KR101471964B1 - Electrode Assembly Having Novel Lead-tap Joint Structure and Electrochemical Cell Containing the Same - Google Patents

Abstract

The present invention relates to an electrode assembly having a positive electrode / separator / negative electrode structure, wherein each electrode plate constituting the electrode assembly has an electrode tab protruding from one end thereof, to which no active material is applied; The electrode tabs of each electrode plate are coupled to one electrode lead to form an electrode lead-electrode tab joint; And the electrode tab-electrode lead coupling part includes a side-by-side arrangement in which two or more electrode tabs are laterally arranged in a state that they are not overlapped with each other and are coupled to adjacent electrode tabs or electrode leads.

Description

[0001] The present invention relates to an electrode assembly and a method of manufacturing the same,

The present invention relates to an electrode assembly comprising a novel electrode lead-electrode tab joint and to an electrochemical cell including the electrode assembly. More particularly, the present invention relates to an electrode assembly comprising a positive electrode / separator / negative electrode structure, An electrode tab protruding from one end of the electrode plate to which no active material is applied; The electrode tabs of each electrode plate are coupled to one electrode lead to form an electrode lead-electrode tab joint; And the electrode tab-electrode lead coupling part includes a side-by-side arrangement in which two or more electrode tabs are laterally arranged in a state that they are not overlapped with each other and are coupled to adjacent electrode tabs or electrode leads.

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.

Typically, in view of the shape of the battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery that can be applied to products such as mobile phones with a small thickness. In terms of materials, lithium ion batteries having high energy density, discharge voltage, There is a high demand for a lithium secondary battery such as a lithium ion polymer battery.

Also, the secondary battery is classified according to how the electrode assembly having the anode / separator / cathode structure is formed. Typically, the long battery-shaped anodes and cathodes are jelly- A stacked (stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator interposed therebetween, a stacked (stacked) electrode assembly in which a predetermined unit of positive and negative electrodes are stacked, A stack / folding type electrode assembly having a structure in which a bi-cell or a full cell stacked in a single state is wound is exemplified.

Recently, a pouch-shaped battery having a structure in which a stacked or stacked / folded electrode assembly is embedded in a pouch-shaped battery case of an aluminum laminate sheet is attracting much attention due to low manufacturing cost, small weight, and easy shape deformation Its usage is also gradually increasing.

As described above, the pouch type secondary battery has a structure in which the electrode assembly is mounted on the pouch-shaped case of the laminate sheet, and the electrode leads connected to the electrode tabs of the electrode assembly have an end opposite to the connection portion with the electrode tabs, And is thermally fused together with the battery case in a state exposed to the outside of the case.

In the secondary battery having such a structure, a plurality of electrode taps are coupled to one electrode lead by ultrasonic welding or the like. In the case where the electrode assembly is formed of a larger number of electrode plates than the conventional one in order to increase the capacity of the battery, There is a problem in that a large amount of energy is required for welding. In addition, the increase of the thickness tends to cause an unfused portion in the process of ultrasonic welding and cause a difference in the electrical connection paths of the electrode tabs to the electrode leads.

This phenomenon tends to occur more seriously, particularly in secondary batteries used in high-power, large-capacity battery packs such as electric vehicles, hybrid electric vehicles, electric power storage devices and the like.

Accordingly, there is a great need for a technique capable of solving these problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

It is an object of the present invention to provide an electrode tab-electrode lead coupling portion having a novel structure including a side-by-side arrangement, thereby reducing the thickness of the electrode tab and thereby reducing the fusing phenomenon and improving the bonding force, The electrode tab and the electrode lead can be easily welded.

Therefore, the electrode assembly of the present invention is an electrode assembly composed of a positive electrode / separator / negative electrode structure. In each electrode plate constituting the electrode assembly, an electrode tab not coated with active material protrudes from one end thereof; The electrode tabs of each electrode plate are coupled to one electrode lead to form an electrode lead-electrode tab joint; And the electrode tab-electrode lead coupling part includes a side-by-side arrangement in which two or more electrode tabs are laterally arranged in a state that they are not overlapped with each other and are coupled to adjacent electrode tabs or electrode leads.

