KR20160043768A - Organic/inorganic composite separator, method for manufacturing the same and electrochemical device containing the same - Google Patents

Abstract

Disclosed are an organic/inorganic composite separation layer, a manufacturing method thereof, and an electrochemical device comprising the same. According to an embodiment of the present invention, provided is the organic/inorganic composite separation layer, comprising: a separation layer; and an inorganic particle binding material arranged on at least one between the inside and a surface of the separation layer and made of a plurality of inorganic particles bound by a cross-linking polymer binder. The purpose of the present invention is to provide an organic/inorganic composite separation layer having an even pore size to improve ion conductivity.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic / inorganic composite separator, a method for producing the same, and an electrochemical device including the same. BACKGROUND ART [0002]

One embodiment of the present invention relates to an organic-inorganic hybrid membrane, a method for producing the same, and an electrochemical device including the same.

Recently, as the importance of energy storage and conversion technology has increased, interest in various kinds of batteries has been greatly increased. Among them, lithium secondary batteries capable of charging and discharging have attracted considerable attention.

One of the important components that determine the characteristics of a battery in a lithium secondary battery is a separator in which an electrolyte is impregnated to function as a passage for lithium ions.

The properties required for such a separator should not cause chemical stability and deterioration at the electrolyte and the electrode interface in the charging and discharging region of the battery, and the porosity and porosity of the electrolyte to ensure the smooth movement of lithium ions in the electrolyte. Size is required. In addition, the separator should have good wettability of the electrolyte, and the electrolyte content should be maintained. Wettability is critical for improving productivity in the electrolyte injection process, and persistent electrolyte content affects battery life.

In addition, the separator must have thermal stability. It is preferable that the separator shrinks when the temperature of the separator becomes higher than the softening temperature of the separator due to a temperature rise inside the cell, and less heat shrinkage occurs at a higher temperature.

As described above, the separation membrane for a secondary battery must have a uniform pore structure so as to exhibit desired ion conductivity by satisfying the function of ion passage, and besides basic ion conductivity, thermal stability and excellent electrolyte wettability should be provided.

Accordingly, researches on separators for lithium secondary batteries having a uniform pore structure and excellent ionic conductivity and excellent thermal stability and electrolyte wettability have been actively conducted.

An embodiment of the present invention is to provide an organic-inorganic hybrid membrane having a uniform pore structure and improved thermal stability and electrolyte wettability, a method for producing the same, and an electrochemical device including the same.

An embodiment of the present invention is a method of manufacturing a semiconductor device, including: a separation membrane; And at least one of an inner surface and a surface of the separation membrane, wherein the inorganic particle composite comprises a plurality of inorganic particles bonded by a crosslinked polymeric binder.

The separation membrane may include a polymer nonwoven fabric, a polyolefin separation membrane, or a combination thereof.

The polymeric nonwoven fabric may be made of a material selected from the group consisting of polyethylene terephthalate, polyimide, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, Polyetherimide, poly-paraphenylene terephthalamide, polyvinylpyrrolidone, polyacrylic acid, polyvinylalcohol, and derivatives thereof and mixtures thereof And at least one selected from the group consisting of

The average diameter of the pores in the polymer nonwoven fabric may be 0.001 to 100 mu m.

The polyolefin-based separation membrane may be subjected to an interface treatment by plasma irradiation, UV irradiation, or grafting of a hydrophilic group.

The graft of the hydrophilic group is obtained by graft-polymerizing a polymer monomer having a hydrophilic group to the polyolefin-based separation membrane. The polymer monomer may have a hydroxyl group (-OH), a sulfonic acid group (-SO ₃ H), a carboxy group (-COOH) -NH ₂ ), ammonium (-NH ₄ ), derivatives thereof, and mixtures thereof.

The inorganic particles are _{SiO 2, Al 2 O 3,} TiO 2, BaTiO 3, Li 2 O, LiF, LiOH, Li 3 N, BaO, Na 2 O, Li 2 CO 3, CaCO 3, LiAlO 2, SrTiO 3, At least one selected from the group consisting of SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiC, and derivatives thereof and mixtures thereof.

The average diameter of the inorganic particles may be 0.001 to 10 mu m.

The crosslinked polymeric binder may be a photopolymerizable crosslinked polymeric binder or a thermally polymerized crosslinked polymeric binder.

The photopolymerizable crosslinked polymeric binder may be at least one selected from the group consisting of polyethylene glycol diacrylate, triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol aethoxylate dimethacrylate Such as bisphenol A ethoxylate dimethacrylate, Carboxyethyl acrylate, Methyl cyanoacrylate, Ethyl cyanoacrylate, Ethyl cyano ethoxyacrylate, At least one selected from the group consisting of cyanoacrylic acid, hydroxyethyl methacrylate, hydroxypropyllacrylate, derivatives thereof, and mixtures thereof.

