CN116888812A

CN116888812A - Secondary battery

Info

Publication number: CN116888812A
Application number: CN202280013946.4A
Authority: CN
Inventors: 姜炅秀; 李在浩; 林鑂熙
Original assignee: Lg Energy Solution
Current assignee: Lg Energy Solution
Priority date: 2021-10-01
Filing date: 2022-09-15
Publication date: 2023-10-13

Abstract

The secondary battery according to an embodiment of the present disclosure includes an electrode assembly to which an electrode lead is attached; a case accommodating the electrode assembly; a sealing part formed to seal the electrode assembly in the case; and a lead film surrounding a portion of an outer surface of the electrode lead and interposed between the electrode lead and the sealing part, wherein at least a partial region of an edge portion of the lead film facing the electrode assembly has an uneven shape.

Description

Secondary battery

Technical Field

The present disclosure relates to a secondary battery, and more particularly, to a secondary battery having improved safety.

The present application claims priority from korean patent application No. 10-2021-01331224, filed on 1-10-2021, and korean patent application No. 10-2022-0099996, filed on 10-8-2022, the disclosures of which are incorporated herein by reference.

Background

Mobile IT devices such as mobile phones, notebook computers, and desktop computers are closely related to modern life, and the demand for secondary batteries as key components is also rapidly increasing with the growth of the IT industry market. The secondary battery is an environmentally friendly battery technology that can be repeatedly used by charge/discharge and does not use harmful substances such as lead, nickel and cadmium, and the secondary battery has advantages in that it has a high energy density, is light in weight, and is capable of storing a large amount of energy in a small volume, thereby forming the core of a new future growing power industry. In particular, lithium secondary batteries are most widely used as an energy source for mobile IT closely related to human life, and recently, the use of lithium secondary batteries as an energy source for electric vehicles and an energy storage device for renewable energy sources has also been continuously expanding.

Generally, a secondary battery is composed of a positive electrode, a negative electrode, a separator separating the positive and negative electrodes, an electrolyte for transferring lithium ions through the separator, a case accommodating these components, and an electrode lead allowing current to flow out of the case. In addition, a lead film may be further included, and the lead film is coupled to the electrode lead for sealing the electrode lead and the case while preventing a short circuit from occurring between the electrode lead and the case.

In the case of such secondary batteries, there is a tendency to be easily affected by the internal pressure caused by the gas generated by the operation of the battery, and therefore it is necessary to develop secondary batteries having sufficient rigidity to withstand such internal pressure.

Disclosure of Invention

Technical problem

The present disclosure is directed to solving the problems of the related art, and therefore it is an object of the present disclosure to provide a secondary battery having improved safety.

Technical proposal

In order to solve the above-described problems, a secondary battery according to an embodiment of the present disclosure includes: an electrode assembly to which an electrode lead is attached; a case accommodating the electrode assembly; a sealing part formed to seal the electrode assembly in the case; and a lead film surrounding a portion of an outer surface of the electrode lead and interposed between the electrode lead and the sealing part, wherein at least a partial region of an edge portion of the lead film facing the electrode assembly has an uneven shape.

The radius of curvature of the edge portion of the lead film facing the electrode assembly may be about 50mm to 200mm.

The lead film may have a shape protruding in a direction away from the electrode assembly on a central portion in a second direction perpendicular to a first direction as an extending direction of the lead film.

The width of the lead film in the first direction may be about 20% to 150% of the width of the sealing portion in the first direction.

The lead film may include: a first lead film relatively close to the electrode assembly; and a second lead film relatively distant from the electrode assembly.

The first and second lead films may be disposed to be spaced apart from each other.

The first lead film may have a shape protruding in a direction toward the electrode assembly on a central portion in a second direction perpendicular to the first direction, which is an extending direction of the electrode leads.

The width of the first lead film in the first direction may be about 10% to 40% of the width of the sealing portion in the first direction.

The width of the interface between the first lead film and the sealing portion in the first direction may be about 10% to 40% of the width of the sealing portion in the first direction.

The second lead film may have a shape protruding in a direction away from the electrode assembly on a central portion in a second direction perpendicular to the first direction as an extending direction of the lead film.

The width of the second lead film in the first direction may be about 10% to 40% of the width of the sealing portion in the first direction.

The width of the interface between the second lead film and the sealing portion in the first direction may be about 10% to 40% of the width of the sealing portion in the first direction.

