Separator for electrochemical device, and method for manufacturing same

Abstract

A separator, according to the present invention, has excellent adhesion to an electrode and can ensure sufficient porosity, and thus exhibits excellent resistance and ion conductivity characteristics. In addition, since lamination time can be shortened during the manufacture of an electrode assembly, high process efficiency in battery manufacturing can be achieved. Furthermore, the height of an inorganic particle filling part is minimized so that the energy density of a lithium secondary battery can be maximized.

Description

Separator for electrochemical devices and method for manufacturing the same

[0001] This application claims priority to Korean Patent Application No. 10-2024-0051016, filed April 16, 2024. The present invention relates to a separator for electrochemical devices such as lithium-ion secondary batteries.

[0002]

[0003] Non-aqueous secondary batteries, such as lithium-ion secondary batteries, are widely used as power sources for portable electronic devices such as laptops, mobile phones, digital cameras, and camcorders. Furthermore, due to their high energy density, these batteries are also being considered for use in automobiles.

[0004] Lithium secondary batteries currently in production use porous polymer substrates, such as polyolefin polymer resins, as separator substrates to prevent short circuits between the positive and negative electrodes. However, these polymer substrates have low heat resistance due to shrinkage or melting at high temperatures. Therefore, when the battery is exposed to internal or external stimuli, the separator shrinks or melts, increasing the likelihood of the positive and negative electrodes contacting each other and causing a short circuit. This can lead to a rapid release of electrical energy, potentially leading to battery explosion or ignition.

[0005] Accordingly, in order to solve the above problems, a method of improving heat resistance by forming a porous filler layer in which inorganic particles and binder resin are mixed on at least one side of a polymer substrate is widely used. However, the filler layer must have sufficient porosity in terms of securing an ion transport path and electrolyte impregnation. The pores of the filler layer originate from the interstitial volume between the inorganic particles. However, if the content of the binder resin is high, the interstitial volume is blocked by the binder resin, making it difficult to secure sufficient porosity. On the other hand, if the content of the binder resin is insufficient, the electrode and the separator may not be closely adhered, resulting in separation between the electrode and the separator during the battery manufacturing process or battery operation.

[0006] To secure porosity in the membrane coating layer, a technique known as a humidified phase separation process is used to distribute an organic binder onto the separator surface, thereby improving adhesion to the electrode. However, this humidified phase separation process not only requires meticulous temperature and humidity control, but also exhibits significant fluctuations in adhesion depending on drying conditions. Furthermore, this phase separation process cannot be applied when using an aqueous binder.

[0007] Meanwhile, a technology has been proposed for manufacturing a separator by forming a separate electrode adhesive layer on the outermost surface of the separator. However, this method has the disadvantage of increasing resistance and reducing air permeability due to the surface of the separator being coated with an organic binder, and requiring an additional coating process to coat the adhesive layer.

[0008] To address these issues, a technique has been proposed for coating a membrane substrate with an aqueous composition using an aqueous solvent and an aqueous emulsion binder during filler layer formation. However, the use of an aqueous composition results in agglomeration of the emulsion binder particles, resulting in reduced air permeability and ionic conductivity.

[0009] Meanwhile, electrode assemblies are typically manufactured using a roll-to-roll continuous process, followed by a lamination process that pressurizes (and, if necessary, applies hot presses) the laminated electrodes and separator. To ensure the desired level of electrode-separator bonding, sufficient lamination time must be secured, but this can lead to reduced productivity, including reduced production speeds.

[0010] Accordingly, continuous research and development is required to secure sufficient porosity and adhesive strength (between electrodes and separators) and process efficiency in separators for electrochemical devices.

[0011]

[0012] The present invention aims to provide a separator for electrochemical devices with high electrode adhesion, resistance characteristics, and porosity, and a method for manufacturing the same. Furthermore, the present invention aims to provide a separator that can improve battery production efficiency, such as by reducing the time required for electrode-separator lamination. It will be readily apparent that other objects and advantages of the present invention can be achieved by the means or methods set forth in the claims, and combinations thereof.

[0013]

[0014] The present invention relates to a separator for an electrochemical device, wherein the separator comprises a porous polymer substrate and an inorganic coating layer covering one surface or both surfaces of the porous polymer substrate.

[0015] The above-mentioned inorganic coating layer comprises a plurality of adhesive polymer columns of a predetermined volume, wherein the polymer columns are made of a polymer material and do not have pores,

[0016] At least a portion of the polymer column is exposed to the surface of the inorganic coating layer and another portion is in contact with the surface of the porous substrate,

[0017] At least one polymer column is spaced apart from the other polymer columns by a predetermined distance,

[0018] The space between the above polymer columns is filled with an inorganic particle filling portion, and the inorganic particle filling portion includes inorganic particles and a binder resin.

[0019] The above polymer column has a phase angle of less than 10°, and the phase angle is calculated according to the following mathematical formula 1.

[0020]

[0021] [Formula 1] Phase angle

[0022] δ = tan -1 (G`` / G`)

[0023] In the above equation 1, G' is the storage modulus (G', storage modulus) and G" is the loss modulus.

[0024]

[0025] In at least one of the embodiments described above, the polymer column may have a ratio of the storage modulus at 60°C to the storage modulus at room temperature (G'(60°C) / G'(room temperature)) of 0.1 or less.

[0026] In at least one of the embodiments described above, the degree of crosslinking (gel fraction) of the polymer column may be 50% or more.

[0027] The present invention comprises at least one of the above-described embodiments, wherein the inorganic particle filling part (T) i ) may be 5% or more and 40% or less of the diameter D50 of the polymer column.

[0028] The present invention, in at least one of the above-described embodiments, has a height (T) of the inorganic particle filling portion i ) may be equal to or less than 2㎛.

[0029] The present invention is characterized in that in at least one of the above-described embodiments, the separation membrane has a protrusion height (T) of the polymer column after a pressure of 3.0 MPa to 4.0 MPa is applied for less than 20 seconds under a temperature condition of 55°C to 65°C. p ) is the height of the inorganic particle filling (T i ) or T i It may be less than 1.1 times.

[0030] The present invention is characterized in that in at least one of the above-described embodiments, the separation membrane has a protrusion height (T) of the polymer column after a pressure of 3.0 MPa to 4.0 MPa is applied for less than 20 seconds under a temperature condition of 55°C to 65°C. p ) may be less than 1㎛.

[0031] The present invention is characterized in that in at least one of the above-described embodiments, D of the polymer column 50 D of silver inorganic particles 50 It can be twice as large or larger.

[0032] The present invention, in at least one of the above-described embodiments, has a thickness (T) of the inorganic particle filling portion i ) is a polymer column D 50 It may be less than 85% of the total.

[0033] The present invention is characterized in that in at least one of the above-described embodiments, D of the polymer column 10 Silver D 50 More than 30% of D90 is D 50 It may be less than 200% of .

[0034] In at least one of the embodiments described above, the surface area of ​​the polymer column may be 10% to 50% of the surface area of ​​the inorganic coating layer based on the top view of the separation membrane.

[0035] In at least one of the above-described embodiments, the present invention may be such that the area (a) of the polymer column cross-section confirmed in the lower 5% from the lowest portion of the inorganic coating layer toward the surface and the area (b) of the column cross-section confirmed in the upper 5% from the top portion toward the bottom may be greater than the area (a).

[0036] The present invention, in at least one of the above-described embodiments, is characterized in that at least one polymer column included in the inorganic coating layer has a diameter (a) at the bottom of the polymer column shorter than a diameter (b) at the top of the column in a cross-section of the polymer column confirmed in a vertical cross-section of the inorganic coating layer, and the ratio of the diameter (b) to the diameter (a) may be 2 to 20.

[0037] In at least one of the embodiments described above, the inorganic coating layer may have a pore structure due to interstitial volume between inorganic particles.

[0038] The present invention can provide an electrochemical device including a separator for an electrochemical device according to at least one of the embodiments described above.

[0039] The above-described embodiments may be implemented independently, or two or more of the above-described embodiments may be implemented in combination.

[0040]

[0041] The separator according to the present invention not only exhibits excellent adhesion to electrodes but also secures sufficient porosity, resulting in superior resistance and ionic conductivity characteristics. Furthermore, it can shorten the lamination process time during electrode assembly manufacturing, thereby achieving high process efficiency in battery manufacturing.

[0042]

[0043] The drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the contents of the invention described above, serve to further enhance the understanding of the technical spirit of the present invention. Therefore, the present invention is not limited to the matters described in these drawings. Meanwhile, the shape, size, scale, or ratio of elements in the drawings included in this specification may be exaggerated to emphasize a clearer explanation.

[0044] Figure 1 is a schematic diagram showing one embodiment of the separation membrane of the present invention.

[0045] Figure 2 is a graph showing the particle size distribution measured by the laser scattering method of the polymer column used in Examples 1 to 3 and Comparative Examples 1 to 2.

[0046] Figure 3 is a graph showing the DMA peak temperature for the polymer columns used in Examples 1 to 3 and Comparative Examples 1 to 2.

[0047] Figure 4 is a graph comparing the phase angles of polymer columns used in Examples 1 to 3 and Comparative Examples 1 to 2.

[0048] Figures 5a to 5c are surface SEM images of the membrane obtained in Example 1 at different magnifications.

