KR20130112383A - Electrode assembly having novel lead-tap joint structure and electrochemical cell containing the same - Google Patents

Abstract

PURPOSE: An electrode assembly improves coupling force and prevents non-fusion phenomenon by reducing the thickness of an electrode tab. CONSTITUTION: An electrode assembly consists of a positive electrode/separator/negative structure. An electrode tab (40') on which active material is not spread is projected from one end part of each polarizing plate which forms the electrode assembly. Electrode tabs of each polarizing plate form an electrode lead-electrode tab coupling part (90') by being coupled to one electrode lead. At the electrode tab-electrode lead coupling part, a side arrangement coupling where two or more electrode tabs are arranged on a side and are coupled to a neighboring electrode tab (41) or electrode lead (60) in a state that they are not overlapped with each other is formed.

Description

Electrode assembly having a novel electrode lead-electrode tab joint and an electrochemical cell comprising the same {Electrode Assembly Having Novel Lead-tap Joint Structure and Electrochemical Cell Containing the Same}

The present invention relates to an electrode assembly comprising a novel electrode lead-electrode tab coupling portion and an electrochemical cell comprising the same, and more particularly, to an electrode assembly comprising an anode / separation membrane / cathode structure, each of which constitutes an electrode assembly. An electrode tab, to which the active material is not applied, protrudes from one end of the electrode plate; The electrode tabs of each electrode plate are joined to one electrode lead to form an electrode lead-electrode tab coupling portion; The electrode tab-electrode lead coupling portion relates to an electrode assembly comprising two or more electrode tabs arranged side by side without overlapping each other and coupled to an adjacent electrode tab or an electrode lead.

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 that 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.

In addition, secondary batteries are classified according to the structure of the electrode assembly having a cathode / separation membrane / cathode structure. Representatively, a jelly having a structure in which long sheet-shaped anodes and cathodes are wound with a separator interposed therebetween -Roll (electrode) electrode assembly, a stack (stacked type) electrode assembly in which a plurality of positive and negative electrodes cut in units of a predetermined size are sequentially stacked with a separator, and the positive and negative electrodes of a predetermined unit are interposed through a separator And a stacked / folding electrode assembly having a structure in which a bi-cell or full cells stacked in a state are wound.

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 type case of the laminate sheet, and the electrode lead connected to the electrode tabs of the electrode assembly has an end portion facing the connection part with the electrode tabs. Heat-sealed together with the battery case in the state exposed to the outside of the case.

In the secondary battery having such a structure, a plurality of electrode tabs are bonded to one electrode lead by ultrasonic welding or the like. When the electrode assembly is composed of a larger number of electrode plates than the conventional one in order to increase the capacity of the battery, the electrode tab The thickness increases with the number of these, there is a problem that requires a lot of energy when welding. In addition, such an increase in thickness tends to cause an unbonded portion in the ultrasonic welding process, and causes a problem in causing a difference in the electrical connection path of each electrode tab to the electrode lead.

Such a phenomenon tends to occur more seriously in secondary batteries used in high-capacity battery packs such as electric vehicles, hybrid electric vehicles, and power storage devices.

Therefore, there is a very high need for a technology that can solve 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 include a novel electrode tab-electrode lead coupling including a side-by-side coupling, thereby reducing the thickness of the electrode tab to reduce the non-fusion phenomenon and at the same time improve the bonding force, The present invention also provides an electrode assembly in which electrode tabs and electrode leads can be easily welded.

Therefore, the electrode assembly of the present invention is an electrode assembly having an anode / separation membrane / cathode structure, in which electrode tabs without an active material are protruded from one end of each electrode plate constituting the electrode assembly; The electrode tabs of each electrode plate are joined to one electrode lead to form an electrode lead-electrode tab coupling portion; 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 the electrode assembly of the general structure, the electrode tabs are coupled to the electrode lead with the electrode plates stacked so that the ends of the electrode tabs coincide. Due to the structure of the electrode tabs stacked so that the ends coincide, not only a large amount of energy is required for welding, but also an unfused portion may occur.

