KR101657263B1 - Separator for electrochemical cell and method for preparing the same - Google Patents

Abstract

The present invention relates to a separation membrane for an electrochemical device improved in chemical resistance by modifying polyethersulfone (PES), which is a kind of high performance plastic, with a crosslinking agent and a method for producing the same, The compound is non-reactive with the electrolyte solution and thus can be stably used as a separation membrane for an electrochemical device, and has flame retardancy and self-extinguishing properties.

Description

Separator for electrochemical device and method for manufacturing the same

The present invention relates to a separator for an electrochemical device and a method of manufacturing the separator. More specifically, the present invention relates to a separator for an electrochemical device, and more particularly, To an invention for use as a separation membrane material for chemical devices.

As the demand for batteries as an energy source increases, interest in electrochemical devices capable of charging and discharging is increasing, and in particular, demand and interest in lithium secondary batteries are increasing.

The lithium secondary battery includes an electrode assembly composed of an anode, a separation membrane, and a cathode. The separation membrane is a 10 to 30 탆 thick polymer membrane having a porous structure located between an anode and a cathode, and provides a passageway through which lithium ions can actively move , And also serves to prevent contact between the positive electrode and the negative electrode. In addition, since the mechanical strength of the separator is related to the safety of the battery from an external force, recently, many kinds of materials have been studied as a separator material. One of them is a high performance plastic, also called a super engineering plastic, to be.

High performance plastics are sold in small quantities compared to commodity plastics, but at much higher price per unit weight, and have recently been widely used due to their excellent mechanical strength and high heat resistance.

Polyethersulfone is a kind of amorphous high-performance plastic, which is an amber transparent resin. Polyethersulfone is used for electrical and electronic fields, hydrothermal fields, automobile fields, heat resistant paints and the like because of excellent heat resistance, hydrolysis resistance, creep resistance and chemical resistance. Although polyethersulfone has excellent physical properties required for a separator film material for electrochemical devices such as self-extinguishing and flame retardancy, there is a problem that it dissolves in a solvent used as an electrolyte solution for an electrochemical device The application as a separation membrane material for electrochemical devices was limited.

The present invention provides a separator for an electrochemical device made from a modified polyethersulfone compound that does not react with an electrolyte solution for an electrochemical device and has excellent mechanical properties.

In addition, the present invention provides a method for producing the separation membrane for an electrochemical device.

The present invention also provides an electrochemical device including the separator.

According to one aspect of the present invention, there is provided a separation membrane for an electrochemical device comprising a modified polyethersulfone as a reaction product of a polyethersulfone and a crosslinking agent, wherein pores are formed.

The modified polyethersulfone may comprise the following repeating units linked by a urethane bond:

In the above formula, n is an integer of 1 to 500.

The modified polyethersulfone may have a weight average molecular weight of 1,000 to 50,000.

The separation membrane may have pores having a long diameter (longest diameter) in the range of 0.1 to 70 μm, an air permeability in the range of 100 sec / 100 cc to 1,000 sec / 100 cc, and a porosity in the range of 30 to 60%.

The crosslinking agent may be a diisocyanate compound.

The diisocyanate compound may be one or a mixture of two or more selected from the group consisting of aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate.

The diisocyanate compound may be a mixture of one or more selected from the group consisting of toluene diisocyanate (TDI) represented by the following formula (1a) or (1b) and methylene diphenyl diisocyanate (MDI) represented by the following formula

[Formula 1a]

[Chemical Formula 1b]

(2)

According to an aspect of the present invention, there is provided an electrochemical device comprising an anode, a cathode, a separator, and an electrolyte, wherein the separator is the separator for the electrochemical device.

The electrochemical device may be a lithium secondary battery.

According to one aspect of the present invention, there is provided a process for producing a separator for an electrochemical device, comprising: dissolving a liquid polyethersulfone resin compound in a solvent together with a crosslinking agent and a pore-forming agent to obtain a blend composition; Coating and drying the blend composition obtained above to form a sheet; And a step of extracting the pore-forming agent from the sheet and fixing the pore-forming agent in an open state.

The pore-forming agent may be one or a mixture of two or more selected from polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol and polyacrylic acid.

The blend composition may include 100 parts by weight of a polyethersulfone compound, 0.01 to 50 parts by weight of a crosslinking agent, and 1 to 100 parts by weight of a pore-forming agent.