The thermally polymerizable crosslinked polymeric binder may be selected from the group consisting of acrylic acid, polyacrylic acid, carboxymethylcellulose, alginate or a polymer having a carboxyl group by synthesis, A group consisting of polyvinyl alcohol, an agarose, a polymer having a hydroxy functional group by synthesis, a derivative thereof, and a mixture thereof, including a hydroxy functional group (-OH) And may include at least one selected.

The inorganic particle binder may include 50 to 99 wt% of the inorganic particles and 1 to 50 wt% of the crosslinked polymer binder.

The organic / inorganic hybrid composite membrane may be a three-dimensional super lattice structure.

The average diameter of the pores of the organic / inorganic hybrid separator may be 0.001 to 10 탆.

The porosity of the organic / inorganic hybrid membrane may be 30 to 90% by volume.

The thickness of the organic / inorganic hybrid separator may be 10 to 60 탆.

Another embodiment of the present invention is a method for preparing a polymer electrolyte membrane, comprising: dispersing a plurality of inorganic particles in a solution containing a crosslinked polymer monomer; Applying a solution in which the inorganic particles are dispersed to at least one of the interior and the surface of the separation membrane; Curing the separation membrane to which the solution is applied; And drying the cured separator. The present invention also provides a method of manufacturing the organic / inorganic composite separator.

The crosslinked polymer monomer may be a photo-crosslinking monomer or a heat-crosslinking monomer.

The photocrosslinking monomer may be selected from the group consisting of polyethylene glycol diacrylate, triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol aethoxylate dimethacrylate ( Bisphenol A ethoxylate dimethacrylate, Carboxyethyl acrylate, Methyl cyanoacrylate, Ethyl cyanoacrylate, Ethyl cyano ethoxyacrylate, Cyanoacrylate, At least one selected from the group consisting of acrylic acid, cyanoacrylic acid, hydroxyethyl methacrylate, hydroxypropyllacrylate, derivatives thereof, and mixtures thereof.

The thermally crosslinked monomer may be at least one selected from the group consisting of acrylic acid, poly acrylic acid, carboxymethylcellulose, alginate, or a polymer having a carboxyl group by synthesis, Selected from the group consisting of polyvinyl alcohol, agarose, or a polymer having a hydroxy functional group by synthesis, and derivatives thereof and a mixture thereof, including a hydroxy functional group (-OH) It can be one.

Applying the solution in which the inorganic particles are dispersed to at least one of the inside and the surface of the separation membrane, the coating may be performed by dip coating, die coating, roll coating, comma coating, or a combination thereof.

Another embodiment of the present invention is directed to a positive electrode comprising: a positive electrode; cathode; A separator disposed between the anode and the cathode; And an electrolyte for impregnating the anode, the cathode, and the separation membrane. The separation membrane is the above-described organic-inorganic hybrid membrane.

The electrochemical device may be a lithium secondary battery or a supercapacitor.

The ionic conductivity of the organic / inorganic hybrid membrane according to one embodiment of the present invention, the method for producing the same, and the electrochemical device including the same can be improved due to the uniform pore size.

Also, according to another embodiment of the present invention, the organic-inorganic hybrid membrane, the method of manufacturing the same, and the electrochemical device including the same may improve the stability of the organic binder in the high-temperature electrolytic solution by introducing the high- , And hence the high-temperature characteristics can be improved.

