WO2020231162A1 - Composite soufre-carbone, et cathode et batterie secondaire au lithium comprenant chacune ledit composite - Google Patents

Composite soufre-carbone, et cathode et batterie secondaire au lithium comprenant chacune ledit composite Download PDF

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Publication number
WO2020231162A1
WO2020231162A1 PCT/KR2020/006256 KR2020006256W WO2020231162A1 WO 2020231162 A1 WO2020231162 A1 WO 2020231162A1 KR 2020006256 W KR2020006256 W KR 2020006256W WO 2020231162 A1 WO2020231162 A1 WO 2020231162A1
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carbon
sulfur
carbon composite
weight
secondary battery
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PCT/KR2020/006256
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English (en)
Korean (ko)
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김봉수
양승보
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주식회사 엘지화학
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Priority claimed from KR1020200056606A external-priority patent/KR102328262B1/ko
Application filed by 주식회사 엘지화학 filed Critical 주식회사 엘지화학
Priority to CN202080007113.8A priority Critical patent/CN113228349A/zh
Priority to US17/298,878 priority patent/US11967702B2/en
Priority to EP20806156.4A priority patent/EP3905392A4/fr
Publication of WO2020231162A1 publication Critical patent/WO2020231162A1/fr

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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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 sulfur-carbon composite applicable as a positive electrode material of a lithium secondary battery, a positive electrode including the same, and a lithium secondary battery.
  • a lithium-sulfur secondary battery uses a sulfur-based compound having a sulfur-sulfur bond as a positive electrode active material, and an alkali metal such as lithium or a carbon-based material in which metal ions such as lithium ions are inserted and deintercalated, or an alloy with lithium It is a secondary battery that uses silicon or tin to form a negative electrode active material.
  • electrical energy is stored by using an oxidation-reduction reaction in which sulfur-sulfur bonds are cut off during discharge, which is a reduction reaction, and the oxidation number of sulfur decreases, and during charging, which is an oxidation reaction, sulfur-sulfur bonds are formed again as the oxidation number of sulfur increases. And create it.
  • sulfur which is used as a positive electrode active material in lithium-sulfur secondary batteries, has a theoretical energy density of 1675 mAh/g, and has a theoretical energy density that is 5 times higher than that of the positive electrode active material used in conventional lithium secondary batteries. It is a battery capable of expressing the density.
  • sulfur is attracting attention as an energy source for mid- to large-sized devices such as electric vehicles as well as portable electronic devices because of its low cost, rich reserves, easy supply, and environmental friendliness.
  • sulfur since sulfur has no conductivity, it is applied as an electrochemical positive electrode active material by forming a porous carbon material and a sulfur-carbon composite.
  • sulfur (S) becomes Li 2 S by the electrons transferred through the carbon in the lead wire and the sulfur-carbon composite and lithium ions transferred through the electrolyte from the negative electrode. Reduce.
  • Korean Patent Publication No. 2016-0051610 a patent that applies carbon having various types of structures in a sulfur-carbon composite, relates to a cathode material for a lithium-sulfur secondary battery, a mixture of a sulfur-carbon nanotube composite and a sulfur-graphene composite. Disclosed is a technology for using a sulfur-carbon composite comprising a cathode material.
  • Patent Document 1 Korean Patent Publication No. 2016-0051610
  • the present inventors when manufacturing a sulfur-carbon composite applied as a positive electrode active material of a lithium secondary battery, contain planar carbon in a certain ratio, and also limit the elution of sulfur by including at least one of point carbon and linear carbon. , To provide a sulfur-carbon composite capable of improving battery performance by facilitating contact with an electrolyte and maintaining a reaction rate.
  • an object of the present invention is to provide a sulfur-carbon composite containing planar carbon in a certain ratio.
  • Another object of the present invention is to provide a positive electrode for a lithium secondary battery comprising a sulfur-carbon composite containing the planar carbon in a certain ratio.
  • Another object of the present invention is to provide a lithium secondary battery comprising a sulfur-carbon composite containing the planar carbon in a predetermined ratio.
