Integrated Electrode Stacking Unit, Method for Manufacturing the Same, and Lithium Secondary Battery Including the Same

Abstract

The present disclosure provides a one-piece electrode laminate unit, a manufacturing method of the one-piece electrode laminate unit, and a lithium secondary battery including the one-piece electrode laminate unit. The one-piece electrode laminate unit includes: a first electrode, a second electrode, and a separator layer disposed between the first electrode and the second electrode. Wherein, the separator layer is a photocurable PSA coating integrally formed on the first electrode. Wherein, the separator layer has a strength of 30 MPa to 50 MPa and an adhesion to the second electrode of 70 gf / 20 mm to 90 gf / 20 mm. And wherein, the first electrode, the separator layer, and the second electrode are laminated.

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to Korean Patent Application No. 10 - 2021 - 0016995, filed on February 5, 2021, and Korean Patent Application No. 10 - 2021 - 0016996, filed on February 5, 2021, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

[0003] The present disclosure relates to an integrated electrode laminate unit, a method of manufacturing the integrated electrode laminate unit, and a lithium secondary battery including the integrated electrode laminate unit. Background Art

[0004] Due to the rapid increase in the use of fossil fuels, there is an increasing demand for alternative or clean energy sources. Among them, the most actively studied field is the field of electrochemical power generation and storage.

[0005] Currently, secondary batteries are representative examples of electrochemical devices that utilize such electrochemical energy, and their range of use has a tendency to gradually expand.

[0006] Recently, with the technological development and increasing demand for mobile devices such as laptops, mobile phones, and cameras, the demand for secondary batteries as an energy source has also increased sharply. Among such secondary batteries, many studies have been conducted on lithium secondary batteries that exhibit high energy density and operating potential, have a long cycle life, and a low self - discharge rate, and they are now commercialized and widely used.

[0007] In addition, with the growing interest in environmental issues, there has been frequent research on electric vehicles, hybrid vehicles, etc., which can replace vehicles using fossil fuels such as gasoline vehicles and diesel vehicles, which are the main causes of air pollution. Although nickel - metal hydride secondary batteries are mainly used as power sources for electric vehicles and hybrid vehicles, active research is being conducted on lithium secondary batteries with high energy density and discharge voltage, and some of them are in the commercialization stage.

[0008] Such lithium secondary batteries are manufactured through the following process: coating a positive electrode active material or a negative electrode active material, a binder, and a conductive material on a current collector in the form of a slurry, drying it to form an electrode mixture layer, and then preparing a positive electrode and a negative electrode accordingly. A separator is placed between the positive electrode and the negative electrode, they are laminated, and the laminated electrode assembly is incorporated into a battery case together with an electrolyte.

[0009] In addition, the electrode assembly may be manufactured by stacking or folding the respective components, but the electrode assembly may be manufactured by manufacturing the unit cell as an electrode laminate unit including an electrode and a separator and then stacking or folding it.

[0010] Figure 1 Method 10 for manufacturing an electrode laminate unit according to the related art is shown.

[0011] Referring to Figure 1 , a separator 12 is stacked on a first electrode 11, a second electrode 13 is stacked on the separator 12, and then lamination is performed by a lamination device 14 and then cutting is performed by a cutter 15 to manufacture a unit cell 16. At this time, optionally, another separator 17 may be further stacked on the other surface of the first electrode 11 on which the separator 12 is not stacked.

[0012] That is, conventionally, as each structure, the first electrode 11, the separator 12, and the second electrode 13 are sequentially stacked as separate members and then laminated to manufacture a unit cell. However, in this case, high heat and pressure must be used to ensure sufficient adhesion between the separator and the electrode. High heat and pressure cause problems such as cracks in the active material, ultimately leading to problems such as deterioration of the performance of the secondary battery, occurrence of short-circuit defects, and reduction in the yield. In addition, in order to ensure sufficient heat resistance and strength of the separator, an SRS separator in which an organic-inorganic hybrid layer is formed on the separator substrate has been developed, but the problem is that manufacturing and applying such a separator separately takes a lot of process time and increases the cost.

[0013] Therefore, there is an urgent need to develop an integrated electrode laminate unit technology that can function as a separator even without manufacturing a separate separator, while solving such problems and solving the problem of adhesion between the electrode and the separator. Summary of the Invention

[0014] Technical Problem

[0015] The object of the present subject matter is to solve the problems of the above-mentioned conventional technologies and the technical problems that have been previously requested.

[0016] Specifically, the object of the present disclosure is to provide an integrated electrode laminate unit and a manufacturing method thereof, in which the electrode and the separation layer serving as a separator are integrated into one body to prevent electrode deformation caused by lamination defects in the process of laminating the electrode and the separator, and reduction in the yield due to wrinkles in the separator.

[0017] Another object of the present disclosure is to provide an integrated electrode laminate unit and a manufacturing method thereof: the integrated electrode laminate unit can improve the adhesion between the separator layer and the electrode, has excellent strength and elongation characteristics, and improves the safety of the secondary battery.

