KR20140022326A - Secondary battery and electrode lead applied for the same - Google Patents

Abstract

A secondary cell according to the present invention includes: an electrode assembly which includes an electrode tap; a case which accommodates the electrode assembly; and a pair of electrode leads which are coupled to the electrode tap and protrude outside the case. At least one among the two electrode leads includes: a first metal plate which is placed outside the case; a second metal plate which is separated from the first metal plate with a gap and is coupled to the electrode tap; a coating layer which is formed on a part of the surfaces of the first and the second metal plates and more specifically, on the surfaces of the ends of the first and the second metal plate facing each other and the surface inside the case except for at least the area coupled to the electrode tap; and a metal bridge which is made of material which has a lower melting point than the first and the second metal plate and is buried in the gap not to expose the ends. According to the present invention, if an over current flows through the electrode leads, the area of the metal plates where the metal bridge is formed is fractured and the over current flowing inside the secondary cell is blocked irreversibly so that the coupling strength between the electrode leads and the electrode tap can be enhanced and the contact resistance can be reduced.

Description

Secondary battery and electrode lead applied thereto {Secondary battery and Electrode lead applied for the same}

The present invention relates to secondary battery technology, and more particularly, to a secondary battery having improved stability and an electrode lead applied thereto.

As the use of portable electric appliances such as video cameras, portable phones, and portable PCs is being activated, the importance of secondary batteries, which are mainly used as driving power sources, is increasing.

Unlike a primary battery, which can not be charged normally, a secondary battery capable of charging and discharging is active in the development of advanced fields such as a digital camera, a cellular phone, a laptop computer, a power tool, an electric bicycle, an electric vehicle, a hybrid vehicle, Research is underway.

In particular, the lithium secondary battery has a higher energy density per unit weight and can be rapidly charged as compared with other secondary batteries such as lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries and nickel-zinc batteries. It is progressing.

Lithium secondary battery is used as a power source for portable electronic devices with operating voltage of 3.6V or more, or by connecting multiple batteries in series and / or in parallel, high power electric vehicles, hybrid vehicles, power tools, electric bicycles, power storage devices, Used for UPS

The lithium secondary battery has a working voltage three times higher than that of a nickel-cadmium battery or a nickel-metal hydride battery, and has an excellent energy density per unit weight, and is rapidly used.

The lithium secondary battery can be classified into a lithium ion battery using a liquid electrolyte and a lithium ion polymer battery using a polymer solid electrolyte depending on the type of electrolyte. The lithium ion polymer battery can be divided into a fully solid lithium ion polymer battery containing no electrolytic solution and a lithium ion polymer battery using a gel polymer electrolyte containing an electrolyte depending on the kind of polymer solid electrolyte.

In the case of a lithium ion battery using a liquid electrolyte, it is usually used in a form in which a cylinder or a rectangular metal can is used as a container and welded and sealed. Since the can type secondary battery using such a metal can as a container is fixed in shape, there is a disadvantage that it restricts the design of an electrical product using the metal can as a power source, and it is difficult to reduce the volume. Accordingly, a pouch type secondary battery in which an electrode assembly and an electrolyte are sealed in a film pouch packaging material has been developed and used.

However, when the lithium secondary battery is overheated, there is a danger of explosion and it is an important task to secure safety. Overheating of a lithium secondary battery occurs for various reasons, for example, a case where an overcurrent flows beyond a limit through a lithium secondary battery. When the overcurrent flows, the internal temperature of the battery rises rapidly because the lithium secondary battery generates heat by joule heat. The rapid rise in temperature also causes decomposition reactions of the electrolyte, causing thermal running, which eventually leads to battery explosion. The overcurrent is a phenomenon in which a pointed metal object penetrates a lithium secondary battery or the insulation between an anode and a cathode is destroyed by contraction of a separator interposed between an anode and a cathode or a rush current is generated due to an abnormality of an external charging circuit or a load, Is applied to the battery or the like.

Therefore, the lithium secondary battery is used in combination with a protection circuit to protect the battery from an abnormal situation such as the occurrence of an overcurrent, and the protection circuit is provided with a fuse element for irreversibly disconnecting a line through which charging or discharging current flows when an over- .

