WO2015065116A1 - Organic-inorganic complex porous membrane, separator comprising same, and electrode structure body - Google Patents

Abstract

The present invention provides an organic-inorganic complex porous membrane for an electrochemical device, the membrane comprising: one or more particles selected from inorganic particles and organic particles; and a binder polymer, the one or more particles selected from inorganic particles and organic particles bind to each other via the binder polymer enclosing surfaces of the particles, wherein the filling ratio of the one or more particles selected from inorganic particles and organic particles is 60 to 70%.

Description

Organic-inorganic composite porous membrane, separator and electrode structure comprising the same

The present invention relates to an organic-inorganic porous membrane used in an electrochemical device such as a lithium secondary battery, a separator and an electrode structure including the same, and more particularly, to uniformly mix inorganic particles and a binder in an organic-inorganic composite porous membrane. To an organic-inorganic porous membrane.

This application claims priority based on Korean Patent Application No. 10-2013-0131527, filed October 31, 2013, and all the contents disclosed in the specification and drawings of the application are incorporated in this application.

In addition, this application claims the priority based on Korean Patent Application No. 10-2014-0150289 filed on October 31, 2014, all the contents disclosed in the specification and drawings of the application is incorporated in this application.

Recently, interest in energy storage technology is increasing. As the field of application extends to the energy of mobile phones, camcorders, notebook PCs, and even electric vehicles, efforts for research and development of electrochemical devices are becoming more concrete. The electrochemical device is the most attracting field in this respect, and the development of a secondary battery capable of charging and discharging has been the focus of attention. Recently, in developing such a battery, research and development on the design of a new electrode and a battery have been conducted in order to improve capacity density and specific energy.

Among the secondary batteries currently applied, lithium secondary batteries developed in the early 1990s have a higher operating voltage and greater energy density than conventional batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries that use an aqueous electrolyte solution. I am in the spotlight. However, such lithium ion batteries have safety problems such as ignition and explosion due to the use of the organic electrolyte, and are difficult to manufacture. Recently, the lithium ion polymer battery has been considered as one of the next generation batteries by improving the weakness of the lithium ion battery, but the capacity of the battery is still relatively low compared to the lithium ion battery, and the discharge capacity is improved due to insufficient discharge capacity at low temperatures. This is urgently needed.

In order to solve the safety problem of such an electrochemical device, Korean Patent Publication No. 10-2007-231 discloses an organic-inorganic compound by coating a mixture of inorganic particles and a binder polymer on at least one surface of a porous substrate having a plurality of pores. A separator having a porous coating layer has been proposed. In the separator, the inorganic particles in the porous organic-inorganic coating layer coated on the porous substrate serve as a kind of spacer that can maintain the physical form of the organic-inorganic porous coating layer, so that the porous substrate is thermally contracted when the electrochemical device is overheated. Will be suppressed.

Meanwhile, the organic-inorganic porous coating layer is prepared by mixing inorganic particles and a binder polymer, wherein the organic-inorganic porous coating layer in which the inorganic particles and the binder polymer are uniformly distributed is determined to be an important factor in preparing a high-performance separator. do. However, as described above, in order to uniformly distribute the distribution of the inorganic particles and the binder polymer in the organic-inorganic porous coating layer, there are many variables that affect the uniform distribution of the organic-inorganic porous coating layer. There is difficulty. Therefore, it is time to study how to uniformly distribute the inorganic particles and the binder polymer in the preparation of the organic-inorganic porous coating layer.

Accordingly, the technical problem to be solved by the present invention is to provide an organic-inorganic composite porous membrane in which the inorganic particles and the binder polymer included in the organic-inorganic composite porous membrane are uniformly distributed and a method of manufacturing the same.

Another technical problem to be solved by the present invention is to provide a separator comprising the organic-inorganic composite porous membrane.

Another technical problem to be solved by the present invention is to provide an electrode structure including the organic-inorganic composite porous membrane.

In order to solve the above problems, the present invention is at least one particle selected from inorganic particles and organic particles; At least one particle selected from the group consisting of a binder polymer and the inorganic particles and the organic particles is bound to each other by a binder polymer surrounded by a surface of the particle, and the filling rate of the at least one selected from the inorganic particles and the organic particles. It provides an organic-inorganic composite porous membrane for an electrochemical device, characterized in that 60 to 70%.

According to a preferred embodiment of the present invention, the content of the binder polymer may be 1 to 30 parts by weight based on 100 parts by weight of at least one particle selected from inorganic particles and organic particles.

According to another preferred embodiment of the present invention, the inorganic particles may be at least one selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transfer ability, and mixtures thereof.

According to another preferred embodiment of the present invention, the organic particles are polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA), polyacetal (POM), polyamide (PA), polycarbonate ( PC), modified polyphenylene ether (m-PPE), and poly butylene terephthalate (PBT).

According to another preferred embodiment of the present invention, the binder polymer is polyvinylidene fluoride-hexafluoropropylene (polyvinylidene fluoride-co-hexafluoropropylene), polyvinylidene fluoride-trichloroethylene (polyvinylidene fluoride -cotrichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate) , Polyethylene oxide, cellulose acetate, cellulose acetate butyrate, celluloseacetate propionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol cyanoethylpolyvinylalcohol, cyanoethyl Cellulose (cyanoethylcellulose), cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide It may be at least one selected from the group consisting of polystyrene (polystyrene) and polyethylene (polyethylene).

