Battery cells and electrical equipment

Abstract

This application discloses a battery cell and an electrical device. The battery cell includes a first pole piece. The first pole piece includes a composite current collector, a first active material layer, a protective layer, and a first electrical connecting member. The composite current collector includes a first section, a second section, and a third section arranged along a first direction. The second section connects the first section and the third section. The first active material layer is connected to the first section. The first active material layer and the composite current collector are arranged along a second direction, which is perpendicular to the second direction. The protective layer is connected to the second section. The first electrical connecting member is connected to the third section. The protective layer, the first active material layer, and the first electrical connecting member are arranged on the same side of the composite current collector. The width W1 of the protective layer along the first direction satisfies 1.0 mm≦W1≦2.4 mm, and the second direction is the thickness direction of the first pole piece. This increases the headspace of the battery cell, facilitates bending of the electrode terminal, and improves the process pass rate.

Description

[Technical Field]

[0001] This application relates to the field of energy storage technology, and in particular to battery cells and electrical devices. [Background technology]

[0002] Currently, composite current collectors are connected to electrode terminals by welding aluminum rods, but there are weld marks between the composite current collector and the aluminum rod. To avoid issues such as weld fractures and incomplete welding that can cause battery capacity loss, the electrode terminals must avoid the location of the weld marks, which causes the electrode terminals to move outward and occupy part of the head space of the battery cell. As a result, it becomes more difficult to bend the electrode terminals within the head space, which can lead to battery cell deformation and breakage due to excessive tension on the electrode terminals. Summary of the Invention [Problem to be solved by the invention]

[0003] In view of this situation, it is necessary to provide a battery cell and an electrical device that can increase the head space of the battery cell and improve the reconnection rate of the electrode terminals. [Means for solving the problem]

[0004] An embodiment of the present application provides a battery cell, the battery cell including a first pole piece. The first pole piece includes a composite current collector, a first active material layer, a protective layer, and a first electrical connection member. The composite current collector includes a first section, a second section, and a third section arranged along a first direction. The second section connects the first section and the third section. The first active material layer is connected to the first section. The first active material layer and the composite current collector are arranged along a second direction, and the first direction is perpendicular to the second direction. The protective layer is connected to at least the second section and isolates burrs in the second section. The first electrical connection member is connected to the third section, and the first electrical connection member is used to connect to an external electrical device. The protective layer, the first active material layer, and the first electrical connection member are arranged on the same side of the composite current collector. The width W1 of the protective layer located in the second section along the first direction satisfies 1.0 mm≦W1≦2.4 mm, and the second direction is the thickness direction of the first pole piece. Covering this area with a protective layer isolates burrs, reducing the risk of burrs piercing the isolation membrane and causing a short circuit. Furthermore, reducing the width of the protective layer increases the distance between the battery cell case and the location where the first electrical connection member connects to the third section, and the distance between the battery cell case and the location where the electrode terminal connects to the first electrical connection member. This also increases the head space of the battery cell, making it easier to bend the electrode terminal and improving the process pass rate.

[0005] Optionally, in some embodiments of the present application, the width W1 of the protective layer along the first direction satisfies 1.0 mm≦W1≦1.5 mm, which can further increase the distance between the position where the first electrical connection member connects to the third section and the battery cell case, and the distance between the position where the electrode terminal connects to the first electrical connection member and the battery cell case, thereby further increasing the head space of the battery cell, making it easier to bend the tab, and improving the process pass rate.

[0006] Optionally, in some embodiments of the present application, the protective layer includes an insulating layer, and the thickness h1 of the insulating layer along the second direction satisfies 12 μm≦h1≦30 μm. The insulating layer is used to reduce the risk of burrs piercing the separator and causing a short circuit between the first pole piece and the second pole piece. The sum S1 of the thickness of the insulating layer and the thickness of the composite current collector along the second direction satisfies 18 μm≦S1≦45 μm, which can reduce the space occupied by the insulating layer along the second direction and increase the head space of the battery cell.

[0007] Optionally, in some embodiments of the present application, the protective layer includes an insulating layer, and the thickness h1 of the insulating layer along the second direction satisfies 12 μm≦h1≦15 μm, and the sum S1 of the thickness of the insulating layer and the thickness of the composite current collector along the second direction satisfies 18 μm≦S1≦30 μm, thereby effectively covering burrs and reducing the possibility that the burrs will protrude from the insulating layer and pierce the separator, and further reducing the space occupied by the insulating layer along the second direction, thereby increasing the headspace of the battery cell.

[0008] Optionally, in some embodiments of the present application, the protective layer includes a conductive underlayer, and the thickness h2 of the conductive underlayer along the second direction satisfies 2 μm≦h2≦30 μm, and the sum S2 of the thickness of the conductive underlayer and the thickness of the composite current collector satisfies 8 μm≦S2≦45 μm, thereby effectively covering burrs and reducing the possibility that the burrs will protrude from the insulating layer and pierce the separator, and further reducing the space occupied by the insulating layer along the second direction, thereby increasing the headspace of the battery cell.

[0009] Optionally, in some embodiments of the present application, the protective layer includes a conductive underlayer, and the thickness h2 of the conductive underlayer along the second direction satisfies 2 μm≦h2≦5 μm, and the sum S2 of the thickness of the conductive underlayer and the thickness of the composite current collector along the second direction satisfies 8 μm≦S2≦20 μm, thereby effectively covering burrs and reducing the possibility that the burrs will protrude from the insulating layer and pierce the separator, and further reducing the space occupied by the conductive underlayer along the second direction, thereby increasing the headspace of the battery cell.

