Separator for electrochemical device and electrochemical device comprising same

Abstract

The present invention relates to a separator for an electrochemical device, and an electrochemical device comprising same. In the separator for an electrochemical device, a polymer binder in an adhesive layer has a core-shell structure. The adhesion of the separator for an electrochemical device is increased by controlling the solubility, in an electrolyte, of a second polymer binder in the shell portion of the core-shell structure. An electrochemical device to which the separator is applied has reduced cell resistance and an improved cell lifespan.

Description

Separator for electrochemical devices and electrochemical devices containing the same

[0001] This invention claims the benefit of Korean Patent Application No. 10-2024-0072929, filed with the Korean Intellectual Property Office on June 4, 2024, and Korean Patent Application No. 10-2025-0069535, filed with the Korean Intellectual Property Office on May 28, 2025, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a separator for an electrochemical device and an electrochemical device including the same.

[0003] Electrochemical devices such as lithium secondary batteries are typically composed of a cathode / separator / cathode / electrolyte. They are high-energy-density energy storage devices that can be recharged and discharged by reversibly converting chemical and electrical energy. They are widely used in small electronic devices such as mobile phones and laptops. Recently, in response to environmental issues, high oil prices, and energy efficiency and storage, electrochemical devices such as lithium secondary batteries are rapidly expanding their applications in hybrid electric vehicles (HEVs), plug-in electric vehicles (EVs), e-bikes, and energy storage systems (ESS).

[0004] As these electrochemical devices advance to higher capacities and outputs, the likelihood of abnormal temperature rises during charge / discharge cycles increases for various reasons. This can lead to, for example, thermal runaway, a phenomenon in which sparks explode at high temperatures. Because thermal runaway in electrochemical devices such as lithium secondary batteries is difficult to extinguish, safety issues are increasingly recognized as a critical issue for high-capacity, high-output lithium secondary batteries. Therefore, ensuring safety is a critical challenge in the manufacture and use of electrochemical devices.

[0005] The present invention provides a separator for an electrochemical device and an electrochemical device including the same, which can reduce cell resistance and improve cell performance by controlling the structure and properties of a binder included in an adhesive layer. For example, the present invention provides a separator for an electrochemical device and an electrochemical device including the same, which can increase adhesive strength, reduce cell resistance, and improve cell lifespan by controlling the solubility of a second polymer binder of the shell portion when the polymer binder of the adhesive layer has a core-shell structure.

[0006] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0007] One embodiment of the present invention provides a separator for an electrochemical device, comprising: a porous polymer substrate; a coating layer provided on at least one surface of the porous polymer substrate and including inorganic particles; and an adhesive layer provided on the coating layer and including a polymer binder having a core-shell structure, wherein the adhesive layer includes a first polymer binder of a core portion of the core-shell structure and a second polymer binder of a shell portion of the core-shell structure, and the solubility of the second polymer binder of the shell portion in an electrolyte is about 95% or more.

[0008] According to one embodiment of the present invention, the solubility of the second polymer binder of the shell portion in the electrolyte may be about 96% or more and 99% or less.

[0009] According to one embodiment of the present invention, the glass transition temperature of the first polymer binder may be about 70°C or higher.

[0010] According to one embodiment of the present invention, the glass transition temperature of the second polymer binder may be about 0°C or more and 40°C or less.

[0011] According to one embodiment of the present invention, the particle size of the core-shell structure may be about 200 nm or more and 800 nm or less.

[0012] According to one embodiment of the present invention, the gel content of the first polymer binder at room temperature is about 99% or more, the gel content of the second polymer binder at room temperature is about 5% or less, and the gel content may be calculated by the following equation 1.

[0013] [Formula 1]

[0014] Gel content (%) = W 24 / W0X 100

[0015] In the above equation 1,

[0016] W 24 is the weight measured after immersion in the electrolyte for 24 hours, and W0 is the weight measured before immersion.

[0017] According to one embodiment of the present invention, the swelling ratio of the polymer binder having the core-shell structure may be about 100% or less.

[0018] According to one embodiment of the present invention, the first polymer binder of the core portion of the core-shell structure may include one selected from polystyrene, polyvinylidene fluoride, an acrylic copolymer, polyvinylacetate, polyvinylalcohol, and combinations thereof.

[0019] According to one embodiment of the present invention, the second polymer binder of the shell portion of the core-shell structure may include one selected from polyvinylidene fluoride, an acrylic copolymer, polyvinyl acetate, polyvinyl alcohol, and a combination thereof.

[0020] One embodiment of the present invention provides an electrochemical device comprising: an anode; a cathode; and a separator interposed between the anode and the cathode.

[0021] According to one embodiment of the present invention, the electrochemical device further includes an electrolyte, and the electrolyte may be an electrolyte including one solvent selected from ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and combinations thereof.

[0022] According to one embodiment of the present invention, the electrolyte may further include one selected from polyvinylidene fluoride, an acrylic copolymer, polyvinyl acetate, polyvinyl alcohol, and combinations thereof, by dissolving the second polymer binder of the shell portion.

[0023] A separator for an electrochemical device according to one embodiment of the present invention can improve cell resistance and cell performance by controlling the solubility of a second polymer binder in the electrolyte of a shell portion of a polymer binder particle having a core-shell structure included in an adhesive layer.

[0024] An electrochemical device according to one embodiment of the present invention has excellent assembly processability by maintaining dry adhesiveness even in a high-temperature moving environment of a separator, and can secure a movement path of lithium by dissolving some of the binder particles that can act as resistance in the coating layer into the electrolyte.

[0025] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0026] Figure 1 is a drawing showing the structure of an electrochemical device according to one embodiment of the present invention.

[0027] FIG. 2 is a drawing showing the structure of a separator of an electrochemical device according to one embodiment of the present invention.

[0028] Figure 3 is a SEM (Scanning Electronic Microscopic) image of the surface of a separator of an electrochemical device according to one embodiment of the present invention.

[0029] Figure 4 is a graph showing the capacity retention rate of an electrochemical device according to one embodiment of the present invention.

[0030] FIG. 5 is a drawing for explaining an automobile including a battery pack composed of the electrochemical device of FIG. 1.

[0031] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will appreciate that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to facilitate understanding of various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated relative to other elements. Furthermore, elements of known technology that are useful or essential in commercially feasible embodiments may often not be depicted so as not to obscure the spirit of various embodiments of the present invention.

[0032] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0033] In this specification, “A and / or B” means “A and B, or A or B.”

[0034] In this specification, when it is said that a component is “on”, this does not exclude other components being placed therebetween, unless otherwise specifically stated, but rather means that other components may be placed thereon.

[0035] In this specification, the characteristic of “having pores” means that the object includes a plurality of pores and that the pores are interconnected with each other, thereby allowing gaseous and / or liquid fluids to pass from one side of the object to the other side.

[0036] In this specification, the separator has a porous characteristic including a large number of pores, and acts as a porous ion-conducting barrier that allows ions to pass while blocking electrical contact between the cathode and the anode in an electrochemical device.

