KR102420616B1 - Electrode Tab with Insulating Coating Layer and Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention relates to an electrode tab having an insulating coating layer including an aqueous binder and a water-dispersible organic dye, and a secondary battery including the same. The insulating coating layer of the electrode tab according to the present invention contains a water-based binder and water-dispersible organic dye, thereby exhibiting improved insulation and image recognition effect, thereby minimizing internal short circuit of the secondary battery, thereby ensuring safety.

Description

Electrode Tab with Insulating Coating Layer and Secondary Battery Comprising the Same

The present invention relates to a secondary battery including an electrode tab having an insulating coating layer, and more particularly, to an electrode tab having an insulating coating layer containing an aqueous binder and a water-dispersible organic dye, and a secondary battery including the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, a lot of research on batteries capable of meeting various needs is being conducted.

Typically, in terms of battery shape, demand for prismatic batteries and pouch-type batteries that can be applied to products such as mobile phones with thin thickness are high, and in terms of materials, lithium cobalt polymer batteries with high energy density, discharge voltage, and output stability are in high demand. Demand for lithium secondary batteries is high.

One of the main research tasks in such a secondary battery is to improve safety. In general, lithium secondary batteries are subject to high temperature and high pressure inside the battery that may be caused by abnormal operating conditions of the battery, such as internal short circuit, overcharge state exceeding the allowed current and voltage, exposure to high temperature, and shock caused by dropping. may cause the battery to explode. As one such case, there is a possibility that an internal short circuit occurs in the secondary battery upon impact such as a fall or the action of an external force.

1 schematically shows a general structure of a pouch-type secondary battery.

Referring to FIG. 1 , the secondary battery 10 includes an electrode assembly 100 , a battery case 200 , electrode tabs 10 and 11 , and electrode leads 20 and 21 .

The electrode assembly 100 includes a positive electrode plate, a negative electrode plate, and a separator. In the electrode assembly 100 , a positive electrode plate and a negative electrode plate may be sequentially stacked with a separator interposed therebetween. The electrode assembly 100 is typically a jelly-roll (winding type) electrode assembly having a structure in which long sheet-shaped positive electrodes and negative electrodes are wound with a separator interposed therebetween, and a plurality of positive and negative electrodes cut into units of a predetermined size. A stack type (stacked type) electrode assembly that is sequentially stacked with a separator interposed therebetween, and a structure in which bi-cells or full cells in which a predetermined unit of anode and cathode are stacked with a separator interposed therebetween of stacked/folding type electrode assembly and the like.

The battery case 200 may be formed in a size capable of accommodating the electrode assembly 100 , electrode tabs 10 and 11 , and electrode leads 20 and 21 to be described later.

The electrode tabs 10 and 11 extend from the electrode assembly 100 . For example, the positive electrode tab 10 extends from the positive electrode plate, and the negative electrode tab 11 extends from the negative electrode plate. Here, when the electrode assembly 100 is configured in a state in which a plurality of positive and negative electrode plates are stacked, the electrode tabs 10 and 11 extend from each of the positive and negative plates. At this time, the electrode tabs 10 and 11 are not directly exposed to the outside of the battery case 200 , but are connected to other components such as the electrode leads 20 and 21 to be exposed to the outside of the battery case 200 . have.

The electrode leads 20 and 21 are partially electrically connected to the electrode tabs 10 and 11 respectively extending from the positive and negative plates. In this case, the electrode leads 20 and 21 may be joined to the electrode tabs 10 and 11 by a method such as welding, which is indicated by a shade (W) in FIG. 1 . For example, the bonding method between the electrode leads 20 and 21 and the electrode tabs 10 and 11 may be general resistance welding, ultrasonic welding, laser welding, riveting, or the like. In addition, the electrode leads 20 and 21 may further include sealing tapes 30 and 31 at portions connected to the exposed portions.

In the embodiment in which a plurality of positive electrodes and negative electrodes are used to configure a pouch-type secondary battery, positive electrode tabs and negative electrode tabs extending from each of them are bonded to the electrode lead in a conventional manner in the art.

In a thermal abuse test, a secondary battery having this configuration has a high possibility of ignition when the separator in the corresponding portion contracts due to a rise in temperature around the electrode tab, for example, the positive electrode tab, and the positive electrode tab and the charged negative electrode come into contact with each other in a thermal abuse test. In particular, heat generation of the electrode tab portion is severe during high-rate charging and discharging, and safety enhancement of the portion is required.