  • the present invention is a sulfur-carbon composite comprising planar carbon
  • the planar carbon provides a sulfur-carbon composite containing more than 0% by weight and less than 50% by weight based on the total weight of the carbon.
  • the present invention also provides a positive electrode for a lithium secondary battery comprising the sulfur-carbon composite.
  • the present invention also provides a lithium secondary battery comprising the positive electrode.
  • the sulfur-carbon composite according to the present invention may improve the performance of a battery by including planar carbon or various types of carbon including planar carbon.
  • the sulfur-carbon composite contains planar carbon, it is possible to support a large amount of sulfur to increase energy density and prevent sulfur from eluting when applied to a positive electrode for a lithium secondary battery.
  • the sulfur-carbon composite includes a sulfur-carbon composite in which sulfur is exposed to the outside, such as a sulfur-carbon composite containing point-like carbon or a linear carbon-composite containing linear carbon, so that contact between sulfur and the electrolyte is possible. It is easy to maintain the reaction rate and prevent voltage drop.
  • the sulfur-carbon composite when applied to a positive electrode of a lithium secondary battery, the discharge capacity and high rate characteristics of the lithium secondary battery can be improved.
  • FIGS. 1A to 1C are schematic diagrams of a planar sulfur-carbon composite, a point-type sulfur-carbon composite, and a linear sulfur-carbon composite, respectively, included in the sulfur-carbon composite according to the present invention.
  • FIG. 2 is a schematic diagram of a positive electrode for a lithium secondary battery comprising a sulfur-carbon composite according to the present invention.
  • FIG. 3A is a graph showing the initial discharge performance of a lithium-sulfur secondary battery in which the sulfur-carbon composites each prepared in Examples 1 to 4 and Comparative Example 1 were applied to a positive electrode
  • FIG. 3B is a graph showing the initial discharge performance of Examples 1 to 4 and Comparative Example 1 Is a graph showing the results of measuring the high rate characteristics of a lithium-sulfur secondary battery in which the sulfur-carbon composites prepared in each were applied to a positive electrode.
  • FIG. 4A is a graph showing the initial discharge performance of a lithium-sulfur secondary battery in which the sulfur-carbon composites each prepared in Examples 5 to 6 and Comparative Example 1 were applied to a positive electrode
  • FIG. 4B is a graph showing the initial discharge performance of Examples 5 to 6 and Comparative Example 1 Is a graph showing the results of measuring the high rate characteristics of a lithium-sulfur secondary battery in which the sulfur-carbon composites prepared in each were applied to a positive electrode.
  • point carbon refers to carbon having a shape similar to a dot, and is also referred to as zero-dimensional carbon.
  • sulfur-carbon composite including the "point-type carbon” is referred to as "point-type sulfur-carbon composite”.
  • linear carbon refers to carbon having a shape similar to a line and is also referred to as one-dimensional carbon.
  • sulfur-carbon composite including the “linear carbon” is referred to as a "linear sulfur-carbon composite”.
  • planar carbon refers to carbon having a shape similar to that of cotton, and is also referred to as two-dimensional carbon.
  • sulfur-carbon composite including the "facet carbon” is referred to as “facet sulfur-carbon composite”.
  • the present invention relates to a sulfur-carbon composite comprising carbon in various shapes. Since the shape of the sulfur-carbon composite formed according to the shape of the carbon may be determined, the sulfur-carbon composite may have various shapes according to the carbon shape.
  • the shape of the sulfur-carbon composite may have the same shape as that of carbon.
  • the sulfur-carbon composite including the planar carbon may also be a planar sulfur-carbon composite having a planar shape
  • the sulfur-carbon composite including the point-like carbon may also be a point sulfur-carbon composite having a point shape
  • the sulfur-carbon composite including the linear carbon may have a linear sulfur-carbon composite shape.
  • the sulfur-carbon composite according to the present invention may include planar carbon.
  • the sulfur-carbon composite may further include at least one selected from point-type carbon and linear carbon in addition to planar carbon.
