Title of the invention: Composition for forming insulating layer for lithium secondary battery and method of manufacturing electrode for lithium secondary battery using the same
Technical field
[One]
Mutual citation with related applications
[2]
This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0013009 filed on February 1, 2018, and all contents disclosed in the documents of the Korean patent application are included as part of this specification.
[3]
Technical field
[4]
The present invention relates to a composition for forming an insulating layer for a lithium secondary battery and a method of manufacturing an electrode for a lithium secondary battery using the same.
Background
[5]
As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, many studies on batteries that can meet various demands are being conducted.
[6]
Typically, in terms of the shape of the battery, the demand for prismatic batteries and pouch-type batteries that can be applied to products such as mobile phones is high due to its thin thickness. There is high demand for secondary batteries.
[7]
One of the major research tasks in these secondary batteries is to improve safety. The main cause of battery safety-related accidents is the arrival of abnormal high temperature conditions due to a short circuit between the positive and negative electrodes. In other words, under normal circumstances, a separator is located between the positive electrode and the negative electrode to maintain electrical insulation, but the battery may overcharge or overdischarge, or cause an internal short circuit due to dendritic growth of the electrode material or foreign matter. , In the abnormal misuse situation, such as a sharp object such as a screw penetrating the battery or an unreasonable deformation of the battery due to an external force, the existing separator alone has limitations.
[8]
In general, the separator is mainly a microporous membrane made of a polyolefin resin, but its heat resistance is about 120 to 160°C, which is insufficient in heat resistance. Accordingly, when an internal short circuit occurs, there is a problem in that the separator contracts due to the heat of the short-circuit reaction to expand the short-circuit and lead to a thermal runaway state in which larger and more reaction heat is generated.
[9]
In addition, in general, a secondary battery is manufactured in a square shape by cutting a positive electrode and a negative electrode into a predetermined size and overlapping several sheets. At this time, the edge of the positive or negative electrode coated with a polymer electrolyte has a very small needle-shaped sharp part that is inconspicuous, and if the electrode is stacked, a minute internal short circuit occurs at this part, which may adversely affect the performance of the battery. In particular, even when the polymer electrolyte is coated on the edge, since there are more irregular sides than the inside, it is not evenly coated and a short circuit is likely to occur. In addition, when the electrodes are stacked, a short circuit between the anode and the cathode may occur if the lower and upper layers of the electrode deviate even a little.
[10]
As described above, various methods have been studied to reduce the possibility of cell deformation, external impact, or physical short circuit between the anode and the cathode.
[11]
For example, in order to prevent the electrode tab from contacting the top of the electrode assembly and causing a short circuit due to the movement of the electrode assembly while the battery is completed, an insulating tape having a predetermined size is placed on the electrode tab adjacent to the top of the current collector. There is a way to attach it. As such an insulating tape, a polyimide film is usually used, and it is generally recommended to wind the insulating tape to a length slightly extended from the top of the current collector to the bottom. In addition, in order to prevent loosening, it is usually wound about 2 to 3 times.
[12]
However, the winding operation of the insulating tape is very cumbersome, and when the insulating tape is wound to a length slightly extending downward from the top of the current collector, such a portion may cause an increase in the thickness of the electrode assembly. Moreover, there is a problem that the electrode tab is easy to be released when bending.
[13]
Korean Patent Publication No. 10-2015-0031724 discloses a secondary battery.
[14]
[Prior technical literature]
[15]
[Patent Literature]
[16]
Korean Patent Publication No. 10-2015-0031724
Detailed description of the invention
Technical challenge
[17]
An object of the present invention is to provide a composition for forming an insulating layer for a lithium secondary battery that can easily check the alignment position when the insulating layer is formed, and can suppress the occurrence of erosion of the active material layer in a portion overlapping with the electrode active material layer. will be.
[18]
In addition, another object of the present invention is to provide a method of manufacturing an electrode for a lithium secondary battery using the above-described composition for forming an insulating layer for a lithium secondary battery.
[19]
In addition, another object of the present invention is to provide an electrode for a lithium secondary battery including an insulating layer formed of the above-described composition for forming an insulating layer for a lithium secondary battery.
[20]
In addition, another object of the present invention relates to a lithium secondary battery including the above-described lithium secondary battery electrode.
Means of solving the task
[21]
The present invention is a binder polymer; A colorant containing at least one selected from the group consisting of organic dyes, oil-soluble dyes, and organic phosphors; And a solvent, and having a viscosity of 1,000 cP or more at 25° C. provides a composition for forming an insulating layer for a lithium secondary battery.
[22]
In addition, the present invention comprises the steps of forming an undried electrode active material layer by applying an active material slurry composition on an electrode current collector; Forming an undried insulating layer by applying the composition for forming an insulating layer for a lithium secondary battery to overlap the undried electrode active material layer in a partial region; And it provides a method of manufacturing an electrode for a lithium secondary battery comprising the step of simultaneously drying the undried electrode active material layer and the undried insulating layer.
[23]
In addition, the present invention is an electrode current collector; An electrode active material layer formed on the electrode current collector; And an insulating layer formed on the electrode contact body and formed to overlap the electrode active material layer in a partial region, wherein the thickness of the insulating layer in the region overlapping the electrode active material layer decreases toward the electrode active material layer, , The insulating layer provides an electrode for a lithium secondary battery, formed of the composition for forming an insulating layer for a lithium secondary battery described above.
[24]
In addition, the present invention provides a lithium secondary battery including the above-described lithium secondary battery electrode.
Effects of the Invention
[25]
The composition for forming an insulating layer for a lithium secondary battery according to the present invention has excellent liquid stability by using an organic dye or the like as a colorant, and the alignment position when the insulating layer is formed can be easily identified.
[26]
In addition, the composition for forming an insulating layer for a lithium secondary battery according to the present invention can easily dissolve the colorant without using a dispersant, and thus, the viscosity of the composition can be easily adjusted, and the insulating layer formed therefrom is combined with the electrode active material layer. In the overlapping area, adhesion is excellent and erosion can be suppressed.
