WO2020059927A1 - Method for manufacturing cathode material for secondary battery electrode - Google Patents

Method for manufacturing cathode material for secondary battery electrode Download PDF

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WO2020059927A1
WO2020059927A1 PCT/KR2018/011365 KR2018011365W WO2020059927A1 WO 2020059927 A1 WO2020059927 A1 WO 2020059927A1 KR 2018011365 W KR2018011365 W KR 2018011365W WO 2020059927 A1 WO2020059927 A1 WO 2020059927A1
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secondary battery
manufacturing
positive electrode
electrode material
electrode
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PCT/KR2018/011365
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French (fr)
Korean (ko)
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최해영
이상민
노판진
최정희
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한국전기연구원
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/362Composites
    • H01M4/366Composites as layered products
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/054Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/04Processes of manufacture in general
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/04Processes of manufacture in general
    • H01M4/0402Methods of deposition of the material
    • H01M4/0404Methods of deposition of the material by coating on electrode collectors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/04Processes of manufacture in general
    • H01M4/0471Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139Processes of manufacture
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139Processes of manufacture
    • H01M4/1397Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection 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
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection 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
    • H01M4/583Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624Electric conductive fillers
    • H01M4/625Carbon or graphite
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/627Expanders for lead-acid accumulators
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Definitions

  • It relates to a method of manufacturing a positive electrode material for an electrode of a secondary battery, an electrode manufacturing method comprising the positive electrode material, an electrode for a secondary battery comprising the positive electrode material, a secondary battery comprising the same, and a charging and discharging method of the secondary battery.
  • lithium secondary batteries have been commercialized, functioning as a core power source in small IT devices, power tools, etc., and expanding the range of power sources such as electric vehicles (EV, HEV, PHEV).
  • Lithium resources which are the main materials of the lithium secondary battery, are limited to South America, such as Argentina, Venezuela, and Chile. As demand for lithium rapidly increases, there are problems such as supply and demand imbalance, raw material price increases, and resource depletion of lithium-bearing countries.
  • sodium is very advantageous in terms of supply and demand of raw materials because of its rich reserves and low price.
  • Sodium ion secondary batteries have also been studied since the 1970s, but lithium secondary batteries were first commercialized and attracted attention, but the need for a non-lithium-based Post-Li battery emerged, and the sodium ion secondary batteries began to be in earnest. Research is ongoing.
  • the sodium ion secondary battery has the same operating principle and similar structure as the lithium secondary battery, and has the potential as a secondary battery, but does not reach many characteristics of the lithium secondary battery.
  • it can be an innovative alternative to overcome the limitations of the current lithium secondary battery market as an energy storage and conversion device based on advantages such as easy resource supply and low cost.
  • the sodium secondary battery that can replace the lithium secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator.
  • the positive electrode is manufactured by casting an active material, a binder, and a conductive agent to a current collector.
  • the positive electrode active material used are oxide-based materials such as NaCrO 2 , NaMnO 2 , NaFePO 4 and Na 3 V 2 (PO 4 ). 3 , polyanion series such as NaFePO 4 , sulfide series such as Na x TiS 2 , fluoride series such as FeF 3 , NASICON (Na 1 + x Zr 2 Si x P 3 - x O 12 , 0 ⁇ x ⁇ 3), etc. Phosphate series of is mainly used.
  • the negative electrode active material used in the negative electrode petroleum cokes, carbon black, hard carbon, and the like are mainly used, and the ether-based or carbonate-based solvent is mainly used as the electrolyte, and As the separator, polyolefin-based films such as polyethylene (PE) and polypropylene (PP) are mainly used.
  • PE polyethylene
  • PP polypropylene
  • the cathode material is known as a method of using Prussian Blue (Prussian Blue, PB) and Prussian White (PW) derivatives (Korean Patent Publication No. 2017-0098529), of which PW is an analog of PB.
  • Prussian Blue Prussian Blue
  • PW Prussian White
  • a x M a [M b (CN) 6 ] (A: alkali metal, M a , M b : transition metal, x0 ⁇ 2, 0 ⁇ a ⁇ 1, and 0 ⁇ b ⁇ 1)
  • MOFs metal It has an organic skeletal structure, metal-organic-frameworks
  • the PW has a high theoretical capacity of the content of the A x higher than the PB and there is the A x is located in the vacancy in the MOFs structure, the size of the space 5.1 3 ( ⁇ 3) sufficient for insertion to desorption of Na ion or higher Since it provides space and can diffuse ions at a rapid rate, and has a high rate characteristic, it is receiving much attention as a candidate group of cathode agents such as SIB.
  • the present invention is to overcome the limitations of the PW material, which has been conventionally used as a cathode material, and prevents crystal water from flowing into the skeletal structure through proper heat treatment after bonding the graphene oxide material to the PW surface, thereby preventing crystal water.
  • the present invention in a method of manufacturing a positive electrode material for a secondary battery,
  • step (S3) of heat-treating the powder of the step S2 reducing the graphene oxide bound to the surface of the prussian white
  • the Prussian white solution provides a method for preparing a positive electrode material for a secondary battery, comprising a compound represented by the following Chemical Formula 1:
  • A is an alkali metal or alkaline earth metal
  • Ma and Mb are transition metals
  • x is 0-2, a is 0-1, and b is 0-1.
  • the spray drying of the step S2 is characterized in that it is carried out at 100 to 150 °C.
  • the reduction of the S3 step is characterized in that it is performed in an air atmosphere.
  • the reduction of the S3 step is characterized in that it is carried out in an oxygen atmosphere.
  • the heat treatment in step S3 is characterized in that it is carried out at 120 to 220 °C.
  • the alkali metal is characterized in that at least one member selected from the group consisting of sodium, lithium, and potassium.
  • the alkaline earth metal is characterized in that at least one member selected from the group consisting of magnesium, calcium, and strontium.
  • the transition metal is characterized in that at least one member selected from the group consisting of manganese, iron, cobalt, nickel, chromium, titanium, vanadium and copper.
  • the present invention is a method of manufacturing an electrode for a secondary battery comprising a positive electrode material manufactured by the above manufacturing method
  • the conductive material is characterized in that at least one member selected from the group consisting of carbon black, graphene, graphite and carbon nanotubes.
  • the binder is one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyamideimide (PAI), polyacrylic acid (PAA) and polyimide (PI). Is done.
  • PVDF polyvinylidene fluoride
  • PAI polyamideimide
  • PAA polyacrylic acid
  • PI polyimide
  • the current collector is characterized in that at least one member selected from the group consisting of aluminum, copper, and nickel.
  • the vacuum drying in step (c) is performed at 150 to 180 ° C.
  • the present invention provides an electrode for a secondary battery comprising a positive electrode material manufactured by the above manufacturing method.
  • the present invention provides a secondary battery comprising the electrode for the secondary battery.
  • the present invention is a method of charging and discharging a secondary battery including a positive electrode material manufactured by the manufacturing method, comprising the steps of repeatedly performing charging and discharging the secondary battery with a constant current and a constant voltage within a range of 1.5 to 4V, Provides a method for charging and discharging a secondary battery.
  • the present invention prepared an anode material for an electrode that prevents trapping of crystal water by preventing crystal water from entering the structure of the Prussian white through proper heat treatment after binding the graphene oxide material to the Prussian white surface.
  • the life characteristics of the battery can be improved.
  • the initial capacity increases by discharging the metal ions by discharging to a low voltage during charging and discharging, thereby improving cycle characteristics.
  • 1 is a view showing the structure of Prussian Blue (left) and Prussian White (right).
  • FIG. 2 is a view showing a position where sodium ions may be located inside a Prussian white structure.
  • FIG 3 is a view schematically showing a method of manufacturing a positive electrode material according to the present invention.
  • FIG. 4 is a view showing the results of confirming the properties of the RGO / PW powder, and confirming the moisture content according to the heat treatment temperature.
  • FIG. 5 is a view showing the results of confirming the properties of the RGO / PW powder, confirming that the graphene oxide has been reduced.
  • FIG. 6 is a view showing the results of confirming the properties of the RGO / PW powder, and confirming the phase change according to the coating and heat treatment environment of the powder.
  • FIG. 7 is a view schematically showing a method of manufacturing an electrode for a secondary battery including a positive electrode material produced by the manufacturing method of the present invention.
  • FIG. 8 is a view showing the results of confirming the performance of the electrode cell according to the RGO / PW heat treatment temperature.
  • 9 is a view showing the results of confirming the performance of the electrode according to the electrode drying temperature.
  • FIG. 10 is a view showing the results of confirming the performance of the electrode cell according to the RGO binding.
  • 11 is a view showing the results of confirming the charge and discharge protocol of the battery produced by the method of the present invention.
  • the present inventors focused on the electrode material for a secondary battery while studying a method for improving the capacity and life of the sodium ion secondary battery, and the Prussian white material with graphene oxide reduced to the electrode material adhered to the surface.
  • the capacity and life of the battery can be improved, thereby completing the present invention.
  • the electrode material proposed in the present invention is a reduced graphene oxide adhered to the surface of Prussian white (reduced graphene oxide coated PW, hereinafter RGO-PW), the core material of Prussian White (Prussian White, PW) is Prussian As an analog (PBA) of Prussian Blue (PB), it basically has a metal-organic-frameworks (MOFs) structure of A x M a [M b (CN) 6 ].
  • the PB has a cubic structure as shown on the left side of FIG. 1, and water is formed as a complex compound inside the structure during manufacture, disintegrating the structure, reducing capacity due to ion transfer interference, and reducing electrical conductivity.
  • the A x in the MOFs structure as in Fig. And has a high theoretical capacity increase the amount of A x in structure compared to the PW is PB, as can be seen from the right side of Fig.
  • the RGO material is bound to the PW surface and then the inflow of crystal water through appropriate heat treatment prevents the trap of crystal water to suppress the reaction between the electrolyte and crystal water during battery manufacturing.
  • the life characteristics of the battery were improved.
  • the diffusion form of Na ions during charging and discharging differs from the charging protocol method to improve the cycle characteristics.
  • the present invention can provide a method of manufacturing a cathode (cathode, cathode) material for a secondary battery including the following steps with reference to FIG. 3.
  • the Prussian white solution includes a compound represented by Formula 1 below.
  • A is an alkali metal or alkaline earth metal
  • Ma and Mb are transition metals
  • x is 0-2
  • a is 0-1
  • b is 0-1.
  • the alkali metal may be sodium, lithium, or potassium
  • the alkaline earth metal may be magnesium, calcium, or strontium, but is not limited to the type of the metal
  • the transition metal is manganese, iron, cobalt , Nickel, chromium, titanium, vanadium or copper, and any transition metal that does not affect safety and synthesis may be used without limitation.
  • the spray drying in step S2 may be performed at 100 to 150 ° C., and the spray drying is based on vacuum drying, and the atmosphere is in an inert gas (argon, helium, nitrogen, etc.) atmosphere during powder recovery. It may be performed by, but is not limited to.
