Secondary battery and electric device

Abstract

The application discloses a secondary battery and a power utilization device. The secondary battery comprises an electrode assembly and a first extension part, and the electrode assembly has a laminated structure. The electrode assembly comprises a first outer layer electrode tab, a separator and a second outer layer electrode tab arranged along a first direction. The first outer layer electrode tab comprises a first outer layer current collector. The second outer layer electrode tab comprises a second outer layer current collector. The first outer layer current collector comprises a first corner position. The second outer layer current collector comprises a second corner position. The first corner position and the second corner position at least partially overlap when viewed along the first direction. The first extension part extends from the first corner position of the first outer layer current collector, and the first extension part is fixedly connected with the second outer layer current collector. By fixedly connecting the first corner position and the second corner position, the problem that the first corner position and the second corner position are lifted and affect the performance of the secondary battery is reduced, and the risk that the first corner position and / or the second corner position are lifted to cause the outer layer current collector to be folded is reduced.

Description

TECHNICAL FIELD

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

[0002] With the continuous updating and development of secondary battery technology, the application field of secondary batteries is also expanding, and the safety problem of secondary batteries is increasingly concerned by the public. The corner position of the outermost electrode tab of the secondary battery with a laminated structure is prone to be raised during the cyclic use, which causes the safety problem of the secondary battery. SUMMARY

[0003] Therefore, it is necessary to provide a secondary battery and a power consumption device to improve the problem of corner position raising and improve the safety of the secondary battery.

[0004] Embodiments of the present application provide a secondary battery, comprising an electrode assembly, the electrode assembly being in a laminated structure. The electrode assembly comprises a first outer layer electrode tab, a separator and a second outer layer electrode tab arranged along a first direction. The first outer layer electrode tab comprises a first outer layer current collector. The second outer layer electrode tab comprises a second outer layer current collector. The first outer layer current collector comprises a first corner position. The second outer layer current collector comprises a second corner position. There is at least partial overlap between the first corner position and the second corner position when viewed along the first direction. The electrode assembly further comprises a first extension, the first extension extending from the first corner position to the first outer layer current collector, and the first extension is fixedly connected to the second outer layer current collector. By fixedly connecting the first corner position and the second corner position through the first extension, the raising of the first corner position and the second corner position is reduced, the poor contact between the first outer layer electrode tab and the separator and between the second outer layer electrode tab and the separator in the raised area is improved, the lithium ion transmission path is blocked, and thus the lithium plating purple stain is generated, which affects the performance of the secondary battery; the raised area repeatedly bears mechanical stress during the charging and discharging process, which is beneficial to reduce the risk of cracks in the active material layer on the first outer layer current collector and / or the second outer layer current collector; the first corner position and / or the second corner position is raised to scratch the adhesive layer of the packaging bag, causing the adhesive layer to accumulate and hinder the extension of the first outer layer current collector and / or the second outer layer current collector, which causes the risk of folding of the first outer layer current collector and / or the second outer layer current collector.

[0005] In one or more optional embodiments above, the electrode assembly further comprises a second extension, the second extension extending from the second corner position to the second outer layer current collector, and the first extension is fixedly connected to the second extension.

[0006] In one or more optional embodiments above, the first extension is welded to the second corner position.

[0007] In one or more optional embodiments above, the first extension is welded to the second extension.

[0008] In one or more optional embodiments above, the first tab is further included, the first outer current collector further includes a second edge, one of the edges of the first corner is a part of the second edge, and the first tab is connected to the second edge. The problem of the corner of the head of the secondary battery being more raised than the bottom is improved.

[0009] In one or more optional embodiments above, along the thickness direction of the first extension, the first extension includes opposite first and second connecting surfaces, the first connecting surface faces the electrode assembly, along the thickness direction of the second extension, the second extension includes opposite third and fourth connecting surfaces, the third connecting surface faces the electrode assembly. The first connecting surface is welded to the fourth connecting surface to form a first welding portion, or the second connecting surface is welded to the third connecting surface to form the first welding portion, or the first connecting surface is welded to the third connecting surface to form the first welding portion arranged in a bent manner along the first direction; along the first direction, the length L1 of the first welding portion is 1mm≤L1≤2mm. By L1≥1mm, the structural strength of the first welding portion is increased, and the risk of separation of the first and second extensions is reduced. The more the first and second extensions overlap, the more space they occupy, and by L1≤2mm, the space occupied by the first welding portion is reduced.

[0010] In one or more optional embodiments above, the first extension is welded to the second corner to form a second welding portion, along the length extension direction of the first extension, the length L2 of the second welding portion is 1mm≤L2≤2mm. By L2≥1mm, the welding strength of the second welding portion is increased, and the risk of separation of the second welding portion from the second corner is reduced, and by L2≤2mm, the space occupied by the second welding portion is reduced.

[0011] In one or more optional embodiments above, the width D1 of the first extension is 1mm≤D1≤5mm; and / or, the width D2 of the second extension is 1mm≤D2≤5mm. The welding difficulty of the first and second extensions is reduced, the welding is facilitated, the influence on the electrode assembly is reduced, and the occupied space is reduced.

[0012] In one or more optional embodiments above, the thickness H1 of the first extension part is 8 μm ≤ H1 ≤ 20 μm. By H1 ≥ 8 μm, the risk of the first extension part and the first tab connected to the first outer layer current collector being too thin to break is reduced. By H1 ≤ 20 μm, the thickness of the first extension part, the first outer layer current collector and the first tab is controlled, and the impact on the energy density of the secondary battery is reduced; and / or, the thickness H2 of the second extension part is 8 μm ≤ H2 ≤ 20 μm. By H2 ≥ 8 μm, the risk of the second extension part and the second tab connected to the second outer layer current collector being too thin to break is reduced. By H2 ≤ 20 μm, the thickness of the second extension part, the second outer layer current collector and the second tab is controlled, and the impact on the energy density of the secondary battery is reduced.

[0013] In one or more optional embodiments above, the electrode assembly includes a second tab, the second tab being opposite in polarity to the first outer layer tab, the second tab being disposed between adjacent isolation films, the adjacent isolation films being bonded to the second tab beyond the area of the second tab and covering the second tab. The risk of the first extension part and the second extension part contacting the second tab and causing short circuit is reduced.