The first lead film and the second lead film may be configured such that an interface between the first lead film and the sealing part breaks first and an interface between the second lead film and the sealing part breaks later when an internal pressure of the secondary battery increases.

The distance between the first and second lead films may be about 10% to 80% of the width of the sealing portion.

The planar shape of the lead film may be a closed loop shape with a hollow center portion.

The first portion of the lead film facing the electrode assembly may have a shape protruding in a direction toward the electrode assembly, and the second portion of the lead film opposite to the first portion may have a shape protruding in a direction away from the electrode assembly.

The first portion may have a shape protruding in a direction toward the electrode assembly on a central portion in a second direction perpendicular to the first direction as an extending direction of the electrode lead, and the second portion may have a shape protruding in a direction away from the electrode assembly on a central portion in the second direction perpendicular to the first direction as an extending direction of the lead film.

The lead film may be configured such that when the internal pressure of the secondary battery increases, an interface between the lead film and the sealing part in a first region where the first portion and the sealing part are bonded breaks first, and an interface between the lead film and the sealing part in a second region where the second portion and the sealing part are bonded breaks later.

The distance between the first region and the second region in the extending direction of the electrode lead may be about 10% to 80% of the width of the sealing part in the extending direction of the electrode lead.

The total width of the lead film in the direction parallel to the extending direction of the electrode leads may be about 50% to 150% of the width of the sealing part in the direction parallel to the extending direction of the electrode leads.

The width of the first region in the extending direction of the electrode lead may be about 10% to 40% of the width of the sealing part in the extending direction of the electrode lead.

The width of the second region in the extending direction of the electrode lead may be 10% to 40% of the width of the sealing part in the extending direction of the electrode lead.

The secondary battery may be a pouch-type secondary battery.

Advantageous effects

The secondary battery according to the embodiments of the present disclosure may ensure sealability of the battery by increasing the contact area between the electrode lead and the lead film.

The secondary battery according to the embodiments of the present disclosure may have enhanced rigidity against internal pressure, so that safety may be enhanced.

Drawings

The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the foregoing disclosure, serve to provide a further understanding of the technical features of the present disclosure, and therefore, the present disclosure is not to be construed as limited to the accompanying drawings.

Fig. 1 is a diagram illustrating an electrode lead, a lead film, and a sealing part of a secondary battery according to an embodiment of the present disclosure.

Fig. 2 is a view illustrating an electrode lead, a lead film, and a sealing part of a secondary battery according to another embodiment of the present disclosure.

Fig. 3 is a view illustrating an electrode lead, a lead film, and a sealing part of a secondary battery according to still another embodiment of the present disclosure.

Fig. 4 is a view illustrating an electrode lead, a lead film, and a sealing part of a secondary battery according to still another embodiment of the present disclosure.

Detailed Description

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the fact that the inventors can appropriately define the terms to achieve the best explanation.

Accordingly, the description herein is for the purpose of illustration only of the preferred embodiments and is not intended to limit the scope of the disclosure, so it should be understood that other equivalents and modifications may be made thereto without departing from the scope of the disclosure.

A secondary battery according to an aspect of the present disclosure includes an electrode assembly to which an electrode lead is attached; a case accommodating the electrode assembly; a sealing part formed to seal the electrode assembly in the case; and a lead film surrounding a portion of an outer surface of the electrode lead and interposed between the electrode lead and the sealing part, wherein at least a partial region of an edge portion of the lead film facing the electrode assembly has an uneven shape.

Referring to fig. 1, a second battery 10 according to an embodiment of the present disclosure includes an electrode assembly 12 to which an electrode lead 11 is attached, and a case.

The electrode assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator. In the electrode assembly 12, the positive and negative electrode plates may be sequentially stacked with a separator interposed therebetween.

The positive electrode plate may include a positive electrode current collector made of a metal thin film having excellent conductivity, for example, aluminum (AL) foil, and a positive electrode active material layer coated on at least one surface of the positive electrode current collector. In addition, the positive electrode plate may include a positive electrode tab made of a metal material, for example, aluminum (AL) material, at one end of the positive electrode plate. The positive electrode tab may extend from and protrude from one end of the positive electrode plate, or may be welded to one end of the positive electrode plate or bonded to one end of the positive electrode plate using a conductive paste.

