KR20160137486A - A separator having porous coating and electrochemical device containing the same - Google Patents

Abstract

Disclosed is a separator which includes a porous substrate having a plurality of pores; and a porous coating layer which is formed on one or more areas from at least one surface of the porous substrate and the pores of the porous substrate and includes a plurality of inorganic particles, a binder connecting and fixing the inorganic particles, and a ligand functional group capable of coordinating with at least one metal ion among the inorganic particles and the binder. The separator can be used in various electrochemical devices such as a lithium secondary battery. So, the service life can be extended and the stability of the electrochemical device can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a separator having a porous coating layer and an electrochemical device comprising the separator.

The present invention relates to a separator having a porous coating layer and an electrochemical device having the separator. More particularly, the present invention relates to a separator having a porous coating layer and an electrochemical device using the inorganic particle and the binder, And a ligand functional group capable of coordinating with a metal ion or more to improve lifetime characteristics and stability of the battery, and an electrochemical device having the separator.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. Electrochemical devices have attracted the greatest attention in this respect, among which the development of rechargeable secondary batteries has become a focus of attention. In recent years, in order to improve the capacity density and specific energy in developing such batteries, And research and development on the design of batteries are underway.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution . However, such a lithium secondary battery has safety problems such as ignition and explosion when using an organic electrolytic solution, and it is disadvantageous in that it is difficult to manufacture. The recent lithium secondary polymer battery is considered as one of the next generation batteries by improving the weakness of the conventional lithium secondary battery. However, the capacity of the battery is relatively low as compared with that of the lithium ion battery and the discharge capacity at low temperature is insufficient There is an urgent need for improvement.

The lithium secondary battery has constituent elements of a cathode, an anode, a separator and an electrolyte as a power generation element. As the anode material, a graphite based material is typical, and lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, .

During the operation of the lithium battery, as the charge and discharge of the battery progresses, the cathode active material is structurally collapsed and the performance of the cathode deteriorates. At the same time, when the cathode structure collapses, the metal ions eluted from the cathode surface are electrodeposited Thereby deteriorating the anode. The metal electrodeposited on the anode generally shows a large reactivity to the electrolyte solution. Therefore, the irreversible reaction due to the progress of charge and discharge is increased due to the decrease of the reversible lithium amount, resulting in deterioration of battery capacity and lifetime characteristics.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a porous battery which comprises forming a porous coating layer on a surface of a porous substrate using inorganic particles and a binder and separating the inorganic particles and the binder from the cathode, And a ligand functional group capable of coordinating with the ligand functional group, thereby improving the lifetime characteristics and stability of the electrochemical device.

Another problem to be solved by the present invention is to provide an electrochemical device having the separator.

According to an aspect of the present invention,

A porous substrate having a plurality of pores; And

And a binder which is formed on at least one surface of the porous substrate and at least one of the pores of the porous substrate and includes a plurality of inorganic particles and a binder for connecting and fixing the inorganic particles,

Wherein the inorganic particles or the binder has a ligand functional group capable of coordinating with a metal ion,

The content of the ligand functional group is 0.01 to 10 parts by weight based on 100 parts by weight of the inorganic particles, or 1 to 50 parts by weight based on 100 parts by weight of the binder.

The ligand functional group is ^{-COOH, -COO -, -CHO, -NH} 2, -SH, -OH, -SO 3 H, -SO 3 -, -C (= NH) -, -CONH 2, -CN, - CS ₂ H, -CS ₂ ^- , a halide group (-Cl, -F, -Br, etc.), a pyridine group, and a pyrazine group.

The metal ion may be an ion of at least one metal selected from the group consisting of Ni, Co, Fe, Ru, Zn, Mn, Y, Zr, Ti, Cr, Mg, Ce, Cu, Pb and V.

The inorganic particles may be selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transporting ability, and mixtures thereof.

Inorganic particles is greater than or equal to the dielectric constant of 5, _{BaTiO 3, Pb (Zr x,} Ti 1-x) O 3 (PZT, 0 <x <1), Pb 1 - x La x Zr 1 - y Ti y O 3 (PLZT , 0 <x <1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPbTiO ₃ (PMN- HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ . Or a mixture of two or more of them.