1 is a circuit diagram illustrating an arrangement structure and an operation mechanism of a fuse device among components of a protection circuit coupled to a battery module including a lithium secondary battery.

As shown in the figure, the protection circuit operates the fuse device 1 when the overcurrent occurs by monitoring the fuse device 1, the sense resistor 2 for sensing the overcurrent, and the overcurrent generation to protect the battery module when the overcurrent occurs. Microcontroller (3) and a switch (4) for switching the flow of operating current to the fuse element (1).

The fuse element 10 is installed on a main line connected to the outermost terminal of the battery module. The main line refers to a wiring through which charging current or discharging current flows. In the figure, the fuse element 1 is shown mounted on a high potential line (Pack +).

The fuse element 1 is a three-terminal element part, two terminals are connected to a main line through which a charging or discharging current flows, and one terminal is connected to the switch 4. The inside includes a fuse 1a connected in series with the main line and having a fusion at a specific temperature, and a resistor 1b for applying heat to the fuse 1a.

The microcontroller 3 periodically detects the voltage across the sense resistor 2 and monitors whether an overcurrent is generated. When it is determined that an overcurrent is generated, the microcontroller 3 turns the switch 4 on. Then, a current flowing in the main line is bypassed to the fuse element 1 and applied to the resistor 1b. Thus, the joule heat generated in the resistor 1b is conducted to the fuse 1a to raise the temperature of the fuse 1a. When the temperature of the fuse 1a rises to the fusing temperature, the fuse 1a is fused, The line is irreversibly disconnected. When the main line is disconnected, the overcurrent does not flow any more, so that the problem caused by the overcurrent can be solved.

However, the above-described conventional techniques have various problems. That is, if a failure occurs in the microcontroller 3, the switch 4 is not turned on even in a state where an overcurrent is generated. In this case, since the current does not flow into the resistor 1b of the fuse element 1, there is a problem that the fuse element 1 does not operate. Further, a space for arranging the fuse element 1 in the protection circuit is separately required, and a program algorithm for controlling the operation of the fuse element 1 must be loaded in the microcontroller 3. Therefore, the space efficiency of the protection circuit is lowered and the load of the microcontroller 3 is increased.

The present invention has been made in view of the problems of the prior art as described above, and provides a secondary battery and an electrode lead applied thereto, which have an overcurrent blocking function as a separate from the active overcurrent blocking function of a protection circuit. have.

The technical problem to be achieved by the present invention is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A secondary battery according to the present invention for achieving the above technical problem, the electrode assembly having an electrode tab; A case for accommodating the electrode assembly; And a pair of electrode leads bonded to the electrode tabs and drawn out of the case, wherein at least one of the pair of electrode leads comprises: a first metal plate positioned outside the case; A second metal plate spaced apart from the first metal plate with a gap therebetween and bonded to the electrode tab; Formed on a portion of the surfaces of the first metal plate and the second metal plate, wherein at least the electrode tab of a surface of an opposite end of each of the first metal plate and the second metal plate and a surface located inside the case; A coating layer formed in a region other than the surface to be bonded with the coating layer; And a metal bridge made of a material having a melting point lower than that of the first metal plate and the second metal plate and embedded in the gap so that the end is not exposed.

The surface of the end portion may include a first surface located inside the gap.

The surface of the end portion may further include a second surface located outside the gap as a surface extending from the first surface.

The first metal plate and the second metal plate may be positioned in parallel on the same plane.

The first metal plate and the second metal plate may be made of aluminum (Al) or copper (Cu).

The coating layer may be made of nickel (Ni).

The metal bridge may be a lead-free alloy containing tin (Sn) and copper (Cu).

The content of tin may be 80wt% to 98wt%, and the content of copper may be 2wt% to 20wt%.

The metal bridge may further include at least one additional metal selected from nickel (Ni), zinc (Zn), and silver (Ag).

The amount of the additional metal may be 0.01 wt% to 10 wt%.

The metal bridge may have a melting point of 150 ℃ to 300 ℃.

The gap may have a width of 25 μm to 45 μm.

The electrode lead including the first metal plate, the second metal plate, the coating layer, and the metal bridge may be a cathode lead, and the first metal plate and the second metal plate may be made of copper.

Opposing surfaces of each of the first metal plate and the second metal plate may have a flat surface shape parallel to each other.