In order to solve the internal short circuit of the battery, a method of attaching an insulating member to the electrode tab has been proposed. It is known that the insulating member is formed by coating the electrode tab portion with a slurry obtained by dispersing a mixture of an insulating binder and an inorganic filler for image recognition in a solvent. However, since the inorganic filler has a high density compared to the solvent, not only a problem of precipitation in the slurry occurs, but also the electrolyte is highly likely to penetrate into the micropores formed by the inorganic filler particles, which needs improvement.

Accordingly, an object of the present invention is to provide an electrode tab having an insulating coating layer capable of improving problems when using an existing inorganic filler, and a secondary battery including the same.

According to one aspect of the present invention, there is provided an electrode tab having an insulating coating layer including a water-based binder and a water-dispersible organic dye.

The insulating coating layer may include the water-dispersible organic dye in an amount of 0.1 to 10% by weight based on the total weight of the water-based binder and the water-dispersible organic dye.

The water-dispersible organic dye may have a density of 2 g/cm ³ or less.

The water-dispersible organic dye may include monoazo, disazo, azo aggregate, phthalocyanine, quinacridone, dioxazine, isoindoline, perylene, anthraquinone, perinone, thioindigo, or a mixture thereof. .

The aqueous binder is styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene , polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulf Ponated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, hydroxypropylmethylcellulose, hydroxypropylcellulose and diacetylcellulose, or mixtures thereof may be included.

The electrode tab may be a positive electrode tab.

According to another aspect of the present invention, there is provided a secondary battery including the electrode tab.

The insulating coating layer provided on the electrode tab of the present invention contains an aqueous binder and a water-dispersible organic dye, thereby exhibiting improved insulation and image recognition effects, thereby minimizing internal short circuit of the secondary battery, thereby ensuring safety.

1 is a cross-sectional view schematically showing the general structure of a conventional pouch-type secondary battery.
2 is a cross-sectional view schematically illustrating a secondary battery according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention. Accordingly, the embodiments described in the present specification and the configurations described in the drawings are only the most preferred embodiment, and do not represent all of the technical spirit of the present invention, so various equivalents and It should be understood that there may be variations.

One embodiment of the present invention relates to an electrode tab having an insulating coating layer including a water-based binder and a water-dispersible organic dye.

In one embodiment of the present invention, the insulating coating layer may be formed by coating a slurry containing an aqueous binder and a water-dispersible organic dye on an electrode tab, that is, a positive electrode tab, a negative electrode tab, or both, preferably a positive electrode tab.

In the insulating coating layer, the water-based binder functions to impart insulation. Examples of such an aqueous binder include styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene , polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepicrohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, Chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methyl cellulose, hydroxypropyl cellulose and diacetyl cellulose may be mentioned, but are not limited thereto. The aqueous binder may be used alone or in combination of two or more.

The water-dispersible organic dye is a component having a function of expressing a color to enable image recognition of the insulating coating layer, and allows the position, size and thickness of the insulating coating layer provided on the electrode tab to be easily checked with the naked eye.

The water-dispersible organic dye included in the insulating coating layer of the present invention has excellent deep color and shows excellent visible properties even when used in a small amount, and thus can be usefully used as a color developer for image recognition. For example, it is possible to overcome the problem that the inorganic filler used as a color developer in the insulating coating layer of the prior art is easy to precipitate in the slurry due to its high density compared to the solvent, and the electrolyte penetrates into the micropores formed by the inorganic particles. In particular, when the water-dispersible organic dye has a density of 2 g/cm ³ or less, it exhibits a density characteristic similar to that of a solvent, and thus is advantageous in terms of securing the dispersibility of the slurry.

Moreover, when an inorganic filler is used, a slurry stabilizer for improving the dispersibility of the inorganic filler in the slurry must be separately used. In the insulating coating layer of the present invention, a water-dispersible organic dye is used as a color developer, so that it has phase stability without a separate stabilizer. By forming from this secured slurry, an improved insulating effect can be exhibited.

In addition, the water-dispersible organic dye is capable of excellent color expression even in a small amount compared to the conventional inorganic filler. That is, the insulating coating layer of the present invention uses the water-dispersible organic dye in a small amount in the range of 0.1 to 10 wt%, preferably 0.1 to 2 wt%, based on the total weight of the water-dispersible organic dye and the water-based binder. Color expression is possible.

On the other hand, color expression is possible only when the amount of the conventional inorganic filler is higher than this. For example, an inorganic filler such as alumina should be used in an amount of about twice or more in order to express color at the same level as that of the water-dispersible organic dye used in the present invention.

Examples of the water-dispersible organic dye usable in the present invention include monoazo, disazo, azo aggregate, phthalocyanine, quinacridone, dioxazine, isoindoline, perylene, anthraquinone, perinone, thioindigo, and the like. and these may be used alone or in combination of two or more.

