KR20230026208A - A separator for a lithium secondary battery and a lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a separator for a lithium secondary battery and a lithium secondary battery including the same. According to one embodiment of the present invention, the separator for a lithium secondary battery comprises an inorganic hybrid porous layer formed on at least one surface a polymer porous support and including a first inorganic filler, a second inorganic filler, and a binder polymer, wherein the average particle diameter of the first inorganic filler has an arithmetic average roughness of the surface of the separator of 400 to 850 nm which is five times or more than the average particle diameter of the second inorganic filler. Accordingly, since the separator includes two different inorganic fillers with average particle diameters different by more than five times, the safety at high temperatures can be secured and the arithmetic mean roughness of the surface of the separator is 400 to 850 nm, such that an assembly process of the separator can be improved.

Description

Separator for lithium secondary battery and lithium secondary battery having the same

The present invention relates to a separator for a lithium secondary battery and a lithium secondary battery having the same.

Recently, interest in energy storage technology is increasing. As the field of application expands to cell phones, camcorders, notebook PCs, and even electric vehicles, the demand for high energy density of batteries used as power sources for these electronic devices is increasing. A lithium secondary battery is a battery that can best satisfy these demands, and research on this is being actively conducted.

These lithium secondary batteries are composed of a positive electrode, a negative electrode, an electrolyte solution, and a separator. Among them, the separator has high ionic conductivity to increase the permeability of lithium ions based on insulation and high porosity to electrically insulate the positive electrode and the negative electrode. is required

Olefin polymer-based separators are widely used as such separators, and olefin polymer-based separators exhibit extreme heat shrinkage behavior at high temperatures due to material characteristics and manufacturing process characteristics, resulting in safety problems such as internal short circuits.

Recently, in order to solve the safety problem of the olefin polymer separator at a high temperature, a separator coated with a mixture of an inorganic filler of fine particles and a binder polymer on one or both sides of the olefin polymer separator has been proposed.

However, such separators have problems in that assembly fairness is not secured, such as meandering and wrinkles occurring due to the use of fine particle inorganic fillers during the battery assembly process.

The present invention is to solve the above problems, to provide a separator for a lithium secondary battery capable of improving safety at high temperature and ensuring assembly fairness, and a lithium secondary battery having the same.

In order to solve the above problems, according to an aspect of the present invention, a separator for a lithium secondary battery of the following embodiments is provided.

In the first embodiment,

As a separator for a lithium secondary battery,

polymeric porous support; and

It is located on at least one surface of the polymeric porous support and includes an inorganic hybrid void layer containing a first inorganic filler, a second inorganic filler, and a binder polymer,

The average particle diameter of the first inorganic filler is 5 times or more than the average particle diameter of the second inorganic filler,

It relates to a separator for a lithium secondary battery, characterized in that the arithmetic mean roughness of the surface of the separator for a lithium secondary battery is 400 nm to 850 nm.

The second embodiment, in the first embodiment,

The weight ratio of the first inorganic filler to the second inorganic filler may be 7:93 to 65:35.

In the third embodiment, in the first embodiment or the second embodiment,

An average particle diameter of the first inorganic filler may be 200 nm to 800 nm.

In the fourth embodiment, in any one of the first to third embodiments,

An average particle diameter of the second inorganic filler may be 20 nm to 40 nm.

In the fifth embodiment, in any one of the first to fourth embodiments,

The first inorganic filler is BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT, 0<x<1, 0<y<1) , Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), Hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, Mg(OH) ₂ , NiO, CaO , ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , AlOOH, Al(OH) ₃ , SiC, TiO ₂ , lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y ( PO ₄ ) ₃ , 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) _x O _y series glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0<x<2, 0<y<3) , lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w < 5), lithium nitride (Li _x N _y , 0<x<4, 0<y<2), SiS ₂ series glass (Li _x Si _y S _z , 0<x<3, 0<y<2, 0<z<4), P ₂ S ₅ series glass (Li _x P _y S _z , 0<x<3, 0<y<3, 0<z<7), or two or more of these.

In the sixth embodiment, in any one of the first to fifth embodiments,

The second inorganic filler may include a fumed type inorganic filler.

In the seventh embodiment, in the sixth embodiment,

The second inorganic filler may include fumed alumina, fumed silica, fumed titanium dioxide, or two or more of them.

In the eighth embodiment, in any one of the first to seventh embodiments,

The inorganic hybrid void layer may further include a first dispersant and a second dispersant,

The first dispersant may include a cellulose-based compound,

The second dispersant may include a single molecular organic acid.

In the ninth embodiment, in the eighth embodiment,

The first dispersant is ethylhydroxy ethyl cellulose (EHEC), methyl cellulose (MC), carboxymethyl cellulose sodium salt (CMC-Na`), hydroxyalkyl methyl cellulose, or two or more of them.

In the tenth embodiment, in the eighth embodiment or the ninth embodiment,

The second dispersant may include citric acid, stearic acid, oxalic acid, acetic acid, formic acid, or two or more of these.

In the eleventh embodiment, in any one of the first to tenth embodiments,

The thermal conductivity of the first inorganic filler measured by a laser flash method may be 15 W/mk to 55 W/mK.

In the twelfth embodiment, in any one of the first to eleventh embodiments,

Thermal conductivity of the second inorganic filler measured by a laser flash method may be 15 W/mk to 55 W/mK.

In the thirteenth embodiment, in any one of the first to twelfth embodiments,

The separator for a lithium secondary battery may have a thermal contraction rate of 10% or less in a machine direction (MD, Machine Direction) and a transverse direction (TD), respectively, measured after being left at 180° C. for 1 hour.

In order to solve the above problems, according to an aspect of the present invention, a lithium secondary battery of the following embodiment is provided.