[0018] Technical solution

[0019] To achieve the above object, according to one aspect of the present disclosure, there is provided an integrated electrode laminate unit, which includes:

[0020] a first electrode, a second electrode, and a separator layer disposed between the first electrode and the second electrode,

[0021] wherein the separator layer is a photocurable PSA coating integrally formed on the first electrode,

[0022] wherein the separator layer has a strength of 30 to 50 MPa, an adhesion to the second electrode of 70 gf / 20 mm to 90 gf / 20 mm, and

[0023] wherein the first electrode, the separator layer, and the second electrode are laminated.

[0024] At this time, the photocurable PSA coating may be a polymer coating containing ceramic particles.

[0025] In a specific embodiment, the ceramic particles may have an average diameter (D50) of 10 nm to 500 nm, and examples thereof may be at least one selected from the group consisting of AlN, BN, BeO, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, and SiC.

[0026] In another specific embodiment, the polymer may be an acrylate-based monomer or an epoxy-based monomer, an acrylate-based oligomer or an epoxy-based oligomer, or a polymer of a monomer and an oligomer.

[0027] Meanwhile, in a specific embodiment, the separator layer may have a patterned structure.

[0028] In addition, the separator layer may be composed of two or more layers, each separator layer having a patterned structure, and each separator layer may have a pattern different from that of an adjacent separator layer.

[0029] When the separator layer is composed of two or more layers, the pattern of each layer in each separator layer is a linear pattern in which coated portions and uncoated portions alternate, and the angle between the lines formed by the patterns of adjacent separator layers is 10 degrees to 90 degrees.

[0030] Regardless of the number of layers that the separator layer is composed of, the total thickness of the separator layer can be from 1 μm to 5 μm, the total porosity can be from 20% to 60%, and the average diameter (D50) of the pores can be from 0.01 μm to 1 μm.

[0031] The separator layer formed in this way can have an elongation rate of 20% to 50%.

[0032] Meanwhile, in a specific embodiment, the integrated electrode laminate unit may further include a separator located on the other surface of the first electrode that does not face the separator layer.

[0033] According to another aspect of the present disclosure, a method is provided, which includes the following steps:

[0034] (a) Coating and curing a PSA (pressure-sensitive adhesive) solvent-free ink of a breathable structure on the first electrode to form a separator layer;

[0035] (b) Stacking a second electrode on the separator layer; and

[0036] (c) Laminating the first electrode, the separator layer, and the second electrode.

[0037] to manufacture an integrated electrode laminate unit.

[0038] The PSA solvent-free ink may contain ceramic particles, monofunctional monomers, polyfunctional monomers, oligomers, and initiators, and

[0039] may contain 10 to 30 wt% (weight percentage) of ceramic particles, 45 to 65 wt% of monofunctional monomers, 10 to 15 wt% of polyfunctional monomers, 5 to 10 wt% of oligomers, and 0.1 to 0.8 wt% of initiators.

[0040] Meanwhile, in a specific embodiment, the PSA solvent-free ink may be coated on the first electrode by inkjet printing, wherein the PSA solvent-free ink may have a viscosity of 5 to 100 cP at room temperature.

[0041] The curing of the PSA solvent-free ink coated on the first electrode in this way can be performed by UV irradiation using an LED lamp.

[0042] Furthermore, in a specific embodiment, a sheet-shaped separator is laminated on the other surface of the first electrode where the separator layer is not formed in step (a), step (c) laminates the sheet-shaped separator, the first electrode, the separator layer, and the second electrode, and the manufacturing method of the electrode laminate unit may further include: after step (c), cutting the sheet-shaped separator to correspond to the first electrode or the second electrode.

[0043] Meanwhile, according to still another aspect of the present disclosure, a lithium secondary battery is provided, which includes an integrated electrode laminate unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic view showing a method of manufacturing an electrode laminate unit according to the related art;

[0045] Figure 2 is a cross-sectional view of an integrated electrode laminate unit in which a separation layer is formed as a single layer according to an embodiment of the present invention;

[0046] Figure 3 is Figure 2 an exploded perspective view of the electrode laminate unit;

[0047] Figure 4 is a cross-sectional view of an integrated electrode laminate unit in which a separation layer is formed of two layers according to another embodiment of the present disclosure;

[0048] Figure 5 is Figure 4 an exploded perspective view of the electrode laminate unit; and

[0049] Figure 6 is a schematic view showing a method of manufacturing Figure 4 the integrated electrode laminate unit. DETAILED DESCRIPTION

[0050] Hereinafter, the present disclosure will be described in more detail for better understanding.

[0051] The terms or words used in this specification and claims should not be construed as limited to ordinary or dictionary terms. The present disclosure should be interpreted with meanings and concepts consistent with the technical concept of the present disclosure based on the principle that the inventor can appropriately define terms to best describe their own disclosure.

[0052] The technical terms provided herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The singular forms "a", "the", and "said" are also intended to include the plural forms unless the context clearly indicates otherwise.

[0053] Furthermore, throughout the specification, when a part is referred to as "including" a certain component, this means that the part may further include other components without excluding other components, unless otherwise specified.

