KR20220010576A - A composite membrane comprising a conductive material layer, and secondary cell battery, electrochemical element, and electrochemical device comprising the same, and the method thereof - Google Patents

Abstract

According to the present specification, provided is a functional composite separator including: a porous substrate; and a conductive material layer laminated on the porous substrate, wherein the conductive material layer includes a conductive material and a binder resin, and the porous substrate includes a functional group having a negative charge.

Description

A functional composite separator including a conductive material layer, a secondary battery including the same, an electrochemical device, an electrochemical device, and a manufacturing method thereof same, and the method thereof}

The present invention relates to a functional composite separator for an electrochemical device on which a high-conductivity conductive material treated with plasma is supported, and a functional composite separator capable of reducing the charge transfer resistance of an active material, improving wettability with an electrolyte, and preventing crossover of the active material And to a secondary battery including the same, and to an electrochemical device.

Recently, as the amount of energy demand increases due to the development of industry, research and development of electrochemical devices capable of charging and discharging that can be used for electric vehicles, portable home appliances, drones, etc. are being actively conducted. In particular, in order to improve the capacity and specific energy of the secondary battery, research and development for a new separator is being actively conducted.

In the configuration of the secondary battery, the separator prevents physical contact between the positive electrode and the negative electrode and selectively transmits ions, thereby greatly affecting battery stability. Therefore, the development of a separation membrane with high stability and excellent performance is required.

Among secondary batteries, lithium-sulfur secondary batteries, which have been studied a lot in recent years, are attracting a lot of attention due to their high battery capacity. There is a problem in that the capacity is rapidly reduced as a cause of this.

As a method for overcoming this, Korean Patent KR 10-2018-0061064 A includes a carbide of an organic polymer material on the surface of the separator to increase the reactivity of the active material. However, it has been reported that there is a problem in that the battery capacity is lowered because the permeation phenomenon of polysulfide, which is the active material, cannot be sufficiently prevented, so that the durability is not good.

In Korean Patent KR 10-2018-0056408 A, the cycle life of the battery is improved by adsorbing active material ions eluted from the positive electrode by including an anionic surfactant on the surface of the separator in the porous coating layer, thereby preventing the deterioration of the negative electrode. . However, due to the limit of not increasing the reactivity of the active material, it showed a low capacity.

In Korean Patent KR 10-2018-0023627 A, a dendrite growth inhibitory layer formed of a composition containing an ionic polymer, an inorganic filler, and a lithium salt is applied to the surface of the separator to effectively inhibit the local growth of dendrites, and at the same time, a low interface By increasing the ionic conductivity with the resistance, the performance of the battery was improved. However, the problem of permeation of the lithium-sulfur active material and the low reactivity of the active material could not be solved. For this reason, the performance maintenance ratio of the battery showed a relatively low result.

Therefore, in the present invention, in order to solve technical problems such as dendrite formation on the surface of the negative electrode, low ionic conductivity, permeation of the active material, and low reactivity of the active material, a plasma-treated high-conductivity conductive material-supported composite polymer separator for electrochemical devices has been developed.

KR 10-2018-0061064 A KR 10-2018-0056408 A KR 10-2018-0023627 A

One aspect of the present invention provides a functional composite separator capable of preventing the permeation of active material ions, improving the reactivity of the positive electrode active material, inhibiting dendrite growth in the negative electrode, and improving ionic conductivity in the positive electrode in order to solve the above technical problem aim to do

In one embodiment of the present invention, a porous substrate; A conductive material layer laminated on the porous substrate; includes, wherein the conductive material layer includes a conductive material and a binder resin, and the porous substrate includes a functional group having a negative charge, a functional composite separator is provided.

In an exemplary embodiment, the negatively charged functional group may include at least one of a hydroxyl group, an amine group, an ammonia group, and a carboxyl group.

In an exemplary embodiment, the porous substrate may include polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, Polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, polyvinylidene difluoride, poly It may include any one material selected from the group consisting of tetrafluoroethylene, silica, alumina, titania, and zeolite, a copolymer of two or more thereof, or a mixture thereof.

In an exemplary embodiment, the porous substrate is a multi-layer substrate, and each layer of the multi-layer substrate is polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether terether ketone, polyaryl ether ketone, polyether imide, polyamide imide, polybenzimidazole, polyether sulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, Any one material selected from the group consisting of glass fiber, polyvinylidene difluoride, polytetrafluoroethylene, silica, alumina, titania, and zeolite, a copolymer of two or more thereof, or a mixture thereof selected from the group consisting of material may be included.

In an exemplary embodiment, the porous substrate may have a thickness of 1-1000 μm.

In an exemplary embodiment, the conductive material layer may include a functional group having a negative charge.

In an exemplary embodiment, the conductive material layer may include a functional group having a negative charge by being treated with _{CO 2 plasma.}

In an exemplary embodiment, the conductive material is a porous carbon-based material, and the carbon-based material is natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, graphite, graphene, activated carbon, carbon fiber, carbon nanotube. , activated carbon, or a combination thereof.

In an exemplary embodiment, the conductive material may be included in an amount of 5 to 80% by weight based on the weight of the binder resin.

In an exemplary embodiment, the binder may be included in an amount of 5 to 80% by weight based on the weight of the conductive material.

In an exemplary embodiment, the conductive material layer may have a thickness of 0.01 - 500 μm.

In one embodiment of the present invention, attaching a functional group having a negative charge to the porous substrate by treating the reactive gas plasma to the porous substrate; and laminating a conductive material layer on the porous substrate, wherein the conductive material layer includes a conductive material and a binder resin, a functional composite separator manufacturing method is provided.

In an exemplary embodiment, the manufacturing method may further include a step of attaching a negatively charged functional group to the conductive material layer by treating the reactive gas plasma to the conductive material layer.

In an exemplary embodiment, the reactive gas is _{from the group consisting of Ar, He, N 2} , NH ₃ , NF ₃ , F ₂ , O ₂ , CO ₂ , H ₂ , NO _x (x=1-3) and air. It may be any one or more selected gases.

In an exemplary embodiment, the reactive gas may be _{CO 2 .}

In an exemplary embodiment, the plasma treatment may include power of any one of DC, RF, and microwave.

In an exemplary embodiment, the plasma treatment may be performed at a pressure of 1 mTorr - 10 Torr and a temperature of -196°C - 500°C.

