KR20160002173A - A separator with porous coating layers comprising lithium salt for a secondary battery and a methode for manufacturing the same - Google Patents

Abstract

The present invention provides a secondary battery separator which has high ion conductivity and permeability to improve output characteristics, and a method for manufacturing the same. The separator includes lithium salt in at least one layer of the separator. After injecting an electrolyte, the lithium salt is dissolved and diffused into the electrolyte. Thereby, the ion conductivity of a lithium secondary battery is provided and a micro cavity formed by the elution of the lithium salt can provide an optimized path for the migration of lithium ions in the separator. Moreover, the electrolyte does not include lithium salt. The electrolyte can be easily stored without deterioration.

Description

Technical Field [0001] The present invention relates to a separator for a secondary battery having a porous coating layer containing a lithium salt, and a separator for a secondary battery having a porous coating layer containing a lithium salt and a method for producing the separator.

The present invention relates to a separator for a secondary battery, and more particularly, to a separator having excellent thermal stability and mechanical strength as well as improved ionic conductivity and porosity. The present invention also relates to a method for producing the separator.

A secondary battery is a chemical battery that can be used semi-permanently by continuously repeating charging and discharging using an electrochemical reaction, and is classified into a lead-acid battery, a nickel-cadmium battery, a nickel-hydrogen battery and a lithium secondary battery. Among them, lithium secondary batteries are superior to other batteries in terms of high voltage and energy density characteristics, leading the secondary battery market. Depending on the types of electrolytes, lithium ion secondary batteries using liquid electrolytes and solid electrolytes Lithium-ion polymer secondary battery.

The lithium secondary battery is composed of an anode, a cathode, an electrolyte, and a separator. Of these, the separator is required to separate the anode and the cathode from each other and electrically insulate it from each other, but also has high porosity, Air permeability) to increase ionic conductivity. The polymer substrate of the separation membrane generally used in the secondary battery is preferably a polyolefin polymer film such as polyethylene (PE) or polypropylene (PP) which is advantageous for forming pores and excellent in chemical resistance, mechanical properties and thermal properties, It is widely used. Polyolefins, however, are highly thermally shrinkable and physically fragile at high temperatures. To overcome such disadvantages, there has been used a method of forming a sheet-shaped polyolefin microporous membrane or nonwoven fabric film and then forming an inorganic material layer containing inorganic particles on the surface thereof to increase the heat resistance and mechanical strength of the separator.

On the other hand, the inorganic layer includes a binder resin for connecting and fixing the inorganic particles to each other and for increasing the binding force between the separator and the electrode. The use of such a binder resin increases the electric resistance in the electric field. As the internal resistance increases, the output characteristics of the electric power deteriorate, and as the charge / discharge cycle progresses, the capacity decreases and the life of the battery is shortened.

Therefore, in the secondary battery, a separator that exhibits excellent output characteristics is required because it does not increase the internal resistance while improving the adhesion strength to the electrode through coating of the binder resin and / or inorganic particles with the separator and ensuring the mechanical strength improvement of the separator. to be.

The present invention provides a secondary battery separator having uniform porosity and high ion conductivity and a secondary battery including the same. It is another object of the present invention to provide a secondary battery including an electrolyte solution with minimal side reaction due to contact with moisture. Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

The present invention provides a porous separator substrate, And a porous coating layer formed on at least one side of the porous separator substrate. The separator has a porous structure that maintains an insulating state between a cathode and an anode and allows movement of ion particles, and the porous coating layer includes inorganic particles, a lithium salt, and a binder resin.

The lithium salt is _{LiC, 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, lithium lower aliphatic carboxylate, and lithium 4-phenylborate.

The porous coating layer has 20% by weight to 64% by weight of lithium salt based on 100% by weight of the porous coating layer.

The inorganic particles include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), hafnia _{(HfO 2), SrTiO 2,} SnO 2, CeO 2, MgO, group consisting of _{NiO, CaO, ZnO, ZrO 2} , Y 2 O 3, Al 2 O 3, and TiO ₂ Or more.