[0037] Separators made of porous polymer substrates, commonly used in electrochemical devices, exhibit extreme thermal shrinkage behavior at high temperatures and other conditions due to their material and manufacturing process characteristics, leading to stability issues such as internal short circuits. Recently, to ensure the safety of lithium secondary batteries, a separator has been developed that forms an organic / inorganic composite porous coating layer by coating a mixture of inorganic particles and polymer binder particles onto a porous polymer substrate.

[0038] Typically, electrode assemblies are manufactured through a lamination process that bonds the separator and electrode using heat and pressure. The higher the heat and pressure applied during this process, the stronger the bonding strength between the electrode and separator. Recently, as the process speed has increased for the purpose of improving productivity, the time for which heat is applied to the separator has shortened, and the adhesive strength has been secured by increasing the pressure. However, the high pressure causes the organic / inorganic composite porous coating layer to press against the porous polymer substrate, reducing its thickness and causing deformation of the pore structure. In addition, if the inorganic particles are locally aggregated or form protrusions, it can damage the porous polymer substrate, ultimately leading to a decrease in the insulating properties of the separator.

[0039] Meanwhile, in order to bond the separator and electrode, an adhesive layer can be coated on the surface of the separator, and various polymers are applied to the adhesive layer. The present invention provides a separator for an electrochemical device and a method for manufacturing the same, which can increase the adhesive strength of the separator while reducing cell resistance and improving cell performance by controlling the structure and properties of the binder included in the adhesive layer of the separator for an electrochemical device.

[0040] Hereinafter, the present invention will be described in more detail.

[0041] Referring to FIG. 1, an electrochemical device (100) (e.g., a lithium secondary battery) to which a separator according to one embodiment of the present invention is applied includes an electrode assembly comprising a positive electrode (110), a negative electrode (120) facing the positive electrode (110), a separator (130) interposed between the positive electrode (110) and the negative electrode (120), and a battery case (150) that accommodates a non-aqueous electrolyte (140) and the electrode assembly and the non-aqueous electrolyte (140). The lithium secondary battery can be manufactured by housing the electrode assembly and then injecting the non-aqueous electrolyte (140) described above.

[0042] A lithium electrochemical device (100) according to one embodiment of the present invention can be manufactured in a prismatic type, a pouch type, and a cylindrical type, for example, depending on the manufacturing form.

[0043] According to one embodiment of the present invention, a separator (130) for an electrochemical device includes a porous polymer substrate (132); a coating layer (134) provided on at least one surface of the porous polymer substrate and including inorganic particles; and an adhesive layer (136) provided on the coating layer (134) and including a polymer binder having a core-shell structure, wherein the separator (130) for an electrochemical device includes a first polymer binder of a core portion of the core-shell structure and a second polymer binder of a shell portion of the core-shell structure, and the solubility of the second polymer binder of the shell portion in an electrolyte is about 95% or more.

[0044] The electrochemical device separator (130) according to one embodiment of the present invention can improve the cell resistance and cell performance of the electrochemical device by controlling the solubility of the second polymer binder in the electrolyte of the shell portion of the polymer binder particle having a core-shell structure included in the adhesive layer (136).

[0045] According to one embodiment of the present invention, the electrochemical device separator (130) includes a porous polymer substrate (132). As described above, the electrochemical device separator (130) includes the porous polymer substrate (132), thereby allowing lithium ions to pass through while blocking electrical contact, and implementing a shutdown function at an appropriate temperature.

[0046] According to one embodiment of the present invention, the porous polymer substrate (132) may be manufactured using a polyolefin-based resin as a base resin. Examples of the polyolefin-based resin include polyethylene, polypropylene, polypentene, etc., and the porous polymer substrate (132) may include one or more of these. A porous separation membrane (130) manufactured using such a polyolefin-based resin as a base resin, i.e., having a large number of pores, can provide a shutdown function at an appropriate temperature.

[0047] According to one embodiment of the present invention, the weight average molecular weight (Mw) of the polyolefin resin may be about 500,000 or more and 1.5 million or less. By controlling the weight average molecular weight of the polyolefin resin within the above-described range, the compression resistance of the separator can be improved. Furthermore, when different types of polyolefin resins are mixed and used or the separator is formed with a multilayer structure made of different types of polyolefin resins, the weight average molecular weight (Mw) of the polyolefin resin can be calculated by adding the weight average molecular weights (Mw) according to the content ratio of each polyolefin resin.

[0048] In one embodiment of the present invention, the weight average molecular weight (Mw) can be measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies), and the measurement conditions can be set as follows.

[0049] - Column: PL Olexis (Polymer Laboratories)

[0050] - Solvent: TCB (Trichlorobenzene)

[0051] - Flow rate: 1.0 ml / min

[0052] - Sample concentration: 1.0 mg / ml

[0053] - Injection volume: 200 ㎕

[0054] - Column temperature: 160 ℃

[0055] - Detector: Agilent High Temperature RI detector

[0056] - Standard: Polystyrene (corrected with a cubic function)

[0057] According to one embodiment of the present invention, the porous polymer substrate (132) may be manufactured by a method (wet method) of mixing a polyolefin resin with a plasticizer (diluent) at a high temperature to form a single phase, separating the polymer material and the plasticizer during a cooling process, extracting the plasticizer to form pores, and then stretching and heat-setting the result.

[0058] According to one embodiment of the present invention, the average size of the pores and the maximum size of the pores of the separation membrane (130) can be easily manufactured by a person skilled in the art by controlling the mixing ratio of the plasticizer, the stretching ratio, the heat-setting treatment temperature, etc. to conform to the scope of the present invention.

[0059] According to one embodiment of the present invention, the thickness of the porous polymer substrate may be about 1 ㎛ to 30 ㎛. For example, the thickness of the porous polymer substrate may be about 2 ㎛ to 28 ㎛, about 3 ㎛ to 26 ㎛, about 4 ㎛ to 24 ㎛, about 5 ㎛ to 22 ㎛, about 6 ㎛ to 20 ㎛, about 7 ㎛ to 18 ㎛, about 8 ㎛ to 16 ㎛, about 9 ㎛ to 14 ㎛, or about 9 ㎛ to 12 ㎛. By controlling the thickness of the porous polymer substrate within the above-described range, the volume of the electrochemical device (100) can be minimized, and the positive electrode (110) and the negative electrode (120) can be electrically insulated.

[0060] According to one embodiment of the present invention, the electrochemical device separator (130) includes a coating layer (134) provided on at least one surface of the porous polymer substrate (132). For example, the electrochemical device separator (130) includes a coating layer (134) provided on one or both surfaces of the porous polymer substrate (132). As described above, since the electrochemical device separator (130) includes a coating layer (134) provided on at least one surface of the porous polymer substrate (132), the heat resistance of the separator (130) can be improved, mechanical properties can be improved, and the separator (130) can be prevented from shrinking at high temperatures, thereby causing an electrical short circuit of the electrode.