[0054] According to an embodiment of the present disclosure, there is provided an integrated electrode laminate unit including:

[0055] a first electrode, a second electrode, and a separation layer disposed between the first electrode and the second electrode,

[0056] wherein the separation layer is a photocurable PSA coating integrally formed on the first electrode,

[0057] Among them, the separation layer has a strength of 30 to 50 MPa and an adhesion force to the second electrode of 70 gf / 20 mm to 90 gf / 20 mm, and

[0058] Among them, the first electrode, the separation layer, and the second electrode are laminated.

[0059] That is to say, conventionally, the separator is laminated on the electrode as a separate component and laminated to manufacture an electrode laminate unit. However, according to the present disclosure, the photocurable PSA coating can be integrally formed on the first electrode, thereby improving the adhesion force and providing a firm separation layer by a simpler method.

[0060] The photocurable PSA coating can be a polymer coating containing ceramic particles.

[0061] Here, the ceramic particles can have an average diameter (D50) of 10 nm to 500 nm.

[0062] The particle diameter (D50) refers to the particle diameter (diameter) at the 50% point in the cumulative distribution of the number of particles relative to the diameter. Specifically, the D50 can be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium, and then a commercially available laser diffraction particle size analyzer (for example, Microtrac S3500) is introduced. When the particles pass through the laser beam, the difference in the diffraction pattern according to the particle size is measured to calculate the particle size distribution. The D50 can be measured by calculating the particle diameter corresponding to the 50% point in the cumulative distribution of the number of particles relative to the particle diameter in the analyzer.

[0063] When the ceramic particles are too small and exceed the above range, there are difficulties in the coating process. When the ceramic particles are too large, the coating thickness becomes too thick, making it difficult to coat, and it is impossible to ensure sufficient strength or heat resistance. Therefore, it is difficult to act as a separation layer, and the adhesion force to the electrode can be reduced, which is not preferable.

[0064] The type of such ceramic particles is not particularly limited as long as it is within the operating voltage range of the secondary battery applied as inorganic particles (for example, based on Li / Li +It is only necessary that no oxidation and / or reduction reaction occurs in the range of 0 to 5V), but preferably, it has high ionic conductivity and low density. For example, the ceramic particles are preferably at least one selected from the group consisting of: (a) high dielectric constant inorganic particles with a dielectric constant of 1 or more, 5 or more, preferably 10 or more, (b) inorganic particles with piezoelectricity, (c) inorganic particles with thermal conductivity, and (d) inorganic particles with lithium ion transfer ability. Specifically, it may be at least one selected from the group consisting of: AlN, BN, BeO, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, and SiC.

[0065] Based on the total weight of the separator layer, the ceramic particles can be contained in an amount of 10 to 30 wt%.

[0066] When the content of the ceramic particles is less than 10 wt% outside the above range, the content of the polymer becomes excessive, the empty spaces formed between the ceramic particles decrease, and the pore diameter and porosity decrease, thereby reducing the mobility of lithium ions, which is not suitable as a separator. On the other hand, when the content is greater than 30 wt%, the adhesion of the particles may be weakened, so the mechanical properties of the final separator layer may deteriorate, which is not preferred.

[0067] In addition, the polymer can be an acrylate-based or epoxy-based monomer, an acrylate-based or epoxy-based oligomer, or a polymer of a monomer and an oligomer.

[0068] That is, a photocurable PSA coating can be formed by the following process: wherein a solvent-free ink containing ceramic particles, a monomer and / or oligomer to be polymerized into the polymer, and an initiator for initiating the polymerization of the polymer is coated on the first electrode and then cured.

[0069] More specifically, by including the following steps:

[0070] (a) Coating and curing a PSA (pressure-sensitive adhesive) solvent-free ink with a breathable structure on the first electrode to form a separator layer;

[0071] (b) Laminating a second electrode on the separator layer; and

[0072] (c) Laminating the first electrode, the separator layer, and the second electrode;

[0073] to manufacture an integrated electrode laminate unit.

[0074] Here, the PSA solvent-free ink can include ceramic particles; at least one selected from the group consisting of monomers and oligomers; and the initiator as described above.

[0075] Specifically, it may include all of the following: ceramic particles, monomers, oligomers, and initiators, and more specifically, it may include ceramic particles, monofunctional monomers, polyfunctional monomers, oligomers, and initiators.

[0076] Specifically, the monomers and oligomers may be epoxy / acrylic monomers or oligomers.

[0077] Since the epoxy / acrylate-based material has the characteristics of epoxy resin, it has good strength, flexibility, adhesion, curability, etc., strong chemical resistance, and good heat resistance and durability. Therefore, it is more preferably used as the separation layer.

[0078] The monomers may be selected from, for example: monofunctional monomers such as BA (butyl acrylate), 2-EHA (2-ethylhexyl acrylate), HEA (2-hydroxyethyl acrylate), SA (stearyl acrylate), MMA (methyl methacrylate), IBOA (isobornyl acrylate), IDA (isodecyl acrylate), LA (lauryl acrylate), CA (ε-caprolactone acrylate), and BZA (benzyl acrylate); and polyfunctional monomers such as TMPTA (trimethylolpropane triacrylate), PETA (pentaerythritol triacrylate), TAOEIC (tris(2-hydroxyethyl)isocyanuric acid triacrylate), GPTA (3-(propoxy)propane-1,2,3-triol triacrylate), and THEICTA (tris(2-hydroxyethyl)isocyanuric acid triacrylate).

