WO2020226329A1 - Functional separator having catalytic sites introduced thereinto, manufacturing method therefor, and lithium secondary battery comprising same - Google Patents

Functional separator having catalytic sites introduced thereinto, manufacturing method therefor, and lithium secondary battery comprising same Download PDF

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Publication number
WO2020226329A1
WO2020226329A1 PCT/KR2020/005615 KR2020005615W WO2020226329A1 WO 2020226329 A1 WO2020226329 A1 WO 2020226329A1 KR 2020005615 W KR2020005615 W KR 2020005615W WO 2020226329 A1 WO2020226329 A1 WO 2020226329A1
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Prior art keywords
catalyst point
catalyst
separation membrane
point
lithium
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PCT/KR2020/005615
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French (fr)
Korean (ko)
Inventor
김기현
김민수
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주식회사 엘지화학
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Priority claimed from KR1020200049799A external-priority patent/KR20200127869A/en
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to JP2021547028A priority Critical patent/JP7162147B2/en
Priority to EP20801822.6A priority patent/EP3859823A4/en
Priority to US17/289,090 priority patent/US20220006131A1/en
Priority to CN202080005806.3A priority patent/CN112913075B/en
Publication of WO2020226329A1 publication Critical patent/WO2020226329A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a functional separator in which a catalyst point is introduced, a method of manufacturing the same, and a lithium secondary battery including the same, and more particularly, in order to solve the problem caused by lithium polysulfide eluted from the anode, lithium on the surface of the separator
  • the present invention relates to a functional separator in which a catalyst point is introduced, a method of manufacturing the same, and a lithium secondary battery including the same, which can improve the capacity and life of a battery by coating a material capable of serving as a reduction catalyst of polysulfide.
  • Electrochemical devices are the field that is receiving the most attention in this respect, and among them, the development of secondary batteries such as lithium-sulfur batteries capable of charging and discharging has become the focus of interest, and in recent years, capacity density and In order to improve the specific energy, research and development on the design of new electrodes and batteries are being conducted.
  • Such an electrochemical device among which a Li-S battery, has a high energy density (theoretical capacity), and is in the spotlight as a next-generation secondary battery that can replace a lithium ion battery.
  • a reduction reaction of sulfur and an oxidation reaction of lithium metal occur during discharge, and at this time, sulfur forms lithium polysulfide (LiPS) of a linear structure from S 8 having a ring structure.
  • the lithium-sulfur battery is characterized by a stepwise discharge voltage until the polysulfide is completely reduced to Li 2 S.
  • Korean Patent Laid-Open No. 10-2017-0108496 (hereinafter referred to as 0108496, Applicant: Ulsan Institute of Science and Technology, Publication Date: 2017.09.27) has a problem in that the performance of a lithium-sulfur battery is deteriorated due to the elution of polysulfide. It discloses a lithium-sulfur battery for improving the. That is, the lithium-sulfur battery of No.
  • 0108496 has a structure in which a positive electrode, an intermediate layer (or porous and conductive film), a separator and a negative electrode are sequentially located, and a porous matrix including metal phthalocyanine in the intermediate layer (i.e., NiPc-PBBA Including COF or ZnPc-Py COF), the purpose of which is to block the migration of polysulfide to the outside of the positive electrode while lithium ions move smoothly.
  • NiPc-PBBA Including COF or ZnPc-Py COF
  • the COF of No. 0108496 is unable to act as a reduction catalyst, contains pores inside, so it only adsorbs lithium polysulfide eluted from the anode, and does not have electron conductivity, so in the area where there is no conductive network (carbon structure) Problems that remain without reduction may occur.
  • the first matrix which is a conductive carbon layer
  • it is disadvantageous to have a thickness of several tens of ⁇ m (actual experimental example: 45 ⁇ m). (It is obvious that the energy density per weight and volume will decrease with the use of such a thick matrix, resulting in a very disadvantageous in terms of battery performance).
  • Patent Document 1 Korean Patent Publication No. 10-2017-0108496
  • an object of the present invention is to provide a metal phthalocyanine catalyst point capable of serving as a catalyst for reduction of lithium polysulfide on the surface of a separator, or a coating layer including conductive carbon, in order to solve the problem caused by lithium polysulfide eluted from the anode. It is to provide a functional separator in which a catalyst point is introduced, a method of manufacturing the same, and a lithium secondary battery including the same, which can improve the capacity and life of a battery by forming.
  • the base separation membrane In order to achieve the above object, the present invention, the base separation membrane; And a coating layer containing a catalyst point located on the surface of the base separation membrane.
  • the present invention (a) dispersing the catalyst point in a solvent to prepare a dispersion containing the catalyst point; (b) filtering the prepared dispersion containing catalyst points; (c) obtaining and drying the catalyst point-containing powder from the upper layer of the filtrate obtained through the filtration; And (d) coating the obtained and dried catalyst point-containing powder on the surface of the base separation membrane; provides a method for producing a functional separation membrane containing a catalyst point is introduced.
  • the present invention provides a lithium secondary battery comprising; and an electrolyte.
  • the functional separator in which a catalyst point is introduced according to the present invention, a method of manufacturing the same, and a lithium secondary battery including the same, serve as a reduction catalyst of lithium polysulfide on the surface of the separator in order to solve the problem caused by lithium polysulfide eluting from the positive electrode. It has the advantage of improving the capacity and life of a battery by forming a coating layer including a metal phthalocyanine catalyst point or conductive carbon thereon.
  • FIG. 1 is a graph showing life characteristics of a lithium secondary battery according to an embodiment and a comparative example of the present invention.
  • FIG. 2 is a real image of a functional separation membrane for introducing a catalyst point according to the present invention.
  • FIG 3 is an electron microscope observation image of the functional separation membrane for introducing a catalyst point according to the present invention.
  • FIGS. 4 and 5 are graphs showing initial discharge capacity (a), secondary discharge capacity (b), and life characteristics (c) of lithium secondary batteries according to an exemplary embodiment and a comparative example of the present invention.
  • the functional separation membrane into which the catalyst point according to the present invention is introduced includes a base separation membrane and a catalyst point-containing coating layer located on the surface of the base separation membrane.
  • the separator is interposed between the positive electrode and the negative electrode (i.e., a physical separator having a function of physically separating the electrode), allowing the transport of lithium ions between the positive electrode and the negative electrode while separating or insulating the positive electrode and the negative electrode from each other. do.
  • a physical separator having a function of physically separating the electrode
  • the resistance to ion migration of the electrolyte is low and the electrolyte-moisture ability is excellent, and may be made of a porous, non-conductive or insulating material.
  • the base separation membrane in which the catalyst point-containing coating layer is not formed may be an independent member such as a film, or a coating layer added (adhesion, etc.) to any one or more of the anode and the cathode, and specifically, a porous polymer film ,
  • a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer is used alone or by laminating them.
  • it may be a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fibers or polyethylene terephthalate fibers, but is not limited thereto.
  • a metal phthalocyanine catalyst point (specifically, a metal phthalocyanine catalyst that can serve as a reduction catalyst of lithium polysulfide on the surface of the base separation membrane) Transition metal-nitrogen-carbon catalyst point) or by forming a catalyst point-containing coating layer on the surface of the base separator by introducing a metal phthalocyanine catalyst point on the inside and outside of the conductive carbon having a high specific surface area and high porosity. It has features that improve and life. Accordingly, the functional separator for introducing a catalyst point of the present invention can be applied to various energy storage devices including lithium secondary batteries such as lithium-sulfur batteries that require high catalytic effect.
  • the catalyst point is a complex formed by bonding a nitrogen atom to a transition metal and a carbon atom to the nitrogen atom, and acts as a catalyst on the surface of the base separation membrane (at least one of the outer surface and the inner surface of the pores) to various energy storage devices It can improve the kinetic of the. That is, the catalyst point 20 is adsorbed and bonded to at least one of the outer surface and the inner surface of the pores of the base separation membrane, and thus, the catalyst point is a lithium secondary battery, especially a separator of a lithium-sulfur battery, among energy storage devices. It may be suitable as a solvent catalyst.
  • the catalyst point is a type of macrocyclic compound having a structure in which rings of nitrogen atoms and carbon atoms cross, and has a chemical structure in which metal ions are coordinated in the center. That is, in other words, the catalyst point may include a transition metal-nitrogen-carbon continuous bond (or sequential bond).
  • the number of nitrogen atoms bonded to the transition metal is preferably four. If the number of nitrogen atoms bonded to the transition metal is less than 4, the activity as a catalyst may be deteriorated. When it exceeds 4, structural stability may be deteriorated and thus catalytic activity may be lowered.
  • nitrogen is bonded to a transition metal, its structure is stable and exhibits excellent catalytic properties. Therefore, it has very high stability and catalyst compared to the catalyst point formed by bonding of atoms other than nitrogen to the transition metal. It can have an effect.
  • the molar ratio of the transition metal and nitrogen may be 1: 2 to 10, preferably 1: 2 to 8, more preferably 1: 3 to 5. If the molar ratio of the transition metal and nitrogen is out of the range, the surface of the base separation membrane may not be sufficiently doped as required or the amount of nitrogen per unit weight may increase, resulting in a decrease in catalytic activity.
  • the catalyst point is a nano-level composite having a size of 0.1 to 10 nm, preferably 0.5 to 8 nm, more preferably 0.5 to 5 nm, and the volume of the pores even if bonded to the inner surface of the pores of the base separation membrane There is almost no reduction in size and, so pore clogging does not occur when passing through pores such as lithium ions.
  • the transition metal may be at least one selected from the group consisting of iron (Fe), nickel (Ni), manganese (Mn), copper (Cu), and zinc (Zn), but a transition metal capable of exhibiting catalytic activity If so, it is not limited thereto.
  • the catalyst point is a metal-phthalocyanine (MePc), iron phthalocyanine (FePc), nickel phthalocyanine (NiPc), manganese phthalocyanine (MnPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc) and these Mixtures and the like can be illustrated.
  • the catalyst point-containing coating layer may be formed on a part of the surface of the base separation membrane, but in order to maximize the effect of the use of the catalyst point (up to conductive carbon, if necessary), it is preferable to form it on the entire surface of the base separation membrane. desirable.
  • the catalyst point-containing coating layer has a thickness of 0.1 to 20 ⁇ m, preferably 0.5 to 10 ⁇ m, more preferably 1 to 8 ⁇ m (even when conductive carbon to be described later is included in the coating layer), the catalyst point-containing coating layer If the thickness of is less than 0.1 ⁇ m, the conductive network is not sufficiently formed, resulting in a problem of lowering the electronic conductivity. If it exceeds 20 ⁇ m, the cell resistance increases by interfering with the passage of lithium ions, and the energy density per volume There is also a concern that adverse problems may arise.
  • the content of the coating layer containing the catalyst point is 1 to 200 ⁇ g/cm 2 , preferably 10 to 150 ⁇ g/cm 2 , more preferably 20 to 120 ⁇ g/cm 2 with respect to the surface area of the base separation membrane to be coated. It may be (even when conductive carbon to be described later is included in the coating layer). If the coating content of the coating layer containing the catalyst point is less than 1 ⁇ g/cm 2 with respect to the surface area of the base separation membrane, the effect of the use of the catalyst point may be insignificant, and if it exceeds 200 ⁇ g/cm 2 , the catalyst point is There may be no further effects that can be obtained with use.
  • the functional separation membrane into which the catalyst point according to the present invention is introduced may further contain conductive carbon in the catalyst point-containing coating layer.
  • the conductive carbon is also coated on the surface of the base separator, serves to support an inorganic material, and the conductive carbon itself has a pore structure, so that the electrolyte can be freely accessed.
  • the conductive carbon has conductivity as the name suggests, and by this property, lithium polysulfide can be reduced by transferring electrons to a supported inorganic material such as the catalyst point.
  • the catalyst point When conductive carbon is further included in the coating layer containing the catalyst point as described above, the catalyst point may be bonded to any one or more of the outer surface of the conductive carbon and the inner surface of the hole, and specifically, the outer surface of the conductive carbon. And adsorbed to the inner surface of the hole through van der Waals attraction. That is, the Van der Waals action has a bond form between faces and faces, not between specific elements, and may exhibit a stronger adsorption power than other types of bonds. Therefore, even if a catalyst point is bonded to the surface of the conductive carbon, conductivity Can maintain the natural characteristics of carbon.
  • the mixing ratio of the catalyst point and the conductive carbon may be 0.1 to 99.9: 10 to 90 as a weight ratio.
  • any conductive carbon material capable of exhibiting the above effects may be applied without particular limitation.
  • carbon nanotubes (CNT), graphene, and reduced graphene oxide (rGO) may be exemplified, and the use of the reduced graphene oxide is preferable, and peeling is advantageous due to thermal expansion, and accordingly, it is thinner. It may be more preferable to use a thermally exfoliated reduced graphene oxide (TErGO), which can exhibit excellent performance due to area coating.
  • TErGO thermally exfoliated reduced graphene oxide
  • the thermally exfoliated reduced graphene oxide may be obtained by heat-treating the graphene oxide to prepare thermally expanded graphene oxide (or thermally exfoliated graphene oxide), followed by reduction treatment.
  • the heat treatment for preparing the thermally expanded graphene oxide may be performed by a known method or various methods of modifying it, and is not particularly limited in the present invention.
  • the heat treatment may be performed for 10 minutes to 3 hours at a temperature range of 300 to 900 °C.
  • the thermal exfoliation-reduced graphene oxide (TErGO) is exfoliated, and may have a thickness of 0.5 to 40 nm, preferably 5 to 30 nm, more preferably 10 to 20 nm, and may have a plate shape or a flake shape.
  • the degree of thermal expansion of the thermally exfoliated reduced graphene oxide (TErGO) may vary from less than 100 m 2 /g to 900 m 2 /g in the range of BET, and the degree of reduction can be measured through XPS or EA. Do.
  • the reduced graphene oxide may be about 9:1.
  • the reduced graphene oxide before peeling has a thickness of about 50 to 500 nm, and because it is easily desorbed when coated in the form of particles, it not only requires the use of a binder (even if it is not a separator), but also has a low coating density to achieve the desired effect. I could't get enough.
  • the present invention can be uniformly and densely coated on a substrate by using a thermally exfoliated reduced graphene oxide in a plate or flake shape having a thickness in a certain range through peeling.
  • pores are formed in the conductive carbon, and the porosity of the pores is 40 to 90%, preferably 60 to 80%, and if the porosity of the pores is less than 40%, lithium ions cannot be transferred normally, and thus the resistance component It may act as a problem, and if it exceeds 90%, a problem of lowering the mechanical strength may occur.
  • the pore size of the conductive carbon is 10 nm to 5 ⁇ m, preferably 50 nm to 5 ⁇ m, and if the pore size is less than 10 nm, there may be a problem in which lithium ion transmission is impossible, and the pore size exceeding 5 ⁇ m In this case, a battery short circuit and safety problems may occur due to contact between electrodes.
  • a binder may be interposed so that the coating layer containing the catalyst point can be more easily coated on the surface of the base separation membrane.
  • TErGO thermally exfoliated reduced graphene oxide
  • rGO reduced graphene oxide
  • the catalyst point-containing coating layer It can be easily coated on the surface of the base separator by being free-standing without a silver binder.
  • the functional separation membrane into which the catalyst point as described above is introduced can be widely used in energy storage devices. Specifically, it can be used as a separator for a lithium secondary battery, and in particular, it can be applied as a separator for a lithium-sulfur battery accompanied by a reduction reaction of sulfur, so that high performance of the battery can be realized, and the manufacturing cost is also inexpensive, so it can be advantageous for commercialization. .
  • the catalyst point of the present invention can serve as a reduction catalyst, whereas the non-conductive COF (Covalent -Organic Framework) is impossible, and because COF contains pores inside, it only plays a role of adsorbing lithium polysulfide eluted from the anode.
  • the catalyst point of the present invention is to increase the reaction rate by reducing sulfur (S8) or long chain polysulfide to reduce it to short chain polysulfide. ) Is advantageous.
  • COF may remain unreduced at a portion where there is no conduction network (carbon structure) because there is no electronic conductivity
  • the energy density per weight and volume will decrease if such a thick matrix is used, and as a result, it is very disadvantageous in terms of battery performance.
  • the present invention it is possible to manufacture the separator as thin as 20 ⁇ m or less by using the membrane as a support, and is advantageous in terms of cell energy density.
  • the catalyst point of the present invention is used as a reduction catalyst, it is possible to improve performance even with a minimum amount.
  • the COF of No. 0108496 since lithium polysulfide must be adsorbed in the internal pores, the effect can be exhibited only when the amount of the amount is increased. For this reason, coupling COF to the catalyst point is very disadvantageous in terms of efficiency and energy density, and if lithium polysulfide accumulates inside the COF due to the loss of the conductive network, active material is lost and the amount of discharge decreases, and these materials act as resistance. As a result, there is a fear of deteriorating the performance of the battery.
  • the method of manufacturing the functional separation membrane into which the catalyst points are introduced includes the steps of: (a) dispersing the catalyst points in a solvent to prepare a dispersion containing the catalyst points, (b) filtering the prepared dispersion containing the catalyst points, (c) the Obtaining and drying the catalyst point-containing powder from the upper layer of the filtrate obtained through filtration, and (d) coating the obtained and dried catalyst point-containing powder on the surface of the base separation membrane, and if necessary, the ( After step a), a step (a-1) of preparing a dispersion containing catalyst points including conductive carbon by supplying conductive carbon to the prepared dispersion containing catalyst points may be further included.
