 is the number of cycles corresponding to when the CR value reaches 80%.

[0146] (2) Hot Box Test: Under 25℃ conditions, the secondary battery 100 was left to stand for 5 minutes, charged to 4.5V at a constant current of 0.5C, then charged to 0.025C at a constant voltage of 4.5V, left to stand for 60 minutes, and then subjected to a hot box test. Before the hot box test, the appearance of the secondary battery 100 was checked and photographed, the temperature sensing wire was attached, and the secondary battery 100 was placed vertically in the hot box and heated from 25℃ to 130℃ at a rate of 5℃ / minute and maintained for 60 minutes. If the secondary battery 100 did not catch fire or explode, the hot box test was considered to have passed. The number of secondary battery samples tested was 50. The number of batteries that passed the hot box test was counted and the hot box test pass rate was calculated. The number of batteries that passed the test was X, and the test pass rate was X / 50.

[0147] (3) Drop test: Secondary batteries 100 were pretreated at 25℃ and left to stand at room temperature for 60 minutes before the drop test. The voltage of the lithium-ion batteries was then measured. Secondary batteries 100 were placed in a fixture and dropped freely from a height of 1.5m using a drop tester in the following sequence: head-tail-right head corner-right tail corner-left head corner-left tail corner (angle: 45±15°), repeated 6 times. After the drops, the batteries were left to stand at room temperature for 24 hours, and the voltage of the secondary batteries 100 was measured and recorded. The appearance of the lithium-ion batteries was inspected and photographed before and after the test. The drop test pass criteria were: no smoke, no leakage, and voltage drop <50mV. Fifty secondary batteries 100 were tested; the number of batteries that passed the test was Y, and the pass rate was Y / 50.

[0148] (4) Lithium plating rate test: 50 secondary batteries were tested for each comparative example and each example.

[0149] Place the secondary battery 100 in an environment with a test temperature of 25℃ for 30 minutes, and then charge it to 4.5V in stages according to the following charging steps: ① Charge at a constant current of 5C to 4.23V; ② Charge at 4C constant current to 4.3V; ③ Charge to 4.5V using 3C constant current; ④ Charge at 2C constant current to 4.5V, then charge at constant voltage to cut off current at 0.05C; After letting it stand for 10 minutes, proceed with the following steps to discharge: Discharge at a constant current of 0.2C to 3V.

[0150] The above charge-discharge process constitutes one cycle. After repeating 1200 cycles, with the secondary battery 100 fully charged (maximum designed voltage 4.5V), the secondary battery 100 is disassembled to obtain the negative electrode. The non-lithium-deposited area on the surface of the negative electrode is golden yellow, while the lithium-deposited area is grayish-white. If the lithium deposition area on the surface of the negative electrode is found to be greater than or equal to 1 mm², then the negative electrode is considered to have a negative electrode. 2 If the number of samples is N, it is considered lithium plating and the test fails; otherwise, the test passes. Each group consists of 50 samples, with N being the number that passes and N / 50 being the non-lithiation rate.

[0151] Wherein, the first non-lithiation rate refers to the non-lithiation rate of the main body region of the electrode assembly 10, and the second non-lithiation rate refers to the non-lithiation rate of the edge region of the electrode assembly 10. The edge region of the electrode assembly 10 refers to the region in the first direction X where the first edge 1125 and the second edge 1126 of the first electrode 11 extend beyond the second electrode 12; the main body region of the electrode assembly 10 refers to the portion located between the edge regions of the electrode assembly 10.

[0152] The specific implementation of the secondary battery 100 in the embodiments and comparative examples will be described below.

[0153] 1. Preparation of secondary battery 100.

