Secondary batteries and electronic devices

Abstract

The present application discloses a secondary battery and an electronic device. The secondary battery includes a housing, a first tab, and an electrode assembly. The electrode assembly includes a first pole piece. The first pole piece includes a first current collector, a first active material layer provided on a first surface of the first current collector, and a second active material layer provided on a second surface of the first current collector. The first active material layer has a first recess exposing a first region of the current collector, and the second region of the first current collector is covered by the second active material layer, with the first region facing the second region in a second direction. The first tab includes a first connection portion, a first bent portion, and a second connection portion connected in this order. The first connection portion extends from the sealed edge of the housing, and at least a portion of the second connection portion is located within the first recess and connected to the first region. The first bent portion is bent in the second direction relative to the second connection portion. This reduces the risk of the secondary battery becoming thicker due to the thickness of the first tab, contributing to improved energy density.

Description

[Technical Field]

[0001] TECHNICAL FIELD Embodiments of the present application relate to the field of energy storage technology, and in particular to secondary batteries and electronic devices. [Background technology]

[0002] A secondary battery is a device that converts external energy into electrical energy, stores it internally, and supplies power to electronic devices when needed. Examples include lithium-ion batteries and sodium-ion batteries. These batteries can be used in electronic devices such as mobile phones, tablets, and laptops. Generally, a secondary battery includes a housing and an electrode assembly. The housing has a chamber in which the electrode assembly is housed. The electrode assembly includes a first pole piece, a separator, and a second pole piece. The separator is disposed between the first pole piece and the second pole piece, and the first pole piece and the second pole piece have opposite polarities. Summary of the Invention

[0003] An object of the present application is to provide a secondary battery and an electronic device that can improve energy density.

[0004] The present application employs the following technical means to solve the above technical problems.

[0005] The secondary battery includes a packaging bag, an electrode assembly, and a first tab. The electrode assembly is housed in the packaging bag, and a sealed edge is provided on the packaging bag. The electrode assembly includes a first electrode piece, a second electrode piece, and a separator, with the separator being provided between the first and second electrode pieces. The first electrode piece includes a first current collector, a first active material layer, and a second active material layer. The first current collector has a first surface and a second surface facing each other, with the first active material layer being provided on the first surface and the second active material layer being provided on the second surface. The first surface includes a first region, and the first active material layer is provided with a first recess exposing the first region. The second surface includes a second region corresponding to the first region, and the second region is covered by the second active material layer. The first tab includes a first connecting portion, a first folded portion, and a second connecting portion connected in sequence. The first connecting portion extends from the sealed edge to the outside of the packaging bag, and at least a portion of the second connecting portion is located within the first recess and connected to the first region. The direction in which the first connection portion extends outside the packaging bag is defined as the first direction, the direction from the first region to the second region is defined as the second direction, the first direction is perpendicular to the second direction, and the first folding portion is folded toward the second direction relative to the second connection portion.

[0006] By providing a first recess in the first pole piece and locating at least a portion of the second connection portion within the first recess, the risk of the secondary battery becoming thicker due to the thickness of the first tab is reduced, which is advantageous for improving the energy density of the secondary battery. Furthermore, by providing a second active material layer in the second region facing the first recess, the risk of poor interface between the first pole piece and the second pole piece due to uneven thickness caused by drilling grooves on both sides of the first pole piece is reduced. The first tab has a first bent portion bent in the second direction, which provides a cushioning effect when the first tab is subjected to an external impact and reduces the tensile force between the second connection portion and the first region when a groove is drilled on one side, thereby reducing the risk of secondary battery failure. At the same time, this also reduces the risk of the first active material layer around the first region and the second active material layer in the second region falling off due to vibration, thereby improving the safety of the secondary battery.

[0007] In some embodiments, a direction perpendicular to both the first and second directions is defined as a third direction. When viewed from the third direction, the acute angle β formed between the first bent portion and the second direction is defined as 20°≦β≦70°. When this relationship is satisfied, the bending angle of the first bent portion relative to the second connecting portion is appropriate, and the first bent portion can provide a certain cushioning effect during a drop, reducing the tensile force between the second connecting portion and the first region of the first current collector, thereby reducing the risk of separation between the second connecting portion and the first current collector. This also reduces the risk of the first bent portion pressing against the pole piece at the end of the electrode assembly, causing a portion of the active material layer to fall off, which is beneficial to improving the stability of the secondary battery. Furthermore, the angle β satisfies the relationship 30°≦β≦60°.

[0008] In some embodiments, the first tab includes a first tab surface and a second tab surface facing each other, and the first tab surface located at the second connection portion is connected to the first region. The secondary battery includes a sealing member and a first insulating member, the sealing member includes a sealing portion and a first extending portion, the sealing portion is used to seal and connect with the sealing edge, the first extending portion extends from the sealing portion toward the inside of the packaging bag, the first extending portion includes a first portion, and the first portion is provided on the first tab surface, and at least a portion of the first insulating member is provided on the first tab surface located at the first folded portion, and one end of the first insulating member abuts on the first portion.

[0009] In this way, the first insulating member reduces the risk of burrs on the edge of the first folded portion piercing the packaging bag, and also reduces the risk of the first tab surface located at the first folded portion coming into contact with the second pole piece and causing a short circuit.

[0010] In some embodiments, the first insulating member covers at least a portion of the first portion, which is advantageous for improving the reliability of the connection between the first insulating member and the first tab, and at the same time, the area of ​​the first insulating member overlapping with the first portion reduces the risk of the first portion separating from the surface of the first tab during the dropping process, which is advantageous for improving the sealing performance of the secondary battery.

[0011] In some embodiments, the first insulating member extends in a direction opposite to the first direction, covering a portion of the second active material layer. This is advantageous in reducing the risk of the first insulating member separating from the first tab surface, and also in reducing the risk of the first bent portion bending during a drop, thereby reducing the risk of separation between the second connecting portion and the first region. At the same time, the first insulating member also reduces the risk of the first bent portion pressing against the second active material layer during a drop, causing material to fall off.

[0012] In some embodiments, the first insulating member and the first portion are integrally formed. This reduces the risk of burrs at the first bent portion breaking through the housing. At the same time, the integral structure of the sealing portion and the first portion of the first extension portion prevents excessive bending of the first bent portion due to the constraint of the sealing portion, improving the stability of the connection between the sealing member and the first tab and the reliability of the secondary battery. This also reduces the sensitivity of the first portion to the nonaqueous electrolyte in the packaging bag, improving the reliability of the attachment of the first portion.

[0013] In some embodiments, the first current collector includes a first side and a second side facing each other in a first direction, the first tab extends from the first side to an outside of the first current collector, the first current collector is provided with a first notch recessed in a direction from the first side to the second side, and the second connection portion and the first notch at least partially overlap in the second direction.

[0014] By providing the first notch in the first region, the risk of the first active material layer being present at the edge of the first region during the slitting process is reduced compared to a design in which the first notch is not provided in the first region, and if the first notch and the first tab overlap, the risk of the thickness of that area increasing due to the presence of the first active material layer at the edge of the first region is reduced.

[0015] In some embodiments, the second connection portion is welded to the first region by irradiating the second connection portion with a laser, which is advantageous for forming a relatively reliable connection between the second connection portion and the first region, while at the same time reducing the impact on the second active material layer provided in the second region during welding.

[0016] In some embodiments, the first extension further includes a second portion provided on the second tab surface, and the secondary battery further includes a second insulating member, at least a portion of which is provided on the second tab surface located at the first folded portion, and one end of the second insulating member abuts the second portion. The isolation of the second insulating member reduces the risk of burrs at the first folded portion piercing the packaging bag and the risk of a short circuit between the first tab and the packaging bag, thereby contributing to improved safety of the secondary battery. At the same time, the second insulating member inhibits bending of the first folded portion, reducing the degree of deformation of the first folded portion and improving the stability of the connection between the second connection portion and the first region.

[0017] In some embodiments, the second insulating member covers at least a portion of the second part, which is advantageous for improving the reliability of the connection between the second insulating member and the first tab; at the same time, during the dropping process, the area of ​​the second insulating member overlapping with the second part reduces the risk of the second part detaching from the surface of the first tab, which is advantageous for improving the sealing performance of the secondary battery.

