Separation membrane for electrochemical elements, and electrochemical elements containing the same

Abstract

The present invention relates to a separator for an electrochemical device and an electrochemical device including the same. Specifically, the present invention relates to a separator for an electrochemical device that contains a boron nitride-based compound in a coating layer, thereby adsorbing transition metal ions eluted from an electrode into an electrolyte and improving the heat resistance of the separator, and an electrochemical device including the same.

Description

[Technical Field]

[0001] This invention claims the benefit as of the filing date of Korean Patent Application No. 10-2023-0103351, filed with the Korean Intellectual Property Office on August 8, 2023, and all of its contents are included in this invention. This invention relates to a separation membrane for an electrochemical element and an electrochemical element containing the same, and more specifically, to a separation membrane for an electrochemical element that can improve the heat resistance of the separation membrane by adsorbing transition metal ions eluted from the electrode into the electrolyte by including a boron nitride-based compound in the coating layer, and an electrochemical element containing the same. [Background technology]

[0002] Among the components of an electrochemical element, the separation membrane includes a porous polymer substrate placed between the positive and negative electrodes. Its role is to isolate the positive and negative electrodes, prevent electrical short circuits between the two electrodes, and allow electrolytes and ions to pass through. While the separation membrane itself does not participate in the electrochemical reaction, its physical properties, such as wettability to the electrolyte, degree of porosity, and thermal shrinkage rate, affect the performance and safety of the electrochemical element.

[0003] Therefore, in order to enhance the physical properties of the separation membrane, various methods have been attempted to change the physical properties of the coating layer by adding a coating layer to a porous polymer substrate and adding various substances to the coating layer. For example, inorganic substances can be added to the coating layer to improve the mechanical strength of the separation membrane, or inorganic substances or hydrates can be added to the coating layer to improve the flame retardancy and heat resistance of the polymer substrate.

[0004] The separation membrane can be bonded to the electrode through a lamination process, and a binder resin can be added to the slurry for the coating layer of the separation membrane to ensure adhesion between the electrode and the separation membrane.

[0005] On the other hand, thinning the separation membrane leads to a decrease in dielectric breakdown voltage, and the formation of dendrites on the electrodes reduces battery performance and can cause short circuits.

[0006] Therefore, there was a need for research on separation membranes that could ensure battery performance, improve battery safety, and prevent dendrite formation. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The technical problem that the present invention aims to solve is to provide a separation membrane for an electrochemical element that can adsorb transition metal ions eluted from an electrode by adding a boron nitride-based compound to the coating layer contained in the separation membrane and adjusting its content to ensure the heat resistance of the separation membrane, and an electrochemical element containing the same.

[0008] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] One embodiment of the present invention provides a porous polymer substrate; and a separation membrane for an electrochemical element, provided on at least one surface of the porous polymer substrate, having a coating layer comprising a boron nitride compound, polymer binder particles, and inorganic particles, wherein the content of the inorganic particles is 80 parts by weight or more per 100 parts by weight of the coating layer.

[0010] According to one embodiment of the present invention, the content of the boron nitride-based compound in the coating layer may be 0.1 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the coating layer.

[0011] According to one embodiment of the present invention, the boron nitride-based compound may be a boron nitride nanotube.

[0012] According to one embodiment of the present invention, the average outer diameter of the boron nitride-based compound may be 10 nm or more and 100 nm or less.

[0013] According to one embodiment of the present invention, the average length of the boron nitride-based compound may be 1 μm or more and 50 μm or less.

[0014] According to one embodiment of the present invention, the aspect ratio of the boron nitride-based compound can be 10 to 5,000.

[0015] According to one embodiment of the present invention, the density of the boron nitride-based compound is 1.0 g / cm³. 3 More than 5.0g / cm 3 The following are possible:

[0016] According to one embodiment of the present invention, the specific surface area of ​​the boron nitride-based compound is 20 m². 2 / g or more 55m 2 It may be less than / g.

[0017] According to one embodiment of the present invention, the inorganic particles may be selected from boehmite, alumina, and combinations thereof.

[0018] One embodiment of the present invention provides an electrochemical element comprising a positive electrode; a negative electrode; and a separation membrane interposed between the positive electrode and the negative electrode. [Effects of the Invention]

[0019] A separation membrane for an electrochemical element according to one embodiment of the present invention utilizes the polarity of the compound generated by the electronegativity difference between nitrogen and boron in the boron nitride compound and the specific surface area of ​​the boron nitride compound to adsorb transition metal ions eluting from the electrode and minimize the formation of dendrites on the electrode.

[0020] In one embodiment of the present invention, the separation membrane for an electrochemical element can have its heat resistance improved by utilizing the heat resistance of boron nitride-based compounds.

[0021] An electrochemical element according to one embodiment of the present invention can minimize the formation of dendrites on the electrodes, thereby ensuring battery safety and improving battery performance. [Brief explanation of the drawing]

[0022] [Figure 1] Figures 1a and 1b are schematic diagrams of a separation membrane for an electrochemical element according to one embodiment of the present invention. Specifically, Figure 1a is a schematic diagram of a separation membrane for an electrochemical element having a coating layer on one surface, and Figure 1b is a schematic diagram of a separation membrane for an electrochemical element having coating layers on both sides. [Figure 2] Figure 2 is a schematic diagram of an electrochemical element according to one embodiment of the present invention. [Modes for carrying out the invention]

[0023] In this specification, when a part is said to "include" a component, unless otherwise stated, this means that it may include other components rather than excluding them.

[0024] In this specification, "A and / or B" means "A and B, or A or B."

[0025] In this specification, when we say that a component is provided "on top of" another component, this does not exclude other components being placed in between, unless otherwise stated, and means that other components may be placed in between.

[0026] In this specification, the characteristic of "having pores" means that the object contains a plurality of pores, and that a gaseous and / or liquid fluid can pass from one surface of the object to the other through a structure in which the pores are interconnected.

[0027] In this specification, the separation membrane has porous properties including numerous pores and acts as a porous ion-conducting barrier, allowing ions to pass through while blocking electrical contact between the negative and positive electrodes using an electrochemical element.

[0028] The present invention will be described in more detail below.

[0029] One embodiment of the present invention provides a separation membrane 100 for an electrochemical element, comprising a porous polymer substrate 110; and a coating layer 130 provided on at least one surface of the porous polymer substrate 110, comprising a boron nitride-based compound 131, polymer binder particles 133, and inorganic particles 135, wherein the content of the inorganic particles 135 is 80 parts by weight or more per 100 parts by weight of the coating layer 130.

