Secondary battery and electronic device

Abstract

The present invention relates to the technical field of energy storage. Particularly, provided are a secondary battery (100) and an electronic device (1000). The secondary battery (100) comprises an electrode assembly (10), the electrode assembly (10) comprising a first electrode plate (11) and a second electrode plate (12), wherein the first electrode plate (11) comprises a first tab (113), and a first current collector (111) and a first active material layer (112) which are stacked, the first active material layer (112) being provided with a first recess (1121), and part of the first current collector (111) being exposed through the first recess (1121) to form a first bare foil region (1111); the first tab (113) is connected to the first bare foil region (1111); a first region (1122) and a second region (1123) of the first active material layer (112) surround the outer periphery of the first recess (1121); the first recess (1121) comprises a first wall (1121b), a second wall (1121c) and a third wall (1121d); extension lines of the second wall (1121c) and the third wall (1121d), and the first wall (1121b) define the second region (1123); and the minimum distance between a second recess (1124) of the second region (1123) and the second wall (1121c) is defined as L1, which satisfies L1>0. While improving the wetting performance of an electrolyte on the electrode plates, the structural strength of the electrode plates can be improved, and the risk of failure of the secondary battery due to drop impact can be reduced.

Description

Secondary battery and electronic device TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a secondary battery and an electronic device. BACKGROUND

[0002] In a secondary battery, the performance of the secondary battery is improved by setting a flow guide groove on the pole piece of the electrode assembly to improve the wetting effect of the electrolyte on the pole piece. However, the setting of the flow guide groove will cause the structure at the position of the tab to be weak. In the drop process, the electrode assembly is impacted, the tab is prone to deflection, and then drives the pole piece substrate at the position of the tab. At this time, due to the weak structure at the position of the tab, the substrate at this position will be damaged, thereby causing the secondary battery to fail to drop.

[0003] SUMMARY

[0004] Therefore, it is necessary to provide a secondary battery and an electronic device which can improve the structure strength of the pole piece and reduce the risk of secondary battery drop failure on the premise of improving the wetting effect of the electrolyte on the pole piece.

[0005] A first aspect of the embodiment of the present application provides a secondary battery, comprising an electrode assembly, the electrode assembly comprising a first pole piece and a second pole piece, the first pole piece and the second pole piece being stacked and forming a winding structure, the first pole piece and the second pole piece having opposite polarities, the first pole piece comprising a first tab, a first current collector and a first active material layer stacked, 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, part of the first current collector is exposed through the first groove to form a first empty foil area, and the first tab is connected to the first empty foil area; the first active material layer comprises a first region and a second region, and the first region and the second region are arranged around the outer periphery of the first groove; the width direction of the first pole piece is the first direction, along the first direction, the first groove comprises a first wall, along the second direction, the first groove comprises a second wall and a third wall arranged oppositely, the first wall connects the second wall and the third wall, and the second direction is perpendicular to the first direction; the second wall and the third wall respectively extend along the first direction, and the extension lines of the second wall and the third wall and the first wall form the second region; the first wall connects the second region; the first active material layer of the first region and the second region is provided with a plurality of second grooves, and the depth of the second grooves 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, and L1>0 is satisfied.

[0006] In the above embodiment, the second groove of the first region and the second region can accommodate electrolyte, thereby facilitating the electrolyte to contact the first pole piece through the second groove and improving the infiltration degree of the electrolyte to the first pole piece. In the first direction, the second groove of the second region and the first wall of the first groove have a spacing, and relative to the position where the first groove and the second groove are arranged, the first active material layer between the second groove of the second region and the first wall of the first groove is more, and has better structural strength, so that the position between the second groove of the second region and the first wall of the first groove is not easily broken and damaged when impacted by the electrolyte or the first tab shakes during the falling process, thereby reducing the risk of secondary battery falling failure.

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

[0008] In the above embodiment, keeping a certain distance between the second groove and the first wall of the first groove can effectively improve the passing rate of the secondary battery falling, but when L1 is too large, it is not conducive to the infiltration of the electrolyte to the electrode assembly, and the interface problem of the secondary battery in the later stage of the cycle will be caused. When 0.01L2≤L1≤0.08L2 is satisfied, not only can the passing rate of the secondary battery falling be improved, but also the interface problem of the first pole piece can be alleviated.

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

[0010] In the above embodiment, when 0.03L2≤L1≤0.06L2 is satisfied, the infiltration degree of the electrolyte to the first pole piece can be further improved, thereby improving the interface problem, and further improving the structural strength between the first groove and the second groove of the second region, so that the first pole piece is not easily damaged.

[0011] In one or more of the above embodiments, the spacing between the two adjacent second grooves is L3, and the first groove has a second wall and a third wall arranged oppositely in the winding direction of the electrode assembly; in the winding direction of the electrode assembly, the minimum distance between the second groove of the first region and the second wall is L4, and 0

[0012] In the above embodiment, L4>0 and L5>0, so that in the second direction, the distance between the second groove and the first groove is not easily too small to satisfy the structural strength between the second wall, the third wall and the second groove; L4≤1.1L3 and L5≤1.1L3, so that the distance between the second groove and the first groove is also not easily too large, thereby facilitating the first region to store more electrolyte.

[0013] In one or more of the above embodiments, the first tab further comprises a first adhesive, the first adhesive being attached to the first tab and the first empty foil area; along the first direction, the first adhesive has a length D1 beyond the first wall, and the portion of the first adhesive beyond the first wall is attached to the second area; along the first direction, the second groove of the second area has opposite fourth and fifth walls, the fourth wall being closer to the first wall than the fifth wall, and the portion of the first adhesive attached to the portion of the second area provided with the second groove; along the first direction, the edge of the second area where the first adhesive is located is a first side edge, and the maximum distance between the fourth wall and the first side edge is D2, satisfying 0.1D1≤D2≤0.8D1.

[0014] In the above embodiments, the portion of the first adhesive beyond the first wall and attached to the second area further increases the thickness of the portion of the first tab between the first groove and the second groove of the second area, which is beneficial to maintaining the structural strength of the portion between the first groove and the second groove of the second area. When 0.1D1≤D2≤0.8D1 is satisfied, not only can the strength requirement of the first tab be met, but also the overlapping portion of the first adhesive and the second groove of the second area is not too large, reducing the negative impact of the electrolyte on the viscosity of the first adhesive. If the overlapping portion is too large, the electrolyte in the second groove is easy to contact the first adhesive, causing impact on the first adhesive, which is easy to reduce the viscosity between the first adhesive and the first active material layer.

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

[0016] In the above embodiments, in a first aspect, the wavy shape design can disperse the stress at the junction of the first side edge 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; in a second aspect, the wavy shape 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, which helps to improve the insulation performance of the electrode assembly, reduce the risk of short circuit, and improve the safety of the secondary battery; in a third aspect, the wavy shape design is beneficial to adapt to thermal expansion and contraction. The secondary battery will undergo temperature changes during the charging and discharging process, and the wavy shape design of the first side edge 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 opposite second and third walls, and at least one of the second and third walls forms a first channel with the edge of the first adhesive.

[0018] In the above embodiments, the first channel is arranged such that the first current collector is partially exposed, which is conducive to rapid heat dissipation and improves the thermal management performance of the electrode assembly and the safety performance of the battery.

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

[0020] In the above embodiments, when the width of the first channel is too large, the width of the first adhesive is too small, which can cause the welding marks of the first tab to be not fully covered, and the exposed welding marks can easily pierce the separator and cause short circuit. When the width of the first channel is too small, it is difficult to achieve good heat dissipation effect. When 0.02P1≤P2≤0.6P1 is satisfied, the heat dissipation effect of the first channel can be improved while the welding marks are not easily exposed.

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

[0022] In the above embodiments, 0.2P1≤P2≤0.45P1 is satisfied, which can further reduce the short circuit caused by the welding marks piercing the separator and improve the heat dissipation capacity of the first channel.

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

[0024] In the above embodiments, the structural strength of the part between the first slot and the second slot of the second region can be further improved, and the negative impact of the electrolyte on the viscosity of the first adhesive can be reduced.

[0025] In one or more of the above embodiments, the first tab is a negative tab, and the second tab is a positive tab. The second tab includes a second current collector and a second active material layer stacked together. The second active material layer is arranged on at least one side of the second current collector. Along the first direction, the width of the first tab is greater than the width of the second tab. Along the first direction, the first active material layer has opposite first and second edges, and the first and second edges extend beyond the edges of the second active material layer on the same side. Compared with the fourth wall, the fifth wall is closer to the second edge and is separated from the second edge.