In an exemplary embodiment, the plasma treatment is an RF plasma power treatment, and may be performed at an RF frequency of 20 kHz - 1 GHz and a power condition in the range of 25 - 10,000 W.

In one embodiment of the present invention, there is provided a secondary battery comprising the functional composite separator according to the embodiment of the present invention.

In an exemplary embodiment, the secondary battery may include a positive electrode, a negative electrode, a functional composite separator, and an electrolyte, wherein the positive electrode and the negative electrode are disposed to face each other, and the functional composite separator and the electrolyte may be positioned between the positive electrode and the negative electrode have.

In one embodiment of the present invention, there is provided an electrochemical device comprising a functional composite separator according to an embodiment of the present invention.

In one embodiment of the present invention, there is provided an electrochemical device comprising a functional composite separator according to an embodiment of the present invention.

The functional composite separator according to an embodiment of the present invention can effectively prevent the movement of sulfides generated in the anode from the anode to the cathode while maintaining the conductivity of metal ions through plasma treatment.

The functional composite separator according to an embodiment of the present invention can effectively prevent a crossover phenomenon in which the sulfide active material moves to the negative electrode while improving the reactivity of the sulfide active material in the positive electrode of the battery to which the conductive material layer is plasma-treated. .

The functional composite separator according to an embodiment of the present invention introduces a plasma-treated conductive material layer together with a plasma-treated substrate, thereby maintaining the permeation rate of the metal active material, and a crossover in which sulfides generated at the anode move to the cathode. By preventing development and improving the reaction activity of the metal active material in the positive electrode, dendrite growth on the metal surface of the negative electrode is suppressed, and the durability, battery capacity, and performance maintenance rate of the secondary battery using the functional separator are improved, Overall, the performance of the secondary battery can be improved.

1 is a schematic schematic view showing a secondary battery equipped with a composite separator according to the present invention.
Figure 2a is an SEM image showing the surface of the composite separator of Comparative Example 1 of the present invention, Figure 2b is an SEM image showing the surface of the composite separator of Example 1 of the present invention, Figure 2c is an SEM image showing the surface of the separator of Example 3 image, and FIG. 2d is an SEM image showing a cross-section of the separator of Example 3.
3 shows FT-IR spectra of the separators according to Comparative Example 1 and Example 1 of the present invention.
4a to 4h show the XPS spectra of the surface of the separator according to the overall comparative examples and examples of the present invention.
5a to 5f show wettability images of the surface of the separator according to the overall comparative examples and examples of the present invention.
6 shows the ionic conductivity with respect to lithium cations of the separators according to Comparative Examples and Examples of the present invention.
7 shows the degree of polysulfide ion permeation concentration of the separation membranes according to all Comparative Examples and Examples of the present invention.
8 shows a Nyquist plot through electrochemical impedance spectroscopy of a secondary battery equipped with a separator according to all comparative examples and examples of the present invention.
9 shows cyclic voltammograms of a secondary battery equipped with a separator according to an overall comparative example and an embodiment of the present invention.
10 shows the results of the initial capacity when the secondary battery equipped with the separator according to all Comparative Examples and Examples of the present invention is driven.
11 shows the battery capacity when the secondary battery equipped with the composite separator according to the overall comparative example and embodiment of the present invention is driven.
12 shows the battery capacity according to a change in current when driving a secondary battery equipped with a composite separator according to all Comparative Examples and Examples of the present invention.

Hereinafter, embodiments of the present invention will be described in more detail.

The embodiments of the present invention disclosed in the text are illustrated for the purpose of explanation only, and the embodiments of the present invention may be embodied in various forms and should not be construed as being limited to the embodiments described in the text. .

The present invention can make various changes and can have various forms, and the embodiments are not intended to limit the present invention to a specific disclosed form, and all changes, equivalents or substitutes included in the spirit and scope of the present invention should be understood as including

Functional Composite Separator

One embodiment according to the present invention is a porous substrate; It includes a conductive material layer laminated on the porous substrate, wherein the conductive material layer includes a conductive material and a binder resin, and the porous substrate includes a functional group having a negative charge, it provides a functional composite separator.

In one embodiment, the functional composite separator 130 may be a separator for a lithium secondary battery, for example, a separator for a lithium-sulfur secondary battery.

In one embodiment, the porous substrate 131 may include a plurality of pores, for example, may be a substrate applied to a conventional electrochemical device. Non-limiting porous substrates may include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, for example, polyacetal, polyamide, polyimide, polycarbonate, polyether terether ketone, polyaryl ether ketone, polyether imide, polyamide imide, polybenzimidazole, polyether sulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, It may include any one material selected from the group consisting of glass fiber, polyvinylidene difluoride, polytetrafluoroethylene, silica, alumina, titania, and zeolite, a copolymer of two or more thereof, or a mixture thereof. , may be a separation membrane using these materials.

In one embodiment, the porous substrate 131 may be a polyolefin-based substrate including polyolefin. In the case of the polyolefin-based substrate, the shutdown function is excellent, which may contribute to the improvement of safety of the battery. In addition, the polyolefin-based resin may include a non-olefin resin in addition to the olefin resin, or may include an olefin and a non-olefin monomer copolymer.

In one embodiment, the porous substrate 131 may be a multi-layered substrate, and each layer of the multi-layered substrate may include the above-described porous substrate material. For example, the porous substrate may be a polyethylene single membrane, a polypropylene single membrane, a polyethylene/polypropylene double membrane, a polypropylene/polyethylene/polypropylene triple membrane, and a polyethylene/polypropylene/polyethylene triple membrane.

In one embodiment, the porous substrate 131 may have a pore size of 1 nm to 10 μm, and the porosity of the porous substrate 131 may be 10% to 99%.

In one embodiment, the thickness of the porous substrate 131 may be 1 - 1000 µm, for example, 1 - 20 µm, 1 - 30 µm, 10 - 50 µm, 50 - 200 µm, 100 - 300 µm, It may have a thickness in the range of 100-500 μm, or 500-1000 μm. When the thickness of the porous substrate is less than 1 μm, the mechanical strength is too low and thus easily damaged, and when the thickness is more than 1000 μm, the mass transfer rate and ionic conductivity may become too small.

In one embodiment, a functional group having a negative charge may be included on one or both surfaces of the porous substrate 131 , and for example, a functional group having a negative charge on the surface of the porous substrate 131 may be included. When the porous substrate includes a negatively charged functional group on one or both sides, the separator may have excellent ionic conductivity, which is because the negatively charged functional group attracts lithium cations by electrostatic attraction and wettability with the electrolyte is improved.