According to another preferred embodiment of the present invention, the organic-inorganic composite porous membrane is filled with at least one or more particles selected from inorganic particles and organic particles by the binder polymer is connected to each other, thereby between An interstitial volume may be formed, and the interstitial volume between the particles may have pores formed by empty spaces.

According to another preferred embodiment of the present invention, the thickness of the organic-inorganic composite porous membrane may be 0.5 to 50㎛.

According to another aspect of the invention, the present invention comprises the steps of preparing unit particles in which at least one selected from inorganic particles and organic particles alone or a group of particles surrounded by a binder polymer; And applying the heat to the unit particles to bind the unit particles to the organic-inorganic composite porous membrane for an electrochemical device.

According to a preferred embodiment of the present invention, the average particle diameter of the unit particles may be 0.01 to 20 ㎛.

According to another preferred embodiment of the present invention, the content of the binder polymer in the unit particles may be 1 to 30 parts by weight based on 100 parts by weight of at least one particle selected from inorganic particles and organic particles.

According to another preferred embodiment of the present invention, the step of applying heat to the unit particles may be heated to a temperature 5 to 100 ℃ higher than the melting temperature of the binder polymer, the unit particles may be bound.

According to another preferred embodiment of the present invention, the inorganic particles may be at least one selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transfer ability, and mixtures thereof.

According to another preferred embodiment of the present invention, the organic particles are polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA), polyacetal (POM), polyamide (PA), polycarbonate ( PC), modified polyphenylene ether (m-PPE), and poly butylene terephthalate (PBT).

According to another preferred embodiment of the present invention, the binder polymer is polyvinylidene fluoride-hexafluoropropylene (polyvinylidene fluoride-co-hexafluoropropylene), polyvinylidene fluoride-trichloroethylene (polyvinylidene fluoride -cotrichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate) , Polyethylene oxide, cellulose acetate, cellulose acetate butyrate, celluloseacetate propionate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol cyanoethylpolyvinylalcohol, cyanoethyl Cellulose (cyanoethylcellulose), cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide It may be at least one selected from the group consisting of polystyrene (polystyrene) and polyethylene (polyethylene).

According to another preferred embodiment of the present invention, the organic-inorganic composite porous membrane is filled with at least one or more particles selected from inorganic particles and organic particles by the binder polymer is connected to each other, thereby between An interstitial volume may be formed, and the interstitial volume between the particles may be empty to form pores.

According to another preferred embodiment of the present invention, the thickness of the organic-inorganic composite porous membrane may be 0.5 to 50㎛.

According to another aspect of the invention, the present invention is an electrochemical device comprising a separator interposed between the positive electrode, the negative electrode, the positive electrode and the negative electrode, the separator is an organic-inorganic composite porous membrane according to the present invention It provides an electrochemical device characterized in that.

According to another aspect of the invention, the present invention is an electrochemical device comprising a separator interposed between the positive electrode, the negative electrode, the positive electrode and the negative electrode, the separator comprises a porous substrate having the pores; And an organic-inorganic composite porous membrane according to the present invention is formed on at least one surface of the porous substrate.

According to another aspect of the invention, the invention the electrode current collector; An electrode active material layer formed on at least one surface of the electrode current collector; And an organic-inorganic composite porous membrane according to the present invention formed on the other surface of the electrode active material layer.

According to another aspect of the present invention, in the electrochemical device comprising a positive electrode, a negative electrode and an electrolyte, at least one or more of the positive electrode and the negative electrode provides an electrochemical device, characterized in that the electrode structure according to the present invention. .

The present invention provides an organic-inorganic composite porous membrane in which the inorganic particles and the binder polymer used in the organic-inorganic composite porous membrane are uniformly distributed, thereby improving the filling rate of the inorganic particles over the conventional organic-inorganic composite porous membrane.

More specifically, the present invention provides an organic-inorganic material in which the particles are bound by applying heat to unit particles surrounded by a binder polymer alone or in a group of particles of at least one selected from inorganic particles and organic particles. It provides a composite porous membrane.

An organic-inorganic composite porous membrane is prepared through the unit particles, and in comparison with a method of drying and drying a suspension in which at least one selected from inorganic particles and organic particles and a binder polymer are dispersed in a solvent at one time, The organic-inorganic porous membrane may be more uniformly formed with the inorganic particles and the binder polymer.

The organic-inorganic composite porous membrane may be included in the separator of the electrochemical device, or may be included in the electrode structure.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical spirit of the present invention, the present invention is limited to the matters described in such drawings. It should not be construed as limited.

1 is a cross-sectional view schematically showing a unit particle according to an embodiment of the present invention.

2 is a cross-sectional view schematically showing a separator according to an embodiment of the present invention.

3 is a cross-sectional view schematically showing an electrode structure according to an embodiment of the present invention.

[Description of the code]

1: inorganic particles or substitute particles thereof

2: binder polymer

3: unit particle

5: electrode active material

10: porous substrate

20: electrode current collector

11, 21: organic-inorganic composite porous membrane

22: electrode active material layer

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The present invention is at least one particle selected from inorganic particles and organic particles; At least one particle selected from the group consisting of a binder polymer and the inorganic particles and the organic particles is bound to each other by a binder polymer surrounded by a surface of the particle, and the filling rate of the at least one selected from the inorganic particles and the organic particles. It provides an organic-inorganic composite porous membrane for an electrochemical device, characterized in that 60 to 70%.