The inorganic particles having lithium ion transferring 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), (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 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x Si y S _{z, 0 <x <3,} 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 <z <7) series glass, or a mixture of two or more thereof.

The binder may be selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, poly But are not limited to, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide Polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolylenes, Vinyl alcohol (cyanoethylpolyvinylalcohol), And may be any one selected from the group consisting of cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more thereof.

The weight ratio of the inorganic particles to the binder may be 50:50 to 99: 1.

The porous substrate may be a polyolefin-based porous membrane or a nonwoven fabric.

The porous substrate may be selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfroid and polyethylene naphthalene (polyethylenenaphthalene), or a mixture of two or more thereof.

According to another aspect of the present invention,

There is provided an electrochemical device comprising a cathode, an anode, and a separator interposed between the cathode and the anode, wherein the separator is the separator described above.

The electrochemical device may be a lithium secondary battery.

A separator including a porous coating layer comprising inorganic particles and a binder and at least one of which is eluted from the cathode or has a ligand functional group capable of coordinating a metal ion impurity introduced into the cell during the manufacturing process, The metal component from the cathode is precipitated in complex with the ligand functional group in the porous coating layer of the separator having a large number of pores, thereby suppressing precipitation of the metal component on the anode or the anode surface. Therefore, the efficiency of the anode is reduced or the internal short circuit of the battery is prevented, thereby improving the lifetime characteristics and stability of the electrochemical device.

Fig. 1 and Fig. 2 are electron micrograph (SEM) photographs of the separator of Example 1-1.
3 is a graph showing the cycle characteristics of the secondary batteries manufactured in Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

According to an aspect of the present invention,

At least one surface of the porous substrate and at least one of the pores of the porous substrate, and includes a plurality of inorganic particles and a binder for connecting and fixing the inorganic particles, wherein at least one of the inorganic particles and the binder And a porous coating layer having ligand functional groups capable of coordinating with metal ions.

When a porous coating layer having at least one of the inorganic particles and the binder and having a ligand functional group capable of coordinating with the metal ion is formed on at least one surface of the separator, it may be eluted from the cathode during charging and discharging, The phenomenon that the metal ion impurity component migrates to the anode surface and precipitates as a metal oxide on the anode surface is suppressed and instead the precipitate is precipitated in the metal complex in the porous coating layer into which the ligand functional group is introduced, Can be improved.

The inorganic particles usable in the porous coating layer may have an average particle diameter of 0.01 to 10 mu m. These inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles are not particularly limited as long as oxidation and / or reduction reactions do not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). Particularly, when inorganic particles having ion transfer ability are used, the ion conductivity in the electrochemical device can be increased to improve the performance.

Further, when inorganic particles having a high dielectric constant are used as the inorganic particles, dissociation of an electrolyte salt, for example, a lithium salt in the liquid electrolyte, can also contribute to enhance the ionic conductivity of the electrolyte.

For the reasons stated above, the inorganic particles may include high-permittivity inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having lithium ion-transporting ability, or a mixture thereof.

Nonlimiting examples of the inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x Ti _1-x ) O ₃ (PZT, where 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, where 0 (x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, TiO ₂ May be used alone or in admixture of two or more.

In particular, a _{BaTiO 3, Pb (Zr x Ti} 1-x) above O ₃ (PZT, where 0 <x <1), Pb 1 - x La x Zr 1 - yTi y O 3 (PLZT, where, 0 <x 1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O _{3 - x} PbTiO ₃ (PMN- ₂ ) exhibits a high dielectric constant with a dielectric constant of 100 or more. In addition, when particles are stretched or compressed by applying a certain pressure, electric charges are generated and piezoelectricity is generated so that a potential difference occurs between both surfaces. It is possible to prevent the occurrence of internal short circuit between both electrodes due to the electrochemical device, thereby improving the safety of the electrochemical device. Further, when the above-mentioned high-permittivity inorganic particles and inorganic particles having lithium ion transferring ability are mixed, their synergistic effect can be doubled.