The modified polyethersulfone compound according to the present invention is non-reactive with an electrolytic solution and thus can be stably used as a separator for electrochemical devices and has excellent flame retardancy. Therefore, the composition containing the compound is useful as a separator material for electrochemical devices Can be used.

Fig. 1 is a photograph taken after the separation membrane of Example 1-1 was stored in the electrolytic solution for one day. Fig.
2 is a photograph taken after storing the separator of Comparative Example 1-1 in the electrolytic solution for 1 day.

The separation membrane for an electrochemical device according to the present invention is based on a modified polyethersulfone produced by a reaction of a polyethersulfone and a crosslinking agent.

According to the present invention, the polyethersulfone is a polyethersulfone having the following repeating units, preferably 20 to 80 wt%, or about 50 wt% of a hydroxy (-OH) group, based on the weight of the polyethersulfone compound Include:

In the above formula, n is an integer of 1 to 500.

According to the present invention, the crosslinking agent is an organic diisocyanate compound containing an NCO group. Specific examples of the organic diisocyanate is an aliphatic diisocyanate, e.g., 1,6-hexamethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 2-ethyl-1,4-butylene diisocyanate, C ₆ Alkylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,4-butylene diisocyanate; Alicyclic diisocyanates such as 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate), 1,4- and 1,3-bis Cyclohexane diisocyanate, 1-methyl-2,4- and -2,6-cyclohexane diisocyanate and the corresponding isomeric mixtures, 4,4'-isocyanatomethyl cyclohexane (HXDI) 2,4'- and 2,2'-dicyclohexylmethane dian cyanate and the corresponding isomer mixtures; And mixtures of aromatic diisocyanates such as 2,4-toluylene diisocyanate, 2,4- and 2,6-toluylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate (TODI ), p-phenylene diisocyanate (PDI), m-, p-xylene diisocyanate (XDI), methylenediphenyldiisocyanate (MDI), 2,4'- and 4,4'- diphenylmethane diisocyanate Mixtures, urethane-modified liquid 4,4'- and 2,4-diphenylmethane diisocyanate, 4,4'-diisocyanato-1,2-diphenylethane (EDI) and 1,5- Isocyanate, isocyanate, m-tetramethyl xylene diisocyanate, p-tetramethyl xylene diisocyanate and 1,5-tetrahydronaphthylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-bicyclohexylmethane diisocyanate, 1,6-hexamethylene diisocyanate. Preferred crosslinking agents are toluene diisocyanate (TDI) represented by the following formula (1a) or (1b) and methylenediphenyldiisocyanate (MDI) represented by the following formula

Formula 1a

1b

(2)

The crosslinking agent is used in an amount of 0.01 to 50 parts by weight or 1 to 10 parts by weight based on 100 parts by weight of the polyether sulfone compound.

According to the present invention, the hydroxy-OH group at the polyether sulfone end is reacted with the -NCO group of the diisocyanate to obtain a modified polyethersulfone comprising the following repeating unit:

In the above formula, n is an integer of 1 to 500.

The modified polyethersulfone containing the repeating unit is non-reactive with an electrolyte solution for an electrochemical device and is not dissolved in an electrolyte solution for an electrochemical device.

In addition, the separation membrane for an electrochemical device according to the present invention is characterized by being a porous separation membrane having pores formed therein. Preferably, the separation membrane for an electrochemical device according to the present invention may have pores having a long diameter (longest diameter) in the range of 0.1 to 70 mu m. Preferably, the separation membrane for an electrochemical device according to the present invention may have an air permeability ranging from 100 sec / 100cc to 1,000 sec / 100cc, and a porosity ranging from 30 to 60%. The thickness of the separation membrane for an electrochemical device according to the present invention is not particularly limited, but is preferably 1 to 100 占 퐉 or 5 to 50 占 퐉.

The separation membrane for an electrochemical device according to the present invention comprises the steps of dissolving a liquid polyethersulfone compound in a solvent together with a crosslinking agent and a pore-forming agent to obtain a blend composition; Coating and drying the obtained blend composition to form a sheet; And a step of extracting and fixing the pore-forming agent from the sheet.

More specifically, the first step of the method for producing a separation membrane for an electrochemical device according to the present invention is a step of dissolving a liquid polyethersulfone compound together with a crosslinking agent and a pore-forming agent in a solvent.

