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 and, specifically, to a separator for an electrochemical device and an electrochemical device comprising same, wherein by comprising a boron nitride-based compound in a coating layer, transition metal ions eluted from an electrode into electrolyte are adsorbed, thereby improving the heat resistance of the separator.

Description

Separator for electrochemical devices and electrochemical devices containing the same

[0001] The present invention claims the benefit of Korean Patent Application No. 10-2023-0103351, filed with the Korean Intellectual Property Office on August 8, 2023, the entire contents of which are incorporated herein by reference. The present invention relates to a separator for an electrochemical device and an electrochemical device comprising the same, and more particularly, to a separator for an electrochemical device comprising the same, which comprises a boron nitride-based compound in a coating layer, thereby adsorbing transition metal ions dissolved from an electrode into an electrolyte and improving the heat resistance of the separator.

[0002] Among the components of electrochemical devices, the separator comprises a porous polymer substrate located between the anode and cathode. It isolates the anode and cathode, prevents electrical short-circuiting between the two electrodes, and allows the passage of electrolytes and ions. While the separator itself does not participate in electrochemical reactions, its physical properties, such as wettability with electrolyte, degree of porosity, and thermal shrinkage, influence the performance and safety of the electrochemical device.

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

[0004] The separator 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 separator to secure adhesion between the electrode and the separator.

[0005] Meanwhile, as the separator became thinner, there was a problem with the breakdown voltage decreasing, and there was a problem with the performance of the battery deteriorating and the battery short-circuiting due to the formation of dendrites on the electrode.

[0006] Therefore, research on a separator that can secure battery performance, improve battery safety, and prevent dendrite formation was necessary.

[0007] The technical problem to be achieved by the present invention is to provide a separator for an electrochemical device capable of securing heat resistance of the separator by adding a boron nitride compound to a coating layer included in the separator and controlling the content thereof, and to adsorb transition metal ions eluted from an electrode, and an electrochemical device including the same.

[0008] However, 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.

[0009] One embodiment of the present invention provides a separator for an electrochemical device, comprising: a porous polymer substrate; and a coating layer provided on at least one surface of the porous polymer substrate, the coating layer including a boron nitride-based compound, polymer binder particles, and inorganic particles, wherein the content of the inorganic particles is 80 parts by weight or more with respect to 100 parts by weight of the coating layer.

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

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

[0012] According to one embodiment of the present invention, the average outer diameter of the boron nitride 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 compound may be 1 ㎛ or more and 50 ㎛ or less.

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

[0015] According to one embodiment of the present invention, the density of the boron nitride compound is 1.0 g / cm 3 More than 5.0 g / cm 3 It could be as follows:

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

[0017] According to one embodiment of the present invention, a separator for an electrochemical device, wherein the inorganic particles are one selected from boehmite, alumina, and a combination thereof.

[0018] One embodiment of the present invention provides an electrochemical device including: an anode; a cathode; and a separator interposed between the anode and the cathode.

[0019] A separator for an electrochemical device according to one embodiment of the present invention can minimize dendrites formed on an electrode by adsorbing transition metal ions eluted from an electrode using the polarity of the compound generated by the difference in electronegativity between nitrogen and boron in a boron nitride-based compound and the specific surface area of ​​the boron nitride-based compound.

[0020] A separator for an electrochemical device according to one embodiment of the present invention can improve the heat resistance of the separator by utilizing the heat resistance of a boron nitride-based compound.

[0021] An electrochemical device according to one embodiment of the present invention can minimize dendrites formed on an electrode, thereby realizing battery safety and improving battery performance.

[0022] Figures 1a and 1b are schematic diagrams of a separator for an electrochemical device according to one embodiment of the present invention. Specifically, Figure 1a is a schematic diagram of a separator for an electrochemical device having a coating layer on one surface, and Figure 1b is a schematic diagram of a separator for an electrochemical device having coating layers on both surfaces.

[0023] Figure 2 is a schematic diagram of an electrochemical device according to one embodiment of the present invention.

[0024] 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.

[0025] In this specification, “A and / or B” means “A and B, or A or B.”

[0026] In this specification, when it is said that a component is “provided on”, this does not exclude other components being placed in between, unless otherwise specifically stated, but rather means that other components may be placed thereon.

[0027] 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.

[0028] 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.

[0029] Hereinafter, the present invention will be described in more detail.

[0030] One embodiment of the present invention provides a separator (100) for an electrochemical device, comprising: a porous polymer substrate (110); and a coating layer (130) provided on at least one surface of the porous polymer substrate (110) and including 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 with respect to 100 parts by weight of the coating layer (130).

[0031] According to an embodiment of the present invention, a separator (100) for an electrochemical device can minimize dendrites formed on an electrode by adsorbing transition metal ions eluted from the electrode using the polarity of the compound generated by the difference in electronegativity between nitrogen and boron in the boron nitride-based compound (131) and the specific surface area of ​​the boron nitride-based compound (131). Furthermore, according to an embodiment of the present invention, a separator (100) for an electrochemical device can improve the heat resistance of the separator by using the excellent heat resistance of the boron nitride-based compound (131).

[0032] FIG. 1A and FIG. 1B are schematic diagrams of a separator (100) for an electrochemical device according to an embodiment of the present invention. Specifically, FIG. 1A is a schematic diagram of a separator (100) for an electrochemical device having a coating layer (130) on one side, and FIG. 1B is a schematic diagram of a separator (100) for an electrochemical device having a coating layer (130) on both sides. Referring to FIG. 1A and FIG. 1B, a separator (100) for an electrochemical device according to an embodiment of the present invention will be described in detail.