Opposing surfaces of each of the first metal plate and the second metal plate may have an inclined surface shape tapered in opposite directions.

Opposing surfaces of each of the first metal plate and the second metal plate may have a convex shape protruding in a direction facing each other.

The secondary battery may further include a sealing tape attached to the electrode lead and interposed between the electrode lead and the inner surface of the case.

The sealing tape may be attached to the surface of the coating layer.

Meanwhile, an electrode lead according to the present invention, which is applied to the secondary battery according to the present invention, is joined to an electrode tab provided in an electrode assembly and drawn out of a case accommodating the electrode assembly. A first metal plate corresponding to any one of a pair of electrode leads, wherein the first metal plate is located outside the case; A second metal plate spaced apart from the first metal plate with a gap therebetween and bonded to the electrode tab; Formed on a portion of the surfaces of the first metal plate and the second metal plate, wherein at least the electrode tab of a surface of an opposite end of each of the first metal plate and the second metal plate and a surface located inside the case; A coating layer formed in a region other than the surface to be bonded with the coating layer; And a metal bridge made of a material having a melting point lower than that of the first metal plate and the second metal plate and embedded in the gap so that the end is not exposed.

According to an aspect of the present invention, when an overcurrent flows through the electrode lead, the metal bridge having a relatively low melting point is broken, thereby overcurrently flowing in the secondary battery.

According to another aspect of the present invention, since the nickel coating layer is not formed in the region where the metal bridge occupies in the metal plate and the metal plate and the metal bridge are joined, the increase in resistance due to the presence of the metal bridge may be limited to a negligible level. In addition, there is no substantial change in the overall size and shape of the electrode leads.

According to another aspect of the present invention, the tensile strength is improved due to the excellent mechanical properties of the metal bridge and the large contact area between the metal plate and the metal bridge.

According to another aspect of the present invention, since the nickel coating layer is not formed in the region where the electrode lead and the electrode tab are bonded, not only the bonding strength between the electrode lead and the electrode tab is improved but also the contact resistance is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given below, serve to further the understanding of the technical idea of the invention. And should not be construed as limiting.
1 is a circuit diagram for explaining an arrangement structure and an operation mechanism of a fuse element in a configuration of a protection circuit coupled to a battery module.
2 is a cross-sectional view showing a secondary battery according to the present invention.
3 is an enlarged partial cross-sectional view of region A of FIG. 2.
4 and 5 are partial cross-sectional views showing a modified form of the electrode lead shown in FIG.
6 is a graph showing an external short-circuit test result for a secondary battery to which an electrode lead according to the present invention is applied as a negative electrode lead.
7 is a graph showing the results of the output characteristics test for the secondary battery to which the electrode lead according to the present invention is applied as a negative electrode lead.
8 is a graph showing the resistance characteristics test results for the secondary battery to which the electrode lead according to the present invention is applied as a negative electrode lead.
9 is a graph showing the tensile strength test results for the electrode lead according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It is to be understood that equivalents and modifications are possible.

Referring to Figure 2 will be described a schematic structure of a secondary battery 100 according to the present invention.

2 is a cross-sectional view showing a secondary battery according to the present invention.

2, the secondary battery 100 according to the present invention includes an electrode assembly 10, a case 20, a negative electrode lead 30, a positive electrode lead 40, and a sealing tape T.

The electrode assembly 10 is a stacked electrode assembly or jelly-roll electrode assembly formed by interposing a separator 13 between a cathode plate 11 and an anode plate 12 that are stacked one time or repeatedly. Can be. The negative electrode plate 11 has a structure in which a negative electrode active material is coated on at least one side of the negative electrode current collector, and the positive electrode plate 12 has a structure in which a positive electrode active material is coated on at least one side of the positive electrode current collector.

An end portion of the negative electrode current collector is provided with a negative electrode tab 11a formed by not being coated with the negative electrode active material, and an end portion of the positive electrode current collector is provided with a positive electrode tab 12a formed by not being coated with the positive electrode active material. In the case where the electrode plates 11 and 12 are repeatedly stacked, each of the plurality of electrode tabs 11a and 12a is gathered into one through the primary welding, and then the cathode through the secondary welding performed by ultrasonic welding or the like, respectively. It is bonded to the lead 30 and the anode lead 40.

