Secondary batteries, battery packs, and electronic devices

Abstract

The present invention provides a secondary battery, battery pack, and electronic device that can improve the cylindricity of a cylindrical battery. [Solution] The electrode assembly 120 is formed by sequentially stacking a first electrode sheet 121, a first separator 141, a second electrode sheet 122, and a second separator 142 and then winding them together, and an insulating film 300 is used to fix the end portion of the electrode assembly. Along the winding direction of the electrode assembly, the insulating film encircles the electrode assembly at least once, the protruding ends of the end portion 141e of the first separator and the end portion 142e of the second separator constitute the end portion 120e of the electrode assembly, the end portion 122e of the second electrode sheet extends beyond the end portion 121e of the first electrode sheet, the end portion of the electrode assembly extends beyond the end portion of the second electrode sheet, and the starting end of the insulating film extends beyond the end portion of the electrode assembly.

Description

Technical Field

[0001] The present invention relates to a secondary battery, a battery pack, and an electronic device.

Background Art

[0002] In the field of new energy power batteries, the application of secondary batteries has become increasingly widespread. For example, secondary batteries (such as lithium-ion batteries) can be applied to electronic devices such as vehicles, energy storage, mobile phones, tablet computers, wearable devices, mobile batteries, electronic cigarettes, digital products, power tools, power units, and energy storage devices. One type of secondary battery is a cylindrical battery, which includes an outer casing and an electrode assembly. The electrode assembly includes a positive electrode sheet, a first separator, a negative electrode sheet, and a second separator. After being sequentially laminated with each other, it is wound up to form an electrode assembly, and then it is enclosed in an outer casing. However, existing secondary batteries still need further improvement in some aspects.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In view of the problems existing in the related art, an object of the present invention is to provide a secondary battery, a battery pack, and an electronic device, and at least improve the cylindricity of a cylindrical battery.

Means for Solving the Problems

[0004] To achieve the above objective, embodiments of the present invention provide a secondary battery. The secondary battery includes an electrode assembly formed by sequentially stacking a first electrode sheet, a first separator, a second electrode sheet, and a second separator and then winding them, and an insulating film used to fix the end portion of the electrode assembly. Here, along the winding direction of the electrode assembly, the insulating film encircles the electrode assembly at least once, the end portion of the first separator and the protruding end portion of the second separator constitute the end portion of the electrode assembly, the end portion of the second electrode sheet extends beyond the end portion of the first electrode sheet, the end portion of the electrode assembly extends beyond the end portion of the second electrode sheet, and the starting end of the insulating film extends beyond the end portion of the electrode assembly.

[0005] In some embodiments, in the reverse direction of the winding of the electrode assembly, the starting end of the second electrode sheet extends beyond the starting end of the first electrode sheet, and in a cross section perpendicular to the winding centerline of the electrode assembly, the orthographic projection of the cross section of the winding centerline forms a projection point, the projection point and the end of the first electrode sheet form a first connection line, the projection point and the starting end of the second electrode sheet form a second connection line, and the end of the second electrode sheet, the end of the electrode assembly, and the starting and ending ends of the insulating film are located within the region between the first connection line and the second connection line along the winding direction.

[0006] In some embodiments, the projection point and the starting end of the first electrode sheet form a third connection line, the angle range of the angle formed by the third connection line with the second connection line along the winding direction is 170°-190°, and the end of the first electrode sheet is located in the region between the third connection line and the second connection line along the winding direction. Alternatively, in some embodiments, in the reverse direction of the winding direction of the electrode assembly, the starting end of the second electrode sheet extends one to two turns beyond the starting end of the first electrode sheet. Alternatively, in some embodiments, the angle range of the angle formed by the first connection line with the second connection line along the winding direction is 80°-90°.

