KR20170057761A - Organic/inorganic composite separator and manufacturing method of the same - Google Patents

Abstract

The present invention relates to an organic and inorganic composite separator and a manufacturing method thereof. The present invention includes: a porous member including a plurality of pores; a porous coating layer coated on at least one side of the porous member, formed with a mixture of a binder polymer and a plurality of inorganic particles of which size is 0.001-10 m, and having a weight ratio of 50:50-99:1 between the inorganic particles and the binder polymer; and at least two areas coated on the surface of the porous coating layer, separated at 0.1-100 m, and comprising binder polymer dots of which average diameter is 1-100 m. A separation distance between the areas is longer than a separation distance between the binder polymer dots.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic / inorganic composite membrane,

The present invention relates to an organic and inorganic composite membrane and a method of manufacturing the same, and more particularly, to an organic and inorganic composite membrane having improved wetting and a method of manufacturing the same.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified.

The electrochemical device has been attracting the most attention in this respect, and interest in the development of a rechargeable secondary battery is increasing.

Among the currently applied secondary batteries, the lithium secondary batteries developed in the early 1990s are attracting attention as they have a high operating voltage and an extremely high energy density. The lithium secondary battery includes a lithium ion battery (LiLB) using a liquid electrolyte, a lithium ion polymer battery (LiPB) using a gel polymer electrolyte, and a lithium polymer battery (LPB) using a solid polymer electrolyte according to an electrolyte to be used. ), And so on.

Meanwhile, currently used lithium polymer batteries have a "bicell" structure in which one negative electrode is positioned between two positive electrodes and a separator is inserted between the positive and negative electrodes in order to improve the high-rate characteristics of the battery.

In order to manufacture a lithium polymer battery having such a bi-cell structure, a separator is laminated on an anode at a predetermined temperature (110 to 140 ° C) and pressure (300 to 450 psi), and then a cathode, a separator, .

The adhesion (resistance) between the anode and the separator is increased by such a pressing process, and the wettability (or impregnability) of the electrolyte is lowered compared with other types of electrode assemblies. Furthermore, it is difficult to smoothly remove the gas generated during the subsequent formation process, and a plating phenomenon of Li may occur at this portion.

As a result, not only is it a fundamental cause of deterioration of the capacity of the lithium polymer battery due to the cycle, lowering the charging and discharging characteristics at high rate, but also insecurity in terms of safety of the battery, Resolution is urgently required.

Korean Patent Laid-Open Publication No. 10-2015-0076897

In order to solve the above-mentioned problems, an object of the present invention is to provide an organic and inorganic composite membrane having improved adhesion and wettability with an electrode.

In addition, the present invention provides a method for producing the organic and inorganic composite membrane.

In one embodiment to achieve the above object,

A porous substrate having a plurality of pores,

A porous coating layer coated on at least one surface of the porous substrate and formed of a mixture of a plurality of inorganic particles having a size of 0.001 to 10 탆 and a binder polymer and having a weight ratio of the inorganic particles and the binder polymer of 50:50 to 99: , And

Wherein the binder polymer is coated on the surface of the porous coating layer and has a spacing of 0.1 to 100 mu m and an average diameter of 1 to 100 mu m. And the separation distance between the dots is larger than the separation distance between the dots.

Further, in the present invention,

Forming a porous coating layer on at least one side of the porous substrate having a plurality of pores; And

And patterning and coating the binder polymer solution on the surface of the porous coating layer to form adhesive binder polymer dots. The present invention also provides a method for preparing the organic and inorganic composite membrane of the present invention.

According to the present invention, adhesive strength to the electrodes is improved by the adhesive binder polymer dots formed on the organic / inorganic composite separation membrane, so that shorting of the separation membrane can be prevented. Further, since the pressing process can be performed under a low pressure by the improvement of the adhesion force, the resistance of the interface between the electrode and the separator can be reduced, and the wettability of the electrolyte can be improved. Thus, it is possible to manufacture a lithium polymer battery in which the gas generated in the forming process is easily removed, and the manufacturing cost is reduced and the safety is secured.