[0079] The oligomers may be selected from, for example: HDDA (1,6-hexanediol diacrylate), TCDDA (tricyclodecane dimethanol diacrylate), PEG200DA (polyethylene glycol 400 diacrylate), TTEGDA (tetraethylene glycol diacrylate), TPGDA (tripropylene glycol diacrylate), DPGDA (dipropylene glycol diacrylate), TEGDA (triethylene glycol diacrylate), etc.

[0080] In addition, the initiator for polymerizing the monomers and oligomers is a photo-curing initiator, and common initiators capable of generating free radicals by irradiation with UV or the like to initiate photopolymerization can be used without limitation, such as acetophenone-based compounds, benzimidazole-based compounds, triazine-based compounds, oxime-based compounds, benzoin-based compounds, hydroxyketone-based compounds, aminoketone-based compounds, or phosphine oxide-based compounds.

[0081] Since the specific materials of these initiators have been disclosed in the art, their detailed descriptions are omitted herein.

[0082] On the other hand, since the contents of these ceramic particles, monomers, oligomers, and initiators also affect the physical properties of the separation layer, it is also preferable to appropriately adjust the contents.

[0083] Specifically, based on the total weight of the PSA solvent-free ink, the ceramic particles can be contained in an amount of 10 to 30 wt%.

[0084] When the content of the ceramic particles is less than 10 wt% outside the above range, the content of the monomer and the oligomer becomes excessive, the empty spaces formed between the ceramic particles decrease, the pore diameter and the porosity decrease, thereby reducing the mobility of lithium ions, which is not suitable as a separator. On the other hand, when the content is greater than 30 wt%, the adhesion of the particles can be weakened, so the mechanical properties of the final separator layer may deteriorate, which is not preferred.

[0085] Meanwhile, based on the total weight of the PSA solvent-free ink, the initiator can be contained in an amount of 0.1 to 0.8 wt%.

[0086] When the content of the initiator is too little outside the above range, curing may not be carried out sufficiently, while when the content of the initiator is too large, it is impossible to obtain a separator layer with the required physical properties, such as a decrease in adhesion, which is not preferred.

[0087] More specifically, when the PSA solvent-free ink includes ceramic particles, monofunctional monomers, polyfunctional monomers, oligomers and initiators, it can contain 10 to 30 wt% of ceramic particles, 45 to 65 wt% of monofunctional monomers, 10 to 15 wt% of polyfunctional monomers, 5 to 10 wt% of oligomers, 0.1 to 0.8 wt% of initiators.

[0088] In the case of monofunctional monomers, this can be used to ensure the adhesion and elongation of the separator layer, while in the case of polyfunctional monomers, this can be used to ensure the shrinkage and strength of the separator layer after curing, and the oligomers can be used to ensure the viscosity of the PSA solvent-free ink and increase the strength and elongation of the separator layer.

[0089] Therefore, when the content of the monofunctional monomer is very small outside the above range, or the content of the polyfunctional monomer and the oligomer is relatively high, sufficient adhesion and elongation cannot be ensured. On the other hand, when the content of the monofunctional monomer is high while the content of the polyfunctional monomer or the oligomer content is relatively low, sufficient strength cannot be obtained, which is not preferred.

[0090] The separator layer prepared in this way can have a strength of 30 to 50 MPa as described above.

[0091] When the strength is less than 30 MPa outside the above range, it cannot function as a separator layer, or the separator layer may be deformed or torn during lamination in the process of manufacturing the electrode laminate unit, which is not preferred. When the strength is greater than 50 MPa, the adhesion or elongation may decrease, which is not preferred.

[0092] The strength was measured at room temperature using a testing machine UTM (manufactured by Zwick / Roell). The measurement sample was prepared as follows: a dog-bone-shaped separator layer with a thickness of 1.0 mm was coated on a demolded (Al-anodized treatment) plate in accordance with ASTM-D638 standard, and then UV curing was performed (ultraviolet wavelength: 395 nm, 3 seconds). Then, when the dog-bone sample was pulled to both sides at a speed of 10 mm / min, the strength at the break of the separator layer sample was measured.

[0093] In addition, as described above, the separator layer may have an adhesion force to the second electrode of 70 gf / 20 mm to 90 gf / 20 mm.

[0094] When the adhesion force is too low outside the above range, the life characteristics of the secondary battery are poor, and it is actually difficult to ensure a high adhesion force deviating from the above range, which is not preferred.

[0095] The adhesion force was measured as follows. The separator layer (thickness: 10 μm) was coated on the first electrode blanked to a size of 20 mm × 150 mm, and after UV curing (UV wavelength: 395 nm, 3 seconds), the second electrode was blanked to a size of 20 mm × 145 mm and laminated, and then passed through a roll laminator at 100 °C and bonded. At this time, the speed of the roll laminator was 0.4 m / min, and the pressure was 2 kgf / cm 2 。

[0096] Next, after being installed on a UTM device (LLOYD Instrument LF Plus), the second electrode was stretched at a measurement speed of 100 mm / min at room temperature, and the force peeled from the separator layer was measured.

[0097] Meanwhile, the separator layer may have a patterned structure.

