KR20190141616A - Double-side coated seperator and metal secondary battery having the same - Google Patents

Abstract

Provided are a double-side coated separation membrane and a metal secondary battery having the same. The metal secondary battery comprises a negative pole and a positive pole which are metal electrodes, and a double-side coated separation membrane arranged between the negative pole and the positive pole. The double-side coated separation membrane has an insulation porous body, a carbon particle layer located on a surface in which the insulation porous material faces the positive pole, and an inorganic particle layer located on the surface in which the insulation porous body faces the negative pole.

Description

Double-side coated separator and metal secondary battery having same {Double-side coated seperator and metal secondary battery having the same}

The present invention relates to a battery, and more particularly to a secondary battery.

The metal secondary battery is a battery using a single metal or an alloy thereof as a negative electrode, and includes a metal-air battery, a metal-sulfur battery, a metal ion battery, and the like.

In such a metal secondary battery, a thick resistive layer may be formed on a negative electrode surface formed of a single metal or an alloy thereof to reduce charge and discharge capacity during driving of the battery, and metal densities, which are dendritic laminates, may be unevenly stacked on the metal electrode surface. A dendrite is formed and the metal dendrites can pass through the separator to reach the counter electrode, causing a short circuit or explosion of the battery.

SUMMARY OF THE INVENTION An object of the present invention is to provide a metal secondary battery capable of suppressing side reactions on a metal electrode surface and suppressing dendrites.

Technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above technical problem, the present invention provides a double-coated membrane. The double coated membrane includes an insulating porous body having a pair of side surfaces facing each other, a carbon particle layer positioned on one side of the insulating porous body, and an inorganic particle layer positioned on the other side of the insulating porous body.

The carbon particle layer may include graphene particles and a binder. Graphene particles in the carbon particle layer may be contained in more weight than the binder. The carbon particle layer may have a thickness of 5 to 30 ㎛.

The inorganic particle layer may include metal oxide nanoparticles and a binder. Metal oxide nanoparticles in the inorganic particle layer may be contained in more weight than the binder. The inorganic particle layer may have a thickness of 1 to 9 ㎛.

In order to achieve the above technical problem, the present invention provides a method of manufacturing a double-coated membrane. The manufacturing method may include providing an insulating porous body having a pair of side surfaces facing each other. Coating the slurry of carbon particles on one side of the insulating porous body. The inorganic particle slurry is coated on the other side of the insulating porous body.

The carbon particle slurry may contain graphene particles, a binder, and a polar aprotic solvent. The carbon particle slurry may contain the graphene particles and the binder in a concentration of 1 to 5 mg with respect to 1 ml of the solvent. The inorganic particle slurry may contain metal oxide nanoparticles, a binder, and a polar aprotic solvent. The inorganic particle slurry may contain 1 to 5 mg of the metal oxide nanoparticles and the binder with respect to 1 ml of the solvent. The polar aprotic solvent may be acetone. The carbon particle slurry or the inorganic particle slurry may be coated using a droplet method.

In order to achieve the above technical problem, the present invention provides a metal secondary battery. The metal secondary battery includes a negative electrode, a positive electrode, and a double-coated separator disposed between the negative electrode and the positive electrode, which is a metal electrode. The double coated membrane includes an insulating porous body, a carbon particle layer positioned on a surface of the insulating porous body facing the anode, and an inorganic particle layer positioned on a surface of the insulating porous body facing the cathode.

The positive electrode may contain a sulfur-containing material as the positive electrode active material.

According to the present invention as described above, in the metal secondary battery having a metal electrode as a negative electrode provides a separator having an inorganic particle layer on one side facing the metal electrode, the inorganic particle layer suppresses side reactions on the metal electrode surface And dendrites can be suppressed.

In addition, the separator further includes a carbon particle layer on the other side facing the anode, thereby improving the electrical conductivity of the anode and reducing the current density. As a result, the electrochemical reaction efficiency of the positive electrode active material can be improved, and the destruction of the positive electrode active material or its performance can be prevented.