1 is a plan view schematically showing the structure of an organic and inorganic composite membrane produced according to an embodiment of the present invention.
2 is a side view schematically showing the structure of an organic and inorganic composite membrane prepared according to an embodiment of the present invention
3 is a SEM photograph of a region of the organic and inorganic composite membrane of the present invention.
4 is a graph showing the results of measurement of the interface resistance between the electrode and the separation membrane according to Experimental Example 2 of the present invention.

Hereinafter, the present invention will be described in more detail.

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

In order to achieve the above object, An improved organic and inorganic composite membrane and a method of manufacturing the same are provided.

Specifically, in one embodiment of the present invention

A porous substrate having a plurality of pores,

A porous coating layer coated on at least one surface of the porous substrate and formed of a mixture of a plurality of inorganic particles having a size of 0.001 to 10 탆 and a binder polymer and having a weight ratio of the inorganic particles and the binder polymer of 50:50 to 99: , And

Wherein the binder polymer is coated on the surface of the porous coating layer and has a spacing of 0.1 to 100 mu m and an average diameter of 1 to 100 mu m. And the separation distance between the dots is larger than the separation distance between the dots.

Specifically, in the organic and inorganic composite separator of the present invention, the binder polymer dots may be patterned and arranged in the form of a dot of a uniform shape, such as a circle, a triangle, a square, or an ellipse.

The organic and inorganic composite separator according to the present invention has a hysteresis distance of about 0.1 to 100 탆, specifically 1 to 50 탆, more specifically 10 탆, and an average diameter of about 1 to 100 탆, Specifically, 1 to 10 mu m, and more specifically, 2.5 mu m.

In addition, the organic and inorganic composite separator according to the present invention is characterized in that the binder polymer dots are formed on the entire surface in order to lower the resistance (adhesive force) between the electrode and the separator interface and simultaneously improve the wettability of the electrolytic solution. It is preferable that the binder polymer dots are formed as a zone, and it is preferable that at least two such zones are included. In this case, the separation distance between the region and the region may be about 1 to 300 μm, specifically 50 to 300 μm, more specifically 100 to 50 μm, which is wider than the separation distance between the binder polymer dots.

The average thickness (loading amount) of the binder polymer dots formed on the organic / inorganic composite separator of the present invention may be about 0.001 to 10 탆, specifically 2 to 3 탆.

Only when the binder polymer dots formed on the organic / inorganic composite separator of the present invention satisfy all of these ranges, it is possible to improve the adhesion between the electrode and the separator and to perform the compression process under low pressure, The effect of improving the wettability of the electrolytic solution can be realized by lowering the (adhesive) resistance of the interface. If the spacing distance between the holes formed by the binder polymer dots is more than 300 mu m, the adhesive force is lowered and the electrodes and the separator are separated from each other. When the separation distance includes the above range, And the effect of increasing the wettability of the electrolytic solution can be realized.

In addition, in the organic and inorganic composite membrane of the present invention, the size and the area of the region 25 composed of the binder polymer dots 23 formed on the separation membrane 22 are, as shown in FIGS. 1 and 2, May be the same or different from each other. In addition, the binder polymer dots in the region may be arranged according to a certain rule, or may be irregularly arranged. In this case, the binder polymer dots arranged in the region may interfere with maintaining the lithium ion transfer capability of the organic and inorganic composite separator But can be formed while appropriately changing the shape, size, and arrangement within a range that can improve the adhesion between the electrode and the separator.

Specifically, in the organic and inorganic composite separator according to the present invention, the area comprising the binder polymer dots may be 1 to 80% based on the total area of the organic and inorganic composite separator, specifically, the total area of the organic and inorganic composite separator May range from about 5 to 50% by weight. If the area of the binder polymer dots is more than 80% of the total area of the separator, the adhesive strength excessively increases and the wettability is lowered. On the other hand, if the area is less than 5% There is a drawback that the separation membrane is desorbed.

