KR101849757B1 - Secondary Battery Including an Electrode Lead Made of a Combination of Metal Layers Having Different Resistance Values - Google Patents

Abstract

The present invention relates to a jelly-roll type electrode assembly (" jelly-roll type electrode assembly ") in which a cathode including a cathode active material coating portion on at least one surface of a cathode current collector and a cathode including an anode active material coating portion on at least one surface of the anode current collector, Roll ") and an electrolyte solution are embedded in the battery case, and at least one of the positive electrode lead bonded to the positive electrode uncoated portion and the negative electrode lead bonded to the negative electrode uncoated portion is bonded to the electrode uncoated portion and / A first metal layer used for bonding and a second metal layer having a lower resistance than the first metal layer;

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a secondary battery including an electrode lead composed of metal layers having different resistance values,

[0001] The present invention relates to a secondary battery having a novel structure, and more particularly, to a secondary battery having a novel structure. More particularly, the present invention relates to a secondary battery comprising a positive electrode collector including a positive electrode active material coating portion on at least one surface of a positive electrode collector and a negative electrode including a negative electrode active material coating portion on at least one surface of the negative electrode collector. (&Quot; jelly-roll ") wound around the positive electrode uncoated portion and at least one of the positive electrode leads coupled to the positive electrode uncoated portion and the negative electrode lead coupled to the negative electrode non- A first metal layer used for bonding to the electrode uncoated portion and / or for bonding to the battery case, and a second metal layer having a lower resistance than the first metal layer.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Many researches have been conducted on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries. .

The secondary battery is classified into a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch-shaped battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet . Among them, the cylindrical battery has a relatively large capacity and is structurally stable.

The electrode assembly incorporated in the battery case is a charge / dischargeable power generating element formed of a laminate structure of a positive electrode / separator / negative electrode. The electrode assembly is composed of a jelly-roll type in which a separator is interposed between a positive electrode and a negative electrode coated with an active material, Sized positive and negative electrodes are stacked in a stacked state in a state in which a separator is interposed therebetween. Among them, the jelly-roll type electrode assembly has an advantage of being easy to manufacture and having a high energy density per weight.

In this regard, Fig. 1 schematically shows a vertical cross-sectional perspective view of a general cylindrical battery.

1, a cylindrical battery 100 includes a cylindrical can 130, a jelly-roll type (wound type) electrode assembly 120 accommodated in the cylindrical can 130, an electrolyte solution injected into the cylindrical can 130, And a top cap 140 having an electrode terminal (for example, a positive electrode terminal;

The electrode assembly 120 includes a positive electrode 121 and a negative electrode 122 and a separator 123 interposed therebetween. The electrode assembly 120 is wound in a round shape. A center pin (Not shown). The center pin 150 is generally made of a metal material to give a predetermined strength and is formed of a hollow cylindrical structure in which a plate material is bent in a round shape. The center pin 150 acts as a channel for fixing and supporting the electrode assembly and a gas for discharging gas generated by an internal reaction during charging, discharging and operation.

On the other hand, the lithium secondary battery has a disadvantage of low safety. For example, when the battery is overcharged to about 4.5 V or more, decomposition reaction of the cathode active material occurs, and dendrite growth of lithium metal at the cathode and decomposition reaction of the electrolyte occur. In this process, the decomposition reaction and the many side reactions are rapidly proceeded with heat accompanied by heat, and the ignition and explosion of the battery may be caused.

In order to solve this problem, a general cylindrical battery includes a current interrupting device (CID) and a safety vent for interrupting the current during abnormal operation of the battery and relieving the internal pressure, And is mounted in a space between the top caps 140.

Specifically, referring to FIG. 2, the top cap 10 is formed with a protruding anode terminal, and an exhaust port is formed. In the lower part of the top cap 10, A positive temperature coefficient element (20), a safety vent (30) which has a shape protruding downward in a normal state and discharges the gas when the pressure rises upward when the pressure inside the battery rises, and a safety vent (30) And a connection plate 50 coupled to the vent 30 and having a lower end connected to the positive electrode of the electrode assembly 40 are sequentially positioned.

The anode of the electrode assembly 40 is connected to the top cap 10 via the cathode lead 42, the connection plate 50, the safety vent 30 and the PTC element 20, It accomplishes.

On the other hand, since the secondary battery for a power tool must be operated under a harsh environment compared with other batteries, it is important to minimize the heat generated by reducing the internal resistance of the battery. In order to solve such a problem, conventionally, a method of increasing the size of the positive electrode lead or using two negative electrode leads has been devised and applied.

