Cylindrical secondary battery, battery pack, and electric device

Abstract

The embodiment of the invention provides a cylindrical secondary battery, a battery pack and a power utilization device, the cylindrical secondary battery comprises a shell and an electrode assembly, the electrode assembly is arranged in the shell, the electrode assembly comprises a first pole piece, a diaphragm and a second pole piece, and the first pole piece, the diaphragm and the second pole piece are stacked and wound to form a winding structure; the first pole piece and the second pole piece are opposite in polarity; the first pole piece comprises a first current collector, the first current collector comprises a first coating area and a first empty foil area along the axial direction of the cylindrical secondary battery, the first empty foil area comprises a first bending area and a first rubbing area, and the first bending area is connected with the first rubbing area and the first coating area. Due to the existence of the first bending area, the bending direction of the first current collector can be guided in a pier pressing process, so that the root stress of the first bending area is released along the bending direction, the risk of contact after the first pole piece is bent towards the second pole piece is reduced, and the volume energy density and the safety reliability of the cylindrical secondary battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a cylindrical secondary battery, a battery pack and an electrical device. Background Art

[0002] In the preparation of cylindrical secondary batteries, after the two ends of the wound electrode assembly are flattened to form a flattened portion, the two ends of the electrode assembly are usually pressed to compact the foil connected to the flattened portion to improve the volume energy density of the cylindrical secondary battery.

[0003] However, in the above-mentioned pressing process, the positive electrode sheet and the negative electrode sheet of the electrode assembly are easily connected to form a short circuit, thereby reducing the safety and reliability of the cylindrical secondary battery. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a cylindrical secondary battery, a battery pack and an electrical device, which are beneficial to improving the volume energy density and safety reliability of the cylindrical secondary battery.

[0005] The first aspect of the present application provides a cylindrical secondary battery, comprising: a shell; an electrode assembly, arranged in the shell, the electrode assembly comprising a first pole piece, a diaphragm and a second pole piece, the first pole piece, the diaphragm and the second pole piece are stacked and wound to form a winding structure, and the first pole piece and the second pole piece have opposite polarities; the first pole piece comprises a first current collector, along the axial direction of the cylindrical secondary battery, the first current collector comprises a first coating area and a first empty foil area, the first empty foil area comprises a first bending area and a first flattening area, and the first bending area connects the first flattening area and the first coating area. In the embodiment of the present application, due to the existence of the first bending area, in the pier pressing process, it is beneficial to guide the bending direction of the first current collector, so that the root stress of the first bending area is released along the bending direction during pier pressing, and the probability of the first pole piece contacting the second pole piece after bending is reduced, which is beneficial to improve the volume energy density of the cylindrical secondary battery, and at the same time improve the safety and reliability of the cylindrical secondary battery.

[0006] In one or more embodiments, in a plane containing the axis of the cylindrical secondary battery, on one side of the axis, the first current collector includes a plurality of first stacking parts, each of which includes a first bending part, the first bending part forms part of the first bending zone, and the bending directions of the first bending parts of the plurality of first stacking parts are the same. In the embodiment of the present application, the bending directions of the first bending parts of the plurality of first stacking parts are the same, which is conducive to the orderly bending of the first bending parts of the plurality of first stacking parts in the same direction during the pier pressing process, reducing the risk of disordered bending of the first bending parts of the plurality of first stacking parts, resulting in reverse extrusion of adjacent first bending parts, and causing the first current collector to bend toward the second pole piece and contact each other, which is conducive to improving the safety and reliability of the cylindrical secondary battery. In addition, since the first bending parts of the plurality of first stacking parts are orderly bent in the same direction, during the pier pressing process, it is conducive to the first bending parts of the plurality of first stacking parts to contact more tightly, reducing the space occupied by the plurality of first stacking parts, which is conducive to improving the volume energy density of the cylindrical secondary battery.

[0007] In one or more embodiments, the first bent portion of the multi-layer first stack is bent toward the axis. In the embodiments of the present application, the first bent portion of the outermost first stack is bent away from the insulating tape wrapped around the electrode assembly, which is beneficial to reduce the probability that the first bent portion of the outermost first stack pierces the insulating tape wrapped around the electrode assembly, which is beneficial to improve the safety and reliability of the cylindrical secondary battery. In one or more embodiments, the first bent portion of the innermost first stack is bent toward the axis, which is beneficial to utilize the space of the center hole of the electrode assembly and improve the volume energy density of the cylindrical secondary battery.

[0008] In one or more embodiments, in a plane containing the axis of the cylindrical secondary battery, along the direction perpendicular to the axis, the projections of the first bends of the multi-layer first stack at least partially overlap. In the embodiments of the present application, in the pier pressing process, it is conducive to the orderly superposition of the first bends of the multi-layer first stack, reducing the risk of the first bends of the multi-layer first stack being staggered and superimposed, resulting in the reverse extrusion of adjacent first bends, causing the first current collector to bend toward the second pole piece and contact each other, which is conducive to improving the safety and reliability of the cylindrical secondary battery. In addition, since the first bends of the multi-layer first stack are superimposed in an orderly manner, in the pier pressing process, it is conducive to the first bends of the multi-layer first stack to contact more tightly, reducing the space occupied by the multi-layer first stack, which is conducive to improving the volume energy density of the cylindrical secondary battery.

