KR20140013177A - Secondary battery and electrochemical cell having the same - Google Patents

Abstract

The present invention relates to manufacture of a high-capacity-stack-type polymer battery by improving the availability of an inner space which is not used as an electrode connection part of a polymer battery. According to the present invention, the inner space availability of a battery is improved by arranging a composition consisting of the welding part of an electrode tap and a lead and the sealing part of a packing material in one region. Damage to the packing material can be prevented due to the welding residue pattern of the electrode tap and a lead welding part. The cost of raw materials can be reduced by not using a separate protection tape.

Description

TECHNICAL FIELD [0001] The present invention relates to a secondary battery and an electrochemical device including the secondary battery.

The present invention relates to a structure of a secondary battery capable of improving space utilization.

With the rapid development of the electronics, telecommunications, and computer industries, the rapid development of camcorders, mobile phones, laptops, and the like, the demand for lithium secondary batteries as a power source capable of driving these portable electronic communication devices is increasing day by day.

As technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries capable of meeting various demands have been conducted.

Representatively, there is a high demand for rectangular secondary batteries and pouch secondary batteries, which can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and lithium ion batteries with high energy density, discharge voltage, and output stability in terms of materials. There is a high demand for lithium secondary batteries such as lithium ion polymer batteries.

FIG. 1 schematically shows a general structure of a typical conventional pouch-type secondary battery as an exploded perspective view.

Referring to FIG. 1, the pouch type secondary battery 100 may include an electrode assembly 300, electrode tabs 310 and 320 extending from the electrode assembly 300, and electrodes welded to the electrode tabs 310 and 320. And a battery case 200 accommodating the leads 410 and 420 and the electrode assembly 300.

The electrode assembly 300 is a power generator in which a positive electrode and a negative electrode are sequentially stacked in a state where a separator is interposed therebetween, and has a stack type or a stack / fold type structure. The electrode tabs 310, 320 extend from each pole plate of the electrode assembly 300, and the electrode leads 410, 420 are welded with a plurality of electrode tabs 310, 320 extending from each pole plate, eg, welded. Each is electrically connected to each other, and part of the battery case 200 is exposed to the outside.

In addition, an insulating film 430 is attached to upper and lower portions of the electrode leads 410 and 420 to increase the sealing degree with the battery case 200 and to secure an electrical insulating state. The case 200 is made of an aluminum laminate sheet, provides a space for accommodating the electrode assembly 300, and has a pouch shape as a whole. In the stacked electrode assembly 300 as shown in FIG. 1, a plurality of positive electrode tabs 310 and a plurality of negative electrode tabs 320 may be coupled together to the electrode leads 410 and 420. The upper end is spaced apart from the electrode assembly 300 at predetermined intervals.

A method for welding the electrode tabs 310 and 320 of the secondary battery having the above-described structure with the leads will be described below with reference to FIG. 2.

FIG. 2 is an enlarged view showing only the recesses of the electrode tab 310 and the electrode lead 410 of the electrode assembly of FIG. 1, and the electrode tab 310 and the electrode lead 410, The welding is performed. A lead film 411 is coated on the outer surface of the electrode lead 410 to be welded. In the illustrated electrode assembly 300, as the number of stacked electrode cells increases, the thickness of the gathered portion of the electrode tab 310 increases, and as the welded portion increases in the constant cell dimension, the dimension of the electrode decreases, Resulting in a disadvantage in terms of the simplicity of the battery cell.

3, when only one of the upper sheet 210 and the lower sheet 220 constituting the battery case 200 is molded to insert the electrode assembly, In the same manner as in the case of FIG. 1, the use of the inner space of the battery is maximized.

4, in the case of inserting the electrode assembly 300 and forming the electrode tab 310 from both sides, in the structure for molding both the upper and lower sheets of the battery case, V "shape. In particular, in the case of a large-capacity cell such as an automobile battery, the lead 410 is thick and is broken into a" V "shape, making it difficult to weld.

Patent Registration No. 10-1068618

SUMMARY OF THE INVENTION The present invention has been conceived in order to solve the above-mentioned problems, and an object of the present invention is to provide a structure in which a structure composed of a welding portion of an electrode tab and a lead, The present invention provides a rechargeable battery which can reduce the cost of raw materials by preventing the use of a separate protective tape because it can increase utilization and prevent damage to the packaging material due to residual welding patterns of electrode tabs and lead welds.