The negative electrode plate may include a negative electrode current collector made of a conductive metal thin film, such as copper (Cu) foil, and a negative electrode active material layer coated on at least one surface of the negative electrode current collector. In addition, the negative electrode plate may include a negative electrode tab formed of a metal material, for example, copper (Cu) or nickel (Ni) material, at one end thereof. The negative electrode tab may extend from and protrude from one end of the negative electrode plate, or may be welded to one end of the negative electrode plate or bonded to one end of the negative electrode plate using conductive paste.

The separator may be interposed between the positive and negative electrode plates to electrically insulate the positive and negative electrode plates from each other, and the separator may be formed as a porous film so that lithium ions or the like may pass between the positive and negative electrode plates. For example, the separator may include a porous film using Polyethylene (PE), polypropylene (PP), or a composite film thereof.

An inorganic coating may be disposed on the surface of the separator. The inorganic coating may have a structure in which inorganic particles are bonded to each other by a binder to form interstitial volumes between the particles.

The electrode assembly 12 may be a wound (wrapping) electrode assembly having a structure in which a long sheet-type positive electrode and a long sheet-type negative electrode are wrapped with a separator interposed between the positive electrode and the negative electrode, a stacked (lamination type) electrode assembly having a structure in which a plurality of positive electrodes and negative electrodes cut into units of a predetermined size are sequentially laminated with a separator interposed between the positive electrode and the negative electrode, a bi-cell (bi-cell) having a structure in which a positive electrode and a negative electrode of a predetermined unit are laminated with a separator interposed between the positive electrode and the negative electrode, a full-cell (full-cell) is wrapped, or the like.

The case includes a receiving part 13a receiving the electrode assembly 12 and a sealing part 13b formed to seal the electrode assembly 12.

The sealing part 13b refers to a portion welded along the outer circumferential surface of the receiving part 13a to seal the electrode assembly 12, and the welding may be thermal welding, ultrasonic welding, or the like, but is not particularly limited as long as the sealing part can be welded.

In an embodiment of the present disclosure, the case may be provided in the form of a film having a multi-layered structure including an outer layer to prevent external impact, a metal barrier layer to block moisture, and a sealant layer to seal the case.

The outer layer may include other polyester-based films such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolyesters, polycarbonates, nylons, and the like, and the outer layer may be configured as a single layer or multiple layers.

The metal barrier layer may include aluminum, copper, and the like.

The sealant layer may include a sealant resin and may be formed as a single layer or multiple layers.

In embodiments of the present disclosure, the sealant resin may include polypropylene (PP), acid modified polypropylene (PPa), random polypropylene, ethylene propylene copolymer, or two or more thereof. The ethylene propylene copolymer may include ethylene propylene rubber, ethylene propylene block copolymer, etc., but is not limited thereto.

In embodiments of the present disclosure, the housing may be in the form of a soft pack.

In embodiments of the present disclosure, when the housing is in the form of a soft pack, the housing may include an upper soft pack and a lower soft pack. When the case includes the upper and lower soft packs, the outer circumferential surfaces of the upper and lower soft packs are welded to each other by heat and pressure to seal the battery.

When the case is in the form of a soft pack, the sealing portion 13b may be sealed at four or three outer circumferences of the case. The three-sided sealing structure refers to a structure in which an upper and lower soft packs are formed on one soft pack sheet, and then boundary surfaces between the upper and lower soft packs are bent to overlap the electrode assembly receiving parts 13a formed in the upper and lower soft packs, and in this state, edges of the remaining three sides except for the bent parts are sealed.

Referring to fig. 1, the electrode lead 11 may be received in the case such that a portion of the electrode lead 11 is exposed to the outside of the case.

Referring to fig. 1, a secondary battery 10 according to an embodiment of the present disclosure includes a lead film 14.

The lead film 14 surrounds a portion of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the sealing part 13b of the case at the point where the electrode lead 11 protrudes. The lead film 14 may be located on at least one surface of the electrode lead 11. At the portion where the electrode leads protrude, a lead film 14 is interposed between the electrode leads 11 and the sealing part 13b of the case to facilitate the coupling of the electrode leads 11 and the sealing part 13b of the case. The sealing of the battery occurs on the surface of the lead film 14 that contacts the sealing portion 13b.

