CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2017-0154709 filed in the Korean Intellectual Property Office on Nov. 20, 2017, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method of manufacturing an irregular electrode.

BACKGROUND ART

Along with the development of technologies of mobile devices and an increase in demands for mobile devices, demands in a rechargeable battery as an energy source are remarkably increased, and such a rechargeable battery necessarily includes an electrode assembly as a power generation component.

An electrode assembly is configured by assembling a positive electrode, a separator, and a negative electrode in a predetermined form, and the positive electrode and the negative electrode may be a plate type electrode formed by coating and drying a positive electrode slurry and a negative electrode slurry including an active material on a current collector formed of metal foil with electric conductivity.

Manufacture of a plate type electrode may include a process of manufacturing an electrode mixture including an electrode active material, a process of coating the electrode mixture on metal foil to manufacture an electrode sheet, a process of forming an electrode tap on an electrode, a process of rolling electrodes, a process of notching the electrodes to a small width with a desired shape and size to manufacture a unit electrode, and so on.

Thereamong, a schematic view of the process of manufacturing the electrode sheet is shown inFIG. 1.

Referring toFIG. 1, according to a process10of manufacturing an electrode sheet, the electrode sheet is manufactured via a process of allowing a metal sheet50moved by a rewinder40to contact a slot die coater20for discharging electrode slurry and then coating the electrode slurry on the metal sheet50to constitute a line52. The electrode line52may be formed in one number or may be formed in two or plural number by repeating a plurality of coating processes.

As such, the metal sheet50on which the electrode line52is formed may be notched with a desired shape and size to manufacture one unit electrode.

To diversify products using a rechargeable battery and apply the rechargeable battery to various devices with a curved line or a curved surface, the rechargeable battery is manufactured with an irregular design of a geometric structure, departing from an already known rectangular or cylindrical structure.

As an example of the irregular design, recently, an ‘L’ shaped irregular rechargeable battery with lack of a portion in a long direction has attracted attention to be applied to a slim type, curved type, or various designs, and to embody this, an electrode has also been manufactured with the aforementioned irregular structure.

However, when a metal sheet shown inFIG. 2is notched in, for example, an irregular shape corresponding to a perforated line c, a portion54of the electrode line52, which is not included in the irregular shape, is discarded, and thus, main components of the electrode line52, i.e., expensive materials such as an electrode active material of electrode slurry, a binder, and a solvent are wasted.

This is the reason for increasing manufacturing costs of an irregular electrode and a rechargeable battery including the irregular electrode, and thus, there is an urgent need for technologies for overcoming this issue.

DISCLOSURE

Technical Problem

The present invention has been made in an effort to overcome the aforementioned problem of the above conventional art and technical objects requested from the past.

In detail, an embodiment of the present invention provides a method of manufacturing an irregular electrode, including forming an electrode line and notching the electrode line in an irregular shape, for manufacturing an electrode in a desired irregular shape and minimizing electrode slurry that is unnecessarily wasted during the manufacturing process.

Technical Solution

According to an embodiment of the present invention, a method of manufacturing an irregular electrode includes: forming a first electrode line by continuously coating a first electrode slurry on a metal sheet, forming at least one second electrode line formed with a dotted line shape including uncoated portions (plain portions) and positioned in parallel to the first electrode line by intermittently coating a second electrode slurry on the metal sheet that does not overlap the first electrode line, and forming the irregular electrode by notching the metal sheet with an irregular shape including the second electrode line and the first electrode line except for the uncoated portions of the at least one second electrode line.

That is, the method of manufacturing an irregular electrode according to the present invention may have a first feature of performing coating to configure an irregular shape in which an electrode line itself has the plain portion by combining the first electrode line with a straight line shape and a second electrode line with a dotted line shape including the plain portion.

This means that electrode slurry is saved by as much as the amount of electrode slurry to be coated on the plain portion of the second electrode line, and thus, it may be possible to reduce manufacturing costs of an electrode.

The method of manufacturing an irregular electrode according to the present invention may include an operation of performing notching on a portion except for the plain portion in which electrode slurry is not present, and thus, may have a second feature of minimizing electrode slurry to be discarded during notching, thereby preventing expensive organic and inorganic materials such as an electrode active material, a binder, a solvent, and a conductive material, which are included in the electrode slurry, from being wasted.

In the present invention, the forming of the first electrode line and the forming of the at least one second electrode line may be simultaneously performed, and the method may further include rolling and drying the first electrode line and the second electrode line prior to the forming of the irregular electrode.

The first electrode and the at least one second electrode line may be formed using a slot die coater including a plurality of slurry discharge nozzles, and in detail, the forming of the first electrode line and the forming of the second electrode line may be simultaneously performed using a slot die coater including a first slot nozzle for forming the first electrode line, and a second slot nozzle positioned at opposite ends of the first slot nozzle and configured to form the at least one second electrode line.

Hereinafter, a detailed process for completing a shape of an irregular electrode using a manufacturing method according to the present invention will be described in detail through unlimited examples.

In one example, in the forming of the at least one second electrode line, a pair of second electrode lines that extends from opposite boundaries of the first electrode line may be formed while the second electrode slurry is coated along the opposite boundaries of the first electrode line.