[0014] In one or more optional embodiments above, the first extension part is bent relative to the first outer layer current collector and forms a first included angle α, 90° ≤ α ≤ 120°. By α ≥ 90°, the first extension part is made to be away from the isolation film and other tabs between the first outer layer tab and the second outer layer tab, the welding difficulty is reduced, and the welding is facilitated. On the basis of facilitating the welding, by α ≤ 120°, the space occupied by the first extension part in the second direction is reduced, and the interference in the subsequent packaging and forming process of the secondary battery is reduced. The second extension part is bent relative to the second outer layer current collector and forms a second included angle β, 90° ≤ β ≤ 120°, and the first extension part is welded to the second extension part. By β ≥ 90°, the second extension part is made to be away from the isolation film and other tabs between the first outer layer tab and the second outer layer tab, the welding difficulty is reduced, and the welding is facilitated. On the basis of facilitating the welding, by β ≤ 120°, the space occupied by the second extension part in the second direction is reduced, and the interference in the subsequent packaging and forming process of the secondary battery is reduced.

[0015] In one or more optional embodiments above, the first outer layer current collector includes a third corner position, the second outer layer current collector includes a fourth corner position, and the third corner position overlaps the fourth corner position when viewed in the first direction. The electrode assembly includes a third extension part extending from the third corner position out of the first outer layer current collector, and the third extension part is welded to the fourth corner position; or the electrode assembly further includes a fourth extension part extending from the fourth corner position out of the second outer layer current collector, and the third extension part and the fourth extension part are welded to each other, thereby improving the problem caused by the third corner position and the fourth corner position being lifted.

[0016] In one or more optional embodiments above, the first tab and the second tab are further included, the first outer current collector includes a second edge, one of the edges of the first corner is part of the second edge, one of the edges of the third corner is part of the second edge, and the first tab is connected to the second edge; the second outer current collector includes a fourth edge, one of the edges of the second corner is part of the fourth edge, one of the edges of the fourth corner is part of the fourth edge, and the second tab is connected to the fourth edge. The problem of the corners of the head of the secondary battery being more prone to warping than the bottom is improved.

[0017] In one or more optional embodiments above, the first outer current collector includes a fifth corner, the second outer current collector includes a sixth corner, and the fifth corner overlaps the sixth corner when viewed in the first direction. The electrode assembly includes a fifth extension that extends from the fifth corner of the first outer current collector and is welded to the sixth corner, or the electrode assembly further includes a sixth extension that extends from the sixth corner of the second outer current collector and is welded to the fifth extension, thereby improving the warping of the fifth corner and the sixth corner.

[0018] Embodiments of the present application provide a kind of electric equipment, including the secondary battery in any one of the above embodiments.

[0019] The electric equipment described above reduces the warping of the first corner and the second corner by fixedly connecting the first corner and the second corner, improves the poor contact between the first outer pole piece and the separator in the warped area and between the second outer pole piece and the separator, causes the lithium ion transmission path to be blocked and thus generates lithium plating purple stain, which affects the performance of the secondary battery; the warped area repeatedly bears mechanical stress during the charging and discharging process, which is beneficial to reduce the risk of cracks in the active material layer on the first outer current collector and / or the second outer current collector; the adhesive layer of the packaging bag is scratched by the warping of the first corner and / or the second corner, which causes the adhesive layer to accumulate and hinder the extension of the first outer current collector and / or the second outer current collector, resulting in the risk of folding of the first outer current collector and / or the second outer current collector; in addition, compared with the existing method of thickening the thickness of the first outer current collector and the thickness of the second outer current collector to slow down the warping of the first corner and / or the second corner, the present application can also reduce the thickness of the first outer current collector and the thickness of the second outer current collector to improve the energy density of the secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Part of the structure of the secondary battery in some embodiments is shown.

[0021] Figure 2 The structure of the first outer pole piece in some embodiments is shown.

[0022] Figure 3 A structural diagram of the second outer layer electrode tab in some embodiments is shown.

[0023] Figure 4 A partial diagram of a secondary battery in another perspective in some embodiments is shown.

[0024] Figure 5 A partial diagram of a secondary battery in another perspective in some embodiments is shown.

[0025] Figure 6 A partial diagram of a secondary battery in another perspective in some embodiments is shown.

[0026] Figure 7 A structural diagram of the first outer layer electrode tab in some embodiments is shown.

[0027] Figure 8 A partial structural diagram of a secondary battery in some embodiments is shown.

[0028] Figure 9 A structural diagram of the first outer layer electrode tab in some embodiments is shown.

[0029] Figure 10 A structural diagram of the second outer layer electrode tab in some embodiments is shown.

[0030] Figure 11 A partial diagram of a secondary battery in another perspective in some embodiments is shown. Figure 8 A partial diagram of a secondary battery in another perspective in some embodiments is shown.

[0031] Figure 12 A structural diagram of the first outer layer electrode tab in some embodiments is shown.

[0032] Explanation of main element symbols:

[0033] Secondary battery 100

[0034] Electrode assembly 10

[0035] First outer layer electrode tab 11

[0036] First outer layer current collector 11a

[0037] First corner 111

[0038] Third corner 112

[0039] Fifth corner 113

[0040] Seventh corner 114

[0041] First active material layer 11b

[0042] First edge 101

[0043] Second edge 102

[0044] Sixth segment 102b

[0045] First intersection A

[0046] First segment 101a

[0047] Second segment 102a

[0048] First line 110

[0049] Second line 120

[0050] Third line 130

[0051] Fourth line 140

[0052] Separation film 12

[0053] Second outer layer tab 13

[0054] Second outer layer current collector 13a

[0055] Second corner 131

[0056] Fourth corner 132

[0057] Sixth corner 133

[0058] Eighth corner 134

[0059] Second active material layer 13b

[0060] Third edge 103

[0061] Fourth edge 104

[0062] Eighth segment 104b

[0063] Third segment 103a

[0064] Fourth segment 104a

[0065] Second intersection B

[0066] Fifth edge 105

[0067] Third intersection C

[0068] Fifth segment 105a

[0069] Sixth edge 106

[0070] Fourth intersection D

[0071] Seventh segment 106a

[0072] Seventh edge 107

[0073] Eighth edge 108

[0074] First extension 14

[0075] First weld 14a

[0076] First connecting surface 141

[0077] Second connecting surface 142

[0078] Second extension 15

[0079] Third connecting surface 151

[0080] Fourth connecting surface 152

[0081] Third extension 16

[0082] Third weld 16a

[0083] Fourth extension 17

[0084] Fifth extension 18

[0085] Sixth extension 19

[0086] Seventh extension 10A

[0087] Eighth extension 10B

[0088] Fifth weld 10C

[0089] Second pole piece 10D

[0090] First pole tab 20

[0091] Second pole tab 30

[0092] Electric device 200

[0093] First direction X

[0094] Second direction Y

[0095] Third direction Z

[0096] The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0097] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments.

[0098] When a component is referred to as being "on" another component or "connected to" another component, it can be directly on the other component or electrically or physically connected to the other component, with intervening components present.