  • a catalyst point dispersion may be prepared by dispersing (or dissolving) the catalyst point in a solvent, and if necessary, after dispersing the catalyst point in a solvent, bath sonication is performed.
  • the concentration of the catalyst point dispersion may be 5 to 15%, preferably 5 to 12%, more preferably 5 to 10% based on the weight of the solid content. If the concentration of the catalyst point dispersion is less than 5% based on the weight of the solid content, the weight of the catalyst point is reduced and there is a fear of poor catalytic activity. If it exceeds 15%, the content of the catalyst point is excessive and coating The pores of the target base separation membrane may be clogged.
  • the catalyst point is metal-phthalocyanine (MePc) as described above, for example, iron phthalocyanine (FePc), nickel phthalocyanine (NiPc), manganese phthalocyanine (MnPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), and And mixtures thereof.
  • the metal-phthalocyanine is a kind of macrocyclic compound having a structure in which rings of nitrogen atom-carbon atom cross, and has a chemical structure in which metal ions are coordinated in the center. As described above, since metal-phthalocyanine is used as a catalyst point, it is possible to prepare a catalyst material including a catalyst point having a stable structure in which four nitrogens are bonded to a transition metal.
  • the solvent used in step (a) is dimethyl carbonate, dimethyl formamide, N-methyl formamide, sulfolane (tetrahydrothiophene-1,1-dioxide), 3-methylsulfolane, N-butyl sulfone, dimethyl Sulfoxide, pyrolidinone (HEP), dimethylpiperidone (DMPD), N-methylpyrrolidinone (NMP), N-methylacetamide, dimethylacetamide (DMAc), N,N-dimethylformamide (DMF) , Diethylacetamide (DEAc), dipropylacetamide (DPAc), ethanol, propanol, butanol, hexanol, isopropyl alcohol (IPA), ethylene glycol, tetrachloroethylene, propylene glycol, toluene, trpentine, methyl acetate , Ethyl acetate, petroleum ether, acetone, cresol, and may be one or more organic solvent
  • step (a-1) is a process of adsorbing (or introducing) the catalyst point to the surface of the conductive carbon, that is, transition metal-nitrogen-on the inner and outer surfaces of the conductive carbon having a high specific surface area and high porosity.
  • the carbon catalyst point is adsorbed and bonded through the van der Waals attraction.
  • the mixing ratio of the catalyst point and the conductive carbon applies mutatis mutandis to the above.
  • ultrasonic treatment may be performed if necessary.
  • the filtering in step (b) may be applied mutatis mutandis to a general filtration method such as a vacuum pump, and after the filtration process is performed, a washing process using alcohol such as ethanol may be additionally performed as necessary. have.
  • the step (c) is a process of obtaining and drying the catalyst point-containing powder from the upper layer of the filtrate obtained through filtration in the step (b), and when applying to the conductive carbon, the bonding force between the catalyst point and the conductive carbon
  • the drying process be performed under a specific temperature and time. At this time, the drying is 1 to 24 hours, preferably 5 to 20 hours, more preferably 10 to 14 hours at a temperature of 60 to 100 °C, preferably 65 to 95 °C, more preferably 70 to 90 °C Can be performed during.
  • the step (d) is a step in which the obtained and dried catalyst point-containing powder is coated on the surface of the base separation membrane to finally prepare a functional separation membrane into which the catalyst point according to the present invention is introduced.
  • the coating is a dropcast method, a dip-coating method, a blade coating method, a spray coating method, a meyer bar coating method, or a vacuum filtration method. It can be performed by the (vacuum filter) method.
  • the lithium secondary battery including the functional separator into which the catalyst point is introduced includes a positive electrode, a negative electrode, the catalyst point introduction functional separator and an electrolyte interposed between the positive electrode and the negative electrode, and a lithium-sulfur battery, a lithium air battery and a lithium All lithium secondary batteries known in the art, such as metal batteries, can be exemplified, and among them, lithium-sulfur batteries are preferred.
  • the description of the functional separator included in the lithium secondary battery is instead of the above, and other positive electrodes, negative electrodes, and electrolytes applied to the lithium secondary battery may be conventional ones used in the art, and a detailed description thereof will be described later. Do it.
  • the battery module or battery pack may include a power tool; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Or a system for power storage; It can be used as a power supply for any one or more of medium and large devices.
  • EVs electric vehicles
  • PHEVs plug-in hybrid electric vehicles
  • a system for power storage It can be used as a power supply for any one or more of medium and large devices.
  • a positive electrode composition including a positive electrode active material, a conductive material, and a binder
  • a slurry prepared by diluting it in a predetermined solvent (dispersion medium) is directly coated on the positive electrode current collector, and By drying, an anode layer can be formed.
  • a film obtained by peeling from the support may be laminated on a positive electrode current collector to prepare a positive electrode layer.
  • a positive electrode may be manufactured in various ways using a method widely known to those skilled in the art.
  • the conducting material serves as a path through which electrons move from the positive electrode current collector to the positive electrode active material, thereby imparting electron conductivity, as well as electrically connecting the electrolyte and the positive electrode active material so that lithium ions (Li+) in the electrolyte At the same time, it acts as a pathway to move to and react to sulfur. Therefore, if the amount of the conductive material is insufficient or the role cannot be performed properly, the non-reactive portion of the sulfur in the electrode increases, resulting in a decrease in capacity. In addition, since it adversely affects the high rate discharge characteristics and charge/discharge cycle life, it is necessary to add an appropriate conductive material.
  • the content of the conductive material is preferably added appropriately within the range of 0.01 to 30% by weight based on the total weight of the positive electrode composition.
  • the conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, for example, graphite; Carbon blacks such as denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.
  • Carbon blacks such as denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black
  • Conductive fibers such as carbon fibers and metal fibers
  • Metal powders such as carbon fluoride, aluminum and nickel powder
  • Conductive whiskers such as zinc oxide and potassium titanate
  • Conductive metal oxides such as titanium oxide
  • Conductive materials such as polyphenylene derivatives may be used.
  • conductive materials include acetylene black-based Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, Ketjenblack, EC-based Armak Company (Armak Company) product, Vulcan (Vulcan) XC-72 Cabot Company (Cabot Company) product and Super-P (Timcal company product), and the like can be used.
  • the binder is for attaching the positive electrode active material to the current collector well, and must be well soluble in a solvent, and must not only form a conductive network between the positive electrode active material and the conductive material, but also have adequate impregnation of the electrolyte.
  • the binder may be any binder known in the art, and specifically, a fluororesin binder including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); Rubber binders including styrene-butadiene rubber, acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulose-based binders including carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; Polyalcohol binder; Polyolefin-based binders including polyethylene and polypropylene; Polyimide-based binder, polyester-based binder, silane-based binder; may be a mixture or a copolymer selected from the group consisting of, but is not limited thereto.
  • PVdF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • Rubber binders including styrene-butadiene rubber,
  • the content of the binder may be 0.5 to 30% by weight based on the total weight of the positive electrode composition, but is not limited thereto.
  • the content of the binder resin is less than 0.5% by weight, the physical properties of the positive electrode are deteriorated, so that the positive electrode active material and the conductive material may fall off, and if it exceeds 30% by weight, the ratio of the active material and the conductive material in the positive electrode is relatively reduced. Battery capacity may be reduced, and efficiency may be lowered by acting as a resistance element.
  • the positive electrode composition including the positive electrode active material, the conductive material, and the binder may be diluted in a predetermined solvent and coated on the positive electrode current collector using a conventional method known in the art.
  • a positive electrode current collector is prepared.
  • the positive electrode current collector has a thickness of 3 to 500 ⁇ m.
  • Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery.
  • stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel Carbon, nickel, titanium, silver, or the like may be used on the surface of the steel.
  • the current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.
  • a slurry obtained by diluting a positive electrode composition including a positive electrode active material, a conductive material, and a binder in a solvent is applied on the positive electrode current collector.
  • the positive electrode composition including the positive electrode active material, the conductive material, and the binder may be mixed with a predetermined solvent to prepare a slurry.
  • the solvent should be easy to dry and can dissolve the binder well, but it is most preferable that the positive electrode active material and the conductive material can be maintained in a dispersed state without dissolving.
  • the solvent may be water or an organic solvent, and the organic solvent may be at least one selected from the group of dimethylformamide, isopropyl alcohol or acetonitrile, methanol, ethanol, and tetrahydrofuran.
  • the method of applying the slurry-like positive electrode composition for example, Doctor blade coating, Dip coating, Gravure coating, Slit die coating. coating), spin coating, comma coating, bar coating, reverse roll coating, screen coating, cap coating, etc. It can be manufactured.
  • evaporation of the solvent (dispersion medium), the denseness of the coating film, and adhesion between the coating film and the current collector are achieved through a subsequent drying process. At this time, drying is carried out according to a conventional method, and this is not particularly limited.
  • any one capable of occluding and releasing lithium ions can be used, and examples thereof include metal materials such as lithium metal and lithium alloys, and carbon materials such as low crystalline carbon and high crystalline carbon.
  • Soft carbon and hard carbon are typical examples of low-crystalline carbon, and natural graphite, kish graphite, pyrolytic carbon, and liquid crystal pitch-based carbon fiber are high-crystalline carbon.
  • High-temperature calcined carbons such as (Mesophase pitch based carbon fiber), Meso-carbon microbeads, Mesophase pitches, and Petroleum or coal tar pitch derived cokes are typical.
  • alloys containing silicon or oxides such as Li 4 Ti 5 O 12 are also well-known cathodes.
  • the negative electrode may include a binder, and as the binder, polyvinylidenefluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), and polyacrylonitrile (Polyacrylonitrile), polymethylmethacrylate (Polymethylmethacrylate), styrene-butadiene rubber (SBR), and various kinds of binder polymers can be used.
  • PVDF polyvinylidenefluoride
  • PVDF-co-HFP polyvinylidene fluoride-hexafluoropropylene copolymer
  • SBR styrene-butadiene rubber
  • the negative electrode may optionally further include a negative electrode current collector for supporting the negative electrode active layer including the negative electrode active material and the binder.
  • the negative electrode current collector may be specifically selected from the group consisting of copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof.
  • the stainless steel may be surface-treated with carbon, nickel, titanium, or silver, and an aluminum-cadmium alloy may be used as the alloy.
  • calcined carbon, a non-conductive polymer surface-treated with a conductive agent, or a conductive polymer may be used.
  • the binder serves as a paste of the negative active material, mutual adhesion between the active materials, adhesion between the active material and the current collector, and a buffering effect on expansion and contraction of the active material.
  • the binder is the same as described above for the binder of the positive electrode.
  • the negative electrode may be a lithium metal or a lithium alloy.
  • the negative electrode may be a thin film of lithium metal, and lithium and one selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, and Sn It may be an alloy with the above metals.
  • the electrolyte solution includes a solvent and a lithium salt, and may further include additives, if necessary.
  • a solvent a conventional non-aqueous solvent serving as a medium through which ions involved in the electrochemical reaction of a battery can move may be used without particular limitation.
  • the non-aqueous solvent include carbonate-based solvents, ester-based solvents, ether-based solvents, ketone-based solvents, alcohol-based solvents, and aprotic solvents.
  • the carbonate-based solvent dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) ), ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC), and the ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethylethyl acetate, methyl Propionate, ethyl propionate, ⁇ -butyrolactone, decanolide, valerolactone, mevalonolactone, and caprolactone, and the ether solvents include di Ethyl ether, dipropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, die
  • the ketone solvent includes cyclohexanone
  • the alcohol solvent includes ethyl alcohol and isopropyl alcohol
  • the aprotic solvent includes nitriles such as acetonitrile, and amino acids such as dimethylformamide.
  • Dioxolanes such as Drew, 1,3-dioxolane (DOL), and sulfolane.
  • Non-aqueous solvents as described above can be used alone or in combination of two or more, and the mixing ratio in the case of mixing two or more can be appropriately adjusted according to the performance of the intended battery, and 1,3-dioxolane and dimethoxyethane A solvent mixed in a volume ratio of 1: 1 can be illustrated.
  • NiPc nickel phthalocyanine
  • DMF N,N-dimethylformamide
  • NiPc nickel phthalocyanine
  • the dried powder was coated on the entire surface of a porous base separator made of polyethylene by vacuum filtration and then dried to prepare a functional separator in which a catalyst point was introduced. Meanwhile, during the coating, the thickness of the coating material was 0.5 ⁇ m, and the coating amount was 10 ⁇ g/cm 2.
  • NiPc nickel phthalocyanine
  • NiPc-PBBA COF containing metal phthalocyanine here, the raw material of COF is 1,4-benzenediboronic acid
  • CNT paper After preparing a composite by coating NiPc-PBBA COF containing metal phthalocyanine (here, the raw material of COF is 1,4-benzenediboronic acid) on CNT paper, it is placed so as to face the separator in the bare state, and in the bare state A conventional separator in which the separator and the composite are physically separated was prepared (corresponding to Korean Patent Publication No. 10-2017-0108496, which is a prior art document).
  • Example 1 The separator prepared in Example 1 and Comparative Examples 1 and 2, and an electrolyte solution (DOL:DME (1:1), 1.0 M LiTFSI, 1 wt% LiNO 3 ) 70 ⁇ l, a coin containing a sulfur anode and a lithium metal anode
  • DOL:DME (1:1), 1.0 M LiTFSI, 1 wt% LiNO 3 a coin containing a sulfur anode and a lithium metal anode
  • a cell-type lithium-sulfur battery was prepared (however, when the separator of Comparative Example 2 was interposed between the positive electrode and the negative electrode, the composite of the entire separator was opposed to the positive electrode side).
  • Example 1 is a graph showing the life characteristics of a lithium secondary battery according to an embodiment and a comparative example of the present invention. As shown in FIG. 1, the lithium-sulfur battery of Example 2 to which a functional separator having a catalyst point is applied is applied.
  • NiPc nickel phthalocyanine
  • DMF N,N-dimethylformamide
  • the mixture was filtered with a vacuum pump and washed with 1000 ml of ethanol, and the upper powder of the filtrate was dried at 80° C. for 12 hours.
  • the dried powder was coated on the entire surface of a porous base separator made of polyethylene by vacuum filtration and then dried to prepare a functional separator in which a catalyst point was introduced.
  • the thickness of the coating material was 1 ⁇ m, and the coating amount was 20 ⁇ g/cm 2.
  • a functional separator in which a catalyst point was introduced was prepared in the same manner as in Example 3 above.
  • a functional separation membrane in which a catalyst point was introduced was prepared in the same manner as in Example 3 above.
  • a conventional separator was prepared by surface coating only reduced graphene oxide (rGO, Sixth Element), which is conductive carbon, on the surface of the bare separator made of polyethylene (PE).
  • rGO reduced graphene oxide
  • PE polyethylene
  • FIGS. 2 and 3 it can be seen that the catalyst point-containing functional separator according to the present invention has a uniformly well formed catalyst point-containing coating layer.
  • the catalyst point-containing functional separator when the catalyst point-introducing functional separator was observed with an electron microscope, it can be seen that the catalyst point-containing coating layer is evenly spread in a plate shape without agglomeration.
  • the discharge current rate of the lithium-sulfur batteries prepared from Examples 6 to 8 and Comparative Example 6 was set to 0.1 C 3 times, 0.2 C 3 times, and then 0.5 C, and then the life characteristics were observed.
  • 4 is a graph showing discharge capacity (a) and life characteristics (b) of lithium secondary batteries according to an embodiment and a comparative example of the present invention. As shown in FIG. 4, Examples 6 to 8 in which the catalyst point introduction functional separator was applied to a lithium-sulfur battery were compared with the lithium-sulfur battery of Comparative Example 6 in which only conductive carbon was coated on the surface of the separator. It was confirmed that all appeared excellently.
  • FIG. 5 is a graph showing discharge capacity (a) and life characteristics (b) of a lithium secondary battery according to an embodiment and a comparative example of the present invention. As shown in FIG. 5, Examples 9 to 11 in which the functional separator introducing a catalyst point was applied to a lithium-sulfur battery. In addition, discharge capacity and lifespan characteristics compared to the lithium-sulfur battery of Comparative Example 7 in which only conductive carbon was coated on the surface of the separator. It was confirmed that all appeared excellently.

Abstract

Disclosed are a functional separator having catalytic sites introduced thereinto, a manufacturing method therefor, and a lithium secondary battery comprising same, wherein in order to solve problems occurring due to lithium polysulfide eluted from a cathode, a material capable of performing a role of a reduction catalyst of lithium polysulfide is coated on a surface of the separator, thereby improving capacity and lifetime of the battery. The functional separator having catalytic sites introduced thereinto comprises: a base separator; and a catalytic site-containing coating layer positioned on a surface of the base separator.

Description

촉매점이 도입된 기능성 분리막, 그 제조 방법 및 이를 포함하는 리튬 이차전지Functional separator with catalyst point introduced, method for manufacturing same, and lithium secondary battery including same
본 출원은 2019년 05월 03일자 한국 특허 출원 제10-2019-0052321호 및 2020년 04월 24일자 한국 특허 출원 제10-2020-0049799호에 기초한 우선권의 이익을 주장하며, 해당 한국 특허 출원의 문헌에 개시된 모든 내용은 본 명세서의 일부로서 포함된다.This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0052321 filed May 03, 2019 and Korean Patent Application No. 10-2020-0049799 filed April 24, 2020. All contents disclosed in the literature are included as part of this specification.