  • the sulfur-carbon composite according to the present invention may contain 40 to 95% by weight of sulfur and 5 to 60% by weight of carbon.
  • the sulfur content of the sulfur-carbon composite may be 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, or 60% by weight or more, and also 75% by weight or less, 80% by weight or less, 85 It may be less than or equal to 90% by weight, or less than or equal to 95% by weight.
  • the sulfur is included in the prescribed range, the energy density of the lithium secondary battery can be improved. Therefore, if the sulfur content is less than 40% by weight, the energy density may be lowered, and if the content is more than 95% by weight, the electron and lithium ion transfer resistance may increase.
  • the content of carbon contained in the sulfur-carbon composite may be 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25% by weight or more, and also 40% by weight or less, 45% by weight It may be less than, 50% by weight or less, 55% by weight or less, or 60% by weight or less.
  • the carbon is included in the prescribed range, electronic conductivity and lithium ion conductivity of a lithium secondary battery may be improved. Therefore, if the carbon content is less than 5% by weight, electronic conductivity and lithium ion conductivity may be lowered, and if it is more than 60% by weight, the sulfur content is relatively lowered, thereby lowering energy density.
  • the sulfur is sulfur (S 8 ), Li 2 S n (n ⁇ 1), an organic sulfur compound and a carbon-sulfur polymer [(C 2 S x ) n , x is an integer of 2.5 to 50, n ⁇ 2] may be one or more selected from the group consisting of.
  • the carbon may further include at least one selected from point-type carbon and linear carbon in addition to planar carbon, and the present invention will be described in more detail below with reference to the drawings.
  • FIG. 1A is a schematic diagram of a planar sulfur-carbon composite according to the present invention.
  • the planar sulfur-carbon composite 11 is a form in which sulfur (S2) is inserted between planar carbon (C2), in other words, planar carbon (C2) supports and wraps sulfur (S2). Form. Due to such morphological characteristics, when the planar sulfur-carbon composite 11 is applied as a positive electrode active material of a lithium secondary battery, elution of sulfur can be prevented.
  • Planar carbon (C2) may be contained in an amount greater than 0% by weight and less than 50% by weight based on the total weight of carbon included in the sulfur-carbon composite according to the present invention. Specifically, the content of the planar carbon (C2) may be more than 0 wt%, 5 wt% or more, or 10 wt% or more, and 30 wt% or less, 35 wt% or less, 40 wt% or less, based on the total weight of the carbon , 45% or less or less than 50% by weight. If the content of the planar carbon (C2) is 0% by weight, the effect of preventing the elution of sulfur from the positive electrode is insignificant and there may be no effect of improving the performance by the planar carbon. Since is lowered, a voltage drop occurs, and sufficient battery capacity may not be implemented.
  • Planar carbon (C2) is selected from the group consisting of non-oxide graphene, graphene oxide, reduced graphene oxide, doped graphene, and carbon nanoribbon. It may be one or more, preferably reduced graphene oxide.
  • the specific surface area of the planar carbon (C2) may be greater than the sum of the specific surface areas of other carbons included in the sulfur-carbon composite.
  • the sulfur-carbon composite includes planar carbon, point carbon and linear carbon
  • the specific surface area of the planar carbon may be greater than the sum of the specific surface areas of the point carbon and the linear carbon.
  • the specific surface area of the planar carbon (C2) may be 200 m2/g to 1000 m2/g, specifically 200 m2/g or more, 300 m2/g or more, 400 m2/g or more, or 500 m2/g or more, and , 700 m2/g or less, 800 m2/g or less, 900 m2/g or less, or 1000 m2/g or less.
  • planar carbon (C2) having such a specific surface area it is possible to support more sulfur to improve the capacity of the battery and to suppress the elution of sulfur.
  • the content of sulfur (S2) contained in the planar sulfur-carbon composite 11 may be 10 to 45% by weight based on the total weight of sulfur contained in the sulfur-carbon composite, and specifically 10% by weight or more, 15 It may be greater than or equal to 20% by weight, or less than or equal to 35%, less than or equal to 40%, or less than or equal to 45% by weight. If it is less than the above range, the sulfur content in the battery decreases and the battery capacity is excessively reduced, and if it exceeds the above range, the electrical conductivity in the electrode excessively decreases, thereby increasing the resistance.