[0099] 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 describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0100] It can be understood that the term "vertical" is used to describe an ideal state between two components. In actual production or use state, there can be a state similar to or equal to vertical between the two components. For example, in combination with numerical description, vertical can refer to the included angle between two straight lines in the range of 90°±10°, vertical can also refer to the dihedral angle between two planes in the range of 90°±10°, and vertical can also refer to the included angle between a straight line and a plane in the range of 90°±10°. The two components described as "vertical" can not be absolute straight lines or planes, but can be approximately straight lines or planes, and as a whole, the overall extension direction is a straight line or a plane, which can be considered as a "straight line" or a "plane".

[0101] Unless otherwise defined, the term "a plurality of" used herein to describe the number of components specifically refers to two or more of the components.

[0102] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0103] Please refer to Figures 1 to 3 An embodiment of the present application provides a secondary battery 100, comprising an electrode assembly 10, the electrode assembly 10 is in a laminated structure, and the electrode assembly 10 comprises a first outer layer electrode tab 11, a separator 12 and a second outer layer electrode tab 13 arranged along a first direction X.

[0104] The first outer layer electrode tab 11 comprises a first outer layer current collector 11a, and the second outer layer electrode tab 13 comprises a second outer layer current collector 13a. The first outer layer current collector 11a comprises a first corner position 111, and the second outer layer current collector 13a comprises a second corner position 131. When viewed along the first direction X, the first corner position 111 and the second corner position 131 at least partially overlap.

[0105] In some embodiments, the electrode assembly 10 comprises a first extension 14 extending from the first corner position 111 to the first outer layer current collector 11a, and the first extension 14 is fixedly connected with the second outer layer current collector 13a. In some embodiments, the secondary battery 100 comprises a packaging bag (not shown in the figure), and the electrode assembly 10 is arranged in the packaging bag. The packaging bag comprises, in sequence along the thickness direction of the packaging bag, an adhesive layer, a metal layer, and an outer layer. The adhesive layer is the innermost side of the packaging bag. The outer layer can be a nylon layer or a composite layer of polyester resin (PET) and nylon, which has the protection function of preventing pollution, corrosion resistance, and preventing damage from external forces. The metal layer can include one of aluminum and steel, which has the functions of waterproofing, blocking, and shaping the packaging bag. The adhesive layer is a heat-seal layer, and the adhesive layer can include a polymer, which includes one of polypropylene and polyethylene, for sealing the packaging bag and separating the metal layer from the electrode assembly 10, thereby reducing the risk of electrolyte leakage in the packaging bag corroding the metal layer.

[0106] The first extension 14 of the present application fixes the first corner position 111 and the second corner position 131, reduces the warping of the first corner position 111 and the second corner position 131, improves the poor contact between the first outer layer tab 11 and the separator 12 and between the second outer layer tab 13 and the separator 12 in the warping area, causes the lithium ion transmission path to be blocked, and thus generates lithium plating purple stains, which affects the performance of the secondary battery 100; improves the repeated mechanical stress of the warping area during the charging and discharging process, which is conducive to reducing the risk of cracks in the active material layer on the first outer layer current collector 11a and / or the second outer layer current collector 13a; reduces the risk of the first corner position 111 and / or the second corner position 131 warping and scratching the adhesive layer of the packaging bag, causing the adhesive layer to accumulate and hinder the extension of the first outer layer current collector 11a and / or the second outer layer current collector 13a, and causing the first outer layer current collector 11a and / or the second outer layer current collector 13a to fold. In addition, compared with the existing method of thickening the thickness of the first outer layer current collector 11a and the thickness of the second outer layer current collector 13a to slow down the warping of the first corner position 111 and / or the second corner position 131, the present application can also reduce the thickness of the first outer layer current collector 11a and the thickness of the second outer layer current collector 13a to improve the energy density of the secondary battery.

[0107] In some embodiments, the first outer layer tab 11 comprises a first active material layer 11b, and along the first direction X, the side of the first outer layer current collector 11a facing the separator 12 is provided with the first active material layer 11b, and the side of the first outer layer current collector 11a away from the separator 12 is not provided with the first active material layer 11b, i.e., the outermost side of the first outer layer current collector 11a is not provided with the first active material layer 11b.

[0108] In some embodiments, the second outer layer electrode tab 13 comprises a second active material layer 13b, the second active material layer 13b is arranged on one side of the second outer layer current collector 13a facing the separator film 12 along the first direction X, and the other side of the second outer layer current collector 13a is not arranged with the second active material layer 13b, i.e., the outermost side of the second outer layer current collector 13a is not arranged with the second active material layer 13b. The first active material layer 11b and the second active material layer 13b are active materials of the same polarity.

[0109] In some embodiments, the first outer layer electrode tab 11 is a positive electrode tab and the second outer layer electrode tab 13 is a positive electrode tab, and the first outer layer current collector 11a and the second outer layer current collector 13a can be aluminum foil or nickel foil. In other embodiments, the first outer layer electrode tab 11 is a negative electrode tab and the second outer layer electrode tab 13 is a negative electrode tab, and the first outer layer current collector 11a and the second outer layer current collector 13a can be at least one of copper foil, nickel foil, or carbon-based current collector.

[0110] The separator film 12 comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene comprises at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.

[0111] Embodiment one

[0112] Please refer to Figure 2 In some embodiments, the first outer layer current collector 11a comprises a first edge 101 and a second edge 102, the first edge 101 and the second edge 102 intersect at a first intersection point A, a first section 101a is formed by extending from the first intersection point A along the first edge 101, the length H1 of the first section 101a is H1≤3mm, a second section 102a is formed by extending from the first intersection point A along the second edge 102, the length H2 of the second section 102a is H2≤3mm, a first connecting line 110 is defined, the first connecting line 110 connects one end of the first section 101a away from the first intersection point A and one end of the second section 102a away from the first intersection point A. The first section 101a, the second section 102a, and the first connecting line 110 enclose a first angular position 111.

[0113] Please refer to Figure 3In some embodiments, the second outer current collector 13a comprises a third edge 103 and a fourth edge 104, the third edge 103 intersects with the fourth edge 104 at a second intersection point B, a third section 103a is formed by extending from the second intersection point B along the third edge 103, a length H3 of the third section 103a is H3≤3mm, a fourth section 104a is formed by extending from the second intersection point B along the fourth edge 104, a length H4 of the fourth section 104a is H4≤3mm, a second connecting line 120 is defined, the second connecting line 120 connects an end of the third section 103a away from the second intersection point B and an end of the fourth section 104a away from the second intersection point B. The third section 103a, the fourth section 104a and the second connecting line 120 enclose a second corner site 131.