The content of inorganic particles in the porous coating layer is 35% by weight to 79% by weight based on 100% by weight of the porous coating layer.

The binder may be selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichlorethylene, polyvinylidene fluoride-chlorotrifluoroethylene, polymethyl methacrylate, polyacryl Polyvinyl pyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetic acid terephonate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol, One or two or more selected from the group consisting of cyanoethyl cellulose, cyanoethyl sucrose, luran, carboxymethyl cellulose, acrylonitrile styrene butadiene copolymer, and polyimide.

The separator base material is characterized by being a polyolefin-based film, or a porous sheet or nonwoven fabric made of glass fiber or polyolefin.

And the thickness of the porous coating layer is 1 占 퐉 to 50 占 퐉.

The air permeability of the separator is 100 cc / sec to 3,000 cc / sec.

The present invention also provides an electrochemical device comprising a cathode, an anode, and a separator according to the present invention interposed between the cathode and the anode, and an electrolyte.

The present invention also provides a slurry for forming a porous coating layer comprising inorganic particles, a binder resin and a lithium salt. The porous coating layer is coated on at least one side of the porous substrate to form a separation membrane for an electrochemical device including the porous substrate and the porous coating layer.

The lithium salt is 20 to 64% by weight based on 100% by weight of the porous coating layer.

In addition, the present invention provides a method of manufacturing an electrochemical device including the separator. The method includes the steps of: preparing an electrode assembly including a cathode, a cathode, and a separator interposed between the anode and the cathode; Charging the battery assembly into a battery case; Preparing an electrolytic solution; And injecting the electrolytic solution into the battery case. The separation membrane includes a lithium salt, and the lithium salt is eluted from the separation membrane into the electrolyte solution.

In addition, the electrolytic solution prepared in (S300) is a lithium salt-free electrolytic solution containing no lithium salt. In addition, the method may further include a step in which the lithium salt contained in the separator is eluted into the electrolytic solution.

The separation membrane according to the present invention has high porosity and ionic conductivity due to the formation of micropores in the place where the lithium salt is contained by elution of the lithium salt. Therefore, when a lithium secondary battery is manufactured using the separator according to the present invention, a battery having improved resistance characteristics and output characteristics can be provided. Further, since the lithium salt is not required to be contained in the electrolyte solution, a side reaction of the electrolyte by moisture contact or the like can be prevented during storage of the electrolyte before the battery production.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. On the other hand, the shape, size, scale or ratio of the elements in the drawings incorporated herein can be exaggerated to emphasize a clearer description.
1 schematically shows a separation membrane according to one embodiment of the present invention.
2 is a process flow chart schematically illustrating a method for producing a separation membrane according to the present invention.
3 is a process flow chart schematically illustrating a method of manufacturing a secondary battery according to the present invention.
4 is a SEM photograph of the surface of the separation membrane produced in the embodiment of the present invention.
5 is a SEM photograph of the surface of the separation membrane prepared in the comparative example of the present invention.

The terms or words used in the present specification and claims should not be construed to be limited to ordinary or dictionary terms and the inventor shall properly define the concept of the term in order to best explain its invention The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

The present invention provides a separator for a secondary battery having improved ionic conductivity and porosity and improved resistance characteristics and output characteristics, and a method for manufacturing the same. The separator according to the present invention may have at least one layer or two or more layers stacked, and the lithium salt is contained in at least one layer or two or more layers forming the separator. As described later, the lithium salt is impregnated with an electrolytic solution and then eluted into an electrolytic solution to provide ion conductivity of the lithium secondary battery. In addition, due to the dissolution of the lithium salt, uniform and fine pores are formed in the separation membrane, and the pores can provide a path optimized for migration of lithium ions.

Figure 1 schematically illustrates an exemplary embodiment of various separators according to the present invention. Hereinafter, the present invention will be described in detail with reference to FIG.

