Secondary battery, electrochemical device, electric equipment and preparation method of secondary battery

Abstract

The embodiment of the invention discloses a secondary battery, an electrochemical device, electric equipment and a preparation method of the secondary battery. The secondary battery comprises an electrode assembly, a first tab and a second tab, the electrode assembly comprises a first edge and a second edge which are oppositely arranged, a third edge and a fourth edge which are oppositely arranged, a fifth edge connected with the second edge and the third edge, and a sixth edge connected with the first edge and the third edge. The supplementary angle of the included angle between the fifth edge and the third edge is alpha 1, the supplementary angle of the included angle between the fifth edge and the second edge is alpha 2, alpha 1 is larger than 0 and smaller than 90 degrees, and alpha 2 is larger than 0 and smaller than 90 degrees. The supplementary angle of the included angle between the sixth edge and the third edge is beta 1, the supplementary angle of the included angle between the sixth edge and the first edge is beta 2, beta 1 is larger than 0 and smaller than 90 degrees, and beta 2 is larger than 0 and smaller than 90 degrees. And the first tab extends out of the electrode assembly from the fifth edge. And the second tab extends out of the electrode assembly from the sixth edge. The secondary battery is favorable for improving the energy density.

Description

Technical Field

[0001] The present application belongs to the field of energy storage technology, and in particular relates to a secondary battery, an electrochemical device, an electrical equipment and a method for preparing the secondary battery. Background Art

[0002] At present, in the packaging structure of secondary batteries, the tabs usually extend from the head of the electrode assembly, occupying space and causing the energy density of the secondary battery to decrease. In the prior art, the top seal can be folded and placed on the battery body to reduce the loss of energy density, but this structure is not suitable for application scenarios such as ultra-thin batteries, and the application scenarios are limited. In addition, after folding, dead wrinkles are likely to appear at the bend, increasing the risk of packaging bag rupture and increasing safety hazards such as electrolyte leakage. Summary of the invention

[0003] In view of the above situation, it is necessary to provide a secondary battery which is conducive to improving its energy density.

[0004] A first aspect of an embodiment of the present application provides a secondary battery, which includes an electrode assembly, a first pole piece and a second pole piece. The electrode assembly includes a first pole piece and a second pole piece, and the polarities of the first pole piece and the second pole piece are opposite; the electrode assembly is a winding structure, and the winding structure is formed by stacking and winding the first pole piece and the second pole piece. Observing along the thickness direction of the electrode assembly, the electrode assembly includes a first edge and a second edge arranged opposite to each other along the first direction, a third edge and a fourth edge arranged opposite to each other along the second direction, a fifth edge connecting the second edge and the third edge, and a sixth edge connecting the first edge and the third edge. The supplementary angle of the angle between the fifth edge and the third edge is α 1 , the supplementary angle between the fifth edge and the second edge is α 2 , 0<α 1 <90°,0<α 2 <90°. The supplementary angle of the angle between the sixth edge and the third edge is β 1 , the supplementary angle between the sixth edge and the first edge is β 2 , 0<β 1 <90°,0<β 2 <90°. The first direction, the second direction and the thickness direction of the electrode assembly are perpendicular to each other. One end of the first pole ear is connected to the electrode assembly, and the other end of the first pole ear extends from the fifth edge and extends to the outside of the electrode assembly. One end of the second pole ear is connected to the electrode assembly, and the other end of the second pole ear extends from the sixth edge and extends to the outside of the electrode assembly.

[0005] In this secondary battery, the first pole ear and the second pole ear extend from the fifth edge and the sixth edge of the electrode assembly respectively. The first pole ear and the second pole ear are located at the corners of the secondary battery, which reduces the occupation of the head space of the secondary battery and is beneficial to improving the energy density of the secondary battery.

[0006] In one or more embodiments of the present application, 40°≤α 1 ≤50°, 40°≤α 2 In this way, the angle between the fifth edge and the third edge and the angle between the fifth edge and the second edge can be set within an appropriate range, which is beneficial to improving the volume energy density of the secondary battery.

[0007] In one or more embodiments of the present application, 40°≤β 1 ≤50°, 40°≤β 2 In this way, the angle between the sixth edge and the third edge and the angle between the sixth edge and the first edge can be set within an appropriate range, which is beneficial to improving the volume energy density of the secondary battery.

[0008] In one or more embodiments of the present application, the first pole piece includes a first notch portion and a second notch portion arranged oppositely along the first direction. The first notch portion is located at the fifth edge, and the first pole ear extends out of the electrode assembly from the first notch portion; the second notch portion is located at the sixth edge, and the second pole ear extends out of the electrode assembly from the second notch portion. The first notch portion is composed of a plurality of first notches, and the plurality of first notches are arranged at intervals along the winding direction of the first pole piece; the second notch portion is composed of a plurality of second notches, and the plurality of second notches are arranged at intervals along the winding direction of the first pole piece. The second pole piece includes a third notch portion and a fourth notch portion arranged oppositely along the first direction. The third notch portion is located at the fifth edge, and when viewed along the thickness direction of the electrode assembly, the third notch portion and the first notch portion at least partially overlap; the fourth notch portion is located at the sixth edge, and when viewed along the thickness direction of the electrode assembly, the fourth notch portion and the second notch portion at least partially overlap. The third notch portion is composed of a plurality of third notches, and the plurality of third notches are arranged at intervals along the winding direction of the second pole piece; the fourth notch portion is composed of a plurality of fourth notches, and the plurality of fourth notches are arranged at intervals along the winding direction of the second pole piece. In this way, after the first notch and the second notch are processed on the first pole piece, the first notch portion and the second notch portion can be formed by winding the first pole piece, and after the third notch and the fourth notch are processed on the second pole piece, the third notch portion and the fourth notch portion can be formed by winding the second pole piece, which facilitates production.

[0009] In one or more embodiments of the present application, the electrode assembly further includes a separator, which is disposed between the first pole piece and the second pole piece, and the first pole piece, the separator, and the second pole piece are sequentially stacked and wound to form a winding structure. The separator includes a fifth notch portion and a sixth notch portion disposed opposite to each other along a first direction; the edge of the fifth notch portion forms a fifth edge, and when viewed along the thickness direction of the electrode assembly, the fifth notch portion at least partially overlaps with the first notch portion and the third notch portion; the edge of the sixth notch portion forms a sixth edge, and when viewed along the thickness direction of the electrode assembly, the sixth notch portion at least partially overlaps with the second notch portion and the fourth notch portion. The fifth notch portion is composed of a plurality of fifth notches, and the plurality of fifth notches are spaced apart along the winding direction of the separator; the sixth notch portion is composed of a plurality of sixth notches, and the plurality of sixth notches are spaced apart along the winding direction of the separator. In this way, it is convenient for the pole ear to extend to the outside of the electrode assembly.

[0010] In one or more embodiments of the present application, when viewed along the thickness direction of the electrode assembly, the included angle between the center line of the first electrode tab and the fifth edge is γ 1 , 60°≤γ 1 ≤120°, where the midline of the first pole ear is perpendicular to the thickness direction of the electrode assembly. Set 60°≤γ 1 ≤120°, controlling the included angle between the first pole ear and the fifth edge within an appropriate range is beneficial to reducing the probability of interference between the first pole ear and the pole piece, while also beneficial to taking into account the space occupied by the first pole ear in the first direction and the second direction, thereby facilitating improving the energy density of the secondary battery.

[0011] In one or more embodiments of the present application, 88°≤γ 1 ≤92°. This is beneficial to further reduce the probability of interference between the first pole ear and the pole piece, and is also beneficial to further consider the space occupied by the first pole ear in the first direction and the second direction, thereby improving the energy density of the secondary battery.

[0012] In one or more embodiments of the present application, when viewed along the thickness direction of the electrode assembly, the included angle between the midline of the second electrode tab and the sixth edge is γ 2 , 60°≤γ 2 ≤120°, where the midline of the second pole ear is perpendicular to the thickness direction of the electrode assembly. Set 60°≤γ 2 ≤120°, controlling the included angle between the second pole ear and the sixth edge within an appropriate range is beneficial to reducing the probability of interference between the second pole ear and the pole piece, while taking into account the space occupied by the second pole ear in the first direction and the second direction, thereby facilitating improving the energy density of the secondary battery.

[0013] In one or more embodiments of the present application, 88°≤γ 2≤92°. This is beneficial to further reduce the probability of interference between the second pole ear and the pole piece, and is also beneficial to further consider the space occupied by the second pole ear in the first direction and the second direction, thereby improving the energy density of the secondary battery.

[0014] In one or more embodiments of the present application, the secondary battery further includes a shell, the shell includes a first shell and a second shell, the first shell and the second shell together enclose a first space, and the electrode assembly is accommodated in the first space. The shell includes a rimming portion and a sealing portion, the sealing portion includes a first sealing portion, a second sealing portion, a third sealing portion, a fourth sealing portion, and a fifth sealing portion; the rimming portion and the fourth edge are located on the same side of the electrode assembly, the first sealing portion and the first edge are located on the same side of the electrode assembly, the second sealing portion and the second edge are located on the same side of the electrode assembly, the third sealing portion and the third edge are located on the same side of the electrode assembly, the fourth sealing portion and the fifth edge are located on the same side of the electrode assembly, and the fifth sealing portion and the sixth edge are located on the same side of the electrode assembly. The fourth sealing portion connects the second sealing portion and the third sealing portion, and the fifth sealing portion connects the first sealing portion and the third sealing portion; part of the first pole ear extends out of the shell from the fourth sealing portion, and part of the second pole ear extends out of the shell from the fifth sealing portion. In this way, the shape of the shell is adapted to the shape of the electrode assembly, so that the inner surface of the shell is as close to the electrode assembly as possible, which is beneficial to reduce the gap between the inner surface of the shell and the electrode assembly and improve the energy density of the secondary battery.

[0015] In one or more embodiments of the present application, when viewed along the first direction, the length of the edge wrapping portion is not less than the length of any edge sealing portion, which is beneficial to reducing the total length of the edge sealing portion and reducing the space occupied by the edge sealing portion, thereby facilitating improving the energy density of the secondary battery.

