Separator for electrochemical device, method for producing same and electrochemical device including same

Abstract

The present invention relates to a separator for an electrochemical device, comprising: a porous polymer substrate; and a porous coating layer formed on at least one surface of the porous polymer substrate; a particle region including polymer binder particles and inorganic particles, and a film region including the modified polymer binder particles, the film region being 3 to 50 wt % based on the total weight of the polymer binder particles.

Description

[Technical field]

[0001] The present invention relates to a separator for an electrochemical device, a method for producing the same, and an electrochemical device including the same. [Background technology]

[0002] Electrochemical elements convert chemical energy into electrical energy by utilizing electrochemical reactions, and in recent years, lithium secondary batteries have been widely used because of their high energy density, high voltage, long cycle life, and applicability in a variety of fields.

[0003] The lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and may be manufactured by housing the electrode assembly in a case together with an electrolyte. The separator may include a porous coating layer including a polymer binder and inorganic particles on at least one surface of a porous substrate. The inorganic particles may be connected to other inorganic particles by the polymer binder to form an interstitial volume, and lithium ions may move through the interstitial volume. In addition to fixing the inorganic particles, the polymer binder may provide an adhesive force to the porous coating layer, and the porous coating layer may be attached to the porous substrate and the electrode, respectively.

[0004] Conventionally, a porous coating layer having excellent heat resistance and adhesiveness has been formed by applying a one-liquid coating to the surface of a porous substrate such as polyolefin using an aqueous particle-type binder as a polymer binder. However, the porous coating layer has low durability and is easily detached from the porous substrate during the manufacturing process of an electrode assembly and an electrochemical device.

[0005] Therefore, research is being conducted into a separator having a structure in which the porous coating layer containing a water-based polymer binder is less likely to be detached from the porous substrate while maintaining the advantages of the porous coating layer and the physical properties of the separator, and a method for manufacturing the same. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a method for manufacturing a separator for an electrochemical device, which has improved durability of a porous coating layer containing a polymer binder and inorganic particles and has excellent adhesion to a porous substrate and an electrode. [Means for solving the problem]

[0007] In one aspect of the present invention, there is provided a separator for an electrochemical device, comprising: a porous polymer substrate; and a porous coating layer formed on at least one surface of the porous polymer substrate, the film region including a particle region made of polymer binder particles and inorganic particles and a film region including the modified polymer binder particles, the film region being 3 to 50 wt % based on the total weight of the polymer binder particles.

[0008] The porous coating layer may have an initial dynamic friction coefficient due to frictional wear of 1 to 2 when the end of a diamond tip is placed in the region between the surface in contact with the porous polymer substrate and the opposite surface opposite the surface, and the diamond tip is moved horizontally across the porous polymer substrate at a speed of 100 mm / min.

[0009] The porous coating layer may have an end of a diamond tip disposed in a region between the surface in contact with the porous polymer substrate and the opposite surface opposite the surface, and when the diamond tip is moved horizontally across the porous polymer substrate at a speed of 100 mm / min, the difference between the static friction coefficient due to frictional wear and the initial dynamic friction coefficient may be 3 or less.

[0010] The adhesive strength between the porous polymeric substrate and the porous coating layer may be 1.5 to 6 times the adhesive strength exhibited by the surface of the porous coating layer opposite the surface in contact with the porous polymeric substrate.

[0011] The polymeric binder particles may include one or more selected from the group consisting of polyacrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, ethylhexyl acrylate, and methyl methacrylate.

[0012] The filmed region may be formed by exposing the polymeric binder particles to a temperature ranging from the glass transition temperature (Tg) of the polymeric binder particles to Tg+40°C.

[0013] One aspect of the present invention provides an electrochemical device including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the separator being a separator for an electrochemical device having the above-mentioned characteristics.

[0014] The electrochemical device may be a lithium secondary battery.

[0015] In one aspect of the present invention, there is provided a method for manufacturing a separator for an electrochemical device, the method including: coating at least one surface of a porous polymer substrate with a coating slurry including polymer binder particles, inorganic particles, and a dispersion medium to form a coating layer including a particle region including polymer binder particles and inorganic particles; drying the coating layer to remove the dispersion medium; and drying the coating layer to remove 3 to 50 wt % of the polymer binder particles based on the total weight of the polymer binder particles to form a film region.

[0016] In the step of removing the dispersion medium, the surface of the coating layer may not exceed 50°C.

[0017] The step of forming the filmed region may involve exposing the coating layer to a temperature ranging from the glass transition temperature (Tg) of the polymeric binder particles to Tg+40° C. for up to 24 hours. Effect of the Invention

[0018] The separator for an electrochemical device according to the present invention can improve the peel strength between a porous coating layer and a porous polymer substrate without deteriorating the air permeability and electrical resistance by converting a predetermined amount of polymer binder particles into a film shape. [Brief description of the drawings]

[0019] [Figure 1] 1 is a plan view of a separation membrane according to an embodiment of the present invention, showing a schematic diagram of a porous coating layer (20). [Diagram 2] This is a conceptual diagram showing a cross-sectional view of a separation membrane (1) according to one embodiment of the present invention, in which a diamond tip (T) is inserted to a depth D into a porous coating layer (20) to measure the friction coefficient according to the contents of one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, each component of the present invention will be described in more detail so that a person having ordinary knowledge in the technical field to which the present invention belongs can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited to the following content.

[0021] As used herein, the term "comprising" is used in listing materials, compositions, devices, methods, etc. that are useful in the present invention, without being limited to the listed examples.

[0022] As used in this specification, the terms "about" and "substantially" are used to mean a range of a numerical value or degree or a similar range, taking into consideration inherent manufacturing and material tolerances, and are used to prevent an infringer from unfairly exploiting the disclosure content in which precise or absolute numerical values ​​provided to aid in the understanding of the present invention are mentioned.

[0023] As used herein, "electrochemical device" may refer to a primary battery, a secondary battery, a supercapacitor, and the like.

[0024] As used herein, the term "filmed region" refers to a region in which a polymer binder contained in a porous coating layer is exposed to a temperature equal to or higher than its inherent glass transition temperature (Tg) and is deformed so that it is no longer able to maintain its original shape, or a region formed by the deformation and being physically or chemically bonded to one or more adjacent polymer binders.

[0025] Hereinafter, the present invention will be described with reference to specific examples and working examples. However, the present invention is not limited thereto and may include combinations of one or more of the specific examples and working examples by a person having ordinary knowledge in the technical field to which the present invention belongs, and various modifications and variations are possible within the technical spirit of the present invention and the equivalent scope of the claims described below.

[0026] Hereinafter, one embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a plan view of a separation membrane according to one embodiment of the present invention, and is a conceptual diagram showing the appearance of a porous coating layer (20), and Figure 2 is a side view of a separation membrane (1), and is a conceptual diagram showing a process of measuring the friction coefficient by inserting a diamond tip (T) into the porous coating layer (20).

[0027] One embodiment of the present invention provides a separator for an electrochemical device (1), comprising a porous polymer substrate (10), a particle region (P) comprising polymer binder particles (21) and inorganic particles (22), and a film region (F) including the modified polymer binder particles, and comprising a porous coating layer (20) formed on at least one surface of the porous polymer substrate (10), the film region (F) being 3 to 50% by weight based on the total weight of the polymer binder particles.