The separation membrane according to the present invention has a porous structure capable of moving ionic particles while maintaining insulation between a cathode and an anode, wherein the separation membrane comprises a porous substrate for a separation membrane; And an organic / inorganic composite porous coating layer formed on at least one side of the substrate.

The porous substrate is preferably a sheet-like thin film, and is preferably one having excellent ion permeability and mechanical strength. As a material of such a separation membrane, a known separation membrane can be used as it is. For example, a polyolefin film such as polypropylene excellent in chemical resistance, a sheet or a nonwoven fabric made of glass fiber, polyolefin or the like is used. Commercially available ones include, for example, the Celgard ^TM series (Celgard ^TM 2400, 2300 (manufactured by Hoechest Celanese Corp.), a polypropylene membrane (manufactured by Ube Industrial Ltd. or Pall RAI), a polyethylene series (Tonen or Entek), and the like.

The thickness of the separator substrate may be, but is not limited to, preferably 5 to 50 탆, or 5 to 20 탆. The thickness of the membrane base material can be appropriately adjusted in consideration of the thickness of the organic / inorganic composite porous coating layer described later and the thickness of the battery in which the separation membrane is used.

In the separation membrane, the porous coating layer may be configured to compensate for heat resistance and mechanical strength, which are difficult to achieve with the separation membrane substrate alone.

According to a specific embodiment of the present invention, the organic / inorganic composite porous coating layer includes inorganic particles, a lithium salt and a binder resin.

The inorganic particles are not particularly limited as long as oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, about 0 to about 5 V based on Li / Li + of a lithium ion battery).

The inorganic particles are, for instance, boehmite, aluminum oxide (alumina), magnesium oxide, silicon oxide (magnesia), calcium, titanium oxide (titania), BaTiO _3, ZrO, alumina-oxide particles such as silica composite oxide; Nitride particles such as aluminum nitride and boron nitride; covalent crystal grains such as silicon and diamond; insoluble ionic crystal grains such as barium sulfate, calcium fluoride and barium fluoride; and clay fine particles such as talc and montmorillonite . However, the present invention is not limited thereto. These particles may be subjected to element substitution, surface treatment, solidification or the like as necessary.

Particularly, when inorganic particles having a high dielectric constant are used as the inorganic particles, the dissociation of the electrolyte salt, for example, the lithium salt in the liquid electrolyte, can be increased, and the ion conductivity of the electrolyte can be improved. Although the kind of the inorganic particles is not particularly limited, inorganic particles selected from the group consisting of inorganic particles having a dielectric constant of about 5 or more, inorganic particles having a lithium ion transferring ability (in the case of a lithium secondary battery), and mixtures thereof may be used . The inorganic particles having a dielectric constant of about 5 or more include 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 (PMN-PT, 0 < x < 1), and half (PZT, 0 <x <1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPbTiO ₃ It is preferable to use 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 , But is not limited thereto. As the inorganic particles having lithium ion transferring ability, 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), (LiAlTiP) _x O _y series glass 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 , x <4, 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 the like is preferably used, but is not limited thereto.

The inorganic particles are connected and fixed to each other by a binder resin described later in the porous coating layer to form a porous structure. The porous coating layer has a porous structure due to an interstitial volume between the inorganic particles, and the interstitial volume is substantially in the form of a closed packed structure or a densely packed structure. It is the space defined by the inorganic particles to be interviewed.

In one embodiment of the present invention, the inorganic particles are 35 to 79% by weight or 50 to 79% by weight based on 100% by weight of the porous coating layer. When the content of the inorganic particles is too small, the interstitial volume between particles is decreased and the binder resin is further added to form a predetermined thickness. Therefore, the porosity of the porous coating layer may be lowered, If the amount is exceeded, the filling density may increase during the slurry coating and drying process, which may hinder the air permeability.