In addition, when one or both surfaces of the porous substrate 131 include a negatively charged functional group, the permeability of polysulfide may be low, which may increase the porosity of the separator due to plasma treatment to attach the negatively charged functional group, and the electrolyte While the wettability of the polysulfide can be improved, the permeability of the polysulfide can be increased, while the negatively charged functional group on the surface of the separator has a greater force to push the polysulfide of the anion to the electrostatic repulsive force.

In addition, when a functional group is provided on the surface of the porous substrate 131, a negatively charged functional group is generated on the surface of the separator to impart hydrophilicity and improve wettability with the electrolyte, thereby lowering the resistance of the conductive material layer.

In one embodiment, the negatively charged functional group may be applied to the surface of the porous substrate by plasma treatment, for example, carbon dioxide plasma treatment. Specifically, one or both surfaces of the porous substrate 131 and the inside of the pores may chemically react with radical ions generated through a plasma device to impart functional groups to the surface. The functional group may push the positive electrode active material by the force of electrostatic repulsion and improve ionic conductivity by improving wettability with the electrolyte.

In one embodiment, the plasma treatment may be performed by applying power of various methods including direct current (DC), radio frequency (RF), glow discharge, or microwave discharge. And, for example, it can be performed by applying RF, which is relatively fast and easy to generate plasma.

In one embodiment, the negatively charged functional group may include at least one of a hydroxyl group, an amine group, an ammonia group, and a carboxyl group.

In one embodiment, the conductive material is a carbon-based material having a porosity, and the carbon-based material is natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, graphite, graphene, activated carbon, carbon fiber, carbon hollow fiber ( hollow carbon fiber), carbon nanotubes, activated carbon, or a combination thereof.

In one embodiment, the conductive material may be included in an amount of 5 to 80% by weight based on the total weight of the binder. When the conductive material is included in less than 5% by weight, electrical conductivity may be too low, and when included in more than 80% by weight, the adhesive force of the conductive material layer may be lowered.

In one embodiment, the binder may include a thermoplastic resin or a thermosetting resin. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexa Fluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoro Loethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, ethylene -Acrylic acid copolymers and mixtures thereof may be included, but not limited thereto, and may be included as long as they can be used as binders in the art.

In one embodiment, the binder resin may be included in an amount of 5 to 80% by weight based on the total weight of the conductive material. When the binder resin is included in less than 5% by weight, the conductive material may be separated because the adhesive force of the conductive material is too low, and when it is included in more than 80% by weight, the electrical conductivity of the conductive material layer may be too low.

In one embodiment, the conductive material layer 132 may have a thickness of 0.01 - 500㎛. If the thickness is less than 0.01 μm, the effect may be lost, and if the thickness is more than 500 μm, the material and ion transfer resistance may be too large.

In one embodiment, at this time, the conductive material layer 132 may be prepared according to a conventional method, and specifically, a slurry for forming a conductive material layer prepared by mixing a conductive material and a binder in an organic solvent is mixed with the porous substrate layer ( 131) may be prepared by coating and drying the above. Here, the organic solvent, the coating method, and the drying method may be the same as in the anode.

In one embodiment, a functional group having a negative charge may be included on one or both surfaces of the porous substrate 131 . Specifically, the negatively charged functional group may include at least one of a hydroxyl group, an amine group, an ammonia group, and a carboxyl group.

In one embodiment, the upper surface of the conductive material layer 132 may be plasma-treated to provide functional groups, and the plasma treatment may be processed in the same manner as in the porous substrate 131 .

When a functional group is provided to the surface of the conductive material layer 132, ionic conductivity may be lower than when a functional group is provided to the surface of the porous substrate without a conductive material layer, which is a relatively dense conductive material layer acting as resistance to ion permeation. Because.

The functional composite separator 130 according to an embodiment of the present invention provides a functional group to one or both surfaces of the porous substrate 131 through plasma treatment, and a conductive material layer 132 on the porous substrate 131 to which the functional group is provided. By providing a functional group through plasma treatment on the upper surface after application, it can have the effects of preventing the permeation of positive electrode active material ions, improving the reactivity of the active material, suppressing dendrite growth, and improving ionic conductivity.

In particular, when functional groups are attached to both surfaces of the porous substrate 131 and the conductive material layer 132 , a negative charge is generated to increase the permeability of lithium cations and improve hydrophilicity, so that it can have an excellent ionic conductivity value.

Functional composite separator manufacturing method

One embodiment according to the present invention comprises the steps of attaching a functional group having a negative charge to the porous substrate by treating the reactive gas plasma to the porous substrate; and laminating a conductive material layer on the porous substrate, wherein the conductive material layer includes a conductive material and a binder resin.

In one embodiment, the manufacturing method may further include; attaching a functional group having a negative charge to the porous substrate by treating the conductive material layer with reactive gas plasma.

In one embodiment, the reactive gas is Ar, He, N ₂ , NH ₃ , NF ₃ , F ₂ , O ₂ , CO ₂ , H ₂ , NO _x . And it may be any one or more gases selected from the group consisting of air. Here, x may be 1≤x≤3.

In one embodiment, the plasma may include a power selected from DC, RF, or microwave power.

In one embodiment, certain conditions may apply when activating the plasma by applying RF power, for example, the frequency of RF is in the range of 20 kHz to 1 GHz, and activating the plasma with power in the range of approximately 25 W to 10,000 W, The pressure of the reaction chamber can be set in the range of 1 mTorr to 10 Torr.

Also in one embodiment, in the plasma treatment, the reaction gas is ^{mixed at a flow rate of 0.1 sccm (cm 3} /min) - 1 slm (L/min), and treated at a temperature in the range of -196°C - 500°C for 10s - 60min it may be

Secondary batteries, electrochemical devices, and electrochemical devices

One embodiment according to the present invention provides a secondary battery including a functional composite separator. Specifically, the secondary battery includes a positive electrode, a negative electrode, a functional composite separator, and an electrolyte, the positive electrode 110 and the negative electrode 120 are disposed to face each other, and the functional composite separator and the electrolyte are the positive electrode 110 and the negative electrode It may be located between (120).

1 is a schematic schematic view showing a secondary battery equipped with a functional composite separator according to the present invention.

