CN117296198A - Secondary battery with improved safety - Google Patents

Abstract

The disclosed invention relates to a secondary battery including an electrode assembly in which a plurality of unit cells are stacked. In one embodiment, the electrode tabs of the respective unit cells extending from the electrode assembly are gathered into one to be electrically connected to the electrode terminals of the secondary battery, and the electrode tabs of the respective unit cells include an ultra-long portion corresponding to expansion of the electrode assembly.

Description

Secondary battery with improved safety

Technical Field

The present invention relates to a secondary battery, and more particularly, to a secondary battery that maintains safety of an electrode tab even when an electrode assembly swells.

The present application claims the benefit of priority based on korean patent application No.10-2022-0045170, filed on 12 months of 2022, and korean patent application No.10-2023-0039585, filed on 27 months of 2023, and the entire contents of the korean patent applications are incorporated herein by reference.

Background

Unlike primary batteries, secondary batteries are rechargeable, and many researches on secondary batteries have been recently conducted due to the possibility of compact size and high capacity. As technology development and demand for mobile devices and electric vehicles and energy storage systems have increased, demand for secondary batteries as energy sources has increased more rapidly, and electric vehicles and energy storage systems have emerged to meet the demand of the environmental protection era.

Secondary batteries are classified into coin-type batteries, cylindrical-type batteries, prismatic-type batteries, and pouch-type batteries according to the shape of a battery case. In such a secondary battery, an electrode assembly mounted in a battery case is a chargeable and dischargeable power generation device of a structure in which electrodes and separators are laminated.

The electrode assembly may be broadly divided into a jelly-roll type electrode assembly in which a separator is interposed between a positive electrode and a negative electrode, each of which is provided in the form of a sheet coated with an active material, and a laminated electrode group and a laminated/folded type electrode assembly, and then the positive electrode, the separator, and the negative electrode are wound; in the laminated electrode assembly, a plurality of positive electrodes and negative electrodes with separators interposed therebetween are laminated in order; and in the laminated/folded electrode assembly, the laminated unit cells are wound together with the separator having a long length.

One of problems that may occur when a secondary battery is used for a long period of time is a swelling phenomenon. The swelling phenomenon is a phenomenon in which the secondary battery gradually swells by repeated charge and discharge. The swelling phenomenon is a phenomenon in which lithium ion electrolyte in a battery evaporates and the resulting pressure causes the battery to bulge and may cause the case to deform, and in severe cases, the electrolyte may leak, which causes a fire or explosion.

The swelling phenomenon affects not only the external appearance of the secondary battery but also the internal structure of the secondary battery. That is, when an expansion phenomenon occurs in the electrode assembly, stress is accumulated as tension acts on the electrode tabs extending from the electrode assembly and welded to the electrode terminals. Once the swelling phenomenon occurs, the electrode tab will continue to be pulled as it will not return to normal, and eventually the stress will exceed the limit, and the electrode tab will be broken.

Therefore, in order to safely use the secondary battery for a long time, a structure capable of preventing the electrode tabs from being disconnected in response to the swelling phenomenon is required.

[ related art literature ]

(patent document 001) Korean registered patent No.10-1767722 (published on 11 days of 2017, 8, month)

Disclosure of Invention

Technical problem

The present invention aims to provide a secondary battery capable of preventing an electrode tab from being disconnected even when an expansion phenomenon occurs during use of the secondary battery.

However, the technical problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned are also apparent to those skilled in the art from the following description of the present invention.

Technical proposal

The present invention relates to a secondary battery including an electrode assembly in which a plurality of unit cells are stacked. In one example, the respective electrode taps of the unit cells extending from the electrode assembly are gathered together and electrically connected to the electrode terminals of the secondary battery, and the electrode taps of each of the unit cells include an ultra-long portion corresponding to expansion of the electrode assembly.

In an embodiment of the present invention, the electrode tab of each unit cell extending from the electrode assembly may be supported by a wire connection part electrically connected to the electrode terminal, and the ultra-long part may be formed after a tightening part of the wire connection part.

Further, an end of the overlength portion may form a welded portion joined to the wire connection portion.