  • step S3 may be performed at 120 to 220 ° C. for 60 to 180 minutes, but is not limited thereto, and the graphene oxide bound to the surface of the prussian white structure is reduced by heat treatment as described above.
  • the reduction may be performed in an air atmosphere or an oxygen atmosphere.
  • the present invention is a method of manufacturing an electrode for a secondary battery including a positive electrode material manufactured by the above manufacturing method with reference to the contents shown in FIG. 7.
  • the conductive material may be carbon black, graphene, graphite, or carbon nanotubes, and SPB, KB, or the like is used among the carbon black, but any material exhibiting conductivity may be used without limitation.
  • the binder may be polyvinylidene fluoride (PVDF), polyamideimide (PAI), polyacrylic acid (PAA) or polyimide (PI), etc., but preparing the slurry by combining the positive electrode active material and a conductive material If the material that can serve as a binder for is not limited thereto.
  • PVDF polyvinylidene fluoride
  • PAI polyamideimide
  • PAA polyacrylic acid
  • PI polyimide
  • the current collector may be aluminum, copper, nickel, or the like, and is not limited thereto as long as it can be used as the current collector of the electrode.
  • the vacuum drying in step (c) may be performed at 150 to 180 ° C. for 8 to 36 hours under 10 ⁇ 4 torr to 10 ⁇ 2 torr air pressure.
  • the vacuum drying step further comprises a step of purging (purging) with an inert gas.
  • Argon gas may be used as the inert gas, but is not limited thereto.
  • the present invention can provide an electrode for a secondary battery including a positive electrode material manufactured by the above manufacturing method, and additives that can be included in the electrode in addition to the positive electrode material described above may be included without limitation.
  • the present invention can provide a secondary battery including the electrode for the secondary battery, there is no limitation on the type of cathode (anode, oxide electrode), electrolyte, and separator required for driving the secondary battery in addition to the electrode.
  • the present invention is a method for charging and discharging a secondary battery including a positive electrode active material prepared by the above manufacturing method, the method comprising repeatedly performing charging and discharging the secondary battery with a constant current and a constant voltage within a range of 1.5 to 4V, Provides a method for charging and discharging a secondary battery.
  • the metal ions are located at the sites where the crystal water, which is an energy-relatively unstable site, is located, so that the other metal ions are smoothly detached while maintaining the PW structure.
  • Na ions are inserted to the position (see 24d in FIG. 2).
  • the moisture content according to temperature was measured for a Prussian white powder (RGO / PW) bound with reduced graphene oxide, a positive electrode material (positive electrode active material) prepared in the same manner as the present invention.
  • a significantly less moisture content was confirmed compared to PW, GO / PW, and the like, and excellent initial capacity and charging / discharging efficiency were confirmed in a battery including an electrode manufactured using the positive electrode active material.
  • a PW solution and a GO solution were prepared as shown in FIG. 3.
  • the PW solution was prepared by dissolving 9.1 g of PW in 100 mL of distilled water
  • the GO solution was prepared by quantifying 0.1 g of GO (9% of the total solution) and dissolving it in 100 mL of distilled water.
  • the PW solution and the GO solution were put in a reaction tank and mixed by stirring at a rate of 300 rpm.
  • the mixed solution was spray dried through a spray dryer equipment to obtain GO / PW powder.
  • the obtained GO / PW powder was heat treated at 220 ° C. for 60-180 minutes to reduce GO bound on the surface of PW.
  • the water content was confirmed through TGA analysis on the RGO / PW powder prepared in Example 1. SDT Q600 TGA thermal analyzer for PW / water samples with maximum moisture content, RGO / PW / water samples, air dry PW samples stored in normal environments, air dry RGO / PW samples, and GO / PW / water samples Through the water content was confirmed.
  • Each obtained powder sample was placed in a measuring holder for X-ray diffraction measurement, mounted on a device, and measured in a 2theta range of 10 to 90 °.
  • TGA X-ray diffraction measurement
  • there is no weight change up to 350 °C in an inert gas atmosphere but it is confirmed that the phase change is below 200 °C in the air atmosphere, so there is a heat treatment process in the oxygen atmosphere during the reduction process of GO.
  • XRD was measured.
  • the reduction method of GO utilized in the present invention is a group of functional groups in GO (-OH, -COOH) as electron transfer occurs through electrostatic binding bound between PW and crystalline water through heat treatment for 3 hours at 220 ° C. in an oxygen atmosphere. etc.), and this group is decomposed into CO 2 to H 2 O, and the reduction proceeds.
  • the heat treatment atmosphere for the phase change confirmation test was tested in a stable Ar atmosphere with PW and an air atmosphere where GO is reduced to RGO, and PW and GO-PW are secured as control data before and after coating and before and after GO is reduced to RGO. In order to do so, it was measured without heat treatment.
  • Example 3 an electrode including the RGO / PW prepared in Example 1 was prepared. As shown in Fig. 7, 0.2 g of SPB was mixed with 0.7 g of RGO / PW as a conductive material, followed by dry mixing, and after adding 0.1 g of PVDF as a binder to prepare the dry-mixed powder as a slurry, a blender (THINKY, Japan) The electrode active material slurry was prepared by mixing at 2000 rpm for 1 minute.
  • the slurry prepared as described above was cast in an aluminum foil having a thickness of 16 ⁇ m as a current collector to 13 ⁇ m by a casting process to prepare a film.
  • the electrode coated with the slurry was sufficiently dried in a vacuum dryer at a temperature of 170 ° C.
  • the coin cell is a lithium metal as a negative electrode, PE Separator, propylene carbonate (PC) and polypropylene (PP) mixed solvent (volume ratio 9.5: 0.5) 1 mol NaClO 4 salt and 2wt% fluoroethylene carbonate ( FEC)
  • PC propylene carbonate
  • PP polypropylene
  • FEC fluoroethylene carbonate
  • Example 4.1 the purpose of this study was to determine the effect of the moisture content in the structure on the performance of the battery by the heat treatment temperature of the RGO / PW powder.
  • an electrode cell prepared in the method of Example 3 was used, and for comparison, an electrode cell using an electrode comprising RGO / PW heat-treated at 170 ° C., which was prepared by the method of manufacturing RGO / PW powder in Example 1 It was prepared.
  • the charging and discharging was performed at a constant current / constant voltage in a voltage range of 2 to 4 V as a charging / discharging condition of the electrode, and the results of confirming the oxidation and reduction behavior of the electrode by a potential scanning method are shown in FIG.
  • Example 4.2 it was intended to confirm the effect of the moisture content contained inside the electrode on the performance of the battery by the drying conditions of the electrode made of the RGO / PW material.
  • a battery prepared in the method of Example 3 was used, and for comparison, a battery prepared by the method of Example 3 was prepared, and the slurry was cast in a current collector and then dried at 120 ° C.
  • each electrode cell was manufactured in five.
  • Charging and discharging was performed at a constant current / constant voltage in a voltage range of 2 to 4 V as a condition for charging and discharging the electrode, and the results of confirming the oxidation and reduction behavior of the electrode by a potential scanning method are shown in FIG. 9.
  • Example 4.3 the initial capacity and cycle characteristics of the electrode cell using RGO / PW powder and the electrode cell using PW powder were examined.
  • an electrode cell prepared in the method of Example 3 was used, and for comparison, an electrode cell using an electrode containing PW without GO treatment was also prepared.
  • Charging and discharging was performed at a constant current / constant voltage in a voltage range of 2 to 4 V as a condition for charging and discharging the electrode, and the results of confirming the oxidation and reduction behavior of the electrode by a potential scanning method are shown in FIG.
  • Example 5 an efficient charging / discharging method of the battery manufactured in the present invention was intended.
  • the charging and discharging method was determined by changing the voltage range and the charging and discharging speed of the initializing condition and the cycle condition.
  • the battery using the electrode containing the positive electrode material of the present invention is preferable to charge and discharge in the manner of CC-CV, 0.05C to 0.1C, voltage range / 1.5 to 4V.
  • the present invention is to provide a positive electrode material for preventing the trapping of crystal water by preventing the inflow of crystal water into the structure of the Prussian white through proper heat treatment after binding the graphene oxide material to the Prussian white surface, Since it is possible to provide a secondary battery with improved life characteristics and capacity by using the positive electrode material, the present invention can be usefully used in the secondary battery industry.

Abstract

The present invention provides a method for manufacturing a cathode material for a secondary battery and, more specifically, provides a method for manufacturing a cathode material for a secondary battery, the method comprising a step of binding graphene oxide onto the surface of a Prussian white structure and then reducing the graphene oxide. A secondary battery manufactured by comprising an electrode using the cathode material can have excellent initial capacity and lifetime characteristics.

Description

이차 전지의 전극용 양극소재의 제조방법Method of manufacturing a positive electrode material for an electrode of a secondary battery
이차 전지의 전극용 양극 소재의 제조방법, 상기 양극 소재를 포함하는 전극 제조방법, 상기 양극 소재를 포함하는 이차전지용 전극, 이를 포함하는 이차전지 및 상기 이차전지의 충방전 방법에 관한 것이다.It relates to a method of manufacturing a positive electrode material for an electrode of a secondary battery, an electrode manufacturing method comprising the positive electrode material, an electrode for a secondary battery comprising the positive electrode material, a secondary battery comprising the same, and a charging and discharging method of the secondary battery.
1990년대 이후 리튬 2차 전지가 상용화되어, 소형 IT 기기, 전동공구 등에서 핵심 전원으로서 기능하고, 전기자동차 (EV, HEV, PHEV) 등의 전원으로 범위를 넓히고 있다.Since the 1990s, lithium secondary batteries have been commercialized, functioning as a core power source in small IT devices, power tools, etc., and expanding the range of power sources such as electric vehicles (EV, HEV, PHEV).
상기 리튬 2차 전지의 주재료인 리튬 자원은 아르헨티나, 볼리비아, 칠레 등 남미대륙에 국한되어 있는데, 리튬 수요가 급증함에 따라 수급 불균형, 원재료 가격 상승, 리튬 보유국의 자원 무기화 등의 문제가 발생하고 있다.Lithium resources, which are the main materials of the lithium secondary battery, are limited to South America, such as Argentina, Bolivia, and Chile. As demand for lithium rapidly increases, there are problems such as supply and demand imbalance, raw material price increases, and resource depletion of lithium-bearing countries.
이에 비하여, 나트륨은 매장량이 풍부하고 가격이 저렴해서 원료 수급 측면에서 매우 유리하다. 나트륨 이온 2차 전지도 1970년대부터 연구가 시작되었으나, 리튬 2차 전지가 먼저 상용화되어 관심을 끌지 못하다가 비-리튬계 Post-Li 전지에 대한 필요성이 대두되어 상기 나트륨 이온 2차 전지에 대한 본격적인 연구가 진행되고 있다. On the other hand, sodium is very advantageous in terms of supply and demand of raw materials because of its rich reserves and low price. Sodium ion secondary batteries have also been studied since the 1970s, but lithium secondary batteries were first commercialized and attracted attention, but the need for a non-lithium-based Post-Li battery emerged, and the sodium ion secondary batteries began to be in earnest. Research is ongoing.