In addition, the insulation coating layer of the present invention may further include additives commonly used in the art, if necessary.

On the other hand, as a solvent or dispersion medium used in the slurry for forming the insulating coating layer, water; alcohols such as methanol, ethanol, propanol, and butanol; ketones such as acetone and kenyl ethyl ketone; ethers such as methyl ethyl ether, diethyl ether, and diisoamyl ether; lactones such as gamma-butyrolactone; lactams such as beta-lactam; Cyclic aliphatic, such as cyclopentane and cyclohexane; aromatic hydrocarbons such as benzene and toluene; Esters such as methyl lactate and ethyl lactate may be used. Among them, in particular, water may be suitably used as an environmentally friendly dispersion medium. The content of the solvent is not particularly limited, but is determined in consideration of the ease of coating and drying time.

Coating methods for forming the insulating coating layer include dipping, spray coating, spin coating, roll coating, die coating, and gravure printing. , bar coating, etc. may be performed, but is not limited thereto.

In one embodiment of the present invention, the insulating coating layer is preferably formed thinner than the active material layer of each electrode. For example, the thickness of the insulating coating layer may be approximately determined in the range of 5 to 100% or 10 to 50% of the thickness of the active material layer. When the insulating coating layer is formed thinner than the lower limit, it is difficult to expect the effect of electrical insulation, and when the insulating coating layer is formed thicker than the upper limit, the volume of the electrode tab becomes unnecessarily large, which is not preferable.

FIG. 2 schematically shows a pouch-type secondary battery according to an embodiment of the present invention, and shows an embodiment in which an insulating coating layer (C) is formed on the positive electrode tab of the pouch-type secondary battery as shown in FIG. 1 .

Since there is a high possibility that the positive electrode tab will preferentially contact the negative electrode (current collector or active material) of the electrode assembly during external impact due to a drop, the slurry for forming an insulating coating layer of the present invention is preferably coated on the positive electrode tab, and the positive electrode tab and the positive electrode tab An insulating coating layer may be formed on both the negative electrode tabs.

In addition, although only one positive electrode tab is shown in FIG. 2 , in a secondary battery including a plurality of positive and negative electrode tabs because a plurality of positive and negative electrodes are used, an insulating coating layer may be formed on each of the plurality of positive and negative tabs. can

In addition, in the present invention, the insulating coating layer may be formed on a part or all of the electrode tab.

As a non-limiting example of the case in which the insulating coating layer is formed on a portion of the electrode tab, the electrode tab may be formed on a portion of the electrode tab adjacent to the electrode assembly, which is a portion with a high probability of contact with the electrode assembly. Alternatively, there may be an embodiment in which an insulating coating layer is formed on a portion of the electrode tab except for a connection portion with an electrode lead.

An insulating coating layer may be formed on the entire electrode tab. Since the electrical insulating coating layer is melted and removed during welding for connection with the electrode lead, it is possible to form an insulating coating layer on the entire electrode tab.

In the present invention, the electrode assembly formed by sequentially stacking with a separator interposed between the positive electrode and the negative electrode is stacked in a stack type or stack-folding type to constitute a secondary battery, or is wound in a jelly-roll type to constitute a secondary battery. can

The battery case may have various shapes, for example, a pouch-type case or a prismatic case.

The positive electrode, for example, is prepared by coating a mixture of a positive electrode active material, a conductive material, and a binder on a positive electrode current collector and then drying, and, if necessary, further adding a filler to the mixture.

The positive active material may include 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 Formula Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; 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 ; Ni site-type lithium nickel oxide represented by the formula LiNi _{1 - x} M _x O ₂ (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _{2 - x} M _x O ₂ (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where 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 an alkaline earth metal ion; disulfide compounds; Although Fe2 _{(MoO4)3 etc. are} mentioned, It is not limited only to these.

The positive electrode current collector is generally made to have a thickness of 3 to 500 μm. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or a surface of aluminum or stainless steel. Carbon, nickel, titanium, silver or the like surface-treated may be used. The current collector may increase the adhesive force of the positive electrode active material by forming fine irregularities on its surface, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, and a nonwoven body are possible.

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 active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change 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 fibers and metal fibers; 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 may be used.

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

The filler is optionally used as a component for suppressing the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. For example, an olefin-based polymer such as polyethylene or polypropylene; A fibrous material such as glass fiber or carbon fiber is used.

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

The negative electrode current collector is generally made to have a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Carbon, nickel, titanium, silver, etc. surface-treated, aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven body, and the like.

