CN209785985U

CN209785985U - Secondary battery

Info

Publication number: CN209785985U
Application number: CN201920774635.5U
Authority: CN
Inventors: 陈雷
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2019-05-27
Filing date: 2019-05-27
Publication date: 2019-12-13
Anticipated expiration: 2029-05-27

Abstract

The utility model provides a secondary battery, it includes electrode subassembly, wrapping bag and electrode lead. The electrode assembly is received in the package bag, the edge of the package bag has a sealing portion, and the electrode lead is connected to the electrode assembly and passes through the sealing portion. The electrode assembly includes a first pole piece, a second pole piece, and a separator separating the first pole piece and the second pole piece. The diaphragm is connected to the seal portion.

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.

An electrode assembly of the secondary battery is received in a packaging bag, and edges of the packaging bag may be connected by heat-pressure sealing to separate the electrode assembly from the outside. The secondary battery further includes an electrode lead connected to the electrode assembly and extending to the outside of the packaging bag. However, when the secondary battery is vibrated, the electrode assembly is relatively displaced from the packaging bag, and the risk of damage to the sealing region of the packaging bag, breakage of the electrode lead, and the like is easily caused.

SUMMERY OF THE UTILITY MODEL

In view of the problems existing in the background art, the present invention is directed to a secondary battery which can reduce the safety risk and improve the safety performance.

in order to accomplish the above object, the present invention provides a secondary battery including an electrode assembly, a pouch, and an electrode lead. The electrode assembly is received in the package bag, the edge of the package bag has a sealing portion, and the electrode lead is connected to the electrode assembly and passes through the sealing portion. The electrode assembly includes a first pole piece, a second pole piece, and a separator separating the first pole piece and the second pole piece. The diaphragm is connected to the seal portion.

The sealing part includes a first sealing region and a second sealing region, the second sealing region is located at a side of the first sealing region which is apart from the electrode assembly in a longitudinal direction, and a thickness of the first sealing region is greater than a thickness of the second sealing region. The diaphragm is connected to the first seal area.

The separator has a base region separating the first and second pole pieces and a first anchor region extending from one end of the base region in the longitudinal direction. The first seal region covers the first fixing region from both sides in the thickness direction.

The first fastening region has a dimension in the longitudinal direction of greater than or equal to 0.2 mm.

In the transverse direction, the ratio of the size of the first fixing zone to the total size of the membrane is less than 2/3.

The diaphragm further includes a second anchor region extending from an end of the first anchor region remote from the base region. The second seal region covers the second fixing region from both sides in the thickness direction.

The diaphragms are arranged in multiple layers, and at least one outermost diaphragm is connected to the sealing part.

The packaging bag includes two layers of packaging films, an electrode assembly being located between the two layers of packaging films, the two layers of packaging films being connected at an edge and forming a seal. Each packaging film comprises a protective layer, a metal layer and a first connecting layer, wherein the first 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 first connecting layer of the two layers of packaging films are welded into a whole. The separator includes a second tie layer that is attached to the first tie layer, and an absolute difference between a melting point of the second tie layer and a melting point of the first tie layer is less than or equal to 40 degrees.

The first connecting layer and the second connecting layer are made of the same material.

The electrode leads are two and extend from the same end of the package bag in the longitudinal direction, and the end of the diaphragm which is away from the electrode leads in the longitudinal direction is connected to the sealing part. Alternatively, two electrode leads are respectively extended from both ends of the package bag in the transverse direction, and the end of the separator in the longitudinal direction is connected to the sealing part. Alternatively, the electrode leads are two and extend from the same end of the package bag in the lateral direction, and the end of the separator in the longitudinal direction is connected to the sealing part.

The utility model has the advantages as follows: in the present application, since the separator is connected to the sealing part, the separator can effectively fix the electrode assembly when the secondary battery vibrates, reduce the relative displacement between the electrode assembly and the packaging bag, reduce the risk of breakage of the sealing part and breakage of the electrode lead, and improve the safety performance of the secondary battery.

Drawings

Fig. 1 is a schematic view of a secondary battery according to a first embodiment of 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 an enlarged view of fig. 2 at block B.

Fig. 5 is another sectional view of the secondary battery of fig. 1.

fig. 6 is an enlarged view of fig. 5 at block C.

Fig. 7 is a schematic view of a packaging film of a packaging bag of the secondary battery of fig. 2.

Fig. 8 is a cross-sectional view of the packaging film of fig. 7.

Fig. 9 is a schematic view of a separator of the secondary battery of fig. 2.

Fig. 10 is a schematic view of a secondary battery according to a second embodiment of the present invention.

fig. 11 is a schematic view of a secondary battery according to a third embodiment of the present invention.

Fig. 12 is a schematic view of a fourth embodiment of a secondary battery according to the present invention.