[27]
Accordingly, the electrode for lithium secondary battery and lithium secondary battery manufactured using the composition for forming the insulating layer can easily detect the position of the insulating layer, so that easy quality evaluation is possible, and the quality and stability of the product can be secured.
Brief description of the drawing
[28]
1 is a photograph of an overlapping region of a positive electrode active material layer and an insulating layer in a cross section of a positive electrode prepared in Example 1 observed with a scanning electron microscope (SEM).
[29]
FIG. 2 is a photograph of an overlapping region of a positive electrode active material layer and an insulating layer in a cross section of the positive electrode prepared in Comparative Example 1, observed with a scanning electron microscope.
[30]
3 shows the results of an electrolyte dissolution evaluation experiment for the positive electrode prepared in Example 1.
[31]
4 shows the evaluation results of the electrolyte dissolution evaluation experiment for the positive electrode prepared in Example 2.
[32]
5 is a photograph for confirming the liquid stability of the composition for forming an insulating layer of Example 1.
[33]
6 is a photograph for confirming the liquid stability of the composition for forming an insulating layer of Comparative Example 2.
[34]
7 is a surface inspection photograph for evaluating the coating properties of the composition for forming an insulating layer of Example 1.
[35]
8 is a surface inspection photograph for evaluating the coating properties of the composition for forming an insulating layer of Example 3.
[36]
9 is an optical micrograph for evaluating the coating properties of the composition for forming an insulating layer of Example 1.
[37]
10 is an optical micrograph for evaluating the coatability of the composition for forming an insulating layer of Example 3.
Mode for carrying out the invention
[38]
The terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of ​​the present invention based on the principle that there is.
[39]
The terms used in the present specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.
[40]
In the present specification, terms such as "comprises", "includes" or "have" are intended to designate the presence of implemented features, numbers, steps, components, or a combination thereof, and one or more other features or It is to be understood that the possibility of the presence or addition of numbers, steps, elements, or combinations thereof is not preliminarily excluded.
[41]
In this specification, "%" means% by weight unless otherwise indicated.
[42]
In the present specification, the average particle diameter (D 50 ) may be defined as a particle diameter corresponding to 50% of the cumulative volume in the particle diameter distribution curve of the particles. The average particle diameter (D 50 ) can be measured using, for example, a laser diffraction method. In general, the laser diffraction method can measure a particle diameter of about several mm from a submicron region, and high reproducibility and high resolution results can be obtained.
[43]
Hereinafter, the present invention will be described in detail.
[44]
[45]
Composition for forming an insulating layer
[46]
The composition for forming an insulating layer of the present invention comprises at least one selected from the group consisting of (1) a binder polymer, (2) an organic dye, an oil soluble dye, and an organic phosphor. It contains a coloring agent and (3) a solvent, and the viscosity at 25 degreeC is 1,000 cP or more.
[47]
For example, the insulating layer may be formed on an uncoated portion of the electrode current collector on which the electrode active material layer is not coated, or may be formed to partially overlap the electrode active material layer. At this time, in general, in order to check the coating position of the insulating layer, it may be used by mixing a pigment or the like with the composition for forming the insulating layer. However, in general, pigments such as inorganic pigments and organic pigments are insoluble in water or organic solvents, and are easily agglomerated in the composition, so that they are difficult to be uniformly distributed in the insulating layer. A dispersant may be added to the composition for forming an insulating layer in order to prevent the problem of aggregation of the pigment. However, in order to perform the process of superimposing the electrode active material layer and the insulating layer, the composition for forming an insulating layer requires a viscosity of a certain level or higher. This is difficult and there is a problem in that aggregation may occur.
[48]
However, the composition for forming an insulating layer for a lithium secondary battery of the present invention uses an organic dye having excellent solubility and dispersibility even at a high level of viscosity as a colorant, and does not require a separate dispersant and has excellent coating properties.
[49]
In addition, the composition for forming an insulating layer for a lithium secondary battery of the present invention is excellent in liquid stability by using an organic dye or the like as a colorant, and the alignment position when the insulating layer is formed can be easily identified.
[50]
In addition, the composition for forming an insulating layer for a lithium secondary battery according to the present invention can easily dissolve the colorant without using a dispersant, and thus, the viscosity of the composition can be easily adjusted, and the insulating layer formed therefrom is combined with the electrode active material layer. In the overlapping area, adhesion is excellent and erosion can be suppressed.
[51]
Accordingly, the electrode for lithium secondary battery and lithium secondary battery manufactured using the composition for forming the insulating layer can easily detect the position of the insulating layer, so that easy quality evaluation is possible, and the quality and stability of the product can be secured.
[52]
[53]
The binder polymer is, for example, a component that imparts binding property to an electrode current collector and/or an electrode active material layer when the composition for forming an insulating layer is formed as an insulating layer.
[54]
The binder polymer is polyvinylidene fluoride, polyvinyl alcohol, styrene butadiene rubber, polyethylene oxide, carboxyl methyl cellulose, cellulose acetate ), cellulose acetate butylate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinylalcohol, cyanoethyl cellulose ), cyanoethyl sucrose, flulan, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone , Polyvinylacetate, ethylene-vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyarylate, and at least one binder polymer selected from the group consisting of a low molecular weight compound having a molecular weight of 10,000 g/mol or less I can. Among them, the binder polymer may be polyvinylidene fluoride in terms of adhesion, chemical resistance, and electrochemical stability.
[55]
The polyvinylidene fluoride polymer may have a weight average molecular weight of 400,000 to 1,500,000, preferably 600,000 to 1,200,000, in terms of improving adhesion to the electrode active material layer and securing a desired viscosity.
[56]
The polyvinylidene fluoride polymer may have a melting point of 150°C to 180°C, preferably 165°C to 175°C, in terms of improving solubility for the composition.
[57]
Preferably, as the binder polymer, a material used as a binder in the electrode active material layer described later, that is, the same material as the binder for the electrode active material layer may be used. In this case, adhesion or adhesion between the insulating layer and the electrode active material layer may be further improved.