In one specific embodiment of the present invention, the inorganic particle has a size of 10 nm to 20 탆, preferably 100 nm to 3.5 탆, more preferably 300 nm to 900 nm. It is preferable that the size of the inorganic particles is small and the uniformity is uniform. The more uneven the particle size, the more the thickness of the porous coating layer becomes uneven. Also, the smaller the particle size, the larger the surface area of the particles, so that the content of the binder resin to be used may be increased and the dispersibility may be lowered. On the other hand, the larger the particle size, the thicker the target coating thickness of the porous coating layer. Therefore, it is preferable to use particles belonging to the above-mentioned range.

On the other hand, the pore size and the air permeability of the organic / inorganic composite porous film mainly depend on the size of the inorganic particles. For example, when inorganic particles having a particle size of 1 μm or less are used, the pores to be formed also become 1 μm or less. Such a pore structure is filled with an electrolyte solution to be injected at a later stage, and the filled electrolyte serves as an ion transfer function.

Therefore, the pore size and porosity are important factors for controlling the ionic conductivity of the organic / inorganic composite porous film. The pore size and the air permeability of the organic / inorganic composite porous coating layer of the present invention are preferably 0.001 to 10 μm, and preferably 100 sec / 100 cc to 3,000 sec / 100 cc or 400 sec / 100 cc to 1000 sec / 100 cc.

The thickness of the organic / inorganic composite porous coating layer of the present invention is not particularly limited, but may be adjusted in consideration of battery performance. More preferably in the range of 1 to 50 mu m, and particularly preferably in the range of 2 to 20 mu m. By adjusting the thickness range, battery performance can be improved.

The lithium salt acts as a supply source of lithium ions in the battery to enable operation of the lithium battery. Conventionally, a battery was prepared by mixing a lithium salt in an electrolyte solution and injecting it into a battery. However, the present invention is configured such that a lithium salt is eluted from the separation membrane. According to the present invention, the lithium salt is eluted from the porous coating layer and flows into the electrolytic solution, thereby providing ionic conductivity of the electrolytic solution. The lithium salt eluted with the electrolytic solution contributes to the charging / discharging action of the electrochemical cell and does not cause any side reaction. Rather, if the lithium salt is eluted slowly over a long period of time, or if the remaining lithium salt is slowly eluted after a large number of lithium salts are eluted first, it may serve to supplement the consumed electrolyte in the continuous charge / discharge process.

The lithium salt is a non-limiting example is _{LiC, 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 carboxylate lithium and lithium 4-phenylborate, and lithium trifluoroacetate. However, the present invention is not particularly limited thereto, and conventional lithium salts conventionally used in the field of lithium secondary batteries can be used in place of or in combination with the lithium salts within a suitable range.

In one embodiment of the present invention, the lithium salt is about 20% by weight to about 64% by weight or 20% by weight to 50% by weight based on 100% by weight of the porous coating layer. When the content of the lithium salt is too small, it is difficult to achieve a desired degree of ionic conductivity since not only the amount of the lithium ions to be eluted is small but also the pores generated due to the elution of the lithium salt are insufficient. On the other hand, when the amount of the lithium salt is more than the above-mentioned range, the amount of the inorganic particles or the binder resin is small and the heat resistance may be deteriorated. Due to the elution of the lithium salt, too much pores may be formed, There is a risk that the adhesion of the electrode and the separation membrane is deteriorated and lithium metal is deposited at the interface between the electrode and the separation membrane.

The binder resin can be used without particular limitation as long as it is a component that exhibits bonding force with the electrode stacked on the separation membrane and binding force between the inorganic particles and lithium salts in the porous coating layer and is not easily dissolved by the electrolyte solution.

The binder resin is not particularly limited as far as it is a component that exhibits the binding force with the electrode stacked on the separation membrane and the binding force between the inorganic components and the lithium salts in the mixed coating layer, but is not easily dissolved by the electrolyte solution. For example, the binder resin may be selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-cohexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, Polyvinylidene fluoride, polyvinylidene fluoride-chlorotrifluoroethylene (PVdF-CTFE), polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, Polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate propionate, Cyanoethylpullulan, cyanoethylpolyvinyl, Cyanoethylpolyvinylalcohol, cyanoethyl cellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, butadiene copolymer, and polyimide, and may preferably be PVdF or PVdF-CTFE.