According to a specific embodiment, the overlength portion may form a U-turn between the tightening portion and the welding portion.

Further, according to an embodiment, the electrode assembly may be provided in a plurality, and an electrode tab extending from each of the plurality of electrode assemblies may form the tightening part independently of the wire connection part.

In one example, the wire parts may be provided in a plurality corresponding to the number of the electrode assemblies, each of the electrode assemblies may be supported by the tightening part of the corresponding wire part, and an end of the ultra-long part provided by the electrode tab extending from each of the electrode assemblies may form the welding part with respect to the corresponding wire part.

In another example, the wire part may include a plurality of tightening parts corresponding to the number of the electrode assemblies, and each of the electrode assemblies may be supported by the corresponding tightening part.

Further, an end portion of the ultra-long portion provided by the electrode tab extending from each of the electrode assemblies forms one welded portion that may be opposite to the wire connection portion.

In addition, the overlength portion provided by the electrode tab extending from each of the plurality of electrode assemblies may form a U-turn portion between the tightening portion and the welding portion.

Meanwhile, according to another embodiment of the present invention, the wire connection part may include a friction reducing structure on a contact surface of the tightening part supporting the electrode tab of the electrode assembly.

In one example, the friction reducing structure may be an embossed structure formed on a contact surface of the tightening part.

In another example, the friction reducing structure may be a low friction coating layer formed on a contact surface of the tightening part.

Further, according to another embodiment of the present invention, the connection part may include an insertion guide part configured to assist the insertion of the electrode tab of each unit cell into the tightening part.

For example, the insertion guide may be a groove provided in a form converging toward the tightening part.

Advantageous effects

In the secondary battery of the present invention having the above-described configuration, the electrode tab includes the ultra-long portion, so that an excessive stress is not applied to the welded portion even when an expansion phenomenon occurs in the electrode assembly due to battery degradation or impact caused by repeated charge and discharge. Therefore, according to the secondary battery of the present invention, even when the swelling phenomenon occurs, the safety of the secondary battery can be reliably maintained for a long period of time by preventing the disconnection of the electrode tabs.

Further, according to the present invention, by supporting the middle portion of the electrode tap and introducing the movement of the electrode tap accompanied by expansion into the sliding movement by using the wire connection portion, the electrode tap can be designed to move only in proportion to the expansion level. Accordingly, the ultra-long part of the electrode tab can effectively respond to the swelling phenomenon of the electrode assembly, and the position and movement of the ultra-long part can be precisely controlled, so that risks such as internal short circuits can be effectively eliminated.

However, technical effects that can be obtained by the present invention are not limited to the above-described effects, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the present invention described below.

Drawings

Since the following drawings attached to the present specification illustrate exemplary embodiments of the present invention and are used to help understand the technical ideas of the present invention together with the detailed description of the present invention described below, the present invention should not be interpreted restrictively based on the drawings.

Fig. 1 is an exploded perspective view illustrating a secondary battery of the present invention.

Fig. 2 is a view showing a coupling structure of an electrode tab and a wiring part of an electrode assembly.

Fig. 3 is a view showing a variation of an electrode tab supported by a wire part when an expansion phenomenon occurs in an electrode assembly.

Fig. 4 is a view showing a case where a plurality of electrode assemblies are supported by a plurality of wire connection parts.

Fig. 5 is a view showing a case where a plurality of electrode assemblies are supported by one wiring part.

Fig. 6 is a view showing a case in which the relief structure is used as the friction reducing structure provided in the tightening part of the wire connecting part.

Fig. 7 is a view showing a case in which a low friction coating layer is applied as a friction reducing structure provided in a tightening part of a wire connecting part.

Fig. 8 is a view showing one embodiment of the insertion guide portion provided in the wiring portion.

Best mode for carrying out the invention

The present invention is capable of various modifications and various embodiments, and therefore, specific embodiments thereof will be described in detail below.

It should be understood, however, that the invention is not limited to the particular embodiments and includes all modifications, equivalents, or alternatives falling within the spirit and technical scope of the invention.

The terms "comprises," "comprising," and "having," as used herein, specify the presence of stated features, integers, steps, actions, components, or groups thereof, or are combinations thereof, and it should be understood that the presence or addition of one or more other features, integers, steps, actions, components, groups, or groups thereof is not previously excluded.

