Electrolyte membrane and electrochemical device comprising same

Abstract

Disclosed is an electrolyte membrane comprising: a porous support including a polyolefin; and an electrolyte polymer impregnated in at least some of the pores of the porous support, wherein at least some functional groups of the electrolyte polymer are lithium-substituted.

Description

Electrolyte membrane and electrochemical device including the same

[0001] This invention relates to an electrolyte membrane and an electrochemical device including the same.

[0002] Lithium-ion batteries are widely used as power sources for various electric products requiring miniaturization and lightweight design, such as smartphones, laptops, and tablet PCs. As their application fields expand to include medium and large-sized batteries for smart grids and electric vehicles, there is a demand for the development of lithium-ion batteries with high capacity, long lifespan, and high stability.

[0003] Conventional lithium secondary batteries use liquid electrolytes, which have excellent ion conductivity but have poor stability due to risks such as ignition or explosion caused by physical shock or high temperatures. In particular, there is a need to further improve stability to utilize them in electric vehicles and ESS that use large quantities of lithium secondary batteries.

[0004] To address these issues, research on next-generation lithium-ion batteries using solid electrolytes is being actively conducted, primarily at universities. Inorganic electrolytes are a representative type of solid electrolyte. In particular, these inorganic electrolytes have the advantage of being able to replace separators due to their characteristics.

[0005] However, solid electrolyte membranes formed by combining an inorganic electrolyte with a binder have the disadvantage of being thicker and having lower ion conductivity compared to conventional separators.

[0006] Another example of a solid electrolyte is a gel-type electrolyte formed by combining a polyethylene oxide-based polymer with a lithium salt. However, gel-type electrolytes have the disadvantages of inferior physical strength, poor heat resistance due to a low polymer melting point, and reduced ion conductivity at room temperature and high temperatures due to a tendency toward crystallization and resistance to ion movement.

[0007] The details described in this specification are devised in consideration of the problems of the aforementioned prior art, and one purpose is to provide an electrolyte membrane that has a thin thickness, excellent mechanical strength, and is capable of conducting lithium ions.

[0008] According to one aspect, an electrolyte membrane is provided comprising: a porous support comprising a polyolefin; and an electrolyte polymer impregnated in at least some of the pores of the porous support; wherein at least some of the functional groups of the electrolyte polymer are lithium substituted.

[0009] In one embodiment, the polyolefin may include a first polyolefin having a weight-average molecular weight (Mw) of 700,000 to 2,000,000 and a second polyolefin having a weight-average molecular weight (Mw) of 30,000 to 700,000.

[0010] Meanwhile, the above porous support may further include an inorganic filler.

[0011] Here, the content of the inorganic filler in the porous support may be 10 to 70 weight percent.

[0012] In addition, the average pore size of the porous support may be 20 to 2,000 nm.

[0013] In another embodiment, the porous support may satisfy at least one of the following conditions i) to x): i) thickness 5 to 50 μm; ii) porosity 30 to 90%; iii) air permeability 50 to 300 sec / 100 mL; iv) puncture strength 100 to 500 gf; v) longitudinal (MD) tensile strength 1,500 to 3,000 kgf / cm² 2 ; vi) Transverse (TD) tensile strength 1,000~2,500 kgf / cm 2 ; vii) Longitudinal (MD) tensile elongation 25% or more; viii) Transverse (TD) tensile elongation 25% or more; ix) Longitudinal thermal shrinkage 15% or less at 120°C; x) Transverse thermal shrinkage 15% or less at 120°C.

[0014] Here, the electrolyte polymer may be a lithiated hydrocarbon polymer selected from the group consisting of polysulfone series, poly(ethersulfone) series, poly(thiosulfone) series, poly(etheretherketone) series, polyimide series, polystyrene series, polyphosphazene series, and mixtures of two or more of these.

[0015] Alternatively, the electrolyte polymer may be lithiated with a fluorine-based compound selected from the group consisting of perfluorosulfonic acid, poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, and two or more copolymers or combinations thereof.

[0016] In addition, the above electrolyte membrane has an ionic conductivity of 4.08 × 10⁻⁶ at 25°C. -5 It may exceed S / cm.

[0017] According to another aspect, an electrochemical device comprising the aforementioned electrolyte membrane is provided.

[0018] According to one aspect, it is possible to provide an electrolyte membrane that has a thin thickness, excellent mechanical strength, and is capable of conducting lithium ions.

[0019] The effects of one aspect of this specification are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configurations described in the detailed description or claims of this specification.

[0020] Hereinafter, one aspect of this specification will be described. However, the details described in this specification may be implemented in various different forms and are therefore not limited to the embodiments described herein. Furthermore, to clearly explain one aspect of this specification, parts unrelated to the description have been omitted.

[0021] Throughout the specification, when it is stated that a part is "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other members interposed between them. Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but rather allows for the inclusion of additional components.

[0022] When a range of numerical values ​​is described in this specification, unless a specific range is otherwise described, the value has the precision of significant figures provided according to the standard rules in chemistry for significant figures. For example, 10 includes a range of 5.0 to 14.9, and the number 10.0 includes a range of 9.50 to 10.49.

[0023] electrolyte membrane

[0024] An electrolyte membrane according to one aspect comprises a porous support comprising a polyolefin; and an electrolyte polymer impregnated in at least some of the pores of the porous support; wherein at least some of the functional groups of the electrolyte polymer may be lithium substituted.

[0025] Conventional lithium secondary batteries used a separator to prevent a short circuit where the positive and negative electrodes come into contact.

[0026] In addition, an electrolyte was injected to facilitate the movement of lithium ions between the anode and cathode. However, due to safety issues arising from the use of the electrolyte, technology is being developed to replace the liquid electrolyte with a solid electrolyte.

[0027] Unlike liquid electrolytes, solid electrolytes can perform the role of a separator within the battery itself. Therefore, in all-solid-state batteries that do not use liquid electrolytes, there have been attempts to replace the separator with a solid electrolyte membrane fabricated by mixing the solid electrolyte with a binder to bind them together.

[0028] However, the solid electrolyte membrane has a thickness exceeding 50 μm, making it inadequate in terms of battery energy density. Furthermore, since solid electrolytes have low ionic conductivity, the disadvantages caused by such a thick thickness are even greater.

[0029] To address these issues, hybrid batteries mixing solid electrolytes and liquid electrolytes have been proposed; however, the disadvantage of low energy density caused by the thick film characteristics of the solid electrolyte membrane cannot be resolved.

[0030] Meanwhile, a technology has been proposed to prevent electrolyte leakage by using a gel polymer electrolyte in which a lithium salt and an organic solvent are impregnated into a polymer such as polyethylene oxide (PEO), PAN, PVdF, PMMA, PVdF-HFP, etc.

[0031] However, these gel polymer electrolytes lack mechanical strength and break easily, so there is a problem in that it is difficult to sufficiently guarantee the stability of the battery.