[0114] In some embodiments, as viewed along a first direction X, a distance between the first edge 101 and the third edge 103 along a second direction Y is less than 0.5mm, a distance between the second edge 102 and the fourth edge 104 along a third direction Z is less than 0.5mm, so that the first corner site 111 and the second corner site 131 at least partially overlap. The second direction Y is one of a length direction and a width direction of the electrode assembly 10, the third direction Z is the other of the length direction and the width direction of the electrode assembly 10, the first direction X, the second direction Y and the third direction Z are perpendicular to each other.

[0115] Referring to Figures 1 to 3 In some embodiments, the electrode assembly 10 comprises a second extension 15, the second extension 15 extends from the second corner site 131 to the second outer current collector 13a, the first extension 14 and the second extension 15 are fixedly connected.

[0116] In some embodiments, the first extension 14 and the second extension 15 are weldedly connected. Specifically, the first extension 14 is bent towards the second outer current collector 13a, the second extension 15 is bent towards the first outer current collector 11a, so that a portion of the first extension 14 and a portion of the second extension 15 overlap, and a first welding portion 14a is formed by welding the overlapping portion.

[0117] Optionally, the first extension 14 extends from the first edge 101 of the region where the first corner site 111 is located to the first outer current collector 11a, and the second extension 15 extends from the third edge 103 of the region where the second corner site 131 is located to the second outer current collector 13a.

[0118] Optionally, the first extension 14 extends from the second edge 102 of the region where the first corner site 111 is located to the first outer current collector 11a, and the second extension 15 extends from the fourth edge 104 of the region where the second corner site 131 is located to the second outer current collector 13a.

[0119] Referring to Figure 4In some embodiments, along the thickness direction of the first extension 14, the first extension 14 includes opposite first and second connecting surfaces 141 and 142, the first connecting surface 141 faces the electrode assembly 10, along the thickness direction of the second extension 15, the second extension 15 includes opposite third and fourth connecting surfaces 151 and 152, the third connecting surface 151 faces the electrode assembly 10. The first connecting surface 141 is welded to the fourth connecting surface 152, and forms a first welding portion 14a. At this time, along the second direction Y, the second connecting surface 142 is located at the outermost side.

[0120] In some embodiments, the second connecting surface 142 is welded to the third connecting surface 151, and forms the first welding portion 14a. At this time, the second connecting surface 142 is located at the outermost side. At this time, along the second direction Y, the fourth connecting surface 152 is located at the outermost side.

[0121] Please refer to Figure 5 In some embodiments, the first connecting surface 141 is welded to the third connecting surface 151, and forms a first welding portion 14a which is arranged in a bent manner along the first direction X.

[0122] In some embodiments, along the first direction X, the length L1 of the first welding portion 14a is 1mm≤L1≤2mm. By L1≥1mm, the structural strength of the first welding portion 14a is increased, and the risk of separation of the first extension 14 and the second extension 15 is reduced. The more the first extension 14 and the second extension 15 overlap, the more space they occupy, and by L1≤2mm, the space occupied by the first welding portion 14a is reduced.

[0123] Alternatively, L1 can be any value within a range consisting of any one or any two of 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm.

[0124] Please refer to Figure 4 In some embodiments, the first extension 14 is bent relative to the first outer current collector 11a, and forms a first included angle a, 90°≤a≤120°. By a≥90°, the first extension 14 is away from the isolation film 12 and other pole pieces between the first outer pole piece 11 and the second outer pole piece 13, the welding difficulty is reduced, and the welding is facilitated. On the basis of facilitating welding, by a≤120°, the space occupied by the first extension 14 along the second direction Y is reduced, and the interference in the subsequent packaging and forming process of the secondary battery 100 is reduced.

[0125] Alternatively, a can be any value within a range consisting of any one or any two of 90°, 95°, 100°, 105°, 110°, 115°, 120°.

[0126] In some embodiments, the second extension 15 is bent relative to the second outer layer current collector 13a and forms a second included angle β, 90°≤β≤120°. By β≥90°, the second extension 15 is away from the isolation film 12 and other electrode plates between the first outer layer electrode plate 11 and the second outer layer electrode plate 13, reducing the difficulty of welding and facilitating welding. On the basis of facilitating welding, by β≤120°, the space occupied by the second extension 15 in the second direction Y is reduced, reducing the interference in the subsequent packaging and forming process of the secondary battery 100.

[0127] Alternatively, β can be any one of 90°, 95°, 100°, 105°, 110°, 115°, 120° or any value within the range composed of any two of them.

[0128] In some embodiments, the first extension 14 extends from the first intersection A, and the second extension 15 extends from the second intersection B, which further helps to improve the problem of the first corner 111 and the second corner 131 being raised.

[0129] Please refer to Figures 4 to 6 The first outer layer current collector 11a includes a third corner 112, and the second outer layer current collector 13a includes a fourth corner 132. When viewed in the first direction X, the third corner 112 overlaps the fourth corner 132, and the third corner 112 is welded to the fourth corner 132. By welding the third corner 112 to the fourth corner 132, the third corner 112 and the fourth corner 132 are reduced to be raised, and the problem of poor contact between the first outer layer electrode plate 11 and the isolation film 12 and between the second outer layer electrode plate 13 and the isolation film 12 in the raised area of the third corner 112 and the fourth corner 132 is improved, which blocks the lithium ion transmission path and causes lithium plating purple stains, affecting the performance of the secondary battery; the raised area repeatedly bears mechanical stress during charging and discharging, which helps to reduce the risk of cracks in the active material layer on the first outer layer current collector 11a and / or the second outer layer current collector 13a, and reduce the risk of the third corner 112 and / or the fourth corner 132 being raised and scratching the adhesive layer of the packaging bag, causing the adhesive layer to accumulate and hinder the extension of the first outer layer current collector 11a and / or the second outer layer current collector 13a, resulting in the risk of the first outer layer current collector 11a and / or the second outer layer current collector 13a being folded.

[0130] Please refer to Figure 2In some embodiments, the first outer current collector 11a comprises a fifth edge 105 intersecting the second edge 102 at a third intersection point C, a fifth section 105a extending from the third intersection point C along the fifth edge 105, the length of the fifth section 105a being H5, H5≤3mm, a sixth section 102b extending from the third intersection point C along the second edge 102, the length of the sixth section 102b being H6, H6≤3mm, a third connecting line 130 connecting one end of the fifth section 105a away from the third intersection point C and one end of the sixth section 102b away from the third intersection point C. The fifth section 105a, the sixth section 102b and the third connecting line 130 enclose a third corner site 112.

