KR100332678B1 - Composition for Novel Polymer Electrolytes Based on the Porous Membrane and Manufactering Method Thereof - Google Patents

Abstract

The present invention relates to a novel polymer electrolyte composition in which a liquid electrolyte is supported in a porous polymer membrane, and a method of manufacturing the same.

The present invention is a new polymer electrolyte prepared by coating a thin layer of a polymer having excellent compatibility with the liquid electrolyte on the surface and the micropore of the porous polymer membrane. It exhibits conductive properties, excellent mechanical properties and electrochemical stability, and excellent charge and discharge characteristics when applied as a polymer electrolyte for lithium polymer secondary batteries.

Description

Composition for Novel Polymer Electrolytes Based on the Porous Membrane and Manufactering Method Thereof}

The present invention relates to a novel polymer electrolyte composition and a method for producing the same. More specifically, polyethylene, polypropylene, vinylidene fluoride, copolymer of vinylidene fluoride and nucleus fluoropropylene, copolymer of vinylidene fluoride and trifluoroethylene, vinylidene fluoride and tetrafluoroethylene Copolymers of vinylidene fluoride and hexafluoropropylene, vinylidene fluoride, and the like on the surface of the porous membrane based on the copolymer, polyimide, polysulfone, polyurethane, polystyrene, polyvinyl chloride, cellulose and the like; Vinylidene fluoride-based polymers such as copolymers of trifluoroethylene, copolymers of vinylidene fluoride and tetrafluoroethylene, or polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethyl methacrylate Latex, polybutylacrylate, polybutylmeth Acrylate-based polymers such as acrylates or polymers such as polyacrylonitrile, polyvinylacetate, polyethylene oxide, and polypropylene oxide, or copolymers thereof, or blends thereof may be used as aluminum oxide, lithium aluminum oxide, silica, zeolite, or the like. After coating a polymer solution prepared by mixing with an inorganic substance, a liquid electrolyte prepared by adding a salt such as lithium perchlorate and lithium hexafluorophosphate to a mixed solvent such as ethylene carbonate, propylene carbonate, and dimethyl carbonate is injected into the liquid electrolyte. A new polymer electrolyte was stably supported inside the micropores of the porous membrane.

With the rapid development of the electrical, electronics, telecommunications and computer industries, the demand for high performance and high safety secondary batteries has been gradually increasing. Secondary batteries are also required to be lighter and smaller. In addition, the necessity of the development of electric vehicles to solve this problem has increased as the need for a new type of energy supply and demand caused by the depletion of oil and environmental pollution such as air pollution and noise caused by the mass distribution of automobiles. There is a demand for development of a battery having a high power and a high energy density. In order to meet such demands, one of the high-performance, next-generation advanced new batteries, which has been attracting the most attention recently, is a lithium polymer battery (LPB). LPB is largely composed of an anode, a polymer electrolyte, and a cathode, and lithium, carbon, etc. are used as the anode active material, and the polymer electrolyte is composed of polymers, salts, non-aqueous organic solvents, and other additives. The positive electrode active material is composed of a transition metal oxide, a metal chalcogen compound, a conductive polymer, and the like.

Conventional lithium ion batteries (LIBs) using liquid electrolytes have raised safety problems, and methods of mounting electrode materials and safety devices to supplement them have been developed. However, manufacturing costs are high and large secondary batteries There is a problem that is difficult to apply. On the contrary, LPB using a polymer electrolyte can be manufactured at a lower cost, can be adjusted in size or shape as desired, and has a strong energy density per unit weight. Therefore, the flexible thin film LPB can be developed as a power source for electric vehicles because it is easy to develop high voltage and large capacity batteries by lamination as well as portable cordless electronic products. In order to commercialize LPB having such excellent advantages, many studies have been conducted to develop polymer electrolytes that satisfy excellent ion conduction properties, electrochemical stability, and interface characteristics with electrodes. Initially, research has been conducted on solvent-free polymer electrolytes prepared by adding salt to polyethylene oxide, polypropylene oxide, and melting in a co-solvent (see European Patent No. 78505, US Patent No. 5,102,752). Due to the problem of very low conductivity, organic solvents such as ethylene carbonate and propylene carbonate are dissolved in a polymer such as polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, polyvinylidene fluoride together with salt and cosolvent. Studies on gel polymer electrolytes prepared in the form of a film and exhibiting high ionic conductivity of 10 ⁻³ S / cm or more (KM Abraham et al., J. Electrochem. Soc., 142, 1789, 1995) ). However, the gel polymer electrolyte has a lower ion conductivity than the liquid electrolyte, and it is impossible to reduce the thickness of the electrolyte to the level of the separator of the lithium ion battery at this stage, and there is a problem in that high rate discharge characteristics are inferior when applied to the battery. In addition, many problems have been raised in the process related to the automation process such as special process conditions and removal of cosolvents when applied to LPB process.