[0032] The above electrolyte membrane can conduct lithium ions by including an electrolyte polymer in which lithium is substituted in at least some of the pores of a porous support.

[0033] In addition, when the above electrolyte membrane is used together with an electrolyte, it can have excellent lithium ion conductivity.

[0034] At the same time, the electrolyte membrane can ensure sufficient stability by including a porous support with excellent mechanical properties. Here, the support may be a type of porous membrane having pores formed inside.

[0035] The above polyolefin may be one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate, ethylene butyl acrylate, and ethylene ethyl acrylate, but is not limited thereto.

[0036] The above polyolefin has a weight-average molecular weight (Mw) of 30,000 to 2,000,000, for example, 30,000, 50,000, 100,000, 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, 850,000, 900,000, 950,000, 1,000,000, 1,050,000, 1,100,000, 1,150,000, 1,200,000, 1,250,000, 1,300,000, 1,350,000, 1,400,000, 1,450,000, 1,500,000, 1,550,000, 1,600,000, 1,650,000, 1,700,000, 1,750,000, 1,800,000, 1,850,000, 1,900,000, 1,950,000, 2,000,000, or a range between two of these values.

[0037] Meanwhile, the above polyolefin may include a first polyolefin having a weight-average molecular weight (Mw) of 700,000 to 2,000,000 and a second polyolefin having a weight-average molecular weight (Mw) of 30,000 to 700,000, but is not limited thereto.

[0038] Here, the weight-average molecular weight (Mw) of the first polyolefin is 700,000, 725,000, 750,000, 775,000, 800,000, 825,000, 850,000, 875,000, 900,000, 925,000, 950,000, 975,000, 1,000,000, 1,025,000, 1,050,000, 1,075,000, 1,100,000, 1,125,000, 1,150,000, 1,175,000, 1,200,000, 1,225,000, 1,250,000, 1,275,000, 1,300,000, 1,325,000, 1,350,000, 1,375,000, 1,400,000, 1,425,000, 1,450,000, 1,475,000, 1,500,000, 1,525,000, 1,550,000, 1,575,000, 1,600,000, 1,625,000, 1,650,000, 1,675,000, 1,700,000, 1,725,000, 1,750,000, 1,775,000, 1,800,000, 1,825,000, 1,850,000, 1,875,000, 1,900,000, 1,925,000, 1,950,000, 1,975,000, 2,000,000, or a range between two of these values, but is not limited thereto.

[0039] In addition, the weight-average molecular weight (Mw) of the second polyolefin is 30,000 to 700,000, for example, 30,000, 50,000, 75,000, 100,000, 125,000, 150,000, 175,000, 200,000, 225,000, 250,000, 275,000, 300,000, 325,000, 350,000, 375,000, 400,000, 425,000, 450,000, 475,000, 500,000, 525,000, 550,000, 575,000, It may be 600,000, 625,000, 650,000, 675,000, 700,000, or a range between two of these values.

[0040] Here, the weight ratio of the first polyolefin and the second polyolefin may be 1 to 9 : 9 to 1, for example, 1 : 9, 1.5 : 8.5, 2 : 8, 2.5 : 7.5, 3 : 7, 3.5 : 6.5, 4 : 6, 4.5 : 5.5, 5 : 5, 5.5 : 4.5, 6 : 4, 6.5 : 3.5, 7 : 3, 7.5 : 2.5, 8 : 2, 8.5 : 1.5, 9 : 1, or a range between two of these values. This can be adjusted by considering the balance of mechanical properties and processability of the electrolyte membrane to be manufactured.

[0041] When the porous support comprises a first polyolefin and a second polyolefin, the first polyolefin and the second polyolefin may each form a discontinuous phase and a continuous phase. In the porous support, the first polyolefin is uniformly dispersed in a matrix composed of the second polyolefin, thereby imparting a substantially uniform affinity to the electrolyte polymer to the entire region along the area and / or thickness direction of the porous support, and accordingly, the impregnation of the electrolyte polymer into the porous support can be improved.

[0042] Meanwhile, the porous support may further include an inorganic filler. If the porous support further includes an inorganic filler, mechanical properties such as puncture strength can be improved.

[0043] The above inorganic filler may be at least one selected from the group consisting of silica (SiO2), TiO2, Al2O3, zeolite, AlOOH, BaTiO2, talc (Talk), Al(OH)3, and CaCO3.

[0044] In one example, the inorganic filler may be a nanoparticle having an average particle size of 10 to 1,000 nm, for example, 10 nm, 25 nm, 50 nm, 75 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, or a range between two of these values, but is not limited thereto.

[0045] Meanwhile, the above-mentioned inorganic filler may be particles with a surface treated to be hydrophobic or hydrophilic. For example, silica (SiO2) may have a hydrocarbon layer formed on its surface consisting of hydrophobic linear hydrocarbon molecules. Since silica itself has hydrophilic properties, it may be coated with linear hydrocarbon molecules, for example, (poly)ethylene, to improve compatibility with hydrophobic polyolefins.

[0046] Here, the content of the inorganic filler in the porous support may be 10 to 70 wt%, for example, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, or a range between two of these values. If the content of the inorganic filler satisfies the aforementioned range, the mechanical strength, acid resistance, chemical resistance, flame retardancy, flexibility, processability, etc. of the porous support may be suitable.

[0047] In such a porous support, the content of the polyolefin may be 30 to 90 wt%, for example, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, or a range between two of these values.

[0048] In addition, the average pore size of the porous support is 20 to 2,000 nm, for example, 20 nm, 25 nm, 50 nm, 75 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, 1050 nm, 1100 nm, 1150 nm, 1200 nm, 1250 nm, 1300 nm, 1350 nm, 1400 nm, 1450 nm, 1500 nm, 1550 nm, 1600 nm, It may be 1650 nm, 1700 nm, 1750 nm, 1800 nm, 1850 nm, 1900 nm, 1950 nm, 2000 nm, or a range between two of these values. The pore size of the porous support may be controlled according to the type and microstructure of the electrolyte polymer. Additionally, selective permeability characteristics may be imparted to the electrolyte membrane by controlling the pore size of the porous support.

[0049] In another embodiment, the porous support and / or the electrolyte membrane may satisfy at least one of the following conditions i) to x): i) thickness 5 to 50 μm; ii) porosity 30 to 90%; iii) air permeability 50 to 300 sec / 100 mL; iv) puncture strength 100 to 500 gf; v) longitudinal (MD) tensile strength 1,500 to 3,000 kgf / cm² 2 ; vi) Transverse (TD) tensile strength 1,000~2,500 kgf / cm 2 ; vii) Longitudinal (MD) tensile elongation 25% or more; viii) Transverse (TD) tensile elongation 25% or more; ix) Longitudinal thermal shrinkage 15% or less at 120°C; x) Transverse thermal shrinkage 15% or less at 120°C.

[0050] The characteristics of the above porous support can have a dominant influence on the mechanical properties of the electrolyte membrane.