[0030] The separation membrane 100 for an electrochemical element according to one embodiment of the present invention utilizes the polarity of the compound generated by the electronegativity difference between nitrogen and boron in the boron nitride-based compound 131 and the specific surface area of ​​the boron nitride-based compound 131 to minimize the formation of dendrites on the electrode by adsorbing transition metal ions eluted from the electrode. Furthermore, the separation membrane 100 for an electrochemical element according to one embodiment of the present invention can improve the heat resistance of the separation membrane by utilizing the excellent heat resistance of the boron nitride-based compound 131.

[0031] Figures 1a and 1b are schematic diagrams of a separation membrane 100 for an electrochemical element according to one embodiment of the present invention. Specifically, Figure 1a is a schematic diagram of a separation membrane 100 for an electrochemical element having a coating layer 130 on one surface, and Figure 1b is a schematic diagram of a separation membrane 100 for an electrochemical element having a coating layer 130 on both sides. The separation membrane 100 for an electrochemical element according to one embodiment of the present invention will be described in detail with reference to Figures 1a and 1b.

[0032] According to one embodiment of the present invention, the separation membrane 100 for the electrochemical element includes a porous polymer substrate 110. As described above, by including the porous polymer substrate 110 in the separation membrane 100 for the electrochemical element, lithium ions can pass through while blocking electrical contact, thereby realizing a shutdown function at an appropriate temperature.

[0033] According to one embodiment of the present invention, the porous polymer substrate 110 can be manufactured using a polyolefin resin as the base resin. Examples of polyolefin resins include polyethylene, polypropylene, and polypentene, and one or more of these can be included. A porous separation membrane, i.e., one with numerous pores, manufactured using such a polyolefin resin as the base resin, can be given a shutdown function at an appropriate temperature.

[0034] According to one embodiment of the present invention, the weight-average molecular weight of the polyolefin resin may be between 500,000 and 2,000,000. By adjusting the weight-average molecular weight of the polyolefin resin within the above range, the compressive resistance of the separation membrane can be improved. Furthermore, when different types of polyolefin resins are mixed and used, or when a separation membrane is formed with a multilayer structure made of different types of polyolefin resins, the weight-average molecular weight of the polyolefin resins can be calculated by adding up the weight-average molecular weights corresponding to the content ratio of each polyolefin resin.

[0035] In this specification, weight-average molecular weight (Mw) can be measured by gel permeation chromatography (GPC, PL GPC220, Agilent Technologies), and the measurement conditions can be set as follows.

[0036] - Column: PL Olexis (Polymer Laboratories Inc.) - Solvent: TCB (Trichlorobenzene) -Flow rate: 1.0ml / min -Sample concentration: 1.0 mg / ml -Injection volume: 200μl - Column temperature: 160℃ -Detector: Agilent High Temperature RI detector - Standard: Polystyrene (corrected with a cubic function)

[0037] According to one embodiment of the present invention, the porous polymer substrate 110 can be manufactured by a method (wet method) in which a polyolefin resin is kneaded with a plasticizer (diluents) at a high temperature to form a single phase, the polymer material and the plasticizer are separated during the cooling process, the plasticizer is extracted to form pores, and then stretching and heat-fixing treatment are performed. Furthermore, the porous polymer substrate using a polyolefin resin may have a core portion which is a mixture of polyethylene and polypropylene, and polyethylene skin portions which are laminated on both sides of the core portion.

[0038] According to one embodiment of the present invention, the average pore size and maximum pore size of the separation membrane 100 can be easily manufactured to suit the scope of the present invention by adjusting the mixing ratio of the plasticizer, the stretching ratio, the heat setting treatment temperature, etc., for the benefit of those skilled in the art.

[0039] According to one embodiment of the present invention, the thickness of the porous polymer substrate 110 may be 1 μm or more and 50 μm or less. Specifically, the thickness of the porous polymer substrate 110 may be 2 μm or more and 45 μm or less, 3 μm or more and 40 μm or less, 4 μm or more and 35 μm or less, 5 μm or more and 30 μm or less, 6 μm or more and 25 μm or less, 7 μm or more and 20 μm or less, or 8 μm or more and 15 μm or less. By adjusting the thickness of the porous polymer substrate 110 within the above range, the energy density of the battery can be improved.

[0040] According to one embodiment of the present invention, the porosity of the porous polymer substrate 110 may be 10% by volume or more and 90% by volume or less. Specifically, the porosity of the porous polymer substrate 110 may be 10% by volume or more and 90% by volume or less, 20% by volume or more and 80% by volume or less, 30% by volume or more and 70% by volume or less, or 40% by volume or more and 60% by volume or less. By adjusting the porosity of the porous polymer substrate 110 within the above range, the permeability of the lithium ion separation membrane can be adjusted.

[0041] According to one embodiment of the present invention, the coating layer 130 is provided on at least one surface of the porous polymer substrate 110. Specifically, the separation membrane 100 for the electrochemical element includes the coating layer 130 provided on one or both surfaces of the porous polymer substrate 110. As described above, by including the coating layer 130 provided on at least one surface of the porous polymer substrate 110 in the separation membrane 100 for the electrochemical element, the heat resistance of the separation membrane can be improved, the mechanical properties can be improved, and the occurrence of electrical short circuits of electrodes due to shrinkage of the separation membrane at high temperatures can be prevented.

[0042] According to one embodiment of the present invention, the separation membrane 100 for the electrochemical element includes a coating layer 130 containing a boron nitride-based compound 131, polymer binder particles 133, and inorganic particles 135. As described above, the inclusion of the boron nitride-based compound 131, polymer binder particles 133, and inorganic particles 135 in the coating layer 130 improves the heat resistance of the separation membrane 100, improves its mechanical properties, prevents electrical short circuits of the electrodes due to the shrinkage of the separation membrane 100 at high temperatures, and allows for the formation of pores inside the coating layer 130. Furthermore, the heat resistance of the separation membrane 100 is improved, and transition metal ions eluted from the electrodes can be adsorbed.

[0043] According to one embodiment of the present invention, the coating layer 130 may uniformly contain the boron nitride-based compound 131, the polymer binder particles 133, and the inorganic particles 135. Specifically, the boron nitride-based compound 131, the polymer binder particles 133, and the inorganic particles 135 are uniformly dispersed in a coating layer slurry for forming the coating layer, the coating layer slurry is applied, and the dispersion medium or solvent is removed, so that the boron nitride-based compound 131, the polymer binder particles 133, and the inorganic particles 135 are distributed in uniform content. The respective content (weight) of the boron nitride-based compound 131, the polymer binder particles 133, and the inorganic particles 135 is uniform in the coating layer, and even if there are some differences, they can be within a difference of about 5%. As described above, the uniform distribution of the boron nitride-based compound 131, the polymer binder particles 133, and the inorganic particles 135 in the coating layer 130 improves the compressibility of the separation membrane.