[0010] Optionally, in some embodiments of the present application, the width W2 of the first electrical connection member along the first direction satisfies 3 mm≦W2≦5 mm. This reduces the space occupied by the first electrical connection member along the first direction and further increases the distance between the position where the first electrical connection member connects to the electrode terminal and the battery cell case, thereby increasing the head space of the battery cell and facilitating bending of the electrode terminal. The thickness h3 of the first electrical connection member along the second direction satisfies 5 μm≦h3≦20 μm. This reduces the space occupied by the first electrical connection member along the second direction and increases the head space of the battery cell, facilitating bending of the electrode terminal.

[0011] Optionally, in some embodiments of the present application, the first electrical connection member is welded to the third section to form a welded region. The width W3 of the welded region along the first direction satisfies 1.8 mm≦W3≦2 mm. Controlling the width of the welded region increases the space between the electrode terminal and the first electrical connection member and the battery cell case along the first direction, further increasing the head space of the battery cell and facilitating bending of the electrode terminal. The thickness S3 of the welded region along the second direction satisfies 18 μm≦S3≦57 μm. This increases the connection strength between the first electrical connection member and the third section, while reducing the space occupied by the welded region along the second direction, increasing the head space of the battery cell and facilitating bending of the electrode terminal.

[0012] Optionally, in some embodiments of the present application, the thickness S3 of the welding region along the second direction satisfies 18 μm≦S3≦37 μm, which can further reduce the space occupied by the welding region along the second direction, further increase the head space of the battery cell, and facilitate bending of the electrode terminal.

[0013] Optionally, in some embodiments of the present application, a first active material layer is provided evenly on both sides of the first section along the second direction, a protective layer is provided on both sides of the second section, and a first electrical connection member is provided on both sides of the third section.

[0014] Optionally, in some embodiments of the present application, the protective layer includes an insulating layer. In the second direction, the total thickness S of the insulating layers on both sides and the thickness of the composite current collector 11 is 30μm≦S 11 When the first active material is applied to both sides of the composite current collector, the space occupied by the insulating layer in the second direction can be reduced, the head space of the battery cell can be increased, and the electrode terminal can be easily bent.

[0015] Optionally, in some embodiments of the present application, the protective layer includes a conductive underlayer. Along the second direction, the total thickness S of the conductive underlayers on both sides and the thickness of the composite current collector 21 is 10μm≦S 21 When the first active material is applied to both sides of the composite current collector, the space occupied by the insulating layer in the second direction can be further reduced, the head space of the battery cell can be further increased, and bending of the electrode terminal can be facilitated.

[0016] Optionally, in some embodiments of the present application, a difference A in width between the protective layers provided on both sides of the second section along the first direction satisfies 0≦A≦0.4 mm.

[0017] Optionally, in some embodiments of the present application, the first electrical connection members provided on both sides of the third section are welded to the third section to form a welded area, and the difference B in width between the welded areas located on both sides of the third section along the first direction satisfies 0≦B≦0.25 mm.

[0018] Optionally, in some embodiments of the present application, a conductive underlayer is further provided between the first active material layer and the composite current collector, and the conductive underlayer has a resistance R satisfying 1 mohm≦R≦20 mohm, and the conductive underlayer located between the first active material layer and the composite current collector has a thickness h along the second direction. 21 is 1 μm ≦ h 21The conductive underlayer is used to improve the interface of the composite current collector, increase the adhesion between the composite current collector and the first active material layer, establish a conductive network between the conductive underlayer, the first active material layer, and the composite current collector, and improve electron transfer efficiency.

[0019] Optionally, in some embodiments of the present application, the width T of the third section along the first direction satisfies 1 mm≦T≦5 mm, thereby increasing the welding strength between the first electrical connection member and the third section and improving the reliability of the welding between the first electrical connection member and the third section.

[0020] Optionally, in some embodiments of the present application, the material of the insulating layer includes at least one of an inorganic ceramic and a non-conductive organic polymeric material.

[0021] Optionally, in some embodiments of the present application, the material of the conductive underlayer includes at least one of aluminum oxide, silicon oxide, silicon carbide, amorphous carbon, lithium phosphate oxynitride (LiPON), and titanium diboride.

[0022] An embodiment of the present application further provides an electrical device, the electrical device including the battery of any of the above-described embodiments. [Brief explanation of the drawings]

[0023] [Figure 1] 1 illustrates a structural schematic diagram of a battery cell according to some embodiments. [Figure 2] 1 shows a partial cross-sectional schematic view of a first pole piece according to some embodiments. [Figure 3] 10 shows a structural schematic diagram of a battery cell according to some embodiments, viewed from a second direction. [Figure 4] 10A and 10B show partial cross-sectional schematic views of a first pole piece in some other embodiments. [Figure 5] 10A and 10B show structural schematic diagrams of battery cells according to other embodiments viewed from a second direction. [Figure 6]1 shows a partial cross-sectional schematic view of a composite current collector according to some embodiments. [Figure 7] 5A and 5B are schematic partial cross-sectional views of the first pole piece shown in FIG. 4 in some other embodiments. [Figure 8] 10A and 10B show partial cross-sectional schematic views of first pole pieces in still other embodiments. [Figure 9] 10A and 10B show partial cross-sectional schematic views of first pole pieces in still other embodiments. [Figure 10] 1 illustrates a structural schematic diagram of an electrical device according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0024] The following specific examples, taken in conjunction with the above-mentioned accompanying drawings, further illustrate the present application.