In a typical structure of the electrode assembly, the electrode plates are bonded to the electrode leads with the electrode tabs stacked so that the ends of the electrode tabs are aligned. Due to the structure of the electrode taps stacked so that the end portions coincide with each other, not only a lot of energy is required in welding but also an unfused portion can occur.

On the other hand, according to the present invention, two or more electrode tabs are laterally arranged in a state in which they are not overlapped with each other, and are laterally arranged to be coupled to adjacent electrode taps or electrode leads. This distinctive coupling structure not only improves the bonding force with the electrode leads but also exhibits a special effect of improving the weldability even with a small amount of energy, compared with the conventional structure in which a large number of electrode taps are stacked.

The electrode assembly having the structure in which the electrode tabs are coupled to the electrode leads is typically a stacked structure or a stacked / folded structure in which a plurality of anodes and cathodes are stacked with a separator interposed therebetween, but is not limited thereto. For example, a structure in which a single separator is arranged on a long separation film and is wound or zigzag-shaped is also possible. As a result, the present invention can be applied to any electrode assembly having a structure in which electrode tabs and electrode leads are laterally aligned.

In one preferred embodiment, the electrode tabs that do not form the side-by-side arrangement may be sequentially stacked so that one or two electrode tabs may overlap one another when viewed side-by-side, The overlapping width of the electrode tabs may preferably be 1/3 to 1/2 of the width of the electrode tabs.

Therefore, compared to the conventional electrode tab structure, the thickness of the electrode tab structure can be remarkably reduced, thereby greatly improving the weldability.

In some cases, the width of the electrode tabs that do not have side-by-side connection may be smaller than the sum of the widths of the electrode tabs that are larger than the respective electrode tabs that are laterally aligned but are laterally aligned.

Therefore, it is possible to ensure a high bonding force of the electrode tabs despite the side-by-side connection.

In the present invention, the electrode tabs forming the side-by-side array connection may protrude from the respective electrode plates at positions corresponding to the side-by-side arrangement.

In the present invention, the method of arranging the electrode tabs may be various, and the electrode tab-electrode lead coupling part may include two or more side-by-side arrangements.

More specifically, two or more electrode tabs arranged on the upper side and two or more electrode tabs arranged on the lower side with respect to one electrode tab may be respectively coupled to the electrode tabs by side array connection.

In the present invention, the electrode lead is not particularly limited as long as it is made of a material capable of electrically connecting electrode tabs, and may be a metal plate. Examples of such a metal plate include, but are not limited to, a nickel plate, a nickel-plated copper plate, an aluminum plate, a copper plate, and an SUS plate.

The electrode leads and the electrode taps at the electrode leads and the electrode tab joints can be coupled in various ways, preferably by welding, and the welding can be performed, for example, by ultrasonic welding .

In the present invention, the electrode plate has a structure in which an electrode assembly including an electrode active material is coated on one surface or both surfaces of a current collector. The electrode assembly has such a structure that the electrode plates, that is, the positive electrode plate and the negative electrode plate are laminated with the separator interposed therebetween.

The positive electrode collector is generally made to a thickness of 3 to 500 mu m. Such a positive electrode collector is not particularly limited as long as it has conductivity without causing chemical change to the battery, and may be formed on the surface of stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel Carbon, nickel, titanium, silver, or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The anode current collector generally has a thickness of 3 to 500 mu m. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered 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.

The positive electrode material mixture may include a positive electrode active material, a conductive material, a binder, a filler, and the like.

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 and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _1-x M _x O ₂ (where 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; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The conductive material is usually added in an amount of 1 to 30% 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 added to the binder in an amount of 1 to 30% by weight, based on the total weight of the mixture containing the cathode active material, as a component that assists in bonding between the active material and the conductive agent and bonding to the current collector. 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, and various copolymers.