In the drawings of the present invention, only the case where the electrode tabs 11a and 12a extend in opposite directions to each other is illustrated, but the present invention is not limited thereto. That is, it is apparent that each of the electrode tabs 11a and 12a may extend in the same direction according to the arrangement direction of the electrode plates 11 and 12.

The case 20 may be formed of an aluminum pouch film having a heat adhesive layer formed on an inner surface of the electrode assembly 10 facing the outer surface of the electrode assembly 10. The case 20 may be sealed by being heat-sealed along an edge while accommodating the electrode assembly 10. The sealed case 20 may be a liquid, solid, or gel type according to the type of the secondary battery 100. Is filled with electrolyte.

The electrode leads 30 and 40 are made of a thin plate-like metal, and are bonded to the electrode tabs 11a and 12a and drawn out of the case 20, respectively. In the drawings of the present invention, only the case in which the electrode leads 30 and 40 extend in opposite directions to each other is illustrated, but the present invention is not limited thereto. That is, it is apparent that the electrode leads 30 and 40 may extend in the same direction according to the direction in which the electrode tabs 11a and 12a extend.

Meanwhile, at least one of the pair of electrode leads 30 and 40 has an electrode lead to which a metal bridge is applied and a coating layer is not formed on a portion of the metal plate surface (hereinafter, the electrode lead according to the present invention). The specific structure and effects of the electrode lead according to the present invention will be described later in detail with reference to FIG. 3.

The sealing tape T is attached to the circumference of the electrode leads 30 and 40 in the width direction and is interposed between the electrode leads 30 and 40 and the inner surface of the case 20. Is done. The sealing tape T is, for example, at least one material layer selected from polyimide (PI), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and the like. (Single membrane or multiple membranes).

The sealing tape T may serve to prevent a short circuit between the electrode leads 30 and 40 and the metal layer of the case 20 and to improve the sealing force of the case 20. In addition, the sealing tape T may serve to prevent a short circuit caused by contact between the electrode leads 30 and 40 when the electrode leads 30 and 40 extend in the same direction. have.

Next, an electrode lead according to the present invention applied to the secondary battery 100 according to the present invention will be described with reference to FIG. 3.

3 is an enlarged partial cross-sectional view of region A of FIG. 2.

Either or both of the electrode leads 30 and 40 may correspond to the electrode leads according to the present invention. When the electrode lead structure according to the present invention is applied to only one of them, it is more effective to apply to the negative electrode leads. to be. This is because the amount of heat generated in the negative electrode of the secondary battery is generally larger than that of the positive electrode. Hereinafter, for convenience of description, an electrode lead according to the present invention will be described with reference to the negative electrode lead 30.

Referring to FIG. 3, the cathode lead 30 includes a first metal plate 31, a second metal plate 32, a coating layer 33, and a metal bridge 34.

The first metal plate 31 and the second metal plate 32 are thin plate-shaped metals and may be disposed side by side on the same plane with a gap therebetween. The metal plates 31 and 32 are generally made of copper (Cu), but this does not limit the material of the metal plates 31 and 32 of the present invention. Meanwhile, in the case of the anode lead 40, a metal plate made of aluminum (Al) is generally used, but likewise, the material of the metal plate constituting the anode lead 40 of the present invention is not limited thereto.

The width d of the gap is directly related to the increase and decrease of the current path through the metal bridge 34, and the increase in the width d may be a factor of the increase in the resistance of the electrode lead 10 itself. Therefore, it is preferable that the width d of the gap be as small as possible. However, if the width d of the gap is too small, the flow of current between the first metal plate 31 and the second metal plate 32 may not be blocked even when the metal bridge 34 is melted. In view of this point, the width d of the gap between the metal plates 31 and 32 is formed in the range of about 1 to 100 mu m, preferably about 25 to 45 mu m.

The coating layer 33 is formed on the surfaces of the metal plates 31 and 32 so that the surfaces of the metal plates 31 and 32 are not exposed to the outside. For example, the coating layer 33 may be made of nickel (Ni). The coating layer 33 prevents the metal plates 31 and 32 from being oxidized in air when the negative electrode lead 30 is applied to the secondary battery and improves the tensile strength of the electrode lead 10. In particular, the coating layer 33 facilitates adhesion between the negative lead 30 and the sealing tape T attached to the negative lead 30 when the negative lead 30 is made of copper. The material of the coating layer 33 may be any material as long as it can perform the above functions.