[0025] The following specific embodiments are illustrative and not restrictive, and are intended to provide a basic understanding of the present application, but are not intended to identify key or critical elements of the present application or to limit the scope of protection. As long as there is no structural contradiction, the technical features mentioned in each embodiment can be combined in any manner.

[0026] When a component is considered to be "mounted" on another component, it may be mounted directly on the other component, or there may be intermediate components present. When a component is considered to be "connected" to another component, it may be mounted directly on the other component, or there may be intermediate components present.

[0027] Unless otherwise defined, the term "plurality" in this document, when describing a quantity of parts, specifically refers to two or more of the parts.

[0028] 1 to 5, one embodiment of the present application provides a battery cell 100, which includes a battery cell case 101, an electrode assembly (not shown), and an electrode terminal 102, where the electrode assembly is disposed within the battery cell case 101, and the electrode terminal 102 is connected to the electrode assembly and protrudes from the battery cell case 101. In one embodiment, the head space of the battery cell 100 refers to the space between the side of the battery cell case 101 from which the electrode terminal 102 protrudes and the electrode assembly.

[0029] In one embodiment, the electrode assembly includes a first pole piece 10, a second pole piece (not shown), and a separator (not shown), and the first pole piece 10, the separator, and the second pole piece are stacked in order to form one electrode assembly unit, and multiple electrode assembly units are further stacked to form an electrode assembly. In another embodiment, the electrode assembly has a wound structure, and is formed by stacking the first pole piece 10, the separator, and the second pole piece in order and then winding them.

[0030] In some embodiments, the first pole piece 10 is a negative pole piece or a positive pole piece, and the second pole piece is a pole piece of opposite polarity to the first pole piece.

[0031] In one embodiment, the battery cell 100 includes two electrode terminals 102, and the polarities of the two electrode terminals 102 are opposite. Optionally, the two electrode terminals 102 protrude from the battery cell case 101 on different sides. Optionally, the two electrode terminals 102 protrude from the battery cell case 101 on the same side.

[0032] 2 to 5, in one embodiment, the first pole piece 10 includes a composite current collector 11, a first active material layer 12, a protective layer 13, and a first electrical connection member 14. The composite current collector 11 includes a first section 111, a second section 112, and a third section 113 arranged along a first direction X, and the second section 112 connects the first section 111 and the third section 113. The composite current collector 11 includes a first side 11a and a second side 11b arranged along a second direction Y. Optionally, the first direction X is a direction in which the electrode terminal 102 protrudes from the battery cell case 101, the second direction Y is a thickness direction of the first pole piece 10, and the first direction X is perpendicular to the second direction Y.

[0033] The first active material layer 12 is connected to the first section 111, the protective layer 13 is connected to the second section 112, the first electrical connection member 14 is connected to the third section 113, and the electrode terminal 102 is connected to the first electrical connection member 14. The first active material layer 12, the protective layer 13, and the first electrical connection member 14 are all connected to the first side 11a. The width W1 of the protective layer 13 located in the second section 112 along the first direction X satisfies 1.0 mm≦W1≦2.4 mm. Burrs that appear in areas of the composite current collector 11 where the first active material layer 12 is not provided are likely to pierce the separator. In the present application, the protective layer 13 covers these areas and sets the minimum width of the protective layer 13 to 1.0 mm, thereby isolating the burrs and reducing the risk of the burrs piercing the separator and causing a short circuit. Furthermore, by reducing the width range of the protective layer 13, the distance between the position where the first electrical connection member 14 connects to the third section 113 and the battery cell case 101 and the distance between the position where the electrode terminal 102 connects to the first electrical connection member 14 and the battery cell case 101 can be increased, which further increases the head space of the battery cell 100, makes it easier to bend the electrode terminal 102, and improves the process pass rate. Optionally, the width W1 of the protective layer 13 located in the second section 112 may be any one of 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, and 2.4 mm.

[0034] Optionally, along the first direction X, the width W1 of the protective layer 13 located in the second section 112 satisfies 1.5 mm < W1 ≤ 1.8 mm. Thereby, the distance between the position where the first electrical connection member 14 connects to the third section 113 and the battery cell case 101, and the distance between the position where the electrode terminal 102 connects to the first electrical connection member 14 and the battery cell case 101 can be increased. Furthermore, the head space of the battery cell 100 can be increased, facilitating the folding of the tab, improving the process qualification rate, and being more advantageous for isolating burrs and reducing the short - circuit risk. Optionally, the width W1 of the protective layer 13 located in the second section 112 may be any one of 1.6 mm, 1.7 mm, and 1.8 mm.

[0035] Optionally, along the first direction X, the width W1 of the protective layer 13 located in the second section 112 satisfies 1.0 mm ≤ W1 ≤ 1.5 mm. Thereby, the distance between the position where the first electrical connection member 14 connects to the third section 113 and the battery cell case 101, and the distance between the position where the electrode terminal 102 connects to the first electrical connection member 14 and the battery cell case 101 can be further increased. Furthermore, the head space of the battery cell 100 can be increased, facilitating the folding of the tab, and further improving the process qualification rate. The width W1 of the protective layer 13 may be any one of 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, and 1.5 mm.