The content of the binder resin is preferably 0.1 to 20% by weight based on 100% by weight of the porous coating layer in consideration of the binding force between the inorganic particles and / or the lithium salt and the binding force between the electrode and the binder resin.

FIG. 2 is a process flow chart schematically showing a method for producing a separation membrane according to the present invention. Next, a method of manufacturing a separation membrane according to the present invention will be described with reference to FIG. The method is illustrative of various embodiments, and the method of manufacturing the separation membrane according to the present invention is not limited to the following description.

First, the binder resin is dissolved in an appropriate organic solvent to prepare a polymer solution (S10). It is preferable that the solvent has a solubility index similar to that of the binder polymer to be used and a low boiling point. This is to facilitate uniform mixing and subsequent solvent removal. Non-limiting examples of usable solvents include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone ( N-methyl-2-pyrrolidone, NMP), cyclohexane, water or a mixture thereof.

Next, inorganic particles and a lithium salt are added to and dispersed in the prepared polymer solution to prepare a slurry for forming a coating layer (S20). Next, the slurry prepared above is applied to at least one side of the porous substrate to form an organic / inorganic composite porous coating layer (S30). The method of coating the slurry on the porous substrate is not limited to any particular method, and conventional coating methods known in the art can be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a combination thereof can be used.

The process may involve a drying step. The drying properly sets temperature and time conditions so as to minimize occurrence of surface defects on the surface of the porous coating layer. The drying may be carried out within a suitable range using a drying aid such as a drying oven or hot air.

The method of coating the surface of the separator substrate with the porous coating layer is not particularly limited. In one embodiment of the present invention, after the slurry for forming a porous coating layer is prepared, the slurry is subjected to a coating treatment such as flow coating, spin coating, dip coating, bar coating and the like. Preferably by dip coating in which a separator substrate is dipped in the slurry to form a coating layer. The slurry may be formed by adding an inorganic particle, a lithium salt and a binder resin to a suitable solvent at a predetermined ratio and stirring to obtain a uniform dispersion.

The present invention also provides a secondary battery including the above-described separation membrane. The secondary battery includes an electrode assembly including a cathode, an anode, and a separator interposed between the cathode and the anode, and an electrolyte solution providing ion mobility between the anode and the cathode.

According to one embodiment of the present invention, the non-aqueous electrolyte containing the non-aqueous electrolyte may be used as the electrolyte. Examples of the nonaqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, But are not limited to, lactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile , Nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, Tetrahydrofuran derivatives, ether, methyl pyrophosphate, ethyl propionate and the like can be used. However, the present invention is not limited thereto, and a large number of electrolytic solution components commonly used in the lithium secondary battery field can be added or subtracted within an appropriate range.

According to one embodiment of the present invention, the electrolyte contained in the secondary battery contains a lithium salt, and a part of the lithium salt may be eluted from the separation membrane. Preferably, the total amount of the lithium salt present in the electrolyte solution contained in the secondary battery may be one derived from the above-described separation membrane.

The secondary battery according to the present invention can be manufactured by a conventional battery manufacturing method and is not limited to a specific method. For example, the electrode assembly may be rolled up into a jelly-roll type according to the end use of the battery, or a plurality of electrode assemblies may be stacked to form a stack / folding type, charged into a suitable battery case, Which is then poured into the battery case.

In the method of manufacturing a secondary battery according to the present invention, the electrolyte solution may be prepared in a state before the pour liquid, without lithium salt. As described above, the separation membrane includes a lithium salt. As the electrolyte is impregnated with the electrolyte, the lithium salt contained in the separation membrane, for example, the organic / inorganic composite porous coating layer of the separation membrane is dissolved and eluted into the electrolyte solution.

Therefore, the secondary battery according to the present invention does not affect the lithium ion conductivity since the lithium salt contained in the separation membrane is eluted and flows into the electrolyte solution as the separation membrane is impregnated after the electrolytic solution is injected even though the lithium salt is not contained in the electrolytic solution before the pouring solution.