[0033] According to one embodiment of the present invention, the separator (100) for an electrochemical device includes a porous polymer substrate (110). As described above, the separator (100) for an electrochemical device includes the porous polymer substrate (110), thereby allowing lithium ions to pass through while blocking electrical contact, and implementing a shutdown function at an appropriate temperature.

[0034] According to one embodiment of the present invention, the porous polymer substrate (110) 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 may include one or more of these. A porous separation membrane 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.

[0035] According to one embodiment of the present invention, the weight average molecular weight of the polyolefin resin may be 500,000 or more and 2,000,000 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 of the polyolefin resin can be calculated by adding the weight average molecular weights according to the content ratio of each polyolefin resin.

[0036] In this specification, 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.

[0037] - Column: PL Olexis (Polymer Laboratories)

[0038] - Solvent: TCB (Trichlorobenzene)

[0039] - Flow rate: 1.0 ml / min

[0040] - Sample concentration: 1.0 mg / ml

[0041] - Injection volume: 200 ㎕

[0042] - Column temperature: 160 ℃

[0043] - Detector: Agilent High Temperature RI detector

[0044] - Standard: Polystyrene (corrected with a cubic function)

[0045] According to one embodiment of the present invention, the porous polymer substrate (110) may be manufactured by a method (wet method) in which a polyolefin resin is mixed with a plasticizer at a high temperature to form a single phase, the polymer material and the plasticizer are phase-separated during a cooling process, the plasticizer is extracted to form pores, and then stretching and heat-setting are performed. In addition, the porous polymer substrate using the polyolefin resin may have a core portion made of a mixture of polyethylene and polypropylene and a polyethylene skin portion laminated on both sides of the core portion.

[0046] 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 (100) 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.

[0047] According to one embodiment of the present invention, the thickness of the porous polymer substrate (110) may be 1 ㎛ or more and 50 ㎛ or less. Specifically, the thickness of the porous polymer substrate (110) may be 2 ㎛ or more and 45 ㎛ or less, 3 ㎛ or more and 40 ㎛ or less, 4 ㎛ or more and 35 ㎛ or less, 5 ㎛ or more and 30 ㎛ or less, 6 ㎛ or more and 25 ㎛ or less, 7 ㎛ or more and 20 ㎛ or less, or 8 ㎛ or more and 15 ㎛ or less. By controlling the thickness of the porous polymer substrate (110) within the above-described range, the energy density of the battery can be improved.

[0048] 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 controlling the porosity of the porous polymer substrate (110) within the above-described range, the permeability of lithium ions through the separator can be controlled.

[0049] 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 electrochemical device separator (100) includes the coating layer (130) provided on one or both surfaces of the porous polymer substrate (110). As described above, the electrochemical device separator (100) includes the coating layer (130) provided on at least one surface of the porous polymer substrate (110), thereby improving the heat resistance of the separator, improving the mechanical properties, and preventing the separator from shrinking at high temperatures and causing an electrical short circuit of the electrode.

[0050] According to one embodiment of the present invention, the electrochemical device separator (100) includes a coating layer (130) including a boron nitride-based compound (131), polymer binder particles (133), and inorganic particles (135). As described above, since the coating layer (130) includes the boron nitride-based compound (131), the polymer binder particles (133), and the inorganic particles (135), the heat resistance of the separator (100) is improved, the mechanical properties are improved, the shrinkage of the separator (100) at high temperatures is prevented, resulting in an electrical short circuit of the electrode, and pores can be formed inside the coating layer (130). Furthermore, the heat resistance of the separator (100) is improved, and transition metal ions eluted from the electrode can be adsorbed.

[0051] According to one embodiment of the present invention, the coating layer (130) may be uniformly comprised of 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) may be uniformly dispersed in a slurry for a coating layer for forming the coating layer, and the slurry for the coating layer may be coated to remove a dispersion medium or solvent, so that the boron nitride-based compound (131), the polymer binder particles (133), and the inorganic particles (135) are distributed in a uniform content. The content (weight) of each of the boron nitride-based compound (131), the polymer binder particles (133), and the inorganic particles (135) may be uniform in the coating layer, and even if there is some difference, the difference may be within 5%. As described above, by uniformly including the boron nitride compound (131), the polymer binder particles (133), and the inorganic particles (135) in the coating layer (130), the compression resistance of the separation membrane can be improved.

[0052] 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 with respect to 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 and less than 100 parts by weight, 82 parts by weight or more and 99 parts by weight or less, 83 parts by weight or more and 98 parts by weight or less, 84 parts by weight or more and 97 parts by weight or less, 85 parts by weight or more and 96 parts by weight or less, 86 parts by weight or more and 95 parts by weight or less, 87 parts by weight or more and 94 parts by weight or less, 88 parts by weight or more and 93 parts by weight or less, 89 parts by weight or more and 92 parts by weight or less, or 90 parts by weight or more and 91 parts by weight or less with respect to 100 parts by weight of the coating layer (130). By controlling the content of the inorganic particles (135) included in the coating layer (130) within the above-described range, the polymer binder and the inorganic particles can be uniformly distributed within the coating layer, and the compression resistance and heat resistance of the coating layer can be improved.