In addition, the carbon particle layer and the inorganic particle layer in the metal-sulfur battery can hold the polysulfide, thereby effectively suppressing the shuttleling effect that the polysulfide moves to the metal electrode side.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a cross-sectional view showing a double-coated separator according to an embodiment.
2 is a schematic diagram illustrating a process of manufacturing a double-coated separator according to an embodiment.
3 is a cross-sectional view schematically showing a metal secondary battery according to an embodiment of the present invention.
4 is a graphene-coated surface (a), an Al ₂ O ₃ coated surface (c), and a cross-section (d) of a polypropylene separator surface (b), and a double-coated separator according to Preparation Example 1 of a double-coated membrane. Scanning electron microscope (SEM) images taken are shown.
FIG. 5 shows SEM images (a) of cross sections of the double coated membrane according to Preparation Example 1 of double coated membrane and Energy Dispersive X-Ray Spectrometer (EDS) images (b, c) of the cross section.
FIG. 6 shows optical photographs of graphene coated surfaces, acetylene black coated surfaces, and super-p coated surfaces of double coated membranes according to Double Coated Membrane Preparation Examples 1 to 3;
7 is a graph illustrating initial charge and discharge characteristics of batteries according to Battery Preparation Example 1 and Battery Comparative Example 1. FIG.
8 and 9 are graphs showing initial charge and discharge characteristics and cycle characteristics of batteries according to Battery Preparation Example 2 and Comparative Example 2, respectively.
10 and 11 are graphs showing initial charge and discharge characteristics and cycle & coulomb efficiency characteristics of batteries according to Battery Preparation Example 3 and Battery Comparative Example 3, respectively.
12A is a graph showing cycle characteristics under the rate change conditions of batteries according to Battery Preparation Example 3 and Battery Comparative Example 3, and FIGS. 12B and 12C show rate changes of batteries according to Battery Preparation Example 3 and Battery Comparative Example 3, respectively. Graphs showing charge and discharge characteristics under conditions.
FIG. 13 is an electrochemical impedance spectrometer measured after 100 cycles of cells according to Preparation Example 3 and Comparative Example 3 at a rate of 1 C in a voltage range of 1.9 V to 2.8 V (vs. Li / Li ⁺ ). impedance spectroscopy) A graph showing the test results.
14 shows the surface of a separator obtained by disassembling and recovering the cells according to Battery Preparation Example 3 and Battery Comparative Example 3 after driving 200 cycles at a rate of 1C in a voltage range of 1.9V to 2.8V (vs. Li / Li ⁺ ). SEM images of the surface of the lithium metal negative electrode and EDS images of the surface of the lithium metal negative electrode are shown.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to describe the present invention in more detail. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. In the figures, where a layer is said to be "on" another layer or substrate, it may be formed directly on the other layer or substrate, or a third layer may be interposed therebetween.

In the present specification, the term “metal secondary battery” includes a metal or metal alloy electrode as a negative electrode, on which a solid metal is oxidized to metal ions in a discharge process and metal ions are reduced to a solid metal in a charge process. Can be. The metal secondary battery is an alkali metal ion battery, an alkali metal-air battery or an alkali metal-sulfur battery, specifically, a lithium ion battery, sodium ion battery, potassium ion battery, lithium-air battery, sodium-air battery, potassium-air battery , Lithium-sulfur batteries, sodium-sulfur batteries, or potassium-sulfur batteries. However, it is not limited to this. The metal secondary battery may be used in a small energy storage device included in a portable device such as a mobile phone, a notebook computer, a camcorder, a large energy storage device used in a hybrid vehicle, an electric vehicle, a defense industry, aerospace and aviation, and the like.

1 is a cross-sectional view showing a double-coated separator according to an embodiment.

Referring to FIG. 1, the double-coated separator 20 may include an insulating porous body 21. The insulating porous body 21 may be referred to as a base separator. It may be a film containing polyethylene or polypropylene or a laminate thereof or a fibrous nonwoven fabric containing cellulose, polyester, or polypropylene, or a porous glass filter. The insulating porous body 21 may have a thickness of about 20 to 30 μm as an example of several tens of micrometers, but is not limited thereto.

The insulating porous body 21 may have two sides facing each other relatively wider than other surfaces, and the carbon particle layer 22 may be located on one side of the side surfaces. The carbon particle layer 22 may be a layer including one or more carbon particles such as graphene, carbon nanotubes, acetylene black, Super-P, Ketjen black, activated carbon, and the like. In addition, the carbon particle layer 22 may further include a binder. The binder in the carbon particle layer 22 may be polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), chitosan, polyethylene glycol, xanthan Gum, gum arabic, polyacrylonitrile (PAN), poly (3,4-ethylenedioxythiophene) (PEDOT), polystyrenesulfonate (PSS), PEDOT: PSS, or mixtures thereof.

Carbon particles in the carbon particle layer 22 may be contained in more weight than the binder. In this case, rather than the carbon particles are dispersed in the binder or the binder is disposed to cover the carbon particles, the binder may be located only in a region between the carbon particles and serve to bond them together. Specifically, the weight ratio of the carbon particles to the binder in the carbon particle layer 22 may be in the range of 2: 1 to 8: 1. In addition, the carbon particle layer 22 may include a plurality of pores of a micrometer size and a nanometer size.

For example, the carbon particle layer 22 may include graphene, which is crystalline carbon particles, as carbon particles. At this time, the average thickness of the graphene particles may be 0.1 to 20nm specifically 1 to 10nm, more specifically 1 to 2nm, and also the average width of the graphene particles is 0.1 to 20㎛, specifically It may be 1 to 15 μm, more specifically 7 to 13 μm. In addition, the graphene particles may have one or several atomic layers, and as an example, may have about one to eight more specifically one to three atomic layers. The binder in the carbon particle layer 22 may be, for example, PVDF. The carbon particle layer 22 may be formed to have a thickness of, for example, several micrometers to several tens of micrometers, for example, 5 to 30 μm, specifically 10 to 20 μm.