[0044] According to one embodiment of the present invention, the content of the inorganic particles 135 in the coating layer 130 is 80 parts by weight or more per 100 parts by weight of the coating layer 130. Specifically, the content of the inorganic particles 135 in the coating layer 130 may be 81 parts by weight or more but less than 100 parts by weight, 82 parts by weight or more but 99 parts by weight or less, 83 parts by weight or more but 98 parts by weight or less, 84 parts by weight or more but 97 parts by weight or less, 85 parts by weight or more but 96 parts by weight or less, 86 parts by weight or more but 95 parts by weight or less, 87 parts by weight or more but 94 parts by weight or less, 88 parts by weight or more but 93 parts by weight or less, 89 parts by weight or more but 92 parts by weight or less, or 90 parts by weight or more but 91 parts by weight or less, per 100 parts by weight of the coating layer 130. By adjusting the content of the inorganic particles 135 in the coating layer 130 within the range described above, the polymer binder and inorganic particles can be uniformly distributed within the coating layer, thereby improving the compressive resistance and heat resistance of the coating layer.

[0045] According to one embodiment of the present invention, the content of the boron nitride-based compound 131 in the coating layer 130 may be 0.1 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the coating layer 130. By adjusting the content of the boron nitride-based compound in the coating layer within the above range, the insulating properties of the boron nitride-based compound can be utilized to improve the insulating and thermal conductivity properties of the separation membrane, and the polarity of the compound can be induced in the boron nitride-based compound due to the electronegativity difference between nitrogen and boron, thereby adsorbing transition metal ions eluted from the electrode.

[0046] According to one embodiment of the present invention, the boron nitride-based compound can form a network within the coating layer. Specifically, the boron nitride-based compounds can be connected to each other, forming a single web. As described above, by forming a network within the coating layer, the heat resistance of the boron nitride-based compound can be uniformly realized throughout the entire coating layer.

[0047] According to one embodiment of the present invention, the boron nitride-based compound 131 may be a boron nitride nanotube (BNNT). As described above, by using the boron nitride-based compound as a boron nitride nanotube, the insulating properties of the boron nitride nanotube can be utilized to improve the insulating and thermal conductivity properties of the separation membrane, and the polarity of the compound due to the electronegativity difference between nitrogen and boron in the boron nitride nanotube can be induced to adsorb transition metal ions eluted from the electrode.

[0048] According to one embodiment of the present invention, the average outer diameter of the boron nitride-based compound 131 may be between 10 nm and 100 nm. Specifically, the average outer diameter of the boron nitride-based compound 131 may be between 20 nm and 90 nm, between 30 nm and 80 nm, between 40 nm and 70 nm, or between 50 nm and 60 nm. By adjusting the average outer diameter of the boron nitride-based compound 131 within the above ranges, a uniform network can be formed within the coating layer, thereby improving the thermal stability, mechanical strength, and electrical insulation properties of the separation film.

[0049] According to one embodiment of the present invention, the average length of the boron nitride-based compound 131 can be 1 μm or more and 50 μm or less. Specifically, the average length of the boron nitride-based compound 131 can be 5 μm or more and 45 μm or less, 10 μm or more and 40 μm or less, 15 μm or more and 35 μm or less, or 20 μm or more and 30 μm or less. By adjusting the average length of the boron nitride-based compound 131 within the above-described range, a uniform network can be formed within the coating layer, and the thermal stability, mechanical strength, and electrical insulation of the separation membrane can be improved.

[0050] According to one embodiment of the present invention, the aspect ratio of the boron nitride-based compound 131 can be 10 or more and 5,000 or less. Specifically, the aspect ratio of the boron nitride-based compound 131 can be 500 or more and 4,500 or less, 1,000 or more and 4,000 or less, 1,500 or more and 3,500 or less, or 2,000 or more and 3,000 or less. By adjusting the aspect ratio of the boron nitride-based compound 131 within the above-described range, a uniform network can be formed within the coating layer, and the thermal stability and mechanical strength of the separation membrane can be improved.

[0051] According to one embodiment of the present invention, the density of the boron nitride-based compound 131 is 1.0 g / cm 3 or more and 5.0 g / cm 3 or less. Specifically, the density of the boron nitride-based compound 131 can be 1.5 g / cm 3 or more and 4.5 g / cm 3 or less, 2.0 g / cm 3 or more and 4.0 g / cm 3 or less, or 2.5 g / cm 3 or more and 3.5 g / cm 3 or less. By adjusting the density of the boron nitride-based compound 131 within the above-described range, while exerting the thermal stability and mechanical strength of the separation membrane, the energy density of the electrochemical device can be improved.

[0052] According to one embodiment of the present invention, the specific surface area (BET) of the boron nitride-based compound 131 is 20 m². 2 / g or more 55m 2 It may be less than / g. Specifically, the specific surface area of ​​the boron nitride-based compound 131 is 21m². 2 / g or more 54m 2 / g or less, 22m 2 / g or more 53m 2 / g or less, 23m 2 / g or more 52m 2 / g or less, 24m 2 / g or more 51m 2 / g or less, 25m 2 / g or more 50m 2 / g or less, 26m 2 / g or more 49m 2 / g or less, 27m 2 / g or more 48m 2 / g or less, 28m 2 / g or more 47m 2 / g or less, 29m 2 / g or more 46m 2 / g or less, 30m 2 / g or more 45m 2 / g or less, 31m 2 / g or more 44m 2 / g or less, 32m 2 / g or more 43m 2 / g or less, 33m 2 / g or more 42m 2 / g or less, 34m 2 / g or more 41m 2 / g or less, 35m 2 / g or more 40m 2 / g or less, 36m 2 / g or more 39m 2 / g or less, or 37m 2 / g or more 38m 2 It may be less than / g. By adjusting the specific surface area of ​​the boron nitride-based compound 131 within the range described above, it is possible to improve the energy density of the electrochemical element while exhibiting the thermal stability and mechanical strength of the separation membrane, thereby improving the adsorption efficiency of transition metals.

[0053] In this specification, "specific surface area" may refer to the BET surface area calculated using the Brunauer-Emmett-Teller model (BET) from the measured N2 adsorption isotherm, obtained by measuring the adsorption isotherm to 1 bar at -196°C using a BET-specific surface area analyzer (BEL, Microtrac).

