Separator for electrochemical device and electrochemical device including 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] The present invention claims the benefit of the filing date 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 including the same, and more particularly 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. [Background technology]

[0002] Among the components of an electrochemical device, the separator, which includes a porous polymer matrix disposed between the positive and negative electrodes, serves to separate the positive and negative electrodes, prevent electrical shorts between the two electrodes, and allow the electrolyte and ions to pass through. Although the separator itself does not participate in the electrochemical reaction, its physical properties, such as its wettability with the electrolyte, its porosity, and its thermal shrinkage, affect the performance and safety of the electrochemical device.

[0003] Therefore, various methods have been attempted to add a coating layer to a porous polymer substrate to enhance the physical properties of the separator, and to change the physical properties of the coating layer by adding various substances to the coating layer. For example, an inorganic substance may be added to the coating layer to improve the mechanical strength of the separator, or an inorganic substance or hydrate may be added to the coating layer to improve the flame retardancy and heat resistance of the polymer substrate.

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

[0005] On the other hand, thinner separators have the problem of lower breakdown voltage, and dendrite formation on the electrodes can reduce battery performance and cause the battery to short-circuit.

[0006] Therefore, there has been a need for research into separators that can ensure battery performance, improve battery safety, and prevent dendrite formation. Summary of the Invention [Problem to be solved by the invention]

[0007] The technical problem to be solved by the present invention is to provide a separator for an electrochemical device, which can adsorb transition metal ions eluted from an electrode by adding a boron nitride-based compound to a coating layer of the separator and adjusting the content thereof, thereby ensuring the heat resistance of the separator and providing an electrochemical device including the separator.

[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 following description. [Means for solving the problem]

[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 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, based on 100 parts by weight of the coating layer.

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

[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 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 compound may 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 / cm 3 More than 5.0g / cm 3 It can be the following:

[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 55m 2 / g or less.

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

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

[0019] A separator for an electrochemical device according to one embodiment of the present invention can adsorb transition metal ions eluted from an electrode by utilizing the polarity of the boron nitride-based compound, which is generated by the electronegativity difference between nitrogen and boron, and the specific surface area of ​​the boron nitride-based compound, thereby minimizing the formation of dendrites on the electrode.

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

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

[0022] [Figure 1] 1a and 1b are schematic diagrams of a separator for an electrochemical device according to an embodiment of the present invention, specifically, Fig. 1a is a schematic diagram of a separator for an electrochemical device having a coating layer on one side, and Fig. 1b is a schematic diagram of a separator for an electrochemical device having coating layers on both sides. [Figure 2] FIG. 2 is a schematic diagram of an electrochemical device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] In this specification, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless specifically stated to the contrary.

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

[0025] In this specification, when something is said to be provided "on" a certain component, unless otherwise specified, this does not exclude other components being disposed therebetween, but rather means that other components may be further disposed thereon.

[0026] As used herein, the characteristic of "having pores" means that an object contains a plurality of pores, and the pores are interconnected to allow gas and / or liquid fluids to pass from one side of the object to the other side.

[0027] In this specification, the separator has a porous property including a large number of pores, and serves as a porous ion-conducting barrier that allows ions to pass through while blocking electrical contact between the negative electrode and the positive electrode in the electrochemical device.

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

[0029] 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, the coating layer 130 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 per 100 parts by weight of the coating layer 130.

[0030] The separator 100 for electrochemical devices according to one embodiment of the present invention can minimize dendrites formed on the electrode by adsorbing transition metal ions eluted from the electrode by utilizing the polarity of the compound 131, which is generated by the electronegativity difference between nitrogen and boron, and the specific surface area of ​​the boron nitride compound 131. Furthermore, the separator 100 for electrochemical devices according to one embodiment of the present invention can improve the heat resistance of the separator by utilizing the excellent heat resistance of the boron nitride compound 131.

[0031] 1a and 1b are schematic views of a separator 100 for an electrochemical device according to one embodiment of the present invention. Specifically, Fig. 1a is a schematic view of a separator 100 for an electrochemical device having a coating layer 130 provided on one side, and Fig. 1b is a schematic view of a separator 100 for an electrochemical device having coating layers 130 provided on both sides. The separator 100 for an electrochemical device according to one embodiment of the present invention will be described in detail with reference to Figs. 1a and 1b.