An inorganic particle layer 23 containing inorganic particles may be coated on the other side of the insulating porous body 21. The inorganic particles may contain metal fluoride, metal oxide, metal nitride, metal carbide, or a combination thereof. At this time, the metal contained in the inorganic particles is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, Fr, Ra, Ac, Si, P, As, Se or Te. The inorganic particles may be nano inorganic particles having a diameter of nanometers. For example, the inorganic particles may be a metal oxide, for example, a metal oxide exhibiting insulation such as aluminum oxide. The inorganic particle layer 23 may further include a binder for bonding the inorganic particles together with the inorganic particles. The binder in the inorganic particle layer 23 is polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), chitosan, polyethylene glycol, xanthan Gum, gum arabic, polyacrylonitrile (PAN), poly (3,4-ethylenedioxythiophene) (PEDOT), polystyrenesulfonate (PSS), PEDOT: PSS, or mixtures thereof.

The inorganic particles in the inorganic particle layer 23 may be contained in more weight than the binder. In this case, rather than the inorganic particles are dispersed in the binder or the binder is disposed to cover the inorganic particles, the binder may be located only in the region between the inorganic particles and serve to bond them together. Specifically, the weight ratio of the inorganic particles and the binder in the inorganic particle layer 23 may be in the range of 2: 1 to 8: 1. In addition, the inorganic particle layer 23 may be provided with a plurality of pores of the nanometer size.

As an example, the inorganic particle layer 23 may include aluminum oxide nanoparticles. The binder in the inorganic particle layer 23 may be, for example, PVDF. The inorganic particle layer 23 may be formed to have a thickness of 1 to several micrometers, for example, 1 to 9 μm and specifically 2 to 5 μm.

2 is a schematic diagram illustrating a process of manufacturing a double-coated separator according to an embodiment.

Referring to FIG. 2, an insulating porous body 21 may be provided. Detailed description of the insulating porous body 21 will be referred to the part described with reference to FIG. 1.

The carbon particle slurry 22a may be coated and dried on one side of the insulating porous body 21. The carbon particle slurry 22a may contain carbon particles, a binder, and a solvent. The description of the carbon particles and the binder will be referred to the parts described with reference to FIG. 1. The solvent may be a polar aprotic solvent, for example, acetone or tetrahydrofuran (THF) having a relatively low volatility and low volatility. The weight ratio of the carbon particles and the binder in the slurry may be in the range of 2: 1 to 8: 1. In addition, the concentration of the carbon particles and the binder, that is, the solute in the slurry may be in the range of 1 to 5 mg / ml, for example, 3 to 4 mg / ml. In addition, the method of coating the carbon particle slurry 22a may be a drop casting or a droplet method. This is done by dropping the slurry onto a plurality of portions of one side of the insulating porous body 21 through a nozzle such as a dropper, so that the carbon particle layer 22 may be formed after the solvent is volatilized or dried from the loaded slurry. As such, when using acetone or THF, which has a relatively high volatility of the solvent while using drop casting, the volatilization time of the solvent is relatively small, and the carbon particle layer 22 is uniformly disposed on the surface of the insulating porous body 21. It may have a low thickness. In addition, the solvent may be volatilized to form a plurality of nano-sized pores in the carbon particle layer 22. The drying may be vacuum drying.

The inorganic particle slurry 23a may be coated and dried on the other side of the insulating porous body 21. The inorganic particle slurry 23a may contain inorganic particles, a binder, and a solvent. The description of the inorganic particles and the binder will be referred to the parts described with reference to FIG. 1. The solvent may be a polar aprotic solvent, for example, acetone or tetrahydrofuran (THF) having a relatively low volatility and low volatility. The weight ratio of the inorganic particles and the binder in the slurry may be in the range of 2: 1 to 8: 1. In addition, the concentration of the inorganic particles and the binder, that is, the solute in the slurry may be in the range of 1 to 5 mg / ml, for example, 3 to 4 mg / ml. In addition, the method of coating the inorganic particle slurry (23a) may be a drop casting or a droplet method. This is done by dropping the slurry onto a plurality of portions of the other side of the insulating porous body 21 through a nozzle such as a dropper, so that the inorganic particle layer 23 may be formed after the solvent is volatilized or dried from the loaded slurry. As such, when using acetone or THF, which has a relatively high volatility of the solvent while using drop casting, the volatilization time of the solvent is relatively small, and the inorganic particle layer 23 is uniformly disposed on the surface of the insulating porous body 21. It may have a low thickness. In addition, as the solvent is volatilized, a plurality of nano-sized pores may be formed in the inorganic particle layer 23. The drying may be vacuum drying.

3 is a cross-sectional view schematically showing a metal secondary battery according to an embodiment of the present invention.

Referring to FIG. 3, the metal secondary battery includes a positive electrode 10, a negative electrode 30, and a double coated separator 20 interposed therebetween. An electrolyte (not shown) may be disposed or filled between the positive electrode 10 and the negative electrode 30. In addition, the positive electrode 10 may be disposed on the positive electrode current collector 50, and the negative electrode 30 may be disposed on the negative electrode current collector 40.