[0054] According to one embodiment of the present invention, the coating layer 130 may contain a plurality of pores. Specifically, the coating layer may be a porous coating layer. More specifically, the coating layer may be a porous coating layer containing a plurality of pores internally. As described above, by the coating layer containing a plurality of pores, it is possible to physically separate the negative electrode and the positive electrode while allowing lithium ions to pass through and current to flow.

[0055] According to one embodiment of the present invention, the coating layer 130 may be formed by binding a boron nitride-based compound and inorganic particles 135 together with polymer binder particles 133 and accumulating within the coating layer. Pores inside the coating layer 130 may be due to interstitial volume, which is the empty space between the boron nitride-based compound and the inorganic particles.

[0056] According to one embodiment of the present invention, the thickness of the coating layer 130 can be formed with a thickness of 1 μm to 20 μm on either of the porous polymer substrates 110. By adjusting the thickness of the coating layer 130 within the above range, the heat resistance and electrical resistance of the separation membrane can be adjusted to an appropriate range.

[0057] In one embodiment of the present invention, the thickness of the porous polymer substrate and / or the coating layer can be measured using a contact-type thickness gauge. For example, the VL-50S-B from Mitutoyo can be used as the contact-type thickness gauge.

[0058] According to one embodiment of the present invention, the polymer binder particles 133 may be an acrylic binder, a polyvinylidene binder, or a combination thereof. The combination of the acrylic binder and the polyvinylidene binder may be a mixture of the acrylic binder and the polyvinylidene binder, a copolymer containing the acrylic repeating units and the polyvinylidene repeating units, or a hybrid of the acrylic binder and the polyvinylidene binder. The polyvinylidene binder may be a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP). By selecting the polymer binder particles from the above, the porosity of the separation membrane can be maintained, the adhesion between the electrodes and the separation membrane can be improved in the battery lamination process, making it easier to manufacture batteries and enabling stable implementation of the stacking process. Furthermore, the porosity of the separation membrane can be maintained, and the adhesion can be maintained even if the coating layer is wetted by the electrolyte after battery activation. Furthermore, the stiffness of the battery can be improved, and bending of the separation membrane can be prevented.

[0059] According to one embodiment of the present invention, the acrylic binder is a polymer containing a carboxylic acid ester as a repeating unit, and is preferably a (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0060] 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, and (meth)acrylate. Examples include decyl acrylate, hydroxymethyl methacrylate, hydroxyethyl methacrylate, ethylene glycol methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, allyl methacrylate, and ethylene dimethacrylate, and one or more of these can be selected. Of these, one or more selected from methyl methacrylate, ethyl methacrylate, and 2-ethylhexyl methacrylate is preferred, and methyl methacrylate is particularly preferred.

[0061] According to one embodiment of the present invention, the acrylic-styrene copolymer may contain an acrylic binder, and the acrylic binder may be polyacrylate-based. For example, the acrylic binder may be one or more selected from the group consisting of styrene-butyl acrylate, styrene-butadiene rubber, nitril-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate polymers, and more specifically, it may be a copolymer containing acrylate.

[0062] According to one embodiment of the present invention, the glass transition temperature (Tg) of the polymer binder particles 133 may be 20°C or more and 60°C or less. Specifically, the glass transition temperature (Tg) of the polymer binder particles may be 22°C or more and 58°C or less, 24°C or more and 56°C or less, 26°C or more and 54°C or less, 28°C or more and 52°C or less, 30°C or more and 50°C or less, 32°C or more and 48°C or less, 34°C or more and 46°C or less, 36°C or more and 44°C or less, or 38°C or more and 42°C or less. By adjusting the glass transition temperature (Tg) of the polymer binder particles within the above range, the viscosity of the slurry for manufacturing the coating layer can be adjusted, thereby improving the convenience of battery manufacturing.

[0063] According to one embodiment of the present invention, the average diameter (D) of the polymer binder particles 133 is 50 There are no particular restrictions on the average diameter (D) of the polymer binder particles 133, but it is preferable that it be in the range of 0.1 μm to 1 μm in order to form a coating layer 130 of uniform thickness and to have an appropriate porosity. Specifically, the average diameter (D) of the polymer binder particles 133 is 50 The average diameter (D) of the polymer binder particles 133 within the above range may be 0.2 μm to 0.9 μm, 0.3 μm to 0.8 μm, 0.4 μm to 0.7 μm, or 0.5 μm to 0.6 μm. 50 By adjusting the ), the dispersibility of the slurry prepared for manufacturing the coating layer can be improved, and the thickness of the formed coating layer can be reduced.

[0064] According to one embodiment of the present invention, the polyvinylidene binder may be a polyvinylidene binder having a hexafluoropropylene (HFP) content of 1% to 50% by weight. Specifically, the hexafluoropropylene (HFP) content in the polyvinylidene binder may be 1% to 50% by weight, 2% to 45% by weight, 3% to 40% by weight, 4% to 35% by weight, 5% to 30% by weight, 7% to 25% by weight, or 10% to 20% by weight. As described above, by selecting a polyvinylidene binder having a hexafluoropropylene content of 1% to 50% by weight, the porosity of the separation membrane can be maintained, and the adhesive strength can be maintained even if the coating layer is wetted by the electrolyte after the battery is activated. In this specification, the degree of substitution of a polyvinylidene-based binder may mean the weight ratio containing hexafluoropropylene.

[0065] According to one embodiment of the present invention, the content of the polymer binder particles 133 may be 20 parts by weight or less per 100 parts by weight of the coating layer 130. Specifically, the content of the polymer binder particles 133 may be more than 0 parts by weight and 20 parts by weight or less, 1 part by weight or more and 19 parts by weight or less, 2 parts by weight or more and 18 parts by weight or less, 3 parts by weight or more and 17 parts by weight or less, 4 parts by weight or more and 16 parts by weight or less, 5 parts by weight or more and 15 parts by weight or less, 6 parts by weight or more and 14 parts by weight or less, 7 parts by weight or more and 13 parts by weight or less, 8 parts by weight or more and 12 parts by weight or less, 9 parts by weight or more and 11 parts by weight or less, or 10 parts by weight or more and 11 parts by weight or less, per 100 parts by weight of the coating layer 130. By adjusting the content of the polymer binder particles 133 within the ranges described above, the ease of assembly in the electrode assembly process can be improved, and the heat resistance of the coating layer can be improved.