[0016] In one or more embodiments of the present application, when viewed along the thickness direction of the electrode assembly, the included angle between the center line of the first electrode tab and the fourth edge sealing portion is θ 1 , 85°≤θ 1 ≤95°, where the midline of the first electrode tab is perpendicular to the thickness direction of the electrode assembly. Set 85°≤θ 1 ≤95°, the angle between the first electrode tab and the fourth edge sealing portion is controlled within an appropriate range, and the distance between the edges of the first electrode tab and the fourth edge sealing portion is not too close, which is beneficial to reducing the influence of the first electrode tab on the sealing performance of the fourth edge sealing portion.

[0017] In one or more embodiments of the present application, 88°≤θ 1 ≤92°. Set 88°≤θ 1 ≤92°, the distance between the first electrode tab and the edge of the fourth edge sealing portion is not too close, which is beneficial to further reduce the influence of the first electrode tab on the sealing performance of the fourth edge sealing portion.

[0018] In one or more embodiments of the present application, when viewed along the thickness direction of the electrode assembly, the included angle between the center line of the second electrode tab and the fifth edge sealing portion is θ 2 , 85°≤θ 2 ≤95°. Set 85°≤θ 2 ≤95°, the angle between the second electrode tab and the fifth edge sealing portion is controlled within an appropriate range, and the distance between the second electrode tab and the edge of the fifth edge sealing portion is not too close, which is beneficial to reducing the influence of the second electrode tab on the sealing performance of the fifth edge sealing portion.

[0019] In one or more embodiments of the present application, 88°≤θ 2 ≤92°. The distance between the second electrode tab and the edge of the fifth edge sealing portion is not too close, which is beneficial to further reduce the influence of the second electrode tab on the sealing performance of the fifth edge sealing portion.

[0020] In one or more embodiments of the present application, the secondary battery further includes a first pole ear glue, the first pole ear glue is arranged on the fourth edge sealing portion, and a portion of the first pole ear passes through the first pole ear glue and extends out of the fourth edge sealing portion. Observed along the thickness direction of the electrode assembly, the angle between the center line of the first pole ear and the first pole ear glue is δ 1 , 85°≤δ 1 ≤95°. Set 85°≤δ 1 ≤95°, controlling the included angle between the first pole ear glue and the first pole ear within an appropriate range is beneficial to improving the sealing of the connection structure between the first pole ear glue and the first pole ear.

[0021] In one or more embodiments of the present application, 88°≤δ 1 ≤92°. This is beneficial to further improve the sealing performance of the connection structure between the first pole ear glue and the first pole ear.

[0022] In one or more embodiments of the present application, the secondary battery further includes a second pole ear glue, the second pole ear glue is arranged on the fifth edge sealing portion, and a portion of the second pole ear passes through the second pole ear glue and extends out of the fifth edge sealing portion. Observed along the thickness direction of the electrode assembly, the angle between the center line of the second pole ear and the second pole ear glue is δ 2 , 85°≤δ 2 ≤95°. Set 85°≤δ 2 ≤95°, controlling the included angle between the second pole ear glue and the second pole ear within an appropriate range is beneficial to improving the sealing of the connection structure between the second pole ear glue and the second pole ear.

[0023] In one or more embodiments of the present application, 88°≤δ 2 ≤92°. This is beneficial to further improve the sealing performance of the connection structure between the second pole ear glue and the second pole ear.

[0024] In one or more embodiments of the present application, the angle between the first electrode ear glue and the fourth edge sealing portion is ω 1 ,0°≤ω 1 ≤30°. Set 0°≤ω 1 ≤30°, so that the angle between the first electrode tab glue and the fourth edge sealing portion is within an appropriate range, which is conducive to reducing the difficulty of connecting the first electrode tab to the electrode assembly.

[0025] In one or more embodiments of the present application, the angle between the second electrode ear glue and the fifth edge sealing portion is ω 2 ,0°≤ω 2 ≤30°. Set 0°≤ω 2 ≤30°, so that the angle between the second electrode tab glue and the fifth edge sealing portion is within an appropriate range, which is conducive to reducing the difficulty of connecting the second electrode tab to the electrode assembly.

[0026] In one or more embodiments of the present application, along the length direction of the first tab, the width of the first tab glue is W 1 , 3mm≤W 1 ≤10mm; along the width direction of the first pole ear, the maximum straight-line distance on one side of the edge of the first pole ear beyond the edge of the first pole ear is L 1 , 2mm≤L 1 ≤4mm.

[0027] In one or more embodiments of the present application, along the length direction of the second electrode ear, the width of the second electrode ear glue is W 2 , 3mm≤W 2 ≤10mm; along the width direction of the second pole ear, the maximum straight-line distance on one side that the edge of the second pole ear glue exceeds the edge of the second pole ear is L 2 , 2mm≤L 2 ≤4mm.

[0028] The second aspect of the embodiment of the present application provides an electrochemical device, which includes a circuit board and a secondary battery as described in any of the above embodiments, wherein the circuit board connects the first electrode tab and the second electrode tab. The secondary battery is connected to the circuit board to facilitate the control of the working process of the secondary battery.

[0029] In one or more embodiments of the present application, the circuit board includes a first circuit board and a second circuit board, the first electrode tab is electrically connected to the first circuit board, the second electrode tab is electrically connected to the second circuit board, and the first circuit board does not exceed the second edge sealing portion in the first direction when viewed along the thickness direction of the electrode assembly. This is conducive to reducing the space occupied by the first circuit board in the first direction and improving the energy density of the electrochemical device.

[0030] In one or more embodiments of the present application, the first circuit board does not extend beyond the third edge sealing portion in the second direction, which is beneficial to reducing the space occupied by the first circuit board in the second direction and improving the energy density of the electrochemical device.

[0031] In one or more embodiments of the present application, the second circuit board does not extend beyond the first edge sealing portion in the first direction, which is beneficial to reducing the space occupied by the second circuit board in the first direction and improving the energy density of the electrochemical device.

[0032] In one or more embodiments of the present application, the second circuit board does not extend beyond the third edge sealing portion in the second direction, which is beneficial to reducing the space occupied by the second circuit board in the second direction and improving the energy density of the electrochemical device.

[0033] A third aspect of the embodiments of the present application provides an electrical device, which includes the electrochemical device involved in any of the aforementioned embodiments.

[0034] A fourth aspect of an embodiment of the present application provides a method for preparing a secondary battery, the method comprising the following steps:

[0035] Take a first pole piece, the first pole piece includes a first side and a second side arranged opposite to each other along a first direction, cut the first side and the second side to obtain a plurality of first notches on the first side and a plurality of second notches on the second side;

[0036] Take a second pole piece, the second pole piece includes a third side and a fourth side arranged opposite to each other along the first direction, cut the third side and the fourth side to obtain a plurality of third notches on the third side and a plurality of fourth notches on the fourth side;

[0037] Taking an isolation film, the isolation film includes a fifth side and a sixth side disposed opposite to each other along a first direction, cutting the fifth side and the sixth side to obtain a plurality of fifth notches on the fifth side and a plurality of sixth notches on the sixth side;

[0038] The first electrode sheet, the isolation membrane and the second electrode sheet are stacked in sequence and then wound to form an electrode assembly; when stacking, the multiple first notches and the multiple third notches are aligned one by one; along the thickness direction of the electrode assembly, the projection of the fifth notch is located within the projection range of the first notch and the third notch; the second notch and the fourth notch are aligned one by one; along the thickness direction of the electrode assembly, the projection of the sixth notch is located within the projection range of the second notch and the fourth notch.

[0039] In one or more embodiments of the present application, the method also includes the following steps: taking a shell, the shell including a first shell and a second shell, the first shell and the second shell are connected by an edge portion, the first shell is folded toward the second shell along the edge portion and enclosed with the second shell to form a first space, and the electrode assembly is accommodated in the first space; the first shell and the second shell are sealed by a heat sealing process, and an edge sealing portion is formed at the heat sealing portion.

[0040] In one or more embodiments of the present application, the method further comprises the following steps: heat-sealing the first shell and the second shell at the first edge to form a first edge-sealing portion; heat-sealing the first shell and the second shell at the second edge to form a second edge-sealing portion; heat-sealing the first shell and the second shell at the third edge to form a third edge-sealing portion; bending the first edge-sealing portion, the second edge-sealing portion and the third edge-sealing portion toward the first space. In this way, the volume of the shell is reduced and the energy density of the secondary battery is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the overall structure of a secondary battery in one embodiment of the present application.

[0042] Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure at point I II I in FIG.

[0043] Figure 3 It is a partial structural schematic diagram of a secondary battery in one embodiment of the present application.

[0044] Figure 4 It is a schematic diagram of the structural decomposition of a secondary battery in one embodiment of the present application.

[0045] Figure 5 It is a schematic diagram of the structure of the first pole piece in a wound state in an embodiment of the present application.

[0046] Figure 6 It is a schematic diagram of the structure of the first pole piece in a flattened state in one embodiment of the present application.

[0047] Figure 7 It is a schematic diagram of the structure of the second pole piece in a wound state in one embodiment of the present application.

[0048] Figure 8 It is a schematic diagram of the structure of the second pole piece in a flattened state in one embodiment of the present application.

[0049] Fig. 9 It is a schematic diagram of the structure of the isolation film in a wound state in one embodiment of the present application.

[0050] Fig.10It is a schematic diagram of the structure of the isolation membrane in a flattened state in one embodiment of the present application.

[0051] Fig.11 It is a schematic diagram of the overall structure of an electrochemical device in one embodiment of the present application.

[0052] Fig.12 It is a schematic diagram of the structure of an electrical device in an embodiment of the present application.

