CN209786105U

CN209786105U - secondary battery

Info

Publication number: CN209786105U
Application number: CN201920928659.1U
Authority: CN
Inventors: 魏曦晨; 陈雷; 朱宝健; 徐守江
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2019-06-19
Filing date: 2019-06-19
Publication date: 2019-12-13
Anticipated expiration: 2029-06-19

Abstract

The utility model provides a secondary battery, it includes electrode subassembly, wrapping bag, electrode lead and insulating adhesive tape. The electrode assembly is accommodated in the packaging bag, and the electrode lead is connected with the electrode assembly and extends out of the packaging bag. The electrode assembly includes a main body portion and a tab extending from the main body portion, and an electrode lead is welded to the tab and forms a weld zone. The insulating tape is wound on the outer side of the welding area and comprises a first insulating layer and a second insulating layer which are integrally arranged and respectively cover two surfaces of the welding area along the thickness direction.

Description

Secondary battery

Technical Field

The utility model relates to a battery field especially relates to a secondary battery.

Background

With the rapid development of portable electronic devices, the demand for energy density of batteries is also increasing. In the secondary battery, a packaging bag made of an aluminum-plastic film or a steel-plastic film may be used instead of the metal case to reduce the weight of the battery and improve the energy density. The electrode assembly of the secondary battery is received in a packaging bag, and the edges of the packaging bag may be connected by heat-pressure sealing. Of course, in order to accomplish the charge and discharge of the electrode assembly, the secondary battery further includes an electrode lead connected to the electrode assembly and extending to the outside of the packaging bag. In the prior art, the electrode leads are connected to the tabs of the electrode assembly by welding; however, burrs are left at the welded positions, and the burrs easily pierce the packaging bag, affecting the sealing performance of the secondary battery.

SUMMERY OF THE UTILITY MODEL

In view of the problems in the background art, an object of the present invention is to provide a secondary battery that can reduce the risk of the packaging bag being punctured and improve the sealing performance.

In order to accomplish the above object, the present invention provides a secondary battery including an electrode assembly, a packing bag, an electrode lead, and an insulating tape. The electrode assembly is accommodated in the packaging bag, and the electrode lead is connected with the electrode assembly and extends out of the packaging bag. The electrode assembly includes a main body portion and a tab extending from the main body portion, and an electrode lead is welded to the tab and forms a weld zone. The insulating tape is wound on the outer side of the welding area and comprises a first insulating layer and a second insulating layer which are integrally arranged and respectively cover two surfaces of the welding area along the thickness direction.

The insulating tape also comprises a bending layer which is connected with the first insulating layer and the second insulating layer and is positioned on the outer side of the welding area along the width direction.

The end of the second insulating layer far away from the bending layer is adhered to the first insulating layer.

In the width direction, the end part of the first insulating layer far away from the bending layer exceeds the electrode lead and the electrode lug, and the end part of the second insulating layer far away from the bending layer exceeds the electrode lead and the electrode lug. The region of the first insulating layer beyond the electrode leads and tabs is bonded to the region of the second insulating layer beyond the electrode leads and tabs.

The two electrode leads are arranged along the width direction, and the two insulating tapes are respectively wound on the two electrode leads. In the width direction, the two electrode leads are positioned between the bending layers of the two insulating tapes.

The insulating adhesive tape is wound into a multilayer structure, and the number of layers of the insulating adhesive tape is 3-5 in the thickness direction. The first insulating layer and the second insulating layer are two layers closest to the welding area.

The insulating tape comprises a base material and an adhesive, wherein the adhesive is arranged on the surface of the base material close to the welding area.

The welding zone comprises a plurality of sub-welding zones which are arranged at intervals along the width direction, and the insulating adhesive tape is adhered to the area between two adjacent sub-welding zones.

The distance between adjacent sub-welding areas is 0.3mm-5 mm.

