KR101868197B1 - Lithium air battery and method for manufacturaing the same - Google Patents

Abstract

The present invention relates to a lithium air cell and a method of manufacturing the same. The lithium air battery includes a separator, a positive electrode including a porous carbon material coated on one side of the separator without a binder, and a negative electrode disposed on the other side of the separator.
The lithium air battery prevents an increase in overvoltage at the end of charging, thereby suppressing the occurrence of various side reactions under an air atmosphere, thereby improving the cycle life of the lithium ion battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lithium-

The present invention relates to a lithium air battery and a method of manufacturing the same. More particularly, the present invention relates to a lithium air battery capable of improving battery performance by improving the structure of a positive electrode, ≪ / RTI >

Lithium air cells use lithium metal for the cathode and oxygen in the air for the cathode active material. In addition, lithium-air cells react with oxygen to generate electricity by reacting lithium ions in the cathode, and it is possible to reduce the weight because it is not necessary to previously contain the cathode active material inside the battery unlike the conventional secondary battery. In addition, it is possible to store a large amount of the negative electrode active material in the container, which can theoretically exhibit a large capacity and a high energy density.

The lithium air battery includes a cathode capable of storing and releasing lithium ions and an anode including oxygen redox catalyst using oxygen in the air as a cathode active material and having a lithium ion conductive medium between the anode and the cathode It is known.

The theoretical energy density of the lithium air battery is 3000Wh / kg or more, which corresponds to about ten times the energy density of a lithium ion battery. In addition, the lithium air battery is eco-friendly, and it can provide improved safety over a lithium ion battery, and many developments have been made.

Important factors that determine the electrochemical characteristics of the lithium air cell include an electrolyte system, an anode structure, a good air reducing catalyst, a kind of a carbon support, and an oxygen pressure.

The reaction formula in the lithium air battery is shown in the following reaction formula 1.

[Reaction Scheme 1]

The oxide pole: Li (s) ↔ Li ⁺ + e ^-

Reducing electrode: 4 Li + O ₂ ? ₂ Li ₂ OV = 2.91 V

_{2Li + O 2 → Li 2 O} 2 V = 3.10V

On the other hand, the anode of the lithium air battery is widely used by mixing carbon black and a binder to prepare a slurry and coating the carbon paper on a carbon paper, which is a gas diffusion layer. The binder is present between the carbon blacks so that the structure of the carbon is not broken, so that the binder can be coated well on the carbon paper.

However, when the binder is used in the electrode production, the binder has a disadvantage in that it deteriorates the performance of the electrode because the conductivity is lowered.

An object of the present invention is to provide a lithium air battery capable of improving battery performance by improving the electrical conductivity by improving the structure of the anode.

It is another object of the present invention to provide a method of manufacturing a lithium air battery capable of reducing the manufacturing cost while improving the electrical conductivity of the lithium air battery.

A lithium air battery according to an embodiment of the present invention includes a separator, a positive electrode including a porous carbon material coated on one side of the separator without a binder, and a negative electrode disposed on the other side of the separator.

The separator may be glass fiber.

Wherein the separator comprises: (a) a polyolefin-based separator substrate; And (b) an active layer coated with a mixture of inorganic particles and a binder polymer, wherein at least one region selected from the group consisting of a surface of the substrate and a porosity portion existing in the substrate is coated with a mixture of a binder polymer and a binder polymer, The inorganic particles may be connected and fixed by the binder polymer and the pore structure may be formed due to the interstitial volume between the inorganic particles.

The inorganic particles may be at least one selected from the group consisting of (a) inorganic particles having a dielectric constant of 5 or more, (b) inorganic particles having piezoelectricity, and (c) inorganic particles having lithium ion transporting ability.

The inorganic particles (a) having a dielectric constant of 5 or more may be SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ or SiC.

Inorganic particles (b) having the piezoelectricity (piezoelectricity) is _{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 may be a _{2/3) O 3 -PbTiO 3} (PMN-PT) or hafnia (hafnia, HfO _2).

