KR20170126108A - Resistance Welding Device Including Electrode Bar Employed with High Melting Point Metal and Method Using the Same - Google Patents

Abstract

The present invention relates to a resistance welding device for welding electrode taps of a battery cell and electrode leads, comprising: electrode taps; upper portion electrode bars located at the top of an overlapped portion of the electrode lead; and a lower portion electrode bar located on the bottom of the overlapped portion, wherein the upper portion electrode bar and the lower portion electrode bar are positioned on a same axis with the overlapped portion as a center, and a heating element for resistance welding which generates heat upon application of current is provided in an end portion of the upper electrode bar and an end portion of the lower portion electrode bar which are respectively in contact with the overlapped portions for resistance welding, thereby capable of securing high weldability and improving efficiency of a manufacturing process of a battery cell.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding machine including an electrode rod having a high melting point metal and a welding method using the resistance welding electrode.

The present invention relates to a resistance welder including an electrode rod having a refractory metal and a welding method using the same.

As technology development and demand for mobile devices are increasing, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, many studies have been made on lithium secondary batteries having high energy density and discharge voltage, Widely used.

The electrode assembly constituting the lithium secondary battery is roughly divided into a jelly-roll type (wound type) and a stack type (laminate type). The jelly-roll type electrode assembly has a problem of peeling of the electrode active material And low space utilization. The stacked electrode assembly has a merit that it is easy to obtain a rectangular shape, but it is disadvantageous in that the manufacturing process is troublesome and the electrode is pushed when the impact is applied, causing a short circuit.

The stacked (stacked) electrode assembly is manufactured by bonding electrode tabs of a plurality of electrode plates or unit cells to one electrode lead by laser welding or ultrasonic welding. However, laser welding has a problem that welding can be performed only when the thickness of the electrode lead is 0.3 mm or less. In ultrasonic welding, the ultrasonic welding machine is expensive and defects such as cutting off the electrode lead in the process of applying ultrasonic waves may occur. On the other hand, the fastening method using a bolt or the like is suitable when the thickness of the electrode lead is 0.3 mm or more, but the working efficiency is lowered and the joining defects such as loosening of the bolting portion due to vibration occur.

However, aluminum (Al) or copper (Cu), which is generally used as the material of the electrode tab, can be used for electric welding There is a problem that resistance welding using resistance heat of metal is difficult because resistance is very small because of high conductivity. In addition, when welding is performed at a high current, a phenomenon occurs in which the electrode is melted and adhered to the electrode rod or the welded portion is worn, so that it is difficult to perform general resistance welding.

Therefore, there is a great need for a technique capable of achieving excellent welding quality even when resistance welding having high weldability is performed for connection of an electrode tab and an electrode lead made of a metal having a high electrical conductivity.

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 have found that when a resistance welder composed of an upper electrode rod and a lower electrode rod positioned respectively at the upper and lower portions of the overlapped portion of the electrode tabs and the electrode leads is used It is possible to perform resistance welding for bonding of a metal having a high electrical conductivity and to weld a plurality of electrode tabs by welding using the resistance welding machine. It came to the following.

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 resistance welding machine for welding electrode tabs and electrode leads of a battery cell to each other, And the upper electrode bar and the lower electrode bar are located on the same axis with respect to the overlapping portion, and an end portion of the upper electrode bar and a lower electrode bar, which are respectively in contact with the overlap portion for resistance welding, And a heating element for resistance welding that generates heat when the heating element is heated.

As described above, the resistance welding machine according to the present invention includes an upper electrode rod positioned on the upper portion of the overlapped portion and a lower electrode rod positioned on the lower portion. The end portion of the upper electrode rod and the end portion of the lower electrode rod, And a heating element for resistance welding is located. Therefore, compared with the case where a metal piece having a high resistance is interposed between the electrode and the welded portion, or a structure similar to the lower metal plate is used instead of the lower electrode, the heat can be generated quickly and the convenience of the process is improved.

Further, since the area of the heat generating element in contact with the welded portion is narrow, welding can be performed at an accurate position, which can be used for precise work and high weldability can be exhibited.

Also, resistance welding of the electrode tabs and the electrode leads of the battery cell is possible, and it is possible to facilitate connection of the electrode leads to the electrode assembly in which a plurality of electrodes are stacked, such as a stacked electrode assembly or a lamination / stacked electrode assembly have.

For example, the overlapped portion may have a shape in which a plurality of electrode tabs are in close contact with one electrode lead. In general, the electrode leads may be disposed on top of overlapping electrode tabs, Or may be located below the electrode tabs.