The inorganic particles having the lithium ion transferring ability refer to inorganic particles that contain a lithium element but do not store lithium but have a function of moving lithium ions. The inorganic particles having lithium ion transferring ability exist in the particle structure Since lithium ions can be transferred and transferred due to a kind of defect, the lithium ion conductivity in the battery is improved and the battery performance can be improved. Examples of the inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (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 O ₅ as such (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 ), Li _{3 . 25 Ge 0 .25 P 0. 75 S} 4 Lithium, such as germanium Mani help thiophosphate lithium nitro, such as _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), Li 3 N fluoride _{(Li x N y, 0 <} x <4, 0 <y <2), Li 3 PO 4 -Li 2 S-SiS 2 SiS 2 based glass, such as _{(Li x Si y S z,} 0 <x <3 , 0 <y <2, 0 <z <4), LiI-Li ₂ SP ₂ S ₅ There is P ₂ S ₅ based glass _{(Li x P y S z,} 0 <x <3, 0 <y <3, 0 <z <7) or a mixture thereof as such.

As described above, the inorganic particles form a porous coating layer on at least one surface of the separator, and a binder is used to bond them to the separator.

In the separator according to one aspect of the present invention, the binder used for forming the porous coating layer may be a polymer commonly used in the art for forming a porous coating layer. In particular, a polymer having a glass transition temperature (T _g ) of -200 to 200 ° C can be used because it can improve mechanical properties such as flexibility and elasticity of a finally formed porous coating layer. Such a binder faithfully performs a binder function to connect and stably fix inorganic particles, thereby contributing to prevention of deterioration of mechanical properties of the separator into which the porous coating layer is introduced.

Further, the binder does not necessarily have the ion-conducting ability, but the performance of the electrochemical device can be further improved by using a polymer having ion-conducting ability. Therefore, a binder having a high permittivity constant can be used. Actually, the dissociation degree of the salt in the electrolytic solution depends on the permittivity constant of the solvent of the electrolyte. Therefore, the higher the permittivity constant of the polymer, the better the salt dissociation degree in the electrolyte. The permittivity constant of such a binder may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), in particular, 10 or more.

In addition to the functions described above, the binder may be characterized by being capable of exhibiting a high degree of swelling of the electrolyte by gelation upon impregnation with a liquid electrolyte. Accordingly, the solubility parameter of the binder is from 15 to 45 MPa ^1/2 or 15 to 25 MPa ^1/2, and 30 to 45 MPa ^1/2 range. Therefore, hydrophilic polymers having many polar groups can be used more than hydrophobic polymers such as polyolefins. If the solubility is more than 15 MPa ^1/2 and less than 45 MPa ^1/2, because it can be difficult to swell (swelling) by conventional liquid electrolyte batteries.

Non-limiting examples of such binders include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate but are not limited to, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, But are not limited to, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, , Cyanoethyl polyvinyl alcohol cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose can be mentioned.

The weight ratio of the inorganic particles to the binder may be 50:50 to 99: 1, or 60:40 to 90:10, or 70:30 to 80:20.

As described above, when a metal ion impurity is introduced into various constituent components in an electrochemical device such as a lithium secondary battery, adversely affecting lifetime characteristics and stability of an electrochemical device such as reduction of capacity and reduction of electrolyte solvent molecules can do.

In order to solve this problem, a separator according to one aspect of the present invention has a ligand functional group in which at least one of the inorganic particles and the binder can coordinate with a metal ion.

Here, the term "ligand functional group" refers to an anionic group or neutral compound containing atoms capable of giving at least one non-covalent electron pair to a metal ion, and they coordinate with a metal ion to form a metal complex, &Lt; / RTI &gt;

The ligand functional group can be selected to form an optional complex with the unwanted metal ions that may be present in the electrolyte solution during operation of the electrochemical device. For example, immobilization of metal ions (manganese, cobalt, nickel, or iron) that can dissolve into the electrolyte solution from the cathode can be used to protect the electrochemical device from degradation of the anode, do.

Accordingly, such a ligand functional group serves as a metal ion scavenger for capturing and immobilizing metal ions in order to prevent the inflow of unnecessary metal ions into the electrolyte solution.

