KR20130108688A - Battery cell of improved connection reliability and battery pack comprising the same - Google Patents

Abstract

PURPOSE: A battery cell improves bonding force between an electrode lead and an electrode tab even if an external impact or vibration is applied. CONSTITUTION: A battery cell has an electrode assembly with a positive electrode/separator/negative electrode structure accommodated in the accommodation part of a battery case; electrode tab on which active material is not spread is protruded from each electrode plate composing the electrode assembly; and an electrode lead (60) which electrically connects the electrode tabs and is placed at one end of the electrode tabs. In the electric connection part of the electrode tabs and electrode leads, the electrode leads are injected into the electrode tabs with physical bonding force.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery cell having improved connection reliability and a battery pack including the same.

The present invention relates to a battery cell having improved connection reliability and a battery pack including the same, and more particularly, to a battery cell in which an electrode assembly having a positive electrode / separator / negative electrode structure is embedded in a housing portion of a battery case, (Electrode tabs) which are not coated with active material are protruded from the respective electrode plates constituting the electrode tabs, and electrode leads for electrically connecting the electrode tabs are located at one end of the electrode tabs, And the electrode lead is physically joined to the electrode tab by the shape deformation at the electrically connecting portion between the electrode lead and the electrode lead, and a battery pack including such a battery cell.

BACKGROUND ART [0002] In recent years, rechargeable secondary batteries have been widely used as energy sources for wireless mobile devices. The secondary battery is also attracting attention as a power source for an electric vehicle (EV) and a hybrid electric vehicle (HEV), which are proposed as solutions for the air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels .

In a small mobile device, one or two or more battery cells are used per device, while a middle- or large-sized battery module such as an automobile is used as a middle- or large-sized battery module in which a plurality of battery cells are electrically connected due to the necessity of a large-

Since the middle- or large-sized battery module is preferably manufactured in a small size and weight, a prismatic battery, a pouch-shaped battery, and the like, which can be charged with a high degree of integration and have a small weight to capacity ratio, are mainly used as the battery cells of the middle- or large-sized battery modules. In particular, a pouch-shaped battery using an aluminum laminate sheet or the like as an exterior member has recently attracted a lot of attention due to its advantages such as small weight, low manufacturing cost, and easy shape deformation.

Meanwhile, a battery module mounted on a middle- or large-sized battery pack is generally manufactured by stacking a plurality of battery cells with a high density, and is manufactured by electrically connecting electrode leads of adjacent battery cells.

1 is a perspective view schematically showing a representative pouch-type battery cell. The pouch-shaped battery cell 10 of Fig. 1 has a structure in which two electrode leads 2 and 3 protrude from the upper end and the lower end of the battery body 13, facing each other. The exterior member 14 is composed of two upper and lower units, and both side surfaces 14b and upper and lower portions 14a, which are mutually contacting portions, with electrode assemblies (not shown) mounted on an accommodating portion formed on an inner surface thereof. The battery cells 10 are made by attaching 14c).

The exterior member 14 has a laminate structure of a resin layer / metal foil layer / resin layer, and can be attached by mutually fusion bonding the resin layer by applying heat and pressure to both side surfaces 14b and the upper and lower ends 14a and 14c which are in contact with each other. In some cases, the adhesive may be attached using an adhesive.

Since both side surfaces 14b are in direct contact with the same resin layer of the upper and lower exterior members 14, uniform sealing is possible by melting. On the other hand, since the electrode leads 2 and 3 protrude from the upper end 14a and the lower end 14c, considering the thickness of the electrode leads 2 and 3 and the heterogeneity with the material of the sheathing member 14, A sealing member 16 in the form of a film is interposed between the electrode leads 2 and 3 so as to increase the height of the electrode leads 2 and 3.

When a plurality of such battery cells are used to construct a middle- or large-sized battery module, the electrode leads of the battery cells are welded to each other or electrically connected to each other using bus bars or the like for mechanical fastening and electrical connection.

2 is a schematic cross-sectional view of a pouch-shaped battery.

2, an electrode assembly 1 having a separator interposed between a cathode current collector and an anode current collector on both sides of which an electrode active material is applied is composed of a plurality of electrode plates, And the electrode tabs 17 extending from the electrode plates are ultrasonically welded to one electrode lead 2 to form the electrode tab-to-lead joint portions 18.