In one specific example, the heating element for resistance welding may be made of a metal having a high melting point, and may be made of a metal having high electrical conductivity and low resistance, such as an electrode tab or an electrode lead made of aluminum (Al) or copper It is possible to prevent the heating element from being damaged by the high temperature heating even in the case of welding.

The high melting point metal may be any one selected from the group consisting of tungsten (W), tungsten alloy, molybdenum (Mo), molybdenum alloy, or tungsten-molybdenum alloy.

Specifically, considering that tungsten has a melting point of about 3,300 캜 and is the highest among the elements, and the melting point of molybdenum is about 2,600 캜, both tungsten are very hard, and tungsten or molybdenum is used as a heating element of the refractory metal .

In the resistance welding machine according to the present invention, the end portions of the upper electrode and the lower electrode, which are respectively in contact with the overlapping portions, have a structure in which a resistance heating welding heat generating heat is applied when current is applied. The heating element may be attached to an end portion of the upper electrode rod and the lower electrode rod in the overlapped portion, respectively. Alternatively, the heating element may protrude from the end of the electrode rod while being partially inserted into each of the upper electrode rod and the lower electrode rod.

When the heating element is attached to the end portion of the electrode and the areas of the heating element and the electrode facing each other are compared, the area of the heating element may be larger than the area of the electrode, or may be the same area, May be smaller than the area of the electrode.

As described above, when the heating element has a large size, welding can be performed quickly over a large area. On the other hand, when the size of the heating element is small, more accurate welding is possible.

In addition, when the heating elements are partially inserted into the electrodes, precise welding is possible and the heating elements can be stably fixed.

When a resistance welder having such a structure is used, there is no need to separately insert a metal having a high resistance between the welder and the weld, and compared with a case where a large area plate is used under the weld, The accuracy of welding is high and the welding surface can be prevented from being deteriorated or oxidized, and space and cost for construction of the equipment are not burdened.

The present invention also provides a welding method, wherein a welding method using the resistance welding machine,

Positioning the electrode tabs and the electrode leads so as to overlap with each other;

A step of mounting a heating element for resistance welding on the upper electrode rod and the lower electrode rod, respectively;

Placing the overlapping portions of the electrode tabs and the electrode leads between the upper electrode bar and the lower electrode bar in a state where the upper electrode bar and the lower electrode bar are arranged on the same axis and bringing the heating element for resistance welding into close contact with the overlapping portion; And

Pressing the overlapped portion while applying an electric current to the upper electrode rod and the lower electrode rod;

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As described above, the resistance welding is performed in a state where the plurality of electrode taps and the electrode leads are overlapped with each other, and the connection of the electrode leads to the electrode assembly composed of the stacked electrode assembly or the lamination / stacked electrode assembly, Can be performed simply and easily.

Further, when an electrode rod including a heating element made of a refractory metal is used, high resistance heat can be used, and it is more preferable when welding is required to a plurality of electrode tabs and an electrode lead as described above.

The present invention also provides a battery cell manufactured using the resistance welding machine and a battery pack including the battery cell.

The battery pack may be used as a power source for devices requiring high temperature stability, long cycle characteristics, and high rate characteristics.

Specific examples of the device include a power tool which is powered by an electric motor and moves; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

INDUSTRIAL APPLICABILITY As described above, the resistance welding machine according to the present invention includes a heating element made of a metal having a high melting point and is located on the upper and lower surfaces of the welded portion. Welding is possible without damaging the heating element. Since the upper and lower individual heating elements are used, rapid heating and welding can be performed.

When a resistance welder having such a structure is used, resistance welding can be performed to a plurality of electrode tabs and an electrode lead, thereby securing high weldability and improving the efficiency of a battery cell manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view of a resistance welder located on an electrode lead overlap and an electrode tab according to one embodiment;
2 is a side view of a resistance welder located on an electrode tab and electrode lead overlap in accordance with another embodiment; And
3 is a photograph showing an electrode tab and an electrode lead portion welded using the resistance welder 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. 1 and 2 schematically show side views of a state where a resistance welder is placed on the overlapped portion of electrode taps and electrode leads. Fig.

1, an electrode assembly 100 having a structure in which an anode 110 and a cathode 120 are alternately stacked and a separator 130 is formed between the anodes 110 and the cathodes 120, And a positive electrode tab 111 protrudes from one end of the anodes 110 to form a bundle.

The positive electrode lead 140 is disposed on the upper surface of the stack of the positive electrode tabs 111 which are sequentially stacked. The positive electrode lead 140 is partially overlapped with the positive electrode tabs in parallel with the ground, May be aluminum or copper with high electrical conductivity. The position of the cathode lead 140 may be located on the lower surface of the bundle of cathode tabs or may be interposed between the bundles of cathode tabs.

