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WO2023013903A1 - Procédé de fabrication d'un matériau de cathode pour batterie lithium-soufre, et matériau de cathode pour batterie au lithium-soufre ainsi fabriqué - Google Patents

Procédé de fabrication d'un matériau de cathode pour batterie lithium-soufre, et matériau de cathode pour batterie au lithium-soufre ainsi fabriqué Download PDF

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WO2023013903A1
WO2023013903A1 PCT/KR2022/009986 KR2022009986W WO2023013903A1 WO 2023013903 A1 WO2023013903 A1 WO 2023013903A1 KR 2022009986 W KR2022009986 W KR 2022009986W WO 2023013903 A1 WO2023013903 A1 WO 2023013903A1
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lithium
carbon
sulfur battery
cathode material
nitrogen
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Korean (ko)
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전영시
박재우
황현진
강희주
이태규
김홍식
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Industry Foundation of Chonnam National University
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Industry Foundation of Chonnam National University
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • 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
    • H01M4/04—Processes of manufacture in general
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/049—Manufacturing of an active layer by chemical means
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/581—Chalcogenides or intercalation compounds thereof
    • H01M4/5815—Sulfides
    • 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
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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 method for manufacturing a cathode material for a lithium-sulfur battery, a cathode material for a lithium-sulfur battery manufactured thereby, and a lithium-sulfur battery including the same.
  • next-generation secondary batteries with higher capacity than existing lithium-ion secondary batteries (price: ⁇ $130/kWh, energy density: ⁇ 240Wh/kg) is increasing.
  • Lithium-sulfur secondary batteries use sulfur as a cathode active material, which is cheap, abundant on earth, and has a high theoretical discharge capacity (1675 mAh/g).
  • lithium-sulfur secondary batteries use light sulfur and lithium metal as active materials (materials that produce electrical energy using a chemical redox reaction), they can be reduced in weight compared to heavy metal-based lithium-ion batteries, and the energy density per mass ( >500 Wh/kg) can be increased.
  • the initial active material is cyclic S 8 , and when it reaches a fully discharged state, Li 2 S is reduced and expands to a volume equivalent to 180% of S 8 .
  • a typical lithium-sulfur secondary battery forms a composite with a carbon support to form an electrode. As the lithium-sulfur secondary battery repeats charge/discharge, the carbon support collapses (or micronization, pulverization) due to the volume expansion of the sulfur active material. A decrease in capacity will occur.
  • the start of the system of the lithium-sulfur secondary battery is not cyclic S8 , but lithium-sulfide using lithium sulfide (Li 2 S), the last reduction target product of lithium-sulfur, as a raw material for sulfur It constitutes a lithium secondary battery.
  • Li 2 S lithium sulfide
  • Korean Patent Registration No. 10-1488244 relates to a method for manufacturing a cathode for a lithium-sulfur battery and a lithium-sulfur battery, and specifically, preparing a thiosulfate solution; Step of infiltrating the thiosulfate into the surface and inside of the carbon structure by stirring after adding the carbon structure in the thiosulfate solution; removing thiosulfate present on the surface of the carbon structure; Reducing the thiosulfate to sulfur by adding an acid to the carbon structure in which thiosulfate is present; And obtaining a carbon structure in which sulfur formed by reduction of the thiosulfate is present therein; including, Obtaining a carbon structure in which sulfur formed by reduction of the thiosulfate is present therein;
  • the weight ratio (S/C) of sulfur to carbon of the carbon structure is 03 to 08, which provides a method for manufacturing a positive electrode for a lithium-sulfur battery.
  • An object of the present invention is to provide a method for manufacturing a cathode material for a lithium-sulfur battery. Another object of the present invention is to provide a cathode material for a lithium-sulfur battery prepared by this method. Furthermore, another object of the present invention is to provide a lithium-sulfur battery including the positive electrode material.
  • It provides a method for manufacturing a cathode material for a lithium-sulfur battery comprising a.
  • a positive electrode material for a lithium-sulfur battery characterized in that lithium sulfide is dispersed in the carbon support prepared by the above method and includes a nitrogen functional group.
  • a cathode material manufacturing method capable of manufacturing an electrode without using a binder or a conductive material in the cathode and a free-standing cathode material are provided.
  • a lithium-sulfur battery including the positive electrode material for the lithium-sulfur battery.