As means for solving the above-mentioned problems, the present invention provides a pouch for accommodating an electrode assembly; A welding area where the electrode tab and the lead are welded to the inside of the pouch, a lead film for coating the outside of the lead, and a sealing area of the pouch are overlapped with each other.

According to the present invention, it is possible to arrange the structure composed of the welding portion of the electrode tab and the lead, and the sealing portion of the lead and the packaging material in one region to improve the space utilization inside the battery, It is possible to prevent the packaging material from being damaged and prevent the use of a separate protective tape, thereby reducing the cost of raw materials.

1 illustrates a structure of a general secondary battery.
2 and 3 are conceptual diagrams for explaining the welding process of the electrode tab and the electrode lead in the structure of FIG.
FIGS. 4 and 5 are conceptual diagrams for explaining a process of welding an electrode tab and an electrode tab of a secondary battery accommodating an electrode assembly after forming both sides of a conventional pouch structure. FIG.
6 is a conceptual view for explaining a welding process of an electrode tab and an electrode lead as a preferred embodiment according to the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration and operation according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description with reference to the accompanying drawings, the same reference numerals denote the same elements regardless of the reference numerals, and redundant description thereof will be omitted. The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The present invention is characterized in that a high capacity stacked polymer battery is manufactured by increasing utilization in an internal space that is not used above an electrode connection portion of a polymer battery.

FIG. 5 is a conceptual view for explaining a welding structure of a conventional electrode tab for explaining the gist of the present invention, and FIG. 6 is a conceptual view for explaining a structure according to the present invention.

5, the electrode assembly 300 is housed in a structure for forming both the upper sheet 210 and the lower sheet 220 forming the pouch of the secondary battery, and a plurality of electrode assemblies 300 extending from the plurality of electrode assemblies The ultrasonic welding is performed in the welding area B where the outer electrode lead 410 and the electrode tab part 311 to be gathered are heated. The sealing region A of the upper sheet 210 and the lower sheet 220 which are pouches formed of an aluminum sheet and the lead film 411 coating the electrode leads 410 are formed on the outer side of the welding region B, .

However, in the conventional general welding structure, the welding region B and the sealing region A are continuously arranged in the pouch, and the non-utilized internal space C is formed in the secondary battery, It becomes a constraint to increase the size.

Accordingly, the present invention proposes a secondary battery having the same structure as that shown in FIG.

Referring to FIG. 6, the secondary battery according to the present invention includes an electrode tab portion (hereinafter, referred to as an overlapped electrode tab portion) in which an electrode tab 310 extending from an electrode assembly 300 in which a plurality of battery cells are stacked A lead film 411 for coating the outer surface of the electrode lead 410 and the welding region B where the electrode lead 410 is welded to the electrode lead 410 and the upper sheet 210 being a pouch formed of an aluminum sheet, And the sealing region (A) of the sheet (220) is superimposed. The electrode assembly 300 is a power generation element in which an anode and a cathode are sequentially stacked with a separation membrane interposed therebetween, and is formed of a stacked or stacked / folded structure. The positive and negative tabs extend from the respective electrode plates of the electrode assembly, and the electrode leads are electrically connected to a plurality of positive and negative tabs extending from the respective electrode plates, for example, by welding, Some are exposed.

That is, in the structure of the secondary battery according to the present invention, the welding region (B) and the sealing region (A) can be partially or wholly overlapped as in the structure shown in FIG. That is, the lead film 411, the upper and lower sheets 210 and 220 are sequentially stacked on the upper and lower portions of the welding area A where the overlapped electrode tab part 311 and the electrode lead 410 are welded .

5, the nonuse period is remarkably reduced, and the usable period is increased, so that the capacity of the battery cell can be increased by the utilization period. As compared with the structure of FIG. 5, A capacity increase of about 3 to 5% can be realized.

In addition, in the structure of FIG. 5, the welding protrusion residue is formed due to the welding result of the surface welded to the aluminum pouches 210 and 220 through the ultrasonic welding, Frequent problems arise. In the present invention, the lead film material is formed on the upper portion of the welding portion to protect the welding portion, and the pouch and the sealing are formed thereon. As a result, the insulation failure is remarkably reduced and the pouch can be prevented from being damaged .

Therefore, in the structure shown in Fig. 6, it is preferable that the lead films 411 disposed on the upper and lower surfaces of the welding area B are formed to be longer than the length of the welding area.

