KR101029020B1 - Electrical Connection Method of Conducting Members - Google Patents

Abstract

The present invention is a method of welding and connecting another conductive member (B) to a conductive member (A) required to form an electrically insulating coating layer on the remaining portions except for the welding portion, the electrically insulating coating layer containing a piezoelectric material Is coated on the entire surface of the conductive member (A), and then pressurizing the conductive member (B) against the conductive member (A) at a pressure capable of conducting electricity by the piezoelectric material. It provides a method of coupling by ultrasonic welding while applying a current to the).

Therefore, even when the thickness of the insulating coating layer of the welded portion, the ultrasonic welding can be effectively performed by the application of the piezoelectric material, it is possible to greatly improve the production efficiency by performing the insulating coating and welding in a simple and easy way. .

Description

Electrical Connection Method of Conducting Members

1 is a schematic diagram of a general structure of a pouch type secondary battery including a stacked electrode assembly;

FIG. 2 is a schematic diagram partially enlarged in an upper part of a case in which the positive electrode tabs are fused in a compact form in the secondary battery of FIG. 1 and connected to the positive electrode lead; FIG.

3 is a schematic view of an upper end of a secondary battery electrode assembly having a stacked or stacked / folding electrode assembly;

4 is a schematic diagram of a method for obtaining an electrode by cutting a metal sheet included in an electrode assembly of a secondary battery according to one embodiment of the present invention;

5 is a cross-sectional view taken along the width direction of the electrode sheet of FIG. 4;

6 is an enlarged schematic view of one electrode of FIG. 4.

The present invention relates to a method of electrically connecting conductive members, and more particularly, to another conductive member (B) to the conductive member (A) required to form an electrically insulating coating layer on the remaining portions except for the welded portion. A method of welding and connecting, comprising coating an electrically insulating coating layer including a piezoelectric material on the entire surface of the conductive member (A), and then conducting electricity to the conductive member (A) at a pressure at which electricity may be supplied by the piezoelectric material. The present invention relates to a method consisting of bonding by ultrasonic welding while pressing a member (B) and applying a current to the conductive members (A, B).

In general, a method of electrically connecting conductive members includes a method such as a Lap Joint, in which the conductive members are overlapped and one or more welding is performed at the overlapping portion to join the overlapping surfaces.

Such a welding method includes laser welding for mutual bonding of two welding base materials, each of which has a molten overlap surface with a laser, and a contact generated at a contact portion between each welding base material by flowing a large current through the two welding base materials under pressure. Resistance welding, which causes the metal to be heated or melted by the heat generated by the resistance and the high resistivity of the metal, causes ultrasonic vibrations by applying ultrasonic waves to the contact portion of the welding base metal, thereby melting and bonding the contact portion with thermal energy due to friction. Ultrasonic welding and the like.

In addition to such electrical connection by welding or the like, there is also a demand for a technique for insulating an area other than the electrical connection so as to prevent the electrical connection from being short-circuited by external factors.

As a method for preventing external short circuits by isolating portions other than the electrical connection, a structure in which an insulating coating layer is formed on all or a part of the conductive members before or after the electrical connection of the conductive members is generally assumed. As one application example, in manufacturing a stack type or stack / fold type electrode assembly of a secondary battery, the electrode tab portion may be coated with an insulating material, and electrical welding may be performed to the current collector.

In this regard, US Pat. No. 4,475,79 includes a step of punching a first member from a metal sheet having an insulating copolymer layer formed on at least one surface thereof; Heating the first member on which the copolymer layer is formed; Simultaneously inserting an electrically conductive wire connected to a second member into the heated copolymer layer, and simultaneously pressing the second member onto the heated copolymer layer of the first member. A method of manufacturing an electronic component part having at least two members joined is disclosed. However, the above technique has a disadvantage in that the overall process is complicated, such as a punching process and an insertion process, and because the electrical connection of the conductive members is made by the bonding force of the copolymer layer, the reliability is lower than the welding in the electrical connection surface.

In this regard, the present invention proposes a technique that can secure the desired insulation while effectively achieving electrical connection using a piezoelectric material.