[0053] 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 based on 100 parts by weight of the coating layer (130). By controlling the content of the boron nitride-based compound in the coating layer within the above-described range, the insulating properties and thermal conductivity properties of the separator are improved by utilizing the insulating properties of the boron nitride-based compound, and the polarity of the compound due to the difference in electronegativity between nitrogen and boron in the boron nitride-based compound is induced, thereby allowing the adsorption of transition metal ions eluted from the electrode.

[0054] According to one embodiment of the present invention, the boron nitride-based compound may form a network within the coating layer. Specifically, the boron nitride-based compounds may be connected to each other to form a single net (web). As described above, the boron nitride-based compound forms a network within the coating layer, thereby enabling the heat resistance of the boron nitride-based compound to be uniformly implemented throughout the entire coating layer.

[0055] 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 are utilized to improve the insulating and thermal conductivity properties of the separator, and the polarity of the compound due to the difference in electronegativity between nitrogen and boron in the boron nitride nanotube can be induced to adsorb transition metal ions eluted from the electrode.

[0056] According to one embodiment of the present invention, the average outer diameter of the boron nitride-based compound (131) may be 10 nm or more and 100 nm or less. Specifically, the average outer diameter of the boron nitride-based compound (131) may be 20 nm or more and 90 nm or less, 30 nm or more and 80 nm or less, 40 nm or more and 70 nm or less, or 50 nm or more and 60 nm or less. By controlling the average outer diameter of the boron nitride-based compound (131) within the above-described range, a uniform network can be formed within the coating layer, thereby improving the thermal stability, mechanical strength, and electrical insulation of the separator.

[0057] According to one embodiment of the present invention, the average length of the boron nitride-based compound (131) may be 1 ㎛ or more and 50 ㎛ or less. Specifically, the average length of the boron nitride-based compound (131) may be 5 ㎛ or more and 45 ㎛ or less, 10 ㎛ or more and 40 ㎛ or less, 15 ㎛ or more and 35 ㎛ or less, or 20 ㎛ or more and 30 ㎛ or less. By controlling 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, thereby improving the thermal stability, mechanical strength, and electrical insulation of the separator.

[0058] According to one embodiment of the present invention, the aspect ratio of the boron nitride-based compound (131) may be 10 or more and 5,000 or less. Specifically, the aspect ratio of the boron nitride-based compound (131) may 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 controlling 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, thereby improving the thermal stability and mechanical strength of the separation membrane.

[0059] According to one embodiment of the present invention, the density of the boron nitride compound (131) is 1.0 g / cm 3 More than 5.0 g / cm 3 It may be as follows. Specifically, the density of the boron nitride compound (131) is 1.5 g / cm 3 More than 4.5 g / cm 3 Below 2.0 g / cm 3 More than 4.0 g / cm 3 or less, or 2.5 g / cm 3 More than 3.5 g / cm 3It may be as follows. By controlling the density of the boron nitride compound (131) within the above-described range, the energy density of the electrochemical device can be improved while ensuring thermal stability and mechanical strength of the separator.

[0060] According to one embodiment of the present invention, the specific surface area (BET) of the boron nitride compound (131) is 20 m 2 / g or more than 55 m 2 / g or less. Specifically, the specific surface area of ​​the boron nitride compound (131) is 21 m 2 / g or more than 54 m 2 / g or less, 22 m 2 / g or more than 53 m 2 / g or less, 23 m 2 / g or more than 52 m 2 / g or less, 24 m 2 / g or more than 51 m 2 / g or less, 25 m 2 / g or more than 50 m 2 / g or less, 26 m 2 / g or more 49 m 2 / g or less, 27 m 2 / g or more 48 m 2 / g or less, 28 m 2 / g or more 47 m 2 / g or less, 29 m 2 / g or more 46 m 2 / g or less, 30 m 2 / g or more than 45 m 2 / g or less, 31 m 2 / g or more 44 m 2 / g or less, 32 m 2 / g or more 43 m 2 / g or less, 33 m 2 / g or more 42 m 2 / g or less, 34 m 2 / g or more 41 m 2 / g or less, 35 m 2 / g or more than 40 m 2 / g or less, 36 m 2 / g or more 39 m 2 / g or less or 37 m 2 / g or more than 38 m 2 / g or less. By controlling the specific surface area of ​​the boron nitride compound (131) within the above-described range, the energy density of the electrochemical device can be improved while ensuring thermal stability and mechanical strength of the separation membrane, and the adsorption efficiency of the transition metal can be improved.

[0061] In this specification, "specific surface area" may be calculated using the Brunauer-Ennett-Teller model (BET) from the measured N2 adsorption isotherm when an adsorption isotherm is measured at -196 ℃ conditions up to 1 bar using a BET-specific surface area analyzer (BEL, Microtrac Co.).

[0062] According to one embodiment of the present invention, the coating layer (130) may include 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 including a plurality of pores therein. As described above, by including a plurality of pores, the coating layer can physically block the negative electrode and the positive electrode while allowing lithium ions to pass through and current to flow.

[0063] According to one embodiment of the present invention, the coating layer (130) may be formed by bonding a boron nitride-based compound and inorganic particles (135) by polymer binder particles (133) and integrating them within the coating layer. The pores within the coating layer (130) may be derived from an interstitial volume, which is an empty space between the boron nitride-based compounds and the inorganic particles.

[0064] According to one embodiment of the present invention, the thickness of the coating layer (130) may be formed to a thickness of 1 μm to 20 μm on either side of the porous polymer substrate (110). By controlling the thickness of the coating layer (130) within the above-described range, the heat resistance or electrical resistance of the separator can be controlled within an appropriate range.