The inorganic particles (c) having lithium ion transferring ability may be 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 or _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 < z < 7) series glass.

The binder polymer may be selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-trichlorethylene, polymethylmethacrylate ), Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide (polyethylene) oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, Cyanoethylcellulose, cyano Til sucrose (cyanoethylsucrose), pullulan can be at least one member selected from the group consisting of (pullulan), carboxymethyl cellulose (carboxyl methyl cellulose) and polyvinyl alcohol (polyvinylalcohol).

The component of the polyolefin-based membrane base material may be at least one selected from the group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultrahigh molecular weight polyethylene and polypropylene.

The anode may further include a gas diffusion layer disposed on a surface of the porous carbon material that is not in contact with the separator.

The method for manufacturing a lithium air cell according to another embodiment of the present invention includes the steps of preparing a composition for forming an anode by mixing a porous carbon material and a solvent and coating the prepared composition for positive electrode with a binder on one surface of the separator .

The solvent may be any one selected from the group consisting of isopropyl alcohol, ethanol, and mixtures thereof.

The lithium air battery of the present invention improves the electric conductivity by improving the structure of the anode, thereby improving battery performance and reducing manufacturing cost.

1 is an SEM photograph of the organic / inorganic composite porous separator (PVdF-CTFE / BaTiO3) prepared in Production Example 1 of the present invention, wherein FIGS. 1A and 1B show the active layer and the separator substrate respectively.
2 is a charge / discharge curve of the lithium air battery manufactured in Example 1 and Comparative Example 1 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

As used herein, the term "air" is not meant to be limited to atmospheric air, but may include a combination of gases containing oxygen, or pure oxygen gas. This broad definition of the term "air" can be applied to all applications, such as air cells, air bubbles, and the like.

A lithium air battery according to an embodiment of the present invention includes a separator, a positive electrode including a porous carbon material coated on one side of the separator without a binder, and a negative electrode disposed on the other side of the separator.

In the lithium air battery, since the positive electrode does not include a binder, the porous carbon materials are more tightly connected to each other to improve electrical conductivity. As the porous carbon materials are coated directly on the separator, the porous carbon materials and the separator Is reduced.

On the other hand, the anode using the oxygen as a cathode active material includes the porous carbon material. Examples of such porous carbon materials include carbon black, graphite, graphene, activated carbon, carbon fiber, and the like.

The anode may further include a catalyst for oxidation / reduction of oxygen. Examples of the catalyst include noble metal catalysts such as platinum, gold, silver, palladium, ruthenium, rhodium and osmium, manganese oxides, Cobalt oxide, nickel oxide and the like, or an organometallic catalyst such as cobalt phthalocyanine may be used, but the present invention is not limited thereto and can be used as an oxidation / reduction catalyst of oxygen in the related art.

In addition, the catalyst may be supported on a carrier. The carrier may be an oxide, zeolite, clay minerals, carbon, or the like. The oxide may be an oxide such as alumina, silica, zirconium oxide or titanium dioxide, or an oxide such as Ce, Pr, Sm, Eu, Tb, Tm, Yb, Sb, Bi, V, Cr, Mn, Fe, , Mo, and W. &lt; / RTI &gt; The carbon may be carbon black such as Ketjen black, acetylene black, tan black, lamp black, graphite such as natural graphite, artificial graphite and expanded graphite, activated carbon, carbon fiber and the like, Anything that can be used as a carrier in the field is possible.

The positive electrode does not include a binder as described above. The binder may be a thermoplastic resin or a thermosetting resin. Examples of the binder include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene- Vinylidene fluoride-vinylidene fluoride copolymer, vinylidene fluoride-vinylidene fluoride copolymer, vinylidene fluoride-vinylidene fluoride copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride- chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, Propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoro Methyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, and the like.

The separator may be a glass fiber or an organic / inorganic composite porous separator. When the separator is a glass fiber or an organic / inorganic composite porous separator, the porous carbon material of the anode can be well bonded to the separator without a binder.