[0009] In one or more embodiments, in a plane containing the axis of the cylindrical secondary battery, along the direction perpendicular to the axis, the width of the first bend is l, 0.5mm≤l≤2.5mm; and / or, along the axis, the length of the first bend is w, 0.5mm≤w≤1.5mm.

[0010] In the embodiment of the present application, the width l of the first bend portion is within this size, which is conducive to the orderly bending of the first bend portions of the multi-layer first stack during the pier pressing process, reducing the risk of excessive extrusion caused by the first bend portions of the multi-layer first stack being too close (caused by l being too large), causing the adjacent first bend portions to be extruded in reverse, and causing the first current collector to bend toward the second pole piece and contact each other, thereby improving the safety and reliability of the cylindrical secondary battery. In addition, the relaxation caused by the first bend portions of the multi-layer first stack being too far away (caused by l being too small) is reduced, which is conducive to the first bend portions of the multi-layer first stack being in closer contact, reducing the space occupied by the multi-layer first stack, and is conducive to improving the volume energy density of the cylindrical secondary battery.

[0011] In the embodiment of the present application, the length w of the first bend is within this size, which is conducive to the orderly bending of the first bends of the multi-layer first stack in the pier pressing process, reducing the risk of excessive extrusion caused by the first bends of the multi-layer first stack being too close (caused by w being too small), causing the adjacent first bends to be extruded in reverse, and causing the first current collector to bend and contact toward the second pole piece, thereby improving the safety and reliability of the cylindrical secondary battery. In addition, the relaxation caused by the first bends of the multi-layer first stack being too far away (caused by w being too large) is reduced, which is conducive to the first bends of the multi-layer first stack being in tighter contact, reducing the space occupied by the multi-layer first stack, and is conducive to improving the volume energy density of the cylindrical secondary battery.

[0012] In one or more embodiments, in a plane, the first bent portion includes a first folded edge and a second folded edge, the first folded edge is close to the first coating area, and the second folded edge is close to the first flattened area; the angle between the first folded edge and the axis is α1, and the angle between the second folded edge and the axis is α2, α1≥α2. In the embodiments of the present application, α1≥α2 is conducive to the folding angle of the first bent portion being away from the first coating area, reducing the probability of the first pole piece bending toward the second pole piece and contacting, and improving the safety and reliability of the cylindrical secondary battery.

[0013] In one or more embodiments, the first folded edge is directly connected to the second folded edge. In the embodiments of the present application, the first folded portion of the structure is easy to manufacture and process, and it is easy to control the bending direction of the first folded portion, reduce the probability of the first pole piece bending toward the second pole piece, and improve the safety and reliability of the cylindrical secondary battery.

[0014] In one or more embodiments, the first coating area includes a first active material coating area and an insulating filler coating area. Axially, the insulating filler coating area connects the first bending area and the first active material coating area; the first pole piece includes an insulating filler, and the insulating filler is arranged in the insulating filler coating area. In the embodiments of the present application, the insulating filler coating area is arranged, which is conducive to improving the hardness of the position where the insulating filler is arranged in the first coating area. In the pier pressing process, bending is not easy to occur, which is conducive to good bending of the first bending portion, reducing the influence of the first bending portion on the first active material coating area, reducing the possibility of powdering of the first active material coating area caused by the bending stress transmission of the current collector during the pier pressing process, reducing the risk of contact between the first pole piece and the second pole piece after bending, and improving the safety and reliability of the cylindrical secondary battery.

[0015] In one or more embodiments, the insulating filler includes Al 2 O 3 ,BaSO 4 、CaSiO 3 ,γ-AlOOH,CaSiO 4 In the embodiment of the present application, the insulating filler adopts the above-mentioned material, which has good insulating performance and mechanical strength, and is conducive to improving the hardness of the insulating filler coating area.

[0016] In one or more embodiments, the first flattened area forms a first flattened portion, the first flattened portion includes a first flattened plane away from the first coating area, and the distance between the first flattened plane and the first coating area is L1 along the axial direction; when the first current collector is in a flattened state, the distance between the end surface of the first flattened area away from the first coating area and the first coating area is L2 along the axial direction; 10%≤L1 / L2≤17%. In the embodiments of the present application, by setting the first bending area, the size of the electrode assembly along the axial direction is reduced, while the size of the first coating area is not affected, which is conducive to improving the volume energy density of the cylindrical secondary battery.

[0017] In one or more embodiments, the second pole piece includes a second current collector, and along the axial direction, the second current collector includes a second empty foil area and a second coating area, the second empty foil area includes a second flattened area and a second bending area, the second bending area connects the second flattened area and the second coating area, and the first flattened area and the second flattened area are arranged at both ends of the electrode assembly along the axial direction. In the embodiments of the present application, due to the presence of the second bending area, in the pier pressing process, it is beneficial to guide the bending direction of the second bending area of ​​the second current collector, reduce the risk of contact after the second current collector is bent toward the first current collector, and improve the safety and reliability of the cylindrical secondary battery. The first flattened area and the second flattened area are arranged at both ends of the electrode assembly along the axial direction, that is, the first bending area and the second bending area are arranged on both sides of the electrode assembly along the axial direction, which is beneficial to reduce the size of the electrode assembly along the axial direction and improve the volume energy density of the cylindrical secondary battery.