Fig. 13 is a sectional view of an electrode assembly of the secondary battery of fig. 12.

Fig. 14 is a schematic view of a fifth embodiment of a secondary battery according to the present invention. Wherein the reference numerals are as follows:

1 electrode Assembly

11 first pole piece

12 second pole piece

13 diaphragm

131 matrix region

132 first fixing area

133 second fixing area

134 second connection layer

135 base layer

2 packaging bag

21 sealing part

211 first seal area

212 second seal area

213 third seal area

22 packaging film

221 protective layer

222 metal layer

223 first connection layer

3 electrode lead

4 insulating part

X longitudinal direction

Y transverse 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", "third" 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 insulator 4.

The electrode assembly 1 is a core member of the secondary battery that realizes the charge and discharge functions. The electrode assembly 1 comprises a first pole piece 11, a second pole piece 12 and a separator 13, the separator 13 separating the first pole piece 11 and the second pole piece 12. One of the first pole piece 11 and the second pole piece 12 is a positive pole piece, and the other of the first pole piece 11 and the second pole piece 12 is a negative pole piece.

The positive pole piece comprises a positive current collector and a positive active substance layer coated on the surface of the positive current collector, 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. The negative pole piece comprises a negative current collector and a negative active substance layer coated on the surface of the negative current collector, the negative current collector can be a copper foil, and the negative active substance layer comprises graphite or silicon.

Referring to fig. 2 to 6, the electrode assembly 1 of the present embodiment may have a laminate type structure. Specifically, the first pole piece 11 and the second pole piece 12 are each provided in plurality, and the plurality of first pole pieces 11 and the plurality of second pole pieces 12 are alternately stacked in the thickness direction Z. A separator 13 is disposed between the first and second pole pieces 11, 12 to separate the first and second pole pieces 11, 12. The diaphragm 13 can be one, and the diaphragm 13 is bent back and forth into a Z-shaped structure to form a plurality of layers; alternatively, the number of the diaphragms 13 may be plural.

The packaging bag 2 includes two layers of packaging films 22, and the two layers of packaging films 22 are arranged up and down along the thickness direction Z. Referring to fig. 7, at least one of the packaging films 22 is punched to form a cavity, and the electrode assembly 1 is positioned between the two packaging films 22 and received in the cavity.

Referring to fig. 8, each of the encapsulation films 22 includes a protective layer 221, a metal layer 222, and a first connection layer 223, and the protective layer 221 and the first connection layer 223 are respectively disposed at both sides of the metal layer 222. Specifically, the protective layer 221 may be fixed to a surface of the metal layer 222, which is away from the electrode assembly 1, by an adhesive, and the first connection layer 223 may be fixed to a 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 first connecting layer 223 may be polypropylene.

The two layers of packaging film 22 are joined at the edges and form a seal 21. Specifically, the first tie layers 223 of the two-layer packaging film 22 are directly or indirectly welded together by heat pressing, thereby forming the sealed packaging bag 2.

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 is connected to the first pole piece 11, and the other electrode lead 3 is connected to the second pole piece 12. 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. In the present embodiment, two electrode leads 3 protrude from the same end of the package bag 2 in the longitudinal direction X.

The insulating member 4 may be two. The two insulators 4 separate the two electrode leads 3 from the sealing part 21, respectively. Each of the insulators 4 surrounds the outside of a corresponding one of the electrode leads 3. A portion of the insulator 4 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 insulating member 4 may be polypropylene.

Preferably, the separator 13 of the electrode assembly 1 is connected to the sealing part 21. Since the separator 13 is coupled to the sealing part 21, the separator 13 can effectively fix the electrode assembly 1 when the secondary battery vibrates, reduce the relative displacement between the electrode assembly 1 and the packaging bag 2, reduce the risk of breakage of the sealing part 21 and breakage of the electrode lead 3, and improve the safety performance of the secondary battery.

The separator 13 is provided in multiple layers; in the laminated electrode assembly 1, the multilayer separators 13 are arranged in the thickness direction Z. If one or more layers of the separator 13 in the middle are fixed to the sealing part 21, the separator 13 can restrict vibration of only a part of the pole piece when the secondary battery vibrates. Therefore, it is preferable that at least the outermost one of the separators 13 is connected to the seal portion 21. The outermost separator 13 is located at one end of the electrode assembly 1, and the separator 13 can restrict vibration of all the pole pieces when the secondary battery vibrates. Preferably, two layers of the diaphragm 13, which are respectively located at both ends in the thickness direction Z, are connected to the sealing portion 21. Further preferably, the membranes 13 of all layers are connected to the seal 21.