[0131] Referring to Figure 3 In some embodiments, the second outer current collector 13a comprises a sixth edge 106 intersecting the fourth edge 104 at a fourth intersection point D, a seventh section 106a extending from the fourth intersection point D along the sixth edge 106, the length of the seventh section 106a being H7, H7≤3mm, an eighth section 104b extending from the fourth intersection point D along the fourth edge 104, the length of the eighth section 104b being H8, H8≤3mm, a fourth connecting line 140 connecting one end of the seventh section 106a away from the fourth intersection point D and one end of the eighth section 104b away from the fourth intersection point D. The seventh section 106a, the eighth section 104b and the fourth connecting line 140 enclose a fourth corner site 132.

[0132] Referring to Figure 4 In some embodiments, the electrode assembly 10 comprises a third extension 16 and a fourth extension 17, the third extension 16 extending from the third corner site 112 out of the first outer current collector 11a, the fourth extension 17 extending from the fourth corner site 132 out of the second outer current collector 13a, the third extension 16 being welded to the fourth extension 17. Specifically, the third extension 16 is bent towards the second outer current collector 13a, the fourth extension 17 is bent towards the first outer current collector 11a, such that a portion of the third extension 16 and a portion of the fourth extension 17 overlap, and the overlapping portion is welded to form a third weld 16a.

[0133] Optionally, the third extension 16 extends from the fifth edge 105 of the region where the third corner site 112 is located out of the first outer current collector 11a, and the fourth extension 17 extends from the sixth edge 106 of the region where the fourth corner site 132 is located out of the second outer current collector 13a.

[0134] Optionally, the third extension 16 extends from the second edge 102 of the region where the third corner site 112 is located out of the first outer current collector 11a, and the fourth extension 17 extends from the fourth edge 104 of the region where the fourth corner site 132 is located out of the second outer current collector 13a.

[0135] In some embodiments, the welding form of the third extension 16 and the fourth extension 17 is the same as the welding form of the first extension 14 and the second extension 15, which is not repeated here.

[0136] In some embodiments, the secondary battery 100 includes the first tab 20, which extends the first outer layer current collector 11a from the second edge 102, to improve the problem that the corner of the head of the secondary battery 100 is more prone to warping than the bottom.

[0137] In some embodiments, the secondary battery 100 includes the second tab 30, which extends the second outer layer current collector 13a from the fourth edge 104, to improve the problem that the corner of the head of the secondary battery 100 is more prone to warping than the bottom.

[0138] In some embodiments, the width D1 of the first extension 14 is 1mm≤D1≤5mm. By D1≥1mm, the welding difficulty of the first extension 14 and the second extension 15 is reduced, and the welding is facilitated. By D1≤5mm, the impact on the electrode assembly 10 is reduced, and the occupied space is reduced.

[0139] Optionally, D1 can be any value within a range consisting of any one or any two of 1mm, 2mm, 3mm, 4mm, and 5mm.

[0140] When the first extension 14 extends the first outer layer current collector 11a from the first edge 101 along the second direction Y, D1 is the width of the first extension 14 along the third direction Z.

[0141] When the first extension 14 extends the first outer layer current collector 11a from the second edge 102 along the third direction Z, D1 is the width of the first extension 14 along the second direction Y.

[0142] In some embodiments, the width D2 of the second extension 15 is 1mm≤D2≤5mm. By D2≥1mm, the welding difficulty of the first extension 14 and the second extension 15 is reduced, and the welding is facilitated. By D2≤5mm, the impact on the electrode assembly 10 is reduced, and the occupied space is reduced.

[0143] Optionally, D2 can be any value within a range consisting of any one or any two of 1mm, 2mm, 3mm, 4mm, and 5mm.

[0144] When the second extension 15 extends the second outer layer current collector 13a from the third edge 103 along the second direction Y, D2 is the width of the second extension 15 along the third direction Z.

[0145] D2 is the width of the second extension 15 along the second direction Y when the second extension 15 extends from the fourth edge 104 of the second outer current collector 13a along the third direction Z.

[0146] In some embodiments, the width D1 of the first extension 14 is equal to the width D2 of the second extension 15.

[0147] In some embodiments, the thickness H1 of the first extension 14 is 8 pm ≤ H1 ≤ 20 pm. By H1 ≥ 8 pm, the risk of the first extension 14 and the first tab 20 being too thin in thickness to break is reduced. By H1 ≤ 20 pm, the thickness of the first extension 14, the first outer current collector 11a and the first tab 20 is controlled, reducing the impact on the energy density of the secondary battery 100.

[0148] In some embodiments, the thickness H2 of the second extension 15 is 8 pm ≤ H2 ≤ 20 pm. 8 pm ≤ H2 ≤ 20 pm. By H2 ≥ 8 pm, the risk of the second extension 15 and the second tab 30 being too thin in thickness to break is reduced. By H2 ≤ 20 pm, the thickness of the second extension 15, the second outer current collector 13a and the second tab 30 is controlled, reducing the impact on the energy density of the secondary battery 100.

[0149] In some embodiments, the thickness H1 of the first extension 14 is equal to the thickness H2 of the second extension 15.

[0150] Please refer to Figure 1 , Figure 6 and Figure 7 In some embodiments, the first outer current collector 11a comprises a fifth corner 113, the second outer current collector 13a comprises a sixth corner 133, and the fifth corner 113 overlaps with the sixth corner 133 when viewed along the first direction X, and the fifth corner 113 is welded to the sixth corner 133. By welding the fifth corner 113 to the sixth corner 133, the fifth corner 113 and the sixth corner 133 are less likely to lift, improving the contact between the first outer tab 11 and the separator 12 and between the second outer tab 13 and the separator 12 in the lifted area of the fifth corner 113 and the sixth corner 133, reducing the risk of lithium ion transport path being blocked and thus causing lithium plating purple stain, affecting the performance of the secondary battery; improving the repeated mechanical stress of the lifted area during charging and discharging, which is conducive to reducing the risk of cracks in the active material layer on the first outer current collector 11a and / or the second outer current collector 13a, reducing the risk of the fifth corner 113 and / or the sixth corner 133 lifting and scratching the adhesive layer of the packaging bag, causing the adhesive layer to accumulate and hinder the extension of the first outer current collector 11a and / or the second outer current collector 13a, resulting in the risk of the first outer current collector 11a and / or the second outer current collector 13a being folded.

[0151] In some embodiments, the first outer layer current collector 11a comprises a seventh edge 107, the seventh edge 107 and the first edge 101 intersect at a fifth corner 113. The fifth corner 113 is defined in the same way as the first corner 111, which will not be repeated here.

[0152] In some embodiments, the second outer layer current collector 13a comprises an eighth edge 108, the eighth edge 108 and the third edge 103 intersect at a sixth corner 133. The sixth corner 133 is defined in the same way as the first corner 111, which will not be repeated here.