[0026] In the above embodiment, if the second groove directly extends to the second edge, the end of the second groove will store more electrolyte, and the interface problem caused by lithium precipitation is more likely to occur compared with the design without the second groove. In the present embodiment, the fifth wall of the second groove is separated from the second edge, and the second groove does not extend to the second edge. In this way, the electrolyte can be guided to the middle part of the first pole piece, improving the wetting effect of the first pole piece, and effectively alleviating the problem of lithium precipitation.

[0027] In one or more of the above embodiments, the distance between the second edge and the second active material layer edge 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 embodiment, when W3<0.6W1, the gap between the fifth wall and the second edge without the second groove is too narrow, the distance between the fifth wall of the second groove and the second edge is too close, and it is difficult to alleviate the problem of lithium precipitation. When W1W3>1.2W1, the gap between the fifth wall and the second edge without the second groove is too large, the distance between the fifth wall of the second groove and the second edge is too far, which easily hinders the inflow of electrolyte to the middle part of the first pole piece, resulting in poor wetting of the first pole piece and interface problems. When 0.6W 11 ≤W3≤1.2W 11 , the electrolyte can be guided to the middle part of the first pole piece, improving the wetting effect of the first pole piece, and effectively alleviating the problem of lithium precipitation.

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

[0030] In the above embodiment, under the premise that the electrolyte can effectively wet the middle part of the first pole piece, the problem of lithium precipitation is further alleviated.

[0031] In one or more of the above embodiments, the second pole piece includes a second current collector and a second active material layer stacked and arranged, and the second current collector has two opposite surfaces in the thickness direction of the second current collector, and each surface of the second current collector is provided with a second active material layer; the second active material layer opposite or away from the first tab is provided with a third groove, and the second pole piece includes a second adhesive, and the second adhesive is arranged in the third groove; in the stacking direction of the first pole piece and the second pole piece, the projection of the part connected by the first tab and the first empty foil area is located in the projection of the second adhesive.

[0032] In the above one or more embodiments, the second adhesive member can further separate the first tab and the second tab, protect the position of the first tab, and reduce the risk of short circuit between the first tab and the second tab and interface problems caused by the protruding welding mark of the first tab.

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

[0034] In the hot box test, as the temperature rises, the surface temperature of the electrode assembly continues to rise, and due to the occurrence of side reactions, heat is continuously released, and gas is generated. If the heat generated by the electrode assembly is greater than the heat dissipation, too much heat accumulation will eventually cause the failure of the secondary battery. In the present embodiment, due to the design of the second adhesive member and the second channel, when a large amount of gas accumulates, the gas can flow out through the second channel, thereby facilitating the heat dissipation of the electrode assembly. By discharging the gas generated during the hot box test out of the electrode assembly through the second channel, the influence of the viscosity of the second adhesive member under the condition of high temperature or gas impact is reduced, and the hot box test pass rate is improved.

[0035] In the above one or more 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 member in the third groove is too small, which may not be able to protect the position of the first tab and may cause the first tab and the second tab to be in contact and short-circuit. When the width of the second channel is too small, the improvement effect of the hot box test is small. When 0.01H1≤H2≤0.1H1 is satisfied, the first tab position can be protected to some extent, and the hot box test pass rate of the secondary battery can be improved.

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

[0038] In the above one or more embodiments, when 0.03H1≤H2≤0.07H1 is satisfied, the width of the second channel can be further increased under the premise that the second adhesive member has sufficient protection effect on the first tab, and the exhaust effect of the second channel can be improved.

[0039] In one or more of the above embodiments, the first tab is a positive tab, and the second tab is a negative tab; the second tab includes a second current collector and a second active material layer stacked together, at least one side of the second current collector is provided with the second active material layer along the thickness direction of the second current collector; along the first direction, the width of the first tab is greater than the width of the second tab; along the first direction, the first active material layer has opposite first and second edges, and the first and second edges exceed the edges of the same side second active material layer.

[0040] In the above embodiments, when the second groove directly extends to the first and second edges, the second groove at the positions of the first and second edges can store more electrolyte, which is more prone to interface problems caused by lithium precipitation compared to the design in which the second groove does not extend to the first and second edges. Therefore, the sixth wall is a certain distance away from the first edge, and the seventh wall is a certain distance away from the second edge, which can effectively alleviate the lithium precipitation problem at the positions of the first and second edges.

[0041] In one or more of the above embodiments, the distance between the first edge and the edge of the same side second active material layer is W1, the distance between the second edge and the edge of the same side second active material layer is W 11 , the distance between the sixth wall and the first edge is W2, and 0.6W1≤W2≤1.2W1 is satisfied; the distance between the seventh wall and the second edge is W3, and 0.6W 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, which cannot effectively alleviate the lithium precipitation problem. If the distance between the seventh wall and the second edge is too large, it is easy to hinder the inflow of electrolyte to the middle part of the first tab, resulting in poor wettability of the first tab and interface problems. When 0.6W1≤W2≤1.2W1 and 0.6W 11 ≤W3≤1.2W 11 are satisfied, not only can the lithium precipitation problem be alleviated, but also the wettability of the electrolyte to the first tab can be satisfied.

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

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

[0045] In one or more embodiments above, the first adhesive member includes a first base material layer and a first adhesive layer arranged in a stack, a material of the first base material layer includes at least one of polyfluoroolefin, polyethylene terephthalate, polyimide, polyamide-imide, polyvinyl chloride, or polyolefin; and the first adhesive layer includes a bonding material including at least one of carboxymethyl cellulose, styrene butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyvinyl alcohol, sodium polyacrylate, polyetherimide, or acrylate.

[0046] A second aspect of the embodiments of the present application also provides an electronic device including the secondary battery of any of the above embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0047] FIG. 1 is a sectional view of a secondary battery according to an embodiment of the present application.

[0048] FIG. 2 is an enlarged view of portion II in FIG. 1.

[0049] FIG. 3 is an enlarged view of portion III in FIG. 2.

[0050] FIG. 4 is a partial view of a first electrode tab in an expanded state according to an embodiment of the present application.

[0051] FIG. 5 is a partial view for showing a positional relationship between a first adhesive member and a first groove according to an embodiment of the present application.

[0052] FIG. 6 is a partial view for showing a positional relationship between a first adhesive member and a first groove according to an embodiment of the present application.

[0053] FIG. 7 is a partial view for showing a positional relationship between a first adhesive member and a second groove according to an embodiment of the present application.

[0054] FIG. 8 is a structural schematic view of a first adhesive member according to an embodiment of the present application.

[0055] FIG. 9 is a partial schematic view of a first electrode tab and a second electrode tab arranged in a stack according to an embodiment of the present application.

[0056] FIG. 10 is a partial schematic view of a first electrode tab according to an embodiment of the present application.

[0057] FIG. 11 is a partial schematic view of a second electrode tab according to an embodiment of the present application.

[0058] FIG. 12 is a structural schematic view of an electronic device according to an embodiment of the present application.

[0059] MAIN ELEMENT SYMBOL EXPLANATION

[0060] Electronic device 1000

[0061] Secondary battery 100

[0062] Electrode assembly 10

[0063] First Polar Film 11

[0064] First current collector 111

[0065] First empty foil area 1111

[0066] Page 111a

[0067] Second page 111b

[0068] First active material layer 112

[0069] First slot 1121

[0070] First Wall 1121b

[0071] Second wall 1121c

[0072] Third Wall 1121d

[0073] Area 1122

[0074] Second area 1123

[0075] Second slot 1124

[0076] fourth wall 1124a

[0077] fifth wall 1124b

[0078] sixth wall 1124c

[0079] seventh wall 1124d

[0080] first edge 1125

[0081] second edge 1126

[0082] first tab 113

[0083] first adhesive 114

[0084] first side 1141

[0085] first channel 1142

[0086] first substrate layer 1143

[0087] first adhesive layer 1144

[0088] second tab 12

[0089] second current collector 121

[0090] third face 121a

[0091] fourth surface 122b

[0092] second active material layer 122

[0093] third groove 1221

[0094] second tab 123

[0095] second adhesive member 124

[0096] second passage 1241

[0097] septum 13

[0098] housing 20

[0099] device main body 200

[0100] first direction X

[0101] second direction Y

[0102] The following detailed description will further describe the present application with reference to the above drawings. DETAILED DESCRIPTION

[0103] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments of the present application.