Further, in the organic and inorganic composite membrane of the present invention, the density (area) of the binder polymer dots in the region is formed in the range of 50 to 90%, specifically 50 to 80% based on the total area of one region . If the area of the binder polymer dots in the region exceeds 90%, the wettability is lowered due to excessive increase of the adhesive force. If the area is less than 50%, the adhesive force is lowered and the electrode and separation membrane are separated.

Further, in the organic and inorganic composite separator of the present invention, the binder polymer is not particularly limited as long as it is a binder polymer used for improving the binding force between the separator and the electrode. Typical examples thereof include polyvinylidene fluoride (PVdF) Polyvinylidene fluoride-trichlorethylene, polyvinylidene fluoride-chlorotrifluoroethylene (PVdF-CTFE), polymethylmethacrylate, polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, Polyvinylacetate, ethylene-co-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol, cyanoethyl Cellulose, cyanoethyl sucrose, pullulan, carboxy Based (organic) binder polymer comprising a single substance selected from the group consisting of methyl cellulose, acrylonitrile styrene-butadiene copolymer and polyimide, or a mixture of two or more of them. Specific examples thereof include water-based polyvinylidene fluoride (PVdF ) Can be used.

In the organic and inorganic composite separator of the present invention, the inorganic particles constituting the porous coating layer may be oxidized and / or reduced at an operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li +) Is not particularly limited. Particularly, when inorganic particles having ion transfer ability are used, the ion conductivity in the electrochemical device can be increased to improve the performance. When inorganic particles having a high dielectric constant are used as the inorganic particles, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte is also increased, and ion conductivity of the electrolyte can be improved.

For the reasons stated above, it is preferable that the inorganic particles use high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having lithium ion transferring ability, or a mixture thereof. Illustrative examples of the inorganic particles is greater than or equal to the dielectric constant of 5, _{BaTiO 3, BaTiO 3, Pb (} Zr, Ti) O 3 (PZT), Pb 1 - x La x Zr 1 - y Ti y O 3 (PLZT, where 0 Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, can be given _{NiO, CaO, ZnO, ZrO 2} , Y 2 O 3, Al 2 O 3, TiO 2, SiC and danilmul or as mixtures of two or more thereof selected from the group consisting of from mixtures thereof. In particular, the above-mentioned _{Pb 1 - x La x Zr 1} - y Ti y O 3 (PLZT, where, 0 <x <1, 0 <y <1 _{Im), Pb (Mg 1/3 Nb 2/3} ) O 3 Inorganic particles such as PbTiO ₃ (PMN-PT) and HfO ₂ show not only high-permittivity characteristics with a permittivity constant of 100 or more, but also electric charges when they are stretched or compressed by applying a certain pressure, It is possible to prevent internal short-circuiting of both electrodes due to an external impact, thereby improving the safety of the electrochemical device. Further, when the above-mentioned high-permittivity inorganic particles and inorganic particles having lithium ion transferring ability are mixed, their synergistic effect can be doubled.

In addition to the inorganic particles, inorganic particles having lithium ion transferring ability, that is, lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O ₉ Al ₂ O ₃ 38TiO ₂ 39P ₂ O _5, including (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2, 0 <y <3) , Li _{3 . 25 Ge 0 .25 P 0. 75 S} 4 lithium such as germanium thiophosphate _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5 ), Li ₃ lithium nitride such as _{N (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 Si _{y S z, 0 <x <} 3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 , etc., such as P ₂ S ₅ based _{glass (Li x P y S z} , 0 <x <3, 0 <y <3, 0 <z <7), or a mixture thereof.