In the present specification, the filling rate of the particles in the organic-inorganic hybrid porous membrane means a volume fraction filled by the particles in the organic-inorganic hybrid porous membrane, and the unit cell (parallel hexahedral space in which the particles are filled in the organic-inorganic hybrid porous membrane) unit cell) Calculated as the ratio of the volume of particles actually filled to the volume.

Conventionally, in organic-inorganic composite porous membranes used in separators, inorganic particles are added and dispersed in a binder polymer solution in which a binder polymer is dissolved in a solvent to prepare a slurry, and then the slurry is coated on a porous substrate and dried to form an organic-inorganic material. A separator comprising a composite porous membrane was prepared. According to the conventional method, it is difficult to uniformly control the distribution of the inorganic particles and the binder polymer in the slurry, and also the organic-inorganic composite porous structure is uniformly formed even when the porous substrate is coated and dried. Since it is difficult to control the preparation of the membrane, there have been problems in that the organic- bookkeeping composite porous membrane is not uniformly distributed in the inorganic particles and the binder polymer.

The present inventors attempted to study a method for uniformly distributing the inorganic particles and the binder polymer in order to produce an organic-inorganic composite porous membrane in which the inorganic particles and the binder polymer are uniformly distributed in the organic-inorganic composite porous membrane.

In general, when the spherical particles are filled as much as face centered cubic (fcc), the filling rate is 74%.

The organic-inorganic composite porous membrane according to an embodiment of the present invention uses unit particles in which the surface of the particles is surrounded by a binder polymer, and in this case, the cores are controlled to have a uniform size by using a filter having a predetermined size. The maximum filling rate of the cubic structure may have a filling rate of 60 to 70% close to 74%.

On the other hand, in the conventional organic-inorganic composite porous membrane, the packing density itself is not uniform because it is prepared through a step of coating the substrate using a slurry of inorganic particles, a binder polymer and a solvent and then drying. As a result, in some cases, the binders agglomerate to have a filling rate of 50% or less, and some have a filling rate of about 60%, or the pores themselves are clogged.

The inventors of the present invention, in order to improve the filling rate of the inorganic particles by uniformly distributed inorganic particles and the binder polymer, in order to improve the filling rate of the inorganic particles, the inorganic particles are first prepared unit particles bound by the binder polymer When the unit particles are bound by heat, the inorganic particles and the binder polymer are fixed in the unit particles and then bound by the heat. The present invention has been completed by contemplating that an organic-inorganic composite porous membrane filled with one distribution can be formed.

That is, in the organic-inorganic composite porous membrane according to the present invention, the binder polymer is uniformly disposed using at least one or more particles selected from inorganic particles and organic particles coated with the binder polymer in the first place, and the particles are uniformly uniformly 60 to 70%. It is preferably filled at a filling rate of 65 to 70%. However, in the conventional organic-inorganic composite porous membrane, since it is essentially impossible to control the distribution of the binder polymer uniformly, there is a difference in the content of the binder polymer locally, so that the portion of the filling rate as low as 50% and the relative amount of 60% As a result, parts of the high filling rate are mixed.

In more detail, the binder polymer is present in the whole or part of at least one selected from the inorganic particles and the organic particles, and the particles are bound by the binder polymer.

Hereinafter, an organic-inorganic composite porous membrane for an electrochemical device according to an embodiment of the present invention, characterized in that at least one particle selected from inorganic particles and organic particles is uniformly dispersed, and a method of manufacturing Is not limited to the following method.

Method for producing an organic-inorganic composite porous membrane in the present invention comprises the steps of preparing unit particles, the inorganic particles and at least one selected from at least one particle selected from the organic particles surrounded by a binder polymer; And binding the unit particles by applying heat to the unit particles.

The organic particles refer to particles having a function such as heat resistance due to light weight and particularly excellent strength, and are used as substitutes for inorganic particles. Specific examples of organic materials usable in the present invention include polyethylene (PE), polystyrene (PS), polymethylmethacrylate (PMMA), polyacetal (POM), polyamide (PA), polycarbonate (PC), modified polyphenyl It may be one or more selected from the group consisting of ethylene ether (m-PPE) and poly butylene terephthalate (PBT), but is not limited to the above examples. That is, the organic particles correspond to a material that can replace the inorganic particles used in the organic-inorganic composite porous membrane conventionally used, at least one selected from the inorganic particles and organic particles in the present invention is "inorganic particles" Or alternatives thereof. "

The unit particles according to the present invention may be surrounded by the binder particles of the inorganic particles or substitute particles thereof alone, or may be surrounded by the binder particles of the inorganic particles or substitute particles thereof.

The cross-sectional view of the form of the unit particle one embodiment is described in FIG. 1 below, and the unit particle form is not limited to the form of FIG. 1. Referring to FIG. 1, the inorganic particles included or the substitute particles 1 thereof are surrounded by the binder polymer 2 to form the unit particles 3. The form of the unit particle is not limited.

The unit particles are preferably uniform in shape and size to provide an organic-inorganic composite porous membrane with a uniform distribution. Therefore, according to one embodiment of the present invention, rather than a shear rupturing method for producing irregular particles to produce unit particles having a uniform shape and size, it is possible to induce the unit particle formation in an emulsion form by a continuous process of a uniform pore separation method. Can be.