[0154] (1) Preparation of the positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), CNT (carbon nanotubes), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:0.5:0.5:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode active material with a solid content of 75wt%, and stirred evenly for later use. A 10μm thick aluminum foil was used as the positive electrode current collector. The above active material was uniformly coated on the first side 111a of the positive electrode current collector using a slit coater to form a positive electrode active material layer, and then dried at 90°C to obtain a positive electrode sheet with a single-sided coating of the positive electrode active material layer. The above steps were then repeated on the second side 111b of the positive electrode current collector to obtain a positive electrode sheet with a double-sided coating of the positive electrode active material layer. The coated positive electrode sheet was then cold-pressed. The positive electrode tabs were then welded to the part of the positive electrode current collector that was not covered by the positive electrode active material layer.

[0155] (2) Preparation of negative electrode sheet: The active materials artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) were mixed in a weight ratio of 97:0.5:1.3:1.2, and deionized water was added as a solvent to prepare a negative electrode active material with a weight percentage of 50 wt%, and stirred evenly for later use. A copper foil with a thickness of 10 μm was used as the negative electrode current collector. The above negative electrode active material was uniformly coated on the third side 121a of the negative electrode current collector using a slit coater, and then dried at 110°C to obtain a negative electrode sheet coated with a negative electrode active material layer. The above steps were then repeated on the fourth side 122b of the negative electrode current collector to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. The coated negative electrode sheet was then cold-pressed. A first groove 1121 and a second groove 1124 were formed on the negative electrode active material layer by laser etching, and a first empty foil area 1111 was formed in the first groove 1121 of the negative electrode current collector. Then, the negative electrode tab is welded to the first empty foil area 1111, and the first adhesive 114 is attached to the negative electrode tab. The third groove 1221 is formed on the negative electrode active material layer by laser etching, and the second adhesive 124 is set in the third groove 1221. (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC=30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0156] (4) Preparation of diaphragm 13: A 7 μm thick polyethylene porous polymer film was used as diaphragm 13.

[0157] (5) Preparation of electrode assembly 10: The positive electrode sheet, the separator 13 and the negative electrode sheet are stacked and wound together along the thickness direction of the negative electrode sheet to obtain electrode assembly 10. After the electrode assembly 10 is wound, the positive electrode tab is located within the projection of the second adhesive member 124 along the stacking direction of the electrode assembly 10.

[0158] (6) Assembly of the secondary battery 100: Place the punched aluminum-plastic film in the assembly fixture with the punched surface facing upwards, place the electrode assembly 10 in the punch, and apply external force to press it firmly. Then, cover the electrode assembly 10 with another punched aluminum-plastic film with the punched surface facing downwards, and heat-seal the three edges of the two aluminum-plastic films by hot pressing. The unsealed edge is the negative electrode tab and the positive electrode tab extending out of the shell 20. Then, inject electrolyte through the unsealed edge, and after vacuum sealing, standing, hot pressing formation, shaping and other processes, the secondary battery 100 is obtained.

[0159] The difference between Examples 1-20 and Examples 1-4 is that in the secondary battery 100 of Examples 1-20, a first groove 1121 and a second groove 1124 are formed on the positive electrode active material layer by laser etching, and a first empty foil region 1111 is formed in the first groove 1121 of the positive electrode current collector. Then, the positive electrode tab is soldered to the first empty foil region 1111, and a first adhesive member 114 is attached to the positive electrode tab. The negative electrode tab is soldered to the portion of the negative electrode current collector not covered by the negative electrode active material layer. After the electrode assembly 10 is wound, along the stacking direction of the electrode assembly 10, the portion where the negative electrode tab connects to the first empty foil region is located within the projection of the second adhesive member 124.

[0160] 2. The main parameter control and test results of each embodiment are shown in Tables 1 to 4: Table 1 Note: " / " indicates that no value is taken.

[0161] Table 2 Note: Except for the parameters shown in Table 2, the other parameters are consistent with those in Examples 1-4.

[0162] Table 3 Note: Except for the parameters shown in Table 3, the other parameters are consistent with those in Examples 1-4.

[0163] Table 4 Note: Except for the parameters shown in Table 4, the other parameters are consistent with those in Examples 1-4.