[0051] Here, the above condition i) may be a thickness of 5 to 50 μm, for example, 5 μm, 7.5 μm, 10 μm, 12.5 μm, 15 μm, 17.5 μm, 20 μm, 22.5 μm, 25 μm, 27.5 μm, 30 μm, 32.5 μm, 35 μm, 37.5 μm, 40 μm, 42.5 μm, 45 μm, 47.5 μm, 50 μm, or a range between two of these values. If the thickness is excessively thick, the energy density of the battery may be disadvantageous, and if it is too thin, the mechanical properties may be insufficient.

[0052] In addition, the above condition ii) may be a porosity of 30 to 90%, for example, 30%, 32.5%, 35%, 37.5%, 40%, 42.5%, 45%, 47.5%, 50%, 52.5%, 55%, 57.5%, 60%, 62.5%, 65%, 67.5%, 70%, 72.5%, 75%, 77.5%, 80%, 82.5%, 85%, 87.5%, 90%, or a range between two of these values. The amount of electrolyte polymer impregnated can be controlled according to the above porosity.

[0053] Meanwhile, the above condition iii) may be an air permeability of 50 to 300 sec / 100 mL, for example, 50 sec / 100 mL, 75 sec / 100 mL, 100 sec / 100 mL, 125 sec / 100 mL, 150 sec / 100 mL, 175 sec / 100 mL, 200 sec / 100 mL, 225 sec / 100 mL, 250 sec / 100 mL, 275 sec / 100 mL, 300 sec / 100 mL, or a range between two of these values. If the above condition is satisfied, the charge / discharge characteristics of the secondary battery may be excellent.

[0054] In addition, the above condition iv) may be a puncture strength of 100 to 500 gf, for example, 100 gf, 125 gf, 150 gf, 175 gf, 200 gf, 225 gf, 250 gf, 275 gf, 300 gf, 325 gf, 350 gf, 375 gf, 400 gf, 425 gf, 450 gf, 475 gf, 500 gf, or a range between two of these values. If the puncture strength satisfies the above range, it may have a strength suitable for battery application.

[0055] In addition, if the above conditions v) to x) each fall within the following ranges, they can have suitable mechanical properties as an electrolyte membrane.

[0056] v) Longitudinal (MD) tensile strength 1,500 kgf / cm² 2 , 1,600 kgf / cm 2 , 1,700 kgf / cm 2 , 1,800 kgf / cm 2 , 1,900 kgf / cm 2 , 2,000 kgf / cm 2 , 2,100 kgf / cm 2 , 2,200 kgf / cm 2 , 2,300 kgf / cm 2 , 2,400 kgf / cm 2 , 2,500 kgf / cm 2 , 2,600 kgf / cm 2 , 2,700 kgf / cm 2 , 2,800 kgf / cm 2 , 2,900 kgf / cm 2 , 3,000 kgf / cm 2 or a range between two of these values;

[0057] vi) Transverse (TD) tensile strength 1,000 kgf / cm² 2 , 1,100 kgf / cm 2 , 1,200 kgf / cm 2 , 1,300 kgf / cm 2 , 1,400 kgf / cm2 , 1,500 kgf / cm 2 , 1,600 kgf / cm 2 , 1,700 kgf / cm 2 , 1,800 kgf / cm 2 , 1,900 kgf / cm 2 , 2,000 kgf / cm, 2,100 kgf / cm, 2,200 kgf / cm 2 , 2,300 kgf / cm 2 , 2,400 kgf / cm 2 , 2,500 kgf / cm 2 or a range between two of these values;

[0058] vii) Longitudinal (MD) Tensile Elongation 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, 180%, 185%, 190%, 195%, 200%, 205%, 210%, 215%, 220%, 225%, 230%, 235%, 240%, 245%, 250%, or a range between two of these values;

[0059] viii) Transverse (TD) Tensile Elongation 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, 180%, 185%, 190%, 195%, 200%, 205%, 210%, 215%, 220%, 225%, 230%, 235%, 240%, 245%, 250%, or a range between two of these values;

[0060] ix) Longitudinal thermal shrinkage rate at 120℃ of 15%, 14.5%, 14%, 13.5%, 13%, 12.5%, 12%, 11.5%, 11%, 10.5%, 10%, 9.5%, 9%, 8.5%, 8%, 7.5%, 7%, 6.5%, 6%, 5.5%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, or a range between two of these values;

[0061] x) Transverse thermal shrinkage rate at 120℃ 15%, 14.5%, 14%, 13.5%, 13%, 12.5%, 12%, 11.5%, 11%, 10.5%, 10%, 9.5%, 9%, 8.5%, 8%, 7.5%, 7%, 6.5%, 6%, 5.5%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1%, or a range between two of these values.

[0062] The above electrolyte polymer may have lithium ion conductivity, with at least a portion of it substituted with lithium.

[0063] In one example, the electrolyte polymer may have at least some of the functional groups bonded with hydrogen cations, sodium cations, potassium cations, etc., substituted for lithium.

[0064] The above electrolyte polymer can have excellent lithium ion conductivity through lithium substitution.

[0065] The lithium substitution degree of the above electrolyte polymer is 50 to 95%, for example, 50%, 50.5%, 51%, 51.5%, 52%, 52.5%, 53%, 53.5%, 54%, 54.5%, 55%, 55.5%, 56%, 56.5%, 57%, 57.5%, 58%, 58.5%, 59%, 59.5%, 60%, 60.5%, 61%, 61.5%, 62%, 62.5%, 63%, 63.5%, 64%, 64.5%, 65%, 65.5%, 66%, 66.5%, 67%, 67.5%, 68%, 68.5%, 69%, 69.5%, 70%, 70.5%, 71%, 71.5%, 72%, 72.5%, 73%, 73.5%, 74%, 74.5%, 75%, 75.5%, 76%, 76.5%, 77%, 77.5%, 78%, 78.5%, 79%, 79.5%, 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, or a range between two of these values. The term “lithium substitution degree” as used herein can be calculated by the formula n / m, where m is the total number of moles of a plurality of monomers constituting the electrolyte polymer and n is the number of moles of monomers in which one or more functional groups of the electrolyte polymer are substituted with lithium, and for example, if n / m is 1, the lithium substitution degree may be 100%.

[0066] The higher the degree of lithium substitution in the above electrolyte polymer, the higher the ionic conductivity of the electrolyte membrane can be.

[0067] The above electrolyte polymer may be impregnated into at least some of the pores inside the support. Meanwhile, the above electrolyte polymer may additionally be coated on at least some of the surface of the support. In this case, the electrolyte polymer inside the pores and the electrolyte polymer on the surface of the support may be interconnected.

[0068] Meanwhile, when the above electrolyte polymer is coated on at least a portion of the surface of the support, the thickness of the coating layer may be 0.1 to 10 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 5 μm, 10 μm, or a range between two of these values, but is not limited thereto.

[0069] In one example, the electrolyte polymer may include a sulfonated polymer, a fluorine-based compound, or a combination thereof.