The positive electrode 10 may vary depending on the specific type of the metal secondary battery. Specifically, when the metal secondary battery is an air battery, the positive electrode 10 may use air as a positive electrode active material, and may include a carbon material, a catalyst for redox of oxygen, or a combination thereof. The catalyst for redox of oxygen may be a transition metal, a transition metal oxide, or a transition metal carbide. The carbon material may include carbon black (super P, ketjen black, etc.), carbon nanotubes (CNT), graphite, graphene, porous carbon, or a combination thereof. The transition metal is ruthenium (Ru), palladium (Pd), iridium (Ir), cobalt (Co), nickel (Ni), iron (Fe), silver (Ag), manganese (Mn), platinum (Pt), gold (Au), nickel (Ni), copper (Cu), aluminum (Al), chromium (Cr), titanium (Ti), silicon (Si), molybdenum (Mo) tungsten (W), or a combination thereof. have. The transition metal oxide may be ruthenium dioxide (RuO ₂ ), iridium dioxide (IrO ₂ ), tricobalt tetraoxide (Co ₃ O ₄ ), manganese dioxide (MnO ₂ ), cerium dioxide (CeO ₂ ), ferric trioxide (Fe ₂ O ₃ ), Ferric tetraoxide (Fe ₃ O ₄ ), nickel monoxide (NiO), copper oxide (CuO), a perovskite-based catalyst or a combination thereof. The transition metal carbide may include titanium carbide (TiC), silicon carbide (SiC), tungsten carbide (WC), molybdenum carbide (Mo ₂ C) -based catalyst, or a combination thereof.

When the metal secondary battery is a metal-sulfur battery, the cathode 10 may contain a sulfur-containing material and carbon as a cathode active material. The carbon may be a conductive carbon and may have a particle form, for example, may be graphene or carbon nanotubes (CNT), and for example, the carbon may be multiwall carbon nanotubes (MWCNT). Can be. The conductive carbon particles may have an oxidized surface as an example of an oxidized surface. The sulfur containing material may be elemental sulfur, metal sulfide, sulfurized polymer, or a mixture of two or more thereof and may have a particle form. The elemental sulfur may specifically be an octasulfur (S ₈ ) molecule, more specifically, a cyclo octa sulfur (cyclo-S ₈ ) molecule. The metal sulfide may be lithium sulfide (Li ₂ S). Sulfurized polymers are, for example, sulfur-polyacrylonitrile (S-PAN), sulfur-polyaniline (sulfur-polyaniline), sulfur- (1,3-diisopropenylbenzene polyvinylidene dichloride) (sulfur- (1,3-diisopropenylbenzene polyvinylidene dichloride)), sulfur- (polyvinylidene dichloride-co-acrylonitrile).

The anode 10 may further include laminated double hydroxide (LDH) particles. LDH particles exhibit a crystal structure having an intermediate layer between a pair of metal hydroxide unit layers (in the formula, M _a ²⁺ _1-x M _b ³⁺ _x (HO ⁻ ) ₂ ), wherein The same neutral molecule and / or anion (in the formula: X ^n- ) is inserted. The LDH may have a chemical formula of [M _a ²⁺ _1-x M _b ³⁺ _x (HO ⁻ ) ₂ ] ^{x +} [(X ⁿ⁻ ) _{x / n} yH ₂ O] ^{x −} . In this chemical formula, M _a ²⁺ is a divalent ion of an alkaline earth metal or a transition metal, and as an example, Ca ²⁺ , Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ Or Zn ²⁺ , M _b ³⁺ is a trivalent ion of a Group 13 metal or transition metal, and may be, for example, Fe ³⁺ , Al ³⁺ , Mn ³⁺ , Co ^3+, or Ni ³⁺ . , X ^n- may be CO ₃ ^2- , NO ₃ ^2- , SO ₄ ^2- , Cl ⁻ , OH ⁻ , or S ^2- , x may be 0.2 to 0.5, n may be 1 or 2 And y may be 0.5 to 4. As an example, the LDH may be [Mg ²⁺ _1-x Al ³⁺ _x (HO ⁻ ) ₂ ] ^{x +} [(NO ₃ ^2- ) _{x / 2} yH ₂ O] ^x- (x is 1/3) Can be. The LDH has abundant hydrophilic and hydroxy groups on its surface to efficiently receive sulfides and to prevent polysulfides from dissolving into the electrolyte solution.

The anode 10 may have, for example, a binder-free free standing film in which sulfur-containing particles and further LDH particles are fixed in a carbon nanotube web formed by interweaving carbon nanotubes.

On the other hand, when the metal secondary battery is a metal ion battery, the positive electrode 40 is a positive electrode active material, a conductive material of at least one of a composite oxide or a composite phosphate of cobalt, manganese, nickel, iron, or a combination thereof and an alkali metal Carbon material, and a binder.

