KR101889593B1 - Electrode Assembly Including Safety Member and Lithium Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention relates to an electrode assembly comprising a plurality of unit cells and a separation film for continuously winding up the unit cells, wherein at least one outermost electrode of the outermost electrodes And at least one safety member made of an electrically conductive metal foil, which is electrically insulated from the outermost electrode, is added to the electrode assembly, and a secondary battery including the electrode assembly.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrode assembly including a safety member and a secondary battery including the electrode assembly.

The present invention relates to an electrode assembly including a safety member and a secondary battery including the electrode assembly.

As technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries as energy sources. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operational potential, long cycle life, Batteries have been commercialized and widely used.

However, since such a lithium secondary battery has a problem in safety, attempts have been made to solve it.

Specifically, when the lithium secondary battery is overcharged, excess lithium comes out from the anode and excess lithium is inserted into the cathode, so that lithium metal having a very high reactivity is deposited on the surface of the cathode, and the anode also becomes thermally unstable. The explosion reaction of the battery causes a sudden exothermic reaction, resulting in safety problems such as ignition and explosion of the battery.

Also, when a needle having electrical conductivity passes through a cell such as a nail, the electrochemical energy inside the cell is converted into thermal energy, and rapid heat generation occurs. As a result, the anode or the cathode material undergoes a chemical reaction, Causing a safety problem such as ignition or explosion of the battery.

In case of needle penetration, squeezing, shock, etc., the anode and the cathode inside the battery are internally short-circuited. At this time, an excessive current flows locally and a heat is generated by this current. Since the magnitude of the short-circuit current due to the local short circuit is inversely proportional to the resistance, the short-circuit current flows through the metal foil, which is mainly used as a current collector. A very high heat is locally generated around the portion.

If a heat is generated in the battery, the separator shrinks and short-circuits the positive and negative electrodes again, and repeated heat generation and shrinkage of the separator shrinks the short-circuit section, resulting in thermal runaway, And the electrolytic solution react with each other or burn, which is a very large exothermic reaction, which eventually causes the battery to ignite or explode. This risk is particularly important as the energy density increases as the capacity of the lithium secondary battery increases.

In order to solve this problem and improve the safety of the battery, Korean Patent Laid-Open No. 10-2011-0024114 attempts to solve this problem by using a separator having a high elongation. However, this method has a problem that the process cost is increased, for example, a better material must be used in order to further increase the elongation of the separator.

Therefore, there is a high need for a secondary battery technology that can improve the safety of a battery effectively without using a better material or requiring additional processes.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and, as described later, in an electrode assembly comprising a plurality of unit cells and a separation film for continuously winding up the unit cells, It is confirmed that a desired effect can be achieved when at least one safety member made of an electrically conductive metal foil is provided on the outer surface of at least one of the outermost electrodes of the outermost electrodes with respect to the direction, I have come to completion.

Accordingly, an electrode assembly according to the present invention includes an electrode assembly including a plurality of unit cells and a separation film for continuously winding the unit cells,

At least one safety member made of an electrically conductive metal foil, which is electrically insulated from the outermost electrode, is provided on the outer surface of at least one of the outermost electrodes of the outermost electrodes based on the stacking direction of the electrode assembly .

Since the safety member is attached to the outermost periphery, the strength of the outer surface of the electrode assembly can be improved. As a result, it is possible to protect the electrode assembly from a physical impact due to an external force, When a physical force such as needle-piercing, pressing, impact or the like is applied, the safety member having a low resistance due to the absence of the electrode active material and having a relatively low caloric value due to short-circuit is preferentially contacted, Short circuit is induced to protect the inside of the battery, to absorb the short circuit heat, and when the battery is penetrated through the needle, the safety member is energized with the internal electrode by the syringe, so that the safety of the battery can be further improved.

Further, since the safety member is additionally provided on the outer surface of the outermost electrode during the manufacture of the unit cell, no separate process is required. The electrode assembly of the present invention has a structure in which a plurality of unit cells are wound into a separation film, Since the safety member can be appropriately fixed to the outer surface of the outermost electrode by the separation film and the movement due to the movement and impact of the battery is small, Can be further improved.