[0164] In Comparative Example 1, L1 = 0, and the second groove 1124 of the second region 1123 extends to the first wall 1121b of the first groove 1121. Under this design, it is beneficial for the electrolyte to wet the interior of the electrode assembly 10 through the second groove 1124 of the second region 1123, thereby improving the undeposited lithium rate of the main body of the electrode assembly 10. However, the setting of the second groove 1124 will also reduce the active material at the junction of the second groove 1124 and the first wall 1121b. During the manufacturing process, the structure at the junction of the second groove 1124 and the first wall 1121b will also be weak, resulting in a low drop pass rate measured in the drop test.

[0165] In Examples 1-1 to 1-10, L1 > 0, and there is a certain distance between the second groove 1124 of the second region 1123 and the first wall 1121b of the first groove 1121, thereby improving the structural strength between the second groove 1124 of the second region 1123 and the first wall 1121b of the first groove 1121. Compared with Comparative Example 1, the drop pass rate is significantly improved. In addition, it can be seen from Table 1 that when L1 / L2 > 0.08, due to the large L1, poor wetting occurs, and the undeposited lithium rate is significantly reduced; when L1 / L2 is between 0.03 and 0.06, it can both improve the lithium deposition of the electrode assembly 10 and improve the drop test.

[0166] In Examples 1-11 to 1-15, 1-4, and 1-16 to 1-19, L4 and L5 gradually increase. Compared to the case where L4 and L5 are 0 in Example 1-11, when 0 < L4 ≤ 1.1L3 and 0 < L5 ≤ 1.1L3 are satisfied in Examples 1-4, 1-12 to 1-18, the setting of the second groove 1124 is beneficial to the wetting of the electrolyte, thereby reducing lithium plating and increasing the non-lithium plating rate. Furthermore, the setting of the second groove 1124 does not easily reduce the structural strength at the connection with the first groove 1121, thereby improving the drop pass rate. However, in Examples 1-19, when the distance between the second groove 1124 and the second wall 1121c of the first groove 1121 is too large, although it is beneficial to improve the structural strength of the electrode assembly 10 and increase the drop pass rate, it will affect the degree of electrolyte wetting.

[0167] Based on the experimental results of Examples 1-4 and Examples 1-20, it can be seen that when the first groove 1121 and the second groove 1124 are disposed on the positive electrode and the negative electrode, respectively, the drop pass rate can be improved and the wetting effect of the electrode can be improved by increasing the structural strength at the connection between the first groove 1121 and the second groove 1124, thereby improving the lithium plating problem.

[0168] In Examples 2-1 to 2-8, compared to Example 2-1, W2 and W3 gradually increase in Examples 2-2 to 2-8. The test results in Table 2 show that W2 and W3 affect the overall lithium plating of the electrode assembly 10, with a greater impact on the edge region. Increasing W2 and W3 leads to more electrolyte accumulation in the edge region of the electrode assembly 10, meeting the lithium-ion transport requirements and thus reducing lithium plating. However, excessive electrolyte in the edge region of the electrode assembly 10 can also lead to lithium plating. When W2 / W1 and W3 / W3 are relatively high... 11 When the value exceeds 1.2, the overall lithium plating situation of electrode assembly 10 will significantly deteriorate. The following conditions must be met: 0.8W1≤W2≤1.1W1, 0.8W11≤W3≤1.1W 11 At that time, the improvement in lithium plating in the edge region of electrode assembly 10 was more obvious.

[0169] In Examples 3-1 to 3-10, compared to the case where P2=0 in Example 3-1, P2≥0.02 in Examples 3-2 to 3-10, meaning that the secondary battery 100 in Examples 3-2 to 3-10 is provided with a first channel 1142, and the cycle life is significantly improved. It can be inferred that the first channel 1142 facilitates heat dissipation of the secondary battery 100, thereby improving cycle life. However, when the first channel 1142 is too large, the first adhesive 114 may not completely cover the solder mark of the first tab 113, and the burrs at the solder mark may easily pierce the separator, leading to short-circuit failure. Compared to the case without a first channel, the improvement in cycle life is more significant when 0.2P1≤P2≤0.45P1 is satisfied.