The filler is optionally used as a component for suppressing expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin-based polymerizers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The positive electrode plate may be prepared by applying a slurry prepared by mixing a positive electrode mixture containing the above-described compounds to a solvent such as NMP, and then drying and rolling the negative electrode plate. The negative electrode plate may be formed, for example, And then drying the mixture. The negative electrode material mixture may contain the above-described components, if necessary, in addition to the negative electrode 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 &lt; 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.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant 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.

The present invention also provides an electrochemical cell comprising such an electrode assembly.

The electrochemical cell may be a small electrochemical cell or a combination of several cells as a unit cell, and a plurality of unit cells may be combined to be a middle or large electrochemical cell.

The electrochemical cell provides electricity through an electrochemical reaction. For example, the electrochemical cell may be an electrochemical secondary battery or an electrochemical capacitor, and may be preferably applied to a lithium secondary battery.

The lithium secondary battery has a structure in which an electrode assembly is impregnated with a lithium salt-containing nonaqueous electrolyte solution.

The lithium salt-containing nonaqueous electrolyte solution is composed of an electrolyte solution and a lithium salt. As the electrolyte solution, a nonaqueous organic solvent, an organic solid electrolyte, and an inorganic solid electrolyte may be used.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO _{4 -} LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO _4- LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene carbonate, PRS (propene sultone), FPC (fluoro-propylene carbonate), and the like.

The battery chemistry cell is sealed in a suitable battery case. Preferably, the battery chemistry cell may have a structure in which an electrode assembly is sealed in a battery case of a laminate sheet including a metal layer and a resin layer.

Also, the secondary battery includes a plurality of battery cells, and can be preferably used as a unit battery when manufacturing a high-output large-capacity battery pack. Since the unit cells used in the high-output large-capacity battery pack are very large and thicker than the battery cells of the small-sized battery pack, the structure in which the electrode lead-electrode tab joint portions are firmly fused can be more preferably applied to the middle- or large- .

As described above, the electrode assembly according to the present invention is configured to include a side-by-side arrangement in which two or more electrode tabs are laterally arranged without being overlapped with each other and are coupled to adjacent electrode tabs or electrode leads, And the weldability of the electrode tabs to the electrode leads can be greatly improved even with a small amount of energy.

1 is a partial schematic view of a top portion of a conventional stacked electrode assembly;
Fig. 2 is a partial enlarged view of the electrode tab-lead coupling portion in the structure of Fig. 1; Fig.
3 is a partial enlarged view of an electrode tab-electrode lead coupling portion according to one embodiment of the present invention;
4 is a partial enlarged view of an electrode tab-electrode lead coupling portion according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

First, for convenience of understanding, the prior art will be described with reference to Figs. 1 and 2. Fig. Specifically, FIG. 1 schematically shows the top end of a typical stacked electrode assembly of the prior art, and FIG. 2 schematically shows a partial enlarged view of the electrode tab-lead joint.

1, the stacked electrode assembly 30 includes a positive electrode plate on which positive electrode active material is applied on both surfaces of a positive electrode collector, and a negative electrode plate on which negative electrode active material is applied on both surfaces of the negative electrode collector, And a laminated structure.

A plurality of electrode tabs 40 which are not coated with an active material protrude from one side end of the positive electrode current collector and the negative electrode current collector so as to be electrically connected to the electrode leads 60 constituting the electrode terminals of the battery, Each electrode tab 40 is welded onto the electrode lead 60 to form an electrode tab-lid joint 90.

Referring to FIG. 2, each of the electrode taps 40 has a structure in which its ends are mutually aligned. Therefore, the thickness W of the electrode tabs 40 becomes thicker as the number of electrode current collectors increases.

For reference, an insulating film 80 is attached to the electrode lead 60 to increase the sealing property of the battery case in a process of attaching the electrode assembly to a battery case (not shown) and sealing the battery case by thermal fusion.