The fourteenth embodiment,

Including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,

It relates to a lithium secondary battery, characterized in that the separator is the separator according to any one of the first to thirteenth embodiments.

The fifteenth embodiment is the fourteenth embodiment,

The lithium secondary battery may be a cylindrical lithium secondary battery.

The separator for a lithium secondary battery according to an embodiment of the present invention includes a first inorganic filler and a second inorganic filler having an average particle diameter that differs by more than 5 times, and has an arithmetic average roughness of 400 nm to 850 nm on the surface of the separator, The heat shrinkage rate of the separator can be improved and the assembly fairness of the separator can be secured.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the contents of the above-described invention, so the present invention is limited to those described in the drawings. It should not be construed as limiting.
1 is a diagram showing the surface roughness of the separator prepared in Example 1.
2 is a diagram showing the surface roughness of the separator prepared in Example 2.
3 is a diagram showing the surface roughness of the separator prepared in Comparative Example 3.
FIG. 4 is a photograph of the winding surface of a cylindrical battery wound with the separator prepared in Example 1. FIG.
5 is a diagram illustrating a photograph of a winding surface of a cylindrical battery wound with a separator manufactured in Comparative Example 1;

Hereinafter, preferred embodiments of the present invention will be described in detail. Prior to this, the terms or words used in this specification and claims should not be construed as being limited to the usual or dictionary meaning, and the inventor appropriately uses the concept of the term in order to explain his/her invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

Therefore, since the configurations described in the embodiments of this specification are only one of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, various equivalents and modifications that can replace them at the time of this application It should be understood that there may be examples.

A separator for a lithium secondary battery according to an aspect of the present invention,

polymeric porous support; and

It is located on at least one surface of the polymeric porous support and includes an inorganic hybrid void layer containing a first inorganic filler, a second inorganic filler, and a binder polymer,

The average particle diameter of the first inorganic filler is 5 times or more than the average particle diameter of the second inorganic filler,

It is characterized in that the arithmetic mean roughness of the surface of the separator for a lithium secondary battery is 400 nm to 850 nm.

A separator for a lithium secondary battery according to one aspect of the present invention includes a porous polymer support.

In one embodiment of the present invention, as the polymeric porous support, any material that can be commonly used as a material for a separator for a lithium secondary battery may be used without particular limitation. Such a polymer porous support is a thin film containing a polymer material, and non-limiting examples of the polymer material include olefin resin, ethylene terephthalate resin, butylene terephthalate resin, acetal resin, amide resin, carbonate resin, and imide resin. , ether ether ketone resins, ether sulfone resins, phenylene oxide resins, phenylene sulfide resins, and polymer resins such as ethylene naphthalene. In addition, the polymeric porous support may be a nonwoven fabric formed of the above-described polymeric material, a polymeric porous film, or a laminate of two or more of them. Specifically, the polymeric porous support may be one of the following a) to e).

a) A porous film formed by melting and extruding a polymer resin

b) a multilayer film in which two or more layers of the porous film of a) are laminated;

c) a non-woven fabric web manufactured by integrating filaments obtained by melting/spinning a polymer resin;

d) a multilayer film in which two or more layers of the nonwoven web of c) are laminated;

e) A porous film having a multilayer structure comprising at least two of a) to d).

In one embodiment of the present invention, the pore size and porosity present in the polymeric porous support are not particularly limited, but may be 0.01 μm to 0.09 μm and 10% to 95%, respectively.

In one embodiment of the present invention, the porosity and pore size of the polymeric porous support can be measured using a scanning electron microscope (SEM) image, a mercury porosimeter, a capillary flow porometer, or a pore size. It can be measured by the BET 6-point method by the nitrogen gas adsorption distribution method using a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini).

A separator for a lithium secondary battery according to an aspect of the present invention includes an inorganic hybrid void layer on at least one surface of the porous polymer support. Specifically, the inorganic hybrid void layer may be formed on one side or both sides of the polymer porous support. When the inorganic hybrid void layer is formed on both sides of the polymer porous support, impregnation with the electrolyte may be more easily performed.

The inorganic hybrid void layer includes an inorganic filler and a binder polymer that attaches the inorganic fillers to each other (ie, the binder polymer connects and fixes the inorganic fillers) so that the inorganic fillers can remain bound to each other, and the binder polymer As a result, the inorganic filler and the polymeric porous support can be maintained in a bound state. The inorganic hybrid void layer can improve the safety of the separator by preventing the polymer porous support from exhibiting extreme heat shrinkage behavior at high temperatures by the inorganic filler.

In the separator for a lithium secondary battery according to an aspect of the present invention, the average particle diameter of the first inorganic filler is 5 times or more than the average particle diameter of the second inorganic filler. Since the average particle diameter of the second inorganic filler is 1/5 times or less than the average particle diameter of the first inorganic filler, the second inorganic filler can be positioned between the first inorganic fillers, so that the inorganic filler distributed per unit area of the separator is more Since it can be provided densely, the thermal stability of the separation membrane can be improved.

In addition, a separator for a lithium secondary battery according to an aspect of the present invention simultaneously uses a first inorganic filler and a second inorganic filler having an average particle diameter that is 5 times or more different from the case of using a particulate inorganic filler alone, thereby reducing heat of the separator. It is possible to secure the shrinkage rate and at the same time prevent the arithmetic average roughness value of the separator surface from rapidly decreasing. That is, the separator for a lithium secondary battery according to one aspect of the present invention may have an arithmetic mean roughness value of the separator surface at a level capable of securing assembly fairness while minimizing deterioration in thermal shrinkage.

For example, in one embodiment of the present invention, the separator for a lithium secondary battery has a thermal contraction rate of 10 in the machine direction (MD, Machine Direction) and the transverse direction (TD, Transverse Direction), respectively, measured after being left at 180 ° C. for 1 hour. % or less, or 2% to 10%, or 3% to 8%, or 2% or less.