  • the present invention is a one-step synthesis method using a carbon-nitrogen organic crystal / carbon composite and lithium sulfate (Li 2 SO 4 ), and then simple mixing and firing to obtain a lithium sulfide / carbon cathode material. synthesize
  • the start of the system of the lithium-sulfur secondary battery is lithium sulfide, which is the last reduction target product of lithium-sulfur, rather than cyclic S 8 ( Li 2 S) was uniformly present in the carbon matrix.
  • a lithium metal-free Li-S battery may be manufactured by using lithium sulfide (Li 2 S) as an active material, which does not require the use of lithium metal in an anode.
  • the in-situ high-temperature firing method induces the conversion of lithium sulfate (Li 2 SO 4 ) to lithium sulfide (Li 2 S) through carbothermal reduction, and due to the generation of gases such as CO 2 and CN x during firing, Appropriate nanopores to be induced are distributed within the carbon matrix. Nanopores can not only provide a space for oxidation/reduction of polysulfide, but also physically adsorb polysulfide.
  • various nitrogen functional groups generated in the carbon matrix after firing the carbon-nitrogen organic crystals can simultaneously obtain chemical adsorption ability capable of suppressing polysulfide elution.
  • it has several nitrogen functional groups from the carbon-nitrogen organic crystal, which can suppress the elution of polysulfide in the lithium-sulfur secondary battery.
  • the nitrogen functional groups can act as a catalyst for the sulfur reduction/lithium sulfide oxidation reaction to lower the overpotential acting on the reaction.
  • a process for preparing a positive electrode material using a compression molding method and without using a binder or a conductive material is provided.
  • a cathode material for a lithium-sulfur battery in a simple way, increase the energy density of the cathode material, prevent the support from being pulverized during charging and discharging, and use low-cost raw materials. It is possible to manufacture a positive electrode material with added value, and there is an effect of preventing a decrease in capacity by suppressing elution of the positive electrode active material into the electrolyte during charging and discharging processes.
  • the start of the system of the lithium-sulfur secondary battery is lithium sulfide, which is the last reduction target product of lithium-sulfur, rather than cyclic S 8 ( Li 2 S) may be uniformly present in the carbon matrix to prevent damage to the carbon matrix during charging and discharging.
  • a lithium metal-free lithium-sulfur battery may be manufactured by using lithium sulfide (Li 2 S) as an active material, which does not require the use of lithium metal in an anode.
  • the in-situ high-temperature firing method induces the conversion of lithium sulfate (Li 2 SO 4 ) to lithium sulfide (Li 2 S) through carbothermal reduction, and due to the generation of gases such as CO 2 and CN x during firing, Appropriate nanopores to be induced are distributed within the carbon matrix. Nanopores can not only provide a space for oxidation/reduction of polysulfide, but also physically adsorb polysulfide. In addition, the nitrogen functional groups remaining after the calcination of the carbon-nitrogen organic crystals can simultaneously obtain a chemical adsorption ability capable of suppressing the elution of polysulfide.
  • the carbon-nitrogen organic crystal has several nitrogen functional groups from the carbon-nitrogen organic crystal, which can suppress the elution of polysulfide in the lithium-sulfur secondary battery.
  • the nitrogen functional groups can act as catalysts for the sulfur reduction/lithium sulfide oxidation reaction to lower the overvoltage accompanying the reaction.
  • the compression molding method since the compression molding method is used, there is an effect of providing a free-standing positive electrode material without a binder or a conductive material.
  • FIG. 1 is a schematic diagram illustrating a cathode material of the present invention
  • 6A to 6C are electrochemical performance evaluation graphs showing charge and discharge characteristics of a lithium-sulfur battery according to the present invention.
  • 7A to 7C are other electrochemical performance evaluation graphs showing charge/discharge characteristics of a lithium-sulfur battery according to the present invention.
  • the present invention provides a method for manufacturing a cathode material for a lithium-sulfur battery.
  • parts not described in the configuration of the present invention mean the same as or similar to the configuration of a conventional lithium-sulfur battery or a cathode material used therein.
  • It provides a method for manufacturing a cathode material for a lithium-sulfur battery comprising a.
  • the method for manufacturing a cathode material for a lithium-sulfur battery of the present invention is a method for producing carbon/carbon by mixing molecular-unit carbon precursors, such as monomers or dimers, and carbon-nitrogen organic crystals. - forming a nitrogen crystal complex. If an oligomer carbon precursor such as cellulose is used, there is a problem of having separate phases of the carbon precursor and the carbon-nitrogen crystal complex, rather than the carbon/carbon-nitrogen crystal complex.