  • FIG. 1B is a schematic diagram of a point-type sulfur-carbon composite according to the present invention
  • FIG. 1C is a schematic diagram of a linear sulfur-carbon composite according to the present invention.
  • the point-type sulfur-carbon composite 12 has a core-shell form by forming sulfur (S0) on the surface of the point-type carbon (C0), and the linear sulfur-carbon composite 13 is linear carbon. Since sulfur (S1) is formed inside and/or on the surface of (C1) to have a tube shape, sulfur (S0, S1) is exposed to the outside. Due to these morphological features, when the point-shaped sulfur-carbon composite 12 or the linear sulfur-carbon composite 13 is applied as a positive electrode active material of a lithium secondary battery, the sulfur (S0, S1) exposed to the surface is It is easy to contact the bar, it is possible to improve the battery performance by preventing the voltage drop.
  • At least one carbon selected from point-like carbon (C0) and linear carbon (C1) may be 50% by weight or more and less than 100% by weight based on the total weight of carbon contained in the sulfur-carbon composite according to the present invention, and specifically , 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, or 70% by weight or more, and also 80% by weight or less, 85% by weight or less, 90% by weight or less, 95% by weight or less or It may be less than 100% by weight.
  • the content of one or more of the carbons selected from point-like carbon (C0) and linear carbon (C1) is less than 50% by weight, the electrolyte is not smoothly in and out of the positive electrode and lithium ion conductivity is lowered, resulting in a voltage drop and sufficient battery capacity.
  • the effect of preventing the elution of sulfur from the positive electrode is insignificant, and the discharge capacity and life characteristics of the lithium secondary battery may be deteriorated.
  • Point carbon (C0) may be at least one selected from the group consisting of ketjen black, denka black, acetylene black, super-p, and fullerene. And, preferably, it may be Ketjen Black.
  • Linear carbon (C1) may be one or more selected from the group consisting of carbon nanotubes (CNT) and carbon fibers, and preferably carbon nanotubes.
  • the content of sulfur (S0, S1) contained in at least one selected from the point-type sulfur-carbon composite 12 and the linear sulfur-carbon composite 13 is 55 to the total weight of sulfur contained in the sulfur-carbon composite. It may be 90% by weight, specifically 55% by weight or more, 60% by weight or more, or 65% by weight or more, and also 85% by weight or less, 90% by weight or less, or 95% by weight or less. If it is less than the above range, the sulfur content in the battery decreases and the battery capacity is excessively reduced, and if it exceeds the above range, the electrical conductivity in the electrode excessively decreases, thereby increasing the resistance.
  • a method for preparing a sulfur-carbon composite is not particularly limited, and a method for producing a sulfur-carbon composite commonly used in the art may be used.
  • the form of carbon contained in the sulfur-carbon composite according to the present invention that is, planar carbon, point-like carbon, or linear carbon may all be applied to the same method for preparing the sulfur-carbon composite.
  • the sulfur-carbon composite may be prepared by a melt diffusion method.
  • the melt diffusion method is a manufacturing method in which sulfur penetrates into carbon particles by melting sulfur through heating.
  • the heat treatment may include various direct or indirect heating methods.
  • the sulfur-carbon composite according to the present invention comprises the steps of (S1) mixing sulfur and carbon; And heat-treating the mixture of sulfur and carbon formed in the step (S1).
  • the amounts and types of sulfur and carbon in the step (S1) are as described above.
  • the heat treatment temperature in the step (S2) is a temperature at which sulfur is dissolved and permeated into the carbon to be supported, and may be higher than the melting point of sulfur.
