KR20180080837A - Battery Cell Comprising Surface-treated Current Collector by Laser Irradiation - Google Patents

Abstract

The present invention relates to a battery cell including an electrode collector surface-treated by laser irradiation. The present invention is to improve the welding force when removing a metallic oxidized layer on the surface of a welding unit for connecting anode taps and the anode tap and an anode lead. According to the present invention, an electrode assembly is formed as multiple anode collectors and multiple cathode collectors are laminated in an electrical insulation state by a separation membrane. The electrode assembly is accommodated in a battery case with an electrolyte. The anode collectors are electrically connected since the anode lead is connected to the outer side of at least one among the outermost anode collectors in a state that the anode taps protruding from the outer surface on one side of the anode collector are connected. Each of the anode taps has a metallic oxidized layer on the surface except for the part connected to the adjacent anode tap or the anode lead.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery cell including a current collecting electrode surface treated by laser irradiation (Battery Cell Comprising Surface-treated Current Collector by Laser Irradiation)

The present invention relates to a battery cell including an electrode current collector surface-treated by laser irradiation.

2. Description of the Related Art As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing, and a lot of research has been conducted on secondary batteries that can meet various demands.

Such a secondary battery is classified according to the structure of the anode assembly, the cathode assembly, and the electrode assembly having the separation membrane structure sandwiched between the anode assembly and the cathode assembly. Typically, the long- (Stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in a unit of a predetermined size are sequentially stacked with a separator interposed therebetween, a jelly-roll (wound type) electrode assembly having a structure A stack / folding type electrode assembly in which unit cells such as a bi-cell or a full cell stacked with a separator interposed between positive and negative electrodes of a unit are wound.

FIG. 1 schematically shows a general structure of a typical conventional pouch-type secondary battery as an exploded perspective view.

1, the pouch type secondary battery 10 includes an electrode assembly 30, electrode taps 40 and 50 extending from the electrode assembly 30, electrodes 40 and 50 welded to the electrode taps 40 and 50, Leads 60 and 70, and a battery case 20 for accommodating the electrode assembly 30. [

The electrode assembly 30 is a power generation element in which an anode and a cathode are sequentially stacked with a separation membrane interposed therebetween. The electrode assembly 30 has a stacked or stacked / folded structure. The electrode tabs 40 and 50 extend from the respective electrode plates of the electrode assembly 30 and the electrode leads 60 and 70 have a plurality of electrode tabs 40 and 50 extending from each electrode plate, Respectively. An insulating film 80 is attached to the upper and lower surfaces of the electrode leads 60 and 70 in order to increase the degree of sealing with the battery case 20 and at the same time to ensure an electrically insulated state.

The electrode tabs 40 and 50 are made of aluminum, copper, aluminum alloy, or the like. The plurality of electrode tabs 40 and 50 protruding from the electrode current collector of the electrode assembly 30 are, for example, And is connected to the electrode leads 60 and 70 in the form of a bonded portion integrally bonded by welding.

However, when the electrode tab is made of aluminum or an aluminum alloy, a porous Al ₂ O ₃ layer is formed on the surface of the electrode tab as shown in the photograph of FIG.

In general aluminum, an Al ₂ O ₃ layer is formed in the air to a thickness of about 4 nm to 10 nm on the surface, and an aluminum electrode tab of a middle- or large-sized secondary battery is formed into a relatively thick three-layered Al ₂ O ₃ layer .

Since the oxide is an insulating material having a high hardness, sparks are generated during energization, and weldability is remarkably deteriorated when ultrasonic welding is performed between the electrode tabs and between the electrode tabs and the electrode leads.

Therefore, there is a high need for a technique capable of improving the weld tensile force by improving the weldability of the electrode tab and the electrode lead of the aluminum material.

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 to improve the welding force in the case of removing the metal oxide layer on the surface of the welded portion for connecting the positive electrode tabs and the positive electrode tabs, The present invention has been accomplished on the basis of these findings.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a battery cell comprising: an electrode assembly including a plurality of positive electrode collectors and negative electrode collectors laminated in an electrically insulated state by a separator, The current collectors are connected to the positive electrode leads on the outer surface of at least one of the outermost positive electrode collectors to form an electrical connection in the state where the positive electrode taps protruding from one outer periphery of the current collector are mutually coupled, Is characterized in that a metal oxide layer is formed on the surface except for a portion to be bonded to the adjacent positive electrode tab or the positive electrode lead.