[0104] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or a middle element can be present at the same time. When an element is considered to be "provided on" another element, it can be directly provided on the other element or a middle element can be present at the same time.

[0105] 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 in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted.

[0106] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0107] It should be noted that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, and the overall thickness, length, width and other dimensions of the integrated device are only exemplary and should not constitute any limitation on the present application.

[0108] In a secondary battery, the performance of the secondary battery is improved by setting a flow guide groove on the pole piece of the electrode assembly to improve the wetting effect of the electrolyte on the pole piece. However, the setting of the flow guide groove will cause the structure to be weak at the position of the tab, and in the drop process, the electrode assembly is impacted, the tab is prone to deflection, and then drives the pole piece substrate at the position of the tab. At this time, due to the weak structure at the position of the tab, the substrate at this position will be damaged, thereby causing the secondary battery to drop out of service.

[0109] Embodiments of the present application provide a secondary battery, comprising an electrode assembly, the electrode assembly comprising a first electrode tab and a second electrode tab, the first electrode tab and the second electrode tab being stacked and forming a winding structure, the first electrode tab and the second electrode tab being opposite in polarity, the first electrode tab comprising a first tab, and a first current collector and a first active material layer being stacked, along a thickness direction of the first current collector, at least one side of the first current collector being provided with the first active material layer; the first active material layer is provided with a first groove, part of the first current collector is exposed through the first groove to form a first empty foil area, and the first tab is connected to the first empty foil area; the first active material layer comprises a first region and a second region, and the first region and the second region are arranged around the outer periphery of the first groove; the width direction of the first electrode tab is the first direction, along the first direction, the first groove comprises a first wall, along the second direction, the first groove comprises a second wall and a third wall arranged oppositely, the first wall connects the second wall and the third wall, and the second direction is perpendicular to the first direction; the second wall and the third wall respectively extend along the first direction, and the extension lines of the second wall and the third wall and the first wall form the second region; the first active material layer of the first region and the second region is provided with a plurality of second grooves, and the depth of the second grooves is less than the thickness of the first active material layer; the minimum distance between the second grooves of the second region and the first wall is L1, and L1>0 is satisfied.

[0110] In the above-mentioned secondary battery, the second grooves of the first region and the second region can accommodate electrolyte, thereby facilitating the electrolyte to contact the first electrode tab through the second grooves and improving the wettability of the electrolyte to the first electrode tab. Along the second direction, the second grooves of the second region and the first wall of the first groove have a spacing, and relative to the positions provided with the first groove and the second groove, there are more first active materials between the second grooves of the second region and the first wall of the first groove, which have better structural strength, so that the positions between the second grooves of the second region and the first wall of the first groove are not easily broken and damaged when the secondary battery is impacted by the electrolyte or the first tab shakes during the falling process, thereby reducing the risk of falling failure of the secondary battery.

[0111] The embodiments of the present application are further described below with reference to the accompanying drawings.

[0112] As shown in FIG. 1, embodiments of the present application provide a secondary battery 100, the secondary battery 100 comprising an electrode assembly 10 and a housing 20, the electrode assembly 10 being accommodated in the housing 20. The electrode assembly 10 comprises a first electrode tab 11 and a second electrode tab 12, the first electrode tab 11 and the second electrode tab 12 being stacked and forming a winding structure, and the first electrode tab 11 and the second electrode tab 12 being opposite in polarity.

[0113] In some embodiments, the electrode assembly 10 further comprises a separator 13, the first electrode tab 11, the separator 13 and the second electrode tab 12 are stacked and wound to form a winding structure, and the separator 13 is used to separate the first electrode tab 11 and the second electrode tab 12.

[0114] In some embodiments, the separator 13 is an insulating film such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0115] 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 hard shell such as a plastic shell, or a metal shell including at least one of a steel alloy, an aluminum alloy, or a copper alloy.

[0116] In some embodiments, the housing 20 is filled with an electrolyte (not shown in the figures), and the electrolyte includes a solvent, an electrolyte salt, and an additive.

[0117] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0118] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium hexafluorocerate (LiCsF6), lithium perchlorate (LiClO4), or lithium trifluoromethanesulfonate (LiCF3SO3).

[0119] Referring to FIGS. 1 and 2, in some embodiments, the first tab 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 in a thickness direction of the first current collector 111. The separator 13 is disposed between the first active material layer 112 and the second tab 12. The thickness direction of the first current collector 111 is the Z direction shown in FIG. 2.

[0120] Referring to FIGS. 2 and 3, in some embodiments, the first current collector 111 has a first surface 111a and a second surface 111b disposed opposite to each other in a thickness direction of the first tab 11. The thickness direction of the first tab 11 is the same as the thickness direction of the first current collector 111, and the thickness direction of the first tab 11 is the Z direction shown in FIG. 2. At least one of the first surface 111a and the second surface 111b is provided with the first active material layer 112. For example, both the first surface 111a and the second surface 111b are provided with the first active material layer 112.

[0121] Referring to FIGS. 2 and 3, in some embodiments, the second tab 12 includes a second current collector 121 and a second active material layer 122 arranged in a stack, and a second tab 123 connected to the second current collector 121. The second current collector 121 has a third face 121a and a fourth face 122b arranged opposite to each other in a thickness direction of the second tab 12, which is consistent with a thickness direction of the second current collector 121, and the thickness direction of the second tab 12 is the Z direction shown in FIG. 2. At least one of the third face 121a and the fourth face 122b is provided with the second active material layer 122, for example, both the third face 121a and the fourth face 122b are provided with the second active material layer 122.

[0122] In some embodiments, the first active material layer 112 and the second active material layer 122 include active materials.

[0123] In some embodiments, the first tab 11 is a positive tab, and the second tab 12 is a negative tab. In other embodiments, the first tab 11 is a negative tab, and the second tab 12 is a positive tab.

[0124] Taking the first tab 11 as a negative tab and the second tab 12 as a positive tab as an example, the first tab 113 is a negative tab, the second tab 123 is a positive tab, and the first current collector 111 and the second current collector 121 can be metal layers. The first current collector 111 is a negative current collector, and the first current collector 111 can be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., for example, a copper foil. The second current collector 121 is a positive current collector, and the second current collector 121 can be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., for example, an aluminum foil.

[0125] The polarity of the first active material layer 112 is negative, and the active material of the first active material layer 112 is a negative active material, which can include at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, silicon-carbon material, etc. The polarity of the second active material layer 122 is positive, and the active material of the second active material layer 122 is a positive active material, which can include at least one of lithium cobaltate, lithium nickel cobalt manganese acid, lithium nickel cobalt aluminum acid, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganate, etc.

[0126] Referring to FIGS. 2-4, 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 outside the first groove 1121 to form a first empty foil area 1111, and the 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, and the first region 1122 and the second region 1123 are arranged around the periphery of the first groove 1121. The width direction of the first tab 11 is the first direction X, and along the first direction X, the first groove 1121 includes a first wall 1121b, and along the second direction Y, the first groove 1121 includes a second wall 1121c and a third wall 1121d arranged oppositely, the first wall 1121b connects the second wall 1121c and the third wall 1121d, and the second direction Y is perpendicular to the first direction X. As shown in FIG. 2, the second wall 1121c and the third wall 1121d respectively extend along the first direction X to form an extension line Q1 and Q2, and the extension line Q1 and Q2 of the second wall 1121c and the third wall 1121d and the first wall 1121b form the second region 1123; the first wall 1121b connects the second region 1123; the first region 1122 and the second region 1123 of the first active material layer 112 are provided with a plurality of second grooves 1124, and the depth of the second grooves 1124 is less than the thickness of the first active material layer 112. The minimum distance between the second groove 1124 of the second region 1123 and the first wall 1121b is L1, and L1>0 is satisfied.

[0127] In some embodiments, at least part of the active material of the first active material layer 112 is removed by laser etching to form the first groove 1121 and the second groove 1124.

[0128] The second groove 1124 of the first region 1122 and the second region 1123 can accommodate electrolyte, thereby facilitating the electrolyte to contact the first tab 11 through the second groove 1124 and improving the degree of electrolyte wetting the first tab 11.