At the same time, in order not to adversely affect the movement of lithium ions between the anode and the cathode at the time when a predetermined current is to be supplied during discharging, the ligand functional group may need to be intimately coupled to lithium ions.

Thus, any ligand functional group meeting these requirements can be introduced into at least one of the inorganic particles and the binder of the porous coating layer of the separator according to one aspect of the present invention.

Specifically, as the ligand functional ^{groups, -COOH, -COO -, -CHO,} -NH 2, -SH, -OH, -SO 3 H, -SO 3 -, -C (= NH) -, -CONH 2 , -CN, -CS ₂ H, -CS ₂ ^- , a halide group (-Cl, -F, -Br, etc.), a pyridine group, and a pyrazine group.

The metal ion is a metal impurity which elutes from the cathode and flows in or is introduced from the outside during the production of the electrochemical device. Specifically, the metal ion corresponds to Ni, Co, Fe, Ru, Zn, Mn, Y, Zr, Ti , And ions of at least one metal selected from the group consisting of Cr, Mg, Ce, Cu, Pb, and V.

More specifically, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, and lithium iron oxide are used alone or in combination as a lithium composite oxide as the cathode active material. Therefore, Mn ions, Co ions, Fe Ions, Ni ions and the like can be moved to the electrolyte solution. In addition, impurity metals may flow in various paths such as wear of the device during the battery manufacturing process, inflow of foreign matter, and catalyst component at the time of manufacturing the conductive material, and may be oxidized and ionized at the cathode to move into the electrolytic solution. The metal ions thus transferred can be reduced to Mn, Co, Fe, Ni or the like after reaching the anode through the separator.

The separator according to one aspect of the present invention is characterized in that such metal ions are trapped in the porous coating layer by the ligand functional groups provided in at least one of the inorganic particles and the binder to form a metal complex, The problem of precipitation from the surface can be prevented in advance.

The content of the ligand functional group introduced into at least one of the inorganic particles and the binder can be applied without limitation as long as it can sufficiently capture the metal ions eluted from the cathode active material as a main cause of metal ion impurities. For example, when the ligand functional group is introduced into the inorganic particles, the content of the ligand functional group is 0.01 to 10 parts by weight, or 0.1 to 7 parts by weight, or 0.5 to 5 parts by weight, based on 100 parts by weight of the inorganic particles forming the porous coating layer Weight portion.

In addition, when the ligand functional group is introduced into the binder, the content of the ligand functional group may be 1 to 50 parts by weight, or 3 to 40 parts by weight, or 5 to 30 parts by weight, based on 100 parts by weight of the binder.

When the content of the ligand functional group satisfies this range, there is an effect of introducing a ligand functional group. By capturing the metal ion impurity eluted from the cathode and forming it as a complex in the porous coating layer, the lifetime characteristics and stability of the electrochemical device are improved Can be improved. If the content of the ligand functional group is less than this range, the effect of adsorbing metal ions may be low. If it is more than this range, it is difficult to stably form the porous coating layer and all performance may be deteriorated due to reduction of lithium ion conductivity .

The thickness of the porous coating layer composed of the inorganic particles and the binder is not particularly limited, but may be in the range of 0.01 to 20 占 퐉. Also, the pore size and porosity of the porous coating layer are not particularly limited, but the pore size may be in the range of 0.01 to 10 μm, and the porosity may be in the range of 5 to 90%.

Further, in the separator of the present invention, the porous substrate on which the porous coating layer is formed may be any porous substrate commonly used in an electrochemical device. For example, a polyolefin porous membrane or a nonwoven fabric may be used However, it is not particularly limited.

Examples of the polyolefin-based porous film include polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high-density polyethylene, linear low density polyethylene, low density polyethylene and ultra high molecular weight polyethylene, One membrane can be mentioned.

The nonwoven fabric may include, in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate ), Polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, and polyethylenenaphthalene are used alone or in combination. Or a nonwoven fabric formed of a polymer mixed with these. The structure of the nonwoven fabric may be a spun bond nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

The thickness of the porous substrate is not particularly limited, but may be 5 to 50 탆, and the pore size and porosity present in the porous substrate are also not particularly limited, but may be 0.01 to 50 탆 and 10 to 95%, respectively.