[0032] 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, which allows lithium ions to 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 may be manufactured using a polyolefin-based resin as a base resin. Examples of polyolefin-based resins include polyethylene, polypropylene, and polypentene, and may include at least one of these. A porous separator having a large number of pores manufactured using such a polyolefin-based resin as a base resin may be provided with a shutdown function at an appropriate temperature.

[0034] According to one embodiment of the present invention, the weight-average molecular weight of the polyolefin-based resin may be from 500,000 to 2,000,000. By adjusting the weight-average molecular weight of the polyolefin-based resin within the above range, the compression resistance of the separator can be improved. Furthermore, when different polyolefin-based resins are mixed or when a separator is formed with a multi-layer structure made of different polyolefin-based resins, the weight-average molecular weight of the polyolefin-based resin can be calculated by adding the weight-average molecular weights of the respective polyolefin-based resins according to their content ratio.

[0035] In this specification, the 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) -Solvent: TCB (Trichlorobenzene) -Flow rate: 1.0ml / min -Sample concentration: 1.0mg / ml -Injection volume: 200μl -Column temperature: 160℃ -Detector: Agilent High Temperature RI detector -Standard: Polystyrene (corrected by a cubic function)

[0037] According to one embodiment of the present invention, the porous polymer substrate 110 may be manufactured by a wet process in which a polyolefin resin is mixed with a plasticizer (diluent) at high temperature to form a single phase, the polymer material and the plasticizer are phase-separated during cooling, the plasticizer is extracted to form pores, and then the porous polymer substrate 110 is stretched and heat-set. The porous polymer substrate using a polyolefin resin may have a core made of a mixture of polyethylene and polypropylene, and polyethylene skins laminated on both sides of the core.

[0038] According to one embodiment of the present invention, the average pore size and maximum pore size of the separator 100 can be easily manufactured by a person skilled in the art to meet the scope of the present invention by adjusting the mixing ratio of the plasticizer, the stretching ratio, the heat setting temperature, etc.

[0039] According to one embodiment of the present invention, the thickness of the porous polymer substrate 110 may be from 1 μm to 50 μm. Specifically, the thickness of the porous polymer substrate 110 may be from 2 μm to 45 μm, from 3 μm to 40 μm, from 4 μm to 35 μm, from 5 μm to 30 μm, from 6 μm to 25 μm, from 7 μm to 20 μm, or from 8 μm to 15 μm. 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 to 90 vol%. Specifically, the porosity of the porous polymer substrate 110 may be 10 to 90 vol%, 20 to 80 vol%, 30 to 70 vol%, or 40 to 60 vol%. By adjusting the porosity of the porous polymer substrate 110 within the above range, it is possible to adjust the lithium ion separation membrane permeability.

[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 separator 100 for an electrochemical device includes the coating layer 130 provided on one or both surfaces of the porous polymer substrate 110. As described above, the separator 100 for an electrochemical device includes the coating layer 130 provided on at least one surface of the porous polymer substrate 110, which improves the heat resistance and mechanical properties of the separator and prevents electrical short circuits of electrodes due to separator shrinkage at high temperatures.

[0042] According to one embodiment of the present invention, the separator 100 for an electrochemical device includes a coating layer 130 containing a boron nitride-based compound 131, polymer binder particles 133, and inorganic particles 135. As described above, the coating layer 130 includes the boron nitride-based compound 131, the polymer binder particles 133, and the inorganic particles 135, which improves the heat resistance and mechanical properties of the separator 100, prevents electrical short circuits of electrodes due to shrinkage of the separator 100 at high temperatures, and forms pores inside the coating layer 130. Furthermore, the separator 100 has improved heat resistance and can adsorb transition metal ions eluted from electrodes.

[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 may be uniformly dispersed in a coating layer slurry for forming the coating layer, the coating layer slurry may be coated, and the dispersion medium or solvent may be removed, resulting in a uniform distribution of the boron nitride-based compound 131, the polymer binder particles 133, and the inorganic particles 135. The respective contents (weight) 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 a partial difference, the difference may be within about 5%. As described above, the boron nitride-based compound 131, the polymer binder particles 133, and the inorganic particles 135 are uniformly contained in the coating layer 130, thereby improving the compression resistance of the separator.