Referring to fig. 4, the sealing part 21 includes a first sealing region 211 and a second sealing region 212, the second sealing region 212 is located at a side of the first sealing region 211 away from the electrode assembly 1 in the longitudinal direction X, and the thickness of the first sealing region 211 is greater than that of the second sealing region 212. The diaphragm 13 is connected to the first sealing region 211.

In the present application, the two-layer packaging film 22 may be heat-pressed using a packaging apparatus to form the seal portion 21. In this embodiment, a portion of the packaging film 22 is subjected to the heat and pressure of the packaging equipment and generates glue, and the glue flows inward. The area of the packaging film 22 directly exposed to the heat and pressure of the packaging device is the second sealing region 212. The inwardly flowing glue bonds the two layers of packaging film 22 together to form a first seal area 211. During the thermal pressing, the second seal region 212 is thinned, so the thickness of the first seal region 211 is greater than that of the second seal region 212. In addition, the gel flowing inward may contact the diaphragm 13, and when the gel is cured, the diaphragm 13 is connected to the first sealing region 211.

the diaphragm 13 has a base region 131 and a first fixing region 132, the base region 131 separating the first and second pole pieces 11 and 12, the first fixing region 132 extending from one end of the base region 131 in the longitudinal direction X. The first seal region 211 covers the first fixing region 132 from both sides in the thickness direction Z. The first fixing region 132 is embedded in the first sealing region 211, thereby achieving the coupling of the diaphragm 13 and the sealing part 21.

Since the diaphragm 13 is provided in multiple layers, the first fixing region 132 may also be multiple layers. The multi-layer first fixing region 132 may be embedded in the first sealing region 211 at the same time.

The size of the first fixing region 132 in the longitudinal direction X is preferably greater than or equal to 0.2mm to secure the coupling strength between the separator 13 and the sealing part 21 and prevent the separator 13 from being separated from the sealing part 21 when the secondary battery vibrates.

In the transverse direction Y, the ratio of the size of the first fixing area 132 to the overall size of the membrane 13 is less than 2/3. If the ratio is too large, a large amount of heat may be transferred to the diaphragm 13 during the hot pressing, resulting in a too high temperature of the diaphragm 13; under the action of high temperature, the diaphragm 13 is easily deformed, and the strength and the performance of the diaphragm 13 are affected.

the separator 13 may be a single-layer structure or a multi-layer structure. For example, in one embodiment, the separator 13 is a single-layer structure and includes the second connection layer 134, and the second connection layer 134 is connected to the first connection layer 223; the second connection layer 134 may be made of polyethylene or polypropylene. In another embodiment, referring to fig. 9, the separator 13 is a multi-layered structure and includes a base layer 135 and a second connection layer 134, the second connection layer 134 being disposed on both sides of the base layer 135 and connected to the first connection layer 223; the material of the base layer 135 may be polyethylene, and the material of the second connection layer 134 may be polypropylene.

In the present application, the second connection layer 134 is welded to the first connection layer 223. The smaller the difference between the melting point of the first connection layer 223 and the melting point of the second connection layer 134 is, the easier the two are connected together during the hot pressing process, and the higher the connection strength between the two is. Thus. Preferably, the absolute difference between the melting point of the second connection layer 134 and the melting point of the first connection layer 223 is less than or equal to 40 degrees.

Further preferably, the first connecting layer 223 and the second connecting layer 134 are made of the same material, so that the welding difficulty between the two layers can be reduced, and the connecting strength between the two layers can be improved.

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.

fig. 10 is a schematic view of a secondary battery according to a second embodiment of the present invention. Referring to fig. 10, the diaphragm 13 further includes a second fixing region 133, the second fixing region 133 extending from an end of the first fixing region 132 remote from the base region 131. The second seal region 212 covers the second fixing region 133 from both sides in the thickness direction Z. During the thermal compression, the second fixing region 133 is also subjected to the thermal compression of the packaging apparatus. The second fixing region 133 is melted in the heat pressing process and integrated with the second sealing region 212.

In the second embodiment, the connection area between the separator 13 and the sealing part 21 can be increased by providing the second fixing region 133, the connection strength can be improved, the risk of breakage of the sealing part 21 and breakage of the electrode lead 3 can be reduced, and the safety performance of the secondary battery can be improved.

Preferably, the dimension of the second fixing zone 133 along the longitudinal direction X is greater than or equal to 1 mm.

Fig. 11 is a schematic view of a secondary battery according to a third embodiment of the present invention. Referring to fig. 11, the sealing part 21 further includes a third sealing region 213, and the third sealing region 213 is located at a side of the second sealing region 212 far from the first sealing region 211. By providing the third seal region 213, the size of the seal portion 21 can be increased, and the seal strength of the packaging bag 2 can be improved.