The average particle diameter of the inorganic particles is preferably in the range of about 0.001 to 10 mu m so as to have a proper porosity in the gel polymer electrolyte with a uniform thickness. If the average particle diameter is less than 0.001 탆, the dispersibility may be deteriorated. If the average particle diameter exceeds 10 탆, the thickness of the porous coating layer may be increased. In addition, aggregation of the inorganic particles may occur, The mechanical strength may be lowered due to exposure to the outside.

In addition, in the organic and inorganic composite separation membrane of the present invention, the binder polymer constituting the porous coating layer is a component that functions to connect inorganic particles and stably fix them. In the binder polymer coating solution, It may be the same as or different from the binder polymer. Specifically, the binder polymer for dispersing the inorganic particles and the solubility parameter can be from 15 to 45 Mpa ^1/2 of the aqueous polymer. In addition, as the binder polymer to be separately migrated for adhesion, an organic polymer may be used.

Typical examples of the aqueous binder polymer include cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpyrrolidone, At least one water-based polymer selected from the group consisting of ethyl polyvinyl alcohol, cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose Typical examples of the organic binder polymer include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co (co-hexafluoropropylene) trichloroeth polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyvinylpyrrolidone, polyvinylpyrrolidone, polymethylmethacrylate, polyacrylonitrile, At least one organic polymer selected from the group consisting of polyethylene oxide, acrylonitrile styrene-butadiene copolymer, and polyimide may be included.

In the organic and inorganic composite membrane of the present invention, the composition ratio of the inorganic particles and the binder polymer in the porous coating layer is preferably in the range of, for example, 50:50 to 99: 1, more preferably 70:30 to 95: 5. When the content ratio of the inorganic particles to the binder polymer is less than 50, the content of the polymer is increased and the thermal stability of the separator may be lowered. In addition, the pore size and porosity due to the reduction of the void space formed between the inorganic particles may be reduced, resulting in deterioration of the final cell performance. If the content of the inorganic particles exceeds 99 parts by weight, the fillerability of the porous coating layer may be weakened because the content of the binder polymer is too small.

The thickness of the porous coating layer composed of the inorganic particles and the binder polymer is not particularly limited, but is preferably in the range of 0.01 to 20 mu m. The pore size and porosity are also not particularly limited, but the pore size is preferably in the range of 0.001 to 10 mu m, and the porosity is preferably in the range of 10 to 99%. The pore size and porosity mainly depend 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 are also about 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.

The organic and inorganic composite separation membrane of the present invention includes a plurality of pores formed by the interstitial volume between the inorganic particles in the porous coating layer formed on the substrate and the binder polymer together with the porous structure contained in the porous substrate itself . At this time, the size and porosity of the pores are not particularly limited, but are preferably 0.001 to 50 탆 and 10 to 99%, respectively.

As described above, the organic and inorganic composite separator of the present invention includes a plurality of pores, thereby significantly mitigating the impact exerted from the outside of the electrode assembly, allowing smooth movement of lithium ions through the pores, Can be filled to show high impregnation rate.

In an embodiment of the present invention,

Forming a porous coating layer on at least one side of the porous substrate having a plurality of pores; And

And patterning and coating the binder polymer solution on the surface of the porous coating layer to form adhesive binder polymer dots.

In the method of the present invention, the step of forming the binder polymer dot may be carried out by dissolving a binder polymer in an organic solvent, followed by using at least one method selected from the group consisting of an ink-jet coating method and a gravure coating method . For example, an inkjet coating method can be used when an aqueous binder is used, and a gravure coating method can be used when an organic binder is used. At this time, when the gravure coating method is used, fine binder polymer dots, for example, binder polymer dots having an average diameter of 1.0 m or less can be formed. When the inkjet coating method is performed, a binder polymer dot having an average diameter of 1.0 占 퐉 or more can be formed. In the present invention, the inkjet coating method and the gravure coating method capable of forming a fine pattern may be used alone or in combination.