[0018] In one or more embodiments, the cylindrical secondary battery is a cylindrical battery, the diameter of the cylindrical battery is D, 17mm≤D≤65mm; and / or the length of the cylindrical battery is L, 40mm≤L≤250mm. The embodiments of the present application are conducive to the preparation of large-capacity cylindrical secondary batteries within the range of D and L.

[0019] A second aspect of the present application provides a battery pack, comprising a cylindrical secondary battery in any one of the above embodiments.

[0020] A third aspect of the present application provides an electrical device, comprising a cylindrical secondary battery or a battery pack according to any one of the above embodiments.

[0021] Beneficial effects of the embodiments of the present invention:

[0022] The cylindrical secondary battery, battery pack and power-consuming device provided by the embodiment of the present invention, the cylindrical secondary battery includes: a shell and an electrode assembly, the electrode assembly is arranged in the shell, the electrode assembly includes a first pole piece, a diaphragm and a second pole piece, the first pole piece, the diaphragm and the second pole piece are stacked and wound to form a winding structure, and the first pole piece and the second pole piece have opposite polarities; the first pole piece includes a first current collector, along the axial direction of the cylindrical secondary battery, the first current collector includes a first coating area and a first empty foil area, the first empty foil area includes a first bending area and a first flattening area, and the first bending area connects the first flattening area and the first coating area. In the embodiment of the present application, due to the existence of the first bending area, in the pier pressing process, it is beneficial to guide the bending direction of the first current collector, reduce the risk of the first pole piece contacting after bending toward the second pole piece, and help to improve the volume energy density of the cylindrical secondary battery, while improving the safety and reliability of the cylindrical secondary battery.

[0023] Of course, any product implementing the present application does not necessarily need to achieve all of the above advantages at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and a person skilled in the art can also obtain other drawings based on these drawings.

[0025] Figure 1 A schematic diagram of the structure of a cylindrical secondary battery according to an embodiment of the present application;

[0026] Figure 2 for Figure 1 A schematic cross-sectional structural diagram of an electrode assembly of a cylindrical secondary battery;

[0027] Figure 3 for Figure 2A schematic diagram of a partial structure of the electrode assembly shown;

[0028] Figure 4 for Figure 1 The schematic cross-sectional structure diagram of the electrode assembly of the cylindrical secondary battery shown is flattened after being wound;

[0029] Figure 5 for Figure 1 A schematic cross-sectional structural diagram of a first flattened area and a first bent area of ​​a first pole piece of an electrode assembly of a cylindrical secondary battery in a flattened state;

[0030] Figure 6 for Figure 1 A schematic structural diagram of a first flattened area and a first bent area of ​​a first pole piece of an electrode assembly of a cylindrical secondary battery shown in FIG. 1 , in a flattened state in an axial direction and a winding direction;

[0031] Figure 7 for Figure 1 A partial cross-sectional structural schematic diagram of an electrode assembly of a cylindrical secondary battery;

[0032] Figure 8 is a schematic diagram of the structure of a battery pack provided in an embodiment of the present application;

[0033] Fig. 9 It is a structural schematic diagram of a first type of electrical device provided in an embodiment of the present application;

[0034] Fig.10 It is a structural schematic diagram of a second electrical device provided in an embodiment of the present application.

[0035] The reference numerals are as follows:

[0036] Axis L0, radial X, axial Y, plane P;

[0037] Shell 10, electrode assembly 20, first pole piece 21, first current collector 211, first coating area 2111, first active material coating area 2111a, insulating filler coating area 2111b, first empty foil area 2112, first flattened area 2112a, first flattened portion 2112c, first flattened surface 2112A, end surface 2111B, first bending area 2112b, first stacking portion 2113, first bending portion 2114, first folding edge 2115, second folding edge 2116, diaphragm 22, second pole piece 23, second current collector 231, second coating area 2311, second empty foil area 2312, second flattened area 231a, second flattened portion 2311a, second bending area 231b, second bending portion 232, center hole 24;

[0038] A cylindrical secondary battery 100 , a battery pack 200 , and an electric device 300 . DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0040] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0041] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0042] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. The various embodiments in the present application may be combined with each other in the absence of conflict.

[0043] In the pressing process of cylindrical secondary batteries, the foil of the positive and negative electrodes of the wound electrode assembly easily passes over the separator between the positive and negative electrodes, causing internal short circuit problems in the battery, reducing the safety and reliability of the cylindrical secondary batteries.

[0044] The present application provides a cylindrical secondary battery, a battery pack and an electrical device, the main purpose of which is to improve the volume energy density and safety reliability of the cylindrical secondary battery.

[0045] Figure 1 A schematic diagram of the structure of a cylindrical secondary battery according to an embodiment of the present application is shown in FIG. Figure 1As shown, an embodiment of the present application provides a cylindrical secondary battery 100. The cylindrical secondary battery 100 may be a nickel-hydrogen battery, a nickel-cadmium battery, a lead-acid (or lead storage) battery, a lithium-ion battery, a polymer lithium-ion battery, etc. The cylindrical secondary battery 100 takes a cylindrical secondary battery as an example, but is not limited to a cylindrical secondary battery. The axis of the cylindrical secondary battery is L0, and the plane containing the axis of the cylindrical secondary battery is P.

[0046] The radial direction of the cylindrical secondary battery is X. The axial direction of the cylindrical secondary battery is Y, and Y is parallel to the axis L0 of the cylindrical secondary battery.