[0098] Here, there is no limitation on the pattern structure as long as it has a certain pattern, and it can be applied in various ways. All of dot shape, line shape, polygon shape, etc. can be used.

[0099] Figure 2 A cross-sectional view of an integrated electrode laminate unit 100 including a separator layer having a patterned structure according to an embodiment is illustrated, while Figure 3 A disassembled perspective view of the electrode laminate unit 100 is shown.

[0100] Referring to Figure 2 and Figure 3 ,a separator layer 120 is formed on the first electrode 110, and a second electrode 130 is formed on the separator layer 120.

[0101] At this time, the separator layer 120 has a linear patterned structure in which coated portions and uncoated portions appear alternately.

[0102] With such a patterned structure, the porosity of the separation layer can be adjusted.

[0103] In addition, the integrated electrode laminate unit 100 may further include a separator 140 on the other surface of the first electrode 110 that does not face the separation layer 120.

[0104] On the other hand, the separation layer is composed of two or more layers, each separation layer having a patterned structure, and each separation layer may have a different pattern structure from an adjacent separation layer.

[0105] At this time, the patterned structure of each separation layer is not limited and can have various structures. In one example, the pattern of each separation layer is a linear pattern in which coated portions and uncoated portions alternate, and the angle between the lines formed by the patterns of adjacent separation layers may be from 10 degrees to 90 degrees.

[0106] For ease of understanding of these configurations, Figure 4 a cross-sectional view of an electrode laminate unit 200 in which two separation layers 220 and 220a are formed is shown, while Figure 5 is an exploded perspective view of the electrode laminate unit 200.

[0107] Referring to Figure 4 and Figure 5 , first, a first separation layer 220 is formed on the first electrode 210 to have a uniform linear patterned structure. Then, the second separation layer 220a is formed to have a linear patterned structure such that it forms an angle of about 90 degrees different from that of the first separation layer 220.

[0108] In addition, a second electrode 230 is formed on the second separation layer 220a.

[0109] In the drawings, only the configuration in which the first separation layer 220 and the second separation layer 220a are formed is shown, but it goes without saying that more than three separation layers can be formed.

[0110] In addition, the integrated electrode laminate unit 200 may further include a separator 240 on the other surface of the first electrode 210 that does not face the first separation layer 220.

[0111] Meanwhile, Figure 6 a method 300 for manufacturing such an integrated electrode laminate unit is shown.

[0112] Referring to Figure 6 , first, the first electrode 310 is cut into unit electrodes by a cutting machine 311, and PSA solvent-free ink 321 is coated on the cut first electrode 310.

[0113] At this time, there is no limitation on the method of applying the PSA solvent-free ink 321 onto the first electrode. However, in order to properly apply the PSA solvent-free ink 321, specifically, it can be applied by inkjet printing.

[0114] When using such inkjet printing, the discharge amount can be adjusted down to several picoliters. Therefore, it is easy to adjust the porosity of the laminated separator and achieve the pore size, and it is also easy to adjust the size of the pattern structure described later. Thus, this is preferred.

[0115] Therefore, the viscosity of the PSA solvent-free ink 321 for smoothly ejecting the PSA solvent-free ink 321 by a method such as inkjet printing can be 5 to 100 cP at room temperature, more specifically, a viscosity of 8 to 50 cP, and more specifically 10 to 20 cP. The viscosity is measured as follows: The Brookfield DV2T LV TJ10 model device is used together with the PSA solvent-free ink at 25 °C, the spindle part of the corresponding model is replaced with a cone and plate, and the CPA-40Z cone is coated and measured at 10 rpm.

[0116] When the viscosity is too low outside the above range, it is difficult to apply an appropriate amount of ink onto the first electrode, while when the viscosity is too high, the ink cannot be discharged, which is not preferred.

[0117] After coating, a separator layer is formed through a curing process.

[0118] Curing is performed by UV irradiation 322 using an LED lamp. Specifically, it can be performed by irradiating UV for 1 to 3 seconds at a short wavelength of 350 nm to 450 nm (specifically, a short wavelength of 380 nm to 400 nm) at an output of 0.5 W / cm 2 to 1.0 W / cm 2 On the other hand, compared with the coating area of the PSA solvent-free ink, curing causes shrinkage, and the shrinkage rate, which is the ratio of the shrinkage area to the original area, can be less than 3%.

[0119] When the shrinkage rate is too large outside the above range, not only can the sufficient strength of the separator layer not be ensured, but it is also difficult to properly perform the function as the separator layer.

[0120] The shrinkage rate (%) after curing can be calculated by measuring the area after curing relative to the coating area of the PSA solvent-free ink as (coating area - area after curing) / coating area × 100.

[0121] The separator layer prepared in this way can have a total thickness of 1 to 5 μm, specifically 2 to 4 μm.

[0122] The separator layer prepared in this way can have a total thickness of 1 to 5 μm, specifically 2 to 4 μm.

[0123] When the separator layer is too thin outside the above range, its function as a separator layer cannot be fully performed. When the separator layer is too thick, the overall volume of the secondary battery can increase, which is not preferable.

[0124] In addition, when the separator layer is two or more layers, the thickness of each separator layer is preferably less than 2 μm.