On the other hand, according to the present invention, the two or more electrode tabs are arranged side by side without overlapping with each other has a structure that is coupled to the side array coupled to the adjacent electrode tab or electrode lead. This differential coupling structure not only improves the bonding force with the electrode lead than the conventional structure in which a large number of electrode tabs are stacked, but also has a special effect of improving weldability with a small amount of energy.

An electrode assembly having a structure in which an electrode tab is coupled with an electrode lead may be a stack type structure and a stack / fold type structure in which a plurality of positive and negative electrodes are stacked with a separator interposed therebetween, but are not limited thereto. For example, a structure in which a single electrode plate is arranged on a long separation film or wound or bent in a zigzag form may be used. As a result, the present invention can be applied to any type of electrode assembly having a structure in which the electrode tab and the electrode lead are arranged side by side.

In one preferred example, the electrode tabs that do not form the side array coupling may be sequentially stacked so that one or two electrode tabs overlap each other when viewed from the side, and the electrode tabs that do not do the side array coupling do not. The width overlapping each other between the electrode tabs may preferably be 1/3 to 1/2 the length of the electrode tabs.

Therefore, compared with the conventional stacked electrode tab structure, the thickness thereof can be significantly reduced, thereby greatly improving weldability.

In some cases, the width of the electrode tabs without the side array coupling may be larger than the sum of the widths of the electrode tabs with the side array coupling and larger than the respective electrode tabs with the side array coupling.

Thus, it is possible to ensure a high bonding force of the electrode tabs despite the side array coupling.

In the present invention, the electrode tabs forming the side array coupling may have a structure protruding from each of the electrode plates at positions corresponding to the side array coupling.

In the present invention, the method of arranging the electrode tabs may vary, and the electrode tab-electrode lead coupler may include two or more side array couplings.

Specifically, two or more electrode tabs arranged at the upper side and two or more electrode tabs arranged at the lower side with respect to one electrode tab may be coupled to the electrode tabs by side array coupling, respectively.

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

The electrode lead and the electrode tab in the electrode lead and electrode tab coupling portion may be coupled in various ways, preferably more stably by welding, and such welding may be performed by, for example, ultrasonic welding or the like. Can be.

In the present invention, the electrode plate has a structure in which an electrode assembly including the electrode active material is coated on one or both surfaces of the current collector. The electrode assembly has a structure in which 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 negative electrode current collector is generally made to a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and examples thereof 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 mixture may include a positive electrode active material, a conductive material, a binder, a filler, and the like.

When the positive electrode active material is a lithium secondary battery, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ), 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 whiskeys 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 compounds in a solvent such as NMP onto a positive electrode current collector and then drying and rolling the negative electrode plate. It is prepared by applying a negative electrode mixture containing a negative electrode active material to the dried to dry, the negative electrode mixture, if necessary, may include the components as described above.

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 composed of such an electrode assembly.

The electrochemical cell may be manufactured in a small electrochemical length by combining three or four as a unit cell, and may be manufactured as a medium-large electrochemical cell by combining a plurality of unit cells as a unit cell.

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

The lithium secondary battery has a structure in which a lithium salt-containing nonaqueous electrolyte is impregnated into the electrode assembly.

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.

As the inorganic solid electrolyte, for example, 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, sulfates and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may 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, and preferably may have a structure in which the electrode assembly is sealed in a battery case of a laminate sheet including a metal layer and a resin layer.

In addition, the secondary battery, including a plurality of battery cells, can be preferably used as a unit battery when manufacturing a high output large capacity battery pack. Since the unit cell used in the high-output large-capacity battery pack is very large and thick compared to the battery cell of the small battery pack, a structure in which the electrode lead-electrode tab coupling portion is firmly fused as in the present invention may be more preferably applied to the medium-large battery cell. .

As described above, the electrode assembly according to the present invention is configured to include a side array coupling in which two or more electrode tabs are arranged side by side without overlapping each other and coupled to adjacent electrode tabs or electrode leads, thereby forming an electrode tab-electrode lead. By firmly combining, the weldability of the electrode tabs to the electrode leads can be greatly improved with a small amount of energy while reducing the unmelting phenomenon.

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

Hereinafter, the present invention will be described in detail by way of examples, but the following examples are provided 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. Specifically, FIG. 1 schematically illustrates an upper end portion of a conventional representative stacked electrode assembly, and FIG. 2 schematically shows an enlarged view of a portion of an electrode tab-lead coupling portion.