[0007] In some embodiments, the projection point and the end of the second electrode sheet form a fourth connecting line, and the angle formed by the first connecting line and the fourth connecting line along the winding direction is A1, 0° <A1≦30°である。

[0008] In some embodiments, the projection point and the end of the second electrode sheet form a fourth connection line, the projection point and the end of the electrode assembly form a fifth connection line, and the angle formed by the fourth connection line and the fifth connection line along the winding direction is A2, 0° <A2≦30°である。

[0009] In some embodiments, the projection point and the end of the electrode assembly form a fifth connection line, the projection point and the beginning of the insulating film form a sixth connection line, and the angle between the fifth connection line and the sixth connection line along the winding direction is A3, where 7.7° ≤ A3 ≤ 30°.

[0010] In some embodiments, the projection point and the starting end of the insulating film form a sixth connection line, the projection point and the ending end of the insulating film form a seventh connection line, and the angle formed by the sixth connection line and the seventh connection line along the winding direction is A4, 0° <A4≦30°である。

[0011] In some embodiments, the secondary battery is a cylindrical battery, the cylindrical battery includes a housing, the housing has an opening at one end in the height direction of the cylindrical battery and an end wall at the other end in the height direction, and a roll groove is provided at the opening that protrudes toward the interior of the housing, the electrode assembly is housed in the housing, the roll groove and the end wall restrict the movement of the electrode assembly in the height direction, and in the winding direction of the electrode assembly, the end portion of the insulating film extends beyond the end portion of the electrode assembly.

[0012] Embodiments of the present invention also provide a battery pack which includes any one of the rechargeable batteries described above.

[0013] Embodiments of the present invention also provide an electronic device which includes at least one of the above-mentioned rechargeable battery and any-mentioned battery pack. [Effects of the Invention]

[0014] The beneficial technical effects of this invention are as follows:

[0015] In the above technical solution, by installing the end portion of the insulating film behind the end portion of the electrode assembly, the overlapping portion of the two-layer insulating film can be arranged at a position where the outer peripheral thickness of the electrode assembly behind the end portion of the electrode assembly is thinner, reducing the diameter range (maximum value - minimum value) of the electrode assembly and optimizing the cylindricity of the electrode assembly.

Brief Description of the Drawings

[0016] To more clearly explain the technical solutions in the embodiments of the present invention or the prior art, the attached drawings that need to be used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention, and it is obvious that those skilled in the art can obtain other embodiments based on these drawings without creative efforts. [Figure 1] FIG. 1 shows a schematic diagram when the electronic device in the embodiment of the present invention is a vehicle. [Figure 2] FIG. 2 shows a perspective view of a secondary battery according to an embodiment of the present invention. [Figure 3] FIG. 3 shows a cross-sectional view of a secondary battery according to an embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view in a cross-section perpendicular to the winding center line of the electrode assembly of a secondary battery according to an embodiment of the present invention. [Figure 5A] FIG. 5A is a partially enlarged schematic view of the structure at the end portions of the first separator and the second separator in a secondary battery according to another embodiment of the present invention. [Figure 5B] FIG. 5B is a partially enlarged schematic view of the structure at the end portions of the first separator and the second separator in a secondary battery according to another embodiment of the present invention.

Embodiments for Implementing the Invention

[0017] To better understand the spirit of the embodiments of the present invention, it will be further described below in combination with some preferred embodiments of the present invention.

[0018] The embodiments of the present invention will be described in detail below. Throughout the entire text of the present invention specification, components having the same or similar configurations and components having the same or similar functions are represented by similar reference numerals. The embodiments regarding the drawings described herein are of an illustrative nature and are used to provide a basic understanding of the present invention. The embodiments of the present invention should not be construed as limiting the present invention.

[0019] As used herein, the terms "substantially", "generally", "essentially" and "about" are used to describe and explain minor variations. When used in combination with an event or situation, these terms can refer to examples where the event or situation occurs exactly, as well as examples where the event or situation occurs very approximately.