상기 나트륨 이온 2차 전지는 리튬 2차 전지와 동일한 작동 원리, 유사한 구조로서 2차 전지로서의 가능성은 보였으나, 리튬 2차 전지의 특성에는 많이 못 미치고 있다. 그러나, 자원 수급이 용이하고, 낮은 cost 등의 장점을 바탕으로 하여 에너지 저장 및 변환 디바이스로서 현재의 리튬 2차 전지 시장의 한계를 극복할 수 있는 혁신적인 대안이 될 수 있다.The sodium ion secondary battery has the same operating principle and similar structure as the lithium secondary battery, and has the potential as a secondary battery, but does not reach many characteristics of the lithium secondary battery. However, it can be an innovative alternative to overcome the limitations of the current lithium secondary battery market as an energy storage and conversion device based on advantages such as easy resource supply and low cost.
상기 리튬 2차 전지를 대체할 수 있는 나트륨 2차 전지는 양극, 음극, 전해액 및 분리막을 포함하여 구성된다.The sodium secondary battery that can replace the lithium secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator.
상기 양극은 활물질, 결합제, 도전제를 집전체에 캐스팅하여 제조되는 것으로, 이에 이용되는 양극 활물질로는 주로 NaCrO2, NaMnO2, NaFePO4 등과 같은 산화물 계열의 물질과 Na3V2(PO4)3, NaFePO4등의 polyanion 계열, NaxTiS2 등의 설파이드 계열, FeF3등의 플루오라이드 계열, NASICON(Na1 + xZr2SixP3 - xO12, 0 < x < 3) 등의 포스페이트 계열 등이 주로 사용된다.The positive electrode is manufactured by casting an active material, a binder, and a conductive agent to a current collector. Examples of the positive electrode active material used are oxide-based materials such as NaCrO 2 , NaMnO 2 , NaFePO 4 and Na 3 V 2 (PO 4 ). 3 , polyanion series such as NaFePO 4 , sulfide series such as Na x TiS 2 , fluoride series such as FeF 3 , NASICON (Na 1 + x Zr 2 Si x P 3 - x O 12 , 0 <x <3), etc. Phosphate series of is mainly used.
상기 음극에 이용되는 음극 활물질로는 석유 코크스(petroleum cokes), 카본 블랙(carbon black), 하드 카본(hard carbon) 등이 주로 사용되고, 상기 전해액으로는 에테르 계열 또는 카보네이트계 용매가 주로 사용되며, 상기 분리막은 폴리에틸렌(Polyethylene, PE), 폴리프로필렌(Polyprophylene, PP)과 같은 폴리올레핀 계열의 필름이 주로 사용되고 있다. As the negative electrode active material used in the negative electrode, petroleum cokes, carbon black, hard carbon, and the like are mainly used, and the ether-based or carbonate-based solvent is mainly used as the electrolyte, and As the separator, polyolefin-based films such as polyethylene (PE) and polypropylene (PP) are mainly used.
상기 양극 소재로 프러시안 블루(Prussian Blue, 이하 PB) 및 프러시안 화이트(Prussian White, 이하 PW) 유도체를 이용하는 방법에 알려져 있는데(국내 공개특허 제2017-0098529호), 이중 PW는 PB의 유사체로서 기본적으로 AxMa[Mb(CN)6] (A: 알칼리금속, Ma, Mb : 전이금속, x0~2, 0<a<1, 및 0<b<1) 의 MOFs(금속유기골격구조, metal-organic-frameworks) 형태의 구조를 가진다. The cathode material is known as a method of using Prussian Blue (Prussian Blue, PB) and Prussian White (PW) derivatives (Korean Patent Publication No. 2017-0098529), of which PW is an analog of PB. Basically A x M a [M b (CN) 6 ] (A: alkali metal, M a , M b : transition metal, x0 ~ 2, 0 <a <1, and 0 <b <1) MOFs (metal It has an organic skeletal structure, metal-organic-frameworks) structure.
상기 PW는 PB에 비하여 Ax의 함량이 높아 높은 이론 용량을 가지고 있고 MOFs 구조 내에 Ax가 vacancy에 위치하게 되는데 이 공간의 사이즈가 5.13(Å3) 이상으로 Na ion의 삽탈리하기에 충분한 공간을 제공하여 빠른 율속으로 이온의 확산이 가능하여 고율특성이 좋기 때문에 SIB 등의 양극제의 후보군으로 많은 관심을 받고 있다. The PW has a high theoretical capacity of the content of the A x higher than the PB and there is the A x is located in the vacancy in the MOFs structure, the size of the space 5.1 3 3) sufficient for insertion to desorption of Na ion or higher Since it provides space and can diffuse ions at a rapid rate, and has a high rate characteristic, it is receiving much attention as a candidate group of cathode agents such as SIB.
그러나 PW 합성시 -C≡N- 결합의 결함(defect)이 형성되기 쉬워 이 위치에 공기 중에 존재하는 H2O가 crystal water로 트랩(trap)되기 쉽다. 이 crystal water는 충방전시 전극밖으로 유출되면서 전해액과 반응하여 분해를 일으키게 되고 전극소재들과의 부반응을 진행시켜 전지의 수명특성에 악영향을 미치게 되는 한계점을 보이고 있다.However, when PW is synthesized, a defect of -C≡N- bond is likely to be formed, and H 2 O present in the air at this position is likely to be trapped by crystal water. As this crystal water leaks out of the electrode during charging and discharging, it reacts with the electrolyte to cause decomposition, and proceeds with side reactions with the electrode materials, which has a limit of adversely affecting the life characteristics of the battery.
본 발명은 종래 양극소재로 활용되었던 PW 소재의 한계점을 극복하고자, 산화그래핀(graphene oxide) 소재를 PW 표면에 결착시킨 후 적절한 열처리를 통하여 crystal water가 골격 구조 내에 유입되는 것을 방지하여, crystal water의 trap을 막음으로써, 전지 제조시 전해액과 crystal water사이의 반응을 억제함으로써 전지의 수명 특성이 향상되고, 소재의 구조특성으로 인한 충방전 시 Na ion의 확산 형태가 충전프로토콜 방식에 다름을 이용하여 충전 사이클 특성을 향상시킨 나트륨 이차전지의 전극의 제조방법을 제공하고자 한다.The present invention is to overcome the limitations of the PW material, which has been conventionally used as a cathode material, and prevents crystal water from flowing into the skeletal structure through proper heat treatment after bonding the graphene oxide material to the PW surface, thereby preventing crystal water. By preventing the trap of, by suppressing the reaction between the electrolyte and crystal water during battery manufacturing, the life characteristics of the battery are improved, and the diffusion form of Na ion during charging and discharging due to the structural characteristics of the material differs from the charging protocol method. It is intended to provide a method for manufacturing an electrode of a sodium secondary battery with improved charging cycle characteristics.
그러나 본 발명이 이루고자 하는 기술적 과제는 이상에서 언급한 과제에 제한되지 않으며, 언급되지 않은 또 다른 과제들은 아래의 기재로부터 당업자에게 명확하게 이해될 수 있을 것이다.However, the technical problem to be achieved by the present invention is not limited to the above-mentioned problems, and other problems that are not mentioned will be clearly understood by those skilled in the art from the following description.
상기의 과제를 해결하기 위하여 본 발명은 이차전지용 양극 소재의 제조방법에 있어서,In order to solve the above problems, the present invention in a method of manufacturing a positive electrode material for a secondary battery,
프러시안 화이트 용액 및 산화그래핀 용액을 혼합하는 단계(S1);Mixing a prussian white solution and a graphene oxide solution (S1);
상기 S1 단계의 용액을 교반한 후, 분무 건조하여 산화그래핀이 프러시안 화이트의 표면에 결착된 분말을 제조하는 단계(S2); 및After stirring the solution of the step S1, spray-dried to prepare a powder of graphene oxide bound to the surface of the prussian white (S2); And
상기 S2 단계의 분말을 열처리하여, 상기 프러시안 화이트의 표면에 결착된 산화그래핀을 환원하는 단계(S3)를 포함하고,Including the step (S3) of heat-treating the powder of the step S2, reducing the graphene oxide bound to the surface of the prussian white,
상기 프러시안 화이트 용액은 하기 화학식 1로 표시되는 화합물을 포함하는 것인, 이차전지용 양극 소재의 제조방법을 제공한다:The Prussian white solution provides a method for preparing a positive electrode material for a secondary battery, comprising a compound represented by the following Chemical Formula 1:
[화학식 1][Formula 1]
AxMa[Mb(CN)6]A x M a [M b (CN) 6 ]
상기 화학식 1에서 A는 알칼리 금속 또는 알칼리토금속이고, Ma 및 Mb는 전이금속이며,In Formula 1, A is an alkali metal or alkaline earth metal, Ma and Mb are transition metals,
x는 0~2, a는 0~1, b는 0~1이다. x is 0-2, a is 0-1, and b is 0-1.
본 발명의 일구현예로, 상기 S2 단계의 분무 건조는 100 내지 150℃로 수행되는 것을 특징으로 한다.In one embodiment of the present invention, the spray drying of the step S2 is characterized in that it is carried out at 100 to 150 ℃.
본 발명의 다른 구현예로, 상기 S3 단계의 환원은 공기 분위기에서 수행되는 것을 특징으로 한다.In another embodiment of the present invention, the reduction of the S3 step is characterized in that it is performed in an air atmosphere.
본 발명의 또다른 구현예로, 상기 S3 단계의 환원은 산소 분위기에서 수행되는 것을 특징으로 한다.In another embodiment of the present invention, the reduction of the S3 step is characterized in that it is carried out in an oxygen atmosphere.
본 발명의 또다른 구현예로, 상기 S3 단계의 열처리는 120 내지 220℃로 수행되는 것을 특징으로 한다.In another embodiment of the present invention, the heat treatment in step S3 is characterized in that it is carried out at 120 to 220 ℃.
본 발명의 또 다른 구현예로, 상기 알칼리 금속은 나트륨, 리튬, 및 칼륨으로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 한다.In another embodiment of the present invention, the alkali metal is characterized in that at least one member selected from the group consisting of sodium, lithium, and potassium.
본 발명의 또 다른 구현예로, 상기 알칼리 토금속은 마그네슘, 칼슘, 및 스트론튬으로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 한다.In another embodiment of the present invention, the alkaline earth metal is characterized in that at least one member selected from the group consisting of magnesium, calcium, and strontium.
본 발명의 또 다른 구현예로, 상기 전이금속은 망가니즈, 철, 코발트, 니켈, 크롬, 티타늄, 바나듐 및 구리로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 한다.In another embodiment of the present invention, the transition metal is characterized in that at least one member selected from the group consisting of manganese, iron, cobalt, nickel, chromium, titanium, vanadium and copper.