The packaging bag comprises two layers of packaging films, the electrode assembly is positioned between the two layers of packaging films, and the two layers of packaging films are connected at the edge. Each packaging film comprises a protective layer, a metal layer and a connecting layer, wherein the connecting layer is arranged on the surface of the metal layer facing the electrode assembly, and the protective layer is arranged on the surface of the metal layer far away from the electrode assembly. The electrode lead passes through the two packaging films.

the utility model has the advantages as follows: in this application, first insulating layer and second insulating layer can cover the burr on welding zone surface to separate welding zone and wrapping bag, thereby reduce the risk that the wrapping bag is punctured, improve sealing performance. Simultaneously, this application sets up first insulating layer and second insulating layer an organic whole, can improve the joint strength in the whole and welding area of insulating tape, reduces the risk of droing, avoids the burr to puncture the wrapping bag.

Drawings

Fig. 1 is a schematic view of a secondary battery according to the present invention.

Fig. 2 is a sectional view of the secondary battery of fig. 1.

fig. 3 is an enlarged view of fig. 2 at block a.

Fig. 4 is a schematic view of a packaging film of a packaging bag for a secondary battery according to the present invention.

Fig. 5 is a cross-sectional view of the packaging film of fig. 4.

Fig. 6 is another schematic view of a secondary battery according to the present invention, in which a packing bag is omitted.

Fig. 7 is a cross-sectional view taken along line B-B of fig. 6.

fig. 8 is a cross-sectional view taken along line C-C of fig. 6.

fig. 9 is a cross-sectional view taken along line D-D of fig. 6.

Fig. 10 is a sectional view of an insulating tape for a secondary battery according to the present invention.

Fig. 11 is a schematic view of the electrode assembly and the electrode lead after welding.

fig. 12 to 14 are schematic views of different embodiments of a secondary battery according to the present invention. Wherein the reference numerals are as follows:

1 electrode Assembly

11 body part

12 pole ear

13 positive pole piece

14 negative pole piece

15 diaphragm

2 packaging bag

21 sealing part

22 packaging film

221 protective layer

222 metal layer

223 connecting layer

3 electrode lead

4 insulating adhesive tape

41 first insulating layer

42 second insulating layer

43 bending layer

44 base material

45 adhesive

5 spacer

G groove

W-shaped welding zone

W1 sub-welding zone

In the X longitudinal direction

Y width direction

In the Z thickness direction

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

In the description of the present application, unless explicitly stated or limited otherwise, the terms "first", "second", and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means more than two (including two); the term "coupled", unless otherwise specified or indicated, is to be construed broadly, e.g., "coupled" may be a fixed or removable connection or a connection that is either integral or electrical or signal; "connected" may be directly connected or indirectly connected through an intermediate. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

In the description of the present application, it should be understood that the terms "upper" and "lower" used in the description of the embodiments of the present application are used in a descriptive sense only and not for purposes of limitation. The present application is described in further detail below with reference to specific embodiments and with reference to the attached drawings.

Referring to fig. 1 to 3, in a first embodiment, a secondary battery of the present application includes an electrode assembly 1, a packaging bag 2, an electrode lead 3, and an insulating tape 4.

the electrode assembly 1 is a core member of the secondary battery that realizes the charge and discharge functions. Referring to fig. 7, the electrode assembly 1 includes a positive electrode tab 13, a negative electrode tab 14, and a separator 15, the separator 15 separating the positive electrode tab 13 and the negative electrode tab 14.

In the present application, the electrode assembly 1 may be a winding type structure. Referring to fig. 7, the positive electrode tab 13, the negative electrode tab 14, and the separator 15 are all in a band-shaped structure, the positive electrode tab 13, the separator 15, and the negative electrode tab 14 are sequentially laminated and wound two or more turns to form the electrode assembly 1, and the electrode assembly 1 is flat. When the electrode assembly 1 is manufactured, the electrode assembly 1 may be wound into a hollow cylindrical structure, and then flattened into a flat shape after being wound.

