KR20080017110A - Sheet-typed separator coated with clay mineral and lithium electrochemical cell employing the same - Google Patents

Abstract

A separator, and an electrochemical cell containing the separator are provided to improve the mechanical strength of a separator and to enhance the infiltration of an electrolyte solution into a separator and an electrode. A separator is a sheet type separator of a porous structure to allow an ion to move with maintaining the insulation state of the electrodes facing each other at both sides, wherein a clay mineral having the affinity to a polar solvent is coated on the surface of the separator. Preferably the clay mineral is at least one selected from the group consisting of smectite, bentonite, laponite, hectorite, gibbsite, chlorite, kaolinite, halloysite, pyrophylite-talc, montmorillonite, vermiculite, illite, mica and brittle mica.

Description

Sheet-typed Separator Coated with Clay Mineral and Lithium Electrochemical Cell Employing the Same}

The present invention relates to a porous sheet-type separator with improved safety and performance, and more particularly, to a sheet-type separator having a porous structure capable of moving ions while maintaining an insulating state of electrodes facing each other on both sides. The coating of clay minerals with affinity for polar solvents on the surface not only increases the mechanical strength of the separator, but also improves the impregnation of the electrolyte into the separator and the electrode, thereby ultimately improving the rate characteristics and storage capacity. It relates to a separator and an electrochemical cell comprising the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing, and lithium secondary batteries having high energy density and voltage are commercially used in such secondary batteries.

The lithium secondary battery is manufactured by using a metal oxide such as LiCoO ₂ as a cathode active material and a carbon material as an anode active material, a polyolefin-based porous separator between the anode and the cathode, and a non-aqueous electrolyte containing lithium salt such as LiPF ₆ . Done. During charging, lithium ions of the positive electrode active material are released and inserted into the carbon layer of the negative electrode, and during discharge, lithium ions of the negative electrode carbon layer are released and inserted into the positive electrode active material, wherein the non-aqueous electrolyte solution is lithium ions between the negative electrode and the positive electrode. It acts as a medium for moving the. Such a lithium secondary battery should basically be stable in the operating voltage range of the battery and have a performance capable of transferring ions at a sufficiently high speed.

The non-aqueous electrolyte is introduced into the battery at the end of the lithium secondary battery manufacturing. At this time, the electrode needs to be wetted quickly and completely by the electrolyte to shorten the time required for manufacturing the battery and to optimize battery performance.

As a non-aqueous electrolyte of a lithium secondary battery, an aprotic organic solvent, such as ethylene carbonate, diethyl carbonate, and 2-methyl tetrahydrofuran, is mainly used. These electrolytes are polar solvents that are polar enough to effectively dissolve and dissociate electrolyte salts, and are aprotic solvents without active hydrogen, and are often high in viscosity and surface tension due to extensive interactions within the electrolyte. Therefore, the non-aqueous electrolyte of the lithium secondary battery has little affinity with the electrode material containing the polytetrafluoroethylene, polyvinylidene fluoride binder, and the like, and does not easily wet the electrode material. In particular, in the case of a separator used in a lithium secondary battery, the wettability of an electrolyte having a hydrophilic property is not good.

In addition, as the capacity of the battery is required to increase, a lithium secondary battery having a higher energy density of the electrode has been developed. However, due to the improvement of the energy density, the porosity of the electrode is very low, thereby increasing the difficulty of evenly infiltrating the electrolyte into the electrode. If the electrolyte does not sufficiently wet the surface of the active material constituting the electrode, the transfer path of lithium ions is limited, causing problems such as a decrease in rate characteristics and a decrease in capacity. Therefore, the structure of the electrode excellent in the wettability with respect to electrolyte solution is calculated | required.

In addition, since the electrode assembly constituting the secondary battery has a structure in which the positive electrode and the negative electrode are sequentially stacked in a state where the separator is interposed therebetween, the impregnation of the electrolyte on the electrode is also greatly affected by the wettability of the separator. That is, in order for the electrolyte to pass to the electrode, the separator must pass through the membrane. If the wettability of the membrane is low, ultimately, the electrolyte impregnation process in the electrode does not proceed easily.