[0125] The total porosity of the separator layer can be 20% to 60%, and the average diameter (D50) of the pores can be 0.01 μm to 1 μm.

[0126] Therefore, when forming the separator layer, the spacing, shape, number of layers, etc. of the patterned structure can be adjusted to meet the above range.

[0127] When the porosity is too small outside the above range or the average diameter (D50) of the pores is too small, the ion transport ability decreases and the ionic conductivity decreases. When the porosity or the average diameter (D50) of the pores is too large, the strength of the separator layer can be weakened, which is not preferable.

[0128] For the porosity of the separator layer, the separator layer is made into a certain size using inkjet equipment, and then the volume is calculated and weighed. The separator is immersed in n-butanol for 2 hours, taken out, all the n-butanol on the surface is removed, and then the weight is measured and calculated by the following formula.

[0129] Porosity ε (%) = W w -W d / ρ b V p ×100 (W w : Weight after impregnation with n-butanol, W d : Weight of the dried separator, ρ b : Density of n-butanol, V p : Volume of the dried separator).

[0130] The average diameter of the pores is to take a SEM photo of the upper surface of the separator layer with a magnification of 2500 times, and then among the surface pores found within the randomly sampled range (width above 10 μm, length above 15 μm) in the measured photo, measure the major axis length as the pore size, and the minimum number of pores to be measured is set to 10 or more, and calculate the average value of the pore sizes obtained after measurement.

[0131] In addition, the separator layer can have an elongation rate of 20% to 50%.

[0132] When the elongation rate is too small outside the above range, local tearing or cracking may occur due to pressure. When the elongation rate is too high, it cannot have the strength as a separator layer, which is not preferable.

[0133] The elongation at break was measured at room temperature using a testing machine UTM (manufactured by Zwick / Roell). The measurement samples were prepared as follows: A dog-bone shaped separator layer with a thickness of 1.0 mm was coated on a demolded (anodized) plate in accordance with the ASTM-D638-5 standard, and then UV cured (ultraviolet wavelength: 395 nm, 3 seconds). Then, the dog-bone sample was pulled to both sides at a speed of 10 mm / min, and the elongation at break of the separator layer sample was measured.

[0134] Elongation at break (%) = (Breaking length / Initial length) × 100.

[0135] Since the separator layer that satisfies these conditions can be sufficiently used as a separator for a lithium secondary battery while ensuring sufficient adhesion to the electrodes. Therefore, it is necessary to form a separator layer that satisfies these conditions.

[0136] Refer again to Figure 6 , after curing is performed in such a manner to form a separator layer 320 having specific physical properties, the second electrode 330 is laminated on the separator layer 320 in a state of being cut into unit electrodes by a cutting machine 331.

[0137] Then, the first electrode 310, the separator layer 320, and the second electrode 330 are laminated by a laminating roller 340, thereby forming an electrode laminate unit 360.

[0138] Meanwhile, as Figure 6 shown, the first electrode 310 can be provided in a state where a sheet-like separator 370 is laminated on the other surface of the first electrode 310 where the separator layer 320 is not formed.

[0139] At this time, all of the sheet-like separator 370, the first electrode 310, the separator layer 320, and the second electrode 330 can be laminated, and the method 300 for manufacturing the electrode laminate unit may further include cutting the sheet-like separator 370 by a cutter 350 to correspond to the laminated electrodes 310 and 330.

[0140] Meanwhile, according to another embodiment of the present disclosure, a lithium secondary battery including an integrated electrode laminate unit is provided.

[0141] Such a lithium secondary battery may have the following structure: An electrode assembly including an integrated electrode laminate unit is incorporated into a battery case together with an electrolyte.

[0142] The specific structure and manufacturing method of the lithium secondary battery are known in the art, and thus detailed descriptions thereof will be omitted herein.

[0143] In the following, preferred embodiments of the present disclosure, comparative examples for comparing them, and experimental examples for evaluating them are described. However, it will be apparent to those skilled in the art that these examples are for illustrative purposes only, and various variations and modifications can be made without departing from the scope and spirit of this specification, and it goes without saying that these modifications and alterations fall within the scope of the appended claims.

[0144] <Preparation Example 1>

[0145] 2-EHA (2-ethylhexyl acrylate): TMPTA (trimethylolpropane triacrylate): PEG200DA (polyethylene glycol 400 diacrylate): initiator (Irgacure 369): Al2O3 as ceramic particles (D50: 200 - 300 nm) were mixed in a weight ratio of 40:19.5:20:0.5:20 to prepare a PSA solvent-free ink.

[0146] <Preparation Example 2>

[0147] 2-EHA (2-ethylhexyl acrylate): TMPTA (trimethylolpropane triacrylate): PEG200DA (polyethylene glycol 400 diacrylate): initiator (Irgacure 369): Al2O3 as ceramic particles (D50: 200 - 300 nm) were mixed in a weight ratio of 70:5:4.5:0.5:20 to prepare a PSA solvent-free ink.

[0148] <Preparation Example 3>

[0149] 2-EHA (2-ethylhexyl acrylate): TMPTA (trimethylolpropane triacrylate): PEG200DA (polyethylene glycol 400 diacrylate): initiator (Irgacure 369): Al2O3 as ceramic particles (D50: 200 - 300 nm) were mixed in a weight ratio of 60:10:9:1:20 to prepare a PSA solvent-free ink.