In one embodiment, the positive electrode 110 may include a positive electrode current collector 111 and a positive electrode active material layer 112, the positive electrode active material layer includes a conductive material and a binder resin, and the positive electrode current collector 111 may be located on the Here, the positive electrode current collector 111 is not limited as long as it can be used as a current collector in the present technical field and is applicable without limitation, and specifically, an aluminum film, a nickel film, foamed aluminum, foamed nickel, etc. having excellent conductivity may be used. .

In one embodiment, the cathode active material may include one or more selected from elemental sulfur (S), a sulfur-based compound, or a mixture thereof. For example, the sulfur-based compound is Li ₂ S _n (n≥1); 2,5-dimercapto-1,3,4-thiadiazole (2,5-dimercapto-1,3,4-thiadiazole), 1,3,5-trithiocyanuic acid (1,3,5- It may be at least one selected from the group consisting of disulfide compounds such as trithiocyanuic acid), organic sulfur compounds, and carbon-sulfur polymers ((C _n S _{x ), 2≤x≤50 n≥2).}

In addition, the cathode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specifically, cobalt, manganese, nickel, aluminum, iron, or a metal that is a combination thereof may be at least one selected from a composite oxide with lithium or a composite phosphorous oxide. More specifically, it may be lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or a combination thereof.

In one embodiment, the conductive material included in the positive electrode active material layer is a conductive material, for example, a metallic conductive material such as the metal fiber and metal mesh, a metallic powder such as copper, silver, nickel, aluminum, or polyphenyl It may include an organic conductive material such as a lene derivative, but is not limited thereto.

In one embodiment, the conductive material included in the positive electrode active material layer may be a porous carbon-based material, for example, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, graphite, graphene, activated carbon, carbon. It may be selected from the group consisting of fibers, carbon nanotubes, activated carbon, and mixtures thereof.

In one embodiment, the conductive material included in the positive electrode active material layer may be included in an amount of 5 to 35% by weight based on the total weight of the positive electrode active material layer. If the content of the conductive material is less than 5% by weight, the effect of improving conductivity according to the use of the conductive material may be insignificant.

In one embodiment, the binder resin included in the positive electrode active material layer may include a thermoplastic resin or a thermosetting resin. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoro Propylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid The copolymer and the like may be used alone or in combination, but it is not necessarily limited thereto, and any one that can be used as a binder in the art may be used.

In one embodiment, the positive electrode 110 may be manufactured according to a conventional method, and specifically, a slurry for forming a positive electrode active material layer prepared by mixing a positive electrode active material, a conductive material, and a binder in an organic solvent is applied on the current collector. and drying, and optionally compression molding on a positive electrode current collector to improve electrode density.

In one embodiment, the organic solvent may be selected to be capable of uniformly dispersing the positive electrode active material, the conductive material, and the binder, and to evaporate easily.

Specifically, the organic solvent may be at least one selected from the group consisting of N-methyl-2-pyrlidone (NMP), acetonitrile, methanol, ethanol, tetrahydrofuran, water, and isopropyl alcohol.

In one embodiment, the application is dip coating, doctor blade coating, spin coating, bar coating, die casting, slit casting ), roll coating, screen printing, or inkjet printing, but is not limited thereto.

In one embodiment, the drying may be performed by, for example, natural drying, hot air, drying by hot or low humidity, vacuum drying, far-infrared rays, or electron beam irradiation, but is not limited thereto. The drying process may be performed, for example, at a temperature of 25 - 200 °C.

In one embodiment, the negative electrode 120 may include a negative electrode current collector 121 and a negative electrode active material layer 122, wherein the negative electrode active material layer includes a conductive material and a binder resin, and the negative electrode current collector 111 may be located on the Here, the negative current collector 121 is limited up to as long as it can be used as a current collector in the present technical field, and specifically, copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. It may be selected from the group consisting of.

In one embodiment, the negative active material is a material capable of reversibly intercalating and deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of applying and de-coating lithium, a transition metal oxide, or a combination thereof.

The material capable of reversibly intercalating and deintercalating the lithium ions may include a carbon-based material, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may include, for example, natural or artificial graphite in amorphous, plate-shape, flake, spherical, or fibrous form. In addition, the amorphous carbon may include, for example, soft carbon or hard carbon, mesophase pitch carbide, or calcined coke. In addition, the lithium metal alloy is composed of lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn. It may include a mixture or alloy of one or more metals selected from the group.

For example, the material capable of applying and de-coating the lithium is Si, SiO _x (0<x<2), Si-C composite, Si-Y alloy, Sn, SnO ₂ , Sn-C composite, Sn- there may be mentioned Y, etc., and may also use a mixture of at least one of these with SiO _2. Here, the element Y is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

Also, for example, the transition metal oxide may include vanadium oxide, lithium vanadium oxide, and the like.

In one embodiment, the negative electrode 120 may further include a conductive material and a binder selectively together with the negative electrode active material. In this case, the types of the conductive material and the binder included in the negative electrode 120 may be the same as the conductive material and the binder included in the positive electrode.

In one embodiment, the negative electrode 120 may be manufactured according to a conventional method, and specifically, a slurry for forming a positive electrode active material layer prepared by mixing a negative electrode active material, a conductive material, and a binder in an organic solvent is applied on the current collector and It may be dried and optionally manufactured by compression molding on the negative electrode current collector in order to improve the electrode density. Here, the organic solvent, the coating method, and the drying method may be the same as in the anode.

In one embodiment, the functional composite separator 130 may function to physically separate the positive electrode 110 and the negative electrode 120 in a secondary battery to be described later.

In one embodiment, the electrolyte is ^{a salt of the A +} B ^- structure, and may be dissolved or dissociated in a solvent. Here, A ⁺ may include an ion consisting of a cation such as ^{Li +} , Na ⁺ , K ⁺ , V _x ^{+ or a combination thereof, and B -} is TFSI ^- , NO ₃ ^- , PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N(CF ₃ SO ₂ ) ₂ ^- , C(CF ₂ SO ₂ ) ₃ ^- , O _x ⁻ may be a salt containing an anion or an ion consisting of a combination thereof, and the solvent is carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dioxolane (DOL), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrlidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone (g-butyrolactone), acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, or mixtures thereof.

In one embodiment, the electrolyte injection may be performed at an appropriate stage in the battery manufacturing process according to the manufacturing process and required physical properties of the final product. That is, it may be applied before assembling the battery or in the final stage of assembling the battery.

In addition, one embodiment according to the present invention provides a functional composite separator comprising a. The electrochemical device and the electrochemical device may be manufactured using a general method known in the art, and the form is not particularly limited.