[0036] Referring to FIG. 6, in one embodiment, the composite current collector 11 includes a first metal layer 114, a polymer layer 115, and a second metal layer 116, and the polymer layer 115 is provided between the first metal layer 114 and the second metal layer 116. The first active material layer 12 is connected to the first metal layer 114 and / or the second metal layer 116.

[0037] In one embodiment, along the second direction Y, the thickness H of the composite current collector 11 satisfies 6 μm ≤ H ≤ 15 μm. The thickness H of the composite current collector 11 may be any one of 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm.

[0038] In one embodiment, the thickness D1 of the first metal layer 114 satisfies 0.5 μm≦D1≦2 μm, and may be any one of 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, and 2.0 μm. The thickness D2 of the second metal layer 116 satisfies 0.5 μm≦D2≦2 μm. The thickness D2 of the second metal layer 116 may be any one of 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, and 2.0 μm.

[0039] In one embodiment, the width T of the third section 113 along the first direction X satisfies 1 mm≦T≦5 mm, thereby increasing the welding strength between the first electrical connection member 14 and the third section 113 and improving the reliability of the welding between the first electrical connection member 14 and the third section 113. Alternatively, the width T of the third section 113 may be any one of 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm.

[0040] In one embodiment, the first active material layer 12 is applied to the first section 111 of the composite current collector 11 by extrusion coating, transfer coating, spray coating, or the like. Optionally, the coating weight M of the first active material layer 12 is 100 mg / 1540.25 mm. 2 ≦M≦400mg / 1540.25mm 2 Alternatively, the coating weight M of the first active material layer 12 may be any one of 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, and 400, and the unit of M is mg / 1540.25mm. 2 is.

[0041] 2, 3, and 6, in one embodiment, the protective layer 13 includes an insulating layer. When the first pole piece 10, separator, and second pole piece are stacked or wound, the insulating layer is located between the separator and the composite current collector 11. This insulating layer isolates burrs on the first metal layer 114 or the second metal layer 116 of the composite current collector 11, reducing the risk of the burrs piercing the separator and causing a short circuit between the first pole piece 10 and the second pole piece. Optionally, the material of the insulating layer includes at least one of an inorganic ceramic and a non-conductive organic polymer material. Along the second direction Y, the thickness h1 of the insulating layer satisfies 12 μm≦h1≦30 μm, and the sum S1 of the thickness of the insulating layer and the thickness of the composite current collector 11 satisfies 18 μm≦S1≦45 μm. This effectively covers the burrs, reducing the likelihood of the burrs protruding from the insulating layer and piercing the separator. It also reduces the space occupied by the insulating layer along the second direction Y, thereby increasing the headspace of the battery cell 100. Alternatively, the thickness h1 of the insulating layer may be any one of 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, and 30 μm. Alternatively, S1 may be any one of 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, and 45 μm.

[0042] Optionally, along the second direction Y, the thickness h1 of the insulating layer is 15 μm.

[0043] Optionally, the thickness h1 of the insulating layer along the second direction Y satisfies 12 μm≦h1≦15 μm, and the sum S1 of the thickness of the insulating layer and the thickness of the composite current collector 11 satisfies 18 μm≦S1≦30 μm. This effectively covers burrs, reducing the possibility that burrs will protrude from the insulating layer and pierce the separator, and further reduces the space occupied by the insulating layer along the second direction Y, thereby further increasing the head space of the battery cell 100. Optionally, the thickness h1 of the insulating layer may be any one of 12 μm, 13 μm, 14 μm, and 15 μm. Optionally, S1 may be any one of 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, and 30 μm.

[0044] During sample preparation, the insulating layer and active material are simultaneously applied to the current collector and dispensed side-by-side from the same nozzle. The insulating layer requires the use of a custom application shim, and the active material and insulating layer have different thicknesses and widths at the shim exit.

[0045] ​Referring to Figures 4, 5 and 6, in one embodiment, the protective layer 13 includes a conductive base layer. When the first pole piece 10, the separator and the second pole piece are stacked or wound, the conductive base layer is located between the separator and the composite current collector 11, and can isolate burrs on the first metal layer 114 or the second metal layer 115 of the composite current collector 11, thereby reducing the risk of the burrs piercing the separator and causing a short circuit between the first pole piece 10 and the second pole piece.

[0046] Optionally, the material of the conductive underlayer includes at least one of aluminum oxide, silicon oxide, silicon carbide, amorphous carbon, lithium phosphate oxynitride, and titanium diboride. Along the second direction Y, the thickness h2 of the conductive underlayer satisfies 2 μm≦h2≦30 μm, and the sum S2 of the thickness of the conductive underlayer and the thickness of the composite current collector 11 satisfies 8 μm≦S2≦45 μm. This effectively covers burrs, reducing the possibility that the burrs will protrude from the insulating layer and pierce the separator, while also reducing the space occupied by the conductive underlayer along the second direction Y and increasing the headspace of the battery cell 100. Alternatively, the thickness h2 of the conductive underlayer may be any one of 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, and 30 μm. Alternatively, S2 may be any one of 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, and 45 μm.

[0047] Optionally, along the second direction Y, the thickness h2 of the conductive base layer satisfies 5 μm < h2 ≤ 10 μm, and the total S2 of the thickness of the conductive base layer and the thickness of the composite current collector 11 satisfies 11 μm ≤ S2 ≤ 25 μm. Thereby, burrs can be more effectively covered, the possibility that the burrs protrude from the insulating layer and pierce the isolation film can be further reduced, the space occupied by the conductive base layer along the second direction Y can be further reduced, and the head space of the battery cell 100 can be enlarged. Optionally, the thickness h2 of the conductive base layer may be any one of 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm. Optionally, S2 may be any one of 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, and 25 μm.