  • the carbon/carbon-nitrogen crystal complex is a material to be a carbon support through a subsequent firing process, and in particular, a carbon-nitrogen organic crystal, which is an organic crystal having a high nitrogen content, is included, so that a reducing atmosphere can be formed during the subsequent firing process.
  • the support of the prepared positive electrode material has various functional groups including nitrogen, polysulfide generated during charging and discharging of the lithium-sulfur battery is eluted into the electrolyte to prevent a rapid decrease in capacity.
  • the nitrogen functional group acts as a catalyst for oxidation/reduction reactions of sulfur species including reduction of sulfur (S 8 ) or oxidation of lithium sulfide (Li 2 S), resulting in overpotential ( reduce the overpotential).
  • the lithium sulfide precursor eg, Li 2 SO 4
  • the lithium sulfide precursor is a component that becomes lithium sulfide (Li 2 S) through a subsequent firing process.
  • a cathode material for a lithium-sulfur battery used, for example, a method of preparing a carbon support and introducing it into a lithium sulfide precursor solution, but the present invention uses a precursor for forming the support and a precursor for forming lithium sulfide.
  • a positive electrode material can be prepared by one-step synthesis by mixing , and a free-standing positive electrode material can be prepared without a binder or a conductive material.
  • the method for manufacturing a cathode material for a lithium-sulfur battery of the present invention includes a step of compressing the mixed powder after obtaining the mixed powder.
  • the mixed powder may be introduced into a mold of a predetermined shape and compressed using a compression molding machine to prepare a compression molded body having a predetermined shape, for example, a pellet shape.
  • the method for manufacturing a cathode material for a lithium-sulfur battery of the present invention includes firing the compressed mixed powder.
  • the carbon/carbon-nitrogen crystal complex becomes a porous carbon support containing a nitrogen functional group
  • the lithium sulfide precursor becomes lithium sulfide.
  • the lithium sulfide precursor Li 2 SO 4
  • the lithium sulfide precursor is chemically converted into lithium sulfide (Li 2 S) by a carbothermal reduction between the carbon/carbon-nitrogen crystal complex and the lithium sulfide precursor in the high-temperature firing process.
  • the manufacturing method of the present invention has the advantage of being able to manufacture a carbon support containing lithium sulfide and a nitrogen functional group, that is, a cathode material, in one-step through a method of firing a compression molded body of a mixed powder.
  • the method for manufacturing a cathode material for a lithium-sulfur battery of the present invention further comprises forming a carbon/carbon-nitrogen crystal composite layer thereon after compressing the mixed powder by the above method and before firing it. It is desirable to do
  • a cathode material for a lithium-sulfur battery has a problem in that a liquid polysulfide intermediate is formed during charging and discharging, and the capacity decreases as the polysulfide is eluted into an electrolyte.
  • the carbon support of the prepared cathode material contains various nitrogen functional groups, and thus has an effect of suppressing the elution of polysulfide.
  • the cathode material for a lithium-sulfur battery manufactured after firing may have a structure of a carbon support layer containing lithium sulfide and an additional carbon support layer not containing lithium sulfide thereon.
  • the nitrogen functional group additionally acts as a catalyst for oxidation/reduction reactions of sulfur species such as reduction of sulfur (S 8 ) or oxidation of lithium sulfide (Li 2 S), resulting in overpotential during oxidation/reduction reactions. (reduce the overpotential).
  • the molecular unit carbon precursor used in the production method of the present invention is not particularly limited as long as it is a material that can be formed as a carbon support through a subsequent firing process, but, for example, glucose can be used, and carbon-nitrogen organic crystals It is not particularly limited as long as it can form a reducing atmosphere in the firing process, form various nitrogen functional groups on the carbon support of the prepared cathode material, and form nitrogen functional groups.
  • a melamine-cyanuric acid mixture can be used.
  • the lithium sulfide precursor used in the production method of the present invention is not particularly limited as long as it is a material that can be chemically converted into lithium sulfide by a thermal carbon reduction reaction in the firing process, but, for example, commercial lithium sulfate (Li 2 SO 4 ) is preferable in consideration of cost and the like.
  • the manufacturing method of the present invention has the advantage of being able to manufacture a high value-added cathode material for a lithium-sulfur battery using raw materials that are easily obtained and inexpensive.