1 is a schematic view of a lithium secondary battery module including an organic / inorganic composite separator according to an embodiment of the present invention.
2 is an FT-IR graph measured in Experimental Example 1 to confirm whether or not the crosslinking binder is crosslinked.
FIG. 3 is a graph showing the electrochemical stability of the lithium secondary battery manufactured in Experimental Example 1 and Comparative Experimental Examples 1 and 2. FIG.
4 is a schematic diagram for comparing the heat resistance improvement effect of the composite separator prepared in Experimental Example 1 and the composite separator prepared using the linear polymer binder used in Comparative Example 2. FIG.
5 shows the results of observing the surface of the nonwoven fabric used as a separator base material in Experimental Example 1 and Comparative Experimental Example 2 with a scanning electron microscope (SEM).
6 shows the results of observation of the surface of the composite membrane prepared in Experimental Example 1 by scanning electron microscope.
7 is a partial enlarged view of Fig.
8 shows the result of observation of the surface of the composite membrane prepared in Comparative Experimental Example 2 with a scanning electron microscope.
Fig. 9 is a partially enlarged view of Fig. 8. Fig.
10 is a graph showing changes in air permeability after immersing the composite separator prepared in Experimental Example 1 and Comparative Experimental Example 2 in an electrolytic solution at 60 ° C for 5 hours.
FIG. 11 shows the results of observing changes in the pore structure of the surface of the composite membrane prepared in Experimental Example 1 after impregnating the electrolyte membrane at 60 ° C. for 5 hours.
12 shows the results of observing changes in the pore structure of the surface after impregnating the composite membrane prepared in Comparative Experimental Example 2 with electrolyte at 60 ° C for 5 hours.
FIG. 13 is a graph showing the results of evaluating the self-discharge characteristics of the composite separator prepared in Experimental Example 1 and the composite separator after impregnating the composite separator in an electrolytic solution at 60.degree. C. for 5 hours, and then using each lithium rechargeable battery.
14 is a graph showing the results of evaluating the self-discharge characteristics of the composite separator prepared in Comparative Experimental Example 2 and the composite separator after impregnating the composite separator in an electrolytic solution at 60 ° C for 5 hours and then preparing each of them with a lithium secondary battery.
15 is a graph showing the results of observing the discharge capacity while changing the charging / discharging current rate of the lithium secondary battery coin cell manufactured in Experimental Example 1, Comparative Experimental Example 1, and Comparative Experimental Example 2 to 1.0C / 1.0C.
16 shows the result of observing the discharge capacity in a high-temperature (60 ° C) chamber while setting the charging / discharging current rate of the lithium secondary battery coin cell manufactured in Experimental Example 1 and Comparative Experimental Example 2 at 1.0 C / Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

As used herein, unless otherwise defined, "combination" means mixing or copolymerization. "Copolymerization" means block copolymerization or random copolymerization, and "copolymer" means block copolymer or random copolymer.

An embodiment of the present invention is a method of manufacturing a semiconductor device, including: a separation membrane; And at least one of an inner surface and a surface of the separation membrane, wherein the inorganic particle composite comprises a plurality of inorganic particles bonded by a crosslinked polymeric binder.

More specifically, in one embodiment of the present invention, the separation membrane may include a polymer nonwoven fabric, a polyolefin separation membrane, or a combination thereof.

The fiber of the polymer nonwoven fabric is not particularly limited as long as it is a polymer capable of producing a nonwoven fabric, but it is advantageous to secure the thermal stability of the organic / inorganic composite separator by selecting it from among the heat resistant polymers. Non-limiting examples thereof include polyethylene terephthalate, polyimide, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, Polyetherimide, poly-paraphenylene terephthalamide, polyvinylpyrrolidone, polyacrylic acid, polyvinylalcohol, derivatives thereof, and the like. And a mixture thereof.

The polyolefin-based separation membrane may be subjected to surface treatment through plasma or UV irradiation, grafting of a polymer monomer having a hydrophilic group, or the like in order to improve mutual adhesion with a crosslinked polymer binder to be described later. The graft polymer monomer having a hydrophilic group used in the surface treatment is a hydroxyl group (-OH), sulfonic acid group (-SO ₃ H), carboxyl group (-COOH), amino group (-NH _2), ammonium (-NH _4), And a derivative thereof, and a mixture thereof.

The nonwoven fabric includes a plurality of nonuniformly distributed pores, and may have a porosity of 50 vol% or more, because the nonwoven fabric is formed of an aggregate of three-dimensionally irregularly and continuously connected fibers. The average diameter of the pores of the nonwoven fabric may be 0.001 to 100 mu m, and more specifically 0.001 to 1 mu m.

However, since the pores of the nonwoven fabric are irregularly distributed, in order to control the pore size and the porosity of the organic-inorganic hybrid membrane, the inorganic particles are densely packed in the pores of the nonwoven fabric via the crosslinked polymer binder.

In one embodiment of the present invention, the inorganic particle binder is located on at least one of the inside and the surface of the above-mentioned separation membrane, and a plurality of inorganic particles are bound by a crosslinked polymer binder.

More specifically, the inorganic particle binder may include 50 to 99 wt% of inorganic particles and 1 to 50 wt% of a crosslinked polymer binder. When the inorganic particles and the crosslinked polymeric binder are contained within the above range, the bonding force between the inorganic particles can be secured easily and the pores can be uniformly formed.

Here, the inorganic particles are not particularly limited as long as they can control the pores of the organic-inorganic hybrid material separation membrane uniformly and improve heat resistance. For example, the inorganic particles may be an inorganic oxide-based materials, non-limiting examples include SiO _2, Al ₂ O _3, TiO _2, BaTiO _3, Li ₂ O, LiF, LiOH, Li ₃ N, BaO, Na ₂ O, At least one selected from the group consisting of Li ₂ CO ₃ , CaCO ₃ , LiAlO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiC, .