It is further preferable that the lead film 411 is partially protruded to the outside of the end portions of the pouches 210 and 220 in order to improve the sealing characteristics and insulation characteristics. In addition, although the structure in which the lead film and the pouches 210 and 220 are directly sealed is illustrated in the illustrated structure, a thermosetting layer may be provided on at least one surface of the lead film. The thermosetting layer formed on the lead film suppresses breakdown of insulation resistance and improves the possibility of penetration of moisture, thereby improving battery safety and battery life.

The thermosetting layer may be formed of at least one thermosetting resin selected from the group consisting of a melamine resin, a phenol resin, a urea resin, an epoxy resin, and a polyurethane. The thermosetting layer is preferably formed to a thickness of 10 to 100 탆 in terms of preventing damage to the pouch and the tab during battery molding.

That is, in the embodiment according to the present invention, the PP film used as the lead film has a characteristic of being vulnerable to heat, so that the position where the lead film is formed is usually such that the upper case and the lower case of the battery case are thermally fused, As a result, high heat or pressure is applied. Therefore, when heat is applied to this portion, the PP film used as the lead film is melted together, resulting in deterioration of the adhesiveness, and water is permeated into this portion, thus posing a problem of battery safety. Accordingly, when a thermosetting layer is included on at least one side of the lead film as in the present invention, even if heat is applied to the tab lead portion, the thermosetting layer is formed mainly from the thermosetting polymer and is transferred to the lower lead film, The problem such as melting of the film does not occur and the lead film can be firmly supported and the electric insulation can be maintained, so that the safety of the battery can be improved.

The electrode assembly according to the present invention may have a structure of a winding type, a stack type, or a stack / folding type structure and constitute a secondary battery. Hereinafter, specific materials and structural features of the components constituting the electrode assembly according to the present invention will be described.

Anode structure

In the present invention, the electrode formed on the base unit is divided into a positive electrode or a negative electrode, and the positive electrode and the negative electrode are prepared by mutually bonding with a separator therebetween. The positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive material, and a binder onto a positive electrode current collector, followed by drying and pressing. If necessary, a filler may be further added to the mixture. This structure is implemented in a sheet form can be applied to the process in the form of mounting on the loading roll.

[Positive collector]

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like on the surface of may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as film, sheet, foil, net, porous body, foam, and nonwoven fabric. In the embodiment according to the present invention described above, the electrode tab may be formed to have the same material as the material of the positive electrode current collector.

[Positive electrode active material]

The cathode active material may be a lithium secondary battery, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _{1 - x} M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3; Formula _{LiMn 2 - x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; and the like, but Fe ₂ (MoO _{4) 3,} but is not limited to these.

The conductive material is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

Cathode structure

The negative electrode is manufactured by coating, drying, and pressing a negative electrode active material on a negative electrode current collector, and optionally, the conductive material, binder, filler, and the like as described above may be further included. This structure is implemented in a sheet form can be applied to the process in the form of mounting on the loading roll.

[Cathode collector]

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics. In the exemplary embodiment according to the present invention, the electrode tab may be formed to have the same material as that of the negative electrode current collector.

[Cathode active material]

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ _x ≦ 1), Li _x WO ₂ (0 ≦ _x ≦ 1), Sn _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me' Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

[Separation membrane]

The separator according to the present invention implements simple lamination by forming a basic unit by a simple lamination process regardless of a folding process or a roll process. In particular, the adhesion of the separator, the positive electrode, and the negative electrode in the laminator is such that the separator sheet itself is melted by heat and adhered to the inside of the laminator. This allows the pressure to be maintained continuously, thereby enabling stable interfacial contact between the electrode and the separator sheet.

As long as the separator interposed between the anode and the cathode of the separator sheet or cell has an insulating property and a porous structure capable of moving ions, the material thereof is not particularly limited, and the separator and the separator sheet may or may not be the same material. It may be.

The separator or separator sheet may be a thin insulating film having high ion permeability and mechanical strength. The separator or separator sheet generally has a pore diameter of 0.01 to 10 mu m, 300 mu m. Examples of the separator or separator sheet include olefin polymers such as polypropylene, which is resistant to chemicals and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane. Preferably, a multilayer film produced by a polyethylene film, a polypropylene film, or a combination of these films, or a film made of polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or poly A polyvinylidene fluoride hexafluoropropylene copolymer or the like, or a polymer film for a gel-type polymer electrolyte.