As described above, the metal oxide layer is formed on the surface of the positive electrode tab protruded from one side of the positive electrode collector to the outside periphery. The metal oxide layer is formed by welding between the laminated positive electrode taps or between the positive electrode tab and the positive electrode lead . However, since the metal oxide layer improves the airtightness of the battery cell, it is not preferable to remove the entire metal oxide layer. Therefore, it is possible to improve the welding strength by removing only the metal oxide layer formed on the portion to be bonded to the adjacent positive electrode tab or the positive electrode lead, and it is possible to prevent the airtightness of the battery cell from being lowered.

In one preferred example, the electrode assembly may be a structure in which a plate-shaped electrode current collector is stacked, for example, a stacked electrode assembly or a stacked / folded electrode assembly or a lamination / stacked electrode assembly And the metal oxide layer may be Al ₂ O ₃ .

The positive electrode tab may have a structure in which a metal oxide layer is formed on a surface and a tab exposing portion in which a metal oxide layer is removed from a portion where welding is required, that is, an adjacent positive electrode tab or a cathode lead to be joined.

Specifically, the tab exposing portion may be formed by removing a metal oxide layer by irradiating a laser to a predetermined joining portion. As described above, the method used for removing the metal oxide layer is performed by a laser etching method in which a laser is irradiated. As a result, the process is very simple as compared with chemical etching, and ultimately the manufacturing cost of the battery can be greatly reduced , It is possible to perform precise partial etching, and it is easy to control the depth of etching.

The tab exposing portion is preferably formed at the same position in the vertical direction with respect to the stacking direction of the positive electrode current collectors, and may be formed only on the upper surface or the lower surface of the positive electrode tab. In addition, considering that the effect of improving the weldability can be obtained when the metal oxide layer formed on all portions facing each other is removed, the tab exposing portion can be formed on the upper surface and the lower surface of the positive electrode tab, respectively.

As described above, the positive electrode tabs adjacent to each other in the state where the current collectors are stacked may be structured such that the respective tab exposures are bonded to each other. In this state, The problem that the welding strength is lowered by the metal oxide film can be solved.

For example, the method of joining the positive electrode tabs is not particularly limited as long as the positive electrode tabs can be stably bonded to each other. However, the method may be performed by ultrasonic welding to prevent the welded portion from being damaged.

On the other hand, the positive electrode tabs bonded by welding are electrically connected to the positive electrode lead, and the positive electrode lead has a metal oxide layer formed on its surface except for a portion to be bonded to the positive electrode tab. The positive electrode lead may be bonded to the outer surface of the outermost positive electrode among the stacked positive electrode tabs, or may be welded with an electrode lead between the positive electrode taps.

The positive electrode lead may include a lead exposed portion obtained by removing the metal oxide layer from a portion to be joined of the outermost positive electrode tab in a state where the metal oxide layer is formed on the surface. The metal oxide layer on one side or both sides can be removed.

Meanwhile, the metal oxide layer may have a structure in which a first oxide layer, a second oxide layer, and a third oxide layer are sequentially formed on the outer surface, and the thickness of the first oxide layer may be in a range of 5 nm to 10 nm , The thickness of the second oxide layer may be in the range of 120 nm to 150 nm, and the thickness of the third oxide layer may be formed in the range of 280 nm to 330 nm. When the second oxide layer and the third oxide layer are compared, the second oxide layer may have a relatively high density, and the third oxide layer may have a porous structure having a relatively low density.

The first metal oxide layer to the third metal oxide layer may be removed or the first metal oxide layer and the second metal oxide layer may be removed to expose the tab exposed portion or the lead exposed portion to form the exposed portion from which the metal oxide layer has been removed from the positive electrode tab and the positive electrode lead. It is preferable that the first metal oxide layer to the third metal oxide layer be removed in order to achieve the purpose of improving the weldability.