또한, 본 발명은 상기 제조방법으로 제조된 양극 소재를 포함하는 이차전지용 전극의 제조방법으로, In addition, the present invention is a method of manufacturing an electrode for a secondary battery comprising a positive electrode material manufactured by the above manufacturing method,
(a) 상기 제조방법으로 제조된 양극 소재와 도전재를 혼합한 후, 결합제를 혼합하여 전극활물질 슬러리를 제조하는 단계;(A) mixing the positive electrode material and the conductive material prepared by the above manufacturing method, and then mixing the binder to prepare an electrode active material slurry;
(b) 상기 슬러리를 집전체에 캐스팅하는 단계;(b) casting the slurry to a current collector;
(c) 상기 슬러리가 캐스팅된 집전체를 진공건조하는 단계를 포함하는 이차전지용 전극의 제조방법을 제공 한다.(c) a method of manufacturing an electrode for a secondary battery comprising vacuum drying the current collector to which the slurry is cast.
본 발명의 또 다른 구현예로, 상기 도전재는 카본블랙, 그라핀, 그라파이트 및 탄소나노튜브로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 한다.In another embodiment of the present invention, the conductive material is characterized in that at least one member selected from the group consisting of carbon black, graphene, graphite and carbon nanotubes.
본 발명의 또 다른 구현예로, 상기 결합제는 폴리비닐리덴플루오라이드(PVDF), 폴리아미드이미드(PAI), 폴리아크릴산(PAA) 및 폴리이미드(PI)로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 한다.In another embodiment of the present invention, the binder is one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polyamideimide (PAI), polyacrylic acid (PAA) and polyimide (PI). Is done.
본 발명의 또 다른 구현예로, 상기 집전체는 알루미늄, 구리, 및 니켈로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 한다.In another embodiment of the present invention, the current collector is characterized in that at least one member selected from the group consisting of aluminum, copper, and nickel.
본 발명의 또 다른 구현예로, 상기 (c)단계의 진공건조는 150 내지 180℃에서 수행되는 것을 특징으로 한다.In another embodiment of the present invention, the vacuum drying in step (c) is performed at 150 to 180 ° C.
또한, 본 발명은 상기 제조방법으로 제조된 양극 소재를 포함하는 이차전지용 전극을 제공한다.In addition, the present invention provides an electrode for a secondary battery comprising a positive electrode material manufactured by the above manufacturing method.
또한, 본 발명은 상기 이차전지용 전극을 포함하는 이차전지를 제공한다.In addition, the present invention provides a secondary battery comprising the electrode for the secondary battery.
아울러, 본 발명은 상기 제조방법으로 제조된 양극 소재를 포함하는 이차전지의 충방전 방법으로, 상기 이차전지를 1.5 내지 4V 범위 내에서 정전류 및 정전압으로 충전과 방전을 반복 수행하는 단계를 포함하는, 이차전지의 충방전 방법을 제공한다.In addition, the present invention is a method of charging and discharging a secondary battery including a positive electrode material manufactured by the manufacturing method, comprising the steps of repeatedly performing charging and discharging the secondary battery with a constant current and a constant voltage within a range of 1.5 to 4V, Provides a method for charging and discharging a secondary battery.
본 발명은 산화그래핀 소재를 프러시안 화이트 표면에 결착시킨 후 적절한 열처리를 통하여 프러시안 화이트의 구조 내부에 crystal water의 유입을 막음으로써 crystal water의 trap을 방지한 전극용 양극 소재를 제조하였다.The present invention prepared an anode material for an electrode that prevents trapping of crystal water by preventing crystal water from entering the structure of the Prussian white through proper heat treatment after binding the graphene oxide material to the Prussian white surface.
상기 양극 소재를 포함하는 전극을 이용하여 전지 제조시, 전해액과 crystal water사이의 반응을 억제할 수 있으므로, 전지의 수명 특성을 향상시킬 수 있다. When the battery is manufactured by using the electrode containing the positive electrode material, since the reaction between the electrolyte and crystal water can be suppressed, the life characteristics of the battery can be improved.
또한 상기 양극 소재의 구조특성으로 인해, crystal water가 위치해있던 자리에 금속 이온이 삽입될 수 있으므로, 충방전 시 낮은 전압까지 방전시켜 금속 이온을 삽입함으로써 초기 용량이 상승하여 사이클 특성을 향상시킬 수 있다.In addition, due to the structural characteristics of the positive electrode material, since metal ions can be inserted in a place where crystal water is located, the initial capacity increases by discharging the metal ions by discharging to a low voltage during charging and discharging, thereby improving cycle characteristics. .
도 1은 프러시안블루(좌)와 프러시안화이트(우)의 구조를 나타낸 도면이다.1 is a view showing the structure of Prussian Blue (left) and Prussian White (right).
도 2는 프러시안 화이트 구조체 내부에 나트륨 이온이 위치할 수 있는 자리를 나타낸 도면이다.2 is a view showing a position where sodium ions may be located inside a Prussian white structure.
도 3은 본 발명의 양극 소재 제조방법을 모식화하여 나타낸 도면이다.3 is a view schematically showing a method of manufacturing a positive electrode material according to the present invention.
도 4는 RGO/PW 분말의 특성을 확인한 결과로, 열처리 온도에 따른 수분 함유량을 확인한 결과를 나타낸 도면이다.4 is a view showing the results of confirming the properties of the RGO / PW powder, and confirming the moisture content according to the heat treatment temperature.
도 5는 RGO/PW 분말의 특성을 확인한 결과로, 산화그래핀이 환원되었는지 확인한 결과를 나타낸 도면이다.5 is a view showing the results of confirming the properties of the RGO / PW powder, confirming that the graphene oxide has been reduced.
도 6은 RGO/PW 분말의 특성을 확인한 결과로, 분말의 코팅 및 열처리 환경에 따른 상변화를 확인한 결과를 나타낸 도면이다.6 is a view showing the results of confirming the properties of the RGO / PW powder, and confirming the phase change according to the coating and heat treatment environment of the powder.
도 7은 본 발명의 제조방법으로 제조된 양극 소재를 포함하는 이차전지용 전극의 제조방법을 모식화하여 나타낸 도면이다.7 is a view schematically showing a method of manufacturing an electrode for a secondary battery including a positive electrode material produced by the manufacturing method of the present invention.
도 8은 RGO/PW 열처리 온도에 따른 전극셀의 성능을 확인한 결과를 나타낸 도면이다.8 is a view showing the results of confirming the performance of the electrode cell according to the RGO / PW heat treatment temperature.
도 9는 전극 건조 온도에 따른 전극의 성능을 확인한 결과를 나타낸 도면이다.9 is a view showing the results of confirming the performance of the electrode according to the electrode drying temperature.
도 10은 RGO 결착에 따른 전극셀의 성능을 확인한 결과를 나타낸 도면이다.10 is a view showing the results of confirming the performance of the electrode cell according to the RGO binding.
도 11은 본 발명의 방법으로 제조된 전지의 충방전 프로토콜을 확인한 결과를 나타낸 도면이다.11 is a view showing the results of confirming the charge and discharge protocol of the battery produced by the method of the present invention.
본 발명자들은 나트륨 이온 이차전지의 용량 및 수명을 향상시킬 수 있는 방안에 대하여 연구하던 중, 이차전지용 전극 소재에 주목하게 되었고, 상기 전극 소재로 환원된 산화그래핀이 표면에 결착된 프러시안화이트 소재를 포함하는 전극으로 이차전지를 제조할 경우 전지의 용량 및 수명을 향상시킬 수 있다는 것을 확인하여, 본 발명을 완성하였다.The present inventors focused on the electrode material for a secondary battery while studying a method for improving the capacity and life of the sodium ion secondary battery, and the Prussian white material with graphene oxide reduced to the electrode material adhered to the surface. When manufacturing a secondary battery with an electrode comprising a, it was confirmed that the capacity and life of the battery can be improved, thereby completing the present invention.
본 발명에서 제안하는 전극 소재는 환원된 산화그래핀이 표면에 결착된 프러시안화이트(reduced graphene oxide coated PW, 이하 RGO-PW)로, 코어 소재인 프러시안화이트(Prussian White, PW)는 프러시안블루(Prussian Blue, PB)의 유사체(PBA)로서, 기본적으로 AxMa[Mb(CN)6]의 MOFs (metal-organic-frameworks) 구조를 가진다.The electrode material proposed in the present invention is a reduced graphene oxide adhered to the surface of Prussian white (reduced graphene oxide coated PW, hereinafter RGO-PW), the core material of Prussian White (Prussian White, PW) is Prussian As an analog (PBA) of Prussian Blue (PB), it basically has a metal-organic-frameworks (MOFs) structure of A x M a [M b (CN) 6 ].
상기 PB는 도 1의 좌측에 나타낸 것과 같이 입방체 구조를 가지고 있으며, 제조시 구조물의 내부에 물이 착화합물을 이루게 되어, 구조를 붕괴시키고 이온 전달 방해로 인하여 용량을 감소시키며, 전기전도도를 감소시키게 된다(J. Mater. Chem. A, 2017, 5,18919). 그러나, 도 1의 우측에서 확인할 수 있는 것과 같이 PW는 PB에 비하여 구조면에서 Ax의 함량이 높아 높은 이론 용량을 가지고 있고, 도 2에서 확인할 수 있는 것과 같이 MOFs구조 내에 Ax가 공격자(vacancy)에 위치하게 되는데 이 공간의 사이즈가 5.13(Å3) 이상으로 Na ion의 삽탈리하기에 충분한 공간을 제공하여 빠른 율속으로 이온의 확산이 가능하여 고율특성이 우수한 장점을 가진다(Adv. Mater. 2016, 28, 7243-7248).The PB has a cubic structure as shown on the left side of FIG. 1, and water is formed as a complex compound inside the structure during manufacture, disintegrating the structure, reducing capacity due to ion transfer interference, and reducing electrical conductivity. (J. Mater. Chem. A, 2017, 5,18919). However, the A x in the MOFs structure as in Fig. And has a high theoretical capacity increase the amount of A x in structure compared to the PW is PB, as can be seen from the right side of Fig. 1, it can also be found in the second attacker (vacancy ), The size of this space is 5.1 33 ) or more, providing sufficient space for the removal and removal of Na ions, so the diffusion of ions at a rapid rate is possible, and it has the advantage of high rate characteristics (Adv. Mater 2016, 28, 7243-7248).
그러나 PW 합성시 -C≡N- bonding에 결함(defect)이 형성되기 쉬워 이 위치에 공기 중에 존재하는 H2O가 crystal water로 trap되기 쉽다. 이 crystal water는 충방전시 전극 밖으로 유출되면서 전해액과 반응하여 분해를 일으키게 되고 전극소재들과의 부반응을 진행시켜 전지의 수명특성에 악영향을 미치게 된다. However, when PW is synthesized, defects are easily formed in -C≡N-bonding, and H 2 O present in the air at this location is easily trapped by crystal water. As this crystal water flows out of the electrode during charging and discharging, it reacts with the electrolyte to cause decomposition, and proceeds with side reactions with the electrode materials, adversely affecting the life characteristics of the battery.