[0047] Along the radial direction X of the cylindrical secondary battery, the diameter of the cylindrical battery is D. In one or more embodiments, 17mm≦D≦65mm. But not limited to this. For example, D can be: 17mm, 19mm, 21mm, 23mm, 25mm, 27mm, 29mm, 31mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, or a value between the ranges of any two values. Within the D range, the diameter D of the cylindrical secondary battery is larger, which is conducive to improving the capacity of the cylindrical secondary battery, making the cylindrical secondary battery suitable for high-power and long-endurance application scenarios.

[0048] Along the axial direction Y of the cylindrical secondary battery, the length of the cylindrical secondary battery is L. In one or more embodiments, 40mm≦L≦250mm. But not limited to this. For example, L can be: 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, or a range of values ​​between any two values. Within this L range, the length L of the cylindrical battery is large, which is conducive to improving the capacity of the cylindrical secondary battery, making the cylindrical secondary battery suitable for high-power and long-range application scenarios.

[0049] Figure 2 for Figure 1 The schematic cross-sectional structure diagram of the electrode assembly of the cylindrical secondary battery shown in FIG. Figure 3 for Figure 2 The schematic diagram of the local structure of the electrode assembly is shown in FIG. Figure 1 , Figure 2 and Figure 3As shown, the first aspect of the present application provides a cylindrical secondary battery, including: a housing 10 and an electrode assembly 20, the electrode assembly 20 is arranged in the housing 10, the electrode assembly 20 includes a first pole piece 21, a separator 22 and a second pole piece 23, and the electrode assembly 20 has a central hole 24. The first pole piece 21, the separator 22 and the second pole piece 23 are stacked and wound to form a winding structure, and the first pole piece 21 and the second pole piece 23 have opposite polarities; the first pole piece 21 includes a first current collector 211, along the axial direction Y of the cylindrical secondary battery 100, the first current collector 211 includes a first coating area 2111 and a first empty foil area 2112, the first empty foil area 2112 includes a first bending area 2112b and a first flattened area 2112a, and the first bending area 2112b connects the first flattened area 2112a and the first coating area 2111.

[0050] In the embodiment of the present application, due to the existence of the first bending zone 2112b, during the pressing process, it is beneficial to guide the bending direction of the first current collector 211, so that the root stress of the first bending zone 2112b is released along the bending direction during pressing, thereby reducing the risk of contact between the first pole piece 21 and the second pole piece 23 after bending, which is beneficial to improving the volume energy density of the cylindrical secondary battery 100 and improving the safety and reliability of the cylindrical secondary battery 100.

[0051] In one or more embodiments, Figure 2 As shown, in one or more embodiments, in a plane P including the axis L0 of the cylindrical secondary battery 100, on one side of the axis L0, the first current collector 211 includes a plurality of first stacking portions 2113, each of the first stacking portions 2113 includes a first bending portion 2114, the first bending portion 2114 forms part of the first bending zone 2112b, and the bending directions of the first bending portions 2114 of the plurality of first stacking portions 2113 are the same.

[0052] In the embodiment of the present application, the first bending portions 2114 of the multi-layer first stacking portion 2113 have the same bending direction, which is conducive to the orderly bending of the first bending portions 2114 of the multi-layer first stacking portion 2113 in the same direction during the pier pressing process, reducing the risk of disorderly bending of the first bending portions 2114 of the multi-layer first stacking portion 2113, which leads to reverse extrusion of adjacent first bending portions 2114, and causes the first current collector 211 to bend toward the second pole piece 23 and contact each other, which is conducive to improving the safety and reliability of the cylindrical secondary battery 100. In addition, since the first bending portions 2114 of the multi-layer first stacking portion 2113 are orderly bent in the same direction, during the pier pressing process, it is conducive to the first bending portions 2114 of the multi-layer first stacking portion 2113 to be in closer contact, reducing the space occupied by the multi-layer first stacking portion 2113, which is conducive to improving the volume energy density of the cylindrical secondary battery 100.

[0053] In one or more embodiments, the first bent portion 2114 of the multi-layer first stacking portion 2113 is bent toward the axis L0. In the embodiment of the present application, the first bent portion 2114 of the outermost first stacking portion 2113 is bent away from the insulating tape wrapping the electrode assembly 20, which is beneficial to reduce the probability that the first bent portion 2114 of the outermost first stacking portion 2113 pierces the insulating tape wrapping the electrode assembly 20, and is beneficial to improve the safety and reliability of the cylindrical secondary battery 100.

[0054] In one or more embodiments, the first bent portion 2114 of the innermost first stacking portion 2113 is bent toward the axis L0 , which is beneficial for utilizing the space of the central hole 24 of the electrode assembly 20 and improving the volume energy density of the cylindrical secondary battery 100 .

[0055] In one or more embodiments, within the plane P, along a direction perpendicular to the axial direction Y, projections of the first bending portions 2114 of the multiple layers of the first stacked portions 2113 at least partially overlap.

[0056] In the embodiment of the present application, in the pier pressing process, the first bends 2114 of the multi-layer first stacking parts 2113 are stacked in order, and the risk of the first bends 2114 of the multi-layer first stacking parts 2113 being staggered and stacked, resulting in the reverse extrusion of adjacent first bends 2114, and the first current collector 211 is bent toward the second pole piece 23 and in contact with each other is reduced, which is conducive to improving the safety and reliability of the cylindrical secondary battery 100. In addition, since the first bends 2114 of the multi-layer first stacking parts 2113 are stacked in order, in the pier pressing process, the first bends 2114 of the multi-layer first stacking parts 2113 are in contact more tightly, reducing the space occupied by the multi-layer first stacking parts 2113, which is conducive to improving the volume energy density of the cylindrical secondary battery 100.