[0150] <Preparation Example 4>

[0151] 2-EHA (2-ethylhexyl acrylate): TMPTA (trimethylolpropane triacrylate): PEG200DA (polyethylene glycol 400 diacrylate): initiator (Irgacure 369): Al2O3 as ceramic particles (D50: 200 - 300 nm) were mixed in a weight ratio of 60:10:9.5:0.5:20 to prepare a PSA solvent-free ink.

[0152] <Preparation Example 5>

[0153] 2-EHA (2-Ethylhexyl acrylate): TMPTA (Trimethylolpropane triacrylate): PEG200DA (Polyethylene glycol 400 diacrylate): Initiator (Irgacure 369): Al2O3 (D50: 200 - 300 nm) as ceramic particles were mixed in a weight ratio of 45:10:24.5:0.5:20 to prepare a PSA solvent-free ink.

[0154] <Preparation Example 6>

[0155] 2-EHA (2-Ethylhexyl acrylate): TMPTA (Trimethylolpropane triacrylate): PEG200DA (Polyethylene glycol 400 diacrylate): Initiator (Irgacure 369): Al2O3 (D50: 200 - 300 nm) as ceramic particles were mixed in a weight ratio of 50:15:14.5:0.5:20 to prepare a PSA solvent-free ink.

[0156] <Experimental Example 1>

[0157] Using the PSA solvent-free inks prepared in Preparation Examples 1 to 6, the strength and elongation were measured as follows, and the results are shown in Table 1 below.

[0158] The strength was measured at room temperature using a testing machine UTM (manufactured by Zwick / Roell). The measurement sample was prepared as follows: According to the ASTM-D638 standard, a dog-bone-shaped separating layer with a thickness of 1.0 mm was coated on a plate that had undergone demolding treatment (Al-anodization treatment), and then UV cured (ultraviolet wavelength: 395 nm, 3 seconds). Then, the dog-bone sample was pulled to both sides at a speed of 10 mm / min, and the strength at the break of the separating layer sample was measured.

[0159] The elongation was performed in the same manner as the strength, and the time when the separating layer sample broke was measured. Then, the elongation (%) was calculated as follows.

[0160] Elongation (%) = Fracture length / Initial length × 100.

[0161] <Comparative Examples 1 to 3, Example 1>

[0162] Manufacture of the electrode stacking unit

[0163] LiNi as the positive electrode active material in N-methylpyrrolidone solvent 0.4 Mn 0.3 Co 0.3O2, carbon black conductive material, and PVdF binder are mixed at a weight ratio of 4.6:87.9:3.5:4 to prepare a cathode slurry coated on an aluminum current collector, and then dry rolled to prepare a cathode. The cathode is punched into a size of 20 mm × 150 mm.

[0164] The PSA solvent-free inks of Preparation Examples 1 to 6 are coated on the cathode by inkjet printing to have a linear pattern structure as shown in Figure 2 and 3 and cured by UV for 3 seconds (UV lamp, wavelength: 395 nm, output: 0.5 - 1 W / cm 2 etc.) to form a separator layer.

[0165] In addition, MCMB (mesocarbon microbeads) of artificial graphite as the negative electrode active material, carbon black conductive material, and PVdF binder are mixed in an N-methylpyrrolidone solvent at a weight ratio of 90:5:5 to prepare a composition for forming a negative electrode (which is coated on a copper current collector to prepare a negative electrode). The negative electrode is punched into a size of 20 mm × 145 mm.

[0166] The negative electrode is laminated on the separator layer and then bonded at 100 °C by a roll laminator to prepare an electrode laminate unit. At this time, the speed of the roll laminator is 0.4 m / min, and the pressure is 2 kgf / cm 2 .

[0167] <Experimental Example 2>

[0168] The comparative examples 1 to 3 and the electrode laminate unit prepared in Example 1 are tested by the following method, and the shrinkage rate (%) and adhesion force (gf / 20 mm) after curing are measured. The results are shown in Table 1 below.

[0169] * The shrinkage rate (%) after curing is calculated by measuring the area after curing relative to the coating area of the PSA solvent-free ink as (coating area - area after curing) / coating area × 100.

[0170] * For the measurement of the adhesion force, after being mounted on a UTM device (LLOYD Instrument LF Plus), the second electrode is pulled at a measurement speed of 100 mm / min at room temperature, and the force peeled off from the separator layer is measured.

[0171] [Table 1]

[0172]

[0173] Referring to Table 1, it can be determined that when preparing the PSA solvent-free ink, the contents of monomers, oligomers, initiators, inorganic materials, etc. have an impact on meeting sufficient strength, adhesion, elongation, etc. according to the present disclosure. Otherwise, the effects to be achieved by the present disclosure cannot be obtained.

[0174] Anyone with ordinary knowledge in the field to which the present disclosure pertains can make various applications and modifications within the scope of the present disclosure based on the above content.