Referring to FIG. 1, the stacked electrode assembly 30 may be sequentially formed in a state in which a positive electrode plate coated with a positive electrode active material on both surfaces of a positive electrode current collector and a negative electrode plate coated with a negative electrode active material on both sides of a negative electrode current collector are interposed with a separator. It consists of a stacked structure.

At one end of the positive electrode current collector and the negative electrode current collector, a plurality of electrode tabs 40 without an active material are protruded so as to be electrically connected to the electrode leads 60 constituting the electrode terminals of the battery. Each electrode tab 40 is attached by welding on the electrode lead 60 to form an electrode tab-lead coupling 90.

Referring to FIG. 2, each electrode tab 40 has a stacked structure so that its ends coincide with each other. Therefore, the thickness W of the electrode tabs 40 becomes thicker as the number of electrode current collectors increases.

For reference, the electrode lead 60 is attached with an insulating film 80 for increasing the sealing property to the battery case in the process of sealing the electrode assembly in a battery case (not shown) by heat fusion.

3 is a partially enlarged view of the positive electrode tab-lead coupling portion 90 'according to one embodiment of the present invention. For convenience of description of the arrangement of the electrode tabs, the electrode leads are relatively small.

Referring to FIG. 3, the positive electrode tab-electrode lead coupling portion 90 ′ has two electrode tabs 42 and 43 arranged on the upper side with respect to one electrode tab 41 and two electrode tabs arranged on the lower side. 44 and 45 are respectively coupled to the electrode tab 41 by side array coupling.

The width a overlapping between the electrode tabs when the electrode assembly is stacked is about 1/2 of the length A based on the width A of the electrode tab, and the electrode lead 60 is formed with the electrode tabs 40 'by ultrasonic welding. Are combined.

In addition, the thickness w of the electrode tab 40 ′ is significantly thinner than the thickness W of FIG. 2 to facilitate welding, thereby providing excellent bonding force.

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

Referring to FIG. 4, two electrode tabs 42 and 43 arranged at an upper side with respect to one electrode tab 41 and two electrode tabs 44 and 45 arranged at a lower side thereof are respectively arranged by side coupling. The structure coupled 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 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 composed of an anode / separator / cathode structure,
Electrode tabs to which the active material is not applied are protruded from one end of each electrode plate constituting the electrode assembly;
The electrode tabs of each electrode plate are joined to one electrode lead to form an electrode lead-electrode tab coupling portion;
And the electrode tab-electrode lead coupling portion includes side-aligned coupling of two or more electrode tabs arranged side by side without overlapping each other and coupled to adjacent electrode tabs or electrode leads. The electrode assembly of claim 1, wherein the electrode assembly has a stack type or a stack / fold type structure. The electrode assembly of claim 1, wherein the electrode tabs that do not form the side array coupling are sequentially stacked so that one or two electrode tabs overlap each other when viewed from the side. The electrode assembly according to claim 3, wherein the width overlapping each other between the electrode tab and the electrode tab to which the side array is coupled is 1/3 to 1/2 of the length of the electrode tab. 2. The electrode of claim 1, wherein the width of the electrode tabs that do not perform side array coupling is larger than each electrode tab that performs side array coupling and smaller than the sum of the widths of the side electrode coupling tabs. Assembly. The electrode assembly according to claim 1, wherein the electrode tabs forming the side array coupling protrude from each electrode plate at a position corresponding to the side array coupling. The electrode assembly of claim 1, wherein the electrode tab-electrode lead coupler comprises two or more side-by-side couplings. The electrode assembly according to claim 1, wherein two or more electrode tabs arranged on the upper side and two or more electrode tabs arranged on the lower side of the electrode tab are respectively coupled to the electrode tab by side array coupling. . 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 lead is coupled to the electrode tabs by welding. The electrode assembly of claim 10, wherein the welding is ultrasonic welding. An electrochemical cell comprising the electrode assembly according to any one of claims 1 to 11. 13. The electrochemical cell of claim 12, wherein said electrochemical cell is a secondary battery or a capacitor. The electrochemical cell of 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. A battery pack comprising the electrochemical cell according to claim 14 as a unit cell.

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