As an example of using a piezoelectric material in the electrical connection configuration, Japanese Patent No. 3188546 has a technique for anodic bonding an insulator and a conductor that does not contain movable ions, and forms a thin conductive film on the insulator that does not contain movable ions. A method is disclosed in which a conductive film is formed at one end of an insulating substrate containing movable ions, anodically bonded an insulating substrate to a conductive film on the insulator, and then anodically bonded the conductor to an insulating substrate. However, although the piezoelectric material is used for the electrical connection of the conductive members, the technique suggests a structure in which the electrical connection is made under the specific conditions using the piezoelectric material. Since there is a limit to the application, there is a problem that can not be used in the general welding method.

On the other hand, as will be described in detail below, the method of the present invention can be preferably used in particular for the manufacture of a secondary battery, the following describes an exemplary structure of a secondary battery with reference to the drawings.

1 schematically illustrates a general structure of a pouch-type secondary battery including a stacked electrode assembly.

Referring to FIG. 1, the pouch type secondary battery 100 includes an electrode assembly 300 made of a positive electrode, a negative electrode, and a solid electrolyte coating separator disposed therebetween in a pouch type battery case 200 of an aluminum laminate sheet. Two electrode leads 400 and 410 connected to the positive and negative electrode tabs 302 and 304 thereof are sealed to be exposed to the outside. In the stacked electrode assembly 300 as shown in FIG. 1, the plurality of positive electrode tabs 302 and the plurality of negative electrode tabs 304 may be fused to each other and coupled to the electrode leads 400 and 410. The upper end of the case 200 is spaced apart from the electrode assembly 300.

FIG. 2 is a partially enlarged view of an upper portion of a case inside the case in which the positive electrode tabs are fused in a compact form in the secondary battery of FIG. 1 and connected to the positive electrode lead.

Referring to FIG. 2, the plurality of positive electrode tabs 302 extending from the positive electrode collector 310 of the electrode assembly 300 may be integrally formed by, for example, ultrasonic welding, laser welding, and spot welding. It is coupled to the positive electrode lead 400 in the form of a combined fusion 322. The positive lead 400 is sealed by the battery case 200 in a state in which the opposite end 402 to which the positive electrode tab fusion unit 322 is connected is exposed. Since the plurality of positive electrode tabs 302 are integrally coupled to form a fusion portion 322, the inner upper end of the battery case 200 is spaced apart from the upper surface of the electrode assembly 300 by a predetermined distance, and the fusion portion The positive electrode tabs 302 of 322 form a V shape.

Therefore, when the battery falls on its upper end, that is, toward the positive electrode lead 400, the electrode assembly 300 may move to the upper end of the inner surface of the case 200 to cause an internal short circuit. That is, the positive electrode tab 302 or the positive electrode lead 400 may contact the negative electrode current collector or the active material of the electrode assembly 300. This phenomenon is true even when a physical external force is applied to the top of the battery. Therefore, it is necessary to coat the electrode tab portion with an insulating material to prevent short circuit during use of the battery.

In the case where an insulating coating layer is formed on all or a part of the conductive members and the electrical connection is to be performed by welding or the like, the coating and welding may be performed, for example, (i) at least part of the portion requiring the coating with the insulating material before welding. The method of coating and welding to the uncoated part, (ii) The method of first welding, then the method of coating the part except the welding part, (iii) The thin coating on the front surface of the conductive member including the expected welding part, and the insulating property at the time of welding The material layer may be melted, and the like may be performed by welding.

However, the method (i) has a problem in that the process of partially coating only a portion requiring coating with an insulating material is problematic, and likewise, the method (ii) has a very process of coating only portions except for welded portions. There is a complicated, cumbersome problem. In the method (iii), the insulating material layer is also applied to the welded portion, which lowers the welding reliability and makes it difficult to form an insulating coating layer having a predetermined thickness or more.

Accordingly, there is a high demand for a technology capable of easily and effectively performing electrical connection of conductive members that need to be coated with an insulating material except for a welded portion.

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.