따라서 본 발명에서는 상기 현상을 방지하기 위해, RGO 소재를 PW 표면에 결착시킨 후 적절한 열처리를 통하여 crystal water의 유입을 막음으로써 crystal water의 trap을 막아 전지 제조시 전해액과 crystal water사이의 반응을 억제함으로써 전지의 수명 특성을 향상시켰다. 또한 소재의 구조특성으로 인한 충방전 시 Na ion의 확산 형태가 충전프로토콜 방식에 다름을 이용하여 사이클 특성을 향상시켰다.Therefore, in the present invention, in order to prevent the above phenomenon, the RGO material is bound to the PW surface and then the inflow of crystal water through appropriate heat treatment prevents the trap of crystal water to suppress the reaction between the electrolyte and crystal water during battery manufacturing. The life characteristics of the battery were improved. In addition, due to the structural characteristics of the material, the diffusion form of Na ions during charging and discharging differs from the charging protocol method to improve the cycle characteristics.
즉, 본 발명은, 도 3에 도시한 것을 참고하여 하기 단계를 포함하는 이차전지용 양극(cathode, 환원전극) 소재의 제조방법을 제공할 수 있다.That is, the present invention can provide a method of manufacturing a cathode (cathode, cathode) material for a secondary battery including the following steps with reference to FIG. 3.
프러시안 화이트 용액 및 산화그래핀 용액을 혼합하는 단계(S1);Mixing a prussian white solution and a graphene oxide solution (S1);
상기 S1 단계의 용액을 교반한 후, 분무 건조하여 산화그래핀이 프러시안 화이트의 표면에 결착된 분말을 제조하는 단계(S2); 및After stirring the solution of the step S1, spray-dried to prepare a powder of graphene oxide bound to the surface of the prussian white (S2); And
상기 S2 단계의 분말을 열처리하여, 상기 프러시안 화이트의 표면에 결착된 산화그래핀을 환원하는 단계(S3).Step S3 of heat-treating the powder of the step S2 to reduce graphene oxide bound to the surface of the prussian white (S3).
본 발명에서 상기 프러시안 화이트 용액은 하기 화학식 1로 표시되는 화합물을 포함하는 것이다.In the present invention, the Prussian white solution includes a compound represented by Formula 1 below.
[화학식 1][Formula 1]
AxMa[Mb(CN)6]A x M a [M b (CN) 6 ]
상기 화학식 1에서 A는 알칼리 금속 또는 알칼리토금속이고, Ma 및 Mb는 전이금속이며, x는 0~2, a는 0~1, b는 0~1이다.In Formula 1, A is an alkali metal or alkaline earth metal, Ma and Mb are transition metals, x is 0-2, a is 0-1, and b is 0-1.
본 발명에서 상기 알칼리 금속은 나트륨, 리튬, 또는 칼륨 등일 수 있고, 알칼리 토금속은 마그네슘, 칼슘, 또는 스트론튬 등일 수 있으며, 상기 금속의 종류에 제한되는 것은 아니고, 상기 전이금속은 망가니즈, 철, 코발트, 니켈, 크롬, 티타늄, 바나듐 또는 구리 등일 수 있으며, 안전성 및 합성에 영향을 미치지 않는 전이금속이라면 제한없이 이용가능하다.In the present invention, the alkali metal may be sodium, lithium, or potassium, and the alkaline earth metal may be magnesium, calcium, or strontium, but is not limited to the type of the metal, and the transition metal is manganese, iron, cobalt , Nickel, chromium, titanium, vanadium or copper, and any transition metal that does not affect safety and synthesis may be used without limitation.
본 발명에서 S2 단계의 분무 건조는 100 내지 150℃로 수행되는 것일 수 있고, 상기 분무 건조는 진공 건조를 기본으로 하며, 분말 회수시 분위기를 비활성 기체 (아르곤, 헬륨, 질소 등) 분위기에서 하는 방식에 의해 수행되는 것일 수 있으나 이에 제한되지 않는다.In the present invention, the spray drying in step S2 may be performed at 100 to 150 ° C., and the spray drying is based on vacuum drying, and the atmosphere is in an inert gas (argon, helium, nitrogen, etc.) atmosphere during powder recovery. It may be performed by, but is not limited to.
상기 S3 단계의 열처리는 120 내지 220℃로 60 내지 180 분 동안 수행될 수 있으나 이에 제한되는 것은 아니며, 상기와 같이 열처리에 의해 프러시안 화이트 구조체의 표면에 결착된 산화그래핀이 환원되는 것이다. 상기 환원은 공기(air) 분위기 또는 산소 분위기에서 수행될 수 있다.The heat treatment of step S3 may be performed at 120 to 220 ° C. for 60 to 180 minutes, but is not limited thereto, and the graphene oxide bound to the surface of the prussian white structure is reduced by heat treatment as described above. The reduction may be performed in an air atmosphere or an oxygen atmosphere.
상기와 같은 분무 건조 및 열처리로 인해 프러시안 화이트 구조체 내부의에 H2O가 crystal water로 트랩되는 현상을 방지할 수 있는 것이다.Due to the spray drying and heat treatment as described above, it is possible to prevent the phenomenon of trapping H 2 O into crystal water inside the Prussian white structure.
또한, 본 발명은 도 7에 도시한 내용을 참고하여, 상기 제조방법으로 제조된 양극 소재를 포함하는 이차전지용 전극의 제조방법으로, In addition, the present invention is a method of manufacturing an electrode for a secondary battery including a positive electrode material manufactured by the above manufacturing method with reference to the contents shown in FIG. 7.
(a) 상기 제조방법으로 제조된 양극 소재와 도전재를 혼합한 후, 결합제를 혼합하여 전극활물질 슬러리를 제조하는 단계;(A) mixing the positive electrode material and the conductive material prepared by the above manufacturing method, and then mixing the binder to prepare an electrode active material slurry;
(b) 상기 슬러리를 집전체에 캐스팅하는 단계;(b) casting the slurry to a current collector;
(c) 상기 슬러리가 캐스팅된 집전체를 진공건조하는 단계를 포함하는 이차전지용 전극의 제조방법을 제공한다.(c) a method of manufacturing an electrode for a secondary battery comprising vacuum drying the current collector to which the slurry is cast.
본 발명에서 상기 도전재는 카본블랙, 그라핀, 그라파이트, 또는 탄소나노튜브 등일 수 있고, 상기 카본블랙 중 SPB, KB 등이 이용되는 것이나, 도전성을 나타내는 물질이라면 제한없이 이용이 가능하다.In the present invention, the conductive material may be carbon black, graphene, graphite, or carbon nanotubes, and SPB, KB, or the like is used among the carbon black, but any material exhibiting conductivity may be used without limitation.
본 발명에서 상기 결합제는 폴리비닐리덴플루오라이드(PVDF), 폴리아미드이미드(PAI), 폴리아크릴산(PAA) 또는 폴리이미드(PI) 등일 수 있으나, 상기 양극활물질과 도전재를 결합하여 슬러리로 제조하기 위한 바인더 역할을 할 수 있는 물질이라면 이에 제한되는 것은 아니다.In the present invention, the binder may be polyvinylidene fluoride (PVDF), polyamideimide (PAI), polyacrylic acid (PAA) or polyimide (PI), etc., but preparing the slurry by combining the positive electrode active material and a conductive material If the material that can serve as a binder for is not limited thereto.
본 발명에서 상기 집전체는 알루미늄, 구리, 또는 니켈 등일 수 있으며, 전극의 집전체로 이용될 수 있는 것이라면 이에 제한되지 않는다.In the present invention, the current collector may be aluminum, copper, nickel, or the like, and is not limited thereto as long as it can be used as the current collector of the electrode.
본 발명에서 상기 (c)단계의 진공건조는 150 내지 180℃에서 10-4 torr 내지 10-2 torr 기압 하에서 8시간 내지 36시간 수행되는 것일 수 있다. 상기 진공건조 단계 이후 불활성 가스로 배기(purging)하는 단계를 더 포함한다. 상기 불활성 가스는 아르곤 가스를 이용할 수 있으나 이에 제한되지는 않는다.In the present invention, the vacuum drying in step (c) may be performed at 150 to 180 ° C. for 8 to 36 hours under 10 −4 torr to 10 −2 torr air pressure. After the vacuum drying step further comprises a step of purging (purging) with an inert gas. Argon gas may be used as the inert gas, but is not limited thereto.
또한, 본 발명은 상기 제조방법으로 제조된 양극 소재를 포함하는 이차전지용 전극을 제공할 수 있으며, 상술한 양극 소재 외에 전극에 포함될 수 있는 첨가제는 제한없이 포함될 수 있다.In addition, the present invention can provide an electrode for a secondary battery including a positive electrode material manufactured by the above manufacturing method, and additives that can be included in the electrode in addition to the positive electrode material described above may be included without limitation.
또한, 본 발명은 상기 이차전지용 전극을 포함하는 이차전지를 제공할 수 있으며, 상기 전극 외에 이차전지의 구동을 위해 필요한 음극(anode, 산화전극), 전해액, 및 분리막의 종류에는 제한이 없다.In addition, the present invention can provide a secondary battery including the electrode for the secondary battery, there is no limitation on the type of cathode (anode, oxide electrode), electrolyte, and separator required for driving the secondary battery in addition to the electrode.
아울러, 본 발명은 상기 제조방법으로 제조된 양극활물질을 포함하는 이차전지의 충방전 방법으로, 상기 이차전지를 1.5 내지 4V 범위 내에서 정전류 및 정전압으로 충전과 방전을 반복 수행하는 단계를 포함하는, 이차전지의 충방전 방법을 제공한다.In addition, the present invention is a method for charging and discharging a secondary battery including a positive electrode active material prepared by the above manufacturing method, the method comprising repeatedly performing charging and discharging the secondary battery with a constant current and a constant voltage within a range of 1.5 to 4V, Provides a method for charging and discharging a secondary battery.
상기와 같이 낮은 전압까지 방전하여, 에너지적으로 상대적으로 불안정한 자리인 crystal water가 위치해 있던 자리에 금속 이온이 위치하도록함으로써, PW 구조를 유지하면서 다른 금속 이온들의 삽탈리가 원활하게 이루어지도록 한 것으로, 상기 충방전 방법을 통해 상기 위치(도 2의 24d 참고)까지 Na ion을 삽입한 것이다.By discharging to a low voltage as described above, the metal ions are located at the sites where the crystal water, which is an energy-relatively unstable site, is located, so that the other metal ions are smoothly detached while maintaining the PW structure. Through the charging and discharging method, Na ions are inserted to the position (see 24d in FIG. 2).