[0061] According to one embodiment of the present invention, the coating layer (134) includes inorganic particles. As described above, by including the inorganic particles in the coating layer (134), the heat resistance of the separator (130) can be improved.

[0062] According to one embodiment of the present invention, the coating layer (134) may further include binder particles. As described above, the coating layer (134) includes inorganic particles and binder particles, thereby improving the heat resistance of the separator (130), improving the mechanical properties, preventing the separator (130) from shrinking at high temperatures and causing an electrical short circuit in the electrode, and forming pores within the coating layer (134).

[0063] According to one embodiment of the present invention, a coating layer (134) may be formed using a composition for forming a coating layer including the mixture of the inorganic particles and the binder particles. By using a composition for forming a coating layer including the mixture of the inorganic particles and the binder particles as described above, the convenience of the work for forming the coating layer (134) can be improved, and the viscosity of the composition for forming the coating layer can be easily controlled.

[0064] According to one embodiment of the present invention, the composition for forming a coating layer may further include a solvent. As described above, by the composition for forming a coating layer further including a solvent, the convenience of the operation for forming a coating layer (134) can be improved, and the mixture of inorganic particles and binder particles can be uniformly dispersed within the composition for forming a coating layer. In the present specification, the solvent may refer to a dispersion medium, and an emulsion in which the mixture of inorganic particles and binder particles is dispersed by the solvent may refer to the composition for forming a coating layer.

[0065] According to one embodiment of the present invention, the solvent may be one selected from water, acetone, ethanol, isopropyl alcohol (IPA), dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), acetonitrile, and combinations thereof. For example, the solvent may be water. By selecting the solvent from the above, the viscosity of the composition for forming the coating layer can be controlled, and the dispersibility of the inorganic particles and the polymer binder within the solvent can be improved.

[0066] According to one embodiment of the present invention, the composition for forming the coating layer may further include an additive. As described above, by further including an additive in the composition for the inorganic coating layer, the binding force of the inorganic particles can be improved, and the dispersibility of the composition for the inorganic coating layer can be improved.

[0067] According to one embodiment of the present invention, the additive may include a dispersant, a surfactant, an antifoaming agent, a flame retardant, an adhesion promoter, etc. By selecting the additive from the above, the dispersibility and phase stability of the composition for the inorganic coating layer can be improved, bubbles can be removed or flame retardancy can be added, adhesive strength can be improved, and wettability between the porous polymer substrate (132) and the composition for forming the coating layer can be improved.

[0068] According to one embodiment of the present invention, the dispersant may include at least one selected from polyacrylic acid, oil-soluble polyamine, oil-soluble amine compound, fatty acid, fatty alcohol, sorbitan fatty acid ester, tannic acid, and pyrogallic acid. For example, the dispersant may be polyacrylic acid (PAA). By selecting the dispersant from the above-described ones, the dispersibility and phase stability of the composition for the inorganic coating layer can be improved.

[0069] According to one embodiment of the present invention, the content of the dispersant may be about 0 to 5 parts by weight based on 100 parts by weight of the composition for forming the coating layer. For example, the content of the dispersant may be about 0 to 5 parts by weight based on 100 parts by weight of the composition for forming the coating layer, about 1 to 4 parts by weight based on 100 parts by weight of the composition for forming the coating layer, or about 1 to 3 parts by weight based on 100 parts by weight of the composition for forming the coating layer. By adjusting the content of the dispersant within the above-described range, the dispersibility and phase stability of the composition for forming the coating layer can be improved.

[0070] According to one embodiment of the present invention, the coating layer (134) includes a plurality of pores. The coating layer (134) includes a plurality of micropores. The plurality of pores may be formed by binder particles and inorganic particles included in the binder particle mixture being densely packed in the coating layer (134), and may be a plurality of micropores resulting from an interstitial volume formed between the inorganic particles. These micropores have a structure in which they are connected to each other, and exhibit a porous structure in which gas or liquid can pass from one side to the other side. As described above, by the coating layer including a plurality of pores, the electrolyte (140) in the battery (100) described below is allowed to permeate the separator (130).

[0071] According to one embodiment of the present invention, the inorganic particles are not particularly limited as long as they are electrochemically stable. For example, the inorganic particles 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 addition, when inorganic particles having ion transfer capability are used, the ion conductivity within the electrochemical device can be increased, thereby improving performance. Meanwhile, when inorganic particles having a high dielectric constant are used as inorganic particles, the ion conductivity of the electrolyte can be improved by contributing to an increase in the degree of dissociation of an electrolyte salt, such as a lithium salt, in a liquid electrolyte. The inorganic particles may include high-dielectric constant inorganic particles having a dielectric constant of 5 or more or 10 or more, inorganic particles having a lithium ion transfer capability, or a mixture thereof. For example, the inorganic particles may include BaSO4, BaTiO3, Pb(Zr, Ti)O3(PZT), Pb 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, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, aluminum peroxide, zinc tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), antimony pentoxide (Sb2O5), boehmite (AlO(OH)) and combinations thereof, but these are only examples and are not limited thereto.

[0072] According to one embodiment of the present invention, the average particle diameter (D50) of the inorganic particles is not particularly limited, but may be in the range of about 0.1 ㎛ to 1 ㎛ in order to form a coating layer (134) of uniform thickness and have an appropriate porosity. For example, if it is less than about 0.1 ㎛, the dispersibility of the inorganic particles in the slurry prepared for manufacturing the coating layer (134) may be reduced, and if it exceeds 1 ㎛, the thickness of the formed coating layer (134) may increase.

[0073] In this specification, "D50 particle size" means the particle size at the 50% point of the cumulative distribution of particle numbers according to particle size. The particle size can be measured using a 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 when the particles pass through the laser beam, the difference in the diffraction pattern according to the particle size is measured to calculate the particle size distribution. By calculating the particle diameter at the point where the cumulative distribution of particle numbers according to particle size in the measuring device becomes 50%, the D50 particle size can be measured.

[0074] According to one embodiment of the present invention, the content of the inorganic particles may be about 70 parts by weight or more and 98 parts by weight or less, based on 100 parts by weight of the composition for a coating layer. For example, the content of the inorganic particles may be about 72 parts by weight or more and 97 parts by weight or less, about 74 parts by weight or more and 96 parts by weight or less, about 76 parts by weight or more and 96 parts by weight or less, about 78 parts by weight or more and 96 parts by weight or less, about 80 parts by weight or more and 96 parts by weight or less, about 82 parts by weight or more and 96 parts by weight or less, about 84 parts by weight or more and 96 parts by weight or less, about 86 parts by weight or more and 96 parts by weight or less, about 88 parts by weight or more and 96 parts by weight or less, or about 90 parts by weight or more and 95 parts by weight or less, based on 100 parts by weight of the composition for a coating layer. By controlling the content of the inorganic particles within the above-described range, the insulation and heat resistance of the separator (130) can be improved, thereby preventing the phenomenon of the separator (130) shrinking at high temperatures.