[0153] In some embodiments, the electrode assembly 10 comprises a fifth extension 18 and a sixth extension 19, the fifth extension 18 extends from the fifth corner 113 of the first outer layer current collector 11a, the sixth extension 19 extends from the sixth corner 133 of the second outer layer current collector 13a, the fifth extension 18 is welded to the sixth extension 19. Specifically, the fifth extension 18 is bent towards the second outer layer current collector 13a, the sixth extension 19 is bent towards the first outer layer current collector 11a, so that a part of the fifth extension 18 and a part of the sixth extension 19 overlap, and the overlapping part is welded to form a fourth welding part 18a.

[0154] In some embodiments, the welding of the fifth extension 18 and the sixth extension 19 is in the same way as the welding of the first extension 14 and the second extension 15, which will not be repeated here.

[0155] In some embodiments, the first outer layer current collector 11a comprises a seventh corner 114, the second outer layer current collector 13a comprises an eighth corner 134, and the seventh corner 114 and the eighth corner 134 overlap when viewed in the first direction X, and the seventh corner 114 is welded to the eighth corner 134. By welding the seventh corner 114 and the eighth corner 134, the warping of the seventh corner 114 and the eighth corner 134 is reduced, the poor contact between the first outer layer tab 11 and the separator film 12 and between the second outer layer tab 13 and the separator film 12 in the warping area of the seventh corner 114 and the eighth corner 134 is improved, the problem of blocked lithium ion transmission path caused by lithium plating is thus avoided, the performance of the secondary battery is affected; the warping area repeatedly bears mechanical stress during the charging and discharging process, which is beneficial to reduce the risk of cracks in the active material layer on the first outer layer current collector 11a and / or the second outer layer current collector 13a, reduce the risk of the seventh corner 114 and / or the eighth corner 134 warping and scratching the adhesive layer of the packaging bag, causing the adhesive layer to accumulate and hinder the extension of the first outer layer current collector 11a and / or the second outer layer current collector 13a, and the risk of the first outer layer current collector 11a and / or the second outer layer current collector 13a folding is reduced.

[0156] In some embodiments, the first outer current collector 11a includes a seventh edge 107, which intersects the fifth edge 105 at an eighth corner 134. The eighth corner 134 is defined in the same manner as the first corner 111, which will not be repeated here.

[0157] In some embodiments, the second outer current collector 13a includes an eighth edge 108, which intersects the sixth edge 106 at the eighth corner 134. The eighth corner 134 is defined in the same manner as the first corner 111, which will not be repeated here.

[0158] In some embodiments, the electrode assembly 10 includes a seventh extension 10A extending from the seventh corner 114 of the first outer current collector 11a and an eighth extension 10B extending from the eighth corner 134 of the second outer current collector 13a, the seventh extension 10A being welded to the eighth extension 10B. Specifically, the seventh extension 10A is bent towards the second outer current collector 13a, and the eighth extension 10B is bent towards the first outer current collector 11a, such that a portion of the seventh extension 10A and a portion of the eighth extension 10B overlap, and the overlapping portion is welded to form a fifth weld 10C.

[0159] In some embodiments, the welding of the seventh extension 10A and the eighth extension 10B is in the same manner as the welding of the first extension 14 and the second extension 15, which will not be repeated here.

[0160] In some embodiments, the widths and thicknesses of the third extension 16, the fourth extension 17, the fifth extension 18, the sixth extension 19, the seventh extension 10A, and the eighth extension 10B are the same as those of the first extension 14, which will not be repeated here.

[0161] In some embodiments, the electrode assembly 10 includes a second tab 10D, which is opposite in polarity to the first outer tab 11, and is disposed between adjacent separators 12, which are bonded to the areas of the second tab 10D and cover the second tab 10D. The first weld 14a, the third weld 16a, the fourth weld 18a, and the fifth weld 10C are in contact with the second tab 10D, which increases the risk of short circuit.

[0162] Embodiment Two

[0163] Please refer to Figures 8 to 11In some embodiments, the first extension 14 extends from the first corner 111 to the first outer current collector 11a, and the first extension 14 is welded to the second corner 131. That is, the first extension 14 extends from the first edge 101 or the second edge 102 of the region where the first corner 111 is located to the first outer current collector 11a, is bent to the side surface of the second outer current collector 13a away from the first outer current collector 11a, and is welded to the side surface in the region where the second corner 131 is located.

[0164] In some embodiments, the first extension 14 and the second corner 131 form a second welding portion 14b, and the length L2 of the second welding portion 14b is 1 mm≤L2≤2 mm in the length extension direction of the first extension 14. By L2≥1 mm, the welding strength of the second welding portion 14b is increased, and the risk of the second welding portion 14b falling off from the second corner 131 is reduced. By L2≤2 mm, the space occupied by the second welding portion 14b is reduced.

[0165] In some embodiments, the first extension 14 extends from the first intersection A, and the second welding portion 14b covers the second intersection B, further improving the problem of the second corner 131 being raised.

[0166] In some embodiments, the third extension 16 extends from the third corner 112 to the first outer current collector 11a, and the third extension 16 is welded to the fourth corner 132.

[0167] In some embodiments, the fifth extension 18 extends from the fifth corner 113 to the first outer current collector 11a, and the fifth extension 18 is welded to the sixth corner 133.

[0168] In some embodiments, the seventh extension 10A extends from the seventh corner 114 to the first outer current collector 11a, and the seventh extension 10A is welded to the eighth corner 134.

[0169] The present application is described in detail below through specific examples and comparative examples. In the present application, the first outer pole piece 11 and the second outer pole piece 13 are taken as examples of positive pole pieces, and the second pole piece 10D is taken as an example of a negative pole piece, and the preparation process and test method are described in detail. It should be understood by those skilled in the art that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.

[0170] Example 1

[0171] Preparation of the positive electrode sheet: the positive electrode active material lithium cobaltate, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1:1.5 in an N-methyl pyrrolidone (NMP) solution to form a positive electrode slurry. An aluminum foil was used as the positive electrode current collector, and the positive electrode slurry was coated on the positive electrode current collector. After drying, cold pressing, and slitting, the positive electrode sheet was obtained. The first outer sheet and the second outer sheet were obtained by cutting. The first outer sheet included a first extension, and the second outer sheet included a second extension.

[0172] Preparation of the negative electrode sheet: the negative electrode active material artificial graphite, the thickening agent sodium carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, and deionized water was added. The mixture was stirred uniformly in a vacuum stirrer to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on a copper foil current collector. After drying, cold pressing, cutting, and slitting, the negative electrode sheet was obtained.

[0173] Preparation of the separator film: a polyethylene (PE) film with a thickness of 9 μm was selected.

[0174] Preparation of the electrolyte: in a dry argon glove box, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 3:5:2. Lithium salt LiPF6 was added, and the mixture was stirred uniformly to obtain an electrolyte. The mass percentage concentration of LiPF6 was 12.5%.