As described above, according to the present invention, the short-circuit heat is absorbed during the internal short-circuit, and the safety member is electrically connected to the internal electrode by the needle-like member when passing through the needle- It is preferable that the metal foil constituting the safety member is made of a metal having a high resistance and a good electrical conductivity. In detail, the metal foil is made of any one metal selected from the group consisting of Cu, Al, Ni, Fe, and Pb And more specifically, it may be made of Al or Cu, which is a material generally used as a current collector for an anode and a cathode. Of course, when another metal is used for the current collector, it is preferable to use a safety member made of the same metal as the metal.

On the other hand, in one specific example, it may be added only to the outermost electrode of one of the outermost electrodes, or may be added to the outer surface of both outermost electrodes, and a safety member may be attached to the outer surface of each outermost electrode Or more.

However, when one or more safety members are added only to the outermost electrodes of one of the outermost electrodes, if a physical force such as needle penetration, compression, shock, or the like is applied on the opposite side, There is a problem that the safety of the battery can not be sufficiently secured, and it is more preferable that the safety members are attached to the outermost electrodes on both sides.

Also, since the overall thickness of the electrode assembly increases according to the number of the safety member, the total volume of the secondary battery including the secondary battery must be increased to obtain the same capacity. In view of the capacity and volume of the electrode assembly, It is more preferable that one safety member is added to each of the outer surfaces of the outer electrodes.

In one example, when only one safety material is added to the outer surface of the outermost electrode, the safety member is not limited, and may be formed of a metal foil having the same polarity or the opposite polarity as the outermost electrode. For example, the outermost electrodes may each be an anode or a cathode, and a safety member added thereto may be one selected from the metal material.

In another example, when two or more safety members are added to the outer surface of the outermost electrode, the outer surface of the outermost electrode may be provided with n (n) pieces from the first safety member facing the outermost electrode to the nth safety member on the outer surface, May be stacked in a state of being electrically insulated from each other. At this time, the confronting safety members may be made of the same metal or may be made of different metals. For example, when two safety members are provided, the first safety member facing the outermost electrode may be one selected from the metal material, and the second safety member facing the first safety member may be a first safety member, Or a metal material other than the metal material.

Here, the electrical insulation of the mutually facing safety members can be achieved by adding an insulator between the safety members. Of course, as described above, the outermost electrode and the safety member facing the outermost electrode are also electrically insulated from each other, and the insulator can also be formed.

The insulator may be a porous separator, a non-porous insulation film, or an insulating adhesive, which has insulation and is formed in the form of a thin film. The material constituting the insulator is not particularly limited as long as it is an insulating material, and may be, for example, a general-purpose resin such as a polyethylene resin, a polypropylene resin, or a polymer resin excellent in heat resistance.

It is preferable that the insulator is configured to be somewhat larger than the size of the outermost electrodes or safety members facing each other.

However, the size of the safety member is preferably smaller than the plane size of the outermost electrode. More specifically, it is preferable that the size of the safety member is smaller than that of the outermost electrode, To 50% to 99% of the planar size of the outermost electrode, and more specifically, 50% to 90% of the planar size of the outermost electrode.

If the size of the safety member is equal to or larger than the plane size of the outermost electrode, the overall size of the electrode assembly is increased by the safety member, and when the safety member is wound out by the edge of the safety member made of metal foil The separation film may be damaged, and continuous damage may be caused thereby adversely affecting the safety of the battery. It is preferable that the safety member is smaller than the size of the electrode.

The thickness of the safety member may be determined in consideration of impact resistance and the like. Specifically, the safety member itself may have a predetermined strength to protect the electrode assembly from 5 micrometers to 100 micrometers, May be between 5 micrometers and 50 micrometers.

Meanwhile, the at least one safety member may be electrically connected to the positive electrode terminal or the negative electrode terminal of the electrode assembly from the beginning. In this case, when an external force is applied, short-circuiting occurs outside and the entire electrode assembly is energized, so that energization can be achieved more effectively.

Other components of the electrode assembly according to the present invention will be described below.

In one specific example, the unit cells are monocells each having one electrode, a bi-cell having a structure in which electrodes of the same polarity are located at both ends of the unit cell, or electrodes of different polarity are located at both ends of the unit cell It can be a full cell of structure.