[0020] In this specification, unless otherwise specified or limited, relative terms such as, for example, "central", "vertical", "horizontal", "front", "rear", "right", "left", "inner", "outer", "lower", "higher", "horizontal", "vertical", "higher than", "lower than", "above", "below", "top", "bottom" and their derivative terms (such as "horizontally", "downwardly", "upwardly", etc.) should be construed as referring to the directions described in the discussion or illustrated in the drawings. These relative terms are used only for convenience of description and do not require the present invention to be constructed or operated in a specific direction.

[0021] For convenience of description, "first", "second", "third", etc. may be used in the text to distinguish different components in one figure or a series of figures. "First", "second", "third", etc. are not intended to describe the corresponding components. Also, where there is no contradiction, the embodiments in the present invention and the features in the embodiments can be combined with each other. Hereinafter, the present invention will be described in detail with reference to the drawings in combination with the embodiments.

[0022] Referring to FIG. 1, for the convenience of explanation, the following embodiments will be exemplified and described with the electronic device being the vehicle 1000. However, it is not difficult to understand that the electronic device provided by the present invention is not limited to a vehicle, and the electronic device may also be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool, etc.

[0023] A battery pack 1002 is installed inside the vehicle 1000, and the battery pack 1002 can be installed at the bottom (as shown in FIG. 1), the head, the rear, or any other appropriate position of the vehicle body 1001. The battery pack 1002 can be used for power supply of the vehicle 1000. For example, the battery pack 1002 can be used as the operating power source or the driving power source of the vehicle 1000. The battery pack 1002 can include a plurality of cylindrical batteries (such as the secondary battery 100 in FIG. 2) and a housing for accommodating the plurality of cylindrical batteries.

[0024] FIG. 2 shows a perspective view of the secondary battery 100 according to an embodiment of the present invention, and FIG. 3 shows a cross-sectional view of the secondary battery 100 according to an embodiment of the present invention. In this embodiment, the secondary battery 100 is a cylindrical battery. Referring to FIGS. 2 and 3 in combination, the secondary battery 100 can include an electrode assembly 120, an electrolyte, an outer casing 200, and a cover plate 202. The outer casing 200 and the cover plate 202 are components that jointly accommodate the electrode assembly 120 and the electrolyte. The material of the outer casing 200 can be any one of a variety of available materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The outer casing 200 can be in a cylindrical shape, defining an accommodation chamber, and the electrode assembly 120 is installed in the accommodation chamber. The diameter size of the outer shell 200 can be determined according to the specific dimension size of the electrode assembly 120, for example, 18 mm, 21 mm, 46 mm, etc. In some embodiments, the secondary battery 100 may be a 4680 cylindrical battery (diameter 46 mm, height 80 mm), the secondary battery 100 may be a 4695 cylindrical battery (diameter 46 mm, height 95 mm), or the secondary battery 100 may be a 46120 cylindrical battery (diameter 46 mm, height 120 mm).

[0025] The outer casing 200 can be connected to the negative electrode of the electrode assembly 120. The outer casing 200 may have a mounting opening 205 at one end along the height direction Z, and the cover plate 202 is installed in the mounting opening 205 to seal the housing. The secondary battery 100 may have an additional terminal 208 at one end relative to the cover plate 202, and the terminal 208 can be connected to the positive electrode of the electrode assembly 120. It should be understood that there is an insulating coordinated state between the electrode post 208 and the outer casing 200, which is to avoid a short circuit in the battery.

[0026] Referring to Figure 3, a pressure contact portion 203 is provided that protrudes inward adjacent to the mounting opening 205 of the outer casing 200. Along the height direction Z of the secondary battery 100, the electrode assembly 120 is installed between the end wall 111 and the pressure contact portion 203, and the pressure contact portion 203 can restrict the axial movement (movement in the height direction Z) of the electrode assembly 120 between the end wall 111 of the outer casing 200 and the pressure contact portion 203. A weak point can be installed on the cover plate 202, and when the battery experiences thermal runaway, the high-temperature, high-pressure discharged material from inside is discharged from the bottom of the battery to the outside after destroying the weak point on the cover plate 202, thereby enabling efficient discharge of the discharged material.