However, when the number of stacked battery cells is increased due to the increase in the capacity of the battery cells, the thickness and width of the electrode leads and the electrode tabs are increased, so that a large amount of energy is required for welding.

In addition, since the middle- or large-sized battery module is used as a power source for an electric vehicle or the like, the battery cells built in such a device are easily exposed to external shocks and vibrations, and thus a structure having high safety is required. Particularly, in the case where the electrode lead of the battery cell and the electrode tab are not firmly coupled to each other, the welded portion may be separated due to vibration or shock applied continuously, so that performance and safety may be significantly deteriorated.

Accordingly, there is a high need for a technique capable of achieving a high bonding force between the electrode lead and the electrode tab in the ultrasonic welding process.

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.

More specifically, it is an object of the present invention to provide an ultrasonic welding method and a manufacturing method thereof, in which an electrode lead and an electrode tab are electrically connected to each other at a connection portion between an electrode lead and an electrode tap, And a battery pack that exhibits a high coupling force between the electrode lead and the electrode tab even when an external force due to vibration is generated, and a battery pack including the same.

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 including a positive electrode / separator / negative electrode structure, (Electrode tabs) protruding from the electrode tabs, and electrode leads for electrically connecting the electrode tabs are disposed at one side end of the electrode tabs where the electrode tabs are stacked, And the leads are physically connected to the electrode tabs by shape deformation.

Therefore, prior to the ultrasonic welding, the shapes of the electrode leads and the electrode taps are deformed by physical pressing to maximize the bonding force, thereby achieving a high electrical coupling force between them.

In one preferred example, the electrode lead may be introduced into the electrode tab at a depth of 30 to 300% based on the total thickness of the electrode tab at the electrical connection site. 5, the electrode tabs are also pushed down in the direction in which the physical force is applied, corresponding to the depth at which the electrode leads are introduced into the electrode tabs, resulting in deformation of the electrode tabs. The depth of introduction of the electrode leads may be larger than the total thickness of the electrode tabs. A more preferred depth may be 50 to 250%.

The shape deformation can be achieved in various ways, and in one specific example, a first die on which a pressing pin is mounted, and a second die on which an inner surface fin receiving portion corresponding to the outer shape of the pressing pin is engraved. The pressing points are formed by pressing the pressing pins in a state where the electrode taps and the electrode leads are positioned, and after the bonding points are pressed and pressed between a pair of third dies where the facing portions are flat, And then ultrasonic welding may be performed.

The coupling by the ultrasonic welding is performed by applying a high frequency vibration generated by a high ultrasonic wave of about 40 KHz to generate vibration energy in accordance with the operation of the horn and the anvil at the interface between the electrode taps and the electrode lead And the welding is performed rapidly by converting into heat energy by friction.

The pressing pin may be configured to be mounted on the central axis of the first die so as to be independently operable in the vertical direction. Preferably, the outer diameter of the pressing pin is 1.0 mm to 2.0 mm, The inner diameter of the pin receiving portion may be 1.5 mm to 2.5 mm.

In addition, the average thickness of the electrical connection portion may be 40 to 90% of the total thickness of the electrode leads and the electrode tabs. Specifically, when the average thickness of the electrically connecting portion is 40% or less, it is difficult to prevent the electrode terminal and the electrode tab from being broken. When the thickness of the electrically connecting portion is more than 90% Which is undesirable.

In the above structure, the bonding points may be formed in a number of 1 to 10 per electrode lead.

Therefore, it is possible to fundamentally prevent the breakage of the electrode terminals and the electrode tabs by forming junction points in an appropriate number in accordance with the welding process environment and the conditions of the electrode leads and the electrode taps.

The electrode assembly may be of various shapes, and may be of a stacked or folded structure in which unit cells such as a pull cell or a bi-cell are wound in a separate film. That is, it may be a stacked structure in which a plurality of electrode plates are laminated with a separator formed thereon, or a stack / folding structure, but is not limited thereto.

The battery cell according to the present invention may be of various types, and preferably has a structure in which an electrode assembly is embedded in a laminate sheet including a resin layer and a metal layer.