FIG. 3 schematically shows a partial enlarged view of a positive electrode tab-and-lead coupling portion 90 'according to an embodiment of the present invention. For ease of explanation of the arrangement of the electrode taps, the electrode leads are expressed relatively small.

Referring to FIG. 3, the positive electrode tab-electrode lead coupling portion 90 'includes two electrode tabs 42 and 43 arranged on the upper side with respect to one electrode tab 41, (44, 45) are respectively coupled to the electrode tabs (41) by side-by-side arrangement.

The width a of the electrode tabs overlapping the electrode tabs in the stacking of the electrode assemblies is about 1/2 of the width A of the electrode tabs and the electrode leads 60 are connected to the electrode tabs 40 ' Lt; / RTI &gt;

In addition, the thickness w of the electrode tab 40 'is much thinner than the thickness W of FIG. 2, thereby facilitating the welding, thereby providing excellent bonding force.

4 is a partially enlarged view of an electrode tab-electrode lead coupling portion according to another embodiment of the present invention.

4, two electrode tabs 42 and 43 arranged on the upper side with respect to one electrode tab 41 and two electrode tabs 44 and 45 arranged on the lower side are arranged in a side-by-side arrangement The structure connected to the electrode tab 41 is the same as in Fig.

The width a 'of the electrode tabs overlapping the electrode tabs in the stacking of the electrode assemblies is set such that the sum of the widths of the electrode tabs 42 and 43 or the electrode tabs 44 and 45 which are laterally arrayed, A), which is almost twice as large as that of the second embodiment.

The above structure is only a few examples, and various modifications are possible within the scope of the present invention.

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 (15)

An electrode assembly comprising a positive electrode / separator / negative electrode structure,
Each of the electrode plates constituting the electrode assembly has an electrode tab protruding from one end thereof, to which no active material is applied;
The electrode tabs of each electrode plate are coupled to one electrode lead to form an electrode lead-electrode tab joint;
Wherein the electrode tab-electrode lead coupling part includes a side-by-side arrangement in which two or more electrode tabs are laterally arranged in a state that they are not overlapped with each other and are coupled to adjacent electrode tabs or electrode leads ,
The electrode tabs which do not form the side-by-side arrangement are sequentially stacked so that one or two electrode tabs can overlap each other when viewed from the side,
Wherein a width overlapping between the electrode tabs forming the side-by-side arrangement and the electrode tabs not overlapping is 1/3 to 1/2 of the width of the electrode tabs. The electrode assembly of claim 1, wherein the electrode assembly is of a stacked or stacked / folded structure. delete delete 2. The electrode of claim 1 wherein the width of the electrode tabs that are not laterally aligned is smaller than the sum of the widths of the electrode tabs that are larger than the respective electrode tabs forming the side- Assembly. The electrode assembly of claim 1, wherein the electrode tabs forming the side-by-side array are protruded from the respective electrode plates at positions corresponding to the side-to-side arrangement. 2. The electrode assembly of claim 1, wherein the electrode tab-electrode lead coupling comprises two or more side-by-side connections. The electrode assembly according to claim 1, wherein at least two electrode tabs arranged on an upper portion of the electrode tab and two or more electrode tabs arranged on the lower portion are coupled to the electrode tabs by side- . The electrode assembly of claim 1, wherein the electrode lead is selected from the group consisting of a nickel plate, a nickel plated copper plate, an aluminum plate, a copper plate, and an SUS plate. The electrode assembly of claim 1, wherein the electrode leads are joined to the electrode tabs by welding. 11. The electrode assembly of claim 10, wherein the welding is ultrasonic welding. An electrochemical cell comprising an electrode assembly according to any one of claims 1, 2 and 5 to 11. 13. The electrochemical cell of claim 12, wherein the electrochemical cell is a secondary cell or a capacitor. The electrochemical cell according to claim 12, wherein the electrochemical cell is embedded in a battery case of a laminate sheet including a metal layer and a resin layer in a sealed state. The battery pack according to claim 14, wherein the electrochemical cell is a unit cell.

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