[0027] The electrode assembly 120 is sequentially stacked and may include a wound first electrode sheet, a first separator, a second electrode sheet, and a second separator (as described below with reference to Figure 4), and the electrode assembly 120 may have a winding center line Lc. Furthermore, the electrode assembly 120 has a winding center hole 120c.

[0028] The electrode assembly 120 can have a positive electrode tab and a negative electrode tab installed at both ends of the secondary battery 100 in the height direction Z, respectively. In some embodiments of the present invention, the positive electrode tab faces the end wall 111 and is electrically connected to the terminal 208, thereby making the terminal 208 positively charged. The negative electrode tab faces the mounting opening 205, and the outer casing 200 is electrically connected to the negative electrode tab, thereby becoming negatively charged. However, in other embodiments, the negative electrode tab can be connected to the terminal 208, and the positive electrode tab can be connected to the outer casing 200.

[0029] Figure 4 is a cross-sectional view of an electrode assembly 120 of a secondary battery according to an embodiment of the present invention, perpendicular to the winding center line Lc. The winding electrode assembly 120 has a winding center line Lc extending in direction Z (see Figure 3), and the XY plane shown in Figure 4 is a cross-section perpendicular to the winding center line Lc, and point P should be understood as the projection point of the winding center line Lc orthographically projected onto this cross-section. The electrode assembly 120 further has a winding center hole 120c, which may have a circular shape in the cross-section shown in Figure 4. The projection point P may be the center of the winding center hole 120c.

[0030] Referring to Figure 4, the electrode assembly 120 may include a first electrode sheet 121, a first separator 141, a second electrode sheet 122, and a second separator 142. The first electrode sheet 121, the first separator 141, the second electrode sheet 122, and the second separator 142 are sequentially stacked and then wound along the winding direction D to form the electrode assembly 120. The secondary battery may further include an electrolyte, which may be located between the first electrode sheet 121, the first separator 141, the second electrode sheet 122, and the second separator 142. In some embodiments, the first electrode sheet 121 is the positive electrode sheet, and the second electrode sheet 122 is the negative electrode sheet.

[0031] The first electrode sheet and the second electrode sheet may be a positive electrode sheet and a negative electrode sheet, respectively. The positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer coated on both surfaces of the positive electrode current collector. The portion of the positive electrode current collector not coated with the positive electrode active material layer constitutes a positive electrode tab. The negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer coated on both surfaces of the negative electrode current collector. The portion of the negative electrode current collector not coated with the negative electrode active material layer constitutes a negative electrode tab. Taking a lithium-ion battery as an example, the material of the positive electrode current collector can be aluminum, the positive electrode active material layer may contain positive electrode active material, and the positive electrode active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The material of the negative electrode current collector can be copper, the negative electrode active material layer may contain negative electrode active material, and the negative electrode active material may be carbon or silicon, etc. In some embodiments, the material of the first separator 141 and the second separator 142 can be, for example, PP (polypropylene) or PE (polyethylene).

[0032] By coating a positive electrode active material layer onto a positive electrode sheet, lithium ions are incorporated into the positive electrode active material layer. When the positive electrode active material layer comes into contact with the electrolyte and the battery is charged, the lithium ions in the positive electrode active material layer move through the electrolyte to the negative electrode active material layer and become embedded within it. This process is both a lithium ion activation process and a battery charging process.

[0033] The secondary battery may further include an insulating film 300, which can be used to secure the terminal portion of the electrode assembly 120. In this embodiment, the insulating film 300 surrounds the electrode assembly 120 at least once. In some embodiments, the insulating film 300 can be synthesized from, for example, PP, PE, PET (polyethylene terephthalate), PVC (polyvinyl chloride), or other polymer materials. The insulating film 300 can be used to electrically insulate the electrode assembly 120 from the outside.