[0129] In the related art, the first groove 1121 and the second groove 1124 are communicated by intersection. Compared with the first active material layer 112 without the first groove 1121, the position of the first active material layer 112 provided with the first groove 1121 has a reduced structural strength of the first current collector 111 due to the removal of a part of the active material. In addition, the laser etching of the second groove 1124 also causes a certain damage to the structural strength of the first current collector 111. Therefore, when the secondary battery 100 falls, the end of the secondary battery 100 provided with the first tab 113 is impacted, and the first tab 113 drives the first empty foil area 1111. At this time, due to the less active material and the low structural strength of the second groove 1124 and the first groove 1121, the first current collector 111 at the junction position of the second groove 1124 and the first groove 1121 is more prone to be damaged during the falling, thereby causing the falling failure of the secondary battery 100.

[0130] In the embodiment, along the first direction X, the second groove 1124 of the second area 1123 and the first wall 1121b of the first groove 1121 have a spacing. Compared with the position provided with the first groove 1121 and the second groove 1124, the first active material layer 112 between the second groove 1124 of the second area 1123 and the first wall 1121b of the first groove 1121 is more, and has a better structural strength. Therefore, during the falling process, the position between the second groove 1124 of the second area 1123 and the first wall 1121b of the first groove 1121 is not prone to be damaged by the impact of the electrolyte or the shaking of the first tab 113, thereby reducing the risk of falling failure of the secondary battery 100.

[0131] Referring to FIG. 4, in some embodiments, the first area 1122 includes two parts, and along the second direction Y, the two parts of the first area 1122 are located on both sides of the first groove 1121. Along the first direction X, the second area 1123 is located on one side of the first groove 1121, and the second area 1123 is located between the two parts of the first area 1122. Along the second direction Y, the first area 1122 and the second area 1123 are divided by the extension lines Q1 and Q2.

[0132] Referring to FIG. 4, in some embodiments, along the first direction X, the first active material layer 112 has opposite first and second edges 1125 and 1126.

[0133] Referring to FIG. 4, in some embodiments, along the first direction X, the length of the first groove 1121 is L2, and 0.01L2≤L1≤0.08L2 is satisfied.

[0134] The distance between the second groove 1124 and the first wall 1121b of the first groove 1121 can effectively improve the pass rate of the secondary battery 100 falling, but when L1 is too large, it is not conducive to the infiltration of the electrolyte to the electrode assembly 10, and the interface problem of the secondary battery 100 in the later stage of the cycle will cause the interface problem. When 0.01L2≤L1≤0.08L2 is met, not only can the pass rate of the secondary battery 100 falling be improved, but also the interface problem of the first pole piece 11 can be alleviated. The interface problem refers to the "interface purple spot lithium precipitation problem caused by poor infiltration in the middle of the electrode assembly 10 in long-term cycling."

[0135] In some embodiments, 0.03L2≤L1≤0.06L2. When 0.03L2≤L1≤0.06L2 is met, the infiltration of the electrolyte to the first pole piece 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, so that the first pole piece 11 is not easy to be damaged.

[0136] 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.

[0137] In some embodiments, the distance between the adjacent two second grooves 1124 is L3, and the first groove 1121 has oppositely arranged second wall 1121c and third wall 1121d in the winding direction of the electrode assembly 10. In the winding direction of the electrode assembly 10, the minimum distance between the second groove 1124 of the first region 1122 and the second wall 1121c is L4, which satisfies 0

[0138] When L4>0 and L5>0 are met, the distance between the second groove 1124 and the first groove 1121 in the second direction Y is not easy to be too small to meet the structural strength between the second wall 1121c, the third wall 1121d and the second groove 1124; L4≤1.1L3, L5≤1.1L3, so that the distance between the second groove 1124 and the first groove 1121 is also not easy to be too large, thereby facilitating the first region 1122 to store more electrolyte.

[0139] In some embodiments, the second slot 1124 is arranged to extend along the first direction X, the length direction of the second slot 1124 is the first direction X, and the width direction of the second slot 1124 is the second direction Y. The second slots 1124 of the first region 1122 and the second slots 1124 of the second region 1123 are arranged to be spaced apart along the second direction Y.

[0140] Referring to FIGS. 2 and 5, in some embodiments, the first tab 11 further comprises a first adhesive 114, which is attached to the first tab 113 and the first empty foil area 1111.

[0141] Referring to FIGS. 2 and 5, in some embodiments, along the first direction X, the length of the first adhesive 114 beyond the first wall 1121b is D1, and the portion of the first adhesive 114 beyond the first wall 1121b is attached to the second region 1123. Along the first direction X, the second slot 1124 of the second region 1123 has opposite fourth and fifth walls 1124a and 1124b, the fourth wall 1124a is closer to the first wall 1121b than the fifth wall 1124b, and the portion of the first adhesive 114 attached to the second region 1123 is arranged in the portion of the second slot 1124; along the first direction X, the edge of the first adhesive 114 in the second region 1123 is a first side 1141, the maximum distance between the fourth wall 1124a and the first side 1141 is D2, and 0.1D1≤D2≤0.8D1 is satisfied.

[0142] The portion of the first adhesive 114 beyond the first wall 1121b and attached to the second region 1123 further increases the thickness of the first tab 11 in the portion between the first slot 1121 and the second slot 1124 of the second region 1123, which is beneficial to maintaining the structural strength of the portion between the first slot 1121 and the second slot 1124 of the second region 1123. When 0.1D1≤D2≤0.8D1 is satisfied, not only can the strength requirement of the first tab 11 be met, but also the overlapping portion of the first adhesive 114 and the second slot 1124 of the second region 1123 is not too large, which reduces the negative impact of the electrolyte on the viscosity of the first adhesive 114. If the overlapping portion is too large, the electrolyte in the second slot 1124 is prone to contact the first adhesive, which causes impact on the first adhesive 114 and reduces the viscosity between the first adhesive 114 and the first active material layer 112.

[0143] In some embodiments, 0.2D1≤D2≤0.5D1, which is beneficial to further improve the structural strength of the portion between the first slot 1121 and the second slot 1124 of the second region 1123 and reduce the negative impact of the electrolyte on the viscosity of the first adhesive 114.

[0144] Referring to FIGS. 1 and 2, in some embodiments, the first adhesive 114 is provided with two, one of which is arranged on the first face 111a of the first foil-free area 1111, and the other of which is arranged on the second face 111b of the first foil-free area 1111, and is arranged on opposite sides of the first tab 113 through the first adhesive 114, further reducing the risk of short circuit caused by the first tab 113 piercing the diaphragm 13 at the welding mark.

[0145] In some embodiments, in the second direction Y, the first adhesive 114 covers the entire first foil-free area 1111, and part of the first adhesive 114 is pasted to the first active material layer 112, thereby further reducing the risk of short circuit caused by the contact between the first tab 113 and the second tab 12.

[0146] Referring to FIG. 6, in some embodiments, in the second direction Y, the first adhesive 114 covers part of the first foil-free area 1111. At least one of the second wall 1121c and the third wall 1121d forms a first channel 1142 with the edge of the first adhesive 114.

[0147] Compared with the first adhesive 114 completely covering the first foil-free area 1111, the arrangement of the first channel 1142 allows part of the first current collector 111 to be exposed, and 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 improves the safety performance of the battery.

[0148] Referring to FIG. 6, in some embodiments, the second wall 1121c and one edge of the first adhesive 114 form a first channel 1142, and the third wall 1121d and the other edge of the first adhesive 114 form another first channel 1142.

[0149] In some embodiments, the first tab 11 is a negative tab, and the second tab 12 is a positive tab. For example, the negative tab is a nickel tab, and the positive tab is an aluminum tab. The first adhesive 114 pastes the nickel tab to the first foil-free area 1111, and the first channel 1142 is formed between the first adhesive 114 pasting the nickel tab and the second wall 1121c and the third wall 1121d. Compared with the nickel tab, the short-circuit resistance between the aluminum tab and the negative active material is smaller, and the failure risk is higher. Therefore, arranging the first channel 1142 at the position of the nickel tab can improve the safety performance of the secondary battery 100 and reduce the failure risk.

[0150] 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.

[0151] When the width of the first channel 1142 is too large, and the width of the first adhesive 114 is too small, the solder print of the first tab 113 cannot be completely covered, and the exposed solder print is prone to pierce the separator 13 and cause short circuit. When the width of the first channel 1142 is too small, it is difficult to achieve good heat dissipation effect. When 0.02P1≤P2≤0.6P1 is satisfied, the heat dissipation effect of the first channel 1142 can be improved under the premise that the solder print is not prone to be exposed.