Referring to fig. 1, in the lead film 14, a portion of the edge portion facing the electrode assembly 12 has an uneven shape. When the lead film 14 has such a shape, the contact area between the lead film 14 and the electrode lead 11 is large. Specifically, in the lead film 14, the contact area between the lead film 14 and the electrode lead 11 is increased as compared to a conventional secondary battery having a flat structure facing the edge portion of the electrode assembly 12. Therefore, the adhesive strength between the electrode lead 11 and the sealing part 13b is increased, and thus the sealing strength between the electrode lead 11 and the sealing part 13b can be increased. When the sealing strength between the electrode lead 11 and the sealing part 13b is increased, the rigidity of the battery against the internal pressure can be increased.

In addition, according to this configuration of the present disclosure, the contact area between the lead film 14 and the sealing portion 13b can also be large. In particular, in the lead film 14, the contact area between the lead film 14 and the sealing part 13b may be increased as compared to a conventional secondary battery having a flat structure facing the edge portion of the electrode assembly 12. Therefore, the adhesive strength between the electrode lead 11 and the sealing part 13b is increased, so that the sealing strength between the electrode lead 11 and the sealing part 13b can be increased. When the sealing strength between the electrode lead 11 and the sealing part 13b is increased, the rigidity of the battery against the internal pressure can be increased.

On the other hand, according to this configuration of the present disclosure, it is possible to uniformly transmit the pressure to the entire lead film 14 for the internal pressure generated inside the battery. Accordingly, the internal pressure is uniformly distributed throughout the lead film 14, and thus the rigidity of the battery against the internal pressure can be increased.

In the embodiment of the present disclosure, the edge portion of the lead film 14 facing the electrode assembly 12 may have a radius of curvature ranging from about 50mm to 200mm. When the radius of curvature of the edge portion satisfies the range defined above, the contact area between the lead film 14 and the electrode lead 11 can be increased, and the contact area between the lead film 14 and the sealing part 13b can also be easily increased.

Meanwhile, the lead film 14 may have a shape in which a central portion in a second direction approximately perpendicular to a first direction, which is an extending direction of the electrode lead 11, protrudes in a direction away from the electrode assembly 12. For example, the lead film 14 may have an approximately arc shape protruding in the outer direction of the case.

Referring to fig. 1, the width h of the lead film 14 in the first direction may be about 20% to 150% of the width d of the sealing portion 13b in the first direction. When the width h of the lead film 14 satisfies the range defined above, the contact area between the lead film 14 and the electrode lead 11 may be increased, and the contact area between the lead film 14 and the sealing part 13b may also be more easily increased.

Referring to fig. 2, the lead film 14 may have a shape in which a central portion in a second direction approximately perpendicular to a first direction, which is an extending direction of the electrode lead 11, protrudes in a direction toward the electrode assembly 12. For example, the lead film 14 may have an approximately arc shape protruding in the inner direction of the case.

Even in this case, similarly to the case where the lead film 14 has the shape shown in fig. 1. The width h of the lead film 14 in the first direction may be about 20% to 150% of the width d of the sealing portion 13b in the first direction. When the width h of the lead film 14 satisfies the range defined above, the contact area between the lead film 14 and the electrode lead 11 may be increased, and the contact area between the lead film 14 and the sealing part 13b may also be more easily increased.

Referring to fig. 3, the lead film 14 may include a first lead film 14a relatively close to the electrode assembly 12 and a second lead film 14b relatively far from the electrode assembly 12. The first lead film 14a and the second lead film 14b may be disposed to be spaced apart from each other.

Referring to fig. 3, the first lead film 14a may have a shape in which a central portion in a second direction approximately perpendicular to a first direction, which is an extending direction of the electrode lead 11, protrudes in a direction toward the electrode assembly 12. For example, the first lead film 14a may have an approximately arc shape protruding in a direction toward the electrode assembly 12.

In fig. 3, the shape of the first lead film 14a is shown as an approximately arc shape protruding in the direction of accommodating the electrode assembly 12, but the shape of the first lead film 14a is not limited thereto.

In another embodiment of the present disclosure, the shape of the first lead film 14a may be an approximately arc shape protruding in the outer direction of the case.

Referring to fig. 3, the second lead film 14b may have a shape in which a central portion in a second direction approximately perpendicular to the first direction, which is the extending direction of the electrode lead 11, protrudes in a direction away from the electrode assembly 12. For example, the second lead film 14b may have an approximately arc shape protruding in a direction away from the electrode assembly 12.