[0018] In some embodiments, the other end of the second insulating member extends in a direction opposite to the first direction, so that the second insulating member covers at least a portion of the first recess. In this way, the second insulating member covers at least a portion of the second connecting portion located in the first recess, which is advantageous in that the second insulating member is more firmly attached to the first bent portion and reduces the risk of some material of the first active material layer falling off due to pressure applied to the sidewall of the first recess during a drop.

[0019] In some embodiments, the second insulating member and the second portion are integrally formed. This reduces the risk of the second insulating member and the second portion coming off the first tab. Furthermore, because the second portion is connected to the sealing portion, the degree of deformation of the second portion due to bending at the first folding portion can be reduced, which is advantageous for improving the sealing performance of the secondary battery. This also reduces the sensitivity of the second portion to the nonaqueous electrolyte in the packaging bag, improving the reliability of the attachment of the second portion.

[0020] In some embodiments, the material of the first extension comprises at least one of polyethylene, polypropylene, polyurethane, or ethylene propylene copolymer.

[0021] In some embodiments, the second pole piece includes a second current collector, a third active material layer, and a fourth active material layer. The second current collector has a third surface and a fourth surface facing each other, the third active material layer being disposed on the third surface, and the fourth active material layer being disposed on the fourth surface. The third surface includes a third region, and the third active material layer has a second recess that exposes the third region. The fourth surface includes a fourth region corresponding to the third region, at least a portion of which is not covered by the fourth active material layer. The secondary battery further includes a second tab, which includes a third connection portion, a second folded portion, and a fourth connection portion connected in this order. The third connection portion extends from the sealed edge to the outside of the housing, and at least a portion of the fourth connection portion is located within the second recess and connected to the third region. The second direction is from the third region to the fourth region, and the second folded portion is folded in the second direction.

[0022] By providing a second recess in the second pole piece and locating at least a portion of the fourth connection part within the second recess, the risk of the secondary battery becoming thicker due to the thickness of the second tab is reduced, contributing to improving the energy density of the secondary battery. Furthermore, because at least a portion of the fourth region facing the second recess is free of the fourth active material layer, the ability of the second tab to dissipate heat via the second current collector during charging and discharging is improved. This also reduces the impact of excessive current density at the connection point between the fourth connection part and the second current collector on the expansion or contraction of the fourth active material layer in the fourth region during charging and discharging, thereby improving the lifespan of the secondary battery. The second tab has a second bent portion bent in a second direction, which acts to cushion impacts on the electrode assembly when the second tab is subjected to external force, reducing the tensile force between the fourth connection part and the third region, reducing the risk of secondary battery failure, and improving the safety of the secondary battery.

[0023] In some embodiments, the fourth connection portion is connected to the third region by ultrasonic welding or resistance welding, which means that the fourth connection portion and the fourth region can be pressed together by welding, thereby improving the connection reliability between the fourth connection portion and the second current collector.

[0024] In some embodiments, the second pole piece includes a second current collector, a third active material layer, and a fourth active material layer, the second current collector having a third surface and a fourth surface facing each other, the third active material layer being disposed on the third surface, and the fourth active material layer being disposed on the fourth surface. The third surface includes a third region, and the third active material layer has a second recess exposing the third region. The fourth surface includes a fourth region corresponding to the third region, and the fourth region is covered by the fourth active material layer. The secondary battery further includes a second tab, the second tab including a third connecting portion, a second folded portion, and a fourth connecting portion connected in this order, the third connecting portion extending from the sealed edge to the outside of the housing, and at least a portion of the fourth connecting portion being located within the second recess and connected to the third region. The second direction is from the third region to the fourth region, and the second folded portion is folded in the second direction.

[0025] By providing a second recess in the second pole piece and locating at least a portion of the fourth connection portion within the second recess, the risk of the secondary battery being thickened by the thickness of the second tab is reduced, contributing to improving the energy density of the secondary battery. Furthermore, by providing a fourth active material layer in the fourth region facing the second recess, the risk of uneven thickness caused by drilling grooves on both sides of the second pole piece is reduced. The second tab has a second bent portion bent in the second direction, which acts to absorb impact on the electrode assembly when the second tab is subjected to an external force, reducing the tensile force between the fourth connection portion and the third region, thereby reducing the risk of secondary battery failure and improving the safety of the secondary battery.

[0026] In some embodiments, the fourth connecting portion is connected to the third region by laser welding, which is advantageous for forming a relatively reliable connection between the fourth connecting portion and the third region, while at the same time reducing the impact on the fourth active material layer provided in the fourth region during welding.

[0027] In some embodiments, the first pole piece, the second pole piece, and the separator are stacked and wound to form a wound structure, the second connection portion and the fourth connection portion are located on both sides of the wound structure along the second direction, and the first recess and the second recess do not overlap, which reduces the risk of the secondary battery becoming excessively thick due to the first tab and the second tab being too close in the thickness direction of the electrode assembly, and the first connection portion and the third connection portion do not overlap and are spaced apart, which is advantageous for improving the sealing performance of the sealing edge.

[0028] In some embodiments, the first electrode piece is a positive electrode piece, the second electrode piece is a negative electrode piece, and the first current collector is aluminum foil. In a first direction, the second electrode piece extends beyond the first electrode piece, and the separator extends beyond the second electrode piece. The positive electrode piece has no grooves in the second region, and the second region is coated with a second active material layer. This is advantageous for increasing the energy density of the secondary battery compared to a positive electrode piece having grooves in the first and second regions. By using aluminum foil as the first current collector, the first current collector can have appropriate flexibility, hardness, and electrical performance to meet manufacturing and usage requirements. At the same time, because the second electrode piece extends beyond the first electrode piece and the separator extends beyond the second electrode piece, the formation of metal dendrites during charging can be reduced, reducing the risk of short-circuiting between the first and second electrode pieces.

[0029] In some embodiments, the first insulating member includes a substrate layer and an adhesive layer, and thus the first insulating member is a viscous structural member that can be quickly adhered to the first tab surface during assembly, thereby saving the time required to assemble the secondary battery.

[0030] In some embodiments, the secondary battery further includes an adhesive member that bonds the packaging bag and the electrode assembly, the adhesive member being attached to an inner surface of the packaging bag facing the first region and contributing to bonding the electrode assembly to the housing, which reduces the risk of the secondary battery being damaged due to relative movement between the electrode assembly and the housing when the secondary battery is dropped, and also reduces the impact of the adhesive member on the reliability of the connection between the second connection part and the first region and on the second active material layer provided in the second region when dropped.

[0031] The present application adopts the following technical means to solve the above technical problems.

[0032] A type of electronic device includes the above-mentioned secondary battery. [Brief explanation of the drawings]

[0033] One or more embodiments are illustratively described by the accompanying drawings, and these illustrative descriptions are not intended to be limiting of the embodiments, and elements in the drawings having the same reference numerals represent similar elements, and the drawing figures are not to be construed as limiting scale unless otherwise specified.