In this case, the average particle diameter of the unit particles may be from 0.01 to 20 μm, preferably from 0.05 to 10 μm, and when the particles in the above range are applied, a separator having a uniform thickness may be formed. Preferred at

In the organic-inorganic composite porous membrane of the present invention, the inorganic particles used for forming the organic-inorganic composite porous membrane are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as the oxidation and / or reduction reactions do not occur in the operating voltage range (for example, 0 to 5 V on the basis of Li / Li ⁺ ) of the applied electrochemical device. In particular, when inorganic particles having a high dielectric constant are used as the inorganic particles, the ionic conductivity of the electrolyte may be improved by contributing to an increase in the dissociation degree of the electrolyte salt, such as lithium salt, in the liquid electrolyte.

For the above reasons, the inorganic particles preferably comprise high dielectric constant inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Non-limiting examples of inorganic particles having a dielectric constant greater than 5 include BaTiO₃, Pb (Zr, Ti) O₃(PZT), Pb_1-xLa_xZr_1-yTi_yO₃ (PLZT, where 0 <x <1, 0 <y <1), Pb (Mg_1/3Nb_2/3) O₃-PbTiO₃ (PMN-PT), Hafnia (HfO₂), SrTiO₃, SnO₂, CeO₂, MgO, NiO, CaO, ZnO, ZrO₂, Y₂O₃, Al₂O₃, TiO_2,SiC Or mixtures thereof.

In addition, the inorganic particles may be inorganic particles having lithium ion transfer capability, that is, inorganic particles containing lithium elements but having a function of transferring lithium ions without storing lithium. Non-limiting examples of inorganic particles having a lithium ion transfer capacity include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), Lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ (LiAlTiP) _x O _y series glass such as O ₅ (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3) , Li germanium thiophosphate such as Li _3.25 Ge _0.25 P _0.75 S ₄ (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5 ), Lithium nitride such as Li ₃ N (Li _x N _y , 0 <x <4, 0 <y <2), SiS ₂ based glass such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ (Li _x Si P ₂ S ₅ series glass (Li _x P _y S _z , 0 <x, such as _y S _z , 0 <x <3, 0 <y <2, 0 <z <4), LiI-Li ₂ SP ₂ S _5, etc. <3, 0 <y <3, 0 <z <7) or mixtures thereof.

In addition, the organic particles are polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA), polyacetal (POM), polyamide (PA), polycarbonate (PC), modified polyphenylene ether (m) -PPE) and poly butylene terephthalate (PBT) may be at least one selected from the group consisting of, but is not limited to the above examples.

 The size of the inorganic particles or the substitute particles thereof of the organic-inorganic composite porous membrane of the present invention is not limited, but is preferably in the range of 0.001 to 10 µm as much as possible for formation of a uniform thickness of the membrane and proper porosity. If it is less than 0.001㎛ dispersibility is not easy to control the physical properties, if it exceeds 10㎛ the thickness of the organic-inorganic composite porous membrane may increase the mechanical properties, and also due to the excessively large pore size The probability of internal short circuits increases during battery charging and discharging.

In the organic-inorganic composite porous membrane of the present invention, the binder polymer used to form the organic-inorganic composite porous membrane is not particularly limited as a binder polymer commonly used in the art.

Non-limiting examples of binder polymers that can be used include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethyl Methacrylate (polymethylmethacrylate), polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyethylene oxide ), Cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyano Ethyl cellulose ulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, polyimide Styrene (polystyrene), polyethylene (polyethylene) or a mixture thereof. In addition, any material having the above-described characteristics may be used alone or in a mixture thereof. In the present invention, polyvinylidene fluoride-hexafluorofluoropropylene, cyanoethyl polyvinyl alcohol, acrylonitrile styrene butadiene One or more selected from the group consisting of a copolymer and polyethylene can be used, and the binder polymer is preferred in that it is easy to secure adhesion between particles.

The content of the binder polymer in the unit particle may include 1 to 30 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the inorganic particles or the replacement particles thereof. When the content of the binder polymer is less than 1 part by weight, problems such as desorption of inorganic materials may occur. When the content of the binder polymer is more than 30 parts by weight, the binder polymer blocks pores of the porous substrate to increase resistance, and the porosity of the organic-inorganic composite porous membrane is increased. Can be degraded.

As the unit particles prepared as described above are heated, the binder polymer is melted in the unit particles, thereby binding the unit particles to each other. Preferably the heat can be applied at a temperature 5 to 100 ℃ higher than the melting temperature of the binder polymer, it is preferable in that the adhesion between the particles can be secured in the range of the temperature. At this time, the binder polymer located at the outermost part of the unit particles is bound by a slight melting method near the melting temperature.

In the organic-inorganic composite porous membrane, a binder polymer is positioned as a coating layer on part or all of the surface of the inorganic particles or the substitute particles thereof, and the inorganic particles or the substitute particles thereof are connected to each other by the coating layer in close contact with each other. The interstitial volume is formed between the inorganic particles or the substitute particles thereof, and the interstitial volume between the inorganic particles or the substitute particles thereof is empty. To form pores. That is, the binder polymer is attached to each other so that the inorganic particles or the substitute particles thereof are bound to each other, for example, the binder polymer is connected and fixed between the inorganic particles or the substitute particles. In addition, the pores of the organic-inorganic porous composite membrane are pores formed by the interstitial volume between the inorganic particles becomes an empty space, which is a packed structure (closed packed or densely) by the inorganic particles or their replacement particles. packed) is a space defined by the inorganic particles that are substantially interviewed. Through the pores of the organic-inorganic porous composite membrane can provide a path for the lithium ions to move the cell essential to operate the battery.