[0034] Continuing to refer to Figure 4, in the winding direction D of the electrode assembly 120, the end portion 122e of the second electrode sheet 122 extends beyond the end portion 121e of the first electrode sheet 121, allowing the second electrode sheet 122 to cover the end portion 121e of the first electrode sheet 121. In this way, lithium ions detached from the positive electrode active material layer of the first electrode sheet 121 (positive electrode sheet) can be smoothly embedded in the negative electrode active material layer of the second electrode sheet 122 (negative electrode sheet), thereby preventing lithium deposition on the second electrode sheet 122 (negative electrode sheet) at the end portion. For similar reasons, in the direction opposite to the winding direction D, the starting end portion 122s of the second electrode sheet 122 extends beyond the starting end portion 121s of the first electrode sheet 121. That is, at the winding start point of the electrode assembly 120, the second electrode sheet 122 is wound longer than the first electrode sheet 121.

[0035] In some embodiments, in the winding direction D of the electrode assembly 120, the starting end 122s of the second electrode sheet 122 extends beyond the starting end 121s of the first electrode sheet 121. By positioning the starting end 122s of the second electrode sheet 122 to extend beyond the starting end 121s of the first electrode sheet 121, lithium ions detached from the positive electrode active material layer of the first electrode sheet 121 (positive electrode sheet) can be smoothly embedded into the negative electrode active material layer of the second electrode sheet 122 (negative electrode sheet), thereby preventing lithium deposition from occurring on the negative electrode sheet at the starting end. However, lithium deposition is still likely to occur at the outermost periphery of the winding electrode assembly 120.

[0036] According to an embodiment of the present invention, along the winding direction D of the electrode assembly 120, the protruding ends of the end portion 141e of the first separator 141 and the end portion 142e of the second separator 142 constitute the end portion 120e of the electrode assembly 120. In the embodiment shown in Figure 4, the end portion 141e of the first separator 141 and the end portion 142e of the second separator 142 are basically aligned. It should be understood that alignment in the present invention means that the difference between the end portions 141e and 142e of the first separator 141 and the second separator 142 is within 5 mm. In such an embodiment, the protruding ends of the end portions 141e and 142e of the first separator 141 and the second separator 142 constitute the end portion 120e of the electrode assembly 120. When the difference between the terminal portions 141e and 142e of the first separator 141 and the second separator 142 is 0 mm, the terminal portions 141e and 142e of the first separator 141 and the second separator 142 can be jointly used as the terminal portion 120e of the electrode assembly 120.

[0037] In other embodiments, the terminal portions 141e and 142e of the first separator 141 and the second separator 142 do not need to be aligned. Figures 5A and 5B are partially enlarged schematic diagrams of the structure at the terminal portions of the first separator and the second separator in a secondary battery according to another embodiment of the present invention. Referring to Figure 5A, the terminal portion 142e of the second separator 142 extends beyond the terminal portion 141e of the first separator 141, and in this embodiment, the terminal portion 142e of the second separator 142 is the outermost end and constitutes the terminal portion 120e of the electrode assembly 120. Referring to Figure 5B, the terminal portion 141e of the first separator 141 extends beyond the terminal portion 142e of the second separator 142, and in this embodiment, the terminal portion 141e of the first separator 141 is the outermost end and constitutes the terminal portion 120e of the electrode assembly 120.

[0038] Referring again to the illustration in Figure 4, along the winding direction D of the electrode assembly 120, the end portion 120e of the electrode assembly 120 extends beyond the end portion 122e of the second electrode sheet 122. The starting end portion 300s of the insulating film 300 extends beyond the end portion 120e of the electrode assembly 120.