[0034] [Figure 1] 1 is a structural schematic diagram of a secondary battery according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram of one example of FIG. 1 cut along the cutting line AA. [Figure 3] FIG. 2 is a schematic diagram of another type of case obtained by cutting FIG. 1 along the cutting line AA. [Figure 4] FIG. 2 is a schematic diagram of still another example obtained by cutting FIG. 1 along the cutting line AA. [Figure 5] FIG. 2 is a partial schematic view of FIG. 1 cut along the cutting line BB. [Figure 6] 6 is a schematic diagram of one surface after the first pole piece and the first tab in FIG. 5 are unfolded. FIG. [Figure 7] 6 is a schematic diagram of another surface of the first pole piece and the first tab in FIG. 5 after being unfolded. FIG. [Figure 8]FIG. 7 is a schematic diagram of FIG. 6 cut along cutting line DD. [Figure 9] FIG. 10 is a schematic diagram showing a first notch provided in a first region of a first pole piece. [Figure 10] 7 is a schematic diagram showing the first insulating member and the first portion in FIG. 6 coming into contact with each other. FIG. [Figure 11] 7 is a side view showing the first portion and the first insulating member in FIG. 6 as an integral structure. FIG. [Figure 12] 7 is a side view of the second portion and the second insulating member in FIG. 6 when they come into contact with each other. FIG. [Figure 13] 7 is a side view of the second portion and the second insulating member in FIG. 6 when they are integrally formed. [Figure 14] FIG. 7 is a schematic diagram showing that the first portion and the first insulating member in FIG. 6 are integrally formed, and the second portion and the second insulating member are integrally formed. [Figure 15] FIG. 2 is a schematic diagram of FIG. 1 cut along cutting line CC. [Figure 16] 16 is a schematic diagram of one surface after the second pole piece and the second tab in FIG. 15 are unfolded. FIG. [Figure 17] 16 is a schematic diagram of another surface after the second pole piece and the second tab in FIG. 15 are unfolded. FIG. [Figure 18] FIG. 17 is a schematic view of FIG. 16 cut along the cutting line EE. [Figure 19] FIG. 2 is a schematic diagram of another type of case obtained by cutting FIG. 1 along the cutting line AA. [Figure 20] FIG. 2 is another schematic view of FIG. 1 cut along the cutting line CC. [Figure 21] FIG. 10 is a structural block diagram of an electronic device according to another embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0035] To facilitate understanding of the present application, the present application will be described in more detail below in conjunction with the drawings and specific examples. It should be noted that when an element is described as being "fixed" / "fixed" / "attached" to another element, it may be directly on the other element, or there may be one or more intermediate elements therebetween. When an element is described as being "connected" to another element, it may be directly connected to the other element, or there may be one or more intermediate elements therebetween. Terms such as "vertical," "horizontal," "left," "right," "inside," "outside," and similar terms used herein are for illustrative purposes only.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art of this application. The terms used in the specification of this application are only for the purpose of describing specific examples and are not intended to limit the scope of this application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0037] Furthermore, the technical features according to different embodiments of the present application described below can be combined as long as they are not inconsistent with each other.

[0038] In this specification, "attachment" includes fixing or restricting an element or device to a specific position or location by means of welding, screwing, engaging, adhesive, etc., and the element or device may remain immobile at the specific position or location or may be movable within a limited range, and the element or device may be removable or non-removable after being fixed or restricted to the specific position or location, and is not limited in the examples of this application.

[0039] The secondary battery in the following embodiments is not limited to a specific battery type, and includes batteries such as lithium ion batteries and sodium ion batteries. Any rechargeable battery is included in the secondary battery described in the present application, and the specific structure thereof is described below.

[0040] As shown in FIG. 1, the secondary battery 100 provided in one embodiment of the present application includes a packaging bag 110, an electrode assembly 120, and a first tab 130. The packaging bag 110 has an accommodating chamber 111 and a sealing edge 112 for sealing the accommodating chamber 111. The accommodating chamber 111 is used to accommodate the electrode assembly 120. One end of the first tab 130 is connected to the electrode assembly 120, and the other end of the first tab 130 extends from the sealing edge 112 to the outside of the packaging bag 110.

[0041] 2 to 4, the electrode assembly 120 includes a first pole piece 121, a second pole piece 122, and a separator 123. The separator 123 is disposed between the first pole piece 121 and the second pole piece 122, and is used to reduce the risk of short-circuiting between the first pole piece 121 and the second pole piece 122. As can be understood, the first pole piece 121 and the second pole piece 122 have different polarities, and when the first pole piece 121 is a positive pole piece, the second pole piece 122 is a negative pole piece, and conversely, when the first pole piece 121 is a negative pole piece, the second pole piece 122 is a positive pole piece.

[0042] It should be understood that the electrode assembly 120 may have a wound structure or a stacked structure, which can be selected according to actual needs. When the electrode assembly 120 has a wound structure, the first pole piece 121, the separator 123, and the second pole piece 122 are stacked and wound, as shown in FIG. 2. When the electrode assembly 120 adopts a stacked structure, the number of first pole pieces 121, second pole pieces 122, and separators 123 are all multiple, and the multiple first pole pieces 121, second pole pieces 122, and separators 123 are stacked in one direction to form a stacked structure, and separators 123 are provided between adjacent first pole pieces 121 and second pole pieces 122. As shown in Figures 3 and 4, in this case, the thickness direction of the electrode assembly 120 may be the same as or different from the thickness direction of the secondary battery 100. As shown in Figure 3, the thickness direction of the electrode assembly 120 is different from the thickness direction of the secondary battery 100, and as shown in Figure 4, the thickness direction of the electrode assembly 120 is the same as the thickness direction of the secondary battery 100.

[0043] For ease of explanation of the present invention, the drawings show an example in which the electrode assembly 120 adopts a wound structure, but the structure of the electrode assembly 120 of the present invention is not limited to a wound structure and may also adopt a stacked structure.

[0044] As shown in Figure 5, Figure 5 is a schematic diagram cut along cutting line BB in Figure 1, and the first pole piece 121 includes a first current collector 1211, a first active material layer 1212 and a second active material layer 1213, the first current collector 1211 includes a first surface 12111 and a second surface 12112 arranged opposite each other, the first active material layer 1212 is arranged on the first surface 12111 of the first current collector 1211, and the second active material layer 1213 is arranged on the second surface 12112 of the first current collector 1211. 6 to 8, FIG. 6 is a schematic diagram of the first surface 12111 when the first pole piece 121 and the first tab 130 are in an unfolded state, FIG. 7 is a schematic diagram of the second surface 12112 when the first pole piece 121 and the first tab 130 are in an unfolded state, and FIG. 8 is a schematic diagram of FIG. 6 cut along the cutting line DD, in which the extension direction of the width side of the first pole piece 121 is the same as the first direction X, and the extension direction of the long side of the first pole piece 121 is the same as the first direction X. The extending direction is the fourth direction U, where the first surface 12111 of the first current collector 1211 includes a first region 1211a, and the first active material layer 1212 is provided with a first recess 1212a exposing the first region 1211a, and the second surface 12112 of the first current collector 1211 includes a second region 1211b facing the first region 1211a, and the second region 1211b is covered with the second active material layer 1213. In other words, the first region 1211a of the first current collector 1211 is not provided with the first active material layer 1212, thereby forming the first recess 1212a in the first pole piece 121. The first current collector 1211 has a first side 1211c and a second side 1211d facing the first direction X.

[0045] Referring again to Figure 5, the first tab 130 includes a first connection portion 131, a first folding portion 132 and a second connection portion 133 connected in sequence, the first connection portion 131 extending from the sealing edge 112 to the outside of the packaging bag 110, and the second connection portion 133 being at least partially located within the first recess 1212a and connected to the first region 1211a.

[0046] The direction in which the first connecting portion 131 extends to the outside of the packaging bag 110 is defined as a first direction X, the direction from the first region 1211a to the second region 1211b is defined as a second direction Y, and the first direction X is perpendicular to the second direction Y.

[0047] Here, the first bent portion 132 is bent toward the second direction Y relative to the second connecting portion 133. The first tab 130 has a first tab surface 1301 and a second tab surface 1302 that are arranged opposite to each other, and the first tab surface 1301 is arranged adjacent to the first recess 1212a in the second direction Y.

[0048] In this way, by providing the first recess 1212a in the first pole piece 121 and providing at least a portion of the second connection portion 133 within the first recess 1212a, the risk of the thickness of the secondary battery 100 increasing due to the thickness of the first tab 130 is reduced, contributing to improving the energy density of the secondary battery 100. In addition, by providing the second active material layer 1213 in the second region 1211b opposite the first region 1211a, the risk of the interface between the first pole piece 121 and the second pole piece 122 becoming defective due to uneven thickness caused by forming grooves on both sides of the first pole piece 121 can be reduced.