Here, the 'machine direction' refers to the direction in which the separator is continuously produced or the direction in which the manufactured separator is wound, and refers to the long length direction of the separator, and the 'transverse direction' A is a transverse direction of the machine direction, that is, a direction perpendicular to the direction in which the separator is continuously produced or a direction in which the manufactured separator is wound, and refers to a direction perpendicular to the long length direction of the separator.

In one embodiment of the present invention, the average particle diameter of the first inorganic filler is 7 times or more, or 5 times to 50 times, or 5 times to 20 times, or 5 times to 10 times the average particle diameter of the second inorganic filler , or 10 to 20 times. In this case, the inorganic filler distributed per unit area of the separator may be more densely provided, and thus the thermal stability of the separator may be further improved.

When the average particle diameter of the first inorganic filler is less than 5 times the average particle diameter of the second inorganic filler, the second inorganic filler is located between the first inorganic fillers to the extent that the thermal stability of the separator at a high temperature can be improved It is difficult to do so, and the thermal stability of the separator is not greatly improved.

In the present specification, the average particle diameter of the inorganic fillers means the D ₅₀ particle diameter, and “D ₅₀ particle diameter” means the particle diameter at the 50% point of the cumulative distribution of the number of particles according to the particle diameter. The particle size can be measured using a laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g. Microtrac S3500) to measure the difference in diffraction pattern according to the particle size when the particles pass through the laser beam to distribute the particle size. yields The D50 particle size can be measured by calculating the particle size 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.

In one embodiment of the present invention, the average particle diameter of the first inorganic filler may be 200 nm to 800 nm, or 200 nm to 700 nm, or 250 nm to 700 nm. When the average particle diameter of the first inorganic filler satisfies the aforementioned range, the arithmetic average roughness of the surface of the separator may easily have a value of 400 nm to 850 nm.

In one embodiment of the present invention, the average particle diameter of the second inorganic filler is 20 nm to 40 nm, or 20 nm to 38 nm, or 20 nm to 35 nm, or 20 nm to 25 nm, or 20 nm to 23 nm can be When the average particle diameter of the second inorganic filler satisfies the aforementioned range, thermal stability of the separator at high temperatures may be further improved. For example, after being left at 180 ° C. for 1 hour, the heat shrinkage rate measured is 2% to 10%, or 3% to 8%, or 2% in the machine direction (MD, Machine Direction) and the transverse direction (TD, Transverse Direction). The following may be easier.

In one embodiment of the present invention, the weight ratio of the first inorganic filler and the second inorganic filler may be 7:93 to 65:35, or 10:90 to 55:45. When the weight ratio of the first inorganic filler to the second inorganic filler satisfies the aforementioned range, the arithmetic average roughness of the surface of the separator can be secured within a predetermined range and thermal stability at high temperatures can be improved. In particular, thermal stability at a high temperature may be improved compared to a separator for a lithium secondary battery containing only an inorganic filler having an average particle diameter of about 500 nm. For example, the heat shrinkage rate measured after being left at 180 ° C. for 1 hour is 10% or less, or 2% to 10%, or 3% to 8% in the machine direction (MD, Machine Direction) and the transverse direction (TD). %, or less than 2%.

When the weight ratio of the first inorganic filler to the second inorganic filler satisfies the aforementioned range, it may be easier to satisfy the arithmetic mean surface roughness of the separator in the range of 400 nm to 850 nm. In addition, the thermal stability of the separator at high temperatures can be further improved. For example, it may be more convenient that the heat shrinkage rate measured after being left at 180 ° C. for 1 hour is 10% or less in the machine direction (MD, Machine Direction) and the transverse direction (TD).

In one embodiment of the present invention, the thermal conductivity of the first inorganic filler may be 15 W/mK to 55 W/mK, or 20 W/mK to 45 W/mk, or 22 W/mk to 40 W/mk. . When the thermal conductivity of the first inorganic filler satisfies the aforementioned range, when the separator or a battery including the separator locally generates heat, heat is dissipated through the inorganic hybrid void layer, and safety can be further improved.

In one embodiment of the present invention, the thermal conductivity of the second inorganic filler is 15 W / mK to 55 W / mK, or 20 W / mK to 45 W / mk, or 22 W / mk to 40 W / mk can be When the thermal conductivity of the second inorganic filler satisfies the aforementioned range, when the separator or a battery including the separator locally generates heat, heat is dissipated through the inorganic hybrid void layer, and safety may be further improved.

In the present specification, the 'thermal conductivity' may be measured by a laser flash method. For example, thermal conductivity can be measured with Metzsch's LFA 457.

The first inorganic filler may not be particularly limited as long as it is electrochemically stable. That is, it may not be particularly limited as long as oxidation and/or reduction reactions do not occur in the operating voltage range of the applied battery (eg, 0 to 5V based on Li/Li ⁺ ). In particular, in the case of using an inorganic filler having an ion transport capability, it is possible to improve performance by increasing ion conductivity in a lithium secondary battery. In addition, when an inorganic filler having a high permittivity is used as the first inorganic filler, the dissociation degree of an electrolyte salt, for example, a lithium salt in the liquid electrolyte may be increased, thereby improving ionic conductivity of the electrolyte solution. For the reasons described above, the first inorganic filler may include a high dielectric constant inorganic filler having a dielectric constant of 5 or more or 10 or more, an inorganic filler having lithium ion transport capability, or a mixture thereof. Non-limiting examples of inorganic fillers having a dielectric constant of 5 or more include BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT, 0<x<1 , 0<y<1), Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, Mg( OH) ₂ , NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , AlOOH, Al(OH) ₃ , SiC, TiO ₂ , or two or more of these.