After extensive research and various experiments, the inventors of the present application form an electrically insulating coating layer including a piezoelectric material on the front surface of the conductive member, and further pressurizes the conductive member to be energized by the piezoelectric material. In the case of performing ultrasonic welding while pressing, it is confirmed that even when the thickness of the insulating coating layer is thick, conductive members having an electrically insulating coating layer can be welded with a desired bonding force by a simple manufacturing process, and complete the present invention. Reached.

Therefore, in the method of welding and connecting the conductive members according to the present invention, another conductive member B is welded to the conductive member A, which is required to form an electrically insulating coating layer on the remaining portions except for the welded portion. In this method, the electrically insulating coating layer including the piezoelectric material is coated on the entire surface of the conductive member (A), and then the conductive member (B) with respect to the conductive member (A) at a pressure that can conduct electricity by the piezoelectric material. Is pressed, and is coupled to each other by ultrasonic welding while applying a current to the conductive members (A, B).

According to the present invention, since the efficiency of ultrasonic welding can be greatly increased by energization of the piezoelectric material included in the insulating coating layer, coating and welding can be performed by a simple manufacturing process even when the insulating coating layer is thick. Moreover, when energizing by the pressurization of the conductive members, the thermal energy generated between the piezoelectric material and the conductive members promotes melting and local plastic deformation of the conductive members of the joint, so that the bonding thereof is made smoother, thereby improving welding reliability. Can be. As a result, the welding method according to the present invention is mainly due to the joining of the conductive members by ultrasonic welding, but in the process until the conductive members are in direct contact with each other, local melting of the coating layer due to the heat generated when the piezoelectric material is energized. This can be important.

Therefore, as described above, welding of another conductive member B to the conductive member A is mainly achieved by ultrasonic welding, as defined above.

In general, laser welding or resistance welding provides a high bonding force, but has a disadvantage in that a lot of heat is generated at the coupling site. In a specific example, in the case where the conductive member A is a current collector to which the electrode active material is coated, and the conductive member B is an electrode tab protruding therefrom, laser welding or resistance welding is performed on this, This may adversely affect the non-welded portion where welding is not performed, such as being transferred to the current collector, causing deterioration of the electrode active material. On the other hand, ultrasonic welding has a relatively low amount of heat generated in welding compared to laser welding or resistance welding, so there is no fear of the above problems.

Although a predetermined current is applied to the conductive member even in the electrical connection method according to the present invention, such a current is not a large current during resistance welding, and heat generated by energization of the piezoelectric material during pressurization is used for easy achievement of ultrasonic welding. It is low enough to help local melting of the coating layer. Therefore, the degree of pressure of the conductive member B against the conductive member A and the magnitude of the current applied to the conductive members A and B can be appropriately determined in consideration of these points.

The welding by the ultrasonic welding is rapidly welding as the vibration energy is converted into thermal energy by friction at the interface between the electrode tab and the electrode tab and between the electrode tab and the electrode lead by using the high frequency vibration generated by the ultrasonic wave of about 20 KHz. As a principle of this, the newly exposed electrode tab surfaces are brought into close contact with each other by local melting and / or plastic deformation of the joint surface coating layer by friction accompanying vibration, and diffusion of atoms by local temperature rise by frictional heat. And recrystallization is promoted to form a firm pressure point.

The piezoelectric material is a material exhibiting insulation in a non-pressurized state and conductive in a pressurized state. Therefore, the piezoelectric material exhibits insulation in the non-pressurized state, but when pressurized for a predetermined welding, electric piezoelectric material can be used to more effectively achieve ultrasonic welding.

The piezoelectric material is not particularly limited as long as it can be included in the coating layer without changing the chemical properties or physical properties of the coating layer, for example, polymer piezoelectric materials such as BaTiO ₃ , SrTiO, PZT, quartz, tourmaline, Rochelle salt , Ceramic piezoelectric materials such as barium titanate, ammonium dihydrogen phosphate, ethylene diamine lead tartarate zirconate titanate (Pb (Ti _X Zr _1-X ) O ₃ ) or lead titanate (PbTiO ₃ ). Among them, BaTiO ₃ , PZT, PbTiO ₃ and the like may be preferably used, and these may be used alone or in combination of two or more.