In fig. 3, the shape of the second lead film 14b is shown as an approximately arc shape protruding in the outer direction of the case, but the shape of the second lead film 14b is not limited thereto.

In another embodiment of the present disclosure, the shape of the second lead film 14b may be an approximately arc shape protruding in a direction of accommodating the electrode assembly 12.

In the case of the secondary battery, an expansion phenomenon in which the battery expands due to an increase in internal pressure may occur, which affects the safety of the battery. When the swelling phenomenon occurs, breakage may occur at the interface with weak adhesion between the lead film 14 and the sealing portion 13b.

When the lead film 14 includes the first lead film 14a and the second lead film 14b, the lead film 14 may be configured such that an interface between the first lead film 14a and the sealing part 13b is first broken, and then an interface between the second lead film 14b and the sealing part 13b is thereafter broken during expansion of the battery.

When the swelling phenomenon occurs, the first lead film 14a is closer to the inner direction of the case than the second lead film 14b, and thus the first lead film 14a may be broken earlier than the second lead film 14b during the occurrence of the swelling phenomenon.

When the swelling phenomenon occurs, most of the pressure is applied to the sealing portion 13b in the inner direction of the housing. Since the first lead film 14a is closer to the inner direction of the case than the second lead film 14b, the rupture occurs preferentially at the interface between the first lead film 14a and the sealing portion 13b in the sealing portion located in the inner direction of the case, and therefore, the expansion pressure can be easily controlled. Therefore, the safety of the battery can be improved by preventing an increase in the swelling pressure.

When the expansion pressure increases even after the rupture preferentially occurs at the interface between the first lead film 14a and the sealing portion 13b, the rupture occurs at the interface between the second lead film 14b and the sealing portion 13b, thereby further preventing the increase of the expansion pressure.

When the interface between the second lead film 14b and the sealing portion 13b breaks, the pressure inside the battery can be discharged to the outside, and thus the expansion pressure can be more easily controlled.

In an embodiment of the present disclosure, a sensor unit (not shown) and a control unit (not shown) connected to the first lead film 14a and/or the second lead film 14b may be further included. The sensor unit measures the inflation pressure and transmits it to the control unit, and when a specific pressure threshold is exceeded, the control unit may allow the first lead film 14a and/or the second lead film 14b to break.

In the embodiment of the present disclosure, the first lead film 14a may be located at an end of the sealing portion in the inner direction of the case.

In the embodiment of the present disclosure, the second lead film 14b may be located at an end of the sealing portion in the outer direction of the case.

In the embodiment of the present disclosure, the distance between the first lead film 14a and the second lead film 14b may be about 10% to 80% of the width d of the sealing portion 13b. Here, the distance between the first lead film 14a and the second lead film 14b refers to the distance between the end of the first lead film 14a closest to the outside direction of the case and the end of the second lead film 14b closest to the inside direction of the case. When the distance between the first lead film 14a and the second lead film 14b satisfies the range defined above, the timing of rupture of the interface between the first lead film 14a and the sealing portion 13b and the interface between the second lead film 14b and the sealing portion 13b can be more easily controlled.

In embodiments of the present disclosure, the radius of curvature of the first lead film 14a may be about 50mm to 200mm. When the radius of curvature of the first lead film 14a satisfies the range defined above, the contact area between the first lead film 14a and the electrode lead 11 and the contact area between the first lead film 14a and the sealing part 13b can be easily increased. In addition, the timing of rupture of the interface between the first lead film 14a and the sealing portion 13b can be more easily controlled.

In embodiments of the present disclosure, the radius of curvature of the second lead film 14b may be about 50mm to 200mm. When the radius of curvature of the second lead film 14b satisfies the range defined above, the contact area between the second lead film 14b and the electrode lead 11 and the contact area between the second lead film 14b and the sealing part 13b can be easily increased. In addition, the timing of rupture of the interface between the second lead film 14b and the sealing portion 13b can be more easily controlled.

Referring to fig. 3, the width h1 of the first lead film 14a in the first direction, which is the extending direction of the electrode lead 11, may be about 10% to 40% of the width d of the sealing part 13b in the first direction. When the width h1 of the first lead film 14a satisfies the range defined above, the contact area between the first lead film 14a and the electrode lead 11 and the contact area between the first lead film 14a and the sealing part 13b can be easily increased, and sufficient sealing strength can be easily ensured during normal operation of the battery.