[0065] In one embodiment of the present invention, the thickness of the porous polymer substrate and / or the coating layer, etc., can be measured using a contact-type thickness measuring device. The contact-type thickness measuring device can be, for example, VL-50S-B from Mitutoyo.

[0066] 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 including the acrylic repeating unit and the polyvinylidene repeating unit, or a hybrid of the acrylic binder and the polyvinylidene binder. In addition, the polyvinylidene binder may be a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP). By selecting the polymer binder particles described above, the porosity of the separator can be maintained, and the adhesive strength between the electrode and the separator can be improved in the lamination process of the battery, so that the battery can be easily manufactured, and the stacking process can be stably implemented. Furthermore, the porosity of the separator can be maintained, and the adhesive strength can be maintained even when the coating layer is wetted by the electrolyte after battery activation. Furthermore, the stiffness of the battery can be improved, and banding of the separator can be prevented.

[0067] According to one embodiment of the present invention, the acrylic binder is a polymer containing a carboxylic acid ester as a repeating unit, and may preferably be a (meth)acrylic acid ester or an acrylic-styrene copolymer.

[0068] 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 may be at least one selected from these. Among these, at least one selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate is preferable, and methyl (meth)acrylate is particularly preferable.

[0069] 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 acrylic binder may be at least one selected from the group consisting of styrene-butyl acrylate, styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate polymers, and more specifically, may be a copolymer including acrylate.

[0070] 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. By controlling the glass transition temperature (Tg) of the polymer binder particles within the above-described range, the viscosity of the slurry for producing the coating layer may be controlled, thereby improving the convenience of battery production.

[0071] According to one embodiment of the present invention, the average diameter (D) of the polymer binder particles (133) 50 ) has no special limitations, but in order to form a coating layer (130) of uniform thickness and an appropriate porosity, it is preferably in the range of 0.1 ㎛ to 1 ㎛. Specifically, the average diameter (D) of the polymer binder particles (135) 50) may be 0.2 ㎛ or more and 0.9 ㎛ or less, 0.3 ㎛ or more and 0.8 ㎛ or less, 0.4 ㎛ or more and 0.7 ㎛ or less, or 0.5 ㎛ or more and 0.6 ㎛ or less. In the above-described range, the average diameter (D of the polymer binder particles (133) 50 ) can improve the dispersibility in the slurry prepared for manufacturing the coating layer, and reduce the thickness of the formed coating layer.

[0072] According to one embodiment of the present invention, the polyvinylidene-based binder may be a polyvinylidene-based binder having a hexafluoropropylene (HFP) content of 1 wt% or more and 50 wt% or less. Specifically, the hexafluoropropylene (HFP) content in the polyvinylidene-based binder may be 1 wt% or more and 50 wt% or less, 2 wt% or more and 45 wt% or less, 3 wt% or more and 40 wt% or less, 4 wt% or more and 35 wt% or less, 5 wt% or more and 30 wt% or less, 7 wt% or more and 25 wt% or less, or 10 wt% or more and 20 wt% or less. As described above, by selecting the polyvinylidene-based binder as a polyvinylidene-based binder having a hexafluoropropylene content of 1 wt% or more and 50 wt% or less, the porosity of the separator can be maintained, and the adhesive strength can be maintained even when the coating layer is wetted by the electrolyte after battery activation. In the present specification, the degree of substitution of the polyvinylidene-based binder may mean the weight ratio containing hexafluoropropylene.

[0073] According to one embodiment of the present invention, the content of the polymer binder particles (133) may be 20 parts by weight or less with respect to 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 less than or equal to 20 parts by weight, 1 parts 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 with respect to 100 parts by weight of the coating layer (130). By controlling the content of the polymer binder particles (133) within the above-described range, the ease of assembly in the process of assembling the electrode can be improved, and the heat resistance of the coating layer can be improved.

[0074] According to one embodiment of the present invention, when combining the acrylic binder and the polyvinylidene binder in the coating layer (130), the weight ratio may be 9:1 to 1:9. Specifically, when combining the acrylic binder and the polyvinylidene binder in the coating layer (130), the weight ratio may 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-described range, the wet adhesiveness and the dry adhesiveness of the separator for an electrochemical device can be simultaneously improved.

[0075] According to one embodiment of the present invention, the inorganic particles (135) that can be used in the coating layer (130) may be electrochemically stable. Specifically, the inorganic particles that can be used in one embodiment of the present invention may be stable within the operating voltage range of the applied electrochemical device (e.g., Li / Li). + It may be that no oxidation and / or reduction reaction occurs at a voltage of 0 V to 5 V as a reference.

[0076] 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 / 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, etc., and may include one or more of these. Specifically, the inorganic particle (135) is preferably one selected from boehmite, alumina, and a combination thereof. As described above, by selecting the inorganic particles as one selected from boehmite, alumina, and a combination thereof, the heat resistance of the separation membrane can be improved.

[0077] According to one embodiment of the present invention, the average diameter (D) of the inorganic particles (135) 50) has no special limitations, but in order to form a coating layer (130) of uniform thickness and an appropriate porosity, it is preferably in the range of 0.3 ㎛ to 1 ㎛. Specifically, the average diameter (D) of the inorganic particles (135) 50 ) may be 0.2 ㎛ or more and 0.9 ㎛ or less, 0.3 ㎛ or more and 0.8 ㎛ or less, 0.4 ㎛ or more and 0.7 ㎛ or less, or 0.5 ㎛ or more and 0.6 ㎛ or less. Specifically, when it is less than 0.3 ㎛, the dispersibility of the inorganic particles in the slurry prepared for manufacturing the coating layer may be reduced, and when it exceeds 1 ㎛, the thickness of the formed coating layer may increase.