[0070] The above support can be hydrophilized and sulfonated to satisfy excellent ion conductivity. The contact angle of the hydrophilized support with water (H2O) may be 15˚ or less, and the absolute value of the zeta potential measured as a negative value (-) on the surface of the porous membrane may be 10mV or more.

[0071] The hydrophilized support can be easily bonded to the electrolyte polymer due to its high affinity with the electrolyte polymer, which is essentially hydrophilic, because the -SO3 groups generated on its surface and the surface of its internal pores are hydrophilic. The bonding strength can also be strengthened, which can significantly improve the durability of the electrolyte membrane, and the loss of hydrophilic groups contained in the support and the electrolyte polymer can be minimized, which can also improve ion conductivity.

[0072] In addition, in one example, the porous support may also have at least a portion of lithium substituted. The -SO3, etc. generated on the surface and the internal pore surface of the porous support may be lithium substituted, thereby having higher lithium ion conductivity and a higher affinity with the electrolyte polymer.

[0073] Here, the electrolyte polymer may be a lithiated hydrocarbon polymer selected from the group consisting of polysulfone series, poly(ethersulfone) series, poly(thiosulfone) series, poly(etheretherketone) series, polyimide series, polystyrene series, polyphosphazene series, and mixtures of two or more of these, but is not limited thereto.

[0074] Alternatively, the above electrolyte polymer may be lithiated with a fluorine-based compound selected from the group consisting of perfluorosulfonic acid, poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, and two or more copolymers or combinations thereof, but is not limited thereto.

[0075] In addition, the above electrolyte membrane has an ionic conductivity of 4.08 × 10⁻⁶ at 25°C. -5 Exceeding S / cm, e.g., 4.1×10⁻⁶ -5 S / cm, 4.5×10 -5 S / cm, 5×10 -5 S / cm, 5.5×10 -5 S / cm, 6×10 -5 S / cm, 6.5×10 -5 S / cm, 7×10 -5 S / cm, 7.5×10 -5 S / cm, 8×10 -5 S / cm, 8.5×10 -5 S / cm, 9×10 -5 S / cm, 9.5×10 -5 S / cm, 10×10 -5S / cm, 10.5×10 -5 S / cm, 11×10 -5 S / cm, 11.5×10 -5 S / cm, 12×10 -5 S / cm, 12.5×10 -5 S / cm, 13×10 -5 S / cm, 13.5×10 -5 S / cm, 14×10 -5 S / cm, 14.5×10 -5 S / cm, 15×10 -5 S / cm, 15.5×10 -5 S / cm, 16×10 -5 S / cm, 16.5×10 -5 S / cm, 17×10 -5 S / cm, 17.5×10 -5 S / cm, 18×10 -5 S / cm, 18.5×10 -5 S / cm, 19×10 -5 S / cm, 19.5×10 -5 S / cm, 20×10 -5 S / cm, 20.5×10 -5 S / cm, 21×10 -5 S / cm, 21.5×10 -5 S / cm, 22×10 -5 S / cm, 22.5×10 -5 S / cm, 23×10 -5 S / cm, 23.5×10 -5 S / cm, 24×10 -5 S / cm, 24.5×10 -5 S / cm, 25×10 -5 S / cm, 25.5×10 -5 S / cm, 26×10 -5 S / cm, 26.5×10 -5 S / cm, 27×10 -5 S / cm, 27.5×10 -5 S / cm, 28×10 -5 S / cm, 28.5×10 -5 S / cm, 29×10 -5 S / cm, 29.5×10-5 S / cm, 30×10 -5S / cm, 30.5×10 -5 S / cm, 31×10 -5 S / cm, 31.5×10 -5 S / cm, 32×10 -5 S / cm, 32.5×10 -5 S / cm, 33×10 -5 S / cm, 33.5×10 -5 S / cm, 34×10 -5 S / cm, 34.5×10 -5 S / cm, 35×10 -5 It can be S / cm or a range between two of these values.

[0076] Method for manufacturing an electrolyte membrane

[0077] Another aspect of the present specification provides a method for manufacturing an electrolyte membrane, comprising: (a) processing a composition comprising a polyolefin to produce a porous support; and (b) impregnating the porous support with an electrolyte solution comprising an electrolyte polymer and a solvent.

[0078] Here, the above (b) electrolyte polymer is lithium substituted, or after step (b), (c) step of lithium substituting the electrolyte membrane may be further included.

[0079] Here, the lithium substitution can be performed by reacting a lithium salt, such as lithium hydroxide or lithium chloride, with the polymer to be substituted.

[0080] Here, based on 100 parts by weight of the polymer to be substituted, a lithium salt in an amount of 10 to 200 parts by weight, for example, 10 parts by weight, 20 parts by weight, 30 parts by weight, 40 parts by weight, 50 parts by weight, 60 parts by weight, 70 parts by weight, 80 parts by weight, 90 parts by weight, 100 parts by weight, 110 parts by weight, 120 parts by weight, 130 parts by weight, 140 parts by weight, 150 parts by weight, 160 parts by weight, 170 parts by weight, 180 parts by weight, 190 parts by weight, 200 parts by weight, or a range between two of these values, can be reacted.

[0081] Meanwhile, this reaction may be carried out by impregnating the target polymer for substitution into an aqueous alcohol solution containing a lithium salt, but is not limited thereto. At this time, the aqueous alcohol solution may be a solution in which alcohol and water are mixed in a volume ratio of 0.5 to 2 : 0.5 to 2.

[0082] The above impregnation may be performed under conditions of 50 to 95°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and 95°C, but is not limited thereto.

[0083] The impregnated polymer can be dried under conditions of 50 to 95°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and 95°C to be lithium substituted.

[0084] In step (a) above, the porous substrate can be manufactured by processing the composition containing polyolefin. Specifically, the composition can be melted and kneaded, then pressurized to produce a base sheet having a predetermined thickness, then the base sheet can be stretched to produce a film, and the pore-forming agent can be extracted and removed from the film to obtain the porous support.

[0085] The above polyolefin may be at least one selected from the group consisting of polyethylene, polypropylene, ethylene vinyl acetate, ethylene butyl acrylate, and ethylene ethyl acrylate, but is not limited thereto.

[0086] For the weight-average molecular weight of the above polyolefin, reference can be made to the previously mentioned details.

[0087] Meanwhile, in one example, the polyolefin may include the aforementioned first polyolefin and second polyolefin, but is not limited thereto.

[0088] In addition, in one example, the above composition may further include an inorganic filler, and regarding this, reference may be made to the foregoing.

[0089] The above composition may further include 60 to 80 parts by weight of a pore-forming agent. The pore-forming agent can perform the role of forming pores by being extracted and removed from within the support by a wet method utilizing thermally induced phase separation.

[0090] The above wet method may involve immersing a support containing the pore-forming agent in an extraction tank containing a solvent. The extraction temperature may be 15 to 80°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or a range between two of these values, and the extraction time may be 0.1 to 60 minutes, for example, 0.1 minutes, 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, or a range between two of these values.