[0049] Figures 6a to 6c are surface SEM images of the membrane obtained in Example 2 at different magnifications.

[0050] Figures 7a to 7c are surface SEM images of the membrane obtained in Example 3 at different magnifications.

[0051] Figures 8a to 8c are surface SEM images at different magnifications of the membrane obtained in Comparative Example 1.

[0052] Figures 9a to 9c are surface SEM images at different magnifications of the membrane obtained in Comparative Example 2.

[0053] Figures 10a and 10b are cross-sectional SEM images of the membrane obtained in Example 1 before the pressurization process.

[0054] Figure 11 is a cross-sectional SEM image of the membrane obtained in Example 1 after the pressurization process.

[0055]

[0056] Hereinafter, the present invention will be described in detail. Prior to this, the terms or words used in this specification and claims should not be interpreted as limited to their conventional or dictionary meanings. Rather, they should be interpreted with meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to best explain his or her invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent the entire technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of this application.

[0057] Throughout this specification, when it is said that a part "includes" a component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated.

[0058] In addition, the terms "about", "substantially", etc. used throughout this specification are used in the sense of numerical values ​​or near numerical values ​​when manufacturing and material tolerances inherent to the meanings stated are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that mention exact or absolute values ​​to aid understanding of this specification.

[0059] Throughout this specification, the description of “A and / or B” means “A or B or both.”

[0060] Entry D in the original specification50 D means the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size. That is, D 50 refers to the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size. In addition, D 10 D means the particle size at the 10% point of the cumulative distribution of particle numbers according to particle size. 90 It means the particle size at the 90% point of the cumulative distribution of the number of particles according to the particle size. The particle size can be measured using the laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and the particle size distribution is calculated by measuring the difference in the diffraction pattern according to the particle size when the particles pass through the laser beam. By calculating the particle diameters at the points where the particle number is 10%, 50%, 90% and 100% of the cumulative distribution of the number of particles according to the particle size in the measuring device, respectively, D 10, D 50, D 90 and D 100 can be measured.

[0061] Certain terminology used in the following detailed description of the invention is for convenience only and is not limiting. The words "left," "right," "upper," and "lower" may indicate directions in the drawings to which reference is made and should not be limiting. The words "inwardly" and "outwardly" indicate directions toward or away from the geometric center of the designated device, system, and its components, respectively. The words "front," "rear," "upper," and "lower," and related words and phrases indicate positions and orientations in the drawings to which reference is made and should not be limiting. These terms include the words listed above, their derivatives, and words of similar import.

[0062] In the present invention, the glass transition temperature (Tg) can be measured through a DSC curve derived from a temperature increase analysis at 10°C / min using a differential scanning calorimeter (DSC).

[0063]

[0064] The present invention relates to a separator for an electrochemical device and an electrochemical device including the same. In the present invention, the electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept that includes a primary battery and a secondary battery. The secondary battery is a concept that encompasses lithium-ion batteries, nickel-cadmium batteries, nickel-hydrogen batteries, etc., and is capable of charging and discharging.

[0065]

[0066] membrane

[0067] In one embodiment of the present invention, the separator includes a porous substrate (10) and an inorganic coating layer (20) formed on at least one side or both sides of the porous substrate. Fig. 1 is a schematic diagram illustrating a cross-section of the separator of the present invention, in which inorganic particles (200) and polymer columns (100) are arranged. In particular, the diagram illustrates an aspect before compression (pressurization) during the manufacturing process of the separator, in which the polymer columns protrude beyond the inorganic particle filling portion. The compression may mean that an external force is artificially applied during the battery assembly process.

[0068] The above separator may have a total thickness of 5.0 μm to 30 μm and may be appropriately adjusted within the above range. For example, it may be 25.0 μm or less, 20.0 μm or less, 15.0 μm or less, 12.0 μm or less, or 10.0 μm or less. In one embodiment of the present invention, the separator preferably has a thickness of 15.0 μm or less, 14.0 μm or less, 13.0 μm or less, 12.0 μm or less, or 11.0 μm or less after flattening by pressing as described below. In addition, the separator may have a porosity of about 25 vol% to 80 vol%.

[0069] The porosity can be appropriately controlled within the aforementioned range. For example, the porosity can be 30 vol% or more, or 35 vol% or more, or 40 vol% or more, or 50 vol% or more, or 55 vol% or more. Alternatively, the porosity can be 70 vol% or less, or 65 vol% or less, or 60 vol% or less, or 55 vol% or less. Meanwhile, the separation membrane can exhibit a permeability in a range of about 50 sec / 100 cc or more and about 250 sec / 100 cc or less. The permeability can be appropriately controlled within the aforementioned range. For example, the permeability can be 60 sec / 100 cc or more, or 70 sec / 100 cc or more, or 100 sec / 100 cc or more, or 120 sec / 100 cc or more, or 150 sec / 100 cc or more. Alternatively, the porosity may be 220 sec / 100cc or less, or 200 sec / 100cc or less, or 180 sec / 100cc or less.

[0070] In one embodiment of the present invention, the thickness of the separator can be determined by cutting a cross-section of a separator sample, observing it through an SEM, and then taking the thickness of the thickest point as the thickness of the separator. Alternatively, the thicknesses of two or more arbitrary points can be measured and the average value thereof can be taken as the thickness of the separator. If the thicknesses of four or more points are measured, the lowest and / or highest values ​​can be excluded and the average value of the remaining values ​​can be taken.

[0071] In one embodiment of the present invention, the porosity can be calculated by calculating the true density of the measurement object from the density (apparent density) of the measurement object such as a membrane, the composition ratio of materials included in the measurement object, and the density of each component, and calculating the porosity from the difference between the apparent density and the true density (net density). For example, the porosity can be calculated by [Formula 3] below.

[0072]

[0073] [Formula 2] Porosity

[0074] Porosity (vol%) = {1-(apparent density / true density)} × 100

[0075]

[0076] Meanwhile, the apparent density in the above formula can be calculated from [Formula 3] below.

[0077]

[0078] [Formula 3] Apparent density

[0079] Apparent density (g / cm) 3 ) = {Weight of the measurement object [g] / (Thickness of the measurement object [cm] × Area of ​​the measurement object [cm 2 ])}

[0080]

[0081] Alternatively, the porosity or pore size can be measured using an adsorbent gas such as nitrogen using BELSORP (BET equipment) from BEL JAPAN, or by a method such as mercury intrusion porosimetry or capillary flow porosimetry.

[0082] The term 'permeability' used in this specification means the time it takes for 100 cc of air to permeate a permeability measurement target such as a membrane or porous substrate, and the unit thereof can be second / 100 cc, can be used interchangeably with permeability, and is typically expressed as a Gurely value, etc. In a specific embodiment of the present invention, the permeability can be measured in accordance with JIS P8117. In addition, the air permeability P1 measured in an object having a thickness T1 can be converted into the permeability P2 when the thickness of the object is 20 µm by the formula: P2 = (P1 × 20) / T1.

[0083]

[0084] porous substrate

[0085] The above porous substrate refers to a substrate having multiple pores formed therein as an ion-conducting barrier that allows ions to pass through while blocking electrical contact between the cathode and anode. The pores are structured to be interconnected, allowing gas or liquid to pass from one side of the substrate to the other.

[0086] The material constituting the porous substrate can be any organic or inorganic material with electrical insulation properties. In particular, from the perspective of imparting a shutdown function to the substrate, it is preferable to use a thermoplastic resin as the constituent material of the substrate. Here, the shutdown function refers to a function in which, when the battery temperature rises, the thermoplastic resin melts and closes the pores of the porous substrate, thereby blocking the movement of ions and preventing thermal runaway of the battery. Suitable thermoplastic resins include those with a melting point below 200°C, and polyolefin is particularly preferred.

[0087] In addition, at least one of polymer resins such as polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene may be further included. The porous substrate may be, but is not particularly limited to, a non-woven fabric, a porous polymer film, or a laminate of two or more thereof.

[0088]

[0089] Specifically, the porous polymer substrate is one of the following a) to e).

[0090]

[0091] a) A porous film formed by melting / extruding a polymer resin,

[0092] b) A multilayer film in which two or more layers of the porous film of a) above are laminated,

[0093] c) A nonwoven web manufactured by accumulating filaments obtained by melting / spinning a polymer resin.

[0094] d) A multilayer film in which two or more layers of the nonwoven web of the above b) are laminated,

[0095] e) A porous composite membrane having a multilayer structure comprising two or more of the above a) to d).

[0096]

[0097] In the present invention, the porous substrate may have a thickness ranging from 3 μm to 12 μm or from 5 μm to 12 μm. If the thickness falls short of the above values, the conductive barrier function is insufficient, whereas if the thickness exceeds the above range (i.e., is too thick), the resistance of the separator may excessively increase.