[0057] like Figure 3 As shown, in one or more embodiments, in the plane P, along the direction perpendicular to the axis Y, the width of the first bending portion 2114 is l, 0.5mm≤l≤2.5mm, but not limited thereto. For example, l can be: 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, or a value between any two values.

[0058] In the embodiment of the present application, the width l of the first bending portion 2114 is within this size, which is conducive to the orderly bending of the first bending portions 2114 of the multi-layer first stacking portion 2113 during the pier pressing process, and reduces the risk of excessive extrusion caused by the first bending portions 2114 of the multi-layer first stacking portion 2113 being too close (caused by l being too large), which causes the adjacent first bending portions 2114 to be reversely extruded, and the first current collector 211 is bent toward the second pole piece 23 and then contacted, thereby improving the safety and reliability of the cylindrical secondary battery 100. In addition, the relaxation caused by the first bending portions 2114 of the multi-layer first stacking portion 2113 being too far away (caused by l being too small) is reduced, which is conducive to the first bending portions 2114 of the multi-layer first stacking portion 2113 being in closer contact, reducing the space occupied by the multi-layer first stacking portion 2113, and is conducive to improving the volume energy density of the cylindrical secondary battery 100.

[0059] In one or more embodiments, along the axial direction Y, the length of the first bending portion 2114 is w, 0.5 mm ≤ w ≤ 1.5 mm, but not limited thereto. For example, w can be: 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm, or a value between any two values.

[0060] In the embodiment of the present application, the length w of the first bend portion 2114 is within this size, which is conducive to the orderly bending of the first bend portions 2114 of the multi-layer first stacking portion 2113 during the pier pressing process, and reduces the risk of excessive extrusion caused by the first bend portions 2114 of the multi-layer first stacking portion 2113 being too close (caused by too small w), which causes the adjacent first bend portions 2114 to be reversely extruded, causing the first current collector 211 to bend and contact toward the second pole piece 23, thereby improving the safety and reliability of the cylindrical secondary battery 100. In addition, the first bend portions 2114 of the multi-layer first stacking portion 2113 are reduced. The relaxation caused by the first bend portions 2114 of the multi-layer first stacking portion 2113 being too far away (caused by too large w) is reduced, which is conducive to the first bend portions 2114 of the multi-layer first stacking portion 2113 being in contact more tightly, reducing the space occupied by the multi-layer first stacking portion 2113, and is conducive to improving the volume energy density of the cylindrical secondary battery 100.

[0061] In one or more embodiments, within the plane P, the first bending portion 2114 includes a first folded edge 2115 and a second folded edge 2116, the first folded edge 2115 is close to the first coating area 2111, and the second folded edge 2116 is close to the first flattening area 2112a; the angle between the first folded edge 2115 and the axis L0 is α1, and the angle between the second folded edge 2116 and the axis L0 is α2, and α1≥α2.

[0062] In the embodiment of the present application, α1≥α2, which is conducive to keeping the corner of the first bent portion 2114 away from the first coating area 2111 , reducing the risk of the first pole piece 21 bending toward the second pole piece 23 and contacting the first pole piece 21 , thereby improving the safety and reliability of the cylindrical secondary battery 100 .

[0063] In one or more embodiments, 105°≤α1≤150°, but not limited thereto. For example, α1 may be: 105°, 110°, 115°, 120°, 125°, 130°, 135°, 140°, 145°, 150°, or a value between any two values.

[0064] In one or more embodiments, 100°≤α2≤135°, but not limited thereto. For example, α2 may be: 100°, 105°, 110°, 115°, 120°, 125°, 130°, 135°, or a value between any two values.

[0065] In one or more embodiments, the first fold 2115 and the second fold 2116 are directly connected.

[0066] In the embodiment of the present application, the first bending portion 2114 of the structure is easy to manufacture and process, and the bending direction of the first bending portion 2114 is easy to control, thereby reducing the probability of the first pole piece 21 bending toward the second pole piece 23 and improving the safety and reliability of the cylindrical secondary battery 100.

[0067] In one or more embodiments, the first bending portion 2114 forms at least one angle or at least one arc, or a combination of at least one angle and an arc.

[0068] In one or more embodiments, the first coating area 2111 includes a first active material coating area 2111a and an insulating filler coating area 2111b. Along the axial direction Y, the insulating filler coating area 2111b connects the first bending area 2112b and the first active material coating area 2111a; the first pole piece 21 includes an insulating filler, and the insulating filler is arranged in the insulating filler coating area 2111b.

[0069] In the embodiment of the present application, an insulating filler coating area 2111b is provided, which is beneficial to improving the hardness of the position where the insulating filler is provided on the first pole piece 21. During the pressing process, bending is not easy to occur, which is beneficial to the good bending of the first bent portion 2114, and the influence of the first bent portion 2114 on the first active material coating area 2111a is reduced. The possibility of powdering of the first active material coating area 2111a caused by the bending stress transmission of the collector during the pressing process is reduced, and the probability of the first pole piece 21 bending and contacting toward the second pole piece 23 is reduced, thereby improving the safety and reliability of the cylindrical secondary battery 100.