The present invention is a thin coating of the surface and the micropore of the porous membrane used as a separator in a lithium ion battery using a polymer having excellent compatibility with the liquid electrolyte, and then injecting the liquid electrolyte to form a liquid electrolyte inside the micropores of the porous membrane. It aims at producing a new polymer electrolyte by carrying it stably. Since the polymer electrolyte is filled with the liquid electrolyte in the micropores of the polymer membrane, and both sides of the membrane are coated with the polymer electrolyte, the ionic conductivity can be obtained higher than that of the conventional gel polymer electrolyte, and the mechanical properties are also superior to those of the conventional gel polymer electrolyte. Do. In addition, due to the polymer electrolyte coated on the inside of the micropores and the surface of the membrane, the supported liquid electrolyte can be stably maintained in the polymer membrane without exuding, and also has an advantageous process condition due to the post-injection of the electrolyte in the manufacturing process.

1 illustrates a structure of a new polymer electrolyte in which a liquid electrolyte is supported in a porous polymer membrane of the present invention.

Figure 1 (a) is seen in cross section.

FIG. 1 (B) is an enlarged view of the micropore portion shown by the circle of FIG. 1 (a).

Figure 2 shows the ion conduction characteristics with the temperature of the polymer electrolyte.

Figure 3 shows the interfacial resistance of the polymer electrolyte with the lithium electrode.

The new polymer electrolyte composition in which the liquid electrolyte is supported in the porous polymer membrane of the present invention comprises a polymer of component (b) having good affinity with liquid electrolyte on the surface of the porous polymer membrane and the micropores of the component (a). After dissolving and coating together with the inorganic material represented by), a liquid electrolyte comprising a component (d) and a component (e) is injected into the micropores, a new polymer electrolyte composition in which a liquid electrolyte is supported in a porous polymer membrane.

The porous polymer membrane of component (a) is a polyethylene, polypropylene, polysulfone, polyimide, polyvinylidene fluoride having a porosity of 20 to 70%, a pore diameter of 0.1 to 5 µm and a thickness of 10 to 50 µm. Polymer membranes or copolymers of vinylidene fluoride and hexafluoropropylene based on polymers or copolymers thereof, such as polyurethane, polystyrene, polyvinyl chloride, cellulose, nylon or blends thereof, vinylidene fluoride and tri It is a polymer film of 1 type chosen from the polymer film which has a porous structure based on the copolymer of fluoroethylene, the copolymer of vinylidene fluoride, tetrafluoroethylene, etc.

In addition, the polymer of component (b) is a polyvinylidene fluoride having a molecular weight of 10,000 to 1,000,000, a copolymer of vinylidene fluoride and hexafluoropropylene having a composition of 1 to 99 mol% of hexafluoropropylene, and trifluoro Copolymers of vinylidene fluoride having 1 to 99 mol% of ethylene and trifluoroethylene and copolymers of vinylidene fluoride having 1 to 99 mol% of tetrafluoroethylene and tetrafluoroethylene Polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polybutyl acrylate, polybutyl of one polymer selected from vinylidene fluoride series polymer or molecular weight of 10,000 to 1,000,000 Acrylate-based polymers such as methacrylate, polyacrylonitrile, polyvinylacetate, polyethyl Oxide, a polypropylene oxide such as a polymer or a copolymer or a polymer of one selected from these blends.

The inorganic material of component (c) uses 1 type of inorganic material chosen from aluminum oxide, lithium aluminum oxide, silica, zeolite, and talc which is 1-100 weight% based on a polymer.

The liquid electrolyte of component (d) is 1 to 1000% by weight of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, gamma butyrolactone, ethyl methyl carbonate, dimethoxyethane, diethoxyethane, 2- One or more mixtures selected from methyltetrahydrofuran are used.

The liquid electrolyte of component (e) is selected from lithium perchlorate, lithium hexafluorophosphate, lithium triplate, lithium bistrifluoromethylsulfonylimide and lithium tetrafluoroborate salt, which is 1 to 100% by weight based on the polymer. One salt is used.

Meanwhile, a method of preparing a composition of a new polymer in which a liquid electrolyte is supported in a porous polymer membrane using the above-mentioned composition is as follows.

