KR20120048404A - Secondary battery including fuse-inserted electrode lead - Google Patents

Abstract

PURPOSE: A pouch type secondary battery equipped with fuse installation position is provided to prevent from separately blocking of excessive current by disconnecting electrode lead in a case of excessive current occurrence. CONSTITUTION: A pouch type secondary battery equipped with fuse installation position comprises a fuse connection part(32) which connects at least 2 of lead pieces(30) and adjacent lead pieces(31), a cell assembly in which the electrode lead is electrically connected, and a pouch case which seals the cell assembly so that the fuse connection part can be exposed to outside. The fuse connection part is combined with end of the lead piece by welding. The welding is either laser welding or ultrasonic welding. The width of the fuse connection part is smaller than the width of the lead piece.

Description

Secondary battery having a fuse-integrated electrode lead {Secondary battery including fuse-inserted electrode lead}

The present invention relates to a secondary battery, and more particularly, to a secondary battery having an electrode lead in which a fuse is integrally coupled.

In general, a secondary battery, unlike a primary battery that cannot be charged, means a battery that can be charged and discharged, and is widely used in electronic devices such as mobile phones, notebook computers, camcorders, and electric vehicles. In particular, the lithium secondary battery has an operating voltage of about 3.6V, and has about three times the capacity of a nickel-cadmium battery or a nickel-hydrogen battery, which is widely used as a power source for electronic equipment, and has a high energy density per unit weight. The degree is increasing rapidly.

Such lithium secondary batteries mainly use lithium-based oxides and carbon materials as positive electrode active materials and negative electrode active materials, respectively. The lithium secondary battery includes a cell assembly in which unit cells having a structure in which a positive electrode plate and a negative electrode plate coated with such a positive electrode active material and a negative electrode active material are respectively disposed with a separator interposed therebetween, and an exterior case for sealing and storing the cell assembly together with an electrolyte solution. Equipped.

Lithium secondary batteries are classified into can-type secondary batteries in which cell assemblies are embedded in metal cans and pouch-type secondary batteries in which cell assemblies are embedded in pouch cases of aluminum laminate sheets, depending on the shape of the outer case.

Pouch-type secondary batteries have been in the spotlight as power sources of electric vehicles and hybrid vehicles because of their low manufacturing cost, high energy density, and easy construction of large-capacity battery packs through series or parallel connection.

The pouch type secondary battery has a structure in which a cell assembly to which an electrode lead made of a plate shape is connected is sealed together with an electrolyte solution in a pouch case. A portion of the electrode lead is exposed outside the pouch case, and the exposed electrode lead is used to electrically connect to a device on which the secondary battery is mounted, or to electrically connect the secondary batteries to each other.

On the other hand, the secondary battery is used in combination with the protection circuit to protect the secondary battery from abnormal situations such as overcharge, overdischarge, overheat, overcurrent. Among the various causes of the abnormal situation, overcurrent mainly occurs when a short circuit occurs in the charging device inside or outside the secondary battery. When an overcurrent flows in the secondary battery, the temperature of the secondary battery rapidly increases due to resistance heating. Then, the gas is generated from the electrolyte to increase the internal pressure of the outer case, and when the inner pressure exceeds the sealing strength of the outer case, the secondary battery may explode or lead to a fire accident. Therefore, a fuse element for irreversibly disconnecting the main line through which charging or discharging current flows is used as a protection circuit of a secondary battery.

1 is a circuit diagram for describing an arrangement structure and an operation mechanism of a fuse element among the secondary battery protection circuits.

As shown in the figure, the secondary battery protection circuit to protect the secondary battery in the event of an overcurrent fuse element 10, the sense resistor 20 for sensing the overcurrent, the overcurrent by monitoring the occurrence of overcurrent fuse element 10 It includes a microcontroller 30 for operating the switch and the switch 40 for switching the inflow of the operating current to the fuse element (10).

The fuse element 10 is installed on a main line connected to the outermost terminal of the cell assembly 20. The main line is the wiring through which the charging or discharging current flows. In the figure, the fuse element 10 is shown installed in a high potential line Pack +.