[0028] The porous polymer substrate (10) may be a porous membrane having a plurality of pores formed therein, which electrically insulates the positive and negative electrodes to prevent short circuits. For example, when the electrochemical device is a lithium secondary battery, the porous polymer substrate (10) may be an ion-conductive barrier that blocks electrical contact between the positive and negative electrodes while allowing lithium ions to pass through. At least a portion of the pores may form a three-dimensional network that connects the surface and the interior of the porous polymer substrate (10), and fluid may pass through the porous polymer substrate (10) through the pores.

[0029] The porous polymer substrate 10 may be made of a material that is physically and chemically stable against the electrolyte, which is an organic solvent. For example, the porous polymer substrate 10 may include, but is not limited to, polyolefins such as polyethylene, polypropylene, and polybutylene, polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, nylon, polytetrafluoroethylene, and copolymers or mixtures thereof. Preferably, a polyolefin resin may be used. Polyolefin resins can be processed to a relatively thin thickness and are easy to apply a coating slurry, making them suitable for manufacturing electrochemical devices with higher energy density.

[0030] The porous polymer substrate (10) may have a single layer or a multi-layer structure. The porous polymer substrate (10) includes two or more polymer resin layers having different melting points (Tm) and may provide a shutdown function during high-temperature runaway of the battery. For example, the porous polymer substrate (10) may include a polypropylene layer having a relatively high melting point and a polyethylene layer having a relatively low melting point. Preferably, the porous polymer substrate (10) may have a three-layer structure in which polypropylene, polyethylene, and polypropylene are laminated in this order. The polyethylene layer can shut down the pores while melting as the temperature of the battery rises above a predetermined temperature, thereby preventing thermal runaway of the battery.

[0031] The thickness of the porous polymer substrate (10) may be 1 μm or more and 100 μm or less. In particular, the thickness of the porous polymer substrate (10) may be 10 μm or more and 90 μm or less, 20 μm or more and 80 μm or less, 30 μm or more and 70 μm or less, or 40 μm or more and 60 μm or less. Preferably, the thickness of the porous polymer substrate (10) may be 1 μm or more and 30 μm or less. More preferably, the thickness of the porous polymer substrate (10) may be 5 μm or more and 15 μm or less, or 8 μm or more and 13 μm or less. By adjusting the thickness of the porous polymer substrate (10) within the above range, the volume of the electrochemical device can be minimized and the amount of active material contained in the electrochemical device can be increased while electrically insulating the positive and negative electrodes.

[0032] The porous polymer substrate (10) may include pores having an average diameter of 0.01 μm to 1 μm. In particular, the size of the pores contained in the porous polymer substrate (10) may be 0.01 μm to 0.09 μm, 0.02 μm to 0.08 μm, 0.03 μm to 0.07 μm, or 0.04 μm to 0.06 μm. Preferably, the size of the pores may be 0.02 μm to 0.06 μm. By adjusting the size of the pores in the porous polymer substrate (10) within the above ranges, the air permeability and ionic conductivity of the entire separation membrane to be manufactured can be adjusted.

[0033] The porous polymer substrate 10 may have an air permeability of 10s / 100cc to 100s / 100cc. In particular, the air permeability of the porous polymer substrate 10 may be 10s / 100cc to 90s / 100cc, 20s / 100cc to 80s / 100cc, 30s / 100cc to 70s / 100cc, or 40s / 100cc to 60s / 100cc. Preferably, the air permeability of the porous polymer substrate 10 may be 50s / 100cc to 70s / 100cc. When the air permeability of the porous polymer substrate 10 is within the above range, the air permeability of the separator to be manufactured may be provided within a range suitable for ensuring the output and cycle characteristics of an electrochemical device.

[0034] The air permeability (s / 100cc) refers to the time (seconds) required for 100cc of air to pass through a porous polymer substrate (10) or a separation membrane (1) having a predetermined area under a certain pressure. The air permeability can be measured using a Gurley densometer in accordance with ASTM D726-58, ASTM D726-94, or JIS-P8117. For example, a Gurley 4110N device is used to measure air at a pressure of 0.304kPa or 1.215kN / m. 2 Under water pressure of 100cc of air, 1 square inch (or 6.54cm 2 For example, the EG01-55-1MR from Asahi Seiko can be used to measure the time it takes for 100cc of air to pass through a 1 inch2 sample at room temperature under a constant pressure of 4.8 inches of water.

[0035] The porous polymer substrate (10) may have a porosity of 10 vol% to 60 vol%. In particular, the porosity of the porous polymer substrate (10) may be 15 vol% to 55 vol%, 20 vol% to 50 vol%, 25 vol% to 45 vol%, or 30 vol% to 40 vol%. Preferably, the porosity of the porous polymer substrate (10) may be 30 vol% to 50 vol%. When the porosity of the porous polymer substrate (10) is within the above-mentioned range, the ionic conductivity of the produced separation membrane (1) may be provided within a range suitable for ensuring the output and cycle characteristics of an electrochemical device.

[0036] The porosity refers to the volume ratio of pores to the total volume of the porous polymer substrate 10. The porosity can be measured by a method known in the art. For example, it can be measured by a BET (Brunauer Emmett Teller) measurement method using nitrogen gas adsorption, a capillary flow porometer, or a water or mercury penetration method.

[0037] The porous coating layer (20) is formed on at least one surface of the porous polymer substrate (10) and includes polymer binder particles (21) and inorganic particles (22). The porous coating layer (20) may be formed by coating at least one surface of the porous polymer substrate (10) with a coating slurry including polymer binder particles (21), inorganic particles (22) and a dispersion medium. The porous coating layer (20) includes interstitial volumes in which inorganic particles (22) and the like are connected by polymer binder particles (21), and is adhered to the porous polymer substrate (10) while allowing lithium ions to pass therethrough, thereby preventing thermal shrinkage of the porous polymer substrate (10).

[0038] The coating slurry includes a dispersion medium, and can dissolve or disperse at least a portion of the polymer binder particles (21) and disperse the inorganic particles (22). The coating slurry can be used in which the polymer binder particles (21) and the inorganic particles (22) are uniformly dispersed by adjusting the type and content of the dispersion medium. For example, the dispersion medium can be one selected from the group consisting of water, ethanol, acetone, isopropyl alcohol (IPA), dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), acetonitrile, and combinations thereof. Preferably, the dispersion medium can be a mixture of water and isopropyl alcohol or water. Using the above-mentioned types of dispersion medium, a porous coating layer (20) in which the polymer binder particles (21) and the inorganic particles (22) are uniformly dispersed can be formed.

[0039] The coating slurry may further include additives such as a dispersant, a surfactant, an antifoaming agent, and a flame retardant to improve dispersibility and flame retardancy, and improve the uniformity of the porous coating layer (20) formed. For example, the dispersant may include one or more selected from the group consisting of polyacrylic acid, oil-soluble polyamine, oil-soluble amine compound, fatty acid, fatty alcohol, sorbitan fatty acid ester, tannic acid, and pyrogallic acid. The use of the above-mentioned types of dispersant can improve the stability of the coating slurry and ensure the uniformity of the porous coating layer (20) formed from the coating slurry.

[0040] Based on the total weight of the coating slurry, the additive may be included in an amount of 0 to 5 wt %. More specifically, the additive may be included in an amount of 0.01 to 4 wt %, 0.1 to 3 wt %, or 1 to 2 wt %. Preferably, the additive may be included in an amount of 1 to 5 wt %. By adjusting the additive content within the above range, uniform dispersion and stability of inorganic particles included in the coating slurry can be achieved.