Wherein the organic / inorganic composite porous separator comprises at least one region selected from the group consisting of (a) a polyolefin-based separator base material and (b) a surface of the base material and a porosity portion existing in the base material, Inorganic composite porous separator comprising a coated active layer, wherein the active layer may be one in which the inorganic particles are connected and fixed by the binder polymer, and the pore structure is formed due to the interstitial volume between the inorganic particles.

The organic / inorganic composite porous separator is produced by using inorganic particles and a binder polymer on the polyolefin-based separator as an active layer component. In addition to the pore structure contained in the separator substrate itself, an empty space between the inorganic particles interstitial volume), which can be used as a separation membrane due to the uniform pore structure. In addition, when a polymer capable of gelation is used as a binder polymer component when a liquid electrolyte is impregnated, it can also be used as an electrolyte.

As shown in FIG. 1, the organic / inorganic composite porous separator has a plurality of uniform pore structures formed on both the active layer and the polyolefin-based separator substrate. Through the pores, lithium ions are smoothly transferred and a large amount of electrolyte is filled A high impregnation rate can be exhibited, so that the performance of the battery can be improved at the same time.

Since the organic / inorganic composite porous separator is formed by coating directly on the polyolefin-based separation membrane, the pores on the surface of the polyolefin-based membrane substrate and the active layer exist as anchoring mutually so that the active layer and the porous substrate are physically and firmly bonded .

In the organic / inorganic composite porous separator, one of the active layer components formed on the surface of the polyolefin-based membrane base material and / or the pores of the base material is an inorganic particle commonly used in the art. The inorganic particles may serve as a kind of spacer capable of forming micropores by allowing an interstitial volume between inorganic particles and maintaining physical shape. In addition, since the inorganic particles generally have a property that their physical properties do not change even at a high temperature of 200 DEG C or more, the formed organic / inorganic composite porous film has excellent heat resistance.

The inorganic particles are preferably high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having lithium ion-transferring ability, inorganic particles having piezoelectricity, or a mixture thereof.

The piezoelectric material refers to a non-conductive material at normal pressure, or a material having electrical conductivity due to a change in internal structure when a certain pressure is applied. Non-limiting examples of the piezoelectric material having piezoelectricity include BaTiO ₃ , _{Pb (Zr, Ti) O 3} (PZT), Pb 1 - x La x Zr 1 - y Ti y O 3 (PLZT), PbB (Mg 3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT), Hafnia (HfO ₂ ) or a mixture thereof.

The inorganic particles having the lithium ion transferring ability are inorganic particles having a function of transferring lithium ions without containing lithium but containing lithium element in the present invention, It is possible to transfer and move lithium ions due to a kind of defect existing in the lithium ion battery, so that the lithium ion conductivity in the battery is improved, thereby improving battery performance. 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 < , Lithium aluminum titanium phosphate (LixAlyTiz (PO4) 3, 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ 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 0 &lt; y &lt; 1, 0 < z < 1, 0 < w _&gt; , such as Li _x Ge _y P _z S _w , 0 <x <4, Ge _{0 .25} P _{0 .75} S ₄ , 5), Li ₃ N lithium nitride _{(Li x N y, 0 <} x <4, 0 <y <2), Li 3 PO 4 SiS 2 family, such as _{-Li 2 S-SiS 2 glass (} Li x such as _{Si y S z, 0 <x} <3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 P 2 S 5 based glass (Li _x P _y S _z, such as 0 < x <3, 0 <y <3, 0 <z <7), or mixtures thereof.

Examples of inorganic particles having a dielectric constant of 5 or more include SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , And the like. When the above-mentioned high-permittivity inorganic particles, the inorganic particles having piezoelectricity, and the inorganic particles having lithium ion transferring ability are mixed, their synergistic effect can be doubled.

Inorganic composite porous separator formed by coating a mixture of the inorganic particles and the binder polymer on the polyolefin separator base material includes not only pores in the separator base material itself as described above, Both the substrate and the active layer form a pore structure due to the void space between the particles. The pore size and porosity of the organic / inorganic composite porous separator depend mainly on the size of the inorganic particles. For example, when inorganic particles having a particle size of 1 탆 or less are used, pores formed also show 1 탆 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 separator.