In addition, as the first inorganic filler, an inorganic filler having a lithium ion transport ability, that is, an inorganic filler having a function of moving lithium ions without storing lithium but containing a lithium element may be used. Non-limiting examples of the inorganic filler having lithium ion transport ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0<x<2, 0<y<3), Lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 < x < 2, 0 < y < 1, 0 < z < 3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ (LiAlTiP) _x O _y series glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0<x<2, 0<y<3), such as O ₅ , Li _3.25 Ge _0.25 P _0.75 S ₄ and the like (Li _x Ge _y P _z S _w , 0<x<4, 0<y<1, 0<z<1, 0<w<5 ), lithium nitride such as Li ₃ N (Li _x N _y , 0<x<4, 0<y<2), SiS ₂ series glass such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ (Li _x Si _y S _z , 0<x<3, 0<y< ₂ , 0<_{z<4), P 2 S 5 series glass (Li x P y S z , 0} <x <3, 0<y<3, 0<z<7), or two or more of these.

In one embodiment of the present invention, the second inorganic filler may include a fumed type inorganic filler. In the present invention, the fumed inorganic filler is a primary particle formed by hydrolysis in a flame of 1,000 ° C or higher connected to each other due to collision to form secondary particles, and these secondary particles are three-dimensional aggregates (aggregates, agglomerates) Refers to the inorganic filler formed. When the second inorganic filler includes a fumed type inorganic filler, it may be easier for the average particle diameter of the second inorganic filler to be 1/5 times or smaller than the average particle diameter of the first inorganic filler, and furthermore, the second inorganic filler It may be more convenient if the average particle diameter of is 20 nm to 40 nm.

In one embodiment of the present invention, the second inorganic filler may include fumed alumina, fumed silica, fumed titanium dioxide, or two or more of them. In particular, when the second inorganic filler includes fumed alumina, the heat shrinkage rate measured after being left at 180 ° C. for 1 hour is 2% to 2% in the machine direction (MD, Machine Direction) and the transverse direction (TD, Transverse Direction) 10%, or 3% to 8%, or 2% or less may be more convenient.

The binder polymer may be a binder polymer commonly used for forming an inorganic hybrid void layer. The binder polymer may have a glass transition temperature (Tg) of -200 to 200 °C. When the glass transition temperature of the binder polymer satisfies the aforementioned range, mechanical properties such as flexibility and elasticity of the finally formed inorganic hybrid porous layer may be improved. The binder polymer may have ion conduction ability. When the binder polymer has ion conductivity, battery performance can be further improved. The binder polymer may have a dielectric constant of 1.0 to 100 (measurement frequency = 1 kHz) or 10 to 100. When the dielectric constant of the binder polymer satisfies the aforementioned range, the degree of salt dissociation in the electrolyte may be improved.

In one embodiment of the present invention, the binder polymer may be a binder polymer having excellent heat resistance. When the binder polymer has excellent heat resistance, heat resistance of the inorganic hybrid porous layer may be further improved.

In one embodiment of the present invention, the binder polymer is poly(vinylidene fluoride-hexafluoropropylene) (poly(vinylidene fluoride-co-hexafluoropropylene)), poly(vinylidene fluoride-chlorotrifluoroethylene) ( poly(vinylidene fluoride-co-chlorotrifluoroethylene)), poly(vinylidene fluoride-co-tetrafluoroethylene)), poly(vinylidene fluoride-trichloroethylene) (poly(vinylidene fluoride-co-trichloroethylene)), acrylic copolymer, styrene-butadiene copolymer, poly(acrylic acid), poly(methylmethacrylate), poly(butylacrylate) (poly(butylacrylate)), poly(acrylonitrile), poly(vinylpyrrolidone), poly(vinylalcohol), poly(vinyl acetate) ) (poly(vinylacetate)), ethylene vinyl acetate copolymer (poly(ethylene-co-vinyl acetate)), poly(ethylene oxide) (poly(ethylene oxide)), poly(arylate) (poly(arylate)), Cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, Cyanoethylcellulose, cyanoethylsucrose ), pullulan, carboxymethyl cellulose, or two or more of them.

The acrylic copolymer is ethyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, ethyl acrylate-acrylic acid-2-(dimethylamino)ethyl acrylate copolymer, ethyl acrylate-acrylic acid-N,N-di ethyl acrylamide copolymer, ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, or two or more thereof, but is not limited thereto.

In one embodiment of the present invention, the weight ratio of the total inorganic filler combined with the first inorganic filler and the second inorganic filler and the binder polymer is determined in consideration of the thickness, pore size, and porosity of the inorganic hybrid void layer to be finally prepared, 50:50 to 99.9:0.1, or 60:40 to 99.5:0.5. When the weight ratio of the entire inorganic filler to the binder polymer is within the above-described range, it may be easy to secure the pore size and porosity of the inorganic hybrid porous layer by sufficiently securing an empty space formed between the inorganic fillers. In addition, it may be easy to secure adhesive strength between inorganic fillers.

In one embodiment of the present invention, the inorganic hybrid porous layer may further include a first dispersing agent and a second dispersing agent.

The first dispersing agent refers to a dispersing agent for the first inorganic filler. The second dispersing agent refers to a dispersing agent for the second inorganic filler.

As the first inorganic filler and the second inorganic filler have different average particle diameters, different types of dispersants may also be used to disperse the first inorganic filler and the second inorganic filler, respectively.

In one embodiment of the present invention, the first dispersant may include a cellulosic compound. The cellulose-based compound is, for example, ethylhydroxy ethyl cellulose (EHEC), methyl cellulose (MC), carboxymethyl cellulose sodium salt (CMC- Na`), hydroxyalkyl methyl cellulose, or two or more of them. When the first dispersant includes the above-described material, the dispersibility of the first inorganic filler may be improved.