  • the manufacturing method of the present invention manufactures a cathode material for a lithium-sulfur battery by mixing the carbon/carbon-nitrogen crystal complex and the lithium sulfide precursor, compression molding, and firing as described above, in the conventional manufacturing process, There is no need to include a binder or a conductive material that was necessary, and as a result, as the materials are not included, the amount of the lithium sulfide component is relatively increased, and thus, the energy density of the cathode material produced is increased. .
  • the content of the carbon precursor in molecular units is preferably mixed at a ratio of 0.1 to 2.0 compared to the carbon-nitrogen organic crystal. If the amount of the carbon precursor in molecular units is less than the above range, there are more C-N bonds than C-C bonds, resulting in poor thermal stability and unsuitable for high-temperature firing, and when the amount exceeds the above range, uncontrolled There is a problem in that micropores are formed and the polysulfide elution problem cannot be effectively prevented because a relatively small number of nitrogen functional groups having good affinity with the liquid polysulfide remain.
  • the lithium sulfide precursor is mixed in a ratio of 0.25 or less relative to the total mixed powder. If the amount of the lithium sulfide precursor exceeds the above range, a large amount of converted lithium sulfide is exposed on the surface of the cathode material and is easily oxidized, thereby lowering the sulfur utilization rate.
  • the step of compressing the mixed powder is preferably performed under a pressure condition of 10 to 30 MPa. If the pressure condition in the compression step is lower than the above condition, the carbon/carbon-nitrogen crystal complex has a problem in the connectivity of the carbon structure during the firing step, and if the pressure is higher than the above condition, the carbon structure may collapse. There is a problem.
  • the step of calcining the compressed mixed powder in the production method of the present invention is preferably performed at a calcining temperature of 750 to 900 °C. If the compressed mixed powder is performed under the above conditions, there is a problem in that 100% conversion from lithium sulfide precursor (Li 2 SO 4 ) to lithium sulfide (Li 2 S) does not occur, and the temperature is higher than the above temperature There is a problem in that the elution of polysulfide cannot be effectively prevented due to diminution of nitrogen functional groups in the carbon matrix.
  • the manufacturing method of the present invention while manufacturing a cathode material for a lithium-sulfur battery in a simple way, the energy density is high, and the problem of pulverization of the cathode material during charging and discharging and the problem of the capacity decrease due to the elution of polysulfide can be solved.
  • the energy density is high, and the problem of pulverization of the cathode material during charging and discharging and the problem of the capacity decrease due to the elution of polysulfide can be solved.
  • a cathode material for a lithium-sulfur battery in a pellet form can be manufactured.
  • the present invention provides a cathode material for a lithium-sulfur battery, characterized in that it is prepared by the above method, lithium sulfide is dispersed in a carbon support, and includes a nitrogen functional group.
  • the positive electrode material of the present invention is prepared using a precursor containing a carbon-nitrogen organic crystal, various nitrogen functional groups are formed on the support to suppress the elution of polysulfide during charging and discharging, thereby preventing the capacity from deteriorating as a result,
  • the nitrogen functional group acts as a catalyst for the oxidation/reduction reaction of sulfur species, such as the reduction of sulfur (S 8 ) or the oxidation of lithium sulfide (Li 2 S), thereby increasing the overpotential of the oxidation/reduction reaction. reduces
  • the positive electrode material for a lithium-sulfur battery according to the present invention preferably further includes an additional carbon layer on the carbon support.
  • the positive electrode material for a lithium-sulfur battery of the present invention contains various nitrogen functional groups and suppresses the elution of liquid polysulfide generated during charging/discharging into the electrolyte.
  • a layer for example, a carbon nitride layer is included, since the layer suppresses the elution of additional polysulfide, it is possible to very effectively suppress a decrease in capacity during charging and discharging, which is effective in increasing battery stability.
  • the "additional carbon layer" formed on the carbon support is a layer prepared from the carbon/carbon-nitrogen crystal complex in the production method of the present invention, and, like the carbon support of the present invention, contains various functional groups including nitrogen. It is a porous carbon support layer.
  • the positive electrode material for a lithium-sulfur battery of the present invention is manufactured by compression molding and firing, it does not contain a binder and a conductive material, unlike conventional positive electrode materials for a lithium-sulfur battery, and therefore, has a relatively high amount of lithium sulfide. It has the advantage of high energy density.