[0152] In one or more of the above embodiments, 0.2P1≤P2≤0.45P1. The situation that the solder print pierces the separator 13 and causes short circuit can be further reduced, and the heat dissipation capacity of the first channel 1142 can be improved.

[0153] Referring to FIG. 7, in some embodiments, the first side edge 1141 is in a wavy shape. First, the wavy design can disperse the stress at the junction of the first side edge 1141 and the first active material layer 112 and the first current collector 111, reduce stress concentration, reduce damage to the first adhesive 114, the first active material layer 112 or the first current collector 111 caused by mechanical stress, and improve the mechanical stability of the electrode assembly 10. Second, the wavy design can increase the insulation distance between the first adhesive 114 and the first active material layer 112, especially during the charging and discharging process of the secondary battery 100, which helps to improve the insulation performance of the electrode assembly 10, reduce the risk of short circuit, and improve the safety of the secondary battery 100. Third, the wavy design is conducive to adapting to thermal expansion and contraction. The secondary battery 100 will undergo temperature changes during the charging and discharging process, and the wavy design of the first side edge 1141 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 10.

[0154] Referring to FIG. 8, in some embodiments, the first adhesive 114 includes a first substrate layer 1143 and a first adhesive layer 1144 arranged in layers. 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 (such as biaxially oriented polyolefin heat shrink film), and the polyfluoroolefin includes but is not limited to polytetrafluoroethylene or polyvinylidene fluoride. The first adhesive layer 1144 includes a bonding material, and the bonding material includes but is not limited to at least one of carboxymethyl cellulose, styrene butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyvinyl alcohol, polyacrylic acid sodium, polyetherimide or acrylate.

[0155] Referring to FIG. 9, in some embodiments, the width of the first tab 11 is greater than the width of the second tab 12 along the first direction X. The first edge 1125 of the first active material layer 112 is beyond the edge of the second active material layer 122 on the same side as the second edge 1126. The dotted line in FIG. 9 is used to represent the edge of the second active material. When the first tab 11 is a negative tab and the second tab 12 is a positive tab, this is conducive to increasing the CB (Cell Balance, ratio of unit area negative electrode capacity to unit area positive electrode capacity) of the first tab 11 and the second tab 12, and is conducive to reducing the possibility of lithium precipitation of the electrode assembly 10 during cycling.

[0156] Referring to FIG. 4 and FIG. 10, in some embodiments, the fifth wall 1124b is closer to the second edge 1126 than the fourth wall 1124a and is away from the second edge 1126.

[0157] It can be understood that there is a gap between the electrode assembly 10 and the inner wall of the shell 20, and the position of the electrode assembly 10 close to the inner wall of the shell 20 is prone to store more electrolyte compared to the middle part of the electrode assembly 10. If the second groove 1124 directly extends to the second edge 1126, the end of the second groove 1124 will store more electrolyte, and the local impedance will be larger, and the interface problem caused by lithium precipitation will be more prone to occur compared to the design without the second groove 1124. In the present embodiment, the fifth wall 1124b of the second groove 1124 is away from the second edge 1126, and the second groove 1124 does not extend to the second edge 1126. In this way, the electrolyte can be guided to soak into the middle part of the first tab 11, improving the soaking effect of the first tab 11, and effectively alleviating the problem of lithium precipitation.

[0158] Referring to FIG. 4 and FIG. 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 11 ; the distance between the fifth wall 1124b and the second edge 1126 is W3, which satisfies 0.6W 11 ≤ W3 ≤ 1.2W 11 .

[0159] When W3 < 0.6W1, the gap width of the second groove 1124 between the fifth wall 1124b and the second edge 1126 is too narrow, and the distance between the fifth wall 1124b of the second groove 1124 and the second edge 1126 is too close, which is difficult to alleviate the problem of lithium precipitation. When W1 < W3 < 1.2W1, the gap of the second groove 1124 between the fifth wall 1124b and the second edge 1126 is too large, and the distance between the fifth wall 1124b of the second groove 1124 and the second edge 1126 is too far, which is prone to hinder the inflow of electrolyte to the middle part of the first tab 11, resulting in poor soaking of the first tab 11 and interface problems. Satisfying 0.6W 11≤ W3≤ 1.2W 11 In this way, the electrolyte can be guided to the middle of the first electrode tab 11, improving the wettability of the first electrode tab 11, and effectively alleviating the problem of lithium precipitation.

[0160] In some embodiments, 0.8W 11 ≤ W3≤ 1.1W 11 In this range, the problem of lithium precipitation can be further alleviated while ensuring that the electrolyte can effectively wet the middle of the first electrode tab 11.

[0161] Referring to FIGS. 4 and 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 to each other, the sixth wall 1124c is closer to the first edge 1125 than the seventh wall 1124d, the sixth wall 1124c is away from the first edge 1125, and the seventh wall 1124d is away from the second edge 1126.

[0162] In the related art, the second groove 1124 directly extends to the first edge 1125 and the second edge 1126, which makes the second groove 1124 store more electrolyte at the positions of the first edge 1125 and the second edge 1126, resulting in a larger local impedance. This is more likely to cause interface problems due to lithium precipitation than the design in which the second groove 1124 does not extend to the first edge 1125 and the second edge 1126. Therefore, the sixth wall 1124c is away from the first edge 1125, and the seventh wall 1124d is away from the second edge 1126, which can reduce the space for storing electrolyte at the positions of the first edge 1125 and the second edge 1126, reduce the local impedance, and effectively alleviate the problem of lithium precipitation at the positions of the first edge 1125 and the second edge 1126.

[0163] Referring to FIGS. 4 and 9, in some embodiments, the distance between the first edge 1125 and the edge of the same side of the second active material layer 122 is W1, and the distance between the second edge 1126 and the edge of the same side of the second active material layer 122 is W 11 The distance between the sixth wall 1124c and the first edge 1125 is W2, which satisfies 0.6W1≤ W2≤ 1.2W1; and the distance between the seventh wall 1124d and the second edge 1126 is W3, which satisfies 0.6W 11 ≤ W3≤ 1.2W 11 .

[0164] 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, which is difficult to alleviate lithium precipitation. The distance between the seventh wall 1124d and the second edge 1126 is too large, which easily hinders the flow of electrolyte to the middle of the first tab 11, resulting in poor wetting effect of the first tab 11 in the middle and interface problems. When 0.6W1≤W2≤1.2W1, 0.6W 11 ≤W3≤1.2W 11 W1W3, not only can alleviate lithium precipitation, but also can meet the wetting effect of electrolyte on the first tab 11.

[0165] In some embodiments, 0.8W1≤W2≤1.1W1, 0.8W 11 ≤W3≤1.1W 11 When this range is met, the lithium precipitation problem can be further improved while reducing the flow resistance of the electrolyte.

[0166] Referring to FIG. 3, in some embodiments, the third face 121a and the fourth face 122b of the second current collector 121 are both provided with the second active material layer 122, and the second adhesive 124 is arranged on the second active material layer 122 opposite or away from the first tab 113. In the stacking direction of the first tab 11 and the second tab 12, the projection of the portion where the first tab 113 is connected 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 tab 11 and the second tab 12, protect the position of the first tab 113, and reduce the contact short circuit between the first tab 11 and the second tab 12 and the interface problem caused by the protruding welding mark of the first tab 113.

[0167] Further, the second active material layer 122 opposite or away from the first tab 113 is provided with a third groove 1221, and the second adhesive 124 is arranged in the third groove 1221.

[0168] By arranging the second adhesive 124 in the third groove 1221, the thickness of the electrode assembly 10 at the position of the first tab 113 can be effectively reduced, which is beneficial to reduce the loss of volume energy density of the secondary battery 100.

[0169] Referring to FIG. 3, in some embodiments, the second adhesive 124 and the first adhesive 114 are at least partially laminated along the stacking direction of the first tab 11 and the second tab 12, which provides secondary protection for the position of the first tab 113 based on the first adhesive 114, reduces the risk of the welding burr of the first tab 113 piercing the separator 13 between the first tab 11 and the second tab 12 to cause short circuit, and also reduces the risk of the first adhesive 114 being incorrectly positioned or omitted during production to cause short circuit.