[0091] The above pore-forming agent may be at least one selected from the group consisting of, for example, paraffin oil, paraffin wax, mineral oil, solid paraffin, soybean oil, rapeseed oil, palm oil, coconut oil, di-2-ethylhexyl phthalate, dibutyl phthalate, diisononyl phthalate, diisodecyl phthalate and bis(2-propylheptyl)phthalate and naphthene oil, but is not limited thereto.

[0092] The solvent for extracting the above pore-forming agent may be at least one selected from the group consisting of pentane, hexane, benzene, dichloromethane, carbon tetrachloride, methyl ethyl ketone, and acetone, but is not limited thereto.

[0093] The above stretching may be performed by known methods such as uniaxial stretching or biaxial stretching (sequential or simultaneous biaxial stretching). In the case of sequential biaxial stretching, the stretching ratio may be 2 to 20 times in the transverse direction (MD) and the longitudinal direction (TD), for example, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, 11 times, 12 times, 13 times, 14 times, 15 times, 16 times, 17 times, 18 times, 19 times, 20 times, or a range between two of these values, and the corresponding surface ratio may be 4 to 400 times.

[0094] In addition, the porous support obtained in step (a) above can be hydrophilized. Here, the hydrophilization modification can be performed through plasma treatment.

[0095] When manufacturing an electrolyte membrane through the above plasma treatment, the surface of the support and the surface of the internal pores are hydrophilized, that is, the surface of the support and the surface of the internal pores are made to carry a negative charge, thereby improving the bonding strength with the electrolyte polymer, and accordingly, the durability of the electrolyte membrane, particularly long-term durability and ion conductivity, can be significantly improved.

[0096] In the past, a wet process was mainly used to hydrophilize the surface of a support and sulfonate it by immersing the support in sulfuric acid or the like for a certain period of time to achieve a certain level of ion conductivity. However, in this case, the wet process is performed separately from the plasma treatment, such as by preceding or succeeding the plasma treatment, which makes the process complex and causes a problem of generating a large amount of process waste liquid.

[0097] In this regard, the process gas used in the above plasma treatment includes not only conventional air, oxygen, and / or inert gas but also a certain amount of sulfur dioxide gas. Therefore, functional groups such as -SO3 are generated on the surface of the support and the internal pores through a single dry process called plasma treatment without a wet process such as immersing the support in sulfuric acid, i.e., sulfonation, thereby maximizing the hydrophilicity and ion conductivity of the support, simplifying the complex conventional process, and is also advantageous in terms of the environment.

[0098] Meanwhile, in one example, the sulfonated support may be lithium substituted to improve the ionic conductivity of the electrolyte membrane. Here, the lithium substitution can be performed by the method described above.

[0099] The mixed gas, which is the process gas used in the above plasma treatment, may comprise 50 to 90 volume% sulfur dioxide and 10 to 50 volume% oxygen, preferably 60 to 80 volume% sulfur dioxide and 20 to 40 volume% oxygen, more preferably 70 to 80 volume% sulfur dioxide and 20 to 30 volume% oxygen. If the content of sulfur dioxide in the mixed gas is less than 50 volume%, the required level of hydrophilicity in the support cannot be achieved, and if it exceeds 90 volume%, the process may become unstable.

[0100] The above plasma treatment can be performed for 0.5 to 90 minutes, preferably 0.5 to 20 minutes. If the above plasma treatment is performed for less than 0.5 minutes, the support cannot be hydrophilized and sulfonated to the required level, and if it is performed for more than 90 minutes, the degree of hydrophilization and sulfonation may converge to a certain level, which may reduce process efficiency.

[0101] Prior to step (b) above, an electrolyte solution can be prepared by dissolving the electrolyte polymer in a solvent.

[0102] The content of the electrolyte polymer in the above electrolyte solution may be 10 to 60 wt%, for example, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or a range between two of these values. If the content of the electrolyte polymer is less than 10 wt%, the amount of electrolyte impregnated into the pores of the porous support is small, which may lower the ionic conductivity of the electrolyte membrane; if it exceeds 60 wt%, the solubility of the electrolyte decreases, making it difficult for the electrolyte to penetrate into the pores of the porous support, and the flowability of the electrolyte solution decreases, making it difficult to uniformly thickness the electrolyte membrane.

[0103] The solvent of the above electrolyte solution may be at least one selected from the group consisting of ester-based, ether-based, alcohol-based, ketone-based, amide-based, sulfone-based, carbonate-based, aliphatic hydrocarbon-based, and aromatic hydrocarbon-based solvents, but is not limited thereto.

[0104] Examples of the above-mentioned amide-based solvents include N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methylformamide, dimethylformamide, dimethylacetamide, etc., but are not limited thereto.

[0105] Examples of the above-mentioned ester-based solvents include methyl acetate, ethyl acetate, n-butyl acetate, cellosolve acetate, propylene glycol monomethyl acetate, 3-methoxybutyl acetate, methyl butyrate, ethyl butyrate, propylpropionate, etc., but are not limited thereto. Examples of the above-mentioned ether-based solvents include diethyl ether, dipropyl ether, dibutyl ether, butyl ethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, octyl ether, hexyl ether, etc., but are not limited thereto.

[0106] Examples of the above alcohol-based solvents include methanol, ethanol, propanol, isopropanol, n-butanol, amyl alcohol, cyclohexanol, octyl alcohol, decanol, etc., but are not limited thereto. Examples of the above ketone-based solvents include acetone, cyclohexanone, methylamyl ketone, diisobutyl ketone, methyl ethyl ketone, methyl isobutyl ketone, etc., but are not limited thereto. Examples of the above carbonate-based solvents include ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, dibutyl carbonate, etc., but are not limited thereto.

[0107] Examples of the above-mentioned sulfone-based solvents include dimethyl sulfoxide, diethyl sulfoxide, diethyl sulfone, tetramethylene sulfone, etc., but are not limited thereto. Examples of the above-mentioned aliphatic hydrocarbon-based solvents include pentane, hexane, heptane, octane, nonane, decane, dodecane, tetradecane, hexadecane, etc., and examples of the above-mentioned aromatic hydrocarbon-based solvents include benzene, ethylbenzene, chlorobenzene, toluene, xylene, etc., but are not limited thereto.

[0108] In step (b) above, the porous support can be impregnated with the electrolyte solution and then dried to obtain an electrolyte membrane. The impregnation (and / or coating) may be performed by (i) impregnating the porous support in an impregnation tank filled with the electrolyte solution for a certain period of time, (ii) coating the porous support with a coating device for delivering the electrolyte solution, such as a roll coater or bar coater, or a combination of (i) and (ii).

[0109] In one example, the electrolyte solution may have undergone lithium substitution by the method described above.

[0110] Meanwhile, after step (b) above, step (c) of lithium substitution of the electrolyte membrane may be performed. In this case, the lithium substitution may be performed by the method described above.