[0078] In this specification, "D 50 "Particle size" means the particle size at the 50% point of the cumulative distribution of the number of particles according to the 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 the particle size distribution is calculated by measuring the difference in the diffraction pattern according to the particle size when the particles pass through the laser beam. By calculating the particle diameter at the point where it becomes 50% of the cumulative distribution of the number of particles according to the particle size in the measuring device, D 50 The mouth diameter can be measured.

[0079] According to one embodiment of the present invention, the porosity of the coating layer (130) may be 30% by volume or more. Specifically, the porosity of the coating layer (130) may be 30% by volume or more and 70% by volume or less, 32% by volume or more and 68% by volume or less, 34% by volume or more and 66% by volume or less, 36% by volume or more and 64% by volume or less, 38% by volume or more and 62% by volume or less, 40% by volume or more and 60% by volume or less, 42% by volume or more and 58% by volume or less, 44% by volume or more and 56% by volume or less, 46% by volume or more and 54% by volume or 48% by volume or more and 52% by volume. By controlling the porosity of the coating layer (130) within the above-described range, it is possible to maintain the movement of ions in the separator and prevent an increase in resistance of the separator. Specifically, if the porosity is 70% by volume or less, mechanical properties that can withstand the pressing process for bonding with the electrode can be secured, and the surface opening ratio is not too high, making it suitable for securing adhesive strength. On the other hand, if the porosity is 30% by volume or more, it is advantageous from the perspective of ion permeability.

[0080] In this specification, “porosity” means the ratio of the volume occupied by pores to the total volume, and uses volume% as its unit, and can be used interchangeably with terms such as porosity and porosity.

[0081] In this specification, porosity may correspond to a value obtained by subtracting a volume converted to the weight and density of each component of the porous polymer substrate (110) and / or coating layer (130) from the volume calculated in the thickness, width, and length of the porous polymer substrate (110) and / or coating layer (130).

[0082] 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) through a nitrogen gas adsorption flow method. In this case, it may be advantageous to use a capillary flow porometer.

[0083] According to one embodiment of the present invention, the polyvinylidene-based binder may be an aqueous binder. Specifically, by selecting the polyvinylidene-based binder as an aqueous binder, pollutants emitted during the manufacturing process of the separator can be minimized, thereby reducing the manufacturing cost of the battery.

[0084] According to one embodiment of the present invention, the separator may further include an adhesive layer on the coating layer. By further including the adhesive layer as described above, the adhesive strength between the coating layer and the electrode described below can be improved.

[0085] According to one embodiment of the present invention, the adhesive layer may include a polymer binder.

[0086] According to one embodiment of the present invention, the polymer binder may be in the form of particles or a solution.

[0087] 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 unit and the polyvinylidene repeating unit, or a hybrid of the acrylic binder and the polyvinylidene binder. In addition, 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 separator can be maintained, and the adhesion can be maintained even when the coating layer is wetted by the electrolyte after activation of the battery. Furthermore, it can improve the stiffness of the battery and prevent banding of the separator. Furthermore, the polymer binder overlaps with the description of the polymer binder particles of the coating layer described above, and thus is omitted.

[0088] According to one embodiment of the present invention, the separator may be provided with a polymer binder on the coating layer. Specifically, the separator may not be provided as a single layer on the coating layer, but may be partially provided with the polymer binder. The polymer binder may be in particulate or soluble form. When the polymer binder on the coating layer is in particulate form, the polymer binder may be partially provided on the coating layer while maintaining the particulate form. When the polymer binder is in soluble form, it may be provided as a layer on a portion of the coating layer. As described above, by providing the separator with the polymer binder on the coating layer, adhesion to the electrode can be secured, and the porosity of the coating layer can be secured.

[0089]

[0090] One embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device, comprising the steps of: mixing a slurry for a coating layer (130) including a boron nitride compound (131), polymer binder particles (133), and inorganic particles (135) (S10); applying the slurry for the coating layer on at least one surface of a porous polymer substrate (110) (S30); and drying the slurry for the coating layer to form a coating layer (130) (S50).

[0091] A method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention can improve the heat resistance of the separator.

[0092] According to one embodiment of the present invention, the method for manufacturing the electrochemical device separator (100) includes a step (S10) of mixing a slurry for a coating layer including a boron nitride-based compound (131), a polymer binder particle (133), and an inorganic particle (135). As described above, by including the step (S10) of mixing a slurry for a coating layer including a boron nitride-based compound (131), a polymer binder particle (133), and an inorganic particle (135), a coating layer can be easily formed on the separator.

[0093] According to one embodiment of the present invention, a polymer emulsion may be prepared by dispersing polymer binder particles (133) in water, which is a suitable dispersion medium, to thereby prepare a slurry for a coating layer. As described above, by dispersing polymer binder particles (133) in water, which is a suitable dispersion medium, to thereby prepare a polymer emulsion and thereby prepare a slurry for a coating layer, contaminants generated during the manufacturing process can be minimized. In the present specification, the dispersion medium may refer to a solvent used in the process of preparing the slurry.