[0039] In the above technical solution, by installing the starting end portion 300s of the insulating film 300 behind the ending end portion 120e of the electrode assembly 120 along the winding direction D, the overlapping portion of the two-layer insulating film 300 can be arranged at a position where the thickness of the outer periphery of the electrode assembly is thinner, the diameter range of the electrode assembly can be reduced, and the cylindricity of the electrode assembly can be optimized.

[0040] The projection point P and the ending end portion 121e of the first electrode sheet 121 form the first connection line L1, and the projection point P and the starting end portion 122s of the second electrode sheet 122 form the second connection line L2. The ending end portion 122e of the second electrode sheet 122, the ending end portion 120e of the electrode assembly 120, and the starting end portion 300s and the ending end portion 300e of the insulating film 300 are located within the region between the first connection line L1 and the second connection line L2 along the winding direction D. That is, in the winding direction D, the ending end portion 120e of the electrode assembly 120, the ending end portion 122e of the second electrode sheet 122, and the starting end portion 300s and the ending end portion 300e of the insulating film 300 do not exceed the starting end portion 122s of the second electrode sheet 122. The region between the ending end portion 121e of the first electrode sheet 121 and the starting end portion 122s of the second electrode sheet 122 (corresponding to the region between the first connection line L1 and the second connection line L2) is usually the region where the thickness of the outer periphery of the electrode assembly is the thinnest. By installing the ending end portion 122e of the second electrode sheet 122, the ending end portion 120e of the electrode assembly 120, and the starting end portion 300s and the ending end portion 300e of the insulating film 300 within this region, the diameter range of the electrode assembly can be reduced, and the cylindricity of the electrode assembly can be optimized.

[0041] In some embodiments, as shown in FIG. 4, along the winding direction D, the ending end portion 300e of the insulating film 300 exceeds the ending end portion 120e of the electrode assembly 120. In this way, the laminated overlapping portion of the two-layer insulating film 300 is located at a position where the thickness of the outer periphery of the electrode assembly is thinner, that is, between the ending end portion 120e of the electrode assembly 120 and the starting end portion 122s of the second electrode sheet 122, so that the diameter range of the electrode assembly can be effectively reduced, and the cylindricity of the electrode assembly can be optimized.

[0042] In some embodiments, in the reverse direction of the winding direction D, the starting end 122s of the second electrode sheet 122 extends one to two turns beyond the starting end 121s of the first electrode sheet 121. If the starting end 122s of the second electrode sheet 122 extends one less turn than the starting end 121s of the first electrode sheet 121, it may not be possible to effectively avoid the lithium deposition phenomenon. If the starting end 122s of the second electrode sheet 122 extends two more turns than the starting end 121s of the first electrode sheet 121, it may adversely affect the energy density of the battery. Therefore, by configuring the starting end 122s of the second electrode sheet 122 to extend one to two turns beyond the starting end 122s of the first electrode sheet 121, it is possible to avoid the lithium deposition phenomenon without excessively affecting the energy density.

[0043] Furthermore, the projection point P and the starting end portion 121s of the first electrode sheet 121 form the third connection line L3. Along the winding direction D, the angular range of the included angle formed by the third connection line L3 and the second connection line L2 is 170° - 190°, preferably 180°. In this embodiment, in the reverse direction of the winding direction D, the starting end portion 122s of the second electrode sheet 122 exceeds the starting end portion 121s of the first electrode sheet 121 by more than about 1.5 turns, and the angular range of the included angle formed by the third connection line L3 and the second connection line L2 is about 180°. The ending end portion 121e of the first electrode sheet 121 is located within the region of the included angle formed by the third connection line L3 and the second connection line L2 (the region above the second connection line L2 and the third connection line L3 in FIG. 4). Along the winding direction D, the angular range of the included angle formed by the first connection line L1 and the second connection line L2 is 80° - 90°, preferably 90°. In some embodiments, the arc length between the first connection line L1 and the second connection line L2 is 35 mm or less (corresponding to the arc length within the 90° range of the circumference of the electrode assembly). In some embodiments, the arc length between the first connection line L1 and the second connection line L2 can be equal to the diameter of the electrode assembly × 3.14 / 4, that is, this corresponds to the arc length within the 90° range of the circumference of the electrode assembly. In some embodiments, for the 46 - series cylindrical battery, the diameter of the electrode assembly can be about 44.7 mm. When the battery is a cylindrical battery, the distance between the electrode assembly 120 of the cylindrical battery and the outer casing 200 is relatively small, and the electrode assembly 120 expands along the radial direction in the cylindrical battery. Therefore, with the corresponding design of the present invention, the technical problem of lithium precipitation on the outer periphery of the electrode assembly 120 is further improved.