In the porous coating layer, the binder attaches the inorganic particles to each other so that the inorganic particles can be maintained in a state of being bonded to each other (that is, the binder binds and fixes the inorganic particles), and the porous coating layer is bound to the porous substrate by the binder . The inorganic particles of the porous coating layer exist in a closely packed state in a state of being substantially in contact with each other, and the interstitial volume generated when the inorganic particles are in contact becomes the pores of the porous coating layer.

The separator according to one aspect of the present invention may further include other additives in addition to the inorganic particles and the binder described above as the porous coating layer component.

The additive is not particularly limited as long as it is a substance required or additionally required for the operation or performance improvement of the electrochemical device and is continuously consumed due to consumption in the operation process.

Non-limiting examples of such an electrochemical device performance improving additive may include any one of additives for forming a solid electrolyte interface, a cell side reaction inhibiting additive, a thermal stability improving additive, an overcharge suppressing additive, or a mixture of two or more thereof .

As the additive for forming the solid electrolyte interface, any one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, cyclic sulfite, saturated sulphone, unsaturated sulphone, acyclic sulphone, Mixtures of two or more of these may be used, but are not limited thereto.

Examples of the cyclic sulfite include ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethylethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, Diethyl propyl sulfite, 4,6-diethyl propyl sulfite, and 1,3-butylene glycol sulfite. The saturated sulphone includes, for example, 1,3-propane sultone, and 1,4-butane sultone. Examples of the unsaturated sultone include ethene sultone, 1,3-propene sultone, 1,4-butene sultone, Phenolsaltone, and the like. Examples of the non-cyclic sulfone include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone.

Examples of the cell side reaction inhibiting additive include ethylenediaminetetraacetic acid, tetramethylethylenediamine, pyridine, dipyridyl, ethylbis (diphenylphosphine), butyronitrile, succinonitrile, iodine, And derivatives thereof, or a mixture of two or more thereof, may be used, but are not limited thereto.

Examples of the thermostability-improving additive include one or two or more selected from the group consisting of hexamethyldisiloxane, hexamethoxycyclotriphosphazene, hexamethylphosphoramide, cyclohexylbenzene, biphenyl, dimethylpyrrole, and derivatives thereof But are not limited thereto.

The overcharge suppression additive may be, but is not limited to, a mixture of one or more selected from the group consisting of n-butylferrocene, a halogen-substituted benzene derivative, cyclohexylbenzene, and biphenyl.

Examples of the additives for improving the performance of the electrochemical device include derivatives in which at least one hydrogen atom bonded to the carbon atom of each compound is substituted with a halogen.

The content of the electrochemical device performance improving additive may be 2 to 20 parts by weight, 4 to 18 parts by weight, or 6 to 15 parts by weight based on 100 parts by weight of the total amount of the inorganic particles and the binder.

When the content of the additive satisfies the above range, the effect of the addition is sufficiently exhibited, the excessive additive is released to prevent the side reaction, and the cycle of the battery can be prevented from being degenerated early.

The method of manufacturing the separator according to one aspect of the present invention is illustrated below, but the present invention is not limited thereto.

First, the above-mentioned binder is dissolved in a solvent to prepare a binder solution. As the solvent, a solubility index similar to that of a binder to be used may be used, and a solvent having a low boiling point may be used. This is because the mixing can be made uniform and then the solvent can be easily removed. Non-limiting examples of the solvent include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (N- methyl-2-pyrrolidone (NMP), cyclohexane, water or a mixture thereof.

Then, the inorganic particles or optionally other additives are added to the prepared binder solution to prepare a coating solution in which inorganic particles and additives are dispersed.

At this time, inorganic particles may be added to the binder solution, followed by pulverization of the inorganic particles. The crushing time is suitably from 1 to 20 hours, and the particle size of the crushed inorganic particles may be 0.01 to 10 탆 as mentioned above. As the crushing method, a conventional method can be used, and in particular, a ball mill method can be used.