Non-limiting examples of usable binder polymers include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, Polyolefins such as polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, , Cyanoethylcellulose, Include cyano ethyl sucrose (cyanoethylsucrose), pullulan (pullulan), carboxymethyl cellulose (carboxyl methyl cellulose), an arc Lee acrylonitrile styrene butadiene copolymers (acrylonitrilestyrene-butadiene copolymer), polyimide (polyimide) or mixtures thereof. In addition, any material including the above-mentioned characteristics may be used alone or in combination.

In the organic / inorganic composite porous separator, a substrate coated with a mixture of inorganic particles and a binder polymer as the active layer constituent is a polyolefin-based separator commonly used in the art. Non-limiting examples of the polyolefin-based separation membrane component include high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene or derivatives thereof.

Wherein the organic / inorganic composite porous separator comprises: (a) dissolving the binder polymer in a solvent to prepare a polymer solution; (b) adding and mixing the inorganic particles to the polymer solution of step (a); And (c) coating at least one region selected from the group consisting of a surface of the polyolefin-based membrane base material and a pierced portion of the substrate with the mixture of step b) and drying.

First, 1) a polymer is dissolved in an appropriate organic solvent to prepare a polymer solution.

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.

2) Inorganic particles and polymer mixtures are prepared by adding and dispersing inorganic particles to the prepared polymer solution.

It is preferable to add inorganic particles to the polymer solution and then crush the inorganic particles. In this case, the disintegration time is preferably 1 to 20 hours, and the particle size of the disintegrated inorganic particles is preferably 0.001 to 10 占 퐉 as mentioned above. As the crushing method, a conventional method can be used, and a ball mill method is particularly preferable.

The composition of the inorganic particles and the polymer is not particularly limited, but the thickness, pore size, and porosity of the final organic / inorganic composite porous separator of the present invention can be controlled.

That is, as the ratio of the inorganic particles (I) to the polymer (P) increases, the porosity of the organic / inorganic composite porous separator of the present invention increases as the ratio of the inorganic particles (I) Inorganic composite porous separator increases in the thickness of the organic / inorganic composite porous separator. In addition, the pore size increases due to an increase in the possibility of pore formation between the inorganic particles. At this time, as the size (particle diameter) of the inorganic particles increases, the interstitial distance between the inorganic particles becomes larger.

3) The organic / inorganic composite porous separator of the present invention can be obtained by coating a prepared mixture of the inorganic particles and the polymer on the prepared polyolefin-based membrane base material and then drying.

In this case, a method of coating a mixture of inorganic particles and polymer on the polyolefin-based separator substrate may be a conventional coating method known in the art. For example, a dip coating, a die coating, a roll coating, ) Coating, comma coating, or a combination thereof. In addition, when the mixture of the inorganic particles and the polymer is coated on the polyolefin-based membrane substrate, it can be carried out on both sides of the membrane base material, or selectively on one side only.

Meanwhile, the anode may be prepared by mixing the porous carbon material with the oxygen oxidation / reduction catalyst, and then adding a suitable solvent to prepare a composition for forming an anode, applying the composition to the surface of the separator, and drying the composition.

Conventionally, the anode is prepared by applying a composition for forming an anode including a binder to a gas diffusion layer such as carbon paper, and drying the composition. However, the present invention is characterized in that the composition for forming an anode The anode may be formed without a binder.

The solvent may be any one selected from the group consisting of isopropyl alcohol, ethanol, and mixtures thereof. The use of the isopropyl alcohol can describe rapid evaporation in the preparation of the electrode slurry, thereby shortening the processing time In addition to absorbing the moisture remaining in the carbon while evaporating, it strengthens the bonds between the carbon atoms and can maintain the shape of the electrode slurry at the time of coating.

The method of applying the composition for forming an anode to the surface of the separator is not particularly limited and may be applied by a screen printing method, a spray coating method, a coating method using a doctor blade, a gravure coating method, a dip coating method, a silk screen method, A coating method using a die, a spin coating method, a roll coating method, a transfer coating method, or the like can be used.