Alternatively, the electrode assembly 1 may also be of a laminated structure. Specifically, the electrode assembly 1 includes a plurality of positive electrode tabs 13 and a plurality of negative electrode tabs 14, the plurality of positive electrode tabs 13 and the plurality of negative electrode tabs 14 being alternately laminated in the thickness direction Z, and separators 15 being disposed between the positive electrode tabs 13 and the negative electrode tabs 14.

The positive electrode sheet 13 includes a positive current collector and a positive active material layer coated on the surface of the positive current collector, and only a partial area of the positive current collector is coated with the positive active material layer. Specifically, the area of the positive electrode current collector coated with the positive electrode active material layer and the positive electrode active material layer form a positive electrode coating area of the positive electrode sheet 13, and the area of the positive electrode current collector not coated with the positive electrode active material layer forms a positive electrode blank area of the positive electrode sheet 13. There may be a plurality of positive electrode blank regions. The positive current collector can be an aluminum foil, and the positive active substance layer comprises a ternary material, lithium manganate or lithium iron phosphate.

Likewise, the negative electrode tab 14 includes a negative electrode collector and a negative electrode active material layer coated on the surface of the negative electrode collector, and only a partial area of the negative electrode collector is coated with the negative electrode active material layer. Specifically, the region of the negative electrode collector coated with the negative electrode active material layer and the negative electrode active material layer form a negative electrode coated region of the negative electrode tab 14, and the region of the negative electrode collector not coated with the negative electrode active material layer forms a negative electrode blank region of the negative electrode tab 14. The number of the blank areas of the negative electrode can be multiple. The negative electrode current collector may be a copper foil, and the negative electrode active material layer includes graphite or silicon.

The electrode assembly 1 of the present application includes a body part 11 and tabs 12 extending from the body part 11, from the external appearance of the electrode assembly 1. The main body 11 includes a positive electrode coating region, a separator 15, and a negative electrode coating region. The tab 12 includes a positive tab and a negative tab, the positive tab is a positive blank area of the positive electrode tab 13, and the negative tab is a negative blank area of the negative electrode tab 14. In order to improve the overcurrent capacity, the positive electrode tabs are arranged in multiple layers and are laminated together, and the negative electrode tabs are arranged in multiple layers and are laminated together. The positive electrode tab and the negative electrode tab may extend from the same end of the main body 11 in the longitudinal direction X, or may extend from both ends of the main body 11 in the longitudinal direction X.

Referring to fig. 3, the packing bag 2 includes two layers of packing films 22, and the two layers of packing films 22 are disposed up and down in the thickness direction Z. Referring to fig. 4, at least one of the packaging films 22 is punched to form a cavity, and the electrode assembly 1 is located between the two packaging films 22 and is accommodated in the cavity.

referring to fig. 5, each of the encapsulation films 22 includes a protective layer 221, a metal layer 222, and a connection layer 223, and the protective layer 221 and the connection layer 223 are respectively disposed on both sides of the metal layer 222. Specifically, the protective layer 221 may be fixed to the surface of the metal layer 222, which is away from the electrode assembly 1, by an adhesive, and the connection layer 223 may be fixed to the surface of the metal layer 222, which is close to the electrode assembly 1, by an adhesive.

The material of the passivation layer 221 may be nylon or polyethylene terephthalate, the material of the metal layer 222 may be aluminum foil or steel foil, and the material of the connection layer 223 may be polypropylene.

the two layers of packaging film 22 are joined at the edges and form a seal 21. Specifically, the connecting layers 223 of the two packaging films 22 are directly or indirectly joined together by heat pressing, thereby forming the sealed packaging bag 2. In the hot press process, the connecting layer 223 is melted and compressed, and therefore, after the hot press molding, the thickness of the sealing portion 21 is smaller than the sum of the thicknesses of the two packaging films 22 before the hot press molding.

