KR20130138371A - Electrode assembly having noble structure and electrochemical cell containing the same - Google Patents

Abstract

The present invention relates to an electrode assembly, which is a stack type or stack/folding type electrode assembly having an anode/separator/cathode structure. The electrode assembly is constituted with electrode plates each of which has protruding electrode taps to which an active material is not applied, wherein the electrode taps are combined to one electrode lead to form an electrode lead-electrode tap joint portion, the electrode lead has an end bifurcated into two or more units, and ends of electrode taps are distributed and combined to each bifurcated unit of the end of the electrode lead.

Description

Electrode Assembly Having Noble Structure and Electrochemical Cell Containing the Same}

The present invention relates to an electrode assembly having a novel structure, and more particularly, to a stack type or a stack type / foldable type electrode assembly having an anode / separation membrane / cathode structure, wherein each electrode plate constituting the electrode assembly is not coated with an active material. The electrode tabs protrude, and the electrode tabs are joined to one electrode lead to form an electrode lead-electrode tab coupling portion, the electrode leads being branched in two or more units, and the ends of the electrode tabs The present invention relates to an electrode assembly that is coupled to each other in a state in which the electrode leads are dispersed in branched end units.

As technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries capable of meeting various demands have been conducted.

Representatively, there is a high demand for rectangular secondary batteries and pouch secondary batteries, which can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and lithium ion batteries with high energy density, discharge voltage, and output stability in terms of materials. There is a high demand for lithium secondary batteries such as lithium ion polymer batteries.

In addition, secondary batteries are classified according to the structure of the electrode assembly having a cathode / separation membrane / cathode structure. Representatively, a jelly having a structure in which long sheet-shaped anodes and cathodes are wound with a separator interposed therebetween -Roll (electrode) electrode assembly, a stack (stacked type) electrode assembly in which a plurality of positive and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator, and the positive and negative electrodes of a predetermined unit are interposed through a separator And a stacked / folding electrode assembly having a structure in which a bi-cell or full cells stacked in a state are wound.

FIG. 1 is a schematic side view of a general structure of a conventional representative stacked electrode assembly.

Referring to FIG. 1, the stacked electrode assembly 10 may include a negative electrode active material 32 on both sides of the positive electrode 20 and the negative electrode current collector 31 having the positive electrode active material 22 coated on both sides of the positive electrode current collector 21. ) Is applied to the cathode 30 is laminated in a state in which the separator 70 is interposed sequentially.

At one end of the positive electrode current collector 21 and the negative electrode current collector 31, an active material is coated to be electrically connected to the positive electrode lead 60 and the negative electrode lead (not shown) constituting the electrode terminals of the battery, respectively. A plurality of positive electrode tabs 41 and negative electrode tabs 51 which are not present protrude. At this time, the positive electrode tabs 41 and the negative electrode tabs 51 are coupled in a dense form and connected to the positive electrode lead 60 and the negative electrode lead, respectively. Such a structure can be more easily confirmed in FIGS. 2 and 3, in which the coupling portion of the positive electrode tabs and the positive lead is schematically illustrated as a partial enlarged view. 2 and 3 illustrate only the coupling structure of the positive electrode tabs and the positive lead for convenience of description, the same applies to the coupling portion of the negative electrode tabs and the negative electrode lead.

Referring to these figures, the positive electrode tabs 40 are closely attached in the direction of the arrow and are connected to the positive electrode lead 60. The anode lead 60 is generally joined by welding, which is located on the upper side of the uppermost positive electrode tab 41 as shown in FIG. 2 or on the lower side of the lowermost positive electrode tab 42 as shown in FIG. Can be combined in a state.

However, due to this structure, the electrode assembly has a problem that the bonding force of the electrode tabs to the electrode lead is reduced. That is, in the electrode assembly, since welding for coupling the electrode leads and the electrode tabs is performed only in one direction, the electrode leads and the electrode tabs are easily separated when an external force is applied.