The positive electrode current collector 50 may include a carbon diffusion layer, a nickel mesh, a stainless mesh, a nickel foam, a glass fiber, a carbon nanotube layer, or graphene. It may be a pinned layer.

The cathode 30 may be a metal electrode, and the metal electrode may be an alkali metal electrode or an alkali metal alloy electrode, for example, a lithium electrode, a sodium electrode, or a potassium electrode, or an alloy electrode of any one thereof. For example, the negative electrode 30 may be lithium foil, sodium foil, or potassium foil.

The electrolyte filled in the pores of the double-coated separator 20 between the positive electrode 10 and the negative electrode 30 may be a non-aqueous electrolyte solution. The non-aqueous electrolyte solution includes an electrolyte and a medium, which may be an alkali metal salt. Among the alkali metal salts, lithium salts include lithium perchloroate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium trifluoromethane sulphonate (LiCF ₃ SO ₃ ), and lithium hexafluoroacetate. Nate (LiAsF ₆ ), lithium trifluoromethanesulfonylimide (Li (CF ₃ SO ₂ ) ₂ N, LiTFSI), LiNO ₃ (Lithium nitrate), LiBr (Lithium bromide), LiI (Lithium iodide), or their May be a combination. The sodium salt in the alkali metal salt may be NaClO ₄ , NaPF ₆ , NaAsF ₆ , NaSbF ₆ , NaBF ₄ , NaCF ₃ SO ₃ , NaN (SO ₂ CF ₃ ) ₂ , NaAlCl ₄ , and the like. The medium is TEGDME (tetraeethyleneglycol dimethylether), DME (dimethoxyethane), DEGDME (diethyleneglycol dimethylether), dioxolane (dioxolane), DMSO (dimethylsulfoxide), DMA (N, N-dimethylacetamide), DMF (dimethylformamide), ACN (Acetonitrile), PC (propylene carbonate) or a combination thereof.

The double coated separator 20 is described with reference to FIGS. 1 and 2, and the inorganic particle layer 23 may be formed on the other side of the carbon particle layer 22 on one side of the insulating porous body 21. . In this case, the carbon particle layer 22 may be disposed to face the anode 10, and the inorganic particle layer 23 may be disposed to face the cathode 30.

The carbon particle layer 22 positioned on the anode 10 may exhibit high ionic and electron conductivity, thereby improving alkali metal ion transfer and relieving current concentration that may occur in the anode 10. Accordingly, breakdown or degradation of the cathode active material in the metal ion battery can be alleviated. In addition, the carbon particle layer 22 may improve the electrochemical reaction efficiency of sulfur in the metal-sulfur battery and effectively suppress the shuttleling effect of the polysulfide moving to the cathode 40. In addition, the inorganic particle layer 23 disposed on the cathode 40 can suppress the shuttleling effect of the polysulfide moving toward the cathode 40, and exhibits appropriate rigidity on the cathode 40, which is a metal electrode. It is possible to physically suppress the growth of metal dendrites, which are easily generated during the battery driving process, to suppress internal short circuits due to metal dendrites.

Hereinafter, preferred examples are provided to aid the understanding of the present invention. However, the following experimental example is only for helping understanding of the present invention, and the present invention is not limited by the following experimental example.

<Production Example 1 of Double Sided Coating Membrane>

45 mg of graphene (1.6 nm thick) and 11.3 mg of polyvinylidene fluoride (PVDF, Arkema) (mass ratio of about 4: 1) were added to 15 ml of acetone and mixed by sonication for 2 hours to obtain a graphene slurry. .

45 mg of Al ₂ O ₃ nanopowder (Aldrich, USA) and 11.3 mg of polyvinylidene fluoride (PVDF, Arkema) (mass ratio of about 4: 1) were added to 15 ml of acetone and mixed by sonication for 2 hours. ₂ O ₃ slurry was obtained.

The Al ₂ O ₃ slurry was coated on one surface of a polypropylene separator (Celgard 2400, USA) using a droplet (or drop-casting) method. The graphene slurry was coated on the other side of the polypropylene separator using a droplet (or drop-casting) method. Thereafter, the polypropylene separator coated with Al ₂ O ₃ slurry and graphene slurry on both surfaces facing each other was vacuum dried at 80 ° C. for 12 hours to remove residual solvent. At this time, the area mass loadings of Al ₂ O ₃ and graphene were 0.15 mg / cm ² and 0.14 mg / cm ² , respectively.

<Production Example 2 of Double-coated Membrane>

Except for using acetylene black instead of graphene to prepare a double-coated membrane using the same method as in Preparation Example 1 double-sided coated membrane.

<Production Example 3 of Double Sided Coating Membrane>

Except for using super-p instead of graphene, a double-coated separator was prepared in the same manner as in Preparation Example 1, double-coated separator.

<Anode manufacturing example 1: CNT-S cathode>

Sulfur and carbon nanotubes were mixed 1: 1 and placed in 200 ml of water, followed by sonication, and evenly dispersed. After filtering the dispersed sulfur-carbon nanotube composite using a filter paper, the electrode obtained by vacuum drying for one day to remove the remaining solvent.