Components of the organic-inorganic composite porous membrane may further include other additives in addition to the inorganic particles and the binder polymer described above.

More specifically, the organic-inorganic composite porous membrane according to the present invention comprises the steps of preparing a suspension including unit particles in which a single or a group of particles of inorganic particles and at least one selected from organic particles is surrounded by a binder polymer; Applying the suspension; And binding the unit particles and the unit particles by applying heat to the applied suspension.

According to a preferred embodiment of the present invention, the unit particles may be made of uniform unit particles, for example by using the pores of the uniform membrane. For example, a binder polymer in a solvent is mixed with inorganic particles or a substitute particle thereof in a solution, and then passed through a membrane filter having uniform pores and dropped into an aqueous solution containing a surfactant. At this time, the temperature of the aqueous solution is maintained above the solvent boiling point, and solidified immediately after the drop of the solution passed by the membrane filter to form the unit particles. Thus, using the aqueous solution containing unit particles to prepare a coating suspension capable of producing an organic-inorganic composite porous membrane according to the present invention. The suspension may further include other additives in addition to the inorganic particles and the binder polymer described above. The solvent for dissolving the binder polymer is preferably one similar in solubility index to the binder polymer to be used. Non-limiting examples of solvents that can be used include acetone, methanol, ethanol, isopropylalcohol, tetrahydrofuran, methylene chloride, chloroform, Dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or a mixture thereof.

The organic-inorganic composite porous membrane according to the present invention can replace the function as a separator alone. That is, the organic-inorganic composite porous membrane of the present invention can be usefully used as a separator by interposing between the positive electrode and the negative electrode, and according to another aspect of the present invention, according to the present invention between the positive electrode, the negative electrode and the positive electrode and the negative electrode It can provide an electrochemical device comprising an organic-inorganic composite porous membrane according to.

In addition, the organic-inorganic composite porous membrane according to the present invention may be formed on at least one surface of the porous substrate having pores to replace the function as a separator. That is, the organic-inorganic composite porous membrane attached to at least one surface of the porous substrate may be interposed between the positive electrode and the negative electrode as a separator, and according to another aspect of the present invention, the positive electrode, the negative electrode, and the positive electrode between the positive electrode and the negative electrode An electrochemical device having a separator including a substrate and an organic-inorganic composite porous membrane formed on at least one surface of the porous substrate may be provided.

Referring to Figure 2 showing a cross-section of the separator according to an embodiment of the present invention, the separator according to the present invention is a porous substrate 10 and at least one surface of the porous substrate, the inorganic particles or its replacement particles (1) It comprises an organic-inorganic composite porous membrane 11 formed by binding to each other by the binder polymer (2) surrounded on the whole or part of the surface of the particles.

The porous substrate may be a porous polymer film substrate or a porous polymer nonwoven substrate. As is well known as the porous polymer film substrate, a separator made of a porous polymer film made of polyolefin such as polyethylene and polypropylene may be used. Such a polyolefin porous polymer film substrate may have a shutdown function at a temperature of, for example, 80 to 130 ° C. Expression. Of course, a porous polymer film may be manufactured using polymers such as polyester in addition to polyolefin.

In addition, the porous polymer nonwoven fabric may use a polyester such as polyethylene terephthalate (PET).

Examples of porous substrates having usable pores include polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenyl There are porous substrates formed of at least one of lensulfide and polyethylene naphthalene, and in general, any one that can be used as a separator of an electrochemical device can be used. As the porous substrate, both membrane and nonwoven fabrics may be used. The thickness of the porous substrate is not particularly limited, but is preferably 5 to 50 μm, and the pore size and pore present in the porous substrate are also not particularly limited, but are preferably 0.01 to 50 μm and 10 to 95%, respectively.

The electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples thereof include capacitors such as all kinds of primary, secondary cells, fuel cells, solar cells, or supercapacitor devices. In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery among the secondary batteries is preferable.

The electrochemical device may be manufactured according to conventional methods known in the art, and for example, may be manufactured by injecting an electrolyte after assembling the separator described above between an anode and a cathode. .

As an electrode to be applied together with the separator of the present invention, an electrode active material may be manufactured in a form bound to an electrode current collector. Among the electrode active materials, the cathode active material may be a lithium composite oxide, such as lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof. Non-limiting examples of the lithium negative electrode active material may be a conventional negative electrode active material that can be used in the negative electrode of the conventional electrochemical device, in particular lithium metal or lithium alloys, carbon, petroleum coke, activated carbon (activated carbon) Lithium adsorbents such as graphite or other carbons are preferred. Non-limiting examples of the positive electrode current collector is a foil made by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

Electrolyte that may be used in the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- is PF _{6 ^{-, BF 4 -, Cl -}} , Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO ₂ ) Salts containing ions consisting of anions such as ₃ ^- or combinations thereof include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC) , Dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC), gamma butyrolactone or mixtures thereof Some are dissolved or dissociated in an organic solvent, but are not limited thereto.

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

Further, according to another aspect of the invention, the present invention is an electrode current collector; An electrode active material layer formed on at least one surface of the electrode current collector; And an organic-inorganic composite porous membrane formed on the other surface of the electrode active material layer.