[0170] In some embodiments, the active material at the position of the third groove 1221 is milled by laser etching to form the third groove 1221, so that at least part of the second adhesive 124 is arranged in the third groove 1221 in the thickness direction, to reduce the impact of the second adhesive 124 on the overall thickness of the electrode assembly 10. For example, the active material at the position of the third groove 1221 is completely milled to expose part of the second current collector 121 through the third groove 1221, and the second adhesive 124 is attached to the exposed part of the second current collector 121. For another example, part of the active material at the position of the third groove 1221 is washed to form the third groove 1221, and the second adhesive 124 is attached to the third groove 1221.

[0171] Referring to FIG. 3 and FIG. 11, in some embodiments, along the winding direction of the electrode assembly 10, the edge of at least one side of the second adhesive 124 and the groove wall of one side of the third groove 1221 form a second channel 1241.

[0172] In the heat box test, as the temperature rises, the surface temperature of the electrode assembly 10 continues to rise, and due to the occurrence of side reactions, heat is continuously released, and gas is generated. If the heat generation of the electrode assembly 10 is greater than the heat dissipation, too much heat accumulation will eventually cause the failure of the secondary battery 100. In the present 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 heat box test is discharged out of the electrode assembly 10 through the second channel 1241, reducing the impact of the viscosity of the second adhesive 124 under high temperature or gas impact, and improving the heat box test pass rate.

[0173] In some embodiments, along the winding direction of the electrode assembly 10, the edges of the opposite sides of the second adhesive 124 respectively form a second channel 1241 between the groove walls of the third groove 1221.

[0174] In some embodiments, the first tab 11 is a negative tab, and the second tab 12 is a positive tab. For example, the negative tab is a nickel tab, and the positive tab is an aluminum tab. The second adhesive 124 is attached to the second active material layer 122 on the side opposite or away from the nickel tab, and the second channel 1241 is located on the second active material layer 122 on the side opposite or away from the nickel tab. Compared with the nickel tab, the short-circuit resistance between the aluminum tab and the negative active material is smaller, and the failure risk is higher. Therefore, by arranging the second channel 1241 at the position of the nickel tab, the safety performance of the secondary battery 100 can be improved, and the failure risk can be reduced.

[0175] 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, and 0.01H1≤H2≤0.1H1 is satisfied.

[0176] When the width of the second channel 1241 is too large, the area covered by the second adhesive 124 in the third groove 1221 is too small, which cannot provide sufficient protection for the position of the first tab 113, and may cause the first tab 11 to be in contact with the second tab 12 and short-circuit failure; when the width of the second channel 1241 is too small, the improvement effect on the hot box test is small. When 0.01H1≤H2≤0.1H1 is satisfied, the position of the first tab 113 can be protected to a certain extent, and the hot box test pass rate of the secondary battery 100 can be improved.

[0177] In some embodiments, 0.03H1≤H2≤0.07H1 is satisfied. When 0.03H1≤H2≤0.07H1 is satisfied, the width of the second channel 1241 can be further increased while ensuring that the second adhesive 124 has sufficient protection for the first tab 113, and the exhaust effect of the second channel 1241 can be improved.

[0178] In some embodiments, the second adhesive 124 includes a second base material layer and a second adhesive layer arranged in a stack, and the material of the second base material layer includes but is not limited to at least one of polyfluoroolefin, polyethylene terephthalate, polyimide, polyamide-imide, polyvinyl chloride, or polyolefin (for example, biaxially oriented polyolefin heat-shrinkable film), and the polyfluoroolefin includes but is not limited to polytetrafluoroethylene or polyvinylidene fluoride. The second adhesive layer includes a bonding material, and the bonding material includes but is not limited to at least one of carboxymethyl cellulose, butadiene-styrene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyvinyl alcohol, polyacrylic acid sodium, polyetherimide, or acrylate. For example, the second adhesive 124 has the same structure as the first bonding agent.

[0179] Referring to FIG. 3, in some embodiments, the second active material layer 122 opposite the first tab 113 is provided with a second adhesive 124, the second active material layer 122 opposite the first tab 113 is provided with another second adhesive 124, and the second adhesive 124 opposite the first tab 113 is arranged in the third groove 1221, and the second adhesive 124 opposite the first tab 113 is directly attached to the second active material layer 122. By arranging one of the second adhesives 124 in the third groove 1221, the thickness of the electrode assembly 10 at the position of the first tab 113 can not be too small, reducing the risk of a thickness difference between the thickness of the electrode assembly 10 at the position of the first tab 113 and the thickness at the position where the first tab 113 is not arranged.

[0180] Referring to FIG. 1, in some embodiments, the first tab 11 includes a plurality of first tabs 113. For example, the first tab 11 is a positive tab, the first tab 11 includes two first tabs 113, and each first tab 113 is arranged at a position corresponding to a first empty foil area 1111, and the first tab 113 is connected to the corresponding first empty foil area 1111.

[0181] Referring to FIG. 12, the embodiments of the present application also provide an electronic device 1000, which includes the secondary battery 100 of any of the above embodiments.

[0182] In some embodiments, the electronic device 1000 can be a mobile phone, a notebook 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 smart watch, etc., which are not listed one by one here.

[0183] In some embodiments, the electronic device 1000 further includes a device body 200, and the secondary battery 100 is mounted on the device body 200. Since the electronic device 1000 adopts the technical solutions of the secondary battery 100 of any of the above embodiments, it at least has the beneficial effects brought by the technical solutions of any of the above secondary batteries 100, which are not listed one by one here.

[0184] To verify the influence of the positional relationship between the second groove 1124 and the first groove 1121, the first adhesive 114, and the second adhesive 124 on the performance of the secondary battery 100, the inventors conducted the following experiments:

[0185] (1) Cycle life test: 50 secondary batteries 100 were taken for test in each group of comparative examples and each group of embodiments. The cycle life of the 50 secondary batteries 100 in each group of comparative examples and each group of embodiments was recorded, and the average value was calculated.

[0186] Experimental conditions for cycle life (CR=80% as the limit):

[0187] The electrode assembly 10 was charged at a constant current of 1C to a full charge voltage (the maximum voltage of the secondary battery 100 was designed to be 4.5V) at an ambient temperature of 25°C, then charged at a constant voltage until the current was 0.02C at the maximum voltage, and then discharged at a constant current of 0.7C until the final voltage was 3.0V, after which the above steps were repeated for 1400 cycles of charging and discharging.

[0188] CR (Capacity retention) definition: the discharge capacity of the third cycle was taken as the base capacity, and CR = discharge capacity of each cycle / base capacity, for example, base capacity = 5000 mAh, 1000 cycle capacity = 4000 mAh, CR = 4000 / 5000 = 80%.

[0189] The cycle life in Table 3 is the number of cycles corresponding to a CR value of 80%.

[0190] (2) Hot box test: the secondary battery 100 was placed at 25°C for 5 minutes, charged at a constant current of 0.5C to 4.5V, then charged at a constant voltage of 4.5V to 0.025C, and then left to stand for 60 minutes, after which the secondary battery 100 was subjected to a hot box test. The appearance of the secondary battery 100 was checked and photographed before the hot box test, the temperature sensing line was attached, the secondary battery 100 was placed vertically in the hot box, and the temperature was raised from 25°C to 130°C at a rate of 5°C / min and maintained for 60 minutes. If the secondary battery 100 did not catch fire or explode, it was considered to have passed the hot box test. The number of secondary battery samples tested was 50, and 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.

[0191] (3) Drop test:

[0192] The secondary battery 100 was pretreated at 25°C, left to stand in a normal temperature environment for 60 minutes, and then the voltage of the lithium ion battery before the drop test was tested. The secondary battery 100 was loaded into a fixture and dropped freely from a distance of 1.5m from the ground in the following order: head-tail-head right corner-tail right corner-head left corner-tail left corner (angle: 45±15°), for 6 rounds. After the drop, the secondary battery 100 was left to stand at room temperature for 24 hours, and the voltage was measured and recorded. The appearance of the lithium ion battery was checked and photographed before and after the test. The drop test pass criteria: no smoke, no leakage, voltage drop <50mV. 50 secondary batteries 100 were tested, and the number of batteries that passed the test was Y, and the test pass rate was Y / 50.

[0193] (4) Lithium precipitation rate test: 50 secondary batteries 100 were taken for each comparative example and each example.