In one embodiment of the present invention, the second dispersant may include a single molecular organic acid. The single molecular organic acid may be, for example, citric acid, stearic acid, oxalic acid, acetic acid, formic acid, or two or more of these. When the second dispersant includes the above-described material, the dispersibility of the second inorganic filler may be improved. In particular, the average particle diameter of the second inorganic filler is 20 nm to 40 nm, or the second inorganic filler is a fumed type inorganic filler, such as fumed alumina, fumed silica, fumed titanium dioxide, or two or more of these When included, dispersibility of the second inorganic filler may be further improved by including the second dispersant.

In one embodiment of the present invention, the inorganic hybrid void layer is bound to each other by the binder polymer in a state in which the inorganic fillers are filled and in contact with each other, thereby forming interstitial volumes between the inorganic fillers. formed, and the interstitial volume between the inorganic fillers may be an empty space to form pores.

In one embodiment of the present invention, the average pore size of the inorganic hybrid porous layer may be 0.001 μm to 10 μm, or 0.01 μm to 0.2 μm. The average pore size of the inorganic hybrid porous layer may be measured according to a capillary flow porometry method. The capillary flow pore diameter measurement method is a method in which the diameter of the smallest pore in the thickness direction is measured. Therefore, in order to measure the average pore size of only the inorganic hybrid void layer by the capillary flow pore size measurement method, the inorganic hybrid void layer was separated from the polymer porous support and wrapped with a nonwoven fabric capable of supporting the separated inorganic hybrid void layer. In this case, the pore size of the nonwoven fabric should be much larger than the pore size of the inorganic hybrid porous layer.

In one embodiment of the present invention, the porosity of the inorganic hybrid porous layer may be 5% to 95%, or 10% to 95%, or 20% to 90%, or 30% to 80%. The porosity corresponds to a value obtained by subtracting the volume converted into the weight and density of each component of the inorganic hybrid void layer from the volume calculated in the thickness, width, and length of the inorganic hybrid void layer.

The porosity of the inorganic hybrid void layer was 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) can be measured by the BET 6-point method by the nitrogen gas adsorption flow method.

In one embodiment of the present invention, the inorganic hybrid porous layer may have a thickness of 0.7 μm to 3.0 μm on one side of the polymeric porous support. When the thickness of the inorganic hybrid void layer satisfies the aforementioned range, the cell strength of the battery may be easily increased while having excellent adhesion to the electrode.

A separator for a lithium secondary battery according to an aspect of the present invention has an arithmetic average roughness (Ra) of 400 nm to 850 nm on the surface of the separator. Here, the 'arithmetic mean roughness of the surface of the separator' means the arithmetic average roughness of the surface of the separator on which the inorganic mixed void layer is formed.

In the case of conventionally using a particulate inorganic filler alone to secure thermal contraction at high temperatures, it is not possible to secure the arithmetic average roughness of the separator surface enough to secure assembly fairness, resulting in wrinkles, meanders, etc. this has occurred

In particular, when the arithmetic average roughness value of the separator surface is small in a cylindrical lithium secondary battery, when winding the separator in the battery assembly process, the separator is not wound well, so securing fairness in assembling the separator has been a more important problem.

Since the separator for a lithium secondary battery according to one aspect of the present invention has an arithmetic mean roughness of 400 nm to 850 nm on the surface of the separator, it is possible to secure driving characteristics in a battery assembly process. For example, wrinkles on separators during battery assembly. It is possible to prevent the occurrence of meandering, etc., and to ensure assembly fairness.

In particular, when the separator for a lithium secondary battery according to an embodiment of the present invention is used in a cylindrical lithium secondary battery, the arithmetic average roughness of the separator surface has a value of 400 nm to 850 nm, so that wrinkles, meanders, etc. Since the occurrence of can be prevented, it may be easier to secure assembly fairness.

A separator for a lithium secondary battery according to an aspect of the present invention includes a first inorganic filler and a second inorganic filler having different average particle diameters, and may have an arithmetic average roughness of 400 nm to 850 nm on the surface of the separator.

In one embodiment of the present invention, the arithmetic average roughness of the surface of the separator may be 450 nm to 800 nm. When the arithmetic mean roughness of the surface of the separator satisfies the above-mentioned range, it may be easier to secure battery assembly fairness by maintaining an appropriate level of frictional force on the surface of the inorganic hybrid porous layer.

In the present specification, the 'arithmetic average roughness' refers to the reference length L as follows in the median average direction of the roughness curve in the roughness curve recorded by enlarging the cut surface when the surface of the separator is cut with a plane perpendicular to the surface of the separator. It refers to a value expressed by Equation 1 below, with the average line direction as the x-axis and the height direction as the y-axis by extracting as much as the amount.

[Equation 1]

The arithmetic mean roughness may be measured using, for example, an optical profiler (NV-2700) of Nano Systems.

When the arithmetic average roughness of the separator surface is less than 400 nm, wrinkles and meanders occur on the separator during the battery assembly process, making it impossible to secure assembly fairness.

When the arithmetic mean roughness of the surface of the separator exceeds 850 nm, it is difficult to ensure thermal shrinkage due to deterioration of heat resistance characteristics due to poor density of the inorganic hybrid porous layer.

In one embodiment of the present invention, when the first dispersant includes a cellulose-based compound or the second dispersant includes a single molecular organic acid, it may be more convenient that the arithmetic average roughness of the surface of the separator is 400 nm to 850 nm. .

A separator for a lithium secondary battery according to an aspect of the present invention may be manufactured by the following method, but is not limited thereto.