The present invention also provides a method of manufacturing the battery cell,

(a) preparing a positive electrode collector including a positive electrode tab protruding from one side of the outer periphery and having a metal oxide layer formed on a surface thereof;

(b) forming a tab-exposed portion by irradiating an outer surface of the anode tab with a laser locally to remove a portion of the metal oxide layer;

(c) forming the electrode assembly by laminating the positive electrode current collectors and the negative electrode current collectors such that the tab exposed portions are in contact with each other with the separator interposed therebetween; And

(d) bonding adjacent cathode tabs through the tab exposures of the anode tabs;

As shown in FIG.

In this way, by locally irradiating a part of the outer surface of the positive electrode tab with a laser to remove a part of the metal oxide layer and bonding the adjacent positive electrode tabs through the tab exposing portion of the positive electrode taps, The problem of the prior art in which the weldability of the positive electrode taps is weakened by the metal oxide layer formed on the negative electrode taps can be solved.

In this case, in the step (b), the laser irradiation may be performed on both outer surfaces of the respective positive electrode tabs, or may be performed on the same outer side surface of the positive electrode tabs.

The method may further include, after the step (d), bonding the electrode leads to the outer surface of at least one positive electrode tab of the outermost positive electrode collectors of the electrode assembly, It is possible to irradiate a laser to remove the metal oxide layer on the surface at the intended bonding site of the electrode lead. As described above, the metal oxide layer is removed on the area where the positive electrode tab and the positive electrode lead are to be joined, so that the weldability of the positive electrode tab and the positive electrode lead can be improved.

The present invention also provides a battery pack including the battery cell and a device including the battery pack. Since the battery pack and the device are known in the art, a detailed description thereof will be omitted. do.

The device may be, for example, a notebook computer, a netbook, a tablet PC, a mobile phone, MP3, a wearable electronic device, a power tool, an electric vehicle (EV), a hybrid electric vehicle (HEV) , A plug-in hybrid electric vehicle (PHEV), an electric bike (E-bike), an electric scooter (E-scooter), an electric golf cart, However, the present invention is not limited thereto.

INDUSTRIAL APPLICABILITY As described above, the battery cell according to the present invention can improve the adhesive force at the time of welding for electrical connection by irradiating a laser on the surface of the electrode tab to remove the metal oxide film by an etching method, It is possible to reduce the defective rate that may occur. In addition, since the oxide film that can cause sparking during power application is removed, it is possible to provide a secondary battery improved in safety.

1 is an exploded perspective view of a general structure of a conventional pouch type secondary battery;
2 is an SEM photograph of the electrode tab surface on which an oxide film is formed;
3 is a TEM photograph of an oxide film of a three-layer structure measured;
4 is a partial schematic view of a cathode current collector schematically showing a tab exposing portion formed on a part of a cathode tab;
5 is an enlarged view of the positive electrode tab exposing portion;
FIG. 6 is a side view showing a state in which positive tabs having tab exposures formed on one surface of positive tabs are connected through tab exposures; FIG.
FIG. 7 is a side view showing a state in which cathode tabs having tab exposures formed on both sides of the cathode tabs are connected through the tab exposures; And
8 is a side view in which a cathode lead having a lead exposure portion is connected to the cathode tabs of FIG.

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.

3 is a TEM photograph for analyzing the structure of the oxide film formed on the surface of the anode tab.

Referring to FIG. 3, the first oxide layer 101, the second oxide layer 102 and the third oxide layer 103 are sequentially formed on the outer surface of the metal oxide layer. The first oxide layer 101 has a thickness of about 7 and the second oxide layer 102 is formed to a thickness of about 135 nm inside the first oxide layer 101 and the third oxide layer 103 is formed to the inside of the second oxide layer 102 On the surface of the positive electrode tab to a thickness of about 295 nm.

It can be seen that the second oxide layer 102 has a relatively high density and the third oxide layer 103 has a porous structure having a relatively low density.