The average diameter of the inorganic particles may be 0.001 to 10 mu m, and more specifically 0.001 to 1 mu m. When the average diameter of the inorganic particles is within the above range, the dispersibility in the coating solution is improved and the occurrence of problems in the coating process can be minimized. In addition, the physical properties of the final separation membrane can be made uniform, the inorganic particles can be uniformly distributed in the pores of the nonwoven fabric to improve the mechanical properties of the nonwoven fabric, and the advantage of easily controlling the pore size of the organic- .

The crosslinked polymeric binder can prevent the inorganic particles from easily falling from the nonwoven fabric fibers by the above-mentioned interconnection and adhesion between the inorganic particles. The crosslinked polymeric binder can stably maintain the adhesion of the inorganic particles at high temperature and adhesion to the nonwoven fabric, as compared with the linear polymeric binder due to the net structure polymer after crosslinking, and forms a highly heat resistant organic / inorganic composite can do.

In this case, the crosslinked polymeric binder may be a photopolymerizable crosslinked polymeric binder or a thermally crosslinked polymeric binder prepared by photopolymerizing or thermally polymerizing thermally crosslinked or crosslinked monomer dissolved in an aqueous or organic solvent.

The photopolymerizable crosslinked polymeric binder may be selected from the group consisting of polyethyleneglycol diacrylate, triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol aethoxylate dimethacrylate, Acrylate, Bisphenol A ethoxylate dimethacrylate, Carboxyethyl acrylate, Methyl cyanoacrylate, Ethyl cyanoacrylate, Ethyl cyano ethoxyacrylate, , At least one photopolymerizable polymer selected from the group consisting of cyanoacrylic acid, hydroxyethyl methacrylate, hydroxypropylacrylate, derivatives thereof, and mixtures thereof, It may be to include a nomeo.

The thermally polymerizable crosslinking binder may be selected from, for example, acrylic acid including carboxyl functional group (-COOH), polyacrylic acid, carboxymethylcellulose, alginate, A polymer having a hydroxyl functional group, a polyvinyl alcohol containing one hydroxyl group (-OH), an agarose, or a polymer having a hydroxy functional group by synthesis, And at least one selected from the group consisting of a mixture of the thermoplastic polymer monomer and the thermoplastic polymer monomer.

The organic / inorganic hybrid membrane according to one embodiment of the present invention may have a super lattice structure in which inorganic particles are bound between polymer nonwoven fabrics by a crosslinked polymer binder. Therefore, the diameter and porosity of the pores or interstitial volumes of the organic / inorganic composite membrane can be controlled within a desired range by controlling the weight ratio of the inorganic particles and the crosslinked polymeric binder to uniformly coating the pores between the nonwoven fibers.

At this time, the average diameter of the pores of the organic / inorganic hybrid separator may be in the range of 0.001 to 10 탆, more specifically 0.001 to 1 탆. When the average diameter of the pores of the organic / inorganic hybrid separator is within the above range, gas permeability and ion conductivity can be controlled within a desired range. In addition, when the battery is manufactured using the organic / inorganic hybrid separator, It is possible to eliminate the possibility of an internal short circuit of the battery by the battery.

The porosity of the organic / inorganic hybrid membrane may be in the range of 30 to 90% by volume. When the porosity is within the above range, the ion conductivity can be increased and the mechanical strength can be enhanced.

The thickness of the organic / inorganic hybrid composite membrane may be in the range of 10 to 60 탆, more specifically 10 to 40 탆. When the thickness is within the above range, the energy density can be enhanced.

Another embodiment of the present invention is a method for preparing a polymer electrolyte membrane, comprising: dispersing a plurality of inorganic particles in a solution containing a crosslinked polymer monomer; Applying a solution in which the inorganic particles are dispersed to at least one of the interior and the surface of the separation membrane; Curing the separation membrane to which the solution is applied; And drying the cured separator. The present invention also provides a method of manufacturing the organic / inorganic composite separator.

First, in the step of dispersing a plurality of inorganic particles in a solution containing the crosslinked polymer monomer, the crosslinked polymer monomer may be a photo crosslinking monomer or a heat crosslinking monomer.

The photocrosslinking monomer may be selected from the group consisting of polyethylene glycol diacrylate, triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol aethoxylate dimethacrylate ( Bisphenol A ethoxylate dimethacrylate, Carboxyethyl acrylate, Methyl cyanoacrylate, Ethyl cyanoacrylate, Ethyl cyano ethoxyacrylate, Cyanoacrylate, At least one selected from the group consisting of acrylic acid, cyanoacrylic acid, hydroxyethyl methacrylate, hydroxypropyllacrylate, derivatives thereof, and mixtures thereof.