A method for manufacturing a separator for a lithium secondary battery according to an embodiment of the present invention,

Preparing a polymeric porous support;

Coating and drying a slurry for forming an inorganic hybrid porous layer including a first inorganic filler, a second inorganic filler, a binder polymer, and a dispersion medium on at least one surface of the polymer porous support,

The average particle diameter of the first inorganic filler may be 5 times or more the average particle diameter of the second inorganic filler.

Hereinafter, a method for manufacturing a separator for a lithium secondary battery according to an embodiment of the present invention will be mainly reviewed.

First, a polymeric porous support is prepared.

For the polymeric porous support, refer to the above description. The polymeric porous support is obtained through a conventional method known in the art, such as a wet method using a solvent, a diluent or a pore forming agent, or a dry method using a stretching method to secure excellent air permeability and porosity from the above-mentioned material. It can be manufactured by forming.

Then, a slurry for forming an inorganic hybrid porous layer including a first inorganic filler, a second inorganic filler, a binder polymer, and a dispersion medium is coated on at least one surface of the polymer porous support and dried.

For the first inorganic filler, the second inorganic filler, and the binder polymer, refer to the above description.

In one embodiment of the present invention, the slurry for forming the inorganic hybrid void layer is prepared by dispersing a first inorganic filler in a dispersion medium to prepare a first slurry, and dispersing a second inorganic filler in a dispersion medium to prepare a second slurry, It may be prepared by mixing the first slurry and the second slurry and dissolving or dispersing the binder polymer therein.

In one embodiment of the present invention, the first dispersant may be added to the first slurry. For the first dispersant, refer to the above description.

In one embodiment of the present invention, the second dispersant may be added to the second slurry. For the second slurry, refer to the above description.

When the slurry is prepared by adding the second dispersant to the first slurry and the first dispersant to the second slurry, or by simultaneously mixing the second inorganic filler and the second inorganic filler, the first inorganic filler and the second inorganic filler It can be difficult to distribute evenly. Alternatively, sedimentation of the inorganic filler may occur, making it difficult to manufacture a separator.

The dispersion medium may serve as a solvent for dissolving the binder polymer or may serve as a dispersion medium for dispersing the binder polymer without dissolving it, depending on the type of the binder polymer.

In one embodiment of the present invention, the dispersion medium is N-methyl-2-pyrrolidone, acetone, methyl ethyl ketone, dimethylformamide (Diemthylformaide) , Dimethyl acetamide, methanol, ethanol, isopropyl alcohol, or two or more of these organic solvents, or water.

The slurry for forming the inorganic hybrid porous layer may be coated on at least one surface of the polymer porous support, and non-limiting examples of the method of coating the slurry include a dip coating method, a die coating method, and a roll coating method. There are a roll coating method, a comma coating method, a microgravure coating method, a doctor blade coating method, a reverse roll coating method, and a direct roll coating method.

In one embodiment of the present invention, after the slurry for forming the inorganic hybrid void layer is coated on at least one surface of the polymeric porous support, phase separation using a non-solvent for the binder polymer according to a conventional method known in the art Further steps may be included. The phase separation step may be performed to form a pore structure in the inorganic hybrid void layer.

Drying of the coated slurry may be performed by drying by a conventional drying method in manufacturing a separator. For example, drying of the coated slurry may be performed by air for 10 seconds to 30 minutes, or 30 seconds to 20 minutes, or 3 minutes to 10 minutes. When the drying time is within the above range, residual solvent may be removed without compromising productivity.

A lithium secondary battery may be manufactured by interposing the separator for a lithium secondary battery between the positive electrode and the negative electrode.

The lithium secondary battery may include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The electrode to be applied with the lithium secondary battery separator of the present invention is not particularly limited, and an electrode active material layer including an electrode active material, a conductive material, and a binder is bound to a current collector according to a conventional method known in the art. can be manufactured

Among the electrode active materials, non-limiting examples of the cathode active material include layered compounds such as lithium cobalt composite oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ), or compounds substituted with one or more transition metals; lithium manganese oxides such as Li _1+x Mn _2-x O ₄ (where x = 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₅ , LiV ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _2-x M _x O ₂ (Where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01-0.1) or Li ₂ Mn ₃ MO ₅ (Where M = Fe, Co, Ni , Cu or Zn); LiMn ₂ O ₄ in which a part of the chemical formula Li is replaced with an alkaline earth metal ion; disulfide compounds; Fe ₂ (MoO ₄ ) ₃ etc. are mentioned, but it is not limited only to these.

Non-limiting examples of the negative electrode active material include conventional negative electrode active materials that can be used for negative electrodes of conventional lithium secondary batteries, and in particular, lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, A lithium adsorption material such as graphite or other carbons may be used.

Non-limiting examples of the anode current collector include a foil made of aluminum, nickel or a combination thereof, and non-limiting examples of the cathode current collector include copper, gold, nickel or a copper alloy or a combination thereof. There are manufactured foils and the like.

In one embodiment of the present invention, the conductive material used in the negative electrode and the positive electrode may be each independently added in an amount of 1% to 30% by weight based on the total weight of the positive electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and server black; conductive fibers such as carbon fibers and metal fibers; fluorinated carbon; metal powders such as aluminum and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

In one embodiment of the present invention, the binder used in the negative electrode and the positive electrode is a component that independently assists in the bonding of the active material and the conductive material and the bonding to the current collector, typically 1 weight based on the total weight of the positive electrode active material layer. % to 30% by weight. Examples of such binders include polyvinylidene fluoride (PVdF), polyacrylic acid (PAA), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers and the like.

In one embodiment of the present invention, the lithium secondary battery includes an electrolyte solution, and the electrolyte solution may include an organic solvent and a lithium salt. In addition, an organic solid electrolyte or an inorganic solid electrolyte may be used as the electrolyte solution.

Examples of the organic solvent include N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane , tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid Triester, trimethoxy methane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-ibidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate An aprotic organic solvent such as may be used.