Therefore, there is a high need for a technology capable of increasing the wettability of the separator with respect to the electrolyte and improving the safety of the battery while having excellent performance.

In this regard, in the present invention, as described below, in order to improve the wettability of an electrolyte, a separator in which a clay mineral having affinity for a polar solvent is coated on its surface is proposed.

Meanwhile, some techniques for adding clay minerals to separators are known. For example, in Korean Patent No. 040793 and Korean Patent No. 0496936, in order to reduce crossover of methanol in a proton conductive polymer membrane for fuel cells, water and hydrogen ions are allowed to pass through by including clay minerals. Disclosed is a technique for separating.

However, all of the above technologies are fuel cell separators, and since the fuel cell includes an ion conductive polymer membrane and differs from the lithium secondary battery in the composition of the electrolyte solution, the fuel cell separator is a lithium secondary battery due to the difference in the mechanism of action during charging and discharging. Is difficult to use as is, and is different in practical applications. Moreover, the above techniques allow the passage of water and hydrogen ions through the layered structure of clay minerals, while selectively separating methanol by the internal charge of the layered structure, which is a large difference from the present invention utilizing the overall polarity of clay minerals. Have a difference.

In addition, Japanese Patent No. 3635302 and Japanese Patent No. 3717092 disclose a technique of adding expandable clay minerals to the inside of a solid polymer electrolyte. The solid polymer electrolyte is added as a kind of insulating bonding layer between the positive electrode and the negative electrode. In the above techniques, expandable clay minerals are added to the inside of the solid polymer electrolyte, thereby achieving effects such as safety improvement and electrical conductivity improvement. .

However, in the manufacture of thin sheet-like separators, the addition of expandable clay minerals, as in the above techniques, results in the formation of dense tissue by largely expanded clay minerals, which results in the repetitive formation of the electrode during charge and discharge. The pressing force and contraction force applied to the separator during shrinkage and expansion cause morphological changes of the separator, which in turn significantly impairs the safety of the battery. In addition, since the clay mineral is included as a kind of filler, since the sheet-type separator exhibits a rigid tendency, there are many problems such as partial rupture due to external impact. In addition, since the above techniques improve the electrical conductivity by increasing the content of expandable clay, the production cost is expected to increase by adding a relatively expensive expandable clay.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After various experiments and in-depth studies, the inventors of the present application improve the wettability of the electrolyte solution to the electrode and ultimately the electrolyte solution when the clay mineral having affinity for polar solvents is coated on the surface of the sheet-type separator. By facilitating the movement, it was confirmed that excellent battery performance could be achieved, and that the mechanical strength of the separator and the safety of the battery could be ensured, and the present invention was completed.

Therefore, the separator according to the present invention is a sheet-type separator of a thin film having a porous structure capable of moving ions while maintaining the insulating state of the electrodes facing each other on both sides, to increase the mechanical strength of the separator and the electrolyte to the separator and the electrode In order to improve the impregnation, the surface of the separator is made of a structure in which a clay mineral having affinity for a polar solvent is coated.

Since the clay mineral has affinity for the polar solvent, it is possible to greatly improve the wettability of the electrolyte solution and ultimately improve the rate characteristic and storage capacity of the battery. More specifically, since the clay mineral having affinity with the polar solvent is coated on the surface of the separator, the interface resistance of the electrolyte is lowered at the membrane interface, so that the electrolyte easily penetrates into the separator and consequently increases the mobility to the electrode. .

In general, since the separator is made of a non-polar material, the interface resistance between the separator and the electrolyte in the process of passing through the separator may act as a rate step of the electrolyte mobility. Therefore, the clay mineral coated on the surface of the separator lowers the interfacial resistance to improve electrolyte mobility.