The thermally crosslinked monomer may be at least one selected from the group consisting of acrylic acid, poly acrylic acid, carboxymethylcellulose, alginate, or a polymer having a carboxyl group by synthesis, Selected from the group consisting of polyvinyl alcohol, agarose, or a polymer having a hydroxy functional group by synthesis, and derivatives thereof and a mixture thereof, including a hydroxy functional group (-OH) It can be one.

The crosslinked polymeric monomer may be used as a crosslinked polymeric binder for uniformly dissolving the crosslinked polymer monomer in an aqueous or organic solvent together with an initiator as a solution to bind a plurality of inorganic particles. When the crosslinked polymeric binder is used, the binder in a net form in the final composite separator can be uniformly distributed among the inorganic particles.

And applying a solution in which the inorganic particles are dispersed to at least one of the inside and the surface of the separator, a conventional method known in the art can be used. For example, dip coating, die coating, , Roll coating, comma coating, or a combination thereof, but is not limited thereto.

Another embodiment of the present invention is directed to a positive electrode comprising: a positive electrode; cathode; A separator disposed between the anode and the cathode; And an electrolyte for impregnating the anode, the cathode, and the separation membrane. The separation membrane is the above-described organic-inorganic hybrid membrane.

Here, the electrochemical device may be a lithium secondary battery or a supercapacitor.

1 is a schematic view of a lithium secondary battery module including an organic / inorganic composite separator according to an embodiment of the present invention.

1, a lithium secondary battery 100 according to an embodiment of the present invention includes a positive electrode 112, a negative electrode 113, and a composite separator 1 disposed between the positive electrode 112 and the negative electrode 113, (Not shown) impregnated into the positive electrode 112, the negative electrode 113 and the composite separator 1, the battery container 120, and the sealing member 140 for sealing the battery container 120, As shown in FIG.

More specifically, the lithium secondary battery 100 includes a composite separator 1 interposed between a positive electrode 112 including a positive electrode active material and a negative electrode 113 including a negative electrode active material, and a positive electrode 112, a negative electrode 113 and the composite separator 1 are accommodated in a battery container 120 and an electrolyte for a lithium secondary battery is injected and the battery container 120 is sealed to form pores in the composite separator 1, And then impregnating the electrolyte.

The battery container 120 may have various shapes such as a cylindrical shape, a square shape, a coin shape, and a pouch shape. In the case of the cylindrical lithium secondary battery, the anode 112, the cathode 113, and the composite separator 1 are stacked in this order, and then wound into a spiral wound state in a battery container 120 to constitute a lithium secondary battery .

Since the structure and manufacturing method of the lithium secondary battery are well known in the art, a detailed description thereof will be omitted in order to avoid an ambiguous interpretation of the present invention.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example

Experimental Example  1: Manufacture of organic and inorganic composite membranes and lithium secondary batteries

A nonwoven fabric (thickness = 16 탆, porosity = 70%) made of poly-paraphenylene terephthalamide (PPTA) was used as the heat resistant separator substrate to which the inorganic particles and the crosslinked polymer binder were to be introduced . A solution (solid content = 1.7 wt%) in which SiO ₂ having an average diameter of 100 nm in average particle size and carboxyethyl acrylate (CEA) was dissolved in ethanol as a crosslinked polymer monomer was used. The solid content means the remaining components except for the solvent (ethanol), which means the content of the CEA monomer dissolved in ethanol.

Hydroxy 3-phenoxypropyl acrylate (HPPA) was used as an initiator of the crosslinked polymeric binder.

SiO ₂ having a particle size of 100 nm was added to the CEA solution prepared above and dispersed for 1 hour to prepare a coating solution having a solid content of 15.3% by weight. The solid content means the remaining elements except for the solvent (ethanol), and here, it means the amount including up to SiO ₂ added in addition to the CEA binder dissolved in ethanol.

The PPTA nonwoven fabric was immersed in the coating solution and dip coated. Then, the solvent was evaporated, and the photocrosslinking monomer was photopolymerized by irradiating ultraviolet rays to prepare a composite membrane having a thickness of about 35 μm.

(LiCoO ₂ ) 95 wt% as a cathode active material, 2 wt% of carbon black as a conductive material, and 3 wt% of polyvinylidene fluoride (PVDF) as a binder in a solvent N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry. The anode mixture slurry was applied to an aluminum (Al) thin film of a cathode current collector having a thickness of 20 μm and dried to produce a cathode, followed by roll pressing.

Graphite as a negative electrode active material, styrene butadiene rubber (SBR), carboxymethyl cellulose sodium (CMC) as a binder and carbon black as a conductive material were dispersed in 96 wt%, 1 wt%, and 1 wt% wt.% and 2 wt.%, respectively, to water as a solvent 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 20 mu m and dried to produce a negative electrode, followed by roll pressing.