  • the temperature during the heat treatment may be 100 to 200°C, specifically, 100°C or more, 105°C or more, 110°C or more, 115°C or more, or 120°C or more, and 180°C or less, 185°C or less , 190°C or less, 195°C or less, or 200°C or less, and may be heat treated by a melt diffusion method. If it is less than the above range, the sulfur-carbon composite itself may not be manufactured because the process of dissolving sulfur and seeping into the carbon does not proceed.If it exceeds the above range, the loss rate increases due to the vaporization of sulfur, and the sulfur-carbon composite is denatured to become a cathode material of a lithium secondary battery. When applied, the effect of improving the performance of the battery may be insignificant.
  • planar sulfur-carbon composite, point-type sulfur-carbon composite, and linear sulfur-carbon composite according to the present invention may be prepared respectively according to the method for preparing a sulfur-carbon composite as described above, or may be prepared simultaneously.
  • the present invention also relates to a lithium secondary battery comprising the sulfur-carbon composite as described above.
  • the sulfur-carbon composite may preferably be included as a positive electrode active material.
  • the lithium secondary battery according to the present invention may include a positive electrode, a negative electrode, a separator and an electrolyte interposed therebetween.
  • FIG. 2 is a schematic diagram of a positive electrode for a lithium secondary battery comprising a sulfur-carbon composite according to the present invention.
  • the positive electrode 1 for a lithium secondary battery may include a positive electrode current collector 20 and a positive electrode active material layer 10 having a positive electrode active material formed on the positive electrode current collector 20.
  • the positive electrode active material may include a sulfur-carbon composite, and the sulfur-carbon composite may include a planar sulfur-carbon composite 11, and a point-shaped sulfur-carbon composite 12 and a linear sulfur-carbon composite ( It may contain one or more selected from among 13).
  • the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes to the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or on the surface of aluminum or stainless steel. Carbon, nickel, titanium, silver or the like surface-treated may be used.
  • the positive electrode current collector may be in various forms such as a film, sheet, foil, net, porous material, foam, non-woven fabric having fine irregularities formed on the surface so as to increase adhesion to the positive electrode active material.
  • the negative electrode of the lithium secondary battery may include a negative electrode current collector and a negative electrode active material layer having a negative electrode active material formed on the negative electrode current collector.
  • lithium metal or a carbon material through which lithium ions can be occluded and released may be used, such as silicon or tin.
  • a carbon material may be used, and both low crystalline carbon and high crystalline carbon may be used as the carbon material.
  • low crystalline carbon soft carbon and hard carbon are typical
  • high crystalline carbon is natural graphite, kish graphite, pyrolytic carbon, liquid crystal pitch-based carbon fiber (mesophase pitch based carbon fiber), meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbons such as petroleum or coal tar pitch derived cokes are typical.
  • the negative electrode may include a binder, and as the binder, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVDF), and polyacrylonitrile ), polymethylmethacrylate, etc., various kinds of binder polymers may be used.
  • VDF-co-HFP vinylidene fluoride-hexafluoropropylene copolymer
  • PVDF polyvinylidenefluoride
  • polyacrylonitrile polymethylmethacrylate
  • the negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes to the battery, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, or the like may be used.
  • the negative electrode current collector like the positive electrode current collector, may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric having fine irregularities on the surface thereof.
  • the positive electrode active material layer or the negative electrode active material layer may further include a binder resin, a conductive material, a filler, and other additives.
  • the binder resin is used for bonding of an electrode active material and a conductive material and bonding to a current collector.
  • binder resins include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetra Fluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber, and various copolymers thereof.
  • PVDF polyvinylidene fluoride
  • CMC carboxymethylcellulose
  • EPDM ethylene-propylene-diene polymer
  • sulfonated-EPDM styrene-butadiene rubber
  • fluorine rubber and various copolymers thereof.
  • the conductive material is used to further improve the conductivity of the electrode active material.
  • a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal 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; Polyphenylene derivatives and the like can be used.
  • the conductive material may be a vapor grown carbon fiber (VGCF).
  • the filler is selectively used as a component that suppresses the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes to the battery, and examples thereof include olefin-based polymers such as polyethylene and polypropylene; Fibrous materials such as glass fiber and carbon fiber are used.