[0041] The dispersion medium contained in the coating slurry may be removed by drying or heating after the formation of the porous coating layer (20). For example, the porous coating layer (20) may contain 5 ppm or less of the dispersion medium. Preferably, the porous coating layer (20) may be composed of polymer binder particles (21) and inorganic particles (22). In the process of removing the dispersion medium, a plurality of pores may be formed on the surface and inside of the porous coating layer (20). The pores may include interstitial volumes formed between the inorganic particles (22) and may have a structure that forms a three-dimensional network to allow fluid to pass through.

[0042] The thickness of the porous coating layer (20) may be 1 μm to 15 μm. In particular, the thickness of the porous coating layer (20) may be 2 μm to 14 μm, 3 μm to 13 μm, 4 μm to 12 μm, 5 μm to 11 μm, 6 μm to 10 μm, or 7 μm to 9 μm. Preferably, the thickness of the porous coating layer (20) may be 1 μm to 5 μm, more preferably 1 μm to 3 μm. By adjusting the thickness of the porous coating layer (20) within the above range, it is possible to minimize the shrinkage of the porous polymer substrate (10) and realize stable adhesion to the porous polymer substrate (10).

[0043] The polymer binder particles (21) can bind the inorganic particles (22) contained in the porous coating layer (20) and provide adhesive strength to the porous coating layer (20). The polymer binder particles (21) can be spherical or elliptical, but can also refer to other shapes excluding irregular shapes. When the polymer binder particles (21) are exposed to a temperature equal to or higher than the glass transition temperature (Tg) of the polymer binder particles (21), they can no longer maintain their particle shape and can be deformed to form a film-like region (F).

[0044] The film region (F) may be an irregular region formed when the polymer binder particles (21) cannot maintain their original shape and are solidified in a collapsed state, but may be formed by one or more polymer binder particles (21) bonding to each other. The porous coating layer (20) may include the film region (F) and a particle region (P) that is the remaining region excluding the film region (F). The particle region (P) may be composed of polymer binder particles (21) and inorganic particles (22) after the dispersion medium is removed from the coating slurry. The film region (F) may be formed by deforming the shape of one or more polymer binder particles (21) that belonged to the particle region (P). Referring to FIG. 1 and FIG. 2, the porous coating layer (20) may include one or more film regions (F). The remaining region of the porous coating layer (20) excluding the film region (F) may be called the particle region (P). The filmed region (F) may be adhered to at least one of the polymer binder particles (21), inorganic particles (22), porous polymer substrate (10), and other filmed regions (F) contained in the adjacent particle region (P). The filmed region (F) may have a smaller surface area than the polymer binder particles (21) of the same weight, but may have a larger surface area in contact with other polymer binder particles (21), other filmed regions (F), or inorganic particles (22) contained in the porous coating layer (20). For example, spherical polymer binder particles (21) may contact and adhere to spherical inorganic particles (22) over a relatively small surface area, whereas the amorphous filmed region (F) may contact and adhere to the spherical inorganic particles (22) over a relatively large surface area. The porous coating layer (20) including the filmed region (F) may exhibit a higher adhesive strength to the porous polymer substrate (10). Furthermore, the porous coating layer (20) including the filmed region (F) can exhibit higher adhesive strength to the surface opposite to the surface in contact with the porous polymer substrate (10), i.e., the electrode.

[0045] The filmed region (F) may be formed by applying a coating slurry to the porous polymer substrate (10), drying the coating slurry to form the porous coating layer (20), and then further drying or heating the coating slurry. The filmed region (F) may be distributed along the thickness direction of the porous coating layer (20). For example, the filmed region (F) may be distributed between the surface of the porous coating layer (20) that contacts the porous polymer substrate (10) and the opposite surface opposite to the surface, i.e., the surface that contacts the electrode. The filmed region (F) may be uniformly distributed between both surfaces of the porous coating layer (20), and may not be densely distributed on either surface. This may mean that more than half of the filmed region (F) is distributed between both surfaces of the porous coating layer (20) based on the weight of the entire filmed region. If more than half of the filmed region (F) is distributed on one or both surfaces of the porous coating layer based on the total weight of the filmed region (F), the pores formed on the surface or inside of the porous coating layer (20) can be closed. Preferably, the filmed region (F) can be uniformly distributed in the thickness direction of the porous coating layer (20).

[0046] The filmed region (F) may have a maximum width of a cross section of 1.1 to 3.5 times the maximum width of the cross section of the polymer binder particle (21) based on a plane parallel to one surface of the porous polymer substrate (10). In particular, the maximum cross-sectional area of ​​the filmed region (F) may be 1.3 to 3.3 times, 1.5 to 3.1 times, 1.7 to 2.9 times, 1.9 to 2.7 times, or 2.1 to 2.5 times the maximum cross-sectional area of ​​the polymer binder particle (21). Preferably, the maximum cross-sectional area of ​​the filmed region (F) may be 1.1 to 2.5 times the maximum cross-sectional area of ​​the polymer binder particle (21). By adjusting the ratio of the cross-sectional areas of the filmed region (F) and the polymer binder particle (21) within the above range, the air permeability of the separator suitable for an electrochemical device can be ensured, and the adhesive strength to the porous polymer substrate (10) can be ensured.

[0047] The filmed region (F) may be 3% by weight or more and 50% by weight or less based on the total weight of the polymer binder particles (21) contained in the porous coating layer (20). The weight of the filmed region (F) may be 3% by weight or more and 50% by weight or less based on the total weight of the polymer binder particles (21) contained in the particle region (P) and the weight of the filmed region (F). In detail, the filmed region (F) may be 5% by weight or more and 45% by weight or less, 10% by weight or more and 40% by weight or less, 15% by weight or more and 35% by weight or less, or 20% by weight or more and 30% by weight or less based on the total weight of the polymer binder particles (21). Preferably, the filmed region (F) may be 3% by weight or more and 10% by weight or less, or 30% by weight or more and 50% by weight or less based on the total weight of the polymer binder particles (21). For example, when the polymer binder particles (21) are contained in an amount of 5 wt% or less based on the total weight of the porous coating layer (20), the filmed region (F) may be 3 wt% to 10 wt% based on the total weight of the polymer binder particles (21). When the polymer binder particles (21) are contained in an amount of more than 5 wt% based on the total weight of the porous coating layer (20), the filmed region (F) may be 30 wt% to 50 wt% based on the total weight of the polymer binder particles (21). When the polymer binder particles (21) contained in the porous coating layer (20) are filmed to an amount of more than 50 wt%, the pores formed inside or on the surface of the porous coating layer (20) are closed, and the air permeability and resistance of the separator (1) to be manufactured are increased, resulting in a decrease in the performance of the electrochemical device. If the polymer binder particles (21) contained in the porous coating layer (20) are formed into a film at less than 3% by weight of the total, the adhesion to the porous polymer substrate (10) cannot be sufficiently ensured, and detachment of the porous coating layer may occur due to repeated use of the electrochemical element.