[0049] The first tab 130 has a first bent portion 132 bent toward the second direction Y. When the secondary battery 100 is dropped or hit, the first bent portion 132 can reduce the impact force on the sealing edge 112 of the electrode assembly 120, reducing the risk of electrolyte leakage due to the sealing edge 112 being impacted by the electrode assembly 120, and improving the safety of the secondary battery 100. Furthermore, compared to a method in which the first bent portion 132 is bent in the direction opposite to the second direction Y relative to the second connecting portion 133, the first bent portion 132 of the present invention is bent in the second direction Y relative to the second connecting portion 133. The first bent portion 132 can function as a buffer portion for the first tab 130, reducing the risk that the first connecting portion 131 will directly pull the second connecting portion 133 when a groove is formed on one side, reducing the risk of separation between the second connecting portion 133 and the first region 1211a, thereby improving the stability of the connection between the second connecting portion 133 and the first region 1211a and improving the reliability of the secondary battery 100. At the same time, the risk that the first active material layer 1212 around the first region 1211a and the second active material layer 1213 in the second region 1211b will fall off due to vibration is also reduced.

[0050] It should be understood that the second connecting portion 133 and the first region 1211a may be connected in various ways, such as by irradiating the second connecting portion 133 with a laser to weld the second connecting portion 133 to the first region 1211a, or by applying a conductive adhesive to connect the second connecting portion 133 to the first region 1211a. Of course, other connection methods are also possible, and are not limited to the connection methods mentioned herein, as long as the second connecting portion 133 and the first region 1211a can be connected. In some embodiments, the second connecting portion 133 and the first region 1211a are welded together by irradiating the second connecting portion 133 with a laser. This is advantageous for forming a relatively reliable connection between the second connecting portion 133 and the first region 1211a, while at the same time reducing the impact on the second active material layer 1213 provided in the second region 1211b during welding.

[0051] As can be understood, since the packaging bag 110 is made of a lightweight flexible material, the secondary battery 100 having the packaging bag 110 as its outer shell has a high energy density, but is easily deformed when subjected to external force. secondary The first tab 130 of the battery 100 is easily pulled. By adopting the attachment method of the first tab 130 and the electrode assembly 120 of the present application, the risk of the first tab 130 and the first pole piece 121 coming off when the first tab 130 is pulled by an external force is reduced, contributing to improving the reliability of the secondary battery manufactured using the packaging bag 110.

[0052] In some embodiments, the first pole piece 121 is a positive pole piece, and the second pole piece 122 is a negative pole piece. In the first direction X, the second pole piece 122 extends beyond the first pole piece 121, and the separator 123 extends beyond the second pole piece 122. This is advantageous for reducing the risk of short-circuiting between the first pole piece 121 and the second pole piece 122, and also reduces the risk of lithium deposition occurring in the electrode assembly 120. Furthermore, the first current collector 1211 is an aluminum foil, which has suitable flexibility, hardness, and electrical properties to meet manufacturing and usage requirements. At the same time, the second pole piece 122 extends beyond the first pole piece 121, and the separator 123 extends beyond the second pole piece 122, thereby reducing the formation of metal dendrites during charging and reducing the risk of short-circuiting between the first pole piece 121 and the second pole piece 122.

[0053] 9 , the first current collector 1211 is provided with a first notch 1211e recessed in a direction from the first side 1211c to the second side 1211d, and the first notch 1211e and the second connecting portion 133 at least partially overlap with each other along the second direction Y. In this way, the risk of the first active material layer 1212 being present at the edge of the first region 1211a of the first pole piece 121 formed by cutting in the slitting process is reduced, and the risk of the first active material layer 1212 remaining in the overlapping portion between the second connecting portion 133 and the first region 1211a and increasing the thickness of that portion is thereby reduced, contributing to an improvement in the energy density of the secondary battery 100.

[0054] In some embodiments, referring again to FIG. 7 , the secondary battery 100 further includes a first insulating member 150, at least a portion of which is provided on a first tab surface 1301 located at the first bent portion 132, and the first insulating member 150 includes a first insulating edge 151 away from the first pole piece 121 in the first direction X, and a second insulating edge 152 opposite the first insulating edge 151 in the first direction X.

[0055] In this way, the isolation of the first insulating member 150 reduces the risk of burrs on the first folded portion 132 piercing the packaging bag 110, reduces the risk of a short circuit between the first folded portion 132 and the packaging bag 110, and reduces the risk of the first folded portion 132 being impacted and short-circuiting with the second pole piece 122 when the secondary battery 100 is dropped, thereby contributing to improving the safety of the secondary battery 100.

[0056] It should be understood that the first insulating member 150 may be an insulating tape, and the first insulating member 150 may include a base layer and an adhesive layer disposed on the base layer, and the adhesive layer is used to adhere to the first tab surface 1301. In some embodiments, the base layer may be made of a material such as polypropylene, polyethylene terephthalate, or polyimide, and the adhesive layer may be made of a material such as acrylate, rubber, silicone, polyurethane, or polyolefin. Of course, the first insulating member 150 may be made of other materials as long as it can provide insulation and adhesion.

[0057] In some embodiments, referring to FIG. 5 again, the secondary battery 100 further includes a sealing member 160. The sealing member 160 includes a sealing portion 161, a first extending portion 162, and a second extending portion 163. The sealing portion 161 is used to seal and connect with the sealing edge 112. The first extending portion 162 extends from the sealing portion 161 into the packaging bag 110, and the second extending portion 163 extends from the sealing portion 161 in a direction extending out of the packaging bag 110. Thus, by providing the sealing member 160, the sealing edge 112 can be adhered more firmly, improving the sealing performance of the secondary battery 100 and reducing the risk of electrolyte leakage in the secondary battery 100. As can be understood, the materials of the sealing portion 161, the first extending portion 162, and the second extending portion 163 include at least one of polyethylene, polypropylene, polyethylene terephthalate, polyurethane, or ethylene-propylene copolymer.

[0058] Furthermore, the first extending portion 162 includes a first portion 1621. The first portion 1621 is provided on the first tab surface 1301, and the first portion 1621 abuts against one end of the first insulating member 150. It should be understood that the abutment of the first portion 1621 against one end of the first insulating member 150 includes the following two schemes.

[0059] (1) As shown in FIG. 8, the first portion 1621 and the first insulating member 150 partially overlap in the second direction Y, that is, the first insulating member 150 covers at least a part of the first portion 1621, which is beneficial to enhancing the reliability of the connection between the first insulating member 150 and the first tab 130. At the same time, in the falling process, the region where the first insulating member 150 overlaps with the first portion 1621 reduces the risk that the first portion 1621 detaches from the first tab surface 1301, which is beneficial to improving the sealing performance of the secondary battery 100. In this case, let the dimension between the end of the first portion 1621 in the direction opposite to the first direction X and the first insulating edge 151 be L1, and the dimension of the second insulating edge 152 and the first side 1211c in the first direction X be L11, satisfying 1mm ≦ L1 and 0mm < L11.

[0060] Furthermore, by satisfying 1 mm≦L1 and 2 mm≦L11, the area that the first insulating member 150 covers the first portion 1621 and the first pole piece 121 is appropriate, which reduces the risk of the first insulating member 150 coming off the first tab 130 during the dropping process and is advantageous for improving sealing performance.

[0061] 10 , the end faces of the first portion 1621 and the first insulating member 150 in the first direction X abut against each other, but the first portion 1621 and the first insulating member 150 do not overlap in the second direction Y. This is advantageous for covering the first tab surface 1301 as much as possible, reducing the risk of burrs on the surface of the first tab surface 1301 being exposed and puncturing the packaging bag 110, and improving the safety performance of the secondary battery 100. Furthermore, when the packaging bag 110 forms the sealing edge 112, it is also advantageous for reducing the risk that the first insulating member 150 will get into the sealing edge 112 and affect the reliability of the seal.

[0062] In some embodiments, one end of the first insulating member 150 extends in the direction opposite to the first direction X, so that the first insulating member 150 covers a portion of the second active material layer 1213. This is advantageous in reducing the risk of the first insulating member 150 coming off the first tab surface 1301, and also in reducing the risk of the first insulating member 150 bending the first bent portion 132 during the dropping process, thereby reducing the risk of the second connecting portion 133 and the first region 1211a becoming separated. At the same time, the first insulating member 150 also reduces the risk of the first bent portion 132 pressing against the second active material layer 1213 during the dropping process, causing material to fall off.