4 is a perspective view schematically showing a positive electrode tab forming portion of a positive electrode current collector, and FIG. 5 is an enlarged view of a positive electrode tab exposing portion

4 and 5, a tab exposing portion 221 in which a metal oxide layer is removed is formed at the central portion of the positive electrode tab 220 protruded from one side of the positive electrode current collector 210, 221 are formed by a laser etching method using laser irradiation. The tab exposing portion may be formed on the upper surface or the lower surface of the positive electrode tab and may be formed on both the upper surface and the lower surface of the positive electrode tab.

The etching mark region may be formed in a continuous dot shape or a plurality of linear shapes in the tab exposed portion through the laser irradiation, and the laser etching shape in FIG. 5 has a continuous dot shape.

6 schematically shows a side view in which a positive electrode tab having a tab exposing part on one surface of a positive electrode tab is connected through a tab exposing part.

Referring to FIG. 6, the positive electrode tabs 310, 320, 330, 340, and 350 are stacked so as to completely overlap each other in the vertical direction, and a portion of the lower surface of each of the positive electrode tabs 310, The tab exposures 311, 321, 331, 341, and 351 in which the metal oxide film of the cathode tabs are removed are formed, and the cathode tabs are connected to each other through the tab exposures.

FIG. 7 schematically shows a side view in which cathode tabs having tab exposures on both sides of the cathode tabs are connected through the tab exposures.

Referring to FIG. 7, the positive electrode tabs 410, 420, 430, 440 and 450 are stacked so as to completely overlap each other in the vertical direction, and the upper surface and the lower surface of each of the positive electrode tabs 410, 420, 430, 440 and 450 In some of them, tab exposures 401, 411, 421, 431, 441 and 451 are formed on the surface of which the metal oxide film is removed, and the cathode tabs are connected to each other through the tab exposures.

FIG. 8 schematically shows a side view in which a cathode lead having a lead exposure portion is connected to the cathode tabs of FIG. 7. FIG.

8, the positive electrode lead 460 is attached to the outer side surface of the outermost positive electrode tab 410 of the stacked positive electrode taps and the lead exposed portion 461 is formed at the contact portion of the positive electrode lead 460 with the positive electrode tab. The positive electrode lead 460 and the positive electrode outermost positive electrode tab 410 may be welded to each other at the positive electrode lead exposing portion 461 and the tab exposing portion 401.

6, the positive electrode lead 460 may be welded to the positive electrode tab formed with only the exposed portion on one side of the positive electrode tab. At this time, The positive electrode tab 350 can be coupled with the lower surface of the positive electrode tab 350 where the tab exposing portion 351 is formed.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but it should be understood that the scope of the present invention is not limited thereto.

≪ Example 1 >

One side of each of the anode tabs of the aluminum material was irradiated with a laser of 1,064 nm, and the cathode tabs were prepared by removing the oxide layer on the surface of the anode tabs by laser etching. The same procedure was repeated to produce three positive electrode tabs with the oxide layer removed on one side of the positive electrode tab.

The positive electrode taps and the electrode leads are formed by ultrasonic welding in a state where the electrode leads of the aluminum material are positioned on the etched surface of the positive electrode tab at one end after lamination in a predetermined direction so that the etched surfaces of the positive electrode tabs do not face each other, Lt; / RTI >

≪ Example 2 >

The positive electrode taps and the electrode leads were bonded to each other in the same manner as in Example 1, except that laser etching was performed on both surfaces of each of the positive electrode tabs.

≪ Comparative Example 1 &

The positive electrode tabs and the electrode leads were bonded by ultrasonic welding in a state in which three positive electrode tabs were stacked and the electrode leads were positioned on one end surface without laser etching on both sides of each of the positive electrode tabs.

<Experimental Example 1>

In order to measure the tensile strength of the electrode leads bonded to the positive electrode tabs prepared in Examples 1 to 2 and Comparative Example, the positive electrode tab portion was fixed to the tensile strength meter, a constant force was applied to the electrode leads, The results are shown in Table 1 below. &Lt; tb &gt; &lt; TABLE &gt;

Tensile strength (Kgf) Number of times Example 1 Example 2 Comparative Example 1 One 38.22 44.90 26.86 2 32.46 56.00 27.44 3 25.70 40.08 39.56 4 46.58 42.94 35.94 5 45.64 48.04 30.46 Average 37.12 46.39 32.05 Comparative Example 1 Tensile Strength Increase Rate (%) 15.8 44.7 -

Referring to Table 1, in Example 1 in which the metal oxide film on one side of the positive electrode tab was removed, the tensile strength was increased by 15.8% as compared with Comparative Example 1 in which the metal oxide film was not removed, The tensile strength was increased by 44.7% as compared with Comparative Example 1. In addition,

Therefore, it can be seen that, when the metal oxide film of the positive electrode tab is removed by welding as in the present invention, the bonding strength between the positive electrode tab and the positive electrode tab is remarkably improved.