Referring to FIG. 3, which shows a cross section of an electrode structure according to an embodiment of the present invention, an electrode structure according to the present invention is formed on an electrode current collector 20, one surface of the electrode current collector, and an electrode active material 5. It is formed on the electrode active material layer 22 and the other surface of the electrode active material layer including, and the inorganic particles or its replacement particles (1) is formed by binding to each other by the binder polymer (2) surrounded on the whole or part of the surface Organic-inorganic composite porous membrane 21.

The organic-inorganic composite porous membrane included in the electrode structure is the same as the organic-inorganic composite porous membrane described above, and more specifically, an electrode structure having an organic-inorganic composite porous membrane formed on an electrode including an electrode current collector and an electrode active material. The manufacturing method of one embodiment is described.

The method of manufacturing an electrode structure according to the present invention includes the steps of preparing a suspension including unit particles, in which at least one selected from inorganic particles and organic particles or a group of particles is surrounded by a binder polymer; Applying the suspension to the other surface of the electrode active material layer formed on at least one surface of the electrode current collector; And binding heat between the unit particles and the unit particles and the electrode active material layer by applying heat to the suspension applied to the electrode active material layer.

In the production of the electrode structure, the suspension is coated on the other side of the electrode active material layer in which the electrode current collector is not formed on the electrode, that is, on the electrode having the electrode active material layer formed on at least one surface of the electrode current collector. .

When the suspension is applied to the electrode active material layer and then heated, the binder polymer is melted in the unit particles, thereby binding the unit particles and the unit particles and the electrode active material layer. At this time, the binder polymer located at the outermost part of the unit particles is bound by a slight melting method near the melting temperature.

The electrode active material layer may have a thickness of 0.5 μm to 200 μm. In the above range, it is possible to perform the function of the electrode active material appropriately for the purpose.

In addition, the thickness of the organic-inorganic composite porous membrane formed on the electrode active material layer may be 0.5 to 50㎛. When the thickness of the organic-inorganic composite porous membrane is within the above range, the organic-inorganic composite porous membrane may be uniformly applied, and may be coated on the electrode active material layer to serve as an insulating layer.

The content of the binder polymer of the organic-inorganic composite porous membrane of the electrode structure is preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight based on 100 parts by weight of the inorganic particles or the replacement particles thereof. When the content of the binder polymer is less than 1 part by weight, the peeling resistance of the organic-inorganic composite porous membrane formed because the binder polymer is low may be weakened. When the content of the binder polymer is more than 30 parts by weight, the content of the binder polymer is The pore size and porosity of the insulating layer formed to increase may be reduced.

The organic-inorganic composite porous membrane according to the present invention may serve as an insulating layer on the electrode, thereby providing an electrode structure including the insulating layer.

The electrode structure prepared as described above may be used in an electrochemical device, and more particularly, the present invention provides an electrochemical device including an anode, a cathode, and an electrolyte, wherein the cathode, the cathode, or the cathode are a manufacturing method according to the present invention. It provides an electrochemical device using the electrode produced by. In the electrochemical device, an organic-inorganic composite porous membrane serving as an insulating layer may be formed on an electrode surface to replace the existing separator.

The electrode current collector may be used as a conventional electrode current collector, and when the electrode is used as a positive electrode, a foil prepared by aluminum, nickel or a combination thereof may be used as the positive electrode current collector. It is not limited to kind. When the electrode is used as a cathode, a foil made of copper, gold, nickel or a copper alloy or a combination thereof may be used, but is not limited to this kind.

The slurry for the electrode active material layer for preparing the electrode active material layer may include an electrode active material, a binder, a solvent, and the like, and may further include a conductive agent and other additives as necessary. As the electrode active material, all of the electrode active materials commonly used may be used, and when the electrode is used as a positive electrode, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide in combination thereof may be used. It is possible but not limited to. In addition, when the electrode is used as a negative electrode, lithium adsorbents or non-carbon materials such as lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite (graphite) or other carbons Furnace metal, metal alloys, etc. may be used, but is not limited thereto.

The electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary cells, fuel cells, solar cells, or capacitors.

As an example of a method of manufacturing an electrochemical device using the electrode prepared as described above, instead of using a conventional polyolefin-based microporous separator, only the electrode having the organic-inorganic composite porous membrane prepared as described above is used. It can be prepared by injecting an electrolyte after assembling through a process such as winding (winding) or stacking (stacking).

In the present invention, the electrolyte injection may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process and the required physical properties of the final product. That is, it may be applied before the assembly of the electrochemical device or the final step of the assembly of the electrochemical device. In addition, since the electrode according to the present invention is an integral type of the separator and the electrode, the separator used in the prior art is not necessarily required, but according to the use and characteristics of the final electrochemical device, the electrode formed with the organic-inorganic composite porous membrane of the present invention is polyolefin-based. It can also be assembled with a microporous separator.