The coating layer 33 is formed in a portion of the surface of the opposite end of the surface of the metal plate (31, 32), specifically, the surface and the case of the opposite end of each of the metal plate (31, 32) ( 20 may be formed in an area except at least the surface to be bonded to the negative electrode tab 11a among the surfaces located inside.

Since the coating layer 33 is not formed on the surface of the opposite ends of the metal plates 31 and 32, it is possible to prevent the electrical resistance from rising excessively in the vicinity of the bonding area of the metal plates 31 and 32.

In addition, since the coating layer 33 is not formed in a region where the second metal plate 32 and the negative electrode tab 11a are joined, the second metal plate 32 and the negative electrode tab 11a are made of the same metal. In this case, the weldability between the negative lead 30 and the negative electrode tab 11a can be improved and the contact resistance can be reduced.

On the other hand, the surface of the opposite end portion may mean only the first surface S1 located inside the gap, and is a surface extending from the first surface S1 and the first surface S1 and located outside the gap. It may also mean all of the second surfaces S2 located. In addition, the surface located inside the case 20 may be a region other than the region to which the sealing tape T is attached, or may include at least a portion of the region to which the sealing tape T is attached.

The metal bridge 34 is embedded in the gap between the metal plates 31 and 32 to serve as an electrical passage between the first metal plate 31 and the second metal plate 32. The metal bridge 34 covers at least an exposed area of the coating layer 33 out of the surfaces of the metal plates 31 and 32 so that the metal plates 31 and 32 are not exposed to the outside.

The metal bridge 34 may form a structure buried between the gaps through a soldering process or the like. For example, a soldering process is performed using a solder alloy material capable of forming a metal bridge 34 in a region adjacent to a gap among one side surfaces of the metal plates 31 and 32. Then, the solder alloy material is melted and introduced into the gap by capillary action, and as a result, a metal bridge 34 structure is formed between the gaps. The same process is then performed on the other side of the metal plates 31 and 32 so that the metal bridge 34 is joined to the opposite ends of the metal plates 31 and 32, respectively.

The metal bridge 34 has a melting point of approximately 150 to 300 ° C. lower than the melting points of the metal plates 31 and 32, and includes tin (Sn) and copper (Cu) as main components, but is harmful to the environment and human body. It consists of a lead-free alloy that does not contain).

The melting point range of the metal bridge 34 is set in consideration of the overcurrent level to be blocked. If the melting point of the metal bridge 34 is lower than 150 ° C., the metal bridge 34 may be melted even when a normal current flows through the negative electrode lead 30. For example, when the negative electrode lead 30 is used in a secondary battery for an electric vehicle, when the melting point is lower than 150 ° C., the metal bridge 34 may be melted by a rapid charge / discharge current.

In addition, when the melting point of the negative electrode lead 30 is higher than 300 ° C., the blocking of overcurrent is not effectively performed, and thus there is a problem in that the effect of using the negative electrode lead 30 to which the metal bridge 34 is applied is virtually eliminated.

Tin among the components of the metal bridge 34 affects the melting point and the characteristics of the metal bridge 34. The content of tin is adjusted in the range of about 80 wt% or more, preferably in the range of about 85 to 98 wt%, so that the metal bridge 34 has a melting point in the range of about 150 to 300 ° C. and good tensile strength. The copper functions to improve the electrical conductivity of the negative electrode lead 30, and in view of this function, the copper content is controlled in the range of about 2 to 20 wt%, preferably in the range of about 4 to 15 wt%. do. Here, the wt% is the same as a unit based on the weight of the entire material constituting the metal bridge 34.

As described above, by adjusting the tin and copper contents to have an appropriate range, not only can the tensile strength of the metal bridge 34 be improved, but the resistance increase of the negative electrode lead 30 by the metal bridge 34 can be increased by several percent. It can be suppressed low within.

The metal bridge 34 may further include a metal having good electrical conductivity, such as nickel (Ni), silver (Ag), zinc (Zn), as an additional alloy component, in addition to tin and copper in order to have more improved physical properties. The content of the additional alloy component is preferably about 0.01 to 10 wt% based on the total weight of the material.