The negative electrode material includes, for example, carbon such as non-graphitizable carbon and graphitic carbon; LixFe 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, elements of Groups 1, 2, and 3 of the periodic table, halogen; lithium metal; lithium alloy; 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 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. Examples of such a separation membrane include olefin-based polymers such as chemical-resistant and hydrophobic polypropylene; A sheet or nonwoven fabric made of glass fiber or polyethylene is 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 consists of a non-aqueous electrolyte and lithium. As the non-aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

Examples of the non-aqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl Rho lactone, 1,2-dimethoxyethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, aceto Nitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative , tetrahydrofuran derivatives, ether, methyl pyropionate, aprotic organic solvents such as ethyl propionate may be used.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, A polymer containing an ionic dissociation group or 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, etc. 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.

In one embodiment of the present invention, the lithium salt included in the electrolyte is, 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, lithium chloroborane, lower aliphatic lithium carboxylate, lithium 4-phenylborate, imide, etc. can be used

In addition, the electrolyte solution for the purpose of improving charge and discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n- glyme (glyme), hexaphosphoric acid triamide, Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. may be added. have. In some cases, in order to impart incombustibility, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics.

The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments and may be modified in various other forms, and those of ordinary skill in the art to which the present invention pertains. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Example One

^The coating slurry ( solid content: 40%).

The slurry was coated on the electrode tab portion of the positive electrode current collector to have a thickness of 30% of the positive electrode active material layer and a width of 1.7 mm to prepare a positive electrode having an insulating coating layer.

Example 2

A positive electrode was manufactured in the same manner as in Example 1, except that an aqueous binder and a water-dispersible organic dye were used in a weight ratio of 99.5:0.5.

comparative example One

After dissolving carboxymethylcellulose (CMC 2200, Daicel), a slurry stabilizer, using water as a solvent, SBR (BM-L301, Zeon) as an aqueous binder and alumina (LS235, Japan Light Metals) as an inorganic filler were added 95:5 was added in a weight ratio of to obtain a coating slurry (solid content 40%). In this case, the slurry stabilizer was used in an amount of 0.5 wt% based on the alumina particles.

The slurry was coated on the electrode tab portion of the positive electrode current collector to have a thickness of 30% of the positive electrode active material layer and a width of 1.7 mm to prepare a positive electrode having an insulating coating layer.

comparative example 2

A positive electrode was manufactured in the same manner as in Comparative Example 1, except that the aqueous binder and the inorganic filler were used in a weight ratio of 80:20.

Experimental example

By applying the positive electrodes prepared in Examples 1 and 2 and Comparative Examples 1 and 2, an image recognition (Vision) inspection and safety test were performed in the following manner.

<Image recognition inspection>

Each positive electrode was put into a lithium secondary battery assembly machine, and it was checked whether the insulation layer coating width was effectively read by the inspection machine.

<Safety check>

After preparing 5 secondary battery specimens for each positive electrode, a hot box test was performed at 150° C. for 1 hour.

The results of the two tests are shown in Table 1 below.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 image recognition test Pass Pass NG Pass safety inspection Pass Pass Pass NG

As can be seen in Table 1, the secondary batteries to which the positive electrodes prepared in Examples 1 and 2 were applied passed both image recognition and safety inspection. On the other hand, the anode of Comparative Example 1 did not pass the image recognition test because the color development was not sufficient and the width of the insulating coating layer was not recognized because it was transparent. And, in the case of Comparative Example 2, ignition occurred in two of the specimens, which caused voids between the insulating coating layers due to excessive use of inorganic fillers, resulting in insufficient insulating function, resulting in an internal short circuit between the positive and negative electrodes. it has occurred

Claims (7)

It has an insulating coating layer comprising a water-based binder and a water-dispersible organic dye,
The aqueous binder is styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene , ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepicrohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, Latex, polyester resin, phenolic resin, epoxy resin, polyvinyl alcohol, hydroxypropylmethylcellulose, hydroxypropylcellulose and diacetylcellulose, or a mixture thereof,
The water-dispersible organic dye is an electrode tab comprising monoazo, disazo, azo aggregate, quinacridone, dioxazine, isoindoline, perylene, anthraquinone, perinone, thioindigo, or a mixture thereof. According to claim 1,
The insulating coating layer is an electrode tab comprising the water-dispersible organic dye in an amount of 0.1 to 10% by weight based on the total weight of the water-based binder and the water-dispersible organic dye. According to claim 1,
The water-dispersible organic dye is an electrode tab having a density of 2 g/cm ³ or less. delete delete According to claim 1,
The electrode tab is a positive electrode tab. A secondary battery comprising the electrode tab according to any one of claims 1 to 3 and 6 .

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