[0066] According to one embodiment of the present invention, the weight ratio of the acrylic binder and the polyvinylidene binder in the coating layer 130 can be 9:1 to 1:9. Specifically, the weight ratio of the acrylic binder and the polyvinylidene binder in the coating layer 130 can be 8:1 to 1:8, 7:1 to 1:7, 6:1 to 1:6, 5:1 to 1:5, 4:1 to 1:4, 3:1 to 1:3, or 2:1 to 1:2. By adjusting the weight ratio of the acrylic binder and the polyvinylidene binder within the above range, the wet and dry adhesive strength of the separation membrane for the electrochemical element can be improved simultaneously.

[0067] According to one embodiment of the present invention, the inorganic particles 135 usable in the coating layer 130 may be electrochemically stable. Specifically, the inorganic particles usable in one embodiment of the present invention may be within the operating voltage range of the electrochemical element to which they are applied (e.g., Li / Li + It is possible that oxidation and / or reduction reactions do not occur at voltages (0V to 5V) relative to the given voltage.

[0068] According to one embodiment of the present invention, the inorganic particles 135 are 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 / 3Examples of inorganic materials include 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, etc., and one or more of these may be included. Specifically, the inorganic particles 135 are preferably selected from boehmite, alumina, and combinations thereof. As described above, the heat resistance of the separation membrane can be improved by selecting the inorganic particles from boehmite, alumina, and a combination thereof.

[0069] According to one embodiment of the present invention, the average diameter (D) of the inorganic particles 135 50 There are no particular restrictions on the average diameter (D) of the inorganic particles 135, but it is preferable that it be in the range of 0.3 μm to 1 μm in order to form a coating layer 130 of uniform thickness and to have an appropriate porosity. Specifically, the average diameter (D) of the inorganic particles 135 is preferable. 50 The particle size may be between 0.2 μm and 0.9 μm, between 0.3 μm and 0.8 μm, between 0.4 μm and 0.7 μm, or between 0.5 μm and 0.6 μm. Specifically, if it is less than 0.3 μm, the dispersibility of inorganic particles in the slurry prepared for manufacturing the coating layer may decrease, and if it exceeds 1 μm, the thickness of the formed coating layer may increase.

[0070] In this specification, "D 50"Particle size" refers to the particle size at the 50% point of the cumulative distribution of particle numbers corresponding to the particle size. The particle size can be measured using the laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500), and the particle size distribution is calculated by measuring the difference in diffraction patterns according to the particle size as the particles pass through the laser beam. By calculating the particle diameter at the point where the cumulative distribution of particle numbers corresponding to the particle size in the measuring device reaches 50%, D 50 It is possible to measure particle size.

[0071] According to one embodiment of the present invention, the porosity of the coating layer 130 may be 30 volume% or more. Specifically, the porosity of the coating layer 130 may be 30 volume% to 70 volume%, 32 volume% to 68 volume%, 34 volume% to 66 volume%, 36 volume% to 64 volume%, 38 volume% to 62 volume%, 40 volume% to 60 volume%, 42 volume% to 58 volume%, 44 volume% to 56 volume%, 46 volume% to 54 volume%, or 48 volume% to 52 volume%. By adjusting the porosity of the coating layer 130 within the above range, it is possible to maintain ion movement in the separation membrane and prevent an increase in the resistance of the separation membrane. Specifically, when the porosity is 70 volume% or less, it is possible to ensure mechanical properties that can withstand the pressing process for bonding with electrodes, and the surface opening ratio does not become too high, which is suitable for ensuring adhesive strength. On the other hand, a porosity of 30% by volume or more is advantageous from the viewpoint of ion permeability.

[0072] In this specification, "porosity" refers to the ratio of the volume occupied by pores to the total volume, and is expressed in units of volume %. It can be used interchangeably with terms such as void ratio and porosity.

[0073] In this specification, porosity may correspond to the subtraction value obtained by subtracting the volume of each component of the porous polymer substrate 110 and / or coating layer 130 converted to weight and density from the volume calculated in terms of thickness, width and length of the porous polymer substrate 110 and / or coating layer 130.

[0074] In one embodiment of the present invention, the porosity and pore size of the porous polymer substrate 110 and / or the coating layer 130 can be measured by the BET 6-point method using a scanning electron microscope (SEM) image, a mercury porosimeter, a capillary flow porometer, or a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini) by nitrogen gas adsorption flow method. In this case, using a capillary flow porometer may be advantageous.

[0075] According to one embodiment of the present invention, the polyvinylidene-based binder may be an aqueous binder. Specifically, by selecting an aqueous binder for the polyvinylidene-based binder, the amount of contaminants discharged during the manufacturing process of the separation membrane can be minimized, thereby reducing the manufacturing cost of the battery.

[0076] According to one embodiment of the present invention, the separation membrane may further include an adhesive layer on the coating layer. As described above, by further including the adhesive layer, the adhesion between the coating layer and the electrode described later can be improved.

[0077] According to one embodiment of the present invention, the adhesive layer may include a polymer binder.

[0078] According to one embodiment of the present invention, the polymer binder may be in particle form or solution form.

[0079] According to one embodiment of the present invention, the polymer binder in the adhesive layer may be an acrylic binder, a polyvinylidene binder, or a combination thereof. The combination of the acrylic binder and the polyvinylidene binder may be a mixture of the acrylic binder and the polyvinylidene binder, a copolymer containing the acrylic repeating units and the polyvinylidene repeating units, or a hybrid of the acrylic binder and the polyvinylidene binder. The polyvinylidene binder may be a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP). By selecting the polymer binder from the above, the adhesion between the coating layer and the electrode can be improved, and the stacking process can be stably implemented. Furthermore, the porosity of the separation membrane can be maintained, and the adhesion can be maintained even if the coating layer is wetted by the electrolyte after the battery is activated. Furthermore, the stiffness of the battery can be improved, and bending of the separation membrane can be prevented. Additionally, the polymer binder is omitted here as it overlaps with the description of the polymer binder particles in the coating layer described above.

[0080] According to one embodiment of the present invention, the separation membrane may be configured by providing a polymer binder on the coating layer. Specifically, the separation membrane may not be provided as a single layer on the coating layer, but rather may be provided in part. The polymer binder may be in particulate form or in soluble form. If the polymer binder on the coating layer is in particulate form, the polymer binder may be provided in part while maintaining its particle shape on the coating layer. If the polymer binder is in soluble form, the polymer binder may be provided to form a layer on a portion of the coating layer. As described above, by providing a separation membrane in which a polymer binder is provided on the coating layer, adhesion to the electrode and porosity of the coating layer can be ensured.