Referring to fig. 3, the width h2 of the second lead film 14b in the first direction, which is the extending direction of the electrode lead 11, may be about 10% to 40% of the width d of the sealing part 13b in the first direction. When the width h2 of the second lead film 14b satisfies the range defined above, the contact area between the second lead film 14b and the electrode lead 11 and the contact area between the second lead film 14b and the sealing part 13b can be easily increased, and sufficient sealing strength can be easily ensured during normal operation of the battery.

In the embodiment of the present disclosure, the width of the interface between the first lead film 14a and the sealing portion 13b where the rupture occurs in the first direction may be about 10% to 40% of the width d of the sealing portion 13b. When the width of the interface between the first lead film 14a and the sealing portion 13b satisfies the range defined above, a sufficient sealing strength can be ensured during normal operation of the battery, and breakage can easily occur during occurrence of the swelling phenomenon.

In the embodiment of the present disclosure, the width of the interface between the second lead film 14b and the sealing portion 13b where the rupture occurs in the first direction may be about 10% to 40% of the width of the sealing portion 13b. When the width of the interface between the second lead film 14b and the sealing portion 13b satisfies the range defined above, sufficient sealing strength can be ensured during normal operation of the battery, and breakage can easily occur during occurrence of the swelling phenomenon.

Referring to fig. 4, the planar shape of the lead film 14 may be a closed loop shape with a hollow center portion. When the lead film 14 has such a closed loop shape, the contact area between the lead film 14 and the electrode lead 11 is large, and the contact area between the lead film 14 and the sealing part 13b can be more easily increased. In addition, the internal pressure is uniformly distributed throughout the lead film 14, and therefore the rigidity of the battery against the internal pressure can be more easily increased.

For example, the lead film 14 may have an approximately annular shape. On the other hand, a first portion of the lead film 14 facing the electrode assembly 12 may have a shape protruding in a direction toward the electrode assembly 12, and a second portion opposite to the first portion may have a shape protruding in a direction away from the electrode assembly 12. The first portion may have a shape in which a central portion in a second direction approximately perpendicular to a first direction, which is an extending direction of the electrode lead 11, protrudes in a direction toward the electrode assembly 12. The second portion may have a shape in which a central portion in a second direction approximately perpendicular to a first direction, which is an extending direction of the electrode lead 11, protrudes in a direction away from the electrode assembly 12.

In the embodiment of the present disclosure, in the lead film 14, when the internal pressure of the secondary battery increases, the interface between the lead film 14 and the sealing part 13B in the first region a is first broken, and then the interface between the lead film 14 and the sealing part 13B in the second region B is thereafter broken.

Here, the first region a refers to a portion of the annular lead film 14 relatively close to the direction in which the electrode assembly 12 is accommodated and corresponding to the sealing portion 13b. Here, the second region B refers to a portion of the annular lead film 14 relatively far from the direction accommodating the electrode assembly 12 and corresponding to the sealing portion 13B.

As the internal pressure of the secondary battery increases, rupture preferentially occurs at the interface between the lead film 14 and the sealing portion 13b, which is a portion receiving most of the pressure, in the first region a in the inner direction of the case, and therefore the expansion pressure can be easily controlled. Therefore, the safety of the battery can be improved by preventing an increase in the swelling pressure.

When the expansion pressure increases even after the rupture preferentially occurs at the interface between the lead film 14 and the sealing portion 13B in the first region a, the rupture occurs at the interface between the lead film 14 and the sealing portion 13B in the second region B, thereby further preventing the expansion pressure from increasing.

When the interface between the lead film 14 and the sealing portion 13B in the second region B is broken, the pressure inside the battery can be discharged to the outside, and thus the expansion pressure can be more easily controlled.

In an embodiment of the present disclosure, a sensor unit (not shown) and a control unit (not shown) connected to the first region a and/or the second region B may be further included. The sensor unit measures the inflation pressure and transmits it to the control unit, and the control unit may allow the first area a and/or the second area B to break when a certain pressure threshold is exceeded.

In an embodiment of the present disclosure, the first region a may be located at an end of the sealing portion in an inner direction of the case.

In an embodiment of the present disclosure, the second region B may be located at an end of the sealing portion in an outer direction of the case.