 An electrochemical device manufactured by the above method is preferably a lithium secondary battery, and the lithium secondary battery includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

Example

Preparation of Separator with Organic-Inorganic Composite Porous Membrane

10 wt% of polystyrene polymer was added to methylene chloride and dissolved at 50 ° C. for about 12 hours or more to prepare a binder polymer solution. The alumina powder was added to the binder polymer solution prepared as inorganic particles such that the binder polymer was added so that the weight ratio of the inorganic particles was 10: 1. The mixed solution is passed through a filter having a pore size of 1 μm or less and dropped into an aqueous solution containing Tween 20 as a surfactant. In this case, the temperature of the aqueous solution is maintained at 25 ° C., and the solution dropped into the aqueous solution is solidified immediately after falling, thereby becoming unit particles surrounded by the binder polymer on the surface of the inorganic particles. Thereafter, CMC was added to the aqueous solution as a thickener to prepare a slurry. The slurry thus prepared was coated on both sides of a polyethylene porous film having a thickness of 12 μm (porosity of 45%) by dip coating, and heated to 80 ° C. to obtain a slurry. The outer binder is bound by a slight melting method. In the prepared organic-inorganic composite porous membrane, the filling rate of the inorganic particles was 70% as a result of observing the SEM photograph.

Fabrication of Lithium Secondary Battery

Preparation of Cathode

N-methyl-2, a solvent, was prepared by using carbon powder as a negative electrode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon black as a conductive material, respectively, at 96% by weight, 3% by weight, and 1% by weight. A negative electrode mixture slurry was prepared by adding to Rollidone (NMP). The negative electrode mixture slurry was coated on a copper (Cu) thin film, which is a negative electrode current collector having a thickness of 10 μm, to prepare a negative electrode through drying, and then roll press was performed.

Manufacture of anode

92% by weight of a lithium cobalt composite oxide as a positive electrode active material, 4% by weight of carbon black as a conductive material, and 4% by weight of PVDF as a binder were added to N-methyl-2 pyrrolidone (NMP) as a solvent to slurry a positive electrode mixture. Was prepared. The positive electrode mixture slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having a thickness of 20 μm, and a positive electrode was manufactured by drying, followed by roll press.

Manufacture of batteries

The electrodes prepared above and the separators prepared in the preparation of the separator according to the embodiment were assembled using a stacking method, and ethylene carbonate / ethyl in which 1 M lithium hexafluorophosphate (LiPF ₆ ) was dissolved in the assembled battery. A lithium secondary battery was prepared by injecting a methyl carbonate (EC / EMC = 1: 2, volume ratio) -based electrolyte.

Example 2-Electrode Structure with Organic-Inorganic Composite Porous Membranes

Preparation of Slurry for Organic-Inorganic Composite Porous Membrane

10 wt% of polystyrene polymer was added to methylene chloride and dissolved at 50 ° C. for about 12 hours or more to prepare a binder polymer solution. The alumina powder was added to the binder polymer solution prepared as inorganic particles such that the binder polymer was added so that the weight ratio of the inorganic particles was 10: 1. The mixed solution is passed through a filter having a pore size of 1 μm or less and dropped into an aqueous solution containing Tween 20 as a surfactant. At this time, the temperature of the aqueous solution is maintained at 25 ° C, and the solution dropped into the aqueous solution is solidified immediately after falling, the unit particles are surrounded by the binder polymer on the surface of the inorganic particles. Thereafter, CMC was added as a thickener in the aqueous solution to prepare a slurry.

Preparation of Slurry for Anode Active Material Layer

A slurry for the negative electrode active material was prepared by adding 96% of carbon powder as a negative electrode active material, 3% by weight of CMC-SBR as a binder, and 1% by weight of carbon black as a conductive agent to distilled water (H ₂ O) as a solvent.

Preparation of Slurry for Positive Electrode Active Material Layer

92% by weight of lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 4% by weight carbon black as a conductive agent, and 4% by weight of CMC-SBR as a binder are added to N-methyl-2 pyrrolidone (NMP) as a solvent. A slurry was prepared.

Fabrication of Electrode with Insulation Layer

A copper current collector having a thickness of 15 μm was placed on the copper current collector, and the slurry for the negative electrode active material layer was applied on the copper current collector to dry and pressurized. Then, the slurry for the organic-inorganic composite porous membrane was applied to the outermost binder by applying heat at 80 ° C. Was bound by a slight melting method to prepare an electrode structure including an insulating layer. In the prepared organic-inorganic composite porous membrane, the filling rate of the inorganic particles was 70% as a result of observing the SEM photograph.

Similarly, a positive electrode structure was produced using an aluminum current collector having a thickness of 15 μm and the slurry for the positive electrode active material.

The coated negative electrode and the coated positive electrode prepared as described above were assembled using a stacking method, and a conventional polyolefin-based separator was not used separately. A battery was prepared by injecting an electrolyte solution (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 30/20/50 wt%, 1 mol of lithium hexafluorophosphate (LiPF6)) into the assembled battery. It was.

Comparative Example 1

A polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) polymer was added to acetone at 5% by weight and dissolved at 50 ° C. for at least 12 hours to prepare a binder polymer solution. Al ₂ O ₃ powder was added to the prepared binder polymer solution to a binder polymer / Al ₂ O ₃ = 10/90 weight ratio, and the Al ₂ O ₃ powder was crushed and dispersed using a ball mill for at least 12 hours. Slurry was prepared. The slurry thus prepared was coated on both sides of a polyethylene porous film (porosity 45%) having a thickness of 12 μm by a dip coating method and dried to form an organic-inorganic coating layer, thereby preparing a separator having an organic-inorganic coating layer.