After immersing the polymer in the surface and the inside of the porous polymer membrane with the inorganic material, and drying it for 24 hours at a temperature of less than 240 ℃, and after coating the surface of the dried membrane with a solution in which the polymer and inorganic dissolved again 240 Drying at a temperature of less than 24 ℃ for 24 hours, and the porous polymer membrane prepared as described above is prepared by being supported with a liquid electrolyte in a mixed solvent in an argon gas atmosphere better than an inert gas atmosphere.

In the above mixed solvent, a mixture of ethylene carbonate and dimethyl carbonate 1: 1 mol is used, and the liquid electrolyte is a mol of liquid prepared by dissolving lithium salt in a mixed solvent of ethylene carbonate and dimethyl carbonate 1: 1 mol. The electrolyte is supported on the polymer membrane at 200 wt% based on the polymer matrix.

Hereinafter, the present invention will be described by the following examples. However, these examples do not limit the technical scope of the present invention.

<Example 1>

Polyethylene-based porous membrane was immersed in a dilute solution of tetrahydrofuran in which polymethyl methacrylate and silica were dissolved together and dried, and the surface of the dried membrane was coated with a thick solution prepared by dissolving polymethyl methacrylate and silica again. After drying. At this time, the thickness of the polymer film coated inside the micropores is within 5㎛, the thickness of the coating film on the surface of the polymer film is within 10㎛. The porous polymer membrane thus prepared is transferred into a glove box in an argon atmosphere to support a 1 mol liquid electrolyte prepared by adding lithium hexafluorophosphate to a mixed solvent of ethylene carbonate and dimethyl carbonate 1: 1 mol (mol) to prepare a polymer electrolyte. At this time, the amount of the supported liquid electrolyte is 200wt% based on the polymer matrix. The polymer electrolyte film was adhered to a stainless steel electrode, sealed with polyethylene-coated aluminum, and then ion conductivity was measured.

<Example 2>

A polymer electrolyte was prepared in the same manner as in Example 1, except that a polypropylene-based porous membrane and a copolymer of acrylonitrile and methyl methacrylate were used. And ionic conductivity was measured.

<Example 3>

Except for using a copolymer of vinylidene fluoride and hexafluoropropylene and polyvinylacetate in a weight ratio of 8: 2 as a coating material having the same composition and composition as in Example 1 above. The mixture was used and the polymer electrolyte was prepared in the same manner and the ionic conductivity was measured.

<Example 4>

A mixture having the same composition and composition as in Example 1 was used except that polyimide was used as the porous polymer membrane. A polymer electrolyte was prepared in the same manner and ionic conductivity was measured.

Example 5

A mixture having the same composition and composition as in Example 1 was used except that polysulfone was used as the porous polymer membrane, and a polymer electrolyte was prepared in the same manner and ionic conductivity was measured.

Comparative Example

Gel polymer electrolytes having the same composition and content of liquid electrolyte as in Example 1 based on the copolymer of vinylidene fluoride and hexafluoropropylene were prepared and ion conductivity was measured.

<Example 6>

Table 1 shows the results of measuring the interfacial resistance of the polymer electrolytes shown in Examples 1, 2, 3, 4, and 5 using lithium electrodes.

Table 1 Measurement of Interface Resistance According to Examples

Example Supported Liquid Electrolyte (wt%) Ion Conductivity (S / cm), 25 ℃ Interface Resistance 2 × 2cm (Ω) Example 1 250 4.8 × 10 ^-3 5 Example 2 300 5.5 × 10 ^-3 3 Example 3 230 4.3 × 10 ^-3 7 Example 4 240 4.4 × 10 ^-3 6 Example 5 320 5.3 × 10 ^-3 1.5 Comparative example 250 8.8 × 10 ^-4 45

From Table 1, the polymer electrolyte according to the present invention has an impregnation rate of 230% or more and an ion conductivity of 4.3 × 10 ⁻³ S / cm or more, which is generally superior to the comparative example, and the interface resistance to the lithium electrode is higher than that of the comparative example. It is small, and it turns out that the various characteristics as a polymer electrolyte are very excellent.

As shown in FIGS. 1 (a) and 1 (b), the cross-sectional structure of the polymer electrolyte of the present invention is easy to inject the electrolyte into the micropores because a polymer having excellent compatibility with the liquid electrolyte is coated in the micropores. In addition, the injected liquid electrolyte can be stably supported in the polymer membrane. In addition, the polymer electrolyte coated on the surface of the polymer membrane prevents the electrolyte from seeping into the surface of the membrane. Figure 2 shows the ion conduction characteristics for the temperature range from the low temperature to room temperature of the polymer electrolyte of Example 1. It contained about 250% by weight based on the weight of the polymer, and showed excellent room temperature ion conductivity of 4.8 × 10 ^-3 S / cm, and high temperature even at low temperature of -25 ° C. It can be seen that it exhibits higher ionic conduction properties than gel polymer electrolytes having the same composition and content of the same liquid electrolyte based on the copolymer of ropropylene. Figure 3 shows the interfacial resistance with the lithium negative electrode of the polymer electrolyte prepared by the above method can be expected to exhibit excellent interfacial properties due to very small interfacial resistance value. Therefore, the polymer electrolyte prepared according to the present invention may be usefully used as a material of the polymer electrolyte for lithium polymer secondary batteries.