[0098] In one embodiment of the present invention, the weight average molecular weight (Mw) of the polyolefin may be 100,000 to 5,000,000. For example, the molecular weight (Mw) may be 200,000 or more, or 500,000 or more, or 700,000 or more, or 1,000,000 or more. Alternatively, the molecular weight may be 4,000,000 or less, or 3,000,000 or less, or 2,500,000 or less, or 2,000,000 or less, or 1,500,000 or less. The unit of the molecular weight (Mw) may be g / mol. If the weight average molecular weight is less than 100,000, it may be difficult to secure sufficient mechanical properties. In addition, if it exceeds 5,000,000, the shutdown characteristics may deteriorate, or molding may become difficult. In addition, the puncture strength of the porous substrate may be 300 gf or more from the viewpoint of improving the manufacturing yield. The puncture strength of a porous substrate refers to the maximum puncture load (gf) measured by performing a puncture test using a Kato tech KES-G5 handy compression tester under conditions of a needle tip curvature radius of 0.5 mm and a puncture speed of 2 mm / sec.

[0099] In a specific embodiment of the present invention, the porous polymer substrate may be any planar porous polymer substrate used in an electrochemical device, and for example, an insulating thin film having high ion permeability and mechanical strength, a pore diameter of generally 10 nm to 200 nm, and a thickness of generally 2 μm to 12 μm may be used. Meanwhile, the porous substrate may have a porosity of 20 vol% to 60 vol% or 30 vol% to 60 vol%, and a pore size of 10 nm to 200 nm, but is not particularly limited thereto.

[0100]

[0101] Inorganic coating layer

[0102] In the present invention, the separator comprises an inorganic coating layer formed on one surface of the porous substrate. The inorganic coating layer comprises a plurality of polymer columns, a plurality of inorganic particles, and a binder resin. The binder resin comprises binder resin A having a surface energy similar to that of the polymer particles.

[0103] In a specific embodiment of the present invention, the inorganic particles in the inorganic coating layer may be included in a range of about 70 wt% to 90 wt% relative to 100 wt% of the inorganic coating layer. In addition, the polymer column may be included in a range of 10 wt% to 40 wt%, preferably 20 wt% to 35 wt%, relative to 100 wt% of the inorganic particles. In one embodiment, the polymer column may be included in a range of 10 wt% to 30 wt%, or 10 wt% to 20 wt% relative to 100 wt% of the inorganic coating layer. For example, it may be included in a range of 14 wt% to 18 wt%.

[0104] If the content of the polymer column in the inorganic coating layer is low, it is difficult to secure the desired level of adhesive strength. However, if the content exceeds the above range and is too large, the Gurley value and / or porosity of the separation membrane may decrease, which is not desirable.

[0105]

[0106] Meanwhile, in the planar image of the inorganic coating layer, the total area of ​​the polymer columns relative to the total area of ​​the inorganic coating layer before or after compression or both may be 10% to 80% of the total area of ​​the inorganic coating layer, and preferably 10% to 50%.

[0107]

[0108] In the above-described inorganic coating layer, the polymer columns may be clustered by two or more polymer columns, or the polymer columns may be spaced apart from each other by a predetermined distance. In one embodiment of the present invention, the amount of the two or more polymer columns clustered is 30 vol% or less, preferably 20 vol% or less, and more preferably 10 vol% or less, based on 100 vol% of the total polymer columns. If the polymer columns are excessively clustered, it may cause non-uniformity of resistance in the separation membrane. Therefore, in terms of increasing the uniformity of resistance, it is preferable that the polymer columns forming the clusters are 10 vol% or less based on 100 vol% of the total polymer columns. In one embodiment of the present invention, preferably, the polymer columns are distributed in an island-like manner in the inorganic coating layer without directly contacting other polymer columns and spaced apart by a predetermined distance. In the inorganic coating layer, a plurality of polymer columns are embedded so as to be exposed or protruded outside the surface of the inorganic coating layer, and the protrusion height (T) of some of the polymer columns p ) can exceed 1㎛. For example, T pThe polymer columns may be greater than 1 μm and less than or equal to 10 μm, for example, less than or equal to 7 μm, less than or equal to 5 μm, or less than or equal to 3 μm. In addition, some of the polymer columns exposed to or protruding from the surface of the inorganic coating layer may be in contact with the porous substrate. In addition, some of the exposed or protruding polymer columns may be in contact with the porous substrate. Here, the protrusion of the polymer columns outside the surface of the inorganic coating layer means that the inorganic particle filling portion (T) of the inorganic coating layer i ) compared to the height of the polymer column (T c ) means that it has a higher height than the inorganic particle filling part.

[0109]

[0110] In one embodiment of the present invention, the average pore size of the inorganic coating layer may be 20 nm to 1,000 nm. In one embodiment of the present invention, the pore size may be measured for the inorganic particle filling portion. Within the above range, the average pore size of the inorganic coating layer may be 800 nm or less, or 500 nm or less, and independently or in combination may be 20 nm or more, 50 nm or more, or 100 nm or more. For example, the average pore size of the inorganic coating layer may be 20 nm to 800 nm. The pore size may be calculated from shape analysis using an SEM image. If the pore size is smaller than the above range, the pores are likely to be blocked due to expansion of the binder resin in the coating layer, and if the pore size is outside the above range, it is difficult to function as an insulating film, and there is a problem that the self-discharge characteristics deteriorate after manufacturing a secondary battery.

[0111]

[0112] In one embodiment of the present invention, the porosity of the inorganic coating layer (porosity in a state where the polymer column is included) is preferably 30 vol% to 80 vol%. The porosity can be appropriately controlled within the above range. For example, the porosity may be 35 vol% or more, or 40 vol% or more, or 45 vol or more. Alternatively, the porosity may be 75 vol% or less, or 70 vol% or less, or 65 vol% or less. If the porosity is 30% or more, it is advantageous in terms of lithium ion permeability, and if the porosity is 80% or less, the surface opening ratio is not too high, which is suitable for securing adhesion between the separator and the electrode.

[0113]

[0114] Meanwhile, in one embodiment of the present invention, the separator can be brought into close contact with the electrode and the separator and the gap can be minimized by introducing a polymer column having the following characteristics, so that the ion conductivity is 9.00×10 -4 It can represent more than S / cm.

[0115]

[0116] polymer column

[0117] The polymer column may comprise a polymer resin in an amount of 90 wt% or more, 95 wt% or more, or 99 wt% or more, based on 100 wt% of the polymer column. Preferably, the polymer column may be formed of a polymer resin. In addition, the polymer column has adhesive properties, and may adhere to a battery material adjacent to the polymer column, such as an inorganic particle or a porous substrate.

[0118] In the present invention, the polymer column may not have open cell-type pores in its body. It is preferable that the polymer column does not have open cell-type pores, so that a fluid such as a gas or liquid does not flow through the polymer column body.

[0119] As described above, at least a portion of one or more of the polymer columns may be exposed or protruding outside the surface of the inorganic coating layer, and another portion thereof may be in contact with the surface of the porous substrate.

[0120] In one embodiment of the present invention, D of the polymer column 10 Silver D 50 It can be more than 10% of D 90 Silver D 50 may be less than 200% of the D of the polymer column, together with or independently of this. 50 Silver inorganic particles D 50 The contrast can be twice or more.

[0121] In one embodiment of the present invention, D of the polymer column 50 silver It can be about 2.0㎛ to 7.0㎛ and can be appropriately adjusted within the above range. For example, D of the polymer column 50 This may have a range of 4.0㎛ to 6.0㎛ or 3.0㎛ to 5.0㎛. D of the polymer column 50 It reflects the state before the separation membrane is pressurized, preferably before the slurry is prepared. Meanwhile, along with this, the D of the polymer column 100 The D of the polymer column may be 30 μm or less, and more preferably 20 μm or less. In addition, in a specific embodiment of the present invention, the D95 of the polymer column may be 20 μm or less, and more preferably 15 μm or less. In addition, the D90 of the polymer column may be 15 μm or less, and more preferably 10 μm or less. The D of the polymer column 100 If the above range is excessively exceeded, the size uniformity of the polymer column is low, so that the thickness of the membrane coating layer is not uniform, and if an excessively large polymer column is compressed, the membrane surface of that part may be covered by the compressed polymer column, resulting in a decrease in porosity and a deterioration in porosity uniformity.

[0122] In one embodiment of the present invention, the separation membrane may have one or more polymer columns higher than the height of the inorganic particle filling portion when not artificially pressurized after manufacture. That is, they may protrude from the surface of the inorganic particle filling portion. That is, they may protrude from the surface of the inorganic particle filling portion. In one embodiment of the present invention, when the polymer columns protrude outside the inorganic coating layer, the thickness of the inorganic particle filling portion is D of the polymer columns. 50 It may be less than 85% of the total.

[0123]

[0124] Meanwhile, in one embodiment of the present invention, the height (T) of the polymer column c ) can be obtained by cutting a cross-section of a membrane specimen and observing it through SEM, and then taking the value of the highest part of the polymer column.

[0125] Meanwhile, in one embodiment of the present invention, the protrusion height (T) of the polymer column p ) can be obtained by cutting a cross-section of a membrane specimen and observing it through SEM, and then taking the value of the part where the gap between the inorganic particle filling part and the polymer column is the largest.