Referring to fig. 3, the electrode lead 3 is connected to the electrode assembly 1, passes through the sealing part 21, and extends to the outside of the packing bag 2. Specifically, the number of the electrode leads 3 may be two, one electrode lead 3 being connected to a positive electrode tab, and the other electrode lead 3 being connected to a negative electrode tab. The two electrode leads 3 connect the electrode assembly 1 with other members outside the package bag 2, thereby achieving charge and discharge of the electrode assembly 1. The material of the electrode lead 3 may be aluminum, nickel or copper-plated nickel.

The electrode lead 3 passes between the two packaging films 22, and since the connection layer 223 is thin, the electrode lead 3 easily comes into contact with the metal layer 222, causing a safety risk. Therefore, the secondary battery of the present application is preferably provided with the separator 5.

The number of the spacers 5 may be two. The two separators 5 respectively separate the two electrode leads 3 from the sealing part 21. Each of the separators 5 surrounds the outside of a corresponding one of the electrode leads 3. A portion of the separator 5 is sandwiched between the two packaging films 22, thereby separating the electrode lead 3 from the packaging films 22, reducing the risk of the electrode lead 3 coming into contact with the metal layer 222. The material of the spacer 5 may be polypropylene. Since a part of the separator 5 is sandwiched between the two packaging films 22, the connecting layer 223 of the two packaging films 22 is welded to the separator 5 when the two packaging films 22 are heat-pressed.

The electrode leads 3 may be connected to the tabs 12 of the electrode assembly 1 by welding. Referring to fig. 8, the electrode lead 3 is welded to the tab 12 and forms a welding zone W. One electrode lead 3 is welded to the positive electrode tab to form a weld zone W, and the other electrode lead 3 is welded to the negative electrode tab to form a weld zone W.

However, after the welding, burrs are left on both surfaces of the welded region W in the thickness direction Z, and the burrs easily pierce the packaging film 22 from the inside, affecting the sealing performance of the secondary battery. In order to avoid the burr from piercing the packaging film 22, the present application preferably winds the insulating tape 4 outside the weld zone W.

Referring to fig. 6 to 9, the welding regions W are formed at the electrode leads 3 and the tabs 12, and thus, the insulating tapes 4 may be directly wound on the outsides of the electrode leads 3 and the tabs 12. The insulating tape 4 has adhesiveness and can be directly adhered to the electrode lead 3 and the tab 12.

The insulating tape 4 may include a first insulating layer 41 and a second insulating layer 42, the first insulating layer 41 and the second insulating layer 42 respectively covering both surfaces of the welding zone W in the thickness direction Z. The first insulating layer 41 and the second insulating layer 42 may cover burrs on the surface of the welding region W and separate the welding region from the packaging film 22, thereby reducing the risk of the packaging film 22 being punctured and improving the sealing performance.

During the use of the secondary battery, the electrolyte in the package bag 2 may infiltrate into the connection interface of the insulating tape 4 and the welded region W, resulting in a decrease in the connection strength of the insulating tape 4 and the welded region W. If the first insulating layer 41 and the second insulating layer 42 are separated from each other, the first insulating layer 41 or the second insulating layer 42 easily falls off from the welding area W when the secondary battery vibrates, causing a risk of burrs piercing the packaging film 22. In the present application, the first insulating layer 41 and the second insulating layer 42 are preferably integrally arranged, so that the connection strength between the whole insulating tape 4 and the welding area W can be improved, the falling risk can be reduced, and the package film can be prevented from being pierced by burrs. For example, when the electrolyte is impregnated into the connection interface of the first insulating layer 41 and the welded region W, the connection strength of the first insulating layer 41 and the welded region W is reduced; when the secondary battery vibrates, the second insulating layer 42 may apply a restraining force to the first insulating layer 41, thereby reducing the vibration of the first insulating layer 41 and reducing the risk of the first insulating layer 41 falling off.