The fuse element 10 is a three-terminal element component, and two terminals are connected to a main line through which charging or discharging current flows, and one terminal is connected to the switch 40. The inside includes a fuse 11 connected in series with a main line and having a fusion at a specific temperature, and a resistor 12 for applying heat to the fuse 11.

 The microcontroller 30 periodically detects the voltage across the sense resistor 20 to monitor whether overcurrent occurs, and turns on the switch 40 when it is determined that a high current has occurred. Then, the current flowing in the main line is bypassed to the fuse element 10 and applied to the resistor 12. Accordingly, the joule heat generated by the resistor 12 is conducted to the fuse 11 to raise the temperature of the fuse 11, and when the temperature of the fuse 11 rises to the melting temperature, the fuse 11 is melted, thereby causing the main heat. The track is irreversibly disconnected. If the main line is disconnected, the overcurrent no longer flows, thus eliminating the problem caused by the overcurrent.

However, the above-described prior art has various problems. That is, if a failure occurs in the microcontroller 30, the switch 40 is not turned on even in a situation in which an overcurrent occurs. In this case, since the current does not flow into the resistor 12 of the fuse element 10, there is a problem that the fuse element 10 does not operate. In addition, a space for arranging the fuse element 10 in the protection circuit is separately required, and a program algorithm for controlling the operation of the fuse element 10 must be loaded in the microcontroller 30. Therefore, there is a disadvantage in that the space efficiency of the protection circuit is lowered and the load of the microcontroller 30 is increased.

On the other hand, in order to configure a large capacity battery pack using a pouch type secondary battery, it is necessary to electrically connect a plurality of batteries.

2 is a view illustrating a process of connecting two pouch-type secondary batteries in series.

As shown in the figure, the pouch type secondary battery 20 includes an electrode lead 22 drawn out of the pouch case 21. The electrode lead 22 is divided into a positive electrode lead and a negative electrode lead according to electrical polarity, and is electrically connected to the cell assembly 21 sealed in the pouch case 23. That is, the positive lead is electrically connected to the positive electrode plate of the cell assembly 21, and the negative electrode lead is electrically connected to the negative electrode plate of the cell assembly.

There may be a number of ways in which the pouch-type secondary battery 20 is connected in series. FIG. 2 illustrates the bending of the electrode lead 22 and then welding the bent electrode lead 22 using the connection bar 24. It shows how to do it. This method has an advantage that no mechanical stress is applied to the secondary battery 20 as compared with the method of directly welding the electrode lead 22. Since the electrode lead 22 is made of a metal plate having a certain strength, when the electrode lead 22 is directly welded without the connecting bar 24, the electrode lead 22 is bent toward the welding site and thus the bending of the electrode lead 22 is prevented. This is because tensile stress is generated. However, in the connection method using the connection bar 24, tensile stress due to bending of the electrode lead 22 may be temporarily applied to the cell assembly 21 in the process of bending the electrode lead 22 having mechanical strength. When tensile stress is applied, not only the adhesive force formed on the joint surface of the electrode lead 22 and the pouch case 23 can be weakened, but also the contact force of the electrode lead 22 and the cell assembly 21 can be weakened to increase the contact resistance. There is a possibility. In order to solve this problem, it is necessary to improve the structure of the electrode lead that can prevent the tensile stress is applied to the cell assembly 21, regardless of the connection method of the electrode lead 22.

The present invention has been made to solve the problems of the prior art as described above, it is an object of the present invention to provide a pouch-type secondary battery that can block the over-current independently of the protection circuit when the over-current is provided by the fuse itself.

Another object of the present invention is to provide a pouch type secondary battery in which a fuse is mounted under design conditions in which a separate space allocation for mounting the fuse is not required.

Still another object of the present invention is to provide a pouch type secondary battery in which a fuse mounting position is designed to prevent tensile stress from being induced even when a plurality of pouch type secondary batteries are electrically connected.

Other objects and advantages of the invention will be described below and will be appreciated by the embodiments of the invention. In addition, the objects and advantages of the present invention can be realized by the configuration and combination of configurations shown in the claims.

Pouch-type secondary battery for achieving the above technical problem, the electrode lead including a fuse connecting portion for connecting at least two lead pieces and the adjacent lead piece arranged in one direction; A cell assembly to which the electrode leads are electrically connected; And a pouch case sealing the cell assembly such that the fuse connection part is exposed to the outside.