On the other hand, when the inorganic particles are coated using a coupling agent so that the inorganic particles can be easily dispersed in the binder solution, the coating solution can be prepared by simply mixing the inorganic particles in the binder solution.

Then, a coating solution in which inorganic particles and other additives are dispersed is applied to at least one side of the porous substrate to form a porous coating layer.

The coating liquid may be coated on the porous substrate using a conventional coating method known in the art, for example, a dip coating, a die coating, a roll coating, a comma coating Or a mixture method thereof may be used. Further, the porous coating layer can be selectively formed on both or only one side of the porous substrate.

When a solvent is added to the coating liquid, it is needless to say that a drying process of the coating layer is further required. Drying conditions are possible in a batch or continuous manner using an oven or a heated chamber in a temperature range that takes into account the vapor pressure of the solvent used.

At this time, as described above, as a method of introducing a ligand functional group into at least one of the inorganic particles and the binder in the porous coating layer, a porous coating layer comprising inorganic particles and a binder is first formed on the porous substrate, and then a ligand functional group A method in which a porous coating layer is formed on a porous substrate using such inorganic particles and a binder after introducing a ligand functional group at the time of polymerization from at least one of inorganic particles and a binder or a binder from a monomer is possible.

Specifically, in the case of the former, a monomer composition having a ligand functional group is applied to the porous coating layer obtained through the above-described processes and polymerized to polymerize the surface of the polymer having a ligand functional group on the porous coating layer, The grafting can introduce a polymer having a ligand functional group. Alternatively, the inorganic particles or the binder of the porous coating layer may be surface-modified with a single molecule having a ligand functional group to facilitate chemical reaction, and then the ligand functional group may be introduced through reaction with the single molecule. In the latter case, it can be applied to form a porous coating layer on a porous substrate after introducing a ligand functional group into one or both of the inorganic particles and the binder.

First, in the case of inorganic particles, a monomolecule having the above-mentioned ligand functional group may be adhered through surface modification of the inorganic particle before forming the porous coating layer, or a monomer having a ligand functional group may be polymerized on the surface of the inorganic particle to form a coating layer You can go through the method.

Further, in the case of a binder, the side chain of the binder is modified with a reactive group, and then the monomers and the polymer having a ligand functional group are reacted with the reactive group, or the monomer itself for forming the binder polymer is modified in advance to form a ligand functional group A method of polymerizing such a monomer to obtain a polymer as a binder, and the like.

The process for producing the separator using the inorganic particles and the binder into which the ligand functional group is introduced is as described above.

The separator according to one aspect of the present invention thus manufactured can be usefully used as a separator of an electrochemical device, that is, as a separator interposed between a cathode and an anode.

An electrochemical device according to one aspect of the present invention includes all devices that perform an electrochemical reaction, and specific examples thereof include capacitors such as all kinds of primary, secondary, fuel cell, solar cell, or super capacitor devices. ). In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery may be included in the secondary battery.

The electrode to be applied together with the separator according to one aspect of the present invention is not particularly limited, and the electrode active material may be bound to an electrode current collector according to a conventional method known in the art. Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof A lithium complex oxide may be used. As a non-limiting example of the anode active material, a conventional anode active material that can be used for an anode of an electrochemical device can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbing materials such as graphite or other carbon-based materials and the like can be used. Non-limiting examples of the cathode current collector include aluminum, nickel, or a combination thereof, and examples of the anode current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

The electrolytic solution which can be used in the electrochemical device according to one aspect of the present invention is a salt having a structure such as A ⁺ B ^- , wherein A ⁺ is an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ And B ^- is a metal ion such as PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N (CF ₃ SO ₂ ) _{^{2 -, C (CF 2 SO}} 2) 3 - anion, or a salt containing an ion composed of a combination of propylene carbonate (PC) such as, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC ), Dimethyl carbonate (DPC), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (G-butyrolactone), or an organic solvent composed of a mixture thereof, but is not limited thereto It is not.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

As a process for applying the separator according to one aspect of the present invention to a battery, a lamination, stacking and folding process of a separator and an electrode can be performed in addition to a general winding process.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

Manufacture of binders

The monomers described in the following Table 1 were added according to the stated contents (weight by part) and polymerized to prepare binders 1 to 4, respectively.