The piezoelectric material is preferably contained in 20 to 80% by weight based on the total weight of the coating layer. Specifically, if the content of the piezoelectric material is too large, conduction is performed even when minute pressure is applied, and thus, it is difficult to perform the desired ultrasonic welding, and also the amount of the insulating material may be relatively reduced, so that the desired insulation may not be exhibited. Not desirable On the contrary, when the content of the piezoelectric material is too small, it is not preferable because sufficient energization is not achieved even by pressurization and thus the desired bonding force cannot be improved.

The coating layer can maintain the desired insulation, and at the same time can be appropriately determined within the range that can be smoothly bonded by the ultrasonic welding of the conductive members by the energization of the piezoelectric material, preferably 3 ㎛ to 20 ㎛ It may be formed in a thickness.

The electrically insulating coating layer may be preferably formed of a structure in which a piezoelectric material is contained in the insulating material. The insulating material is electrically insulating and easily melted locally by heat generation of the piezoelectric material. Typically, an insulating polymer resin such as synthetic resin such as polypropylene, polyethylene, polyimide, synthetic rubber such as polybutadiene, or a complex thereof may be used, but is not limited thereto.

In one preferred example, the electrically insulating coating layer may have a structure in which a piezoelectric material is dispersed in a polymer resin selected from the group consisting of polyolefin, polyimide, polyamide, silicone resin, PP and PE.

The method of forming the electrically insulating coating layer is not particularly limited, and for example, a method of melting and applying a composition by a combination of a piezoelectric material and a molten polymer resin, and a method of melting and applying a composition by a combination of a piezoelectric material and a monomer. After coating, the coating may be performed while curing by heat or ultraviolet irradiation, and a method of coating and drying the coating solution by a combination of a piezoelectric material, a polymer resin, and a solvent.

Welding method according to the present invention can be preferably used in the manufacture of a secondary battery, as described above with respect to FIG.

Accordingly, the present invention also relates to a secondary battery having a stacked or stacked / folding electrode assembly, wherein electrode tabs of each electrode plate in the electrode assembly are connected to one electrode lead, and the electrode tab is connected thereto. It provides a secondary battery characterized in that the electrical current is made while being coupled to the electrode lead by ultrasonic welding in a state in which an insulating material including a piezoelectric material is coated on the front surface.

The electrode tabs of the stacked or stacked / foldable secondary battery are arranged substantially parallel to the direction of the electrode plate, and in order to connect the tabs to one electrode lead, the plurality of tabs are collected and aligned, and then welded. The process is necessary. Thus, when a plurality of tabs are integrated in one direction, a change occurs in the thickness of the battery depending on the length up to the fusion portion and the number of stacked electrode plates, and naturally, curved portions of the electrode tabs are formed. The curved portion is a portion of the current collector to which the active material extending from each current collector is not applied, and the contact portion of the electrode assembly causes a short circuit of the battery when contact with the current collector or the active material occurs.

In order to prevent a short circuit caused by contact of the electrode tab and / or the lead with the current collector or the active material of the electrode assembly, the secondary battery of the present invention is coated with an insulating material including a piezoelectric material on the front surface of the electrode tab. Bar electrode is energized while being coupled to the electrode lead by ultrasonic welding. Even though the electrode tab and / or the electrode lead are in contact with the electrode assembly, the insulating coating layer can maintain the electrical insulation state to prevent a short circuit and prevent the short circuit. As a result, the coupling between the respective electrode tabs and the electrode leads can be further strengthened. In addition, the insulating coating layer can also prevent a short circuit with the battery case.

The coating layer of the insulating material is preferably formed in the non-coated portion to a thickness of approximately 0.5 to 5 ㎛, more preferably coated to a thickness of 2 to 3 ㎛. When the thickness of the coating is too small, it is difficult to expect the insulation effect according to the coating, on the contrary, when the thickness of the coating is too large, it may be difficult to conduct electricity by ultrasonic welding between the electrode tabs and the electrode tab and the electrode lead, Not desirable

The electrode of the electrode tab including the insulating coating layer may be a positive electrode and / or a negative electrode. Specifically, the coating layer made of an insulating material may be a non-coating portion of a positive electrode or a non-coating portion of a negative electrode, or a non-coating portion of a positive electrode and a negative electrode. Can be formed. In general, in the lithium secondary battery, the size of the negative electrode plate is made larger than that of the positive electrode plate in consideration of a problem that lithium ions in the electrolyte are deposited as lithium metal in the negative electrode plate during the charge and discharge process. Therefore, since the positive electrode tab has a high possibility of preferential contact with the negative electrode (current collector or active material) of the electrode assembly when an external impact such as a drop is applied, the insulating coating layer is preferably formed at least on the uncoated portion of the positive electrode.