본 발명은 촉매점이 도입된 기능성 분리막, 그 제조 방법 및 이를 포함하는 리튬 이차전지에 관한 것으로서, 더욱 상세하게는, 양극에서 용출되는 리튬 폴리설파이드로 인하여 발생하는 문제를 해결하기 위하여, 분리막 표면에 리튬 폴리설파이드의 환원 촉매 역할이 가능한 물질을 코팅시킴으로써 전지의 용량과 수명을 향상시킬 수 있는, 촉매점이 도입된 기능성 분리막, 그 제조 방법 및 이를 포함하는 리튬 이차전지에 관한 것이다.The present invention relates to a functional separator in which a catalyst point is introduced, a method of manufacturing the same, and a lithium secondary battery including the same, and more particularly, in order to solve the problem caused by lithium polysulfide eluted from the anode, lithium on the surface of the separator The present invention relates to a functional separator in which a catalyst point is introduced, a method of manufacturing the same, and a lithium secondary battery including the same, which can improve the capacity and life of a battery by coating a material capable of serving as a reduction catalyst of polysulfide.
에너지 저장 기술에 대한 관심이 갈수록 높아짐에 따라, 휴대폰, 태블릿(tablet), 랩탑(laptop) 및 캠코더, 나아가서는 전기 자동차(EV) 및 하이브리드 전기 자동차(HEV)의 에너지까지 적용분야가 확대되면서, 전기화학소자에 대한 연구 및 개발이 점차 증대되고 있다. 전기화학소자는 이러한 측면에서 가장 주목을 받고 있는 분야이고, 그 중에서도 충방전이 가능한 리튬-황 전지와 같은 이차전지의 개발은 관심의 초점이 되고 있으며, 최근에는 이러한 전지를 개발함에 있어서 용량 밀도 및 비 에너지를 향상시키기 위하여, 새로운 전극과 전지의 설계에 대한 연구개발로 이어지고 있다.As the interest in energy storage technology increases, the field of application of mobile phones, tablets, laptops, camcorders, and even electric vehicles (EVs) and hybrid electric vehicles (HEVs) is expanded. Research and development of chemical devices are gradually increasing. Electrochemical devices are the field that is receiving the most attention in this respect, and among them, the development of secondary batteries such as lithium-sulfur batteries capable of charging and discharging has become the focus of interest, and in recent years, capacity density and In order to improve the specific energy, research and development on the design of new electrodes and batteries are being conducted.
이와 같은 전기화학소자, 그 중 리튬-황 전지(Li-S battery)는 높은 에너지 밀도(이론 용량)를 가져, 리튬이온전지를 대체할 수 있는 차세대 이차전지로 각광받고 있다. 이와 같은 리튬-황 전지 내에서는, 방전 시 황의 환원 반응과 리튬 메탈의 산화반응이 일어나며, 이 때 황은 고리 구조의 S8로부터 선형 구조의 리튬 폴리설파이드(Lithium Polysulfide, LiPS)를 형성하게 되는데, 이러한 리튬-황 전지는 폴리설파이드가 완전히 Li2S로 환원되기까지 단계적 방전 전압을 나타내는 것이 특징이다.Such an electrochemical device, among which a Li-S battery, has a high energy density (theoretical capacity), and is in the spotlight as a next-generation secondary battery that can replace a lithium ion battery. In such a lithium-sulfur battery, a reduction reaction of sulfur and an oxidation reaction of lithium metal occur during discharge, and at this time, sulfur forms lithium polysulfide (LiPS) of a linear structure from S 8 having a ring structure. The lithium-sulfur battery is characterized by a stepwise discharge voltage until the polysulfide is completely reduced to Li 2 S.
하지만, 리튬-황 전지의 상업화에 있어서 가장 큰 걸림돌은 리튬 폴리설파이드의 용출 및 셔틀현상이고, 이로 인하여 리튬-황 전지의 용량이 감소된다는 커다란 문제점을 가지고 있다. 즉, 양극에서 용출된 폴리설파이드는 유기 전해액으로의 용해도가 높기 때문에, 전해액을 통해 음극 쪽으로 원치 않는 이동(PS shuttling)이 일어날 수 있으며, 그 결과, 양극 활물질의 비가역적 손실로 인한 용량의 감소 및 부반응에 의한 리튬 메탈 표면에의 황 입자 증착으로 인한 전지 수명의 감소가 발생하게 되는 것이다. 이와 같은 문제점을 해결하기 위하여, 양극 복합체에 PS 흡착 물질을 첨가하거나, 기존 PE 등으로 이루어진 분리막을 개질시키는 등의 다양한 연구가 진행되고 있지만, 뚜렷한 해결책을 제시하지는 못하고 있는 실정이다.However, the biggest obstacle to the commercialization of lithium-sulfur batteries is the elution and shuttle phenomenon of lithium polysulfide, which has a big problem that the capacity of the lithium-sulfur battery is reduced. That is, since the polysulfide eluted from the positive electrode has high solubility in the organic electrolyte, unwanted movement (PS shuttling) toward the negative electrode may occur through the electrolyte, and as a result, the capacity decrease due to irreversible loss of the positive electrode active material and The battery life is reduced due to the deposition of sulfur particles on the surface of the lithium metal by side reactions. In order to solve such a problem, various studies such as adding a PS adsorption material to a positive electrode composite or modifying a separator made of existing PE or the like have been conducted, but a clear solution has not been proposed.
이와 관련하여, 대한민국 특허공개 제10-2017-0108496호(이하 0108496호, 출원인: 울산과학기술원, 공개일: 2017.09.27)는, 폴리설파이드의 용출로 인해 리튬-황 전지의 성능이 저하되는 문제점을 개선하기 위한 리튬-황 전지를 개시하고 있다. 즉, 상기 0108496호의 리튬-황 전지는 양극, 중간층(또는, 다공성 및 전도성 막), 분리막 및 음극이 순차적으로 위치한 구조를 취하고 있고, 상기 중간층에 메탈 프탈로시아닌을 포함한 다공성의 매트릭스(즉, NiPc-PBBA COF 또는 ZnPc-Py COF 등을 포함)를 포함시켜, 리튬 이온은 원활히 이동시키면서도 폴리설파이드는 양극 외로의 이동을 차단시키는 것을 목적으로 두고 있다.In this regard, Korean Patent Laid-Open No. 10-2017-0108496 (hereinafter referred to as 0108496, Applicant: Ulsan Institute of Science and Technology, Publication Date: 2017.09.27) has a problem in that the performance of a lithium-sulfur battery is deteriorated due to the elution of polysulfide. It discloses a lithium-sulfur battery for improving the. That is, the lithium-sulfur battery of No. 0108496 has a structure in which a positive electrode, an intermediate layer (or porous and conductive film), a separator and a negative electrode are sequentially located, and a porous matrix including metal phthalocyanine in the intermediate layer (i.e., NiPc-PBBA Including COF or ZnPc-Py COF), the purpose of which is to block the migration of polysulfide to the outside of the positive electrode while lithium ions move smoothly.
하지만, 상기 0108496호의 중간층과 같이 메탈 프탈로시아닌을 포함한 기재가 분리막과 물리적으로 분리되고, 또한, 메탈 프탈로시아닌(NiPc, ZnPc)에 비전도성의 COF(Covalent-Organic Framework)가 결합되는 경우, 다양한 문제가 발생하여 전지의 성능을 저하시킬 우려가 적지 않다. 즉, 상기 0108496호의 COF는, 환원 촉매 역할이 불가능하며, 내부에 기공을 포함하고 있어 양극에서 용출된 리튬 폴리설파이드를 흡착하는 것에 그치고 있고, 전자 전도성이 없어 전도 네트워크(탄소 구조체)가 없는 부위에서는 환원되지 않고 잔존하는 문제가 발생할 수 있다. 이에, 상기 0108496호는 이를 보완하기 위하여 전도성 탄소층인 제1 매트릭스를 사용해야만 하며, 이를 프리-스탠딩(free-standing)으로 만들기 위하여 수십 ㎛의 두께(실제 실험예: 45 ㎛)로 만들어야 하는 단점이 있다(이와 같이 두꺼운 매트릭스를 사용하면 무게 및 부피당 에너지 밀도가 감소할 것이 자명하며, 결과적으로 전지 성능 측면에서 매우 불리해짐).However, when a substrate containing metal phthalocyanine is physically separated from the separator, like the intermediate layer of No. 0108496, and a non-conductive COF (Covalent-Organic Framework) is combined with metal phthalocyanine (NiPc, ZnPc), various problems arise Therefore, there is not little concern about deteriorating the performance of the battery. In other words, the COF of No. 0108496 is unable to act as a reduction catalyst, contains pores inside, so it only adsorbs lithium polysulfide eluted from the anode, and does not have electron conductivity, so in the area where there is no conductive network (carbon structure) Problems that remain without reduction may occur. Accordingly, in the 0108496, the first matrix, which is a conductive carbon layer, must be used to compensate for this, and to make it free-standing, it is disadvantageous to have a thickness of several tens of µm (actual experimental example: 45 µm). (It is obvious that the energy density per weight and volume will decrease with the use of such a thick matrix, resulting in a very disadvantageous in terms of battery performance).
또한, 상기 0108496호의 COF의 경우에는, 내부 기공에 리튬 폴리설파이드를 흡착시켜야 하기 때문에 그 사용량이 많아져야만 효과를 나타낼 수 있다. 이와 같은 이유로 촉매점에 COF를 결합시키는 것은 효율성과 에너지 밀도 측면에서 매우 불리하며, 또한, 전도성 네트워크가 손실되어 리튬 폴리설파이드가 COF 내부에 쌓이게 되면 활물질 손실이 되어 방전량이 하락하고, 이러한 물질들이 저항으로 작용하여 결과적으로 전지의 성능을 저하시킬 우려가 있다. 따라서, 이상의 문제점들을 원천적으로 방지할 수 있는 신규한 분리막 및 리튬 이차전지의 개발이 절실하다.In addition, in the case of the COF of No. 0108496, since lithium polysulfide must be adsorbed in the internal pores, the effect can only be exhibited only when the amount of use thereof is increased. For this reason, coupling COF to the catalyst point is very disadvantageous in terms of efficiency and energy density.In addition, when lithium polysulfide accumulates inside the COF due to loss of the conductive network, active material is lost and the amount of discharge decreases. As a result, there is a risk of deteriorating the performance of the battery. Therefore, there is an urgent need to develop a novel separator and lithium secondary battery that can prevent the above problems.
[선행기술문헌][Prior technical literature]
[특허문헌][Patent Literature]
(특허문헌 1) 대한민국 특허공개 제10-2017-0108496호(Patent Document 1) Korean Patent Publication No. 10-2017-0108496
따라서, 본 발명의 목적은, 양극에서 용출되는 리튬 폴리설파이드로 인하여 발생하는 문제를 해결하기 위하여, 분리막 표면에 리튬 폴리설파이드의 환원 촉매 역할이 가능한 메탈 프탈로시아닌 촉매점 또는 여기에 전도성 탄소까지 포함한 코팅층을 형성시킴으로써 전지의 용량과 수명을 향상시킬 수 있는, 촉매점이 도입된 기능성 분리막, 그 제조 방법 및 이를 포함하는 리튬 이차전지를 제공하는 것이다.Accordingly, an object of the present invention is to provide a metal phthalocyanine catalyst point capable of serving as a catalyst for reduction of lithium polysulfide on the surface of a separator, or a coating layer including conductive carbon, in order to solve the problem caused by lithium polysulfide eluted from the anode. It is to provide a functional separator in which a catalyst point is introduced, a method of manufacturing the same, and a lithium secondary battery including the same, which can improve the capacity and life of a battery by forming.
상기 목적을 달성하기 위하여, 본 발명은, 베이스 분리막; 및 상기 베이스 분리막의 표면에 위치한 촉매점 함유 코팅층;을 포함하는 촉매점이 도입된 기능성 분리막을 제공한다.In order to achieve the above object, the present invention, the base separation membrane; And a coating layer containing a catalyst point located on the surface of the base separation membrane.
또한, 본 발명은, (a) 촉매점을 용매에 분산시켜 촉매점 함유 분산액을 제조하는 단계; (b) 상기 제조된 촉매점 함유 분산액을 여과하는 단계; (c) 상기 여과를 통하여 얻어진 여과물의 상층부로부터 촉매점 함유 파우더를 수득하여 건조시키는 단계; 및 (d) 상기 수득 및 건조된 촉매점 함유 파우더를 베이스 분리막의 표면에 코팅시키는 단계;를 포함하는 촉매점이 도입된 기능성 분리막의 제조 방법을 제공한다.In addition, the present invention, (a) dispersing the catalyst point in a solvent to prepare a dispersion containing the catalyst point; (b) filtering the prepared dispersion containing catalyst points; (c) obtaining and drying the catalyst point-containing powder from the upper layer of the filtrate obtained through the filtration; And (d) coating the obtained and dried catalyst point-containing powder on the surface of the base separation membrane; provides a method for producing a functional separation membrane containing a catalyst point is introduced.
또한, 본 발명은, 양극; 음극; 상기 양극과 음극의 사이에 개재되는 상기 촉매점 도입 기능성 분리막; 및 전해질;을 포함하는 리튬 이차전지를 제공한다.In addition, the present invention, the anode; cathode; A functional separator for introducing the catalyst point interposed between the anode and the cathode; It provides a lithium secondary battery comprising; and an electrolyte.
본 발명에 따른 촉매점이 도입된 기능성 분리막, 그 제조 방법 및 이를 포함하는 리튬 이차전지는, 양극에서 용출되는 리튬 폴리설파이드로 인하여 발생하는 문제를 해결하기 위하여, 분리막 표면에 리튬 폴리설파이드의 환원 촉매 역할이 가능한 메탈 프탈로시아닌 촉매점 또는 여기에 전도성 탄소까지 포함한 코팅층을 형성시킴으로써 전지의 용량과 수명을 향상시킬 수 있는 장점을 가지고 있다.The functional separator in which a catalyst point is introduced according to the present invention, a method of manufacturing the same, and a lithium secondary battery including the same, serve as a reduction catalyst of lithium polysulfide on the surface of the separator in order to solve the problem caused by lithium polysulfide eluting from the positive electrode. It has the advantage of improving the capacity and life of a battery by forming a coating layer including a metal phthalocyanine catalyst point or conductive carbon thereon.
도 1은 본 발명의 일 실시예 및 비교예에 따른 리튬 이차전지의 수명특성을 보여주는 그래프이다.1 is a graph showing life characteristics of a lithium secondary battery according to an embodiment and a comparative example of the present invention.
도 2는 본 발명에 따른 촉매점 도입 기능성 분리막의 실물 이미지이다.2 is a real image of a functional separation membrane for introducing a catalyst point according to the present invention.
도 3은 본 발명에 따른 촉매점 도입 기능성 분리막의 전자 현미경 관찰 이미지이다.3 is an electron microscope observation image of the functional separation membrane for introducing a catalyst point according to the present invention.
도 4 및 5는 본 발명의 일 실시예 및 비교예에 따른 리튬 이차 전지의 초기 방전용량(a), 2차 방전용량(b) 및 수명특성(c)을 보여주는 그래프이다.4 and 5 are graphs showing initial discharge capacity (a), secondary discharge capacity (b), and life characteristics (c) of lithium secondary batteries according to an exemplary embodiment and a comparative example of the present invention.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
본 발명에 따른 촉매점이 도입된 기능성 분리막은, 베이스 분리막 및 상기 베이스 분리막의 표면에 위치한 촉매점 함유 코팅층을 포함한다.The functional separation membrane into which the catalyst point according to the present invention is introduced includes a base separation membrane and a catalyst point-containing coating layer located on the surface of the base separation membrane.
상기 분리막은 양극과 음극의 사이에 개재되는 것으로서(즉, 전극을 물리적으로 분리하는 기능을 갖는 물리적인 분리막), 양극과 음극을 서로 분리 또는 절연시키면서 양극과 음극 사이에 리튬 이온의 수송을 가능하게 한다. 특히 전해질의 이온 이동에 대하여 저항이 낮으면서 전해질 함습 능력이 우수할수록 바람직하며, 다공성이고 비전도성 또는 절연성인 물질로 이루어질 수 있다.The separator is interposed between the positive electrode and the negative electrode (i.e., a physical separator having a function of physically separating the electrode), allowing the transport of lithium ions between the positive electrode and the negative electrode while separating or insulating the positive electrode and the negative electrode from each other. do. In particular, it is preferable that the resistance to ion migration of the electrolyte is low and the electrolyte-moisture ability is excellent, and may be made of a porous, non-conductive or insulating material.