[0075] According to one embodiment of the present invention, the binder particles in the coating layer (134) may be an acrylic binder and / or a polyvinylidene binder. As described above, by selecting an acrylic binder, the binder particles can maintain the porosity of the separator (130), and improve the adhesive strength between the electrodes (110, 120) and the separator (130) in the lamination process of the battery, thereby improving the ease of battery manufacturing, and stably implementing the stacking process. In addition, by selecting a polyvinylidene binder as the binder particles, the porosity of the separator (130) can be maintained, and even if the coating layer is wetted by an electrolyte after activation of the battery, the adhesive strength can be maintained. Furthermore, the stiffness of the battery can be improved, and bending of the battery can be prevented.

[0076] The above acrylic polymer is a polymer containing a carboxylic acid ester as a repeating unit, and may be, for example, a (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0077] According to one embodiment of the present invention, specific examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, n-amyl (meth)acrylate, i-amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, ethylene glycol (meth)acrylate, di(meth)acrylate, propylene glycol (meth)acrylate, Examples thereof include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, and ethylene di(meth)acrylate, and the like, and may be at least one selected from these. Among these, the compound may be at least one selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, or may be methyl (meth)acrylate.

[0078] According to one embodiment of the present invention, the acrylic-styrene copolymer may include an acrylic binder, and the acrylic binder may be a polyacrylate. For example, the binder may be at least one selected from styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate polymers, and for example, may be a copolymer including acrylate.

[0079] In addition, the polyvinylidene-based binder may be a copolymer of polyvinylidene fluoride and hexafluoropropylene. For example, it may be a polyvinylidene-based binder having a hexafluoropropylene content of about 1 wt% or more and 50 wt% or less. As described above, by selecting the polyvinylidene-based binder as a polyvinylidene-based binder having a hexafluoropropylene content of about 1 wt% or more and 50 wt% or less, the porosity of the separator (130) can be maintained, and even if the coating layer (134) is wetted by the electrolyte (140) after activation of the battery, the adhesive strength can be maintained.

[0080] According to one embodiment of the present invention, the coating layer (134) has a microporous structure due to the interstitial volume between the inorganic particles and the binder particles. In addition, it also functions as a kind of spacer that can maintain the physical shape of the coating layer. The interstitial volume refers to a space defined by the substantial contact between the inorganic particles and the binder particles. In addition, since the inorganic particles generally have a characteristic in which their physical properties do not change even when exposed to a high temperature of about 200°C or higher, the separation membrane (130) has excellent heat resistance due to the coating layer (134).

[0081] According to one embodiment of the present invention, the content of the binder particles may be about 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the coating layer (134). For example, the content of the binder particles may be about 2 parts by weight or more and 9 parts by weight or less, about 3 parts by weight or more and 8 parts by weight or less, about 4 parts by weight or more and 7 parts by weight or less, about 4 parts by weight or more and 6 parts by weight or less, or about 4 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the coating layer. By controlling the content of the binder particles within the above-described range, the resistance of the separator (130) can be reduced and the adhesive strength can be improved.

[0082] According to one embodiment of the present invention, the coating layer (134) may have a thickness of about 0.1 ㎛ to 5 ㎛, about 0.5 ㎛ to 4 ㎛, or about 0.5 ㎛ to 3 ㎛, about 0.5 ㎛ to 2 ㎛, or about 0.5 ㎛ to 1.5 ㎛, based on the thickness formed on one side of the porous polymer substrate (132), and may be, for example, about 1.5 ㎛. By controlling the thickness of the coating layer within the above-described range, it is possible to thin the separation membrane.

[0083] In one embodiment of the present invention, the thickness of the porous polymer substrate (132) and / or the coating layer (134) can be measured using a contact thickness measuring device. For example, the VL-50S-B from Mitutoyo can be used as the contact thickness measuring device.

[0084] According to one embodiment of the present invention, the separator (130) is provided on the coating layer (134) and includes an adhesive layer (136) including a polymer binder having a core-shell structure. The core-shell structure refers to a multi-layer structure formed by a shell portion covering the surface of a core portion. As described above, by including the adhesive layer (136) including the polymer binder having the core-shell structure, two binders having a multi-layer structure are included in one particle, and the adhesive strength can be controlled within a desired range by utilizing the characteristics and advantages of each binder, while at the same time, a lithium movement path can be secured even after the electrolyte (140) is injected.

[0085] According to one embodiment of the present invention, the core-shell structure can be maintained even after the electrolyte (140) is injected, a part of the shell portion can be dissolved in the electrolyte (140) so that a part of the remaining shell portion can remain on the core portion, or the entire shell portion can be dissolved in the electrolyte (140) so that only the core portion remains. However, this may vary depending on the degree of solubility of the polymer binder particles included in the shell portion and the core portion in the electrolyte (140).

[0086] According to one embodiment of the present invention, the adhesive layer (136) includes a first polymer binder of the core portion of the core-shell structure and a second polymer binder of the shell portion of the core-shell structure.

[0087] According to one embodiment of the present invention, the first polymer binder of the core portion of the core-shell structure may include one selected from polystyrene, polyvinylidene fluoride, an acrylic copolymer, polyvinylacetate, polyvinylalcohol, and combinations thereof. As described above, the first polymer binder includes one selected from the elements or combinations thereof, so that it is not easily dissolved by an electrolyte solvent even after the electrolyte (140) is injected, thereby improving adhesive strength and membrane resistance.

[0088] According to one embodiment of the present invention, the acrylic copolymer may include an ethyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(dimethylamino)ethyl acrylate copolymer, an ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, butyl acrylate, or two or more thereof, and may be, for example, butyl acrylate.

[0089] According to one embodiment of the present invention, the second polymer binder of the shell portion of the core-shell structure may include one selected from polyvinylidene fluoride, an acrylic copolymer, polyvinyl acetate, polyvinyl alcohol, and a combination thereof. As described above, the second polymer binder includes one selected from the above elements or a combination thereof, so that after the electrolyte (140) is injected, some of the second polymer binder is dissolved by the electrolyte solvent to secure a movement path of lithium, thereby improving the resistance of the separator (130).

[0090] According to one embodiment of the present invention, the acrylic copolymer may include any one monomer selected from the group consisting of methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, acrylonitrile, and acrylamide. For example, the acrylic copolymer may include, but is not limited to, an ethyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(dimethylamino)ethyl acrylate copolymer, an ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, an acrylonitrile-methyl acrylate copolymer, an acrylonitrile-ethyl acrylate copolymer, an acrylonitrile-butyl acrylate copolymer, or two or more thereof.

[0091] According to one embodiment of the present invention, the second polymer binder of the shell portion of the core-shell structure may be, for example, a copolymer of methyl methacrylate and butyl acrylate. As described above, by selecting a copolymer of methyl methacrylate and butyl acrylate as the second polymer binder of the shell portion of the core-shell structure, the solubility in the electrolyte (140) can be controlled, thereby improving the cell resistance and cell performance of the electrochemical device.