The lithium salt is a material that is easily soluble in the organic solvent, and is, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, lithium chloroborane, lithium lower aliphatic carbonate, lithium 4-phenyl borate, imide, and the like can be used. there is.

In addition, for the purpose of improving charge and discharge characteristics, flame retardancy, etc. in the electrolyte solution, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. there is. In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included to impart incombustibility, and carbon dioxide gas may be further included to improve high-temperature storage properties.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, A polymer containing an ionic dissociation group or the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitride, halide, sulfate, and the like of Li such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , etc. may be used.

The injection of the electrolyte may be performed at an appropriate stage in the battery manufacturing process according to the manufacturing process and required physical properties of the final product. That is, it may be applied before battery assembly or at the final stage of battery assembly.

In one embodiment of the present invention, as a process of applying the separator for a lithium secondary battery to a battery, in addition to winding, which is a general process, lamination, stack, and folding processes of the separator and the electrode are possible.

In one embodiment of the present invention, the separator for a lithium secondary battery may be interposed between a positive electrode and a negative electrode of a lithium secondary battery, and may be interposed between adjacent cells or electrodes when configuring an electrode assembly by assembling a plurality of cells or electrodes. It can be. The electrode assembly may have various structures such as a simple stack type, a jelly-roll type, a stack-folding type, and a lamination-stack type.

Hereinafter, examples will be described in detail to aid understanding of the present invention. However, the embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the following examples. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1

As a polymeric porous support, a polyethylene porous film (Senior, SW311H) having a thickness of 11 μm was prepared.

A first slurry was prepared by mixing fumed alumina (Evonik, average particle diameter: 20 nm) with citric acid at a ratio of 98:2 and then dispersing in water. A second slurry was prepared by mixing pulverized alumina (CiS , average particle diameter: 500 nm) with carboxymethyl cellulose sodium salt (Daicel, 1220) at a ratio of 99:1 and then dispersing in water. The first slurry and the second slurry were mixed so that the weight ratio of alumina was 93:7.

To 100 parts by weight of the fumed alumina and alumina mixture, 2.5 parts by weight of an acrylic emulsion binder (Toyo Ink Co., CSB-130) was added and dispersed as a binder polymer to prepare a slurry for forming an inorganic hybrid void layer.

The slurry for forming the inorganic hybrid void layer was coated on both sides of a polyethylene porous film and dried at 80° C. for 1 minute to prepare a separator.

Example 2

A separator was manufactured in the same manner as in Example 1, except that the first slurry and the second slurry were mixed so that the weight ratio of alumina was 70:30.

Example 3

Instead of pulverized alumina (CiS , average particle diameter: 500 nm), pulverized alumina (CiS , average particle diameter: 200 nm) was used, and the first slurry and the second slurry were mixed so that the weight ratio of alumina was 50:50. A separator was prepared in the same manner as in Example 1, except for the above.

Comparative Example 1

A separator was prepared in the same manner as in Example 1, except that only fumed alumina (Evonik, average particle diameter: 20 nm) was used as an inorganic filler.

Comparative Example 2

A separator was prepared in the same manner as in Example 1, except that only pulverized alumina (CiS , average particle diameter: 500 nm) was used as the inorganic filler.

Comparative Example 3

Separator in the same manner as in Example 1, except that fumed alumina (Evonik, average particle diameter: 20 nm) and pulverized alumina (CiS , average particle diameter: 500 nm) were mixed in a weight ratio of 30:70. was manufactured.

Comparative Example 4

A separator was prepared in the same manner as in Example 1, except that carboxymethyl cellulose sodium salt (Daicel Co., 1220) was used instead of citric acid when preparing the first slurry.

Comparative Example 5

A separator was prepared in the same manner as in Example 1, except that citric acid was used instead of carboxymethyl cellulose sodium salt when preparing the second slurry.

At this time, the sedimentation of the inorganic filler in the prepared slurry for forming the mixed inorganic void layer occurs so severely that it is impossible to normally coat the slurry for forming the mixed inorganic void layer on one side of the polymer porous support, making it impossible to manufacture a separator. did

Evaluation Example 1: Measurement of surface arithmetic average roughness of separator and thermal shrinkage of separator in machine direction (MD, Machine Direction) and transverse direction (TD, Transverse Direction) after being allowed to stand at 180 ° C for 1 hour

The arithmetic mean roughness of the surface of the separators prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was measured by the following method using Nano System's optical profiler (NV-2700), and then shown in Table 1 and Figures 1 to 4. 3.

After taking a separator sample in a square shape of 5 cm each in the machine direction and the perpendicular direction, after placing it on a stage maintained at 23 ° C., setting it as a WSI filter, the surface arithmetic average roughness was measured. Thereafter, the surface arithmetic average roughness was calculated through the Nanomap program, and the median value after repeating the same measurement 5 times was presented as a representative value.

1 is a diagram showing the surface roughness of the separator prepared in Example 1.

2 is a diagram showing the surface roughness of the separator prepared in Example 2.

3 is a diagram showing the surface roughness of the separator prepared in Comparative Example 3.

In addition, the separators prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were each cut into a square shape with MD 10 cm x TD 10 cm, left in a constant temperature oven maintained at 180 ° C. for 1 hour, and then changed in length. After being measured with a ruler and left at 180 ° C. for 1 hour, the thermal contraction rate of the separator in the machine direction (MD, Machine Direction) and the transverse direction (TD, Transverse Direction) is shown in Table 1 below.

As can be seen in Table 1, the separators prepared in Examples 1 to 3 have an arithmetic average roughness of 400 nm to 850 nm on the surface of the separator, and after being left at 180 ° C. for 1 hour, the MD (Machine Direction) and It was confirmed that the thermal contraction rate of the separator in the transverse direction (TD) was very low.