According to the present invention, as the crosslinking agent, an organic diisocyanate compound containing an NCO group is used and is used in an amount of 0.01 to 50 parts by weight or 1 to 10 parts by weight based on 100 parts by weight of the polyether sulfone compound. When the content of the cross-linking agent satisfies this range, resistance to an electrolytic solution is generated, and it can function as a separation membrane without dissolving.

According to the present invention, as the pore-forming agent, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polyacrylic acid, or a mixture of two or more selected from them is used. The pore-forming agent is used in an amount of 1 to 100 parts by weight or 5 to 50 parts by weight based on 100 parts by weight of polyether sulfone. If the content of the pore-forming agent is greater than the lower limit, the network structure can be easily formed to facilitate the production of the porous film. If the content of the pore-forming agent is less than the upper limit value, the pores of the porous film can be sufficiently formed. These linear pore formers should be used to easily extract the solvent and leave vacant space. If the content is appropriate, the pores are connected to each other to make a path through which lithium ions can pass.

According to the present invention, the solvent of the liquid polyethersulfone compound, the crosslinking agent and the pore-forming agent includes 1-methyl-2-pyrrolidone (NMP), acetone, ethanol (ethanol), n - propanol (n -propanol), n - butanol (n -butanol), n - hexane (n -hexane), cyclohexanol (cyclohexanol), acetic acid (acetic acid), ethyl acetate (ethyl acetate) Diethyl ether, dimethyl formamide (DMF), dimethylacetamide (DMAc), dioxane, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO) ), Cyclohexane, benzene, toluene, xylene, water, and derivatives thereof. However, the present invention is not limited thereto. It is not. The solvent may be used in an amount sufficient to dissolve the polyethersulfone compound, the crosslinking agent and the pore-forming agent. For example, the solvent may be used in an amount of 50 to 500 parts by weight based on 100 parts by weight of polyether sulfone.

Various additives such as a surfactant, an antioxidant, an ultraviolet absorber, an anti-blocking agent, a pigment, a dye, and an inorganic filler may be added to the composition for preparing a separator for electrochemical device according to the present invention, Can be added.

The above-mentioned dissolution composition can be blended by a conventional method such as kneading and the like used in the art. Although such a method is not particularly limited, stirring using an impeller is preferably carried out between a polyethersulfone compound and a pore- It is preferable from the viewpoint of enhancing the kneading property. The kneading temperature is preferably from 25 to 60 ° C. If the kneading temperature is not lower than 25 ° C, sufficient kneading can be performed more easily. If the kneading temperature is lower than 60 ° C, the constituent components are not decomposed well. The pore-forming agent can be added both to the liquid polyethersulfone compound before the start of dissolution and to the addition of the other solution after the solution is prepared, but the latter is preferable for more uniform kneading.

The second step of the method for producing a separation membrane for an electrochemical device according to the present invention is a step of coating and drying the obtained dissolved composition to form a sheet. Through this process, the blended composition can be made into a uniform and thick sheet.

The third step of the separation membrane production method for an electrochemical device according to the present invention is a step of extracting and fixing the pore-forming agent from the sheet. Water or an organic solvent may be used to extract the porogen. Specific examples of the organic solvent include saturated hydrocarbons such as pentane, hexane and heptane; Chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride; Ethers such as diethyl ether and dioxane; Ketones such as methyl ethyl ketone; Trifluoro _{ethane, C 6 F 14, C 7} F in carbon chain-fluoroalkyl, such as _16; Cyclic hydrofluorocarbons such as C ₅ H ₃ F ₇ ; Hydrofluoroethers such as C ₄ F ₉ OCH ₃ and C ₄ F ₉ OC ₂ H ₅ ; C ₄ F ₉ OCF ₃ , and C ₄ F ₉ OC ₂ F _5, and the like.

The heat setting is performed by thermally setting the sheet at a temperature not higher than the melting point of the polymer after the high temperature stretching for a predetermined time in the state of being subjected to the tension. The heat setting is preferably carried out at a temperature in the range of the melting point of the polymer (-80 ° C) to the melting point (-5 ° C).

The manufacturing method of the present invention may add other processes or modify some processes within the scope of not damaging the effects of the invention, and these should be construed as being included in the scope of the present invention.