[0092] According to one embodiment of the present invention, the solubility of the second polymer binder of the shell portion in the electrolyte (140) is about 95% or more. As described above, the solubility of the second polymer binder of the shell portion in the electrolyte is about 95% or more, so that the dry adhesive force is maintained even in a high-temperature moving environment of the separator, thereby improving the assembly processability, and some of the binder particles that can act as resistance to the adhesive layer (136) can be dissolved in the electrolyte (140) to secure a movement path of lithium.

[0093] According to one embodiment of the present invention, the solubility of the second polymer binder of the shell portion in the electrolyte (140) may be about 96% or more and 99% or less. As described above, by including the solubility of the second polymer binder of the shell portion in the electrolyte (140) being about 96% or more and 99% or less, the dry adhesive force is maintained even in a high-temperature moving environment of the separator, so that the assembly process is excellent, and some of the binder particles that may act as resistance to the adhesive layer can be dissolved in the electrolyte, thereby securing a movement path of lithium.

[0094] According to one embodiment of the present invention, the glass transition temperature of the first polymer binder may be about 70°C or higher. For example, the glass transition temperature of the first polymer binder may be about 70°C or higher and 120°C or lower, about 75°C or higher and 115°C or lower, about 80°C or higher and 110°C or lower, about 85°C or higher and 105°C or lower, about 87°C or higher and 103°C or lower, about 89°C or higher and 101°C or lower, or about 90°C or higher and 100°C or lower. By controlling the glass transition temperature of the first polymer binder within the above-described range, the fluidity of the binder can be reduced, thereby preventing film formation and preventing changes in adhesive strength over time.

[0095] According to one embodiment of the present invention, the glass transition temperature of the second polymer binder may be about 0°C or more and 40°C or less. For example, the glass transition temperature of the second polymer binder may be about 5°C or more and 35°C or less, about 10°C or more and 30°C or less, or about 15°C or more and 30°C or less. By controlling the glass transition temperature of the second polymer binder within the above-described range, the adhesive strength between the separator (130) and the electrodes (110, 120) may be improved.

[0096] According to one embodiment of the present invention, the particle size of the core-shell structure may be about 200 nm to 800 nm. For example, the particle size of the core-shell structure may be about 250 nm to 750 nm, about 300 nm to 700 nm, about 350 nm to 650 nm, about 370 nm to 630 nm, about 390 nm to 610 nm, or about 400 nm to 600 nm. In the above-described range, the phenomenon of the particles of the core-shell structure being soaked between inorganic substances in the coating layer is suppressed, and the rate of blocking the surface of the separation membrane does not become unnecessarily high, and an appropriate resistance can be maintained.

[0097] According to one embodiment of the present invention, the gel content of the first polymer binder at room temperature is about 99% or more, the gel content of the second polymer binder at room temperature is about 5% or less, and the gel content may be calculated by the following equation 1.

[0098] [Formula 1]

[0099] Gel content (%) = W 24 / W0X 100

[0100] In the above equation 1,

[0101] W 24 is the weight measured after immersion in the electrolyte for 24 hours, and W0 is the weight measured before immersion.

[0102] That is, the above gel content (%) may refer to the proportion of polymer that remains undissolved when immersed in an electrolyte for 24 hours.

[0103] According to one embodiment of the present invention, the electrolyte (140) is a solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, in which LiPF6 as an electrolyte salt is dissolved at a concentration of 1.0 M.

[0104] According to one embodiment of the present invention, the gel content of the first polymer binder at room temperature may be about 99% or more and 100% or less. By controlling the gel content of the first polymer binder at room temperature within the above-described range, the core portion of the adhesive layer is entirely crosslinked and does not dissolve in the electrolyte (140), thereby enabling adhesive strength to be realized.

[0105] According to one embodiment of the present invention, the gel content of the second polymer binder at room temperature may be about 0% or more and 5% or less. By controlling the gel content of the second polymer binder at room temperature within the above-described range, a significant portion of the shell portion of the adhesive layer is dissolved in the electrolyte, thereby forming pores in the shell portion, thereby facilitating the movement of lithium ions.

[0106] According to one embodiment of the present invention, the swelling ratio of the polymer binder having the core-shell structure may be 100% or less. The swelling ratio may be calculated by the following equation 2.

[0107] [Formula 2]

[0108] Swelling (%) = V 24 / V0X 100

[0109] In the above equation 2,

[0110] V 24 is the volume measured after immersion in the electrolyte for 24 hours, and V0 is the volume measured before immersion.

[0111] According to one embodiment of the present invention, the electrolyte is a solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, in which LiPF6 as an electrolyte salt is dissolved at a concentration of 1.0 M.

[0112] For example, the swelling ratio of the polymer binder of the core-shell structure may be about 0% to 100%, about 45% to 100%, about 10% to 90%, about 20% to 80%, about 30% to 70%, about 40% to 60%, or about 45% to 55%. In the above-described range, the volume change of the binder does not increase unnecessarily, and the blocking of pores on the surface of the membrane can be prevented or suppressed.

[0113] According to one embodiment of the present invention, the thickness of the shell portion of the core-shell structure may be about 40 nm or more and 600 nm or less. For example, the thickness of the shell portion of the core-shell structure is about 40 nm to 580 nm, about 40 nm to 560 nm, about 40 nm to 540 nm, about 40 nm to 520 nm, about 40 nm to 500 nm, about 40 nm to 480 nm, about 40 nm to 460 nm, about 40 nm to 440 nm, about 40 nm to 420 nm, about 40 nm to 400 nm, about 40 nm to 380 nm, about 40 nm to 360 nm, about 40 nm to 340 nm, about 40 nm to 320 nm, about 40 nm to 300 nm, about 50 nm to 280 nm, about 60 nm to 260 nm, about 70 nm to 70 It may be 240 nm or less, about 80 nm or more and 220 nm or less, about 90 nm or more and 200 nm or less, about 90 nm or more and 180 nm or less, about 90 nm or more and 160 nm or less, about 90 nm or more and 140 nm or less, about 90 nm or more and 120 nm or less, or about 90 nm or more and 100 nm or less. As described above, by controlling the thickness of the shell portion of the core-shell structure, the adhesive force can be maintained and the cell resistance of the electrochemical device (100) can be suppressed and the performance can be improved as the shell portion is dissolved after impregnation with the electrolyte (140).

[0114] One embodiment of the present invention provides a method for manufacturing a separator (130) for the electrochemical device (100) and a method for manufacturing the electrochemical device (100).

[0115] According to one embodiment of the present invention, first, in order to form an adhesive layer, polymer binder particles having a core-shell structure are added and dispersed to prepare a slurry for forming an adhesive layer. The polymer binder particles having the core-shell structure can be prepared by various known methods such as emulsion polymerization, suspension polymerization, massive polymerization, solution polymerization, or bulk polymerization, and for example, can be prepared by an emulsion polymerization or solution polymerization method.

[0116] According to one embodiment of the present invention, the method of applying the slurry for forming the adhesive layer (136) to the surface of the coating layer (134) on the porous polymer substrate (132) is not particularly limited to any one method, and a conventional method known in the art can be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a mixture thereof can be used.