[0044] The projection point P and the ending end portion 122e of the second electrode sheet 122 form the fourth connection line L4. The included angle formed by the first connection line L1 and the fourth connection line L4 along the winding direction D is A1, and 0° < A1 ≤ 30°. In some embodiments, the range of the arc length of the section corresponding to the angle A1 is 3 mm - 11.7 mm. In some embodiments, the arc length of the section corresponding to the angle A1 can be equal to the diameter of the electrode assembly × 3.14 / 12, that is, this corresponds to the arc length within the 30° range of the circumference of the electrode assembly.

[0045] The projection point P and the end portion 1220e of the electrode assembly 120 form the fifth connection line L5. The included angle A2 formed by the fourth connection line L4 and the fifth connection line L5 along the winding direction D is such that in some embodiments, 5° < A2 < 160°. Preferably, 0° < A2 ≤ 30°. In some embodiments, the range of the arc length of the section corresponding to the angle A1 is 3 mm - 11.7 mm. In some embodiments, the arc length of the section corresponding to the angle A2 can be equal to the diameter of the electrode assembly × 3.14 / 12.

[0046] The projection point P and the start portion 300s of the insulating film 300 form the sixth connection line L6. The included angle A3 formed by the fifth connection line L5 and the sixth connection line L6 along the winding direction D is such that 7.7° ≤ A3 ≤ 30°. In some embodiments, the arc length of the section corresponding to the angle A3 is greater than 3 mm.

[0047] The projection point P and the end portion 300e of the insulating film 300 form the seventh connection line L7. The included angle A4 formed by the sixth connection line L6 and the seventh connection line L7 along the winding direction D is such that 0° < A4 ≤ 30°. In some embodiments, the range of the arc length of the section corresponding to the angle A4 is 3 mm - 11.7 mm. In some embodiments, the arc length of the section corresponding to the angle A4 can be equal to the diameter of the electrode assembly × 3.14 / 12.

[0048] By designing the angles A1 - A4 between the first connection line L1 and the second connection line L2, the thickness changes caused by the end portion 121e of the first electrode sheet 121, the end portion 122e of the second electrode sheet 122, and the start portion 300s and the end portion 300e of the insulating film 300 can be made uniform, thereby further improving the cylindricity of the electrode assembly.

[0049] The above description represents only preferred embodiments of the present invention and does not limit it. To those skilled in the art, various modifications and changes are possible. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should equally fall within the scope of protection. [Industrial applicability]

[0050] The secondary battery, battery pack, and electronic device of the present invention can improve the cylindricity of at least a cylindrical battery. [Explanation of Symbols]

[0051] A1, A2, A3, A4: Angle D: Winding direction L1: First connection line L2: Second connection line L3: Third connection line L4: Fourth connection line L5: Fifth connection line L6: Sixth connection line L7: Seventh connection line Lc: Winding centerline P: Projection point Z: Height direction 100: Secondary battery 111: End wall 120: Electrode assembly 120c: Winding center hole 120e, 121e, 122e, 141e, 142e, 300e: Termination section 121: First electrode sheet 121s, 122s: Starting end 122: Second electrode sheet 141: First Separator 142: Second separator 200: Outer case 202: Cover Plate 203: Pressure-welded section 205: Mounting opening 208: Terminal 300: Insulating film 300s: Starting end 1000: Vehicle 1001: Vehicle body 1002: Battery pack