Further, in the present invention, when a part of a layer, a film, a region, a plate, or the like is provided "on" another part, this includes not only the case where one part is provided "directly" on the other part but also the case where the other part is interposed therebetween. In contrast, when a portion of a layer, film, region, plate, or the like is provided "under" another portion, this includes not only the case where one portion is provided "directly under" another portion but also the case where another portion is interposed therebetween. In addition, in this application, "upper" may include not only the case of being disposed at the upper portion but also the case of being disposed at the lower portion.

The present invention relates to a secondary battery including an electrode assembly in which a plurality of unit cells are stacked. In one example, the respective electrode taps of the unit cells extending from the electrode assembly are gathered together and electrically connected to the electrode terminals of the secondary battery, and the electrode taps of the respective unit cells include an ultra-long portion corresponding to the expansion of the electrode assembly.

In a specific embodiment, in the secondary battery of the present invention, the electrode tabs of the respective unit cells extending from the electrode assembly are supported by the wire connection parts electrically connected to the electrode terminals, and the ultra-long parts are formed after the tightening parts of the wire connection parts.

Therefore, in the present invention, since the electrode tab includes the ultra-long portion, an excessive stress is not applied to the welded portion even when swelling (i.e., swelling phenomenon) of the electrode assembly occurs due to battery degradation or impact caused by repeated charge and discharge of the secondary battery. Therefore, according to the secondary battery of the present invention, even when the swelling phenomenon occurs, the safety of the secondary battery can be reliably maintained for a long period of time by preventing the disconnection of the electrode tabs.

Further, by supporting the intermediate portion of the electrode tab and introducing the movement of the electrode tab accompanying the expansion (pulled by a pulling force) into the sliding movement by using the wire connection portion, the electrode tab can be designed to move only in proportion to the expansion level. Accordingly, the ultra-long part of the electrode tab can effectively respond to the swelling phenomenon of the electrode assembly, and the position and movement of the ultra-long part are precisely designed, so that risks such as internal short circuits can be effectively eliminated.

Detailed Description

Hereinafter, specific embodiments of the secondary battery of the present invention will be described in detail with reference to the accompanying drawings. For reference, the front, rear, upper, lower, left and right directions indicating relative positions are used in the following description for the purpose of understanding the present invention, and refer to directions shown in the drawings unless otherwise indicated.

First embodiment

Fig. 1 is an exploded perspective view illustrating a secondary battery 10 of the present invention, and fig. 2 is a view illustrating a coupling structure of an electrode tab 120 and a wire part 300 of an electrode assembly 100.

As shown in the drawings, the present invention relates to a structure applicable to a secondary battery 10, the secondary battery 10 including an electrode assembly 100 in which a plurality of unit cells 110 are stacked, for example, the secondary battery 10 shown in the drawings having a square shape, and herein, respective electrode taps 120 of the unit cells 110, which extend from the electrode assembly 100, are gathered together and electrically connected to electrode terminals 200 of the secondary battery 10, and the electrode taps 120 of the unit cells 110 have an ultra-long part 130 corresponding to expansion of the electrode assembly 100.

The swelling phenomenon simply refers to a phenomenon in which the electrode assembly 100 repeatedly charged and discharged gradually swells. The swelling phenomenon is a phenomenon in which lithium ion electrolyte in the battery evaporates and the generated pressure causes the battery to bulge, and may cause the case 20 to deform, and in severe cases, the electrolyte may leak, which causes a fire or explosion.

One of the problems of the swelling phenomenon on the internal structure of the secondary battery 10 is the generation of stress in the electrode tabs 120. In the electrode assembly 100, for example, in the stacked-type electrode assembly 100, the electrode tabs 120 (positive electrode tabs or negative electrode tabs) of the respective stacked unit cells 110 are welded to the electrode terminal 200, and the distances from the respective unit cells 110 to the electrode terminal 200 are different.