[0117] According to one embodiment of the present invention, the loading amount of the slurry for the adhesive layer is about 0.3 g / m 2 More than 1.5 g / m 2 It may be as follows. The phenomenon of the bonded area increasing after the lamination process within the above-described range is prevented or suppressed, and accordingly, the wettability by the electrolyte is not reduced, and the phenomenon of the bonded area narrowing after the lamination process is prevented or suppressed, and accordingly, the decrease in adhesive strength can be prevented.

[0118] According to one embodiment of the present invention, a step of drying the slurry for forming the adhesive layer (136) to form the adhesive layer (136) is included. By including a step of drying the slurry for forming the adhesive layer as described above to form the coating layer (134), damage to the adhesive layer (136) can be minimized, and the solvent included in the slurry can be easily removed.

[0119] According to one embodiment of the present invention, the drying process appropriately sets time conditions so as to minimize the occurrence of surface defects in the adhesive layer (136). The drying may be performed using a drying auxiliary device such as a drying oven or hot air within an appropriate range.

[0120] According to one embodiment of the present invention, the separator (130) is interposed between the negative electrode (120) and the positive electrode (110) and is manufactured into an electrochemical device (100) through a lamination process that applies heat and / or pressure to bond them. In one embodiment of the present invention, the lamination process can be performed by a roll press device including a pair of pressure rollers. For example, the negative electrode (120), the separator (130), and the positive electrode (110) can be sequentially laminated and placed between the pressure rollers to achieve interlayer bonding. At this time, the lamination process can be performed by a hot press method.

[0121] In addition, the electrochemical device (100) can be manufactured by loading an electrode assembly in which a cathode (120), a separator (130), and an anode (110) are laminated and assembled into a battery case (150) and then injecting an electrolyte (140).

[0122] According to one embodiment of the present invention, the injection of the electrolyte (140) may be performed at an appropriate stage during the battery manufacturing process, depending on the manufacturing process and required physical properties of the final product. That is, it may be applied before battery assembly or at the final stage of battery assembly. In addition to the general winding process, lamination (stack) and folding processes of the separator (130) and the electrodes (110, 120) may be possible as a process for applying the electrode assembly of the present invention to a battery.

[0123] Figure 3 is an SEM image of the surface of an adhesive layer (136) according to one embodiment of the present invention. For example, SEM images are shown for the initial coating state (Fresh), the state after lamination at 60°C and 6.5 MPa (After Lamination (60°C / 6.5 MPa)), and the state after electrolyte impregnation (After Wetting Electrolyte), respectively.

[0124] According to the above FIG. 3, it can be seen that the core-shell structured polymer binder particles are bonded to each other after the lamination process, and after the electrolyte impregnation, some of the polymer binder particles of the shell portion among the core-shell structured polymer binder particles bonded to each other can dissolve into the electrolyte to secure a lithium movement path, and the polymer binder particles of the core portion remain as they are, so that the adhesive force between the electrode (110, 120) and the separator (130) is maintained. At this time, the core-shell structure may be maintained in the same manner even after the electrolyte impregnation, and some of the shell portion may dissolve into the electrolyte (140) so that some of the remaining shell portion may remain on the core portion, or the entire shell portion may dissolve into the electrolyte (140) so that only the core portion remains. However, this may vary depending on the degree of electrolyte solubility of the polymer binder particles included in the shell portion and the core portion.

[0125] One embodiment of the present invention includes an electrochemical device (100) including a positive electrode (110); a negative electrode (120); and a separator (130) interposed between the positive electrode (110) and the negative electrode (120). The electrochemical device (100) includes all devices that perform an electrochemical reaction, and includes, for example, all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. For example, among the secondary batteries, it may be a lithium ion secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0126] An electrochemical device (100) according to one embodiment of the present invention has excellent assembly processability because dry adhesiveness is maintained even in a high-temperature moving environment of a separator (130), and a portion of binder particles that can act as resistance to the coating layer (134) can be dissolved in an electrolyte (140) to secure a movement path of lithium.

[0127] According to one embodiment of the present invention, the positive electrode (110) 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, LiV3O4, 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 1-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.

[0128] According to one embodiment of the present invention, the negative electrode (120) 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 negative electrode current collector. The negative electrode includes carbon such as lithium metal oxide, non-graphitizable carbon, and graphite carbon as the negative electrode active material; LixFe2O3(0≤x≤1), Li x WO2(0≤x≤1), Si, SiO x (0 <x<2), SiC, Si 합금 등의 실리콘계 재료; 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; 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.

[0129] According to one embodiment of the present invention, the positive electrode current collector and / or the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the electrochemical device (100), and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., etc. can be used.

[0130] According to one embodiment of the present invention, the conductive material may be one or a mixture of two or more conductive materials selected from graphite, carbon black, carbon fibers or metal fibers, metal powder, conductive whiskers, conductive metal oxides, carbon nanotubes, activated carbon, and polyphenylene derivatives. The carbon nanotubes have a graphite sheet having a cylindrical shape with a nano-sized diameter, and sp 2 It has a bonding structure, and exhibits the characteristics of a conductor or a semiconductor depending on the angle and structure at which the graphite plane is rolled. Carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs) depending on the number of bonds forming the wall, and these carbon nanotubes can be appropriately selected depending on the use of the dispersion. According to one embodiment, it can be one selected from 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 therefrom.

[0131] According to one embodiment of the present invention, the binder resin may be a binder resin commonly used in electrodes in the art. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, 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, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxyl methyl cellulose.

[0132] According to one embodiment of the present invention, the positive electrode slurry for manufacturing the positive electrode active material layer may include a dispersant, and the dispersant may be a pyrrolidone-based compound. Specifically, it may be N-methylpyrrolidone (ADC-01, LG Chemical).

[0133] According to one embodiment of the present invention, the content of the dispersant included in the positive electrode slurry may be about 0 part by weight or more and 0.5 part by weight or less with respect to 100 parts by weight of the positive electrode slurry. For example, the content of the dispersant included in the positive electrode slurry may be about 0.05 part by weight or more and 0.4 part by weight or less with respect to 100 parts by weight of the positive electrode slurry.

[0134] According to one embodiment of the present invention, the negative electrode slurry for manufacturing the negative electrode active material layer may include a dispersant, and the dispersant may be a polypyrrolidone-based compound. For example, the dispersant may be polyvinylpyrrolidone (Polyvinylpyrrolidone, Junsei, Japan).

[0135] According to one embodiment of the present invention, the content of the dispersant included in the cathode slurry may be about 0 part by weight or more and 0.5 part by weight or less with respect to 100 parts by weight of the cathode slurry. For example, the content of the dispersant included in the cathode slurry may be about 0.05 part by weight or more and 0.4 part by weight or less with respect to 100 parts by weight of the cathode slurry.

[0136] According to one embodiment of the present invention, the electrochemical device (100) further includes an electrolyte (140), and the electrolyte may be an electrolyte (140) including one solvent selected from ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and combinations thereof.