[0111] In addition, the above lithium substitution method can be applied to a conventional ion exchange membrane to manufacture an electrolyte membrane.

[0112] In such cases, the process may be carried out as follows: i) a step of preparing an ion exchange membrane; ii) a step of cutting the ion exchange membrane; and iii) a step of lithium substitution on the cut ion exchange membrane.

[0113] In this way, when a membrane impregnated with an electrolyte in a porous support is lithium-substituted, at least a portion of the porous support is also lithium-substituted in addition to the impregnated polymer, so that it can have higher ionic conductivity.

[0114] electrochemical device

[0115] According to another aspect, an electrochemical device comprising the aforementioned electrolyte membrane is provided.

[0116] Here, the electrochemical device may include both a battery containing an electrolyte and an all-solid-state battery that does not contain a liquid electrolyte.

[0117] The embodiments of this specification will be described in more detail below. However, the following experimental results represent only representative results among the above embodiments, and the scope and content of this specification should not be interpreted as being narrowed or limited by the embodiments. The respective effects of various embodiments of this specification not explicitly presented below will be described in detail in the relevant sections.

[0118] Preparation Example 1-1

[0119] 30 parts by weight of high-density polyethylene with a weight-average molecular weight (Mw) of 600,000 and 70 parts by weight of paraffin oil with a kinematic viscosity of 70 cSt at 40°C were mixed and fed into a twin-screw extruder (inner diameter 58 mm, L / D=56, Twin screw extruder). After being extruded from the twin-screw extruder into a T-die with a width of 300 mm under conditions of 200°C and a screw rotation speed of 40 rpm, a base sheet was manufactured by passing it through a casting roll at a temperature of 40°C.

[0120] A film was prepared by stretching the above base sheet 6 times in the longitudinal direction (MD) in a roll stretcher at 115°C and stretching it 7 times in the transverse direction (TD) in a tenter stretcher at 120°C. The film was immersed in a dichloromethane leaching bath at 25°C to extract and remove paraffin oil for 1 minute, and then dried at 50°C for 5 minutes. Afterward, a porous support was prepared by heating it to 123°C in a tenter stretcher, stretching it 1.5 times in the transverse direction (TD), and then relaxing it 1.25 times.

[0121] The surface of the porous support was treated with vacuum plasma to modify it. Prior to plasma treatment, the porous support was placed in a mold capable of maintaining it in a flat state and purged with nitrogen to remove impurities from the support.

[0122] The chamber of the device for vacuum plasma treatment had a width of 150 mm, a depth of 200 mm, and a height of 120 mm, and a flat electrode for generating plasma was used, mounted parallel to the upper surface of the chamber at a position 25 mm away from the top surface. The porous support was positioned parallel to the flat electrode at a position 20 mm away from the flat electrode, and vacuum conditions were created until the pressure inside the chamber became 0.1 torr.

[0123] A 3:7 mixture of oxygen (O2) and sulfur dioxide (SO2) was introduced into the chamber at a flow rate of 100 sccm, and the chamber pressure was maintained at 0.5 torr for 2 minutes while purging. Additionally, a high-frequency power supply with a frequency of 50 kHz was applied at an output of 100 W to treat the porous support for 90 minutes. After treatment, the inflow of gas into the chamber was blocked, and while maintaining the pressure at 0.5 torr, the chamber was purged with air for 2 minutes to relieve the vacuum condition and open the chamber.

[0124] The upper and lower surfaces of the porous support were flipped over and positioned inside the chamber in the same manner as above, and the same process was repeated so that both sides of the porous support, namely the upper and lower surfaces, were evenly treated.

[0125] Preparation Example 1-2

[0126] 30 parts by weight of high-density polyethylene with a weight-average molecular weight (Mw) of 650,000, 70 parts by weight of paraffin oil with a kinematic viscosity of 70 cSt at 40°C, and 20 parts by weight of nanosilica with an average particle size of 600 nm and a surface coating of ethylene were mixed, and the nanosilica particles were dispersed using a high-speed mixer. After removing fine bubbles generated during the mixing process through a vacuum degassing process, the mixture was fed into a twin-screw extruder (inner diameter 58 mm, L / D=56). Under conditions of 210°C and a screw rotation speed of 40 rpm, the mixture was extruded from the twin-screw extruder into a T-die with a width of 300 mm, and then passed through a casting roll at a temperature of 40°C to produce a base sheet.

[0127] A film was prepared by stretching the above base sheet twice in the longitudinal direction (MD) in a roll stretcher at 118°C and twice in the transverse direction (TD) in a tenter stretcher at 122°C. The film was immersed in a dichloromethane leaching bath at 40°C to extract and remove paraffin oil for 1 minute, and then dried at 50°C for 5 minutes. Afterward, a porous support was prepared by heating in a tenter stretcher to 121°C, stretching it 1.4 times in the transverse direction (TD), and then relaxing it 1.15 times.

[0128] Subsequently, the porous support was hydrophilized and modified in the same manner as in Preparation Example 1-1 above.

[0129] Preparation Examples 1-3

[0130] 20 parts by weight of a first polyethylene having a weight-average molecular weight (Mw) of 1,400,000, 20 parts by weight of a second polyethylene having a weight-average molecular weight (Mw) of 300,000, and 70 parts by weight of paraffin oil having a kinematic viscosity of 70 cSt at 40°C were mixed and fed into a twin-screw extruder (inner diameter 58 mm, L / D=56). After being extruded from the twin-screw extruder into a T-die with a width of 300 mm under conditions of 220°C and a screw rotation speed of 40 rpm, a base sheet was manufactured by passing it through a casting roll at a temperature of 40°C.

[0131] A film was prepared by stretching the above base sheet eight times in the longitudinal direction (MD) in a roll stretcher at 125°C and stretching it eight times in the transverse direction (TD) in a tenter stretcher at 123°C. The film was immersed in a dichloromethane leaching bath at 25°C to extract and remove paraffin oil for 1 minute, and then dried at 50°C for 5 minutes. Subsequently, a porous support was prepared by heating it to 125°C in a tenter stretcher, stretching it 1.3 times in the transverse direction (TD), and then relaxing it 1.18 times.

[0132] Subsequently, the porous support was hydrophilized and modified in the same manner as in Preparation Example 1-1 above.

[0133] Preparation Examples 1-4

[0134] 20 parts by weight of a first polyethylene with a weight-average molecular weight (Mw) of 1,200,000, 20 parts by weight of a second polyethylene with a weight-average molecular weight (Mw) of 375,000, 60 parts by weight of paraffin oil with a kinematic viscosity of 70 cSt at 40°C, and 20 parts by weight of nanosilica with an average particle size of 600 nm and a surface coating of ethylene were mixed, and the nanosilica particles were dispersed using a high-speed mixer. After removing fine bubbles generated during the mixing process through a vacuum degassing process, the mixture was fed into a twin-screw extruder (inner diameter 58 mm, L / D=56). After being extruded from the twin-screw extruder into a T-die with a width of 300 mm under conditions of 225°C and a screw rotation speed of 40 rpm, a base sheet was manufactured by passing it through a casting roll at a temperature of 40°C.