[58]
The binder polymer is 5 parts by weight to 15 parts by weight, preferably 7 parts by weight to 12 parts by weight, more preferably 7.5 parts by weight based on 100 parts by weight of the solvent in terms of realization of desired viscosity properties and easy formation of an insulating layer. It may be included in parts by weight to 10 parts by weight.
[59]
[60]
The colorant may be included in the composition to determine the position of the insulating layer formation through a detection device when the composition for forming an insulating layer for a lithium secondary battery is coated with the insulating layer.
[61]
The colorants include organic dyes, oil soluble dyes and/or organic phosphors. The colorant according to the present invention including an organic dye, an oil-soluble dye and/or an organic phosphor has excellent solubility in a solvent, and when using it, the dye or phosphor can be uniformly distributed in the insulating layer. The composition for forming the insulating layer significantly reduces the occurrence of aggregation of the colorant compared to the case of using a pigment as a colorant, and phase separation that may occur when a dispersant is used to prevent the aggregation of the pigment, decreases liquid stability, and electrode The occurrence of erosion in the overlapping region between the active material layer and the insulating layer may be significantly reduced.
[62]
The organic dyes include anthraquinone dyes, anilino azo dyes, triphenylmethane dyes, pyrazole azo dyes, pyridone azo dyes, atrapyridone dyes, oxonol dyes, benzylidene dyes, xanthene dyes It may be at least one selected from the group consisting of, preferably at least one selected from the group consisting of benzylidene dyes and azo dyes, more preferably benzylidene dyes in terms of improving liquid stability and improving the effect of preventing phase separation. have.
[63]
The organic phosphor may be, for example, an organic phosphor having a carboxyl group, a phosphate group, or both.
[64]
The oil-soluble dyes include benzimidazolone compounds, azo compounds, quinophthalone compounds, quinacridone compounds, phthalocyanine compounds, DPP (Diketo -Pyrrolo-Pyrrole)-based compounds, combinations of two or more thereof, and the like may be used, and preferably, a benzimidazolone-based compound, an azo-based compound, a combination of two or more thereof, etc. may be used in terms of improving recognition.
[65]
The colorant may further include metal ions in addition to the organic dye, the oil-soluble dye and/or the organic phosphor. Specifically, the colorant may include an organic dye, an oil-soluble dye, and/or an organic phosphor having a metal ion and a complex salt structure. The organic dye, the oil-soluble dye, and/or the organic phosphor has a structure complexed with the metal ions, so that the solubility or dispersibility in an organic solvent is excellent, light stability, heat resistance, and clarity are further improved. And can achieve a uniform distribution in the composition.
[66]
The metal ion is not particularly limited as long as it is a metal ion capable of forming a complex salt structure with the organic dye, the oil-soluble dye and/or the organic phosphor, and, for example, of copper, cobalt, chromium, nickel and/or iron. Ions, preferably chromium ions.
[67]
The solubility of the colorant in the solvent may be 300g/L to 500g/L, preferably 350g/L to 450g/L at 25°C. desirable.
[68]
The colorant may be included in an amount of 0.01 to 10 parts by weight, preferably 0.01 to 5 parts by weight, more preferably 0.01 to 0.3 parts by weight, based on 100 parts by weight of the solvent, and detection when within the above range It is preferable in terms of securing visibility and even distribution within the insulating layer when checking the position of the insulating layer formed by the device.
[69]
The solvent may include methylpyrrolidone (NMP) in terms of solubility of the above-described components and implementation of a viscosity range to be described later.
[70]
The solid content of the composition for forming an insulating layer for a lithium secondary battery may be 5 wt% to 15 wt%, preferably 8 wt% to 12 wt%, more preferably 8.5 wt% to 10 wt%. In the above-described range, it is preferable in terms of securing a desired coating property and a viscosity range.
[71]
The viscosity at 25° C. of the insulating layer-forming composition may be 1,000 cP or more, and thus, it has a high viscosity to realize desired adhesion when realizing the overlapping region of the electrode active material layer and the insulating layer, and to prevent the problem of erosion of the electrode active material layer. Good in If the viscosity of the composition is less than 1,000 cP at 25° C., the liquid stability is remarkably deteriorated and there is a concern that erosion may occur in the overlapping region.
[72]
Preferably, the composition for forming an insulating layer for a lithium secondary battery may have a viscosity of 1,000 cP to 10,000 cP, more preferably 5,000 cP to 8,000 cP at 25° C., and when it is in the above-described range, adhesion and overlapping areas The effect of preventing erosion of the electrode active material layer can be further improved, and excellent coating properties can be implemented.
[73]
The above-described composition for forming an insulating layer for a lithium secondary battery has the above-described viscosity range, so that adhesion with the electrode active material layer and the effect of preventing erosion of the electrode active material layer in the overlapping region can be excellently implemented. In addition, an organic material having excellent solubility in a solvent is used as a colorant to enable uniform distribution of the colorant, and a high viscosity range can be realized because a dispersant is not used. In addition, adhesion to the electrode current collector or the electrode active material layer is excellent, and the alignment position of the insulating layer can be easily evaluated and observed.
[74]
[75]
Secondary battery electrode
[76]
In addition, the present invention provides an electrode for a lithium secondary battery including an insulating layer formed of the above-described composition for forming an insulating layer for a lithium secondary battery.
[77]
The lithium secondary battery electrode may include an electrode current collector; An electrode active material layer formed on the electrode current collector; And an insulating layer formed on the electrode contact body and formed to overlap the electrode active material layer in a partial region, wherein the thickness of the insulating layer in the region overlapping the electrode active material layer decreases toward the electrode active material layer, , The insulating layer is formed of the aforementioned composition for forming an insulating layer for a lithium secondary battery.
[78]
The electrode for a lithium secondary battery includes an insulating layer formed of the above-described composition for forming an insulating layer for a lithium secondary battery, and can improve adhesion between the insulating layer and the electrode active material layer and at the same time have sufficient insulation. In addition, when manufacturing a lithium secondary battery by stacking a plurality of electrodes for a lithium secondary battery, a problem of a decrease in capacity or an increase in resistance due to disconnection of the battery is prevented, and the quality and stability of the battery can be improved.