  • the separator may be made of a porous substrate, and the porous substrate may be used as long as it is a porous substrate commonly used in an electrochemical device, for example, a polyolefin-based porous membrane or a nonwoven fabric. It can be used, but is not particularly limited thereto.
  • polyolefin-based porous membrane examples include polyolefin-based polymers such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polyolefin-based polymers such as polypropylene, polybutylene, and polypentene, respectively, or a mixture of them. There is one membrane.
  • nonwoven fabric in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polycarbonate ), polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, and polyethylenenaphthalene, respectively, alone or Nonwoven fabrics formed of polymers obtained by mixing them are exemplified.
  • the structure of the nonwoven fabric may be a spunbond nonwoven fabric composed of long fibers or a melt blown nonwoven fabric.
  • the thickness of the porous substrate is not particularly limited, but may be 1 ⁇ m to 100 ⁇ m, or 5 ⁇ m to 50 ⁇ m.
  • the size and porosity of the pores present in the porous substrate are also not particularly limited, but may be 0.001 ⁇ m to 50 ⁇ m and 10% to 95%, respectively.
  • the electrolyte may be a nonaqueous electrolyte, and the electrolyte salt contained in the nonaqueous electrolyte is a lithium salt.
  • the lithium salt may be used without limitation, those commonly used in an electrolyte for a lithium secondary battery.
  • the lithium salt is LiFSI, LiPF 6 , LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiPF 6 , LiAlCl 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, it may be one or more selected from the group consisting of lithium chloroborane and lithium 4-phenyl borate.
  • organic solvents included in the above-described non-aqueous electrolyte those commonly used in electrolytes for lithium secondary batteries can be used without limitation, and for example, ethers, esters, amides, linear carbonates, cyclic carbonates, etc. can be used alone or in two or more types. It can be mixed and used. Among them, representatively, a cyclic carbonate, a linear carbonate, or a carbonate compound that is a slurry thereof may be included.
  • cyclic carbonate compound examples include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, Any one selected from the group consisting of 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or two or more of these slurries.
  • halides include, for example, fluoroethylene carbonate (FEC), but are not limited thereto.
  • linear carbonate compound is any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, or Two or more of these slurries may be representatively used, but are not limited thereto.
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethylmethyl carbonate
  • methylpropyl carbonate methylpropyl carbonate
  • EMC ethylmethyl carbonate
  • ethylpropyl carbonate methylpropyl carbonate
  • ethylpropyl carbonate methylpropyl carbonate
  • ethylpropyl carbonate methylpropyl carbonate
  • ethylpropyl carbonate methylpropyl carbonate
  • ethylpropyl carbonate methylpropyl carbonate
  • the ether of the organic solvent is selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, ethylpropyl ether, dimethoxyethane (DME) and dioxolane (DOL). Any one or two or more of these slurries may be used, but the present invention is not limited thereto.
  • esters in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -caprolactone, Any one selected from the group consisting of ⁇ -valerolactone and ⁇ -caprolactone, or two or more types of slurry may be used, but is not limited thereto.
  • the injection of the non-aqueous electrolyte may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process and required physical properties of the final product. That is, it can be applied before assembling the electrochemical device or at the final stage of assembling the electrochemical device.
  • the lithium secondary battery according to the present invention in addition to winding, which is a general process, lamination, stacking, and folding of a separator and an electrode are possible.
  • the shape of the battery case is not particularly limited, and may be in various shapes such as a cylindrical shape, a stacked type, a square shape, a pouch type, or a coin type.
  • the structure and manufacturing method of these batteries are widely known in this field, and thus detailed descriptions are omitted.
  • the lithium secondary battery can be classified into various batteries, such as lithium-sulfur secondary batteries, lithium-air batteries, lithium-oxide batteries, and lithium all-solid batteries, depending on the material of the positive electrode/cathode used.
  • the present invention also provides a battery module including the lithium secondary battery as a unit cell.
  • the battery module can be used as a power source for medium and large-sized devices that require high temperature stability, long cycle characteristics, and high capacity characteristics.