Ethyl acrylate n-butyl acrylate Acrylonitrile Acrylic acid Isobutyl acrylate Binder 1 20 30 30 0 20 Binder 2 25 45 0 30 0 Binder 3 30 40 0 0 30 Binder 4 25 45 0 0 30

In this case, the content of "-CN" as the ligand functional group of the binder 1 is 16 parts by weight based on 100 parts by weight of the binder 1, and the content of "-COOH" as the ligand functional group of the binder 2 is 19 Parts by weight.

Examples 1-1 to 1-2 and Comparative Examples 1-1 to 1-2. Manufacture of separator

Each of the binders 1 to 4 was mixed and dissolved in acetone to prepare a binder solution. Alumina Al ₂ O ₃ (average particle diameter: 400 nm) was added to the binder solution so that the weight ratio of binder / inorganic particles was 1/9, and the inorganic particles were dispersed for 3 hours or more using a ball mill Crushed and dispersed to prepare a slurry.

The particle size of the inorganic particles of the slurry thus prepared can be controlled according to the size (particle size) and the ball mill time of the beads used in the ball mill method, but in the present invention, the particle size was reduced to about 400 nm to prepare a slurry. The slurry thus prepared was coated on both sides of a polypropylene-ethylene-propylene porous film having a thickness of 16 탆 to prepare Examples 1-1 and 1-2 and Comparative Example 1-1 in which Binders 1 to 4 were respectively employed according to the following Table 2 , And the separator according to Comparative Example 1-2.

The separator of Example 1-1 manufactured by employing the binder 1 was observed by a scanning electron microscope (SEM) to confirm that a porous coating layer was formed, which is shown in FIG. 1 and FIG.

The prepared separator was cut into 50 mm x 50 mm, and the thickness, the Gurley number, and the weight of the porous coating layer were measured and are shown in Table 2 below.

Binder Type Thickness (㎛) Coated gun weight
(g / m ² ) Gulliver number
(Sec / 100 ml Example 1-1 Binder 1 26.2 14.2 524 Examples 1-2 Binder 2 26.1 13.9 5.15 Comparative Example 1-1 Binder 3 26.2 14.1 5.22 Comparative Example 1-2 Binder 4 26.0 14.0 5.20

Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2: Manufacture of electrochemical device (lithium secondary battery)

(1) Manufacture of cathode

90 parts by weight of a lithium nickel manganese cobalt composite oxide as cathode active material particles, 5 parts by weight of carbon black as a conductive material and 5 parts by weight of PVDF as a binder were dissolved in 40 parts by weight of N-methyl-2-pyrrolidone (NMP) To prepare a cathode active material slurry. The cathode active material slurry was applied to an aluminum (Al) thin film of a cathode current collector having a thickness of 100 탆 and dried to produce a cathode, followed by roll pressing.

* (2) Manufacture of anode

95 parts by weight, 2 parts by weight and 3 parts by weight, respectively, of a carbon powder as an anode active material, polyvinylidene fluoride (PVdF) as a binder and carbon black as a conductive material were respectively dissolved in N-methyl- 100 parts by weight of NMP to prepare an anode active material slurry. The anode active material slurry was coated on a copper (Cu) thin film as an anode current collector having a thickness of 90 占 퐉 and dried to produce an anode, followed by roll pressing.

(3) Production of lithium secondary battery

The unit cells were assembled using the cathode and anode manufactured by the above-described method, and the separators of Examples 1-1, 1-2, and Comparative Examples 1-1 and 1-2 using the stacking method. Then, an electrolyte (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 3/2/5 (volume ratio) and 1 mol of lithium hexafluorophosphate (LiPF ₆ ) 2-1 and 2-2, and Comparative Examples 2-1 and 2-2 were produced.

Cycle performance evaluation of secondary battery

FIG. 3 shows the result of cycle evaluation of the secondary batteries manufactured in Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2 by charging at 1C at 45 ° C and discharging at 2C. Referring to FIG. 3, it can be seen that the lithium secondary batteries of Examples 2-1 and 2-2 exhibit the best cycle performance as compared with Comparative Examples 2-1 and 2-2.