[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 relative 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 but less than 100 parts by weight, 82 parts by weight or more but less than 99 parts by weight, 83 parts by weight or more but less than 98 parts by weight, 84 parts by weight or more but less than 97 parts by weight, 85 parts by weight or more but less than 96 parts by weight, 86 parts by weight or more but less than 95 parts by weight, 87 parts by weight or more but less than 94 parts by weight, 88 parts by weight or more but less than 93 parts by weight, 89 parts by weight or more but less than 92 parts by weight, or 90 parts by weight or more but less than 91 parts by weight relative to 100 parts by weight of the coating layer 130. By adjusting the content of the inorganic particles 135 contained in the coating layer 130 within the above range, the polymer binder and the inorganic particles can be uniformly distributed within the coating layer, thereby improving the compression 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 from 0.1 to 20 parts by weight based on 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 separator, and the polarity of the boron nitride-based compound due to the electronegativity difference between nitrogen and boron can be induced to adsorb transition metal ions eluted from the electrode.

[0046] 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 compound may be connected to each other to form a web. As described above, the boron nitride-based compound forms a network within the coating layer, which allows the heat resistance of the boron nitride-based compound to be uniformly realized throughout the 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 a boron nitride-based compound as the 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 electronegativity difference between nitrogen and boron in the boron nitride nanotube is induced, thereby making it possible 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 from 10 to 100 nm. Specifically, the average outer diameter of the boron nitride-based compound 131 may be from 20 to 90 nm, from 30 to 80 nm, from 40 to 70 nm, or from 50 to 60 nm. By adjusting the average outer diameter of the boron nitride-based compound 131 within the above range, a uniform network may be formed within the coating layer, thereby improving the thermal stability, mechanical strength, and electrical insulation of the separator.

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

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

[0051] According to one embodiment of the present invention, the density of the boron nitride-based compound 131 is 1.0 g / cm 3 More than 5.0g / cm 3 Specifically, the density of the boron nitride compound 131 may be 1.5 g / cm or less. 3 More than 4.5g / cm 3 Below 2.0g / cm 3 More than 4.0g / cm 3 or less, or 2.5g / cm 3 More than 3.5g / cm 3 By adjusting the density of the boron nitride-based compound 131 within the above range, the thermal stability and mechanical strength of the separator can be improved, and 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 compound 131 is 20 m 2 / g or more 55m 2 / g or less. Specifically, the specific surface area of ​​the boron nitride compound 131 may be 21 m 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 / g or less. By adjusting the specific surface area of ​​the boron nitride-based compound 131 within the above range, the thermal stability and mechanical strength of the separator can be improved, while the energy density of the electrochemical device can be improved and the adsorption efficiency of transition metals can be improved.

[0053] As used herein, the "specific surface area" may be calculated using the Brunauer-Emmett-Teller (BET) model from the measured N adsorption isotherm when the adsorption isotherm is measured up to 1 bar using a BET-specific surface area analyzer (BEL, Microtrac) at -196°C.

[0054] 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 having a plurality of pores therein. As described above, the coating layer having a plurality of pores may physically isolate the anode and cathode while allowing lithium ions to pass through to allow 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 with polymer binder particles 133 and accumulating them in the coating layer. Pores within the coating layer 130 may be due to interstitial volumes, which are empty spaces between the boron nitride-based compound and the inorganic particles.

[0056] According to one embodiment of the present invention, 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 adjusting the thickness of the coating layer 130 within the above range, the heat resistance and electrical resistance of the separator 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 may be measured using a contact-type thickness gauge, such as Mitutoyo's VL-50S-B.

[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 unit and the polyvinylidene repeating unit, or a hybrid of the acrylic binder and the polyvinylidene binder. The polyvinylidene binder may also be a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP). Selecting the polymer binder particles from the above may maintain the porosity of the separator and improve the adhesive strength between the electrode and the separator during the battery lamination process, thereby facilitating battery fabrication and stably implementing the stacking process. Furthermore, the porosity of the separator may be maintained, and the adhesive strength may 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 bending of the separator 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 methyl (meth)acrylate. Examples of suitable acrylates include decyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, ethylene glycol (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, and ethylene di(meth)acrylate, and the acrylate may be one or more selected from these. Among these, the acrylate may be one or more selected from methyl (meth)acrylate, ethyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, with methyl (meth)acrylate being particularly preferred.