Also, since the electrolyte is composed of only a solvent and does not contain a lithium salt, it is easy to manage moisture and a side reaction that may be generated in the electrolyte is prevented.

For example, lithium salts such as LiPF6 react violently with water. When such a lithium salt is exposed to moisture, phenomena such as generation of HF gas, discoloration of the electrolyte solution, and deterioration of the electrode may occur, thereby deteriorating the cycle characteristics of the battery. Therefore, when a lithium salt is contained in an electrolytic solution, the electrolytic solution is managed by using a vacuum packing material so that the electrolytic solution is not exposed to water even in a small amount, and the electrolytic solution is stored only in a place where moisture is controlled. On the other hand, if the lithium salt is removed in the electrolyte solution, the complicated management and storage procedure may not be performed.

3 schematically shows a method of manufacturing the secondary battery of the present invention. As shown in the figure, the electrolyte solution before the pouring solution may be prepared without lithium salt, and after the lithium salt-free electrolyte solution is injected into the battery case, the lithium salt is eluted from the separation membrane as the separation membrane is impregnated, The conductivity can reach a predetermined range.

According to a specific embodiment of the present invention, the anode or the cathode may be easily manufactured by a process and / or a method known in the art. The anode is prepared by binding a cathode active material to a cathode current collector according to a conventional method known in the art. As the cathode active material, a conventional cathode active material that can be used for a cathode of a conventional electrochemical device can be used. Examples of the cathode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, a + b + c = 1), LiNi _{1 -Y} Co _Y O ₂ , LiCo _{1 -Y} Mn _{Y 2} O, LiNi _{1 -Y} Mn _Y O ₂ (where, 0≤Y <1), Li ( Ni a Co b Mn c) O 4 (0 <a <2, 0 <b <2, a + b + c = 2), LiMn 2-Z Ni _Z O _4, LiMn include _2-Z Co _Z O ₄ (where, 0 <Z <2), LiCoPO 4, LiFePO 4 , and mixtures thereof. The anode current collector may be made of aluminum, nickel, or a combination thereof.

The negative electrode is prepared by adhering the negative electrode active material to the negative electrode current collector according to a conventional method known in the art. At this time, the negative electrode active material may be carbon such as non-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' : Metal complex oxides of Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 < x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{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, Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used. On the other hand, as the negative electrode current collector, stainless steel, nickel, copper, titanium or an alloy thereof can be used.

The separator according to the present invention can be used in all kinds of electrochemical devices such as a primary cell, a secondary cell, a fuel cell, a solar cell, or a capacitor such as a supercapacitor, It is possible. Particularly, 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 is preferable among the above secondary batteries.

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

1.7 g of PVDF-HFP as a binder resin and 0.3 g of an acrylic binder were mixed with acetone to prepare a polymer solution. Next, 18 g of alumina (Al 2 O 3) as inorganic particles and 8 g of LiPF 6 as a lithium salt were sequentially added to the above polymer solution and stirred to disperse them to prepare a slurry for forming an organic / inorganic composite porous coating layer. The amount of LiPF 6 added corresponds to the total amount of the lithium salt eluted with the electrolyte solution in the battery to be produced. Using the slurry, a 10 μm thick polyolefin separator base material was dip-coated to obtain a separator having an organic / inorganic composite porous coating layer formed thereon. The thickness of the separation membrane was about 15 to 20 mu m.

Comparative Example

1.7 g of PVDF-HFP as a binder resin and 0.3 g of an acrylic binder were mixed with acetone to prepare a polymer solution. Next, 18 g of alumina (Al 2 O 3) as inorganic particles was added to the polymer solution and dispersed by stirring to prepare a slurry for forming an organic / inorganic composite porous coating layer. Using the slurry, a polyolefin separator base material having a thickness of 10 탆 was dip-coated to obtain a separator having an organic / inorganic composite porous coating layer. The thickness of the separation membrane was about 15 to 20 mu m.