[0053] Main component symbols

[0054] Secondary battery 100

[0055] Housing 10

[0056] First housing 11

[0057] Second housing 12

[0058] Hemming 101

[0059] Edge banding 102

[0060] The first edge sealing part 1021

[0061] Second edge sealing part 1022

[0062] The third edge sealing part 1023

[0063] Fourth edge sealing part 1024

[0064] Fifth edge sealing part 1025

[0065] Electrode assembly 20

[0066] The first pole piece 21

[0067] First notch portion 211

[0068] First Gap 2111

[0069] First benchmark gap 2112

[0070] First side line 2112a

[0071] Second side line 2112b

[0072] First curved edge 2112c

[0073] First reference point 2112d

[0074] The second notch 212

[0075] The second gap 2121

[0076] First side 21a

[0077] Second side 21b

[0078] The second pole piece 22

[0079] The third notch 221

[0080] The third gap 2211

[0081] Fourth notch 222

[0082] Fourth Gap 2221

[0083] The second benchmark gap 2222

[0084] The third sideline 2222a

[0085] Fourth sideline 2222b

[0086] Second curved edge 2222c

[0087] Second reference point 2222d

[0088] The third side 22a

[0089] Fourth side 22b

[0090] Isolation film 23

[0091] Fifth notch 231

[0092] Fifth Gap 2311

[0093] Sixth notch 232

[0094] Sixth Gap 2321

[0095] First Edge 201

[0096] Second Edge 202

[0097] Third Edge 203

[0098] Fourth Edge 204

[0099] Fifth Edge 205

[0100] Sixth Edge 206

[0101] First tab 30

[0102] The Seventh Edge 31

[0103] Second pole ear 40

[0104] Eighth Edge 41

[0105] First ear glue 50

[0106] Second ear glue 60

[0107] Electrochemical device 1000

[0108] Circuit board 200

[0109] First circuit board 210

[0110] Second circuit board 220

[0111] Electrical equipment 10000

[0112] First direction X

[0113] Second direction Y

[0114] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0115] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0116] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centrally disposed element at the same time. When an element is considered to be "disposed on" another element, it may be directly disposed on the other element or there may be a centrally disposed element at the same time.

[0117] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0118] 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.

[0119] In the description of the embodiments of the present application, the term "perpendicular" is used to describe an ideal state between two components. In actual production or use, there may be a state that is approximately perpendicular between the two components. The two components described as "perpendicular" may not be absolutely straight lines or planes, but may be roughly straight lines or planes. From a macroscopic point of view, if the overall extension direction is a straight line or a plane, the components can be considered to be "straight lines" or "planes".

[0120] The term "parallel" is used to describe the ideal state between two parts. In actual production or use, two parts may be approximately parallel. The two parts described as "parallel" may not be absolutely straight lines or planes, but may be roughly straight lines or planes. From a macroscopic point of view, if the overall extension direction is a straight line or a plane, the parts can be considered "straight" or "plane".

[0121] 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.

[0122] An embodiment of the present application provides a secondary battery, which includes an electrode assembly, a first pole ear, and a second pole ear. The electrode assembly includes a first pole sheet and a second pole sheet, and the polarities of the first pole sheet and the second pole sheet are opposite; the electrode assembly is a winding structure, and the winding structure is formed by stacking the first pole sheet and the second pole sheet and winding them. Observing along the thickness direction of the electrode assembly, the electrode assembly includes a first edge and a second edge arranged opposite to each other along the first direction, a third edge and a fourth edge arranged opposite to each other along the second direction, a fifth edge connecting the second edge and the third edge, and a sixth edge connecting the first edge and the third edge. The supplementary angle of the angle between the fifth edge and the third edge is α 1 , the supplementary angle between the fifth edge and the second edge is α 2 , 0<α 1 <90°,0<α 2 <90°. The supplementary angle of the angle between the sixth edge and the third edge is β 1 , the supplementary angle between the sixth edge and the first edge is β 2 , 0<β 1 <90°,0<β 2 <90°. The first direction, the second direction and the thickness direction of the electrode assembly are perpendicular to each other. One end of the first pole ear is connected to the electrode assembly, and the other end of the first pole ear extends from the fifth edge and extends to the outside of the electrode assembly. One end of the second pole ear is connected to the electrode assembly, and the other end of the second pole ear extends from the sixth edge and extends to the outside of the electrode assembly.

[0123] In this secondary battery, the first pole ear and the second pole ear extend from the fifth edge and the sixth edge of the electrode assembly respectively. The first pole ear and the second pole ear are located at the corners of the secondary battery, which reduces the occupation of the head space of the secondary battery and is beneficial to improving the energy density of the secondary battery.

[0124] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0125] like Figure 1 and Figure 2 As shown, a first aspect of an embodiment of the present application provides a secondary battery 100 , which includes a housing 10 and an electrode assembly 20 , wherein the electrode assembly 20 is accommodated in the housing 10 .

[0126] In some embodiments, the housing 10 is a flexible packaging bag, such as an aluminum-plastic film.

[0127] In some embodiments, Figure 2 As shown, the electrode assembly 20 includes a first electrode plate 21 and a second electrode plate 22 , and the polarities of the first electrode plate 21 and the second electrode plate 22 are opposite, that is, one of the first electrode plate 21 and the second electrode plate 22 is a positive electrode plate, and the other is a negative electrode plate.

[0128] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is disposed on two opposite sides of the positive electrode current collector along the thickness direction thereof.

[0129] In some embodiments, the positive electrode current collector is a metal layer. As an illustrative example, the positive electrode current collector can be a metal layer including at least one of aluminum, nickel, tantalum, and titanium, such as aluminum foil.

[0130] In some embodiments, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.

[0131] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is disposed on two opposite sides of the negative electrode current collector along the thickness direction thereof.

[0132] In some embodiments, the negative electrode current collector is a metal layer. As an illustrative example, the negative electrode current collector may be a metal layer including at least one of copper, nickel, tantalum, and titanium, such as copper foil.

[0133] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, and silicon-carbon material.

[0134] In some embodiments, Figure 2 As shown, the electrode assembly 20 further includes an isolation film 23 , which is disposed between the first pole piece 21 and the second pole piece 22 to insulate the first pole piece 21 from the second pole piece 22 .

[0135] In some embodiments, the material of the isolation film 23 is one of polyethylene film, polypropylene film, polyester film or polyimide film.

[0136] In some embodiments, Figure 2 As shown, the electrode assembly 20 is a winding structure, which is formed by stacking and winding a first electrode sheet 21 and a second electrode sheet 22 .

[0137] In some embodiments, Figure 1 As shown, the secondary battery 100 further includes a first pole tab 30 and a second pole tab 40, both of which are connected to the electrode assembly 20. Specifically, the first pole tab 30 is connected to the first pole sheet 21, and the second pole tab 40 is connected to the second pole sheet 22.

[0138] In some embodiments, the secondary battery 100 further includes an electrolyte, and the electrolyte is filled in the housing 10 .

[0139] In some embodiments, the electrolyte salt is not limited to lithium hexafluorophosphate (LiPF 6 ), bis(trifluoromethanesulfonyl)imide lithium LiN (CF 3 SO 2 ) 2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO 2 F) 2 )(LiFSI), lithium hexafluorocesium oxide (LiCsF 6 ), lithium perchlorate (LiClO 4 ) or lithium trifluoromethanesulfonate (LiCF 3 SO 3 ) at least one of.

[0140] In some embodiments, Figure 3 As shown, when viewed along the thickness direction of the electrode assembly 20, the electrode assembly 20 includes a first edge 201 and a second edge 202 arranged opposite to each other along the first direction X, a third edge 203 and a fourth edge 204 arranged opposite to each other along the second direction Y, a fifth edge 205 connecting the second edge 202 and the third edge 203, and a sixth edge 206 connecting the first edge 201 and the third edge 203. The supplementary angle between the fifth edge 205 and the third edge 203 is α 1 , the supplementary angle between the fifth edge 205 and the second edge 202 is α 2 , 0<α 1 <90°,0<α 2 <90°. The supplementary angle between the sixth edge 206 and the third edge 203 is β 1 , the supplementary angle between the sixth edge 206 and the first edge 201 is β 2 , 0<β 1 <90°,0<β 2<90°. The first direction X, the second direction Y and the thickness direction of the electrode assembly 20 are perpendicular to each other. One end of the first pole ear 30 is connected to the electrode assembly 20, and the other end of the first pole ear 30 extends from the fifth edge 205 and extends to the outside of the electrode assembly 20; one end of the second pole ear 40 is connected to the electrode assembly 20, and the other end of the second pole ear 40 extends from the sixth edge 206 and extends to the outside of the electrode assembly 20.

[0141] It should be noted that the fifth edge 205 does not necessarily extend in a straight line as a whole. In some embodiments, the portion of the fifth edge 205 including the intersection point between the fifth edge 205 and the third edge 203 is a curve. Therefore, in the embodiment of the present application, when measuring α 1 When the fifth edge 205 overlaps with the first electrode tab 30 in the thickness direction of the electrode assembly 20, the measurement is performed based on the extending direction of the portion, and the extending direction of this portion can also be used as the measurement direction of α 2 The sixth edge 206 does not necessarily extend along a straight line as a whole. In some embodiments, the portion of the fifth edge 205 including the intersection with the third edge 203 is a curve. Therefore, in the embodiment of the present application, the measurement of β 1 When the sixth edge 206 is measured based on the extending direction of the portion overlapping the second electrode tab 40 in the thickness direction of the electrode assembly 20, this portion can also be used as the measurement β 2 basis.

[0142] In this secondary battery 100, the first pole ear 30 and the second pole ear 40 extend from the fifth edge 205 and the sixth edge 206 of the electrode assembly 20 respectively. The first pole ear 30 and the second pole ear 40 are located at the corners of the secondary battery 100, which reduces the occupation of the head space of the secondary battery 100 and is beneficial to improving the energy density of the secondary battery 100.

[0143] In some embodiments, 40°≤α 1 ≤50°, 40°≤α 2 In this way, the angle between the fifth edge 205 and the third edge 203 and the angle between the fifth edge 205 and the second edge 202 can be set within an appropriate range, which is beneficial to improving the volume energy density of the secondary battery 100 .

[0144] In some embodiments, 40°≤β 1 ≤50°, 40°≤β 2 ≤50°. In this way, the included angle between the sixth edge 206 and the third edge 203 and the included angle between the sixth edge 206 and the first edge 201 can be set within an appropriate range, which is beneficial to improving the volume energy density of the secondary battery 100 .

[0145] In some embodiments, the first direction X corresponds to the width direction of the first pole piece 21 and the second pole piece 22 in the flattened state, and the winding direction of the electrode assembly 20 corresponds to the length direction of the first pole piece 21 and the second pole piece 22 in the flattened state.