The secondary battery, which is energized while being coupled to the electrode lead by ultrasonic welding in a state where an insulating material is coated on the front surface of the electrode tab, is disclosed in Korean Patent Application Publication No. 2004-0107116 of the present applicant. Incorporated by reference in the context of the present invention.

The battery according to the present invention is preferably a lithium secondary battery, in general, the lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, and a lithium salt-containing nonaqueous electrolyte.

The positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive material, and a binder to a positive electrode current collector, followed by drying, and optionally, a filler is further added to the mixture.

The cathode active material may be 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; Li _{1 + x} Mn _{2 - x} O ₄ (Where x is 0 to 0.33), lithium manganese oxides such as 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 (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The conductive material is typically added in an amount of 1 to 50% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks 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 powder, aluminum powder 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 a component that assists in bonding the active material and the conductive material to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, 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 suppressing the 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 polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The negative electrode is manufactured by coating and drying a negative electrode active material on a negative electrode current collector, and if necessary, the components as described above may be further included.

As said negative electrode active material, For example, carbon, such as hardly graphitized carbon and graphite type 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': Al, B, P, Si, Group 1, 2, 3 of the periodic table) Metal composite oxides such as a group element, halogen, 0 <x ≦ 1, 1 ≦ y ≦ 3, 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; 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 metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The separator 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 from 0.01 to 10 ㎛ ㎛, thickness is generally 5 ~ 300 ㎛. As such a separator, for example, olefin polymers such as chemical resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The lithium salt-containing non-aqueous electrolyte solution consists of a polar organic electrolyte solution and a lithium salt. As the electrolyte, a non-aqueous liquid electrolyte, an organic solid electrolyte, an inorganic solid electrolyte, and the like are used.

As said non-aqueous liquid electrolyte solution, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma, for example Butyl lactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxorone, formamide, dimethylformamide, dioxolon , Acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxorone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbo Aprotic organic solvents such as nate derivatives, tetrahydrofuran derivatives, ethers, methyl pyroionate and ethyl propionate 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, Polymers containing ionic dissociation groups, and the like can 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, 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.

In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., the non-aqueous electrolyte solution includes, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, and hexaphosphate triamide. Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, etc. It may be. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

Such a lithium secondary battery may be manufactured by conventional methods known in the art. That is, it may be prepared by inserting a porous separator between the anode and the cathode and injecting the electrolyte therein.

The present invention also provides a method of manufacturing the secondary battery through a process of manufacturing a plate-shaped electrode by applying an electrode mixture containing an active material on a metal sheet and then cut.

Specifically, based on the size of the electrode plate height and the electrode tab height ('electrode length'), using a metal sheet having a width of at least twice the length of the electrode and at least twice the width of the electrode plate,

Successively patterning the electrode mixture on the metal sheet except for the portion corresponding to the electrode tab so that at least two electrodes can be obtained adjacent in the longitudinal and width directions thereof,

The secondary battery may be manufactured by a process including coating a piezoelectric material-containing insulating material on a portion ('uncoated portion') to which the electrode mixture is not applied, and then cutting it in the form of an electrode.

In the present invention, the 'uncoated portion' is a tab of the electrode assembly having a stacked or stacked / folded electrode structure, protruding from the upper end of the current collector and joined to the electrode lead, wherein the electrode is not coated with the electrode active material. It means the corresponding part of.

The metal sheet is preferably extended in the width and length directions to cut a plurality of electrodes in order to improve productivity. Specifically, the width of the metal sheet may have a size corresponding to four to eight times the length of the electrode and the length of the metal sheet may be five times or more the width of the electrode plate. In the present specification, the 'electrode length' means the sum of the height of the electrode plate and the height of the electrode tab.