The nonaqueous electrolytic solution was prepared by dissolving LiPF _{6 in} an organic solvent (EC: DEC = 1: 1 (v: v)) to a concentration of 1M.

The positive electrode, negative electrode, and composite separator thus prepared were put into a coin type cell, and then a nonaqueous electrolyte was injected to prepare a coin cell of a lithium secondary battery.

Comparative Experimental Example  1: Preparation of Membrane and Lithium Secondary Battery

A lithium secondary battery coin cell was manufactured in the same manner as in Experimental Example 1, except that a polyolefin film (thickness: about 20 μm, manufactured by Tonen Co., Ltd.) was used as a separator in Experimental Example 1.

Comparative Experimental Example  2: Preparation of separator and lithium secondary battery

A lithium secondary battery coin cell was prepared in the same manner as in Experimental Example 1, except that a composite separator was prepared by using polyvinylidene fluoride hexafluoropropylene, which is a linear polymer binder, as a binder in Experimental Example 1 .

evaluation

Evaluation 1: Property evaluation

First, the peak change of the FT-IR measured to confirm the crosslinking of the crosslinking monomer in Experimental Example 1 is shown in FIG.

Referring to FIG. 2, it was confirmed that the peak (1620 ~ 1640 cm ^-1 ) corresponding to C = C double bonds disappeared in the composite membrane after crosslinking.

FIG. 3 is a graph showing the electrochemical stability of the lithium secondary battery manufactured in Experimental Example 1 and Comparative Experimental Examples 1 and 2. FIG.

Referring to FIG. 3, the lithium secondary battery manufactured in Experimental Example 1 exhibited the best electrochemical stability as compared with Comparative Examples 1 and 2.

4 is a schematic diagram for comparing the heat resistance improvement effect of the composite separator prepared in Experimental Example 1 and the composite separator prepared using the linear polymer binder used in Comparative Example 2. FIG.

Referring to FIG. 4, the composite membrane produced in Experimental Example 1 includes an interstitial volume introduced by inorganic particles distributed between nonwoven fabrics made of nonwoven fabric and nonwoven fibers via a crosslinking binder. The crosslinking binder may be a polymer having a net structure prepared by photopolymerizing a crosslinking monomer.

The composite separator prepared in Experimental Example 1 retains the organic coating layer and maintains the pores even after being impregnated with the high temperature electrolytic solution because of the advantage of the crosslinked binder that can be uniformly distributed in a net form by being crosslinked between the inorganic particles. Accordingly, the lithium secondary battery including the composite separator has safety at high temperature, and particularly can suppress internal short-circuits.

Referring to FIG. 4, in the composite separator prepared in Comparative Experimental Example 2, the coating layer is retained by the adhesion of the linear polymer between the inorganic particles, and depending on the characteristics of the linear polymer binder dissolved in the high temperature electrolytic solution, The organic coating layer can not be maintained afterwards. Accordingly, the lithium secondary battery including the composite separator exhibits unstable behavior at high temperatures, and in particular, an internal short circuit may occur.

On the other hand, the thickness of the composite separator prepared in Experimental Example 1 is 35 탆, and the thickness of the composite separator prepared in Comparative Experiment 1 is 20 탆. However, the air permeability of the composite membrane of Experimental Example 1 is 46.5 (sec / 100cc), which is significantly improved compared with 240 (sec / 100cc) of the air permeability of the composite membrane of Comparative Experiment Example 1.

On the other hand, the thickness of the composite membrane prepared in Comparative Experiment 2 was 35 μm, and the air permeability at this time was 48.7 (sec / 100 cc), which was very similar to Experimental Example 1.

Evaluation 2: Porcine observation

5 shows the results of observing the surface of the nonwoven fabric used as a separator base material in Experimental Example 1 and Comparative Experimental Example 2 with a scanning electron microscope (SEM).

FIG. 6 shows the result of observation of the surface of the composite separator prepared in Experimental Example 1 with a scanning electron microscope, and FIG. 7 is a partially enlarged view of FIG.

Referring to FIGS. 6 and 7, it can be seen that the composite membrane prepared in Experimental Example 1 exhibited uniform pores among the 100 nm silica nanoparticles.

FIG. 8 shows the result of observation of the surface of the composite separator prepared in Comparative Experiment 2 with a scanning electron microscope, and FIG. 9 is a partial enlarged view of FIG.

Evaluation 3: Heat resistance measurement

10 is a graph showing changes in air permeability after immersing the composite separator prepared in Experimental Example 1 and Comparative Experimental Example 2 in an electrolytic solution at 60 ° C for 5 hours.