[0094] According to one embodiment of the present invention, a boron nitride-based compound (131) and inorganic particles (135) can be added 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 in consideration of the thickness, pore size, and porosity of the coating layer according to one embodiment of the present invention to be finally manufactured.

[0095] According to one embodiment of the present invention, a slurry for a coating layer can be prepared by dispersing a boron nitride-based compound (131), a polymer binder particle (133), and an inorganic particle (135) in water as a dispersion medium. Specifically, as described above, a slurry for a coating layer can be prepared by directly dispersing a boron nitride-based compound (131), a polymer binder particle (133), and an inorganic particle (135) in water as a dispersion medium without forming a polymer emulsion.

[0096] According to one embodiment of the present invention, the solid content of the slurry for the coating layer may be 10 wt% or more and 50 wt% or less. Specifically, the solid content of the slurry for the coating layer may be 15 wt% or more and 40 wt% or less, 20 wt% or more and 35 wt% or less, or 15 wt% or more and 40 wt% or less. By controlling the solid content of the slurry for the coating layer within the above-described range, the workability of the coating layer manufacturing process can be improved.

[0097] According to one embodiment of the present invention, the method for manufacturing the electrochemical device separator (100) includes a step (S30) of applying the slurry for the coating layer on at least one surface of the porous polymer substrate (110). As described above, by including the step of applying the slurry for the coating layer on at least one surface of the porous polymer substrate (110), the coating layer (130) can be formed with a single application, and the slurry for the coating layer can form a uniform coating layer by distributing inorganic particles, polymer binder particles, and boron nitride-based compounds at a uniform concentration.

[0098] According to one embodiment of the present invention, the method of applying the slurry for the coating layer to the surface of the porous polymer substrate (110) is not particularly limited to any one method, and a conventional method known in the art may be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a mixture thereof may be used.

[0099] According to one embodiment of the present invention, the method for manufacturing the electrochemical device separator (100) includes a step (S50) of drying the slurry for the coating layer to form a coating layer (130). As described above, by including the step (S50) of drying the slurry for the coating layer to form a coating layer (130), damage to the coating layer can be minimized, and the dispersion medium included in the slurry can be easily removed.

[0100] According to one embodiment of the present invention, the temperature of the drying process may be 25°C or more and 75°C or less. Specifically, the temperature of the drying process 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 controlling the temperature of the drying process within the above-described range, the denaturation of the porous polymer substrate can be prevented, and the dispersion medium can be effectively removed.

[0101] 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 coating layer (130). The drying may be performed using a drying auxiliary device such as a drying oven or hot air within an appropriate range.

[0102] According to one embodiment of the present invention, the step of forming an adhesive layer by applying a slurry for an adhesive layer containing a polymer binder onto the coating layer may be further included. By further including the step of forming an adhesive layer by applying a slurry for an adhesive layer containing a polymer binder as described above onto the coating layer, the adhesive strength between the separator and the electrode can be improved, the adhesive strength can be maintained during the lamination process with the electrode, and the adhesive strength can be maintained after battery activation to improve stiffness or prevent the pouch type cell from bending.

[0103] 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, environmental contamination by the dispersion medium or solvent can be prevented.

[0104] According to one embodiment of the present invention, a step of drying the applied adhesive layer may be further included.

[0105] According to one embodiment of the present invention, the separator (100) is interposed between the positive electrode (300) and the negative electrode (500) and is manufactured into an electrochemical device (1000) through a lamination process in which heat and / or pressure are applied to bond the separator. In one embodiment of the present invention, the lamination process can be performed by a roll press device including a pair of pressure rollers. That is, the negative electrode (500), the separator (100), and the positive electrode (300) are sequentially laminated and inserted between the pressure rollers to achieve interlayer bonding. At this time, the lamination process can be performed by a hot press method.

[0106]

[0107] One embodiment of the present invention provides an electrochemical device (1000) including: an anode (300); a cathode (500); and a separator (100) interposed between the anode (300) and the cathode (500).

[0108] An electrochemical device (1000) according to one embodiment of the present invention can minimize dendrites formed on an electrode, thereby realizing battery safety and improving battery performance.

[0109] Figure 2 is a schematic diagram of an electrochemical device (1000) according to one embodiment of the present invention. Referring to Figure 2, the electrochemical device (1000) according to one embodiment of the present invention will be described in detail.

[0110] In one embodiment of the present invention, the electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept encompassing a primary battery and a secondary battery. In the present specification, the secondary battery is capable of charging and discharging, and refers to a lithium secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, etc. The lithium secondary battery uses lithium ions as an ion conductor, and examples thereof include, but are not limited to, a non-aqueous electrolyte secondary battery including a liquid electrolyte, an all-solid-state battery including a solid electrolyte, a lithium polymer battery including a gel polymer electrolyte, and a lithium metal battery using lithium metal as an anode.

[0111] In one embodiment of the present invention, the electrochemical device may have a cylindrical shape. Specifically, the electrochemical device may be one in which an electrode assembly including the positive electrode, the separator, and the negative electrode is built into a cylindrical metal case. More specifically, the electrochemical device 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 bonding a cap having an electrode terminal formed on the open top of the metal case. As described above, the electrochemical device is manufactured in a cylindrical shape, thereby improving capacity and structural safety.

[0112] According to one embodiment of the present invention, the positive electrode has a positive electrode current collector and a positive electrode active material layer including a positive electrode active material, a conductive material, and a binder resin on at least one surface of the positive electrode current collector. The positive electrode active material is a layered compound such as lithium manganese oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-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 LiMn1-xM xA 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.