In a preferred example of applying the electrode mixture to the metal sheet, the electrode mixture is applied so that the electrodes (outermost electrodes) can be oriented so that the electrode tabs toward the center at both ends thereof based on the width of the metal sheet. And an electrode mixture applied to the outermost electrode in the width direction of the metal sheet so that its electrode tabs can be oriented to face the outermost electrode.

Thus, in the structure in which the electrode tabs of the adjacent electrodes in the width direction of the metal sheet are arranged to face each other, it is desirable to minimize the amount of the metal sheet discarded after cutting to the electrode. In one preferred embodiment, in the electrodes in which the electrode tabs are arranged in a direction facing each other with respect to the width direction of the metal sheet, a method of cutting the electrodes so that the electrode tabs can be arranged in an alternating manner without contacting each other Can be.

In this case, the distance between the electrodes is configured to be equal to or smaller than the sum of the heights of the electrode tabs of the two electrode plates facing each other with respect to the uncoated portion, thereby further reducing the amount of metal sheet discarded after cutting.

By this cutting method, the maximum number of electrodes can be cut out from the unit metal sheet, and the amount of the piezoelectric substance-containing insulating material applied to the uncoated portion can be saved, thereby improving productivity and reducing manufacturing costs.

Application of the piezoelectric material-containing insulating material to the uncoated portion may be performed in the range of 80 to 110% based on the width between the electrode plates.

When the piezoelectric substance-containing insulating material is applied at 80% or less based on the width of the non-coating portion, a large portion of the uncoated portion of the piezoelectric substance-containing insulating material is present in the non-coating portion of the electrode tab made after cutting, and thus prevents short circuits. Hard to exert effect. On the contrary, when the piezoelectric material-containing insulating material is applied at 110% or more based on the width of the non-coated portion, a large part of the electrode to which the electrode mixture is applied is covered by the piezoelectric material-containing insulating material, and thus the electrochemical reaction of the electrode active material. This disturbance eventually results in a decrease in battery capacity.

As such, the piezoelectric material-containing insulating material may be applied to the corresponding portions in a predetermined tolerance range, and thus, flexibility of the battery manufacturing process may be provided. As the inventors of the present application apply the manufacturing method of the present invention to the actual manufacturing process of the battery, it becomes possible to design to reduce the tolerance, the electrode volume increases by about 3% or more, the process tolerance It has been confirmed that the increase in productivity increases by about 2% or more.

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.

3 schematically illustrates a vertical cross-sectional view of an electrode assembly upper end portion of a secondary battery having a stacked electrode assembly.

Referring to FIG. 3, the electrode assembly 300 having a structure in which a separator is interposed between a positive electrode current collector and a negative electrode current collector coated on both surfaces of the electrode active material is composed of a plurality of electrode plates. A plurality of protruding electrode tabs 350 are attached to the top and / or bottom of the electrode lead 400 to form an electrode tab-lead coupling part 375.

A portion of the electrode tab 350 to which the electrode mixture including the electrode active material is not coated is coated on its entire surface with a material that does not affect the electrochemical reaction of the battery, that is, an insulating material containing a piezoelectric material.

The plurality of electrode tabs 350 coated with the piezoelectric material-containing insulating material are coupled by performing ultrasonic welding while applying a predetermined pressure in the direction of the arrow to the electrode lead 400, thereby forming the electrode tab-lead coupling part 375. To form. In the process of applying a predetermined pressure, the coating layer is energized by the piezoelectric material, and when the current is applied to the electrode lead 400, the local melting of the coating layer upon application of ultrasonic waves by heat generation due to the high resistance at the time of energization This becomes easy.

For example, thermal energy is generated by friction of vibration energy at the interface between the electrode tab 350 and the electrode tab and between the electrode tab 350 and the electrode lead 400 due to the high frequency vibration generated by ultrasonic waves of about 20 KHz. The surface of the electrode tab 350 is newly adhered by the breakdown of the coating layer of the bonding surface and the local plastic deformation while converting to, and the diffusion and recrystallization of atoms are promoted by the temperature rise due to the frictional heat to form a firm pressure point. Welding is performed rapidly.