Comparative Example 2

₂ parts by weight of sodium carboxyl methyl cellulose (CMC) and 4 parts by weight of styrene-butadien rubber (SBR) are added to 100 parts by weight of the inorganic particles Al ₂ O ₃ powder, and mixed with distilled water (H ₂ O) as a solvent. It was dissolved to prepare a polymer solution. The polymer solution was crushed and dispersed in Al ₂ O ₃ powder using a ball mill method for at least 12 hours to prepare a slurry for the insulating layer. In addition, a copper current collector having a thickness of 15 μm was placed on the copper current collector, and the slurry for the negative electrode active material layer was applied to the copper current collector to dry and compress. Then, the slurry for the insulating layer was applied to dry and compress the electrode structure including the insulating layer. Prepared.

Experimental Example

Distribution of Inorganic Particles and Polymer Binders in Organic-Inorganic Composite Porous Membranes

By the cross-sectional analysis, the inorganic particles bound to the binder were composed of a uniform pore size as a whole, and calculated with a filling rate of 70% (porosity of 30%).

Claims (20)

At least one particle selected from inorganic particles and organic particles; At least one particle selected from the group consisting of a binder polymer and the inorganic particles and the organic particles is bound to each other by a binder polymer surrounded by the surface of the particles, Organic-inorganic composite porous membrane for an electrochemical device, characterized in that the filling rate of at least one selected from the inorganic particles and organic particles is 60 to 70%. The method of claim 1, The content of the binder polymer is an organic-inorganic composite porous membrane for an electrochemical device, characterized in that 1 to 30 parts by weight based on 100 parts by weight of at least one particle selected from inorganic particles and organic particles. The method of claim 1, The inorganic particles are at least one selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transfer capacity, and mixtures thereof. The method of claim 1, The organic particles are polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA), polyacetal (POM), polyamide (PA), polycarbonate (PC), modified polyphenylene ether (m-PPE) ) And poly butylene terephthalate (PBT) organic-inorganic composite porous membrane for an electrochemical device, characterized in that at least one selected from the group consisting of. The method of claim 1, The binder polymer is polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate. , Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl co-vinyl acetate, polyethylene oxide, cellulose acetate acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, Cyanoethylsucrose (cyanoethylsucrose), pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, polystyrene and polyethylene ( polyethylene) organic-inorganic composite porous membrane for electrochemical device, characterized in that at least one selected from the group consisting of. The method of claim 1, The organic-inorganic composite porous membrane is filled with at least one selected from inorganic particles and organic particles by the binder polymer is connected to each other, thereby forming an interstitial volume between the particles, An organic-inorganic composite porous membrane for an electrochemical device, characterized in that the interstitial volume between the particles has pores formed by empty spaces. The method of claim 1, The organic-inorganic composite porous membrane for an electrochemical device, characterized in that the thickness of 0.5 to 50㎛. Preparing unit particles in which a single or a group of particles of at least one selected from inorganic particles and organic particles is surrounded by a binder polymer; And applying the heat to the unit particles to bind the unit particles to the organic-inorganic composite porous membrane for an electrochemical device. The method of claim 8, Method for producing an organic-inorganic composite porous membrane for an electrochemical device, characterized in that the average particle diameter of the unit particles is 0.01 to 20 ㎛. The method of claim 8, The content of the binder polymer in the unit particles is an organic-inorganic composite porous membrane for an electrochemical device, characterized in that 1 to 30 parts by weight based on 100 parts by weight of at least one particle selected from inorganic particles and organic particles. The method of claim 8, The step of applying heat to the unit particles is a method of manufacturing an organic-inorganic composite porous membrane for an electrochemical device, characterized in that the unit particles are bonded by applying heat to a temperature 5 to 100 ℃ higher than the melting temperature of the binder polymer. . The method of claim 8, The inorganic particles are at least one selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transfer ability, and mixtures thereof. The method of claim 8, The organic particles are polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA), polyacetal (POM), polyamide (PA), polycarbonate (PC), modified polyphenylene ether (m-PPE) And polybutylene terephthalate (PBT) is at least one selected from the group consisting of organic-inorganic composite porous membrane for an electrochemical device. The method of claim 8, The binder polymer is polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate. , Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl co-vinyl acetate, polyethylene oxide, cellulose acetate acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, Cyanoethylsucrose (cyanoethylsucrose), pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, polystyrene and polyethylene ( polyethylene) method for producing an organic-inorganic composite porous membrane for an electrochemical device, characterized in that at least one selected from the group consisting of. The method of claim 8, The organic-inorganic composite porous membrane is filled with at least one selected from inorganic particles and organic particles by the binder polymer is connected to each other, thereby forming an interstitial volume between the particles, Method for producing an organic-inorganic composite porous membrane for an electrochemical device, characterized in that the interstitial volume between the particles become voids to form pores. The method of claim 8, The organic-inorganic composite porous membrane has a thickness of 0.5 to 50㎛ method for producing an organic-inorganic composite porous membrane for an electrochemical device. In the electrochemical device comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, The separator is an electrochemical device, characterized in that the organic-inorganic composite porous membrane according to any one of claims 1 to 7. In the electrochemical device comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, The separator includes a porous substrate having the pores; And an organic-inorganic composite porous membrane according to any one of claims 1 to 7 formed on at least one surface of the porous substrate. Electrode current collectors; An electrode active material layer formed on at least one surface of the electrode current collector; And an organic-inorganic composite porous membrane according to any one of claims 1 to 7 formed on the other surface of the electrode active material layer. In the electrochemical device comprising a positive electrode, a negative electrode and an electrolyte, At least one of the positive electrode and the negative electrode is an electrochemical device, characterized in that the electrode structure according to claim 19.

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