[0061] 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 one or more selected from the group consisting of styrene-butyl acrylate, styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and acrylate-based polymers, and more particularly, may be an acrylate-containing copolymer.

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

[0063] According to one embodiment of the present invention, the average diameter (D 50 Although there is no particular limitation on the average diameter (D ) of the polymer binder particles 133, it is preferable that the average diameter (D ) is in the range of 0.1 μm to 1 μm in order to form a coating layer 130 with a uniform thickness and an appropriate porosity. 50 The average diameter (D ) of the polymer binder particles 133 within the above range can be 0.2 μm or more and 0.9 μm or less, 0.3 μm or more and 0.8 μm or less, 0.4 μm or more and 0.7 μm or less, or 0.5 μm or more and 0.6 μm or less. 50 By adjusting the ratio of the hydroxyl group to the total weight of the coating layer, the dispersion of the slurry prepared for producing the coating layer can be improved, and the thickness of the coating layer formed can be reduced.

[0064] According to one embodiment of the present invention, the polyvinylidene-based binder may have a hexafluoropropylene (HFP) content of 1 to 50 wt%. Specifically, the hexafluoropropylene (HFP) content of the polyvinylidene-based binder may be 1 to 50 wt%, 2 to 45 wt%, 3 to 40 wt%, 4 to 35 wt%, 5 to 30 wt%, 7 to 25 wt%, or 10 to 20 wt%. As described above, by selecting the polyvinylidene-based binder having a hexafluoropropylene content of 1 to 50 wt%, 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 this specification, the degree of substitution of the polyvinylidene-based binder may refer to the weight ratio of hexafluoropropylene included.

[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, based on 100 parts by weight of the coating layer 130. Specifically, the content of the polymer binder particles 133 may be greater than 0 parts by weight and less than 20 parts by weight, 1 part by weight to 19 parts by weight, 2 parts by weight to 18 parts by weight, 3 parts by weight to 17 parts by weight, 4 parts by weight to 16 parts by weight, 5 parts by weight to 15 parts by weight, 6 parts by weight to 14 parts by weight, 7 parts by weight to 13 parts by weight, 8 parts by weight to 12 parts by weight, 9 parts by weight to 11 parts by weight, or 10 parts by weight to 11 parts by weight, based on 100 parts by weight of the coating layer 130. Adjusting the content of the polymer binder particles 133 within the above range can improve ease of assembly in an electrode assembling process and can improve the heat resistance of the coating layer.

[0066] According to one embodiment of the present invention, the weight ratio of the acrylic binder to the polyvinylidene-based binder in the coating layer 130 may be 9:1 to 1:9. Specifically, the weight ratio of the acrylic binder to the polyvinylidene-based binder in the coating layer 130 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 to the polyvinylidene-based binder within the above range, both the wet adhesive strength and the dry adhesive strength of the separator for an electrochemical device can be improved.

[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 electrochemically stable within the operating voltage range (e.g., Li / Li) of the applied electrochemical device. + The oxidation and / or reduction reaction may not occur at a voltage between 0 V and 5 V relative to the reference voltage.

[0068] According to one embodiment of the present invention, the inorganic particles 135 are selected from the group consisting of 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 the inorganic particles 135 may include one or more of these. Specifically, the inorganic particles 135 are preferably boehmite, alumina, and combinations thereof. As described above, the inorganic particles may be one selected from the group consisting of boehmite, alumina, and combinations thereof, thereby improving the heat resistance of the separator.