Thus, by ultrasonic welding between the tab 350 and the tab and between the tab 350 and the electrode lead 400, electrical connection is possible between the tabs coated with the insulating material.

4 is a schematic view of a method of manufacturing an electrode by cutting a metal sheet according to another embodiment of the present invention, Figure 5 is a cross-sectional view of the electrode sheet of Figure 4 is shown schematically in the width direction 6 is an enlarged schematic view of one electrode of FIG. 4 for better understanding of the present invention.

Referring to these drawings, the metal sheet 500 may have a width W of the metal sheet to cut the plurality of electrode plates 512, 514, 516... And the electrode tabs 522, 524. ) And a length extending in a length (L) direction by at least two times the width (2 x C) of the electrode length (C) and at least two times the length (2 x D) of the electrode plate width (D).

The electrode tabs 522 are positioned at both end portions 530 and 540 with respect to the width W of the metal sheet 500 so as to face the center of the metal sheet 500. The electrode mixture 610 is applied. Further, the electrode plate 514 adjacent to the width W of the outermost electrode plate 512 and the metal sheet 500 is positioned so that its tab 524 is directed toward the outermost electrode plate 512. In, the electrode mixture 610 is applied to its upper surface.

The width of the portion 510 to which the electrode mixture 610 is applied is approximately twice the height A of the electrode plate 512 of the electrode, and one electrode each of the upper and lower portions based on the center (not shown) of the coating portion. The electrode mixture is applied to a sufficient range to include both the plates 514 and 516.

The non-coating portion 520, which is a portion where the electrode mixture 610 is not applied, applies the piezoelectric material-containing insulating material 620 and based on the width W direction of the metal sheet 500, the electrode tabs 522 and 524. ) And the electrode tabs 512 and 514 and the electrode tabs 522 and 524 such that the electrode tabs 522 and 524 are alternately arranged without being in contact with each other. Cut off. Such an alternating arrangement is shorter in width of the non-coating portion 520 compared to a symmetrical arrangement in which the electrode tabs 522, 524 are in contact with each other based on the center line in the width direction of the non-coating portion 520. The insulating material 620 applied to the 500 and the metal sheet 500 may be saved.

In the application of the piezoelectric substance-containing insulating material 620 to the uncoated portion 520, which is a portion of the metal sheet 500 to which the electrode mixture 610 is not applied, the width of the applied area prevents internal short circuit of the battery. While the piezoelectric material-containing insulating material 620 is applied in a range without deterioration of the battery, that is, in a range of 80 to 110% based on the width of the non-coating portion 520.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are provided to illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1

1-1. Manufacture of anode

LiCoO ₂ was used as the positive electrode active material, 94% by weight of LiCoO ₂ , 3.5% by weight of Super-P (conductive material) and 2.5% by weight of PVdF (binder) were added to N-methyl-2-pyrrolidone (NMP) as a solvent. After preparing the positive electrode mixture slurry, the positive electrode tab was attached to the aluminum foil, and the positive electrode mixture slurry was coated, dried and pressed on the remaining portions except for the positive electrode tab portion, and then the positive electrode tab portion was formed of BaTiO ₃ , PZT as piezoelectric material. Alternatively, the positive electrode was prepared by completely coating an insulating resin including PbTiO ₃ .

1-2. Preparation of Cathode

Artificial negative electrode was used as the negative electrode active material, 94% by weight of artificial graphite, 1% by weight of Super-P (conductive material), and 5% by weight of PVdF (binder) were added to NMP as a solvent to prepare a negative electrode mixture slurry. The negative electrode was prepared by coating, drying and pressing on copper foil.

1-3. Manufacture of batteries

Positioning the porous separator (Celgard ^TM ) between the positive electrode and the negative electrode prepared in each of the above 1-1 and 1-2, and align the positive electrode tabs arranged side by side with the electrode plates of 1-1, pressurizing and After bonding by ultrasonic welding while applying a current, an EC / EMC-based non-aqueous electrolyte containing lithium salt of 1M LiPF ₆ was added to prepare a lithium secondary battery having a capacity of 800mAh.