<Anode Preparation Example 2: Carbon-Spolymer / PAA Cathode>

Slurry was prepared by mixing sulfide polymer (sulfur-polyacrylonitrile), super-p, and polyacrylic acid binder in a weight ratio of 80:10:10 in ethanol. The resulting slurry was then coated on aluminum foil and vacuum dried for 24 hours to remove residual solvent.

<Anode Manufacturing Example 3: Freestanding MgAl-LDH @ CNT-S Cathode>

3 mmol of Mg (NO ₃ ) ₂ · 6H ₂ O, 1 mmol of Al (NO ₃ ) ₃ · 9H ₂ O and 0.16 mol of urea (Junsei Chemical, Japan) were dissolved in 200 ml of deionized water to give solution 1 Got it. The urea was used as a base and readily hydrolyzed in the presence of water at 100 ° C. to produce (NH ₄ ) ₂ CO ₃ . Meanwhile, 0.2 g of functionalized carbon nanotubes (MWCNT) using nitric acid was ultrasonically dispersed in 10 ml of isopropanol solution to obtain solution 2. Solution 2 was added dropwise to Solution 1 being stirred for 1 hour and the resulting mixture was refluxed at 100 ° C. with continued stirring for 4 hours. The precipitated product was filtered, washed with deionized water to remove unreacted reactants, and dried in a vacuum oven at 80 ° C. for 24 hours to obtain a microscale MgAl-LDH (Layered Double Hydroxide) complex grafted to MVCNT. A freestanding MgAl-LDH @ CNT-S electrode was prepared by adding additional MWCNTs and elemental sulfur powder to the obtained MgAl-LDH @ CNT composite. The MgAl-LDH: CNT: elemental sulfur (S8) was 4.5 wt%: 40.5 wt%: 55 wt% at the MgAl-LDH @ CNT-S electrode. The freestanding MgAl-LDH @ CNT-S cathode was dried in a vacuum oven at 80 ° C. for 12 hours.

<Battery Production Example 1>

A lithium-sulfur battery in the form of a laminated pouch cell was prepared by cutting a CNT-S positive electrode sheet having a sulfur content of 5 mg / cm ² and a lithium metal foil having a size of 3 cm x 5 cm, and using a total of eight sheets. It was. At this time, the double-coated separator obtained in the double-coated separator Preparation Example 1 between the positive electrode and the negative electrode was disposed so that the graphene layer toward the positive electrode and the Al ₂ O ₃ layer toward the negative electrode, 1: 1 (v / 1M LiTFSI (lithium bis (trifluoromethane sulfonyl) imide) in a mixed solvent of 1,3-dioxolane (1,3-dioxolane) and 1,2-dimethoxyethane (v) with a ratio of v) ) And 0.8 M of LiNO ₃ were used.

<Battery Production Example 2>

Except that a lithium-sulfur battery in the form of a laminated pouch cell was manufactured by cutting a positive electrode having a sulfur content of 3 mg / cm ² and a lithium metal foil having a size of 3 cm x 5 cm, and then using each of two sheets. The same battery as in Battery Preparation Example 1 was prepared.

<Battery Production Example 3>

The freestanding MgAl-LDH @ CNT-S obtained in the positive electrode preparation example 3 was cut into the shape of the disk which has a diameter of 10 mm, and the positive electrode was obtained. The sulfur mass loading in this anode was 4.0-4.5 mg / cm ² . Lithium metal foil was used as the negative electrode. 1 M LiTFSI (lithium) in a mixed solvent of 1,3-dioxolane (1,3-dioxolane) and 1,2-dimethoxyethane having a ratio of 1: 1 (v / v) An electrolyte solution containing bis (trifluoromethane sulfonyl) imide) and 0.8M LiNO ₃ was obtained. The double-coated separator obtained in Preparation Example 1 of the double-coated separator between the positive electrode and the negative electrode was disposed such that the graphene layer faced the positive electrode and the Al ₂ O ₃ layer faced the negative electrode, and injected the electrolyte into the coin cell CR2032. Configured. Preparation of the cells was carried out in a dry box (MBRAUN) filled with Ar.

<Comparative Battery Example 1>

A battery was manufactured in the same manner as in Battery Preparation Example 1, except for using the non-coated polypropylene separator (Celgard 2400, USA) instead of the double coated membrane obtained in Preparation Example 1 as the double-coated separator.

<Battery Comparative Example 2>

A battery was manufactured in the same manner as in Battery Preparation Example 2, except for using the non-coated polypropylene separator (Celgard 2400, USA) instead of the double-coated separator obtained in Preparation Example 1 as a separator.

<Comparative Battery Example 3>

A battery was manufactured in the same manner as in Battery Preparation Example 3, except for using the uncoated polypropylene separator (Celgard 2400, USA) instead of the double coated membrane obtained in Preparation Example 1 as a double-coated separator.