[0146] In some embodiments, Figure 4 As shown, the shell 10 includes a first shell 11 and a second shell 12, the first shell 11 and the second shell 12 are together enclosed to form a first space, and the electrode assembly 20 is accommodated in the first space; the shell 10 includes a rim portion 101 and a sealing portion 102, the sealing portion 102 includes a first sealing portion 1021, a second sealing portion 1022, a third sealing portion 1023, a fourth sealing portion 1024 and a fifth sealing portion 1025; the rim portion 101 and the fourth edge 204 are located on the same side of the electrode assembly 20, the first sealing portion 1021 and the first edge 201 are located on the same side of the electrode assembly 20, and the second sealing portion 1022 and the second edge 202 are located on On the same side of the electrode assembly 20, the third edge seal 1023 and the third edge 203 are located on the same side of the electrode assembly 20, the fourth edge seal 1024 and the fifth edge 205 are located on the same side of the electrode assembly 20, and the fifth edge seal 1025 and the sixth edge 206 are located on the same side of the electrode assembly 20; the fourth edge seal 1024 connects the second edge seal 1022 and the third edge seal 1023, and the fifth edge seal 1025 connects the first edge seal 1021 and the third edge seal 1023; part of the first pole tab 30 extends out of the shell 10 from the fourth edge seal 1024, and part of the second pole tab 40 extends out of the shell 10 from the fifth edge seal 1025. In this way, the shape of the shell 10 is adapted to the shape of the electrode assembly 20, so that the inner surface of the shell 10 is as close to the electrode assembly 20 as possible, which is conducive to reducing the gap between the inner surface of the shell 10 and the electrode assembly 20, and improving the energy density of the secondary battery 100.

[0147] In some embodiments, Figure 1 As shown, when viewed along the first direction X, the length of the edge portion 101 is not less than the length of any edge sealing portion 102. This is beneficial to reducing the total length of the edge sealing portion 102 and reducing the space occupied by the edge sealing portion 102, thereby facilitating improving the energy density of the secondary battery 100.

[0148] In some embodiments, Figures 5 to 8As shown, the first electrode piece 21 includes a first notch portion 211 and a second notch portion 212 that are arranged opposite to each other along the first direction X; the first notch portion 211 is located at the fifth edge 205, and the first electrode tab 30 extends out of the electrode assembly 20 from the first notch portion 211; the second notch portion 212 is located at the sixth edge 206, and the second electrode tab 40 extends out of the electrode assembly 20 from the second notch portion 212. The first notch portion 211 is composed of a plurality of first notches 2111, and the plurality of first notches 2111 are arranged at intervals along the winding direction of the first electrode piece 21; the second notch portion 212 is composed of a plurality of second notches 2121, and the plurality of second notches 2121 are arranged at intervals along the winding direction of the first electrode piece 21. The second pole piece 22 includes a third notch portion 221 and a fourth notch portion 222 which are arranged opposite to each other along the first direction X; the third notch portion 221 is located at the fifth edge 205, and when observed along the thickness direction of the electrode assembly 20, the third notch portion 221 and the first notch portion 211 at least partially overlap; the fourth notch portion 222 is located at the sixth edge 206, and when observed along the thickness direction of the electrode assembly 20, the fourth notch portion 222 and the second notch portion 212 at least partially overlap; the third notch portion 221 is composed of a plurality of third notches 2211, and the plurality of third notches 2211 are arranged at intervals along the winding direction of the second pole piece 22; the fourth notch portion 222 is composed of a plurality of fourth notches 2221, and the plurality of fourth notches 2221 are arranged at intervals along the winding direction of the second pole piece 22. In this way, after the first notch 2111 and the second notch 2121 are processed on the first pole piece 21, the first notch portion 211 and the second notch portion 212 can be formed by winding the first pole piece 21. After the third notch 2211 and the fourth notch 2221 are processed on the second pole piece 22, the third notch portion 221 and the fourth notch portion 222 can be formed by winding the second pole piece 22, which is convenient for production.

[0149] In some embodiments, Fig. 9 and Fig.10 As shown, the separator 23 includes a fifth notch 231 and a sixth notch 232 which are arranged opposite to each other along the first direction X; the edge of the fifth notch 231 forms a fifth edge 205, and when viewed along the thickness direction of the electrode assembly 20, the fifth notch 231 at least partially overlaps with the first notch 211 and the third notch 221; the edge of the sixth notch 232 forms a sixth edge 206, and when viewed along the thickness direction of the electrode assembly 20, the sixth notch 232 at least partially overlaps with the second notch 212 and the fourth notch 222; the fifth notch 231 is composed of a plurality of fifth notches 2311, and the plurality of fifth notches 2311 are arranged at intervals along the winding direction of the separator 23; the sixth notch 232 is composed of a plurality of sixth notches 2321, and the plurality of sixth notches 2321 are arranged at intervals along the winding direction of the separator 23. In this way, it is convenient for the tab to extend to the outside of the electrode assembly 20.

[0150] In some embodiments, Figure 6As shown, along the winding direction of the first pole piece 21, the first pole ear 30 is connected to the middle of the first pole piece 21; Figure 8 As shown, along the winding direction of the second pole piece 22, the second pole lug 40 is connected to the middle of the second pole piece 22. This is beneficial to reduce the moving distance of electrons when forming a current, and is beneficial to reduce the internal resistance of the electrode assembly 20.

[0151] In some embodiments, Figure 6 As shown, the first pole ear 30 is connected to the first pole piece 21, one of the first notches 2111 is a first reference notch 2112, and when the first pole piece 21 is flattened, the first pole ear 30 extends from the first reference notch 2112, and when viewed along the thickness direction of the first pole piece 21, the first pole piece 21 includes a first edge 21a, the opening of the first reference notch 2112 faces the first edge 21a, the first reference notch 2112 includes a first edge line 2112a, a second edge line 2112b, and a first curved edge 2112c, the first curved edge 2112c connects the first edge line 2112a and the second edge line 2112b, and the first pole ear 30 extends from the first edge line 2112a. The extension line of the first edge line 2112a away from the first edge 21a and the extension line of the second edge line 2112b away from the first edge 21a intersect to form a first reference point 2112d. Observed along the thickness direction of the first pole tab 30, the first pole tab 30 includes a seventh edge 31, which is the length side of the first pole tab 30, and the seventh edge 31 faces the first reference notch 2112. Along the extension direction of the first sideline 2112a, the distance from the intersection of the first sideline 2112a and the seventh edge 31 to the first reference point 2112d is L; along the extension direction of the first pole tab 30, the length from the intersection of the extension line of the first side 21a close to the seventh edge 31 and the seventh edge 31 to the first sideline 2112a is R, and the angle between the center line of the first pole tab and the side of the first sideline facing the first reference point is γ 1 , γ 1 ≤90°, This helps reduce the possibility of interference between the first pole sheet 21 and the first pole ear 30 during the winding process of the electrode assembly 20 , and helps reduce the difficulty of preparing the electrode assembly 20 .

[0152] The center line of the first pole lug 30 can be marked by the following method: observe the first pole lug 30 along the thickness direction of the first pole lug 30, measure the two width sides of the first pole lug 30 with a ruler, mark the midpoints of the two width sides of the first pole lug 30, and connect the two midpoints to obtain the center line of the first pole lug 30. Figure 5The center line of the first pole lug 30 is shown by a dotted line. The interference length of the first pole lug 30 refers to the length of the portion of the first pole lug 30 that may interfere with the pole piece during the winding process of the electrode assembly 20. The interference length of the first pole lug 30 can be measured by the following method: observe the first pole lug 30 along the thickness direction of the first pole lug 30, the first pole lug 30 has a first pole lug 30 side, the first pole lug 30 side faces the inside of the first reference notch 2112, and the first pole lug 30 side is the length side of the first pole lug 30, the first pole piece 21 has a first side 21a, the first reference notch 2112 is located at the first side 21a, the first side 21a is extended to intersect with the first pole lug 30 side, and the length of the portion of the first pole lug 30 side located at the intersection to the root of the first pole lug 30 is measured, and this length is the interference length of the first pole lug 30.

[0153] In some embodiments, Figure 8 As shown, the second pole ear 40 is connected to the second pole piece 22, one of the fourth notches 2221 is a second reference notch 2222, and when the second pole piece 22 is flattened, the second pole ear 40 extends from the second reference notch 2222, and when viewed along the thickness direction of the second pole piece 22, the second pole piece 22 includes a fourth side 22b, the opening of the second reference notch 2222 faces the fourth side 22b, the second reference notch 2222 includes a third side line 2222a, a fourth side line 2222b, and a second curved side 2222c, the second curved side 2222c connects the third side line 2222a and the fourth side line 2222b, and the second pole ear 40 extends from the third side line 2222a. The extension line of the third side line 2222a away from the fourth side 22b and the extension line of the fourth side line 2222b away from the fourth side 22b intersect to form a second reference point 2222d. Observed along the thickness direction of the second pole tab 40, the second pole tab 40 includes an eighth edge 41, which is the length side of the second pole tab 40, and the eighth edge 41 faces the second reference notch 2222. Along the extension direction of the third sideline 2222a, the distance from the intersection of the third sideline 2222a and the eighth edge 41 to the second reference point 2112d is D, and along the extension direction of the second pole tab 40, the length from the intersection of the extension line of the fourth side 22b close to the eighth edge 41 and the eighth edge 41 to the third sideline 222a is A; the included angle between the center line of the second pole tab and the side of the third sideline facing the second reference point is γ 2 , γ 2 ≤90°, This helps reduce the possibility of interference between the second pole sheet 22 and the second pole ear 40 during the winding process of the electrode assembly 20 , and helps reduce the difficulty of preparing the electrode assembly 20 .

[0154] The marking method of the center line of the second pole lug 40 can refer to the marking method of the center line of the first pole lug 30, which will not be repeated here. The measurement method of the interference length of the second pole lug 40 can refer to the measurement method of the interference length of the first pole lug 30, which will not be repeated here.

[0155] In some embodiments, ω=μ, α 1 =β 1 .

[0156] In some embodiments, Figure 3 As shown, when viewed along the thickness direction of the electrode assembly 20, the included angle between the midline of the first electrode tab 30 and the fifth edge 205 is γ 1 , 60°≤γ 1 ≤120°, wherein the center line of the first electrode tab 30 is perpendicular to the thickness direction of the electrode assembly 20. Set 60°≤γ 1 ≤120°, controlling the included angle between the first pole ear 30 and the fifth edge 205 within an appropriate range is beneficial to reducing the probability of interference between the first pole ear 30 and the pole piece, while taking into account the space occupied by the first pole ear 30 in the first direction X and the second direction Y, thereby facilitating improving the energy density of the secondary battery 100.