  • the present invention provides a lithium-sulfur battery including the positive electrode material for a lithium-sulfur battery according to the present invention.
  • the lithium-sulfur battery of the present invention has high energy density, can solve the problem of pulverization of the carbon support during the charging and discharging process, and the problem of lowering the capacity due to the elution of polysulfide, and also uses a relatively inexpensive raw material and is a simple process. It has the advantage of being able to manufacture lithium-sulfur batteries.
  • Glucose (1 g) was dissolved in a mixed solvent of 30 mL of ethanol and 10 mL of tertiary distilled water. 1 g of MCA synthesized above was added in the same mass ratio to the completely dissolved glucose solution.
  • the MCA-glucose mixture (MCA-Glucose complex, hereinafter MG-1 or MG-X, where X is the mass ratio of glucose to MCA) formed white organic crystals within a few seconds. At this time, organic crystals having different microstructural characteristics may be formed according to the mass ratio of glucose to MCA.
  • the mixture was dried at room temperature in a fume hood with constant wind blowing. When the mixed solvent was not visible with the naked eye, drying was performed in an oven at 80° C. for 12 hours or more to completely remove the trace amount of the mixed solvent remaining in MG-1.
  • the synthesized MG-1 (148 mg) and commercially available Li 2 SO 4 (19.5 mg) were mixed for 3 hours using a stirrer (hereinafter referred to as MG-1-Li 2 SO 4 ).
  • the amount of commercially available Li 2 SO 4 may be included from 10 to 50 mg depending on the amount of Li 2 S obtained through thermal carbon reduction.
  • the amount of Li 2 SO 4 was adjusted to 19.5 mg.
  • Sufficiently mixed MG-1-Li 2 SO 4 was placed in a compression molding machine having a diameter of 13 mm and pressed at a pressure of 20 MPa for 1 minute. Then, MG-1 powder was spread evenly on one side of the compression molded body at 40 mg/cm 2 .
  • the compression-molded molded body was charged into a tube firing furnace, the temperature was raised to 800 °C at a rate of 2.3 °C/min, and firing was performed while maintaining the temperature at 800 °C for 4 hours.
  • the compression molded body after firing contained 8 mg of Li 2 S, and thus the positive electrode material of Example 1 was denoted as MG-1-Li 2 S-8@L. '@L' here means that an additional carbon layer was formed.
  • a lithium-sulfur battery was assembled using the synthesized MG-1-Li 2 S-8@L as a cathode material.
  • the composition of the battery excluding the cathode material is as follows.
  • Lithium-metal counter electrode, diameter: 10 mm, thickness: 075 mm, Alfa Aesar Co
  • separator (ceramic coated PP, diameter 19 mm, thickness: 026 mm, MTI KOREA Co),
  • a lithium-sulfur battery was manufactured in the same manner as in Example 1, except that the amount of Li 2 SO 4 was adjusted to 32.5 mg.
  • the cathode material after firing contained 13.5 mg of Li 2 S, and thus the cathode material of Example 2 is indicated as MG-1-Li 2 S-13.5@L.
  • a lithium-sulfur battery was prepared in the same manner as in Example 1, except that the amount of Li 2 SO 4 was adjusted to 49.5 mg.
  • the cathode material after firing contained 20 mg of Li 2 S, and thus the cathode material of Example 3 is indicated as MG-1-Li 2 S-20@L.
  • Example 1 in the “compression molding” step, "then MG-1 powder was spread evenly at 40 mg/cm 2 on one side of the compression molded body. It was pressed again at a pressure of 20 MPa for 5 minutes.”
  • a lithium-sulfur battery was prepared in the same manner as in Example 1, except that the additional carbon layer was not formed because the part was not performed. Accordingly, the positive electrode material of Example 4 is indicated as MG-1-Li 2 S-8.
  • Example 1 in the “compression molding” step, "then MG-1 powder was spread evenly at 40 mg/cm 2 on one side of the compression molded body. It was pressed again at a pressure of 20 MPa for 5 minutes.”
  • a lithium-sulfur battery was prepared in the same manner as in Example 1, except that no additional carbon layer was formed, and the same amount of Li 2 SO 4 as in Example 2 was used. Accordingly, the positive electrode material of Example 5 is indicated as MG-1-Li 2 S-13.5.
  • Example 1 in the “compression molding” step, "then MG-1 powder was spread evenly at 40 mg/cm 2 on one side of the compression molded body. It was pressed again at a pressure of 20 MPa for 5 minutes.”