[0126]

[0127] Meanwhile, in one embodiment of the present invention, when the one or more polymer columns are pressed at a pressure of 0.5 MPa or more and 20.0 MPa or less, for example, when pressed at a pressure of 2.0 MPa to 8.0 MPa, the protruding portions are pressed and flattened, so that the thickness of the inorganic coating layer becomes uniform. Meanwhile, the pressing may be hot pressing. This property is advantageous in strengthening the adhesion between the electrode and the separator during the manufacture of the electrode assembly and in preventing the occurrence of a gap between the electrode and the separator. That is, under conditions for lamination of the electrode and the separator, i.e., hot press conditions, the polymer columns may exhibit softening properties.

[0128]

[0129] The separation membrane according to the present invention has a height (T) of the inorganic coating layer when compressed under pressure conditions of 2.0 MPa to 7.0 MPa and 55°C to 65°C. 코팅층 ) is 1.1 x T i is less than . In addition, T, the protrusion height of the polymer column after compression under the above conditions, p The separation membrane is flattened by being 1㎛ or less or less than 1㎛. Referring to Fig. 1, in the present invention, the T c refers to the total height of the inorganic coating layer (one side), and is based on the highest part of the inorganic coating layer in the porous substrate. In the present invention, the T c may be equal to the height of the tallest protruding member among the polymer columns. In addition, the T p It is based on the highest part of the inorganic coating layer from the inorganic particle filling part.

[0130]

[0131] Meanwhile, in the present invention, the pressurization may be performed for a period ranging from several seconds to several minutes. For example, it may be within 60 seconds or within 30 seconds. Since the separation membrane according to the present invention can be flattened in a short period of time, process efficiency can be improved.

[0132]

[0133] The above compression conditions typically assume the lamination process conditions for electrodes and separators used in electrode assembly manufacturing. These properties are advantageous in strengthening the adhesion between the electrodes and separators during battery manufacturing and ensuring close contact between the electrodes and separators, preventing gaps.

[0134] In the present specification, the term "flattening" means that the thickness of the inorganic particle filling portion and the height of the polymer column are the same under the aforementioned pressurization conditions, or that the deviation between the heights of the inorganic particle filling portion and the polymer column is 1 μm or less, preferably less than 0.5 μm, and more preferably less than 0.3 μm. In one embodiment of the present invention, the height of the polymer column may be based on the highest height among the polymer columns.

[0135] That is, when the separator according to the present invention is applied to battery manufacturing, the thickness of the inorganic particle filling part after lamination of the electrode and the separator is polymer column D 50 Smaller is preferable.

[0136] Meanwhile, the flattened polymer column may have a larger planar surface area than before pressurization. In this case, the planar major axis length of the polymer column after flattening is D of the polymer column before flattening. 50 It is desirable that it be less than 10 times.

[0137]

[0138] In the present invention, it is preferred that the polymer column have a phase angle of less than 10°, more preferably less than 7°, at a temperature condition of 180°C to 200°C. In one embodiment, the phase angle exceeds 0°. On the other hand, when the phase angle exceeds the above range, the elastic properties of the polymer column are reduced, and as a result, flattening of the binder after pressurization is aggravated, and the air permeability and ionic conductivity properties may deteriorate.

[0139]

[0140] The above phase angle can be calculated according to the following equation 1.

[0141]

[0142] [Formula 1] Phase angle

[0143] Phase angle (δ) = tan -1 (G`` / G`)

[0144] In the above equation 1, G' is the storage modulus (G', storage modulus) and G" is the loss modulus.

[0145]

[0146] The above phase angle, storage modulus and loss modulus can be calculated based on Dynamic Mechanical Analysis (DMA) data. DMA is a method of analyzing the elastic and viscous properties of a material by applying periodic stress or deformation to the material (mainly deformation in the form of a sinusoidal wave) and measuring the response of the material. The amplitude of the deformation is the maximum size of the deformation applied to the material, which can generally be obtained by measuring the displacement (physical movement distance) applied to the material. G' is the ability of the material to store energy, which corresponds to the part where there is no phase angle between the deformation and stress, and can be calculated from σ0× cos(δ) / ε0. Here, σ0 is where ε0 is the amplitude of stress, δ is the amplitude of strain, and δ is the phase angle. In addition, G'' is the ability of the material to dissipate energy, which corresponds to the part where there is a phase angle between strain and stress, and can be calculated from σ0× sin(δ) / 0.

[0147]

[0148] In a specific embodiment, the phase angle can be measured using a rheological property measuring equipment (Dynamic Mechanical Analyzer, DMA). A polymer column can be subjected to a frequency sweep test at a temperature range of -80°C to 120°C under predetermined frequency and oscillation strain conditions to measure the storage modulus (G') and the loss modulus (G"), and the phase angle can be calculated using Equation 1. Meanwhile, the storage modulus, the loss modulus, and the phase angle can also be measured using an Advanced Rheometric Expansion System (ARES).

[0149]

[0150] In addition, in the present invention, it is preferable that the polymer column has a storage modulus (G') at room temperature of 100 Pa or more and 3,500 Pa or less in terms of flattening by pressurization. Preferably, the storage modulus may be for the material forming the polymer column. When the storage modulus at room temperature is high, the elastic properties are high, and aggregation between binder particles is reduced. As a result confirmed through examples and comparative examples of the present invention, D 100 This example was confirmed to be smaller than the comparative example. This is due to an increase in the ionic conductivity of the separator and a decrease in its resistance. As confirmed by the experimental data below, the example exhibits a relatively higher ionic conductivity than the comparative example. In one embodiment of the present invention, the room temperature may range from 20°C to 27°C.

[0151] Meanwhile, in at least one of the embodiments described above, the polymer column may have a ratio of the storage modulus at 60°C to the storage modulus at room temperature (G'(60°C) / G'(room temperature)) of 0.1 or less.

[0152] Together with or independently of any of these, the polymer column may have at least one tan δ peak in the range of 45°C to 80°C when measured by a rheological property measuring device. If the tan δ peak appears at a temperature lower than 45°C, the adhesive properties between the wound membranes are expressed, which is not preferable, and if the temperature exceeds 80°C, the storage modulus (G') does not drop sharply even when the temperature is applied, making it difficult to flatten the polymer column in high-temperature pressurization.

[0153] In one embodiment of the present invention, the elastic modulus values ​​such as the storage modulus and the loss modulus and the tangent delta peak can be measured using a rheological property measuring equipment (Dynamic Mechanical Analyzer (DMA)). In a specific embodiment, the elastic moduli and the tangent delta peak can be confirmed by performing a temperature sweep test under temperature conditions of -60°C to 80°C and a frequency of 1.0 rad / s. The rheological property measuring equipment may be, for example, ARES-G2 (TA Instrument) or Q800 DMA (TA Instrument).

[0154]

[0155] In one embodiment of the present invention, the polymer column is preferably a material having the above-described characteristics, being non-reactive within a lithium secondary battery, and capable of imparting bonding strength between a separator and an electrode. The polymer column may, for example, contain 10 wt% or more, 30 wt% or more, 50 wt% or more, 70 wt% or more, or 90 wt% or more of the acrylic polymer relative to 100 wt% of the polymer column. In one embodiment of the present invention, in the present invention, the polymer column may contain an acrylic polymer. For example, the acrylic material is an acrylate series acrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexylacrylate, heptyl acrylate, octylacrylate, 2-ethylhexylacrylate, nonylacrylate, decylacrylate, lauryl acrylate, n-tetradecylacrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, It may include one or more repeating units of 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. However, it is not limited thereto. Meanwhile, in a specific embodiment, one or more hydrogens in the unit may be substituted with another substituent. In one embodiment of the present invention, the acrylic polymer may include the above-described repeating unit in an amount of 30 wt% or more, 50 wt% or more, 70 wt% or more, or 90 wt% or more, based on 100 wt% of the acrylic polymer.

[0156] However, since there is a concern that the polymer column may dissolve after liquid electrolyte injection and lose adhesiveness, or the viscosity of the liquid electrolyte may increase due to the dissolved components, which may increase the resistance of the lithium secondary battery, it is desirable to have an appropriate solubility as follows. For example, the solubility in an organic solvent or electrolyte can be reduced by cross-linking the surface of the material forming the polymer column. In a specific embodiment, the polymer column may have a cross-linking degree (gel fraction) of 50% or more, 55% or more, preferably 65% ​​or more, and more preferably 75% or more. The cross-linking degree can be expressed as a percentage (%) of the remaining amount after dissolving in THF (Tetrahydrofuran) for 1 to 48 hours based on the volume or mass of the initial polymer column, and can be calculated by the method of Equation 4 below. The temperature of the THF (Tetrahydrofuran) can range from 20°C to 70°C. For example, a temperature condition of about 25°C and an immersion time of about 24 hours can be applied.

[0157]

[0158] [Formula 4]

[0159] Cross-linking degree (%) = (Weight measured after immersion / Weight measured before immersion) x 100

[0160]

[0161] Meanwhile, in a specific embodiment of the present invention, the acrylic polymer may have a weight average molecular weight (Mw) in the range of 10,000 to 2,000,000, preferably 10,000 to 1,000,000, and more preferably 10,000 to 500,000. When the molecular weight is within the above-mentioned range, it is advantageous in securing a desired level of crosslinking. If the molecular weight is excessively large exceeding the above range, the glass transition temperature (Tg) may increase.