[0048] The occurrence of detachment of the porous coating layer (20) from the porous polymer substrate (10) due to repeated use of the electrochemical device can be confirmed by the friction coefficient due to friction wear on the porous coating layer (20) and the occurrence of detachment due to friction. The friction coefficient can be measured using a friction wear tester according to JIS K 7125, JIS P 8147, or JIS K 5600. For example, a Heidon surface property tester type 14FW can be used to measure the static friction coefficient at the time when the first tip moves and the dynamic friction coefficient at the time of the first friction wear when repeated friction is applied using 5g / diamond tip as a deposit. Referring to FIG. 2, the friction wear tester (not shown) has a horizontal and flat test surface, and the separator (1) is placed and fixed on the test surface, and then the diamond tip (T) is moved horizontally or repetitively (A or B) on the porous polymer substrate (10) at a predetermined speed to generate friction. The moving speed of the tip (T) may be 50 to 200 mm / min. For example, the end of the diamond tip (T) may be disposed in the region between the surface of the porous coating layer (20) that contacts the porous polymer substrate (10) and the surface opposite to the surface, and the friction coefficient may be measured while the diamond tip (T) is moved horizontally across the porous polymer substrate (10) at a speed of 100 mm / min. The end of the tip (T) is not disposed so as to contact any one of the surfaces of the porous coating layer (20). For example, the end of the diamond tip (T) may be disposed at a depth (D) smaller than the thickness of the porous coating layer (20). For example, when the thickness of the porous coating layer (20) is 3 μm, the end of the tip (T) may be repeatedly moved at a distance of 1.0 μm to 1.5 μm from the surface of the porous coating layer (20) that contacts the porous polymer substrate (10). For example, when the thickness of the porous coating layer (20) is 2 μm, the end of the tip (T) may be disposed at a depth (D) of 1 μm.The diamond tip (T) may induce peeling of the porous coating layer (20) and the porous polymer substrate (10) while reciprocating in directions A and B, or between A and B. The occurrence of detachment can be determined by visually observing the point at which the porous coating layer (20) is peeled off from the porous polymer substrate (10) while repeatedly applying friction to the separator (1), and the peel strength of the porous coating layer (20) can be confirmed from the number of repeated frictions until the peeling occurs.

[0049] In the separator for electrochemical devices according to the embodiment, an end of a diamond tip (T) is disposed in a region between a surface of the porous coating layer (20) contacting the porous polymer substrate (10) and an opposite surface opposite to the surface, and when the diamond tip is moved horizontally across the porous polymer substrate (10) at a speed of 100 mm / min, the initial dynamic friction coefficient due to frictional wear may be 1 to 2. In particular, the initial dynamic friction coefficient due to frictional wear against the porous coating layer (20) may be 1.1 to 1.9, 1.2 to 1.8, 1.3 to 1.7, or 1.4 to 1.6. Preferably, the initial dynamic friction coefficient due to frictional wear against the porous coating layer (20) may be 1.2 to 1.5. The initial dynamic friction coefficient is a dynamic friction coefficient exhibited when the tip starts to move and makes an initial reciprocating motion, and may be expressed in proportion to the content of the filmed region (F) contained in the porous coating layer (20). If the initial kinetic friction coefficient exceeds 2, the content of the filmed region (F) may be excessive or more than half of the filmed region (F) may be densely distributed on one side of the porous coating layer (20), which may close the pores of the porous coating layer (20), increasing the air permeability and resistance of the separator (1) produced and degrading the performance of the electrochemical device. If the initial kinetic friction coefficient is less than 1, the adhesive force to the porous polymer substrate (10) may not be sufficiently secured, and the porous coating layer (20) may detach from the porous polymer substrate (10) due to repeated use of the electrochemical device.

[0050] In the separator for electrochemical devices (1) according to the embodiment, the end of the diamond tip (T) is disposed in an area between the surface of the porous coating layer (20) that contacts the porous polymer substrate (10) and the opposite surface opposite to the aforementioned surface, and when the diamond tip (T) is moved horizontally across the porous polymer substrate (10) at a speed of 100 mm / min, the difference between the static friction coefficient due to frictional wear and the initial kinetic friction coefficient may be 3 or less. In particular, the difference between the static friction coefficient due to frictional wear and the initial kinetic friction coefficient against the porous coating layer (20) may be 2.9 or less, 2.8 or less, 2.6 or less, 2.4 or less, 2.2 or less, 2.0 or less, or 1.8 or less. Preferably, the difference between the static friction coefficient due to frictional wear and the initial kinetic friction coefficient against the porous coating layer (20) may be 1.0 or more and 2.9 or less. When the filmed regions (F) are densely distributed on one surface of the porous coating layer (20), the difference between the static friction coefficient and the initial kinetic friction coefficient becomes large, which means that more pores formed inside or on the surface of the porous coating layer (20) are closed. If the difference exceeds 3, the pores formed inside or on the surface of the porous coating layer (20) are closed, increasing the air permeability and resistance of the separator (1) produced and degrading the performance of the electrochemical device.

[0051] In one specific example of the separator for electrochemical devices (1), the end of a diamond tip (T) is disposed in the region between the surface of the porous coating layer (20) that contacts the porous polymer substrate (10) and the opposite surface opposite the surface, and the diamond tip is moved horizontally against the porous polymer substrate (10) at a speed of 100 mm / min, causing frictional wear that can be repeated 5 to 35 times, resulting in detachment of the porous coating layer (20). Specifically, the porous coating layer (20) may be peeled off from the porous polymer substrate (10) after the friction and abrasion is repeated 6 to 34 times, 7 to 33 times, 8 to 32 times, 9 to 31 times, 10 to 30 times, 11 to 29 times, 12 to 28 times, 13 to 27 times, 14 to 26 times, 15 to 25 times, 16 to 24 times, 17 to 23 times, 18 to 22 times, or 19 to 21 times. The peeling means that at least a part of the porous coating layer (20) is detached from the porous polymer substrate (10). Preferably, the porous coating layer (20) may be peeled off from the porous polymer substrate (10) when the friction and abrasion is repeated 18 to 32 times. The separator (1) satisfying the above-mentioned range can exhibit air permeability and electrical resistance suitable for application to an electrochemical element.

[0052] The separator (1) for electrochemical devices may have an air permeability of 20s / 100cc or more and 90s / 100cc or less. In particular, the air permeability of the separator (1) may be 25s / 100cc or more and 85s / 100cc or less, 30s / 100cc or more and 80s / 100cc or less, 35s / 100cc or more and 75s / 100cc or less, 40s / 100cc or more and 70s / 100cc or less, 45s / 100cc or more and 65s / 100cc or less, or 50s / 100cc or more and 55s / 100cc or less. Preferably, the air permeability of the separator (1) may be 80s / 100cc or more and 90s / 100cc or less. When the air permeability of the separator (1) is within the above-mentioned range, the output, stability, and cycle characteristics of the electrochemical device can be ensured.

[0053] When a cell is manufactured using the separator for an electrochemical device (1), the cell may have an electrical resistance of 0.5 Ohm to 1.5 Ohm. More specifically, the electrical resistance of the cell may be 0.6 Ohm to 1.4 Ohm, 0.7 Ohm to 1.3 Ohm, 0.8 Ohm to 1.2 Ohm, or 0.9 Ohm to 1.1 Ohm. Preferably, the electrical resistance of the cell may be 0.6 Ohm to 0.8 Ohm.