FIG. 11 shows the results of observing changes in the pore structure of the surface of the composite membrane prepared in Experimental Example 1 after impregnating the electrolyte membrane at 60 ° C. for 5 hours.

12 shows the results of observing changes in the pore structure of the surface after impregnating the composite membrane prepared in Comparative Experimental Example 2 with electrolyte at 60 ° C for 5 hours.

Referring to FIGS. 10 and 12, it can be seen that the composite separator using the linear polymeric binder prepared in Comparative Experiment Example 2, after impregnation with the high temperature electrolyte, desorbed the coating layer and formed a non-uniform pore structure. As a result, it can be confirmed that the air permeability value is significantly lowered. The air permeability change rate is about 90.6%.

10 and 11, the composite separator using the crosslinked polymeric binder prepared in Experimental Example 1 maintains a uniform pore structure even after impregnation with a high-temperature electrolytic solution, and the difference in the air permeability value is also very small . The air permeability change rate is about 5.4%.

Evaluation 4: Evaluation of self-discharge characteristics

FIG. 13 is a graph showing the results of evaluating the self-discharge characteristics of the composite separator prepared in Experimental Example 1 and the composite separator after impregnating the composite separator in an electrolytic solution at 60.degree. C. for 5 hours, and then using each lithium rechargeable battery.

Referring to FIG. 13, it can be seen that the composite membrane prepared in Experimental Example 1 maintains a uniform pore structure before and after the impregnation in the high-temperature electrolytic solution, thereby suppressing self-discharge.

14 is a graph showing the result of evaluating the self-discharge characteristics of the composite separator prepared in Comparative Experimental Example 2 and the composite separator after impregnating the composite separator in an electrolytic solution at 60 ° C for 5 hours and then each being made of a lithium secondary battery.

Referring to FIG. 14, in the case of the composite separator prepared in Comparative Experiment Example 2, it was confirmed that the composite separator before impregnation with the high-temperature electrolyte suppressed the self-discharge, but after the impregnation into the high temperature electrolytic solution, It can be seen that a pore structure is formed and severe self-discharge occurs.

Therefore, it can be seen that the composite membrane prepared in Experimental Example 1 is structurally stable in the high-temperature electrolyte as compared with the composite membrane prepared in Comparative Example 2. [

Evaluation 5: Evaluation of room temperature battery performance

15 is a graph showing the results of observing the discharge capacity while changing the charging / discharging current rate of the lithium secondary battery coin cell manufactured in Experimental Example 1, Comparative Experimental Example 1, and Comparative Experimental Example 2 to 1.0C / 1.0C.

Referring to FIG. 15, it can be seen that the lithium secondary batteries manufactured in Experimental Example 1 and Comparative Experimental Example 2 have a higher discharge capacity than the lithium secondary batteries manufactured in Comparative Experiment Example 1.

Evaluation 6: Evaluation of high temperature battery performance

16 shows the result of observing the discharge capacity in a high-temperature (60 ° C) chamber while setting the charge / discharge current rate of the lithium secondary battery coin cell manufactured in Experimental Example 1 and Comparative Experimental Example 2 at 1.0 C / Fig.

16, it can be seen that the lithium secondary battery manufactured in Experimental Example 1 has a higher capacity retention ratio than the lithium secondary battery manufactured in Comparative Experiment Example 2. [

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1: composite separator 100: lithium secondary battery
112: anode 113: cathode
120: battery container 140: sealing member

Claims (23)