[0069] According to one embodiment of the present invention, the average diameter (D 50 Although there is no particular limitation on the average diameter (D) of the inorganic particles 135, it is preferable that the average diameter (D) is in the range of 0.3 μm to 1 μm in order to form a coating layer 130 with a uniform thickness and to have an appropriate porosity. 50 ) may be 0.2 μm or more and 0.9 μm or less, 0.3 μm or more and 0.8 μm or less, 0.4 μm or more and 0.7 μm or less, or 0.5 μm or more and 0.6 μm or less. Specifically, if it is less than 0.3 μm, the dispersibility of the inorganic particles in the slurry prepared for producing 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 50% 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, the powder to be measured is dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500). When the particles pass through a laser beam, the difference in the diffraction pattern according to the particle size is measured to calculate the particle size distribution. By calculating the particle diameter at 50% of the cumulative distribution of the number of particles according to the particle size in the measuring device, D 50 The particle size can be measured.

[0071] According to one embodiment of the present invention, the porosity of the coating layer 130 may be 30 vol% or more. Specifically, the porosity of the coating layer 130 may be 30 vol% to 70 vol%, 32 vol% to 68 vol%, 34 vol% to 66 vol%, 36 vol% to 64 vol%, 38 vol% to 62 vol%, 40 vol% to 60 vol%, 42 vol% to 58 vol%, 44 vol% to 56 vol%, 46 vol% to 54 vol%, or 48 vol% to 52 vol%. Adjusting the porosity of the coating layer 130 within the above ranges can maintain ion mobility in the separator and prevent an increase in the separator resistance. Specifically, a porosity of 70 vol% or less can ensure mechanical properties that can withstand the press process for bonding to an electrode and is suitable for ensuring adhesive strength without an excessively high surface opening ratio. On the other hand, if the porosity is 30% by volume or more, it is advantageous from the viewpoint of ion permeability.

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

[0073] In this specification, the porosity may correspond to a value obtained by subtracting the weight and volume converted to 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.

[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 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 a nitrogen gas adsorption flow method using a BET 6-point method. In this case, it may be advantageous to use a capillary flow porosimeter.

[0075] According to one embodiment of the present invention, the polyvinylidene-based binder may be an aqueous binder. Specifically, by selecting an aqueous binder as the polyvinylidene-based binder, it is possible to minimize contaminants discharged during the manufacturing process of the separator, thereby reducing the manufacturing cost of the battery.

[0076] According to one embodiment of the present invention, the separator may further include an adhesive layer on the coating layer. As described above, the adhesive layer may improve adhesion between the coating layer and an electrode, which will be described later.

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

[0078] According to one embodiment of the present invention, the polymer binder may be in particle 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 unit and the polyvinylidene repeating unit, or a hybrid of the acrylic binder and the polyvinylidene binder. The polyvinylidene binder may also be a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP). Selecting the polymer binder from the above may improve the adhesion between the coating layer and the electrode, thereby enabling a stable stacking process. Furthermore, the porosity of the separator may be maintained, and the adhesion may 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 bending of the separator can be prevented. Furthermore, the polymer binder is the same as that described above for the polymer binder particles of the coating layer, so a description thereof will be omitted.

[0080] According to one embodiment of the present invention, the separator may be configured by providing a polymer binder on the coating layer. Specifically, the separator may be partially provided with the polymer binder on the coating layer rather than being provided as a single layer. The polymer binder may be particulate or soluble. When the polymer binder on the coating layer is particulate, the polymer binder may be partially provided while maintaining the particle shape on the coating layer. When the polymer binder is soluble, the polymer binder may be provided to form a layer on a portion of the coating layer. As described above, providing a separator with a polymer binder on the coating layer can ensure adhesion to the electrode and porosity of the coating layer.

[0081] One embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device, including the steps of: mixing a slurry for a coating layer 130, which includes a boron nitride-based 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 the coating layer (S50).

[0082] The method for producing a separator for an electrochemical device according to one embodiment of the present invention can improve the heat resistance of the separator.

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

[0084] According to one embodiment of the present invention, a slurry for a coating layer may be prepared by dispersing polymer binder particles 133 in water, which is a suitable dispersion medium, to prepare a polymer emulsion. As described above, by dispersing polymer binder particles 133 in water, which is a suitable dispersion medium, to prepare a polymer emulsion to prepare a slurry for a coating layer, it is possible to minimize contaminants generated during the manufacturing process. In this specification, the dispersion medium may refer to a solvent used in the process of preparing the slurry.