  • a lithium-sulfur battery was prepared in the same manner as in Example 1, except that no additional carbon layer was formed, and the same amount of Li 2 SO 4 as in Example 3 was used. Accordingly, the positive electrode material of Example 6 is indicated as MG-1-Li 2 S-20.
  • Example 1 glucose was used at a mass ratio of 0.5 to MCA mass, and in the "compression molding” step, MG-1 powder was spread evenly at 40 mg/cm 2 on one side of the compression molded body. It was again pressurized at a pressure of 20 MPa for 5 minutes.”
  • a lithium-sulfur battery was prepared in the same manner as in Example 1, except that no part was performed and no additional carbon layer was formed. Accordingly, the positive electrode material of Example 7 is indicated as MG-0.5-Li 2 S-8.
  • Example 1 glucose was used at a mass ratio of 0.5 to MCA mass, and in the "compression molding” step, MG-1 powder was spread evenly at 40 mg/cm 2 on one side of the compression molded body. It was again pressurized at a pressure of 20 MPa for 5 minutes.”
  • a lithium-sulfur battery was prepared in the same manner as in Example 1, except that no additional carbon layer was formed, and the same amount of Li 2 SO 4 as in Example 2 was used. Accordingly, the positive electrode material of Example 8 is indicated as MG-0.5-Li 2 S-13.5.
  • Example 1 glucose was used at a mass ratio of 0.5 to MCA mass, and in the "compression molding” step, MG-1 powder was spread evenly at 40 mg/cm 2 on one side of the compression molded body. It was again pressurized at a pressure of 20 MPa for 5 minutes.”
  • a lithium-sulfur battery was prepared in the same manner as in Example 1, except that no additional carbon layer was formed, and the same amount of Li 2 SO 4 as in Example 3 was used. Accordingly, the positive electrode material of Example 9 is indicated as MG-0.5-Li 2 S-20.
  • FIG. 2 A photograph of the positive electrode material prepared in the process of manufacturing a lithium-sulfur battery in Example 1 is shown in FIG. 2 . According to FIG. 2 , it can be confirmed that a cathode material having a diameter of 11 mm and a thickness of 0.5 to 1.5 mm was formed.
  • the boiling point of Li 2 SO 4 is 1377 °C, and as can be seen in FIG. 3 , thermal decomposition of Li 2 SO 4 does not occur until 900 °C.
  • the MG-1 graph shows the profile during the carbonization process of glucose included in MG-1 at a temperature of 150 ° C or higher, and at this time, it shows the mass loss due to the condensation reaction and dehydration reaction of the hydroxyl functional group included in the glucose. .
  • the mass loss at a temperature of 400 ° C or higher is a mass loss due to the generation of ammonia gas due to the thermal polycondensation reaction of the triazine molecular structure of MCA included in MG-1.
  • CN x gas is generated, a tri-s-triazine structure is formed, and nanopores are developed.
  • ammonia, CN x gas, etc. generated by the thermal polycondensation reaction of MG-1 contribute to the formation of a reducing atmosphere that helps the reduction of Li 2 SO 4 to Li 2 S mentioned in the present invention.
  • MG-1-Li 2 SO 4 follows the profile and thermal reaction mechanism of MG-1, and is formed by the thermal carbon reduction reaction between MG-1, which serves as a carbon source, and Li 2 SO 4 , which is a metal oxide, at a temperature of 755 ° C or higher. A mass loss occurs due to the chemical conversion of Li 2 SO 4 to Li 2 S.
  • X-ray diffraction analysis was performed on the positive electrode material prepared during the process of Example 4 of the present invention three times, and the resultant X-ray diffraction analysis graph is shown in FIG. 4 .
  • MG-1-Li 2S The pellet shows Li 2 S crystal peaks at 27 °, 31 °, 45 °, and 53 °, which means complete conversion (reduction) of Li 2 SO 4 to Li 2 S has been performed.
  • peaks caused by LiOH are seen at 20 °, 32 °, and 56 °, which are peaks that appear when Li 2 S in contact with external air is oxidized during ex-situ XRD analysis.
  • a scanning electron micrograph (SEM) of the positive electrode material produced during the process of Example 4 of the present invention is shown in FIG. 5 .
  • the SEM image on the left is a surface image of the cathode material pellets manufactured during the process of Example 4.