[0162] If Tg is higher than the pressurization temperature applied to the membrane, the polymer column may not be deformed by the pressurization and may maintain its original shape. In this case, the adhesion between the electrode and the membrane, especially the dry adhesion, may be reduced. In addition, if the molecular weight increases, the amount of electrolyte uptake of the binder resin may be reduced, failing to reach an appropriate swelling ratio, which may result in a reduction in wet adhesion.

[0163] In one embodiment of the present invention, the acrylic polymer may have a (G'(60°C) / G'(room temperature)) not exceeding 0.1 and a weight average molecular weight (Mw) in the range of 10,000 to 2,000,000, preferably 10,000 to 1,000,000, and more preferably 10,000 to 500,000.

[0164]

[0165] In one embodiment of the present invention, the polymer column may have a swelling ratio (%) in the range of 170% to 230%. In the present invention, the swelling ratio may be expressed as in Equation 5 below.

[0166]

[0167] [Formula 5]

[0168] Swelling ratio (%) = {(W swollen - W dry ) / (W dry )} x100

[0169]

[0170] In the above formula 5, W dry Is is the weight of the dried polymer column, W swollen Is It refers to the weight of a swollen polymer column after being immersed in a solvent for a specified period of time. The swelling ratio can be measured by immersing a sample of a specified weight in an immersion solution for 40 to 100 hours, for example, 60 to 85 hours, and then removing the sample and measuring the weight. The solvent is not limited to a specific component as long as it is an organic solvent that can be used as an electrolyte for a lithium-ion secondary battery. Non-limiting examples of the organic solvent may include propylene carbonate (PC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), vinyl carbonate (VC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (g-butyrolactone), ester compounds, or mixtures of two or more thereof. Meanwhile, in one embodiment of the present invention, the immersion solution may further include an electrolyte salt in a range of about 0.5 to 1 molar concentration. The temperature of the solvent when measuring the swelling ratio may range from 20°C to 80°C. For example, a temperature condition of about 60°C and about 72 hours may be applied. The above electrolyte salt is A + B - As a salt with the same structure, A + is Li + , Na + , K + B containing an ion composed of an alkali metal cation or a combination thereof; - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3- There may be one or more of them. However, there is no particular limitation as long as it is commonly used in the secondary battery field.

[0171] Meanwhile, in the present invention, the molecular weight measurement (weight average molecular weight / number average molecular weight) can be measured through gel permeation chromatography (GPC). For example, PL GPC220 from Agilent Technologies can be used, and the measurement conditions can be set as follows.

[0172]

[0173] - Column (maker, model no.): 2 x TSKgel SupermultiporeHZ-M + TSKgel SuperHZ-2500

[0174] - Eleunt: THF

[0175] - Temperature: 40℃

[0176] - Flow rate: 1.0 mL / min

[0177] - Injection volume, sample concentration: 30 ㎕, 1~10 mg / mL

[0178] - Standard: Polystyrene

[0179] - Detector: RI

[0180]

[0181] In one embodiment of the present invention, one or more polymer columns may have a cross-sectional area (a) of the polymer column ascertained in a cross-section at the lower 5% from the bottom of the inorganic coating layer toward the surface, and a cross-sectional area (b) of the polymer column ascertained in a cross-section at the upper 5% from the top of the inorganic coating layer toward the bottom, wherein the area (a) is greater than the area (a). This characteristic of the polymer column may apply when the polymer column protrudes from the surface of the inorganic coating layer and / or is flattened by pressurization. Preferably, the characteristic may be confirmed in the shape of the polymer column after it is flattened after protrusion.

[0182]

[0183] Together with or independently of this, one or more polymer columns may have a diameter (a) of the lower portion of the polymer column that is shorter than a diameter (b) of the upper portion of the column in a cross-section of the polymer column as seen in the vertical cross-section of the inorganic coating layer. In one embodiment, the ratio of the upper diameter (b) to the lower diameter (a) may be greater than 1 and less than or equal to 20, or from 1.2 to 20, or from 1.5 to 20, or from 2 to 20. This characteristic of the polymer column may apply when the polymer column protrudes from the surface of the inorganic coating layer and / or when it is flattened by pressing. Preferably, the characteristic may be found in the shape of the polymer column after being flattened. In one embodiment of the present invention, the upper diameter refers to the diameter at the upper 5% point from the top of the polymer column toward the bottom, and the lower diameter refers to the diameter at the lower 5% point from the bottommost portion of the polymer column toward the top.

[0184]

[0185] In one embodiment of the present invention, the height of the polymer column, the length of the diameter of the polymer column, and / or the size of the cross-section can be calculated from an SEM image of a horizontal or vertical cross-section of the membrane. Fig. 2 shows an SEM image of the surface of the membrane of Example 1 of the present invention, and the dimensions of each component can be confirmed. Another method of utilizing the SEM image is to divide the SEM image into gray levels and measure an area corresponding to a specific gray level corresponding to the polymer column. The gray level refers to a brightness value for a plurality of pixels included in the SEM image. For example, in an SEM image of 256 gray levels with steps of 0 to 255, the brightness value range can be a value of 0 to 255. In a specific embodiment of the present invention, the polymer column can have a gray level of 10 to 50, and the inorganic particles can have a gray level of 160 to 220. Accordingly, the region of the polymer column can be set and defined from pixels having 10 to 50 gray levels in the SEM image of an arbitrary cross-section of the membrane, and its length and area can be calculated. In the present invention, the electrode cross-section SEM image can be obtained by performing EDS mapping of the components using an energy dispersive X-ray spectroscopy (EDS) detector of a scanning electron microscope (SEM) equipment on a cross-section of an electrode obtained by argon ion milling, and then performing image processing.

[0186] In another specific embodiment of the present invention, the diameter or area of ​​the polymer column can be calculated by three-dimensionally modeling the separation membrane and / or the inorganic coating layer and then obtaining an arbitrary cross-section therefrom.

[0187]

[0188] Inorganic particle filling section

[0189] The space between the polymer columns in the inorganic coating layer of the above-described separation membrane may be filled with a mixture containing inorganic particles and a binder resin. In the present specification, the portion filled with the mixture containing inorganic particles and a binder resin is referred to as an “inorganic particle filling portion.” The inorganic particle filling portion has pores resulting from an interstitial volume formed between adjacent inorganic particles. Due to the pores, the inorganic coating layer may have a porous structure having a predetermined porosity, and gas or liquid may pass from one side to the other side. The inorganic particles and the polymer columns may be bound by the adhesive properties of the polymer columns or may be bound by means of a binder resin.

[0190]

[0191] In one embodiment of the present invention, before flattening the separation membrane, the thickness (T) of the inorganic particle filling portion i ) is the D of the polymer column 50 It can be 5% to 40% of T. In a specific embodiment, T i The T may be 0.5㎛ to 5㎛ or less and can be appropriately adjusted within the above range. i For example, it can be 4㎛ or less, 3㎛ or less, 2㎛ or less, and preferably 1.5㎛ or less, 1.0㎛ or less. T i go Within the above numerical range, adhesion to the electrode is advantageous in terms of the cycle characteristics and resistance characteristics of the battery. In addition, since the thickness of the separator is reduced, the energy density of the battery can be improved when applied to the battery. When the inorganic coating layer is disposed on both sides of the porous substrate, the thickness of the inorganic particle filling portion refers to the value measured for the inorganic coating layer disposed on either side.

[0192]

[0193] In one embodiment of the present invention, the height (thickness, T) of the inorganic particle filling portion (one side) i ) is a cross-section of a membrane specimen, observed through SEM, and the thickness of two or more arbitrary points in an area where no polymer column is located is measured, and the average value thereof is taken as the height. If the thickness of four or more points is measured, the lowest and / or highest values ​​are excluded, and the average value of the remaining values ​​is taken. The lowest point of the inorganic particle-filled portion is the surface of the porous substrate.

[0194] Meanwhile, in one embodiment of the present invention, the height of the inorganic particle-filled portion may tend to increase as it gets closer to the polymer column in the inorganic particle-filled portion. This tendency may be more noticeable with respect to the periphery of the polymer column. That is, the height of the outer portion of the periphery may gradually increase from any point of the inorganic particle-filled portion toward the polymer column, and may relatively rapidly increase as it goes from the boundary of the periphery toward the polymer column. In one embodiment of the present invention, the periphery may mean a portion having a width of about 2 μm from the boundary between the inorganic particle-filled portion and the polymer column toward the inorganic particle-filled portion.

[0195]

[0196] inorganic particles

[0197] In a specific embodiment of the present invention, the inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as they do not undergo oxidation and / or reduction reactions within the operating voltage range of the applied electrochemical device (e.g., 0 to 5 V based on Li / Li+). In particular, when inorganic particles having a high dielectric constant are used as the inorganic particles, they can contribute to increasing the degree of dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte.

[0198] For the reasons mentioned above, it is preferable that the inorganic particles include high-k inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO3, Pb(Zr,Ti)O3(PZT), b 1-x La x Zr 1-y Ti y O3(PLZT, 0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3(PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC and TiO2 or mixtures thereof.