[79]
In addition, since the insulating layer formed of the above-described composition for forming an insulating layer for a lithium secondary battery has the above-described colorant and viscosity range, erosion of the electrode active material layer in the overlapping region can be significantly prevented.
[80]
Hereinafter, the electrode for a lithium secondary battery according to the present invention will be described in detail.
[81]
The electrode for a lithium secondary battery includes an electrode current collector, an electrode active material layer, and an insulating layer.
[82]
The electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes to the battery, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or stainless steel. Surface treatment with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, or the like may be used. In addition, the electrode current collector may have a thickness of typically 3 μm to 500 μm, and fine unevenness may be formed on the surface of the electrode current collector to enhance bonding strength with an electrode active material to be described later. For example, the electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous material, a foam, and a nonwoven fabric.
[83]
The electrode active material layer is formed on the electrode current collector.
[84]
The electrode active material layer may include an electrode active material, and specifically, a positive active material or a negative active material. Preferably, the electrode active material may include a positive electrode active material.
[85]
The positive active material is not particularly limited, and for example, the positive active material may be a commonly used positive active material. Specifically, the positive electrode active material may include a layered compound such as lithium cobalt oxide (LiCoO 2 ) or lithium nickel oxide (LiNiO 2 ), or a compound substituted with one or more transition metals; Lithium iron oxides such as LiFe 3 O 4 ; Lithium manganese oxides such as formula Li 1+c1 Mn 2-c1 O 4 (0≦ c1 ≦0.33), LiMnO 3 , LiMn 2 O 3 , and LiMnO 2 ; Lithium copper oxide (Li 2 CuO 2 ); LiV 3 O 8 , V 2 O 5 , Cu Vanadium oxides such as 2 V 2 O 7 ; Formula LiNi 1-c2 M c2 O 2 (here, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and satisfies 0.01≤c2≤0.3) Ni-site type lithium nickel oxide; Formula LiMn 2-c3 M c3 O 2 (wherein, M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≦c3≦0.1) or Li 2 Mn 3 MO A lithium manganese composite oxide represented by 8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn 2 O 4 where part of Li in the formula is substituted with alkaline earth metal ions And the like, but are not limited thereto. The anode may be Li-metal.
[86]
The negative active material is not particularly limited, and, for example, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Metal compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0 <β <2), SnO 2Metal oxides capable of doping and undoping lithium such as vanadium oxide and lithium vanadium oxide; Or a composite including the metal compound and a carbonaceous material, such as a Si-C composite or an Sn-C composite, and any one or a mixture of two or more of them may be used. In addition, a metal lithium thin film may be used as the negative electrode active material. Further, as the carbon material, both low crystalline carbon and high crystalline carbon may be used. As low crystalline carbon, soft carbon and hard carbon are typical, and high crystalline carbon is amorphous, plate-like, scale-like, spherical or fibrous natural or artificial graphite, Kish graphite (Kish). graphite), pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch High-temperature calcined carbon such as derived cokes) is typical.
[87]
The electrode active material may be included in an amount of 80 wt% to 99.5 wt%, preferably 88 wt% to 99 wt%, based on the total weight of the electrode active material layer.
[88]
[89]
The electrode active material layer may further include a binder for an electrode active material layer.
[90]
The binder for the electrode active material layer may serve to improve adhesion between electrode active materials and adhesion between the electrode active material and the electrode current collector.
[91]
The binder for the electrode active material layer is specifically polyvinylidene fluoride, polyvinyl alcohol, styrene butadiene rubber, polyethylene oxide, carboxyl methyl cellulose, and cellulose. Cellulose acetate, cellulose acetate butylate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinylalcohol, cyanoethyl Cellulose (cyanoethyl cellulose), cyanoethyl sucrose (cyanoethyl sucrose), flulan (pullulan), polymethylmethacrylate (polymethylmethacrylate), polybutylacrylate (polybutylacrylate), polyacrylonitrile, polyvinylpyrrolyse It may be at least one kind from the group consisting of polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyarylate, and low molecular weight compounds having a molecular weight of 10,000 g/mol or less. And, preferably, polyvinylidene fluoride is particularly preferred in terms of adhesion, chemical resistance and electrochemical stability.
[92]
The binder for the electrode active material layer may be the same material as the binder polymer included in the above-described composition for forming an insulating layer for a lithium secondary battery. In this case, as will be described later, the bonding force in the overlapping region of the electrode active material layer and the insulating layer can be further improved, so that the stability and quality of the product can be improved, and it is preferable in terms of improving fairness such as adhesion, adhesion, and weldability. .
[93]
The binder for the electrode active material layer may be included in an amount of 0.1 wt% to 10 wt%, preferably 0.5 wt% to 5 wt%, based on the total weight of the electrode active material layer.
[94]
[95]
The electrode active material layer may further include a conductive material in addition to the above-described components. The conductive material is not particularly limited as long as it has conductivity without causing chemical changes to the battery, and examples thereof include graphite such as natural graphite or artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, Parnes black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Conductive tubes such as carbon nanotubes; Metal powders such as fluorocarbon, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.
[96]
The conductive material may be included in an amount of 0.1 wt% to 20 wt%, preferably 0.3 wt% to 10 wt%, based on the total weight of the electrode active material layer.
[97]
[98]
The insulating layer is formed on the electrode current collector, and is formed to overlap the electrode active material layer in a partial region. For example, the electrode active material layer and the insulating layer may be stacked or formed to overlap each other in some areas.
[99]
The insulating layer may be formed of the above-described composition for forming an insulating layer for a lithium secondary battery. Accordingly, since it has a high viscosity range, it is possible to significantly prevent erosion of the electrode active material layer in the overlapping region, and to implement excellent adhesion between the electrode active material layer and the electrode current collector. In addition, the lithium secondary battery electrode has a low risk of an internal short circuit of the battery, and a problem of an increase in resistance or a decrease in capacity due to disconnection may be remarkably improved.