Specifically, a mono cell as a unit cell is a positive electrode or a negative electrode, and a pull cell is a cell having a unit structure of a positive electrode / separator / negative electrode, and a positive electrode and a negative electrode are positioned on both sides of the cell. Such a pull cell may include a cathode / separator / cathode cell and an anode / separator / cathode / separator / anode / separator / cathode cell having the most basic structure. Among them, a schematic diagram of a pull cell having a positive electrode / separator / negative electrode structure is shown in FIG. Also, the bi-cell as a unit cell may have a structure such as a unit structure (A-type bi-cell) of a cathode / separator / cathode / separator / anode and a unit structure (C-type bi-cell) of a cathode / separator / anode / In which the same electrode is located. A schematic diagram of a bipolar cell having a cathode / separator / cathode / separator / cathode structure is shown in FIG. 2, and a schematic diagram of a bipolar cell having a cathode / separator / anode / separator / cathode structure is shown in FIG.

2 and 3 illustrate one example and, in some cases, more bipolar cells of the stack number are possible, such as anode / separator / cathode / separator / anode / separator / cathode / separator / anode structure Cathode, separator, anode, separator, cathode, separator, anode, separator, and bipolar cell structure.

The electrode assembly according to the present invention may include such a mono cell, a bi-cell, and a pull cell, and may include only one type or a combination thereof. That is, if the positive electrode and the negative electrode alternate in the stacking direction, any type of unit cell can be used singly or in combination.

In addition, the electrodes at the outermost portions of the electrode assemblies manufactured using such unit cells may be the same electrode or different electrodes.

The present invention also provides a lithium secondary battery in which the electrode assembly is embedded in a battery case together with a non-aqueous electrolyte.

Here, the battery case is a pouch-shaped battery case made of a laminate sheet including an outer coating layer made of a weatherproof polymer, an inner sealant layer made of a heat-sealable polymer, and a barrier layer interposed between the outer coating layer and the inner sealant layer Specifically, a pouch-shaped battery case made of an aluminum laminate sheet having a barrier layer of Al.

The anode, the cathode, the separator, and the non-aqueous electrolyte, which are the basic constituent elements of other unit cells, are well known in the art, and a description thereof will be omitted herein.

The present invention also provides a battery pack including the battery module including the lithium secondary battery as a unit cell and the battery module, and provides the device including the battery pack.

Specific examples of such devices include small devices such as a computer, a mobile phone, a wearable electronic device, and a power tool, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug- An electric vehicle including a plug-in hybrid electric vehicle (PHEV); An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; Power storage systems, and the like, but are not limited thereto.

As described above, the electrode assembly including a plurality of unit cells according to the present invention and a separation film for continuously winding up the unit cells may include at least one of the outermost electrodes based on the stacking direction of the electrode assembly, And at least one safety member made of an electrically conductive metal foil is provided on the outer surface of the outermost electrode of the outermost electrode so that the safety member is brought into contact first in a short circuit and the active material is not applied, It absorbs heat, so that the safety of the battery can be improved.

In addition, the above process can be carried out simultaneously in the electrode stacking process, and the safety of the battery can be effectively improved without any additional process.

1 is a schematic view showing a pull cell as one form of a unit cell of the present invention;
2 is a schematic diagram showing an A-type bi-cell as one type of unit cell of the present invention;
3 is a schematic view showing a C-type bicycle as one type of unit cell of the present invention;
4 is a schematic diagram of an electrode assembly according to one embodiment of the present invention;
5 is a schematic view of an outermost electrode to which the safety member of FIG. 4 is attached;
6 is a schematic diagram of an electrode assembly according to another embodiment of the present invention;
7 is a schematic diagram of an electrode assembly according to another embodiment of the present invention;
8 is a schematic view of one of the outermost electrodes to which the safety member of Fig. 7 is added;
9 is a schematic view of an electrode assembly according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIGS. 4, 6, 7, and 9 are schematic diagrams of electrode assemblies according to embodiments of the present invention. 4, 6, 7 and 9 schematically show an electrode assembly having a structure in which five unit cells are stacked. However, the number of unit cells is not limited to this, But they are not limited thereto, and both outermost electrodes may be both positive electrodes or may be different electrodes.