In the embodiment of the present disclosure, the distance between the first region a and the second region B in the extending direction of the electrode lead 11 may be about 10% to 80% of the width d of the sealing part 13B in the extending direction of the electrode lead 11. Here, the distance between the first region a and the second region B refers to the closest distance among the distances between the first region a and the second region B. When the distance between the first region a and the second region B satisfies the range defined above, the timing of rupture between the first region a and the second region B can be more easily controlled.

In embodiments of the present disclosure, the radius of curvature of the lead film 14 having a closed loop shape may be about 50mm to 200mm. When the radius of curvature of the annular lead film 14 satisfies the range defined above, the contact area between the lead film 14 and the electrode lead 11 and the contact area between the lead film 14 and the sealing part 13b in the first region a can be easily increased. In addition, the contact area between the lead film 14 and the electrode lead 11 and the contact area between the lead film 14 and the sealing part 13B in the second region B can be easily increased. The timing of the rupture of the first region a and/or the second region B can be more easily controlled.

Referring to fig. 4, the total width h of the lead film 14 in the direction parallel to the extending direction of the electrode lead 11 may be about 50% to 150% of the width d of the sealing part 13b in the direction parallel to the extending direction of the electrode lead 11. When the total width of the lead film 14 satisfies the range defined above, the contact area between the lead film 14 and the electrode lead 11 may be increased, and the contact area between the lead film 14 and the sealing part 13b may also be more easily increased.

Referring to fig. 4, a width h1 of a first portion of the ring-shaped lead film 14 facing the electrode assembly 12 in the first direction may be about 10% to 40% of a width of the sealing portion 13b in the first direction. When the width h1 satisfies the range as defined above, the contact area between the lead film 14 and the electrode lead 11 and the contact area between the lead film 14 and the sealing part 13b can be easily increased, and sufficient sealing strength can be easily ensured during normal operation of the battery.

Referring to fig. 4, a width h2 of a second portion of the ring-shaped lead film 14 opposite to the first portion in the first direction may be about 10% to 40% of a width of the sealing portion 13b in the first direction. When the width h2 satisfies the range as defined above, the contact area between the lead film 14 and the electrode lead 11 and the contact area between the lead film 14 and the sealing part 13b can be easily increased, and sufficient sealing strength can be easily ensured during normal operation of the battery.

Referring to fig. 4, the width of the first region a in the extending direction of the electrode lead 11 may be about 10% to 40% of the width d of the sealing part in the extending direction of the electrode lead 11. When the width of the first region a satisfies the range defined above, a sufficient sealing strength can be ensured during normal operation of the battery, and breakage can easily occur during occurrence of the swelling phenomenon.

Referring to fig. 4, the width of the second region B in the extending direction of the electrode lead 11 may be about 10% to 40% of the width d of the sealing part in the extending direction of the electrode lead 11. When the width of the second region B satisfies the range as defined above, sufficient sealing strength may be ensured during normal operation of the battery, and breakage may easily occur when the internal pressure of the secondary battery increases.

The secondary battery may be a cylindrical, square, or soft pack type secondary battery. Among these secondary batteries, the secondary battery may be a soft pack type secondary battery.

In the case of the soft pack type secondary battery, the strength of the soft pack case is weak, and since the soft pack case has various shapes, the soft pack case is more susceptible to the internal pressure. Therefore, when the secondary battery according to the embodiment of the present disclosure is a soft pack type secondary battery, it may be more advantageous in terms of safety.

While the present disclosure has been described above with respect to a limited number of embodiments and drawings, the present disclosure is not limited thereto, and it will be apparent to those skilled in the art that various modifications and changes may be made thereto within the technical aspects of the present disclosure and the equivalent scope of the appended claims.

[ reference numerals description ]

10: secondary battery

11: electrode lead

12: electrode assembly

13 a-receiving portion

13b: sealing part

14: lead film

14a: first lead film

14b: second lead film

A: first region

B: second region

Claims

1. A secondary battery, comprising:

an electrode assembly to which an electrode lead is attached;

a case accommodating the electrode assembly;

a sealing part formed to seal the electrode assembly in the case; and

a lead film surrounding a portion of an outer surface of the electrode lead and interposed between the electrode lead and the sealing part,

wherein at least a partial region of the lead film facing the edge portion of the electrode assembly has an uneven shape.