The drying may be performed at 20 to 200 ° C, preferably 20 to 150 ° C, and more preferably 60 to 120 ° C. If the drying temperature is lower than 20 ° C, a solvent may remain in the electrode, and if it exceeds 200 ° C, the structure of the separator may be changed.

The anode may further include a gas diffusion layer disposed on a surface of the porous carbon material that is not in contact with the separator. The gas diffusion layer plays a role of supporting the porous carbon material and diffusing air with the porous carbon material so that air can be easily accessed. As the gas diffusion layer, a conductive substrate may be used. Typical examples of the gas diffusion layer include a carbon paper, a carbon cloth, a carbon felt, or a metal cloth (a porous film composed of a metal in a fiber state or A metal film formed on the surface of a cloth formed of polymer fibers) may be used, but is not limited thereto.

The negative electrode capable of intercalating and deintercalating lithium includes a lithium metal, a lithium-metal-based alloy, or a material capable of absorbing and desorbing Li, but the present invention is not limited thereto. The negative electrode determines the capacity of the lithium air battery. The lithium metal-based alloy may be, for example, aluminum, tin, magnesium, indium, calcium, germanium, antimony, bismuth,

The positive electrode and the negative electrode may further include a current collector. The current collector on the positive electrode may use a porous material such as a mesh or mesh shape to accelerate the diffusion of oxygen, and may be made of a porous material such as stainless steel, nickel, The metal plate may be used, but is not limited thereto, and any metal plate may be used as a current collector in the related art. The current collector may be coated with an oxidation-resistant metal or alloy coating to prevent oxide.

The electrolyte may be an aqueous electrolyte or a non-aqueous electrolyte. Alternatively, the electrolyte may be formed by mixing an aqueous electrolyte and a non-aqueous electrolyte.

The non-aqueous electrolyte may include an aprotic solvent. As the aprotic solvent, for example, a carbonate-based, ester-based, ether-based, ketone-based, amine-based or phosphine-based solvent may be used.

The ether solvent includes acyclic ethers or cyclic ethers.

Non-limiting examples of such non-cyclic ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane (1, 2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether dimethyl sulfoxide and N, N-dimethyl acetamide. Lt; / RTI &gt; group.

Also, as non-limiting examples, the cyclic ethers may be 1,3-dioxolane, 4,5-dimethyl-dioxolane, Ethyl-dioxolane, 4-methyl-1,3-dioxolane, 4-ethyl-1,3-dioxolane, 4-ethyl-1,3-dioxolane, tetrahydrofuran, 2-methyl tetrahydrofuran, 2,5-dimethyl tetrahydrofuran, 2-ethoxy tetrahydrofuran, 2-methoxy-1,3-dioxolane, 2,5-dimethoxy tetrahydrofuran, dioxolane, 2-vinyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, dioxolane, 2-methoxy-1,3-dioxolane, 2-ethyl-2-methyl -1,3-dioxolane, tetrahydropyran, 1,4-dioxane, 1,2-dimethoxane, Benzene, 1,2-dimethoxy benzene, 1,3-dimethoxy benzene, 1,4-dimethoxy benzene, and isosorbide dimethyl ether) may be used.

The electrolyte may include a lithium salt dispersed in the non-aqueous organic solvent.

As the lithium salt, those generally applicable to a lithium air battery can be used without any particular limitation. Preferably, the lithium salt is _{LiSCN, LiBr, LiI, LiPF 6} , LiBF 4, LiSbF 6, LiAsF 6, LiCH 3 SO 3, LiCF 3 SO 3, LiClO 4, Li (Ph) 4, LiC (CF 3 SO _{2) 3, LiN (CF 3} SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiN (SFO 2) 2, and _{LiN (CF 3 CF 2 SO 2} ) at least one member selected from the group consisting of ₂ Lt; / RTI &gt;

The concentration of the lithium salt may be determined in consideration of ionic conductivity and the like, preferably 0.2 to 2.0 M, or 0.5 to 1.6 M. That is, the concentration of the lithium salt is preferably 0.2 M or more in order to secure ion conductivity suitable for driving the battery. However, when the lithium salt is added in an excessive amount, the viscosity of the electrolyte solution may be increased to lower the mobility of the lithium ion, and the decomposition reaction of the lithium salt itself may increase, thereby deteriorating the performance of the battery. Therefore, the concentration of the lithium salt is preferably 2.0 M or less.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. However, the following embodiments are intended to illustrate the invention, but the invention is not limited thereto.