[0070] In one or more embodiments, the insulating filler includes Al 2 O 3 ,BaSO 4 、CaSiO 3 ,γ-AlOOH (Boehmite), CaSiO 4 Or at least one of polytetrafluoroethylene.

[0071] In the embodiment of the present application, the insulating filler is made of the above-mentioned material, which has good insulating properties and mechanical strength, and is beneficial to improving the hardness of the insulating filler coating area 2111b.

[0072] In one or more embodiments, along the axial direction Y, the distance between the first bending portion 2114 and the first coating area 2111 is b, 0mm<b≤0.2mm, but not limited thereto. For example, b can be: 0.01mm, 0.02mm, 0.03mm, 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm, or a value between any two values.

[0073] In one or more embodiments, the first flattened zone 2112a is rolled and flattened to form a first flattened portion 2112c, which includes a first flattened surface 2112A away from the first coating zone 2111. Along the axial direction Y, the distance between the first flattened surface 2112A and the first coating zone 2111 is L1.

[0074] In one or more embodiments, 0.5 mm ≤ L1 ≤ 1.1 mm, but not limited thereto. For example, L1 may be: 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm, 1.05 mm, 1.1 mm, or a value between any two values.

[0075] Testing method of the distance L1 between the first kneading plane 2112A and the first coating area 2111:

[0076] Use CT (Zeiss Xradia620Versa) to observe a cross-section of a cylindrical secondary battery, which is a plane P passing through the axis L0 of the cylindrical secondary battery; select an area on the same side of the axis L0, and divide the area into 10 equal sections along the radial direction X to obtain 11 first test points along the radial direction X; measure the distance between each first test point and the coating area in the axial direction Y, and take the average of the 11 measured distances to obtain L1.

[0077] Figure 4 for Figure 1 The cross-sectional structure diagram of the electrode assembly 20 of the cylindrical secondary battery 100 is shown in the flattened state after winding. Figure 4 As shown, during the preparation of the electrode assembly 20, after the first pole piece 21, the separator 22 and the second pole piece 23 are wound to form a winding core, the end of the first empty foil area 2112 of the first current collector 211 is flattened to form a first flattened area 2112a. The unflattened portion of the first empty foil area 2112 of the first current collector 211 is rolled to form a first pre-bent structure (not shown). Afterwards, the two ends of the winding core are pressed to compress the first pre-bent structure to form a first bent area 2112b.

[0078] Figure 5 for Figure 1 The schematic cross-sectional structure diagram of the first flattened area 2112a and the first bent area 2112b of the first pole piece 21 of the electrode assembly 20 of the cylindrical secondary battery 100 is shown in the flattened state along the axial direction Y. Figure 5 As shown, the electrode assembly 20 is in a state of not being flattened and rolled after winding, and the first bending area 2112b and the first flattened area 2112a of the first current collector 211 are in a flattened state along the axial direction Y.

[0079] Figure 6 for Figure 1 The schematic structural diagram of the first flattened area 2112a and the first bent area 2112b of the first electrode sheet 21 of the electrode assembly 20 of the cylindrical secondary battery 100 is shown in the flattened state along the axial direction and the winding direction, as shown in FIG. Figure 6 As shown, the first bending area 2112b and the first flattened area 2112a of the first current collector 211 are in a flattened state along the axial direction Y and the winding direction R (straightened along the axial direction Y and the winding direction R).

[0080] like Figure 5 and Figure 6 As shown, when the first current collector 211 is flattened in the axial direction Y, the distance between the end surface 2111B of the first flattened area 2112a and the first coated area 2111 is L2 along the axial direction Y; 10%≤L1 / L2≤17%. In the embodiment of the present application, by providing the first bending area 2112b, the size of the electrode assembly 20 along the axial direction Y is reduced, while the size of the first coated area 2111 is not affected, which is beneficial to improving the volume energy density of the cylindrical secondary battery 100.

[0081] In one or more embodiments, 5 mm ≤ L2 ≤ 7 mm, but is not limited thereto. For example, L2 may be: 5 mm, 5.1 mm, 5.2 mm, 5.3 mm, 5.4 mm, 5.5 mm, 5.6 mm, 5.7 mm, 5.8 mm, 5.9 mm, 6.0 mm, 6.1 mm, 6.2 mm, 6.3 mm, 6.4 mm, 6.5 mm, 6.6 mm, 6.7 mm, 6.8 mm, 6.9 mm, 7 mm, or a value between any two values.

[0082] Method for testing the distance L2 between the end surface 2111B of the first flattening area 2112a away from the first coating area 2111 and the first coating area 2111:

[0083] The first bending area 2112b and the first flattened area 2112a of the first current collector 211 of the electrode assembly 20 are straightened along the axial direction Y and the winding direction R, and the first current collector 211 is in a flattened state; 10 second test points are selected on the end surface 2111B; the distance between each second test point and the coating area in the axial direction Y is measured, and the average of the 10 measured distances is taken to obtain L2.