That is, the first electrode line and the second electrode lines may be integrated into each other on a plane to form one irregular line.

In an example of the irregular line, one of the pair of second electrode lines is connected with a first boundary of the opposite boundaries and another of the pair of second electrode lines is connected with a second boundary of the opposite boundaries may be symmetrical to each other based on an imaginary line for uniformly dividing the first electrode line between the opposite boundaries.

As another example, one of the pair of second electrode lines is connected with a first boundary of the opposite boundaries and another of the pair of second electrode lines is connected with a second boundary of the opposite boundaries may be asymmetrical based on an imaginary line for uniformly dividing the first electrode line between the opposite boundaries.

The forming of the irregular electrode may be performed to form an irregular electrode at each of one side and another side based on an imaginary line for uniformly dividing the first electrode line between boundaries of the first electrode line.

Accordingly, while notching may be performed at one side and the other side based on an imaginary line, two irregular electrodes may be manufactured per notching.

As an example, the irregular shape may include a first electrode portion included in the first electrode line, and a second electrode portion that is included in the at least one second electrode line, extends from the first electrode portion, and has a smaller size than the first electrode portion to form at least one step difference on a plane, and the forming of the irregular electrode may include notching the metal sheet corresponding to the first electrode portion and the second electrode portion.

The at least one step difference may include a step difference corner formed at a portion at which an external side of the first electrode portion and an external side of the second electrode portion cross each other at an angle equal to or greater than 30 degrees an angle less than 180 degrees, and the metal sheet may be further notched to form an external indented portion formed by indenting a portion of each of the first electrode portion and the second electrode portion inwardly at the step difference corner.

The step difference may include two or less of the step corner, and in detail, may include only one of the step corner to form the irregular electrode with an ‘L’ shape on a plane.

FIG. 3is a schematic diagram of a battery cell including an irregular electrode according to the conventional art.

Referring toFIG. 3, a battery cell100may be configured in such a way that external circumference sides121,122,123, and124of a cell case120are sealed via thermal bonding in a state in which an electrode assembly110is installed in the cell case120along with an electrolyte solution.

In detail, the electrode assembly110may be configured in such a way that two electrode portions110aand110bwith different planar shapes and sizes with respect to the ground are separated based on a boundary A, and accordingly, a step difference130formed due to the different sizes of the electrode portions110aand110bmay be formed on the electrode assembly110. The cell case120may be configured in a shape corresponding to the electrode assembly110, and the external circumference sides121,122,123, and124may be sealed along end portions of the electrode assembly110, and thus, the battery cell100may be configured with an irregular structure including the step difference130to correspond to a shape of the electrode assembly110, but not a conventional rectangular structure.

In the structure of the battery cell100shown inFIG. 3, the cell case120may be configured in such a way that the different external circumference sides121and122cross each other to correspond to a shape of an external circumference corner C at the external circumference corner C at a portion at which external circumference sides of the electrode portions110aand110bcross each other, and thus, a relatively wide sealing area may be formed at an intersection portion of the external circumference sides121and122.

In addition, a point that shares a sealing portion while the external circumference sides121and122cross each other has relatively low sealing force compared with other portions, and thus, the external circumference sides121and122of the cell case120, adjacent to the external circumference corner C, also requires a relatively wide thermal bonding sealing area compared with the other external circumference sides123and124.

Accordingly, the structure of the battery cell100may be disadvantageous in that spatial utility of a device is degraded by as much as a sealing area which is unnecessarily occupied by the external circumference sides121and122at the external circumference corner C.

In general, except for the external circumference side124on which electrode leads101and102are formed, each of the external circumference sides121,122, and123that is sealed via thermal bonding in the cell case120needs to be bent in a direction of a side surface of the electrode assembly110to prevent moisture from penetrating and to reduce an area of a battery cell, but in the structure ofFIG. 2, the external circumference sides121and122of the cell case120, adjacent to the external circumference corner C, are connected with each other to correspond to the external circumference corner C, and thus, it may not be easy to bend the external circumference sides121,122, and123in the direction of the side surface of the electrode assembly110.

If a portion at which the external circumference sides121and122are connected with each other is cut for being bent, a sealing region of the cell case120is not ensured between the external circumference corner C and the cutting portion, and thus, there is a problem in that a sealing state is easily released.

Accordingly, according to the present invention, an irregular electrode may be manufactured to form an external circumference indented portion at an intersection point of the first electrode portion and the second electrode portion cross each other, and thus, a battery cell including the irregular electrode may improve sealing reliability while a cell case is further sealed via thermal bonding at the external circumference indented portion.

The external indented portion may include, on a plane, a rounded structure including a curved line, a composite structure formed by connecting a curved line and a straight line, or a polygon structure formed by connecting a plurality of straight lines.

The method of manufacturing the irregular electrode may further include performing additional notching to form an electrode tap that protrudes outward from at least one of the first electrode portion and the second electrode portion.

The method of manufacturing the irregular electrode may further include performing additional notching to form chamfered edges of at least one of the first electrode portion and the second electrode portion.