[0085] According to one embodiment of the present invention, a boron nitride-based compound 131 and inorganic particles 135 may 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 produced.

[0086] According to one embodiment of the present invention, a slurry for a coating layer can be prepared by dispersing a boron nitride compound 131, polymer binder particles 133, and inorganic particles 135 in water as a dispersion medium. Specifically, as described above, a polymer emulsion is not prepared, but the slurry for a coating layer can be prepared by immediately dispersing the boron nitride compound 131, polymer binder particles 133, and inorganic particles 135 in water as a dispersion medium.

[0087] According to one embodiment of the present invention, the solid content of the slurry for the coating layer may be 10% by weight or more and 50% by weight or less. Specifically, the solid content of the slurry for the coating layer 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 slurry for the coating layer within the above range, 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 separator 100 for an electrochemical device includes the step (S30) of applying the coating layer slurry to at least one surface of the porous polymer substrate 110. As described above, by applying the coating layer slurry to 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 allows the inorganic particles, polymer binder particles, and boron nitride-based compound to be distributed at a uniform concentration, thereby forming a uniform coating layer.

[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 particular method, and any conventional method known in the art may be used, such as dip coating, die coating, roll coating, comma coating, or a combination thereof.

[0090] According to one embodiment of the present invention, the method for manufacturing the separator 100 for an electrochemical device 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 range, denaturation 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 under appropriate time conditions to minimize the occurrence of surface defects on the coating layer 130. The drying process may be performed using auxiliary drying devices such as a drying oven or hot air within an appropriate range.

[0093] According to one embodiment of the present invention, the method may further include forming an adhesive layer by applying a slurry for an adhesive layer containing a polymer binder onto the coating layer. As described above, by applying a slurry for an adhesive layer containing a polymer binder onto the coating layer to form an adhesive layer, the adhesive strength between the separator and the electrode can be improved, the adhesive strength can be maintained during a lamination process with the electrode, and the adhesive strength can be maintained after activation of the battery, thereby improving stiffness and preventing bending of a pouch-type cell.

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

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

[0096] According to one embodiment of the present invention, the separator 100 is interposed between the positive electrode 300 and the negative electrode 500 and fabricated into an electrochemical device 1000 through a lamination process in which heat and / or pressure are applied to bond them together. In one embodiment of the present invention, the lamination process can be performed using a roll press device including a pair of pressure rollers. That is, the negative electrode 500, the separator 100, and the positive electrode 300 can be sequentially stacked and then inserted between the pressure rollers to achieve interlayer bonding. In this case, the lamination process can be performed using a hot press method.

[0097] One embodiment of the present invention provides an electrochemical device 1000 including a positive electrode 300; a negative electrode 500; and the separator 100 interposed between the positive electrode 300 and the negative electrode 500.

[0098] The electrochemical device 1000 according to an embodiment of the present invention can minimize dendrites formed on the electrodes, thereby realizing battery safety and improving battery performance.

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

[0100] 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 that encompasses primary batteries and secondary batteries. In this specification, the secondary battery is capable of charging and discharging, and refers to a lithium secondary battery, a nickel-cadmium battery, a nickel-metal hydride 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.

[0101] In one embodiment of the present invention, the electrochemical device may have a cylindrical shape. Specifically, the electrochemical device may have an electrode assembly including the positive electrode, the separator, and the negative electrode embedded in a cylindrical metal case. More specifically, the cylindrical electrochemical device may be fabricated by placing a jelly-roll-type electrode assembly in a cylindrical metal case, injecting an electrolyte into the cylindrical metal case, and then attaching a cap having electrode terminals to the open top of the metal case. As described above, fabricating the electrochemical device in a cylindrical shape can improve capacity and structural stability.

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

[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, the negative electrode active material layer including a negative electrode active material, a conductive material, and a binder resin. The negative electrode comprises a lithium metal oxide, carbon such as non-graphitizable carbon, graphite carbon, or the like; 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 an 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 an 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 surface-treated 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 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-co-trichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples of suitable cellulose acetate include, but are not limited to, cyanoethyl acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxyl methyl cellulose.

[0107] According to one embodiment of the present invention, the positive electrode slurry for preparing the positive electrode active material layer may include a dispersant, and the dispersant may be a pyrrolidone-based compound, specifically, N-methylpyrrolidone (ADC-01, LG Chemicals).