[0170] In Examples 4-1 to 4-8, compared to the case where H2=0 in Example 4-1, H2≥0.005 in Examples 4-2 to 4-8. This means that the secondary battery 100 in Examples 4-2 to 4-8 is equipped with a second channel 1241, which improves the pass rate of the hot box test for the secondary battery 100. It can be inferred that the design of the second adhesive 124 and the second channel 1241 allows gas to flow out through the second channel 1241 when a large amount of gas accumulates during the hot box test, thus facilitating heat dissipation of the electrode assembly 10. By venting the gas generated during the hot box test outside the electrode assembly 10 through the second channel 1241, the viscosity of the second adhesive 124 is reduced under high temperature or gas impact conditions, thereby improving the pass rate of the hot box test.

[0171] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of this application.

Claims

1. A secondary battery, characterized in that, The secondary battery includes an electrode assembly, which includes a first electrode and a second electrode. The first electrode and the second electrode are stacked and form a wound structure. The first electrode and the second electrode have opposite polarities. The first electrode includes a first tab and a first current collector and a first active material layer stacked together. Along the thickness direction of the first current collector, at least one side of the first current collector is provided with the first active material layer. The first active material layer is provided with a first groove, and a portion of the first current collector is exposed through the first groove to form a first empty foil area. The first tab is connected to the first empty foil area. The first active material layer includes a first region and a second region, which surround the outer periphery of the first groove. The width direction of the first electrode is a first direction. Along the first direction, the first groove includes a first wall. Along the second direction, the first groove includes a second wall and a third wall disposed opposite to each other. The first wall connects the second wall and the third wall. The second direction is perpendicular to the first direction. The second wall and the third wall are respectively extended along the first direction. The extension lines of the second wall and the third wall, along with the first wall, enclose the second region. The first wall connects to the second region. The first active material layer in the first region and the second region is provided with a plurality of second grooves. The depth of the second groove is less than the thickness of the first active material layer. The minimum distance between the second groove in the second region and the first wall is L1, which satisfies L1 > 0. Along the first direction, the length of the first groove is L2, which satisfies 0.01L2≤L1≤0.08L2.

2. The secondary battery as described in claim 1, characterized in that, 0.03L2≤L1≤0.06L2.

3. The secondary battery as described in claim 1, characterized in that, The spacing between two adjacent second slots is L3. Along the winding direction of the electrode assembly, the first slot has a second wall and a third wall disposed opposite to each other. In the winding direction of the electrode assembly, the minimum distance between the second slot and the second wall in the first region is L4, satisfying 0 < L4 ≤ 1.1L3. In the winding direction of the electrode assembly, the minimum distance between the second slot and the third wall in the first region is L5, satisfying 0 < L5 ≤ 1.1L3.

4. The secondary battery as described in claim 1, characterized in that, The first electrode also includes a first adhesive element, which is attached to the first electrode tab and the first empty foil area; along the first direction, the first adhesive element extends beyond the first wall by a length D1, and the portion of the first adhesive element extending beyond the first wall is attached to the second area; Along the first direction, the second groove in the second region has opposing fourth and fifth walls, with the fourth wall being closer to the first wall than the fifth wall, and a portion of the first adhesive is attached to the portion of the second region where the second groove is provided; Along the first direction, the first adhesive member is located at the edge of the second region as the first side, and the maximum distance between the fourth wall and the first side is D2, which satisfies 0.1D1≤D2≤0.8D1.

5. The secondary battery as described in claim 4, characterized in that, The first side is designed in a wavy shape.

6. The secondary battery as described in claim 4 or 5, characterized in that, Along the winding direction of the electrode assembly, the first groove has a second wall and a third wall disposed opposite to each other, and at least one of the second wall and the third wall forms a first channel between the second wall and the edge of the first adhesive.

7. The secondary battery as described in claim 6, characterized in that, Along the winding direction of the electrode assembly, the width of the first groove is P1, and the width of the first channel is P2, satisfying 0.02P1≤P2≤0.6P1.