Claims

1. An electrode assembly is formed by sequentially stacking a first electrode sheet, a first separator, a second electrode sheet, and a second separator, and then winding them together. A secondary battery comprising an insulating film used to fix the terminal portion of the electrode assembly, A secondary battery characterized in that, along the winding direction of the electrode assembly, the insulating film encircles the electrode assembly at least once, the end portion of the first separator and the protruding end portion of the second separator constitute the end portion of the electrode assembly, the end portion of the second electrode sheet extends beyond the end portion of the first electrode sheet, the end portion of the electrode assembly extends beyond the end portion of the second electrode sheet, and the starting end of the insulating film extends beyond the end portion of the electrode assembly.

2. In the reverse direction of the winding of the electrode assembly, the starting end of the second electrode sheet extends beyond the starting end of the first electrode sheet. In a cross-section perpendicular to the winding center line of the electrode assembly, the orthographic projection of the winding center line onto the cross-section forms a projection point, the projection point and the end portion of the first electrode sheet form a first connecting line, and the projection point and the beginning portion of the second electrode sheet form a second connecting line. The secondary battery according to claim 1, characterized in that the end portion of the second electrode sheet, the end portion of the electrode assembly, and the start and end portions of the insulating film are located within the region between the first connecting line and the second connecting line along the winding direction.

3. The projection point and the starting end of the first electrode sheet form a third connecting line, and the angular range of the angle formed by the third connecting line and the second connecting line along the winding direction is 170°–190°. The end portion of the first electrode sheet is located within the region between the third connecting wire and the second connecting wire along the winding direction, or, In the reverse direction of the winding of the electrode assembly, the starting end of the second electrode sheet extends beyond the starting end of the first electrode sheet by one or two turns, or The secondary battery according to claim 2, characterized in that the angular range of the angle formed between the first connecting wire and the second connecting wire along the winding direction is 80°-90°.

4. The secondary battery according to claim 2, characterized in that the projection point and the end portion of the second electrode sheet form a fourth connecting line, and the angle formed by the first connecting line and the fourth connecting line along the winding direction is A1, and 0° < A1 ≤ 30°.

5. The secondary battery according to claim 2, characterized in that the projection point and the end portion of the second electrode sheet form a fourth connecting line, the projection point and the end portion of the electrode assembly form a fifth connecting line, and the angle between the fourth connecting line and the fifth connecting line along the winding direction is A2, and 0° < A2 ≤ 30°.

6. The secondary battery according to claim 2, characterized in that the projection point and the terminal end of the electrode assembly form a fifth connection line, the projection point and the starting end of the insulating film form a sixth connection line, and the angle of attachment formed by the fifth connection line and the sixth connection line along the winding direction is A3, and 7.7° ≤ A3 ≤ 30°.

7. The secondary battery according to claim 2, characterized in that the projection point and the starting end of the insulating film form a sixth connection line, the projection point and the ending end of the insulating film form a seventh connection line, and the angle of attachment formed by the sixth connection line and the seventh connection line along the winding direction is A4, and 0° < A4 ≤ 30°.

8. The aforementioned secondary battery is a cylindrical battery, The cylindrical battery includes a housing, the housing has an opening at one end in the height direction of the cylindrical battery, an end wall at the other end in the height direction, and a roll groove is provided in the opening that protrudes toward the interior of the housing. The electrode assembly is housed within the housing, and the roll groove and the end wall restrict the movement of the electrode assembly in the height direction. The secondary battery according to claim 1, characterized in that, in the winding direction of the electrode assembly, the end portion of the insulating film extends beyond the end portion of the electrode assembly.

9. A battery pack characterized by including a secondary battery according to any one of claims 1 to 8.

10. An electronic device characterized by including at least one of the battery packs described in claim 9.

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