In particular, existing cathode leads use a single material such as nickel and have a single size. A material having a lower resistance than nickel, such as copper, may be used for the negative electrode lead, but it is difficult to apply because it is difficult to secure the processability for welding with the electrode foil or the can.

Therefore, there is a great need for a secondary battery capable of reducing resistance and heat generation during use while fundamentally solving these problems.

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 present inventors have found that at least one of the positive electrode lead bonded to the positive electrode uncoated portion and the negative electrode lead bonded to the negative electrode uncoated portion has a first metal layer used for bonding to the electrode uncoated portion and / The resistance and the heat generation can be reduced by the second metal layer having a low resistance during use of the secondary battery when the secondary battery is constructed so that the resistance of the second metal layer is lower than that of the second metal layer. .

Therefore, the secondary battery according to the present invention comprises a positive electrode including a positive electrode active material coating portion on at least one surface of a positive electrode current collector, and a negative electrode including a negative electrode active material coating portion on at least one surface of the negative electrode current collector, A rolled electrode assembly (" jelly-roll "), and an electrolytic solution are built into the battery case,

At least one of the positive electrode lead bonded to the positive electrode uncoated portion and the negative electrode lead bonded to the negative electrode uncoated portion includes a first metal layer used for bonding to the electrode uncoated portion and / or for bonding to the battery case, And a second metal layer having a low resistance.

Therefore, in the secondary battery according to the present invention, at least one of the positive electrode lead bonded to the positive electrode uncoated portion and the negative electrode lead bonded to the negative electrode uncoated portion is at least one selected from the group consisting of an electrode used for bonding to the electrode non- 1 metal layer and a second metal layer having a relatively lower resistance than the first metal layer so that the first metal layer having a relatively high resistance can secure a predetermined binding force to the electrode non- The resistance of the positive electrode lead and / or the negative electrode lead is reduced by the second metal layer, so that resistance and heat generated in the electrode lead during use of the secondary battery can be reduced.

The battery case may be a cylindrical can, a square can, or a pouch type case depending on the shape. In order to manufacture a cylindrical battery having a relatively large capacity and structurally stable, it is preferable that the cell can be made of a cylindrical can.

In one preferred example, the first metal layer may be welded to the electrode uncoated portion or the battery case. The welding method may preferably be a resistance welding, and the relatively high resistance of the first metal layer provides a high bonding force to the electrode uncoated portion or the battery case in such resistance welding.

The resistance of the second metal layer is preferably 10 to 70% of the resistance of the first metal layer.

Specifically, if the resistance of the second metal layer is less than 10% with respect to the resistance of the first metal layer, it may be difficult to exhibit the desired effect of the present invention. Conversely, if the resistance exceeds 70% Which is undesirable.

For example, the electrode lead made of a combination of the first metal layer and the second metal layer may have a resistance value of 2.0 to 5.0 mΩ as a whole, and this may be a single metal layer having the same cross-sectional area (for example, ) Is about 7.5 mΩ, which is a value obtained by reducing the resistance by about 50%.

The bonding of the first metal layer and the second metal layer is not particularly limited as long as the bonding method can easily achieve bonding between the first metal layer and the second metal layer, but can be achieved by, for example, a dissimilar material bonding method. As a specific example, the dissimilar material bonding method may be a thermal welding method, a rolling method, a chemical bonding method, a laser welding, a spot welding, a plating method, or a coating method.

Meanwhile, the bonding structure of the first metal layer and the second metal layer may be variously configured.

In one preferred embodiment, the first metal layer and the second metal layer may be vertically coupled.

In another preferred embodiment, the first metal layer may be bonded to both sides of the second metal layer.

Generally, a structure in which the positive electrode lead is formed of aluminum or an aluminum alloy and the negative electrode lead is formed of nickel or a nickel alloy is mainly used. However, a negative electrode lead formed of nickel or a nickel alloy has a high resistance of nickel itself, which causes a problem of generating a lot of heat during charging and discharging of the secondary battery. In addition, since the portion where the negative electrode plate and the negative electrode lead are welded and the portion where the negative electrode lead is welded with the aluminum battery case are welded to each other, welding may not be easy. Further, Can be concentrated, which causes a short circuit at a high temperature, resulting in explosion of the secondary battery.