[0113] According to one embodiment of the present invention, the negative electrode has a negative electrode current collector and a negative electrode active material layer including a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The negative electrode includes carbon such as lithium metal oxide, non-graphitizable carbon, and graphite carbon as the negative electrode active material; LixFe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함할 수 있다.

[0114] According to one embodiment of the present invention, the conductive material may be, for example, one selected from the group consisting of graphite, carbon black, carbon fibers or metal fibers, metal powders, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials among these. More specifically, the conductive material may be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more conductive materials among these.

[0115] According to one embodiment of the present invention, the current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used.

[0116] According to one embodiment of the present invention, the binder resin may be a polymer commonly used in electrodes in the art. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples thereof include, but are not limited to, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose.

[0117] 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).

[0118] According to one embodiment of the present invention, the content of the dispersant included in the positive electrode slurry may be more than 0 part by weight and less than or equal to 0.5 part by weight with respect to 100 parts by weight of the positive electrode slurry. Specifically, the content of the dispersant included in the positive electrode slurry may be more than 0.05 part by weight and less than or equal to 0.4 part by weight with respect to 100 parts by weight of the positive electrode slurry.

[0119] According to one embodiment of the present invention, the negative electrode slurry for producing the negative electrode active material layer may include a dispersant, and the dispersant may be a polypyrrolidone-based compound. Specifically, the dispersant may be polyvinylpyrrolidone (Polyvinylpyrrolidone, Junsei, Japan).

[0120] According to one embodiment of the present invention, the content of the dispersant included in the cathode slurry may be more than 0 part by weight and less than or equal to 0.5 part by weight with respect to 100 parts by weight of the cathode slurry. Specifically, the content of the dispersant included in the cathode slurry may be more than 0.05 part by weight and less than or equal to 0.4 part by weight with respect to 100 parts by weight of the cathode slurry.

[0121] According to one embodiment of the present invention, an electrochemical device prepared as described above can be placed in an appropriate case and an electrolyte solution is injected to manufacture a battery.

[0122] According to one embodiment of the present invention, the electrolyte is A + B - As a salt with the same structure, A + is Li + , Na + , K +B containing an ion composed of an alkali metal cation or a combination thereof; - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - 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.

[0123] One embodiment of the present invention provides a battery module including a battery 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, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0124] 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 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.

[0125] <Example 1>

[0126] 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.

[0127] Boron nitride nanotubes (average outer diameter: 50 nm, length: 25 ㎛, aspect ratio: 100, density 3.0 g / cm) made of boron nitride compounds 3 , specific surface area (BET): 40 m 2 / g), styrene-butyl acrylate (glass transition temperature 40°C), an acrylic binder with a particle size of 500 nm as a polymer binder particle, and boehmite (particle size: 500 nm) as an inorganic particle were added to water and dispersed to prepare a slurry for a coating layer (solid concentration 20 wt%). The weight ratio of the boron nitride compound, the polymer binder particles, and the inorganic particles was 2:5:93.

[0128] The slurry for the coating layer was applied to both sides of the surface of the porous polymer substrate using a doctor blade by bar coating, and dried with wind at 50°C using a heat gun to form a coating layer with a thickness of 1.5 μm on each side, thereby manufacturing a separator with a total thickness of 12 μm.

[0129] <Example 2>

[0130] A separation membrane was manufactured in the same manner as in Example 1, except that the weight ratio of the boron nitride compound, the polymer binder particles, and the inorganic particles was 0.05:4.95:95.

[0131]

[0132] <Comparative Example 1>

[0133] A separation membrane was manufactured in the same manner as in Example 1, except that the weight ratio of the boron nitride compound, the polymer binder particles, and the inorganic particles was 0:5:95.

[0134] Comparative Example 2

[0135] A separation membrane was manufactured in the same manner as in Example 1, except that the weight ratio of the boron nitride compound, the polymer binder particles, and the inorganic particles was 25:5:70.

[0136] <Manufacturing of electrochemical devices>

[0137] 1) Manufacturing of the anode

[0138] 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).

[0139] 2) Manufacturing of cathode

[0140] 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).

[0141]

[0142] <Experimental Example 1: Ventilation>

[0143] The air permeability of the membranes of Examples 1 and 2 and Comparative Examples 1 and 2 was measured by the ASTM D-2873 method. Specifically, the measurement was performed using a Gurley type Densometer (No. 158) from Toyoseiki according to the JIS Gurley measurement method of the Japanese Industrial Standard. The air permeability value was calculated by applying 100 ml of air under a pressure of 12.2 in H2O to the membrane 1 in. 2 The time (in seconds) it takes to pass through the cross section is expressed as the ventilation time.

[0144]

[0145] <Experimental Example 2: Dry Heat Shrinkage Measurement>

[0146] The 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 A4 papers, and placed in a convection oven at 150°C for 30 minutes, and then the dry heat shrinkage in the machine direction (MD) and transverse direction (TD) was measured.

[0147] The above dry heat shrinkage rate (%) was calculated using the following mathematical formula 1.

[0148] [Mathematical Formula 1]

[0149] Dry heat shrinkage (%) = (Initial length - length after heat treatment) / (Initial length) X 100

[0150]

[0151] <Experimental Example 3: Wet Heat Shrinkage Measurement>

[0152] The separators of Examples 1 and 2 and Comparative Examples 1 and 2 were cut to 50 mm X 50 mm, placed in a pouch together with an electrolyte, sealed, and then heat-treated at 135°C for 30 minutes to observe dimensional changes.