[0137] The above electrolyte (140) is A + B- As a salt with the same structure as 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 - , FSi - , PO2F2 - Salts containing anions such as or combinations thereof are dissolved or dissociated in organic solvents such as 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 mixtures thereof, but are not limited thereto.

[0138] In one embodiment, the electrolyte may include a solvent comprising a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC). Specifically, the electrolyte may include ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0139] According to one embodiment of the present invention, the electrolyte (140) is a solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, in which LiPF6 as an electrolyte salt is dissolved at a concentration of 1.0 M.

[0140] According to one embodiment of the present invention, the electrolyte (140) may further include one selected from polyvinylidene fluoride, an acrylic copolymer, polyvinylacetate, polyvinylalcohol, and combinations thereof, in which the second polymer binder of the shell portion is dissolved. For example, the electrolyte may include methyl methacrylate (MMA) and butyl acrylate (BA) monomers, in which the second polymer binder of the shell portion is dissolved. As described above, the electrolyte (140) can reduce resistance by forming pores at the shell location as much as the second polymer binder of the shell portion is dissolved and containing methyl methacrylate (MMA) and butyl acrylate (BA).

[0141] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not construed as being limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0142]

[0143] <Examples 1 and 2>

[0144] Polyethylene resin (weight average molecular weight 900,000) was extruded and a porous polymer substrate (total thickness of approximately 9 ㎛, porosity of 40% by volume) was manufactured using a wet method.

[0145] Inorganic particles (Al2O3, particle size (D50) 500 nm) and a dispersant (BYK, PAA type) were added to water and dispersed. Then, an acrylic emulsion (CSB-130, Toyo Ink) as a binder particle was added and stirred to prepare a slurry for a coating layer (solid concentration 40 wt%). The weight ratio of the inorganic particles: dispersant: binder particles was 95:1:4 wt%.

[0146] The dispersion was applied to both sides of the porous polymer substrate using a doctor blade by bar coating, and dried with air at 50°C using a heat gun to form a coating layer with a thickness of 1.5 μm on each side.

[0147] Afterwards, as polymer binder particles, the first polymer binder of the core part was a copolymer of polystyrene and butyl acrylate (BA), and the second polymer binder of the shell part was a copolymer of methyl methacrylate (MMA) and butyl acrylate (BA), and these were added to water and dispersed to prepare a slurry for the adhesive layer (solid content concentration 5 wt%).

[0148] The dispersion was applied to both sides of the surface of the coating layer using a doctor blade by bar coating, and dried with wind at 50°C using a heat gun to form an adhesive layer with a thickness of 0.5 μm on each side, thereby manufacturing a separator.

[0149] The characteristics of the polymer binder particles were controlled and shown in Table 1 below, and the separation membranes of Examples 1 and 2 were manufactured.

[0150]

[0151] <Comparative Example 1>

[0152] A separation membrane was manufactured in the same manner as in Example 1, except that the polymer binder particles did not have a core-shell structure and that the polymer binder particles were a copolymer of polystyrene and butyl acrylate (BA), which was the same as the first polymer binder of the core portion of Example 1.

[0153] The characteristics of the polymer binder particles are shown in Table 1 below.

[0154]

[0155] <Comparative Example 2>

[0156] A separator was manufactured in the same manner as in Example 1, except that the polymer binder particles did not have a core-shell structure, and the polymer binder particles were a copolymer of butyl acrylate (BA), methyl methacrylate (MMA), and styrene, and had a crosslinking degree of 95% and were polymers having no solubility in an electrolyte.

[0157] The characteristics of the polymer binder particles are shown in Table 1 below.

[0158]

[0159] <Comparative Example 3>

[0160] A separator was manufactured in the same manner as in Example 1, except that the polymer binder particles did not have a core-shell structure, and the polymer binder particles were a copolymer of butyl acrylate (BA), methyl methacrylate (MMA), and styrene, and had a crosslinking degree of 40% and a solubility in an electrolyte of 49%.

[0161] The characteristics of the polymer binder particles are shown in Table 1 below.

[0162]

[0163] <Comparative Examples 4 to 6>

[0164] Separators of Comparative Examples 4 to 6 were manufactured by controlling the properties of the polymer binder particles, including a core-shell structure having the same binder composition as Examples 1 and 2, as shown in Table 1 below.

[0165]

[0166] <Manufacturing of electrochemical devices>

[0167] 1) Manufacturing of the anode

[0168] Cathode active material (LiNi) 0.8 Mn 0.1 Co 0.1 O2), a conductive agent (carbon black), a dispersant (N-methylpyrrolidone, ADC-01, LG Chemical), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a positive electrode active material layer with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of an aluminum thin film (thickness 10 μm) and dried to manufacture a positive electrode having a positive electrode active material layer (thickness 120 μm).

[0169] 2) Manufacturing of cathode

[0170] Graphite (natural graphite and artificial graphite blend), conductive agent (carbon black), dispersant (polyvinylpyrrolidone, Junsei, Japan), and binder resin (PVDF-HFP and PVDF blend) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for an anode active material layer with a concentration of 50 wt% of the remaining components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 10 μm) and dried to manufacture an anode having an anode active material layer (thickness 120 μm).

[0171]

[0172] <Experimental Example 1: SEM observation of the membrane surface>

[0173] Figure 3 is an SEM image of the surface of a separator according to one embodiment of the present invention. For example, SEM images are shown for the initial coating state (Fresh), the state after lamination (After Lamination), and the state after electrolyte impregnation (After Wetting Electrolyte), respectively.

[0174] Referring to the above Figure 3, it can be seen that after the separator surface of Example 1 is impregnated with the electrolyte, most of the polymer binder particles in the shell portion among the core-shell structured polymer binder particles bonded to the surface are dissolved in the electrolyte, thereby securing a path for lithium movement, and the polymer binder particles in the core portion remain as they are, thereby maintaining the adhesive force between the electrode and the separator.

[0175] In contrast, Comparative Example 2 has a low glass transition temperature of the polymer binder particles, so a film-formed state can be confirmed after lamination. In addition, since it does not have a core-shell structure and the solubility of the polymer binder particles in the electrolyte is 0, a film-formed state was observed with surface adhesion even after electrolyte impregnation.

[0176] Furthermore, in Comparative Example 6, it can be confirmed that the solubility of the polymer binder particles of the shell portion in the electrolyte is low, so that after impregnation with the electrolyte, only a portion of the shell portion is dissolved and the surface is adhered to maintain a film-like state.

[0177]

[0178] <Experimental Example 2: Measurement of Electrode-Separator Dry Adhesion>

[0179] The separators of the above examples and comparative examples were cut into 70 mm (length) x 20 mm (width), and the electrodes and separators were laminated using a press under the conditions of 60 ℃, 6.5 Mpa, and 1 sec to produce specimens. The second specimen was prepared by storing the separator at 60 ℃ for 7 days, then cutting it into 70 mm (length) x 20 mm (width), and laminating the electrodes and separators using a press under the conditions of 60 ℃, 6.5 Mpa, and 1 sec. The prepared specimens were fixed by attaching them to a glass plate using double-sided tape, and at this time, the electrodes were positioned facing the glass plate. The separator portion of the specimen was peeled at an angle of 90° at a speed of 200 mm / min at 25 ℃.