[0054] The separator for electrochemical devices (1) according to the specific example may have an adhesive strength between the surfaces of the porous coating layer and the porous polymer substrate (10), i.e., a peel strength of 100 gf / 15 mm to 200 gf / 15 mm. More specifically, the peel strength of the separator (1) may be 110 gf / 15 mm to 190 gf / 15 mm, 120 gf / 15 mm to 180 gf / 15 mm, 130 gf / 15 mm to 170 gf / 15 mm, or 140 gf / 15 mm to 160 gf / 15 mm. Preferably, the peel strength of the separator (1) may be 100 gf / 15 mm to 130 gf / 15 mm. If the peel strength is less than 100 gf / 15 mm, the porous coating layer will peel off from the porous polymer substrate (10) during the cycle life of the electrochemical element, and if the peel strength exceeds 200 gf / 15 mm, it means that the filmed region (F) is densely distributed on one surface of the porous coating layer (20), particularly the surface in contact with the porous polymer substrate (10), which is reflected in an increase in air permeability and electrical resistance.

[0055] In the separator for electrochemical devices (1) according to one embodiment of the present invention, the adhesive strength between the surfaces of the porous coating layer (20) in contact with the electrode, i.e., the electrode-separator adhesive strength, may be 10 gf / 25 mm to 50 gf / 25 mm. More specifically, the electrode-separator adhesive strength may be 15 gf / 25 mm to 45 gf / 25 mm, 20 gf / 25 mm to 40 gf / 25 mm, or 25 gf / 25 mm to 35 gf / 25 mm. Preferably, the electrode-separator adhesive strength may be 35 gf / 25 mm to 50 gf / 25 mm. If the electrode-separator adhesion strength is less than 10 gf / 25 mm, detachment of the electrode and separator occurs after the electrode assembly is manufactured, and if the electrode-separator adhesion strength exceeds 50 gf / 25 mm, the separator (1) in the electrode assembly is not uniformly wetted by the electrolyte, and lithium dendrites may precipitate on the surface of the separator (1).

[0056] The peel strength of the separator (1) and the electrode-separator adhesion can be measured by attaching double-sided tape to the separator (1), adhering a slide glass, and then peeling the slide glass from the separator in a direction 180° to the adhesion direction. For example, the peel strength of the porous coating layer (20) can be measured by attaching double-sided tape to the separator (1) and peeling the slide glass at a speed of 300 min / mm using a Universal Testing Machine (UTM) from Instron. For example, after adhering the electrode and separator (1), the double-sided tape can be attached to the separator, and the slide glass can be peeled off at a speed of 300 min / mm using a UTM to measure the electrode-separator adhesion.

[0057] In the separator for electrochemical devices according to the embodiment, the adhesive strength between the porous polymer substrate (10) and the porous coating layer (20) may be 1.5 to 6 times the adhesive strength of the surface of the porous coating layer (20) opposite to the surface in contact with the porous polymer substrate (10). That is, the peel strength of the separator (1) may be 1.5 to 6 times the electrode-separator adhesive strength. In more detail, the peel strength of the separator (1) may be 2 to 5.5 times, 2.5 to 5 times, 3 to 4.5 times, or 3.5 to 4 times the electrode-separator adhesive strength. Preferably, the peel strength of the separator (1) may be 3 to 6 times the electrode-separator adhesive strength. The durability of the electrode assembly manufactured by adhering the separator (1) to the electrode within the above range can be ensured.

[0058] The polymer binder particles (21) may have a glass transition temperature (Tg) of 0° C. or more and 60° C. or less. More specifically, the glass transition temperature of the polymer binder particles (21) may be 5° C. or more and 55° C. or less, 10° C. or more and 50° C. or less, 15° C. or more and 45° C. or less, 20° C. or more and 40° C. or less, or 25° C. or more and 35° C. or less. Preferably, the glass transition temperature of the polymer binder particles (21) may be 20° C. or more and 40° C. or less. The polymer binder particles (21) having a glass transition temperature in the above-mentioned range maintain their particle shape in the drying process for removing the dispersion medium contained in the coating slurry, and can form a region (F) in which at least a part of the polymer binder particles (21) is turned into a film by drying or heating in the temperature range described below.

[0059] The weight average molecular weight (Mw) of the polymer binder particles (21) may be from 1,000 to 10,000,000. In particular, the weight average molecular weight of the polymer binder particles (21) may be from 1,000 to 10,000,000, from 10,000 to 9,000,000, from 100,000 to 8,000,000, from 200,000 to 7,000,000, from 300,000 to 6,000,000, from 500,000 to 5,000,000, from 1,000,000 to 4,000,000, or from 2,000,000 to 3,000,000. By adjusting the weight average molecular weight of the polymer binder particles (21) within the above-mentioned range, the mechanical properties of the porous coating layer (20) can be ensured, and a separator (1) having a durable porous coating layer can be produced.

[0060] The weight average molecular weight can be measured by gel permeation chromatography (GPC, PL GPC220, Agilent Technologies). For example, the weight average molecular weight can be measured using an Agilent High Temperature RI detector under the conditions of a PL Olexis (Polymer Laboratories) column (column temperature 160° C.) with TCB (trichlorobenzene) as a solvent, a sample concentration of 1.0 mg / mL, a flow rate of 1.0 mL / min, and an injection volume of 200 μL (standard: Polystyrene).

[0061] The porous coating layer (20) may contain the polymer binder particles (21) and the inorganic particles (22) in a weight ratio of 5:95 to 80:20. In particular, the weight ratio of the polymer binder particles (21) and the inorganic particles (22) in the porous coating layer (20) may be 10:90 to 80:20, 20:80 to 80:20, 30:70 to 70:30, 40:60 to 60:40, or 50:50. Preferably, the weight ratio of the polymer binder particles (21) and the inorganic particles (22) may be 60:40 to 80:20. By controlling the composition of the porous coating layer (20) within the above range, the above content range of the total polymer binder particles (21) can be made into a film, thereby simultaneously ensuring the durability of the porous polymer substrate (10) and the adhesive strength of the separator (1).

[0062] The polymer binder particles (21) may be an acrylic polymer resin or a copolymer containing an acrylic monomer. The acrylic polymer resin may be one or more selected from the group consisting of polyacrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, ethylhexyl acrylate, and methyl methacrylate, or a copolymer thereof. The copolymer containing an acrylic monomer may be one or more selected from the group consisting of styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber. Preferably, the polymer binder particles (21) may be styrene-butadiene rubber. By selecting the above-mentioned types of polymer binder particles (21), a film-formed region (F) can be sequentially formed after removing the dispersion medium during the manufacturing process of the porous coating layer (20), and a separator (1) having both the durability and adhesive strength of the porous coating layer (20) can be obtained.

[0063] The inorganic particles (22) can be those that are electrochemically stable. The inorganic particles (22) are not particularly limited as long as oxidation and / or reduction reactions do not occur within the operating voltage range of the electrochemical device (for example, 0 to 5 V based on Li / Li + standard). In particular, when using inorganic particles with a high dielectric constant as the inorganic particles (22), it can contribute to an increase in the dissociation degree of the electrolyte salt in the liquid electrolyte, such as a lithium salt, and improve the ionic conductivity of the electrolyte solution. For the reasons described above, etc., the inorganic particles (22) preferably include high-dielectric-constant inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Non-limiting examples of inorganic particles (22) 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, Al(OH)3, SiC, AlOOH, TiO2, or a mixture thereof, etc.