In this structure, when an expansion phenomenon occurs in the electrode assembly 100, the relative position of the unit cells 110 is changed more as the unit cells 110 are further apart from the electrode terminals 200, and thus a strong tensile force acts on the electrode tabs 120 of the apart unit cells 110. Since only the allowance of the process deviation is considered in the design of the welding part 320 of the electrode tab 120 and the electrode terminal 200, when the battery is deteriorated and the swelling phenomenon occurs, the electrode tab 120 subjected to the strong tensile force is easily short-circuited at the electrode terminal 200, and the disconnection of the electrode tab 120 adversely affects the safety of the secondary battery 10.

In order to prevent the electrode tabs 120 accompanying such swelling phenomenon from being disconnected, in the present invention, the electrode tabs 120 of the unit cells 110 include an ultra-long portion 130 corresponding to the swelling of the electrode assembly 100. Even when the swelling phenomenon occurs and thus the relative position between the unit cell 110 and the electrode terminal 200 is significantly changed, the ultra-long part 130 is changed in response to the change in the relative position, so that the electrode tab 120 is not stressed.

According to the embodiment of the present invention shown in fig. 1 and 2, the electrode tabs 120 of the respective unit cells 110 extending from the electrode assembly 100 are supported by the wire connection parts 300 electrically connected to the electrode terminals 200, and the ultra-long parts 130 are formed after the tightening parts 310 of the wire connection parts 300. Further, the end of the ultra-long part 130 forms a welding part 320 to be coupled to the wire part 300, and thus, the electrode tab 120 is electrically connected to the electrode terminal 200 through the wire part 300.

The wire connection part 300 of the present invention relates to a means for physically holding and supporting a bundle of electrode tabs 120 regardless of the shape thereof. For example, as shown in the drawing, the electrode tab 120 may be inserted and temporarily fixed in a slit provided in the wire connection part 300. Here, the temporary fixation means that the position of the electrode tab 120 inserted into the wire connection part 300 is generally fixed, but relative movement may occur when a certain amount of tension is applied.

The tightening part 310 of the wire part 300 is a part (e.g., the above-described slit) that presses and temporarily fixes the electrode tab 120, and the ultra-long part 130 formed after the tightening part 310 of the wire part 300 corresponds to the expansion of the electrode assembly 100. When the electrode assembly 100 expands and tension is applied to the electrode tabs 120 of the unit cells 110, the ultra-long part 130 passing through the tightening part 310 moves toward the electrode assembly 100, so that the stress applied to the electrode tabs 120 is greatly relieved.

For reference, in the drawings, since the configuration of the wire connection part 300 and the ultra-long part 130 of the electrode tab 120 may be applied regardless of the positive and negative electrodes, the polarities of the electrode tab 120 and the electrode terminal 200 are not particularly distinguished.

According to a specific embodiment, the overlength portion 130 may form a U-turn 132 between the cinch portion 310 and the weld portion 320. The U-turn portion 132 has a gentle curve toward the tightening portion 310 of the wire connecting portion 300, thereby reducing resistance to the movement of the ultra-long portion 130.

Fig. 3 is a view showing a change in the electrode tab 120 supported by the wire part 300 when an expansion phenomenon occurs in the electrode assembly 100. As the thickness of the electrode assembly 100 expands (the thickness increases from d to d') as compared to fig. 2, when the unit cells 110 are further outward, the relative movement of the tightening part 310 away from the wire connection part 300 occurs more, but since the movement of the ultra-long part 130 is as much as the displacement of the electrode tab 120, the disconnection of the electrode tab 120 can be prevented.

When the movement of the electrode tap 120 accompanying the expansion is introduced into the sliding movement while supporting the middle portion of the electrode tap 120 by using the wire connection part 300 as in the illustrated embodiment, the electrode tap 120 can be precisely designed such that the electrode tap 120 moves in proportion to the expansion level. Accordingly, the ultra-long part 130 of the electrode tab 120 can effectively respond to the swelling phenomenon of the electrode assembly 100, and the position and movement of the ultra-long part 130 can be precisely controlled, thereby eliminating risks such as internal short circuits.

Meanwhile, according to an embodiment, a plurality of electrode assemblies 100 may be provided, and in this case, the electrode tabs 120 extending from each of the plurality of electrode assemblies 100 may form the tightening part 310 independently of the wire part 300.