[0194] The secondary battery 100 was placed in an environment with a test temperature of 25°C for 30 min, and was subjected to step charging to 4.5 V according to the following charging steps:

[0195] ① 5C constant current charging to 4.23 V;

[0196] ② 4C constant current charging to 4.3 V;

[0197] ③ 3C constant current charging to 4.5 V;

[0198] ④ 2C constant current charging to 4.5 V, and constant voltage charging to 0.05C;

[0199] After standing for 10 min, the following steps were performed for discharging:

[0200] 0.2C constant current discharging to 3 V.

[0201] The above charging and discharging process was one cycle, and after 1200 cycles, when the secondary battery 100 was in a fully charged state (the maximum voltage of the battery was designed to be 4.5 V), the secondary battery 100 was disassembled to obtain a negative electrode sheet. The surface of the negative electrode sheet was golden yellow in the region where lithium was not deposited, and was grayish white in the region where lithium was deposited. If the area of lithium deposition on the surface of the negative electrode sheet was greater than or equal to 1 mm 2 , it was determined that lithium was deposited, and the test was failed. Otherwise, the test was passed. There were 50 tests in each group, the number of passes was N, and the non-lithium deposition rate was N / 50.

[0202] The first non-lithium deposition rate refers to the non-lithium deposition rate of the main body region of the electrode assembly 10, and the second non-lithium deposition rate refers to the non-lithium deposition rate of the edge region of the electrode assembly 10. The edge region of the electrode assembly 10 refers to the region where the first edge 1125 and the second edge 1126 of the first electrode sheet 11 exceed the second electrode sheet 12 in the first direction X; and the main body region of the electrode assembly 10 refers to the portion between the edge regions of the electrode assembly 10.

[0203] The specific embodiments of the secondary battery 100 in the examples and comparative examples are described below.

[0204] 1. Preparation of the secondary battery 100.

[0205] (1) Preparation of the positive electrode sheet: mix active material lithium cobaltate (LiCoO2), conductive carbon black (Super P), CNT (carbon nanotube), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:0.5:0.5:1.5, add N-methyl pyrrolidone (NMP) as a solvent, and adjust to a solid content of 75 wt% of the positive electrode active material, and stir uniformly for standby use. Use an aluminum foil with a thickness of 10 μm as the positive electrode current collector. Use a slot coater to uniformly coat the above active material on the first surface 111a of the positive electrode current collector to form a positive electrode active material layer, and then dry at 90°C to obtain a positive electrode sheet coated with a positive electrode active material layer on one side. Then repeat the above steps on the second surface 111b of the positive electrode current collector to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. Then cold-press the coated positive electrode sheet. Then weld the positive electrode tab to the part of the positive electrode current collector not covered by the positive electrode active material layer.

[0206] (2) Preparation of the negative electrode sheet: mix active material artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) in a weight ratio of 97:0.5:1.3:1.2, add deionized water as a solvent, and adjust to a weight percentage of 50 wt% of the negative electrode active material, and stir uniformly for standby use. Use a copper foil with a thickness of 10 μm as the negative electrode current collector. Use a slot coater to uniformly coat the above negative electrode active material on the third surface 121a of the negative electrode current collector, and then dry at 110°C to obtain a negative electrode sheet coated with a negative electrode active material layer. Then repeat the above steps on the fourth surface 122b of the negative electrode current collector to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. Then cold-press the coated negative electrode sheet. Form a first groove 1121 and a second groove 1124 on the negative electrode active material layer by laser etching, and the negative electrode current collector forms a first empty foil area 1111 in the first groove 1121. Then weld the negative electrode tab to the first empty foil area 1111, and paste the first adhesive 114 on the negative electrode tab. Form a third groove 1221 on the negative electrode active material layer by laser etching, and set the second adhesive 124 in the third groove 1221.

[0207] (4) Preparation of the separator 13: use a 7 μm thick polyethylene porous polymer film as the separator 13.

[0208] (5) Preparation of the electrode assembly 10: The positive electrode sheet, the separator 13, and the negative electrode sheet are stacked along the thickness direction of the negative electrode sheet and then wound to obtain the electrode assembly 10. After the electrode assembly 10 is wound, the positive tab is located within the projection of the second adhesive 124 along the stacking direction of the electrode assembly 10.

[0209] (6) Assembly of the secondary battery 100: The punched aluminum laminate film is placed in an assembly jig with the punched surface facing upward, and the electrode assembly 10 is placed in the punch. An external force is applied to press the electrode assembly 10. Then, another punched aluminum laminate film is placed on the electrode assembly 10 with the punched surface facing downward, and the three edges of the two aluminum laminate films are heat-sealed by hot pressing. The edge that is not heat-sealed is the side from which the negative tab and the positive tab protrude from the case 20. Then, the electrolyte is injected through the edge that is not heat-sealed, and the secondary battery 100 is obtained by performing processes such as vacuum packaging, standing, hot-pressing formation, and shaping.

[0210] Example 1-20 differs from Example 1-4 in that in the secondary battery 100 of Example 1-20, the first groove 1121 and the second groove 1124 are formed on the positive active material layer by laser etching, and the positive current collector forms the first empty foil region 1111 in the first groove 1121. Then, the positive tab is welded to the first empty foil region 1111, and the first adhesive 114 is attached to the positive tab. The negative tab is welded to the portion of the negative current collector that is not covered by the negative active material layer. After the electrode assembly 10 is wound, the portion of the negative tab that connects to the first empty foil region is located within the projection of the second adhesive 124 along the stacking direction of the electrode assembly 10.

[0211] 2. The main parameter controls and test results of each example are shown in Tables 1 to 4:

[0212] Table 1

[0213] Note: " / " represents no value.

[0214] Table 2

[0215] Note: The remaining parameters are consistent with Example 1-4 except for the parameters shown in Table 2.

[0216] Table 3

[0217] Note: The remaining parameters are consistent with Example 1-4 except for the parameters shown in Table 3.

[0218] Table 4

[0219] Note: The remaining parameters are consistent with Example 1-4 except for the parameters shown in Table 4.

[0220] In Comparative Example 1, L1 = 0, the second groove 1124 of the second region 1123 extends to the first wall 1121b of the first groove 1121. In this design, the electrolyte can infiltrate the inside of the electrode assembly 10 through the second groove 1124 of the second region 1123, thereby improving the non-lithiation rate of the main region of the electrode assembly 10. However, the setting of the second groove 1124 also reduces the active material at the junction of the second groove 1124 and the first wall 1121b, and causes structural weakness at the junction of the second groove 1124 and the first wall 1121b during manufacturing, resulting in a low drop pass rate in drop test.

[0221] In Example 1-1 to Example 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, from Table 1, when L1 / L2 > 0.08, the poor infiltration caused by the large L1 leads to a significant decrease in the non-lithiation rate; when L1 / L2 is between 0.03 and 0.06, the lithium precipitation of the electrode assembly 10 can be improved, and the drop test can be improved.

[0222] In Example 1-11 to Example 1-15, Example 1-4, and Example 1-16 to Example 1-19, L4 and L5 gradually increase. Compared with 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 Example 1-4, Example 1-12 to Example 1-18, the setting of the second groove 1124 is beneficial to the infiltration of the electrolyte, thereby reducing lithium precipitation and improving the non-lithiation rate, and the setting of the second groove 1124 is not easy to reduce the structural strength at the junction with the first groove 1121, thereby improving the drop pass rate. However, in Example 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 improve the drop pass rate, it will affect the infiltration degree of the electrolyte.

[0223] According to the experimental results of Example 1-4 and Example 1-20, when the first groove 1121 and the second groove 1124 are arranged on the positive electrode sheet and the negative electrode sheet, the structural strength at the junction of the first groove 1121 and the second groove 1124 can be improved, thereby improving the drop pass rate and improving the infiltration effect of the electrode sheet and improving the lithium precipitation problem.

[0224] In Examples 2-1 to 2-8, compared with Example 2-1, W2 and W3 of Examples 2-2 to 2-8 gradually increase. From the test results in Table 2, it can be concluded that W2 and W3 have an impact on the overall lithium precipitation of the electrode assembly 10, and have a greater impact on the edge region of the electrode assembly 10. The increase of W2 and W3 will make the edge region of the electrode assembly 10 richer in electrolyte, meet the transmission needs of lithium ions, and thus reduce lithium precipitation. However, when the electrolyte in the edge region of the electrode assembly 10 is too much, it will also cause lithium precipitation. When W2 / W1, W3 / W1 11 When exceeding 1.2, the overall lithium precipitation of the electrode assembly 10 will be significantly deteriorated. When 0.8W1≤W2≤1.1W1, 0.8W11≤W3≤1.1W 11 The improvement of the lithium precipitation of the edge region of the electrode assembly 10 is more obvious.