The lithium secondary battery, for example, a lithium-sulfur secondary battery, may have excellent battery characteristics such as current efficiency, energy efficiency, durability, and capacity retention rate. In addition, the functional composite separator can be applied to various electrochemical devices and electrochemical devices using acidic and basic electrolytes to improve excellent performance and lifespan. For example, the electrochemical device may include a fuel cell, an electrolysis device, a redox flow battery, and the like.

Hereinafter, the configuration and effect of the present invention will be described in more detail by way of examples. However, these examples are provided for the purpose of illustration only to help the understanding of the present invention, and the scope and scope of the present invention are not limited by the following examples.

[Production of functional composite separator]

[Comparative Example 1]

As a porous substrate (simple separation membrane), a multilayer porous substrate (simple separation membrane) having a three-layer structure of pure polypropylene/polyethylene/polypropylene was prepared (thickness 21 μm, porosity 39%).

[Comparative Example 2]

It was prepared by coating a conductive material layer on the porous substrate of Comparative Example 1. Here, the slurry for forming the conductive material layer is 25:25: conductive material carbon black (Super P), Ketjen black, and binder polyvinylidene fluoride (PVDF) in N-methyl-2-pyrlidone (NMP) organic solvent: What was prepared by mixing in a mass ratio of 50 was used. Then, the prepared slurry was applied to one side of the porous substrate to a thickness of about 10 μm using a doctor blade equipment, and dried at 40° C. for 12 hours using a dryer to prepare a functional composite separator (simple composite separator).

[Example 1]

Carbon dioxide plasma was irradiated to both surfaces of the porous substrate of Comparative Example 1 to generate negatively charged hydroxyl and carboxyl functional groups on the outer surface of the porous substrate or the surface of the pore interior. RF plasma was generated with a power of 80W at room temperature, and the RF frequency was maintained at 50kHz. CO ₂ reaction gas was introduced into the reaction chamber at a flow rate of 50 sccm to generate plasma while maintaining the pressure of the reaction chamber at 0.5 Torr, and the porous substrate was treated for 8 minutes to prepare a functional composite separator (plasma-treated functional separator) .

[Example 2]

A composite separator made by applying a conductive material layer on a pure porous substrate was treated with plasma to prepare a functional composite separator.

Specifically, the conductive material layer of the functional composite separator (simple composite separator) of Comparative Example 2 was treated with carbon dioxide plasma to give a negatively charged hydroxyl group and a carboxyl group functional group. Here, the conductive material layer was treated with plasma under the same plasma treatment conditions as in Example 1, except that the plasma was treated for 30 seconds.

[Example 3]

After applying a carbon conductive material layer on the plasma-treated porous substrate, this was again treated with plasma to prepare a functional composite separator.

Specifically, a conductive material layer was applied to one surface of the functional composite separator of Example 1 in the same manner as in Comparative Example 2. Then, the conductive material layer was treated with carbon dioxide plasma on the upper surface of the formed conductive material layer under the same plasma treatment conditions as in Example 2 to prepare a functional composite separator.

[Evaluation Example 1] Analysis of the shape and structure of a porous substrate (separation membrane)

Figure 2a is an SEM image showing the surface of the porous substrate (separator) of Comparative Example 1 of the present invention, Figure 2b is an SEM image showing the surface of the separator of Example 1 of the present invention. According to this, it can be confirmed that the porosity of the porous substrate slightly increased by the plasma treatment. FIG. 2c is an SEM image showing the surface of the conductive material layer of the separator of Example 3. FIG. Through this, it can be confirmed that the nanoparticles of carbon black and ketjen black are evenly applied to the surface of the porous substrate. Figure 2d is an SEM image showing a cross section of the separator of Example 3. Through this, it can be confirmed that the conductive material layer of Example 3 was applied to a thickness of about 10 μm.

[Evaluation Example 2] Characteristics analysis of porous substrate (separator)

3 is a result of analyzing the surface characteristics of the separator surfaces of Comparative Example 1 and Example 1 of the present invention using a Fourier transform infrared spectrometer (FT-IR spectrometer (NICOLET iS10, Thermo Scientific). According to this, Comparative Example 1 In comparison with , in the case of the separation membrane of Example 1, a peak representing (COC) ether at a frequency of 1255 cm ^-1 , a peak representing carboxylic acid at 1600-1750 cm ^-1 , and a hydroxyl group at 3580-3750 cm -1 New peaks were generated, and it was confirmed that negatively charged carboxyl groups and hydroxyl groups were generated on the surface of the separator.

4 shows the XPS spectrum of the surface of the separator according to the overall comparative examples and examples of the present invention. Figures 4a-d are XPS spectra for a wide range of binding energy on the surface of the separator according to the entire Comparative Examples and Examples, and Figures 4e-h are the narrow binding energy corresponding to C 1s of the surface of the separator according to the entire Comparative Examples and Examples. Deconvolution XPS spectral results for the range. According to FIGS. 4A, 4B, 4E, and 4F, C-O corresponding to 288.83 eV and O=C-O peaks corresponding to 290.58 eV were newly generated in Example 1 compared to Comparative Example 1. Through this, it was confirmed that negatively charged carboxyl groups and hydroxyl groups were generated on the surface of the separator. In addition, according to FIGS. 4c, 4d, 4f, and 4h, compared to Comparative Example 2, C-O corresponding to 288.83 eV and O=C-O peak corresponding to 290.58 eV in Example 2 and Example 3 were newly generated. Through this, it was confirmed that negatively charged carboxyl groups and hydroxyl groups were generated on the surface of the conductive material layer. The XPS analysis results are shown in more detail in Table 1.

separator C=C sp ²
(At. %) CC sp ³
(At. %) CO
(At. %) O=CO
(At. %) CF
(At. %) CF
(At. %) Comparative Example 1 3.74 96.26 - - - - Example 1 9.51 85.59 3.40 1.50 - - Comparative Example 2 63.51 18.50 4.74 2.22 10.03 1.00 Example 2, Example 3 61.39 20.57 5.59 2.67 8.96 0.82