[100]
Components and contents included in the insulating layer or the composition for forming an insulating layer for a lithium secondary battery have been described above.
[101]
In a region where the electrode active material layer and the insulating layer overlap, the electrode active material layer may have an inclined surface.
[102]
The length of the area where the electrode active material layer and the insulating layer overlap may be 0.05mm to 1.3mm, preferably 0.1mm to 1.0mm, in this case, minimizing the decrease in capacity due to overlapping of the electrode active material layer and the insulating layer. , It is preferable because the adhesion or adhesion of the electrode active material layer and the insulating layer can be further improved.
[103]
In terms of preventing a decrease in capacity due to overlapping of the electrode active material layer and the insulating layer, the thickness of the insulating layer in a region overlapping with the electrode active material layer may decrease toward the electrode active material layer.
[104]
In a region where the electrode active material layer and the insulating layer overlap, when the insulating layer thickness at the end of the electrode active material layer is A 0 and the insulating layer thickness at the end of the insulating layer is A, A/A 0 is It may be 0.05 or more and less than 1, preferably 0.1 to 0.7, and when it is in the above-described range, while minimizing the reduction in capacity due to overlapping of the electrode active material layer and the insulating layer, the adhesion and adhesion between the insulating layer and the electrode active material layer It can be further improved, and the interface between the insulating layer and the active material layer can be prevented from being broken due to erosion.
[105]
The A 0 may be 3 μm to 20 μm, preferably 5 μm to 12 μm, and A may be 0.15 μm or more and less than 20 μm, and preferably 1 μm to 5 μm.
[106]
In a region where the electrode active material layer and the insulating layer do not overlap, for example, in the electrode active material layer or the insulating layer in a region excluding the overlapping region, the thickness of the insulating layer relative to the thickness d 1 of the electrode active material layer The ratio of (d 2 ) (d 2 /d 1 ) may be 0.02 to 0.4, preferably 0.05 to 0.1.
[107]
The lithium secondary battery electrode has excellent insulation and adhesive strength by having the thickness ratio of the electrode active material layer and the insulating layer in the above-described range, as well as preventing the occurrence of electrode tab disconnection when manufacturing a lithium secondary battery through stacking a plurality of electrodes. And, accordingly, a decrease in capacity or an increase in resistance due to disconnection can be prevented.
[108]
In a region where the electrode active material layer and the insulating layer do not overlap, the thickness of the insulating layer may be 3 μm to 20 μm, and the thickness of the electrode active material layer may be 50 μm to 150 μm. In the above range, the above-described insulation, adhesiveness, and fairness may be more excellently implemented.
[109]
The electrode for a lithium secondary battery may be a positive electrode for a lithium secondary battery or a negative electrode for a lithium secondary battery, and preferably may be a positive electrode for a lithium secondary battery.
[110]
The aforementioned electrode for a lithium secondary battery includes an insulating layer formed of the composition for forming an insulating layer for a lithium secondary battery, so that adhesion between the insulating layer and the electrode active material layer or an electrode current collector may be improved, and at the same time, sufficient insulation may be provided. In addition, the above-described composition for forming an insulating layer for a lithium secondary battery can be used to significantly prevent erosion of the electrode active material layer in the overlapping region. In addition, when manufacturing a lithium secondary battery by stacking a plurality of lithium secondary battery electrodes, etc., it has excellent weldability and process stability, preventing the problem of decreasing capacity or increasing resistance due to disconnection of the battery, etc., and Stability can be improved.
[111]
[112]
Electrode manufacturing method
[113]
In addition, the present invention provides a method of manufacturing an electrode for a lithium secondary battery using the above-described composition for forming an insulating layer for a lithium secondary battery.
[114]
The method of manufacturing an electrode for a lithium secondary battery includes the steps of forming an undried electrode active material layer by applying an active material slurry composition on an electrode current collector; Forming an undried insulating layer by applying the composition for forming an insulating layer for a lithium secondary battery to overlap the undried electrode active material layer in a partial region; And simultaneously drying the undried electrode active material layer and the undried insulating layer.
[115]
The method of manufacturing an electrode for a lithium secondary battery is excellent in adhesion to an electrode active material layer or an electrode current collector by applying the above-described composition for forming an insulating layer for a lithium secondary battery to form an undried insulating layer or an insulating layer. In addition, since the above-described composition for forming an insulating layer for a lithium secondary battery has a high viscosity, it is possible to significantly prevent erosion of the electrode active material layer in an overlapping region with the electrode active material layer. Accordingly, the electrode for a lithium secondary battery manufactured therefrom has improved stability, and disconnection due to an internal short circuit, an increase in resistance, and a decrease in capacity can be remarkably improved.
[116]
In addition, the method of manufacturing the electrode for the lithium secondary battery may use a wet-wet coating method. For example, in the above manufacturing method, after forming an undried electrode active material layer in which an active material slurry composition is applied on an electrode current collector but not dried, the composition for forming an insulating layer is partially overlapped to form an undried insulating layer. , By simultaneously drying the undried electrode active material layer and the undried insulating layer, the aforementioned electrode for a lithium secondary battery may be manufactured. Accordingly, the electrode active material layer and the insulating layer prepared accordingly can be adhered with excellent adhesion, and adhesion, welding ease and fairness are improved by forming a long overlapping area. And stability.
[117]
[118]
Hereinafter, a method of manufacturing the electrode for a lithium secondary battery will be described in detail.
[119]
The method of manufacturing an electrode for a lithium secondary battery includes forming an undried electrode active material layer by applying an active material slurry composition on an electrode current collector.
[120]
The electrode current collector may be used in the same type, material, and thickness as the electrode current collector described above.
[121]
[122]
The active material slurry composition may be applied on the electrode current collector to form the undried electrode active material layer. For example, the undried electrode active material layer may be simultaneously dried with an undried insulating layer to be described later to form an electrode active material layer.