[0063] 11 , the first insulating member 150 and the first portion 1621 are integral with each other. In other words, the extension of the first portion 1621 replaces the existing first insulating member 150, reducing the risk of burrs at the first bent portion 132 breaking through the housing. At the same time, because the sealing portion 161 and the first portion 1621 of the first extending portion 162 are integral with each other, the first portion 1621 is constrained by the sealing portion 161 to suppress bending of the first bent portion 132, improving the stability of the connection between the sealing member 160 and the first tab 130 and the reliability of the secondary battery 100.

[0064] 5-6 , in some embodiments, the secondary battery 100 further includes a second insulating member 170, which is disposed on the second tab surface 1302 of the first bent portion 132. The second insulating member 170 can block burrs on the second tab surface 1302 of the first bent portion 130, reducing the risk of the packaging bag 110 being punctured by the burrs and contributing to improving the safety performance of the secondary battery 100. At the same time, the second insulating member 170 can inhibit the first bent portion 132 from bending, reducing the degree of deformation of the first bent portion 132 during a drop, reducing the impact force on the sealing edge 112 of the electrode assembly 120, and reducing the risk of the sealing edge 112 being forced open, which is beneficial to improving the reliability of the secondary battery 100. The second insulating member 170 includes a third insulating piece 171 that is spaced apart from the first pole piece 121 in the first direction X, and a fourth insulating piece 172 that is disposed opposite the third insulating piece 171 in the first direction X.

[0065] In some embodiments, the first extension 162 further includes a second portion 1622 facing the first portion 1621, the second portion 1622 being disposed on the second tab surface 1302, and the second portion 1622 abutting against one end of the second insulating member 170. It should be understood that the abutment of the second portion 1622 against one end of the second insulating member 170 includes the following two cases:

[0066] (3) The second portion 1622 and the second insulating member 170 partially overlap in the second direction Y, i.e., the second insulating member 170 covers at least a portion of the second portion 1622, which is advantageous to improving the reliability of the connection between the second insulating member 170 and the first tab 130. At the same time, during a drop, the second insulating member 170 reduces the degree of bending deformation of the first bent portion 132 and reduces the impact force on the sealing edge 112 of the electrode assembly 120, which is advantageous to improving the sealing performance of the secondary battery 100. In addition, the area of ​​the second insulating member 170 that overlaps with the second portion 1622 also reduces the risk of the second portion 1622 detaching from the first tab surface 1301. In this case, if the dimension between the end of the second portion 1622 facing away from the first direction X and the third insulating edge 171 is L2, and the dimension between the fourth insulating edge 172 and the first edge 1211c in the first direction X is L22, then L2≦3 mm and L2≦6 mm are satisfied. This ensures that the area that the second insulating member 170 covers the second portion 1622 and the first pole piece 121 is appropriate, reducing the impact on the sealing performance of the secondary battery 100 caused by the second insulating member 170 and the second portion 1622 covering an excessively large area, and reducing the impact on the energy density of the secondary battery caused by the second insulating member 170 and the first pole piece 121 covering an excessively large area.

[0067] 12, the end surfaces of the second portion 1622 and the second insulating member 170 in the first direction X abut against each other, but the second portion 1622 and the second insulating member 170 do not overlap in the second direction Y. This is advantageous for covering the second tab surface 1302 as much as possible, reducing the risk of burrs on the surface of the second tab surface 1302 being exposed and puncturing the packaging bag 110, and improving the safety performance of the secondary battery 100. It also reduces the risk of the second insulating member 170 getting into the sealing edge 112 when the packaging bag 110 forms the sealing edge 112, which could affect the reliability of the seal.

[0068] In some embodiments, one end of the second insulating member 170 extends in a direction opposite to the first direction X, so that the second insulating member 170 covers at least a portion of the first recess 1212a. In this way, the second insulating member 170 covers at least a portion of the second connecting portion 133 located in the first recess 1212a, which is advantageous for the second insulating member 170 to be more firmly attached to the first bent portion 132. In addition, the second insulating member 170 reduces the risk of the sidewall of the first recess 1212a being pressed and some material of the first active material layer 1212 falling off during the dropping process. Furthermore, the second insulating member 170 can completely cover the first recess 1212a, further restricting the second connection portion 133 and preventing the second connection portion 133 from separating from the first region 1211a, which is more advantageous in improving the stability of the connection between the second connection portion 133 and the first region 1211a, and also reduces the risk of burrs on the inner wall of the first recess 1212a breaking through the isolation membrane 123.

[0069] 13 , the second insulating member 170 and the second portion 1622 are integral with each other. In other words, the second portion 1622 extends toward the second connecting portion 133. When replacing the second insulating member 170, the integral structure of the second insulating member 170 and the second portion 1622 reduces the risk of the second insulating member 170 and the second portion 1622 coming off the first tab 130 compared to a separate design. Furthermore, because the second portion 1622 is connected to the sealing portion 161, the second portion 1622 can reduce the degree of deformation caused by bending the first folding portion 132, which is beneficial to improving the sealing performance of the secondary battery 100. This also reduces the sensitivity of the second portion 1622 to the nonaqueous electrolyte in the packaging bag 110 and improves the reliability of the attachment of the second portion 1622.

[0070] It should be understood that the dimension L1 between the end of the first portion 1621 facing away from the first direction X and the first insulating edge 151, the dimension L11 between the second insulating edge 152 and the first edge 1211c in the first direction X, the dimension L2 between the end of the second portion 1622 facing away from the first direction X and the third insulating edge 171, and the dimension L22 between the fourth insulating edge 172 and the first edge 1211c in the first direction X are all measured when the first tab 130 is in an unfolded state. Naturally, when the first pole piece 121 is in a wound state, these distances should be measured after unfolding the first pole piece 121, and at this time, the first tab 130 and the first current collector 1211 are perpendicular to each other, as shown in FIGS. 6-7 .

[0071] Similarly, the second insulating member 170 may be an insulating tape, and the second insulating member 170 includes a base layer and an adhesive layer disposed on the base layer, the adhesive layer being used to adhere to the second tab surface 1302. In some embodiments, the base layer may be made of a material such as polypropylene, polyethylene terephthalate, or polyimide, and the adhesive layer may be made of a material such as acrylate, rubber, silicone, polyurethane, or polyolefin. Of course, the second insulating member 170 may be other materials and is not limited to the insulating tape mentioned herein, as long as it can provide insulation and adhesion.

[0072] In some embodiments, as shown in FIG. 14 , the first insulating member 150 and the first part 1621 are integrally formed, and the second insulating member 170 and the second part 1622 are integrally formed, which is more advantageous for reducing the degree of deformation of the first folding portion 132, and further for extending the time during which the electrode assembly 120 impacts the sealing edge 112 during the dropping process, thereby reducing the impact force of the electrode assembly 120 on the sealing edge 112, thereby reducing the risk of the sealing edge 112 being pushed open, and improving the reliability of the secondary battery 100.

[0073] 5 , in some embodiments, a direction perpendicular to both the first direction X and the second direction Y is defined as a third direction Z, and the angle formed between the first bent portion 132 and the second direction Y when viewed from the third direction Z is defined as β. It should be understood that because the shape of the first bent portion 132 may be non-linear, the angle formed between the first bent portion 132 and the second direction Y refers to the angle formed between the line connecting the head and tail ends of the first bent portion 132 and the second direction Y.

[0074] The inventors of the present application have discovered that when the angle β between the first bent portion 132 and the second direction Y satisfies a certain relationship, the reliability and safety of the secondary battery 100 can be improved.

[0075] Below, a comparative example and an experimental example are compared through drop tests. In the comparative example, the first bent portion 132 is bent in the opposite direction to the second direction Y, while in the experimental examples, the first bent portion 132 is bent in the second direction Y with different angle β values. The test conditions for each example were that 10 battery cells were dropped five times, each on six sides and four corners, from a height of 1 m. The passing criteria were that the sealed edge of the battery cell was not pushed open after the drop and the voltage drop was less than 50 mV. The experimental results obtained are as follows:

[0076] [Table 1]

[0077] In the above-mentioned experimental examples, the second insulating member 170 and the sealing member 160 in Experimental Examples 1-12 are both separate designs, while the second insulating member 170 and the sealing member 160 in Experimental Example 13 are integral structures.