[0157] In some embodiments, 88°≤γ 1 ≤92°. In this way, the probability of interference between the first pole tab 30 and the pole piece is further reduced, and the space occupied by the first pole tab 30 in the first direction X and the second direction Y is further taken into account, thereby improving the energy density of the secondary battery 100.

[0158] In some embodiments, Figure 3 As shown, when viewed along the thickness direction of the electrode assembly 20, the included angle between the midline of the second electrode tab 40 and the sixth edge 206 is γ 2 , 60°≤γ 2 ≤120°. The midline of the second electrode tab 40 is perpendicular to the thickness direction of the electrode assembly 20. Set 60°≤γ 2 ≤120°, controlling the included angle between the second pole ear 40 and the sixth edge 206 within an appropriate range is beneficial to reducing the probability of interference between the second pole ear 40 and the pole piece, while also beneficial to taking into account the space occupied by the second pole ear 40 in the first direction X and the second direction Y, thereby facilitating improving the energy density of the secondary battery 100.

[0159] In some embodiments, 88°≤γ 2 ≤92°. This is beneficial to further reduce the probability of interference between the second pole tab 40 and the pole piece, and is beneficial to further consider the space occupied by the second pole tab 40 in the first direction X and the second direction Y, thereby improving the energy density of the secondary battery 100.

[0160] In some embodiments, Figure 1 As shown, when viewed along the thickness direction of the electrode assembly 20, the included angle between the center line of the first electrode tab 30 and the fourth edge sealing portion 1024 is θ 1 , 85°≤θ 1 ≤95°, wherein the center line of the first electrode tab 30 is perpendicular to the thickness direction of the electrode assembly 20. Set 85°≤θ 1 ≤95°, the angle between the first electrode tab 30 and the fourth edge sealing portion 1024 is controlled within an appropriate range, and the distance between the edges of the first electrode tab 30 and the fourth edge sealing portion 1024 is not too close, which is beneficial to reducing the influence of the first electrode tab 30 on the sealing performance of the fourth edge sealing portion 1024.

[0161] In some embodiments, 88°≤θ 1 ≤92°. Set 88°≤θ 1 ≤92°, the distance between the first electrode tab 30 and the edge of the fourth edge sealing portion 1024 is not too close, which is beneficial to further reduce the influence of the first electrode tab 30 on the sealing performance of the fourth edge sealing portion 1024.

[0162] In some embodiments, Figure 1 As shown, when viewed along the thickness direction of the electrode assembly 20, the included angle between the center line of the second electrode tab 40 and the fifth edge sealing portion 1025 is θ 2 , 85°≤θ 2 ≤95°. Set 85°≤θ 2 ≤95°, the included angle between the second electrode tab 40 and the fifth edge sealing portion 1025 is controlled within an appropriate range, and the distance between the second electrode tab 40 and the edge of the fifth edge sealing portion 1025 is not too close, which is beneficial to reducing the influence of the second electrode tab 40 on the sealing performance of the fifth edge sealing portion 1025.

[0163] In some embodiments, 88°≤θ 2 The distance between the second electrode tab 40 and the edge of the fifth edge sealing portion 1025 is not too close, which is beneficial to further reduce the influence of the second electrode tab 40 on the sealing performance of the fifth edge sealing portion 1025 .

[0164] In some embodiments, Figure 1 As shown, the secondary battery 100 further includes a first pole ear glue 50, which is disposed on the fourth edge sealing portion 1024, and a portion of the first pole ear 30 passes through the first pole ear glue 50 and extends out of the fourth edge sealing portion 1024; when viewed along the thickness direction of the electrode assembly 20, the angle between the center line of the first pole ear 30 and the first pole ear glue 50 is δ 1 , 85°≤δ 1 ≤95°. Set 85°≤δ 1≤95°, controlling the included angle between the first pole ear glue 50 and the first pole ear 30 within an appropriate range is beneficial to improving the sealing of the connection structure between the first pole ear glue 50 and the first pole ear 30.

[0165] In some embodiments, 88°≤δ 1 ≤92°. This is beneficial to further improve the sealing performance of the connection structure between the first electrode tab glue 50 and the first electrode tab 30.

[0166] In some embodiments, Figure 1 As shown, the secondary battery 100 further includes a second pole ear glue 60, which is disposed on the fifth edge sealing portion 1025, and a portion of the second pole ear 40 passes through the second pole ear glue 60 and extends out of the fifth edge sealing portion 1025; when viewed along the thickness direction of the electrode assembly 20, the angle between the center line of the second pole ear 40 and the second pole ear glue 60 is δ 2 , 85°≤δ 2 ≤95°. Set 85°≤δ 2 ≤95°, controlling the included angle between the second pole ear glue 60 and the second pole ear 40 within an appropriate range is beneficial to improving the sealing of the connection structure between the second pole ear glue 60 and the second pole ear 40.

[0167] In some embodiments, 88°≤δ 2 ≤92°. This is beneficial to further improve the sealing performance of the connection structure between the second electrode tab glue 60 and the second electrode tab 40.

[0168] In some embodiments, Figure 1 As shown, the angle between the first electrode ear glue 50 and the fourth edge sealing portion 1024 is ω 1 ,0°≤ω 1 ≤30°. Here, the extension direction of the first pole ear glue 50 intersects with the extension direction of the fourth edge sealing portion 1024 to form four angles, and the angle between the first pole ear glue 50 and the fourth edge sealing portion 1024 is the angle value of the smaller two angles of the four angles. When the angle between the first pole ear glue 50 and the fourth edge sealing portion 1024 is too large, the first pole ear glue 50 is likely to interfere with the fourth edge sealing portion 1024, and the first pole ear 30 is usually connected to the first pole ear glue 50 before being connected to the electrode assembly 20. Therefore, when the first pole ear glue 50 interferes with the fourth edge sealing portion 1024, it may cause difficulty in connecting the first pole ear 30 to the electrode assembly 20. Therefore, setting 0°≤ω 1 ≤30°, so that the included angle between the first electrode tab glue 50 and the fourth edge sealing portion 1024 is within an appropriate range, which is conducive to reducing the difficulty of connecting the first electrode tab 30 with the electrode assembly 20.

[0169] In some embodiments, Figure 1As shown, the angle between the second electrode ear glue 60 and the fifth edge sealing portion 1025 is ω 2 ,0°≤ω 2 ≤30°. Here, the extension direction of the second pole ear glue 60 intersects with the extension direction of the fifth edge sealing portion 1025 to form four angles, and the angle between the second pole ear glue 60 and the fifth edge sealing portion 1025 is the angle value of the smaller two angles of the four angles. When the angle between the second pole ear glue 60 and the fifth edge sealing portion 1025 is too large, the second pole ear glue 60 is likely to interfere with the fifth edge sealing portion 1025, and the second pole ear 40 is usually connected to the second pole ear glue 60 before being connected to the electrode assembly 20. Therefore, when the second pole ear glue 60 interferes with the fifth edge sealing portion 1025, it may cause difficulty in connecting the second pole ear 40 to the electrode assembly 20. Therefore, setting 0°≤ω 2 ≤30°, so that the included angle between the second electrode tab glue 60 and the fifth edge sealing portion 1025 is within an appropriate range, which is conducive to reducing the difficulty of connecting the second electrode tab 40 to the electrode assembly 20.

[0170] In some embodiments, Figure 3 As shown, along the length direction of the first electrode tab 30, the width of the first electrode tab glue 50 is W 1 , 3mm≤W 1 ≤10mm; along the width direction of the first pole ear 30, the maximum linear distance on one side of the edge of the first pole ear glue 50 beyond the edge of the first pole ear 30 is L 1 , 2mm≤L 1 Here, the length direction of the first electrode tab 30 refers to the extending direction of its length side when it is in a flat state.

[0171] In some embodiments, Figure 3 As shown, along the length direction of the second electrode tab 40, the width of the second electrode tab glue 60 is W 2 , 3mm≤W 2 ≤10mm; along the width direction of the second pole ear 40, the maximum linear distance on one side of the edge of the second pole ear glue 60 beyond the edge of the second pole ear 40 is L 2 , 2mm≤L 2 Here, the length direction of the second electrode tab 40 refers to the extending direction of the length side thereof when it is in a flattened state.

[0172] like Fig.11 As shown, a second aspect of an embodiment of the present application provides an electrochemical device 1000 , which includes a circuit board 200 and a secondary battery 100 as described in any of the above embodiments, wherein the circuit board 200 is connected to the secondary battery 100 .

[0173] In some embodiments, Fig.11As shown, the electrochemical device 1000 further includes a circuit board 200, the circuit board 200 includes a first circuit board 210 and a second circuit board 220, the first pole tab 30 is connected to the first circuit board 210, and the second pole tab 40 is connected to the second circuit board 220. The secondary battery 100 is connected to the circuit board 200 to facilitate the control of the working process of the secondary battery 100.

[0174] In some embodiments, Fig.11 As shown, when viewed along the thickness direction of the electrode assembly 20 , the first circuit board 210 does not extend beyond the second edge sealing portion 1022 in the first direction X. This helps reduce the space occupied by the first circuit board 210 in the first direction X and improves the energy density of the electrochemical device 1000 .

[0175] In some embodiments, Fig.11 As shown, when viewed along the thickness direction of the electrode assembly 20 , the first circuit board 210 does not exceed the third edge sealing portion 1023 in the second direction Y. This is beneficial to reducing the space occupied by the first circuit board 210 in the second direction Y and improving the energy density of the electrochemical device 1000 .

[0176] In some embodiments, Fig.11 As shown, the second circuit board 220 does not extend beyond the first edge sealing portion 1021 in the first direction X. This is beneficial to reducing the space occupied by the second circuit board 220 in the first direction X, and is beneficial to improving the energy density of the electrochemical device 1000.

[0177] In some embodiments, Fig.11 As shown, the second circuit board 220 does not extend beyond the third edge sealing portion 1023 in the second direction Y. This is beneficial to reducing the space occupied by the second circuit board 220 in the second direction Y, and is beneficial to improving the energy density of the electrochemical device 1000.