Referring to fig. 9, the insulating tape 4 further includes a bending layer 43, and the bending layer 43 connects the first insulating layer 41 and the second insulating layer 42 and is located outside the welding region W in the width direction Y. The bending layer 43 integrally connects the first insulating layer 41 and the second insulating layer 42.

The first insulating layer 41 may be located at one side of the welding zone W in the thickness direction Z while covering partial areas of the welding zone W and the tab 12, the bending layer 43 extending from one end of the first insulating layer 41 in the width direction Y and being bent toward a side close to the electrode lead 3, and the second insulating layer 42 extending from one end of the bending layer 43 remote from the first insulating layer 41 and being bent with respect to the bending layer 43. The second insulating layer 42 is located on the other side of the weld zone W in the thickness direction Z and covers both the weld zone W and a partial area of the electrode lead 3.

In the present embodiment, the insulating tape 4 is bent into a U-shaped structure to cover both surfaces of the fusion-spliced region W in the thickness direction Z simultaneously. The bending layer 43 may be bonded to ends of the electrode lead 3 and the tab 12 in the width direction Y to improve the coupling strength of the insulating tape 4, the electrode lead 3, and the tab 12.

Referring to fig. 1, in the present embodiment, two electrode leads 3 are protruded from the same side of the packaging bag 2 in the length direction X, and the two electrode leads 3 are arranged in the width direction Y. The two insulating tapes 4 are wound around the two electrode leads 3, respectively.

Each of the insulating tapes 4 is bent in a U-shape and covers the welding area W on the corresponding ground electrode lead 3. In the width direction Y, the two electrode leads 3 are located between the bending layers 43 of the two insulating tapes 4.

Referring to fig. 9, when the insulating tape 4 is bonded, the insulating tape 4 is first bonded to the tab 12, and then the insulating tape 4 is bent to bond the insulating tape 4 to the electrode lead 3. Referring to fig. 6, the distance between the two electrode leads 3 in the width direction Y is small, and when one insulating tape 4 is bonded to the electrode leads 3, if the bending layer 43 is located between the two electrode leads 3, the insulating tape 4 may interfere with the other electrode lead 3 when the insulating tape 4 is bent, affecting the bonding efficiency and quality. Therefore, the bending layer 43 of the insulating tape 4 is arranged on one side of one electrode lead 3 far away from the other electrode lead 3, so that the electrode lead 3 is prevented from interfering with the bending of the insulating tape 4, and the bonding efficiency and quality are ensured.

Referring to fig. 10, the insulating tape 4 includes a base 44 and an adhesive 45, and the adhesive 45 is provided on a surface of the base 44 near the weld W. The adhesive 45 bonds the base material 44 to the weld region W, and the base material 44 has high strength and is not easily pierced by the burr of the weld region W. The first insulating layer 41, the second insulating layer 42, and the bending layer 43 are different regions of the insulating tape 4, and each region includes the base 44 and the adhesive 45.

The electrode lead 3 and the tab 12 of the present application may be connected and form a weld zone W by ultrasonic welding. Specifically, the ultrasonic welding apparatus includes a horn and a holder between which the electrode lead 3 and the multilayer tab 12 are clampable, the horn and the holder transmitting high-frequency vibration waves to the electrode lead 3 and the tab 12 so that the electrode lead 3 and the tab 12 are rubbed against each other and welded together.

In order to realize ultrasonic welding, tooth-shaped structures are arranged on the welding head and the welding seat, the lug 12 and the electrode lead 3 are extruded by the tooth-shaped structures, the lug 12 and the electrode lead 3 are melted around the tooth-shaped structures, and the lug 12 and the electrode lead 3 are further welded. Referring to fig. 8 and 9, a plurality of grooves G are left on the surface of the weld zone W after the welding is completed. The shape, position and number of the grooves G correspond to the tooth-shaped structures on the welding head and the welding seat.