본 발명의 실시예에서, 본 발명과 같은 방식으로 제조된 양극소재(양극활물질)인 환원된 산화그래핀이 결착된 프러시안 화이트 분말(RGO/PW)을 대상으로 온도에 따른 수분 함유량을 측정한 결과, PW, GO/PW 등과 비교하여 현저히 적은 수분 함유량이 확인되었으며, 상기 양극활물질을 이용하여 제조된 전극을 포함한 전지에서 우수한 초기 용량 및 충방전 효율이 확인되었다.In an embodiment of the present invention, the moisture content according to temperature was measured for a Prussian white powder (RGO / PW) bound with reduced graphene oxide, a positive electrode material (positive electrode active material) prepared in the same manner as the present invention. As a result, a significantly less moisture content was confirmed compared to PW, GO / PW, and the like, and excellent initial capacity and charging / discharging efficiency were confirmed in a battery including an electrode manufactured using the positive electrode active material.
이하, 실시예를 통하여 본 발명을 상세하게 설명하고자 한다. 이들 실시예는 오로지 본 발명을 예시하기 위한 것으로서, 본 발명의 범위가 이들 실시예에 의해 제한되는 것으로 해석되지는 않는 것은 당업계에서 통상의 지식을 가진 자에게 있어서 자명할 것이다.Hereinafter, the present invention will be described in detail through examples. These examples are only for illustrating the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not to be construed as limited by these examples.
[실시예][Example]
이하, 실시예를 통하여 본 발명을 더욱 상세히 설명하기로 한다. 이들 실시예는 단지 본 발명을 예시하기 위한 것이므로, 본 발명의 범위가 이들 실시예에 의해 제한되는 것으로 해석되지는 않는다.Hereinafter, the present invention will be described in more detail through examples. Since these examples are only for illustrating the present invention, it should not be construed that the scope of the present invention is limited by these examples.
실시예 1. RGO/PW 분말의 제조Example 1. Preparation of RGO / PW powder
양극 소재의 제조를 위해, 도 3의 방법과 같이 PW 용액과 GO 용액을 준비하였다. 상기 PW 용액은 PW 9.1g을 증류수 100 mL에 용해시켜 제조된 것을 이용하였고, GO 용액은 GO 0.1g을 정량(전체 용액의 9%) 하여 증류수 100mL에 용해시켜 제조된 것을 이용하였다.For the production of the positive electrode material, a PW solution and a GO solution were prepared as shown in FIG. 3. The PW solution was prepared by dissolving 9.1 g of PW in 100 mL of distilled water, and the GO solution was prepared by quantifying 0.1 g of GO (9% of the total solution) and dissolving it in 100 mL of distilled water.
상기 PW 용액 및 GO 용액을 반응조에 넣고, 300rpm의 속도로 교반하여 혼합해주었다. 혼합된 용액은 스프레이 드라이어 장비를 통해 분무 건조하여, GO/PW 분말을 수득하였다.The PW solution and the GO solution were put in a reaction tank and mixed by stirring at a rate of 300 rpm. The mixed solution was spray dried through a spray dryer equipment to obtain GO / PW powder.
상기 수득된 GO/PW 분말은 220℃에서 60-180분 동안 열처리하여, PW의 표면에 결착된 GO를 환원시켜주었다.The obtained GO / PW powder was heat treated at 220 ° C. for 60-180 minutes to reduce GO bound on the surface of PW.
실시예 2. RGO/PW 분말의 특성 확인Example 2. Confirmation of the properties of the RGO / PW powder
2.1. RGO/PW 분말의 수분 함유량 확인2.1. Check the moisture content of RGO / PW powder
상기 실시예 1에서 제조된 RGO/PW 분말을 대상으로 TGA 분석을 통해 수분 함유량을 확인하였다. 수분 함량을 최대화한 PW/water 시료, RGO/PW/water 시료, 일반 환경에서 보관한 air dry PW 시료, air dry RGO/PW 시료, GO/PW/water 시료를 대상으로, SDT Q600 TGA 열분석기를 통해 수분 함유량을 확인하였다.The water content was confirmed through TGA analysis on the RGO / PW powder prepared in Example 1. SDT Q600 TGA thermal analyzer for PW / water samples with maximum moisture content, RGO / PW / water samples, air dry PW samples stored in normal environments, air dry RGO / PW samples, and GO / PW / water samples Through the water content was confirmed.
그 결과, 도 4에 나타낸 것과 같이, 열처리 온도가 증가하여도 air dry RGO/PW 및 RGO/PW/water 에서 무게변화가 거의 없고, 특히 air dry RGO/PW에서 100~220℃에서 99.5%로 무게가 변화하지 않는 결과를 보였다. 상기 결과를 통해 계산된 수분 함유량은 1.6% 미만으로 확인되었으며, 이를 볼 때 구조체 내부에 트랩된 수분이 거의 없다는 점을 알 수 있다.As a result, as shown in FIG. 4, even when the heat treatment temperature is increased, there is little weight change in air dry RGO / PW and RGO / PW / water, especially in air dry RGO / PW, the weight is 99.5% at 100-220 ° C. Showed unchanged results. Through the above results, the calculated moisture content was found to be less than 1.6%, and it can be seen that there is little trapped moisture inside the structure.
2.2. GO reduction 확인2.2. GO reduction check
상기 실시예 1에서 제조된 RGO/PW 분말을 대상으로 라만 분석을 통해 GO가 잘 환원되었는지 확인하였다. RGO-PW 시료, GO-PW 시료, 및 PW 시료를 대상으로, NTEGRA SPECTRA, NT-MDT 라만분광기를 통해 0-4000cm-1까지 스펙트럼을 획득하여 확인하고자 하였다.It was confirmed through the Raman analysis on the RGO / PW powder prepared in Example 1 that GO was well reduced. For RGO-PW samples, GO-PW samples, and PW samples, spectra were obtained by acquiring up to 0-4000 cm -1 through NTEGRA SPECTRA and NT-MDT Raman spectrometers.
그 결과, 도 5에 나타낸 것과 같이, PW의 표면에 결착된 GO가 RGO로 잘 환원되었는지 D/G ratio 값을 확인함으로써 1.02 → 1.22 수치로의 향상된 결과를 보였는바, GO-PW 분말의 열처리를 통해 GO가 RGO로 일정 비율 잘 환원되었음을 알 수 있다.As a result, as shown in Fig. 5, by confirming the D / G ratio value of whether the GO bound to the surface of PW was reduced to RGO well, it showed an improved result to a value of 1.02 → 1.22, heat treatment of GO-PW powder It can be seen that GO has been reduced to a certain percentage by RGO.
2.3. GO reduction 전후 및 열처리 환경에 따른 상변화 확인2.3. Confirmation of phase change according to GO reduction before and after and heat treatment environment
RGO-PW 시료, GO-PW 시료, 및 PW 시료를 대상으로, XRD (X-pert PRO MPD)를 이용하여 코팅 및 열처리 환경에 따른 상변화를 확인하였으며, 분석 조건은 하기와 같다.For RGO-PW samples, GO-PW samples, and PW samples, phase changes according to coating and heat treatment environments were confirmed using XRD (X-pert PRO MPD), and the analysis conditions are as follows.
획득한 각 파우더 샘플들을 X-ray diffraction측정을 위한 측정 홀더에 넣고 장비에 장착한 후 2theta 범위 10~90°에서 측정하였다. TGA결과상으로 비활성 기체 분위기에서 350℃까지는 무게변화가 없으나 air분위기에서는 상변화가 200℃ 이하부터 있는 것으로 확인되어 GO의 환원과정 중 산소분위기에서 열처리 과정이 존재하기 때문에 이때 PW의 상변화가 일어나는지를 확인하기 위하여 환원 단계별로 열처리 분위기별 전후의 상변화를 XRD를 측정하여 확인하였다. 이때 본 발명에서 활용한 GO의 환원 방법이 산소분위기에서 220℃ 3시간 동안 열처리를 통하여 PW와 결정수 사이에 결합되어 있는 electrostatic binding을 통하여 electron transfer가 일어나면서 GO에 작용기 그룹 (-OH, -COOH etc.)에 에너지 전달을 하며 이 그룹이 CO2 내지 H2O로 분해되어 배출하는 형태로 환원이 진행된다. 상변화 확인 테스트를 위한 열처리 분위기는 PW가 안정한 Ar 분위기 및 GO가 RGO 로 환원되는 air 분위기에서 테스트 하였고, PW와 GO-PW는 코팅되기 전후 및 GO가 RGO로 환원되기 전후 단계의 대조군 데이터로 확보하기 위하여 열처리를 하지 않고 측정하였다.Each obtained powder sample was placed in a measuring holder for X-ray diffraction measurement, mounted on a device, and measured in a 2theta range of 10 to 90 °. As a result of TGA, there is no weight change up to 350 ℃ in an inert gas atmosphere, but it is confirmed that the phase change is below 200 ℃ in the air atmosphere, so there is a heat treatment process in the oxygen atmosphere during the reduction process of GO. In order to check the phase change before and after the heat treatment atmosphere in the reduction step, XRD was measured. At this time, the reduction method of GO utilized in the present invention is a group of functional groups in GO (-OH, -COOH) as electron transfer occurs through electrostatic binding bound between PW and crystalline water through heat treatment for 3 hours at 220 ° C. in an oxygen atmosphere. etc.), and this group is decomposed into CO 2 to H 2 O, and the reduction proceeds. The heat treatment atmosphere for the phase change confirmation test was tested in a stable Ar atmosphere with PW and an air atmosphere where GO is reduced to RGO, and PW and GO-PW are secured as control data before and after coating and before and after GO is reduced to RGO. In order to do so, it was measured without heat treatment.
그 결과, 도 6의 좌측의 as-prepared 상태의 샘플들의 XRD 스펙트럼에서 나타낸 것과 같이, PW는 Rhombohedral-monoclinic phase가 공존하는 것이 나타났고, GO를 코팅한 GO/PW는 열처리 되지 않은 상태에서 monoclinic 상을 보여주었다. 또한, 도 6의 우측의 열처리 환경에 따른 XRD 스펙트럼결과에서 나타낸 것과 같이, as-prepared 상태의 PW를 air 코팅된 GO를 환원한 RGO/PW의 경우 확실한 Rhombohedral 상을 보여주었다. 상기 결과를 통해, 본 발명의 제조방법을 통해 제조되는 RGO/PW는 수분에 거의 노출되지 않고, 금속 이온이 쉽게 삽탈리될 수 있는 안정한 Rhombohedral상을 가지고 있다는 것을 확인하였다.As a result, as shown in the XRD spectrum of the samples in the as-prepared state on the left side of FIG. 6, it was shown that the Rhombohedral-monoclinic phase coexisted, and the GO / PW coated with GO was a monoclinic phase without heat treatment. Showed. In addition, as shown in the XRD spectrum result according to the heat treatment environment on the right side of FIG. 6, in the case of RGO / PW in which PW in the as-prepared state was reduced by air-coated GO, a clear Rhombohedral phase was shown. Through the above results, it was confirmed that the RGO / PW produced through the manufacturing method of the present invention is hardly exposed to moisture and has a stable Rhombohedral phase in which metal ions can be easily desorbed.