[0048] Optionally, along the second direction Y, the thickness h2 of the conductive base layer satisfies 2 μm ≤ h2 ≤ 5 μm, and the total S2 of the thickness of the conductive base layer and the thickness of the composite current collector 11 satisfies 8 μm ≤ S2 ≤ 20 μm. Thereby, burrs can be effectively covered, the possibility that the burrs protrude from the insulating layer and pierce the isolation film can be reduced, the space occupied by the conductive base layer along the second direction Y can be further reduced, and the head space of the battery cell 100 can be further enlarged. Optionally, the thickness h2 of the conductive base layer may be any one of 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, and 5 μm. Optionally, S2 may be any one of 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, and 20 μm.

[0049] 7 , in one embodiment, a conductive underlayer is provided between the first active material layer 12 and the composite current collector 11. The conductive underlayer is used to improve the interface of the composite current collector 11, increase adhesion between the composite current collector 11 and the first active material layer 12, establish a conductive network between the conductive underlayer, the first active material layer 12, and the composite current collector 11, and improve electron transfer efficiency. The resistance R of the conductive underlayer satisfies 1 mohm≦R≦20 mohm. Alternatively, the resistance R may be any one of 1 mohm, 2 mohm, 3 mohm, 4 mohm, 5 mohm, 6 mohm, 7 mohm, 8 mohm, 9 mohm, 10 mohm, 11 mohm, 12 mohm, 13 mohm, 14 mohm, 15 mohm, 16 mohm, 17 mohm, 18 mohm, 19 mohm, and 20 mohm.

[0050] In one embodiment, the thickness h of the conductive underlayer located between the first active material layer 12 and the composite current collector 11 is 21 is 1 μm ≦ h 21 The cold compression process can reduce the thickness of the conductive underlayer located between the first active material layer 12 and the composite current collector 11, allowing more pole pieces to be accommodated in the same space, which is advantageous for improving the energy density of the battery. Optionally, the thickness h of the conductive underlayer located between the first active material layer 12 and the composite current collector 11 can be reduced. 21 may be any one of 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, and 2.5 μm.

[0051] Referring to FIGS. 2 to 5, in one embodiment, along the first direction X, the width W2 of the first electrical connection member 14 satisfies 3 mm ≤ W2 ≤ 5 mm. Thereby, the space occupied by the first electrical connection member 14 along the first direction X is reduced, and further, the distance between the position where the first electrical connection member 14 is connected to the electrode terminal 102 and the battery cell case 101 is enlarged, the head space of the battery cell 100 is enlarged, and the bending of the electrode terminal 102 can be facilitated. Optionally, W2 may be any one of 3 mm, 3.2 mm, 3.4 mm, 3.6 mm, 3.8 mm, 4 mm, 4.2 mm, 4.4 mm, 4.6 mm, 4.8 mm, 5 mm.

[0052] In one embodiment, along the first direction X, the thickness h3 of the first electrical connection member 14 satisfies 5 μm ≤ h3 ≤ 20 μm. Thereby, the space occupied by the first electrical connection member 14 along the second direction Y is reduced, the head space of the battery cell 100 is enlarged, and the bending of the electrode terminal 102 can be facilitated. Optionally, h3 may be any one of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm.

[0053] Optionally, along the first direction X, the thickness h3 of the first electrical connection member 14 satisfies 7 μm < h3 ≤ 13 μm. Thereby, the space occupied by the first electrical connection member 14 along the second direction Y is further reduced, the head space of the battery cell 100 is further enlarged, and the bending of the electrode terminal 102 can be facilitated. Optionally, h3 may be any one of 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm.

[0054] Optionally, the thickness h3 of the first electrical connection member 14 satisfies 5 μm≦h3≦7 μm along the first direction X. By further reducing the thickness h3 of the first electrical connection member 14, the space occupied by the first electrical connection member 14 along the second direction Y can be further reduced, the head space of the battery cell 100 can be further increased, and bending of the electrode terminal 102 can be facilitated. Optionally, h3 can be any one of 5 μm, 5.2 μm, 5.4 μm, 5.6 μm, 5.8 μm, 6 μm, 6.2 μm, 6.4 μm, 6.6 μm, 6.8 μm, and 7 μm.

[0055] In one embodiment, the first electrical connection member 14 is welded to the third section 113 to form a welded region 14a. The width W3 of the welded region along the first direction X satisfies 1.8 mm≦W3≦2 mm. When the electrode terminal 102 is welded to the first electrical connection member 14, the welded region 14a must be avoided. Therefore, by controlling the width of the welded region, the space between the welding position of the electrode terminal 102 and the first electrical connection member 14 and the battery cell case 101 along the first direction X can be increased, which in turn increases the headspace of the battery cell 100 and facilitates bending of the electrode terminal 102. Optionally, the width W3 of the welded region may be any one of 1.8 mm, 1.82 mm, 1.84 mm, 1.86 mm, 1.88 mm, 1.9 mm, 1.92 mm, 1.94 mm, 1.96 mm, 1.98 mm, and 2.0 mm.