[0064] In addition, as the inorganic particles (22), inorganic particles having lithium ion transfer ability, that is, inorganic particles (22) that contain lithium element but do not store lithium and have the function of moving lithium ions can be used. Non-limiting examples of inorganic particles (22) having lithium ion transfer ability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (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), (LiAlTiP) such as 14Li2O-9Al2O3-38TiO2-39P2O5 x O ySystem glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), Li 3.25 Ge 0.25 P 0.75 S4 and other lithium germanium thiophosphates (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitrides such as Li3N (Li x N y , 0 < x < 4, 0 < y < 2), SiS2-based glasses such as Li3PO4-Li2S-SiS2 (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5-based glasses such as LiI-Li2S-P2S5 (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), or mixtures thereof, etc.

[0065] In addition, as the inorganic particles (22), inorganic particles having flame retardancy can be used, which can impart flame retardancy to the separation membrane or prevent the temperature inside the electrochemical element from rising rapidly. Non-limiting examples of the inorganic particles (22) having flame retardancy include Sb2O3, Sb2O4, Sb2O5, SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, SiO2, Al2O3, AlOOH, Al(OH)3, SiC, TiO2, H3BO3, HBO2, and mixtures thereof, etc.

[0066] The inorganic particles (22) may have an average particle size (D50) of 50 nm to 5,000 nm. In particular, the inorganic particles (22) may have an average particle size (D50) of 100 nm to 4,500 nm, 200 nm to 4,000 nm, 300 nm to 3,000 nm, 400 nm to 2,000 nm, or 500 nm to 1,000 nm. If the inorganic particles (22) have an average particle size of less than 50 nm, the specific surface area increases, and an additional polymer binder is required for bonding between the inorganic particles (22), which is disadvantageous in terms of electrical resistance. If the inorganic particles (22) have an average particle size of more than 5,000 nm, the uniformity of the coating layer surface decreases, which may cause damage to the porous polymer substrate (10) or electrodes during lamination.

[0067] The aspect ratio of the inorganic particles (22) may be 1 or more and 2 or less. In particular, the aspect ratio of the inorganic particles (22) may be 1.1 or more and 1.9 or less, 1.2 or more and 1.8 or less, 1.3 or more and 1.7 or less, or 1.4 or more and 1.6 or less. By adjusting the aspect ratio of the inorganic particles (22) within the above range, the polymer binder particles (21) can easily move due to the gaps between the inorganic particles (22), and a porous coating layer (20) in which the film-like regions (F) are uniformly distributed can be formed by forming the film-like regions (F) after the movement of the polymer binder particles (21).

[0068] The BET specific surface area of ​​the inorganic particles (22) is 5 m 2 / g or more 25m 2 In particular, the BET specific surface area of ​​the inorganic particles (22) may be 6 m 2 / g or more 24m 2 / g or less, 7m 2 / g or more 23m 2 / g or less, 8m 2 / g or more 22m 2 / g or less, 9m 2 / g or more 21m 2 / g or less, 10m 2 / g or more 20m 2 / g or less, 11m 2 / g or more 19m2 / g or less, 12m 2 / g or more 18m 2 / g or less, 13m 2 / g or more 17m 2 / g or less, or 14m 2 / g or more 26m 2 / g or less. By adjusting the BET specific surface area of ​​the inorganic particles (22) within the above range, the movement of the polymer binder particles (21) through the voids between the inorganic particles (22) can be adjusted.

[0069] One embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device (1), comprising the steps of: coating at least one surface of a porous polymer substrate (10) with a coating slurry including polymer binder particles (21), inorganic particles (22) and a dispersion medium to form a coating layer including a particle region (P) including polymer binder particles (21) and inorganic particles (22), drying the coating layer to remove the dispersion medium, and drying the coating layer to reduce the polymer binder particles (21) by 3 to 50% by weight based on the total weight to form a film region (F). The contents that overlap with those described in the separator for an electrochemical device are substituted for the description in the above embodiment.

[0070] In the step of forming the coating layer, at least one side of the porous polymer substrate (10) is coated with a coating slurry containing polymer binder particles (21), inorganic particles (22) and a dispersion medium. The coating can be formed by, for example, but not limited to, a bar coater, a wire bar coater, a roll coater, a spray coater, a spin coater, an inkjet coater, a screen coater, a reverse coater, a gravure coater, a knife coater, a slot die coater, a hot melt coater, a comma coater, a direct metering coater, or the like. Preferably, the step of forming the coating layer can be performed by simultaneously coating both sides of the porous polymer substrate (10) with the coating slurry using a bar coater or a slot die coater.

[0071] The step of forming the coating layer may further include a step of subjecting at least one surface of the porous polymer substrate 10 to a corona discharge treatment. After the corona discharge treatment, the coating slurry may be coated on the porous polymer substrate 10. The step of subjecting at least one surface of the porous polymer substrate 10 to a corona discharge treatment can prevent a decrease in the adhesive strength between the surface of the porous polymer substrate 10 and the surface of the coating layer at high temperatures, and can prevent a decrease in the adhesive strength between the surface of the polymer substrate 10 and the surface of the coating layer due to an electrolyte.

[0072] The corona discharge treatment may be performed by treating at least one surface of the porous polymer substrate (10) in air at a voltage of 0.1 kV to 10 kV. Specifically, the corona discharge treatment may be performed in air at a voltage of 0.2 kV to 9 kV, 0.3 kV to 8 kV, 0.4 kV to 7 kV, 0.5 kV to 6 kV, 0.6 kV to 5 kV, 0.7 kV to 4 kV, 0.8 kV to 3 kV, 0.9 kV to 2 kV, or 1.0 kV to 2 kV. Preferably, the corona discharge treatment may be performed in air at a voltage of 1.8 kV. By adjusting the applied voltage of the corona discharge treatment within the above-mentioned range, an appropriate number of functional groups can be formed on the surface of the polymer substrate (10), and damage to the surface of the polymer substrate (10) can be prevented.

[0073] In the step of removing the dispersion medium, the coating layer is dried or heated to evaporate the dispersion medium contained in the coating layer, which can be called a first heating step. The first heating step may be performed at a temperature that can evaporate only the dispersion medium contained in the coating layer without deforming the polymer binder particles (21) contained in the coating layer. For example, the first heating step may heat the coating layer to a predetermined temperature, but the temperature of the coating layer surface may not exceed 50°C. For example, the coating layer that has undergone the first heating step may be composed of a particle region (P) composed of polymer binder particles (21) and inorganic particles (22). When the coating layer is heated under the above conditions, the thermal energy may be used first to heat the dispersion medium to cause a phase change, and not to deform the polymer binder particles (21). After the dispersion medium is removed, at least a portion of the polymer binder particles (21) may be deformed by a second heating step described below to form a film region (P).

[0074] In the step of forming the filmed region (F), the coating layer is exposed to a temperature of not less than the glass transition temperature (Tg) of the polymer binder particles (21) but not more than Tg+40°C, which can be called a second heating step. In detail, the second heating step can be a step of heating the coating layer to not less than Tg+5°C but not more than Tg+35°C, not less than Tg+10°C but not more than Tg+30°C, or not less than Tg+15°C but not more than Tg+25°C of the polymer binder particles (21). Preferably, the second heating step can be heating the coating layer to not less than Tg+20°C but not more than Tg+40°C.