[0225] In Examples 3-1 to 3-10, compared with the case of P2=0 in Example 3-1, P2≥0.02 in Examples 3-2 to 3-10, that is, the secondary battery 100 in Examples 3-2 to 3-10 is provided with the first channel 1142, and the cycle life is significantly improved. It can be inferred that the first channel 1142 is beneficial to the heat dissipation of the secondary battery 100, thereby improving the cycle life. However, when the first channel 1142 is set too large, the first adhesive 114 is not easy to completely cover the welding marks of the first tab 113, and the burrs at the welding marks are easy to pierce the separator and cause short circuit failure. Compared with the case of not setting the first channel, when 0.2P1≤P2≤0.45P1, the improvement effect on the cycle life is more obvious.

[0226] In Examples 4-1 to 4-8, compared with the case of H2=0 in Example 4-1, H2≥0.005 in Examples 4-2 to 4-8, that is, the secondary battery 100 in Examples 4-2 to 4-8 is provided with the second channel 1241, and the setting of the second channel 1241 improves the heat chamber test pass rate of the secondary battery 100. It can be inferred that the design of the second adhesive 124 and the second channel 1241, when a large amount of gas accumulates during the heat chamber test, 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 heat chamber test is discharged out of the electrode assembly 10 through the second channel 1241, reducing the influence of the viscosity of the second adhesive 124 under high temperature or gas impact, and improving the heat chamber test pass rate.

[0227] Those skilled in the art should know that the above-mentioned embodiments are only used to explain the present application, but not as a limitation to the present application, as long as the changes and modifications made to the above embodiments are within the scope of the present application.

Claims

1. A secondary battery characterized by comprising: The secondary battery comprises an electrode assembly, the electrode assembly comprises a first electrode sheet and a second electrode sheet, the first electrode sheet and the second electrode sheet are arranged in a stacked manner and form a winding structure, the first electrode sheet and the second electrode sheet have opposite polarities, the first electrode sheet comprises a first tab, a first current collector and a first active material layer arranged in a stacked manner, at least one side of the first current collector is provided with the first active material layer along the thickness direction of the first current collector; the first active material 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, and the first tab is connected to the first empty foil area; The first active material layer comprises a first region and a second region, and the first region and the second region are arranged around the outer periphery of the first groove; the width direction of the first electrode sheet is a first direction, along the first direction, the first groove comprises a first wall, along a second direction, the first groove comprises oppositely arranged second and third walls, the first wall connects the second and third walls, and the second direction is perpendicular to the first direction; the second and third walls respectively extend along the first direction, and the extension lines of the second and third walls and the first wall form the second region; the first wall connects the second region; the first region and the second region of the first active material layer are provided with a plurality of second grooves, and the depth of the second grooves 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, and L1>0.

2. The secondary battery according to claim 1, wherein Along the first direction, the length of the first groove is L2, and 0.01L2≤L1≤0.08L2.

3. The secondary battery according to claim 2, wherein 0.03L2≤L1≤0.06L2.

4. The secondary battery according to claim 1, wherein The distance between adjacent two second grooves is L3, along the winding direction of the electrode assembly, the first groove has oppositely arranged second and third walls; in the winding direction of the electrode assembly, the minimum distance between the second groove of the first region and the second wall is L4, and 0 5. The secondary battery according to claim 1, wherein The first electrode sheet further comprises a first adhesive, and the first adhesive is attached to the first tab and the first empty foil area; along the first direction, the length of the first adhesive beyond the first wall is D1, and the part of the first adhesive beyond the first wall is attached to the second region; Along the first direction, the second groove of the second region has oppositely arranged fourth and fifth walls, and the fourth wall is closer to the first wall than the fifth wall, and part of the first adhesive is attached to the part of the second region provided with the second groove; Along the first direction, the edge of the second region where the first adhesive is located is a first side edge, the maximum distance between the fourth wall and the first side edge is D2, and 0.1D1≤D2≤0.8D1.

6. The secondary battery according to claim 5, wherein The first side edge is arranged in a wavy shape.

7. The secondary battery according to claim 5 or 6, wherein The first groove has a second wall and a third wall oppositely arranged along a winding direction of the electrode assembly, and at least one of the second wall and the third wall forms a first channel with an edge of the first adhesive.

8. The secondary battery according to claim 7, wherein The first groove has a width P1, and the first channel has a width P2 along the winding direction of the electrode assembly, and 0.02P1≤P2≤0.6P1 is satisfied.

9. The secondary battery according to claim 7, wherein the negative electrode is a lithium metal electrode. 0.2P1≤P2≤0.45P1.

10. The secondary battery according to claim 5 or 6, wherein 0.2D1≤D2≤0.5D1.

11. The secondary battery according to claim 5 or 6, wherein The first tab is a negative tab, and the second tab is a positive tab; the second tab includes a second current collector and a second active material layer which are arranged in a stack, and at least one side of the second current collector is provided with the second active material layer; The first tab has a width greater than that of the second tab along the first direction. The first active material layer has a first edge and a second edge oppositely arranged along the first direction, and the first edge and the second edge exceed edges of the second active material layer on the same side. The fifth wall is closer to the second edge than the fourth wall and is separated from the second edge.

12. The secondary battery according to claim 11, wherein The distance between the second edge and the same-side second active material layer edge is W 11 ; the distance between the fifth wall and the second edge is W3, satisfying 0.6W 11 ≤ W3 ≤ 1.2W 11 .

13. The secondary battery according to claim 12, wherein 0.8W 11 ≤ W3≤ 1.1W 11 .

14. The secondary battery according to any one of claims 1 to 10, wherein The second tab includes a second current collector and a second active material layer which are arranged in a stack, and along a thickness direction of the second current collector, the second current collector has two opposite sides, and each side of the second current collector is provided with the second active material layer; the second active material layer opposite or away from the first tab is provided with a third groove, and the second tab includes a second adhesive arranged in the third groove. Along a stacking direction of the first tab and the second tab, a projection of a portion where the first tab and the first empty foil area are connected is located in a projection of the second adhesive.

15. The secondary battery according to claim 14, wherein Along a winding direction of the electrode assembly, at least one side of the second adhesive forms a second channel with a groove wall of one side of the third groove.

16. The secondary battery according to claim 15, wherein The third groove has a width H1, and the second channel has a width H2 along the winding direction of the electrode assembly, and 0.01H1≤H2≤0.1H1 is satisfied.

17. The secondary battery of claim 16, wherein the cathode comprises a cathode active material, a cathode binder, and a cathode conductive agent. 0.03H1≤H2≤0.07H1.

18. The secondary battery according to any one of claims 1 to 10, wherein The first tab is a negative tab, and the second tab is a positive tab; the second tab includes a second current collector and a second active material layer which are arranged in a stack, and along a thickness direction of the second current collector, at least one side of the second current collector is provided with the second active material layer; and the first tab has a width greater than that of the second tab along the first direction. The first active material layer has a first edge and a second edge oppositely arranged along the first direction, and the first edge and the second edge exceed edges of the second active material layer on the same side. The second groove of the first area has a sixth wall and a seventh wall oppositely arranged along the first direction, and the sixth wall is closer to the first edge than the seventh wall, the sixth wall is separated from the first edge, and the seventh wall is separated from the second edge.

19. The secondary battery of claim 18, wherein the cathode is a lithium cobalt oxide cathode. The distance of the first edge beyond the edge of the second active material layer on the same side is W1, and the distance of the second edge 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 0.6W 11 ≤W3≤1.2W 11 .

20. The secondary battery of claim 19, wherein the cathode is a lithium cobalt oxide cathode. 0.8W1≤W2≤1.1W1, 0.8W 11 ≤W3≤1.1W 11 .

21. The secondary battery according to any one of claims 1 to 20, wherein The first adhesive member includes a first base material layer and a first adhesive layer stacked, a material of the first base material layer includes at least one of polyfluoroolefin, polyethylene terephthalate, polyimide, polyamide-imide, polyvinyl chloride, or polyolefin; and the first adhesive layer includes a bonding material including at least one of carboxymethyl cellulose, styrene butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polyvinyl alcohol, sodium polyacrylate, polyetherimide, or acrylate.

22. An electronic device, comprising: A secondary battery including the secondary battery according to any one of claims 1 to 21.

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