2. The secondary battery according to claim 1, wherein a radius of curvature of the edge portion of the lead film facing the electrode assembly is 50mm to 200mm.

3. The secondary battery according to claim 1, wherein the lead film has a shape in which a central portion in a second direction perpendicular to a first direction as an extending direction of the lead film protrudes in a direction away from the electrode assembly.

4. The secondary battery according to claim 3, wherein a width of the lead film in the first direction is 20% to 150% of a width of the sealing portion in the first direction.

5. The secondary battery according to claim 1, wherein the lead film has a shape in which a central portion in a second direction perpendicular to a first direction, which is an extending direction of the electrode lead, protrudes in a direction toward the electrode assembly.

6. The secondary battery according to claim 5, wherein a width of the lead film in the first direction is 20% to 150% of a width of the sealing portion in the first direction.

7. The secondary battery according to claim 1, wherein the lead film comprises:

a first lead film relatively close to the electrode assembly; and

and a second lead film relatively distant from the electrode assembly.

8. The secondary battery according to claim 7, wherein the first lead film and the second lead film are disposed to be spaced apart from each other.

9. The secondary battery according to claim 7, wherein the first lead film has a shape in which a central portion in a second direction perpendicular to a first direction, which is an extending direction of the electrode leads, protrudes in a direction toward the electrode assembly.

10. The secondary battery according to claim 9, wherein a width of the first lead film in the first direction is 10% to 40% of a width of the sealing portion in the first direction.

11. The secondary battery according to claim 9, wherein a width of an interface between the first lead film and the sealing portion in the first direction is 10% to 40% of a width of the sealing portion in the first direction.

12. The secondary battery according to claim 7, wherein the second lead film has a shape in which a central portion in a second direction perpendicular to a first direction that is an extending direction of the lead film protrudes in a direction away from the electrode assembly.

13. The secondary battery according to claim 12, wherein a width of the second lead film in the first direction is 10% to 40% of a width of the sealing portion in the first direction.

14. The secondary battery according to claim 12, wherein a width of an interface between the second lead film and the sealing portion in the first direction is 10% to 40% of a width of the sealing portion in the first direction.

15. The secondary battery according to claim 7, wherein the first lead film and the second lead film are configured such that an interface between the first lead film and the sealing portion breaks first and an interface between the second lead film and the sealing portion breaks later when an internal pressure of the secondary battery increases.

16. The secondary battery according to claim 8, wherein a distance between the first lead film and the second lead film is 10% to 80% of a width of the sealing portion.

17. The secondary battery according to claim 1, wherein the planar shape of the lead film is a closed ring shape with a hollow center portion.

18. The secondary battery according to claim 17, wherein a first portion of the lead film facing the electrode assembly has a shape protruding in a direction toward the electrode assembly, and a second portion of the lead film opposite to the first portion has a shape protruding in a direction away from the electrode assembly.

19. The secondary battery according to claim 18, wherein the first portion has a shape in which a central portion in a second direction perpendicular to a first direction that is an extending direction of the electrode leads protrudes in a direction toward the electrode assembly, and

the second portion has a shape in which a central portion in a second direction perpendicular to a first direction as an extending direction of the lead film protrudes in a direction away from the electrode assembly.

20. The secondary battery according to claim 18, wherein the lead film is configured such that when an internal pressure of the secondary battery increases, an interface between the lead film and the sealing portion in a first region where the first portion and the sealing portion are bonded breaks first, and an interface between the lead film and the sealing portion in a second region where the second portion and the sealing portion are bonded breaks later.

21. The secondary battery according to claim 20, wherein a distance between the first region and the second region in the extending direction of the electrode lead is 10% to 80% of a width of the sealing part in the extending direction of the electrode lead.

22. The secondary battery according to claim 17, wherein a total width of the lead film in a direction parallel to an extending direction of the electrode lead is 50% to 150% of a width of the sealing portion in a direction parallel to the extending direction of the electrode lead.

23. The secondary battery according to claim 20, wherein a width of the first region in the extending direction of the electrode lead is 10% to 40% of a width of the sealing part in the extending direction of the electrode lead.

24. The secondary battery according to claim 20, wherein a width of the second region in the extending direction of the electrode lead is 10% to 40% of a width of the sealing part in the extending direction of the electrode lead.

25. The secondary battery according to claim 1, which is a soft pack type secondary battery.