Evaluation of metal ion adsorption performance of secondary battery

After the 300-cycle performance evaluation, the secondary battery was disassembled and the anode active material was sampled to determine the amount (in ppm) of metal ions contained in the anode active material by inductively coupled plasma-atomic emission spectrometry (ICP-AES) Respectively.

Mn (ppm) Co (ppm) Ni (ppm) Example 2-1 57 8 2 Example 2-2 55 8 3 Comparative Example 2-1 150 18 17 Comparative Example 2-2 121 13 12

Referring to Table 3, the lithium secondary batteries of Examples 2-1 and 2-2 showed less metal in the anode active material than Comparative Examples 2-1 and 2-2. From this, it can be deduced that the metal ion precipitates on the surface of the anode due to formation of a complex with the ligand functional group of the separator provided in the secondary batteries of Examples 2-1 and 2-2.

Claims (16)

A porous substrate having a plurality of pores; And
And a binder which is formed on at least one surface of the porous substrate and at least one of the pores of the porous substrate and includes a plurality of inorganic particles and a binder for connecting and fixing the inorganic particles,
Wherein the content of the ligand functional group is 0.01 to 10 parts by weight based on 100 parts by weight of the inorganic particles, or 100 parts by weight of the binder is 100 parts by weight of the inorganic particles or binder, And 1 to 50 parts by weight in terms of part by weight. The method according to claim 1,
The ligand functional group is ^{-COOH, -COO -, -CHO, -NH} 2, -SH, -OH, -SO 3 H, -SO 3 -, -C (= NH) -, -CONH 2, -CN, - CS ₂ H, -CS ₂ ^- , a halide group, a pyridine group, and a pyrazine group. The method according to claim 1,
Wherein the metal ion is an ion of at least one metal selected from the group consisting of Ni, Co, Fe, Ru, Zn, Mn, Y, Zr, Ti, Cr, Mg, Ce, Cu, Pb and V. The method according to claim 1,
Wherein the inorganic particles have an average particle diameter of 0.01 to 10 mu m. The method according to claim 1,
Wherein the inorganic particles are selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transporting ability, and mixtures thereof. 6. The method of claim 5,
The inorganic particles is greater than or equal to the dielectric constant of _{5 BaTiO 3, Pb (Zr x} , Ti 1-x) O 3 (PZT, 0 <x <1), Pb 1 - x La x Zr 1 - y Ti y O 3 (PLZT , 0 <x <1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPbTiO ₃ (PMN- HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ . Or a mixture of two or more of them. 6. The method of claim 5,
Wherein the inorganic particles having lithium ion transferring ability are 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 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x Si y S _{z, 0 <x <3,} 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 <z &Lt; 7) -glass, or a mixture of two or more thereof. The method according to claim 1,
Wherein the binder is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, poly But are not limited to, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide Polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolylether, Vinyl alcohol (cyanoethylpolyvinylalcohol), Wherein the separator is any one selected from the group consisting of cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more thereof. The method according to claim 1,
Wherein the weight ratio of the inorganic particles to the binder is 50:50 to 99: 1. The method according to claim 1,
Wherein the thickness of the porous coating layer is 0.01 to 20 占 퐉. The method according to claim 1,
Wherein the porous coating layer further comprises any one selected from the group consisting of an additive for forming a solid electrolyte interface, a cell side reaction inhibiting additive, a thermal stability improving additive, and an overcharge inhibiting additive, or two or more of the additives. 12. The method of claim 11,
Wherein the content of the additive is 2 to 20 parts by weight based on 100 parts by weight of the total amount of the inorganic particles and the binder. The method according to claim 1,
Wherein the porous substrate is a polyolefin porous film or a nonwoven fabric. The method according to claim 1,
Wherein the porous substrate is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfroid and polyethylene naphthalene (polyethylenenaphthalene), or a mixture of two or more thereof. An electrochemical device comprising a cathode, an anode, and a separator interposed between the cathode and the anode, wherein the separator is the separator according to any one of claims 1 to 14. 16. The method of claim 15,
Wherein the electrochemical device is a lithium secondary battery.

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