The irregular electrode may be a positive electrode or a negative electrode.

The positive electrode may be manufactured by coating and then drying a mixture of a positive active material, a conductive material, and a binder on, for example, a positive electrode current collector and/or an extension current collector, and as necessary, the mixture may further include a filler.

In general, the positive electrode current collector and/or the extension current collector may be formed to a thickness of 3 to 500 micrometers. The positive electrode current collector and the extension current collector are not particularly limited as long as a corresponding battery has high conductivity while a chemical change is not caused in the battery, and for example, may be formed of stainless steel, aluminum, nickel, titanium, bake carbon, or aluminum, or a material formed by surface-processing a surface of stainless steel with carbon, nickel, titanium, silver, or the like. The positive electrode current collector and the extension current collector may have fine protrusions and depressions formed on a surface thereof to enhance adherence of a positive active material, and may be formed in various forms such as a film, a sheet, a foil, a net, a porous body, a foaming body, and a non-woven fabric structure.

The positive active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2) or a compound substituted with one or more transition elements; lithium manganese oxide represented by chemical formulae Li1+xMn2−xO4(where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; Ni site-type lithium nickel oxide represented by chemical formula LiNi1−xMxO2(where M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x=0.01 to 0.3); lithium manganese composite oxide represented by chemical formula LiMn2−xMxO2(where M=Co, Ni, Fe, Cr, Zn or Ta and x=0.01 to 0.1) or Li2Mn3MO8(where M=Fe, Co, Ni, Cu, or Zn); LiMn2O4with an Li portion of chemical formula substituted with an alkaline earth metal ion; a disulfide compound; Fe2(MoO4)3, and so on, but is not limited thereto.

In general, the conductive material may be included with 1 to 30 wt % based on a total weight of a mixture including a positive active material. The conductive material is not particularly limited as long as a corresponding battery has high conductivity while a chemical change is not caused in the battery, and for example, may use a conductive material including graphite such as natural graphite or artificial graphite; carbonblack such as carbonblack, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; conductive finer such as carbon fiber or metal fiber; metal powder such as fluoro carbon, aluminum, or nickel powder; conductive whisky such as zinc oxide and potassium titanate; conductive metal oxide such as oxidation titanium; and polyphenylene derivative.

The binder may be a component that facilitates coupling of an active material, a conductive material, and so on, and coupling of a current collector, and in general, may be added with 1 to 30 wt % based on a total weight of a mixture including a positive active material. An example of the binder may include poly vinylidene fluoride, polyvinylalcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonate EPDM, styrene butylene rubber, fluorine rubber, and various copolymers.

The filler may be selectively used as a component for suppressing expansion of a positive electrode, and is not particularly limited as long as the filler is formed of any material in a fiber phase while a chemical change is not caused in the filler, and may use a material in a fiber phase, for example, an olefin-based polymer such as polyethylene or polypropylene; glass fiber, or carbonfiber.

The negative electrode may be manufactured by coating and drying a negative active material on a negative electrode current collector and/or an extension current collector, and as necessary, may selectively and further include the aforementioned components.

In general, the negative electrode current collector and/or the extension current collector may be formed to a thickness of 3 to 500 micrometers. The negative electrode current collector and the extension current collector are not particularly limited as long as a corresponding battery has high conductivity while a chemical change is not caused in the battery, and for example, may be formed of copper, stainless steel, aluminum, nickel, titanium, or bake carbon, or a material formed by surface-processing a surface of copper or stainless steel with carbon, nickel, titanium, silver, or the like, or may use an aluminum-cadmium alloy or the like. Like the positive electrode current collector, the negative electrode current collector and the extension current collector may have fine protrusions and depressions formed on a surface thereof to enhance adherence of a negative active material, and may be formed in various forms such as a film, a sheet, a foil, a net, a porous body, a foaming body, and a non-woven fabric structure.

The negative electrode active material may be, for example, carbon such as hard graphitized carbon or graphite-based carbon;

LixFe2O3(0≤x≤1), LixWO2(0≤x≤1), metal composite oxide such as SnxMe1−xMe′yOz(Me: Mn, Fe, Pb, Ge; Me′: Al, B, P, Si, group 1, 2, or 3 elements in the periodic table, halogen; 0<x≤1; 1≤y≤3; 1≤z≤8); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxide such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; and a conductive polymer such as polyacetylene, and a Li—Co—Ni-based material.

Advantageous Effects

As described above, the method of manufacturing the irregular electrode according to exemplary embodiments of the present invention may perform coating to configure an irregular shape in which an electrode line itself has the plain portion by combining the first electrode line with a straight line shape and a second electrode line with a dotted line shape including the plain portion, and accordingly, electrode slurry may be advantageously saved by as much as the amount of electrode slurry to be coated on the plain portion of the second electrode line.

In addition, the method may include an operation of performing notching on a portion except for the plain portion in which electrode slurry is not present, and thus, may minimize electrode slurry to be discarded during notching, thereby preventing expensive organic and inorganic materials such as an electrode active material, a binder, a solvent, and a conductive material, which are included in the electrode slurry, from being wasted.