However, the grooves G are recessed with respect to the surface of the weld W, and the adhesive 45 of the insulating tape 4 is thin, so the adhesive 45 cannot adhere to the inner walls of the grooves G. Therefore, the presence of the grooves G may reduce the connection strength of the insulating tape 4 to the electrode lead 3 and the connection strength of the insulating tape 4 to the tab 12.

Referring to fig. 9 and 11, the weld zone W includes a plurality of sub-weld zones W1 arranged at intervals in the width direction Y. In the ultrasonic welding, the tooth profile of the horn and the anvil is applied to each sub-fusion area W1. Therefore, after the welding is completed, only the sub-fusion-joined region W1 has the groove G formed therein; the grooves G are not formed in the region between the adjacent two sub-fusion-bonding regions W1, and the surface of the region is relatively flat. When the insulating tape 4 is wound around the electrode lead 3 and the tab 12, the insulating tape 4 is bonded to the region between the adjacent two sub-fusion-bonded regions W1.

This application is divided into the sub-welding zone W1 of a plurality of interval arrangements with welding zone W, can make insulating tape 4 bond in the smooth region between two adjacent sub-welding zone W1 to improve the homogeneity that insulating tape 4 bonded, increase joint strength reduces the risk that insulating tape 4 drops.

If the adjacent sub-fusion-bonded regions W1 are spaced apart less, the flat area between the adjacent two sub-fusion-bonded regions W1 is narrower, resulting in a lower bonding strength of the insulating tape 4. The electrode lead 3 and the tab 12 have a limited dimension in the width direction Y, and the larger the distance between the adjacent sub-fusion-bond regions W1, the smaller the dimension of the sub-fusion-bond region W1, and the lower the connection strength between the electrode lead 3 and the tab 12. Therefore, if the adjacent sub-fusion-bonding regions W1 are too far apart, the connection strength between the electrode lead 3 and the tab 12 will be low, and the overcurrent capacity will be insufficient. Therefore, it is preferable that the interval between the adjacent sub-fusion-bonding regions W1 is 0.3mm to 5 mm.

Other examples of the secondary battery of the present application are explained below. For the sake of simplifying the description, only the differences of the other embodiments from the first embodiment will be mainly described below, and the undescribed portions can be understood with reference to the first embodiment.

Referring to fig. 12, in the second embodiment, the end of the second insulating layer 42 away from the bending layer 43 is bonded to the first insulating layer 41. Specifically, on the basis of the first embodiment, the size of the second insulating layer 42 is extended, and the portion of the second insulating layer 42 that exceeds the electrode lead 3 is folded back onto the first insulating layer 41, so that the end of the second insulating layer 42 that is away from the bending layer 43 is bonded to the first insulating layer 41.

In the second embodiment, the insulating tape 4 is wound one turn and connected end to end, and at this time, even if the connection interface of the second insulating layer 42 to the electrode lead 3 or the connection interface of the first insulating layer 41 to the tab 12 fails, the insulating tape 4 can be wound around the outer circumference of the welding region W to prevent the burr of the welding region W from being exposed. That is, the second embodiment can reduce the risk of the insulating tape 4 falling off compared to the first embodiment.

Referring to fig. 13, in the third embodiment, in the width direction Y, the end of the first insulating layer 41 remote from the bent layer 43 exceeds the electrode lead 3 and the tab 12, and the end of the second insulating layer 42 remote from the bent layer 43 exceeds the electrode lead 3 and the tab 12. The region of the first insulating layer 41 beyond the electrode lead 3 and the tab 12 is bonded to the region of the second insulating layer 42 beyond the electrode lead 3 and the tab 12.