[0056] In one embodiment, along the second direction Y, the thickness S3 of the welding region 14a satisfies 18 μm ≤ S3 ≤ 57 μm. Thereby, the connection strength between the first electrical connection member 14 and the third section 113 can be increased, the space occupied by the welding region 14a along the second direction Y can be reduced, the head space of the battery cell 100 can be expanded, and the bending of the electrode terminal 102 can be facilitated. Optionally, the thickness S3 of the welding region 14a may be any one of 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm. Optionally, the thickness S3 of the welding region 14a includes the sum of the thickness of the current collector 11, the thickness of the first electrical connection member 14, and the thickness of the weld mark.

[0057] Optionally, along the second direction Y, the thickness S3 of the welding region 14a satisfies 28 μm < S3 ≤ 47 μm. Thereby, it is advantageous for further increasing the connection strength between the first electrical connection member 14 and the third section 113, reducing the space occupied by the welding region 14a along the second direction Y, expanding the head space of the battery cell 100, and facilitating the bending of the electrode terminal 102. Optionally, the thickness S3 of the welding region 14a may be any one of 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm.

[0058] Optionally, the thickness S3 of the welding region 14a along the second direction Y satisfies 18 μm≦S3≦37 μm. By further reducing the thickness S3 of the welding region 14a, the space occupied by the welding region 14a along the second direction Y can be further reduced, the head space of the battery cell 100 can be further increased, and bending of the electrode terminal 102 can be facilitated. Optionally, the thickness S3 of the welding region 14a can be any one of 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, and 37 μm.

[0059] Referring to Figures 8 and 9, in one embodiment, a first active material layer 12 is provided on both sides of the first section 111, a protective layer 13 is provided on both sides of the second section 112, and a first electrical connection member 14 is provided on both sides of the third section 113.

[0060] In one embodiment, the widths of the first electrical connection members 14 on both sides of the third section 113 along the first direction X may or may not be equal.

[0061] Optionally, the electrode terminal 102 is simultaneously connected to two first electrical connection members 14. Optionally, the electrode terminal 102 is connected to one of the two first electrical connection members 14. Optionally, along the first direction X, the electrode terminal 102 is connected to the one of the two first electrical connection members 14 that has a larger width.

[0062] In one embodiment, along the second direction Y, the thickness of the first electrical connection member 14 on both sides of the third section 113 is equal.

[0063] In one embodiment, the thickness of the first electrical connection member 14 on both sides of the third section 113 is not equal along the second direction Y. When the total thickness of the first electrical connection member 14 on both sides is the same, increasing the thickness of the first electrical connection member 14 on one side of the third section 113 is advantageous for improving the welding strength, and decreasing the thickness of the first electrical connection member 14 on the other side of the third section 113 is advantageous for increasing the head space of the battery cell 100.

[0064] In one embodiment, the difference A in width between the protective layers 13 on both sides of the second section 112 along the first direction X satisfies 0≦A≦0.4 mm, and may alternatively be any one of 0 mm, 0.1 mm, 0.2 mm, 0.3 mm, and 0.4 mm.

[0065] In one embodiment, the first electrical connection member 14 is welded to the third section 113 to form welded regions 14a on both sides of the third section 113. A difference B in width between the welded regions 14a on both sides of the third section 113 along the first direction X satisfies 0≦B≦0.25 mm. Alternatively, the difference B may be any one of 0 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, and 0.25 mm.

[0066] In one embodiment, when the protective layer 13 is an insulating layer, the total thickness S of the insulating layers on both sides and the thickness of the composite current collector 11 along the second direction Y is 11 is 30μm≦S 11 ≦75 μm. When the first active material layer 12 is applied to both sides of the composite current collector 11, it can cover burrs on both sides of the composite current collector 11, reducing the risk of the burrs piercing the separator, and also reducing the space occupied by the insulating layer in the second direction Y, thereby increasing the head space of the battery cell 100 and facilitating bending of the electrode terminal 102. Optionally, S 11may be any one of 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, and 75 μm.

[0067] Optionally, the total thickness S of the insulating layers on both sides and the thickness of the composite current collector 11 along the second direction Y 11 is 36 μm≦S 11 ≦55 μm. When the first active material layer 12 is applied to both sides of the composite current collector 11, it can more effectively cover burrs on both sides, further reducing the possibility that the burrs will protrude from the insulating layer and pierce the separator, and it can also reduce the space occupied by the insulating layer in the second direction Y, enlarging the head space of the battery cell 100 and facilitating bending of the electrode terminal 102. Optionally, S 11 may be any one of 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, and 55 μm.

[0068] Optionally, when the protective layer 13 is an insulating layer, the total thickness S of the insulating layers on both sides and the thickness of the composite current collector 11 along the second direction Y is 11 is 30μm≦S 11 ≦45 μm. When the first active material layer 12 is applied to both sides of the composite current collector 11, it can effectively cover burrs on both sides, reducing the possibility that the burrs will protrude from the insulating layer and pierce the separator, and further reducing the space occupied by the insulating layer in the second direction Y, further increasing the head space of the battery cell 100, and facilitating bending of the electrode terminal 102. Optionally, S 11may be any one of 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, and 45 μm.