4 is a graphene-coated surface (a), an Al ₂ O ₃ coated surface (c), and a cross-section (d) of a polypropylene separator surface (b), and a double-coated separator according to Preparation Example 1 of a double-coated membrane. Scanning electron microscope (SEM) images taken are shown.

Referring to FIG. 4, the surface of the commercially available polypropylene separator (b) showed uniform submicron porosity. SEM images of the graphene coated surface (a) and the Al ₂ O ₃ coated surface (c) show that the dense graphene and Al ₂ O ₃ powders cover both sides of the polypropylene separator, respectively. In addition, the cross-section (d) of the double-coated separator shows that the graphene layer and the Al ₂ O ₃ layer were formed with thicknesses of about 15 μm and 3 μm, respectively. Thus, the double coated membrane (including 27 μm polypropylene layer) was approximately 45 μm thick overall.

FIG. 5 shows SEM images (a) of cross sections of the double coated membrane according to Preparation Example 1 of double coated membrane and Energy Dispersive X-Ray Spectrometer (EDS) images (b, c) of the cross section.

Referring to FIG. 5, it can be seen that graphene layers and Al ₂ O ₃ nanopowder layers are formed on both sides of the porous polypropylene layer, respectively.

FIG. 6 shows optical photographs of graphene coated surfaces, acetylene black coated surfaces, and super-p coated surfaces of double coated membranes according to Double Coated Membrane Preparation Examples 1 to 3;

Referring to FIG. 6, the graphene coating surface was found to be uniformly coated with graphene, but acetylene black or super-p was not uniformly coated. This was presumed to be due to the graphene particles having a flat plate shape.

7 is a graph illustrating initial charge and discharge characteristics of batteries according to Battery Preparation Example 1 and Battery Comparative Example 1. FIG. Initial charge and discharge characteristics were measured at a rate of 0.1C at a temperature of 30 ℃ and a voltage range of 1.9V-2.6V (vs. Li / Li ⁺ ). In the experimental examples herein, the rate was based on the theoretical capacity of sulfur (1675 mAh / g).

Referring to FIG. 7, it can be seen that the battery according to Preparation Example 1 of the battery using the double-coated separator is improved in initial capacity compared to the battery of Comparative Example 1 of the battery using the uncoated separator. This can be understood that the graphene layer coated on the surface facing the anode of the double-coated separator used in the battery preparation example 1 improves the electrical conductivity of the anode to improve the electrochemical reaction efficiency of sulfur.

8 and 9 are graphs showing initial charge and discharge characteristics and cycle characteristics of batteries according to Battery Preparation Example 2 and Comparative Example 2, respectively. Initial charging and discharging characteristics were measured at a rate of 0.1C at a voltage range of 1V-3V (vs. Li / Li ⁺ ) at a temperature of 30 ° C., and the cycle characteristics were charged and discharged except that the rate was changed to 0.5C. Measurement was carried out under the same conditions as the characteristic measurement conditions.

Referring to FIG. 8, there was no significant difference between the battery preparation example 2 and the battery comparative example 2 in the case of the initial capacity, but showed a slight difference in the charge / discharge efficiency.

Referring to FIG. 9, the capacity at high rate (0.5 C) was higher in Battery Preparation Example 2, and the battery life example also showed better performance after the cycle.

10 and 11 are graphs showing initial charge and discharge characteristics and cycle & coulomb efficiency characteristics of batteries according to Battery Preparation Example 3 and Battery Comparative Example 3, respectively. Initial charging and discharging characteristics were measured at a rate of 0.1C at a temperature of 30 ° C and a voltage range of 1.9V-2.8V (vs. Li / Li ⁺ ), and the cycle characteristics were changed except that the rate was changed to 1C. Measurement was performed under the same conditions as the discharge characteristic measurement conditions.

Referring to FIG. 10, it can be seen that the battery according to Preparation Example 3 using the double-coated separator is improved in initial capacity compared to the battery according to Comparative Example 3, the battery using the uncoated separator. This can be understood that the graphene layer coated on the surface facing the positive electrode of the double-coated separator used in Preparation Example 3 improves the electrical conductivity of the positive electrode, thereby improving the electrochemical reaction efficiency of sulfur.

Referring to FIG. 11, as a result of driving the battery for 200 cycles at a high rate (1 C), the battery according to Preparation Example 3 using the double-coated separator was compared with the cell according to Comparative Example 3 using the uncoated separator. It can be seen that the life characteristics and the coulomb efficiency characteristics are very excellent.

12A is a graph showing cycle characteristics under the rate change conditions of batteries according to Battery Preparation Example 3 and Battery Comparative Example 3, and FIGS. 12B and 12C show rate changes of batteries according to Battery Preparation Example 3 and Battery Comparative Example 3, respectively. Graphs showing charge and discharge characteristics under conditions. It was measured at rate conditions of 0.1 C, 0.2 C, 0.5 C, 1 C, 3 C, and 5 C at a temperature of 30 ° C. and a voltage range of 1.9 V-2.8 V (vs. Li / Li ⁺ ).