Fig. 4 is a view showing a case where a plurality of electrode assemblies 100 are supported by a plurality of wire parts 300. In other words, a plurality of the wire parts 300 are provided corresponding to the number of the electrode assemblies 100, each of the electrode assemblies 100 is supported by the tightening part 310 of the wire part 300 corresponding thereto, and the welding part 320 of the corresponding wire part 300 is formed by the end of the ultra-long part 130 provided by the electrode tab 120 extending from each electrode assembly 100. That is, the embodiment of fig. 4 corresponds to a plurality of the embodiments of fig. 2 arranged in parallel.

Alternatively, as shown in fig. 5, a plurality of electrode assemblies 100 may be supported by one wire part 300. Referring to fig. 5, one wire part 300 includes a plurality of tightening parts 310 corresponding to the number of electrode assemblies 100, and each electrode assembly 100 is supported by a corresponding tightening part 310.

In addition, the end of the ultra-long part 130 provided by the electrode tab 120 extending from each electrode assembly 100 may form the welding part 320 thereof, but as shown, a plurality of the ultra-long parts 130 may form one welding part 320. In terms of process efficiency, it is advantageous to reduce the number of welds 320.

Here, the above-described fact that the ultra-long part 130 provided by the electrode tab 120 extending from each of the plurality of electrode assemblies 100 may form the U-turn part 132 between the tightening part 310 and the welding part 320 may be applied as it is.

Second embodiment

The second embodiment of the present invention further includes a structure for reducing resistance related to sliding of the ultra-long part 130 temporarily fixed to the tightening part 310 of the wire connecting part 300 when the ultra-long part 130 slides due to the swelling phenomenon. That is, the present embodiment is to prevent the electrode tab 120 from being accidentally disconnected due to strong resistance applied when the ultra-long part 130 is slidingly moved.

For this, in the second embodiment of the present invention, the friction reducing structure 330 is provided on the contact surface of the tightening part 310 of the wire part 300 supporting the electrode tab 120 of the electrode assembly 100. By providing the friction reducing structure 330 on the contact surface of the tightening part 310 pressing the electrode joint 120, the sliding of the ultra-long part 130 can be smoothly performed.

The friction reducing structure 330 provided in the tightening part 310 may be implemented in various forms. For example, as shown in fig. 6, the relief structure 332 may be used as the friction reducing structure 330 provided in the tightening part 310 of the wire connection part 300. The relief structure 332 shaped like a hemisphere reduces sliding resistance by reducing the contact area. In addition, various types of protrusion structures may be used as the friction reducing structure 330.

Alternatively, the low friction coating 334 shown in fig. 7 may be applied as the friction reducing structure 330. As the term implies, the low friction coating 334 refers to various coatings that reduce the surface coefficient of friction. For example, a chemically stable Teflon coating or a mechanically good diamond-like carbon (DLC) coating may be applied.

Third embodiment

Fig. 8 shows a third embodiment of the present invention, which includes a structure in which an insertion guide portion is provided in a wiring portion.

The electrode assembly 100 in which a plurality of unit cells 110 are stacked includes bundles of the electrode tabs 120 corresponding to the number of the unit cells 110, and the bundles of the electrode tabs 120 need to be aggregated into one and temporarily fixed to the tightening part 310 of the wire connection part 300. The tightening part 310 may have, for example, a slit structure in which the wire connection part 300 as shown in fig. 1 is thinly cut in the longitudinal direction.

When the thickness of the electrode assembly 100 increases due to the swelling phenomenon, the electrode tabs 120 of the unit cells 110 slidably move with respect to the tightening part 310, and in order to offset the same, it is necessary to smoothly insert the bundles of the electrode tabs 120 into the tightening part 310 without damaging the electrode tabs 120. For example, when the thickness of the electrode assembly 100 is increased to increase the capacity, the bundle of the electrode tabs 120 may become thicker accordingly, and bending, folding, tearing, etc. may occur when the bundle of the electrode tabs 120 is inserted into the tightening part 310.

The third embodiment is to prevent such a problem, and as shown in fig. 8, the wire connection part 300 includes an insertion guide part 312 for inserting the electrode tab 120 of each unit cell 110 into the tightening part 310.