In this regard, FIG. 4 is a vertical cross-sectional view schematically showing a process of manufacturing a conventional electrode lead-electrode tab coupling portion.

Referring to FIG. 4, the electrode tabs 512 of the electrode assembly 510 are positioned above the electrode lead 530 and move the welding tool 500 downward from the top to the electrode lead 530 and the electrode tabs 512. ), An electrode lead-electrode tab coupling portion (A) is formed.

However, in this manufacturing process, since a plurality of electrode tabs 512 are positioned on one electrode lead 530 and then welded using the welding tool 500, the coupling force between the electrode lead 530 and the electrode tabs 512 is increased. Low and this causes a problem that the electrode lead 530 and the electrode tabs 512 are easily separated when the external force is applied.

In addition, the number of such electrode tabs varies depending on the type of battery cell, but in general, dozens of one battery cells are used, which causes many problems in terms of weldability at the joint of the electrode lead and the electrode tabs.

Furthermore, the electrode assembly 510 manufactured by the above-described manufacturing process causes deformation of the electrode lead 530 at the coupling portion A of the electrode tab-electrode lead when moved by an external force, thereby causing the electrode assembly ( There is a drawback that the possibility of shorting of the electrode lead 530 with respect to 510 is very high.

In order to solve this problem, an electrode assembly having a structure in which the ends of the electrode leads are branched so that the electrode leads can be coupled to the structure surrounding the upper and lower surfaces of the electrode tab stack in which the electrode tabs are stacked is studied. There is a bar.

However, the electrode assembly of the above structure has a structure in which the electrode leads surround the upper and lower surfaces of the electrode tab stack at the same time, so that the contact area between the electrode leads and the electrode tabs is small when the electrode leads and the electrode tabs are joined by welding. The resistance increases, the welding heat is not evenly transmitted to the center portion of the electrode tab stack, and even after manufacturing, the electrode tabs constituting the electrode tab stack are easily separated by external force.

Therefore, the bonding force between the electrode leads and the electrode tabs is improved, and at the same time, the internal short-circuit is prevented at the electrode lead-electrode tab coupling portion, and the bonding force between the electrode leads and the electrode tabs is improved, thereby preventing the electrode tabs from being separated by external force even after manufacture. There is a great need for technology that can be done.

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

An object of the present invention is to increase the output area of the battery cell expressed through the electrode lead by increasing the contact area between the electrode tab and the electrode lead, and at the same time to improve the binding force of the electrode tab-electrode lead when the electrode tab and the electrode lead is coupled. It is to provide an electrode assembly that can be.

In addition, another object of the present invention is to provide an electrode assembly which can secure excellent reliability by improving the bonding force of the electrode tab-electrode lead.

Still another object of the present invention is to provide an electrode assembly capable of preventing an internal short circuit by inhibiting deformation of the electrode lead at the coupling portion of the electrode tab-electrode lead.

An electrode assembly according to the present invention for achieving the above object, as a stack or stack / folding type electrode assembly of the anode / separator / cathode structure,

Each electrode plate constituting the electrode assembly protrudes an electrode tab to which no active material is applied.

These electrode tabs are joined to one electrode lead to form an electrode lead-electrode tab coupling portion,

The electrode leads are branched into two or more units, and the ends of the electrode tabs are configured to be coupled to each other in a state in which they are dispersed in the branched end units of the electrode lead.

Accordingly, the electrode assembly according to the present invention has a structure in which the ends of the electrode leads are branched into two or more units, and the ends of the electrode tabs are mutually coupled in a state in which they are dispersed in the branched end units of the electrode lead. Therefore, the bonding force of the electrode lead-electrode tab coupling portion can be greatly increased.

Specifically, since the ends of the electrode leads are branched into two or more units, the electrode tabs are positioned at the ends of the electrode branches, which are divided into several branches, and then the electrode leads and the electrode tabs are joined to each other so that the electrode leads are connected with each other. After placing the electrode tabs on the ends, a contact area of 2 to 3 times may be improved compared to a structure in which the electrode leads and the electrode tabs are coupled to each other.