[0078] As can be seen from Comparative Example 1 and Experimental Examples 1-13, when the first bent portion 132 is bent in the second direction Y, the reliability and safety of the battery cell are significantly improved.

[0079] As can be seen from Experimental Examples 1-8, when the angle β satisfies the condition 20°≦β≦70°, the pass rate of the battery cells in each experiment is at least 70% and the reliability and safety performance of the battery cells is relatively high. When the angle β satisfies the condition 30°≦β≦60°, the pass rate of the battery cells in each experiment reaches 100%, and the reliability and safety performance of the battery cells is even higher.

[0080] As can be seen from a comparison between Experimental Examples 4 and 9, if the value of L22 is too large, i.e., if the area that the second insulating member 170 covers with the first pole piece 121 in the first direction X becomes large, the capacity of the battery cell decreases and the energy density of the battery cell decreases.

[0081] As can be seen from a comparison between Experimental Example 4 and Experimental Example 10, the partial overlap between the second insulating member 170 and the first pole piece 121 is beneficial to improving the pass rate of the battery cell, i.e., the partial overlap between the second insulating member 170 and the first pole piece 121 is beneficial to improving the reliability and safety performance of the battery cell.

[0082] As can be seen from a comparison between Experimental Examples 4 and 11, when the second insulating member 170 and the sealing member 160 partially overlap, it is beneficial to improving the pass rate of the battery cell, that is, when the second insulating member 170 and the sealing member 160 partially overlap, it is beneficial to improving the reliability and safety performance of the battery cell.

[0083] Comparing Experimental Examples 4 and 12, it can be seen that if the overlapping area between the second insulating member 170 and the sealing member 160 in the first direction X is too large, the pass rate of the battery cells decreases. This is because if the overlapping area between the second insulating member 170 and the sealing member 160 in the first direction X is too large, it will affect the sealing performance of the sealing edge 112, and the battery cells will be easily pushed open during the dropping process due to the poor sealing performance of the sealing edge 112.

[0084] As can be seen from a comparison between Experimental Examples 11 and 13, when the second insulating member 170 and the second portion 1622 are integral with each other, i.e., when the second portion 1622 extends in the direction opposite to the first direction X to replace the second insulating member 170, the second portion 1622 is connected to the sealing portion 161, and the portion of the second portion 1622 that extends in the first direction X and overlaps with the first pole piece 121 can be firmly attached to the surface of the first tab 130, thereby improving the reliability and safety of the battery cell.

[0085] It should be understood that the second pole piece 122 may have recesses on both sides, i.e., a portion of the current collector of the second pole piece 122 may not be covered with an active material layer, and may have the same structure as the first pole piece 121 or another structure, and the specific structure can be selected according to actual needs. In some embodiments, as shown in FIGS. 15-18 , the second pole piece 122 has a similar structural design to the first pole piece 121. Specifically, the second pole piece 122 includes a second current collector 1221, a third active material layer 1222, and a fourth active material layer 1223. The second current collector 1221 has a third surface 12211 and a fourth surface 12212 facing each other. The third active material layer 1222 is disposed on the third surface 12211 of the second current collector 1221, and the fourth active material layer 1223 is disposed on the fourth surface 12212 of the second current collector 1221. 16-17, FIG. 16 is a schematic diagram of the second pole piece 122 and the second tab 140 in an unfolded state, the extension direction of the width side of the second pole piece 122 is the same as the first direction X, the extension direction of the long side of the second pole piece 122 is the fourth direction U, the third surface 12211 of the second current collector 1221 includes a third region 1221a, the third active material layer 1222 is provided with a second recess 1222a exposing the third region 1221a, the fourth surface 12212 of the second current collector 1221 includes a fourth region 1221b facing the third region 1221a, and the fourth region 1221b is covered by the fourth active material layer 1223. In other words, the second current collector 1221 does not have the third active material layer 1222 provided in the third region 1221a, and thereby the second pole piece 122 is formed with the second recess 1222a.

[0086] The secondary battery 100 further includes a second tab 140, which includes a third connection portion 141, a second bent portion 142, and a fourth connection portion 143 connected in this order, and at least a portion of the fourth connection portion 143 is located within the second recess 1222a and connected to the third region 1221a. Here, the two opposing surfaces of the second tab 140 are a third tab surface 1401 and a fourth tab surface 1402, respectively.

[0087] In some embodiments, the third connection portion 141 extends from the sealing edge 112 to the outside of the packaging bag 110, in which case the third connection portion 141 can be directly used as an electrode of one polarity of the secondary battery 100, which may be a positive electrode or a negative electrode, and correspondingly, the first connection portion 131 is used as an electrode of the other polarity of the secondary battery 100.

[0088] In the above case, the second folding portion 142 can reduce the risk of the electrode assembly 120 rattling relative to the packaging bag 110, reduce the impact force on the sealing edge 112 of the electrode assembly 120 when the secondary battery 100 is dropped, reduce the risk of the sealing edge 112 being pushed open, and improve the reliability of the secondary battery 100.

[0089] 15-18 , in some embodiments, the secondary battery 100 further includes a third insulating member 180, which is provided on a third tab surface 1401 at least partially located at the second folded portion 142. In this manner, the isolation of the third insulating member 180 reduces the risk of burrs at the second folded portion 142 piercing the packaging bag 110 and reducing the risk of a short circuit between the second folded portion 142 and the packaging bag 110. Similarly, the isolation of the third insulating member 180 reduces the risk of a short circuit between the second folded portion 142 and the first pole piece 121 due to an impact when the secondary battery 100 is dropped, which is advantageous to improving the safety and reliability of the secondary battery 100.

[0090] 17-18 , in some embodiments, the secondary battery 100 further includes a fourth insulating member 190, which is disposed on the fourth tab surface 1402 located on the second bent portion 142. In this manner, the fourth insulating member 190 can block burrs on the fourth tab surface 1402 of the second tab 140, reducing the risk of the burrs of the second bent portion 142 breaking through the separator 123. This reduces the risk of a short circuit between the fourth connecting portion 143 and the first pole piece 121, thereby improving the safety of the secondary battery 100.

[0091] In some embodiments, the fourth insulating member 190 covers the second recess 1222a, completely covering a portion of the fourth connecting portion 143 located in the second recess 1222a, so that the fourth insulating member 190 and the second current collector 1221 have a larger covering area, which can improve the connection between the fourth insulating member 190 and the second current collector 1221 and can also more firmly attach the fourth insulating member 190 to the second folded portion 142. The fourth insulating member 190 can also prevent the fourth connecting portion 143 from separating from the third region 1221a and reduce the risk of burrs on the fourth connecting portion 143 breaking through the separator 123. As can be seen, the above-mentioned sealing member 160 can also be provided between the third connecting portion 141 and the sealing edge 112, which can strengthen the connection between the third connecting portion 141 and the sealing edge 112 and improve the sealing at the sealing edge 112.

[0092] A portion of the fourth insulating member 190 is further provided on the surface of the portion extending from the third region 1221a of the fourth connection portion 143, which can suppress the second bending portion 142 from bending toward the electrode assembly 120, thereby indirectly extending the time during which the electrode assembly 120 impacts the sealing edge 112, reducing the impact force of the electrode assembly 120 on the sealing edge 112, and reducing the risk of rupture at the sealing edge 112. It should be understood that the sealing member 160 disposed between the second tab 140 and the sealing edge 112 has a first portion 1621 disposed on the third tab surface 1401 and a second portion 1622 disposed on the fourth tab surface 1402. The dimensional relationship between the first portion 1621 located on the third tab surface 1401 and the third insulating member 180 in the first direction X can refer to the dimensional relationship between the first portion 1621 located on the first tab surface 1301 and the first insulating member 150 in the first direction X, and will not be described in detail here.

[0093] Similarly, the dimensional relationship in the first direction X between the second portion 1622 located on the fourth tab surface 1402 and the fourth insulating member 190 can refer to the dimensional relationship in the first direction X between the second portion 1622 located on the second tab surface 1302 described above and the second insulating member 170, and a detailed description thereof will be omitted here.