[0135] A film was prepared by stretching the above base sheet twice in the longitudinal direction (MD) in a roll stretcher at 126°C and twice in the transverse direction (TD) in a tenter stretcher at 121°C. The film was immersed in a dichloromethane leaching bath at 40°C to extract and remove paraffin oil for 1 minute, and then dried at 50°C for 5 minutes. Afterward, a porous support was prepared by heating in a tenter stretcher to 120°C, stretching it 1.3 times in the transverse direction (TD), and then relaxing it 1.1 times.

[0136] Subsequently, the porous support was hydrophilized and modified in the same manner as in Preparation Example 1-1 above.

[0137] Preparation Example 2-1

[0138] 354.4 g (0.8 mol) of polysulfone and 3,900 ml of dichloroethane were added to a 5 L, 5-neck reactor equipped with a mechanical stirrer, a gas inlet, and a cooler, and stirred at room temperature for more than 12 hours under a nitrogen atmosphere.

[0139] Once dissolution was complete, 259.3 ml (2 mol) of chlorotrimethylsilane was added using a dropping funnel, followed by the slow addition of a mixture of 134.4 ml (2 mol) of chlorosulfonic acid and 100 ml of dichloroethane. After the addition was complete, the reaction was carried out for 6 hours.

[0140] After the reaction is complete, the product is slowly added to methanol to precipitate it, then washed 2 to 3 times to remove residual dichloroethane, and finally placed in an aqueous NaCl solution to form Na₂S in the form of salt. + After ion conversion, it was ground and washed.

[0141] After neutralizing the product using a 10 N NaOH aqueous solution with a mechanical stirrer, it was washed with water and filtered, and then dried under reduced pressure in an 80°C vacuum oven for more than 24 hours to obtain sulfonated polysulfone with a degree of sulfonation of 80%. An electrolyte was prepared by dissolving the sulfonated polysulfone in NMP at a concentration of 30 to 60 wt% at 60°C for 2 hours.

[0142] Preparation Example 2-2

[0143] 20 g of perfluorosulfonic acid, a fluorinated ionomer, 30 mL of water, and 70 mL of alcohol were added to a 5-neck 150 mL reactor equipped with a mechanical stirrer, a gas inlet, and a cooler, and stirred at room temperature for more than 2 hours under a nitrogen atmosphere. After stirring, 10 mL of NMP was additionally added and stirred for more than 30 minutes to prepare an electrolyte.

[0144] Preparation Example 2-3

[0145] After mixing ion-exchanged water and ethanol in a volume ratio of 1:2, a reaction solution was prepared by mixing 1 part by weight of lithium hydroxide based on 100 parts by weight of these.

[0146] The sulfonated polysulfone of Preparation Example 2-1 was added to the reaction solution and mixed and reacted at 80°C for 12 hours. Afterward, it was centrifuged for 15 minutes and dried in an oven at 80°C. Subsequently, an electrolyte was prepared by dissolving it in NMP at a concentration of 30 to 60 wt% at 60°C for 2 hours.

[0147] Preparation Example 2-4

[0148] 20 g of perfluorosulfonic acid, a fluorinated ionomer, 30 mL of water, and 70 mL of alcohol were added to a 5-neck 150 mL reactor equipped with a mechanical stirrer, a gas inlet, and a cooler, and stirred at room temperature for more than 2 hours under a nitrogen atmosphere.

[0149] Subsequently, 1 g of lithium hydroxide was added, and the mixture was mixed and reacted at 80°C for 12 hours. Afterward, the mixture was centrifuged for 15 minutes and dried in an oven at 80°C. An additional 10 mL of NMP was added, and the mixture was stirred for at least 30 minutes to prepare the electrolyte.

[0150] Comparative Example 1

[0151] An electrolyte membrane was prepared by impregnating the porous support of Preparation Example 1-1 with the electrolyte of Preparation Example 2-1.

[0152] Comparative Example 2

[0153] An electrolyte membrane was prepared by cutting the sulfonated polysulfone prepared in Preparation Example 2-1 above without dissolving it in NMP.

[0154] Example 1

[0155] After mixing ion-exchanged water and ethanol in a volume ratio of 1:2, a reaction solution was prepared by mixing 50 parts by weight of lithium hydroxide based on 100 parts by weight of an electrolyte membrane.

[0156] After adding the electrolyte membrane of Comparative Example 1 to the reaction solution, the mixture was mixed and reacted at 80°C for 12 hours. Afterward, the mixture was centrifuged for 15 minutes and dried in an oven at 80°C to produce a lithium-substituted electrolyte membrane.

[0157] Example 2

[0158] A lithium-substituted electrolyte membrane was prepared in the same manner as in Example 1, except that instead of the electrolyte membrane of Comparative Example 1, an electrolyte membrane prepared by impregnating the porous support of Preparation Example 1-2 with the electrolyte of Preparation Example 2-1 was used.

[0159] Example 3

[0160] A lithium-substituted electrolyte membrane was prepared in the same manner as in Example 1, except that instead of the electrolyte membrane of Comparative Example 1, an electrolyte membrane prepared by impregnating the porous support of Preparation Example 1-1 with the electrolyte of Preparation Example 2-2 was used.

[0161] Example 4

[0162] A lithium-substituted electrolyte membrane was prepared by impregnating the porous support of Preparation Example 1-1 with the electrolyte of Preparation Example 2-3.

[0163] Example 5

[0164] A lithium-substituted electrolyte membrane was prepared by impregnating the porous support of Preparation Example 1-3 with the electrolyte of Preparation Example 2-4.

[0165] Example 6

[0166] A lithium-substituted electrolyte membrane was prepared by impregnating the porous support of Preparation Example 1-4 with the electrolyte of Preparation Example 2-3.

[0167] Example 7

[0168] A lithium-substituted electrolyte membrane was prepared in the same manner as in Example 1, except that lithium chloride was used instead of lithium hydroxide.

[0169] Experimental Example 1

[0170] The mechanical properties of the electrolyte membranes according to the above manufacturing example and comparative example 2 were measured and indicated in Table 1 below as ○ for those suitable for secondary batteries and × for those difficult to apply due to insufficient properties. The measured properties and standards are as follows.

[0171] -Thickness (㎛): Measured using a fine thickness gauge, and a thickness exceeding 50 ㎛ was considered unsuitable.

[0172] - Porosity (%): In accordance with ASTM F316-03, the porosity of a specimen with a radius of 25 mm was measured using a PMI Capillary Porometer, and a value of less than 30% was considered non-compliant.

[0173] - Air permeability (Gurley, sec / 100 mL): Using the Asahi Seiko Densometer EGO2-5 model, the time it takes for 100 mL of air to pass through a specimen with a diameter of 29.8 mm at a measuring pressure of 0.025 MPa was measured, and a value exceeding 300 sec / 100 mL was considered unsuitable.