[123]
The active material slurry composition may be a positive active material slurry composition or a negative active material slurry composition, preferably a positive active material slurry composition.
[124]
The positive active material slurry composition may include a positive active material, a binder, and/or a conductive material, and the negative active material slurry composition may include a negative active material, a binder, and/or a conductive material. The positive electrode active material, the negative electrode active material, the binder, and/or the conductive material may be the positive electrode active material, the negative electrode active material, the binder and/or the conductive material described above.
[125]
The active material slurry composition may be applied on the electrode current collector to form an undried electrode active material layer. In the present specification, “non-dried” includes not only the case where the active material slurry composition is applied and then dried, but also the case where the active material slurry composition is not dried and thus not substantially dried.
[126]
The method of manufacturing an electrode for a lithium secondary battery includes forming an undried insulating layer by applying the above-described composition for forming an insulating layer for a lithium secondary battery so as to overlap the undried electrode active material layer in a partial region.
[127]
The above-described composition for forming an insulating layer for a lithium secondary battery may be applied on the electrode current collector so as to overlap the undried electrode active material layer in a partial region to form an undried insulating layer. For example, the undried insulating layer may form the above-described insulating layer after simultaneous drying with the undried electrode active material layer to be described later, and an overlapping region with the electrode active material layer may be formed.
[128]
Components and contents included in the insulating layer or the composition for forming an insulating layer for a lithium secondary battery have been described above.
[129]
The active material slurry composition may further include a binder for an electrode active material layer. Concrete components of the binder for the electrode active material layer have been described above.
[130]
Preferably, the binder for the electrode active material layer may be the same material as the binder polymer included in the above-described composition for forming an insulating layer for a lithium secondary battery. In this case, as will be described later, the bonding force in the overlapping region of the electrode active material layer and the insulating layer can be further improved, so that the stability and quality of the product can be improved, and it is preferable in terms of improving fairness such as adhesion, adhesion, and weldability. .
[131]
The method of manufacturing an electrode for a lithium secondary battery includes simultaneously drying the undried electrode active material layer and the undried insulating layer.
[132]
The method of manufacturing an electrode for a lithium secondary battery does not apply and dry an active material slurry composition to prepare an electrode active material layer and then apply a composition for forming an insulating layer, but simultaneously dry the undried electrode active material layer and the undried insulating layer. By doing so, adhesion and adhesion between the electrode active material layer and the insulating layer can be further improved. In addition, accordingly, the overlapping region of the undried electrode active material layer and the undried insulating layer or the overlapping region of the electrode active material layer and the insulating layer is relatively long, and the thickness of the insulating layer in the overlapping region can be formed to be thin. Fairness and ease of welding are remarkably improved, and the quality and stability of the battery can be improved.
[133]
In addition, since the method of manufacturing an electrode for a lithium secondary battery uses the above-described composition for forming an insulating layer for a lithium secondary battery, erosion of the electrode active material layer in the overlapping region can be significantly prevented.
[134]
The drying is not particularly limited as long as the undried electrode active material layer and the undried insulating layer can be sufficiently dried, and a drying method commonly known in the art may be used. For example, the drying may be applied by changing a hot air method, a direct heating method, an induction heating method, and the like, and specifically, the drying may be performed at 50 to 180° C. for 1 to 5 minutes.
[135]
The difference in viscosity at 25° C. between the active material slurry composition and the insulating layer-forming composition may be 5,000 cP or less, preferably 2,000 cP or less, and more preferably 1,000 cP or less. Since the difference in viscosity of the active material slurry composition and the composition for forming the insulating layer is adjusted within the above-described range, the undried electrode active material layer and the undried insulating layer may be further improved their adhesion or adhesion after drying. , Erosion in the overlapping area is effectively prevented.
[136]
The viscosity at 25° C. of the insulating layer-forming composition may be 1,000 cP to 10,000 cP, preferably 5,000 cP to 8,000 cP. In the above range, adhesion with the undried electrode active material layer or the electrode active material layer may be further improved.
[137]
The viscosity of the active material slurry composition at 25° C. may be 5,000 cP to 15,000 cP, preferably 5,000 cP to 13,000 cP, and when within the above range, adhesion with the undried electrode active material layer or electrode active material layer may be improved. In addition, coating properties and processability can be further improved.
[138]
The above-described viscosity range can be achieved by appropriately adjusting components and solid content of the active material slurry composition or the insulating layer-forming composition.
[139]
[140]
Secondary battery
[141]
In addition, the present invention provides a lithium secondary battery including the above-described lithium secondary battery electrode.
[142]
The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, a separator and an electrolyte interposed between the positive electrode and the negative electrode. In this case, as the positive electrode and/or the negative electrode, the aforementioned electrode for a lithium secondary battery may be used. In addition, the lithium secondary battery may optionally further include a battery container accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.
[143]
On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions, and can be used without particular limitation as long as it is used as a separator in a general lithium secondary battery. On the other hand, it is preferable that it has low resistance and excellent electrolyte-moisturizing ability. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these A stacked structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and optionally, a single layer or a multilayer structure may be used.
[144]
In addition, electrolytes used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc. that can be used in the manufacture of lithium secondary batteries, and are limited to these. It does not become.
[145]
Specifically, the electrolyte may include an organic solvent and a lithium salt.
[146]
The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of a battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), propylene carbonate (PC) ) Carbonate-based solvents; Alcohol solvents such as ethyl alcohol and isopropyl alcohol; Nitriles, such as R-CN (R is a C2-C20 linear, branched or cyclic hydrocarbon group, and may contain a double bonded aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Alternatively, sulfolanes, etc. may be used. Among them, carbonate-based solvents are preferable, and cyclic carbonates having high ionic conductivity and high dielectric constant that can increase the charge/discharge performance of the battery (for example, Ethylene carbonate or propylene carbonate, etc.), and a low-viscosity linear carbonate-based compound (eg, ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate) are more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte may exhibit excellent performance.