[ Manufacturing example : Organic / inorganic composite porous Separator  Produce]

( Manufacturing example  One)

A polymer solution was prepared by adding about 5% by weight of polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVdF-CTFE) polymer to acetone and dissolving at a temperature of 50 ° C for about 12 hours or longer. The BaTiO ₃ powder was added to the polymer solution so as to have a BaTiO ₃ / PVdF-CTFE = 90/10 (weight% ratio), and the BaTiO ₃ powder was crushed and pulverized for 12 hours or longer using a ball mill method to prepare a slurry . The BaTiO ₃ particle size of the thus-prepared slurry can be controlled according to the size (particle size) of the beads used in the ball mill method and the application time of the ball mill method, but here, the slurry was pulverized to about 400 nm. The slurry thus prepared was coated on a polyethylene separator (porosity of 45%) having a thickness of about 18 탆 by a dip coating method, and the coating thickness was adjusted to about 3 탆. As a result of measurement with a porosimeter, the pore size and porosity in the active layer coated on the polyethylene membrane were 0.5 탆 and 58%, respectively.

The surface of the organic / inorganic composite porous separator prepared in Preparation Example 1 was confirmed by a scanning electron microscope (SEM), and the result is shown in FIG. 1A and 1B show an active layer and a separation membrane substrate, respectively. 1A and 1B, it is confirmed that the organic / inorganic composite porous separator has a uniform pore structure in both the polyethylene separator substrate (see FIG. 1B) and the active layer into which the inorganic particles are introduced (see FIG. 1A) I could.

[ Manufacturing example : Manufacture of lithium air battery]

( Example  One)

0.5 g of ketjen black as a kind of carbon black as a porous carbon material was added to 7.5 g of isopropyl alcohol and then mixed to prepare a composition for forming an anode.

The composition for forming an anode was applied to one surface of the organic / inorganic composite porous separator manufactured in Preparation Example 1, followed by vacuum drying at 120 ° C for 12 hours to form a positive electrode.

Was used as a negative electrode and lithium metal of 150㎛ thickness, ether-based solvent is tetraethylene glycol dimethyl ether (TEGDME), as a lithium salt of _{1.0 M LiN (CF 3 SO 2} ) 2 (LiTFSI, lithium-bis (trifluoromethanesulfonyl) imide) was added to prepare an electrolyte solution.

The prepared electrode current collector was housed in a battery case, and then the electrolyte solution was injected to prepare a lithium air battery.

( Example  2)

0.5 g of ketjen black as a kind of carbon black as a porous carbon material was added to 7.5 g of isopropyl alcohol and then mixed to prepare a composition for forming an anode.

The composition for forming an anode was coated on one side of a glass fiber separator, followed by vacuum drying at 120 ° C for 12 hours to form a positive electrode.

Was used as a negative electrode and lithium metal of 150㎛ thickness, the ether-based solvent is tetraethylene glycol dimethyl ether (TEGDME), as a lithium salt, _{1.0 M LiN (CF 3 SO 2} ) ₂ was added to prepare an electrolyte solution.

The prepared electrode current collector was housed in a battery case, and then the electrolyte solution was injected to prepare a lithium air battery.

( Comparative Example  One)

Ketjen black, a kind of carbon black, was prepared as a positive electrode for a lithium air battery. The binder was PVDF. The slurry was prepared using N-methyl-2-pyrrolidone as a solvent at a ratio of carbon black to binder of 8: 2 by weight. carbon paper using a doctor blade, followed by vacuum drying at 120 DEG C for 12 hours. The prepared electrode was used as an electrode by tapping with a diameter of 19 phi. Lithium metal having a thickness of 150 μm was used as a cathode, and glass fiber was used as a separator.