[Evaluation Example 3] Contact angle measurement

5 shows an image of the wettability measurement result of the surface of the separator according to all Comparative Examples and Examples of the present invention. Figure 5a is the contact angle of Comparative Example 1 (porous substrate) with respect to water, Figure 5b is the contact angle of Comparative Example 1 (porous substrate) with respect to the electrolyte, Figure 5c is the contact angle of the functional composite separator of Example 1 with respect to water, 5D is the contact angle of the functional composite separator of Example 1 with respect to the electrolyte, FIG. 5E is the contact angle of Comparative Example 2 with respect to water, and FIG. 5F is the contact angle of Examples 2 and 3 with respect to water. According to FIGS. 5a-d, it can be confirmed that, compared to Comparative Example 1, in Example 1, hydrophilicity is imparted to the surface of the separator by the generation of negatively charged functional groups, so that wettability with water and electrolyte is improved, thereby reducing the contact angle. According to FIGS. 5E-F , it can be confirmed that in Examples 2 and 3, compared with Comparative Example 2, hydrophilicity is imparted to the surface of the conductive material layer due to the generation of negatively charged functional groups, so that wettability to water is always maintained, thereby reducing the contact angle. The contact angle of the conductive material layer with respect to the electrolyte was almost 0° in Comparative Example 2, Example 2, and Example 3, which made it impossible to compare the contact angle. was known from

[Evaluation Example 4] Ion conductivity measurement

6 is a graph showing the lithium ion conductivity of various separators according to all Comparative Examples and Examples of the present invention. Exact ionic conductivity values are shown in Table 2.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Ion Conductivity (mScm ^-1 ) 0.34 0.19 0.30 0.27 0.15 Active material permeability (molcm ^-2 s ^-1 ) 1.07×10 ^-8 1.72×10 ^-9 1.74×10 ^-10 1.13×10 ^-8 1.74×10 ^-9 Initial capacity Q _H (mAhg ^-1 ) 260.51 312.26 379.63 251.58 292.01 Initial capacity Q _L (mAhg ^-1 ) 543.01 676.62 824.84 517.22 610.64

6 and Table 2, it can be seen that Example 1 has improved ionic conductivity compared to Comparative Example 1. This is because negatively charged functional groups are generated on the surface of the separator to improve the permeability of lithium cations, and the hydrophilicity is increased to improve wettability with the electrolyte. Similarly, according to FIG. 6 and Table 2, it can be confirmed that Example 2 (functional composite membrane) has higher ionic conductivity than Comparative Example 2 (simple composite membrane). This is because the negatively charged functional group generated on the surface of the conductive material layer attracts lithium cations by electrostatic attraction, and the hydrophilicity of the conductive material layer is increased, so that the electrolyte and wettability are improved. On the other hand, as in Comparative Examples 2 and 2, when the carbon layer was formed on the surface of the separator, the ionic conductivity was lower than when only the porous substrate was used as in Comparative Examples 1 and 1, because the dense conductive material layer had ions. This is because it acts as a resistance to penetration. However, according to Figure 6 and Table 2, in the functional composite membrane 2 of Example 3, negative charges are generated on each surface of the porous substrate and the conductive material layer, so that the permeability of lithium cations is increased and the hydrophilicity is improved. However, it exhibited a higher ionic conductivity value than Comparative Example 1.

[Evaluation Example 5] Polysulfide Permeability Measurement

7 is a graph showing the permeability of the ionic active material (polysulfide) of the separation membrane according to all Comparative Examples and Examples of the present invention. The numerical values indicating the permeability of polysulfide are shown in Table 2. 7 and Table 2, Example 1 had a lower polysulfide transmittance than Comparative Example 1. This is because in Evaluation Example 1, the wettability of the electrolyte is improved due to the increase in the porosity of the separator due to plasma treatment, and the permeability of polysulfide may be increased. because it worked. Similarly, when comparing Example 2 and Comparative Example 2 in which a conductive material layer was applied to a porous substrate, Example 2 had lower polysulfide permeability than Comparative Example 2. This is because the negatively charged functional group generated on the surface of the conductive material layer by plasma exerted a force to push the anion polysulfide by electrostatic repulsion. Example 3 showed the lowest polysulfide permeability value, because negatively charged functional groups generated in the separation membrane and the conductive material layer, respectively, prevented the permeation of the anionic polysulfide.

[Production of Lithium-Sulfur Battery Containing Functional Composite Separator]

A coin cell was prepared by assembling the positive electrode and the negative electrode, and the separators of Comparative Examples 1-2 and 1-3, respectively. Here, in addition to the separator, the positive electrode, the negative electrode, and the electrolyte used in the manufacture of the lithium-sulfur battery were prepared and used as follows.

Preparation of anode

Elemental sulfur (S) is used as a cathode active material, carbon black and Ketjen black are used as conductive materials, polyvinylidene fluoride (PVDF) is used as a binder, and N-methyl-2-pyrlidone (NMP) is used as an organic solvent. to prepare a slurry with a composition ratio of (mass ratio: 60:30:10), and then coated on an aluminum current collector having a thickness of 20 μm. This was dried and pressed to prepare a positive electrode plate.

Preparation of the cathode

Non-oxidized lithium metal was used as the negative electrode active material, and the negative electrode plate was manufactured by compression molding on a nickel current collector having a thickness of 825 μm.

Preparation of electrolytes

_{It was prepared by dissolving 1M LiTFSI and 0.1M LiNO 3} lithium salt in a 1:1 (volume ratio) mixed solution of dioxolane (DOL) and dimethoxyethane (DME).

Hereinafter, performance characteristics were evaluated using the battery cells to which each Example or Comparative Example was applied.

[Evaluation Example 6] Measurement of electrochemical impedance spectroscopy

8 is a graph showing the electrochemical impedance of separators according to all Comparative Examples and Examples of the present invention. The exact impedance measurement values are shown in Table 3.

separator R _e (Ω) R _f (Ω) R _ct (Ω) Comparative Example 1 8.32 - 73.18 Example 1 7.10 - 70.33 Comparative Example 2 12.31 9.55 4.87 Example 2 12.81 9.42 6.68 Example 3 10.26 8.01 2.95