  • Examples of the medium and large-sized devices include a power tool that is powered by an omniscient motor and moves; Electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; Electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf cart; Power storage systems, etc., but are not limited thereto.
  • Electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like
  • Electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf cart; Power storage systems, etc., but are not limited thereto.
  • the sulfur-carbon composite according to the present invention can be applied to a positive electrode of a lithium-sulfur secondary battery among lithium secondary batteries.
  • the lithium-sulfur secondary battery may be a battery including the sulfur-carbon composite as a positive electrode active material.
  • the sulfur-carbon composite can exhibit high ionic conductivity by securing the path of lithium ions to the inside of the pores, and acts as a sulfur carrier to increase reactivity with sulfur, which is a positive electrode active material, to increase the initial discharge capacity of a lithium-sulfur secondary battery. And high rate performance can be improved at the same time.
  • the carbon powder is linear carbon and is a carbon nanotube (CNT) powder.
  • the mixture obtained in (1-1) was heat-treated at 155° C. to prepare a sulfur-carbon composite through a melt diffusion method.
  • the sulfur-carbon complex includes a linear sulfur-carbon complex.
  • the sulfur-carbon composite obtained in (1) above as a positive electrode active material, VGCF (Vapor grown carbon fiber) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed in a weight ratio of 8:1:1, and a concentration of 20% Disperse in water to prepare a positive electrode slurry.
  • the positive electrode slurry was coated on Al foil and dried to prepare a positive electrode.
  • the electrolyte was DOL/DME (1:1, v/v) as a solvent, and 1M LiTFSI and 3% by weight of LiNO 3 were included.
  • a lithium-sulfur secondary battery in the form of a coin cell was manufactured using the electrolyte solution and polyolefin separator prepared as the composition.
  • DOL means dioxolane
  • DME means dimethoxyethane.
  • the carbon powder includes 10% by weight of reduced graphene oxide powder as planar carbon and 90% by weight of CNT powder as linear carbon.
  • the specific surface area of the reduced graphene oxide is 600 m 2 /g.
  • the mixture obtained in (1-1) was heat-treated at 155° C., so that sulfur was supported on the carbon through a melt diffusion method to prepare a sulfur-carbon composite.
  • the prepared sulfur-carbon composite includes a planar sulfur-carbon composite and a linear sulfur-carbon composite.
  • the sulfur-carbon composite obtained in (1) above as a positive electrode active material, and polyvinylidene fluoride (PVDF) as a VGCF (Vapor grown carbon fiber) binder as a conductive material were mixed in a weight ratio of 8:1:1, and at a concentration of 20%. Disperse in water to prepare a positive electrode slurry.
  • PVDF polyvinylidene fluoride
  • the positive electrode slurry was coated on Al foil and dried to prepare a positive electrode.
  • the electrolyte was DOL/DME (1:1, v/v) as a solvent, and 1M LiTFSI and 3% by weight of LiNO 3 were included.
  • a lithium-sulfur secondary battery in the form of a coin cell was manufactured using the electrolyte solution and polyolefin separator prepared as the composition.
  • DOL means dioxolane
  • DME means dimethoxyethane.
  • Example 2 In the same manner as in Example 1, a sulfur-carbon composite was prepared in the composition as shown in Table 1 below. At this time, as shown in Table 1 below, the surface carbon content is 26% by weight and 35% by weight, respectively, based on the total weight of carbon contained in the sulfur-carbon composite, and the sulfur-carbon composite, the positive electrode, and the lithium-sulfur secondary battery are Was prepared.
  • Example 1 Unit:% by weight Sulfur-carbon complex carbon sulfur Sulfur content Carbon content Cotton type carbon content Linear carbon content Cotton sulfur content Linear sulfur content Comparative Example 1 75 25 0 100 0 100 Example 1 75 25 10 90 10 90 Example 2 75 25 20 80 20 80 Example 3 75 25 30 70 30 70 Example 4 75 25 40 60 40 60 Example 5 76.5 23.5 26 74 31 69 Example 6 77 23 35 65 42 58
  • FIG. 3A is a graph showing the initial discharge performance of a lithium-sulfur secondary battery in which the sulfur-carbon composites each prepared in Examples 1 to 4 and Comparative Example 1 were applied to a positive electrode
  • FIG. 3B is a graph showing the initial discharge performance of Examples 1 to 4 and Comparative Example 1 Is a graph showing the results of measuring the high rate characteristics of a lithium-sulfur secondary battery in which the sulfur-carbon composites prepared in each were applied to a positive electrode.