[0178] like Fig.12 As shown, a third aspect of the embodiments of the present application provides an electrical device 10000, which includes the electrochemical device 1000 involved in any of the aforementioned embodiments.

[0179] A fourth aspect of an embodiment of the present application provides a method for preparing a secondary battery 100, and the method for preparing the secondary battery 100 comprises the following steps:

[0180] Take a first pole piece 21, the first pole piece 21 includes a first side 21a and a second side 21b arranged opposite to each other along a first direction X, cut the first side 21a and the second side 21b to obtain a plurality of first notches 2111 on the first side 21a, and a plurality of second notches 2121 on the second side 21b;

[0181] Take a second pole piece 22, the second pole piece 22 includes a third side 22a and a fourth side 22b arranged opposite to each other along the first direction X, cut the third side 22a and the fourth side 22b to obtain a plurality of third notches 2211 on the third side 22a, and obtain a plurality of fourth notches 2221 on the fourth side 22b;

[0182] Take the isolation film 23, the isolation film 23 includes a fifth side and a sixth side arranged opposite to each other along the first direction X, cut the fifth side and the sixth side to obtain a plurality of fifth notches 2311 on the fifth side and a plurality of sixth notches 2321 on the sixth side;

[0183] The first electrode sheet 21, the isolation membrane 23 and the second electrode sheet 22 are stacked in sequence and then wound to form the electrode assembly 20; when stacking, the multiple first notches 2111 and the multiple third notches 2211 are aligned one by one; along the thickness direction of the electrode assembly 20, the projection of the fifth notch 2311 is located within the projection range of the first notch 2111 and the third notch 2211; the second notch 2121 and the fourth notch 2221 are aligned one by one; along the thickness direction of the electrode assembly 20, the projection of the sixth notch 2321 is located within the projection range of the second notch 2121 and the fourth notch 2221.

[0184] In some embodiments, the method for preparing the secondary battery 100 includes the following steps:

[0185] Take a shell 10, the shell 10 includes a first shell 11 and a second shell 12, the first shell 11 and the second shell 12 are connected by a rim portion 101, the first shell 11 is folded toward the second shell 12 along the rim portion 101 and enclosed with the second shell 12 to form a first space, the electrode assembly 20 is accommodated in the first space, the first shell 11 and the second shell 12 are sealed by a heat sealing process, and a sealing rim portion 102 is formed at the heat sealing.

[0186] In some embodiments, the preparation method of the secondary battery 100 includes the following steps: heat-sealing the first shell 11 and the second shell 12 at the first edge 201 to form a first edge-sealed portion 1021, heat-sealing the first shell 11 and the second shell 12 at the second edge 202 to form a second edge-sealed portion 1022, and heat-sealing the first shell 11 and the second shell 12 at the third edge 203 to form a third edge-sealed portion 1023; bending the first edge-sealed portion 1021, the second edge-sealed portion 1022, and the third edge-sealed portion 1023 toward the direction of the first space. In this way, the volume of the shell 10 is reduced and the energy density of the secondary battery 100 is improved.

[0187] In order to verify the effect of the solution in the embodiment of the present application, the inventor of the present application conducted the following experiment, which includes 1 comparative example and 31 embodiments, each embodiment including 20 secondary batteries 100. In the experiment, the first pole piece 21 is a positive pole piece, the second pole piece 22 is a negative pole piece, the first pole tab 30 is a positive pole tab, and the second pole tab 40 is a negative pole tab.

[0188] The preparation process of the secondary battery in Comparative Example 1 includes the following steps:

[0189] (1) Preparation of positive electrode: The active material lithium cobalt oxide (LiCoO 2 ), conductive carbon black (Super P), CNT (carbon nanotube), polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:0.5:0.5:1.5, N-methylpyrrolidone (NMP) is added as a solvent, and a positive active material with a solid content of 75wt% is prepared, and stirred evenly for use. Aluminum foil with a thickness of 10μm is used as the positive current collector. The above active material material is evenly coated on one side of the positive current collector using a slit coater, and then dried at 90°C to obtain a positive electrode sheet coated with a single-sided positive active material material. At this time, the thickness of the positive active material layer is 50μm. The above coating steps are then repeated on the other side of the positive current collector. The coated positive electrode sheet is then cold pressed, and after cold pressing, the thickness of the positive active material layer is 35μm. The positive electrode ear is then welded to the portion of the positive current collector that is not covered by the positive active material layer. The positive electrode ear is located at the starting end of the winding of the positive electrode sheet, and the positive electrode ear extends along the width direction of the positive electrode sheet.

[0190] (2) Preparation of negative electrode sheet: Active materials artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), CMC (sodium carboxymethyl cellulose) are mixed in a weight ratio of 97:0.5:1.3:1.2, deionized water is added as a solvent, and a weight percentage of 50wt% of negative electrode active material is prepared, and the mixture is stirred evenly for use. A copper foil with a thickness of 10μm is used as a negative electrode current collector. The above negative electrode active material is evenly coated on one side of the negative electrode current collector using a slit coater, and then dried at 110°C to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. At this time, the thickness of the negative electrode active material layer is 55μm. Then repeat the above steps on the other side of the negative electrode current collector to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. Then the coated negative electrode sheet is cold pressed, and the thickness of the negative electrode active material layer after cold pressing is 45μm. Then, the negative electrode ear is welded to the portion of the negative electrode current collector not covered by the negative electrode active material layer. The negative electrode ear is located at the winding start end of the negative electrode sheet and extends along the width direction of the negative electrode sheet.

[0191] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed at a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF4) was added to the basic organic solvent. 6 ) are dissolved and mixed evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0192] (4) Preparation of the isolation membrane 23: A 7 μm thick polyethylene porous polymer film was used as the isolation membrane 23.

[0193] (5) Preparation of the electrode assembly 20: The positive electrode sheet, the separator 23 and the negative electrode sheet are stacked in sequence and then wound to form the electrode assembly 20.

[0194] (6) Assembly of secondary battery 100: Place the aluminum-plastic film with a hole formed in an assembly fixture with the hole facing upward, place the electrode assembly 20 in the hole, and apply external force to press it. Then, cover the electrode assembly 20 with another aluminum-plastic film with a hole formed in the hole facing downward, and heat-seal the edges of the two aluminum-plastic films by hot pressing. The unsealed edge is the side where the negative and positive tabs extend out of the shell 10. Then, inject electrolyte through the unsealed edge, and after vacuum packaging, standing, hot pressing, shaping and other processes, the secondary battery 100 is obtained. In the obtained secondary battery 100, except for the edge sealing part (top sealing position) where the positive and negative tabs extend out, the other edge sealing parts are bent in the thickness direction of the secondary battery 100.

[0195] The preparation process of the secondary battery 100 in Example 1 includes the following steps:

[0196] (1) Preparation of positive electrode: The active material lithium cobalt oxide (LiCoO 2), conductive carbon black (Super P), CNT (carbon nanotube), polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:0.5:0.5:1.5, N-methylpyrrolidone (NMP) is added as a solvent, and a positive electrode active material with a solid content of 75wt% is prepared, and stirred evenly for use. Aluminum foil with a thickness of 10μm is used as the positive current collector. The above active material materials are evenly coated on one side of the positive current collector using a slit coater, and then dried at 90°C to obtain a positive electrode sheet coated with a single-sided positive electrode active material. At this time, the thickness of the positive electrode active material layer is 50μm. The above coating steps are then repeated on the other side of the positive current collector. The coated positive electrode sheet is then cold pressed, and after cold pressing, the thickness of the positive electrode active material layer is 35μm. The positive electrode sheet includes a first edge 21a and a second edge 21b arranged opposite to each other along a first direction X. The first edge 21a and the second edge 21b are cut to obtain a plurality of first notches 2111 on the first edge 21a and a plurality of second notches 2121 on the second edge 21b. The positive electrode ear is then welded to a portion of the positive electrode current collector that is not covered by the positive electrode active material layer. The positive electrode ear is located at the starting end of the winding of the positive electrode sheet, and part of the positive electrode ear extends out from a first notch 2111.

[0197] (2) Preparation of negative electrode sheet: Active materials artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), CMC (sodium carboxymethyl cellulose) are mixed in a weight ratio of 97:0.5:1.3:1.2, deionized water is added as a solvent, and a weight percentage of 50wt% of negative electrode active material is prepared, and the mixture is stirred evenly for use. A copper foil with a thickness of 10μm is used as a negative electrode current collector. The above negative electrode active material is evenly coated on one side of the negative electrode current collector using a slit coater, and then dried at 110°C to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. At this time, the thickness of the negative electrode active material layer is 55μm. Then repeat the above steps on the other side of the negative electrode current collector to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. Then the coated negative electrode sheet is cold pressed, and the thickness of the negative electrode active material layer after cold pressing is 45μm. The negative electrode sheet includes a third side 22a and a fourth side 22b which are arranged opposite to each other along a first direction X. The third side 22a and the fourth side 22b are cut to obtain a plurality of third notches 2211 on the third side 22a and a plurality of fourth notches 2221 on the fourth side 22b. Then, the negative electrode ear is welded to a portion of the negative electrode current collector not covered by the negative electrode active material layer. The negative electrode ear is located at the starting end of the winding of the negative electrode sheet, and part of the negative electrode ear extends out from a fourth notch 2221.

[0198] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed at a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF4) was added to the basic organic solvent. 6 ) are dissolved and mixed evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0199] (4) Preparation of the isolation film 23: A 7 μm thick polyethylene porous polymer film is used as the isolation film 23. The isolation film 23 includes a fifth side and a sixth side that are oppositely arranged along the first direction X. The fifth side and the sixth side are cut to obtain a plurality of fifth notches 2311 on the fifth side and a plurality of sixth notches 2321 on the sixth side.