실시예 3. 전극 제조Example 3. Preparation of electrodes
본 실시예 3에서는 실시예 1에서 제조된 RGO/PW를 포함하는 전극을 제조하였다. 도 7에 나타낸 것과 같이 RGO/PW 0.7 g에 도전재로 SPB를 0.2g 혼합하여 건믹싱하였고, 건믹싱된 분말을 슬러리로 제조하기 위해 바인더로 PVDF 0.1g를 첨가한 후 믹서기(THINKY, Japan)를 이용하여 2000rpm으로 1분 동안 혼합하여 전극활물질 슬러리를 제조하였다. In Example 3, an electrode including the RGO / PW prepared in Example 1 was prepared. As shown in Fig. 7, 0.2 g of SPB was mixed with 0.7 g of RGO / PW as a conductive material, followed by dry mixing, and after adding 0.1 g of PVDF as a binder to prepare the dry-mixed powder as a slurry, a blender (THINKY, Japan) The electrode active material slurry was prepared by mixing at 2000 rpm for 1 minute.
상술한 바와 같이 제조된 슬러리는 집전체로 16㎛ 두께의 알루미늄 호일(Al foil)에 캐스팅 공정에 의해 13㎛로 캐스팅하여 필름 형태로 제조하였다. 슬러리가 도포된 전극은 170℃의 온도에서 진공 건조기에서 충분히 건조(overnight)하였다.The slurry prepared as described above was cast in an aluminum foil having a thickness of 16 μm as a current collector to 13 μm by a casting process to prepare a film. The electrode coated with the slurry was sufficiently dried in a vacuum dryer at a temperature of 170 ° C.
이와 같이 준비된 전극의 전기화학 특성을 평가하기 위하여 코인셀 및 3극셀을 제작하였다. 상세하게는, 코인셀은 리튬 메탈을 음극으로 하고, PE Separator, 프로필렌 카보네이트(PC)와 폴리 프로필렌(PP) 혼합용매(부피비 9.5:0.5)에 1몰 NaClO4 염 및 2wt% 플루오로에틸렌 카보네이트(FEC) 첨가제가 용해된 용액을 전해액으로 사용하고, 조립순서에 의해 2032 규격의 코인형 전지를 제작하였다. 그리고 3극셀은 특수 제작된 셀을 이용하였으며, 작동전극은 상술한 실시예에 의해 제조된 양극복합소재, 대극은 Na 메탈, 그리고 참조전극은 Na 메탈로 하였다.In order to evaluate the electrochemical properties of the prepared electrode, coin cells and 3-pole cells were manufactured. Specifically, the coin cell is a lithium metal as a negative electrode, PE Separator, propylene carbonate (PC) and polypropylene (PP) mixed solvent (volume ratio 9.5: 0.5) 1 mol NaClO 4 salt and 2wt% fluoroethylene carbonate ( FEC) A solution in which the additive was dissolved was used as an electrolytic solution, and a coin-type battery of 2032 standard was manufactured by assembly order. And the three-pole cell used a specially manufactured cell, the working electrode was a positive electrode composite material prepared by the above-described embodiment, the counter electrode was made of Na metal, and the reference electrode was made of Na metal.
실시예 4. 전극의 전기화학적 특성 확인Example 4. Confirmation of the electrochemical properties of the electrode
4.1. RGO/PW 열처리 온도에 따른 전극셀의 성능 확인4.1. Confirmation of electrode cell performance according to RGO / PW heat treatment temperature
본 실시예 4.1에서는 RGO/PW 분말의 열처리 온도에 의해 구조체 내에 포함된 수분의 함량이 전지의 성능에 미치는 영향을 확인하고자 하였다. 이에 실시예 3의 방법을 제조한 전극셀을 이용하였고, 비교를 위해 실시예 1의 RGO/PW 분말의 제조방법으로 제조되되, 170℃에서 열처리된 RGO/PW를 포함하는 전극을 이용한 전극셀도 제조하였다.In Example 4.1, the purpose of this study was to determine the effect of the moisture content in the structure on the performance of the battery by the heat treatment temperature of the RGO / PW powder. Thus, an electrode cell prepared in the method of Example 3 was used, and for comparison, an electrode cell using an electrode comprising RGO / PW heat-treated at 170 ° C., which was prepared by the method of manufacturing RGO / PW powder in Example 1 It was prepared.
상기 전극의 충방전 조건으로 2~4V 전압 범위에서 정전류/정전압으로 충방전을 실시하였으며, 상기 전극의 산화 및 환원 거동을 전위주사법으로 확인한 결과를 도 8에 기재하였다. The charging and discharging was performed at a constant current / constant voltage in a voltage range of 2 to 4 V as a charging / discharging condition of the electrode, and the results of confirming the oxidation and reduction behavior of the electrode by a potential scanning method are shown in FIG.
도 8에서 확인할 수 있는 것과 같이, 170℃로 열처리한 RGO/PW 분말을 이용한 경우 초기 용량이 220℃로 열처리한 경우와 비교하여 낮은 초기용량을 보였고, 충방전 싸이클의 증가함에 따라 용량이 감소되는 결과를 보여, 용량 보존율 역시 떨어진다는 것이 확인되었다.As can be seen in FIG. 8, when using RGO / PW powder heat-treated at 170 ° C, the initial capacity showed a lower initial capacity compared to the case at heat-treatment at 220 ° C, and the capacity decreased as the charge / discharge cycles increased. As a result, it was confirmed that the capacity retention rate also fell.
상기 결과를 통해, 본 발명에서 제안하는 전극활물질 제조 후 파우더의 열처리 온도를 220℃로 할 경우 용량 보존율이 낮은 온도에서 보다 우수하다는 것을 확인하였다.Through the above results, it was confirmed that when the heat treatment temperature of the powder after preparing the electrode active material proposed in the present invention is 220 ° C, the capacity retention rate is better at a lower temperature.
4.2. 전극 건조 온도에 따른 전극의 성능 확인4.2. Confirmation of electrode performance according to electrode drying temperature
본 실시예 4.2에서는 RGO/PW 소재를 포함하여 제조된 전극의 건조 조건에 의해 전극 내부에 포함된 수분의 함량이 전지의 성능에 미치는 영향을 확인하고자 하였다. 이에 실시예 3의 방법을 제조한 전지를 이용하였고, 비교를 위해 실시예 3의 제조방법으로 제조되되, 집전체에 슬러리를 캐스팅한 후 건조 온도를 120℃에서 수행한 전지를 제조하였다. 전극셀들이 안정적으로 제조되는지 확인하기 위하여 각 전극셀을 5개씩 제조하였다.In Example 4.2, it was intended to confirm the effect of the moisture content contained inside the electrode on the performance of the battery by the drying conditions of the electrode made of the RGO / PW material. Thus, a battery prepared in the method of Example 3 was used, and for comparison, a battery prepared by the method of Example 3 was prepared, and the slurry was cast in a current collector and then dried at 120 ° C. In order to confirm that the electrode cells were manufactured stably, each electrode cell was manufactured in five.
상기 전극의 충방전 조건으로 2~4V 전압 범위에서 정전류/정전압으로 충방전을 실시하였으며, 상기 전극의 산화 및 환원 거동을 전위주사법으로 확인한 결과를 도 9에 기재하였다. Charging and discharging was performed at a constant current / constant voltage in a voltage range of 2 to 4 V as a condition for charging and discharging the electrode, and the results of confirming the oxidation and reduction behavior of the electrode by a potential scanning method are shown in FIG. 9.
도 9 에서 확인할 수 있는 것과 같이, 170℃로 열처리한 전극셀의 경우 170℃로 열처리한 경우와 비교하여 셀간 편차가 적은 것이 확인되어, 본 발명의 제조방법에 의해 전지가 안정적으로 제조된다는 것을 알 수 있다.As can be seen in Figure 9, in the case of the electrode cell heat-treated at 170 ° C, it was confirmed that the variation between cells is less than that when heat-treated at 170 ° C, it is found that the battery is stably manufactured by the manufacturing method of the present invention. You can.
4.3. RGO 결착에 따른 전극셀의 성능 확인4.3. Confirmation of electrode cell performance according to RGO binding
본 실시예 4.3에서는 RGO/PW 분말을 이용한 전극셀과 PW 분말을 이용한 전극셀의 초기 용량 및 사이클 특성을 확인하고자 하였다. 이에 실시예 3의 방법을 제조한 전극셀을 이용하였고, 비교를 위해 GO가 처리되지 않은 PW를 포함하는 전극을 이용한 전극셀도 제조하였다.In Example 4.3, the initial capacity and cycle characteristics of the electrode cell using RGO / PW powder and the electrode cell using PW powder were examined. Thus, an electrode cell prepared in the method of Example 3 was used, and for comparison, an electrode cell using an electrode containing PW without GO treatment was also prepared.
상기 전극의 충방전 조건으로 2~4V 전압 범위에서 정전류/정전압으로 충방전을 실시하였으며, 상기 전극의 산화 및 환원 거동을 전위주사법으로 확인한 결과를 도 10에 기재하였다. Charging and discharging was performed at a constant current / constant voltage in a voltage range of 2 to 4 V as a condition for charging and discharging the electrode, and the results of confirming the oxidation and reduction behavior of the electrode by a potential scanning method are shown in FIG.
도 10에서 확인할 수 있는 것과 같이, RGO/PW 분말을 이용한 경우, PW를 단독으로 사용한 경우와 비교하여 더 높은 초기용량을 보였고, 충방전 싸이클이 증가함에 따라 용량이 덜 감소되는 결과를 보여, 용량 보존율 역시 우수하다는 것을 확인하였다.As can be seen in Figure 10, when using the RGO / PW powder, it showed a higher initial capacity compared to the case of using PW alone, the results show that the capacity decreases less as the charge / discharge cycle increases, the capacity It was confirmed that the preservation rate was also excellent.
상기 결과를 통해, 본 발명의 제조방법으로 제조된 RGO/PW를 이용할 경우 초기 용량이 우수하며 용량 보존율이 우수하다는 것을 확인하였다.Through the above results, when using the RGO / PW produced by the production method of the present invention was confirmed that the initial capacity is excellent and the capacity retention rate is excellent.
실시예 5. 충방전 특성 확인Example 5. Checking the charge and discharge characteristics
본 실시예 5에서는 본 발명에서 제조한 전지의 효율적인 충방전 방식을 확인하고자 하였다. 이에 실시예 3의 방법을 제조한 전극셀을 이용하여, 충방전 방법을 초기화성 조건과 사이클 조건의 전압범위 및 충방전 속도를 변화시켜 줌으로써 충방전 프로토콜을 결정하고자 하였다.In Example 5, an efficient charging / discharging method of the battery manufactured in the present invention was intended. Thus, by using the electrode cell prepared in Example 3, the charging and discharging method was determined by changing the voltage range and the charging and discharging speed of the initializing condition and the cycle condition.