  • the synthesized Li 2 S has a particle size of about 100 ⁇ m, is connected due to thermal polycondensation reaction, and is located on the MG-1 support with developed nanopores can know
  • the SEM image on the right is an image of the MG-1 scaffold remaining after dissolving and extracting Li 2 S inside the synthesized pellet with ethanol, and it can be confirmed that the carbon structure has nanopores and is well connected to each other due to thermal polycondensation reaction.
  • Example 1 Example 4, Example 7 (Fig. 6a), Example 2, Example 5, Example 8 (Fig. 6b), Example 3, Example 6, Example 9 (Fig. 6c)
  • a rest time of 6 hours was placed in an oven at 30 °C to optimize the movement of lithium ions by uniformly distributing the electrolyte inside the battery.
  • Li/Li + was charged at a current density of 0.5 mA/cm 2 , and 3.5 V vs.
  • the potential was maintained until the current flowed below 0.05 mA/cm 2 .
  • Discharge was performed at 0.5 mA/cm 2 until Li/Li + , and repeated charge/discharge cycles were 1.8-2.6 V vs.
  • the test was performed at a current density of 1.5 mA/cm 2 in the Li/Li + voltage range, and the results are shown in FIGS. 6a to 6c.
  • each cell shows a rapid capacity decrease within 20 to 30 cycles, which is due to the fact that the polysulfide formed during the charging/discharging process of Li 2 S exposed to the outside is used as an electrolyte. It is expected to be caused by the problem of elution or the resulting micronization of the carbon support.
  • FIGS. 6A to 6C it can be confirmed that such a rapid capacity decrease is effectively suppressed by the additional carbon layer.
  • the discharge capacities of Example 1, Example 2, and Example 3 were 800 mAh/g, 700 mAh/g, and 400 mAh/g, respectively, and Li 2 S utilization rates were 68.6%, 60.0%, and 34.3, respectively. %am.
  • the lithium-sulfur battery of the present invention has a very low activation energy of Li 2 S, which is because the positive electrode according to the present invention is doped with a small amount of nitrogen, It is expected to lower the activation energy.
  • FIGS. 6A to 6C according to Experimental Example 6 it can also be seen that there is an excellent effect of maintaining capacity after a capacity decrease of about 20 to 30% after the second cycle charge / discharge, and FIGS. 7A to 7C Even through (comparison of the profiles of the 5th, 10th, and 15th charge/discharge cycles), it can be seen that there is an advantage in that the capacity decrease does not occur significantly even when the charge/discharge cycle is repeated.

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Abstract

Un objet de la présente invention est de fournir un procédé de fabrication d'un matériau de cathode pour une batterie lithium-soufre. Un autre objectif de la présente invention est de fournir un matériau de cathode pour batterie lithium-soufre fabriqué par le procédé. À cet effet, la présente invention concerne un procédé de fabrication d'un matériau de cathode pour une batterie lithium-soufre, comprenant les étapes consistant à : former un complexe de cristaux de carbone/carbone-azote en mélangeant un cristal organique de carbone-azote et un précurseur de carbone dans une unité moléculaire, tel qu'un précurseur de carbone moléculaire tel qu'un monomère ou un dimère ; mélanger un complexe de cristaux de carbone/carbone-azote et un précurseur de sulfure de lithium pour obtenir une poudre mélangée ; comprimer la poudre mélangée ; et calciner la poudre mélangée comprimée. De plus, la présente invention concerne un matériau de cathode pour une batterie lithium-soufre dans lequel du sulfure de lithium est dispersé dans un support de carbone préparé par le procédé susmentionné et qui comprend un groupe fonctionnel azoté. La présente invention permet non seulement de fabriquer un matériau de cathode pour une batterie lithium-soufre par un procédé simple, mais également d'augmenter la densité énergétique du matériau de cathode, d'empêcher le support d'être pulvérisé dans un processus de charge ou de décharge, de fabriquer un matériau de cathode à valeur ajoutée élevée avec des matières premières à faible coût, et d'éviter une diminution de capacité par inhibition de l'élution d'un matériau actif de cathode dans un électrolyte pendant un processus de charge ou de décharge.
PCT/KR2022/009986 2021-08-04 2022-07-08 Procédé de fabrication d'un matériau de cathode pour batterie lithium-soufre, et matériau de cathode pour batterie au lithium-soufre ainsi fabriqué Ceased WO2023013903A1 (fr)

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