[0084] Figure 7 for Figure 1 A partial cross-sectional structural diagram of the electrode assembly 20 of the cylindrical secondary battery 100 is shown in FIG. Figure 7 As shown, in one or more embodiments, the second pole piece 23 includes a second current collector 231, and along the axial direction Y, the second current collector 231 includes a second empty foil area 2312 and a second coating area 2311, the second empty foil area 2312 includes a second flattened area 231a and a second bending area 231b, the second bending area 231b connects the second flattened area 231a and the second coating area 2311, and the first flattened area 2112a and the second flattened area 231a are arranged at both ends of the electrode assembly 20 along the axial direction Y. In the embodiment of the present application, due to the presence of the second bending area 231b, in the pier pressing process, it is beneficial to guide the bending direction of the second bending area 231b of the second current collector 231, reduce the risk of the second current collector 231 bending toward the first current collector 211 and causing contact, and improve the safety and reliability of the cylindrical secondary battery 100. The first flattened area 2112a and the second flattened area 231a are arranged at the two ends of the electrode assembly 20 along the axial direction Y, that is, the first bending area 2112b and the second bending area 231b are arranged at the two ends of the electrode assembly 20 along the axial direction Y, which is beneficial to reducing the size of the electrode assembly 20 along the axial direction Y and improving the volume energy density of the cylindrical secondary battery 100.

[0085] In one or more embodiments, the second kneaded area 231a is rolled and kneaded to form the second kneaded portion 2311a.

[0086] In one or more embodiments, in plane P, on one side of axis L0, the second current collector 231 includes a plurality of second stacking portions, each of which includes a second bending portion 232, the second bending portion 232 forming part of the second bending zone 231b, and the bending directions of the second bending portions 232 of the plurality of second stacking portions are the same.

[0087] In one or more embodiments, the second bent portion 232 of the multi-layer second stacked portion is bent toward the axis L0 .

[0088] In one or more embodiments, in a plane including the axis of the cylindrical secondary battery, along a direction perpendicular to the axial direction Y, projections of the second bending portions 232 of the plurality of second stack parts at least partially overlap.

[0089] In one or more embodiments, the second bending portion 232 forms at least one angle or at least one arc, or a combination of at least one angle and an arc.

[0090] In one or more embodiments, the thickness of the first current collector 211 is d1, 10μm≤d1≤15μm, but not limited thereto. For example, d1 can be: 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, or a value between any two values. The thickness of the first current collector 211 is within this range, which is beneficial to improving the tensile strength of the first current collector 211. In one or more embodiments, the material of the first current collector 211 is aluminum or aluminum alloy. In one or more embodiments, the first current collector 211 is a positive electrode current collector.

[0091] In one or more embodiments, the thickness of the second current collector 231 is d2, 6μm≤d2≤10μm, but not limited thereto. For example, d2 can be: 6μm, 6.2μm, 6.4μm, 6.6μm, 6.8μm, 7μm, 7.2μm, 7.4μm, 7.6μm, 7.8μm, 8μm, 8.2μm, 8.4μm, 8.6μm, 8.8μm, 9μm, 9.2μm, 9.4μm, 9.6μm, 9.8μm, 10μm, or a value between any two values. The thickness of the second current collector 231 is within this range, which is conducive to improving the tensile strength of the second current collector 231. In one or more embodiments, the material of the second current collector 231 is copper or copper alloy. In one or more embodiments, the second current collector 231 is a negative electrode current collector.

[0092] In a second aspect, the present application provides a method for preparing an electrode assembly 20, comprising:

[0093] The first pole piece 21, the diaphragm 22 and the second pole piece 23 are stacked and wound to form a winding core. The first pole piece 21 and the second pole piece 23 have opposite polarities. The first pole piece 21 includes a first current collector 211. Along the axial direction Y of the winding core, the first current collector 211 includes a first coated area 2111 and a first empty foil area 2112. The first empty foil area 2112 includes a first sub-portion and a second sub-portion. The first sub-portion connects the first coated area 2111 and the second sub-portion.

[0094] rolling the first sub-portion to form a first pre-bent structure;

[0095] Flattening the second sub-portion to form a first flattened portion 2112c;

[0096] The electrode assembly 20 is formed by pressing the two ends of the winding core in the axial direction Y. After the pressing process, the first pre-bent structure forms a first bent portion 2114.

[0097] The electrode assembly 20 prepared in the embodiment of the present application, due to the presence of the first bent portion 2114, is conducive to guiding the bending direction of the first current collector 211 during the pressing process, so that the root stress of the first bent portion 2114 is released along the bending direction, reducing the risk of contact caused by the first pole piece 21 bending toward the second pole piece 23, thereby improving the safety and reliability of the cylindrical secondary battery 100.

[0098] In one or more embodiments, in the preparation method of the electrode assembly 20, the second pole piece 23 includes a second current collector 231, and along the axial direction Y, the second current collector 231 includes a second empty foil area 2312 and a second coated area 2311, and the second empty foil area 2312 includes a third sub-portion and a fourth sub-portion, and the third sub-portion connects the second coated area 2311 and the fourth sub-portion.

[0099] Before the step of pressing both ends of the winding core in the axial direction Y, the method further includes:

[0100] rolling the third sub-portion to form a second pre-bent structure;

[0101] The fourth sub-portion is flattened to form a second flattened portion 2311a;

[0102] After the pressing process, the second pre-bent structure forms a second bent portion 232 .