Fig. 12 is a schematic view of a fourth embodiment of a secondary battery according to the present invention. Fig. 13 is a sectional view of an electrode assembly of the secondary battery of fig. 12. Referring to fig. 12 and 13, in the fourth embodiment, the electrode assembly 1 is of a winding type structure.

Specifically, the first pole piece 11 and the second pole piece 12 are both one, and the first pole piece 11 and the second pole piece 12 are in a strip structure. The first pole piece 11, the separator 13, and the second pole piece 12 are sequentially stacked and wound two or more turns to form the electrode assembly 1. 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. The winding axis of the electrode assembly 1 may be parallel to the longitudinal direction X.

In the fourth embodiment, two electrode leads 3 are protruded from the same end of the package bag 2 in the longitudinal direction X, and the end of the separator 13 distant from the electrode leads 3 in the longitudinal direction X is connected to the sealing part 21.

Fig. 14 is a schematic view of a fifth embodiment of a secondary battery according to the present invention. Referring to fig. 14, in the fifth embodiment, two electrode leads 3 are respectively protruded from both ends of the envelope 2 in the transverse direction Y, and the end of the separator 13 in the longitudinal direction X is connected to the sealing part 21. This can prevent the electrode lead 3 from interfering with the connection of the diaphragm 13 and the sealing portion 21. Alternatively, two electrode leads 3 may also protrude from the same end of the package bag 2 in the transverse direction Y, and the end of the diaphragm 13 in the longitudinal direction X is connected to the sealing portion 21 in order to avoid the electrode leads 3 from interfering with the connection of the diaphragm 13 to the sealing portion 21.

Claims

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

The electrode assembly (1) is accommodated in the packaging bag (2), the edge of the packaging bag (2) is provided with a sealing part (21), and the electrode lead (3) is connected to the electrode assembly (1) and penetrates through the sealing part (21);

The electrode assembly (1) comprises a first pole piece (11), a second pole piece (12) and a diaphragm (13), wherein the diaphragm (13) separates the first pole piece (11) from the second pole piece (12);

The diaphragm (13) is connected to the seal section (21).

2. The secondary battery according to claim 1,

the seal part (21) comprises a first seal region (211) and a second seal region (212), the second seal region (212) is positioned on one side of the first seal region (211) far away from the electrode assembly (1) along the longitudinal direction (X), and the thickness of the first seal region (211) is larger than that of the second seal region (212);

The diaphragm (13) is connected to the first seal region (211).

3. The secondary battery according to claim 2,

The diaphragm (13) has a base region (131) and a first fixing region (132), the base region (131) separating the first pole piece (11) from the second pole piece (12), the first fixing region (132) extending from one end of the base region (131) in the longitudinal direction (X);

The first seal region (211) covers the first fixing region (132) from both sides in the thickness direction (Z).

4. The secondary battery according to claim 3, wherein a dimension of the first fixing region (132) in the longitudinal direction (X) is greater than or equal to 0.2 mm.

5. The secondary battery according to claim 3, wherein a ratio of a size of the first fixing region (132) to an overall size of the separator (13) in the transverse direction (Y) is less than 2/3.

6. The secondary battery according to claim 3,

The membrane (13) further comprises a second anchor region (133), the second anchor region (133) extending from an end of the first anchor region (132) remote from the base region (131);

The second seal region (212) covers the second fixing region (133) from both sides in the thickness direction (Z).

7. The secondary battery according to any one of claims 1 to 6, wherein the separators (13) are provided in a plurality of layers, and at least the outermost one of the separators (13) is connected to the sealing part (21).

8. The secondary battery according to any one of claims 1 to 6,

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 edges and form a sealing part (21);

each packaging film (22) comprises a protective layer (221), a metal layer (222) and a first connecting layer (223), wherein the first 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 first connecting layer (223) of the two layers of packaging films (22) are welded into a whole;

the separator (13) includes a second connection layer (134), the second connection layer (134) is connected to the first connection layer (223), and an absolute difference between a melting point of the second connection layer (134) and a melting point of the first connection layer (223) is less than or equal to 40 degrees.

9. the secondary battery according to claim 8, wherein the first connection layer (223) and the second connection layer (134) are the same material.

10. The secondary battery according to claim 1,

The two electrode leads (3) extend out from the same end of the packaging bag (2) along the longitudinal direction (X), and the end part of the diaphragm (13) far away from the electrode leads (3) along the longitudinal direction (X) is connected with the sealing part (21); or,

Two electrode leads (3) respectively extend out of two ends of the packaging bag (2) along the transverse direction (Y), and the end part of the diaphragm (13) along the longitudinal direction (X) is connected with the sealing part (21); or,

The two electrode leads (3) extend from the same end of the packaging bag (2) in the transverse direction (Y), and the end of the diaphragm (13) in the longitudinal direction (X) is connected to the sealing part (21).