As described above, the negative electrode lead 30 applied to the secondary battery 100 according to the present invention is not exposed to the outside of the surface of the metal plates 31 and 32, particularly the surface of the region where the metal bridge 34 is formed. At the opposite ends of the metal plates 31 and 32, the coating layer 33 is not formed. Therefore, the negative electrode lead 30 may have a high tensile strength while maintaining low electrical resistance at the junction portions of the metal plates 31 and 32.

In addition, the negative electrode lead 30 applied to the secondary battery 100 according to the present invention may improve weldability by having a structure in which a coating layer 34 is not formed in a region bonded to the negative electrode tab 11a. In addition, the contact resistance can be reduced.

4 and 5, the opposite ends of the metal plates 31 and 32 may be formed as shown in FIG. 3 except when the opposite surfaces, that is, the first surface S1 have a flat surface shape parallel to each other. It may have various shapes, and accordingly, the metal bridge 34 may also have various shapes.

The structure shown in FIG. 4 differs from the structure shown in FIG. 3 in that the first surface S1 of each of the metal plates 31 and 32 has a shape of inclined surfaces tapered in opposite directions to each other. The structure shown in FIG. 5 differs from the structure shown in FIG. 3 in that the first surface S1 of each of the metal plates 31 and 32 has a shape which protrudes substantially convex in a direction facing each other.

4 and 5 have a larger contact area between the metal bridge 34 and the metal plates 31 and 32 as compared with the structure shown in FIG. Not only is the effect of strengthening the coupling force between the bridges 34, but also the effect of reducing the contact resistance.

In the present invention, the shapes of the opposite ends of the metal plates 31 and 32 are described using the structure shown in FIGS. 3 to 5 as an example, but the present invention is not limited thereto. That is, the shape of the end portion is when the first surface (S1) is inclined surface shape tapered in the same direction, when the concave shape in the inner direction of the metal plate (31, 32) or when the peak and valley are repeated shape, etc. Obviously, it can have various shapes.

Excellent performance of the secondary battery 100 according to the present invention is shown in the graph shown in Figures 6 to 9 derived according to the experimental example.

6 to 8 are graphs illustrating an external short test result, an output characteristic test result, and a resistance test result for the secondary battery to which the electrode lead according to the present invention is applied as a negative electrode lead, respectively, and FIG. 9 is an electrode lead according to the present invention. This graph shows the results of tensile strength tests for.

The negative electrode lead 30 used in the experiment was a 0.3 mm thick copper plate 31 and 32 having a nickel coating layer 33 and a metal bridge containing 89 wt% tin, 10 wt% copper, and 1 wt% nickel ( 34 is applied, the width of the gap d (see FIG. 3) is 35 μm, the maximum width W1 (see FIG. 3) of the metal bridge 34 is 6 μm, and the distance between the ends of the coating layer 34 ( W2) used was 4.5 micrometers.

On the other hand, the negative electrode lead applied to the secondary battery according to the comparative example is a negative electrode lead applied to the secondary battery according to the embodiment, except that the metal bridge 34 is not applied and the nickel coating layer is formed on the entire surface of the copper plate ( The same as 30) was used.

Referring to the result of the external short circuit shown in FIG. 6, when the overcurrent 1170A flows due to an external short circuit, the secondary lead 100 is negatively charged in a state in which the temperature of the secondary battery 100 does not substantially increase. ) Is surely broken within a few seconds, the phenomenon that the secondary battery 100 is overheated does not occur. 7 and 8, the output and resistance values according to the state of charge (SOC) of the secondary battery 100 according to the embodiment are the secondary batteries according to the comparative example. Compared with, the difference was within 2% which is the error range of the conventional cell.

The result is that the surfaces of the metal plates 31 and 32 are not exposed to the outside, but the cathode tabs 11a and the structure in which the coating layer 33 is not formed at opposite ends of the metal plates 31 and 32 are formed. This is due to the structure in which the nickel coating layer is not formed on the surface of the negative electrode lead 30 to be bonded.