The present invention also provides a battery pack including two or more battery cells as a unit cell and a device using the battery pack as a power source. A preferable example of such a device is a battery pack using the battery pack as a power source An electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle or a power storage device having a mounting space and being exposed to frequent vibration and strong impact. It goes without saying that battery packs used as power sources for automobiles can be manufactured in combination according to a desired output and capacity.

The middle- or large-sized battery pack and the electric vehicle, the hybrid electric vehicle, and the plug-in hybrid electric vehicle using the same as the power source are well known in the art, so a detailed description thereof will be omitted.

As described above, the battery cell and the battery pack including the same according to the present invention can be manufactured by joining the electrode lead to the electrode tab at the connection portion between the electrode lead and the electrode tab by the specific physical deformation before the ultrasonic welding process , It is possible to provide an excellent electrical coupling force between the electrode lead and the electrode tab even if an external force is generated due to external impact or vibration.

1 is a perspective view of a typical representative pouch type battery;
2 is a perspective view showing the electrical connection structure of a typical representative battery module;
3 is a perspective view of a battery cell according to one embodiment of the present invention;
4 is a cross-sectional view illustrating an electrical connection structure of a pouch-shaped battery cell according to an embodiment of the present invention;
Figure 5 is a side view of one exemplary die and punch used in the present invention and a profiled side view of an electrode lead and electrode tab formed using the same;
Figure 6 is a side view of one exemplary second die and second punch used in the present invention and a side view of the electrode lead and the reinforced shape of the electrode tab of Figure 5;
7 is a side view of a shape of an electrode lead and an electrode tab welded by ultrasonic welding according to one embodiment of the present invention, which is fused by ultrasonic welding;
8 is a graph of a tensile strength test before / after the conventional battery pack process;
9 is a graph of tensile strength test before / after the battery pack process according to one 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.

FIG. 3 is a perspective view of a battery cell according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view illustrating an electrical connection structure of a pouch-shaped battery cell according to an embodiment of the present invention. Respectively.

3 and 4, an electrode assembly 30 having a separator interposed between a cathode current collector and an anode current collector, on which electrode active materials are coated on both surfaces, is composed of a plurality of electrode plates. The electrode tabs 40 protruding from the electrode plates are formed on the electrode leads 60 and the electrode tabs 40 are formed on the electrode leads 60 in the process of forming the junction points 200. [ So as to form an electrical connection 90 between the electrode tabs and the electrode leads.

The junction point 200 is formed by an introduction portion formed by introducing the electrode lead 60 into the electrode tabs 40 by a first die (see FIGS. 5 and 6) and a second die (see FIGS. 5 and 6) : Figures 5 and 6).

The process of forming the bonding point 200 having such a structure will be described in more detail below.

Since the electrode leads 60 are protruded outwardly, the electrode leads 60 and the electrode leads 60 are formed between the electrode leads 60 and the electrode lead 60 so that the sealing properties can be improved in consideration of the thickness of the electrode leads 60, The sealing member 80 is thermally fused.

Figure 5 is a side view of one exemplary die and punch used in the present invention and schematically shows a modified side view of an electrode lead and electrode tabs formed therefrom. Figure 6 shows one example A side view of the second die and the second punch and a side view of the electrode lead formed by using the second die and the second punch are schematically shown. A side view of a shape in which leads and electrode tabs are welded by ultrasonic welding is schematically shown.

Referring to these figures, the plate-like electrode leads 60 of the battery cells 10 are electrically connected to the electrode tabs 40, and in the electrical connection portions 90 of the electrode leads 60 and the electrode tabs 40, The electrode leads 60 are introduced into the electrode tabs 40 by the shape deformation.

This shape change was observed when the inner diameter was worn on the first die 101 having an outer diameter of about 6.0 mm and the outer diameter W was about 3.0 mm and the inner diameter w was about 2.0 mm corresponding to the pressing pin 100 By positioning the electrode lead 60 and the electrode tabs 40 of the battery cell (not shown) on the pin receiving portion 210 which is formed on the upper surface of the pin receiving portion 210 and then pressing the same using the pressing pin 100, Structure is formed. The joint point 200 formed at one side of the electrical connection portion 90 is formed with an introduction portion 102 having an inner diameter W and a depth H of about 2.5 mm so that the pressing pin 100 is accommodated .