According to the present invention, an electrode assembly used in an electrochemical device can be manufactured by laminating a sheet prepared as described above between an anode and a cathode to use as a separator. The electrochemical device includes all devices that perform an electrochemical reaction, and specific examples include capacitors such as all kinds of primary, secondary, fuel cell, solar cell, or super-capacitor devices. Particularly, 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 is preferable.

The positive electrode and the negative electrode to be used together with the separator of the present invention are not particularly limited, and the electrode active material may be bound to an electrode current collector according to a conventional method known in the art.

The positive electrode is prepared, for example, by coating a positive electrode current collector with a mixture of a positive electrode active material, a conductive agent and a binder (positive electrode mixture), and drying the positive electrode current collector. If necessary, a filler may be further added to the mixture .

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 -x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide represented by the formula LiNi _{1 - x} MxO ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); Formula _{LiMn 2 - x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon or a surface of aluminum or stainless steel Treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The conductive agent is usually added in an amount of 1 to 50% by weight based on the total weight of the positive electrode material mixture containing the positive electrode active material. Such a conductive agent is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component which assists in binding of the active material and the conductive agent and bonding to the current collector, and is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene -Propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The negative electrode is manufactured by applying and drying the negative electrode active material on the negative electrode collector, and if necessary, may include some or all of the positive electrode material mixture components as described above.

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

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1 - x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4 , and Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The non-aqueous electrolyte containing a lithium salt is composed of a nonaqueous electrolyte and lithium. As the non-aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte and the like are used.

Examples of the nonaqueous electrolytic solution include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane , Tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid Diethyl ether, tetrahydrofuran derivative, ether, methyl pyrophosphate, ethyl propionate, methyl propionate, ethyl propionate, ethyl propionate, And the like can be used.

Examples of the organic solid electrolyte include organic polymers such as polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, Polymers containing ionic dissociation groups, and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt may be dissolved in the non-aqueous electrolyte. For example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

For the purpose of improving charge / discharge characteristics, flame retardancy, etc., non-aqueous electrolytes may be used in the form of, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like are added It is possible. In some cases, a halogen-containing solvent such as carbon tetrachloride, ethylene trifluoride and the like may be further added to impart nonflammability, and a carbon dioxide gas may be further added to improve high temperature storage characteristics.

As a process for applying the separation membrane according to an embodiment of the present invention, a lamination, stacking and folding process of a separation membrane and an electrode can be performed in addition to a general winding process.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

Example  1-1: Preparation of Membrane

100 parts by weight of polyethersulfone (BASF, Ultrason ^R E 2020 SR) were dissolved in 100 parts by weight of N-methyl-2-pyrrolidone to make a liquid. 5 parts by weight of toluene diisocyanate and 10 parts by weight of polyvinylpyrrolidone 10 And the mixture was coated on a glass plate with a thickness of 100 μm on a coater using a knife, followed by drying at 100 ° C. for 1 hour. Thereafter, the obtained sheet was immersed in water and then separated from the glass plate, and the pore-forming agent was removed. The sheet was dried to obtain a final separation membrane.

Example  1-2: The lithium secondary battery  Produce

(1) Preparation of positive electrode

90 parts by weight of lithium manganese oxide as a positive electrode active material, 5 parts by weight of carbon black as a conductive material and 5 parts by weight of polyvinylidene fluoride (PVdF) as a binder were dissolved in N-methyl-2-pyrrolidone (NMP) To 40 parts by weight of a positive electrode active material slurry. The positive electrode active material slurry was applied to an aluminum (Al) thin film of a positive electrode current collector having a thickness of 100 탆 and dried to prepare a positive electrode, followed by roll pressing.

(2) Manufacture of cathodes

95 parts by weight, 2 parts by weight and 3 parts by weight, respectively, of carbon powder as a negative electrode active material, PVdF as a binder and carbon black as a conductive material were added to 100 parts by weight of N-methyl-2-pyrrolidone (NMP) To prepare a negative electrode active material slurry. The negative electrode active material slurry was applied to a copper (Cu) thin film as an anode current collector having a thickness of 90 탆 and dried to form a negative electrode, followed by roll pressing.

(3) Production of lithium secondary battery

The unit cells were assembled by stacking the positive and negative electrodes prepared in the above-described manner and the separator prepared in Example 1-1. Then, an electrolyte (ethylene carbonate (EC) / dimethyl carbonate (DMC) = 5/5 (volume ratio) and 1 mole of lithium hexafluorophosphate (LiPF ₆ )) was injected to prepare a lithium secondary battery.