[0075] The second heating step may be heating the coating layer for 1 hour to 24 hours in the above temperature range. In particular, the second heating step may be heating the coating layer for 2 hours to 23 hours, 3 hours to 22 hours, 4 hours to 21 hours, 5 hours to 20 hours, 6 hours to 19 hours, 7 hours to 18 hours, 8 hours to 17 hours, 9 hours to 16 hours, 10 hours to 15 hours, 11 hours to 14 hours, or 12 hours to 13 hours in the above temperature range. Preferably, the second heating step may be heating the coating layer for 6 hours to 24 hours in the above temperature range. At the above temperature or temperature and time range, 3 to 50% by weight based on the total weight of the polymer binder particles (21) may be deformed to form a filmed region (F). If the heating temperature or time deviates from the above-mentioned range, the film-like region (F) will be formed excessively or densely on one surface of the porous coating layer (20), and the air permeability and electrical resistance of the separator (1) will increase sharply.

[0076] The second heating step may be a single step performed at a heating temperature in the above-mentioned range. Alternatively, the second heating step may be a combination of a plurality of steps having the same or different heating temperatures and times. For example, the second heating step may include a 2-1 heating step of heating to a temperature of Tg+30°C to Tg+40°C for 1 hour or less, a 2-2 heating step of heating to a temperature of Tg+20°C to Tg+30°C for 1 hour or less to 2 hours, a 2-3 heating step of heating to a temperature of Tg+10°C to Tg+20°C for 2 hours or less to 4 hours, and a step of heating to a temperature of Tg to Tg+10°C for 4 hours or less to 8 hours. Preferably, the preceding heating step is heated to a higher temperature than the succeeding heating step, so that the filmed region (F) is uniformly formed in the thickness direction of the porous coating layer (20).

[0077] The polymer binder particles (21) contained in the porous coating layer (20) may not maintain their original shape within the above-mentioned temperature and time range, but may be turned into a film. The polymer binder particles (21) are turned into a film, and may further bind inorganic particles (22) or the like, or may further bind the inorganic particles (22) and the porous polymer substrate (10), or may further bind the polymer binder particles (21) and the inorganic particles (22) or the polymer binder particles (21) and the porous polymer substrate (10). As a result, the film-formed region (F) improves the mechanical properties of the porous coating layer (20) itself and improves the adhesive strength between the porous coating layer (20) and the porous polymer substrate (10), thereby providing a separator (1) with improved durability of the porous coating layer (20).

[0078] The method for producing the separator (1) may further include, after the step of forming the filmed region (F), storing or cooling the separator (1) having the porous coating layer (20) formed thereon at room temperature. The filmed region (F) may be left at a temperature equal to or lower than the glass transition temperature of the polymer binder particles (21) to harden the irregularly formed filmed region (F) to a state in which the additional bonds are formed as described above.

[0079] One embodiment of the present invention provides an electrochemical device including a positive electrode, a negative electrode, and a separator (1) interposed between the positive electrode and the negative electrode, the separator (1) being the separator for an electrochemical device of the above embodiment. The electrochemical device can be manufactured by inserting an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode into a case or pouch and sealing the case or pouch. Before sealing the case or pouch, an electrolyte can be injected to impregnate the electrode assembly with the electrolyte. The shape of the case or pouch is not limited. For example, the electrochemical device can be a cylindrical, square, coin, or pouch type lithium secondary battery.

[0080] The positive electrode and the negative electrode may be coated by applying and drying an electrode active material to at least one surface of each current collector. The current collector may be made of a material that is conductive without inducing a chemical change in the electrochemical device. For example, the positive electrode current collector may be made of, but is not limited to, aluminum, nickel, titanium, calcined carbon, stainless steel, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, or the like. For example, the negative electrode current collector may be made of, but is not limited to, copper, nickel, titanium, calcined carbon, stainless steel, or copper or stainless steel surface treated with carbon, nickel, titanium, silver, or the like. The current collector may be in various forms, such as a metal sheet, a film, a foil, a net, a porous body, or a foam.

[0081] The positive electrode comprises a positive electrode current collector and a positive electrode active material layer on at least one surface of the current collector, the positive electrode active material layer including a positive electrode active material, a conductive material, and a binder resin. The positive electrode active material may be a layered compound such as lithium manganese composite oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; 1+x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Lithium nickel oxide with Ni site represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x=0.01 to 0.3); 1-x M xLithium manganese composite oxides represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the chemical formula Li is substituted with alkaline earth metal ions; disulfide compounds; It may contain one or a mixture of two or more of Fe2(MoO4)3.

[0082] The negative electrode includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. As the negative electrode active material, the negative electrode includes carbon such as lithium metal oxide, graphitized carbon, and graphite-based carbon; LixFe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), Si, SiO x (0 < x < 2), silicon-based materials such as SiC and Si alloys; Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), etc. metal composite oxides; lithium metal; lithium alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; It may contain one or a mixture of two or more selected from titanium oxide.

[0083] The conductive material may be any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, carbon nanotube, activated carbon, and polyphenylene derivative, or a mixture of two or more of these conductive materials. The carbon nanotube has a cylindrical form with a nanosize diameter of a graphite sheet and sp 2Carbon nanotubes have a bond structure and exhibit conductive or semiconductive properties depending on the angle and structure of the graphite plane. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT) and multi-walled carbon nanotubes (MWCNT) depending on the number of bonds forming the wall, and these carbon nanotubes can be appropriately selected depending on the use of the dispersion. More specifically, the carbon nanotube may be one or a mixture of two or more conductive materials 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.

[0084] As the binder resin, a binder resin that is usually used for electrodes of electrochemical elements can be used. Non-limiting examples of the binder resin include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionic acid. Examples of suitable cellulose acetate copolymers include, but are not limited to, cyanoethyl acetatepropionate, cyanoethyl pullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose.

[0085] The electrolyte is A + B - A salt having the structure: + Li + , Na + , K +or a combination thereof, such as B - PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - or a combination thereof may be dissolved or dissociated in an organic solvent such as, but not limited to, propylene carbonate (PC), ethylene carbonate (EC), 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 (γ-butyrolactone), or a mixture thereof.

[0086] The electrochemical device including the electrode assembly may be a lithium secondary battery. The battery may be used as a unit cell, and may be used as a battery module including the unit cell, a battery pack including the battery module, or a device including the battery pack as a power source. The devices include small devices such as computers, mobile phones, and power tools; electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), etc., which are powered by electric motors; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; and the like. cart); medium and large devices such as power storage systems, but are not limited to these.

[0087] The present invention will be described in more detail below with reference to specific examples and experimental examples. The following examples and experimental examples are provided to illustrate the present invention, and the present invention is not limited to the following examples and experimental examples.

[0088] Example 1 Preparation of coating slurry Water and isopropyl alcohol were mixed at room temperature (25°C) in a weight ratio of 95:5 to prepare 100 mL of an aqueous dispersion medium. An acrylic polymer binder (Styrene-acrylic, particle size: 350 to 400 nm, T g 7.7 g of ethanol (40° C.) and 27.3 g of inorganic particles (Al2O3, particle size: 400 nm) were added and stirred for 60 minutes with a shaker to produce a coating slurry in which the polymer binder particles and inorganic particles were dispersed.

[0089] Preparation of porous substrate The porous substrate was (MI: 0.2g / 10min, T m A polyethylene film with dimensions of 20 cm x 30 cm and thickness of 9 μm (temperature: 135°C, porosity: 45%, average pore size: 45 nm) was used.