[0199] In addition, as the inorganic particles, inorganic particles having lithium ion transfer capability, i.e., inorganic particles containing lithium element but having the function of transferring lithium ions without storing lithium, can be used. Non-limiting examples of inorganic particles having lithium ion transfer capability include lithium phosphate (Li3PO4), lithium titanium phosphate (LixTiy(PO4)3, 0 < x <2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z(PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), 14Li2O-9Al2O3-38TiO2-39P2O5, etc. (LiAlTiP) x O y Series glass (0 <x < 4, 0 < y < 13), 리튬란탄티타네이트(Li x La y TiO3, 0 < x < 2, 0 < y < 3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4 x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li 3 N ), etc. x N y , 0 < x <4, 0 < y < 2), SiS2 series glass (Li) such as Li3PO4-Li2S-SiS2 x Si y S z , 0 < x < 3, 0 <y < 2, 0 < z < 4), LiI-Li2S-P2S5등과 같은 P2S5계열 glass(Li x P y S z , 0 < x < 3, 0< y < 3, 0 < z < 7) or mixtures thereof.

[0200]

[0201] In addition, the average particle diameter of the inorganic particles is not particularly limited, but is preferably in the range of 0.1 μm to 1.5 μm for the formation of a coating layer of uniform thickness and an appropriate porosity. If it is less than 0.1 μm, dispersibility may be reduced, and if it exceeds 1.5 μm, the thickness of the formed coating layer may increase. Meanwhile, in one embodiment of the present invention, the inorganic particles may be included in about 50 wt% to 90 wt% of the inorganic coating layer.

[0202] According to a non-limiting embodiment of the present invention, the inorganic particles have a diameter (D 50 ) can be appropriately adjusted in the range of 0.1㎛ to 1.5㎛, and may have a range of, for example, 200nm to 1㎛.

[0203]

[0204] Meanwhile, in one embodiment of the present invention, the inorganic coating layer may include a binder resin to secure bonding strength between the inorganic particles and between the inorganic particles and the porous substrate. In the inorganic particle filling portion, the binder resin may be included in an amount of 0.1 to 30 parts by weight, 0.1 to 20 parts by weight, 0.1 to 10 parts by weight, or 0.1 to 5 parts by weight relative to 100 parts by weight of the inorganic particles.

[0205]

[0206] Meanwhile, in a specific embodiment of the present invention, non-limiting examples of the binder resin include (meth)acrylic polymers, vinylidene fluoride polymers, polyvinyl alcohol, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan. (pullulan), carboxyl methyl cellulose, hydroxyalkyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylhydroxyethyl cellulose, methyl cellulose, etc., and these may be used alone or in combination of two or more thereof.

[0207]

[0208] The above (meth)acrylic polymer may include, but is not limited to, one or more of (meth)acrylic acid ester, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, butylacrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, n-oxyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, and tetradecyl (meth)acrylate as monomers.

[0209] The above vinylidene fluoride polymer may include at least one of a homopolymer of vinylidene fluoride (polyvinylidene fluoride), a copolymer of vinylidene fluoride and a monomer capable of copolymerizing the same, and a mixture thereof. In one embodiment of the present invention, the monomer may include, for example, a fluorinated monomer and / or a chlorinated monomer. Non-limiting examples of the fluorinated monomer include vinyl fluoride; trifluoroethylene (TrFE); chlorofluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkylvinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethylvinyl) ether (PEVE), and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD), and may include one or more of these. For example, it may be polyvinylidene fluoride-co-hexafluoropropylene or polyvinylidene fluoride-co-trichloroethylene.

[0210]

[0211] Additionally, in one embodiment of the present invention, the inorganic coating layer may further include additives such as a dispersant and / or a thickener in an amount ranging from 0.5 to 3.0 parts by weight relative to 100 parts by weight of the inorganic particles. If there is a material among the examples of the binder resins described above that can improve dispersibility and / or viscosity, it can be used as an additive for such purposes.

[0212]

[0213] Membrane manufacturing method

[0214] Next, a method for manufacturing the membrane of the present invention will be described. However, the following description is for one embodiment of manufacturing the present invention and is not particularly limited thereto.

[0215] Specifically, a mixture is first prepared by adding inorganic particles to an appropriate solvent. Next, polymer particles for polymer columns are added to the mixture to prepare a slurry for an inorganic coating layer. Next, the slurry is applied to a porous substrate and dried.

[0216] In one embodiment of the present invention, when the inorganic coating layer further comprises a binder resin, the binder resin may be dissolved in a solvent to prepare a polymer solution, and then inorganic particles and polymer particles for polymer columns may be sequentially or simultaneously added to the polymer solution to prepare a slurry for the inorganic coating layer. The binder resin is preferably a water-soluble binder resin.

[0217] Thereafter, the obtained separator can be dried to form an inorganic coating layer integrally on the porous substrate. At this time, the drying temperature of the separator is preferably set to a temperature of +20°C or lower than the glass transition temperature of the polymer column material to prevent deformation of the polymer column.

[0218]

[0219] In the production of the above slurry, water or an aqueous solvent containing water may be used as the solvent. In addition, when there are limitations on drying speed and temperature, methanol, ethanol, isopropyl alcohol, etc., which have a lower boiling point than water, may be used as a co-solvent.

[0220]

[0221] The above slurry can be applied using conventional coating methods such as a Meyer bar, die coater, reverse roll coater, or gravure coater.

[0222] Meanwhile, in addition to the above-described manufacturing method, any manufacturing method that can achieve the above-described membrane structure can be applied without limitation.

[0223]

[0224] Meanwhile, the present invention provides a secondary battery including the separator. The battery includes a negative electrode, a positive electrode, and a separator interposed between the negative electrode and the positive electrode, wherein the separator is a separator having the characteristics described above.

[0225]

[0226] In the present invention, the positive electrode has a positive electrode current collector and a positive electrode active material layer including a positive electrode active material, a conductive material, and a binder resin on at least one surface of the positive electrode current collector. The positive electrode active material is a layered compound such as lithium manganese oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M xNi-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn 2-x M x A lithium manganese composite oxide represented by O2 (wherein, M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein, M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced by an alkaline earth metal ion; a disulfide compound; or a mixture of two or more of Fe2(MoO4)3.

[0227]

[0228] In the present invention, the negative electrode has a negative electrode current collector and a negative electrode active material layer including a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The negative electrode includes carbon such as lithium metal oxide, non-graphitizable carbon, and graphite carbon as the negative electrode active material; Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함할 수 있다.

[0229]

[0230] In a specific embodiment of the present invention, the conductive material may be, for example, one selected from the group consisting of graphite, carbon black, carbon fibers or metal fibers, metal powders, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials thereof. More specifically, the conductive material may be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more conductive materials thereof.

[0231]

[0232] The above-mentioned current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used.

[0233]

[0234] As the above binder resin, a polymer commonly used in electrodes in the art can be used. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples thereof include, but are not limited to, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose.

[0235]

[0236] Battery manufacturing

[0237] The battery manufacturing method of the present invention is characterized in that a first compression is performed during the manufacturing of the electrode assembly or before impregnation with an electrolyte (dry compression), and then a second compression is performed after the electrode assembly is impregnated with an electrolyte and the polymer column is softened by the electrolyte.

[0238] First, a laminate including one or more positive electrodes, one or more separators, and one or more negative electrodes is prepared. The laminate is laminated one or more times with a separator interposed between the positive electrode and the negative electrode. The electrodes and separators, etc., constituting the laminate are not in close contact with each other but are simply stacked. Thereafter, the laminate is pressed at a strength of 3.0 MPa to 4.0 MPa under temperature conditions of 55°C to 65°C to manufacture a first electrode assembly. Here, the polymer columns in the separator are not completely flattened. In this way, since the separator and the electrode are not completely flattened before electrolyte impregnation and a certain distance is maintained between them, the electrolyte can easily flow into the first electrode assembly. That is, there is an advantage of securing a movement path of the electrolyte.

[0239] Thereafter, the first electrode assembly is impregnated with an electrolyte, and a second compression is performed thereafter. The second compression includes a step of applying a pressure of 0.5 MPa to 1.5 MPa to the impregnated first electrode assembly. Pressure is applied to the impregnated first electrode assembly so that the separator and the positive electrode and / or the separator and the negative electrode are in close contact with each other, and the pressure application is preferably performed under a temperature condition of 35°C to 45°C. After the electrode assembly is sufficiently impregnated with the electrolyte in this way, the second compression is performed so that the electrode and the separator are in close contact with each other. Therefore, there is an advantage in that the wettability of the electrode assembly is improved. Meanwhile, the step of impregnating the first electrode assembly with the electrolyte includes housing the first electrode assembly in a battery case, and an aging step may be further performed after the impregnation and before the pressure application. The aging may preferably be performed at a temperature of 20°C or higher. An excessively high temperature may deteriorate the materials used in the battery, and is therefore not preferable. The above aging temperature can be performed within a range of, for example, the glass transition temperature (Tg) of the binder resin used + 20°C or less.

[0240]

[0241] In the present invention, the electrolyte is A + B - As a salt with the same structure, A + is Li + , Na + , K + B containing an ion composed of an alkali metal cation or a combination thereof; - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 -A salt containing an anion such as or a combination thereof is dissolved or dissociated in an organic solvent including propylene carbonate (PC), ethylene carbonate (EC), vinyl carbonate (VC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (g-butyrolactone), ester compounds, and mixtures of one or more selected from these, but is not limited thereto.