Then, 1.0 M of LiN (CF ₃ SO ₂ ) ₂ as a lithium salt was added to tetraethylene glycol dimethyl ether (TEGDME) as an ether solvent to prepare an electrolyte solution.

A separator was interposed between the prepared anode and cathode, and the electrolyte solution was injected into the battery case to prepare a lithium air cell.

[ Experimental Example : Lithium air battery Charging and discharging  Characteristic measurement]

The lithium air cells prepared in Example 1 and Comparative Example 1 were discharged at a voltage cut-off range of 2.0 V under a condition of 0.1 mA / cm ² , and the results are shown in FIG. 2 .

Referring to FIG. 2, it can be seen that the lithium ion battery produced in Example 1 has improved charging / discharging characteristics compared with the lithium ion battery manufactured in Comparative Example 1. This is because, in the case of the lithium air cell prepared in Example 1, the structure of the positive electrode was improved by coating the positive electrode on the side of the separator without using a binder, thereby improving the electrical conductivity.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (10)

Separators,
A positive electrode coated on one surface of the separator and containing a porous carbon material but not including a binder,
And a negative electrode disposed on the other surface of the separator,
The separator is an organic / inorganic composite porous separator,
The organic / inorganic composite porous separator comprises: (a) a polyolefin-based membrane separator; And (b) an active layer coated with a mixture of inorganic particles and a binder polymer, wherein at least one region selected from the group consisting of a surface of the substrate and a porosity portion existing in the substrate is coated with a mixture of inorganic particles and a binder polymer,
Wherein the active layer has a pore structure due to the interstitial volume between the inorganic particles, and the inorganic particles are connected and fixed by the binder polymer. delete delete The method according to claim 1,
Wherein the inorganic particles are at least one selected from the group consisting of (a) inorganic particles having a dielectric constant of 5 or more, (b) inorganic particles having piezoelectricity, and (c) inorganic particles having lithium ion- battery. 5. The method of claim 4,
The inorganic particles (a) having a dielectric constant of 5 or more are SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ or SiC;
Inorganic particles (b) having the piezoelectricity (piezoelectricity) is _{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) or hafnia (hafnia, HfO _2), and;
The inorganic particles (c) having lithium ion transferring ability may be 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 or _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 < z < 7) series glass. The method according to claim 1,
The binder polymer may be selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-trichlorethylene, polymethylmethacrylate ), Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide (polyethylene) oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, Cyanoethylcellulose, cyano Til sucrose (cyanoethylsucrose), pullulan (pullulan), carboxymethyl cellulose (carboxyl methyl cellulose) and polyvinyl lithium air battery is at least one member selected from the group consisting of alcohol (polyvinylalcohol). The method according to claim 1,
Wherein the component of the polyolefin-based membrane base material is at least one selected from the group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultrahigh molecular weight polyethylene and polypropylene. The method according to claim 1,
Wherein the anode further comprises a gas diffusion layer disposed on a surface of the porous carbon material that is not in contact with the separator. Preparing a composition for forming an anode without mixing a binder and a porous carbon material and a solvent; and
Coating the prepared anode-forming composition on one side of the separator without a binder,
The separator is an organic / inorganic composite porous separator,
The organic / inorganic composite porous separator comprises: (a) a polyolefin-based membrane separator; And (b) an active layer coated with a mixture of inorganic particles and a binder polymer, wherein at least one region selected from the group consisting of a surface of the substrate and a porosity portion existing in the substrate is coated with a mixture of inorganic particles and a binder polymer,
The method of claim 1, wherein the active layer is formed by bonding and fixing inorganic particles with a binder polymer and forming a pore structure due to an interstitial volume between inorganic particles. 10. The method of claim 9,
Wherein the solvent is any one selected from the group consisting of isopropyl alcohol, ethanol, and mixtures thereof.

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