For example, the insertion guide 312 may be provided in the form of a groove converging toward the tightening part 310. The groove converging toward the tightening part 310 means a groove whose width gradually decreases as it approaches the tightening part 310. Fig. 8 (a) shows a case in which the insertion guide portion 312 is formed as a wedge-shaped inclined surface, and fig. 8 (b) shows a case in which the insertion guide portion 312 is formed as a semicircle.

In addition to the exemplary illustrated form, any form of groove converging toward the cinching portion 310 is suitable for use as the insertion guide 312. By the convergent guiding action of the insertion guide 312, even the bundle of the electrode tabs 120 having a large thickness can smoothly enter the tightening part 310, thereby remarkably reducing the possibility of occurrence of problems such as bending, folding, or tearing of the electrode tabs 120 during insertion.

As described above, the present invention is described in more detail by the drawings and the embodiments. However, since the configuration described in the drawings or the embodiment described herein is only one embodiment of the present invention and does not represent the overall technical spirit of the present invention, it should be understood that the present invention covers various equivalents, modifications and substitutions at the time of filing the present application.

[ description of reference numerals ]

10: secondary battery 20: shell body

100: electrode assembly 110: unit cell

120: electrode tab 130: ultra-long part

132: u-turn 200: electrode terminal

300: wiring portion 310: tightening part

312: insertion guide 320: welded part

330: friction reducing structure 332: relief structure

334: low friction coating

Claims (14)

1. A secondary battery includes an electrode assembly in which a plurality of unit cells are stacked,

wherein the respective electrode tabs of the unit cells extending from the electrode assembly are gathered together and electrically connected to the electrode terminals of the secondary battery, and

the electrode tab of each unit cell includes an ultra-long portion corresponding to expansion of the electrode assembly.

2. The secondary battery according to claim 1, wherein the electrode tab of each unit cell extending from the electrode assembly is supported by a wire part electrically connected to the electrode terminal, and

the ultra-long portion is formed after the tightening portion of the wire connecting portion.

3. The secondary battery according to claim 2, wherein an end of the ultra-long portion forms a welded portion joined to the wire connection portion.

4. The secondary battery according to claim 3, wherein the ultra-long portion forms a U-turn portion between the tightening portion and the welding portion.

5. The secondary battery according to claim 3, wherein the electrode assembly is provided in plurality, and

an electrode tab extending from each of the plurality of electrode assemblies forms the tightening portion independently of the wire connecting portion.

6. The secondary battery according to claim 5, wherein the wire connection parts are provided in a plurality corresponding to the number of the electrode assemblies,

each of the electrode assemblies is supported by the tightening part of the corresponding wiring part, and

the welded portion is formed by an end portion of the ultra-long portion provided by the electrode tab extending from each of the electrode assemblies with respect to a corresponding wire connection portion.

7. The secondary battery according to claim 5, wherein the wire connection part includes a plurality of tightening parts corresponding to the number of the electrode assemblies, and

each of the electrode assemblies is supported by a respective tightening portion.

8. The secondary battery according to claim 7, wherein an end portion of the ultra-long portion provided by the electrode tab extending from each of the electrode assemblies forms one welded portion with respect to the wire connection portion.

9. The secondary battery according to claim 5, wherein the ultra-long portion provided by the electrode tab extending from each of the plurality of electrode assemblies forms a U-turn portion between the tightening portion and the welding portion.

10. The secondary battery according to claim 2, wherein the wire connection part includes a friction reducing structure on a contact surface of the tightening part supporting the electrode tab of the electrode assembly.

11. The secondary battery according to claim 10, wherein the friction reducing structure is a relief structure formed on a contact surface of the tightening part.

12. The secondary battery according to claim 10, wherein the friction reducing structure is a low friction coating layer formed on a contact surface of the tightening part.

13. The secondary battery according to claim 2, wherein the wire connection part includes an insertion guide part configured to assist the insertion of the electrode tab of each unit cell into the tightening part.

14. The secondary battery according to claim 13, wherein the insertion guide portion is a groove provided in a form converging toward the tightening portion.