In addition, the clay mineral coated on the surface of the separator forms a composite with a polymer-based binder to enhance the mechanical strength of the separator to prevent deformation of the separator due to the pressing force and contraction force of the electrode applied during the expansion and contraction of the electrode during charging and discharging. Prevent it.

Coating amount of the clay mineral is preferably 0.1 ~ 75 mg / cm ² compared to the surface area of the separator. When the coating amount is less than 0.1 mg / cm ² , it is difficult to exert the desired electrolyte wettability. On the contrary, when the coating amount exceeds 75 mg / cm ² , the electrical resistance increases due to the excess clay mineral, and the conductivity of ions in the electrolyte is lowered. It is not preferable because it is made.

Clay minerals usually exist in two forms. That is, it may exist in an initial form of several hundred nanometers to several tens of micrometers, or the interlayer separation may occur, and may have a plate shape of about 1 nm in thickness and several to about 100 micrometers on the side. Therefore, the average particle diameter of the clay mineral may vary depending on the form, for example, it can be used in the range of 1 nm ~ 100 ㎛.

The clay mineral is not particularly limited as long as it is a clay mineral having affinity for a polar solvent without adversely affecting the operation characteristics of the battery. Preferably, smectite, bentonite, laponite , Hectorite, gibbsite, chlorite, kaolinite, halosite, hallosite, pyrophylite-talc, montmorilonite (MMT) , Vermiculit, illite, mica and brittle mica.

More preferably, the bar montmorillonite may be used, montmorillonite is in place of the Mg ^{2 +,} Fe ^{2 +,} Fe ^{3 +} ions in place of Al ^{3 +} ion in an alumina octahedral sheet and the Si ^{4 +} a silicate tetrahedral sheet on Al ^It is a structure in which ^{3 +} ions are substituted, and it has a negative charge as a whole, and contains cation and water molecules which can be exchanged between the silicate layers in order to balance the charge as a whole. Therefore, since the polarity is strong, it is a polar solvent and at the same time, the capturing power of the electrolyte solution which is an aprotic solvent is very excellent.

As the sheet-type separator, an insulating thin film which prevents internal short circuit between the anode and the cathode and has high ion permeability and mechanical strength is used. The pore diameter of the separator is generally from 0.01 to 10 ㎛ ㎛, thickness is generally 5 ~ 300 ㎛.

The material of such a separator is not particularly limited, and a known separator may be used as it is, for example, an olefin polymer such as polypropylene having chemical resistance and hydrophobicity; Sheets or non-woven fabrics made of glass fibers or polyethylene are used. Typical examples on the market include Celgard series (Celgard ^R 2400, 2300 (manufactured by Hoechest Celanese Corp.), polypropylene membrane (manufactured by Ube Industries Ltd. or Pall RAI), and polyethylene series (Tonen or Entek). Can be used, but is not limited to these.

In general, however, when a solid polymer electrolyte such as a polymer is used as an electrolyte, the solid polymer electrolyte may also serve as a separator, but the sheet separator according to the present invention should coat the clay mineral on the surface thereof. Electrolyte is not included.

The method of coating the clay mineral on the surface of the separator is not particularly limited, and various methods such as flow coating, spin coating, dip coating, bar coating, etc. It can be formed by the method. As a specific example, the separator sheet may be dipped into a solution in which clay minerals (or organic clay minerals) are dispersed, or a dispersion of clay minerals in the separator sheet on the separator sheet surface may be performed by a spray coating method. In this coating process, a predetermined bonding aid may be added to increase the binding strength of the clay mineral to the surface of the separator. For example, a fluorine-based polymer such as PVdF, PTFE, etc. may be added to the clay mineral and the binding aid in a solvent such as NMP. Coating may be performed by applying a coating solution containing a PVdF-based copolymer polymer, PMMA, PAN, PEO, SBR, and the like to a separator.