[0069] In one embodiment, when the protective layer 13 is a conductive underlayer, the total thickness S of the conductive underlayers on both sides and the thickness of the composite current collector 11 along the second direction Y is 21 is 10μm≦S 21 ≦75 μm. When the first active material layer 12 is applied to both sides of the composite current collector 11, it can cover burrs on both sides of the composite current collector 11, reducing the risk of the burrs piercing the separator, and also reducing the space occupied by the conductive base layer in the second direction Y, thereby increasing the head space of the battery cell 100 and facilitating bending of the electrode terminal 102. Optionally, S 21 are 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, 51μm, 52μm, 53μm, 54μm, 55μm, 56μm, 57μm, 58μm, 59μm, 60μm, 61μm, 62μm, 63μm, 64μm, 65μm, 66μm, 67μm, 68μm, 69μm, 70μm, 71μm, 72μm, 73μm, 74μm, 75μm, 76μm, 77μm, 78μm, 79μm, 80μm, 81μm, 82μm, 83μm, 84μm, 85μm, 86μm, 87μm, 88μm, 89μm, 90μm, 91μm, 92μm, 93μm, 94μm, The thickness may be any one of 4 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, and 75 μm.

[0070] Optionally, when the protective layer 13 is a conductive underlayer, the total thickness S of the conductive underlayers on both sides and the thickness of the composite current collector 11 along the second direction Y is 21 is 16μm≦S 21≦35 μm. When the first active material layer 12 is applied to both sides of the composite current collector 11, it can more effectively cover burrs on both sides, further reducing the possibility that the burrs will protrude from the insulating layer and pierce the separator, and it can also further reduce the space occupied by the conductive base layer in the second direction Y, enlarging the head space of the battery cell 100 and facilitating bending of the electrode terminal 102. Optionally, S 21 may be any one of 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, and 35 μm.

[0071] Optionally, when the protective layer 13 is a conductive underlayer, the total thickness S of the conductive underlayers on both sides and the thickness of the composite current collector 11 along the second direction Y is 21 is 10μm≦S 21 ≦25 μm. When the first active material layer 12 is applied to both sides of the composite current collector 11, it can cover burrs on both sides of the composite current collector 11, reducing the risk of the burrs piercing the separator, and further reducing the space occupied by the conductive base layer in the second direction Y, further increasing the head space of the battery cell 100, and facilitating bending of the electrode terminal 102. Optionally, S 21 may be any one of 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, and 25 μm.

[0072] In one embodiment, the sum S of the thicknesses of the welded regions 14a on both sides along the second direction Y 31 is 28μm≦S 31≦67 μm. This increases the connection strength between the first electrical connection member 14 and the third section 113 on both sides, reduces the space occupied by the welding area 14 a in the second direction Y, increases the head space of the battery cell 100, and makes it easier to bend the electrode terminal 102. Alternatively, the thickness S3 of the welding region 14a may be any one of 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, and 67 μm.

[0073] Optionally, the sum S of the thicknesses of the welded regions 14a on both sides along the second direction Y 31 is 38 μm≦S 31 ≦57 μm. This is advantageous in further increasing the connection strength between the first electrical connection member 14 and the third section 113, and also in reducing the space occupied by the welding area 14a in the second direction Y, thereby increasing the head space of the battery cell 100 and facilitating bending of the electrode terminal 102. Optionally, the thickness S3 of the welding area 14a may be any one of 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, and 57 μm.

[0074] Optionally, the sum S of the thicknesses of the welded regions 14a on both sides along the second direction Y 31 is 28μm≦S 31 The sum of the thicknesses of the welded regions 14a on both sides is ≦47 μm. 31By further reducing the thickness S3 of the welding region 14a, the space occupied by the welding region 14a in the second direction Y can be further reduced, the head space of the battery cell 100 can be further increased, and the electrode terminal 102 can be easily bent. Optionally, the thickness S3 of the welding region 14a can be any one of 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, and 47 μm.

[0075] During sample preparation, the conductive underlayer and active material are applied separately to the current collector, with the underlayer applied first and then the active material. The width of the conductive underlayer must be larger than the width of the active material.

[0076] The present application will be further described below through specific examples.

[0077] In each comparative example and each example, the test is carried out using 10 battery cells as one set.

[0078] [Table 1] [Table 2] As can be seen from Tables 1 and 2, the present application reduces the headspace loss rate of the battery cell 100 by reducing the width of the protective layer 13, and reduces the thickness of the protective layer 13 to facilitate welding of the first electrical connection member 14 and the third section 113, increase the distance between the welding area 14a and the battery cell casing 101, and increase the headspace of the battery cell 100. Reducing the width and thickness of the welding area 14a further increases the distance between the welding area 14a and the battery cell casing 101, reducing the headspace loss rate of the battery cell 100 and facilitating bending of the electrode terminal 102 after welding the electrode terminal 102 to the first electrical connection member 14, reducing the capacity loss rate, improving the process pass rate, and benefiting production.

[0079] 10 , the present application further provides an electric device 200 employing the above-described battery cell 100. In one embodiment, the electric device 200 of the present application may be, but is not limited to, an electronic device, a drone, a backup power source, an electric car, an electric motorcycle, an electric assist bicycle, a power tool, a large-scale household storage battery, etc.

[0080] Those skilled in the art should understand that the above examples are merely for illustrating the present application and are not intended to limit the present application. Any appropriate modifications and variations to the above examples within the true spirit of the present application are included in the disclosure scope of the present application. [Explanation of symbols]

[0081] Battery cells 100 Battery Cell Case 101 Electrode terminal 102 First pole piece 10 Composite current collector 11 1st side 11a 2nd side 11b 1st Section 111 2nd Section 112 Section 3 113 First metal layer 114 Polymer layer 115 Second metal layer 116 First active material layer 12 protective layer 13 First electrical connection member 14 Welding area 14a 1st direction Second direction Y Electrical equipment 200.