[0200] (5) Preparation of electrode assembly 20: positive electrode sheet, separator 23 and negative electrode sheet are stacked in sequence and then wound to form electrode assembly 20; during stacking, the first notches 2111 and the third notches 2211 are aligned one by one; along the thickness direction of electrode assembly 20, the projection of the fifth notch 2311 is located within the projection range of the first notch 2111 and the third notch 2211; the second notch 2121 and the fourth notch 2221 are aligned one by one; along the thickness direction of electrode assembly 20, the projection of the sixth notch 2321 is located within the projection range of the second notch 2121 and the fourth notch 2221. In the wound electrode assembly 20, the centerline of the first pole tab 30 passes through the midpoint of the fifth edge 205 (ignoring manufacturing error), and the centerline of the second pole tab 40 passes through the midpoint of the sixth edge 206.

[0201] (6) Assembly of secondary battery 100: Place the aluminum-plastic film with a hole punched into an assembly fixture, with the hole facing upward, place the electrode assembly 20 in the hole, and apply external force to press it. Then, cover the electrode assembly 20 with another aluminum-plastic film with a hole punched into it, with the hole facing downward. Heat-seal the edges of the two aluminum-plastic films by heat pressing. The unsealed edge is the side where the negative and positive tabs extend out of the housing 10. Then, inject electrolyte through the unsealed edge, and after vacuum packaging, standing, hot pressing, shaping, and other processes, the secondary battery 100 is manufactured.

[0202] The preparation process of the secondary battery 100 in Examples 2 to 32 is basically the same as that in Example 1, except that some parameters of the secondary battery 100 in Examples 2 to 32 are different from those in Example 1, and the specific differences are recorded in Table 1. In Examples 1 to 32, α 1 +α 2 =90°, β 1 +β 2 =90°,γ 1 =γ 2,θ 1 =θ 2 , δ 1 =δ 2 It should be noted that the projection areas of the electrode assemblies 20 of the secondary batteries 100 in Examples 1 to 32 along the thickness direction are equal (ignoring manufacturing errors). In addition, except for the edge sealing portions (the fourth edge sealing portion 1024 and the fifth edge sealing portion 1025) where the positive and negative tabs extend, the other edge sealing portions are bent in the thickness direction of the secondary battery 100.

[0203] In Examples 1 to 32, 10 secondary batteries 100 are taken from each group. After the secondary batteries 100 are prepared, the secondary batteries 100 are observed to see if they leak, and the number of secondary batteries 100 without leakage is counted to calculate the preparation qualification rate Q of the secondary batteries, where Q=number of secondary batteries without leakage / 10×100%.

[0204] Subsequently, a discharge capacity test is performed on each group of secondary batteries that have not leaked. The process of the discharge capacity test is as follows:

[0205] 1) Maintain the test temperature at 25°C;

[0206] 2) leaving the secondary battery 100 to stand for 30 minutes;

[0207] 3) 5C constant current charging to 4.25V, then constant voltage charging to 3C;

[0208] 4) 3C constant current charge to 4.35V, then constant voltage charge to 1.5C;

[0209] 5) 1.5C constant current charge to 4.45V, then constant voltage charge to 0.05C;

[0210] 6) Let stand for 5 minutes;

[0211] 7) Discharge at 0.7C constant current to 3V and record the first discharge capacity.

[0212] Subsequently, the average volume energy density P of each group of secondary batteries without leakage is calculated. The volume energy density ρ of the secondary battery 100 participating in the discharge capacity test = the discharge energy E of the secondary battery / the volume of the secondary battery, and P is the average value of the volume energy density ρ of the secondary batteries participating in the discharge capacity test in each group.

[0213] Table 1

[0214]

[0215]

[0216] Note: In Table 1, “ / ” indicates that there is no such data.

[0217] It can be seen from Table 1 that the secondary batteries 100 in Examples 1 to 32 satisfy 0<α 1 <90°,0<α 2 <90°,0<β 1 <90°,0<β 2 <90°, compared with Comparative Example 1, the average volume energy density of the secondary battery 100 in Examples 1 to 32 is higher. It can be seen that in the embodiments of the present application, the first pole tab 30 and the second pole tab 40 extend from the fifth edge 205 and the sixth edge 206 of the electrode assembly 20 respectively, and the first pole tab 30 and the second pole tab 40 are located at the corner of the secondary battery 100, which reduces the occupation of the head space of the secondary battery 100, which is conducive to improving the energy density of the secondary battery 100.

[0218] In the first, fourth and fifth embodiments, the secondary battery 100 satisfies 40°≤α 1 ≤50°, compared with Example 3, Example 6 and Example 7, the average volume energy density of the secondary battery 100 in Example 1, Example 4 and Example 5 is higher, because, under the premise that the projection of the electrode assembly 20 along its thickness direction is the same, as α 1 As the difference from the 45° angle increases, the length of the fifth edge 205 increases, and correspondingly, the length of the fourth edge sealing portion 1024 increases, but the fourth edge sealing portion 1024 does not bend in the thickness direction of the secondary battery 100, thereby occupying a volume. Therefore, as the length of the fourth edge sealing portion 1024 increases, the volume energy density of the secondary battery 100 decreases. 1 ≤50°, the included angle between the fifth edge 205 and the third edge 203 and the included angle between the fifth edge 205 and the second edge 202 can be set within an appropriate range, which is beneficial to improving the volume energy density of the secondary battery 100.

[0219] In the first embodiment, the tenth embodiment and the eleventh embodiment, the secondary battery 100 satisfies 40°≤β 1 ≤50°, compared with Example 8, Example 9, Example 12 and Example 13, the average volume energy density of the secondary battery 100 in Example 1, Example 10 and Example 11 is higher, because, under the premise that the projection of the electrode assembly 20 along its thickness direction is the same, as β 1 The difference between the value of β and 45° increases, the length of the sixth edge 206 increases, and correspondingly, the length of the fifth edge sealing portion 1025 increases, but the fifth edge sealing portion 1025 does not bend in the thickness direction of the secondary battery 100, thereby occupying a volume. Therefore, as the length of the fifth edge sealing portion 1025 increases, the volume energy density of the secondary battery 100 decreases. It can be seen that setting 40°≤β 1≤50°, the included angle between the sixth edge 206 and the third edge 203 and the included angle between the sixth edge 206 and the first edge 201 can be set within an appropriate range, which is beneficial to improving the volume energy density of the secondary battery 100.

[0220] In the first embodiment and the fifteenth to the eighteenth embodiments, the secondary battery 100 satisfies 60°≤γ 1 ≤120°, there is no interference between the first pole ear 30 and the first pole piece 21. 1 <60°, interference occurs between the first pole ear 30 and the first pole sheet 21, and problems may occur in the winding process of the electrode assembly 20, affecting the manufacturing efficiency of the secondary battery 100. 1 >120°, interference occurs between the first pole tab 30 and the first pole sheet 21, and problems may occur in the winding process of the electrode assembly 20, which may affect the manufacturing efficiency of the secondary battery 100. 1 The difference between the value of and 90° increases, and the average volume energy density of the secondary battery 100 is lower. 1 ≤120°, which is beneficial to reducing the risk of interference between the first pole tab 30 and the first pole sheet 21 , while taking into account the space occupied by the first pole tab 30 in the first direction X and the second direction Y, thereby facilitating improving the energy density of the secondary battery 100 .

[0221] In the first embodiment, the sixteenth embodiment and the seventeenth embodiment, the secondary battery 100 satisfies 88°≤γ 1 ≤92°, compared with Example 15 and Example 18, the volume energy density of the secondary battery 100 in Example 16 and Example 17 is further improved. 1 ≤92°, which is beneficial to further improve the energy density of the secondary battery 100.

[0222] In Examples 1 and 21 to 24, the secondary battery 100 satisfies 85°≤θ 1 ≤95°, compared with Example 20 and Example 25, the qualified rate of the secondary battery 100 in Example 21 to Example 24 is higher. 1 ≤95°, the distance between the first electrode tab 30 and the edge of the fourth edge sealing portion 1024 is not too close, the effective sealing width between the first electrode tab glue 50 and the fourth edge sealing portion 1024 is larger, which is beneficial to reduce the influence of the first electrode tab 30 on the sealing performance of the fourth edge sealing portion 1024.

[0223] In Example 1, Example 22 and Example 23, the secondary battery 100 satisfies 88°≤θ 1≤92°, compared with Example 21 and Example 24, the qualified rate of the secondary battery 100 in Example 21 and Example 22 is higher. 1 ≤92°, which is beneficial to further reduce the influence of the first electrode tab 30 on the sealing performance of the fourth edge sealing portion 1024 .

[0224] In Examples 27 to 30, the secondary battery 100 satisfies 85°≤δ 1 ≤95°, compared with Example 26 and Example 31, the qualified rate of the secondary battery 100 in Example 27 to Example 30 is higher. 1 ≤95°, the angle between the first pole ear glue 50 and the first pole ear 30 is controlled within an appropriate range, the effective sealing width between the first pole ear glue 50 and the fourth edge sealing portion 1024 is larger, which is beneficial to improving the sealing between the first pole ear glue 50 and the fourth edge sealing portion 1024.

[0225] In Example 1, Example 28 and Example 29, the secondary battery 100 satisfies 88°≤δ 1 ≤92°, compared with Example 27 and Example 30, the qualified rate of the secondary battery 100 in Example 28 and Example 29 is higher. 1 ≤92°, which is beneficial to further improve the sealing between the first electrode ear glue 50 and the fourth edge sealing portion 1024.

[0226] The length of the hemming portion of the secondary battery 100 in Example 32 is less than at least one of the sealing portions, and the volume energy density of the secondary battery 100 in Example 32 is less than that of the secondary battery 100 in Example 1. It can be seen that setting the length of the hemming portion to be not less than the length of any sealing portion is conducive to reducing the total length of the sealing portion and reducing the space occupied by the sealing portion, thereby facilitating improving the energy density of the secondary battery.

[0227] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of the present application.