8. The secondary battery as described in claim 6, characterized in that, 0.2P1≤P2≤0.45P1.

9. The secondary battery as described in claim 4 or 5, characterized in that, 0.2D1≤D2≤0.5D1.

10. The secondary battery as described in claim 4 or 5, characterized in that, The first electrode is a negative electrode, and the second electrode is a positive electrode; the second electrode includes a second current collector and a second active material layer stacked together, and the second active material layer is disposed on at least one side of the second current collector; Along the first direction, the width of the first electrode is greater than the width of the second electrode; Along the first direction, the first active material layer has opposing first edges and second edges, the first edges and the second edges extending beyond the edge of the second active material layer on the same side; Compared to the fourth wall, the fifth wall is closer to the second edge and is separate from the second edge.

11. The secondary battery as described in claim 10, characterized in that, The distance between the second edge and the edge of the second active material layer on the same side is W. 11 The distance between the fifth wall and the second edge is W3, which satisfies 0.6W. 11 ≤W3≤1.2W 11 .

12. The secondary battery as described in claim 11, characterized in that, 0.8W 11 ≤W3≤1.1W 11 。 13. The secondary battery as described in any one of claims 1 to 9, characterized in that, The second electrode includes a second current collector and a second active material layer stacked together. Along the thickness direction of the second current collector, the second current collector has two opposing surfaces. Each surface of the second current collector is provided with the second active material layer. The second active material layer on the side opposite or back from the first electrode tab is provided with a third groove. The second electrode includes a second adhesive member, which is disposed in the third groove. Along the stacking direction of the first electrode and the second electrode, the projection of the portion where the first electrode tab connects to the first empty foil area is located within the projection of the second adhesive.

14. The secondary battery as described in claim 13, characterized in that, Along the winding direction of the electrode assembly, a second channel is formed between at least one edge of the second adhesive and the groove wall of one side of the third groove.

15. The secondary battery as described in claim 14, characterized in that, Along the winding direction of the electrode assembly, the width of the third groove is H1, and the width of the second channel is H2, satisfying 0.01H1≤H2≤0.1H1.

16. The secondary battery as described in claim 15, characterized in that, 0.03H1≤H2≤0.07H1.

17. The secondary battery as described in any one of claims 1 to 9, characterized in that, The first electrode is a negative electrode, and the second electrode is a positive electrode. The second electrode includes a second current collector and a second active material layer stacked together. Along the thickness direction of the second current collector, at least one side of the second current collector is provided with the second active material layer. Along the first direction, the width of the first electrode is greater than the width of the second electrode. Along the first direction, the first active material layer has opposing first edges and second edges, the first edges and the second edges extending beyond the edge of the second active material layer on the same side; Along the first direction, the second groove in the first region has opposing sixth and seventh walls, wherein the sixth wall is closer to the first edge than the seventh wall, the sixth wall is away from the first edge, and the seventh wall is away from the second edge.

18. The secondary battery as described in claim 17, characterized in that, The distance by which the first edge extends beyond the edge of the second active material layer on the same side is W1, and the distance by which the second edge extends beyond the edge of the second active material layer on the same side is W. 11 The distance between the sixth wall and the first edge is W2, satisfying 0.6W1≤W2≤1.2W1; the distance between the seventh wall and the second edge is W3, satisfying 0.6W1≤W2≤1.2W1. 11 ≤W3≤1.2W 11 .

19. The secondary battery as described in claim 18, characterized in that, 0.8W1≤W2≤1.1W1,0.8W 11 ≤W3≤1.1W 11 。 20. The secondary battery as described in claim 4 or 5, characterized in that, The first adhesive comprises a first substrate layer and a first adhesive layer stacked together. The material of the first substrate layer includes at least one of polyfluoroolefin, polyethylene terephthalate, polyimide, polyamide-imide, polyvinyl chloride, or polyolefin. The first adhesive layer includes an adhesive material, which includes at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyacryl alcohol, sodium polyacrylate, polyetherimide, or acrylate.

21. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 20.

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