More specifically, in the gravure coating method of the present invention, a gravure roll formed with binder polymer dots is rotated at a speed of 100 to 300 m / min, specifically about 250 m / min, and the porous substrate with the porous coating layer formed thereon is contacted And the ink on the upper surface of the gravure roll is transferred onto the surface of the porous coating layer.

The binder polymer dots formed on the gravure roll may be formed by dissolving the organic binder in an organic solvent at a concentration of about 1 to 25% by weight using a PD mixer or a high-speed stirrer. The distance between the binder polymer dots formed on the gravure roll is about 0.1 to 100 탆, the average diameter is about 1 to 100 탆, and the average thickness is 0.001 to 10 탆.

In addition, in the inkjet coating method of the present invention, the binder polymer solution is prepared by dissolving about 1 to 25% by weight of the binder polymer in an organic solvent (NMP), and then the porous substrate having the porous coating layer formed thereon is coated at 20 to 100 m / minute, specifically at a rate of 50 m / min, while spraying the binder polymer solution onto the surface of the porous coating layer at a rate of 1 to 3 m / sec, specifically 1 m / sec. At this time, the distance of the binder polymer dots dispersed on the surface of the porous coating layer is about 0.1 to 100 탆, the average diameter is about 1 to 100 탆, and the average thickness is 0.001 to 10 탆.

The organic solvent used in the coating is not particularly limited as long as it is an organic solvent capable of dissolving the binder polymer and having a low boiling point. Typical examples thereof include acetone, tetrahydrofuran, methylene chloride a single substance selected from the group consisting of methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, Or a mixture of two or more.

According to another embodiment of the present invention, there is provided a secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte, wherein the separator includes a lithium secondary Battery can be provided.

The positive electrode may be formed by coating a positive electrode current collector with a positive electrode active material, a binder, a conductive material, and a solvent.

Wherein the positive electrode active material is selected from the group consisting of LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiFePO ₄ , LiNiMnCoO _2, and LiNi _{1 -xy- z} Co _x M _{y y} M2 _z O ₂ X, y and z are independently selected from the group consisting of Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, 0 < y < 0.5, 0 < z &lt; 0.5, and x + y + z &lt; 1), and the cathode active material is not limited thereto.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material.

Such a conductive material is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and includes, for example, graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey 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. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc.), Ketjenblack, EC (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

The binder is a component which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluorine rubber, various copolymers and the like.

The positive electrode collector is not particularly limited as long as it has electrical conductivity without causing chemical change in the battery. For example, the positive electrode collector may be formed of a metal such as carbon, stainless steel, aluminum, nickel, titanium, sintered carbon, , Nickel, titanium, silver, or the like may be used.

The negative electrode may be prepared by coating a negative electrode current collector on a negative electrode active material, a binder, a conductive material, and a solvent.

Examples of the negative electrode active material include natural graphite, artificial graphite, carbonaceous material; Lithium-containing titanium composite oxide (LTO), metals (Me) with Si, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; An alloy composed of the metal (Me); An oxide of the metal (Me) (MeOx); And a composite of the metal (Me) and the carbon (C).

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

Also, the electrolytic solution is composed of an electrolytic solution and a lithium salt. As the electrolytic solution, a non-aqueous organic solvent, an organic solid electrolyte, and an inorganic solid electrolyte are used.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, formic acid And examples thereof include methyl, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, Ethers, methyl pyrophonate, ethyl propionate and the like can be used.

The lithium salt is a material that is readily soluble 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.

As described above, in the present invention, by forming a binder polymer dot on the organic / inorganic composite separation membrane, the adhesion between the anode and the separation membrane is improved, and the compression process can be performed under low pressure. Accordingly, the resistance of the interface between the electrode and the separator is reduced, so that the wettability of the electrolyte can be improved, and the gas generated during the forming process can be easily removed. Therefore, in the case of the lithium polymer secondary battery employing the organic and inorganic composite separator according to the present invention having such a structure, it is possible to secure the manufacturing cost reduction and safety, and further improve the cycle capacity, high rate charging and discharging characteristics.