On the other hand, the separator prepared in Comparative Example 1 was left alone at 180 ° C. for 1 hour using only fumed alumina, and then the separator in the machine direction (MD, Machine Direction) and the transverse direction (TD, Transverse Direction). Although the thermal contraction rate was very low, it was confirmed that the arithmetic mean roughness of the surface of the separator was less than 400 nm.

The separator prepared in Comparative Example 2 uses only pulverized alumina, and the arithmetic mean roughness of the separator surface is 400 nm to 850 nm, but after being left at 180 ° C for 1 hour, the MD (Machine Direction) and right angles It was confirmed that the thermal contraction rate of the separator in the direction (TD, Transverse Direction) was very high.

The separator prepared in Comparative Example 3 has high thermal shrinkage in the machine direction (MD, Machine Direction) and transverse direction (TD, Transverse Direction) after being left at 180 ° C. for 1 hour, and the arithmetic average roughness of the separator surface is 850 nm was found to be exceeded.

In the separator prepared in Comparative Example 4, fumed alumina was not well dispersed in the slurry because carboxymethyl cellulose sodium salt was used as a dispersant when preparing the first slurry. Accordingly, the arithmetic mean roughness of the surface of the separator exceeded 850 nm due to poor dispersibility of the slurry for forming the inorganic mixed void layer. In addition, the heat shrinkage rate in the machine direction (MD, Machine Direction) and the right angle direction (TD, Transverse Direction) after being left at 180 ° C. for 1 hour was also high.

Evaluation Example 2: Evaluation of Assembly Fairness of Separator

Cylindrical batteries were prepared by winding the separators prepared in Example 1 and Comparative Example 1, and the cylindrical assembly fairness thereof was evaluated and shown.

As can be seen in FIG. 4, in the separator prepared in Example 1, the separator is uniformly wound in the longitudinal direction together with the electrodes, there is no color change between the inner and outer surfaces of the winding, and the separator secures a stable length on the outermost part to obtain a white color. showed color.

On the other hand, in the separator prepared in Comparative Example 1, as can be seen in FIG. 5, the separator was meandered in the process of winding the separator along with the electrode in the longitudinal direction, causing a problem in which the electrode was partially exposed.

Claims (15)

As a separator for a lithium secondary battery,
polymeric porous support; and
It is located on at least one surface of the polymeric porous support and includes an inorganic hybrid void layer containing a first inorganic filler, a second inorganic filler, and a binder polymer,
The average particle diameter of the first inorganic filler is 5 times or more than the average particle diameter of the second inorganic filler,
A separator for a lithium secondary battery, characterized in that the arithmetic mean roughness of the surface of the separator for a lithium secondary battery is 400 nm to 850 nm. According to claim 1,
A separator for a lithium secondary battery, characterized in that the weight ratio of the first inorganic filler and the second inorganic filler is 7:93 to 65:35. According to claim 1,
A separator for a lithium secondary battery, characterized in that the average particle diameter of the first inorganic filler is 200 nm to 800 nm. According to claim 1,
A separator for a lithium secondary battery, characterized in that the average particle diameter of the second inorganic filler is 20 nm to 40 nm. According to claim 1,
The first inorganic filler is BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT, 0<x<1, 0<y<1) , Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), Hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, Mg(OH) ₂ , NiO, CaO , ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , AlOOH, Al(OH) ₃ , SiC, TiO ₂ , lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y ( PO ₄ ) ₃ , 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) _x O _y series glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0<x<2, 0<y<3) , lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w < 5), lithium nitride (Li _x N _y , 0<x<4, 0<y<2), SiS ₂ series glass (Li _x Si _y S _z , 0<x<3, 0<y<2, 0<z<4), P ₂ S ₅ series A separator for a lithium secondary battery comprising glass (Li _x P _y S _z , 0 <x < 3, 0 <y <3, 0 <z <7), or two or more of these. According to claim 1,
The second inorganic filler is a separator for a lithium secondary battery, characterized in that it comprises a fumed (fumed) type of inorganic filler. According to claim 6,
The second inorganic filler is a separator for a lithium secondary battery, characterized in that it comprises fumed alumina, fumed silica, fumed titanium dioxide, or two or more of them. According to claim 1,
The inorganic hybrid void layer further includes a first dispersant and a second dispersant,
The first dispersant includes a cellulose-based compound,
Separator for a lithium secondary battery, characterized in that the second dispersant comprises a single molecular organic acid. According to claim 8,
The first dispersant is ethylhydroxy ethyl cellulose (EHEC), methyl cellulose (MC), carboxymethyl cellulose sodium salt (CMC-Na`), A separator for a lithium secondary battery comprising hydroxyalkyl methyl cellulose or two or more of them. According to claim 8,
A separator for a lithium secondary battery, wherein the second dispersant comprises citric acid, stearic acid, oxalic acid, acetic acid, formic acid, or two or more of these. According to claim 1,
A separator for a lithium secondary battery, characterized in that the thermal conductivity of the first inorganic filler measured by a laser flash method is 15 W / mk to 55 W / mK. According to claim 1,
A separator for a lithium secondary battery, characterized in that the thermal conductivity of the second inorganic filler measured by a laser flash method is 15 W / mk to 55 W / mK. According to claim 1,
The separator for a lithium secondary battery, characterized in that the thermal shrinkage rate measured after being left at 180 ° C for 1 hour is 10% or less in the machine direction (MD, Machine Direction) and the transverse direction (TD, Transverse Direction), respectively. . Including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
A lithium secondary battery, characterized in that the separator is the separator according to any one of claims 1 to 13. According to claim 14,
The lithium secondary battery is a lithium secondary battery, characterized in that the cylindrical lithium secondary battery.

Images