[0242]

[0243] Meanwhile, in a specific embodiment of the present invention, the organic solvent may include an ester compound, and preferably, the ester compound may be 30 wt% or more, 50 wt% or more, 60 wt% or more, or 65 wt% or more, based on 100 wt% of the organic solvent.

[0244] In a specific embodiment of the present invention, the ester compound may include at least one selected from the group consisting of isobutyl propionate, isoamyl propionate, isobutyl butyrate, isopropyl propionate, methylpropionate, ethylpropionate, propylpropionate, butylpropionate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0245]

[0246] In addition, the present invention provides a battery module including a battery including the electrode assembly as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0247] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain it. However, the embodiments according to the present invention can be modified in various different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art. In the present invention, each of the above embodiments can be implemented independently. Alternatively, two or more of the above embodiments can be implemented in combination.

[0248]

[0249] Example

[0250] Measurement of the degree of cross-linking of polymer columns

[0251] A 0.3 g sample was prepared using the polymer material to be used as the polymer column in the comparative examples and examples. The sample was placed in an 80-mesh mesh bag and dissolved in THF (Tetrahydrofuran) at 25°C for 24 hours. The residual weight was compared to the initial weight. The degree of crosslinking was calculated based on [Equation 4] below. This is summarized and presented in Table 3 below.

[0252]

[0253] [Formula 4]

[0254] Cross-linking degree (%) = (Weight measured after immersion / Weight measured before immersion) x 100

[0255]

[0256] The data confirmed in each of the above experiments are summarized as shown in [Table 1] below. Referring to this, it was confirmed that the crosslinking degree was 80% or more for Examples 1 to 3, and the comparative example was confirmed to have a very low crosslinking degree.

[0257]

[0258] Measurement of swelling ratio of polymer columns

[0259] In comparative examples and examples, 0.3 g of polymer material to be used as a polymer column was prepared. The sample was placed in an 80-mesh mesh net and immersed in an immersion solution at approximately 60°C for approximately 72 hours, and then calculated based on [Formula 5] below. The immersion solution is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, and contains approximately 2 wt% of vinyl carbonate (VC) and approximately 1 M of LiPF6. This is summarized and shown in Table 3 below.

[0260]

[0261] [Formula 5]

[0262] Swelling ratio (%) = {(W swollen - W dry ) / (W dry )} x100

[0263]

[0264] In the above formula 5, W dry Is is the initial weight of the polymer column, W swollen Is This is the weight of the swollen polymer column after being immersed in an electrolyte for a specified period of time.

[0265]

[0266] The data confirmed in the above experiment are summarized as shown in [Table 1] below. Referring to this, it was confirmed that the swelling ratios of Examples 1 to 3 had values ​​between 170% and 230%. On the other hand, it was confirmed that the comparative examples had higher swelling ratios than the examples.

[0267]

[0268] Example 1

[0269] Inorganic particles (Al2O3, D50 approximately 0.6 ㎛), acrylic emulsion (Toyo, CSB-130) as binder resin, and carboxyl methyl cellulose (Daicel, Daicel1220) were added in a 96:2:2 ratio to a 95:5 water:ethanol solution and a dispersion process using a bead mill was performed to obtain a mixture. Polymer particles for polymer columns (acrylic polymer a, D) were added to the mixture. 50 3.84㎛) was added and stirred to obtain a dispersion slurry. The concentration of solids in the dispersion slurry was 30 wt%. The content of polymer particles for polymer columns in the mixture was about 11 parts by weight per 100 parts by weight of inorganic particles. The dispersion slurry was applied to a porous substrate (Asahi, ND506, thickness 6㎛) by a microgravure coating method and dried at a temperature of 80℃ to obtain a separator. In addition, the opposite side was coated and dried in the same manner to obtain a double-coated separator. The loading amount (one side) of the inorganic coating layer in the separator was 5.3 g / m 2 It was.

[0270]

[0271] Meanwhile, using the SEM image of the membrane of Example 1, the ratio of the length of the lower diameter (a) and the upper diameter (b) of the polymer column before and after pressurization was confirmed, and the values ​​are summarized and shown in Table 2 below. Measurements were made on both sides of the membrane below, and are listed separately as the upper surface and the lower surface in Table 2. Referring to this, it was confirmed that the ratio of b / a before and after pressurization both exceeded 2. This is shown in Table 2 below and Figures 10a, 10b, and 11.

[0272]

[0273] a(㎛)b(㎛)b / aPressurized upper surface0.834.415.31Lower surface2.114.572.17Pressurized upper surface2.426.192.56Lower surface1.072.372.21

[0274] Example 2

[0275] A membrane was manufactured in the same manner as in Example 1, except that acrylic polymer b for polymer columns was used. The loading of the inorganic coating layer on one side of the porous substrate in the membrane was 3.54 g / m 2 It was.

[0276]

[0277] Example 3

[0278] A membrane was manufactured in the same manner as in Example 1, except that an acrylic polymer c for a polymer column was used. The loading of the inorganic coating layer on one side of the porous substrate in the membrane was 3.26 g / m 2 It was.

[0279]

[0280] Comparative Example 1

[0281] A membrane was manufactured in the same manner as in Example 1, except that an acrylic polymer d for a polymer column was used. In the membrane, the loading of the inorganic coating layer on one side of the porous substrate was 3.25 g / m 2 It was.

[0282]

[0283] Comparative Example 2

[0284] A membrane was manufactured in the same manner as in Example 1, except that an acrylic polymer e for a polymer column was used. The loading of the inorganic coating layer on one side of the porous substrate in the membrane was 3.19 g / m 2 It was.

[0285]

[0286] Surface SEM images of the membranes obtained in each of Examples 1 to 3 and Comparative Examples 1 to 2 at different magnifications are shown in FIGS. 5a to 9c. FIGS. 5a to 5c are surface SEM images of the membranes obtained in Example 1, FIGS. 6a to 6c are surface SEM images of the membranes obtained in Example 2, FIGS. 7a to 7c are surface SEM images of the membranes obtained in Example 3, FIGS. 8a to 8c are surface SEM images of the membranes obtained in Comparative Example 1, and FIGS. 9a to 9c are surface SEM images of the membranes obtained in Comparative Example 2 at different magnifications.

[0287] The components and characteristics of the polymer columns used in each example and comparative example are summarized in Table 2 below. Meanwhile, the particle size measurement results of each polymer column using the laser scattering method are shown in Fig. 2.

[0288]

[0289] Example 1 Acrylic polymer for polymer column a Example 2 Acrylic polymer for polymer column b Example 3 Acrylic polymer for polymer column c Comparative Example 1 Acrylic polymer for polymer column d Comparative Example 2 Acrylic polymer for polymer column e Phase angle (°) 5.43 5.42 6.06 8.82 20.18 Storage modulus (G', 25℃, Pa) 1,38 12,18 32,62 325.06 2.15 tan δ peak (℃, 45℃ to 80℃) 69.64 52.15 59.26 3.38 58.84 Crosslinking degree (%) 8 17 68 118 2 Swelling ratio, %)184215200241362Tg(℃)59.4342.2147.1541.0939.16

[0290] Additionally, the types and contents of the ingredients used in each example and comparative example are summarized in Table 3 below.

[0291]

[0292] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Polymer column D10 (㎛) 0.68 0.70 0.64 0.62 0.74 D50 (㎛) 4.36 4.85 4.10 4.92 6.43 D90 (㎛) 7.63 8.42 7.25 18.50 33.00 D95 (㎛) 8.76 10.50 8.31 52.30 44.70 D100 (㎛) 14.40 18.50 14.10 308.00 97.70 Inorganic particle component Al2O3 (ALK-S1) Left Left Left Left Left Left Right Coating layer Content (wt%) 80.80 Left left ... 2 )3.623.543.263.253.19

[0293] Measurement of elastic modulus and phase angle of polymer columns

[0294] In comparative examples and examples, samples measuring 10 mm in length, 6 mm in width, and 1 mm in thickness were prepared using polymer materials to be used as polymer columns. The elastic moduli of the samples were measured. The elastic moduli were measured using a rheological property measuring equipment (Dynamic Mechanical Analyzer (DMA), Q800, TA Instrument). The elastic moduli were in the range of -80°C to 120°C, and the heating rate was 5°C / min. The storage modulus (G') and loss modulus (G'') in the solid state were measured by applying a strain defined as an oscillation strain of 0.1% at a frequency of 1 Hz. Meanwhile, the phase angle was measured using ARES. The storage modulus (G') and loss modulus (G'') were measured at an angular frequency of 0.05 to 500 rad / s at a measurement temperature of 190°C, and the phase angle was measured. The measured storage modulus, loss modulus, and phase angle are summarized and shown in Table 1. In addition, FIGS. 3 and 4 are graphs comparing the modulus and phase angle of each polymer column of Examples 1 to 3 and Comparative Examples 1 to 2.

[0295]

[0296] Check the flatness of the polymer column

[0297] The separator obtained in Example 1 was pressed at 3.3 MPa for 20 sec at about 60°C using a hot press. Figures 10a and 10b show cross-sectional SEM images of the separator obtained in Example 1, showing the cross-section before pressing, and Figures 11a and 11b show the cross-section images after pressing. Referring to these, the polymer column was pressed and flattened. From this, it was confirmed that the polymer column can be flattened and exhibit adhesive force under moderate pressurization process conditions during the lamination process with the electrode, and there is no concern that a gap will occur between the separator and the electrode.