Example

Hereinafter, the present invention will be described in detail by way of examples with reference to the following 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.

(Anode manufacture)

94 wt% of lithium cobalt composite oxide, 3 wt% of carbon black and 3 wt% of PVDF as a cathode active material were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having a thickness of 20 탆 and dried to produce a positive electrode, followed by roll pressing.

(Cathode manufacture)

N-methyl-2-pyrrolidone (NMP) was used as a negative electrode active material, with 96 wt%, 3 wt% and 1 wt% of carbon powder, polyvinylidene fluoride (PVdF) and carbon black, To prepare a negative electrode mixture slurry.

The negative electrode mixture slurry was applied to a copper (Cu) thin film as an anode current collector having a thickness of 10 탆 and dried to produce a negative electrode, followed by roll pressing.

(Preparation of Organic and Inorganic Composite Membranes with Binder Polymer Dots)

5% by weight of a polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) polymer was added to acetone and dissolved at 50 ° C for about 12 hours or more. Then, the Al ₂ O ₃ powder was mixed with a binder polymer: Al ₂ O ₃ = 10: 90 by weight. Then, the Al ₂ O ₃ powder was pulverized and dispersed using a ball mill for 12 hours or longer to prepare a binder polymer slurry. The Al ₂ O ₃ particle size of the binder polymer slurry was about 400 nm.

Next, the slurry was coated to a thickness of about 3 mu m on a polyethylene porous film (porosity of 45%) having a thickness of 18 mu m using a dip coating method to prepare an organic and inorganic composite membrane. The organic and inorganic composite membrane was measured with a porosimeter. As a result, the pore size and porosity in the porous coating layer coated on the polyethylene porous membrane were 0.4 μm and 55%, respectively.

Next, a binder polymer solution was prepared by dissolving polyvinylidene fluoride copolymer (PVdF) at a concentration of 5 wt% in an acetone solution, and then the porous substrate with the porous coating layer formed thereon was moved at a speed of 50 m / min, The binder polymer dots 13 were formed using an inkjet method in which the binder polymer solution was sprayed onto the surface of the organic and inorganic composite separator 11 on which the coating layer was formed at a rate of 1 m / sec.

The formed binder polymer dots 13 include a region of binder polymer dots having an average diameter of 2.5 mu m, an interval between the patterns of 10 mu m and an average thickness of the pattern of 2 mu m (see Fig. 3) The separation distance of the region may be formed to be 50 mu m.

(Manufacture of electrode assembly)

The anode, the cathode and the separator were laminated sequentially, laminated at a temperature of 100 to 120 ° C. and a pressure of 200 to 300 psi, and assembled using a stack / folding method to produce an electrode assembly .

Example 2.

In the same manner as in Example 1, except that the coating was carried out at a coating speed of 250 m / min for the coating of 1 탆 thin film instead of the ink-jet coating method in the preparation of the organic and inorganic composite separation membrane in which the binder polymer dot was formed, And an electrode assembly including the organic and inorganic composite separator was prepared.

At this time, the gravure coating may be performed such that the gravure roll on which the binder polymer dot is formed is rotated at a speed of about 250 m / min, and the porous substrate having the porous coating layer formed thereon is contacted to transfer the ink on the surface of the gravure roll to the surface of the porous coating layer.

The binder polymer dots formed comprised a zone of binder polymer dots having an average diameter of 0.5 mu m, an interval between the patterns of 1 mu m and an average thickness of the pattern of 0.5 mu m, .

Comparative Example 1

An electrode assembly including an organic and inorganic composite membrane was prepared in the same manner as in Example 1, except that the binder polymer coating layer pattern was not included in preparing the organic and inorganic composite membrane.