[0081] One embodiment of the present invention provides a method for manufacturing a separation membrane for an electrochemical element, comprising the steps of: mixing a slurry for a coating layer 130 containing a boron nitride compound 131, polymer binder particles 133, and inorganic particles 135 (S10); applying the slurry for the coating layer onto at least one surface of a porous polymer substrate 110 (S30); and drying the slurry for the coating layer to provide a coating layer 130 (S50).

[0082] A method for manufacturing a separation membrane for an electrochemical element according to one embodiment of the present invention can improve the heat resistance of the separation membrane.

[0083] According to one embodiment of the present invention, the method for manufacturing the separation membrane 100 for the electrochemical element includes a step (S10) of mixing a slurry for a coating layer containing a boron nitride-based compound 131, polymer binder particles 133, and inorganic particles 135. As described above, by including the step (S10) of mixing a slurry for a coating layer containing a boron nitride-based compound 131, polymer binder particles 133, and inorganic particles 135, a coating layer can be easily formed on the separation membrane.

[0084] According to one embodiment of the present invention, polymer binder particles 133 can be dispersed in water, which is a suitable dispersion medium, to produce a polymer emulsion and provide a slurry for a coating layer. As described above, by dispersing polymer binder particles 133 in water, which is a suitable dispersion medium, to produce a polymer emulsion and provide a slurry for a coating layer, contaminants generated during the manufacturing process can be minimized. In this specification, the dispersion medium is used in the process of producing the slurry and may mean a solvent.

[0085] According to one embodiment of the present invention, a boron nitride-based compound 131 and inorganic particles 135 can be added to and dispersed in the polymer emulsion. The content ratio of the boron nitride-based compound, inorganic particles and polymer binder particles is as described above and is appropriately adjusted considering the thickness, pore size, and porosity of the coating layer according to one embodiment of the present invention that is ultimately produced.

[0086] According to one embodiment of the present invention, a coating layer slurry can be produced by dispersing a boron nitride-based compound 131, polymer binder particles 133, and inorganic particles 135 in water as a dispersion medium. Specifically, as described above, a coating layer slurry can be produced by immediately dispersing the boron nitride-based compound 131, polymer binder particles 133, and inorganic particles 135 in water, which is the dispersion medium, without preparing a polymer emulsion.

[0087] According to one embodiment of the present invention, the solid content of the coating layer slurry may be 10% by weight or more and 50% by weight or less. Specifically, the solid content of the coating layer slurry may be 15% by weight or more and 40% by weight or less, 20% by weight or more and 35% by weight or less, or 15% by weight or more and 40% by weight or less. By adjusting the solid content of the coating layer slurry within the above range, the workability in the manufacturing process of the coating layer can be improved.

[0088] According to one embodiment of the present invention, the method for manufacturing the separation membrane 100 for the electrochemical element includes the step (S30) of applying the coating layer slurry onto at least one surface of the porous polymer substrate 110. As described above, by including the step of applying the coating layer slurry onto at least one surface of the porous polymer substrate 110, the coating layer 130 can be formed in a single application, and the coating layer slurry can form a uniform coating layer with inorganic particles, polymer binder particles, and boron nitride-based compounds distributed at uniform concentrations.

[0089] According to one embodiment of the present invention, the method for applying the coating layer slurry to the surface of the porous polymer substrate 110 is not limited to any one method, and conventional methods 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.

[0090] According to one embodiment of the present invention, the method for manufacturing the separation membrane 100 for the electrochemical element includes the step (S50) of drying the slurry for the coating layer to provide the coating layer 130. As described above, by including the step (S50) of drying the slurry for the coating layer to provide the coating layer 130, damage to the coating layer can be minimized and the dispersion medium contained in the slurry can be easily removed.

[0091] According to one embodiment of the present invention, the temperature of the drying step may be 25°C or more and 75°C or less. Specifically, the temperature of the drying step may be 30°C or more and 70°C or less, 35°C or more and 65°C or less, 40°C or more and 60°C or less, or 45°C or more and 55°C or less. By adjusting the temperature of the drying step within the above ranges, modification of the porous polymer substrate can be prevented and the dispersion medium can be effectively removed.

[0092] According to one embodiment of the present invention, the drying process is performed by appropriately setting time conditions to minimize the occurrence of surface defects in the coating layer 130. The drying can be performed using drying aids such as a drying oven or hot air within an appropriate range.

[0093] According to one embodiment of the present invention, the step of applying an adhesive layer slurry containing a polymer binder onto the coating layer to form an adhesive layer can be further included. As described above, by further including the step of applying an adhesive layer slurry containing a polymer binder onto the coating layer to form an adhesive layer, the adhesion between the separation membrane and the electrode can be improved, the adhesion can be maintained during the lamination process with the electrode, the adhesion can be maintained after the battery is activated to improve stiffness, and the pouch-type cell can be prevented from bending.

[0094] According to one embodiment of the present invention, the dispersion medium or solvent of the slurry for the adhesive layer may be water. As described above, by selecting the dispersion medium or solvent of the slurry for the adhesive layer, it is possible to prevent the environment from being contaminated by the dispersion medium or solvent.

[0095] According to one embodiment of the present invention, the step of drying the applied adhesive layer may further be included.

[0096] According to one embodiment of the present invention, the separation membrane 100 is interposed between the positive electrode 300 and the negative electrode 500 and manufactured as an electrochemical element 1000 by a lamination process in which heat and / or pressure is applied to bond them together. In one embodiment of the present invention, the lamination process can be carried out by a roll press device including a pair of pressure rollers. That is, the negative electrode 500, the separation membrane 100 and the positive electrode 300 can be sequentially laminated and placed between the pressure rollers to achieve interlayer bonding. In this case, the lamination process can be carried out by a hot pressurization method.

[0097] One embodiment of the present invention provides an electrochemical element 1000 comprising a positive electrode 300; a negative electrode 500; and a separation membrane 100 interposed between the positive electrode 300 and the negative electrode 500.

[0098] An electrochemical element 1000 according to one embodiment of the present invention can minimize the formation of dendrites on the electrodes, thereby ensuring battery safety and improving battery performance.

[0099] Figure 2 is a schematic diagram of an electrochemical element 1000 according to one embodiment of the present invention. The electrochemical element 1000 according to one embodiment of the present invention will be described in detail with reference to Figure 2.

[0100] In one embodiment of the present invention, the electrochemical element is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept that encompasses both primary and secondary batteries. In this specification, the secondary battery is capable of charging and discharging, and includes lithium secondary batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and the like. In the case of lithium secondary batteries, lithium ions are used as ion conductors, and examples include, but are not limited to, non-aqueous electrolyte secondary batteries containing a liquid electrolyte, all-solid-state batteries containing a solid electrolyte, lithium polymer batteries containing a gel polymer electrolyte, and lithium metal batteries using lithium metal as the negative electrode.