[0094] In some other embodiments, the electrode assembly 120 adopts a wound structure, i.e., the first pole piece 121, the second pole piece 122, and the separator 123 are stacked and wound, and the second connecting portion 133 and the fourth connecting portion 143 are located on both sides of the wound structure along the second direction Y. For ease of understanding, referring to Fig. 19, the first pole piece 121 includes a plurality of flat portions 121a, i.e., the plurality of flat portions 121a is the portion of the first pole piece 121 located between the lines MM and NN in Fig. 2, and the plurality of flat portions 121a are all perpendicular to the second direction Y. The first pole piece 121 has a winding start edge 1210 along the winding direction, and a plane parallel to the plurality of flat portions 121a and passing through the winding start edge 1210 is defined as the winding center plane P. When viewed from the first direction X, the first tab 130 and the second tab 140 are located on both sides of the winding center plane P, and thus the risk of the second connection portion 133 and the fourth connection portion 143 being too close in the second direction Y and affecting the sealing effect of the sealing edge 112 can be reduced.

[0095] Furthermore, the first recess 1212a and the second recess 1222a do not overlap in the second direction Y. In other words, there is a gap between the second connection portion 133 and the fourth connection portion 143 in the third direction Z, and the third direction Z is a direction perpendicular to the first direction X and the second direction Y. In this way, it is possible to reduce the risk of a partial increase in thickness of the electrode assembly 120 due to the second connection portion 133 and the fourth connection portion 143 overlapping in the second direction Y.

[0096] It should be understood that the third insulating member 180 and the fourth insulating member 190 may be insulating tape or other materials as long as they can provide insulation. In this embodiment, the third insulating member 180 and the fourth insulating member 190 each independently include a base layer and an adhesive layer, and the adhesive layer is used to directly adhere to the second tab 140. The base layer may be made of a material such as polypropylene, polyethylene terephthalate, or polyimide, and the adhesive layer may be made of a material such as acrylic ester, rubber, silicone, polyurethane, or polyolefin.

[0097] 20, unlike the structure in which the second pole piece 122 in the above-described embodiments has a recess on one side, the fourth active material layer 1223 has a third recess 1223a that at least partially exposes the fourth region 1221b, and the third recess 1223a is provided opposite the second recess 1222a. In other words, at least a portion of the fourth region 1221b is not covered by the fourth active material layer 1223.

[0098] By providing the second recess 1222a in the second pole piece 122 and providing at least a portion of the fourth connecting portion 143 within the second recess 1222a, the risk of the secondary battery 100 becoming thicker due to the thickness of the second tab 140 is reduced, contributing to improving the energy density of the secondary battery 100. Furthermore, because the fourth active material layer 1223 is not provided in at least a portion of the fourth region 1221b facing the second recess 1222a, the ability of the second tab 140 to dissipate heat via the second current collector 1221 during charge and discharge processes is improved, and the influence of excessively high current density at the connection point between the fourth connecting portion 143 and the second current collector 1221 on expansion or contraction of the fourth active material layer 1223 in the fourth region 1221b during charge and discharge processes is reduced, thereby improving the life of the secondary battery 100. The second tab 140 has a second bending portion 142 bent toward the second direction Y, and the second bending portion 142 serves to absorb the impact on the electrode assembly 120 when the second tab 140 is subjected to an external force, reducing the tensile force between the fourth connection portion 143 and the third region 1221a, reducing the risk of failure of the secondary battery 100, and improving the safety of the secondary battery 100.

[0099] In some embodiments, the fourth connecting portion 143 is connected to the third region 1221a by ultrasonic welding or resistance welding, which means that the fourth connecting portion 143 and the fourth region 1221b can be pressed together by welding, thereby providing high connection reliability between the fourth connecting portion 143 and the second current collector 1221.

[0100] As can be seen, the third insulating member 180 extends in the direction opposite to the first direction X and covers at least a portion of the third recess 1223a, thereby reducing the risk of burrs in the fourth region 1221b of the second current collector 1221 breaking through the separator 123 and causing a short circuit, and also reducing the risk of material falling off from the third recess 1223a, which is advantageous for improving the safety and stability of the secondary battery 100.

[0101] 2 or 19 , in some embodiments, the secondary battery 100 includes an adhesive member 200 that bonds the packaging bag 110 and the electrode assembly 120, fixing the packaging bag 110 and the electrode assembly 120 relative to each other. This reduces the risk of the electrode assembly 120 rattling relative to the packaging bag 110 and reduces the impact of the adhesive member 200 on the reliability of the connection between the second connection portion 133 and the first region 1211a and on the second active material layer 1213 provided in the second region 1211b when the battery is dropped. In this embodiment, the adhesive member 200 is a double-sided adhesive tape. Of course, the adhesive member 200 may be other materials and is not limited thereto, as long as it can bond and fix the packaging bag 110 and the electrode assembly 120. Furthermore, when the electrode assembly 120 adopts a wound structure, the adhesive member 200 can be provided on the surface of the outermost layer of the electrode assembly 120, and the adhesive member 200 is adhered to the inner surface facing the first region 1211a of the packaging bag 110, and the edge of the adhesive member 200 extends beyond the end of the winding of the outermost pole piece (first pole piece or second pole piece) of the electrode assembly 120 along the winding direction, which is advantageous for bundling the electrode assembly 120 and reduces the risk of the electrode assembly 120 unraveling.

[0102] The secondary battery 100 provided in the embodiment of the present application includes a packaging bag 110, an electrode assembly 120, and a first tab 130. The electrode assembly 120 is contained in the packaging bag 110, and the packaging bag 110 has a sealing edge 112. The electrode assembly 120 includes a first pole piece 121, a second pole piece 122, and a separator 123. The separator 123 is disposed between the first pole piece 121 and the second pole piece 122. The first pole piece 121 includes a first current collector 1211, a first active material layer 1212, and a second active material layer 1213. The first current collector 1211 has a first surface 12111 and a second surface 12112 facing each other. The first active material layer 1212 is disposed on the first surface 12111, and the second active material layer 1213 is disposed on the second surface 12112. The first surface 12111 includes a first region 1211a, and a first recess 1212a exposing the first region 1211a is provided in the first active material layer 1212. The second surface 12112 includes a second region 1211b corresponding to the first region 1211a, and the second region 1211b is covered by the second active material layer 1213. The first tab 130 includes a first connecting portion 131, a first folded portion 132, and a second connecting portion 133 connected in this order, the first connecting portion 131 extending from the sealing edge 112 to the outside of the packaging bag 110, at least a portion of the second connecting portion 133 being located within the first recess 1212a and connected to the first region 1211a, and the first folded portion 132 being folded in the second direction Y with respect to the second connecting portion 133.

[0103] By providing the first recess 1212a in the first pole piece 121 and providing at least a portion of the second connection portion 133 in the first recess 1212a, the risk of the secondary battery 100 becoming thicker due to the thickness of the first tab 130 is reduced, contributing to improving the energy density of the secondary battery 100. Furthermore, by providing the second active material layer 1213 in the second region 1211b opposite the first region 1211a, the risk of uneven thickness caused by forming grooves on both sides of the first pole piece 121 is reduced. The first tab 130 has a first bent portion 132 bent in the second direction Y. When the secondary battery 100 is dropped or hit, the first bent portion 132 can reduce the impact force on the sealed edge 112 of the electrode assembly 120. This reduces the risk of electrolyte leakage when the sealed edge 112 is impacted by the electrode assembly 120, thereby improving the safety of the secondary battery 100. At the same time, the first bending portion 132 can also provide a buffer portion for the first tab 130, reducing the direct pulling of the first connection portion 131 on the second connection portion 133, thereby improving the stability of the connection between the second connection portion 133 and the first region 1211a and improving the reliability of the secondary battery 100.

[0104] As shown in Figure 21, an electronic device 300 provided in another embodiment of the present application includes the secondary battery 100 of the above-described embodiment. The electronic device 300 of the present application is not particularly limited and may be any electronic device known in the prior art. For example, the electronic device 300 may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an e-book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a headphone stereo, a video recorder, an LCD television, a portable vacuum cleaner, a portable CD player, a minidisc player, a walkie-talkie, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a powered bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large-scale household storage battery, and a lithium-ion capacitor.