[147]
The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt is LiPF 6 , LiClO 4 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAl0 4 , LiAlCl 4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiN(C 2 F 5 SO 3 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , LiN(CF 3 SO 2 ) 2 . LiCl, LiI, or LiB(C 2 O 4 ) 2 or the like may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is within the above range, since the electrolyte has an appropriate conductivity and viscosity, excellent electrolyte performance can be exhibited, and lithium ions can move effectively.
[148]
In addition to the electrolyte constituents, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, tri- Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride may be further included. At this time, the additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.
[149]
Lithium secondary batteries according to embodiments are useful in portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).
[150]
Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.
[151]
The battery module or battery pack may include a power tool; Electric vehicles including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); Alternatively, it may be used as a power source for any one or more medium and large-sized devices in a power storage system.
[152]
The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape using a can, a square shape, a pouch type, or a coin type.
[153]
The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source of a small device, but also can be preferably used as a unit cell in a medium or large battery module including a plurality of battery cells.
[154]
[155]
Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various different forms, and is not limited to the embodiments described herein.
[156]
[157]
Examples and Comparative Examples
[158]
Example 1: Preparation of a composition for forming an insulating layer for a lithium secondary battery
[159]
As a binder polymer, polyvinylidene fluoride (product name: KF9700, manufacturer: Kureha, weight average molecular weight: 880,000) 9 parts by weight, as a colorant benzylidene organic dye yellow 081 (manufactured by BASF) 0.1 parts by weight methylpyrrolidone (NMP ) To prepare a composition for forming an insulating layer by dissolving in 100 parts by weight. At this time, the viscosity of the composition for forming the insulating layer was 6,000 cP.
[160]
[161]
Example 2: Preparation of a composition for forming an insulating layer for a lithium secondary battery
[162]
9 parts by weight of polyvinylidene fluoride (product name: KF9700, manufacturer: Kureha, weight average molecular weight: 880,000) as a binder polymer, 0.1 parts by weight of azo-based organic dye red 395 (manufactured by BASF) as a colorant, methylpyrrolidone (NMP) Dissolved in 100 parts by weight to prepare a composition for forming an insulating layer. At this time, the viscosity of the composition for forming the insulating layer was 6,000 cP.
[163]
[164]
Example 3: Preparation of a composition for forming an insulating layer for a lithium secondary battery
[165]
As a binder polymer, polyvinylidene fluoride (product name: KF9700, manufacturer: Kureha, weight average molecular weight: 880,000) 10.5 parts by weight, as a colorant, benzylidene organic dye yellow 081 (manufactured by BASF) 0.1 parts by weight methylpyrrolidone (NMP ) To prepare a composition for forming an insulating layer by dissolving in 100 parts by weight. At this time, the viscosity of the composition for forming the insulating layer was 12,000 cP.
[166]
[167]
Comparative Example 1: Preparation of a composition for forming an insulating layer for a lithium secondary battery
[168]
12 parts by weight of polyvinylidene fluoride (product name: KF1100, manufacturer: Kureha, weight average molecular weight: 280,000) as a binder polymer, 0.1 parts by weight of a benzylidene organic dye yellow 081 (manufactured by BASF) as a colorant, methylpyrrolidone (NMP) ) To prepare a composition for forming an insulating layer by dissolving in 100 parts by weight. At this time, the viscosity of the composition for forming the insulating layer was 670 cP.
[169]
[170]
Comparative Example 2: Preparation of a composition for forming an insulating layer for a lithium secondary battery
[171]
As a binder polymer, polyvinylidene fluoride (product name: KF9700, manufacturer: Kureha, weight average molecular weight: 880,000) 6 parts by weight, pigment as colorant (product name: yellow 139, manufacturer: BASF) 0.08 parts by weight, dispersant CR-V (manufacturer : Shin-Etsu Chemical) 1.5 parts by weight of methylpyrrolidone was dissolved in 100 parts by weight to prepare a composition for forming an insulating layer having a viscosity of 1,000 cP.
[172]
[173]
Experimental example
[174]
Experimental Example 1: SEM observation evaluation
[175]
A positive electrode for a lithium secondary battery was prepared using the composition for forming an insulating layer prepared according to Example 1 and Comparative Example 1.
[176]
Specifically, LiNi 0.6 Mn 0.2 Co 0.2 O 2 as a positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder for an electrode active material layer were mixed in a weight ratio of 97.3:1.5:1.2, and 69 A positive electrode active material slurry composition having a viscosity of 8,000 cP at 25° C. was prepared by adding it to the NMP solvent in wt %.
[177]
Thereafter, the positive electrode active material slurry composition is applied on an aluminum current collector to form an undried positive electrode active material layer, and the insulating layer-forming composition is applied on the aluminum current collector so as to overlap the undried positive electrode active material layer in a partial area. Thus, an undried insulating layer was formed.
[178]
Thereafter, the undried positive electrode active material layer and the undried insulating layer were simultaneously dried (about 3 minutes) at 160° C. to form a positive electrode active material layer and an insulating layer, respectively, and rolled to prepare a positive electrode for a lithium secondary battery.
[179]
Thereafter, a cross-section of an overlapping region of the positive electrode active material layer and the insulating layer among the cross-sections of the positive electrode was observed with a scanning electron microscope, and the SEM image of Example 1 is shown in FIG. 1 and the SEM image of Comparative Example 1 is shown in FIG. Referring to FIGS. 1 and 2, it can be seen that in the positive electrode of Example 1, the overlapping region of the insulating layer and the electrode active material layer is formed by excellent adhesion, and erosion does not occur. However, it was confirmed that the positive electrode of Comparative Example 1 caused erosion in the overlapping region of the insulating layer and the electrode active material layer, causing difficulty in product application.
[180]
[181]
Experimental Example 2: Electrolyte elution evaluation
[182]
The composition for forming the insulating layer of Examples 1 and 2 was coated on an aluminum foil, cut into a size of 5 cm × 5 cm, and 1.0 mol of LiPF 6 was dissolved and ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were used. The non-aqueous electrolyte solvent mixed at a volume ratio of 3:7 was impregnated at room temperature for 18 hours, and it was tested whether the colorant was eluted into the electrolyte. After the experiment, the results of Example 1 are shown in Fig. 3 and the results of Example 2 are shown in Fig. 4, respectively.