[0101] In one embodiment of the present invention, the electrochemical element may have a cylindrical shape. Specifically, the electrochemical element may have an electrode assembly, including the positive electrode, the separation membrane, and the negative electrode, embedded in a cylindrical metal case. More specifically, the electrochemical element having a cylindrical shape may be manufactured by housing a jelly-roll type electrode assembly in a cylindrical metal case, injecting an electrolyte into the cylindrical metal case, and then attaching a cap with electrode terminals formed thereon to the open upper end of the metal case. As described above, manufacturing the electrochemical element in a cylindrical shape can improve capacity and structural safety.

[0102] According to one embodiment of the present invention, 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, comprising a positive electrode active material, a conductive material, and a binder resin. The positive electrode active material is 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; 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 x Ni-site type lithium nickel oxide represented as 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 Lithium manganese composite oxides represented as 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 Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compounds; and mixtures of one or more of Fe2(MoO4)3 may be included.

[0103] According to one embodiment of the present invention, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer on at least one surface of the current collector, comprising a negative electrode active material, a conductive material, and a binder resin. The negative electrode comprises carbon such as lithium metal oxide, non-graphitizable carbon, and graphite-based carbon as the negative electrode active material; Li x Fe2O3 (0 ≤ x ≤ 1), Li x WO2(0≦x≦1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, 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 alloys; silicon-based alloys; tin-based alloys; 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; one or more mixtures selected from titanium oxides can be included.

[0104] According to one embodiment of the present invention, the conductive material can be, for example, any one selected from the group consisting of graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, activated carbon, and polyphenylene derivative, or a mixture of two or more of these conductive materials. More specifically, it can be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more of these conductive materials.

[0105] According to one embodiment of the present invention, the current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, stainless steel, copper, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used.

[0106] According to one embodiment of the present invention, the binder resin can be a polymer commonly used in electrodes in the industry. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, 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 include, but are not limited to, acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methylcellulose.

[0107] According to one embodiment of the present invention, the cathode slurry for producing the cathode active material layer may contain a dispersant, and the dispersant may be a pyrrolidone compound. Specifically, it may be N-methylpyrrolidone (ADC-01, LG Chemical Co., Ltd.).

[0108] According to one embodiment of the present invention, the amount of dispersant contained in the positive electrode slurry may be more than 0 parts by weight and 0.5 parts by weight or less per 100 parts by weight of the positive electrode slurry. Specifically, the amount of dispersant contained in the positive electrode slurry may be more than 0.05 parts by weight and 0.4 parts by weight or less per 100 parts by weight of the positive electrode slurry.

[0109] According to one embodiment of the present invention, the negative electrode slurry for producing the negative electrode active material layer may contain a dispersant, and the dispersant may be a polypyrrolidone compound. Specifically, the dispersant may be polyvinylpyrrolidone (Junsei Corporation).

[0110] According to one embodiment of the present invention, the content of the dispersant in the negative electrode slurry may be more than 0 parts by weight and 0.5 parts by weight or less per 100 parts by weight of the negative electrode slurry. Specifically, the content of the dispersant in the negative electrode slurry may be more than 0.05 parts by weight and 0.4 parts by weight or less per 100 parts by weight of the negative electrode slurry.

[0111] According to one embodiment of the present invention, the electrochemical element prepared as described above can be placed in a suitable case and an electrolyte solution injected to manufacture a battery.

[0112] According to one embodiment of the present invention, the electrolyte is A + B - A salt with a structure like this, + is Li + kaNa + , K + It contains alkali metal cations such as, or ions consisting of combinations thereof, B - PF6 -, BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - Salts containing anions such as these, or ions composed of combinations thereof, are dissolved or dissociated in an organic solvent composed of 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.

[0113] One embodiment of the present invention provides a battery module including the electrochemical element as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include power tools powered by a battery motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheel vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; power storage systems, etc., but are not limited thereto.

Examples

[0114] The present invention will be described in detail below with reference to examples. However, the examples of the present invention can be modified into various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples herein are provided to give a more complete explanation of the present invention to a person of average skill in the art.

[0115] <Example 1> A porous polymer substrate (total thickness approximately 9 μm, porosity 40% by volume) was manufactured by extruding polyethylene resin (weight-average molecular weight 900,000) using a wet process. Boron nitride-based compounds include boron nitride nanotubes (average outer diameter: 50 nm, length: 25 μm, aspect ratio: 100, density: 3.0 g / cm³). 3 , Specific surface area (BET): 40m 2 A slurry for a coating layer (solid content concentration 20% by weight) was prepared by dispersing a boron nitride compound, styrene-butyl acrylate (glass transition temperature 40°C), which is an acrylic binder with a particle size of 500 nm, as polymer binder particles, and boehmite (particle size: 500 nm) as inorganic particles in water. The weight ratio of the boron nitride compound, the polymer binder particles, and the inorganic particles was 2:5:93.

[0116] The coating slurry was applied to both sides of the porous polymer substrate using a doctor blade in a bar coating method, and dried with a heat gun at 50°C to form a 1.5 μm thick coating layer on each side, thereby producing a separation film with a total thickness of 12 μm.

[0117] <Example 2> A separation membrane was manufactured in the same manner as in Example 1, except that the weight ratio of the boron nitride-based compound, the polymer binder particles, and the inorganic particles was set to 0.05:4.95:95.

[0118] <Comparative Example 1> In Example 1, a separation membrane was produced in the same manner as in Example 1, except that the weight ratio of the boron nitride-based compound, the polymer binder particles, and the inorganic particles was 0:5:95.

[0119] <Comparative Example 2> In Example 1, a separation membrane was produced in the same manner as in Example 1, except that the weight ratio of the boron nitride-based compound, the polymer binder particles, and the inorganic particles was 25:5:70.

[0120] <Manufacture of Electrochemical Element> 1) Manufacture of positive electrode Positive electrode active material (LiNi 0.8 Mn 0.1 CO 0.1 O2), conductive material (carbon black), dispersant (N-methylpyrrolidone (N-methylpyrrolidone), ADC-01, LG Chem), and binder resin (mixture of PVDF-HFP and PVDF) were mixed with water at 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).