[0103] In a third aspect, the present application provides a battery pack 200, Figure 8 is a schematic diagram of the structure of the battery pack provided in the embodiment of the present application, such as Figure 8As shown, the battery pack 200 includes the cylindrical secondary battery 100 of any of the above embodiments. There is at least one cylindrical secondary battery 100. In one or more embodiments, there are multiple cylindrical secondary batteries 100, and the multiple cylindrical secondary batteries 100 are connected in series or in parallel, or the multiple cylindrical secondary batteries 100 are combined in series and in parallel.

[0104] In a fourth aspect, the present application provides an electric device 300 , comprising the cylindrical secondary battery 100 or the battery pack 200 according to any one of the above embodiments.

[0105] In one or more embodiments, Fig. 9 is a schematic diagram of the structure of the first electrical device provided in the embodiment of the present application, such as Fig. 9 As shown, the electric device 300 includes the battery pack 200 in the above embodiment, and the battery pack 200 includes the cylindrical secondary battery 100 in the above embodiment.

[0106] In one or more embodiments, Fig.10 is a schematic diagram of the structure of a second electrical device provided in an embodiment of the present application, such as Fig.10 As shown, the electric device 300 includes the cylindrical secondary battery 100 in the above-mentioned embodiment.

[0107] The present application does not specifically limit the electrical device, and the electrical device includes electrical devices known in the prior art. For example, the electrical device includes but is not limited to a backup power supply, a two-wheeled vehicle, an unmanned aerial vehicle, a power tool, or an energy storage device.

[0108] The above are only preferred embodiments of the present application and are not intended to limit the protection scope of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application are included in the protection scope of the present application.

Claims

1. A cylindrical secondary battery, characterized in that: include: case; An electrode assembly is disposed in the housing, the electrode assembly comprising a first pole piece, a diaphragm and a second pole piece, the first pole piece, the diaphragm and the second pole piece are stacked and wound to form a winding structure, and the first pole piece and the second pole piece have opposite polarities; The first pole piece includes a first current collector. Along the axial direction of the cylindrical secondary battery, the first current collector includes a first coated area and a first empty foil area. The first empty foil area includes a first bending area and a first flattened area. The first bending area connects the first flattened area and the first coated area.

2. The cylindrical secondary battery according to claim 1, characterized in that: In a plane containing the axis of the cylindrical secondary battery, on one side of the axis, the first current collector includes a plurality of first stacking parts, each of which includes a first bending portion, which forms part of the first bending zone, and the first bending portions of the plurality of first stacking parts have the same bending direction.

3. The cylindrical secondary battery according to claim 2, characterized in that: The first bent portion of the multi-layer first stacked portion is bent toward the axis.

4. The cylindrical secondary battery according to claim 2 or 3, characterized in that: In the plane, along a direction perpendicular to the axial direction, projections of the first bent portions of the plurality of first stacked portions at least partially overlap.

5. The cylindrical secondary battery according to any one of claims 2 to 4, characterized in that: In the plane, along the direction perpendicular to the axial direction, the width of the first bending portion is l, 0.5mm≤l≤2.5mm; and / or, Along the axial direction, the length of the first bending portion is w, 0.5mm≤w≤1.5mm.

6. The cylindrical secondary battery according to any one of claims 2 to 5, characterized in that: In the plane, the first bending portion includes a first folding edge and a second folding edge, the first folding edge is close to the first coating area, and the second folding edge is close to the first flattening area; The included angle between the first folded edge and the axis is α1, the included angle between the second folded edge and the axis is α2, and α1≥α2.

7. The cylindrical secondary battery according to claim 6, characterized in that: The first folded edge and the second folded edge are directly connected.

8. The cylindrical secondary battery according to any one of claims 1 to 7, characterized in that: The first coating area includes a first active material coating area and an insulating filler coating area, and along the axial direction, the insulating filler coating area connects the first bending area and the first active material coating area; The first pole piece includes an insulating filler, and the insulating filler is arranged in the insulating filler coating area.

9. The cylindrical secondary battery according to claim 8, characterized in that: The insulating filler includes at least one of Al2O3, BaSO4, CaSiO3, γ-AlOOH, CaSiO4 or polytetrafluoroethylene.

10. The cylindrical secondary battery according to any one of claims 1 to 9, characterized in that: The first flattening zone forms a first flattening portion, the first flattening portion includes a first flattening plane away from the first coating zone, and along the axial direction, the distance between the first flattening plane and the first coating zone is L1; When the first current collector is in a flattened state, along the axial direction, a distance between an end surface of the first flattened area away from the first coating area and the first coating area is L2; 10%≤L1 / L2≤17%.

11. The cylindrical secondary battery according to any one of claims 1 to 10, characterized in that: The second pole piece includes a second current collector. Along the axial direction, the second current collector includes a second empty foil area and a second coated area. The second empty foil area includes a second flattened area and a second bent area. The second bent area connects the second flattened area and the second coated area. The first flattened area and the second flattened area are arranged at two ends of the electrode assembly along the axial direction.

12. The cylindrical secondary battery according to any one of claims 1 to 11, characterized in that: The cylindrical secondary battery is a cylindrical secondary battery; The diameter of the cylindrical secondary battery is D, 17 mm ≤ D ≤ 65 mm; and / or, The length of the cylindrical secondary battery is L, 40 mm ≤ L ≤ 250 mm.

13. A battery pack, characterized in that: A cylindrical secondary battery comprising any one of claims 1 to 12.

14. An electrical device, characterized in that: The invention comprises the cylindrical secondary battery according to any one of claims 1 to 12 or the battery pack according to claim 13.

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