Experimental Example

EXPERIMENTAL EXAMPLE 1. Evaluation of Interfacial Adhesion between Electrode and Separator (Peeling Test)

The interfacial adhesion was evaluated by desorbing the separator from the anode of the electrode assembly manufactured in Examples 1 and 2 and Comparative Example 1.

As a result, in the separator of Comparative Example 1, all of the electrode surfaces were clean and separated, while the separator of Examples 1 and 2 was separated with some components of the dots remaining on the anode surface. According to these results, it was found that the adhesion of the separator to the electrode was increased even if the organic and inorganic composite separator prepared by the method of the present invention was subjected to a compression process with an electrode under a low pressure.

The separation membranes prepared in Examples 1 and 2 and Comparative Example 1 were sufficiently wetted with an electrolyte solution (EC / EMC = 1: 2 by volume ratio, 1 mole LiPF ₆ ), and coin cells were produced using only such separation membranes. The prepared coin cell was allowed to stand at room temperature for 48 hours, and the resistance of the separator was measured and evaluated by impedance measurement. The results are shown in FIG.

As shown in FIG. 4, it can be seen that the interfacial resistance of the batteries of Examples 1 and 2 is lower than that of Comparative Example 1.

Therefore, when the organic and inorganic composite separator of the present invention is used, the wettability of the electrolytic solution can be improved. In addition, when the secondary battery is manufactured using the same, it can be predicted that the gas generated during the forming process can be easily removed have.

11, 22: Organic and inorganic composite membranes
13, 23: Binder polymer dots
25: Zone consisting of binder polymer dots

Claims (11)

A porous substrate having a plurality of pores,
A porous coating layer coated on at least one surface of the porous substrate and formed of a mixture of a plurality of inorganic particles having a size of 0.001 to 10 탆 and a binder polymer and having a weight ratio of the inorganic particles and the binder polymer of 50:50 to 99: , And
Wherein the binder is coated on the surface of the porous coating layer and comprises at least two zones of binder polymer dots spaced from 0.1 to 100 μm and having an average diameter of 1 to 100 μm, Wherein the separation distance between the polymer dots is larger than the separation distance between the polymer dots.
The method according to claim 1,
Wherein the separation distance between the zone and the zone is between 1 and 300 mu m.
The method according to claim 1,
Wherein the area is comprised between 1 and 80% of the total area of the separator.
The method according to claim 1,
Wherein the widths of the respective zones are the same or different from each other.
The method according to claim 1,
Wherein the area comprises a rectangular shape.
The method according to claim 1,
Wherein the binder polymer dots are uniformly or non-uniformly distributed in the region.
The method according to claim 1,
Wherein the binder polymer dots are formed in a range of 50 to 90% based on the total area of the one region.
Forming a porous coating layer on at least one side of the porous substrate having a plurality of pores; And
The method of claim 1, further comprising the step of patterning and coating a binder polymer solution on the surface of the porous coating layer to form an adhesive binder polymer dot.
The method of claim 8,
Wherein the step of patterning and coating the binder polymer solution is performed by at least one method selected from the group consisting of an inkjet coating method and a gravure coating method.
The method of claim 9,
The inkjet coating method comprises dissolving a binder polymer in an organic solvent to prepare a binder polymer solution, and then transferring the binder polymer solution onto the surface of the porous coating layer while moving the porous substrate having the porous coating layer formed thereon at a speed of 20 to 100 m / To about 3 m / sec. The method for producing an organic / inorganic composite separation membrane according to claim 1,
The method of claim 9,
In the gravure coating method, the gravure roll on which the binder polymer dots are formed is rotated at a speed of 100 to 300 m / min, and the porous substrate on which the porous coating layer is formed is brought into contact with the surface of the gravure roll to transfer the ink on the surface of the porous coating layer Wherein the organic and inorganic composite membranes are prepared by mixing the organic and inorganic composite membranes.

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