In this regard, in one preferred embodiment, the first metal layer in the positive electrode lead and / or the negative electrode lead of the present invention may be a nickel layer or an aluminum layer, and the second metal layer may be composed of a copper layer or a silver layer, 2 metal layer, it is possible to fundamentally solve the problem that heat generation occurs due to an increase in resistance, unlike the structure of the conventional positive electrode lead or negative electrode lead.

The positive electrode lead and / or negative electrode lead may be formed by a combination of a nickel layer and a copper layer, a combination of a nickel layer and a silver layer, a combination of an aluminum layer and a copper layer, or a combination of an aluminum layer and a silver layer It goes without saying that they can be selectively used.

The positive electrode lead or negative electrode lead may preferably be composed of 5 to 95% of copper and 95 to 5% of nickel, more preferably, the positive electrode lead or negative electrode lead comprises 50% And 50% nickel.

For example, when the nickel layer is formed at a ratio of 5% of the thickness of the entire positive electrode lead or the negative electrode lead, the copper layer may be formed at a thickness ratio of 95%, and conversely, , The copper layer may be formed at a thickness ratio of 5%. Here, if the nickel layer is formed at a thickness ratio of less than 5%, it may be difficult to provide a desired level of bonding force to the electrode uncoated portion, the battery case, and the like. On the other hand, if copper is formed at a thickness ratio of less than 5%, there is a problem that it is difficult to expect a desired resistance reduction effect.

When the nickel layer or the copper layer exceeds the thickness ratio of 95%, the opposite result is obtained, which is also undesirable.

As a specific example, the thickness of the positive electrode lead or the negative electrode lead may be 0.05 to 0.15 mm.

Meanwhile, the thickness of the first metal layer may be the same as the thickness of the second metal layer, or the width of the first metal layer may be the same as the width of the second metal layer, but is not limited thereto Of course.

The present invention also provides a secondary battery that secures electrical insulation and improves safety by attaching an insulating tape to a cathode active material coating interface at a position where the cathode active material coating portion (non-coated portion) and the anode active material coating portion face each other.

In one preferred embodiment, the winding start portion of the positive electrode includes a positive electrode uncoated portion for containing the positive electrode uncoated portion by having the positive electrode active material coating portion on both the top and bottom portions of the positive electrode collector,

The boundary surface of the cathode active material coating portion facing the cathode may include an insulating tape.

In another example, the winding starting portion of the positive electrode includes a positive electrode uncoated portion for containing the positive electrode uncoated portion by having the positive electrode active material coating portion on both the top and bottom portions of the positive electrode collector, The cathode active material coating portion may further include a cathode active material coating portion on at least one surface of the anode uncoated portion and the interface of the cathode active material coating portion facing the cathode may include an insulating tape.

On the other hand, the insulating tape is not particularly limited as long as it has an excellent insulating property, and for example, a material which is not thermally shrunk to 200 DEG C is preferable. In addition, if a material that is stretched and contracted slightly upon receiving heat is used, even if a problem occurs in the separation membrane positioned between the electrodes, the part can be solved.

The insulating tape may be at least one selected from the group consisting of polyimide tape, acetate tape, glass cloth tape, polyester tape, polyphenylenesulfide (PPS), and polypropylene, A polyethylene terephthalate film is preferable.

The thickness of the insulating tape is preferably 10 to 100 mu m.

Meanwhile, the combination of the first metal layer and the second metal layer can be achieved by various methods.

As one example, the first metal layer and the second metal layer may be bonded to the electrode uncoated portion in a pre-bonded state, and such a bonding method is preferable from the viewpoint of manufacturing processability.

As another example, the first metal layer and the second metal layer may be bonded together in the process of bonding to the electrode uncoated portion.

The present invention also provides a power tool comprising the secondary battery as a power source.

Particularly, in the case of a power tool, a secondary battery used as a power source for such a power tool is preferably a structure having a small internal resistance because it is used for a work with many vibrations.

Therefore, unlike the conventional secondary battery, the secondary battery according to the present invention can be easily used for a power tool because the electrode lead has a low resistance.

As described above, in the secondary battery according to the present invention, at least one of the positive electrode lead coupled to the non-conductive portion of the positive electrode and the negative electrode lead coupled to the non-conductive portion of the negative electrode, The first metal layer used for bonding and the second metal layer having a lower resistance than the first metal layer are combined with each other to provide a predetermined bonding force to the electrode uncoated portion or the battery case, The occurrence of resistance and heat generation at the middle electrode lead portion can be greatly reduced.