An upper electrode rod 161 is positioned above the overlapped portion 112 of the positive electrode tabs 111 and the positive electrode lead 140 and a lower electrode rod 163 is located below the upper electrode rod 161 and the lower electrode rod 163. And is positioned on the same axis perpendicular to the paper surface about the overlapping portion 112.

The heating elements 162 and 164 made of a metal material having a high melting point are attached to the ends of the upper electrode rod 161 and the lower electrode rod 163 in the direction of the overlapping portion 112, Even when the thickness of the positive electrode tabs and the positive electrode leads is large, resistance welding using high resistance heat is possible.

On the other hand, the heating elements 162 and 164 having a structure attached to the end portion of the electrode may have the same area as the area of the end portion of the electrode contacting the overlap portion, or may have an area smaller or larger than the area of the end portion of the electrode .

Although the resistance welding has been described in connection with the positive electrode tabs and the positive electrode leads, it goes without saying that the same applies to the case where the negative electrode tab and the negative electrode lead are connected.

2, an electrode assembly 200 having a structure in which an anode 210 and a cathode 220 are alternately stacked and a separator 230 is formed between the anodes 210 and the cathodes 220, And a positive electrode tab 211 protrudes from one end of the anodes 210 to form one bundle.

The positive electrode lead 240 is disposed on the upper surface of the stack of the positive electrode tabs 211 sequentially stacked. The positive electrode lead 240 is partially overlapped with the positive electrode tabs in parallel with the ground, May be aluminum or copper with high electrical conductivity. The position of the cathode lead 140 may be located on the lower surface of the bundle of cathode tabs or may be interposed between the bundles of cathode tabs.

The upper electrode bar 261 and the lower electrode bar 263 are positioned on the upper portion of the overlapping portion 212 of the positive electrode tabs 211 and the positive electrode lead 240, And is positioned on the same axis perpendicular to the paper surface around the overlapping portion 212.

The heating elements 262 and 264 are made of a metal material having a high melting point at the ends of the upper electrode rod 261 and the lower electrode rod 263 in the direction of the overlapping portion 212, Is partially inserted into each of the lower electrode electrode 261 and the lower electrode electrode 263. Therefore, even when the thickness of the positive electrode tabs and the positive electrode tabs stacked in the overlapping portion 212 is large, resistance welding using high resistance heat is possible.

Although the resistance welding has been described in connection with the positive electrode tabs and the positive electrode leads, it goes without saying that the same applies to the case where the negative electrode tab and the negative electrode lead are connected.

Fig. 3 shows a welding portion of the electrode tab and the electrode lead welded by using the resistance welder of the present invention.

3 (A) is a welding surface in the direction of the negative electrode lead, and (B) is a welding surface in the direction of the negative electrode tab, and is applied to precise welding such as connection of electrode taps or electrode leads having a narrow width Since the adhesive strength is high, the risk of separation of the electrode tabs and the electrode leads is low, and safety can be 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 (5)

1. A resistance welder for welding electrode taps of an electrode cell to electrode taps of a battery cell,
And a lower electrode rod positioned at an upper portion of the overlapped portion of the electrode tabs and the electrode lead and at a lower portion of the overlapped portion, wherein the upper electrode rod and the lower electrode rod are located on the same axis with the overlap portion as a center,
Wherein an end portion of the upper electrode rod and an end portion of the lower electrode rod which are respectively in contact with the overlapped portion for resistance welding are positioned with a heating element for resistance welding which generates heat upon application of current. The resistance welding machine according to claim 1, wherein the resistance welding heat generating element is made of a metal having a high melting point. The resistance welding machine according to claim 2, wherein the metal is made of any one selected from the group consisting of tungsten (W), tungsten alloy, molybdenum (Mo), molybdenum alloy, and tungsten-molybdenum alloy. The heat sink for resistance welding according to claim 1, characterized in that the heating element for resistance welding is attached to each end of the upper electrode rod and the lower electrode rod, or protrudes from the end of the electrode rod in a state of being partially inserted into each of the upper electrode rod and the lower electrode rod Resistant welding machine. Positioning the electrode tabs and the electrode leads so as to overlap with each other;
A step of mounting a heating element for resistance welding on the upper electrode rod and the lower electrode rod, respectively;
Placing the overlapping portions of the electrode tabs and the electrode leads between the upper electrode bar and the lower electrode bar in a state where the upper electrode bar and the lower electrode bar are arranged on the same axis and bringing the heating element for resistance welding into close contact with the overlapping portion; And
Pressing the overlapped portion while applying an electric current to the upper electrode rod and the lower electrode rod;
Welded to the weld.

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