[0180] At this time, the initial adhesive strength and the adhesive strength after 7 days were measured respectively and summarized in Table 1 below.

[0181]

[0182] <Experimental Example 3: Membrane Resistance Measurement>

[0183] Resistance was measured by sandwiching each separator between SUS and injecting electrolyte into coin cells, and measuring resistance (ER) using the EIS method. The frequency range was 100,000 to 10,000 Hz.

[0184]

[0185] <Experimental Example 4: Cell Performance Evaluation>

[0186] The manufactured cell was charged and discharged once at 0.1 C in the voltage range from 3.0 V to 4.25 V in a 25 ℃ chamber, and the capacity retention was confirmed by repeating 100 cycles of 1 C charge and 1 C discharge. The capacity retention was calculated as the ratio of the discharge capacity after 100 cycles to the initial discharge capacity.

[0187]

[0188] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Binder Characteristics Structure Core-Shell Core-Shell Particle Type Particle Type Particle Type Core-Shell Core-Shell Core-Shell Particle Size (nm) 400 600 400 400 400 120 400 400 Tg (℃) Core 90 100 90 40 40 90 90 Shell 30 15 30 60 30 Electrolyte Content (%) Core 0 000 49 00 10 Shell 9 6 9 ... ℃)3135010126530Separator resistance (Ω)0.750.770.750.780.900.770.721.12Cell performanceCapacity retention rate after 100 cycles (%)94.894.5-91.790.8--88.0Evaluation resultAdhesion degradationChange over timeChange over timeResistance degradationAdhesion degradationAdhesion degradationResistance degradation

[0189]

[0190] According to Table 1 above, it can be confirmed that by controlling the binder properties of the core-shell structure in Examples 1 and 2, the adhesive strength is maintained while suppressing the increase in resistance and the cell performance is excellent.

[0191] In contrast, it can be seen that the adhesive strength of Comparative Example 1 is inferior to that of the core-shell structures of Examples 1 and 2 due to the binder having a particle-like structure.

[0192] It can be seen that the above comparative examples 2 and 3 also have a particle-like structure and a swelling degree exceeding 100%, resulting in changes over time and a deterioration in cell performance.

[0193] In the above Comparative Example 4, it can be seen that the binder has a core-shell structure, but the core-shell particle size is insufficient, so the binder penetrates between the inorganic materials of the coating layer, resulting in poor adhesive strength. In the above Comparative Example 5, it can be seen that the binder has a core-shell structure, but the glass transition temperature of the shell portion is too high, resulting in poor adhesive strength.

[0194] It can be seen that the above comparative example 6 has a core-shell structure in terms of binder properties, but the electrolyte solubility of the shell portion is low and the swelling degree is high, resulting in poor resistance.

[0195] In addition, Fig. 4 is a graph showing the capacity retention rate of an electrochemical device (100) according to one embodiment of the present invention. According to Fig. 4, it can be seen that the capacity retention rate (%) after 100 cycles of Comparative Examples 2, 3, and 6 is inferior compared to the capacity retention rate (%) after 100 cycles of Example 1 according to the embodiment of the present invention.

[0196] As described above, the electrochemical device separator (130) according to one embodiment of the present invention and the electrochemical device (100) including the same have a core-shell structure in which the polymer binder of the adhesive layer (136) has a core-shell structure, and the solubility of the second polymer binder of the shell portion of the core-shell in the electrolyte can be controlled to increase adhesive strength, reduce cell resistance, and improve cell lifespan.

[0197] FIG. 5 is a drawing for explaining a vehicle (300) including a battery pack (200) composed of the electrochemical device (100) of FIG. 1. Referring to FIG. 5, a vehicle (300) according to an embodiment of the present invention may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle, and includes a battery pack (200) composed of the electrochemical device (100) according to an embodiment of the present invention. The vehicle (300) includes a four-wheeled vehicle and a two-wheeled vehicle. The vehicle (300) operates by receiving power from the battery pack (200) according to an embodiment of the present invention.

[0198] Although the present disclosure has been described above with reference to embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes to the various embodiments of the present disclosure may be made without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims

1. Porous polymer substrate; A coating layer provided on at least one surface of the porous polymer substrate and including inorganic particles; and It comprises an adhesive layer provided on the above coating layer and including a polymer binder having a core-shell structure, It comprises a first polymer binder in the core portion of the core-shell structure and a second polymer binder in the shell portion of the core-shell structure, A separator for an electrochemical device, wherein the solubility of the second polymer binder of the above shell portion in the electrolyte is 95% or more.

2. In claim 1, A separator for an electrochemical device, wherein the solubility of the second polymer binder of the above shell portion in an electrolyte is 96% or more and 99% or less.

3. In claim 1, A separator for an electrochemical device, wherein the glass transition temperature of the first polymer binder is 70°C or higher.

4. In claim 1, A separator for an electrochemical device, wherein the glass transition temperature of the second polymer binder is 0°C or more and 40°C or less.

5. In claim 1, A separator for an electrochemical device, wherein the particle size of the core-shell structure is 200 nm or more and 800 nm or less.

6. In claim 1, The gel content of the above first polymer binder at room temperature is 99% or more, The gel content of the second polymer binder at room temperature is 5% or less, A separator for an electrochemical device, wherein the gel content is calculated by the following equation 1. [Formula 1] Gel content (%) = W 24 / W0X 100 In the above equation 1, W 24 is the weight measured after immersion in the electrolyte for 24 hours, and W0 is the weight measured before immersion.

7. In claim 1, A separator for an electrochemical device, wherein the swelling ratio of the polymer binder of the core-shell structure is 100% or less.

8. In claim 1, A separator for an electrochemical device, wherein the first polymer binder of the core portion of the core-shell structure comprises one selected from polystyrene, polyvinylidene fluoride, an acrylic copolymer, polyvinyl acetate, polyvinyl alcohol, and combinations thereof.

9. In claim 1, A separator for an electrochemical device, wherein the second polymer binder of the shell portion of the core-shell structure comprises one selected from polyvinylidene fluoride, an acrylic copolymer, polyvinyl acetate, polyvinyl alcohol, and combinations thereof.

10. An electrochemical device comprising a positive electrode; a negative electrode; and a separator interposed between the positive electrode and the negative electrode, wherein the separator comprises the separator of claim 1.

11. In claim 10, The above electrochemical device further includes an electrolyte, An electrochemical device, wherein the electrolyte comprises one solvent selected from ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and combinations thereof.

12. In claim 11, The above electrolyte is dissolved in the second polymer binder of the shell portion, An electrochemical device further comprising one selected from polyvinylidene fluoride, an acrylic copolymer, polyvinylacetate, polyvinylalcohol, and combinations thereof.

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