1 is a vertical cross-sectional perspective view of a conventional cylindrical battery;
Figure 2 is a partial cross-sectional perspective view of Figure 1;
3 is a partial horizontal cross-sectional schematic view of a jelly-roll type electrode assembly according to an embodiment of the present invention before winding the jelly-roll type electrode assembly;
4 is a perspective view of the positive electrode lead and the negative electrode lead of FIG. 3;
5 is a perspective view of a cathode lead and a cathode lead according to another embodiment of the present invention;
Figures 6 and 7 are partial horizontal cross-sectional schematic views before reeling the jelly-roll type electrode assembly according to various embodiments 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 partial horizontal sectional schematic view of a jelly-roll type electrode assembly according to an embodiment of the present invention, and FIG. 4 is a perspective view of a cathode lead and a cathode lead of FIG. 3 .

The cylindrical battery includes an anode 152 including a cathode active material coating portion 155 on both surfaces of a cathode current collector 151 and an anode active material coating portion 156 on both surfaces of the anode current collector 153. [ A jelly-roll type electrode assembly 200 in which a negative electrode 154 including a separator 142 interposed therebetween is embedded in a cylindrical can (not shown).

The positive electrode lead 114 coupled to the positive electrode uncoated portion 158 has a first metal layer 1142 used for bonding to the positive electrode uncoated portion 158 and a second metal layer 1142 having a relatively lower resistance than the first metal layer 1142 The second metal layer 1144 is vertically coupled by rolling and the negative electrode lead 112 coupled to the negative electrode uncoated portion 157 is bonded to the first metal layer 1122 used for bonding to the negative electrode non- And a second metal layer 1124 having a resistance lower than that of the first metal layer 1122 are vertically coupled by rolling.

The first metal layer 1122 of the negative electrode lead 112 is coupled to the cathode uncoated portion 157 in a resistance welding manner and the resistance of the second metal layer 1124 is about 50% It has a size.

The first metal layer 1142 of the positive electrode lead 114 is coupled to the positive electrode uncoated portion 158 in a resistance welding manner and the resistance of the second metal layer 1144 is about the resistance of the first metal layer 1142 It has a size of 50%.

On the other hand, the positive electrode lead 114 and the negative electrode lead 112 are made of 50% copper and 50% nickel on the basis of the thickness, and the thickness of the first metal layers 1142 and 1122 is larger than that of the second metal layers 1144 and 1124 And the thickness of the second insulating layer is the same as the thickness of the second insulating layer.

The widths of the first metal layers 1142 and 1122 are equal to the widths of the second metal layers 1144 and 1124. The first metal layers 1142 and 1122 are nickel layers or aluminum layers, The second metal layers 1144 and 1124 are composed of a copper layer or a silver layer.

The first metal layers 1142 and 1122 and the second metal layers 1144 and 1124 are coupled to the positive electrode uncoated portion 114 and the negative electrode uncoated portion 112 in a state where they are combined in advance.

As described above, since the structure of FIG. 4 is an exemplary structure, it is needless to say that a multilayer structure such as a first metal layer (a) -second metal layer (b) -first metal layer (c) is also possible. It goes without saying that the components, thicknesses, widths, and the like of the first metal layer (a) and the first metal layer (c) may not be the same in this structure.

5 is a perspective view illustrating a cathode lead and a cathode lead according to another embodiment of the present invention.

5, the positive electrode lead 114a and the negative electrode lead 112a are coupled to the first metal layers 1142a and 1122a on both sides of the second metal layers 1144a and 1124a, respectively.

The thickness and width of the first metal layers 1142a and 1122a are formed to be the same as the thickness and width of the second metal layers 1144a and 1124a.

Figs. 6 and 7 show partial horizontal cross-sectional schematic views before winding the jelly-roll type electrode assembly according to various embodiments of the present invention.

Referring to these drawings, in the jelly-roll type electrode assembly 200a of FIG. 6, the winding start portion of the anode 252 has cathode active material coating portions 220a and 220b on both the top and bottom of the cathode current collector 258 And includes a positive electrode uncoated portion 258 'for mounting the positive electrode lead 214 only at the winding end portion of the positive electrode 252. [

The insulating tapes 216a and 216b are located at the winding end portion of the anode 252 and are attached to the interface of the cathode active material coating portion 220a facing the cathode 254. [

The negative electrode 254 includes negative electrode active material coating portions 240a and 240b on both sides of the negative electrode current collector 256 and a negative electrode uncoated portion 256 that does not include the negative electrode active material coating portion on the winding end portion of the negative electrode current collector 256 'Are connected to a negative electrode lead 212 for connection to an external terminal.