[183]
3 and 4, in the composition for forming the insulating layer of Example 1, the colorant did not ooze or elute in the electrolyte, but the composition for forming the insulating layer of Example 2 using the colorant was used as an electrolyte solution of the colorant. It was confirmed that some elution phenomenon occurred.
[184]
[185]
Experimental Example 3: Liquid stability evaluation
[186]
The composition for forming an insulating layer according to Example 1 and Comparative Example 2 was left at room temperature (25°C) for 31 days to evaluate the liquid stability of the composition, and the observation result of Example 1 is shown in FIG. 5 and the observation result of Comparative Example 1 is shown. It is shown in 6.
[187]
5 and 6, it can be confirmed that the composition for forming the insulating layer of Example 1 does not cause phase separation even after 31 days after storage, so that the liquid stability is excellent, but the composition for forming the insulating layer of Comparative Example 2 It can be seen that as time passed, phase separation occurred and stability deteriorated.
[188]
[189]
Experimental Example 4: Evaluation of coating properties
[190]
An insulating layer was formed by coating and drying the composition for forming an insulating layer of Examples 1 and 3 on an aluminum foil to a width of 3.8 mm, and the appearance was observed with a surface inspection device (manufactured by NSYS Co., Ltd.). The surface inspection photograph of Example 1 is shown in FIG. 7, and the surface inspection photograph of Example 3 is shown in FIG. 8.
[191]
7 and 8, the composition for forming an insulating layer of Examples 1 and 3 was evaluated as having excellent viscosity level and generally excellent coating properties. However, in the case of Example 1, the insulating layer was formed without generation of bubbles, whereas in the case of Example 3, the viscosity of the composition was slightly high, so that some bubbles were found in the insulating layer.
[192]
[193]
Experimental Example 5: Evaluation of coating properties
[194]
An insulating layer was formed by coating and drying the composition for forming an insulating layer of Examples 1 and 3 on an aluminum foil to a width of 3.8 mm, and its appearance was observed with an optical microscope. The optical microscope observation picture of Example 1 is shown in FIG. 9, and the optical microscope observation picture of Example 3 is shown in FIG. In FIGS. 9 and 10, a portion shown in yellow is a coating portion of the composition for forming an insulating layer.
[195]
9 and 10, the composition for forming an insulating layer of Examples 1 and 3 was evaluated as having excellent coating properties due to excellent viscosity levels.
[196]
In the case of the insulating layer formed of the composition for forming the insulating layer of Example 1, it can be confirmed that the coating width is uniform, but in Example 3, the viscosity is slightly high, so the uniformity of the coating width is slightly lower, and a wave shape is formed to expose the aluminum foil. It can be confirmed. Compared to the coating area of ​​Example 1, the exposed area of ​​the aluminum foil by the wave shape of Example 3 was calculated to be about 30%, and accordingly, in Example 3, it was confirmed that the coating property was slightly lowered compared to Example 1. I can.
Claims
[Claim 1]
Binder polymer; A colorant containing at least one selected from the group consisting of organic dyes, oil-soluble dyes, and organic phosphors; And a solvent, and having a viscosity of 1,000 cP or more at 25° C., a composition for forming an insulating layer for a lithium secondary battery.
[Claim 2]
The composition for forming an insulating layer for a lithium secondary battery according to claim 1, wherein the viscosity at 25° C. is 1,000 cP to 10,000 cP.
[Claim 3]
The composition for forming an insulating layer for a lithium secondary battery according to claim 1, wherein the colorant has a solubility in the solvent of 300g/L to 500g/L at 25°C.
[Claim 4]
The composition for forming an insulating layer for a lithium secondary battery according to claim 1, wherein the colorant is contained in an amount of 0.01 parts by weight to 10 parts by weight based on 100 parts by weight of the solvent.
[Claim 5]
The method of claim 1, wherein the colorant further comprises a metal ion, and the metal ion forms a complex salt structure with at least one selected from the group consisting of the organic dye, the oil-soluble dye, and the organic phosphor. A composition for forming an insulating layer for a secondary battery.
[Claim 6]
The composition for forming an insulating layer for a lithium secondary battery according to claim 5, wherein the metal ion is an ion of at least one metal selected from the group consisting of copper, cobalt, chromium, nickel and/or iron.
[Claim 7]
The composition for forming an insulating layer for a lithium secondary battery according to claim 1, wherein the binder polymer is contained in an amount of 5 to 15 parts by weight based on 100 parts by weight of the solvent.
[Claim 8]
The method according to claim 1, wherein the solid content of the composition for forming an insulating layer for a lithium secondary battery is 5% by weight to 15% by weight, the composition for forming an insulating layer for a lithium secondary battery.
[Claim 9]
Electrode current collector; An electrode active material layer formed on the electrode current collector; And an insulating layer formed on the electrode contact body and formed to overlap the electrode active material layer in a partial area, wherein the insulating layer is formed of the composition for forming an insulating layer for a lithium secondary battery according to claim 1, for a lithium secondary battery electrode.
[Claim 10]
Forming an undried electrode active material layer by applying an active material slurry composition on the electrode current collector; Forming an undried insulating layer by applying the composition for forming an insulating layer for a lithium secondary battery according to claim 1 so as to overlap the undried electrode active material layer in a partial region; And simultaneously drying the undried electrode active material layer and the undried insulating layer.
[Claim 11]
The method of claim 10, wherein the difference in viscosity at 25° C. between the active material slurry composition and the insulating layer-forming composition is 5,000 cP or less.
[Claim 12]
The method of claim 11, wherein the active material slurry composition has a viscosity of 5,000 cP to 15,000 cP at 25°C.
[Claim 13]
The method of claim 10, wherein the active material slurry composition contains the same polymer material as the binder polymer.
[Claim 14]
A lithium secondary battery comprising the electrode for a lithium secondary battery according to claim 9.