Specifically, the lead-in portion 102 has an electrode lead 60 having a thickness of about 0.2 mm and an aluminum electrode lead 60 having a depth of about 130% based on the thickness of the electrode taps 40 having a total thickness of about 0.4 mm . The electrode tabs 40 are pushed down in the direction in which physical force is applied corresponding to the depth of the electrode leads 60 that are introduced into the electrode tabs 40 in the process of forming the lead- Can be introduced up to about 130% based on the thickness of the electrode tabs 40.

As a result, the electrode lead 60 is introduced into the electrode tabs 40 by the shape deformation to form the bonding points 200, whereby the electrode leads 60 and the electrode tabs 40 are physically coupled.

Thereafter, the pressurized portions of the electrode leads 60 and the electrode tabs 40 are secondarily pressed by using the third dies 110 and 210 whose top surfaces are horizontal so that the lead portions 60 formed by the pressing of the pressing pins 100 The ultrasonic welding is performed by the operation of the horn 300 and the anvil 500 in the extruded portion. In other words, since both end portions of the downwardly projecting portions of the electrode lead 60 are formed in a stepped shape, the stepped portions are pushed into the electrode tabs 40 by the third dies 110 and 210 And then fused by ultrasonic welding.

The punching operation of the first die 101 and the second die 400 on which the pressing pins 100 are mounted and the pressing of the third dies 110 and 210 causes the electrode leads 60 and the electrode tabs 40 ) Is pressed, ultrasound welding is performed, so that the electrical coupling force can be maximized.

FIG. 8 shows a tensile strength test graph before and after a conventional battery pack process, and FIG. 9 shows a tensile strength test graph before and after a battery pack process according to an embodiment of the present invention.

1 to 7, conventional ultrasonic welding is performed on the electrode leads 2 and 3 and the electrode taps 17, and then, when the battery pack process is performed, It can be seen that the density depending on the value is greatly reduced from about 0.035 g / cm 3 to 0.023 g / cm 3.

On the other hand, when the punching process to induce physical bonding according to the present invention is performed and the ultrasonic process is performed, the density according to the average data value of the welded portion is reduced from about 0.054 g / cm3 to 0.049 g / It can be confirmed that there is almost no width. It can be seen from the graph that this drop width is the same in standard deviation.

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 (12)

A battery cell in which an electrode assembly having a positive electrode / separator / negative electrode structure is embedded in a housing portion of a battery case,
A tab (electrode tab) to which no active material is applied is protruded from each electrode plate constituting the electrode assembly. An electrode lead for electrically connecting the electrode tabs is disposed at one end of the electrode tabs on which the electrode tabs are stacked ,
Wherein the electrode leads are brought into physical contact with the electrode tabs by shape deformation at a position where the electrode tabs and the electrode leads are electrically connected to each other. The battery cell according to claim 1, wherein the electrode leads are introduced into the electrode tabs at a depth of 30 to 300% based on the thickness of the electrode tabs at the electrical connection sites. The method according to claim 1,
Pressing the pressing pin in a state in which the electrode tabs and the electrode lead are positioned between the first die on which the pressing pin is mounted and the second die on which the inner surface of the pressing pin is engraved, Point,
The bonding points are pressed and squeezed between a pair of third dies which face portions are flat,
And the joint point is formed by ultrasonic welding. The battery cell according to claim 3, wherein the pressing pin is mounted on a central axis of the first die so as to be independently operable in a vertical direction. The battery cell according to claim 4, wherein an outer diameter of the pressing pin is 1.0 mm to 2.0 mm, and an inner diameter of the pin receiving portion is 1.5 mm to 2.5 mm. 2. The battery cell according to claim 1, wherein the average thickness of the electrically connected portion is 40 to 90% of the total thickness of the electrode tabs and the electrode leads. The battery cell according to claim 3, wherein the junction points are formed in a number of 1 to 10 per one electrode lead. The method of claim 1, wherein the electrode assembly is a battery cell, characterized in that the stack or stack / folding type structure. The battery cell of claim 1, wherein the battery case is formed of a laminate sheet including a resin layer and a metal layer. A battery pack comprising the battery cell according to claim 1 as two or more unit cells. A device comprising a battery pack according to claim 10. The device of claim 11, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage device.

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