According to one aspect of the invention, the fuse connection portion may be coupled by welding with the end of the lead piece. Here, the welding may be laser welding or ultrasonic welding.

According to another aspect of the present invention, the fuse connecting portion may be inserted into a pressing flange bent and extended from both ends of the lead piece to be compressed. Preferably, welding may be made to the pressing portion by the pressing flange.

According to another aspect of the invention, the fuse connecting portion is inserted into the groove formed along the end of the lead piece is compressed. Preferably, the welding is made to the pressing portion of the groove.

Optionally, the width of the fuse connection portion may be smaller than the width of the lead piece. It is also possible that there are two or more fuse connections.

In the present invention, the fuse connecting portion may be selectively provided on the electrode lead corresponding to the positive electrode or the negative electrode. Alternatively, the fuse connection may be provided in both the electrode leads corresponding to the positive electrode and the negative electrode.

According to an aspect of the present invention, since the fuse is mounted on the electrode lead itself, when the overcurrent is generated, the electrode lead is disconnected and thus the overcurrent is blocked.

According to another aspect of the present invention, since the fuse is mounted on the electrode lead itself, there is an advantage of not having to devote a separate space for mounting the fuse.

According to another aspect of the present invention, when a fuse is provided at a point at which the electrode lead is bent, even if a plurality of pouch-type secondary batteries are electrically connected, tensile stress may be prevented.

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 illustrating an operation mechanism of a fuse included in a conventional secondary battery protection circuit.
2 is a perspective view illustrating a state in which two pouch type secondary batteries are electrically connected using a connection bar.
3 is a perspective view showing the structure of an electrode lead according to a first embodiment of the present invention.
4 is a perspective view illustrating a modified example of the electrode lead structure according to the first embodiment.
5 is a perspective view illustrating a structure of an electrode lead according to a second exemplary embodiment of the present invention.
6 is a perspective view illustrating a structure of an electrode lead according to a third exemplary embodiment of the present invention.
7 is a perspective view showing the structure of an electrode lead according to a modification of the present invention.
8 is a perspective view illustrating a structure of an electrode lead according to another modified example of the present invention.
9 is a perspective view showing a state in which the electrode lead is bent once around the fuse connection unit according to the present invention.
10 is a perspective view showing a state in which the electrode lead is bent twice around the fuse connecting portion according to the present invention.
11 is a plan view illustrating an example of a pouch type secondary battery provided with an electrode lead according to the present invention.
12 is a plan view illustrating another example of a pouch-type secondary battery provided with an 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 or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The pouch type secondary battery according to the present invention includes an electrode lead including at least two lead pieces and a fuse connection part connecting the lead pieces, a cell assembly to which the electrode leads are electrically connected, and the fuse connection part exposed to the outside. And a pouch case for sealing the cell assembly with the electrolyte.

Since the main feature of the present invention is in the structure of the electrode lead, the configuration of the present invention will be described in detail with reference to the structure of the electrode lead.

3 is a plan view illustrating an electrode lead structure of the pouch type secondary battery according to the first embodiment of the present invention.

Referring to the drawings, the electrode lead according to the first exemplary embodiment includes an upper lead piece 30, a lower lead piece 31, and a fuse connection part 32 connecting the upper and lower lead pieces 30 and 31. do.

End portions of the upper lead piece 30 and the lower lead piece 31 may be joined to the intermediate fuse connecting portion 32 by laser welding. In this case, since the end of the upper lead piece 30 and the lower lead piece 31 and the end of the fuse connecting portion 32 are directly joined, no step is formed at the joining interface (see A).

As an alternative, the upper lead piece 30 and the lower lead piece 31 may be joined to the fuse connecting portion 32 by ultrasonic welding. In this case, as shown in FIG. 4, a joining structure is formed in which the ends of the upper lead piece 30 and the lower lead piece 31 and the ends of the fuse connecting portion 32 overlap a predetermined width, and are ultrasonically welded at the overlapping portions between the ends. This is done (see B).