Comparative Example  1-1: Preparation of Membrane

A separator for an electrochemical device was prepared in the same manner as in Example 1-1, except that toluene diisocyanate was not added.

Comparative Example  1-2: The lithium secondary battery  Produce

A lithium secondary battery was produced in the same manner as in Example 1-2 except that the separator of Comparative Example 1-1 was used.

Experimental Example  1: Safety evaluation

The separator obtained in Example 1-1 and Comparative Example 1-1 was stored in an electrolyte consisting of EC / DMC = 5/5 at 25 占 폚 for one day, that is, for 24 hours, taken out from the electrolyte solution, The results are shown in Fig. 1 and Fig.

As can be seen from FIG. 1, in the case of the separator of Example 1-1, crosslinking occurred in the polyethersulfone compound and the chemical resistance was secured and the separator form was not deformed. However, in Comparative Example 1-1 using polyether sulfone Of the electrolyte membrane reacted with the electrolytic solution partially and melted.

The separators of Example 1-1 and Comparative Example 1-1 were weighed and placed in a lattice net (size: 40 μm), immersed in an electrolyte solution, taken out after one day (ie, 24 hours), washed with the same electrolyte solution And dried at 120 ° C for 1 hour and then weighed. These measurement values were substituted into the following equation (1) to calculate the membrane weight loss ratio (%) due to dissolution of electrolyte solution, and the results are shown in Table 1 below.

[Equation 1]

Weight loss rate (%) = [(W _o -W _t )] / W _o * 100

W _o : Initial sample weight

W _t : t Sample weight after elapsed and after drying

The separator of Example 1-1 The separator of Comparative Example 1-1 Weight loss rate (%) 0.05 4.52

From the above results, it was found that the separation membrane of Example 1-1 had little reactivity with the electrolyte solution and was almost insoluble in the electrolyte solution, whereas the separation membrane of Comparative Example 1-1 had a part of polyethersulfone dissolved in the electrolyte solution to cause weight loss see.

Claims (12)

In the form of a sheet formed from a modified polyethersulfone modified with a diisocyanate,
Wherein pores are formed in the sheet,
Wherein the pores are formed by pore-forming agent extraction from a mixture of one or more selected from polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol and polyacrylic acid
Membranes for electrochemical devices.
The method according to claim 1,
Wherein the modified polyethersulfone comprises the following repeating unit connected by a urethane bond:

In the above formula, n is an integer of 1 to 500.
The method according to claim 1,
Wherein the modified polyethersulfone has a weight average molecular weight of 1,000 to 50,000.
The method according to claim 1,
Wherein the separation membrane has a pore having a longest diameter in the range of 0.1 to 70 mu m, an air permeability in the range of 100 sec / 100cc to 1,000 sec / 100cc, and a porosity in the range of 30 to 60%.
delete The method according to claim 1,
Wherein the diisocyanate compound is a mixture of at least one member selected from the group consisting of an aliphatic diisocyanate, an alicyclic diisocyanate, and an aromatic diisocyanate.
The method according to claim 1,
Wherein the diisocyanate compound is a mixture of one or more selected from the group consisting of toluene diisocyanate (TDI) represented by the following formula (1a) or (1b) and methylenediphenyldiisocyanate (MDI) represented by the following formula Separator for electrochemical device:
Formula 1a

1b

(2)

1. An electrochemical device comprising an anode, a cathode, a separator, and an electrolyte,
Wherein the separation membrane is a separation membrane for an electrochemical device according to any one of claims 1 to 4, 6 and 7.
9. The method of claim 8,
Wherein the electrochemical device is a lithium secondary battery.
A pore-forming agent formed from a liquid polyethersulfone resin compound, a diisocyanate crosslinking agent, and a mixture of one or more selected from polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, and polyacrylic acid, Kneading at 60 DEG C to obtain a blend composition;
Molding the blend composition obtained above into a sheet; And
Extracting the pore-forming agent from the sheet with water or an organic solvent and heat-setting the pore-forming agent;
The method of manufacturing a separation membrane for an electrochemical device according to claim 1,
delete 11. The method of claim 10,
Wherein the blend composition comprises 100 parts by weight of a polyether sulfone compound, 0.01 to 50 parts by weight of a crosslinking agent, 1 to 100 parts by weight of a pore-forming agent, and 50 to 500 parts by weight of a solvent.

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