Therefore, the resistance of the electrode lead-electrode tab coupling portion according to the present invention increases the contact area between the electrode lead and the electrode tab according to the principle that the resistance is inversely proportional to the area, so that the output performance of the battery cell expressed through the electrode lead is decreased. Increased effects can be achieved.

The stacked electrode assembly has a structure in which two or more positive electrodes and two or more negative electrodes are stacked with a separator interposed therebetween, and two or more electrode tabs protruding from the positive and negative electrode current collectors are coupled to one electrode lead. It may be made of.

In addition, the stack / foldable electrode assembly includes two or more stacked unit cells wound by one sheet separator film, and two or more electrode tabs protruding from the positive and negative electrode current collectors are coupled to one electrode lead. It may be a structure.

In the stack type electrode assembly and the stack / fold type electrode assembly, the stacked unit cell may be a bicell or a full cell in which positive and negative electrodes of a predetermined unit are stacked with a separator therebetween.

In one preferred embodiment, the end of the electrode lead may be a structure that is divided into three or more units.

Specifically, when the end of the electrode lead is less than three, it is not preferable because the weldability of the electrode lead and the electrode tab may be deteriorated and the bonding force of the electrode lead-electrode tab coupling portion may be weakened.

As one example of the above structure, more preferably, the end portion of the electrode lead may be a branch of 3 to 10 units.

Specifically, when the end of the electrode lead is less than three, there is a problem that the bonding force of the electrode lead-electrode tab coupling portion is weakened as mentioned above, and when the end of the electrode lead is more than 10, the manufacturability of the electrode lead This is not preferable because of the problem of deterioration.

As another example of the structure, the end of the electrode lead is divided into three units, consisting of a first end bent upward, a second end formed in a structure parallel to the electrode tabs, and a third end bent downward. Can be.

As a specific example, in the above structure, the electrode tabs are welded to each other in a state where they are respectively positioned above the first end, between the first end and the second end, and above the third end of the electrode lead, so that the electrodes are in terms of the principle of resistance welding. Welding of the lead-electrode tab coupling can be achieved uniformly.

In another preferred example, the ends of the electrode tabs may have a structure that is distributed in the same number in the branched end units of the electrode lead.

Such a structure is highly desirable because it can make the weldability of the electrode lead and the electrode tab uniform as mentioned above.

In some cases, the branched end of the electrode lead may have a symmetrical structure or an asymmetrical structure in a vertical cross section.

Specifically, the branched end of the electrode lead may have a vertically symmetrical structure with respect to the electrode tab located in the center of the electrode tabs on the vertical cross section, and may be asymmetrical by being deflected from one surface selected from the electrode tabs.

The asymmetrical structure may be formed, for example, as the length or form of the end, and more specifically, may be formed as a structure in which the length of the end is extended on one surface selected from the tabs. At this time, the branched end of the electrode lead, it is preferable to form a symmetrical structure to further improve the bonding force of the electrode lead to the electrode tabs.

In another example, the electrode lead may be manufactured by joining the remaining portions except the branched end portions in a state in which the three lead members are in close contact with each other.

Specifically, the electrode lead may be manufactured in a structure in which the remaining portions other than the branched end portions are joined while three lead members having the same size are in close contact with each other.

As one example of the structure, the three lead members may include a first lead member having an end bent downward, a second lead member having an end portion parallel to the electrode tabs, and a third lead having an end bent upwardly It may be made of a member.

As another preferred example, the electrode lead leads one end of the lead members b in a state where the lead members b of a relatively small length are brought into close contact with the lead member a of a relatively long length. It can be manufactured in a structure to bond on the member (a). At this time, one end of the lead member (b) is an end opposite to the branched end of the electrode lead, as described above, the lead member (b) is V-shaped or U in the vertical section with respect to the lead member (a) In order to achieve the shape of-, it is preferable to be coupled at approximately the center of the lead member a.

In one preferred embodiment, the electrode lead-electrode tab coupling portion may be manufactured by grouping the electrode tabs and placing them on top of the branched ends of the electrode leads, followed by welding.