Claims (9)

In the polymer electrolyte, after dissolving and coating the polymer of the component (b) having a good affinity with the liquid electrolyte together with the inorganic material represented by the component (c) on the surface of the porous polymer membrane of the component (a) and inside the micropores, A new polymer electrolyte composition in which a liquid electrolyte is supported in a porous polymer membrane, characterized by injecting a liquid electrolyte comprising components (d) and (e) into the micropores. The method of claim 1, wherein the porous polymer membrane of component (a) has a porosity of 20 to 70%, a pore diameter of 0.1 to 5 mu m and a thickness of 10 to 50 mu m, polyethylene, polypropylene, polysulfone, polyimide, poly Polymer membranes or copolymers of vinylidene fluoride and hexafluoropropylene based on polymers such as vinylidene fluoride, polyurethane, polystyrene, polyvinyl chloride, cellulose, nylon or blends thereof or blends thereof, vinylidene A liquid electrolyte in the porous polymer membrane, characterized in that the polymer membrane is one selected from a polymer membrane having a porous structure based on a copolymer of fluoride and trifluoroethylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, and the like. New Supported Polymer Electrolyte Composition The polymer of component (b) is a mixture of vinylidene fluoride and hexafluoropropylene having a molecular weight of 10,000 to 1,000,000 polyvinylidene fluoride and a composition of hexafluoropropylene of 1 to 99 mol%. Copolymer, copolymer of vinylidene fluoride having 1 to 99 mol% of trifluoroethylene and trifluoroethylene, and vinylidene fluoride and tetrafluoroethylene having 1 to 99 mol% of tetrafluoroethylene Polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polybutyl, selected from polymers of vinylidene fluoride series such as copolymers of Acrylate-based polymers such as acrylate and polybutyl methacrylate, polyacrylonitrile, polyvinylacetate New polymer electrolyte composition in which a liquid electrolyte is supported in a porous polymer membrane, characterized in that the polymer is one or more selected from polymers such as polyethylene oxide, polypropylene oxide, copolymers thereof, or blends thereof. 2. The porous polymer membrane according to claim 1, wherein the inorganic material of component (c) is one inorganic material selected from aluminum oxide, lithium aluminum oxide, silica, zeolite and talc, which is 1 to 100% by weight based on the polymer. New Polymer Electrolyte Composition Supported with Liquid Electrolyte The liquid electrolyte of component (d) according to claim 1, wherein the liquid electrolyte of component (d) is 1 to 1000% by weight based on the polymer, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, gamma butyrolactone, ethyl methyl carbonate, dimethoxyethane, A novel polymer electrolyte composition in which a liquid electrolyte is supported in a porous polymer membrane, characterized in that the mixture is one or more selected from diethoxyethane and 2-methyltetrahydrofuran. The liquid electrolyte of component (e) according to claim 1, wherein the liquid electrolyte of component (e) is 1 to 100% by weight of lithium perchlorate, lithium hexafluorophosphate, lithium triflate, lithium bistrifluoromethylsulfonylimide and lithium tetra A novel polymer electrolyte composition in which a liquid electrolyte is supported in a porous polymer membrane, characterized in that the salt is one salt selected from fluoroborate salts. Immersing and drying the polymer in the solution in which the polymer is dissolved together with the inorganic material on the surface and the inside of the porous polymer membrane using the composition as recited in claim 1, and again coating the surface of the dried membrane with a solution in which the polymer and the inorganic solution are dissolved. And a method of preparing a new polymer composition in which the liquid electrolyte is supported in the porous polymer membrane, wherein the porous polymer membrane prepared as described above is supported with the liquid electrolyte in a mixed solvent under an argon atmosphere. 8. The method of claim 7, wherein the mixed solvent is mixed with ethylene carbonate and dimethyl carbonate 1: 1 mol. 8. The liquid electrolyte of claim 7, wherein the liquid electrolyte is formed by dissolving a 1 mol liquid electrolyte prepared by dissolving lithium salt in the mixed solvent of claim 8 on the polymer membrane at 200 wt% based on the polymer matrix. Method for preparing a composition of supported new polymer