[0298]

[0299] Manufacturing of anodes

[0300] A slurry of positive electrode active material was prepared by adding LiCoO2 as a positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder to N-methylpyrrolidone (NMP) as a solvent at a weight ratio of 96:2:2. The positive electrode active material slurry was coated on a sheet-shaped aluminum current collector and dried to obtain a final positive electrode loading of 3.8 mAh / cm. 2 To achieve this, a positive electrode active material layer was formed.

[0301]

[0302] Manufacturing of cathode

[0303] Artificial graphite as a negative active material, carbon black as a conductive agent, carboxymethyl cellulose as a dispersant, and styrene butadiene emulsion as a binder were mixed in a weight ratio of 96:0.5:1.5:2.0, respectively, and added to water as a solvent to prepare a negative electrode slurry. The negative electrode slurry was coated on a copper current collector at a loading of 4.0 mAh / cm2 and dried to prepare a negative electrode having a negative electrode active material layer formed thereon.

[0304]

[0305] Evaluation of dry adhesion between cathode and separator

[0306] The membrane samples obtained in each example or comparative example were cut into a size of 100 mm (length) x 25 mm (width) to prepare each test piece. After each test piece was laminated with the negative electrode, a laminate was obtained by heating and pressing at 60°C for 20 seconds. The laminate was fixed to an adhesive strength measuring device (LLOYD Instrument, LF plus), and the membrane portion was peeled at an angle of 180° at a speed of 25 mm / min at 25°C, and the strength at this time was measured.

[0307] Referring to Table 3 below, Examples 1 to 3 demonstrated adhesive strength suitable for battery manufacturing. That is, the separators of Examples 1 to 3 were confirmed to be able to maintain an appropriate bonding state with the electrode during the process of laminating with the electrode and inserting into the battery case during battery manufacturing. In the present invention, dry adhesive strength refers to the adhesive strength between the electrode and the separator when not in contact with the electrolyte.

[0308]

[0309] Method for evaluating wet adhesion between anode and separator

[0310] The membrane samples obtained in each example or comparative example were cut into a size of 100 mm (length) x 25 mm (width) to prepare each test piece. After each test piece was laminated with the positive electrode, a laminate was obtained by heating and pressing at 60°C for 20 seconds. This was immersed in an electrolyte and maintained for 24 hours. Afterwards, each laminate was taken out of the electrolyte and fixed to an adhesive strength measuring device (LLOYD Instrument, LF plus), and the separator portion was peeled at an angle of 180° at a speed of 25 mm / min at 25°C, and the strength at this time was measured. The electrolyte was a mixture of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 7:3, and contained LiPF6 at a concentration of 1 M. In the present invention, wet adhesion refers to the adhesive strength of the electrode and the separator after contact with the electrolyte for a predetermined period of time.

[0311]

[0312] Referring to Table 4 below, it was confirmed that the examples had higher adhesive strength than the comparative examples. In particular, although the dry adhesive strength of Comparative Examples 1 and 2 was very high, the adhesive strength decreased significantly after electrolyte impregnation, showing an adhesive strength at a very low level compared to Examples 1 to 3. This decrease in adhesive strength may be the cause of increased resistance between the electrode and the separator.

[0313]

[0314] Resistance measurement method

[0315] The resistance of the separators of each example and comparative example was measured by impedance measurement. Coin cells were fabricated by sandwiching each separator between stainless steel plates, and 1 MLiPF6 was injected into an ethylene carbonate / ethyl methyl carbonate (EC / EMC, volume ratio 30:70) electrolyte. The resistance was measured through electrochemical impedance spectroscopy analysis using Solaton's 1470E cell test system and frequency response analyzer 1255B at 25°C with a scan range of 100,000 Hz to 10,000 Hz.

[0316] Referring to Table 3 below, it was confirmed that the separators of Examples 1 to 3 had superior resistance characteristics compared to the separators of Comparative Examples 1 to 2.

[0317]

[0318] Air permeability measurement

[0319] The time (sec) required for 100 cc of air to pass through the membrane at a constant pressure (0.05 MPa) was measured using an air permeability tester (manufacturer: Asahi Seiko, product name: EG01-55-1MR). A total of three points were measured (one point each on the left, center, and right of the sample), and the average was recorded.

[0320]

[0321] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Air permeability (Sec / 100cc) 100 100 102 108 109 Ionic conductivity (S / cm) 9.22*10 -4 9.27*10 -4 9.25*10 -4 8.03*10 -4 7.92*10 -4 Dry adhesion(gf / 25mm)12.6633.5346.4849.3948.06Wet adhesion(gf / 25mm)13.816.320.59.40.3

[0322] Measurement of glass transition temperature

[0323] The glass transition temperature (Tg) was measured using a DSC (Differential Scanning Calorimetry, TA Instrument). Samples weighing 10 to 15 mg each were obtained, cooled from ambient temperature to -30°C, and then heated to 200°C at 10°C / min. Measurements were then taken after cooling to -30°C and reheating at 10°C / min.

[0324]

[0325] [Explanation of symbols]

[0326] 10 Porous substrates

[0327] 20 layers of weapon coating

[0328] 100 polymer columns

[0329] 200 inorganic particles

[0330] T s Thickness of the membrane

[0331] T p Protrusion height of polymer column

[0332] T i Height of the inorganic particle filling, T c Height of the inorganic coating layer

Claims

1. It comprises a porous polymer substrate and an inorganic coating layer covering one surface or both surfaces of the porous polymer substrate, The above-mentioned inorganic coating layer comprises a plurality of adhesive polymer columns of a predetermined volume, wherein the polymer columns are made of a polymer material and do not have pores, At least a portion of the polymer column is exposed to the surface of the inorganic coating layer and another portion is in contact with the surface of the porous substrate, At least one polymer column is spaced apart from the other polymer columns by a predetermined distance, The space between the above polymer columns is filled with an inorganic particle filling portion, and the inorganic particle filling portion includes inorganic particles and a binder resin. The polymer column has a phase angle of less than 10°, and the phase angle is calculated according to the following equation 1: [Formula 1] δ = tan -1 (G`` / G`) In the above equation 1, G' is the storage modulus (G', storage modulus) and G" is the loss modulus.

2. In paragraph 1, The above polymer column is a separator for an electrochemical device, wherein the ratio (G'(60°C) / G'(room temperature)) of the storage modulus at 60°C to the storage modulus (G') at room temperature is 0.1 or less.

3. In paragraph 1, A separator for an electrochemical device, wherein the crosslinking degree (gel fraction) of the above polymer column is 50% or more.

4. In paragraph 1, Inorganic particle filling part (T i ) is a separation membrane having a thickness of 5% or more and 40% or less of the diameter D50 of the polymer column.

5. In paragraph 1, The height of the above inorganic particle filling part (T i ) is a separation membrane having a thickness of 2㎛ or less.

6. In paragraph 1, The above separation membrane is applied with a pressure of 3.0 MPa to 4.0 MPa for 20 seconds under temperature conditions of 55°C to 65°C, and then the protrusion height (T) of the polymer column is p ) is the height of the inorganic particle filling (T i ) or T i A membrane having a thickness less than 1.1 times that of the membrane.

7. In paragraph 1, The above separation membrane is applied with a pressure of 3.0 MPa to 4.0 MPa for 20 seconds under temperature conditions of 55°C to 65°C, and then the protrusion height (T) of the polymer column is p ) is a separation membrane having a thickness of 1㎛ or less.

8. In paragraph 1, D of the above polymer column 50 D of silver inorganic particles 50 A separator for electrochemical devices that is more than twice as large.

9. In paragraph 1, The thickness of the above inorganic particle filling part (T i ) is a polymer column D 50 A separator for electrochemical devices having a content of 85% or less.

10. In paragraph 1, D of the above polymer column 10 Silver D 50 More than 30% of D90 is D 50 A separator for electrochemical devices having a purity of 200% or less.

11. In paragraph 1, A separator for an electrochemical device, wherein the area occupied by the polymer column is 10% to 50% of the surface area of ​​the inorganic coating layer based on the surface view of the separator (top view).

12. In paragraph 1, A separator for an electrochemical device, wherein at least one polymer column included in the inorganic coating layer has an area (a) of a polymer column cross-section confirmed in a cross-section at the lower 5% from the lowest portion of the inorganic coating layer toward the surface, and an area (b) of a column cross-section confirmed in a cross-section at the upper 5% from the top toward the bottom, wherein the area (a) is greater than the area (a).

13. In paragraph 1, A separator for an electrochemical device, wherein at least one polymer column included in the inorganic coating layer has a diameter (a) of a lower portion of the polymer column that is shorter than a diameter (b) of an upper portion of the column in a cross-section of the polymer column confirmed in a vertical cross-section of the inorganic coating layer, and the ratio of the diameter (b) to the diameter (a) is 2 to 20.

14. In paragraph 1, A separator for an electrochemical device, wherein the above-mentioned inorganic coating layer has a pore structure due to the interstitial volume between inorganic particles.

15. An electrochemical device comprising a separator for an electrochemical device according to paragraph 1.

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