It is preferable that the separator has an adhesive function by heat fusion in order to form a basic unit cell, and the separator sheet does not necessarily have such a function, but it is preferable to use an adhesive function.

The electrode assembly according to the present invention can be applied to an electrochemical cell that produces electricity by an electrochemical reaction between a positive electrode and a negative electrode. Representative examples of the electrochemical cell include a super capacitor and an ultra capacitor. ), Secondary batteries, fuel cells, various sensors, electrolysis devices, electrochemical reactors, and the like, and secondary batteries are particularly preferred.

The secondary battery has a structure in which the electrode assembly capable of charging and discharging is embedded in a battery case in a state impregnated with an ion-containing electrolyte solution. In one preferred embodiment, the secondary battery may be a lithium secondary battery.

Recently, a lithium secondary battery has attracted much attention as a power source for large devices as well as small mobile devices, and it is desirable to have a small weight when applied to such a field. As one way to reduce the weight of the secondary battery, a structure in which the electrode assembly is incorporated in a pouch type case of an aluminum laminate sheet may be preferable. Since such a lithium secondary battery is known in the art, the description thereof will be omitted.

In addition, as described above, when used as a power source for a medium-to-large device, a secondary battery having a structure capable of minimizing the deterioration of operation performance even during long-term use, having excellent life characteristics, and capable of mass production at low cost is preferable. In this regard, the secondary battery including the electrode assembly of the present invention may be preferably used in a medium-large battery module having the unit cell.

In the case of a battery pack including a battery module including a plurality of secondary batteries, a power tool (power tool); Electric vehicles selected from the group consisting of electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); E-bikes; E-scooters; Electric golf cart; Electric truck; And it can be used as one or more power source selected from the medium-large device group consisting of electric commercial vehicles.

The medium-large battery module is configured to provide a high output capacity by connecting a plurality of unit cells in series or in series / parallel manner, which is well known in the art, and thus, description thereof is omitted herein.

In the foregoing detailed description of the present invention, specific examples have been described. However, various modifications are possible within the scope of the present invention. The technical idea of the present invention should not be limited to the embodiments of the present invention but should be determined by the equivalents of the claims and the claims.

100: secondary battery
200: battery case
300: electrode assembly
310, 320: electrode tab
410, 420: lead portion (electrode lead)
411: lead film
430: insulating film
A: sealing area
B: Welding area
C: unused space

Claims (12)

A pouch for receiving the electrode assembly;
A welding region in which the electrode tab and the lead are welded to the inside of the pouch;
A lead film for coating the outside of the lead and a sealing region of the pouch;
A secondary battery arranged in an overlapping structure.
The method according to claim 1,
A welding region of the electrode tab and the lead portion disposed inside the sealing region of the pouch,
And a lead film sealed with the pouch is disposed between the pouch and the welding region.
The method according to claim 1,
The lead films disposed on the upper and lower surfaces of the welding region are,
The length of the welding area being longer than the length of the welding area.
The method according to claim 2,
In the lead film,
A part of which protrudes outside the distal end of the pouch.
The method of claim 4,
And a thermosetting layer is provided on at least one side of the lead film.
The method according to claim 5,
Wherein the thermosetting layer is composed of at least one thermosetting resin selected from the group consisting of a melamine resin, a phenol resin, a urea resin, an epoxy resin, and a polyurethane.
The method of claim 6,
Wherein the thermosetting layer is formed to a thickness of 10 mu m to 100 mu m.
The method according to any one of claims 1 to 7,
Wherein the pouch comprises:
Wherein the pouch comprises a first sheet which is a laminate sheet including a resin layer and a metal layer, and a second sheet which faces the first sheet.
The method according to claim 8,
Wherein both the first sheet and the second sheet are formed to form a receiving portion for receiving the electrode assembly.
The method of claim 9,
The electrode assembly includes:
The secondary battery is a secondary battery comprising any one of a winding type, a stack type, and a stack / folding type structure.
The method of claim 9,
The electrochemical device,
Wherein the positive electrode slurry coated on the positive electrode current collector is Li ₂ MnO ₃ and LiMO ₂ as a positive electrode active material, wherein M is a transition metal element.
A battery pack including the secondary battery of claim 1, and a battery pack including a plurality of battery modules.

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