[0105] Finally, it should be noted that the above examples are merely illustrative of the technical solutions of the present application and are not intended to limit the same. Within the spirit of the present application, the technical features in the above examples or different examples can be combined, the steps can be implemented in any order, and many other variations exist in different aspects of the present application, which have not been provided in detail for the sake of brevity. Although the present application has been described in detail with reference to the above examples, those skilled in the art may still make modifications to the technical solutions described in the above examples or substitute equivalent technical features for the packaging bags therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the respective examples of the present application. [Explanation of symbols]

[0106] 100, secondary battery; 110, packaging bag; 120, electrode assembly; 130, first tab; 140, second tab; 150, first insulating member; 160, sealing member; 170, second insulating member; 180, third insulating member; 190, fourth insulating member; 200, adhesive member; 300, electronic device; 111, housing; 112, sealing edge; 121, first pole piece; 122, second pole piece; 123, separator; 1211, first current collector; 1212, first active material layer; 1213, second active material layer; 1211a, first region; 1211b, second region; 1212a, first recess; 1211c, first edge; 1211d, second edge; 121a, flat portion; 131, first connecting portion; 132, first bent portion; 133, second connecting portion; 1301, first tab surface; 13 02, second tab surface; 1211e, first notch; 12211, third surface; 12212, fourth surface; 12111, first surface; 12112, second surface; 1210, winding start edge; 151, first insulating edge; 152, second insulating edge; 161, sealing portion; 162, first extension portion; 163, second extension portion; 1621, first portion; 1622, second portion; 171, Third insulating edge; 172, fourth insulating edge; 1221, second current collector; 1222, third active material layer; 1223, fourth active material layer; 1221a, third region; 1221b, fourth region; 1222a, second recess; 141, third connecting portion; 142, second folded portion; 143, fourth connecting portion; 1401, third tab surface; 1402, fourth tab surface; 1223a, third recess.

Claims

1. A secondary battery comprising: a packaging bag, an electrode assembly, and a first tab; the electrode assembly is accommodated in the packaging bag, and the packaging bag has a sealing edge; the electrode assembly comprises a first pole piece, a second pole piece, and a separator; and the separator is disposed between the first pole piece and the second pole piece; the first pole piece includes a first current collector, a first active material layer, and a second active material layer, the first current collector having a first surface and a second surface facing each other, the first active material layer being disposed on the first surface, the second active material layer being disposed on the second surface, the first surface including a first region, the first active material layer being provided with a first recess exposing the first region, the second surface including a second region corresponding to the first region, the second region being covered with the second active material layer, the first tab includes a first connecting portion, a first folded portion, and a second connecting portion connected in this order, the first connecting portion extending from the sealing edge to the outside of the packaging bag, and the second connecting portion being at least partially located within the first recess and connected to the first region; A secondary battery characterized in that the direction in which the first connection portion extends outside the packaging bag is defined as a first direction, the direction from the first region to the second region is defined as a second direction, the first direction is perpendicular to the second direction, and the first folding portion is folded toward the second direction relative to the second connection portion.

2. 2. The secondary battery of claim 1, wherein a direction perpendicular to both the first direction and the second direction is defined as a third direction, and when observed from the third direction, the acute angle formed between the first bent portion and the second direction is defined as β, and 20°≦β≦70°.

3. 3. The secondary battery according to claim 2, wherein β satisfies 30°≦β≦60°.

4. the first tab includes a first tab surface and a second tab surface facing each other, the first tab surface located at the second connection portion being connected to the first region; the secondary battery includes a sealing member, the sealing member including a sealing portion and a first extending portion, the sealing portion being used to seal and connect with the sealing edge, the first extending portion extending from the sealing portion toward the inside of the packaging bag, the first extending portion including a first portion, and the first portion being provided on a surface of the first tab; 2. The secondary battery of claim 1, further comprising a first insulating member, at least a portion of which is provided on the first tab surface located at the first bent portion, and one end of the first insulating member abuts the first portion.

5. The secondary battery according to claim 4 , wherein the first insulating member covers at least a part of the first portion.

6. The secondary battery according to claim 5 , wherein the first insulating member extends in a direction opposite to the first direction, and the first insulating member covers a portion of the second active material layer.

7. The secondary battery according to claim 4 , wherein the first insulating member and the first portion are integrally formed.

8. 2. The secondary battery of claim 1, wherein the first current collector includes a first side and a second side facing each other in the first direction, the first tab extends from the first side to an outside of the first current collector, the first current collector is provided with a first notch recessed in a direction from the first side toward the second side, and the second connection portion and the first notch at least partially overlap in the second direction.

9. The secondary battery according to claim 1 , wherein the second connection portion and the first region are welded together by irradiating the second connection portion with a laser.

10. the first extension further includes a second portion disposed on the second tab surface; The secondary battery of any one of claims 4 to 9, further comprising a second insulating member, at least a portion of which is provided on the second tab surface located at the first bent portion, and one end of the second insulating member abuts the second portion.

11. The secondary battery according to claim 10 , wherein the second insulating member covers at least a part of the second portion.

12. The secondary battery according to claim 11 , wherein the other end of the second insulating member extends in a direction opposite to the first direction so that the second insulating member covers at least a portion of the first recess.

13. The secondary battery according to claim 11 , wherein the second insulating member and the second portion are integrally formed.

14. the second pole piece includes a second current collector, a third active material layer, and a fourth active material layer, the second current collector including a third surface and a fourth surface facing each other, the third active material layer being disposed on the third surface, the fourth active material layer being disposed on the fourth surface, the third surface including a third region, the third active material layer being provided with a second recess exposing the third region, the fourth surface including a fourth region corresponding to the third region, and at least a portion of the fourth region not covered by the fourth active material layer, the secondary battery further includes a second tab, the second tab including a third connection portion, a second folded portion, and a fourth connection portion connected in this order, the third connection portion extending from the sealed edge to the outside of the packaging bag, at least a portion of the fourth connection portion being located within the second recess and connected to the third region, and the fourth connection portion being connected to the third region by ultrasonic welding or resistance welding; The secondary battery according to claim 1 , wherein the second direction is a direction from the third region to the fourth region, and the second bent portion is bent in the second direction.

15. the second pole piece includes a second current collector, a third active material layer, and a fourth active material layer, the second current collector includes a third surface and a fourth surface facing each other, the third active material layer is disposed on the third surface, the fourth active material layer is disposed on the fourth surface, the third surface includes a third region, the third active material layer is provided with a second recess exposing the third region, the fourth surface includes a fourth region corresponding to the third region, and the fourth region is covered with the fourth active material layer, the secondary battery further includes a second tab, the second tab including a third connection portion, a second folded portion, and a fourth connection portion connected in this order, the third connection portion extending from the sealed edge to the outside of the packaging bag, at least a portion of the fourth connection portion being located within the second recess and connected to the third region, and the fourth connection portion being connected to the third region by laser welding; The secondary battery according to claim 1 , wherein the second direction is a direction from the third region to the fourth region, and the second bent portion is bent in the second direction.

16. 16. The secondary battery of claim 15, wherein the first pole piece, the second pole piece, and the separator are stacked and wound to form a wound structure, the second connection portion and the fourth connection portion are located on both sides of the wound structure along the second direction, and the first recess and the second recess do not overlap.

17. 2. The secondary battery according to claim 1, wherein the first pole piece is a positive pole piece, the second pole piece is a negative pole piece, the first current collector is an aluminum foil, and in the first direction, the second pole piece exceeds the first pole piece and the separator exceeds the second pole piece.

18. the sealing member comprises at least one of polyethylene, polypropylene, polyurethane, polyethylene terephthalate, or ethylene propylene copolymer; and / or The secondary battery according to claim 4 , wherein the first insulating member includes a base layer and an adhesive layer provided on the base layer.

19. 2. The secondary battery according to claim 1, further comprising an adhesive member that adheres the packaging bag and the electrode assembly, the adhesive member being attached to an inner surface of the packaging bag facing the first region.

20. An electronic device, characterized in that it comprises a secondary battery according to any one of claims 1 to 19.

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