[0174] - Tensile strength (kgf / cm²) 2 Using a tensile strength tester, stress was applied to a specimen measuring 20×200 mm, and the applied stress was measured until fracture occurred, with 1,000 kgf / cm² in each direction. 2 It was considered unsuitable if it was less than that.

[0175] - Tensile elongation (%): Stress was applied to a specimen measuring 20×200 mm using a tensile strength tester, and the tensile elongation was calculated by measuring the maximum length until fracture occurred; a value of less than 50% in each direction was considered unsuitable.

[0176] - Drilling strength (gf): Using the KES-G5 drilling strength tester model from KATO TECH, a force was applied at a speed of 0.05 cm / sec with a stick of 0.5 mm diameter to a specimen of 100×50 mm, and the force applied at the time the specimen was drilled was measured; a value of less than 100 gf was considered unsuitable.

[0177] - Thermal shrinkage rate (%): A specimen measuring 200×200 mm was placed between A4 papers and left in an oven at 120℃ for 1 hour, then cooled to room temperature. The thermal shrinkage rate was calculated by measuring the shrinkage length in the horizontal and vertical directions of the specimen, and a value exceeding 15% in each direction was considered unsuitable.

[0178] Classification Manufacturing Example 1-1 Manufacturing Example 1-2 Manufacturing Example 1-3 Manufacturing Example 1-4 Comparative Example 2 Degree of Suitability ○○○○×

[0179] In particular, the specimen of Comparative Example 2 was unsuitable for secondary batteries due to insufficient tensile properties and puncture strength.

[0180] Experimental Example 2

[0181] The electrolyte membrane of Comparative Example 1 was cut into a circular shape with a diameter of 16 mm. A coin cell was manufactured by inserting the electrolyte membrane between stainless steel (SUS) electrodes with a thickness of 1 mm. As the electrolyte, a solution was used in which LiPF6 was dissolved at a concentration of 1.15 M in a solvent in which ethylene carbonate and methylene carbonate were mixed in a volume ratio of 30:70, respectively.

[0182] The characteristics of the coin cell were analyzed using linear sweep voltammetry (LSV) while increasing the voltage at a rate of 0.1 mV / s. As a result of the analysis, a stable graph was observed up to 7 V.

[0183] A coin cell was manufactured using the electrolyte membrane of Example 1 in the same manner, and its characteristics were verified. As a result of LSV analysis, an increase in current was confirmed at approximately 3.5 V, and the current surged in the region of 6.3 V or higher. Although this has not been precisely determined, it may be due to the decomposition of the electrolyte salt.

[0184] The electrolyte membrane of Example 1 was cut into a circular shape with a diameter of 16 mm. A coin cell was manufactured by stacking the cathode material (LFP), the electrolyte membrane, and lithium metal in that order. As the electrolyte, LiPF6 was dissolved at a concentration of 1.15 M in a solvent in which ethylene carbonate and methylene carbonate were mixed in a volume ratio of 30:70, respectively.

[0185] As a result of analyzing the characteristics of the coin cell using electrochemical impedance spectroscopy (EIS), it was confirmed that the capacity was well maintained up to 200 cycles under the condition of 0.1 C. In addition, as a result of measuring the rate capability while changing the C value in 10-cycle increments from 0.1 C / 0.5 C / 1 C / 0.1 C, it was confirmed that the electrolyte membrane has stable lifespan characteristics at various current densities.

[0186] After cutting the electrolyte membrane to 1 cm x 3 cm, it was mounted in a conductivity measuring cell equipped with a platinum electrode. The measuring cell was immersed in ultrapure water at 25°C, and then the ion conductivity was measured using a measuring instrument (Bio-Logic VSP300 equipped with an impedance module) under conditions of 100% relative humidity (RH) and is shown in Table 2 below.

[0187] Classification Comparison Example 1 Example 1 Example 4 Example 7 Ion Conductivity (S / cm) 4.08×10 -5 1.96×10 -4 1.54×10 -4 3.27×10 -4

[0188] Referring to Table 2, it can be seen that the ion conductivity characteristics of the electrolyte membrane of the example are significantly improved compared to the comparative example.

[0189] The foregoing description of this specification is for illustrative purposes only, and those skilled in the art to which one aspect of this specification pertains will understand that other specific forms can be easily modified without altering the technical concept or essential features described in this specification. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0190] The scope of this specification is defined by the claims, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of this specification.

Claims

1. A porous support comprising a polyolefin; and The above-mentioned porous support comprises an electrolyte polymer impregnated in at least some of the pores; At least some of the functional groups of the above electrolyte polymer are lithium-substituted, Electrolyte membrane.

2. In Paragraph 1, The above polyolefin comprises a first polyolefin having a weight-average molecular weight (Mw) of 700,000 to 2,000,000 and a second polyolefin having a weight-average molecular weight (Mw) of 30,000 to 700,000. Electrolyte membrane.

3. In Paragraph 1, The above porous support further comprises an inorganic filler, Electrolyte membrane.

4. In Paragraph 3, The content of the inorganic filler in the above porous support is 10 to 70 weight percent, Electrolyte membrane.

5. In Paragraph 1, The average pore size of the above porous support is 20 to 2,000 nm, Electrolyte membrane.

6. In Paragraph 1, The above porous support satisfies at least one of the following conditions i) to x), Electrolyte membrane: i) Thickness 5~50 µm; ii) Porosity 30~90%; iii) Air permeability 50~300 sec / 100 mL; iv) Drilling strength 100~500 gf; v) Longitudinal (MD) tensile strength 1,500~3,000 kgf / cm² 2 ; vi) Transverse (TD) tensile strength 1,000~2,500 kgf / cm² 2 ; vii) Longitudinal (MD) tensile elongation 25% or more; viii) Transverse (TD) tensile elongation of 25% or more; ix) Longitudinal thermal shrinkage rate of 15% or less at 120℃; x) Transverse thermal shrinkage rate of 15% or less at 120℃.

7. In Paragraph 1, The above electrolyte polymer is a lithiated hydrocarbon polymer selected from the group consisting of polysulfone series, poly(ethersulfone) series, poly(thiosulfone) series, poly(etheretherketone) series, polyimide series, polystyrene series, polyphosphazene series, and mixtures of two or more of these. Electrolyte membrane.

8. In Paragraph 1, The above electrolyte polymer is lithiated with a fluorine-based compound selected from the group consisting of perfluorosulfonic acid, poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, polytetrafluoroethylene, polyvinylfluoride, polyvinylidene fluoride, polyhexafluoropropylene, and copolymers or combinations of two or more of these. Electrolyte membrane.

9. In Paragraph 1, Ionic conductivity at 25℃ is 4.08×10⁻⁶ -5 Exceeding S / cm, Electrolyte membrane.

10. An electrolyte membrane comprising any one of claims 1 to 9, Electrochemical device.