The present invention also provides an electrochemical cell consisting of an electrode assembly wherein the porous separator is interposed between an anode and a cathode, the electrochemical cell provides electricity through an electrochemical reaction, for example For example, it may be an electrochemical secondary battery or an electrochemical capacitor.

In particular, the present invention may be preferably applied to a lithium secondary battery manufactured by injecting a lithium electrolyte in a state in which the electrode assembly is mounted inside the battery case.

In addition, the secondary battery may be used in the manufacture of a high output large capacity battery pack, preferably in combination with a plurality of unit cells. Since high power large-capacity battery packs are frequently subjected to external forces such as vibration and external shock, excellent mechanical strength is required for external forces, and in the structure of the battery cells constituting the battery pack, the amount of loading of the electrode active material to the current collector is large. Therefore, the electrolyte impregnation may act as an important factor in order to exhibit predetermined operating characteristics.

Other components of the lithium secondary battery according to the present invention will be described in detail below.

The positive electrode for a lithium secondary battery is prepared by, for example, applying a mixture of a positive electrode active material, a conductive agent, and a binder in the form of a slurry on a positive electrode current collector, followed by drying and compressing the filler, and optionally adding a filler to the mixture. It can also be added.

The positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Li _{1 + x} Mn _{2 - x} O ₄ (Where x is 0 to 0.33), lithium manganese oxides such as LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein 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 (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like, but are not limited to these.

The positive electrode current collector is generally made to a thickness of 3 to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver or the like can be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The conductive agent is typically added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Such a conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive agent include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder 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 and the like can be used.

The binder is a component that assists in bonding the active material and the conductive agent to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials, such as glass fiber and carbon fiber, are used.

The negative electrode for a lithium secondary battery is manufactured by coating, drying, and compressing a negative electrode material on a negative electrode current collector, and if necessary, components of the positive electrode (binder, conductive agent, filler, etc.) as described above may be further included.

The negative electrode current collector is generally made to a thickness of 3 to 500 ㎛. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like, aluminum-cadmium alloy, and the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode material may be, for example, carbon such as hardly graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me ': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 <x≤1;1≤y≤3; 1≤ metal composite oxides such as z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The nonaqueous electrolyte for lithium secondary batteries consists of a nonaqueous electrolyte and a lithium salt. As the nonaqueous electrolyte, a nonaqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

As said non-aqueous electrolyte, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl Low lactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolon, formamide, dimethylformamide, dioxolon, aceto Nitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxorone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyroionate and ethyl propionate can be used.

Examples of the organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyedgetion lysine, polyester sulfides, polyvinyl alcohols, polyvinylidene fluorides, Polymers containing ionic dissociating groups and 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 , Nitrides, halides, sulfates and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may be used.

The lithium salt is a good material to be dissolved in the non-aqueous electrolyte, 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, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

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

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are provided to illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1

1-1. Manufacture of anode

LiCoO ₂ was used as the positive electrode active material, and 95% by weight of LiCoO ₂ , 2.5% by weight of Super-P (conductor) and 2.5% by weight of PVdF (binder) were added to N-methyl-2-pyrrolidone (NMP) as a solvent. After preparing the positive electrode mixture slurry, the positive electrode was prepared by coating, drying and pressing on a long sheet aluminum foil.

1-2. Preparation of Cathode

Artificial negative electrode was used as the negative electrode active material, 95% by weight of artificial graphite, 2.5% by weight of Super-P (conductor), and 2.5% by weight of PVdF (binder) were added to NMP as a solvent to prepare a negative electrode mixture slurry. The negative electrode was prepared by coating, drying and pressing on an elongated sheet copper foil.

1-3. Preparation of Membrane

A porous polyethylene separator (Celgard ^™ ) was used as a bare film of the separator, and a separator was prepared by coating 0.1 mg of montmorillonite per unit area (cm ² ) by dip coating on both surfaces of the separator.