Claims

1. A secondary battery, characterized in that: include: An electrode assembly, the electrode assembly comprising a first pole piece and a second pole piece, wherein the first pole piece and the second pole piece have opposite polarities; The electrode assembly is a winding structure, which is formed by winding the first electrode sheet and the second electrode sheet after being stacked; when viewed along the thickness direction of the electrode assembly, the electrode assembly includes a first edge and a second edge arranged opposite to each other along the first direction, a third edge and a fourth edge arranged opposite to each other along the second direction, a fifth edge connecting the second edge and the third edge, and a sixth edge connecting the first edge and the third edge; The supplementary angle between the fifth edge and the third edge is α1, the supplementary angle between the fifth edge and the second edge is α2, 0<α1<90°, 0<α2<90°; the supplementary angle between the sixth edge and the third edge is β1, the supplementary angle between the sixth edge and the first edge is β2, 0<β1<90°, 0<β2<90°; the first direction, the second direction and the thickness direction of the electrode assembly are perpendicular to each other; a first electrode tab, one end of which is connected to the electrode assembly, and the other end of which extends from the fifth edge and in a direction away from the fifth edge; A second pole tab, one end of which is connected to the electrode assembly, and the other end of which extends from the sixth edge and in a direction away from the sixth edge.

2. The secondary battery according to claim 1, wherein: 40°≤α1≤50°, 40°≤α2≤50°, and / or 40°≤β1≤50°，40°≤β2≤50°。 3. The secondary battery according to claim 1, wherein: The first electrode sheet includes a first notch portion and a second notch portion which are arranged opposite to each other along the first direction; the first notch portion is located at the fifth edge, and the first electrode tab extends out of the electrode assembly from the first notch portion; the second notch portion is located at the sixth edge, and the second electrode tab extends out of the electrode assembly from the second notch portion; the first notch portion is composed of a plurality of first notches, and the plurality of first notches are arranged at intervals along the winding direction of the first electrode sheet; the second notch portion is composed of a plurality of second notches, and the plurality of second notches are arranged at intervals along the winding direction of the first electrode sheet; the second electrode sheet includes a third notch portion and a fourth notch portion which are arranged opposite to each other along the first direction; the third notch portion is located at the fifth edge, and when viewed along the thickness direction of the electrode assembly, the third notch portion and the first notch portion at least partially overlap; the fourth notch portion is located at the sixth edge, and when viewed along the thickness direction of the electrode assembly, the fourth notch portion and the second notch portion at least partially overlap; the third notch portion is composed of a plurality of third notches, and the plurality of third notches are arranged at intervals along the winding direction of the second electrode sheet; the fourth notch portion is composed of a plurality of fourth notches, and the plurality of fourth notches are arranged at intervals along the winding direction of the second electrode sheet.

4. The secondary battery according to claim 3, characterized in that: The electrode assembly also includes an isolation membrane, which is arranged between the first pole piece and the second pole piece, and the first pole piece, the isolation membrane and the second pole piece are stacked and wound in sequence to form the winding structure; the isolation membrane includes a fifth notch portion and a sixth notch portion arranged opposite to each other along the first direction; the edge of the fifth notch portion forms the fifth edge, and when observed along the thickness direction of the electrode assembly, the fifth notch portion and the first notch portion and the third notch portion at least partially overlap; the edge of the sixth notch portion forms the sixth edge, and when observed along the thickness direction of the electrode assembly, the sixth notch portion and the second notch portion and the fourth notch portion at least partially overlap; the fifth notch portion is composed of a plurality of fifth notches, and the plurality of fifth notches are arranged at intervals along the winding direction of the isolation membrane; the sixth notch portion is composed of a plurality of sixth notches, and the plurality of sixth notches are arranged at intervals along the winding direction of the isolation membrane.

5. The secondary battery according to claim 1, wherein: When observed along the thickness direction of the electrode assembly, the included angle between the center line of the first pole tab and the fifth edge is γ1, 60°≤γ1≤120°, wherein the center line of the first pole tab is perpendicular to the thickness direction of the electrode assembly; and / or Observing along the thickness direction of the electrode assembly, the included angle between the center line of the second pole tab and the sixth edge is γ2, 60°≤γ2≤120°, wherein the center line of the second pole tab is perpendicular to the thickness direction of the electrode assembly.

6. The secondary battery according to claim 5, characterized in that: 88°≤γ1≤92°; and / or 88°≤γ2≤92°.

7. The secondary battery according to any one of claims 1 to 6, characterized in that: The secondary battery also includes a shell, the shell includes a first shell and a second shell, the first shell and the second shell are together enclosed to form a first space, and the electrode assembly is accommodated in the first space; the shell includes a rimming portion and a sealing portion, the sealing portion includes a first sealing portion, a second sealing portion, a third sealing portion, a fourth sealing portion and a fifth sealing portion; the rimming portion and the fourth edge are located on the same side of the electrode assembly, the first sealing portion and the first edge are located on the same side of the electrode assembly, the second sealing portion and the second edge are located on the same side of the electrode assembly, the third sealing portion and the third edge are located on the same side of the electrode assembly, the fourth sealing portion and the fifth edge are located on the same side of the electrode assembly, and the fifth sealing portion and the sixth edge are located on the same side of the electrode assembly; the fourth sealing portion connects the second sealing portion and the third sealing portion, and the fifth sealing portion connects the first sealing portion and the third sealing portion; part of the first pole ear extends out of the shell from the fourth sealing portion, and part of the second pole ear extends out of the shell from the fifth sealing portion.

8. The secondary battery according to claim 7, characterized in that When viewed along the first direction, the length of the edge-wrapping portion is not less than the length of any of the edge-sealing portions.

9. The secondary battery according to claim 7, wherein: When observed along the thickness direction of the electrode assembly, the included angle between the center line of the first electrode tab and the fourth edge sealing portion is θ1, 85°≤θ1≤95°, wherein the center line of the first electrode tab is perpendicular to the thickness direction of the electrode assembly; and / or Observed along the thickness direction of the electrode assembly, the included angle between the center line of the second electrode tab and the fifth edge sealing portion is θ2, and 85°≤θ2≤95°.

10. The secondary battery according to claim 9, characterized in that 88°≤θ1≤92°; and / or 88°≤θ2≤92°.

11. The secondary battery according to claim 9, wherein The secondary battery further includes a first pole ear glue; the first pole ear glue is arranged on the fourth edge sealing portion, and part of the first pole ear passes through the first pole ear glue and extends out of the fourth edge sealing portion; when observed along the thickness direction of the electrode assembly, the angle between the center line of the first pole ear and the first pole ear glue is δ1, 85°≤δ1≤95°; and / or The secondary battery also includes a second pole ear glue, which is arranged on the fifth edge sealing portion, and part of the second pole ear passes through the second pole ear glue and extends out of the fifth edge sealing portion; observed along the thickness direction of the electrode assembly, the angle between the center line of the second pole ear and the second pole ear glue is δ2, 85°≤δ2≤95°.

12. The secondary battery according to claim 11, wherein: 88°≤δ1≤92°; and / or 88°≤δ2≤92°.

13. The secondary battery according to claim 11, wherein: The angle between the first electrode ear glue and the fourth edge sealing portion is ω1, 0°≤ω1≤30°; and / or The included angle between the second electrode ear glue and the fifth edge sealing portion is ω2, 0°≤ω2≤30°.

14. The secondary battery according to claim 13, characterized in that: Along the length direction of the first pole ear, the width of the first pole ear glue is W1, 3mm≤W1≤10mm; along the width direction of the first pole ear, the maximum linear distance on one side of the edge of the first pole ear glue beyond the edge of the first pole ear is L1, 2mm≤L1≤4mm; and / or Along the length direction of the second pole ear, the width of the second pole ear glue is W2, 3mm≤W2≤10mm; along the width direction of the second pole ear, the maximum single-side straight-line distance that the edge of the second pole ear glue exceeds the edge of the second pole ear is L2, 2mm≤L2≤4mm.

15. An electrochemical device, characterized in that: The invention comprises a circuit board and a secondary battery as claimed in any one of claims 7 to 14, wherein the circuit board connects the first electrode tab and the second electrode tab.

16. The electrochemical device according to claim 15, characterized in that The circuit board comprises a first circuit board and a second circuit board, the first electrode tab is electrically connected to the first circuit board, the second electrode tab is electrically connected to the second circuit board, and when viewed along the thickness direction of the electrode assembly, the first circuit board does not extend beyond the second edge sealing portion in the first direction; and / or The first circuit board does not extend beyond the third edge sealing portion in the second direction; and / or The second circuit board does not extend beyond the first edge sealing portion in the first direction; and / or The second circuit board does not extend beyond the third edge sealing portion in the second direction.

17. An electrical equipment, characterized in that: Comprising the electrochemical device as claimed in claim 15 or 16.

18. A method for preparing a secondary battery, for manufacturing the secondary battery as claimed in claim 4, characterized in that: The following steps are involved: Take the first pole piece, the first pole piece comprising a first side and a second side arranged opposite to each other along the first direction, cut the first side and the second side to obtain the plurality of first notches on the first side and the plurality of second notches on the second side; Take a second pole piece, the second pole piece includes a third side and a fourth side arranged opposite to each other along the first direction, cut the third side and the fourth side to obtain the plurality of third notches on the third side and the plurality of fourth notches on the fourth side; Take the isolation film, the isolation film includes a fifth side and a sixth side arranged opposite to each other along the first direction, cut the fifth side and the sixth side to obtain the plurality of fifth notches on the fifth side and the plurality of sixth notches on the sixth side; The first pole piece, the isolation membrane and the second pole piece are stacked in sequence and then wound to form the electrode assembly; when stacking, the multiple first notches and the multiple third notches are aligned one by one; along the thickness direction of the electrode assembly, the projection of the fifth notch is located within the projection range of the first notch and the third notch; the second notch and the fourth notch are aligned one by one; along the thickness direction of the electrode assembly, the projection of the sixth notch is located within the projection range of the second notch and the fourth notch.

19. The method for preparing a secondary battery according to claim 18, characterized in that: The following steps are also included: A shell is taken, the shell comprising a first shell and a second shell, the first shell and the second shell are connected by a rim portion, the first shell is folded toward the second shell along the rim portion and enclosed with the second shell to form a first space, and the electrode assembly is accommodated in the first space; The first shell and the second shell are sealed by a heat sealing process, and a sealed edge portion is formed at the heat sealing portion.

20. The method for preparing a secondary battery according to claim 19, characterized in that: The following steps are also included: heat-sealing the first shell and the second shell at the first edge to form a first edge-sealed portion; heat-sealing the first shell and the second shell at the second edge to form a second sealed edge portion; heat-sealing the first shell and the second shell at the third edge to form a third sealed edge portion; The first edge sealing portion, the second edge sealing portion and the third edge sealing portion are bent toward the first space.

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