Referring to the tensile strength test result shown in FIG. 9, the negative electrode lead 30 was gradually increased as the tensile force applied increased and then fractured when a tensile force of about 120 (lbf) was applied. This figure is larger than a general negative lead, i.e., a negative lead made of a single copper plate, and has excellent mechanical properties of the tin-copper alloy constituting the metal bridge 34 and the copper plates 31 and 32 and the metal. This is due to the large contact area between the bridges 34.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the details thereof and that various changes and modifications will be apparent to those skilled in the art. And various modifications and variations are possible within the scope of the appended claims.

100: secondary battery 10: electrode assembly
11: cathode plate 11a: cathode tab
12: anode plate 12a: anode tab
13: separator 20: case
30: negative electrode lead 31: first metal plate
32: second metal plate S1: first surface
S2: second surface 33: coating layer
34: metal bridge 40: anode lead
T: sealing tape

Claims (19)

An electrode assembly having an electrode tab; A case for accommodating the electrode assembly; And a pair of electrode leads bonded to the electrode tabs and drawn out of the case.
At least one of the pair of electrode leads,
A first metal plate positioned outside the case;
A second metal plate spaced apart from the first metal plate with a gap therebetween and bonded to the electrode tab;
Formed on a portion of the surfaces of the first metal plate and the second metal plate, wherein at least the electrode tab of a surface of an opposite end of each of the first metal plate and the second metal plate and a surface located inside the case; A coating layer formed in a region other than the surface to be bonded with the coating layer; And
And a metal bridge made of a material having a lower melting point than the first metal plate and the second metal plate and embedded in the gap so that the end portion is not exposed. The method of claim 1,
The surface of the end portion
And a first surface located inside the gap. 3. The method of claim 2,
The surface of the end portion
And a second surface positioned outside the gap as a surface extending from the first surface. The method of claim 1,
The first metal plate and the second metal plate may be formed of a metal,
Secondary battery, characterized in that located side by side on the same plane. The method of claim 1,
The first metal plate and the second metal plate may be formed of a metal,
A secondary battery comprising aluminum (Al) or copper (Cu). The method of claim 1,
The coating layer,
A secondary battery comprising nickel (Ni). The method of claim 1,
The metal bridge,
A secondary battery comprising tin (Sn) and copper (Cu). The method of claim 7, wherein
The content of tin is 80 wt% to 98wt%,
The copper content is a secondary battery, characterized in that 2 wt% to 20wt%. 9. The method of claim 8,
The metal bridge,
A secondary battery further comprising at least one additional metal selected from nickel (Ni), zinc (Zn), and silver (Ag). 10. The method of claim 9,
The content of the additional metal,
Secondary battery, characterized in that from 0.01wt% to 10wt%. The method of claim 1,
The metal bridge has a melting point of 150 ℃ to 300 ℃ secondary battery. The method of claim 1,
The width of the gap is a secondary battery, characterized in that 25㎛ to 45㎛. The method of claim 1,
The electrode lead including the first metal plate, the second metal plate, the coating layer, and the metal bridge is a cathode lead,
The first metal plate and the second metal plate is a secondary battery, characterized in that made of copper. The method of claim 1,
The opposite surface of each of the first metal plate and the second metal plate has a flat surface form parallel to each other. The method of claim 1,
The opposite surface of each of the first metal plate and the second metal plate has a shape of the inclined surface tapered in the opposite direction to each other. The method of claim 1,
The opposite surface of each of the first metal plate and the second metal plate has a shape convexly protruding in a direction toward each other. The method of claim 1,
And a sealing tape attached to the electrode lead and interposed between the electrode lead and the inner surface of the case. 18. The method of claim 17,
The sealing tape
Secondary battery, characterized in that attached to the surface of the coating layer. An electrode lead of any one of a pair of electrode leads bonded to an electrode tab provided in an electrode assembly and drawn out of a case accommodating the electrode assembly,
A first metal plate positioned outside the case;
A second metal plate spaced apart from the first metal plate with a gap therebetween and bonded to the electrode tab;
Formed on a portion of the surfaces of the first metal plate and the second metal plate, wherein at least the electrode tab of a surface of an opposite end of each of the first metal plate and the second metal plate and a surface located inside the case; A coating layer formed in a region other than the surface to be bonded with the coating layer; And
And a metal bridge made of a material having a melting point lower than that of the first metal plate and the second metal plate and embedded in the gap so that the end is not exposed.

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