[0121] 2) Manufacture of negative electrode Graphite (blend of natural graphite and artificial graphite graphite), conductive material (carbon black), dispersant (Polyvinylpyrrolidone, Junsei Co., Ltd.), and binder resin (mixture of PVDF-HFP and PVDF) were mixed with water at a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a negative 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 a copper thin film (thickness 10 μm) and dried to manufacture a negative electrode having a negative electrode active material layer (thickness 120 μm).

[0122] <Experimental Example 1: Air Permeability> The permeability of the separation membranes of Examples 1 and 2 and Comparative Examples 1 and 2 was measured according to the ASTM D-2873 method. Specifically, the measurement was performed using a Gurley type densometer (No. 158) manufactured by Toyoseiki Co., Ltd., in accordance with the Japanese Industrial Standard (JIS) Gurley measurement method. The permeability value was calculated by passing 100 ml of air through the separation membrane at a pressure of 12.2 in H2O. 2 This is expressed as the time (in seconds) it takes for air to pass through the cross-section, i.e., the permeability time.

[0123] <Experimental Example 2: Measurement of Dry Heat Shrinkage Ratio> The separation membranes of Examples 1 and 2 and Comparative Examples 1 and 2 were cut to a size of 50 mm x 50 mm, placed between sheets of A4 paper, and placed in a 150°C convection oven for 30 minutes. After that, the dry heat shrinkage rates in the mechanical direction (MD) and transverse direction (TD) were measured.

[0124] The aforementioned dry heat shrinkage rate (%) was calculated using the following formula 1. [Formula 1] Dry heat shrinkage rate (%) = (Initial length - Length after heat treatment) / (Initial length) × 100

[0125] <Experimental Example 3: Measurement of Wet Thermal Shrinkage> The separation membranes of Examples 1 and 2 and Comparative Examples 1 and 2 were cut to 50 mm x 50 mm, placed in pouches with the electrolyte, sealed, and then heat-treated at 135°C for 30 minutes. The dimensional changes were then observed.

[0126] The electrolyte was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF6) in an organic solvent consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (combined volume ratio of EC / EMC / DEC = 3:4:3).

[0127] The aforementioned wet thermal shrinkage rate was calculated using the following formula 2.

[0128] [Formula 2] Wet heat shrinkage rate (%) = (Initial length - Length after heat treatment) / (Initial length) × 100

[0129] <Experimental Example 4: Measurement of Peel Strength> In the separation membranes of Examples 1 and 2 and Comparative Examples 1 and 2, the peel strength was measured according to the following method to evaluate the adhesive strength between the porous polymer substrate and the coating layer.

[0130] First, each of the separation membranes was cut to a size of 15 mm x 100 mm. Double-sided adhesive tape was attached to a glass plate, and the cut separation membranes were attached so that the surface of the coating layer of the membrane was in contact with the adhesive tape.

[0131] Subsequently, the end portion of the bonded separation membrane was mounted on a UTM device (LLOYD Instrument LF Plus), and the force required to separate the porous polymer substrate from the coating layer was measured by applying force at a measurement speed of 300 mm / min and an angle of 180°. Furthermore, in the manufacturing process of the separation membranes of Examples 1 and 2 and Comparative Examples 1 and 2, the surface to which the coating layer slurry was first applied was designated as surface A, and the surface to which it was second applied was designated as surface B, and the peel strength was measured for both surface A and surface B.

[0132] <Experimental Example 5: Measurement of Dielectric Breakdown Voltage> For each of the separation membranes of Examples 1 and 2 and Comparative Examples 1 and 2, a sample cut to 5 cm x 5 cm was placed between aluminum fixtures (upper fixture diameter 30 mm, lower fixture 50 mm x 100 mm), and the voltage at which the fail condition (>0.5 mA, 3 sec) occurred was measured using a Hi-pot tester. The measurement conditions were set to DC, current 0.5 mA, and voltage boost 100 V / s (maximum up to 3 kV). The measured values ​​are expressed as the average of 30 samples.

[0133] [Table 1]

[0134] Referring to Table 1 above, Example 1, which included BNNT as the boron nitride compound, achieved air permeability and peel strength at a level equivalent to that of conventional separation membranes. Furthermore, it was confirmed that the dry and wet thermal shrinkage rates decreased, and the dielectric breakdown voltage increased.

[0135] In contrast, Comparative Example 1 and Example 2, which had low BNNT content, showed a sharp increase in both dry and wet heat shrinkage rates, resulting in decreased heat resistance and a reduction in dielectric breakdown voltage. Furthermore, Comparative Example 2, which contained an excess of BNNT, showed a decrease in both dry and wet heat shrinkage rates, but also a decrease in peel strength.

[0136] Therefore, as in one embodiment of the present invention, the heat resistance can be improved by including a boron nitride-based compound in the coating layer of the separation membrane. [Explanation of Symbols]

[0137] 100: Separation membrane for electrochemical elements 110: Porous polymer base material 130: Coating layer 130a:partial 130b: Other parts 131: Boron nitride compounds 133: Polymer Binder Particles 135: Inorganic particles 300: Positive electrode 500: Negative electrode 1000: Electrochemical elements

Claims

1. Porous polymer substrates; and A coating layer is provided on at least one surface of the porous polymer substrate, comprising a boron nitride-based compound, polymer binder particles, and inorganic particles. It has, The amount of inorganic particles is 80 parts by weight or more per 100 parts by weight of the coating layer. The boron nitride-based compound is a boron nitride nanotube, A separation membrane for an electrochemical element, wherein the content of the boron nitride-based compound in the coating layer is 0.1 parts by weight or more and 20 parts by weight or less per 100 parts by weight of the coating layer.

2. The separation membrane for an electrochemical element according to claim 1, wherein the average outer diameter of the boron nitride-based compound is 10 nm or more and 100 nm or less.

3. The separation membrane for an electrochemical element according to claim 1, wherein the average length of the boron nitride-based compound is 1 μm or more and 50 μm or less.

4. The aspect ratio of the boron nitride-based compound is 10 to 5,000, wherein the separation membrane for an electrochemical element is as described in claim 1.

5. The density of the boron nitride-based compound is 1.0 g / cm³. ３ 5.0g / cm or more ３ The separation membrane for an electrochemical element according to claim 1 is as follows:

6. The specific surface area of ​​the boron nitride-based compound is 20 m². ２ / g or more 55m ２ A separation membrane for an electrochemical element according to claim 1, wherein the amount is less than or equal to / g.

7. The separation membrane for an electrochemical element according to claim 1, wherein the inorganic particles are selected from boehmite, alumina, and combinations thereof.

8. An electrochemical element comprising a positive electrode; a negative electrode; and a separation membrane according to any one of claims 1 to 7, interposed between the positive electrode and the negative electrode.

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