[0175] Preparation of the electrode assembly: the positive electrode sheet, the separator film, and the negative electrode sheet were stacked and arranged such that the separator film covered the negative electrode sheet. The first extension and the second extension were welded, and the first corner was connected to the second corner. A plurality of first tabs were gathered to form a tab assembly and were welded to the first adapter. A plurality of second tabs extended out of the separator film, were gathered to form a tab assembly, and were welded to the second adapter.

[0176] Assembly of the electrode assembly: an aluminum plastic film with a punched pit was placed in an assembly clamp with the pit surface facing up. The electrode assembly was placed in the pit, and an external force was applied to compress it. Then, another aluminum plastic film with a punched pit was placed on the electrode assembly with the pit surface facing down. The periphery of the two aluminum plastic films was heat-sealed by hot pressing to obtain an assembled electrode assembly.

[0177] Liquid injection packaging: the electrolyte was injected into the assembled electrode assembly. After vacuum packaging, standing, hot pressing, and shaping, a secondary battery was obtained.

[0178] Example 2

[0179] The difference between Example 1 and Example 2 is that, in the preparation of the electrode assembly, in addition to welding the first corner to the second corner, the third corner is also welded to the fourth corner.

[0180] Example 3

[0181] The difference from Example 1 is that, during the preparation of the electrode assembly, in addition to welding the first corner position to the second corner position, the third corner position is welded to the fourth corner position, the fifth corner position is welded to the sixth corner position, and the seventh corner position is welded to the eighth corner position.

[0182] Example 4

[0183] The difference from Example 1 is that, during the preparation of the electrode assembly, the first corner position is welded to the second corner position through the first extension.

[0184] Comparative Example 1

[0185] The difference from Example 1 is that the outermost positive electrode tab is not provided with the first extension and the second extension.

[0186] Then, 50 secondary batteries of each example and comparative example are taken for purple spot lithium precipitation area test and outer layer current collector folding test, respectively. The test results are recorded in Table 1.

[0187] The outer layer current collector folding test method is as follows: (1) maintain the test temperature at 25°C, and place the secondary battery 100 for 30 min; (2) 2.5C constant current charging to 4.25V, and then constant voltage charging to 2C; (3) 2C constant current charging to 4.35V, and then constant voltage charging to 1.5C; (4) 1.5C constant current charging to 4.3V, and then constant voltage charging to 1C; (5) 1.0C constant current charging to 4.53V, and then constant voltage charging to 0.025C; (6) stand for 5 min, 1.0C constant current discharging to 3V; (7) stand for 5 min; (8) cycle steps 2 to 7 for 800 times.

[0188] Judgment standard: after the cycle is completed, the secondary battery is disassembled, and whether the first outer layer current collector and the second outer layer current collector are folded is observed; the number of test batteries is 50, the number of batteries with folding is Y, and the occurrence ratio is Y / 50.

[0189] Purple spot / lithium precipitation area test: after 800 cycles, the secondary battery is disassembled, and the purple spot and lithium precipitation state of the negative electrode tab are observed. The area of the negative electrode tab surface without lithium precipitation is golden yellow, the purple spot area is dark purple, and the lithium precipitation area is grayish white. The percentage of purple spot and lithium precipitation area is calculated based on the total area of the single-sided negative electrode material layer. High-resolution optical microscopy combined with color threshold segmentation;

[0190] The surface image of the pole piece is taken by optical microscope, and the different regions are identified by significant color difference (golden yellow lithium precipitation-free area, deep purple purple spot area, and gray white lithium precipitation area). The color threshold is segmented using image processing software (ImageJ, PythonOpenCV), and the area ratio of each region can be quantitatively calculated.

[0191] The judgment standard of the purple spot lithium precipitation state on the surface of the negative pole piece is as follows: the purple spot lithium precipitation area is less than or equal to 2% for no lithium precipitation, the purple spot lithium precipitation area is less than or equal to 5% for slight lithium precipitation, the purple spot lithium precipitation area is 5% to 10% for moderate lithium precipitation, and the purple spot lithium precipitation area is greater than 10% for severe lithium precipitation. The number of test batteries is 50, the number of lithium precipitation-free batteries is A, the number of slightly lithium precipitated batteries is B, the number of moderately lithium precipitated batteries is C, and the number of severely lithium precipitated batteries is D. The lithium precipitation state is A / 50, B / 50, C / 50, and D / 50.

[0192] It should be noted that, in addition to the parameters in the table, the other parameters of Comparative Example 1 are the same as those of Example 1.

[0193] Table 1 (other parameters of Examples 1 to 11 except the parameters involved in Table 1 are the same as those of Example 1)

[0194]

[0195] From the data in Table 1, compared with Comparative Example 1, Example 1 connects the first corner position to the second corner position by the first extension and the second extension, thereby improving the problem of purple spot lithium precipitation of the secondary battery in Example 1 and reducing the risk of folding of the outermost current collector. Example 4 connects the first corner position to the second corner position by the first extension, thereby improving the problem of purple spot lithium precipitation of the secondary battery in Example 4 and reducing the risk of folding of the outermost current collector.

[0196] Compared with Example 1, Example 2 connects the first corner position to the second corner position and the third corner position to the fourth corner position, thereby further improving the problem of purple spot lithium precipitation of the secondary battery in Example 2 and reducing the risk of folding of the outermost current collector.

[0197] Compared with Example 1, Example 3 connects the first corner position to the second corner position, the third corner position to the fourth corner position, the fifth corner position to the sixth corner position, and the seventh corner position to the eighth corner position, thereby further improving the problem of purple spot lithium precipitation of the secondary battery in Example 3 and further reducing the risk of folding of the outermost current collector.

[0198] Examples 4 to 20

[0199] The difference from Example 1 is that L 1、The values of L2, D1, D2, H1 and H2 are recorded in Table 2.

[0200] Then, 20 secondary batteries of each example were taken for peel strength test and volume energy density test, and the test results are recorded in Table 2.

[0201] Peel strength test method:

[0202] The test temperature was 20±5℃, 100 secondary batteries were disassembled, and the first welding part was taken out. Then, the first extension part of the sample was fixed on the upper clamp, and the second extension part (second outer current collector) of the sample was fixed on the lower clamp, to ensure that the sample would not break or separate from the clamp during the peeling process. The force applied to the sample was recorded using a load sensor, and the deformation of the sample was recorded by a displacement sensor. The peeling angle was set to 180°, and the peeling speed was set to 3mm / min. The sample was stretched until it was completely pulled apart, and the test was stopped. The force value and displacement data during the peeling process were recorded, and the peel strength = maximum peeling force (N) / sample width (mm). The average value was taken as the test result.