Experiment result

Ventilation sec / 100cc Example 500 to 600 sec / 100 cc Comparative Example 300 to 400 sec / 100 cc

FIG. 4 is a SEM image of the separation membrane prepared in the above embodiment, and FIG. 5 is an SEM image of the separation membrane prepared in the comparative example. As can be seen from the comparison of the drawings, the lithium salt is evenly distributed on the surface of the separator of the embodiment of FIG. However, when the separator is assembled with a battery and impregnated with the electrolytic solution, the space in which the lithium salt is applied is not limited to the moving path of the lithium ion, And thus the air permeability is more excellent.

100 membrane
110 Oil / inorganic complex porous coating layer
111 inorganic particles
112 lithium salt
120 Porous substrate

Claims (15)

A porous membrane substrate; And
A porous coating layer formed on at least one side surface of the porous membrane substrate;
Wherein the separator is a separator for an electrochemical device,
Here, the separation membrane has a porous structure capable of maintaining the insulating state between the cathode and the anode and capable of moving ion particles,
Wherein the porous coating layer comprises inorganic particles, a lithium salt, and a binder resin.
The method according to claim 1,
The lithium salt is _{LiC, 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 &gt; SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lithium lower aliphatic carboxylate and lithium 4-phenylborate. .
The method according to claim 1,
Wherein the porous coating layer comprises lithium salt in an amount of 20 wt% to 64 wt% based on 100 wt% of the porous coating layer.

The method according to claim 1,
The inorganic particles include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), hafnia _{(HfO 2), SrTiO 2,} SnO 2, CeO 2, MgO, group consisting of _{NiO, CaO, ZnO, ZrO 2} , Y 2 O 3, Al 2 O 3, and TiO ₂ Wherein the separator is at least one selected from the group consisting of a metal oxide and a metal oxide.
The method according to claim 1,
Wherein the porous coating layer comprises inorganic particles in an amount of 35% by weight to 79% by weight based on 100% by weight of the porous coating layer.
The method according to claim 1,
The binder may be selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichlorethylene, polyvinylidene fluoride-chlorotrifluoroethylene, polymethyl methacrylate, polyacryl Polyvinyl pyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetatetraponate, cyanoethylpolylane, cyanoethylpolyvinyl alcohol, Wherein the separator is one or two or more selected from the group consisting of cyanobutyl cellulose, cyanoethyl cellulose, cyanoethyl sucrose, lauran, carboxymethyl cellulose, acrylonitrile styrene butadiene copolymer, and polyimide. .
The method according to claim 1,
Wherein the separator base material is a polyolefin film, or a porous sheet or nonwoven fabric made of glass fiber or polyolefin. .
The method according to claim 1,
Wherein the thickness of the porous coating layer is 1 占 퐉 to 50 占 퐉.
The method according to claim 1,
Wherein the separation membrane has an air permeability of 100 cc / sec to 3,000 cc / sec.
An electrochemical device comprising a negative electrode, a positive electrode, and a separator interposed between the negative electrode and the positive electrode, and an electrolyte solution, wherein the separator is according to any one of claims 1 to 9.
A binder resin and a lithium salt, wherein the porous coating layer is coated on at least one side of the porous substrate to form a separation membrane for an electrochemical device including the porous substrate and the porous coating layer, , Slurry for forming a porous coating layer.
12. The method of claim 11,
Wherein the lithium salt is 20 to 64% by weight based on 100% by weight of the porous coating layer.
(S100) fabricating an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode;
(S200) charging the battery assembly into a battery case;
(S300) preparing an electrolytic solution;
(S400) injecting the electrolytic solution into the battery case; / RTI &gt;
Wherein the separation membrane comprises a lithium salt as a separation membrane, and the lithium salt is eluted from the separation membrane into the poured electrolytic solution.
14. The method of claim 13,
Wherein the electrolytic solution prepared in (S300) is a lithium salt-free electrolytic solution containing no lithium salt.
14. The method of claim 13,
(S500) further comprising the step of dissolving the lithium salt contained in the separator into the electrolyte solution.

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