Separation membrane; And
A plurality of inorganic particles bonded to each other by a crosslinking polymer binder,
/ RTI >
The method according to claim 1,
The separator includes a polymer nonwoven fabric, a polyolefin separator, or a combination thereof.
3. The method of claim 2,
The polymeric nonwoven fabric may be made of a material selected from the group consisting of polyethylene terephthalate, polyimide, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, Polyetherimide, poly-paraphenylene terephthalamide, polyvinylpyrrolidone, polyacrylic acid, polyvinylalcohol, and derivatives thereof and mixtures thereof Wherein at least one of the organic and inorganic composite membranes comprises at least one selected from the group consisting of:
3. The method of claim 2,
Wherein the average diameter of the pores in the polymer nonwoven fabric is 0.001 to 100 탆.
3. The method of claim 2,
Wherein the polyolefin-based separation membrane is subjected to surface treatment by plasma irradiation, UV irradiation, or graft of a hydrophilic group.
6. The method of claim 5,
The graft of the hydrophilic group is obtained by graft polymerization of a polymer monomer having a hydrophilic group to the polyolefin separator,
The polymeric monomer may be a polymeric monomer having a hydroxyl group (-OH), a sulfonic acid group (-SO ₃ H), a carboxyl group (-COOH), an amino group (-NH ₂ ), ammonium (-NH ₄ ) Wherein at least one of the organic and inorganic composite membranes is selected from the group consisting of:
The method according to claim 1,
The inorganic particles are _{SiO 2, Al 2 O 3,} TiO 2, BaTiO 3, Li 2 O, LiF, LiOH, Li 3 N, BaO, Na 2 O, Li 2 CO 3, CaCO 3, LiAlO 2, SrTiO 3, At least one selected from the group consisting of SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiC, and derivatives thereof and mixtures thereof.
The method according to claim 1,
Wherein the inorganic particles have an average diameter of 0.001 to 10 mu m.
The method according to claim 1,
Wherein the crosslinked polymeric binder is a photopolymerizable crosslinked polymeric binder or a thermally polymerized crosslinkable polymeric binder.
10. The method of claim 9,
The photopolymerizable crosslinked polymeric binder may be at least one selected from the group consisting of polyethylene glycol diacrylate, triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol aethoxylate dimethacrylate Such as bisphenol A ethoxylate dimethacrylate, Carboxyethyl acrylate, Methyl cyanoacrylate, Ethyl cyanoacrylate, Ethyl cyano ethoxyacrylate, Which comprises at least one selected from the group consisting of cyanoacrylic acid, hydroxyethyl methacrylate, hydroxypropyllacrylate, and derivatives thereof, and mixtures thereof. Rimak.
10. The method of claim 9,
The thermally polymerizable crosslinked polymeric binder may be selected from the group consisting of acrylic acid, polyacrylic acid, carboxymethylcellulose, alginate or a polymer having a carboxyl group by synthesis, A group consisting of polyvinyl alcohol, an agarose, a polymer having a hydroxy functional group by synthesis, a derivative thereof, and a mixture thereof, including a hydroxy functional group (-OH) And at least one selected from the group consisting of carbon and nitrogen.
The method according to claim 1,
Wherein the inorganic particle binder comprises 50 to 99 wt% of the inorganic particles and 1 to 50 wt% of the crosslinker polymer binder.
The method according to claim 1,
Wherein the organic-inorganic hybrid membrane is a three-dimensional densely packed structure (super lattice).
The method according to claim 1,
Wherein the organic / inorganic hybrid composite membrane has an average pore diameter of 0.001 to 10 mu m.
The method according to claim 1,
Wherein the organic / inorganic hybrid membrane has a porosity of 30 to 90% by volume.
The method according to claim 1,
Wherein the organic / inorganic hybrid membrane has a thickness of 10 to 60 mu m.
Dispersing a plurality of inorganic particles in a solution containing a crosslinking polymer monomer;
Applying a solution in which the inorganic particles are dispersed to at least one of the interior and the surface of the separation membrane;
Curing the separation membrane to which the solution is applied; And
Drying the cured separator
Based composite separator.
18. The method of claim 17,
Wherein the crosslinked polymer monomer is a photo-crosslinking monomer or a thermally crosslinked monomer.
19. The method of claim 18,
The photocrosslinking monomer may be selected from the group consisting of polyethylene glycol diacrylate, triethyleneglycol diacrylate, trimethylolpropaneethoxylate triacrylate, bisphenol aethoxylate dimethacrylate ( Bisphenol A ethoxylate dimethacrylate, Carboxyethyl acrylate, Methyl cyanoacrylate, Ethyl cyanoacrylate, Ethyl cyano ethoxyacrylate, Cyanoacrylate, A method for producing an organic / inorganic hybrid membrane which is at least one selected from the group consisting of acrylic acid, cyanoacrylic acid, hydroxyethyl methacrylate, hydroxypropyllacrylate, derivatives thereof, .
19. The method of claim 18,
The thermally crosslinked monomer may be at least one selected from the group consisting of acrylic acid, poly acrylic acid, carboxymethylcellulose, alginate, or a polymer having a carboxyl group by synthesis, Selected from the group consisting of polyvinyl alcohol, agarose, or a polymer having a hydroxy functional group by synthesis, and derivatives thereof and a mixture thereof, including a hydroxy functional group (-OH) A method for producing an organic / inorganic hybrid membrane.
18. The method of claim 17,
Applying a solution in which the inorganic particles are dispersed to at least one of the interior and the surface of the separation membrane,
Wherein the application is performed by dip coating, die coating, roll coating, comma coating, or a combination thereof.
anode;
cathode;
A separator disposed between the anode and the cathode; And
And an electrolyte that impregnates the anode, the cathode, and the separator,
The separator is an organic / inorganic hybrid separator according to any one of claims 1 to 16.
23. The method of claim 22,
Wherein the electrochemical device is a lithium secondary battery or a supercapacitor.

Images