[0203] The volume energy density test steps are as follows:

[0204] 1) Under the environmental conditions of 25℃, the secondary battery was placed for 10min, and then charged at 0.2C constant current to 4.5V, and charged at constant voltage to 0.02C, and then placed for 5min; then discharged at 0.2C constant current to 3V, and then placed for 5min, and then the discharge capacity C0was recorded; 2) The volume energy density was calculated by the following formula: volume energy density = platform voltage x C0 / volume of secondary battery.

[0205] It should be noted that the parameters in Table 2 are different from those in Examples 1-20, except that the parameters in Table 2 are different from those in Examples 1-20.

[0206] Table 2

[0207]

[0208]

[0209] From Table 2, Examples 1, 5-8, the length of the first welding part L1 is 1mm≤L1≤2mm, and the first extension part and the second extension part have high peel strength. At the same time, the welding part occupies a reasonable space, and has little effect on the energy density of the secondary battery.

[0210] From Table 2, Examples 4, 9-12, the length of the second welding part L2 is 1mm≤L2≤2mm, and the peel strength of the first extension part and the second outer current collector is high. And the welding part occupies a reasonable space, and has little effect on the energy density of the secondary battery.

[0211] As can be seen from Table 2, Example 1, Examples 13-16, when 1mm≤D1≤5mm, 1mm≤D2≤5mm, the first and second extensions are easy to weld, have high peel strength, and the secondary battery has high energy density.

[0212] As can be seen from Table 2, Example 1, Examples 17-20, when 8μm≤H1≤20μm, the first extension has high peel strength, and the secondary battery has high energy density. When 8μm≤H2≤20μm, the second extension has high peel strength, and the secondary battery has high energy density.

[0213] Referring to Figure 12 The application also provides a power consuming device 200 using the secondary battery 100. In an embodiment, the power consuming device 200 of the application can be, but is not limited to, an electronic device, a drone, a backup power supply, an electric vehicle, an electric motorcycle, an electric power-assisted bicycle, an electric tool, a household large-scale battery module, etc.

[0214] Those skilled in the art should recognize that the above examples are only used to illustrate the application, and are not used as a limitation of the application. Any suitable changes and variations to the above examples, as long as they fall within the spirit and scope of the application, are within the scope of the disclosure of the application.

Claims

1. A secondary battery, characterized in that, The device includes an electrode assembly, which has a stacked structure. The electrode assembly includes a first outer electrode, a separator, and a second outer electrode arranged along a first direction. The first outer electrode includes a first outer current collector, and the second outer electrode includes a second outer current collector. The first outer current collector includes a first corner position, and the second outer current collector includes a second corner position. When viewed along the first direction, the first corner position and the second corner position at least partially overlap. The first outer electrode also includes a first extension, which extends out of the first outer current collector from the first corner, and the first extension is welded and fixedly connected to the second outer current collector.

2. The secondary battery as described in claim 1, characterized in that, The electrode assembly further includes a second extension that extends from the second corner position into the second outer current collector, and the first extension is fixedly connected to the second extension.

3. The secondary battery as described in claim 1, characterized in that, The first extension is welded to the second corner.

4. The secondary battery as described in claim 2, characterized in that, The first extension is welded to the second extension.

5. The secondary battery as described in claim 1, characterized in that, It also includes a first tab, and the first outer current collector also includes a second edge, one of the edges of the first corner is a part of the second edge, and the first tab is connected to the second edge.

6. The secondary battery as described in claim 4, characterized in that, Along the thickness direction of the first extension, the first extension includes opposing first connecting surfaces and second connecting surfaces, the first connecting surfaces facing the electrode assembly; along the thickness direction of the second extension, the second extension includes opposing third connecting surfaces and fourth connecting surfaces, the third connecting surfaces facing the electrode assembly. The first connecting surface is welded to the fourth connecting surface to form a first welded part; or the second connecting surface is welded to the third connecting surface to form a first welded part; or the first connecting surface is welded to the third connecting surface to form a first welded part that is bent along the first direction. Along the first direction, the length L1 of the first welded portion is 1mm≤L1≤2mm.

7. The secondary battery as described in claim 3, characterized in that, The first extension is welded to the second corner position to form a second welded part. The length L2 of the second welded part is 1mm≤L2≤2mm along the length extension direction of the first extension.

8. The secondary battery as described in claim 2, characterized in that, The width D1 of the first extension is 1mm ≤ D1 ≤ 5mm; and / or the width D2 of the second extension is 1mm ≤ D2 ≤ 5mm.

9. The secondary battery as described in claim 2, characterized in that, The thickness H1 of the first extension is 8μm ≤ H1 ≤ 20μm; and / or the thickness H2 of the second extension is 8μm ≤ H2 ≤ 20μm.

10. The secondary battery as described in claim 1, characterized in that, The electrode assembly includes a second electrode sheet with the opposite polarity to the first outer electrode sheet. The second electrode sheet is disposed between adjacent insulating films, and the adjacent insulating films are bonded to the regions extending beyond the second electrode sheet and cover the second electrode sheet.

11. The secondary battery as described in claim 2, characterized in that, The first extension is bent relative to the first outer current collector and forms a first included angle α, 90°≤α≤120°; The second extension is bent relative to the second outer current collector and forms a second included angle β, 90°≤β≤120°, and the first extension is welded to the second extension.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, The first outer current collector includes a third corner position, and the second outer current collector includes a fourth corner position. When viewed along the first direction, the third corner position and the fourth corner position overlap. The electrode assembly also includes a third extension, which extends out of the first outer current collector from the third corner position. The third extension is welded to the fourth corner position; Alternatively, the electrode assembly may further include a fourth extension that extends from the fourth corner of the second outer current collector, and the third extension is welded to the fourth extension.

13. The secondary battery as described in claim 12, characterized in that, It also includes the first and second pole ears; The first outer current collector includes a second edge, one of the edges of the first corner position is a part of the second edge, one of the edges of the third corner position is a part of the second edge, and the first electrode tab is connected to the second edge; The second outer current collector includes a fourth edge, one of the edges of the second corner position is a part of the fourth edge, and one of the edges of the fourth corner position is a part of the fourth edge, and the second electrode is connected to the fourth edge.

14. The secondary battery as described in claim 12, characterized in that, The first outer current collector includes a fifth corner position, and the second outer current collector includes a sixth corner position. When viewed along the first direction, the fifth corner position and the sixth corner position overlap. The electrode assembly also includes a fifth extension, which extends out of the first outer current collector from the fifth corner position. The fifth extension is welded to the sixth corner position; Alternatively, the electrode assembly may further include a sixth extension that extends from the sixth corner of the second outer current collector, and the fifth extension is welded to the sixth extension.

15. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 14.

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