Therefore, the electrode lead-electrode tab coupling portion can be more stably coupled by welding, and such welding can be performed, for example, by ultrasonic welding, laser welding, resistance welding, or the like.

In the present invention, the electrode lead is not particularly limited as long as it is made of a material capable of electrically connecting the electrode tabs, and preferably may be a metal plate. Examples of such a metal plate include, but are not limited to, an aluminum plate, a copper plate, a nickel plate, a nickel-coated copper plate, and an SUS plate.

The present invention also provides an electrochemical cell composed of such an electrode assembly.

The electrochemical cell may be manufactured as a small electrochemical cell by combining three or four as a unit cell, and may be manufactured as a medium-large electrochemical cell by combining a plurality as a unit cell. In this case, the small electrochemical cell preferably includes an electrode lead having a thickness of 0.1 mm or less, and the medium and large electrochemical cell preferably includes an electrode lead having a thickness of 0.1 to 0.5 mm.

The electrochemical cell provides electricity through an electrochemical reaction, and may be, for example, an electrochemical secondary battery or an electrochemical capacitor, and may be preferably applied in a lithium secondary battery.

Such a lithium secondary battery may be a lithium ion secondary battery or a lithium ion polymer secondary battery.

The secondary battery is a secondary battery in which an electrode assembly capable of charging and discharging is embedded, and preferably, may be a structure in which the electrode assembly is sealed in a battery case of a laminate sheet including a metal layer and a resin layer. A secondary battery having such a structure may also be referred to as a pouch type secondary battery.

The present invention also provides a battery pack containing a plurality of the electrochemical cells in a pack case.

The present invention also provides a device including the battery pack as a power source.

The device may be selected from mobile phones, portable computers, smartphones, smart pads, netbooks, LEVs (Light Electronic Vehicles), electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage devices, in particular, high power It can be a large-capacity electric vehicle, a power storage device.

Specifically, the secondary battery may be suitably used as a unit cell when manufacturing a high output large capacity battery pack by combining a plurality of battery cells. In particular, the battery cells used in the high output large capacity battery pack is very large compared to the battery cells of the small battery pack, the relatively large impact due to the large weight of the electrode assembly itself when the external force is applied Can be applied. Therefore, the structure of the electrode assembly having excellent stability of the electrode lead-electrode tab coupling portion as in the present invention may be more preferably applied to the battery cells constituting the medium-large battery pack.

As described above, in the electrode assembly according to the present invention, since the electrode lead-electrode tab coupling portion has a structure in which the contact area between the electrode lead and the electrode tab is increased, the resistance decreases and the battery cell is expressed through the electrode lead. Can greatly increase the output performance.

In addition, the electrode assembly according to the present invention can secure excellent reliability by improving the bonding force of the electrode lead-electrode tab coupling portion, and can prevent deformation of the electrode lead in the electrode lead-electrode tab coupling portion to prevent internal short circuit. It has an effect.

1 is a schematic diagram of a general structure of a conventional stacked electrode assembly;
2 and 3 are enlarged views of portions of the electrode assembly of FIG. 1 in which the positive electrode tabs are coupled in a dense form and connected to the positive electrode lead;
4 is a vertical cross-sectional view showing a process of manufacturing a conventional electrode lead-electrode tab coupling portion;
5 is a vertical cross-sectional view illustrating a process of manufacturing an electrode lead-electrode tab coupling portion according to an embodiment of the present invention;
6 to 8 are enlarged views of an electrode lead-electrode tab coupling part in which an anode tab is coupled in a dense form and connected to an anode lead in 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.

5 is a vertical cross-sectional view schematically showing a process of manufacturing the electrode lead-electrode tab coupling portion according to an embodiment of the present invention.

Referring to FIG. 5, the electrode assembly 510a may protrude electrode tabs 512, 514, and 516 that are not coated with an active material on each electrode plate constituting the electrode assembly 510a. 514 and 516 are coupled to one electrode lead 531 to form an electrode lead-electrode tab coupling portion B. As shown in FIG.