The upper lead piece 30 and the lower lead piece 31 are made of a metal plate. The material constituting the metal plate may be one or an alloy thereof selected from the group consisting of aluminum, copper, nickel, stainless steel, titanium, gold, and silver. In addition, although not essential, the surface of the metal plate may be provided with a surface treatment layer surface-treated with carbon, nickel, titanium, silver, or the like. However, the present invention is not limited by the material of the metal plate, so any material known to have excellent conductivity and corrosion resistance may be employed as the material of the metal plate.

The fuse connection part 32 provides a current flow path when a current within the specification of the secondary battery flows through the electrode lead, but when the overcurrent flows through the electrode lead, the resistance heats rapidly rises above the melting point while the temperature rises above the melting point. Is done. When the fuse connector 32 is fused, the electrode lead is irreversibly disconnected.

The present invention prevents the overcurrent from flowing through the secondary battery independently of the overcurrent protection operation of the secondary battery protection circuit by introducing the fuse connecting portion 32 into the electrode lead structure.

Preferably, the fuse connection part 32 may be made of an alloy of lead and tin, or an alloy of lead and tin to which additional components such as zinc, antimony, bismuth, and the like are added. The melting temperature of the fuse connector 32 may be controlled by the composition of the material contained in the alloy, but the present invention is not limited to the specific material of the fuse connector 32.

5 is a perspective view and a plan view illustrating a lead structure of a pouch type secondary battery according to a second embodiment of the present invention.

Referring to FIG. 5, an electrode lead according to the second embodiment may include a fuse connecting portion 32 extending from left and right sides of the upper lead piece 30 and the lower lead piece 31 to the left and right by bending the bent flange 33. It has a mechanically compressed structure after being inserted. In order to improve the bonding strength of the fuse connecting portion 32, the welding of the fuse connecting portion 32 to the pressing flange 33 may be additionally ultrasonic welding to the crimp fixing portion.

The pressurizing flange 33 electrically connects the upper lead piece 30 and the lower lead piece 31 to the fuse connecting part 32 and serves to firmly fix the fuse connecting part 32. Since the shape of the pressing flange 33 is not particularly limited, various other shapes may be adopted in addition to the shape shown in the drawings.

6 is a perspective view and a plan view illustrating a lead structure of a pouch type secondary battery according to a third embodiment of the present invention.

Referring to FIG. 6, in the electrode lead according to the third exemplary embodiment, an end portion of the fuse connection part 32 is inserted into a U-shaped groove 34 formed along the end portions of the upper lead piece 30 and the lower lead piece 31. It has a compressed structure. In order to improve the bonding strength of the fuse connector 32, the fuse connector 32 may be inserted into the U-shaped groove 34 and compressed, and then ultrasonic welding may be further performed.

On the other hand, the width of the fuse connecting portion 32 provided in the electrode lead is preferably substantially the same as the width of the upper lead piece 30 and the lower lead piece 31. However, in some cases, as shown in FIG. 7, the width of the fuse connecting portion 32 is not particularly limited to that of the upper lead piece 30 and the lower lead piece 31. In addition, as illustrated in FIG. 8, at least two fuse connecting portions 32 provided in the electrode lead may be provided. In this case, the number of lead pieces increases to three or more. Even in this case, all of the configurations described in the above-described embodiments may be applied to the method of joining the lead piece and the fuse connecting part 32 and the structure of the joined part. That is, a joining method by welding, a joining method by a crimping flange and a crimping groove, etc. may be applied as it is, and the width of the fuse connecting portion 32 may be the same as or smaller than the width of the lead piece.

More preferably, the position where the fuse connection part 32 is located corresponds to the bending point of the electrode lead. FIG. 9 illustrates an electrode lead structure when the electrode lead is bent once with the fuse connector 32 as the bending point when there is one fuse connector 32. FIG. 10 illustrates an electrode lead structure when the electrode lead is bent twice using the fuse connecting portion 32 as a bending point when the fuse connecting portion 32 is two.

For example, bending of the electrode lead may be performed when the pouch type secondary batteries are connected to each other in series or in parallel using a connection bar. The fuse connection part 32 has an advantage that the deformation of the shape is easy even with a small force because the mechanical strength is not large. Therefore, it is possible to minimize the occurrence of tensile stress in the process of bending the electrode lead, and furthermore, it is possible to prevent the tensile stress from remaining after the bending process is completed.