Comparative Example 1

An electrode and a battery were manufactured in the same manner as in Example 1, except that the piezoelectric material-containing insulating coating layer was not formed on the positive electrode tab portion.

Experimental Example 1

In order to compare the safety of the batteries prepared by Example 1 and Comparative Example 1, after charging each 10 cells of Example 1 and Comparative Example 1 to 4.2 V 50 drops at 1.8 m drop test (Drop Test As a result, the battery of Example 1 did not generate heat or ignite even one out of ten when the battery of Example 1 fell 50 times. However, in the battery of Comparative Example 1, heat generation or ignition occurred in three out of ten batteries after 50 drops.

Through the experimental results, it can be seen that the safety of the secondary battery in which the insulating coating layer including the piezoelectric material is formed on the positive electrode tab portion is greatly improved.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, in the method according to the present invention, when the conductive members required to form the electrically insulating coating layer are joined by welding, the ultrasonic welding is effectively applied by the application of the piezoelectric material even if the insulating coating layer of the welding portion is thickly applied. Since it can carry out, a desired bonding force can be obtained by a simple and easy method, and a production efficiency can be improved significantly.

Claims (17)

A method of welding and connecting another conductive member (B) to a conductive member (A) required to form an electrically insulating coating layer on the remaining portions except for the welded portion, wherein the electrically insulating coating layer containing a piezoelectric material is connected to the conductive member (A). After coating the entire surface of the member (A), while pressing the conductive member (B) against the conductive member (A) at a pressure that can be energized by the piezoelectric material and at the same time the current to the conductive members (A, B) Method of coupling by ultrasonic welding while applying. The method of claim 1, wherein the piezoelectric material is insulating material in a non-pressurized state and conductive in a pressurized state, and is selected from the group consisting of BaTiO ₃ , PZT, and PbTiO ₃ . The method of claim 1, wherein the piezoelectric material is included in an amount of 20 to 80 wt% based on the total weight of the coating layer. The method of claim 1, wherein the coating layer is formed to a thickness of 3 μm to 5 μm. The method of claim 1, wherein the electrically insulating coating layer has a structure in which a piezoelectric material is dispersed in a polymer resin selected from the group consisting of polyolefin, polyimide, polyamide, silicone resin, PP, and PE. delete delete delete delete delete As a method of manufacturing a secondary battery for producing a plate-shaped electrode by applying an electrode mixture containing an active material on a metal sheet and then cut, Based on the size of the electrode plate height and the electrode tab height ('electrode length'), using a metal sheet having a width of 2 to 8 times the electrode length and at least 2 times the electrode plate width, In order to obtain at least two electrodes adjacent to each other in the electrode length direction and the electrode plate width direction, the electrode mixture is successively patterned and coated on the metal sheet except for the portion corresponding to the electrode tab, And coating the insulating material on a portion of the electrode mixture to which the electrode mixture is not applied ('uncoated portion'), and then cutting the electrode mixture in the form of an electrode. The method of claim 11, wherein the width of the metal sheet corresponds to four to eight times the length of the electrode. The method of claim 11, wherein the length of the metal sheet is at least five times the width of the electrode plate. 12. The electrode mixture of claim 11, wherein an electrode mixture is applied to both ends of the metal sheet so that the electrodes (outermost electrodes) can be oriented so that the electrode tabs face the center portion. Adjacent electrode is coated with an electrode mixture such that its electrode tabs are oriented toward the outermost electrode. 13. The method of claim 12, wherein in the electrodes in which the electrode tabs are arranged in a direction facing each other with respect to the width direction of the metal sheet, cutting the electrodes so that the electrode tabs are not adjacent to each other and arranged in an alternating manner. How to feature. 16. The method of claim 15, wherein in electrodes in which the electrode tabs are arranged in a direction facing each other, the distance between the electrode plates is equal to or smaller than the sum of the heights of the electrode tabs thereof. 12. The method of claim 11, wherein the application of the insulating material to the plain is performed in the range of 80 to 110% based on the width between the electrode plates.

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