In addition, the electrode lead 531 is branched into three units 532, 534, and 536, and the ends of the electrode tabs 512, 514, and 516 are branched end units of the electrode lead 531. 532, 534, and 536, which are distributed and coupled together.

Specifically, the end of the electrode lead 531 is branched into three units, the first end 536 is bent upward, the second end 534 formed in a structure parallel to the electrode tabs 514, and the downward bend Consisting of a third end 532.

The ends of the electrode tabs 512, 514, 516 are each distributed in three equal numbers to the three branched units of the electrode lead 531, and the branched ends of the electrode lead 531 are symmetric in a vertical cross section. It is structured.

In addition, the electrode lead-electrode tab coupling portion B groups the electrode tabs 512, 514, and 516 into three groups on the branched end of the electrode lead 531, and then moves the welding tool 500 downward. It is manufactured by welding while moving to.

On the other hand, an insulating lead film 533 is attached to a portion adjacent to the branched ends 532, 534, and 536 of the electrode lead to insulate the battery case (not shown).

6 to 8 schematically show enlarged views of an electrode lead-electrode tab coupling part in which the positive electrode tabs are densely coupled in the electrode assembly according to another embodiment of the present invention and are connected to the positive electrode lead.

First, referring to FIG. 6, the electrode lead-electrode tab coupling portion C may contact the branched end portions 112, 122, and 132 in a state where the three lead members 110, 120, and 130 are in close contact with each other. It is prepared by combining the remaining sites.

In detail, the three lead members 110, 120, and 130 are formed of a first lead member 120 having an end bent downward and an end portion formed in a structure parallel to the ends of the electrode tabs 210, 220, and 230. 2 lead member 110, and the third lead member 130 is bent up end.

Next, referring to FIG. 7, in the electrode lead-electrode tab coupling part D, the end of the first lead member 120a is secondarily bent downward and the end of the third lead member 130a is upwardly two. 6 is bent, except that the stable coupling of the ends 112a, 122a, 132a of the lead members 110a, 120a, 130a and the electrode tabs 210, 220, 230 is achieved. Since the same, detailed description thereof will be omitted.

In the electrode lead-electrode tab coupling part E of FIG. 8, the electrode lead is in a state in which the lead members 120b and 130b having a relatively small length are in close contact with the lead member 110b having a relatively long length. Since the ends of the members 120b and 130b are manufactured by joining the end portions of the members 120b and 130b on the lead member 110b, detailed descriptions thereof will be omitted.

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

Using one aluminum metal plate of the same size and one copper metal plate of the same size, a positive electrode lead and a negative electrode lead of the structure as shown in Figure 5 on the vertical cross section was prepared. Then, the positive lead and the negative lead is connected to three groups of the positive electrode tabs and the negative electrode tabs of the electrode assembly in which the positive electrode / separation membrane / anode is sequentially stacked as shown in FIG. 5, and then mounted in the battery case. The battery was completed by injecting and sealing the battery case.

[Example 2]

Except that the positive lead and the negative lead is separated into three lead members as shown in FIG. 6, and the ends of the first lead member and the third lead member are firstly bent downward and upward, respectively. The battery was completed in the same manner as in Example 1.

[Example 3]

Except that the positive lead and the negative lead is separated into three lead members, respectively, as shown in FIG. 7, and then the ends of the first lead member and the third lead member are secondly bent downward and upward, respectively. The battery was completed in the same manner as in Example 1.

Example 4

The length of the first lead member and the third lead member in the structure of FIG. 7 is different from that of the second lead member, except that the positive lead and the negative lead of the structure shown in FIG. 8 are manufactured in a vertical cross section. The battery was completed in the same manner as in Example 1.

Comparative Example 1

A battery was completed in the same manner as in Example 1, except that a cathode lead made of an aluminum metal plate and a cathode lead made of a copper metal plate were connected to the anode tabs and the cathode tabs as shown in FIG. 4.