  • the discharge capacity per weight of sulfur is increased in the lithium-sulfur secondary batteries of Examples 1 to 4 including both planar carbon and linear carbon compared to Comparative Example 1 that does not include planar carbon and includes only linear carbon.
  • Examples 1 to 4 as the content of planar carbon increased, the discharge capacity increased, and it was confirmed that the discharge capacity of Example 3 in which the content of planar carbon was 30% by weight was the highest. On the other hand, it was confirmed that the discharge capacity did not increase any more when the content of planar carbon was 40% by weight as in Example 4 exceeding 30% by weight.
  • Example 3 in which the content of planar carbon is 30% by weight is the highest as in the initial discharge performance curve of FIG. Similarly, as in Example 4, when the content of planar carbon was 40% by weight, it was confirmed that the discharge capacity did not increase any more.
  • FIG. 4A is a graph showing the first initial discharge performance of a lithium-sulfur secondary battery in which the sulfur-carbon composites each prepared in Examples 5 to 6 and Comparative Example 1 were applied to a positive electrode
  • FIG. 4B is A graph showing the results of measuring the high rate characteristics of a lithium-sulfur secondary battery in which the sulfur-carbon composites each prepared in 1 were applied to a positive electrode.
  • Example 5 is the highest at a high rate, similar to the initial discharge performance curve of FIG. 4A.
  • Example 2 The sulfur-carbon composites of Example 2, Example 3, and Example 4 are the case where the content of reduced graphene oxide, which is planar carbon, is 20% by weight, 30% by weight, and 40% by weight, respectively, based on the total weight of carbon.
  • C0 point carbon
  • C1 linear carbon
  • C2 planar carbon

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  • Chemical Kinetics & Catalysis (AREA)
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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

La présente invention concerne un composite soufre-carbone et une cathode pour une batterie secondaire au lithium et une batterie secondaire au lithium comprenant chacune ledit composite. Plus spécifiquement, les carbones contenus dans le composite soufre-carbone peuvent comprendre diverses formes de carbones. En particulier, lorsqu'il est appliqué en tant que matériau actif de cathode dans une batterie au lithium, le composite soufre-carbone contenant une quantité prédéterminée de carbones en forme de plan peut empêcher l'élution de soufre et améliorer le taux de réaction dans la cathode, améliorant ainsi les performances de la batterie secondaire au lithium.
PCT/KR2020/006256 2019-05-14 2020-05-13 Composite soufre-carbone, et cathode et batterie secondaire au lithium comprenant chacune ledit composite WO2020231162A1 (fr)

Priority Applications (3)

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CN202080007113.8A CN113228349A (zh) 2019-05-14 2020-05-13 硫碳复合物以及各自包含所述硫碳复合物的正极和锂二次电池
US17/298,878 US11967702B2 (en) 2019-05-14 2020-05-13 Sulfur-carbon composite, and cathode and lithium secondary battery each comprising same
EP20806156.4A EP3905392A4 (fr) 2019-05-14 2020-05-13 Composite soufre-carbone, et cathode et batterie secondaire au lithium comprenant chacune ledit composite

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KR20190056010 2019-05-14
KR10-2019-0056010 2019-05-14
KR1020200056606A KR102328262B1 (ko) 2019-05-14 2020-05-12 황-탄소 복합체, 이를 포함하는 양극 및 리튬 이차전지
KR10-2020-0056606 2020-05-12

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KR20190056010A (ko) 2017-11-16 2019-05-24 인하대학교 산학협력단 시각장애인용 점자블록
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