4, 6, 7, and 9 use only the bi-cells shown in Figs. 2 and 3 as unit cells. However, only the pull cells of Fig. 1 are used, or they are combined, It is a matter of course that the present invention can be used as a mono cell including only a mono cell.

4, the electrode assembly 100 includes a plurality of bi-cells 111, 112, and 113 having a separator interposed between an anode and a cathode, 114, and 115 are wound by a separating film 120. [0064]

Specifically, the electrode assembly 100 includes five bi-cells 111, 112, 113, 114, and 115, and the electrode assembly 100 is formed such that the separation film 120 is separated from the first bi- 111 and the second bi-cell 112 and the third bi-cell 113 are disposed on the upper and lower sides of the first bi-cell 111, the outer surfaces of the first and second bi- And the fourth and sixth biscelles 114 and 115 are positioned on the lower portion of the second bicell 112 and the upper portion of the third bicell 113, And is wrapped around the film 120 once.

On the outer surface of the outermost electrode 117 of the fifth bi-cell 115 among the outermost electrodes 116 and 117 of the fourth and sixth bi-cells 114 and 115, The insulator 140 is provided in a state in which the safety member 130 is electrically insulated from the outermost electrode 117. FIG. 5 shows an enlarged view of a fifth bi-cell 115 in which the safety member 130 is attached to the outermost electrode 117 in an insulated state by an insulator.

6, five bi-cells 211, 212, 213, 214 and 215 are wound by a separation film 220 in the same manner as the electrode assembly 100 of FIG. 4 have.

Compared with the electrode assembly 100 of FIG. 4, the electrode assembly 200 of FIG. 6 includes safety members (not shown) formed of an electrically conductive metal foil on the outer surfaces of the outermost electrodes 216, 230, and 250 are electrically insulated from the outermost electrodes 216 and 217 by the insulators 240 and 260, respectively.

When the safety members 230 and 250 are added to the outermost electrodes 216 and 217, respectively, as shown in FIG. 6, only the outermost electrodes of the outermost electrodes, as shown in FIG. 4, As compared with the case where an external force is applied in any direction, short-circuit current can be easily conducted, thereby ensuring safety of the battery.

As another example, an electrode assembly 300 having two or more safety members added to the outermost electrode is shown in Fig.

The electrode assembly 300 of FIG. 7 also includes five bi-cells 311, 312, 313, 314 and 315 and the bi-cells 311, 312, 313, 314, And is wound by a coil spring (not shown).

As described above, the electrode assembly 300 shown in FIG. 7 is different from the electrode assembly 100 shown in FIG. 4 in that the outer surface of the outermost electrode 317 of the fifth bi-cell 315 has two or more safety members And the outermost electrodes 317 and the safety members 330 and 331 are electrically insulated from each other by an insulator 340. [ 8 shows an enlarged view of a fifth bi-cell 315 to which more than two safety members 330 and 331 are attached to the outermost electrode 317. FIG.

The safety member 331 stacked to face the safety member 330 may be made of the same material as the safety member 330 facing the outermost electrode 317 or a different material.

9, five bipolar cells 411, 412, 413, 414 and 415 are wound by a separation film 420 in the same manner as the electrode assembly 200 of FIG. 6 have.

The electrode assembly 400 of FIG. 9 has two or more safety members 330 and 331 on the outer surface of the outermost electrode 417 of the fifth bi-cell 415 as compared with the electrode assembly 300 of FIG. One safety member 450 is attached to the outer surface of the outermost electrode 416 of the fourth bi-cell 414 in a state in which the insulator 460 is electrically insulated from each other by the insulators 440, And is electrically insulated from the outermost electrode 416 by the insulating layer 416. [ In this way, when the safety members are added to the outer surfaces of the outermost electrodes, the number of safety members added to each surface may be different.

Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

≪ Example 1 >

As shown in FIG. 6, a safety member composed of an aluminum foil was added to the outermost unit cell so that the safety member was positioned on the outer surface of the outermost electrodes with respect to the stacking direction, a separator film was wound thereon to manufacture an electrode assembly, The battery was mounted on a case, and then an electrolyte solution was injected and the battery case was sealed.

≪ Example 2 >

As shown in FIG. 4, a battery was manufactured in the same manner as in Example 1, except that the electrode assembly was manufactured by adding the safety member to only the outer surface of the outermost one electrode.