R _e in Table 3 is the value of the x-axis intercept of the high frequency region for which represents the resistance of the separation membrane. _{R f} in Table 3 is the diameter value of a semicircle appearing in the intermediate frequency band, and represents the resistance of the conductive material layer in contact with the surface of the anode. _{R ct} in Table 3 is a diameter value of a semicircle appearing in a low frequency band, and represents the charge transfer resistance of the active material. According to Fig. 8 and Table 3 in Example 1 of R _e and R _ct resistance it was lower than in Comparative Example 1. This is a result of improved wettability with electrolytes due to the formation of negatively charged functional groups on the surface of the separator to impart hydrophilicity. The conductive material layer is applied in Comparative Example 2, Example 2 and Example 3 is Comparative Example 1, the embodiment is R _e resist were increased compared to Example 1, which is applied to the porous substrate surface with a high dense conductive material layer porosity the pores This is because the resistance of the separator increased by preventing wetting with the electrolyte. However, the separators to which the conductive layer was applied had much lower _{R ct resistance than the separators to which the conductive layer was not applied.} This is because the conductive material layer easily helps the charge transfer of the low reactive sulfur active material to significantly lower the charge transfer resistance. In Example 2, R _ct was higher and R _f was measured lower than in Comparative Example 2, which is that the sp ² _{bond of the conductive material layer is broken due to plasma treatment and the R ct} resistance is decreased due to the decrease in conductivity due to the generation of negatively charged functional groups of the hydroxyl and carboxyl groups. However, this is because the negatively charged functional group improved wettability with the electrolyte and the resistance of the conductive material layer to the electrolyte decreased. Although R _ct of Example 2 increased slightly compared to Comparative Example 2, it was significantly lower than Comparative Examples 1 and 1, and the overall resistance of the separator was very small, so it can be said that it is a much higher performance separator compared to Comparative Example 1 and Example 1. . In the case of Example 3, the negatively charged functional groups on the surfaces of the porous substrate and the conductive material layer increased the wettability, and the ionic conductivity was improved, so that the _Re , R _f , and R _ct resistances all showed low values.

[Evaluation Example 7] Cyclic voltammetry analysis

9 is a graph showing cyclic voltage-current analysis results of separators according to all comparative examples and examples of the present invention. Cyclic voltage-current analysis measured the current by changing the voltage at a scan rate of ^{0.1mV s -1} in a voltage range between 1.7V and 2.8V at room temperature. The detailed analysis results are shown in Table 4.

separator E1 _pa & E2 _pa E1 _pc & E2 _pc Peak separation
(E1 _pa ~ E2 _pc ) Comparative Example 1 2.42 & 2.52 2.25 & 1.98 0.44 Example 1 2.38 & 2.49 2.26 & 1.99 0.39 Comparative Example 2 2.37 & 2.45 2.30 & 1.97 0.40 Example 2 2.34 & 2.41 2.31 & 1.98 0.36 Example 3 2.34 & 2.42 2.32 & 1.99 0.35

According to FIG. 9 and Table 4, Example 1 was measured to have a narrow voltage range interval between the reduction peak and the oxidation peak compared to Comparative Example 1. This is because the negatively charged functional group on the surface of the separator pushes the anionic polysulfide by electrostatic repulsion, and the reversibility is increased by preventing contamination of the negative electrode. Similarly, when comparing Example 2 and Comparative Example 2 in which a conductive material layer was applied to a porous substrate, Example 2 was measured to have a narrower voltage range interval between the reduction peak and the oxidation peak than Comparative Example 2. This is because the functional groups created on the surface of the conductive color layer push the anionic polysulfide by electrostatic repulsion, and the reversibility is increased by preventing contamination of the negative electrode. In Example 3, the voltage range interval between the reduction peak and the oxidation peak was measured to be narrow, which is because a double electrostatic repulsive force was generated between the negatively charged functional group on the surface of the separator and the conductive material layer and the anionic polysulfide to repel the polysulfide. .

[Evaluation Example 8] Initial capacity measurement

10 is a graph showing the initial capacity results of the separation membranes according to all Comparative Examples and Examples of the present invention. The initial capacity was measured while discharging from 2.8V to 1.6V at room temperature at a current density of 0.2C-rate. Detailed measurement results are shown in Table 2. _{Q H} in FIG. 10 is the capacity expressed when elemental sulfur (S) is reduced to long-chain lithium polysulfide (Li ₂ S _n , 4 < n ≤ 8), and Q _L is long-chain lithium polysulfide Capacity expressed when sulfide is reduced to lithium sulfide (Li ₂ S ₂ /Li _{2 S).} High Q _H , Q _L values indicate effective permeation prevention of the active material and improved reactivity of the active material. According to FIG. 10 and Table 2, Example 1 had a higher initial capacity than Comparative Example 1. This is because the negatively charged functional group on the surface of the separator acts as an electrostatic repulsive force to push the anionic polysulfide, thereby preventing the polysulfide from permeating. Comparative Examples 2, 2, and 3, in which a conductive material layer was applied to a porous substrate, had a significantly increased initial capacity compared to Comparative Examples 1 and 1, which was due to the fact that the conductive material layer facilitated the charge transfer reaction of polysulfide. This is because the responsiveness has been greatly improved. When comparing the separator coated with the conductive material layer, Example 2 had a higher initial capacity than Comparative Example 2. This is because the negatively charged functional group on the surface of the conductive material exerts a force that pushes the anionic polysulfide with an electrostatic repulsive force, thereby preventing the polysulfide from penetrating. The initial capacity could be reduced due to the reduced reactivity with polysulfide due to the decrease in conductivity, but this is because the permeation prevention effect of polysulfide was greater. Example 3 had the highest initial capacity, because negatively charged functional groups and anionic polysulfide on the surfaces of the separator and conductive material layer generated double electrostatic repulsion, effectively preventing the permeation of polysulfide.

[Evaluation Example 9] Secondary battery performance measurement

11 is a graph showing the performance of the separator according to the overall comparative examples and examples of the present invention. The battery was measured while charging and discharging at a current density of 0.2C-rate between 1.6V and 2.8V at room temperature. According to FIG. 11, the battery performance of Example 1 was improved compared to Comparative Example 1, and the performance maintenance rate increased by about 4% from 64.8% to 69.1% based on 100 charge/discharge cycles. This is because the formation of negatively charged functional groups on the surface of the separator prevents permeation of polysulfide ions, suppresses dendrite growth at the anode, and improves lithium ion conductivity. Comparative Examples 2, 2, and 3, in which the conductive material layer was applied to the porous substrate, significantly increased the battery performance compared to Comparative Examples 1 and 1, which was achieved by the conductive material layer helping the charge transfer reaction of the active material. This is because the reactivity is greatly improved and the permeation phenomenon is prevented by physically adsorbing polysulfide. When the separator coated with the conductive material layer was compared, the battery performance of Example 2 was improved compared to that of Comparative Example 2, and the performance retention rate increased by about 4% from 76.7% to 80.7% based on 100 charge/discharge cycles. This is because the formation of negatively charged functional groups on the surface of the conductive color layer prevents permeation of active material ions, suppresses dendrite growth, and improves ionic conductivity. Example 3 had the highest battery performance, because negatively charged functional groups on the surfaces of the separator and conductive material layer double prevented permeation of anionic polysulfide, suppressed dendrite growth, and improved ionic conductivity.