Claims

1. A battery cell comprising: a first pole piece; the first pole piece comprising a composite current collector, a first active material layer, a protective layer, and a first electrical connection member; the composite current collector includes a first section, a second section, and a third section arranged along a first direction, the second section connecting the first section and the third section; the first active material layer is connected to the first section, the first active material layer and the composite current collector are disposed along a second direction, and the first direction is perpendicular to the second direction; the protective layer is connected to at least the second section and isolates burrs in the second section; the first electrical connection member is connected to the third section, and the first electrical connection member is used to connect to an external electrical device; the protective layer, the first active material layer, and the first electrical connection member are provided on the same side of the composite current collector, The width W of the protective layer located in the second section along the first direction １ is 1.0 mm ≦ W １ ≦2.4 mm, and the second direction is a thickness direction of the first pole piece.

2. The width W of the protective layer along the first direction １ is 1.0 mm ≦ W １ 2. The battery cell according to claim 1, wherein the thickness satisfies ≦1.5 mm.

3. The protective layer includes an insulating layer, and the insulating layer has a thickness h １ is 12 μm≦h １ ≦30 μm, and the sum S of the thickness of the insulating layer and the thickness of the composite current collector along the second direction １ is 18 μm≦S １ 2. The battery cell according to claim 1, wherein the thickness satisfies ≦45 μm.

4. The thickness h of the insulating layer along the second direction １ is 12 μm≦h １ ≦15 μm, and the sum S of the thickness of the insulating layer and the thickness of the composite current collector along the second direction １ is 18 μm≦S １ 4. The battery cell according to claim 3, wherein the thickness satisfies ≦30 μm.

5. The protective layer includes a conductive underlayer, and the conductive underlayer has a thickness h along the second direction. ２ is 2 μm≦h ２ ≦30 μm, and the sum S of the thickness of the conductive underlayer and the thickness of the composite current collector along the second direction ２ is 8 μm≦S ２ 2. The battery cell according to claim 1, wherein the thickness satisfies ≦45 μm.

6. The thickness h of the conductive underlayer along the second direction ２ is 2 μm≦h ２ ≦5 μm, and the sum S of the thickness of the conductive underlayer and the thickness of the composite current collector along the second direction ２ is 8 μm≦S ２ 6. The battery cell according to claim 5, wherein the thickness satisfies ≦20 μm.

7. The width W of the first electrical connection member along the first direction ２ is 3mm≦W ２ ≦5 mm, and the thickness h of the first electrical connection member along the second direction ３ is 5 μm≦h ３ 2. The battery cell according to claim 1, wherein the thickness satisfies ≦20 μm.

8. The first electrical connection member is welded to the third section to form a welded area, and the width W of the welded area along the first direction ３ is 1.8mm≦W ３ ≦2 mm, and the thickness S of the welded area along the second direction ３ is 18 μm≦S ３ 2. The battery cell according to claim 1, wherein the thickness satisfies ≦57 μm.

9. The thickness S of the welded area along the second direction ３ is 18 μm≦S ３ The battery cell according to claim 8, characterized in that the thickness satisfies ≦37 μm.

10. 2. The battery cell of claim 1, wherein the first active material layer is provided on both sides of the first section, the protective layer is provided on both sides of the second section, and the first electrical connection member is provided on both sides of the third section along the second direction.

11. The protective layer includes an insulating layer, and a total thickness S of the insulating layer on both sides and the thickness of the composite current collector along the second direction. １１ is 30 μm≦S １１ The battery cell according to claim 10, characterized in that the thickness satisfies ≦75 μm.

12. The protective layer includes a conductive underlayer, and the total thickness S of the conductive underlayers on both sides and the thickness of the composite current collector along the second direction is ２１ is 10 μm≦S ２１ The battery cell according to claim 10, characterized in that the thickness satisfies ≦75 μm.

13. The battery cell according to claim 10 , wherein a difference A in width between the protective layers provided on both sides of the second section along the first direction satisfies 0≦A≦0.4 mm.

14. 11. The battery cell of claim 10, wherein the first electrical connection members provided on both sides of the third section are welded to the third section to form welded areas, and a difference B in width of the welded areas located on both sides of the third section along the first direction satisfies 0≦B≦0.25 mm.

15. The conductive underlayer is further provided between the first active material layer and the composite current collector, and the resistance R of the conductive underlayer satisfies 1 mohm≦R≦20 mohm. The thickness h of the conductive underlayer located between the first active material layer and the composite current collector along the second direction is ２１ is 1 μm≦h ２１ 13. The battery cell according to claim 5 or 12, wherein the thickness satisfies ≦2.5 μm.

16. The battery cell according to claim 1 , wherein the width T of the third section along the first direction satisfies 1 mm≦T≦5 mm.

17. 4. The battery cell according to claim 3, wherein the material of the insulating layer includes at least one of an inorganic ceramic and a non-conductive organic polymer material.

18. 7. The battery cell according to claim 5, wherein the material of the conductive underlayer includes at least one of aluminum oxide, silicon oxide, silicon carbide, amorphous carbon, lithium phosphate oxynitride, and titanium diboride.

19. An electrical device comprising the battery cell according to any one of claims 1 to 18.

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