한편, 상기 촉매점 함유 코팅층이 형성되지 않은 베이스 분리막은, 필름과 같은 독립적인 부재이거나, 또는 양극 및 음극 중 어느 하나 이상에 부가(접착 등)된 코팅층일 수 있으며, 구체적으로는, 다공성 고분자 필름, 예를 들어 에틸렌 단독중합체, 프로필렌 단독중합체, 에틸렌/부텐 공중합체, 에틸렌/헥센 공중합체 및 에틸렌/메타크릴레이트 공중합체 등과 같은 폴리올레핀계 고분자로 제조한 다공성 고분자 필름을 단독으로 또는 이들을 적층하여 사용한 것이거나, 통상적인 다공성 부직포, 예를 들어, 고융점의 유리 섬유 또는 폴리에틸렌테레프탈레이트 섬유 등으로 된 부직포일 수 있으나, 이에 한정되는 것은 아니다.On the other hand, the base separation membrane in which the catalyst point-containing coating layer is not formed may be an independent member such as a film, or a coating layer added (adhesion, etc.) to any one or more of the anode and the cathode, and specifically, a porous polymer film , For example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer is used alone or by laminating them. Or, it may be a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fibers or polyethylene terephthalate fibers, but is not limited thereto.
본 발명은, 전술한 바와 같이, 양극에서 용출되는 리튬 폴리설파이드로 인하여 발생하는 문제를 해결하기 위하여, 상기 베이스 분리막의 표면에 리튬 폴리설파이드의 환원 촉매 역할이 가능한 메탈 프탈로시아닌 촉매점(구체적으로는, 전이금속-질소-탄소 촉매점)을 형성시키거나, 고 비표면적 및 고 기공도를 가지는 전도성 탄소의 내외부에 메탈 프탈로시아닌 촉매점을 도입한 촉매점 함유 코팅층을 베이스 분리막의 표면에 형성시킴으로써 전지의 용량과 수명을 향상시킨 특징을 가진다. 따라서, 본 발명의 촉매점 도입 기능성 분리막은, 높은 촉매 효과가 요구되는 리튬-황 전지 등의 리튬 이차전지를 포함한 다양한 에너지 저장 디바이스에 적용될 수 있다.The present invention, as described above, in order to solve the problem caused by lithium polysulfide eluted from the anode, a metal phthalocyanine catalyst point (specifically, a metal phthalocyanine catalyst that can serve as a reduction catalyst of lithium polysulfide on the surface of the base separation membrane) Transition metal-nitrogen-carbon catalyst point) or by forming a catalyst point-containing coating layer on the surface of the base separator by introducing a metal phthalocyanine catalyst point on the inside and outside of the conductive carbon having a high specific surface area and high porosity. It has features that improve and life. Accordingly, the functional separator for introducing a catalyst point of the present invention can be applied to various energy storage devices including lithium secondary batteries such as lithium-sulfur batteries that require high catalytic effect.
상기 촉매점은 전이금속에 질소 원자가 결합되고, 상기 질소 원자에는 탄소 원자가 결합되어 형성된 복합체로서, 상기 베이스 분리막의 표면(외부 표면 및 기공 내 표면 중 어느 하나 이상)에서 촉매 역할을 하여 다양한 에너지 저장 디바이스의 키네틱(kinetic)을 향상시킬 수 있다. 즉, 상기 촉매점(20)은 상기 베이스 분리막의 외부 표면 및 기공 내 표면 중 어느 하나 이상에 흡착 결합되는 것이며, 따라서, 상기 촉매점은 에너지 저장 디바이스 중에서도 리튬 이차전지, 특히 리튬-황 전지의 분리막용 촉매로서 적합할 수 있다.The catalyst point is a complex formed by bonding a nitrogen atom to a transition metal and a carbon atom to the nitrogen atom, and acts as a catalyst on the surface of the base separation membrane (at least one of the outer surface and the inner surface of the pores) to various energy storage devices It can improve the kinetic of the. That is, the catalyst point 20 is adsorbed and bonded to at least one of the outer surface and the inner surface of the pores of the base separation membrane, and thus, the catalyst point is a lithium secondary battery, especially a separator of a lithium-sulfur battery, among energy storage devices. It may be suitable as a solvent catalyst.
보다 구체적으로, 상기 촉매점은 질소 원자-탄소 원자의 고리가 교차하는 구조를 가진 거대 고리 화합물의 한 종류이며, 중심부에 금속 이온이 배위하고 있는 화학 구조를 가진다. 즉, 다시 말해, 상기 촉매점은 전이금속-질소-탄소의 연속 결합(또는, 순차 결합)을 포함한 것일 수 있다. 상기 촉매점에 있어서, 상기 전이금속에 결합되는 질소 원자의 개수는 4개가 바람직하다. 만일, 상기 전이금속에 결합된 질소 원자의 개수가 4개 미만이면 촉매로서의 활성이 저하될 수 있고, 4개를 초과하는 경우에는 구조적인 안정성이 저하되어 촉매 활성까지 저하될 우려가 있다. 이와 같이, 전이금속에 질소가 결합되면, 그 구조가 안정할 뿐만 아니라 촉매적으로 뛰어난 특성을 나타내기 때문에, 질소가 아닌 다른 종류의 원자가 전이금속에 결합되어 형성된 촉매점에 비하여 매우 높은 안정성 및 촉매 효과를 나타낼 수 있다.More specifically, the catalyst point is a type of macrocyclic compound having a structure in which rings of nitrogen atoms and carbon atoms cross, and has a chemical structure in which metal ions are coordinated in the center. That is, in other words, the catalyst point may include a transition metal-nitrogen-carbon continuous bond (or sequential bond). In the catalyst point, the number of nitrogen atoms bonded to the transition metal is preferably four. If the number of nitrogen atoms bonded to the transition metal is less than 4, the activity as a catalyst may be deteriorated. When it exceeds 4, structural stability may be deteriorated and thus catalytic activity may be lowered. As described above, when nitrogen is bonded to a transition metal, its structure is stable and exhibits excellent catalytic properties. Therefore, it has very high stability and catalyst compared to the catalyst point formed by bonding of atoms other than nitrogen to the transition metal. It can have an effect.
상기 촉매점에 있어서, 전이금속과 질소의 몰비는 1 : 2 내지 10, 바람직하게는 1 : 2 내지 8, 더욱 바람직하게는 1 : 3 내지 5일 수 있다. 만일, 상기 전이금속과 질소의 몰비 범위를 벗어나는 경우에는, 상기 베이스 분리막의 표면에 촉매점이 필요로 하는만큼 충분히 도핑되지 않거나 단위 중량당 질소의 양이 많아져 촉매 활성이 저하될 수 있다.In the catalyst point, the molar ratio of the transition metal and nitrogen may be 1: 2 to 10, preferably 1: 2 to 8, more preferably 1: 3 to 5. If the molar ratio of the transition metal and nitrogen is out of the range, the surface of the base separation membrane may not be sufficiently doped as required or the amount of nitrogen per unit weight may increase, resulting in a decrease in catalytic activity.
또한, 상기 촉매점은 0.1 내지 10 nm, 바람직하게는 0.5 내지 8 nm, 더욱 바람직하게는 0.5 내지 5 nm 크기를 가지는 나노 수준의 복합체로서, 상기 베이스 분리막의 기공 내부 표면상에 결합되더라도 기공의 부피와 크기 감소가 거의 없어, 리튬 이온 등의 기공 통과 시 기공 막힘 현상이 발생하지 않는다.In addition, the catalyst point is a nano-level composite having a size of 0.1 to 10 nm, preferably 0.5 to 8 nm, more preferably 0.5 to 5 nm, and the volume of the pores even if bonded to the inner surface of the pores of the base separation membrane There is almost no reduction in size and, so pore clogging does not occur when passing through pores such as lithium ions.
그밖에, 상기 전이금속은 철(Fe), 니켈(Ni), 망간(Mn), 구리(Cu) 및 아연(Zn)으로 이루어진 군으로부터 선택되는 1종 이상일 수 있으나, 촉매 활성을 나타낼 수 있는 전이금속이라면 이에 제한되지 않는다. 또한, 상기 촉매점은 메탈-프탈로시아닌(Metal-phthalocyanine, MePc)으로서, 철 프탈로시아닌(FePc), 니켈 프탈로시아닌(NiPc), 망간 프탈로시아닌(MnPc), 구리 프탈로시아닌(CuPc), 아연 프탈로시아닌(ZnPc) 및 이들의 혼합물 등을 예시할 수 있다.In addition, the transition metal may be at least one selected from the group consisting of iron (Fe), nickel (Ni), manganese (Mn), copper (Cu), and zinc (Zn), but a transition metal capable of exhibiting catalytic activity If so, it is not limited thereto. In addition, the catalyst point is a metal-phthalocyanine (MePc), iron phthalocyanine (FePc), nickel phthalocyanine (NiPc), manganese phthalocyanine (MnPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc) and these Mixtures and the like can be illustrated.
상기 촉매점 함유 코팅층은 상기 베이스 분리막의 표면 일부에 형성될 수도 있으나, 촉매점(필요에 따라, 전도성 탄소까지)의 사용에 따른 효과 발현을 극대화시키기 위하여, 상기 베이스 분리막의 표면 전체에 형성시키는 것이 바람직하다. 상기 촉매점 함유 코팅층의 두께는 0.1 내지 20 ㎛, 바람직하게는 0.5 내지 10 ㎛, 더욱 바람직하게는 1 내지 8 ㎛로서(후술할 전도성 탄소가 코팅층에 포함되는 경우에도 해당), 상기 촉매점 함유 코팅층의 두께가 0.1 ㎛ 미만이면, 전도성 네트워크가 충분하게 형성되지 않아 전자 전도성이 낮아지는 문제가 발생할 수 있고, 20 ㎛를 초과하는 경우에는, 리튬 이온의 통행을 방해하여 셀 저항이 커지며 또한 부피당 에너지 밀도 면에서도 불리한 문제가 발생할 우려가 있다.The catalyst point-containing coating layer may be formed on a part of the surface of the base separation membrane, but in order to maximize the effect of the use of the catalyst point (up to conductive carbon, if necessary), it is preferable to form it on the entire surface of the base separation membrane. desirable. The catalyst point-containing coating layer has a thickness of 0.1 to 20 µm, preferably 0.5 to 10 µm, more preferably 1 to 8 µm (even when conductive carbon to be described later is included in the coating layer), the catalyst point-containing coating layer If the thickness of is less than 0.1 µm, the conductive network is not sufficiently formed, resulting in a problem of lowering the electronic conductivity. If it exceeds 20 µm, the cell resistance increases by interfering with the passage of lithium ions, and the energy density per volume There is also a concern that adverse problems may arise.
또한, 상기 촉매점 함유 코팅층의 함량은, 그 코팅 대상인 베이스 분리막의 표면적에 대하여 1 내지 200 ㎍/cm2, 바람직하게는 10 내지 150 ㎍/cm2, 더욱 바람직하게는 20 내지 120 ㎍/cm2일 수 있다(후술할 전도성 탄소가 코팅층에 포함되는 경우에도 해당). 만일, 상기 촉매점 함유 코팅층의 코팅 함량이 베이스 분리막의 표면적에 대하여 1 ㎍/cm2 미만이면, 촉매점의 사용에 따른 효과가 미미할 수 있고, 200 ㎍/cm2를 초과하는 경우에는 촉매점을 사용함에 따라 얻을 수 있는 더 이상의 효과가 없을 수 있다.In addition, the content of the coating layer containing the catalyst point is 1 to 200 µg/cm 2 , preferably 10 to 150 µg/cm 2 , more preferably 20 to 120 µg/cm 2 with respect to the surface area of the base separation membrane to be coated. It may be (even when conductive carbon to be described later is included in the coating layer). If the coating content of the coating layer containing the catalyst point is less than 1 μg/cm 2 with respect to the surface area of the base separation membrane, the effect of the use of the catalyst point may be insignificant, and if it exceeds 200 μg/cm 2 , the catalyst point is There may be no further effects that can be obtained with use.
한편, 본 발명에 따른 촉매점이 도입된 기능성 분리막은, 촉매점 함유 코팅층에 전도성 탄소가 더 포함된 것일 수 있다. 따라서, 상기 전도성 탄소 또한 상기 베이스 분리막의 표면에 코팅되며, 무기물을 담지하는 역할을 하고, 전도성 탄소 자체가 기공 구조를 가지고 있어 전해액의 출입이 자유롭다. 또한, 상기 전도성 탄소는 이름 그대로 전도성을 가지고 있고, 이와 같은 성질에 의해, 상기 촉매점 등의 담지된 무기물에 전자를 전달함으로써, 리튬 폴리설파이드를 환원시킬 수 있다.Meanwhile, the functional separation membrane into which the catalyst point according to the present invention is introduced may further contain conductive carbon in the catalyst point-containing coating layer. Accordingly, the conductive carbon is also coated on the surface of the base separator, serves to support an inorganic material, and the conductive carbon itself has a pore structure, so that the electrolyte can be freely accessed. In addition, the conductive carbon has conductivity as the name suggests, and by this property, lithium polysulfide can be reduced by transferring electrons to a supported inorganic material such as the catalyst point.
상기와 같이 촉매점 함유 코팅층에 전도성 탄소가 더 포함되는 경우, 상기 촉매점은 상기 전도성 탄소의 외부 표면 및 홀 내부 표면 중 어느 하나 이상에 결합될 수 있으며, 구체적으로는, 상기 전도성 탄소의 외부 표면 및 홀 내부 표면에 반데르발스 인력을 통하여 흡착되어 결합된 것일 수 있다. 즉, 상기 반데르발스 작용은 특정 원소간 결합이 아닌 면과 면 사이의 결합 형태를 가져, 다른 종류의 결합에 비해 강한 흡착력을 나타낼 수 있으며, 따라서, 상기 전도성 탄소의 표면에 촉매점이 결합되더라도 전도성 탄소 본연의 특성을 유지할 수 있다. 또한, 상기와 같이 촉매점 함유 코팅층에 전도성 탄소가 더 포함되는 경우, 상기 촉매점과 전도성 탄소의 혼합비는, 중량비로서 0.1 내지 99.9 : 10 내지 90일 수 있다.When conductive carbon is further included in the coating layer containing the catalyst point as described above, the catalyst point may be bonded to any one or more of the outer surface of the conductive carbon and the inner surface of the hole, and specifically, the outer surface of the conductive carbon. And adsorbed to the inner surface of the hole through van der Waals attraction. That is, the Van der Waals action has a bond form between faces and faces, not between specific elements, and may exhibit a stronger adsorption power than other types of bonds. Therefore, even if a catalyst point is bonded to the surface of the conductive carbon, conductivity Can maintain the natural characteristics of carbon. In addition, when conductive carbon is further included in the coating layer containing the catalyst point as described above, the mixing ratio of the catalyst point and the conductive carbon may be 0.1 to 99.9: 10 to 90 as a weight ratio.
상기 전도성 탄소로는, 상기와 같은 효과를 나타낼 수 있는 전도성의 탄소재라면 특별한 제한 없이 적용될 수 있다. 그 중에서도 탄소나노튜브(CNT), 그래핀(graphene) 및 환원 그래핀 옥사이드(rGO)를 예로 들 수 있으며, 상기 환원 그래핀 옥사이드의 사용이 바람직하고, 열팽창으로 인하여 박리가 유리하고 이에 따라 얇게 대면적 코팅이 가능하여 우수한 성능을 나타낼 수 있는 열적 박리 환원 그래핀 옥사이드(thermally exfoliated reduced graphene oxide; TErGO)를 사용하는 것이 더욱 바람직할 수 있다.As the conductive carbon, any conductive carbon material capable of exhibiting the above effects may be applied without particular limitation. Among them, carbon nanotubes (CNT), graphene, and reduced graphene oxide (rGO) may be exemplified, and the use of the reduced graphene oxide is preferable, and peeling is advantageous due to thermal expansion, and accordingly, it is thinner. It may be more preferable to use a thermally exfoliated reduced graphene oxide (TErGO), which can exhibit excellent performance due to area coating.
상기 열적 박리 환원 그래핀 옥사이드(TErGO)는, 그래핀 옥사이드를 열처리하여 열팽창 그래핀 옥사이드(또는, 열적 박리 그래핀 옥사이드)를 제조한 후 이를 환원 처리한 것일 수 있다. 이때 열팽창 그래핀 옥사이드의 제조를 위한 열처리는, 공지의 방법 또는 이를 변형하는 다양한 방법에 의해 수행될 수 있으며, 본 발명에서 특별히 한정하지는 않는다. 일 예로, 상기 열처리는 300 내지 900 ℃의 온도 범위에서 10분 내지 3시간 동안 수행될 수 있다.The thermally exfoliated reduced graphene oxide (TErGO) may be obtained by heat-treating the graphene oxide to prepare thermally expanded graphene oxide (or thermally exfoliated graphene oxide), followed by reduction treatment. At this time, the heat treatment for preparing the thermally expanded graphene oxide may be performed by a known method or various methods of modifying it, and is not particularly limited in the present invention. For example, the heat treatment may be performed for 10 minutes to 3 hours at a temperature range of 300 to 900 °C.