12 is a graph showing the performance of the separator according to the overall comparative examples and examples of the present invention. The battery was measured by charging and discharging between 1.6V and 2.8V at room temperature at various current densities of 0.1, 0.2, 0.5, 1, and 2C-rate. According to FIG. 12, the battery performance of Example 1 was improved compared to Comparative Example 1. This is because the negatively charged functional group on the surface of the separator prevents the permeation of anionic polysulfide ions to suppress contamination of the negative electrode, thereby increasing reversibility, and improving ionic conductivity, which facilitates oxidation/reduction reactions of active materials even at high current densities. Comparative Examples 2, 2, and 3, in which the conductive material layer was applied to the porous substrate, significantly increased the battery performance compared to Comparative Examples 1 and 1, which was achieved by the conductive material layer helping the charge transfer reaction of the active material. This is because the reactivity was greatly improved and the permeation phenomenon was prevented by physically adsorbing polysulfide. When comparing the separator coated with the conductive material layer, Example 2 improved the battery performance compared to Comparative Example 2. This is because the negatively charged functional groups on the surface of the conductive material block the permeation of anionic polysulfide ions to suppress contamination of the negative electrode, thereby increasing reversibility and improving ionic conductivity, which facilitates oxidation/reduction reactions of active materials even at high current densities. Example 3 had the highest battery performance, because negatively charged functional groups generated on each surface of the separator and the conductive material layer double prevented permeation of polysulfide and improved lithium ion conductivity.

The embodiments of the present invention described above should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can improve and change the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the protection scope of the present invention as long as they are apparent to those of ordinary skill in the art.

Claims (17)

porous substrate; and
a conductive material layer laminated on the porous substrate; and
The conductive material layer includes a conductive material and a binder resin, which are carbon-based materials having porosity,
The porous substrate and the conductive material layer include a functional group including at least one of a hydroxyl group, an amine group, an ammonia group, and a carboxyl group attached on one or both surfaces, and the functional group exists between at least the porous substrate and the conductive material layer. Ha, a functional composite separator for lithium-sulfur secondary batteries. The method of claim 1,
The porous substrate is polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, poly Amideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, polyvinylidene difluoride, polytetrafluoroethylene, silica , Alumina, titania, any one material selected from the group consisting of zeolite, a copolymer of two or more thereof, or a mixture thereof, a lithium-sulfur secondary battery functional composite separator. According to claim 1,
The porous substrate is a multi-layer substrate,
Each layer of the multi-layer substrate is polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherE Mead, polyamideimide, polybenzimidazole, polyether sulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, polyvinylidene difluoride, polytetrafluoro A functional composite separator for lithium-sulfur secondary batteries, comprising a material selected from the group consisting of any one material selected from the group consisting of ethylene, silica, alumina, titania, and zeolite, a copolymer of two or more thereof, or a mixture thereof. The method of claim 1,
The porous substrate is a functional composite separator for a lithium-sulfur secondary battery, having a thickness of 1-1000 μm. According to claim 1,
The conductive material layer is CO ₂ Plasma treatment to include a functional group including at least one of a hydroxyl group, an amine group, an ammonia group, and a carboxyl group attached to the surface of the conductive material layer, a lithium-sulfur secondary battery functional composite separator. According to claim 1,
The carbon-based material includes natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, graphite, graphene, activated carbon, carbon fiber, carbon nanotube, activated carbon, or a combination thereof, a lithium-sulfur secondary battery functional composite separator. According to claim 1,
The conductive material is included in 5-80% by weight based on the weight of the binder resin, a lithium-sulfur secondary battery functional composite separator. The method of claim 1,
The binder is included in 5-80% by weight based on the weight of the conductive material, a lithium-sulfur functional composite separator for a secondary battery. According to claim 1,
The conductive material layer has a thickness of 0.01 - 500㎛, a lithium-sulfur secondary battery functional composite separator. attaching a functional group including at least one of a hydroxyl group, an amine group, an ammonia group, and a carboxyl group to one or both surfaces of the porous substrate by treating the porous substrate with reactive gas plasma;
laminating a conductive material layer on one surface of the porous substrate to which the functional group is attached; and
Attaching a functional group comprising at least one of a hydroxyl group, an amine group, an ammonia group, and a carboxyl group to the conductive material layer by treating the conductive material layer with reactive gas plasma;
The conductive material layer is a method for manufacturing a functional composite separator for a lithium-sulfur secondary battery comprising a conductive material and a binder resin, which are carbon-based materials having a porosity. 11. The method of claim 10,
The reactive gas is any one or more gases selected from the group consisting of Ar, He, N ₂ , NH ₃ , NF ₃ , F ₂ , O ₂ , CO ₂ , H ₂ , NO _{x , and air, and x is 1≤} A method for manufacturing a functional composite separator for a lithium-sulfur secondary battery, wherein x≤3. 12. The method of claim 11,
The reactive gas is CO ₂ , a lithium-sulfur secondary battery functional composite separator manufacturing method. 11. The method of claim 10,
The plasma treatment includes a power of any one of DC, RF, and microwave, a lithium-sulfur secondary battery functional composite separator manufacturing method. 11. The method of claim 10,
The plasma treatment is performed at a pressure of 1 mTorr - 10 Torr and a temperature of -196°C - 500°C, a lithium-sulfur secondary battery functional composite separator manufacturing method. 11. The method of claim 10,
The plasma treatment is RF plasma power treatment, which will be treated at an RF frequency of 20kHz - 1GHz and a power condition in the range of 25 - 10,000W, a lithium-sulfur secondary battery functional composite separator manufacturing method. A lithium-sulfur secondary battery comprising a functional composite separator for a lithium-sulfur secondary battery according to any one of claims 1 to 9. 17. The method of claim 16,
The lithium-sulfur secondary battery includes a positive electrode, a negative electrode, a functional composite separator for a lithium-sulfur secondary battery, and an electrolyte, wherein the positive electrode and the negative electrode are disposed to face each other, and the functional composite separator for a lithium-sulfur secondary battery and the electrolyte are the positive electrode and a lithium-sulfur secondary battery located between the negative electrode.

Images