[0108] According to one embodiment of the present invention, the content of the dispersant in the positive electrode slurry may be more than 0 parts by weight and not more than 0.5 parts by weight per 100 parts by weight of the positive electrode slurry. Specifically, the content of the dispersant in the positive electrode slurry may be more than 0.05 parts by weight and not more than 0.4 parts by weight per 100 parts by weight of the positive electrode slurry.

[0109] According to an embodiment of the present invention, the negative electrode slurry for preparing 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 (manufactured by 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 not more than 0.5 parts by weight 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 not more than 0.4 parts by weight per 100 parts by weight of the negative electrode slurry.

[0111] According to one embodiment of the present invention, the electrochemical device prepared as described above can be placed in a suitable case and filled with an electrolyte to fabricate a battery.

[0112] According to one embodiment of the present invention, the electrolyte is A + B - A salt having the structure: + Li + , Na + , K. + or a combination thereof, - is PF6 -, BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - or a salt containing an anion such as, or a combination thereof, dissolved or dissociated in an organic solvent such as, but not limited to, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (γ-butyrolactone), or a mixture thereof.

[0113] One embodiment of the present invention provides a battery module including a battery containing the electrochemical device 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, power tools powered by a battery motor; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles, including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems. [Example]

[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 in this specification are provided to more completely explain the present invention to those skilled 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) and using a wet method. Boron nitride nanotubes (average outer diameter: 50 nm, length: 25 μm, aspect ratio: 100, density: 3.0 g / cm) were used as boron nitride compounds. 3 , Specific surface area (BET): 40m 2 A slurry for the coating layer (solid concentration 20 wt%) was prepared by dispersing a boron nitride compound (0.1g / g), styrene-butyl acrylate (a polymer binder particle with a particle size of 500 nm, an acrylic binder) (glass transition temperature 40°C) and boehmite (particle size: 500 nm) as inorganic particles in water. The weight ratio of the boron nitride compound, polymer binder particles and inorganic particles was 2:5:93.

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

[0117] <Example 2> A separator 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.

[0118] <Comparative Example 1> A separator 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.

[0119] <Comparative Example 2> A separator 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.

[0120] <Manufacturing of electrochemical elements> 1) Manufacturing of the positive electrode Cathode active material (LiNi 0.8 Mn 0.1 CO 0.1 O2), conductive material (carbon black), dispersant (N-methylpyrrolidone, ADC-01, LG Chemicals), and 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 the positive electrode active material layer with a concentration of 50 wt% of the remaining components excluding water. The slurry was then applied to the surface of an aluminum thin film (10 μm thick) and dried to prepare a positive electrode having a positive electrode active material layer (120 μm thick).

[0121] 2) Manufacturing of negative electrodes Graphite (a blend of natural and artificial graphite), conductive material (carbon black), dispersant (Polyvinylpyrrolidone, Junsei), and binder resin (a blend 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 the negative electrode active material layer, with the remaining components (excluding water) at a concentration of 50 wt%. The slurry was then applied to the surface of a copper thin film (10 μm thick) and dried to prepare a negative electrode having a negative electrode active material layer (120 μm thick).

[0122] <Experimental Example 1: Air permeability> The air 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 JIS Gurley measurement method. The air permeability value was measured by measuring the air permeability of 100 ml of air at a pressure of 12.2 in H2O through 1 in of the separation membrane. 2 The time (seconds) required for the air to pass through the cross section of the sample was expressed as the ventilation time.

[0123] <Experimental Example 2: Measurement of Dry Heat Shrinkage> The separators of Examples 1 and 2 and Comparative Examples 1 and 2 were cut into pieces of 50 mm x 50 mm, placed between sheets of A4 paper, 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.

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

[0125] <Experimental Example 3: Wet Heat Shrinkage Measurement> The separators of Examples 1 and 2 and Comparative Examples 1 and 2 were cut into 50 mm x 50 mm pieces, placed in pouches together with the electrolyte, sealed, and then heat-treated at 135°C for 30 minutes, after which the dimensional change was observed.