특히, 상기 열적 박리 환원 그래핀 옥사이드(TErGO)는 박리된 것으로서, 두께가 0.5 내지 40 nm, 바람직하게는 5 내지 30 nm, 더욱 바람직하게는 10 내지 20 nm일 수 있고, 판상 또는 플레이크 형상일 수 있다. 또한, 상기 열적 박리 환원 그래핀 옥사이드(TErGO)의 열팽창 정도는, BET의 범위로 100 m2/g 미만에서 900 m2/g까지 다양할 수 있고, 환원의 정도는 XPS나 EA를 통하여 측정 가능하다. 또한, 일반적인 그래핀 옥사이드는 탄소와 산소의 질량비가 약 1 : 1인 것에 비하여, 환원된 그래핀 옥사이드는 약 9 : 1 정도가 될 수 있다.In particular, the thermal exfoliation-reduced graphene oxide (TErGO) is exfoliated, and may have a thickness of 0.5 to 40 nm, preferably 5 to 30 nm, more preferably 10 to 20 nm, and may have a plate shape or a flake shape. have. In addition, the degree of thermal expansion of the thermally exfoliated reduced graphene oxide (TErGO) may vary from less than 100 m 2 /g to 900 m 2 /g in the range of BET, and the degree of reduction can be measured through XPS or EA. Do. In addition, compared to the general graphene oxide having a mass ratio of carbon and oxygen of about 1:1, the reduced graphene oxide may be about 9:1.
일반적으로, 박리 전의 환원 그래핀 옥사이드는 두께가 약 50 내지 500 nm로서, 입자 형태로 코팅 시 쉽게 탈리되기 때문에 (분리막이 아니더라도) 바인더의 사용을 필요로 할뿐만 아니라 코팅 밀도가 낮아 목적한 효과를 충분히 얻을 수 없었다. 하지만 본 발명은, 박리를 통해 일정 범위의 두께를 가지는 판상 또는 플레이크 형상의 열적 박리 환원 그래핀 옥사이드를 사용함으로써 기재 상에 균일하고 치밀하게 코팅할 수 있다.In general, the reduced graphene oxide before peeling has a thickness of about 50 to 500 nm, and because it is easily desorbed when coated in the form of particles, it not only requires the use of a binder (even if it is not a separator), but also has a low coating density to achieve the desired effect. I couldn't get enough. However, the present invention can be uniformly and densely coated on a substrate by using a thermally exfoliated reduced graphene oxide in a plate or flake shape having a thickness in a certain range through peeling.
그밖에, 상기 전도성 탄소에는 기공이 형성되어 있으며, 상기 기공의 공극률은 40 내지 90 %, 바람직하게는 60 내지 80 %로서, 상기 기공의 공극률이 40 % 미만이면 리튬 이온 전달이 정상적으로 이루어지지 않아 저항성분으로 작용하여 문제가 발생할 수 있고, 90 %를 초과하는 경우에는 기계적 강도가 저하되는 문제가 발생할 수 있다. 또한, 상기 전도성 탄소의 기공 크기는 10 ㎚ 내지 5 ㎛, 바람직하게는 50 ㎚ 내지 5 ㎛로서, 상기 기공의 크기가 10 ㎚ 미만이면 리튬 이온 투과가 불가능한 문제가 발생할 수 있고, 5 ㎛를 초과하는 경우에는 전극 간 접촉에 의한 전지 단락 및 안전성 문제가 발생할 수 있다.In addition, pores are formed in the conductive carbon, and the porosity of the pores is 40 to 90%, preferably 60 to 80%, and if the porosity of the pores is less than 40%, lithium ions cannot be transferred normally, and thus the resistance component It may act as a problem, and if it exceeds 90%, a problem of lowering the mechanical strength may occur. In addition, the pore size of the conductive carbon is 10 nm to 5 μm, preferably 50 nm to 5 μm, and if the pore size is less than 10 nm, there may be a problem in which lithium ion transmission is impossible, and the pore size exceeding 5 μm In this case, a battery short circuit and safety problems may occur due to contact between electrodes.
한편, 상기 베이스 분리막과 촉매점 함유 코팅층의 사이에는, 상기 촉매점 함유 코팅층이 상기 베이스 분리막의 표면에 보다 용이하게 코팅될 수 있도록 하는 바인더가 개재될 수 있다. 하지만, 본 발명의 전도성 탄소, 특히, 환원 그래핀 옥사이드(rGO) 중에서도 열적 박리 환원 그래핀 옥사이드(TErGO)를 사용하는 경우에는, 전도성 탄소가 판상 또는 플레이크 구조로 이루어지기 때문에, 상기 촉매점 함유 코팅층은 바인더 없이도 프리-스탠딩(free-standing)되어 베이스 분리막의 표면에 용이하게 코팅될 수 있다.On the other hand, between the base separation membrane and the coating layer containing the catalyst point, a binder may be interposed so that the coating layer containing the catalyst point can be more easily coated on the surface of the base separation membrane. However, in the case of using thermally exfoliated reduced graphene oxide (TErGO) among the conductive carbon of the present invention, in particular, reduced graphene oxide (rGO), since the conductive carbon is formed in a plate or flake structure, the catalyst point-containing coating layer It can be easily coated on the surface of the base separator by being free-standing without a silver binder.
이상에서 전술한 바와 같은 촉매점이 도입된 기능성 분리막은, 에너지 저장 디바이스에 광범위하게 사용될 수 있다. 구체적으로는, 리튬 이차전지의 분리막으로 사용될 수 있으며, 특히, 황의 환원반응이 수반되는 리튬-황 전지의 분리막으로도 적용되어 전지의 고성능화를 구현할 수 있고, 제조 비용 또한 저렴하여 상업화에 유리할 수 있다.The functional separation membrane into which the catalyst point as described above is introduced can be widely used in energy storage devices. Specifically, it can be used as a separator for a lithium secondary battery, and in particular, it can be applied as a separator for a lithium-sulfur battery accompanied by a reduction reaction of sulfur, so that high performance of the battery can be realized, and the manufacturing cost is also inexpensive, so it can be advantageous for commercialization. .
여기서, 앞서 언급한 선행기술문헌(대한민국 특허공개 제10-2017-0108496호)과 대비하여 보다 구체적으로 설명하면, 본 발명의 촉매점은 환원 촉매 역할이 가능한데 반하여, 상기 0108496호의 비전도성 COF(Covalent-Organic Framework)는 그것이 불가능하며, COF가 내부에 기공을 포함하고 있어 양극에서 용출된 리튬 폴리설파이드를 흡착하는 역할만 수행한다. 이에 비하여, 본 발명의 촉매점은 설퍼(S8) 또는 장 사슬(long chain) 폴리설파이드를 환원시켜 단 사슬(short chain) 폴리설파이드로 환원시키는 역할을 하여 반응 속도를 높이는 것이며 고율 방전(C-rate)에 유리하다.Here, in contrast to the aforementioned prior art document (Korean Patent Publication No. 10-2017-0108496), the catalyst point of the present invention can serve as a reduction catalyst, whereas the non-conductive COF (Covalent -Organic Framework) is impossible, and because COF contains pores inside, it only plays a role of adsorbing lithium polysulfide eluted from the anode. In contrast, the catalyst point of the present invention is to increase the reaction rate by reducing sulfur (S8) or long chain polysulfide to reduce it to short chain polysulfide. ) Is advantageous.
또한, 상기 0108496호의 경우 COF는 전자 전도성이 없어 전도 네트워크 (탄소 구조체)가 없는 부위에서는 환원되지 않고 남아있을 수 있는데 반하여, 본 발명의 경우에는 활물질의 활용도를 높여 방전량 측면에서 유리하다. 즉, 상기 0108496호의 경우, 주 물질인 COF가 전자 전도성이 없기 때문에 이를 보완하고자 전도성 탄소층인 제1 매트릭스를 사용해야만 하며, 이를 프리-스탠딩(free-standing)으로 만들기 위하여 수십 ㎛의 두께(실제 실험예: 45 ㎛)로 만들어야 하는 단점이 있다. 이렇게 두꺼운 매트릭스를 사용하면 무게 및 부피당 에너지 밀도가 감소할 것이 자명하여, 결과적으로 전지 성능 측면에서 매우 불리하다. 반면, 본 발명에서는 분리막을 지지체로 이용하여 20 ㎛ 이하로 얇게 제작이 가능하며, 셀 에너지 밀도 측면에서 유리하다.In addition, in the case of No. 0108496, COF may remain unreduced at a portion where there is no conduction network (carbon structure) because there is no electronic conductivity, whereas in the case of the present invention, it is advantageous in terms of discharge amount by increasing the utilization of the active material. That is, in the case of No. 0108496, since COF, which is the main material, does not have electronic conductivity, the first matrix, which is a conductive carbon layer, must be used to compensate, and to make it free-standing, a thickness of several tens of µm (actual Experimental example: 45 ㎛) there is a disadvantage to be made. It is obvious that the energy density per weight and volume will decrease if such a thick matrix is used, and as a result, it is very disadvantageous in terms of battery performance. On the other hand, in the present invention, it is possible to manufacture the separator as thin as 20 μm or less by using the membrane as a support, and is advantageous in terms of cell energy density.
또한, 본 발명의 촉매점은 환원 촉매로 이용하기 때문에 최소량으로도 성능 개선이 가능하다. 하지만 상기 0108496호의 COF의 경우에는 내부 기공에 리튬 폴리설파이드를 흡착시켜야 하기 때문에 그 사용량이 많아져야만 효과를 나타낼 수 있다. 이와 같은 이유로 촉매점에 COF를 결합시키는 것은 효율성과 에너지 밀도 측면에서 매우 불리하며, 또한 전도성 네트워크가 손실되어 리튬 폴리설파이드가 COF 내부에 쌓이게 되면 활물질 손실이 되어 방전량이 하락하고 이러한 물질들이 저항으로 작용하여 결과적으로 전지의 성능을 저하시킬 우려가 있다.In addition, since the catalyst point of the present invention is used as a reduction catalyst, it is possible to improve performance even with a minimum amount. However, in the case of the COF of No. 0108496, since lithium polysulfide must be adsorbed in the internal pores, the effect can be exhibited only when the amount of the amount is increased. For this reason, coupling COF to the catalyst point is very disadvantageous in terms of efficiency and energy density, and if lithium polysulfide accumulates inside the COF due to the loss of the conductive network, active material is lost and the amount of discharge decreases, and these materials act as resistance. As a result, there is a fear of deteriorating the performance of the battery.
다음으로, 본 발명에 따른 촉매점이 도입된 기능성 분리막의 제조 방법에 대하여 설명한다. 상기 촉매점이 도입된 기능성 분리막의 제조 방법은, (a) 촉매점을 용매에 분산시켜 촉매점 함유 분산액을 제조하는 단계, (b) 상기 제조된 촉매점 함유 분산액을 여과하는 단계, (c) 상기 여과를 통하여 얻어진 여과물의 상층부로부터 촉매점 함유 파우더를 수득하여 건조시키는 단계 및 (d) 상기 수득 및 건조된 촉매점 함유 파우더를 베이스 분리막의 표면에 코팅시키는 단계를 포함하며, 필요에 따라, 상기 (a) 단계 이후, 상기 제조된 촉매점 함유 분산액에 전도성 탄소를 공급하여, 전도성 탄소까지 포함한 촉매점 함유 분산액을 제조하는 단계(a-1)를 더 포함할 수 있다.Next, a method of manufacturing a functional separation membrane into which a catalyst point according to the present invention is introduced will be described. The method of manufacturing the functional separation membrane into which the catalyst points are introduced includes the steps of: (a) dispersing the catalyst points in a solvent to prepare a dispersion containing the catalyst points, (b) filtering the prepared dispersion containing the catalyst points, (c) the Obtaining and drying the catalyst point-containing powder from the upper layer of the filtrate obtained through filtration, and (d) coating the obtained and dried catalyst point-containing powder on the surface of the base separation membrane, and if necessary, the ( After step a), a step (a-1) of preparing a dispersion containing catalyst points including conductive carbon by supplying conductive carbon to the prepared dispersion containing catalyst points may be further included.
상기 (a) 단계에서는, 촉매점을 용매에 분산(또는, 용해)시켜 촉매점 분산액을 제조할 수 있으며, 필요에 따라, 상기 촉매점을 용매에 분산시킨 후에는 초음파 처리(bath sonication)를 수행하여 촉매점 분산액을 제조할 수 있다. 상기 촉매점 분산액의 농도는 고형분 중량에 대하여 5 내지 15 %, 바람직하게는 5 내지 12 %, 더욱 바람직하게는 5 내지 10 %일 수 있다. 만일, 상기 촉매점 분산액의 농도가 고형분 중량에 대하여 5 % 미만이면, 촉매점의 중량이 감소되어 촉매 활성이 좋지 않을 우려가 있고, 15 %를 초과하는 경우에는, 촉매점의 함량이 과다하여 코팅 대상인 베이스 분리막의 기공이 막힐 수 있다.In step (a), a catalyst point dispersion may be prepared by dispersing (or dissolving) the catalyst point in a solvent, and if necessary, after dispersing the catalyst point in a solvent, bath sonication is performed. Thus, the catalyst point dispersion can be prepared. The concentration of the catalyst point dispersion may be 5 to 15%, preferably 5 to 12%, more preferably 5 to 10% based on the weight of the solid content. If the concentration of the catalyst point dispersion is less than 5% based on the weight of the solid content, the weight of the catalyst point is reduced and there is a fear of poor catalytic activity. If it exceeds 15%, the content of the catalyst point is excessive and coating The pores of the target base separation membrane may be clogged.
상기 촉매점은 전술한 바와 같이 메탈-프탈로시아닌(MePc)이며, 예를 들어, 철 프탈로시아닌(FePc), 니켈 프탈로시아닌(NiPc), 망간 프탈로시아닌(MnPc), 구리 프탈로시아닌(CuPc), 아연 프탈로시아닌(ZnPc) 및 이들의 혼합물 등일 수 있다. 상기 메탈-프탈로시아닌은 질소 원자-탄소 원자의 고리가 교차하는 구조를 가진 거대 고리 화합물의 한 종류이며, 중심부에 금속 이온이 배위하고 있는 화학 구조를 가진다. 이와 같이, 메탈-프탈로시아닌을 촉매점으로 사용하므로, 전이금속에 4개의 질소가 결합된 안정적인 구조를 가지는 촉매점을 포함하는 촉매 물질의 제조가 가능하다. 일반적으로, 전이금속에 4개의 질소를 결합시키기 위해서는 N을 포함하는 전구체 물질과 반응시키고, 또한, 암모니아(NH3) 분위기 하에서 추가적인 반응을 진행하는 등 다수 단계의 공정을 거쳐야만 하는 번거로움이 있으나, 본 발명에서는 전술한 바와 같은 화학 구조를 가지는 메탈-프탈로시아닌을 사용함으로써, 간단한 공정으로 촉매 물질의 제조가 가능한 것이다.The catalyst point is metal-phthalocyanine (MePc) as described above, for example, iron phthalocyanine (FePc), nickel phthalocyanine (NiPc), manganese phthalocyanine (MnPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), and And mixtures thereof. The metal-phthalocyanine is a kind of macrocyclic compound having a structure in which rings of nitrogen atom-carbon atom cross, and has a chemical structure in which metal ions are coordinated in the center. As described above, since metal-phthalocyanine is used as a catalyst point, it is possible to prepare a catalyst material including a catalyst point having a stable structure in which four nitrogens are bonded to a transition metal. In general, in order to bind the four nitrogens to the transition metal, there is a hassle of having to go through a number of steps such as reacting with a precursor material containing N, and performing an additional reaction under an ammonia (NH 3 ) atmosphere In the present invention, by using a metal-phthalocyanine having the chemical structure as described above, it is possible to prepare a catalyst material in a simple process.
상기 (a) 단계에서 사용되는 용매는 디메틸 카보네이트, 디메틸 포름아미드, N-메틸 포름아미드, 술폴란(테트라히드로티오펜-1,1-디옥사이드), 3-메틸술폴란, N-부틸 술폰, 디메틸 설폭사이드, 피로리디논(HEP), 디메틸피페리돈(DMPD), N-메틸 피롤리디논(NMP), N-메틸아세트아미드, 디메틸아세트아미드(DMAc), N,N-디메틸포름아미드(DMF), 디에틸아세트아마이드(DEAc), 디프로필아세트 아마이드(DPAc), 에탄올, 프로판올, 부탄올, 헥산올, 이소프로필알코올(IPA), 에틸렌글리콜, 테트라클로로에틸렌, 프로필렌글리콜, 톨루엔, 트르펜틴, 메틸 아세테이트, 에틸 아세테이트, 페트롤 에테르, 아세톤, 크레졸 및 글리세롤로 이루어진 군에서 선택되는 1종 이상의 유기 용매일 수 있으며, 상기 촉매점의 용해도를 높이기 위하여 DMF를 사용하는 것이 바람직할 수 있다. The solvent used in step (a) is dimethyl carbonate, dimethyl formamide, N-methyl formamide, sulfolane (tetrahydrothiophene-1,1-dioxide), 3-methylsulfolane, N-butyl sulfone, dimethyl Sulfoxide, pyrolidinone (HEP), dimethylpiperidone (DMPD), N-methylpyrrolidinone (NMP), N-methylacetamide, dimethylacetamide (DMAc), N,N-dimethylformamide (DMF) , Diethylacetamide (DEAc), dipropylacetamide (DPAc), ethanol, propanol, butanol, hexanol, isopropyl alcohol (IPA), ethylene glycol, tetrachloroethylene, propylene glycol, toluene, trpentine, methyl acetate , Ethyl acetate, petroleum ether, acetone, cresol, and may be one or more organic solvents selected from the group consisting of glycerol, and it may be preferable to use DMF to increase the solubility of the catalyst point.