[0090] Separation membrane manufacturing The coating slurry was coated on both sides of a polyethylene film using a bar coater to form a porous coating layer with a thickness of 2 μm.

[0091] A low-temperature airflow was applied to the polyethylene film on which the porous coating layer was formed, and the process of drying (first heating) and removing the dispersion medium while controlling the surface temperature of the porous coating layer not to exceed 50° C. was repeated five times.

[0092] Next, a high temperature air flow rate of 70° C. was applied to the separator for 24 hours (second heating) to produce a separator having an overall thickness of 13 μm.

[0093] Example 2 A separation membrane was prepared in the same manner as in Example 1, except that after removing the dispersion medium, a high-temperature air flow rate of 80° C. was applied to the separation membrane for 24 hours.

[0094] Example 3 A separation membrane was prepared in the same manner as in Example 1, except that after removing the dispersion medium, a high-temperature air flow rate of 70° C. was applied to the separation membrane for 1 hour.

[0095] Example 4 A separation membrane was prepared in the same manner as in Example 1, except that after removing the dispersion medium, a low-temperature air flow rate of 40° C. was applied to the separation membrane for 24 hours.

[0096] Comparative Example 1 A separation membrane was produced in the same manner as in Example 1, except that in the production of the separation membrane, after removing the dispersion medium, no additional high-temperature air flow was applied to the separation membrane.

[0097] Comparative Example 2 A separation membrane was prepared in the same manner as in Example 1, except that after removing the dispersion medium, a high-temperature air flow rate of 80° C. was applied to the separation membrane for 48 hours.

[0098] Comparative Example 3 A separation membrane was prepared in the same manner as in Example 1, except that after removing the dispersion medium, a high-temperature air flow rate of 90° C. was applied to the separation membrane for 24 hours.

[0099] Experimental example 1. Confirmation of durability of porous coating layer The separation membranes of the Examples and Comparative Examples were placed in a Heidon Surface Property Tester type 14FW device, and a 5 g / dia tip was attached to the device as an attachment, and the end of the dia tip was inserted to a depth of 1 μm in the porous coating layer of the separation membrane.

[0100] Then, the diamond tip was reciprocated at a speed of 100 mm / min to generate repeated friction, and the stopping friction coefficient was measured at the moment when the diamond tip started to move, and the initial kinetic friction coefficient was measured during the first reciprocating motion. The number of reciprocating motions required until the porous coating layer was peeled off from the porous polymer substrate was counted while the diamond tip was reciprocating. The measured friction coefficient and the number of reciprocating motions until the peeling point are shown in Table 1 below.

[0101] Experimental example 2. Confirmation of the physical properties of the separation membrane Peel strength measurement Each separation membrane was sampled to a width of 20 mm and attached to a slide glass using 18 mm-wide double-sided tape (3M) to prepare a test sample.

[0102] The peel strength was measured while peeling the slide glass from the separation film in a direction of 180° to the adhesion direction at a speed of 300 mm / min using a UTM.

[0103] Measurement of adhesion strength between electrode and separator The negative electrode active material (natural graphite and artificial graphite in a weight ratio of 5:5), conductive material (Super P), and binder (polyvinylidene fluoride (PVdF)) were mixed in a weight ratio of 92:2:6, dispersed in water, and then coated onto copper foil to produce the negative electrode.

[0104] The separators and the negative electrodes of the examples and comparative examples were sampled and stacked to a width of 20 mm, and then pressed at 60° C. and 6.5 MPa for 1 second to prepare samples for electrode adhesion tests.

[0105] The negative electrode was peeled off from the separator in a direction of 180° to the adhesion direction at a speed of 300 mm / min using a UTM, and the electrode adhesive strength of the separator was measured.

[0106] Measurement of air permeability The air permeability was measured using a Gurley densometer (Gurley, 4110N) by measuring the diameter of 28.6 mm and the area of ​​645 mm for 100 cc of air. 2 The time it took for the solution to permeate the separation membrane was measured.

[0107] Measurement of electrical resistance The electrical resistance was measured by manufacturing a 2016 size coin cell using each of the separators of the Example and Comparative Example, leaving it for 3 hours, and then measuring the resistance of the coin cell using an EIS (Electrochemical Impedance Spectroscopy) device.

[0108] The electrolyte for the coin cell was a drop of a solvent containing ethylene carbonate (EC) / ethyl methyl carbonate (EMC) mixed in a ratio of 3 / 7, and containing 3 mol of vinylene carbonate (VC), 1.5 mol of propane sultone (PS), 1 mol of ethylene sulfate (ESa), and 1 mol of lithium salt LiPF6 as additives.

[0109] [Table 1] [Explanation of symbols] 1: Separation membrane 10: Porous polymer base material 20: Porous coating layer 21: Polymer binder particles 22: Inorganic particles P: Particle area F: Filmed area T: Diamond tip

Claims

1. A porous polymeric substrate; and a porous coating layer formed on at least one surface of the porous polymer substrate, the porous coating layer including a particle region made of polymer binder particles and inorganic particles and a film region including the deformed polymer binder particles; Including, The film region is 3 to 50 wt % based on the total weight of the polymer binder particles.

2. 2. The separator for electrochemical elements according to claim 1, wherein the porous coating layer has an initial dynamic friction coefficient due to frictional wear of 1 to 2 when an end of a diamond tip is placed in the region between the surface in contact with the porous polymer substrate and the opposite surface opposite the surface, and the diamond tip is moved horizontally across the porous polymer substrate at a speed of 100 mm / min.

3. 2. The separator for electrochemical elements according to claim 1, wherein the porous coating layer has an end of a diamond tip disposed in the region between the surface in contact with the porous polymer substrate and the opposite surface opposite the surface, and when the diamond tip is moved horizontally across the porous polymer substrate at a speed of 100 mm / min, the difference between the static friction coefficient due to frictional wear and the initial dynamic friction coefficient is 3 or less.

4. 2. The separator for electrochemical devices according to claim 1, wherein an adhesive strength between the porous polymer substrate and the porous coating layer is 1.5 to 6 times an adhesive strength between the surface of the porous coating layer opposite to the surface in contact with the porous polymer substrate.

5. 2. The separator for an electrochemical element according to claim 1, wherein the polymer binder particles include at least one selected from the group consisting of polyacrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, ethylhexyl acrylate, methyl methacrylate, styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber.

6. 2. The separator for an electrochemical device according to claim 1, wherein the film-formed region is formed by exposing the polymer binder particles to a temperature in the range of a glass transition temperature (Tg) of the polymer binder particles to Tg+40°C.

7. An electrochemical device comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, An electrochemical element, wherein the separator is the separator for electrochemical elements according to claim 1 .

8. A step of coating at least one surface of a porous polymer substrate with a coating slurry including polymer binder particles, inorganic particles, and a dispersion medium to form a coating layer including a particle region including polymer binder particles and inorganic particles; drying the coating layer to remove the carrier medium; and drying the coating layer to form a filmed region by changing the weight of the polymer binder particles by 3 to 50% based on the total weight of the polymer binder particles; The method for producing a separator for an electrochemical element comprises the steps of:

9. The method of claim 8, wherein the surface of the coating layer does not exceed 50° C. during the removing of the dispersion medium.

10. 9. The method of claim 8, wherein the forming of the film region comprises exposing the coating layer to a temperature in the range of a glass transition temperature (Tg) of the polymer binder particles to Tg+40° C. for up to 24 hours.

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