1-4. Manufacture of batteries

The separator of 1-4 was interposed between the cathode and the anode of 1-1 and 1-2 to inject a 1M LiPF ₆ EC / EMC electrolyte to prepare a lithium secondary battery.

Example 2

A lithium secondary battery was manufactured in the same manner as in Example 1, except that 10 mg / cm ² of montmorillonite was coated on the separator.

Example 3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that 50 mg / cm ² of montmorillonite was coated on the separator.

Example 4

A lithium secondary battery was manufactured in the same manner as in Example 1, except that 75 mg / cm ² of montmorillonite was coated on the separator.

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as in Example 1, except that montmorillonite was not coated on the separator.

Comparative Example 2

A lithium secondary battery was manufactured in the same manner as in Example 1, except that 0.05 mg / cm ² of montmorillonite was coated on the separator.

Comparative Example 3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that 100 mg / cm ² of montmorillonite was coated on the separator.

Experimental Example 1

30 batteries prepared in Examples 1 to 4 and 30 batteries prepared in Comparative Examples 1 to 3 were charged to 4.2 V, respectively, and the number of batteries ignited by performing an impact test is shown in Table 1 below. The impact test was conducted by dropping a 9.1 kg metal bar of 15.8 mm length from the 61 cm height to the center of the cell.

Experimental Example 2

After charging and discharging the batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 3, the capacity after 300 cycles was calculated as a ratio with an initial capacity, and the results are shown in Table 1 below.

Experimental Example 3

Table 1 shows the ratios of the capacities when the batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were charged to 4.2 V and then discharged to currents of 0.5 C and 5 C, respectively.

TABLE 1

As shown in Table 1, the battery of Examples 1 to 4, it can be seen that the safety, life and rate characteristics are significantly improved compared to the battery of Comparative Example 1. In addition, the batteries of Comparative Examples 2 and 3 have all improved safety, lifespan, and rate characteristics compared with those of Comparative Example 1, but it can be seen that the lifespan and rate characteristics are lower than those of Examples 1 to 4.

The increase in stability is a result of the clay minerals increase the mechanical strength of the separator, the improvement of the life and rate characteristics is due to the coating of the clay mineral on the surface of the separator, ultimately the electrolyte impregnability of the electrode by excellent electrolyte wetting on the separator This is because the amount of the electrolyte solution content of the electrode is increased compared to the same time.

As described above, the sheet-like separator according to the present invention is coated with a clay mineral having affinity for the polar solvent on the surface, thereby improving the mechanical strength and the wettability of the electrolyte with high efficiency, ultimately the safety and rate characteristics of the battery and It has the effect of improving the storage capacity.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (8)

A sheet-type separator having a porous structure that can move ions while maintaining the insulation state of electrodes facing each other on both sides, and enhances the mechanical strength of the separator and improves the impregnation of the electrolyte into the separator and the electrode. Separator, characterized in that the clay mineral is coated with a polar solvent having affinity to the polar solvent. The separator according to claim 1, wherein the clay mineral is coated on the surface of the separator with a coating amount of 0.1 to 75 mg / cm ² . The separation membrane of claim 1, wherein the particle diameter of the clay mineral is in the range of 1 nm to 100 μm. The method of claim 1, wherein the clay mineral is smectite, bentonite, laponite, hectorite, gibbsite, chlorite, kaolinite, Halloysite, pyrophylite-talc, montmorilonite (MMT), vermiculit, illite, mica and brittle mica Separation membrane, characterized in that one or two or more selected from the group consisting of. An electrochemical cell comprising the electrode assembly in which the sheet separator according to any one of claims 1 to 4 is interposed between an anode and a cathode. 6. The electrochemical cell of claim 5, wherein said cell is a secondary battery or a capacitor. 8. The electrochemical cell of claim 7, wherein the secondary battery is a lithium secondary battery. 7. The electrochemical cell of claim 6, wherein the secondary battery is used as a unit cell in a battery pack of a high output large capacity.