한편, 상기 (a) 단계 이후 제조된 촉매점 함유 분산액에 전도성 탄소를 공급하는 경우(단계 a-1) 교반이 이루어질 수 있으며, 이때 상기 교반은 상온 내지 60 ℃ 하에서 1 내지 24 시간 동안 수행될 수 있다. 상기 (a-1) 단계는 촉매점을 전도성 탄소의 표면에 흡착 결합시키는(또는, 도입시키는) 과정으로서, 즉, 고 비표면적 및 고 기공도를 가지는 전도성 탄소의 내외부 표면에 전이금속-질소-탄소 촉매점을 반데르발스 인력을 통하여 흡착 결합시키는 것이다. 이때, 상기 촉매점과 전도성 탄소의 혼합비는 전술한 바를 준용한다. 한편, 상기 촉매점 함유 분산액에 상기 전도성 탄소를 첨가한 후에도, 필요에 따라, 초음파 처리가 수행될 수 있다.On the other hand, in the case of supplying conductive carbon to the dispersion containing catalyst points prepared after step (a) (step a-1), stirring may be performed, and the stirring may be performed at room temperature to 60° C. for 1 to 24 hours. have. The step (a-1) is a process of adsorbing (or introducing) the catalyst point to the surface of the conductive carbon, that is, transition metal-nitrogen-on the inner and outer surfaces of the conductive carbon having a high specific surface area and high porosity. The carbon catalyst point is adsorbed and bonded through the van der Waals attraction. At this time, the mixing ratio of the catalyst point and the conductive carbon applies mutatis mutandis to the above. On the other hand, even after adding the conductive carbon to the dispersion containing the catalyst point, ultrasonic treatment may be performed if necessary.
상기 (b) 단계의 여과(filtering)는 진공펌프 등 일반적인 여과 방식을 준용할 수 있고, 상기 여과 공정이 이루어진 후에는, 필요에 따라, 에탄올 등의 알코올 등을 이용한 세척 공정이 추가로 수행될 수 있다.The filtering in step (b) may be applied mutatis mutandis to a general filtration method such as a vacuum pump, and after the filtration process is performed, a washing process using alcohol such as ethanol may be additionally performed as necessary. have.
상기 (c) 단계는 상기 (b) 단계에서 여과를 통하여 얻어진 여과물의 상층부로부터 촉매점 함유 파우더를 수득한 후 건조시키는 공정으로서, 상기 전도성 탄소까지 적용하는 경우에는, 상기 촉매점과 전도성 탄소의 결합력을 향상시키기 위하여, 상기의 건조 공정이 특정 온도 및 시간 하에서 이루어지는 것이 바람직할 수 있다. 이때, 상기 건조는 60 내지 100 ℃, 바람직하게는 65 내지 95 ℃, 더욱 바람직하게는 70 내지 90 ℃의 온도에서 1 내지 24 시간, 바람직하게는 5 내지 20 시간, 더욱 바람직하게는 10 내지 14 시간 동안 수행될 수 있다.The step (c) is a process of obtaining and drying the catalyst point-containing powder from the upper layer of the filtrate obtained through filtration in the step (b), and when applying to the conductive carbon, the bonding force between the catalyst point and the conductive carbon In order to improve, it may be desirable that the drying process be performed under a specific temperature and time. At this time, the drying is 1 to 24 hours, preferably 5 to 20 hours, more preferably 10 to 14 hours at a temperature of 60 to 100 °C, preferably 65 to 95 °C, more preferably 70 to 90 °C Can be performed during.
상기 (d) 단계는 상기 수득 및 건조된 촉매점 함유 파우더를 베이스 분리막의 표면에 코팅시킴으로써 본 발명에 따른 촉매점이 도입된 기능성 분리막이 최종 제조되는 단계이다. 이때, 상기 코팅은 드롭캐스트(dropcast) 방식, 딥-코팅(dip-coating) 방식, 블레이드 코팅(blade coating) 방식, 스프레이 코팅(spray coating) 방식, 마이어 바 코팅(meyer bar coating) 방식 또는 진공여과(vacuum filter) 방식에 의해 수행될 수 있다.The step (d) is a step in which the obtained and dried catalyst point-containing powder is coated on the surface of the base separation membrane to finally prepare a functional separation membrane into which the catalyst point according to the present invention is introduced. At this time, the coating is a dropcast method, a dip-coating method, a blade coating method, a spray coating method, a meyer bar coating method, or a vacuum filtration method. It can be performed by the (vacuum filter) method.
마지막으로, 본 발명이 제공하는 촉매점이 도입된 기능성 분리막을 포함하는 리튬 이차전지에 대하여 설명한다. 상기 촉매점이 도입된 기능성 분리막을 포함하는 리튬 이차전지는, 양극, 음극, 상기 양극과 음극의 사이에 개재되는 상기 촉매점 도입 기능성 분리막 및 전해질을 포함하며, 리튬-황 전지, 리튬 공기 전지 및 리튬 메탈 전지 등, 당업계에 알려진 모든 리튬 이차전지를 예로 들 수 있고, 이 중 리튬-황 전지인 것이 바람직하다. 상기 리튬 이차전지에 포함되는 기능성 분리막에 대한 설명은 전술한 것으로 대신하며, 그밖에 리튬 이차전지에 적용되는 나머지 양극, 음극 및 전해질은 당업계에서 사용하는 통상의 것일 수 있으며, 이에 대한 구체적인 설명은 후술하도록 한다.Finally, a lithium secondary battery including a functional separator into which a catalyst point provided by the present invention is introduced will be described. The lithium secondary battery including the functional separator into which the catalyst point is introduced includes a positive electrode, a negative electrode, the catalyst point introduction functional separator and an electrolyte interposed between the positive electrode and the negative electrode, and a lithium-sulfur battery, a lithium air battery and a lithium All lithium secondary batteries known in the art, such as metal batteries, can be exemplified, and among them, lithium-sulfur batteries are preferred. The description of the functional separator included in the lithium secondary battery is instead of the above, and other positive electrodes, negative electrodes, and electrolytes applied to the lithium secondary battery may be conventional ones used in the art, and a detailed description thereof will be described later. Do it.
한편, 본 발명은, 상기 리튬 이차전지를 단위 셀로 포함하는 전지 모듈 및 이를 포함하는 전지팩의 제공 또한 가능하다. 상기 전지모듈 또는 전지팩은 파워 툴(Power tool); 전기자동차(Electric vehicle, EV), 하이브리드 전기자동차, 및 플러그인 하이브리드 전기자동차(Plug-in hybrid electric vehicle, PHEV)를 포함하는 전기차; 또는 전력 저장용 시스템; 중 어느 하나 이상의 중대형 디바이스 전원으로 이용될 수 있다.Meanwhile, in the present invention, it is also possible to provide a battery module including the lithium secondary battery as a unit cell and a battery pack including the same. The battery module or battery pack may include a power tool; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Or a system for power storage; It can be used as a power supply for any one or more of medium and large devices.
이하, 본 발명에 따른 리튬 이차전지에 적용되는 양극, 음극 및 전해질에 대한 설명을 부가한다.Hereinafter, a description of the positive electrode, the negative electrode, and the electrolyte applied to the lithium secondary battery according to the present invention will be added.
양극anode
본 발명에 사용되는 양극에 관하여 설명하면, 양극 활물질, 도전재 및 바인더를 포함하는 양극 조성물을 제조한 후, 이를 소정의 용매(분산매)에 희석하여 제조된 슬러리를 양극 집전체 상에 직접 코팅 및 건조함으로써 양극층을 형성할 수 있다. 또는, 상기 슬러리를 별도의 지지체 상에 캐스팅한 후, 상기 지지체로부터 박리하여 얻은 필름을 양극 집전체 상에 라미네이션하여 양극층을 제조할 수 있다. 이외에도, 당해 기술 분야에서 통상의 지식을 가지는 기술자들에게 널리 알려진 방법을 사용하여 다양한 방식으로 양극을 제조할 수 있다.When describing the positive electrode used in the present invention, after preparing a positive electrode composition including a positive electrode active material, a conductive material, and a binder, a slurry prepared by diluting it in a predetermined solvent (dispersion medium) is directly coated on the positive electrode current collector, and By drying, an anode layer can be formed. Alternatively, after casting the slurry on a separate support, a film obtained by peeling from the support may be laminated on a positive electrode current collector to prepare a positive electrode layer. In addition, a positive electrode may be manufactured in various ways using a method widely known to those skilled in the art.
상기 도전재(Conducting material)는 양극 집전체로부터 전자가 양극 활물질까지 이동하는 경로의 역할을 하여 전자 전도성을 부여할 뿐만 아니라, 전해질과 양극 활물질을 전기적으로 연결시켜 주어 전해질 내 리튬 이온(Li+)이 황까지 이동하여 반응하게 하는 경로의 역할을 동시에 하게 된다. 따라서, 도전재의 양이 충분하지 않거나 역할을 제대로 수행하지 못하게 되면 전극 내 황 중 반응하지 못하는 부분이 증가하게 되고, 결국은 용량 감소를 일으키게 된다. 또한, 고율 방전 특성과 충방전 사이클 수명에도 악영향을 미치게 되므로, 적절한 도전재의 첨가가 필요하다. 상기 도전재의 함량은 양극 조성물 총 중량을 기준으로 0.01 내지 30 중량% 범위 내에서 적절히 첨가하는 것이 바람직하다.The conducting material serves as a path through which electrons move from the positive electrode current collector to the positive electrode active material, thereby imparting electron conductivity, as well as electrically connecting the electrolyte and the positive electrode active material so that lithium ions (Li+) in the electrolyte At the same time, it acts as a pathway to move to and react to sulfur. Therefore, if the amount of the conductive material is insufficient or the role cannot be performed properly, the non-reactive portion of the sulfur in the electrode increases, resulting in a decrease in capacity. In addition, since it adversely affects the high rate discharge characteristics and charge/discharge cycle life, it is necessary to add an appropriate conductive material. The content of the conductive material is preferably added appropriately within the range of 0.01 to 30% by weight based on the total weight of the positive electrode composition.
상기 도전재는 당해 전지에 화학적 변화를 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니며, 예컨대, 그라파이트; 덴카 블랙, 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 퍼니스 블랙, 램프 블랙 및 서머 블랙 등의 카본 블랙; 탄소 섬유나 금속 섬유 등의 도전성 섬유; 불화 카본, 알루미늄 및 니켈 분말 등의 금속 분말; 산화아연 및 티탄산 칼륨 등의 도전성 위스커; 산화 티탄 등의 도전성 금속 산화물; 폴리페닐렌 유도체 등의 도전성 소재 등이 사용될 수 있다. 시판 중인 도전재의 구체적인 예로는, 아세틸렌 블랙 계열인 쉐브론 케미칼 컴퍼니(Chevron Chemical Company)나 덴카 블랙(Denka Singapore Private Limited), 걸프 오일 컴퍼니(Gulf Oil Company) 제품, 케첸 블랙(Ketjenblack), EC 계열 아르막 컴퍼니(Armak Company) 제품, 불칸(Vulcan) XC-72 캐보트 컴퍼니(Cabot Company) 제품 및 슈퍼-피(Super-P; Timcal 사 제품) 등이 사용될 수 있다.The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, for example, graphite; Carbon blacks such as denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used. Specific examples of commercially available conductive materials include acetylene black-based Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, Ketjenblack, EC-based Armak Company (Armak Company) product, Vulcan (Vulcan) XC-72 Cabot Company (Cabot Company) product and Super-P (Timcal company product), and the like can be used.
상기 바인더는 양극 활물질을 집전체에 잘 부착시키기 위한 것으로서, 용매에 잘 용해되어야 하며, 양극 활물질과 도전재와의 도전 네크워크를 잘 구성해주어야 할 뿐만 아니라, 전해액의 함침성도 적당히 가져야 한다. 상기 바인더는 당해 업계에서 공지된 모든 바인더들일 수 있고, 구체적으로는, 폴리비닐리덴 플루오라이드(Polyvinylidene fluoride, PVdF) 또는 폴리테트라플루오로에틸렌(Polytetrafluoroethylene, PTFE)을 포함하는 불소 수지계 바인더; 스티렌-부타디엔 고무, 아크릴로니트릴-부티디엔 고무, 스티렌-이소프렌 고무를 포함하는 고무계 바인더; 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈를 포함하는 셀룰로오스계 바인더; 폴리 알코올계 바인더; 폴리에틸렌, 폴리프로필렌를 포함하는 폴리 올레핀계 바인더; 폴리 이미드계 바인더, 폴리 에스테르계 바인더, 실란계 바인더;로 이루어진 군에서 선택된 1종 이상의 혼합물이거나 공중합체일 수 있으나, 이에 제한되지는 않는다.The binder is for attaching the positive electrode active material to the current collector well, and must be well soluble in a solvent, and must not only form a conductive network between the positive electrode active material and the conductive material, but also have adequate impregnation of the electrolyte. The binder may be any binder known in the art, and specifically, a fluororesin binder including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); Rubber binders including styrene-butadiene rubber, acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulose-based binders including carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; Polyalcohol binder; Polyolefin-based binders including polyethylene and polypropylene; Polyimide-based binder, polyester-based binder, silane-based binder; may be a mixture or a copolymer selected from the group consisting of, but is not limited thereto.
상기 바인더의 함량은 양극 조성물 총 중량을 기준으로 0.5 내지 30 중량%일 수 있으나, 이에 한정되는 것은 아니다. 상기 바인더 수지의 함량이 0.5 중량% 미만인 경우에는, 양극의 물리적 성질이 저하되어 양극 활물질과 도전재가 탈락할 수 있고, 30 중량%를 초과하는 경우에는 양극에서 활물질과 도전재의 비율이 상대적으로 감소되어 전지 용량이 감소될 수 있으며, 저항 요소로 작용하여 효율이 저하될 수 있다.The content of the binder may be 0.5 to 30% by weight based on the total weight of the positive electrode composition, but is not limited thereto. When the content of the binder resin is less than 0.5% by weight, the physical properties of the positive electrode are deteriorated, so that the positive electrode active material and the conductive material may fall off, and if it exceeds 30% by weight, the ratio of the active material and the conductive material in the positive electrode is relatively reduced. Battery capacity may be reduced, and efficiency may be lowered by acting as a resistance element.
상기 양극 활물질, 도전재 및 바인더를 포함하는 양극 조성물은 소정의 용매에 희석되어, 양극 집전체 상에 당업계에 알려진 통상의 방법을 이용하여 코팅할 수 있다. 먼저, 양극 집전체를 준비한다. 상기 양극 집전체는 일반적으로 3 내지 500 ㎛의 두께를 사용한다. 이와 같은 양극 집전체는, 당해 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되는 것은 아니며, 예를 들어, 스테인레스 스틸, 알루미늄, 니켈, 티탄, 소결 탄소, 또는 알루미늄이나 스테리인레스 스틸의 표면에 카본, 니켈, 티탄, 은 등으로 표면 처리한 것 등이 사용될 수 있다. 집전체는 그것의 표면에 미세한 요철을 형성하여 양극 활물질의 접착력을 높일 수도 있으며, 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태가 가능하다.The positive electrode composition including the positive electrode active material, the conductive material, and the binder may be diluted in a predetermined solvent and coated on the positive electrode current collector using a conventional method known in the art. First, a positive electrode current collector is prepared. In general, the positive electrode current collector has a thickness of 3 to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel Carbon, nickel, titanium, silver, or the like may be used on the surface of the steel. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.
다음으로, 상기 양극 집전체 상에 양극 활물질, 도전재 및 바인더를 포함하는 양극 조성물을 용매에 희석한 슬러리를 도포한다. 전술한 양극 활물질, 도전재 및 바인더를 포함하는 양극 조성물을 소정의 용매와 혼합하여 슬러리로 제조할 수 있다. 이때 용매는 건조가 용이해야 하며, 바인더를 잘 용해시킬 수 있으되, 양극 활물질 및 도전재는 용해시키지 않고 분산 상태로 유지시킬 수 있는 것이 가장 바람직하다. 용매가 양극 활물질을 용해시킬 경우에는 슬러리에서 황의 비중(D = 2.07)이 높기 때문에 황이 슬러리에서 가라앉게 되어 코팅 시 집전체에 황이 몰려 도전 네트워크에 문제가 생겨, 전지의 작동에 문제가 발생하는 경향이 있다. 상기 용매(분산매)는 물 또는 유기 용매가 가능하며, 상기 유기 용매는 디메틸포름아미드, 이소프로필알콜 또는 아세토니트릴, 메탄올, 에탄올, 테트라하이드로퓨란 군으로부터 선택되는 1종 이상일 수 있다.Next, a slurry obtained by diluting a positive electrode composition including a positive electrode active material, a conductive material, and a binder in a solvent is applied on the positive electrode current collector. The positive electrode composition including the positive electrode active material, the conductive material, and the binder may be mixed with a predetermined solvent to prepare a slurry. At this time, the solvent should be easy to dry and can dissolve the binder well, but it is most preferable that the positive electrode active material and the conductive material can be maintained in a dispersed state without dissolving. When the solvent dissolves the positive electrode active material, the specific gravity of sulfur in the slurry (D = 2.07) is high, so sulfur settles in the slurry, and sulfur gathers in the current collector during coating, causing problems in the conductive network, causing problems in battery operation. There is this. The solvent (dispersion medium) may be water or an organic solvent, and the organic solvent may be at least one selected from the group of dimethylformamide, isopropyl alcohol or acetonitrile, methanol, ethanol, and tetrahydrofuran.