[0153] The above 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) (mixed volume ratio of EC / EMC / DEC = 3:4:3).

[0154] The above wet heat shrinkage rate was calculated using the following mathematical formula 2.

[0155] [Equation 2]

[0156] Wet heat shrinkage rate (%) = (Initial length - length after heat treatment) / (Initial length) X 100

[0157]

[0158] <Experimental Example 4: Peel Strength Measurement>

[0159] In order to evaluate the adhesive strength between the porous polymer substrate and the coating layer in the separators of Examples 1 and 2 and Comparative Examples 1 and 2, the peel strength was measured according to the following method.

[0160] First, each of the above separators was cut to a size of 15 mm X 100 mm. Double-sided adhesive tape was attached to a glass plate, and the surface of the coating layer of the cut separator was attached so that it adhered to the adhesive tape.

[0161] Afterwards, the end of the bonded separator was mounted on a UTM device (LLOYD Instrument LF Plus) and force was applied at a measurement speed of 300 mm / min and an angle of 180° to measure the force required to peel off the porous polymer substrate and the coating layer. Additionally, in the manufacturing process of the separator of Examples 1 and 2 and Comparative Examples 1 and 2, the side on which the slurry for the coating layer was first applied was set as side A, and the side on which the slurry for the coating layer was applied second was set as side B, and the peel strength was measured for each of sides A and B.

[0162]

[0163] <Experimental Example 5: Measurement of Insulation Breakdown Voltage>

[0164] For each of the 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 jigs (upper jig diameter 30 mm, lower jig 50 mm X 100 mm), and the voltage at which a Fail condition (>0.5 mA, 3 sec) occurred was measured using a Hi-pot tester. At this time, the measurement conditions were set to direct current (DC), current 0.5 mA, and voltage increase 100 V / s (up to 3 kV). The measured value was expressed as the average value of 30 samples.

[0165] Example 1 Comparative Example 1 Example 2 Comparative Example 2 Thickness (unit: ㎛) 12 12 12 12 12 Air permeability (unit: S / 100cc) 17 5 17 0 16 9 19 0 Dry heat shrinkage (unit: %) MD direction 3 14 13 2 TD direction 2 1 1 1 2 1 Wet heat shrinkage (unit: %) MD direction 9 5 4 5 6 TD direction 9 5 2 5 4 4 Peel strength (unit: Gf / 15mm) A side 3 5 3 7 3 6 10 B side 3 9 3 3 3 4 1 1 Insulation breakdown voltage (unit: V) 1,438 1,284 1,275 1,567

[0166] Referring to Table 1 above, it was confirmed that Example 1, which includes BNNT as a boron nitride compound, has similar levels of air permeability and peel strength as conventional separators, while reducing dry heat shrinkage and wet heat shrinkage and increasing breakdown voltage.

[0167] In this regard, Comparative Example 1 without BNNT and Example 1 with a low BNNT content showed a rapid increase in dry heat shrinkage and wet heat shrinkage, which resulted in a decrease in heat resistance, and a decrease in dielectric breakdown voltage. Furthermore, Comparative Example 2 showed a decrease in dry heat shrinkage and wet heat shrinkage due to the excessive inclusion of BNNT, but a decrease in peel strength, which resulted in a rapid increase in dielectric breakdown voltage.

[0168] Therefore, heat resistance can be improved by including a boron nitride compound in the coating layer of the separation membrane, which is an embodiment of the present invention.

[0169] [Explanation of symbols]

[0170] 100: Separator for electrochemical devices

[0171] 110: Porous polymer substrate

[0172] 130: Coating layer

[0173] 130a: Partial

[0174] 130b: Other parts

[0175] 131: Boron nitride compounds

[0176] 133: Polymer binder particles

[0177] 135: Inorganic particles

[0178] 300: Bipolar

[0179] 500: Negative

[0180] 1000: Electrochemical devices

Claims

1. Porous polymer substrate; and It is provided on at least one side of the porous polymer substrate, and includes a coating layer including a boron nitride compound, polymer binder particles, and inorganic particles. A separator for an electrochemical device, wherein the content of the above-mentioned inorganic particles is 80 parts by weight or more with respect to 100 parts by weight of the above-mentioned coating layer.

2. In claim 1, A separator for an electrochemical device, wherein the content of the boron nitride compound in the coating layer is 0.1 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the coating layer.

3. In claim 1, A separator for an electrochemical device, wherein the above boron nitride compound is a boron nitride nanotube.

4. In claim 1, A separator for an electrochemical device, wherein the average outer diameter of the above boron nitride compound is 10 nm or more and 100 nm or less.

5. In claim 1, A separator for an electrochemical device, wherein the average length of the above boron nitride compound is 1 ㎛ or more and 50 ㎛ or less.

6. In claim 1, A separator for an electrochemical device, wherein the aspect ratio of the above boron nitride compound is 10 to 5,000.

7. In claim 1, The density of the above boron nitride compound is 1.0 g / cm 3 More than 5.0 g / cm 3 A separator for an electrochemical device, comprising:

8. In claim 1, The specific surface area of ​​the above boron nitride compound is 20 m 2 / g or more than 55 m 2 A separator for an electrochemical device having a mass of / g or less.

9. In claim 1, A separator for an electrochemical device, wherein the above inorganic particles are one selected from boehmite, alumina, 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, the separator being any one of claims 1 to 9.

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