11 and 12 are plan views illustrating the structure of a pouch type secondary battery having an electrode lead according to the present invention.

As shown in the figure, the electrode lead 50 according to the present invention may be sealed together with the electrolyte solution in the pouch case 52 after the one or more unit cells are coupled to the assembled cell assembly 51. Since the technique of sealing the cell assembly 51 having the electrode lead 50 coupled to the pouch case 52 by heat fusion is widely known, a detailed description thereof will be omitted.

As shown in FIG. 11, the electrode lead structure having the fuse connecting portion 53 may be employed only in either the positive electrode lead or the negative electrode lead, and as shown in FIG. 12, the electrode lead structure may be employed in both the positive electrode lead and the negative electrode lead. It is possible.

The electrode lead 50 is electrically connected to the positive electrode plate and the negative electrode plate included in the cell assembly 51. For the electrical connection, the positive electrode plate and the negative electrode plate may be provided with electrode tabs 55 formed in a structure extending from the positive electrode plate and the negative electrode plate. In this case, the electrode lead 50 may be bonded to the electrode tab 55 through ultrasonic welding, resistance welding, laser welding, conductive adhesive, or the like. An insulating tape 54 may be interposed between the pouch case 52 and the electrode lead 50. The insulating tape 54 improves adhesion between the pouch case 52 and the electrode lead 50 and prevents moisture from penetrating into the pouch case 52 through the electrode lead 50.

According to the configuration of the present invention described above, since the fuse is mounted on the electrode lead itself, when the overcurrent is generated, the electrode lead itself is disconnected, and thus the overcurrent is cut off independently of the secondary battery protection circuit. Therefore, even if the overcurrent blocking function of the secondary battery protection circuit does not operate, it is possible to block the flow of the overcurrent. In addition, since the fuse is mounted on the electrode lead itself, there is an advantage that a separate space is not required for mounting the fuse. Furthermore, when the fuse is provided at the point where the electrode lead is to be bent, even if the electrode lead is bent, it is possible to minimize the occurrence of tensile stress.

The present invention provides a structure of a cell assembly mounted on a pouch, a structure of a unit cell constituting the cell assembly, a type of unit cell, a kind of material used to form the unit cell, a structure and a material of the pouch case, a sealing parameter of the pouch case, and the like. It is obvious to those skilled in the art that the present invention is not limited thereto.

In the above-described embodiment, terms expressed as top, bottom, or top and bottom are merely instrumental concepts for relatively classifying or defining components, and are not used to classify physical configurations in absolute terms. Do.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

21: cell assembly 23: pouch case
22: electrode lead 24: connecting bar
30: upper lead 31: lower lead
32: fuse connection 33: pressurized flange

Claims (11)

An electrode lead including at least two lead pieces arranged in one direction and a fuse connection part connecting the adjacent lead pieces;
A cell assembly to which the electrode leads are electrically connected; And
A pouch type secondary battery comprising a pouch case for sealing the cell assembly such that the fuse connection part is exposed to the outside. The method of claim 1,
The fuse connection portion is a pouch type secondary battery, characterized in that coupled to the end of the lead piece by welding. The method of claim 2,
The welding is a pouch type secondary battery, characterized in that the laser welding or ultrasonic welding. The method of claim 1,
The fuse connecting part is inserted into a pressing flange bent extending from both ends of the lead piece is pouch type secondary battery, characterized in that the compression. The method of claim 4, wherein
Pouch type secondary battery characterized in that the welding is made to the pressing portion by the pressing flange. The method of claim 1,
And the fuse connection part is inserted into a groove formed along an end of the lead piece and pressed. The method of claim 6,
Pouch-type secondary battery, characterized in that the welding is made to the pressing portion of the groove. The method of claim 1,
A pouch type secondary battery, wherein a width of the fuse connection portion is smaller than that of a lead piece. The method of claim 1,
Pouch-type secondary battery, characterized in that two or more fuse connection. The method of claim 1,
The fuse connection part is a pouch type secondary battery, characterized in that selectively provided in the electrode lead corresponding to the positive electrode or the negative electrode. The method of claim 1,
The fuse connection part is a pouch type secondary battery, characterized in that provided in both the electrode lead corresponding to the positive electrode and the negative electrode.

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