In the third embodiment, the first insulating layer 41 is adhered to the second insulating layer 42 such that the insulating tape 4 surrounds the outer circumferences of the electrode lead 3 and the tab 12. The third embodiment can reduce the risk of the insulating tape 4 falling off compared to the first embodiment.

referring to fig. 14, in the fourth embodiment, the insulating tape 4 is wound in a multilayer structure, and the number of layers of the insulating tape 4 in the thickness direction Z is 3 to 5. The first insulating layer 41 and the second insulating layer 42 are two layers closest to the weld zone W. Compared with the first embodiment, the fourth embodiment winds the insulating tape 4 into a multilayer structure, and the multilayer structure can improve the adhesive strength of the insulating tape 4 and reduce the risk of the insulating tape 4 falling off. In addition, if the number of layers is too large, the insulating tape 4 occupies too much space, affecting the energy density of the secondary battery, and therefore, it is preferable that the number of layers of the insulating tape 4 is not more than 5.

Claims

1. A secondary battery, characterized by comprising an electrode assembly (1), a packaging bag (2), an electrode lead (3), and an insulating tape (4);

The electrode assembly (1) is accommodated in the packaging bag (2), and the electrode lead (3) is connected with the electrode assembly (1) and extends out of the packaging bag (2);

The electrode assembly (1) comprises a main body part (11) and a tab (12) extending from the main body part (11), and an electrode lead (3) is welded to the tab (12) and forms a welding zone (W);

The insulating tape (4) is wound outside the welding zone (W) and includes a first insulating layer (41) and a second insulating layer (42), the first insulating layer (41) and the second insulating layer (42) being integrally provided and covering both surfaces of the welding zone (W) in the thickness direction (Z), respectively.

2. The secondary battery according to claim 1, wherein the insulating tape (4) further comprises a folded layer (43), the folded layer (43) connecting the first insulating layer (41) and the second insulating layer (42) and being located outside the welding region (W) in the width direction (Y).

3. The secondary battery according to claim 2, wherein an end of the second insulating layer (42) remote from the folded layer (43) is bonded to the first insulating layer (41).

4. The secondary battery according to claim 3,

In the width direction (Y), the end part of the first insulating layer (41) far away from the bent layer (43) exceeds the electrode lead (3) and the electrode lug (12), and the end part of the second insulating layer (42) far away from the bent layer (43) exceeds the electrode lead (3) and the electrode lug (12);

The region of the first insulating layer (41) which exceeds the electrode lead (3) and the tab (12) is bonded to the region of the second insulating layer (42) which exceeds the electrode lead (3) and the tab (12).

5. The secondary battery according to claim 2,

the two electrode leads (3) are arranged along the width direction (Y), and the two insulating tapes (4) are respectively wound on the two electrode leads (3);

In the width direction (Y), the two electrode leads (3) are located between the bent layers (43) of the two insulating tapes (4).

6. The secondary battery according to claim 1,

The insulating adhesive tape (4) is wound into a multilayer structure, and the number of layers of the insulating adhesive tape (4) in the thickness direction (Z) is 3-5;

The first insulating layer (41) and the second insulating layer (42) are two layers closest to the welding region (W).

7. The secondary battery according to any one of claims 1 to 6, wherein the insulating tape (4) comprises a base material (44) and an adhesive (45), the adhesive (45) being provided on a surface of the base material (44) near the weld region (W).

8. The secondary battery according to claim 7, wherein the welding regions (W) include a plurality of sub-welding regions (W1) arranged at intervals in the width direction (Y), and the insulating tape (4) is bonded to a region between adjacent two sub-welding regions (W1).

9. The secondary battery according to claim 8, wherein the interval between the adjacent sub-welding regions (W1) is 0.3mm to 5 mm.

10. The secondary battery according to claim 1,

the packaging bag (2) comprises two layers of packaging films (22), the electrode assembly (1) is positioned between the two layers of packaging films (22), and the two layers of packaging films (22) are connected at the edge;

Each packaging film (22) comprises a protective layer (221), a metal layer (222) and a connecting layer (223), wherein the connecting layer (223) is arranged on the surface, facing the electrode assembly (1), of the metal layer (222), and the protective layer (221) is arranged on the surface, far away from the electrode assembly (1), of the metal layer (222);

The electrode lead (3) passes through the two layers of packaging films (22).