[Experimental Example 1]

The front drop experiment was performed on the batteries prepared in Examples 1 to 4 and Comparative Example 1, and the results are shown in Table 1 below. In this experiment, 20 cells were repeatedly performed, and the forward drop test was performed by freely dropping the electrode terminals at the height of 1.5 m so as to collide with the floor. Separation was observed.

[Table 1]

As shown in Table 1, the batteries of Examples 1 to 4 according to the present invention did not cause the separation of the internal short and the electrode tab-electrode lead in all 20 cells in the front drop test. That is, by the branched end of the electrode lead, the bonding force of the electrode lead to the electrode tabs is improved, it is possible to prevent the separation of the electrode tab-electrode lead at the internal short and the coupling portion due to the deformation of the electrode lead. On the other hand, the battery of Comparative Example 1 was able to confirm the internal short circuit and separation phenomenon in a plurality of batteries.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (20)

A stacked or stacked / folded electrode assembly having an anode / separator / cathode structure,
Each electrode plate constituting the electrode assembly protrudes an electrode tab to which no active material is applied.
These electrode tabs are joined to one electrode lead to form an electrode lead-electrode tab coupling portion,
The electrode lead is divided into two or more units, the electrode assembly, characterized in that the ends of the electrode tabs are coupled to each other in a state that is dispersed in the branched end units of the electrode lead. The electrode assembly of claim 1, wherein an end portion of the electrode lead is branched into three or more units. The electrode assembly of claim 2, wherein the end of the electrode lead is branched into three to ten units. 3. The electrode lead of claim 2, wherein the end of the electrode lead is divided into three units, and includes a first end bent upward, a second end formed in a structure parallel to the electrode tabs, and a third end bent downward. Electrode assembly. The electrode assembly of claim 1, wherein the ends of the electrode tabs are distributed in equal numbers in the branched end units of the electrode lead. The electrode assembly according to claim 1, wherein the branched end of the electrode lead has a symmetrical structure or an asymmetrical structure in a vertical cross section. The electrode assembly according to claim 1, wherein the electrode leads are manufactured by joining the remaining portions except for the branched end portions in a state in which the three lead members are in close contact with each other. The method of claim 7, wherein the three lead members are a first lead member having an end bent downward, a second lead member having an end portion parallel to the electrode tabs, and a third lead member having an end bent upwardly. Electrode assembly, characterized in that made. 3. The electrode lead of claim 2, wherein the electrode lead leads one end of the lead members b in a state in which the lead members b of a relatively small length are brought into close contact with the lead member a of a relatively long length. Electrode assembly characterized in that is produced by bonding on the member (a). The electrode assembly of claim 1, wherein the electrode lead-electrode tab coupling portion is manufactured by grouping the electrode tabs and placing the electrode tabs on top of the branched ends of the electrode leads. The electrode assembly of claim 1, wherein the electrode lead is a metal plate. The electrode assembly of claim 11, wherein the metal plate is selected from an aluminum plate, a copper plate, a nickel plate, a nickel plated copper plate, and an SUS plate. An electrochemical cell comprising an electrode assembly according to any one of claims 1 to 12. The electrochemical cell of claim 13, wherein the electrochemical cell is a small electrochemical cell, the electrode comprising an electrode lead having a thickness of 0.1 mm or less. 15. The electrochemical cell of claim 13, wherein said electrochemical cell is a medium to large electrochemical cell, comprising an electrode lead having a thickness of 0.1 to 0.5 mm. The electrochemical cell of claim 13, wherein the electrochemical cell is a secondary battery or a capacitor. The electrochemical cell of claim 16, wherein the secondary battery is embedded in a battery case of a laminate sheet including a metal layer and a resin layer in a sealed state. A battery pack containing a plurality of electrochemical cells according to claim 17 in a pack case. A device comprising the battery pack according to claim 18 as a power source. 20. The device of claim 19, wherein the device is selected from mobile phones, portable computers, smartphones, smart pads, netbooks, light electronic vehicles (LEVs), electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage devices. Device characterized in that.

Images