[0126] The electrolyte solution 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) (mixing volume ratio of EC / EMC / DEC = 3:4:3).

[0127] The wet heat shrinkage was calculated using the following Equation 2.

[0128] [Formula 2] Wet heat shrinkage rate (%) = (initial length - length after heat treatment) / (initial length) x 100

[0129] <Experimental Example 4: Peel strength measurement> In the separators of Examples 1 and 2 and Comparative Examples 1 and 2, the peel strength was measured in the following manner to evaluate the adhesive strength between the porous polymer substrate and the coating layer.

[0130] First, each of the separators was cut into 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 to the adhesive tape.

[0131] The end of the bonded separator was then placed in a UTM device (LLOYD Instrument LF Plus), and a force was applied at a measurement speed of 300 mm / min and an angle of 180° to measure the force required to peel the porous polymer substrate from the coating layer. Furthermore, in the process of manufacturing the separators of Examples 1 and 2 and Comparative Examples 1 and 2, the side to which the coating layer slurry was first applied was designated as side A, and the side to which it was secondly applied was designated as side B, and the peel strength was measured for each of side A and side B.

[0132] <Experimental Example 5: Measurement of Breakdown Voltage> For each of the separators of Examples 1 and 2 and Comparative Examples 1 and 2, a 5 cm x 5 cm sample was cut and placed between aluminum jigs (upper jig diameter 30 mm, lower jig 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 direct current (DC), current 0.5 mA, and voltage step-up 100 V / s (up to 3 kV). The measured value was expressed as the average value of 30 samples.

[0133] [Table 1]

[0134] Referring to Table 1, it was confirmed that Example 1, which contained BNNT as the boron nitride-based compound, achieved the same level of breathability and peel strength as the conventional separator, and further, the dry heat shrinkage rate and wet heat shrinkage rate were reduced, and the breakdown voltage was increased.

[0135] In contrast, it was confirmed that Comparative Example 1 and Example 2, which both had low BNNT contents, showed a sharp increase in dry heat shrinkage and wet heat shrinkage, resulting in a decrease in heat resistance and a decrease in breakdown voltage. Furthermore, it was confirmed that Comparative Example 2, which contained an excessive amount of BNNT, showed a decrease in dry heat shrinkage and wet heat shrinkage, but also a decrease in peel strength.

[0136] Therefore, as in one embodiment of the present invention, the coating layer of the separator contains a boron nitride-based compound, thereby improving heat resistance. [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 element

Claims

1. a porous polymeric substrate; and a coating layer provided on at least one surface of the porous polymer substrate, the coating layer including a boron nitride compound, polymer binder particles, and inorganic particles; and The separator for an electrochemical device, wherein the content of the inorganic particles is 80 parts by weight or more relative to 100 parts by weight of the coating layer.

2. 2. The separator for an electrochemical device according to claim 1, wherein the content of the boron nitride-based compound in the coating layer is 0.1 parts by weight to 20 parts by weight, both inclusive, based on 100 parts by weight of the coating layer.

3. 2. The separator for an electrochemical device according to claim 1, wherein the boron nitride compound is a boron nitride nanotube.

4. 2. The separator for an electrochemical device according to claim 1, wherein the average outer diameter of the boron nitride compound is 10 nm or more and 100 nm or less.

5. 2. The separator for an electrochemical device according to claim 1, wherein the boron nitride compound has an average length of 1 μm or more and 50 μm or less.

6. 2. The separator for an electrochemical device according to claim 1, wherein the boron nitride compound has an aspect ratio of 10 to 5,000.

7. The density of the boron nitride compound is 1.0 g / cm ３ 5.0g / cm or more ３ The separator for electrochemical elements according to claim 1, wherein:

8. The specific surface area of ​​the boron nitride compound is 20 m ２ / g or more 55m ２ The separator for electrochemical elements according to claim 1, wherein the surface roughness is 0.1 μm or less.

9. 2. The separator for an electrochemical device according to claim 1, wherein the inorganic particles are one selected from the group consisting of boehmite, alumina, and combinations thereof.

10. An electrochemical element comprising: a positive electrode; a negative electrode; and the separator according to any one of claims 1 to 9 interposed between the positive electrode and the negative electrode.

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