기존 PW를 사용한 충방전시 crystal water가 위치해 있던 자리는 에너지적으로 훨씬 불안정한 자리로, 본 발명의 방법으로 제조된 RGO/PW를 사용할 경우 이 부분에 Na ion이 위치하게 되어 PW 구조를 유지하면서 다른 Na ion들의 삽탈리가 원활하게 이루어질 것으로 판단되었다. 따라서 본 실시예 5에서는 이 위치까지 Na ion을 삽입하게 하기 위하여 초기 사이클에서 1.5V의 낮은 전압까지 방전하여 강제적으로 Na ion을 위치시키고자 하였다.The place where crystal water was located during charging and discharging using the existing PW is a much more unstable place in energy, and when using RGO / PW manufactured by the method of the present invention, Na ion is located in this part while maintaining the PW structure. It was judged that the removal and removal of Na ions would be smooth. Therefore, in Example 5, in order to insert Na ions up to this position, the Na ion was forcibly positioned by discharging to a low voltage of 1.5 V in the initial cycle.
그 결과 도 11에서 확인할 수 있는 것과 같이, 초기 효율 증가 및 columbic efficiency가 향상되는 결과를 보여, 본 발명에서 제안한 충방전 프로토콜 변화를 통한 Na ion 삽탈리 형태의 변화가 수명 효율에 긍정적인 효과를 준다는 것이 확인되었다. As a result, as can be seen in FIG. 11, the initial efficiency increase and the columbic efficiency are improved, and the change in Na ion spatali form through the change in the charging and discharging protocol proposed in the present invention has a positive effect on life efficiency. Was confirmed.
상기 결과를 통해, 본 발명의 양극 소재를 포함하는 전극을 이용한 전지는 CC-CV, 0.05C~0.1C, voltage range/1.5~4V의 방식으로 충방전하는 것이 바람직하다는 것을 확인하였다.Through the above results, it was confirmed that the battery using the electrode containing the positive electrode material of the present invention is preferable to charge and discharge in the manner of CC-CV, 0.05C to 0.1C, voltage range / 1.5 to 4V.
이상에서 본 발명의 바람직한 실시예에 대하여 상세하게 설명하였지만 본 발명의 권리는 이에 한정되는 것은 아니고 다음의 청구범위에서 정의하고 있는 본 발명의 기본 개념을 이용한 당업자의 여러 변형 및 개량 형태 또한 본 발명의 권리범위에 속하는 것이다.Although the preferred embodiments of the present invention have been described in detail above, the rights of the present invention are not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.
본 발명은 산화그래핀 소재를 프러시안 화이트 표면에 결착시킨 후 적절한 열처리를 통하여 프러시안 화이트의 구조 내부에 crystal water의 유입을 막음으로써 crystal water의 trap을 방지한 전극용 양극 소재를 제공하는 것으로, 상기 양극 소재를 이용하여 수명 특성과 용량이 향상된 이차전지를 제공할 수 있으므로, 본 발명은 이차전지 산업 분야에서 유용하게 이용될 수 있다.The present invention is to provide a positive electrode material for preventing the trapping of crystal water by preventing the inflow of crystal water into the structure of the Prussian white through proper heat treatment after binding the graphene oxide material to the Prussian white surface, Since it is possible to provide a secondary battery with improved life characteristics and capacity by using the positive electrode material, the present invention can be usefully used in the secondary battery industry.

Claims (16)

  1. 이차전지용 양극 소재의 제조방법에 있어서,In the method of manufacturing a positive electrode material for a secondary battery,
    프러시안 화이트 용액 및 산화그래핀 용액을 혼합하는 단계(S1);Mixing a prussian white solution and a graphene oxide solution (S1);
    상기 S1 단계의 용액을 교반한 후, 분무 건조하여 산화그래핀이 프러시안 화이트의 표면에 결착된 분말을 제조하는 단계(S2); 및After stirring the solution of the step S1, spray-dried to prepare a powder of graphene oxide bound to the surface of the prussian white (S2); And
    상기 S2 단계의 분말을 열처리하여, 상기 프러시안 화이트의 표면에 결착된 산화그래핀을 환원하는 단계(S3)를 포함하고,Including the step (S3) of heat-treating the powder of the step S2, reducing the graphene oxide bound to the surface of the prussian white,
    상기 프러시안 화이트 용액은 하기 화학식 1로 표시되는 화합물을 포함하는 것인, 이차전지용 양극 소재의 제조방법:The Prussian white solution is to include a compound represented by the formula (1), a method for producing a positive electrode material for a secondary battery:
    [화학식 1][Formula 1]
    AxMa[Mb(CN)6]A x M a [M b (CN) 6 ]
    상기 화학식 1에서 A는 알칼리 금속 또는 알칼리토금속이고, Ma 및 Mb는 전이금속이며,In Formula 1, A is an alkali metal or alkaline earth metal, M a and M b are transition metals,
    x는 0~2, a는 0~1, b는 0~1이다.x is 0-2, a is 0-1, and b is 0-1.
  2. 제1항에 있어서,According to claim 1,
    상기 S2 단계의 분무 건조는 100 내지 150℃로 수행되는 것을 특징으로 하는, 이차전지용 양극 소재의 제조방법.The spray drying of the step S2 is characterized in that is performed at 100 to 150 ℃, the method of manufacturing a positive electrode material for a secondary battery.
  3. 제1항에 있어서,According to claim 1,
    상기 S3 단계의 환원은 공기 분위기에서 수행되는 것을 특징으로 하는, 이차전지용 양극 소재의 제조방법.The reduction of the S3 step is characterized in that it is performed in an air atmosphere, a method of manufacturing a positive electrode material for a secondary battery.
  4. 제1항에 있어서,According to claim 1,
    상기 S3 단계의 환원은 산소 분위기에서 수행되는 것을 특징으로 하는, 이차전지용 양극 소재의 제조방법.The reduction of the step S3 is characterized in that is carried out in an oxygen atmosphere, a method of manufacturing a positive electrode material for a secondary battery.
  5. 제1항에 있어서,According to claim 1,
    상기 S3 단계의 열처리는 120 내지 220℃로 수행되는 것을 특징으로 하는, 이차전지용 양극 소재의 제조방법.Heat treatment of the step S3 is characterized in that is performed at 120 to 220 ℃, the method of manufacturing a positive electrode material for a secondary battery.
  6. 제1항에 있어서,According to claim 1,
    상기 알칼리 금속은 나트륨, 리튬, 및 칼륨으로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 하는, 이차전지용 양극 소재의 제조방법.The alkali metal is sodium, lithium, and potassium, characterized in that at least one member selected from the group consisting of, the method of manufacturing a positive electrode material for a secondary battery.
  7. 제1항에 있어서,According to claim 1,
    상기 알칼리 토금속은 마그네슘, 칼슘, 및 스트론튬으로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 하는, 이차전지용 양극 소재의 제조방법.The alkaline earth metal is characterized in that at least one member selected from the group consisting of magnesium, calcium, and strontium, a method of manufacturing a positive electrode material for a secondary battery.
  8. 제1항에 있어서,According to claim 1,
    상기 전이금속은 망가니즈, 철, 코발트, 니켈, 크롬, 티타늄, 바나듐 및 구리로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 하는, 이차전지용 양극 소재의 제조방법.The transition metal is characterized in that at least one member selected from the group consisting of manganese, iron, cobalt, nickel, chromium, titanium, vanadium and copper, the method of manufacturing a positive electrode material for a secondary battery.
  9. 제1항의 제조방법으로 제조된 양극 소재를 포함하는 이차전지용 전극의 제조방법으로, A method of manufacturing an electrode for a secondary battery comprising a positive electrode material manufactured by the method of claim 1,
    (a) 상기 양극 소재와 도전재를 혼합한 후, 결합제를 혼합하여 전극활물질 슬러리를 제조하는 단계;(A) after mixing the positive electrode material and the conductive material, mixing the binder to prepare an electrode active material slurry;
    (b) 상기 슬러리를 집전체에 캐스팅하는 단계; 및(b) casting the slurry to a current collector; And
    (c) 상기 슬러리가 캐스팅된 집전체를 진공건조하는 단계를 포함하는 이차전지용 전극의 제조방법.(c) A method of manufacturing an electrode for a secondary battery, comprising vacuum drying the current collector to which the slurry is cast.
  10. 제9항에 있어서,The method of claim 9,
    상기 도전재는 카본블랙, 그라파이트, 탄소나노튜브, 및 그라핀으로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 하는, 이차전지용 전극의 제조방법.The conductive material is characterized in that at least one member selected from the group consisting of carbon black, graphite, carbon nanotubes, and graphene, a method for manufacturing an electrode for a secondary battery.
  11. 제9항에 있어서,The method of claim 9,
    상기 결합제는 폴리비닐리덴플루오라이드(PVDF), 폴리아미드이미드(PAI), 폴리아크릴산(PAA) 및 폴리이미드(PI)로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 하는, 이차전지용 전극의 제조방법.The binder is polyvinylidene fluoride (PVDF), polyamideimide (PAI), polyacrylic acid (PAA) and polyimide (PI), characterized in that at least one member selected from the group consisting of, the method for manufacturing a secondary battery electrode .
  12. 제9항에 있어서,The method of claim 9,
    상기 집전체는 알루미늄, 구리, 및 니켈로 이루어지는 군으로부터 선택되는 1종 이상인 것을 특징으로 하는, 이차전지용 전극의 제조방법.The current collector is a method of manufacturing an electrode for a secondary battery, characterized in that at least one member selected from the group consisting of aluminum, copper, and nickel.
  13. 제9항에 있어서,The method of claim 9,
    상기 (c)단계의 진공건조는 150 내지 180℃에서 수행되는 것을 특징으로 하는, 이차전지용 전극의 제조방법.Vacuum drying in step (c) is characterized in that is performed at 150 to 180 ℃, the method of manufacturing a secondary battery electrode.
  14. 제1항의 제조방법으로 제조된 양극 소재를 포함하는 이차전지용 전극.An electrode for a secondary battery comprising a positive electrode material manufactured by the method of claim 1.
  15. 제14항의 이차전지용 전극을 포함하는 이차전지.A secondary battery comprising the electrode for secondary battery of claim 14.
  16. 제15항의 이차전지의 충방전 방법으로, 상기 이차전지를 1.5 내지 4V 범위 내에서 정전류 및 정전압으로 충전과 방전을 반복 수행하는 단계를 포함하는, 이차전지의 충방전 방법.A method of charging and discharging a secondary battery according to claim 15, comprising repeatedly performing charging and discharging the secondary battery with a constant current and a constant voltage within a range of 1.5 to 4V.
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