[0175] Industrial Applicability

[0176] As described above, the integrated electrode laminate unit and its manufacturing method according to the embodiments of the present disclosure can integrate the electrode and the separator layer into a separator. Therefore, the manufacturing process can be simplified, and at the same time, problems such as electrode deformation and separator folding that occur in the lamination process of the electrode and the separator can be solved, thereby improving the yield of the electrode and the adhesion to the electrode.

[0177] In addition, when applying the above separator layer, the type and content of the material forming the separator layer can be easily adjusted, so that excellent physical properties such as required adhesion, strength, and elongation of the separator layer can be easily ensured.

Claims

1. An integrated electrode laminate unit, the integrated electrode laminate unit comprising: A first electrode, a second electrode, and a separator layer disposed between the first electrode and the second electrode, and the separator layer is in contact with the first electrode and the second electrode, Wherein, the separator layer is a photocurable pressure-sensitive adhesive PSA coating integrally formed on the first electrode, Wherein, the separator layer has a strength of 30 MPa to 50 MPa and an adhesion to the second electrode of 70 gf / 20 mm to 90 gf / 20 mm, Wherein, the first electrode, the separator layer, and the second electrode are laminated.

2. The integrated electrode laminate unit according to claim 1, wherein, The photocurable pressure-sensitive adhesive PSA coating is a polymer coating containing ceramic particles.

3. The integrated electrode laminate unit according to claim 2, wherein, The ceramic particles have an average diameter of 10 nm to 500 nm.

4. The integrated electrode laminate unit according to claim 2, wherein, The ceramic particles are at least one selected from the group consisting of AlN, BN, BeO, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, and SiC.

5. The integrated electrode laminate unit according to claim 2, wherein, The polymer is an acrylate-based oligomer, an epoxy-based oligomer, or a polymer of one of an acrylate-based monomer and an epoxy-based monomer and one of the acrylate-based oligomer and the epoxy-based oligomer.

6. The integrated electrode laminate unit according to claim 1, wherein, The separator layer has a patterned structure.

7. The integrated electrode laminate unit according to claim 1, wherein, The separator layer is composed of two or more layers, each separator layer has a patterned structure, and each separator layer has a pattern different from that of the adjacent separator layer.

8. The integrated electrode laminate unit according to claim 7, wherein, The pattern of each layer in each separator layer is a linear pattern in which coating portions and non-coated portions appear alternately, and the included angle of the lines formed by the patterns of adjacent separator layers is 10 degrees to 90 degrees.

9. The integrated electrode laminate unit according to claim 1 or 7, wherein, The total thickness of the separator layer is 1 μm to 5 μm.

10. The integrated electrode laminate unit according to claim 7, wherein, The thickness of each separator layer is less than 2 μm.

11. The integrated electrode laminate unit according to claim 1 or 7, wherein, The total porosity of the separator layer is 20% to 60%, and the average diameter of the pores is 0.01 μm to 1 μm.

12. The integrated electrode laminate unit according to claim 1, wherein, The separator layer has an elongation of 20% to 50%.

13. The integrated electrode laminate unit according to claim 1, wherein, The integrated electrode laminate unit further includes a separator membrane, and the separator membrane is located on the other surface of the first electrode that does not face the separator layer.

14. A method for manufacturing an integrated electrode laminate unit according to any one of claims 1 to 13, the method for manufacturing the integrated electrode laminate unit comprising the following steps: Step (a): Coating and curing a pressure-sensitive adhesive PSA solvent-free ink for a breathable structure on a first electrode to form a separation layer; Step (b): Stacking a second electrode on the separation layer; And Step (c): Laminating the first electrode, the separation layer, and the second electrode.

15. The method for manufacturing an integrated electrode laminate unit according to claim 14, wherein the pressure-sensitive adhesive PSA solvent-free ink contains ceramic particles, a monofunctional monomer, a polyfunctional monomer, an oligomer, and an initiator.

16. The method for manufacturing an integrated electrode laminate unit according to claim 15, wherein the pressure-sensitive adhesive PSA solvent-free ink contains 10 wt% to 30 wt% of the ceramic particles, 45 wt% to 65 wt% of the monofunctional monomer, 10 wt% to 15 wt% of the polyfunctional monomer, 5 wt% to 10 wt% of the oligomer, and 0.1 wt% to 0.8 wt% of the initiator.

17. The method for manufacturing an integrated electrode laminate unit according to claim 14, wherein the pressure-sensitive adhesive PSA solvent-free ink is coated on the first electrode by inkjet printing.

18. The method for manufacturing an integrated electrode laminate unit according to claim 14, wherein the pressure-sensitive adhesive PSA solvent-free ink has a viscosity of 5 cP to 100 cP at room temperature.

19. The method for manufacturing an integrated electrode laminate unit according to claim 14, wherein the curing is performed by UV irradiation using an LED lamp.

20. The method for manufacturing an integrated electrode laminate unit according to claim 14, wherein a sheet-like separator is laminated on the other surface of the first electrode where the separation layer is not formed in step (a), in step (c), the sheet-like separator, the first electrode, the separation layer, and the second electrode are laminated, and the method for manufacturing the electrode laminate unit further includes: after step (c), cutting the sheet-like separator to correspond to the first electrode or the second electrode.

21. A lithium secondary battery, the lithium secondary battery comprising an integrated electrode laminate unit according to any one of claims 1 to 13.

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