The separators 242a and 242b are designed to extend longer than the ends of the cathodes 254 so that the cathodes 254 are blocked even if the separators 242a and 242b are contracted by heat.

The negative electrode active material coating portion 240a on the negative electrode current collector 256 which is the winding termination portion is disposed on the positive electrode active material coating interface portion under the positive electrode current collector 258 on the side where the positive electrode lead 214 is provided with the separator 242a therebetween At this time, an insulating tape 216b is added to the cathode active material coating interface to prevent a short circuit between the cathode uncoated portion 258 'and the anode active material coating portion 240a, which are not coated with the cathode active material.

On the other hand, the negative electrode active material coating portion 240b under the negative electrode current collector 256, which is the winding termination portion, is sandwiched between the separator 242b and the positive electrode active material coating 254 on the positive electrode collector 258, An insulating tape 216a is added to the interface of the cathode active material coating to prevent the cathode active material from coming into contact with the anode current collector which is an uncoated portion which is not coated with the anode active material.

In the jelly-roll electrode assembly 200b of FIG. 7, the winding start portion of the anode 252 includes cathode active material coating portions 219c and 219d on both the top and bottom of the cathode current collector 258, And includes a positive electrode uncoated portion for mounting the positive electrode lead 214 only in the positive electrode winding end portion.

The first and second insulating tapes 219a and 219b are attached to the top and bottom surfaces of the cathode active material coating portions 217a and 217b, respectively, .

The first insulating tapes 216a and 216b are attached to the interface between the cathode 254 and the cathode active material coating portions 219c and 219d at the anode winding end portion, respectively.

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 (14)

A positive electrode comprising a positive electrode active material coating portion on at least one surface of a positive electrode collector, and a negative electrode including a negative electrode active material coating portion on at least one surface of the negative electrode collector, wherein the negative electrode is wound with a separator interposed therebetween (jelly- ) And an electrolytic solution are embedded in the battery case,
At least one of the positive electrode lead coupled to the positive electrode uncoated portion and the negative electrode lead coupled to the negative electrode uncoated portion comprises a first metal layer and a second metal layer used for bonding to the electrode uncoated portion and for bonding to the battery case, The metal layer has a lower resistance than the first metal layer;
A first metal layer is coupled to both sides of the second metal layer on the same plane, and the first metal layer and the second metal layer are coupled together to the electrode uncoated portion and the battery case;
Wherein a resistance of the second metal layer is 10 to 70% of a resistance of the first metal layer, the thickness of the first metal layer is the same as the thickness of the second metal layer;
Wherein the first metal layer and the second metal layer can be selectively used in combination of a nickel layer and a silver layer, a combination of an aluminum layer and a copper layer, or a combination of an aluminum layer and a silver layer. The secondary battery according to claim 1, wherein the battery case is a cylindrical can. The secondary battery according to claim 1, wherein the first metal layer is welded to the electrode uncoated portion or the battery case. The secondary battery according to claim 1, wherein the coupling of the first metal layer and the second metal layer is achieved by a dissimilar material bonding method. 5. The secondary battery according to claim 4, wherein the dissimilar material bonding method is a thermal welding method, a rolling method, a chemical bonding method, a laser welding, a spot welding, a plating method, or a coating method. delete delete delete The secondary battery according to claim 1, wherein the thickness of the positive electrode lead or the negative electrode lead is 0.05 to 0.15 mm. The method as claimed in claim 1, wherein the winding start portion of the positive electrode includes a positive electrode uncoated portion for both the upper and lower portions of the positive electrode collector so as not to include the positive electrode uncoated portion,
And an insulating tape is disposed on an interface of the cathode active material coating portion facing the cathode and located at the cathode winding end portion. The method as claimed in claim 1, wherein the winding start portion of the positive electrode includes a positive electrode uncoated portion for both the upper and lower portions of the positive electrode collector so as not to include the positive electrode uncoated portion,
Further comprising a positive electrode active material coating portion on at least one side of the end portion of the positive electrode uncoated portion and an insulating tape at an interface between the positive electrode winding end portion and the positive electrode active material coating portion facing the negative electrode. The secondary battery according to claim 1, wherein the first metal layer and the second metal layer are coupled to the electrode non-conductive portion in a state where the first metal layer and the second metal layer are coupled in advance. The secondary battery according to claim 1, wherein the first metal layer and the second metal layer are bonded together in the process of bonding to the electrode non-conductive portion. A power tool comprising a secondary battery according to any one of claims 1 to 5 and 9 to 13 as a power source.

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