계속해서, 상기 슬러리 상태의 양극 조성물을 도포하는 방법에는 특별한 제한이 없으며, 예컨대, 닥터 블레이드 코팅(Doctor blade coating), 딥 코팅(Dip coating), 그라비어 코팅(Gravure coating), 슬릿 다이 코팅(Slit die coating), 스핀 코팅(Spin coating), 콤마 코팅(Comma coating), 바 코팅(Bar coating), 리버스 롤 코팅(Reverse roll coating), 스크린 코팅(Screen coating), 캡 코팅(Cap coating) 방법 등을 수행하여 제조할 수 있다. 이와 같은 코팅 과정을 거친 양극 조성물은, 이후 건조 과정을 통해 용매(분산매)의 증발, 코팅막의 조밀성 및 코팅막과 집전체와의 밀착성 등이 이루어진다. 이때, 건조는 통상적인 방법에 따라 실시되며, 이를 특별히 제한하지는 않는다.Subsequently, there is no particular limitation on the method of applying the slurry-like positive electrode composition, for example, Doctor blade coating, Dip coating, Gravure coating, Slit die coating. coating), spin coating, comma coating, bar coating, reverse roll coating, screen coating, cap coating, etc. It can be manufactured. In the positive electrode composition that has undergone such a coating process, evaporation of the solvent (dispersion medium), the denseness of the coating film, and adhesion between the coating film and the current collector are achieved through a subsequent drying process. At this time, drying is carried out according to a conventional method, and this is not particularly limited.
음극cathode
음극으로는 리튬이온을 흡장 및 방출할 수 있는 것을 모두 사용할 수 있으며, 예를 들어, 리튬 금속, 리튬 합금 등의 금속재와, 저결정 탄소, 고결정성 탄소 등의 탄소재를 예시할 수 있다. 저결정성 탄소로는 연화탄소(Soft carbon) 및 경화탄소(Hard carbon)가 대표적이며, 고결정성 탄소로는 천연 흑연, 키시 흑연(Kish graphite), 열분해 탄소(Pyrolytic carbon), 액정 피치계 탄소섬유(Mesophase pitch based carbon fiber), 탄소 미소구체(Meso-carbon microbeads), 액정피치(Mesophase pitches) 및 석유와 석탄계 코크스(Petroleum or coal tar pitch derived cokes) 등의 고온 소성 탄소가 대표적이다. 이 외에, 실리콘이 포함된 얼로이 계열이나 Li4Ti5O12 등의 산화물도 잘 알려진 음극이다.As the negative electrode, any one capable of occluding and releasing lithium ions can be used, and examples thereof include metal materials such as lithium metal and lithium alloys, and carbon materials such as low crystalline carbon and high crystalline carbon. Soft carbon and hard carbon are typical examples of low-crystalline carbon, and natural graphite, kish graphite, pyrolytic carbon, and liquid crystal pitch-based carbon fiber are high-crystalline carbon. High-temperature calcined carbons such as (Mesophase pitch based carbon fiber), Meso-carbon microbeads, Mesophase pitches, and Petroleum or coal tar pitch derived cokes are typical. In addition, alloys containing silicon or oxides such as Li 4 Ti 5 O 12 are also well-known cathodes.
이때, 음극은 결착제를 포함할 수 있으며, 결착제로는 폴리비닐리덴플루오라이드(Polyvinylidenefluoride, PVDF), 폴리비닐리덴플루오라이드-헥사플루오로프로필렌 코폴리머(PVDF-co-HFP), 폴리아크릴로니트릴(Polyacrylonitrile), 폴리메틸메타크릴레이트(Polymethylmethacrylate), 스티렌-부타디엔 고무(SBR) 등, 다양한 종류의 바인더 고분자가 사용될 수 있다.At this time, the negative electrode may include a binder, and as the binder, polyvinylidenefluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), and polyacrylonitrile (Polyacrylonitrile), polymethylmethacrylate (Polymethylmethacrylate), styrene-butadiene rubber (SBR), and various kinds of binder polymers can be used.
상기 음극은 상기 음극 활물질 및 바인더를 포함하는 음극 활성층의 지지를 위한 음극 집전체를 선택적으로 더 포함할 수도 있다. 상기 음극 집전체는 구체적으로 구리, 스테인리스스틸, 티타늄, 은, 팔라듐, 니켈, 이들의 합금 및 이들의 조합으로 이루어진 군에서 선택되는 것일 수 있다. 상기 스테인리스스틸은 카본, 니켈, 티탄 또는 은으로 표면 처리될 수 있으며, 상기 합금으로는 알루미늄-카드뮴 합금이 사용될 수 있다. 그 외에도 소성 탄소, 도전제로 표면 처리된 비전도성 고분자, 또는 전도성 고분자 등이 사용될 수도 있다.The negative electrode may optionally further include a negative electrode current collector for supporting the negative electrode active layer including the negative electrode active material and the binder. The negative electrode current collector may be specifically selected from the group consisting of copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel may be surface-treated with carbon, nickel, titanium, or silver, and an aluminum-cadmium alloy may be used as the alloy. In addition, calcined carbon, a non-conductive polymer surface-treated with a conductive agent, or a conductive polymer may be used.
상기 바인더는 음극 활물질의 페이스트화, 활물질간 상호 접착, 활물질과 집전체와의 접착, 활물질 팽창 및 수축에 대한 완충 효과 등의 역할을 한다. 구체적으로 상기 바인더는 앞서 양극의 바인더에서 설명한 바와 동일하다. 또한 상기 음극은 리튬 금속 또는 리튬 합금일 수 있다. 비제한적인 예로, 음극은 리튬 금속의 박막일 수도 있으며, 리튬과 Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al 및 Sn으로 이루어진 군으로부터 선택되는 1종 이상의 금속과의 합금일 수 있다.The binder serves as a paste of the negative active material, mutual adhesion between the active materials, adhesion between the active material and the current collector, and a buffering effect on expansion and contraction of the active material. Specifically, the binder is the same as described above for the binder of the positive electrode. In addition, the negative electrode may be a lithium metal or a lithium alloy. As a non-limiting example, the negative electrode may be a thin film of lithium metal, and lithium and one selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, and Sn It may be an alloy with the above metals.
전해질Electrolyte
전해액은 용매(Solvents) 및 리튬염(Lithium Salt)을 포함하며, 필요에 따라, 첨가제(Additives)를 더 포함할 수 있다. 상기 용매로는 전지의 전기화학적 반응에 관여하는 이온들이 이동할 수 있는 매질 역할을 하는 통상의 비수성 용매를 특별한 제한 없이 사용할 수 있다. 상기 비수성 용매의 예로는, 카보네이트계 용매, 에스테르계 용매, 에테르계 용매, 케톤계 용매, 알코올계 용매 및 비양자성 용매 등을 들 수 있다.The electrolyte solution includes a solvent and a lithium salt, and may further include additives, if necessary. As the solvent, a conventional non-aqueous solvent serving as a medium through which ions involved in the electrochemical reaction of a battery can move may be used without particular limitation. Examples of the non-aqueous solvent include carbonate-based solvents, ester-based solvents, ether-based solvents, ketone-based solvents, alcohol-based solvents, and aprotic solvents.
보다 구체적인 예를 들면, 상기 카보네이트계 용매로서 디메틸카보네이트(DMC), 디에틸카보네이트(DEC), 디프로필카보네이트(DPC), 메틸프로필카보네이트(MPC), 에틸프로필카보네이트(EPC), 메틸에틸카보네이트(MEC), 에틸렌카보네이트(EC), 프로필렌카보네이트(PC) 및 부틸렌 카보네이트(BC) 등이 있고, 상기 에스테르계 용매로는 메틸 아세테이트, 에틸 아세테이트, n-프로필 아세테이트, 1,1-디메틸에틸 아세테이트, 메틸프로피오네이트, 에틸프로피오네이트, γ-부티로락톤, 데카놀라이드(decanolide), 발레로락톤, 메발로노락톤(mevalonolactone) 및 카프로락톤(carprolactone) 등이 있으며, 상기 에테르계 용매로는 디에틸 에테르, 디프로필 에테르, 디부틸 에테르, 디메톡시메탄, 트리메톡시메탄, 디메톡시에탄, 디에톡시에탄, 디글라임, 트리글라임, 테트라글라임, 테트라하이드로퓨란, 2-메틸테트라하이드로퓨란 및 폴리에틸렌 글리콜 디메틸 에테르 등이 있다. 또한, 상기 케톤계 용매로는 시클로헥사논 등이 있고, 상기 알코올계 용매로는 에틸알코올 및 이소프로필알코올 등이 있으며, 상기 비양자성 용매로는 아세토니트릴 등의 니트릴류, 디메틸포름아미드 등의 아미드류, 1,3-디옥솔란(DOL) 등의 디옥솔란류 및 술포란(sulfolane) 등이 있다. 이상과 같은 비수성 용매는 단독 또는 둘 이상 혼합하여 사용할 수 있고, 둘 이상 혼합할 경우의 혼합 비율은 목적으로 하는 전지의 성능에 따라 적절하게 조절할 수 있으며, 1,3-디옥솔란과 디메톡시에탄을 1 : 1의 부피비로 혼합한 용매를 예시할 수 있다.For a more specific example, as the carbonate-based solvent, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) ), ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC), and the ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethylethyl acetate, methyl Propionate, ethyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, and caprolactone, and the ether solvents include di Ethyl ether, dipropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane, diglyme, triglyme, tetraglyme, tetrahydrofuran, 2-methyltetrahydrofuran and Polyethylene glycol dimethyl ether and the like. In addition, the ketone solvent includes cyclohexanone, and the alcohol solvent includes ethyl alcohol and isopropyl alcohol, and the aprotic solvent includes nitriles such as acetonitrile, and amino acids such as dimethylformamide. Dioxolanes such as Drew, 1,3-dioxolane (DOL), and sulfolane. Non-aqueous solvents as described above can be used alone or in combination of two or more, and the mixing ratio in the case of mixing two or more can be appropriately adjusted according to the performance of the intended battery, and 1,3-dioxolane and dimethoxyethane A solvent mixed in a volume ratio of 1: 1 can be illustrated.
이하 본 발명의 이해를 돕기 위하여 바람직한 실시예를 제시하나, 하기 실시예는 본 발명을 예시하는 것일 뿐, 본 발명의 범주 및 기술사상 범위 내에서 다양한 변경 및 수정이 가능함은 당업자에게 있어서 명백한 것이며, 이러한 변경 및 수정이 첨부된 특허청구범위에 속하는 것도 당연한 것이다.Hereinafter, preferred embodiments are presented to aid in the understanding of the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It is natural that such changes and modifications fall within the scope of the appended claims.
[실시예 1] 촉매점이 도입된 기능성 분리막의 제조 [Example 1] Preparation of a functional separation membrane into which a catalyst point was introduced
먼저, 촉매점인 니켈 프탈로시아닌(NiPc, Aldrich社) 60 mg을 용매인 N,N-디메틸포름아미드(DMF) 500 mL에 분산시킨 후, 10 분 동안 초음파 처리(bath sonication)를 하여 니켈 프탈로시아닌(NiPc) 분산액을 제조하였다.First, 60 mg of nickel phthalocyanine (NiPc, Aldrich) as a catalyst point was dispersed in 500 mL of N,N-dimethylformamide (DMF) as a solvent, and then sonicated for 10 minutes to obtain nickel phthalocyanine (NiPc). ) A dispersion was prepared.
이어서, 상기 제조된 니켈 프탈로시아닌(NiPc) 분산액을 진공펌프로 여과시킨 후 에탄올 1000 ml로 세척하였고, 여과물의 상층 파우더를 80 ℃에서 12 시간 동안 건조시켰다.Subsequently, the prepared nickel phthalocyanine (NiPc) dispersion was filtered with a vacuum pump and washed with 1000 ml of ethanol, and the upper powder of the filtrate was dried at 80° C. for 12 hours.
마지막으로, 상기 건조된 파우더를 진공여과 방식으로 폴리에틸렌 재질의 다공성 베이스 분리막의 표면 전체에 코팅한 후 건조하여, 촉매점이 도입된 기능성 분리막을 제조하였다. 한편, 상기 코팅 시 코팅물의 두께는 0.5 ㎛로, 코팅량은 10 ㎍/㎠가 되도록 하였다.Finally, the dried powder was coated on the entire surface of a porous base separator made of polyethylene by vacuum filtration and then dried to prepare a functional separator in which a catalyst point was introduced. Meanwhile, during the coating, the thickness of the coating material was 0.5 µm, and the coating amount was 10 µg/cm 2.
[비교예 1] 통상적인 분리막의 제조 [Comparative Example 1] Preparation of a conventional separator
촉매점인 니켈 프탈로시아닌(NiPc)의 코팅 없이, 폴리에틸렌(PE)으로 이루어진 bare 상태의 분리막을 제조하였다.Without coating of nickel phthalocyanine (NiPc) as a catalyst point, a bare separator made of polyethylene (PE) was prepared.
[비교예 2] 통상적인 분리막의 제조 [Comparative Example 2] Preparation of a conventional separator
메탈 프탈로시아닌을 포함하는 NiPc-PBBA COF(여기서, COF의 원료 물질은 1,4-benzenediboronic acid)를 CNT 페이퍼 상에 코팅시켜 복합체를 제조한 후, 이를 bare 상태의 분리막에 대면되도록 위치시켜, bare 상태의 분리막과 복합체가 물리적으로 분리된 통상의 분리막을 제조하였다(선행기술문헌인 대한민국 특허공개 제10-2017-0108496호에 해당함).After preparing a composite by coating NiPc-PBBA COF containing metal phthalocyanine (here, the raw material of COF is 1,4-benzenediboronic acid) on CNT paper, it is placed so as to face the separator in the bare state, and in the bare state A conventional separator in which the separator and the composite are physically separated was prepared (corresponding to Korean Patent Publication No. 10-2017-0108496, which is a prior art document).
[실시예 2, 비교예 3-4] 리튬 이차전지의 제조 [Example 2, Comparative Example 3-4] Preparation of lithium secondary battery
상기 실시예 1, 비교예 1 및 2에서 제조된 분리막과, 전해액(DOL:DME (1:1), 1.0 M LiTFSI, 1 wt% LiNO3) 70 ㎕, 황 양극 및 리튬 메탈 음극을 포함하는 코인셀 형태의 리튬-황 전지를 제조하였다(단, 비교예 2의 분리막을 양극과 음극의 사이에 개재시킴에 있어, 전체 분리막 중 복합체를 양극 측에 대향시켰다).The separator prepared in Example 1 and Comparative Examples 1 and 2, and an electrolyte solution (DOL:DME (1:1), 1.0 M LiTFSI, 1 wt% LiNO 3 ) 70 µl, a coin containing a sulfur anode and a lithium metal anode A cell-type lithium-sulfur battery was prepared (however, when the separator of Comparative Example 2 was interposed between the positive electrode and the negative electrode, the composite of the entire separator was opposed to the positive electrode side).
[실험예 1] 리튬 이차전지의 수명특성 평가 [Experimental Example 1] Evaluation of life characteristics of lithium secondary batteries
상기와 같이 실시예 2, 비교예 3 및 4에서 제조된 리튬-황 전지의 방전 전류 속도를 0.2 C로 고정하고 방전량을 일정하게 제한(5 mAh)하여 수명특성을 관찰하였으며, 그 결과를 도 1에 나타내었다. 도 1은 본 발명의 일 실시예 및 비교예에 따른 리튬 이차전지의 수명특성을 보여주는 그래프로서, 도 1에 도시된 바와 같이, 촉매점이 도입된 기능성 분리막을 적용한 실시예 2의 리튬-황 전지는, 촉매점을 도입하지 않은 통상적인 분리막을 적용한 비교예 3의 리튬-황 전지와, 촉매점은 도입하였으나 분리막에 코팅시키지는 않은 비교예 4의 리튬-황 전지에 비하여, 수명특성이 우수한 것을 확인할 수 있었다.As described above, the discharge current rate of the lithium-sulfur batteries prepared in Example 2 and Comparative Examples 3 and 4 was fixed at 0.2 C, and the discharge amount was constantly limited (5 mAh) to observe the life characteristics, and the results are shown. It is shown in 1. 1 is a graph showing the life characteristics of a lithium secondary battery according to an embodiment and a comparative example of the present invention. As shown in FIG. 1, the lithium-sulfur battery of Example 2 to which a functional separator having a catalyst point is applied is applied. , Compared to the lithium-sulfur battery of Comparative Example 3 to which a conventional separator was applied without introducing a catalyst point and the lithium-sulfur battery of Comparative Example 4 to which a catalyst point was introduced but not coated on the separator, it was confirmed that the life characteristics were excellent. there was.
[실시예 3] 촉매점이 도입된 기능성 분리막의 제조 [Example 3] Preparation of functional separation membrane into which catalyst points were introduced
먼저, 촉매점인 니켈 프탈로시아닌(NiPc, Aldrich社) 60 mg을 용매인 N,N-디메틸포름아미드(DMF) 500 mL에 분산시킨 후, 10 분 동안 초음파 처리(bath sonication)를 하여 니켈 프탈로시아닌(NiPc) 분산액을 제조하였다.First, 60 mg of nickel phthalocyanine (NiPc, Aldrich) as a catalyst point was dispersed in 500 mL of N,N-dimethylformamide (DMF) as a solvent, and then sonicated for 10 minutes to obtain nickel phthalocyanine (NiPc). ) A dispersion was prepared.