≪ Comparative Example 1 &

A battery was prepared in the same manner as in Example 1, except that the safety member was not used.

<Experimental Example 1>

Impact tests and penetration tests of the sludge bodies were conducted on the batteries manufactured in Examples 1 and 2 and Comparative Example 1, respectively, and the results are shown in Tables 1 and 2 below. In this experiment, 20 cells were repeatedly performed. At the height of 60 cm of the impact test, a force of 9.1 kgf was applied to the center of the cell, and the cell was freely dropped in the direction of bumping against the center of the cell. The experiment was carried out under conditions of a diameter of 2.5 mm and a speed of 12 m / min.

Number of impact ignition batteries
(Safety-absent direction /
Safety-free direction) Number of ignition cells when passing through bed
(Safety-absent direction /
Safety-free direction) Example 1 0/- 0/- Example 2 0/5 0/4

Number of impact ignition batteries Number of ignition cells when passing through bed Comparative Example 1 12 15

As shown in Tables 1 and 2, the batteries of Example 1 according to the present invention did not cause ignition in all 20 batteries in the impact test and the needle penetration test. In other words, since the safety member is located on the outer surface of both outermost electrodes, the safety member first contacts and short-circuiting in spite of a large impact or needle penetration, thereby energizing and suppressing the temperature rise of the battery. It has not happened.

On the other hand, in the battery of Example 2, the safety member was added to only one side, and no ignition was caused in the test in the direction in which the safety member was present, but the ignition was somewhat confirmed in the test in which the safety member was not attached. Nevertheless, since the safety member itself enhances the strength and absorbs short-circuit heat when a short circuit is caused, it is possible to confirm that the possibility of ignition is greatly reduced as compared with the battery of Comparative Example 1 in which the safety member is not added have.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (19)

An electrode assembly comprising a plurality of unit cells and a separation film for continuously winding up the unit cells,
At least one safety member made of an electrically conductive metal foil, which is electrically insulated from the outermost electrode, is provided on the outer surface of at least one of the outermost electrodes of the outermost electrodes based on the stacking direction of the electrode assembly The electrode assembly comprising:
The safety member facing the outermost electrode is electrically insulated from the outermost electrode by an insulator interposed between the outermost electrode and the safety member,
The unit cells are a full cell having a structure in which a mono cell composed of one electrode, a bi-cell having a structure in which electrodes of the same polarity are located at both ends of the unit cell,
And the safety member is electrically connected to the internal electrode by the needle-shaped member when the needle-shaped member is passed through the needle-shaped member. The electrode assembly according to claim 1, wherein the metal foil is made of any one selected from the group consisting of Cu, Al, Ni, Fe, and Pb. The electrode assembly of claim 1, wherein the metal foil is made of Cu or Al. The electrode assembly of claim 1, wherein the outermost electrodes are each an anode or a cathode. [2] The apparatus of claim 1, wherein n outermost electrodes (n is an integer greater than or equal to 2) from the first safety member facing the outermost electrode to the nth safety member on the outer surface are electrically insulated from each other And the electrode assembly is laminated. 6. The electrode assembly of claim 5, wherein the facing members are made of different metals. 6. The electrode assembly of claim 5, wherein an insulator is added between the facing members. delete The electrode assembly according to claim 7, wherein the insulator is a porous separator, an insulating adhesive, or a non-porous insulating film. The electrode assembly according to claim 1, wherein the size of the safety member is 50 to 99% of the size of the outermost electrode. 11. The electrode assembly of claim 10, wherein the size of the safety member is 50 to 90% of the size of the outermost electrode. The electrode assembly of claim 1, wherein the thickness of the safety member is between 5 micrometers and 100 micrometers. delete delete The lithium secondary battery according to claim 1, wherein the electrode assembly is embedded in the battery case together with the nonaqueous electrolyte solution. A battery module comprising the lithium secondary battery according to claim 15 as a unit cell. A battery pack comprising the battery module according to claim 16. A device comprising a battery pack according to claim 17. 19. The device of claim 18, wherein the device is a computer, a mobile phone, a wearable electronic device, a power tool, an electric vehicle (EV), a hybrid electric vehicle, a plug- , Or a system for power storage.

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