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 (18)

An electrode assembly in which a plurality of positive electrode collectors and negative electrode collectors are laminated in an electrically insulated state by a separator is accommodated in a battery case together with an electrolyte;
Wherein the positive electrode current collectors are electrically connected to at least one of the outermost positive electrode current collectors by bonding the positive electrode leads to each other while the positive electrode taps protruding from the outer periphery of one side of the current collector are coupled to each other;
Wherein each of the positive electrode tabs has a metal oxide layer formed on its surface except for a portion to be bonded to the adjacent positive electrode tab or positive electrode lead. The battery cell of claim 1, wherein the electrode assembly is a stacked electrode assembly, a stacked / folded electrode assembly, or a lamination / stacked electrode assembly. The battery cell according to claim 1, wherein the positive electrode collector is made of aluminum or an aluminum alloy. The battery cell according to claim 1, wherein the positive electrode tab includes a tab exposing portion in which a metal oxide layer is removed from an adjacent positive electrode tab or a region where the positive electrode lead is to be joined, with the metal oxide layer formed on the surface. The battery cell according to claim 4, wherein the tab exposing portion is formed by removing a metal oxide layer by irradiating a laser to a predetermined joining portion. The battery cell according to claim 4, wherein the tab exposing portion is formed on the upper surface and the lower surface of the positive electrode tab, respectively, with respect to the stacking direction of the current collectors. The battery cell according to claim 6, wherein the mutually adjoining positive electrode taps are coupled with each tab exposing portion in contact with each other. The battery cell according to claim 7, wherein the bonding is performed by ultrasonic welding. The battery cell according to claim 1, wherein the cathode lead has a metal oxide layer formed on its surface except for a portion to be bonded to the positive electrode tab. 10. The battery cell according to claim 9, wherein the positive electrode lead includes a lead-exposed portion in which the metal oxide layer is removed from a portion to be joined of the outermost positive electrode tab in a state in which the metal oxide layer is formed on the surface. The battery cell according to claim 1, wherein the metal oxide layer has a first oxide layer, a second oxide layer, and a third oxide layer sequentially formed on an outer surface thereof. The battery cell according to claim 11, wherein the first metal oxide layer to the third metal oxide layer are removed, or the first metal oxide layer and the second metal oxide layer are removed to form a tab exposing portion or a lead exposing portion. 13. A method for manufacturing a battery cell according to any one of claims 1 to 12,
(a) preparing a positive electrode collector including a positive electrode tab protruding from one side of the outer periphery and having a metal oxide layer formed on a surface thereof;
(b) forming a tab-exposed portion by irradiating an outer surface of the anode tab with a laser locally to remove a portion of the metal oxide layer;
(c) forming the electrode assembly by laminating the positive electrode current collectors and the negative electrode current collectors such that the tab exposed portions are in contact with each other with the separator interposed therebetween; And
(d) bonding adjacent cathode tabs through the tab exposures of the anode tabs;
Wherein the step of forming the battery cell comprises the steps of: 14. The method according to claim 13, wherein laser irradiation is performed on both outer surfaces of each positive electrode tab in the step (b). The method according to claim 13, further comprising, after the step (d), bonding the electrode leads to the outer surface of at least one positive electrode tab of the outermost positive electrode collectors of the electrode assembly Gt; The manufacturing method of a battery cell according to claim 15, wherein a laser is irradiated to remove a metal oxide layer on a surface of the electrode lead at a joining site. A battery pack comprising a battery cell according to any one of claims 1 to 12. A device comprising a battery pack according to claim 17.

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