이어서, 상기 제조된 니켈 프탈로시아닌(NiPc) 분산액에 환원 그래핀 옥사이드(rGO, Sixth Element社) 940 mg을 첨가한 후, 10 분 동안 초음파 처리하고, 4 시간 동안 500 rpm의 속도로 상온에서 교반시켜 혼합물을 얻었다.Subsequently, 940 mg of reduced graphene oxide (rGO, Sixth Element) was added to the prepared nickel phthalocyanine (NiPc) dispersion, followed by ultrasonic treatment for 10 minutes, followed by stirring at room temperature at a speed of 500 rpm for 4 hours. Got it.
계속해서, 상기 혼합물을 진공펌프로 여과시킨 후 에탄올 1000 ml로 세척하였고, 여과물의 상층 파우더를 80 ℃에서 12 시간 동안 건조시켰다.Subsequently, the mixture was filtered with a vacuum pump and washed with 1000 ml of ethanol, and the upper powder of the filtrate was dried at 80° C. for 12 hours.
마지막으로, 상기 건조된 파우더를 진공여과 방식으로 폴리에틸렌 재질의 다공성 베이스 분리막의 표면 전체에 코팅한 후 건조하여, 촉매점이 도입된 기능성 분리막을 제조하였다. 한편, 상기 코팅 시 코팅물의 두께는 1 ㎛로, 코팅량은 20 ㎍/㎠가 되도록 하였다.Finally, the dried powder was coated on the entire surface of a porous base separator made of polyethylene by vacuum filtration and then dried to prepare a functional separator in which a catalyst point was introduced. On the other hand, during the coating, the thickness of the coating material was 1 μm, and the coating amount was 20 μg/cm 2.
[실시예 4] 촉매점이 도입된 기능성 분리막의 제조 [Example 4] Preparation of functional separation membrane into which catalyst points were introduced
코팅물의 두께를 4 ㎛로, 코팅량을 60 ㎍/㎠가 되도록 변경한 것을 제외하고는, 상기 실시예 3과 동일하게 수행하여 촉매점이 도입된 기능성 분리막을 제조하였다.Except that the thickness of the coating material was changed to 4 µm and the coating amount was changed to 60 µg/cm 2, a functional separator in which a catalyst point was introduced was prepared in the same manner as in Example 3 above.
[실시예 5] 촉매점이 도입된 기능성 분리막의 제조 [Example 5] Preparation of functional separation membrane into which catalyst points were introduced
코팅물의 두께를 8 ㎛로, 코팅량을 120 ㎍/㎠가 되도록 변경한 것을 제외하고는, 상기 실시예 3과 동일하게 수행하여 촉매점이 도입된 기능성 분리막을 제조하였다.Except that the thickness of the coating material was changed to 8 µm and the coating amount was changed to 120 µg/cm 2, a functional separation membrane in which a catalyst point was introduced was prepared in the same manner as in Example 3 above.
[비교예 5] 통상적인 분리막의 제조 [Comparative Example 5] Preparation of a conventional separator
폴리에틸렌(PE)으로 이루어진 bare 상태의 분리막 표면에 전도성 탄소인 환원 그래핀 옥사이드(rGO, Sixth Element社)만을 표면 코팅시켜 통상적인 분리막을 제조하였다.A conventional separator was prepared by surface coating only reduced graphene oxide (rGO, Sixth Element), which is conductive carbon, on the surface of the bare separator made of polyethylene (PE).
[실험예 2] 촉매점이 도입된 기능성 분리막의 코팅 균일성 평가 [Experimental Example 2] Evaluation of coating uniformity of functional separation membranes with catalyst points introduced
상기 실시예 3 내지 5에서 제조된 촉매점 도입 기능성 분리막의 코팅 균일성을 평가하였다. 도 2는 본 발명에 따른 촉매점 도입 기능성 분리막의 실물 이미지로서, 도 2의 (a) 내지 (c)는 각각 실시예 3 내지 5에 해당하며, 도 3은 본 발명에 따른 촉매점 도입 기능성 분리막의 전자 현미경 관찰 이미지로서, 도 3의 (a) 내지 (c) 또한 각각 실시예 3 내지 5에 해당한다. 도 2 및 3에 도시된 바와 같이, 본 발명에 따른 촉매점 도입 기능성 분리막은, 촉매점 함유 코팅층이 균일하게 잘 형성되어 있음을 확인할 수 있다. 특히, 촉매점 도입 기능성 분리막을 전자 현미경으로 관찰한 도 3으로부터, 촉매점 함유 코팅층이 뭉침 현상 없이 판상형으로 고르게 잘 펴져 있음을 알 수 있다.The coating uniformity of the functional separation membrane for introducing catalyst points prepared in Examples 3 to 5 was evaluated. Figure 2 is a real image of a catalyst point introduction functional separation membrane according to the present invention, Figure 2 (a) to (c) respectively correspond to Examples 3 to 5, Figure 3 is a catalyst point introduction functional separator according to the present invention As an electron microscope observation image of, Figs. 3 (a) to (c) also correspond to Examples 3 to 5, respectively. As shown in FIGS. 2 and 3, it can be seen that the catalyst point-containing functional separator according to the present invention has a uniformly well formed catalyst point-containing coating layer. In particular, from FIG. 3, when the catalyst point-introducing functional separator was observed with an electron microscope, it can be seen that the catalyst point-containing coating layer is evenly spread in a plate shape without agglomeration.
[실시예 6~8, 비교예 6] 분리막을 적용한 리튬 이차전지의 제조 [Examples 6 to 8, Comparative Example 6] Preparation of a lithium secondary battery to which a separator was applied
상기 실시예 3 내지 5 및 비교예 5에서 제조된 각각의 분리막과, 전해액(DOL:DME (1:1), 1.0 M LiTFSI, 1 wt% LiNO3) 70 ㎕, 황 양극 및 리튬 메탈 음극을 포함하는 코인셀 형태의 리튬-황 전지를 제조하였다.Each of the separators prepared in Examples 3 to 5 and Comparative Example 5, and an electrolyte solution (DOL:DME (1:1), 1.0 M LiTFSI, 1 wt% LiNO 3 ) 70 μl, including a sulfur anode and a lithium metal anode A lithium-sulfur battery in the form of a coin cell was prepared.
[실시예 9~11, 비교예 7] 분리막을 적용한 리튬 이차전지의 제조 [Examples 9 to 11, Comparative Example 7] Preparation of a lithium secondary battery to which a separator was applied
상기 실시예 3 내지 5 및 비교예 5에서 제조된 각각의 분리막과, 전해액(DOL:DME (1:1), 1.0 M LiTFSI, 3 wt% LiNO3) 70 ㎕, 황 양극 및 리튬 메탈 음극을 포함하는 코인셀 형태의 리튬-황 전지를 제조하였다.Each of the separators prepared in Examples 3 to 5 and Comparative Example 5, and an electrolyte solution (DOL:DME (1:1), 1.0 M LiTFSI, 3 wt% LiNO 3 ) 70 µl, a sulfur anode and a lithium metal anode A lithium-sulfur battery in the form of a coin cell was prepared.
[실험예 3] 리튬 이차전지의 방전용량 및 수명특성 평가 [Experimental Example 3] Evaluation of discharge capacity and life characteristics of lithium secondary battery
먼저, 상기 실시예 6 내지 8 및 비교예 6으로부터 제조된 리튬-황 전지의 방전 전류 속도를 0.1 C로 3회, 0.2 C로 3회, 이후 0.5 C로 설정한 후, 수명특성을 관찰하였다. 도 4는 본 발명의 일 실시예 및 비교예에 따른 리튬 이차전지의 방전용량(a) 및 수명특성(b)을 보여주는 그래프이다. 도 4에 도시된 바와 같이, 촉매점 도입 기능성 분리막을 리튬-황 전지에 적용한 실시예 6 내지 8은, 분리막 표면에 전도성 탄소만을 코팅시킨 비교예 6의 리튬-황 전지에 비하여 방전용량 및 수명특성 모두 우수하게 나타나는 것을 확인할 수 있었다.First, the discharge current rate of the lithium-sulfur batteries prepared from Examples 6 to 8 and Comparative Example 6 was set to 0.1 C 3 times, 0.2 C 3 times, and then 0.5 C, and then the life characteristics were observed. 4 is a graph showing discharge capacity (a) and life characteristics (b) of lithium secondary batteries according to an embodiment and a comparative example of the present invention. As shown in FIG. 4, Examples 6 to 8 in which the catalyst point introduction functional separator was applied to a lithium-sulfur battery were compared with the lithium-sulfur battery of Comparative Example 6 in which only conductive carbon was coated on the surface of the separator. It was confirmed that all appeared excellently.
또한, 상기 실시예 9 내지 11 및 비교예 7로부터 제조된 리튬-황 전지의 방전 전류 속도를 0.1 C로 3회, 0.2 C로 3회, 이후 0.5 C로 설정한 후, 수명특성을 관찰하였다. 도 5는 본 발명의 일 실시예 및 비교예에 따른 리튬 이차전지의 방전용량(a) 및 수명특성(b)을 보여주는 그래프이다. 도 5에 도시된 바와 같이, 촉매점 도입 기능성 분리막을 리튬-황 전지에 적용한 실시예 9 내지 11 또한, 분리막 표면에 전도성 탄소만을 코팅시킨 비교예 7의 리튬-황 전지에 비하여 방전용량 및 수명특성 모두 우수하게 나타나는 것을 확인할 수 있었다.In addition, after the discharge current rate of the lithium-sulfur batteries prepared from Examples 9 to 11 and Comparative Example 7 was set to 0.1 C 3 times, 0.2 C 3 times, and then 0.5 C, the life characteristics were observed. 5 is a graph showing discharge capacity (a) and life characteristics (b) of a lithium secondary battery according to an embodiment and a comparative example of the present invention. As shown in FIG. 5, Examples 9 to 11 in which the functional separator introducing a catalyst point was applied to a lithium-sulfur battery. In addition, discharge capacity and lifespan characteristics compared to the lithium-sulfur battery of Comparative Example 7 in which only conductive carbon was coated on the surface of the separator. It was confirmed that all appeared excellently.
아울러, 실시예 6 내지 11의 리튬-황 전지 모두, 전해질의 종류에 관계 없이 분리막 표면에 전도성 탄소만을 코팅시킨 리튬-황 전지에 비하여 방전용량 및 수명특성이 우수하게 나타나는 것을 알 수 있었다.In addition, it was found that all of the lithium-sulfur batteries of Examples 6 to 11 exhibited superior discharge capacity and life characteristics compared to the lithium-sulfur batteries in which only conductive carbon was coated on the separator surface regardless of the type of electrolyte.

Claims (15)

  1. 베이스 분리막; 및 Base separator; And
    상기 베이스 분리막의 표면에 위치한 촉매점 함유 코팅층;을 포함하는 촉매점이 도입된 기능성 분리막.A catalyst point-containing coating layer located on the surface of the base separation membrane;
  2. 청구항 1에 있어서, 상기 촉매점은 전이금속-질소-탄소의 연속 결합을 포함하는 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The functional separation membrane according to claim 1, wherein the catalyst point comprises a continuous bond of a transition metal-nitrogen-carbon.
  3. 청구항 1에 있어서, 상기 촉매점은 철 프탈로시아닌(FePc), 니켈 프탈로시아닌(NiPc), 망간 프탈로시아닌(MnPc), 구리 프탈로시아닌(CuPc), 아연 프탈로시아닌(ZnPc) 및 이들의 혼합물로 이루어진 군으로부터 선택되는 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The method according to claim 1, wherein the catalyst point is selected from the group consisting of iron phthalocyanine (FePc), nickel phthalocyanine (NiPc), manganese phthalocyanine (MnPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), and mixtures thereof. Functional separation membrane into which a catalyst point is introduced.
  4. 청구항 1에 있어서, 상기 촉매점의 크기는 0.1 내지 10 nm인 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The method according to claim 1, characterized in that the size of the catalyst point is 0.1 to 10 nm, the catalyst point is introduced functional separation membrane.
  5. 청구항 1에 있어서, 상기 촉매점 함유 코팅층의 두께는 0.1 내지 20 ㎛인 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The method according to claim 1, characterized in that the thickness of the coating layer containing the catalyst point is 0.1 to 20 ㎛, the catalyst point is introduced functional separation membrane.
  6. 청구항 1에 있어서, 상기 촉매점 함유 코팅층의 함량은 상기 베이스 분리막의 표면적에 대하여 1 내지 200 ㎍/cm2인 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The method according to claim 1, characterized in that the content of the coating layer containing the catalyst point is 1 to 200 ㎍ / cm 2 relative to the surface area of the base separation membrane, the catalyst point is introduced functional separation membrane.
  7. 청구항 1에 있어서, 상기 촉매점 함유 코팅층은 전도성 탄소를 더 포함하는 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The method according to claim 1, wherein the catalyst point-containing coating layer is characterized in that it further comprises conductive carbon, a catalyst point is introduced functional separation membrane.
  8. 청구항 7에 있어서, 상기 촉매점은 상기 전도성 탄소의 외부 표면 및 홀 내부 표면에 반데르발스 인력을 통하여 흡착되어 결합되는 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The method according to claim 7, wherein the catalyst point is characterized in that adsorbed and bonded to the outer surface of the conductive carbon and the inner surface of the hole through van der Waals attraction, the catalyst point is introduced functional separation membrane.
  9. 청구항 7에 있어서, 상기 촉매점과 전도성 탄소의 혼합비는 중량비로서 0.1 내지 99.9 : 10 내지 90인 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The method according to claim 7, wherein the mixing ratio of the catalyst point and the conductive carbon is 0.1 to 99.9: 10 to 90 as a weight ratio, the catalyst point is introduced functional separation membrane.
  10. 청구항 7에 있어서, 상기 전도성 탄소는 탄소나노튜브, 그래핀 및 환원 그래핀 옥사이드로 이루어진 군으로부터 선택되는 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막.The method according to claim 7, wherein the conductive carbon is characterized in that selected from the group consisting of carbon nanotubes, graphene and reduced graphene oxide, a catalyst point is introduced functional separation membrane.
  11. (a) 촉매점을 용매에 분산시켜 촉매점 함유 분산액을 제조하는 단계; (a) dispersing the catalyst point in a solvent to prepare a dispersion containing the catalyst point;
    (b) 상기 제조된 촉매점 함유 분산액을 여과하는 단계; (b) filtering the prepared dispersion containing catalyst points;
    (c) 상기 여과를 통하여 얻어진 여과물의 상층부로부터 촉매점 함유 파우더를 수득하여 건조시키는 단계; 및 (c) obtaining and drying the catalyst point-containing powder from the upper layer of the filtrate obtained through the filtration; And
    (d) 상기 수득 및 건조된 촉매점 함유 파우더를 베이스 분리막의 표면에 코팅시키는 단계;를 포함하는 촉매점이 도입된 기능성 분리막의 제조 방법.(d) coating the obtained and dried catalyst point-containing powder on the surface of the base separation membrane;
  12. 청구항 11에 있어서, 상기 촉매점이 도입된 기능성 분리막의 제조 방법은, 상기 (a) 단계에서 제조되는 촉매점 함유 분산액에 전도성 탄소를 공급하여 전도성 탄소까지 포함한 촉매점 함유 분산액을 제조하는 단계(a-1)를 더 포함하는 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막의 제조 방법.The method of claim 11, wherein the method of manufacturing a functional separation membrane into which the catalyst points are introduced comprises: supplying conductive carbon to the catalyst point-containing dispersion solution prepared in step (a) to prepare a catalyst point-containing dispersion solution including conductive carbon (a- 1), characterized in that it further comprises, a method for producing a functional separation membrane introduced with a catalyst point.
  13. 청구항 12에 있어서, 상기 촉매점을 용매에 분산시키거나 전도성 탄소까지 용매에 분산시킨 후에는 초음파 처리가 수행되는 것을 특징으로 하는, 촉매점이 도입된 기능성 분리막의 제조 방법.The method of claim 12, wherein ultrasonic treatment is performed after the catalyst point is dispersed in a solvent or even conductive carbon is dispersed in the solvent.
  14. 양극; 음극; 상기 양극과 음극의 사이에 개재되는 청구항 1 내지 10 중 어느 한 항의 촉매점 도입 기능성 분리막; 및 전해질;을 포함하는 리튬 이차전지.anode; cathode; The catalyst point introduction functional separator of any one of claims 1 to 10 interposed between the anode and the cathode; And an electrolyte; a lithium secondary battery containing.
  15. 청구항 14에 있어서, 상기 리튬 이차전지는 리튬-황 전지인 것을 특징으로 하는, 리튬 이차전지.The lithium secondary battery according to claim 14, wherein the lithium secondary battery is a lithium-sulfur battery.
PCT/KR2020/005615 2019-05-03 2020-04-28 Functional separator having catalytic sites introduced thereinto, manufacturing method therefor, and lithium secondary battery comprising same WO2020226329A1 (en)

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