12A, 12B, and 12C, the battery according to Battery Preparation Example 3 using the double-coated separator and the cycle characteristics at the rate change condition compared to the battery according to Comparative Example 3 using the uncoated separator and The charge and discharge characteristics were all excellent.

FIG. 13 is an electrochemical impedance spectrometer measured after 100 cycles of cells according to Preparation Example 3 and Comparative Example 3 at a rate of 1 C in a voltage range of 1.9 V to 2.8 V (vs. Li / Li ⁺ ). impedance spectroscopy) A graph showing the test results.

Referring to FIG. 13, it can be seen that the battery according to Battery Preparation Example 3 using the double-coated separator showed lower resistance than the battery according to Comparative Example 3, the battery using the uncoated separator. This is solved because the graphene layer coated on one side of the separator improves the interfacial charge transfer between the electrolyte, the sulfur anode, and the separator. Furthermore, the graphene layer coated on one side of the separator and the Al ₂ O ₃ layer coated on the other side serve to trap lithium polysulfide to suppress the accumulation of sulfur species on the cathode, and also the electrochemical kinetics ( kinetics).

14 shows the surface of a separator obtained by disassembling and recovering the cells according to Battery Preparation Example 3 and Battery Comparative Example 3 after driving 200 cycles at a rate of 1C in a voltage range of 1.9V to 2.8V (vs. Li / Li ⁺ ). SEM images of the surface of the lithium metal negative electrode and EDS images of the surface of the lithium metal negative electrode are shown.

Referring to FIG. 14, it can be seen that the surface facing the lithium metal of the uncoated polypropylene separator, which was provided in the battery of Comparative Example 3, was melted and the pores were blocked (particularly, the dotted inner region). On the other hand, it can be seen that the surface coated with the Al ₂ O ₃ layer of the double-sided coating separator provided in the battery of Battery Preparation Example 3 was hardly damaged. In addition, it can be seen that sulfur accumulates on the lithium metal negative electrode surface of the battery of Comparative Example 3, and dendrites are grown to show a very rough surface. However, it can be seen that the amount of sulfur accumulated on the surface of the lithium metal negative electrode provided in the battery of Battery Preparation Example 3 was relatively small and the surface was relatively flat, thereby suppressing the growth of dendrites. From these results, the graphene layer and the Al ₂ O ₃ layer respectively coated on both sides of the double-coated separator prevent the polysulfide from passing to the cathode side and the Al ₂ O ₃ layer is formed on the lithium metal negative electrode during the battery driving process. It can be seen that it inhibits the production of dendrites that can be formed. This may support the improvement of the life characteristics shown in FIG. 11.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes by those skilled in the art within the spirit and scope of the present invention. This is possible.

Claims (16)

An insulating porous body having a pair of side surfaces facing each other;
A carbon particle layer located on one side of the insulating porous body; And
A double-coated separator comprising an inorganic particle layer located on the other side of the insulating porous body. The method of claim 1,
The carbon particle layer is a double-coated separator having graphene particles and a binder. The method of claim 2,
Graphene particles in the carbon particle layer is a double-coated separator containing more weight than the binder. The method of claim 2,
The carbon particle layer is a double coated membrane having a thickness of 5 to 30 ㎛. The method of claim 1,
The inorganic particle layer is a double-coated separator having a metal oxide nanoparticles and a binder. The method of claim 5,
The metal oxide nanoparticles in the inorganic particle layer is a double-coated separator containing more weight than the binder. The method of claim 5,
The inorganic particle layer is a double-coated separator having a thickness of 1 to 9 ㎛. Providing an insulating porous body having a pair of sides facing each other;
Coating a slurry of carbon particles on one side of the insulating porous body; And
Method for producing a double-coated separator comprising the step of coating the inorganic particle slurry on the other side of the insulating porous body. The method of claim 8,
The carbon particle slurry is a double-coated separator manufacturing method containing graphene particles, a binder, and a polar aprotic solvent. The method of claim 9,
The carbon particle slurry is a double-coated separator manufacturing method containing the graphene particles and the binder in a concentration of 1 to 5 mg with respect to 1 ml of the solvent. The method of claim 8,
The inorganic particle slurry comprises a metal oxide nanoparticles, a binder, and a polarized coated membrane manufacturing method containing a polar aprotic solvent. The method of claim 11,
The inorganic particle slurry is a double-coated separator manufacturing method containing the metal oxide nanoparticles and the binder in a concentration of 1 to 5 mg with respect to 1 ml of the solvent. The method according to claim 9 or 11,
The polar aprotic solvent is acetone double-coated membrane manufacturing method. The method of claim 9,
The carbon particle slurry or the inorganic particle slurry is coated on both sides coated membrane using a droplet method. A cathode which is a metal electrode;
anode; And
It comprises a separator coated on both sides disposed between the cathode and the anode,
The double-coated separator is a metal secondary battery having an insulating porous body, a carbon particle layer positioned on the surface facing the anode and the inorganic porous layer located on the surface facing the anode. The method of claim 15,
The positive electrode is a metal secondary battery containing a sulfur-containing material as a positive electrode active material.

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